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Biomedical subjects

H L Ozer

Publications and source records attributed to H L Ozer.

70 records · Page 4Linked to original sources
PubMed1973

Transfer of genetic information by purified metaphase chromosomes.

Transfer of genetic information from isolated mammalian chromosomes to recipient cells has been demonstrated. Metaphase chromosomes isolated from Chinese hamster fibroblasts were incubated with mouse A(9) cells containing a mutation at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus. Cells were plated in a selective medium, resulting in death of all unaltered parental A(9) cells. However, colonies of cells containing hypoxanthine phosphoribosyl transferase (EC 2.4.2.8) appeared with a variable frequency of about 10(-6) to 10(-7). The enzyme from these cells was indistinguishable from that from Chinese hamster cells, as shown by DEAE-cellulose chromatography and gel electrophoresis, and differed clearly from the mouse enzyme. The colonies, thus, did not result from reversion of A(9) parental cells to wild type, but appeared to represent progeny of individual cells that had ingested chromosomes, replicated, and expressed the hprt gene. These colonies differed from each other in stability of expression of the transferred gene.

Animals↗
PubMed1972

Some structural and antigenic properties of intracisternal A particles occurring in mouse tumors (complement fixation-immunodiffusion-neuroblastoma-plasma-cell tumor).

Intracisternal A-particles were isolated from three different myeloma lines in BALB/c mice and from cultured neuroblastoma cells of A/J origin. All preparations contained a major structural protein with an apparent molecular weight near 70,000 as estimated by electrophoretic mobility in sodium dodecyl sulfate-containing polyacrylamide gels. Solubilization of this component by sodium dodecyl sulfate was dependent on prior or concomitant treatment with sulfhydryl compounds. The size distribution of A-particle proteins was markedly different from that observed for extracellular murine leukemia and mammary tumor viruses. Rabbit antiserum was developed that reacted with the major A-particle protein in both complement fixation and immunodiffusion assays. The antigen was detected in isolated neuroblastoma A-particles, in cytoplasmic membrane fractions prepared from various mouse tumors known to contain intracisternal particles, but not in preparations from normal mouse cells, in samples of leukemia and mammary tumor virus, or in JLS-V9 cells infected with Rauscher leukemia virus. Conversely, isolated A-particles did not react in complement fixation or immunodiffusion assays with antisera against leukemia virus antigens.

Animals↗
PubMed1972

Characterization of an endonuclease associated with simian virus 40 virions.

An endonucleolytic activity associated with purified simian virus 40 (SV40) virions has been found. The enzyme is present in virions prepared from a number of different host lines. The enzyme is present in all early and late temperature-sensitive mutants examined. Some aspects of the endonucleolytic activity have been examined with SV40 deoxyribonucleic acid as substrate.

Animals↗
PubMed1972

Synthesis and assembly of simian virus 40. I. Differential synthesis of intact virions and empty shells.

Intact virions and empty shells of simian virus 40 may be rapidly separated from each other and from cell contaminants by a procedure employing a CsCl cushion. This approach permits quantitation of their respective syntheses in infected cells labeled with radioactive amino acids. As much as 5 to 10% of the total acid-precipitable radioactive lysine in infected cell extracts was incorporated into viral particles in a two-hour pulse late in infection. Evidence for multiple origins of empty shells is presented. Some of the empty shells result from breakdown of intact virions. However, empty shells can also form independently of intact virions. First, labeling for periods of 15 min to 2 hr late in the course of infection results in preferential incorporation of (3)H-lysine into empty shells. Secondly, treatment with the deoxyribonucleic acid inhibitor cytosine-beta-d-arabinofuranoside late in infection results in a 50% inhibition in the rate of formation of intact virions with minimal reduction in the rate of appearance of empty shells.

Amino Acids↗
PubMed1972

Synthesis and assembly of simian virus 40. II. Synthesis of the major capsid protein and its incorporation into viral particles.

African green monkey kidney cells infected by simian virus 40 were analyzed for the presence of the major capsid protein (capsid protein I) by immunological and radiolabeling techniques. Antisera with different specificities were prepared by immunization with intact or denatured viral particles. Antisera prepared against intact virus reacted by complement fixation with viral particles and with an 8S subunit containing the capsid protein I. Antisera prepared against denatured viral particles reacted with unassembled capsid protein(s) as well as with viral particles. These antisera were used to detect 8S viral subunits or unassembled viral capsid protein in soluble extracts of infected cells after centrifugation at 100,000 x g to remove viral particles. The soluble antigen pool was found to be small during infection with wild-type virus or a temperature-sensitive mutant deficient in the synthesis of viral particles. Pulse-chase experiments, performed at a high multiplicity of infection, also indicated a small pool of nonparticle capsid protein I. Radioactive lysine was incorporated into capsid protein I of virus particles during a 2-hr pulse. A subsequent chase with excess unlabeled lysine resulted in only a slight increase in the radio-activity found in capsid protein I of viral particles. Furthermore, in the same experiments, capsid protein I was incorporated preferentially into empty shells during the pulse with a shift in radioactivity to intact virions during the chase period, indicating a possible precursor relationship between the two types of virus particles.

Animals↗
PubMed1971

Temperature-sensitive mutants of simian virus 40: infection of permissive cells.

Ten temperature-sensitive mutants of simian virus 40 have been isolated and characterized in permissive cells. The mutants could be divided into three functional groups and two complementation groups. Seven mutants produced T antigen, infectious viral deoxyribonucleic acid (DNA), and structural viral antigen but predominantly the empty shell type of viral particles. Two mutants produced T antigen and infectious viral DNA, but, although viral structural protein(s) could be detected immunologically, no V antigen or viral particles were found. These two functional groups of mutants did not complement each other. A single mutant was defective in the synthesis of viral DNA, viral structural antigens, and viral particles. T antigen could be detected in infected cells by fluorescent antibody but was reduced by complement fixation assay. This mutant stimulated cell DNA synthesis at the restrictive temperature and complemented the other two functional groups of mutants.

Animals↗
PubMed1971

Structural proteins of adenovirus-associated virus type 3.

Three major structural proteins were found in adenovirus-associated virus (AAV) type 3H virions which were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weights of the polypeptides were determined to be approximately 66,000 (VP1), 80,000 (VP2), and 92,000 (VP3). The component having a molecular weight of 66,000 comprised about 80% of the total virion protein in the major AAV-3H particle, and the other two components comprised about 10% each. Proteins of the same molecular weight were found in the minor dense AAV-3H virion, but the 80,000- and 92,000-molecular-weight components were present at about one-half the concentration. The AAV-3H virion contains about 72 molecules of VP1 and 8 and 7 molecules of VP2 and VP3, respectively.

Adenoviridae↗
PubMed1969

Immunochemical characterization of plaque mutants of simian virus 40.

Analysis of large and small plaque mutants of simian virus 40 using antisera prepared against each has revealed quantitative and possibly qualitative antigenic differences for each plaque type. A sensitive micro radioisotope precipitation test permitted evaluation of immunochemical similarities and differences of capsid antigens by inhibition of precipitation.

Amino Acids↗
PubMed1969

Site of host restriction of simian virus 40 mutants in an established African green monkey kidney cell line.

A previously described large-plaque morphology mutant of SV40 (SV-L) in primary African green monkey kidney (AGMK) cells has been shown to be restricted in the established AGMK line CV-1. The site of restriction is an early step in infection, involving the virus particle. A block in penetration or uncoating has been tentatively proposed. Restriction is observed in a number of other established lines, including monkey, human, and mouse. Independent large-plaque mutants were isolated in AGMK and their properties were compared with SV-L (temperature restriction, host restriction, and virion antigen). They can be separated into two classes. Both are restricted on CV-1, though to a lesser degree than SV-L. Further-more, both are coat mutants as determined by immunological analysis of their virions, suggesting a relationship between coat mutants associated with large-plaque morphology in AGMK and host restriction in established cell lines. Temperature restriction is seen with one but not the other of the mutants.

Adsorption↗
PubMedDate not supplied

SV40-mediated immortalization of human fibroblasts.

We have identified a multistep mechanism by which the DNA virus SV40 overcomes cellular senescence. Expression of SV40 T antigen is required for both transient extension of life span and unlimited life span or immortalization. These effects are mediated through inactivation of function of growth suppressors pRB and p53 via complex formation with T antigen. However, immortalization additionally requires inactivation of a novel growth suppressor gene, which has recently been identified to be on the distal portion of the long arm of chromosome 6, designated SEN6. We propose that SEN6 is responsible for cellular senescence in fibroblasts and other cells.

Antigens, Polyomavirus Transforming↗