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Biomedical subjects

K Takeuchi

Publications and source records attributed to K Takeuchi.

At least 541 records · Page 30Linked to original sources
PubMed1996

Hepatocyte growth factor (HGF)-induced cell migration is negatively modulated by epidermal growth factor through tyrosine phosphorylation of the HGF receptor.

Hepatocyte growth factor (HGF) stimulated cell migration of human gastric carcinoma cell lines MKN1, MKN7, and MKN28. Epidermal growth factor (EGF) also stimulated the cell migration of these three cell lines. In MKN7 cells, HGF-stimulated cell migration was rather reduced in the presence of EGF, whereas such an observation was not made with MKN1 and MKN28 cells. Therefore, we compared the effect of EGF on HGF-stimulated HGF receptor phosphorylation in these cell lines. HGF induced a rapid tyrosine phosphorylation of the HGF receptor in all these cell lines. In MKN7 cells, the increased phosphorylation was further enhanced by EGF, although EGF alone did not affect tyrosine phosphorylation of the HGF receptor. In MKN1 and MKN28 cells, EGF did not influence tyrosine phosphorylation of the HGF receptor, whether HGF was present or not. The data presented here suggest that EGF negatively modulates the cellular response to HGF by increasing tyrosine phosphorylation of the HGF receptor in certain types of epithelial cells, e.g., MKN7 cells.

Carcinoma↗
PubMed1996

Dissociation of c-fos induction and mitogen-activated-protein kinase activation from the hepatocyte-growth-factor-induced motility response in human gastric carcinoma cells.

The function of hepatocyte growth factor/scatter factor (HGF/SF) is to increase proliferation as well as to stimulate motility and disperse cell colonies of epithelial cells. In this study, we examined the motogenic and mitogenic responses of two human gastric carcinoma cell types, MKN7 and MKN74. Cell motility of both cell lines was markedly stimulated by HGF/SF. In contrast, HGF/SF stimulated cell growth of MKN74 cells, but did not stimulate growth of MKN7 cells. To address the cause of the difference in response of these cells, which may reflect some differences in signaling pathways downstream from the HGF/SF receptor, c-Met, we investigated the induction of the proto-oncogene c-fos. The level of c-fos mRNA increased and reached a maximum approximately 40 min after HGF/SF stimulation in MKN74 cells, and thereafter its level rapidly decreased. In contrast, the level of c-fos expression was very low irrespective of the stimulation in MKN7 cells. c-Fos protein was transiently induced only in MKN74 cells l h after treatment with HGF/SF, and its levels subsequently decreased. We subsequently examined the activation of mitogen-activated-protein kinase, which is a major mediator in the signaling pathway leading to the stimulation of c-fos transcription, after HGF/SF treatment in both cell lines. Mitogen-activated-protein kinase was markedly activated by this treatment in MKN74 cells, but was only slightly activated in MKN7 cells. These results suggest that although mitogen-activated-protein kinase activation and c-fos induction play an essential role in the signaling pathway leading to cell growth, they are not required for the motility response induced by HGF/SF.

Adenocarcinoma↗
PubMed1996

Prevention of lpr-graft-versus-host disease and transfer of autoimmune diseases in normal C57BL/6 mice by transplantation of bone marrow cells plus bones (stromal cells) from MRL/lpr mice.

C57BL/6 (B6) (H-2b) mice were lethally irradiated and then reconstituted with T cell-depleted MRL/Mp-lpr/lpr (MRL/lpr) (H-2k) bone marrow cells. The mice showed a short survival with splenic atrophy and fibrosis, as previously described as lpr-graft-vs-host disease (GVHD). However, when these mice received bone marrow transplantation (BMT) plus bone grafts (to recruit donor-derived stromal cells) from MRL/lpr mice, they survived for almost 1 yr without showing GVH symptoms, but showing autoimmune symptoms such as elevated serum IgG2a concentrations, autoantibody production and glomerulonephritis. When MRL/lpr bone marrow cells plus MRL/+ bones (instead of MRL/lpr bones) were transplanted into B6 mice, such improved survival was also obtained, although the MRL/+ bone grafts were less effective in prolonging survival than MRL/lpr bone grafts. H-2 typing of stromal cells in the bone marrow of the B6 mice revealed that the stromal cells had been replaced by donor(H-2k) derived stromal cells. Analyses of TCR repertoires showed that the percentage of CD4+V beta 8.1,2+ cells significantly decreased in the B6 mice that received bone marrow transplantation plus bone grafts from MRL/lpr mice. These findings suggest that stromal cells present in the bone marrow play a crucial role in the development of lpr-GVHD and autoimmune diseases.

Animals↗
PubMed1996

An epitope on Ki antigen recognized by autoantibodies from lupus patients shows homology with the SV40 large T antigen nuclear localization signal.

OBJECTIVE: Epitopes on Ki antigen were analyzed using synthetic peptides, including KILT, a 16-mer peptide with an amino acid sequence homologous to the SV40 large T antigen nuclear localization signal (SV40 T NLS). METHODS: In addition to KILT, 4 synthetic peptides, all potential epitopes on Ki antigen according to computer analysis, were prepared and tested for reactivity with 49 anti-Ki-positive lupus sera by enzyme-linked immunosorbent assay. RESULTS: Eighteen sera reacted with KILT, but not with other peptides. The reaction of anit-Ki sera with KILT was specifically inhibited by recombinant Ki antigen. Eight of 49 anti-Ki sera reacted with a 7-mer synthetic peptide of SV40 T NLS, and the reaction was specifically inhibited by KILT. CONCLUSION: The 16-mer Ki peptide containing the sequence homologous to the SV40 T NLS is one of the antigenic epitopes recognized by anti-Ki antibodies in lupus sera.

Amino Acid Sequence↗
PubMed1996

Autoantibodies recognizing proteins copurified with PCNA in patients with connective tissue diseases.

OBJECTIVE: Proliferating cell nuclear antigen (PCNA), one of the target antigen recognized by lupus sera, has been reported to be present as a subnuclear multi-peptide complex. But autoantibodies reacting with components of PCNA complex are poorly understood. To study the specificity of those autoantibodies, immunoreactivities of autoimmune sera against purified PCNA antigen were studied. METHODS: PCNA antigens were purified from rabbit thymus extract by affinity column using murine monoclonal antibodies (mAbs) to PCNA, TOB7, TO17 and TO30. Immunoreactivities of autoimmune sera against purified PCNA were analyzed by WB. RESULTS: PCNA antigen purified by serum AK predominantly showed a 34 kD band specific for PCNA in SDS-PAGE. When antigens were purified by anti-PCNA mAb TOB7 and TO30 which are known to be targeting different epitopes on PCNA antigen, SDS-PAGE analysis showed various mol. wt of proteins in addition to the 34 kD PCNA while both AK and mAbs reacted only with 34 kD PCNA in WB. In WB using PCNA purified by TOB7, various immunoreactivities were observed at 150, 66, 58, 48, 45, 37, 32 and 16 kDa in sera from patients with connective tissue diseases. CONCLUSIONS: These results suggested that many of the proteins copurified with PCNA were also targets of autoimmune responses and these autoantibody expression may be induced through antigen-driven mechanisms.

Animals↗
PubMed1996

Increased susceptibility of rat gastric mucosa to ulcerogenic stimulation with aging. Role of capsaicin-sensitive sensory neurons.

We examined the influences of aging on gastric damage and gastric mucosal blood flow (GMBF) responses induced by acid back-diffusion, following the barrier disruption, and investigated the relation of capsaicin-sensitive sensory nerves to these changes. Male Fischer rats 3, 13, and 24 months old were used. Under urethane anesthesia, a rat stomach was mounted on a chamber, and gastric potential difference (PD), luminal H+ loss, and GMBF were measured before, during, and after exposure to 20 mM sodium taurocholate (TC) for 30 min, in the presence of 50 mM HCl. Mucosal exposure to TC caused surface cell damage, PD reduction, and acid back-diffusion (luminal H+ loss) in all groups of rats; delta PD reduction and the amount of H+ loss were not significantly different between young and aged rats. In young rats, a marked increase of GMBF was observed with luminal acid loss following TC treatment, yet it resulted in less damage in the gastric mucosa. In aged rats, however, such GMBF responses were apparently mitigated, leading to a significant worsening of gastric mucosal lesions induced by TC. Mucosal application of capsaicin (0.1 mg/ml) caused an increase of GMBF in young rats, but this response was significantly attenuated in aged rats. In addition, the amount of calcitonin gene-related peptide (CGRP) released in the isolated stomach in response to capsaicin (1 X 10(-5) M) was significantly lower in aged animals when compared to young rats. These findings suggest that the gastric mucosa of aged rats is more vulnerable to acid back-diffusion following the barrier disruption, partly because of dysfunction of GMBF responses mediated by capsaicin-sensitive sensory neurons in the acidic conditions.

Aging↗
PubMed1996

Pathways mediating pentagastrin-induced mucosal blood flow response in rat stomachs.

The mechanisms of pentagastrin-induced gastric mucosal blood flow (GMBF) response were investigated in anesthetized rats. A rat stomach was mounted on an ex vivo chamber, perfused with saline, and GMBF was measured by a laser Doppler flowmetry simultaneously with acid secretion. Pentagastrin infused intravenously produced a dose-dependent increase of GMBF as well as acid secretion, and its effect reached a maximum at 120 microgram/kg/hr (maximal dose). Pretreatment with omeprazole (60 mg/kg, intraperitoneally) completely inhibited the acid secretory response and the enhancement of GMBF induced by both submaximal (60 micrograms/kg/hr) and maximal doses of pentagastrin. In contrast, the luminal perfusion with glycine (200 mM) to remove luminal H+ almost totally attenuated the increase of GMBF caused by the submaximal dose of pentagastrin, without any effect on acid secretion, but partially suppressed such GMBF responses caused by the maximal dose. Subcutaneous pretreatment with indomethacin, a cyclooxygenase inhibitor, significantly mitigated GMBF response caused by both submaximal and maximal doses of pentagastrin, whereas 8-phenyltheophylline (8-PT), an adenosine antagonist, showed a significant inhibition of GMBF response caused by only the maximal dose. However, the combined administration of 8-PT with glycine perfusion further attenuated GMBF response caused by the maximal dose of pentagastrin, and the additional treatment with indomethacin completely blocked this this GMBF response. We conclude that pentagastrin-induced GMBF responses are mediated by at least two different pathways; one is related to luminal H+ and the other to the parietal cell activity, depending on the dose of pentagastrin. In addition, the latter pathway may be mediated by adenosine, while endogenous prostaglandins may be involved in both pathways.

Animals↗
PubMed1996

Phosphorus magnetic resonance spectroscopy in schizophrenia: correlation between membrane phospholipid metabolism in the temporal lobe and positive symptoms.

1. To determine any correlations between phosphorus metabolites in the temporal lobes and clinical symptoms in schizophrenic patients, the authors performed 31phosphorus magnetic resonance spectroscopy in 31 medicated patients and age- and sex- matched normal subjects. 2. Schizophrenic patients demonstrated an increased level of phosphodiesters (PDE) in the temporal lobes bilaterally and a decreased level of beta-adenosine triphosphate (beta-ATP) in the left temporal lobe. 3. A significant positive correlation was observed between the level of PDE in the left temporal lobe and the score of positive symptoms on the Brief Psychiatric Rating Scale. 4. These results suggest that altered membrane phospholipid metabolism in the left temporal lobe is associated with neuroleptic-resistant positive symptoms in schizophrenic patients.

Adenosine Triphosphate↗
PubMed1996

Stimulation of acid secretion in rat stomach following exposure to taurocholate in the presence of the nitric oxide synthase inhibitor.

1. The role of nitric oxide (NO) in the acid secretory response of the rat stomach following damage was investigated. A rat stomach was mounted in an ex-vivo chamber, perfused with saline, and the potential difference (PD), luminal pH, acid and HCO3- responses were measured before and after the mucosal exposure to 20 mM taurocholate (TC) for 30 min, with or without pretreatment with NG-nitro-L-arginine methyl ester (L-NAME). 2. Exposure of the stomach to TC caused a reduction of PD, a decrease of acid secretion and an increase in luminal HCO-. Pretreatment with L-NAME did not affect such PD and HCO3- responses, but completely attenuated the decreased acid secretory response and rather enhanced this secretion. 3. These effects of L-NAME were significantly antagonized by the co-administration of L-arginine but not D-arginine. The enhanced acid secretory response in the presence of L-NAME was significantly inhibited by prior administration of cimetidine or FPL-52694 (a mast-cell stabilizer). 4. The mucosal exposure to TC significantly decreased the number of mucosal mast cells and increased the luminal histamine output. 5. Damage in the stomach may activate the histamine-dependent acid stimulatory pathway in addition to the NO-dependent inhibitory mechanism, although the latter effect overcomes the former, resulting in a decrease of acid secretion. L-NAME unmasks the stimulation of acid secretion by suppressing the inhibitory pathway.

Animals↗
PubMed1996

Regional differences of endogenous ATP release in rabbit arteries.

The releases of endogenous ATP from ear, femoral, renal and pulmonary arteries of rabbit were compared. Adenyl purines, such as ATP, ADP, AMP and adenosine, and norepinephrine (NE) were quantified by HPLC-fluorescence detection and HPLC-electrochemical detection, respectively. In all four blood vessels, electrical stimulation (ES) at 16 Hz significantly increased overflow of adenyl purine and NE. ATP was the main largest among adenyl purine released; release of adenosine was very small. The rank order of amounts of total purine released by ES was ear artery > renal artery = femoral artery >> pulmonary artery. There was no significant difference among the amounts of NE release induced by ES from these four arteries. ES-induced purine release was notably reduced by denudation of endothelium and prazosin at 1 muM. Methoxamine, alpha 1-adrenoceptor agonist, also produced release of adenyl purines in the four arteries. The rank order of amount of total purine released was ear artery > renal artery = femoral artery >> pulmonary artery. These suggest that the sources of ATP released by sympathetic nerve stimulation, which seems to be alpha 1-adrenoceptors on endothelial cells, not distributed homogeneously in the vasculature.

Adenosine Diphosphate↗
PubMed1996

The consequences of engineering an extra disulfide bond in the Penicillium camembertii mono- and diglyceride specific lipase.

The extracellular lipase from Penicillium camembertii has unique substrate specificity restricted to mono- and diglycerides. The enzyme is a member of a homologous family of lipases from filamentous fungi. Four of these proteins, from the fungi Rhizomucor miehei, Humicola lanuginosa, Rhizopus delemar and P. camembertii, have had their structures elucidated by X-ray crystallography. In spite of pronounced sequence similarities the enzymes exhibit significant differences. For example, the thermostability of the P. camembertii lipase is considerably lower than that of the H. lanuginosa enzyme. Since only the P. camembertii enzyme lacks the characteristic long disulfide bridge, corresponding to Cys22-Cys268 in the H. lanuginosa lipase, we have engineered this disulfide into the former enzyme in the hope of obtaining a significantly more stable fold. The properties of the double mutant (Y22C and G269C) were assessed by a variety of biophysical techniques. The extra disulfide link was found to increase the melting temperature of the protein from 51 to 63 degrees C. However, no difference is observed under reducing conditions, indicating an intrinsic instability of the new disulfide. The optimal temperature for catalytic activity decreased by 10 degrees C and the optimum pH was shifted by 0.7 units to more acidic.

Base Sequence↗
PubMed1996

Quantitative cytology of nasal secretions and scrapings in Japanese cedar pollinosis patients.

To explore the dynamics of the cellular response to natural allergen exposure, the authors of this study performed quantitative cytology in both the nasal secretions and nasal scrapings of 16 normal control subjects and 23 Japanese cedar pollinosis patients before and during the pollen season. In nasal scrapings, the number of metachromatic cells increased significantly during the pollen season, although there was no significant difference between the normal subjects and the preseason pollinosis patients. The cell differential count in the patients with pollinosis showed that lymphocytes were predominant in scrapings; however, the majority of inflammatory cells in the nasal secretions were neutrophils before the season and eosinophils during the season. The study findings suggest that the appearance of metachromatic cells in nasal scrapings is specific to the pollen exposure and that the cytology in nasal secretions is significantly different from that in nasal scrapings.

Adult↗
PubMed1996

Effect of 8-sulfophenyl theophylline on endogenous noradrenaline release from sympathetic nerves of the rabbit ear artery.

1. The release of endogenous noradrenaline (NA) and adenyl purine (ATP, ADP, AMP and adenosine) from the rabbit ear artery, evoked by electrical stimulation (ES; 16 Hz), was examined. 2. ES evoked a significant release of NA and purine; the ratio of the amount of total purine released to NA released was approximately 180 on a molar base. 3. ES-evoked purine release was significantly reduced by the denudation of the endothelium and abolished by the alpha 1-adrenoceptor antagonist, prazosin (1 mumol/L). 4. ES-evoked NA release was significantly reduced by a P1-purinoceptor antagonist, 8-sulfophenyl theophylline (8SPT). Purine release was slightly reduced by 8SPT. 5. These results suggest that endogenous NA released by ES results in the release of a large amount of purine, which may, in turn, increase the release of NA by acting on prejunctional purinoceptors on sympathetic nerve terminals.

Animals↗
PubMed1996

Pancreatic calculi superimposed upon slow growing pancreatic cancer.

We report on a 59 year old male patient with cancer of the head of the pancreas, upon which pancreatic calculi were superimposed during the 3 year clinical course. Pancreatic calculi were noted in the main pancreatic duct (MPD) on both computed tomographic scans and ultrasonographs of the abdomen approximately 10 months after the recognizable dilatation of the MPD. Existence of the calculi was confirmed by autopsy. Elemental analysis and infrared spectrophotometry of the calculi demonstrated that the main constituent of the calculi was calcium carbonate. Histopathological examination showed that the pancreatic cancer was moderately differentiated adenocarcinoma. Immunohistochemical studies revealed that pancreatic stone protein (lithostathine) was present in the cytoplasm of tumour cells. In this case, pancreatic cancer progressed to obstruct the MPD unusually slowly, resulting in stagnation of pancreatic secretion and subsequent formation of the calculi.

Adenocarcinoma↗
PubMed1996

Changes in gastric HCO-3 secretory response to NG-nitro-L-arginine methyl ester in rats following repeated administration.

The effect of repeated administration of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) on gastric HCO-3 secretion was examined using ex vivo chambered stomachs of anaesthetized rats. Intravenous administration of L-NAME (5 mg/kg) increased gastric HCO-3 secretion with a concomitant rise in arterial blood pressure (BP). The HCO-3 stimulatory action of L-NAME diminished when rats were pretreated with L-NAME (20 mg/kg, p.o., twice daily) for 1 or 3 days and an inverse relationship was found between the degree of secretory stimulation and the period of pretreatment. The increased BP response to L-NAME was also significantly lessened following repeated pretreatment; basal BP showed a stepwise increase during repeated pretreatment and did not change at all in response to i.v. L-NAME after 3 days pretreatment. When delta HCO-3 output induced by i.v. L-NAME was plotted against delta BP (from basal values) during repeated pretreatment with L-NAME, a significant relationship was found between these two factors. The reduction in the HCO3 secretory response to L-NAME was restored when animals were pretreated with L-arginine (500 mg/kg, i.p., twice daily) together with L-NAME. However, prostaglandin E2 (300 micrograms/kg, i.v.) caused a gastric HCO-3 secretory response similar to L-NAME, regardless of whether rats had been pretreated with L-NAME or not. In contrast, the attenuation by L-NAME of the acid (0.2 nmol/L HCl)-induced gastric hyperaemic response was not influenced by repeated pretreatment with L-NAME. We conclude that repeated p.o. pretreatment with L-NAME reduces the HCO-3 stimulatory action of i.v. L-NAME and that this phenomenon may be explained by the lack of further elevation of BP in response to i.v. L-NAME following repeated pretreatment with this agent. Thus, the stimulation of HCO-3 secretion by i.v. L-NAME may be causally related with increased BP in response to this agent.

Administration, Oral↗
PubMed1996

Argyria and convulsive seizures caused by ingestion of silver in a patient with schizophrenia.

The case study of a schizophrenic patient with argyria which resulted from the chronic and excessive ingestion of antismoking pills contain silver, is presented. Convulsive seizures developed after the patient had been addicted to the pills for 40 years. An extremely high concentration of silver was detected in serum. This case provides support for the hypothesis that silver may cause convulsive seizures as a result of systemic poisoning.

Administration, Oral↗
PubMed1996

Assignment of the gene for rat thromboxane receptor (Tbxa2r) to chromosome 7q11 by fluorescence in situ hybridization.

Thromboxane plays physiological and pathophysiological roles in many tissues. Recently, we cloned a cDNA for rat kidney thromboxane receptor (Tbxa2r) and showed that Tbxa2r is expressed in the renal glomerulus, vasculature, and transitional cell epithelium of renal pelvis. Here, we map the gene for this receptor (Tbxa2r) to rat chromosome 7q11 by fluorescence in situ hybridization.

Animals↗