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Biomedical subjects

N Sakamoto

Publications and source records attributed to N Sakamoto.

At least 19 recordsLinked to original sources
PubMed1995

Comparison of the hypervariable region of hepatitis C virus genomes in plasma and liver.

Nucleotide sequences of the hypervariable region of hepatitis C virus genomes obtained from plasma change rapidly during the course of infection and are believed to play a part in immunological escape and consequently in the development of persistent infection. It is not known, however, whether these changes also occur in the liver. To clarify this aspect, RNA was extracted from the plasma and liver tissue of eight patients with chronic hepatitis C. After cDNA synthesis, DNA fragments that included the hypervariable region were amplified by the polymerase chain reaction. Consensus nucleotide sequences were determined directly from the polymerase chain reaction products by the dideoxy chain termination method. The diversity of the hypervariable region was analyzed further by the polymerase chain reaction-single strand conformation polymorphism analysis. Consensus nucleotide sequences of the hypervariable region were identical between the plasma and the liver in each patient. The polymerase chain reaction-single strand conformation polymorphism analysis showed multiple DNA bands that represented different hypervariable region sequences. Comparison of the single strand conformation polymorphism patterns revealed that the number, the mobility, and the density of bands were the same between the plasma and the liver. It is concluded that the population and the diversity of hepatitis C virus quasispecies as detected by the hypervariable region sequence are the same between the plasma and the liver despite rapid mutations, indicating that rapid changes in the population of hepatitis C virus quasispecies also occur in the liver.

Amino Acid Sequence↗
PubMed1995

Severe chronic active hepatitis induced by UFTR containing tegafur and uracil.

A 77-year-old female patients developed severe hepatic injury after the administration of UFTR, which contains tegafur and uracil, for postoperative chemotherapy of colon cancer. Liver damage was recognized 10 months after its administration. Serum markers for viral hepatitis and various autoantibodies were negative. The wedged biopsied liver specimen revealed advanced chronic active hepatitis with periportal confluent necrosis, marked intralobular spotty necrosis, and significant proliferation of pseudo-bile ductules. Although the cessation of the drug and conservative therapies improved hepatic function, an accidental readministration of UFTR caused her severe hepatic damage again. These findings suggest that liver injury in the present case was caused by UFTR. Histological findings were unique. Although tegafur is known to worsen hepatic function when given to patients with liver cirrhosis, UFTR may also cause severe hepatic injury in those without preexisting liver disease.

Aged↗
PubMed1995

Pressor response induced by the hippocampal administration of neostigmine is suppressed by M1 muscarinic antagonist.

We investigated the roles played by three muscarinic receptors (M1, M2, and M3) in the pressor response with bradycardia that followed the injection of neostigmine (5 x 10(-8) mol) into the hippocampus of anesthetized rats. These changes were blocked by the co-administration of methylatropine (5 x 10(-8) mol). The intrahippocampal injection of pirenzepine (M1 antagonist) (5 x 10(-9) - 5 x 10(-7) mol) suppressed the neostigmine-induced pressor response dose-dependently. However injection of gallamine (M2 antagonist) (5 x 10(-8) - 5 x 10(-7) mol) and of 4-DAMP (M1 and M3 antagonist) (5 x 10(-8) - 5 x 10(-7) mol) did not suppress this hypertensive response. These findings suggest that the neostigmine-induced pressor response with bradycardia is mediated through the M1 muscarinic receptor subtype.

Animals↗
PubMed1995

Detection and analysis of replicating hepatitis C virus RNA in hepatocellular carcinoma tissues.

Although persistent hepatitis C virus infection is closely associated with the development of hepatocellular carcinoma, the nature of hepatitis C virus replication in the hepatocellular carcinoma tissue has not been fully characterized. To study this, carcinoma and non-carcinoma tissues were obtained from five patients with hepatocellular carcinoma. Total RNA was recovered from each tissue, and a portion of the envelope gene of replicating hepatitis C virus was amplified by minus-strand-specific reverse transcription and nested polymerase chain reaction. The amplified cDNA was examined by single strand conformation polymorphism analysis and sequencing. Hepatitis C virus replication was detected in both carcinoma and non-carcinoma tissues in four patients who were positive for serum hepatitis C virus markers. In one patient, a single species with identical envelope 2 genome was obtained from both carcinoma and non-carcinoma tissues. In the other three patients, the replicating hepatitis C virus existed as a mixture of 2-5 species with different but highly homologous (82-99%) envelope 2 genomes (quasispecies populations). The constitution of viral populations was different between carcinoma and non-carcinoma tissues. A total of ten sequences were recovered; four sequences were found in both tissues, two were found in carcinoma tissues, and four were found in non-carcinoma tissues. The difference in the constitution of quasispecies populations between carcinoma and non-carcinoma tissues confirms the unequivocal replication of hepatitis C virus in both tissues, and may imply the presence of different biological properties among hepatitis C virus with different sequences.

Amino Acid Sequence↗
PubMed1995

Effects of an aldose reductase inhibitor, epalrestat, on diabetic neuropathy. Clinical benefit and indication for the drug assessed from the results of a placebo-controlled double-blind study.

The clinical efficacy of epalrestat (150 mg/day, 50 mg tid, po; A group), an aldose reductase inhibitor, was evaluated in 196 patients with diabetic neuropathy by a double-blind study using placebo (9 mg/day, 3 mg tid, po; P group) as a control for 12 weeks. The disappearance rates of upper limb spontaneous pain were 42.9% and 12.0% in the A and P groups, respectively, and those of lower limb spontaneous pain 48.6% and 22.6%, thus being significantly higher in the A group (p < 0.05, logrank-test). The motor nerve conduction velocity of the peroneal nerve significantly increased only in the A group (delta 1.6 +/- 0.6 m/sec, p < 0.01, paired t-test), and the extent of increase in that of the median nerve was significantly greater in the A group than in the P group (p < 0.05). Thresholds of vibratory sensation and autonomic nerve function were also significantly improved in the A group (p < 0.05). The data were reanalyzed by dividing patients into two groups according to their HbA1c values. The improvement ratings of subjective symptoms and of nerve function tests for cases with HbA1c > or = 7.5% were both significantly different between the A and P groups, with the improvement rate being higher in the A group, and also higher as compared to the analysis for cases with HbA1c < 7.5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Effects of glucose and SNK-860, an aldose reductase inhibitor, on the polyol pathway and chemiluminescence response of human neutrophils in vitro.

An in vitro incubation study was conducted to investigate whether increased activity of the polyol pathway in human neutrophils under diabetic conditions resulted in a decrease of superoxide anion produced by NADPH oxidase on the membrane of neutrophils. Lucigenin-enhanced chemiluminescence (CL) to phorbol myristate acetate as respiratory burst and sorbitol levels in neutrophils after incubation with glucose and an aldose reductase (AR) inhibitor, SNK-860 (SNK) were measured. Sorbitol levels increased from 0.210 +/- 0.029 nmol 10(7) cells-1 in 5 mmol l-1 glucose to 0.446 +/- 0.036 nmol 10(7) cells-1 in 40 mmol l-1 glucose, while CL decreased from 0.542 +/- 0.034 cpm cell-1 in 5 mmol l-1 glucose to 0.430 +/- 0.018 cpm cell-1 in 40 mmol l-1 glucose. The addition of 10 mumol l-1 SNK normalized the increased sorbitol levels in neutrophils exposed to 40 mmol l-1 glucose and improved, but did not normalize, the decrease in CL induced by 40 mmol l-1 glucose (p < 0.001). Galactose (40 mmol l-1) also reduced CL, which was improved by the addition of SNK (p < 0.01). These results suggest that impaired respiratory burst induced by high-glucose concentrations is caused by competition for NADPH resulting from increased polyol pathway activity and/or glycation and that an AR inhibitor may be capable in part of preventing increased susceptibility to infection in diabetic patients.

Adult↗
PubMed1995

Changes of K vitamins in portal and femoral venous plasma of rats after oral administration of phylloquinone and menaquinone-4.

To clarify the mechanism of absorption and metabolism of K vitamins (VK), we administered phylloquinone (K1) and menaquinone-4 (MK-4) orally to male Wistar rats whose portal and femoral veins were cannulated. Blood was collected 9 times up to 120 min later, and 50 microliters plasma was used for VK analysis by high performance liquid chromatography (HPLC) using a modification of our previous method. There were no significant differences between portal and femoral venous VK concentrations throughout all the experiments. When K1 and MK-4 were administered simultaneously, K1 appeared in plasma at 15 min, and MK-4 at 10 min. The concentration of MK-4 was significantly higher than that of K1 up to 60 min. In contrast to the single administration, the MK-4 concentration was reduced after 60 min. After K1 single administration, the MK-4 was not detected in either portal or femoral venous plasma up to 120 min. These results suggested that (1) the main absorption route of both VK may be the extra-portal pathway, (2) MK-4 is absorbed faster than K1 (3) some interactions may exist between K1 and MK-4 and (4) the intestinal cells might not be the major site to transform K1 into MK-4.

Administration, Oral↗
PubMed1994

Effects of adrenoceptor antagonists on the hyperthermia and hyperglycemia induced by prostaglandin F2 alpha in rats.

We investigated the effects of intraperitoneal administration of adrenoceptor antagonists to the hyperthermia and hyperglycemia induced by prostaglandin F2 alpha (50 micrograms) injected into the third cerebral ventricle in anesthetized rats. Phentolamine inhibited the hyperthermia and hyperglycemia induced by prostaglandin F2 alpha. Prazosin inhibited the hyperthermia induced by prostaglandin F2 alpha, while enhancing the hyperglycemia. Yohimbine inhibited the prostaglandin F2 alpha-induced hyperglycemia without an effect on the hyperthermia. Propranolol had no effect on either prostaglandin F2 alpha-induced hyperglycemia or hyperthermia. These observations suggest that the hyperglycemia induced by prostaglandin F2 alpha is regulated by alpha 2-adrenoceptor systems while the hyperthermia is regulated by alpha 1-adrenoceptor systems in rats.

Adrenergic alpha-Antagonists↗
PubMed1994

Protein phosphatase inhibitors induce the release of serotonin from rat basophilic leukemia cells (RBL-2H3).

Effects of okadaic acid (OA) and calyculin-A (CL-A), selective inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), on the release of serotonin from the rat basophilic leukemia cell line (RBL-2H3) were investigated. Both OA and CL-A induced the long-lasting release of serotonin in an extracellular Ca(2+)-independent manner. CL-A did not increase intracellular Ca2+ concentration in the fura-2-loaded cells. CL-A was 100-fold more potent than OA in inducing the release, suggesting that PP1 is a dominant protein phosphatase in regulating RBL-2H3 cells. The CL-A-induced release of serotonin was completely inhibited by the nonselective protein kinase inhibitors, staurosporine and K-252a. CL-A induced phosphorylation of several cellular proteins in RBL-2H3 cells, which could be inhibited by staurosporine. These findings suggest that the release of serotonin is subject to tonic, Ca(2+)-independent, inhibition by PP1 in RBL-2H3 cells.

Alkaloids↗
PubMed1994

Sequential change of the hypervariable region of the hepatitis C virus genome in acute infection.

Hepatitis C virus (HCV) infection is characterized by persistence of liver inflammation that often leads to end-stage liver disease, although the mechanisms are not fully understood. A hypervariable region (HVR) has been reported in the E2/NS1 region of the HCV genome, in which striking diversity is found among different HCV isolates. To investigate the association of the HVR alterations with the clinical courses of HCV infection, a longitudinal analysis of the HVR in patients with acute HCV infection was carried out. Plasma samples were obtained at several times in three patients with acute hepatitis C. Plasma RNA was extracted and reverse transcribed, and DNA fragments that included the HVR were amplified by PCR. The sequences of the HVR were directly determined from the PCR products by the dideoxy chain termination method, from which amino acid sequences were deduced. In all cases, plasma HCV-RNA disappeared with the improvement of the initial alanine aminotransferase (ALT) elevation, but HCV-RNA reappeared about 1 year later with or without deterioration of the hepatitis. In a case of sporadic acute hepatitis, the HCV in the recurrent phase had seven amino acid substitutions in the HVR compared with that in the acute phase, although no amino acid changes were noted during the initial acute phase. In a case of posttransfusion hepatitis, a marked difference was observed between the acute and the recurrent phases, with an amino acid homology of 30% (8/27). The mutation rate of the HVR had a tendency to accelerate as the HCV infection progressed to the chronic stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Unusual splice sites in the E1A-E1B cotranscripts synthesized in adenovirus type 40-infected A549 cells.

The adenovirus E1 DNA region consists of two transcription units, E1A and E1B. In this paper we report that the E1A-E1B cotranscripts containing sequences of both the E1A and E1B regions are synthesized during adenovirus type 40 (Ad40) infection of A549 cells. Cytoplasmic RNA was isolated from Ad40-infected A549 cells at 24, 72, and 100 h post infection (p.i.). The complementary (c) DNA was synthesized by reverse transcription using an oligo-dT primer and then amplified by the polymerase chain reaction (PCR) using primers derived from the E1A and E1B regions. The cDNAs thus amplified were sequenced either directly or after cloning into bacteriophage M13 vectors. Analysis of cDNA indicated that the E1A-E1B cotranscripts are synthesized at 72 h p.i., but not at 24 or 100 h p.i. Nucleotide sequences of three cDNAs of the E1A-E1B cotranscripts indicated that the cotranscripts originate from the E1A promoter and lack sequences for both the E1A poly(A) site and E1B cap site. The splices create open reading frames for E1A-E1B fused polypeptides around the E1A-E1B junctions in these mRNAs. Most interestingly, the sequence analysis showed that the 5' and 3' splice junctions in the two E1A-E1B cotranscripts do not conform to the splice consensus GT-AG rule. Our results thus suggest that factor(s) which lead to unusual splicing in the E1 mRNAs are present in Ad40-infected A549 cells.

Adenovirus E1A Proteins↗
PubMed1994

Correlation between serum levels of alanine aminotransferase and ferritin in male blood donors with antibody to hepatitis C virus.

Chronic hepatitis C has been demonstrated to be associated with hepatic iron overload, and the hypothesis that the disease activity of hepatitis C is associated with iron cytotoxicity was tested in male volunteer blood donors. Sera with either antibody to hepatitis C virus or hepatitis B surface antigen were selected for determination of ferritin concentration and alanine aminotransferase activity. A correlation between serum ferritin concentration (Y; microgram/l) and alanine aminotransferase activity (X; IU/l) was found in donors with antibody to hepatitis C (log Y = 0.65 x log X + 0.98, r = 0.53, and P < 0.01). The correlation was lower in donors with hepatitis B surface antigen (r = 0.37; P < 0.01). Hepatitis C virus infection probably induces time-dependent iron accumulation associated with the progression of disease activity, while hepatitis B virus infection results in a variety of iron loads with different clinical features. The high disease activity related to hyperferritinemia suggests the presence of iron-induced liver damage in donors with hepatitis C.

Adult↗
PubMed1994

A deductive database system for analyzing human nucleotide sequence data.

The analysis of the human genome is one of the most significant topics in both biology and medical science. There is a growing need for a well-designed database system for searching and analyzing the human genome data. We developed a deductive database system to search and analyze nucleotide sequence data derived from the GenBank primates data. A deductive database system is a next generation one and it contains an inference mechanism that can handle problems beyond the capabilities of classical database systems. Database queries are described in logical rules. These rules are simple even for molecular biologists who are not experts in computer programs because they are declarative and do not require the procedural commands that are usually used in computer programs. Furthermore, queries based on logical rules are powerful enough to express complicated biological problems. Particularly, recursive rules are suitable for examining secondary structures of nucleotide sequences. In our analysis of TfR's IRE, we noted five stem-and-loop structures.

Artificial Intelligence↗
PubMed1994

Activation of central GABAA receptors suppresses the alteration of plasma catecholamine levels induced by neostigmine or histamine in rats.

We investigated the effects of intraventricular injection of muscimol, the GABAA receptor agonist, on the alteration of plasma epinephrine (E) and norepinephrine (NE) levels induced by neostigmine or histamine in anesthetized rats. Injection of neostigmine (10 nmol) into the third cerebral ventricle increased plasma levels of E more than NE, while histamine (500 nmol) increased plasma levels of NE more than E. Concomitant injection of muscimol (2.5 nmol) with neostigmine or histamine significantly suppressed the alteration of E and NE levels induced by neostigmine or histamine. These findings suggest that activation of central cholinergic neuron stimulates the adrenal medullary response more than the sympathetic nervous system, while activation of central histaminergic neuron stimulates the sympathetic nervous system more than the adrenal medullary response in anesthetized rats. Activation of GABAA receptors in the CNS suppresses these effects.

Animals↗
PubMed1994

Effects of central GABA receptors activation on catecholamine secretion in rats.

We investigated the effects of muscimol, the GABAA receptor agonist, and baclofen, the GABAB receptor agonist, injected into the third cerebral ventricle on plasma epinephrine (E) and norepinephrine (NE) levels in anesthetized rats. Baclofen (0.4-5 nmol) increased plasma NE levels in a dose dependent manner but did not affect plasma E levels. Muscimol (2.5 nmol) affected neither plasma E nor NE levels. Concomitant injection of muscimol (2.5 nmol) with baclofen (5 nmol) attenuated the baclofen (5 nmol)-induced NE secretion. These findings suggest that activation of GABAB receptors in the central nervous system (CNS) stimulates the sympathetic nervous system but not the adrenal medullary response. In contrast, activation of GABAA receptors in the CNS affects neither the sympathetic nervous system nor the adrenal medullary response, but inhibits the sympathetic neural activity induced by activation of GABAB receptors in anesthetized rats.

Animals↗
PubMed1994

CNS regulation of blood lactate concentration in anesthetized rats.

This study evaluated the effect of stimulating the central nervous system (CNS) with neostigmine, an inhibitor of acetylcholinesterase, on the blood lactate concentration in fed rats and in rats fasted for 48 hours. After the rat was anesthetized with pentobarbital, neostigmine was stereotaxically injected into the third cerebral ventricle. In fed rats, the central injection of neostigmine significantly increased the blood lactate level, while concomitantly increasing plasma glucagon, epinephrine and norepinephrine concentrations. Constant infusion of somatostatin throughout the experiments, to inhibit glucagon secretion from the pancreas, did not affect alterations in blood lactate by central injection of neostigmine. In adreno-medullated rats, CNS-stimulation by neostigmine still increased plasma norepinephrine significantly, however, the alteration in blood lactate was only one-third of that in intact rats. Intraperitoneal propranolol, but not phentolamine, prevented the rise in lactate. Neostigmine increased lactate in fasted rats as well as in fed rats. We conclude that in anesthetized rats, stimulation of the CNS by neostigmine increases blood lactate mainly through circulating epinephrine and partially through circulating norepinephrine or direct sympathetic nervous stimulation; glucagon does not appear to be involved in the increase in blood lactate.

Anesthesia, General↗