Chronic extrinsic denervation of the small bowel: effect on adrenergic and cholinergic contractile mechanisms in canine ileal circular muscle

BACKGROUND: Small bowel transplantation necessitates chronic extrinsic denervation and is often followed by enteric dysfunction. Our aim was to study canine ileal contractile activity after extrinsic denervation. METHODS: In vitro dose responses to cholinergic and adrenergic agonists were evaluated in canine ileal muscle strips in control subjects and after jejunoileal extrinsic denervation (EX DEN) at 0, 2, and 8 weeks after operative preparation. RESULTS: Spontaneous activity and the increased activity after tetrodotoxin (enteric nerve blockade) did not differ between groups. Response to acetylcholine and bethanechol did not differ at any time in the control or EX DEN group. In contrast, the EX DEN group demonstrated a procontractile hypersensitivity to norepinephrine at 2 and 8 weeks that was not seen in the control group. This adrenergic hypersensitivity in the EX DEN group was insensitive to intramural neural blockade with tetrodotoxin. CONCLUSIONS: Extrinsic denervation does not affect basal contractile activity, augmented contractile activity to intramural neural blockade, nor response to cholinergic agonists. However, it induces a procontractile adrenergic hypersensitivity in canine ileal circular muscle mediated at the level of the smooth muscle and not at the enteric nervous system.     

Differential adrenergic response to extrinsic denervation in canine longitudinal jejunal and ileal smooth muscle

Early postoperative complications after small bowel transplantation (SBT) are likely mediated, at least in part, by dysmotility caused by the obligate disruption of extrinsic and enteric nerves in the graft. Adrenergic hypersensitivity of gut smooth muscle has been observed in some (but not all) segments of intestine in various experimental models of SBT, highlighting regional and species variability in response to denervation. Little is known about changes in canine longitudinal muscle after extrinsic denervation. Six dogs each underwent either complete extrinsic denervation of the jejunoileum or a control operation (transection and reanastomosis of the proximal jejunum and distal ileum). In vitro contractile response of longitudinal muscle strips to norepinephrine was evaluated at the time of the operation, and 2 weeks and 8 weeks later. After extrinsic denervation, the jejunal response to norepinephrine was preserved at all time points; however, the ileum displayed a decreased sensitivity to norepinephrine, an effect unmasked after intramural neural blockade with tetrodotoxin. These data support a potential for neurally mediated dysmotility after SBT and reinforce the differences in responses to extrinsic denervation between species, as well as differences within different regions and between anatomic segments of small intestine in the same species. Presented in part at the Ross Residents and Fellows Research Conference and the Forty-Second Annual Meeting of The Society for Surgery of the Alimentary Tract, Atlanta, Georgia, May 20–23, 2001 (poster presentation); and published as an abstract in Gastroenterology 120:A351, 2001. Supported by grants from the National Institutes of Health (NIH DK39337 and NIH DK07198) and the Mayo Foundation.     

Role of extrinsic innervation in jejunal absorptive adaptation to subtotal small bowel resection: A model of segmental small bowel transplantation

Segmental small bowel transplantation offers theoretic advantages over total jejunoileal transplantation, but the regional ability of the transplanted segment to adapt is unknown. Absorption was measured in an 80 cm jejunal segment via a triple-lumen perfusion technique. Separate experiments measuring absorption of four nutrients (glucose, glutamine, oleic acid, and taurocholic acid) were performed before and 2 and 12 weeks after operative intervention. Control dogs (CON, n = 6) underwent distal 50% enterectomy. Experimental dogs (EXT DEN, n = 6), in addition to resection, underwent complete extrinsic denervation of the remaining jejunum. All dogs developed diarrhea, which rhesolved in all CON dogs but persisted in all EXT DEN dogs. Maximal weight loss was greater in the EXT DEN group. Glucose and oleate absorption was decreased 2 weeks after ileal resection in both the CON and EXT DEN dogs; glutamine absorption was decreased at 2 weeks in EXT DEN dogs only. Taurocholate and water absorption remained unchanged in both groups. Absorption of all solutes returned to baseline at 12 weeks in both groups. Despite greater weight loss and persistent diarrhea in EXT DEN dogs, at 12 weeks there were no differences in net absorptive fluxes between the EXT DEN and the CON group after extrinsic denervation. The extrinsic denervation necessitated by small bowel transplantation does not appear to blunt the net jejunal adaptive response to total ileal resection, but may temporarily alter glutamine absorption. Presented in part at the Forty-Second Annual Meeting of The Society for Surgery of the Alimentary Tract, Atlanta, Georgia, May 20–23, 2001 (oral presentation) and published as an abstract in Gastroenterology 120:A63, 2001. Supported in part by a grant from the National Institutes of Health (NIH RO1 39337 toM.G.S.) and the Department of Surgery, Mayo Clinic.     

Ileal resection enhances jejunal absorptive adaptation for water and electrolytes to extrinsic denervation: implications for segmental small bowel transplantation

Background/Purpose: Segmental small bowel transplantation (SBT) may be an alternative to whole jejunoileal SBT. The aim of this study was to evaluate adaptability of extrinsically denervated jejunum after ileectomy. Methods: Baseline absorption of an isomolar, nonnutrient electrolyte solution was measured in an 80-cm in situ jejunal segment. Control (CON) and extrinsically denervated dogs (EXT DEN) then underwent distal 50% enterectomy; EXT DEN dogs also underwent a complete extrinsic denervation of remnant jejunum. Absorption was remeasured 2 and 12 weeks later; jejunal biopsies at 12 weeks were compared with baseline. Results: All dogs experienced weight loss and diarrhea, which resolved by 10 weeks in CON but persisted in EXT DEN dogs. Net absorptive fluxes of water, Na⁺, K⁺, and Cl^{[minus ]}, however, remained unchanged in both groups 2 weeks and 12 weeks after denervation. Morphometric evaluation showed an increase in crypt depth in both groups at the 12-week time-point. Conclusions: Despite a clinical short bowel syndrome, more weight loss, and diarrhea in EXT DEN, there were no temporal differences in net absorptive fluxes of water and electrolytes within or between these 2 groups, and both developed increased crypt depth at 12 weeks. Extrinsic denervation does not blunt jejunal adaptive response to ileectomy. J Pediatr Surg 38:502-507.     

Small bowel extrinsic denervation does not alter water and electrolyte absorption from the colon in the fasting or early postprandial state

Small bowel transplantation (SBT) causes watery diarrhea. The decreases shown previously in absorption of water, electrolytes, and bile salts in the jejunum and ileum, although present, are not dramatic and seem not to be great enough to explain the diarrhea. Our aim was to determine changes in water and electrolyte absorption in the colon during fasting and postprandially in a canine preparation of jejunoileal extrinsic denervation, which serves as a model of jejunoileal autotransplantation. We hypothesized that colonic absorption of water and electrolytes decreases transiently in the colon after SBT. Six dogs had cannulas implanted in the colon to study absorption of an ileal-like basal electrolyte solution with or without 10 mmol/L glucose. Absorption during fasting and postprandially was measured before and 2 and 12 weeks after a validated preparation of jejunoileal extrinsic denervation. All dogs developed diarrhea after SBT. Net colonic absorptive fluxes of water and electrolytes in the colon did not change from baseline values at 2 or 12 weeks after extrinsic denervation, either during fasting or postprandially; glucose in the infusate did not alter absorptive fluxes during fasting or postprandially. Extrinsic denervation of the small intestine does not appear to alter colonic absorption of water or electrolytes during fasting or postprandially. These observations suggest that the neurally intact colon has a minimal role in the diarrhea after SBT. Presented at the Forty-Third Annual Meeting of The Society for Surgery of the Alimentary Tract, San Francisco, California, May 19–22, 2002 (poster presentation). Supported by grant DK 39337 from the National Institutes of Health (M.G.S.) and the Mayo Foundation.     

Long-Term Effects of Extrinsic Denervation on VIP and Substance P Innervation in Circular Muscle of Rat Jejunum

Intestinal denervation contributes to enteric motor dysfunction after small bowel transplantation (SBT). Our aim was to determine long-term effects of extrinsic denervation on function of nonadrenergic, noncholinergic innervation with substance P and vasoactive intestinal polypeptide (VIP). Contractile activity of jejunal circular muscle strips from six age-matched, naive control rats (NC) and eight rats 1 year after syngeneic SBT was studied in tissue chambers. Spontaneous contractile activity did not differ between groups. Exogenous VIP inhibited contractile activity dose-dependently to a comparable degree in both groups. The VIP antagonist ([d-p-Cl-Phe⁶,Leu¹⁷]-VIP) and the nitric oxide synthase inhibitor l-N^G-nitro-arginine did not affect VIP-induced inhibition but increased contractile activity during electrical field stimulation (EFS) in both groups. Exogenous substance P increased contractile activity dose-dependently, greater in NC than SBT. The substance P antagonist ([d-Pro²,d-Trp^7,9]-substance P) inhibited effects of exogenous substance P and decreased the excitatory EFS response. Immunohistofluorescence showed tyrosine hydroxylase staining after SBT indicating sympathetic reinnervation. In jejunal circular muscle after chronic denervation, response to exogenous substance P, but not VIP, is decreased, whereas endogenous release of both neurotransmitters is preserved. Alterations in balance of excitatory and inhibitory pathways occur despite extrinsic reinnervation and might contribute to enteric motor dysfunction after SBT. Parts of this work were presented at the annual meeting of the Society for Surgery of the Alimentary Tract in Washington, DC, on May 21, 2007 and published in abstract form in Gastroenterology 2007;132:A890.     

Chronic extrinsic denervation after small bowel transplantation in rat jejunum: Effects and adaptation in nitrergic and non-nitrergic neuromuscular inhibitory mechanisms

BACKGROUND. Extrinsic denervation of the transplanted small bowel could play a substantial role in motor dysfunction of the transplanted gut. We attempted to determine the effect of chronic extrinsic denervation on intestinal contractility. METHODS. Jejunal longitudinal muscle strips were obtained from rats 1 week and 8 weeks after (1) syngeneic small bowel transplantation, (2) ischemia/reperfusion, or (3) gut transection/reanastomosis. Nonoperated rats (naive controls) and sham-operated rats (sham controls), 1 week after celiotomy/gut manipulation, served as controls. We evaluated the effects of exogenous nitric oxide, increasing doses of cholinergic and adrenergic agonists, and electrical field stimulation (EFS) in the presence or absence of N(G)-monomethyl-l-arginine, methylene blue, tetraethylammonium, or tetrodotoxin. RESULTS. Spontaneous contractile activity (_chi +/- SEM), when compared with the naive controls (11.3 +/- 2.0 g.5 min/mg), was increased in all 4 groups at 1 week (15.9 +/- 10 to 19.4 +/- 2 g.5 min/mg; P < or =.03 each) but not at 8 weeks postoperatively. The inhibition of contractile activity by nitric oxide was increased in small bowel transplantation in naive controls at 8 weeks to 80% +/- 10% versus 50% +/- 7% (P <.02). EFS induced an inhibition of contractile activity that was tetraethylammonium- and tetrodotoxin-sensitive but N(G)-monomethyl-l-arginine- and methylene blue-insensitive; the maximal EFS-induced inhibition was increased at 1 week and 8 weeks but only in the small bowel transplantation groups to 103% +/- 5% and 95% +/- 7%, respectively, versus 72% +/- 8% in naive controls (P 相似文献   

Ileal absorptive adaptation to jejunal resection and extrinsic denervation: Implications for living-related small bowel transplantation

Net absorption of water, electrolytes, and simple nutrients decreases early after jejunoileal autotransplantation (extrinsic denervation) in a canine model but recovers toward normal by 8 weeks. However, the ability of the extrinsically denervated ileum to adapt after total jejunectomy, which would be relevant as a model of segmental small bowel transplantation, remains unknown. Two groups of five dogs each were studied before and 2 weeks and 12 weeks after 50% proximal enterectomy. A control group remained neurally intact, whereas the other group underwent extrinsic denervation (Ext Den) of the remaining ileum. Using a perfusion technique, net absorption of water, electrolytes, and five simple nutrients (glucose, arginine, glutamine, and oleic and taurocholic acids) was measured at the three time points. Heal morphometry was also evaluated. All dogs developed diarrhea, which resolved by 12 weeks in all but two of the Ext Den dogs. Weight in both groups was decreased at 2 weeks (P <0.05), returned to normal at 12 weeks in control dogs, but remained low in Ext Den dogs (P <0.05). Maximal weight loss was greater in the Ext Den group (P <0.05). No consistent or important differences in net absorptive fluxes of water, electrolytes, or simple nutrients were noted either within or between groups at any time point. Villous height, crypt depth, and longitudinal muscle width increased significantly at 12 weeks after jejunectomy in the Ext Den dogs, but not in the control dogs (P <0.05). Extrinsic denervation of the ileum results in persistent weight loss after proximal 50% enterectomy. Despite diarrhea, only minor changes in electrolyte absorption occur, and ileal net absorption of simple nutrients remains unaffected. The ileum of extrinsically denervated dogs undergoes a more prominent morphometric adaptation after jejunectomy. Extrinsic denervation necessitated by small bowel transplantation, independent of immune effects, does not appear to suppress the ileal adaptive response to maintain net absorption of water, electrolytes, and simple nutrients. Supported in part by a grant from the National Institutes of Health (N1H RO1 39337—MGS). Presented in part at the Thirty-Eighth Annual Meeting of the Society for Surgery of the Alimentary Tract, New Orleans, La., May 17–20, 1998, and published as an abstract in Gastroenterology 114:A1431, 1998.     

Nitric oxide pathways in circular muscle of the rat jejunum before and after small bowel transplantation

Previous studies suggest that nitric oxide synthase is upregulated after small bowel transplantation which may have implications in enteric dysfunction after small bowel transplantation. The aim of this study was to determine the role of nitric oxide in nonadrenergic, noncholinergic inhibitory function after small bowel transplantation in rat jejunal circular muscle. The following four groups of rats (n =≥8 rats per group) were studied: Neurally intact control animals; 1 week after anesthesia and sham celiotomy, and either 1 week or 8 weeks after isogeneic, orthotopic small bowel transplantation. Full-thickness jejunal circular muscle strips were evaluated under isometric conditions for spontaneous contractile activity, response to electrical field stimulation, and effects of exogenous nitric oxide and nitric oxide antagonists. Spontaneous activity did not differ among groups. Electrical field stimulation inhibited activity similarly in all groups. Exogenous nitric oxide, N^G-monomethyl L-arginine monoacetate salt (a nitric oxide synthase inhibitor), and methylene blue (cGMP antagonist) had no effect on spontaneous activity. Neither nitric oxide antagonist altered the inhibitory response to neural excitation by electrical field stimulation in any group. Nitric oxide, a known inhibitory neurotransmitter in other gut smooth muscle, has no apparent role in rat jejunal circular muscle before or after small bowel transplantation. Supported by grant DK 39337 from the National Institutes of Health, United States Public Health Service, the Mayo Foundation, the Swiss National Foundation, and the Department of Visceral and Transplantation Surgery, University of Bern, Switzerland. Part of this study was presented at a poster session at the Fortieth Annual Meeting of The Society for Surgery of the Alimentary Tract, Orlando, Fla., May 16–19, 1999. An abstract of this work was published in Gastroenterology 116:A1349, 1999.     

Small bowel transplantation induces adrenergic hypersensitivity in heal longitudinal smooth muscle in rats

Our aim was to determine the effects of small bowel transplantation on contractility of longitudinal muscle in the rat ileum. Full-thickness longitudinal muscle strips from four groups of rats (naive controls, sham-operated controls, and 1 week and 8 weeks after syngeneic orthotopic small bowel transplantation) were studied in vitro. Neither baseline contractility nor response to neural blockade (tetrodotoxin) or adrenergic/cholinergic blockade differed among the groups. Although the dose response to the cholinergic agonist bethanechol and to nitric oxide did not differ among groups, the ED₅₀ (negative log of concentration giving half-maximal effect) for the adrenergic agonist norepinephrine was increased 1 week and 8 weeks after transplantation, indicating a hypersensitivity response not blocked by tetrodotoxin. Nonadrenergic, noncholinergic inhibitory responses to electrical field stimulation were of greater amplitude and occurred at lesser frequencies (≤5 Hz) 1 week after small bowel transplantation, but returned to control values 8 weeks postoperatively. These inhibitory responses were blocked by the nitric oxide synthase inhibitor L-NMMA but not by methylene blue, a nonspecific inhibitor of guanylate cyclase. Small bowel transplantation induces a persistent adrenergic denervation hypersensitivity at the muscle and appears to upregulate, at least transiently, other inhibitory mechanisms mediated by neural release of nitric oxide. Small bowel transplantation does not alter muscle response to cholinergic pathways. These alterations in smooth muscle contractility may affect gut function early after clinical small bowel transplantation. Supported in part by grant DK 39337 from the National Institutes of Health, the Mayo Foundation, and the First Department of Surgery, Tohoku University, Sendai, Japan. Parts of this work were presented at the Fortieth Annual Meeting of The Society for Surgery of the Alimentary Tract, May 16–19,1999, and the annual meeting of the American Gastroenterological Association, May 16–19,1999, Orlando, Fla., and published as two abstracts in Gastroenterology 116:A139 and A1075, 1999.     

Inhibition by nitric oxide and nonadrenergic, noncholinergic (NANC) nerves is preserved in a canine model of extrinsic denervation: implications for small bowel transplantation

BACKGROUND: Small bowel transplantation (SBT) is complicated by changes in graft motility, especially in the early postoperative period. This dysmotility may be related in part to the extrinsic denervation necessitated by the procedure, but specific neurotransmitter response to SBT is incompletely understood. The aim of this study was to evaluate the role of nitric oxide and nonadrenergic, noncholinergic (NANC) enteric neural input in the nonimmunologic etiology of the dysmotility seen after SBT. METHODS: A technique of jejunoileal extrinsic denervation (without disruption of mesenteric vascular supply) was used as a model of canine jejunoileal autotransplantation to avoid potential confounding factors such as ischemia-reperfusion and postallotransplant immunologic effects. Longitudinal smooth muscle strips from ileum and jejunum were studied with in vitro tissue chamber methodology at 0, 2, and 8 weeks after this experimental model to explore early and late effects of denervation. Effects of exogenous nitric oxide (NO) and electric field stimulation (EFS), which releases native, endogenous enteric neurotransmitters) were evaluated in neurally intact control dogs and those undergoing extrinsic denervation. RESULTS: Exogenous NO caused a dose-dependent inhibition of spontaneous contractile activity and in some muscle strips a decrease in basal tone in both groups of dogs. These effects were unchanged by neural blockade with tetrodotoxin and preserved after extrinsic denervation. EFS produced inhibition of spontaneous contractile activity in ileum and a complex, inconsistent response in jejunum. The response to EFS in both ileum and jejunum was unchanged after extrinsic denervation. CONCLUSIONS: Nitric oxide inhibits contractile activity in canine longitudinal muscle of small bowel. Motility changes seen after this large animal model of extrinsic denervation are not caused by changes in NO or NANC neural function. The variability observed between different segments of intestine is important to consider in the context of SBT.     

Effects of transection and extrinsic denervation and a model of autotransplantation of the porcine jejunoileum on cholesterol biodynamics

Background/Purpose:

Small bowel transplantation impairs enteric function, necessitating transection, extrinsic denervation, and ischemia-reperfusion of the small intestine. The authors investigated how each of these nonimmunologic insides of the transplantation procedure modulates biodynamics of cholesterol and absorption of lipids.

Methods:

Twenty-three pigs with similar food, cholesterol, and fat intake underwent sham laparotomy (group 1), transection (group 2), extrinsic jejunoileal denervation (group 3), or a model of autotransplantation, including extrinsic jejunoileal denervation with in situ ischemia-reperfusion (group 4). Serum lipids, absorption, and excretion of cholesterol, bile acids, and fat were determined after 8 weeks. Plasma cholesterol precursors and plant sterols, respective markers of cholesterol synthesis, and absorption, were measured after 2 and 8 weeks.

Results:

When compared with sham laparotomy and transection groups, denervation and autotransplantation significantly decreased weight gain and increased plasma cholesterol precursors and fecal excretion of bile acids. In relation to sham operated animals, transection alone modestly increased plasma plant sterols at 2 weeks and biliary secretion and mass absorption of cholesterol. The latter changes were not observed after denervation or autotransplantation, ie, fractional and total absorption of cholesterol were significantly decreased in autotransplanted pigs when compared with transected controls. As compared with all the other groups, autotransplantion significantly increased bacterial metabolites of neutral sterols in feces and net fecal elimination of cholesterol, mainly as bile acids.

Conclusions:

Extrinsic autonomic denervation of the jejunoileum, with or without synchronous ischemia-reperfusion, results in increased cholesterol synthesis, bile acid malabsorption, and decreased weight gain. Cholesterol malabsorption may develop gradually after intestinal autotransplantation, and even a short period of ischemia further impairs absorptive function of the denervated jejunoileum, resulting in increased fecal elimination of cholesterol mainly as bile acids.     

Postprandial augmentation of absorption of water and electrolytes in jejunum is neurally modulated: implications for segmental small bowel transplantation

Postprandial augmentation of absorption of water and electrolytes is believed to occur in the jejunum. Neural mechanisms of control, however, have not been studied in the in situ jejunum or in the transplanted bowel. The aim of this study was to determine if postprandial augmentation of absorption occurs in the in situ jejunum and to evaluate neural mechanisms controlling postprandial jejunal absorption. Based on our previous work, we hypothesized that postprandial augmentation of absorption does not occur in the jejunum in situ and that extrinsic denervation of the jejunum is associated with decreased postprandial absorption. Absorption was studied in an 80 cm, in situ jejunal segment in six dogs by using an isosmolar electrolyte solution alone, or with 80 mmol/L glucose before and after jejunal transection to disrupt intrinsic neural continuity of the study segment with the remaining gut. Net absorptive fluxes of water and electrolytes were measured in the fasted state and after a 400-kcal meal. Another six dogs were studied 3 weeks after our validated model of extrinsic denervation of jejunoileum; identical fasting and postprandial absorptive states were evaluated. Postprandial augmentation of absorption of water and electrolytes did occur in the jejunum (P<0.03) both in the absence and in the presence of intraluminal glucose. After intrinsic neural transection or extrinsic denervation, no postprandial augmentation of absorption occurred, with or without glucose. Postprandial augmentation of absorption of water and electrolytes occurs in the in situ jejunum. Disrupting intrinsic neural continuity or extrinsic denervation (as after intestinal transplantation) abolishes postprandial augmentation. Presented at the Resident’s Section of the Society of University Surgeons in Nashville, TN, February 10, 2005. Supported in part by a grant from the National Institutes of Health (NIH RO1 39337[15] to MGS) and the Department of Surgery, Mayo Clinic (M.G.S., A.E.Z., K.D.L., and S.G.H.).     

Intrinsic neuromuscular defects in the neurogenic bladder: VIII. Effects of unilateral pelvic and pelvic plexus neurectomy on ultrastructure of the feline bladder base

It has been shown previously that unilateral parasympathetic decentralization of the feline bladder by sacral ventral rhizotomy results in early degenerative and eventual regenerative ultrastructural neuromuscular changes in the bladder base. The present study was conducted to define the effects of unilateral parasympathetic decentralization by pelvic neurectomy and postganglionic “denervation” by pelvic plexus neurectomy on the neuromuscular ultrastructure of the feline bladder base. Eighteen sexually mature male cats were used. Three cats provided the control material; six cats underwent unilateral pelvic and nine unilateral pelvic plexus neurectomy. Bladders were collected for study 2, 3, and 10 weeks following the former and 1–4 days, 3 weeks, and 7–12 weeks following the latter procedure. Samples from both the neurectomized and the intact sides of each bladder were obtained for electron microscopic study. The ultrastructural neuromuscular changes observed after pelvic neurectomy were identical to those previously described following unilateral sacral ventral rhizotomy, except for early developing and persistent, widespread degeneration of myelinated axons in the former model. As in the rhizotomy model, there was cholinergic axonal regeneration, adrenergic hyperinnervation, and a prominent population of probable copeptidergic axons in long-term samples of the bladder base following pelvic neurectomy. In contrast, pelvic plexus neurectomy (a postganglionic “denervation” procedure) resulted in early developing and persistent degeneration of all axons in the bladder base: i.e., myelinated, cholinergic and adrenergic, with long-term hypoinnervation by both cholinergic and adrenergic neural elements. Our observations indicate that two forms of the experimentally induced lower-motor neurogenic bladder can be distinguished ultrastructurally.     

The effect of oestrogen on stromal growth of the dog prostate: A quantitative ultrastructural study

Summary The stromal tissue of the prostate in normal castrated dogs and castrated and oestrogen treated dogs were studied by quantitative morphological methods. Quantitative morphological (=stereological) procedures provide values of volume, surface and number of tissue and cell components. The stereological data show an activation of the smooth muscle cell of the stromal tissue in the oestrogen treated dog compared with the control group; related to the unit volume of smooth muscle cell cytoplasm, a threefold increase of the endoplasmic reticulum was observed in castrated and oestrogen treated dogs.Abbreviations SMC Smooth muscle cell - N Nucleus - EX Extracellular space - CYT Cytoplasm - MF Myofilaments - R Ribosomes - ER Endoplasmic reticulum - G Golgi apparatus - M Mitochondria - VAC Vacuoles - VES Vesicles - LY Lysosomes - V_V Volume density - COMP Cellular compartments Supported by the Swiss National Science Foundation, (3.286-0.78) Switzerland and by the Fonds zur Förderung der wissenschaftlichen Forschung (3278 and 4030), Austria     

Peptidergic nerves persist after jejunal autotransplantation: an experimental study in the piglet

The gut has been shown to contain four types of peptidergic nerves besides the adrenergic and cholinergic ones. They store substance P, enkephalin, somatostatin and VIP (vasoactive intestinal peptide) respectively. It is not previously known which of the neurons are intrinsic or extrinsic to the gut wall. Jejunal autotransplantation was performed in 10 piglets. This procedure implies degeneration of the extrinsic neurons (extrinsic denervation). The transplants were examined 1 to 4 mo postoperatively with histochemical techniques for demonstration of the intramural adrenergic and the different peptidergic nerves. The distribution of the peptidergic nerves was not changed indicating that they all originate within the gut. Following extrinsic denervation adrenergic nerves on the contrary were completely missing.     

Extrinsic neural innervation mediates absorption of water and electrolytes in canine proximal colon in vivo

INTRODUCTION: Extrinsic innervation mediates a proabsorptive effect in small intestine. Our aim was to determine whether extrinsic neural input modulates similar effects in the proximal colon in vivo. METHODS: Ten adult dogs underwent enteric isolation of a 50-cm proximal colon loop; five each were randomized to undergo extrinsic denervation (Ext Den) of the isolated colonic segment or to serve as neurally innervated controls. After recovery, a 38 degrees C electrolyte solution (Na(+) 125 meq/L, K(+) 9 meq/L, Cl(-) 75 meq/L, HC03(-) 65 meq/L) was infused at 4 ml/min into the segment. Effluent was collected in 30-min intervals for 2 h after achieving steady state (determined by 14C nonabsorbable marker recovery); four studies were conducted at 1 and 12 weeks postoperatively. Net flux of H20, Na(+), K(+), and Cl(-) was determined. Colon morphometry was evaluated at 0 and 14 weeks. Data are presented as mean +/- SEM. Unpaired t test was applied for comparisons. RESULTS: Net absorptive flux of H20 (microL/min/cm) was decreased in Ext Den vs controls at 1 week (4.40 +/- 0.63 vs 7.92 +/- 0.92, P = 0.03) but was not different at 12 weeks (4.70 +/- 1.20 vs 5.97 +/- 0.69; P > 0.05). Na(+) and Cl(-) followed the trends in H20 absorption (P < or = 0.05). Crypt depth (microm) decreased in controls at 14 weeks vs 0 week (915 +/- 20 vs 740 +/- 07, P = 0.01) but remained unchanged in Ext Den. CONCLUSIONS: Loss of extrinsic neural input decreases colonic absorption. This observation suggests that extrinsic neural innervation provides net proabsorptive mechanisms for absorption of water and electrolytes in the proximal canine colon.     

Development of a Simple Model of Extrinsic Denervation of the Small Bowel in Mouse

Small bowel transplantation (SBT) is associated with poorly understood enteric dysfunction. The study of SBT in mice is hindered by the technical difficulty of orthotopic SBT in the mouse. Our aim was to develop an easy preparation of extrinsic denervation of the entire jejunoileum in mice as a model of orthotopic SBT. All neurolymphatic tissues accompanying the superior mesenteric artery (SMA) and vein (SMV) were ligated just distal to the middle colic vessels. The SMA and SMV were then stripped of investing adventitia, and the mesentery to jejunum and colon were transected radially. Jejunum and colon were not transected and reanastomosed. To confirm extrinsic denervation 1, 3, and 6 months later, segments of small bowel were stained for protein gene product 9.5 (PGP9.5) and tyrosine hydroxylase (TH). Tyrosine hydroxylase immunoreactive intensity was then quantified using a semiquantitative analysis. Immunohistochemical fluorescence showed persistence of PGP9.5 immunoreactivity confirming enteric nerves in jejunoileum; however, there was no TH immunoreactivity in jejunoileum in denervated mice despite the expected preservation of TH immunoreactivity in the still-innervated duodenum at 1 month. At 3 months, sparse immunoreactivity for TH was present, and by 6 months, reinnervation of TH-containing nerves appeared similar to controls. Quantification of intensity at each time-point further confirmed this trend. This technique in the mouse accomplishes a complete extrinsic denervation of jejunoileum early postoperatively (1 and 3 months); reinnervation occurs by 6 months. This is an easily learned murine model of orthotopic SBT. Presented at the American Gastroenterological Association during Digestive Disease Week in Los Angeles, CA, as a poster presentation on May 23 2006. Abstract published in GastroenterologyE 2006; 130:A604.     

Extrinsic denervation alters postprandial absorption of glucose and glutamine in the ileum: Implications for small bowel transplantation

In the postprandial period, augmentation of absorption of water, electrolytes, and taurocholate is believed to occur in the ileum. The role of extrinsic innervation in this postprandial augmentation has not been well studied and may be an important concept in small bowel transplantation. Our aim was to investigate extrinsic neural mechanisms mediating postprandial absorptive patterns. The study hypothesis was that postprandial augmentation of absorption in the ileum is blunted in transplanted (extrinsically denervated) bowel. Ileal absorption was studied in six dogs with an 80-cm in situ ileal segment via a triple-lumen perfusion technique using an iso-osmolar, ileal-like electrolyte solution alone and containing either glucose 2.5 mM, glutamine 2.5 mM, oleic acid 5 mM, or taurocholate 5 mM. Net absorptive fluxes of each substrate, as well as water and electrolytes, were measured in both the fasted state and after a 400-Kcal mixed meal before and at 2 and 12 weeks after our validated model of complete extrinsic denervation of the jejunoileum. At baseline, there were no differences in absorption of water, electrolytes, or any nutrient postprandially compared with the fasted state. Two weeks after extrinsic denervation, absorption of glucose at both 1 and 2 hours postprandially was decreased compared with absorption during fasting. Glutamine absorption was also decreased at 2 hours postprandially. At 12 weeks after extrinsic denervation, net postprandial absorption of glucose and glutamine returned toward normal and was not different from fasting absorption. No differences were noted in postprandial absorption of oleic acid or taurocholate at any time point. Decreases in absorption of nutrients postprandially after extrinsic denervation (which is necessitated by small bowel transplantation) may play an important role in post-transplant enteric absorptive dysfunction. The previously described postprandial augmentation in net absorption may be a function of enterically isolated gut and does not appear to occur in the in situ ileum. Presented in part at the Forty-Third Annual Meeting of The Society for Surgery of the Alimentary Tract and The American Gastroenterological Association, San Francisco, California, May 19–22, 2002, during Digestive Disease Week (poster presentation). Supported in part by a grant from the National Institutes of Health (NIH RO1 39337) (to M.G.S.) and the Department of Surgery, Mayo Clinic.     

Intrinsic neuromuscular defects in the neurogenic bladder: IV. Loss of somatomotor and preservation of autonomic innervation of the male feline rhabdosphincter following bilateral sacral ventral rhizotomy

Innervation of the male feline rhabdosphincter was studied ultrastructurally 1 and 2 weeks following bilateral sacral ventral rhizotomy. In all samples, there was virtual loss of myelinated axons, degeneration and loss of the axonal element of all motor end-plates, and preservation of autonomic nonrnyelinated (cholinergic, adrenergic, and probable copcptidergic) axons, as well as their nonspecialized surface contacts with myofibers of the rhabdosphincter. These observations provide solid evidence for the existence of both somatomotor and autonomic cholinergic innervation of the male feline rhabdosphincter and indicate that its potential neural control shortly after somatic denervation is exercised exclusively by autonomic axonlmyofiber surface contacts.