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Biomedical subjects

A Okuda

Publications and source records attributed to A Okuda.

At least 109 records · Page 6Linked to original sources
PubMed1988

Non-specific elongation of cell cycle phases by cycloheximide in rat 3Y1 cells, and specific reduction of G1 phase elongation by simian virus 40 large T antigen.

Partial inhibition of protein synthesis by cycloheximide caused prolongation of G1, S and G2 phases in rat 3Y1 fibroblasts. In cells expressing simian virus 40 (SV40) large T antigen, by infection with SV40 in the previous generation, the prolongation of G1 phase in the presence of cycloheximide was suppressed. However, the prolongation of S and G2 phases in the presence of cycloheximide was not suppressed in cells expressing large T antigen, by infection with SV40 in the current generation. Similarly, when density-arrested cells (cells in G0 phase) were infected with SV40 (either wild-type strain or a mutant deleted in the unique coding region for small t antigen) and reseeded sparsely in the presence of cycloheximide, the cycloheximide-induced delay of entry into S phase was suppressed. In this case, the reduction in [35S]methionine incorporation, that in protein accumulation and that in cell volume increase, were not surmounted by SV40 infection. In T-antigen-negative cells, all the regions in G1 phase seemed to be sensitive to cycloheximide, i.e. they suffered elongation. These results suggest that, in comparison with cells that enter S phase by the action of growth factors, cells expressing large T antigen can enter S phase more efficiently through a quite different process.

Animals↗
PubMed1988

Factors affecting heat production of rat 3Y1 fibroblasts in flow microcalorimetry.

Quiescent 3Y1 cells in monolayer cultures were dispersed with trypsin-EDTA, suspended in various media, and the cellular heat production was measured in a flow-type microcalorimeter set at 37 degrees C. A linear relationship was found to exist between the number of cells applied to the microcalorimeter and the heat output. Increasing concentrations of bovine serum albumin (BSA) and of fetal calf serum (FCS) added in Dulbecco's modified Eagle's medium (DEM) enhanced the heat output to the same saturation level. Trypsin inhibitor added in DEM enhanced the heat output, but to a lower saturation level than FCS or BSA did, indicating that BSA has an activity to enhance cellular heat production by a mechanism other than neutralizing residual trypsin. The heat output was found to gradually decrease in the microcalorimeter. This reduction was not enhanced by a two-fold dilution of the medium (DEM plus FCS) with phosphate-buffered saline, indicating that this reduction is not caused by the depletion of nutrients and serum factors in the medium. Similarly, when cells were incubated for 155 or 220 min in suspension in DEM plus BSA at 37 degrees C and applied to the microcalorimeter, the heat output decreased. However, no significant reduction of the heat output was observed after holding the cells at 0 degree C in suspension for the same period. This and other facts suggest that depletion of O2 dissolved in the medium is involved in the gradual decrease in heat output.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Pancreatoduodenectomy for periampullary cancer associated with celiac occlusion: a case report.

A 62-year-old man with atherosclerotic occlusion of the celiac axis underwent pancreatoduodenectomy because of cancer of the common bile duct. Preoperative angiography showed that the arterial blood supply to the celiac viscera was sustained through the gastroduodenal artery via the pancreaticoduodenal arcades from the superior mesenteric artery. Therefore reconstruction of the celiac circulation was attempted before division of the gastroduodenal artery. An autograft of the saphenous vein was placed between the infrarenal aorta and the common hepatic artery. The postoperative course was uneventful. Patency of the graft was demonstrated angiographically on the 50th postoperative day.

Adenocarcinoma↗
PubMed1987

The structure of the rat glutathione S-transferase P gene and related pseudogenes.

We have isolated the rat placental-type glutathione S-transferase (GST-P) gene from a lambda phage library using GST-P cDNA clone, pGP5 (Sugioka, Y., Kano, T., Okuda, A., Sakai, M., Kitagawa, T., and Muramatsu, M. (1985) Nucleic Acids Res. 13, 6049-6057), as a probe. The rat GST-P gene is about 3 kilobase pairs long and contains 7 exons and 6 introns, encoding the same GST-P protein specified by pGP5. The cap site maps 70 nucleotides upstream from the translation initiation site. The canonical promoter "TATA" box was found 27 base pairs upstream from the putative cap site. Two hundred base pairs upstream from the cap site are rich in G + C residues (61%), and the hexanucleotide sequence 5'-GGGCGG-3' is found at position -47 to -42. We have also isolated several processed-type pseudogenes which were presumably originated by reverse transcription followed by insertion at target sites.

Amino Acid Sequence↗
PubMed1986

Accumulation of cells with 4N DNA content at nonpermissive temperature in rat embryo diploid cells transformed by tsA mutant of simian virus 40.

Primary rat embryo cells were transformed by a tsA mutant (tsA640) of simian virus 40 (SV40). Proliferation of all four independent diploid transformants was suppressed at a nonpermissive temperature (40.3 degrees C), being accompanied by a marked increase in the fraction of cells with a 4N DNA content (a 4N peak in the flow cytofluorogram). However, in this case, the fraction of cells with a 2N DNA content (a 2N peak in the flow cytofluorogram) was preserved. Both effects (suppression of proliferation and increase in the 4N peak) diminished when transformed cells were superinfected with wild-type SV40. The increased 4N peak was preserved, albeit not completely, for at least 24 hours, when cells were further incubated in the presence of hydroxyurea at the nonpermissive temperature. On the other hand, the preserved 2N peak all but disappeared within 24 hours, when cells were further incubated in the presence of colcemid at the nonpermissive temperature. These results suggest that the thermolabile large T antigen of SV40 directly or indirectly induces an accumulation of cells with a 4N DNA content, at the nonpermissive temperature, by prolonging the G2 (and/or late S) period.

Animals↗
PubMed1986

Serum-dependent control of entry into S phase of next generation in rat 3Y1 fibroblasts. Effect of large T antigen of simian virus 40.

When rat 3Y1 fibroblasts are deprived of serum in S phase and/or G2 phase in the first generation, the cells delay entry into S phase in the second generation for the duration of the serum deprivation. We can now show that when resting 3Y1 cells are infected with Simian virus 40 (SV40), the removal of serum through S and G2 phases in the first generation does not markedly delay entry into S phase in the second generation. These observations suggest that the serum-dependent control of entry into S phase of the second generation continues from the first generation, and that the abolition of this control by infection with SV40 in the first generation involves the mechanism operative when the resting cells are stimulated to enter S phase (of the first generation) by infection with SV40.

Alpha-Globulins↗
PubMed1986

Optimal perfusion flow rate for the brain during deep hypothermic cardiopulmonary bypass at 20 degrees C. An experimental study.

The relationship between the perfusion flow rate and cerebral oxygen consumption during deep hypothermic cardiopulmonary bypass at 20 degrees C was investigated in dogs. In 10 dogs the perfusion flow rate was decreased in steps from 100 to 60, 30, and 15 ml/kg/min every 30 minutes. Although cerebral blood flow decreased as perfusion flow rate decreased, the ratio of cerebral blood flow to the perfusion flow rate increased significantly (p less than 0.05) at a perfusion flow rate of 15 ml/kg/min compared to that at a perfusion flow rate of 100 or 60 ml/kg/min. The arterial-sagittal sinus blood oxygen content difference increased as perfusion flow rate decreased. Consequently, cerebral oxygen consumption did not vary significantly at perfusion flow rates of 100 (0.48 +/- 0.10), 60 (0.43 +/- 0.14), and 30 ml/kg/min (0.44 +/- 0.12 ml/100 gm/min), and it decreased significantly to 0.31 +/- 0.22 ml/100 gm/min at a perfusion flow rate of 15 ml/kg/min. In five dogs the perfusion flow rate was decreased in one step from 100 to 15 ml/kg/min, and after 60 minutes' perfusion at a perfusion flow rate of 15 ml/kg/min, the perfusion flow rate was returned to 100 ml/kg/min. Cerebral oxygen consumption decreased significantly during 60 minutes' perfusion at a perfusion flow rate of 15 ml/kg/min and did not return to its initial value after the perfusion flow rate was returned to 100 ml/kg/min. These data indicate that the optimal perfusion flow rate for the brain during deep hypothermic cardiopulmonary bypass at 20 degrees C appears to be 30 ml/kg/min, with a possible oxygen debt in the brain resulting in anaerobic metabolism if the perfusion flow rate is kept at 15 ml/kg/min or less.

Animals↗
PubMed1985

Cloning and the nucleotide sequence of rat glutathione S-transferase P cDNA.

A cDNA library prepared from poly(A)+ RNA of 2-acetylaminofluorene (AAF) induced rat hepatocellular carcinoma was screened by synthetic DNA probes deduced from a partial amino acid sequence of glutathione S-transferase P subunit that had been isolated from the tumor by two-dimensional gel electrophoresis. One of the four clones analyzed contained an mRNA region encoding the total amino acid sequence of this enzyme subunit and the complete 3'-noncoding region. The nucleotide sequence indicates that this enzyme subunit has 209 amino acids (calculated Mr=23,307) distinct from other glutathione S-transferase subunits such as Ya and Yc. Comparison of the amino acid sequences between these proteins indicates that glutathione S-transferase P subunit gene has been evolved from the ancestral gene at an earlier stage than the separation of Ya and Yc and that there are at least three domains having a considerable homology with each other in these enzymes. The very large increase of this mRNA in chemically induced hepatocellular carcinoma suggests a characteristic derepression of this gene during hepatocarcinogenesis.

Amino Acid Sequence↗
PubMed1985

Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. III. Large T antigen level and cell proliferation and survival in an SV40 tsA640-transformed macrophage line.

The levels of simian virus 40 (SV40) large T antigen in a tsA-transformed mouse macrophage line at the permissive (33 degrees C) and the nonpermissive (39 degrees C) temperature were examined by immunofluorescence, sodium dodecylsulfate-polyacrylamide gel electrophoresis, complement fixation, and enzyme-linked immunosorbent assay. When the cells were confluent and rested at 33 degrees C, and then were shifted to 39 degrees C, the amount of large T antigen per cell decreased, and most cells survived and remained phagocytic. When the cells were proliferating at 33 degrees C, and then were shifted to 39 degrees C, the cells died with only a small reduction in the amount of large T antigen. Therefore, the physiological state of the cells may determine the survival of cells by affecting the level of large T antigen after exposure to 39 degrees. The confluent cells may be rested with a concomitant decrease of large T antigen. The proliferating cells may not survive in the presence of a relatively high level of functionally defective large T antigen at 39 degrees C.

Animals↗
PubMed1985

Crystallographical analysis of tooth enamel using milligram samples.

An X-ray diffraction microanalytical method, in which sample is loaded onto a silver membrane filter, was applied to assess the crystal content in tooth enamel. Each enamel powder was first examined at room temperature, and then examined again at intervals after heating to 200, 400, 600, 800, and 1000 degrees C. The hydroxyapatite composition weight and crystal weight of the samples were derived from the standard calibration curves. The "crystal content ratio" was defined as the ratio of crystal weight to sample weight. The following results were obtained: (1) beta-tricalcium phosphate (beta-TCP) replaced the hydroxyapatite after heating at the high temperatures; (2) the "crystal content ratio" in the tooth enamel increased with the rise in temperature; and (3) the lattice parameters of the enamel apatite and the beta-TCP were changed by the heating. The X-ray diffraction technique has the potential to analyze the crystal content using milligram samples.

Calcium Phosphates↗
PubMed1985

[A case of multiple cerebral aneurysms caused by cardiac myxoma].

A case of neoplastic aneurysm caused by left atrial myxoma is reported. The patient was a 50-year-old woman who has been suffered from occasional vertigo and syncopal attack. She was admitted with a sudden loss of consciousness and cerebellar ataxia on December 1, 1983. Cerebral angiogram revealed multiple aneurysms in the periphery of both middle cerebral arteries and obstruction of the right superior cerebellar artery. Echocardiography displayed a cardiac myxoma in the left atrium. She suddenly died from recurrent cerebral embolism on January 7, 1984. The diagnosis was confirmed by the autopsy. The histopathological examination revealed that the wall of cerebral arteries were destroyed by the tumor cells of myxoma, and it caused cerebral aneurysms. We presented the detail of this case, and discussed about a mechanism and a treatment of neoplastic aneurysms.

Female↗