RESUMO
The South American opossum Didelphis marsupialis is known to be highly resistant to snake envenomation. In this paper it is shown that the opossum serum inhibits haemorrhage induced by both Crotalinae and Viperinae venoms. Tested against Bothrops jararaca (jararaca) venom, the antibothropic complex (ABC) isolated from the opossum serum was at least six times more antihaemorrhagic than the commercial antivenom. ABC showed no proteolytic activity by itself and was not hydrolysed by the venom. It inhibited the hydrolysis of casein by B. jararaca venom, but did not inhibit its hydrolytic activities upon N alpha-benzoyl-L-arginine ethyl ester (BAEE) and N alpha-benzoyl-DL-arginine p-nitroanilide (BAPNA). The inhibitor did not interfere with trypsin and bacterial collagenase activities on BAPNA and N-(3-[2-furyl]acryloyl)-Leu-Gly-Pro-Ala (FALGPA), respectively. It reduced chymotrypsin hydrolysis of N-acetyl-L-tyrosine ethyl ester (ATEE) because ABC is also a substrate for this enzyme. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, B. jararaca venom preferentially degraded fibrinogen A alpha-chain and fibrin alpha-chain. Tested on extracellular matrix proteins, the venom hydrolysed collagen IV, gelatins I and V, laminin and fibronectin, besides depolimerizing collagen I alpha-chain dimers. Fibrillar collagen V was not digested. These hydrolyses were inhibited by ABC and by EDTA. Our results show that the antibothropic complex is a venom metalloproteinase inhibitor, which could, at least partially, account for its antihaemorrhagic activity. Electrophoretic evidence indicated non-covalent complex formation between the antihaemorrhagic factor and component(s) of B. jararaca venom.
Assuntos
Antivenenos/uso terapêutico , Bothrops , Venenos de Crotalídeos/antagonistas & inibidores , Hemorragia/tratamento farmacológico , Gambás/sangue , Venenos de Víboras/antagonistas & inibidores , Animais , Hemorragia/induzido quimicamente , Hidrólise , CamundongosRESUMO
The pathogenesis of hemorrhage and other local effects induced by the metalloproteinase BaP1, isolated from Bothrops asper venom, was investigated using various in vivo and in vitro models. Upon intramuscular injection in mice BaP1 caused rapid hemorrhage in muscular and adipose tissues. Vital microscopy using mouse cremaster muscle evidenced the formation of multiple hemorrhagic foci of an explosive character, originating from capillaries and small venules. In contrast to crude B. asper venom, which besides hemorrhage also induced myonecrosis and thrombosis, vital microscopy detected only hemorrhage after application of BaP1, during the 40-min observation period. However, histological observation in mouse gastrocnemius muscle evidenced a few areas of limited myonecrosis was followed by an incomplete regenerative response, since regenerating muscle fibers were interspersed with fibrosis in some areas. Metalloproteinase BaP1 was not cytotoxic to human and murine endothelial cells in culture, causing only a mild detachment from the culture plate. BaP1 hydrolyzed types I and IV collagen, fibronectin, and laminin upon incubation with these extracellular matrix proteins in vitro. These results suggest that hemorrhage induced by BaP1 is due primarily to the proteolytic degradation to basement membrane components of microvessels and that endothelial cell disruption may be a secondary event. It is concluded that, in addition to hemorrhage, BaP1 contributes to the local tissue damage caused by the venom by inducing myonecrosis, inflammation, and extracellular matrix alterations.
Assuntos
Venenos de Crotalídeos/enzimologia , Metaloendopeptidases/toxicidade , Animais , Bothrops , Creatina Quinase/sangue , Endotélio Vascular/enzimologia , Proteínas da Matriz Extracelular/metabolismo , Masculino , Camundongos , Músculos/efeitos dos fármacos , Músculos/ultraestruturaRESUMO
No immunological cross-reactivity was observed between BaH1 and BaP1, two hemorrhagic metalloproteinases isolated from B. asper venom, by gel immunodiffusion, Western blotting and neutralization studies. Cross-reactivity was detected with antisera against these toxins in several crotaline and viperine snake venoms by ELISA, whereas no reactivity was observed with either antiserum against the venoms of Bothrops nummifer, Crotalus durissus terrificus, Vipera russelli and several elapid venoms. Antiserum against native BaH1 neutralized hemorrhagic activity of the venoms of B. asper, B. atrox, B. jararaca, Crotalus atrox, C. durissus durissus, Echis carinatus and Trimeresurus flavoviridis, being ineffective against the venoms of Agkistrodon bilineatus and Lachesis muta.
Assuntos
Venenos de Crotalídeos/enzimologia , Venenos de Crotalídeos/imunologia , Hemorragia/induzido quimicamente , Metaloendopeptidases/imunologia , Animais , Bothrops , Hemorragia/imunologia , Soros Imunes/farmacologia , Metaloendopeptidases/toxicidadeRESUMO
Respiratory syncytial virus (RSV), a common cause of respiratory infections in children, has only rarely been associated with acquired heart disease. We reviewed hospital charts, rhythm strips, and electrocardiograms of 8 infants with abnormal supraventricular tachycardia (SVT), > 250 beats/min, associated with acute RSV infections. Cultures of nasopharyngeal specimens from six of eight infants grew RSV. Two infants with negative viral culture results had symptoms typical of an RSV infection during a documented RSV epidemic. Two infants had congenital heart defects. Seven of the eight infants had an ectopic atrial tachycardia, chaotic atrial tachycardia, or atrial flutter, and five of eight had episodes of nonsustained wide-complex SVT. One patient was initially treated with intravenously administered lidocaine for an incorrect diagnosis of ventricular tachycardia. SVT was unrelated to either beta-agonist therapy or hypoxic episodes. SVT did not recur after discharge in any infant with a structurally normal heart. Both patients with structural heart disease had recurrences of SVT. We conclude that RSV infections in infants may be associated with unusual atrial tachycardias and that the diagnosis may be complicated by episodes of nonsustained, wide-complex tachycardias. In patients with RSV and structurally normal hearts, chaotic and ectopic atrial tachycardias are self-limited and do not require prolonged drug therapy.