PubMed Health⌕ Search

Biomedical subjects

A Lo

Publications and source records attributed to A Lo.

At least 73 records · Page 4Linked to original sources
PubMed1989

Isolation of a species-specific DNA probe for Neisseria gonorrhoeae using a novel technique particularly suitable for use with closely related species displaying high levels of DNA homology.

The use of nucleic acid probes has become an increasingly common method for detecting pathogenic micro-organisms in clinical specimens. In the course of our efforts to isolate species-specific DNA probes for bacterial pathogens, we encountered a special problem with regard to Neisseria gonorrhoeae. As a consequence of the high degree of DNA homology that this organism displays with its nearest relative, Neisseria meningitidis, the isolation of such probes could not be readily achieved. We therefore developed a novel method of probe isolation which overcomes this problem. This methodology relies upon the application of a 'sandwich' hybridization assay to screen an M13 'shotgun' library derived from N. gonorrhoeae genomic DNA. For this, genomic DNA from N. gonorrhoeae and N. meningitidis was immobilized on nitrocellulose filters and probed with recombinant phage DNA from candidate clones. Those clones which had hybridized to target sequences were then detected using labelled vector sequences in a second hybridization step. By this means we obtained a numerical assessment of the degree of specificity of candidate clones for the target organism as compared to one or more related species. Using this technique we have isolated three DNA probes which are highly specific for N. gonorrhoeae and which display no cross-reactivity with N. meningitidis or other members of the Neisseriaceae. This paper presents the basis of the methodology and describes the isolation and characterization of three N. gonorrhoeae-like specific probes.

Cloning, Molecular↗
PubMed1986

Structure of a Bacillus subtilis endo-beta-1,4-glucanase gene.

The nucleotide sequence of the portion of a Bacillus subtilis (strain PAP115) 3 kb Pst I fragment which contains an endo-beta-1, 4-glucanase gene has been determined. This gene encodes a protein of 499 amino acid residues (Mr = 55,234) with a typical B. subtilis signal peptide. Escherichia coli which has been transformed with this gene produces an extracellular endoglucanase with an amino-terminus corresponding to the thirtieth encoded amino acid residue. The gene is preceded by a cryptic reading frame with a rho-independent terminator structure, and itself has such a structure in the immediate 3'-flanking region. We have also identified, in the 5'-flanking region, nucleotide sequences which resemble promoter elements recognized by Bacillus RNA polymerase E sigma 43. Comparison of the encoded amino acid sequence to other known beta-glucanases reveals a small region of similarity to the encoded protein of the Clostridium thermocellum celB gene. These similar regions may contain substrate-binding and/or catalytic sites.

Amino Acid Sequence↗
PubMed1981

Nonlytic simian virus 40-specific 100K phosphoprotein is associated with anchorage-independent growth in simian virus 40-transformed and revertant mouse cell lines.

Normal fibroblasts display two distinct growth controls which can be assayed as requirements for serum or for anchorage. Interaction of mouse 3T3 fibroblasts with simian virus 40 (SV40) thus generates four classes of transformed cells. We have examined viral gene expression in these four classes of cell lines. Immunoprecipitation of [35S]methionine-labeled cell extracts with an antiserum obtained from tumor-bearing hamsters detected the SV40 large T and small t proteins (94,000 molecular weight [94K], 17K) and the nonviral host 54K protein in all cell lines tested. A tumor antigen with an apparent molecular weight of 100,000 was also found in some, but not all, lines. Similar "super T" molecules have been found by others in many rodent transformed lines. We carried out an analysis of the relation of phenotype to relative amounts of these proteins in cell lines of the four classes, using the Spearman rank correlation test. The amount of the 100K T antigen relative to the 94K T antigen or to total viral protein was well correlated with the ability to form colonies in semisolid medium. No significant correlation was found between quantities of labeled 94K T antigen, 54K host antigen, or 17K t antigen and either serum or anchorage independence. Mouse cells transformed with the small t SV40 deletion mutant 884 synthesized a 100K T antigen, suggesting that small t is not required for the production of this protein. The 100K T antigen migrated more slowly than lytic T. Since mixtures of extracts from cells expressing and lacking the 100K T antigen yielded the expected amount of this protein, it is unlikely that the 100K T derives from the 94K protein by a posttranslational modification.

Animals↗
PubMed1981

Endotracheal artificial larynx -- preliminary report.

In experimental animals a one stage surgical procedure has been developed which at laryngectomy allows for the creation of a wide and patent tracheopharyngeal fistula. An endotracheal artificial larynx has been developed which has been found effective in prevention of aspiration in experimental animals. Bench studies indicate that an adequate voice probably can be obtained with this device.

Animals↗