Spontaneous changes of neocortical code for associative memory during consolidation

After learning, the medial prefrontal cortex (mPFC) gradually comes to modulate the expression of memories that initially depended on the hippocampus. We show that during this consolidation period, neural firing in the mPFC becomes selective for the acquired memories. After acquisition of memory associations, neuron populations in the mPFC of rats developed sustained activity during the interval between two paired stimuli, but reduced activity during the corresponding interval between two unpaired stimuli. These new patterns developed over a period of several weeks after learning, with and without continued conditioning trials. Thus, in agreement with a central tenet of consolidation theory, acquired associations initiate subsequent, gradual processes that result in lasting changes of the mPFC's code, without continued training.     

Dependence of self-tolerance on TRAF6-directed development of thymic stroma

The microenvironments of the thymus are generated by thymic epithelial cells (TECs) and are essential for inducing immune self-tolerance or developing T cells. However, the molecular mechanisms that underlie the differentiation of TECs and thymic compartmentalization are not fully understood. Here we show that deficiency in the tumor necrosis factor receptor-associated factor (TRAF) 6 results in disorganized distribution of medullary TECs (mTECs) and the absence of mature mTECs. Engraftment of thymic stroma of TRAF6(-/-) embryos into athymic nude mice induced autoimmunity. Thus, TRAF6 directs the development of thymic stroma and represents a critical point of regulation for self-tolerance and autoimmunity.     

Spontaneous iron accumulation in hepatocytes of a 7-week-old female rat

Spontaneous iron accumulation in hepatocytes was observed in a 7-week-old female Han Wistar GALAS rat. Very fine yellowish brown pigments, which showed a positive reaction with Berlin Blue stain, were apparent in the cytoplasm close to the bile canaliculi, with a diminishing periportal-to-centrilobular gradient. There were also differences in distribution between and within lobes. Transmission electron microscopy revealed cytosolic ferritin and pericanalicular siderosomes in hepatocytes. No degeneration or necrotic changes were observed, and non-hepatocyte cells did not demonstrate any obvious accumulation of iron. There were no abnormalities in the animal other than this finding in the liver.     

Female scent mobilizes leukocytes to airways in BALB/c male mice

The scent of receptive females as a signal to reproduction stimulates male mice to olfactory search of a potential breeding partner. This searching behavior is coupled with infection risk due to bacterial contamination of the fecal and urine scent marks. We hypothesized that sniffing of female soiled bedding induced the migration of immuno‐competent cells into airways as a possible adaptation to breeding‐related infection. Using bronchoalveolar lavage in a study on mice, we found the number of leukocytes to be significantly higher in male mice that were provided new portions of soiled bedding daily from female cages, in comparison with male mice that were kept in isolation from female scent. The number of leukocytes in blood was equal in both groups. However, monocytes were fewer in number in male mice exposed to female scent than in male mice isolated from female mice. Scent‐induced migration of leukocytes was accompanied by typical behavioral (increased sniffing activity and aggressiveness) and morphological (increase preputial glands and seminal vesicles) responses to olfactory sexual stimulus.     

Novel reovirus isolation from an Ostrich (Struthio camelus) in Japan

An orthoreovirus was isolated from an Ostrich (Struthio camelus) and rapidly identified as orthoreovirus by the rapid determination of viral RNA sequences (RDV) system and electron microscopy. Phylogenetic analysis of the sigma A protein indicated that the isolate belonged to avian species and was closely related to chicken orthoreovirus strain 138. The results of the present study indicated that an ostrich orthoreovirus is slight different from other chicken orthoreoviruses and provided evidence of diversity among avian orthoreoviruses. To our knowledge, this is the first genetic report of an orthoreovirus isolated from an ostrich.