Immunization with native surface protein NcSRS2 induces a Th2 immune response and reduces congenital Neospora caninum transmission in mice.

NcSRS2, a tachyzoite surface protein of Neospora caninum, is an immunodominant protein with respect to induction of antibody production and has a role in attachment and invasion of host cells. Native NcSRS2 was isolated from whole tachyzoite lysate antigen by affinity chromatography using NcSRS2 specific monoclonal antibody and used to immunize BALB/c mice in a congenital transmission study. NcSRS2 was a highly conserved protein as indicated by comparison of deduced amino acid sequence obtained from NcSRS2 gene sequences of 10 geographically distinct N. caninum isolates. Mice immunized with purified native NcSRS2 produced antigen-specific antibody, primarily of IgG 1 subtype. Following challenge during gestation with 10(7) tachyzoites, immunized mice had a statistically significant decreased frequency of congenital transmission compared to non-immunized mice (P

Multistep expression and assembly of neuronal nicotinic receptors is both host-cell- and receptor-subtype-dependent.

We tested the hypothesis that the folding, assembly and insertion of neuronal nicotinic receptors are critically dependent on the host cell line. We used recombinant adenoviruses encoding either the rat alpha7, alpha4 or beta2 subunits in which expression of the subunit is controlled by a tetracycline-dependent promoter to screen five cell lines (GH4C1, SH-EP1, CV1, SN-56, and CHO-CAR). All five lines do not express detectable nicotinic receptor but do express receptor for human adenovirus, and all expressed mRNA for alpha7, alpha4 and beta2 subunits when infected with viruses. Each cell line expressed varying levels of alpha4beta2 receptors that bound [3H]cytisine, but only the GH4C1 and SH-EP1 cell lines expressed either surface or internal alpha7 receptors that bound [125I]alpha-bungarotoxin ([125I]alpha-BGT). All five cell lines expressed a 60 kDa protein immunoblotted by anti-alpha7 antibodies when infected with the alpha7 virus, presumably representing unassembled alpha7 subunits. In addition, GH4C1 cells expressed over 10-fold more surface alpha7 receptor than SH-EP1 cells, even though the total alpha7 receptor in the two cell lines was similar. Sedimentation experiments indicate that SH-EP1 cells only partially assemble alpha7 receptors compared with GH4C1 cells and control alpha7 from rat brain. These data suggest that not only is surface alpha7 receptor expression a multistep process, but that each step may involve cell-specific assembly factors.

Novelty-associated locomotion: correlation with cortical and sub-cortical GABAA receptor binding.

The present study was designed to determine whether variability in GABA (eta-aminobutyric acid)A receptor binding in cortical and subcortical brain regions was correlated with locomotor activity in a novel environment. Twenty four animals were rated for locomotor activity in a novel circular runway. Eight days later, locomotor activity was assessed following 1.5 mg/kg amphetamine sulfate (i.p.). After four to six days, animals were killed and samples were pooled in groups of four animals ranked according to novely locomotor score, and specific binding of the GABAA receptor antagonist [2-(3'-carboxy-2'-propyl)-3-amino-6-p-methoxy phenylpyridazinium bromide] ([3H]SR95531) was determined. Significant negative correlations were seen between specific ([3H]SR95531) binding and novelty induced locomotion in the cingulate and prefrontal cortices, and in the ventral pallidum. A near-significant negative correlation was seen in the striatum. Correlation coefficients between locomotion scores in the novel environment and specific [3H]SR95531 binding were: cingulate cortex, R = -0.91, P = 0.012; prefrontal cortex, R = -0.85, P = 0.032; ventral pallidum, R = -0.85, P = 0.030; striatum, R = -0.73, P = 0.097; and nucleus accumbens, R = -0.09, P = 0.85. The positive correlation between novelty- and amphetamine-induced locomotion was also quite high (R = 0.95, P = 0.004). These results are discussed in terms of their relevance to potential biochemical correlates of drug abuse vulnerability.

Alterations in GABAA receptor binding in the prefrontal cortex following exposure to chronic stress.

The present study was designed to examine the effects of chronic stress on GABAA receptor binding. Animals were randomly assigned to either a control, acute, or chronic stress condition and changes in specific binding were assessed using the GABAA receptor antagonist [3H]SR 95531. Exposure to chronic restraint stress led to a significant reduction in GABAA receptor binding in the prefrontal cortex. Alterations in specific binding were not observed in the cerebellum, caudate-putamen, hippocampus, or cingulate cortex however, suggesting that the effects of chronic stress may be regionally specific. Exposure to acute restraint did not lead to a significant alteration in [3H]SR 95531 binding in any brain region examined.