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M Rasia

Publications and source records attributed to M Rasia.

11 recordsLinked to original sources
PubMed2005

Study of intrinsic flow properties at the normal pregnancy second trimester.

During normal pregnancy the cardiovascular system undergoes extensive changes. In a previous work we demonstrated the role of the haemorheological profile as predictor of hypertensive gestational disorders through a retrospective study. In an attempt to clarify the rheological characteristics during normal gestation, blood and plasma viscosity, erythrocyte deformability and aggregation, and plasma fibrinogen levels were measured at second trimester of pregnancy. The interrelationships of different haemorheologic parameters, were analysed by Pearson correlation coefficient. The results showed decreased erythrocyte deformability, and increased plasma viscosity and erythrocyte aggregation due to increased fibrinogen in pregnant women. Despite these modifications blood viscosity did not increase, but there was a decrease in relative blood viscosity, therefore, a profile in accordance, from the haemorheological point of view, with the classical concept stating that haemodilution is of the utmost importance to maintain an adequate microcirculation in the uteroplacental unit during normal gestation.

Adolescent↗
PubMed2004

Haemorheological variables as a rheumatoid arthritis activity indicator.

OBJECTIVE: To investigate if blood hyperviscosity in RA patients is due to a reduced erythrocyte deformability and, therefore, turning it into a reliable activity indicator, as well as a therapy follow-up marker for this pathology. METHODS: (1) The haemorheological profile consisting of erythrocyte deformability, blood and plasma viscosity, and erythrocyte membrane fluidity was determined in 24 AR patients and 17 healthy controls. (2) A 4 year follow-up was carried on in 16 patients monitoring blood viscosity, erythrocyte deformability and biochemical variables in relation to clinical assessment of disease activity (Disease Activity Score "DAS 28-4"). RESULTS: Erythrocyte deformability and membrane fluidity were impaired in RA patients compared to controls (p<0.001). Blood viscosity was significantly increased and correlated with the cell rigidity index (r=0.85, p<0.0000) in RA patients. The follow-up showed a good correlation between haemorheological parameters and DAS 28-4 during disease evolution. CONCLUSION: our results support the hypothesis that in RA, blood hyperviscosity is determined by deformability loss, which in turn is due to a membrane rigidization. This could evidenced that a widespread cell membrane damage is expressed through an impaired erythrocyte deformability, turning haemorheological parameters into reliable tools to study disease evolution. The follow-up study enabled us to confirm that erythrocyte deformability is an efficient indicator of rheumatoid arthritis activity.

Adult↗
PubMed2003

Proposal of a haemorheological profile for early detection of hypertensive gestational disorders.

The objective of this study was to emphasise the potential power of simple and inexpensive haemorheological tests as predictors of hypertensive gestational disorders through a retrospective study. Blood samples of 195 primigravids with gestational age 18-23 weeks were studied. For data processing pregnant women were allocated into 3 groups, based on difference of SBP and DBP values measured at first and last consultation, and presence of proteinuria and oedema: Normotensive pregnants (n=149), hypertensive pregnants; n=26 and preeclamptic pregnants; n=20. Whole blood viscosity, plasma viscosity, erythrocyte rigidity and aggregability, haemoglobin, hematocrit, total protein, albumin and fibrinogen were assayed. Increased relative viscosity (eta(r)) (p<0.01), decreased erythrocyte deformability (p<0.05), lower O(2) release (p<0.01) and birth weight (p<0.01), showed a negative correlation with filterability index in preeclamptics. There was a decrease of erythrocyte deformability in hypertensive women. Erythrocyte deformability and blood viscosity could be an early indicator in preeclamptics, and erythrocyte deformability in hypertensive ones, therefore they could be considered alert factors in order to decide a thorough control in these patients to prevent further complications.

Birth Weight↗
PubMed2001

Influence of adsorbed plasma proteins on erythrocyte rheological properties: in vitro and ex vivo studies.

The influence of plasma protein adsorption on the mechanical properties characterizing erythrocyte behaviour under flow was studied in human and rats. The deformability index, elastic modulus and surface viscosity were measured by laser diffractometry. In in vitro studies, human and rat erythrocytes were washed to remove their original protein coating, and then incubated in saline-diluted plasma media. For erythrocytes incubated in the most diluted solutions (plasma/saline 1:3, v/v), the deformability index increased 30% for both species (human, P<0.01 and rat, P<0.2); the elastic modulus decreased 20% (human, P<0.05) and 60% (rat, P<0.01); and surface viscosity decreased 20% (human, P<0.05) and 40% (rat, P<0.01), relative to values for erythrocytes incubated in pure plasma. Ex vivo experiments were performed using rats. Plasma proteins were diluted replacing 15% volemic plasma by saline in three consecutive plasmapheresis steps. The rheological properties of erythrocytes, tested after each step, followed the general trends of the in vitro pattern. These results suggest that the decrease in plasma protein concentration affects blood rheology in two ways. The first is the well known decrease in plasma viscosity, and the second is an improvement of erythrocyte deformability, as has been shown in this work. Thus, a new argument supporting the benefits of normovolemic hemodilution in patients with poor peripheral perfusion is provided.

Adsorption↗
PubMed2001

Influence of plasma proteins on erythrocyte aggregation in three mammalian species.

The aggregation capacity of human erythrocytes lies between that of the non-aggregating bovine erythrocytes and the remarkably aggregating equine ones. As the ability to aggregate is attributed to cell factors and the composition of the plasma proteins, the role that plasma proteins play in the aggregation process in these three species was studied. Washed erythrocytes were suspended in phosphate-buffered saline (PBS; pH 7.4, 300 mOsm/L) plus polyvinylpyrrolidone (PVP) in a suitable concentration to obtain an average intensity of aggregation (control media). The superimposed effect of replacing 80% of the medium by either autologous plasma, serum or albumin solution was studied. The plasma proteins appeared to enhance aggregation by human and equine erythrocytes, but impaired this process in bovine erythrocytes. Some evidence was obtained supporting the existence of serum factors capable of reducing aggregation of erythrocytes in cattle and it was concluded that the non-aggregating behaviour of bovine erythrocytes may be due to the cells interacting particularly with the macromolecules in the serum.

Animals↗
PubMed1998

Red blood cell shape as a function of medium's ionic strength and pH.

Glycocalyx, the characteristic first line of interaction between membrane and environment, can be visualized as a polyelectrolyte anchored to a bending-resistant matrix. This structure has an amazing resemblance with the ionized monolayers, in which, the cohesion among hydrocarbon chains is counteracted by the repulsion among similarly charged ionic heads, and thus the balance determines the curvature of the membrane. Likewise, it could be assumed that in biological membranes, repulsion among similarly charged groups in the glycocalyx could generate different curving trends. Hence, the factors directly influencing the electrostatic interaction among surface charged groups were studied, assessing the effect of the medium's ionic strength (mu) and pH, in an extensive range of values around the physiological one. The results point out mu variations inducing different shapes, depending on whether mu values were lower or higher than the physiological ones; which could be explained by the polyelectrolyte theory. The occurrence of more invaginated shapes as the medium's pH decreases, and the opposite event, when the pH increases, could be attributed to the coupling between the dissociation of the glycocalyx ionic groups and the H+ concentration. The behavior of the cells with reduced surface charges (by neuraminidase degradation) supports the hypothesis that the observed mu and the pH effect on erythrocyte shape could be mediated by glycocalyx charged groups.

Adult↗
PubMed1998

Effects of an amphipathic drug on the rheological properties of the cell membrane.

Sodium thiopental, as other amphiphilic molecules, interacts with the membrane by inserting into the lipid bilayer and causing alterations of the membrane properties such as curvature and hypotonic lysis resistance. But can it modify the mechanical properties of the membrane? In the present work it was observed that sodium thiopental affected the membrane rheological properties by improving erythrocyte deformability; this effect resulted from a reduction of both the elastic modulus and surface viscosity. In erythrocytes devoid of sialic acid after treatment with neuraminidase, sodium thiopental membrane concentration was significantly higher than in normal cells, suggesting that drug access to the lipid bilayer be facilitated by the absence of the steric and electrostatic barrier of the glycocalyx negative charges. From a rheological point of view, desialated and normal cells showed the same response to the anesthetic as regards elastic modulus but in opposite direction if surface viscosity was considered. This finding supports the hypothesis that sodium thiopental molecules enter the bilayer of desialated cells in a higher proportion, as compared to the normal erythrocyte, promoting a disorganization that results in a greater inner friction. The changes in the rheological parameters, triggered by sodium thiopental, could be attributed to the bilayer contribution to the membrane mechanical properties, either directly or through interaction between the bilayer and the cytoskeleton.

Adult↗
PubMed1996

Comparison between internal microviscosity of low-density erythrocytes and the microviscosity of hemoglobin solutions: an electron paramagnetic resonance study.

The hypothesis that the internal viscosity of erythrocytes is governed by the intracellular hemoglobin (Hb) concentration is examined. Here viscosity is determined by labeling of the cytoplasmic reduced glutathione with the spin label maleimido-Tempo. Erythrocyte populations with different Hb concentrations in isosmotic conditions were obtained through incomplete lysis, followed by cell resealing, and discontinuous density gradient separation. This procedure maintains normal cell shape and volume. Microviscosity of membrane-free Hb solutions was measured by addition of spin labeled glutathione. It was found that microviscosity values are similar for the erythrocyte cytoplasm and for Hb solutions of equivalent concentrations, showing that the erythrocyte membrane does not have any influence on internal microviscosity. The dependence of the microviscosity on the concentration of Hb solutions was compared with results of macroscopic viscosity obtained by other authors. It is concluded that microviscosity is sensitive to individual properties of the Hb molecule (intrinsic viscosity), but that it is not sensitive to intermolecular interactions. As the microviscosity behavior as a function of Hb concentration is the same in Hb solutions as in the erythrocyte cytoplasm, the inferences regarding macroscopic viscosity in Hb solutions could be translated to the rheological properties of the erythrocyte cytoplasm. Thus, these properties could be predicted from the values of the mean corpuscular Hb concentration.

Biophysical Phenomena↗
PubMedDate not supplied

Kinetic model for erythrocyte aggregation.

It is well known that light transmission through blood is the most widely utilized method for the study of erythrocyte aggregation. The curves obtained had been considered empirically as exponential functions. In consequence, the process becomes characterized by an only parameter that varies with all the process factors without discrimination. In the present paper a mathematical model for RBC aggregation process is deduced in accordance with von Smoluchowski's theory about the kinetics of colloidal particles agglomeration. The equation fitted the experimental pattern of the RBC suspension optical transmittance closely and contained two parameters that estimate the most important characteristics of the aggregation process separately, i.e., (1) average size of rouleaux at equilibrium and (2) aggregation rate. The evaluation of the method was assessed by some factors affecting erythrocyte aggregation, such as temperature, plasma dilutions, Dextran 500, Dextran 70 and PVP 360, at different media concentrations, cellular membrane alteration by the alkylating agent TCEA, and decrease of medium osmolarity. Results were interpreted considering the process characteristics estimated by the parameters, and there were also compared with similar studies carried out by other authors with other methods. This analysis allowed us to conclude that the equation proposed is reliable and useful to study erythrocyte aggregation.

Blood Cell Count↗
PubMedDate not supplied

Effect of tetracaine chlorhydrate on the mechanical properties of the erythrocyte membrane.

Pharmacologically active agents that locate in the cell membrane are useful tools to investigate the interactions taking place between its molecular components. In the present work, the effect of tetracaine chlorhydrate (Tc) on the membrane mechanical properties of intact and desialated erythrocytes was studied. Our results evince the complex interaction between the drug and the membrane structures. The effect of Tc on erythrocyte shape suggests that this drug locates in the inner hemilayer of the lipid bilayer. Since Tc also modifies osmotic fragility and mechanical properties ascribed to the cytoskeleton, it can be inferred that the lipid bilayer has an effect on the rheology of the membrane, in a direct or indirect way, in this case through the close interaction with the structural proteins. Moreover, our results support the hypothesis of a second localization of the drug in the membrane, i.e., as monovalent cations intercalated among the glycocalix sialic endings, where it generates an effect superimposed on that produced from its typical site in the lipid bilayer.

Adult↗