Activity and distribution of phosphoinositidase C in rat sciatic nerve.

The hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) by rat sciatic nerve cytosolic phosphoinositidase C [phosphoinositide-specific phospholipase C (PIC)] was studied at neutral pH and at ionic concentrations that approximate intracellular conditions. The principal water-soluble product formed was shown to be inositol trisphosphate by anion exchange chromatography. The maximum hydrolysis rate (2.5 nmol/min/mg protein) was achieved at less than 100 nM Ca2+. Hydrolysis was markedly increased to 15 nmol/min/mg protein by inclusion of K+ in the reaction mixture. In the presence of 200 mM K+, the optimum Ca2+ was increased to approximately 600 nM. Higher Ca2+ concentrations progressively inhibited PIP2 hydrolysis. Mg2+ also inhibited the reaction, but the presence of equimolar amounts of ATP and Mg2+ had no effect. Appreciable degradation of phosphatidylinositol-4-phosphate (PIP) also occurred in the nanomolar Ca2+ range, whereas breakdown of phosphatidylinositol (PI) required millimolar Ca2+. The presence of PIP but not PI inhibited PIP2 hydrolysis. Upon subcellular fractionation of nerve, more than 50% of recovered PIC activity was in the cytosol and about 20% was located in a myelin-enriched fraction. Using PIP2 as substrate, PIC activities in nerves from normal and streptozotocin-induced diabetic animals were not different. However, the myelin-associated enzyme from diabetic animals was more labile to freezing and thawing.     

Amiodarone-induced experimental acute neuropathy in rats.

Amiodarone was injected endoneurially at increasing doses into the exposed tibial nerve of rats to study its electrophysiologic and pathologic effects on peripheral nerve fibers. Forty-five male Wistar rats were used, and each of the following concentrations was injected into 15 nerves: 25 micrograms/mL, 50 micrograms/mL, and 100 micrograms/mL. Microinjection of a 25 micrograms/mL concentration of amiodarone resulted in a subacute, incomplete conduction block evident at day 3 postinjection. This conduction block remained stable until day 10 and recovery was complete at day 35. Microinjection of a 50 micrograms/mL concentration of amiodarone produced a faster evolving conduction block, and significant axon degeneration (approximately 40% of fibers). Injection of a 100 micrograms/mL concentration resulted in severe acute motor axon degeneration followed by complete but delayed regeneration. Results of morphological studies closely correlated with electrophysiological findings. Amiodarone thus seems to have a direct toxic effect on axons at high concentrations in the peripheral nerve, and we suggest that different pathological changes described in human amiodarone neuropathy could be related to different concentrations of the drug in the nerve, perhaps due to variability of blood-nerve barrier efficacy.     

Neuropathy in children and adolescents with diabetes mellitus

Nerve conduction velocities were studied in the median, posterior tibial, radial and sural nerves of 50 juvenile diabetics, average age 13 +/- 1.3 years and mean duration of diabetes 2.3 +/- 1.4 years. Motor conduction velocity (MCV) in the median nerve was reduced in 10% of the subjects, and in the posterior tibial in 32%. Sensory conduction velocity (SCV) in the radial nerve was reduced in 30% of the subjects, and in the sural in 44%. No relationship was found between the reduction in conduction velocity and the duration of diabetes; nevertheless, a correlation was observed between this reduction and the degree of glycaemic control represented by the glycosylated haemoglobin concentration. The authors emphasize the importance of good glycaemic control for the prevention of diabetic neuropathy.     

Simultaneous noninvasive evaluation of gastric emptying and orocaecal transit times

Summary The aim of the study was to use a novel combination of two methods for the simultaneous evaluation of two effects of oral cisapride in 10 diabetic patients with autonomic neuropathy; gastric emptying time was measured by following radio-opaque markers and orocaecal transit time by the sulphasalazine-sulphapridine method. The study was of double-blind, randomized, placebo-controlled, cross-over design.It was possible to evaluate the effect of a prokinetic drug on gastric emptying and orocaecal transit times using these two noninvasive techniques at the same time. Cisapride significantly reduced both the gastric emptying (1.2 h versus 2.1 h) and orocaecal tansit (5.9 h versus 7.7 h) times.     

Expression of tyrosine hydroxylase and neuropeptide tyrosine in mouse sympathetic airway-specific neurons under normal situation and allergic airway inflammation

BACKGROUND: The traditional neurotransmitter catecholamine and the neuropeptide tyrosine in sympathetic airway nerves have been proposed to be involved in the pathogenesis of airway diseases. OBJECTIVE: The aim of the present study was to investigate the effect of allergic airway inflammation on the expression of catecholamine enzyme tyrosine hydroxylase (TH), neuropeptide tyrosine (NPY) and tachykinins in mouse sympathetic airway ganglia. METHODS: Using neuronal tracing in combination with immunohistochemistry, the present study was designed to characterize TH, NPY and tachykinin profiles of superior cervical (SCG) and stellate ganglia after allergen challenge. RESULTS: The vast majority of fast blue-labelled SCG neurons (allergen: 97.5+/-1.22% (mean+/-SEM) vs. controls: 94.5+/-1.48%, P=0.18) and stellate neurons (allergen: 95.3+/-1.01% vs. controls: 93.6+/-1.33%, P=0.34) were immunoreactive for TH. Of the TH immunoreactive and fast blue-labelled SCG neurons, 52.0+/-1.01% allergen vs. 51.2+/-3.58% controls (P=0.83) and stellate neurons, 57.3%+/-0.97 allergen vs. 56.4+/-1.65% controls (P=0.64) were positive for TH only but not NPY, whereas 45.3+/-1.05% allergen vs. 43.3+/-1.18% controls (P=0.47) of fast blue-labelled SCG neurons and 37.9+/-0.86% allergen vs. 37.1+/-1.24% controls (P=0.62) of fast blue-labelled stellate neurons were immunoreactive for both TH and NPY immunoreactivities. There was a trend of an increase, but not significant one, in the percentage of TH-/NPY-immunoreactive and fast blue-labelled neurons in allergen-treated animals in comparison with the controls. Tachykinins, however, were not expressed by sympathetic neurons and were also not induced in sympathetic neurons after allergen challenge. CONCLUSION: The present study indicates that allergic airway inflammation does not alter the expression of noradrenalin and NPY in sympathetic ganglia and also shows that sympathetic neurons do not respond to allergic airway inflammation with tachykinins induction. However, a participation of catecholamine and NPY in the pathogenesis of allergic airway inflammation cannot be excluded in the present study as a higher neurotransmitter output per neuron following allergen challenge could be possible.     

Sympathetic skin response in patients with myasthenia gravis★ A comparative analysis

BACKGROUND: The examination of sympathetic skin response is an important index for assessing the autonomic nerve function, and patients with myasthenia gravis are always accompanied by dysautonomia. Therefore, it will be important to know whether sympathetic skin response can be used as the index for the clinical evaluation of myasthenia gravis. OBJECTIVE: To investigate the diagnostic value of sympathetic skin response in the damage of autonomic nerve function of patients with myasthenia gravis. DESIGN: A case-controlled comparative observation. SETTING: Department of Neurology and Room of Nerve Electromyogram, the Affiliated Hospital of North Sichuan Medical College. PARTICIPANTS: Thirty outpatients or inpatients with myasthenia gravis were selected from the Department of Neurology, the Affiliated Hospital of North Sichuan Medical College from May 2006 to May 2007, including 9 males and 21 females, aged 8–72 years with a mean age of (28±5) years old. They were all accorded with the diagnostic standards of myasthenia gravis, accompanied by different severity of autonomic nerve symptoms, including poor skin nutrition, sweating of hands and feet, pyknocardia, persistent hypotension, abdominal pain, constipation, etc. They all had not taken any drug affecting the autonomic nerve function before the examination. Informed consents were obtained from all the patients. Meanwhile, 30 healthy physical examinees were enrolled as the normal control group, including 10 males and 20 females, aged 10–75 years with a mean age of (31±5) years old. Approval was obtained from the hospital ethic committee. METHODS: After admission, the patients were examined with sympathetic skin response using DANTEC keypoint 2.0 electromyography evoked potential apparatus (Danmark). The changes of the latency and wave amplitude of sympathetic skin response were observed. The subjects in the normal control group were examined with the same methods at physical examination. Abnormality was judged by the disappearance of wave form, latency longer than that in the normal control group by Mean±2.5SD, or wave amplitude lower than the average value in the normal control group by 50%. MAIN OUTCOME MEASURES: The results of the latency and wave amplitude of sympathetic skin response were compared between the patients with myasthenia gravis and normal controls. RESULTS: All the 30 patients with myasthenia gravis and 30 healthy physical examinees were involved in the final analysis of results. There were no significant differences between the left and right upper and lower limbs in both the myasthenia gravis group and normal control group (P > 0.05). In the myasthenia gravis group, the abnormal rate of sympathetic skin response was 37% (11/30), the latency was prolonged and the wave amplitude was decreased as compared with those in the normal control group, and there were significant differences (P < 0.01). CONCLUSION: Sympathetic skin response can be used as an electrophysiological index for judging the damages of autonomic nerve function in patients with myasthenia gravis.     

AC/A ratios in myopic and emmetropic Hong Kong children and the effect of timolol§

Purpose: Caucasian children with myopia have elevated response accommodative vergence to accommodation (AC/A) ratios. The purpose of this study was twofold: to determine if response AC/A ratios vary with refractive error and with myopic progression rate in Hong Kong Chinese children, and to determine the effect of beta‐adrenergic antagonism with topical timolol application on AC/A ratios. Methods: Thirty children aged eight to 12 years participated in the study. All refractive errors were corrected with spectacle lenses. Accommodative responses were measured using a Shin‐Nippon autorefractor and concurrent changes in vergence were assessed using a vertical prism and a Howell‐Dwyer card at three metres and 0.33 metre. Accommodative demand was altered using plus or minus two dioptre lenses and lens‐ and distance‐induced response AC/A ratios were calculated. Measurements were repeated 30 minutes after the instillation of topical timolol maleate (0.5 per cent). Results: AC/A ratios appeared higher in progressing myopic children but the difference was not statistically significant. Timolol application reduced accommodative convergence (AC) in the stable myopes (reduction = ‐3 ± 1.14^A) but not in the emmetropes (0.69 ± 0.9^P) or progressing myopes (0.16 ± 0.43^A) and this difference between refractive groups was statistically s ignificant (F^2,27= 3.766; P= 0.036). However, timolol did not produce a significant change in the accommodative response to positive or negative lenses or response AC/A ratios. Conclusions: We did not find that AC/A ratios in myopic Chinese children were elevated and therefore, it is unlikely that elevated AC/A ratios are responsible for the high levels of myopia that occur in Hong Kong. The finding that timolol reduced AC in the stable myopes suggests that the autonomic control of accommodative convergence in these children may be different from that in emmetropic children and those with progressing myopia.