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Biomedical subjects

M Kihara

Publications and source records attributed to M Kihara.

At least 235 records · Page 13Linked to original sources
PubMed1988

The Na+-Ca2+ exchange system in vascular smooth muscle cell membrane vesicles isolated from cultured cells and from tissue is similar.

The existence of a Na+-Ca2+ exchange system was investigated in sarcolemmal vesicles isolated from cultured cells of dog mesenteric artery. When Na+-loaded membrane vesicles were suspended in a Na+-free KCl medium to create an outwardly directed Na+ concentration gradient across the membrane, a time-dependent uptake of Ca2+ was observed. This uptake of Ca2+ was drastically reduced when the vesicles were suspended in NaCl medium to eliminate the Na+ concentration gradient across the membrane. Monensin also decreased Ca2+ uptake in Na+-loaded vesicles. The apparent Km for Ca2+ was 2.97 microM and the apparent maximum velocity was 4.27 nmol/min per mg protein. The data indicate that a Na+-Ca2+ exchange system exists in sarcolemmal membranes isolated from cultured cells and that it is similar to the system in membranes isolated from the tissue.

Animals↗
PubMed1988

Effects of thyrotropin releasing hormone on human sudomotor and cutaneous vasomotor activities.

At an ambient temperature of 34-41 degrees C (rh = 40%) forearm sweat rates were measured by capacitance hygrometry in 9 male volunteers. Thyrotropin releasing hormone (TRH) was infused intravenously at 0.1 mg.min-1 for 20 to 30 min. Sweat rate increased rapidly within a minute after initiation of TRH infusion, decreased rapidly after the peak sweat rate was attained in 2-5 min of TRH infusion, and then levelled off in 6-10 min near the level before TRH infusion. Core temperature (Tre, Tty) started to decline at the time of the peak sweat rate and levelled off almost coincidentally with the levelling off in sweat rate. Average values for the rate of sweat expulsions (Fsw), sweat rate and mean body temperature (Tb) were obtained from the data of the last 10 min period of TRH infusion. The regression line for the relationship of Fsw to Tb shifted during the TRH infusion to the left of the line for the control; that of sweat rate to Fsw hardly shifted. At an ambient temperature of 24-27 degrees C TRH produced vasodilation as evidenced by an increase in skin blood flow (measured by means of thermal distribution), an increase in amplitude of the photoelectric plethysmogram and an elevation of skin temperature in the finger tips. It is suggested that TRH may act, either directly or indirectly, on the central thermoregulatory mechanism (or on the thermoreceptive mechanism) to lower the reference temperature for heat dissipation.

Adult↗
PubMed1988

GABA transaminase inhibitors enhance the release of endogenous GABA but decrease the release of beta-alanine evoked by electrical stimulation of slices of the rat medulla oblongata.

Slices of the rat medulla oblongata were superfused and electrically stimulated. The amount of endogenous GABA, beta-alanine and glutamate release from the slices was determined by high performance liquid chromatography with fluorometric detection. Inhibitors of GABA-transaminase (GABA-T), aminooxyacetic acid (10(-5) M), gamma-acetylenic GABA (10(-4) and 10(-3) M) and gabaculine (10(-5) M), enhanced the stimulus-evoked release of GABA and reduced that of beta-alanine, while no change was observed in the release of glutamate. These changes in amino acid release from the slices were accompanied by an increase in the content of GABA and a decrease in that of beta-alanine. The stimulus-evoked release of these amino acids was abolished by Ca2+-deprivation, in either the presence or absence of GABA-T inhibitors. These results suggest a modulatory role of GABA-T for synaptically releasable GABA and involvement of this enzyme in the synthesis of releasable beta-alanine.

4-Aminobutyrate Transaminase↗
PubMed1988

Effects of low-dose chronic diltiazem treatment on hemodynamic changes in spontaneously hypertensive rats.

The effects of long-term diltiazem treatment on hemodynamic and cardiovascular characteristics were investigated in young spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY) and their respective untreated controls. The drug was administered to treated rats over a period of 24 weeks. Body weight, left ventricular weight, mean arterial pressure (MAP), heart rate, max dp/dt or maximum velocity of the contractile element (Vmax) were not significantly different in diltiazem-treated SHR and untreated SHR. In diltiazem-treated SHR, cardiac index (CI) and stroke volume index (SI) were significantly increased and total peripheral resistance and the index of left ventricular compliance (delta P/delta V) were significantly decreased compared with untreated SHR. Left ventricular pumping ability in treated SHR was higher than that in untreated SHR, despite the low dose of diltiazem given. However, there was no significant difference between treated and untreated WKY. Long-term diltiazem treatment did not affect left ventricular function or biochemical properties in SHR and WKY. These data suggest that long-term diltiazem treatment improves pump function in SHR without changing blood pressure.

Animals↗
PubMed1988

4-Hydroxy-2-methyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline (PI-OH): a new potentiator of sympathomimetic amines on the rat anococcygeus muscle.

1. The potentiating effects of racemic 4-hydroxy-2-methyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline (PI-OH), cocaine, desipramine and nomifensine on the concentration-response curves of the rat anococcygeus muscle to noradrenaline (NA) and field stimulation were examined. 2. PI-OH and cocaine concentration-dependently potentiated the responses of anococcygeus muscle to NA and field stimulation, but the activity of PI-OH was stronger than that of cocaine on both responses. 3. At high concentrations the potentiating activities of desipramine and nomifensine were less, a fact that was explained by their postsynaptic inhibitory properties; the actions of nomifensine and desipramine as antagonists against NA were competitive and non-competitive, respectively. 4. It is concluded that PI-OH may be an ideal potentiator of the response to NA in adrenergically-innervated tissues because it has no side effects such as postsynaptic inhibition.

Animals↗
PubMed1988

[Magnetic resonance imaging of hypothalamic hamartoma].

Magnetic resonance (MR) findings of two patients with a hypothalamic hamartoma are discussed. The two girls showed clinical symptoms and endocrinological signs of precocious puberty. MR imaging was of diagnostic value superior to that of CT in the demonstration of the characteristic location of this tumor and relationships to the neighboring structures because of its multi-dimensional utility. Although it has been reported that CT showed this lesion as isodense to the grey matter with and without injection of contrast medium, MR imaging depicted the lesion as a high signal intensity area on T 2-weighted images in both patients. MR imaging is a useful method for the evaluation of the hypothalamic hamartoma.

Child↗
PubMed1987

Blood pressure modulation by substance P in the rat nucleus tractus solitarius.

Substance P in a dose of 0.1-10 ng injected into the nucleus tractus solitarii (NTS) of the rat caused hypotension, bradycardia and apnea whereas a dose of 100 ng led to no response. A substance P antagonist injected into the NTS abolished the cardiovascular responses to substance P. The antagonist alone increased blood pressure and heart rate. The data suggest a role for substance P in the cardiovascular regulation by the NTS.

Animals↗
PubMed1987

Evidence for the presence of GABAergic and glycine-like systems responsible for cardiovascular control in the nucleus tractus solitarii of the rat.

Microinjections of gamma-aminobutyric acid (GABA) and glycine, into the medial area of the nucleus tractus solitarii (NTS) of the rat, led to an increase in arterial pressure and heart rate. The GABA receptor antagonist bicuculline and the glycine receptor antagonist strychnine decreased both of these cardiovascular parameters whereas the GABA uptake inhibitor nipecotic acid produced hypertension. High K+ stimulation caused a calcium-dependent release of GABA and glycine from tissues in the area of the NTS. Our results suggest that GABA and glycine may modulate the cardiovascular control within the NTS.

Animals↗
PubMed1987

Cardiovascular effects in rats of alpha 1 and alpha 2 adrenergic agents injected into the nucleus tractus solitarii.

The cardiovascular effects of selective alpha 1 and alpha 2 agonists and antagonists injected into the nucleus tractus solitarii (NTS) were studied in urethane-anesthetized rats. Methoxamine (0.3-3 micrograms) injected bilaterally into the NTS caused a dose-dependent increase in blood pressure and heart rate. Phenylephrine (6 micrograms) and an imidazolidine derivative St 587 (3 micrograms) similarly injected also produced an increase in blood pressure, whereas alpha-methylnoradrenaline and an azepine derivative B-HT 920 (1 and 3 micrograms) caused a decrease in blood pressure and heart rate. The pressor response to methoxamine (1 microgram) was markedly inhibited by prazosin (0.3 microgram) injected into the same sites or hexamethionum (25 mg/kg, i.v.). Prazosin (0.3 microgram) alone injected bilaterally into the NTS did not affect the blood pressure, while yohimbine (0.1 microgram) similarly injected increased the pressure. These results suggest that in the rat NTS there exist alpha 1 adrenoceptors responsible for an increase in arterial pressure. The NTS alpha 2 adrenoceptors seem to be involved in the tonic regulation of arterial pressure.

Adrenergic alpha-Agonists↗
PubMed1987

Phenol: a complex chemoeffector in bacterial chemotaxis.

Earlier observations that phenol is a repellent for Salmonella typhimurium but an attractant for Escherichia coli were confirmed. This behavioral difference was found to correlate with a difference in the effect phenol had on receptor methylation levels; it caused net demethylation in S. typhimurium but net methylation in E. coli. On the basis of mutant behavior and measurement of phenol-stimulated methylation, the attractant response of E. coli was shown to be mediated principally by the Tar receptor. In S. typhimurium, two receptors were found to be sensitive to phenol, namely, an unidentified receptor, which mediated the repellent response and showed phenol-stimulated demethylation; and the Tar receptor, which (as with E. coli) mediated the attractant response and showed phenol-stimulated methylation. In wild-type S. typhimurium, the former receptor dominated the Tar receptor, with respect to both behavior and methylation changes. However, when the amount of Tar receptor was artificially increased by the use of Tar-encoding plasmids, S. typhimurium cells exhibited an attractant response to phenol. No protein analogous to the phenol-specific repellent receptor was evident in E. coli, explaining the different behavioral responses of the two species toward phenol.

Aspartic Acid↗
PubMed1987

Potassium induced release of endogenous glutamate, gamma-aminobutyric acid (GABA) and glycine from the caudal dorsomedial medulla of the rat.

Release of endogenous glutamate, gamma-aminobutyric acid (GABA) and glycine was investigated in the caudal dorsomedial (CDM) region of the rat medulla oblongata. High potassium stimulation (50 mM) produced an increase in release of glutamate, GABA and glycine by 579.1, 303.4 and 774.5 (pmol/mg protein), respectively. The release was abolished by Ca2+ deprivation. These results indicate a possible neurotransmitter role for glutamate, GABA and glycine in the CDM medulla of the rat.

Animals↗
PubMed1987

Studies on GABAergic mechanisms responsible for cardiovascular regulation in the rostral ventrolateral medulla of the rat.

Cardiovascular effects of chemical stimulation of the rostral ventrolateral medulla were studied in pentobarbital-anesthetized, paralyzed rats to examine the medullary GABAergic mechanisms responsible for cardiovascular regulation. Bilateral microinjections of 3-mercaptopropionic acid (10 micrograms), an inhibitor of gamma-aminobutyric acid (GABA) synthesis, into the ventrolateral medulla produced an increase in blood pressure and heart rate. Unilateral microinjection of nipecotic acid (3 micrograms), a reuptake inhibitor of GABA, elicited a fall in arterial pressure and heart rate. Bilateral microinjections of bicuculline (100 pmol), a GABA antagonist, into the ventrolateral medulla produced a sustained increase in arterial pressure and heart rate and, in addition, inhibited the hypotensive action induced by veratrine (0.3 mg/kg, i.v.). Lesioning of the rat nucleus tractus solitarii did not alter GABA content in the rostral ventrolateral medulla. These results support the hypothesis that in the rostral ventrolateral medulla, there exist GABAergic mechanisms involved in cardiovascular regulation. It seems unlikely that the GABAergic mechanisms originate mainly from neurons in the nucleus tractus solitarii.

3-Mercaptopropionic Acid↗
PubMed1986

Decreased content in left atrium and increased plasma concentration of atrial natriuretic polypeptide in spontaneously hypertensive rats (SHR) and SHR stroke-prone.

The atrial contents and concentrations, and the plasma concentrations of atrial natriuretic polypeptide (ANP) in spontaneously hypertensive rats (SHR) and SHR stroke-prone (SHRSP) were measured and compared with those of age-matched Wistar Kyoto rats (WKY) using a specific radioimmunoassay (RIA) for alpha-rat ANP (alpha-rANP). The contents of alpha-rANP-LI in the atria of SHR (19.0 +/- 0.9 micrograms, mean +/- SEM) and SHRSP (19.3 +/- 0.6 micrograms) were significantly lower than that of WKY (22.8 +/- 1.4 micrograms) (p less than 0.05). The atrial concentration of alpha-rANP-LI was also significantly lower in SHR (248.2 +/- 11.3 ng/mg, p less than 0.05) and tended to be lower in SHRSP (272.2 +/- 12.4 ng/mg) than that of WKY (300.0 +/- 14.2 ng/mg). Furthermore, the concentrations in the left auricles of SHR and SHRSP were significantly lower than that of WKY (p less than 0.01 and p less than 0.05, respectively). In contrast, no significant difference was observed in the alpha-rANP-LI concentrations in the right auricles of WKY, SHR and SHRSP. Gel filtration studies coupled with RIA showed that gel filtration profiles of the extracts from the right and left auricles of WKY, SHR and SHRSP were essentially identical. The plasma alpha-rANP-LI levels in SHR (260 +/- 34 pg/ml) and SHRSP (319 +/- 19 pg/ml) were significantly higher than that in WKY (170 +/- 17 pg/ml) (p less than 0.05 and p less than 0.01, respectively). These results suggest that the secretion of ANP from the heart is increased in SHR and SHRSP compared with WKY.

Animals↗
PubMed1986

Glioblastoma with sarcomatous component associated with myxoid change. A histochemical, immunohistochemical and electron microscopic study.

The case of a 22-year-old female suffering from glioblastoma with sarcomatous component (WHO; gliosarcoma) is presented. The tumor consisted of glioblastomatous and sarcomatouos components, and in part of the pleomorphic astrocytomatous region of the glioblastoma there was a prominent production of myxoid matrix. On the basis of its histochemical and immunohistochemical characteristics, the present case strongly suggested that glial cells of neuroectodermal origin assume part of the responsibility for production of myxoid material.

Adult↗