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Biomedical subjects

T C Hall

Publications and source records attributed to T C Hall.

At least 109 records · Page 6Linked to original sources
PubMed1980

Microheterogeneity of globulin-1 storage protein from French bean with isoelectrofocusing.

The major storage protein fraction, globulin-1 protein, of French bean (Phaseolus vulgaris L.) was analyzed by two-dimensional electrophoresis. The protein pattern suggested a more complex system for globulin-1 protein than the model of three polypeptides, alpha, beta, and gamma, differing in molecular weight. Isoelectrofocusing analyses of the individual proteins showed that each exhibited charge microheterogeneity over a similar pH range. Isoelectrofocusing banding patterns may help to understand the relationships between the globulin-1 polypeptide subunits.

Journal Article↗
PubMed1980

Peptide Mapping Reveals Considerable Sequence Homology among the Three Polypeptide Subunits of G1 Storage Protein from French Bean Seed.

The major storage protein, G1 globulin, of bean (cv. Tendergreen) seeds was subjected to limited proteolysis with trypsin, chymotrypsin, papain, proteinase K, and protease V8 and to cleavage with cyanogen bromide and 2-(2-nitrophenylsulfanyl)-3-methyl-3'bromoindolenine. Mapping of peptides separated from each of the three G1 subunits by polyacrylamide gel electrophoresis revealed that many proteolytic cleavage sites were present at similar positions on the subunits. Evidence was adduced that the G1 subunits are homologous in amino acid sequence for about 61% of their length. The remaining region (possibly COOH-terminal) of the subunits appears to be heterologous, with the alpha subunit bearing an additional methionine residue.

Journal Article↗
PubMed1979

Highly active template-specific RNA-dependent RNA polymerase from barley leaves infected with brome mosaic virus.

The extraction of a template-dependent and template-specific RNA-dependent RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) from a eukaryotic source is described. The enzyme, extracted from barley leaves infected with brome mosaic virus (BMV), is capable of incorporating high levels of radioactivity into trichloroacetic acid-insoluble products. The purification procedure included solubilization with nonionic detergent and precipitation with polyethylene glycol. The enzyme was more than 50 times more active than was a comparable preparation from mock-inoculated leaves and was stimulated more than 15-fold by the addition of BMV RNA to the reaction. Other viral RNA templates were less than 25% as efficient as was BMV RNA in stimulating UMP incorporation; poly(A), tRNA, and mRNA gave little stimulation and rRNA was inactive. Autoradiographic analysis after electrophoretic separation of the radioactive products from reaction mixtures containing BMV RNA template revealed prominent bands that coelectrophoresed with replicative forms of BMV RNAs. When BMV RNA template was enriched in RNA3 or RNA4, larger proportions of the products were replicative forms of RNA3 or RNA4, respectively.

DNA-Directed RNA Polymerases↗
PubMed1979

Efficient ribosome binding of brome mosaic virus (BMV) RNA4 contributes to its ability to outcompete the other BMV RNAs for translation.

Analysis of translation products synthesized in vitro in the presence of a mixture of brome mosaic virus (BMV) RNAs 1, 2, 3, and 4 usually shows a predominance of coat protein, coded by RNA4. The proportion of products directed by RNAs 1 and 2 decreased at saturating concentrations of BMV RNA and in the presence of 7-methylguanosine 5'-phosphate (m7G5'p) at nonsaturating concentrations of RNA. No differences in the relative proportions of the various proteins produced were detected in the presence of T-2 toxin, which interferes with the formation of the first peptidyl bond rather than competing for initiation factor, as has been suggested for m7G5'p. These data show that the ability of BMV RNA4 to outcompete BMV RNAs 1, 2, and 3 results, at least in part, from its ability to bind more efficiently to ribosomes.

Cell-Free System↗
PubMed1979

Bioassay procedure for the detection of mutagenic metabolites in human urine with the use of sister chromatid exchange analysis.

A short-term bioassay system for the detection of activated mutagenic metabolites in urine from humans exposed to promutagens was described. Human diploid fibroblasts were grown in medium containing 5--20% urine from smokers, from nonsmokers, and from individuals undergoing cyclophosphamide (Cp) chemotherapy for treatment of cancer. The cells were then subjected to sister chromatid exchange (SCE) analysis. Activated Cp metabolic products in urine specimens produced up to a ten-fold increase in SCE's over preinjection SCE levels for the same individuals. Linear dose-response curves over a urine concentration range from 5 to 20% in culture medium were obtained from cells grown in urine specimens from 7 nonsmokers and 8 cigarette smokers. This test system proved to be sensitive to ambient exposure levels of environmental mutagens and demonstrated that urine from smokers was significantly more mutagenic than was urine from nonsmokers. Replicate experiments showed highly reproducible SCE values for each individual as well as for average SCE values for each group of subjects. The ability of this bioassay system to detect trace mutagenic activity in human urine reproducibly makes it an attractive choice for the monitoring of humans who have been exposed to environmental and/or industrial mutagens.

Adult↗
PubMed1978

A phase II study of phenesterin (NSC-104469).

Phenesterin was evaluated in 222 patients with two different dosage regimens, one by daily treatment and the other with an intermittent schedule. Toxicity was moderate with both programs. The largest group of patients treated had breast cancer; they experienced a 10% response rate. Of interest was a higher percentage of responses in ovarian cancer (36%). An expanded study of patients with ovarian cancer would be of interest.

Adult↗
PubMed1978

Messenger RNA for G1 protein of French bean seeds: Cell-free translation and product characterization.

The fraction of poly(A)-containing RNA isolated from ripening bean (Phaseolus vulgaris) cotyledons that sedimented at 16 S in linear logarithmic sucrose gradients was at least as active a messenger as viral RNA when added to a cell-free protein-synthesizing system from wheat germ. The major products synthesized in vitro were polypeptides of about 47,000 and 43,000 daltons, corresponding to two of the three subunits of G1 protein, the most abundant bean seed storage protein. No trace of the largest (53,000 daltons) subunit was found among the polypeptides synthesized in vitro. Proof that the 47,000- and 43,000-dalton polypeptides coded by the 16S RNA were indeed subunits of G1 protein was obtained by immunoprecipitation with monovalent antibody to G1 protein and by electrophoretic mapping of peptides on acrylamide gels after digestion of mixtures of authentic protein and radioactive translation products with protease V8, chymotrypsin, and trypsin. The subunits synthesized in vitro were slightly smaller than the native subunits, probably because they lacked the sugar residues present on the holoprotein.

Journal Article↗
PubMed1978

Protein Synthesis and Accumulation in Bean Cotyledons during Growth.

Analysis of total protein, of specific proteins by gel electrophoresis and immunoelectrophoresis, and of protein synthetic activity in vitro confirmed that intense protein synthesis and accumulation occurred as the French bean (Phaseolus vulgaris L). seed grew from 12 to 20 millimeters. These techniques showed that there was no globulin-1 (G1) fraction (requiring high salt for solubility) present in 6-millimeter seeds, and only very small amounts were synthesized in seeds less than 9 millimeters long. The 7- to 9-millimeter stages represent a 2-day transition period over which genetic information for the G1 protein becomes actively expressed, accounting for at least 50% of all protein synthesized in this tissue during the following 14 days. At maturity, the electrophoretic analysis confirmed that G1 globulin was the major storage protein, representing some 50% of the dry seed protein. Cell-free protein synthesis assays, including immunoprecipitation of the in vitro products, clearly showed G1 polypeptides to be among the polysome-directed products.

Journal Article↗