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S G Baum

Publications and source records attributed to S G Baum.

29 records · Page 2Linked to original sources
PubMed1972

Studies of the mechanism of enhancement of human adenovirus infection in monkey cells by simian virus 40.

The defect which prevents human adenovirus replication in monkey cells and the mechanism whereby this restriction is overcome by coinfection with simian virus 40 (SV40) have been studied. Adenovirus capsid proteins are not synthesized efficiently in monkey cells in the absence of SV40. Adenovirus "enhancement" by SV40 was found to be the product of increased efficiency of replication by a small percentage of cells. This enhancement effect apparently occurred only when SV40 and adenovirus infected the same cells. These findings suggest that the replicative block occurs prior to virion assembly, and an accompanying report seeks to locate the site of restriction more precisely at the post-transcriptional level.

Adenoviridae↗
PubMed1972

Synthesis of viral ribonucleic acid during restricted adenovirus infection.

The mechanism by which simian virus 40 converts the abortive adenovirus type 7 infection of monkey cells into an efficient lytic infection has been investigated. Analysis of ribonucleic acid (RNA) synthesis during unenhanced and enhanced infection of monkey cells has shown that adenovirus RNA synthesized in the abortive infection contains both "early" and "late" sequences. In hybridization competition experiments, early adenovirus RNA from human cells prevented the hybridization of only 20% of the adenovirus RNA transcribed in unenhanced infection. Further, the RNA from unenhanced cells was able to completely block the hybridization of RNA synthesized during enhanced infection. Finally, virus-associated RNA, which is a late RNA transcribed in lytic adenovirus infection, is also produced in the unenhanced infection. An accompanying paper describes a marked deficiency in adenoviral capsid protein synthesis in the unenhanced infection. We conclude that RNA sequences, which are sufficient to code for the synthesis and assembly of structural proteins of adenovirus, are transcribed but are not efficiently translated in the unenhanced adenovirus infection of monkey cells.

Adenoviridae↗
PubMed1971

Components of adenovirus-simian virus 40 hybrid viruses.

The DNA and protein components of the adenovirus 7-simian virus (SV)40 hybrid virus "E46(+)" have been investigated. The Ad.7-SV40 hybrid DNA genome could be distinguished from nonhybrid Ad. 7 genome on the basis of its molecular weight in an alkaline sucrose gradient. The hybrid genome could also be separated from nonhybrid adenovirus 2 DNA when purified transcapsidant adenovirus 2(+t7) (Ad.7-SV40 DNA within an Ad.2 capsid) was studied. The presence and amount of SV40 DNA in the hybrid virus genome was determined by DNA-RNA hybridization. The results presented suggest: (i) that about 10% of the particles in the E46(+) preparations contained SV40 DNA covalently linked to adenovirus DNA; (ii) that the hybrid virus genome has a molecular weight 10-12% lower than that of nonhybrid virus, consistent with a deletion of adenovirus DNA; and (iii) that the hybrid virus contained only 40-50% of a total SV40 genome. The protein components of the Ad.7-SV40 hybrid virus were examined by acrylamide gel electrophoresis in sodium dodecyl sulfate. No significant quantitative or qualitative differences between the proteins of hybrid and nonhybrid adenovirus were demonstrated.

Adenoviridae↗
PubMed1970

Density differences between hybrid and nonhybrid particles in two adenovirus-simian virus 40 hybrid populations.

The adenovirus 7-simian virus 40 hybrid virus population E46(+) was subjected to fixed-angle equilibrium density gradient centrifugation in CsCl. A difference in buoyant density between the hybrid virion and its nonhybrid adenovirus 7 counterpart was noted, the hybrid virion possessing the lower buoyant density. This difference in buoyant density appeared to be accentuated in a population of adenovirus 2(+t7), a derivative of E46(+) in which the adenovirus 7-simian virus 40 genome had been transferred to an adenovirus 2 capsid.

Journal Article↗
PubMed1965

Studies of adenovirus SV40 hybrid viruses. I. Assay system and further evidence for hybridization.

The titers of adenovirus and SV40 genetic carriers in hybrid preparations (E46(+)) can be quantitated by determining the percentage of cells showing neoantigens stainable with fluorescent antibody (FA) at 21 to 24 hours; both titers can be obtained with a single coverslip. The adenovirus and SV40 antigen-inducing titers so obtained are of the same order of magnitude in stock preparations of E46(+) grown in either African green monkey kidney (AGMK) or human embryonic kidney tissue culture (HEK), and are generally within one log of the infectivity titer. Quantitative studies of 50 degrees C heat inactivation, ultracentrifugation, and equilibrium density gradient centrifugation of E46(+) gave no indication that SV40 neoantigen induction could be dissociated from adenovirus, whereas adenovirus and SV40 virus grown as a mixed infection were readily dissociated by these procedures. Pretreatment of HEK cells with a medium containing 5-fluorouracil desoxyriboside (FUDR) did not affect induction of either adenovirus or SV40 neoantigen or development of cytopathic effects after infection with E46(+), but did prevent formation of Ad. 7 viral antigen.

Adenoviridae↗