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Biomedical subjects

M Oren

Publications and source records attributed to M Oren.

At least 181 records · Page 10Linked to original sources
PubMed1983

Analysis of recombinant DNA clones specific for the murine p53 cellular tumor antigen.

Three cDNA clones, corresponding to two non-overlapping regions of the mRNA coding for the mouse p53 cellular tumor antigen, were isolated and characterized. In hybridization-selection assays, these clones were capable of selectively binding p53 mRNA, as demonstrated by in vitro translation and immunoprecipitation with anti-p53 monoclonal antibodies. The p53 mRNA appeared to be the only messenger species specifically selected by these clones. The size of the p53 mRNA was found to be approximately 2 kb, and its levels to vary substantially among different types of transformed cells. Evidence was found for the existence of two distinct p53-specific genes in mouse genomic DNA. Two partially overlapping recombinant phage clones were obtained, both derived from the same p53-specific genomic DNA region. The orientation of the various cDNA clones relative to that of the p53 mRNA was established by S1 analysis and the relationship between the cDNA clones and the genomic ones was determined by comparative restriction enzyme mapping and nucleic acid hybridization.

Animals↗
PubMed1983

Excess mortality and morbidity associated with right bundle branch and left anterior fascicular block.

Excess mortality and morbidity associated with right bundle branch and left anterior fascicular block were evaluated in 108 patients with block (age 74 +/- 10 years, 69% male) and 108 age- and sex-matched control patients with normal conduction. Clinical characteristics were similar initially except for more congestive heart failure in patients with block. Life table analysis revealed a higher 12 year mortality with block, even after omitting patients with moderate or severe congestive heart failure (risk ratio 1.47, p less than 0.05). Compared with control subjects, the group of patients with block had more sudden death and deaths of unknown cause, but a similar number of noncardiac and diagnosed cardiac deaths. More patients with block developed new second and third degree atrioventricular block or new overt coronary artery disease, but this finding did not support prophylactic pacing in asymptomatic patients. The importance of internal controls in assessing the natural history of clinical and electrocardiographic abnormalities is emphasized.

Adult↗
PubMed1983

Molecular cloning of a cDNA specific for the murine p53 cellular tumor antigen.

A cDNA library was constructed from sucrose-gradient-fractionated mRNA from SVT2, a mouse cell line transformed by simian virus 40. Polysomes containing the p53 messenger were specifically immunoprecipitated with monoclonal antibodies against the protein and used to prepare mRNA. This immunoselected mRNA, enriched 1,000-to 2,000-fold for p53-specific sequences, was used to make a cDNA probe and to screen the cDNA library. When approximately 10,000 colonies were screened by differential hybridization with probes made from immunoselected vs. nonenriched mRNA, a single clone was found that contained p53-specific sequences. The identity of this clone, termed pp53-208, was confirmed by the ability of its DNA to hybridize the mRNA coding for p53 (hybrid selection assay). When hybridized to a blot of EcoRI digested mouse DNA, the pp53-208 insert reacted with a single 3.3-kilobase band, suggesting that it is complementary to a single gene.

Animals↗
PubMed1983

Two distinct mechanisms regulate the levels of a cellular tumor antigen, p53.

The steady-state levels of p53 protein and p53 mRNA in transformed and nontransformed cells were examined to elucidate the mechanisms controlling expression of p53. mRNA levels were determined by Northern blot hybridization analysis, employing a p53-specific cDNA clone (M. Oren and A.J. Levine, Proc. Natl. Acad. Sci. U.S.A. 80:56-59, 1983), and protein levels were determined by the Western blotting technique. Analysis of p53 mRNA revealed a single polyadenylated mRNA species migrating at ca. 18S. Levels of p53 mRNA in simian virus 40-transformed cell line (SVT2) and in an homologous nontransformed cell line (3T3) were equivalent, although the steady-state levels of p53 protein were 25- to 100-fold higher in the SVT2 cells than in the 3T3 cells. A study with a non-virus-transformed cell system revealed a different result. Embryonal carcinoma cells (F9) were found to have nearly 20-fold higher levels of p53 mRNA in comparison with differentiated benign progeny cells. In this system the difference in p53 mRNA levels corresponded to the difference in p53 protein levels. Pulse-chase experiments were performed to study the half-life of p53 protein in these four types of cells. The turnover of p53 protein occurred with biphasic kinetics. In addition, it was found that protein synthesis inhibitors placed in the medium during the chase period prevented the turnover of p53 protein in transformed cells, but not in nontransformed (3T3) cells. These results provide evidence that the regulation of p53 expression in cells can occur at the level of p53 mRNA abundancy or p53 protein stability depending upon the experimental system under study, and that a regulated degradation process controls the turnover of p53 protein.

Animals↗
PubMed1982

SV40 large tumor antigen can regulate some cellular transcripts in a positive fashion.

Eleven cDNA clones identified from a cDNA library prepared from the mRNA fraction of SV40 transformed cells detected, by hybridization, higher levels of cellular mRNA in SV40-transformed cells than in nontransformed cells. Three of these cDNA clones detected levels of cellular mRNA that were more than 100-fold greater in SV40tsA transformed cell lines grown at the permissive temperature than in those grown at the nonpermissive temperature. Northern blot hybridizations confirmed these results and in some cases detected RNA species of multiple sizes that were regulated in a temperature-dependent fashion in SV40tsA transformed cell lines. Infection of 3T3 cells with SV40 stimulated the levels of RNAs complementary to these cDNA clones. The results demonstrate that the SV40 large T antigen can regulate the steady state levels of some cellular RNA species.

Animals↗
PubMed1982

Different forms of simian virus 40 large tumor antigen varying in their affinities for DNA.

In various permissive monkey cell lines infected with simian virus 40 there are two major forms of large T antigen which differ in their rate of sedimentation through sucrose gradients. The lighter (5 to 7S) form sedimented slightly more rapidly than the 4S tRNA marker, whereas the heavier (16S) form sedimented slightly more slowly than the 18S rRNA marker. The small t antigen did not form complexes which sedimented as rapidly as those formed by the large T antigen. The 16S T antigen form was converted to the slowly sedimenting 5 to 7S form in the presence of 1.0 M NaCl. The majority of large T antigen synthesized in cell-free protein-synthesizing systems primed by mRNA isolated from infected cells sedimented as the 5 to 7S form even when premixed with excess quantities of cellular T antigen. The formation of the 16S form in infected cells did not require ongoing viral or cellular DNA replication because considerable quantities of this T antigen class were produced in the presence of DNA synthesis inhibitors, such as cytosine arabinoside. Both 5 to 7S and 16S forms could be isolated separately and, therefore, each could be analyzed as to its individual properties. The 5 to 7S T antigen form bound more efficiently and tightly to DNA and had specific affinity for sequences at the viral origin of replication, whereas the 16S form bound less efficiently to DNA and exhibited very little specificity for origin-containing DNA sequences. It is therefore likely that the active DNA-binding species of T antigen isolated from infected cells is the 5 to 7S form.

Antigens, Viral↗
PubMed1982

Regulation of the cellular p53 tumor antigen in teratocarcinoma cells and their differentiated progeny.

F9 embryonal carcinoma cells express high levels of a 53,000-molecular-weight cellular tumor antigen called p53. When F9 cell cultures are treated with retinoic acid and dibutyryl adenosine 3',5'-phosphate, they differentiate, predominantly into endoderm-like cells. This differentiation is accompanied by a marked decrease in the levels of p53. The mechanism(s) responsible for this decline in the level of p53 in differentiated cells was investigated. The results demonstrate that the high levels of p53 in F9 cells relative to their differentiated progeny were not due to alterations in the stability or turnover of this protein. Rather, the regulation during differentiation involved a marked decrease in the amount of in vitro translatable p53 mRNA detected in the differentiated cell cultures. This mechanism is unlike the one operating during the simian virus 40 infection or transformation, where the increased levels of p53 are largely due to the increased stability of the p53 protein.

Animals↗
PubMed1982

Establishment of neuromuscular contacts in cultures of rat embryonic cells: effect of tetrodotoxin on maturation of muscle fibers and on formation and maintenance of acetylcholinesterase and acetylcholine receptor clusters.

The part played by muscle activity was mainly studied in relation to the formation and persistence of cytochemically detectable spots of acetylcholinesterase (AChE) during synaptogenesis. A correlation was found between AChE spot evolution and that of two other morphological synapse markers, silver salt-impregnated nerve endings and clusters of acetylcholine receptors (AChR) exposed to 125I-alpha-bungarotoxin and revealed by radioautography. The formation and persistence of AChE spots were activity-dependent but in the case of neuronally induced synaptic nerve endings and AChR clusters, both morphological markers were independent of such activity. The final evolution and maturation of neuromuscular contacts were linked to the differentiation stage reached by the muscle fibers at the time when they established contact with nerve endings. The fibers acquired this differentiated state independently of tetrodotoxin-blocked muscle activity.

Acetylcholine↗
PubMed1981

Post-translational regulation of the 54K cellular tumor antigen in normal and transformed cells.

The 54K cellular tumor antigen has been translated in vitro, using messenger ribonucleic acids from simian virus 40 (SV40)-transformed cells or 3T3 cells. The in vitro 54K product could be immunoprecipitated with SV40 tumor serum and had a peptide map that was similar, but not identical, to the in vivo product. The levels of this 54K protein in SV3T3 cells were significantly higher than those detected in 3T3 cells (D. I. H. Linzer, W. Maltzman, and A. J. Levine, Virology 98:308-318, 1979). In spite of this, the levels of translatable 54K messenger ribonucleic acid from 3T3 and SV3T3 cells were roughly equivalent or often greater in 3T3 cells. Pulse-chase experiments with the 54K protein from 3T3 or SV3T3 cells demonstrated that this protein, once synthesized, was rapidly degraded in 3T3 cells but was extremely stable in SV3T3 cells. Similarly, in an SV40 tsA-transformed cell line, temperature sensitive for the SV40 T-antigen, the 54K protein was rapidly turned over at the nonpermissive temperature and stable at the permissive temperature, whereas the levels of translatable 54K messenger ribonucleic acid at each temperature were roughly equal. These results demonstrate a post-translational regulation of the 54K cellular tumor antigen and suggest that this control is mediated by the SV40 large T-antigen.

Animals↗
PubMed1981

Congenital lactic acidosis associated with pyruvate carboxylase deficiency.

Two cases of congenital lactic acidosis associated with pyruvate carboxylase deficiency are described. One 2-mo-old infant had a fulminant clinical course with extremely severe intractable acidosis and died after 48 h in hospital. The second infant, aged 2 1/2 mo, had a milder clinical course, characterized by moderate acidosis and frequent convulsive episodes. He died at the age of 3 mo due to respiratory arrest following prolonged status epilepticus. Pyruvate carboxylase activity in liver biopsy specimens obtained from the two patients was 1 and 50% of normal, respectively. Both patients failed to respond to treatment, including massive doses of thiamine and high serum levels of lactate and pyruvate were found throughout their illnesses. Cerebral autopsy performed in both cases was unremarkable. Absence of neuropathological findings ruled out the possibility of Leigh's disease.

Acidosis↗