Subject thiamin

Subject Thiamin Intake 7 Per day Free Thiamin Excretion in Stools 7 per day ... 

This has been the subject of many investigations starting from thiamine itself or derivatives, with the aim of explaining the role of pyrimidine group in coenzymatic activity. 

This volume is intended to present a comprehensive description of the chemistry of thiazole and its monocyclic derivatives, based on the chemical literature up to December, 1976. It is not concerned with polycyclic thiazoles, such as benzo- or naphthothiazole, nor with hydrogenated derivatives, such as thiazolines or thiazolidines later volumes in this series are devoted to these derivatives. The chemistry of thiamine has also been excluded from the present volume because of the enormous amount of literature corresponding to the subject and is developed in another volume. On the other hand, a discussion of selenazole and its monocyclic derivatives has been included, and particular emphasis has been given to the cyanine dyes derived from thiazolium salts. 

The normal values for thiamine in human blood vary from 25-80 mpg/ml (average of 27 cases), from 110-370 mfig/ml in urine (27 cases), and from 13-17 mpg/ml in cerebrospinal fluid (45 cases). These specimens were obtained from normal subjects, receiving no vitamin therapy and in the fasting state, to eliminate dietary influences. The... 

The question of how much thiamine human beings need has been subjected to a great deal of study, and the literature on the subject will not be reviewed here. Most of the investigation has been based upon the assumption that "normal man" has a requirement at the adult level which is subject to relatively small variation and that "the normal infant" has likewise a fairly definite requirement. If this assumption is valid, it is easy to see that, when three or a half-dozen individuals have been found to give reasonably concordant results, an investigator may be satisfied that he has found the answer. 

The experiment was nonetheless instructive, and one could hardly ask human subjects to participate in a more rigorous test. Two facts stand out in addition to what has already been said (1) Substantial variation was observed among the nine individuals, and (2) this variation may have been due to differences in intestinal flora rather than to more direct differences in need. It should be pointed out, however, that differences in need based upon differences in intestinal flora may be real and just as exacting as if the differences had a different origin. Presumably differences in intestinal flora are due to the different "climates" which are distinctive for each individual (p. 149). If we take the experiments and the authors interpretation at face value, we are led to conclude that some individuals can get along with practically no thiamine in their dieta conclusion which certainly points toward high variability of needs. 

Nutritional Deficiency-Related Dementias. We have already mentioned that chronic alcoholics are subject to thiamine deficiency that can cause dementia. It usually occurs only after heavy, prolonged abuse of alcohol. In developed countries, the other key nutritional concern is vitamin deficiency. Vitamin deficiency can surprisingly strike even those with a healthy diet. Such people are missing a vital protein, intrinsic factor, which would enable them to absorb it from their digestive tract. 

Dwivedi and Arnold (89) determined the thiazole moiety in thiamine by derivatizing first to form the TMS analog. Samples were chromatographed on 3% OV-17 on Chromosorb G (DMCS treated) at 110°C. Vitamin D2 (calciferol) and its analog Vitamin have been the subject of many applications in GC analyses. The compounds have been derivatized as the TMS analog and chromatographed on OV-17 (90) and SE-30 (91) and on 3% silicone on Celite after treatment with antimony trichloride (92). Several references to vitamine E (oi-tocopherol) are included in the review by Kern et al. (39) on GLC determinations of pharmaceuticals and drugs. The acetate was determined on 3% OV-17 on Chrom W-HP at 280°C. Vecci and Kaiser (93) determined Vitamin C as the TMS derivative on 3% SE-30 or 10% XE-60 on Anachrom ABS. Column... 

Synthetic allithiamin derivatives, such as thiamin propyl and tetrahydro-furfuryl disulfides, have been used for the prevention and treatment of thiamin deficiency. Because they are lipid soluble, and are not subject to the normal control of thiamin absorption by saturation of the intestinal transport system, they have potential benefits in the treatment of thiamin-deficient alcoholics, whose absorption of thiamin is impaired. 

The role of thiamin diphosphate in pymvate dehydrogenase means that, in deficiency, there is impaired conversion of pymvate to acetyl GoA, and hence impaired entry of pymvate into the citric acid cycle. Especially in subjects on a relatively high carbohydrate diet, this results in increased plasma concentrations oflactate and pymvate, which may lead to life-threateninglactic acidosis. 

Although there are a number of urinary metabolites of thiamin, a significant amount of the vitamin is excreted unchanged or as thiochrome, especially if intake is adequate, and therefore the urinary excretion can provide useful information on nutritional status. Excretion decreases proportionally with intake in adequately nourished subjects but, at low intakes, there is a threshold below which further reduction in intake has litde effect on excretion. 

The excretion of a test dose of thiamin has also been used as an index of status after a parenteral dose of 5 mg (19 /rmol) of thiamin, adequately nourished subjects excrete more than 300 nmol of the vitamin over 4 hours, whereas deficient subjects excrete less than 75 nmol. 

Among the water-soluble vitamins subject to photodegradation during administration, thiamine, ascorbic acid, and riboflavine must be considered. A multivitamin product containing all of these vitamins was added to both 0.9% NaCl and 5% dextrose infusion solutions packaged in PVC and Clearflex containers. These admixtures were then exposed to photonic energy (2000 lux) for 24 hours and showed a rapid degradation of both riboflavine and ascorbic acid (95). 

Clomethiazole is structurally related to vitamin B 1 (thiamine) and is a hypnotic, sedative and anticonvulsant. It is comparatively free from hangover it can cause nasal irritation and sneezing. Dependence occurs and use should always be brief. When taken orally, it is subject to extensive hepatic first-pass metabolism (which is defective in the elderly and in liver damaged alcoholics who get higher peak plasma concentrations), and the usual t) is 4 h (with more variation in the old than the young) it may also be given i.v. 

The most reliable method for assessing thiamin status involves the measurement of red blood cell transketolase. This enzyme is measured with and without the addition of TPP to the enzyme assay mixtures. In dietary thiamin deficiency, synthesis of transketolasc continues, but conversion of the apoet zyme to the holoenzyme in the cell is inhibited, resulting in the accumulation of the enzyme in the apoenzyme form. Addition of TPP to cell homogenates results in the conversion of apoenzyme to holoenzyme. This conversion can easily be detected by enzyme assays. The amount of shmulation of enzyme activity by the added TPP is used to assess thiamin status. A deficiency is indicated by a shmulation of over 20%, The TPP-dependent stimulation, using red blood cells from normal subjects, ranges from 0 to 15%. 

Stabilization of vitamin B12 solutions in the presence of thiamine, niacinamide, and ascorbic acid has been the subject of a number of patents. Newmark (290) has described... 

Riboflavin is unstable to light therefore, riboflavin-containing foods subjected to either ultraviolet or visible light can show significant losses of riboflavin. Riboflavin is much less water soluble than thiamin, but long-term storage in water can cause leaching. For instance, tofu stored in water can lose 80-90% of the riboflavin. 

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