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  #1  
Old 09-17-2010
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Question Which of these organs?

An animal is made diabetic by injection of a drug that destroys pancreatic Beta cells. Removal of which of the following organs would most likely produce a decrease in blood glucose concentration in this animal?

A. Anterior pituitary
B. Colon
C. Gonads
D. Kidney
E. Pancreas

I know this question might seem easy to many of the forum members but it would be nice if anyone who answers mentions the logic behind the answer along with other options as well.
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  #2  
Old 09-17-2010
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Let's first mention the hormones that increase glucose in the body so when we remove their organs this would lead to hypoglycemia(since no insulin bcz beta cells were destroyed):
Glucagon, Growth Hormone & Cortisol
hmm... I am stucked between A) Anterior pituitary & E) Pancreas
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Old 09-17-2010
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Same here. either Glucagon or GH, but isnt glucagon much hyperglycemic than GH?
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  #4  
Old 09-17-2010
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i would go with
A. Anterior pituitary

We are looking for an organ producing hyperglycemic hormone or causing hyperglycemia in any other way..

Explanation :-

B. Colon No effect on glucose homeostasis

C. Gonads No effect on glucose homeostasis

D. Kidney Involved in reabsorption of filtered glucose from the plasma & excretion of excess glucose if Transport maximum reached. Also involved in the metabolism & excretion of insulin. But removing kidneys will not lower blood glucose.

E. Pancreas
As only beta cells destroyed, Alpha cells are intact which produce Glucagon. It causes hyperglycemia but it is released only when blood glucose level is very low.

A. Anterior pituitary secretes Growth hormone, ACTH & TSH. All are hyperglycemic hormones.

I hope i am right though ..... these simple question are also the most tricky ones...
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Old 09-17-2010
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well its A. Anterior pituitary.....reason behind this is "cortisol" that is regulated by ACTH....

well glocagon do stimulate gluconeogenesis by increasing intracellular cAMP and activating CRE (cAMP response element) n thus upregulating PEPCK the rate limiting enzyme in gluconeogenesis...but poor glucagon cant do it by itself....it requires permissive action of cortisol....that act on GRE (glucocorticoid response element) and upregulate PEPCK production by its own n also that is induced by glucagon....

so if we remove ant. pituitary....no ACTH..no crtisol....no permissive effect on glucagon or any other gluconeogenic hormone....so without cortisol they r all useless....

but if we remove source of any other gluconeogenic hormone like glucagon....cortisol is still present to do its job.....

hope this helps...
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  #6  
Old 09-18-2010
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Thanks @ Khushboo for pointing that out.. Totally forgot to mention the permissive action of cortisol.
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Old 09-19-2010
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The correct answer is A. Two of the secretions of the anterior pituitary affect the sensitivity of peripheral tissues to the action of insulin. Growth hormone has a direct effect on liver and muscle to decrease insulin sensitivity.
This may be partly through a growth hormone-induced decline in insulin receptors or to unknown post-receptor defects. In excess, growth hormone is "diabetogenic," and about 25% of patients with acromegaly have diabetes. ACTH indirectly has anti-insulin effects by virtue of the cortisol secretion it evokes. Like growth hormone, cortisol also decreases insulin sensitivity in peripheral tissues. A third anterior pituitary hormone, TSH, also tends to increase blood glucose levels. In this case, the effect is probably mediated mostly through increased glucose absorption by the gut. Patients with hyperthyroidism can sometimes exhibit a postprandial glucosuria because of excessive intestinal glucose absorption. In diabetic animals, the removal of the anterior pituitary may lower blood glucose by increasing tissue sensitivity to whatever insulin remains.

Removal of the colon (choice B) should have little effect on blood glucose since dietary glucose is absorbed in the small intestine.

Sex steroids secreted by the gonads (choice C) have little effect on blood glucose concentration.

The kidney (choice D) plays an important role in reabsorbing filtered glucose. In diabetes, the tubular reabsorption maximum is exceeded and glucose spills over into the urine. The loss of glucose in the urine helps to reduce the severity of the plasma hyperglycemia. Removal of the kidneys would, if anything, make the hyperglycemia worse.

Pancreatectomy (choice E) would make the hyperglycemia worse by removing the source of any remaining insulin.

@khushboo and @step1an were correct.
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  #8  
Old 09-19-2010
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Another great question that proves that explanations are more important than the actual question... thanks for posting.
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  #9  
Old 09-19-2010
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Quote:
Originally Posted by donofitaly View Post
Pancreatectomy (choice E) would make the hyperglycemia worse by removing the source of any remaining insulin.
I think u should review this statement regarding the question asked, as the beta cells have already been destroyed so its unlikely that the animal will have any ability to produce insulin. I think the action of glucagon should be considered.
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Quote:
Originally Posted by step1an View Post
I think u should review this statement regarding the question asked, as the beta cells have already been destroyed so its unlikely that the animal will have any ability to produce insulin. I think the action of glucagon should be considered.
Ok, "pancreatectomy wouldn't help the situation any better" would be better paraphrased??
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Old 09-20-2010
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very nice discussion...
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Old 11-07-2016
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this question also helped me understand why for an experiment to show the permissive effect of cortisol they hypophysectomized the animals before administering norepinephrine alone and then norepinephrine with cortisol pretreatment. the graph showed higher vascular responsiveness with pretreatment.This is permissiveness not synergism because cortisol has no vasoconstrictive effect all on its own. That's why a hypotensive crisis occurs when there is adrenal insufficiency! there is no cortisol to potentiate the effects of the catecholamines (which are less too ,I guess) and of the angiotensin2.
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Default Answer

I guess E. The alha cells secreting glucagon are also in the pancreas. Abolishing the unopposed action of gucagon (no glycogenolysis and gluconeogenesis)
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  #14  
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Both cortisol and T3/T4 increase blood glucose concentration. Both would decrease with removal of anterior pituitary.
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