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Biomedical subjects

K Ohashi

Publications and source records attributed to K Ohashi.

At least 91 records · Page 5Linked to original sources
PubMed2001

Troglitazone inhibits atherosclerosis in apolipoprotein E-knockout mice: pleiotropic effects on CD36 expression and HDL.

Atherosclerotic coronary heart disease is a common complication of the insulin resistance syndrome that can occur with or without diabetes mellitus. Thiazolidinediones (TZDs), which are insulin-sensitizing antidiabetic agents, can modulate the development of atherosclerosis not only by changing the systemic metabolic conditions associated with insulin resistance but also by exerting direct effects on vascular wall cells that express peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor for TZDs. Here we show that troglitazone, a TZD, significantly inhibited fatty streak lesion formation in apolipoprotein E-knockout mice fed a high-fat diet (en face aortic surface lesion areas were 6.9+/-2.5% vs 12.7+/-4.7%, P<0.05; cross-sectional lesion areas were 191 974+/-102 911 micrometer(2) vs 351 738+/-175 597 micrometer(2), P<0.05; n=10). Troglitazone attenuated hyperinsulinemic hyperglycemia and increased high density lipoprotein cholesterol levels. In the aorta, troglitazone markedly increased the mRNA levels of CD36, a scavenger receptor for oxidized low density lipoprotein, presumably by upregulating its expression, at least in part, in the macrophage foam cells. These results indicate that troglitazone potently inhibits fatty streak lesion formation by modulating both metabolic extracellular environments and arterial wall cell functions.

Animals↗
PubMed2001

Myosin light chain kinase regulates capacitative ca(2+) entry in human monocytes/macrophages.

Monocytes/macrophages are present in all stages of atherosclerosis. Although many of their activities depend to various extents on changes in intracellular Ca(2+) concentration ([Ca(2+)](i)), mechanisms regulating [Ca(2+)](i) in these cells remain unclear. We aimed to explore the role of myosin light chain kinase (MLCK) in Ca(2+) signaling in freshly isolated human monocytes/macrophages. Large capacitative Ca(2+) entry (CCE) was observed under fura 2 fluoroscopy in human monocytes/macrophages treated with thapsigargin and cyclopiazonic acid. ML-9 and wortmannin, 2 structurally different inhibitors of MLCK, dose-dependently (1 to 100 micromol/L) prevented CCE and completely did so at 100 micromol/L, whereas inhibitors of tyrosine kinase and protein kinase C had only partial effects. Western blotting showed that thapsigargin significantly caused myosin light chain phosphorylation, which was almost completely blocked by ML-9 (100 micromol/L) and wortmannin (100 micromol/L). ML-9 also dose-dependently (1 to 100 micromol/L) inhibited this phosphorylation, which was well correlated with its inhibition of CCE. Transfection with MLCK antisense completely prevented CCE in response to thapsigargin and cyclopiazonic acid, whereas MLCK sense had no effect. These data strongly indicate that MLCK regulates CCE in human monocytes/macrophages. The study suggests a possible involvement of MLCK in many Ca(2+)-dependent activities of monocytes/macrophages.

Androstadienes↗
PubMed2001

N-WASP, WAVE and Mena play different roles in the organization of actin cytoskeleton in lamellipodia.

WASP- and Ena/VASP-family proteins have been reported to regulate the cortical actin cytoskeleton as downstream effectors of the Rho-family small G-proteins Rac and Cdc42, but their functions are little understood. We observed the localization of the WASP family proteins, N-WASP and WAVE, and the Ena/VASP family protein, Mena, in protruding lamellipodia. Rat fibroblast cell line 3Y1 protruded lamellipodia on poly-L-lysine-coated substrate without any trophic factor. N-WASP and Cdc42 were concentrated along the actin filament bundles of microspikes but not at the tips. By immunofluorescence and immunoelectron microscopy, both WAVE and Mena were observed to localize at the lamellipodium edge. Interestingly, Mena tended to concentrate at the microspike tips but WAVE did not. At the edge of the lamellipodium, the correlation between the fluorescence from Mena and actin filaments stained with the specific antibody and rhodamine-phalloidin, respectively, was much higher than that between WAVE and actin filament. The Ena/VASP homology 2 (EVH2) domain of avian Ena, an avian homolog of Mena, was localized to the lamellipodium edge and concentrated at the tip of microspikes. The SCAR homology domain (SHD) of human WAVE was distributed along the lamellipodium edge. These results indicate that N-WASP, WAVE and Mena have different roles in the regulation of the cortical actin cytoskeleton in the protruding lamellipodium. WAVE and Mena should be recruited to the lamellipodium edge through SHD and the EVH2 domain, respectively, to regulate the actin polymerization near the cell membrane. N-WASP should regulate the formation of the actin filament bundle in addition to activating Arp2/3 complex in lamellipodium under the control of Cdc42.

Actins↗
PubMed2001

Survey of Theileria parasite infection in cattle in Cambodia and Vietnam using piroplasm surface protein gene-specific polymerase chain reaction.

A survey of Theileria parasite infection in cattle in Cambodia and Vietnam was carried out by using allele-specific polymerase chain reaction. A total of 137 blood samples from draught animals in Cambodia and 40 blood samples from dairy cattle in Vietnam were analyzed. In Cambodia, 69 out of 137(50.4%) samples were PCR-positive containing mainly the Thai and the C type parasites. In Vietnam, 11 (27.5%) samples were positive and all were of the Thai type parasite.

Alleles↗
PubMed2001

Heparin inhibits plaque formation by cell-free Marek's disease viruses in vitro.

The mechanisms of Marek's disease virus (MDV) entry to host cells have not yet been analyzed. Heparan sulfate (HS) on the cell surface serves as a receptor for several herpesviruses in mammalian species. In this study, we demonstrated that plaque formation by cell-free MDV is inhibited by the addition of soluble heparin to the cell culture. Moreover, pretreatment of susceptible cells, chicken embryo fibroblasts, with heparinase, partially reduced infectivity of the cell-free MDV. From these results, it was suggested that the MDV entry, at least in the case of cell-free MDV, is dependent on the presence of cell surface glycosaminoglycans, principally HS.

Animals↗
PubMed2001

Host immune responses in the course of bovine leukemia virus infection.

Bovine leukemia virus (BLV) is a type C retrovirus infecting bovine B cells and causing enzootic bovine leukosis. Since it takes long periods to develop the disease, it is believed that BLV and host immune responses are closely related. In this review, the accumulated data showing close relationship between BLV and host immune responses are summarized in 4 sections. First, we discuss the role of cell-mediated immunity in protecting hosts from BLV infection. Second, several reports showing the relationship between the disease progression and the change of cytokine profiles are summarized. In the third section, we have focused on tumor necrosis factor alpha (TNFalpha) and its two types of receptors, and the possible involvement of TNFalpha in the BLV-induced leukemogenesis is discussed. The expression of TNFalpha has been shown to be regulated by major histocompatibility complex (MHC) haplotype. The resistance to BLV infection is supposed to be established by some innate factors, which are closely related to MHC haplotype. Finally, we propose that a breeding strategy based on the MHC haplotype could be a good approach to control BLV infection. This review includes some recent data from us and other groups.

Animals↗
PubMed2001

Immunohistochemical diagnosis of Cryptococcus neoformans var. gattii infection in chronic meningoencephalitis: the first case in Japan.

Cryptococcus neoformans (C. neoformans) var. gattii infection usually occurs in tropical and subtropical areas, and rarely in the northern hemisphere. We report the first Japanese with cryptococcal meningoencephalitis caused by C. neoformans var. gattii infection that occurred during a trip to Australia. This agent was identified in a cerebellar biopsy specimen by immunohistochemical technique with serotype-specific anti-sera. Because the meningitis caused by it did not respond well to conventional therapy, we used an aggressive therapeutic regimen to successfully treat the patient. Even in areas where C. neoformans var. gattii does not exist, this infection should be considered possible as a travel-related infection.

Aged↗
PubMed2001

Effects of CYP3A4 inhibition by diltiazem on pharmacokinetics and dynamics of diazepam in relation to CYP2C19 genotype status.

Diazepam is metabolized by CYP2C19 and CYP3A4 in the liver. CYP2C19 shows genetic polymorphism associated with the poor metabolizer (PM) and extensive metabolizer (EM) phenotypes. The aim of this study was to assess the effect of diltiazem, a CYP3A4 inhibitor, on pharmacokinetics and dynamics of diazepam in relation to CYP2C19 genotype status. Thirteen healthy volunteers (eight EMs and five PMs) were given placebo or diltiazem (200 mg) orally for 3 days before and for 7 days after the oral 2-mg dose of diazepam in a double-blind, randomized, crossover manner. The pharmacokinetics and pharmacodynamics of diazepam were assessed with and without diltiazem. Plasma concentrations and area under the plasma concentration-time curves (AUCs) of diazepam and N-desmethyldiazepam were significantly greater in the PM compared with the EM group during the placebo phase. Diltiazem significantly increased AUC and prolonged elimination t(1/2) of diazepam in both the PM and EM groups. These pharmacokinetic changes, however, caused no significant difference in the pharmacodynamics between the two trial phases. Diltiazem affects the pharmacokinetics of diazepam in the PM and EM groups of CYP2C19. Inhibition of CYP3A4 by a concomitant substrate drug like diltiazem may cause a pharmacokinetic interaction with diazepam irrespective of CYP2C19 genotype status, but whether this interaction would reflect a pharmacodynamic change of diazepam remains unconfirmed by our study.

Adult↗
PubMed2001

[A case of spinocerebellar ataxia type 6 with hypochondriasis and severe parkinsonism].

We report a case of 68-year-old woman who was diagnosed spinocerebellar ataxia type 6 (SCA 6) by genomic testing. She presented hypochondriasis, parkinsonism, and ataxia. Since the age of 60, she noted difficulty in walking due to dizziness, and MRI showed minimal cerebellar atrophy. She became unable to walk without assistance at the age 67. She was referred to us when she was 68 years old. She had no family history of cerebellar ataxia, and her general physical examination was normal. Her speech was fluent, with neither slurring nor scanning, and she complained of much anxiety regarding her physical condition and was diagnosed as having hypochondriasis. Neurological examination revealed parkinsonism consisting of small steppage gait, mask-like face, akinesia, rigidity of neck and limbs, and postural instability. She also showed cerebellar signs such as saccadic smooth pursuit, ataxia of upper and lower limbs, and increased tendon reflexes. Her parkinsonism had developed slowly and symmetrically yet she showed a lack of response to levodopa. Our results suggest that the genomic testing is useful for differential diagnosis for the diseases presenting ataxia and parkinsonism, even if the family history is negative.

Aged↗
PubMed2001

Influence of age on the pharmacokinetics of vapiprost, a thromboxane A2 receptor antagonist, and platelet aggregation: comparison of pharmacokinetics by routine approach and population pharmacokinetics.

The effects of a single-dose oral administration of a thromboxane A2 receptor antagonist, vapiprost (SN-309), on pharmacokinetic profile and inhibition of platelet aggregation were investigated in six healthy elderly volunteers (age: 65-72 years) and the influence of age on these parameters was studied by comparison with the results obtained in phase-I data involving healthy young participants. Although direct comparison of pharmacokinetic parameters was inappropriate because of different models, high Cmax and AUC values were obtained on comparison with the young. The inhibition of platelet aggregation in platelet rich plasma induced by U-46619 or collagen was rapidly established and remained suppressed for more than 8 h, although the effect was short-acting compared with the inhibition period in the young. This suggests that dose adjustment in the elderly is unnecessary In addition to a routine pharmacokinetic approach to determine the time-profile of vapiprost, population pharmacokinetics were studied using data from 51 volunteers in five clinical trials including the two above-mentioned studies. By fitting 812 plasma-monitoring points into the two-compartment model, the effects of several factors including age on parameters were investigated, based on the nonlinear mixed effect model. Clearance in the elderly attenuated 82.2% of that in the young, the distribution volume varied with platelet counts and delayed absorption was observed in volunteers with, rather than without, food intake. Closer bridging studies with other countries have resulted in the current local situation of abbreviating phase-III studies. Consequently to clarify the pharmacokinetic profile of the elderly in Japan and other countries, the population pharmacokinetics approach based on the data in the various phase I-II trials is useful.

Aged↗
PubMed2001

Population pharmacokinetics, protein binding and antiarrhythmic effects of disopyramide enantiomers in arrhythmic patients.

Disopyramide (DP) is widely used as an antiarrhythmic agent. The antiarrhythmic effects of its enantiomers differ from each other and its metabolism and protein binding are also stereoselective. Population pharmacokinetic parameters of DP racemate, enantiomers (S(+)-DP, R(-)-DP), and their unbound concentrations (uDP, S(+)-uDP and R(-)-uDP) were analyzed using the nonlinear mixed effect model (NONMEM) program. Data were available from 108 points of 33 arrhythmic patients on maintenance therapy with DP racemate. We evaluated the factors to which pharmacokinetic parameters are attributed and the relationships between each serum concentration and the antiarrhythmic effect. A one-compartment model was fitted to the data using NONMEM. For DP, S(+)-DP and R(-)-DP, elimination rate constants (kes) were estimated as 0.0648, 0.0663 and 0.0691/h, respectively and the mean apparent volume of distribution (Vd/F) were estimated as 63.2, 54.1 and 71.6 l, respectively. Using the ke and Vd/F values estimated by NONMEM, time-concentration curves were well fitted to the observed data. Unbound fractions of both DP enantiomers showed nonlinearity and the binding ratio of S(+)-DP was 0.84 +/- 0.07, which was higher than that of R(-)-DP [0.70 +/- 0.11 (p < 0.01)]. Unbound fractions of both DP enantiomers correlated with alpha1-acid glycoprotein (AGP) (p < 0.01). On the other hand, using NONMEM, a significant proportion of the variability of Vd/F could be attributed only to AGP (p < 0.001). NONMEM was able to clarify the pharmacokinetic features in the protein binding of DP. Individual steady state concentrations were estimated by NONMEM using the Bayesian method. The average unbound concentrations of all nine responders were higher than those of the four non-responders, even though this difference was not significant. Unbound concentrations may reflect drug concentrations in the tissue, which suggests that these concentrations may indicate an antiarrhythmic effect rather than the total concentration.

Adolescent↗
PubMed2000

Severity of chronic atrophic gastritis and subsequent gastric cancer occurrence: a 10-year prospective cohort study in Japan.

Chronic atrophic gastritis is regarded as a predisposing factor for gastric cancer associated with Helicobacter pylori infection, and its severity is suggested to be a key influence on gastric cancer risk. Our purpose was to elucidate chronological change in cumulative risk of gastric cancer occurrence with various degrees of chronic atrophic gastritis by long-term follow-up. A total of 5373 subjects without cancer or resected stomachs who underwent gastroscopic examination and completed a life-style questionnaire between 1985-1989 were prospectively followed until December 1999. Relative risks of gastric cancer associated with baseline endoscopic findings were estimated using hazard ratios and their 95% confidence intervals with the Cox proportional hazard model, adjusting for gender, age and gastric cancer family history. After an average of 10 years of follow-up, 117 gastric cancer cases were identified. The risk was greatest among the subjects with moderate atrophy at baseline (hazard ratio: 2.22) and 4-6 years of follow-up (hazard ratio: 4.6-5.0). After this time point, risk attenuation with the length of follow-up period was observed. Our study gives the supportive evidence to the hypothesis that incomplete chronic atrophic gastritis and the processes occurring in atrophy are associated with development of gastric cancer.

Cohort Studies↗
PubMed2000

Myosin light-chain kinase regulates endothelial calcium entry and endothelium-dependent vasodilation.

Activation of smooth muscle myosin light-chain kinase (MLCK) causes contraction. Here we have proven that MLCK controls Ca2+ entry (CE) in endothelial cells (ECs): MLCK antisense oligonucleotides strongly prevented bradykinin (BK)- and thapsigargin (TG)-induced endothelial Ca2+ response, while MLCK sense did not. We also show that the relevant mechanism is not phosphorylation of myosin light-chain (MLC): MLC phosphorylation by BK required CE, but MLC phosphorylation caused by the phosphatase inhibitor calyculin A did not trigger Ca2+ response. Most important, we provide for the first time strong evidence that, in contrast to its role in smooth muscle cells, activation of MLCK in ECs stimulates the production of important endothelium-derived vascular relaxing factors: MLCK antisense and MLCK inhibitors abolished BK- and TG-induced nitric oxide production, and MLCK inhibitors substantially inhibited acetylcholine-stimulated hyperpolarization of smooth muscle cell membrane in rat mesenteric artery. These results indicate that MLCK controls endothelial CE, but not through MLC phosphorylation, and unveils a hitherto unknown physiological function of the enzyme: vasodilation through its action in endothelial cells. The study discovers a counter-balancing role of MLCK in the regulation of vascular tone.

Acetylcholine↗