Test 212 (Miscellaneous)

1. Optic neuropathy occurs in deficiency of the following vitamin B:

a. vitamin B₁

b. vitamin B₂

c. vitamin B₃

d. vitamin B₆

e. vitamin B₁₂

Answer
a.T   b.T   c.F   d.F   e.F
B1 (thiamine) deficiency causes corneal epithelial changes, ophthalmoplegia, nystagmus, optic atrophy 
B2 (riboflavin) deficiency causes peripheral corneal 
vascularization, angular blepharoconjunctivitis
B3 (niacin) deficiency causes optic neuropathy
B6 (pyridoxine) deficiency causes optic neuritis, angular blepharoconjunctivitis, gyrate atrophy (rare)
B12 deficeincy causes optic neuropathy and atrophy, central scotomas, flame-shaped and dot-blot hemorrhages
 

2. The following are true about vitamin A:

a. it is fat soluble

b. it is usually ingested as retinoid acid

c. it is stored mainly in the retinal pigment epithelium

d. deficency causes dry eye due to decreased production
    of the aqueous layer.

e. subclinical deficiency can be detected by 
    electrophysiology tests.

Answer
a.T   b.F   c.F   d.F   e.T
Vitamin A is fat soluble and usually ingested as retinyl 
ester. It is stored mainly in the liver. Defiency of vitamin A causes dry eye by interfeing with mucin production. Impairment of retinal function can be confirmed by electroretinography and dark-adaptation studies even during subclinical vitamin A deficiency.

3. Regarding vitamin A:

a. it is stored mainly as retinyl ester 

b. it is found in the inner segment of the photoreceptors
    and the retinal pigment epithelium

c. during bleaching, all-trans-retinaldehyde is released 
    from the opsins and is transported to the pigment 
    epithelium in the form of all-trans-retinol

d. the pigment epithelium is the site of isomerization of 
    all-trans- to 11-cis-retinol

e. optic disc swelling can result from excessive intake

Answer
a.T   b.F   c.T   d.T   e.T
It is found in the outer segment of the photoreceptors.

4. True statement about vitamin B₁ include:

a. it is water soluble

b. its defiency is responsible for beri-beri

c. its defiency causes congestive cardiac failue

d. its defiency causes Wernicke's encephalopathy

e. its defiency causes nystagmus

Answer
a.T   b.T   c.T   d.T   e.T
Systemic disease resulting from vitamin B1 deficiency is beriberi. In the wet form of beriberi, the cardiovascular system is affected with biventricular congestive heart
failure and sodium and water retention; in the dry form, there is evidence of Wernicke's encephalopathy, 
peripheral neuropathy, and Korsakoff's encephalopathy.
The ocular manifestations of thiamine deficiency include corneal epithelial changes, ophthalmoplegia, nystagmus, and, most important, optic atrophy..

5. Mitomycin C:

a. is an antibiotic

b. inhibits DNA synthesis

c. inhibtis RNA and protein synthesis

d. requires NADPH for it to become active

e. is used in pterygium surgery to prevent its recurrence

Answer
a.T   b.T   c.T   d.T   e.T
Mitomycin C is a naturally occurring antibiotic 
antimetabolite isolated from the broth of Streptomyces caespitosus. Mitomycin C is an alkylating agent that is metabolized to active species that cross-link DNA and inhibit RNA and protein synthesis. Mitomycin C is metabolized to active agents that cross-link DNA and produce membrane-damaging free radicals by the enzyme NADPH (nicotinamide-adenine dinucleotide hydrogen phosphate). It is used in pterygium operation to prevent its recurrence and in trabeculectomy to reduce scarring.

 

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