Biomedical subjects

H Kosaka

Publications and source records attributed to H Kosaka.

At least 91 records · Page 5Linked to original sources

PubMed1997

Cloning, functional expression and tissue distribution of rabbit alpha1a-adrenoceptor.

A cDNA clone, which has an open reading frame of 1398 nucleotides encoding a 466-amino-acid peptide, has been isolated from rabbit liver cDNA library. Compared with the peptide sequence, it shows high homology to alpha1a adrenoceptors of human, bovine and rat. We expressed this clone in COS-7 and investigated the pharmacological properties, revealing similarity to those of human alpha1a adrenoceptors. Competitive RT/PCR has detected the mRNA in variety of rabbit tissues, especially abundantly in liver, vas deferens, brain, and aorta, but not in heart.

Amino Acid Sequence↗

PubMed1997

Elevation of oxygen release by nitroglycerin without an increase in blood flow in the hepatic microcirculation.

The effect of nitroglycerin on oxygen (O2) release in the microcirculation was investigated by examining single, unbranched hepatic sinusoids of rats using dual-spot microspectroscopy. Nitroglycerin significantly increased O2 release from erythrocytes flowing in the sinusoids. Differences in O2 saturation of hemoglobin per unit length of the sinusoid were significantly enhanced, while there were no significant changes in erythrocyte velocity, hemoglobin concentration or oxyhemoglobin flow into the sinusoids, or in regional hepatic blood flow measured with a laser tissue blood flow meter. No change was noted for hepatic O2 consumption measured in isolated liver perfused with hemoglobin-free oxygenated buffer. Isosorbide dinitrate showed a similar but slower effect. These findings suggest that nitroglycerin and isosorbide dinitrate enhance O2 release from erythrocytes without significantly increasing tissue blood flow.

Animals↗

PubMed1997

Roles of NO and Ca2+-activated K+ channels in coronary vasodilation induced by 17beta-estradiol in ischemic heart failure.

Estrogen induces the generation of nitric oxide (NO) and produces coronary vasodilation by opening the Ca2+-activated K+ (K[Ca]) channels. The hypothesis that 17beta-estradiol produces NO and activates K(Ca) channels during coronary hypoperfusion was investigated. In open-chest dogs, the left anterior descending coronary artery was perfused through an extracorporeal bypass tube from the left carotid artery. 17beta-Estradiol was infused into the bypass tube for 20 min after coronary blood flow was reduced by partial occlusion of the bypass tube. 17beta-Estradiol increased the difference in NO concentrations between the coronary venous and arterial blood as well as coronary blood flow. The lactate extraction ratio and pH of coronary venous blood were both also increased by 17beta-estradiol, indicating a reduction in myocardial anaerobic metabolism. Whereas the increase in the coronary arteriovenous difference in NO concentration was completely attenuated by N(G)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase), the increase in coronary blood flow induced by 17beta-estradiol was only partially attenuated by L-NAME. The combination of L-NAME and iberiotoxin (a blocker of high-conductance K(Ca) channels) completely abolished the coronary vasodilatory effect of 17beta-estradiol. The data indicate that during coronary hypoperfusion in canine hearts, 17beta-estradiol increases coronary blood flow and improves metabolic dysfunction by increasing NO release and opening K(Ca) channels.

Animals↗

PubMed1997

Reduced plasma concentrations of nitrogen oxide in individuals with essential hypertension.

Patients with essential hypertension exhibit blunted endothelium-dependent vasodilator responses, which may be largely attributable to reduced bioactivity of nitric oxide (NO). Therefore, we measured the end product of NO, nitrate plus nitrite (nitrogen oxide), and examined the relationship between the degree of hypertension and plasma nitrate plus nitrite levels in patients with essential hypertension. The combined plasma concentration of nitrate plus nitrite, end products of NO metabolism, was reduced in individuals with essential hypertension relative to that in control subjects (15.7+/-1.1 versus 22.8+/-1.4 mmol x L(-1), P<.001); individuals with borderline hypertension showed values that were intermediate between those of the other two groups (18.2+/-1.2 mmol x L(-1), P<.001). The plasma nitrogen oxide concentration showed significant inverse correlations with both systolic and diastolic blood pressures. The basal concentration of nitrogen oxide in the plasma was reduced, at least in the peripheral circulation, in individuals with essential hypertension.

Female↗

PubMed1997

[Serum bone Gla-protein increases following short-term oral administration of active vitamin D3 in the elderly with vitamin D deficiency].

Serum bone Gla-protein (BGP) is produced by osteoblasts in a vitamin K-dependent process. It is well known that serum BGP levels increase after oral administration of active vitamin D3 in postmenopausal women and patients with chronic renal failure before dialysis. These findings indicate that active vitamin D3 increases the BGP production by osteoblasts. In the present study, a daily oral dose of 2 micrograms of 1 alpha (OH)D3 was administered to 10 elderly males (age, 75.0 +/- 10.9 years) and 8 young males (age, 29.0 +/- 3.2 years) to compare the changes in serum BGP levels between the two groups. None of the subjects had severe renal or hepatic dysfunction or abnormalities in calcium (Ca) metabolism. Serum BGP and 1,25(OH)2D levels in both groups were measured before the initial administration, at 24 h and at 1, 2 and 3 weeks after the start of administration. Serum parathyroid hormone (m-PTH), alkaline phosphatase (ALP), Ca and phosphorus levels were also measured in the elderly group. Serum BGP levels before the initial administration were 4.63 +/- 1.8 ng/ml in the elderly group and 4.33 +/- 0.92 ng/ml in the young group, with no significant difference between the two groups. In both group serum 1,25(OH)2D levels were slightly increased at 24 h after administration. In the elderly group serum BGP levels increased significantly to 11.5 +/- 3.0 ng/ml, an increase of approximately 250%, 1 week after the initial administration and the increase was maintained for up to 3 weeks after the administration commenced. However, no changes in serum BGP levels were noted in the young group. In the elderly group serum m-PTH levels were 544 +/- 257 pg/ml, almost the upper normal limit, before, and decreased slightly after, the administration of 1 alpha (OH)D3. Serum ALP levels also decreased slightly after the administration and serum Ca levels were slightly increased, however, the changes were within normal limits. We conclude that osteoblastic function is activated after short-term administration of active vitamin D3 in vitamin D deficient elderly subjects.

Administration, Oral↗

PubMed1997

Rat stem cells developing in irradiated SCID mice fail to become tolerized and cause lethal graft-versus-host disease.

Graft-versus-host disease (GVHD) is prominent in irradiated hosts given whole allogeneic bone marrow cells but is generally undetectable when T-depleted stem cells are transferred; under these conditions, the mature T cells arising from the donor stem cells become tolerant to host antigens and fall to cause GVHD. We show here that a radically different situation can occur when hosts are reconstituted with xenogeneic stem cells. When lightly irradiated, adult C.B-17 SCID mice injected with Lewis rat fetal liver (FL) cells show near-total repopulation with rat-derived lymphohemopoietic cells, including T and B cells. However, in marked contrast to chimeras prepared with allogeneic mouse FL cells, rat FL-->SCID chimeras develop severe and often lethal chronic GVHD. In these rat-->mouse chimeras, the rat T cells show limited tolerance to host mouse antigens as determined by various parameters including mixed lymphocyte reaction and cytotoxic T lymphocyte assays in vitro, adoptive transfer of T cells to secondary SCID hosts, and the lack of V beta deletion to endogenous host mtv antigens. GVHD in irradiated rat-->SCID chimeras is most prominent with Lewis FL but also applies to Fisher 344 and Wistar Furth FL cells. The failure of newly formed rat T cells in rat-->SCID chimeras to become fully tolerant to host mouse antigens appears to be due to depletion of host antigen-presenting cells by irradiation. Thus, rat-->SCID chimeras generated by transplanting rat FL cells into unirradiated neonatal SCID mice fail to develop GVHD, and the rat T cells display self-tolerance. As allogeneic H-2-different mouse FL-->irradiated SCID chimeras display strong self-tolerance, presumably through recognition of host antigens on thymic epithelial cells, the implication is that mouse thymic epithelial cells are tolerogenic only for mouse and not for rat immature T cells.

Adoptive Transfer↗

PubMed1997

Absence of mast cell involvement in leukocyte adhesion and emigration induced by inhibition of nitric oxide synthase.

Leukocyte adhesion on venules and their emigration to extravascular connective tissue are induced by administration of a nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester. In the present study, the involvement of mast cells in the process was examined in genetically mast cell-deficient and normal rats by intravital microscopy. Superfusion of the NOS inhibitor into the mesentery induced partial degranulation of mast cells in normal rats. However, leukocyte adhesion on mesenteric venules and emigration to extravascular connective tissue occurred even in mast cell-deficient rats, with no significant difference from the normal rats. When the reverse-passive Arthus reaction, characterized by generalized antigen-antibody complex formation, was induced in the rat mesentery, the immune complex increased both the adhesion and emigration in normal rats but not in mast cell-deficient rats. These results show that mast cells are not involved in the leukocyte adhesion and emigration induced by NOS inhibition, but are in the reverse-passive Arthus reaction.

Animals↗

PubMed1996

Hypothermia suppresses nitric oxide elevation during reperfusion after focal cerebral ischemia in rats.

We aimed to investigate effect of temperature on the jugular levels of nitric oxide (NO) at reperfusion after focal cerebral ischemia. Both nitrosyl hemoglobin (HbNO) (2.5 +/- 0.4 microM) and plasma nitrite plus nitrate levels (61 +/- 5 microM) in rats under normothermia (approximately 37 degrees C) after 30 min of reperfusion following 2 h of left middle cerebral artery occlusion were significantly high, compared with sham operated rats (1.3 +/- 0.1 microM, 40 +/- 4 microM, respectively). Both HbNO (1.5 +/- 0.3 microM) and nitrite plus nitrate levels (43 +/- 7 microM) under moderate hypothermia (approximately 32 degrees C) were significantly low, compared with normothermic rats. HbNO (2.8 +/- 0.8 microM) and nitrite plus nitrate levels (65 +/- 8 microM) under mild hyperthermia (approximately 39 degrees C) were not significantly high. These results firstly demonstrated that hypothermia suppresses the elevation in intrajugular NO after cerebral ischemia-reperfusion.

Animals↗

PubMed1996

Cardiovascular effects of an ultra-short-acting nitric oxide-releasing compound, zwitterionic diamine/NO adduct, in dogs.

BACKGROUND: This study was conducted to clarify the cardiovascular effects of a new NO-releasing compound, NOC-7, and to compare it with other nitrovasodilators, sodium nitroprusside (SNP) and nitroglycerin, in dogs anesthetized with pentobarbital. METHODS AND RESULTS: A bolus injection of NOC-7 decreased mean aortic blood pressure in a dose-dependent manner. The onset was rapid and the recovery quick. Continuous infusion of NOC-7 decreased mean aortic pressure from 115 +/- 3.9 to 84 +/- 2.9 mm Hg and infusion of SNP, from 118 +/- 3.8 to 87 +/- 3.1 mm Hg. The optimum doses of NOC-7 and SNP were determined to be 2.73 +/- 0.77 and 11.5 +/- 6.1 micrograms.kg-1.min-1, respectively. During infusion of NOC-7, heart rate and cardiac output were increased (P < .05), pulmonary artery pressure was not changed, and systemic and pulmonary vascular resistances were decreased (P < .05). Electromagnetic flowmetry showed that portal venous and internal carotid arterial blood flow were increased (P < .05) and that hepatic and renal arterial blood flows were not changed. These hemodynamic changes during NOC-7 infusion were similar to those with SNP. The plasma level of NO2-/NO3 did not change, but methemoglobin increased slightly (P < .05). Comparison between hypotensive responses before and after a 3.5-hour infusion of NOC-7 or nitroglycerin showed that acute tolerance developed to nitroglycerin but not to NOC-7. CONCLUSIONS: The results indicate that NOC-7 may be useful as an ultra-short-acting nitrovasodilator that has no major adverse effect or tolerance.

Animals↗

PubMed1996

Constitutive class I-restricted exogenous presentation of self antigens in vivo.

Ovalbumin (OVA)-specific CD8+ T cells from the T cell receptor-transgenic line OT-I (OT-I cells) were injected into unirradiated transgenic RIP-mOVA mice, which express a membrane-bound form of OVA (mOVA) in the pancreatic islet beta cells and the renal proximal tubular cells. OT-I cells accumulated in the draining lymph nodes (LN) of the kidneys and pancreas and in no other LN. They displayed an activated phenotype and a proportion entered cell cycle. Unilateral nephrectomy 7-13 d before inoculation of OT-I cells into RIP-mOVA mice allowed the injected T cells to home only to the regional LN of the remaining kidney (and pancreas), but when the operation was performed 4 h before injecting the T cells, homing to the LN of the excised kidney was evident. When the bone marrow of RIP-mOVA mice was replaced with one of a major histocompatibility haplotype incapable of presenting OVA to OT-I cells, no homing or activation was detectable. Therefore, OT-I cells were activated by OVA presented by short-lived antigen-presenting cells of bone marrow origin present in the draining LN of OVA-expressing tissue. These results provide the first evidence that tissue-associated "self" antigens can be presented in the context of class I via an exogenous processing pathway. This offers a constitutive mechanism whereby T cells can be primed to antigens that are present in nonlymphoid tissues, which are not normally surveyed by recirculating naive T cells.

Animals↗

PubMed1996

Physiological role of nitric oxide as an enhancer of oxygen transfer from erythrocytes to tissues.

The present study revealed the physiological role of NO as an enhancer of oxygen release from erythrocytes to peripheral tissue by breaking or stretching the heme iron-proximal histidine bond in the alpha subunit of hemoglobin (Hb), while maintaining oxygen binding capacity by restoring the bond in the lungs. Oxygen affinity was significantly decreased in blood containing NO-bound Hb alpha. The results may partly explain nitrosothiols in blood as an NO reservoir for an emergency and why cytokines induce NO synthase in the vascular system during such events as inflammation.

Animals↗

PubMed1996

Increased release of NO during ischemia reduces myocardial contractility and improves metabolic dysfunction.

BACKGROUND: We have reported that myocardial ischemia increases nitric oxide (NO) production. Several lines of evidence suggest that NO reduces myocardial contraction. Therefore, we tested whether endogenous NO decreases the inotropic response of the ischemic myocardium and whether endogenous NO is beneficial in the metabolic function of ischemic myocardium. METHODS AND RESULTS: The left anterior descending coronary artery was perfused with blood from the left carotid artery in 72 dogs. An infusion of NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, did not affect fractional shortening (FS) under nonischemic conditions. After reduction of perfusion pressure so that coronary blood flow decreased to 60% of the control value, FS of the perfused area decreased, and intravenous infusion of isoproterenol increased FS. Before and during intravenous infusion of isoproterenol under conditions of coronary hypoperfusion, FS was significantly increased in the L-NAME group compared with the untreated group. Both lactate extraction ratio and the pH in coronary venous blood were significantly lower in the L-NAME-treated group than in the untreated group during coronary hypoperfusion. Infusion of L-arginine prevented the effects of L-NAME in the ischemic myocardium. CONCLUSIONS: These results indicate that endogenous NO reduces myocardial contractile function and improves myocardial metabolic function in the ischemic heart. The myocardial energy-sparing effect as well as coronary vasodilation due to NO may be beneficial to the ischemic myocardium.

Animals↗

PubMed1996

Effect of hypothermia on skeletal muscle metabolism in perfused rat hindlimb.

Temperature-induced metabolic change was studied with isolated rat hindlimb muscle to elucidate how tissue viability is maintained under hypothermia. The hindlimb was perfused with Krebs-bicarbonate buffer containing 4% (w/v) polyvinylpyrrolidone (PVP-40T) in a flowthrough mode at 35-8 degrees C. When the temperature was lowered, the following results were observed: (i) Vascular resistance (defined as perfusion pressure divided by flow rate) increased proportionally with elevation of the viscosity of the perfused medium, suggesting that the capillary bed in the perfused muscle is maintained under a similar condition under these temperatures; (ii) the Arrhenius plot of the O2 uptake rate showed a break at ca. 20 degrees C; (iii) the rates of O2 uptake and lactate release decreased, but the lactate/pyruvate ratio increased even under aerobic conditions; (iv) oxygenation of myoglobin and oxidation of cytochromes increased, suggesting a reduced electron-transfer rate in spite of improved or sufficient oxygenation of the tissue. Based on these results, we concluded that oxidative phosphorylation is more affected by temperature than glycolysis, and thus under hypothermia, the role of glycolysis in energy production increases in rat skeletal muscle, especially below 20 degrees C.

Adenosine Triphosphate↗

PubMed1996

Role of nitric oxide in regulation of coronary blood flow during myocardial ischemia in dogs.

OBJECTIVES: This study was undertaken to examine whether nitric oxide released in ischemic myocardium decreases the coronary vascular resistance and attenuates the severity of contractile and metabolic dysfunction. BACKGROUND: Endothelium-derived relaxing factor, recently identified as nitric oxide, is a potent relaxant of coronary smooth muscle. METHODS: The left anterior descending coronary artery was perfused through an extracorporeal bypass tube placed in the carotid artery in 56 open chest dogs. After hemodynamic stabilization, we occluded this bypass tube to decrease coronary blood flow to one third of the control flow. Thereafter, we maintained a constant coronary perfusion pressure (40.9 +/- 3.1 mm Hg). RESULTS: Under ischemic conditions, the coronary arteriovenous differences in nitrate and nitrite (end products of nitric oxide) increased (from 3.5 +/- 0.4 [mean +/- SEM] to 12.9 +/- 2.1 mumol/liter, p < 0.01). NG-Monomethyl L-arginine (3 micrograms/kg body weight per min, intracoronary) decreased the coronary arteriovenous differences in nitrate and nitrite (5.0 +/- 0.9 mumol/liter, p < 0.05) and coronary blood flow (from 29.8 +/- 0.5 to 18.1 +/- 1.1 ml/100 g per min, p < 0.001). Fractional shortening (from 3.7 +/- 1.0 to -1.3 +/- 0.7%, p < 0.001) and lactate extraction ratio (from -44.0 +/- 4.1 to -59.2 +/- 4.9%, p < 0.005) of the perfused area also decreased. These values were restored by the concomitant administration of L-arginine. Blood flow to the endomyocardium was decreased relative to the epimyocardium. A reduction in coronary blood flow and worsening of myocardial contractile and metabolic functions due to the administration of NG-monomethyl L-arginine during ischemia were observed in denervated hearts. A reduction in coronary blood flow in ischemic myocardium was observed with the administration of NW-nitro-L-arginine methyl ester as well, although neither NW-nitro-L-arginine methyl ester nor NG-monomethyl L-arginine changed coronary blood flow and myocardial contractile and metabolic functions in the nonischemic myocardium. The cyclic guanosine monophosphate content of epicardial coronary artery increased due to myocardial ischemia; this increase was attenuated with NG-monomethyl L-arginine treatment. CONCLUSIONS: We conclude that endogenous nitric oxide predominantly decreases the coronary vascular resistance of ischemic endomyocardium, thereby improving myocardial contractility and metabolic function.

Animals↗

PubMed1996

Dual function of Drosophila cells as APCs for naive CD8+ T cells: implications for tumor immunotherapy.

With unseparated mouse spleen cells as responders, Drosophila cells expressing MHC class I (L(d)) molecules alone lead to peptide-specific responses of CD8+ cells in the absence of exogenous cytokines. Under these conditions, DNA released from dying cells stimulates the B cells in spleen to up-regulate costimulatory molecules; these activated B cells then provide bystander costimulation for CD8+ cells responding to class I-peptide complexes on the Drosophila APCs. By stimulating B cells and presenting antigen to T cells, Drosophila cells thus serve two different functions in promoting primary responses of CD8+ cells in vitro. With this system, we show that Ld-transfected Drosophila cells are able to induce autologous spleen cells to respond to a tumor-specific peptide in vitro and, after transfer, cause tumor rejection in vivo.

Animals↗

PubMed1996

Generation of nitric oxide and superoxide during reperfusion after focal cerebral ischemia in rats.

We investigated the levels of nitrosyl hemoglobin (HbNO) in rat jugular blood by electron spin resonance (ESR) spectroscopy during and after middle cerebral artery occlusion. The levels of plasma nitric oxide (NO) end products, nitrate plus nitrate, were compared with the levels of HbNO. Small amounts of HbNO were detected in sham-operated rats (n=4) and those subjected to 2 h of occlusion (n=4), whereas nitrite plus nitrate was increased only in the latter (P<0.01; vs.sham). Upon reperfusion after 2 h of occlusion both HbNO and nitrite plus nitrate clearly increased after 15 min (n=4) and 30 min (n=6) reperfusion (P<0.01; vs.occlusion). Administration of superoxide dismutase (5 mg/kg) significantly increased HbNO (P<0.05) but not plasma nitrate plus nitrate (n=5). The increase in HbNO suppressed by administration of NG-nitro-L-arginine methyl ester (20mg/kg; n=4,P<0.01), and this suppression could be reversed by L-arginine (200 mg/kg) (n=4). The present study clearly showed that the L-arginine-NO synthase pathway was activated during reperfusion after focal cerebral ischemia and indicated the involvement of a reaction between NO and superoxide during early reperfusion.

Animals↗

PubMed1996

Detection of nitric oxide production and its role in pancreatic ischemia-reperfusion in rats.

Partial ischemia of rat pancreas body and tail was obtained by occlusion of the celiac axis for 1 h after gastrectomy. The plasma level of nitrite plus nitrate in both systemic and portal venous blood after reperfusion was significantly higher than that after sham operation and ischemia alone. The elevation after reperfusion was significantly decreased by NG-nitro-L-arginine methyl ester (L-NAME). Simultaneous administration of L-arginine counteracted the L-NAME-induced decrease in the level of nitric oxide (NO) end products. Generation of NO was further demonstrated by nitrosylhemoglobin detection by electron spin resonance in the blood after reperfusion. On the other hand, the plasma level of lipase, a marker of damage to pancreatic exocrine tissue, was significantly increased after ischemia-reperfusion and further increased by administration of L-NAME. This increase in lipase correlated with a decrease in tissue blood flow in the pancreas. These results suggest that NO is generated during and may have a protective role in ischemia-reperfusion of the rat pancreas.

Animals↗

PubMed1996

Involvement of ICE family proteases in apoptosis induced by reoxygenation of hypoxic hepatocytes.

Cell death due to reoxygenation after hypoxia was characterized in primary cultured hepatocytes. Fluorescence and electron microscopic analyses of reoxygenated hepatocytes revealed morphological characteristics of apoptosis, including chromatin condensation, nuclear fragmentation, and formation of apoptotic bodies. Few necrotic hepatocytes, defined by loss of plasma membrane integrity, mitochondrial swelling, and formation of large vacuoles, were observed. Activation of interleukin-1 beta-converting enzyme (ICE)-like and CPP32/Yama-like proteases, which are known to drive apoptosis, was observed during reoxygenation, and addition of their respective inhibitors inhibited the induction of apoptosis, indicating the involvement of ICE family proteases in apoptosis by reoxygenation. Production of oxygen radicals was enhanced by reoxygenation of hypoxic cells, and reoxygenation-induced apoptosis was inhibited by oxygen radical scavengers, suggesting a role for reactive oxygen species as a triggering factor in cell death. Electrophoretic analysis revealed the presence of 50-kb DNA fragments but not oligonucleosomal DNA fragments in reoxygenation-induced apoptotic hepatocytes.

Animals↗