Search

Mutant hemoglobins thermodynamic phase transitions (HbS, HbC, etc.) have been the causes of serious hemoglobinopathies that have been affecting mankind since the dawn of human race. HbS polymerization is the best known of these transitions and the original cause of sickle cell anemia. Hydroxyurea (HU, NH2CONHOH) is widely used as the main drug administered for the treatment of Sickle Cell Anemia (SCA). Several hypotheses have been raised on the effects of HU on SCA. The most widespread and accepted one points to the production of fetal hemoglobin by the bone marrow, hindering the polymerization of deoxygen-ated HbS. Moreover, recent studies have reported that the short term in vivo effects of the HU have not been elucidated. By ordinary techniques of Materials Science (scanning electron microscopy, viscoelasticity, vis-cosity measurements, DSC and weight loss) we assessed the anti-nucleating, depolymerizing, and anti-gelling direct effects of HU on suspensions and type I bovine collagen gels. Scanning electron microscopy (SEM) revealed that the addition of HU results in the disappearance of the percolating three-dimensional network typical of collagen gels. Vane Rheometry tests pointed to a reduction in the yield stress (σ0) by add-ing HU into collagen gels with a concentration of 2.2 % w/v. In the liquid phase (sol), suspensions increased viscosity over time but decreased with the addition of HU, highlighting the depolymerizing effect of this substance. The weight loss of the sols is also affect by the addition of HU probably related to the lowering of the interactions between collagen/water as HU is added. The DSC essays indicated changes in the Cp curves as HU is added to the gel, decreasing the structural relaxations commonly observed in those gels. As a result, HU showed an effect on the phase transition of the studied gel, strengthening the hypothesis of anti-nucleating and anti-gelling action thereof on physical, reversible gels, and possibly on physical, reversible gels of mutant hemoglobin (HbS). Keywords: hydroxyurea, gelation, collagen, polymerization, sickle cell anemia.

Aragonite is a metastable polymorph of calcium carbonate found in mollusk’s shells, appearing in tiles and prismatic columns, cemented in a protein matrix - mainly proteins - that acts as a framework on which the aragonite is nucleated forming nacre, besides selecting the morphology of the nucleated cristaline phase. The presence of the mineralyzing organic matrix may affect osteoinductive properties of biogenic aragonite, hypothesis tested by combinated tests, comparing viability and bioactivity of biomineralizated aragonite and nacre. Bioactivity was observed by deposition of Ca-P (presumably calcium phosphate) on the surface of samples immersed in Simulated Body Fluid; biocompatibility was verified by adhesion with VERO cells; cytotoxicity and alkaline phosphatase activity assays were performed with human adipose stem cells (hASC). Samples were characterized by scanning electron microscopy and X-ray diffraction. Both materials showed similar behaviour on bioactivity assay; in contrast, exhibited different behaviours in the presence of hASC.

Applying the theories of Materials Science and Engineering to describe the composition and hierarchy of microstructures that comprise biological systems could help the search for new materials and results in a deeper insight into evolutionary processes. The layered microstructure that makes up the freshwater bivalve Limnoperna fortunei shell, an invasive specie in Brazil, was investigated utilizing SEM and AFM for the determination of the morphology and organization of the layers; and XRD was used to determine the crystalline phases of the calcium carbonate (CaCO3) present in the shell. The presence of the polymorphs calcite and aragonite were confirmed and the calcite is present only on the external side of the shell. The shell of L. fortunei is composed of two layers of aragonite with distinct microstructures (the aragonite prismatic layer and the aragonite sheet nacreous layer) and the periostracum (a protein layer that covers and protects the ceramic part of the shell). A new morphology of the calcite layer was found, below the periostracum, without defined form, albeit crystalline.

A presença de algumas macromoléculas no sangue esta associada a fenômenos de hiperviscosidade sangüínea e hiperagregação eritrocitária, quadro freqüente em algumas patologias (Diabetes, Hipertensão Arterial,etc). Este estudo investiga a agregação eritrocitária e sedimentação em amostras de sangue suíno, humano e bovino utilizando duas técnicas experimentais. O sangue humano e o de suínos agregam naturalmente formando roleaux enquanto o sangue bovino não agrega. A microestrutura foi investigada por microscopia óptica em amostras de sangue bovino (hematócrito 40%), suíno (hematócrito 1%, 5%, 10%, 30% e 40%) e humano (hematócrito 40%) e amostras de sangue bovino (hematócrito 40%) com adição de fibrinogênio nas concentrações de 5g/l, 10g/l, 20g/l, 25g/l e 30g/l. Os ensaios no Leitor de Microplacas foram realizados para se determinar o comportamento da agregação eritrocitária e sedimentação do sangue em função do hematócrito com e sem adição de fibrinogênio (para o sangue bovino). A microscopia óptica de luz transmitida permite a caracterização das microestruturas do sangue sob diferentes condições experimentais. Com o Leitor de Microplacas é possível distinguir-se três regiões no processo: a- Região I onde ocorre a agregação eritrocitária; b-Região II onde ocorre à predominância da etapa de sedimentação dos eritrócitos; e c- Região III onde ocorre um aumento lento da absorbância ocasionado também pela sedimentação dos eritrócitos. Associando a microscopia óptica com o Leitor de Microplacas é possível criar parâmetros para quantificar o processo de agregação e sedimentação do sangue, ferramentas úteis no diagnóstico e evolução de patologias que afligem tanto seres humanos como animais. The presence of some macromolecules in the blood is associated with blood hiperviscosity and hyperaggregation. We have studied erythrocyte aggregation and blood sedimentation on samples of swine, human and bovine blood. Bovine blood does not present erythrocyte aggregation while human and swine blood naturally aggregates at low shear rates and at stasis. The action of different bovine fibrinogen concentrations on the microstructure of bovine blood was analyzed and compared with swine and human blood. The phenomena were investigated using optical microscopy (to analyze blood microstructures) and Microplate Reader to measure absorbance (at a fixed wavelength, l=655nm) versus time(s). Experiments were performed using samples of bovine blood (hematocrit 40%), swine blood (H= 1%, 5%, 10%, 30% and 40%) and human blood (H= 40%); and samples of bovine blood (H= 40%) with the addition of bovine fibrinogen at different concentrations (5g/l, 10g/l, 20g/l, 25g/l and 30g/l). Using the Microplate Reader it was possible to distinguish three regions in the process: a-The region I where the erythrocyte aggregation occurs; b-region II where the sedimentation process is predominant and c-Region III where a very slow increase indicates that the persistence of sedimentation process. The association of the optical microscopy with the Microplate Reader technique makes possible the determination of quantitative parameters for the process of aggregation and sedimentation. These parameters will facilitate the diagnosis and a more accurate analysis of the evolution of pathologies that afflict both humans as animals.

A agregação eritrocitária excessiva está intimamente ligada à ocorrência de alguns processos patológicos e diretamente relacionada ao fenômeno de sedimentação eritrocitária. Neste trabalho investigamos as características cinéticas do processo de agregação e sedimentação eritrocitária. Para este estudo foram realizados ensaios de VHS (Velocidade de Hemossedimentação) com sangue suíno (hematócrito H de 20%, 25%, 30% e 35%) e absorbância em função do tempo, utilizando espectrofotometria UV-Vis, em amostras de sangue suíno (hematócrito de 1%, 5%, 10%, 15%, 20% e 30%) e sangue humano (hematócrito de 5%, 10%, 15% e 20%). Os ensaios de VHS indicaram que a sedimentação diminui com o aumento do hematócrito (H); entretanto, nos ensaios de espectrofotometria o fenômeno não é observado. O VHS é uma técnica essencialmente macroscópica enquanto a espectrofotometria fornece informações que facilitam uma análise da microestrutura do sangue e a compreensão das etapas dos processos de agregação e sedimentação. É possível distinguir, com o UV-Vis, quatro regiões no processo: a- Região I onde ocorre a agregação eritrocitária; b- Região II onde ocorre crescimento dos agregados e termina o início da sedimentação; c- Região III onde ocorre a sedimentação da amostra; e d- Região IV, um platô que indica a parte final do processo de sedimentação. Erythrocyte aggregation is at the root of many pathological processes and directly related to the phenomenon of erythrocyte sedimentation. Here we have investigated the kinetic characteristics of the erythrocyte aggregation and erythrocyte sedimentation of swine blood samples using the ESR (Erythrocyte Sedimentation Rate) technique and the UV-Vis spectrophotometer (absorbance) at a fixed wavelength (655 nm) versus time(seconds) of swine and human blood samples. For the ESR experiments of swine blood we have used samples with different hematocrits H= 20%, 25%, 30% e 35%. For the UV-Vis experiments of swine blood samples we have used the hematocrits H= 1%. 5%, 10%, 15% and 20% at a fixed 655 nm wavelength and for the human blood the hematocrits chosen were H=5%, 10%, 15% and 20%. Blood sedimentation rate data has been measured at 300s intervals during a period of 10,000s. While the UV-Vis assays had been carried through during 1.200s with data acquisition every 1s. ESR results show that the sedimentation rate of swine blood decreases as the hematocrit increases while the reverse phenomenon occurs in the UV-Vis experiments. From the ESR it is possible to distinguish three regions: I-the red blood cell aggregation process which is a plateau; II- the sedimentation process and III- a plateau indicating the end of sedimentation. With the UV-Vis it is possible to observe the sedimentation in much more detail with at least four regions: I-the aggregation slope; II-The aggregation and growth of roleaux followed by an "avalanche" of erythrocyte sedimentation; III-the sedimentation; IV- end of sedimentation.

In the past forty years considerable progress has been achieved on the knowledge of human blood as a non-Newtonian shear-thinning suspension, whose initial state, that is at rest (stasis) or at very low shear rates, has a gel-like internal structure which is destroyed as shear stress increases. The main goal of this communication is to describe the role of geometrical aspects during RBC (red blood cell) aggregate formation, growth and compaction on naturally aggregate (porcine blood) and non-aggregate (bovine blood) samples. We consider how these aspects coupled with tension equilibrium are decisive to transform red cell linear roleaux to three-dimensional aggregates or clusters. Geometrical aspects are also crucial on the compaction of red blood cell aggregates. These densely packed aggregates could precipitate out of blood- either as dangerous deposits on arterial walls, or as clots which travel in suspension until they block some crucial capillary.