Biomedical subjects
Publications and source records attributed to R Hayashi.
Mg2+-ATPase deficient mutant of Escherichia coli showed an evident dependency of thiamine uptake on the oxidative metabolism of glucose, whereas the parent strain did not. In both cells, this uptake was completely inhibited by H+ conductors.
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Injections of 2 mg of progesterone into ovariectomized estrogen-primed rats significantly increased serum LH and FSH concentrations 3, 5 and 8 hr later. Receptor blockers of noradrenaline (NA), dopamine (DA) or acetylcholine (ACH), phenoxybenzamine (20 mg/kg body weight), pimozide (1mg/kg body weight) or atropine (700 mg/kg body weight), respectively, prevented the progesterone-induced gonadotropin release. On the other hand, none of them blocked the gonadotropin release following unilateral electrochemical stimulation (100 microA for 60 sec) of the medial preoptic area which occurred 0.5 and 1.5 hr later, although pimozide or atropine reduced serum LH concentrations at 4.0 hr after stimulation. Furthermore, the sites of action of NA, DA and ACH with respect to LH release were examined by intracerebral implantation in ovariectomized estrogen-primed rats DA or ACH, when implanted unilaterally into the medial preoptic urea, induced a significant increase in serum LH 5 hr later, whereas NA decreased LH levels. Implantations of NA or ACH into the bed nucleus of the stria terminalis or the medial amygdala increased serum LH although the effect of NA into the latter was not statistically significant. Only implantations of NA among the three substances into the lateral septum induced LH release. These results suggest that all of NA, DA and ACH play stimulatory roles in the regulation of gonadotropin secretion, and that there are regional differences of their effectivenesses in releasing LH within the limbic-preoptic area.
Experimental osteomyelitis was produced in mice by the Ueno's method for the purpose of evaluating therapeutic effects of the antibiotics. The results were as follows: 1) Experimental osteomyelitis produced with penicillin-G sensitive bacteria was completely cured by PC-G 1.8 mg per mouse a day, which provided maintenance of the concentration in serum more than 10 times of MIC for over 12 hours. The dosis of 0.18 mg per mouse per day was insufficient to bring a complete healing. 2) Experimental osteomyelitis produced with penicillin-G resistant bacteria did not heal completely, despite the administration of MPI-PC, a synthetic penicillin designed against penicillin resistant staphylococci, in a dosis of 5 mg twice a day, probably by the following reasons. Since MPI-PC is water-soluble, it is difficult to maintain the concentration in serum more than 10 times of MIC for over 1 hour. In other word, the bacteria was exposed to the effective antibiotic concentration for only one hour twice a day. 3) It was experimentally proved that earlier administration of antibiotics following inoculation provided quicker elimination of bacteria. 4) When bactericidal antibiotics were used, administration twice a day in half dosis gave better results compared with the full dosis once a day. 5) This experimental model of osteomyelitis proved quite useful for quantitative analysis of the effects of antibiotics, which would be applicable as a good method for evaluation of antibiotics to be developed in the future.
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Umbilical cord hematoma is a rare cause of intrauterine morbidity and mortality. There have been many theories about the etiology of this entity, but its cause remains unknown. Intrauterine death occurred in a postmature (44 weeks) fetus and was associated with an umbilical cord hematoma. Histologic examination of the cord showed a thinning of the wall of the umbilical vein with splitting of the elastic membrane.
A simple modified Roux-en-Y anastomosis--esophagojejunoduodenostomy with circuit duodenal loop (circuit Roux-en-Y anastomosis) after total gastrectomy--has been performed in ten consecutive patients without any operative death or complications. The simplicity and safety of this procedure may well be more worthwhile than other forms of alimentary tract reconstruction.
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The possible role of histidine residues in the catalytic function of carboxypeptidase Y from bakers' yeast has been investigated using site-specific reagents. Among the reagents tested, benzyloxy-L-phenylalanylchloromethane (Z-PheCH2Cl) was the most powerful inhibitor of the enzyme. It irreversibly inactivated both the peptidase and esterase activities with an apparent second order rate constant of 3.8 M-minus 1 S-minus 1; the D isomer caused essentially no effect on either activity. Inhibition by L-Z-PheCH2Cl, the reaction retarded by certain competitive inhibitors of the enzyme. Using radioactive L-Z-PheCH2Cl, the reaction with the enzyme was shown to be essentially stoichiometric. Diisopropylphosphorofluoridate (iPr2PF)-inactivated enzyme failed to react with Z-PheCH2Cl, and conversely, the Z-PheCH2Cl-inhibited enzyme failed to react with radioactive iPr2PF. Amino acid analyses of the Z-PheCH2Cl-inactivated enzyme revealed the loss of essentially 1 residue, with a concomitant yield of a 0.62 residue of N-t-carboxymethylhistidine. Since carboxypeptidase Y has a reactive serine at its active center, we concluded from these results that the mechanism involves a charge-relay system in the hydrolysis of peptide and ester substrates, as in chymotrypsin. An -SH group of carboxypeptidase Y was not affected during the reaction with L-Z-PheCH2Cl. The generic name "serine carboxypeptidase" has been proposed for carboxypeptidase Y and for the iPr2PF-sensitive carboxypeptidases from plants, molds, and animal tissues, in order to distinguish them from "metal carboxypeptidase" to which carboxypeptidase A (EC 3.4.12.2) and B (EC 3.4.12.3) belong.
Kinetic parameters for carboxypeptidase Y [EC 3.4.12.1], characterized as a nonspecific enzyme, are given for the hydrolysis of a series of acylated peptides, acylated amino acid esters, and amides. We confirmed that the enzyme released COOH-terminal proline and beta-alanine at an appreciable rate, as well as neutral amino acids with aromatic and aliphatic side chains at a very high speed. The rates of hydrolysis of ester and amide substrates were compatible with those produced by chymotrypsin [EC 3.4.21.1]. Stereospecificity was also demonstrated by the failure to hydrolyze peptide, ester, amide, and anilide substrates containing a D-amino acid. The effects of pH, solvents, and salt concentrations on the kinetic parameters of hydrolysis of peptide and ester substrates are also described.
Reversible inhibition of the peptidase and esterase activities of CPase Y [EC 3.4.12.1] was investigated with substrate and product analogs known to be inhibitors or effectors of pancreatic carboxypeptidases A or B [EC 3.4.12.2 or 3]. L-Amino acids and NH2-blocked L-Amino acids showed competitive-type inhibition, whereas their D-enantiomers caused less inhibition than the L-enantiomers, and showed non-competitive or mixed-type inhibition. Some phenylalanine analogs, e.g. beta-phenylpropionic acid and t-cinnamic acid, were also reversible inhibitors of CPase Y. The type of these inhibitors and their K1 values were generally parallel for both the peptidase and esterase activities.
Kinetic parameters of carboxypeptidase Y are given for the hydrolyses of ester, amide, and anilide substrates. The kcat/Km values were compatible with those of chymotrypsin [EC 3.4.21.1] with a few exceptions. One ionizable group with a pK of around 5.8 was suggested to be involved in the free enzyme in hydrolyzing all the substrates, including peptide substrates. In addition, hydroxylaminolysis and the kinetic isotope effects of deuterium oxide indicated, with some reservations, a reaction mechanism which proceeds via the formation of an acyl intermediate.