Cardiovascular Techniques I

Question 1

Describe an equation relating resistance to vessel radius, viscosity and length.

Answer 1

• η = viscosity
• L = length
• R = radius

Question 2

Describe how large organ baths are prepared for large vessels.

Answer 2

• Large vessels > 1.5mm in diameter
• Segments mounted as ring preparations on two fixed steel hooks
• Kept in a chamber with physiological salt solution at 37°C with oxygen
• Viable > 6 hours

Question 3

Describe how wire myography is used.

Answer 3

• For small vessels: diameter 100-400μm
• Segments are mounted as ring preparations on two fixed steel hooks
• Kept in a chamber with physiological salt solution at 37°C with oxygen
• Viable > 12 hours

Question 4

How would you investigate the following question: “Is methoxamine-induced contraction mediated by α₁ adrenoceptors?”

Answer 4

• Mount vessel on a wire myograph/organ bath
• Measure contraction in the presence of methoxamine with and without an α₁ antagonist

Question 5

How would you investigate the following question: “Is methoxamine as effecive as the contractile agent endothelin?”

Answer 5

• Plot concentration-response curves for methoxamine and endothelin
• Compare EC₅₀ and R_max values

Question 6

How would you test whether contractions to α₁ adrenoceptoragonist are modified in hypertension?

Answer 6

• Measure α₁-induced contractions in normotensive and hypertensive vessels
• Plot concentration response curves, compare EC₅₀ and R_max

Question 7

Describe 3 disadvantages of isometric tension recording.

Answer 7

1. Dissection and mounting of vessels requires skills and suitable apparatus
2. Isolation of vessels might remove influences from surrounding tissues
3. Difficult to study longer-term changes in vascular function using the same vessels

Question 8

What type of contractions and relaxations can isometric tension recording not measure?

Answer 8

• Myogenic contractions
• Flow-induced relaxations