Biomedical subjects

C A Machado

Publications and source records attributed to C A Machado.

7 recordsLinked to original sources

PubMed2001

Nucleotide sequences provide evidence of genetic exchange among distantly related lineages of Trypanosoma cruzi.

Simple phylogenetic tests were applied to a large data set of nucleotide sequences from two nuclear genes and a region of the mitochondrial genome of Trypanosoma cruzi, the agent of Chagas' disease. Incongruent gene genealogies manifest genetic exchange among distantly related lineages of T. cruzi. Two widely distributed isoenzyme types of T. cruzi are hybrids, their genetic composition being the likely result of genetic exchange between two distantly related lineages. The data show that the reference strain for the T. cruzi genome project (CL Brener) is a hybrid. Well-supported gene genealogies show that mitochondrial and nuclear gene sequences from T. cruzi cluster, respectively, in three or four distinct clades that do not fully correspond to the two previously defined major lineages of T. cruzi. There is clear genetic differentiation among the major groups of sequences, but genetic diversity within each major group is low. We estimate that the major extant lineages of T. cruzi have diverged during the Miocene or early Pliocene (3-16 million years ago).

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PubMed2001

Phylogenetic relationships, historical biogeography and character evolution of fig-pollinating wasps.

Nucleotide sequences from the cytochrome oxidase I (COI) gene were used to reconstruct phylogenetic relationships among 15 genera of fig-pollinating wasps. We present evidence supporting broad-level co-cladogenesis with respect to most but not all of the corresponding groups of figs. Using fossil evidence for calibrating a molecular clock for these data, we estimated the origin of the fig-wasp mutualism to have occurred ca. 90 million years ago. The estimated divergence times among the pollinator genera and their current geographical distributions corresponded well with several features of the break-up of the southern continents during the Late Cretaceous period. We then explored the evolutionary trajectories of two characteristics that hold profound consequences for both partners in the mutualism: the breeding system of the host (monoecious or dioecious) and pollination behaviour of the wasp (passive or active). The fig wasp mutualism exhibits extraordinarily long-term evolutionary stability despite clearly identifiable conflicts of interest between the interactors, which are reflected by the very distinct variations found on the basic mutualistic theme.

Animals↗

PubMed2001

Testing Hamilton's rule with competition between relatives.

Hamilton's theory of kin selection suggests that individuals should show less aggression, and more altruism, towards closer kin. Recent theoretical work has, however, suggested that competition between relatives can counteract kin selection for altruism. Unfortunately, factors that tend to increase the average relatedness of interacting individuals--such as limited dispersal--also tend to increase the amount of competition between relatives. Therefore, in most natural systems, the conflicting influences of increased competition and increased relatedness are confounded, limiting attempts to test theory. Fig wasp taxa exhibit varying levels of aggression among non-dispersing males that show a range of average relatedness levels. Thus, across species, the effects of relatedness and competition between relatives can be separated. Here we report that--contrary to Hamilton's original prediction but in agreement with recent theory--the level of fighting between males shows no correlation with the estimated relatedness of interacting males, but is negatively correlated with future mating opportunities.

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PubMed2001

Evolutionary history of microsatellites in the obscura group of Drosophila.

The evolutionary origins of microsatellites are not well understood. Some investigators have suggested that point mutations that expand repeat arrays beyond a threshold size trigger microsatellites to become variable. However, little empirical data has been brought forth on this and related issues. In this study, we examine the evolutionary history of microsatellites in six species within the obscura group of Drosophila, tracing changes in microsatellite alleles using both PCR product size and sequence data. We found little evidence supporting a general role of point mutations triggering initial microsatellite expansion, and no consistent threshold size for expansion was observed. Flanking region length variation was extensive when alleles were sequenced in distantly related species, and some species possessed altogether different repeat arrays between the same primer binding sites. Our results suggest extreme caution in using microsatellite allele sizes for phylogenetic analyses or to infer divergences between populations.

Alleles↗

PubMed2001

[National campaign to detect suspected diabetes cases in Brazil: a preliminary report].

The Ministry of Health of Brazil is implementing a National Plan for the Reorganization of Health Care for Hypertension and Diabetes Mellitus, with the aim of reducing the morbidity and mortality associated with diabetes. This plan is divided into four stages, one of which was a national campaign to detect suspected diabetes cases that was carried out in March and April 2001. This was the first survey of its kind carried out by public health services in Brazil, and the preliminary results are described in this article. Out of a total of 5,507 participating municipalities, 4,446 of them (81%) submitted data to the Ministry of Health. Twenty million people were tested (71% of the target population), and 3.3 million of them were identified as possibly having diabetes. The campaign will contribute towards restructuring the systematic and resolution-oriented care that the national, public Unified Health System provides to diabetics. The preliminary results confirm that diabetes is one of the main health problems in Brazil. Priority should be given to preventing type 2 diabetes.

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PubMed1995

Laparoscopic reoperations after failed and complicated antireflux operations.

Nineteen patients underwent laparoscopic reoperations for failed or complicated antireflux operations from a total of 248 patients with gastroesophageal reflux disease who had been operated on by this approach. Sixteen had been submitted to open surgery and three to laparoscopic surgery over a period ranging from 5 days to 31 years before the study. Three patients had been submitted to two open antireflux surgeries previously. Seventeen patients had recurrent reflux esophagitis after different types of surgeries, and two patients presented with gastric strangulation after fundoplication. The causes of recurrence were: slipped total fundoplications (3), disruption of total and partial fundoplications (6), too-tight total fundoplication (1), too-low (gastric) partial fundoplication (1), Allison procedure (1), partial fundoplication and paraesophageal hernia (2), and unknown (3). The laparoscopic approach was used in 18 patients and a laparoscopic-thoracoscopic approach in 1. The procedures included laparoscopic total fundoplications (11), partial fundoplications (4), transhiatal esophagectomy (1), Collis-Nissen (1), Roux-en-Y gastrectomy and thoracoscopic vagotomy (1), and intrathoracic fundoplication (1). One patient was converted to open surgery. Intraoperative complications included 1 pneumothorax, 1 gastric perforation, and 1 esophageal perforation during the introduction of a Maloney dilator. Mean operative time was 210 min, ranging from 140 to 320 min. Mean hospital stay was 3.1 days after treatment of failed operations and 22 days after treatment of complications. Postoperative complications included subcutaneous infection (1), gastric fistula (1), and liver hematoma (1). The results have been excellent and good in 84.3% of the patients after a mean follow-up of 13 months. We concluded that laparoscopic reoperations are technically feasible with good preliminary results provided that the mandatory expertise is available.

Aged↗

PubMed1990

The interaction of parafluorohexahydrosiladiphenidol at muscarinic receptors in vitro.

1. The antagonistic actions of parafluorohexahydrosiladiphenidol (pFHHSiD) at muscarinic receptors has been studied in cardiac muscle, smooth muscle and cell culture preparations. In this paper, the classification scheme of Doods et al. (1987) is employed. This scheme is based upon differential affinities of muscarinic antagonists. pFHHSiD exhibited high pA2 values at M3 receptors mediating contractions of guinea-pig ileum and oesophageal muscularis mucosae (7.8 and 8.2 respectively) whereas low values were determined at M2 receptors mediating negative inotropic responses in guinea-pig atria (6.0). Intermediate pA2 values were determined at M1 receptors mediating contractions of the canine femoral and saphenous veins. 2. The pA2 values of pFHHSiD at receptors mediating endothelial-dependent relaxation of rat aortic rings, rabbit jugular vein and canine femoral artery (7.6-7.9) were similar to those determined on the ileum. However, the pA2 values of pFHHSiD at receptors mediating contractions of the guinea-pig trachea (7.1), which has been previously shown to possess M3 receptors, were different from those determined in the ileum. 3. The similarity in pA2 values of pFHHSiD between the M3 receptors in guinea-pig ileum and the receptors mediating endothelial-dependent relaxations provide further evidence for the role of M3 receptors in this vascular response. Taken together, pA2 values for pFHHSiD range from 7.1 to 8.2, depending upon the M3 preparation used. The selectivity of the compound therefore for the M3 versus the M2 muscarinic receptor ranged from 13 to 163 fold. 4. At muscarinic receptors mediating stimulation of phosphatidylinositol hydrolysis, pFHHSiD paradoxically displayed a high affinity for the M1 receptor in the SH-SY5Y cell line (pA2 = 7.9) as well as for the M3 receptor in the human astrocytoma (1321 NI cell line (pA2 = 7.6). The value at the M1 receptor in SH-SY5Y cells was greater than was observed at M1 receptors mediating contractions of both the canine saphenous and femoral veins (7.1). 5. pFHHSiD, therefore, clearly delineated M3 from M2 muscarinic receptors, whilst the separation between M1 and M3 receptors was variable. The reason for the anomalous affinity estimates in some functional studies remains unclear. These data indicate that the pA2 values for pFHHSiD appear to be tissue-dependent since the M3 selectivity varies according to the preparations studied. As a result the utility of pFHHSiD in muscarinic receptor classification is limited.

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