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1.
Article Dans Anglais | LILACS, VETINDEX | ID: biblio-976031

Résumé

Lachesis muta rhombeata (Lmr) is the largest venomous snake in Latin America and its venom contains mainly enzymatic components, such as serine and metalloproteases, L-amino acid oxidase and phospholipases A2. Metalloproteases comprise a large group of zinc-dependent proteases that cleave basement membrane components such as fibronectin, laminin and collagen type IV. These enzymes are responsible for local and systemic changes, including haemorrhage, myonecrosis and inflammation. This study aimed the isolation and enzymatic characterization of the first metalloprotease (Lmr-MP) from Lmr venom (LmrV). Methods and results: Lmr-MP was purified through two chromatographic steps and submitted to enzymatic characterization. It showed proteolytic activity on azocasein with maximum activity at pH 7.0-9.0. It was inhibited by EDTA (a metal chelator that removes zinc, which is essential for enzymatic activity) and no effect was observed with PMSF, iodoacetic acid or pepstatin (inhibitors of serine, cysteine and aspartyl proteases, respectively). Ca2+, Mg2+ and Ba2+ ions increased its activity, while Al3+, Cu2+, Ni2+ and Zn2+ inhibited it. Additionally, ZnCl2 showed a dose dependent inhibition of the enzyme. Lmr-MP activity was also evaluated upon chromogenic substrates for plasma kallikrein (S-2302), plasmin and streptokinase-activated plasminogen (S-2251) and Factor Xa (S-2222) showing the highest activity on S-2302. The activity in different solutions (5 mM or 50 mM ammonium bicarbonate, pH 7.8; 0.1% trifluoroacetic acid + 50% acetonitrile; phosphate buffer saline, pH 7.4; 50 mM sodium acetate, pH 4.0 or ammonium acetate pH 4.5) was also evaluated and the results showed that its activity was abolished at acidic pHs. Its molecular mass (22,858 Da) was determined by MALDI-TOF and about 90% of its primary structure was verified by high-resolution mass spectrometry using HCD and ETD fragmentations and database search against the sequence of closely related species. It is a novel enzyme which shared high identity with other snake venom metalloproteases (svMPs) belonging to the P-I group. Conclusion: The purification procedure achieved a novel pure highly active metalloprotease from LmrV. This new molecule can help to understand the metalloproteases mechanisms of action, the Lachesis envenoming, as well as to open new perspectives for its use as therapeutic tools.(AU)


Sujets)
Animaux , Peptide hydrolases , Venins de serpent , Lachesis trigonocephalus , Metalloproteases , Aspartic acid proteases
2.
Article Dans Anglais | LILACS, VETINDEX | ID: biblio-954786

Résumé

Background In the Atlantic forest of the North and Northeast regions of Brazil, local population often uses the fruit juice and the aqueous extract of leaves of soursop (Annona muricata L.) to treat Lachesis muta rhombeata envenomation. Envenomation is a relevant health issue in these areas, especially due to its severity and because the production and distribution of antivenom is limited in these regions. The aim of the present study was to evaluate the relevance of the use of soursop leaf extract and its juice against envenomation by Lachesis muta rhombeata. Methods We evaluated the biochemical, hematological and hemostatic parameters, the blood pressure, the inflammation process and the lethality induced by Lachesis muta rhombeata snake venom. We also assessed the action of the aqueous extract of leaves (AmL) and juice (AmJ) from A. muricata on the animal organism injected with L. m. rhombeata venom (LmrV) in the laboratory environment. Results LmrV induced a decrease of total protein, albumin and glucose; and increase of creatine kinase, aspartate aminotransferase, and urea concentrations. It provoked hemoconcentration followed by reduction of hematocrit, an increase in prothrombin time and partial thromboplastin time and a decrease of the blood pressure. LmrV induced the release of interleukin-6, an increase in neutrophils and changes in the serum protein profile, characteristic of the acute inflammatory process. LD50 values were similar for the groups injected with LmrV and treated or untreated with AmJ and AmL. Both treatments play a role on the maintenance of blood glucose, urea and coagulation parameters and exert a protective action against the myotoxicity. However, they seem to worsen the hypotension caused by LmrV. Conclusion The treatments with AmJ and AmL present some beneficial actions, but they might intensify some effects of the venom. Therefore, additional studies on A. muricata are necessary to enable its use as natural antivenom for bushmaster snakebite.(AU)


Sujets)
Morsures de serpent , Venins de serpent , Sérums antivenimeux , Lachesis trigonocephalus , Viperidae , Creatine kinase , Annona , Myotoxicité
3.
Niterói; s.n; 1997. 818 p. ilus, tab.
Thèse Dans Portugais | LILACS | ID: lil-682584

Résumé

Duas toxinas foram purificadas do veneno de Lachesis muta rhombeata com uma rendimento de aproximadamente 74 a 76%, empregando uma etapa de focalização isoelétrica preparativa seguida por gel filtração (HPLC)...Quando injetada em camundongos (0,25 ug/g), a LMR 47 induziu episódios de opistótono e giros, evidenciando a atividade giroxina. A análise histopatológica mostrou microhemorragias focais e outras alterações celulares a nível do cerebelo. A injeção intraplantar de 10ug da proteína, LMR 32, em camundongos induziu um incremento do volume (edema) de 45% e a inoculação de 0,1 e 0,25 ug/g da mesma proteína em ratos causou uma queda significativa na pressão arterial.


Sujets)
Animaux , Souris , Kallicréines , Lachesis trigonocephalus , Souris , Protéases à sérine , Venins de serpent
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