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Biomedical subjects

G Marin

Publications and source records attributed to G Marin.

At least 109 records · Page 6Linked to original sources
PubMed1969

Reversion in polyoma-transformed cells: retransformation, induced antigens and tumorigenicity.

We studied the properties of two morphologically reverted cell clones isolated as chromosomal segregants from a "hybrid" clone of BHK 21/13 hamster fibroblasts, transformed with polyoma virus. Both clones were less tumorigenic than control transformed cells. They contained no detectable polyoma-specific complement-fixing antigen. Induced transplantation antigen also appeared to be lost or reduced. Both clones could be retransformed with polyoma virus, suggesting that their reversion is due to the loss of viral genes from the transformed cell.

Animals↗
PubMed1968

Selection of morphologically normal cell lines from polyoma-transformed BHK21/13 hamster fibroblasts.

A selective method was devised for the isolation of "revertants" from polyoma-transformed sublines derived from BHK21/13 Syrian hamster fibroblasts. A hybrid, polyploid subline was obtained by growing together, in mixed culture in the presence of aminopterin, two variant BHK21/13 sublines lacking either inosinic acid pyrophosphorylase or thymidine kinase. Whereas these variant sublines were resistant to 6-thioguanine or to 5-bromodeoxyuridine, the hybrid had regained sensitivity to both analogues. By plating a polyoma-transformed subline derived from this hybrid in the presence of 6-thioguanine, resistant clones were obtained with a frequency of about 10(-4). All of these surviving clones had a reduced chromosome complement and some of them had regained a normal phenotype.

Aminopterin↗
PubMed1967

Effect of the inhibition of protein synthesis on the establishment of transformation by polyoma virus.

Puromycin was used to study the effect of the inhibition of protein synthesis on transformation of hamster cells (BHK21) by polyoma virus. The drug was used at a concentration (10(-4)m) which caused in these cells a drastic but fully reversible inhibition of protein synthesis. A two- to threefold enhancement of transformation rate was obtained when the cells were exposed to puromycin for a period of 5 hr that started at the end of the virus adsorption period. No further enhancement was produced by prolonging puromycin treatment up to 13 hr after infection. The possibility that the observed effect on transformation rate could be mainly attributed to cell selection by puromycin was excluded. In addition, the relevance of a number of possible secondary effects of puromycin (inhibition of cell division, inhibition of deoxyribonucleic acid synthesis, etc.) was also ruled out. The effect of puromycin on transformation appeared to be dependent on the time (relative to infection) of addition of the drug. In fact, no transformation enhancement was observed when the cells were exposed to puromycin prior to infection or beyond the 10th hr after infection. Since another drug known to affect protein synthesis (p-fluorophenylalanine) was also shown to produce similar effects, it is suggested that transformation enhancement results from the inhibition of protein synthesis during a sensitive period closely following adsorption of the virus.

Animals↗
PubMedDate not supplied

Genetic effects of chromium compounds.

Seven different test systems were utilized to investigate the genetic activity of chromium compounds: infidelity of DNA replication in vitro by DNA pol alpha from calf thymus, damage of DNA detected by alkaline elution in treated mammalian cells or in DNA purified and treated in vitro, DNA repair synthesis in mammalian cells in vitro detected by autoradiography or scintillation counting after labelling with [3H]dThd, gene mutations in the Salmonella typhimurium Ames test, gene mutations (6TG resistance) in cultured hamster cells, sister-chromatid exchanges in different rodent cell cultures, and transformation to anchorage-independent growth of hamster cells in vitro (soft-agar assay). Potassium dichromate and chromium chloride were used as water-soluble Cr(VI) and Cr(III) salts. Several reference mutagens (EMS, MMS, MMC, 4NQO) were included in the single tests as positive controls. Cr(VI) was active in all the tested systems, except in the induction of DNA damage and DNA repair synthesis in cultured cells. Cr(III), on the other hand, was absolutely inactive unless a direct interaction with purified DNA was permitted by the test conditions. The relevance of data from the various tests to the understanding of the mechanisms of the genotoxic activity of chromium is discussed. Effects other than the direct interaction of Cr(III) with DNA are inferred, which can cause infidelity of the DNA polymerase functions.

Animals↗
PubMedDate not supplied

Risk factors for post-operative wound infection in cardiac surgery patients.

In a prospective study of 372 patients undergoing cardiac surgery, we evaluated the relative contribution of host factors and patient care variables to the risk of post-operative wound infection. Host factors studied were age, sex, country of origin, the diagnosis for which the operation was performed and, for coronary artery by-pass operations, the functional cardiac status according to modified New York Heart Association criteria. The performance of more than one operation during a single admission carried the highest risk for infection, followed by a coronary artery by-pass operation lasting for more than six hours or performed on patients 65 years or older. In patients undergoing coronary artery by-pass surgery, host factors (age and cardiac function) were associated with infections in the chest wound, while the length of the operation was found to affect the occurrence of infections at the "donor" site.

Adolescent↗
PubMedDate not supplied

The retinal targets of centrifugal neurons and the retinal neurons projecting to the accessory optic system.

In birds, neurons of the isthmo-optic nucleus (ION), as well as "ectopic" neurons, send axons to the retina, where they synapse on cells in the inner nuclear layer (INL). Previous work has shown that centrifugal axons can be divided into two anatomically distinct types depending on their model of termination: either "convergent" or "divergent" (Ramon y Cajal, 1889; Maturana & Frenk, 1965). We show that cytochrome-oxidase histochemistry specifically labels "convergent" centrifugal axons and target neurons which appear to be amacrine cells, as well as three "types" of ganglion cells: two types found in the INL (displaced ganglion cells) and one in the ganglion cell layer. Labeled target amacrine cells have distinct darkly labeled "nests" of boutons enveloping the somas, are associated with labeled centrifugal fibers, and are confined to central retina. Lesions of the isthmo-optic tract abolish the cytochrome-oxidase labeling in the centrifugal axons and in the target amacrine cells but not in the ganglion cells. Cytochrome-oxidase-labeled ganglion cells in the INL are large; one type is oval and similar to the classical displaced ganglion cells of Dogiel, which have been reported to receive centrifugal input; the other type is rounder. Rhodamine beads injected into the accessory optic system results in retrograde label in both types of cells, showing that two distinct types of displaced ganglion cells project to the accessory optic system in chickens. The ganglion cells in the ganglion cell layer that label for cytochrome oxidase also project to the accessory optic system. These have proximal dendrites that ramify in the outer inner plexiform layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

CT and ACTH treatment in infantile spasms.

Computed tomography of 8 cases with West's syndrome before, during and after ACTH treatment are reported. The scans, performed at the third week of therapy, showed consistent widening of the sulci, cisterns and ventricles in all the patients. Of these, 2 patients underwent ICP monitoring which showed higher than normal values. A return to the normal ICP values in association with the disappearance of the CT findings was observed in both cases. It is concluded that widening of the sulci, cisterns and ventricles are not findings of atrophy, but a condition of initial communicating hydrocephalus, which is in accordance with the hypotheses of Riikonen and Lyen.

Adrenocorticotropic Hormone↗