Sensitive eyes vitamin

In the retinal cells of the eye, vitamin A (all-trans-retinol) is converted into the 11-ds-isomer, which is then oxidised to 11-cts-retinaldehde. In the dark the latter then combines with the protein opsin to form rhodopsin (visual purple), which is the photoreceptor for vision at low light intensities. When light falls on the retina, the czs-retinaldehyde molecule is converted back into the aW-trans form and is released from the opsin. This conversion results in the transmission of an impulse up the optic nerve. The all-frans-retinaldehyde is converted to all-trans-retinol, which re-enters the cycle, thus continually renewing the light sensitivity of the retina (Rg. 5.2). 

In a 6-week study to evaluate the effectiveness of Vitamin D supplementation (vitamin D2 or D3 2000lU, or vitamin D2 50,000 lU weekly) compared with calcium for treatment of vitamin D sufficiency in children with inflammatory bowel disease was examined [49 ]. The most commonly reported events were nausea (n=6) increased thirst and loss of appetite (n=5 each) pruritus (n=4) drowsiness and increased urinary frequency (n=3 each) abdomirwl pain, hone pain, headache and constipation (n=2 each) rash, sensitive eyes, vomiting, irregular heartbeat, dry mouth and muscle pain (n=1 each). There were no significant differences in the frequency of adverse events between groups, and no serious adverse events were observed. 

Another set of significant photochemical reactions in human biochemistry is contained in the chemistry of vision. These reactions involve vitamin A (retinol), which is a C20 compound belonging to a class of compounds known as diterpenes. These compounds are molecules formally constructed by the biopolymerization of four isoprene, CH2=C(CH3)—CH=CH2, molecules. Retinol (an all-trans pentaene) is first oxidized via liver enzymes (biological catalysts) to vitamin A aldehyde (frans-retinal). The frans-retinal, which is present in the light-sensitive cells (the retina) of the eye, undergoes further enzymatic transformation (retinal isomerase) to give cfs-retinal (a second form of vitamin A aldehyde) in which one of the double bonds of the aU-trans compound is isomerized. 

The best-understood role of vitamin A is its participation in the visual cycle, where it is used to make the photoactive component of rhodopsin, the light-sensitive pigment in our eyes. 

In mutagenesis the main condition of success is the development of a sensitive and rapid method of mutant selection. Vitamin B12 production by propionic acid bacteria correlates with acid production. But the method of selection based on picking colonies with the maximal diameter of dissolution zones of calcium carbonate (added to solid medium) did not give positive results, since the size of colonies is not identical while acid production is dependent on the quantity of biomass. Selection based on the intensity of pink color that correlates with vitamin B12 production has a disadvantage in that selection of small mutations is made step by step, when differences in color can hardly be noticed by eye. Another method used was based on direct determination of vitamin B12 in single colonies. This method is labor-intensive and severely limits the testing of large numbers of colonies. 

In the body, vitamin A Is converted to 11-c/s-retlnal, the light-sensitive compound responsible for vision In all vertebrates (Section 21.11B). it isaiso needed for healthy mucous membranes. A deficiency of vitamin A causes night biindness, as well as dry eyes and skin. 

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