Decreased cutaneous sensory axon-reflex vasodilatation below the lesion in patients with complete spinal cord injury

The histamine-induced skin flare response has been considered of practical value in determining the level of a spinal cord lesion, but clinical observations have varied widely with regard to the nature and degree of change below the lesion. We have quantified cutaneous sensory axon-reflex vasodilatation in patients with complete spinal cord injury (SCI) above and below the lesion, and compared the findings with normal subjects. Axon-reflex vasodilatation was induced by intradermal histamine injection, and measured by (a) laser Doppler fluxmetry and (b) tracing the surface area of the flare. Axon-reflex vasodilatation was present in all SCI patients above and below the lesion, but was significantly diminished below the lesion by both measures (pflux rise = 0.0008; pflare = 0.023), and in comparison with controls (by 39%). The flux increase was significantly correlated with the area of flare (r = 0.82; p = 0.02). Axon-reflex vasodilatation and visual analogue scale (VAS) pain scores on histamine injection were not significantly different above the lesion in SCI patients from controls. Baseline laser Doppler flux was not different at any test site in SCI and normal subjects. The cutaneous sensory axon-reflex is thus significantly diminished in SCI patients below the level of the lesion, but the underlying mechanism is unclear. A possible explanation under investigation is that increased basal or reflex sympathetic vasoconstriction mediated via the isolated spinal cord may counteract the vasodilatation produced by the cutaneous sensory terminals.

Idiopathic slow transit constipation and megacolon are not associated with neurturin mutations

Chronic idiopathic slow-transit constipation (ISTC) and idiopathic megacolon (IMC) are early-onset gastrointestinal motility disorders of unknown aetiology. The gene encoding the neurotrophic factor neurturin may be a candidate for these disorders, as neurturin-deficient mice have a similar enteric phenotype. In the present study, we tested this hypothesis. Genomic DNA from 26 cases of chronic idiopathic STC [with a family history of constipation in 15 (58%) and Hirschsprung's disease in two (8%)], and five cases of IMC [two familial (40%)] was screened by direct DNA sequencing using the fluorescent dideoxy terminator method. Results were compared with published sequence data and 24 control DNAs. Our results revealed several previously unreported common sequence polymorphisms, but overall frequencies were comparable between patients and controls. We conclude that mutation of neurturin is not a frequent cause of ISTC or IMC.

TRPV3 is a temperature-sensitive vanilloid receptor-like protein

Vanilloid receptor-1 (VR1, also known as TRPV1) is a thermosensitive, nonselective cation channel that is expressed by capsaicin-sensitive sensory afferents and is activated by noxious heat, acidic pH and the alkaloid irritant capsaicin. Although VR1 gene disruption results in a loss of capsaicin responses, it has minimal effects on thermal nociception. This and other experiments--such as those showing the existence of capsaicin-insensitive heat sensors in sensory neurons--suggest the existence of thermosensitive receptors distinct from VR1. Here we identify a member of the vanilloid receptor/TRP gene family, vanilloid receptor-like protein 3 (VRL3, also known as TRPV3), which is heat-sensitive but capsaicin-insensitive. VRL3 is coded for by a 2,370-base-pair open reading frame, transcribed from a gene adjacent to VR1, and is structurally homologous to VR1. VRL3 responds to noxious heat with a threshold of about 39 degrees C and is co-expressed in dorsal root ganglion neurons with VR1. Furthermore, when heterologously expressed, VRL3 is able to associate with VR1 and may modulate its responses. Hence, not only is VRL3 a thermosensitive ion channel but it may represent an additional vanilloid receptor subunit involved in the formation of heteromeric vanilloid receptor channels.

Use of an orthopaedic fixator for external fixation of the mandible

A patient presented with a chronically infected, non-united fracture of the mandible, with considerable bone loss. He was treated with a metacarpal fixator, the miniPennig external fixator. The fixator is stable and smaller than conventional mandibular fixators. It can be applied and removed under local anaesthesia, if necessary, requires little maintenance and produces minimal scarring. The successful outcome in this patient is encouraging and we commend the use of the fixator in similar difficult cases.

Calcium-activated potassium channel SK1- and IK1-like immunoreactivity in injured human sensory neurones and its regulation by neurotrophic factors

Calcium-activated potassium ion channels SK and IK (small and intermediate conductance, respectively) may be important in the pathophysiology of pain following nerve injury, as SK channels are known to impose a period of reduced excitability after each action potential by afterhyperpolarization. We studied the presence and changes of human SK1 (hSK1)- and hIK1-like immunoreactivity in control and injured human dorsal root ganglia (DRG) and peripheral nerves and their regulation by key neurotrophic factors in cultured rat sensory neurones. Using specific antibodies, hSK-1 and hIK-1-like immunoreactivity was detected in a majority of large and small/medium-sized cell bodies of human DRG. hSK1 immunoreactivity was decreased significantly in cell bodies of avulsed human DRG (n = 8, surgery delay 8 h to 12 months). There was a decrease in hIK1-like immunoreactivity predominantly in large cells acutely (<3 weeks after injury), but also in small/medium cells of chronic cases. Twenty-three injured peripheral nerves were studied (surgery delay 8 h to 12 months); in five of these, hIK1-like immunoreactivity was detected proximally but not distally to injury, whereas neurofilament staining confirmed the presence of nerve fibres in both regions. These five nerves, unlike the others, had all undergone Wallerian degeneration previously and the loss of hIK1-like immunoreactivity may therefore reflect reduced axonal transport of this ion channel across the injury site in regenerated fibres, as well as decreased expression in the cell body. In vitro studies of neonatal rat DRG neurones showed that nerve growth factor (NGF) significantly increased the percentage of hSK1-positive cells, whereas neurotrophin 3 (NT-3) and glial cell line-derived neurotrophic factor (GDNF) failed to show a significant effect. NT-3 stimulated hIK1 expression, while NGF and GDNF were ineffective. As expected, NGF increased expression of the voltage-gated sodium channel SNS1/PN3 in this system. Decreased retrograde transport of these neurotrophic factors in injured sensory neurones may thus reduce expression of these ion channels and increase excitability. Blockade of IK1-like and other potassium channels by aminopyridines (4-AP and 3,4-DAP) may also explain the paraesthesiae induced by these medications. Selective potassium channel openers are likely to represent novel therapies for pain following nerve injury.

Increased sodium channel SNS/PN3 immunoreactivity in a causalgic finger

The sodium channels SNS/PN3 and NaN/SNS2 are regulated by the neurotrophic factors-nerve growth factor (NGF) and glial-derived neurotrophic factor (GDNF), and may play an important role in the development of pain after nerve injury or inflammation. These key molecules have been studied in an amputated causalgic finger and control tissues by immunohistochemistry. There was a marked increase in the number and intensity of SNS/PN3-immunoreactive nerve terminals in the affected finger, while GDNF-immunoreactivity was not observed, in contrast to controls. No differences were observed for NGF, trk A, NT-3 or NaN/SNS2-immunoreactivity. While further studies are required, these findings suggest that accumulation of SNS/PN3 and/or loss of GDNF may contribute to pain in causalgia, and that selective blockers of SNS/PN3 and/or rhGDNF may provide effective novel treatments.

Restoration of sensory function and lack of long-term chronic pain syndromes after brachial plexus injury in human neonates

Obstetric complications are a common cause of brachial plexus injuries in neonates. Failure to restore sensation leads to trophic injuries and poor limb function. It is not known whether the infant suffers chronic neuropathic or spinal cord root avulsion pain; in adults, chronic pain is usual after spinal root avulsion injuries, and this is often intractable. The plexus is repaired surgically in severe neonatal injures; if no spontaneous recovery has occurred by 3 months, and if neurophysiological investigations point to poor prognosis, then nerve trunk injures are grafted, while spinal cord root avulsion injuries are treated by transferring an intact neighbouring nerve (e.g. intercostal) to the distal stump of the damaged nerve, in an attempt to restore sensorimotor function. Using a range of non-invasive quantitative measures validated in adults, including mechanical, thermal and vibration perception thresholds, we have assessed for the first time sensory and cholinergic sympathetic function in 24 patients aged between 3 and 23 years, who had suffered severe brachial plexus injury at birth. While recovery of function after spinal root avulsion was related demonstrably to surgery, there were remarkable differences from adults, including excellent restoration of sensory function (to normal limits in all dermatomes for at least one modality in 16 out of 20 operated cases), and evidence of exquisite CNS plasticity, i.e. perfect localization of restored sensation in avulsed spinal root dermatomes, now presumably routed via nerves that had been transferred from a distant spinal region. Sensory recovery exceeded motor or cholinergic sympathetic recovery. There was no evidence of chronic pain behaviour or neuropathic syndromes, although pain was reported normally to external stimuli in unaffected regions. We propose that differences in neonates are related to later maturation of injured fibres, and that CNS plasticity may account for their lack of long-term chronic pain after spinal root avulsion injury.

A double-blind placebo-controlled clinical trial of recombinant human brain-derived neurotrophic factor (rhBDNF) in diabetic polyneuropathy

A randomized, double-blind, placebo-controlled study of brain-derived neurotrophic factor (rhBDNF) was conducted in 30 patients with insulin-treated diabetes mellitus, with obligatory abnormalities of sural nerve conduction studies and vibration perception threshold (VPT) at the great toe on recruitment. Nine patients received placebo, 11 rhBDNF (25 microg/ kg) and 10 rhBDNF (100 microg/kg) s.c. daily for 3 months, and were assessed at days 0, 8, 15, 29, 43, 57 and 85 with nerve conduction and quantitative sensory and autonomic tests including VPT, thermal and light touch thresholds, and cutaneous axon-reflexes. No statistically significant differences were found among the 3 treatment groups between baseline and day 85 values. To examine possible reasons for lack of effect, post hoc analysis was performed. In the subset of patients with abnormal but detectable cool detection threshold (CDT) at baseline, there was improvement of CDT at day 85 when compared to baseline in the treated (p < 0.02) but not placebo group. Further, from days 43 to 85, in the treated group but not the placebo group, CDT was indistinguishable from a group of matched normal subjects (p > 0.05). Skin biopsies failed to show evidence of structural change; assessment of innervation of hair follicles, which is partly dependent on BDNF, was not possible because of the marked loss of this end-organ in diabetic neuropathic skin. The only side effects of rhBDNF were infrequent non-painful injection-site skin reactions and increased gut motility at the higher dose. We conclude that further preclinical studies are warranted before any future clinical trials to see if rhBDNF improves CDT and constipation in diabetics.

Ribosomal protein S6 phosphorylation and function during late gestation liver development in the rat

The phosphorylation of ribosomal protein S6 is thought to be required for biosynthesis of the cell's translational apparatus, a critical component of cell growth and proliferation. We have studied the signal transduction pathways involved in hepatic S6 phosphorylation during late gestation in the rat. This is a period during which hepatocytes show a high rate of proliferation that is, at least in part, independent of mitogenic signaling pathways that are operative in mature hepatocytes. Our initial studies demonstrated that there was low basal activity of two S6 kinases in liver, S6K1 and S6K2, on embryonic day 19 (2 days preterm). In addition, insulin- and growth factor-mediated S6K1 and S6K2 activation was markedly attenuated compared with that in adult liver. Nonetheless, two-dimensional gel electrophoresis demonstrated that fetal liver S6 itself was highly phosphorylated. To characterize the fetal hepatocyte pathway for S6 phosphorylation, we went on to study the sensitivity of hepatocyte proliferation to the S6 kinase inhibitor rapamycin. Unexpectedly, administration of rapamycin to embryonic day 19 fetuses in situ did not affect hepatocyte DNA synthesis. This resistance to the growth inhibitory effect of rapamycin occurred even though S6K1 and S6K2 were inhibited. Furthermore, fetal hepatocyte proliferation was sustained even though rapamycin administration resulted in the dephosphorylation of ribosomal protein S6. In contrast, rapamycin blocked hepatic DNA synthesis in adult rats following partial hepatectomy coincident with S6 dephosphorylation. We conclude that hepatocyte proliferation in the late gestation fetus is supported by a rapamycin-resistant mechanism that can function independently of ribosomal protein S6 phosphorylation.

Long-term trans-synaptic glial responses in the human thalamus after peripheral nerve injury

Limb denervation leads to reorganization of the representational zones of the somatosensory cortex. Using [11C](R)-PK11195, a sensitive in vivo marker of glial cell activation, and PET, we provide first evidence that limb denervation induces a trans-synaptic increase in [11C](R)-PK11195 binding in the human thalamus but not somatosensory cortex: these brain structures appeared morphologically normal on magnetic resonance imaging (MRI). The increased thalamic signal was detectable many years after nerve injury, indicating persistent reorganization of the thalamus. This glial activation, beyond the first-order projection area of the injured neurons, may reflect continually altered afferent activity. Our findings support the view that long-term rearrangement of cortical representational maps is significantly determined within the thalamus.

Novel capsaicin (VR1) and purinergic (P2X3) receptors in Hirschsprung's intestine

BACKGROUND/PURPOSE

Studies of Hirschsprung's disease (HSCR) have shown that hypertrophic nerves in aganglionic bowel are mainly of extrinsic origin and may contain sensory elements. Recent advances have shown a specific capsaicin receptor VR1 (vanilloid receptor-1), and an ATP-gated ion channel P2X(3), which are expressed by sensory neurons.

METHODS

This study investigated, for the first time, the distribution of VR1- and P2X(3)-immunoreactivity in normal adult, infant, and HSCR large intestine, using specific antibodies for immunohistochemistry.

RESULTS

VR1-immunoreactive fibers and nerve fascicles, but not somata, were detected in all regions of the bowel in controls with few weakly immunostained fibers in the mucosa/lamina propria. Hypertrophic nerve bundles in hypoganglionic and aganglionic bowel showed intense VR1-immunoreactivity, whereas normoganglionic regions of HSCR were similar to controls. P2X(3)-immunoreactive neuronal cell bodies, in some instances with long axonal processes, were detected in the myenteric and submucous plexuses in control infant, adult, and ganglionic HSCR samples. Aganglionic samples showed weak P2X(3)-immunoreactivity in hypertrophic nerve fasciculi in the submucous and myenteric plexuses.

CONCLUSIONS

The presence of VR1- and P2X(3)-immunoreactivities in aganglionic HSCR bowel indicates that sensory nerves may form a significant proportion of its hypertrophic innervation. The functional significance of P2X(3) and VR1 receptors in enteric nerves deserves further investigation.

The natural history of diabetic peripheral neuropathy determined by a 12 year prospective study using vibration perception thresholds

The development and long term progression of diabetic peripheral neuropathy was studied using vibration perception threshold (VPT) as a validated measure. Three hundred and ninety-two patients had a normal age corrected VPT (12.1 +/- 3.7 volts) at baseline, with an age corrected logarithmic VPTscore < 12. 19.9% developed an abnormal VPT over a 12 year period, increasing from 14.2 +/- 3.7 volts (VPTscore 10.4 +/- 0.6) at baseline to 35.9 +/- 9.5 volts (VPTscore 12.6 +/- 0.45) at follow up (P = 0.0001), and from 10.1 +/- 3.7volts (VPTscore 9.4 +/- 0.8) to 14.2 +/- 4.7 (VPTscore 9.8 +/- 0.8) in the rest. Over 80% thus retained a "normal" VPT after a mean diabetes duration of 16 years despite only average glycaemic control, suggesting that non-ideal long term glycaemic control leads to neuropathy in a subset of predisposed patients. VPT was correlated in 123 diabetic patients with definitive criteria for neuropathy and a range of quantitative sensory and autonomic tests. 62/63 patients with abnormal VPT fulfilled neuropathy criteria; of patients with normal VPT who fulfilled neuropathy criteria, all had at least one abnormal thermal threshold test result. We conclude that a combination of log-transformed VPT values (VPTscore > 10.1) and thermal thresholds can identify diabetic patients at risk of developing peripheral neuropathy and select patients likely to benefit from prophylaxis in clinical trials.

ATP-gated ion channel P2X(3) is increased in human inflammatory bowel disease

P2X(3) is a novel ATP-gated cation channel that is selectively expressed by small-diameter sensory neurones in rodents, and may play a role in nociception by binding ATP released from damaged or inflamed tissues. We have studied, for the first time, P2X(3) immunoreactivity in human inflammatory bowel disease, using Western blotting and immunohistochemistry. A major 66-kDa specific protein was found by Western blotting in all colon extracts. In the inflamed group there was a significant two-fold increase in the relative optical density of the 66-kDa band (21.2 +/- 3.1; n=8) compared to controls (11.4 +/- 3.7; n=8; P=0.009). In the control colon, P2X(3)-immunoreactive neurones were scattered throughout the myenteric and submucosal plexuses, with some neurones showing immunopositive axons/dendrites. The pattern of immunostaining was similar to the neuronal marker peripherin. In general, the intensity of the staining was greater in myenteric than submucosal neurones. The number of P2X(3)-immunoreactive neurones was significantly increased in the myenteric plexus of inflamed colon compared to controls (n=13; P=0.01). In humans, unlike rodents, P2X(3) is thus not restricted to sensory neurones. Increased P2X(3) in inflamed intestine suggests a potential role in dysmotility and pain, for which it represents a new therapeutic target.

Increased acid-sensing ion channel ASIC-3 in inflamed human intestine

OBJECTIVES

Acid-sensing ion channels (ASICs) are expressed by rat sensory neurons and may mediate pain associated with tissue acidosis after inflammation or injury. Our aim was to examine the molecular forms and localization of ASICs in human intestine and dorsal root ganglia using immunochemical techniques, and to measure the effects of inflammation and injury.

DESIGN AND METHODS

Inflamed Crohn's disease intestine and injured human dorsal root ganglia, with appropriate controls, were studied by Western blotting and immunohistochemistry, using specific affinity-purified ASIC antibodies.

RESULTS

In the Western blot, there was a significant three-fold increase in the mean relative optical density of the ASIC-3 55-kDa band (but not ASIC-1 or ASIC-2) in full-thickness inflamed intestine, as well as in separated muscle and mucosal layers. There was a corresponding trend for an increased immunoreactive density and increased number of ASIC-3-positive neurons in the myenteric and sub-mucous plexus of inflamed intestine. In dorsal root ganglia, immunoreactivity for all ASICs was restricted to a sub-population (about 50%) of small-diameter (nociceptor) sensory neurons, and was generally less intense after injury.

CONCLUSIONS

Increased ASIC-3 in inflamed intestine suggests a role in pain or dysmotility, for which ASICs represent new therapeutic targets.

Dendritic cells (DCs) in rheumatoid arthritis (RA): progenitor cells and soluble factors contained in RA synovial fluid yield a subset of myeloid DCs that preferentially activate Th1 inflammatory-type responses

There is evidence that mature dendritic cells (DCs) present in the rheumatoid arthritis (RA) joint mediate immunopathology in RA. In this study, we indicate that early myeloid progenitors for DCs and DC growth factors existing in RA synovial fluid (SF) are also likely participants in the RA disease process. A fraction of cells lacking markers associated with mature DCs or DC precursors and enriched in CD34(negative) myeloid progenitors was isolated from RA SF. These cells proliferated extensively when cultured in vitro with cytokines that promote the growth of myeloid DCs (GM-CSF/TNF/stem cell factor/IL-4) and, to a lesser degree, when cultured with monocyte/granulocyte-restricted growth factors (M-CSF/GM-CSF). Mature DCs derived from RA SF progenitors with CD14-DC cytokines known to be prevalent in the inflamed RA joint (GM-CSF/TNF/stem cell factor/IL-13) were potent stimulators of allogeneic T cells and inflammatory-type Th1 responses and included CD14-DC subtypes. Cell-free RA SF facilitated DC maturation from myeloid progenitors, providing direct evidence that the inflamed RA joint environment instructs DC growth. Enhanced development of CD14-derived DCs was correlated with the presence of soluble TNFR (p55), raising the possibility that soluble TNFR also regulate CD14-derived DC growth in vivo. SF from patients with osteoarthritis contained neither myeloid DC progenitors nor DC growth factors. The existence of DC progenitors and myeloid DC growth factors in RA SF supports the concept that RA SF may be a reservoir for joint-associated DCs and reveals a compelling mechanism for the amplification and perpetuation of DC-driven responses in the RA joint, including inflammatory-type Th1 responses.

Capsaicin receptor VR1 and ATP-gated ion channel P2X3 in human urinary bladder

OBJECTIVES

To determine the presence, distribution and molecular forms of the vanilloid receptor VR1, and confirm the presence and distribution of the ATP-gated ion channel P2X3 in the human urinary bladder. Materials and methods Normal urinary bladder tissues were obtained at postmortem from four subjects. Eight urinary bladder biopsies were also taken from patients with detrusor hyper-reflexia treated with intravesical resiniferatoxin. The specimens were studied using affinity-purified specific antibodies to VR1 and P2X3 by Western blotting and immunocytochemistry, and compared with immunostaining using antibodies to the pan-neuronal marker PGP 9.5 and Schwann cell marker S-100.

RESULTS

VR1- and P2X3-immunoreactive fine nerve fibres were scattered throughout the suburothelium of the normal bladder and cystoscopic biopsies, and traversed the muscle layer. They had a similar distribution to PGP 9.5-immunoreactive fibres, but there were fewer, suggesting localization in subsets of axons. Western blot studies showed an expected 100-kDa VR1 protein and a P2X3-immunoreactive 66-kDa protein. Conclusion VR1 and P2X3 are present in the human urinary bladder and may contribute to distinct pathophysiological states of bladder overactivity, in accord with their differential expression in sensory neurones. Intravesical vanilloids act via VR1 and are effective in the treatment of detrusor hyper-reflexia. P2X3 may represent a selective therapeutic target for other causes of overactive bladder.

Vanilloid receptor 1 immunoreactivity in inflamed human bowel

Vanilloid receptor 1 (VR1) is expressed by sensory neurons. Once activated, these neurons evoke the sensation of burning pain and release neuropeptides that induce neurogenic inflammation. We used immunoblotting and immunostaining to estimate the density of VR1 in colonic tissues of patients with inflammatory bowel disease and of controls. Our study results indicate that VR1 immunoreactivity is greatly increased in colonic nerve fibres of patients with active inflammatory bowel disease. Thus, the discovery of new drugs that can bind the VR1 receptor, or antagonise endogenous inflammatory substances that activate this receptor, could lead to new therapies for pain and dysmotility.

Decreased tyrosine kinase C expression may reflect developmental abnormalities in Hirschsprung's disease and idiopathic slow-transit constipation

BACKGROUND

Some patients with Hirschsprung's disease have refractory constipation following excision of aganglionic bowel, as do patients with idiopathic slow-transit constipation (STC). Gut motility depends on enteric neuronal development in response to expression of trophic factors and their receptors. Recent studies indicate the importance of neurotrophin 3 (NT-3) and its high-affinity receptor tyrosine kinase C (trk C) in enteric neuronal development.

METHODS

Blinded quantitative immunohistochemical analysis of colon from patients with Hirschsprung's disease (aganglionic, hypoganglionic and normoganglionic) (n = 5), STC (n = 6) and appropriate age-matched control tissues (n = 5) was performed for NT-3 and trk C. Sural nerve morphometry and immunostaining were undertaken in three patients with STC who had abnormalities on limb autonomic and sensory testing.

RESULTS

A significantly higher proportion of submucous plexus neurones was trk C immunoreactive in control infant than adult colon (mean(s.e.m.) 73(9) versus 16(3) per cent of the total; P < 0.001), in accord with a role in development. The proportion of submucous plexus trk C-immunoreactive neurones was reduced in colon from patients with Hirschsprung's disease (28(7) per cent of total in normoganglionic Hirschsprung's disease; P < 0.007 versus infant controls) and STC (10(1) per cent of total; P = 0.053 versus adult controls). No abnormalities of STC sural nerves were detected by morphometry or immunostaining.

CONCLUSION

Decreased trk C expression may reflect developmental abnormalities in Hirschsprung's disease and idiopathic STC. Trk C activation by NT-3 or drugs may provide novel treatments. Presented in abstract form to the Pacific Association of Pediatric Surgeons, Las Vegas, Nevada, USA, May 2000

Sodium channel beta1 and beta2 subunits parallel SNS/PN3 alpha-subunit changes in injured human sensory neurons

Voltage-gated sodium channels consist of a pore-containing alpha-subunit and one or more auxiliary beta-subunits, which may modulate channel function. We previously demonstrated that sodium channel SNS/PN3 alpha-subunits were decreased in human sensory cell bodies after spinal root avulsion injury, and accumulated at injured nerve terminals in pain states. Using specific antibodies for immunohistochemistry, we have now detected sodium channel beta1 and beta2 subunits in sensory cell bodies within control human postmortem sensory ganglia (78% of small/medium (< or = 50 microm) and 68% of large (> or = 50 microm) cells); their changes in cervical sensory ganglia after avulsion injury paralleled those described for SNS/PN3 alpha-subunits. Our results suggest that alpha- and beta-subunits share common regulatory mechanisms, but present distinct targets for novel analgesics.

Plasticity of TTX-sensitive sodium channels PN1 and brain III in injured human nerves

Sensory neurones co-express voltage-gated sodium channels that mediate TTX-sensitive (TTX-S) and TTX-resistant (TTX-R) currents, which may contribute to chronic pain after nerve injury. We previously demonstrated that TTX-R channels were decreased acutely in human sensory cell bodies after central axotomy, but accumulated in nerve terminals after peripheral axotomy. We have now studied the TTX-S channels PN1 and Brain III, using specific antibodies for immunohistochemistry, in dorsal root ganglia (DRG) from 10 patients with traumatic central axotomy, nerves from 16 patients with peripheral axotomy, and controls. PN1 showed temporal changes similar to the TTX-R channels in sensory cell bodies of injured DRG. In contrast, Brain III was found only in injured nerves (not control nerves, or control/central axotomy DRG). PNI and Brain III are distinct targets for novel analgesics.

Double-blind randomized phase II study of hyperbaric oxygen in patients with radiation-induced brachial plexopathy

BACKGROUND

Radiation-induced brachial plexopathy (RIBP) is an untreatable complication of curative radiotherapy for early breast cancer, characterized by chronic neuropathic pain and limb paralysis. Hyperbaric oxygen (HBO2) therapy is known to promote healing of tissue rendered ischaemic by radiotherapy, but is untested in RIBP.

METHODS

Thirty four eligible research volunteers suffering from RIBP were randomized to HBO2 or control group. The HBO2 group breathed 100% oxygen for 100 min in a multiplace hyperbaric chamber on 30 occasions over a period of 6 weeks. The control group accompanied the HBO2 group and breathed a gas mixture equivalent to breathing 100% oxygen at surface pressure. All volunteers and investigators, except the operators of the hyperbaric chamber and the trial statistician, were blind to treatment assignments. The warm sensory threshold, which measures the function of small sensory fibres, was selected as the primary endpoint.

FINDINGS

Pre-treatment neurophysiological tests were grossly abnormal in the affected hand compared to the unaffected hand in both HBO2 and control groups, as expected, but no statistically significant differences were noted in either group at any time up to 12 months post-treatment. However, normalization of the warm sensory threshold in two of the HBO2 group was reliably recorded. Two cases with marked chronic arm lymphoedema reported major and persistent improvements in arm volume for at least 12 months after treatment with HBO2. IINTERPRETATION: There is no reliable evidence to support the hypothesis that HBO2 therapy slows or reverses RIBP in a substantial proportion of affected individuals, although improvements in warm sensory threshold offer some suggestion of therapeutic effect. Improvement in long-standing arm lymphoedema was not anticipated, and justifies further investigation.

Hirschsprung's disease: a more generalised neuropathy?

BACKGROUND/PURPOSE

Aberrant neural crest migration is implicated in the pathogenesis of hindgut aganglionosis in Hirschsprung's disease (HSCR). Neural crest progenitors also give rise to a variety of cell types outside the gut, including nerves of the inner ear and peripheral nervous system. This study aims to determine whether such nerves are also affected in HSCR.

METHODS

Pure tone audiometry and oto-acoustic emission tests were performed on 53 patients with Hirschsprung's disease and 28 age-matched controls. Forty-two children with Hirschsprung's disease and 30 age-matched controls also underwent neurologic evaluation, including quantitative peripheral tests of sensory function.

RESULTS

Moderate to severe sensorineural hearing loss (1 profound [Waardenburg syndrome] and 3 high frequency) was detected in 4 children (8%) from the Hirschsprung's group. Abnormal (absent or reduced) oto-acoustic emission was detected in 77 of 102 ears (41 of 51 patients) in the HSCR group and 8 out of 48 ears (6 of 24 children) in the control group (75% v 17%; P<.0001). Two HSCR children had marked abnormalities on tests of peripheral nerve function. Significantly higher thresholds for vibration sensation were detected in HSCR versus controls (P<.05).

CONCLUSION

Hirschsprung's disease may have a more generalised neuropathy than just that involving the affected bowel.

Identification and characterization of a novel human vanilloid receptor-like protein, VRL-2

Remarkable progress has been made recently in identifying a new gene family related to the capsaicin (vanilloid) receptor, VR1. Using a combination of in silico analysis of expressed sequence tag (EST) databases and conventional molecular cloning, we have isolated a novel vanilloid-like receptor, which we call VRL-2, from human kidney. The translated gene shares 46% and 43% identity with VR1 and VRL-1, respectively, and maps to chromosome 12q23-24.1, a locus associated with bipolar affective disorder. VRL-2 mRNA was most strongly expressed in the trachea, kidney, and salivary gland. An affinity-purified antibody against a peptide incorporating the COOH terminal of the receptor localized VRL-2 immunolabel in the distal tubules of the kidney, the epithelial linings of both trachea and lung airways, serous cells of submucosal glands, and mononuclear cells. Unlike VR1 and VRL-1, VRL-2 was not detected in cell bodies of dorsal root ganglia (DRG) or sensory nerve fibers. However, VRL-2 was found on sympathetic and parasympathetic nerve fibers, such as those innervating the arrector pili smooth muscle in skin, sweat glands, intestine, and blood vessels. At least four vanilloid receptor-like genes exist, the newest member, VRL-2 is found in airway and kidney epithelia and in the autonomic nervous system.

Cizolirtine citrate (E-4018) in the treatment of chronic neuropathic pain

This study was performed to determine the efficacy and safety of oral cizolirtine citrate, a novel agent, in the treatment of chronic neuropathic pain. Cizolirtine was tested in a double-blind, placebo-controlled, two-way crossover study, having previously been shown to have significant analgesic and anti-hyperalgesic action in neuropathic pain models and preliminary human studies. Twenty-five patients with neuropathic pain, which was persistent for at least three months, and scored > 30 mm on a 100 mm visual analogue scale (VAS), were included. A subgroup of five patients had primary skin allodynia, i.e. pain evoked by non-noxious stimuli in the territory of the injured nerve. Cizolirtine 200 mg or placebo was administered twice daily for a treatment period of 21 days, each separated by a washout interval of 7 days. Assessments of skin allodynia were performed using the graded monofilaments (von Frey hairs) on days 1 (predose), 14 and 21 (90 min postdose). All patients were instructed to maintain a daily pain diary throughout the study. Results showed that the differences in VAS and allodynia scores between cizolirtine and placebo treatments were not significant in the overall analysis (p > or = 0.05); cizolirtine was well tolerated. In a subgroup of five patients with primary allodynia, a 53% reduction in VAS score from baseline at rest (p = 0.007) and 55% on movement (p = 0.0002) at day 21 was observed with cizolirtine, as compared to 8% at rest (p = 0.5215) and 13% on movement (p = 0.4187) with placebo. Similarly, allodynia improved with cizolirtine (p = 0.03) but not with placebo (p = 0.9) in this subgroup. Cizolirtine may be effective in primary allodynia after peripheral nerve injury, and a further trial in a larger number of such subjects is warranted.

The effects of ciliary neurotrophic factor on the hypothalamo-pituitary gonadal axis in vitro in female rats

Ciliary neurotrophic factor (CNTF) is a member of the neuropoietic family of cytokines. CNTF exerts its actions through activation of a receptor complex, which shows similarity of sequence, second messenger systems and distribution to the leptin receptor. Leptin has been demonstrated to exert profound effects on the hypothalamo-pituitary gonadal axis. This study examines the in vitro effects of CNTF on hypothalamic luteinizing hormone releasing hormone release (LHRH) and pituitary luteinizing hormone (LH) release compared to those of leptin in the female. We report that CNTF stimulates LHRH release from medial basal hypothalamic explants harvested from proestrous female rats and this effect is of similar magnitude to that seen with leptin. In contrast, CNTF suppresses LHRH-stimulated LH release from dispersed anterior pituitary cells harvested from proestrous female rats but has no effect on basal LH release. Leptin stimulates basal LH release but has no effect on LHRH-stimulated LH release. The suppressive effect of CNTF on LHRH-stimulated LH release has been confirmed in perifused anterior hemipituitaries. These results suggest a differential effect of CNTF on the hypothalamo-pituitary gonadal axis and a possible role in the modulation of pituitary gonadal function.

Spinal nerve root repair and reimplantation of avulsed ventral roots into the spinal cord after brachial plexus injury

OBJECT

The authors review the first series of 10 cases in which injured intraspinal brachial plexus were surgically repaired. They describe the technique of spinal cord implantation or repair of ruptured nerve roots, as well as patient outcome.

METHODS

Spinal root repair/implantation was performed from 10 days to 9 months postinjury. There were nine male patients and one female patient. Postoperatively in most cases, regeneration of motor neurons from the spinal cord to denervated muscles could be demonstrated. The first signs of regeneration were noted approximately 9 to 12 months postoperatively. Useful function with muscle power of at least Medical Research Council Grade 3 occurred in three of 10 cases. Magnetic brain stimulation studies revealed a normal amplitude and latency from the cortex to reinnervated muscles on surgically treated and control sides. A certain degree of cocontraction between antagonistic muscles (for example, biceps-triceps) compromised function. With time there was a reduction of cocontractions, probably due to spinal cord plasticity. In these cases there was also, surprisingly, a return of sensory function, although the mechanism by which this occurred is uncertain. Sensory stimulation (thermal and mechanical) within the avulsed dermatomes was perceived abnormally and/or experienced at remote sites. There was some return of patients' sense of joint position.

CONCLUSIONS

A short time lag between the accident and the surgery was recognized as a significant factor for a successful outcome. Reimplantation of avulsed nerve roots may be combined with other procedures such as nerve transfers in severe cases of brachial plexus injury.

Idiopathic slow-transit constipation is not associated with mutations of the RET proto-oncogene or GDNF

PURPOSE

Idiopathic slow-transit constipation is a severe disorder of unknown cause. The onset in early childhood and history of constipation or Hirschsprung's disease in close family relatives suggest that slow-transit constipation could have a genetic basis. Several germline mutations have been described in Hirschsprung's disease, including mutations of RET and the gene encoding its ligand glial cell-derived neurotrophic factor. The aim of this study was to screen a panel of 16 cases of familial idiopathic slow-transit constipation, including 4 families in which there were relatives with Hirschsprung's disease, for RET and glial cell-derived neurotrophic factor mutations previously identified in Hirschsprung's disease.

METHODS

Genomic DNA from 16 patients with slow-transit constipation and four relatives with Hirschsprung's disease was analyzed using single strand and heteroduplex conformation polymorphism analysis at two conditions and by direct DNA sequencing using the fluorescent dideoxy terminator method.

RESULTS

Although common sequence polymorphisms were demonstrated with a frequency comparable with published data, no published or new mutation was seen in any of the exons of RET or glial cell-derived neurotrophic factor.

CONCLUSIONS

Mutation of RET or glial cell-derived neurotrophic factor is not a frequent cause of idiopathic slow-transit constipation.

P2X3 receptor in injured human sensory neurons

The ATP-gated cation channel P2X3 is expressed selectively by rat sensory neurones, and may play a role in nociception by binding ATP released from damaged or inflamed tissues. However, the distribution of this channel in human sensory neurons is not known. Using a specific antibody, we have demonstrated intense P2X3 immunoreactivity within a subset (60%) of small/medium diameter sensory neurones and fine nerve fibres in intact post-mortem human dorsal root ganglia (DRG). Co-localization studies showed < 15% overlap with the trkA immunostaining in DRG, indicating that P2X3 was expressed predominantly in sensory neurons that are also isolectin B4 positive. There was a significant decrease in numbers of P2X3-like immunoreactive neurons in human DRG after central axotomy (to 36%), similar to the decrease in rat DRG after peripheral axotomy. However, Western blotting demonstrated a specific 66 kDa band in human DRG and peripheral organs, including intestine, where histochemistry showed P2X3 immunoreactivity in myenteric plexus neurons. Thus P2X3 antagonists may be analgesic, but are unlikely to have a selective effect on pain in humans.

QALYs and the integration of claims in health-care rationing

The paper argues against the polarization of the health economics literature into pro- and anti-QALY camps. In particular, we suggest that a crucial distinction should be made between the QALY measure as a metric of health, and QALY maximization as an applied social choice rule. We argue against the rule but for the measure and that the appropriate conceptualization of health-care rationing decisions should see the main task as the integration of competing and possibly incommensurable normative claim types. We identify the main types as consequences, rights, social contracts, individual votes and community values and note situations in which the contribution of each claim type is limited. We go on to show that the integration of (at least some of) these claim types can be formalized within the mathematical framework provided by non-linear programming.

Immunolocalization of SNS/PN3 and NaN/SNS2 sodium channels in human pain states

The tetrodotoxin-resistant (TTX-R) voltage-gated sodium channel SNS/PN3 and the newly discovered NaN/SNS2 are expressed in sensory neurones, particularly in nociceptors. Using specific antibodies, we have studied, for the first time in humans, the presence of SNS/PN3 and NaN/SNS2 in peripheral nerves, including tissues from patients with chronic neurogenic pain. In brachial plexus injury patients, there was an acute decrease of SNS/PN3- and NaN/SNS2-like immunoreactivity in sensory cell bodies of cervical dorsal root ganglia (DRG) whose central axons had been avulsed from spinal cord, with gradual return of the immunoreactivity to control levels over months. In contrast, there was increased intensity of immunoreactivity to both channels in some peripheral nerve fibers just proximal to the site of injury in brachial plexus trunks, and in neuromas. These findings suggest that the expression of these sodium channels in neuronal cell bodies is reduced after spinal cord root avulsion injury in man, but that pre-synthesized channel proteins may undergo translocation with accumulation at sites of nerve injury, as in animal models of peripheral axotomy. The latter may contribute to positive symptoms, as our patients all showed a positive Tinel's sign. Nerve terminals in distal limb neuromas and skin from patients with chronic local hyperalgesia and allodynia all showed marked increases of SNS/PN3-immunoreactive fibers, but little or no NaN/SNS2-immunoreactivity, suggesting that the former may be related to the persistent hypersensitive state. Axonal immunoreactivity to both channels was similar to control nerves in sural nerve biopsies in a selection of neuropathies, irrespective of nerve inflammation, demyelination or spontaneous pain, including a patient with congenital insensitivity to pain. Our studies suggest that the best target for SNS/PN3 blocking agents is likely to be chronic local hypersensitivity.

Do nerve growth factor-related mechanisms contribute to loss of cutaneous nociception in leprosy?

While sensory loss in leprosy skin is the consequence of invasion by M. leprae of Schwann cells related to unmyelinated fibres, early loss of cutaneous pain sensation, even in the presence of nerve fibres and inflammation, is a hallmark of leprosy, and requires explanation. In normal skin, nerve growth factor (NGF) is produced by basal keratinocytes, and acts via its high affinity receptor (trk A) on nociceptor nerve fibres to increase their sensitivity, particularly in inflammation. We have therefore studied NGF- and trk A-like immunoreactivity in affected skin and mirror-site clinically-unaffected skin from patients with leprosy, and compared these with non-leprosy, control skin, following quantitative sensory testing at each site. Sensory tests were within normal limits in clinically-unaffected leprosy skin, but markedly abnormal in affected skin. Sub-epidermal PGP 9.5- and trk A- positive nerve fibres were reduced only in affected leprosy skin, with fewer fibres contacting keratinocytes. However, NGF-immunoreactivity in basal keratinocytes, and intra-epidermal PGP 9.5-positive nerve fibres, were reduced in both sites compared to non-leprosy controls, as were nerve fibres positive for the sensory neurone specific sodium channel SNS/PN3, which is regulated by NGF, and may mediate inflammation-induced hypersensitivity. Keratinocyte trk A expression (which mediates an autocrine role for NGF) was increased in clinically affected and unaffected skin, suggesting a compensatory mechanism secondary to reduced NGF secretion at both sites. We conclude that decreased NGF- and SNS/PN3-immunoreactivity, and loss of intra-epidermal innervation, may be found without sensory loss on quantitative testing in clinically-unaffected skin in leprosy; this appears to be a sub-clinical change, and may explain the lack of cutaneous pain with inflammation. Sensory loss occurred with reduced sub-epidermal nerve fibres in affected skin, but these still showed trk A-staining, suggesting NGF treatment may restore pain sensation.

SNS/PN3 and SNS2/NaN sodium channel-like immunoreactivity in human adult and neonate injured sensory nerves

Two tetrodotoxin-resistant voltage-gated sodium channels, SNS/PN3 and SNS2/NaN, have been described recently in small-diameter sensory neurones of the rat, and play a key role in neuropathic pain. Using region-specific antibodies raised against different peptide sequences of their alpha subunits, we show by Western blot evidence for the presence of these channels in human nerves and sensory ganglia. The expected fully mature 260 kDa component of SNS/PN3 was noted in all injured nerve tissues obtained from adults; however, for SNS2/NaN, smaller bands were found, most likely arising from protein degradation. There was increased intensity of the SNS/PN3 260 kDa band in nerves proximal to the site of injury, whereas it was decreased distally, suggesting accumulation at sites of injury; all adult patients had a positive Tinel's sign at the site of nerve injury, indicating mechanical hypersensitivity. Injured nerves from human neonates showed similar results for both channels, but neonate neuromas lacked the SNS2/NaN 180 kDa molecular form, which was strongly present in adult neuromas. The distribution of SNS/PN3 and SNS2/NaN sodium channels in injured human nerves indicates that they represent targets for novel analgesics, and could account for some differences in the development of neuropathic pain in infants.

Quantitative study of plasticity in the auditory nuclei of chick under conditions of prenatal sound attenuation and overstimulation with species specific and music sound stimuli

Morphological effects of prenatal sound attenuation and sound overstimulation by species specific and music sounds on the brainstem auditory nuclei of chick have been evaluated quantitatively. Changes in length, volume, neuron number, size of neuronal nuclei and glial numbers of second and third order auditory nuclei, n. magnocellularis (NM) and n. laminaris (NL), were determined from thionine-stained serial sections of control and experimental groups on posthatch day 1 using stereological methods. Significant increase in volume of both auditory nuclei attributable to increase in length of nucleus, number and size of neurons, number of glia as well as neuropil was observed in response to both species specific and music overstimulation given during the critical period of development. The enhanced development of auditory nuclei in response to enriched environment prenatally indicates a positive effect of activity on neurons which may have clinical implications in addition to providing explanation for preference to auditory cues in the postnatal life. Reduction in neuron number with a small increase in proportion of cell nuclei of large size as well as an increase in glial numbers was seen in both NM and NL of the prenatally sound attenuated chicks. The increase in size of some neuronal nuclei may probably be evidence of enhanced synthesis of proteins involved in cell death or an attempt at recovery. The dissociated response of neurons and glia under sound attenuated and auditory stimulated conditions suggests that they are independently regulated by activity-dependent signals with glia also being under influence of other signals for a role in removal of dead cell debris.

Decreased CGRP, but preserved Trk A immunoreactivity in nerve fibres in inflamed human superficial temporal arteries

The peptidergic sensory innervation of cranial blood vessels may play an important part in vascular head pain. The neuropeptides calcitonin gene-related peptide (CGRP) and substance P in sensory fibres are dependent on nerve growth factor (NGF) produced by the blood vessels, and when released from nerve terminals mediate neurogenic inflammation. NGF is increased in inflamed tissues, and acts via its high affinity receptor trk A on nociceptor fibres to produce hyperalgesia. CGRP and trk A immunoreactive nerve fibres have therefore been studied, for the first time, in inflamed (n=7) and non-inflamed (n=10) temporal arteries biopsied from patients with headache and suspected giant cell arteritis. CGRP immunoreactivity was markedly decreased to absent in adventitial nerve fibres in inflamed regions of vessels, which may reflect secretion from nerve terminals, as CGRP immunoreactivity could still be seen in nerve trunks in periadventitial tissue. Trk A immunoreactive nerve fibres were found in a similar distribution to CGRP containing nerve fibres in non-inflamed vessels, and the trk A immunoreactivity was virtually unchanged in inflamed vessels. The evidence supports a role for NGF related mechanisms in inflammatory vascular head pain. Anti-NGF or anti-trk A agents may represent novel analgesics in this condition.

Increased nerve growth factor mRNA in lateral calf skin biopsies from diabetic patients

AIMS

This study set out to establish a novel procedure for the measurement of human nerve growth factor (NGF) messenger ribonucleic acid (mRNA) and to use this method to measure NGF expression in skin biopsies from control subjects and from patients with early neuropathies. NGF mRNA levels were related to functional measures of the competence of NGF-responsive nerves.

METHODS

mRNA levels were measured by competitive reverse transcription with polymerase chain reaction amplification (cRT-PCR). Functional correlates of this observation were assessed by indices of thermal sensitivity--mediated by C-fibres, whose phenotype is regulated by NGF.

RESULTS

NGF mRNA was increased in skin biopsies from 19 diabetic patients (5.12+/-3.88 (SD)) compared with samples from eight controls (1.57+/-0.95; P=0.001). Diabetic patients showed significantly (P < 0.001) diminished detection of cool and warm stimuli compared to age matched control group (n=24), but there were no differences in detection of heat as pain, or correlation with NGF mRNA levels.

CONCLUSIONS

These findings suggest abnormally increased expression of NGF in diabetic neuropathy, which may represent a compensatory mechanism for impaired phenotype in NGF-responsive neurones.

Sensory and autonomic neuropathy in patients with idiopathic slow-transit constipation

BACKGROUND

Slow-transit constipation (STC) is a severe disorder of unknown aetiology, which may result from an autonomic or sensory neuropathy. This study aimed to investigate patients with STC for the presence of neural dysfunction, and relate the findings to other factors, including any familial associations.

METHODS

Thirty-three patients with STC were studied using standard neurophysiological tests and a range of quantitative sensory and autonomic tests. The findings were compared with those of 20 matched control subjects and nine diabetic patients with gastrointestinal symptoms.

RESULTS

Twenty of the 33 patients with STC gave a family history of constipation, including an affected identical twin and Hirschsprung's disease (n = 3). None had abnormalities on neurological examination or nerve conduction studies. Fifteen of the 33 patients had abnormalities on quantitative tests, including all six who required a colectomy. Eleven patients with STC had reduced axon-reflex sweating in the presence of normal sweat gland responses (P < 0.001, all patients with STC versus controls). Twelve patients with STC had small sensory fibre dysfunction, with significantly increased thermal thresholds (cool, P < 0.05; warm, P < 0.01); these included six of nine patients with STC and rectal hyposensation. There were similar findings on quantitative testing in diabetic patients.

CONCLUSION

Quantitative tests in patients with STC provide evidence of a small fibre neuropathy. The high incidence of a positive family history, particularly a possible association with Hirschsprung's disease, suggests a genetic basis, which deserves further investigation.

Quantitative sensory and autonomic testing in male diabetic patients with erectile dysfunction

OBJECTIVE

To correlate abnormalities of nerve fibres in the lower limbs with erectile dysfunction in male diabetic patients, using a range of quantitative sensory and autonomic function tests.

PATIENTS AND METHODS

The study included 68 male diabetic patients with symptomatic erectile dysfunction and 11 matched diabetics without erectile dysfunction; none had clinical evidence of peripheral vascular disease or psychological disorder. Patients were evaluated with a symptom questionnaire based on the Michigan Neuropathy Screening Instrument questionnaire and examined clinically. Sural and peroneal nerve-conduction studies, and quantitative sensory and autonomic tests (vibration, thermal, light-touch thresholds, sensory and autonomic cutaneous axon-reflexes) were used to detect nerve abnormalities in the lower limbs, which were correlated with erectile dysfunction.

RESULTS

Symptoms of neuropathy were more common in the group with male erectile dysfunction (MED), but statistically significant only for neuropathic pain (53% MED, 18% nonMED, P<0.05, chi-square test) and gastroparesis (44% MED, 0% nonMED, P<0.05). Tests of unmyelinated afferents (warming perception and capsaicin-induced sensory axon-reflex vasodilatation) were most often abnormal, sometimes with no other abnormalities on tests or neurological examination. However, abnormality of warm perception was not significantly different between groups (81% MED, 70% nonMED), suggesting that it is a poorer discriminant than abnormal sensory axon-reflex vasodilatation (89% MED, 22% nonMED, P<0.001). The only other significant test difference was decreased sural nerve action potential (70% MED, 22% non-MED, P<0.01).

CONCLUSIONS

There appeared to be preferential involvement of unmyelinated sensory fibres that mediate axon-reflex vasodilatation in the limbs of diabetic patients with erectile dysfunction. This test appears to be a helpful indicator of neurological involvement in erectile dysfunction, and may be used to monitor the effect of new treatments.

Correlation of quantitative tests of nerve and target organ dysfunction with skin immunohistology in leprosy

Loss of nociception and hypohidrosis in skin are hallmarks of leprosy, attributed to early invasion by Mycobacterium leprae of Schwann cells related to unmyelinated nerve fibres. We have studied skin lesions and contralateral clinically unaffected skin in 28 patients across the leprosy spectrum with a range of selective quantitative sensory and autonomic tests, prior to biopsy of both sites. Unaffected sites showed normal skin innervation, when antibodies to the pan-neuronal marker PGP (protein gene product) 9.5 were used, with the exception of intraepidermal fibres which were not detected in the majority of cases. Elevation of thermal thresholds and reduced sensory axon-reflex flare responses in affected skin correlated with decreased nerve fibres in the subepidermis, e.g. axon-reflex flux units (means+/-SEM) for no detectable innervation; decreased innervation; and clinically unaffected skin, were 23+/-3.1; 41.2+/-7.3; and 84.5+/-4.0, respectively. Reduced nicotine-induced axon-reflex sweating was correlated with decreased innervation of sweat glands. Where methacholine-induced direct activation of sweat glands was affected, there was inflammatory infiltrate and loss of sweat gland structure. This study demonstrates a correlation between selective nerve dysfunction on clinical tests and morphological changes in skin, irrespective of the type of leprosy, and is the first to show that loss of sweating in leprosy may result either from decreased innervation and/or involvement of the sweat glands. The findings have implications for the selection and monitoring of patients with leprosy in clinical trials which aim to restore cutaneous function.

Neurotrophin-3 is increased in skin in human diabetic neuropathy

Neurotrophin-3 (NT-3), a member of the neurotrophin family, has been shown to be necessary for the development of muscle spindle and Merkel cell afferent nerve fibres in animal models. The presence of NT-3 in the suprabasal epidermis, where many unmyelinated sensory fibres terminate, has been shown for the first time. As these fibres are affected in early diabetic neuropathy and a clinical trial of recombinant human NT-3 in diabetic neuropathy is in progress, the concentrations of endogenous NT-3 in skin of 24 patients at different stages of diabetic polyneuropathy have been investigated. NT-3 concentrations, measured with a specific immunoassay, were significantly higher in affected skin biopsies from patients with diabetic neuropathy than matched control skin (diabetic skin 6.32 (1.18) pg/mg v control skin 1.28 (0.05) (mean (SEM)); p<0.004, Mann-Whitney U test), particularly in the later stages. The optical density of NT-3-immunostaining was also significantly greater in the epidermis in diabetic patients (diabetic epidermis 0.30 (0.06) v controls 0.24 (0.01); p<0.02). No correlation was found between individual quantitative sensory tests and the increase of NT-3 concentration. The increase of NT-3 seems to reflect the degree of skin denervation in diabetic neuropathy, and may represent a compensatory mechanism. The concentrations of NT-3 in other peripheral targets deserve study in diabetic neuropathy.

Rapid increase of NGF, BDNF and NT-3 mRNAs in inflamed bladder

Nerve growth factor (NGF) is a mediator of hyperalgesia and has been previously associated with sensory and reflex changes after inflammation of the urinary bladder. A sensitive assay was developed to examine neurotrophin gene expression after bladder inflammation by turpentine, which causes a short-lived inflammatory response. Two hours, but not 6 or 24 h after induction of inflammation, there were significant increases in levels of NGF, brain-derived neurotrophic factor and neurotrophin-3 mRNAs. NGF immunoreactivity was elevated with a similar time course to its mRNA. Our results suggest that during bladder inflammation, endogenous NGF is rapidly up-regulated and released to mediating sensory and reflex changes. Brain-derived neurotrophic factor and neurotrophin-3 may also have a role in the inflammatory response.

RET-like immunostaining of spinal motoneurons in amyotrophic lateral sclerosis

The receptor tyrosine kinase RET is part of a functional receptor for glial cell derived neurotrophic factor (GDNF) and neurturin (NTN) which are potent neurotrophic factors for motoneurons. Here, we have studied RET-like immunoreactivity of motoneurons in post-mortem spinal cords of patients with amyotrophic lateral sclerosis (ALS) and in controls. We report that the intensity of RET-like immunostaining of motoneurons in ALS is decreased significantly to 81% of control values. Despite this change, the proportion of all large (>40 micron diameter) motoneurons showing RET-like immunoreactivity in ALS remains high (82-85%) and is not significantly different to controls. The persistence of RET-like immunoreactivity in the majority of large motoneurons in ALS could be important in the design of clinical trials of GDNF and NTN.