Neuroendocrine modulation of stress response in the anuran, Rana esculenta

In amphibians, as in other vertebrates, stress stimuli have been found to affect different functions, including development, growth, and reproduction. A wide range of responsiveness to stressors has been reported for amphibians; for instance, capture and/or captivity stress induced changes both in the hypothalamus-pituitary-interrenal and hypothalamus-pituitary-gonadal axes. However, few studies have examined the response to stress in terms of recovery and/or adaptation by applying stress paradigms for a short and long-term duration. In the present paper, the short-term captivity stress responses were evaluated in the anuran Rana esculenta by measuring peripheral corticosterone, androgens, prolactin (PRL), and growth hormone (GH) changes. Moreover, in long-term captivity and salinity stress, effects were evaluated by measuring peripheral PRL changes and those of PRL mRNA in the pituitary together with plasma corticosterone and androgens. Short-term (24 h) captivity stress induced an increase of peripheral corticosterone together with that of GH and PRL since these hormones are involved in the "alarm phase" and in energy demand of stressed animals. The opposite trend was found for peripheral androgens, in view of the negative effects exerted by stress in the reproductive axis. In long-term (1 month) captivity and salinity stress, responses were consistent with the increasing of PRL mRNA at pituitary level, through a long-loop feed-back mechanism depending on the decreasing levels of peripheral PRL, whereas no changes were found in the levels of plasma corticosterone and androgens. Therefore, it seems that Rana esculenta activates different neuroendocrine mechanisms depending on the duration of stress and on the types of stressors. © Koninklijke Brill NV 2006

HOXB4 Gene Expression Is Regulated by CDX2 in Intestinal Epithelial Cells

The mammalian Caudal-related homeobox transcription factor 2 (CDX2) plays a key role in the homeobox regulatory network and is essential in regulating the expression of several homeobox (HOX) genes during embryonic development, particularly in the gut. Genome-wide CDX2 chromatin immunoprecipitation analysis and expression data from Caco2 cells also suggests a role for CDX2 in the regulation of HOXB4 gene expression in the intestinal epithelium. Thus, the aim of this study was to investigate whether HOXB4 gene expression is regulated by CDX2 in the intestinal epithelium. We demonstrated binding of CDX2 to four different CDX2 binding sites in an enhancer region located upstream of the HOXB4 transcription start site. Mutations in the CDX2 binding sites reduced HOXB4 gene activity, and knock down of endogenous CDX2 expression by shRNA reduced HOXB4 gene expression. This is the first report demonstrating the CDX2 regulation of HOXB4 gene expression in the developed intestinal epithelium, indicating a possible role for HOXB4 in intestinal homeostasis

Supplementation of Male Pheromone on Rock Substrates Attracts Female Rock Lizards to the Territories of Males: A Field Experiment

Background: Many animals produce elaborated sexual signals to attract mates, among them are common chemical sexual signals (pheromones) with an attracting function. Lizards produce chemical secretions for scent marking that may have a role in sexual selection. In the laboratory, female rock lizards (Iberolacerta cyreni) prefer the scent of males with more ergosterol in their femoral secretions. However, it is not known whether the scent-marks of male rock lizards may actually attract females to male territories in the field. Methodology/Principal Findings: In the field, we added ergosterol to rocks inside the territories of male lizards, and found that this manipulation resulted in increased relative densities of females in these territories. Furthermore, a higher number of females were observed associated to males in manipulated plots, which probably increased mating opportunities for males in these areas. Conclusions/Significance: These and previous laboratory results suggest that female rock lizards may select to settle in home ranges based on the characteristics of scent-marks from conspecific males. Therefore, male rock lizards might attract more females and obtain more matings by increasing the proportion of ergosterol when scent-marking their territories. However, previous studies suggest that the allocation of ergosterol to secretions may be costly and only high quality male