Intestinal fatty acid binding protein may favor differential apical fatty acid binding in the intestine.

The intestinal mucosa metabolizes fatty acids differently when presented to the lumenal or basolateral membrane. Expression of both liver and intestinal fatty acid binding proteins (L- and I-FABPs) uniquely in the enterocyte offers a possible explanation of this phenomenon. An organ explant system was used to analyze the relative binding of fatty acids to each protein. More fatty acid was bound to L-FABP than to I-FABPs (28% vs. 6% of cytosolic radioactivity), no matter on which side the fatty acid was added. However, a 2-3-fold increase in fatty acid binding to the intestinal paralog was noted after apical addition of palmitic or oleic acid in mucosa from chow fed rats. When oleic acid was added apically, a 1.4-fold increase in binding to I-FABP was observed in mucosa derived from chronically fat fed rats, consistent with the previously observed 50% increase in the content of that protein. Immunocytochemical localization of both FABPs in vivo demonstrated an apical cytoplasmic localization in the fasting state, and redistribution to the entire cytoplasm after fat feeding. These data are consistent with the hypothesis that I-FABP may contribute to the metabolic compartmentalization of apically presented fatty acids in the intestine.

Abundance of surfactant-like particles reflects mucosal integrity in patients with peptic ulcer disease.

BACKGROUND: Surfactant-like particles, normal products of the human enterocyte, are released into the lumen and secreted into blood. AIMS: To assess their role as markers for mucosal functional integrity, this study examined their content in biopsy specimens and serum of patients with duodenal ulcer disease, compared with non-diseased control subjects. PATIENTS: Endoscopic biopsy specimens were taken 1-2 cm from areas of active inflammation or ulcer (peptic ulcer patients) or just beyond the duodenal bulb (normals) in 35 consecutive subjects. METHODS: After staining for phospholipid, extracellular and intracellular particles were counted on transmission electron micrographs of coded specimens. Serum was obtained from 24 patients, and densitometry of the 59 kDa band detected on western blot by antiserum against human jejunal particle was measured. RESULTS: Normal duodenum (n = 15) contained more particles (44 (4.7)) particles/block, mean (SD) than active duodenal ulcer (n = 13, 17 (3.9)) or gastritis/duodenitis patients (n = 4, 9 (2.7)). Three patients examined after healing of duodenal ulcers showed abundant particles (n = 3, 67 (2.2)). Similarly, the 59 kDa band was decreased in serum of patients with active peptic ulcer disease (n = 11, 0.25 (0.04) absorbance units) compared with normal patients (n = 10, 0.40 (0.03)) or healed ulcers (n = 3, 0.62 (0.04)). There was good correlation between morphological mucosal particle abundance and particle protein content of serum assayed from the same patients (r = 0.831). These changes were independent of Helicobacter pylori status. CONCLUSION: The mucosal and serum content of surfactant-like particles may reflect general mucosal integrity of the enterocytes from which they are derived.

The secretion of intestinal alkaline phosphatase (IAP) from the enterocyte.

Rat intestinal alkaline phosphatase exists in two separate forms, differing markedly in the carboxyterminal coding region, as well as in the 3' untranslated regions. It is secreted bound to a phospholipid-rich particle (surfactant-like particle) which appears to have unique properties, but whose role is still uncertain. Evidence is presented to suggest that intestinal alkaline phosphatase secretion is mediated by this particle. The challenge for the future is to study the biology of the surfactant-like particle, to ascertain its role in gut physiology, and to determine how the dual alkaline phosphatases are involved in this specialized secretory apparatus.

A possible role for rat intestinal surfactant-like particles in transepithelial triacylglycerol transport.

To further examine whether surfactant-like particles (DeSchryver-Kecskemeti, K., R. Eliakim, S. Carroll, W. F. Stenson, M. A. Moxley, and D. H. Alpers. 1989. J. Clin. Invest. 84:1355-1361) were involved in the transepithelial transport of lipid, alkaline phosphatase activity and surfactant-like particle content were measured in apical mucosal scrapings, enterocytes, lamina propria, and serum after inhibition of chylomicron transport. Serum triacylglycerol levels were decreased 60-76% by Pluronic L-81, fenfluramine, and choline deficiency compared with fat-fed controls. 5 h after triacylglycerol feed, alkaline phosphatase activity in all three experimental groups was decreased compared with controls by 52-69% in mucosal scrapings and by 33-72% in serum. A parallel decline (60%) in alkaline phosphatase activity occurred in the lamina propria of Pluronic-treated animals. Total particle content (measured by an ELISA using antiserum against purified particle) after Pluronic treatment was decreased in mucosal scrapings, lamina propria, and serum by 16, 22, and 29% at 3 h and by 33, 40, and 8%, respectively, at 5 h after fat feeding. In contrast, particle content was increased in enterocytes by 29% 3 h and by 8% 5 h after fat feeding. By electron microscopy, enterocytes from Pluronic- and fenfluramine-treated animals exhibited a two- to threefold increase in large intracellular cytoplasmic lipid globules and the appearance of lamellae in apposition, with a marked decrease in the number of surfactant-like particles overlying the brush border. These changes, produced by inhibition of chylomicron transport, in the distribution of surfactant-like particles and particle-bound alkaline phosphatase are consistent with a role for these particles in transepithelial triacylglycerol transport across and out of the enterocyte.

Characterization of proteins in rat and human intestinal surfactant-like particles.

Phospholipid-rich particles isolated from the apical surface of rat enterocytes have surfactant-like properties and are enriched for intestinal alkaline phosphatase. Purified intact rat particles were used to produce antibodies in rabbits. Antiserum against the rat particle identified major proteins of 48, 68, 98, and 118 kDa on Western blots of isolated rat surfactant-like particle and did not detect any protein in rat intestinal basolateral membranes, rat brush border membranes, or human particles, but did detect a single 180-kDa protein in a preparation of rat milk fat globules, and two proteins (66 and 103 kDa) in rat pulmonary surfactant. The proteins detected on Western blot corresponded with the major proteins identified by Coomassie blue staining. Similar particles were isolated from the apical surface of human intestine and had an enzyme composition, buoyant density, and lipid content similar to those of the rat particles. Antiserum raised against the human jejunal particle detected proteins in the human particle by Western blot that were similar in size with the rat particle proteins (33, 52, 75, 82, and 118 kDa), but did not cross-react with human brush border or rat particle proteins. These studies demonstrate that the surfactant-like particles are present in human as well as rat intestinal tissue, demonstrate similar enzyme and protein content, and confirm their unique identity, distinct from apical brush border or basolateral membranes.

Pericrypt eosinophilic enterocolitis and chronic diarrhea.

An unusual pattern of eosinophilic infiltration around intestinal crypts was detected in mucosal biopsy specimens of 10 patients with chronic diarrhea, half of whom had evidence of systemic connective tissue disease. The median duration of symptoms was 11 months, and no other explanation for diarrhea could be determined in any case. The cellular infiltrate on biopsy specimens was present deep in the mucosa of small and large intestinal specimens, separating crypt bases from the muscularis mucosae and penetrating the latter. Consistent with the microscopic findings, surface mucosal appearance by endoscopy was uniformly normal. These histological features of colonic biopsy specimens were statistically differentiated from those of asymptomatic subjects (n = 8), subjects with diarrhea-predominant irritable bowel syndrome (n = 6), and subjects with collagenous colitis (n = 7) or lymphocytic colitis (n = 5). Diarrhea improved in five of seven subjects treated with oral prednisone or prednisone in conjunction with azathioprine (median follow-up period, 2.2 years). Histological changes on subsequent biopsy specimens correlated closely with symptomatic status. These findings strongly suggest that chronic diarrhea is related to this pericrypt eosinophilic enterocolitis, a pathological lesion often associated with features of systemic connective tissue disease. The disorder appears responsive to corticosteroid therapy in some cases.

Mast cell granules within endothelial cells: a possible signal in the inflammatory process?

Mast cell-endothelial cell interactions have long been suspected to be important in inflammation. The detail of the pathways of communication have yet to be elucidated. In this report we describe, for the first time, mast cell granules within endothelial cells of colonic capillaries in a patient with florid colitis, as well as rats with experimentally induced mast cell degranulation. We postulate that this phenomenon may occur more generally during immunologically mediated inflammatory cell degranulation, and may be one mechanism of communication to endothelium.

Dietary supplementation with fish oil in ulcerative colitis.

OBJECTIVE: To determine the efficacy of fish oil supplementation in patients with active ulcerative colitis. DESIGN: Multicenter, randomized, double-blind, placebo-controlled, crossover trail with 4-month treatment periods (fish oil and placebo) separated by a 1-month washout. SETTING: Four gastroenterology divisions. PATIENTS: Twenty-four patients with active ulcerative colitis entered the study. Five dropped out, and one was noncompliant. Eighteen patients completed the study. All patients had active disease as manifested by diarrhea and rectal inflammation. INTERVENTIONS: Treatment with prednisone and sulfasalazine was continued. Fish oil supplementation consisted of 18 Max-EPA (eicosapentaenoic acid) capsules daily (eicosapentaenoic acid, 3.24 g; and docosahexaenoic acid, 2.16 g). Placebo supplementation consisted of 18 identical capsules containing isocaloric amounts of vegetable oil. MEASUREMENTS: Patients were evaluated at study entry and after each diet period. Evaluations included a review of symptoms, flexible sigmoidoscopy, rectal biopsy, and rectal dialysis to measure prostaglandin E2 and leukotriene B4 levels. RESULTS: Fish oil supplementation resulted in a significant decrease in rectal dialysate levels of leukotriene B4 from 71.0 to 27.7 pg/mL (average change, -43.3 pg/mL; 95% CI, -83 to -3.6). Significant improvements were seen in acute histology index (average change, -8.5 units from a baseline of 10.5 units; CI, -12.9 to -4.2) and total histology index (average change, -8.5 units from a baseline of 14.80; CI, -13.2 to -3.8) as well as significant weight gain (average weight gain, 1.74 kg, CI, 0.94 to 2.54). No significant changes occurred in any variable during the placebo period. Seven patients received concurrent treatment with prednisone. During the fish oil supplementation period, the mean prednisone dose decreased from 12.9 mg/d to 6.1 mg/d and rose from 10.4 mg/d to 12.9 mg/d during the placebo diet period (P greater than 0.20). CONCLUSIONS: Four months of diet supplementation with fish oil in patients with inflammatory bowel disease resulted in reductions in rectal dialysate leukotriene B4 levels, improvements in histologic findings, and weight gain.

Stromal amyloid in pheochromocytomas.

Amyloid has been documented in the stroma of a number of neuroendocrine tumors. It is usually associated with elaboration of a polypeptide hormone product. Twenty-three adrenal pheochromocytomas occurring in 18 patients were graded for the extent of amyloid deposits on the hematoxylin-eosin-stained slides, confirmed to be amyloid by Congo red stain and polarization microscopy. Fourteen of 20 cases (70%) showed evidence of stromal amyloid; in two thirds of these cases, it was considered abundant. The awareness of amyloid deposits in approximately 70% of pheochromocytomas is important for surgical pathologists, as this occurrence has not been thought to be common in these tumors and might be a source of diagnostic difficulty.

The minor components of the rat asialoglycoprotein receptor are apically located in neonatal enterocytes.

Because specific uptake of the asialoglycoprotein haptocorrin has been reported in suckling distal intestine, evidence of the asialoglycoprotein receptor in rat ileum was sought. On Western blot, two different polyclonal antisera against purified rat holoreceptor recognized only proteins of the size of the minor receptor components (51 and 55 kilodaltons) in both suckling and adult rat intestine. Messenger RNA encoding the minor component (RHL-2/3) was detected in total RNA extracted from rat ileum. Calcium-specific binding of porcine or rat haptocorrin-[57Co]cobalamin complexes was detected in the brush border membranes of distal suckling rat and porcine small intestine. This binding was almost completely blocked by another asialoglycoprotein, asialofetuin. The pH optimum for binding was 6-9, with a Ka of 0.25 nmol/L and a capacity of 4.6 fmol/mg protein. These properties, with the exception of the low capacity, are all consistent with those of the intact receptor on hepatocytes. The intestinal receptor was localized not to the basolateral membrane, as in the liver, but to the apical brush border, as suggested by the binding data. Furthermore, immunoperoxidase stains of paraffin-embedded tissue detected strong binding to the brush border and apical phagolysosome of mid and distal suckling rat intestine. These data show that, contrary to expectations, the minor components of the asialoglycoprotein receptor are functional and expressed in the apical membrane of the suckling intestine. The abundance of the protein by Western blot suggests possible roles for it in the neonatal gut other than haptocorrin binding.

A novel intracellular pathway for rat intestinal digestive enzymes (alkaline phosphatase and sucrase) via a lamellar particle.

To identify the mechanism of intestinal alkaline phosphatase (IAP) release into serum that is known to be associated with fat feeding, both luminal and serum IAP as well as sucrase-isomaltase levels were monitored by rocket electroimmunoassays and by immunogold labeling electron microscopy. Luminal and serum IAP, and to a much lesser extent sucrase-isomaltase, peaked at 7 hours after fat feeding. Analysis of the luminal IAP by isoelectric focusing showed that the enzyme had a slightly different pI than brush border IAP, but was still partially membrane bound, whereas serum IAP was no longer membrane bound. In parallel, by morphology, IAP and sucrase-isomaltase localized to intra- and extracellular lamellar membranous particles, most conspicuous at 7 hours after fat feeding, while very scarce in nonfat-fed animals. The membranous particles bearing the enzymes were commonly associated with fat droplets. These data are consistent with the existence of a novel pathway, possibly secretory, for IAP and sucrase-isomaltase via lamellar bodies, leading to appearance of the enzymes in lumen and serum, with subsequent release from the membrane extracellularly. They also offer an explanation for the known association of the increased secreted IAP after fat feeding.

Environmental pathology. Mast cell and eosinophil infiltration in intestinal mucosa of Lewis rats treated with L-tryptophan implicated in human eosinophilia myalgia syndrome.

A recently developed animal model for the L-tryptophan-associated eosinophilia myalgia syndrome was used to examine the small intestine and colon, because there is clinical involvement at these sites in patients. Increased perivascular inflammatory infiltrates rich in degranulating mast cells, eosinophils, and monocytes were seen in the lamina propria of experimental animals when compared with controls. L-Tryptophan-associated disease also shares many clinical features with idiopathic scleroderma/eosinophilic fasciitis, in which there is gastrointestinal involvement as well. These features are similar to those found in the recently described animal model. The apparent morphologic and clinical similarities between these entities suggest that the animal model is suitable for further studying the pathogenesis of the gastrointestinal involvement in all these diseases.

Small intestinal lesion resembling graft-vs-host disease. A case report in immunodeficiency and review of the literature.

We report graft-vs-host disease-like histology in a small intestinal biopsy specimen that was obtained from a patient with common variable immunodeficiency and related T-cell defect. We include findings from immunohistochemical studies and follow-up information. Review of the literature yielded only a small number of histologically documented cases of this lesion without previous bone marrow transplantation. Awareness of this clinicopathologic entity is important in the interpretation of gastrointestinal biopsy specimens.

Thickening of muscularis mucosae in Crohn's disease.

Crohn's disease (CD) of the bowel showed a statistically significant thickening of the muscularis mucosae when compared with disease controls. In areas of gross stricture in CD, the muscularis mucosae comprised almost 10% of total wall thickness. Similar findings were also present in a previously characterized experimental model of CD (trinitrobenzene sulfonic acid-induced colitis in rats), particularly in what appeared to be grossly strictured areas. Taken together, these findings suggest that increased mass of muscularis mucosae smooth muscle may be responsible in part for the commonly observed stricture formation in CD. As extreme muscularis mucosae hyperplasia appears to be peculiar to CD, it may serve as an additional marker differentiating CD from other diseases.

Glomus tumor of the coccyx. A curable cause of coccygodynia.

A 30-year-old woman presented with recurrent severe coccygodynia. She underwent exploration for a possible pilonidal sinus and was found to have a precoccygeal glomus tumor that also involved bony trabeculae of the coccyx. To our knowledge, a glomus tumor involving the coccygeal bone has not been previously documented. In view of the relief of this patient's pain following the surgical excision of coccyx and tumor, a causal role is suggested.

Effect of mucosal thickening near gastric carcinoma on the endoscopic diagnosis of malignancy.

Gastric mucosal thickening of variable degree occurs in the vicinity of gastric carcinomas and is possibly related to simultaneous tumor expression of epidermal growth factor and its receptor. Seventeen cases in which both endoscopic biopsy and subsequent resection for gastric carcinoma had been performed were studied to see if putative tumor-related mucosal thickening had an effect on endoscopic biopsy sensitivity. Biopsy fragment positivity rate was greater in cases with exophytic, protruding tumor masses (46.8 +/- 8.5%) than in all other cases (17.0 +/- 4.7%; P = 0.02). Thickness of nontumorous mucosa adjacent to carcinomas did not significantly affect the biopsy fragment positivity rate in cases with exophytic masses ("thin" subgroup, 51.0 +/- 16.2%; "thick" subgroup, 44.0 +/- 10.8%; P = 0.7) but did reduce the positivity rate significantly (P = 0.05) in ulcerative or infiltrative tumors without exophytic components ("thin" subgroup, 23.3 +/- 4.1%; "thick" subgroup, 8.4 +/- 2.1%). This reduction in biopsy sensitivity related to mucosal thickening occurring adjacent to nonprotuberant lesions may explain, at least in part, the variable rates of positive biopsies observed with gastric cancers.

Isolation and characterization of a small intestinal surfactant-like particle containing alkaline phosphatase and other digestive enzymes.

Digestive brush-border enzymes in particulate form have been reported in the intestinal lumen in vivo and in medium from organ explants in vitro. It has been suggested that these particles derive from membrane shedding of the apical brush border. This study describes the isolation and characterization of particles derived from the 105,000 x g supernatant fraction of intestinal luminal washings and from light scrapings of the mucosa itself after fat feeding of rats. These fractions were separated in a continuous NaBr gradient, producing a visible band of 1.07-1.08 g/liter density and resulting in a 15-fold enrichment of intestinal alkaline phosphatase in the band fraction. Other brush-border hydrolases were represented in the banded fraction, but at specific activities only 1/5th to 1/36th that of the brush border. The major phospholipid in the fraction was phosphatidylcholine (58 +/- 15%), containing 75% saturated fatty acids. In contrast, the major brush-border phospholipid was phosphatidyl-ethanolamine. These characteristics showed that the particles derived from the lumen and mucosal surface were not identical to fragments of the brush border. Electron microscopy of the banded fraction revealed partially coiled membrane fragments. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blots, some proteins (e.g. surfactant protein B, collagenous protein 4) were found in common between the intestinal particles and rat pulmonary surfactant. These data suggest the production of a particle secreted by rat intestine that differs from brush-border membranes and that shares some morphological and biochemical similarities with pulmonary surfactant.