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N Sakamoto

Publications and source records attributed to N Sakamoto.

At least 181 records · Page 10Linked to original sources
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↗
PubMed1994

A transfer-function representation for the input-output relation in consecutive Michaelis-Menten-type reactions.

A transfer-function representation is devised to describe analytically and approximately the reaction velocity (output) in response to the substrate influx rate (input) in single and two consecutive Michaelis-Menten-type reactions in an open and homogeneous system. The transfer function for single reactions has an expression of first-order system, the time constant of which is dependent on the kinetic parameters and flow rate (steady-state value of the input and output), but independent of the magnitude of the input change. The transfer function for the two-reaction system can be formed with successive multiplication of the transfer functions for the first and second reactions. The validity of the representation is examined with variation in the kinetic parameters and flow rate by comparing the output of the transfer function with the actual response obtained from the computer simulation, that is, numerical integration of the rate equation. The analysis of the indicial responses indicates that the transfer functions for single and two consecutive reactions are valid within a certain error for the response around a steady state.

Enzymes↗
PubMed1994

Metallothionein expression is correlated with cisplatin resistance in transitional cell carcinoma of the urinary tract.

Metallothioneins (MTs) are small cysteine-rich, metal-binding proteins involved in resistance to heavy-metal toxicity, and are known to bind cisplatin. Several experiments suggest possible involvement of MT in cellular resistance to cisplatin. To investigate the relationship between MT expression and cisplatin resistance in urinary tract transitional cell carcinoma (TCC), immunohistochemical staining for MT was performed in 31 untreated TCCs of the urinary tract. The results were compared with the sensitivity of the tumors to cisplatin as assessed by the microtiter succinate dehydrogenase inhibition (mSDI) test. Variable MT expression was observed in all 31 TCCs, but there was no specific correlation between histopathological parameters and MT expression. Fourteen (87.5%) of the 16 TCCs with less than 10% of their tumor cells positive for MT were sensitive to cisplatin. On the other hand, 6 (75.0%) of the 8 TCCs with MT expression by more than 30% of their tumor cells were resistant to cisplatin, and there was a significant correlation between MT expression and cisplatin resistance (p < 0.01). These results suggest the possible involvement of MT in the intrinsic cisplatin resistance of urinary tract TCC and that immunohistochemical investigation of MT may be useful for predicting the response of these tumors to cisplatin therapy.

Adult↗
PubMed1994

Detection and quantification of hepatitis C virus RNA replication in the liver.

To investigate the correlation between the replication of hepatitis C virus in liver and the clinical and histopathological features, we detected and quantified plus and minus strands of HCV-RNA in plasma and in livers of patients with chronic hepatitis C by a quantitative polymerase chain reaction. RNA was extracted from the plasma and liver tissue of ten patients with biopsy-proven chronic hepatitis C. The plus and minus strands of HCV-RNA were detected by a strand-specific reverse transcription with either sense or anti-sense oligonucleotide primers deduced from the hepatitis C virus genome, and a standard HCV-RNA with an enzyme restriction site was used to quantify the amount of HCV-RNA. Both plus and minus strands of HCV-RNA were detected from the liver tissue of all patients included. The amount of plus-stranded HCV-RNA in the liver was 10 times higher than that of minus-stranded HCV-RNA. Plus-stranded HCV-RNA was detected in the plasma in all patients, while the minus strand was not detected in any patient. There was a weak correlation between the amount of both strands of HCV-RNA in the liver and that of the plus strand in plasma. There was no significant correlation between the amount of liver HCV-RNA and serum alanine transaminase and aspartate transaminase levels, or histopathological findings in the liver. The present method of detecting and quantifying liver HCV-RNA is simple and sensitive; it may be used to detect residual hepatitis C virus replication after the disappearance of plasma HCV-RNA in acute hepatitis or in chronic hepatitis after interferon treatment.

Adult↗
PubMed1994

A novel mutation in the erythrocyte protein 4.2 gene of Japanese patients with hereditary spherocytosis (protein 4.2 Fukuoka).

Human erythrocyte protein 4.2 (band 4.2; pallidin) is a major membrane protein that comprises 5% of the total weight of the human erythrocyte membrane. Deficiencies of this protein have been observed in hereditary spherocytosis with anaemia, suggesting a role of protein 4.2 in erythrocyte stability and integrity. The molecular basis of this disorder remains unknown. As a first step in elucidating the pathogenesis of hereditary spherocytosis associated with protein 4.2 deficiency, we cloned and sequenced the erythrocyte protein 4.2 gene from a normal Japanese person. We prepared sets of oligonucleotide primers for polymerase chain reaction (PCR) and determined nucleotide sequences of exons and exon-intron boundaries of the protein 4.2 gene from three unrelated Japanese patients with hereditary spherocytosis due to a complete defect of protein 4.2, using PCR-related techniques. Two patients were homozygous for a missense mutation in codon 142 with the Ala (GCT)-->Thr (ACT) amino acid substitution that has been reported previously (protein 4.2NIPPON), whereas one patient was compound heterozygous for the same missense mutation in codon 142 and a guanine-adenine transition in codon 119 that changes the codon for Trp (TGG) to the termination codon (TGA) (protein 4.2Fukuoka). No additional mutation was identified in other exons of the protein 4.2 genes. Dot-blot hybridization with allele-specific oligonucleotide probes showed that homozygosity for the missense mutation in codon 142 and compound heterozygosity for the codon 142 and the codon 119 mutations were related to protein 4.2 deficiency in the families. Although two alleles of missense mutation of the codon 142 were also detected in 100 alleles of healthy Japanese, results obtained in this study indicate that the two mutations described above are closely related to the pathogenesis of hereditary spherocytosis due to protein 4.2 defect.

Adult↗
PubMed1994

Bicuculline methiodide influences the central nervous system to produce hyperglycemia in rats.

The influence of bicuculline methiodide (BMI), a gamma-aminobutyric acid (GABA) receptor antagonist, on central nervous system regulation of blood glucose homeostasis was studied in fed rats. Injection of BMI (1-10 nmol) into the third ventricle was found to produce hepatic venous hyperglycemia in a dose-dependent manner. This change was associated with increased secretion of epinephrine and glucagon. The role of epinephrine in hyperglycemia was then studied in bilaterally adrenalectomized (ADX) rats injected with BMI. Plasma glucose concentration was found to increase in ADX rats although the level was approximately half that for intact rats and significantly higher than for controls. The increase in epinephrine and glucagon secretion seen in intact rats, but not in ADX rats, suggests BMI induced epinephrine release is responsible for the glucagon secretion. Three possible mechanisms are suggested to account for the rise in plasma glucose in the hepatic vein after injection of BMI: 1) that epinephrine is secreted by the adrenal medulla, 2) that epinephrine secretion stimulates glucagon secretion or 3) that there may be some direct innervation of the liver in rats.

Adrenal Medulla↗
PubMed1994

Relationship of ultrasonographic findings to histology in prostate cancer.

We compared ultrasonic findings and histology in 25 patients with prostate cancer. Ultrasonically guided transperineal biopsy of focal prostatic lesions was performed in 19 patients, in whom prostate cancer was suspected. Six of them had two different echogenic areas in the same focal lesion, so a total of 25 echogenic areas were assessed. Fourteen of these 25 areas were hypoechoic. The Gleason score varied, but residual prostatic glands and cancer glands with slightly enlarged lumen did not exist. Six of the areas were slightly more echogenic than the above 14 areas, and cribriform cancer with slightly enlarged glands occupied the greater part of these specimens. Four of the areas were isoechoic, and they contained residual prostatic glands showing a normal distribution, regardless of the Gleason score or grade of tumor infiltration. The only hyperechoic lesion contained numerous tiny areas of calcification. In the 6 patients without focal lesions, the peripheral and transition zones showed a normal echogenicity. Two of these patients had cancer in the transition zone, and biopsy showed tumor glands with slightly enlarged lumens. In the 4 patients, various-sized tumors were seen, but there was a normal distribution of residual prostatic glands and stroma. These results indicated that prostatic echogenicity is determined by the presence of tumor glands with enlarged lumina as well as residual prostatic glands and stroma.

Adenocarcinoma↗
PubMed1994

Proliferating cell nuclear antigen in needle biopsy specimens of prostatic carcinoma.

The expression of proliferating cell nuclear antigen (PCNA) was immunohistochemically determined using a monoclonal antibody PC10 in 54 prostatic carcinoma samples. The samples were taken from needle biopsy specimens which had been paraffin-embedded after routine fixation with 10% formaldehyde solution (formalin) for less than 24 h. The PCNA index was calculated as the percentage of positive tumor cell nuclei. There was a significant difference in the PCNA index according to the growth pattern (p < 0.001), nuclear anaplasia (p < 0.001) and T stage (p < 0.01). Regarding the growth pattern, solid carcinomas showed a significantly higher PCNA index than did either separate gland carcinomas (p < 0.05) or trabecular/fused gland carcinomas (p < 0.05). The PCNA index correlated closely with either the nuclear anaplasia or T stage, and increased in conjunction with the increased nuclear anaplasia (rs = 0.641; p < 0.001) or T stage (rs = 0.435; p < 0.01). The patients in the high PCNA index (> or = 15%) group showed a significantly worse survival than did those in the lower PCNA index group (p < 0.01), and multivariate analyses indicated that the PCNA index had an independent prognostic significance. These results suggest that the PCNA index, as determined by PC 10 on needle biopsy specimens of prostatic carcinoma, can thus be an objective and quantitative means for evaluating the biological malignancy of prostatic carcinoma.

Adenocarcinoma↗
PubMed1994

Effects of leukotriene D4 on myocardial blood flow and high energy phosphate concentration in anesthetized dogs.

The effects of intracoronary administration of leukotriene D4 (LTD4) on myocardial blood flow (MBF) and myocardial energy metabolism in anesthetized open-chest dogs were examined, and compared with those of coronary ligation. Two series of experiments were conducted. In the first, LTD4 (0-3.0 micrograms/kg) was injected into the left anterior descending coronary artery (LAD) and MBF was measured. While no changes in MBF were observed after 0.5 microgram/kg of LTD4, a significant decrease in MBF in the LAD area was apparent after 1.0 micrograms/kg of LTD4, with a return to baseline values by within 10 min after the injection. With 3.0 micrograms/kg of LTD4, MBF remained decreased up to 15 min after the injection. In the second study, myocardial high energy phosphate concentrations in the LAD area were determined 5 min after LTD4 administration and compared to those after ligation. ATP levels in the 1.0-3.0 micrograms/kg LTD4 groups were significantly less than those in the ligation group, although there were no associated significant differences in MBF values in the LAD area. These results indicate that LTD4 brings about changes in myocardial energy metabolism which are not secondary to reduced blood flow.

Anesthesia↗
PubMed1994

Effects of long-term enalapril treatment on persistent micro-albuminuria in well-controlled hypertensive and normotensive NIDDM patients.

OBJECTIVE: To determine whether long-term treatment with an angiotensin-converting enzyme (ACE) inhibitor has a beneficial effect on the urinary microalbumin excretion and renal function in non-insulin-dependent diabetes mellitus (NIDDM) patients, enalapril (5 mg/day) was administered for 48 months. RESEARCH DESIGN AND METHODS: -Fifty-two patients with NIDDM who had persistent microalbuminuria in the range of 20-300 mg/24 h, serum creatinine < 106.1 microM (1.2 mg/dl), supine systolic blood pressure (BP) < 150 mmHg, supine diastolic BP < 90 mmHg, and HbA1c < 10% were divided into four groups. Twenty-six patients with normotension were divided at random into two groups; one group received enalapril (5 mg/day) (NE group), the other did not receive enalapril (NC group). In the same way, 26 other patients who were already well-controlled with nifedipine (30 mg/day) over a long-term period (4-6 years) were divided at random into two groups; one received enalapril (5 mg/day) (HE group), the other did not receive enalapril (HC group). RESULTS: After 48 months, urinary albumin excretion (UAE) was markedly reduced in group NE from 102.4 x/divided by 1.3 to 55.5 x/divided by 1.3 mg/24 h (P < 0.005), whereas no significant change occurred in group NC. In the well-controlled hypertensive groups, a significant reduction in UAE occurred in group HE (P < 0.05), whereas no significant change occurred in group HC. No changes in creatinine clearance, BP, or blood glucose control were seen during the study. CONCLUSIONS: Treatment with enalapril for 48 months may have a beneficial effect on the decline of microalbumin excretion in NIDDM patients.

Acetylglucosaminidase↗
PubMed1994

Beneficial effects of iloprost on acute myocardial ischemia in dogs.

The effects of intravenous administration of iloprost, a prostacyclin analogue, on myocardial energy metabolism and myocardial blood flow (MBF) were examined in anesthetized open-chest dogs subjected to 60 min of myocardial ischemia by coronary ligation. Iloprost administration at levels of 0.1 or 0.2 micrograms/kg/min was started 30 min before the commencement of ischemia and continued throughout the 90 min observation period. Since systolic aortic pressure in the iloprost 0.2 micrograms/kg/min group showed significantly lower values than that in the control group, whereas no clear effect was observed with the lower concentration (0.1 micrograms/kg/min), this latter group was further investigated. This 0.1 microgram/kg/min dose of iloprost lacked influence on MBF in both ischemic and nonischemic areas but did result in a significantly higher value for high energy phosphate contents in the ischemic myocardium. Moreover, myocardial mitochondrial respiratory function in the ischemic area was significantly improved. These results indicate that iloprost brought about preservation of myocardial energy metabolism without alteration of coronary perfusion, suggesting that it may exert a direct cardioprotective effect.

Animals↗
PubMed1994

Myocardial metabolic markers of total ischemia in vitro.

The influence of total ischemia on the formation of products of anaerobic metabolism was investigated in canine hearts in vitro. Contents of organic acids were quantitatively analyzed by gas chromatography-mass spectrometry, and high energy phosphate compounds were determined using the luciferin-luciferase enzyme system. During a 10-min period of total ischemia, myocardial creatine phosphate significantly decreased, while ATP remained unchanged as compared with preischemic values. Both 10 min and 60 min of ischemia induced significant increase in tissue succinic acid levels. In contrast, a significant increase in myocardial lactic acid content was only induced with 60 min of ischemia. The data obtained indicate that the accumulation of succinic acid may be regarded as a potential metabolic marker of myocardial total ischemia.

Animals↗