PubMed · 8420263
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D P Dooley, M Rhodes, D Drehner. 1993. Psyllium worm.. https://pubmed.ncbi.nlm.nih.gov/8420263/
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The projections of enteric neurons showing immunoreactivity for vasoactive intestinal peptide (VIP), nitric oxide synthase (NOS) and galanin were investigated in the myenteric plexus of the intestine of the Atlantic cod, Gadus morhua. Quantification of immunoreactive material on the proximal and distal side of a myotomy was performed by means of confocal laser scanning microscopy. NOS immunoreactivity was reduced anal to the myotomy, whereas there was an accumulation of immunoreactivity for VIP and for galanin oral to the cut. These results suggest the presence of VIP, NOS and galanin in neurons with oral-to-anal projections along the intestine of the cod. Since descending neurons in the myenteric plexus of many other vertebrates also contain these substances, we conclude that the oral-to-anal projections of neurons containing VIP, NOS and galanin are highly conserved features and important for the descending phase of intestinal peristalsis on an evolutionary basis.
In sacral anoplasty, it is frequently found that an outer layer of the rectal wall, which resembles the structure of the taenia bands of the colon, limits the elasticity of the rectum making it different from the small intestine, hence preventing the rectal stump from being advanced to reach the perineum. Results of autopsy studies on 40 human babies and 40 dogs showed that a special collagenous fibrous layer called adventitia rectalis was found to limit the free expansion of the rectal wall. This was responsible for keeping the rectum a straight tubular shape with a fixed volume. This tissue plays an important role in bowel movement by defining a threshold of intrarectal pressure in the bowel reflex of defecation and by transmitting the expulsive force from the abdomen above down to the anal opening. This discovery may explain why (1) in Hirschsprung's disease, the preservation of the rectal wall in Soave's or Rehbein's procedure or partial preservation in Duhamel's operation will preserve better bowel function; (2) in atresia ani, rectal tapering results in better bowel control than rectal pouch amputation; and (3) in sacral anoplasty, multiple releasing incisions of adventitia rectalis at different levels will lengthen the rectal stump to about double its original length to reach the perineal incision, and the divided fibers will soon regenerate.
An electromyogram (EMG) of the external and sphincter (EAS) was obtained both before and after surgery in five patients with Hirschsprung's disease and eight normal control patients. The EMG, evoked by the transrectal stimulation of the pudendal nerve, was recorded at both the sacral and anal regions to investigate the deep and superficial EAS, respectively. In eight control patients, the EMG at the sacral region consisted of a polyphasic wave with apparently two or three major peaks, and the simple monophasic wave with one or two peaks was found at the anal region. Its peak corresponded to the early peaks in the sacral region. The mean onset latency of the EMG in the sacral region was 2.8 ms. Four patients with Hirschsprung's disease also exhibited responses that were similar to the controls, and their postoperative bowel habits were satisfactory. However, the remaining one patient, who still required a daily enema after surgery, exhibited an apparently different response, which was monophasic at both the sacral and anal regions with a long onset latency of 5.0 ms before and after surgery. It is postulated that some cases with Hirschsprung's disease might be associated with an EAS dysfunction before surgery, which possibly led to the development of postoperative bowel dysmotility.