Vitamins radiation, effect

The i j -configuration of the 6,7-double bond in pre-vitamin D is critical to its subsequent thermal rearrangement to the active vitamin. A photochemical isomerization of pre-vitamin D to yield the inactive trans-isoTnen occurs under conditions of synthesis, and is especially detrimental if there is a significant short wavelength component, eg, 254 nm, to the radiation continuum used to effect the synthesis. This side reaction reduces overall yield of the process and limits conversion yields to ca 60% (71). Photochemical reconversion of the inactive side product, tachysterol, to pre-vitamin D allows recovery of the product which would otherwise be lost, and improves economics of the overall process (70). 

A number of studies have shown that vitamins moderate the induction of chromosomal aberrations by radiation. Vitamins C and E given orally to mice either 2 h before, immediately after, or 2 h after 1 Gy (100 rad) of y-ray TBI significantly reduce the frequencies of micronuclei and chromosomal aberrations in BM cells. Vitamin E is the more effective (95). Administration of vitamins C and E within 5 min of irradiation is as effective as pretreatment. Protection by vitamin C has also been shown in humans. Whereas chronic treatment of rats using vitamin C (100 or 300 mg/(kg/d)) for six months prior to TBI protects against chromosomal aberrations, vitamin E is not radioprotective in this setting (96). 

There are numerous reports of the effects of antioxidant vitamins on transformation. Vitamin C suppresses x-ray-induced transformation when CSHlOTy cells are treated daily for one week following irradiation (97), suppresses transformation by y-rays or neutrons, and prevents the promotion of radiation-induced transformation by 12-0-tetradecanoylphorbol 13-acetate (TPA), but has no effect on cell survival (98). In these studies, the continuous presence of vitamin C for a critical period appears to be necessary for suppression of transformation. Vitamin C may act on the promotion stage of... 

Efficiency use of pectincontaining enterosorbents is shown in experiment with exposure of Cs and Sr on nonline white rats on base of Ukrainian Scientific Centre for Radiation Medicine. It was concluded that the medicine containing low— etheric citro —pectin (it called as pectin —vitamin complex) is more effectively in this responce (Fig. 5). 

Empey, L.R., Papp, J.D., Jewell, L.D. and Fedorak, R.N. (1992). Mucosal protective effects of vitamin E and misoprostol during acute radiation-induced enteritis. Dig. Dis. Sci. 37, 205-214. 

Some effects of irradiation on vitamins have been mentioned earlier. It appears that irradiation and heat treatment affect vitamins differendy. Apparendy, vitamins Br B6, B12 and folic acid decompose less under as high a radiation dose as 60 kGy than under autoclaving at 120°Cfor 20 minutes. On the other hand, vitamin C is much more sensitive to irradiation. Generally, the radiosensitive vitamins are also sensitive to light, heat, and oxygen. In fresh foods, the vitamins that are most susceptible to irradiation are A and E. There is also some decomposition of vitamins B, and C. Other vitamins are fairly stable under irradiation. However, for the most part, the vitamins are more susecptible to heat treatment than to irradiation. 

Nakamura, T. et al., Vitamin C abrogates the deleterious effect of UVB radiation on cutaneous immunity by a mechanism that does not depend on TNF-a, J. Invest. Dermatol. 109, 20-24, 1997. 

All of Belarus was contaminated. But the only people who are monitored for the effects of radiation, and who receive vitamins and medicines and humanitarian aid, are those who were directly involved in the cleanup or who lived in the area now known as the Dead Zone. All the others, no one cares what happens to them. They aren t even monitored. So kids are dying. They are taken to hospital when it s too late because no one monitors them. 

We have mentioned microwave ovens a few times already. Although we might employ such an oven regularly, no one has actually seen microwave radiation. The photons are wholly invisible. The phenomenon of sight can be simplified to the photo-effected transformation of a pigment related to retinal within the retina at the back of the eye. Retinal is derived from vitamin A. 

Tretinoin or retinoic acid is the acid form of vitamin A. Actually it is the all-trans isomer of retinoic acid. It is an effective topical agent for acne vulgaris. Its mechanism of action is believed to be associated with increased epidermal cell turnover. Some 10% of the topically applied dose is absorbed, metabolized by the liver and excreted in the urine and bile. To be effective tretinoin should be applied in a concentration that results in mild irritation and erythema. Patients should be advised to avoid or minimize sun exposure and use a protective sun screen as animal studies have raised some concern about possible carcinogenic effects under the influence of ultraviolet radiation. There are no indications that topical tretinoin is associated with an increased risk for birth defects. 

The fat-soluble vitamins are photosensitive, and therefore all operations with vitamin solutions and vitamin-containing materials should be carried out in subdued light or in low-actinic amber glassware. Ideally, the laboratory or a dedicated room within the laboratory should have the windows (if any) covered with effective blinds, and artificial lighting should be provided by F40GO gold (or equivalent) fluorescent lamps, which exclude radiation wavelengths of less than 500 nm. 

Vitamins, effect on stability of organisms to ionizing radiation 90KFZ(1)4. 

The degradation rate of vitamin A palmitate under UV radiation was significantly lower in the presence of mixtures of amino acids (85). Tween 80 provides a good inhibitory effect on chloramphenicol photolysis due to incorporation of the drug within the micelles (86). 

The degradation of vitamin A palmitate solution exposed to ultraviolet radiation was found to degrade exponentially during the initial exposure period after which the rate of photodegradation was progressively reduced. This reduction was attributed to the protective absorption effect provided the degradation product. UV radiation provided by two fluorescent tubes was filtered to produce... 

There are some vitamins, which are adversely effected by exposure to UV-VIS radiation during administration if not photoprotected. Among the fat-soluble vitamins, vitamin A (retinol, retinyl palmitate) photodegradation is of clinical significance. 

---