Medial prefrontal lesions in the rat and spatial navigation: Evidence for impaired planning.

Rats with medial prefrontal cortical lesions were tested in a modified water maze navigation task. In Stage 1, the rats were trained to locate a hidden platform from a single start location. They were then subjected to a series of trials during which a second start position was used (Stage 2). In Stage 3, the rats had to navigate to a new goal location from the 2 experienced start positions. Stage 4 required the rats to navigate to the same goal as in Stage 3, starting from 4 distinct positions. Finally, a single probe trial with no platform was conducted. Rats with prefrontal lesions were impaired only during Stage 4. This deficit was specific to the 2 start positions newly introduced during this stage, suggesting a dysfunction of planning processes. This impairment might result from a working memory deficit, precluding the animal from forming an adequate representation of the whole course of movements required to reach the platform. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unexpected Interacting Effects of Physical (Radiation) and Chemical (Bisphenol A) Treatments on Male Reproductive Functions in Mice

For decades, numerous chemical pollutants have been described to interfere with endogenous hormone metabolism/signaling altering reproductive functions. Among these endocrine disrupting substances, Bisphenol A (BPA), a widely used compound, is known to negatively impact germ and somatic cells in the testis. Physical agents, such as ionizing radiation, were also described to perturb spermatogenesis. Despite the fact that we are constantly exposed to numerous environmental chemical and physical compounds, very few studies explore the impact of combined exposure to chemical and physical pollutants on reproductive health. The aim of this study was to describe the impact of fetal co-exposure to BPA and IR on testicular function in mice. We exposed pregnant mice to 10 µM BPA (corresponding to 0.5 mg/kg/day) in drinking water from 10.5 dpc until birth, and we irradiated mice with 0.2 Gy (γ-ray, RAD) at 12.5 days post-conception. Co-exposure to BPA and γ-ray induces DNA damage in fetal germ cells in an additive manner, leading to a long-lasting decrease in germ cell abundance. We also observed significant alteration of adult steroidogenesis by RAD exposure independently of the BPA exposure. This is illustrated by the downregulation of steroidogenic genes and the decrease of the number of adult Leydig cells. As a consequence, courtship behavior is modified, and male ultrasonic vocalizations associated with courtship decreased. In conclusion, this study provides evidence for the importance of broadening the concept of endocrine disruptors to include physical agents, leading to a reevaluation of risk management and regulatory decisions.     

Working memory, response selection, and effortful processing in rats with medial prefrontal lesions.

Examined the effects of lesions of the prelimbic area of the prefrontal cortex on acquisition and retention of nonmatching (NMTS) and matching-to-sample (MTS) tasks. 64 male rats participated. Both tasks involved a reference and a working memory component, but only working memory was impaired by the lesions. A comparison of the 2 tasks revealed quantitatively similar deficits in postoperatively trained rats. In preoperatively trained rats, however, the deficits were more important in the MTS task than in the NMTS task. In addition, an effect of interference between successive trials was observed in the NMTS task but not in the MTS task. Perseverative tendencies were observed in the MTS task only. Results suggest that prefrontal lesions induce working memory deficits as a result of poor temporal encoding and increased susceptibility to interference, and impair effortful processing, such as that engaged in response selection mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recombinant C-terminal domain of pancreatic lipase retains full ability to bind colipase

The organization of the pancreatic lipase in two well defineddomains has been correlated to a specific function for eachdomain, catalytic activity for the N-terminal domain and colipasebinding for the C-terminal domain. In order to see if such anorganization implies that the two domains can behave as separateentities, we expressed the N- and C-terminal domains in insectcells. The recombinant proteins secreted in the cell supernatantspresent the expected molecular properties. However, whereasthe C-terminal domain retains its function of colipase binding,the N-terminal domain appears to be unable to ensure catalysis.The lack of activity of the recombinant N-terminal domain couldresult either from a (partially) incorrect folding or from anincapacity to function by itself. These results suggest that,although both are structurally well defined, the two domainsof the pancreatic lipase behave differently when they are expressedas separate entities.