NK activity during graft-versus-host disease and graft rejection in rats following intestinal semiallogenic and allogenic transplantation with or without mesenteric lymphadenectomy

Graft-versus-host disease (GVHD) and graft rejection are major problems following intestinal transplantation (IT). Natural killer (NK) cells may be important effector cells in both conditions. In this study, Sprague-Dawley (SD) or SD-Brown Norway (BN) F1 rat intestine was transplanted into BN recipients with and without associated graft mesenteric lymphadenectomy (GML). Cyclosporine (15 mg/kg day) was administered to all animals. Pieces of the intestinal graft were examined 4 days posttransplant and again at death. NK activity calculated using intestinal intraepithelial lymphocytes (IL) was determined utilizing an 18-hr cytotoxic assay assessing 51Cr release and the results are reported as lytic units. YAC-1 cells were used as the target. NK activity was reduced 4 days after IT both in native (8.02 +/- 0.64) and in grafted bowel (3.14 +/- 1.51), with histological evidence of rejection as compared with that of control bowel in ungrafted rats (21.1 +/- 2.14). Survival was increased, on mean, a total of 6 days with the addition of GML in both semiallogenic and allogenic transplanted rats. At the time of death, the NK activity in the native bowel had increased (17.1 +/- 3.02) and histologic evidence of GVHD was present. These data suggest that: (1) NK cells are important in GVHD and (2) both semiallogenic and allogenic transplants survive longer if they are combined with GML (P < or = 0.05 and P < or = 0.01, respectively).

Immunohistochemical studies indicate multiple enteroendocrine cell differentiation pathways in the mouse proximal small intestine

The enteroendocrine cell system of the mammalian gastrointestinal tract is comprised of at least 16 different subpopulations. Each subpopulation shows a characteristic distribution along both the crypt-villus and cephalo-caudal axes. In both the small intestine and colon of adult mice, multilabel immunohistochemistry has demonstrated that two or more neuroendocrine products can be coexpressed in various combinations in single cells along the crypt-villus axis, suggesting that enteroendocrine phenotypes may be actively regulated. Using bromodeoxyuridine (BrdU) incorporation and multilabel immunohistochemistry, we have previously demonstrated an enteroendocrine cell differentiation pathway consisting of two subpopulations of cells in the mouse proximal small intestine--one involving the sequential expression of substance P, serotonin, and secretin in cells migrating out of the crypts into the villi, and a second involving the expression of substance P and serotonin in cells which remain in the crypts. In this report, we use double label immunohistochemistry and BrdU incorporation to define the temporal and spatial interrelationships between gastrin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and gastric inhibitory peptide (GIP) immunoreactive cells in the mouse proximal small intestine. The expression of these products was compared with that of substance P, serotonin, and secretin. Minimal overlap of expression was found in cells immunoreactive for substance P or serotonin with gastrin, CCK, GLP-1, or GIP; however, secretin was found colocalized in villus-associated gastrin, CCK, and GLP-1 containing cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Inductive action of epithelium on differentiation of intestinal connective tissue of Xenopus laevis tadpoles during metamorphosis in vitro

The action of the epithelium on differentiation of connective tissue cells of Xenopus small intestine during metamorphosis was investigated by using culture and morphological techniques. Connective tissue fragments isolated from the small intestine at stage 57 were cultivated in the presence or absence of homologous epithelium. In the presence of the epithelium, metamorphic changes in the connective tissue were fully induced by hormones including thyroid hormone (T3), as during spontaneous metamorphosis, whereas they were partially induced in the absence of the epithelium. Macrophage-like cells showing non-specific esterase activity in the connective tissue were much fewer in the absence of the epithelium than in the presence of it, and aggregates of fibroblasts possessing well-developed rough endoplasmic reticulum developed only in the presence of the epithelium. Just before the aggregation of the fibroblasts, the connective tissue close to the epithelium became intensely stained with concanavalin A (ConA) and wheat germ agglutinin (WGA). The present results indicate that the epithelium plays important roles in the differentiation of intestinal connective tissue cells, which in turn affect the epithelial transformation from larval to adult form during anuran metamorphosis. Thus, the tissue interaction between the epithelium and the connective tissue in the anuran small intestine is truly bidirectional.

Characterization of gangliosides of epithelial cells of calf small intestine, with special reference to receptor-active sequences for enteropathogenic Escherichia coli K99

Glycolipids were prepared from epithelial cells of the small intestine of a newborn calf and assayed for Escherichia coli K99 binding activity on thin-layer chromatograms and in microtiter wells. The bacteria did not bind to any of the non-acid glycolipids, while in the acid fraction several binding-positive glycolipids were detected. The acid glycolipids were isolated and characterized by mass spectrometry, proton NMR spectroscopy and other methods. The following gangliosides were identified, mainly from the epithelial cells from the upper part of the small intestine: NeuAc alpha 2-3Gal beta 1-4Glc beta 1-Cer (NeuAc-GM3), NeuGc alpha 2-3Gal beta 1-4Glc beta 1-Cer (NeuGc-GM3), GalNAc beta 1-4(NeuGc alpha 2-3)Gal beta 1-4Glc beta 1-Cer (NeuGc-GM2), Gal beta 1-3GalNAc beta 1-4(NeuGc alpha 2-3)Gal beta 1-4Glc beta 1-Cer (NeuGc-GM1), and NeuGc alpha 2-3Gal beta 1-3GalNAc beta 1-4(NeuGc alpha 2-3)Gal beta 1-4Glc beta 1-Cer (NeuGc-GD1a). A positive binding was demonstrated to NeuGc-GM3, NeuGc-GM2, and NeuGc-GD1a, while NeuAc-GM3 and NeuGc-GM1 were negative. The binding pattern differed somewhat for total acid glycolipids of epithelial cells from three different parts of the small intestine. Based on binding preferences of E. coli K99 to a number of glycolipids of various origins, in comparison with calculated minimum energy conformations, a binding epitope was delineated.

Generation of neomucosa in vivo by transplantation of dissociated rat postnatal small intestinal epithelium

A novel method to study the generation of rat small intestinal mucosa, by transplantation of disaggregated postnatal rat small intestinal epithelium is described. Cellular aggregates, comprised of epithelium with attached proliferative cells and closely associated stromal tissue, were isolated from postnatal rat small intestine by enzymatic digestion, then grafted immediately to the subcutaneous plane of adult recipients. On graft retrieval after 14 days, 39% of cellular transplants to nude mice, and 84% of cellular transplants to inbred rats had developed into small intestine-like structures. These structures were comprised of a circumferential layer of epithelium surrounding a central mucin filled lumen. This neomucosal layer exhibited well formed crypts and villi, and contained all epithelial stem cell lineages i.e. absorptive enterocytes, goblet cells, Paneth's cells and entero-endocrine cells. Proliferative activity within this neomucosa was confined to crypt regions as in normal postnatal small intestine. Developmental maturation within the regenerated neomucosa was demonstrated by organotypic morphogenesis, i.e. formation of mature crypts and villi, and progressive cytodifferentiation with increased numbers of goblet cells, entero-endocrine cells and Paneth's cells. Altered patterns of brush border enzyme expression further confirmed a temporal progression of development within neomucosal enterocytes. It is concluded that after "extensive" mucosal disaggregation, postnatal small intestinal epithelial progenitor cells retain the capacity for organotypic regeneration of neomucosa when transplanted to ectopic sites in adult recipients. These small aggregates of epithelium and stroma are capable of generating the topographical signals necessary for the three dimensional regeneration of this tissue. Furthermore, the multipotent generative potential of the stem cells within these cellular aggregates is maintained with production of all progeny.

A similar expression pattern of adhesion molecules between intermediate TCR cells in the liver and intraepithelial lymphocytes in the intestine

Two major populations of extrathymically differentiated T cells exist in the liver and intestine. Such T cells in the liver have TCR of intermediate intensity (i.e., intermediate TCR cells) and constitutively express IL-2 receptor beta-chain (IL-2R beta), whereas those in the intestine, especially intraepithelial lymphocytes, have TCR of bright intensity, consisting of a mixture of IL-2R beta+ and IL-2R beta-. All mature thymocytes and thymus-derived T cells seen in the peripheral immune organs are TCR-bright+ IL-2R beta- under resting conditions. When the expression pattern of adhesion molecules, including CD44, L-selectin, LFA-1 and ICAM-1, was compared among these T-cell populations, they displayed quite unique patterns of expression. All extrathymic T cells in the liver, intestine, and even other organs were CD44+ L-selectin-LFA-1++ICAM-1+, whereas thymocytes and thymus-derived T cells were CD44-L-selectin+LFA-1+ICAM-1-. This inverted expression of adhesion molecules between extrathymic T cells and thymus-derived T cells might be associated with their unique tissue-localization.

Glucose, galactose, and glutamine metabolism in pig isolated enterocytes during development

In the pig, the gastrointestinal tract grows rapidly after birth and undergoes a short postnatal maturation. The objective of the present work was to assess the metabolic characteristics of the small intestinal mucosa during this period by investigating glucose, galactose, and glutamine metabolism in pig isolated enterocytes. Piglets were used immediately after birth or at various stages during suckling or postweaning. Fed animals were taken in a postabsorptive state. The jejunoileum was excised and perfused with an EDTA (5 mM)-containing buffer. The epithelial cell layer was further dissociated in the presence of hyaluronidase (0.01%). The resulting cell suspension (95% absorbing enterocytes; viability greater than 90%) was incubated with 14C-labeled substrates to measure 14CO2 production in parallel with substrate disappearance. The capacity to utilize glutamine was high and remained steady during the suckling period. Glucose utilization capacity was limited at birth and increased more than 3-fold during the first week of suckling. Such an increase was not observed in piglets kept unsuckled since birth. Galactose utilization capacity remained steady during the first week but afterward gradually disappeared. Lactate and pyruvate production through glycolysis was the major pathway accounting for glucose or galactose disappearance. A capacity for a net glucose production from galactose was evidenced during the first week of suckling. Thus, isolated newborn pig enterocytes exhibit specific and transient metabolic characteristics during the first postnatal week.

Identification and characterization of rat gamma/delta T lymphocytes in peripheral lymphoid organs, small intestine, and skin with a monoclonal antibody to a constant determinant of the gamma/delta T cell receptor

A mAb called V65 was raised to a CD3+, TCR-alpha/beta- rat/mouse T cell hybrid that selectively reacts with all CD3+, TCR-alpha/beta- rat lymphocytes. Both anti-CD3 and V65 precipitate a 48- to 50-kDa heterodimeric protein from digitonin-lysed surface-iodinated cells. V65+ but not V65- T cells and T cell hybridoma cells express TCR-gamma mRNA. Together, these results show that V65 detects a constant determinant of the rat TCR-gamma/delta. In the presence of either IL-2 or IL-4, V65 stimulates proliferation in peripheral rat gamma/delta T cells. Approximately 90% of gamma/delta T cells from peripheral lymphoid organs have the same cell surface phenotype as thymus-derived MHC class I-restricted alpha/beta T cells, i.e., they are CD4- but express the CD8 alpha/beta heterodimer together with CD2 and CD5. In contrast, gamma/delta T cells from the epithelium of the small intestine lack CD2, CD4, and CD5 and express CD8 alpha only. Finally, V65 directly identifies a dense network of dendritic cells in the epidermis as gamma/delta T cells. These dendritic epidermal T cells are absent from athymic rats, indicating that like their mouse counterparts, they are thymus dependent.

Lamina propria macrophages involved in cell death (apoptosis) of enterocytes in the small intestine of rats

In the rat small intestine, apoptotic enterocytes are exfoliated at the villus tip as a whole cell, in contrast to guinea pig enterocytes which are phagocytosed by macrophages in their cell body and shed off only in their apical cortex. While macrophages gather in the lamina propria of the intestinal villi in both species, their functions seem to differ. Unlike the guinea pig, lamina propria macrophages observed in the rat small intestine did not show morphological signs of phagocytosis, revealing few cellular elements in their phagosomes. At the "shoulder" of the villus, i.e., a certain distance proximal to the villus tip, subepithelial macrophages extended a thick process deep into the epithelium; their branched terminals penetrated the cytoplasm of enterocytes, resulting in the formation of excavated spaces in the cell body. Processes of macrophages frequently reached close to the brush border. At the shoulder of the villus, a few effete cells showed typical apoptotic signs and appeared to be pushed out into the lumen; still, the shedding of apoptotic enterocytes was recognized mainly at the very top of the villus, where no intraepithelial processes of macrophages could be seen. The present findings indicate that in the rat, lamina propria macrophages do not engulf aged enterocytes, but are involved in inducing their apoptosis.

Subtractive hybridization cloning of novel genes differentially expressed during intestinal development

Intestinal genes whose expression is regulated during development and differentiation were identified and cloned from a rat villi cDNA library using a subtracted cDNA probe. The isolated clones are transcribed in the fully differentiated intestinal epithelium 21 days after birth and absent or poorly expressed in the fetal gut at 15 days of gestation. Two of the DRI (differentially-expressed in rat intestine) genes are novel, while the others encode the microvillar protein ezrin and intracellular carrier proteins for retinol and fatty acids. Expression of the newly isolated DRI27 and DRI42 clones parallels epithelial differentiation during development and it is more pronounced in the distal portions of the small intestine. In situ hybridization experiments indicate that the DRI mRNAs are expressed in the differentiated cell types of the gut epithelium. Moreover, the expression of DRI27 and DRI42 is strongly related to the stage of epithelial differentiation during gut development. This relationship holds true also for the expression of DRI42 in other tissues. These clones will be a valuable tool to identify regulatory sequences and factors responsible for confining gene expression to the differentiated epithelial cell types in mammalian small intestine.

Localization of mucin (MUC2 and MUC3) messenger RNA and peptide expression in human normal intestine and colon cancer

BACKGROUND/AIMS

Several studies have reported Northern blot data showing that mucin is expressed in a tissue-specific manner. To determine whether expression is limited to specific cell types within these tissues requires histological analysis.

METHODS

Both immunocytochemistry and in situ hybridization were used to identify cell types expressing the MUC2 and MUC3 mucins in the human small intestine, colon, and colon carcinoma.

RESULTS

In the normal small intestine and colon, an antibody recognizing the MUC2 apomucin stained goblet cells. In contrast, an antibody recognizing the MUC3 apomucin stained both goblet and absorptive cells. Consistent with this, in situ hybridization showed MUC2 messenger RNA (mRNA) only in goblet cells and MUC3 mRNA in both goblet and absorptive cells. In several samples of moderately well-differentiated colon cancer, MUC2 and MUC3 showed distinct patterns of expression, but the expression level of each was reduced compared with levels in normal tissue; there was considerable tumor-to-tumor and cell-to-cell variability using both mucin antibodies and complementary DNA probes.

CONCLUSIONS

Individual mucin genes have distinct patterns of expression within mucin-producing tissues, suggesting that the various mucin gene products play distinct functional roles.

Derivation of conditionally immortalized cell lines containing the Min mutation from the normal colonic mucosa and other tissues of an "Immortomouse"/Min hybrid

The Multiple Intestinal Neoplasia (Min) mouse carries the murine homologue of the human APC gene. To overcome the difficulties of culturing normal colonic mucosal cells in vitro we developed an F1 hybrid mouse ("Immortomouse" (H-2Kb-tsA58 SV40 large T)x Min) which carries both the Min mutation and a temperature-sensitive mutant of the SV40 large T gene. We have derived epithelial cell lines from both isolated colonic crypts and the liver of this hybrid mouse. The colonic epithelial cultures are only conditionally immortalized and growth ceases at the non-permissive temperature indicating that these cells have retained their normal phenotype. Fibroblast cultures have also been obtained from both small intestinal stroma and skin. The polymerase chain reaction (PCR) assays indicated that the cell lines all contain both the Min mutation and the SV40 large T gene. This study demonstrates the usefulness of the "Immortomouse" for developing cultures from tissues such as the intestine that have previously proved very difficult to culture in vitro.

Absence of calcitriol-mediated nongenomic actions in isolated intestinal cells of the damara mole-rat (Cryptomys damarensis)

Calcitriol [1,25(OH)2D3] actions on intestinal calcium transport involve genomic and nongenomic pathways. Whether nongenomic 1,25(OH)2D3-mediated actions are employed was investigated using isolated intestinal epithelial cells of naturally vitamin D-deficient underground-dwelling damara mole-rats (Cryptomys damarensis). 1,25(OH)2D3-mediated nongenomic pathways of intestinal calcium uptake, measured by opening of 1,25(OH)2D3-activated voltage-sensitive Ca2+ channels (VSCC), did not occur. Rapid (1 min) 45Ca2+ transmembrane influx in intestinal cells was not significantly increased by the addition of 1,25(OH)2D3 (at concentrations from 10(-12) to 10(-6) nM), when compared to opening of VSCC in the presence of a depolarizing (elevated K+) buffer. Furthermore, even after 30 min calcium uptake was not significantly enhanced by the hormone. These findings support earlier reports that duodenal calcium absorption is independent of vitamin D and is a highly adaptive feature of a subterranean existence.

[Protective effects of glutamine and elemental diet in acute actinic enterocolitis: histological evaluation]

Radiotherapy plays nowadays an important role in malignancies treatment. However, collateral effects and severe complications owing to cellular damage of peritumoral tissues may occur. Different nutritional resources have been recently indicated to achieve intestinal protection during cancer irradiation. PURPOSE--The aim of this study was to set the role of glutamine and elemental diets in acute actinic enteritis prevention. METHOD--Sixty-five adult male Wistar rats with average weight of 200g were maintained in individual metabolic cages; daily body weight and food ingestion were carefully monitored. The animals were randomized into three groups and fed isocaloric and isonitrogenous diets: 1) CRt-polymeric-casein diet; 2) GRt-polymeric-casein diet supplemented with 2% glutamine and 3) ERt-elemental diet supplemented with 2% glutamine. After an adaptation period (seven days), all rats received abdominal radiation in five daily doses of 300cGy. Four days after the rats were operated on to resect the small intestine and colon for histological evaluation. RESULTS--Small intestine histological data in ERt and GRt rats were better than CRt rats, by preserving mucosal cellularity and increasing mitosis number and villi length. Simultaneously, ERt group had greater number of rats with normal villus-crypt relation than CRt or GRt groups. Large intestine histological data showed that the average crypts length in ERt and GRt rats were greater than in CRt ones. CONCLUSION--Glutamine-supplemented polymeric or elemental diets given to rats before, during and after abdominal radiotherapy showed protective effects against radiation injury, by supporting mucosal structure and recovery.

Regulation of expression of the human fructose transporter (GLUT5) by cyclic AMP

The effect of cyclic AMP on the expression of the fructose transporter, GLUT5, was studied in Caco-2 cells, a human colon cancer cell line that differentiates spontaneously in culture into cells with the properties of small intestine enterocytes. Treatment of differentiated Caco-2 cells with 50 microM forskolin, which stimulates adenylate cyclase and raises intracellular cyclic AMP levels, increased fructose uptake 2-fold and raised GLUT5 protein and mRNA levels 5- and 7-fold respectively. The increased GLUT5 mRNA levels in forskolin-treated cells are a result of stabilization of GLUT5 mRNA in these cells and increased transcription. The effect of cyclic AMP on GLUT5 transcription was assessed by measuring the activity of human GLUT5 promoter-reporter gene constructs in forskolin-treated differentiated Caco-2 cells. The results showed that forskolin stimulated the activity of the GLUT5-reporter gene constructs and this stimulatory effect was mediated by cis-acting regulatory sequences.

Primary culture of salamander intestinal epithelial cells from nests: whole cell Na+ currents induced by valine

Methods are described for isolating the cell nests, subepithelial clusters of germinative cells, from salamander intestinal mucosa and for growing the nests in culture into polarized monolayers of intestinal epithelial cells. Cells were viable in culture for up to 3 wk. The capacity of the monolayer cells to engage in membrane transport was evaluated using the patch-clamp technique in the whole cell mode. L-Valine (25 mM) induced an inward current in small intestinal cells of 25.8 +/- 5.7 pA and depolarized the cell membrane 14.5 +/- 1.6 mV. L-Alanine and L-phenylalanine were similarly effective, whereas D-valine was ineffective. The Km of the transporter for valine was 90 mM. Replacement of bath Na with tris(hydroxymethyl)aminomethane eliminated the inward current induced by valine. The basal (solute-independent) inward current was also reduced by Na+ replacement. Glucose did not induce a Na+ current. In contrast to the effect of valine on small intestinal cells, large intestinal cells were unresponsive to valine. It is concluded that the cultured small intestinal cells possess Na-amino acid but not Na-sugar cotransport. This profile of behavior is characteristic of undifferentiated small intestinal cells. Primary cultures of salamander small intestinal cells should be useful for studying enterocyte function and the developmental biology of the small intestinal mucosa.

Crypt and villous epithelial cells in adult rat small intestine: numerical and volumetric variation along longitudinal and vertical axes

Previous studies on the small intestines of certain adult rodents have suggested that the total number of crypt epithelial cells is equal to the number of villous epithelial cells. This possibility is examined on adult male Sprague-Dawley rats using design-based stereological methods. Small intestines were removed and divided into four segments of equal length. For each segment, numbers and mean volumes of epithelial cells in crypts and villi were estimated and then combined to give values for the entire intestine. Variations along the vertical (crypt-villus) axis and the intestinal long (pyloro-ileocaecal) axis were examined. Cell numbers in crypts and on villi varied from segment to segment. Villus:crypt cell ratios proximally were roughly double those found distally. The ratio for the entire intestine was, on average, 1.6 villous cells per crypt cell. These results demonstrate that numbers of crypt and villous cells need not be equivalent. Previous findings may reflect the fact that ratios fluctuate according to circumstances (e.g., with species, age, nutritional status, disease, etc) or may be due to technical differences in tissue sampling and morphometry. Cell volumes varied along the crypt-villus axis as well as between segments, confirming known gradients of maturation and activity. Finally, the size of the intestinal epithelial proliferon was calculated in terms of the average numbers of epithelial cells per villus and of crypt epithelial cells feeding on to it.

A Paneth cell analogue in Xenopus small intestine expresses antimicrobial peptide genes: conservation of an intestinal host-defense system

Antimicrobial peptides are a widespread component of host defense. We characterized the tissue distribution and cellular localization of expression of the magainin family of antimicrobial peptide genes in Xenopus laevis. Two genes from this family, magainin and PGLa, are expressed at high levels in the skin and throughout the gastrointestinal tract. Magainin and PGLa mRNAs are synthesized in the granular multinucleated cell (GMC) of the gastric mucosa, a cell shown previously to contain magainin and PGLa peptides by immunohistochemical methods. In addition, we have localized magainin and PGLa mRNAs to distinct cells of Xenopus small intestine. Further characterization of this large, granule-filled cell by electron microscopy demonstrates features in common with the Paneth cell of mammalian small intestine, previously identified as a site of expression of antimicrobial peptide genes of the defensin family in mouse and human. Our identification of granule-laden, eosinophilic intestinal cells in Xenopus as a site of magainin and PGLa antimicrobial peptide gene expression suggests that these cells are functional analogues of mammalian Paneth cells and further supports a conserved role of antimicrobial peptides in host defense of the vertebrate small intestine.

Identification of interstitial cells of Cajal. Significance for studies of human small intestine and colon

BACKGROUND

Interstitial cells of Cajal (ICC) were described a century ago by Ramón y Cajal a.o. as primitive neurons in the intestines. In the period 1900-1960 a large number of light microscopical studies of ICC were published, in which ICC were identified by heir characteristic morphology. After 1960 electron microscopical studies emphasized similarities between ICC and fibroblasts. In our early studies of ICC in the external musculature of mouse small intestine, we identified ICC by their characteristic morphology and topography, and we analyzed the relation between ICC, autonomic nerves and smooth muscle. These studies strongly suggested that ICC were fundamental regulators of external muscle function. These hypotheses have since been supported by independent morphological and electrophysiological evidence, strongly suggesting a pacemaker role of some ICC populations as well as other regulatory functions (mechanoreceptive, mediating inhibitory nervous input). In spite of this possible fundamental importance for G-I motility, ICC have not been adequately described or even identified in human intestine, and hence, never included in ultrastructural studies of G-I neuropathology. This survey presents the concepts of ultrastructure necessary for identification and morphological studies of ICC in human intestine.

METHODOLOGY

Several light microscopical methods have been claimed selective for intestinal ICC (and nerves), including vital methylene blue, Golgi methods, silver impregnations and ZIO-methods. Unfortunately, even the most reliable of them (ZIO, vital methylene blue) do not work at all in some animal species and in some, regions of the intestinal wall. In our hands, the best results have been obtained in mouse small intestine with vital methylene blue staining (AP only) and with ZIO methods (all levels of the musculature). None of them have yet proved their value in human intestine, although we have occasionally stained ICC-SMP in human colon with ZIO methods. Optimal ultrastructural preservation of ICC for TEM studies in laboratory animals, has been achieved by fixation by vascular perfusion. In humans, the ultrastructural preservation was satisfactory, but not ideal, after optimizing the immersion fixatives (Karnovsky-types, addition of picrate).

RESULTS AND DISCUSSION

General architecture of musculature externa. ICC differ markedly in their organization and ultrastructure from one part of the gut and from one region to another. For understanding the extent and distribution of ICC plexuses it is therefore critical to preserve a stringency and uniformity with respect to terminologies and descriptions of topography. Auerbach's plexus (AP) designates the ganglionated plexus between the main muscle layers in small and large intestine, whereas we prefer to use the term myenteric plexus for all nerves in the external muscle. The deep muscular plexus (DMP) designates the two-dimensional, non-ganglionated nerve plexus between the thick outer and thin inner subdivision of the circular muscle layer in the small intestine. In our material a similar plexus was not present in colon. The submuscular plexus (SMP) indicates the non-ganglionated, two-dimensional nerve plexus present at the submucosal surface of the colonic circular muscle. The circular muscle in small- and large intestine of large animals (dogs, humans) is organized into lamellae, separated by main septa piercing the whole layer. Both in the small intestine and colon the innermost circular muscle cells, are smaller, and, particularly in colon, more irregular than the bulk of the circular muscle. Identification of ICC in laboratory animals. By TEM ICC are distinguishable as a separate cell type in the small- and large intestine of all species investigated.(ABSTRACT TRUNCATED)