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C Zapata

Publications and source records attributed to C Zapata.

At least 19 recordsLinked to original sources
PubMed1998

[Comparison of low-molecular-weight heparin and unfractionated heparin in the treatment of unstable angina].

BACKGROUND: Low molecular weight heparin can be administered by the subcutaneous route and has a stable and prolonged antithrombotic effect. These features have prompted clinical essays about its use as an alternative to unfractionated heparin in the treatment of unstable angina. AIM: To compare the clinical effects of low molecular weight heparin and unfractionated conventional heparin in patients with unstable angina or non Q infarction. PATIENTS AND METHODS: Seventy patients (47 male) admitted to the hospital with the diagnosis of unstable angina or non Q acute myocardial infarction were randomly assigned to receive unfractionated intravenous heparin or subcutaneous low molecular weight heparin bid. All received aspirin p.o. and i.v. nitroglycerin. The incidence of recurrent angina, acute myocardial infarction or a need for emergency surgical revascularization during hospital stay were assessed in both groups. RESULTS: Compared to patients with low molecular weight heparin, patients receiving unfractionated heparin had a higher incidence of recurrent resting angina (23 and 47.5% respectively, p < 0.04) and higher need for emergency surgical revascularization (3.3 and 17.5% respectively, p < 0.06). Patients treated with unfractionated conventional heparin had a 3 times higher risk of having an adverse cardiovascular event than patients receiving low molecular weight heparin (O.R. 0.33, confidence intervals 0.11-0.58). CONCLUSIONS: Low molecular weight heparin is superior to unfractionated conventional heparin in the treatment of unstable angina and non Q acute myocardial infarction.

Adult↗
PubMed1997

A study of genetic association between manic-depressive illness and a highly polymorphic marker from the GABRbeta-1 gene.

We report on an association study between a tetranucleotide repeat polymorphism in the GABR beta1 gene and manic-depressive illness in a Spanish population. This gene may be an important candidate for bipolar affective disorders since severe GABergic alterations have been described in patients. Although our results do not reveal a clear evidence for association between manic-depressive illness and GABR beta1, we have found significant differences between patients and controls in the female subpopulation.

Alleles↗
PubMed1997

On Fisher's exact test for detecting gametic disequilibrium between DNA polymorphisms.

Nonrandom associations between DNA polymorphisms are commonly tested by Fisher's exact test in spite of it is seriously conservative. Theoretical statistical studies have shown that the exact test with Tocher's correction does not present this problem but Tocher's correction is never used by experimentalists for detecting gametic associations. We have examined the practical consequences of using these two alternative tests for the detection of nonrandom associations in populations. A total of 1566 pairs of RFLPs of eleven gene regions and sixteen populations from previously published human and Drosophila disequilibrium data were examined. The analysis reveals remarkable differences between the two tests for detecting gametic associations. In some gene regions, the exact test with Tocher's correction detects a percentage of significant associations between RFLPS which is twice or three times higher than that detected by the exact test without correction. Therefore, the widely used exact test can be seriously underestimating disequilibrium in populations. In addition, the study shows that the standard chi-square test for independence in 2 x 2 tables detects a similar percentage of significant associations between RFLPs than Tocher's test.

Animals↗
PubMed1997

Conditions for protected inversion polymorphism under supergene selection.

Conditions for protected inversion polymorphism under the operation of both karyotype and supergene selection in a viability model have been analytically determined. When supergene selection (the effect of recombination in homokaryotypes lowering the mean fitness of their offspring) is acting on gene arrangements and there is no karyotype selection, it is demonstrated that a polymorphic stable equilibrium is reached by the population, which is a function of only the recombination effects in homokaryotypes. Under both supergene and karyotype selection the degree of dominance (h) of karyotype selection is critical to produce a protected inversion polymorphism. In general, the opportunity for protected polymorphism increases as the degree of dominance decreases. For small s values, the conditions for protected polymorphism are r > 2sh and c > 2s(h-1), where r and c are the average loss of viability for offspring of ST/ST and IN/IN homokaryotypes, respectively. These findings suggest that supergene selection may be an important balancing mechanism contributing to the maintenance of inversion polymorphism.

Chromosome Inversion↗
PubMed1996

Dynamics of gametic disequilibria between loci linked to chromosome inversions: the recombination-redistributing effect of inversions.

The total gametic disequilibrium between two loci linked to polymorphic inversions can be partitioned into two types of components: within and between chromosome arrangements. The within components depend on the gametic disequilibrium within each chromosome arrangement. The between components depend on the locus-inversion disequilibria. This partitioning has practical applications and is indispensable for studying the dynamics of these systems because inversions greatly reduce recombination in the heterokaryotypes while allowing free, and sometimes different, recombination in each of the homokaryotypes. We provide equations for the per generation change of the various disequilibria for systems with two and three chromosome arrangements, and the general recursive equations predicting the disequilibria after any number of generations for the case of two arrangements. Simulation studies were carried out using different values of the recombination parameters and all possible initial conditions. The results show a complex convergence to linkage equilibrium in inversion systems. The various disequilibria can have local maxima and minima while approaching equilibrium and, moreover, their dynamics cannot be described, in general, using a single parameter, i.e. an effective recombination rate. We conclude that the effects of inversions on gametic disequilibria must be carefully considered when dealing with disequilibria in inversion systems. The formulae provided in this paper can be used for such purpose.

Alleles↗
PubMed1996

Measuring selective effects of modifier gene polymorphisms on the Bare locus of Drosophila subobscura.

An attempt to quantify the effects of modifier gene polymorphisms on the operation of natural selection on a major locus has been carried out. The modifier system we have investigated is constituted by a set of polygenic modifier loci affecting the morphological expression of the Bare (Ba) bristle mutant of Drosophila subobscura. Ba is a dominant mutant that is lethal in homozygous condition and both the polygenic modifiers and Ba are located on the O chromosome of this species. Experimental populations were found with Ba/+ individuals and two different types of populations were started according to their modifier genetic background: populations with wild O chromosomes of either high or low modifier effect (cages H and L, respectively). Fitness estimates (total fitness, viability and fertility) for genotypes of the Ba locus were obtained under the two different modifier backgrounds. In the populations with high modifier background the total fitness of the Ba/+ heterozygote was very similar to that of the +/+ homozygote (fitness equal to 1). However, in cages with low modifier background a strong selection against the Ba/+ heterozygote was detected (average of total fitnesses over generations was 0.66 +/- 0.10), and fertility appears to be the fitness component responsible for this effect (mean fertility was 0.55 +/- 0.08). These findings demonstrate that modifier gene polymorphisms affecting the expression of the Ba mutant may be associated with large selective effects on the major locus.

Animals↗
PubMed1996

Time-series analysis of seasonal changes of the O inversion polymorphism of Drosophila subobscura.

We have studied seasonal variation (spring, early summer, last summer and autumn) of inversion polymorphisms of the O chromosome of Drosophila subobscura in a natural population over 15 years. The length of the study allowed us to investigate the temporal behavior (short-term seasonal changes and long-term directional trends) of the O arrangements by the powerful statistical method of time series analysis. It is shown that the O inversion polymorphisms varied on two different time scales: short-term seasonal changes repeated over the years superimposed on long-term directional trends. All the common arrangements (O3+4+7, Osr, O3+4+8) showed significant cyclic seasonal changes, and all but one of these arrangements (O3+4+7) showed significant long-term trends. Moreover, the degree of seasonality was different for different arrangements. Thus, O3+4+7 and OST showed the highest seasonality, which accounted for approximately 61 and 47% of their total variances, respectively. The seasonal changes in the frequencies of chromosome arrangements were significantly associated with the seasonal variation of the climate (temperature, rainfall, humidity and insolation). In particular, O3+4+7 and OST, the arrangements with the greatest seasonal component, showed the strongest association with all climatic factors investigated, especially to the seasonal changes of extreme temperature and humidity.

Animals↗
PubMed1995

Distinct genetic subdivision in sympatric and sibling species of the genus Littorina (Gastropoda: Littorinidae).

The genetic structure of two sibling and sympatric species of the genus Littorina was compared using allozymic loci. The two species are biologically and ecologically well-known and mostly show similar life history characteristics. Three populations of L. mariae Sacchi & Rastelli and L. obstusata (L.) were studied in the Muros-Noya Ria (Galicia, NW Spain). In addition, four microgeographical subsamples taken from one of the populations were analysed for each species. Age, sex and genotypes for nine polymorphic loci were studied in 1250 snails of both species. L. mariae showed larger genetic population subdivision and lower heterozygosity levels for the loci studied than did L. obtusata. Heterozygote deficiencies were found in only a few cases in natural populations of both species, usually affecting the Lap-1 locus. No significant genetic differences among age or sex classes were found. These results may be explained by the lower effective population size in L. mariae than in L. obtusata. Known differences between these species in generation interval and population density during the winter can cause the different effective population sizes suggested. These life history characteristics appear to provide the most likely explanations for the differences in genetic differentiation and heterozygosity between the two species. A previously unknown L. mariae morph from exposed shores is tentatively suggested to be conspecific.

Animals↗
PubMed1994

Serum factors inhibitory for in vitro development of Plasmodium falciparum blood-stage parasites.

Sera from 29 individuals residing in a malaria-endemic region of Colombia were evaluated by an inhibition assay for their capacity to retard the growth of Plasmodium falciparum in vitro. The inhibitory activity was found to be independent of antibody activity. Furthermore, the degree of inhibition of parasite development was variable, depending on the parasite isolate used for the assay and the season of malaria transmission. We selected sera with high inhibitory activity and carried out partial analytical characterization by anion exchange fast protein liquid chromatography (FPLC) to identify the chemical nature of the inhibitory factor(s). The results suggested that the in vitro inhibitory activity might result from the additive effect of different molecules. It appears that these molecules could be non-specifically induced by stimulation of the immune system, they seem to play a role in the immunity to malaria.

Adolescent↗
PubMed1993

On the detection of nonrandom associations between DNA polymorphisms in natural populations of Drosophila.

The capacity to detect nonrandom associations between restriction-map variants was examined in eight gene regions of Drosophila melanogaster (yellow-achaetescute, white, Zw, Adh, Est6, and rosy) and D. pseudoobscura (Adh and Xdh), on the basis of published population data. The statistical power from individual pairwise tests was both heterogeneous and generally low across gene regions. Sample sizes larger than those currently being used are needed to ensure any power to detect disequilibrium by individual tests. It is found that the heterogeneity in power is mostly explained by large differences in the intensity of sample disequilibrium among regions. The yellow-achaete-scute, Zw, and Adh loci of D. melanogaster displayed both the highest mean power (approximately 0.4) and a very great disequilibrium (mean absolute values of D' were 0.8-1). By contrast, all the other gene regions exhibited lower mean power (approximately 0.2) and moderate levels of disequilibrium (0.4-0.6). Although the proportion of significant pairwise associations, especially for white, Est6, and rosy in D. melanogaster and for Adh and Xdh in D. pseudoobscura, is more or less close to the type I error, simultaneous-inference significance tests show that gametic disequilibrium is occurring at the eight DNA regions examined.

Alcohol Dehydrogenase↗
PubMed1990

Genetic variation in a modifier system affecting the expression of bare mutant of Drosophila subobscura.

Genetic variation affecting the expression of Bare (Ba), a morphological mutant of Drosophila subobscura that reduces the number of bristles and is located on the O chromosome of this species, is reported. Our results show that O chromosomes extracted from a natural population (El Pedroso, Santiago de Compostela, Spain) show considerable genetic variation in modifier effect upon Ba expression. The amount of modifier variability is dependent on the chromosomal arrangement (OST and O3 + 4 + 7), since modifier variation is higher in OST than in O3 + 4 + 7 chromosomes. Investigations of the genetic architecture of this modifier system on the O chromosome carried out using biometrical methods indicate that a relatively small number of genetic "factors" can explain the differences in modifier effect between a wild O chromosome of high modifier effect and a marker chromosome of low score. In addition, the modifier effects show a non-uniform distribution along the O chromosome and some indication of clustering of modifier "factors" around the major locus (Ba) is also observed.

Analysis of Variance↗
PubMed1990

[Use of a specific DNA probe to confirm sickle cell anemia in a caucasian woman].

A specific DNA probe containing part of the structural B-globulin gene was used to confirm the diagnosis of sickle cell anemia in a caucasian woman. The patient's genomic DNA was digested with the restriction endonuclease Dde I, fractioned by agarose electrophoresis and Southern blotting. Molecular hybridization was performed with the DNA probe prepared by chemical labelling with photobiotin. The beta 8/beta 8 genotype rendered only 1 fragment of length 376 bp. Upon digestion with Dde I, the DNA of an individual with the normal genotype containing the enzyme recognition sequence at the site of sickle cell mutation, resulted in 2 fragments of 201 and 175 bp. The pedigree of the patient's caucasian family was studied by Hb electrophoresis. Four out of 7 brothers carried the sickle cell trait.

Adult↗
PubMed1990

[Second neoplasms in malignant hematologic disorders. Experience from 1978 to 1987].

Neoplasia may develop in patients with malignant hematologic disorders, during remission after radio and/or chemotherapy. A multifactorial origin related to therapy may be postulated. From 1978 to 1987, among 142 patients with malignant hematologic disorders (Hodgkin lymphoma 33, non-Hodgkin lymphoma 51, Multiple Myeloma 35 and Chronic Myeloid Leukemia 31) we observed 3 patients developing another neoplasia. An additional patient with acute non-lymphatic leukemia had been submitted to chemotherapy for gastric cancer. Four other patients with double neoplasia, one of them a hematologic one, had not been submitted to chemotherapy. The lack of national registries for neoplastic diseases precludes an estimation of the odd ratios involved in our findings.

Adolescent↗
PubMed1990

[Lymphomas of the parotid region].

Parotid gland lymphomas are very uncommon. Two patients with this condition were treated in the last decade. Surgery should be used only for diagnosis and becomes unnecessary when adenopathy is present, since a lymph node biopsy will establish the diagnosis.

Adolescent↗