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Biomedical subjects

M A Martin

Publications and source records attributed to M A Martin.

At least 199 records · Page 11Linked to original sources
PubMed1982

Variation in the number of copies and in the genomic organization of ecotropic murine leukemia virus proviral sequences in sublines of AKR mice.

DNAs isolated from individual mice of four AKR sublines (AKR/J, AKR/N, AKR/Cum, and AKR/Boy) were examined by hybridization of electrophoretically separated restriction enzyme fragments to a 500-base pair, 32P-labeled probe specific for env sequences of ecotropic murine leukemia virus. Variation in the number of proviral DNA copies and in their genomic organization, as reflected by the location of restriction enzyme sites in flanking cellular sequences, was observed both between and within AKR sublines. Evidence is presented for the continual acquisition of new proviruses in the four sublines studied. The ecotropic proviral DNA copies present in the four AKR sublines can be related to their genealogy; each subline contains two or three copies of proviral DNA in common with other sublines and from one to six unique ecotropic proviruses. Overall, a new copy appears about every 12 generations of inbreeding. Some of the unique proviral DNA copies contain internal alterations, as reflected by restriction enzyme maps that differ from those of prototype ecotropic proviruses.

Animals↗
PubMed1982

Cloning of endogenous murine leukemia virus-related sequences from chromosomal DNA of BALB/c and AKR/J mice: identification of an env progenitor of AKR-247 mink cell focus-forming proviral DNA.

Recombinant phages containing murine leukemia virus (MuLV)-reactive DNA sequences were isolated after screening of a BALB/c mouse embryo DNA library and from shotgun cloning of EcoRI-restricted AKR/J mouse liver DNA. Twelve different clones were isolated which contained incomplete MuLV proviral DNA sequences extending various distances from either the 5' or 3' long terminal repeat (LTR) into the viral genome. Restriction maps indicated that the endogenous MuLV DNAs were related to xenotropic MuLVs, but they shared several unique restriction sites among themselves which were not present in known MuLV proviral DNAs. Analyses of internal restriction fragments of the endogenous LTRs suggested the existence of at least two size classes, both of which were larger than the LTRs of known ecotropic, xenotropic, or mink cell focus-forming (MCF) MuLV proviruses. Five of the six cloned endogenous MuLV proviral DNAs which contained envelope (env) DNA sequences annealed to a xenotropic MuLV env-specific DNA probe; in addition, four of these five also hybridized to an ecotropic MuLV-specific env DNA probe. Cloned MCF 247 proviral DNA also contained such dual-reactive env sequences. One of the dual-reactive cloned endogenous MuLV DNAs contained an env region that was indistinguishable by AluI and HpaII digestion from the analogous segment in MCF 247 proviral DNA and may therefore represent a progenitor for the env gene of this recombinant MuLV. In addition, the endogenous MuLV DNAs were highly related by AluI cleavage to the Moloney MuLV provirus in the gag and pol regions.

Animals↗
PubMed1981

Identification and cloning of endogenous retroviral sequences present in human DNA.

Using nonstringent annealing conditions and a 2.75-kilobase segment of cloned African green monkey DNA that specifically hybridizes to the proviruses of AKR ecotropic murine leukemia virus (MuLV) and baboon endogenous virus (BaEV) as a probe, we detected related sequences in three different preparations of human brain DNA fragments. The blot-hybridization pattern obtained with cleaved human DNA was similar to that previously reported for the interaction of MuLV cDNA and cleaved mouse DNA and suggested the presence of numerous copies of retrovirus-related sequences in the human genome. The labeled 2.75-kilobase fragment derived from cloned monkey DNA was used to screen a human DNA library in Charon 4A. One clone obtained hybridized to three contiguous MuLV-and BaEV-reactive fragments of the cloned monkey DNA and to multiple fragments of human DNA including a prominent 1.0-kilobase EcoRI fragment also present in the clone.

Animals↗
PubMed1981

Detection and cloning of murine leukemia virus-related sequences from African green monkey liver DNA.

By using low-stringency nucleic acid hybridization conditions and specific subgenomic segments of the AKR ecotropic provirus as probes, murine leukemia virus (MuLV)-related sequences were detected in African green monkey (AGM) liver DNA. The MuLV-reactive segments present in restricted AGM DNA ranged from 1.9 kilobases (kb) to greater than 10 kb in size. On the basis of this finding, a 17-kb segment was cloned from a partial EcoRI AGM library in lambda Charon 4A which shared nearly 5 kb of homology with AKR ecotropic MuLV DNA. The MuLV-related sequences detected in restricted preparations of AGM DNA or present in the cloned monkey DNA reacted with probes mapping 2.0 to 7.0 kb from the 5' terminus of the AKR ecotropic provirus. The AGM clone also contained repeated sequences that flanked the MuLV-related segment. Labeled, subgenomic, MuLV-reactive segments of the monkey clone hybridized to multiple restriction fragments of AGM liver DNA, indicating the presence of several copies of the MuLV-related sequences.

Animals↗
PubMed1980

Characterization of polyoma viral DNA sequences in polyoma-induced hamster tumor cell lines.

The polyoma (PY) viral DNA sequences present in a series of hamster tumor cell lines were evaluated using the blotting technique of Southern ((1975) J. Mol. Biol. 98, 503-517). Remarkably, no cell line contained an intact distal portion of the early gene region which encodes a portion of the large T antigen. All cell lines examined contained the PY DNA Bum I fragment which contains most of the genetic information encoding PY small and middle T antigens, as well as the origin of viral DNA replication. These results provide an explanation for our previous observation that PY virus-induced hamster tumors do not contain the large species of T antigen.

Animals↗
PubMed1980

Brachial plexus involvement in familial pressure-sensitive neuropathy: electrophysiological and morphological findings.

Two family members with hereditary pressure-sensitive neuropathy are reported. One patient presented atypically with acute brachial plexus neuropathy following transaxillary removal of the first rib. Electrophysiological studies showed slowing of motor nerve conduction in clinically affected and unaffected nerves. In vitro recording of the compound action potential of the subclinically involved sural nerve showed pronounced slowing in conduction of large and small myelinated fiber groups. These alterations correlated with morphological studies of the sural nerve that showed tomacula with acute and healed segmental demyelination. An inherited, generalized neuropathy manifested by a morphological abnormality of myelination may render peripheral nerves unduly susceptible to mechanical trauma, including positional pressure or traction effects during general anesthesia.

Adult↗
PubMed1980

Identification of ecotropic proviral sequences in inbred mouse strains with a cloned subgenomic DNA fragment.

A specific probe for detecting ecotropic murine leukemia virus sequences was constructed by cloning a 500-base-pair DNA segment, corresponding to a portion of the env region of the AKR ecotropic virus, in a pBR322/Escherichia coli K-12 host/vector system. This probe was used to screen the cellular DNAs of six inbred strains of mice for the presence of ecotropic retroviral DNA sequences by the Southern blot hybridization procedure. Three copies of ecotropic viral DNA were detected in AKR/N (a high-ecotropic virus strain) and two were found in BALB/c (a low-ecotropic virus strain) DNAs. As expected, no sequences reactive with this probe were found in NFS mouse DNA (a virus-negative strain). However, cellular DNA sequences that reacted strongly with the ecotropic-specific DNA probe were detected in certain NZB, C57L, and 129 mice (all virus-negative strains). In contrast to the reactive sequences in AKR and BALB/c, the reactions were chiefly associated with EcoRI segments that were subgenomic in size.

Animals↗
PubMed1980

Polyoma large tumor antigen is not required for tumorigenesis mediated by viral DNA.

The arrangement of viral DNA sequences in a hamster cell line derived from a tumor induced by a recombinant plasmid DNA preparation containing the entire polyoma virus genome was examined. In the recombinant plasmid employed, viral DNA sequences specifying the large species of polyoma tumor antigen but not the small and middle tumor antigens were interrupted by the insertion of plasmid DNA at the EcoRI restriction endonuclease site. Blot-hybridization analyses of tumor cell DNA indicated that the "joints" linking viral and plasmid DNAs in the original recombinant plasmid used in animal inoculation had been preserved. Integration into the hamster cell genome had apparently occurred within plasmid DNA sequences. These results indicate that polyoma large tumor antigen is not required for tumorigenesis mediated by viral DNA.

Animals↗
PubMed1980

Disopyramide and lignocaine. A comparison of cardiac effects using echocardiography.

1 The cardiac effects of disopyramide (D) and lignocaine (L) were measured and compared in normal volunteers (D n=4; L n=3) following the establishment of a series of three steady-state drug plasma concentrations spanning the therapeutic range (1.5-5 micrograms base ml-1). 2 During control and steady-state periods multiple measurements were made of heart rate, blood pressure, drug concentrations and echocardiographic measurement of cardiac dimensions and estimated left ventricular function. 3 No change in heart size or estimated function occurred with L except for a small increase in estimated cardiac output (+0.5 1 min-1) secondary to a small rise in heart rate (maximum +7 beats min-1). Blood pressure rose slightly (maximum +11 mmHg). 4 D caused an increase in heart size, marked at end systole (+0.63 cm), and a decrease in echo indices of ventricular function (25-33%). These changes were related to plasma drug concentration but were not reflected in cardiac output estimation since heart rate rose (+15 beats min-1). Blood pressure also rose (+10 mmHg). 5 Significant differences were shown between D and L at similar plasma drug concentrations. The negative inotropic effect of D may be greater than previously suggested and clinically important.

Adult↗
PubMed1980

Molecular cloning of the Harvey sarcoma virus circular DNA intermediates. II. Further structural analyses.

Three species of unintegrated supercoiled Harvey sarcoma virus DNA (6.6, 6.0, and 5.4 kilobase pairs) have been molecularly cloned from Harvey sarcoma virus-infected cells. On the basis of restriction enzyme analyses, the 6.6- and 6.0-kilobase pair viral DNAs contain two and one copies, respectively, of a 650-base pair DNA segment which contains sequences present at the 3' and 5' termini of the viral genome. R-loop structures formed between Moloney leukemia virus RNA and the cloned Harvey sarcoma virus DNA indicated that about 500 base pairs of the 650-base pair repeating segment was complementary to the 3' end of the viral RNA. During amplification in the Escherichia coli host, some recombinants containing the 6.6- or the 6.0-kilobase pair Harvey sarcoma virus DNA insert acquired or lost the complete 650-base pair DNA segment. These changes occurred in both recA+ and recA- E. coli.

Animals↗
PubMed1980

Relationship among Tau antigens isolated from various lines of simian virus 40-transformed cells.

In addition to the virus-specified tumor antigens, simian virus 40-transformed cells contain at least one other protein which can be immunoprecipitated with serum from animals bearing simian virus 40-induced tumors. This protein, which is designated Tau antigen, has an apparent molecular weight of 56,000 as determined by electrophoresis on acrylamide gels. The relationship among Tau antigens isolated from different lines of simian virus 40-transformed cells was examined by comparing the methionine-labeled tryptic peptides of these proteins by two-dimensional fingerprinting on thin-layer cellulose plates. In this fashion, we initially determined that the Tau antigens isolated from three different lines of transformed mouse cells were very similar. Second, we found that Tau antigen isolated from a line of rat transformants was closely related, but not identical, to the mouse cell Tau antigens. Approximately 70% of their methionine peptides comigrated in two dimensions. Finally, we showed that Tau antigen isolated from a line of transformed human cells was only partially related to the mouse and rat proteins. About 40% of the methionine peptides of the human protein were also contained in the Tau antigens from the other two species. These results strongly indicate that the Tau antigens isolated from these various simian virus 40-transformed cell lines contain common amino acid sequences.

Animals↗
PubMed1980

Identification of ecotropic proviral sequences in twelve inbred mouse strains.

A specific probe for detecting ecotropic murine leukemia virus sequences was constructed by cloning a 400 base-pair DNA, corresponding to a portion of the env region of the AKR ecotropic virus. We have employed this probe to detect the presence or absence of ecotropic retroviral DNA sequences in 12 inbred strains of mice using the Southern blotting hybridization procedure. Our results show that between 2 and 6, and 1-2 copies of the ecotropic viral genome are present in mice with high or low incidence of leukemia, respectively. Ecotropic viral sequences are either absent or present in partial copies in mouse strains which heretofore failed to yield ecotropic viruses.

Animals↗
PubMed1979

Molecular cloning of polyoma virus DNA in Escherichia coli: oncogenicity testing in hamsters.

Inoculation of suckling hamsters with 2 x 10(8) live cells of Escherichia coli K12 strain chi1776, carrying the complete genome of polyoma virus in a recombinant plasmid, failed to induce tumors in any of 32 recipients. Also, lambda phage DNA and particles with a monomeric insert of polyoma DNA did not induce tumors. Purified recombinant plasmid DNA, as well as phage particles and DNA containing a head-to-tail dimer of polyoma DNA, showed a low degree of oncogenicity, comparable to that of polyoma DNA prepared from mouse cells. These findings support the previous conclusions, based on infectivity assays in mice, that propagation of polyoma virus DNA as a component of recombinant DNA molecules in E. coli K12 reduces its biologic activity many orders of magnitude relative to the virus itself.

Animals↗
PubMed1979

A rapid method for detecting and mapping homology between heterologous DNAs. Evaluation of polyomavirus genomes.

A new approach for evaluating homologous sequences among related DNAs is presented. Conventional filter hybridization techniques are employed at 35 degrees C in a range of formamide concentrations in order to perform annealings at effective temperatures as low as Tm -50 degrees C which permits the detection of regions of homology with as much as 33% base mismatch. Under such nonstringent conditions, high levels of specific annealing can be obtained at plateau levels. In combination with the Southern "blotting" technique (1975), this approach can be used to perform biochemical heteroduplex melting experiments. The homology among the genomes of the murine polyoma virus (Py), the simian virus 40 (SV40), and the human papovavirus BK was evaluated using this new methodology.

DNA, Viral↗