Ingestion of subthreshold doses of environmental toxins induces ascending Parkinsonism in the rat.

Increasing evidence suggests that environmental neurotoxicants or misfolded α-synuclein generated by such neurotoxicants are transported from the gastrointestinal tract to the central nervous system via the vagus nerve, triggering degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and causing Parkinson's disease (PD). We tested the hypothesis that gastric co-administration of subthreshold doses of lectins and paraquat can recreate the pathology and behavioral manifestations of PD in rats. A solution containing paraquat + lectin was administered daily for 7 days via gastric gavage, followed by testing for Parkinsonian behavior and gastric dysmotility. At the end of the experiment, brainstem and midbrain tissues were analyzed for the presence of misfolded α-synuclein and neuronal loss in the SNpc and in the dorsal motor nucleus of the vagus (DMV). Misfolded α-synuclein was found in DMV and SNpc neurons. A significant decrease in tyrosine hydroxylase positive dopaminergic neurons was noted in the SNpc, conversely there was no apparent loss of cholinergic neurons of the DMV. Nigrovagally-evoked gastric motility was impaired in treated rats prior to the onset of parkinsonism, the motor deficits of which were improved by l-dopa treatment. Vagotomy prevented the development of parkinsonian symptoms and constrained the appearance of misfolded α-synuclein to myenteric neurons. These data demonstrate that co-administration of subthreshold doses of paraquat and lectin induces progressive, l-dopa-responsive parkinsonism that is preceded by gastric dysmotility. This novel preclinical model of environmentally triggered PD provides functional support for Braak's staging hypothesis of idiopathic PD.

Anatomically discrete functional effects of adenoviral clostridial light chain gene-based synaptic inhibition in the midbrain.

The gene for the Light Chain fragment of Tetanus Toxin (LC) induces synaptic inhibition by preventing the release of synaptic vesicles. The present experiment applied this approach within the rat midbrain in order to demonstrate that LC gene expression can achieve functionally and anatomically discrete effects within a sensitive brain structure. The deep layers of the superior colliculus/deep mesencephalic nucleus (dSC/DpMe) that are located in the rostral midbrain has been implicated in fear-induced increase of the acoustic startle reflex (fear potentiated startle) but exists in close proximity to neural structures important for a variety of critical functions. The dSC/DpMe of adult rats was injected bilaterally with adenoviral vectors for LC, green fluorescent protein, or vehicle. Synaptobrevin was depleted in brain regions of adenoviral LC expression. LC gene expression in the dSC/DpMe inhibited the increase in startle amplitude seen with the control viral infection, and blocked context-dependent potentiation of startle induced by fear conditioning. Although LC gene expression reduced the absolute amount of cue-specific fear potentiated startle, it did not decrease percent potentiated startle to a cue, nor did it reduce fear-induced contextual freezing, nonspecific locomotor activity, or general health, indicating that its effects were functionally and anatomically specific. Thus, vector-driven LC expression inhibits the function of deep brain nuclei without altering the function of surrounding structures supporting its application to therapeutic neuromodulation.

Tacrolimus, cyclosporine and plasma lipoproteins in renal transplant recipients.

To compare the effect of tacrolimus (FK506) and cyclosporine (CsA) on plasma lipoproteins in renal transplant recipients receiving maintainance therapy, the following prospective study was undertaken. Blood from nineteen recipients on tacrolimus (FK group) and from twenty-one on CsA (CsA group) was collected at baseline, 3-, 6-, and 10-month intervals. Plasma lipids, lipoproteins and oxidation properties of lipoproteins were determined. Plasma total cholesterol, low density lipoprotein (LDL) cholesterol, and apolipoprotein B (apoB) were substantially increased in both groups, although only the CsA group showed significant differences at all time intervals and at the baseline. High density lipoprotein cholesterol, triglycerides, and apolipoprotein A varied in both groups at time intervals from the baseline, but not significantly. The susceptibility to oxidation of LDL isolated from the FK group at all times was uninfluenced by the tacrolimus treatment, and values were comparable to those obtained from LDL isolated from healthy individuals. A significantly higher susceptibility to oxidation as indicated by the shorter time required to start the formation of conjugated dienes was observed in LDL isolated from the CsA group at 3 and at 6 months of therapy. Tacrolimus-treated patients appear to have less hyperlipidemic and have LDL less susceptible to oxidation than patients treated with CsA.

Cell-specific, activation-dependent regulation of neutrophil CD32A ligand-binding function.

Neutrophils express 2 low-affinity FcgammaR, FcgammaRIIIB (CD16B), and FcgammaRIIA (CD32A). CD16B is a glycosyl-phosphatidyl inositol-anchored molecule, whereas CD32A is a polypeptide-anchored molecule. These 2 receptors also differ in their signaling. The biological significance of coexpression of 2 FcgammaRs with distinct membrane anchors and signaling capacities is not clearly understood. Using neutrophils from a CD16B-deficient donor and normal neutrophils treated with anti-CD16 monoclonal antibodies, the authors demonstrated that affinity modulation of CD32A is one of the mechanisms by which neutrophils regulate their FcgammaR-dependent functions. Neutrophils isolated from a CD16B(- )donor rosetted poorly with sheep erythrocytes opsonized with rabbit IgG (EA) (12% +/- 2% versus 80% +/- 6% for control) and were unable to mediate immunophagocytosis. However, activation of CD16B(-) neutrophils with fMLP, a bacterial chemotactic peptide, increased the CD32A-dependent EA rosetting to 58%. The CD32A-dependent rosetting of fMLP-activated normal neutrophils also increased nearly 5-fold, but there was no increase in CD32A expression. The CD32A-dependent immune complex (IC) binding was also increased in activated neutrophils. This affinity regulation was not observed with CD32A expressed on Chinese hamster ovary cells. These results suggest that in resting neutrophils CD32A is in a low-affinity state and that these cells primarily engage CD16B for IC binding. However, once the neutrophils are activated, the CD32A is converted to a high-affinity state that leads to CD32A-dependent ligand binding and signaling. These results suggest that neutrophils adopt a novel strategy to engage the 2 different FcgammaR selectively during physiologic and pathologic conditions to carry out their functions efficiently.