Biomedical subjects

K Ohashi

Publications and source records attributed to K Ohashi.

At least 271 records · Page 15Linked to original sources

PubMed1996

Interferon-gamma-inducing factor, a novel cytokine, enhances Fas ligand-mediated cytotoxicity of murine T helper 1 cells.

Fas ligand (FasL), expressed on activated T cells, plays a central role in regulating the immune response by inducing apoptosis in activated lymphocytes through binding to its receptor, Fas. We report here that a newly discovered cytokine, interferon-gamma-inducing factor (IGIF) (H. Okamura et al., Nature 378, 88, 1995), selectively enhances the FasL-mediated cytotoxicity of cloned murine Th1 cells, but not Th0 or Th2 cells. Anti-IFN-gamma antibody (Ab) did not block the IGIF-induced cytotoxicity of Th1 cells, nor did IFN-alpha, IFN-gamma, or TNF-alpha augment the cytotoxic activity of Th1, thus indicating that this enhanced cytotoxicity of Th1 cells was mediated by IGIF. In addition, IL-12 was also found to enhance the FasL-mediated cytotoxicity of Th1 cells, suggesting that Th1 cells possesses receptors for both cytokines although these cytokines can act via different pathways. The results thus show that IGIF, recently proposed as IL-18, might play a potential role in immunoregulation or in inflammation by augmenting the functional activity of FasL on Th1 cells.

Animals↗

PubMed1996

Characterization of the complete genomic structure of human thromboxane synthase gene and functional analysis of its promoter.

Thromboxane A2 (TXA) is a potent vasoconstrictor and mediator of platelet aggregation. Thromboxane synthase (TXAS), which catalyzes the biosynthesis of TXA, is a member of the cytochrome P450 superfamily. We report here the complete genomic structure of the human TXAS gene. The gene contains 13 exons and is 193 kb long, the largest P450 gene ever isolated. The physical localization of the TXAS gene on the genetic map of human chromosome 7 was established. A major transcription start site is located at a motif similar to the initiator element where the transcription factor TFII-I binds. We have sequenced up to 1.6 kb of the 5'-flanking region of the TXAS gene and characterized the promoter activity in a human megakaryocyte cell line and endothelial cells. Our results demonstrated that the nucleotides -248/+137 relative to the major transcription start site conferred a full promoter activity of the TXAS gene. This region was regulated negatively by cis-elements located between -1562 and -248. Moreover, the regions outside -1562/+137 might control tissue-specific TXAS expression.

Base Sequence↗

PubMed1996

Induction of macrophage colony-stimulating factor receptor (c-fms) expression in vascular medial smooth muscle cells treated with heparin binding epidermal growth factor-like growth factor.

Vascular smooth muscle cells migrate, proliferate, and transform to foam cells during the atherosclerotic process. We have reported that smooth muscle cells derived from the intima of atherosclerotic lesions express the proto-oncogene c-fms and a scavenger receptor, which are not normally expressed in normal medial smooth muscle cells. In the present study, we demonstrated that heparin binding epidermal growth factor-like growth factor (HB-EGF) induced the expression of c-fms and the scavenger receptor in normal human medial smooth muscle cells to the level observed in the intima. The expression of c-fms was partially inhibited by a protein kinase C inhibitor, suggesting that HB-EGF induces c-fms via pathways that are both dependent on and independent of protein kinase C. By contrast, most of the scavenger receptor induction by HB-EGF was suppressed by protein kinase C inhibitors. These results indicate that two characteristic genes of monocyte-derived macrophages were induced by HB-EGF via different mechanisms. The alteration of gene expression in response to HB-EGF may play an important role in the phenotypic change of smooth muscle cells to macrophage-like foam cells during the atherosclerotic process.

Blotting, Western↗

PubMed1996

Role of the low density lipoprotein (LDL) receptor pathway in the metabolism of chylomicron remnants. A quantitative study in knockout mice lacking the LDL receptor, apolipoprotein E, or both.

Two receptor pathways are thought to mediate the hepatic clearance of chylomicron remnants, (i) the low density lipoprotein receptor (LDLR) pathway and (ii) non-LDLR pathway. The current study was undertaken to quantitatively assess the contribution of each receptor pathway to hepatic catabolism of chylomicron remnants, by using mice that are deficient in apolipoprotein E (apoE) (apoE(-/-)), the LDLR (LDLR(-/-)), and both (apoE(-/-);LDLR(-/-)). Vitamin A fat tolerance tests showed that the area under the curves of the plasma excursions of retinyl ester in the LDLR(-/-), apoE(-/-), and apoE(-/-);LDLR(-/-) mice were 4, 12, and 12 times larger than those in wild-type mice. The retinyl ester accumulated in the plasma of the LDLR(-/-) mice was distributed in larger subfractions of triglyceride-rich lipoproteins, chylomicrons through very low density lipoprotein-C. These results indicate that the LDLR constitutes the major pathway for the clearance of retinyl ester. In support of this, agarose gel electrophoresis revealed that an oral fat load resulted in retention of chylomicrons in the LDLR(-/-) mice, which was not seen in wild-type mice. The observation that the apoE(-/-) mice showed larger retinyl ester excursion than LDLR(-/-) mice indicates that an apoE-dependent non-LDLR pathway is involved in the rest of the clearance of the retinyl ester. Together, we conclude that the LDLR pathway plays a significant role in the chylomicron remnant metabolism in mice fed a normal chow.

Animals↗

PubMed1996

Enhancement of N-nitrosodiethylamine-initiated hepatocarcinogenesis caused by a colchicine-induced cell cycle disturbance in partially hepatectomized rats.

The effects of a colchicine-induced M-phase block of regeneration after partial hepatectomy on early-stage liver carcinogenesis were studied in rats. When administered 1 or 3 days after N-diethylnitrosamine initiation and partial hepatectomy, colchicine increased the mitotic index of regenerating hepatocytes at days 4-6 without evidence of liver cell necrosis. When the protocol was combined with a selection procedure (E. Cayama et al., Nature (Lond.), 275: 60-62, 1978), a significant increase in the size but not number of gamma-glutamyltranspeptidase-positive foci at week 5 was observed in a colchicine dose-dependent manner. This was associated with an elevated incorporation of 5-bromo-2-deoxyuridine into the gamma-glutamyltranspeptidase-positive cells. In a longer-term experiment, the numbers, sizes, and 5-bromo-2-deoxyuridine labeling index of persistent nodules were increased significantly in colchicine-treated rats at week 9. This was associated with significant increases in the incidences and numbers of hepatocellular carcinomas at week 42. The above results raise the interesting possibility that a cell cycle disturbance in the early stage of liver carcinogenesis provides a persisting growth advantage for initiated cells, resulting in enhanced growth of foci and persistent nodules that evolve into hepatocellular carcinomas.

Animals↗

PubMed1996

Suppression of diet-induced atherosclerosis in low density lipoprotein receptor knockout mice overexpressing lipoprotein lipase.

Lipoprotein lipase (LPL) is a key enzyme in the hydrolysis of triglyceride-rich lipoproteins. Conflicting results have been reported concerning its role in atherogenesis. To determine the effects of the overexpressed LPL on diet-induced atherosclerosis, we have generated low density lipoprotein receptor (LDLR) knockout mice that overexpressed human LPL transgene (LPL/LDLRKO) and compared their plasma lipoproteins and atherosclerosis with those in nonexpressing LDLR-knockout mice (LDLRKO). On a normal chow diet, LPL/LDLRKO mice showed marked suppression of mean plasma triglyceride levels (32 versus 236 mg/dl) and modest decrease in mean cholesterol levels (300 versus 386 mg/dl) as compared with LDLRKO mice. Larger lipoprotein particles of intermediate density lipoprotein (IDL)/LDL were selectively reduced in LPL/LDLRKO mice. On an atherogenic diet, both mice exhibited severe hypercholesterolemia. But, mean plasma cholesterol levels in LPL/ LDLRKO mice were still suppressed as compared with that in LDLRKO mice (1357 versus 2187 mg/dl). Marked reduction in a larger subfraction of IDL/LDL, which conceivably corresponds to remnant lipoproteins, was observed in the LPL/LDLRKO mice. LDLRKO mice developed severe fatty streak lesions in the aortic sinus after feeding with the atherogenic diet for 8 weeks. In contrast, mean lesion area in the LPL/LDLRKO mice was 18-fold smaller than that in LDLRKO mice. We suggest that the altered lipoprotein profile, in particular the reduced level of remnant lipoproteins, is mainly responsible for the protection by LPL against atherosclerosis.

Animals↗

PubMed1996

Sexual diversity of the lipid metabolism in the Harderian gland of the golden hamster.

Fatty acid and alkyl compositions of 1-alkyl-2,3-diacylglycerols (ADG) in the Harderian gland of the golden hamster were determined. Fatty acids of male ADG consisted of straight chain saturated acids ranging from C12 to C22. Both even- and odd-numbered acids were observed, indicating that acetyl- and propionyl-CoAs were equally used as primers in the fatty acid synthesis. In female ADG a large amount of iso- and anteiso-branched fatty acids were detected. Odd-numbered acids (C15, 17, 19, and 21) contained iso- together with anteiso-branchings, and even-numbered acids (C16 and 18) contained iso-branchings. These findings suggested that isobutyryl-, isovaleryl-, and 2-methylbutyryl-CoAs were used as primers in addition to acetyl- and propionyl-CoAs in fatty acid synthesis in the female gland. Such unusual primers are catabolic intermediates of valine, leucine, and isoleucine, respectively. Male ADG contained straight chain saturated alkyl residues ranging from C14 to 21. In the case of female ADG, though the main component was C18:O, most alkyl components had branchings at the iso- and anteiso-positions. NMR data suggested the presence of propionic acid at the C3 position of glycerol in the male ADG and of isovaleric and 2-methylbutyric acids at the same position in the female ADG. These results suggest that the sexual differences of the lipids in the Harderian gland of the golden hamster are determined at the step of fatty acid synthesis depending on the available precursors in the male and female glands. We speculate that sex hormones affect the metabolism of branched chain amino acids and bring about the dramatic diversities of the lipid compositions in the male and female glands.

Amino Acids↗

PubMed1996

Molecular cloning of cDNA and analysis of expression of the gene for alpha-glucosidase from the hypopharyngeal gland of the honeybee Apis mellifera L.

Previously, we identified and purified an alpha-glucosidase with a molecular mass of 70 kDa from a homogenate of the hypopharyngeal gland of the older worker bee (forager bee) Apis mellifera L. (T. Kubo et al, J. Biochem., 1996, 119, 291-295). Here, we isolated and sequenced a cDNA for the alpha-glucosidase. The cDNA encoded a protein consisting of 650 amino acids, which had high sequence identity with fruit fly and mosquito possible maltase gene products. RT-PCR showed that the gene was expressed specifically in the hypopharyngeal gland of the forager bee.

Amino Acid Sequence↗

PubMed1996

Telomere changes in human hepatocellular carcinomas and hepatitis virus infected noncancerous livers.

BACKGROUND: Telomeres, at the ends of eukaryotic chromosomes, are defined functionally as necessary for chromosome stability. Chromosome instability induced in part by loss of telomeric DNA has been considered to play a significant role in the development of human cancers. However, little is known about the status of telomeres per se during human hepatocellular carcinoma (HCC) development. METHODS: The study was conducted to determine the length of terminal restriction fragments (TRFs) at the telomeric ends in 23 HCCs and 23 corresponding noncancerous liver tissues from the same patients harboring hepatitis virus infections, and in 5 samples of noncancerous livers without the hepatitis virus. The latter samples had been obtained as controls at surgery for metastatic liver tumors. RESULTS: All 23 HCCs demonstrated reduction in TRF length compared with the corresponding noncancerous liver tissues with viral infection. The TRF in the latter cases also demonstrated a significant shortening as compared with the virus free control tissue, the degree being calculated to represent an average of 42 cell divisions. Reduction in TRF length in HCC samples tended to increase with the tumor diameter, although this failed to show statistical significance. CONCLUSIONS: These results indicate that telomere shortening occurs during HCC development. The fact that this change is already evident in noncancerous liver tissues from patients with viral hepatitis suggests that it may play an important role in the associated generation of tumors.

Adult↗

PubMed1996

No evidence of a direct venodilatory effect of furosemide in healthy human subjects.

The present study was undertaken to examine whether furosemide, a loop diuretic, has a direct venodilatory effect in healthy male subjects. Furosemide, or amrinone, an inotropic agent with a vasodilatory action, was infused into a dorsal hand vein that had been preconstricted by phenylephrine. The diameter of the vein was measured by a linear variable differential transformer. Venodilation was observed during the infusion of amrinone, but such a response was not detected with furosemide. These findings do not support the hypothesis that furosemide has a direct venodilatory effect in healthy human subjects.

Adult↗

PubMed1996

Influences of bathing and hot weather on the pharmacokinetics of a new transdermal clonidine, M-5041T.

The influences of bathing and hot weather on plasma concentrations of clonidine were examined during application of a new transdermal clonidine system, M-5041T, in eight healthy volunteers. An M-5041T patch containing 6 mg of clonidine was applied on the right chest for 96 hours during winter with or without bathing (40 degrees C for 5 minutes) and also during summer without bathing. Plasma concentrations and urinary excretion of clonidine were determined for a 160-hour period after application. Plasma concentrations of clonidine in the winter trials did not differ significantly with or without bathing. Plasma drug concentration as a whole was significantly higher in the summer trial than in the winter trial, however. The maximum plasma concentration (Cmax), area under the plasma concentration-time curve (AUC), and urinary excretion (Ae) of clonidine also tended to be higher in the summer trial. These results suggest that plasma levels of clonidine are higher after application of M-5041T during hot weather. Although the period of bathing used in this study was short, the influence of bathing seems to be negligible.

Administration, Cutaneous↗

PubMed1996

Pharmacokinetics of a new thromboxane A2 receptor antagonist, S-1452, and its effect on platelet aggregation in healthy volunteers.

To study the pharmacokinetics of a new thromboxane A2 (TXA2) receptor antagonist, S-1452, eight healthy volunteers were given placebo or S-1452 orally on four occasions in step-wise increasing doses of 10 mg, 25 mg, and 50 mg separated by 2-week intervals. Blood samples for measurement of plasma concentrations of the drug and of its inhibitory effect on platelet aggregation were obtained for 24 hours after administration. Bleeding time after administration was measured. S-1452 was rapidly absorbed, with a peak plasma concentration at 30 minutes after administration. Thereafter, the drug was rapidly eliminated (elimination half-life, 0.4-0.5 hours), and no drug was detected at 6 hours. The inhibitory effect of S-1452 on platelet aggregation, which was stimulated by the TXA2 receptor agonist U-46619, persisted more than 6 hours after drug administration. Bleeding time was slightly prolonged after a single dose of S-1452. These results suggest that although S-1452 is rapidly eliminated in plasma, its inhibitory effects on platelet aggregation persist for a longer period. Careful observations are needed to prevent potential bleeding episodes during repeated treatment with the drug.

Administration, Oral↗

PubMed1996

Role of reactive oxygen intermediates in lipopolysaccharide-mediated hepatic injury in the rat.

Because reactive oxygen intermediates derived from xanthine oxidase may have an important role in the pathophysiology of lipopolysaccharide-mediated tissue injury, we studied hydrogen peroxide generation using 3-amino-1,2,4-triazole inactivation of hepatic catalase and the ratio of xanthine oxidase to xanthine dehydrogenase activity in rat livers after in vivo lipopolysaccharide administration. We also studied the effect of tungsten, a potent inhibitor of xanthine oxidase, on the toxicity of lipopolysaccharide. There was increased hydrogen peroxide production and enhanced proteolytic conversion from xanthine dehydrogenase to xanthine oxidase in rat livers after lipopolysaccharide administration. Feeding rats a tungsten-rich diet for 4 weeks greatly diminished hepatic xanthine oxidase activity and lessened the rise in intracellular hydrogen peroxide production after lipopolysaccharide treatment. Liver damage, as assessed by the serum transaminase levels and mortality, was also ameliorated by the tungsten-rich diet. These findings suggest that hydrogen peroxide derived from xanthine oxidase contributes to the development of systemic toxicity and liver damage after lipopolysaccharide administration.

Adenosine↗

PubMed1996

Increased matrix metalloproteinases as possible cause of osseoarticular tissue destruction in long-term haemodialysis and beta 2-microglobulin amyloidosis.

Immunolocalization of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in periarticular tissues of beta 2-microglobulin amyloidosis patients was investigated. MMP-1 (interstitial collagenase) the most strongly expressed of the MMPs, was localized in the synovial lining cells, mesenchymal cells in granulation tissue and nodular amyloid deposits, and chondrocytes within areas of cartilage erosion. Expression of MMP-1 was correlated with the degree of macrophage infiltration and synovial cell hyperplasia, but it was not correlated with the degree of amyloid deposition or haemodialysis period. Expression of MMP-1 appeared more intense than that of TIMP-1 and TIMP-2 in highly inflammatory cases. MMP-2 was mildly expressed in the interstitial fibroblasts and MMP-3 was faintly stained in the extracellular matrix of the synovial membrane. MMP-9 (gelatinase B) was found to be strongly positive in the osteoclasts which increased in the progressing osteolytic lesion from the destructive arthropathy. These results suggest involvement of MMPs in inflammation with an imbalance between expression of MMPs and TIMPs being closely related to pathogenesis of the destructive arthropathy.

Amyloidosis↗

PubMed1996

Apoptosis and CD8-down-regulation in the thymus of chickens infected with Marek's disease virus.

Marek's disease virus (MDV)-infected chickens show thymic atrophy during the acute phase of infection. We examined whether the thymic atrophy by MDV-infection was mediated by apoptosis. Apoptosis-specific DNA ladderings were clearly observed in thymocytes one week after MDV-infection. Histological and flow cytometry studies revealed that immature CD4+ CD8+ thymocytes underwent apototic cell death. In addition, the expression level of CD8 molecules on both CD4(-)CD8+ and CD4+ CD8+ thymocyte populations was down-regulated in the infected chickens. These thymic changes might be involved in the pathogenesis of Marek's disease.

Animals↗

PubMed1996

Effect of alpha 1-adrenoceptor antagonists, prazosin and urapidil, on a finger skin vasoconstrictor response to cold stimulation.

OBJECTIVES: Cold stimulation causes a finger skin vasoconstrictor response, which is regulated by stimulation of alpha-adrenergic receptors and is reduced by administration of prazosin. The purpose of this study was to investigate, using a laser Doppler flowmeter, whether the decrease in the finger skin vasoconstrictor response to cold stimulation produced by administration of two different alpha 1-adrenoceptor antagonists, prazosin and urapidil, was correlated with the corresponding plasma drug concentration, and whether this method could be used to evaluate the relative potency of these alpha 1-adrenoceptor antagonists in human subjects. METHOD: In thirteen healthy male subjects (20-42 y), finger tip skin blood flow was measured during cold stimulation before and 1, 2, 3, 6, and 9 h after administration of placebo, prazosin (1 mg) or urapidil (60 mg). RESULTS: Both prazosin and urapidil significantly decreased the vasoconstrictor response to cold stimulation. The degree of the decrement in the response indicated by the reduction ratio was significantly correlated with the plasma concentration of prazosin and urapidil. The alpha 1-adrenoceptor blocking activity of prazosin estimated by the regression lines was about 130-times more potent than that of urapidil. CONCLUSION: These findings suggest that the cold stimulation response of finger skin vasoconstriction may be used to evaluate the relative alpha 1-adrenoceptor blocking potency of drugs.

Administration, Oral↗

PubMed1996

Influence of age on venodilator effect of isoproterenol and amrinone.

OBJECTIVE: To investigate the influence of age on the venodilator effect of isoproterenol, a beta-adrenoceptor agonist, and amrinone, a selective phosphodiesterase (PDE) III inhibitor, in human subjects. METHODS: In eight young and eight elderly male subjects, the drugs were infused into a dorsal hand vein preconstricted with phenylephrine and its diameter was measured using a linear variable differential transformer. RESULTS: The maximum venodilation (Emax) induced by isoproterenol was significantly smaller and the infusion rate of isoproterenol required to induce 50% of maximum venodilation (ED50) was significantly larger in the elderly than in the young subjects [Emax: 29.8 vs 95.1%, ED50: 97.3 vs 51.6 ng.min-1]. A significant age-related change in Emax or ED50 was not observed for amrinone (Emax: 95.8 vs 100.8%, ED50: 40.1 vs 31.6 micrograms.min-1). CONCLUSION: The data show that the venodilator effect of amrinone is not influenced by age. As amrinone increases cyclic AMP by inhibition of PDE III, it is suggested that the action of cyclic AMP is not altered by age. The decreased effect of isoproterenol might be caused by reduced production of cyclic AMP in elderly subjects.

Adrenergic beta-Agonists↗

PubMed1996

Effect of food intake on pharmacokinetics and effects of a new thromboxane A2 receptor antagonist, S-1452.

OBJECTIVE: To examine the effect of food ingestion on the pharmacokinetics of a new thromboxane A2 (TXA2) receptor antagonist, S-1452, and the inhibitory effect on platelet aggregation. METHODS: Fifty milligrams of S-1452 was given orally to eight healthy subjects with or without food. Blood samples for determinations of plasma drug concentrations and of its effects on platelet aggregation were taken for a 12-h post-drug period. RESULTS: The maximum plasma concentration of S-1452 was reduced by 47% and the time to maximum concentration was prolonged from 0.5 to 1.9 h after dosing with food. The inhibitory effect of S-1452 on platelet aggregations induced by U-46619, a TXA2 receptor agonist, and collagen persisted up to 9 h after dosing with and without food. The degrees of inhibition in the two trials did not differ significantly at any point. CONCLUSION: These results suggest that although the absorption of S-1452 is delayed and, consequently, its plasma concentration is decreased after dosing with food, the inhibitory effect on platelet aggregation is not significantly influenced after 50 mg of the drug.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗