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Biomedical subjects

J Yamamoto

Publications and source records attributed to J Yamamoto.

At least 199 records · Page 11Linked to original sources
PubMed1994

Beta-adrenoceptor-G protein-adenylate cyclase complex in rat hearts with ischemic heart failure produced by coronary artery ligation.

We examined the role of the myocardial beta-adrenoceptor-G protein-adenylate cyclase complex in 10-week-old Wistar rats with ischemic heart failure produced by ligating the left coronary artery (l) and in sham-operated control rats (C). We determined the number of beta-adrenoceptors (Bmax), the dissociation constant (Kd) using a binding assay and adenylate cyclase activity. Levels of mRNA encoding for the alpha subunit of the stimulatory guanine nucleotide-binding protein (Gs alpha) and the alpha subunit of the inhibitory guanine nucleotide-binding protein (Gi alpha) were measured by Northern blot analysis. The amounts of Gs alpha and Gi alpha were measured by Western blot analysis. Bmax and Kd did not differ significantly between the two groups: Bmax: l, 14.7 +/- 1.3 v C, 13.4 +/- 0.9 f mol/mg protein; Kd: l, 345 +/- 31 v C, 340 +/- 28 pM (mean +/- standard error, S.E.). There were no significant differences in Gs alpha and Gi alpha concentrations between the two groups as measured by Northern blot analysis (Gs alpha: l, 91.6 +/- 4.5 v C, 96.5 +/- 2.3%; Gia; l, 95.4 +/- 3.6 v C, 90.0 +/- 3.0%) or by Western blot analysis (Gs alpha: l, 95.2 +/- 2.0 v C, 94.5 +/- 2.6%; Gi alpha: l, 91.5 +/- 3.0 v C, 95.1 +/- 2.9%). Activity of basal and MnCl2-stimulated adenylate cyclase did not differ significantly in the two groups: basal: l, 7.5 +/- 0.7 v C, 8.1 +/- 0.5 pmol cAMP/mg protein/min; MnCl2 l, 80.8 +/- 5.8 v C, 86.4 +/- 6.7 pmol cAMP/mg protein/min. Sodium fluoride and forskolin-stimulated adenylate cyclase activity were significantly lower in the hearts with ischemic failure compared with controls (sodium fluoride: l, 68.5 +/- 5.6 v C, 103 +/- 4.8 pmol cAMP/mg protein/min; forskolin: l, 84.6 +/- 6.5 v C, 117.1 +/- 5.6 pmol cAMP/mg protein/min). These data suggest the presence of myocardial Gs alpha dysfunction in ischemic heart failure. We conclude that such a dysfunction in Gs alpha may contribute to the contractile abnormalities in ischemic heart failure.

Adenylyl Cyclases↗
PubMed1994

Gastrin receptor genes are expressed in gastric parietal and enterochromaffin-like cells of Mastomys natalensis.

Although gastric enterochromaffin-like (ECL) carcinoid tumors are known to develop in patients with long-standing hypergastrinemia, the expression of the gastrin receptor gene in ECL cells has not yet been demonstrated. Therefore, this study was designed to examine gastrin receptor gene expression in ECL cells. Mastomys gastric mucosal cells isolated by enzyme dispersion were separated into 10 fractions (F1-10) by centrifugal elutriation. Each fraction was examined histologically to determine whether they contained ECL and/or parietal cells and Northern blot analysis was used to confirm the presence of histidine decarboxylase and H+, K(+)-ATPase gene expression. ECL cells were found only in fractions 1 and 2, whereas parietal cells were detected in fractions 6-10. Gastrin receptor gene expression was demonstrated in both parietal cell-rich and ECL cell-rich fractions. In addition, the gastrin receptor cDNA sequences obtained from the two of the fractions (F1 and 8) were identical. These results suggest that gastrin receptor genes are expressed in ECL cells as well as in parietal cells and that these receptors are identical.

Animals↗
PubMed1994

Psychiatric disorders among elderly Koreans in the United States.

This study examines the lifetime prevalence of various psychiatric disorders among 100 Korean elderly in Los Angeles. The instrument used in this study is the Diagnostic Interview Schedule, Version III (DIS III, 1-10). The main finding is of relatively low prevalence of most DSM-III disorders with the exception of alcohol abuse and dependence. The rate of alcoholism is astonishingly high among elderly Korean males in Los Angeles. The findings are compared with the U.S. Epidemiological Catchment Area studies, and with other much larger community studies conducted in Korea. A comparison shows that there are no significant differences in the prevalence of mental disorders between elderly Koreans in Los Angeles and elderly Americans in St. Louis (N = 576) except for the prevalence of alcohol abuse and dependence. The lifetime prevalence of DSM-III disorders among Koreans in Korea (N = 5100) is generally higher than among elderly Koreans in Los Angeles.

Aged↗
PubMed1994

Predictive factors for postoperative recurrence of hepatocellular carcinoma.

BACKGROUND/AIMS: The survival rate for hepatocellular carcinoma after hepatectomy remains unsatisfactorily low because of the high recurrence rate. The purpose of this study was to elucidate predictive factors for postoperative recurrence of hepatocellular carcinoma. METHODS: Univariate analysis and a multiple regression model were used to retrospectively determine the factors potentially related to recurrence in 98 patients with hepatocellular carcinoma who had undergone curative hepatic resection. RESULTS: DNA diploidy, absence of alcohol abuse, and absence of vascular invasion were determined to be independent favorable predictive factors using a multivariate analysis with Cox's proportional hazards model. A predictive index was developed using these three factors according to the following equation: 1.486 x (O = DNA diploidy or 1 = DNA aneuploidy) + 1.138 x (O = absence or 1 = presence of alcohol abuse) + 0.946 x (O = absence or 1 = presence of vascular invasion). This index was used to classify the patients into two groups with good or poor prognosis. The median time for disease recurrence for the two groups was 24.1 and 9.2 months, respectively (P < 0.001). CONCLUSIONS: The results may be useful in the determination of treatment strategies and postoperative follow-up schedules and in the design and analysis of future clinical trials of therapy for hepatocellular carcinoma.

Aged↗
PubMed1994

Effect of insulin on sodium reabsorption in hypertensive patients.

The effect of insulin on sodium reabsorption was studied with the hyperinsulinemic euglycemic clamp technique, using lithium clearance as a marker of sodium reabsorption in the proximal tubule. The subjects were 12 nondiabetic hypertensive patients who were divided into two groups. In the first group, the effect of insulin on sodium and lithium reabsorption was examined. The second group served as a control. Blood glucose was continuously monitored from 9 AM to 10 AM (baseline period). Hyperinsulinemic euglycemic clamp was performed with an artificial endocrine pancreas by infusing insulin at a rate of 2 mU/kg.min from 10 AM to noon. In the control group the protocol was exactly the same except that glucose clamp was not performed. Urine was collected hourly from 9 AM to noon. In the glucose clamp group, urinary sodium excretion (UNaV) decreased by 42% during the second hour of the glucose clamp (P < .02). Clearance of lithium (CLi) and fractional distal sodium reabsorption [(CLi-CNa)/CLi] increased, and CNa/CLi decreased significantly during the glucose clamp. In the control group, UNaV and (CLi-CNa)/CLi remained unchanged, and CLi decreased significantly. As shown by the increase of CLi and (CLi-CNa/CLi, and the decrease of UNaV and CNa/CLi in the glucose clamp group, insulin decreases urinary sodium excretion by increasing distal sodium reabsorption, whereas it inhibits sodium reabsorption in the proximal tubule.

Absorption↗
PubMed1994

Comparison of effects of nicardipine and trichlormethiazide on insulin sensitivity in hypertensive patients.

We performed a randomized, crossover study comparing the effects of nicardipine and trichlormethiazide on insulin sensitivity in 8 untreated essential hypertensive patients. They were treated either with nicardipine or trichlormethiazide for 12 weeks, after which they were treated with the alternative drug for a further 12 weeks. Insulin sensitivity was determined by the hyperinsulinemic euglycemic clamp technique. Nicardipine had no adverse effect on insulin sensitivity. Trichlormethiazide decreased insulin sensitivity index by 12%. As nicardipine does not have an adverse effect on insulin sensitivity, it should be preferred in patients who have a proven metabolic abnormality.

Adult↗
PubMed1994

The inhibitory effect of sulfated schizophyllans and related oligosaccharides on coagulation and fibrinolysis.

Sulfated schizophyllans and sulfated oligosaccharides were prepared and their inhibitory effects on coagulation and fibrinolysis were examined. Some sulfated schizophyllans, which had a sulfur content of more than 10%, prolonged prothrombin time (PT) and thrombin time (TT). Interestingly, some sulfated schizophyllans and related oligosaccharides were able to inhibit plasmin toward fibrinolysis and amidolysis.

Amino Acid Sequence↗
PubMed1994

Amino acids and peptides. XXXVII. Synthesis of stereoisomeric nonapeptides corresponding to sequence 41-49 of eglin c and examination of their inhibitory activity against human leukocyte cathepsin G and alpha-chymotrypsin.

A nonapeptide, H-Ser-Pro-Val-Thr-Leu-Asp-Leu-Arg-Tyr-OH, corresponding to sequence 41-49 of eglin c inhibited leukocyte cathepsin G and alpha-chymotrypsin with Ki values of 2.2 x 10(-5) and 7.2 x 10(-6) M, respectively, although eglin c itself inhibited leukocyte elastase, cathepsin G and alpha-chymotrypsin with Ki values of 6.0 x 10(-9), 5.5 x 10(-9) and 2.5 x 10(-9) M, respectively. The inhibitory activity of the nonapeptide decreased following incubation with cathepsin G due to the cleavage of the Leu45-Asp46 peptide bond. Therefore, Leu45 and/or Asp46 were replaced with D-amino acids and the inhibitory activities of the resultant nonapeptides were examined. Their inhibitory activities against cathepsin G and alpha-chymotrypsin were much weaker than those of the all-L-type nonapeptide, suggesting that the amino acids at the active site, Leu45 and Asp46 are required to be in the L-configuration for potent activity.

Amino Acid Sequence↗
PubMed1994

Increased levels of inhibitory G protein in myocardium with heart failure.

To identify any differences in inhibitory G protein (Gi) attributable to species or the cause of heart failure, we studied the changes in this protein in different animal models of heart failure: 1) different species; rats vs. hamsters (F1B) with cardiomyopathy induced by adriamycin (ADR) and 2) different etiologies; rats with ischemic heart failure (IHD) due to coronary artery ligation vs. rats with cardiomyopathy induced by ADR and F1B (20-week-old) hamsters with cardiomyopathy induced by ADR vs Syrian hamsters BIO 14.6 (40-week-old) with genetic cardiomyopathy, using Western blotting methods and ADP-ribosylation. We also sought to determine whether changes in the amount of Gi protein reflected the regulation of adenylate cyclase. The amount of immunodetectable Gi rose by 35% (p < 0.05) in ADR rats, 25% (p < 0.05) in ADR hamsters, 15% (p < 0.05) in IHD rats, and 28% (p < 0.05) in BIO 14.6 hamsters, as compared with control rats, F1B (20-week-old) hamsters, sham-operated control rats, and F1B (40-week-old) hamsters, respectively. Assessment of Gi by pertussis toxin-catalyzed ADP-ribosylation revealed increases in Gi of 24% (p < 0.05) in ADR rats and of 44% (p < 0.05) in BIO 14.6 hamsters, as compared with their respective controls. Gi function, as assayed by the acetylcholine-induced inhibition of adenylate cyclase, also increased. Thus, Gi protein appears to contribute to the changes in signal transduction in myocardium with heart failure.

Adenylyl Cyclases↗
PubMed1994

Scintigraphic and ultrasonographic diagnosis of soft tissue injury in a thoroughbred horse.

A 2.5-year-old female Thoroughbred horse was referred to the veterinary teaching hospital for right front limb lameness of 1 year duration. Physical examination and diagnostic nerve blocks failed to localize the origin of the lameness. Scintigraphy with 99mTc-MDP suggested increased radionuclide uptake in the palmar metacarpal soft tissues of the right front limb. Ultrasonographic examination revealed hypoechoic lesions in the superficial digital flexor tendon and the suspensory ligament, suggesting tendinitis and desmitis. Combined imaging modalities improved detection and characterization of the cause of a long-standing obscure lameness.

Animals↗
PubMed1994

[Advances in the experimental analysis of behavior: issues of choice behavior, comparative cognition, and human language].

As the opportunity to contact with related areas has increased, the study of of the experimental analysis of behavior has experienced revolutionary changes. Some of the most active and important areas-studies of choice, comparative cognition, and human language--are reviewed to acquaint readers. Studies of CHOICE have linked to the molar theories of behavioral economics and behavioral ecology, which promoted research of choice by animals under uncertainty conditions. Further approach has been made to integrate the molar and molecular analyses on the basis of the ideas of behavior dynamics. COMPARATIVE COGNITION is a part of a larger field including cognitive science, behavioral neuroscience, and biological science. Recent developments, aided with a comparative perspective, made significant contributions to our understanding of the phylogeny and ontogeny of cognition. Advances in analysis of human behavior provided tools to study behavioral aspects of semantics, syntax, and pragmatics of HUMAN LANGUAGE. Using the paradigm of stimulus equivalence, the emergence of stimulus relations, stimulus-stimulus networks, hierarchical structure of verbal behavior, and other language-related behaviors have been investigated.

Choice Behavior↗
PubMed1994

Perioperative blood transfusion promotes recurrence of hepatocellular carcinoma after hepatectomy.

BACKGROUND: Recent advances in liver surgery have reduced operative blood loss drastically, and in more than one half of the patients in our hospital, the liver resection can be accomplished without blood transfusion. METHODS: Two hundred fifty-two patients who underwent complete resection for hepatocellular carcinoma (HCC) were evaluated to assess the effect of perioperative blood transfusion on the recurrence of carcinoma. RESULTS: Carcinoma recurred in 55 (74.3%) of the 74 patients who received a transfusion, but in only 89 (50%) of the 178 patients who did not receive a transfusion (p = 0.0001). This effect was significant even when only a small amount of blood was transfused (p = 0.0001). Based on multivariate analysis, perioperative blood transfusion was a significant predictor for accelerated recurrence (p = 0.003), as were tumor invasiveness (vascular invasion or intrahepatic metastasis) (p = 0.0008) and background liver cirrhosis (p = 0.04). The recurrence-promoting effect of blood transfusion was markedly significant when the patient had either noninvasive HCC (p = 0.0005) or a cirrhotic liver (p < 0.0001). CONCLUSIONS: These results strongly suggest that perioperative blood transfusion substantially promotes the recurrence of HCC after hepatectomy. This effect must be considered and added to the risks of perioperative blood transfusion when formulating a surgical strategy for HCC.

Adult↗
PubMed1993

Expression and characterization of recombinant mouse mastocytoma histidine decarboxylase.

The possibility of post-translational processing of mouse mastocytoma histidine decarboxylase (HDC; EC 4.1.1.22) was investigated. The molecular mass of the recombinant HDC expressed in Sf9 cells using HDC cDNA from mouse mastocytoma cells was determined to be 74 kDa by SDS-PAGE. In contrast to the native HDC from mastocytoma cells, the recombinant 74 kDa HDC was essentially inactive and precipitable in Sf9 cells. On the other hand, deletion mutants of the recombinant HDC lacking a C-terminal region equivalent to 10 (64 kDa) or 20 kDa (54 kDa) in size were present as active forms in the soluble fraction of Sf9 cells. To examine the C-terminal deletion of the 74 kDa species yielding the 53 kDa species by means of the immunoblotting analysis, two peptides (corresponding to residues 323-337 and 572-586 of the recombinant 74 kDa HDC peptide) were synthesized, and rabbit antiserum specific for each peptide was prepared. On immunoblotting analysis, anti-peptide 323-337 antiserum recognized both the recombinant 74 kDa and native enzyme subunit peptides, but anti-peptide 572-586 antiserum recognized only the recombinant 74 kDa peptide, i.e., not the native enzyme subunit peptide. Furthermore, HDC activity in the crude extract from Sf9 cells was not precipitable with antipeptide 572-585 antiserum. These results strongly suggest that the 53 kDa subunit peptide of native mastocytoma HDC is derived from the unidentified inactive 74 kDa HDC peptide, probably by post-translational processing of HDC in its C-terminal region.

Amino Acid Sequence↗
PubMed1993

Enhanced expression of the mouse L-histidine decarboxylase gene with a combination of dexamethasone and 12-O-tetradecanoylphorbol-13-acetate.

We previously reported that the induction of L-histidine decarboxylase (HDC) in mouse mastocytoma cells was synergistically potentiated with a combination of dexamethasone and 12-O-tetradecanoylphorbol-13-acetate (TPA) [Biochim. Biophys. Acta, 1133, 172-178 (1992)]. To clarify the molecular mechanism of this synergistic action on HDC expression, we have isolated genomic DNA clone (MGH5), including 5'-flanking region of the mouse HDC gene. The transcription start site and the nucleotide sequences of the promoter regions were determined. We found that this clone contains a TATA-like box and a GC-box in the promoter region, and several putative binding sites for regulatory proteins in the 5'-flanking region. With mastocytoma cells transiently transfected with 5' deletion constructs of HDC-CAT fusion gene, it was found that the sequence from -267 to -43 is essential for the regulatory elements(s) involved in the increased transcription of the HDC gene with dexamethasone and TPA.

Amino Acid Sequence↗
PubMed1993

Effect of leucocyte products on platelet thrombus formation, coagulation and spontaneous thrombolysis, as measured from native human blood, in vitro.

Contribution of leucocytes to formation and lysis of arterial (platelet) thrombi was investigated. Secretory products of polymorphonuclear leucocytes (PMNs) during phagocytosis and cell lysates were prepared from eight volunteers. Platelet-rich thrombi were formed in flowing native human blood either by shear-stress or by collagen fibre, by haemostatometry. Tested in eight volunteers, PMN products significantly enhanced both thrombotic reactions and induced lysis of these thrombi. A specific inhibitor of leucocyte proteases (eglin c) inhibited platelet reaction to shear-stress and collagen and spontaneous thrombolysis. Our findings provide further evidence for the prothrombotic and potent thrombolytic effect of leucocytes associated with an arterial thrombus.

Biological Factors↗
PubMed1993

Different effects of substitutions at residues 224 and 228 of MHC class I on the recognition of CD8.

Previous studies indicated that weak xenoresponse to HLA class I by mouse T cells is due to the inefficient interaction of mouse CD8 with the alpha 3 domain of HLA class I. The present study using chimeric H-2Kb molecules with recombinant alpha 3 domain between H-2Kb and HLA-B7 as well as single amino acid mutants of H-2Kb demonstrated that each substitution at residues 224 and 228 affects recognition of CD8-dependent mouse CTL clones. On the other hand, reactivity of IL-2-producing H-2Kb-specific T cell hybridoma transfected with mouse CD8 alpha was abrogated by substitution at residue 224 but not by that at residue 228. This indicates that the substitution at residue 228 affects recognition of CD8-dependent CTL but does not critically affect binding of CD8 to MHC class I molecules, although residue 224 abrogates binding of CD8. The model structure of the alpha 3 domain of H-2Kb suggests that the substitution at residue 224 induces conformational change of CD8 binding loop, whereas minimum structure change by the substitution at residue 228 is expected. It is therefore speculated that minimum structure change of CD8 binding loop by substitution at residue 228 may influence binding affinity of CD8, which abrogates recognition of CD8-dependent CTL but not IL-2 production of the CD8-dependent T cell hybridoma.

Amino Acid Sequence↗