Mechanism of strengthening of the contractile activity in the duodenum and in the jejunum in psychogenic stress in rabbits

In experiments on unanaesthetized rabbits myoelectric activity (contractile activity index) of proximal (postpyloric) and distal sites of duodenum, and proximal part of jejunum was studied under stress induced by fastening a rabbit to a table in supine position. In both sites of duodenum, the stress impact induced a short-time decrease of contractile activity which was followed by its increase that exceeded the initial level. In the proximal part ofjejunum, the increase of contractile activity took place only during the second part of stress response. The strengthening of the contractile activity of the proximal part of duodenum was preserved after muscarinic or nicotinic cholinoceptor blockage, and after beta-receptor blockage. It was concluded that the contractile response of the proximal part of duodenum did not result from the contribution of central or local neurogenic mechanism, including excitatory cholinergic one, but was humoral in origin. The strengthening of the contractile activity of the distal part of duodenum and proximal part ofjejunum was abolished by muscarinic cholinoceptor and beta-receptor blockage, and resulted from the action of circulating catecholamines on the excitatory beta-adrenoceptor, localized on the cholinergic neurones of the enteric nervous system.     

Non-adrenergic mechanisms of inhibition of the contractile activity of the cat small intestine by histamine, bradykinin, and met-enkephalin

I. a. histamine and bradykinin caused both an activation and an inhibition of jejunal contractile activity. The inhibitory effect was preserved after blockade of muscarinic cholinoreceptors, alpha- and beta-adrenoceptors, and abolished with the nicotinic cholinoceptor blockade. Metenkephalin inhibited the jejunal contractile activity after first activating it. The inhibitory effect of the peptide was preserved after blockade of alpha- and beta-adrenoceptors as well as the nicotinic cholinoceptors. The data obtained suggest that the non-adrenergic inhibitory effect of metenkephalin on intestinal contractions was the result of its depressing action on motor cholinergic neurons, whereas the inhibition of intestinal contractile activity with histamine and bradykinin resulted from their activating action on cholinergic interneurons which activate non-adrenergic inhibitory neurons through nicotinic cholinoceptors.     

Mechanisms of inhibition of the contractile activity in the ileo-caecal zone in rabbits under psychogenic stress

In experiments on unanaesthetized rabbits, myoelectric activity (contractile activity index) of distal ileum, caecum, and proximal colon in two sites was studied under stress induced by fastening a rabbit to the table in supine position. The stress caused sharp decrease (up to complete disappearance) of the contractile activity in all studied compartments of the ileocaecal intestine with partial or complete restoration after release of the animal. Nonselective blockade of pre- and postsynaptic alpha-adrenoceptor with dihydroergotoxin abolished the initial component of the specified inhibitory response. The latter was caused by "adrenergic inhibition" as a result of action of catecholamines circulating in blood on inhibitory smooth muscle alpha-adrenoceptor. Against the background of muscarinic cholinoceptor blockade, the stressor inhibition of ileocaecal contractile activity observed in control experiments was completely preserved. The periods of supression of ileoceacal contractile activity under stress resistant to blockade of alpha-, beta-adrenoceptor and muscarinic cholinoceptor, are caused by the mechanism of "nonadrenergic noncholinergic inhibition", which is realized at the expence of activation of the enteric inhibitory neurones.     

The mechanism of the duodenal motility strengthening under psychogenic stress in rabbits

In experiments on unanaesthetized rabbits, myoelectric activity (contractile activity index) of two sites of duodenum and of antral and pyloric parts of the stomach was studied under stress induced by fastening a rabbit to a table in supine position. In both sites of duodenum, the stress impact induced a short-time inhibition of contractile activity which was followed by its strengthening that exceeded the initial level. Meanwhile in antrum and pylorus, the whole period of stress impact was characterized by suppression of contractile activity, the latter being more pronounced in the antrum. The strengthening of the duodenal contractile activity was preserved after muscarinic ornicotinic cholinoceptor blockade. It was concluded that the contractile response of duodenum seemed to be of humoral origin.     

On the mechanism of gastroduodenal motility inhibition under psychogenic stress in rabbits

In experiments on unanaesthetized rabbits, myoelectric activity (contractile activity index) in antral and pyloric parts of the stomach and in two sites of proximal duodenum was studied under stress induced by fastening rabbit to a table in supine position. The stressor impact induced inhibition of contractile activity in antrum and pylorus. The duodenal contractile activity after initial complete suppression overshot its initial level. Blockade of beta1/beta2-adrenoceptor with propranolol and blockade of alpha2-adrenoceptor with yohimbine did not influence qualitatively the pattern of the stressor responses of antrum and pylorus, and of the postpyloric part of duodenum. In conditions of unselective blockade of alpha-adrenoceptor with dihydroergotoxin there was no initial complete inhibition of duodenal contractile activity, and its strengthening was more expressed than in the control experiments. The received data indicate that the stressor inhibition of antral and pyloric contractile activity possibly results from activation of non-adrenergic inhibitory neurons of the enteric nervous system. The initial short-term suppression of duodenal motility resulted from its "adrenergic" inhibition which can also be a factor limiting the manifestation of stimulating effect of the humoral agent on the duodenal motility. In the period after release of the animal, index of antral and pyloric contractile activity did not significantly differ from its initial level; after beta1/beta2-adrenoceptor blockade in antral and after alpha2-adrenoceptor blockade or nonselective alpha-blockade in antral and pyloric parts of the stomach, there was decrease of contractile activity compared with its initial level; after alpha2- or beta1/beta2-adrenoceptor blockade there was no poststressor exceeding of the initial level of the duodenal contractile activity, observed in the control experiments.     

Influence of PGF2 alpha on gastrointestinal activity in the conscious piglet.

In 5 conscious piglets with electrodes implanted on the antrum pylori, duodenum, jejunum and ileum, the effect of intravenous infusion of PGF2 alpha, 1 and 10 micrograms/kg/min during 2 h, on gastrointestinal electrical activity was studied. The influence of the PG, 10(-8) to 10(-4) M, on longitudinal tissue strips from the same segments was also examined. The in vitro results demonstrate that PGF2 alpha has only a weak contractile effect on duodenal and jejunal strips. This effect was enhanced in the presence of atropine and indomethacin. In the in vivo part of the study PGF2 alpha induced an inhibition of antral electrical activity as evidenced by a prolongation of the inhibitory phases and a reduction of the frequency of the fast oscillations. In the small intestine only ileal activity was changed significantly. PGF2 alpha provoked an increase in the phase II or irregular spiking activity and an increase in the interval of the migrating myoelectrical complexes in this segment.     

Changes of contractile activity of the colon under psychogenic stress before and after blockade of M- and N-cholinergic and beta-adrenoceptors

In experiments on conscious rabbits, myoelectric activity (contractile activity index) was recorded in 2 sites of proximal and in 2 sites of distal part of the colon under psychogenic stress induced by firm fastening of the animal to a frame in supine position. Stressor impact caused decrease of the contractile activity in proximal and distal parts of the colon, due to "alpha-adrenergic" (in initial stage of stress reaction) and "nonadrenergic noncholinergic" inhibition. Stress-induced increase of the contractile activity of the colon was limited to the initial segment of its distal part, and was due to centrogenic stimulation of the preganglionic neurons of the parasympathetic nervous system and effector cholinergic neurons of the enteric nervous system.     

Ultrastructural localization of acid phosphatase activity in the small intestinal absorptive cells of adult rats.

Ultrastructural localization of acid phosphatase activity was investigated in ultrathin (0.05 micron) and semithin (0.5 and 0.75 micron) sections of the small intestinal epithelial cells of adult rats. The results showed that the enzyme activity was localized on the membrane of microvilli, lateral cell membranes, lysosomes, the Golgi complex, and the GERL of Novikoff (a part of the smooth-surfaced endoplasmic reticulum located in close proximity to the inner Golgi saccules) of duodenal absorptive cells. The lysosomes contained within the duodenal and jejunal absorptive cells appeared to be mainly heterolysosomes rather than autolysosomes. The enzyme activity of absorptive cells was lower in the jejunum than in the duodenum, and was barely detectable except in the GERL and lysosomes of the ileum. The average numbers of lysosomes having a diameter of 0.2 approximately 1.0 microns, per cell profile in sections of 214 duodenal, 226 jejunal and 318 ileal epithelial cells were 8.9 +/- 0.189, 6.4 +/- 0.155 and 3.5 +/- 0.027 (mean +/- SE), respectively. From these results, it was assumed that both the Golgi apparatus and GERL produce some lysosomes in the duodenal and jejunal absorptive cells, but only GERL does so in the ileum. It was considered also that because of an unexpectedly high number of lysosomes containes within the epithelial absorptive cells of the proximal intestine of adult rats, these cells may possess the strong heterophagic, as well as absorptive capacity.     

Determinants of regional sucrase-isomaltase expression in adult rat small intestine

Sucrase-isomaltase (SI) expression along the longitudinal and vertical axis of the small intestine was studied by sequentially isolating enterocytes from villus to crypt of rat proximal jejunum and distal ileum. Gradients of sucrase activity were observed with greatest activity occurring in jejunal and villus regions. Along the villus-to-crypt axis, gradients of SI mRNA abundance corresponded with activity. However, along the longitudinal axis no differences in SI mRNA levels were observed, thus not accounting for the observed 3-5-fold difference in SI activities between jejunum and ileum. Comparison of SI immunoprecipitates from jejunal and ileal mucosal scrapings showed significant differences in gel mobilities of the more mature forms, which did not appear to affect SI functional activities. When relative rates of de novo SI protein synthesis were compared, [35S]methionine incorporation into all SI forms was observed to be 3-5-fold greater in jejunum than in ileum at all time points. Because these results suggested differences in regional translational regulation, subcellular distribution of SI mRNA in jejunal and ileal epithelial cells was compared. A greater proportion of jejunal SI mRNA was found to be associated with membrane-bound polyribosomes. We conclude 1) sucrase expression along the villus-to-crypt axis correlates with SI mRNA abundance, 2) post-translational processing of SI differ in ileum and jejunum, but appear not to determine SI expression, and 3) differences in translational processing in distal ileum and proximal jejunum may determine sucrase activity along the longitudinal axis of rat small intestine.     

Localization of acyl-coenzyme A: cholesterol acyltransferase in villus and crypt cells of chick intestine

Endogenous cholesterol esterification by acyl-CoA:cholesterol acyltransferase (EC 2.3.1.26) was studied in isolated enterocytes obtained from chick duodenal, jejunal, and ileal villi and crypts, using [14C]oleoyl-CoA as substrate. The maximal specific activity in each cell fraction was found in chick jejunum, followed by duodenum and ileum. Jejunal upper and mid villi showed higher specific activities than lower villi and crypts. Epithelial cells isolated from chick intestine also incorporated oleoyl-CoA into different lipids using the endogenous substrates. Upper and mid villus cells showed the maximal incorporation of oleoyl-CoA into triglycerides in duodenum and jejunum. Levels of oleoyl-CoA incorporation into phospholipids were higher than those found in the synthesis of triglycerides or cholesterol esters, whatever may be the cell fraction considered. Upper villus cells also showed the highest specific activity in the incorporation of oleoyl-CoA into phospholipids. The acyl-CoA hydrolase specific activity was practically similar in all the cell fractions obtained from chick duodenum, jejunum, and ileum.     

Mechanism of the serotonin effect on motility of the duodenum,ileum, and jejunum in awake rabbits

I. v. administration of serotonin to alert rabbits produced a phasic change of contractile activity of duodenum, ileum, and jejunum including excitatory and inhibitory components. It is shown that stimulation of the small bowel motility is caused by serotonin activation of non-cholinergic excitatory mechanism with participation of effector cholinergic neurones. The initial suppression of the motility is caused by participation of nonadrenergic noncholinergic inhibitory mechanism, and the secondary inhibition of contractile activity of a small bowel with serotonin has an adrenergic nature.     

Transport of putrescine across duodenal,jejunal and ileal brush-border membrane of chicks (Gallus domesticus)

Luminal polyamines and their absorption are essential for proliferation of the enterocytes and, therefore, nutrition, health and development of the animal. The transport systems that facilitate the uptake of putrescine were characterized in chick duodenal, jejunal and ileal brush-border membrane vesicles prepared by MgCl2 precipitation from three-week-old chicks. An inwardly-directed Na+ gradient did not stimulate putrescine uptake and, therefore, putrescine transport in chick intestine. In the duodenum, jejunum and ileum, kinetics of putrescine transport fitted a model with a single affinity component plus a non-saturable component. The affinity (Kt) for [3H]putrescine transport across the brush-border membrane increased along the length of the small intestine. A model of intermediate affinity converged to the data obtained for [3H]putrescine transport with Kt approximating 1.07 and 1.05 mM or duodenum and jejunum, respectively; and high affinity with a Kt of 0.35 mM for the ileum. The polyamines cadaverine, putrescine, spermidine and spermine strongly inhibited the uptake of [3H]putrescine into chick brush-border membrane vesicles, more so for the jejunum and ileum than the duodenum. The kinetics of cadaverine, spermidine and spermine inhibition are suggestive of competitive inhibition of putrescine transport. These uptake data indicate that a single-affinity system facilitates the intestinal transport of putrescine in the chick; and the affinity of transporter for putrescine is higher in the ileum than in the proximal sections of the small intestine. In addition, this study shows that the ileum of chicks plays an important role in regulating cellular putrescine concentration.     

Distribution and heterogeneity of immunoreactive cholecystokinin (CCK) in the mucosa of the porcine gastrointestinal tract

The concentration and molecular nature of cholecystokinin-like immunoreactivity (CCK-LI) in extracts of porcine intestinal mucosa were determined using sequence-specific radioimmunoassays. Highest CCK concentrations were measured in duodenal mucosa (258 +/- 60 pmol/g in the distal duodenum) followed by jejunal mucosa (204 +/- 36 pmol/g in the proximal jejunum) and pylorus (51 +/- 9 pmol/g). All other gastrointestinal regions proximal to the pylorus and distal to the jejunum contained less than 20 pmol/g. Pancreas contained less than 1 pmol/g. Gel chromatography in 6 M urea revealed four immunoreactive forms and this was confirmed by reverse-phase high-pressure liquid chromatography (HPLC). The predominant molecular form in acid extracts of duodenal mucosa resembled CCK-33 although high concentrations of the larger CCK form ('CCK-58') and of the form intermediate in size between CCK-33 and CCK-8 were measured. A molecular form resembling CCK-8 was the principal form in neutral extracts of the duodenum.     

Characterization of brush border membrane-bound alkaline phosphatase activity in different segments of the porcine small intestine

This study was conducted to characterize enterocyte apical membrane-bound alkaline phosphatase activity in different segments of the porcine small intestine. Duodenal, jejunal, and distal ileal segments were isolated from three 26-kg pigs and enterocyte brush border membrane, enriched between 19- and 24-fold in sucrase specific activity, was prepared by Mg(2+) precipitation and differential centrifugation. With P-nitrophenyl phosphate as substrate, the optimum pH for porcine brush border membrane-bound alkaline phosphatase activity was defined to be 10.5 for all three segments. At the optimal pH, the kinetics of membrane-bound alkaline phosphatase were determined for the three intestinal segments. The affinity of this enzyme (K(m), mM) in the jejunum (0.64 +/- 0.07) was four times greater than that in the duodenum (2.75 +/- 0.59) and the distal ileum (2.71 +/- 1.14). These results indicate that different isomers of membrane-bound alkaline phosphatase might have been expressed in different segments of porcine small intestine. The maximal specific activity (V(max), micromol/mg protein . min) of this enzyme was highest in the duodenal (7.74 +/- 0.95), intermediate in the jejunal (4.31 +/- 0.18), and lowest in the distal ileal (3.53 +/- 0.84) brush border membrane. Therefore, the maximal specific activity of brush border membrane-bound alkaline phosphatase along the intestinal longitudinal axis in growing pigs decreases from the duodenum toward the distal ileum.     

Effects of met-enkephalin on the mechanical activity and distribution of met-enkephalin-like immunoreactivity in the cat small intestine

Naloxone-dependent effects of Met-enkephalin (10(-8) M) on the spontaneous and electrically induced mechanical activities were studied in longitudinal and circular preparations isolated from the cat duodenum, jejunum and ileum. Met-Enkephalin changed the spontaneous activity of all preparations tested with the exception of the circular preparations from the ileum. Met-Enkephalin-induced responses of the longitudinal preparations from the ileum were abolished by treatment with tetrodotoxin (10(-7) M), while the responses of both longitudinal and circular preparations from the duodenum and jejunum were only partially depressed, being resistant to tetrodotoxin components. The latter were most pronounced in the duodenum. The neurogenic electrically induced (0.5 msec, 5 Hz, 150 pulses) responses of all the preparations consisted mainly of contractile components which were significantly and naloxone-dependently reduced by Met-enkephalin (10(-8) M). The contractile components of the responses, which were reduced by Met-enkephalin, were entirely abolished by atropine (3 x 10(-6) M). Both Met-enkephalin and atropine inhibitory effects on the neurogenic responses were more pronounced in the ileum. Met-Enkephalin was found in nerve fibers of the myenteric plexus distributed mainly among the circular muscle. Single immunoreactive nerve fibers were observed in the longitudinal muscle layer of the duodenum but not in the jejunum and ileum. The distribution of Met-enkephalin-like immunoreactivity along the small intestine did not show significant differences among the three intestinal regions tested. The results obtained suggest that Met-enkephalin can modulate the mechanical activity of the cat small intestine, inhibiting cholinergic transmission and/or activating smooth muscle opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Small Bowel Stromal Tumors: Different Clinicopathologic and Computed Tomography Features in Various Anatomic Sites

Gastrointestinal stromal tumors (GISTs) can present with different clinical and immunohistochemical characteristics according to different anatomic sites. The aim of this study was to compare clinicopathologic and computed tomography (CT) features of small bowel stromal tumors located in the duodenum, jejunum, and ileum. In total, 197 patients (109 male, 88 female) with small bowel GISTs were retrospectively reviewed. All tumors had definite anatomic sites in the small bowel tract with surgical confirmation. The clinicopathologic variables included age, sex, onset of symptoms, and tumor risk category. CT variables included tumor size, degree enhancement, enhancement pattern (region of necrosis), adjacent tissue involvement, lymphadenopathy, and distant metastasis. We assessed any possible differences according to different GIST site of origin. Based on tumor size and mitotic count, the risk categories in different anatomic sites did not differ significantly between duodenal and jejunal GISTs. However, high risk ileum GISTs accounted for 66.0% of ileal cases, which was higher than duodenum cases (36.8%, P = 0.002) and jejunum cases (43.9%, P = 0.004). The mean size of GISTs in the ileum was 9.77 cm, which was significantly larger than in the duodenum (7.41 cm, P = 0.043), and in the jejunum (8.14 cm, P = 0.027). On CT images, enhancement degree appeared to gradually increase from the duodenum to the ileum in the portal phase, and the enhancement pattern presented a tendency for heterogeneity. In Conclusions, the clinicopathologic and CT features of small bowel GISTs can differ according to different primary anatomic sites.     

Regional differences in the appearance of adult-type glycosphingolipids in the small intestine of inbred rats at weaning time

The small intestine of 15- to 33-day-old rats was cut into four segments: duodenum, proximal jejunum, distal jejunum, and ileum. Neutral glycosphingolipids and gangliosides were purified from each segment and analyzed by thin-layer chromatography in order to study the developmental appearance of adult-type glycolipids at each level of the small intestine. Type 1 A-6 glycolipid was first detected in the ileum at 15 days and subsequently in the jejunum and duodenum at 19 days of age. N-Glycolylneuraminic acid was expressed first in the ileum at 17 days, then in the proximal jejunum at 21 days, but only after 29 days in the duodenum. In each region, 6-8 days were required between first detection and full expression of N-glycolylneuraminic acid. The presence of 2-hydroxylated fatty acids in glucosylceramide was found first in the ileum at 19 days, 2-3 days before appearing in the duodenum and proximal jejunum. A period of 2-3 days was necessary to reach full adult-type level of 2-hydroxylated fatty acids in glucosylceramide. These results show that adult-type glycolipids appear earlier in the distal than in the proximal region of the rat small intestine, and that different glycolipids appear at different times and at different rates. The finding that the biochemical differentiation of the whole small intestine expands over a period of 3 days to 2 weeks, depending on the region and the glycolipid, before being fully completed indicates that, in addition to the time lag observed between the distal and the proximal region, the new cells arising from the crypt of Lieberkhün after 15 days of age are not at once fully differentiated.     

The effects of ethylenediamine in the rat small intestine: a powerful relaxant of the muscularis.

The pharmacology of ethylenediamine (EDA) actions in the rat small intestine was examined using isolated gut-bath preparations of proximal segments of the duodenum, jejunum, and ileum. EDA evoked concentration-dependent tetrodotoxin-insensitive relaxations of the intestine, evidently by direct action on the muscularis. Such actions were simultaneous on the longitudinal and circular muscle layers. Investigation of EDA actions on the circular muscle showed that EDA actions were unrelated to any intrinsic GABAergic mechanisms. Moreover, EDA interacted with muscle sites distinct from ATP, histamine, bradykinin, muscarinic, and adrenergic receptors. The ability of EDA to relax the intestinal musculature was generally greater than the smooth muscle relaxant papaverine and substantially better than nicotinic stimulation of the intrinsic inhibitory neurones. It would appear that EDA may be useful as a direct acting smooth muscle relaxant for the study of the physiology-pharmacology of the rodent small intestine.     

Opioid-induction of migrating motor activity in chickens.

Enkephalin and morphine initiation of phase III of MMC has been reported in dog and humans. In chickens, a similar migrating activity initiated at the duodenum occurs 7-9 times a day while the gastric activity ceases. The main objective was to determine whether this migrating activity could be induced by opioids. Electrodes for electromyography were implanted in the stomach, proximal and distal duodenum, jejunum and proximal and distal ileum of 4 wk old chickens. Met-enkephalin, morphine and beta-casomorphin-5 (5 x 10(-7) moles/Kg) were infused i.v.. All these substances initiated an intestinal migrating activity concurrent with gastric inhibition. The mean duration of gastric inhibition depended on the substance, lasting from 5 min (met-enkephalin) to 27 min (beta-casomorphin-5). The migrating activity started in the distal duodenum and propagated to the ileum in about 18 min. These effects were partially blocked by naloxone at equimolar doses. In conclusion, in chickens, as in dogs and humans, migrating myoelectrical activity can be initiated by opioids.