QUESTIONS

1. We call Vitamin D "the sunshine vitamin".  Why is this? If you were a dog, would you still think of Vitamin D as "the sunshine vitamin?"
    
2. Dioxygenase is an important enzyme in Vitamin A metabolism.  What exactly does it do?
    
3. What vitamin deficiency involves widening of the epiphyseal plates?
    
4. How does one store Vitamin A?
    
5. What are rhodopsins & iodopsins?
    
6. How might a cat get "yellow fat disease?"
    
7. If you were a dog with "black tongue" what vitamine deficiency would you have?
    
8. What bone changes are seen in Vitamin A deficiency?
    
9. If you were a small animal, how might you get "Chastek paralysis."
    
10. What is the "other name" for vitamin B2? How about vitamin B6?
    
    
    
    
     

ANSWERS

1. We eat ergosterol from plants. It is transported to our skin where UV light changes it into vitamin D2 (ergocalciferol).  We also eat 7-dehydrocholesterol in animal tissue. It is changed by UV light into cholecalciferol (vitamin D3). Because of all this UV light activation, we think of vitamine D as the sunshine vitamin.  Dogs do not do all this uv light stuff.
   
   
   
   
    
2. Dioxygenase is a cytosolic enzyme of the enterocyte. It cleaves beta-carotene from the diet into 2 molecules of retinal. (The enterocyte isn't the only place to find dioxygenase. The liver & kidney have it, too, but the intestine has most of it.)  Controlling this enzyme is one way of protecting the body against Vitamin A toxicity since uptake can be contolled this way. Animals that eat retinal directly in animal tissue (carotenes come from plants) are not so protected.
   
   *Note cats don't have any dioxygenase and must get their vitamin A as retinal.
   
   
   
   
    
3. Epiphyseal plates are widened in Vitamin D deficiency.
   
   
   
   
    
4. Retinal is reduced to retinyl esters which get bound to VLDL's which they are stored in the liver in huge quantities. The kidney also stores some Vitamin A but this is not a significant storage except in the cat. When you are ready to use your vitamin A, the retinyl esters are hydrolyzed to RetinOL which is bound to a complex of "retinol binding protein" & proalbumin (a process which renders retinol water soluble.)  At the target tissue, retinol is plucked away & the transport proteins go floating away.
   
   
   
   
    
5. Rhodopsins are the light sensitive pigments of the retinal rods (which see color) & iodopsins are the light sensitive pigments of retinal cones (for black & white vision).  Light cleaves these pigments into colorless opsins & retinal.  In vitamin A deficiency, rhodopsins deplete first thus the syndrome begins with night blindness.
   
   
   
   
    
6. A cat might get yellow fat disease by eating a diet so high in PUFAs that its vitamin E supply is overwhelmed & the fat actually oxidizes (goes rancid) internally.  A diet high in fish (which are high in PUFAs & low in Vitamin E) would be classic (like a cat eating tuna canned for human consumption & no other food.) The canine version is called "brown bowel syndrome."
   
   
   
   
    
7. You would have a niacin (B5) deficiency & your owner might very well have pellagra.  Oral necrosis is an inital sign of niacin deficiency in the dog.
   
   
   
   
    
8. Vitamin A is involved in osteoclast bone resorption. It is the growing young-uns that really have it rough with vitamin A deficiency because they are trying to remodel all that bone. Their vertebrae thicken which leads to a narrowing of the vertebral canal. Assorted cranial nerves get pinched off as they leave their skull foramina.  :(
   
   
   
   
    
9. Chastek paralysis is an expression of Thiamine (B1) deficiency.  You would probably have gotten it from eating a lot of fish. Fish contain Thiaminases in case you didn't know. If you were a cow or horse, you would have to get your thiamine deficiency either from expired food or from eating too much bracken fern.  The test you'd run to diagnose thiamine deficiency is ERYTHROCYTE TRANSKETOLASE SATURATION.
   
   
   
   
    
10. Vitamin B2 is riboflavin & B6 is pyridoxine.