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Biomedical subjects

H Okabayashi

Publications and source records attributed to H Okabayashi.

At least 91 records · Page 5Linked to original sources
PubMed1986

Attenuated development of hypertension by chronic administration of bromocriptine in Doca-salt hypertensive rats.

The aim of the study was to investigate whether or not the development of hypertension is influenced by chronic treatment with bromocriptine and/or domperidone. Rats treated with DOCA-salt were divided into 4 groups: control with vehicle, bromocriptine, bromocriptine with domperidone, and domperidone. Increased blood pressure by DOCA-salt treatment was significantly suppressed by treatment with bromocriptine and this bromocriptine suppression was significantly blocked by treatment with domperidone. Increased urinary excretion of norepinephrine by DOCA-salt treatment was significantly suppressed by bromocriptine and the inhibiting effect of bromocriptine disappeared with domperidone. In the four groups of rats, there were significant correlations between systolic blood pressure and urinary excretion of norepinephrine, systolic blood pressure and urinary excretion of epinephrine, and urinary excretion of dopamine and sodium. These results suggest that the chronic effect of bromocriptine is to suppress development of DOCA-salt hypertension, mainly through peripheral mechanisms which are involved in the decreased release of norepinephrine.

Animals↗
PubMed1986

Augmented vasodepressor and sympathetic responses to intracerebroventricular injections of diltiazem, a calcium channel blocker, in DOCA-salt hypertensive rats.

The role of the calcium ion in central cardiovascular regulation was investigated by injecting a calcium channel blocker, diltiazem, intracerebroventricularly (i.c.v.) in urethane-anaesthetized, DOCA-salt hypertensive rats. This produced a fall in blood pressure and bradycardia with corresponding decreases in abdominal sympathetic nerve activity. However, a similar amount of diltiazem injected intravenously (i.v.) did not affect abdominal sympathetic nerve activity despite an accompanying vasodepression. The responses to i.v. injections of diltiazem were not different between the two groups; however, the magnitude of the blood pressure fall, bradycardia and sympathetic inhibition with i.c.v. injections was greater in the DOCA rats than in the sham-operated animals. These results suggest that diltiazem causes the central nervous system to decrease the sympathetic nerve outflow. The augmented central vasodepressor responses to diltiazem in DOCA-salt hypertensive rats may indicate that calcium metabolism in the central nervous system is disrupted and that this is of importance in the pathogenesis of DOCA-salt hypertension in rats.

Animals↗
PubMed1986

Evidence for a digitalis-like substance in the hypothalamo-pituitary axis in rats.

The origin of an endogenous digitalis-like substance in rats was investigated. The tissue content of the substance measured by radio-immunoassay was highest in the pituitary gland, with a decreasing gradient through the hypothalamus, forebrain, cerebellum, brain stem, heart, liver and kidney. Sodium loading decreased the content in the hypothalamus and increased the urinary excretion of the substance. The urinary output of the substance decreased after electrical lesions of the anteroventral third ventricle in the brain. The content increased in the hypothalamus and decreased in the plasma when the axonal flow of neurosecretion was interrupted with intracerebroventricular injections of colchicine. These results suggest that the digitalis-like substance could be produced in the hypothalamus and secreted from the pituitary gland like vasopressin, and that sodium loading increases the turnover of the substance in the hypothalamus.

Animals↗
PubMed1984

A proton nuclear magnetic resonance study on the release of bound water by inhalation anesthetic in water-in-oil emulsion.

Water-in-oil emulsion was prepared from glycerol-alpha-monooleate, n-decane and water, and was used to analyze the behavior of bound water molecules in response to the addition of an inhalation anesthetic, enflurane. The motion of water molecules is monitored by proton nuclear magnetic resonance spectroscopy. To the first approximation, the half-height width of the proton signal of dispersed water is related to the spin-spin relaxation time and represents the motion of the water molecule. It appears that one of the two OH moieties of glycerol-alpha-monooleate forms a hydrogen bond with the water molecule in average. The half-height width of the dispersed water proton showed a maximal value when the glycerol alpha-monooleate/n-decane mole ratio was 4 X 10(-2). The cause of this maximum is not immediately clear, but it is suggested that the assembly mode of glycerol-alpha-monooleate may be different between the lower and higher concentration range. Enflurane decreased the half-height width of the dispersed water, indicating an increase in the motion of water molecules. This results demonstrates that the anesthetic weakened the hydrogen bond between water and glycerol-alpha-monooleate molecules, and released bound interfacial water. It is postulated that dehydration of the interface, as shown by the release of bound water, would interfere with the transport of current-carrying hydrated ions through membranes and may constitute a molecular mechanism of anesthesia.

Anesthesia, Inhalation↗
PubMed1984

Spatial cognition: systematic distortions in cognitive maps.

Stevens and Coupe demonstrated that people tend to regularize their cognitive maps by distorting the position of relatively small features (e.g., cities) to make them conform with the position of larger features (e.g., state boundaries). The present studies replicated those of Stevens and Coupe by asking college students to study prototypical maps with three kinds of boundaries: none, straight, and curved. They extended Stevens and Coupe's work by asking students to (a) physically reproduce the maps rather than simply answer questions about them, (b) recall the information not only immediately after study, but also one hour later and again two days later, and (c) reproduce the state boundaries as well as the city locations. Students who studied the curved boundary maps made more distortion errors than those who studied the straight boundary and the no-boundary maps. In addition, students' distortion errors were greatest when recall was delayed, and distortion errors in the recall of state boundaries were correlated with their distortion errors in the recall of city locations. In general, the findings provide additional evidence for the notion that memory for map information is schematic.

Cognition↗
PubMed1982

Conformational effects of organic solvents on histone complexes.

Changes in the conformations of H3-H4, H2A-H2B, and the core histone complex brought about by the addition of organic solvents have been examined by circular dichroism spectroscopy. All three complexes assume increased alpha helicity with increasing amounts of the organic solvent. An amount of secondary structure equal to that obtained in phosphate-buffered 2 M NaCl solution can be induced in low-salt solutions of the complexes by the addition of 40-50% ethylene glycol, 50% glycerol, or approximately 2% hexafluoro-2-propanol. H3-H4 was found to be somewhat more flexible than H2A-H2B in its response to changes in solvent polarity. Upon being heated, H3-H4 and the core histone complex both undergo irreversible alpha leads to beta transitions in 50% ethylene glycol under low-salt conditions, while H2A-H2B undergoes an essentially reversible alpha leads to beta random-coil transition under the same conditions. These results are discussed in terms of the dynamics of the nucleosome particle.

Circular Dichroism↗
PubMed1981

Study of conformational states and reversibility of histone complexes.

The core histone complex (H3:H4:H2A:H2B)2 and products of dissociation, the H2A:H2B: dimer and the H3:H4 tetramer, were isolated from chicken erythrocyte chromatin by several literature methods as well as gel filtration on Bio-Gel A15m at various salt concentrations. The conformational and oligomeric characteristic of these histone complexes were compared to analogous histone complexes prepared by renaturation of individually acid-extracted histones by circular dichroism (CD) and analytical gel filtration chromatography. The salt-extracted core histone complex (independent of method of preparation), the purified dissociation products, the H2A:H2B dimer, and the H3:H4 tetramer in 2 M NaCl, 10 mM sodium phosphate, 0.25 mM EDTA and 0.1 mM DTT, pH 7.0, have conformation which are identical, by the criteria of similar CD spectra, with complexes prepared from acid-extracted histones, Likewise, the salt-extracted complexes may be cycled through solvents of low ionic strength (10 mM sodium phosphate, pH 7.0 or 50 mM NaOAc, pH 5.0) or 1 mM HCl and returned to 2.0 M NaCl, 10 mM sodium phosphate, 0.25 mM EDTA, and 0.1 mM DTT, pH 7.0, in a completely reversible manner. Thus it would appear that acid-denatured histones are capable of being fully renatured to yield native-like complexes.

Animals↗