Alterations of the intramural nervous distributions in a chick intestinal atresia model

A Pilot Study on Histopathology of the Jejunoileal Atresia-Can it Be Used as a Guide to Determine the Length of Adequate Resection?

Introduction:

Some studies reported that there is abnormality in the histopathology of atretic bowel in jejunoileal atresia (JIA). We have made an attempt to assess sequential histopathologic changes in the resected atretic segment.

Material and methods:

The histopathology of the resected segment was evaluated at 1, 3, 5, 7, 9, and 11 cm from atretic end (Sections A to F, respectively). The ratio of inner and outer muscle layer (measured by NIS-Element D software) was calculated at every section. Immunohistochemistry for α-smooth muscle actin (α-SMA) was also done. The findings were compared with control.

Results:

In control set (n = 5), the ratio of inner and outer muscle layer was 1.03. In patients with JIA, the ratio was 0.68 to 0.9 at section A. This ratio varied at various sections in all specimens. In section F, this ratio was 0.95 to 1.09, which is close to control ratio. There were no specific findings related to α-SMA staining.

Conclusions:

It appears that the bowel proximal to the atresia is abnormal for a varied length. It may be a possibility that this abnormality is present at least up to about 10 cm proximal to atresia. Adequate resection is important for optimal outcome.

Regenerative capacity of the enteric nervous system: is immaturity defining the point of no return?

BACKGROUND

Intestinal obstruction in newborns is associated with intestinal motility disorders after surgery. Alterations in the enteric nervous system (ENS) might cause abnormal peristalsis, which may then result in intestinal motility disorders. We aimed to quantify alterations in the myenteric plexus after a ligation and to test if these alterations were reversible.

METHODS

Small intestines of chicken embryos were ligated in ovo at embryonic day (ED) 11 for either 4 d (ED 11-15) or 8 d (ED 11-19). Both treated groups and control group were sacrificed and intestinal segments examined by means of both light and electron microscopy.

RESULTS

The number of proximal myenteric ganglia increased (ED 19, 30.7 ± 3.16 versus 23.1 ± 2.03; P < 0.001) in the 8-d ligature group but had values similar to the control group in the 4-d ligature group. The size distribution was skewed toward small ganglia in the 8-d ligature group (ED 19, 83.71 ± 11.60% versus 3.88 ± 4.74% in the control group; P < 0.001) but comparable with the control group in the 4-d ligature group. Subcellular alterations in the 4-d ligature group were reversible.

CONCLUSIONS

The pathologic alterations in the ENS were fully reversible in the 4-d ligature group. This reversibility might be linked to the degree of immaturity of the ENS.

A functional study on small intestinal smooth muscles in jejunal atresia

AIM

The present study was aimed to assess the contractile status of neonatal small intestinal smooth muscle of dilated pre-atretic part of intestinal atresia to resolve debatable issues related to mechanisms of persistent dysmotility after surgical repair.

MATERIALS AND METHODS

A total of 34 longitudinally sectioned strips were prepared from pre-atretic dilated part of freshly excised 8 jejunal atresia type III a cases. Spontaneous as well as acetylcholine- and histamine-induced contractions were recorded in vitro by using organ bath preparations. Chemically evoked contractions were further evaluated after application of atropine (muscarinic blocker), pheniramine (H1 blocker), and lignocaine (neuronal blocker) to ascertain receptors and neuronal involvement. Histological examinations of strips were made by using Masson trichrome stain to assess the fibrotic changes.

RESULTS

All 34 strips, except four showed spontaneous contractions with mean frequency and amplitude of 5.49 ± 0.26/min and 24.41 ± 5.26 g/g wet tissue respectively. The response to ACh was nearly twice as compared to histamine for equimolar concentrations (100 μM). ACh (100 μM) induced contractions were attenuated (by 60%) by atropine. Histamine (100 μM)-induced contractions was blocked by pheniramine (0.32 μM) and lignocaine (4 μM) by 74% and 78%, respectively. Histopathological examination showed varying degree of fibrotic changes in muscle layers.

CONCLUSIONS

Pre-atretic dilated part of jejunal atresia retains functional activity but with definitive histopathologic abnormalities. It is suggested that excision of a length of pre-atretic part and early stimulation of peristalsis by locally acting cholinomimetic or H1 agonist may help in reducing postoperative motility problems in atresia patients.

Reversible small bowel obstruction in the chicken foetus

BACKGROUND

Ligation of the embryonic gut is an established technique to induce intestinal obstruction and subsequently intestinal atresia in chicken embryos. In this study, we modified this established chicken model of prenatal intestinal obstruction to describe (1) the kinetics of morphological changes, (2) to test if removal of the ligature in ovo is possible in later embryonic development and (3) to describe morphological adaptations following removal of the ligature.

MATERIALS AND METHODS

On embryonic day (ED) 11, small intestines of chick embryos were ligated micro surgically in ovo. In Group 1 (n = 80) gut was harvested proximal and distal to the ligation on ED 12-19. In Group 2 (n = 20) the induced obstruction was released on day 15 and gut was harvested on ED 16-19. Acetyl choline esterase staining was used as to assess resulting morphological changes.

RESULTS

A marked intestinal dilatation of the proximal segment can be seen 4 days after the operation (ED 15). The dilatation increased in severity until ED 19 and intestinal atresia could be observed after ED 16. In the dilated proximal segments, signs of disturbed enteric nervous system morphology were obvious. In contrast to this, release of the obstruction on ED 15 in Group 2 resulted in almost normal gut morphology at ED 19.

CONCLUSION

Our model not only allows the description of morphological changes caused by an induced obstruction on ED 11 but also-more important - of morphological signs of adaptation following the release of the obstruction on ED 15.

Prenatal intestinal obstruction affects the myenteric plexus and causes functional bowel impairment in fetal rat experimental model of intestinal atresia

Background

Intestinal atresia is a rare congenital disorder with an incidence of 3/10 000 birth. About one-third of patients have severe intestinal dysfunction after surgical repair. We examined whether prenatal gastrointestinal obstruction might effect on the myenteric plexus and account for subsequent functional disorders.

Methodology/Principal Findings

We studied a rat model of surgically induced antenatal atresia, comparing intestinal samples from both sides of the obstruction and with healthy rat pups controls. Whole-mount preparations of the myenteric plexus were stained for choline acetyltransferase (ChAT) and nitric oxide synthase (nNOS). Quantitative reverse transcription PCR was used to analyze mRNAs for inflammatory markers. Functional motility and permeability analyses were performed in vitro. Phenotypic studies were also performed in 8 newborns with intestinal atresia. In the experimental model, the proportion of nNOS-immunoreactive neurons was similar in proximal and distal segments (6.7±4.6% vs 5.6±4.2%, p = 0.25), but proximal segments contained a higher proportion of ChAT-immunoreactive neurons (13.2±6.2% vs 7.5±4.3%, p = 0.005). Phenotypic changes were associated with a 100-fold lower concentration-dependent contractile response to carbachol and a 1.6-fold higher EFS-induced contractile response in proximal compared to distal segments. Transcellular (p = 0.002) but not paracellular permeability was increased. Comparison with controls showed that modifications involved not only proximal but also distal segments. Phenotypic studies in human atresia confirmed the changes in ChAT expression.

Conclusion

Experimental atresia in fetal rat induces differential myenteric plexus phenotypical as well as functional changes (motility and permeability) between the two sides of the obstruction. Delineating these changes might help to identify markers predictive of motility dysfunction and to define guidelines for post-surgical care.

Significance of abnormalities in systems proximal and distal to the obstructed site of duodenal atresia

BACKGROUND

Duodenal atresia (DA) is a well-known neonatal intestinal disease. Even after surgery, the proximal segment can continue to be severely dilated with hypoperistalsis, resulting in intestinal dysmotility problems in later life. No data have been published regarding the morphologic differences between the proximal and distal regions of obstructed sites of the intramural components in DA.

METHODS

Operative duodenal samples (N = 12) from cases with DA (age 1-3 days) were used. Age-matched controls (N = 2) were used. All of the specimens were immunohistochemically stained with antibodies to S-100 protein, α-smooth muscle actin, and c-kit protein.

RESULTS

At the proximal segments of the obstructed site in DA, the number of neuronal cells decreased in size and number. The circular musculature was moderately to severely hypertrophic. Unusual ectopic smooth muscle bundles were also identified. The innermost layer of the circular musculature was thinner. Interstitial cells of Cajal are decreased, even around the myenteric plexus. All of the staining in the distal segments in DA was similar to the control tissues.

CONCLUSIONS

Proximal and distal segments in DA differ in the neural cells, musculature, and distributions of the interstitial cells of Cajal. Based on the present study, these morphologic changes may contribute to the onset of postoperative duodenal dysmotility.

Alterations of Cajal cells in patients with small bowel atresia

PURPOSE

Interstitial cells of Cajal (ICC) are regarded as the pacemaker cells of the gastrointestinal tract. There are some well-designed studies investigating the structure and function of ICC subsequent to experimentally induced intestinal obstructions. However, it remains unclear whether reduction of number of ICC primarily leads to mechanical obstruction of the bowel such as seen in intestinal atresia. We aimed to investigate the number of ICC in proximal and distal parts of the atresias of patients with small bowel atresia.

PATIENTS AND METHODS

Twenty-one patients (13 male and 8 female; median age, 3 days; median gestation age, 38 weeks) with jejunal or ileal atresia underwent primary repair between 2001 and 2009. The demographic data were reviewed. The specimen of the distal and proximal parts of the atretic segments was investigated according to presence and number of ICC in the myenteric plexus using immunohistochemical methods. The jejunum segments of 14 newborns who died from causes other than bowel disease were examined as a control. Scoring and count systems were developed for the evaluation of ICC. A continuous layer of CD-117 immunoreactive Cajal cells around the myenteric plexus was scored as 3, whereas discontinuous and diminished Cajal cells were scored as 2. Few and sparse Cajal cells around the myenteric ganglia and in the muscle layer were scored as 1. If there was no Cajal cell at all, it was scored as zero. In addition, the number of ICC per field was counted. The scores and the numbers of ICC per field were compared in patients with small bowel atresia and control group.

RESULTS

All patients but one survived. One patient was lost because of congenital cardiac anomalies. The median score of control subjects was 3 (range, 1-3). Both the proximal and distal segments of the atretic bowel had a median score of 1 in patients with atresia. Twenty patients' score of proximal (95%) and 19 patients' score of distal bowel segment (90%) had an ICC score of 2 or less. Only 1 control subject (7%) had an ICC score of less than 2. Results were statistically significant in controls and patients. The mean number of ICC in the control group was 5.36 +/- 2.36; in distal segments of patients with atresia, it was 1.03 +/- 1.4; and in proximal segments, it was 0.82 +/- 1.56. The difference between the control group and the patients was statistically significant (P < .05).

CONCLUSION

We demonstrated a remarkable decrease of ICC in small bowel wall of patients with intestinal atresia; but we could not show whether the reduction of ICC is a primary event, which also participates in the pathogenesis of intestinal atresia, or whether the mechanical obstruction caused by any unknown etiology (eg, ischemia) leads to decrease in number of ICC.

A new rat model of prenatal bowel obstruction: development and early assessment

PURPOSE

Although intestinal motility disorders often complicate the postoperative surgical management of newborns with congenital intestinal atresia, their pathogenesis remains unclear. Animal models of prenatal intestinal obstruction have been mainly developed in the lamb and the chicken. Despite new insights brought by these models, they have one or more limitations, such as high fetal mortality rates, high costs, long gestation periods, and an insufficient number of fetuses per litter. Moreover, some species are phylogenetically distant from mammals.

METHODS

We developed a reproducible model of prenatal intestinal obstruction in the rat to study the histologic changes induced by the obstruction. We report, the technical devices and the first assessment of this atresia model in a didactic way to allow other researchers to easily reproduce the model.

RESULTS

Prenatal intestinal obstructions in this study fulfilled all the macroscopic and histologic criteria usually listed by other models of prenatal intestinal obstruction that have been developed in other species. Furthermore with our model, we obtained a high success rate at a low cost.

CONCLUSIONS

We presented in this study a reproducible model of prenatal intestinal obstruction in the rat with the macroscopical and histologic features of prenatal intestinal obstruction.

Endocrine cells in atresic chick embryo intestine: histochemical and immunohistochemical study

Intestinal motility disorders are an important problem in the postoperative management of patients with intestinal atresia. Intestinal motility could be initiated by luminal factors that activate intrinsic and extrinsic primary afferent nerves involved in the peristaltic reflex. Endocrine cells act as a key point, because they transfer information regarding the intestinal contents and intraluminal pressure to nerve fibers lying in close proximity to the basolateral surface of the epithelium. In chick embryo, experimental intestinal atresia is associated with disorders in the development of the enteric nervous system, related to the severity of intestinal dilation. Our aim was to investigate the distribution pattern of endocrine cells in the developing endocrine system of chick embryo small intestine with experimentally-induced atresia on day 12 and on day 16. Changes in enteroendocrine population were examined in gut specimens (excised proximal and distal to the atresia) from experimental embryos 19 days old and in control sham-operated chick embryos at the same age. Sections from proximal and distal bowel and control bowel were stained with Grimelius silver stain, a valuable histochemical method for detecting the argyrophil and argentophilic cells, and with an immunohistochemical procedure for detecting serotonin and neurotensin immunoreactive cells. In chick embryo proximal bowel, intestinal dilation differed in the various embryos. We found significantly higher enteroendocrine cell counts in proximal bowel than in distal and control bowel. The differences depended on the precociousness of surgery and the severity of dilation. Considering the major contribution of enteroendocrine cells to the peristaltic reflex, our data may help to explain the pathogenesis of motility disorders related to intestinal atresia.

C-kit receptor in the human vas deferens: distinction of mast cells, interstitial cells and interepithelial cells

The molecular mechanisms underlying the regulation of vas deferens (VD) motility and semen emission are still poorly understood. Interstitial cells of Cajal (ICC), which harbour the c-kit receptor (CD117), provide the basis of coordinated gut motility. We investigated whether c-kit receptor-positive cells also exist in the normal human VD. Enzyme and fluorescence immunohistochemical techniques were applied on serial sections of human proximal, middle, and distal VD segments (n=49) employing 13 different monoclonal and polyclonal antibodies recognizing the c-kit receptor. The c-kit receptor was detected in either round- or spindle-shaped cells. On account of their antigenic profile, the round- and oval-shaped c-kit receptor-positive cells were identified as mast cells (MC) occurring in all layers of the VD except the epithelium. In contrast, two distinct populations of exclusively c-kit receptor-positive spindle-shaped cells were found within the lamina propria and, rarely, in the inner and outer smooth muscle layers, as well as within the epithelium. Different shaped c-kit receptor-positive MC and IC were present in all layers of the human VD. Our findings demonstrate the presence of different c-kit receptor-positive cells also in the human VD. Their rather ubiquitous distribution within the lamina propria and muscle layers suggests that IC and MC may modulate the neuromuscular transmission and the propagation of electrical signals in multiple systems involved in the draining of fluids. The importance of the c-kit receptor-positive interepithelial cells remains unclear.

C-Kit receptor (CD117) in the porcine urinary tract

C-Kit positive interstitial cells of Cajal (ICC) play an important role in the regulation of the smooth muscle motility, acting as internal pacemakers to provide the slow wave activity within various luminal organs. Recently c-Kit-(CD117)-positive interstitial cells (IC) have been shown in the genitourinary tract, but systematic studies on the distribution and density of IC within the urinary tract are still lacking. Therefore the aim of the present study was to analyze systematically the localization and distribution of the c-Kit receptor in the urinary tract of the pig using immunohistochemical and molecular methods. Tissue samples were harvested from the porcine urinary tract including renal calices and pelvis, ureteropelvic junction, proximal, middle and distal ureter, ureteral orifice, fundus, and corpus of the bladder and the internal urethral orifice. Small and large intestine specimen served as controls. Immunohistochemistry (APAAP, IF) was applied on serial frozen sections using four monoclonal and polyclonal antibodies recognizing CD117. Whole mounts of the porcine upper urinary tract were prepared and investigated using conventional and confocal fluorescence microscopy followed by three-dimensional reconstruction. UV-laser microdissection and RT-PCR were applied to confirm the immunohistochemical results. CD117-immunoreactivity labeled bipolar IC and round-shaped mast cells (MC) throughout the adventitia, tunica muscularis and submucosa within the whole porcine urinary tract. While MC were found continuously in all investigated segments, a gradient of bipolar IC was evident. The whole mount preparations gave a detailed cytomorphology of IC within the various layers of the porcine urinary tract. Whole mount preparations revealed closed apposition of bi- and tripolar c-Kit positive IC parallel to the smooth muscle bundles and to veins of the tunica muscularis and adventitia. In the urothelium single CD117-positive interepithelial cells were found. The highest density of CD117-positive cells was found at the ureteropelvic junction, however the differences in between the segments were minimal. Microdissection and RT-PCR confirmed the results uncovered by immunohistochemistry. The ubiquitous distribution of IC and their close relationship to smooth muscle provides strong evidence that IC could contribute to the intrinsic pacemaker activity within the porcine (upper and lower) urinary tract. The role of the interepithelial CD117-positive cells as mechanosensors or as a precursor cell in the regeneration of the urothelium, is conceivable.

Cajal-like cells in the upper urinary tract: comparative study in various species

The interstitial cells of Cajal (ICC) play an important role in the control of gut motility. The recognition that the ICC cell membrane harbors the c-kit receptor (CD117) sparked rapid advancement in ICC research on the gut and certain pathologies using immunochemical and molecular methods. The question arises whether ICC exist in the upper urinary tract (UUT) and trigger motility. The present study analyzed the distribution of the c-kit receptor in the normal human UUT compared with various species. Immunohistochemistry (alkaline-phosphatase-anti-alkaline-phosphatase technique, immunofluorescence) was applied on serial sections using monoclonal and polyclonal antibodies recognizing the c-kit receptor. C-kit staining was compared with standard endothelial, epithelial, neurogenic, histiocytic, mast cell, and smooth muscle markers, as well as a negative control. Normal proximal, middle, and distal ureter segments were analyzed in rodents, carnivores, porcines, cow, and humans. In all species the c-kit receptor was detected in either round or spindle-shaped cells. Because of their antigenic profile, the round cells were identified as mast cells occurring in all layers of the ureteral wall except the urothelium and were more frequent in humans. In contrast, the population of spindle-shaped cells was marked only by anti-c-kit receptor antibodies, thus resembling ICC. These ICC-like cells were found among the inner and outer smooth muscle layers and in the lamina propria of all species. In humans, spindle-shaped cells were also found vertically oriented within the urothelium. Our morphological data present for the first time the distribution of ICC in the UUT of various species. The ubiquitous distribution in the entire pyeloureteral complex provides strong evidence that ICC generate electrical pacemaker activity within the UUT as an intrinsic system. Animal studies may help to understand the physiological importance of these ICC-like cells. The significance of these findings needs to be evaluated by functional studies and investigations of certain congenital pathologies with disturbance of the urinary outflow.

Fetal intestinal obstruction induces alteration of enteric nervous system development in human intestinal atresia

Intestinal motility disorders are a major cause of morbidity after surgical repair of intestinal atresia of unknown mechanism. We hypothesized that interruption of antenatal peristalsis may disturb the normal development of the enteric nervous system. Using a series of neuronal (synaptophysin, neuronal nitric oxide synthase, neurofilaments) and nonneuronal markers (glial acidic fibrillary protein and c-Kit) and immunohistochemistry, we have defined developmental steps of the enteric nervous system in normal intestine (12 fetuses, 15 children, and 4 adults) and their alterations above and below the obstacle in 22 human intestinal atresia compared with age-matched controls. Antisynaptophysin antibody revealed the progressive conversion of the myenteric plexus from a continuous belt into regularly spaced ganglions during normal fetal gut development and, by contrast, the significantly delayed appearance of individual neuronal ganglions in the distal segments of atresia (p < 0.05). Staging using three other markers for neuronal (neurofilaments and neuronal nitric oxide synthase) and nonneuronal cells (glial acidic fibrillary protein) confirmed that maturation of the myenteric plexus was significantly delayed below atresia (p < 0.01). These results indicate that intestinal atresia impairs the development of the enteric nervous system and provide an anatomical substrate for the motility disorders observed after surgical repair. They point to the role of peristalsis in normal gut development and suggest that stimulation of peristalsis might be used to accelerate recovery.

Nervous system development in normal and atresic chick embryo intestine: an immunohistochemical study

Intestinal motility disorders are a common complication after surgery for neonatal intestinal atresia. Although intestinal atresia causes alterations in the enteric nervous system, especially in its inner structures (nervous fibers in the mucosa, submucous and deep muscular plexuses), how these alterations develop is unclear. The chick model is a useful research tool for investigating the ontogenesis of the enteric nervous system and the pathogenesis of congenital bowel diseases. More information is needed on the overlap between the developing enteric nervous system and intestinal atresia. Because vasoactive intestinal polypeptide and substance P are typical intestinal neuropeptides, and vasoactive intestinal polypeptide acts as a modulator in neurodevelopment and an inhibitor of smooth muscle cell proliferation, our aim in this study was to investigate the distribution of their immunoreactivity in the developing enteric nervous system of normal and experimental chick models. We studied gut specimens excised from normal chick embryos (aged 12-20 days) and experimental chick embryos (aged 15-20 days) that underwent surgical intervention on day 12 to induce intestinal atresia (atresic embryos) or simply to grasp the bowel loop (sham-operated embryos). In normal chick embryos we showed vasoactive intestinal polypeptide and substance P immunoreactivity from day 12 in the submucous and myenteric plexuses. The distribution of peptide immunoreactivity differed markedly in atresic and normal or sham-operated gut embryos. These differences especially affected the inner structures of the enteric nervous system of specimens proximal to atresia and were related to the severity of dilation. Because nerve structures in the gut wall mucosa and submucous and deep muscular plexuses play a role in motility control and stretch sensation in the intestinal wall, our findings in the chick embryo may help to explain how gut motility disorders develop after surgery for neonatal intestinal atresia.

Cajal-like cells in the human upper urinary tract

PURPOSE

Interstitial cells of Cajal (ICCs) have an important role in the regulation of gut motility as they are responsible for the slow wave activity of smooth muscle. It is still unknown if ICCs also occur in the human upper urinary tract. Since these cells express and are marked by the c-kit receptor CD117, we investigated its occurrence and distribution along the human upper urinary tract.

MATERIALS AND METHODS

Tissues from 56 human ureters, spanning proximal, middle and distal ureter segments, were analyzed by indirect immunohistochemistry using the alkaline phosphatase-anti-alkaline phosphatase method and double labeling immunofluorescence on consecutive tissue sections. Several monoclonal and polyclonal antibodies to c-kit receptor were used in combination with various cell markers for histiocytic, mast cell, endothelial, epithelial, neuronal, smooth muscle and stem cell differentiation.

RESULTS

The c-kit receptor was found in 3 cell types of the ureter and in round or spindle-shaped cells. Due to their antigenic profile the first one was revealed as mast cells occurring in all layers of the ureteral wall except the urothelium. In contrast, the population of spindle-shaped cells was only marked by c-kit receptor, thus, resembling ICCs. These ICC-like cells were found among the inner and outer smooth muscle layers, and in the lamina propria. They showed a slight decrease from proximal to distal ureteral segments. However, unlike intestinal ICCs their cytomorphology differed and some cells, representing the third group of c-kit receptor positive cells, were found within the urothelium.

CONCLUSIONS

Our data demonstrate the presence of ICC-like cells and their ubiquitous distribution in the human ureter. The physiological importance and pathological significance of these findings must be evaluated by functional studies and investigations of certain pathological with urinary outflow disturbance conditions.

Exercise assessment of transgenic models of human cardiovascular disease

Exercise provides one of the most severe, yet physiological, stresses to the intact cardiovascular system and is a major determinant of the utilization of metabolic substrates. The adaptations to exercise are the result of a coordinated response of multiple organ systems, including cardiovascular, pulmonary, endocrine-metabolic, immunologic, and skeletal muscle. With the proliferation of genetically altered murine models of cardiovascular disease, the importance of developing methods of accurate physiological phenotyping is critical. There are numerous examples of transgenic models in which the baseline cardiovascular phenotype is unchanged or minimally changed from the wild type, only to become manifest during the stress of exercise testing. In this review, we cover the basics of the murine cardiovascular response to exercise and the importance of attending to strain differences, compare different exercise methodologies (constant workload treadmill, incremental workload treadmill, swimming) and hemodynamic monitoring systems, and examine the murine response to exercise conditioning. Several examples where exercise studies have contributed to the elucidation of cardiovascular phenotypes are reviewed: the beta-adrenergic receptor knockouts, phospholamban knockout, dystrophin knockout (mdx), and the mutant alpha-myosin heavy chain (R403Q) transgenic.

The occurrence of unusual smooth muscle bundles expressing alpha-smooth muscle actin in human intestinal atresia

BACKGROUND/PURPOSE

Intestinal dysmotility is an important problem in the postoperative management of patients with intestinal atresia (IA). Changes in the intramural components have so far been histochemically and immunohistochemically examined in both the proximal and distal segments of IA, but no detailed analysis of the muscular elements has been performed. The aim of this study was to carefully examine any alterations in the muscular elements in the intestines from patients with IA.

METHODS

Resected intestines were obtained from 6 patients with ileal atresia, 4 patients with jejunal atresia, and 3 controls without gastrointestinal diseases obtained by autopsy (congenital diaphragmatic hernia). All specimens were immunochemically stained with a monoclonal antibody to alpha-smooth muscle actin (alpha-SMA) as a smooth muscle marker.

RESULTS

In the normal small intestine, almost all the enteric smooth musculature were positive for alpha-SMA antiserum, except for the bulk of the circular musculature. In the proximal segments of all cases with IA, a reduced staining intensity for alpha-SMA was observed mainly in the severely hypertrophic muscle layers. In addition, some bundles of smooth muscle also were located in the submucosal connective tissue near the border of the innermost layer of the circular musculature, in which large amounts of smooth muscle fibers extended occasionally from the innermost layer of the circular musculature to the muscularis mucosae in the proximal segments of 4 cases. In the distal segments of IA, the distribution of alpha-SMA-positive smooth muscle fibers was similar to that in the control intestines, excluding mild to moderate hypertrophy of the muscular layers.

CONCLUSIONS

Both severe hypertrophy and a reduced immunoreactivity for alpha-SMA were observed in the circular muscle layer of the proximal segments. In addition, the occurrence of alpha-SMA-positive abnormal smooth muscle fibers was recognized in the submucosal layers of the proximal segments, thus, suggesting a delay in the intestinal muscular formation or a regressive reaction secondary to dilatation. These muscular alterations in the proximal segments might be considered to contribute to the postoperative intestinal dysmotility in IA cases.

Experimental small bowel obstruction in chick embryos: Effects on the developing enteric nervous system

BACKGROUND/PURPOSE

After surgical repair of congenital small bowel atresias, intestinal motility disorders often are observed. These may be caused by changes in the enteric nervous system (ENS) secondary to obstruction. To assess these changes, small bowel atresias were induced experimentally in chick embryos.

METHODS

On day 11, the small intestines of 90 chicken embryos were ligated microsurgically in ovo. Breeding of the eggs was continued until day 19. The small bowel was removed, fixed, and embedded for silver-staining, semithin serial sections, and transmission electron microscopy. Additionally, acetyl-cholinesterase (AChE)-staining was performed. Normal chick embryos of the same age served as controls.

RESULTS

Macroscopically, experimentally induced small bowel atresias had the same characteristics as human newborns. Microscopically, the wall structure was preserved; however, the ENS differed markedly from controls. Both proximal and distal to the obstruction, the submucosal plexus was almost completely absent, whereas the myententeric plexus was diminished only in the proximal dilated blind pouch. The axonal net was disrupted additionally. Ganglion cells of the myenteric plexus in the proximal segment were arranged in longitudinal clusters of densely packed cells. In the distal segment ganglion cells formed round clusters. The cells of Cajal, which normally surround the myenteric ganglia, were absent in the proximal and distal segments.

CONCLUSIONS

In our experiments, structural changes in the ENS could be observed secondary to experimentally induced small bowel atresias in the chick. Because of the lack of ischemia in this model, the main cause of these ENS changes seems to be the dilatation oft the proximal gut. Dilatations are common features in intestinal atresias, anorectal malformations, and Hirschsprung's disease. Our observations, thus, explain motility disorders after the surgical repair of these diseases.

Natural history of experimental intestinal atresia: morphologic and ultrastructural study

PURPOSE

The aim of this study was to evaluate a natural history of congenital intestinal atresia (IA) in the chick embryo and to assess the type and nature of changes in the intestine at various developmental stages.

METHODS

Chick embryos underwent operative induction of IA on the 12th day of incubation. The procedure consisted of electrocoagulation of the mesenteric vessels supplying a 7- to 8-mm intestinal segment. The embryos were subjected to macroscopic examination, histologic and ultrastructural studies of the preatretic and postatretic bowel using the light microscope, scanning, and transmission electron microscopes. All investigations were performed in an experimental group (operated embryos), in a control group, and in a sham-operated group on the 15th, 17th, 19th, and 21st day of incubation.

RESULTS

The original technique of an iatrogenic "vascular event" proved to be effective because IA developed in 96% of embryos surviving the procedure. The affected portion of the bowel underwent progressive necrosis, and signs of bowel obstruction could be observed 48 hours after operation. Cord atresia (type II) developed in 81% of embryos. Histologic investigations showed progressive thinning of mucosa, flattening of mucosal folds, and epithelial detachment within the intestine proximal to atresia. There was only mild hypertrophy of the muscular layers. All these pathomorphologic changes were of rapidly progressive nature until the 17th day of incubation. Later, the rate of distension of preatretic bowel and histologic changes were less. Ultrastructural investigation of the proximal bowel showed progressive flattening of the enterocytes associated with their apical bulging, widening of the intercellular spaces, and microvilli atrophy. Surprisingly, at days 19 and 21 of incubation, signs of induction of adaptive mechanisms with partial restoration of near-normal microvilli pattern were observed.

CONCLUSIONS

Study of natural history of experimental IA indicates that histologic and ultrastructural lesions of the bowel are of dynamic nature and are not only the effect of pathologic intraluminal pressure.

Two-dimensional alterations of myenteric plexus in jejunoileal atresia

PURPOSE

The purpose of this report is to investigate changes in the myenteric plexus associated with the dilated proximal segment of jejunoileal atresia (JA). Two-dimensional morphologic changes in the myenteric nerve plexuses were investigated using whole-mount preparation.

METHODS

Proximal (P) and distal (D) intestinal segments from 7 cases with JA and control (C) segments from 5 postmortem neonates were investigated. The circumference of the jejunoileal segments was measured after fixation. Antibodies for protein gene product 9.5 and neurofilament protein were used in whole-mount preparation. The sizes of neural networks were calculated by measuring the longest circular distance in a neural network (x) and the longest longitudinal distance (y), and the width of the internodal strands (i) with a videomicrometer.

RESULTS

Median circumference of the segments was 8.5 in P, 2.0 in D, and 2.0 cm in C. The neural networks in P were expanded longitudinally as well as circularly (x = 817.10 microm, y = 561.26, i = 31.04: median) while comparing them to those in D (x = 431.40 microm y = 288.07, i = 26.05) or C (x = 285.03 microm y = 372.20, c = 1113.57, i = 32.39). The nerve plexus was less expanded than the intestinal wall.

CONCLUSIONS

Proximal intestinal segments showed a restructuring that resulted in mild hypoplasia of the enteric nerve plexuses in the proximal segments. The less expansion of the myenteric nerve plexus seen in the proximal bowel in infants with JA suggests a histologic basis for the efficacy of tapering or plication of the dilated bowel.

Abnormalities of enteric neurons, intestinal pacemaker cells, and smooth muscle in human intestinal atresia

BACKGROUND/PURPOSE

Intestinal dysmotility, which usually has been encountered in the severely dilated proximal segment, is an important problem in postoperative management of patients with intestinal atresia (IA). Changes of enteric nerves had been histochemically examined in both the proximal and distal segments of IA, but a systemic immunohistochemical analysis is still lacking. The aim of this study was to examine precisely alterations of neuronal and muscular elements and pacemaker cells in intestines from patients with IA.

METHODS

Resected intestines were obtained from 5 patients with ileal atresia, 3 patients with jejunal atresia, and 3 controls without gastrointestinal diseases (congenital diaphragmatic hernia). All specimens were immunochemically stained with a monoclonal antibody to alpha-smooth muscle actin (SMA) as a smooth muscle marker, polyclonal antibodies to protein gene product (PGP) 9.5 as a general neuronal marker, and to c-kit protein as a maker of intestinal pacemaker cells. In addition, all specimens also were stained by NADPH-diaphorase (NADPH-d) to know the distribution of inhibitory nitrergic nerves.

RESULTS

A hypoplasia of the myenteric ganglia and a marked reduction of intramuscular nerve fibers, including nitrergic neurons, were observed in the dilated proximal segment of IA. C-kit-positive cells were localized around the myenteric plexus, but rarely found within the muscularis propria in the proximal segment. The distribution of nerves and c-kit-positive cells in the distal segment was comparable with that seen in controls. A reduced staining intensity for alpha-SMA was mainly observed in the hypertrophic circular muscle layer of the proximal segment.

CONCLUSIONS

A hypoplasia of intramural nerves and pacemaker cells was seen predominantly in the proximal segments of IA. Hypertrophy and reduced immunoreactivity for alpha-SMA also were observed in the circular muscle layer of the proximal segment. These alterations of the proximal segment may thus contribute to the postoperative intestinal dysmotility in IA cases.