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Biomedical subjects

H Yamamura

Publications and source records attributed to H Yamamura.

At least 415 records · Page 23Linked to original sources
PubMed1979

Why should dialysis benefit schizophrenia?

If dialysis is successful for the treatment of schizophrenia, the artificial kidney must be removing something which the human kidney cannot, unless other nonspecific factors are involved. Either there is an abnormal compound present which is retained by normal renal tubular transport processes, or the kidney of a schizophrenic must be abnormal in that it fails to excrete a normally present compound. Since the latter explanation is less probable, biochemical research should focus on classes of compounds which are known to be handled differently by the artificial kidney than by the human kidney. A dialyzable "schizophrenic toxin" might be a nonprotein, nonprotein-bound of molecular weight below 500 daltons such as an organic acid or base. Proteins, peptides, amino acids, and trace elements are less likely possibilities.

Amino Acids↗
PubMed1979

PaCO2 for optimum washout of inhalational anesthetics from the brain. A model study.

A hypothesis was established that, during emergence of inhalational anesthesia, hyperventilation and accompanying hypocapnia beyond a certain limit may actually disturb rather than enhance the washout of inhalational anesthetics from the brain because of a decreased cerebral blood flow. Two mathematical models were constructed and the washout of nitrous oxide, halothane and methoxyflurane were studied. In model I, the whole body consisted of a single compartment, and blood flow to this compartment was assumed to change proprotionally with the PaCO2. In model 2, the body was divided into two compartments, brain and the rest of the body. It was assumed that the blood flow to the brain compartment varies proportionally with the PaCO2, while that to the rest of the body remains constant. The analysis indicated that there indeed existed the PaCO2 values at which the washout of anesthetics from the brain can be maximally achieved. In model 1, they were 49.0, 22.1 and 9.7 mmHg for nitrous oxide, halothane, and methoxyflurane, respectively. In model 2, these PaCO2 values varied with time. While the hypothesis was proven to be valid, we conclude that it is of limited clinical significance. For halothane and methoxyflurane, these theoretically optimum PaCO2 values are sufficiently low. For nitrous oxide, the variation of PaCO2 makes little difference clinically, because its washout is fast enough regardless of PaCO2.

Anesthesia, Inhalation↗
PubMed1978

Danger of bucolome in infants with hyperbilirubinaemia. Experimental evidence.

Effects of bucolome on congenitally jaundiced Gunn rats were examined. Plasma total bilirubin level fell immediately after a single injection of bucolome and the lowered level persisted for more than 6 hours. Plasma unbound-bilirubin level and cerebellar bilirubin content increased simultaneously with the drop in total plasma bilirubin level. Kernicterus was observed in the brains of the treated rats 6 hours after the treatment. LD50 of the drug in jaundiced rats was about 37 mg/kg, about one-tenth of the value in nonjaundiced rats. It is suggested that bucolome displaces bilirubin from albumin, transferring bilirubin from blood into tissues including the brain, and resulting in kernicterus. The use of bucolome in infants with hyperbilirubinaemia is inadvisable.

Animals↗
PubMed1977

GTP stimulates and inhibits adenylate cyclase in fat cell membranes through distinct regulatory processes.

GTP and hormones activate, synergistically, adenylate cyclase in purified plasma membranes from rat adipocytes. Addition of chelating reagents (EDTA or ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid) or thiol-reducing reagents (dithiothreitol or 2-mercaptoethanol) results in marked inhibition of enzyme activity without altering the synergistic stimulatory effects of GTP and hormones. The inhibitory effects of the reagents required the presence of GTP, indicating that inhibition involves a GTP-dependent process. This process is separate from the GTP-dependent process responsible for activation of the enzyme since it is selectively abolished by pretreatment of fat cell membranes with trypsin. It is suggested that inhibition and activation of fat cell adenylate cyclase by GTP occur through distinct regulatory processes.

Adenylyl Cyclase Inhibitors↗
PubMed1977

Solubilization and separation of the glucagon receptor and adenylate cyclase in guanine nucleotide-sensitive states.

Adenylate cyclase in liver membranes was solubilized with Lubrol PX and partially purified by gel filtration. The partially purified enzyme was susceptible to activation by guanyl-5'-yl imidodiphosphate (Gpp(NH)p). Studies on the binding of [3H]Gpp(NH)p to various fractions eluted from the gels revealed that an upper limit of 1% of the Gpp(NH)p binding sites is associated with adenylate cyclase activity stimulated by the nucleotide. The glucagon receptor, pretagged with 125I-glucagon in the membranes, solubilized with Lubrol PX, and fractionated on the same gel columns, eluted in a peak fraction that overlaps with, but is separate from, adenylate cyclase in its Gpp(NH)p-stimulated form. Addition of GTP to the solubilized glucagon-receptor complex caused complete dissociation of the complex, as has been shown with the membrane-bound form of the complex. Since the GTP-sensitive form of the glucagon receptor complex separates from the Gpp(NH)p-sensitive form of adenylate cyclase, it is concluded that the receptor and the enzyme are separate molecules, each associated with a distinct nucleotide regulatory site or component. These findings are discussed in terms of the possible structure of the hormone-sensitive state of adenylate cyclase.

Adenylyl Cyclases↗
PubMed1977

Effect of fundusectomy on serum and antral gastrin levels in rats.

In adult male rats, fundusectomy decreased acid secretion but significantly increased total antral gastrin and both fasting and food-stimulated serum gastrin levels. The rise in fasting serum gastrin could be inhibited by antral acidification, suggesting that decreased acidity caused postfundusectomy hypergastrinemia. The mechanism for the increase in total gastrin in antral tissue is probably the same. These studies provide a useful experimental model for the increasing of antral gastrin and for the production of hypergastrinemia.

Animals↗
PubMed1977

Studies on serum gastrin of the patients with gastric cancer.

In patients with gastric cancer who were to undergo gastrectomy, the fasting serum gastrin concentration in the peripheral vein was estimated by radioimmunoassay. The blood samples were also collected from the gastric veins and artery during the time of operations. These gastrin values were compared with morphological findings in the resected stomach. No significant differences in serum gastrin concentration was found between the patients of gastric cancer and normal subjects. In the patients with mucosal atrophy in the oxyntic gland area but with no atrophy in the pyloric gland area, however, significant increase in serum gastrin concentration was observed. In cases where fundal atrophy was accompanied by atrophy in the pyloric gland area, the increase was not observed. The amount of gastrin content in cancer tissue was negligible. These results indicate that the increase in serum gastrin concentration in some patients with gastric cancer might be due to the accompanied atrophy of oxyntic glands in the stomach.

Adult↗