VITAMINS

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A thiamin deficient liquid diet was prepared and its effect on rats was compared with the ordinarily used thiamin deficient powder diet. Ethanol was also added to this liquid diet to investigate the effect of ethanol on the development of thiamin deficiency. The composition of the liquid diet was essentially the same as that of the Lieber-DeCarli diet. Homogenous emulsion was obtained by adding sodium carboxymethylcellulose. In the ethanol formula, carbohydrate was isocalorically replaced to the extent of 36% of the total calories. For thiamin deficient rats, thiamin was withheld from the formula, and these rats were compared with the rats fed with an ordinary thiamin deficient powder diet. In the ethanol administration experiment, Wistar rats were divided into four groups: control, ethanol, thiamin deficient and thiamin deficient-ethanol groups. Effects of ethanol administration on liver and alimentary tracts were also studied histopathologically. The decrease in weight was slower in the rats fed with thiamin deficient liquid diet than the rats fed with powder diet. Convulsion occurred 7 days later in the former rats. The intake of the diet did not decrease until a later stage in the former rats. When ethanol was added to the diet of the former rats the lesser gain in body weight was noted, but the development of neurological signs was slower than the former rats. In conclusion, the liquid diet was proved to be better than the ordinary powder diet to make thiamin deficient rats because it seemed not to have other factors causing malnutrition except thiamin deficiency. It is also suitable for the administration of ethanol to the rats, as is the Lieber-DeCarli diet, having good reproducibility. Therefore, this liquid diet seems to be ideal to make an experimental model to study the influences of ethanol on thiamin deficiency.

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In connection with the development of peroxisomes (microbodies), carnitine acetyltransferase (CAT) was induced in the alkane-grown cells of Candida tropicalis. CAT was found to be distributed among peroxisomes, mitochondria and cytoplasm in the yeast cells. An "acetylcarnitine shuttle" is proposed as a transport system of acetyl units, derived from the alkane degradation, from the peroxisomes to the mitochondria and to the cytoplasm, based on the subcellular localization of CAT. Thus, CAT seems to be the key enzyme for the complete operation of glyoxylate cycle in the yeast with the concerted functions of peroxisomes and mitochondria. CAT localized in the cytoplasm was supposed to be related to the de novo synthesis of fatty acids.

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In alkane-utilizing yeasts, fatty acids derived from alkanes are degraded by the β-oxidation system located in peroxisome with concomitant reduction of NAD to NADH. This indicates that re-oxidation of NADH to NAD is necessary for the continuous operation of β-oxidation in the organelles. Of various NAD-linked enzymes tested, NAD-linked glycerol-3-phosphate dehydrogenase (NAD-G3PDH) was found to be localized in the peroxisomes of alkane-grown Candida tropicalis. In the meantime, FAD-linked glycerol-3-phosphate dehydrogenase (FAD-G3PDH) was located exclusively in the mitochondria of the yeast. These results, together with the inducible nature of NAD-G3PDH with alkanes, strongly suggested the operation of "glycerophosphate shuttle (NAD-G3PDH/FAD-G3PDH)" between the peroxisomes and mitochondria for the transport of reducing equivalents produced in the peroxisomes.

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