Impaired nitrergic innervation in rat colitis induced by dextran sulfate sodium

BACKGROUND & AIMS: The pathophysiological role of neuronal nitric oxide synthase (nNOS) in colitis remains unknown. METHODS: We investigated colonic transit, nonadrenergic, noncholinergic (NANC) relaxation, nNOS activity, and nNOS synthesis in the myenteric plexus in dextran sulfate sodium (DSS)-induced colitis in rats. RESULTS: Oral administration of 5% DSS for 7 days induced predominant distal colitis and delayed colonic transit. In the proximal colon, carbachol-, sodium nitroprusside-, and electrical field stimulation (EFS)-induced responses were not different between control and DSS-treated rats. In the distal colon, EFS-evoked cholinergic contraction, NANC relaxation, and orphanin FQ-induced contraction were significantly impaired in DSS-treated rats compared with those in control rats, but carbachol- and sodium nitroprusside-induced responses remained intact in DSS-treated rats. The number of nNOS-immunopositive cells, catalytic activity of NOS, and nNOS synthesis in the colonic wall were significantly reduced in the distal colon of DSS-treated rats. In contrast, the number of PGP 9.5-immunopositive cells and PGP 9.5 synthesis in the colonic wall remained intact in the distal colon of DSS-treated rats. CONCLUSIONS: These results suggest that impaired NANC relaxation in the distal colon is associated with reduced activity and synthesis of nNOS in the myenteric plexus in DSS-induced colitis.     

Decreased density of interstitial cells of Cajal and neuronal cells in patients with slow-transit constipation and acquired megacolon

BACKGROUND: The pathophysiology of constipation is not clearly identified as yet, and the interstital cells of Cajal (ICC), known to generate the slow wave activity and to be involved in intestinal neurotransmission and the enteric nervous system (ENS), are suspected to play an important role. The aims of the present study were to assess the distribution of ICC and neuronal cells of ENS in patients with slow-transit constipation and acquired megacolon. METHODS: Sigmoid colon specimens were obtained from patients who underwent colectomy due to slow-transit constipation (n = 10), acquired megacolon (n = 9) and non-obstructive colon cancer (n = 10) as a control group. The ICC were visualized by c-Kit immunohistochemistry and neuronal cells of the ENS were demonstrated by protein gene product (PGP) 9.5. Density of cells stained by c-Kit and PGP 9.5 was calculated as percent area (area stained/area of X-Y plane) x 100, when images were collected at a magnification of x40 objective, with maximum area examined in the horizontal X-Y plane of 400 microm x 400 microm using an image analyzer. RESULTS: The densities of ICC and PGP 9.5 reactive neuronal structures were significantly decreased in all layers of sigmoid colon specimens in patients with slow-transit constipation and acquired megacolon, compared with that of the control group. However, there was no statistically significant difference in either the density of ICC or that of neuronal structures between the patients with slow-transit constipation and acquired megacolon. CONCLUSIONS: Slow-transit constipation and acquired megacolon were associated with alteration of ICC and neuronal cells of ENS in the sigmoid colon.     

Abnormalities of the enteric nervous system in heterozygous endothelin B receptor deficient (spotting lethal) rats resembling intestinal neuronal dysplasia

BACKGROUND: A homozygous mutation of the endothelin B receptor (EDNRB) gene in spotting lethal (sl/sl) rats leads to Hirschsprung's disease (HSCR) with long segmented aganglionosis. However, the effects on the development of the enteric nervous system (ENS) promoted by a heterozygous mutation of the EDNRB gene are not known. The present study aimed to describe and morphometrically assess the phenotypic abnormalities of the ENS in heterozygous (+/sl) EDNRB deficient rats in comparison with homozygous (sl/sl) EDNRB deficient and wild-type (+/+) rats. METHODS: The distal small intestine, caecum, and colon were obtained from sl/sl, +/sl, and +/+ rats. To demonstrate the three dimensional organisation of the ENS, the intestinal wall was microdissected into wholemounts and incubated against the pan-neuronal marker protein gene product 9.5. Assessment of the ENS included morphometric quantification of ganglionic size and density, the number of nerve cells per ganglia, and the diameter of nerve fibre strands within both the myenteric and submucous plexus. RESULTS: Sl/sl rats were characterised by complete aganglionosis resembling the same histopathological features observed in patients with HSCR. +/sl rats revealed more subtle abnormalities of the ENS: the submucous plexus was characterised by a significantly increased ganglionic size and density, and the presence of hypertrophied nerve fibre strands. Morphometric evaluation of the myenteric plexus did not show statistically significant differences between +/sl and +/+ rats. CONCLUSIONS: In contrast with sl/sl rats, +/sl rats display non-aganglionated malformations of the ENS. Interestingly, these innervational abnormalities resemble the histopathological criteria for intestinal neuronal dysplasia (IND). Although IND has been described in several intestinal motility disorders, the concept of a clearly defined clinical-histopathological entity is still controversially discussed. The present findings support the concept of IND based on clearly defined morphological criteria suggesting a genetic link, and thus may provide a model for human IND. Furthermore, the data underline the critical role of the "gene dose" for the phenotypic effects promoted by the EDNRB/EDN3 system and confirm that the development of the ENS is not an "all or none" phenomenon.     

Changes of smooth muscle contractile filaments in small bowel atresia

AIM: To investigate morphological changes of intestinal smooth muscle contractile fibres in small bowel atresia patients.METHODS: Resected small bowel specimens from small bowel atresia patients (n = 12) were divided into three sections (proximal, atretic and distal). Standard histology hematoxylin-eosin staining and enzyme immunohistochemistry was performed to visualize smooth muscle contractile markers α-smooth muscle actin (SMA) and desmin using conventional paraffin sections of the proximal and distal bowel. Small bowel from age-matched patients (n = 2) undergoing Meckel’s diverticulum resection served as controls.RESULTS: The smooth muscle coat in the proximal bowel of small bowel atresia patients was thickened compared with control tissue, but the distal bowel was unchanged. Expression of smooth muscle contractile fibres SMA and desmin within the proximal bowel was slightly reduced compared with the distal bowel and control tissue. There were no major differences in the architecture of the smooth muscle within the proximal bowel and the distal bowel. The proximal and distal bowel in small bowel atresia patients revealed only minimal differences regarding smooth muscle morphology and the presence of smooth muscle contractile filament markers.CONCLUSION: Changes in smooth muscle contractile filaments do not appear to play a major role in postoperative motility disorders in small bowel atresia.     

Submucosal hypoganglionosis causing chronic idiopathic intestinal pseudo-obstruction.

A 39-year-old woman presented with recurrent symptoms suggestive of intestinal obstruction. She was put on total parenteral nutrition (TPN) and consequently developed sepsis and endocarditis. TPN was stopped and a venting enterostomy was performed. Biopsies of mucosa and submucosa were taken at surgery; immunohistochemistry for neuronal proteins, protein gene product 9.5 (PGP 9.5) and the glial S-100-protein was done. Many enlarged nerve fiber strands were found in the submucosa. Few small ganglia containing a small number of nerve cells could be observed, suggesting hypoganglionosis. This patient with chronic idiopathic intestinal pseudoobstruction of neurogenic type had a defect in the submucous plexus, whereas visceral neuropathies are usually characterized by defects of the myenteric plexus with normal submucous plexus.     

Electron microscopy of myenteric nerves in Hirschsprung''s disease and in normal bowel

The ultrastructure of the myenteric nerves of colon and rectum removed from 10 children with Hirschsprung's disease has been studied and compared with normal infant bowel.Distal aganglionic (Hirschsprung) bowel often showed a rich supply of nerves within the muscle layers and there was no obvious morphological abnormality of constituent axons. The numbers of nerves diminished as more proximal parts of the bowel were examined and the fewest nerves were found where ganglia first appeared. These ganglia were similar in structure to the ganglia of normal bowel, and a striking feature of them all was the absence of collagen between constituent neuronal units. The larger nerve trunks of aganglionic bowel frequently contained myelinated axons and these have been observed within the myenteric plexus of normal rectum.This study supports previous histochemical investigations of the nerves in bowel from patients with Hirschsprung's disease and indicates that the condition is due to a complex and variable abnormality of the arrangement of the nervous tissue of the bowel wall, involving myenteric nerves as well as ganglia.     

Probiotics in Experimental Ulcerative Colitis: Mast Cell Density and Neuronal Hypertrophy

Background:Probiotics such as Lactobacillus and Bifidobacterium are among the supportive treatment methods to achieve effective results in ulcerative colitis. This study was established to investigate the effect of probiotics in experimental ulcerative colitis and to detect changes in mast cell and neuronal structures in this treatment method.Methods:A total of 48 adult male rats were used to study the effects of probiotics on ulcerative colitis. The animals were divided into 6 groups as control, experimental colitis, and four probiotic protective groups. Three different bacterial strains were administered to the protective groups individually and in combination by gavage. PGP 9.5 antibody and mast cell tryptase were used for the detection of neuronal structures and mast cells. The number of Schwann cells and ganglia, size measurements of ganglia, and density of mast cells were evaluated.Results:Compared to the control, an increase in the number of mast cells was detected in all groups. Especially the increase in the number of mast cells was found to be statistically significant in combined probiotic administration. In the detection of neuronal structures, a significant increase in the number of Schwann cells and ganglia was detected in groups where probiotics were administered combined and individually.Conclusion:These results suggest that probiotics may play a role in the supporting effect of increasing the number of mast cells and neuronal structures, protecting the intestinal wall. We think that more specific and detailed studies should be conducted to evaluate the protective/therapeutic effect of probiotics in future studies.     

Changes in Muscularis Externa of Rat Small Intestine After Myenteric Ablation with Benzalkonium Chloride: Electron Microscopic and Morphometric Study

The influence of the intrinsic innervation onthe muscularis externa of the rat small intestine wasstudied by chemical ablation of the myenteric plexuswith benzalkonium chloride (BAC). The resulting severe hypertrophy (cell hypertrophy of 96-133% andhyperplasia) differs from working hypertrophy by thedistribution and degree of muscle thickening and bycharacteristics of the extracellular matrix: narrowing of muscle interspaces of 43%; lack of increasedcollagen; changes in the ratio of interstitial cells ofCajal (ICCs) to fibroblasts from 1.6:1 to 0.8:1 with nonumerical decrease in either type of cell; decreased interconnections of ICCs to musclesand nerves due to deformed ICCs; a 197% increase invascularization (capillaries, venules) and lymphatics inboth muscle layers and in the myenteric plexus cleft, possibly initiated by release offibroblast growth factor from myelin fragmentation afternerve damage; and increased macrophages, plasma cells,monocytes and mast cells in the myenteric plexus cleft. These all signify the neural influence on themorphodifferentiation of the muscularis externa inconcert with the extracellular matrixcomponents.     

The development of colon innervation in trisomy 16 mice and Hirschsprung's disease

AIM: To study the colon innervation of trisomy 16 mouse, an animal model for Down's syndrome, and the expression of protein gene product 9.5 (PGP 9.5) in the stenosed segment of colon in Hirschsprung's disease (HD). METHODS: Trisomy 16 mouse breeding;cytogenetic analysis of trisomy 16 mice; and PG P9.5 immunohistochemistry of colons of trisomy 16 mice and HD were carried out. RESULTS: Compared with their normal littermates, the nervous system of colon in trisomy 16 mice was abnormally developed. There existed developmental delay of muscular plexuses of colon, no submucosal plexus was found in the colon, and there was 5mm aganglionic bowel aparting from the anus in trisomy 16 mice. The mesentery nerve fibers were as well developed as shown in their normal littermates. Abundant proliferation of PGP 9.5 positive nerve fibers was revealed in the stenosed segment of HD colon. CONCLUSION: Trisomy 16 mice could serve as an animal model for Hirschsprung's disease for aganglionic bowel in the distal part of colon.Abundant proliferation of PGP 9.5 positive fibers resulted from extrinsic nerve compensation, since no ganglionic cells were observed in the stenosed segment of the colon in HD. HD has a genetic tendency.     

Notable postnatal alterations in the myenteric plexus of normal human bowel

BACKGROUND: Nitric oxide is the most important transmitter in non-adrenergic non-cholinergic nerves in the human gastrointestinal tract. Impaired nitrergic innervation has been described in Hirschsprung's disease, hypertrophic pyloric stenosis, and intestinal neuronal dysplasia (IND). Recent findings indicate that hyperganglionosis, one of the major criteria of IND, is age dependent. However, information is scanty regarding the neurone density in normal human bowel in the paediatric age group. AIMS: To determine neurone density, morphology, and nitric oxide synthase distribution of the normal myenteric plexus at different ages during infancy and childhood. METHODS: Specimens were obtained from small bowel and colon in 20 children, aged one day to 15 years, at postmortem examination. Whole mount preparations were made of the myenteric plexus, which were subsequently stained using NADPH diaphorase histochemistry (identical to nitric oxide synthase) and cuprolinic blue (a general neuronal marker). The morphology of the myenteric plexus was described and the neurone density estimated. RESULTS: The myenteric plexus meshwork becomes less dense during the first years of life. The density of ganglion cells in the myenteric plexus decreases significantly with age during the first three to four years of life. The NADPH diaphorase positive (nitrergic) subpopulation represents about 34% of all neurones in the myenteric plexus. CONCLUSIONS: The notable decrease in neurone density in the myenteric plexus during the first years of life indicates that development is still an ongoing process in the postnatal enteric nervous system. Applied to the clinical situation, this implies that interpretation of enteric nervous system pathology is dependent on the age of the patient.     

Oligoneuronal Hypoganglionosis in Patients with Idiopathic Slow-Transit Constipation

PURPOSE: Several alterations of the enteric nervous system have been described as an underlying neuropathologic correlate in patients with idiopathic slow-transit constipation. To obtain comprehensive data on the structural components of the intramural nerve plexus, the colonic enteric nervous system was investigated in patients with slow-transit constipation and compared with controls by means of a quantitative morphometric analysis. METHODS: Resected specimens were obtained from ten patients with slow-transit constipation and ten controls (nonobstructive neoplasias) and processed for immunohistochemistry with the neuronal marker Protein Gene Product 9.5. The morphometric analysis was performed separately for the myenteric plexus and submucous plexus compartments and included the quantification of ganglia, neurons, glial cells, and nerve fibers. RESULTS: In patients with slow-transit constipation, the total ganglionic area and neuronal number per intestinal length as well as the mean neuron count per ganglion were significantly decreased within the myenteric plexus and external submucous plexus. The ratio of glial cells to neurons was significantly increased in myenteric ganglia but not in submucous ganglia. On statistical analysis, the histopathologic criteria (submucous giant ganglia and hypertrophic nerve fibers) of intestinal neuronal dysplasia previously described in patients with slow-transit constipation were not completely fulfilled. CONCLUSION: The colonic motor dysfunction in slow-transit constipation is associated with quantitative alterations of the enteric nervous system. The underlying defect is characterized morphologically by oligoneuronal hypoganglionosis. Because the neuropathologic alterations primarily affect the myenteric plexus and external submucous plexus, superficial submucous biopsies are not suitable to detect these innervational disorders.     

沉香化气胶囊对糖尿病大鼠小肠ICC和肌间神经丛的影响

目的:探讨沉香化气胶囊对糖尿病(diabetes mellitus,DM)大鼠小肠Cajal间质细胞(interstitial cells of Cajal,ICC)、肌间神经丛的影响.方法:将健康♂SD大鼠分为正常对照组、DM模型组、DM模型+中药组.大鼠一次性腹腔注射(ip)链脲佐菌素(STZ,60mg/kg)造模,选取成功模型,DM模型+中药组每天给予中药灌胃,模型组和正常对照组每天给予同等容量的蒸馏水,持续灌胃4wk.所有大鼠干预4wk结束后,给予印度墨汁灌胃测定小肠传输速率,利用免疫组织化学和图像分析观察十二指肠c-Kit、突触素(synaptophysin,Syn)、蛋白基因产物9.5(protein gene product 9.5,PGP9.5)的表达.结果:灌胃4wk后,DM模型+中药组小肠传输速率均比DM模型组明显增加(71.26±5.22 vs 45.52±6.42,P<0.01),仍低于对照组(71.26±5.22 vs 80.40±7.33,P<0.05);DM模型+中药组c-Kit、突触素、PGP9.5的阳性产物面积和吸光度值均比DM模型组明显增加(443.28±24.40 vs 358.83±35.03,832.33±58.78 vs 488.83±58.56,889.17±82.75 vs 445.17±64.06,0.16±0.02 vs 0.13±0.02,0.25±0.02 vs 0.16±0.01,0.24±0.02 vs 0.15±0.01,均P<0.01),仍低于正常对照组(443.28±24.40 vs 557.28±42.35,P<0.01;832.33±58.78 vs 937.67±101.23,P<0.05;889.17±82.75 vs 1050.50±90.22,P<0.01;0.16±0.02 vs 0.18±0.02,P<0.05;0.25±0.02 vs 0.29±0.03,P<0.01;0.24±0.02 vs 0.27±0.02,P<0.01).结论:沉香化气胶囊可以促进糖尿病大鼠小肠肌间神经丛c-Kit、突触素和PGP9.5的表达,提示对受损的DM大鼠小肠ICC、肌间神经丛有部分恢复作用,从而对糖尿病大鼠的胃肠动力障碍有一定的改善效应.     

Regeneration of nerve fibres across a colonic anastomosis in the guinea-pig

Resection and re-anastomosis of the bowel interrupts enteric neuronal pathways. The re-establishment of neuronal connections across a colonic anastomosis was studied using immunohistochemical, retrograde tracing and physiological techniques. In control guinea-pig proximal colon, retrograde labelling with 1,1′-didodecyl-3,3,3,3′-tetramethylindocarbocyanine perchlorate (DiI) revealed that enteric neurons with anally-directed projections are more numerous and have longer axons than orally-projecting neurons. In resected bowel, up to 26 weeks after re-anastomosis, descending neuronal pathways were substantially interrupted. Immunohistochemical labelling of nerve fibres revealed that some enteric nerve fibres did regenerate across narrow regions of the anastomosis, growing preferentially in the oral to anal direction. However, nerve fibres immunoreactive for neurofilament protein triplet were substantially depleted in myenteric ganglia anal to the anastomosis, even after the longest recovery periods, demonstrating that axonal regrowth was limited. This was confirmed in retrograde tracing studies, as no nerve cell bodies oral to an anastomosis were labelled when DiI was placed on myenteric ganglia just anal to the anastomosis. Physiological studies confirmed that regrowth of nerve fibres across the anastomosis occurred and that it was asymmetric, as electrical stimulation led to aboral conduction across the anastomosis more reliably than oral conduction, as measured by circular muscle contraction. After resection and re-anastomosis of the colon, the disruption of neuronal pathways in the enteric nervous system was observed, with limited and preferential re-establishment of aborally-directed long connections.     

PGP9.5 overexpression in esophageal squamous cell carcinoma

BACKGROUND/AIMS: PGP9.5 is a ubiquitin hydrolase widely expressed in neuronal tissue at all stages of neuronal differentiation and has been used as a neuroendocrine marker. Recently, it has been proved that PGP9.5 expression was highly observed in squamous cell carcinoma of lung cancer, suggesting that it might be a tumor marker for squamous cell carcinoma. To better characterize its role in digestive tract cancers, we examined PGP9.5 expression retrospectively in esophageal cancers. METHODOLOGY: We examined PGP9.5 expression retrospectively in 40 resected esophageal cancers (squamous cell carcinoma) and 10 gastric cancers (adenocarcinoma) using immunohistochemistry. RESULTS: Of 40 esophageal cancer specimens, 19 (48%) exhibited positive staining with PGP9.5 in most tumor cells, while no PGP9.5 expression was observed in any of the 10 gastric cancers. CONCLUSIONS: Although the precise mechanism underlying the effect of PGP9.5 on oncogenicity remains to be proven, it was confirmed that it may be a potential marker for esophageal squamous cell carcinoma.     

The development of colon innervation in trisomy mice and Hirschsprungs disease

AIM To study the colon innervation of trisomy16 mouse, an animal model for Downssyndrome, and the expression of protein geneproduct 9.5 ( PGP 9.5) in the stenosed segmentof colon in Hirschsprungs disease (HD).METHODS Trisomy 16 mouse breeding;cytogenetic analysis of trisomy 16 mice; andPGP 9.5 immunohistochemistry of colons oftrisomy 16 mice and HD were carried out.RESULTS Compared with their normalIittermates, the nervous system of colon intrisomy 16 mice was abnormally developed.There existed developmental delay of muscularplexuses of colon, no submucosal plexus wasfound in the colon, and there was 5mmaganglionic bowel aparting from the anus intrisomy 16 mice. The mesentery nerve fiberswere as well developed as shown in their normallittermates. Abundant proliferation of PGP 9.5positive nerve fibers was revealed in thestenosed segment of HD colon.CONCLUSION Trisomy 16 mice could serve asaganglionic bowel in the distal part of colon.Abundant proliferation of PGP 9.5 positive fibersresulted from extrinsic nerve compensation,since no ganglionic cells were observed in thestenosed segment of the colon in HD. HD has agenetic tendency.     

Interstitial cells of Cajal in the human fetal small bowel as shown by c-kit immunohistochemistry

Background—Interstitialcells of Cajal (ICCs) express the tyrosine kinase receptor c-kit, whichis required for their development and spontaneous pacemaker activity inthe bowel. From murine models it has been proposed that ICCs do notdevelop until after birth, but more recent findings indicate that c-kitis expressed early in the embryonic period. The temporal development ofICCs in the human gut remains unknown.
Aim—To investigateICCs in the human fetal small bowel using c-kit immunohistochemistry.
Subjects—Small bowelspecimens were obtained at post mortem examination of 16 fetuses andnine neonates, eight of whom were premature, born at gestational agesof 13 to 41 weeks, without gastrointestinal disorders.
Methods—Immunohistochemicalanalysis was performed on material fixed in formalin and embedded inparaffin. The specimens were exposed to antibodies raised against c-kit(an ICC marker) and neurone specific enolase (a general neuronalmarker). The ABC complex method was used to visualise binding ofantibodies to the corresponding antigens.
Results—c-kitimmunoreactive cells were visualised from 13 weeks of gestation. Theimmunoreactivity was mainly localised in association with the myentericplexus. From about 17-18 weeks of gestation, the ICCs formed a layeralong the myenteric plexus, whereas this layer appeared to be disruptedat 13-16 weeks of gestation.
Conclusions—ICCs arec-kit immunoreactive at least from a gestational age of 13 weeks inthe human fetal small intestine. From 17-18 weeks of gestation untilbirth, they form a continuous layer around the myenteric ganglia.

Keywords:interstitial cells of Cajal; c-kit; myentericplexus; human; fetal; development

     

Changes of protein gene product 9.5 (PGP 9.5) immunoreactive nerves in inflamed appendix

The existence of chronic appendicitis is controversial. In this prospective study, we investigated possible changes in the innervation of the appendix under different pathological conditions and correlated histological findings with clinical observation. Thirty appendectomy specimens and 14 appendices obtained from organ donors or patients who underwent right hemicolectomy were immediately fixed in Bouin's solution and processed for immunocytochemistry using an antiserum directed against the panneuronal marker protein gene product 9.5 (PGP 9.5). The density of PGP 9.5 immunostaining was evaluated by digitized morphometry. Significant differences in the density of the PGP 9.5-immunoreactive area were detected in the mucosal layer. In the nonacute appendicitis group, PGP 9.5 was increased (10.99±3.15%) as compared to acute appendicitis (3.89±1.77%) and controls (4.98±1.25%). The significant increase of PGP 9.5 in nonacute appendicitis may suggest axonal sprouting leading to hyperinnervation of the mucosa. This may be a neuronal factor in the pathophysiology of the disease and pain symptoms.     

Regional differences in the nitrergic innervation between the proximal and the distal colon in rats

Background & Aims: Functional differences in the inhibitory neural pathway between the proximal and the distal colon are unknown. Methods: We investigated the nonadrenergic, noncholinergic (NANC) relaxation, nitric oxide synthase (NOS) synthesis, and NOS messenger RNA (mRNA) expression of the myenteric plexus in the proximal and the distal colon in rats. Results: Transmural nerve stimulation of the neuromuscular preparations from the proximal colon showed greater NANC relaxations than those from the distal colon. NANC relaxations were abolished by the NO biosynthesis inhibitor (N^G-nitro-L-arginine methyl ester) in the proximal and the distal colon, suggesting mediation by NO released from the myenteric plexus. The average number of NOS-immunoreactive cells was significantly higher in the tissue from the proximal colon than in the tissue from the distal colon. Western and Northern blot analyses showed a higher density of the immunoreactive NOS band and the NOS mRNA band in the tissue from the proximal colon than in that from the distal colon. Conclusions: These observations indicate that the number of NOS-containing neurons and the NOS activity are increased in the myenteric plexus of the proximal colon compared with the distal colon, resulting in greater NANC relaxation in the proximal colon. These findings may explain the physiological role of the proximal colon as an organ for fecal storage and absorption of excess fluid.GASTROENTEROLOGY 1998;115:1504-1512     

Immunohistochemical study on gastroenteric nervous system in trisomy 16 mice:an animal model of Down syndrome

AIM:To study the development of gastroenteric nervous system in trisomy 16 mouse embryos.The gastroenteric nervous system in trisomy 16 mice and their normal littermates, serving as controls from embryonic days 13 to 18 (ED13-18) was identified by using primary antibody against protein gene product (PGP) 9.5.METHODS:Trisomy 16 mouse breeding and trisomy 16 mouse embryos were identified from their normal littermates by chromosome examination; PGP 9.5 immunohistochemical stainning.RESULTS:In normal littermates embryos, the precursor cells from the neural crest migrated into stomach and intestine at ED 13 and ED 14 respectively.Numerous nervous processes connected to each other and formed early nervous networks at ED 14 stomach and ED 15 intestine. Original ganglia in the muscular nervous plexus of the stomach appeared at ED15 with very simple arrangement. At ED 16 the early developed myenteric nervous plexuses were regularly found in the stomach and intestine respectively. In both stomach and intestine, the development of submucosal nervous plexuses were finished at ED17. However, the myenteric nervous plexus and the internal and external submucosal nervous plexuses were differentiated only in the stomach at ED 18.In comparison with the normal littermates, stomach and intestine nervous system developed much slower in trisomy 16 mice. Their immature neurons did not appear in the stomach and intestine until ED 14 and ED 15. Between ED 14 and ED 16, the gastroenteric nervous system was composed of only some scattered neurons with different distribution density and size. The development and differentiation of the gastroenteric nervous system were delayed and the myenteric nervous plexus did not appear until ED 18. There was no submucosal nervous plexus in all stomach and intestine specimens. A semiquantitative analysis and rank sum test of the data showed that the trisomy 16 mouse embryos were markedly retarded in the gastroenteric nervous development compared with their normal littermates.CONCLUSION:Trisomy 16 mice, as an animal model for Down syndrome, has abnormality not only in several systems and organs but also in gastroenteric innervation. This report describes for the first time that the development of the gastroenteric nervous system was not only delayed but also pathological.     

The development of colon innervation in trisomy 16 mice and Hirschsprung’s disease

AIM To study the colon innervation of trisomy16 mouse, an animal model for Downssyndrome, and the expression of protein geneproduct 9.5 (PGP 9.5) in the stenosed segmentof colon in Hirschsprungs disease (HD).METHODS Trisomy 16 mouse breeding;cytogenetic analysis of trisomy 16 mice; andPGP 9.5 immunohistochemistry of colons oftrisomy 16 mice and HD were carried out.RESULTS Compared with their normallittermates, the nervous system of colon intrisomy 16 mice was abnormally developed.There existed developmental delay of muscularplexuses of colon, no submucosal plexus wasfound in the colon, and there was 5mmaganglionic bowel aparting from the anus intrisomy 16 mice. The mesentery nerve fiberswere as well developed as shown in their normallittermates. Abundant proliferation of PGP 9.5positive nerve fibers was revealed in thestenosed segment of HD colon.CONCLUSION Trisomy 16 mice could serve asan animal model for Hirschsprung s disease foraganglionic bowel in the distal part of colon.Abundant proliferation of PGP 9.5 positive fibersresulted from extrinsic nerve compensation,since no ganglionic cells were observed in thestenosed segment of the colon in HD. HD has agenetic tendency.