Biomedical subjects

P A Somogyi

Publications and source records attributed to P A Somogyi.

5 recordsLinked to original sources

PubMed1990

A solid phase reverse transcriptase micro-assay for the detection of human immunodeficiency virus and other retroviruses in cell culture supernatants.

A simple and rapid solid-phase reverse transcriptase assay was developed based on the use of poly(rA):oligo(dT)12-18 as template primer immobilized on DEAE cellulose paper squares to detect human immunodeficiency virus (HIV) and/or other retroviruses in cell culture supernatants. It was found that PEG (per se) -up to 4% concentrations (w/v)--did not inhibit reverse transcriptase activity. Optimal conditions of the assay were determined. This solid-phase technique is much faster and more convenient than the methods described previously.

Cells, Cultured↗

PubMed1983

DNA-methylating activity of mycobacteria.

The methylating activity of the four mycobacterium strains Mycobacterium phlei, Mycobacterium smegmatis strain Butyricum, Mycobacterium smegmatis strain Rabinowitz, lysogenic Mycobacterium smegmatis strain Rabinowitz was studied in vitro. All the four strains were found to have methylating activity; enzyme containing extracts of M. smegmatis strain Butyricum and M. phlei showed a stronger activity than those of M. smegmatis strain Rabinowitz and the lysogenic Rabinowitz strain. The methylases of all the four strains methylated the adenine and cytosine residues of the acceptor DNA-forming 5-methyl-cytosine and 6-methyl-aminopurine. The mycobacterial DNAs were methylated by the corresponding mycobacterial methylases in vitro only to 25-30% as compared to the methylation on phage Sd-DNA. This is comparable with the low in vivo methylation of mycobacterial DNAs. The kinetics of methylation indicated a low non-specific nuclease content of the mycobacterium cells.

5-Methylcytosine↗

PubMed1982

Methylated nucleic acid bases in Mycobacterium and mycobacteriophage DNA.

Methylated bases of the DNA of two mycobacteria (Mycobacterium phlei and Mycobacterium smegmatis var. butyricum) and two mycobacteriophages (Phage phlei and Phage butyricum) have been studied. In both the bacterial and the phage DNAs 5-methyl-cytosine and 6-methyl-aminopurine could be detected. Using L-(methyl-H3)-methionine as methyl donor not only the methylated bases of bacterium and phage DNA proved to be radioactive, but also the non-methylated purine residues and thymine. Possible pathways of this phenomenon are discussed.

5-Methylcytosine↗

PubMed1975

Biophysical properties of mycobacteriophages.

Biophysical characterization of two mycobacteriophages (Phlei phage and Butyricum phage) was carried out. Biophysical parameters obtained were: (i) buoyant densities in CsCl of I . 51 g/ml for both phages; (ii) sedimentation coefficient of 490 S and 410 S; (iii) DNA content of 42 and 34% and (iv) mol. wt. calculated by electron microscopic dimensions to be 123 x 10(6) and 116 x 10(6) for Butyricum and Phlei phage, respectively.

DNA, Viral↗

PubMedDate not supplied

Incorporation of thymine, thymidine, adenine and uracil into nucleic acids of Mycobacterium phlei and its phage.

Like other prototroph bacteria, Mycobacterium phlei was found to incorporate thymine into its DNA very poorly. As a result of a rapid thymidine-to-thymine conversion, thymidine incorporation also proved to be inefficient. Thymidine incorporation could be somewhat enhanced by pretreatment of the cells with uridine. When radioactive adenine, and particularly uracil, were used as precursors, highly labelled DNA could be obtained from the cells, although the majority of radioactivity was found in the RNA. Uracil was thus found to be the most suitable precursor for labelling phage DNA. On the basis of these findings, uracil is recommended for in vivo labelling of Mycobacterium and mycobacteriophage DNA.

Adenine↗