The present experiments investigated the role of the prelimbic-infralimbic areas in behavioral flexibility using a place-response learning paradigm. All rats received a bilateral cannula implant aimed at the prelimbic-infralimbic areas. To examine the role of the prelimbic-infralimbic areas in shifting strategies, rats were tested on a place and a response discrimination in a cross-maze. Some rats were tested on the place version first followed by the response version. The procedure for the other rats was reversed. Infusions of 2% tetracaine into the prelimbic-infralimbic areas did not impair acquisition of the place or response discriminations. Prelimbic-infralimbic inactivation did impair learning when rats were switched from one discrimination to the other (cross-modal shift). To investigate the role of the prelimbic-infralimbic areas in intramodal shifts (reversal learning), one group of rats was tested on a place reversal and another group tested on a response reversal. Prelimbic-infralimbic inactivation did not impair place or response intramodal shifts. Some rats that completed testing on a particular version in the cross-modal and intramodal experiments were tested on the same version in a new room for 3 d. The transfer tests revealed that rats use a spatial strategy on the place version and an egocentric response strategy on the response version. Overall, these results suggest that the prelimbic-infralimbic areas are important for behavioral flexibility involving cross-modal but not intramodal shifts.

No abstract

Although largely unrelated, many bovine type III GBS appear to share a common ancestor with an important human clone.

Previous work divided serotype III group B streptococci (GBS) into 3 major phylogenetic lineages (III-1, III-2, and III-3) on the basis of bacterial DNA restriction digest patterns (RDPs). Most neonatal invasive disease was caused by III-3 strains, which implies that III-3 strains are more virulent than III-2 or III-1 strains. In the current studies, all RDP III-3 and III-1 strains expressed hyaluronate lysase activity; however, all III-2 strains lack hyaluronate lysase activity, because the gene that encodes hyaluronate lysase, hylB, is inactivated by IS1548. Subtractive hybridization was used to identify 9 short DNA sequences that are present in all the III-3 strains but not in any of the III-2 or III-1 strains. With 1 exception, these III-3-specific sequences were not detected in nonserotype III GBS. These data further validate the RDP-based subclassification of GBS and suggest that lineage-specific genes will be identified, which account for the differences in virulence among the lineages.

Phylogenetic lineages of pathogenic Streptococcus agalactiae (group B streptococci [GBS]) can be identified by analysis of restriction-digestion patterns (RDPs) of chromosomal DNA. The purpose of the present study was to correlate GBS RDP types and (1) alleles of the highly conserved gene encoding translation-initiation factor IF2, infB, and/or (2) the inserted elements IS1548 and GBSi1. Only 1 combination of serotype and infB allele was found within each RDP type. Strains within a particular RDP type also tend to have the same inserted elements in each of 3 loci examined. A novel insertion sequence, designated "IS1563," was found within all RDP type II-2 strains. Most RDP types could be identified by a combination of serotype, infB allele, and inserted elements at each of the loci. These molecular markers can be used to identify GBS populations and to correlate RDP types and phylogenetic lineages identified by different methods.