Smooth muscle fascicular reorientation is required for esophageal morphogenesis and dependent on Cdo.

Postnatal maturation of esophageal musculature involves proximal-to-distal replacement of smooth muscle with skeletal muscle by elusive mechanisms. We report that this process is impaired in mice lacking the cell surface receptor Cdo and identify the underlying developmental mechanism. A myogenic transition zone containing proliferative skeletal muscle precursor cells migrated in a proximal-distal direction, leaving differentiated myofibers in its wake. Distal to the transition zone, smooth muscle fascicles underwent a morphogenetic process whereby they changed their orientation relative to each other and to the lumen. Consequently, a path was cleared for the transition zone, and smooth muscle ultimately occupied only the distal-most esophagus; there was no loss of smooth muscle. Cdo(-/-) mice were specifically defective in fascicular reorientation, resulting in an aberrantly proximal skeletal-smooth muscle boundary. Furthermore, Cdo(-/-) mice displayed megaesophagus and achalasia, and their lower esophageal sphincter was resistant to nitric oxide-induced relaxation, suggesting a developmental linkage between patterning and sphincter function. Collectively, these results illuminate mechanisms of esophageal morphogenesis and motility disorders

Effects of scleroderma antibodies and pooled human immunoglobulin on anal sphincter and colonic smooth muscle function.

BACKGROUND & AIMS: Patients with systemic sclerosis (SSc) have impairments in gastrointestinal smooth muscle function. The disorder has been associated with circulating antibodies to cholinergic muscarinic the type-3 receptor (M(3)-R). We investigated whether it is possible to neutralize these antibodies with pooled human IgGs (pooledhIgG). METHODS: We studied the effects of IgGs purified from patients with SSc (SScIgGs) on cholinergic nerve stimulation in rat colon tissues. We also examined the effects of SScIgGs on M(3)-R activation by bethanechol (BeCh), M(3)-R occupancy, and receptor binding using immunofluorescence, immunoblot, and enzyme-linked immunosorbent analyses of human internal anal sphincter (IAS) smooth muscle cells, before and after administration of pooledhIgG. Functional displacement of M(3)-R occupancy by the SScIgGs was compared with that of other IgGs during the sustained phase of BeCh-induced contraction of intact smooth muscles from rats. RESULTS: SScIgG significantly attenuated neurally mediated contraction and acetylcholine release in rat colon as well as BeCh-induced sustained contraction of the IAS smooth muscle. In immunofluorescence analysis, SScIgG co-localized with M(3)-R. In immunoblot and enzyme-linked immunosorbent analyses, M(3)-R loop-2 peptide and human IAS SMC membrane lysates bound significant amounts of SScIgG, compared with IgGs from healthy individuals and pooledhIgG. Binding was attenuated significantly by application of pooledhIgG, which by itself had no significant effect. Incubation of samples with pooledhIgG, or mixing pooledhIgG with SScIgG before administration to tissues, significantly reduced binding of SScIgG, indicating that pooledhIgG prevents SScIgG blockade of M(3)-R. CONCLUSIONS: In studies of rat and human tissues, pooled human IgG prevent and reverses the cholinergic dysfunction associated with the progressive gastrointestinal manifestations of SSc by neutralizing functional M(3)-R antibodies present in the circulation of patients with SSc

Studies on the release and degradation of vasoactive peptides in the gut wall

SIGLEAvailable from British Library Document Supply Centre- DSC:D170534 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Involvement of cAMP and cGMP in relaxation of internal anal sphincter by neural stimulation, VIP, and NO

We examined simultaneous changes in resting tension and tissue levels of the two second messengers, adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP), in the opossum internal anal sphincter (IAS). The influence of the nonadrenergic noncholinergic (NANC) nerve stimulation (NS) by electrical field stimulation (EFS) and the putative neurotransmitters nitric oxide (NO) and vasoactive intestinal peptide (VIP) on the above modalities was investigated. The fall in resting IAS tension in response to NS, NO, and VIP was accompanied by significant rises in both cGMP and cAMP. This fall and the levels of cAMP and cGMP were dependent on the intensity of EFS and the concentration of VIP and NO. EFS (2 Hz) caused a 63.5% fall of the resting tension with 61.7 and 118.2% rise of the tissue levels of cAMP and cGMP, respectively (P &lt; 0.05). VIP (1 x 10(-6) M) caused an 81.5% fall of resting tension and 64.2 and 87.0% increases in cAMP and cGMP, respectively. Similarly, NO (1 x 10(-6) M) caused 69.6% fall in tension and an accompanying 93.4 and 415.9% rise of cAMP and cGMP, respectively. Although EFS, VIP, and NO all lowered IAS tension and raised both cyclic nucleotides, the changes in cAMP and cGMP in the IAS are otherwise stimulus specific, since fall in IAS tension by calcitonin gene-related peptide has been shown to be associated with an increase in cAMP without any change in cGMP, whereas the reverse was the case with atrial natriuretic factor. The common second messenger systems in IAS relaxation with NS, VIP, and NO suggest the involvement of VIP and NO as inhibitory neurotransmitters. </jats:p

Evidence for VIP-induced increase in NO production in myenteric neurons of opossum internal anal sphincter

A significant interaction between vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) has been reported in neurotransmission of the gastrointestinal tract, including the internal anal sphincter (IAS). The exact site of this NO release from the IAS in response to VIP is not known. Studies were carried out to determine the site of this VIP-induced NO release in opossum IAS. NO synthase (NOS) activity was quantitated by determining L--3H-citrulline production from L[3H]arginine in isolated myenteric ganglia and smooth muscle cells of the IAS. L-[3H]citrulline production was determined before and after treatment with either the ganglionic stimulant 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), VIP, or peptide histidine isoleucine (PHI) in the absence and presence of the neurotoxin tetrodotoxin and the NOS inhibitor NG-nitro-L-arginine (L-NNA). Smooth muscle cells and ganglia were preloaded with L-[3H]arginine for 5 min and treated with VIP for 1 and 5 min. DMPP and VIP caused a significant increase in L-[3H]citrulline formation in myenteric ganglia at both time periods, whereas in smooth muscle cells there was a moderate but significant increase in L-[3H]citrulline production only at 5 min of VIP treatment. VIP-induced relaxation of isolated smooth muscle cells of the IAS was not affected by L-NNA. The increase in NOS activity of myenteric ganglia by DMPP and VIP was sensitive to neurotoxin and the NOS inhibitor. The data suggest that the increase in NO production in response to VIP in the IAS occurs mainly from the myenteric neurons, with some contribution from the smooth muscle cells. </jats:p