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Biomedical subjects

M Kozuka

Publications and source records attributed to M Kozuka.

At least 73 records · Page 4Linked to original sources
PubMed1989

Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels.

Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using 125I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.

Animals↗
PubMed1989

Preischemic hyperglycemia enhances postischemic depression of cerebral metabolic rate.

The objective of the present study was to explore metabolic correlates to the appearance of postischemic seizures and the enhancement of brain damage observed in subjects that are made hyperglycemic prior to the induction of ischemia. To that end, transient forebrain ischemia of 10-min duration was induced in normo- and hyperglycemic rats, with subsequent measurements of local CMRglc (LCMRglc) after 3, 6, 12, and 18 h of recirculation. We posed the questions of whether postischemic depression of LCMRglc is exaggerated by preischemic hyperglycemia and whether there are signs of localized increases in LCMRglc in hyperglycemic rats, reflecting subclinical seizure activity. The results confirmed the presence of a long-lasting postischemic depression of LCMRglc in normoglycemic rats. This depression was partially but not tightly related to the degree of reduction of local CBF during ischemia. The depression was most pronounced in neocortical areas and in the hippocampus, but notably it was less pronounced in the densely ischemic caudoputamen. Little or no reduction of LCMRglc was observed in moderately or mildly ischemic structures such as the hypothalamus, red nucleus, and cerebellum. Preischemic hyperglycemia markedly accentuated the postischemic depression of LCMRglc. For example, although the subjects quickly regained wakefulness and motility, they had LCMRglc values in neocortical areas that remained below 50% of control. Corresponding but quantitatively less pronounced reductions in LCMRglc were observed in other areas. Notably, preischemic hyperglycemia reduced postischemic LCMRglc also in areas that showed only moderate to mild reductions in CBF during the ischemia. The results thus demonstrate that preischemic hyperglycemia has pronounced metabolic effects in the postischemic recovery period. The data provide no indication that postischemic seizures, which develop after a recovery period of approximately 24 h, are preceded by the appearance of hypermetabolic "seizure" foci.

Animals↗
PubMed1989

Immunohistochemical localization of atrial natriuretic peptide receptor in bovine kidney and lung.

Receptors for atrial natriuretic peptide (ANP) were localized in the alveoli and bronchiolar smooth muscle cells of bovine lung and in podocytes of the kidney by immunofluorescence and immunoperoxidase methods. Two specific antisera were raised against the ANP receptor purified from bovine lung plasma membranes: anti-Rc 140 and anti-Rc 70. Anti-Rc 140 was raised against the 140 KD native receptor having a homodimeric structure, and anti-Rc 70 was elicited by immunizing a rabbit with the 70 KD reduced subunits. Essentially identical staining patterns were obtained with both antisera. Identification of ANP receptor sites would provide useful information in understanding the pulmonary and renal actions of ANP.

Animals↗
PubMed1989

[Anti-tumor promoting activities and inhibitory effects on Epstein-Barr virus activation of Shi-un-kou and its constituents].

The Kampo-prescription, Shi-un-kou, and its constituent crude drugs [Lithospermum erythrorhizon (1), Macrotomia euchroma (2) and Angelica acutiloba (3)] were assayed for their inhibitory effects on Epstein-Barr virus activation induced by the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). The crude drugs exhibited inhibitory activity singly and in combinations. In particular, the combination of 2 and 3 yielded enhanced inhibition and lower cytotoxicity. The anti-tumor promoter activity suggested by these results was further investigated in an in vivo study, which demonstrated that Shi-un-kou markedly inhibited TPA-induced skin tumor formation in mice.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

S-adenosyl-L-methionine ameliorates ischemic brain metabolism in spontaneously hypertensive rats.

Effects of S-adenosyl-L-methionine (SAM) on the metabolism in ischemic brain were investigated. The ischemic model employed was an incomplete cerebral ischemia of the spontaneously hypertensive rat (SHR) produced by the occlusion of both common carotid arteries. One hundred mg/kg of SAM was administered (i.p.) 6 times from the beginning of occlusion at 30 min intervals. At 3 hr after the onset of occlusion, animals were killed by microwave irradiation and creatine phosphate (CrP), ATP, glucose, lactate and gamma-aminobutyric acid (GABA) contents in the brain were measured. SAM significantly mitigated both the reductions in CrP, ATP and glucose levels and the increase in GABA level due to the cerebral ischemia. In another set of experiments with the same experimental schedule, water content in the brain was examined. SAM significantly suppressed the increase in water content due to the cerebral ischemia. These results indicate ameliorating effects of SAM on the metabolism in ischemic brain.

Adenosine Triphosphate↗
PubMed1988

Inhibitory effects of 12-O-tetradecanoylphorbol-13-acetate and teleocidin B induced Epstein-Barr virus by saponin and its related compounds.

The inhibitory effects of triterpene glycosides and monoterpene glycosides on 12-O-tetradecanoylphorbol-13-acetate (TPA) and teleocidin B in the Epstein-Barr virus (EBV) activation in Raji cells were studied. Concomitant treatment of Raji cells with TPA or Teleocidin B and these glycosides showed the inhibition of EBV activation. We herein report in vitro structure-activity studies using a biological test system on a variety of triterpene glycosides having 1 sugar chain (monodesmoside), 2 sugar chain (bisdesmoside) and an acyl side-chain. Among these glycosides, triterpene 3-O-glycosides and acylated saponin exhibited an effective inhibition of EBV activation; therefore, the sugar chain at C-3 of the triterpene and/or the acyl side-chain were determined to be essential to the inhibitory activities in this test system. The data suggested that these triterpenoid glycosides which were originally used as herbal drugs and folk remedies in many areas of the world, were in fact inhibitory compounds, thus explaining the EBV activation in the in vitro test system.

Antineoplastic Agents↗
PubMed1988

Effects of S-adenosyl-L-methionine upon ischemia-induced brain edema in Mongolian gerbils and spontaneously hypertensive rats.

Effects of S-adenosyl-L-methionine (SAMe).2 sulphate.tosylate upon the ischemia-induced brain edema and survival rate in Mongolian gerbils and spontaneously hypertensive rats were investigated, since SAMe is known to be important as a physiologically active substance in numerous metabolic processes including those that are inhibited in ischemia. SAMe suppressed increases in water and Na+ content in the ischemic brain which was produced by ligation of the common carotid artery for a short term (20-30 min) in Mongolian gerbils. This ameliorating effect of SAMe was observed dose-dependently at higher doses than 100 mg/kg administered repeatedly every 0.5 or 1 hr, starting within 2 hr, at least, after the reperfusion. Similar effects were also obtained in spontaneously hypertensive rats whose common carotid artery on both sides were ligated permanently. SAMe also increased survival rate in Mongolian gerbils with ischemic brain. Although the SAMe solution employed in the present experiments was hypertonic and contained mannitol as a filler, the beneficial effects were due to neither the hypertonicity of the solution nor mannitol, but due to SAMe itself.

Animals↗
PubMed1982

Changes in holding and ion-channel currents during activation of an ascidian egg under voltage clamp.

1. The unfertilized egg of an ascidian, Halocynthia roretzi, was activated by the divalent ionophore A23187 in natural or artificial sea water (nSW or ASW) or by an external solution containing a high concentration of Ca ions (high-Ca ASW) under voltage-clamp condition.2. Activation current began with an abrupt increase in the holding current and decayed relatively slowly with a common time course in various ASWs. Activation current was both Na- and Ca-dependent. The peak time, T(p), and the peak amplitude, D, of the activation current in nSW at 15 degrees C and -90 mV were 27 +/- 4 sec and -1.50 +/- 0.47 nA, respectively.3. The currents through Na, Ca and anomalous K channels were evoked by test pulses with constant intervals in nSW and high-Sr, high-Ca and high-K ASWs. Na-channel current was enhanced during activation. In contrast, Ca-channel current decreased. In high-Ca, Na-free ASW the Ca current through Na channels increased while the Ca current through Ca channels decreased. The time for the maximum of Na current, T(max), was (7.2 +/- 1.5) x 10 sec at 15 degrees C and index R, the ratio of the maximum amplitude to the amplitude before activation, was 2.31 +/- 0.18 in nSW. The time for the minimum of Ca-channel current, T(min), was about 70 sec, being almost the same as T(max) of Na current.4. The current through anomalous K channels increased initially and decreased later with a time lag behind the decrease in Ca-channel current.5. Both T(p) of activation current and T(max) of Na current were reduced by raising the temperature. Q(10) for T(p) and T(max) was 2.2 and 2.3, respectively.6. When the egg was activated in ASW containing scorpion toxin, the Na current through normal channels increased strongly while the Na current through toxinmodified channels increased less markedly.7. There was no significant change in the total membrane capacity before and during activation.

Animals↗
PubMed1980

Antitumor agents XXXVIII: Isolation and structural elucidation of novel germacranolides and triterpenes from Elephantopus mollis.

The ethanolic extract of Elephantopus mollis yielded three novel cytotoxic antitumor germacranolides, molephantin, molephantinin, and phantomolin. The extract also yielded three inactive known triterpenes, beta-amyrin acetate, lupeol acetate, and epifriedelanol, as well as stigmasterol. The structure and stereochemistry of the cytotoxic antitumor agents molephantin, molephantinin, and phantomolin were determined on the basis of chemical transformations and spectral evidence. Preliminary in vivo tumor assays indicated that molephantinin and phantomolin were potent inhibitors of Ehrlich ascites carcinoma and Walker 256 carcinosarcoma. Molephantinin also showed significant antileukemic activity in the P-388 lymphocytic leukemia screen.

Animals↗
PubMed1979

Studies on bacterial chemotaxis. II. Effect of cheB and cheZ mutations on the methylation of methyl-accepting chemotaxis protein of Escherichia coli.

Radioactive proteins from chemotactic mutants of Escherichia coli with continuous tumbling phenotype (cheB and cheZ) and their otherwise isogenic parent were compared by two-dimensional gel electrophoresis. The system was capable of separating non-methylated methyl-accepting chemotaxis protein (MCP) from its methylated equivalent. The analysis of proteins from the envelope fraction of the bacteria showed that the cheB mutants contained a larger portion of methylated MCP than did the parent. However, the change of MCP methylation level was small, if any, in cheZ strains. The results suggest that the product of cheB gene and the product of cheZ gene are not functional complementary. The product of cheB gene functions in controlling the level of methylation at the stationary state of the organisms. In addition to known MCP species, a new MCP of about 43,000 daltons was found. This MCP appears to be involved in transducing signals of some sugars.

Bacterial Proteins↗
PubMed1977

Studies on bacterial chemotaxis. I. Separation of proteins from cell envelope of Escherichia coli.

Radioactive proteins from Escherichia coli cell envelope fraction were separated by two-dimensional polyacrylamide gel electrophoresis. Electrophoresis was carried out under several sets of conditions, and autoradiographs were obtained. Many of the proteins were separated at well-defined positions with good reproducibility. Some of the proteins moved relative to these stationary proteins depending at least two factors, i.e. the amount of proteins applied in the first dimension and the electric current applied in the second dimension. Among more than 200 spots, methyl-accepting chemotaxis protein and flagellin were identified by using labelled or cold preparations of these proteins as markers. Some of the spots were assigned to proteins from the outer membrane of the bacteria. The results provide a good foundation for comparative studies of membrane proteins from genetically altered strains of the bacteria.

Bacterial Proteins↗