Downregulation of Galphaq-11 protein expression in guinea pig antral and colonic circular muscle during pregnancy.
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Pregnancy has an inhibitory effect on motility of the gastrointestinal tract. The present study was designed to examine the mechanisms responsible for antral and colonic hypomotility in pregnant guinea pigs. Circular smooth muscle cells from the antrum and left colon were isolated by enzymatic digestion with collagenase from pregnant and nonpregnant guinea pigs. Contractile responses to agonists were expressed as percent shortening from resting cell length. The function of G proteins in antral and colonic circular smooth muscle was assessed by [35S]guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) binding induced by CCK-8 and G protein quantitation. The contraction of antral and colonic circular smooth muscle from pregnant guinea pigs was reduced in response to CCK-8 and to GTPgammaS but was normal in response to KCl and D-myo-inositol 1,4,5-trisphosphate compared with nonpregnant animals. The stimulation of [35S]GTPgammaS binding to Galphaq-11 induced by 1 microM CCK-8 was significantly lower in antral and colonic circular smooth muscle from pregnant guinea pigs than that in controls. Furthermore, Western blot analysis showed a decreased Galphaq-11 and an increased Gsalpha protein content in both tissues during pregnancy. It is concluded that pregnancy appears to impair gastrointestinal circular smooth muscle contractility by downregulating G proteins such as Galphaq-11 protein, which mediates muscle contraction, and upregulating Gsalpha protein, which mediates muscle relaxation. (+info)
Increased gastrointestinal permeability is an early lesion in the spontaneously diabetic BB rat.
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The BB rat spontaneously develops autoimmune diabetes. Feeding these animals a hydrolyzed casein diet significantly reduces the incidence of this disease, suggesting that a dietary antigen is involved in the pathogenesis of this disease. In other syndromes associated with luminal antigens, including celiac and Crohn's disease, increased intestinal permeability has been suggested to play an etiological role. Therefore, the objective of this study was to evaluate whether increased permeability was also present in BB rats before disease development. By measuring gastrointestinal permeability, in animals on a regular or hydrolyzed casein diet, we were able to demonstrate that increased gastric and small intestinal permeability appeared before the development of both insulitis and clinical diabetes. Although hydrolysis of dietary protein significantly reduced the incidence of diabetes, it did not alter the small intestinal permeability abnormality, suggesting that this is an early event. Increased permeability appears to have an early role in the genesis of several immunological diseases and may represent a common event in these diseases. (+info)
Vagus nerve modulates secretin binding sites in the rat forestomach.
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Secretin is well known for its inhibitory action on gastric motility. It has been reported that secretin in a physiological dose inhibits gastric motility through mediation by the vagal afferent pathway. Secretin also elicited relaxation of carbachol-stimulated rat forestomach muscle strips by binding to its receptors, suggesting a direct action on this peripheral tissue. We hypothesized that vagal input may affect the action of secretin by modulating the level of secretin receptor in the forestomach. Several treatments, including vagal ligation, vagotomy, perivagal application of capsaicin or colchicine, intravenous infusion of tetrodotoxin, and intraperitoneal injection of atropine, were performed to investigate their effects on secretin receptor binding to forestomach membranes. Specific binding of 125I-labeled secretin to forestomach membranes was significantly decreased (45%) by vagal ligation, vagotomy (50%), or perivagal colchicine treatment (40%). On the contrary, specific binding of 125I-secretin was not affected by perivagal capsaicin treatment, intravenous infusion of tetrodotoxin, or intraperitoneal injection of atropine. By Scatchard analysis of the binding data, the capacity of the high-affinity binding sites in forestomach membranes was found to decrease significantly after vagal ligation compared with membranes from the sham-operated group. However, the affinity at the high-affinity binding sites, the binding parameters of the low-affinity binding sites, and binding specificity were not changed. Vagal ligation but not perivagal capsaicin treatment reduced the inhibitory effect of secretin on bethanechol-stimulated contraction of isolated forestomach muscle strips, causing a right shift in the dose-response curve. These results suggest that vagal input through axonal transport plays a significant role on secretin action by modulating the capacity of secretin binding sites (but not affinity or specificity), at least in rat forestomach. (+info)
Noninvasive measurement of anatomic structure and intraluminal oxygenation in the gastrointestinal tract of living mice with spatial and spectral EPR imaging.
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EPR imaging has emerged as an important tool for noninvasive three-dimensional (3D) spatial mapping of free radicals in biological tissues. Spectral-spatial EPR imaging enables mapping of the spectral information at each spatial position, and, from the observed line width, the localized tissue oxygenation can be mapped. We report the development of EPR imaging instrumentation enabling 3D spatial and spectral-spatial EPR imaging of small animals. This instrumentation, along with the use of a biocompatible charcoal oximetry-probe suspension, enabled 3D spatial imaging of the gastrointestinal (GI) tract, along with mapping of oxygenation in living mice. By using these techniques, the oxygen tension was mapped at different levels of the GI tract from the stomach to the rectum. The results clearly show the presence of a marked oxygen gradient from the proximal to the distal GI tract, which decreases after respiratory arrest. This technique for in vivo mapping of oxygenation is a promising method, enabling the noninvasive imaging of oxygen within the normal GI tract. This method should be useful in determining the alterations in oxygenation associated with disease. (+info)
Serological discrimination of dogs infected with gastric Helicobacter spp. and uninfected dogs.
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Characterization of the humoral immune responses of people to Helicobacter pylori infection has facilitated the investigation of the host response to bacterial virulence factors and the development of sensitive and specific diagnostic tests. Dogs are commonly infected with gastric Helicobacter spp., but the presence of multiple Helicobacter spp. and possible coinfection in individual dogs have complicated serological evaluation. Evaluation of the antigenic homology of Helicobacter spp. revealed that the major protein bands of Helicobacter felis and Helicobacter bizzozeronii, two Helicobacter spp. that infect dogs, were very similar to UreA (29 to 31 kDa), UreB (63 to 66 kDa), and HSP (58 to 60 kDa) of H. pylori, and sera from infected and uninfected dogs bound in a similar way to each antigen. Immunoblotting and an enzyme-linked immunosorbent assay (ELISA) with H. felis ATCC 49179 antigen were performed with 101 serum samples (from 78 infected dogs and 23 uninfected dogs). Samples from uninfected dogs (median = 8) had fewer bands on immunoblotting than samples from infected dogs (median = 16) (P < 0.05). Combinations of the presence of any two of the low-molecular-mass bands (19, 25, 30, 32, and 37 kDa) or the high-molecular-mass bands (86 and 94 kDa) were found almost solely in samples from infected dogs (P < 0.0001). Kinetic ELISA results were significantly higher for samples from infected dogs (median = 0. 0802 optical density unit [OD]/min) than for samples from uninfected dogs (median = 0.01428 OD/min). The combination of ELISA and immunoblotting results gave a specificity of 95.6% and a sensitivity of 79.8%. No correlation between ELISA results, colonization density, degree of inflammation, and presence of lymphoid follicles was observed. The results indicate substantial antigenic homology between H. felis, H. pylori, and H. bizzozeronii. The combination of ELISA and immunoblotting was a highly specific and moderately sensitive indicator of infection. The degree of seropositivity assessed by ELISA was not related to bacterial colonization density, the degree of gastric inflammation, or the presence of lymphoid follicles. (+info)
Role of endosonography in the evaluation of gastric malignancies.
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The aims of this study were to stage gastric malignancies and differentiate between carcinomas and lymphomas. Twenty-two patients were evaluated with endosonography. Tumoral infiltration depth (T stage) and presence of metastatic lymph nodes (N stage) were investigated. Five percent of the cases were staged as T2, 36% as T3, and 59% as T4. According to the endosonographic examination, 14% were NO, 68% were N1, and 18% were N2 malignancies. When compared with results of surgery and histopathologic examination, the accuracy was 82% for both T and N stages. It can be concluded that endosonography is a valuable imaging modality for the local staging of gastric malignancies. Early stage lymphomas can be differentiated from carcinomas, but in advanced stages both have similar appearance. (+info)
The beta-subunits of Na+,K+-ATPase and gastric H+,K+-ATPase have a high preference for their own alpha-subunit and affect the K+ affinity of these enzymes.
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The alpha- and beta-subunits of Na+,K+-ATPase and H+,K+-ATPase were expressed in Sf9 cells in different combinations. Immunoprecipitation of the alpha-subunits resulted in coprecipitation of the accompanying beta-subunit independent of the type of beta-subunit. This indicates cross-assembly of the subunits of the different ATPases. The hybrid ATPase with the catalytic subunit of Na+,K+-ATPase and the beta-subunit of H+,K+-ATPase (NaKalphaHKbeta) showed an ATPase activity, which was only 12 +/- 4% of the activity of the Na+,K+-ATPase with its own beta-subunit. Likewise, the complementary hybrid ATPase with the catalytic subunit of H+,K+-ATPase and the beta-subunit of Na+,K+-ATPase (HKalphaNaKbeta) showed an ATPase activity which was 9 +/- 2% of that of the recombinant H+,K+-ATPase. In addition, the apparent K+ affinity of hybrid NaKalphaHKbeta was decreased, while the apparent K+ affinity of the opposite hybrid HKalphaNaKbeta was increased. The hybrid NaKalphaHKbeta could be phosphorylated by ATP to a level of 21 +/- 7% of that of Na+,K+-ATPase. These values, together with the ATPase activity gave turnover numbers for NaKalphabeta and NaKalphaHKbeta of 8800 +/- 310 min-1 and 4800 +/- 160 min-1, respectively. Measurements of phosphorylation of the HKalphaNaKbeta and HKalphabeta enzymes are consistent with a higher turnover of the former. These findings suggest a role of the beta-subunit in the catalytic turnover. In conclusion, although both Na+,K+-ATPase and H+,K+-ATPase have a high preference for their own beta-subunit, they can function with the beta-subunit of the other enzyme, in which case the K+ affinity and turnover number are modified. (+info)
Overexpression of glycine-extended gastrin in transgenic mice results in increased colonic proliferation.
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Gastrin is a peptide hormone involved in the growth of both normal and malignant gastrointestinal tissue. Recent studies suggest that the glycine-extended biosynthetic intermediates mediate many of these trophic effects, but the in vivo relevance of glycine-extended gastrin (G-Gly) has not been tested. We have generated mice (MTI/G-GLY) that overexpress progastrin truncated at glycine-72 to evaluate the trophic effects of G-Gly in an in vivo model. MTI/G-GLY mice have elevated serum and colonic mucosal levels of G-Gly compared with wild-type mice. MTI/G-GLY mice had a 43% increase in colonic mucosal thickness and a 41% increase in the percentage of goblet cells per crypt. MTI/G-GLY mice exhibited increased colonic proliferation compared with wild-type controls, with an expansion of the proliferative zone into the upper third of the colonic crypts. Continuous infusion of G-Gly into gastrin-deficient mice for two weeks also resulted in elevated G-Gly levels, a 10% increase in colonic mucosal thickness, and an 81% increase in colonic proliferation when compared with gastrin-deficient mice that received saline alone. To our knowledge, these studies demonstrate for the first time that G-Gly's contribute to colonic mucosal proliferation in vivo. (+info)