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Biomedical subjects

A S Rabson

Publications and source records attributed to A S Rabson.

At least 19 recordsLinked to original sources
PubMed1989

Characterization and tumorigenicity of a butyrate-adapted T24 bladder cancer cell line.

We have adapted T24P, a tumorigenic subline of the T24 human bladder cancer cell line, to grow in 5 mM butyrate. In the presence of butyrate, the adapted cells (T24P/B) grow more slowly than the unadapted cells (T24P/C), have a lower saturation density, increased serum requirement for growth, loss of ability to form colonies when plated at low cell density, and decreased ouabain sensitivity. Morphologically, T24P/B cells in butyrate are large and flattened with increased cytoplasm. When T24P/B cells are grown without butyrate, the morphological changes, growth rate, plating efficiency, and ouabain sensitivity return to those of T24P/C. While the saturation density increases, it does not return to levels of T24P/C, and the size of colonies never reaches that of the T24P/C colonies. Both T24P/C and T24P/B are tumorigenic in nude mice, however, the T24P/B tumors differ grossly and microscopically from those produced by T24P/C in that they contain large cystic structures filled with clear fluid and lined by transitional cell epithelium with flattened surface layers. Although the transformed phenotype and tumorigenicity of T24P are modified by adaptation to growth in butyrate, no significant changes in ras oncogene RNA or protein expression were identified.

Acetylation↗
PubMed1987

Tumorigenicity of T24 urinary bladder carcinoma cell sublines.

Two sublines of the T24 human urinary bladder carcinoma cell line which differ in tumorigenicity in nude mice have been studied (T24A and T24P). T24A obtained directly from the American Type Culture Collection is non-tumorigenic while T24P obtained after multiple passages in several NCI laboratories produces tumors in 100% of inoculated mice. T24P cells differ morphologically from T24A, have a higher saturation density, are less serum-dependent for growth, and are more sensitive to ouabain toxicity. Cytogenetic studies show that the 2 sublines differ significantly in chromosome number, with a modal chromosome range of 76-89 in T24A and a modal chromosome number of 48-51 in T24P. Southern blot analysis of MspI cleaved T24A and T24P DNAs with the H-ras SmaI probe indicates that both contain only the activated mutant allele originally described in T24. Northern blot analysis shows equal amounts of the 1.2kB ras polyadenylated message, and immunoblotting with rasHa antibody demonstrates no significant difference in the amounts of ras proteins. These results indicate that 2 sublines of a ras oncogene-containing tumor cell line can differ greatly in tumorigenicity and other in vitro characteristics of transformation, and yet have similar expression of the ras oncogene. The fact that the tumorigenic cell line contains fewer chromosomes suggests that tumorigenicity may be related to the loss of some regulatory gene.

Animals↗
PubMed1987

Human cytomegalovirus (HCMV) enhances bovine papilloma virus (BPV) transformation in vitro.

Infection of NIH 3T3 cells with a combination of HCMV and BPV resulted in more foci than infection with BPV alone. Foci were microscopically apparent at 4 days in the mixed infection and did not appear until 2 days later in the cultures infected with BPV alone. The enhancement was abolished by heat inactivation of the HCMV and also when the HCMV was replaced by a "mock inoculum." Southern blot analysis of cellular DNA from transformed cells showed a similar amount of extrachromosomal BPV DNA in cells infected by BPV alone and in cells co-infected with HCMV. No HCMV antigens could be found in these cells by immunofluorescence. The mechanisms of the enhancement are not known. Stimulation of host DNA synthesis by HCMV could possibly increase the transforming efficiency of BPV. Alternatively, the increase in BPV transforming efficiency could be due to a transient increase in BPV-1 transcription by an HCMV transcriptional transactivation factor. Since both HCMV and human papillomaviruses are commonly found in the uterine cervix, HCMV may play a role in human cervical cancer by enhancing the carcinogenic potential of human papillomavirus.

Animals↗
PubMed1987

Further studies on the Mycoplasma pneumoniae extract: ciliostatic and cell recruitment activities.

Since inactivated vaccines have proved disappointing in preventing Mycoplasma pneumoniae disease, we have initiated studies to identify protective immunogens as candidates for an acellular, purified component vaccine. A cell-free extract was prepared, and was shown to have hemagglutination, attachment inhibition, and ciliostasis activities. Ciliostatic activity in hamster tracheal organ cultures was dependent on the time of incubation and on the amount of added extract. The ciliostatic factor was resistant to boiling and to trypsin and chymotrypsin digestion. When administered intratracheally to Golden Syrian hamsters, the extract induced lung lesions with histopathologic characteristics similar to those caused by virulent M. pneumoniae infection. Thus, in addition to attachment and ciliostatic factors, the extract contains factors that induce inflammatory responses in hamster lungs and cause cytotoxic damage to lung tissues.

Animals↗
PubMed1984

Mixed infection with human cytomegalovirus and human polyomavirus (BKV).

Mixed infection, the infection of a single cell by two distinguishable viruses, has been demonstrated electron microscopically in human embryo lung (HEL) and human embryo kidney (HEK) cells infected with human cytomegalovirus (HCMV) and human polyomavirus (BKV). There was no evidence of enhancement of HCMV by BKV in either cell system; however, in HEL cells under certain conditions, HCMV enhanced the growth rate of BKV. Since both BKV and HCMV are often found in the urine of immunosuppressed patients, the enhancement of BKV by HCMV may be of clinical significance.

Cells, Cultured↗
PubMed1984

Butyrate prevents Harvey Sarcoma virus focus formation but permits oncogene expression.

Since butyrate inhibits DNA synthesis and cell growth, we adapted NIH 3T3 cells to grow in butyrate to study its effects on retroviral cell transformation. In cultures of butyrate-adapted NIH 3T3 cells infected with Harvey Sarcoma Virus, no foci were formed; however, there was evidence of retroviral replication, and the P21 oncogene product was demonstrated by immunofluorescence in its characteristic localization beneath the cytoplasmic membrane of single cells and pairs of cells. When the butyrate was removed, these cells proliferated to form foci. Butyrate therefore does not prevent oncogene expression but does reversibly inhibit focus formation.

Animals↗
PubMed1983

Butyrate increases type-A and type-R virus-like particles in BKV-transformed hamster spleen cells.

A cell line derived from hamster spleen transformed by human papovavirus BK was adapted to grow in 5 mM butyrate. Ultrastructurally, the butyrate-adapted cells were found to contain large numbers of type-R and intracytoplasmic type-A virus-like particles (VLP). In contrast, the unadapted cells contained only rare VLP. Treatment of the unadapted cells with nontoxic and toxic concentrations of butyrate for 24 and 48 hr failed to induce VLP, indicating the importance of butyrate adaptation in the induction of VLP. The increase in type-R VLP was stable after removal of the adapted cells from butyrate; however, the increase in type-A VLP was not.

Animals↗
PubMed1983

Murine type C retroviruses and intracisternal A-particles in human tumors serially passaged in nude mice.

An ultrastructural survey of 11 human tumors passaged in N:NIH(S) (nu/nu) mice showed two instances of type C virus production. In one instance type C virus particles were observed in the endothelial murine stromal cell component of an embryonal carcinoma but not in the human tumor cells. In another instance type C virus particles were seen replicating in the chondroblastic human cells of a xenografted osteosarcoma. The type C virus produced in the human cells failed to transform NIH/3T3 cells, the C-127 rat cell line, or mink cells. Nucleic acid hybridization studies in which a human endogenous retroviral probe and a xenotropic murine leukemia virus envelope probe were used suggested that the retrovirus present in the human osteosarcoma cells is related to murine leukemia viruses. Intracisternal A-particles (IAP) were also detected in the human osteosarcoma cells. Their presence in the human cells was demonstrated by simultaneous visualization of IAP and human HLA determinants at the cell surface. The literature on type C virus infection of human cells and tumors grafted in nude mice is reviewed.

Animals↗
PubMed1983

Recombinant DNA technology and laboratory medicine.

Recombinant DNA technology has already had a major impact on our understanding of microbiology, cell biology, and genetic diseases and it will certainly have extensive applications in laboratory medicine. The techniques of restriction endonuclease analysis of DNA, nucleic acid hybridization after electrophoretic separation of nucleic acid fragments, and molecular cloning of bacterial, viral, and human genes are already being used in epidemiologic studies and the prenatal diagnosis of certain genetic diseases, such as sickle cell anemia and the thalassemias. New insights into genes that may be involved in human cancer are being developed and may lead to improved methods for diagnosis and classification of tumors.

Animals↗
PubMed1980

Stimulation of N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate of ectopic production of the free beta subunit of chorionic gonadotropin by a human brain tumor cell line.

Previous studies have favored a basic difference in the regulation of specialized protein production by cells derived from the usual tissue of origin (eutopic) and cancer cells derived from a tissue not normally producing the protein (ectopic). Thus N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate was believed to stimulate only eutopic (but not ectopic) chorionic gonadotropin production, and butyrate to stimulate only ectopic (but not eutopic). However, in CBT, a human brain tumor cell line, we find that N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate, but not butyrate, stimulated ectopic production of the beta subunit of chorionic gonadotropin. We conclude that neither butyrate nor cyclic adenosine 3':5'-monophosphate derivatives reliably discriminate ectopic from eutopic regulation.

Brain Neoplasms↗
PubMed1979

Latent infection by herpes simplex virus.

The experimental evidence contributing to the understanding of herpes simplex virus latent infection has been reviewed. The site of residence of the virus during silent periods of the disease appears to be, in the majority of instances, the sensory ganglion innervating the territory of prime infection. Little is known about the factors that bring about latent infection, maintain it, and regulate the production of infectious particles that cause recurrences.

Adolescent↗