Histomorphometric assessment of bone necrosis produced by two cryosurgery protocols using liquid nitrogen: an experimental study on rat femurs

OBJECTIVE: The aim of this study was to evaluate the effects of liquid nitrogen cryosurgery on the femoral diaphysis of rats. MATERIAL AND METHODS: The femoral diaphyses of 42 Wistar rats were exposed to three local and sequential applications of liquid nitrogen for 1 or 2 min, intercalated with periods of 5 min of passive thawing. The animals were sacrificed after 1, 2, 4 and 12 weeks and the specimens obtained were processed and analyzed histomorphometrically. RESULTS: The depth and extent of peak bone necrosis were 124.509 µm and 2087.094 µm for the 1-min protocol, respectively, and 436.424 µm and 12046.426 µm for the 2-min protocol. Peak necrosis was observed in the second experimental week with both cryotherapy protocols. CONCLUSIONS: The present results indicate that the 2-min protocol produced more marked bone necrosis than the 1-min protocol. Although our results cannot be entirely extrapolated to clinical practice, they contribute to the understanding of the behavior of bone tissue submitted to different cycles of liquid nitrogen freezing and may serve as a basis for new studies

Social approach in genetically engineered mouse lines relevant to autism

Profound impairment in social interaction is a core symptom of autism, a severe neurodevelopmental disorder. Deficits can include a lack of interest in social contact and low levels of approach and proximity to other children. In this study, a three-chambered choice task was used to evaluate sociability and social novelty preference in five lines of mice with mutations in genes implicated in autism spectrum disorders. Fmr1(tm1Cgr/Y) (Fmr1(−)(/y)) mice represent a model for fragile X, a mental retardation syndrome that is partially co-morbid with autism. We tested Fmr1(−)(/y) mice on two genetic backgrounds, C57BL/6J and FVB/N-129/OlaHsd (FVB/129). Targeted disruption of Fmr1 resulted in low sociability on one measure, but only when the mutation was expressed on FVB/129. Autism has been associated with altered serotonin levels and polymorphisms in SLC6A4 (SERT), the serotonin-transporter gene. Male mice with targeted disruption of Slc6a4 displayed significantly less sociability than wildtype controls. Mice with conditional overexpression of Igf-1 (Insulin-like growth factor-1) offered a model for brain overgrowth associated with autism. Igf-1 transgenic mice engaged in levels of social approach similar to wildtype controls. Targeted disruption in other genes of interest, En2 (Engrailed 2) and Dhcr7, was carried on genetic backgrounds that demonstrated low levels of exploration in the choice task, precluding meaningful interpretations of social behavior scores. Overall, results show that loss of Fmr1 or Slc6a4 gene function can lead to deficits in sociability. Findings from the fragile X-model suggest that the FVB/129 background confers enhanced susceptibility to consequences of Fmr1 mutation on social approach