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Biomedical subjects

R Stephens

Publications and source records attributed to R Stephens.

At least 145 records · Page 8Linked to original sources
PubMed1975

Improved recognition and quantitation technique for oncornaviruses.

A technique to recognize and quantitate oncornaviruses using perforated pointed BEEM capsules has been developed in our laboratory. Virus samples that presented problems in counting, or those which could not be evaluated at all by negative staining, could be clearly defined and counted using the thin-sectioning BEEM capsule technique. Perforation of the BEEM capsule allowed rapid infiltration of reagents into the tip of the virus pellet and made further manipulation and orientation unnecessary. The sensitivity of this technique, determined by making serial dilutions of viral concentrates, allows observation of as few as 5 times 10(5) virus particles per ml. Precision in counting by this technique varied only +/- 0.3 log in repeat aliquots of identical concentrated virus samples quantitated, making this a highly useful and reliable system.

Evaluation Studies as Topic↗
PubMed1975

New method for the removal of extraneous proteins from purified oncornaviruses.

Conventional methods (i.e. gradient centrifugation) for the purification of oncornaviruses are usually not effective in complete removal of nonviral proteins. Such contaminants often prove to be a nuisance in subsequent immunological or biochemical studies. Hyperimmune sera prepared from these viruses must be absorbed to assure specificity; cell-derived proteins can be shown to interfere with studies of virus structural proteins, nucleic acids, or viral enzymes. Herein is described a method for removal of most of these contaminants. Viruses are diluted in a high concentration of NaCl to achieve a final concentration of 15%, incubated for 30 min, sedimented, and resuspended in buffer. This procedure results in reductions of up to 48% of the protein without affecting particle count. Immunological, biochemical, and biological properties are not adversely affected. Of the proteins removed, fetal calf serum components and a ribonuclease (presumably cell-derived) were identified. This technique differs significantly from other high-salt methods in that the virus is not precipitated from suspension. It is believed that absorbed proteins are desorbed and left in solution (or suspension) as the virus is sedimented by centrifugation.

Cell Line↗