Intestinal occlusion: morphological features

In this research we studied the possible relationships between the level and the distribution of peroxidase-catalase activity and the degree of the morphological changes in the intestinal wall during mechanical occlusion. These researches have really proved that the increase of the peroxidase-catalase enzymes correlate proportionally with the damage of intestinal wall.     

Effect of Schistosoma mansoni-induced granulomatous inflammation on murine gastrointestinal motility

In Schistosoma mansoni-infected mice, gastrointestinal transit was measured in vivo and the neuromuscular function of longitudinal muscle strips of inflamed ileum and noninflamed gastric fundus was assessed in vitro. Eight weeks after infection, the ileal wall was acutely inflamed, as shown by a mucosal inflammatory infiltrate, leading to an increase in mucosal thickness, in myeloperoxidase (MPO) activity, and in interleukin (IL)-1beta production. At that time, both gastrointestinal transit and in vitro ileal contractility were normal. Twelve weeks after infection, chronic granulomatous inflammation led to proliferation of the muscle layer and to a further increase in MPO activity, whereas IL-1beta production normalized. Gastrointestinal transit was decreased, whereas in vitro ileal contractility was increased irrespective of the contractile stimulus. In vitro incubation with IL-1beta (10 ng/ml for 60 min) significantly increased ileal contractility only at 8 wk after infection. Indomethacin, tetrodotoxin, and atropine had no differential effect on ileal contractility in controls and infected mice. In vitro contractility of noninflamed gastric fundus was normal both 8 and 12 wk after infection. We conclude that intestinal schistosomiasis 8 wk after infection is associated only with structural changes of the ileum, whereas 12 wk after infection, both structural and functional changes are present. These changes are characterized by increased ileal wall thickness, decreased gastrointestinal transit, and increased smooth muscle contractility restricted to the inflamed gut segment.     

Effect of CCK-8 on myoelectrical activity of the gastrointestinal tract in the conscious miniature pig

In conscious miniature pigs, with implanted electrodes in the wall of the antrum pylori, duodenum, jejunum, and ileum, the influence of IV infusions of CCK-8 (17.5 and 175 pM/kg/min) on gastrointestinal myoelectrical activity was measured. Although both doses under study induced a decrease in antral spike activity, only the higher dose resulted in an overall decrease in integrated myoelectrical activity. In the ileum both doses augmented spiking activity during the infusion, but inhibited electrical activity after the end of the infusion. No response was observed in the duodenum and jejunum. The experiments demonstrate the overall inhibitory effect of CCK-8 on antral electrical activity and its stimulatory influence on ileal smooth muscle.     

Significance of microflora in proteolysis in the colon.

Protease activities in human ileal effluent and feces were compared by using a variety of native and diazotized protein substrates. In many cases the diazotized proteins had altered susceptibilities to hydrolysis compared with the native proteins. Proteolytic activity was significantly greater than (P less than 0.001) in small intestinal effluent than in feces (319 +/- 45 and 11 +/- 6 mg of azocasein hydrolyzed per h per g, respectively). Moreover, fecal proteolysis was qualitatively different in that ileal effluent did not hydrolyze the highly globular protein bovine serum albumin, whereas all fecal samples tested degraded this substrate. Inhibition experiments provided further evidence that fecal protease activity differed from that in the small intestine. Physical disruption of fecal bacteria released large quantities of proteases, indicating that the lysis of bacteria in the colon may contribute to the extracellular proteolytic activity in feces. Protease inhibition studies with washed fecal bacteria showed that they produced serine, cystine, and metalloproteases, and experiments with synthetic p-nitroanilide substrates indicated that low levels of trypsin- and chymotrypsin-like activities were associated with whole cells. An elastase-like enzyme was bound to the outer membranes of some fecal bacteria.     

Significance of microflora in proteolysis in the colon

Protease activities in human ileal effluent and feces were compared by using a variety of native and diazotized protein substrates. In many cases the diazotized proteins had altered susceptibilities to hydrolysis compared with the native proteins. Proteolytic activity was significantly greater than (P less than 0.001) in small intestinal effluent than in feces (319 +/- 45 and 11 +/- 6 mg of azocasein hydrolyzed per h per g, respectively). Moreover, fecal proteolysis was qualitatively different in that ileal effluent did not hydrolyze the highly globular protein bovine serum albumin, whereas all fecal samples tested degraded this substrate. Inhibition experiments provided further evidence that fecal protease activity differed from that in the small intestine. Physical disruption of fecal bacteria released large quantities of proteases, indicating that the lysis of bacteria in the colon may contribute to the extracellular proteolytic activity in feces. Protease inhibition studies with washed fecal bacteria showed that they produced serine, cystine, and metalloproteases, and experiments with synthetic p-nitroanilide substrates indicated that low levels of trypsin- and chymotrypsin-like activities were associated with whole cells. An elastase-like enzyme was bound to the outer membranes of some fecal bacteria.     

Mutants of Streptococcus pneumoniae that contain a temperature-sensitive autolysin

Two mutants of Streptococcus pneumoniae deficient in autolysin activity produced a protein that showed immunological identity with the N-acetyl-muramyl-L-alanyl-amidase present in the wild-type strain, when tested with antiserum obtained against this enzyme. The protein was produced by the mutant cultures grown either at 37 degrees C or at 30 degrees C, although only the cell extracts obtained at 30 degrees C showed significant cell wall hydrolysing activity. In contrast to the lysis resistance of these bacteria grown at 37 degrees C, mutant cultures grown at 30 degrees C exhibited significant degrees of autolysis when treated with detergent or cell wall inhibitors. Extracts of the mutant cultures contained a cell wall hydrolysing activity that was rapidly inactivated during incubation at 37 degrees C.     

The ectopic expression of a pectin methyl esterase inhibitor increases pectin methyl esterification and limits fungal diseases in wheat

Cell wall pectin methyl esterification can influence plant resistance because highly methyl-esterified pectin can be less susceptible to the hydrolysis by pectic enzymes such as fungal endopolygalacturonases (PG). Pectin is secreted into the cell wall in a highly methyl-esterified form and, here, is de-methyl esterified by pectin methyl esterase (PME). The activity of PME is controlled by specific protein inhibitors called PMEI; consequently, an increased inhibition of PME by PMEI might modify the pectin methyl esterification. In order to test the possibility of improving wheat resistance by modifying the methyl esterification of pectin cell wall, we have produced durum wheat transgenic lines expressing the PMEI from Actinidia chinensis (AcPMEI). The expression of AcPMEI endows wheat with a reduced endogenous PME activity, and transgenic lines expressing a high level of the inhibitor showed a significant increase in the degree of methyl esterification. These lines showed a significant reduction of disease symptoms caused by the fungal pathogens Bipolaris sorokiniana or Fusarium graminearum. This increased resistance was related to the impaired ability of these fungal pathogens to grow on methyl-esterified pectin and to a reduced activity of the fungal PG to hydrolyze methyl-esterified pectin. In addition to their importance for wheat improvement, these results highlight the primary role of pectin despite its low content in the wheat cell wall.     

Radiation effects on diamine oxidase activities in intestine and plasma of the rat

Diamine oxidase (DAO; EC 1.4.3.6) activity was measured in plasma and in ileal tissue homogenates prepared from male Sprague-Dawley rats euthanized at 1-15 days after acute whole-body irradiation with 14.5-MeV electrons. Animals irradiated with 1 Gy showed no diminution in plasma and ileal DAO activities through Day 13 relative to nonirradiated controls. Animals irradiated with 5, 10, and 12 Gy displayed marked declines in ileal DAO activity, with levels reaching a nadir on Day 3. This was paralleled by a decrease in plasma DAO activity in all three dose groups. Recovery of ileal and plasma DAO levels was later seen as early as Day 4 in animals irradiated with 5- and 10-Gy doses, but animals receiving 12 Gy did not survive beyond Day 3. The relationship between radiation dose and levels of plasma and ileal DAO on Day 3, the time of maximum decrease at all doses, was also investigated. Ileal DAO activity decreased almost linearly between 2 and 8 Gy. Plasma DAO activity closely paralleled the dose dependency of the ileal levels. These data suggest that plasma DAO activity might be useful as a biologic marker of intestinal epithelial injury and recovery after acute radiation exposure.     

Vasoactive intestinal polypeptide: increased tone, enhancement of acetylcholine release, and stimulation of adenylate cyclase in intestinal smooth muscle

Vasoactive intestinal polypeptide (VIP) was examined $\text{in vitro}$ for effects on tone and neuronal release mechanisms in intestinal smooth muscle since this is a site of high peptide concentration. VIP contracted the guinea pig ileum and rabbit jejunum in concentrations ranging from 10^?9 to 10^?7 M. Increased tone in the guinea pig ileum was partially antagonized by the anticholinergic agent, atropine (4.38 × 10^?6 M) suggesting that one component of the contractile response was due to the indirect release of acetylcholine. The H₁ receptor antagonist, pyrilamine, did not alter the increased tone produced by VIP indicating that histamine release did not contribute to the ileal contractile response and that VIP exerted a selective effect to enhance neuronal release of acetylcholine. The ability of VIP to modulate acetylcholine release was confirmed in field stimulated ileal preparations where VIP increased the force developed to endogenously released acetylcholine without altering the direct response to acetylcholine. In rabbit jejunum and ileal smooth muscle, VIP related cyclic AMP levels. However, inhibition of phosphodiesterase with papaverine did not potentiate either the VIP-induced ileal contraction or enhancement of the field stimulated response. This raises the possibility that increases in intestinal cyclic AMP may be involved more in VIP-induced alterations in ion transport or secretory phenomenon than in intestinal motility. These studies describing the ability of VIP to modulate acetylcholine release and to increase ileal tone are consistent with the proposed role of VIP in intestinal patholgies involving excessive mucous secretion and motility.     

Biological characteristics of an enterotoxin produced by Bacillus cereus.

An enterotoxin synthesized during exponential growth by Bacillus cereus produces fluid accumulation in rabbit ileal loops, alters vascular permeability in the skin of rabbits, and kills mice when injected intravenously. All activities are eluted simultaneously from a Sephadex G-75 column and are distinct from the hemolysin and egg yolk turbidity factor of B. cereus. The enterotoxin is a true exotoxin. It interacts with intestinal receptor sites in a highly transient manner in the ileal loop system. Rabbit immune serum produced against the culture fluids from one strain of B. cereus neutralized the three biological activities in all other strains tested except strain B-6-ac for which none of the activities were neutralized. Enterotoxin proved to be unstable under a wide variety of conditions; ionic strength was especially critical. Enterotoxin was most stable in a pH range of 5.0 to 10.0, but lost activity rapidly outside this range. Alkylation provided some protection of enterotoxin activity in crude preparations but failed to protect activity during purification procedures. It did not appear to affect critically the enterotoxin molecule itself, since elution profiles on Sephadex G-75 chromatography were unchanged after alkylation.     

Potential pathogenic factors produced by a clinical nontoxigenicVibrio cholerae O1

A clinical isolate of nontoxigenicVibrio cholerae O1 that caused intestinal fluid accumulation (FA) in adult mice produced proteolytic, hemolytic, and cytotoxic activities in in vitro assays. The linkage of these secreted factors to the FA activity was studied by transposon (TnphoA) mutagenesis. Ten of the 12 TnphoA insertion mutants that were defective for proteolytic activity produced FA, hemolytic and cytotoxic activities; the remaining two mutants lost these latter three activities. These results indicate that FA activity is independent of proteolytic activity but closely associated with cytotoxic and hemolytic activities. Our results with the adult mouse model and a nontoxigenicV. cholerae O1 are in general agreement with previous studies that demonstrated linkage of cytotoxin and hemolysin of toxigenicV. cholerae O1 and non-O1 with FA activity in rabbit ileal loops.     

Proton-Binding Capacity of Staphylococcus aureus Wall Teichoic Acid and Its Role in Controlling Autolysin Activity

Wall teichoic acid (WTA) or related polyanionic cell wall glycopolymers are produced by most Gram-positive bacterial species and have been implicated in various cellular functions. WTA and the proton gradient across bacterial membranes are known to control the activity of autolysins but the molecular details of these interactions are poorly understood. We demonstrate that WTA contributes substantially to the proton-binding capacity of Staphylococcus aureus cell walls and controls autolysis largely via the major autolysin AtlA whose activity is known to decline at acidic pH values. Compounds that increase or decrease the activity of the respiratory chain, a main source of protons in the cell wall, modulated autolysis rates in WTA-producing cells but did not affect the augmented autolytic activity observed in a WTA-deficient mutant. We propose that WTA represents a cation-exchanger like mesh in the Gram-positive cell envelopes that is required for creating a locally acidified milieu to govern the pH-dependent activity of autolysins.     

Organ-dependent differences in composition and function observed in hepatic and intestinal granulomas isolated from mice with Schistosomiasis mansoni

In murine schistosomiasis mansoni, eggs deposited in the liver and intestines induce a cell-mediated granulomatous reaction. Previous studies have shown that maximal granuloma size differs in the liver and various segments of the gastrointestinal tract. The objective of this investigation was to isolate intestinal granulomas and to determine whether organ-dependent differences in cell composition and granuloma function exist. Intestinal granulomas representative of those in tissue were isolated by a combination of chemical and mechanical techniques. When dissociated by collagenase, these lesions yielded a viable heterogeneous population of inflammatory cells. Granulomas from the liver, colon, and ileum showed differences in cellular composition. Liver lesions contained the largest number of T and B lymphocytes, eosinophils, and mast cells whereas ileal granulomas comprised mostly macrophages. Immunofluorescence studies on frozen tissue sections revealed that T and B lymphocytes also displayed different patterns of distribution within granulomas from different tissues. In contrast to isolated cultured liver granulomas that produced MIF-like substances, isolated colonic and ileal granulomas had weak or no MIF activity. It thus appears that granuloma formation in various organs is influenced by local factors that could affect the ultimate resolution of the lesions.     

Effect of dietary carbohydrates on bacterial cholyltaurine hydrolase in poultry intestinal homogenates.

The bile salt hydrolase activity in intestinal homogenates reflects composite activities of the gastrointestinal microbial consortia. We have proposed that specific transformations of conjugated bile acids by the intestinal microflora result in the production of metabolites which depress the growth of poultry. The influence of dietary carbohydrates on the physical and kinetic properties of cholyltaurine hydrolase activity, one such bile acid-transforming enzyme in gastrointestinal homogenates of young chickens, was characterized by using a sensitive radiochemical assay. Cholyltaurine hydrolase activity in crude extracts of ileal homogenates was increased twofold by 0.25% Triton X-100 and a freeze-thaw cycle. The pH optimum for cholyltaurine hydrolase from ileal homogenates was very broad and reflected the pH range of poultry intestinal contents (i.e., 5.8 to 6.4). The carbohydrate component of the diet did not affect the apparent temperature optimum (41 degrees C) or stability profile, nor did it affect the apparent Km for taurocholic acid hydrolysis (approximately 0.43 mM). The enzymes in intestinal homogenates were active on all taurine-conjugated bile acids tested. The carbohydrate component of the diet did, however, affect the specific activity of cholyltaurine hydrolase in ileal homogenates from chickens. The levels of cholyltaurine hydrolase activity (rye greater than sucrose greater than corn) in homogenates from birds fed the different diets were directly related to the amount of growth depression (rye greater than sucrose greater than corn) associated with feeding these dietary carbohydrates. These data suggest that intestinal levels of cholyltaurine hydrolase are correlated with the amount of carbohydrate-induced growth depression in poultry.     

Effect of dietary carbohydrates on bacterial cholyltaurine hydrolase in poultry intestinal homogenates

The bile salt hydrolase activity in intestinal homogenates reflects composite activities of the gastrointestinal microbial consortia. We have proposed that specific transformations of conjugated bile acids by the intestinal microflora result in the production of metabolites which depress the growth of poultry. The influence of dietary carbohydrates on the physical and kinetic properties of cholyltaurine hydrolase activity, one such bile acid-transforming enzyme in gastrointestinal homogenates of young chickens, was characterized by using a sensitive radiochemical assay. Cholyltaurine hydrolase activity in crude extracts of ileal homogenates was increased twofold by 0.25% Triton X-100 and a freeze-thaw cycle. The pH optimum for cholyltaurine hydrolase from ileal homogenates was very broad and reflected the pH range of poultry intestinal contents (i.e., 5.8 to 6.4). The carbohydrate component of the diet did not affect the apparent temperature optimum (41 degrees C) or stability profile, nor did it affect the apparent Km for taurocholic acid hydrolysis (approximately 0.43 mM). The enzymes in intestinal homogenates were active on all taurine-conjugated bile acids tested. The carbohydrate component of the diet did, however, affect the specific activity of cholyltaurine hydrolase in ileal homogenates from chickens. The levels of cholyltaurine hydrolase activity (rye greater than sucrose greater than corn) in homogenates from birds fed the different diets were directly related to the amount of growth depression (rye greater than sucrose greater than corn) associated with feeding these dietary carbohydrates. These data suggest that intestinal levels of cholyltaurine hydrolase are correlated with the amount of carbohydrate-induced growth depression in poultry.     

Humoral factors released during trauma ofAplysia body wall

1. Mechanical or electrical stimulation of isolated sections of body wall produced contractions that were graded with the intensity of the stimulus. Injury of body wall with shallow incisions produced extremely persistent contractions. 2. Long-lasting contraction of isolated body wall was also produced by brief application of "stimulated body wall wash" (SBW), sea water which was first washed through another section of body wall subjected to intense mechanical or electrical stimulation. Contractions were produced by SBW diluted to concentrations as low as 1% of the initial concentration. Contractions produced by prolonged application of SBW showed little fatigue, tachyphylaxis, or desensitization. 3. SBW caused contraction of isolated sections of body wall from all regions of the body, including tail, parapodia, siphon, purple gland, rhinophores, and anterior tentacles. SBW also caused contraction of isolated lateral columellar muscle and of the gill. 4. 30 mM CoCl2 blocked the release of contractile factors into electrically stimulated body wall and reduced but did not abolish contractile responses of unstimulated body wall to perfused SBW. SBW contractions were unchanged by disconnection of the perfused tissue to the CNS. 5. Hemolymph collected from the neck of an intact donor following strong electrical stimulation of the tail or excision of a parapodium ('stimulated hemolymphh, SHL) caused long-lasting contractions which were larger than those produced by control hemolymph (CHL) collected prior to stimulation of the donor. 6. Similarities between body wall contractions produced by SHL and by SBW, including their occurrence in 30 mM CoCl2, suggest that some of the contractile activity in SHL may be directly released from traumatized body wall. 7. SHL caused significantly greater cardioacceleration of the isolated heart than did CHL. Similarities between the cardioacceleration produced by SHL and by SBW suggest that a source of cardiac activity in SHL may be traumatized body wall. 8. SBW suppressed the gill-withdrawal reflex when applied selectively to the sheathed or desheathed abdominal ganglion. SBW-induced suppression was associated with significant reduction of evoked spike activity in identified gill motor neurons. SHL collected 1-2 h after noxious stimulation caused weak but significant suppression of the gill-withdrawal reflex when applied to the fully sheathed abdominal ganglion.     

Effects of ethinyl estradiol on intestinal membrane structure and function in the rabbit

Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment.     

Changes in bacterial composition and enzymatic activity in ileostomy and ileal reservoir during intermittent occlusion: a study using dogs.

Bacterial flora, activities of 10 potential mucus- and dietary polysaccharide-degrading enzymes, blood group antigenicity of the intestinal glycoproteins, and proteolytic activity in the output from experimentally colectomized dogs with conventional ileostomies and dogs with valveless ileal reservoirs (pouches) were determined. The ileostomies of dogs with conventional surgery (group II) and with pouches (group III) were occluded intermittently during a 6-week period. The duration of occlusion was progressively increased. Group I, five dogs with conventional ileostomies, served as a control group. After occlusion of the ileal pouch for 7 h, total numbers of bacteria increased threefold, glycosidase activity increased fivefold, and blood group antigenicity of the intestinal glycoproteins, which was high in the output from the nonoccluded pouch, was no longer detectable. Proteolytic activity was not influenced by occlusion of the pouch. Significantly lower numbers of bacteria, only minor glycosidase activity, high blood group antigenicities of the intestinal glycoproteins, and higher proteolytic activity were found in ileostomy effluents from groups I and II. Histopathological examination showed chronic inflammation and changes in crypt-villus ratio in all dogs with ileal reservoirs; the ileal mucosa from the dogs with conventional ileostomies did not show any abnormalities. Consequences of the flora-related enzyme activities for the ileal mucosa are discussed.     

Changes in bacterial composition and enzymatic activity in ileostomy and ileal reservoir during intermittent occlusion: a study using dogs.

Bacterial flora, activities of 10 potential mucus- and dietary polysaccharide-degrading enzymes, blood group antigenicity of the intestinal glycoproteins, and proteolytic activity in the output from experimentally colectomized dogs with conventional ileostomies and dogs with valveless ileal reservoirs (pouches) were determined. The ileostomies of dogs with conventional surgery (group II) and with pouches (group III) were occluded intermittently during a 6-week period. The duration of occlusion was progressively increased. Group I, five dogs with conventional ileostomies, served as a control group. After occlusion of the ileal pouch for 7 h, total numbers of bacteria increased threefold, glycosidase activity increased fivefold, and blood group antigenicity of the intestinal glycoproteins, which was high in the output from the nonoccluded pouch, was no longer detectable. Proteolytic activity was not influenced by occlusion of the pouch. Significantly lower numbers of bacteria, only minor glycosidase activity, high blood group antigenicities of the intestinal glycoproteins, and higher proteolytic activity were found in ileostomy effluents from groups I and II. Histopathological examination showed chronic inflammation and changes in crypt-villus ratio in all dogs with ileal reservoirs; the ileal mucosa from the dogs with conventional ileostomies did not show any abnormalities. Consequences of the flora-related enzyme activities for the ileal mucosa are discussed.