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Biomedical subjects

T Kamada

Publications and source records attributed to T Kamada.

At least 19 recordsLinked to original sources
PubMed1992

Influence of oxidative stress on induced tolerance to ischemia in gerbil hippocampal neurons.

We investigated whether reversible oxidative stress induced by the administration of the superoxide dismutase inhibitor, diethyldithiocarbamate, could induce tolerance to subsequent cerebral ischemia in gerbil hippocampal neurons. Mature male gerbils received intraperitoneal injections of diethyldithiocarbamate (1.0 g/kg), which led to reduced superoxide dismutase activity and increases in thiobarbituric acid-reactive substance in the brain. Cerebral ischemia was produced by occluding the bilateral common carotid arteries for 5 min, either 2 or 4 days after diethyldithiocarbamate injection. One week after ischemia, samples from each brain were stained with hematoxylin-eosin to evaluate ischemic neuronal damage in the hippocampal CA1 sector. Diethyldithiocarbamate treatment 4 days before ischemia had significant protective effects against cerebral ischemia, while diethyldithiocarbamate 2-day pretreatment and vehicle treatment failed to show neuroprotection. Biochemical examinations showed a clear induction of heat shock protein 72 and a significant increase in manganese-containing superoxide dismutase in the hippocampus in animals treated with diethyldithiocarbamate 4 days prior to ischemia. These results suggested that the oxidative stress caused by diethyldithiocarbamate could induced tolerance to ischemia in the gerbil brain, and that the increase in the biosynthesis of manganese-containing superoxide dismutase and heat shock protein 72 could provide a biochemical explanation of the tolerance induced under these conditions.

Animals↗
PubMed1992

cDNA cloning of rat LRP, a receptor like protein tyrosine phosphatase, and evidence for its gene regulation in cultured rat mesangial cells.

Protein tyrosine phosphatases (PTPases) are a family of enzymes that play a crucial role in the regulation of signal transduction mediated by reversible protein tyrosine phosphorylation. To understand the significance of PTPases in physiological and pathophysiological processes in the kidney, we isolated three cDNA segments encoding PTPases (LAR, LRP and a novel PTPase) from rat kidney by polymerase chain reaction (PCR). Using PCR product as a probe, we isolated a full-length cDNA of rat LRP. LRP cDNA encoded a single membrane spanning protein consisted of 796 amino acids, with two tandemly located intracellular PTPase domains. By Northern analysis, a ubiquitous pattern of LRP gene expression in rat tissues was demonstrated. In cultured rat mesangial cells, LRP mRNA was detected and the mRNA level was suppressed by either interleukin-1 or interleukin-6 treatment.

Amino Acid Sequence↗
PubMed1992

Enhancement of hepatitis-B surface-antigen expression by 5-azacytidine in a hepatitis-B-virus-transfected cell line.

The human hepatoblastoma-derived cell line HB611 secretes hepatitis-B surface antigen (HBsAg) and hepatitis-B e antigen (HBeAg) into the medium. Hepatitis-B-virus (HBV) DNA integrated into the cellular genome was found to be hypermethylated. When the cells were treated with 5-azacytidine for 3 days, the level of HBsAg in the medium increased, while the level of HBeAg remained constant. The level of alpha-fetoprotein (AFP) decreased with the 5-azacytidine treatment. Southern blot analysis of DNA digested with HpaII or MspI showed that 5-azacytidine treatment resulted in hypomethylation of the integrated HBV DNA, suggesting that 5-azacytidine increased HBsAg production in the cells through hypomethylation of the HBV genomic DNA.

Azacitidine↗
PubMed1992

Ammonia: a possible promotor in Helicobacter pylori-related gastric carcinogenesis.

Helicobacter pylori (HP) has been shown to possibly be a pathogen of gastric carcinoma. HP has urease activity and produces ammonia in the stomach. In this study, the role of ammonia on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in rats. After 24 weeks pretreatment with MNNG (83 mg/l), 0.01% ammonia or tap water as a drinking water was administered for 24 weeks. The ammonia-treated rats showed a significantly higher incidence of gastric cancer (percent of animals with tumors and number of tumors per rat). Ammonia would thus appear to have an important role in HP-related human gastric carcinogenesis.

Adenocarcinoma↗
PubMed1992

Expression of MBP-HCV NS1/E2 fusion protein in E. coli and detection of anti-NS1/E2 antibody in type C chronic liver disease.

To characterize the putative NS1/E2 (non-structural protein 1/envelope 2) domain of HCV (hepatitis C virus), we expressed the hydrophilic three-quarters of this domain in a form of MBP (maltose binding protein) fusions in Escherichia coli. When we checked the positive frequency of antibody to this fusion protein, 17% of patients with type C chronic liver disease had this antibody. However, they were all positive for HCV-RNA in sera. These results suggest that the appearance of anti-NS1/E2 antibody does not serve as evidence of viral clearance.

ATP-Binding Cassette Transporters↗
PubMed1992

Auditory response properties and spatial response areas of single neurons in the pontine nuclei of the big brown bat, Eptesicus fuscus.

Using free-field acoustic stimulation conditions, we studied the response properties and spatial sensitivity of 146 pontine neurons of the big brown bat, Eptesicus fuscus. The best frequency (BF) and minimum threshold (MT) of a pontine neuron were first determined with a sound broadcast from a loudspeaker placed ahead of the bat. A BF sound was delivered from the loudspeaker as it moved across the frontal auditory space in order to locate the response center at which the neuron had its lowest MT. Then the basic response properties of the neuron to a sound delivered from the response center were studied. As in inferior collicular and auditory cortical neurons, pontine neurons can be characterized as phasic responders, phasic bursters and tonic responders. They have both monotonic and non-monotonic intensity-rate functions. However, most of them are broadly tuned as are cerebellar neurons. Auditory spatial sensitivity was studied for 144 pontine neurons. In 9 neurons, variation of MT with a BF sound delivered from several azimuthal and elevational angles along the horizontal and vertical planes crossing the neuron's response center was measured. In addition, variation in the number of impulses with several stimulus intensities at 10 dB increments above a neuron's MT delivered from each angle was also studied. The auditory spatial sensitivity of other pontine neurons was studied by measuring the response area of each neuron with stimulus intensities at 3, 5, 10, 15 or 40 dB above its lowest MT. The response areas of pontine neurons expanded asymmetrically with stimulus intensity, but the size of the response area was not correlated with either MT or BF. In half of the pontine neurons studied, the response area expanded greatly and eventually covered almost the entire frontal auditory space. The response areas of the other half of the pontine neurons only expanded to a restricted area of frontal auditory space. Two possible neural mechanisms underlying these two types of response areas are hypothesized. The response centers of all 144 neurons were located within a small area of the frontal auditory space. The locations of response centers of these neurons are not correlated with their BFs. The distribution pattern of these response centers is comparable to that of superior collicular and cerebellar neurons but is different from that of inferior collicular and auditory cortical neurons. The results of our study suggest that auditory information is integrated in the pontine nuclei before being further sent into the cerebellum.

Acoustic Stimulation↗
PubMed1992

Effects of proton pump inhibitor on gastric mucosa hemodynamics and tissue oxygenation in anesthetized rats.

Proton pump inhibitors have been reported to have a cytoprotective action in addition to the anti-secretory action of acid. The precise mechanism, however, remains obscure. In this study, the effects of proton pump inhibitors (omeprazole and NC-1300) on gastric mucosa hemodynamics and tissue oxygenation were investigated using organ reflectance spectrophotometry in a hemorrhagic shock-reperfusion model involving anesthetized rats. Neither drug affected gastric mucosa hemodynamics nor tissue oxygenation in the basal state before hemorrhage. During the hemorrhagic shock state, however, these drugs maintained tissue oxygenation and reduced ulcer formation, although they did not show a significant effect on gastric mucosa blood volume. The results suggest that both proton pump inhibitors have an anti-ulcer action by maintaining mucosal oxygenation in addition to the anti-secretory activity of acid.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1992

Detection of hepatitis C virus RNA in serum of patients with chronic hepatitis C treated with interferon-alpha.

We tested serial serum samples for hepatitis C virus RNA from patients undergoing treatment for chronic hepatitis C with interferon-alpha using an assay that combined reverse transcription and polymerase chain reaction. The subjects studied were 20 patients with chronic hepatitis who had serum antibody to hepatitis C virus (anti-C100-3). Before therapy, hepatitis C virus RNA was detected in 18 (90%) and 20 (100%) patients using primer sets derived from the NS3 region or the 5'-noncoding region of hepatitis C virus, respectively. Hepatitis C virus RNA became undetectable in all patients whose ALT level fell into the normal range during therapy. However, hepatitis C virus RNA reappeared in all patients whose ALT levels rose again after therapy, usually before the relapse. In patients whose ALT levels did not become normal, hepatitis C virus RNA did not disappear during therapy. Thus therapy with interferon-alpha appears to be beneficial in chronic hepatitis C because of its suppressive effects on hepatitis C virus replication. Detection of hepatitis C virus RNA in serum is useful for evaluating the antiviral effect of interferon.

Adult↗
PubMed1992

Detection of the minus strand of hepatitis C virus RNA by reverse transcription and polymerase chain reaction: implications for hepatitis C virus replication in infected tissue.

The combination of reverse transcription and polymerase chain reaction is a very powerful tool for the detection of hepatitis C virus RNA in sera of patients with hepatitis C virus infection. However, when studying the presence of this virus in tissue using polymerase chain reaction, it may be difficult to distinguish between blood viral particles adhering to the tissue and viral RNA contained within the tissue. Because hepatitis C virus has a single-stranded RNA of positive polarity, a minus-strand RNA is expected to be found in hepatitis C virus-replicating tissues as a template for the synthesis of genomic RNA. To see whether the detection of the minus strand of hepatitis C virus RNA by polymerase chain reaction can be used for the determination of hepatitis C virus-replicating tissues, we examined the presence of the minus strand of hepatitis C virus RNA in the plasma, peripheral blood mononuclear cells and liver specimens of patients with hepatitis C virus infection. The plus-strand RNA was detected in the plasma, peripheral blood mononuclear cells and the liver specimens, but the minus-strand RNA was only detected in the liver. These results suggest that hepatitis C virus replicates in the liver but not in peripheral blood mononuclear cells. This detection method for the minus strand of hepatitis C virus RNA should be useful for determining hepatitis C virus replication in tissues other than liver tissue.

Adult↗
PubMed1992

Intracellular calcium as a second messenger for human hepatocyte growth factor in hepatocytes.

Human hepatocyte growth factor is a newly discovered substance that stimulates DNA synthesis in vitro. In this study, we examined intracellular Ca2+ movement as one of the second messengers for human hepatocyte growth factor in primary-cultured hepatocytes. The addition of hHGF induced Ca2+ oscillation, but the frequency of oscillations varied from cell to cell. We also saw marked intercellular heterogeneity in the initial latent period for the Ca2+ response; the mean latent period was rather longer than those seen with phenylephrine and vasopressin. This difference in the initial latent period may be due to the difference in the pathways of Ca2+ elevation. Duration of culture determined the number of human hepatocyte growth factor-responsive cells; their number peaked at 2 to 5 hours of confluent culture, whereas the peak was earlier in a low-density culture. These changes in responsiveness during culture can be explained by the cell cycle-dependent sensitivity to human hepatocyte growth factor of hepatocytes. The Ca2+ response to human hepatocyte growth factor was dose dependent; 10(-10) mol/L hHGF gave the highest Ca2+ response, similar to the dose-response curve of DNA synthesis. We even observed the Ca2+ response in the Ca(2+)-free buffer, so the increase in Ca2+ was considered due to release from intracellular Ca2+ stores. These results suggest that human hepatocyte growth factor causes the intracellular Ca2+ elevation in the early stage of the cell cycle and that it plays important roles in the signal transduction systems for human hepatocyte growth factor and the proliferation of hepatocytes.

Animals↗
PubMed1992

Immunohistochemical detection of hepatitis C virus-infected hepatocytes in chronic liver disease with monoclonal antibodies to core, envelope and NS3 regions of the hepatitis C virus genome.

The localization of hepatitis C virus-infected hepatocytes in the human liver remains unclear despite the development of a serological assay for the antibody to hepatitis C virus. We studied their localization immunohistochemically with monoclonal antibodies to core, envelope and NS3 antigens of hepatitis C virus. We examined 48 liver biopsy samples from C100-3 antibody-positive patients with chronic liver disease (chronic persistent hepatitis, 5 cases; chronic active hepatitis, 41 cases; cirrhosis, 2 cases) and 12 liver biopsy samples from C100-3 antibody-negative patients with chronic liver disease (type B chronic hepatitis, 8 cases; alcoholic liver disease, 4 cases). In the C100-3 antibody-positive group, positive immunostaining for core antigen, envelope antigen and NS3 antigen was found in 23% (11 of 48), 24% (11 of 45) and 24% (11 of 46), respectively. Negative results were obtained in the C100-3 antibody-negative group. Hepatocytes with positive staining were scattered in the lobules, and they were found in the same regions irrespective of whether the antibody to core antigen, to envelope antigen or to NS3 antigen was used. Each positive cell was strongly stained in the cytoplasm; these decorations disappeared after absorption of the primary antibody with purified antigen. mean ALT levels in the patients with positive immunostaining for core, envelope or NS3 antigen (174.8 +/- 105.7 U/L) tended to be higher than in those with negative immunostaining (142.0 +/- 93.8 U/L). On histological evaluation of liver specimens with a scoring system of the histological activity index, intralobular inflammation and fibrosis had higher scores for samples with positive rather than negative immunostaining (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Epidermal growth factor induces dose-dependent calcium oscillations in single fura-2-loaded hepatocytes.

Digital imaging fluorescence microscopy has been used to investigate epidermal growth factor-induced calcium responses of fura-2-loaded hepatocytes in primary culture at the single-cell level. Epidermal growth factor induced oscillations in cytosolic free calcium ([Ca2+]i) consisting of a periodic train of spikes unlike the monophasic elevation in cell suspensions reported previously. In this study, 79% of the cells in the microscopic field responded to 0.1 nmol/L epidermal growth factor, and 78% of the responsive cells displayed oscillations. However, the frequency of oscillations differed considerably from cell to cell. [Ca2+]i measurement in a cell population was simulated using these data, but only a slightly biphasic pattern was obtained, indicating the significance of single-cell measurement of [Ca2+]i. Because considerable heterogeneity existed in the sensitivity to epidermal growth factor between the cells, single hepatocytes were stimulated sequentially with increasing concentrations of epidermal growth factor to investigate the dose dependence of the oscillations. The frequency of the oscillations increased with increasing epidermal growth factor concentration, but the amplitude was similar for all concentrations, suggesting the existence of frequency-encoded information even in the pathway through tyrosine kinase for epidermal growth factor signaling. The pattern of the oscillations with epidermal growth factor, especially the latency, was considerably different from that with phenylephrine, which is known to use the phosphatidylinositol pathway, possibly because of the difference in the pathway toward phosphatidylinositol turnover between these agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Tumor necrosis factor and endotoxin in the pathogenesis of liver and pulmonary injuries after orthotopic liver transplantation in the rat.

This study examines whether tumor necrosis factor and endotoxin are involved in the pathogenesis of primary nonfunction of graft and pulmonary complication after orthotopic liver transplantation. Livers from Lewis rats were stored for either 1 or 4 hr in ice-cold Euro-Collins solution (1-hr storage and 4-hr storage group, respectively). Subsequently, donor livers were implanted orthotopically. In some experiments, anti-tumor necrosis factor antibody was administered intravenously before and immediately after the surgery into animals that received livers stored for 4 hr. Blood samples for the measurement of tumor necrosis factor and endotoxin were collected by way of an indwelling catheter placed in the suprahepatic vena cava. Serum tumor necrosis factor was elevated at all time points studied postoperatively in rats of the 4-hr storage group; however, tumor necrosis factor was not detected in the serum in the 1-hr storage group. Endotoxin was also elevated significantly in the serum of the former group compared with levels in the serum of the latter group. The peak value of endotoxin occurred 1 hr earlier than that of tumor necrosis factor, suggesting that the rise in endotoxin stimulated release of tumor necrosis factor. The histological study of livers stored for 4 hr showed substantial hepatocellular degeneration 24 hr after surgery, whereas hepatocellular damage was minimal in the 1-hr storage group. Serum ALT levels 24 hr after the operation in the 1-hr and 4-hr storage groups were 169 +/- 46 IU/L and 374 +/- 41 IU/L (mean +/- S.E.M., p less than 0.05), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMed1992

Improved serodiagnosis of chronic hepatitis C in Japan by a second-generation enzyme-linked immunosorbent assay.

To clarify the role of hepatitis C virus (HCV) infection in chronic liver disease, sera from Japanese patients which were negative by the original anti-HCV assay (Ortho) were subjected to a second-generation anti-HCV assay based on a combination of structural (C22) and nonstructural (C200) recombinant HCV proteins. Of 29 patients with chronic non-A, non-B hepatitis, 20 (69%) were anti-HCV-positive by the second-generation enzyme-linked immunosorbent assay (ELISA) and also positive by the reverse transcription-polymerase chain reaction (RT-PCR) which detects the HCV genome. Of 41 chronic hepatitis B virus carriers, 3 (7%) were positive by the second-generation ELISA; 1 of 3 was positive by RT-PCR. The HCV genome was detected in all cases positive for anti-HCV with high titers. Of 59 healthy subjects negative by the second-generation ELISA, none were positive by RT-PCR. These findings indicate that HCV is a major causative agent of chronic non-A, non-B hepatitis in Japan and that second-generation ELISA is specific and a more sensitive diagnostic assay for chronic hepatitis C.

Base Sequence↗
PubMed1992

Antibodies to a putative hepatitis C virus polyprotein in Japanese patients with chronic liver disease.

To investigate the frequency of exposure to hepatitis C virus (HCV) in chronic liver disease, sera from Japanese patients were tested with the original anti-HCV assay (Ortho) and an anti-HCV assay based on synthetic peptides corresponding to a variety of regions in the HCV genome. Thirty-one (67%) of 46 patients with chronic non-A,non-B hepatitis were anti-HCV-positive by the Ortho ELISA, 20 of whom were also positive by ELISA based on synthetic HCV peptides. Eight (53%) of the 15 patients negative by the Ortho ELISA tested positive for anti-HCV by ELISA based on HCV peptides. Serum HCV RNA was detected in all cases positive for antibody to the HCV peptide and in 14 (78%) of 18 cases without antibody. Thirty-seven hepatitis B virus carriers were without anti-HCV by the Ortho ELISA and were negative for serum HCV RNA, six (16%) of whom were positive by ELISA based on HCV peptides. Antibody responses were directed against each synthetic HCV peptide used, with a considerable difference in incidence, indicating possible expression of the corresponding region in the course of HCV propagation. These findings indicate that exposure to HCV may be more common than expected based on the results of the Ortho ELISA.

Amino Acid Sequence↗
PubMed1992

Assessment of portosystemic shunting from superior mesenteric vein by duodenal administration of iodoamphetamine I123.

Portosystemic shunting (PSS) from the superior mesenteric vein (SMV) was evaluated with the duodenal administration of iodoamphetamine I123 (IMP) in patients with chronic hepatitis and liver cirrhosis. After duodenal intubation, IMP was administered through a tube, and then scintigraphy including the pulmonary and hepatic regions was performed. In all patients, images of the liver and/or lungs were observed within 10 min and became clear with time, due to a good absorption of IMP from the intestine. On the other hand, IMP appears not to be absorbed from the stomach. The portosystemic shunt index was calculated by dividing counts of lungs by counts of liver and lungs. The shunt index (mean +/- SE) was 1.5% +/- 0.8%, 12.6% +/- 3.7% and 28.3% +/- 4.5% in chronic hepatitis, compensated cirrhosis and decompensated cirrhosis, respectively. This index was significantly higher in cirrhosis, especially in decompensated cirrhosis. Therefore, transintestinal portal scintigraphy with IMP could be a useful method for the non-invasive and quantitative evaluation of PSS from the SMV in portal hypertension.

Amphetamines↗
PubMed1992

The characteristics of blood-brain barrier in three different conditions--infarction, selective neuronal death and selective loss of presynaptic terminals--following cerebral ischemia.

We investigated the extravasation of serum albumin using immunohistochemistry in three different conditions, i.e., infarction, selective neuronal death and selective loss of presynaptic terminals following cerebral ischemia in gerbils. In selective neuronal death, which is typically found in the CA1 neurons of the hippocampus after 5-min bilateral cerebral ischemia, selective damage of postsynaptic components with intact presynaptic sites was demonstrated by immunohistochemical examination for microtubule-associated protein 2 and synapsin I, and albumin extravasation did not become apparent before postsynaptic structures were destroyed. In cerebral infarction, which was consistently observed in the thalamus after 15-min forebrain ischemia, massive albumin extravasation was visible early after ischemia due probably to the ischemic endothelial necrosis. In selective loss of presynaptic terminals, which was detected at the molecular layer of the dentate gyrus in the contralateral, nonischemic hippocampus after unilateral cerebral ischemia, immunoreaction for albumin was not visualized. Since endothelium and glial cells were intact in morphological aspects in selective damage of both pre- and postsynaptic sites, it was thought that extravasation was facilitated by the stimulation of endothelial cells and glial cells with unknown factors that were induced by the destruction of post- but not presynaptic elements.

Albumins↗