Paw withdrawal thresholds and persistent hindlimb flexion in experimental mononeuropathies.

Hypersensitivity of the foot produced by a number of sciatic mononeuropathies was assessed and compared. A new tool was used, the strain-gauge algometer, that delivers a noxious stimulus and gives a direct measurement of the force for paw withdrawal. In addition, we report observations of another alteration of the flexion reflex, persistent hindlimb flexion. The mean mechanical threshold for naive rats was 5.9 +/- 0.97 centinewton (standard deviation). A superficial surgical procedure had no effect on mechanical sensitivity. Sham surgeries and a surgery in which a silicone pellet was glued to the sciatic nerve produced moderate increases in mechanical sensitivity. Interventions that produced the greatest reductions in thresholds were carrageenan neuritis, complete Freund's adjuvant neuritis, and the chronic constriction injury (CCI) model. Mechanical thresholds returned to baseline in 2 weeks in all groups. Neuropathic behaviors (licking and holding the paw after the stimulus) were observed more frequently in the CCI group. Persistent hindlimb flexion was only observed in the CCI group. The results support that midaxonal inflammation is sufficient to induce hyperalgesia. The strain-gauge algometer proved to be efficient and reliable, and calculations support that used as described in this report one can demonstrate changes in paw withdrawal thresholds as small as 15%.

The roles of toc34 and toc75 in targeting the toc159 preprotein receptor to chloroplasts.

The Toc complex at the outer envelope of chloroplasts initiates the import of nuclear-encoded preproteins from the cytosol into the organelle. The core of the Toc complex is composed of two receptor GTPases, Toc159 and Toc34, as well as Toc75, a beta-barrel membrane channel. Toc159 is equally distributed between a soluble cytoplasmic form and a membrane-inserted form, suggesting that assembly of the Toc complex is dynamic. In the present study, we used the Arabidopsis thaliana orthologs of Toc159 and Toc34, atToc159 and atToc33, respectively, to investigate the requirements for assembly of the trimeric Toc complex. In addition to its intrinsic GTPase activity, we demonstrate that integration of atToc159 into the Toc complex requires atToc33 GTPase activity. Additionally, we show that the interaction of the two GTPase domains stimulates association of the membrane anchor of atToc159 with the translocon. Finally, we employ reconstituted proteoliposomes to demonstrate that proper insertion of the receptor requires both Toc75 and Toc34. Collectively these data suggest that Toc34 and Toc75 act sequentially to mediate docking and insertion of Toc159 resulting in assembly of the functional translocon.