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Biomedical subjects

K Hosoda

Publications and source records attributed to K Hosoda.

At least 163 records · Page 9Linked to original sources
PubMed1991

Resolution of acute hepatitis C after therapy with natural beta interferon.

To test whether interferon can prevent acute non-A, non-B hepatitis from becoming chronic, a prospective controlled trial was conducted in 25 patients; 11 were treated for an average of 30 days with a mean of 52 megaunits of interferon and 14 acted as controls. 4 patients in the treatment group who continued to have raised serum aminotransferase concentrations after a year's follow-up were given a second course of interferon. Follow-up at 3 years has revealed that all but 1 of those treated showed normal serum aminotransferase, whereas only 3 controls showed such change (p less than 0.02). Serum hepatitis C virus RNA became undetectable in 10 of 11 treated and in only 1 of 12 control patients, which suggests that interferon prevents the progression of acute non-A, non-B hepatitis to chronicity by eradicating HCV.

Acute Disease↗
PubMed1991

Cloning and expression of human endothelin-1 receptor cDNA.

We isolated a human endothelin-1 (ET-1) receptor cDNA from a human placenta cDNA library. The cDNA encodes a 427-amino acid protein with seven putative transmembrane domains. The rank order of the binding to the receptor expressed in COS-7 cells was: ET-1 greater than or equal to ET-2 much greater than ET-3. The receptor expressed in Xenopus oocytes showed a potent electrophysiological response to 1 x 10(-7) M ET-1 under voltage clamp at -60 mV, while a much weaker response was produced by 1 x 10(-7) M ET-3. Northern blot analysis with RNA from human tissues revealed a single band with a size of 4.3 kb in a wide variety of human tissues, especially highly in the blood vessel.

Amino Acid Sequence↗
PubMed1991

Molecular cloning of a non-isopeptide-selective human endothelin receptor.

We isolated several complementary DNA (cDNA) clones encoding a non-isopeptide-selective human endothelin receptor (ETBR) from a human placenta cDNA library. The clones, different in the length of their 3'-untranslated regions, encoded the same 442-amino acid protein with a transmembrane topology similar to that of other G protein-coupled receptors. The rank order of the binding of ET isopeptides (ET-1, ET-2 and ET-3) to the receptor expressed in COS-7 cells was ET-1 = ET-2 = ET-3. Northern blot analysis identified three mRNA species, 4.3 kb, 2.7 kb and 1.7 kb in size, probably generated by their use of alternative polyadenylation sites. These mRNAs were expressed in a wide variety of human tissues, at the highest level in the brain and at a significant level in cultured endothelial cells.

Amino Acid Sequence↗
PubMed1991

Mutations in the precore region of hepatitis B virus DNA in patients with fulminant and severe hepatitis.

BACKGROUND: The presence of the hepatitis B e antigen (HBeAg) in serum is known to be a marker of a high degree of viral infectivity. However, fulminant hepatitis may occur in persons who are negative for HBeAg. A single point mutation has been reported to produce a stop codon in the precore region of hepatitis B virus DNA and prevent the formation of the precore protein required to make HBeAg. To determine whether a precore-mutant virus is causally related to severe liver injury, we analyzed the entire precore region in viral strains isolated from patients with fatal cases and uncomplicated cases of hepatitis B. METHODS: Serum was obtained from 9 patients with fatal hepatitis B (5 with fulminant and 4 with severe exacerbations of chronic hepatitis) and 10 patients with acute, self-limited hepatitis B. Serum samples from a sex partner implicated as the source of the virus in one case of fulminant hepatitis were also studied. The 87 nucleotides in the precore region of the hepatitis B virus were amplified by the polymerase chain reaction and then directly sequenced. RESULTS: Of the nine patients with fatal hepatitis, seven had retrievable hepatitis B DNA: In all seven there was a point mutation from G to A at nucleotide 1896 of the precore region, converting tryptophan (TGG) to a stop codon (TAG). In contrast, this mutation was not found in the 10 patients with acute, self-limited hepatitis B. The hepatitis B DNA from the implicated source contained a sequence with the stop-codon mutation that was identical to the sequence in her partner, who had fulminant hepatitis. CONCLUSIONS: The presence of a mutant viral strain is associated with and may be involved in the pathogenesis of fulminant hepatitis B and severe exacerbations of chronic hepatitis B.

Acute Disease↗
PubMed1991

Randomized, double-blind, placebo-controlled trial of eight-week course of recombinant alpha-interferon for chronic non-A, non-B hepatitis.

Forty-nine Japanese patients were enrolled in a randomized, placebo-controlled, double-blind trial of alpha-interferon for chronic non-A, non-B hepatitis: 24 patients received 3 million units of recombinant human alpha alpha-interferon (alpha-2a) thrice weekly for eight weeks, and 25 patients received placebo in a similar schedule. The mean serum alanine aminotransferase (ALT) dropped from 155 +/- 91 (SD) to 69 +/- 72 during interferon treatment, but remained unchanged (158 +/- 140 to 147 +/- 130) during placebo treatment (P less than 0.001). Serum ALT level fell to the normal range in 29% of interferon-treated patients, but in only 4% of placebo-treated patients. Pre- and posttreatment liver biopsies were obtained in all but one case. Average histological activity indices (HAI) were markedly improved in the interferon-treated group (9.5 +/- 3.7 to 7.0 +/- 4.3), but were unchanged in the placebo group (8.5 +/- 4.3 to 8.5 +/- 4.9). In addition, we compared the efficacy of interferon treatment between anti-hepatitis C virus (HCV) antibody positive and negative groups. Biochemical and histological improvements were similar and statistically significant in patients with and without antibody to hepatitis C virus. These data indicate that a eight-week course of alpha-interferon induces biochemical and histological improvement in more than half the patients with chronic non-A, non-B hepatitis.

Alanine Transaminase↗
PubMed1991

Detection and partial sequencing of hepatitis C virus RNA in the liver.

To detect hepatitis C virus RNA, total RNA was extracted from liver tissue, reverse transcribed to complementary DNA, and amplified by polymerase chain reaction. The reaction products were analyzed by ethidium bromide staining in acrylamide gel and hybridization with a radiolabeled probe. Hepatitis C virus RNA was thereby detected in 17 of 27 (63%) liver tissue specimens obtained from patients with non-A, non-B chronic liver diseases. Of these 27 patients, viral RNA was detected in 12 of 17 (71%) liver tissues from anti-hepatitis C virus-positive patients and in 5 of 10 (50%) liver tissues from anti-hepatitis C virus-negative patients. Direct sequencing of amplified complementary DNA (35 nucleotides) of the 17 RNA-positive samples showed only 66% to 77% homology to the reported hepatitis C virus complementary DNA sequence. These results indicate that the majority of anti-hepatitis C virus-positive patients are currently infected with hepatitis C virus, and some of the anti-hepatitis C virus-negative patients with non-A, non-B hepatitis are harboring hepatitis C virus in the liver. Detection of hepatitis C virus RNA appears to provide a useful indicator in the study of hepatitis C virus infection.

Base Sequence↗
PubMed1991

Detection and direct sequencing of hepatitis B virus genome by DNA amplification method.

Hepatitis B virus (HBV) DNA was detected with amplification by the polymerase chain reaction method. Cloned HBV DNA equivalent to one virus genome (3 x 10(-6) pg) was detectable by ethidium bromide staining after 50 cycles of polymerase chain reaction. By applying this method, presence of HBV DNA was studied in 23 hepatitis B surface antigen (HBsAg)-positive and 11 HBsAg-negative sera from patients with chronic liver disease. Hepatitis B virus DNA was positive in 8 of 8 hepatitis B e antigen (HBeAg)-positive, in 2 of 2 HBeAg- and anti-HBe-negative, and in 12 of 13 anti-HBe-positive sera. Hepatitis B virus DNA was undetectable in all HBsAg-negative sera even with amplification. To confirm specificity, the amplified product was directly sequenced. Sequences around 122nd and 160th codon of HBs gene, which determines subtypes d/y and w/r, respectively, were analyzed. The results were compatible with recent reports regarding the relation between HBV subtypes and HBV DNA sequence at those codons. Hepatitis B virus DNA could be detected at the level of one virion by gene amplification method, and its sequence could be determined by direct sequencing in a few days.

Base Sequence↗
PubMed1991

Acute pulmonary alveolar hypoxia increases lung and plasma endothelin-1 levels in conscious rats.

To investigate the effect of pulmonary alveolar hypoxia on the synthesis and release of endothelin (ET)-1, ET-1-like immunoreactivity (-LI) levels of the lung and plasma were measured in conscious unrestrained rats under hypoxic conditions. Sixty-min exposure to alveolar hypoxia (10% O2 or 5% O2) increased the ET-1-LI level in the lung. The plasma ET-1-LI level in hypoxic rats also increased significantly. The increase of plasma and lung ET-1-LI levels were parallel to the severity of hypoxia. These results demonstrates that acute pulmonary alveolar hypoxia increases lung and plasma ET-1-LI levels in conscious unrestrained rats, suggesting a possible physiological or pathophysiological significance of ET in alveolar hypoxia.

Animals↗
PubMed1991

Pathophysiological role of augmented atrial natriuretic polypeptide gene expression in DOCA-salt hypertension. Effects of atrial natriuretic polypeptide monoclonal antibody.

To elucidate the pathophysiological significance of endogenous atrial natriuretic polypeptide (ANP) in hypertension, we investigated the biosynthesis and secretion of ANP in deoxycorticosterone acetate (DOCA)-salt hypertensive rats and also examined the effect of passive immunization with monoclonal antibody raised against alpha-rat ANP on the development of hypertension in DOCA-salt rats. The plasma ANP level in DOCA-salt rats was significantly elevated in comparison to control rats. While the atrial ANP concentration in DOCA-salt rats was not significantly altered, the atrial level of ANPmRNA in DOCA-salt rats was two-fold higher than that in control rats. These results suggest the augmented biosynthesis of ANP in the atrium and the oversecretion of ANP from the heart in DOCA-salt rats. The levels of ANP and ANPmRNA in the ventricle of DOCA-salt rats exhibited significant increases, compared with those in control rats, suggesting the induction of ANP gene expression in the ventricle of DOCA-salt hypertensive rats under pre/after overload. Weekly intravenous administrations of monoclonal antibody with high affinity for alpha-rat ANP significantly augmented the rise in blood pressure of DOCA-salt rats. These results support the hypothesis that the augmented secretion of ANP is one of the defensive mechanisms to counteract high arterial pressure in this model of hypertension.

Animals↗
PubMed1991

Isolation and characterization of porcine endothelin-like peptide.

Two endogenous molecules possessing an endothelin-like sequence with an apparent molecular weight of 7 kDa were isolated from serum-free culture medium of porcine aortic endothelial cells, using a specific radioimmunoassay. N-terminal sequences of two molecules were identical to each other and were Ser-Leu-Lys-Asp-Leu-Phe-Pro-Ala-Lys-Ala-Ala-Asp-Arg-Arg-Asp-Arg-X-Gln-X- Ala-X- Gln-Lys-Asp, which corresponds to the sequence [94-117] of preproendothelin-1. This finding indicates that these two molecules may be closely related peptides such as the oxidized form or disulfide analogues and also suggests that the endogenous peptide possessing an endothelin-like sequence is generated by proteolytic cleavage at paired basic amino acids Arg92-Arg93. Further studies on the structure and function of new endogenous peptides possessing an endothelin-like sequence are ongoing in our laboratory.

Amino Acid Sequence↗
PubMed1991

Endothelin in patients with chronic renal failure.

To investigate the pathophysiological significance of endothelin-1 (ET-1) in renal failure, we measured plasma and urine concentrations of ET-1-like immunoreactivity (LI) by radioimmunoassay (RIA). The plasma ET-1-LI level was significantly increased in hemodialyzed and nonhemodialyzed patients with chronic renal failure (CRF). The increase in the plasma ET-1-LI level in CRF was much larger than that in other diseases in which the plasma ET-1-LI level was reported to be increased. The urine ET-1-LI level was lower, and daily excreted amounts of ET-1-LI were smaller in CRF patients than in normal subjects. These findings indicate that the increased plasma level of ET-1-LI in CRF results from the decreased clearance rate of ET-1-LI in the kidney. Gel permeation chromatographic analysis revealed that ET-1-LI in plasma from CRF consisted of small and large molecular forms of ET-1-LI. The small molecular form is presumably ET-1, and large molecular forms are big ET-1 and another component with the molecular weight of 6,000 as is the case of that in normal plasma (1). However, the ratio of the smaller to large molecular forms of ET-1-LI in CRF was 1:13 and was quite different from that in normal plasma (1:4). These observations clearly indicate that the elevation of plasma ET-1-LI level in CRF was mainly due to the increase in the large molecular form of ET-1-LI.

Chromatography, Gel↗
PubMed1991

Rapid diagnosis of cytomegalovirus infections by direct immunoperoxidase staining with human monoclonal antibody against an immediate-early antigen.

Direct immunoperoxidase technique using a horseradish peroxidase (HRP)-conjugated Fab' fragment of human monoclonal antibody (humab C7), designated HRP-C7, was evaluated as a rapid diagnosis of cytomegalovirus (CMV) infection. A total of 138 clinical specimens consisting of 124 urine samples and 14 oral swabs were examined for CMV by the direct HRP-C7 staining in comparison with conventional virus isolation. The number of CMV-positive samples by each method was 40 (29.0%) for the former and 37 (26.8%) for the latter, respectively. By HRP-C7 staining, CMV was identifiable within 24 hr after inoculation. By conventional isolation method, an average of 10.3 days had passed before cytopathic effect characteristic of CMV appeared in the cell culture. Some false-positive and false-negative cases were discussed in relation to toxicity of urine samples, storage of the samples, and amount of CMV in the sample. The sensitivity and specificity of HRP-C7 method against conventional isolation method were 89.2% and 93.1%, respectively. Thus, HRP-C7 staining is useful for a rapid diagnosis of CMV infections.

Antibodies, Monoclonal↗
PubMed1991

Biosynthesis, secretion, and receptor selectivity of human brain natriuretic peptide.

Biosynthesis, secretion and receptor selectivity of human brain natriuretic peptide (hBNP) were studied. The BNP mRNA level in the ventricle was approximately 40% of that in the atrium and, taking tissue weight into account, the total amount of BNP mRNA in the ventricle was about twofold greater than the total amount in the atrium. The plasma BNP-like immuno-reactivity (-LI) level in normal subjects was 0.90 +/- 0.07 fmol/mL, which was 16% of the ANP-LI level. In contrast, the plasma BNP-LI level markedly increased in patients with congestive heart failure, with a progressive rise in proportion to its severity. There was a significant step-up of the plasma BNP-LI level in the coronary sinus (CS) compared with that in the aortic root, and the difference in the plasma BNP-LI level between the CS and the aorta (Ao), delta (CS-Ao)BNP, increased with the severity of congestive heart failure. In addition, the difference in the BNP-LI level between the anterior inverventricular vein (AIV) draining the ventricle and the aorta (delta (AIV-Ao)BNP) was comparable to delta (CS-Ao) BNP, indicating that BNP is secreted predominantly from the ventricle. Binding ability to human clearance receptors (C receptors) and cyclic GMP (cGMP) production of hBNP were investigated and compared with those of ANP. hBNP bound to human C receptors very weakly (about 7%), but exerted cGMP production similar to ANP in cultured human mesangial cells and bovine endothelial cells. In conclusion, hBNP is a novel cardiac hormone mainly synthesized in and secreted from the ventricle and plays physiological and pathophysiological roles in the dual cardiac natriuretic peptide system.

Adolescent↗
PubMed1991

Expression of brain natriuretic peptide gene in human heart. Production in the ventricle.

To elucidate the expression of the brain natriuretic peptide gene in the human heart, we have measured brain natriuretic peptide mRNA levels in hearts using the Northern blot hybridization method. Brain natriuretic peptide mRNA was present with a size of approximately 0.9 kb in the ventricle as well as in the atrium. The brain natriuretic peptide mRNA level in the ventricle was 52% of that in the atrium, whereas the atrial natriuretic peptide mRNA level in the ventricle was approximately two orders of magnitude lower than that in the atrium. Taking atrial and ventricular weights into account, the total amount of brain natriuretic peptide mRNA in the ventricle represented 77% of that in the whole heart. These results demonstrate that most of brain natriuretic peptide mRNA occurs in the ventricle, in contrast with atrial natriuretic peptide mRNA, which is present mainly in the atrium, indicating that the ventricle is a major production site of brain natriuretic peptide.

Aged↗
PubMed1991

Natriuretic peptides as cardiac hormones in normotensive and spontaneously hypertensive rats. The ventricle is a major site of synthesis and secretion of brain natriuretic peptide.

To study synthesis, storage, and secretion of brain natriuretic peptide (BNP) in the heart, we have measured BNP mRNA and BNP concentrations in the hearts of Wistar-Kyoto rats and also have investigated its secretion from the isolated perfused heart. The atrium expressed the BNP gene at a high level, and a considerable amount of BNP mRNA also was present in the ventricle, which corresponded to approximately 40% of the atrial BNP mRNA concentration. When tissue weight was taken into account, the total content of BNP mRNA in the ventricle was approximately threefold larger than that in the atrium, although the atrial natriuretic peptide (ANP) mRNA content in the ventricle was only 7% of that in the atrium. By contrast, the BNP concentration in the ventricle was 4.07 +/- 0.97 pmol/g, which was less than 1% of that in the atrium (451 +/- 86 pmol/g). The basal secretory rate of BNP from the isolated perfused whole heart was 49.3 +/- 6.1 fmol/min, approximately 60% of which was maintained even after atrial removal, whereas the secretory rate of ANP was reduced to less than 5%. We also studied age-matched spontaneously hypertensive rats-stroke prone. The rank order of the BNP mRNA concentration in the hearts of these rats was left ventricle greater than right ventricle greater than right atrium = left atrium, and the total BNP mRNA content and BNP secretory rate in the ventricle were twice as large as in Wistar-Kyoto rats. These results demonstrate that BNP is a novel cardiac hormone in rats and is predominantly synthesized in and secreted from the ventricle. This is in striking contrast to ANP, which occurs mainly in the atrium. The results also suggest possible pathophysiological roles of BNP in certain cardiovascular disorders.

Animals↗
PubMed1991

Brain natriuretic peptide as a novel cardiac hormone in humans. Evidence for an exquisite dual natriuretic peptide system, atrial natriuretic peptide and brain natriuretic peptide.

Using a specific radioimmunoassay for human brain natriuretic peptide (hBNP) with a monoclonal antibody, we have investigated its synthesis, secretion, and clearance in comparison with those of atrial natriuretic peptide (ANP) in normal subjects and patients with congestive heart failure (CHF). Mean BNP-like immunoreactivity (-LI) levels in normal atrium and ventricle were 250 and 18 pmol/g, respectively. The plasma BNP-LI level in normal subjects was 0.90 +/- 0.07 fmol/ml, which was 16% of the ANP-LI level. In contrast, the plasma BNP-LI level markedly increased in patients with CHF in proportion to its severity, and surpassed the ANP-LI level in severe cases. There was a significant step-up of the plasma BNP-LI level in the coronary sinus (CS) compared with that in the aortic root (Ao) and the difference between these BNP-LI levels, delta(CS-Ao)BNP, also increased with the severity of CHF. In addition, the step-up of the BNP-LI level in the anterior interventricular vein [delta(AIV-Ao)BNP] was comparable to delta(CS-Ao)BNP, indicating that BNP is secreted mainly from the ventricle. Predominant BNP synthesis in the ventricle was also confirmed by Northern blot analysis. Catheterization and pharmacokinetic studies revealed that hBNP is cleared from the circulation more slowly than alpha-hANP; this was in part attributed to lower (about 7%) binding affinity of hBNP to clearance receptors than that of alpha-hANP. A predominant molecular form of BNP-LI in the heart and plasma was a 3-kD form corresponding to hBNP. These results indicate that BNP is a novel cardiac hormone secreted predominantly from the ventricle, and that the synthesis, secretion and clearance of BNP differ from those of ANP, suggesting discrete physiological and pathophysiological roles of BNP in a dual natriuretic peptide system.

Antibodies, Monoclonal↗
PubMed1991

C-type natriuretic peptide (CNP) in rats and humans.

We have established a specific radioimmunoassay (RIA) for C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, and have elucidated its tissue distribution and molecular form. In rats, high concentrations of CNP-like immunoreactivity (-LI) were detected in the anterior lobe (19.8 +/- 8.6 pmol/g) and neurointermediate lobe (4.64 +/- 0.74 pmol/g) of the pituitary gland. CNP-LI was present throughout the brain with its high concentrations in the hypothalamus and cerebellum. Small amounts of CNP-LI were also detected in the lower part of gastrointestinal tract and the kidney. However, no significant amount of CNP-LI was present in other organs including the heart. Considerable amounts of CNP-LI were detected throughout the human brain. High performance-gel permeation chromatography coupled with the RIA detected two peaks of CNP-LI in the rat brain; CNP and presumably its N-terminally elongated form with 53 amino-acid residues, CNP-53. These findings indicate that the tissue distribution and processing pattern of CNP are clearly different from those of atrial natriuretic peptide and brain natriuretic peptide and suggest possible roles of CNP as a neurotransmitter or neuromodulator rather than as a cardiac hormone.

Animals↗