Determination of vitamin B12 using the enzyme glycerol dehydrase.

Glycerol dehydrase is an enzyme that catalyzes dehydration of glycerol into beta-propionaldehyde. It requires 5'-deoxyadenosylcobalamin, one of the forms of vitamin B12, as a coenzyme. The enzyme is inactivated in vitro by all forms of vitamin B12 stoichiometrically. The objective of this study was to determine vitamin B12 content by utilizing the inactivation of the enzyme by vitamin B12. After various examinations, an excellent standard curve was obtained up to 1 pmol vitamin B12 using 14 mU of the enzyme per tube. Glycerol dehydrase does not respond to vitamin B12 if it is bound to haptocorrin, a vitamin B12-binding protein. This necessitates a procedure for extraction of vitamin B12 from samples before assay. The enzyme was less inactivated by 5'-deoxyadenosylcobalamin than any other form of vitamin B12. However, this did not matter because all forms of vitamin B12 were converted into cyanocobalamin during the extraction procedure cited above, which was performed in a buffer containing potassium cyanide.

Wallerian degeneration of the pyramidal tract does not affect stroke rehabilitation outcome.

OBJECTIVE: To test whether Wallerian degeneration (WD) of the pyramidal tract as signaled by MRI affects rehabilitation outcome in patients with subcortical infarction (internal capsule or corona radiata). BACKGROUND: Recent radiologic evidence suggests that WD occurs no earlier than 3 months after a subcortical infarction. METHODS: A total of 77 consecutive patients with pure motor hemiparesis due to an initial subcortical infarction were assessed on admission and discharge with the Functional Independence Measure (FIM) for disability and Stroke Impairment Assessment Set (SIAS, full = 25) for impairment. WD was defined by a high-intensity area detected along the pyramidal tract below the level of lesion on T2-weighted MR image (WD+). RESULTS: Age, sex, side of stroke, Mini-Mental State Examination score, and volume of lesion were comparable for each group. Length of stay (LOS) was significantly longer (p < 0.05) in WD+ (130 days) than in WD- (105 days). There was no difference in the change of FIM (WD+, 99 to 111; WD-, 95 to 107) or SIAS measures (WD+, 12 to 16; WD-, 13 to 16) made on admission and discharge, nor was there any effect of the timing of the rehabilitation experience (< or = 90 days or >90 days after stroke). CONCLUSIONS: After stroke, apparent WD of the pyramidal tract may slow functional recovery but does not limit final rehabilitation outcome of pure motor hemiparesis. Study of the mechanisms of compensation for this delayed pyramidal tract degeneration will enhance the scientific basis for rehabilitation.

[On the potential protective properties of vitamin A in carcinogenesis]. / Pro potentsial'ni zakhisni vlastivosti vitaminu a za kantserogenezu.

The effect of massive doses of vitamin A was studied as applied to the tumor growth in rats with Guerin's carcinoma, protein biosynthesis in them and enzymic activity. It is established that intraperitoneal administration of vitamin A massive doses (the total quantity being 4000 000 and 2000 000 I.U.) in equal doses for 6 days decreases tumor sizes and weight, intensity of protein biosynthesis by the cell-free protein-synthetizing system of the small intestine mucosa, intensifies activity of retinylpalmitate hydrolase, decreases that of retinylpalmitate synthetase, increases the activity of alanine aminotransferase. The authors assume that under the effect of vitamin A massive doses the capacity of retinol-binding protein transporting vitamin A is exhausted, the latter being transported in a cell by lipoproteids, which causes the cell membrane lysis.