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R F Zeigel

Publications and source records attributed to R F Zeigel.

6 recordsLinked to original sources
PubMed1978

Characterization of virus-like particles released from the hamster cell line CHO-K1 after treatment with 5-bromodeoxyuridine.

Simple biochemical measurements have been shown to seriously overestimate the production of C-type particles by Chinese hamster ovary (CHO) cells treated with 5-bromodeoxyuridine. First, most particle-bound DNA polymerase activity released by induced cells was associated with particles which had a different density from C-type particles. Second, when labelled with radioactive uridine, induced CHO cells released small amounts of particle-bound radioactivity. Most of the radioactivity, however, was in DNA and did not sediment with the particle-bound polymerase. Thus, few particles which had RNA, an associated DNA polymerase, and the density typical of RNA tumour viruses were released by BrdUrd-induced CHO cells. In spite of this, some immature C-type forms were observed by electron microscopy in partially purified preparations of DNA polymerase-containing particles from induced CHO cells.

Animals↗
PubMed1977

A status report: human prostatic carcinoma, with emphasis on potential for viral etiology.

Several parameters of the biology of cancer of the prostate have been reviewed with a continuing assessment of the possible etiologic role of virus. These aspects include epidemiology, clinical studies, morphology, pathology, enzymology, immunology, endocrinology, model animal studies, in vitro systems, and viral investigations. From available literature it is concluded that, to date, the association with several urogenital tissues of herpes-type viruses has been best documented. It is suggested that a fundamental barrier to more sophisticated virologic and biologic studies is the lack of long term cell cultures of normal and pathologic prostate epithelium from males of all ages.

Acid Phosphatase↗
PubMed1976

RNA tumor virus-like activities in human solid tissues: endogenous RNA:DNA polymerase activities in the prostate.

Several human prostatic tissues have been examined for possible particles and associated DNA polymerizing activity generally associated with the C-type RNA tumor virus family. Partially purified tissue extracts, when centrifuged to equilibrium in sucrose gradients, yield fractions which contain actinomycin D resistant, endogenous DNA polymerase activity; this activity bands at a density of 1.15-1.18 gm/cm3. Further analysis of the endogenous products by sucrose gradient sedimentation suggested the presence of high molecular weight RNA:DNA hybrids generally felt to be indicative of a faithful copy of a lengthy stretch of viral specific RNA. However, most of the DNA products synthesized in these endogenous reactions sedimented in much lower molecular weight regions of these sucrose gradients. Clearly, the relative distributions of "high" and "low" molecular weight products could critically depend on the nuclease content of the subcellular fraction under study, and the prostate may be relatively enriched in nucleases. Further, oligo (dT) stimulated the endogenous DNA polymerase activity contained in these extracts, and omission of one of the DNA precursor nucleotides depressed it. Thus, it seems unlikely that terminal transferase activity, rather than genuine DNA polymerization, was being measured primarily. Because of the spectrum of molecular weight classes formed by these DNA:RNA hybrids, as well as their apparent presence in normal prostatic tissue, we find it difficult to ascribe their presence with certainty either to the presence of typical C-type RNA viruses or to the exclusive behavior of the neoplastic prostatic tissue. Thus, our studies lend support to the growing evidence for functions similar to those of C-type RNA viruses being relatively widespread in human tissues without the apparent necessity for a possible etiologic role in neoplastic production (Strand and August, 1974; Sherr et al., 1974). At the same time, our current studies emphasize the need for caution in drawing conclusions from results utilizing probes generally felt quite useful in scoring for presence of virus in lower animals at least in the human prostate.

Centrifugation, Density Gradient↗
PubMedDate not supplied

The search for "virogene" in human prostatic tissues: prostatic DNA polymerases.

The "virogene-oncogene" hypothesis of Huebner and Todaro and the "provirus" hypothesis of Temin implicate RNA tumor viruses in the neoplastic transformation of mammalian cells. These hypotheses have been substantiated in several animal systems including primates and, presumably, in man. Because the detection in a tissue of one or two activities allegedly related to RNA tumor virus may not be conclusive evidence for viral presence, we have developed a scheme of coordinated morphologic, biologic, and biochemical investigations of human prostatic tissues. We report here the more recent progress we have made in one of the segments of our scheme of investigations. Two, possibly three, DNA polymerase activities from human prostatic tissue have been isolated and partially purified by DEAE-cellulose and phosphocellulose chromatography. These activities have been partially characterized. Based on template preferences and non-inhibition by selective inhibitors of reverse transcriptase, neither of the major polymerase activities appears to be the reverse transcriptase-type activity.

Adenine↗
PubMedDate not supplied

RNA tumor virus-like activities in human prostate: possible novel pharmacologic approaches.

The cytoplasmic extracts of human prostatic tissues yield two classes of "particles" when centrifuged to equilibrium in a sucrose density gradient, one class banding at a density of 1.15-1.18 g/cm3 ("high density particles") and another at a density of 1.07-1.14 g/cm3 ("low density particles"). Both bands display endogenous DNA polymerase activity which is largely resistant to actinomycin D inhibition. The endogenous DNA products synthesized by high density particles give some indication of high molecular weight RNA:DNA complexes. The tissue extracts from normal, hyperplastic, and neoplastic prostate behave similarly in these assays. In addition, explant cultures of hyperplastic and neoplastic prostate either release, or can be induced to release, particles by treatment with bromodeoxyuridine. These particles band at a density of 1.15-1.18 g/cm3 in a sucrose density gradient and possess RNA and associated DNA polymerase activity which utilizes poly(A):oligo(dT). Our results suggest that human prostatic tissues may contain functions analogous in some ways to those of known RNA tumor viruses of other species.

Bromodeoxyuridine↗