RESUMEN
In wide-ranging taxa with historically dynamic ranges, past allopatric isolation and range expansion can both influence the current structure of genetic diversity. Considering alternate historical scenarios involving expansion from either a single refugium or from multiple refugia can be useful in differentiating the effects of isolation and expansion. Here, we examined patterns of genetic variability in the trans-continentally distributed painted turtle (Chrysemys picta). We utilized an existing phylogeographic dataset for the mitochondrial control region and generated additional data from nine populations for the mitochondrial control region (n = 302) and for eleven nuclear microsatellite loci (n = 247). We created a present-day ecological niche model (ENM) for C. picta and hindcast this model to three reconstructions of historical climate to define three potential scenarios with one, two, or three refugia. Finally, we employed spatially-explicit coalescent simulations and an approximate Bayesian computation (ABC) framework to test which scenario best fit the observed genetic data. Simulations indicated that phylogeographic and multilocus population-level sampling both could differentiate among refugial scenarios, although inferences made using mitochondrial data were less accurate when a longer coalescence time was assumed. Furthermore, all empirical genetic datasets were most consistent with expansion from a single refugium based on ABC. Our results indicate a stronger role for post-glacial range expansion, rather than isolation in allopatric refugia followed by range expansion, in structuring diversity in this species. To distinguish among complex historical scenarios, we recommend explicitly modeling the effects of range expansion and evaluating alternate refugial scenarios for wide-ranging taxa.
Asunto(s)
Especiación Genética , Variación Genética , Tortugas/genética , Animales , Teorema de Bayes , Cambio Climático , ADN Mitocondrial/genética , Demografía , Ecosistema , Genética de Población , Repeticiones de Microsatélite/genética , Modelos Biológicos , Filogeografía , Refugio de Fauna , Tortugas/clasificaciónRESUMEN
Bilateral lesions centered in the posterodorsal amygdala of female rats resulted in hyperphagia and excessive weight gain. The brain damage extended posteriorly through the amygdalohippocampal area and into the ventral hippocampus and subiculum. Lesions centered in the ventral hippocampal formation had a less pronounced, although still significant, effect on body weight. Damage to large areas of the amygdala, including the anterior, basolateral, and corticomedial groups of nuclei, was without effect. A serial reconstruction of overlapping areas of destruction for both effective and ineffective lesions is presented.
Asunto(s)
Amígdala del Cerebelo/fisiología , Peso Corporal/fisiología , Ingestión de Alimentos/fisiología , Animales , Mapeo Encefálico , Dominancia Cerebral/fisiología , Femenino , Vías Nerviosas/fisiología , Ratas , Núcleo Hipotalámico Ventromedial/fisiologíaRESUMEN
Adrenalectomized female rats with lesions of the ventromedial hypothalamus or sham lesions were given SC implants of wax pellets or a fused mixture of corticosterone-cholesterol (40, 75, or 130% by weight). In animals with sham lesions, high dosages of corticosterone proved to be catabolic (r = -0.61 between plasma corticosterone and weight change). In marked contrast, animals with VMH lesions displayed substantial weight gains at all circulating levels of corticosterone, with a significant positive correlation (r = +0.48) between these two variables. It is concluded that: a) damage to the basomedial hypothalamus alters an organism's response to corticosterone at both ends of the dose-response curve, and b) both Type I and Type II corticosterone receptors in the brain play a role in hypothalamic obesity.
Asunto(s)
Glándulas Suprarrenales/fisiología , Corticosterona/sangre , Núcleo Hipotalámico Ventromedial/fisiología , Aumento de Peso/fisiología , Adrenalectomía , Hormona Adrenocorticotrópica/sangre , Animales , Glucemia/metabolismo , Mapeo Encefálico , Corticosterona/administración & dosificación , Ingestión de Alimentos/fisiología , Femenino , Insulina/sangre , Ratas , Receptores de Esteroides/efectos de los fármacos , Receptores de Esteroides/fisiología , Núcleo Hipotalámico Ventromedial/efectos de los fármacos , Aumento de Peso/efectos de los fármacosRESUMEN
Damage to the temporal lobes in cats, dogs, and primates has long been known to result in hyperphagia and obesity, but research into the role of this area of the brain in feeding behavior has largely been neglected because of an inability to produce similar results in rats. The present study reports hyperphagia and obesity in female rats with small electrolytic lesions centered in the posterodorsal amygdala. Daily food intake more than doubled in the first few days after surgery and mean weight gain was more than four times that observed in animals with sham lesions during the first 26 days. The rats with lesions were not hyperresponsive to a switch in diets (lab chow to high-fat, and back). In all animals that gained abnormal amounts of weight, the posterior extent of the lesions extended through the amygdalohippocampal area into the ventral hippocampal formation. The results suggest that the temporal lobe is an important extrahypothalamic site for the regulation of food intake in rodents.
Asunto(s)
Hiperfagia/fisiopatología , Obesidad/fisiopatología , Lóbulo Temporal/fisiología , Animales , Peso Corporal/fisiología , Ingestión de Alimentos/fisiología , Femenino , Hipotálamo/fisiología , Ratas , Lóbulo Temporal/anatomía & histología , Aumento de Peso/fisiologíaRESUMEN
Marked weight gain was observed in female rats given small electrolytic lesions in the dorsal posterior portion of the amygdala. With a standard lab pellet diet, weight gains typically ranged between 20-30 g during the first 3 postoperative days, and between 60-100 g over the first 20 days. Rats with sham lesions generally gained only 5-15 g in 20 days. The results are consistent with much older studies that reported obesity in cats, dogs, and primates with lesions of the amygdala.