ACT exam

Question 1

Q1. A 60-year-old man with diabetes mellitus, hypertension, and coronary artery disease has
shown decline in estimated glomerular filtration rate from 40 to 14 ml/min over the past two
years. The patient reports fatigue, and a complete blood count evaluation reveals anemia. Red
blood cell indexes are normal, and serum iron, folate, and vitamin B12 concentrations are within
normal parameters.
Which of the following is the most proximate cause of the patient’s anemia?
A. Diabetes mellitus
B. Erythropoietin deficiency
C. Multiple myeloma
D. Extramedullary hematopoiesis

Answer 1

B. Erythropoietin is a hormone primarily produced by the kidneys that stimulates red blood cell production. In stage 5 chronic kidney disease, anemia is common, especially among patients with diabetes.

افت واضح GFR → نشانگر نارسایی کلیه:
کلیه اریترپوئتین (EPO) کافی تولید نم

اریتروپوئتین هورمونی است که مغز استخوان را تحریک می‌کند تا گلبول قرمز بسازد.

مولتیپل میلوما: سرطان پلاسمای مغز استخوان. غلایمش کلسیم بالا , نارسایی کلیه, کم خونی, شکستگی و درد استخوان

Question 2

Q2. Which of the following solvent exposures is associated with mutations in the von Hippel-
Lindau tumor suppressor gene and kidney cancer in humans?
A. Benzene
B. Trichloroethylene
C. Ethyl benzene
D. Methylene chloride

Answer 2

B. Trichloroethylene (TCE) → A chlorinated solvent. Strongly linked to VHL gene mutations and clear cell RCC in humans (epidemiological and mechanistic studies).

Benzene → Aplastic anemia, Acute myeloid leukemia (AML)

Vinyl chloride (PVC industry, plastics) → Hepatic angiosarcoma

Asbestos → Mesothelioma, bronchogenic carcinoma (lung cancer; risk ↑ especially with smoking)

Aflatoxin B1 (from Aspergillus in stored grains) → Hepatocellular carcinoma

Arsenic → Skin cancer, lung cancer, angiosarcoma

Trichloroethylene (TCE) → Renal cell carcinoma (VHL mutation)

Naphthylamine (dyes, rubber industry) → Bladder cancer

Nitrosamines (smoked foods) → Gastric cancer

Question 3

Q3. Which is the primary site of kidney damage resulting from exposure to inorganic mercury
salts?
A. Glomerulus
B. Proximal tubule
C. Loop of Henle
D. Renal papilla

Answer 3

B. Inorganic mercury salts are directly toxic to the proximal tubular epithelial cells.

This leads to acute tubular necrosis (ATN), especially in the proximal tubule.

Organic mercury (like methylmercury) affects the** CNS** more, but inorganic mercury → kidney.

Question 4

Q4. Excessive, chronic ingestion of nonsteroidal anti-inflammatory drugs (NSAIDs) initially
causes damage most commonly in what region of the kidney?
A. Glomerulus
B. Proximal tubule
C. Collecting duct
D.Interstitial tissue of the papilla

Answer 4

D. NSAIDs inhibit cyclooxygenase (COX) → ↓ prostaglandin synthesis.

Prostaglandins normally dilate the afferent arteriole → preserve renal blood flow, especially in the papilla (most hypoxic area).

Chronic NSAID use → ischemia of the renal papilla → analgesic nephropathy.

Histology shows chronic interstitial nephritis + papillary necrosis.**

A. گلومرولوس (Glomerulus):
در گلومرولونفریت‌ها درگیر می‌شود

B. توبول پروگزیمال (Proximal tubule):
داروهایی مثل آمینوگلیکوزیدها یا فلزات سنگین بیشتر این ناحیه را تخریب می‌کنند.

C. مجرای جمع‌کننده (Collecting duct):
بیشتر در اثر** لیتیم آ**سیب می‌بیند (دیابت بی‌مزه نفروژنیک).

Question 5

Q5. Excitotoxins are associated with inappropriate activation by which class of neurotransmitter
receptor?
A. Dopamine D2 receptors
B. Nicotinic acetylcholine receptors
C. Glutamate receptors
D. Gamma aminobutyric acid (GABA) receptors

Answer 5

Excitotoxins → compounds that cause neuronal injury/death by excessive stimulation of excitatory neurotransmitter receptors.

The main excitatory neurotransmitter in the CNS is** glutamate.**

Overactivation of glutamate receptors → excessive **Ca²⁺ influx **→ free radical generation, mitochondrial damage → neuronal death.

This process is called **excitotoxicity **and is implicated in stroke, trauma, Alzheimer’s, ALS, Huntington’s disease.

A. Dopamine D2 receptors → involved in movement (Parkinson’s, schizophrenia) but not excitotoxicity.

B. Nicotinic acetylcholine receptors → excitatory, but not the main excitotoxin pathway.

D. GABA receptors → inhibitory, not excitotoxic.

Question 6

Q6. Donepezil, sold under the trade name Aricept®, is an acetylcholinesterase inhibitor that
increases cholinergic signaling in the brain and is used in treatment of patients with Alzheimer’s
disease. Which of the following is most likely a mechanism-based side effect of this
medication?
A. Dry mouth
B. Diarrhea
C. Dry eyes
D. Hot, dry skin

Answer 6

Acetylcholinesterase inhibitor → ↑ acetylcholine at synapses → ↑ cholinergic signaling.
Expected side effects (cholinergic excess)

Remember SLUDGE (Salivation, Lacrimation, Urination, Diarrhea, GI upset, Emesis).

سیستم کولینرژیک چیست؟

بر پایهٔ استیل‌کولین (ACh)
عمل می‌کند.

گیرنده‌ها:

موسکارینی (Muscarinic)
– در اندام‌های هدف (قلب، ریه، روده، غدد و …).

نیکوتینی (Nicotinic)
– در محل اتصال عصب-عضله و گانگلیون‌ها.

🔹 اثرات تحریک موسکارینی (به خاطر بیاور: SLUDGE-M)

S = Salivation → افزایش ترشح بزاق

L = Lacrimation → افزایش اشک‌ریزی

U = Urination → تکرر یا بی‌اختیاری ادرار

D = Diarrhea → افزایش حرکات روده‌ای

G = GI cramps → دل‌پیچه، کرامپ شکمی

E = Emesis → تهوع و استفراغ

M = Miosis → تنگی مردمک

🔸 به‌علاوه: برادی‌کاردی، تعریق زیاد، افزایش ترشحات تنفسی.

🔹 اثرات تحریک نیکوتینی

انقباض عضلات اسکلتی (و در دوز بالا → فاسیکولاسیون و فلج).

تحریک سیستم عصبی خودکار (اول افزایش فشار خون و ضربان قلب، بعد خستگی و بلاک).**

Question 7

Q7. According to the World Health Organization, which of the following dietary deficiencies is
associated with impaired cognitive development?
A. Selenium
B. Calcium
C. Iodine
D. Trivalent chromium (Cr+3)

Answer 7

C. Thyroid hormone, which contains iodine, is critical for late prenatal and early postnatal development. Iodine deficiency reduces available thyroid hormone, resulting in impaired cognitive development and potentially more severe mental retardation (cretinism).

Question 8

Q8. During reporting of telemetry studies, which of the following is independent from group
size?
A. Minimum detectable difference (MDD)
B. Confidence intervals (CI)
C. Least significant differences (LSD)
D. Root-mean-square deviation (RMSE)

Answer 8

D. Root-mean-square deviation (RMSE) is independent of sample size. The minimum detectable difference is specific to a precise study design and therefore affected by group size.

Question 9

Q9. Which of the following is a Principle of Teratology described by James G. Wilson in his
monograph published in 1973?
A. Poison is in everything, and nothing is without poison. The dosage makes it either a
poison or a remedy.
B. Susceptibility to teratogenesis varies with the developmental stage at the time of
exposure to an adverse influence.
C. Teratogenic agents act in specific ways (mechanisms) on developing cells and tissues
to initiate sequences of abnormal developmental events (including gametogenesis,
spermatogenesis, pathogenesis).
D. The three-segment protocol consists of fertility and embryonic development, embryo-
fetal development, and a pre- and postnatal exposure.

Answer 9

B. e proposed a set of guiding principles in his classic monograph “Environment and Birth Defects.” Key points include:

Susceptibility to teratogenesis varies with the developmental stage at the time of exposure.

Teratogenic agents act in specific mechanisms on cells/tissues to trigger abnormal development.

Access of an agent to developing tissues depends on nature of the agent and placental transfer.

Manifestations of abnormal development include death, malformation, growth retardation, and functional deficits.

Manifestations increase in frequency/severity with dose.

Question 10

Q10. While visiting friends and family in a coastal town, a woman in her 10th week of pregnancy
spends the weekend helping repaint vintage sailboats as part of a community regatta
restoration project. Unbeknownst to her, the marine paint they used contains Mystexin
(fictitious name), a volatile compound known to linger in enclosed areas and potentially cross
the placental barrier. After returning home, she stumbles across a news article about recent
safety concerns related to the chemical. Alarmed, she does some research and confirms its
potential risks. She promptly calls her OB/GYN to schedule a check-up.
Given the timing of exposure during the first trimester, which of the following is least likely to be
a potential adverse outcome associated with in utero exposure to Mystexin?
A. No or slight effect on growth
B. Death through overwhelming damage
C. Functional anomalies of the reproductive organs
D. Malformations (eye, brain, and face) indicative of damage to the neural plate

Answer 10

در سه‌ماههٔ اول (به‌خصوص هفته‌های ۳ تا ۸)، مرحلهٔ اصلی ارگان‌زایی (Organogenesis) است.

در این دوره، خطر اصلی → مالفورماسیون‌ (نقایص ساختمانی) مثل چشم، مغز، صورت.

اگر آسیب خیلی شدید باشد → می‌تواند باعث مرگ جنین شود.

اثرات خفیف‌تر ممکن است بدون تغییر یا با اثر کم روی رشد دیده شوند.

🔹 اما:

اختلالات عملکردی ارگان‌ها (Functional anomalies) مثل سیستم تناسلی، معمولاً در سه‌ماههٔ دوم و سوم یا دوره‌های دیرتر رشد اتفاق می‌افتند (وقتی اندام‌ها از نظر ساختاری شکل گرفته‌اند و فقط عملکردشان تحت‌تأثیر قرار می‌گیرد).

Question 11

Q11. At 36 weeks pregnant, a woman travels to a mountain resort town to attend an outdoor art
and craft retreat with friends. One afternoon, she participates in a DIY resin art workshop held in
a small, poorly ventilated cabin. The resin used in the workshop contains Lumorex (fictitious
name), a volatile chemical known for its luminous finish but also for its potential to be absorbed
through inhalation. Unaware of any risk, she completes the project and enjoys the rest of her
weekend. A few days later, she reads an article warning about recent safety concerns linked to
craft resins containing Lumorex, especially in enclosed, high-altitude settings. Alarmed, she
investigates further and discovers the compound’s potential to cross the placenta late in
pregnancy. She promptly contacts her OB/GYN for evaluation.
Given the timing of exposure during late gestation, which of the following is most likely a
potential adverse outcome associated with in utero exposure to Lumorex?
A. Low intrauterine birth weight
B. Death
C. Functional anomalies of the central nervous system
D. Excessive craniofacial malformations indicative of damage to the neural plate

Answer 11

C

A (Low birth weight):
نیازمند مواجهه طولانی/مزمن است.

C (Functional CNS anomalies):
حتی مواجهه حاد در اواخر بارداری هم می‌تواند آن را ایجاد کند.

Question 12

Q12. Which of the following statements most accurately reflects key factors influencing
placental transfer and potential placental toxicity of a chemical during pregnancy?
A. The placenta passively transfers all chemicals from maternal to fetal circulation, and the
transfer rate remains constant throughout gestation.
B. Placental transfer is primarily influenced by maternal diet and fetal size, while blood flow
and drug properties have minimal impact.
C. The extent of placental transfer depends on placental structure, chemical properties
(e.g., lipophilicity, molecular weight), and the rate of placental metabolism.
D. The rate of chemical passage across the placenta is unrelated to the chemical’s
diffusion constant or the concentration gradient between maternal and fetal plasma.

Answer 12

C. The placenta is not just a passive barrier → it regulates, metabolizes, and sometimes blocks substances.

Factors influencing transfer include:

Placental structure & blood flow

Chemical properties → lipid solubility, molecular weight, ionization, protein binding

Placental metabolism (some xenobiotics are partially metabolized before reaching fetus)

Passive diffusion is the main route for many chemicals → depends on diffusion constant and maternal–fetal concentration gradient.

Question 13

Q13. Which of the following testing guidance best describes the following study schematic and
can be used to evaluate an environmental chemical that may have adverse impacts on
neurodevelopment and immune function in the F1 offspring?

A. OECD Test No. 443: Extended One-Generation Reproductive Toxicity Study, OECD
Guidelines for the Testing of Chemicals, Section 4.
B.OECD Developmental Neurotoxicity Study, OECD Guideline for Testing of Chemicals, No.
426.
C. ICH S5(R3): Detection of Toxicity to Reproduction for Medicinal Products & Toxicity to
Male Fertility.
D. United States EPA Health Effects Test Guidelines OPPTS 870.3800, Reproduction and
Fertility Effects (Two-Generation Reproduction Toxicity Study OECD Guideline 416).

Answer 13

A. Why: OECD 443 is designed for environmental chemicals and lets you add optional cohorts in the F1 generation to probe:

Developmental neurotoxicity (DNT) → Cohort 2 (behavioral/functional neuro tests)

Developmental immunotoxicity (DIT) → Cohort 3 (immune function/endpoints)

OECD 426 focuses on DNT only (no immune function).

ICH S5(R3) is for medicinal products, not general environmental chemicals.

EPA OPPTS 870.3800 / OECD 416 is the older two-generation repro study and doesn’t natively include the targeted DNT/DIT cohorts like 443.

Question 14

Q14. Which of the following is associated with corneal deposits and bull’s eye pattern of retinal
degeneration:
A. Digoxin
B. Chlorpromazine
C. Hydroxychloroquine
D. Tamoxifen

Answer 14

Hydroxychloroquine (and chloroquine) → corneal deposits and bull’s-eye maculopathy (retinal degeneration).

Digoxin → yellow/green vision changes, scotomas, blurry vision.

Chlorpromazine → corneal deposits, anterior subcapsular lens opacity (stellate pattern).

Tamoxifen → crystalline retinopathy, macular edema.

Question 15

Q15. During a dermal exposure risk assessment, the octanol-water partition coefficient (Kow) of
a chemical is found to be high (log Kow > 4). Which of the following best describes the
significance of this value in relation to percutaneous (skin) absorption?
A. A high Kow indicates the chemical is too lipophilic to effectively penetrate the stratum
corneum and will remain on the skin surface.
B. A high Kow suggests the chemical will readily dissolve in sweat and be quickly
eliminated through perspiration.
C. A high Kow implies enhanced partitioning into the stratum corneum, potentially
increasing percutaneous absorption.
D. A high Kow means the chemical will be completely blocked by the hydrophilic layers of
the skin and have negligible systemic absorption.

Answer 15

C.
Kow (log Kow) is a measure of a chemical’s lipophilicity.
High log Kow (>4) → chemical is highly lipophilic.

The skin barrier is mainly the stratum corneum, which is rich in lipids.

Lipophilic compounds → partition well into this layer → enhanced absorption potential.

If a compound is too hydrophilic → poor penetration.

If extremely lipophilic, it can “stick” in stratum corneum, but generally a high Kow correlates with increased uptake (unless it’s very extreme, like >7, where penetration may plateau).

Question 16

Q16. A small molecule in development for topical treatment of mild dermatitis has molar
extinction coefficient >1,000 L·mol⁻¹·cm⁻¹ at 350 nm. Systemic exposure is minimal, but the
compound accumulates in the stratum corneum. Do you need to perform phototoxicity testing?
A. No, the compound’s systemic exposure is low, ruling out significant phototoxic
potential.
B. No, high accumulation in the stratum corneum is not relevant since this layer lacks
viable cells.
C. Yes, the compound’s strong absorption in the UVA range and local exposure to viable
skin layers suggest a potential phototoxic risk.
D. Yes, the compound is intended for topical use, so phototoxicity testing is automatically
required.

Answer 16

C.

Phototoxicity refers to skin damage that occurs when a chemical is present in the skin (or systemically) and the person is exposed to ultraviolet (UV) or high-energy visible light.

The chemical absorbs the light → becomes excited (higher energy state) → generates reactive oxygen species (ROS) or directly interacts with DNA, proteins, and lipids.

The result is cellular damage and inflammation.

Phototoxicity risk depends on (1) skin exposure, (2) absorption of UV/visible light (typically ≥ ε 1000 L·mol⁻¹·cm⁻¹ in 290–700 nm), and (3) sufficient concentration near viable cells to generate ROS upon irradiation.

Question 17

Q17. Following ozone inhalation, what region of the respiratory tract receives the greatest
exposure (dose per unit surface area)?
A. Nasal passages
B. Larynx
C. Centriacinar region
D. Alveolar region

Answer 17

C. Ozone is a highly reactive oxidant gas.

Because of its reactivity, most of it is consumed in the conducting airways before reaching the deepest alveoli.

The region where ozone exposure per unit surface area is greatest is the transition zone → where bronchioles meet alveolar ducts.

A. Nasal passages → Ozone is reactive, but the nasal epithelium and scrubbing reduce deposition.

B. Larynx → Not the main target.

D. Alveolar region → Ozone rarely penetrates this far in high amounts, because it’s already consumed earlier.

Question 18

Q18. Which respiratory tract deposition mechanism is particularly important for inhaled fibers?
A. Impaction
B. Interception
C. Sedimentation
D. Electrostatic attraction

Answer 18

B. Deposition of particles occurs primarily by interception, impaction, sedimentation and diffusion (Brownian movement). Interception occurs only when the trajectory of a particle brings it near enough to a surface so that an edge of the particle contacts the airway surface.

**Impaction **→ for large particles (>5 µm), especially at airway bifurcations.

Sedimentation → for medium particles (1–5 µm), settling in smaller bronchioles/alveoli.

Diffusion (Brownian motion) → for ultrafine particles (<0.5 µm).

Interception → especially important for fibers (like asbestos, glass fibers).

Even if the fiber is small enough to follow airflow, its length/shape can cause it to physically contact and “intercept” airway walls**

Question 19

Q19. Which respiratory tract toxicity is caused by systemic exposure to the cancer
chemotherapeutic drug bleomycin?
A. Pulmonary inflammation
B. Lung cancer
C. Pulmonary fibrosis
D. Laryngeal epithelial erosion

Answer 19

C. Bleomycin, a mixture of several structurally similar compounds, is a widely used cancer chemotherapeutic agent. Pulmonary fibrosis, often fatal, represents the most serious form of toxicity.

Mechanism: bleomycin induces f**ree radical formation **→ oxidative damage to alveolar epithelium and endothelial cells.

Leads first to pulmonary inflammation → then progresses to pulmonary fibrosis.

Classic adverse effect: bleomycin-induced pulmonary fibrosis (restrictive lung disease).

Question 20

Q20. The respiratory tract disease byssinosis, typified chronically by restrictive lung disease and
chronic bronchitis, is caused by which agent?
A. Acrolein
B. Aspergillus
C. Carbides of tungsten or titanium
D. Cotton dust

Answer 20

D. Industrial toxicants that produce lung disease include cotton dust from manufacture of textiles. Cotton dust causes byssinosis in workers in textile industry.

بیسینوزیس (Byssinosis)

نام دیگر: بیماری ریهٔ قهوه‌ای (Brown lung disease)

یک بیماری شغلی ریه است که در کارگران صنایع نساجی (پنبه، کتان، کنف) دیده می‌شود.

علت: گرد و غبار پنبه (Cotton dust) که معمولاً با اندوتوکسین‌های باکتریایی آلوده است

Question 21

Q21. Nanoparticles can be best defined as having at least one physical length dimension less
than or equal to which length:
A. ≤ 1 µm
B. ≤ 100 nm
C. ≤ 10 nm
D. ≤1 nm

Answer 21

B. At least one physical dimension ≤ 100 nanometers (nm).

Question 22

Q22. What agent is most strongly implicated in adverse respiratory tract responses resulting
from polluted indoor atmospheres in newly constructed buildings?
A. Acrolein
B. Formaldehyde
C. Styrene
D. Xylene

Answer 22

B. Indoor air pollution in newly constructed buildings

Known as “sick building syndrome.”

Major culprit = formaldehyde (from pressed wood products, glues, insulation, new carpets, furnishings).

Causes eye, nose, throat irritation, cough, wheezing, and asthma-like symptoms.

Question 23

Q23. In general, which biological level of organization is ecological risk assessment focused
on?
A. Cellular
B. Individual
C. Population
D. Ecosystem

Answer 23

C. Risk assessment decisions are focused on preserving populations, not individual organisms.

Question 24

Q24. Which chemical physical parameter can be useful for predicting bioavailability and
bioaccumulation of organic substances to ecological receptors?
A. Water solubility
B. Octanol/water partition coefficient (log Kow)
C. Dipole moment
D. Oxidation state

Answer 24

B.

A key predictor = lipophilicity.

Measured by the octanol–water partition coefficient (Kow).

High log Kow (>4–5) → compound is lipophilic, tends to bioaccumulate in fatty tissues and biomagnify in food chains.

Low log Kow (<1) → compound is hydrophilic, less likely to bioaccumulate.

Question 25

Q25. Vitellogenin is a protein that is normally produced by the liver of female fish and is the measured outcome for some ecotoxicological assays. Lower systemic levels in circulation during reproduction can be an indicator of what toxic response? A. Malnutrition B. Genotoxicity C. Feminization D. Endocrine disruption

Answer 25

D. Vitellogenin (VTG) = yolk precursor protein, normally made in the liver of female fish under control of estrogen (estradiol). Male fish normally have very low/undetectable VTG. In ecotoxicology, VTG is a biomarker of estrogenic activity. ## Footnote ↑ VTG in males → sign of estrogenic endocrine disruption (feminization). ↓ VTG in females during reproduction → indicates anti-estrogenic or general endocrine disruption (interference with estrogen signaling → impaired reproduction).

Question 26

Q26. Populations of Asian Vultures dropped precipitously from foraging on dead cattle containing what substance? A. Erythromycin B. Lead C. DDT D. Diclofenac

Answer 26

D. In the 1990s–2000s, populations of Gyps vultures in South Asia (India, Pakistan, Nepal) collapsed by >95%. Cause: feeding on carcasses of cattle that had been treated with the NSAID diclofenac. ## Footnote کرکس‌ها توانایی متابولیسم دیکلوفناک را ندارند → دارو در بدنشان تجمع می‌کند. نتیجه: نارسایی حاد کلیه و نقرس احشایی (رسوب کریستال‌های اورات در اندام‌ها). پیامد: مرگ گسترده کرکس‌ها → افزایش لاشه‌های در حال فساد → افزایش جمعیت سگ‌های ولگرد → شیوع بیشتر هاری در انسان‌ها.

Question 27

Q27. Which study design is appropriate for exposing Daphnia magna using a test substance that has a relatively high vapor pressure? A. Static B. Flow-through C. Mixture D. Static renewal

Answer 27

B. Flow-through system continuously supplies fresh solution of the test chemical at a controlled concentration. This minimizes losses due to volatilization, degradation, or sorption. OECD and EPA aquatic toxicity guidelines recommend flow-through exposure for volatile or unstable chemicals.

Question 28

Q28. Which of the following statements is FALSE? A. In the kidney, weak acids are excreted faster when the urine is adjusted to alkaline pH. B. In the kidney, weak bases are excreted faster when the urine is adjusted to alkaline pH. C. Bicarbonate is a treatment for salicylic acid overdose. D. The excretion of amphetamine is increased with the administration of ascorbic acid.

Answer 28

B. Many chemicals are weak organic acids or bases, which in solution are ionized according to Arrhenius’ theory. The ionized form usually has low lipid solubility and thus does not permeate readily through the lipid membrane of renal tubules. ## Footnote Trap acids in base; trap bases in acid to boost renal clearance: _ Weak acids are ionized in alkaline urine → ↓ reabsorption → faster excretion. — Bicarbonate alkalinizes urine → enhances salicylate (weak acid) elimination. — Ascorbic acid acidifies urine → increases excretion of amphetamine (weak base).

Question 29

Q29. A 24-year-old male presents to the emergency department following an intentional ingestion of an unknown quantity of amphetamine tablets. On examination, he is agitated, hypertensive, and tachycardic. The medical team initiates supportive care and considers strategies to enhance drug elimination. A toxicologist is consulted to guide urinary pH adjustment as part of treatment. What is the best approach to enhance drug excretion by urinary pH in the context of this case? A. Acidification of urine with ascorbic acid can enhance the renal excretion of weak bases, such as amphetamine. B. Alkalinization of urine can enhance the renal excretion of weak acids, such as amphetamine. C. Bicarbonate administration may be used to increase urinary elimination of amphetamine. D. Alkalinization of urine with salicylate acid enhances the renal clearance of weak bases such as amphetamine.

Answer 29

A. Urine acidification is sometimes used to enhance the excretion of weakly basic drugs like amphetamine by ion trapping them in the renal tubules. Urine acidification is commonly achieved with weak acids like ascorbic acid (vitamin C).

Question 30

Q30. For cell survival, all cells must maintain some common activities. Which of the following statements is most indicative of a loss of cell viability or initiation of cell death? A. Assemble macromolecular complexes and cell organelles B. Maintain a sustained increase in cytosolic calcium C. Produce energy for operation D. Synthesize endogenous molecules

Answer 30

B. Cytoplasmic calcium is strictly controlled to maintain cellular viability. Toxic alteration of cellular maintenance by impairment of internal cellular maintenance can cause cell death. Sustained increase in cytosolic calcium is a classic trigger of cell death, because: Activates proteases, nucleases, and phospholipases. Damages mitochondria → loss of ATP → necrosis or apoptosis.

Question 31

Q31. Which of the following describes a mechanism of toxicant-induced cellular dysfunction? A. A conformational or structural change in a protein B. The formation of bifunctional electrophiles C. The activation of proteins into reactive electrophiles D. The abstraction of hydrogen from lipids

Answer 31

A. A conformational or structural **change in a protein** — Toxicants often act by altering protein shape/function, impairing normal cell processes and leading to dysfunction.

Question 32

Q32. Which of the following statements is correct about metabolism-mediated drug-drug interactions (DDI)? A. “Precipitant” is defined as the drug for which its PK is impacted by the administration of another drug. B. CYP induction can result in a clinically relevant DDI by increasing the concentration of the substrate drug, leading to toxicity. C. As per ICH M12, in vitro DDI studies are regulated studies that need to be conducted in compliance with GLP regulations. D. A CYP2D6 substrate drug is expected to have high plasma concentrations in humans with the poor metabolizer phenotype, similar to the effect observed with a strong CYP2D6 inhibitor.

Answer 32

D. A** CYP2D6** substrate drug is expected to have high plasma concentrations in **poor metabolizers** — Lack of enzyme activity mimics the effect of inhibition, leading to higher drug levels. در افراد poor metabolizer آنزیم CYP2D6 فعالیت ندارد، بنابراین داروی وابسته به این مسیر به‌خوبی دفع نمی‌شود و غلظت پلاسمایی بالا می‌رود. این وضعیت شبیه زمانی است که یک مهارکننده قوی CYP2D6 تجویز شود ## Footnote The precipitant drug is the one causing the interaction. The other one is object drug. CYP induction decreases substrate concentration (faster metabolism → reduced efficacy, not toxicity). In vitro DDI studies (e.g., CYP inhibition/induction assays) do not need GLP compliance; they are not regulated safety studies.

Question 33

Q33. Which statement about drug transporters is correct? A. The ATP-binding cassette (ABC) transporters are not expressed in intestine. B. Inhibition of the OATP1B1 hepatic uptake transporter can result in an increase in the plasma concentration of a substrate drug. C. Renal excretion by glomerular filtration is mediated by the solute carrier (SLC) transporters. D. P-glycoprotein efflux at the blood-brain barrier facilitates drug uptake into the CNS.

Answer 33

B. OATP1B1 normally transports drugs (e.g., statins) from blood into hepatocytes. If inhibited → reduced hepatic uptake → plasma concentrations rise → risk of toxicity (e.g., statin-induced myopathy). ## Footnote Thee ATP binding cassette (aBC) are expressed in the intestine and limit oral absorption. Glomerular filtration is a passive process, not transporter-mediated. SLC transporters mediate tubular secretion/reabsorption. P-glycoprotein pumps drugs out of the brain, limiting CNS penetration.

Question 34

Q34. What statement about drug metabolites is true? A. Drug metabolites are not able to elicit clinically relevant DDIs. B. A disproportionate metabolite is defined as one identified only in humans or present at higher levels in humans than animals. C. A metabolite of concern is one that circulates in human plasma at <10% of total drug-related AUC. D. Phase 2 glucuronide conjugates do not pose toxicity concerns.

Answer 34

B**. Disproportionate metabolites are those unique or elevated in humans **— These raise safety concerns since they may not be fully evaluated in animal studies. A disproportionate metabolite is defined as one identified only in humans or present at higher levels in humans than animals. ## Footnote A metabolite of concern is one that circulates in human plasma at >10% of total drug-related AUC

Question 35

Q35. A pest control worker exposed to insecticide develops tonic-clonic seizures without tremors, along with autonomic signs. Which insecticide is consistent? A. Carbamate (aldicarb) B. Organophosphate (chlorpyrifos) C. Cyclodiene (chlordane) D. Organochlorine (DDT)

Answer 35

C. Cyclodiene such as chlordane — These insecticides cause CNS hyperexcitation with seizures (convulsions) but not cholinergic tremors typical of organophosphates/carbamates. ## Footnote Cyclodienes (such as chlordane and lindane) interfere with neurotransmission by **antagonizing the inhibitory effects of the neurotransmitter GABA**, which results in a particular spectrum of toxic effects that includes convulsions but not tremors. The other insecticides listed above have different mechanisms of action (**acetylcholinesterase inhibition for carbamates and organophosphates, and sodium channel modulation for DDT**) and overexposure would result in tremors.

Question 36

Q36. Which of the following is a TRUE statement about insecticides? A. Those targeting insect nervous system may also affect human nervous system. B. Crops with Bacillus thuringiensis PIPs are restricted to livestock. C. Botanicals have few effects in non-target species. D. Sarin resembles organochlorines like DDT.

Answer 36

A. Nervous system-targeting insecticides may also affect humans — Shared mechanisms between insects and mammals mean potential human neurotoxicity. Insecticides are not species-selective with regard to toxicity. B is not correct because Bt exhibits low mammalian toxicity (p. 1081). C is not correct because nicotine, for example, can cause green tobacco sickness upon absorption of the alkaloid by farm workers (p. 1077). D is not correct because chemical warfare agents such as the nerve gas sarin have structural similarities to organophosphate insecticides (p. 1063).

Question 37

Q37. Which statement about paraquat is TRUE? A. Accumulates in liver → hepatotoxicity. B. Most used insecticide worldwide. C. Inhibits acetylcholinesterase. D. Lung toxicant regardless of route; redox cycling drives toxicity.

Answer 37

D. **paraquate** is a bipyridyl **herbicide**. Toxicokinetics: selectively accumulates **in lungs, **not liver. Mechanism: undergoes **redox cycling** → generates reactive oxygen species (**ROS**). Toxicity: causes severe** p****ulmonary injury and fibrosis**, independent of exposure route (oral, dermal, inhalation).

Question 38

Q38. Which best describes fumigants? A. Selective to nematodes and fungi, low non-target toxicity. B. Active against wide range: insects, nematodes, weed seeds, fungi, rodents. C. Limited to structural pest control only. D. Must be bioactivated by liver enzymes.

Answer 38

B. Fumigants are volatile, gaseous pesticides used in soil, grain storage, and buildings. They act by** diffusion as gases, reaching hidden pest**s. They are** broad-spectrum biocide**s: active against insects, nematodes, fungi, weed seeds, even rodents. Examples: **methyl bromide**, phosphine, chloropicrin. They are not selective and **can be quite toxic to non-target species**, including humans.****

Question 39

Q39. A 3-month-old infant has cyanosis, chocolate-brown blood after being fed formula prepared with well water. What is the cause? A. Carbon monoxide poisoning B. Viral bronchiolitis C. Nitrate-induced methemoglobinemia D. Cyanotic congenital heart disease

Answer 39

C. Cyanosis + chocolate-brown colored blood → classic for **methemoglobinemia**. **Nitrate**s in well water (often from fertilizer runoff) can be converted in the gut to **nitrites**, which oxidize Hb → methemoglobin (**Fe³⁺ state, can’t bind O₂**). Infants are especially vulnerable because they have lower levels of NADH-dependent methemoglobin reductase.

Question 40

Q40. What criteria support an on-target toxicity for a receptor antagonist? A. Toxicity in an organ where target not expressed. B. Toxicity with chemically distinct modulator. C. Toxicity absent in KO model lacking the target. D. Toxicity with inactive analog.

Answer 40

C. On-target toxicity (also called **mechanism-based toxicity**) Occurs when the toxic effect is due to the intended pharmacological action of the drug at its target receptor. Clues that support this: Effect occurs in organs/tissues where the target is expressed. Effect is reproducible with different drugs (chemically distinct modulators) acting on the same target. Effect is absent in knockout (KO) animals that lack the target. Effect does not occur with inactive analogs that don’t bind the target. ## Footnote On-target toxicity = اثر دارو روی گیرنده/مسیر درست، اما شدید یا در بافتی حساس (مثل بتابلاکر → برادی‌کاردی). Off-target toxicity = اثر دارو روی مسیر/گیرنده‌ای که اصلاً هدف اصلی دارو نیست (مثل دوکسوروبیسین → کاردیوتوکسیسیتی).

Question 41

Q41. Which statement is correct for Therapeutic Index (TI)? A. Smaller TI = safer. B. Narrow TI drugs not used. C. TI can be projected from preclinical studies. D. If effective concentration > toxic concentration, TI is wide.

Answer 41

C. Definition: **TI = TD₅₀ / ED₅₀** TD₅₀ = dose toxic to 50% ED₅₀ = dose effective in 50% Larger TI → wider margin of safety. Smaller TI → narrow safety margin (more dangerous). TI can be estimated in preclinical animal studies, then refined in humans. Narrow TI drugs (e.g., warfarin, digoxin, lithium) are used clinically but require careful monitoring.

Question 42

Q42. Examples of real-world data sources are: A. Electronic health records B. Insurance claims data C. Patient-generated data D. All of the above

Answer 42

D. According to FDA and EMA guidance, RWD can come from: Electronic health records (EHRs) → clinical practice data. Insurance claims / billing data → large-scale health utilization patterns. Patient-generated data → registries, apps, wearables, patient surveys..

Question 43

Q43. Miracle Drug A: NOAEL rat 124 mg/kg, dog 18 mg/kg. What is appropriate starting dose for Phase 1? A. 6.2 mg/kg B. 2.0 mg/kg C. 1.8 mg/kg D. 1.0 mg/kg

Answer 43

C. First, convert the NOAEL to human equivalent doses (HED) using body surface area (mg/m2) conversion factors: **6.2 for rat and 1.8 for dog**. Rat NOAEL / conversion factor = HED (124 mg/kg / 6.2 = 20 mg/kg). Dog NOAEL / conversion factor = HED (18 mg/kg / 1.8 = 10 mg/kg). Second, using the **most sensitive species** (species that provides the lowest HED), incorporate **a 10-fold safety margin **to identify a safety clinical starting dose: Dog HED = 10 mg/kg / 10 = 1 mg/kg start dose in humans.

Question 44

Q44. biologic is being developed for myasthenia gravis and monkey is the only pharmacologically relevant species. In a GLP 13-week repeat-dose toxicity study, 4/sex/group cynomolgus monkeys were administered the biologic at target doses of 0, 30, 100, 300 mg/kg by IV infusion once weekly followed by a 4-week recovery period. Clinical signs consisted of transient redness and swelling in the face starting on Day 15 (3rd dose) within 15 min of infusion and resolving 1 hour after the end of infusion in the low dose (LD) (2/8) and mid-dose (MD) (1/8) animals. Clinical pathology at 24h post last dose revealed mild to moderate, transient increases in C-reactive protein, fibrinogen, and complement activation in all dose groups (LD 7/8, MD 4/8, HD 1/8). Antidrug antibody (ADA) was present in 100% of the treated animals and 0% of controls at the end of the study. Minimal exposure loss between the first and last doses. Histopathology revealed minimal to moderate mononuclear infiltrates in the sciatic nerve of animals in the LD (2/8) and MD (1/8) with no inflammation, degeneration, or necrosis. What is the NOAEL? A. NOAEL cannot be established due to the infiltrates in the sciatic nerve at 30 and 100 mg/kg B. NOAEL = 30 mg/kg based on the sciatic nerve infiltrates observed at 30 and 100 mg/kg C. NOAEL = 100 mg/kg based on the sciatic nerve infiltrates observed at 30 and 100 mg/kg D. NOAEL = 300 mg/kg based on nonadverse findings at all doses, clinical signs and histopathology findings are likely secondary to immunogenicity and not directly related to the test article given the high incidence of ADA and increased inflammatory markers (fibrinogen, C-reactive protein, complement activation)

Answer 44

D. NOAEL = 300 mg/kg — Findings were immune-mediated (due to ADA), not directly toxic effects. For biologics, immunogenicity-related changes (transient infusion reactions, complement/CRP/fibrinogen blips, minimal mononuclear infiltrates without injury) are often nonadverse—especially when exposure is confirmed and findings aren’t dose-related. With no adverse effects at the top dose, set NOAEL at 300 mg/kg. اگر ADA خیلی زود دارو را پاک کند، حیوان‌ها اصلاً در معرض دارو قرار نمی‌گیرند → آن وقت نمی‌توان NOAEL تعیین کرد (چون معلوم نیست عدم سمیت به‌خاطر نبود دارو بوده یا دارو واقعاً بی‌خطر است). در این مطالعه نوشته شده: “minimal exposure loss between first and last doses” → یعنی با وجود ADA ، سطح دارو در خون تقریباً پایدار مانده است. ✅ پس حیوان‌ها واقعاً در معرض دوزهای مورد نظر قرار گرفتند

Question 45

Q46. Which of the following best describes the relationship between hazard quotient (HQ) and hazard index (HI) in risk assessment? A. The HQ is the product of individual HIs for each chemical. B. The HQ is the inverse of the HI. C. The HI is the sum of individual HQs for chemicals with a common target organ or effect. D. The HI is a ratio of exposure to the reference dose for a single chemical.

Answer 45

C. The HI is the sum of HQs — When multiple chemicals affect the same organ/system, their HQs are added to give an HI. Hazard Quotient (HQ): Ratio of exposure dose ÷ reference dose (RfD) for a single chemical. HQ < 1 → acceptable risk HQ > 1 → potential concern Hazard Index (HI): The sum of HQs for multiple chemicals that act on the same target organ or endpoint.

Question 46

Q47. When should the core batter of nonclinical safety pharmacology studies be conducted for a new pharmaceutical? A. Prior to FIH B. Prior to Phase 2 C. Prior to Phase 3 D. Post marketing

Answer 46

A.According to ICH S7A/S7B: The core battery covers: Cardiovascular system (e.g., hERG assay, telemetry for QT) Central nervous system (CNS) Respiratory system These studies are designed to identify acute functional effects on vital organ systems. 👉 Timing: The core safety pharmacology studies must be completed before first-in-human (FIH) dosing to ensure no unexpected, life-threatening effects.

Question 47

Q48. What is an acceptable assay for CNS safety pharmacology for a new pharmaceutical? A. Modified Irwin test B. Delayed neurotoxicity of organophosphates C. Langendorff perfusion model D. Plethysmography

Answer 47

A. Modified Irwin test — It is the standard observational test for CNS safety evaluation in rodents. ## Footnote The modified Irwin test is the standard observational battery for CNS safety pharmacology (per ICH S7A). Langendorff → cardiovascular. Plethysmography → respiratory. Delayed OP neurotoxicity → not a general CNS safety assay.

Question 48

Q49. What is the most likely condition under which safety pharmacology studies are not necessary? A. Intravenously administered new molecular entities B. Changes to the drug product formulation that substantially alter PK C. Locally applied agents with predicted low systemic exposures D. Locally applied agents where systemic exposure is demonstrated to be low

Answer 48

D. Locally applied agents with proven low systemic exposure — If absorption is negligible, systemic safety pharmacology studies are unnecessary.

Question 49

Q50. The table below shows results from a modified Irwin’s test in a rat after acute exposure. What compound or class of compound was most likely tested in this species? A. Benzo(a)pyrene B. Organophosphates C. Rotenoids D. Atropine

Answer 49

B. Organophosphates — Irwin test signs typically show cholinergic effects from organophosphate poisoning.

Question 50

Q51. Tidal volume, inspiratory reserve volume, and expiratory reserve volume were measured to be 20 mL/kg, 10 mL/kg, and 10 mL/kg, respectively. Calculate the vital capacity. A. 10 mL/kg B. 30 mL/kg C. 40 mL/kg D. 60 mL/kg

Answer 50

C. 40 mL/kg — Vital capacity = TV + IRV + ERV = 20 + 10 + 10. ## Footnote Tidal Volume (TV) The normal breath in and out at rest. Inspiratory Reserve Volume (IRV) Extra air you can inhale after a normal inspiration. Expiratory Reserve Volume (ERV) Extra air you can forcefully exhale after a normal expiration. Residual Volume (RV) Air that never leaves the lungs (prevents collapse). 📌 Capacities (just sums of volumes) Vital Capacity (VC) = TV + IRV + ERV Maximum air you can move in/out voluntarily. Inspiratory Capacity (IC) = TV + IRV How much you can inhale starting from rest. Functional Residual Capacity (FRC) = ERV + RV Air left in lungs after a normal breath out. Total Lung Capacity (TLC) = VC + RV

Question 51

Q52. What is tidal volume? A. Amount of air in an average breath at rest B. Amount of air that can be forced into the lungs C. Amount of air that can be forced out of the lungs D. Amount of air that can be used by the animal

Answer 51

A. Amount of air in an average breath at rest — This is the definition of tidal volume.

Question 52

Q53. Which methods assess tidal volume directly? A. Plethysmography B. Pulse oximetry C. Electrocardiogram D. Spirometry

Answer 52

d: A spirometer can directly measure tidal volume and vital capacity. Plethysmography is used to calculate air volumes by measuring airway resistance. A pulse oximeter measures blood oxygen saturation via light sensors. An electrocardiogram records electrical signals in the heart.

Question 53

Q54. Which is the best method to assess blood oxygen saturation in a nonclinical safety pharmacology study? A. Sphygmomanometer B. Pulse oximeter C. Plethysmography D. NMR spectroscopy

Answer 53

B. Pulse oximeter — Noninvasive and widely used to measure arterial oxygen saturation.

Question 54

Q55. Which test assesses pupillary reaction and righting reflex? A. Morris water maze B. Eye blink conditioning C. Functional observation battery D. Radial arm maze

Answer 54

C. Functional observation battery — Includes assessment of reflexes like pupil response and righting reflex. Functional observation battery or the modified Irwin’s test used in safety pharmacology studies are similar to acute toxicity tests used for agrochemical testing. All test for autonomic responses such as pupillary reaction and motor reflexes like righting reflex.

Question 55

Q56. What is the length of time for one complete spermatogenic cycle in rats? A. ~56 days B. ~70 days C. ~160 days D. ~180 days

Answer 55

A. ~56 days — A full spermatogenic cycle in rats is about 8 weeks.

Question 56

Q57. In a male fertility test, how long should male rats be treated with test article prior to mating? A. 2 weeks B. 4 weeks C. 8 weeks D. 10 weeks

Answer 56

B. 4 weeks — Ensures coverage of spermatogenesis and maturation before mating.

Question 57

Q58. What is the experimental unit of an embryofetal development study? A. The pup B. The dam C. The litter D. The dam and her litter

Answer 57

C. The litter — Litter is the statistical unit for developmental studies.

Question 58

Q59. What species is used in an enhanced Pre- and Postnatal Development (ePPND) study? A. Rat B. Rabbit C. Dog D. Non-human primate

Answer 58

D. Non-human primate — ePPND is conducted in primates when they are the relevant species.

Question 59

Q60. Which is correct regarding the timing of developmental and reproductive toxicology (DART) testing of pharmaceuticals in the US? A. A male fertility study should be completed before the initiation of first-in-human clinical trials. B. A male fertility study should be completed before the initiation of large scale or long duration clinical trials (e.g., Phase 3 trials). C. Standard fertility study for pharmaceuticals includes evaluation of sperm morphology, motility, and count; hormone levels; and estrous/menstrual cycle. D. A male fertility study should be conducted in two species with rats and rabbits as the commonly used species for fertility.

Answer 59

B. Before Phase 3 — Male fertility studies should be done before large/long clinical trials. 📌 Fertility study timing Male fertility study: NOT required before first-in-human (FIH). Should be completed before large-scale or long-duration trials (e.g., Phase 3), where longer exposures might risk fertility effects. 📌 Standard fertility study design Typically in rats (one species, rodent). Assess male & female fertility: Male → sperm count, motility, morphology, testicular histopathology. Female → estrous cycle, ovarian/uterine histology, mating/fertility indices. Not usually hormone levels as standard endpoints.

Question 60

Q61. According to the Gell and Coombs classification system, exposure to poison ivy, oak, or sumac falls into which category? A. Type I B. Type II C. Type III D. Type IV

Answer 60

D. Type IV — Delayed-type hypersensitivity mediated by T-cells. ## Footnote ``` نوع I (فوری، وابسته به IgE) آنافیلاکسی، آسم آلرژیک، کهیر شروع سریع (دقایق) نوع II (سیتوتوکسیک، وابسته به IgG/IgM) کم‌خونی همولیتیک، ترومبوسیتوپنی خودایمنی آنتی‌بادی‌ها مستقیماً سلول‌ها را تخریب می‌کنند نوع III (ایمون‌کمپلکس) بیماری سرمی، لوپوس (SLE)، واکنش Arthus تشکیل کمپلکس آنتی‌ژن–آنتی‌بادی و رسوب در بافت‌ها نوع IV (تاخیری، وابسته به سلول T) درماتیت تماسی (مثل بلوط سمی، سماق سمی، پیچک سمی) تست پوستی توبرکولین (PPD) رد پیوند شروع ۲۴–۷۲ ساعت بعد از تماس ```

Question 61

Q62. Which of the following signals is not typically associated with drug- or xenobiotic-induced immunosuppression? A. Myelosuppression B. Decreased immune organ weight C. Decreased incidence of infections and/or tumors D. Decreased serum immunoglobulin levels

Answer 61

C. Decreased incidence of infections/tumors — Immunosuppression usually increases infection/tumor risk.

Question 62

Q63. Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen and naproxen, decrease pro-inflammatory signaling through which mechanism? A. Inhibition of cyclooxygenase 1 and 2 B. Inhibition of dihydrofolate reductase C. Inhibition of the glucocorticoid receptor D. Inhibition of HMG-CoA reductase

Answer 62

A. Inhibition of COX-1 and COX-2 — Blocks prostaglandin synthesis. ## Footnote Cyclooxygenase (COX-1 and COX-2) enzymes convert** arachidonic acid → prostaglandin**s & thromboxanes. **Prostaglandins mediate inflammation, pain, fever**. NSAIDs (aspirin, ibuprofen, naproxen) inhibit COX-1 and COX-2, → ↓ prostaglandin synthesis → ↓ inflammation & pain.

Question 63

Q64. Which of the following regarding the oxyhemoglobin dissociation curve is true? A. Carboxyhemoglobinemia induces a right shift. B. Sulfhemoglobinemia induces a left shift. C. Methemoglobinemia induces a left shift. D. Fetal hemoglobin is right-shifted relative to adult hemoglobin.

Answer 63

C. Methemoglobinemia induces a left shift — Higher affinity reduces O₂ release. ## Footnote منحنی نشان می‌دهد هموگلوبین در شرایط مختلف چه‌قدر به اکسیژن تمایل دارد و چه‌طور آن را به بافت‌ها تحویل می‌دهد. محور x = فشار اکسیژن (PaO₂) محور y = درصد اشباع هموگلوبین با اکسیژن (SaO₂) 📌 تغییرات منحنی ➡️** شیفت به راست (Right shift)** تمایل Hb به O₂ کم می‌شود → اکسیژن راحت‌تر به بافت‌ها آزاد می‌شود. یادآوری: Right = Release (آزادسازی O₂ بیشتر). **Sulfhemoglobinemia ** ⬅️ شیفت به چپ (Left shift) تمایل Hb به O₂ زیاد می‌شود → اکسیژن سخت‌تر به بافت‌ها تحویل داده می‌شود. علل: ↓ CO₂, pH (آلکالوز), ,,دما ↓ 2,3-BPG, **HbF (هموگلوبین جنینی), Carboxyhemoglobinemia (Hb-CO), Methemoglobinemia (Hb-Fe³⁺)**

Question 64

Q65. The terms “hazard” and “risk” are often used interchangeably by the public, but they are not the same. One key distinction is: A. Risk refers to effects that occur over an extended period of time, whereas hazard refers to instantaneous effects. B. Risk accounts for the degree of exposure whereas hazard does not. C. Risk is a term primarily used in the United States and Canada whereas hazard is primarily used in the European Union. D. Risk can be based on either animal or human data whereas hazard is primarily based on animal or mechanistic data.

Answer 64

B. Risk accounts for exposure — Hazard is intrinsic; risk = hazard × exposure.

Question 65

Q66. Which of the following best describes an Adverse Outcome Pathway (AOP)? A. A newer term for the mode of action. B. A way of summarizing all of the critical steps in the disease or adverse effect process. C. Describes the mechanism rather than the mode of action. D. Describes the exposure route(s) by which a chemical produces adverse effects on the organism.

Answer 65

B. AOP summarizes steps **linking molecular events to adverse outcomes.**

Question 66

Q67. Which of the following best describes the “Mega Mouse” study? A. Shared tissues from arsenic exposed mice across 40 different research groups in an effort to determine the mechanism of arsenic carcinogenesis. B. Demonstrated that chemicals (at least those studied) cause cancer with no threshold. C. Gave conflicting results regarding the existence of a threshold for carcinogenesis. D. Involved exposing mice to TCDD across a dose range encompassing 5 orders of magnitude.

Answer 66

B. Showed carcinogens may act with no threshold. ## Footnote The Mega Mouse study (or ED01 study), carried out by the US National Center for Toxicological Research (NCTR), involved exposing over 24,000 mice to 2-acetylamino fluorine for up to 33 months. Famous large-scale carcinogenicity testing program led by Bruce Ames, William P. Weisburger, and others in the 1960s–70s. Involved testing thousands of mice (hence “Mega Mouse”) across many chemicals. Goal: **to determine whether there is a threshold for chemical carcinogenesis.** Findings: Some results suggested no safe threshold (any exposure might pose risk), but other data suggested possible thresholds → overall** conflicting evidence.**

Question 67

Q68. Regarding the Cramer Decision Tree, which of the following is true? A. Classification is based on factors such as water solubility, pKa, Kow, and biological half-life. B. Class II chemicals are those that affect reproduction or development. C. Class V chemicals are those that are known human carcinogens. D. Class III is the highest risk; complex structures or functional groups associated with toxicity.

Answer 67

D. Class III is highest risk — Complex structures linked with toxicity.

Question 68

Q69. Which of the following best describes Assessment or uncertainty factors (AFs/UFs)? A. Were initially rather arbitrarily set at 10 each, but this has subsequently been shown to be generally reasonable in most cases B. Can range from 0 to 10,000 depending on the degree of extrapolation required C. Are used in converting animal tumor incidence data into human cancer slope factors D. Are being replaced with the BMD approach for estimating safe exposure levels

Answer 68

A. Default uncertainty factors of 10 for interspecies/intraspecies variation.

Question 69

Q70. When developing a small molecule for advanced ductal carcinoma, toxicologists generally follow ICH S9. According to ICH S9, what nonclinical studies should be available when the marketing application is submitted, but are not considered essential to support clinical trials intended for treatment of patients with advanced cancer? A. Fertility and early embryonic (FEED) studies in a single species B. Embryofetal development (EFD) studies in two species C. EFD studies in a single relevant species D. Pre- and postnatal development (PPND) in a single species

Answer 69

b. iCH S9 section 2.5 Reproductive Toxicology states that EFD studies should be made available when the marketing application is submitted to communicate potential risk for the developing embryo or fetus to patients who are or might become pregnant. As this is a small molecule for an indication that includes women of childbearing potential, EFD studies are typically conducted in two species as described in ICH S5(R3). Note: in cases where an EFD study is positive for embryofetal lethality or teratogenicity, a confirmatory study in a second species is usually not warranted. **C is less correct for a small molecule and more relevant for biopharmaceuticals.** A and D are incorrect because **FEED and PPND is generally not warranted to support clinical trials or for marketing of pharmaceuticals for the treatment of patients with advanced cancer** as per ICH S9. | i

Question 70

Q71. When developing a biopharmaceutical for ductal carcinoma, toxicologists generally follow ICH S9 and ICH S6. According to ICH S9, what nonclinical studies should be available when the marketing application is submitted, but are not considered essential to support clinical trials intended for treatment of patients with advanced cancer? A. Fertility and early embryonic (FEED) studies in a single species B. Embryofetal development (EFD) studies in two species C. EFD studies in a single relevant species D. Pre- and postnatal development (PPND) in a single species

Answer 70

C. : ICH S9 section 2.5 Reproductive Toxicology states that EFD studies should be made available when the marketing application is submitted to communicate potential risk for the developing embryo or fetus to patients who are or might become pregnant. As this is a large molecule for an indication that includes women of childbearing potential, EFD studies are typically conducted in one relevant species as described in ICH S9 and ICH S6(R1).

Question 71

Q72. When designing a fertility and early embryonic development (FEED) study for a pharmaceutical, what should be assessed? A. Maturation of gametes, male epididymal sperm maturation, female estrous cycle and tubal transport, mating behavior, fertility, preimplantation development of the embryo, and implantation B. Maternal toxicity in pregnant females, embryo-fetal survival, intrauterine growth, and morphological development C. Maternal toxicity in pregnant females, pre- and postnatal viability of offspring, altered growth and development, and functional deficits in offspring, including sexual maturation, reproductive capacity at maturity, sensory functions, motor activity, and learning and memory D. All of the above

Answer 71

A. Assess fertility and early embryo endpoints — Gamete maturation, mating, and implantation.

Question 72

Q73. Endpoints of an embryofetal development (EFD) and pre- and postnatal development (PPND) study are combined in an enhanced PPND (ePPND) study for pharmaceutical development. What best describes an ePPND study as described in ICH S5(R3)? A. PPND studies are conducted in nonhuman primates (NHP) with at least 4 groups (1 control group) to assess dose response and establish margins to human exposure. B. ePPND studies are conducted in the nonrodent species, often rabbit, but can be conducted in rodent to conserve animals. C. ePPND studies are conducted in NHP, therefore require only 4 pregnant females compared to the 16 per group in rats. D. ePPND studies are conducted in NHP with dosing on GD20-50 when this is the only relevant species.

Answer 72

d. iCH S5(R3) Annex 1 describes the study designs for developmental and reproductive toxicity studies. A is incorrect because **ePPND studies require at least 2 groups (1 control group)** to identify potential hazards to embryofetal and postnatal development. B is incorrect because ePPND studies are conducted in NHP and not a design described in ICH S5(R3). C is incorrect because** ePPND studies require approximately 16 pregnant females per group. **D is correct because it describes the species and dosing days correctly as per ICH S5(R3). ----2 groups (I control)/ each 16 pregnant NHP.

Question 73

Q74. Review the Ames assay results in the following table to answer the question below: Which of the following is the best interpretation of the tabulated data? A. Test article is negative for mutagenicity under the conditions of the assay. B. Test article is equivocal for mutagenicity under the conditions of the assay. C. Test article is positive for mutagenicity with metabolic activation in the assay. D. Uninterpretable, as the controls did not produce expected results.

Answer 73

A. Test article is negative for mutagenicity under the conditions of the assay ## Footnote Across all strains (TA97, TA98, TA100, TA102, TA1535) with and without S9, there’s no dose-related, ≥2-fold increase in revertants vs vehicle control. Some minor fluctuations (e.g., TA97 +S9 at 100 μg/plate) are <2× and not monotonic. High-dose precipitation (ppt) occurs but doesn’t coincide with a biologically meaningful rise. Positive/negative controls are acceptable per the note, so the study is valid → not “uninterpretable.”

Question 74

Q75. In the Ames assay, what is the purpose of the following chemicals: benzo[a]pyrene; 9,10-dimethylanthracene; 7,12-dimethylbenzanthracene; Congo red; cyclophosphamide; and 2-aminoanthracene? A. Negative control with metabolic activation B. Positive control with metabolic activation C. Negative control without metabolic activation D. Positive control without metabolic activation

Answer 74

B. Positive controls with metabolic activation — Pro-mutagens requiring S9 activation.

Question 75

Q76. During a 28-day repeat-dose toxicity study in beagle dogs evaluating a novel immunomodulatory compound, hematology assessments on Day 21 reveal a marked reduction in circulating neutrophils. To investigate potential bone marrow suppression, a colony forming unit (CFU) assay is conducted using bone marrow aspirates from affected animals. Which colony forming unit should be assessed as the most relevant indicator of neutrophil lineage development? A. BFU-E B. CFU-E C. CFU-M D. CFU-G

Answer 75

D. CFU-G — Colony-forming unit–granulocyte is the progenitor for neutrophils. ## Footnote All blood cells start from** Hematopoietic Stem Cells (HSCs). **** HSCs → Common **Myeloid** Progenitors and Common** Lymphoid **Progenitors. Myeloid progenitors give rise to **RBCs, platelets, granulocytes, monocytes.** Each lineage has colony-forming units (CFUs) that we can measure in vitro with CFU assays. 2. Key CFUs to Remember BFU-E (Burst-Forming Unit–Erythroid): Early red cell progenitor → RBC lineage. “Burst” = lots of small colonies (immature). CFU-E (Colony-Forming Unit–Erythroid): Later-stage progenitor → RBC lineage. More mature than BFU-E. CFU-G (Granulocyte): Progenitors of neutrophils, eosinophils, basophils. If neutrophils are ↓ → check CFU-G. CFU-M (Macrophage): Progenitors of monocytes/macrophages. CFU-GM (Granulocyte-Macrophage) Mixed progenitor → gives rise to both granulocytes and macrophages. Often tested in toxicology because it covers 2 lineages. If the question mentions anemia **(low RBCs**) → think **BFU-E / CFU-E.** If the question mentions **neutropenia** (low neutrophils) → think **CFU-G.** If the question mentions **monocytopenia** → think** CFU-M.** If the question mentions **pancytopenia** (all blood cell types ↓) → multiple CFUs affected (HSC issue).

Question 76

Q77. Positive results from the bacterial reverse mutation test (Ames assay) indicate that a substance induces point mutations by base substitutions or frameshifts. Which bacterial strains detect frameshift mutations? A. TA98, TA1537, TA97 B. TA100 and TA1535 C. TA102, WP2 uvrA, and WP2 uvrA (pKM101) D. All of the above

Answer 76

A. TA98, TA1537, TA97 — These strains detect frameshift mutations. ## Footnote A. TA98, TA1537, TA97 ✅ Correct for frameshift mutations. B. TA100 and TA1535 ❌ These detect base-pair substitutions. C. TA102, WP2 uvrA, WP2 uvrA (pKM101) ❌ Detect oxidative damage and base substitutions, not frameshifts.

Question 77

Q78. A 42-year-old male chemical plant worker with chronic benzene exposure presents with pancytopenia and leukemia. Which malignancy is most strongly associated? A. Hepatocellular carcinoma B. Acute myelogenous leukemia C. Small cell lung cancer D. Hodgkin’s lymphoma

Answer 77

B. A Benzene toxicity Chronic **benzene **exposure → **bone marrow toxicity.** Early effect: **pancytopenia, aplastic anemia**. Long-term effect: hematologic malignancies, especially **leukemias**. Strongest link: **Acute Myelogenous Leukemia (AML**). ## Footnote Benzene → Bone marrow failure + AML Vinyl chloride → Angiosarcoma of the liver Asbestos → Mesothelioma, bronchogenic carcinoma Aflatoxin B1 → Hepatocellular carcinoma Arsenic → Skin cancers, lung cancers, angiosarcoma

Question 78

Q79. What are the Bradford Hill criteria for causation in toxicology? A. Risk assessment, risk management, and risk communication B. NOEL, NOAEL, LOAEL, MTD, STD C. Strength of association, consistency, specificity, temporality, biological gradient, plausibility, coherence D. Hazard identification, dose-response assessment, exposure assessment, and risk characterization

Answer 78

C describes the seven criteria to build a weight of evidence for causality. When assessing toxicological responses, causation can be established using the Bradford Hill criteria largely aimed at evaluating relationships using epidemiological and occupational data; however, a similar framework can be applied to evaluate experimental and observational data regarding the toxicity of chemicals.

Question 79

Q80. A new compound is tested in OECD 202: Daphnia sp. Acute Immobilization Test. What is the primary endpoint? A. LC90 B. EC50 C. NOAEC D. LD50

Answer 79

B. EC50 — Effective concentration immobilizing 50% of Daphnia. ECD 202: Daphnia sp. Acute Immobilization Test Standard ecotoxicology assay. Species: usually Daphnia magna. Duration: 24–48 hours. Endpoint: not mortality, but immobilization (inability to swim within 15 seconds of gentle agitation). The main reported value is: EC50= concentration of test substance causing immobilization of 50% of daphnids

Question 80

Q81. The in vitro micronucleus assay is a surrogate for chromosomal aberration analysis and can be used to assess the potential to induce which of the following? A. Gene mutation B. Gene duplication C. Point mutations D. Chromosomal breaks and aneuploidy

Answer 80

D. Chromosomal breaks and aneuploidy — Micronuclei reflect chromosomal damage or loss. In vitro micronucleus assay Purpose: detect structural and numerical chromosomal damage in cells. Mechanism: Micronuclei = small, extra-nuclear bodies formed from lagging chromosome fragments (clastogenicity) or whole chromosomes lost during mitosis (aneugenicity). Therefore, the assay detects: Chromosomal breaks (clastogens), Aneuploidy (aneugens) آزمون میکرونوکلئوس در شرایط in vitro این تست برای بررسی آسیب کروموزومی استفاده می‌شود. میکرونوکلئوس = هسته‌های کوچک جداگانه‌ای که در تقسیم سلولی ایجاد می‌شوند. علت تشکیل میکرونوکلئوس: شکستگی‌های کروموزومی (Clastogenicity) → قطعات کروموزوم جدا می‌شوند. از دست رفتن کل کروموزوم در تقسیم (Aneugenicity) → باعث آنئوپلوئیدی می‌شود.

Question 81

Q82. Which statement relative to cardiac biomarkers is correct? A. Troponin T (cTnT) and I (cTnI) are expressed in various muscles, including cardiomyocytes. B. C-reactive protein (CRP) is a selective biomarker of cardiac inflammation. C. Creatine kinase-BB is predominant in myocardium. D. B-type natriuretic peptide (BNP) is secreted by ventricular myocardium in response to overload.

Answer 81

D. BNP secreted by ventricles in response to pressure/volume overload — marker of heart failure. Troponins = cardiac-specific (must recognize this). BNP = ventricular overload marker. CK isoenzymes → know which one is cardiac (MB), which one isn’t (BB). CRP is NOT cardiac specific (common exam trick)

Question 82

Q83. Which statement relative to the electrocardiogram (ECG) is correct? A. The QRS interval represents conduction pathways through the atria. B. The PR interval measures onset of ventricular activation to end of repolarization. C. The QT interval reflects the action potential of the ventricles. D. Heart failure is associated with upregulation of K channels and short QT syndrome.

Answer 82

C. QT interval reflects ventricular action potential — includes depolarization and repolarization. 📌 ECG Basics P wave → atrial depolarization. PR interval → from onset of atrial depolarization to onset of ventricular depolarization (time through AV node & conduction system). QRS complex → ventricular depolarization (fast). QT interval → ventricular depolarization + repolarization (i.e., ventricular action potential duration). در نارسایی قلبی (Heart Failure) جریان‌های پتاسیمی (K⁺) که مسئول رپولاریزاسیون هستند، کاهش می‌یابند (Downregulation). در نتیجه: مدت پتانسیل عمل طولانی‌تر → فاصله QT طولانی می‌شود (Long QT).

Question 83

Q84. Regarding responsible use of laboratory animals in biomedical research, which statement is TRUE? A. The US FDA administers the Animal Welfare Act (AWA). B. The 3Rs require animal testing. C. The AWA requires each facility to establish an Institutional Animal Care and Use Committee (IACUC). D. AAALAC accreditation is mandatory.

Answer 83

C. IACUC required — The Animal Welfare Act mandates IACUC at research facilities. ----------------------------- **Animal Welfare Act (AWA) **→ **US law regulating the care and use of certain animals in research.** Administered/enforced by the **USDA**, not the FDA. 3Rs (Replacement, Reduction, Refinement) → guiding principles to minimize animal use, not require it. **IACUC** (Institutional Animal Care and Use Committee) → **mandated by the AWA.** Every covered facility must have one. AAALAC (Association for Assessment and Accreditation of Laboratory Animal Care International) → accreditation is voluntary, not mandatory.

Question 84

Q85. Which of the following is CORRECT concerning good laboratory practices (GLPs)? A. Not required for ecotoxicity hazard studies B. Statistical analyses need not be described C. Requires training and expertise of study personnel D. Does not set standards for documentation/reporting

Answer 84

C. GLP requires trained personnel — Ensures qualified staff and data integrity. ## Footnote Good Laboratory Practice (GLP) principles Purpose: Ensure quality, integrity, reproducibility, and traceability of nonclinical safety studies. Covers: Personnel training, SOPs, documentation, reporting, data archiving, facilities, and equipment.

Question 85

Q86. What are the three stages of carcinogenesis? A. Initiation, promotion, progression B. Mutation, growth, division C. Reduce, reuse, recycle D. Clastogenicity, mutagenicity, malignancy

Answer 85

A. Initiation, promotion, progression — Classical model of carcinogenesis.

Question 86

Q87. What is an appropriate point of departure for deriving a first-in-human start dose for an anticancer small molecule drug? A. NOAEL in sensitive species B. LOAEL in relevant species C. Maximum tolerated dose (MTD) D. Severely toxic dose in 10% of animals (STD10) in rodent or highest non-severely toxic dose (HNSTD) in nonrodent

Answer 86

D. STD10 or HNSTD — Oncology guidelines use these as starting points. For **non-oncology drugs** → starting dose often based on **NOAEL in the most sensitive species**, with safety factors applied. For **oncology drugs** (small molecules) → patients already have life-threatening disease, so higher risk is tolerated. ICH S9 guideline: the starting dose can be derived from more severe toxicology endpoints. Specifically: **STD10 (Severely Toxic Dose in 10% of rodents) or **HNSTD (Highest Non-Severely Toxic Dose in nonrodents).******

Question 87

Q88. When developing a new antibiotic for human use, what is the appropriate test for mutagenicity? A. Ames assay B. Ames + mammalian cell mutagenicity C. Ames + in vitro micronucleus D. Ames + in vivo micronucleus

Answer 87

B. Standard mutagenicity battery = Ames + one in vitro mammalian mutagenicity test. ## Footnote In cases where compounds are highly toxic to bacteria (e.g., some antibiotics), the bacterial reverse mutation (Ames) test should still be carried out, just as cytotoxic compounds are tested in mammalian cells, because mutagenicity can occur at lower, less toxic concentrations. In such cases any one of the in vitro mammalian cell assays should also be done. In vitro and in vivo micronucleus tests are for detection of clastogenicity (chromosomebreaking) and aneugenic (chromosome mis-segregating) events, not mutagenicity. In vitro mammalian cell mutagenicity tests include, 1) mouse lymphoma assay (MLA) in the l5178Y TK- /+ mouse lymphoma cells, which can detect gene mutations and chromosomal events and 2) the HPRT (hypoxanthine-guanine phosphoribosyltransferase), which detects mutations at the HPRT gene in CHO cells.

Question 88

Q89. Why does cadmium exhibit relatively low acute toxicity despite its classification as a toxic metal? A. Sequestered by metallothionein B. Sequestered by ferritin/hemosiderin C. Conjugated with glutathione D. Sequestered in bone

Answer 88

A. Chronic toxicity is well known: kidney damage, bone effects (Itai-Itai disease), carcinogenicity. Acute toxicity is relatively low because cadmium is quickly bound and sequestered in the body. The key player: Metallothionein, a cysteine-rich protein that tightly binds metals (like Cd, Zn, Cu). This binding reduces the amount of free Cd²⁺ → lowers acute toxicity. But over time, Cd–metallothionein complexes accumulate in organs (especially kidney) → chronic damage. ## Footnote Cd → metallothionein binding → low acute, high chronic kidney/bone toxicity. Pb → bone storage → neuro + hematologic + renal issues. Hg → neuro + kidney (depends on form). As → skin, nails, cancer, neuropathy.

Question 89

Q90. High doses of radium 224 (mean bone surface dose of 30 Gy) resulted in which type of major cancers? A. Mesothelioma B. Osteosarcoma C. Hemangioma D. Acute myelogenous leukemia

Answer 89

B. Radium is a bone-seeking radionuclide (like strontium, plutonium). It deposits on bone surfaces, where it irradiates osteogenic cells. Historical cases: patients treated with Ra-224 for ankylosing spondylitis and other conditions. Major cancer outcome = osteosarcoma (bone sarcoma).

Question 90

Q91. A toxicology study exposes rodents to carbon tetrachloride (CCl4) via oral gavage. They show lethargy, elevated ALT/AST, and centrilobular hepatic necrosis. What is the likely mechanism? A. Inhibition of glutathione peroxidase B. Covalent binding of parent compound to DNA C. Bioactivation by CYP450 to trichloromethyl radical causing lipid peroxidation D. Induction of peroxisomal beta-oxidation

Answer 90

C. What happens with CCl₄ (Carbon tetrachloride)? Organ target: Liver (especially centrilobular zone where CYP450 activity is highest). Observed effects: ↑ ALT/AST (hepatocyte damage), centrilobular necrosis, lethargy. Mechanism: CCl₄ itself is not directly toxic. In hepatocytes, CYP2E1 bioactivates CCl₄ → forms trichloromethyl radical (*CCl₃). This radical reacts with O₂ → trichloromethyl peroxyl radical (*OOCCl₃). These radicals attack lipids → lipid peroxidation of membranes → cell death.

Question 91

Q92. Which cytochrome P450 enzyme is the most abundant in adult human liver? A. CYP2D6 B. CYP2E1 C. CYP3A4 D. CYP1A2

Answer 91

C. **CYP3A4** 🔹 Most abundant in adult human liver (~30–40% of total hepatic CYPs). Handles metabolism of ~50% of marketed drugs.

Question 92

Q93. What is the local lymph node assay (LLNA) used for? A. Immunogenicity B. Skin sensitization C. Genotoxicity D. Carcinogenicity

Answer 92

B. Local Lymph Node Assay (LLNA) Purpose: **An in vivo method in mice**. What it measures: **Proliferation of lymphocytes** in the auricular (ear-draining) lymph nodes after topical application of a test substance. Use: Detects whether a chemical can act as a **skin sensitizer** (i.e., induce allergic contact dermatitis). Why important: OECD Test Guideline 429 — standard alternative to guinea pig sensitization tests.

Question 93

Q94. Sponsor plans a multiple ascending dose (MAD) trial with 3-week dosing. According to ICH M3(R2), what minimum repeat-dose toxicity study duration is required? A. 2 weeks in both species B. 3 weeks in both species C. 3 months in both species D. 6 months rodent, 9 months nonrodent

Answer 93

B. 3 weeks — Nonclinical studies must match intended human dosing duration. For clinical trials, the duration of nonclinical repeat-dose toxicity studies must be at l**east equal to, or longer than, **the duration of the human trial. Applies to MAD (multiple ascending dose) studies too.

Question 94

Q95. Toluene is a widely used solvent and inhalant. What is the primary target organ for toluene-induced toxicity? A. CNS B. Liver C. Bone marrow D. Kidney

Answer 94

A. CNS — Toluene mainly causes CNS depression and neurotoxicity. ## Footnote Toluene Toxicity Widely used: industrial solvent, component of paints, glues, fuels; also an abused inhalant. Absorption: mainly by inhalation. Primary target: Central nervous system (CNS): Acute: euphoria, headache, dizziness, ataxia, CNS depression. Chronic: neurobehavioral changes, cognitive impairment, white matter damage.

Question 95

Q96. What is an advantage of the benchmark dose (BMD) approach vs. NOAEL in risk assessment? A. Relies on a single dose B. Does not require modeling C. Utilizes full dose-response data D. Excludes variability

Answer 95

C.BMD (Benchmark Dose) A model-based approach. Fits a dose–response curve to the data. Identifies the dose that produces a predefined benchmark response (e.g., 10% increase in effect = BMD10). Advantages over NOAEL: Uses all dose–response data, not just one dose. Provides confidence limits (BMDL) for uncertainty. Less dependent on arbitrary dose spacing.

Question 96

Q97. Which effect is most associated with chronic methylene chloride inhalation? A. Hepatocellular carcinoma B. CNS depression via oxidative stress C. Carboxyhemoglobinemia from CO formation D. Liver fibrosis

Answer 96

C. Carboxyhemoglobinemia — From metabolic conversion to CO, impairing oxygen delivery. ## Footnote Methylene chloride is metabolized in humans through two main pathways: 1) oxidative metabolism via CYP2E1, producing formyl chloride and formaldehyde, which may contribute to genotoxicity. 2) Reductive metabolism via glutathione-S-transferase, leading to the formation of carbon monoxide (CO). The production of CO results in carboxyhemoglobin (COHb) formation, which reduces oxygen-carrying capacity and contributes to cardiovascular and CNS effects, particularly in individuals with pre-existing heart disease. This mechanism has been a concern for regulatory evaluations, such as those conducted by the US EPA and OSHA.

Question 97

Q98. What best distinguishes a cohort study from a case-control study? A. Cohort studies are retrospective; case-control prospective B. Cohort starts with disease; case-control with exposure C. Cohort measures incidence; case-control estimates odds ratios D. Case-control studies are more expensive

Answer 97

****C. C📌 Cohort Study Starts with exposure status (exposed vs. unexposed). Follows groups over time to see who develops the disease. Can be prospective or retrospective. Measures incidence and allows calculation of relative risk (RR). 📌 Case-Control Study **Starts with disease status** (cases vs. controls). Looks backward to assess exposures. Always retrospective. Can’t measure incidence directly → uses odds ratio (OR) as measure of association.

Question 98

Q99. According to 21 CFR Part 58, which constitutes a deviation from GLP that must be documented? A. Minor calculation errors not affecting conclusions B. Use of alternate instrument without protocol/raw data documentation C. Failure to maintain correspondence beyond 6 months D. Replacement of injured animal with documentation

Answer 98

B. Undocumented instrument use — Any deviation must be recorded in the report.

Question 99

Q100. Which organophosphate caused “Ginger Jake” syndrome during Prohibition? A. Chlorpyrifos B. Diazinon C. TOCP (tri-o-cresyl phosphate) D. Parathion

Answer 99

C. TOCP — Caused delayed neuropathy in the Ginger Jake epidemic. ## Footnote During U.S. Prohibition (1920s–30s), people drank Jamaican Ginger Extract (“Jake”), a medicinal alcohol substitute. To pass government standards, some manufacturers adulterated it with TOCP (tri-ortho-cresyl phosphate). TOCP is an organophosphate that’s not a strong cholinesterase inhibitor (unlike parathion or chlorpyrifos). Instead, it causes delayed neuropathy → paralysis and foot drop. This outbreak became known as “Jake paralysis” or “Ginger Jake” syndrome.

Question 100

Q101. What are biomarkers for neurodegeneration? A. KIM-1, CLU, OPN, CysC, NAG, NGAL B. Troponin I/T, CK-MB, BNP, Galectin-3 C. ALT, AST, GGT, bilirubin, ALP D. NfL, GFAP, UCH-L1, pTau217, β-Amyloid 1-42

Answer 100

D. NfL, GFAP, UCH-L1, pTau217, β-Amyloid — Common biomarkers of neurodegeneration. ## Footnote کلیه: KIM-1, CLU, OPN, CysC, NAG, NGAL قلب: Troponin I/T (gold standard) + CK-MB, FABP3, BNP, Galectin-3 کبد: ALT (اختصاصی‌ترین)، AST، ALP، GGT، بیلی‌روبین مغز: NfL, GFAP, UCH-L1 (قدیمی) + pTau217, β-Amyloid 1-42 (جدید، مخصوص آلزایمر)

Question 101

Q102. The majority of blood flow enters the liver via which vessel? A. Hepatic artery B. Portal vein C. Vena cava D. Terminal hepatic vein

Answer 101

B. About 60–70% of blood entering the liver comes from the **portal vein.** This blood is nutrient-rich but relatively low in oxygen, since it drains the intestines, stomach, pancreas, and spleen. The **hepatic artery** contributes the remaining 30–40% of blood flow,** providing oxygen-rich blood.** Together, they form part of the portal triad **(portal vein, hepatic artery, bile duct**). The mixed blood flows through** sinusoids** →** central (terminal hepatic) vein** → **hepatic veins **→ **inferior vena cava.** So, while both vessels are important, the majority of blood flow is delivered by the portal vein.

Question 102

Q103. Two concepts exist for structural organization of the liver (lobular and acinus). Which of the following correspond to one of the three regions of the liver acinus? A. Zone 1 and centrilobular B. Zone 2 and periportal C. Zone 3 and midzonal D. Zone 1 and periportal

Answer 102

D. Zone 1 = periportal — Acinus zones are 1 (periportal), 2 (mid), 3 (centrilobular). ## Footnote The liver acinus model divides the liver parenchyma based on blood flow (f**rom portal triad → central vein**) and oxygen/nutrient gradients. It has three zones: Zone 1 (periportal): Closest to the portal triad (receives the most oxygen and nutrients). **Zone 2 (midzonal):** Intermediate between portal triad and central vein. **Zone 3 **(centrilobular): Closest to the central vein+ high abundance of cytochrome P450 enzymes, (**lowest oxygen, more vulnerable to hypoxia and toxic injury**).

Question 103

Q104. Bile is a specialized fluid formed by the liver with which of the following functions? A. Protects intestine from oxidative insult B. Prevents lipid solubilization C. Stores xenobiotics until metabolized D. Contains transporters for nutrient uptake

Answer 103

a .Bile is a yellow fluid containing bile acids, GSH, phospholipids, cholesterol, bilirubin and other organic anions, proteins, metals, ions, and xenobiotics. Formation of bile fluid is a specialized function of the hepatocytes that secrete it into the bile duct. Adequate bile formation is essential for **uptake of lipid nutrients from the small intestine**, protects the sm**all intestine from oxidative insu**lt, and for **excretion of endogenous and xenobiotic compounds**.****

Question 104

Q105. Which best characterizes cholestasis? A. Increase in bile volume formed B. Increase in serum bile salts and bilirubin C. Cirrhosis D. Transporter induction

Answer 104

B. Increased bile salts/bilirubin — Hallmark of cholestasis.

Question 105

Q106. Metabolic dysfunction-associated steatohepatitis (MASH) is defined as: A. Fatty liver but no damage B. Also referred to as MAFLD C. Cannot progress to cirrhosis D. Fatty liver + inflammation + cell damage

Answer 105

D. Metabolic dysfunction–associated steatohepatitis (MASH) is the newer term for what was previously called NASH (nonalcoholic steatohepatitis). It is characterized by: Hepatic steatosis (fatty liver) Inflammation Hepatocyte ballooning / cell injury

Question 106

Q107. ACME Biotech is developing AB505 to reduce excess body weight and maintain weight reduction in patients with obesity, which is considered a chronic use indication. AB505 is a small molecule directed toward a neuronal receptor known to modulate appetite that differs from available therapies and would be a first in class treatment for obesity. ACME Biotech hired a toxicology consultant to determine whether a carcinogenicity assessment will be needed as part of the nonclinical development program for AB505. Which guideline would the toxicology consultant use to determine whether an assessment of carcinogenic risk is warranted to support a marketing application for AB505? A. ICH S1A B. ICH S6R1 C. ICH S1BR1 D. ICH M3R2

Answer 106

A. ICH S1BR1 — Guidance on need for carcinogenicity studies. ## Footnote S1A → تصمیم می‌گیریم آیا بررسی سرطان‌زایی لازم است. S1B(R1) → استراتژی و جایگزین‌ها را تعیین می‌کنیم. S1C → طراحی و اجرای دقیق مطالعه.

Question 107

Q108. The toxicology consultant for ACME Biotech determined that a 2-year rat bioassay is warranted for an adequate carcinogenicity assessment of AB505, a small molecule pharmaceutical. Selection of the high dose for the 2-year rat study would be based on the completed 6-month toxicology study in the same strain planned for the bioassay. Daily doses of 2, 50, and 200 mg/kg were evaluated with the following key results (note, no difference in response noted between male/female rats). * 2 mg/kg: No observed adverse effect level (NOAEL) * 50 mg/kg: Reduction in body weight gain (5%), minimal/mild hepatocellular hypertrophy, increased liver weight (3%). * 200mg/kg: Reduction in body weight gain (14%), moderate/severe hepatocellular hypertrophy with subcapsular necrosis, moderate/severe biliary degeneration, 3 early mortalities. Exposure was approximately 25-fold higher than human exposure, based on area under curve (AUC). Based on these data, the toxicology consultant recommended 2 mg/kg as the most appropriate high dose for testing in the 2-year rat study. Was the toxicology consultant’s recommendation correct? A. Yes, because 2 mg/kg is the 3-month NOAEL and would be tolerated over a 2-year dosing duration. B. No, because 50mg/kg was tolerated for a 3-month duration without severe toxicity; therefore, 50 mg/kg is a maximum tolerated dose and a more appropriate high dose for the 2-year bioassay. C. No, because 200mg/kg would provide at least a 25-fold multiple of human exposure and provide the most robust test for carcinogenic risk. Any mortalities encountered in the 2- year study would be minimal; therefore, 200mg/kg is a more appropriate high dose. D. No, the most appropriate high dose would be consistent with a limit dose of 1500mg/kg.

Answer 107

B. 50 mg/kg — Appropriate maximum tolerated dose for long-term study. ## Footnote Why: The high dose in a 2-year rat carcinogenicity study should be near the MTD—producing minimal, non–life-limiting toxicity without compromising survival.

Question 108

Q109. Which is not a key factor in weight-of-evidence (WoE) per S1B(R1)? A. Genetic toxicology per ICH S2(R1) B. Results from Phase 3 clinical trials C. Drug target biology/mechanism D. Histopathology from 6-month rat study E. Evidence of immune modulation per ICH S8

Answer 108

B. Phase 3 clinical results — WoE is based on preclinical and mechanistic data, not Phase 3 outcomes. ## Footnote Drug target biology/mechanism (primary pharmacology, class effects), ICH Database Secondary pharmacology/off-target selectivity, ICH Database Histopathology from repeated-dose studies (esp. 6-month rat), ICH Database Genetic toxicology per ICH S2(R1), and Evidence of immune modulation per ICH S8.

Question 109

Q110. A new mutagenic impurity was identified in the AB505 drug product. Carcinogenicity data from rodent bioassays with the mutagenic impurity are not available; however, the toxicology consultant has determined that N-nitrosodiphenylamine is an appropriate surrogate for a read-across assessment of carcinogenic risk. Rodent carcinogenicity data is available for N-nitrosodiphenylamine and the most appropriate TD50 is reported as 178 mg/kg/day, based on the occurrence of urinary bladder tumors. Using the TD50 from the surrogate, what would be an acceptable intake (AI) for the new mutagenic impurity that corresponds to a theoretical 1 in 10^5 excess lifetime risk of cancer? Assume a human body weight of 50kg. A. 1.5 ug/day B. 1500 ug/day C. 180 ug/day D. 350 ug/day

Answer 109

C. AI (mg/day)≈ 2𝑅×TD50 (mg/kg/day)×BW (kg) ## Footnote **TD₅₀ (Tumorigenic Dose 50%) is a potency metric for carcinogens.** The chronic daily dose (usually in mg/kg/day) that would **halve the fraction of tumor-free animals** over a standard lifespan in a rodent bioassay. In other words: the dose that would make 50% of animals that would have remained tumor-free develop tumors (after adjusting for survival). **Used in ICH M7(R2) calculations to set an Acceptable Intake (AI) for mutagenic impurities via a simple linear low-dose model**. At low doses, risk is approximated by a slope of ≈ 0.5 / TD₅₀. For a target lifetime cancer risk R, dose (mg/kg/day) ≈ 2R × TD₅₀. Daily intake for body weight BW: **AI (mg/day)≈ 2𝑅×TD50 (mg/kg/day)×BW (kg)**