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Biomedical subjects

M Kasai

Publications and source records attributed to M Kasai.

At least 379 records · Page 21Linked to original sources
PubMed1987

Vacuolar ion channel of the yeast, Saccharomyces cerevisiae.

Ionic flux is most likely to regulate the chemiosmotic potential differences across vacuolysosomal membranes in animal, plant, and fungal cells. We found a membrane potential-dependent cation channel in yeast vacuolar membrane and characterized its several features by an electrophysiological method using artificial planar bilayer membranes incorporated with isolated yeast vacuolar membrane vesicles. This ion channel conducts K+ (single channel conductance, 435 pS in 0.3 M KCl) and several other monovalent cations (Cs+, Na+, and Li+) with broad selectivity, but does not conduct Cl-. The opening of this channel is regulated by the membrane potential and the presence of calcium ion on the cytoplasmic face. These characteristics suggested that the vacuolar cation channel functions as one of essential components for formation and regulation of the chemical and electrical potential differences across the vacuolar membrane.

Calcium↗
PubMed1987

gamma-Aminobutyric acid antagonist blocks baroreceptor-activated inhibition of neurosecretory cells in the hypothalamic paraventricular nucleus of rats.

The effects of gamma-aminobutyric acid (GABA) antagonists on baroreceptor-activated inhibition of neurosecretory cells in the paraventricular nucleus (PVN) were examined in urethane-chloralose anesthetized rats. In 11 neurosecretory cells which were inhibited by baroreceptor activation induced by intravenous application of phenylephrine, microiontophoretically applied bicuculline and/or picrotoxin blocked the inhibition (n = 9) completely or partially, whereas strychnine (n = 4) did not. The results suggest that GABA is, at least in part, involved in the baroreceptor-activated inhibition of PVN neurosecretory cells.

Action Potentials↗
PubMed1987

Inhibitory effects of 2-deoxytetronic acid, a putative endogenous satiety factor, on paraventricular neurons of rats, in vitro.

The endogenous sugar acid, 2-deoxytetronic acid (2-DTA) was investigated for its effects on activity of paraventricular nucleus (PVN) neurons in slice preparations from rats. 2-DTA dose-responsively inhibited the spontaneous activity of 23 of the 53 PVN neurons tested at concentrations of 10(-5) to 10(-2) M, and 2 were excited. The inhibitory responses were not due to osmotic changes by 2-DTA administration. The high concentration of 2-DTA needed to produce responses suggests that it acts as substrate for oxidative metabolism rather than as a neurotransmitter or neuromodulator in the suppression of feeding behavior.

Action Potentials↗
PubMed1987

Oxytocin predominantly excites putative oxytocin neurons in the rat supraoptic nucleus in vitro.

To determine the oxytocin (OXT) sensitivity of neurons in the supraoptic nucleus (SON), extracellular recordings were made from the rat hypothalamic slice preparation. OXT added to the bathing medium (3 X 10(-7) M) excited 13 (93%) of 14 cells which fired continuously (average 4.9 +/- 0.7 spikes/s) and 26 (81%) of 32 cells which fired slowly and irregularly (average 1.4 +/- 0.4 spikes/s). By contrast, only 2 (8%) of 26 phasically firing neurons were excited and none of the SON cells tested were inhibited. The excitation was reversibly antagonized by a synthetic OXT analogue, 1-deamino-[2-(O-methyltyrosine), 4-valine, 8-D-arginine]vasopressin. The results suggest that OXT exerts predominantly excitatory effects in the SON and that putative OXT cells are more likely to be affected than putative vasopressin cells.

Action Potentials↗
PubMed1987

Neurons in the paraventricular nucleus projecting to the median eminence: a study of their afferent connections from peripheral baroreceptors, and from the A1-catecholaminergic area in the ventrolateral medulla.

In male rats anesthetized with urethane-chloralose, extracellular recordings were made from tuberoinfundibular (TI) neurons in the paraventricular nucleus (PVN) identified by antidromic stimulation of the median eminence. Activation of baroreceptors induced by intravenous administration of phenylephrine inhibited approximately two-thirds of the 32 TI-neurons tested. Electrical stimulation of the A1-catecholaminergic area in the ventrolateral medulla produced an excitation in one half of the 28 neurons. Microinjection of L-glutamate (40 nl of 0.5 M solution of pH 7.4-7.6) to the same A1-area evoked an excitation in 7 out of 8 TI-neurons tested. The results show that some TI-neurons in the PVN receive inhibitory synaptic inputs from the baroreceptors and excitatory inputs from neurons in the A1-catecholaminergic area.

Adrenergic Fibers↗
PubMed1987

An anion channel of sarcoplasmic reticulum incorporated into planar lipid bilayers: single-channel behavior and conductance properties.

An anion channel of sarcoplasmic reticulum vesicle has been incorporated into planar lipid bilayers by means of a fusion method and its basic properties were investigated. Analysis of fusion processes suggested that one SR vesicle contained approximately one anion channel. The conductance of this channel has several substates and shows a flickering behavior. The occupation probability of each substate was voltage dependent, which induced an inward rectification of macroscopic currents. Further, the anion channel was found to have the following properties. (1) The single-channel conductance is about 200 pS at 100 mM Cl-. (2) The channel does not select among monovalent anions but SO2-4 hardly permeates through the channel. (3) SO2-4 added to the cis side (the side to which SR vesicles were added) inhibits Cl- current competitively in a voltage-dependent manner. (4) An analysis of this voltage dependence suggests that the binding site of SO2-4 is located at about 36% of the way across the channel from the cis entrance.

Animals↗
PubMed1987

Decrease in blood pressure by stimulation of the rat hypothalamic paraventricular nucleus with L-glutamate or weak current.

Effects of electrical and chemical stimulation of the paraventricular nucleus (PVN) of the hypothalamus on blood pressure were examined in rats anesthetized with urethane-chloralose. Focal electrical stimulation (10-25 microA, 50 Hz, 0.5 ms) of sites within the PVN consistently decreased blood pressure, while the stimulation of regions adjacent to the PVN produced no change or weak depressor response. Microinjection of L-glutamate (0.5 M, 80 nl) to the PVN consistently led to decreased blood pressure, while the same amount of saline injection had no effect. The depressor response was not affected by cervical vagotomy but was markedly reduced after intravenous administration of hexamethonium. The results suggest that activation of PVN neurons in rats leads to a decrease in blood pressure.

Animals↗
PubMed1987

Histologic characteristics of gonadotropin-producing hepatoblastoma: a survey of seven cases from Japan.

Histologic studies of the human chorionic gonadotropin (hCG) producing hepatoblastoma were made for seven cases encountered in Japan. It was found in all cases that multinucleated tumor giant cells in several figures were admixed in usual hepatoblastoma tissue and one of them was confirmed to be hCG positive immunohistochemically. Round and clear cells adjacent to or separate from the giant cells showed squamoid metaplasia with occasional pearl formation. These histologic elements were highly suspected to be derivatives of choriocarcinoma and were ascertained to be characteristic of the hCG-producing hepatoblastomas. Only one among seven cases survived long after hepatic lobectomy. At the time of recurrence, none showed elevation of serum or urinary hCG level, while serum alpha-fetoprotein (AFP) level became high again. That was because recurrent tumors contained none of the characteristic elements that had been found in preceding tumors.

Carcinoma, Hepatocellular↗
PubMed1987

Variation in the course of vessels in the vicinity of the hepatic port in biliary atresia.

Among 114 patients with biliary atresia, the type of obstruction of the extrahepatic bile duct and the course of the hepatic artery, cystic artery, and portal vein were determined and analyzed from the view point of their mutual relationships and in comparison with postoperative bile excretion. As a result, the following findings characteristic of biliary atresia were obtained: (1) The course and location of the extrahepatic bile duct did not deviate greatly from normal conditions, excluding some exceptional cases, but the site of the origin of the cystic artery differed from that in normal cases. (2) The pattern of the course of the vessels varied among different types of obstruction of the extrahepatic bile duct. (3) There was a difference in postoperative bile excretion in relation to the type of obstruction of the extrahepatic bile duct, the course of the vessels, and their combinations.

Bile Ducts↗
PubMed1987

Voltage-gated anion channel of the electric organ of Narke japonica incorporated into planar bilayers.

Voltage-gated anion channels in vesicles prepared from the electric organ of Narke japonica were studied using two methods. Ionic permeability was measured by the light scattering method, which could be used to measure the ion permeation of whole vesicles but only at a time scale of slower than about 0.1 s. The single channel conductances and permeability ratios for various ions were measured after fusing the vesicles to phospholipid bilayers. Both sets of results coincided, indicating that the anion channels observed with the planar bilayer method are the major route for anion passage in these vesicles. The channels showed anion selectivity and did not allow the permeation of cations such as K+ and choline+. The single channel conductance was 18 pS in 0.1 M Cl-. SCN- inhibited the conductance in a voltage-dependent reversible manner on both sides of a channel. SCN- may bind to the Cl- binding site in a channel and thus block it. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) blocked a channel on the cis (extracellular) side irreversibly. The number of anion channels per vesicle was estimated to be about 50. It was also shown that all anion channels in the vesicles were open at the very instance of fusion with planar membranes.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1987

Optimum conditions for electric pulse-mediated gene transfer to mammalian cells in suspension.

A pulse-generating machine which delivers exponentially decaying pulses over broad range of pulse lengths was used to determine the optimum pulse conditions for gene transfer to FM3A cells. In the transformation of tk- cells with pTK1, a single pulse of 100-2000 microseconds gave a high transformation frequency at 1.5-6 kV/cm and room temperature, the highest transformation frequency obtained being 3 X 10(-3). As the suspension buffer for cells exposed to the pulse, Saline G was better than PBS(-) for obtaining a large number of transformants because it ensured high cell viability.

Animals↗
PubMed1987

Characterization studies of suppressor cells in murine bone marrow chimaeras.

When BALB/c bone marrow cells were transferred to lethally X-irradiated C3H/He mice either intrasplenically (i.s.) or intravenously (i.v.), suppressor cells were detected by means of MLR coculture assays in the spleen of i.s. and i.v. chimaeras. Some but not all of the suppressor cells expressed a Thy 1.2 antigen, indicating that suppressor cells either sensitive or insensitive to anti-Thy 1.2 antibody plus complement treatment were generated in the spleen of i.s. and i.v. chimaeras. According to the examination of Lyt alloantigen expression on suppressor T cells, Lyt 1+2-, Lyt 1-2+, and Lyt 1+2+ suppressor T cells appeared to be present. The culture supernatants from several T-cell clones showed the suppressor activity against alloreactive MLR. Cell surface markers of these clones were composed of Lyt 1+2-, Lyt 1+2+ and Lyt 1-2+. In addition, since Carrageenan treatment abrogated the suppressor activity of plastic dish adherent cells, we conclude that some of them were composed mainly of macrophages.

Animals↗