Lauro Mello Vieira

Revisão sobre óxido nítrico

Nitric oxide (NO) is an inorganic and incolor free radical gas containing seven electrons from nitrogen and eigth from oxigen and one unpaired electron. Until midlle of 1980 decade, NO was considered as a member of an undesiderable and envirommental poluents family and as a potential carcinogen agents. At the moment, NO constitutes one of the most important mediators of intra and extra cellular processes. This radical is produced from the L-arginine envolving a reaction mediated by constitutive and inducible NO synthase. NO presents a dubious role, sometimes it brings benefits, sometimes it is harmful. It is envolved in the vascular relaxing and it protects the blood vessels. It constitutes an important cytotoxic mediator on immune activated cells capable of killing pathogenic agents and tumor cells. It also has a role as messager/modulator in a variety of essential biological processes. However, NO is a potentially toxic agent, whose toxicity could be particulary denoted in stress oxidative conditions, by the generation of O2 intermediates and antioxidant system deficiency. Laboratory measurement of NO is complex and the characterization of specific activators and inhibitors of the NO synthesis constitutes the new challenge for a better comprehension and treatment of a number of pathologies. NO studies have been one of the main target for pharmaceutical industries.

Acquired Pelger–Huët: What does it really mean?

Pelger-Huët anomaly (PHA) is a benign inherited condition characterized by hyposegmentation of the neutrophils nucleus and excessive chromatin clumping. An acquired neutrophil dysplasia similar to PHA has been described in hematological diseases and in some clinical conditions. It has been known as acquired or pseudo PHA. Although some hypotheses have been proposed to explain this phenomenon, the mechanism of nuclear change is still unclear. Only the laboratory and clinical data combined will yield a better understanding on the need for follow-up and management of patients in the appropriate cases. In addition, a possible cause of pseudo PHA must always be investigated to add insights to the full understanding of this abnormality. Whether this neutrophil phenomenon has clinical implications remains to be elucidated. It is clear that only a small number of patients under drugs (immunosuppressive and others) may present these neutrophil abnormalities. Most of them do not show this phenomenon and we are unable to explain the different responses in drug users. Whether these patients display a predisposition for developing bone marrow or other diseases in the future, it is a very intriguing matter and only a follow-up will solve this question.

Revisão sobre alterações hemostáticas na doença hipertensiva específica da gravidez (DHEG)

Preeclampsia (PE) characterises by development of hypertension, proteinuria and swelling in pregnant women around 20th pregnancy week. The hemodynamic changes observed in the normal pregnancy comprising renal and cardiovascular adaptations that did not occur in PE. The most important feature of this disease is a pronounced arteriolar vasoconstriction leading to a increase of the peripheral vascular resistance responsable to high blood pressure. Evidences of platelet consumption and endothelial cell disfunction have been observed in PE. Conflicting opinions related to the fibrinolytic system have been raised on the literature including increase, decrease or even no changes in this system preeclamptic compared to normal pregnant women. Efforts have been carried out in order to define hemostatic parameters with diagnostic and prognostic value, considering that PE diagnosis is essentially based on clinical data and often hard to be established. In this way, platelet count, thrombomodulin, thrombin-antithrombin complex and plasminogen activator inhibitor type 2 measurement were performed as helpful parameters for PE diagnosis. However, it remains to be established the usefulness of all these laboratory markers. Recently, it was suggested an association between the occurence of pregnancy complication, including PE, and the presence of genetic mutations which favors the development of thromboembolic events. It has been proposed a hemostatic the assessment in preeclamptic women, even if there was no previous thromboembolic episody, by using thrombotic markers as an useful parameter for planning future pregnancies, once PE recurrence is about 20%.

Plasma Total Homocysteine Levels and Methylenetetrahydrofolate Reductase Gene Polymorphism in Patients with Type 2 Diabetes Mellitus

Background: Thrombotic episodes account for approximately 80% of deaths in type 2 diabetic patients. Hyperhomocysteinaemia is a well recognized independent risk factor for atherosclerosis and thromboembolism. Increased homocysteine levels may occur due to a number of factors including inherited gene polymorphism of methylenetetrahydrofolate reductase (MTHFR) C677T. Here, we evaluate plas- ma total homocysteine (tHcy) levels and frequency of the MTHFR C677T gene polymorphism in asymptomatic healthy volunteers and type 2 diabetic patients with hypertension but without nephropathy. We have also investigated the relationship between tHcy levels and the presence of MTHFR C677T gene polymorphism. Methods: Plasma tHcy levels and MTHFR C677T genotype were investigated in a total of 53 subjects. These included asymptomatic healthy volunteers (n = 16), patients with type 2 diabetes (n = 7), subjects with hypertension (n = 12) and patients with both type 2 diabetes and hypertension (n = 18). Renal function, serum lipids and other metabolites were also assessed. Results: There was no significant difference in tHcy levels between the groups studied. The frequency of MTHFR C677T gene polymorphism observed was similar to that obtained for the general Brazilian population. In patients with type 2 diabetes and hypertension but without impaired renal function, we observed no meaningful correlation between increased tHcy levels and the presence of MTHFR C677T gene polymorphism. Conclusions: Type 2 diabetics who are homozygous or heterozygous for the MTHFR C677T gene polymorphism showed normal tHcy levels. Our results further suggest that diabetes without an associated adverse risk profile is not an independent correlate of increased tHcy levels.

Platelet antiaggregants in primary and secondary prevention of atherothrombotic events.

Atherothrombosis and its complications are currently the leading cause of worldwide mortality and its incidence is increasing . Platelets play an essential role in the pathogenesis of atherothrombotic events, justifying the use of antiplatelet agents in their prevention. Thus, it is essential to know the efficacy and safety profile of these drugs in primary and secondary prevention of atherothrombotic events. In this context, this review was performed with the aim of describing and summarizing the outcomes of the main trials involving the use of antiplatelet agents in the two levels of prevention, and evaluating the effectiveness and major adverse events related to therapy.

Pseudo-Pelger-Huët in kidney-transplanted patients.

Pelger-Huët anomaly is an inherited condition characterized by hyposegmentation of the neutrophil nucleus and excessive chromatin clumping. Acquired Pelger-Huët, also known as pseudo-Pelger-Huët, has been described in several clinical conditions including transplant recipients who received immunosuppressive drugs. The incidence of pseudo-Pelger-Huët in kidney transplant patients, characterized as neutrophil dysplasia, was observed in 9 of 170 patients (5.3%) at the São Francisco Hospital de Assis, Belo Horizonte, Brazil. Awareness of possible circulating neutrophil alterations in transplant patients is important for laboratory professionals who should report these findings of cell changes. It should be highlighted that the poor segmentation and the chromatin hypercondensation observed initially in pseudo-Pelger-Huët patients can be suggestive of early-stage neutrophils. Only a combination of laboratory and clinical data will facilitate a better understanding of this anomaly and its correct follow-up and management.

Captura de lipossomas pelas placas de Peyer de camundongos após administração oral

The aim of this study was to employ a model protein, the bovine serum albumin (SAB), radiolabelled with 99mTechnetium (99mTc) (99mTc-SAB) and encapsulated into liposomes, in order to determine the amount de 99mTc-SAB taken up by Peyer´s patches following per os administration in mice Balb/c. The 99mTc-SAB, labelling yield of 94.9±2.4 % (n=25), was encapsulated within multilamellar large vesicles (MLV), small unilamellar vesicles (SUV) or large unilamellar vesicles (LUV) composed of soybean phosphatidylcholine (PC); PC and cholesterol (CH) (molar ratio 8/2); PC, CH and phosphatidylglicerol (PG) (molar ratio 7/2/1) or distearoylphosphatidylcholine (DSPC), CH and PG (molar ratio 7/2/1). A gel electrophoresis and a gel immunoelectrophoresis, using a specific anti-SAB serum immunoglobulin, were employed to evaluate the integrity of SAB after labelling with 99mTc and after encapsulation into liposomes. Labelling with 99mTc and liposome encapsulation did not result in degradation of SAB. SUVencapsulated-99mTc-SAB was preferentially taken up by Peyer´s patches. Uptake of LUV-encapsulated-99mTc-SAB by Peyer´s patches was reduced when compared with that observed for the SUV-encapsulated-99mTc-SAB. 99mTc-SAB encapsulated into SUV composed of PC or PC/CH was not uptaked by Peyer´s patches. The lipid composition (PC or DSPC/CH/PG) of SUV did not modify 99mTc-SAB uptake by Peyer´s patches. In conclusion, SUV might be an effective carrier for unstable antigens administered per os to induce mucosal immune response.

Otimização da técnica de citometria de fluxo para análise do fator tissular em monócitos de sangue periférico

The development of the flow cytometric assay using monoclonal antibodies labeled with different fluorescent substances enables the identification of a particular cell population even if it is present in heterogeneous cell samples. This technique has been applied to oncohematology and bone marrow transplantation studies. Two combined fluorescent monoclonal antibodies enable the study of a particular cell population in the expression of procoagulant substances produced by cells involved in homeostatic mechanisms. The application of this methodology creates the perspective of pathophysiologic studies related to hypercoagulability states. Considering that monocytes are highly involved in pathophysiologic mechanisms contributing to thrombus formation and atheromatous plaques and that Tissue Factor represents the principal physiologic activator of the clotting system, this study constitutes a potential tool for obtaining new insights of the role of monocytes in diseases associated to hypercoagulability states. The present work aimed to establish the optimization of conditions for measuring the tissue factor expression in monocytes stimulated or not by lipopolysaccharides from Escherichia coli and analyzed by flow cytometric assay based on a previous methodology. Blood samples were collected from healthy subjects and divided in two age ranges. Studies on monocytes were carried out comparing two methods of analysis, which define the percentage of cells expressing tissue factor on their surface. From the results, it was concluded that there is no difference between the two age ranges related to the tissue factor expression in monocytes. In addition, there were no significant differences between the two assessed methods of analysis.

Avaliação da incidência das mutações G1691A no gene do fator V (fator V Leiden) e G20210A no gene da protrombina em pacientes com diabetes mellitus tipo 2

Em virtude da alta prevalencia de Diabetes mellitus tipo 2 (DM2) na populacao mundial e da alta taxa de mortalidade decorrente de eventos tromboticos, e de extrema importância o conhecimento das alteracoes no sistema hemostatico em pacientes portadores deste disturbio. A mutacao no gene do fator V (G1691A - fator V Leiden) em heterozigose ou homozigose confere aos portadores o fenotipo de resistencia a proteina C ativada, situacao que aumenta em sete vezes o risco de desenvolver uma trombose. A mutacao G20210A no gene da protrombina resulta no quadro de hiperprotrombinemia, aumentando o risco de trombose em tres vezes. A pesquisa dessas mutacoes de interesse em trombofilia e de grande relevância considerando que a presenca das mesmas pode exacerbar o estado de hipercoagulabilidade acelerando as complicacoes no diabetes. O presente estudo teve como objetivo avaliar a incidencia dessas mutacoes em individuos higidos (Controle, n=16), pacientes com DM2 (n=7), com hipertensao (HAS, n=12) e com DM2+HAS (n=18), atraves da tecnica de PCR-RFLP. As frequencias encontradas nos grupos estudados foram baixas e similares aquelas observadas na populacao brasileira em geral. Nao foi possivel estabelecer correlacao entre a presenca da mutacao e caracteristicas especificas de cada grupo. Dessa forma, ainda nao esta claro se ha ou nao uma maior prevalencia dessas mutacoes em individuos diabeticos e se a presenca das mesmas contribui para o aumento do risco de desenvolver trombose nesses individuos, sendo necessario estudos mais amplos para a elucidacao da questao.

Avaliação de coagulação, fibrinólise e proteína C em pacientes de risco e com doenças coronarianas

Hemostasia consists of a balance between procoagulants and anticoagulants involving vessels, platelets, clot and fibrinolysis proteins and natural anticoagulants. All the components are interrelated constituting the coagulation, anticoagulation and fibrinolysis systems. Many genetic or acquired factors may contribute to break this balance leading to hypo or hypercoagulability states. In coronarian diseases, such as angina pectoris and acute myocardial infarction, an exacerbated activation of the platelets and clot proteins occurs, favouring thrombus formation. In order to restore hemostasia, the fibrinolytic system intervention occurs, what promotes the clot lysis removing obstruction from the vessels. In this work, the clot and fibrinolysis systems and protein C, a natural anticoagulant, were evaluated. Twenty patients with coronarian diseases including angina pectoris (n = 8) and acute myocardial infarction (n = 12) were studied, besides patients showing potential risk for developing cardiovascular disease (n = 17). The group of infarcted patients was matched to healthy subjects under the clinical and laboratory points of view (control group, n = 12). The results for angina and infarction groups revealed a significant difference in fibrinogen plasma levels compared to control group. Activated protein C plasma levels also showed a significant difference between the risk and infarction groups. The other hemostatic evaluated parameters did not differ significantly between the studied groups. However, a tendency to hypercoagulability was observed in the patient groups compared to the control group.