Search PubMed⌕ Search

Biomedical subjects

Y Nishikawa

Publications and source records attributed to Y Nishikawa.

At least 127 records · Page 7Linked to original sources
PubMed1996

Involvement of transforming growth factor beta1 in autocrine enhancement of gelatinase B secretion by murine metastatic colon carcinoma cells.

We have reported previously that highly metastatic LuM1 cells derived from colon carcinoma colon 26 secrete larger amounts of gelatinase B than NM11 cells with poor metastatic potential, and that an increase in this gelatinase B secretion can be induced by autocrine factors (Hyup et A, Cancer Res., 54: 3611-3616, 1994). In the present study, a partial characterization was achieved by comparison of the autocrine factor preparation (fraction G) from serum-free medium conditioned with metastatic LuM1 cells with soluble factors known to stimulate gelatinase B secretion. Secretion of gelatinase B by LuM1 cells was augmented by tumor necrosis factor alpha, transforming growth factor beta1 (TGF-beta1), interleukin 1beta, or epidermal growth factor, and specific neutralizing antibodies abolished the induced increases. Platelet-derived growth factor and insulin-like growth factor 1 had no effect on gelatinase B secretion by LuM1 cells. The enhancement of gelatinase B secretion by fraction G was partially inhibited by the antibody to TGF-beta1. TGF-beta1 was detected in both active and latent forms in serum-free medium conditioned with LuM1 or NM11 cells, with the amount of TGF-beta1 higher in the former case. Gelatinase B secretion by LuM1 cells was enhanced by the addition of TGF-beta1 to the culture medium, but that by NM11 cells was not seriously affected, although the latter bound more of the factor. These results indicate the involvement of this growth factor in the autocrine stimulation of gelatinase B secretion by LuM1 cells. However, the autocrine factor effect was not fully explained by TGF-beta1 in the medium, and the involvement of some other unknown factor(s) was thus indicated.

Animals↗
PubMed1996

Alteration of cell cycle-dependent histone phosphorylations by okadaic acid. Induction of mitosis-specific H3 phosphorylation and chromatin condensation in mammalian interphase cells.

Effects of okadaic acid (OA), a protein phosphatase inhibitor, on chromatin structure and phosphorylation of histones were examined using HeLa and N18 cells. The chromatin condensation in HeLa cells was mild and resemble prometaphase nuclei, while the condensation in N18 cells was extensive and chromatin became a compact body. H2A in HeLa cells was extensively and consistently phosphorylated at the same site throughout the cell cycle, and H3 was demonstrated to be phosphorylated at the mitosis-specific site Ser10. In contrast, H1 phosphorylation was rapidly decreased in most sites within 3 h. The reduction of H1 phosphorylation was accompanied by a quantitative change in the set of H1 phosphopeptides. During the early phase of the OA treatment, H1 phosphorylation was transiently elevated in tandem, whereas H3 phosphorylation reached a maximum somewhat later. The results suggest that mitosis-specific events (cdc2/H1 kinase activation, H1 superphosphorylation, mitosis-specific H3 phosphorylation and chromatin condensation) induced by OA are sequentially associated. The changes appear to reflect a molecular mechanism similar to that operating in normal mitosis.

Adenine↗
PubMed1996

Differential distribution of four types of tooth pulp neurons in the caudal medulla oblongata of the cat.

The medulla oblongata caudal to the obex was explored for neurons responsive to tooth pulp (TP) stimulation in cats. Four different classes of TP neurons were found. They were TP specific neurons, trigeminal wide dynamic range neurons with TP input, trigeminal subnucleus reticularis ventralis (SRV) neurons with TP input and convergent reticular formation with TP input. They were differentially distributed within the caudal medulla oblongata.

Animals↗
PubMed1996

Hepatocytic cells form bile duct-like structures within a three-dimensional collagen gel matrix.

It has been suggested that hepatocytes have the ability to form bile ductal structures during normal development and in various pathological conditions of the liver. In the present study, we attempted to establish an in vitro model of ductal morphogenesis of hepatocytic cells by combining an aggregate culture and a type I collagen gel culture. When spheroidal aggregates of rat or mouse primary hepatocytes were embedded within the collagen gel matrix and then cultured with a medium containing a fibroblast-conditioned medium, the aggregates extended many dendritic processes composed of a trabecular arrangement of cells. Dendritic morphogenesis was also seen in embedded aggregates of immortal liver epithelia] cell lines, which spontaneously emerged during long-term cultures of mouse primary hepatocytes. A similar morphogenesis was induced by the presence of insulin in the medium. Although epidermal growth factor (EGF) and hepatocyte growth factor (HGF) showed only a small effect on the morphogenesis of most of the hepatocytic cells when used alone, these factors, especially EGF, enhanced the morphogenetic effect of insulin. Electron microscopical observations revealed luminal structures lined by microvilli within these dendritic processes, indicating ductal differentiation. Immunocytochemically, the dendritic processes were positive for cytokeratin 19, a marker for bile duct cells. On the other hand, an H-ras-transformed mouse liver epithelial cell line and rat hepatocellular carcinoma cell lines did not demonstrate the organized morphogenesis. Our results indicate that hepatocytic cells can produce bile duct-like structures in the presence of the type I collagenous matrix and soluble morphogenetic factors.

Animals↗
PubMed1996

DNA-binding sperm proteins with oligo-arginine clusters function as potent activators for egg CK-II.

The stimulatory effect of DNA-binding sperm proteins (histone and protamine) on the phosphorylation of p98 (ERp99/GRp94, one of the Hsp-90 family of proteins) by egg casein kinase II (CK-II) was investigated in vitro. It was found that (i) phosphorylation of p98 by egg CK-II in vitro is greatly stimulated by poly-Arg, but not by poly-Lys; and (ii) similar stimulation is observed with sperm histones H2B2 and H2B3 (sea urchin) and fish protamines, such as salmine A1 (salmon) and protamine 3a (rainbow trout). These findings suggest that these DNA-binding sperm proteins function as potent activators for CK-II in fertilized eggs. All of these DNA-binding sperm proteins contain at least an oligo-Arg cluster as a common feature, which can interact with an acidic amino acid cluster of the regulatory beta-subunit CK-II.

Amino Acid Sequence↗
PubMed1996

Organ variation in the mutagenicity of dimethylnitrosamine in Big Blue mice.

Organ specificity in the lacI mutant frequency (MF) induced by dimethylnitrosamine (DMN) was analyzed in lung, liver, kidney, bone marrow, urinary bladder, and testis of Big Blue mice. Cell proliferative activity was also analyzed in some of these tissues by immunohistochemical staining of proliferating cell nuclear antigen (PCNA). Clastogenicity of DMN was concomitantly analyzed by the peripheral blood micronucleus assay with the same animals used for the lacI mutation assay. Five daily intraperitoneal (i.p.) treatments with DMN (1 mg/kg) increased MF in liver (6.2 x control), kidney (2.4 x control), and lung (2.1 x control). These are known target organs for DMN carcinogenesis. No MF increase was observed in nontarget organs studied, i.e., bone marrow, bladder, and testis. Single ip treatment with DMN also increased lacI MF in liver but the increases were smaller than in a 5-daily-treatment regimen. This result suggests that multiple dosing is more effective in the transgenic mutation assay. The enhancement of cell proliferation observed was in bronchial epithelia 7 days after treatment. No micronucleus induction in peripheral blood was observed 24 hours after 2 and 3 daily ip treatments with 1 mg/kg DMN. An increase in the incidence of micronucleated reticulocytes in peripheral blood was observed 48 hours after single ip treatment with 5 or 10 mg/kg DMN. The present study demonstrated organ-specific induction of gene mutations by DMN which suggests a relevance of this assay for the prediction of organ-specific carcinogenesis.

Animals↗
PubMed1996

Evaluation of serotyping, biotyping, plasmid banding pattern analysis, and HEp-2 vacuolation factor assay in the epidemiological investigation of Bacillus cereus emetic-syndrome food poisoning.

To assess the value of the plasmid banding patterns, the vacuolation factor (VF) assay, biotyping, and serological typing as epidemiological markers for strains of Bacillus cereus causing emetic-syndrome illness, 43 isolates from five outbreaks and an additional 76 strains isolated in food-poisoning outbreaks caused by other enteric pathogens were examined by these techniques, and the results were compared. Thirty-eight (88%) of the 43 outbreak strains produced vacuolation responses in HEp-2 cells and were all starch-hydrolysis negative. The other 76 strains associated with outbreaks caused by other food-poisoning bacteria gave all negative VF production results except four strains, and 56 (74%) of these strains produced positive reactions in starch hydrolysis tests. Starch hydrolysis emerged as a convenient screen for VF production, because no starch hydrolysis-positive strains produced VF. With the exception of one isolate, all 38 VF-positive isolates from emtic-syndrome outbreaks were serotype H.1. Isolates from four of the five outbreaks revealed identical plasmid banding patterns in each outbreak, whereas only three of eight serotype H.1 strains from the fifth outbreak exhibited indistinguishable plasmid banding patterns. These results suggest that the plasmid banding pattern analysis may be of value in discriminating between isolates of the same serotype, and establishing if an outbreak arises from a common food source. In conclusion, the vacuolation factor assay combined with the plasmid banding patterns proved to be a valuable tool for the epidemiological investigation of emetic-syndrome outbreaks caused by B. cereus. Moreover, these methods are particularly useful for laboratories that do not have ready access to serotyping facilities.

Bacillus cereus↗
PubMed1996

Methamphetamine modifies the photic entraining responses in the rodent suprachiasmatic nucleus via serotonin release.

We examined whether methamphetamine modifies the photic entraining responses in the rat suprachiasmatic nucleus. Optic nerve stimulation increased vasoactive intestinal polypeptide release from rat suprachiasmatic nucleus slices, and methamphetamine inhibited this increase in a concentration-dependent manner. Optic nerve stimulation has been reported to evoke field potentials in rat suprachiasmatic nucleus slices. Methamphetamine attenuated this field potential, and maximal inhibition (75.5%) was achieved at a concentration of 100 microM. Systemic administration of methamphetamine (1-5 mg/kg) inhibited light (300 lux, 1h)-induced Fos expression in the suprachiasmatic nucleus; methamphetamine at a dose of 5 mg/kg, i.p. caused 40% inhibition of light-induced Fos expression. We examined whether the inhibitory effect of methamphetamine on photic entraining responses mediates serotonin release from the suprachiasmatic nucleus. High-performance liquid chromatographic analysis revealed that methamphetamine application increased serotonin release from rat suprachiasmatic nucleus slices in a concentration-dependent manner, but did not affect noradrenaline release. In addition, reduction of serotonin content attenuated the effect of methamphetamine on field potential induced by optic nerve stimulation in vitro and also light-induced phase advances of wheel running activity rhythm in vivo. The present results support the idea that methamphetamine produces an inhibitory effect on photic entrainment in the suprachiasmatic nucleus via serotonin release.

Animals↗
PubMed1996

Serum tumor necrosis factor-alpha does not mediate endotoxin-induced myocardial depression in rabbits.

Tumor necrosis factor-alpha (TNF-alpha) is an endogenous mediator for several effects of endotoxin. To evaluate whether TNF-alpha mediates endotoxin-induced left ventricular (LV) dysfunction, we measured LV function (sonomicrometers) and serum TNF-alpha (cytolytic assay) in anesthetized rabbits given endotoxin (100 micrograms/kg iv). In the control group (n = 8), systolic depression (defined by a > 10% increase in end-systolic volume at a matched end-systolic pressure) developed in four rabbits and diastolic dilation (> 10% increase in end-diastolic volume at a matched end-diastolic pressure) developed in three rabbits. Neither the increase in end-systolic volume nor the increase in end-diastolic volume correlated with the increase in TNF-alpha, which reached a peak of 2,875 +/- 762 U/ml. In a second group of rabbits (n = 7), a goat polyclonal anti-rabbit antibody to TNF-alpha was given 30-60 min before endotoxin. Anti-TNF-alpha antibody alone did not alter LV function. Although the TNF-alpha response to endotoxin was effectively blunted (peak TNF-alpha remained < 100 U/ml), all seven rabbits developed systolic depression (P = 0.08 compared with control group) and diastolic dilation (P = 0.03). We conclude that serum TNF-alpha does not mediate endotoxin-induced LV systolic depression or diastolic dilation in this model.

Animals↗
PubMed1996

Intercellular adhesion molecule-1 release from human hepatocellular carcinoma.

Serum levels of E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were measured in 38 patients with chronic hepatitis (CH), 29 with liver cirrhosis (LC), and 43 with hepatocellular carcinoma (HCC) using enzyme-linked immunosorbent assays. All the patients showed significantly higher serum levels of these circulating adhesion molecules than 40 normal controls. The serum E-selectin level showed no relationship to the levels of the other adhesion molecules. Serum VCAM-1 levels were well correlated with serum ICAM-1 levels in CH and LC patients. In HCC patients, however, the close correlation between VCAM-1 and ICAM-1 was lost, because the patients with large tumors (100 cm2) showed relatively high ICAM-1 levels. The amount of ICAM-1 shed from the tumor cells was calculated in the HCC patients as follows: actual serum ICAM-1 level minus basal ICAM-1 level released from the noncancerous liver (obtained from the regression line between ICAM-1 and VCAM-1 in CH and LC patients). Although there was no relationship between the actual ICAM-1 level and the tumor size in HCC patients, the predicted ICAM-1 shedding was closely correlated with tumor size. When in situ expression of these adhesion molecules was evaluated in 10 HCC tissues using immunohistochemistry, the tumor cells exhibited enhanced ICAM-1 expression but did not express E-selectin and VCAM-1. These results suggest that the elevated serum levels of adhesion molecules in HCC patients are mainly attributable to the associated liver inflammation, although some ICAM-1 is shed into the circulation by tumor cells.

Carcinoma, Hepatocellular↗
PubMed1995

Growth inhibition of hepatoma cells induced by vitamin K and its analogs.

Congeners of vitamin K are known to inhibit cell growth, although the precise mechanisms of growth inhibition are not well understood. To investigate the mechanisms involved, we synthesized several vitamin K analogs and examined their growth inhibitory activities for a human hepatoma cell line (Hep3B). The analogs included 2-methyl-1,4-naphthoquinone and trimethyl-benzoquinone, with and without aliphatic side chains at position 3. The side chains were all-carbon, thioethers, or O-ethers. Growth inhibition was potent in the compounds with short chains. The presence of a sulfur (thioether) or oxygen atom (O-ether) at the site of attachment of the side chain to the ring potentiated the activity. Apoptotic cell death was induced by the potent growth inhibitory compounds at low concentrations (20-60 microM), whereas necrotic cell death followed treatment with the same compounds at high concentrations. Expression of c-myc, which is thought to be associated with apoptosis, was increased by most of the compounds tested. Both reduced glutathione and cysteine almost completely abrogated the growth inhibitory effects of the thioether analogs as well as of vitamin K3. The effect of glutathione was less prominent for the all-carbon and O-ether analogs, and cysteine had no effect on these analogs. Catalase and deferoxamine mesylate had no significant effect on the thioether analogs, although they showed partial antagonistic effects on the growth inhibition of vitamin K3 and the all-carbon and O-ether analogs. Other non-thiol antioxidants tested had no effect on any of the analogs. Our results indicated that vitamin K-related quinoid compounds cause growth inhibition and both apoptotic and necrotic cell death and that the effects may be mediated by interaction at position 3 of their quinoid nuclei with cellular thiols.

Amino Acid Sequence↗
PubMed1995

Circadian changes in long-term potentiation of rat suprachiasmatic field potentials elicited by optic nerve stimulation in vitro.

Optic nerve stimulation caused a postsynaptic field potential in the rat suprachiasmatic nucleus (SCN) of hypothalamic slices. In the present experiment, we demonstrated whether tetanic stimulation of optic nerve can produce a long-term potentiation (LTP) in the SCN postsynaptic field potential. The amplitude of SCN field potential was higher in the subjective day animals than that in the subjective night animals. Tetanic stimulation of optic nerve (100 Hz, 1 s) at subjective daytime (projected zeitgeber time: ZT 0-8) produced a LTP in this field potential, although the onset of LTP was slow. When tetanic stimulation was applied at ZT4, the percent increase of amplitude was 116.6% immediately after, 159.8% 30 min after and 215.4% 120 min after tetanic stimulation, whereas tetanic stimulation of optic nerve at subjective night-time caused a weak LTP in the SCN. Although tetanic stimulation of Schaffer collaterals induced a LTP formation in the CA1 region of rat hippocampal slices, there were no obvious circadian changes in this LTP formation. The present results demonstrated that excitatory influence on the SCN caused a synaptic plasticity such as LTP. Although the physiological meaning of this LTP is uncertain at present, LTP may be related to adaptation mechanism to photic stimulation.

Animals↗
PubMed1995

Growth control and gene expression in a new hepatocellular carcinoma cell line, Hep40: inhibitory actions of vitamin K.

The growth characteristics of a newly established cell line, Hep40, derived from a human hepatoma are described. An absolute requirement was found for serum to mediate cell growth. Neither EGF, TGF-alpha, nor HGF altered cell growth in the presence or absence of serum. A partial suppression of cell growth was achieved by several TGF-beta family proteins. Affinity crosslinking gels using 125I-labeled TGF-beta showed a significant decrease in the TGF-beta cell-surface type II receptor in Hep40 cells, compared to the TGF-beta-sensitive Hep3B cell line. However, growth could be completely suppressed by addition of vitamins K to the culture medium in both Hep40 and several other hepatoma cell lines. Growth suppression by vitamins K was accompanied by an increased level of transcripts for c-myc, c-jun, and prothrombin genes, in contrast to the actions of TGF-beta 1 protein, which caused a decrease in the level of c-myc transcripts. These data show that this new human hepatoma cell line has partial resistance to growth inhibition by TGF-beta with a unique TGF-beta receptor defect. However, growth was completely suppressed by vitamins K. The differing gene expression patterns in response to TGF-beta as compared to vitamin K suggest that these two growth inhibitors act through differing pathways.

Animals↗