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Ligaria cuneifolia (Lc) (R. et P.) Tiegh. (Loranthaceae), popularmente conocida como “muérdago criollo”, “liga” o “liguilla”, es una especie hemiparásita, que se encuentra en el centro y norte de Argentina. En medicina tradicional es utilizada para disminuir la presión arterial y el colesterol. Basándonos en las observaciones empíricas, planteamos como objetivo demostrar científicamente que Ligaria cuneifolia tiene propiedades hipotensoras e hipocolesterolémicas. En ratas Wistar machos adultas alimentadas con dieta normal, enriquecida en colesterol y en hiperlipémicas (alimentadas con High Fat Diet), demostramos que el tratamiento por vía intraperitoneal con una fracción enriquecida en Proantocianidinas extraídas de Lc (PLc) produce disminución del 40% del colesterol plasmático (Co) debido al aumento de la velocidad de excreción biliar de sales biliares, así como disminución de triglicéridos y LDLCo, sin producir cambios en la fluidez de la sangre. Evaluamos el efecto vasoactivo de PLc in vitro en anillos de aorta aislada de ratas determinando su tensión isométrica, presentando efecto vasodilatador dependiente de endotelio, ya que la remoción mecánica del mismo anula completamente la relajación. El tratamiento con infusión de extracto liofilizado de hojas y tallos de Lc ingerida tres veces por semana durante dos meses por pacientes hipercolesterolémicos de ambos sexos (edad: 50 ± 15 años), permitió observar descenso en los niveles Co y LDLCo, sin mostrar alteraciones en la fluidez de la sangre ni en la funcion hepático. Conclusión: Ligaria cuneifolia sería una potencial herramienta en la prevención de enfermedades cardiovasculares, por disminuir el Colesterol plasmático y presentar un marcado efecto hipotensor.

El accidente cerebrovascular (ACV) isquémico es causado por evolución de procesos aterotrombóticos que se relacionan con daño y disfunción endotelial debido a patologías crónicas como hipertensión arterial y dislipemia. En trabajos previos se ha informado sobre alteraciones hemorreológicas en el curso de la patología vascular cerebral, en particular el incremento en la agregación eritrocitaria (AE). El presente trabajo tiene como objetivo principal estudiar las modificaciones de las propiedades hemorreológicas y en particular de la AE, en 20 pacientes con ACV isquémico durante la etapa aguda, en comparación a un grupo control (n = 20) con similares factores de riesgo. Se determinó en plasma: concentración de fibrinógeno, proteína C reactiva y triglicéridos. En sangre: agregación eritrocitaria por densitometría óptica, obteniéndose el tamaño promedio de los agregados y la velocidad inicial del proceso, velocidad de eritrosedimentación, índice de rigidez eritrocitaria, viscosidad sanguínea, viscosidad plasmática y viscosidad sanguínea relativa estandarizada a un hematocrito del 45%. Se encontró que los eritrocitos de los pacientes con ACV agregaron a mayor velocidad (0,92 ± 0,64 vs 0,49 ± 0,24; p < 0,00001) y formaron agregados de mayor tamaño (1,84 ± 0,07 vs 1,81 ± 0,07; p

Ligaria cuneifolia (R. et P.) Tiegh. (Loranthaceae) is a hemiparasitic species that develops on different hosts. It has a wide geographic distribution ranging from Peru to central Argentina and southern Brazil. In Argentina it is popularly known as: “muerdago criollo”, “liga” or “liguilla”. This species is traditionally used as a hypotensive agent. Due to its morphological similarity, it constitutes the natural substitute for the European mistletoe (Viscum album L. -Santalaceae-). Like other species of the Loranthaceae family, L. cuneifolia is rich in flavonoids, especially flavonols that could be determinant of its pharmacological activity. Aqueous extracts proved to be inhibitors of the proliferation of LB tumor cells, alcoholic extracts have a high antioxidant activity, and infusions have the property of lowering plasma cholesterol in patients with a history of hypercholesterolemia. Considering this background information, and the difficulties experienced in its field cultivation, strategies are being developed to produce the metabolites responsible for its different biological activities in in vitro cultures.

Background: Epstein Barr Virus (EBV) infection has been associated with the Rheumatoid Arthritis (RA) etiopathology, thus, considering it a relevant etiological agent in the disease development. We have previously observed the Hyaluronic Acid (HA) serum increase in active RA patients (DAS 28-4 > 2.6) which might be responsible for the erythrocyte deformability, estimated by the erythrocyte Rigidity Index (RI). Objective: In the present study, we analyzed in one hundred RA patients if anti-EBV serum antibodies (TsEBV) and HA and RI levels are related with the disease activity. Results: [HA] s [[controls]]: 20.0 ± 9; [HA] s [[AR]]: 155.8 ± 44 (p< 0.00001 vs. controls (n:40). Antibodies anti-EBV (1/ TsEBV) [[controls]]: 2.55 ± 0.49; [[RA]]: 1.85 ± 0.35 (p< 0.00001 vs. controls). There were significant correlations between DAS 28-4 vs. log2 1/TsEBV (r: 0.70, p < 0.00001) and DAS 28-4 vs. RI (r: 0.75, p < 0.00001) in active RA patients. However, we observed a strong positive correlation between [HA] s in active RA patients vs. log2 1/TsEBV (r: 0.83, p < 0.00001) and [HA] s vs. RI (r: 0.91, p < 0.00001). Conclusion: The correlation obtained points out that the TsEBV may be related with the degree of RA activity determined by DAS28-4 and [HA]s in these patients. There was also a decrease in erythrocyte deformability estimated as RI, which is correlated with the DAS 28-4 activity index. Therefore, RI can be used as a reliable marker of RA activity. These findings might suggest a role of EBV infection regarding an autoimmune mechanism present in RA. Fil: Perez, Germán. Instituto de Biología Molecular y Celular de Rosario; Argentina. Universidad Nacional de Rosario; Argentina Fil: Svetaz, María José. Universidad Nacional de Rosario; Argentina Fil: Leda Urli. Universidad Nacional de Rosario. Facultad de Ciencias Médicas; Argentina Fil: Volpintesta, Ricardo. Universidad Nacional de Rosario. Facultad de Ciencias Médicas; Argentina Fil: Taborda, Miguel Ángel. Universidad Nacional de Rosario; Argentina Fil: Gardiol, Daniela Nora. Instituto de Biología Molecular y Celular de Rosario; Argentina. Universidad Nacional de Rosario; Argentina Fil: Gir, Adriana. Instituto de Biología Molecular y Celular de Rosario; Argentina. Universidad Nacional de Rosario; Argentina Fil: Luquita, Alejandra Nora. Universidad Nacional de Rosario. Facultad de Ciencias Médicas; Argentina. Universidad Nacional de Rosario; Argentina

BACKGROUND Ligaria cuneifolia (Lc) (R. et P.) Tiegh. (Loranthaceae) (Argentine mistletoe) is usually used in local folk medicine. OBJECTIVE We studied the effect of treatment with the Lc proanthocyanidin-enriched fraction (PLc) in rats fed with Cho-enriched diet on plasma lipids levels, the hemorheological parameters, and biliary secretion. METHOD Adult male Wistar rats were fed ad libitum with a Cho-enriched diet (Cho (97% purity) 8 g/kg of diet and corn oil 280 g/kg of diet) during 28 days. Then, were separated in six experimental groups (n=5 each one), which were injected ip every 24 h with: 1) saline solution (control group, C) and 2) PLc, 3 mg/100 g body weight (treated group, C+PLc), during 3, 7 and 10 days. Group C presented an increase in plasma levels of Cho and Triglycerides (TG), and also, accumulation of hepatic lipid droplets. Also, cell shape and their corresponding morphological index (MI) were altered too. RESULTS The treatment with PLc at 3, 7 and 10 days produces a diminution in the plasma Cho, LDL-Cho and serum TG levels, accompanied by a diminution of the lipid accumulation in the liver. The rates of bile acid output in bile can explain the diminution of plasma Cho, evidencing that some of the enzymes involved in the cholesterol conversion into bile acids could be up regulated by the treatment with PLc, leading to the observed increase bile flow. PLc treatment leads to a diminution of plasma levels of Cho and TG. CONCLUSION Essentially, the treatment with PLc, despite the duration produces a modification in hemorheological parameters approaching the values of the experimental group with standard diet. Plasma levels of Cho, LDL-Cho and TG represent selected markers to evaluate the effect of enriched extract from Ligaria cuneifolia. Further work is necessary to better evaluate the mechanisms by which PLc induces modifications in the lipids metabolism.

Increase in erythrocyte aggregation (EA) is pathognomonic for rheumatoid arthritis (RA), and its estimation through erythrocyte sedimentation rate (ESR) is part of DAS 28-4 activity diagnosis, with low correlation with EA and that does not discriminate the contribution of cell factors that increase aggregation. Objective: To analyse cell and plasma factors that might be involved in EA increase, to understand how RA affects blood components, thus modifying blood fluid behavior. Methodology: One hundred women presenting active RA were compared with age-matched controls (C). EA was measured by transmitted light, obtaining two parameters: 2k 2 n 0 , characterizing the aggregation process kinetics and s 0 /n 0 , estimating aggregates size. Cell factors assays: erythrocyte deformability, by filtration through nucleopore membranes, cell shape, by microscopy, and membrane fluidity by EPR. Plasma: total proteins and CRP, albumin, fibrinogen (Fb), by gravimetry, and IgG and IgM by single radial immuno-diffusion. Results: AR and C (x ± SE). 2k 2 n 0 : 31.83 ± 2.84, 23.75 ± 1.91; so/no: 0.92 ± 0.05, 0.87 ± 0.04. Rigidity index (RI): 14.79 ± 4.71, 6.92 ±1.31. Morphological index: 0.28 ± 0.03, 0.30 ± 0.05, n.s. Fb (mg/dl): 382 ± 80, 299 ± 70. IgG (mg/dl): 1580 ± 219, 1296 ± 158; IgM (mg/dl) 233 ± 28, 183 ± 23; albumin (g/dl) 3.84 ± 0.44, 3.77 ± 0.51 n.s. p < 0.05 accepted. Correlations: 2k 2 n 0 vs. Fb r = 0.66; so/no vs. Fb r = 0.51; 2k 2 n 0 vs. Igs r = 0.65; s 0 /n 0 vs. Igs r = 0.56. 2k 2 n 0 vs. RI r = -0.59; s 0 /n 0 vs. RI = -0.52, p < 0.05. Conclusions: Plasma factors, Igs and Fb increased aggregation, since RI is altered, this reduces the process efficiency regarding aggregation. Patients with active RA present an increased EA, with values modifications associated with the activity index DAS 28-4, thus becoming an RA activity indicator.

Electrostatic contributions to the conformational stability of apoflavodoxin were studied by measurement of the proton and salt-linked stability of this highly acidic protein with urea and temperature denaturation. Structure-based calculations of electrostatic Gibbs free energy were performed in parallel over a range of pH values and salt concentrations with an empirical continuum method. The stability of apoflavodoxin was higher near the isoelectric point (pH 4) than at neutral pH. This behavior was captured quantitatively by the structure-based calculations. In addition, the calculations showed that increasing salt concentration in the range of 0 to 500 mM stabilized the protein, which was confirmed experimentally. The effects of salts on stability were strongly dependent on cationic species: K(+), Na(+), Ca(2+), and Mg(2+) exerted similar effects, much different from the effect measured in the presence of the bulky choline cation. Thus cations bind weakly to the negatively charged surface of apoflavodoxin. The similar magnitude of the effects exerted by different cations indicates that their hydration shells are not disrupted significantly by interactions with the protein. Site-directed mutagenesis of selected residues and the analysis of truncation variants indicate that cation binding is not site-specific and that the cation-binding regions are located in the central region of the protein sequence. Three-state analysis of the thermal denaturation indicates that the equilibrium intermediate populated during thermal unfolding is competent to bind cations. The unusual increase in the stability of apoflavodoxin at neutral pH affected by salts is likely to be a common property among highly acidic proteins.

It was demonstrated that Ligaria cuneifolia (Lc) crude extract increased blood viscosity and decreased plasma cholesterol in rats. In the present study, we analyzed the Lc proanthocyanidin enriched fraction (PLc) to determine if it is capable of altering the hemorheological parameters while diminishing the plasma cholesterol. In vivo studies in adult male Wistar rats, randomized in three groups (n = 6 each one) were performed: 1. Control: saline intraperitoneal (i.p.); 2. PLc 0.6 mg/100 g body weight (b.w.) i.p. and 3. PLc 3 mg/100 g b.w. i.p., every 24 hours during 3 days. In vitro studies: with blood obtained by cardiac puncture, separated in aliquots and incubated with: 1. Saline solution (Control); 2. PLc 0.1 mg/mL, and 3. PLc 1.0 mg/mL, equivalent to doses in vivo experiments. The results demonstrated that in vivo PLc 0.6 and PLc 3 reduced plasma cholesterol (Cho) and LDL-Cho. Neither blood nor plasma viscosity was altered. Decrease of plasma cholesterol could be due to an increase of cholesterol and bile salts excretion leading to an increase of bile flow. In vitro experiments showed a direct interaction of PLc, at high concentration, with the erythrocyte membrane, inducing a switch from discocyte to stomatocyte. Only, PLc without hepatic metabolism produces hemorheological changes. Thus, PLc in vivo might be a pharmacological agent capable of decreasing plasma cholesterol. Fil: Dominighini, Alicia. Universidad Nacional de Rosario. Facultad de Cs.medicas; Argentina Fil: Ferrero, Mariana Cristina. Universidad Nacional de Rosario. Facultad de Cs.medicas; Argentina Fil: Crossetti, D.. Universidad Nacional de Rosario. Facultad de Cs.medicas; Argentina Fil: Ronco, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Fisiología Experimental (i); Argentina Fil: Gonzalves, Jose. Universidad Nacional de Rosario. Facultad de Cs.medicas; Argentina Fil: Urli, Leda. Universidad Nacional de Rosario. Facultad de Cs.bioquimicas y Farmaceuticas. Departamento de Cs.fisiologicas; Argentina Fil: Wagner, Marcelo Luis. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina Fil: Gurni, Alberto Angel. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina Fil: Carnovale, Cristina Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Fisiología Experimental (i); Argentina Fil: Luquita, Alejandra Nora. Universidad Nacional de Rosario. Facultad de Cs.medicas; Argentina

On the basis of sequence and three-dimensional structure comparison between Anabaena PCC7119 ferredoxin-NADP(+) reductase (FNR) and other reductases from its structurally related family that bind either NADP(+)/H or NAD(+)/H, a set of amino acid residues that might determine the FNR coenzyme specificity can be assigned. These residues include Thr-155, Ser-223, Arg-224, Arg-233 and Tyr-235. Systematic replacement of these amino acids was done to identify which of them are the main determinants of coenzyme specificity. Our data indicate that all of the residues interacting with the 2'-phosphate of NADP(+)/H in Anabaena FNR are not involved to the same extent in determining coenzyme specificity and affinity. Thus, it is found that Ser-223 and Tyr-235 are important for determining NADP(+)/H specificity and orientation with respect to the protein, whereas Arg-224 and Arg-233 provide only secondary interactions in Anabaena FNR. The analysis of the T155G FNR form also indicates that the determinants of coenzyme specificity are not only situated in the 2'-phosphate NADP(+)/H interacting region but that other regions of the protein must be involved. These regions, although not interacting directly with the coenzyme, must produce specific structural arrangements of the backbone chain that determine coenzyme specificity. The loop formed by residues 261-268 in Anabaena FNR must be one of these regions.

Ligaria cuneifolia (R. et P.) Tiegh. (Loranthaceae) (Argentine mistletoe) is usually used in local folk medicine “to produce an increase of blood fluidity and a decrease of plasma cholesterol level”. The present work was carried out to evaluate the effect of L. cuneifolia treatment on blood fluidity and biliary secretion. Adult male Wistar rats were divided into five groups (n = 5): control animals were injected intraperitoneally with water and treated rats received 1.5, 2.5, 3.5 and 5.5 mg/100 g body weight of aqueous extract of L. cuneifolia each 24 h during 3 days. The relative viscosity of blood [(? r) 45/Hct] was measured and the rigidity index (RI) in the diluted red cell suspensions was determined. L. cuneifolia treatment produces a significant increase in (? r) 45/Hct and in RI at doses of 2.5, 3.5 and 5.5 mg/100 g body weight. Also, a decrease of plasma cholesterol level was observed, which showed a negative association with RI increase (rs: -0.65; p < 0.05). Increases in bile flow and biliary...

Deformability of normocytic hypochromic human erythrocytes was studied as a function of their mean corpuscular hemoglobin content (MCHC). Erythrocyte populations with subnormal MCHC but with normal cell shape and volume and preserved cell surface area, were obtained by incomplete lysis, followed by cell resealing and density gradient separation. Erythrocyte rheological properties were measured in the erythrodeformeter, apparatus in which the erythrocyte laser diffraction pattern is recorded in shear flow. It was found that the deform ability index, proportional to the ellipticity of the diffraction pattern at the maximum shear stress, has a negative correlation with MCHC. Membrane elastic shear modulus and membrane surface viscosity have a positive correlation with MCHC. These facts are indicative of a concentration dependent membrane-hemoglobin interaction, and thus hemoglobin concentration must be included as one of the factors influencing erythrocyte deformability, even at low concentrations. We propose a simple model to demonstrate that the maximum oxygen delivery to tissues occurs at the physiological MCHC values.

UNLABELLED We tested the in vivo and the in vitro effects of both Ligaria cuneifolia catechin- and quercetin-enriched fractions on erythrocyte shape and deformability, and on plasma cholesterol level. For in vivo studies, adult male Wistar rats were randomized in three experimental groups which received intraperitoneally, once a day, 3 days: CONTROL saline solution (C; n = 6); catechin from L. cuneifolia, 0.60 mg/100 g body weight (CLc; n = 6), or quercetin from L. cuneifolia, 2.3 mg/100 g body weight (QLc; n = 6). For in vitro studies, blood samples obtained from male Wistar rats were divided into three fractions, which were incubated with saline solution (C), catechin (CLc; n = 5) and quercetin (QLc; n = 5), in a concentration equivalent to 0.60 mg/100 g body weight, and 2.3 mg/100 g body weight, respectively. CLc significantly reduced the rigidity index due to a diminished mean concentration volume. QLc induced erythrocyte rigidization (less deformability), thus increasing blood viscosity. Neither of the two treatments produced any changes in plasmatic or biliary excretion of cholesterol. Opposite results were observed in rigidity index with CLc and QLc. In vitro studies showed an interaction of both CLc and QLc with the erythrocyte membrane, which induced changes in the erythrocyte shape from discocyte to stomatocyte.

Ligaria cuneifolia (R et P) Tiegh. (Loranthaceae) (Lc) aqueous extract-treated rats by via intraperitoneal (i.p.) show increased blood viscosity and decreased plasma cholesterol (Chol) levels. In this work, we analize the effect of the vehicle polyvinylpyrrolidone (PVP) and that of the Methanolic Fraction of the extract of Lc (MFLc) on hemorrheological properties in vivo and in vitro and on biliary excretion. For in vivo conditions, adult male Wistar rats were divided in five experimental groups (n=5 each one) which were injected, every 24 hr during 3 days by via i.p., with: (1) saline solution (Control); (2) PVP 0.47 mg/100 g bw; (3) MFLc 0.95 mg/100 g bw plus PVP 0.47 mg/100 g bw; (4) PVP 12.5 mg/100 g bw; and (5) MFLc 23.0 mg/100 g bw plus PVP 12.5 mg/100 g bw. Intended for in vitro conditions, blood samples obtained by heart puncture were divided into three fractions, which were incubated with: saline solution (Control), PVP 12.5 mg%, and MFLc 25 mg% plus PVP 12.5 mg%. We demonstrated a direct effect of PVP alone and of MFLc "per se" on the erythrocyte membrane resulting in a cell shape change from dyscocyte to spherostomatocyte (MI more negative) as well as a decrease in erythrocyte deformability (increased RI). These changes induce an increase in blood viscosity. Decreased plasma Chol is a consequence of an increased bile salts biliary excretion.

Ligaria cuneifolia (R. et P.) Tiegh. (Loranthaceae) (Argentine mistletoe) is usually used in local folk medicine. This work focuses on the hemorrheologic parameters in the treatment with an aqueous extract of Ligaria cuneifolia (Lc) by two different administration routes: intraperitoneal (i.p.) and intravenous (i.v.). Adult male Wistar rats were injected by via i.p. or by via i.v. with: saline solution; 2.5 mg/100 g body weight of Lc and 5.5 mg/100 g body weight of Lc. The relative viscosity of blood (eta r)(45/Hct) was measured showing that Lc-treatment by via i.p. produced an increase of about 69% while Lc by via i.v. enhanced the parameter about 47%. All of Lc-treated animals showed a significant increase in the rigidity index (RI). The mean corpuscular hemoglobin concentration (MCHC) exhibited an increase of about 15% in all the treated groups. Lc-treatment by via i.p. produced a diminution of plasma cholesterol level associated with RI augmentation which induced an increase of (eta r)(45/Hct). By via i.v. Lc produces both RI and (eta r)(45/Hct) augmentation by increasing MCHC but without modifying plasma cholesterol level, indicating a direct Lc-action on the internal viscosity of the erythrocyte.

Previous studies indicated that the determinants of coenzyme specificity in ferredoxin-NADP+ reductase (FNR) from Anabaena are situated in the 2′-phosphate (2′-P) NADP+ binding region, and also suggested that other regions must undergo structural rearrangements of the protein backbone during coenzyme binding. Among the residues involved in such specificity could be those located in regions where interaction with the pyrophosphate group of the coenzyme takes place, namely loops 155–160 and 261–268 in Anabaena FNR. In order to learn more about the coenzyme specificity determinants, and to better define the structural basis of coenzyme binding, mutations in the pyrophosphate and 2′-P binding regions of FNR have been introduced. Modification of the pyrophosphate binding region, involving residues Thr-155, Ala-160, and Leu-263, indicates that this region is involved in determining coenzyme specificity and that selected alterations of these positions produce FNR enzymes that are able to bind NAD+. Thus, our results suggest that slightly different structural rearrangements of the backbone chain in the pyrophosphate binding region might determine FNR specificity for the coenzyme. Combined mutations at the 2′-P binding region, involving residues Ser-223, Arg-224, Arg-233, and Tyr-235, in combination with the residues mentioned above in the pyrophosphate binding region have also been carried out in an attempt to increase the FNR affinity for NAD+/H. However, in most cases the analyzed mutants lost the ability for NADP+/H binding and electron transfer, and no major improvements were observed with regard to the efficiency of the reactions with NAD+/H. Therefore, our results confirm that determinants for coenzyme specificity in FNR are also situated in the pyrophosphate binding region and not only in the 2′-P binding region. Such observations also suggest that other regions of the protein, yet to be identified, might also be involved in this process.

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

Flavodoxins are one domain α β electron transfer proteins that participate in photosynthetic reactions. All flavodoxins carry a molecule of flavin mononucleotide (FMN), non-covalently bound, that confers redox properties to the protein. There are two structurally distinct flavodoxins, short ones and long flavodoxins; the latter contain an extra loop with unknown function. We have undertaken the study of the stability and folding of the apoflavodoxin from Anabaena (a long flavodoxin) and the analysis of the interaction between the apoflavodoxin and FMN. Our studies indicate that apoflavodoxin folds in a few seconds to a form that is competent in FMN binding. The stability of this apoflavodoxin is low and its urea denaturation can be described by a two-state mechanism. The role of the different parts of the apoflavodoxin is the stability and structure of the whole protein is being investigated using mutagenesis and specific cleavage to generate apoflavodoxin fragments. The X-ray structure of apoflavodoxin is very similar to that of its complex with FMN, the main difference being the conformation of the two aromatic residues that sandwich FMN in the complex. In apoflavodoxin these groups interact with each other so closing the FMN binding site. Despite this fact, apoflavodoxin binds FMN tightly and rapidly, and the resulting holoflavodoxin displays a high conformational stability. We have found that one role of the aromatic residues that interact with FMN is to help to retain bound the reduced form of the cofactor whose complex with apoflavodoxin is otherwise too weak.

Background: Hyaluronic acid (HA) is present in many tissues; its presence in serum may be related to certaininflammatory conditions, tissue damage, sepsis, liver malfunction and some malignancies. In the present work, ourgoal was to investigate the significance of hyaluronic acid effect on erythrocyte flow properties. Therefore weperformed in vitro experiments incubating red blood cells (RBCs) with several HA concentrations. Afterwards, in orderto corroborate the pathophysiological significance of the results obtained, we replicated the in vitro experiment with exvivo RBCs from diagnosed rheumatoid arthritis (RA) patients, a serum HA-increasing pathology.Methods: Erythrocyte deformability (by filtration through nucleopore membranes) and erythrocyte aggregability (EA)were tested on blood from healthy donors additioned with purified HA. EA was measured by transmitted light andanalyzed with a mathematical model yielding two parameters, the aggregation rate and the size of the aggregates.Conformational changes of cytoskeleton proteins were estimated by electron paramagnetic resonance spectroscopy(EPR).Results: In vitro, erythrocytes treated with HA showed increased rigidity index (RI) and reduced aggregability, situationstrongly related to the rigidization of the membrane cytoskeleton triggered by HA, as shown by EPR results. Also, asignificant correlation (r: 0.77, p Conclusions: Our results lead us to postulate the hypothesis that HA interacts with the erythrocyte surface leading tomodifications in erythrocyte rheological and flow properties, both ex vivo and in vitro. Fil: Luquita, A.. Universidad Nacional de Rosario; Argentina Fil: Urli, L.. Universidad Nacional de Rosario; Argentina Fil: Svetaz, M. J.. Universidad Nacional de Rosario; Argentina Fil: Gennaro, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Universidad Nacional del Litoral; Argentina Fil: Giorgietti, M.. Universidad Nacional de Rosario; Argentina Fil: Pistone, G.. Universidad Nacional de Rosario; Argentina Fil: Volpintesta, R.. Universidad Nacional de Rosario; Argentina Fil: Palatnik, S.. Universidad Nacional de Rosario; Argentina Fil: Rasia, M.. Universidad Nacional de Rosario; Argentina