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Biomedical subjects

Y Uehara

Publications and source records attributed to Y Uehara.

At least 73 records · Page 4Linked to original sources
PubMed1998

Effect of herbimycin A on tyrosine kinase receptors and platelet derived growth factor (PDGF)-induced signal transduction.

Herbimycin A is widely used as an inhibitor of Src family protein tyrosine kinases but is also reported to induce the downregulation of epidermal growth factor (EGF) receptor number in A431 cells without inhibiting its tyrosine kinase activity. To determine the specificity of the receptor downregulation, we examined its effect on a variety of cell lines which express different levels of EGF receptor and on other tyrosine kinase receptors. Long-term herbimycin A treatment decreased the amounts of all the tyrosine kinase receptors examined in a dose-dependent manner. It also reduced ligand-stimulated receptor autophosphorylation in accordance with the reduction in the receptor level. Herbimycin A inhibited platelet derived growth factor (PDGF)-induced tyrosine phosphorylation of cellular proteins and DNA synthesis in NIH3T3 cells but did not affect the serum-stimulated DNA synthesis. PDGF-induced tyrosine phosphorylation and activation of c-Src was inhibited but the protein level of c-Src was not reduced by herbimycin A. The reduced level of c-Src kinase activity correlated with the levels of both PDGF receptor and DNA synthesis. These results indicate that the herbimycin A treatment selectively downregulates receptor tyrosine kinases, independent of the number of receptors, and suggest that c-Src is to some degree involved in the selective inhibition of PDGF-induced mitogenesis by herbimycin A.

3T3 Cells↗
PubMed1998

Inhibitory effects of 5-S-GAD on phosphorylation of V-SRC and BCR-ABL tyrosine kinase.

We examined the inhibitory effects of N-beta-alanyl-5-S-glutathionyl-3,4-dihydroxyphenylalanine (5-S-GAD), a novel antibacterial substance from the immunized adult Sarcophaga peregrina (flesh fly), on protein phosphorylation using immune complexes of protein tyrosine kinases (PTKs) with anti-PTKs monoclonal antibody. We found that 5-S-GAD directly inhibited not only tyrosine phosphorylation of PTK p60(v-src), but also tyrosine phosphorylation of PTK p210(BCR-ABL). The inhibitory potency of 5-S-GAD was comparable to that of radicicol and herbimycin A of PTK inhibitor.

3T3 Cells↗
PubMed1998

Hemodynamic changes during administration of drugs for mitral regurgitation in dogs.

Each of 5 drugs, i.e., 4 different vasodilator drugs (captopril, enalapril, hydralazine and prazosin) and a cardiotonic drug (digoxin), was administered to dogs with mitral regurgitation (MR) for 1-72 days in order to quantitatively evaluate the influence of therapeutic agents on blood flow in heart disease. Hemodynamic changes were assessed before and after administration of each drug by determining mitral regurgitant jet mapping area (MRMA) and aortic forward flow mapping area (AFMA), which were displayed by the color Doppler method, and the ratio of MRMA to AFMA (MRMA/AFMA) as parameters. When the four vasodilator drugs were used appropriately, MRMA and MRMA/AFMA decreased in all cases, compared with the values before the administration. These two parameters showed dose-dependent changes after administration of captopril, enalapril and hydralazine. When the cardiotonic drug was used. MRMA and MRMA/AFMA increased in 4 of 5 cases. The MRMA/AFMA values were slightly more reproducible than the MRMA values, whereas the AFMA values showed no constant tendency when any vasodilator drug or the cardiotonic drug was used. These results suggest that the efficacy of cardiotonic and vasodilator drugs in MR can be quantitatively evaluated by determining MRMA/AFMA in particular, and MRMA.

Animals↗
PubMed1998

Hypothalamic corticotropin-releasing hormone is a mediator of the anorexigenic effect of leptin.

Leptin, ob gene product, inhibits feeding behavior and stimulates energy expenditure in rodents. Corticotropin-releasing hormone (CRH) and neuropeptide Y (NPY), which act in the hypothalamus to influence energy homeostasis, may mediate the anorexic effect of leptin. The present studies were undertaken to examine the possible involvement of hypothalamic CRH in the anorexigenic action of leptin in male Wistar rats. Recombinant leptin (2 microg/rat), microinjected into the third ventricle, inhibited food intake at 2 h by 33.3% (P < 0.01) in rats that were deprived of food for 18 h. The intracerebroventricular injection of 2 microg leptin also increased hypothalamic CRH content (P < 0.05) at 2 h after its administration. Simultaneous intracerebroventricular administration of 5 microg/rat alpha-helical CRH 9-41 (alpha-hCRH), a CRH antagonist, with 2 microg/rat leptin attenuated the anorexic effect of leptin by 2 h. In contrast, single intracerebroventricular injection of alpha-hCRH did not affect food consumption in food-deprived rats. These results implicate hypothalamic CRH as an important mediator of the anorexic effect of leptin in food-deprived rats.

Animals↗
PubMed1998

Effect of nephropathy on the composition of apolipoprotein-containing particles in NIDDM.

We investigated the effect of nephropathy on the composition of apolipoprotein-containing particles in non-obese NIDDM patients with normocholesterolemia. Sixty-seven normal control subjects (group A), 48 NIDDM patients without nephropathy (group B) and 36 NIDDM patients with nephropathy (group C) were studied. Apolipoprotein AI or B100 containing particles (Apo AI or Apo B100) were isolated by immunoaffinity columns prepared with monoclonal antibodies. The total cholesterol (CH), esterified cholesterol (EC) and free cholesterol (FC) content in these particles was analyzed. Both the EC/FC ratio levels in Apo AI and in Apo B100 in group C were significantly higher than those in group A or B. Both the CH in Apo AI/apolipoprotein AI ratio and in Apo B100/apolipoprotein B100 ratio levels in group C were significantly lower than those in group A or B. The insulin resistance index showed significant positive correlation with the EC/FC ratio levels in Apo AI and in Apo B100, and showed significant negative correlation with the CH levels in Apo AI/apolipoprotein AI ratio and the CH levels in Apo B100/apolipoprotein B100 ratio levels in group C. Those compositional changes of lipoproteins in NIDDM patients with nephropathy may reflect partial insulin resistance and deteriorating atherosclerosis.

Antibodies, Monoclonal↗
PubMed1998

Signal transduction inhibitors, hibarimicins, A, B, C, D and G produced by Microbispora. I. Taxonomy, fermentation, isolation and physico-chemical and biological properties.

Strain TP-AO121 which produces a complex of novel tyrosine kinase inhibitors designated hibarimicins A, B, C, D and G was considered to be a new subspecies of Microbispora rosea, and the name, Microbispora rosea subsp. hibaria, was proposed. Hibarimicins A, B, C and D specifically inhibited the src tyrosine kinase activity without affecting protein kinase A or protein kinase C. They also showed in vitro anti-Gram-positive bacterial and antitumor activities. The molecular formulae of hibarimicins A, B, C, D and G were assigned to be C85H112O37, C85H112O37, C83H110O36, C85H112O38, and C85H112O39 respectively.

Actinomycetales↗
PubMed1998

Signal transduction inhibitors, hibarimicins A, B, C, D and G produced by Microbispora. II. Structural studies.

The structure of hibarimicins A, B, C, D and G which are inhibitors for tyrosine specific protein kinase are determined using spectroscopic techniques. Hibarimicins described in this report consist of a common aglycon and six deoxyhexoses. The aglycon contains a highly oxidized naphtylnaphthoquinone as a chromophore. Among them, hibarimicin B was identical with angelmicin B.

Actinomycetales↗
PubMed1997

Inhibition of protein tyrosine kinase by 5-S-GAD, a novel antibacterial substance from an insect.

The effect of N-beta-alanyl-5-S-glutathionyl-dopa (5-S-GAD), a compound originally isolated from Sarcophaga peregrina (a flesh fly) as an antibacterial substance, on protein phosphorylation was examined using v-src-transformed NIH3T3 cell lysates. 5-S-GAD was found to inhibit tyrosine phosphorylation of protein tyrosine kinase v-src, but not serine/threonine phosphorylation of protein kinase C. The potency of this compound was comparable to that of herbimycin A. Our results suggested that a substitution at position 5 of the catechol in 5-S-GAD with the sulfur of cysteine is essential for 5-S-GAD to inhibit protein tyrosine kinase v-src.

3T3 Cells↗
PubMed1997

Induction of p27Kip1 degradation and anchorage independence by Ras through the MAP kinase signaling pathway.

While most untransformed cells require substrate attachment for growth (anchorage dependence), the oncogenic transformed cells lack this requirement (anchorage independence) and are often tumorigenic. However, the mechanism of loss of anchorage dependence is not fully understood. When rat normal fibroblasts were cultured in suspension without substrate attachment, the cell cycle arrested in G1 phase and the cyclin-dependent kinase inhibitor p27Kip1 protein and its mRNA accumulated. Conditional expression of oncogenic Ras induced the G1-S transition of the cell cycle and significantly shortened the half-life of p27Kip1 protein without altering its mRNA level. Inhibition of the activation of mitogen-activated protein (MAP) kinase by cyclic AMP-elevating agents and a MEK inhibitor prevented the oncogenic Ras-induced degradation of p27Kip1. These results suggest that the loss of substrate attachment induces the cell cycle arrest through the up-regulation of p27Kip1 mRNA, but the oncogenic Ras confers anchorage independence by accelerating p27Kip1 degradation through the activation of the MAP kinase signaling pathway. Furthermore, we have found that p27Kip1 is phosphorylated by MAP kinase in vitro and the phosphorylated p27Kip1 cannot bind to and inhibit cdk2.

Amino Acid Sequence↗
PubMed1997

Diagnostic value of immunochemical fecal occult blood test for small colorectal neoplasms.

This study was designed to assess the diagnostic value of an immunochemical fecal occult blood test for small colorectal adenomas. In a screening program based comparative study, 60 colorectal adenomas under 1 cm (small polyp group), 60 colorectal adenomas 1 cm or larger (large polyp group) and 60 colorectal cancers (cancer group) detected by occult blood screening, and 120 healthy controls (control group), served as subjects. Moreover, 50 small adenomas, 50 large adenomas and 50 cancers detected in out-patient clinics, and 100 controls, served as subjects of a hospital based comparative study. Each of these subjects was tested by an immunochemical occult blood with 3 consecutive days, after removal of these colorectal neoplasms in a screening program based study and before as well as after removal in a hospital based study, and the positivity rate of this test was evaluated among these four groups in the two comparative studies. The positivity rate in a screening program based study was 23% for small polyp group, 8% for large polyp group, 5% for cancer group and 6% for control group, respectively. Significant difference was noted between small polyp and cancer as well as control groups (p <0.01), and between small polyp and large polyp groups (p <0.05). In a hospital based study, however, there was no significant difference in the positivity rate among four groups. These results suggest that high proportion of small polyps detected by fecal occult blood test screening may not be associated with bleeding from adenomas but probably from another gastrointestinal pathology.

Adenoma↗
PubMed1997

In vivo gene transfection of human endothelial cell nitric oxide synthase in cardiomyocytes causes apoptosis-like cell death. Identification using Sendai virus-coated liposomes.

BACKGROUND: Nitric oxide (NO) has various actions on the cardiovascular system, although its pathophysiological significance in myocardial cells remains obscure. The aim of the present study was to identify direct NO actions on cardiomyocytes by gene transfection in vivo using a newly developed vector under physiological conditions. METHODS AND RESULTS: Liposomes containing the beta-galactosidase (beta-gal) gene alone or with the human endothelial cell nitric oxide synthase (ecNOS) gene were coated with UV-inactivated Sendai virus and injected into the left ventricular wall of rat heart in vivo. Histological examination confirmed that the transfection efficiency was comparable to adenovirus-mediated transfection and that the new vector per se caused no inflammation. beta-Gal expression was confined to cardiomyocytes between two intercalated discs, suggesting that the transfected gene did not permeate the discs. An immunohistochemical study showed that cotransfection of the ecNOS gene induced massive myocardial cell shrinkage in both transfected cells and the adjacent myocytes in a time- and dose-dependent manner. Histochemical findings in shrunk cells coincided with apoptosis as identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling. Electron microscopy of the lesion revealed myofibrillar degradation and accumulation of mitochondria but no apoptotic bodies. Pre-treatment with the NOS inhibitor N omega-nitro-L-arginine methyl ester abolished these morphological alterations. CONCLUSIONS: The efficient expression of the human ecNOS gene in vivo suggests that NO or its toxic metabolite caused myocardial degradation, a part of which was compatible with apoptosis of the transfected cardiomyocytes themselves and the adjacent cells as a paracrine effect. These morphological features mimicked acute myocarditis or ischemic injury.

Animals↗
PubMed1997

Inhibition of anchorage-independent growth of ras-transformed cells on polyHEMA surface by antisense oligodeoxynucleotides directed against K-ras.

We examined the effect of antisense oligodeoxynucleotides (AS ODNs) directed against v-Ki-ras on the anchorage-independent growth of v-Ki-ras-transformed rat fibroblasts using plates coated with an antiadhesive polymer, poly(2-hydroxyethyl methacrylate) (polyHEMA). Among AS ODNs tested, 17mer AS ODN centered around codon 12 of v-Ki-ras inhibited the v-Ki-Ras expression and v-Ki-Ras-induced anchorage-independent growth, while its sense sequence did not affect it. Using polyHEMA plates, the direct addition of AS ODNs to the cells growing anchorage-independently and various treatment schedules of AS ODNs are now available to identify the most desirable conditions for AS ODNs treatment.

Animals↗
PubMed1997

Leptin stimulates insulin secretion and synthesis in HIT-T 15 cells.

Leptin, an ob gene product, corrects hyperinsulinemia in ob/ob mice. The leptin receptor may exist in pancreatic islets. The present studies were undertaken to determine the direct effect of 1-100 ng/ml recombinant leptin on insulin secretion and synthesis in HIT-T 15 cells by using static culture system. The addition of recombinant leptin significantly increased insulin secretion for 20 min at the highest concentration (100 ng/ml). The addition of recombinant leptin dose-dependently increased insulin secretion for 24 h in the 7 mM glucose-containing F-12 K medium. The incubation with recombinant leptin for 24 h increased preproinsulin mRNA expression, assessed with reverse transcription-polymerase chain reaction (RT-PCR) method. It was furthermore demonstrated that HIT-T 15 cells possessed the specific binding site for [125I]-labeled leptin. The present study demonstrated the existence of the leptin-specific binding sites that mediate its stimulatory effect on insulin secretion and synthesis in HIT-T 15 cells.

Actins↗
PubMed1997

Relation of 24-h ambulatory blood pressure with plasma potassium in essential hypertension.

The established associations between blood pressure (BP) and electrolytes are mostly based on either dietary intake or urinary excretion data. We measured office BP, ambulatory BP (ABP) using the automated oscillometric ABPM-630 device, and plasma electrolytes in 82 essential hypertensive patients to examine the relation between BP and plasma electrolytes. Significant negative correlations were observed between plasma potassium concentration and 24-h systolic BP (r = -0.336) and diastolic BP (r = -0.298) in our patients. Plasma potassium concentration inversely correlated also with both daytime and nighttime systolic and diastolic BPs. There was no relation between office BP and plasma potassium concentration. These findings indicate that in essential hypertensives plasma potassium concentration is inversely related to ABP including daytime and nighttime BPs and suggest that potassium may be a factor determining the whole day BP in essential hypertension.

Adult↗
PubMed1997

Preventive effect of iganidipine on renal and cerebral injuries in salt-induced hypertension.

Iganidipine, a new water-soluble calcium antagonist, was administered at a nonhypotensive dose (NHD) of 0.3 mg/kg/day, a moderate-hypotensive dose (MHD) of 1.0 mg/kg/day, and a sustained-hypotensive dose (SHD) of 3.0 mg/kg/day to Dahl salt-sensitive (Dahl-S) rats fed a high-salt diet for 8 weeks. The effects on survival, and on renal and cerebral injuries, were then examined. Iganidipine completely prevented hypertensive death at the SHD and tended to increase the survival at the NHD and MHD. Iganidipine reduced glomerulosclerosis and renal arterial and tubular injuries in a dose-dependent manner. Iganidipine at the SHD, but not NHD or MHD, improved plasma creatinine, serum urea nitrogen, and glomerular filtration rate. Iganidipine at all doses examined increased the urinary prostaglandin (PG) I2 and PGE2, but not PGF2alpha or thromboxane B2, and decreased plasma angiotensin II (AII) level and renin activity. The renal glomerular, tubular, and arterial injuries were significantly correlated with blood pressure (r = 0.56 to 0.80) and plasma AII level (r = 0.50 to 0.71) but not with urinary prostanoids. Iganidipine also reduced the incidence of cerebral infarction. The infarction area was slightly and significantly correlated with urinary PGI2 (r = 0.42) and PGE2 (r = 0.41) but not with blood pressure or plasma AII. In conclusion, iganidipine prevented renal and cerebral injuries in Dahl-S rats. In addition to the reduced blood pressure, the reduction of plasma AII and the increase of vasodilatory prostanoids may also partially contribute to the renal and cerebral protective effects of iganidipine.

Animals↗
PubMed1997

Thromboxane inhibition potentiates antihypertensive effects of alpha 1 adrenoceptor antagonists in the rat.

We investigated the influence of the vascular and renal thromboxane system on the antihypertensive effects of the alpha 1 adrenoceptor antagonist (alpha 1 blocker) bunazosin in spontaneously hypertensive rats (SHR). SHR were treated for 2 weeks with the alpha 1, blocker bunazosin (0.5 mg/kg body weight/day). The systolic blood pressure immediately declined with bunazosin treatment, and then rose toward the level observed in untreated SHR. This antihypertensive effect was accompanied by a decrease in the ratio of prostacyclin to thromboxane A2 in the vascular wall and the kidney. A subdepressor dose of the thromboxane synthase inhibitor OKY-046 lessened the thromboxane generation during bunazosin treatment, and synergistically potentiated the antihypertensive action of the alpha 1 blocker. Such synergy was also observed between OKY-046 and prazosin, an alternative alpha 1 blocker, but not with amosulalol, an alpha 1 blocker having no quinazoline moiety. alpha 1 blockers with a quinazoline moiety dose-dependently stimulate thromboxane generation in cultured smooth muscle cells from SHR. These data indicate that alpha 1 blockers enhance thromboxane generation in the arterial wall and kidney, thereby contributing to the lessening of the antihypertensive effects observed during alpha 1 blocker treatment.

Adrenergic alpha-Antagonists↗
PubMed1997

Thromboxane inhibition and monocrotaline-induced pulmonary hypertension in rats.

Monocrotaline (MCT)-induced pulmonary hypertension (PH) is a useful model for the investigation of this disorder in humans. The role of thrombocytes in the genesis of PH has already been addressed; however, the exact mechanism by which they induce PH remains to be elucidated. We investigated the effects of a thromboxane A2 (TXA2) synthase inhibitor (OKY-046) and a TXA2/prostaglandin H2 (PGH2) receptor antagonist (ONO-8809) on the development of MCT-induced PH. A single dose of MCT (60 mg/kg bodyweight; BW) was injected subcutaneously in Wistar rats 24 h after the administration of OKY-046 or ONO-8809. The TXA2 inhibitors were administered by gavage daily for 3 weeks. Urinary excretion of eicosanoids was determined by radioimmunoassay. At the end of the treatment period, the lungs, heart and kidneys were morphologically examined. The per cent medial thickness of the muscular pulmonary arteries (%MT) and the ratio of the right to the left ventricular mass including the septum (RV/LV + S) increased significantly in MCT-treated rats compared with the control rats. The %MT was attenuated by the administration of ONO-8809. Either OKY-046 or ONO-8809 attenuated the increase in RV/LV + S. In addition, both TXA2 inhibitors reduced urinary excretion of 11-dehydro-TXB2, particularly during the early phase of PH, suggesting that platelet aggregation was reduced. These findings suggest that the inhibition of TXA2 by synthase inhibition or receptor antagonism reduces or delays the development of MCT-induced PH in rats, probably by inhibiting platelet aggregation.

Animals↗