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Y Kakinuma

Publications and source records attributed to Y Kakinuma.

108 records · Page 6Linked to original sources
PubMed1990

Beneficial effect of nipradilol (K-351) on acute myocardial ischemia. Study of the relationship between regional myocardial blood flow and energy metabolism.

To examine the effects of nipradilol on ischemic myocardium, experiments were performed on regional myocardial blood flow (MBF) and energy metabolism in anesthetized, open-chest dogs. Nipradilol at a dose of 0.3 mg/kg was i.v.-administered 10 min after coronary ligation. MBFs at various sites, including ischemic and non-ischemic areas, were determined by the hydrogen gas clearance method. The levels of ATP and creatine phosphate (CP) at the site of MBF determination were measured 60 min after ligation, and mitochondrial function (RCI, QO2) in the ischemic and non-ischemic areas was determined. Following nipradilol administration, aortic pressure and heart rate were significantly lowered. In ischemic areas with MBF below 40 ml/min/100 g, nipradilol had no influence on MBF. However, the tissue level of ATP in nipradilol treated hearts was significantly higher as compared with untreated hearts. In the area of mild ischemia with MBF of 40-60 ml/min/100 g, nipradilol preserved the tissue ATP and CP levels in spite of a decrease in MBF. Moreover, an inhibition of the decrease in mitochondrial respiratory function was observed in ischemic areas with MBF below 20 ml/min/100 g. Thus, nipradilol administered following ischemia preserved ATP content and mitochondrial function in the ischemic myocardium with reduction of heart rate and aortic pressure. This suggests that nipradilol exerts a cardioprotective effect in acute ischemia. It seems that the cardioprotective effect is due to a decrease in myocardial oxygen demand and preservation of mitochondrial function.

Adenosine Triphosphate↗
PubMed1989

Sodium-translocating adenosine triphosphatase in Streptococcus faecalis.

Sodium-translocating ATPase in the fermentative bacterium Streptococcus faecalis exchanges sodium for potassium ions. Sodium ions stimulate its activity, but K+ ions have no significant effect at present. Although the molecular nature of the sodium ATPase is not clear, the enzyme is distinct from other ion-motive ATPases (E1E2 type and F1F0 type) as judged by its resistance to vanadate as well as dicyclohexylcarbodiimde. The sodium ATPase is induced when cells are grown on media rich in sodium, particularly under conditions that limit the generation of a proton potential or block the constitutive sodium proton antiporter, indicating that an increase in the cytoplasmic sodium level serves as the signal. The enzyme is not induced in response to K+ deprivation. The sodium ATPase may have evolved to cope with a sodium-rich environment under conditions that limit the magnitude of the proton potential.

Adenosine Triphosphatases↗
PubMed1989

Histopathological studies on experimental marine toxin poisoning--4. Pathogenesis of experimental maitotoxin poisoning.

Repeated injections of 45 ng/kg of maitotoxin into the peritoneal cavities of male ICR mice resulted in marked atrophy of lymphoid tissues, a reduction of lymphocytes in the circulating blood, reduced immunoglobulin M in serum, and an increase of calcium content in the adrenal glands. A single injection of 200 ng/kg of maitotoxin induced a marked increase in total calcium content of the adrenal glands as well as in plasma cortisol concentration (about seven times control) within 1 hr. In contrast, mice pretreated with CoCl2, a calcium channel inhibitor, and/or adrenalectomized mice, showed no discernible changes in the lymphoid tissues after repeated injections of maitotoxin. It is thus suggested that maitotoxin first stimulates calcium influx in the adrenal glands, which then causes the release of cortisol into the blood. The excess amount of cortisol in serum produces acute involution of the thymus and other lymphoid tissues.

Adrenal Cortex↗
PubMed1988

Active potassium extrusion regulated by intracellular pH in Streptococcus faecalis.

Potassium extrusion in bacteria is thought to play a role in the regulation of the cytoplasmic pH; in several organisms, it has been ascribed to secondary antiport of K+ for protons. Streptococcus faecalis exhibited a distinctive pattern: potassium extrusion occurred only when the cytoplasmic pH was alkaline and required the generation of ATP. The key observation is that glycolyzing cells suspended in an alkaline medium extruded K+, even against a K+ concentration gradient, provided the medium contained a weak permeant base (e.g. diethanolamine or methylamine). The amines render the cytoplasmic pH alkaline; when conditions were arranged to keep the cytoplasm neutral, no K+ extrusion was seen. Potassium extrusion required the presence of either glucose or arginine and was unaffected by protonophores and by inhibition of the F1Fo-ATPase. When the medium contained [14C]methylamine, the cells accumulated the base to an extent stoichiometrically equivalent to the K+ lost. Concurrently, the cytoplasmic pH fell from 8.8 to 7.6, at which point K+ extrusion ceased. The results suggest that K+ extrusion is due to an ATP-driven transport system that expels K+ by exchange for H+ and is active only at alkaline cytoplasmic pH.

Adenosine Triphosphate↗
PubMed1988

Characterization of the inducible polyamine transporter in bovine lymphocytes.

The polyamine uptake system in bovine lymphocytes was activated by concanavalin A. The system was common to putrescine, spermidine and spermine. The Kt values for uptake activities of putrescine, spermidine and spermine were 3.7 microM, 0.38 microM and 0.23 microM in that order. The uptake activity was inhibited by carbonyl cyanide m-chlorophenylhydrazone, gramicidin D or valinomycin in the presence of 20 mM K+ suggesting that polyamine uptake depends on the membrane potential. The uptake activity appeared 10 h after addition of concanavalin A, and the maximum was reached at 28 h indicating that induction of the polyamine transporter precedes the initiation of DNA synthesis. Addition of polyamine antimetabolites, such as alpha-difluoromethylornithine and ethylglyoxal bis(guanylhydrazone), to the medium enhanced at least eightfold the induction of the polyamine transporter. The induction was repressed by addition of 50 microM spermidine or spermine, but not putrescine. We propose here that the induction of the membrane-potential-dependent polyamine transporter is regulated by the intracellular level of spermidine and spermine.

Animals↗
PubMed1987

Relationship among activation of the Na+/H+ antiporter, ornithine decarboxylase induction, and DNA synthesis.

The relationship among activation of the Na+/H+ antiporter, ornithine decarboxylase, and DNA synthesis was examined with bovine small lymphocytes stimulated by concanavalin A (Con A). The Na+/H+ antiport activity was activated immediately after addition of concanavalin A; the maximum was reached 1 h after Con A addition and the activation continued at least 6 h. With increasing concanavalin A concentrations, the activities of the Na+/H+ antiporter, ornithine decarboxylase, and DNA synthesis increased in a parallel manner. In the presence of HCO3- in the medium, the internal alkalinization of lymphocytes was not induced by Con A. Ornithine decarboxylase and DNA synthetic activities were not inhibited by 5-(N-ethyl-N-isopropyl) amiloride (EIPA), a specific inhibitor of the Na+/H+ antiporter. In contrast, in the absence of HCO3- in the medium, the internal pH was alkalinized approximately 0.06 pH units by Con A. EIPA did inhibit the alkalinization of the internal pH or DNA synthesis significantly. Ornithine decarboxylase activity was not inhibited by EIPA. These results indicate that the activation of a Na+/H+ antiporter is not a trigger for cell proliferation, but its activation is important probably through the maintenance of the internal pH optimum, especially in HCO3(-)-free medium.

Animals↗
PubMed1987

Sodium/proton antiporter in Streptococcus faecalis.

Streptococcus faecalis, like other bacteria, accumulates potassium ions and expels sodium ions. This paper is concerned with the pathway of sodium extrusion. Earlier studies (D.L. Heefner and F.M. Harold, Proc. Natl. Acad. Sci. USA 79:2798-2802, 1982) showed that sodium extrusion is effected by a primary, ATP-linked sodium pump. I report here that cells grown under conditions in which sodium ATPase is not induced can still expel sodium ions. This finding suggested the existence of an alternate pathway. Sodium extrusion by the alternate pathway requires the cells to generate a proton motive force. This conclusion rests on the following observations. (i) Sodium extrusion required glucose. (ii) Sodium extrusion was observed at neutral pH, which allows the cells to generate a proton motive force, but not at alkaline pH, which reduces the proton motive force to zero. (iii) Sodium extrusion was inhibited by the addition of dicyclohexylcarbodiimide and of proton-conducting ionophores. (iv) In response to an artificial pH gradient (with the exterior acid), energy-depleted cells exhibited a transient sodium extrusion which was unaffected by treatments that dissipated the membrane potential and which was blocked by proton conductors. I propose that streptococci have two independent systems for sodium extrusion: an inducible sodium ATPase and a constitutive sodium/proton antiporter.

Carrier Proteins↗
PubMed1987

Lowering of cytoplasmic pH is essential for growth of Streptococcus faecalis at high pH.

The growth of Streptococcus faecalis at high pH was significantly stimulated by carbonate. In the absence of added carbonate the cells were unable to grow at a pH above 9.5, but in media containing 50 mM HCO3- they grew even at pH 10.5. Both rate and yield of growth at pH 9.5 were significantly stimulated by as little as 5 mM carbonate. The cytoplasmic pH in growing cells was maintained at about 7.8 to 8.2, whereas the medium pH ranged from 8.4 to 9.5. Nigericin and gramicidin D, ionophores which conduct protons, blocked growth at pH 9.5 but not at pH 7.5. These results indicate that lowering of the cytoplasmic pH is essential for the growth of this organism at high pH.

Carbonates↗
PubMed1986

[Mitral stenosis of the postoperative state evaluated by echocardiography].

Echocardiography was performed to compare pre- and postoperative findings and to evaluate the postoperative state in 109 patients with mitral stenosis (MS) including 22 who underwent closed mitral commissurotomy (CMC) (34.3 +/- 6.9 y.o.); 71, open mitral commissurotomy (OMC) (42.9 +/- 8.7 y.o.); and 16, mitral valve replacement (MVR) (44.5 +/- 8.9 y.o.). Echocardiographic examinations were performed using a Toshiba SSL-51H with a mechanical sector scanner or an SSH-11A with a phased-array electronic sector scanner, one or two weeks before and about one month after surgery, and were reviewed yearly. The results were as follows: The E-F slope of the anterior mitral leaflet (AML) and mitral valve orifice area (MVA) were significantly increased after cardiac surgery in both the CMC and OMC groups. The amplitude of the mitral valve was slightly increased in the CMC group, but was unchanged in the OMC group. Before surgery, the left atrial dimension (LAD) was larger in the MVR group than in the other two groups, and it was significantly decreased after surgical intervention in all three groups. The aortic dimension (AOD) was slightly increased in the majority of patients, and the ratio of the aortic dimension to the sum of the aortic and left atrial dimensions [AOD/(AOD + LAD)] was significantly increased after cardiac surgery due to the improvement of cardiac function and the resolution of the left atrial enlargement. Repeated echocardiography facilitated follow-up of the state of the mitral valve and of cardiac performance, and is considered useful in determining indication for reoperation.

Adult↗
PubMed1985

ATP-driven exchange of Na+ and K+ ions by Streptococcus faecalis.

We describe the characterization of KtrII, a novel potassium transport system of Streptococcus faecalis, first discovered by H. Kobayashi [1982) J. Bacteriol. 150, 506-511). KtrII requires sodium ions and mediates the stoichiometric exchange of internal Na+ for external K+. Potassium accumulation is not energized by the electrochemical potentials of either H+ or Na+; the energy source is probably ATP. Two lines of evidence indicate that KtrII is a manifestation of the sodium-stimulated ATPase reported earlier (Heefner, D. L., and Harold, F. M. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 2798-2802). (i) Mutants that lack the ATPase also lack KtrII, and revertants recover both in parallel. (ii) KtrII and the Na+-ATPase are induced in parallel when cells are grown on media rich in sodium, particularly under conditions that limit the generation of a proton potential. KtrII is not induced in response to K+ deprivation. We propose that the Na+-ATPase exchanges Na+ for K+ ions.

Adenosine Triphosphatases↗
PubMed1985

Sucrose uptake is driven by the Na+ electrochemical potential in the marine bacterium Vibrio alginolyticus.

Na+ was found to be essential for the accumulation of sucrose by Vibrio alginolyticus. Sucrose uptake was completely inhibited by the addition of proton conductor at neutral pH, but not at alkaline pH, where the primary electrogenic Na+ pump generates the Na+ electrochemical gradient. We therefore conclude that sucrose transport is driven by the electrochemical potential of Na+ in this organism.

Biological Transport↗
PubMed1981

Properties of H+-translocating adenosine triphosphatase in vacuolar membranes of SAccharomyces cerevisiae.

The properties of Mg2+-ATPase in the vacuole of Saccharomyces cerevisiae were studied, using purified intact vacuoles and right-side-out vacuolar membrane vesicles prepared by the method of Y. Ohsumi and Y. Anraku ((1981) J. Biol. Chem. 256, 2079). The enzyme requires Mg2+ ion but not Ca2+ in. Cu2+ and Zn2+ ions inhibit the activity. The optimal pH is at pH 7.0. The enzyme hydrolyzes ATP, GTP, UTP, and CTP in this order and the Km value for ATP was determined as 0.2 mM. It does not hydrolyze ADP, adenosyl-5'-yl imidodiphosphate, or p-nitrophenyl phosphate. ADP does not inhibit hydrolysis of ATP by the enzyme. The activities of intact vacuoles and of vacuolar membrane vesicles were stimulated 3- and 1.5-fold, respectively, by the protonophore uncoupler 3,5-di-tert-butyl-4-hydroxybenzilidenemalononitrile and the K+/H+ antiporter ionophore nigericin. Sodium azide at a concentration exerting an uncoupler effect also stimulated the activity. The activity was sensitive to the ATPase inhibitor N,N'-dicyclohexylcarbodiimide, but not to sodium vanadate. The ATP-dependent formation of an electrochemical potential difference of protons, measured by the flow-dialysis method, was determined as 180 mV, with contribution of 1.7 pH units, interior acid, and of a membrane potential of 75 mV. It is concluded that the Mg2+-ATPase of vacuoles is a new marker enzyme for these organelles and is a N,N'-dicyclohexylcarbodiimide-sensitive, H+-translocating ATPase whose catalytic site is exposed to the cytoplasm.

Adenosine Triphosphatases↗
PubMedDate not supplied

Fundamental rhythm of sympathetic nerve discharges in animals with total artificial hearts.

To evaluate the effect of total artificial heart replacement on the autonomic nervous system, sympathetic neurograms were analyzed by power spectrum and coherence function. Two pneumatically driven, sac type ventricular assist devices were implanted as biventricular bypasses (BVB) in adult, mongrel dogs. After initiation of BVB pumping, the natural heart was electrically fibrillated to form a BVB TAH model. Renal sympathetic nerve activity (RSNA) was recorded using a bipolar electrode attached to the left renal sympathetic nerve. RSNA was amplified and integrated by use of an R-C integrator. Power spectra of the RSNA and values of squared coherence between the arterial pressure wave form and the RSNA were calculated by computer. In animals with total artificial hearts (TAHs), coherence at the cardiac rhythm frequency was decreased, and coherence at the TAH pumping rhythm frequency was increased. These results indicate that the arterial pulse wave observed in TAH animals contributed to the sympathetic neurogram.

Animals↗
PubMedDate not supplied

Deterministic chaos in the hemodynamics of an artificial heart.

To analyze the hemodynamic parameters during prosthetic circulation as an entity, non linear mathematical techniques were used. To compare natural and prosthetic circulation, two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses in chronic animal experiments using adult goats to consitute the biventricular bypass complete prosthetic circulation model with ventricular fibrillation. After implantation, these goats were placed in a cage and extubated after waking. All hemodynamic parameters with the natural circulation without biventricular bypass pumping, and the artificial circulation with biventricular bypass pumping under ventricular fibrillation were recorded under awake conditions. By the use of a non linear mathematical technique, the arterial blood pressure waveform was embedded into a four dimensional phase space and projected into three dimensional phase space. The Lyapunov numeric method is used as an adjunct to the graphic analysis of the state space. A phase portrait of the attractor showed a high dimension complex structure, with three dimensional solid torus suggesting deterministic chaos during natural circulation. However, a simple attractor, such as a limit cycle attractor, was observed during artificial circulation. Positive Lyapunov exponents during artificial circulation suggest the lower dimensional chaotic system. Thus, hemodynamic parameters during prosthetic circulation must be carefully controlled when unexpected stimuli are fed from outside.

Animals↗