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Biomedical subjects

A Pereira

Publications and source records attributed to A Pereira.

At least 109 records · Page 6Linked to original sources
PubMed1997

On the functional anatomy of the nucleus of the optic tract-dorsal terminal nucleus commissural connection in the opossum (Didelphis marsupialis aurita).

Immunocytochemical methods revealed the presence of GABA in cell bodies and terminals in the nucleus of the optic tract-dorsal terminal nucleus, the medial terminal nucleus, the lateral terminal nucleus and the interstitial nucleus of the superior fasciculus of the opossum (Didelphis marsupialis aurita). Moreover, after unilateral injections of rhodamine beads in the nucleus of the optic tract-dorsal terminal nucleus complex and processing for GABA, double-labelled cells were detected in the ipsilateral complex, up to 400 microns from the injected site, but not in the opposite. Analysis of the distributions of GABAergic and retrogradely-labelled cells throughout the contralateral nucleus of the optic tract-dorsal terminal nucleus showed that the highest density of GABAergic and rhodamine-labelled cells overlapped at the middle third of the complex. Previous electrophysiological data obtained in the opossum had suggested the existence, under certain conditions, of an inhibitory action between the nucleus of the optic tract-dorsal terminal nucleus of one side over the other. The absence of GABAergic commissural neurons may imply that this inhibition is mediated by an excitatory commissural pathway that activates GABAergic interneurons.

Animals↗
PubMed1997

Genetic and environmental factors regulating blood pressure in childhood: prospective study from 0 to 3 years.

OBJECTIVES: Blood pressure (BP) regulation depends on the interaction between multiple environmental and genetic factors. Of these, BP sensitivity to dietary sodium intake has been one that has been investigated in adults but not in children. The aim of the present study was to investigate, prospectively, the BP profile in relation to different genetic and hormonal factors, in the first 3 years of life. POPULATION AND METHODS: Thirty-nine children born at term following normal pregnancies, with uncomplicated neonatal periods, were randomly selected to take part in the study. BP, weight and length were evaluated every 3 months from birth to 3 years. At the age of 12 months, haptoglobin phenotypes and plasma active renin concentration were determined as well as random urine evaluation of aldosterone, cAMP, dopamine and digoxin-like immunoreactive substances (DLIS). Family history of cardio-vascular diseases was also recorded. RESULTS: Systolic BP (SBP) demonstrated a gradual increase until the age of 6 months with little variation up to 36 months. Tracking of SBP values was also observed from the first year as infants with high values (above the 75 percentile) maintained this tendency up to, at least, the age of 36 months. The comparison between SBP and diastolic BP (DBP) according haptoglobin phenotypes demonstrated that SBP was systematically higher in allele 1, with apparently an increasing tendency with age, although the differences did not have statistical significance. The comparative study between haptoglobin phenotypes, with correction for the covariates fractional excretion of sodium and potassium, showed that allele 1 carriers had significantly lower plasma renin and urine aldosterone and cAMP concentrations than allele 2, but dopamine excretion was found to be higher in allele 1 than in allele 2. There were no differences among variables relating to family history of cardiovascular disease. CONCLUSIONS: There was an early tracking process of BP values from the first 6 months of life which persists through, at least, to the age of 36 months. Differences in sodium handling between haptoglobin 1 and 2 phenotypes were already present in early childhood, although no significant repercussion in BP values could be demonstrated in the 3-year duration of this study.

Age Factors↗
PubMed1997

A murine model of human cold agglutinin disease.

Progress has been limited in the treatment of cold agglutinin (CA) disease by the absence of an animal model. We have recently studied at the molecular level one CA displaying the rare anti-Sia-1b specificity (CAGAS), CAGAS displays strong CA activity and is able to haemolyse mouse RBC in the presence of complement, thus constituting a suitable Ab for creating a murine model of CA disease. In the present work we introduced CAGAS VH and VL domains into eukaryotic expression vectors and transfected them into the non-secreting mouse myeloma X63 cell line. Clones expressing complete engineered pentameric IgM kappa CAGAS (eCAGAS) recapitulating the characteristics of serum CA (sCAGAS) could be obtained. The i.p. injection of eCAGAS to normal BALB/c mice induced a typical haemolytic anaemia, as demonstrated by the presence of spontaneous cold agglutination of RBC, induction of anaemia and significant reticulocytosis. Of interest, conspicuous bilateral ear loss was observed in one of these animals. In addition, i.p. injection of X63 transfected line into BALB/c nude mice induced ascites, typical haemolytic anaemia, and shortening of the mean RBC survival. These findings validate the practical interest of constructing a transgenic mouse model expressing eCAGAS.

Anemia, Hemolytic, Autoimmune↗
PubMed1997

Identification of 'short-lived' and 'long-lived' patients at presentation of idiopathic myelofibrosis.

To contribute to a better knowledge of the prognosis of idiopathic myelofibrosis (IM), the prognostic value of the presenting features in 106 patients diagnosed with IM at a single institution during a 21-year period was retrospectively analysed. Median survival was 59.4 months (95% CI 40.7-75.4). Using univariate analysis, age > 64 years, constitutional symptoms (fever, night sweats, weight loss), Hb < 10 g/dl, circulating blasts (> or= 1%), and serum LDH > 3 times upper normal level were associated with a significantly shorter survival; male sex, platelet count < 100 x 10(9)/l, blood percentage of immature granulocytes (excluding blasts), low cholesterol levels and advanced marrow histological stage had borderline significance. Using multivariate study, only age > 64 years, constitutional symptoms, Hb < 10 g/dl, and circulating blasts retained their prognostic relevance. The latter three variables confirmed their predictive value in patients above and below the series median age, and were able to identify two groups of patients: a low-risk group of 67 patients with none or one bad prognostic factor, in whom IM had an indolent course (median survival 98.8 months, 95% CI 68.7-127.6), and a high-risk group, including 39 patients with two or three factors, with a more aggressive disease (median survival 20.6 months, 95% CI 10-28.2). Finally, the application of two recently proposed scoring systems (in which three prognostic groups are considered) was unable to separate intermediate- from high-risk patients.

Adolescent↗
PubMed1997

The Arabidopsis MALE STERILITY 2 protein shares similarity with reductases in elongation/condensation complexes.

The Arabidopsis thaliana MALE STERILITY 2 (MS2) gene product is involved in male gametogenesis. The first abnormalities in pollen development of ms2 mutants are seen at the stage in microsporogenesis when microspores are released from tetrads. Expression of the MS2 gene is observed in tapetum of wild-type flowers at, and shortly after, the release of microspores from tetrads. The MS2 promoter controls GUS expression at a comparable stage in the tapetum of transgenic tobacco containing an MS2 promoter-GUS fusion. The occasional pollen grains produced by mutant ms2 plants have very thin pollen walls. They are also sensitive to acetolysis treatment, which is a test for the presence of an exine layer. The MS2 gene product shows sequence similarity to a jojoba protein that converts wax fatty acids to fatty alcohols. A possible function of the MS2 protein as a fatty acyl reductase in the formation of pollen wall substances is discussed.

Amino Acid Sequence↗
PubMed1997

Prolonged holding of whole blood at 22 degrees C does not increase activation in platelet concentrates.

OBJECTIVES: Platelets prepared after holding of whole blood overnight at 22 degrees C have a well-preserved metabolism. However, the possibility that such prolonged incubation with active granulocytes may increase platelet activation has not been fully tested. METHODS: We investigated this possibility by flow cytometric analysis of membrane glycoproteins (GPs) Ib and IIb/IIIa and the activation markers CD62P and CD63 in platelet concentrates (PCs) prepared from whole blood that was held for either 6 h without cooling plates (n = 20) or for 24 h on cooling plates of 1,4-butanediol (n = 20). PCs were prepared by the platelet-rich plasma method and analyzed on the second storage day. RESULTS: Platelet yield and aggregation response to ristocetin, collagen and epinephrine + ADP were similar in both types of PCs, as was the mean fluorescence intensity for GPs Ib and IIb/IIIa. PCs prepared by the overnight-hold method did not differ from those obtained 6 h after collection in the percentage of platelets expressing CD62P (12.3 +/- 6.2% vs. 14.1 +/- 4.0%; p > 0.1) or CD63 (9.8 +/- 6.4% vs. 8.8 +/- 3.6%; p > 0.1). CONCLUSION: Prolonged holding of whole blood at 22 degrees C prior to component preparation does not increase the level of platelet activation.

Adenosine Diphosphate↗
PubMed1997

Growth of bacteria in platelet concentrates obtained from whole blood stored for 16 hours at 22 degrees C before component preparation.

BACKGROUND: Previous studies have shown that cooling whole blood to 22 degrees C immediately after collection allows it to be held for up to 16 hours before component preparation (overnight-hold method) without a significant decrease in the quality of components obtained. A study was designated to evaluate the effect of the overnight-hold method on the growth of bacteria in experimentally contaminated blood units. STUDY DESIGN AND METHODS: Twenty whole-blood units were inoculated with Staphylococcus epidermidis (300 colony-forming units [CFU]/mL; n = 10) or Escherichia coli (50 CFU/mL; n = 10) immediately after collection. Half the units of each group were fractionated 6 hours after collection and the other half after storage for 16 hours at 22 degrees C. Twenty additional whole-blood units were divided in two equal parts, one of which was white cell reduced before inoculation. These 40 half-units were inoculated with S. epidermidis or E. coli and processed by the overnight-hold method. The growth of bacteria was assessed in platelet concentrates on the second and fifth days of storage, in packed red cells on Day 35, and in fresh-frozen plasma after 60 days. RESULTS: No bacteria growth was detected in plasma or red cell units. On the second day of storage, both bacteria strains grew more slowly in platelet concentrates obtained from blood processed by the overnight-hold method. This difference disappeared for S. epidermidis on the fifth day. When white cell-reduced and non-white cell-reduced whole-blood units were compared, platelet concentrates from the latter showed a delayed growth of both bacterial strains on the second and fifty days of storage. CONCLUSION: Prolonged storage of whole-blood units at 22 degrees C before component preparation delays bacteria growth. This effect seems to be mediated by white cells.

Blood↗
PubMed1997

[A structural analysis of the entrance exams for specialist interns from 1994 to 1996].

In order to obtain specialist training in Portugal, doctors must pass a multiple-choice examination. The aim of this article is to present a structural and mathematical analysis of the examinations in the last three years. We based our work on the calculation of reliability coefficient of the examinations, and the difficulty and discrimination index of the questions and the examinations as a whole. A detailed analysis of the examinations, including that of each of the three hundred questions, will be published by the Department of Health Manpower in January, 1997.

Education, Medical↗
PubMed1997

[Blood pressure normal values in children and adolescents according to age and height].

The assessment of blood pressure in children and adolescents is of great importance in order to gain a better understanding of its pattern of evolution. The authors publish the normal values of blood pressure in Portuguese children and adolescents, according to age and sex, as well as the mean values of the 90th percentile, which are very important to separate normal children from those with high blood pressure. In this study the fifth Korotkoof sound is used to define diastolic blood pressure in all ages. New blood pressure tables are also published, for children and adolescents, that now include the height percentile for age and blood pressure. These new charts have been developed to guide practising clinicians in antihypertensive drug therapy, when indicated.

Adolescent↗
PubMed1997

[Blood pressure in a population of youngsters and adults observed after 17 years].

Many studies have assessed the blood pressure tracking among children and adolescents, but the results have been controversial. This study assessed the blood pressure tracking in 224 Portuguese school children and young adults following them for 17 years. The correlations obtained for systolic and diastolic blood pressure in both sexes are not very high, although positive and statistically significant. On the other hand, there was a stronger correlation between anthropometric variables and blood pressure and indices of obesity.

Adolescent↗
PubMed1996

Clinical and laboratory factors associated with platelet transfusion refractoriness: a case-control study.

In recent years clinical factors have largely surpassed alloimmunization as the predominant cause of platelet refractoriness. This makes it necessary to properly identify and weigh the non-immune factors that have a major impact of refractoriness. A case-control study is suitable for such an analysis, and to our knowledge has not previously been performed to assess this issue. Fifty-two refractory patients were compared with 52 control patients who were transfused at the same time. Only one transfusion event was analysed per patient. Clinical and laboratory data were recorded at the time of selected transfusion, and their association with refractoriness was investigated by the contingency table method and the Cox stepwise logistic regression. There were 16 (31%) patients with HLA antibodies in the index group and only one in the control group. The corrected count increment in the group of patients refractory due to HLA antibodies was significantly lower than that in non-alloimmunized refractory patients [median (range): 48.5 (-3560, 4614) and 4058 (-4417, 6886), respectively; U = 493, P < 0.0001]. In the multivariate analysis, factors associated with refractoriness were the presence of HLA antibodies (odds ratio (OR) 50.7; 95% CI 5.5-463); fever (odds ratio 7.2; 95% CI 2.5-21) and BMT because of chronic myeloid leukaemia (odds ratio 7.3; 95% CI 1.8-30). The latter two were the only factors that remained independently associated with refractoriness after excluding alloimmunized patients and their controls. We conclude that HLA antibodies are strongly associated with platelet transfusion refractoriness, but account for less than a third of these patients. Fever and BMT because of chronic myeloid leukaemia were the only non-immune factors independently associated with refractoriness.

Adolescent↗
PubMed1996

Influence of the red blood cell preparation method on the efficacy of a leukocyte reduction filter.

The performance of a leukocyte reduction bedside filter with different types of RBC concentrates was analyzed. Three types of RBCs were prepared: buffycoat-depleted RBCs suspended in saline-adenine-glucose-mannitol (SAGM)-additive solution (BC-RBCs; n = 20), RBCs suspended in SAGM-additive solution without buffy coat removal (SAGM-RBCs; n = 20), and RBCs drawn in CPDA-I conservative solution and processed for component preparation by the platelet-rich plasma method (CPDA-RBCs; n = 20). The units were filtered within 8 h of collection. One filter was used for every 2 units. High numbers of residual WBCs were found even in the units filtered first. Filtration of CPDA-RBCs resulted in a higher residual WBC content than SAGM-RBCs or BC-RBCs (p = 0.0032 and p = 0.0002, respectively). The filter performance strikingly decreased when the WBC load per filter exceeded 4 x 10(9) or the platelet load was less than 100 x 10(9). We conclude that filter performance varies with the WBC and platelet content of the RBC concentrates. Under the experimental conditions assayed in this study CPDA-RBCs are the least appropriate ones to be used for bedside leukocyte reduction.

Blood Transfusion↗
PubMed1996

Procoagulant effect of incompatible platelet transfusions in alloimmunized refractory patients.

The clinical effectiveness of platelet transfusion in refractory patients is still a subject of debate. We have evaluated the possible hemostatic effect of platelet transfusion in 16 alloimmunized thrombocytopenic patients whose platelet counts were less than 20,000/microliters. Platelet concentrates were always obtained by apheresis procedures from incompatible donors. The posttransfusion platelet recovery was greater than 15% only in 3 cases. In the first 6 patients, measurements of bleeding time performed immediately before transfusion were in all cases longer than 30 min and did not change significantly 10 and 60 min after platelet transfusions. In all patients, ex vivo perfusion experiments with Baumgartner's platelet adhesion model, using native nonanticoagulated blood, were performed immediately before and 10 and 60 min after transfusion. No difference in platelet deposition onto the subendothelial surface was observed after platelet transfusion. Unexpectedly, the deposition of fibrin on the subendothelial surface was statistically augmented in the posttransfusion studies. Quantification of thrombin-antithrombin complexes (TAT) in plasma showed statistically significant elevations (p < 0.01) in the posttransfusion samples (31.9 +/- 12.6 vs. baseline 5.8 +/- 1.7 ng/ml), not justified by TAT levels in the transfused material (2.3 +/- 0.17 ng/ml). Transfusion of incompatible platelets to refractory patients may activate coagulation mechanisms in the absence of an increase in peripheral platelet count.

Blood Group Incompatibility↗
PubMed1996

Ovarian dermoid cyst-associated autoimmune hemolytic anemia: a case report with emphasis on pathogenic mechanisms.

Autoimmune hemolytic anemia (AIHA) as a manifestation of ovarian dermoid cyst (ODC) is a rare paraneoplastic syndrome of unknown pathogenesis. Among mechanisms postulated to explain this association, cross-reactivity between cyst and red blood cell (RBC) antigens, and local production of RBC autoantibodies by intracyst B lymphocytes are the most likely. Studies to test these hypothesis were done in a patient diagnosed of AIHA associated with a nonpalpable ODC, in whom the AIHA subsided after tumor excision. The RBC-bound autoantibody was an IgG directed against the Rh complex. The cyst's fluid content lacked detectable RBC autoantibodies or immunoglobulins, the latter being measured by a high-sensitivity assay. It also failed to inhibit the ability of the purified autoantibody to agglutinate RBCs. Ovarian dermoid cyst histology disclosed that (1) the biotin-labelled RBC autoantibody did not bind to ODC structures; (2) scanty amounts of small mature lymphocytes (50% CD45RO+; 50% CD20+) were present only in a few tissue sections; (3) plasma cells producing IgM or IgG were extremely scarce; and (4) deposits of immunoglobulins were not detected into the ODC. These data fail to support any of the aforementioned hypotheses on the pathogenesis of this paraneoplastic syndrome. Other possible mechanisms are discussed, and a wider use of imaging diagnosis to search for ODC in women with AIHA is emphasized.

Adult↗