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Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 235 records · Page 13Linked to original sources
PubMed1981

The mobilization of plasma lipids by histamine in dogs.

The aim of the present work was to study the mechanism of the mobilization of plasma lipids produced by histamine in the dog, in vivo. The increase of plasma lipids by histamine in vivo was suppressed by cimetidine, but not by diphenhydramine. Although, histamine increased the level of plasma adrenaline, adrenaline does not appear to contribute to the lipolysis stimulated by histamine, because propranolol and alprenolol, beta-adrenergic blocking agents, did not affect the lipolysis stimulated by histamine. From these data it is concluded that the increase of plasma lipids in vivo is not attributable to the release of adrenaline from adrenal glands by histamine, but is produced by the stimulation through H2-receptors in fat cells.

Adrenergic beta-Antagonists↗
PubMed1981

[Effects of adrenaline, noradrenaline and pilocarpine on the oxygen uptake in rat submandibular gland (author's transl)].

This investigation was undertaken to clarify the oxygen uptake caused by adrenaline, noradrenaline and pilocarpine in rat submandibular gland. 1. Adrenaline (55 microM), noradrenaline (55 microM) and pilocarpine (10 microM) significantly stimulated the oxygen uptake. 2. When Na+ in Ringer solution was substituted by Li+ or choline, the stimulation by adrenaline, noradrenaline and pilocarpine was blocked. However, when Na+ (50%) was contained in the Li+ -Ringer solution, the response by these agents were observed. 3. When K+ in the Ringer solution was removed, the stimulation by adrenaline and noradrenaline was observed, but that by pilocarpine was not. 4. Adrenaline-, noradrenaline- and pilocarpine-induced oxygen uptake was not observed when Ca2+-deficient tissue was incubated in Ca2+-free Ringer solution. When the normal tissue was incubated in Ca2+-free Ringer solution, the stimulation by adrenaline and noradrenaline was observed, but that by pilocarpine was diminished. 5. The oxygen uptake of Ca2+-deficient tissue due to adrenaline and noradrenaline was recovered by the addition of 3 or 5 mM Ca2+ to the Ca2+-free Ringer solution, while the response of pilocarpine was recovered by the addition of 5 mM Ca2+. 6. The stimulation by adrenaline, noradrenaline and pilocarpine was considerably blocked by the addition of 2.5 or 5 mM La3+ to the Ringer solution. 7. The stimulation by adrenaline and noradrenaline was significantly blocked by the addition of 5 mM procaine. On the other hand, the stimulation by pilocarpine was blocked by 0.5 or 5 mM procaine. These results suggest that the increase in the oxygen uptake seen with adrenaline, noradrenaline and pilocarpine is dependent on the presence of Na+ and Ca2+.

Animals↗
PubMed1980

Enzymic determination of serum oxalate.

A new colorimetric, enzymic method for determination of serum oxalate is described using oxalate oxidase from barley seedlings. This method, based on a specific reaction of oxalate with oxidase is rapid, simple and precise. The percentage recoveries of oxalate added to serum ranged from 91.5 to 103. The oxalate content in the serum obtained from 50 healthy non-fasting donors varied from 0.06 mg/dl to 0.41 mg/dl. The proposed method showed a good correlation with a chemical method.

Colorimetry↗
PubMed1980

Electronic spectroscopy and deuteration kinetics of tyrosine and tryptophan residues: an application to the study of erabutoxin b.

The fluorescence increase on the deuterium oxide addition to the solvent medium was studied in various tryptophan- (or indole-) and/or tyrosine-containing model compounds. It was shown how the rates of the deuteration at the indole NH group of tryptophan and at the OH group of tyrosine could be followed independently of each other. The method was applied to a study of erabutoxin b molecule, a neurotoxic protein from a sea snake, to analyze the microenvironments of its single tryptophan and tyrosine residues. It was shown that the "functionally invariant" single tryptophan residue was exposed to the solvent in the surface of the molecule and that the "structurally conserved" single tyrosine residue was buried in the molecule. The rate of deuteration of the tyrosine residue (80 s(-1) at pH 6.3 and 33 degrees C) was 1/20 of that of an exposed tyrosine. It was also found that the amino group of Lys-27 quenched the fluorescence of Trp-29 but its deuteration had no effect on the fluorescence.

Deuterium↗
PubMed1980

Intersubunit interactions in proton-translocating adenosine triphosphatase as revealed by hydrogen-exchange kinetics.

The rates of hydrogen-deuterium exchange in the peptide groups of the alpha and beta subunits and the alpha-beta subunit complex of proton-translocating adenosine triphosphatase from the thermophilic bacterium PS3 were examined. The exchange was found to be much slower in the isolated beta subunit than in the isolated alpha subunit. This has been taken as indicating that the structure of the beta subunit is tighter than that of the alpha subunit. Adenosine 5'-triphosphate (ATP) caused tightening of a relatively tight portion of the alpha subunit and of a relatively loose portion of the beta subunit. When the alpha and beta subunits are brought into contact, tightening of the alpha subunit, but not the beta subunit, occurs. The effect of ATP on the structure of the beta subunit is more pronounced in the presence of the alpha subunit than in its absence. These findings support the idea proposed previously that the alpha subunit has an allosteric site and the beta subunit a catalytic site and that the conformation of the beta subunit is controlled by the alpha subunit.

Adenosine Triphosphatases↗
PubMed1980

On the base-stacking in the 5'-terminal cap structure of mRNA: a fluorescence study.

The fluorescence at 370 nm of the 7-methylguanosine residue (m7G) is found to be quenched when the base residue is involved in a stacking interaction with the adenosine residue in the cap structure m7G5' pppA of an eukaryotic mRNA. On the basis of the observed degree of quenching, the amounts of the stacked and unstacked forms in the cap structure have been determined at various temperatures and pH's. It has been found that at pH 6.2 effective enthalpy and entropy in the unstacked leads to stacked change are delta H degrees = 4.4 +/- 0.1 kcal/mole and delta S degrees = - 14.3 +/- 0.2 e.u., respectively. The pka value for the m7G residue is found to be 7.7 at 10 degrees C and 7.3 at 30 degrees C. The stacked structure seems to be less favourable in the deprotonated form that occurs in the higher pH solution. A similar analysis of some other cap structures indicates that the stacked form in m7G5' pppN structure is favourable if N is a purine nucleoside or a 2'-O-methylpyrimidine nucleoside but not for an unmethylated pyrimidine nucleoside.

Adenosine↗
PubMed1980

State of Tyr49 in a mutant tryptophan synthase alpha-subunit substituted at position 49.

The states of tyrosine residues in an alpha-subunit of wild-type tryptophan synthase from Escherichia coli and a mutant protein which has tyrosine in place of glutamic acid at position 49, were examined by absorption spectrum, spectrophotometric titration of phenolic hydroxyl ionization, and deuteration kinetics of phenolic hydrogen monitored by fluorescence measurement. The difference absorption spectrum of the mutant protein against the wild-type protein at pH 7.0 and 25 degrees C had peaks at 289, 282, and 276.5 nm. These positions corresponded to those in the absorption spectrum of L-tyrosine derivatives in a non-aqueous solvent at 77 K and these bands were well-resolved even at 25 degrees C as if the tyrosine residue were fixed at lower temperature. The titration curve of the mutant protein at 3 degrees C differed from that of the wild-type protein only above pH 12.7, where the difference molar extinction coefficient at 295 nm reached a plateau, indicating that ionization of Tyr49 took place at an abnormally high pH. These results suggest that Tyr49 is buried in the hydrophobic interior and fixed in a certain orientation. The deuterium exchanges of phenolic hydrogen at pH 7.0 and 13 degrees C in the wild-type and mutant proteins consisted of a single and two first order processes, respectively, all three having smaller rate constants than that of free tyrosine, indicating that these tyrosine residues are buried. It is concluded that Tyr49 in the mutant protein is not on the surface of the molecule.

Chemical Phenomena↗
PubMed1980

Comparative study of human intestinal and hepatic esterases as related to enzymatic properties and hydrolizing activity for ester-type drugs.

In attempts to determine the exact role of intestinal esterase in the body, we purified esterases from human intestinal mucosa and liver, and compared the enzymatic properties and substrate specificities with those of purified esterases. Esterase from human liver was purified 58-fold, by treatment with butanol, DE-52 and DEAE Sephadex A-50 column chromatographies, Sephadex G-200 gel filtration, and isoelectric focusing. The purified preparation showed a single band by polyacylamide gel electrophoresis. The molecular weights of intestinal and hepatic esterases were determined to be 53,000-55,000 and 180,000, respectively, by gel filtration on Sephadex G-200. The activity of the purified intestinal and hepatic esterases was strongly inhibited by diethyl-p-nitrophenyl phosphate and diisopropyl fluorophosphate, and was not inhibited by eserine sulfate and p-chloromercuribenzoate. Moreover, the purified esterases hydrolyzed ester-type drugs such as aspirin, clofibrate, indanyl carbenicillin and procaine. Hepatic esterase had properties similar to those of intestinal esterase with respect to the sensitivity to organophosphate and the substrate specificity. However, the two purified esterases differed in properties such as molecular weight, isoelectric point, thermostability and optimal pH.

Esterases↗
PubMed1979

Hydrolysis of ester-type drugs by the purified esterase from human intestinal mucosa.

Esterase from human intestinal mucosa was purified 210 fold by solubilization with Triton X-100, chromatography on DEAE-cellulose, Sephadex G-100 and hydroxylapatite, and isoelectric focusing. The purified esterase showed a single band by polyacrylamide gel electrophoresis. The molecular weight of the purified esterase was estimated to be about 55,000 by gel filtration on Sephadex G-150, and the isoelectric point was 5.02. The purified esterase was strongly inhibited by diethyl p-nitrophenyl phosphate (E-600) and diisopropyl fluorophosphate (DFP), and was not inhibited by eserine sulfate and p-chloromercuribenzoate. The purified esterase from human intestinal mucosa was found to be one of the carboxylesterases. The purified esterase hydrolyzed ester-type drugs, i.e., aspirin, clofibrate, indanyl carbenicillin and procaine, but did not hydrolyze amide-type drugs and choline-type drugs.

Aspirin↗
PubMed1979

Effects of adrenergic agonists on the oxygen uptake and amylase output in rat submandibular gland slices.

Oxygen uptake and amylase output in rat submandibular gland slices were measured by utilizing adrenergic agonists. Adrenaline, noradrenaline and isoproterenol significantly stimulated the oxygen uptake and amylase output. In the presence of propranolol or phenoxybenzamine, adrenaline-stimulated oxygen uptake was obviously blocked. Adrenaline-stimulated amylase output was inhibited by propranolol, but was not inhibited by phenoxybenzamine. The increase in oxygen uptake by nornol-stimulated oxygen uptake and amylase output were strongly inhibited by propranolol. The oxygen uptake due to isoproterenol was little affected by phenoxybenzamine. These results suggest that the increase in oxygen uptake seen with adrenergic agonists is mediated by both alpha- and beta-receptors, and that the amylase output is evoked through the stimulation of beta-receptors.

Adrenergic Agonists↗
PubMed1979

Species difference and characterization of intestinal esterase on the hydrolizing activity of ester-type drugs.

The ability of the esterase from intestine was studied for hydrolysis of ester-type drugs during absorption. The intestinal esterase is present in the absorption sites in the intestine and hydrolyzes to a large extent during the absorption. In a study of the dietary effect on intestinal esterase, the esterase activity increased in rats fed a high-fat diet, decreased in those fasted or fed a fat-free diet, whereas the esterase activity in the rat treated with phenobarbital showed no marked change. Thus the esterase from intestinal mucosa appears to be characteristically quite different from hepatic esterase. The esterase from human intestine was characterized and compared with esterase from rats, mice, rabbits, guinea pigs and dogs. There was a difference in the substrate specificity of the esterase and there were significant species differences in the electrophoretic behavior of the enzyme among the species tested. These results indicate that intestinal esterase from humans differs characteristically from esterases in experimental animals.

Animals↗
PubMed1979

Electron microscopic features of a brain tumor induced in hamster by BK virus, a human papova virus.

In order to locate the target cells for malignant transformation by BK virus (a human papova virus) in hamster brain, electron microscopic observation of tumor originally induced in hamster brain by BK virus was performed. With light microscopy, the BK virus-induced tumor (Vn 17) bore a close resemblance to human malignant ependymoma. Under the electron microscope, numerous microvilli and few cilia were visible on the surface of the tumor cells. These tumor cells were joined to each other by desmosomes. Gap junctions were not observed. Multilayered cuboidal cells were observed around the lumen and blood vessels in the tumor. With regard to fine structure, three types of Vn 17 cells were recognized; ependymal like cells, tanycytes with prominent cell processes, and undifferentiated cells with few cytoplasmic organelles. There was no basal lamina between the ependymal cells and the connective tissue stroma. The Vn 17 cells showed some similarity to the ultrastructural features of the epemdymal cells of newborn rabbits, suggesting that the target cells for Vn 17 may be cells related to ependyma. Malignant transformation of the cells would be initiated in the early stages after BK virus inoculation into the brain of newborn hamsters.

Animals↗