Characterization of projections of longitudinal muscle motor neurons in human colon.

BACKGROUND: The enteric nervous system contains inhibitory and excitatory motor neurons which modulate smooth muscle contractility. Cell bodies of longitudinal muscle motor neurons have not been identified in human intestine. METHODS: We used retrograde tracing ex vivo with DiI, with multiple labeling immunohistochemistry, to characterize motor neurons innervating tenial and inter-tenial longitudinal muscle of human colon. KEY RESULTS: The most abundant immunohistochemical markers in the tertiary plexus were vesicular acetylcholine transporter, nitric oxide synthase (NOS), and vasoactive intestinal polypeptide (VIP). Of retrogradely traced motor neurons innervating inter-tenial longitudinal muscle, 95% were located within 6mm oral or anal to the DiI application site. Excitatory motor neuron cell bodies, immunoreactive for choline acetyltransferase (ChAT), were clustered aborally, whereas NOS-immunoreactive cell bodies were distributed either side of the DiI application site. Motor neurons had small cell bodies, averaging 438 + 18µm2 in cross-sectional area, similar for ChAT- and NOS-immunoreactive subtypes. Motor neurons innervating the tenia had slightly longer axial projections, with 95% located within 9mm. ChAT-immunoreactive excitatory motor neurons to tenia were clustered aborally, whereas NOS-immunoreactive inhibitory motor neurons had both ascending and descending projections. VIP immunoreactivity was rarely present without NOS immunoreactivity in motor neurons. CONCLUSIONS AND INFERENCES: Tenial and inter-tenial motor neurons innervating the longitudinal muscle have short projections. Inhibitory motor neurons have less polarized projections than cholinergic excitatory motor neurons. Longitudinal and circular muscle layers are innervated by distinct local populations of excitatory and inhibitory motor neurons. A population of human enteric neurons that contribute significantly to colonic motility has been characterized.

Use of a modified chitosan-dextran gel to prevent peritoneal adhesions in a porcine hemicolectomy model.

BACKGROUND: The prevention of peritoneal adhesions following abdominal surgery remains an ongoing challenge, with the ideal product for adhesion reduction still elusive. This study examines the outcome of application of a modified chitosan-dextran (CD) gel within the intraperitoneal cavity of a porcine model to assess its effect on adhesion formation. This is a unique synthetic gel, its active ingredients being succinyl chitosan and dextran aldehyde. MATERIALS AND METHODS: Twenty female domestic pigs were randomized to undergo surgery alone or to receive CD gel at the time of surgery. The surgical procedures comprised of laparotomy and ileocaecal resection with ileo-colic anastomosis. At postoperative d 21, a laparoscopy was performed, and adhesions graded using a predetermined adhesion measurement score. Adhesiolysis was then performed and CD gel applied to all animals. After a further 21 d animals were euthanized and adhesions graded using the same scoring regimen. RESULTS: Adhesions involving the wound were significantly reduced following application of the gel at the time of open surgery (P = 0.01). Following adhesiolysis and further application of the gel, a decrease in adhesion scores involving the bowel was noted (P = 0.03). No significant adverse outcomes were observed with application of the gel, specifically no anastomotic leak occurred. CONCLUSIONS: Chitosan-dextran gel is a well tolerated hydrogel with beneficial properties, which has been designed in an effort to reduce postoperative peritoneal adhesion formation. The observed reduction of adhesion scores following the application of the gel is encouraging and should stimulate further development of this product. The lack of adverse outcomes following application of CD gel is reassuring when used around a bowel anastomosis.

Use of a modified chitosan-dextran gel to prevent peritoneal adhesions in a rat model.

BACKGROUND: Intra-abdominal adhesions are a major cause of morbidity and a significant drain on healthcare resources. Numerous anti-adhesion products have reached clinical use but none has been wholly satisfactory. This study examines the application of a modified chitosan-dextran (CD) gel to the intraperitoneal cavity to reduce adhesion formation. This is a unique synthetic gel, its active ingredients being succinyl chitosan and dextran aldehyde. MATERIALS AND METHODS: Eighty adult male Wistar albino rats were randomized to undergo surgery alone or to receive CD gel at the time of surgery. Control groups using modified dextran only gel were also included. The surgical procedures comprised of laparotomy and either cecal abrasion or anastomotic simulation by enterotomy of the cecum with primary closure. At postoperative d 21 rats were euthanized by CO2 inhalation, and adhesions graded by an investigator blinded to the treatment groups, using a predetermined adhesion measurement score. RESULTS: Adhesions were significantly reduced in the cecal abrasion group with median adhesion scores for the treatment group of 0 versus 3 in the control group (P<0.001, Fisher's exact test). Further reduction in adhesion formation was noted in the enterotomy group with median scores of 2 versus 5 for treatment and control groups respectively (P=0.003, Fisher's exact test). CONCLUSIONS: Chitosan-dextran gel appears to significantly reduce the formation of intra-abdominal adhesions without adversely affecting wound healing. This is a noteworthy advancement in the safe prevention of post operative, intra-abdominal adhesions.

Abdominal adhesion prevention: still a sticky subject?

BACKGROUND: Adhesion formation remains an almost inevitable consequence of abdominal procedures, potentially resulting in significant morbidity and mortality. There is an ongoing need to evaluate current understanding of adhesion formation and products aimed at prevention. Failure to keep up to date with adhesion treatment may subject clinicians to a greater medico-legal risk. DESIGN: Review of published studies exploring the problem of peritoneal adhesion formation. This encompasses the underlying processes of adhesion formation combined with general approaches to reduce formation. An overview of products trialled to prevent formation in both the animal model and clinical setting describes products of scientific interest and commercial success. RESULTS: Advances in surgical technique, such as laparoscopic surgery, can help minimize the probability of adhesion formation. Currently barrier products, whilst reducing adhesion formation, have not been shown to reduce the risk of readmission with complications related to adhesions. Hybrid products may improve upon this situation. CONCLUSIONS: No single approach has been wholly satisfactory in reducing adhesions. Research into the processes driving adhesion formation is providing exciting new targets for therapeutic agents. It would seem plausible that with many promising avenues of research a revolutionary agent to reduce the incidence of adhesional small bowel obstruction may result.