Angiotensin II type 2 receptor (AT2 R) localization and antagonist-mediated inhibition of capsaicin responses and neurite outgrowth in human and rat sensory neurons

BACKGROUND

The angiotensin II (AngII) receptor subtype 2 (AT2 R) is expressed in sensory neurons and may play a role in nociception and neuronal regeneration.

METHODS

We used immunostaining with characterized antibodies to study the localization of AT2 R in cultured human and rat dorsal root ganglion (DRG) neurons and a range of human tissues. The effects of AngII and AT2 R antagonist EMA401 on capsaicin responses in cultured human and rat (DRG) neurons were measured with calcium imaging, on neurite length and density with Gap43 immunostaining, and on cyclic adenosine monophosphate (cAMP) expression using immunofluorescence.

RESULTS

AT2 R expression was localized in small-/medium-sized cultured neurons of human and rat DRG. Treatment with the AT2 R antagonist EMA401 resulted in dose-related functional inhibition of capsaicin responses (IC50  = 10 nmol/L), which was reversed by 8-bromo-cAMP, and reduced neurite length and density; AngII treatment significantly enhanced capsaicin responses, cAMP levels and neurite outgrowth. The AT1 R antagonist losartan had no effect on capsaicin responses. AT2 R was localized in sensory neurons of human DRG, and nerve fibres in peripheral nerves, skin, urinary bladder and bowel. A majority sub-population (60%) of small-/medium-diameter neuronal cells were immunopositive in both control post-mortem and avulsion-injured human DRG; some very small neurons appeared to be intensely immunoreactive, with TRPV1 co-localization. While AT2 R levels were reduced in human limb peripheral nerve segments proximal to injury, they were preserved in painful neuromas.

CONCLUSIONS

AT2 R antagonists could be particularly useful in the treatment of chronic pain and hypersensitivity associated with abnormal nerve sprouting.

The menthol and cold sensation receptor TRPM8 in normal human nasal mucosa and rhinitis

BACKGROUND

Menthol and cold sensation trigger symptoms and reflex responses in the upper airway, but the underlying molecular mechanisms are unknown. We have therefore studied nerve fibres expressing the menthol and cold receptor TRPM8 in normal human mucosa, and in rhinitis. TRPM8 nerve fibres were compared with those expressing other TRP receptors including TRPV1 (capsaicin and heat receptor), and TRPA1 (mechano-cold receptor).

METHODS

Immunohistology and image-analysis were used to study TRP receptors in biopsies of nasal turbinate from control subjects, patients with allergic rhinitis, and non-allergic rhinitis.

RESULTS

TRPM8-immunoreactive nerve fibres were observed in the sub-epithelium, and were profuse around blood vessels in deeper regions, where they were markedly greater in number than TRPV1+ fibers. Image analysis of TRPM8 in sub-epithelial and vascular regions showed no significant differences between control and the rhinitis patient groups. TRPA1-immunoreactivity was weak and seen rarely in nerve fibres.

CONCLUSION

We show that TRPM8 nerve fibres are abundant in nasal mucosa particularly around blood vessels, and may mediate neurovascular reflexes. TRPM8 antagonists deserve consideration for therapeutic trial in rhinitis.

Increased capsaicin receptor TRPV1-expressing sensory fibres in irritable bowel syndrome and their correlation with abdominal pain

OBJECTIVE

The capsaicin receptor TRPV1 (transient receptor potential vanilloid type-1) may play an important role in visceral pain and hypersensitivity states. In irritable bowel syndrome (IBS), abdominal pain is a common and distressing symptom where the pathophysiology is still not clearly defined. TRPV1-immunoreactive nerve fibres were investigated in colonic biopsies from patients with IBS, and this was related to abdominal pain.

METHODS

Rectosigmoid biopsies were collected from 23 IBS patients fulfilling Rome II criteria, and from 22 controls. Abdominal pain scores were recorded using a validated questionnaire. TRPV1-, substance P- and neuronal marker protein gene product (PGP) 9.5-expressing nerve fibres, mast cells (c-kit) and lymphocytes (CD3 and CD4) were quantified, following immunohistochemistry with specific antibodies. The biopsy findings were related to the abdominal pain scores.

RESULTS

A significant 3.5-fold increase in median numbers of TRPV1-immunoreactive fibres was found in biopsies from IBS patients compared with controls (p<0.0001). Substance P-immunoreactive fibres (p = 0.01), total nerve fibres (PGP9.5) (p = 0.002), mast cells (c-kit) (p = 0.02) and lymphocytes (CD3) (p = 0.03) were also significantly increased in the IBS group. In multivariate regression analysis, only TRPV1-immuno-reactive fibres (p = 0.005) and mast cells (p = 0.008) were significantly related to the abdominal pain score.

CONCLUSIONS

Increased TRPV1 nerve fibres are observed in IBS, together with a low-grade inflammatory response. The increased TRPV1 nerve fibres may contribute to visceral hypersensitivity and pain in IBS, and provide a novel therapeutic target.

TRPA1 receptor localisation in the human peripheral nervous system and functional studies in cultured human and rat sensory neurons

TRPA1 is a receptor expressed by sensory neurons, that is activated by low temperature (<17 degrees C) and plant derivatives such as cinnamaldehyde and isoeugenol, to elicit sensations including pain. Using immunohistochemistry, we have, for the first time, localised TRPA1 in human DRG neurons, spinal cord motoneurones and nerve roots, peripheral nerves, intestinal myenteric plexus neurones, and skin basal keratinocytes. TRPA1 co-localised with a subset of hDRG neurons positive for TRPV1, the heat and capsaicin receptor. The number of small/medium TRPA1 positive neurons (< or =50 microm) was increased after hDRG avulsion injury [percentage of cells, median (range): controls 16.5 (7-23); injured 46 (34-55); P<0.005], but the number of large TRPA1 neurons was unchanged [control 19.5 (13-31); injured 21 (11-35)]. Similar TRPA1 changes were observed in cultured hDRG neurons, after exposure to a combination of key neurotrophic factors NGF, GDNF and NT-3 (NTFs) in vitro. We used calcium imaging to examine responses of HEK cells transfected with hTRPA1 cDNA, and of human and rat DRG neurons cultured with or without added NTFs, to cinnamaldehyde (CA) and isoeugenol (IE). Exposure to NTFs in vitro sensitized cultured human sensory neuronal responses to CA; repeated CA exposure produced desensitisation. In rDRG neurons, low (225 microM) CA preincubation enhanced capsaicin responses, while high (450 microM and 2mM) CA caused inhibition which was partially reversed in the presence of 8 bromo cAMP, indicating receptor dephosphorylation. While TRPA1 localisation is more widespread than TRPV1, it represents a promising novel drug target for the treatment of chronic pain and hypersensitivity.

Normalization of substance P levels in rectal mucosa of patients with faecal incontinence treated successfully by sacral nerve stimulation

Background

Sacral nerve stimulation (SNS) may improve faecal incontinence by modulating rectal sensation. This study measured changes in the peripheral expression of various neural epitopes in response to SNS.

Methods

Rectal mucosal biopsies were taken from 12 patients before and after temporary SNS, and from ten responders at 90 days after permanent stimulation. Sections were immunostained for substance P, transient receptor potential vanilloid (TRPV) 1, vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP). Levels were compared with those in nine continent controls.

Results

Baseline levels of percentage area immunoreactivities of substance P (median 0·51 (95 per cent confidence interval 0·31 to 0·73) versus 0·13 (0·07 to 0·27) per cent; P &lt; 0·001) and TRPV1 (0·76 (0·41 to 1·11) versus 0·09 (0·04 to 0·14) per cent; P &lt; 0·001), but not of VIP (1·26 (0·37 to 2·15) versus 1·28 (0·39 to 2·17); P = 0·943), were significantly greater than in controls. Successful SNS resulted in a significant decrease in substance P immunostaining after temporary (0·15 (0·06 to 0·51) per cent; P = 0·051) and permanent (0·17 (0 to 0·46) per cent; P = 0·051) stimulation. Immunoreactivity of TRPV1, VIP, CGRP and neural markers showed no qualitative change.

Conclusion

Patients with faecal incontinence demonstrate normalization of raised rectal mucosal substance P levels following successful SNS.

The potential role of nerve growth factor (NGF) in painful neuromas and the mechanism of pain relief by their relocation to muscle

Painful neuromas have been successfully treated by surgical procedures including relocation to muscle, but the underlying molecular mechanism remains unclear. Nerve growth factor (NGF) is secreted by tissues and promotes the expression of ion channels and neuropeptides in sensory neurons involved in pain transmission. We hypothesised that excess of NGF may lead to pain in neuromas and that the efficacy of surgical relocation results from deprivation of NGF, i.e. translocation from NGF-rich regions, particularly sub-cutaneous structures associated with injury or inflammation, to NGF-poor structures such as muscle or bone. Using immunohistological methods with primary antibodies to rhNGF, we report that NGF levels were elevated in 13 painful neuromas in comparison with six control nerves. However, in four painful neuromata re-located into muscle with pain relief, the NGF level was similar to that of controls. NGF levels suggest an explanation for the development of painful neuromas and the efficacy of relocation.

A histological study of the hph-1 mouse mutant: an animal model of phenylketonuria and infantile hypertrophic pyloric stenosis

AIM

To quantify the chronological sequence of changes in the morphology and immunoreactivity for neurotransmitters in the pylorus of an animal model of infantile hypertrophic pyloric stenosis and phenylketonuria.

METHOD

Thirty specimens of pylorus from hph-1 mice and age/sex matched controls (age range: 10-180 days) were examined using conventional histology and immunohistochemistry for a variety of antigens: protein gene product 9.5, a pan neuronal marker; vasoactive intestinal polypeptide; nitric oxide synthase two antigens coalesced to the same inhibitory neurons in humans; substance P, a potent excitatory neurotransmitter; and calcitonin gene related peptide, a neurotransmitter implicated in the somatic afferent innervation of the stomach. The changes in the morphology of the muscle layers were quantified and statistically analysed for each age group (10, 20, 40, 90 and 180 days).

RESULTS

Between 10 and 90 days of age, all muscle layers of the hph-1 mice were hypertrophied, for example, 10 days, hph-1 longitudinal muscle mean diameter = 3.4, control = 1.8; hph-1 circular muscle width = 11.5, control = 4.7. The hph-1 mice were significantly smaller during this period (40 days, hph-1 weight = 10 g, control = 25 g). There was no change in the pattern of expression of the antigens examined within the hph-1 mice compared with the controls.

CONCLUSION

Hph-1 mice develop a transient smooth muscle hypertrophy of the pylorus attended by gastric distension and failure to gain weight. These changes resolve as the pyloric muscle hypertrophy resolves.

Sensory fibres expressing capsaicin receptor TRPV1 in patients with rectal hypersensitivity and faecal urgency

BACKGROUND

Faecal urgency and incontinence with rectal hypersensitivity is a distressing, unexplained disorder that is inadequately treated. We aimed to determine whether expression of the heat and capsaicin receptor vanilloid receptor 1 (TRPV1 or VR1) was changed in rectal sensory fibres, and to correlate nerve fibre density with sensory abnormalities.

METHODS

We compared full-thickness rectal biopsy samples from nine patients with physiologically characterised rectal hypersensitivity with tissue samples from 12 controls. Sensory thresholds to rectal balloon distension and heating the rectal mucosa were measured before biopsy. We assessed specimens with immunohistochemistry and image analysis using specific antibodies to TRPV1; nerve growth factor (NGF) receptor tyrosine kinase A; glial cell line-derived neurotrophic factor (GDNF); neuropeptides calcitonin gene-related peptide (CGRP) and substance P; the related vanilloid receptor-like protein (VRL) 2; glial markers S-100 and glial fibrillary acid protein (GFAP); and the nerve structural marker peripherin.

FINDINGS

In rectal hypersensitivity, nerve fibres immunoreactive to TRPV1 were increased in muscle, submucosal, and mucosal layers: in the mucosal layer, the median% area positive was 0.44 (range 0.30-0.59) in patients who were hypersensitive and 0.11 (0.00-0.21) in controls (p=0.0005). The numbers of peripherin-positive fibres also increased in the mucosal layer (hypersensitive 3.00 [1.80-6.50], controls 1.20 [0.39-2.10]: (p=0.0002). The increase in TRVP1 correlated significantly with the decrease in rectal heat (p=0.03) and the distension (p=0.02) sensory thresholds. The thresholds for heat and distension were also significantly correlated (p=0.0028). Expression of nerve fibres positive for GDNF (p=0.001) and tyrosine kinase A (p=0.002) was also increased, as were cell bodies of the submucosal ganglia immunoreactive to CGRP (p=0.0009).

INTERPRETATION

Faecal urgency and rectal hypersensitivity could result from increased numbers of polymodal sensory nerve fibres expressing TRPV1. The triggering factor or factors remain uncertain, but drugs that target nerve terminals that express this receptor, such as topical resiniferatoxin, deserve consideration.

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.

A quantitative study of the neural changes underlying pyloric stenosis in dogs

This study aimed to quantify the neural changes in congenital pyloric stenosis in dogs and to study the comparative anatomy between this condition in dogs and that in infantile hypertrophic pyloric stenosis. Eight specimens from the pylorus of dogs with pyloric stenosis and six control specimens were examined using conventional histology and immunohistochemistry for a range of neural antigens. The changes in the proportion of nerves immunoreactive for each antigen were quantified and analysed statistically. The morphology of the nerves in the diseased dogs was similar to that in controls. Only vasoactive intestinal peptide was reduced in expression in dogs (median proportion in control dogs 0.57, in diseased dogs 0.17; P = 0.065). This study demonstrates both morphological similarities and significant differences between closely related conditions in dogs, humans and other species.

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.

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.

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

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.

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.

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.

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.

GDNF and its receptor component Ret in injured human nerves and dorsal root ganglia

Glial cell line-derived neurotrophic factor (GDNF) is trophic to motor and sensory neurones in animal models. GDNF mRNA is up-regulated in Schwann cells after peripheral nerve injury in rats. We have quantified and localized GDNF and its receptor component Ret, for the first time in any species, in injured human peripheral nerves and dorsal root ganglia (DRG) avulsed from the spinal cord. Significantly higher levels of GDNF were found in nerve distal to the site of the injury than in proximal or intact nerve, and in avulsed DRG than in post-mortem control DRG. GDNF immunostaining was seen in Schwann cells and in DRG neurones, especially of small and medium size, with significantly increased numbers of medium sized sensory neurones immunoreactive for GDNF after avulsion. Ret immunoreactivity was restricted to DRG neurones and axons, with no significant changes in numbers of positive DRG cells after injury. Our findings suggest that GDNF may play a role in injured human nerves and sensory ganglia, particularly in medium sized sensory neurones.

Glial-derived neurotrophic factor in human adult and fetal intestine and in Hirschsprung's disease

BACKGROUND & AIMS

Glial cell line-derived neurotrophic factor (GDNF) signals through the product of the ret proto-oncogene, which is known to be mutated in Hirschsprung's disease and other conditions with gut dysmotility. The aim of this study was to determine the presence of GDNF and its receptor component (RET) in human adult and developing intestine and to evaluate their distribution pattern in Hirschsprung's disease.

METHODS

GDNF and RET were detected immunohistochemically, and GDNF was quantified by immunoassay in specimens of human adult and fetal colon and Hirschsprung's disease intestine.

RESULTS

GDNF-like immunoreactivity was detected in all specimens. Immunostaining of GDNF was restricted to neural fiber-like structures across the gut wall and was similar to staining with markers of glia and Schwann cells. In contrast, RET immunoreactivity was found only in neural cell bodies. GDNF levels determined by immunoassay were higher in muscle than mucosal gut layers, and there was no difference between affected and unaffected segments of Hirschsprung's disease.

CONCLUSIONS

GDNF is present in adult and fetal human gut, where it may play a neurotrophic role. Its staining pattern suggests that it is localized in glia or Schwann cells. There seems to be no difference of GDNF levels between affected and unaffected intestinal segments in Hirschsprung's disease.

Secretoneurin: a new peptide in the human enteric nervous system

Secretoneurin is a functional neuropeptide derived from secretogranin II (chromogranin C). This proprotein is processed to varying degrees in neuroendocrine tissues. In the present study we established by gel filtration high performance liquid chromatography that in human intestinal wall and mucosa an antiserum against secretoneurin detects as the major immunoreactive moiety the free peptide secretoneurin. In the mucosa some larger immunoreactive peptides were also present, however, a significant amount of the intact proprotein secretogranin II could not be detected. By immunohistochemistry we studied the distribution of secretoneurin within the gut. Antibodies to protein gene product 9.5 and chromogranin A were used to identify all neurons and endocrine cells, respectively, whilst those to the peptides substance P, CGRP and somatostatin were used for the further characterization of individual secretoneurin-positive structures. Secretoneurin immunoreactivity was found in nerve fibres in all layers of the gut wall. In both myenteric and submucous plexuses, nerve fibres and the majority of ganglion cells were secretoneurin-immunoreactive. In the mucosa, some secretoneurin-positive nerve processes ran parallel to the basal membrane of epithelial cells, occasionally invading the epithelial layer. Secretoneurin immunoreactivity was found in endocrine cells, mostly D cells, in the following regions in descending order of density: stomach/duodenum; rectum; colon; ileum. Thus, secretoneurin is a new major peptide within the human enteric neuroendocrine system. Its presence in abundant myenteric ganglion cells may imply a role in the modulation of gastrointestinal motility. The chemotactic properties of secretoneurin and its possible localization in sensory fibres suggest that this peptide may be involved in the genesis of intestinal inflammation.

Increased expression of cell adhesion molecule P-selectin in active inflammatory bowel disease

The pathogenic changes of inflammatory bowel disease (IBD) depend on migration of circulating leucocytes into intestinal tissues. Although leucocyte rolling and tenuous adhesion are probably regulated by inducible selectins on vascular endothelia, little is known about the expression of these molecules in Crohn's disease and ulcerative colitis. Using immunohistochemistry on surgically resected specimens, this study investigated endothelial P-selectin (CD62, granular membrane protein-140) in frozen sections of histologically uninvolved tissues adjacent to inflammation (Crohn's disease = 10; ulcerative colitis = 10), from highly inflamed areas (Crohn's disease = 20; ulcerative colitis = 13), and from normal bowel (n = 20). By light microscopy, two forms of P-selectin immunoreactivity were detected that apparently corresponded ultrastructurally to stored and released distributions. Compared with the normal gut, there was a 3.7-fold increase of P-selectin immunoreactivity on veins (p < 0.0001), venules (p < 0.0001), and capillaries (p < 0.05) in the highly inflamed gut, without differences between Crohn's disease and ulcerative colitis. In the uninvolved gut, P-selectin expression was similar to that seen in normal controls, except for a focal increase of P-selectin in the vicinity of small lymphocyte aggregates. The dramatic upregulation of P-selectin in the inflamed tissue and its potential role in leucocyte trafficking support the concept of P-selectin blocking therapy for the control of active IBD.

A computer-assisted stereological quantification program: OpenStereo

At present, the stereological assessment of histological sections is made possible by the use of manual counting techniques which estimate measurement parameters. These methods are tedious, time-consuming, and subject to operator error. This paper describes a UNIX-based computer program, OpenStereo, which was developed to facilitate the quantitative investigation of innervation and vascularity from histological sections. We designed OpenStereo to reduce operator error and increase the efficiency of stereological point counting for volume estimation and intercept counting for surface area analysis. The program was written in the C language for the Sun Workstation and uses the XView graphics user interface. Digital images, obtained by a variety of modalities, may be processed using stereological point counting, interceptions, planimetry, or thresholding techniques. The program displays selected images in a random fashion for analysis or processing and records the number of manually selected points or interceptions. Delineation of the reference space provides the computer with the data necessary to calculate volume or surface densities. The efficiency of OpenStereo was demonstrated by performing a pilot study on the quantification of innervation in the normal human colon and ileum. This stereological package benefits from the features of the X-windowing environment and has proved to be suitable for what has hitherto been a tedious and time-consuming task.

Altered expression of cell adhesion molecules in uninvolved gut in inflammatory bowel disease

Adhesion of circulating cells to vascular endothelium occurs in the early phase of inflammation, and is mediated by specific cell adhesion molecules. Many such adhesion molecules are increased in inflamed regions of ulcerative colitis (UC) and Crohn's disease (CD) but there is limited knowledge of their expression in the uninvolved gut, adjacent to inflammation. We investigated immunohistochemically the expression of platelet endothelial cell adhesion molecule-1 (PECAM-1), intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) on resected specimens taken at a distance of 2-4 cm from the inflamed area and without histological signs of inflammation. Compared with normal gut, we found (i) a significant increase of PECAM-1-positive vessels in the mucosa of uninvolved UC (149.0 +/- 24.1 vessels/mm2 (mean +/- s.d.); normal colon = 123.1 +/- 21.6; P = 0.004); (ii) a significant decrease of ICAM-1-positive vessels in uninvolved CD (111.9 +/- 22.6 vessels/mm2; normal ileum = 136.9 +/- 27.6; P = 0.04); and (iii) a moderate but statistically insignificant increase of LFA-1-positive cells in the mucosa of uninvolved UC and Crohn's ileitis. This altered expression of cell adhesion molecules may contribute to the early lesion in inflammatory bowel disease and provide new therapeutic opportunities.

Calretinin and calbindin-D28k immunoreactivity in the human gastrointestinal tract

BACKGROUND

Calretinin and calbindin-D28k are similar Ca(2+)-binding proteins previously described in specific central neurons and other cells.

METHODS

The immunocytochemical distribution of these two proteins was studied in the human gastrointestinal tract.

RESULTS

In gastric and small intestinal endocrine cells, calbindin-D28k immunoreactivity was confirmed, but calretinin immunoreactivity was not found. Nerve cell bodies in both submucous and myenteric ganglia were immunoreactive for calbindin (13% and 38% of total cells, respectively) or calretinin (23% and 21%), some containing both proteins. In nerve processes, calretinin was generally more abundant than calbindin and was found particularly around blood vessels. Calretinin co-localized with immunoreactive vasoactive intestinal peptide, neuropeptide Y, galanin, or substance P in submucous ganglion cells and with substance P in myenteric cells. Calbindin-D28k colocalized with fewer peptides, specifically vasoactive intestinal peptide or galanin in submucous cells. By 8 weeks of fetal development, discrete neuronal localizations for both proteins and for calbindin-D28k in endocrine cells were apparent.

CONCLUSIONS

In the enteric neuroendocrine system, calretinin and calbindin-D28k are useful markers that may help elucidate Ca(2+)-mediated functions in health and disease.

Effect of streptozotocin-diabetes on the level of VIP mRNA in myenteric neurones

The effect of streptozotocin-induced diabetes on the production of vasoactive intestinal polypeptide messenger RNA in the myenteric neurones of 8 weeks diabetic rat intestine was examined using in situ hybridization. Total ganglion cell number per length (mm) of tissue section was measured using NADH diaphorase histochemistry. Although ganglion cells were more numerous in the control preparations compared with diabetic samples, a significantly greater number of vasoactive intestinal polypeptide messenger RNA-containing cells was detected in the diabetic tissues. These observations suggest that there is either a decrease in the breakdown of vasoactive intestinal polypeptide messenger RNA or an increase in its synthesis in myenteric neurones of diabetic rat intestine.

Vasoactive intestinal polypeptide gene expression in the developing human gastrointestinal tract

Expression of vasoactive intestinal polypeptide has been shown, by immunocytochemistry and biochemical assay, to follow the craniocaudal neural colonization of the mammalian gut. The aim of this study was to use in situ hybridization to see if it could provide more information on vasoactive intestinal polypeptide gene expression in the developing human gut. Immunocytochemistry of vasoactive intestinal polypeptide and, to visualize the total innervation, protein gene product 9.5 was also applied. By 8 weeks of gestation, protein gene product 9.5-immunoreactive neurons had colonized the gut lengthwise (17% of intestinal muscle area) but not transversely. Vasoactive intestinal polypeptide immunoreactivity was first detected at 9 weeks of gestation in a few nerve fibers of the upper gut, the origin of which could not be determined. Vasoactive intestinal polypeptide-immunoreactive ganglion cells were not seen until 18 weeks of gestation, whereas in situ hybridization showed messenger RNA in ganglion cells of the upper gut at 9 weeks. An adultlike pattern of peptide gene products (e.g., 2.5% and 3.1% of intestinal mucosal or muscle area, respectively) was detected by 20 weeks' gestation. The finding that the vasoactive intestinal polypeptide gene is expressed first in the upper human gut is consistent with craniocaudal neuronal colonization and maturation.

Developmental profile of chromogranin, hormonal peptides, and 5-hydroxytryptamine in gastrointestinal endocrine cells

In this immunocytochemical study, we have analyzed the developmental profile and phenotypic expression of the endocrine cell antigens chromogranin, 5-hydroxytryptamine, gastrin/cholecystokinin, cholecystokinin (9-20), somatostatin, somatostatin 28 (1-14), somatostatin cryptic peptide, glucagon, glucagonlike peptides 1 and 2, glicentin, peptide YY, glucose-dependent insulinotropic peptide, secretin, neurotensin, and substance P in human fetal stomach and intestine. All currently identifiable endocrine cell types were detected by 10 wk of gestation. Immunostaining for the endocrine cell marker chromogranin revealed abundant endocrine cells in the earliest specimens (8 wk of gestation) with a relatively higher frequency in both proximal duodenum and distal colon/rectum compared with other areas. Quantification of endocrine cells showed an increase with age that was roughly parallel to the growth of the gut as a whole. These studies show that the diversity of the endocrine component of the gut appears to be established by 10 wk of gestation and that gut activity is preceded by the development of a fully differentiated endocrine component, which may subserve or even initiate the onset of functional maturity.

Pancreastatin distribution and plasma levels in the pig

Pancreastatin is a peptide isolated from porcine pancreas which has insulin-suppressive actions in vitro and sequence homology with chromogranin A. Using radioimmunoassay and immunocytochemistry we investigated whether pancreastatin has a more widespread distribution and a possible endocrine role in the pig. Pancreastatin immunoreactivity was found in plasma, adrenal gland, pancreas, anterior pituitary and throughout the gastrointestinal tract. The immunoreactivity was colocalized with chromogranin immunoreactivity in endocrine cells and ultrastructurally (in the pancreas) to storage granules. Characterization of pancreastatin-like immunoreactivity, using gel permeation and high performance liquid chromatography, separated 3 different pancreastatin-like immunoreactive forms: one molecular form, indistinguishable from synthetic pancreastatin 1-49, was predominant in pancreas and thyroid and released into the circulation postprandially. However, a high dose (greater than 1 nmol/l) infusion of pancreastatin 33-49 (the biologically active moiety in vitro) into conscious pigs had no effect on either basal or glucose-stimulated insulin secretion.

Ontogeny of peptide- and amine-containing neurones in motor, sensory, and autonomic regions of rat and human spinal cord, dorsal root ganglia, and rat skin

The developmental patterns of neurofilament triplet proteins, peptide and amine immunoreactivities were compared in motor (ventral spinal cord), sensory (dorsal spinal cord, dorsal root ganglia, epidermis), and autonomic (intermediolateral cell columns, dermis) regions in the rat and human. In the rat, neurofilament triplet proteins first appeared in motoneurones (embryonic day 13). In the youngest human fetuses studied (6 weeks), immunoreactivity was present throughout the spinal cord. Peptides and amines occurred later. Calcitonin gene-related peptide, galanin, somatostatin, neuropeptide Y and its C-flanking peptide (CPON) were the first to appear localized to motoneurones (embryonic days 15-17 rat; fetal weeks 6-14 human). Numbers of immunoreactive motoneurones decreased toward birth, but immunoreactive fibers increased in the ventral horn with enkephalin, thyrotrophin-releasing hormone, and the monoaminergic markers 5-hydroxytryptamine and tyrosine hydroxylase (all presumably of supraspinal origin) the last to appear perinatally. In the dorsal horn, particularly in the rat, a transient expression of substance P-, somatostatin-, and neuropeptide Y/CPON-immunoreactive cells was detected (embryonic days 15-17). A pronounced increase of calcitonin gene-related peptide-, galanin-, somatostatin- and substance P- immunoreactive fibers was found perinatally in both species. This coincided with an increased detection of cells in the dorsal root ganglia containing these peptides and the earliest appearance of calcitonin gene-related peptide-, somatostatin-, and substance P-immunoreactive fibers in the rat epidermis. Few antigens were localized to the intermediolateral cell columns before embryonic day 20 (rat), fetal week 20 (human), with thyrotrophin-releasing hormone-, 5-hydroxytryptamine-, tyrosine hydroxylase-, and vasoactive intestinal polypeptide-immunoreactive nerves appearing perinatally. In the rat dermis, tyrosine hydroxylase-immunoreactive fibers (sympathetic fibers) and fibers immunoreactive for neuropeptide Y/CPON and vasoactive intestinal polypeptide were detected from postnatal day 1. In conclusion, 1) peptide and amine immunoreactivity develops in motor before sensory or autonomic regions, 2) many peptide-containing cells are transient in fetal life, and 3) central terminals of dorsal root ganglion cells express peptides before terminals in the skin.

Production of pituitary protein 7B2 immunoreactivity by endocrine tumors and its possible diagnostic value

7B2 is a protein originally isolated from pituitary, which has been shown to be present in the central nervous system and in certain peripheral tissues, with very high concentrations in pancreatic islets. Endocrine and nonendocrine tumors from 185 patients were investigated by RIA for the presence of immunoreactive pituitary protein 7B2. The highest mean concentration of 7B2 immunoreactivity was found in insulinomas [452 +/- 174 (+/- SEM) pmol/g wet wt tissue; n = 16], which was significantly higher than the concentration in normal adult pancreatic tissue (28.3 +/- 4.4 pmol/g; n = 7). High concentrations of 7B2 immunoreactivity also were found in other endocrine tumors. The cellular localization of 7B2 was studied in normal pancreas, pancreas with hyperplastic islets, and endocrine tumors. 7B2 immunoreactivity was localized to B-cells in the normal pancreas and to variable proportions of cells in islet cell hyperplasias, B-cell tumors, and pheochromocytomas. Plasma concentrations of 7B2 immunoreactivity also were determined in 255 patients with established diagnoses of endocrine or nonendocrine tumors. The proportion of patients with elevated plasma concentrations (arbitrarily set at more than 4 SD above the mean) were 42 of 72 with pancreatic islet cell tumors, 7 of 11 with midgut carcinoid tumors, and 5 of 13 with medullary carcinomas of the thyroid. Especially high values were found in patients with glucagonomas (14 of 20), vipomas (12 of 13), and pancreatic polypeptide-producing tumors (5 of 6). Thus, 7B2 immunoreactivity is produced by a variety of different tumors and may serve as a tumor marker, especially in patients with certain pancreatic islet tumors.

Chromogranin: a newly recognized marker for endocrine cells of the human gastrointestinal tract

Existing methods for the histochemical demonstration of gastrointestinal cells are somewhat limited. Chromogranin represents a family of proteins that coexist with catecholamines in the secretory vesicles of adrenal medulla cells. In the present study, immunocytochemistry was used to test whether chromogranin is a marker for gut endocrine cells. Serial sections of each area of human gut were immunostained for chromogranin and for the amine and each of the peptides known to be present in mucosal endocrine cells. Chromogranin was immunostained in large numbers of endocrine cells in all tissues examined. All identified endocrine cell types were found, in serial sections or by sequential silver impregnations, to be chromogranin immunoreactive. However, the possibility exists that some chromogranin-immunoreactive cells contain a yet to be discovered endocrine substance. Immunostaining of chromogranin thus appears to provide a means for demonstrating all gastrointestinal mucosal endocrine cells identifiable by the methods described in this study.

Immunocytochemical localisation of katacalcin, a calcium-lowering hormone cleaved from the human calcitonin precursor

Katacalcin is a newly discovered calcium-lowering hormone predicted from the nucleotide sequence of a cloned cDNA derived from human calcitonin mRNA. The aim of the study was to localise katacalcin by immunocytochemistry at both light and electron microscope levels. Antisera to synthetic katacalcin and calcitonin were used to investigate 8 cases of medullary thyroid carcinoma and 6 normal human thyroids (3 adult and 3 fetal). We have been able to demonstrate the co-localisation of these peptides in normal and neoplastic C-cells in all cases studied. Our results suggest that peptide sequences predicted by recombinant DNA technology can be localised using immunocytochemistry and that the combination of these techniques may have applications in diagnostic pathology.

Improved section adhesion for immunocytochemistry using high molecular weight polymers of L-lysine as a slide coating

Poly-L-lysine (PPL) has been used to coat glass slides in the preparation of tissue sections for immunocytochemical staining. The adhesive properties of different molecular weight (m.w.) polymers of L-lysine have been tested on pre-fixed cryostat sections which were subjected to a 3 day washing treatment. It has been found that the higher the molecular weight of the polymer, the greater the adhesive force it provides. PLL (m.w. 350,000) at concentrations in the range of 0.05-0.1% was found to be the most effective polymer.

Neuron specific enolase: a common marker for the endocrine cells and innervation of the gut and pancreas

Neuron specific enolase, the most acidic isoenzyme of the glycolytic enzyme enolase, was first believed to be present exclusively in central neurons. More recently, it has been found in peripheral autonomic nerves and in a number of endocrine cells. An immunocytochemical study was carried out concerning the distribution of neuron specific enolase in the gastrointestinal tract and pancreas of humans and rats. In addition, immunocytochemistry and histochemistry were used to obtain a characterization of the different types of cells and nerves in which neuron specific enolase can be detected. Neuron specific enolase was found in all currently identifiable endocrine cell types and nerves of the gut and pancreas. Neuron specific enolase is therefore a common marker for both endocrine cells and enteric nerves, thus providing a simple means for their simultaneous demonstration and examination of their morphologic characteristics and integration.

Immunocytochemistry: its applications and drawbacks for the study of gut neuroendocrinology

Localization of gut peptide hormones by immunological staining methods is known generally as "immunocytochemistry". These immunostaining techniques depend upon the correct processing of the tissue under study and careful characterization of the antisera used. Many years of research in our laboratory have enabled us to present here our approach to the application and pitfalls of immunocytochemistry in the study of gut neuroendocrinology.

Immunocytochemical demonstration of 5-hydroxytryptamine in gastrointestinal endocrine cells

We have been able to demonstrate 5-hydroxytryptamine in the enterochromaffin cells of the mammalian gastrointestinal tract, using a highly specific antiserum. Conventional histochemical techniques for identifying amines as cell markers can thus be replaced by more reliable and sensitive immunocytochemical methods. This has been facilitated by the use of p-benzoquinone as fixative which has been shown to preserve the localization and antigenicity of amines, as well as peptides.