This ecological profile, in combination with the increasingly high numbers of envenomations reported annually by the Brazilian Ministry of Health ( Ministério da Saúde, Governo Federal), calls for LY294002 nmr more detailed research not only on known species, but also on other species that may prove to be a threat

to human health in the future. In line with this approach, L. similis (Moenkhaus, 1898) has been the focus of some recent biological studies ( Machado et al., 2005 and Silvestre et al., 2005). This species is one of the three reported in the state of Minas Gerais, Brazil, together with L. laeta and L. anomala (Mello-Leitão, 1917). Based on morphology, this species belongs to the gaucho group, together with L. gaucho, L. adelaida, and L. variegata ( Gertsch, 1967). Until recently, it was thought to be mainly a cave-dwelling spider that frequented the areas of Pará, Gefitinib purchase Bahia, Minas Gerais, Mato Grosso do Sul, and São Paulo ( Andrade et al., 2001, Ferreira et al.,

2000, Ferreira et al., 2005 and Trajano and Gnaspini, 1990). However, Machado et al. (2005) reported its presence inside residences of Belo Horizonte in Minas Gerais Province, which added another species to the list of synanthropic members of this genus and increased the potential risk of loxoscelism at higher levels. Because of this, and because of an ongoing interest in speleology and touristic activities around the caves of Minas Gerais, Silvestre et al. (2005) conducted the first characterization of the L. similis venom and identified its main biological effects. L. similis venom is capable of inducing haemolysis of human erythrocytes, dermonecrotic lesions in rabbits, and lethality in mice at a relatively low LD50 (0.32 mg/kg). Importantly, these biological effects are of similar intensity to those of other species, such as L. intermedia, L. laeta, and L. gaucho. Recently, the number of incidents of loxoscelism caused by L. similis has markedly increased in one of the biggest cities of Brazil, Belo Horizonte. This increase in occurrence has justified additional investigation of

the L. similis venom, sex-linked variation of its potency, and the neutralization effect of anti-L. similis-venom on rabbit skin. much L. similis spiders (350 individuals) were collected in a country house in the area of Sabará (Minas Gerais, Brazil) and identified using the method described by Gertsch (1967). Venom glands were removed, macerated, and centrifuged, and the cleaned supernatant was stored at −80 °C before use. Protein quantification of venom was performed using the Bradford technique ( Bradford, 1976). Bovine serum albumin (BSA) was used as a protein standard. Absorbance was measured at 600 nm with a Spectra MAX 340 microplate spectrophotometer system (Molecular Devices, CA, USA). Adult female New Zealand white rabbits (2.