Two types of mutants have been produced from a thiamine auxotroph of E.coli, 70-23. One (70-23-107) requires thiamine diphosphate (TDP) and the other (70-23-102) thiamine monophosphate (TMP) or TDP.Thiamine, TMP and TDP are all equally active for the parent, whereas thiamine is inactive for mutants, 70-23-102 and 70-23-107 ; TMP is inactive for mutant 70-23-107. The different growth responses between the parent and mutant organisms appear to be due to the second mutation which effects the phosphorylating steps of thiamine. Experimental results obtained with such mutant strains indicated that free thiamine is not involved in the de novo synthesis of TDP, but TMP, an exclusive product formed through the reaction between 2-methyl-4-amino-5-hydroxymethylpyrimidine pyrophosphate and 4-methyl-5-β-hydroxyethylthiazole monophosphate, is directly phosphorylated to form TDP. Exogenous thiamine, on the other hand, must be converted to TDP via the intermediate formation of TMP. Thus, thiamine pyrophosphokinase in E. coli, which was reported to exist in this organism, should be separated into two different enzymes, thiamine monophosphokinase and thiamine monophosphatekinase. It is suggested then that if the phosphorylation of thiamine were involved in the process of thiamine uptake, thiamine monophosphokinase would have play a role, because exogenous thiamine is first converted into TMP by this enzyme. Our experiments, however, revealed that the uptake of both TMP and TDP by mutant 70-23 cells were stimulated by glucose. Furthermore, the stimulatory effect of glucose was observed in the uptake of mutant 70-23-102 cells for thiamine and of mutant 70-23-107 cells for TMP. Since mutant 70-23-102 was lacking in the thiamine monophosphokinase activity and mutant 70-23-107 was the same in the thiamine monophosphatekinase activity, both enzymes might not be involved as an essential component in the uptake system. TMP and TDP are actually utilized by the mutant cells without dephosphorylation to thiamine.

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The regulation of thiamine biosynthesis in E. coli has been studied. The thiamine biosynthesis is regulated by repression and derepression of the formation of enzymes involved in the thiamine synthesis from OMP and Th depending on the cellular TDP concentration, which is varied by addition of exogenous thiamine, adenine, or phenylalanine to the growth medium. This mechanism of the regulation is supported by the isolation of two kinds of thiamine regulatory mutants ; one is assumed to be an operator-constitutive strain of thiamine operon (s) and the other shows altered regulatory properties of thiamine synthesis probably due to an alteration in the promotor region of thiamine operon (s). These mutants were selected as pyrithiamineresistant strains of E.coli K12 and its derivative.

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Effect of α-linolenate on the essential fatty acid deficient symptoms of rats was investigated to confirm if it can be replaced with linoleate. Each 100mg/rat/day of linoleate, α-linolenate or oleate was orally administered for 14 days to the essential fatty acid deficient rats fed with fat-free diet. Linoleate recovered all the deficient symptoms, whereas α-linolenate recovered the decreasements of body weight and liver mitochondrial swelling rate except dermatosis. These results indicated that α-linolenate could replace with linoleate on certain functions of biological membranes except skin. No efficiency of α-linolenate on the skin disease might be due to either the difference of the membrane systems in skin from those in internal organs or the difference of the effects on the lipid metabolism in skin between α-linolenate and linoleate.

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The effects of thiosemicarbazide (TSC) were studied during the postnatal development in the mouse. From the behavioral-and electroencephalographical (EEG) examinations, lower threshold and longer latent period of the first convulsions were observed in the younger mice treated with TSC.A running fit which was not accompanied with EEG seizure discharge was never observed in the young mice, until the EEG pattern showed the similar to that of the adult. Other several antagonists of vitamine B_6 which induce running fit as well as convulsions showed the same tendency. However, the uptake of TSC into the brain seemed to be no significant differences between the young and the adult from the results of the macroautoradiographic examination. Pyridoxal phosphate could not prevent the convulsions and the tremor in the young, while pyridoxin hydrochloride could do so. Influence of TSC in mice at the various ages was discussed, related to the brain development.

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