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Biomedical subjects

S Kanazawa

Publications and source records attributed to S Kanazawa.

At least 127 records · Page 7Linked to original sources
PubMed1988

Characterization of erythropoietin receptor on erythropoietin-unresponsive mouse erythroleukemia cells.

A membrane receptor for erythropoietin was identified in various erythropoietin-unresponsive mouse erythroleukemia cells. Scatchard analyses of the binding of human 125I-labeled erythropoietin to T3C1-2-0, K-1, GM86 and 707 cells showed the presence of a single class of binding sites with apparent Kd values of 0.27-0.78 nM, which are slightly higher than those of erythropoietin-responsive cells. The number of binding sites varied from 110 to 930 per cell. Crosslinking of 125I-erythropoietin to its binding sites with disuccinimidyl suberate revealed the existence of a single binding protein with molecular mass of 63 kDa. No binding sites with higher molecular mass, as observed in erythropoietin-responsive cells, were detected, nor was any specific binding observed to the non-erythroid hematopoietic cell or to the human erythroleukemia cells examined.

Animals↗
PubMed1988

Effect of methotrexate on the deoxyuridine suppression test: results with different cell preparations.

Recently, the deoxyuridine suppression test was used to detect folate deficiency. Several cell preparations were used in this test, and the sensitivity of the test seems to vary with them. We used whole blood (micro-dU test) and bone marrow cells for the deoxyuridine suppression test, and the effects of methotrexate were compared. [3H]Thymidine incorporation into DNA was highest when the concentration of methotrexate was 1 microM in the whole blood culture and bone marrow culture. Methotrexate concentrations from 100 nM to 1 mM did not affect the results of the micro-dU test. However, the bone marrow deoxyuridine test became abnormal with methotrexate, and the abnormality in test values was corrected by the addition of N5-formyltetrahydrofolate. Differences in the results between the micro-dU test and the bone marrow deoxyuridine suppression test seem to represent specificity of each dU test.

Bone Marrow↗
PubMed1988

Coronary flow characteristics of left coronary artery in aortic regurgitation before and after aortic valve replacement.

In 6 patients with pure aortic regurgitation, the velocity waveform in the left anterior descending coronary artery (LAD) was measured using an 80-channel 20-MHz-pulse Doppler velocimeter before and immediately after aortic valve replacement. All patients showed normal coronary angiograms. Flow velocity was analyzed by both zero-cross and fast Fourier transform methods in real time. The LAD flow in severe aortic regurgitation was characterized by an increase in the systolic flow component, a small and rapidly decreased diastolic flow, an irregular velocity profile across the vessel, and a wider velocity spectrum. After aortic valve replacement, systolic flow decreased by 36.3 +/- 21.7% (p less than 0.01), whereas diastolic flow increased by 81.4 +/- 51.8% (p less than 0.05). The ratio of diastolic flow to total LAD flow increased from 63 +/- 13% to 82 +/- 7% (p less than 0.05). The velocity profile became more parabolic and had a narrow spectrum. These results suggest that operation for aortic regurgitation induces beneficial effects on the myocardial inflow immediately after valve replacement.

Adult↗
PubMed1988

ATR1, a Saccharomyces cerevisiae gene encoding a transmembrane protein required for aminotriazole resistance.

In Saccharomyces cerevisiae, 3-amino-1,2,4-triazole (aminotriazole) competitively inhibits the activity of imidazoleglycerolphosphate dehydratase, the product of the HIS3 gene. Wild-type strains are able to grow in the presence of 10 mM aminotriazole because they induce the level of imidazoleglycerolphosphate dehydratase. However, strains containing gcn4 mutations are unable to grow in medium containing aminotriazole because they lack the GCN4 transcriptional activator protein necessary for the coordinate induction of HIS3 and other amino acid biosynthetic genes. Here, we isolated a new gene, designated ATR1, which when present in multiple copies per cell allowed gcn4 mutant strains to grow in the presence of aminotriazole. In wild-type strains, multiple copies of ATR1 permitted growth at extremely high concentrations of aminotriazole (80 mM), whereas a chromosomal deletion of ATR1 caused growth inhibition at very low concentrations (5 mM). When radioactive aminotriazole was added exogenously, cells with multiple copies of ATR1 accumulated less aminotriazole than wild-type cells, whereas cells with the atr1 deletion mutation retained more aminotriazole. Unlike the mammalian mdr or yeast PDR genes that confer resistance to many drugs, ATR1 appears to confer resistance only to aminotriazole. Genetic analysis, mRNA mapping, and DNA sequencing revealed that (i) the primary translation product of ATR1 contains 547 amino acids, (ii) ATR1 transcription is induced by aminotriazole, and (iii) the ATR1 promoter region contains a binding site for the GCN4 activator protein. The deduced amino acid sequence suggests that ATR1 protein is very hydrophobic with many membrane-spanning regions, has several potential glycosylation sites, and may contain an ATP-binding site. We suggest that ATR1 encodes a membrane-associated component of the machinery responsible for pumping aminotriazole (and possibly other toxic compounds) out of the cell.

Amino Acid Sequence↗
PubMed1988

Comparison of blood-flow velocity waveforms in different coronary artery bypass grafts. Sequential saphenous vein grafts and internal mammary artery grafts.

Characteristics of blood-flow velocities were investigated at different sites in two types of coronary artery bypass grafts, sequential saphenous vein grafts (SSVG) and internal mammary artery grafts (IMAG). The latter appear to have the longest life span. The patency rate of the side-to-side anastomosis of the SSVG is better than that of the end-to-side anastomosis. The SSVG was anastomosed to the major diagonal branch by side-to-side anastomosis and to the left anterior descending coronary artery (LAD) by end-to-side anastomosis in 13 patients who had 75-100% and 75-90% stenoses in the LAD and major diagonal branch, respectively. IMAG anastomoses were performed to the LAD in 10 patients with 75-100% stenoses of the artery. The blood-flow velocities were measured by the 20-MHz, eighty-channel ultrasound pulsed Doppler method during surgery. In six patients in the SSVG group, we investigated the configuration of velocity profiles at the region just proximal to the side-to-side anastomosis and at the bridge portion between the side-to-side and end-to-side anastomosis. In the other seven patients, we measured the blood-flow velocity at several centimeters proximal to the side-to-side anastomosis and compared it with that in the IMAG. At the region just proximal to the side-to-side anastomosis, the velocity profile skewed toward the anastomosis side wall in all patients, and the flow velocity near the wall opposite to the side-to-side anastomosis was reversed in five of six patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Chicken ornithine transcarbamylase: its unexpected expression.

Ornithine transcarbamylase (OTC), one of the enzymes of the urea cycle, is detectable in some strains of chickens, although they have no functional urea cycle. The enzyme consists of three identical subunits of 36 kd and is present in mitochondria of the kidney. Using immunoabsorbent column chromatography, we found further evidence that the enzyme is detectable as a precursor form (40 kd) in chicken brain, heart, liver, pancreas, gizzard, small intestine, and breast muscle. When an extract of small intestine containing only precursor OTC was treated with a kidney extract, the precursor was converted into OTC. This suggests that there is a tissue-specific processing protease in the kidney which splits a peptide off the precursor, causing the expression of OTC activity in this organ. However, the reason why the enzyme or its precursor is expressed in these organs is not known. The results of this study suggest that, unlike mammals, chickens are more organ specific with regard to the ability to incorporate precursor OTC into mitochondria.

Animals↗
PubMed1987

Specific binding of erythropoietin to its receptor on responsive mouse erythroleukemia cells.

Erythropoietin (Epo) is a glycoprotein factor that specifically regulates the proliferation and differentiation of erythroid progenitor cells. Here we describe the isolation of Epo-responsive mouse erythroleukemia cell line SKT6, the characterization of the specific binding of biologically active 125I-labeled human Epo (125I-Epo) to its membrane receptor, and, finally, report information concerning the molecular structure of the receptor. About 75% of erythroid colony-forming precursor cell-like colonies derived from SKT6 cells were hemoglobin-positive after 3- to 4-day exposure to Epo in methylcellulose culture. Radioiodinated Epo bound specifically to SKT6 cells, and Scatchard analysis of the data showed a high affinity for 125I-Epo (Kd = 0.15 nM) but displayed only a small number of specific receptors (approximately equal to 470 per cell). Membrane components that specifically interact with 125I-Epo were identified by covalent crosslinking with disuccinimidyl suberate, and three receptor species with apparent Mr 63,000, 94,000, and 119,000 were found in membrane from SKT6 cells, suggesting the complex structure of the receptor molecules. Specific bindings were also detected in all of the Epo-unresponsive Friend erythroleukemia cells examined, and cross-linking study revealed the presence of only the 63,000 species as a binding site.

Animals↗
PubMed1987

Analysis of flow characteristics in poststenotic regions of the human coronary artery during bypass graft surgery.

Poststenotic blood flow velocities were evaluated in nine patients with 75% to 99% stenosis of the left anterior descending coronary artery (LAD) during coronary artery bypass graft surgery. We used the 20 MHz 80-channel pulsed Doppler velocimeter developed in our laboratory. An operator placed a specially designed probe on the native LAD with his fingers. Before induction of extracorporeal circulation, LAD blood velocities were measured at several locations distal to the stenosis. The poststenotic flow velocities were rich in systolic flow component with reduced diastolic component. The velocity configuration in the poststenotic portions was characterized by the presence of reverse flow velocities and/or irregularity of the velocity pattern near the vessel wall, indicating the existence of flow separation and recirculation in the regions. The broadening of the velocity spectrum observed at central axial regions suggested the occurrence of flow disturbances. After grafting, the velocity waveform in the LAD beyond a vein bypass graft changed to a diastolic-predominant pattern with a relatively small systolic component. A transient bypass graft occlusion caused a marked reduction in diastolic flow velocity. The systolic-to-diastolic velocity ratio increased from 0.27 +/- 0.07 to 1.50 +/- 0.50 (p less than .01) by the graft occlusion.

Adult↗
PubMed1987

Effects of trichloroethylene, tetrachloroethylene and dichloromethane on soil biomass and microbial counts.

Trichloroethylene, tetrachloroethylene and dichloromethane in concentrations of 10, 100, and 1000 micrograms per 100 g brown soil (dry weight) had different effects on soil microorganisms. The ATP content of the soil biomass decreased significantly in the first and second week of incubation when 100 micrograms of trichloroethylene and tetrachloroethylene were added to the soil, and it was strongly reduced during the two months of the experiment duration when 1000 micrograms of the individual chlorinated solvents under test was added. Similar inhibitory effects could be observed with soil fungi. Tetrachloroethylene in a dose of 1000 micrograms, however, exerted mainly a stimulative influence as shown by the counts of oligotrophic and copiotrophic aerobic soil bacteria and also by the total counts of anaerobic microorganisms. The same concentrations of trichloroethylene and dichloromethane inhibited both groups of aerobic bacteria in the soil. Actinomycetes were mainly inhibited by addition of 1000 micrograms of the volatile chlorinated solvents but they were not affected by lower concentrations. No significant effects were observed in aerobic spore-forming bacteria, and only slight effects were found also in the spore-forming anaerobic microorganisms of Clostridium sp. In conclusion, with the concentrations of chlorinated solvents which were from 10(3) to 10(6) higher than the actual 'in situ' soil contamination, some negative effects on soil microorganisms could be observed. However, one or two month after the soil was contaminated, the microbial counts increased again.

Adenosine Triphosphate↗