Publications by authors named "Lomonte B"

Phospholipases A(2) (PLA(2)) are important constituents of snake venoms, being responsible for several of their toxic actions. Extracts from plants used in folk medicine were screened for inhibition of the enzymatic activity of myotoxin I, a PLA(2) from Bothrops asper. Piper umbellatum and Piper peltatum extracts tested positive, and their fractionation resulted in the isolation of 4-nerolidylcatechol.

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The activities of short synthetic, nonhemolytic peptides derived from the C-terminal region of myotoxin II, a catalytically inactive phospholipase A2 homologue present in the venom of the snake Bothrops asper, have been shown to reproduce the bactericidal activity of the parent protein. They combine cationic and hydrophobic-aromatic amino acids, thus functionally resembling the antimicrobial peptides of innate defenses. This study evaluated the antimicrobial and antiendotoxic properties of a 13-mer derivative peptide of the C-terminal sequence from positions 115 to 129 of myotoxin II, named pEM-2.

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Lys49 phospholipase A(2) homologues are abundant in viperid snake venoms. These proteins have substitutions at the calcium-binding loop and catalytic center which render them enzymatically inactive; however, they display a series of toxic activities, particularly cytotoxicity upon various cell lines in vitro. In this study we explored whether myotoxin II (MT-II), a Lys49 phospholipase A(2) homologue from the venom of the snake Bothrops asper, is capable of inducing various effects in a single cell type, using the lymphoblastoid B cell line CRL-8062 as a model.

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Group II phospholipase A(2) (PLA(2)) myotoxins isolated from Viperidae/Crotalidae snake venoms induce a rapid cytolytic effect upon diverse cell types in vitro. Previous studies suggested that this effect could be more pronounced on skeletal muscle myotubes than on other cell types, including undifferentiated myoblasts. This study utilized the murine skeletal muscle C2C12 cell line to investigate whether differentiated myotubes are more susceptible than myoblasts, and if this characteristic is specific for the group II myotoxic PLA(2)s.

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Envenomations after bites inflicted by snakes of the genus Bothrops constitute a public health hazard in Perú, and the intravenous administration of equine-derived antivenoms represents the only scientifically validated treatment. This study presents a preclinical assessment of the efficacy of two whole IgG antivenoms, prepared in Perú and Costa Rica, to neutralize the most relevant toxic effects induced by the venoms of Bothrops atrox, B. brazili, B.

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Myotoxin II, a Lys49 catalytically inactive phospholipase A(2) homologue from Atropoides nummifer venom, was purified, characterized and crystallized. The crystals belongs to the tetragonal system, space group P4(3)2(1)2, with unit cell parameters (a=b=68.66 and c=63.

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Early adverse reactions occur in a number of patients treated with heterologous antivenoms and have been associated with anticomplementary activity (ACA). In order to reduce the ACA of equine whole IgG antivenoms produced by caprylic acid fractionation, three different fractionation protocols were compared: (a) routine caprylic acid fractionation; (b) caprylic acid fractionation followed by beta-propiolactone treatment; and (c) caprylic acid fractionation followed by ion-exchange chromatography using a quaternary ammonium membrane. The three protocols yielded products with similar physicochemical characteristics and anti-Bothrops asper venom antibody titers, except that ion-exchange purified antivenom had a lower protein concentration.

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The aim of this work was to study the effect of recombinant ACL myotoxin, a Lys49PLA2 from Agkistrodon contortrix laticinctus snake venom and Lys49PLA2-derived synthetic peptides corresponding to the region 115-129 of venom of the two different Agkistrodon species on water permeability in the toad urinary bladder. The water flow through the membrane was measured gravimetrically in bag preparations of the bladder. The addition of recombinant ACL myotoxin-MBP (maltose binding protein) fusion protein (10 nM) to the bathing solution significantly increased (above 60%) the water transport compared with the control hemibladders.

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A new myotoxin was isolated from the venom of Bothrops atrox from Colombia. B. atrox myotoxin I is a homodimer, with a subunit molecular mass of 13,826, and a pI of 8.

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The venom of Bothrops asper induces severe coagulation disturbances in accidentally envenomed humans. However, only few studies have been conducted to identify components that interact with the hemostatic system in this venom. In the present work, we fractionated B.

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Snakebites constitute a serious public health problem in Central and South America, where species of the lancehead pit vipers (genus Bothrops) cause the majority of accidents. Bothrops envenomations are very painful, and this effect is not neutralized by antivenom treatment. Two variants of secretory phospholipases A2 (sPLA2), corresponding to Asp49 and Lys49 PLA2s, have been isolated from Bothrops asper venom.

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In 1984, the first venom phospholipase A2 (PLA2) with a lysine substituting for the highly conserved aspartate 49 was discovered, in the North American crotalid snake Agkistrodon p. piscivorus [J. Biol.

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Myotoxic phospholipases A(2) account for most of the muscle necrosis that results from envenenomation by crotaline snakes. In this study, we investigated the protective effect of fucoidan, a natural sulfated polysaccharide obtained from the brown seaweed Fucus vesiculosus, against the cytotoxic and myotoxic activities of a group of phospholipase A(2) myotoxins from crotaline snake venoms: Bothrops asper myotoxins I, II, III, and IV, Cerrophidion godmani myotoxins I and II, Atropoides nummifer myotoxins I and II, and Bothriechis schlegelii myotoxin I. All of the toxins tested were efficiently inhibited by fucoidan, in both their cytotoxic and myotoxic effects.

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Lys49 phospholipase A2 homologues constitute a group of catalytically-inactive proteins, present in the venoms of many crotalid snakes, which induce myonecrosis. Current evidence supports the mapping of their toxic site to the C-terminal region, where amino acids comprised within the sequence 115-129 appear to play a central role in toxicity. This study evaluated the possible toxic effects of several synthetic peptides corresponding to the sequence 115-129 of different Lys49 myotoxins, using in vitro cytotoxicity and in vivo myotoxicity assays.

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This study analyzed the publications of authors from Costa Rican institutions that were included in the Science Citation Index (SCI) during 1999-2001. Out of the 722 references detected, distributed in 328 journals, 90.7% corresponded to original research articles.

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Parenteral administration of horse- and sheep-derived antivenoms constitutes the cornerstone in the therapy of envenomations induced by animal bites and stings. Depending on the type of neutralising molecule, antivenoms are made of: (i) whole IgG molecules (150 kDa), (ii) F(ab')(2) immunoglobulin fragments (100 kDa) or (iii) Fab immunoglobulin fragments (50 kDa). Because of their variable molecular mass, these three types of antivenoms have different pharmacokinetic profiles.

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The ability of Lys49 and Asp49 phospholipases A(2) (PLA(2)), from Bothrops asper snake venom, to cause hyperalgesia was investigated in rats, using the paw pressure test. Intraplantar injection of both toxins (5-20 micro g/paw) caused hyperalgesia, which peaked 1h after injections. Incubation of both proteins with heparin, prior to their injection, partially reduced this response.

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Bothrops snake venoms are known to induce local tissue damage such as hemorrhage and myonecrosis. The opossum Didelphis marsupialis is resistant to these snake venoms and has natural venom inhibitors in its plasma. The aim of this work was to clone and study the chemical, physicochemical and biological properties of DM64, an antimyotoxic protein from opossum serum.

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Accidents by Thalassophryne nattereri fish venom are characterised by severe local symptoms and signs including pain of fast onset, oedema and necrosis with impaired muscle regeneration. These effects have been related to alterations in hemostatic mechanisms and cytolytic effects rather than to conventional inflammatory pathways. In this work we evaluated the effects induced by the venom on microcirculatory vessels, platelets and blood coagulation.

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In order to analyze its structure-function relationships, the complete amino acid sequence of myotoxin II from Atropoides (Bothrops) nummifer from Costa Rica was determined. This toxin is a Lys49-type phospholipase A(2) (PLA(2)) homologue, devoid of catalytic activity, structurally belonging to class IIA. In addition to the Asp49 --> Lys change in the (inactive) catalytic center, substitutions in the calcium-binding loop suggest that its lack of enzymatic activity is due to the loss of ability to bind Ca(2+).

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Background: To characterize the host response to venom from snakes of the family Viperidae in Costa Rica, we investigated the release of cytokines: IL-1, IL-6, IL-8, TNF-alpha, MIP-1beta, and RANTES in pediatric patients who were bitten by a snake.

Methods: Patients were included in this study if they were admitted to the hospital within 24 hours of the snakebite. Blood samples were taken immediately on admission to the hospital, and then at intervals of 3, 12, and 24 hours, and on days 3, 5, and 7 after the accident.

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We evaluated children (15-months old and older) with recurrent upper respiratory tract infections and normal levels of immunoglobulins in serum for specific polysaccharide immunodeficiency using an enzyme-linked immunosorbent assay method. Results showed that of 12 patients vaccinated with Act-HIB vaccine, one did not develop specific antibodies to Haemophilus influenzae type b, demonstrating that such immunodeficiency is present in Costa Rican children.

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Group II phospholipase A(2) (PLA(2)) myotoxins found in the venoms of Crotalidae snakes can be divided into 'Asp49' and 'Lys49' isoforms, the latter being considered catalytically-inactive variants. Previous studies on one Lys49 isoform, myotoxin II from Bothrops asper, indicated that its myotoxic activity is due to the presence of a short cationic/hydrophobic sequence (115-129) near its C-terminus, which displays membrane-damaging properties. Since the C-terminal region of different group II PLA(2) myotoxins presents considerable sequence variability, synthetic peptides homologous to region 115-129 of myotoxin II, but corresponding to B.

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A comparative study was performed on the venoms of the crotaline snake Atropoides nummifer from Guatemala and Honduras. SDS-polyacrylamide gel electrophoresis, under reducing conditions, revealed a highly similar pattern of these venoms, and between them and the venom of the same species from Costa Rica. Similar patterns were also observed in ion-exchange chromatography on CM-Shephadex C-25, in which a highly basic myotoxic fraction was present.

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Stings by Thalassophryne nattereri are responsible for envenomation of fishermen in north-eastern Brazil. Its venom induces prominent local tissue damage, characterized by pain, oedema and necrosis. The pathogenesis of acute muscle damage induced by T.

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