Stable isotope analysis (SIA) is becoming a commonly used tool to study the ecology of elasmobranchs. However, the retention of urea by elasmobranchs for osmoregulatory purposes may bias the analysis and interpretation of SIA data. We examined the effects of removing urea and lipid on the stable isotope composition of 14 species of sharks, skates, and rays from the eastern North Pacific Ocean. While effects were variable across taxa, removal of urea generally increased δ15N and C:N. Urea removal had less influence on δ13C, whereas extracting urea and lipid generally increased δ15N, C:N, and δ13C. Because C:N values of nonextracted tissues are often used to infer lipid content and adjust δ13C, shifts in C:N following urea extraction will change the inferred lipid content and bias any mathematical adjustment of δ13C. These results highlight the importance of urea and lipid extraction and demonstrate the confounding effects of these compounds, making it impossible to use C:N of non-urea-extracted samples as a diagnostic tool to estimate and correct for lipid content in elasmobranch tissues.

Rationale It is presently unclear whether diabetic rats experience greater rewarding effects of nicotine and/or negative affective states produced by nicotine withdrawal. Objective The present study utilized a rodent model of diabetes to examine the rewarding effects of nicotine and negative affective states and physical signs produced by withdrawal. Methods Separate groups of rats received systemic administration of either vehicle or streptozotocin (STZ), which destroys insulin-producing beta cells in the pancreas and elevates glucose levels. Place conditioning procedures were utilized to compare the rewarding effects of nicotine (conditioned place preference; CPP) and negative affective states produced by withdrawal (conditioned place aversion; CPA) in vehicle- and STZ-treated rats. CPA and physical signs of withdrawal were compared after administration of the nicotinic receptor antagonist mecamylamine to precipitate withdrawal in nicotine-dependent rats. A subsequent study utilized elevated plus maze (EPM) procedures to compare anxiety-like behavior produced by nicotine withdrawal in vehicle- and STZ-treated rats. Results STZ-treated rats displayed greater rewarding effects produced nicotine and a larger magnitude of aversive effects and physical signs produced by withdrawal as compared to vehicle-treated controls. STZ-treated rats also displayed higher levels of anxiety-like behavior on the EPM during nicotine withdrawal as compared to controls. Conclusion The finding that both nicotine reward and withdrawal are enhanced in a rodent model of diabetes implies that the strong behavioral effects of nicotine promote tobacco use in persons with metabolic disorders, such as diabetes.

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INTRODUCCIÓN: La distonía mioclónica es un trastorno del movimiento con poca prevalencia, pero muy discapacitante, en el cual es frecuente la refractariedad al tratamiento médico. Cómo opción terapéutica se ha planteado la estimulación cerebral profunda, buscando con ello mejorar la función motora, la discapacidad y la calidad de vida de estos pacientes. MATERIALES Y MÉTODOS: Se presentan 3 pacientes con diagnóstico clínico de distonía mioclónica sin confirmación genética, que fueron llevados a estimulación cerebral profunda bilateral del globo pálido interno. RESULTADOS: Se evidenció una mejoría significativa en la evaluación de la escala unificada de mioclonías (80-90 %) y en la escala de distonía de Burke-Fahn-Marsden (tanto en movilidad como en discapacidad). La mejoría clínica se evidenció en los tres pacientes, en periodos de seguimiento que estuvieron entre los 6 meses y los 5 años luego de la estimulación cerebral profunda. DISCUSIÓN Y CONCLUSIONES: Los hallazgos en esta serie de 3 pacientes colombianos son consistentes con lo reportado en la literatura. Sin embargo, aportan información sobre el desenlace de pacientes sin genotipificación sometidos a estimulación cerebral profunda, dado que la eficacia de la intervención en pacientes con distonía sin confirmación genética aún no ha sido determinada, y depende de otros factores como la edad, el tiempo de evolución y el tipo de distonía.