Navegando por Palavras-chave "Loxosceles"

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    Analysis of therapeutic benefits of antivenin at different time intervals after experimental envenomation in rabbits by venom of the brown spider (Loxosceles intermedia)
    (Elsevier B.V., 2009-05-01) Pauli, Isolete; Minozzo, Joao Carlos; Silva, Paulo Henrique da; Chaim, Olga Meiri [UNIFESP]; Veiga, Silvio Sanches; Univ Fed Parana; Universidade Federal de São Paulo (UNIFESP)
    Bites by the brown spider (Loxosceles spp.) are an important health problem in South America, where three species predominate (Loxosceles laeta, Loxosceles gaucho, Loxosceles intermedia). Brown spider bites (loxoscelism) induce a block of cutaneous necrosis and, less commonly, may cause fatal systemic poisoning. A variety of controversial protocols are used to treat loxoscelism, while treatment with antivenin is the only venom specific treatment.Here we studied the action of the venom as well as the response to the antivenin for Loxosceles through an experimental study that simulates bites of L intermedia (bites of this species are the most common in Brazil). Beneficial effects are known for antivenin applied quickly (within 4 h) after envenomation. Here we wished to examine the temporal development of the brown spider bite as well as the temporal patterns of the action of the antivenin to determine the time limits for beneficial use of the antivenin after envenomation. This information is important since most patients only appear for treatment several hours after being bitten.New Zealand rabbits were experimentally exposed to the venom from brown spiders by the injection of venom from L intermedia (2x minimum necrotic dose), followed at regular time intervals by antivenin. the use of the loxoscelic antivenin - CPPI (4 mL per animal) minimized the effects of envenomation when applied for up to 12 h after the injection of the venom, as evaluated by cutaneous (erythrema, edema, ecchymosis and necrosis) and systemic (blood cell and platelet counts, hematimetrics and fibrinogen dosage) criteria. Also, antivenin reduced the size of the necrotic area when applied up to 48 h after envenomation. Thus, therapy with loxoscelic antivenin, CPPI, may provide beneficial results by interfering with envenomation well after the bite occurred and therefore may become an important tool for medical treatment of brown spider bites. (C) 2009 Elsevier B.V. All rights reserved.
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    Astacin-like metalloproteases are a gene family of toxins present in the venom of different species of the brown spider (genus Loxosceles)
    (Elsevier B.V., 2010-01-01) Trevisan-Silva, Dilza; Gremski, Luiza H. [UNIFESP]; Chaim, Olga M.; Silveira, Rafael B. da; Meissner, Gabriel O.; Mangili, Oldemir C.; Barbaro, Katia C.; Gremski, Waldemiro; Veiga, Silvio S.; Senff-Ribeiro, Andrea; Univ Fed Parana; Universidade Federal de São Paulo (UNIFESP); State Univ Ponta Grosso; Butantan Inst; Catholic Univ Parana
    Brown spiders have a worldwide distribution, and their venom has a complex composition containing many different molecules. Herein, we report the existence of a family of astacin-like metalloprotease toxins in Loxosceles intermedia venom, as well as in the venom of different species of Loxosceles. Using a cDNA library from the L. intermedia venom gland, we cloned two novel cDNAs encoding astacin-like metalloprotease toxins, LALP2 and LALP3. Using an anti-serum against the previously described astacin-like toxin in L. intermedia venom (LALP1), we detected the presence of immunologically-related toxins in the venoms of L. intermedia, Loxosceles laeta, and Loxosceles gaucho. Zymographic experiments showed gelatinolytic activity of crude venoms of L. intermedia, L. laeta, and L. gaucho (which could be inhibited by the divalent metal chelator 1,10-phenanthroline) at electrophoretic mobilities identical to those reported for immunological cross-reactivity. Moreover, mRNAs extracted from L. laeta and L. gaucho venom glands were screened for astacin-like metalloproteases, and cDNAs obtained using LALP1-specific primers were sequenced, and their deduced amino acid sequences confirmed they were members of the astacin family with the family signatures (HEXXHXXGXXHE and MXY), LALP4 and LALP5, respectively. Sequence comparison of deduced amino acid sequences revealed that LALP2, LALP3, LALP4, and LALP5 are related to the astacin family. This study identified the existence of gene family of astacin-like toxins in the venoms of brown spiders and raises the possibility that these molecules are involved in the deleterious effects triggered by the venom. (C) 2009 Elsevier Masson SAS. All rights reserved.
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    Biotechnological applications of brown spider (Loxosceles genus) venom toxins
    (Elsevier B.V., 2008-05-01) Senff-Ribeiro, Andrea; Silva, Paulo Henrique da; Chaim, Olga Meiri [UNIFESP]; Gremski, Luiza Helena [UNIFESP]; Paludo, Katia Sabrina [UNIFESP]; Silveira, Rafael Bertoni da; Gremski, Waldemiro; Mangili, Oldemir Carlos; Veiga, Silvio Sanches; Univ Fed Parana; Universidade Federal de São Paulo (UNIFESP); Univ Estadual Ponta Grossa; Catholic Univ Parana
    Loxoscelisin (the term used to define accidents by the bite of brown spiders) has been reported worldwide. Clinical manifestations following brown spider bites are frequently associated with skin degeneration, a massive inflammatory response at the injured region, intravascular hemolysis, platelet aggregation causing thrombocytopenia and renal disturbances. the mechanisms by which the venom exerts its noxious effects are currently under investigation. the whole venom is a complex mixture of toxins enriched with low molecular mass proteins in the range of 5-40 kDa. Toxins including alkaline phosphatase, hyaluronidase, metalloproteases (astacin-like proteases), low molecular mass (5.6-7.9 kDa) insecticidal peptides and phospholipases-D (dermonecrotic toxins) have been identified in the venom. the purpose of the present review is to describe biotechnological applications of whole venom or some toxins, with especial emphasis upon molecular biology findings obtained in the last years. (C) 2007 Elsevier Inc. All rights reserved.
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    Conformational changes of Loxosceles venom sphingomyelinases monitored by circular dichroism
    (Elsevier B.V., 2005-02-04) Andrade, S. A. de; Pedrosa, MFF; Andrade, RMG de; Oliva, MLV; van den Berge, C. W.; Tambourgi, D. V.; Inst Butantan; Universidade Federal de São Paulo (UNIFESP); Cardiff Univ
    Envenomation by arachnids of the genus Loxosceles can induce a variety of biological effects, including dermonecrosis and hemolysis. We have previously identified in L. intermedia venom two highly homologous proteins with sphingomyelinase activity, termed P1 and P2, responsible for all these pathological events, and also an inactive isoform P3. the toxins P1 and P2 displayed 85% identity with each other at the amino acid level and showed a 57% identity with SMase I, an active toxin from L. laeta venom. Circular dichroism was used to determine and compare the solution structure of the active and inactive isoforms. Effects of pH and temperature change on the CD spectra of the toxins were investigated and correlated with the biological activities. This study sheds new light on the structure-function relationship of homologous proteins with distinct biological properties and represents the first report on the structure-function relationship of Loxosceles sphingomyelinases D. (C) 2004 Elsevier Inc. All rights reserved.
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    Delicate fangs, smart killing: the predation strategy of the recluse spider
    (Elsevier B.V., 2015-03-01) Segovia, Julio M. G.; Del-Claro, Kleber; Willemart, Rodrigo Hirata [UNIFESP]; Inst Biol; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    Prey consumption depends on the predator's ability to locate, capture and handle prey. We investigated these three steps in interactions between the delicate-bodied recluse spider Loxosceles gaucho (Araneae) and a heavy-bodied and armoured harvestman, Mischonyx cuspidatus (Opiliones). Although previous research suggested that the hard integument of such harvestmen protects them from being preyed upon by spiders larger than Loxosceles, indirect evidence suggested that Loxosceles spiders can subdue these prey. in the present study, we tested the following three hypotheses with regard to L. gaucho: (1) spiders use chemical cues left by prey to select foraging sites; (2) vibratory cues of prey are essential information in the predatory process; and (3) the spider's web sheet allows adequate handling of prey so vulnerable body regions of the prey can be bitten. To understand how a delicate predator can overcome the defences of a heavy-bodied and well-defended prey, we also quantitatively described the spider's behaviour. To test hypothesis 1, we compared the time spent in areas with harvestmen, crickets and no cues. for hypothesis 2, we compared latency to bite and number of bites in the presence or absence of vibratory information, and for hypothesis 3, we compared latency to detect prey, latency to capture prey and predation success. All three hypotheses were rejected. Loxosceles gaucho seems to be exceptional among spiders by not needing its web, indirect prey chemical cues, or prey's substrate borne vibrations to hunt the tested prey. What enables L. gaucho to prey upon M. cuspidatus is its unique hunting strategy, compared to previously studied spiders: it touches the prey with its tarsi possibly to locate weak parts of the prey's body, such as joints and distal parts of the legs, then it delivers several bites to these vulnerable areas. Our study is the first to document and describe how recluse spiders overcome the defences of an armoured harvestman. (C) 2015 the Association for the Study of Animal Behaviour. Published by Elsevier B.V. All rights reserved.
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    Identification of proteases in the extract of venom glands from brown spiders
    (Elsevier B.V., 2002-06-01) Silveira, R. B. da; Santos, J. F. dos; Mangili, O. C.; Veiga, S. S.; Gremski, W.; Nader, H. B.; von Dietrich, C. P.; Univ Fed Parana; Universidade Federal de São Paulo (UNIFESP)
    In the present investigation, in order to dispute the rational criticism against the presence of proteolytic enzymes in the electrostimulated venom obtained from spiders of the genus Loxosceles, as a consequence of contamination with abdominal secretions, venoms of L. intermedia and L. laeta were directly collected from venom glands by microdissection and gentle homogenization. Gel electrophoresis stained by silver method carried out to compare L. intermedia electrostimulated venom and venom gland extract demonstrated no significant differences in protein profile. Zymogram analysis of L. intermedia venom gland extract detected a gelatinolytic activity in the 32-35 kDa region. the inhibitory effect of 1,10-phenanthroline on this proteolytic activity further supported its metalloprotease nature. in proteolytic digestion experiments L. intermedia venom gland extract was also able to cleave purified fibronectin and fibrinogen. the inhibitory effect of 1, 10-phenanthroline on these degrading activities confirmed the presence of metalloproteases in the venom. in addition, when purified fibrinogen was incubated with L. intermedia abdominal extract, the fibrinogenolysis was completely different, generating low mass fragments that ran away from the gel, a proteolytic event not blocked by 1,10-phenanthroline. Zymogram experiments using L. laeta venom gland extracts further detected a gelatinolytic band at 32-35 kDa, also inhibited by 1,10-phenanthroline, confirming the presence of metalloproteases in both species. (C) 2002 Elsevier B.V. All rights reserved.