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Biomedical subjects

G Contreras

Publications and source records attributed to G Contreras.

At least 73 records · Page 4Linked to original sources
PubMed1985

Activation of metastatic potential in African green monkey kidney cell lines by prolonged in vitro culture.

Studies on the tumorigenicity of Vero kidney cells of Cercopithecus aethiops monkey origin were extended to various passage levels of BSC-1 aneuploid cells and to low passage CV-1 diploid cells (derived also from C. aethiops monkey kidney). It was found that BSC-1 cells -- like Vero cells -- showed increased tumorigenicity with increasing passage level in antithymocyte globulin (ATG) treated newborn rats and in nude mice. Cells passaged over 250 times in cultures formed invasive adenocarcinomas in newborn rats. Their malignant tumor growth was further demonstrated around the 500 passage level when tumor metastases were detected in the lungs of four of the 14 inoculated rats. Vero cells induced such lung metastases in rats already at passage 227. CV-1 diploid cells at low passage level produced small nodules of epithelioid cells in newborn rats at 6th day after inoculation that had disappeared by the 21st day, and caused no local invasion nor lung metastasis. In vitro tumorigenicity tests on BSC-1 and CV-1 cells, using chick embryo skin, human muscle and colony formation in agarose, confirmed the animal test results. The results of this study indicate that BSC-1 and Vero cell lines at low and high passage levels may prove to be useful tools to study the molecular basis of malignancy.

Adenocarcinoma↗
PubMed1985

Heterotransplantation studies with tissue culture cell lines in various animal and in vitro host systems.

The human amnion cell line FL was found to be more tumorigenic than HeLa cells when used as a positive control in heterotransplantation assays. FL cells formed significantly larger locally invasive tumors than HeLa cells in both Balb/c/nu/nu mice and ATG-treated newborn Wistar rats. In addition, FL cells resulted in metastatic growths in the lungs of two of 12 mice six weeks and in 10 of 36 rats three weeks after inoculation. HeLa cells did not produce metastases in either mice or rats. Both these cell lines were obtained from the American Type Culture Collection. Heterotransplantation experiments with a variety of animal host systems confirmed previous findings that newborn Wistar rats treated with rat ATG were the most sensitive to tumor growth. Vero and LLC-MK2 continuous monkey kidney cells formed small, non-progressively growing tumors showing tubule formation and occasional mitoses. LLC-MK2 cells were found to be more pleomorphic in appearance and with more mitoses than Vero cells but neither cell line showed any evidence of distant metastatic growth in any of several organs examined. The human lymphoblastoid cell line Namalwa produced large invasive tumors at the inoculation site but no distant metastases. In the chick embryo skin test it was found that MI values (mitotic index--percentage of cells in mitosis) gave more reproducible results and were less time-consuming than counting mean mitoses per section. Significant differences were found between Vero, LLC-MK2, HeLa and FL cells with Vero giving the lowest and FL the highest values. The use of MI values enhanced the sensitivity of the chick embryo skin test which was found to be a rapid and valuable screening test for tumorigenicity.

Animals↗
PubMed1984

Use of monoclonal antibodies prepared with Sabin vaccine viruses for the characterization of poliovirus strains isolated in Canada.

Eleven of 90 hybridomas that secreted neutralizing antibodies to various types of poliovirus, were cloned and their monoclonal antibodies tested for the intratypic differentiation of poliovirus isolates. All monoclonal antibodies (MAs) prepared with three types of Sabin vaccine viruses were specific with their homologous viruses but only one of three Saukett MAs was found suitable for intratypic serodifferentiation. A total of 112 poliovirus strains isolated from specimens of human or sewage origin in Canada from 1962 to 1981 were tested with these MAs. Approximately 90% of the virus isolates tested confirmed the findings previously obtained in the antigenic marker assays. Either pools or panels of individual MAs are suitable for the characterization of poliovirus isolates. Preliminary results of experiments conducted with pools of MAs and with single MAs added in various sequences, demonstrated that the location of the virus epitopes played an important role in the neutralization process.

Animals↗
PubMed1983

Axoplasmic incorporation of amino acids in myelinated fibers of the cat.

Incorporation of amino acids into the axoplasm of nerve fibers of the cat was studied with radioautography. The dorsal funiculus of the spinal cord, or the sciatic nerve, was exposed to tritiated leucine, lysine, and proline; the tissue was processed 1 h later or the following day. In all instances, a radioautographic response of widely varying intensity was observed over the axoplasm; this response could not be adscribed to emissions originating from axonal mitochondria or myelin. The axoplasmic response ranged to as much as 56% compared with that over nearby glial cytoplasm and was often conspicuously greater than that over the surrounding myelin. We interpret our findings as axoplasmic synthesis of proteins. This finding has implications in the maintenance of the neuron.

Amino Acids↗
PubMed1981

[Effect of vitamin and mineral supplements on the protein utilization of mixtures of corn and beans].

The present study was undertaken to establish the effect of some vitamins and minerals on protein utilization of maize:bean mixtures fed in an 87:13 and 70:30 weight ratio. The experiments were carried out by feeding such diets without thiamine, niacin, pyridoxin, riboflavin and vitamin A and without iron, zinc, iodine and magnesium, alone or in combination. Completely supplemented diets were used as reference. The results indicated better protein utilization from the 70:30 maize:bean mixture than from the 87:13. Even though it was not possible to detect significant differences due to the lack of single nutrients, either vitamins or minerals, probably due to the relatively short experimental period, the results strongly suggest the importance of these nutrients in increasing protein utilization. The same result was true when both mixtures were supplemented with their limiting amino acids lysine, methionine and tryptophan. Furthermore, the addition of these amino acids without vitamins or minerals did not improve protein utilization, suggesting that nutrition is not due to single nutrients but to a nutrient balance. Chemical carcass composition of the rats showed an increased fat accumulation for the animals fed the 70:30 mixture over those fed the 87:13 blend. No explanation was given, and this should be a subject of further research.

Amino Acids↗
PubMed1980

Lipids and lipoproteins in Venezuelan and American schoolchildren: within and cross-cultural comparisons.

This study was designed to focus upon within-culture differences in plasma lipids and lipoproteins in Venezuelan schoolchildren having different socioeconomic and nutritional backgrounds and also to provide cross-cultural comparisons of lipids, lipoproteins, and anthropometric measurements between Venezuelan and American schoolchildren. The study was carried out in 1298 schoolchildren, ages 7 to 12 years, 428 in private and 870 in public schools in Merida, Venezuela, with comparison to 472 public schoolchildren in the (Cincinnati, OH) Princeton School District. Within Venezuelan schools, private shcoolchildren were heavier, taller, had marginally higher Quetelet indices, and had considerably higher fasting plasma cholesterol, plasma high-density lipoprotein (C-HDL), and plasma low-density lipoprotein (C-LDL) levels. These lipid-lipoprotein differences were highly significant after adjusting (by covariance analysis) for Quetelet index, sex, and age. Children from private Venezuelan schools ingested more total calories, more protein, more fat, and more carbohydrate. When the diet compositions were calculated as percentage of total calories, the private schoolchildren ingested nearly twice as many calories as fat and a somewhat lower proportion of calories as carbohydrate, with a comparable proportion as protein, when compared to the public Venezuelan schoolchildren. Male-female comparisons within Venezuelan schools revealed patterns of sex-related lipoprotein differences which were qualitatively similar to those in Princeton schoolchildren. Thus, 7- to 12-year-old females had higher total plasma cholesterol and triglyceride, lower C-HDL, and higher C-LDL. Within sex, cross-cultural comparisons of lipids, lipoproteins, and Quetelet indices revealed two major differences. Venezuelan children had significantly higher fasting plasma triglyceride and lower C-HDL levels, differences not attributable to systematic differences in measures of ponderosity, because Quetelet indices in Venezuelan and Cincinnati schoolchildren did not differ appreciably. In regard to total and low-density lipoprotein cholesterol, Venezuelan and Princeton public schoolchildren were remarkably comparable, although Venezuelan private schoolchildren had somewhat higher plasma cholesterol and C-LDL levels than did Princeton public schoolchildren. We speculate that increasing "westernization" and "urbanization" of Venezuelan society is associated with convergence of Venezuelan and American pediatric plasma lipid and lipoprotein levels. Maintenance of comparable total plasma cholesterol and C-LDL levels with lower C-HDL into adulthood in Venezuela would, in fact, suggest augmented risks for coronary heart disease for Venezuela within this lipid-lipoprotein frame of reference.

Age Factors↗
PubMed1979

Persistence of influenza serum antibodies in humans following immunization with a bivalent A/Victoria and A/New Jersey vaccine.

The persistence of serum antibodies 1 year after immunization with a bivalent vaccine containing recombinant viruses that were antigenically identical with A/Victoria/3/75 (H3N2) and A/New Jersey/8/76 (Hsw1N1) viruses was measured in 128 persons aged 18 to 65 years. Serum samples were tested with the hemagglutination inhibition assay against the two vaccine antigens and against A/Texas/1/77 (H3N2) and A/USSR/90/77 (H1N1) viruses. Prior to vaccination 56% and 79% of the participants had been found to be seronegative to A/Victoria and A/New Jersey antigens respectively; the geometric mean antibody titres were low (1:5 to 1:11) except in persons aged 51 to 65 years, whose mean titre of antibody to the A/New Jersey antigen was 1:23, and persons aged 26 to 35 years, whose mean titre of antibody to the A/USSR antigen was 1:25. By 3 weeks after vaccination 85% of the seronegative persons had a fourfold or greater rise in titres of antibodies to the viruses in the vaccine, and 70% had a fourfold increase in titre of antibody to the A/Texas antigen. Of the persons aged 26 to 35 years (seronegative and seropositive) 68% had a fourfold or greater increase in titre of antibody to the A/USSR antigen. There was no change in the mean titres of 19 unvaccinated control subjects during the observation period. At 6 and 12 months after vaccination the titres of antibodies to the A/Victoria and A/New Jersey antigens had declined moderately in all age groups from those observed 3 weeks after vaccination. The rate of decline was similar for the various antibodies except that to the A/USSR antigen in persons 26 to 35 years of age, in whom the decline was much slower.

Adolescent↗
PubMed1979

Inhibitory activity of alpha 1-antitrypsin in infants with idiopathic respiratory distress syndrome.

In two groups of neonates serum concentrations of alpha-1-antitrypsin (1-AT) were determined by means of radial immunodiffusion, and 1-AT inhibitory capacity determinations were made using benzoyl-1-arginine-p-nitroanilide as a substrate. There were 66 children in the first group of neonates with idiopathic respiratory distress syndrome (IRDS), and 82 healthy children in the second group with birth weight and gestational and post natal ages similar to those of neonates with IRDS. In the latter, 1-AT concentration and inhibitory activity levels were lower than those found in healthy children; these differences were statistically significant. These findings explain both the retardation in the lysis of the hyaline membrane and the fact that a decrease in serum 1-AT levels elicits lung tissue damage by the action of proteolytic enzymes contained in leucocytes.

Birth Weight↗