Biomedical subjects

T Chiba

Publications and source records attributed to T Chiba.

801 records · Page 45Linked to original sources

PubMedDate not supplied

Involvement of beta-adrenergic receptor kinase-1 in homologous desensitization of histamine H2 receptors in human gastric carcinoma cell line MKN-45.

The poorly differentiated human gastric carcinoma cell line MKN-45 possesses histamine H2 receptors which are homologously desensitized by histamine. In order to clone the cDNA of a receptor kinase specific for H2 receptors, we performed RT-PCR at a low annealing temperature using oligo-DNA primers bearing the conserved sequences of the kinase domain of the G protein-coupled receptor kinase (GRK) family. However, we were able to isolate only cDNAs for beta-adrenergic receptor kinase 1 (beta ARK1) and GRK6. Interestingly, treatment of MKN-45 cells with beta ARK1 antisense phosphorothioate oligo-DNA (PON) resulted in significant loss of desensitization of H2 receptors by histamine, whereas GRK6 antisense PON had no effect. Thus, beta ARK1 appears to be involved in the homologous desensitization of H2 receptors in MKN-45 cells.

Blotting, Northern↗

PubMedDate not supplied

Immunohistochemical detection of estrogen receptor in invasive human breast cancer: correlation with heat shock proteins, pS2 and oncogene products.

The authors immunohistochemically studied the expression of the estrogen receptor (ER), 27-kD heat shock protein (HSP27) and pS2 in 118 invasive primary human breast cancers. Positive nuclear staining of the ER was detected in 64% of the cases and was closely correlated with the biochemical assay (p < 0.0001). ER-positive tumors were significantly decreased with tumor size and stage (p < 0.001 each), but not with lymph node status. Positivity of the ER was correlated with the cytoplasmic expression of HSP27 (p < 0.005), pS2 (not significant) and HSP70 (not significant). ER negativity was significantly correlated with the expression of p53, epidermal growth factor receptor (EGFR) and c-erbB-2 (p < 0.05 each). Thus, it was concluded that ER-positive breast carcinomas, relatively small in size, preferentially expressed HSP27, HSP70 and pS2 and that ER-negative tumors, relatively large in size, were predisposed to express p53, EGFR and c-erbB-2.

Breast Neoplasms↗

PubMedDate not supplied

Utility of 3-O-methyl-N-acetyl-D-glucosamine, an N-acetylglucosamine kinase inhibitor, for accurate assay of glucokinase in pancreatic islets and liver.

Glucokinase, an enzyme that catalyzes the phosphorylation of glucose, constitutes the key regulatory step in glucose metabolism in pancreatic islets and liver. We found that 3-O-methyl-N-acetyl-D-glucosamine (3-O-methyl-GlcNAc) potently inhibits glucose phosphorylation by N-acetylglucosamine kinase whereas glucokinase is not at all affected by this hexosamine. The addition of 3-O-methyl-GlcNAc to the assay system for glucokinase in rat liver extracts, which contain a high activity of glucokinase (glucose as substrate) relative to N-acetylglucosamine kinase (N-acetyl-D-glucosamine as substrate), affected neither Km nor Vmax values of glucokinase. On the other hand, both Km and Vmax values of glucokinase in rat pancreatic islet extracts, in which N-acetylglucosamine kinase activity is higher than glucokinase activity, were significantly lowered by the use of 3-O-methyl-GlcNAc as an inhibitor of N-acetylglucosamine kinase.

Acetylglucosamine↗

PubMedDate not supplied

Ultrasonography as a method of nutritional assessment.

The composition of the upper arms of five healthy individuals was measured by anthropometry (AN), ultrasonography (US), and computerized tomography (CT). Measurements of midarm fat area (MAFA) and midarm muscle area (MAMA) by CT correlated well with AN and US, but both AN and US overestimated MAMA by 22.8 +/- 17% and 10 +/- 12%, respectively, (mean +/- SD). The overestimate was largest with AN because with this method bone area cannot be excluded. To evaluate the usefulness of US measurements, 10 patients with advanced liver disease were studied. Measurement of MAFA by US, using triceps skinfold thickness as the standard, was found to be an accurate index of fat stores. MAMA measured by US correlated well with lean muscle mass, using creatinine height index as the standard. Ultrasonography is a reliable method of measuring body fat and lean muscle status.

Adipose Tissue↗

PubMedDate not supplied

Do we still need to collect stool? Evaluation of visualized fatty acid absorption: experimental studies using rats.

BACKGROUND: Short-gut syndrome is likely to impair enteric fat utilization. This study was undertaken to develop a clinical test of lipid absorption without fecal collection. METHODS: The absorption of enterally fed radioactive long-chain fatty acid, beta-methyl-p-(123I)-iodophenylpentadecanoic acid was investigated with continuous chyle collection in rats. The changes in excretion and time-dependent biodistribution of radioactivity of the enterally fed agent were assessed in normal control animals. Similarly, sequential urinary excretion and biodistribution were studied along with scintigraphy using sham-operated and short-gut animals. RESULTS: Approximately 64% of the enterally fed radioactivity was recovered in the collected chyle (24 hours). A comparison of normal control, sham-operated, and short-gut animals showed significantly less urinary and greater fecal excretions of radioactivity in short-gut animals. With the use of sequential scintigraphy, the small intestine, whole-body soft tissues, and urinary bladder were well visualized in sham-operated animals, whereas the large intestine and feces were demonstrated earlier in short-gut animals. CONCLUSIONS: Our results suggest that enteral feeding of the agent might be feasible for determining lipid absorption from the the dynamic changes of radioactivity in visualized abdominal organs and in urine.

Animals↗

PubMedDate not supplied

The role of endogenous gastrin in the development of enterochromaffin-like cell carcinoid tumors in Mastomys natalensis: a study with the specific gastrin receptor antagonist AG-041R.

We examined the effects of a newly synthesized gastrin receptor antagonist, AG-041R, on the growth of enterochromaffin-like (ECL) carcinoid tumors in Mastomys natalensis both in vitro and in vivo. AG-041R was as potent as the well known gastrin antagonist L365,260 in inhibiting not only the gastrin-induced release of histamine from but also histidine decarboxylase (HDC) gene expression in the ECL carcinoid tumor cells. AG-041R also inhibited gastrin-induced DNA synthesis and c-fos gene expression in the tumor cells. Furthermore, AG-041R significantly inhibited the growth of the transplanted Mastomys ECL carcinoid tumors in vivo. From these data, it is concluded that endogenous gastrin is involved in the growth of ECL carcinoid tumors in Mastomys natalensis. Moreover, AG-041R is shown to have a potential as an anti-neoplastic agent for ECL carcinoid tumor of the stomach.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMedDate not supplied

Activation of two distinct anti-proliferative pathways, apoptosis and p38 MAP kinase-dependent cell cycle arrest, by tumor necrosis factor in human melanoma cell line A375.

The proliferation of human melanoma cell line A375-6 cells is inhibited by several cytokines, including interleukin-1 (IL-1). A375-R8 cells, a subclone of A375-6, are resistant to IL-1-induced growth inhibition. The proliferation of both cell lines is inhibitable by tumor necrosis factor (TNF). In this study, we characterized the mechanisms of TNF-induced growth inhibition. TNF-induced growth inhibition in both cell lines was partially suppressed by a selective p38 mitogen-activated protein kinase (MAPK) inhibitor (SB203580), whereas a combination of SB203580 and Z-VAD-fmk, an inhibitor for a wide range of caspases, completely blocked TNF-induced growth inhibition, indicating that TNF-induced growth inhibition is mediated by both p38 MAPK and caspases. However, Z-VAD-fmk alone suppressed TNF-induced growth inhibition in A375-R8, but not A375-6, cells, suggesting that there may exist a TNF-induced anti-apoptotic mechanism in A375-6 cells which is lost or mutated in A375-R8 cells. Evidence in support of this notion includes (1) TNF-induced apoptosis only in A375-R8, but not A375-6 cells; (2) cycloheximide enabled TNF to induce apoptosis even in A375-6 cells; and (3) somatic hybrid cells between A375-6 and A375-R8 cells are resistant to TNF-induced apoptosis. Since TNF-induced NF-kappa B activation, cell cycle arrest, RB dephosphorylation, and E2F downregulation are indistinguishable in both cell lines, none of these factors is likely to be involved in the TNF-induced anti-apoptotic mechanism in A375-6 cells. Our results indicate that TNF activates two distinct anti-proliferative pathways including p38 MAPK-dependent cell cycle arrest and caspase-mediated apoptosis, as well as an anti-apoptotic mechanism in melanoma cells.

Apoptosis↗

PubMedDate not supplied

Adenovirus-mediated p16 gene transfer changes the sensitivity to taxanes and Vinca alkaloids of human ovarian cancer cells.

BACKGROUND: Deletions and point mutations of the p16 gene are detectable in more than 50% of ovarian cancer cells. In this study, we examined the effect of p16 gene transduction on the growth of ovarian cancer cells and on the effect of anti-cancer agents. MATERIALS AND METHODS: p16-null human ovarian cancer cell lines, SKOV-3 and OVCAR-5, were used in this study. We transduced the full-length human p16 gene using recombinant adenovirus (AxCA-hp16). RESULTS: The spontaneous growth of these cells was significantly inhibited by hp16 transduction. MTT assay revealed that AxCA-hp16 infection induced chemoresistance in both cell lines. Flow cytometric analysis revealed that only hp16 -transduced SKOV-3, were arrested at the G1-phase for 3 days whereas those infected with AxCA-mock and OVCAR-5 infected with both recombinant viruses did not. Western blot analysis showed increased microtubule-associated proteins 4 (MAP4) in both cell lines. CONCLUSION: These results suggest that in SKOV-3 cells, G1-arrest induced by p16-transduction prevents paclitaxel- and vindesine-induced cell death, and in OVCAR-5 cells, the other unknown mechanisms play a role of chemoresistance.

Adenoviridae↗

PubMedDate not supplied

Antagonistic action of DS-4574 against leukotrienes in guinea-pig smooth muscle.

We investigated the effect of a new antiallergic agent, DS-4574, on the guinea-pig smooth muscle contractions induced by leukotriene C4, D4 and E4 (LTC4, D4 and E4) in vitro. In isolated guinea-pig ileum, DS-4574 antagonized the contraction induced by LTC4, LTD4 and LTE4 with IC50 values of 3.5 x 10(-7), 2.0 x 10(-7) and 2.6 x 10(-7) M, respectively. In contrast, at 10(-4) M this compound inhibited the contractions induced by histamine, acetylcholine, 5-hydroxytryptamine, bradykinin and prostaglandin F2 alpha by less than 50%. In isolated tracheal strip preparations of guinea-pigs, DS-4574 produced a parallel concentration-dependent rightward shift of the leukotriene concentration-response curves without affecting the maximal response. The dissociation constant of DS-4574, obtained against LTC4, LTD4 and LTE4, was 3.07 +/- 0.47 x 10(-8), 1.81 +/- 0.36 x 10(-8) and 7.30 +/- 3.40 x 10(-8) M, respectively. The slopes of Schild plots for DS-4574 against leukotrienes did not differ significantly from unity. In the presence of an inhibitor of the metabolism of LTC4 to LTD4, about 100 times higher concentrations of DS-4574 were required to antagonize LTC4-induced contractions. Moreover, DS-4574 competed with the [3H]LTD4-, [3H]LTE4- and [3H]LTC4-specific binding to the receptor in guinea-pig lung membranes with Ki values of 7.2 x 10(-7), 4.5 x 10(-7) and 3.9 x 10(-5) M, respectively. The present data suggest that DS-4574 is a selective and competitive leukotriene antagonist. When the leukotriene antagonism by DS-4574 is confirmed in other species, it might be useful in a variety of diseases associated with excessive production of leukotrienes.

Acetophenones↗