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Biomedical subjects

R Hayashi

Publications and source records attributed to R Hayashi.

At least 289 records · Page 16Linked to original sources
PubMed1982

Lysinoalanine as a metal chelator. An implication for toxicity.

Synthetic lysinoalanine (N epsilon-DL-(2-amino-2-carboxyethyl)-L-lysine) was found to have a strong chelating ability for metals. It became colored when mixed with Cu+2 and showed absorption characteristics typical of a complex. Lysinoalanine could inactivate metalloenzymes such as carboxypeptidases A and B and yeast alcohol dehydrogenase, by removing the zinc ion from the active site. Model building for a mononuclear complex of the metal and lysinoalanine with space-filling models was possible for the LD-isomer, N epsilon-D-(2-amino-2-carboxymethyl)-L-lysine. Etiological studies of its toxicity to humans should be made because the chelating ability of lysinoalanine is sufficiently strong to remove the metal from the enzyme active center at millimolar concentration.

Alcohol Dehydrogenase↗
PubMed1982

Radioimmunoassay of serum group I and group II pepsinogens in normal controls and patients with various disorders.

A radioimmunoassay (RIA) for human group I pepsinogens (PgI) in serum was developed, using PgI purified from gastric mucosa. The sensitivity (0.7 micrograms/l) and reproducibility of the assay were satisfactory for clinical use. In normal controls, total serum pepsinogen (T-Pg) level was 58.9 +/- 31.7 micrograms/l (mean +/- SD) (PgI, 43.6 +/- 25.0 micrograms/l; PgII, 15.3 +/- 11.1 micrograms/l). Peptic ulcer cases had elevated T-Pg levels (gastric ulcer, gastroduodenal ulcer and duodenal ulcer, in increasing order of magnitude). T-Pg levels were not useful for diagnosis of peptic ulcer because of a large overlap with normal controls. T-Pg levels were low in patients with gastric polyp and in aged subjects. In these groups, the decrease of PgI was more marked than that of PgII.

Adult↗
PubMed1982

Electrophysiological correlates of pulsatile gonadotropin release in rats.

In order to reveal the electrophysiological correlates of pulsatile LH release in ovariectomized rats, changes in multiple unit activity (MUA) in the arcuate nucleus (ARC), the medial preoptic area, the ventromedial nucleus, the anterior hypothalamic area and other areas of the brain were recorded in lightly anesthetized female rats. Rats were ovariectomized at least 7 weeks prior to the experiment. 0.1 -ml blood samples were withdrawn from a cardiac catheter at 10-min intervals during the recording in order to measure the changes in the plasma LH concentration by radioimmunoassay. The LH concentration showed pulsatile changes under continuous intravenous infusion of thiopental sodium while cortical EEG was stable throughout the experiment. The firing rate in the middle part of the ARC (8 recordings) changed in parallel with the increase in the plasma LH concentration and was abruptly raised just prior to an increase in LH secretion. The number of MUA spike discharges per minute increased to 1.5-5 times that of the basal level. MUA started to increase 2-9 min prior to the LH rise and the high level of MUA lasted for 1-5 min. The firing rate in the ARC (14 recordings) and in other areas (54 recordings) recorded did not change periodically in parallel with the increase in LH. As these changes in MUA were localized in the ARC and were not reflected in cortical EEG, they might be specific local changes distinguished from generalized systemic effects involving the whole brain. These extreme increases in MUA seem to be due to the high activity either of neurons that secrete LH-RH or those that control the secretion of LH-RH.

Animals↗
PubMed1982

Coma preceded by severe dysphagia in type II diabetes mellitus.

A 62-year-old man with 11 years' duration of type II diabetes was hospitalized because of non-ketotic diabetic coma. He had never noted any symptoms of swallowing difficulty until 3 days before admission when they developed gradually and he became comatous. He had never received special medication such as diuretics except anticonvulsants. Even after the recovery from diabetic coma he could hardly swallow solid foods or saliva for about 15 days, but these symptoms subsided gradually. Motility dysfunction of esophagus and pharynx in diabetes mellitus, in most cases they are mild, has been described, although diabetic coma preceded by dysphagia has not been documented except in one report. We studied, therefore, the autonomic nerve function of the present patient and discussed the relationship between dysphagia and diabetic coma together with the description of the clinical course of this patient. The relationship between this case and the previously reported cases were compared in terms of the sex, age, type of diabetes, clinical course, medication and the autonomic nerve function.

Autonomic Nervous System Diseases↗
PubMed1982

Effect of ipratropium bromide on the action of bronchoactive agents.

The effect of (8r)-3 alpha-hydroxy-8-isopropyl-1 alpha H, 5 alpha H-tropanium-bromide-(+/-)-tropate (ipratropium bromide, Sch 1000), a newly developed anticholinergic agent, on the action of various bronchoactive agents was examined using isolated guinea pig strips. Ipratropium bromide has not only an anticholinergic effect but also has an attenuating one on the contractile responses induced by serotonin, prostaglandin F2 alpha, histamine and bradykinin, and has a potentiating one on the relaxation responses induced by prostaglandin E2, isoprenaline and adrenaline. Ipratropium bromide could be a useful therapeutic agent for patients with chronic obstructive lung diseases.

Acetylcholine↗
PubMed1982

Studies on aspartase VIII. Protease-mediated activation: comparative survey of protease specificity for activation and peptide cleavage.

The active species of aspartase from Escherichia coli is further 3-5 fold activated upon limited proteolysis with trypsin releasing carboxy-terminal peptides as reported previously (N. Yumoto, M. Tokushige, and R. Hayashi. Biochim. Biophys. Acta, 616, 319 (1980) ). Survey of the protease specificity for the activation revealed that subtilisin BPN' and several other proteases having far broader substrate specificity than trypsin also activated the enzyme. The results of sequence analyses revealed that subtilisin BPN' cleaved mainly the serylarginine bond near the carboxy-terminal and released an octapeptide, while trypsin cleaved mainly the arginyltyrosine bond which is just next to the subtilisin cleavage site. These results suggest that the protease-mediated activation does not necessarily require a site-specific peptidyl cleavage, but the cleavage of any bond within a certain region centered at arginine, the eighth residue from the carboxy-terminal, is sufficient.

Ammonia-Lyases↗
PubMed1981

Counterflow efflux of thiamin in Escherichia coli.

A resting cell of Escherichia coli lacking thiamin kinase incorporated external thiamin with an energy-dependent counterflow efflux (C-efflux). This C-efflux could be separated frm an energy-dependent exit by a selective inhibition of exit by 2 x 10(-2) M NaN3. The extracellular thiamin could be replaced by thiamin diphosphate, resulting in the same rate of C-efflux, but the rate of C-efflux of intracellular thiamin diphosphate against the external thiamin was markedly low. This low rate of C-efflux of thiamin diphosphate could explain the higher accumulation of the compound than that of free thiamin in the thiamin-kinase-defective mutant as well as in its wild-type parent. Basic characteristics of free thiamin uptake and exit in E. coli W mutant were compared with those reported in K 12 mutant: a marked difference existed in the rate of exit. The low rate of exit in E. coli W 70-23-102 was inferred as the reason for the absence of an overshoot phenomenon of thiamin uptake in this strain.

Biological Transport↗
PubMed1981

Involvement of ovarian innervation in steroid secretion.

The effects of electrical stimulation of the brain on the ovarian venous plasma concentrations of estradiol (E2) and progesterone (P) were investigated in female rats hypophysectomized and adrenalectomized at 1000 h on the day of proestrus. Stimulation was applied during the proestrous critical period under pentobarbital anesthesia, and contralateral ovarian venous blood was collected from 105-120 min after the stimulation E2 and P concentrations, estimated by RIA, were significantly increased by stimulation of the medial basal prechiasmatic area (PVA), ventromedial hypothalamus, and areas in the mesencephalon and decreased by stimulation of the dorsal hippocampus, lateral amygdala, and mesencephalic areas. Ovarian blood flow was not affected by these stimulations. Ovarian nervotomy in the proestrous rats abolished E2 secretion induced by PVA stimulation. In intact proestrous rats, electrochemical stimulation of the PVA but not the preoptic suprachiasmatic area increased E2 and P concentrations, although stimulation of both areas commonly potentiated gonadotropin secretion. Present findings suggest that the efferent neural system from the brain to the ovaries is supplementary to the brain-pituitary-ovarian hormonal mechanisms in the regulation of ovarian steroid secretion, and the system may be required for the adjustment of ovarian responsiveness and sensitivity to gonadotropins. In addition, evidence for neural feedback on basal FSH secretion in the ovarian-denervated proestrous rats is presented in this study.

Animals↗