You’ve been hired by a drug company to create a drug that will prevent high-alti

Question

You’ve been hired by a drug company to create a drug that will prevent high-altitude climbers from suffering from frostbite on their faces, fingers and toes. You have been given a choice of experimental animal: Antarctic icefish, Alaskan tree frogs or Arctic ground squirrels.

a) Which animal would you choose and why?

b) Describe how your new drug will prevent tissue from freezing.

c) Using lab rats as a subject, describe one experiment that you would perform during the development of your new drug. Knee Ankle

Explanation / Answer

a) Frostbite is a traumatic injury caused by the failure of normal protective mechanisms against the thermal environment, resulting in local tissue temperatures falling below freezing. Frostbite occurs when the temperature falls to 28 °F (2 °C) and tissue freezes, resulting in formation of intracellular ice crystals and microvascular occlusion.

Arctic ground squirrels will be selected to research for a drug that prevents frost bite. Because prolonged Vit C therapy in large dose preceded by rapid rewarming at water-bath close to body temperature (37 °C) is suitable as an immediate treatment for cold injuries in animals like squirrels or rats. After rewarming, vitamin C helps in scavenging free-radicals and reduces tissue injury.

b) The immediate response of exposure to severe cold is peripheral vasoconstriction, mainly of small arteries and arterioles leading to reduction in blood flow especially to the extremities. This makes these areas more vulnerable to cold injury, which is believed to occur partly due to anoxia resulting from circulatory insufficiency and partly due to direct freezing effect ofcold on the exposed parts. Insufficient circulation leads to stasis is in the capillaries and this blocks these small vessels which results in thrombosis. Thrombosis aggravates anoxia and leads to necrosis.

The beneficial effect of long term administration of Vit C therapy (prevention of frost bite) might be due to the improvement in the cold tolerance because of increased metabolism, and this might have kept the tissues warmer by increasing the extremity blood flow.
The effect may be through thyroid hormone .

c) In this experiment, frostbite was produced on 20 rats, in each limb separately with and without Vit C therapy. The result showed that administration of Vit C for a short period (7 days) prior to cold exposure was of no significant benefit. However, administration of high dose of Vit C for prolonged period (21 days) maintained higher rectal temperature and significantly reduced the incidence of frostbite

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