[Effect of electroacupuncture on ultrastructural changes of facial nerve in rabbits with facial nerve injury].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on ultrastructure of facial nerve and Schwann cells in facial nerve injury rabbits so as to explore its mechanism underlying improving facial palsy. METHODS: A total of 60 Japanese white rabbits were randomly assigned to normal control (normal, n = 6), sham-operation (sham, n = 18), model (n = 18) and EA (n = 18) groups. The facial nerve injury model was established by clamping the right facial nerve for 5 min by using a pair of forceps. EA (1.5 V, 3 Hz/60 Hz) was applied to "Yifeng" (TE 17)-"Hegu" (LI 4), and "Dicang" (ST4)-"Jiache" (ST6) on the affected side for 30 min, respectively, once daily for 3 weeks. Morphologic changes of the myelin sheath and Schwann cells of the facial nerve were observed by using electron microscope after 1, 2 and 3 weeks' treatment. RESULTS: Compared with the normal control group, the number of the myelin sheaths and the thickness values of the facial nerve after treatment of 1, 2 and 3 weeks in the model group were decreased significantly (P < 0.01, P < 0.05). While in comparison with the model group, the thickness value of the facial nerve 2 weeks after modeling in EA group was increased considerably (P < 0.01). In the model group, there were many vacuoles in the cytoplasm of Schwann cells instead of organells in the facial nerve. In the sham group, the demyelination was milder than that of the model group, and majority of myelin sheaths showed integral structure after 2 and 3 weeks, being similar to the normal group. Compared with the model group, the extent of demyelination was less distinct, with relatively more abundant organells in the facial nerve of the EA group, especially after 1 week of treatment. Among the three time points in the EA group, demyelination was milder in the 1st week not in the other time points. In contrast, along with the continuous EA treatment, the situation became worse after 3 weeks of treatment in the EA group. CONCLUSION: In the acute stage of facial nerve injury, EA intervention can play a positive effect on the repair of the nerve and Schwann cells. However, continuous 3- weeks' EA intervention may worsen the facial nerve injury.

Mechanism of acid tolerance in a rhizobium strain isolated from Pueraria lobata (Willd.) Ohwi.

The Rhizobium sp. strain PR389 was isolated from the root nodules of Pueraria lobata (Willd.) Ohwi, which grows in acidic (pH 4.6) yellow soil of the Jinyun Mountains of Beibei, Chongqing, China. While rhizobia generally have a pH range of 6.5-7.5 for optimum growth, strain PR389 grew in a liquid yeast extract - mannitol agar medium at pH 4.6, as well as in a pH 4.1 soil suspension, suggesting acid tolerance in this specific strain of rhizobium . However, at pH 4.6, the lag phase before vigorous growth was 40 h compared with 4 h under neutral conditions (pH 7.0). For PR389, the generation time after the lag phase remained the same at different pH levels despite the different durations of the lag phase. Except in the pH 4.4 treatment, the pH of the culturing media increased from 4.6, 4.8, 5.0, and 5.5 to neutral and slightly alkaline after 70 h of culture. Chloramphenicol was added to determine if protein production was involved in the increasing pH process. Chloramphenicol significantly inhibited PR389 growth under acid stress but had little effect under neutral conditions. Proton flux measured during a short acid shock (pH 3.8) revealed that this strain has an intrinsic ability to prevent H(+) from entering cells when compared with acid-sensitive rhizobia. We propose that the mechanism for acid tolerance in PR389 involves both intracellular and extracellular processes. When the extracellular pH is lower than pH 4.4, the cell membrane blocks hydrogen from entering the cell. When the pH exceeds 4.4, the rhizobium strain has the ability to raise the extracellular pH, thereby, potentially decreasing the toxicity of aluminum in acid soil.