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Biomedical subjects

G M Martin

Publications and source records attributed to G M Martin.

At least 199 records · Page 11Linked to original sources
PubMed1978

Regulation of growth and gene activity in euploid hybrids between human neonatal fibroblasts and epithelioid amniotic fluid cells.

Pure populations of proliferating synkaryons were obtained from polyethylene glycol-mediated crosses between diploid human foreskin fibroblasts and epithelioid amniotic fluid cells. These hybrids proved to be chromosomally stable tetraploids. They continuously produced heteropolymeric G6PD and showed strictly additive patterns of silver staining of both parental sets of nucleolar organizing chromosomes. Collagenous proteins characteristic of the fibroblast parent were synthesized, while fibronectin production appeared to be directed by the epithelioid portion of the genome. Even though these heterotypic hybrids proliferated at a reduced rate and achieved fewer population doublings relative to homotypic (fibroblast X fibroblast) crosses, they survived passage by trypsinization better than pure populations of epithelioid cells. These observations suggest a concerted action of both parental genomes with respect to proteins responsible for "household" functions, but complementation and possibly modulation of gene action with respect to "luxury" protein synthesis and cell growth.

Amniotic Fluid↗
PubMed1977

Children who age rapidly--progeroid syndromes: case report of a new variant.

A case report of an apparently unique progeroid syndrome is reported here. Major clinical characteristics included growth failure with onset of senility in the early teens, atrophic skin, hypogonadism, and retinal and vascular sclerosis. Mental retardation was present, but could have been attributable to trauma. The replicative life spans of several lines of cultured skin fibroblasts were within the normal range, in contrast to the limited life-spans of such cultures from patients with Werner's syndrome, whom our patient most closely resembles. Also, in contrast to Werner's syndrome, our patient did not have white or gray hair or cataracts.

Adult↗
PubMed1976

Evidence contrary to the protein error hypothesis for in vitro senescence.

A strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose-6-phosphate dehydrogenase (G-6-PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 +/- 1%, S.E.), in comparison with that in 19 old cultures (4.9 +/- 1%, S.E.). Old cultures had ceased active cell division (49-60 doublings); DNA replication, measured by [3H]thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5-22 doublings) had a [3H]thymidine labeling index of 75-85%. Titration of G-6-PD activity in extracts of young and old cells with neutralizing antibody directes specifically against G-6-PD failed to detect an increment of enzymatically defective G-6-PD in old cells. The thermostability studies were capable of detecting altered G-6-PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G-6-PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G-6-PD from the thermolabile mutant and G-6-PD inactivated with N-ethylameimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.

Adult↗
PubMed1976

Dimethyl sulfoxide enhances polyethylene glycol-mediated somatic cell fusion.

The efficiency of fusion of human diploid cells by polyethylene glycol was greatly enhanced by addition of dimethyl sulfoxide. The extent of fusion was directly proportional to the concentrations of both of these compounds. At all except the highest concentrations, cell loss was moderate to minimal and perturbation of cell cycle function as measured by [3H] thymidine labeling indices and mitotic indices was minimal in the surviving cells. This technique is potentially useful for heterokaryon studies as well as for the isolation of hybrids of mammalian somatic cells.

Cell Fusion↗
PubMed1975

Reinitiation of DNA synthesis in senescent human fibroblasts upon fusion with cells of unlimited growth potential.

Postreplicative, "senescent" human fibroblasts were fused to HeLa or to SV-40 transformed human fibroblasts with Sendai virus. DNA synthesis was reinitiated in senescent nuclei in a high proportion of the heterodikaryons. The [3H]thymidine labeling index of senescent fibroblast nuclei in heteropolykaryons was a function of the ratio of HeLa to senescent nuclei.

Cell Fusion↗
PubMed1975

Variegated translocation mosaicism in human skin fibroblast cultures.

The term "variegated translocation mosaicism" is used to describe the repeated occurrence, within cultures of human skin fibroblasts, of a multiplicity of chromosomal rearrangements. With respect to the frequencies of such cytogenetically aberrant clones we found that they (1) were not detectable in routine diagnostic skin fibroblast cultures from 29 subjects with a wide variety of indications for biopsy; (2) were not detectable during in vitro aging of diploid strains with four normal individuals; (3) could be detected after rescue from bacterial contamination of a culture from an otherwise normal diploid male; (4) occurred with high frequencies in independent cultures from another apparently normal subject; (5) occurred with high frequencies in multiple biopsies obtained at autopsy from a patient with Werner's syndrome who died of sepsis; (6) were of pseudodiploid nature; and (7) involved a different spectrum of chromosomes in different individuals. A consistent association with mycoplasma contamination could not be made.

Adolescent↗
PubMed1975

Cultivated cells from diagnostic amniocentesis in second trimester pregnancies. II. Cytogenetic parameters as functions of clonal type and preparative technique.

From a total of 418 primary amniotic fluid colonies, 5.5% were fibroblast-like (F), 33.7% epithelioid (E) and 60.8% had characteristics of what was previously shown to be the principal class of clonable amniotic fluid cells (AF). Polyploidy occurred in all three categories, although both pure tetraploidy and mixoploidy were more frequent in E colonies. The incidence of non-constitutional chromosomal changes was identical in AF and E type colonies if primary spreads were analyzed in situ without prior trypsinization. Spreads from pooled cell suspensions showed higher base-line levels of both aneuploidy and structural changes. Analysis of individual colonies employing an in situ preparative technique is clearly the method of choice for a reliable cytogenetic prenatal diagnosis within the shortest possible period of time.

Amniocentesis↗