Enteric nerves in diabetic rats: increase in vasoactive intestinal polypeptide but not substance P

The distribution of vasoactive intestinal polypeptide (VIP) and substance P-like immunoreactivities was studied by immunohistochemistry in the myenteric plexus and circular muscle layer of the ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin. A consistent increase was observed in fluorescence intensity of VIP-like immunoreactivity in the nerve fibers, and intensely stained cell bodies were significantly more frequent in the myenteric plexus of the ileum (p less than 0.001) from diabetic animals. Some varicosities of VIP-like immunoreactive fibers in the myenteric plexus appeared to be enlarged. Vasoactive intestinal polypeptide-like immunoreactivity was increased and VIP-like immunoreactive nerves appeared thicker in the circular muscle layer of both diabetic ileum and proximal colon. The VIP levels were measured biochemically in tissue consisting of the smooth muscle layers and myenteric plexus. A significant increase in the VIP content per centimeter of intestine was found in both the ileum (p less than and proximal colon (p less than 0.01) from diabetic rats. In contrast, no apparent change in substance P innervation was observed immunohistochemically in the myenteric plexus and circular muscle layer of either diabetic ileum or proximal colon when compared with controls. The results are discussed in relation to the symptoms of autonomic neuropathy of the gut in diabetes.     

Jejunal diverticulosis with perforation as a complication of Fabry's disease

This study presents the case of a patient who had jejunal diverticulosis with perforation and abscess formation as a complication of Fabry's disease. Light microscopy disclosed glycolipid deposition in the neurons and nerve fibers of the intestinal nerve plexuses and smooth muscle. Silver stains of the myenteric plexus in the involved segment of the bowel showed enlarged, granular argyrophobic neurons and a marked decrease in the number of argyrophilic neurons, with those remaining being enlarged and distorted by the cytoplasmic glycolipid accumulation. These abnormalities of the myenteric plexus suggest that jejunal diverticulosis may be the result of a variety of disorders of the smooth muscle or myenteric plexus, or both. We propose that jejunal diverticulosis in our patient was a consequence of uncoordinated smooth muscle activity resulting from Fabry's involvement of myenteric plexus neurons, with mucosal protrusion through the smooth muscle.     

Pathophysiological significance of neuronal nitric oxide synthase in the gastrointestinal tract

It has been demonstrated that nitric oxide (NO) is a major inhibitory nonadrenergic, noncholinergic (NANC) neurotransmitter in the gastrointestinal (GI) tract. NO released in response to nerve stimulation of the myenteric plexus causes relaxation of the smooth muscle. NO is synthesized by the activation of neuronal NO synthase (nNOS) in the myenteric plexus. Released NO plays an important physiological role in various parts of the GI tract. NO regulates the muscle tone of the sphincter in the lower esophagus, pylorus, sphincter of Oddi, and anus. NO also regulates the accommodation reflex of the fundus and the peristaltic reflex of the intestine. Previous studies have shown that NOS inhibitors delay gastric emptying and colonic transit. The reduction of nNOS expression, associated with impaired local production of NO, may be responsible for motility disorders in the GI tract. There is accumulated evidence that dysfunction of NO neurons in the myenteric plexus may cause various GI diseases. These reports are reviewed and possible mechanisms of altered nNOS expression are discussed in this article. In particular, impaired nNOS synthesis of the myenteric plexus seems to be an important contributing factor to the pathogenesis of achalasia, diabetic gastroparesis, infantile hypertrophic pyloric stenosis, Hirschsprung's disease, and Chagas' disease. Reduced NO release and/or nNOS expression are suspicious in a subset of patients with functional dyspepsia. Although the etiology of intestinal pseudo-obstruction remains unknown, it is conceivable that extrinsic denervation may upregulate nNOS expression, resulting in enhanced muscular relaxation and disturbed peristalsis. An animal model of colitis showed impaired nNOS expression in the colonic myenteric plexus. Antecedent infection may be associated with the impaired NO pathways observed in functional dyspepsia, colitis, and Chagas' disease.     

Diagnosis and treatment of neuromuscular disorders of the stomach

Gastric neuromuscular disorders encompass a spectrum of dysfunction in nerve and smooth muscle that includes gastric visceral hypersensitivity, gastric dysrhythmias, fundic dysfunction, antral hypomotility, and gastroparesis. Patients with each disorder may present with such vague dyspepsia symptoms as early satiety, upper abdominal discomfort, bloating, or nausea with or without vomiting. A careful history and physical examination may suggest a gastric neuromuscular disorder, but symptoms are nonspecific. Gastroparesis is the most severe form of neuromuscular dysfunction. Such reversible causes of gastroparesis as mechanical obstruction of the stomach and chronic mesenteric ischemia must be excluded. Gastroparesis, gastric dysrhythmias, and hypersensitivity may follow viral infection or be due to degenerative processes that affect the gastric enteric neurons, smooth muscle, or interstitial cells of Cajal. Commonly, the cause of these gastric neuromuscular disorders is unknown. An approach to the diagnosis and treatment of gastric neuromuscular disorders is reviewed, including dietary counseling, drugs, and medical devices.     

Electron microscopic study of neuropeptide Y-containing nerve elements of the guinea pig small intestine

Neuropeptide Y-containing nerve cell bodies and processes were identified by electron microscopic immunocytochemistry in the guinea pig small intestine. Labeled nerve processes were numerous in the myenteric plexus. However, a few immunoreactive nerve fibers were found in all layers of the small intestine. Some of the immunoreactive nerve processes were found in close apposition to the epithelial cells of the crypts of Lieberkühn and to endothelial and smooth muscle cells. The neuropeptide Y-containing nerve cell bodies were preferentially located in the submucous ganglia. In the myenteric plexus many synaptic connections were observed between the neuropeptide Y-immunoreactive nerve fibers and unlabeled nerve cell bodies and other nerve fibers. These findings provide a morphologic basis for the possibility that neuropeptide Y may act as a transmitter and exert postsynaptic effects on intrinsic neurons, in addition to participating in the regulation of smooth muscle activity and epithelial cell functions.     

A deficiency of gastric interstitial cells of Cajal accompanied by decreased expression of neuronal nitric oxide synthase and substance P in patients with type 2 diabetes mellitus

Background Gastrointestinal motility is impaired in patients with diabetes mellitus (DM). Interstitial cells of Cajal (ICC) in the gastrointestinal tract play a central role in gastrointestinal motility. The present study examined whether ICC density, or expression of neuronal nitric oxide synthase (nNOS)- and substance P (SP)-containing nerves in the gastric antrum, were altered in patients with type 2 DM. Methods Paraffin-embedded gastric specimens from 51 controls and 36 male DM patients with gastric cancer were used for immunohistochemistry. Serial sections were stained with Kit and mast cell tryptase-specific antibodies. Fresh-frozen gastric specimens from patients with gastric cancer were used for immunofluorescence. The specimens were stained with antibodies to Kit, nNOS, and SP, and levels of expression of these three markers were compared between controls and DM patients. Results ICC density in the inner circular muscle layer, but not in the myenteric plexus, was lower in patients with severe DM than in controls in paraffin-embedded specimens. In addition, decreased expression of nNOS and SP accompanied by reduced ICC density was observed in frozen specimens from patients with DM. Conclusions These results suggest that lower gastric ICC, nNOS, and SP densities in patients with DM may be associated with the pathogenesis of diabetic gastroparesis.     

Localization of neurokinin B receptor in mouse gastrointestinal tract

AIM: To observe the location of neurokinin receptor (NK3r)in the mouse gastrointestinal tract.METHODS: The abdomen of 8 male Kunming mice wereopened under anaesthesia with sodium pentobarbital. Theexposed gut organs were cleaned and kept moisture andtemperature. Then the esophagus, jejulum, ileum, colon,etc were respectively cut and the segments from thestomach to the distal colon were opened along themesenteric border. A circular 4mm ～ 6mm enteric part(pieces of 1 cr2 were to be prepared) and mucosa andsubmucosa were removed, then the longitudinal musclelayer was pulled off from the circular muscle layer undermicrophotography. They were rinsed in 50nmol @ L-1potassium phosphate-buffered saline ( PBS ).Immunohistochemistry and immunoreactive fluorescencewere used in the staining procedure.RESULTS: There was not NK3r-Like(-Li) positive material onthe smooth muscle cells of the esophagus, stomach,intestines and other regions. The nerve cell bodies withimmunoreactivity for NK3r were mainly distributed in thesubmucousal nerve plexus or myenteric nerve plexus of thegastrointestinal tract except for the esophagus, stomachand rectum. The reaction product was located on thesurface of the nerve cell plasma. lt was observedoccasionally in the cell plasma endosomes, but was veryweakly stained. Among the NK3-Like positive neurons in theplexus, the morphological type in many neurons' appenaedlike Dogiel Ⅱ type cells. Some neuron cell bodies were big,having many profiles, Some were long ones or havinggrading structure. Cell bodiy diameter was about 10μm-46μmand 8μm-42μm in myenteric plexus and submucous plexus.CONCLUSION: This study not only described the distributionof neurokinin B receptor in the mouse gut, but alsoprovided a morphological basis for deducing the functionalidentity of the NK3r-LI immunoreactivity neurons,suggesting the possibility that these neurons were closelyrelated to gastrointestinal tract contraction and relaxingactivity.     

Distribution of peptide-containing nerve fibres in achalasia of the oesophagus

In this study the innervation of the normal human oesophagus was compared with samples taken from 12 patients undergoing Heller's cardiomyotomy for achalasia. The distribution of all nerve fibres in the oesophageal wall was revealed by immunoreactivity to neuron specific enolase and subpopulations of nerve fibres were revealed by immunoreactivity to vasoactive intestinal peptide, neuropeptide Y, enkephalin and substance P. In healthy oesophagus, many nerve fibres immunoreactive for vasoactive intestinal peptide and neuropeptide Y were present in the circular and longitudinal muscle layers of the oesophageal wall and in the cardia of the stomach, whereas fibres immunoreactive for enkephalin and substance P were uncommon. Neuropeptide Y-reactive fibres were commonly seen around blood vessels. In the myenteric plexus cell bodies reactive for vasoactive intestinal peptide and neuropeptide Y were prevalent, as were varicose and non-varicose fibres. In contrast, samples from patients with achalasia revealed few nerve fibres immunoreactive for vasoactive intestinal peptide or neuropeptide Y in either circular or longitudinal muscle, suggesting damage to the inhibitory motor neurons to the muscle layers. Very few fibres were found that were reactive for neuron-specific enolase, indicating that other fibre populations (e.g. excitatory cholinergic motor neurons) are also damaged in achalasia. These abnormalities were observed in biopsies from both the constricted and dilated portions of the oesophagus, but the pattern of innervation in the gastric cardia was normal. Myenteric ganglion cells were seen in the oesophagus in only two patients and varicose nerve fibres in the myenteric plexus were uncommon. Neuropeptide Y-reactive perivascular nerve fibres were still found in achalasia as well as non-varicose nerve fibres in the myenteric plexus. These findings indicate damage to all intrinsic neurons in the oesophageal wall in achalasia; however, extrinsic nerve fibres appear to be intact.     

Neuromuscular control of esophageal peristalsis

The esophagus is a muscular conduit connecting the pharynx and the stomach. Its function is controlled by an intrinsic nervous system and by input from the central nervous system through the vagus nerve. Peristalsis in its striated muscle is directed by sequential vagal excitation arising in the brain stem, whereas peristalsis in its smooth muscle involves complex interactions among the central and peripheral neural systems and the smooth muscle elements of the esophagus. The peripheral neuronal elements responsible for producing esophageal off-response, relaxation of the lower esophageal sphincter, and hyperpolarization of the circular esophageal muscle cells reside in the myenteric plexus of the esophagus. For many years these nerves were considered nonadrenergic and noncholinergic because the inhibitory neurotransmitter released on their activation was unknown. We now know that nitric oxide or a related compound is that inhibitory neurotransmitter. The primary excitatory neurotransmitter controlling esophageal motor function is acetylcholine. Some disorders of esophageal motor function, including diffuse esophageal spasm and achalasia, may result from defects in or an imbalance between these excitatory and inhibitory neuromuscular systems.     

糖尿病胃轻瘫大鼠胃窦内ICC和SP变化的实验研究

目的观察Cajal间质细胞和P物质在糖尿病胃轻瘫大鼠胃窦的改变,进而探讨糖尿病胃轻瘫发生的相关机制。方法SD大鼠30只,随机分为正常对照组（n=10）和糖尿病组（n=20）。用链脲佐菌素建立大鼠糖尿病胃轻瘫模型,3个月后用放射性核素（^99Tc）灌胃测定大鼠胃液体排空率,取正常对照组及模型组大鼠胃窦标本,应用免疫组化染色法检测c—kit阳性Cajal间质细胞和P物质在大鼠胃窦的变化,应用彩色病理图像分析软件进行分析,并行统计学比较。结果与正常大鼠相比,糖尿病大鼠胃排空明显延迟（P〈0．01）,胃窦c—kit阳性Cajal间质细胞减少（P〈0．01）,P物质表达减少（P〈0．01）。结论糖尿病胃轻瘫与Cajal间质细胞和P物质的变化有一定的相关性。     

Intestinal Auerbach plexus structures with NADH histochemistry in three strains of spontaneous diabetic rats

The enteric nervous system comprises two major systems: the submucosal and the myenteric plexus. The aim of this study was to describe the myenteric plexus from three strains of spontaneous diabetic rats from the histological point of view. Samples of small intestine and of proximal and distal colon were obtained fom three spontaneous diabetic rats i.e., eSS, eSMT, beta strains and 1-year old Wistar rats. Specimens were stained with NADH (beta-nicotinamide adenine dinucleotide, reduced form) histochemical technique and examined with light microscope. Microscopically little modifications in mesh-like structure of intestinal Auerbach's plexus from eSS were detected in comparison with Wistar rats samples. Intestinal plexus of eSMT and beta rats showed disruption of mesh-like structures, modifications in the slightly colored background (smooth muscle) and augmented vascularization. Small intestine and colon are affected. In short: In our spontaneously diabetic rat models, mesh-like structure of Auerbach's plexus is strain dependent.     

Chronic idiopathic intestinal pseudo-obstruction caused by a degenerative disorder of the myenteric plexus: the use of Smith's method to define the neuropathology

In this paper we report the pathologic basis of chronic idiopathic intestinal pseudo-obstruction in a patient who had a subtotal colectomy and ileorectal anastomosis for severe obstipation. Conventional light microscopy of the resected intestine showed an increased thickness of the longitudinal muscle, minimal amounts of smooth muscle fibrosis, and normal smooth muscle cells. The morphology of the myenteric plexus was difficult to interpret with this technique, but quantification of colonic neurons revealed a significantly decreased number compared with controls. Silver stains of the myenteric plexus by Smith's method showed: (a) patchy loss of nerve tracts with replacement by Schwann cells, (b) degeneration and decreased numbers of both argryophilic and argyrophobic neurons, (c) fragmentation and dropout of many axons, and (d) increased thickness and disorganized spatial arrangement of other axons. The pathology of this intestinal neuropathy could be missed by conventional light microscopy and may be apparent only when a silver technique is used to visualize the myenteric plexus.     

Severe gastroparesis causing splenic rupture: a unique, early complication after heart-lung transplantation

Several weeks or even months after heart-lung transplantation, gastroparesis-or delayed gastric emptying-commonly presents with cough, early satiety, and bloating. As it progresses, gastroparesis can cause substantial malnutrition and impair drug absorption. Gastroparesis after heart-lung transplantation can be attributed to bilateral vagus nerve injury, which probably occurs just above the level of the carina, where the recipient's trachea is resected. We report a highly unusual case wherein gastroparesis presented early after heart-lung transplantation and was managed conservatively. However, 19 days postoperatively, the patient developed acute abdominal pain and hypotension. Laparotomy revealed a massively dilated stomach and total avulsion of the splenic capsule with hemorrhage. The patient was fed via jejunostomy tubes until the gastroparesis resolved spontaneously. This case illustrates an important sequela of heart-lung transplantation. In order to decrease the morbidity from gastroparesis in these fragile patients, a drainage procedure should be considered as an adjunct to heart-lung transplantation.     

Interstitial cells of Cajal mediate inhibitory neurotransmission in the stomach.

The structural relationships between interstitial cells of Cajal (ICC), varicose nerve fibers, and smooth muscle cells in the gastrointestinal tract have led to the suggestion that ICC may be involved in or mediate enteric neurotransmission. We characterized the distribution of ICC in the murine stomach and found two distinct classes on the basis of morphology and immunoreactivity to antibodies against c-Kit receptors. ICC with multiple processes formed a network in the myenteric plexus region from corpus to pylorus. Spindle-shaped ICC were found within the circular and longitudinal muscle layers (IC-IM) throughout the stomach. The density of these cells was greatest in the proximal stomach. IC-IM ran along nerve fibers and were closely associated with nerve terminals and adjacent smooth muscle cells. IC-IM failed to develop in mice with mutations in c-kit. Therefore, we used W/W(V) mutants to test whether IC-IM mediate neural inputs in muscles of the gastric fundus. The distribution of inhibitory nerves in the stomachs of c-kit mutants was normal, but NO-dependent inhibitory neuro-regulation was greatly reduced. Smooth muscle tissues of W/W(V) mutants relaxed in response to exogenous sodium nitroprusside, but the membrane potential effects of sodium nitroprusside were attenuated. These data suggest that IC-IM play a critical serial role in NO-dependent neurotransmission: the cellular mechanism(s) responsible for transducing NO into electrical responses may be expressed in IC-IM. Loss of these cells causes loss of electrical responsiveness and greatly reduces responses to nitrergic nerve stimulation.     

Natriuretic Peptide-Dependent cGMP Signal Pathway Potentiated the Relaxation of Gastric Smooth Muscle in Streptozotocin-Induced Diabetic Rats

A common gastrointestinal complication of diabetes is gastroparesis, and patients with gastroparesis may present with early satiety, nausea, vomiting, bloating, postprandial fullness, or upper abdominal pain. However, the pathogenesis is not clear yet. A recent study indicated that atrial natriuretic peptide (ANP) was secreted from the gastric mucosa and the ANP family plays an inhibitory role in the regulation of gastrointestinal motility, but the effect of the natriuretic peptide signal pathway on diabetic gastroparesis has not been reported. The study investigated the effect of C-type natriuretic peptide (CNP) particulate guanylyl cyclase (pGC) cyclic guanosine monophosphate (cGMP) signaling on gastroparesis in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were divided into two groups; group I: normal control rats; group II: STZ-induced diabetic rats; 4 weeks after induction, the experiments were performed. The spontaneous contraction of gastric smooth muscle strips was recorded by using physiographs in control and diabetic rats. The pGC activity in response to CNP and cGMP production in gastric smooth muscle were measured by using radioimmunoassay (RIA) in normal and diabetic rats. CNP induced a longer lasting relaxation of gastric antral circular smooth muscle strips in STZ-induced diabetic rats. The inhibitory effect of CNP on spontaneous contraction revealed a dose-dependency, and the inhibitory percentages were 25.5 ± 1.7%, 43.6 ± 3.2%, 85.1 ± 2.5% in diabetic rats and 20.5 ± 1.5%, 31.1 ± 1.7%, 58.9 ± 3.7% in the control group at the concentrations of 0.01, 0.03, and 0.1 μmol/l, respectively. The cGMP production and pGC activity in response to CNP in gastric muscle tissues were significantly potentiated in STZ-induced diabetic rats. Natriuretic peptide receptor type B (NPR-B) gene was expressed in the gastric smooth muscles of normal and diabetic rats, and the expression was increased in diabetic rats. The results suggest that natriuretic peptide-dependent pGC-cGMP signal is upregulated and may contribute to diabetic gastroparesis in STZ-induced diabetic rats.     

Distributions of neuropeptides in the human esophagus

The distributions of nerve cells and fibers with immunoreactivity for the peptides substance P, somatostatin, enkephalin, vasoactive intestinal peptide, gastrin-releasing peptide, and neuropeptide Y and the enzyme tyrosine hydroxylase were examined in 25 samples of human esophagus. These were compared with samples of stomach and intestine. In the smooth muscle of the muscularis externa, the muscularis mucosae, and beneath the epithelium, the most abundant nerve fibers contained vasoactive intestinal peptide and neuropeptide Y, in contrast to the scarcity of substance P, enkephalin, somatostatin, and gastrin-releasing peptide. Gastric and intestinal samples contained dense populations of fibers containing vasoactive intestinal peptide, neuropeptide Y, substance P, and enkephalin in the equivalent layers, but somatostatin- and gastrin-releasing peptide-immunoreactive fibers were scarce. Complete coexistence of vasoactive intestinal peptide and neuropeptide Y in nerve fibers within the muscle layers was demonstrated in the esophagus, but not in gastric and intestinal samples. The myenteric plexus along the length of the esophagus contained cell bodies and fibers reactive for vasoactive intestinal peptide, neuropeptide Y, enkephalin, and substance P. Somatostatin-immunoreactive cell bodies were very rare in the myenteric plexus, no gastrin-releasing peptide-immunoreactive cell bodies were seen, and both somatostatin and gastrin-releasing peptide-immunoreactive fibers were rare. In the upper esophagus, striated muscle bundles did not contain nerve fibers reactive for these peptides but immunoreactive fibers were seen in the muscularis mucosae and subepithelium. It is concluded that the esophagus has a different pattern of innervation by peptide-containing neurons than the stomach and intestines. Esophageal neurons can be classified into separate classes on the basis of their peptide content.     

糖尿病胃动力障碍大鼠胃窦平滑肌组织中CNP和NPR-B蛋白含量变化

目的探讨糖尿病胃动力障碍大鼠胃窦平滑肌组织中C型钠尿肽（CNP）和B型钠尿肽受体（NPR-B）的蛋白含量变化。方法腹腔注射链脲佐菌素（STZ）（65 mg/kg）4周,制备糖尿病动物模型。利用多道生理信号记录系统记录糖尿病大鼠胃窦平滑肌收缩活动,将发生胃窦平滑肌收缩活动紊乱的大鼠列入糖尿病胃动力障碍模型。采用免疫组织化学方法观察糖尿病大鼠胃窦平滑肌中CNP和NPR-B的分布。结果糖尿病胃动力障碍组大鼠与正常对照组相比胃窦平滑肌组织CNP表达无明显差异,但NPR-B表达明显增多（P〈0.01）。结论糖尿病大鼠发生胃动力障碍可能与胃窦平滑肌中NPR-B上调有关,提示糖尿病大鼠胃CNP-NPR-B/pGC-cGMP转导系统的改变可能参与胃动力障碍的发生。     

Distribution of nitric oxide synthase in stomach myenteric plexus of rats

AIM:To study the distribution of nitdc oxide synthese(NOS)in rat stomach myenteric plexus.METHODS:The distribution of NOS in gastric wall wasstudied in quantity and location by the NADPH-diaphorase(NDP)histochemical staining method and whole mountpreperation technique.RESULTS:NOS was distributed in whole stomach wall,mostof them were located In myenteric plexus,and distributed insubmucosal plexus.The shape of NOS positive neuronswas baslcally similar,most of them being round and oval inshape.But their density,size and staining intensity variedgreatly in the different parts of stomach.The density was 62±38 cells/mm~2(antrum),43±32 cells/mm~2(body),and 32±28 cells/mm~2(fundus),respectively.The size andstaining intensity of NOS positive neurons in the funduswere basically the same,the neurons being large and darkstained,while they were obviously different in antrum.Inthe body of the stomach,the NOS positive neurons were inan Intermediate state from fundus to antrum.There weresome beedlike structures which were strung together byNOS positiva varicosities in nerve fibers,some were closelyadherent to the outer walls of blood vessels.CONCLUSION:Nitric oxide might he involved in themodulation of motility,secretion and blood circulation ofthe stomach,and the significant difference of NOS positiveneurons in different parts of stomach myenteric plexus maybe related to the physiologic function of stomach.     

Selective damage of intrinsic calcitonin gene-related peptide-like immunoreactive enteric nerve fibers in streptozotocin-induced diabetic rats

The distribution of calcitonin gene-related peptidelike immunoreactive (CGRP-LI) nerve fibers in the myenteric plexus of ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin was studied using immunohistochemical techniques. A marked decrease in CGRP-LI nerve fibers mainly around the ganglion cells of the myenteric plexus of both ileum and proximal colon was observed in diabetic rats. The sparsely located immunoreactive nerve cell bodies in the control rats were absent in the diabetic preparations. There were, however, intensely stained CGRP-LI varicose nerve fibers that ran through the internodal strands and over the myenteric ganglia of the diabetic intestines. These findings indicate the presence of CGRP-LI nerve fibers of dual origin in the intestinal wall. The absence of positive cell bodies and diminished CGRP-LI nerve fibers around the ganglion cells in the diabetic tissues suggest that the state of diabetes selectively affects CGRP-LI nerve fibers of intrinsic rather than extrinsic origin. Furthermore, the absence of change in substance P-like immunoreactivity in the enteric system of rats with streptozotocin-induced diabetes of the same duration suggests that calcitonin gene-related peptide and substance P are contained in different populations of intrinsic nerve fibers in the gastrointestinal tract of the rat.     

Immunochemical localization of aminopeptidase M in the alimentary tract of the guinea pig and rat.

Aminopeptidase M (APM) was localized in the kidney and alimentary tract of guinea pigs and rats by indirect immunohistochemistry. APM was detected in the brush border of the epithelium of the proximal convoluted tubule of the kidney and of the small intestine, and it was localized to cells scattered throughout lymphoid tissue in the small intestine and colon. The gastric mucosa was unstained. APM was localized to numerous fibers supplying the myenteric plexus of the stomach, small intestine, and colon. The submucosal plexus was sparsely supplied by immunoreactive fibers. Occasional cell bodies were stained in the myenteric plexus. Staining was abolished by preabsorption of the primary antibody with APM. APM was characterized in membranes prepared from the muscle and mucosa of the guinea pig and rat stomach, small intestine, and colon by Western blotting. The major immunoreactive protein identified in membranes prepared from all tissues had an apparent molecular weight of 140, corresponding to the monomer of APM. In the brush border APM has a digestive function, whereas in neural tissue it may degrade and inactivate neuropeptides.