Additive effects of thermal injury and infection on the small bowel.

Thermal injury is associated with functional alterations of multiple organ systems, including the gastrointestinal tract. To study the effects of ongoing infection after thermal injury on bowel mass, composition, and blood flow, male Wistar rats were randomized to receive either 30% scald burn, 30% scald burn with Pseudomonas aeruginosa wound inoculation, sham burn, or sham burn with pair feeding to burned and infected animals. On days 3 and 7 after injury, intestinal blood flow was measured with 51Cr-labeled microspheres, and intestinal mass and composition were analyzed. Burned and infected animals demonstrated a chronic loss of small bowel mass not seen in burned animals without infection by day 7 after injury. Compositional alterations of the small bowels of burned and infected animals included protein wasting similar to but occurring earlier than that seen with anorexia alone and significantly decreased deoxyribonucleic acid and ribonucleic acid content, whereas tissue water content remained unchanged. These chronic intestinal alterations in the burned and infected group could not be explained by ongoing ischemia because intestinal blood flow in these animals was not significantly altered at either time point, implying mediation by other pathophysiologic mechanisms.

Molecular variants of cholecystokinin after endogenous stimulation in humans: a time study.

The time-dependent release of molecular variants of cholecystokinin (CCK) into the circulation was studied before and 1, 2, and 4 h after a test meal in six healthy volunteers. At each time period, 100 ml of blood were drawn in a manner to inhibit CCK degradation. Plasma was formed and CCK concentrated by Sep-Pak C18 cartridge chromatography. Molecular variants of CCK and gastrin were well separated from each other by high-performance liquid chromatography (HPLC). Molecular forms of CCK and gastrin were measured by radioimmunoassay using an antibody that requires the presence of the carboxyl-terminal phenylalanine amide for full recognition, implying that biologically active forms were detected. HPLC elution positions of gastrin forms were determined using a gastrin-specific antibody. Chromatographic separation of CCK from gastrin forms was complete, allowing separate integration of gastrin and CCK forms. Therefore no subtraction of gastrin-like immunoreactivity from CCK-like immunoreactivity (CCK-LI) was necessary and CCK-LI could be directly determined. Peaks of CCK-LI were integrated in the column eluates and the plasma concentrations were calculated. Total plasma CCK-LI rose from a value of 2.4 +/- 0.6 pM before the test meal to 6.4 +/- 0.8, 6.6 +/- 0.9, and 5.8 +/- 1.2 pM 1, 2, and 4 h postprandially. The major molecular forms released into the circulation eluted on HPLC in the position of CCK-58 and CCK-39 (which coelutes with CCK-33). Minor amounts were detected in the position of CCK-8. There was no significant difference in the relative proportions of the molecular forms released at the different time periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunolocalization of transferrin and transferrin receptor in mouse small intestinal absorptive cells.

The mechanisms by which the duodenal mucosa absorbs iron are unknown. Insorption into absorptive cells of luminal iron bound to transferrin via receptor-mediated endocytosis has been hypothesized, but transferrin and transferrin receptor are absent in apical microvillous brush borders of small bowel biopsies taken from fasted patients and normal volunteers. We hypothesized that a normal iron-containing diet might induce the transient appearance of transferrin and transferrin receptor in apical brush borders of small intestinal absorptive cells in a normal mouse that was provided iron-containing chow until the moment of sacrifice. Light and electron microscopic immunolocalization of transferrin and transferrin receptor in proximal small intestinal absorptive cells was limited to basolateral membranes and coated pits of cells predominantly in the crypts and basal regions of the villi. Transferrin and transferrin receptor were not detected in apical microvillous brush border membranes of these enterocytes. In parallel immunolocalization protocols designed to show the ability to immunodetect other antigens at these locations, maltase and proteoglycan were demonstrated in apical microvillous brush border membranes and in basolateral membranes, respectively, in absorptive cells of small intestinal villous tip, base, and crypt regions. Furthermore, transferrin and transferrin receptor were immunolocalized in hepatocyte sinusoidal microvillus membranes. We conclude that food does not induce the appearance of immunodetectable transferrin and transferrin receptor in the apical microvilli of small intestinal absorptive cells and, therefore, that these iron transport proteins are not involved in the apical microvillous membrane transport of luminal dietary iron.

Interleukins 1 and 3 stimulate anion secretion in chicken intestine.

Interleukin 1 or 3 added to the serosal side of chicken small intestine transiently increases short-circuit current. Replacement of bathing-medium Cl and HCO3 with gluconate and HEPES abolished the short-circuit current increase, consistent with these cytokines stimulating electrogenic anion secretion. Cytokine-stimulated short-circuit current changes were inhibited by preincubation with piroxicam (10(-5) M), an inhibitor of arachidonic acid cyclooxygenase, suggesting prostaglandin formation as an intermediate step for cytokine stimulation of short-circuit current. In intact mucosal strips, interleukin 1 and 3 stimulated prostaglandin E2 release and elevated tissue 3',5'-cyclic adenosine monophosphate concentration. When prostaglandin E2 release from epithelial and subepithelial fractions of the mucosa by interleukin 1 was determined, increases were found only from the subepithelium. The secretory actions of cytokines appear to be mediated by arachidonic acid metabolites most likely produced by cells of the lamina propria and submucosa and may play a role in inflammatory processes in which intestinal secretion is enhanced.

Diet-induced alterations of lipids during cell differentiation in the small intestine of growing rats: effect of an essential fatty acid deficiency.

The lipid components of columnar cells harvested from rat small intestine were analyzed at each step of cell maturation. The effect of dietary lipids on the evolution of lipids in differentiating cells was studied using two diets representative either of a control or of an essential polyunsaturated fatty acid deficient lipid supply. Two groups of weanling rats were fed a semisynthetic diet composed of corn oil (control diet) or hydrogenated coconut oil (deficient diet) for 11 weeks. Intestinal cells were extracted according to their position along the villus column. Linoleic and arachidonic acids constitutive of cell phospholipids increased as cells migrated from the lower to the mid-part of the crypt-villus axis only with the control diet. This gradient disappeared after a 3-week feeding period with hydrogenated coconut oil diet so that columnar cells of essential fatty acid deficient rats exhibited the same overall fatty acid composition all along the crypt-villus axis. Essential fatty acid deficiency resulted in an increase of both the triene to tetraene and arachidonic acid to linoleic acid weight ratios regardless of the maturational step of cells. As compared to the control diet, the essential fatty acid deficient diet induced a decrease of both the cholesterol and free fatty acid to phospholipid molar ratios only in lower villus cells. We conclude that (a) progressive compositional modifications of lipids occur while ascending the crypt-villus axis and (b) essential fatty acid deficiency induces substantial alterations of the lipid evolution normally linked to cell differentiation.

Isolation and microsequence analysis of a novel form of neuromedin U from guinea pig small intestine.

A multidimensional chromatographic regimen has been used to isolate and purify a peptide showing immunoreactivity for neuromedin U from guinea pig small intestine. Microsequence Edman N-terminal analysis and C-terminal analysis by enzymatic digestion showed this peptide to be a nonapeptide with the following sequence: H-Gly-Tyr-Phe-Leu-Phe-Arg-Pro-Arg-Asn-NH2. The C-terminal octapeptide of this sequence is the same as porcine NMU-8, and the C-terminal heptapeptide is identical to rat NMU(17-23).

Purification and amino acid sequence of vasoactive intestinal peptide, peptide histidine isoleucinamide (1-27) and secretin from the small intestine of guinea pig.

The neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucinamide (1-27) (PHI) and the hormone secretin were purified from the small intestine of guinea pig, being detected by radioimmunoassay and radioreceptor assay throughout six to seven chromatographic steps. After elution on a reverse-phase C18 column, the three peptides were separated on a Fractogel column. After cation-exchange chromatography of each peptide on Mono S, the final steps were performed using a reverse-phase RP8-e column. Guinea pig PHI differed from porcine PHI in having Tyr and Arg residues instead of Phe and Lys in, respectively, position 10 and 20. We confirmed the original sequence of guinea pig VIP previously documented (with Leu5, Thr9, Met19 and Val26). We also established the similarity of the primary structure of guinea pig secretin with that of porcine and bovine.

Determination of collagen and protein turnover by high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for the determination of tissue collagen and protein synthesis rates in vivo, together with an index of collagen degradation. The technique utilises post-column reaction with 7-chloro-4-nitrobenzofurazan (NBDCl), which shows higher reactivity towards the secondary amino acids, proline and hydroxyproline, and also exploits differences in absorbance and fluorescence spectra to avoid interference by primary amino acids, including cysteine which reacts rapidly with NBDCl. The relative benefits of using fluorescence or absorbance detection are discussed. A detailed description is given of the steps involved in sample preparation and data for five normal tissues in the mouse are presented using fluorescence detection.

A cholecystokinin-metabolizing enzyme in rat intestine.

Acid extracts of rat intestine contain a material which metabolizes cholecystokinin-33 (CCK-33) to CCK-12. Soybean trypsin inhibitor had little effect on CCK metabolism by the intestinal material. The molecular weight of the CCK-metabolizing activity, estimated by gel filtration, was 34,000. These data suggest rat intestine contains a nontrypsin CCK-metabolizing enzyme. Results from gel filtration also suggest that large CCK forms can be artifactually degraded to smaller ones during chromatography.

[The effect of a supplement of citric acid on the bioavailability of zinc from corn germ]. / Effekt einer Zulage an Citronensäure auf die Bioverfügbarkeit von Zink aus Maiskeimen.

The purpose of this 2 factorial designed study was to investigate the influence of citric acid on the availability of zinc from diets containing 140 g corn germs as a native phytate source (0.5% phytate in diet). Growing male rats with an average initial weight of 42 g were divided into 8 groups of 8 animals each. After a 7 d depletion period (2.4 micrograms Zn/g diet) the animals were fed ad libitum for 21 d a diet on the basis of egg white solid and corn germs. The diets were supplemented with zinc in order to obtain phytate:zinc molar ratios of 31, 20, 14, and 0 (control without corn germs, 11 micrograms Zn/g diet). Each diet was fed with and without a supplementation of 1% citric acid. A phytate:Zn molar ratio of 31:1 resulted in typical symptoms of zinc-deficiency like anorexia, alopecia and a significant depression of growth. These effects were apparently reduced by citric acid. The zinc concentration in serum and organs followed the graded levels of phytate:zinc molar ratios. Primary significant effects of the phytate:Zn molar ratio but also effects of citric acid and interactions between the 2 factors phytate:Zn and citric acid could be detected. Only total liver zinc but not liver zinc based on fresh matter was affected by the phytate:Zn molar ratio. In serum and tissues the activity of alkaline phosphatase showed a significant response to the phytate:zinc molar ratio. Furthermore the supplementation with citric acid increased the femur alkaline phosphatase and slightly reduced it in the liver. The concentrations of metallothionein in liver duodenum, jejunum and ileum were significantly affected by the phytate:Zn molar ratio.

Transferrin receptor distribution and regulation in the rat small intestine. Effect of iron stores and erythropoiesis.

A combination of biochemical quantitation and immunohistochemistry has been used to examine in detail transferrin receptor distribution and expression in the rat small intestine and its relationship to iron absorption. Receptor numbers were quantitated by transferrin binding to preparations of basolateral or brush-border membranes. Receptors were demonstrated on the basolateral membranes of the gut cells, but not on the brush-border fraction. Apotransferrin demonstrated little binding to basolateral membranes at physiological pH. Dietary or parenteral iron loading of animals produced a significant decline in transferrin binding, whereas binding was increased in iron deficiency. These data were confirmed by immunohistochemical studies using a monoclonal antibody to the transferrin receptor. When iron absorption was increased threefold following acute hemolysis and without a decrease in body iron stores, there was no change in transferrin receptor number. These data indicate that intestinal transferrin receptors may be regulated by body iron stores but suggest that they are not directly involved in iron absorption.

Microtubule-associated protein 3 (MAP3) expression in non-neuronal tissues.

Microtubule-associated protein 3 (MAP3, Mr 180,000), which in previous studies has been shown to be associated with glial processes and neurofilament-rich axons in rat brain, was examined in various non-neuronal rat tissues. Immunoblots of adult rat tissues (brain, liver, heart, spleen, adrenal medulla and kidney) showed that MAP3 is present in all organs tested. In addition we demonstrated that MAP3 is a heat-stable protein. Using immunohistochemistry, we established the localisation of MAP3 in various cell types. MAP3-containing cells appeared to have in common an asymmetric morphology with long processes that need structural support. In kidney MAP3 is limited to epithelial podocytes and in liver to Kupffer cells. In the adrenal gland, the cells of the cortex are devoid of MAP3 compared to the cells of the medulla. High concentrations of MAP3 are also found in cardiac muscle along the Z-disc and in the smooth muscle cells of the digestive tract. In spleen MAP3 is found in cells of the white pulp surrounding central blood vessels. A co-distribution of MAP3 with microtubules and intermediate filaments but not with microfilaments was found in each cell type examined. The widespread distribution pattern of MAP3 together with its molecular size and heat-stability indicate that MAP3 might be a member of the recently postulated family of homologous 200,000 Mr mammalian tissue MAPs. Potential functions for MAP3 in specific cell types are discussed.

Molecular characterization of a functional cDNA encoding the rat substance P receptor.

Substance P is a member of the tachykinin peptide family and participates in the regulation of diverse biological processes. The polymerase chain reaction and conventional library screening were used to isolate a complementary DNA (cDNA) encoding the rat substance P receptor from brain and submandibular gland. By homology analysis, this receptor belongs to the G protein-coupled receptor superfamily. The receptor cDNA was expressed in a mammalian cell line and the ligand binding properties of the encoded receptor were pharmacologically defined by Scatchard analysis and tachykinin peptide displacement as those of a substance P receptor. The distribution of the messenger RNA for this receptor is highest in urinary bladder, submandibular gland, striatum, and spinal cord, which is consistent with the known distribution of substance P receptor binding sites. Thus, this receptor appears to mediate the primary actions of substance P in various brain regions and peripheral tissues.

[The x-ray microanalysis of the mucosa of the rat small intestine]. / Rentgenovskii mikroanaliz slizistoi tonkoi kishki krysy.

A rat small intestine mucosa is shown to accumulate significant amount of potassium and chloride. There was found a correlation between the content of these chemical elements and glycoprotein compartmentalization in goblet cell secret, brush border of enterocytes and a mucus layer. In this connection a role of mucus glycoproteins in membrane digestion is discussed. For preparation of samples the cryotechniques of electron microscopy are used.

Amino acid sequence of VIP, PHI and secretin from the rabbit small intestine.

VIP, PHI and secretin were purified from rabbit small intestine throughout a maximum of 6 chromatographic steps. After elution on a reverse phase C18 column, the 3 peptides were separated on a Fractogel column using specific radioimmunoassays for detection. After cation exchange chromatography on Mono S, the final steps were performed using a reverse phase RP8-e column. For these steps, radioreceptor assays were utilized to detect VIP and PHI. We confirmed that the VIP sequence of rabbit was identical to that of porcine VIP. The PHI sequence was also found identical to that of porcine PHI. By contrast, rabbit secretin was highly original, differing from porcine secretin in having Leu, Arg and Leu-NH2 residues instead of Phe, Ser and Val-NH2 in, respectively, position 6, 16 and 27.

Isolation and microsequence analysis of guinea pig alpha-neo-endorphin.

A multidimensional chromatographic regimen was used to isolate and purify alpha-neo-endorphin-like immunoreactive material from guinea pig small intestine. Microsequence analysis of the material obtained showed that the sequence of this peptide in guinea pig is the same as that previously reported for pig and rat, namely: H-Tyr-Gly-Gly-Phe-Leu-Arg-Lys-Tyr-Pro-Lys(OH). Thus, the sequence of alpha-neo-endorphin is conserved in all species thus far examined.

N-terminal amino acid sequence, immunohistochemical localization and tissue distribution of a plasma membrane protein (Prot17) of rat enterocytes.

Prot17, a protein of the basolateral membrane of rat small intestine with a mol.wt. of 17 kDa, can be isolated using a previously described method (Schiechl 1988). It occurs in the membrane as an oligomer with a mol.wt. of 90 kDa. In the present study a polyclonal antibody specific for Prot17 was used to explore by immunohistochemical techniques the tissue distribution of Prot17 and its ultrastructural localization within the cells. Furthermore the amino acid sequence of the N-terminal part of this molecule up to position 17 could be analyzed. The results are summarized as follows: Prot17 is a membrane anchored protein. Its partial amino acid sequence suggests that it is neither identical nor related to other known proteins. Immunofluorescence studies revealed, that it occurs only in epithelial cells. It is mainly found in the absorptive and goblet cells of the intestine and the acinar cells of the pancreas. Smaller quantities are found also in the bile duct epithelium of the liver, in the proximal tubule cells of the kidney and in the cells of the respiratory epithelium. Ultrastructural localization of Prot17 was possible in the intestinal epithelium and pancreas acinar cells. In both cell types it was found in the basolateral and microvillous membrane. In pancreas, Prot17 was also detected in the membrane of the zymogen granules. In the absorptive cells of the intestine Prot17 was found in both the membrane and the contents of subluminal vesicles. Furthermore, in apical granules of secretory cells of the respiratory epithelium binding of Prot17 specific antibody was found in the granular content, the membrane being negative.

Expression of the VLA family of integrins in human intestine.

The distribution of cells expressing the integrins VLA-1 to 6 in human intestine was examined by alkaline phosphatase immunohistochemistry using monoclonal antibodies specific for the individual alpha-chains of the VLA heterodimer. VLA-2,3, and 6 were expressed on all epithelial cells in the small and large bowel. VLA-1 was expressed on crypt cells in the small and large bowel, but was only weakly expressed or was absent on villus epithelial cells in the small bowel and colonic surface epithelial cells. All epithelia were negative for VLA-4 and VLA-5. Intraepithelial lymphocytes were VLA-1+ and VLA-4+. VLA-1,3, and 5 were expressed uniformly by muscularis propria, muscularis mucosae, pericrypt cells, and smooth muscle fibres within the villi. By contrast, VLA-2 and 4 were present only in pericrypt cells and fibres within the villi; they were absent from the muscularis mucosae. VLA-1,3,5, and 6 were expressed by endothelium. Staining of muscle fibres and endothelium in the lamina propria made it difficult to determine the extent of VLA expression on lamina propria lymphocytes. However, VLA-1+ cells with lymphoid morphology were only rarely seen. All mononuclear cells in the lamina propria were VLA-4+.

Effect of transplantation on tissue levels of substance P, vasoactive intestinal polypeptide, and serotonin in rat small intestine.

Denervation of the gut, resulting in altered bowel function, has been viewed as an impediment to the clinical success of small intestinal transplantation. This study examined the effect of complete extrinsic denervation of the jejunum and ileum on tissue levels of VIP, SP, and 5-HT in a rat model of small intestinal transplantation. Orthotopic total small bowel isograft transplants were performed in 18 Lewis inbred rats. Sham operations consisted of occluding the superior mesenteric artery of 18 Lewis rats for 10 minutes to provide comparable degrees of ischemia. Six rats from each group were sacrificed 1, 2, and 4 weeks following transplantation or sham operation. The jejunum and ileum were removed and extracted in acid for measurement of VIP, SP, and 5-HT by radioimmunoassay. There were no statistically significant differences in the jejunal or ileal content of VIP or 5-HT or the jejunal content of SP between the transplant and sham groups. An initial decrease in ileal SP content at 1 week following transplantation was no longer evident by the fourth week. We conclude that the extrinsic denervation of small intestinal transplantation has minimal effects on the intestinal content of VIP, SP, and 5-HT and should not significantly affect physiologic function controlled by these gastrointestinal hormones.