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Biomedical subjects

T Ohno

Publications and source records attributed to T Ohno.

At least 919 records · Page 51Linked to original sources
PubMed1977

Assembly of tobacco mosaic virus in vitro: elongation of partially reconstituted RNA.

It was reported that the rate of elongation of partially reconstituted RNA, if prepared without centrifugation, showed dependency upon the state of protein aggregation like that found when free RNA was used as the nucleic acid source [Butler, P. J. G. (1974) J. Mol. Biol. 82, 333-341]. Butler concluded from this result that disks are the kinetically favored protein source for the elongation of the tobacco mosaic virus rod. We show that partially reconstituted RNA prepared without centrifugation always contains a significant amount of free RNA and conclude that the dependency of its elongation rate upon the state of protein aggregation is due to contamination of his partially reconstituted RNA preparation by free RNA. The elongation rate of partially reconstituted RNA, which had been pelleted and contained no free RNA, was found to be about the same regardless of the state of aggregation of the added protein.

Centrifugation, Density Gradient↗
PubMed1977

Purification and characterization of the DNA polymerase of human breast cancer particles.

Previous studies have identified human breast tumor particles possessing many of the features characteristic of RNA tumor viruses. In addition to the expected size (600 S) and density (1.16 g/ml) these include possession of an outer membrane and an inner one surrounding a "core" containing a DNA polymerase and a large-molecular-weight (70S) RNA possessing detectable homology to the RNAs of the mouse mammary tumor virus (MMTV) and of the Mason-Pfizer monkey virus (MPMV). We report here the purification and characterization of the DNA polymerase from the human breast cancer particles. Its key properties are very similar to those ofthe RNA-dependent DNA nucleotidyltransferase (reverse transcriptase) found in MMTV and MPMV. Thus like these viral enzymes, the purified human breast cancer DNA polymerase exhibits the following three features that together distinguish the known viral reverse transcriptases from normal cellular DNA polymerases: (i) a strong preference for oligo(dT)-poly(rA) over oligo(dT)-poly(dA) as a template for the synthesis of poly(dT); (ii) the acceptance of the highly specific oligo(dG)-poly(rCm) as a template for the formation of poly(dG); (iii) the ability to use a viral RNA (AMV) as a template to fashion a faithful DNA complementary copy; and (iv) its preference for Mg++ over Mn++. In summary, the data described here on the enzyme of the human breast cancer particles add further evidence of similarities to the viral agents associated with the corresponding malignancies in the mouse and monkey models. To date, an enzyme with these properties has not been detected in normal breast tissues or in benign tumors of the breast.

Breast Neoplasms↗
PubMed1977

Reconstitution of tobacco mosaic virus rods occurs bidirectionally from an internal initiation region: demonstration by electron microscopic serology.

RNA of a common strain of tobacco mosaic virus was sequentially reconstituted first with protein of the same strain and then with protein of a tomato strain. The reconstituted particles were treated with specific antibodies against the two strain particles and were examined electron microscopically to locate the regions of rods encapsidated with the respective proteins. The results demonstrated that reconstitution starts at an internal region of the RNA about 830 nucleotides from an end that recent studies indicate to be the 3' terminus. Evidence was obtained to show that reconstitution proceeds toward the 5' terminus of the RNA until it is fully encapsidated. Encapsidation of the 3' distal portion of the RNA apparently occurs later and in a direction opposite to that of the encapsidation of the 5' distal portion.

Binding Sites↗
PubMed1977

Antigenic relatedness of the DNA polymerase of human breast cancer particles to the enzyme of the Mason-Pfizer monkey virus.

We have previously reported [(Ohno, T., Sweet, R.W., Hu, R., DeJak, D. & Spiegelman, S. (1977) Proc. Natl. Acad. Sci. USA 74, 764-768)] on the purification and characterization of the DNA polymerase from human breast cancer particles. Its preference for certain synthetic templates and its ability to use a viral RNA to fashion a faithful DNA transcript identify it as a reverse transcriptase similar to that found in the mouse mammary tumor virus and in the Mason-Pfizer monkey virus (MPMV). We report here that the human breast cancer enzyme crossreacts immunologically with the reverse transcriptase of MPMV. The crossreactivity was shown both by inhibition of enzyme activity and by complex formation between purified enzyme and isolated IgG against MPMV polymerase. No such interactions were observed with other oncornavirus reverse transcriptases of avian, murine, feline, or simian origin. Further, the IgG failed to neutralize the reverse transcriptases from human mesenchymal neoplasias (leukemias and lymphomas) or the activities of normal cellular DNA polymerases (alpha, beta, gamma).

Animals↗
PubMed1977

Relation between liver amino acid-catabolizing enzymes and free amino acids of liver and plasma in adult cockerels fed diets containing graded levels of protein.

Activities of liver amino acid-catabolizing enzymes and liver and plasma free amino acid concentrations in adult cockerels fed diets containing 3% to 21% casein were determined 2 hours after a meal. Liver tryptophan pyrrolase activity and liver tryptophan increased with an increase in dietary casein level, but plasma tryptophan decreased with the increase dietary casein level. As the dietary casein level increased, liver lysine-ketoglutarate reductase activity decreased, but liver and plasma lysine increased proportionally, and the rate of increase was larger in the plasma than in the liver. Liver phenylalanine hydroxylase activity increased with the increase in dietary casein level from 3% to 12%, and thereafter remained unchanged. Reflecting the change of this enzyme, phenylalanine increased in the liver and decreased in the plasma with the increase in dietary casein level from 3% to 12%, and thereafter the rate of increase in liver phenylalanine became small and plasms phenylalanine increased. Liver tyrosine was not influenced by the dietary casein level, whereas plasma tyrosine increased sharply from 3% to 12%, and thereafter the rate of increase decreased. Thus, the difference between liver and plasma free amino acid responses might be due to the changes in the activities of liver amino acid-catabolizing enzymes.

Amino Acids↗
PubMed1977

Improved cold tolerance and its mechanism in cold-acclimated rats by high fat diet feeding.

Cold tolerance and metabolic responses to cold were studied in cold-acclimated rats on high fat diet (CAHF). Cold tolerance at-5 degrees C was assessed by fall of colonic temperature of clipped rats after 18 h of fasting. Rate of fall in colonic temperature was greatest in warm-acclimated control rats (WAST), slowest in cold-acclimated rats on standard diet (CAST), and remained unchanged in CAHF during cold exposure for 240 min. Increment in blood free fatty acid (FFA) concentration 80 min after cold exposure was greatest in WAST, less in CAST, and least in CAHF. Blood glucose decreased similarly in WAST and CAST after cold exposure, while it remained unchanged in CAHF. Blood beta-hydroxybutyrate also increased similarly in WAST and CAST, while it did not change in CAHF. Nonshivering thermogenesis tested by noradrenaline was greatest in CAHF, followed by CAST and WAST. Shivering induced by cold exposure was less pronounced in CAST than in WAST and did not develop in CAHF; changes in colonic temperature were inversely related to the extent of shivering during cold exposure for 90 min. These results suggest that an integrating effect of cold and high fat diet could improve cold tolerance much more than cold acclimation itself, possibly through enhanced nonshivering thermogenesis caused by metabolic modifications such as increased lipid use and gluconeogenesis.

Acclimatization↗
PubMed1977

Reduced hyperglycemic action of glucagon in cold-acclimated rats, especially in venous drainage from brown adipose tissue.

Glucagon infusion at a rate of 2 microgram/min for 30 min into warm-acclimated rats induced a marked rise of glucose concentration in venous blood both in the external jugular vein and in Sulzer's vein from the interscapular brown adipose tissue. In cold-acclimated rats the increase in the concentration of glucose was significantly reduced in the former vein and abolished in the latter one. These results suggest an enhanced use of glucose in the brown adipose tissue in cold-acclimated animals under the influence of glucagon.

Acclimatization↗