The Gila monster (Heloderma suspectum)

[Mr Rayon]

The Gila monster is a venomous lizard, native to several south-western US states. This lizard eats only four times a year. It has the ability to activate its pancreas at these times, whereas at other times the pancreas is inactive. The saliva of this lizard has a hormone, exendine-4. This a 39-amino acid peptide that is secreted when the lizard eats. The effect of exenrine-4 is to stimulate insulin production, inhibit glucagon secretion and slow down the rate of the stomach emptying.

 

a) Name the cells in the pancreas that produce insulin.

 

b) Why is it necessary for the lizard to produce insulin at a meal?

 

c) Explain the significance of the action of exendin-4 in inhibiting glucagon production.

 

Synthetic exendin-4 is currently being trialled as a drug teatment for people with type 2 diabetes. Excess glucagon production is a major factor in their heperglycaemia. Synthetic exendin-4 has all the properties of the naturally occurring exendin-4,

d) How does slowing down the emptying of the stomach help people suffering from type 2 diabetes?

 

The drug, exendin-4, stimulates insulin secretion in the presence of elevated glucose concentrations, but not when blood glucose levels are low.

 

e) Explain how this property of exendin-4 gives an advantage over insulin injections for diabetics.

 

f) Exendin-4 has the disadvantage that it needs to be injected. Give one possible reason why it needs to be injected rather than taken orally.

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Are these reponses right? Well, any help, clarification or/and confirmation on the above will be appreciated.

 

6a) Beta cells of the pancreas

b) The insulin production would decrease the blood-glucose levels after the lizard has finish eating its meal.

c) If glucagon production production were to take place (as is the case in the absence of exendin-4) the blood-glucose levels would skyrocket after the meal. This would lose the lizard lots of energy, and make it harder for it to survive if it only eats four times a year.

d) Slowing down the emptying of the stomach helps people suffering from type 2 diabetes by making them feel fuller, longer.

e) Not sure

f) Not sure

[John Cuthber]

Shouldn't this be in "homework help"?

[Mr Rayon]

Shouldn't this be in "homework help"?

 

Oh yes, I guess so. When I go on here my mind always tell me to go the biology section instead. Woops...do I have the power to move a thread? I wonder...

[gsawiris]

You can actually keep a gila monster legally if you purchase captive born offspring in some states. Gila monsters make interesting and hardy captives.

[Mokele]

D isn't right - think about what happens to a diabetic when blood sugar rises too much, and why a drug that can inhibit glucagon would help.

 

E - think about how insulin & glucagon work, and the difficulties of dealing with even natural fluctuations in blood sugar if you can't naturally make insulin. You want to maintain blood sugar within a narrow range.

 

F - What's the molecular structure of the drug (see the initial problem statement)? What happens to that sort of structure in the stomach?

 

You can actually keep a gila monster legally if you purchase captive born offspring in some states. Gila monsters make interesting and hardy captives.

 

I would note, however, that while they can become quite tame, A) expect to pay more than $1000 for a hatchling and more importantly, B) They are venomous. Technically they haven't killed anyone yet, but two prominent herpetologists have died from bites of animals which they didn't treat medically because "it's never killed anyone before". Plus, with *any* envenomation, there is always a risk of an allergic reaction, which can lead to anaphylactic shock and kill you far faster than the venom.