Short term effects of interleukin-1 beta on insulin secretion and cyclic nucleotide levels in rat islets of Langerhans cultured with arginine and arginine analogues.
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Animals↗
Biomedical subjects
C A Delaney
Publications and source records attributed to C A Delaney.
Denervation impairs cutaneous microvascular function and blister healing in the rat hindlimb.
Skin sensory nerve nocifensor functions were investigated non-invasively in rats by measuring neurogenic inflammation and blister healing-rate after unilateral hindlimb denervation. Axon reflexes were evoked by transdermal iontophoresis of acetylcholine (ACh) or noxious electrical stimulation (TNS). Sodium nitroprusside (SNP) evoked direct dilator responses. Resultant changes in skin microvascular blood flux were measured by laser Doppler flowmetry. Compared with their sham-operated control limbs, denervation reduced inflammatory responses (ACh or TNS) by more than 85% and SNP responses by 28% (p < 0.05). Healing of dry-ice blisters raised on the hindpaw 14d post-denervation was significantly slower to complete healing (42d) than controls (26d) and initial inflammation was attenuated, confirming that innervation is important for inflammation and blister-healing.
Acetylcholine↗
The role of skin nociceptive afferent nerves in blister healing.
Because sensory neuropeptides improve survival of critical skin and muscle flaps in rats, skin nociceptive sensory nerve function in blister healing was examined. Sensory nerve ablation by unilateral hindlimb denervation or cutaneous axon reflex enhancement by 14 days systemic nicotine treatment (5 mg kg-1 day-1) decreased and increased, respectively, peripheral motor functions of nociceptive (peptidergic) skin nerves. Effects on nociception were measured by a radiant heat tail-flick test. Axon reflex flares were evoked by transdermal iontophoresis of acetylcholine or noxious electrical stimulation under pentobarbitone 40 mg kg-1 anaesthesia. Resultant changes in cutaneous microvascular blood flux were measured non-invasively by laser Doppler flowmetry. In nicotine-treated rats compared with placebo-treated controls, acetylcholine-evoked axon reflex flare was enhanced by 240% (p < 0.01) without enhancement of electrically evoked flare. Thus, nicotine-sensitized nociceptors show stimulus specificity in their enhancement of neurogenic flare responses. No significant changes were seen in other endothelial-dependent or smooth muscle-dependent microvascular dilator responses. Nicotine-treated rats had prolonged tail-flick withdrawal latencies to noxious radiant heat stimuli compared with placebo-treated controls (p < 0.05), suggesting an antinociceptive or analgesic effect of nicotine-treatment. Neurogenic effects on wound healing rate were assessed by measuring the dimensions of standardized blisters twice daily. The blisters were raised on hindpaw glabrous skin using a constant weight and diameter of compressed dry ice pellet applied for 30 secs at constant force. Dry-ice blisters raised on the hindpaw 14 days post-denervation were significantly slower to heal completely (42 days) than controls (30 days: P < 0.05) and the surrounding inflammation was reduced. By contrast, nicotine-treated rats showed more rapid blister healing (25 days) than controls (30 days), seen only in the later phase after day 15. Finally, resting substance P release from blisters, after direct cutaneous nerve stimulation, appears to be enhanced in nicotine-treated rats. Thus nociceptive innervation appears critical for inflammation and rapid healing of blisters in rat skin. The data signal a possible important role for neuropeptides in these processes and question the function of nicotinic receptors on sensory nerves.
Animals↗
Confounding factors in non-invasive tests of neurovascular function in diabetes mellitus.
Disturbances of neurovascular function in the extremities may occur in patients with diabetes mellitus, exposure to toxic substances and chronic exposure to vibrating hand tools, as well as in Raynaud's phenomena. In these conditions symptoms of paraesthesia, finger numbness and blanching occur, so nerve conduction studies, vibration and temperature threshold measurements and neurovascular function tests are used for objective assessment of neurological dysfunction. The aim of the present study was to examine some factors which may confound quantitative neuro-vascular function measurements if used to assess neuropathy in diabetics. All subjects were consenting volunteers without exposure to known neurotoxic chemicals. The 5 groups were (a) healthy non-diabetic subjects not exposed to vibration (n = 10, mean age 52.3 yrs) (b) 2 insulin dependent and 8 non-insulin dependent diabetic subjects with a mean of 6 years treatment (n = 10, mean age 55.7 yrs) (c) maintenance employees exposed to high frequency pneumatic hand tools (n = 10, mean age 52.2 yrs) (d) subjects who were not diabetic or exposed to vibrating tools, but were being treated with the ACE-inhibitor enalapril 20 mg daily for hypertension (n = 5, mean age 54 yrs) (e) subjects who had smoked more than 10 cigarettes daily for at least 15 yrs (n = 10, mean age 51 yrs). Neurovascular tests included axon reflex responses measured by laser Doppler velocimeter evoked on the dorsum of the finger by iontophoresis of acetylcholine 16 mC in a circumferential chamber: cutaneous microvascular dilator responses to endothelial stimulation by iontophoretic application of the muscarinic agonist pilocarpine 16 mC and to direct nitrodilator sodium nitroprusside 16 mC. The skin temperature of the digits was held between 33 degrees and 34 degrees C during testing and dilator responses were measured as flux change by on-line computer analysis using 'Perisoft'. There was a significant reduction (P < 0.05) in the neurovascular responses of both diabetics and vibration--exposed subjects to acetylcholine and, in the case of vibration-exposed subjects, to pilocarpine, but nitroprusside responses were not significantly different. Our findings of reductions in neurovascular responses in diabetics and in subjects exposed to higher frequency vibration is consistent with recent epidemiological findings. Furthermore, subjects treated with an ACE-inhibitor (enalapril) showed significant reduction in acetylcholine-evoked axon reflex responses, while the test group of smokers showed a significant reduction in their dilator response to pilocarpine.(ABSTRACT TRUNCATED AT 400 WORDS)
Acetylcholine↗
Hereditary sensory radicular neuropathy: defective neurogenic inflammation.
Hereditary sensory radicular neuropathy exhibits autosomal dominant inheritance with complete penetrance in males and incomplete penetrance in females. Newer tests of small sensory nerve function were used in screening 8 family members aged between 14 and 66 years. All exhibited some frequent features of the disorder with an onset in the 2nd or 3rd decade, foot ulceration, foot callus, loss of pin prick, thermal and light touch sensation, and some reduction in vibration acuity and proprioception in the lower limbs. The hands were involved in 3 of 8, muscle involvement was present in 5 of 8, but deafness was not detected by audiometry. Nerve conduction velocity, sensory action potentials, latency and amplitude, thermal acuity, vibration acuity and axon reflex flares were measured in all patients. One sural nerve biopsy confirmed the presence of peripheral fibre loss in this predominantly sensory neuropathy. Chemically evoked axon reflex tests were used to evaluate the extent of primary sensory nerve fibre involvement. All patients were tested using a Moor MBF 3-D dual channel laser Doppler velocimeter. Acetylcholine or phenylephrine iontophoretically applied as 16 mC doses evoked absent or tiny axon reflexes in areas of impaired pin prick sensation. By contrast, direct microvascular dilator responses to nitroprusside (smooth muscle dependent) and acetylcholine (endothelium-dependent) were present but somewhat reduced in areas with defective neurogenic inflammation. These results differ significantly from the responses obtained in age-matched healthy controls (P < 0.05). Foot pressure analysis was performed for orthoses in 2 affected members with foot ulceration using the Musgrave Footprint system.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Palmar cold threshold test and median nerve electrophysiology in carpal tunnel compression neuropathy.
The diagnosis of median nerve compression neuropathy at the carpal tunnel is usually confirmed by clinical electrophysiology. The classical findings of a significantly slowed median nerve conduction velocity for both sensory and motor fibres, with a prolonged distal motor latency and a reduced amplitude compared to age-related norms are unambiguous, but these criteria are often present only in part. In such cases another quantitative indicator of compression neuropathy would be extremely helpful. The present study aimed to test whether measurement of warm and cold sensory acuity in cases of putative median nerve carpal tunnel compression would aid diagnostic certainty. Warm sensation is mediated by unmyelinated C-afferents, while cold sensation is conveyed by thinly myelinated A delta afferents. Because compression usually blocks larger diameter fibres first, cold perception on the skin of the palm distal to the compression should be more impaired than is warm perception. Standard electrophysiological measurements (median and ulnar motor and sensory nerve conduction velocities) were made, then perceptual thresholds for both warm and cold stimuli were measured on the skin of the wrist above the carpal tunnel and on the palm of the affected hand in 59 subjects. There was a significantly reduced median motor nerve conduction velocity and prolonged distal motor latency compared to normals. Further, although both thermal thresholds at the wrist were normal, those on the palm were elevated, cold being significantly raised (P less than 0.02) compared both to warm and to age-matched controls. Correlation of the nerve conduction velocity findings and thermal sensory acuity did not yield significant covariance of the positive and negative findings. Overall the results suggest that detection of preferentially elevated cold perceptual threshold (ie reduced cold sensory acuity) on the skin of the palm may aid in the diagnosis of putative carpal tunnel compression in patients with minimal or ambiguous electrophysiological data and provide a functional index of recovery after decompression.
Adult↗
Noxious heat hyperalgesia test instrument.
A simple feedback thermode has been developed to quantify cutaneous hyperalgesia to noxious heat. A noxious temperature set between 42 degrees C and 60 degrees C is applied to a test site by the subject. A resettable impedance timing circuit measures the contact duration to +/- 0.01s. Despite site-to-site, inter- and intra-subject variability, the test sensitivity is enhanced by comparing affected and corresponding normal skin in the same subject. This test strategy was used in 55 subjects in whom topical 0.025 to 0.05% capsaicin application provoked hyperalgesia on the forearm and foot. Capsaicin-treated sites showed a significant reduction of 52 degrees C withdrawal latency (0.51-0.77 x normal mean; P less than 0.05). The device has been tested clinically in patients with diabetic neuropathy who had hypersensitivity to pinprick on one foot. A significant 42% difference was found between corresponding contralateral sites (P less than 0.05). These data suggest that even mild hyperalgesia is detectable using this instrument. It provides an objective measure of hyperalgesia which can be used to assess changes in nociceptive acuity.
Capsaicin↗
Roentgenographic changes in headbangers.
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Adolescent↗