Cytoplasm Of Enterocytes Research Articles

Subcellular location of heme oxygenase 1 and 2 and divalent metal transporter 1 in relation to endocytotic markers during heme iron absorption

Heme is an important dietary micronutrient, although its absorptive mechanisms are poorly understood. One hypothesis suggests enterocytes take up heme by receptor-mediated endocytosis (RME) which then undergoes catabolism by heme oxygenase (HO) inside internalized vesicles. This would require the translocation of HO-1 or HO-2 to endosomes and/or lysosomes and the presence of a transporter, possibly divalent metal transporter 1 (DMT1), to transfer released iron to the cytoplasm. Currently, the location of HO-1 and HO-2 in enterocytes is unknown. We studied the subcellular location of HO-1, HO-2, and DMT1 in the proximal small intestine of rats by confocal immunofluorescence microscopy up to 4 h after a dose of heme or ferrous iron. Double-labeling was performed with endocytotic (EEA1, Lamp1) and structural markers (F-actin). HO-1 was distributed evenly throughout the cytoplasm of enterocytes and did not colocalize with endocytotic markers in any condition. HO-2 staining remained constant with dosing, presenting as a dense band in the apical cytoplasm that colocalized extensively with endosomes. DMT1 staining was markedly reduced by ferrous iron, but not heme and did not exhibit colocalization with endocytotic markers. The subcellular location of HO-2 is consistent with the RME hypothesis for heme uptake and may suggest a possible role for this enzyme in heme degradation. The lack of translocation of DMT1 with heme dosing suggests another protein may be present to transport iron released from heme.

Examination of the Role of Intestinal Fatty Acid-Binding Protein in Drug Absorption Using a Parallel Artificial Membrane Permeability Assay

Transcellular diffusion across the absorptive epithelial cells (enterocytes) of the small intestine is the main route of absorption for most orally administered drugs. The process by which lipophilic compounds transverse the aqueous environment of the cytoplasm, however, remains poorly defined. In the present study, we have identified a structurally diverse group of lipophilic drugs that display low micromolar binding affinities for a cytosolic lipid-binding protein - intestinal fatty acid-binding protein (I-FABP). Binding to I-FABP significantly enhanced the transport of lipophilic drug molecules across a model membrane, and the degree of transport enhancement was related to both drug lipophilicity and I-FABP binding affinity. These data suggest that intracellular lipid-binding proteins such as I-FABP may enhance the membrane transport of lipophilic xenobiotics and facilitate drug access to the enterocyte cytoplasm and cytoplasmic organelles.

Histological, digestive, metabolic, hormonal and some immune factor responses in Atlantic salmon, Salmo salar L., fed genetically modified soybeans

The paper reports the second and final part of an experiment aiming to study physiological and health-related effects of genetically modified (GM) soybean meal (SBM) type Roundup Ready soybean (RRS) in diets for post-smolt Atlantic salmon. For 3 months salmon were fed diets containing 172 g kg(-1) full-fat SBM from RRS (GM-soy) or an unmodified, non-isogenic line (nGM-soy), or a reference diet with fishmeal as the sole protein source (FM). Slight differences in anti-nutrient levels were observed between the GM and nGM-soy. Histological changes were observed only in the distal intestine of the soy-fed fish. The incidence of moderate inflammation was higher in the GM-soy group (9 of 10 sampled fish) compared with the nGM-soy group (7 of 10). However, no differences in the concomitant decreases in activities of digestive enzymes located in the brush border (leucine aminopeptidase and maltase) and apical cytoplasm (acid phosphatase) of enterocytes or in the number of major histocompatibility complex class II+ cells, lysozyme activity, or total IgM of the distal intestine were observed. GM compared with nGM-soy fed fish had higher head kidney lysozyme (11,856 vs. 10,456 units g(-1) tissue) and a tendency towards higher acid phosphatase (0.45 vs. 0.39 micromol h(-1) kg(-1) body mass in whole tissue) activities, respectively. Plasma insulin and thyroxin levels, and hepatic fructose-1,6-bisphosphatase and ethoxyresorufin-O-deethylase activities were not significantly affected. It is not possible, however, to conclude whether the differences in responses to GM-soy were due to the genetic modification or to differences in soy cultivars in the soy-containing diets. Results from studies using non-modified, parental line soybeans as the control group are necessary to evaluate whether genetic modification of soybeans in diets poses any risk to farmed Atlantic salmon.

Immunolocalization of duodenal cytochrome B: a relationship with circulating markers of iron status

The brush border ferric reductase (Dcytb) is critical for the absorption of dietary iron and appears to be expressed on the duodenal enterocyte brush border. The Dcytb expression is increased in severe iron-deficient anaemia, but the situation in a more typical mild iron deficiency is unclear. This study investigated Dcytb expression in patients with normal iron status or mild iron deficiency and its relationships with enterocyte iron status. Duodenal biopsy specimens and blood samples were obtained from 32 patients undergoing routine upper gastrointestinal endoscopy. Twenty-three specimens (six iron-deficient and 17 iron-replete) were processed for light-microscopy (LM) and for immunohistochemistry with antibodies against Dcytb and heavy/light chain ferritin subunits. The nine remaining biopsies (three iron-deficient and six iron-replete) were processed for electron microscopy (EM). Immunolocalization of Dcytb and intracellular ferritin was performed with appropriate primary antibodies followed by 10-nm gold conjugate labels. The LM process showed a strong negative correlation between immunolabelling intensity of Dcytb on the enterocyte brush border and serum iron saturation (P < 0.001), but only a weak negative correlation between this antigen and haemoglobin (P = 0.08) or serum ferritin concentrations (P = 0.4). EM confirmed anti-Dcytb preferential labelling of microvilli rather than enterocyte cytoplasm (P = 0.001), but preferential antiferritin labelling of cytoplasm (P < 0.02). There was no correlation with enterocyte cytoplasmic ferritin labelling (i.e. enterocyte iron status and Dcytb expression). Enterocyte Dcytb brush border expression is increased even in mild iron deficiency and may be related to serum iron saturation. The lack of correlation with enterocyte ferritin expression deserves further study with direct measurement of intracellular iron.

Pathophysiology in Microvillus Inclusion Disease

Microvillus inclusion disease (MID) is a congenital disorder with the clinical signs of watery diarrhea often beginning in the first days of life. The main pathological features of the disease include a villus atrophy and an accumulation of periodic acid-Schiff (PAS)-positive material within the apical cytoplasm of enterocytes on the light microscopy level. Electron microscopic criteria are pathognomonic consisting of an increased amount of secretory granules preferentially in crypt epithelial cells and of the presence of microvillus inclusion bodies (MIBs) which are most frequently found in villus enterocytes. Until now the basic molecular defects have not been disclosed completely. In this review we discuss the actual pathogenetic hypothesis and the therapeutic options besides small bowel transplantation.

Effects of gestation and lactation on Vitamin D receptor amounts in goats and sheep

During gestation and lactation, an increased demand for calcium (Ca) due to the development of fetal skeleton and excretion via milk is observed. The higher need for Ca is met by an augmented mobilisation of Ca from bones and by an increased absorption from the intestines. The main influence on this physiological process of active absorption has Vitamin D, acting through Vitamin D receptors (VDR) located in the mucosal wall of the intestines, thus increasing Ca absorption. As a consequence of inadequate Ca absorption, metabolic diseases like milk fever can develop. In this study immunohistochemical procedures were applied to colon mucosa biopsies of pregnant and lactating goats and sheep, to study the effect of late gestation, parturition and lactation on VDR amount. Colon mucosa biopsies were collected 2 weeks before parturition, 1 and 4 weeks post partum (pp), 2, 3, 4, and 5 months pp from 11 dairy goats and 11 sheep. Immunohistochemistry was performed employing a biotinylated monoclonal rat anti-VDR antibody and streptavidin peroxidase techniques. Nuclei and cytoplasm of enterocytes stained positively for VDRs. Strongest immunoreactions were observed in intermediate and superficial glandular cells. The biopsy samples taken during early lactation revealed a lower immunoreaction for VDR compared with samples taken during later stages of lactation. In conclusion, immunochemistry and biopsy technology are useful tools to assess changes in VDR expression in relation to varying demands for Ca in the process of a reproductive cycle. These results show that in dairy goats and sheep, an influence of gestation and lactation on VDR is obvious.

Unusual ultrastructural features in microvillous inclusion disease: a report of two cases

Microvillous Inclusion Disease (MID) is an inherited disorder characterized by intractable diarrhea in infancy. Ultrastructural detection of pathognomonic microvillous inclusions in the enterocytes is essential for diagnosis. The aim of this research is to contribute to the knowledge of MID studying enterocytes and goblet cells (gc). Samples of duodenal mucosa from two young infants with MID (aged 75 days and 3 months, respectively) were studied by light and electron microscopy. Detection in the intestinal villi of immature gc (with microvilli) in one of the cases led us to seek them in control samples. The total number of gc with microvilli (immature) and without microvilli (mature) were counted. In both MID specimens, light microscopy showed atrophy of villi and PAS-positive material in the enterocyte cytoplasm. The ultrastructure of villous enterocytes was characterized by brush-border abnormalities, microvillous inclusions, dense apical granules, and lysosomes. Intermediate structures between microvillous inclusions and lysosomes were also detected within a cell, as were rare microvilli on the lateral membrane of the enterocytes. In one MID specimen, immature gc were also identified in the absorptive compartment. Only mature gc were observed in the controls. The significance of the latter finding requires further studies.

Histochemical distribution of digestive enzymes in intestine of goldline, Sarpa salpa L. 1758

Histochemical localization of non-specific esterase, alkaline and acid phosphatase in the intestine of free-living goldline (Sarpa salpa L. 1758) was investigated. Fish were caught in the vicinity of the town of Zadar(Adriatic Sea Croatia), and samples of three parts of the intestine proper (anterior, middle and posterior) as well as the rectum were used for presentation of non-specific esterases, alkaline phosphatase and acid phosphatase. Non-specific esterase activity was found in the cytoplasm and brush border of enterocytes in all investigated intestinal segments and the rectum. The activity was stronger in the middle and posterior part of intestine but weaker in the anterior segment of the intestine as well as in the rectum. Intestinal alkaline phosphatase was detected in brush border and supranuclear cytoplasm of enterocytes of all investigated intestinal segments. Enzymatic activity gradually decreased in a posterior direction. Acid phosphatase activity was observed as fine granular reaction product in supranuclear region of enterocytes and was almost equal in all investigated intestinal segments as well as in the rectum. The possible role of enzymes in intracellular digestion and transport is discussed.

Experimental transmission of abnormal prion protein (PrPsc) in the small intestinal epithelial cells of neonatal mice.

Using an immunohistochemical method, we attempted to detect the transmission of abnormal prion protein (PrPsc) to the enterocytes of the small intestine of neonatal mice by oral exposure with sheep brain affected by scrapie. Five 1-day-old neonatal mice were exposed by oral inoculation to the homogenized brain of a scrapie-affected sheep. In the small intestine of all mice 1 hour after inoculation, immunoreactivity with antinormal prion protein (PrPc) antibody was seen in the cytoplasm of villus enterocytes. This finding suggests transmission of abnormal PrPsc into the cytoplasm of enterocytes. In control mice treated with normal sheep brain, no PrPc signal was seen in enterocytes of the small intestine. Immunopositivity for neurofilament protein and glial fibrillary acidic protein was seen in the cytoplasm of enterocytes of mice inoculated with scrapie and normal sheep brain. This suggests that the enterocytes of neonatal mice can absorb PrPsc and other macromolecular proteins of the sheep brain affected by scrapie and may be more important than previously thought as a pathway for PrPsc transmission in neonatal animals.

Microvillous Inclusion Disease with Abundant Vermiform, Electron-Lucent Vesicles

A 3-month-old girl with congenital secretory diarrhea underwent a duodenal biopsy. Histologic study showed villous atrophy and large amounts of PAS-positive material within enterocyte cytoplasm. Despite a clinical suspicion of microvillous inclusion disease, 2 sessions of electron microscopy were unsuccessful in detecting the diagnostic inclusions. Instead, large aggregates of electron-lucent, vermiform membranous vesicles were observed in enterocyte cytoplasm, corresponding to the PAS-positive material. A third attempt at electron microscopy was successful in detecting small numbers of microvillous inclusions. These and other recently reported cases document an expanding spectrum of ultrastructural findings in this disease, including examples where the classic microvillous inclusions are overshadowed by other features.

Microvillous Inclusion Disease with Abundant Vermiform, Electron-Lucent Vesicles

A 3-month-old girl with congenital secretory diarrhea underwent a duodenal biopsy. Histologic study showed villous atrophy and large amounts of PAS-positive material within enterocyte cytoplasm. Despite a clinical suspicion of microvillous inclusion disease, 2 sessions of electron microscopy were unsuccessful in detecting the diagnostic inclusions. Instead, large aggregates of electron-lucent, vermiform membranous vesicles were observed in enterocyte cytoplasm, corresponding to the PAS-positive material. A third attempt at electron microscopy was successful in detecting small numbers of microvillous inclusions. These and other recently reported cases document an expanding spectrum of ultrastructural findings in this disease, including examples where the classic microvillous inclusions are overshadowed by other features.

Toxicity, histopathological alterations and immunohistochemical CYP1A induction in the early life stages of the seabream, Sparus aurata, following waterborne exposure to B(a)P and TCDD.

In this paper, the toxicity (percentage of hatching and LC50) and histopathological alterations induced by benzo(a)pyrene (B(a)P; 0.032, 0.056, 0.1, 0.32, 0.56 and 0.1 microg l(-1)) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 0.025, 0.05, 0.1, 1.5 and 5 pg l(-1)) have been studied in the early life stages of the seabream, Sparus aurata, from 0 to 15 days post-hatching (dph). Toxicity assays showed that the percentage of hatching decreased with increasing the contaminant concentration. Moreover, the number of hatched larvae was lower for TCDD-exposed eggs in comparison with the B(a)P exposed ones. The sensitivity of the larvae, in terms of LC50, towards B(a)P and TCDD increased with age of the larvae. The LC50 were 0.81 microg l(-1) for B(a)P and 4.37 pg l(-1) for TCDD in neonate larvae and 0.11 microg l(-1) for B(a)P and 1.45 pg l(-1) for TCDD in 5 dph larvae. For histopathological examination, samples from LC50 experiments were taken at different concentrations of B(a)P (between 0.032 and 0.1 microg l(-1)) and TCDD (between 0.025 and 5 pg l(-1)). In both, B(a)P- and TCDD-exposed larvae, a concentration-dependency of the histopathological alterations was detected. In contrast, an age-dependency was not clearly detected, possibly due to the lack of development of mostly the organs in the early life stages. Cytoplasmic vacuolization of hepatocytes, as well as subcutaneous edema and necrosis of the trunk musculature, were the most common histopathological disorders detected in both B(a)P- and TCDD-exposed larvae. On the other hand, there were differences in histopathology on exposure to B(a)P and TCDD. Epithelial desquamation in gills, lack of inflation of the swim bladder, as well as lesions in the nervous system were specific for TCDD, while hepatic, vascular and muscular alterations were common for both toxicants. In parallel to the histopathological examinations, immunohistochemical analyses on cytochrome P450-1A isoenzyme (CYP1A) expression were performed on the same samples. The basal/constitutive distribution of CYP1A and its induction was also analysed in similar stages of larval development of the seabream under control conditions and after sublethal exposure to B(a)P (between 0.032 and 0.1 microg l(-1)) and TCDD (between 0.025 and 5 pg l(-1)). During the endogenous nutrition period (from hatching until 4 dph), constitutive CYP1A immunoreactivity was observed in the syncytium and in the matrix of the yolk sac. On the other hand, during exogenous feeding (between 4 and 10 dph), basal CYP1A immunoreactivity was detected in vascular hepatic system, whereas exocrine pancreas showed no reactivity. In gut, basal CYP1A immunoreactivity was restricted to the intestinal brush border and the apical cytoplasm of some enterocytes. Induced CYP1A immunoreactivity in B(a)P-exposed larvae was detected within cytoplasm of hepatocytes, intestinal enterocytes and endothelial cells of the heart. Finally, in TCDD-exposed larvae, CYP1A induction was also detected in pancreatic acinar cells, as well as in renal epithelial cells. The results of this study provided preliminary evidence that constitutive and inducible CYP1A organ distribution in S. aurata larvae was similar to that existing in adult fish. Moreover, exposure to TCDD was more toxic for the larvae and induced more CYP1A that exposure to B(a)P.

Transferrin Receptor 1 (TfR1) and Putative Stimulator of Fe Transport (SFT) Expression in Iron Deficiency and Overload: An Overview

ABSTRACT Transferrin Receptor 1 (TfR1) and putative Stimulator of Fe Transport (SFT) represent two different proteins involved in iron metabolism in mammalian cells. The expression of TfR1 in the duodenum of subjects with normal body iron stores has been mainly localized in the basolateral portion of the cytoplasm of crypt cells, supporting the idea that this molecule may be involved in the sensing of body iron stores. In iron deficiency anemia TfR1 expression demonstrated an inverse relationship with body iron stores as assessed by immunohistochemistry with anti-TfR1 antibodies. In iron overload, TfR1 expression in the duodenum differed according to the presence or absence of the C282Y mutation in the HFE gene, being increased in HFE-related hemochromatosis and similar to controls in non-HFE-related iron overload. SFT is characterized by its ability to increase iron transport both through the transferrin dependent and independent uptake, and could thus affect iron absorption in the intestine. Immunohistochemistry using anti-SFT antibodies which recognize a putative stimulator of Fe transport of ∼80 KDa revealed a localization of this protein in the apical part of the cytoplasm of enterocytes localized at the tip of the villi. The expression of the protein recognized by these antibodies was increased in iron deficiency, as well as in patients carrying the C282Y HFE mutation. Thus, the increased expression of both proteins only in patients with HFE-related hemochromatosis suggests that other factors should be involved in determining non-HFE-related iron overload.

Distribution of aquaporins in the colon of Octodon degus, a South American desert rodent.

Octodon degus is a desert rodent of northern Chile, adapted to survive with a limited supply of water. This rodent has a high degree of fecal dehydration, related to colon water absorption. With the hypothesis that aquaporins (AQPs) might be present in the colon epithelium of O. degus and involved in fluid absorption, we studied colon water absorption in vivo and the distribution of AQPs and Na(+) transporters by immunocytochemistry. AQP-1 was found in apical and basolateral membranes of surface-absorptive and crypt epithelial cells. AQP-8 was found in the cytoplasm of enterocytes of surface colon. AQP-3 immunolabeling, on the other hand, was absent from the epithelium but present in a subepithelial fibroblast layer, pericryptal cells, and muscularis mucosae. The hydration state did not modify the amount of immunostaining for any of the AQPs. Colon water absorption was markedly decreased by the mercurial agent p-chloromercuribenzenesulfonic acid and was not affected by water deprivation. The NHE3 isoform of Na(+)/H(+) exchanger and alpha-1 subunit of the Na(+)-K(+)-ATPase were found in apical and basolateral membranes of surface-absorptive cells, respectively. These results suggest that colon water absorption is mostly transcellular and mediated by water channels like AQP-1. Apical Na(+)/H(+) exchanger and basolateral Na(+)-K(+)-ATPase in surface cells could be part of the Na(+) absorption pathway. It is hypothesized that this transport is necessary to provide an osmotic gradient for water absorption. The roles of AQP-8 and AQP-3 in water absorption remain to be established.

DGAT1 Is Not Essential for Intestinal Triacylglycerol Absorption or Chylomicron Synthesis

Dietary triacylglycerols are a major source of energy for animals. The absorption of dietary triacylglycerols involves their hydrolysis to free fatty acids and monoacylglycerols in the intestinal lumen, the uptake of these products into enterocytes, the resynthesis of triacylgylcerols, and the incorporation of newly synthesized triacylglycerols into nascent chylomicrons for secretion. In enterocytes, the final step in triacylglycerol synthesis is believed to be catalyzed primarily through the actions of acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes. In this study, we analyzed intestinal triacylglycerol absorption and chylomicron synthesis and secretion in DGAT1-deficient (Dgat1(-/-)) mice. Surprisingly, DGAT1 was not essential for quantitative dietary triacylglycerol absorption, even in mice fed a high fat diet, or for the synthesis of chylomicrons. However, Dgat1(-/-) mice had reduced postabsorptive chylomicronemia (1 h after a high fat challenge) and accumulated neutral-lipid droplets in the cytoplasm of enterocytes when chronically fed a high fat diet. These results suggest a reduced rate of triacylglycerol absorption in Dgat1(-/-) mice. Analysis of intestine from Dgat1(-/-) mice revealed activity for two other enzymes, DGAT2 and diacylglycerol transacylase, that catalyze triacylglycerol synthesis and apparently help to compensate for the absence of DGAT1. Our findings indicate that multiple mechanisms for triacylglycerol synthesis in the intestine facilitate triacylglycerol absorption.

Distribution of the long leptin receptor isoform in brush border, basolateral membrane, and cytoplasm of enterocytes.

Leptin, a hormone mainly produced by fat cells, acts primarily on the hypothalamus regulating energy expenditure and food intake. Leptin receptors are expressed in several tissues and the possible physiological role of leptin is being extensively investigated, with the result that important peripheral actions of the hormone in the organism are being discovered. Recent studies have demonstrated leptin and leptin receptor expression in gastric epithelial cells. In the present study, we report the presence of the long leptin receptor isoform (OB-Rb) in human, rat, and mouse small intestine, supporting the hypothesis of leptin as a hormone involved in gastrointestinal function. The presence of the leptin receptor was determined by immunocytochemical methods using antibodies against the peptide corresponding to the carboxy terminus of the long isoform of the leptin receptor. Human duodenal biopsies from normal individuals undergoing gastrointestinal endoscopy, and intestinal fragments of Wistar rats and Swiss mice were processed for the study. Immunoreactivity for the long leptin receptor isoform was observed in the three studied species. Staining was located throughout the cytoplasm of the enterocytes, of both villi and crypts, and in the basolateral plasma membrane. Immunolabelling for OB-Rb protein was also found in the brush border of human enterocytes of formol and paraformaldehyde fixed samples. This report demonstrates the presence of the long leptin receptor isoform in the absorptive cells of rat, mouse, and human small intestine, suggesting that leptin could have a physiological role in the regulation of nutrient absorption.

Up-regulation of IL-18 and IL-12 in the ileum of neonatal rats with necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease of premature infants. Because the proinflammatory cytokines IL-18, IL-12, and interferon (IFN)-gamma have been implicated in other diseases of the small intestine, we hypothesized that these cytokines would play an important role in NEC pathogenesis. NEC was induced in newborn rats via enteral feeding with rat milk substitute and asphyxia and cold stress (RMS). Dam-fed, asphyxia- and cold-stressed littermates were used as controls (DF). After 96 h, the distal ileum was removed from all animals and processed to determine expression and localization of IL-18, IL-12, and IFN-gamma using real-time reverse transcriptase PCR and immunohistology. IL-18 and IL-12 mRNA from the RMS group were increased (p < or = 0.05) compared with DF controls, and there was a correlation between increasing IL-18 and IL-12 mRNA levels and progression of tissue damage (r = 0.629 and 0.588, respectively; p < or = 0.05). Immunohistology revealed IL-18 in the cytoplasm of villi and crypt enterocytes and IL-12-positive monocytes/macrophages were increased with disease progression (r = 0.503, p < or = 0.05). No differences in the number of IFN-gamma-positive cells were observed between groups. These data demonstrate up-regulation of IL-18 and IL-12 in experimental NEC and a correlation between production of these proinflammatory cytokines and progression of tissue damage.

Incomplete gastric metaplasia in children with insulin-dependent diabetes mellitus and celiac disease. An ultrastructural study.

BackgroundThe association of insulin-dependent diabetes mellitus (IDDM) and celiac disease (CD) has been widely reported in children but the relationship between the two conditions is incompletely understood. Moreover, specific studies on intestinal biopsies of patients with the association of the two diseases are still lacking.MethodsWe studied the ultrastructure of the duodenal mucosa in 12 patients with both IDDM and CD.ResultsAll patients had either total or partial atrophy of duodenal mucosa. In seven subjects, an accumulation of electrondense granules in the apical cytoplasm of groups of enterocytes was found. In four of them, a double population of granules existed (mean diameter: 400-800 nm and 100-200 nm respectively) showing a biphasic pattern. In the other three patients, only smaller granules (100- 200 nm) were found in the enterocytes.ConclusionsThe present work suggests that patients with IDDM/CD may represent a subgroup in the context of the CD population. Intestinal biopsies of such individuals often show accumulation of electrondense granules in the apical cytoplasm of enterocytes that can be interpreted as incomplete gastric metaplasia.

Microvillous Inclusion Disease: Report of a Case with Atypical Features

Microvillous inclusion disease is a rare lethal disorder characterized by intractable, severe, watery diarrhea beginning in early infancy. The underlying defect is thought to be an autosomal recessive genetic abnormality resulting in defective brush-border assembly and differentiation. Normally, this diagnosis is easily established through the electron microscopic demonstration of characteristic microvilli-lined inclusions lying within the apical cytoplasm of surface enterocytes. In a small number of patients appearing to have microvillous inclusion disease it has not proven possible to demonstrate the typical inclusions. The existence of another entity, termed intestinal microvillous dystrophy, has been proposed to account for such occurrences. This assertion was founded in large part upon the observation that the few subjects studied all displayed a slightly atypical clinical presentation. The case now being presented exhibited the morphologic features ascribed to intestinal microvillous dystrophy but had a clinical presentation that was entirely typical of microvillous inclusion disease. It serves thus to conceptually unite intestinal microvillous dystrophy with microvillous inclusion disease.

Anomalous apical plasma membrane phenotype in CK8-deficient mice indicates a novel role for intermediate filaments in the polarization of simple epithelia.

Previous results from our laboratory have indicated a requirement for CK intermediate filaments (IF) for the organization of the apical domain in polarized epithelial cells in culture. The results seemed to be challenged by the phenotype of cytokeratin (CK) 8-deficient mice, which comprises only colorectal hyperplasia, female sterility and a weaker hepatocyte integrity. In this work localization with anti-CK antibodies indicated that many Ck8-/- epithelia still form IF in CK8-deficient mice, perhaps because of the expression of the promiscuous CK7. In the small intestine, only villus enterocytes lacked IFs. These cells appeared to lose syntaxin 3, and three apical membrane proteins (alkaline phosphatase, sucrase isomaltase and cystic fibrosis transmembrane conductance regulator) as they progressed along the villus. At the distal third of the villi, gamma-tubulin was found scattered within the cytoplasm of enterocytes, in contrast to its normal sub-apical localization, and the microtubules were disorganized. These results could not be attributed to increased numbers of apoptotic or necrotic cells. The only other cell type we found without IFs in CK8 null mice, the hepatocyte, displayed increased basolateral levels of one apical marker (HA4), indicating a correlation between the lack of intermediate filaments and an apical domain phenotype. These data suggest a novel function for intermediate filaments organizing the apical pole of simple polarized epithelial cells.