Age-related changes in the myenteric plexus of the porcine bowel.

INTRODUCTION: Myenteric plexus (MP) is well recognized as an important regulator of peristaltic activity. Knowledge regarding prenatal and postnatal normal morphological changes is important when interpreting histopathologic findings in motility disorders of childhood. The aim of this study was to determine the neuronal density and morphology of the myenteric plexus (MP) of the porcine bowel from fetal life to adulthood. METHOD: Small and large bowel whole-mount preparations of the MP were stained using NADPH diaphorase histochemistry in animals from 6 different age groups (60 and 90 days of gestation, newborn, 4-week and 12-week-old, and adult pigs). Using light microscopy, above parameters was quantified, and cell/nucleus sizes were measured. Results were analyzed using 1-way analysis of variance test. RESULTS: There were significant regional and age-related differences in cell numbers per ganglia noted in MP throughout the lifetime of a pig. There was an abrupt increase in cell numbers per ganglia from the newborn to 4-week-old animals, which then stabilized in most parts of the bowel, except in the distal large bowel, where it continued to increase. Ganglion density and ganglia cell density both decreased steadily with advancing age. Cell size increased with age, mostly secondary to increase in the cytoplasm. CONCLUSION: Our results show that significant changes occur in the MP in relation to age and the region of the bowel. These changes are most evident in the immediate period after birth but continue throughout life. Such age-related changes must be taken into account during morphological evaluation of biopsy specimens taken from infants who had constipation.

Postnatal changes in enteric plexus axonal thickness.

PURPOSE: Chronological age has not always been an accurate predictor of gut motility in newborns. We hypothesized that the enteric plexus is immature at birth. We studied whole-mount preparations of the myenteric plexus in pigs from mid-point of gestation to adulthood. METHODS: Distal large bowel whole-mount preparations of the myenteric plexus were stained using ACHE histochemistry in five pigs from six different age groups (60 and 90 days gestation, newborn, 4 and 12 weeks old, and adult pigs). With the aid of light micrographs and Image J program the axonal diameter, distance between ganglia, neuronal size and neuronal nucleus size were measured. Statistical significance was measured using one-way ANOVA test. RESULTS: There was significant increase in axonal diameter and interganglionic distance, with increasing age in the myenteric plexus of rectum in pigs (P < 0.05). Neuronal cell size and nucleus size of the enteric neurons also increased with age, but was not statistically significant. CONCLUSION: This study shows for the first time that the axonal thickness in the enteric myenteric plexus undergoes striking changes during the first 12 weeks of life in piglets. Assessment of axonal thickness in rectal biopsies may be a valuable morphological feature in diagnosing functional intestinal obstruction in infants.

Developmental changes of the adrenergic network in the myenteric plexus of the porcine small bowel.

Knowledge about the foetal development of the normal enteric nervous system (ENS) is crucial for the understanding of congenital and acquired functional abnormalities of the gut. The ENS is the largest and most complex division of the peripheral nervous system and consists of intrinsic and extrinsic components. Although previous studies have described sympathetic innervation of the myenteric plexus, little is known regarding its age-related changes. The aim of this study was to investigate the age-related changes in the sympathetic innervation of the myenteric plexus. Whole mount and paraffin sections of the small bowel specimens from six different age groups (60 and 90 days gestation; newborn; 4 and 12 weeks old; and adult) were stained using tyrosine hydroxylase immunohistochemistry. Specimens were then analysed using fluorescence and laser scanning microscopy in detail. The tyrosine hydroxylase positive nerve fibres were first seen within the myenteric plexus at 90 days of gestation (E90). There was a significant increase in nerve fibres and varicosities observed from E90 to 12 weeks of age and stabilisation thereafter. The degree of varicosities around the ganglia, clearly seen on the whole-mount preparations, was also noted to increase up to 12 weeks of age, after which time there was no general variation noted into adulthood. Our findings show, for the first time, that sympathetic innervation of the myenteric plexus starts in the last quarter of gestation and continues till 12 weeks of age. Segmental sympathetic denervation, following bowel resection and anastomosis, during this developmental period may explain the motility dysfunction seen in newborn infants operated for necrotising enterocolitis, bowel atresia and Hirschsprung's disease.

Long-term results of delayed primary anastomosis for pure oesophageal atresia: a 27-year follow up.

The management of a newborn with pure oesophageal atresia continues to be challenging. We started treating babies with pure oesophageal atresia by delayed primary anastomosis in 1977. The purpose of this study was to review the long-term outcome in infants with pure oesophageal atresia (EA) treated by delayed primary anastomosis with special emphasis on gastroesophageal reflux (GOR) related morbidity. The medical charts of all patients treated by delayed primary anastomosis between 1977 and 2004 were retrospectively reviewed. All survivors were followed up with completion of a questionnaire and personal/phone interviews. There were 26 patients in total admitted during the 27-year study period with the diagnosis of pure oesophageal atresia. Three died prior to surgery due to associated anomalies; two had almost no distal oesophageal segment and underwent oesophageal replacement surgery. The remaining 21 children were treated with delayed primary anastomosis and made up our study group. There were four deaths (19%) in this group, and all were prior to 1980. The median gestational age was 35.5 weeks and the median birth weight was 2.6 kg; median initial gap was 3.7 cm and median preoperative gap was 1.5 cm; median age at operation was 80 days and the median hospital stay was 5.5 months. The median follow-up period was 13.5 years. Fourteen children (66%) developed symptomatic gastroesophageal reflux and nine of these needed fundoplication (43%). Sixteen children developed strictures at the anastomotic site; ten responded to repeated dilatations while six needed resection and reanastomosis. At the time of this study, 15 out of the 17 survivors (88%) were on normal diet with no respiratory problems and 2 (12%) were dependent on gastrostomy feeds. Our long-term follow-up data shows that the delayed primary anastomosis provides excellent functional results in patients born with pure oesophageal atresia. The high incidence of gastroesophageal reflux and associated morbidity requires early intervention to prevent ongoing feeding problems due to oesophagitis and stricture formation.

Developmental changes in submucosal nitrergic neurons in the porcine distal colon.

BACKGROUND/PURPOSE: As our understanding of the enteric nervous system improves, it becomes clear that it is no longer sufficient to simply determine whether enteric ganglion cells are present but also to determine whether correct number and types of ganglion cells are present. Nitric oxide is recognized as a potent mediator of inhibitory nerves responsible for the relaxation of the smooth muscle of the gastrointestinal tract. The aim of this study was to determine the normal nitrergic neuronal density and morphology in the submucosal plexus of the porcine distal bowel from fetal life to adulthood. METHODS: Distal large bowel specimens were obtained from porcine fetuses of gestational age E60 (n = 5), E90 (n = 5), 1-day-old piglets (n = 5), 4-week-old piglets (n = 5), 12-week-old piglets (n = 5), and adult pigs (n = 5). Whole-mount preparations of the submucosal plexus were made and stained with NADPH diaphorase histochemistry. The ganglia density, the number of ganglion cells per ganglia, and nucleus and cytoplasmic area were measured. RESULTS: Ganglia density decreased progressively and markedly with age until the adulthood (P < .001). On the contrary, ganglion cells increased their size over time predominantly because of increase in cytoplasm (P < .001). The number of ganglion cells per ganglia increased significantly during the fetal life. However, there was a significant reduction in the number of ganglion cells per ganglia during the period from birth to 4 weeks, remaining constant thereafter (P < .001). CONCLUSIONS: The quantitative and qualitative morphometric analysis of the colonic submucous plexus shows that significant developmental changes occur during fetal and postnatal life. These findings indicate that the age of the patient is of utmost importance during histopathologic evaluation of enteric nervous system disorders.