Chicken Small Intestine Research Articles

Radioligand binding and functional characterisation of tachykinin receptors in chicken small intestine.

Tachykinin receptors in chicken intestine were studied using radioligand binding and functional techniques. Mechanisms of tachykinin-induced contraction were also investigated. Binding of [125I]Bolton-Hunter substance P ([125I]BH-SP) to chicken ileal membranes was rapid, saturable, of high affinity and to a single population of binding sites with Kd 0.72 nM and Bmax 0.48 fmol/ wet weight tissue. The rank order of agonists competing for [125I]BH-SP binding sites was [Sar9]SP > [Arg3]SP (natural tachykinin in chickens) > SP > [Pro9]SP > or = NKA > eledoisin > [Sar9,Met(O2)11]SP >> [Lys5,MeLeu9,Nle10]-NKA(4-10) >> senktide, suggesting similarities to the mammalian NK1 receptor. The NK1 receptor antagonist CP 99994, and NK2 receptor antagonist SR 48968 were weak competitors while spantide, RP 67580, GR 82334, GR 94800 and MEN 11420 were ineffective. The radioligand [125I]NKA showed no specific binding to ileal membranes. The potency order of most tachykinins in contacting isolated ileal longitudinal segments was in good agreement with that obtained from competition binding studies. Contractions to [Arg3]SP, NKA and senktide were greatly reduced by tetrodotoxin, suggesting that neurally-mediated responses were primarily involved. [Arg3]SP and NKA acted mainly by increasing release of acetylcholine, prostaglandins and probably tachykinins. Responses to [Arg3]SP were virtually abolished by nifedipine but were unaffected by NK1 receptor antagonists. Senktide-induced contraction was inhibited by the NK3 receptor antagonist, SR 142801, but was unaffected by atropine or L-NAME. The study provides evidence for a tachykinin receptor with similarities to the NK1 receptor in the chicken small intestine. In addition, senktide may act on a receptor similar to the mammalian NK3 receptor.

Changes in Growth and Function of Chick Small Intestine Epithelium Due to Early Thermal Conditioning

The effect of exposure to heat at 3 d of age on small intestine functionality and development was assayed by measuring villus size, proliferating enterocytes, and brush-border membrane (BBM) enzyme expression and activity. Results showed that thermal conditioning caused an immediate effect characterized by lowered triiodothyronine (T3) level, reduced feed intake, and depressed enterocyte proliferation and BBM enzyme activity. A second series of effects, observed 48 h posttreatment, was characterized by elevated T3, increased feed intake, increased enterocyte proliferation, and higher expression and activity of BBM enzymes. The association between ambient temperature, feed intake, growth rate, and plasma T3 levels was reflected in the structure and function of the intestinal tract. The results suggest that thermal conditioning at an early age influences T3 concentrations, which in turn alter the intestinal capacity to proliferate, grow, and digest nutrients. However, these experiments were not able to discriminate between effects due to feed intake and those due to thermal conditioning. The treatments modulated changes in the intestinal tract following thermal treatment.

Hormonal regulation of chicken intestinal NHE and SGLT-1 activities.

The effects of aldosterone and arginine vasotocin (AVT) on intestinal Na(+)/H(+) exchange (NHE) and Na(+)-sugar cotransport (SGLT-1) activities have been investigated using brush-border membrane vesicles isolated from Hubbard chicken small and large intestines, and they were compared with those induced by either Na(+) depletion or dehydration. Na(+) depletion was induced by feeding the chickens with either a low- or a high-Na(+) diet for either 0.5, 1, 2, 4, or 8 days. Ileal and colonic NHE2 activity increased with the duration of the Na(+) depletion, whereas that of intestinal SGLT-1 decreased, reaching a plateau after 2 days of treatment. Three-hour incubation of the intestine with aldosterone produced the same effects on NHE activity as does Na(+) depletion, without altering SGLT-1 activity. However, 3-h incubation of the intestine with AVT increased intestinal SGLT-1 activity, without affecting intestinal NHE activity. It is concluded that aldosterone regulates apical ileal and colonic NHE2 activity, whereas that of SGLT-1 is regulated by AVT.

Intestinal anaphylaxis in chickens: epithelial ion secretion as a determinant and potential component of functional immunity

Immunity to secondary protozoan infections in chickens is accompanied by rapid onset of intestinal permeability to serum proteins, an event in mammals associated with local anaphylaxis. The permeability changes in the chicken intestine are hypothesized to be mediated by mast cell-derived paracrine factors. In a test of this hypothesis, we demonstrated, using an electrophysiological correlate of intestinal anaphylaxis (antigen-induced Cl − secretion), that the response of the chicken intestine to antigenic stimulation is consistent with type I hypersensitivity reactions. Day-old, single-comb-white-Leghorn chickens were sensitized to bovine serum albumin (BSA). At 3 weeks of age ileal segments were mounted in Ussing-type chambers. Serosal challenge with BSA elevated the transmural short circuit current (ΔIsc) within 1 min and was maximally expressed (ΔIsc=50–60 μA/cm 2) within 2–3 min. The magnitude of the ΔIsc was directly related to the concentration of antigen (10–200 μg antigen/ml), was only expressed in immunized chickens, and was blocked by the mucosal application of a Cl − channel blocker. Data obtained in the present investigation identify epithelial ion secretion as a potential mechanism of functional immunity in the mucosal immune system of the chicken small intestine.

A Na+-dependent D-mannose transporter in the apical membrane of chicken small intestine epithelial cells

The presence of a Na+/D-mannose cotransporter in brush-border membrane vesicles (BBMV) isolated from chicken small intestine was examined. In the presence of an electrochemical gradient for Na+, but not in its absence, D-mannose was accumulated transiently by the BBMV. D-Mannose uptake into the BBMV was energized by both the membrane potential and the chemical gradient for Na+. The relationship between D-mannose transport and external D-mannose concentration was described by an equation that represented the superposition of a saturable component (Michaelis-Menten constant Km 12.5 microM) and another component unsaturatable up to 80 microM D-mannose. D-Mannose uptake was inhibited by various substances in the following order of potency: D-mannose>>D-glucose>phlorizin>phloretin>D-fructose. For the uptake of alpha-methyl-glucopyranoside the order was D-glucose=phlorizin>>phloretin=D-fructose=D-mannose. The initial rate of D-mannose uptake increased as the extravesicular [Na+] increased, with a Hill coefficient of 1, suggesting that the Na+:D-mannose cotransport stoichiometry is 1:1. It is concluded that the intestinal apical membrane has a saturable, electrogenic and concentration- and Na+-dependent mannose transport mechanism that differs from the sodium-dependent glucose transporter SGLT1.

Vitamin A deficiency interferes with proliferation and maturation of cells in the chicken small intestine

1. The effect of vitamin A on the small intestine was examined in vitamin-A-deficient meat-type chickens. 2. Maturation and activity of the small intestinal cells were assayed by detection of proliferating cells with proliferating cells nuclear antigen, goblet cells with Alcian blue, mature cells with alkaline phosphatase and extent of RNA expression with dot blot analysis. 3. Vitamin A deficiency caused hyperproliferation of enterocytes, a decrease in the number of goblet cells, decreased alkaline phosphatase activity and decreased expression of 2 brush-border enzymes. 4. Our findings suggest that the absence of vitamin A interferes with the normal growth rate in chickens because it influences functionality of the small intestine by altering proliferation and maturation of cells in the small intestinal mucosa.

Quantitative distribution of NADPH-diaphorase-positive myenteric neurons in different segments of the developing chicken small intestine and colon.

NADPH-diaphorase (NADPH-d) was used as a marker for neuronal nitric oxide synthase in order to investigate the nitrergic neurons of the developing myenteric ganglia on whole-mount preparations in the proximal and distal segments of the small intestine and in the colon of the chicken embryo, between incubation days 12 and 19. Neurons that were positive for NADPH-d were counted in randomly selected myenteric ganglia. The data obtained from each area and each age group were subjected to two-way analysis of variance (ANOVA) and the Student-Newman-Keuls test. Between incubation days 12 and 19, the originally narrow-meshed myenteric plexus with its high ganglionic density progressively became wide-meshed and the ganglionic density decreased significantly. Quantitative analysis further revealed a significant decrease in the NADPH-d-positive nerve cell density with age. At the same time, the constant or even increasing number of nitrergic cells per ganglion may indicate that the decreasing cell density may be a result of the growth of the bowel with decreasing ganglion density rather than a decrease in the total number of myenteric nitrergic cells. Regional differences in the dynamics of the quantitative changes were revealed. A significant decrease in the nitrergic cell number appeared earlier in the proximal than in the distal segments of the small intestine or in the colon. In contrast, the significant decline of the ganglionic density was first noticed in the colon at the same time.

Electrical properties of the intestinal mucosa of the chicken and the effects of luminal glucose

Transmural potential difference (PD), short-circuit current (Isc), and electrical resistance (R) were measured in the isolated mucosa of the duodenum, jejunum, ileum, proximal cecum, and rectum in order to characterize the electrical properties of the chicken small and large intestine. The chicken intestine was classified into three categories, regarding its electrical characteristics: 1) the duodenum, with four to five times higher R than the other segments and the lowest PD; 2) the group formed by the jejunum, the ileum, and the proximal cecum, with high PD and low R; 3) the rectum, with low PD and low R. In all segments, the addition of D-glucose into the luminal side stimulates Isc, and this effect can be reversed by phloridzin, indicating that the glucose-induced Isc increase is due to Na+-D-glucose co-transport. The effect of glucose is maximal in the rectum, with a fivefold Isc increase, suggesting that this segment may have an important role in the absorption of Na+ as well as of nutrients co-transported with Na+.

Chick small intestine brush border contains lipase and phospholipase activity

1. Uptake of triglycerides and phosphoglycerides was demonstrated in ligated washed chick intestinal segments in situ . Mucosal uptake was observed both in the jejunum and ileum of chicks and was not accompanied by significant luminal hydrolysis of acyglycerides. 2. Brush border membrane vesicles were prepared and lipase and phospholipase activities were demonstrated. These activities were enriched in parallel to the increase in activity of maltase and gamma-glutamyl transpeptidase in all small intestinal areas. 3. In order to determine if the pancreatic and brush border membrane lipolytic activities were similar different properties of these activities were examined. The relative activities of pancreatic and brush border membranes towards triolein and phosphatidylcholine differed. The pH-triolein activity curve and the use of different additives showed some diverging effects between the activities. These differences were not, however, sufficient to conclude that the brush border activity towards triolein is distinct from that of pancreatic lipase. 4. Lipolytic activity in the brush border may play a role in acylglyceride digestion, uptake and transport in the small intestine of the chick.

Analysis of a phenobarbital-responsive enhancer sequence located in the 5' flanking region of the chicken CYP2H1 gene: identification and characterization of functional protein-binding sites.

We previously identified in the chicken CYP2H1 gene an upstream enhancer domain (-5900/-1100) that responds to phenobarbital. Deletion and restriction enzyme analyses of this domain have now identified two separate enhancer regions that respond to phenobarbital (from -5900 to -4550 and from -1956 to -1400). We have focused here on the latter and in particular a resident 240-base pair (bp) restriction enzyme fragment that retains drug responsiveness. Using deletion analysis and in vitro DNase I footprinting, transcription factor binding sites have been located in the 240-bp fragment. The sites identified are an E-box-like element, a consensus hepatocyte nuclear factor 1 site, a CCAAT box motif, and a novel site. Mutagenesis demonstrated that each site contributed to enhancer activity, although there was a weaker contribution from the CCAAT box, and that no individual site was critical for responsiveness. In keeping with the tissue-restricted expression of the CYP2H1 gene, gel shift experiments established that the proteins binding to these enhancer sites are enriched in chicken liver, kidney, and small intestine. In vitro footprint experiments showed a stronger protection with liver nuclear extracts from drug-treated chickens compared with control extracts on the E-box-like element, the CCAAT box motif, and the novel binding site; however, the basis for this apparent increase in binding remains to be determined. The proteins binding to the 240-bp fragment are different from those recently reported to be required for the activity of the phenobarbital responsive enhancer domains of rodent CYP2 genes.

Vitamin A deficiency induces morphometric changes and decreased functionality in chicken small intestine

The effect of vitamin A on chicken intestinal mucosal morphology and functionality was tested in relation to severe and mild vitamin A deficiency and vitamin A repletion. Compared with rats and mice, chickens have a very quick response to a deficient dietary intake. Severe vitamin A deficiency altered the small intestine of chickens at both the biochemical and the morphological levels. It caused the loss of mucosal protein, reduced villus height and crypt depth and diminished activities of disaccharidases, transpeptidase and alkaline phosphate (EC 3.1.3.1). The ratios RNA:DNA, RNA:protein and protein:DNA, and the DNA concentrations in 1 g intestinal tissue, together with morphological measurements, provided knowledge about the pattern of lesion. The results indicated that (1) lack of vitamin A influenced cellular hyperplasia as it caused an increase in DNA content and in the number of enterocytes per villus; (2) lack of vitamin A influenced cellular hypertrophy as it decreased the protein:DNA ratio. There was no difference in mucosal enzyme activity between the two deficient groups. The repletion group exhibited a remarkable increase in mucosal enzyme activity only 4 d after switching to the control diet. The evidence presented in our paper suggests that the low vitamin A supply interferes with the normal activity of chicken intestinal mucosa as it influences the processes of proliferation and maturation of enterocytes.

Distribution of phosphate-activated glutaminase isozymes in the chicken: absence from liver but presence of high activity in pectoralis muscle

The distribution of glutaminase expression in a uricotelic species, the chicken, has been examined using cDNA probes to the rat isozymes. The results suggest that chickens do not possess a glutaminase isozyme equivalent to the liver-type isozyme of mammalian liver. Measurements of enzymic activity also showed very low glutaminase activity in chicken liver. Extra-hepatic tissues in the chicken do express a glutaminase isozyme mRNA which is detected by rat kidney-type glutaminase cDNA. The abundance of this mRNA was highest in kidney and breast muscle and relatively abundant in brain, spleen and adipose tissue. Chicken small intestine expressed relatively low levels of the mRNA. The high level of glutaminase mRNA in chicken pectoralis muscle was accompanied by high glutaminase enzymic activity. In contrast, in mixed leg muscle glutaminase mRNA was barely detectable by Northern blot and glutaminase activity was relatively low. Starvation for 48 h resulted in a slight decrease in the activity of glutaminase in pectoralis muscle, but a large decrease in the relative abundance of the mRNA. The results suggest that in the chicken, hepatic glutamine hydrolysis is not quantitatively important, but skeletal muscle may be a major site of glutamine catabolism.

Taurocholate transport by brush border membrane vesicles from different regions of chicken intestine

Taurocholate transport was studied in brush border membrane vesicles (BBMV) isolated from chicken small (duodenum, jejunum, and ileum) and large (proximal cecum and rectum) intestines, using a rapid filtration technique. The purity of the BBMV was verified by the finding that the specific activity of sucrase (a brush border membrane enzyme marker) was severalfold greater in vesicles than corresponding values in mucosal homogenate. The functional integrity of isolated BBMV was evaluated by the uptake of D-glucose, which showed a transient increase in the presence of Na+. A Na+-dependence of taurocholate uptake was shown in BBMV prepared from ileum, cecum, and rectum, as taurocholate transport was transiently increased (accumulation) in the presence of a Na+ gradient between the external medium and intravesicular medium. The magnitude of the accumulation was similar among ileum, cecum, and rectum. In contrast, BBMV prepared from duodenum and jejunum did not show any Na+-dependent taurocholate transport, as the taurocholate uptake was not affected when a Na+ gradient was replaced by a K+ gradient. The use of taurochenodeoxycholate in the incubation medium inhibited Na+-dependent taurocholate transport in the ileum, cecum, and rectum. This study is the first to show the presence of a Na+-dependent bile salt transport in BBMV obtained from chicken ileum, proximal cecum, and rectum.

Evolutionary origins of the mammalian apolipoproteinB RNA editing enzyme, apobec-1: structural homology inferred from analysis of a cloned chicken small intestinal cytidine deaminase.

Mammalian apolipoproteinB (apoB) RNA editing is a site-specific deamination reaction that mediates the C to U conversion responsible for apoB48 production in the mammalian small intestine. This process is not detected in chicken apoB RNA. Mammalian apoB RNA editing is mediated by a multicomponent enzyme complex that includes a single catalytic subunit, apobec-1. In order to examine the evolution of apobec-1, we have cloned and characterized an orthologous cytidine deaminase cDNA isolated from chicken small intestine. Northern blot analysis revealed expression restricted to the small intestine, colon and lung but not the liver or other tissues. The cDNA encodes a single 31 kDa protein with features reminiscent of other cytidine deaminases and with approximately 39% overall homology to rat apobec-1. The recombinant protein is a cytidine deaminase with activity on a monomeric substrate that was found to be zinc-dependent. However, no RNA editing activity was detectable towards cytidine nucleotides presented in the context of an optimally configured mammalian apoB RNA template. These studies provide information concerning the evolution of the apoB RNA editing machinery and indicate that a chicken small intestinal cytidine deaminase with homology to apobec-1 demonstrates no activity on an RNA substrate.

Broiler chicken body weights, feed intakes, plasma lipid and small-intestinal bile acid concentrations in response to feeding of chitosan and pectin.

One-day-old broiler chickens were fed on a control diet based on maize and maize starch or diets containing 30 g/kg of 89% deacetylated chitin (chitosan) or low-methoxyl (34% degree of esterification) pectin. Feeding of the chitosan diet to chickens significantly reduced body weights and feed intakes compared with animals fed on control or pectin diets on days 5 and 11 of the experiment. On day 12, significant reductions in total plasma cholesterol and HDL-cholesterol concentrations were observed among birds fed on the chitosan but not the pectin diet in relation to control-fed animals. A concomitant increase in the plasma HDL-cholesterol:total cholesterol ratio was observed among chitosan-fed chickens. The generally reduced concentrations of primary and total bile acids in the duodenum of birds fed on the fibre-containing diets on day 13 may have been an indication of a delay in the production and/or secretion of bile. Viscosity of the three broiler-chicken diets was measured after suspension in water, acidification and finally neutralization of the suspensions, in an attempt to simulate the effect of changes in pH and dilution of diets occurring in the gizzard and small intestine of chickens. Viscosity of the chitosan diet was significantly elevated after acidification and significantly reduced at neutralization in comparison with the control and pectin-containing diets suggesting that the hypolipidaemic influence of chitosan observed in the present study may be due to interruption of enterohepatic bile acid circulation rather than increased viscosity in the small intestine of chickens. The low viscosity of the pectin diet in vitro together with the absence of a hypocholesterolaemic effect of this diet when fed in vivo precludes any conclusion regarding the hypocholesterolaemic mechanism of pectin observed in earlier studies.

Association of a Brush Border Myosin I-Like Protein with Vesicular Organelles of the Secretory Pathway in Chicken Enterocytes

Brush border myosin I (BBMI) was first identified as a major constituent of the microvillus cytoskeleton, where it links the actin filaments of the microvillus core to the overlying plasma membrane. Recently, however, BBMI was also found on isolated Golgi membranes. This observation suggests that cytoplasmic BBMI might act as a molecular motor for apically targeted secretory vesicles.In an earlier study from this laboratory a 105-110 kD protein was isolated from the chicken small intestine, which displayed several characteristics of the BBMI. Using an antibody against this BBMI- like protein (MLP), the protein was detected in the apical brush border of the enterocytes. The limited resolution of the light microscopic immunohistochemical techniques used in that investigation, however, did not provide information about the intracellular distribution of MLP in the enterocytes.In this study the intracellular localization of MLP was characterized using post-embedding colloidal gold immunocytochemistry. Pieces of the jejunum from 6-week-old male White Leghorn chickens were fixed and embedded in LR Gold resin.

Rhythmic oscillating complexes in gastrointestinal tract of chickens: a role for motilin.

Rhythmic oscillating complex (ROC) is a highly organized gastrointestinal motility pattern recently described in fasted avian species. ROCs show several high-speed aborad-propagated contractions that progressively change into others of orad direction. In addition, chickens show migrating motor complexes (MMC) in both fed and fasting states. Recently, motilin was isolated and characterized from chicken small intestine. Accordingly, the aim of this study was to learn whether chicken motilin might be involved in either ROC or MMC induction. Electromyographic recordings were obtained from different areas of the gastrointestinal tract of chickens while motilin was infused. The response to chicken motilin was dose dependent in both fed and fasted animals; a bolus of 4 x 10(-11) mol/kg (n = 5) did not modify the intestinal motor pattern, whereas 4 x 10(-10) and 4 x 10(-9) mol/kg (n = 5 each) induced a complete ROC pattern of 5.2 +/- 0.6 and 10.8 +/- 0.9 min, respectively. ROCs induced by chicken motilin presented exactly the same pattern as that described during a spontaneous ROC. Furthermore, motilin concentration in plasma, measured by radioimmunoassay, increased during a spontaneous ROC. This study suggests that chicken motilin triggers an ROC in chickens. The fact that plasma motilin levels increased during spontaneous ROC strongly suggests that motilin is involved in the induction of the ROC pattern. Motilin seems to play a different role in avian and mammalian species, because a phase III of the MMC was never induced by motilin infusion.

Kinetic constants of α-methyl- d-glucoside transport in the chick small intestine during perinatal development

The kinetic parameters of α-methyl- d-glucoside (αGlclMe) have been determined in the small intestine in order to establish developmental and regional changes in the apical transport in embryos and newly hatched chicks. Results show that the apparent Michaelis constant ( K m) values did not change during the period studied in each region of the small intestine. However, the ileum showed a smaller K m than that of the duodenum and jejunum, indicating an increase of the affinity of the carrier in the distal portion of the intestine and a significant contribution of the ileum to overall sugar absorption in the perinatal period. There were important changes in the diffusional component and in the mediated transport system capacity during this period, as well as in the different regions of the intestine. Significant increase in the maximal rate of transport ( V max) were observed in all regions during the embryonic period until the second day after hatching, followed by a decline during the first week. During all the period studied, V max values from the jejunum were significantly greater than those from both the duodenum and the ileum at every age studied showing that the jejunum is the segment that is best suited for Na + -mediated uptake. Such changes which occur when the need for nutrients for rapid development are at their highest are not solely a result of diet composition, but rather in accordance with a genetic programme.

Transport of various forms of L-tryptophan in the small intestine of chicks. Mechanism and regulation.

Tryptophan belongs under the irreplacable amino acids, the presence of which is needed in the ration for keeping up the life of organism. The ways of their absorption in mammal intestines were studied by Munck and Rasmussen (1975). They had stated that the entrance of L-tryptophan across the apical membrane of enterocytes was performed by the carriers of neutral amino acids. At its exit across the basolateral membrane a mechanism is used common with L-lysine. The study of mechanism for L-tryptophan absorption has been carried out on chicks in our laboratory as well. At this investigation the active character of L-tryptophan transport process was found out, its stereospeciflcity was revealed as well as dependence of the presence of sodium and hydrogen ions in the incubation medium and the presence of oxygen in it. A stimulating impact of a number of L-amino acids and carbohydrates was observed on the absorption of this irreplacable amino acid (Kushak et al., 1984; Kushak and Basova, 1987; Basova and Kushak, 1987).KeywordsSmall IntestineNeutral Amino AcidRabbit JejunumMammal IntestineSensitive Spectrophotometric MethodThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Cell Apical Surface Area in Enterocytes from Chicken Small and Large Intestine During Development

The absorptive surface of epithelial cells from chicken small and large intestine was studied at the day of hatch (1 d group) and at 2 and 6 wk after hatch. The segments considered were duodenum, jejunum, ileum, cecum (proximal, medial, and distal regions), and rectum. The length, diameter, and density of microvilli as well as cell apical diameter were measured in tip-villous enterocytes by transmission electron microscopy. The results obtained showed that during development: 1) microvillus length remained constant in duodenum and jejunum and decreased in the other segments; 2) microvillus diameter increased only in the jejunum and the rectum; 3) microvillus density increased in duodenum, ileum, distal cecum, and rectum (especially from 1 d to 2 wk) and did not change in the other segments; 4) cell apical diameter did not change; 5) apical surface area increased both in the duodenum (2nd to 6th wk) and in the jejunum (1 d to 2 wk) but did not change in the ileum. In the proximal-medial cecum and in the rectum there was a decrease in apical surface, whereas no changes were observed in distal cecum. Results indicated that microvillus length and density are the variables that best explain the changes observed in apical surface that occurred during development.