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Biomedical subjects

K Enomoto

Publications and source records attributed to K Enomoto.

At least 163 records · Page 9Linked to original sources
PubMed1994

The LEC rat: a model for human hepatitis, liver cancer, and much more.

The LEC rat is an inbred mutant strain with spontaneous hepatitis isolated from Long-Evans rats. Since approximately 40% of LEC rats die of fulminant hepatitis, the rat serves an animal model for studying the pathogenesis and treatment of human fulminant hepatitis. The remaining 60% of LEC rats survive and develop chronic (prolonged) hepatitis and subsequently develop liver cancer. Therefore, the LEC rat serves an important animal model for studying the significance of chronic hepatitis in the development of human liver cancer, which often develops in association with chronic hepatitis. The LEC rat can also be used as an animal model of Wilson's disease, since recent studies have disclosed high copper accumulation in the liver and low ceruloplasmin concentration in the serum of this mutant rat.

Animals↗
PubMed1994

[Phase I study of CGS16949A--a new aromatase inhibitor. Cooperative Study Group for CGS16949A].

Phase I study of CGS16949A--a new aromatase inhibitor--was performed in postmenopausal women with advanced breast cancer who received either single oral administration of 4 and 8 mg, or multiple oral daily administration of 1, 2, 4, 8 and 16 mg for 5.5 days. No side effects were observed after single dose administration of 4 mg and 8 mg of CGS16949A. In the multiple administration, one patient received 1 mg/day for 3 days complained of abdominal pain (Grade 2), but administration of CGS16949 A was continued despite of the pain. In order to assess the causal relationship of the drug with the abdominal pain, the number of patients in 1 mg/day group was doubled from 3 to 6 patients, but no side effects were observed in the remaining five patients. In addition, no side effects, including abdominal pain, were noted in the other 2, 4, 8 and 16 mg/day groups. After multiple administration, plasma concentrations of estradiol at 5 hrs after the final dosage in the respective dose groups were reduced to 47.1 +/- 8.3%, 37.3 +/- 3.0%, 28.0 +/- 7.8%, 26.0 +/- 11.3% and 26.6 +/- 13.8% respectively. Similar tendencies were observed in estrone plasma levels and urinary estrogens levels. In this study, the reduction of plasma estrogen levels was confirmed following administration of CGS 16949A. The clinical usefulness of this new aromatase inhibitor remains to be studied further.

Administration, Oral↗
PubMed1993

Proliferation-associated increase in sensitivity of mammary epithelial cells to inositol-1,4,5-trisphosphate.

Injection of D-myo-inositol-1,4,5-trisphosphate (IP3) was found to induce a transient increase of intracellular Ca2+ concentration in cancerous mammary cells (MMT060562) and in normal mammary cells treated with epidermal growth factor. Responses to injection of either D-myo-inositol-1,4-bisphosphate (IP2) or D-myo-inositol-1,3,4,5-tetrakisphosphate (IP4) were small or absent. Furthermore, normal mammary cells cultivated with low-protein serum replacement alone or in the presence of differentiation-inducing hormones (insulin + cortisol + prolactin) were less sensitive to IP3. Thapsigargin induced a transient increase of Ca2+ due to the release of Ca2+ from an intracellular pool. There was no difference in the peak heights of the thapsigargin-induced Ca2+ increase when mammary cells were cultivated in the presence or absence of epidermal growth factor or insulin + cortisol + prolactin. These findings suggest that the releasable intracellular Ca2+ pool remained unchanged whereas sensitivity to IP3 increases during the proliferation stage. Mechanical stimulus of a mammary cell induces an increase of intracellular Ca2+ in the stimulated cell. A certain stimulating factor is released from the mechanically stimulated cell into the extracellular space, and it induces an increase of Ca2+ in surrounding cells. In contrast, the IP3-induced Ca2+ increase in both cancerous and epidermal growth factor-treated normal mammary cells did not spread to adjacent cells. Therefore, increase of Ca2+ is not sufficient to account for the release of stimulating substances from mammary cells in the mechanically-induced spreading response.

Animals↗
PubMed1993

The t(8;21) translocation in acute myeloid leukemia results in production of an AML1-MTG8 fusion transcript.

The t(8;21) translocation is one of the most frequent chromosome abnormalities in acute myeloid leukemia. It has been shown that the t(8;21) breakpoints on chromosome 21 cluster within a single specific intron of the AML1 gene, which is highly homologous to the Drosophila segmentation gene runt. Here we report that this translocation juxtaposes the AML1 gene with a novel gene, named MTG8, on chromosome 8, resulting in the synthesis of an AML1-MTG8 fusion transcript. The fusion protein predicted by the AML1-MTG8 transcript consists of the runt homology region of AML1 and the most part of MTG8, which contains putative zinc finger DNA binding motifs and proline-rich regions constituting a characteristic feature of transcription factors. The MTG8 gene is not expressed in normal hematopoietic cells, whereas AML1 is expressed at high levels. Our results indicate that the production of chimeric AML1-MTG8 protein, probably a chimeric transcription factor, may contribute to myeloid leukemogenesis.

Acute Disease↗
PubMed1993

Increase in portal flow induces c-myc expression in isolated perfused rat liver.

We examined expression of the c-myc oncogene in isolated perfused livers to elucidate the mechanisms involved in triggering the proliferation of hepatocytes after partial hepatectomy (PH). During perfusion with a 1:1 mixture of Dulbecco's modified Eagle's medium and the oxygen transport fluid FC-43, rat livers were two-thirds resected (PH), and further perfused for 1 1/2 hours at the physiological portal flow throughout the perfusion. Expression of c-myc in the perfused livers with PH(+) was ten times higher than in those with PH(-). Furthermore, expression of c-myc in the PH(-) livers perfused with a threefold volume of the physiological portal flow was 5-10 times higher than that in the livers perfused with the physiological portal flow. The perfusates that passed through the livers did not induce DNA synthesis of primary cultured hepatocytes. These results suggest that an increase in the portal flow volume may act as a trigger for hepatocyte proliferation after PH.

Animals↗
PubMed1993

Spontaneous calcium oscillations and mechanically and chemically induced calcium responses in mammary epithelial cells.

Changes of intracellular calcium activity (Ca2+i) in mouse mammary epithelial cells in primary culture (normal) and in an established cell line (MMT060562, cancerous) were investigated by microfluorometry and image analysis of fura-2 fluorescence. In both types of cells, some populations exhibited occasional Ca2+i oscillations with a period of 50-160 s. Slight mechanical stimulation of a cell with a fine glass pipette induced a Ca2+i increase, which spread from the stimulated cell to the surrounding cells with a speed of 7-12 microns/s. ATP (> 1 mumol/l) and ADP, but not AMP induced a Ca2+i increase in both cell types. Bradykinin was highly effective (> 10 nmol/l) only in the cancerous mammary epithelial cells. In Ca(2+)-free solution, all these Ca2+i responses remained unchanged at the first application, and decreased abruptly at the second trial. La3+ (> 0.5 mmol/l) suppressed the response to ATP but not the response to bradykinin. Addition of extracellular Mn2+ rapidly quenched the fura-2 fluorescence in the cell even in a non-stimulated state. Influx of Mn2+ did not increase during Ca2+i responses. These results indicate that the sources of Ca2+i responses in mammary epithelial cells are intracellular stores, which exchange Ca2+ with the extracellular medium.

Adenosine Triphosphate↗
PubMed1993

Monoclonal antibody 7H6 reacts with a novel tight junction-associated protein distinct from ZO-1, cingulin and ZO-2.

The tight junction is an essential element of the intercellular junctional complex; yet its protein composition is not fully understood. At present, only three proteins, ZO-1 (Stevenson, B. R., J. D. Siliciano, M. S. Mooseker, and D. A. Goodenough. 1986. J. Cell Biol. 103:755-766), cingulin (Citi, S., H. Sabanay, R. Jakes, B. Geiger, and J. Kendrick-Jones. 1988. Nature (Lond.). 333:272-275) and ZO-2 (Gumbiner, B., T. Lowenkopf, and D. Apatira. 1991. Proc. Natl. Acad. Sci. USA. 88:3460-3464) are known to be associated with the tight junction. We have generated a monoclonal antibody (7H6) against a bile canaliculus-rich membrane fraction prepared from rat liver. This 7H6 antigen was preferentially localized by immunofluorescence at the junctional complex regions of hepatocytes and other epithelia, and 7H6-affiliated gold particles were shown electron microscopically to localize at the periphery of tight junctions. Immunoblot analysis of a bile canaliculus-rich fraction of rat liver using 7H6, anti-ZO-1 antibody (R26.4C), and anti-cingulin antibody revealed that 7H6 reacted selectively with a 155-kD protein, whereas R26.4C reacted only with a 225-kD protein. Anti-cingulin antibody reacted solely with 140 and 108-kD proteins, indicating that the protein recognized by 7H6 is immunologically different from ZO-1 and cingulin. Immunoprecipitation of detergent extracts obtained from metabolically labeled MDCK cells with R26.4C coprecipitated a 160-kD protein, which corresponds to ZO-2, with ZO-1. However, 7H6 did not react with the 160-kD protein. These results strongly suggest that the 7H6 antibody recognizes a novel tight junction-associated protein different from ZO-1, cingulin and ZO-2.

Animals↗
PubMed1993

High sensitivity of LEC rats with chronic hepatitis to hepatocarcinogenesis: decreases in unscheduled and replicative DNA synthesis of the hepatocytes.

We carried out the following three experiments to clarify the mechanism of hepatocarcinogenesis in Long-Evans Cinnamon (LEC) rats. (1) Sensitivity to diethylnitrosamine (DEN): LEC rats (8 and 25 weeks old) without and with hepatitis and age-matched F344 rats were administered an intraperitoneal injection of a low dose of DEN. Eight weeks after the injection, the numbers of glutathione-S-transferase placental-form (GST-P)-positive foci in the 33-week-old LEC rat liver were significantly higher than those in the livers of the other three groups of rats. (2) Potential for unscheduled DNA synthesis (UDS): Isolated hepatocytes of 25-week-old LEC rats with chronic hepatitis showed about one-third the level of UDS induced by UV irradiation, as compared to that of age-matched F344 rats, while no significant difference was found between the UDS of isolated hepatocytes of 8-week-old LEC rats and age-matched F344 rats. (3) Potential for proliferation: Isolated hepatocytes from 8-week-old LEC rats responded well to epidermal growth factor (EGF) in culture, to almost the same degree as F344 rat hepatocytes, while a remarkable decrease in the responsiveness of hepatocytes isolated from 25-week-old LEC rats to EGF was found. These results suggested that LEC rat hepatocellular carcinoma could be naturally initiated after the onset of hepatitis by carcinogens contaminating food and the environment, probably due to the reduction of DNA repair activity, after which initiated hepatocytes selectively proliferate in response to growth stimuli endogenously produced as a result of continuous loss of hepatocytes (chronic hepatitis), because of a decrease in growth activity of non-initiated hepatocytes.

Animals↗
PubMed1993

Establishment of a novel monoclonal antibody, SE-1, which specifically reacts with rat hepatic sinusoidal endothelial cells.

A monoclonal antibody, SE-1, which specifically reacted with rat hepatic sinusoidal endothelial cells (HSE), was established with elutriator-separated HSE as immunogen. No crossreactivity was observed with other types of endothelial cells or non-endothelial cells. By immunoelectron microscopy, the antigen recognized by MAb SE-1 was localized to the membrane surface of HSE. Immunoblot analysis revealed that SE-1 recognized a single 45 KD band. Although the SE-1 antigen is not yet characterized, the above evidence strongly suggests that it is related to the specific function of HSE. Therefore, SE-1 may be a useful marker to study the role of HSE in various pathophysiological conditions of the liver.

Animals↗
PubMed1993

[Structure of adenylate cyclase and the coupling with the receptor-G protein system].

Adenylate cyclase is a key enzyme that couples with both the stimulatory and inhibitory G proteins (Gs and Gi). The cyclase has been purified and shown to be a glycoprotein of molecular weight 115,000-180,000. Cloning of cDNAs for adenylate cyclase showed that the cyclase is a member of a large family consisting of a variety of subtypes of the enzyme. These subtypes show different responses to calmodulin and G protein beta gamma subunits, and their distributions in tissues and organs are also different. This suggests that each subtype is involved in a particular physiological function. The general structure of adenylate cyclase is composed of two cytoplasmic domains and two membrane-spanning domains, each of which contains 6 transmembrane spans (12 spans in a molecule). The amino acid sequence of each cytoplasmic domain, which is thought to contain a nucleotide (ATP) binding site, is well-conserved among the various subtypes. This review also focuses on the regulation of adenylate cyclase activity by G protein subunits, particularly on several models for adenylate cyclase inhibition by Gi. As one of these mechanisms, direct inhibition of adenylate cyclase by the beta gamma subunits recently demonstrated by us will be discussed.

Adenylyl Cyclases↗
PubMed1993

G protein beta gamma-subunits inhibit purified adenylate cyclase independent of the activation by Ca2+ and calmodulin.

Adenylate cyclase purified by affinity chromatography was activated about 2.5-fold in a Ca(2+)- and calmodulin-dependent fashion. G protein beta gamma-subunits, an inhibitor in the receptor-mediated inhibition of adenylate cyclase, inhibited the purified cyclase by more than 80%. The extent of beta gamma-induced inhibition was not affected by the activation with Ca2+ and calmodulin. Moreover, the prior addition of the beta gamma-subunits to the cyclase did not prevent the subsequent activation of the enzyme by Ca2+ and calmodulin. We conclude that the beta gamma-subunits inhibit adenylate cyclase activity in a calmodulin-independent mode.

Adenylyl Cyclase Inhibitors↗
PubMed1993

[Evaluation of the cases of benign disease with high accumulation on the examination of 18F-fluorodeoxyglucose PET].

In this study 39 cases of abdominal benign disease were examined by PET using 18F-fluorodeoxyglucose (FDG), and 11 cases of them (i.e. 4 cases of liver abscess, 1 of pelvic abscess, 1 of omental abscess, 2 of chronic pancreatitis, 1 of inflammatory pseudotumor of liver, 1 of retroperitoneal leiomyoma and 1 of solid and cystic tumor of pancreas) which showed as high accumulation of FDG as malignant lesion were investigated of their clinical and pathological feature. We used Ci/Cp ratio as index to express the accumulation of FDG in the lesion, which was calculated from radioactivities of the lesion (Ci) and the plasma (Cp) at 60 mins after injection of FDG. The Ci/Cp ratio of the 11 cases was 3.64 +/- 0.77. The pathological feature of the 9 inflammatory cases was high accumulation of inflammatory cells and that of the 2 benign tumor cases was solid proliferation of tumor cells. The serum of the 9 inflammatory cases showed high CRP value. It was considered that the high accumulation of FDG in inflammatory lesions was due to piles of FDG uptake of the many inflammatory cells, while the 2 benign tumors of high accumulation were considered that the tumor cell had as high glucose metabolism as malignancies.

Chronic Disease↗
PubMed1993

[Correlations between estrogen receptor and prognostic factors of patients with breast cancer. The Kanto Cooperative Study Group of Adjuvant Chemoendocrine Therapy for Breast Cancer, Japan].

We investigated possible correlations between estrogen receptor (ER) and prognostic factors in 3,789 patients with stage II or stage IIIa breast cancer in Japan. The patients with ER-positive tumors showed a significantly better prognosis in the 5-year survival rate and the 5-year disease-free survival rate compared with the patients with ER-negative-tumor. Positivities increased with increasing patient age, with increasing tumor size, and lowering degree of cell differentiation, and no relation was observed between the positivities and tumor sites, obesity index, and lymph-node metastasis.

Adult↗
PubMed1993

Mechanically induced calcium signal in mammary epithelial cells.

In mouse mammary epithelial cells, mechanical stimulation of a cell induced an increase of intracellular Ca2+ concentration (Ca2+i), which spread from the stimulated cell to the surrounding cells with a conduction velocity of about 10 microns/s. The Ca2+i signal was transmitted between isolated cells or separated colonies, where there was no physical contact between them. The flow of medium changed the spreading pattern of Ca2+ wave. The Ca2+ wave was induced even in Ca(2+)-free solution. These findings suggested that a certain factor was released from stimulated cell to extracellular medium and it induced the Ca2+i increase from intracellular store in the surrounding cells.

Animals↗
PubMed1993

[Effect of enalaprilat, an angiotensin converting enzyme inhibitor, on the membrane potential of cultured neuroblastoma-glioma hybrid NG108-15 cells].

The effect of enalaprilat on the membrane potential of cultured neuroblastoma-glioma hybrid NG108-15 cells was investigated using the current clamp method. The NG108-15 cell line characteristically differentiates into neurons after addition of 1 mM dibutyryl cAMP to the culture medium. First it was found that enalaprilat inhibits both sodium and calcium currents in the cell membrane of differentiated NG108-15 cells. At concentrations between 10 and 100 microM, this inhibitory effect was reversible and transient, and occurred in a dose-dependent manner. Prolonged washing with normal saline (> 20 min) was needed to completely reverse the inhibitory effect of enalaprilat. The higher the concentration of enalaprilat, the greater its suppressant action on the membrane potential, and at high concentrations (100 microM), enalaprilat caused the peak membrane potential to disappear. When cells were incubated with enalaprilat, 100 microM, for longer periods, however, this inhibitory effect appeared to become irreversible. These findings suggest that enalaprilat has an inhibitory effect on the electrophysiological activity of neurons especially on membrane calcium currents.

Animals↗
PubMed1993

[Targeting therapy using monoclonal antibody directed against growth factor receptors].

Targeting therapy is expected to be a new effective anti-cancer treatment in near future. Major advances are achieved by considerable effort in this area. Monoclonal antibodies that recognize tumour-associated antigens were conjugated to chemotherapeutic drugs, toxins and radionuclides with various procedures. To apply this new therapy for clinical use, many problems still remain to be clarified. These problems consist of human anti-mouse antibody, antigenic heterogeneity and low tumour uptake. By our experiment, growth factor receptor was an ideal target for targeting therapy and immunoconjugate directed against growth factor receptor showed selective cytotoxicity to cancer cells with expression of growth factor receptor. Moreover, cytotoxic effect was positively correlated with expression level of growth factor receptor.

Animals↗