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The putative human helper virus SKA-21/A204V, isolated by Nooter et al. in 1977 from human leukemic bone-marrow cells following co-culture with normal fetal canine thymus cells, Cf2th, has been characterized with respect to its major viral core protein, reverse transcriptase, and nucleic acid sequences. The results of these analyses show that this virus is not distinguishable from the woolly monkey type-C virus, SSAV-1, by the techniques employed.

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Media from cells producing RNA tumor viruses, when treated with sodium dodecyl sulfate and polyvinyl sulfate, yield 70 S RNA as the major species binding oligo(dT)-cellulose. The procedure described for purifying 70 S RNA requires no special equipment and is suitable for rapidly processing large quantities of media or for purifying RNA from commercially available virus, with a 5- to 10-fold higher yield than was obtained using existing methods.

This is intended to be a practical review for the clinical chemist of the laboratory procedures most commonly used to quantitate hormone receptors in various cellular fractions. These procedures include use of charcoal adsorption and hydroxylapatite for intracellular receptors and of centrifugation and filtration for membrane receptors. We discuss the use of the Scatchard analysis to establish the steroid-receptor affinity and the quantity of steroid-receptor binding sites. Both pre- and post-labeled sucrose density gradient methods are outlined. One section is devoted to the direct and indirect methods used in nuclear “exchange” assays. Basic theory underlying each assay is presented, but, more importantly, we assess the advantages and disadvantages of each procedure. On the basis of this information, one may decide which assay is best suited for a particular laboratory and (or) specimen.