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H Miyazawa

Publications and source records attributed to H Miyazawa.

159 records · Page 9Linked to original sources
PubMed1985

Characterization of a temperature-sensitive mutant of mouse FM3A cells defective in DNA replication.

The characterization of a temperature-sensitive mutant (tsFT20 strain, dnats) of mouse FM3A cells is reported. After incubation of tsFT20 cells at the nonpermissive temperature (39 degrees C), DNA synthesis ceased with little change in either RNA or protein synthesis. Flow-microfluorometric analysis revealed that the cell cycle of tsFT20 cells grown at 39 degrees C for 16 hr was similar to that of wild-type cells that were synchronized at the G1/S boundary and at S phase by treatment with aphidicolin, a specific inhibitor of DNA polymerase alpha. The DNA polymerase alpha activity of tsFT20 cells measured in crude cell extracts or in purified preparations was inactivated more rapidly at 39 degrees C than the activity of wild-type cells. In the growth revertants of the tsFT20 cell strain, the heat lability of DNA polymerase alpha decreased. These data suggest that tsFT20 is a temperature-sensitive mutant of DNA polymerase alpha or of a factor associated with DNA polymerase alpha that is essential for its activity.

Animals↗
PubMed1985

Assignment of the human gene for DNA polymerase alpha to the X chromosome.

An interspecific cell hybrid was constructed between a temperature-sensitive mutant cell line of mouse FM3A cells (FT20-M6, a 6-thioguanine-resistant derivative of tsFT20) that has heat-labile DNA polymerase alpha and a human diploid fibroblast derived from a patient with the fragile X syndrome. After extensive segregation of the human chromosomes, a hybrid clone, named M6-39-11, was obtained that contained an X chromosome as the only human chromosome, was able to grow at the nonpermissive temperature and contained human DNA polymerase alpha. These data strongly suggest that the functional human gene for DNA polymerase alpha is located on the X chromosome.

Animals↗
PubMed1984

Human DNA polymerase alpha. Compensation for heat-labile mouse DNA polymerase alpha and its gene localization on the X chromosome.

The chromosomal location of human DNA polymerase alpha gene was determined by studies on somatic cell hybrids between a temperature-sensitive mutant cell line of mouse FM3A cells and normal human lymphocytes or a line of human diploid fibroblasts derived from a patient with the fragile X syndrome. A temperature-sensitive mutant, FT20-M6, a 6-thioguanine-resistant derivative of tsFT20, has heat-labile DNA polymerase alpha. Interspecific cell hybrids between FT20-M6 and human cells grew at the non-permissive temperature, indicating that some human chromosomes can compensate for the temperature-sensitive defect of tsFT20 in mouse-human cell hybrids. Three of these hybrid clones were examined further, and were shown to contain heat-stable DNA polymerase alpha that was neutralized with human DNA polymerase alpha-specific monoclonal antibody. Subcloning and segregation tests of these hybrid clones showed a positive correlation between the expression of human DNA polymerase alpha and the presence of the human X chromosome. Two subclones, however, did not conform to this relationship: they grew at the nonpermissive temperature but not in hypoxanthine/amethopterin/thymidine medium. Detailed examination of the human chromosomes in these subclones revealed that these clones had only one human chromosome, an X chromosome with a terminal deletion of the long arm including the locus of the gene for hypoxanthine phosphoribosyltransferase (EC 2.4.2.8). From these data, the functional DNA polymerase alpha gene was located on the human X chromosome.

Antibodies, Monoclonal↗
PubMed1979

Quantitative structure-activity relationships in 2,5-bis(1-aziridinyl)-p-benzoquinone derivatives against leukemia L-1210.

Antileukemic activities of more than 30 2,5-bis(1-aziridinyl)-p-benzoquinones (4) were correlated against well-defined physicochemical constants. These compounds were evaluated against lymphoid leukemia L1210 in BDF1 mice. The best equations obtained exhibited a linear dependence on the hydrophobic constant, pi. Characteristic aspects of the equations are that the larger the relative hydrophilicity of the drugs the stronger the antileukemic activity will be and that the more hydrophilic compounds have a greater chemotherapeutic index. Steric and electronic effects were also determined to be important. Based on the correlations, three compounds (11, 15 and 19) were designed, synthesized, and biologically evaluated.

Animals↗
PubMedDate not supplied

Effects of somatostatin deficiency on cell distribution within the Langerhans islets.

Insulin, glucagon and somatostatin (SLI) in the pancreas and the gastrointestinal tissue of rats were measured following a high (300 mg/kg) or low (150 mg/kg) dose of cysteamine, given intermittently for 14 days. In addition, the effect of prolonged cysteamine-induced depletion of pancreatic SLI upon the cell distribution within the Langerhans islets was compared with that of chronic insulin-deficient rats produced by streptozotocin. The high or low dose of cysteamine reduced pancreatic SLI to 8.3% and gastrointestinal SLI to 5.6% of control levels without duodenal ulcer. The high dose of cysteamine also reduced pancreatic insulin to 37% of controls without hyperglycemia. No change in the glucagon concentration was observed. In SLI-deficient rats, distribution of A and B cells was similar to that of controls, even though D cells were rarely seen. In insulin-deficient rats, however, the number of A and D cells per islet area increased with a concomitant decrease in B cells. Intermittent administration of a low dose of cysteamine, thus, appears to be useful to produce a chronic SLI-deficient rat. However, a high dose of cysteamine is not a specific depletor of pancreatic SLI. Although insulin may be important to maintain normal cell distribution within the islets, pancreatic SLI may not have such a role.

Animals↗
PubMedDate not supplied

In vivo influence of prostaglandin I2 on systemic and renal circulation in the rat.

The effect of prostaglandin I2 and two other vasodilator agents, acetylcholine and sodium nitroprusside, on systemic and renal circulation was studied in 29 adult euvolemic Sprague-Dawley rats. Intra-aortic infusion of prostaglandin I2 (3.6 micrograms/kg/hr; n = 6 rats) produced significant vasodilation (p less than 0.05), as indicated by an average reduction in total peripheral vascular resistance of 24.8 +/- 2.0%, while renal vascular resistance remained essentially unchanged. Essentially identical findings were obtained in a separate group of six rats pretreated with intravenous administration of saralasin (0.5 mg/kg/hr). In contrast, in another group of six rats pretreated with saralasin, intraaortic infusion of acetylcholine (0.35 mg/kg/hr), which caused a reduction in total peripheral vascular resistance (21.4 +/- 3.8%) comparable to that induced by prostaglandin I2, produced a significant fall in renal vascular resistance (average, 27.7 +/- 5.0%) and, hence, an increase in renal blood flow (average, 26.2 +/- 2.9%). The effect of sodium nitroprusside (0.4 mg/kg/hr i.v.) was intermediate between those of prostaglandin I2 and acetylcholine: both renal vascular resistance and total peripheral vascular resistance fell mildly. These results indicate that prostaglandin I2, given in a dose sufficient to cause systemic vasodilation, fails to induce any discernible renal vasodilative response and that this absence of renal vasodilation by prostaglandin I2 in vivo is not due, as previously postulated, to the highly efficient offsetting influence of intrarenal angiotensin II release.

Acetylcholine↗
PubMedDate not supplied

Induction of anti-tumor immunity by mouse tumor cells transfected with mouse interleukin-12 gene.

Interleukin-12 (IL-12) is a heterodimeric cytokine. In order to transduce both cDNAs for p35 and p40 of IL-12 in the tumor cells, a polycistronic retroviral vector was constructed by inserting the internal ribosome entry site gene of encephalomyocarditis virus between two cDNAs. On the other hand, two cDNAs were sequentially transfected in the tumor cells. Both polycistronic gene transfectants and double transfectants produced biologically active mouse IL-12. IL-12-expressing tumor cells were all rejected in syngeneic mice, and induced cytotoxic T lymphocyte activity. The capacity to induce anti-tumor memory may depend on the amount of IL-12 produced by the transfectants, because the relatively higher IL-12 producer tumor cell line induced the anti-tumor memory in the rejected mice, but the lower producer did not.

Animals↗