Expression of the type III TGFbeta receptor during chick organogenesis.
Transforming growth factor beta (TGFbeta) is a regulator of embryonic development. The role of specific TGFbeta receptors is emerging, and a unique role for the type III TGFbeta receptor (TBRIII) has been suggested. We report the pattern of TBRIII expression in chicken embryos from 2 to 14 days in ovo. (+info)
Functions of a chitosan-orotic acid salt in the gastrointestinal tract.
A chitosan (CS)-orotic acid salt (CS-OT) was prepared, and the release of orotic acid (OT) from CS-OT as well as the adsorption of bile acids by CS-OT was investigated in vitro. The amount of OT released from CS-OT was about 2-2.7 micromol/mg CS-OT and this changed depending on the species of CS. CS-OT also adsorbed bile acids and the amount increased incrementally according to the number of amino group contained in CS. Furthermore, CS-OT was given to rats as feed in order to investigate the influence on serum cholesterol levels. A decrease in serum cholesterol levels was observed in the group, which was fed a diet containing CS-OT or CS for 1-2 weeks, but no differences in body weight changes were recognized. Therefore, CS-OT may be applied to treating hyperlipidemia. (+info)
The pacemaker activity of interstitial cells of Cajal and gastric electrical activity.
Interstitial cells of Cajal (ICC) are the pacemaker cells in the gut. They have special properties that make them unique in their ability to generate and propagate slow waves in gastrointestinal muscles. The electrical slow wave activity determines the characteristic frequency of phasic contractions of the stomach, intestine and colon. Slow waves also determine the direction and velocity of propagation of peristaltic activity, in concert with the enteric nervous system. Characterization of receptors and ion channels in the ICC membrane is under way, and manipulation of slow wave activity markedly alters the movement of contents through the gut. Gastric myoelectrical slow wave activity produced by pacemaker cells (ICC) can be reflected by electrogastrography (EGG). Electrogastrography is a perspective non-invasive method that can detect gastric dysrhythmias associated with symptoms of nausea or delayed gastric emptying. (+info)
Claudins in Caenorhabditis elegans: their distribution and barrier function in the epithelium.
Claudins ( approximately 23 kDa) with four transmembrane domains are major cell adhesion molecules working at tight junctions in vertebrates, where the intercellular space is tightly sealed (reviewed in ). We examined here the possible occurrence of claudin-like proteins in invertebrates, which do not bear typical tight junctions. Close blast searching of the C. elegans genome database identified four claudin-related, approximately 20-kDa integral membrane proteins (CLC-1 to -4), which showed sequence similarity to the vertebrate claudins. The expression and distribution of CLC-1 was then examined in detail by GFP technology as well as by immunofluorescence microscopy. CLC-1 was mainly expressed in the epithelial cells in the pharyngeal region of digestive tubes and colocalized with AJM-1 at their intercellular junctions. Then, to examine the possible involvement of CLC-1 in the barrier function, we performed RNA interference in combination with a tracer experiment: in CLC-1-deficient worms, the barrier function of the pharyngeal portion of the digestive tubes appeared to be severely affected. CLC-2 was expressed in seam cells in the hypodermis, and it also appeared to be involved in the hypodermis barrier. These findings indicated that multiple species of the claudin homologs, which are involved in the barrier function of the epithelium, exist in C. elegans. (+info)
Screening of Mongolian plants for influence on amylase activity in mouse plasma and gastrointestinal tube.
Mongolian plants were screened for their influence on alpha-amylase activity in mouse plasma. Methanolic extracts of Geranium pratense, Rhodiola rosea, Ribes pullchelum and Vaccinium uliginosum inhibited the enzyme activity in isolated mouse plasma by greater than 40% and the effect was concentration dependent. Vaccinium uliginosum also showed a depressive effect on elevation of postprandial blood glucose to some extent. (+info)
PNA-positive glycoconjugates are negatively correlated with the access of neural crest cells to the gut in chicken embryos.
Neural crest cells give rise to many derivatives, including the neurons and glia of the peripheral nervous system, adrenomedulary cells, and melanocytes, and migrate through precise pathways that differ according to their axial level and/or state of specification. The migratory routes taken by neural crest cells are reported to be regulated by extracellular matrix molecules. We examined the possible influence of glycoconjugates on the establishment of barriers to neural crest access to ventral regions leading to the gut, by labeling stage-16-28 white Leghorn (WL) and Silky (SK) embryos with peanut agglutinin (PNA) at vagal, thoracic, and sacral levels. We observed a transitory expression of glycoconjugates that correlate with a barrier to the entrance of neural crest cells into the gut at the thoracic level, which is not present at vagal and sacral levels. In later stages, neural crest cells of melanocytic lineage were observed entering the gut in embryos of the SK chicken, a mutant with an altered pattern of pigmentation. The ventral regions occupied by melanoblasts in SK embryos were free of PNA labeling, while in WL embryos, in which PNA-positive molecules are strongly expressed, melanoblasts were restricted to peripheral regions. We suggest that PNA-binding glycoconjugates are good molecular marker for barriers that control the access of neural crest cells to the gut. (+info)
Differential and history-dependent modulation of a stretch receptor in the stomatogastric system of the crab, Cancer borealis.
Neuromodulators can modify the magnitude and kinetics of the response of a sensory neuron to a stimulus. Six neuroactive substances modified the activity of the gastropyloric receptor 2 (GPR2) neuron of the stomatogastric nervous system (STNS) of the crab Cancer borealis during muscle stretch. Stretches were applied to the gastric mill 9 (gm9) and the cardio-pyloric valve 3a (cpv3a) muscles. SDRNFLRFamide and dopamine had excitatory effects on GPR2. Serotonin, GABA, and the peptide allatostatin-3 (AST) decreased GPR2 firing during stretch. Moreover, SDRNFLRFamide and TNRNFLRFamide increased the unstimulated spontaneous firing rate, whereas AST and GABA decreased it. The actions of AST and GABA were amplitude- and history-dependent. In fully recovered preparations, AST and GABA decreased the response to small-amplitude stretches proportionally more than to those evoked by large-amplitude stretches. For large-amplitude stretches, the effects of AST and GABA were more pronounced as the number of recent stretches increased. The modulators that affected the stretch-induced GPR2 firing rate were also tested when the neuron was operating in a bursting mode of activity. Application of SDRNFLRFamide increased the bursting frequency transiently, whereas high concentrations of serotonin, AST, and GABA abolished bursting altogether. Together these data demonstrate that the effects of neuromodulators depend on the previous activity and current state of the sensory neuron. (+info)
Polarization of specific tropomyosin isoforms in gastrointestinal epithelial cells and their impact on CFTR at the apical surface.
Microfilaments have been reported to be polarized in a number of cell types based both on function and isoform composition. There is evidence that microfilaments are involved in the movement of vesicles and the polarized delivery of proteins to specialized membrane domains. We have investigated the composition of actin microfilaments in gastrointestinal epithelial cells and their role in the delivery of the cystic fibrosis transmembrane conductance regulator (CFTR) into the apical membrane using cultured T84 cells as a model. We identified a specific population of microfilaments containing the tropomyosin (Tm) isoforms Tm5a and/or Tm5b, which are polarized in T84 cell monolayers. Polarization of this microfilament population occurs very rapidly in response to cell-cell and cell-substratum contact and is not inhibited by jasplakinolide, suggesting this involves the movement of intact filaments. Colocalization of Tm5a and/or Tm5b and CFTR was observed in long-term cultures. A reduction in Tm5a and Tm5b expression, induced using antisense oligonucleotides, resulted in an increase in both CFTR surface expression and chloride efflux in response to cAMP stimulation. We conclude that Tm isoforms Tm5a and/or Tm5b mark an apical population of microfilaments that can regulate the insertion and/or retention of CFTR into the plasma membrane. (+info)