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Biomedical subjects

M A Martin

Publications and source records attributed to M A Martin.

At least 217 records · Page 12Linked to original sources
PubMed1979

Molecular cloning of polyoma virus DNA in Escherichia coli: plasmid vector system.

A series of recombinant plasmids containing polyoma virus (PY) DNA were constructed, and their biological activity was evaluated in mice and in cultured mouse cells. While all of the recombinants studied contain the complete, potentially infectious viral DNA, in no case was the intact recombinant PY-plasmid DNA, or live Escherichia coli containing the recombinant plasmids, capable of inducing PY infection of mice, either by feeding or by parenteral injection.

Animals↗
PubMed1979

Molecular cloning of polyoma virus DNA in Escherichia coli: lambda phage vector system.

The biological activity of recombinant phage and recombinant phage DNA containing monomeric or dimeric polyoma DNA inserts was examined in mice and cultured mouse cells. Recombinant preparations containing a single copy of viral DNA were invariably noninfectious; molecules containing a dimeric polyoma DNA insert were at least seven orders of magnitude less infectious than polyoma virions after parenteral inoculation. No infection was detected with any recombinant preparation after oral administration.

Animals↗
PubMed1979

Interrupting the early region of polyoma virus DNA enhances tumorigenicity.

The tumorigenicity of DNA from polyoma virus after cleavage with a variety of restriction enzymes was evaluated in suckling hamsters. Cleavage with enzymes that interrupt the region of the genome coding for the large tumor (T) antigen of polyoma virus markedly enhanced the tumorigenicity above that observed with DNA I of the virus. Cell lines established in vitro from tumors induced by polyoma virions, polyoma virus DNA I, or polyoma virus DNA that had been cleaved with restriction endonucleases in the early region all contain the polyoma virus middle and small T antigens but not the large T antigen of polyoma virus is not required for maintenance of the transformed state and probably not for initiation of tumorigenesis by viral DNA.

Animals↗
PubMed1979

Multiple forms of polyoma virus tumor antigens from infected and transformed cells.

At least three distinct forms of polyoma virus tumor antigens were isolated from productively infected and transformed hamster cells by immunoprecipitation with anti-T serum. These proteins had approximate molecular weights of 105,000 (large T antigen), 63,000 (middle T antigen), and 20,000 (small T antigen) as estimated by acrylamide gel electrophoresis. An examination of the appearance of these antigens in polyoma-infected mouse cells showed that all three polypeptides were synthesized maximally at approximately the same time after infection. Analysis of the methionine-containing tryptic peptides of these proteins indicated that the large, middle, and small forms of polyoma T antigens contained five similar or identical peptides. In addition, the 63,000- and 20,000-dalton antigens contained two other methionine peptides absent from the large T-antigen species. Other methionine peptides were found only in the large or middle T-antigen forms. These results and results obtained previously suggested that the three T-antigen species have the same NH2-terminal end regions but different COOH termini. A model is presented describing the synthesis of these polypeptides from different regions of the polyoma virus genome.

Animals↗
PubMed1979

Biological activity of polyoma viral DNA in mice and hamsters.

The biological activity of polyoma viral DNA was evaluated in mice and hamsters. Viral DNA administered parenterally is about 4 to 5 logs less efficient than polyoma virions in establishing infection in mice. Supercoiled viral DNA was infectious for mice after parenteral administration, giving mean infective doses of 10(-3) to 10(-4) microgram. However, animals fed microgram quantities of polyoma DNA I did not become infected. Linearization of viral DNA with R.EcoRI or R.BamHI, which are single-cut enzymes cleaving in the early and late regions of the genome, respectively, reduced the infectivity for mice approximately fivefold. Approximately 10% of newborn hamsters inoculated intraperitoneally with polyoma DNA I developed tumors. In contrast, the same amount of viral DNA which had been cleaved in the early region with R.EcoRI induced tumors in 50% of inoculated hamsters.

Animals↗
PubMed1979

Identification and partial characterization of new antigens from simian virus 40-transformed mouse cells.

Two new species of antigens were detected in simian virus 40-transformed mouse cells, in addition to the large (94,000 daltons) and small (20,000 daltons) tumor antigens. These antigens were immunoprecipitated from cell extracts by using anti-T serum and not normal, nonimmune serum. One of these was a protein with a molecular weight of approximately 130,000 and was present in some but not all SV40-transformed mouse cells. The other, which we have named Tau antigen, has a molecular weight of 56,000 as estimated by electrophoresis through acrylamide gels and was found in all virus-transformed cells examined. The 13,000-daltons antigen contained about 15 methionine-tryptic peptides which were also present in the large SV40 tumor antigen as determined by ion-exchange chromatography. This strongly suggested that the protein was virus coded. The 56,000-dalton Tau antigen appeared to share only two methionine-tryptic peptides with the large species of SV40 tumor antigen, as determined by ion-exchange and paper chromatographies. Our results are compatible with a cellular origin for Tau antigen. However, our data do not exclude the possibility that this protein contains sequences specified by the virus DNA.

Animals↗
PubMed1979

Molecular cloning of the Harvey sarcoma virus closed circular DNA intermediates: initial structural and biological characterization.

Supercoiled Harvey sarcoma virus (Ha-SV) DNA was extracted from newly infected cells by the Hirt procedure, enriched by preparative agarose gel electrophoresis, and digested with EcoRI, which cleaved the viral DNA at a unique site. The linearized Ha-SV DNA was then inserted into lambda gtWESlambda B at the EcoRI site and cloned in an approved EK2 host. Ha-SV DNA inserts from six independently derived recombinant clones have been analyzed by restriction endonuclease digestion, molecular hybridization, electron microscopy, and infectivity. Four of the Ha-SV DNA inserts were identical, contained about 6.0 kilobase pairs (kbp), and comigrated in agarose gels with the infectious, unintegrated, linear Ha-SV DNA. One insert was approximately 0.65 kbp smaller (5.35 kbp) and one was approximately 0.65 kpb larger (6.65 kpb) than the 6.0 kpb inserts. R-looping with Ha-SV RNA revealed that the small (5.35 kbp) insert contained one copy of the Ha-SV RNA. Preliminary restriction endonuclease digestion of the recombinant DNAs suggested that the middle-size inserts contained a 0.65-kbp tandem duplication of sequences present only one in the small-size insert; this duplication corresponded to the 0.65-kpb terminal duplication of the unintegrated linear Ha-SV DNA. The large-size insert apparently contained a tandem triplication of these terminally located sequences. DNA of all three sized inserts induced foci in NIH 3T3 cells, and focus-forming activity could be rescued from the transformed cells by superinfection with helper virus. Infectivity followed single-hit kinetics, suggesting that the foci were induced by a single molecule.

Animals↗
PubMed1978

Common methionine-tryptic peptides near the amino-terminal end of primate papovavirus tumor antigens.

The tumor antigens directed by human papovaviruses BK and JC and the monkey papovavirus simian virus 40 have two methionine-containing tryptic peptides in common. These peptides are constituents of the small forms of papovavirus tumor antigen (17,000 daltons) which are present in lytically infected and transformed cells and which are believed to share some amino acid sequences with the amino-terminal portion of the larger tumor antigen species (97,000 daltons). In addition to the two peptides, which are present in all three papovavirus tumor antigens, the larger forms of the tumor antigens specified by simian virus 40 and BK virus share four other methionine-containing tryptic peptides, two of which are also present in the smaller (17,000 daltons) species of antigen. The occurrence of common peptides at the amino-terminal portion of tumor antigens of primate papovaviruses suggests that these conserved regions may play a fundamental role in the function of these proteins and in the propagation of these viruses in nature. The tryptic peptides of the small forms of papovavirus tumor antigen were examined and compared to those present in the large species. Out of a total of nine and ten methionine-containing peptides in the 17,000-dalton tumor antigens of simian virus 40 and BK virus, seven and nine peptides, respectively, are constituents of the corresponding larger (97,000 daltons) forms of the antigen.

Amino Acid Sequence↗
PubMed1978

Acebutolol in hypertension--double-blind trial against placebo.

1. Eleven hypertensive patients were studied in a double-blind comparison of acebutolol, a beta-adrenoceptor blocker, and placebo. 2. Optimum dosage defined in an open assessment varied from 200--600 mg twice daily. 3. Blood pressure and pulse rate fell significantly while patients were lying, standing and after exercise. 4. Blood pressure remained as well controlled on each patient's optimum daily dose when taken once daily, and assessed 24 h post dose. 5. There was no correlation between blood pressure reduction and changes in heart rate. On once daily therapy while blood pressure remained unchanged at 24 h post dose there was a signficant reduction in beta-adrenoceptor blockade as measured by percentage reduction in exercise tachycardia. 6. There was no significant change in urinary catecholamine excretion or echocardiographically estimated cardiac output. 7. A correlation was found between the change in plasma renin activity (log transformed) and blood pressure reduction.

Acebutolol↗