Hematological, hemostatic and clinical chemistry disturbances induced by Crotalus durissus terrificus snake venom in dogs.

The aim of this study was to investigate the hematological, hemostatic and biochemical disturbances induced by the injection of Crotalus durissus terrificus venom in dogs under controlled conditions. For this purpose three groups of animals were used: an experimental group (E), which was injected i.m. with C. durissus terrificus venom (1 mg/kg); and two control groups--antivenom (AV) and control (C)--which were injected i.m. with 150 mM NaCl. Groups E and AV were treated i.v. with Crotalus antivenom 2 hours after the first injection. Serum levels of alkaline phosphatase and alanine aminotransferase were increased in groups E and AV at 24 and 48 hours after serumtherapy, respectively. The increased serum levels of myoglobin, creatine kinase and aspartate aminotransferase demonstrated that animals developed rhabdomyolysis. A persistent neutrophilic leukocytosis was already noticeable at 2 hours after envenomation and lasted even after serumtherapy. The animals of groups E and AV presented eosinopenia 24 hours after serumtherapy, and collagen-induced platelet hypoaggregation was observed without thrombocytopenia. Increased levels of fibrinogen/fibrin degradation products (FnDP/FgDP), hypofibrinogenemia, and alpha2-antiplasmin consumption were observed at 2 hours after envenomation, indicating secondary activation of fibrinolysis. Our data suggest that the biochemical and hemostatic disturbances induced by C. durissus terrificus venom in dogs are related to its myotoxic and thrombin-like activities.

Clinical diagnosis of heterozygous dystrophin gene deletions by fluorescence in situ hybridization.

Two-thirds of patients affected by Duchenne or Becker muscular dystrophy (DMD/BMD) carry large intra-genic deletions in the dystrophin gene. In males, the deletions can be efficiently detected using multiplex polymerase chain reaction (PCR) and Southern blotting. In contrast, deletion detection in carrier females is complicated by the presence of a normal gene copy on the second X-chromosome. We have analyzed the boundaries of 570 deletions and 34 duplications in the dystrophin gene identified in the São Paulo and Leiden diagnostic laboratories. The data were used to select an optimal set of cosmid probes for the detection of the most frequently deleted areas of the dystrophin gene. Six cosmids were evaluated in fluorescence in situ hybridization (FISH) experiments to assess deletions in 21 heterozygous deletion-carriers and nine controls. No discrepancy was found between the FISH analysis and the molecular data, demonstrating the accuracy of the technique for carrier detection in Duchenne and Becker muscular dystrophy.

Effect of X inactivation on fragile X frequency and mental retardation.

The probability of a heterozygote being affected was estimated from the distribution of frequencies of early-replicating fragile X [fra(X)] chromosome in normal and mentally retarded heterozygotes, taking into account the prior probabilities of 0.35 for mental retardation and 0.65 for normality. The estimated probability of a heterozygote with 100% early-replicating fra(X) being mentally retarded was 78%, which coincides with the value of penetrance in males. Therefore, the manifestation of retardation in females seems to differ from that in males due solely to X inactivation. The frequencies of early-replicating fra(X) were significantly increased among the heterozygotes with the highest frequencies of fra(X) both in the normal group and in the mentally retarded. The mean frequencies of early-replicating fra(X) were 0.42 and 0.68 for normal and mentally retarded heterozygotes, respectively. Considering the overall frequency of retarded heterozygotes as 0.35, the mean frequency of early-replicating fra(X) obtained for all heterozygotes was 0.51, which is in accordance with the hypothesis of random X inactivation. Thus the fragile site appears to have equal chances of being detected when located either on the early- or on the late-replicating X. This leads to the conclusion that the frequency of the fragile site is a consequence of the proportion of cells with the active Martin-Bell syndrome (MBS) gene and not the result of a better visualization of the site on the early-replicating X.