Selective effects of PHA on rat brush border hydrolases along the crypt-villus axis

Summary The mechanism of the toxicity of lectin fromPhaseolus vulgaris seeds has been investigated on rat enterocytes. Cell isolation procedures showed a selectivity in the loss of brush border hydrolases; this indicated that the microvilli blebbing was not the only mechanism of action of lectins on rat enterocytes.     

Effect of dexamethasone on Fc gamma receptor expression in foetal and neonatal rat gut

When injected into 12-day-old suckling rats, dexamethasone caused a precocious disappearance of Fc gamma receptors from enterocytes of the proximal small intestine. However, dexamethasone appeared to be necessary for the maintenance or production of such receptors in foetal rat gut cultured in vitro.     

Effect of dexamethasone on Fc γ receptor expression in foetal and neonatal rat gut

Summary When injected into 12-day-old suckling rats, dexamethasone caused a precocious disappearance of Fc receptors from enterocytes of the proximal small intestine. However, dexamethasone appeared to be necessary for the maintenance or production of such receptors in foetal rat gut cultured in vitro.Supported by an award from the Science and Engineering Research Council.     

Dsg2 via Src-mediated transactivation shapes EGFR signaling towards cell adhesion

Rapidly renewing epithelial tissues such as the intestinal epithelium require precise tuning of intercellular adhesion and proliferation to preserve barrier integrity. Here, we provide evidence that desmoglein 2 (Dsg2), an adhesion molecule of desmosomes, controls cell adhesion and proliferation via epidermal growth factor receptor (EGFR) signaling. Dsg2 is required for EGFR localization at intercellular junctions as well as for Src-mediated EGFR activation. Src binds to EGFR and is required for localization of EGFR and Dsg2 to cell–cell contacts. EGFR is critical for cell adhesion and barrier recovery. In line with this, Dsg2-deficient enterocytes display impaired barrier properties and increased cell proliferation. Mechanistically, Dsg2 directly interacts with EGFR and undergoes heterotypic-binding events on the surface of living enterocytes via its extracellular domain as revealed by atomic force microscopy. Thus, our study reveals a new mechanism by which Dsg2 via Src shapes EGFR function towards cell adhesion.     

Autoradiographic analysis of alanine uptake by newborn pig intestine

Summary All villus enterocytes in the newborn pig intestine take up alanine by a process which is largely Na-dependent. Uptake in the adult rabbit intestine is cinfined to enterocytes near the tips of villi. Previous conclusions about how transport changes during development are reviewed on the basis of these findings.     

Intestinal vasoactive peptide receptors in enterocytes : specific binding and stimulation of cyclic AMP]

Receptors for the vasoactive intestinal peptide (VIP) were characterized on enterocytes isolated from Rat small intestine. Native VIP inhibited competitively the binding of 125I-VIP to enterocytes and strongly stimulated cyclic AMP production; both these effects were observed for concentrations of VIP as low as 0.5-1.0 ng/ml (0.15-0.30 nM) which are compatible with the VIP concentration in the gut.     

Le fer dans les villosites intestinales du cobaye en carence protidique

Summary During the regression of exocrine pancreas caused by a diet poor in protides, an organic iron compound accumulates at the end of intestinal villi: small granules in the upper part of enterocytes, larger particles in macrophages of the connective axis. Alkaline phosphatase activity disappears from the striated border of the enterocytes concerned.     

Nerve-mediated action of forskolin on guinea pig ileal mucosa

The effects of forskolin on myenteric neuronal activity and mucosal function were examined in guinea pig ileum. Forskolin increased the excitability of myenteric neurons, and increased mucosal chloride secretion by stimulating enteric neurons as well as by acting directly on enterocytes.     

Direct evidence for pH-dependent Fc receptors on proximal enterocytes of suckling rat gut.

By means of an erythrocyte-antibody rosette technique, Fc receptors, functional at pH 6.0 but not at 7.2, were shown to be present on enterocytes isolated from duodenum and jejunum (but absent from ileum) of 12-20-day-old suckling rats.     

Direct evidence for pH-dependent Fc receptors on proximal enterocytes of suckling rat gut

Summary By means of an erythrocyte-antibody rosette technique, Fc receptors, functional at pH 6.0 but not at 7.2, were shown to be present on enterocytes isolated from duodenum and jejunum (but absent from ileum) of 12–20-day-old suckling rats.     

Changes in brush-border enzyme activities of intestinal epithelial cells isolated from the villus-crypt axis during the early phase of alloxan diabetes in rats

The sucrase activity in enterocytes isolated from the villus crypt axis was found to increase in all regions of the villus from day 2 after induction of diabetes, and the increase continued until day 4. In contrast, alkaline phosphatase activity increased mainly in the apical one-third of the villus-crypt column, and the increase occurred abruptly on day 4 with increase in food intake.     

Changes in brush-border enzyme activities of intestinal epithelial cells isolated from the villus-crypt axis during the early phase of alloxan diabetes in rats

Summary The sucrase activity in enterocytes isolated from the villus crypt axis was found to increase in all regions of the villus from day 2 after induction of diabetes, and the increase continued until day 4. In contrast, alkaline phosphatase activity increased mainly in the apical one-third of the villus-crypt column, and the increase occurred abruptly on day 4 with increase in food intake.     

Somatostatin and 3-oxy-methyl-D-glucose (3-OMG) uptake in isolated chicken intestinal epithelial cells

The direct effect of somatostatin on the absorption of 3-oxymethylglucose in epithelial cells isolated from the small intestine of chicken was studied. The presence of somatostatin in the incubation medium at concentrations of 3.5 X 10(-8) M and 7 X 10(-8) M produced significant dose-dependent increases in the accumulation of sugar in the enterocytes. This effect might be due to an increase in the cell membrane permeability caused by hormone action.     

Nerve-mediated action of forskolin on guinea pig ileal mucosa

Summary The effects of forskolin on myenteric neuronal activity and mucosal function were examined in guinea pig ileum. Forskolin increased the excitability of myenteric neurons, and increased mucosal chloride secretion by stimulating enteric neurons as well as by acting directly on enterocytes.Acknowledgment. The authors thank E. Martens, S. Bowen for technical assistance and N. Schaad for secretarial assistance. This work was supported by National Institutes of Health Grants, F32-AM07301, K-104-AM1004, RO1-AM29699, RO1-AM26742 and an Eloise Gerry Fellowship.     

Somatostatin and 3-oxy-methyl-D-glucose (3-OMG) uptake in isolated chicken intestinal epithelial cells

Summary The direct effect of somatostatin on the absorption of 3-oxymethylglucose in epithelial cells isolated from the small intestine of chicken was studied. The presence of somatostatin in the incubation medium at concentrations of 3.5×10^–8 M and 7×10^–8 M produced significant dose-dependent increases in the accumulation of sugar in the enterocytes. This effect might be due to an increase in the cell membrane permeability caused by hormone action.     

A pathogenic hypothesis of malformation caused by amniocentesis.

The role of amniocentesis in producing fetal malformations has been investigated in the rat. Relevant uterine contractions were observed after amniocentesis. The pathogenetic mechanism of fetal malformations is discussed on the basis of the present results.     

Composition and functional role of the mucus layers in the intestine

In discussions on intestinal protection, the protective capacity of mucus has not been very much considered. The progress in the last years in understanding the molecular nature of mucins, the main building blocks of mucus, has, however, changed this. The intestinal enterocytes have their apical surfaces covered by transmembrane mucins and the whole intestinal surface is further covered by mucus, built around the gel-forming mucin MUC2. The mucus of the small intestine has only one layer, whereas the large intestine has a two-layered mucus where the inner, attached layer has a protective function for the intestine, as it is impermeable to the luminal bacteria.     

A pathogenic hypothesis of malformation caused by amniocentesis

Summary The role of amniocentesis in producing fetal malformations has been investigated in the rat. Relevant uterine contractions were observed after amniocentesis. The pathogenetic mechanism of fetal malformations is discussed on the basis of the present results.This research was supported by a grant of CNR.     

Demonstration of a tryptaminergic mechanism in the rat beta-cell.

Yellow 5-HT fluorescence has been histochemically demonstrated in rat pancreatic islet cells in animals injected with L-5-HTP with or without pretreatment with the monoaminoxidase inhibitor nialamide. This fluorescence was not observed after inhibition of the aromatic amino acid decarobxylase. The results strongly suggest the presence of a tryptaminergic mechanism in the rat islet cells.     

2-Br-alpha-ergokryptin: influence on fertility and lactation in the rat

The effects of alpha-ergocryptin and 2-bromo-alpha-ergocryptin on fertility and lactation in rats were studied. The inhibitory actions of alpha-ergocryptin on fertility and lactation in the rat are altered differentially in the 2-bromo derivative of this ergot alkaloid. It is therefore unlikely that the fertility-inhibiting and the lactation inhibiting effects of 2-bromo-alpha-ergocryptin are governed by a single mechanism of action.