To attain fully functional biological activity, vitamin-K dependent coagulation factors (VKDCF) are g-carboxylated prior to secretion from liver. Warfarin impairs the g-carboxylation, and consequently their physiological function. Bothrops jararaca snake venom (BjV) contains several activators of blood coagulation, especially procoagulant enzymes (prothrombin and factor X activators) and thrombin-like enzymes. In order to clarify the relative contribution of prothrombin and factor X activators to the hemostatic disturbances occurring during experimental B. jararaca envenomation, warfarin was used to deplete VKDCF, prior to BjV administration. Male Wistar rats were pretreated with saline (Sal) or warfarin (War) and inoculated subsequently with BjV or saline, thus forming four groups: Sal þ Sal (negative control), Sal þ BjV (positive control), War þ Sal (warfarinization control), and War þ BjV. Three hours after inoculation, prothrombin and factor X levels fell 40% and 50%, respectively; levels of both factors decreased more than 97% in the War þ Sal and War þ BjV groups. Platelet counts dropped 93% and 76% in Sal þ BjV and War þ BjV, respectively, and plasma fibrinogen levels decreased 86% exclusively in Sal þ BjV. After 6 and 24 h, platelet counts and fibrinogen levels increased progressively. A dramatic augmentation in plasma hemoglobin levels and the presence of schizocytes and microcytes in the Sal þ BjV group indicated the development of intravascular hemolysis, which was prevented by warfarin pretreatment. Our findings show that intravascular thrombin generation has the foremost role in the pathogenesis of coagulopathy and intravascular hemolysis, but not in the development of thrombocytopenia, in B. jararaca envenomation in rats; in addition, fibrinogenases (metalloproteinases) may contribute to coagulopathy more than thrombin-like enzymes.

Culex (Culex) dolosus (Lynch Arribálzaga, 1891) is re-described and compared with Cx. eduardoi Casal & Garcia (1968) based on morphological characteristics. Both species are morphologically similar, and they have been largely misidentified throughout Brazil. Adult male and female, fourth instar larvae, and pupae of Cx. dolosus were examined, based on specimens from Pico do Itapeva, Pindamonhangaba Municipality, Serra da Mantiqueira, São Paulo State, southern Brazil. Male genitalia, larvae and pupae are illustrated. Geographical distribution is summarized from published records, and information on bionomics is based on the literature and field data.

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Lynch Arribálzaga (1891) described Culex (Culex) dolosus as a species of the genus Heteronycha. Since then, there were many controversies relative to the classification and nomenclature of the taxon. Casal and García (1968) described Culex eduardoi, a species morphologically similar to Cx. dolosus. Consequently, Cx. eduardoi has been largely misidentified as Cx. dolosus. Aiming to contribute to the systematics of the subgenus Culex and to morphological studies on Cx. dolosus, this species is redescribed based on morphological characteristics of adults, male and female, fourth instar larva and pupa of specimens collected in Pindamonhangaba, State of São Paulo, Brazil. Male genitalia, larva and pupa are illustrated. Species geographical distribution data are based on the published literature records, and bionomics data are based on both literature records and field data.