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Biomedical subjects

N Ohta

Publications and source records attributed to N Ohta.

At least 325 records · Page 18Linked to original sources
PubMed1980

Pathophysiological significance of coronary collaterals for preservation of the myocardium during coronary occlusion and reperfusion in anaesthetised dogs.

The significance of pre-existing coronary collaterals for preservation of the myocardium during coronary occlusion and reperfusion was studied in anaesthetised open-chest dogs. The extent of myocardial ischaemic damage was assessed by the accumulation of calcium in the central zone of the ischaemic area and the size of myocardial infarct by the p-nitroblue tetrazolium staining method. Myocardial creatine kinase release was considered as an index reflecting both the extent of ischaemic myocardial damage and the size of the infarct. Reperfusion with the arterial blood of a main branch of the left coronary artery following the 60 min occlusion aggravated the ischaemic myocardial damage, as evidenced by exaggerated cardiac irregularity, myocardial calcium accumulation, and creatine kinase release. The myocardial calcium content and the logarithm of the creatine kinase release during reperfusion were linearly related to the infarct size. These parameters of myocardial damage were inversely related to the retrograde blood flow through the peripheral end of the occluded artery or the ratio of the retrograde-to-orthograde flow, indicating that the pre-existing collaterals influence preservation of the ischaemic myocardium. Thus, it is suggested that the collateral flow available during an ischaemic episode determines the viability of the myocardial cells during ischaemia, and in turn during reperfusion.

Animals↗
PubMed1978

Characterization of unstable poly (A)-RNA in Caulobacter crescentus.

A significant amount of poly(A)-RNA in Caulobacter crescentus is located on polysomes and the size distribution of this polysomal poly(A)-RNA is small compared to the total pulse-labeled RNA in these cells. These observations suggest that the poly (A)-RNA represents a subset of small messenger RNA molecules. Poly (A)-RNA, and presumably the poly (A) portion of these molecules is extremely unstable: as assayed by binding to oligo (dT)-cellulose the poly (A)-RNA turns over with a chemical half-life of 15--20 s compared to a half-life of approx. 2 min for total cellular messenger RNA. The presence of adenosine in hydrolysates of poly(A) tracts showed that these sequences are located at the 3'-OH end of the RNA. The ratios of AMP/adenosine in the samples confirmed that the length of the A-tracts is approx. 13-17 nucleotides (Ohta, N., Sanders, M. and Newton, A. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 2343--2346)

Bacteria↗
PubMed1975

Identification of a chloroplast ribosomal protein altered by a chloroplast mutation in Chlamydomonas.

Direct evidence is presented that a chloroplast gene mutation in Chlamydomonas reinhardi alters one of the chloroplast ribosomal proteins. Proteins of 30 S subunits of chloroplast ribosomes from mutant strains, carrying maternally inherited antibiotic resistances, were compared with those from the wild type strain by CM-cellulose column chromatography and gel electrophoresis. When 30 S ribosomal proteins from a [3H]arginine-labeled streptomycin-resistant strain and a [14C]arginine-labeled wild type strain, or vice versa, were cochromatographed on a CM-cellulose column, one peak (Peak 17) was absent from the mutant profile. Instead, a pronounced peak was observed to elute at a slightly lower ionic strength than Peak 17 in the region of Peak 16. The molecular weights in both Peak 16 and Peak 17 regions determined by discontinuous sodium dodecyl sulfate polyacrylamide gel electrophoresis were indistinguishable, approximately 18,000. Thus, a chloroplast gene mutation to streptomycin resistance has altered the chromatographic behavior of a chloroplast ribosomal protein of the 30 S subunit. We interpret the additional protein in the mutant eluting at Peak 16 as most likely the mutationally altered form of the Peak 17 protein.

Cell Fractionation↗
PubMed1975

Poly(adenylic acid) sequences in the RNA of Caulobacter crescenus.

Poly(adenylic acid) sequences have been isolated from the Gram-negative bacterium Caulobacter crescentus. Most of these A-rich tracts are associated with large RNA molecules that constitute an important fraction of the unstable RNA in these bacteria, and, as estimated by poly(U) filter binding, they are not present in the 16S or 23S ribosomal RNA. Preliminary estimates of size from polyacrylamide gel electrophoresis suggest that the majority of the A-rich tracts ranges from 15 to approximately 50 residues in length.

Adenine Nucleotides↗
PubMedDate not supplied

Purification, characterization and molecular cloning of Cha o 1, a major allergen of Chamaecyparis obtusa (Japanese cypress) pollen.

Pollen of Chamaecyparis obtusa (Japanese cypress) is one of the causes of allergic pollinosis in Japan. A major allergen of the pollen designated Cha o 1, was purified by two-step ion exchange chromatography. Cha o 1 was separated into four components with molecular masses of 48.5 kDa and 52.0 kDa, each with pIs of 6.77 and 6.82. The 23-residue N-terminal sequence of Cha o 1 was determined and shown to have high identity with that of Cry j 1, a major allergen of Cryptomeria japonica pollen. cDNA coding for Cha o 1 was cloned by hybridization screening using Cry j 1 cDNA as a probe. One of the cDNA clones, pCHA-1 was sequenced and found to code for a putative 21-residue signal peptide and a 354-residue native protein with a derived molecular mass of 38.1 kDa. The deduced amino acid sequence of Cha o 1 showed 79-80% identity with those of Cry j 1. These findings were consistent with observations of a close crossreaction between the two allergens. Homology analyses revealed that Cha o 1 had 46-49% identity with Amb a 1 families and Amb a 2, the major allergens of short ragweed. Cry j 1 has pectate lyase enzyme activity, suggesting that Cha o 1 may have the same enzyme activity as Cry j 1.

Allergens↗
PubMedDate not supplied

Selective pericyte degeneration in the retinal capillaries of galactose-fed dogs results from apoptosis linked to aldose reductase-catalyzed galactitol accumulation.

Galactose-fed dogs develop retinal capillary changes similar to diabetic retinopathy with pericyte degeneration as the initial lesion. This is followed by the formation of microaneurysms, hemorrhages, and some areas of acellularity. To investigate the mechanisms for selective pericyte degeneration, retinal capillary pericytes and endothelial cells isolated from beagle dog retina were cultured for 2 weeks in Dulbecco's modified Eagle's medium (DMEM) containing 50 mM D-galactose. Apoptosis was detected in pericytes but not endothelial cells by in situ terminal deoxynucleotidyl transferase (TdT)-mediated biotin-dUTP nick end labelling (TUNEL) staining and the DNA fragmentation assay on agarose gel electrophoresis. This apoptosis was prevented by the addition of the aldose reductase inhibitor AL 1576 to the culture medium containing galactose. Apoptosis was not observed when pericytes were similarly cultured in control DMEM medium. These data support the premise that the selective degeneration of retinal capillary pericytes observed in galactose-fed dogs is linked to increased aldose reductase activity in these cells.

Aldehyde Reductase↗
PubMedDate not supplied

Neutrophils in galactose-fed dogs: suppressed apoptosis and increased adhesion to retinal capillary endothelial cells.

Dogs fed a diet containing 30% galactose develop diabetes-like retinal capillary changes. As retinal capillary occlusion is commonly observed in diabetic retinopathy, neutrophil apoptosis and the interaction of neutrophils with retinal capillary endothelial cells were investigated. Neutrophils were isolated with Ficoll-Hypaque centrifugation from dogs fed a 30% galactose diet and dogs fed a normal, control diet containing 30% non-nutrient filler. Apoptosis of neutrophils was microscopically examined after incubation at 37 degrees C for 3 hours with either 100 U/mL tumor necrosis factor alpha (TNF-alpha), 2 microg/mL cycloheximide or 50 ng/mL phorbol 12-myristate 13-acetate (PMA). Neutrophil adhesion to dog retinal capillary endothelial cells was examined by counting the cells attached to the surface of endothelial cells after the incubation in the presence of either 100 U/mL TNF-alpha or 5 microg/mL lipopolysaccharides (LPS) at 37 degrees C for 3 hours. With all three stimulants TNF-alpha, cycloheximide and PMA, the rate of apoptosis was significantly lower for neutrophils isolated from galactose-fed dogs compared to control dogs fed a normal diet. Preincubation of neutrophils from control dogs in medium containing 30% galactose for 3 hours did not affect the rate of apoptosis. Neutrophil adhesion to retinal capillary endothelial cells induced by incubation in the presence of either 100 U/mL TNF-alpha or 5 microg/ml LPS was significantly higher with neutrophils isolated from galactose-fed dogs than those from control dogs. The data indicate that long-term galactose feeding is essential with development of various neutrophil dysfunctions. These neutrophil changes may contribute to the development of retinal microangiopathy associated with diabetes and galactosemia.

Animals↗
PubMedDate not supplied

HLA-DQ is epistatic to HLA-DR in controlling the immune response to schistosomal antigen in humans.

Antigens that produce an antibody response in some members of a species may fail to do so in others. The response to an antigen is controlled by a gene termed the immune response (Ir) gene, which is transmitted as a single dominant trait. We have provided evidence for similar immune suppression (Is) genes which control non-responsiveness through the antigen specific suppressor T cell. The non-responsiveness is also dominantly inherited and the Is genes are linked to the histocompatibility (HLA) antigen system. Here we report that the HLA-DR2 molecule from a non-responder haplotype (HLA-Dw12-DR2-DQwl) is required for the proliferative T cell response to schistosoma japonicum (Sj) antigen, as a restriction element, indicating that the HLA-DR2 is the product of the Ir gene, and that the HLA-DQwl molecule of the non-responder haplotype is important in the antigen-specific suppression of the response to this antigen, suggesting that it is the product of the Is gene. We therefore conclude that the HLA-DR and DQ molecules, which are controlled by the distinct genes in the MHC multigene family, regulate immune response and immune suppression and that the gene for HLA-DQ is epistatic to that for HLA-DR in controlling the immune response to schistosomal antigen in humans.

Antigens, Helminth↗