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Biomedical subjects

A Gazit

Publications and source records attributed to A Gazit.

141 records · Page 8Linked to original sources
PubMed1979

Type C virus and immunoglobulin A production by murine myeloma MOPC-315: two independent activities.

The suspected correlation between cessation of type C virus production and halt in immunoglobulin secretion by murine myeloma cells was studied. Employing two variants of the murine myeloma MOPC-315, immunoglobulin A-producing and nonproducing cells, we demonstrated that the two myelomas release similar levels of type C viruses which share common nucleotide sequences and that the viral genomes are equally expressed within the cells. Thus, the suggested relation between these two activities does not apply for MOPC-315 cells and probably for other murine myelomas also.

Animals↗
PubMed1979

Biochemical characterization of the type C retrovirus associated with lymphoproliferative disease of turkeys.

Turkeys inoculated with spleen extracts from lymphoproliferative disease (LPD)-affected birds developed viremia, followed by typical LPD lesions. Electron microscopy and biochemical characterization established that the virus present in the blood of infected turkeys is a type C retrovirus. The viral particles possess a buoyant density of 1.17 g/ml in sucrose gradients; they contain high-molecular-weight RNA and an RNA-instructed DNA polymerase with efficient exogenous and endogenous activity. The LPD virus polymerase is preferentially activated by magnesium ions. Cross nucleic acid hybridization assays revealed no sequence homology between the viral genome of LPD and avian myeloblastosis virus or reticuloendotheliosis virus, thus indicating that the LPD virus belongs to a distinct group unrelated to the avian leukosis-sarcoma virus complex or to the reticuloendotheliosis virus group.

Animals↗
PubMed1979

Molecular evidence for a type C retrovirus etiology of the lymphoproliferative disease of turkeys.

Recently, we isolated from the blood of lymphoproliferative disease (LPD)-affected turkeys a type C retrovirus distinct from the avian leukosis-sarcoma virus complex and the reticuloendotheliosis virus group. We present molecular evidence for the implication of this virus in the LPD of turkeys. Using complementary DNA of LPD viral RNA, we found that the LPD viral genome is specifically and efficiently transcribed (2,500 copies per cell) in LPD tumor cells. Moreover, the LPD tumor cells contained newly inserted LPD viral information (5 to 10 copies per haploid genome), which was not present before the infection. From the absence of LPD virus-specific sequences in the normal cell genome of turkeys, it was concluded that the LPD virus is not an endogenous virus of turkeys. DNA-DNA annealing experiments revealed that the degree of sequence homology between LPD viral complementary DNA and cellular DNA of turkeys was not higher than that between LPD viral complementary DNA and cellular DNA of other species, thus indicating that the virus does not originate from turkeys.

Animals↗
PubMed1979

Potentiation of leukemogenicity and infectivity of Rauscher leukemia virus by an enhancing factor present in egg fluids.

Sequential intraperitoneal administration of a low molecular-weight-enhancing factor, isolated from egg fluids, in mice infected with Rauscher leukemia virus (RLV) significantly stimulated viral replication. This was evidenced by elevated levels of viral DNA-polymerase in mouse sera. This stimulation of viral replication correlated with aggrevation of viral leukemogenicity, as reflected by increment of splenomegalic response and shortening of survival time. The in vivo potentiation of replication and leukemogenicity of RLV is achieved at least partly by the enhancing factor at the cellular level, since RLV replication was found to be stimulated also in an in vitro system. We assume that the stimulatory effect of the enhancing factor on viral replication is connected with its stimulatory effect on the synthesis of cellular DNA.

Aging↗
PubMed1978

Biological characteristics of a stimulatory factor for viral replication detected in egg fluids.

Yolk sac and allantoic fluids and albumen from uninfected chicken eggs contain a low-molecular weight factor which, after 90 minutes of contact with cell cultures, significantly enhances viral replication. Of several viruses tested, Semliki Forest virus exhibited the highest (10(5)-fold) responsiveness to this enhancing factor. Maximal enhancement was obtained with cells subjected to low multiplicities of infection. The stimulation of viral replication was linear with the age of the cells in culture. The enhancing factor did not operate through an anti-interferon mechanism. However, it exerted a boosting effect on the low-grade cellular metabolism of ageing cell monolayers. Some of the physico-chemical features of the enhancing factor were determined and conjectures concerning its chemical makeup are discussed.

Allantois↗
PubMed1978

Chicken egg yolk stabilizes the reverse transcriptase activity in type C particles produced by cultured MOPC-315 murine myeloma cells.

Type C particles released from cultured murine myeloma MOPC-315 cells were significantly protected when the purification steps were all conducted in the presence of 10% chicken egg yolk fluid. The yolk fluid also slowed down the inactivation of viral particles during incubation at 37 degrees C and enabled full recovery of viral particles through several cycles of freezing and thawing. The purification of viral particles in the presence of yolk fluid did not affect the capability of the viral DNA polymerase to reverse-transcribe the virion RNA in vitro, nor that of the viral RNA to act as a functional template.

Animals↗
PubMed1978

Establishment and characterization of a cell line derived from human colon adenocarcinoma (HuCCL-14).

A continuous human colon carcinoma cell line (HuCCL-14) was established whose cells possess an epithelial-like morphology and are capable of growing in soft agar and on monolayers of normal cells. HuCCL-14 cells yielded high levels of carcinoembryonic antigen, and the analysis of their chromosomal constitution revealed a mode of 70 chromosomes per cell. HuCCL-14 cells produce malignant tumors when injected into nude mice. Preliminary virologic studies indicate the release of RNA particles having a density of 1.15--1.19 g/ml.

Adenocarcinoma↗
PubMed1978

Stimulated production of interferon by a low-molecular-weight factor from chicken-egg fluids.

Exposure of five-year-old L-929 cell monolayers to low-molecular-weight factor obtaiend from chicken egg-yolk fluids stimulated the production of Semliki Forest virus (SFV)-induced interferon, particularly when the cells were infected with a low-input multiplicity of SFV. The stimulatory effect on interferon production was not expressed in polyriboinosinic acid:polycytidylic acid-induced interferon. Furthermore, the high yield of interferon was correlated with and followed the increase in viral yield, thus suggesting that the yolk factor stimulates the growth of SFV, which in turn triggers the higher production of interferon. The outstanding feature of the yolk factor is its ability to stimulate the production of virus-induced interferon during the lytic cycle of virus replication.

Animals↗
PubMed1977

Crosslinking of nucleic acids and proteins by bisulfite.

Sodium bisulfite is a food and beverage additive. It is also a salt of the urban air pollutant, sulfur dioxide. Bisulfite catalyzes, at neutral pH and physiological temperatures, the transamination reactions of cytosine derivatives with amines. The products of the reactions are N4-substituted cytosines. Both the alpha and epsilon-amino groups of L-lysine react with cytosine, and its nucleosides, in the presence of bisulfite. Bisulfite catalyzes the binding of cytosine to polylysine, lysine to polycytidylic acid, and polysine to polycytidylic acid. Polylysine crosslinks with heat-denatured, but not native, calf thymus DNA, in the presence of bisulfite. Other workers have demonstrated crosslinking of viral RNA with maturation and coat protein, after treatment of bacteriophage MS2 with bisulfite. Nucleic acid-protein crosslinking reactions may contribute to the adverse effects of sulfur dioxide and bisulfite upon health.

Chemical Phenomena↗
PubMedDate not supplied

Fluoro-clomiphene and its synthetic precursors: synthesis and receptor binding.

In an attempt to synthesize compounds with selective estrogen-receptor binding, fluoro- and amino-clomiphene were totally synthesized from benzyl chloride, and their estrogenic/antiestrogenic activity as well as that of some of their chemical intermediates was evaluated. The triazene prepared from the amino-clomiphene was converted into fluoro-clomiphene with 39% yield. In the uterotropic test, both amino- and fluoro-clomiphene exerted mild equipotent estrogenic activity, with minimal saturation doses being 50 and 100 micrograms/rat/day for three days. In the receptor binding test both derivatives demonstrated similar displacement, with an A50% value in the 10(-5) M range, as compared to 10(-6) M for clomiphene and 10(-9) M for diethyl-stilbestrol. This synthesis may be useful for the preparation of 18F-labeled clomiphene for biodistribution studies.

Animals↗
PubMedDate not supplied

Nucleotide sequence evidence for relationship of AIDS retrovirus to lentiviruses.

Lentiviruses are a subfamily of retroviruses which have been aetiologically linked to the induction of arthritis, encephalitis, progressive pneumonia and slow neurological diseases in certain species. Relatively little is known about their genome structure, mechanisms of pathogenesis or evolutionary relationships with other retroviral subfamilies. In an effort to understand better the mechanisms by which these viruses induce such a variety of chronic diseases, we have molecularly cloned and physically characterized the genomes of caprine arthritis-encephalitis virus (CAEV) and equine infectious anaemia virus (EIAV) (A.Y. et al., in preparation). The latter, which bears some morphological similarity to the lentiviruses, has yet to be classified definitively as one. Here, we have determined the nucleotide sequence of a highly conserved region within the CAEV and EIAV pol genes. We demonstrate a much closer relationship of their predicted pol gene products to that of the presumed aetiological agent of human acquired immune deficiency syndrome (AIDS) than to those of other retroviruses. Additional pairwise comparisons allowed us to generate an evolutionary tree showing that the pol genes of lentiviruses and oncoviruses have evolved from a common progenitor.

Acquired Immunodeficiency Syndrome↗