Search PubMed⌕ Search

Biomedical subjects

A Cravioto

Publications and source records attributed to A Cravioto.

At least 55 records · Page 3Linked to original sources
PubMed1990

Studies on the microheterogeneity of chorionic gonadotrophin secreted by the human cytotrophoblast in culture.

In the present study, we investigated the biological characteristics of different molecular forms of chorionic gonadotrophin (HCG) secreted by the human cytotrophoblast during its morphological and functional differentiation in culture. Highly purified cytotrophoblasts were prepared from term placentae and cultured for 24 to 96 h in the absence or presence of 8-bromo-3',5'-cAMP. Media were collected at 24 h intervals and the secreted isoforms of HCG were then separated by polyacrylamide gel isoelectric focusing (pH range 8.0-3.0) and quantified by radioimmunoassay. The secretion of HCG was significantly increased by 8-bromo-cAMP (from 23.5 +/- 6.3 ng/ml at 24 h to 1619 +/- 835.8 ng/ml at 96 h; controls, 9.3 +/- 0.1 ng/ml at 24 h and 26.6 +/- 3.5 ng/ml at 96 h, mean +/- SD). Analysis of media concentrates from cAMP-stimulated cultures by isoelectric focusing revealed the presence of several distinct peaks of HCG within the pH range of 7.3-4.8; major peaks consistently exhibited isoelectric points (pI) of 7.3-7.0 (peak 1), 5.6-5.4 (peak 2) and 5.1-4.8 (peak 3). The relative HCG content of the most acidic peak (as % of total on gel) progressively increased with time of exposure to the cAMP analogue (from 19.8 +/- 1.6% at 24 h to 34.4 +/- 4.3% at 96 h, mean +/- SEM, P less than 0.01). HCG recovered from peak 1 exhibited the highest receptor-binding capacity and in-vitro biological potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Assay↗
PubMed1990

Evolutionary genetic relationships of clones of Salmonella serovars that cause human typhoid and other enteric fevers.

Multilocus enzyme electrophoresis was employed to measure chromosomal genotypic diversity and evolutionary relationships among 761 isolates of the serovars Salmonella typhi, S. paratyphi A, S. paratyphi B, S. paratyphi C, and S. sendai, which are human-adapted agents of enteric fever, and S. miami and S. java, which are serotypically similar to S. sendai and S. paratyphi B, respectively, but cause gastroenteritis in both humans and animals. To determine the phylogenetic positions of the clones of these forms within the context of the salmonellae of subspecies I, comparative data for 22 other common serovars were utilized. Except for S. paratyphi A and S. sendai, the analysis revealed no close phylogenetic relationships among clones of different human-adapted serovars, which implies convergence in host adaptation and virulence factors. Clones of S. miami are not allied with those of S. sendai or S. paratyphi A, being, instead, closely related to strains of S. panama. Clones of S. paratyphi B and S. java belong to a large phylogenetic complex that includes clones of S. typhimurium, S. heidelberg, S. saintpaul, and S. muenchen. Most strains of S. paratyphi B belong to a globally distributed clone that is highly polymorphic in biotype, bacteriophage type, and several other characters, whereas strains of S. java represent seven diverse lineages. The flagellar monophasic forms of S. java are genotypically more similar to clones of S. typhimurium than to other clones of S. java or S. paratyphi B. Clones of S. paratyphi C are related to those of S. choleraesuis. DNA probing with a segment of the viaB region specific for the Vi capsular antigen genes indicated that the frequent failure of isolates of S. paratyphi C to express Vi antigen is almost entirely attributable to regulatory processes rather than to an absence of the structural determinant genes themselves. Two clones of S. typhisuis are related to those of S. choleraesuis and S. paratyphi C, but a third clone is not. Although the clones of S. decatur and S. choleraesuis are serologically and biochemically similar, they are genotypically very distinct. Two clones of S. typhi were distinguished, one globally distributed and another apparently confined to Africa; both clones are distantly related to those of all other serovars studied.

Alleles↗
PubMed1989

[Factors affecting the duration of maternal breast-feeding in a cohort of urban mothers studied longitudinally].

A prospective study on the incidence and duration of breastfeeding in a cohort of urban women of the city of Tlaxcala was carried-out in a private pediatric clinic from January, 1983 to December, 1987. In a total of 547 women studied, breastfeeding had a median of three months, and only 5% of the children continued to be breastfed at one year of age. Family tradition of breastfeeding, late introduction of solid foods and/or whole milk and less formal education of the mother were factors related with breastfeeding beyond three months. About 70% of the mothers weaned their children claiming a rejection of the breast-milk by the child, a lack of sufficient quantity to fulfill the child's needs or because of their work outside the home.

Adult↗
PubMed1989

[New approaches in the prevention of diarrhea caused by Escherichia coli].

This article reviews the possibility of preventing diarrhea in young children by knowing how the different enteropathogenic or enterotoxigenic strains of Escherichia coli cause the disease. New approaches on the prevention of diarrheal disease associated to the colonization of these bacteria are discussed based on the response evoked by some of the antigens from maternal milk fed to children with a risk of falling ill at a young age.

Bacterial Adhesion↗
PubMed1988

Prospective study of diarrhoeal disease in a cohort of rural Mexican children: incidence and isolated pathogens during the first two years of life.

Colonization of the intestine by putative pathogens was followed longitudinally in a cohort of 56 infants born during one calendar year in a rural Mexican village with faecal cultures taken every fortnight and every time a child had diarrhoea. The frequency of isolation of pathogens during episodes of diarrhoea was compared with that of matched controls from the same cohort. Incidence of diarrhoea during the first year of life was 98%, diminishing to 93% during the second year. The incidence curves for each year were not significantly different (P greater than 0.1). Isolation of enteropathogenic Escherichia coli, enterotoxigenic Escherichia coli producing heat-stable (ST) and/or heat-labile (LT) enterotoxins and rotaviruses was significantly higher in infants with diarrhoea during the first 2 years of life. In the case of shigella, although no significant differences were found by semester of life, 13 of 16 children in which these strains were found had diarrhoea. Isolation of Salmonella spp., Campylobacter spp. and protozoa were not significantly different in the two groups during the period studied. Strains showing localized adherence to HEp-2 cells or the presence of colonization factor antigens I or E8775 were found with significantly higher frequency in children with diarrhoea. Eighty-two percent of ST+ or LT+ ETEC strains isolated produced one of the three known colonization factors.

Bacterial Infections↗
PubMed1988

Toward a population genetic analysis of Salmonella: genetic diversity and relationships among strains of serotypes S. choleraesuis, S. derby, S. dublin, S. enteritidis, S. heidelberg, S. infantis, S. newport, and S. typhimurium.

Variation in the chromosomal genomes of 1527 isolates of eight common serotypes (O and H antigen profiles) of Salmonella was assessed by analysis of electrophoretically demonstrable allelic polymorphism at 23 metabolic enzyme loci. Seventy-one distinctive electrophoretic types, representing multilocus genotypes, were identified. A basically clonal population structure was indicated by the presence of strong linkage disequilibrium among enzyme loci, the association of each serotype with a relatively small number of multilocus enzyme genotypes, and the global distribution of certain genotypes. For each of six of the serotypes, 83-96% of isolates were members of a single clone. The occurrence of each of four serotypes (S. derby, S. enteritidis, S. infantis, and S. newport) in isolates of clones belonging to several evolutionary lineages, some of which are distantly related, suggests that the horizontal transfer and recombination of chromosomal genes mediating expression of cell-surface antigens has been a significant process in the evolution of the salmonellae. Two divergent clone clusters of S. derby differ in the relative frequency with which they cause disease in birds versus mammals, and two major lineages of S. newport differ in the frequency with which their clones are associated with disease in humans versus animals.

Alleles↗
PubMed1982

New fimbrial antigenic type (E8775) that may represent a colonization factor in enterotoxigenic Escherichia coli in humans.

An enterotoxigenic strain of Escherichia coli O25:H42 (strain E8775), isolated from a patient in Bangladesh with diarrhea, caused mannose-resistant hemagglutination (MRHA) of human and bovine erythrocytes. The strain did not show slide agglutination or immunodiffusion precipitin lines with antiserum specific for the colonization factor antigen CFA/I or CFA/II. A variant E. coli strain, E8775-B, did not cause MRHA or produce enterotoxin. Electron microscopy revealed the presence of fimbriae on the surface of strain E8775 but not strain E8775-B. When strain E8775 was grown at 22 degrees C, it became MRHA negative and fimbriae were absent. An antiserum prepared against strain E8775 was absorbed with strain E8775-B to make an antiserum specific for the fimbrial antigen. Using this absorbed antiserum, we found the fimbrial antigen in 48 of 742 enterotoxigenic E. coli strains. The 48 strains belonged to serogroups O25, O115, and O167. It is suggested by analogy to the properties of previously described colonization factors that these fimbriae may play a part in the colonization of the intestinal epithelium.

Antigens, Bacterial↗
PubMed1982

Hemagglutination activity and colonization factor antigens I and II in enterotoxigenic and non-enterotoxigenic strains of Escherichia coli isolated from humans.

We examined 205 enterotoxigenic strains of Escherichia coli for colonization factor antigens (CFA) I and II, using an immunodiffusion technique with specific antisera. A total of 36 strains of serogroups O63, O78, O114, O128, and O153 and 1 rough strain possessed CFA/I and gave a single precipitin line; 47 strains of serogroups O6, O8, O80, and O115 possessed CFA/II. The latter strains gave a major precipitin line (component 3) when tested with specific antisera prepared against strain E1392 or PB-176 (both E. coli O6.H16; biotype A). However, all 16 strains of E. coli O6.H16 belonging to biotype A gave a second precipitin line (component 1) when tested with both antisera. When CFA/II-positive strains were tested with a specific antiserum prepared against E. coli O6.H16 strains of biotype B or C, all strains gave component 3, but 16 of 17 strains of E. coli O6.H16 belonging to biotype B, C, or F gave a second precipitin line (component 2) not given by strains of biotype A. CFA/II-positive strains of serogroups other than O6 gave only component 3 in tests with all specific antisera. Nine enterotoxigenic strains of serotypes O7, O15, O25, O115, and O128 gave mannose-resistant hemagglutination of human or calf erythrocytes but lacked CFA/I or CFA/II. Although mannose-resistant hemagglutination was common in non-enterotoxigenic strains of E. coli, none of the non-enterotoxigenic strains possessed CFA/I or CFA/II; these strains included fecal strains of serogroups O6, O8, O63, and O78, fecal strains of enteropathogenic serogroups, and strains from extraintestinal sources.

Animals↗