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Biomedical subjects

D R Dubbs

Publications and source records attributed to D R Dubbs.

67 records · Page 4Linked to original sources
PubMed1967

Nonidentiy of some simian virus 40-induced enzymes with tumor antigen.

The complement-fixing tumor (T) antigen induced by simian virus 40 (SV40) has been prepared from SV40-infected cell cultures, from infected cell cultures treated at the time of infection with 1-beta-d-arabinofuranosylcytosine (ara-C), and from SV40-transformed cells. Upon partial purification, the T antigen exhibited the following properties: it was tightly adsorbed by calcium phosphate gel, it was precipitated by acetic acid at pH 5 or by ammonium sulfate at about 20 to 32% saturation, and it had a molecular weight greater than 250,000, as estimated by Sephadex G-200 gel chromatography. In contrast, deoxycytidylate (dCMP) deaminase, thymidylate (dTMP) kinase, and thymidine (dT) kinase were less strongly bound to calcium phosphate and were not precipitated at pH 5; these enzymes also had much lower molecular weights than the T antigen, as did dihydrofolic (FH(2)) reductase. Furthermore, higher ammonium sulfate concentrations were required to precipitate dCMP deaminase, dTMP kinase, and FH(2) reductase activities than to precipitate the T antigen. Another difference was that the T antigen was not stabilized, but dCMP deaminase, dTMP kinase, and dT kinase, were stabilized, respectively, by dCTP, dTMP, and dT or dTTP. Deoxyribonucleic acid (DNA) polymerase activity resembled the T antigen in adsorption to calcium phosphate, in precipitation by ammonium sulfate or at pH 5, and in the rate of inactivation when incubated at 38 C. However, the polymerase activity could be partly separated from the T antigen by Sephadex G-200 gel chromatography. The cell fraction containing partially purified T antigen also contained a soluble complement-fixing antigen (presumably a subunit of the viral capsid) which reacted with hyperimmune monkey sera. The latter antigen was present in very low titers or absent from cell extracts prepared from SV40-infected monkey kidney cell cultures which had been treated with ara-C at the time of infection, or from SV40-transformed mouse kidney (mKS) or hamster tumor (H-50) cells. The T antigen, however, was present in usual amounts in SV40-transformed cells or ara-C treated, infected cells.

Aminohydrolases↗
PubMed1967

Induction of cellular deoxyribonuleic acid synthesis by simian virus 40.

The incorporation of (3)H-thymidine ((3)H-dT) into deoxyribonucleic acid (DNA) has been studied in uninfected confluent monolayer cultures of monkey kidney and mouse kidney cells, simian virus 40 (SV40)-infected cells, and in SV40-transformed mouse kidney cells. Radioautographic measurements revealed that during the period from 28 to 51 hr after productive SV40 infection of monkey kidney cultures about 80% of the cells synthesized DNA, compared to about 16% in uninfected cultures. At 28 to 43 hr after abortive SV40 infection of mouse kidney cultures, 24 to 37% of the cells synthesized DNA, compared to about 6 to 8% in uninfected cultures. The infected monkey kidney and mouse kidney cultures, respectively, incorporated about 5 to 10 times and 3 to 5 times as much (3)H-dT into DNA as did uninfected cultures. Moreover, the net DNA synthesized by SV40-infected monkey kidney cultures, estimated by colorimetric methods, substantially exceeded that of uninfected cultures. Nitrocellulose chromatography and band centrifugation experiments were performed to elucidate the kinds of DNA synthesized in the cultures. In uninfected monkey kidney cultures and at 2 to 12 hr after SV40 infection, almost all of the (3)H-dT labeled DNA sedimented more rapidly than SV40 DNA, and the radioactive DNA was denatured by heating for 12 min at 100 C (cellular DNA). Almost all of the labeled DNA obtained from abortively infected mouse kidney cultures and from SV40-transformed cells also had the properties of cellular DNA. However, approximately one-third to one-half of the labeled DNA obtained from monkey kidney cultures 28 to 51 hr after infection sedimented more slowly than cellular DNA and was not denatured by the heating (SV40 DNA). It is concluded that cellular DNA synthesis was induced during either the productive or abortive SV40 infections.

Animals↗
PubMed1967

Virogenic properties of bromodeoxyuridine-sensitive and bromodeoxyuridine-resistant simian virus 40-transformed mouse kidney cells.

When simian virus 40 (SV40)-transformed mouse kidney cells (mKS) were grown in the presence of susceptible indicator cells, SV40 was readily recovered from: (i) 15 transformed cell lines, (ii) transformed cells subcultured 45 times over a 7-month period in medium containing antiviral serum and bromodeoxyuridine (dBU), (iii) 45 of 46 clonal lines isolated in the presence of antiviral serum, (iv) 19 of 19 secondary clones isolated from two clonal lines, and (v) dBU-resistant transformed cell lines. dBU-resistant SV40-transformed mouse kidney cell lines were selected and shown to contain the T antigen and to have normal levels of thymidylate kinase and deoxyribonucleic acid (DNA) polymerase, but to be deficient in thymidine (dT) kinase. Radioautographic and biochemical experiments demonstrated that very little (3)H-dT was incorporated into DNA of dBU-resistant cells during a 6-hr labeling period. After infection of dT kinase-deficient mKS cells with vaccinia virus, high levels of dT kinase were induced. The properties of SV40 recovered from dBU-sensitive and dBU-resistant cells were studied. SV40 recovered from transformed cells was shown to express in CV-1 cells at least six functions characteristic of parental virus: synthesis of capsid antigen, synthesis of T antigen, synthesis of viral DNA, induction of dT kinase, induction of DNA polymerase, and induction of host cell DNA synthesis. In addition, SV40 recovered from the transformed cells induced T antigen, dT kinase, deoxycytidylate deaminase, thymidylate kinase, and DNA polymerase in abortively infected mouse kidney cultures, and the virus was also capable of transforming primary cultures of mouse kidney cells.

Animals↗
PubMed1966

Inapparent viral infection of cells in vitro. 3. Manifestations of infection of L mouse cells by Japanese encephalitis virus.

Dubbs, D. R. (University of Minnesota, Minneapolis), and W. F. Scherer. Inapparent viral infection of cells in vitro. III. Manifestations of infection of L mouse cells by Japanese encephalitis virus. J. Bacteriol. 91:2349-2355. 1966.-Nine strains of Japanese encephalitis (JE) virus were propagated serially in cultures of L cells reaching titers of 10(3.5) to 10(6.3). Although cytopathic effects were not seen in cultures of contiguous L cells after infection with JE virus, cell growth was inhibited. Moreover, cell destruction was readily apparent in infected cultures of sparse, noncontiguous L cells. Differences in the size of cell population of infected and noninfected cultures (i) occurred despite only 0.2 to 3.5% of the cells in infected cultures being associated with infectious virus, (ii) were greater in actively growing cultures than in those kept in maintenance media, and (iii) were probably in part related to an interferon produced in infected cultures.

Animals↗