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A Tavares

Publications and source records attributed to A Tavares.

At least 19 recordsLinked to original sources
PubMed2006

Fast detection of arbitrarily shaped disease clusters.

Disease cluster detection and evaluation have commonly used spatial statistics methods that scan the map with a fixed circular window to locate candidate clusters. Recently, there has been interest in searching for clusters with arbitrary shape. The circular scan test retains high power of detecting a cluster, but does not necessarily identify the exact regions contained in a non-circular cluster particularly well. We propose, implement and evaluate a new procedure that is fast and produces clusters estimates of arbitrary shape in a rich class of possible cluster candidates. We showed that our methods contain the so-called upper level set method as a particular case. We present a power study of our method and, among other results, the main conclusion is that the likelihood-based arbitrarily shaped scan method is not appropriate to find a cluster estimate. When the parameter space includes the set of all possible spatial clusters in a map, a large and discrete parameter space, maximum likely cluster estimates tend to overestimate the true cluster by a large extent. This calls for a new approach different from the maximum likelihood method for this important public health problem.

Brazil↗
PubMed2003

Changes in heat shock protein 27 phosphorylation and immunocontent in response to preconditioning to oxygen and glucose deprivation in organotypic hippocampal cultures.

Organotypic hippocampal cultures have been recently used to study in vitro ischaemic neuronal death. Sub-lethal periods of ischaemia in vivo confer resistance to lethal insults and many studies have demonstrated the involvement of heat shock proteins in this phenomenon. We used organotypic hippocampal cultures to investigate the involvement of heat shock protein (HSP) 27 in preconditioning to oxygen and glucose deprivation. Neuronal damage was assessed using propidium iodide fluorescence; HSP27 phosphorylation and immunocontent were obtained using (32)Pi labelling followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting. We observed that immunocontent of HSP27 was increased after lethal or sub-lethal treatment, indicating it is a response to metabolic stress. Treatments with 5 or 10 min of oxygen and glucose deprivation (OGD) or 1- microM N-methyl-D-aspartate (NMDA) induced tolerance to 40 min of OGD associated with an increase in HSP27 immunocontent and phosphorylation. These data suggest that, in vitro, phosphorylated HSP27 might be involved in preconditioning, probably acting as a modulator of actin filaments or by the blockage of neurodegenerative processes.

Animals↗
PubMed2001

An investigation of the neuroprotective effect of lithium in organotypic slice cultures of rat hippocampus exposed to oxygen and glucose deprivation.

Brain ischemia results in cellular degeneration and loss of function. Here we investigated the neuroprotective effect of lithium in an in vitro model of ischemia. Organotypic hippocampal slice cultures were exposed to oxygen and glucose deprivation. Cellular death was quantified by measuring uptake of propidium iodide (PI). Lithium chloride (0.2-1.2 mM) was added to the medium before, during and after lesion induction. A decrease in incorporation of PI was observed, indicating a neuroprotective effect in all doses tested. We also studied the effect of lithium on the phosphorylation of HSP27, a heat shock protein involved in cellular protection in its dephosphorylated state. In the lesioned hippocampus, 0.4 mM lithium chloride decreased the proportion of phosphorylated HSP27 to total HSP27. These results suggest that lithium may be useful in the treatment of brain ischemia.

Animals↗
PubMed2001

Profile of phosphoprotein labelling in organotypic slice cultures of rat hippocampus.

In recent years organotypic slice cultures of hippocampal tissue of rats have been widely used to study factors involved in neuronal death. Here we used 2D electrophoresis to study the phosphoprotein profile in such cultures and the effect of oxygen/glucose deprivation on this profile. Cultures were prepared from 7-day-old rats. After 14 days in culture the phosphorylation profile in the cultures, as shown by phospho-protein markers undergoing developmental change, closely resembled the profile of fresh tissue from 23-day-old rats. The results suggest that this model could be a good method to observe the development of the tissue and its response to an ischaemic lesion

Aging↗
PubMed2001

Effects of global cerebral ischemia and preconditioning on heat shock protein 27 immunocontent and phosphorylation in rat hippocampus.

Global cerebral ischemia, with or without preconditioning, leads to an increase in heat shock protein 27 (HSP27) immunocontent and alterations in HSP27 phosphorylation in CA1 and dentate gyrus areas of the hippocampus. We studied different times of reperfusion (1, 4, 7, 14, 21 and 30 days) using 2 min, 10 min or 2+10 min of ischemia. The results showed an increase in HSP27 immunocontent of about 300% after 10 min of ischemia in CA1 and dentate gyrus. CA1, a hippocampal vulnerable area, showed an increase in HSP27 phosphorylation, parallel with immunocontent. In dentate gyrus, a resistant area, the increase in HSP phosphorylation was lower than immunocontent. After preconditioned ischemia (2+10 min), when CA1 neurons are protected to a lethal, 10 min insult, we observed an increase in HSP immunocontent and a decrease in phosphorylation in both regions of the hippocampus, suggesting that, when there is no neuronal death, HSP27 in a vulnerable area responds similarly to the resistant area.When dephosphorylated, HSP27 acts as a chaperone, protecting other proteins from denaturation. As it is markedly expressed in astrocytes, we suggest that HSP27 could be protecting hippocampal astrocytes, which could then be helping neurons to resist to the insult, maintaining tissue normal homeostasis.

Animals↗
PubMed2001

Polo kinase and Asp are needed to promote the mitotic organizing activity of centrosomes.

Interfering with the activity of polo-like kinases can lead to the formation of monopolar spindles. Polo-like kinases also regulate mitotic entry, activation of the anaphase-promoting complex and the necessary preconditions for cytokinesis. Similarities between the phenotypes of the Drosophila mutants asp and polo point towards a common role in spindle pole function. The abnormal spindles of asp mutants are bipolar but have disorganized broad poles at which gamma-tubulin has an abnormal distribution. Moreover, the synergism or of polo1 aspE3 double mutants indicates a possible involvement of these genes in a common process. Asp is a microtubule-associated protein of relative molecular mass 220,000 (Mr 220K) found at the face of the centrosome that contacts spindle microtubules. In partially purified centrosomes, it is required with gamma-tubulin to organize microtubule asters. Here, we show that Asp is the previously identified Mr 220K substrate of Polo kinase. Polo phosphorylates Asp in vitro, converting it into an MPM2 epitope. Polo and Asp proteins immunoprecipitate together and exist as part of a 25-38S complex. Extracts of polo-derived embryos are unable to restore the ability of salt-stripped centrosomes to nucleate microtubule asters. This can be rescued by addition of phosphorylated Asp or active Polo kinase.

Animals↗
PubMed2001

New mutations in exon 28 of the von Willebrand factor gene detected in patients with different types of von Willebrand's disease.

BACKGROUND AND OBJECTIVES: von Willebrand's disease (vWD), the most common hereditary bleeding disorder in humans, is caused by qualitative and/or quantitative deficiencies of von Willebrand factor, and can manifest itself under several different phenotypes. Most of the molecular defects have been detected in qualitative variants involving exon 28 of the vWF gene. Patients from four unrelated families with different types of vWD were included in the mutation screening of this region. DESIGN AND METHODS: The whole exon 28 was analyzed in three gene specific fragments, two of them comprising the region involved in the platelet glycoprotein Ib vWF interaction. The search for mutations was carried out by single-stranded conformation polymorphism analysis. The mutations were then identified by automatic sequencing of the anomalous electrophoretic pattern samples. RESULTS: The following candidate mutations were detected. The 3941T-->A transversion, which predicts the amino acid change V1314D, was detected in a sporadic patient with type 2B vWD and severe thrombocytopenia. The 4309G-->A transition, resulting in the amino acid substitution A1437T, was identified in four patients classified as having type 2M vWD. Six unclassified patients from another family carry the 4135C-->T mutation, which gives rise to a cysteine instead of the normal arginine (R1379C) that segregates with the phenotype. The amino acid change C1227R, predicted by the mutation 4135C-->T, was identified as a compound heterozygote in a patient with moderately severe type 1 vWD. None of these mutations had been described previously. INTERPRETATION AND CONCLUSIONS: These findings confirm the importance already given to this region for the correct function of von Willebrand factor since the mutations detected, which affect the D3 and A1 domains, could give rise to different variants of the disease.

Child↗
PubMed2001

Fluorescence in situ hybridization study of TEL/AML1 fusion and other abnormalities involving TEL and AML1 genes. Correlation with cytogenetic findings and prognostic value in children with acute lymphocytic leukemia.

BACKGROUND AND OBJECTIVES: The TEL/AML1 fusion is the most common genetic abnormality found in childhood acute lymphoblastic leukemias (ALL). Although it is very difficult to identify by conventional cytogenetic techniques it can be readily detected using fluorescence in situ hybridization (FISH). We carried out cytogenetic and FISH studies on 42 children with ALL in order to know the frequency of this translocation in our population, the incidence of TEL and/or AML1 gene alterations, and their correlation with clinical evolution and prognosis. In addition, we performed reverse transcription polymerase chain reaction (RT-PCR) in some cases, confirming the feasibility of FISH techniques in the detection of this translocation. DESIGN AND METHODS: Bone marrow samples were obtained from 42 childhood ALL patients. The copy number of AML1 and TEL genes were studied using fluorescent in situ hybridization with a dual color DNA probe specific for the AML1 and TEL genes. RESULTS: We found a frequency of TEL/AML1 fusion of 17% in our sample. Double TEL/AML1 fusion, lack of TEL signal and extra AML1 signals were frequent additional FISH abnormalities. Duplication of a chromosomal complement, deletion of chromosome 12p arm, and polysomies of chromosome 21 are plausible explanations for these additional FISH findings. However, a relatively high proportion of our cases (9.5%) presented specific amplification of AML1. A statistically significant difference in prognosis was found between patients with and without these additional AML1 or TEL FISH alterations (p<0.02), which could be related to the presence of specific karyotypes. INTERPRETATIONS AND CONCLUSIONS: The frequency of TEL/AML1 fusion is similar to that found in other populations (17%). We found that FISH analysis of AML and TEL is related to the evolution of the disease. The absence of alterations in these genes revealed by FISH could be indicative of bad prognosis, while the presence of alterations is related to a good evolution. Our results suggest that interphase FISH analysis to search for alterations in AML and TEL genes could be extremely useful for complementing cytogenetic studies and for providing additional information about the possible outcome of the disease in patients with ALL.

Adolescent↗
PubMed2000

Intima-media thickness evaluation by B-mode ultrasound. Correlation with blood pressure levels and cardiac structures.

The aim of this study was to analyze the thickness of the intima-media complex (IMC) using a noninvasive method. The carotid and femoral common arteries were evaluated by noninvasive B-mode ultrasound in 63 normotensive and in 52 hypertensive subjects and the thickness of the IMC was tested for correlation with blood pressure, cardiac structures and several clinical and biological parameters. The IMC was thicker in hypertensive than in normotensive subjects (0.67 +/- 0.13 and 0.62 +/- 0.16 vs 0.54 +/- 0.09 and 0.52 +/- 0.11 mm, respectively, P<0.0001). In normotensive patients, the simple linear regression showed significant correlations between IMC and age, body mass index and 24-h systolic blood pressure for both the carotid and femoral arteries. In hypertensives the carotid IMC was correlated with age and 24-h systolic blood pressure while femoral IMC was correlated only with 24-h diastolic blood pressure. Forward stepwise regression showed that age, body mass index and 24-h systolic blood pressure influenced the carotid IMC relationship (r2 = 0.39) in normotensives. On the other hand, the femoral IMC relationship was influenced by 24-h systolic blood pressure and age (r2 = 0.40). In hypertensives, age and 24-h systolic blood pressure were the most important determinants of carotid IMC (r2 = 0.37), while femoral IMC was influenced only by 24-h diastolic blood pressure (r2 = 0.10). There was an association between carotid IMC and echocardiographic findings in normotensives, while in hypertensives only the left posterior wall and interventricular septum were associated with femoral IMC. We conclude that age and blood pressure influence the intima-media thickness, while echocardiographic changes are associated with the IMC.

Adult↗
PubMed2000

Blood pressure and sympathetic activity in normotensive aviators during short-haul fixed-wings flights.

BACKGROUND: In order to evaluate the impact of in-flight stress on BP and sympathetic activity during a short fixed-wing flight, we have studied 18 healthy and normotensive commercial captain aviators, aged 37.5 +/- 4.9 yr. METHODS: The protocol consisted of a 120-min flight period, divided into segments of pre-flight, take off, mid-cruise, approach and landing, and a 120-min control period. In both flight and control periods, all subjects underwent BP monitoring, heart rate recording and urine collection for catecholamines. RESULTS: Systolic and diastolic BP (SBP/DBP) were higher during the flight, as a whole, when compared with the control period (134 +/- 11 vs. 121 +/- 8 mmHg, p < 0.05 and 84 +/- 8 vs. 76 +/- 9 mmHg, p < 0.05, respectively). During the flight period, SBP increased in the pre-flight, take-off, approach and landing segments, whereas DBP increased in the take-off, mid-cruise, approach and landing segments. Heart rate did not change in any flight segment. Urinary catecholamines increased during the flight period in comparison to control period 0.20 (0.10 1.8) mg x mg-1 creatinine vs. 0.10 (0.10-1.0) mg x mg-1 creatinine; p < 0.05). CONCLUSION: We conclude that inflight stress increases BP of the normotensive aviators by sympathetic activation during short-haul flights.

Adaptation, Physiological↗
PubMed2000

Molecular genetic analysis of factor XI deficiency: identification of five novel gene alterations and the origin of type II mutation in Portuguese families.

Coagulation factor XI (FXI) deficiency is an inherited autosomal recessive mild bleeding disorder. In this study, we report the molecular genetic analysis of FXI deficiency in six unrelated families of Portuguese origin. The Jewish type II mutation was found in two families, of seemingly Portuguese origin. Haplotype analysis in these families demonstrated that this mutation is of Jewish origin. In the remaining families, five novel FXI mutations have been identified. Two of these mutations (FXI IVS K -10T-->A and FXI 1026G-->T, cd 324) affect the FXI pre-mRNA splicing. A further two (FXI 307 ins AAGCAAT, cd 85 and FXI 1072 del A, cd 340) introduce frameshifts leading to premature termination codons. The FXI splicing mutation, 1026G-->T cd 324, was found in compound heterozygosity with missense mutation FXI K518N. Analysis of the FXI mRNA from the latter genotype demonstrated new donor splice site usage. All reported mutations most likely result in functional null-alleles. In addition, three novel polymorphisms have been identified: at nt -138 in intron A, at codon D125 in exon 5 and at codon T249 in exon 8.

Alleles↗
PubMed1998

Mouse polo-like kinase 1 associates with the acentriolar spindle poles, meiotic chromosomes and spindle midzone during oocyte maturation.

We have examined the dynamics of the localisation of the polo-like kinase 1 (Plk1) during maturation of the mouse oocyte. Levels of Plk1 protein increase following germinal vesicle breakdown, at which time the enzyme begins to accumulate at discrete positions on the condensing chromosomes and, subsequently, at the poles of the meiotic spindle, which moves towards the cortex of the egg. Interestingly, at metaphase in both meiotic divisions, Plk1 shows a punctate localisation along the broad spindle poles. Moreover, the punctate distribution of Plk1 on the meiotic chromosomes appears at early anaphase to correspond to the centromeric regions. The protein relocates to the spindle midzone during late anaphase and then associates with the midbody at telophase. We have confirmed the specific pattern of immuno-localisation seen in fixed preparations by observing the distribution of Plk1 tagged with green fluorescent protein in living oocytes. We discuss the localisation of the enzyme in light of the structure of the spindle poles, which are known to lack centrioles, and the highly asymmetric nature of the meiotic divisions.

Anaphase↗
PubMed1998

Expression of alpha2-adrenergic receptors in normal and atherosclerotic rabbit aorta.

Alpha2-adrenergic receptors (alpha2-ARs) in vascular smooth muscle cells are known to mediate vasoconstriction; however, it is unknown which of the 3 subtypes of alpha2-AR (alpha2A, alpha2B, or alpha2C) is expressed in vascular tissue. We have used subtype-specific probes in in situ hybridization and RNase protection assays to analyze the expression of alpha2-AR in the thoracic aorta of New Zealand White (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbits, a model for atherosclerosis. We found that the alpha2A-AR mRNA was in endothelial and smooth muscle cells in both NZW and WHHL aorta. In addition, the shoulders and subendothelial regions of the atherosclerotic lesions in WHHL aorta showed abundant expression of alpha2A-AR mRNA. Antibodies to macrophage (RAM-11) and smooth muscle cell (HHF-35) antigens were used to localize macrophage and smooth muscle cells in aortic sections from WHHL rabbits. The expression of alpha2A-AR mRNA within the lesions of WHHL rabbits correlated with the presence of infiltrating macrophages. We discuss the potential role of alpha2A-ARs in macrophage function and in promoting atherosclerosis.

Animals↗
PubMed1997

Role of substance P in blood pressure regulation in salt-dependent experimental hypertension.

The participation of substance P in the pathogenesis of five models of experimental hypertension, ie, DOCA-salt, subtotal nephrectomy, one-kidney-one clip renovascular, two-kidney-one clip renovascular, and spontaneous hypertension, was evaluated via an acute infusion of a newly synthesized potent, specific nonpeptide antagonist of substance P at the NK-1 receptor, the agent CP 96,345. In conscious unrestrained rats, CP 96,345 induced significant and sustained increases in mean arterial pressure of DOCA-salt, subtotal nephrectomy, and one-kidney-one clip renovascular hypertensive rats but only small and nonsignificant changes in blood pressure of two-kidney-one clip renovascular and spontaneously hypertensive rats. CP 96,345 had no effect on the blood pressure of sham-treated controls and Wistar-Kyoto rats. This NK-1 receptor antagonist did not significantly affect the heart rate of any experimental model studied. The data suggest that endogenous substance P may act as a partial counterregulatory mechanism against vasoconstriction in models of salt-dependent hypertension.

Animals↗
PubMed1996

Isolated teratozoospermia and in vitro fertilization.

PURPOSE: To show whether increased amounts of spermatozoa used in insemination of preovulatory oocytes in isolated teratozoospermia according to Kruger's strict criteria gives good fertilization rates. METHODS: This study was carried out from September 1993 to November 1994 for a total of 77 cycles, with sperm samples classified according to Kruger's strict classification. Group 1 (C; control) included 37 couples with normal sperm morphology (> 14% normal; SC). Group 2 (GP; good prognosis) included 18 couples (morphology, > or = 4 and < or = 14% normal) and group 3 (T; teratozoospermic) included 11 couples, with isolated teratozoospermia in the male partner (morphology, < 4% normal). RESULTS: No statistically significant difference was seen in the three groups regarding age, duration of infertility, aspirated follicles, oocytes collected, and embryos transferred. There is a statistically significantly difference (P < 0.001) in the number of spermatozoa used in insemination in group 3. CONCLUSIONS: In conclusion, a morphological classification using strict criteria in the assessment of sperm morphology is still very important, as increasing the sperm number of spermatozoa inseminated per oocyte may improve zona pellucida binding and give better IVF results.

Adult↗