Search PubMed⌕ Search

Biomedical subjects

H Nakata

Publications and source records attributed to H Nakata.

At least 91 records · Page 5Linked to original sources
PubMed1998

Rat gastric mucosal cells express ICAM-1 and proinflammatory cytokines during indomethacin-induced mucosal injury.

Adhesion molecules and cytokines are known to be involved in the formation of acute gastric mucosal injury. However, it is not clear whether the gastric mucosal cells express these molecules and modulate the inflammation. To clarify whether gastric mucosal cells express intercellular adhesion molecule-1 (ICAM-1) and proinflammatory cytokines (tumor necrosis factor-alpha (TNF-alpha), interleukin-1-alpha (IL-1-alpha), and cytokine-induced neutrophil chemoattractant-2-beta (CINC-2-beta)) in the formation of gastric mucosal injury, we have used rat indomethacin-induced gastric mucosal lesions as an in vivo model. The gene expression of all cytokines and ICAM-1 increases at the early stages of indomethacin-induced gastritis (TNF-alpha and IL-1-alpha gene expression began to increase earlier than that of ICAM-1 and CINC-2-beta) and can mainly be detected in the gastric epithelial layer. To further identify the source of those molecules, the epithelial cells were separated into seven fractions according to their sizes by a counterflow elution. ICAM-1 and CINC-2-beta gene expressions are particularly enhanced in the middle-sized cell fractions that are rich in gastric mucous-producing cells. The effect of TNF-alpha or IL-1-alpha on the gene expression of ICAM-1 and cytokines was examined by using RGM-1 cells as a model for gastric mucosal cells. RGM-1 cells show an augmented ICAM-1 and proinflammatory cytokine expression in response to TNF-alpha or IL-1-alpha stimulation. Moreover, immunohistochemical staining also reveals an increase in ICAM-1 and CINC protein production in RGM-1 cells in response to TNF-alpha stimulation. We conclude that gastric mucosal cells express various cytokines and an adhesion molecule during the formation of acute gastric mucosal injury and that they may modulate the inflammation.

Animals↗
PubMed1998

An EGF receptor-mediated signal attenuates the inhibitory effect of LPA on an adenylate cyclase activity.

A tyrosine kinase receptor-mediated and a heterotrimeric G protein-coupled receptor-mediated signals have been shown to evoke distinct intracellular signaling events. There has been increasing evidence that cross-talk exists between a tyrosine kinase receptor-mediated and a heterotrimeric G protein-coupled receptor-mediated signal transduction pathways. In the present study, we have studied effects of EGF receptor activation on activities of inhibitory G protein (Gi). We show that the amounts of Gi/Go ADP-ribosylated by islet-activating protein (IAP) increased by 30-40% in the membranes of Rat 1 fibroblast cells pretreated with EGF compared with those without pretreatment. When an effect of lysophosphatidic acid (LPA) stimulation on an adenylate cyclase activity was examined, LPA partly attenuated forskolin-stimulated adenylate cyclase activity via Gi because IAP pretreatment blocked the inhibitory effect of LPA. Pretreatment with EGF reduced the ability of LPA to inhibit the forskolin-stimulated adenylate cyclase activity, while the pretreatment did not have any effects on the forskolin-stimulated activity. Thus, the EGF receptor-mediated signal appears to cause the impairment of Gi function in Rat 1 fibroblast cells.

Adenylate Cyclase Toxin↗
PubMed1998

In vitro inhibition of hepatic cytochrome P450 and enzyme activity by butyltin compounds in marine mammals.

The present study attempted to examine the in-vitro inhibition of hepatic microsomal P450 content and activity by butyltins in marine mammals and discussed on their possible effects in animals in the wild. Decreases in P450 content and the activities of ethoxyresorufin O-deethylase (EROD, catalyzed by CYPIA subfamily) and penthoxyresorufin O-depentylase (PROD, catalyzed by CYP2B subfamily) by tributyltin (TBT) were observed in in-vitro experiments using hepatic microsomes of a pinniped and a cetacean. Among P450 family, EROD activity is more sensitive to TBT than P450 content and PROD activity, indicating a specific mode of action of TBT on different P450 forms. On the other hand, dibutyltin and monobutyltin have no inhibitory effect on EROD activity at concentrations less than 0.5 mM, indicating that the inhibition of enzyme activity in hepatic microsome of marine mammal is mainly by TBT. TBT concentrations that affect P450 contents and activities are above 10 times higher than the values found in the liver of various marine mammals.

Journal Article↗
PubMed1998

Comparative study of p120 GTPase-activating protein and its point mutant in the pleckstrin homology domain.

GTPase-activating protein (GAP) enhances the intrinsic GTPase activity of cellular Ras. In addition to two Src homology 2 (SH2) domains and one Src homology 3 (SH3) domain, it contains a pleckstrin homology (PH) domain. The wild-type or point mutant in the PH domain of p120 GAP (W568A) was expressed by using the baculovirus/Sf9 cell system. Direct effects of the G protein beta gamma subunit (G beta gamma) and several sphingolipids and the effects of phosphorylation by c-Src on the GTPase-stimulating activity of these GAPs on Ras were examined by using immunoprecipitates of these GAPs. The activities of neither of these GAPs were affected by the addition of G beta gamma, although the W568A mutant bound less to G beta gamma compared with the wild type. Several sphingolipids had no effect on the activity of these GAPs. Only in the W568A mutant was GTPase-stimulating activity reduced by tyrosine phosphorylation by c-Src.

Blood Proteins↗
PubMed1998

Heterogeneity of protein profiles of Helicobacter pylori isolated from individual patients.

BACKGROUND: In order to characterize the diversity of Helicobacter pylori (H. pylori) in infected individuals, 10 colonies of H. pylori were isolated from the gastric juice of 25 patients with gastroduodenal diseases (total 250 isolates). METHODS: Protein profiles of isolates were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Results were confirmed by Western blotting (immunoblotting) test using rabbit antisera against three different strains of H. pylori. RESULTS: The protein profiles of 18 of 25 cases (72%) showed a single type of H. pylori with the same polypeptide pattern. In contrast, heterogeneity in the protein profiles was seen in isolates from seven cases (28%). Two differing H. pylori types with two very different polypeptide patterns were found in 10 isolates from one case. In six patients, the protein profiles of isolates were found to have variations in their polypeptides between molecular weights of 30,000 (30K) and 14K, which are thought to be associated with bacterial membrane protein. In some isolates, a polypeptide band of the 16K was missing. Each of three different antisera confirmed differences among the distinct isolates from individual patients. CONCLUSIONS: These findings suggest that more than one antigenically different strain of H. pylori may exist in same infected individuals.

Animals↗
PubMed1998

Inhibitory effects of ginsenoside Rh2 on tumor growth in nude mice bearing human ovarian cancer cells.

Ginsenoside Rh2 (Rh2), isolated from an ethanol extract of the processed root of Panax ginseng CA Meyer, inhibits the growth of B16 melanoma cells. This study was designed to evaluate the ability of Rh2 to inhibit growth of human ovarian cancer cells (HRA) in vitro and in nude mouse. Rh2 inhibited proliferations of various established human ovarian cancer cell lines in a dose-dependent manner between 10 and 60 microM in vitro and induced apoptosis at around the IC50 dose. When HRA cells were inoculated s.c. into the right flank of nude mice, all mice formed a palpable tumor within 14 days. Although i.p. administration of Rh2 alone hardly inhibited the tumor growth, when Rh2 was combined with cis-diamminedichloroplatinum(II) (CDDP) the tumor growth was significantly inhibited, compared to treatment with CDDP alone. When mice were treated p.o. with Rh2 daily (but not weekly), the tumor growth was significantly (P<0.01) inhibited, compared to CDDP treatment alone. When Rh2 was combined with CDDP, the degree of tumor growth retardation was not potentiated. The survival time was significantly (P<0.05) longer than that of medium alone-treated controls or the group treated with CDDP alone. Then, we examined whether p.o. administration of Rh2 has a dose-dependent inhibitory effect on the tumor growth. I.p. and weekly administration of CDDP had more potent antitumor activity in the order of 1 mg/kg, 2 mg/kg and 4 mg/kg, whereas p.o. and daily administration of Rh, (0.4 to 1.6 mg/kg) not only had antitumor activity comparable to that of 4 mg/kg CDDP, but also resulted in a significant increase of the survival. Doses of Rh2 used in this study did not result in any adverse side-effects as confirmed by monitoring hematocrit values and body weight, unlike 4 mg/kg CDDP, which had severe side-effects. It is noteworthy that p.o. but not i.p. treatment with Rh2 resulted in induction of apoptotic cells in the tumor in addition to augmentation of the natural killer activity in spleen cells from tumor-hearing nude mice. Thus, particularly in view of the toxicity of CDDP, Rh2 alone would seem to warrant further evaluation for treatment of recurrent or refractory ovarian tumor.

Animals↗
PubMed1998

Effect of growth factor on GTPase-activating protein (Ras GAP) in Chinese hamster ovary cells.

GTPase-activating proteins (GAPs) stimulate the hydrolysis of GTP bound to small G-proteins and regulate the signal transduction pathway. Changes in the expression of p21-Ras p120-GAP induced by growth factor treatment were examined in cultured Chinese hamster ovary (CHO) and human choriocarcinoma (BeWo) cells. Expression of p120-GAP and GAP activity were measured. Fetal bovine serum induced a significant increased level of GAP in CHO cells, but did not increase GAP in BeWo cells. The results suggest that growth factors affect Ras GAP expression in CHO cells, while they do not in other cells such as BeWo cells.

Animals↗
PubMed1998

Indirect tactual discrimination of heights by blind and blindfolded sighted subjects.

The ability of blind and blindfolded sighted subjects to discriminate cubes of different heights was measured using the method of constant stimuli. Five male blind and 5 male blindfolded sighted students, ages 22 to 28 years, were subjects. All blind subjects had undergone orientation and mobility training at a school for the blind. The cubes, made of wood, were explored using a long cane. Subjects were presented the standard cube and a comparison cube and required to judge whether the comparison cube height was taller, the same, or shorter than the standard. Analysis showed that the difference thresholds of blind and blindfolded sighted subjects were 1.93 and 2.14 cm, respectively. No significant difference in accuracy of discrimination was found between the two groups. The blind subjects showed significantly better performance than the blindfolded sighted subjects on the discrimination task. The blind subjects performed the task significantly faster than the blindfolded sighted subjects. The results suggest that braille reading, use of a long cane, and daily physical activities which required prolonged haptic or proprioceptive learning, may enhance nonvisual motor skills.

Adult↗
PubMed1997

RGS8 accelerates G-protein-mediated modulation of K+ currents.

Transmembrane signal transduction via heterotrimeric G proteins is reported to be inhibited by RGS (regulators of G-protein signalling) proteins. These RGS proteins work by increasing the GTPase activity of G protein alpha-subunits (G alpha), thereby driving G proteins into their inactive GDP-bound form. However, it is not known how RGS proteins regulate the kinetics of physiological responses that depend on G proteins. Here we report the isolation of a full-length complementary DNA encoding a neural-tissue-specific RGS protein, RGS8, and the determination of its function. We show that RGS8 binds preferentially to the alpha-subunits G(alpha)o and G(alpha)i3 and that it functions as a GTPase-activating protein (GAP). When co-expressed in Xenopus oocytes with a G-protein-coupled receptor and a G-protein-coupled inwardly rectifying K+ channel (GIRK1/2), RGS8 accelerated not only the turning off but also the turning on of the GIRK1/2 current upon receptor stimulation, without affecting the dose-response relationship. We conclude that RGS8 accelerates the modulation of G-protein-coupled channels and is not just a simple negative regulator. This property of RGS8 may be crucial for the rapid regulation of neuronal excitability upon stimulation of G-protein-coupled receptors.

Amino Acid Sequence↗
PubMed1997

Molecular identification of a G protein-coupled receptor family which is expressed in planarians.

We identified four guanine nucleotide binding protein (G protein)-coupled receptors from planarians by polymerase chain reaction (PCR) with degenerate primers. They all showed a significant homology to human 5HT1A serotonin receptor and therefore were designated as serotonin receptor-like planarian receptor 1 similar to 4 (5HTLpla1 similar to 4). cDNA clones of 5HTLpla4 and 5HTLpla1 were isolated from the planarian cDNA library and their complete nucleotide sequences were determined. The deduced amino acid sequences of these planarian receptors, which are highly homologous to one another, show significant similarity to that of Drosophila 5HTdrol serotonin receptor. Northern blot analysis revealed that expression of 5HTLpla4 mRNA increased during planarian regeneration, suggesting that 5HTLpla4 might be involved in the regeneration mechanism.

Amino Acid Sequence↗
PubMed1997

Interphase cytogenetic analysis of myxoid soft tissue tumors by fluorescence in situ hybridization and DNA flow cytometry using paraffin-embedded tissue.

BACKGROUND: Myxoid liposarcoma is one of the major myxoid malignancies of soft tissue and its histologic differentiation from other myxoid tumors is sometimes difficult. Recent cytogenetic analysis revealed that a characteristic reciprocal chromosomal translocation of t(12;16)(q13;p11) occurs in myxoid liposarcomas. In this study, retrospective cytogenetic analysis by means of fluorescence in situ hybridization (FISH) and DNA flow cytometry were performed on free nuclei isolated from paraffin embedded myxoid liposarcoma cells, and they were compared with myxoid malignant fibrous histiocytomas (MFHs), low grade fibromyxoid sarcomas, and intramuscular myxomas. METHODS: Nine myxoid liposarcomas, five myxoid MFHs, two low grade fibromyxoid sarcomas, and four intramuscular myxomas were examined. Chromosomal aberrations in chromosomes 12 and 16 were investigated by FISH, using both centromeric DNA probes and whole chromosome painting probes. Cellular DNA contents were determined by flow cytometry. RESULTS: All nine myxoid liposarcomas were shown to be diploid by DNA flow cytometry and exhibited the translocation t(12; 16), as shown by FISH. Four of the five myxoid MFHs exhibited aneuploidy, as shown by flow cytometry, and remarkable numeric aberrations of chromosomes 12 and 16. No abnormal DNA content or chromosomal aberrations were identified in the two low grade fibromyxoid sarcomas or the four intramuscular myxomas. CONCLUSIONS: FISH analysis performed on paraffin embedded materials can be used to differentiate myxoid liposarcomas from other myxoid soft tissue tumors.

Adult↗
PubMed1997

Regenerating gene expression in normal gastric mucosa and indomethacin-induced mucosal lesions of the rat.

Regenerating (reg) gene expression was tested in rat gastrointestinal mucosa to investigate the role played by this gene in the healing of mucosal lesions. Expression of reg mRNA was higher in the stomach than in any other region of the gastrointestinal tract. The gastric cells that expressed reg mRNA were located in the deepest mucosal layer and were small in diameter. In an injured state following indomethacin treatment, reg gene expression was markedly augmented, accompanied by an increase of c-fos expression and healing of the mucosal lesions. These results suggest a role of the reg gene in the healing of gastrointestinal mucosal lesions.

Animals↗
PubMed1997

Treatment strategy for patients with surgically discovered N2 stage IIIA non-small cell lung cancer.

BACKGROUND: The treatment strategy for patients with non-small cell lung cancer and clinically negative, but surgically detected mediastinal lymph node metastasis (surgically discovered N2 disease) is controversial. METHODS: From August 1979 through December 1994, 53 patients with non-small cell lung cancer were found to have surgically discovered N2 disease. We retrospectively studied the clinical characteristics and the factors that influenced the prognosis in these patients. RESULTS: The 3-year and 5-year survival rates and the median survival for the 53 patients with surgically discovered N2 disease were 44%, 21%, and 26 months. Two thirds of the patients had adenocarcinoma. Only complete resection affected long-term survival; adjuvant therapy had no effect on survival. In regard to lymph node status, a single metastatic focus in the aortic area was associated with long-term survival. CONCLUSIONS: Patients with adenocarcinoma may require histologic determination of N2 disease. Complete resection, including extensive and complete mediastinal lymph node dissection, is warranted in patients with surgically discovered N2 disease. In particular, when the aortic lymph node (including stations 5 and 6) alone is involved, the patients should undergo as complete a resection as possible.

Adenocarcinoma↗
PubMed1997

Helicobacter pylori induces proinflammatory cytokines and major histocompatibility complex class II antigen in mouse gastric epithelial cells.

Although Helicobacter pylori has been reported to stimulate the release of various cytokines from gastric tissue, it remains unknown whether normal and nontumorous gastric epithelial cells produce these cytokines. Therefore, in this study, we used a normal mouse gastric surface mucous cell line (GSM06) to determine whether gastric epithelial cells produce proinflammatory cytokines in response to H. pylori. The expression of MHC class II antigen was also examined, to investigate whether gastric epithelial cells participate in the immune response to H. pylori. In the study, GSM06 cells were incubated with H. pylori or its lipopolysaccharide (LPS). Proinflammatory cytokines were detected by Northern and Western blot analysis. The expression of MHC class II antigen was examined by fluorescence activated cell sorter (FACS) analysis. Genetic expression of proinflammatory cytokines such as interleukin-1alpha, tumor necrosis factor-alpha, and cytokine-induced neutrophil chemoattractant-2beta was enhanced by both intact and sonicated H. pylori, but not by H. pylori LPS. The expression of MHC class II antigen was induced by H. pylori more strongly than by interferon-gamma. We conclude that H. pylori induces the expression of proinflammatory cytokines and MHC class II antigen in gastric epithelial cells. Gastric epithelial cells may act as antigen-presenting cells and participate in the immune response to H. pylori infection.

Animals↗
PubMed1997

Distribution of prostaglandin E receptors in the rat gastrointestinal tract.

AIMS: In order to study the role of prostaglandin in the regulation of the gastrointestinal functions, gene expression of prostaglandin receptors along the rat gastrointestinal tracts were investigated. METHODS: Rats were used for the study. The combination of counterflow elutriation separation of mucosal cells and Northern blot analysis was used to detect the gene expression of prostaglandin receptors in gastrointestinal tracts. RESULTS: In small intestine and colon, prostaglandin E2 EP1 and EP3 receptor mRNAs were mainly localized in the deeper intestinal wall containing muscle layers. EP4 receptor gene expression, on the other hand, was detected in the intestinal mucosal layer. In the stomach, EP1 mRNA was detected in gastric muscle layers, whereas EP3 and EP4 receptor gene expression was mainly present in the gastric mucosal layer containing epithelial cells. In gastric epithelial cells, parietal cells were found to have both EP3 and EP4 receptors. At lower concentrations, prostaglandin E2 inhibited gastric acid secretion by parietal cells probably through EP4 receptors. At higher concentrations, however, it stimulated it. On the other hand, mucous cells possessed only EP4 receptor mRNA. CONCLUSIONS: Thus, it is suggested that prostaglandin E2 modulates gastrointestinal functions through at least three different prostaglandin receptors (EP1, EP3, and EP4), each of which has a distinct contribution in the gastrointestinal tract.

Aminopyrine↗
PubMed1997

Bioaccumulation profiles of polychlorinated biphenyls including coplanar congeners and possible toxicological implications in Baikal seal (Phoca sibirica).

Isomer specific concentrations of individual polychlorinated biphenyls (PCBs) including toxic non-ortho (IUPAC 77, 126, 169), mono-ortho (105, 118, 156) and di-ortho (137, 138, 153, 180) coplanar congeners were determined in the blubber of 40 Baikal seals (Phoca sibirica) and as their fish diet collected from Lake Baikal, Siberia. Residue levels of total PCBs in Baikal seals were noticeably high and comparable to those reported for seals from the North Sea, suggesting the recent usage of this compound in the watershed of Lake Baikal. Non-, mono-, and di-ortho coplanar congeners were also detected in Baikal seals and fish. An approach to estimate bioaccumulation profiles of PCB congeners revealed that the non-ortho PCBs, IUPAC 77, 126 and 169 seemed to be less persistent than other congeners. Furthermore, selective biotransformation of PCB congeners having either meta-para vicinal H atoms or both adjacent chlorinated meta-para and ortho-meta positions has been suggested. Comparison of 2,3,7,8-TCDD toxic equivalents (TEQ) of non-, mono- and di-ortho coplanar congeners in Baikal seals with those for other marine mammals suggested higher enrichment of mono-ortho congeners, particularly IUPAC 105 and 118, which contributed significantly to the total TEQs in Baikal seals. Results imply that the TCDD-like toxicity is relatively serious in Baikal seals, because of the enrichment of these toxic PCB congeners in tissues.

Journal Article↗
PubMed1997

Phosphorylation of H-ras proteins by protein kinase A.

Protein phosphorylation is one of several representative post-translational modifications. Cyclic AMP-dependent protein kinase (PKA) plays the crucial and varying role of signal transduction. On the other hand, ras proteins plays an important role in cell proliferation and growth. Although a previous report showed that H-ras protein was phosphorylated by PKA, the stoichiometry was not determined, so we investigated the stoichiometry of phosphorylation of the protein by PKA. H-ras cDNA inserted into a pGEX-2T expressing vector produced high levels of recombinant H-ras (rH-ras) in a fusion protein with glutathione S-transferase. rH-ras was obtained after cleavage by thrombin. Phosphorylation of ras protein by the catalytic subunit of PKA was performed, and the radioactivity was counted after SDS-PAGE and autoradiography. The results indicate that less than 0.1 mol of phosphate was incorporated per mol of H-ras protein, and suggest that H-ras protein could not be a physiologically meaningful substrate for PKA.

Cyclic AMP-Dependent Protein Kinases↗