吸收不良综合征十二指肠降部粘膜病理及超微结构观察

采用常规胃镜下十二指肠降部粘膜活检，对２０例吸收不良综合征十二指肠降部粘膜绒毛病理，及微绒毛超微结构进行观察，并行相应图像作定量分析。结果表明：吸收不良综合征组绒毛高度降低、宽度增加、陷窝深度加深，与对照组比较差异均有非常显著性（Ｐ＜０．０１）；微绒毛密度减低、高度减低、表面积缩小，与对照组相比差异均有非常显著性（Ｐ＜０．００１）．结论：十二指肠降部粘膜活检可用于吸收不良综合征的诊断     

The development of the fetal rat intestine and its reaction to maternal diabetes. II. Effect of mild and severe maternal diabetes

Diabetes during pregnancy induces specifically structural and functional changes in the fetal endocrine pancreas. Other organs are affected as well. In this study, the fetal intestinal tract which is in close connection with the endocrine pancreas was analysed during diabetic gestation. The disease was induced by two different doses of streptozotocin which led to a mild or severe diabetic state in the mother. In fetuses from mildly diabetic as well as from severely diabetic rats, the time sequence in the appearance of the differentiated cells was identical and similar to that of controls. However, morphometric analysis of the intestine of fetuses from severely diabetic rats revealed a decrease in each of the parameters measured which led to a general hypotrophy of the intestine. In the fetuses from mildly diabetic rats, the values of the morphometric parameters of the duodenal mucosa remained unchanged and comparable to those of the control group. The vascularisation of the duodenum is modified in these fetuses because the volume density of the blood vessels is significantly increased. In conclusion, both diabetic states of the mother induce various alterations in the fetal intestine, including the blood vessels. The nature of the structural changes observed in the intestine could lead to modifications in the function of the entero-pancreatic system in these fetuses.     

Fetal characteristics of small intestinal crypt cells.

Nine monoclonal antibodies were prepared against luminal membranes purified from rat intestinal cells at day 19 of gestation, and seven of them were found to define antigens common to adult crypt cells and fetal or embryonic intestinal epithelial cells. The FBB 2/29 antigen was first detected over the entire intestinal epithelial population at days 14-15 of gestation, a period of development characterized by formation of a stratified intestinal epithelium and differentiation of the surrounding mesenchyme. This antigen, identified as a set of high molecular mass proteins, became restricted to the crypt and lower villus cells after birth and was exclusively expressed by the crypt cells in adult intestine. It also was found to be expressed by the epithelial cells of the distal tubuli in the kidney of adult rats and by cultured human tumor colonic cells. The FBB 1/54/1, FBB 3/46, and FBB 3/78/9 antibodies stained only the epithelial cells present at the base of the villi in fetal intestine, starting at days 20-21 of gestation (about 1-2 days before birth), and stained the crypt and lower villus cells in newborn and adult intestine; these antigens may be regarded as specific markers for the developing crypt cells in fetal intestine shortly before birth. The FBB 1/20 and FBB 4/2 antigens were first detected on the fetal intestinal cells at day 18 of gestation; they were located over the entire epithelium in newborn rats and became restricted to the crypts after weaning. The FBB 2/28 antigen was expressed by the entire intestinal epithelium at all stages of development, starting from days 18-19 of gestation in the fetus. Two antibodies, FBB 3/4 and FBB 3/24, were found to be specific for lactase. These results have demonstrated the expression of cell- and tissue-specific components in rat intestine during early embryonic development and revealed a marked similarity in surface membrane antigens between fetal intestinal epithelial cells and adult crypt cells.     

Transmission of rotavirus gastroenteritis from children to a monkey.

A pooled suspension of rotavirus was prepared from the stools of eight children with acute non-bacterial gastroenteritis. The suspension was infused into the duodenum and stomach of an infant monkey (Nemestrina macaque). Biopsy samples of duodenal mucosa were taken at several intervals after inoculation, examined by light and electron microscopy, and assayed for lysosomal activity. Virus-like particles were seen within and around microvilli and intracellularly within vesicles as early as 20 minutes after the infusion. On the fourth and fifth days, large lysosomal bodies containing numerous virus-like particles were found within epithelial cells of the duodenal villi. No such particles were seen in the pre-inoculation sample or at days 16 or 25 after infection. The present study would appear to be the first demonstration of the transmission of this human virus to another species.     

Cell-specific immunohistochemical localization of a cellular retinol-binding protein (type two) in the small intestine of rat.

One of us recently has reported the purification of a new retinol-binding protein that is distinctly different from the well-known cellular retinol-binding protein, CRBP. This protein, which we propose to name cellular retinol-binding protein type II [CRBP(II)], was found almost exclusively in the small intestine of the adult rat at levels 1000 times greater than that of CRBP. Here we have determined the cellular location of these two proteins in the small intestine of the rat. By using an immunohistochemical technique, the absorptive cells of the small intestine, from the duodenum to the ileum, were strongly stained when antiserum against CRBP(II) was used. More intense staining was observed in absorptive cells near the tips of the villi than in those located at the base of the villi. However, the proliferative cells in the crypts of Lieberkühn were stained only lightly if at all. In contrast to absorptive cells, goblet cells in the villi did not stain. When tissue sections containing the gastroduodenal junction were examined, no staining was observed in the gastric epithelium, while the epithelium of the most proximal portion of the duodenum showed very strong staining. In tissue sections containing the ileocecal junction, staining terminated abruptly at the end of the distal ileum. No staining was observed in the epithelium of the colon. In contrast, the cellular location of CRBP in the small intestine was quite different from the cellular location of CRBP(II). The epithelial cells of the small intestine showed no staining when affinity-purified anti-CRBP was used. Staining was observed for connective tissue cells in the lamina propria and in cells located within the gut-associated lymphoid tissue. The cell-specific localization pattern determined for these two proteins suggests that CRBP(II), rather than CRBP, is the protein that plays a role in the absorption of retinol.     

Anisotropic growth shapes intestinal tissues during embryogenesis

Embryogenesis offers a real laboratory for pattern formation, buckling, and postbuckling induced by growth of soft tissues. Each part of our body is structured in multiple adjacent layers: the skin, the brain, and the interior of organs. Each layer has a complex biological composition presenting different elasticity. Generated during fetal life, these layers will experience growth and remodeling in the early postfertilization stages. Here, we focus on a herringbone pattern occurring in fetal intestinal tissues. Common to many mammalians, this instability is a precursor of the villi, finger-like projections into the lumen. For avians (chicks’ and turkeys’ embryos), it has been shown that, a few days after fertilization, the mucosal epithelium of the duodenum is smooth, and then folds emerge, which present 2 d later a pronounced zigzag instability. Many debates and biological studies are devoted to this specific morphology, which regulates the cell renewal in the intestine. After reviewing experimental results about duodenum morphogenesis, we show that a model based on simplified hypothesis for the growth of the mesenchyme can explain buckling and postbuckling instabilities. Being completely analytical, it is based on biaxial compressive stresses due to differential growth between layers and it predicts quantitatively the morphological changes. The growth anisotropy increasing with time, the competition between folds and zigzags, is proved to occur as a secondary instability. The model is compared with available experimental data on chick’s duodenum and can be applied to other intestinal tissues, the zigzag being a common and spectacular microstructural pattern of intestine embryogenesis.     

Morphological properties and residual strain along the small intestine in rats

AIM: Residual stress and strain are important for gastrointestinal function and relate to the geometric configuration, the loading conditions and the zero-stress state of the gastrointestinal tract. The purpose of this project is to provide morphometric data and residual strains for the rat small intestine ( n =11). METHODS: To approach the no-load state, the intestine was surgically excised, transferred to an organ bath and cut transversely into short ring-shaped segments. Each ring was cut radially for obtaining the zero-stress state. The residual stress can be characterised by an opening angle. The strain difference between the zero-stress state and the no-load state is called residual strain. RESULTS: Large morphometric variations were found along the small intestine. The wall thickness was highest in the proximal duodenum and decreased in distal direction along the axis of the small intestine (P<0.001). The circumferential length of the inner and outer surfaces decreased rapidly along the length of duodenum by 30-50% (P<0.001). The wall area and lumen area showed a similar pattern (P<0.001). In zero-stress state the rings always opened up after making the cut. The experiments resulted in larger inner circumferential length and smaller outer circumferential length when compared to the no-load state. The wall thickness and wall area did not differ between the no-load and zero-stress state. The opening angle and tangent rotation angle increased along the length of the duodenum and had its highest value 30% down the intestine. Further down the intestine it decreased again (P<0.001). The serosal residual strain was tensile with the highest value close to the ligament of Treitz (P<0.001). The mucosal residual strain was compressive in all segments of the small intestine with average values between -0.25 and -0.4 and with the lowest values close to the ligament of Treitz (P<0.001). CONCLUSION: Axial variation in morphometric properties and residual strains were found in the small intestine. Existence of large residual strains indicates that the zero-stress state must be considered in future biomechanical studies in the gastrointestinal tract.     

Hypertrophy of the small intestine after its partial resection in the rat

The authors investigated the ultrastructure of small intestinal epithelium in the rat, 3 weeks after resection of the proximal half of the small intestine. They sought to determine: (1) whether the compensatory hypertrophy of the mucosa of the residual small intestine results in changes in the microvilli, in addition to prolongation of the villi; and, (2) whether it is possible to provide evidence of less complete morphologic differentiation in the more rapidly migrating enterocytes. The epithelium on the surface of villi in animals after resection does not differ ultrastructurally from controls and is formed by completely differentiated cellular elements. It is apparent that the compensatory enlargement of the intestinal absorption surface is a result of the hypertrophy of the mucosal villi, and not of changes in the microvilli.     

Cellular and subcellular localization of the Nramp2 iron transporter in the intestinal brush border and regulation by dietary iron.

Genetic studies in animal models of microcytic anemia and biochemical studies of transport have implicated the Nramp2 gene in iron transport. Nramp2 generates two alternatively spliced mRNAs that differ at their 3' untranslated region by the presence or absence of an iron-response element (IRE) and that encode two proteins with distinct carboxy termini. Antisera raised against Nramp2 fusion proteins containing either the carboxy or amino termini of Nramp2 and that can help distinguish between the two Nramp2 protein isoforms (IRE: isoform I; non-IRE: isoform II) were generated. These antibodies were used to identify the cellular and subcellular localization of Nramp2 in normal tissues and to study possible regulation by dietary iron deprivation. Immunoblotting experiments with membrane fractions from intact organs show that Nramp2 is expressed at low levels throughout the small intestine and to a higher extent in kidney. Dietary iron starvation results in a dramatic upregulation of the Nramp2 isoform I in the proximal portion of the duodenum only, whereas expression in the rest of the small intestine and in kidney remains largely unchanged in response to the lack of dietary iron. In proximal duodenum, immunostaining studies of tissue sections show that Nramp2 protein expression is abundant under iron deplete condition and limited to the villi and is absent in the crypts. In the villi, staining is limited to the columnar absorptive epithelium of the mucosa (enterocytes), with no expression in mucus-secreting goblet cells or in the lamina propria. Nramp2 expression is strongest in the apical two thirds of the villi and is very intense at the brush border of the apical pole of the enterocytes, whereas the basolateral membrane of these cells is negative for Nramp2. These results strongly suggest that Nramp2 is indeed responsible for transferrin-independent iron uptake in the duodenum. These findings are discussed in the context of overall mechanisms of iron acquisition by the body.     

Morphometric study of the rat exocrine pancreas after diversion of bile and pancreatic juice from the intestine

The effects of 6 h of diversion of bile and pancreatic juice from the intestine on the ultrastructure of rat pancreatic acinar cells were studied by morphometric procedures. After diversion the volume of zymogen granules decreased markedly, representing a reduction of 77%. The volume of autophagic vacuoles increased twofold after diversion. The volume of rough endoplasmic reticulum and Golgi apparatus was not different from that of control. It has been proved by electron microscopic morphometry that the degree of reduction of zymogen granules was similar to that after stimulation by exogenous cholecystokinin or introduction of trypsin inhibitor to the duodenum. This suggests that hypersecretion caused by diversion is due to failure of a negative feedback regulation normally induced by proteases found in pancreatic juice. An increased number of autophagic vacuoles suggests an increase of organelle turnover due to heightened secretory activity of acinar cells.     

Infection by Leishmania (Leishmania) infantum chagasi causes intestinal changes B‐1 cells dependent

Evaluating the histopathological and morphometric changes caused by Leishmania (Leishmania) infantum chagasi infection either in the presence or absence of B‐1 cells. Wild‐type Balb/c and XID mice were used. Half of XID mice received B‐1 cells adoptive transfer (XID + B1). Five animals from each group were infected (Balb/c I, XID I and XID + B1 I), totalizing six groups (n = 5). After 45 days of infection, the ileum was collected for histological processing and analysis. After infection, the XID animals showed an increase in the thickness of the intestinal layers, in the depth and width of the crypt and in the villi width. However, the Balb/c I group showed a reduction in almost all these parameters, whereas the villi width was increased. The villi height decreased in the infected XID animals; however, it was increased in the XID + B1 I group. Leishmania (L) infantum chagasiinfection caused a decrease in the number of Paneth cells; however, their area was increased. Finally, goblet cells and enterocytes presented different change profiles among groups. This study showed that the parasite infection causes structural and histopathological alterations in the intestine. These changes might be influenced by the absence of B‐1 cells.     

Cellular differentiation in the emerging fetal rat small intestinal epithelium: mosaic patterns of gene expression.

We have examined the pattern of differentiation of the small intestinal epithelium in fetal rats during the 17th through 21st days of gestation. Five genes expressed in late fetal, neonatal, and adult enterocytes were used as markers of differentiation. They encode three homologous small cytoplasmic hydrophobic ligand binding proteins--liver fatty acid binding protein (L-FABP), intestinal fatty acid binding protein (I-FABP), and cellular retinol binding protein II (CRBP II)--and two apolipoproteins--apoAI and apoAIV. RNA blot hybridization studies indicated that gradients in mRNA concentration from the proximal small intestine to colon appear coincident with the initiation of rapid epithelial cell proliferation and villus formation (days 17-19 of the 22-day gestation period). Immunocytochemical studies disclosed a remarkably heterogeneous pattern of cell-specific expression of the three hydrophobic ligand binding proteins that was not apparent with either apoAIV or apoAI. This "mosaic" staining pattern was observed in morphologically similar cells occupying identical topographic positions along nascent villi in 17- to 18-day fetuses. The onset and resolution of this mosaicism varies between I-FABP, L-FABP, and CRBP II in the proximal small bowel, although it completely resolves by the first postnatal day. The distal small intestine exhibits a developmental delay of 1-2 days in the appearance of this heterogeneous pattern of initial gene expression. Double-label immunofluorescent analyses using L-FABP and I-FABP antibodies indicated that on the 18th day of gestation the proximal small intestinal columnar epithelium contains several populations of enterocytes expressing neither, one, or both proteins. The potential significance of this mosaic pattern of intestinal epithelial differentiation is discussed in light of recent studies with transgenic and chimeric mice.     

Repair of microvilli in the rat small intestine after damage with lectins contained in the red kidney bean

That microvilli of intestinal absorptive cells in the duodenum and jejunum are disrupted by acute challenge with lectins contained in raw kidney beans (RKB) was shown nearly 10 yr ago by light microscopy. However, the precise morphologic damage produced by RKB has not been characterized, and it is not known whether microvilli, once damaged, undergo repair. We have examined these issues by challenging rats with suspensions of 300 mg of RKB, boiled beans, or standard laboratory chow by orogastric lavage. Microvillus length was measured in electron micrographs from 6 to 20 h after challenge. Epithelial cell migration was determined by autoradiography after injection of [3H]thymidine. After challenge with RKB, microvilli (a) showed extensive vesiculation along the length of villi 2-4 h after challenge; (b) were reduced significantly in length along the entire villus 6 h after challenge; and (c) were near normal in length by 20 h after challenge. Microvillus length was also reduced significantly 6 h after challenge with boiled beans. The rate of cell migration was not accelerated by treatment with RKB. These data suggest that damage to microvilli caused by 300 mg of RKB is self-limited and reversible; microvilli once damaged by RKB are repaired. Repair of microvilli is due to intrinsic reparative processes rather than accelerated replacement of damaged cells. We speculate that microvilli may be repeatedly damaged and repaired after ingestion of dietary lectins.     

Response of the rat small-intestine epithelium to methotrexate.

We studied jejunal epithelial structure and function in rats 24, 48, 96, and 192 hours after a single intravenous injection of methotrexate (MTX) 30 mg/kg. The acute effect of the drug on the gut at 24 and 48 hours was characterised, as expected, by reduced mitoses in crypts, shortened villi, and depressed activity of thymidine kinase (an enzyme normally confined to intestinal crypt cells). At 96 hours, when MTX was no longer detectable in serum, the intestine had entered a proliferative phase characterised by increased crypt mitoses, accelerated migration of enterocytes along villi, and the presence on villi of epithelial cells with the enzyme profile of crypt cells, decreased disaccharidase, alkaline phosphatase, and Na+-K+ATPase activities and increased thymidine kinase activity. Although the enzyme data suggested that enterocyte maturation was defective during this proliferative phase, glucose-stimulated Na+ transport, normally a function of fully differentiated villus cells, was normal at 96 hours. Measured both in Ussing chambers and in suspensions of enterocytes isolated from villi, Na+ transport responded normally to glucose at 96 hours, although the response had been significantly depressed at 24 hours. These findings cannot be attributed to MTX-induced malnutrition, as all comparisons included pair-fed controls. We conclude that, in the MTX-induced malnutrition, as all comparisons included pair-fed controls. We conclude that, in the small intestine under conditions of altered epithelial renewal, some components of enterocyte function may be affected more than others. Comparing the present experimental model with another intestinal disorder, acute viral enteritis, in which proliferative activity is excessive, it is clear that the nature of the original intestinal injury is a significant determinant of the pattern of enterocyte response.     

Structural and Morphometric Analysis of Murine Small Intestine after Indomethacin Administration

Ettarh RR, Carr KE. Structural and morphometric analysis of murine small intestine after indomethacin administration. Scand J Gastroenterol 1993;28:795-802.

Indomethacin, a nonsteroidal anti-inflammatory drug, induces the formation of gastrointestinal ulceration both in experimental animals and in humans. A study of indomethacin-induced ulcers in the mouse showed that two doses of indomethacin, each administered subcutaneously at 85 mg/kg body weight, induced well-defined gastrointestinal ulcers in C57 mice, accompanied by inflammatory and vascular changes in the stomach and small intestine. Maximal damage was observed 20 h after the second dose of indomethacin. Morphometric analysis identified changes in all compartments of the small intestine. There was a marked reduction in the length of the small intestine, intestinal dilatation, a significant decrease in villous height, with the formation of subepithelial blisters or blebs within villi, and submucosal vascular dilatation. There was no change in the number of villi or of submucosal arterioles or in the total amount of muscle present in the wall of the intestine. The tissue changes identified in this study may have implications for gut function at specific periods during indomethacin treatment.     

Quantitative alterations in the structural development of jejunal absorptive epithelial cells and their subcellular organelles in protein-energy-malnourished rats: a stereologic analysis

The effect of protein-energy malnutrition (PEM) on the structural development of rat jejunal absorptive epithelial cells was evaluated. Stereologic characteristics of jejunal histologic subcompartments, epithelial cell surfaces and volumes, and volumes of key subcellular organelles (nuclei, mitochondria, Golgi apparatus, lysosomes) in crypt and villus mid and tip cells were determined by morphometric analysis of light and electron micrographs in well-nourished rats and rats with PEM. In rats with PEM there were developmental alterations in cells migrating on villi that were not seen in crypt cells. The amplification of the apical microvillus surface between mid and tip levels in well-nourished rats (679-1085 micron2/cell) failed to occur in rats with PEM (807-729 micron2/cell). This resulted in an estimated 60% reduction of total jejunal absorptive surface, from 10,070 cm2 in well-nourished rats to 3975 cm2 in rats with PEM. In contrast, the development of the basolateral surface, which requires much less membrane accrual, was unaffected by PEM. Villus mid and tip cells of rats with PEM also had increased cell volume and mitochondrial volumes. Microvillus surface area per cell appears dependent on the number of microvilli per cell, which equals the cell flat surface times the microvillus numerical density (number of microvilli per square micrometer) in well-nourished rats. However, this relationship was not demonstrable in rats with PEM.     

Modifications of the trophism of intestinal mucosa after intestinal and bilio-pancreatic diversion in the rat.

Morphofunctional alterations to the intestinal mucosa are influenced by three main factors: food, bilio-pancreatic secretions, intestinal hormones. In order to assess the importance of each one, histological and histochemical tests were performed on different segments of intestine taken from rats which were sacrificed one month after the following procedure: gastrojejunal anastomosis on a Roux loop (Model I); same procedure plus biliopancreatic bypass into the jejunum (Model II). When compared to the controls, Model I duodenum samples revealed hypertrophy of the entire wall with "bundles" of villi, while Model II samples showed a clear hypotrophy and reduction in the number of duodenal villi. To such modifications of the duodenum correspond longer, thinner villi in the other bowel segments, particularly in the jejunum and distal ileum. These results suggest that the predominant trophic effect derives from contact with biliopancreatic secretions at a proximal level. The modifications of the duodenal mucosa appear to regulate the trophism of the distal segments probably by the secretion of distant acting enterohormones.     

Ultrastructural localization of a neutral and basic amino acid transporter in rat kidney and intestine.

A sodium-independent neutral and basic amino acid transporter (NBAT) from rat kidney was recently cloned and its amino acid sequence deduced. We used light and electron microscopic immunoperoxidase labeling to determine the cellular localization of NBAT in rat kidney and small intestine. The localization was carried out using site-directed antisera raised against synthetic peptides within NBAT. The most prominent localization of NBAT was in microvilli of epithelial cells lining renal proximal tubules. Microvilli of small intestinal epithelia were less frequently immunoreactive. Unexpectedly, the most intense labeling in the small intestine was seen within enteroendocrine cells and submucosal neurons. The neuronal labeling was highly localized within dense core vesicles in axon terminals apposed to the basal lamina near fenestrated blood vessels. These results support the proposal that NBAT plays a role in reabsorption of amino acids in renal tubules. In addition, they suggest that NBAT (or NBAT-like proteins) may have multiple functions in the small intestine, including luminal uptake of amino acids and vesicular uptake of related substrates into enteroendocrine cells and enteric neurons.     

非甾体消炎药对大鼠小肠黏膜机械屏障功能的影响

目的 探讨非甾体消炎药对大鼠小肠黏膜机械屏障功能的影响.方法 雄性SD大鼠32只,分为模型组和对照组,模型组予双氯芬酸灌胃,2次/d,每次7.5 mg/kg,对照组使用相同剂最的生理盐水灌胃,分别按造模后1 d和5 d时相点分为2个亚组(每组8只).进行胃及小肠大体损伤评分、小肠黏膜病理组织损伤评分,采用Carl Zeiss Imaging Systems图像分析系统进行绒毛高度、黏膜厚度、黏膜截面积定量分析,观察透射电镜下肠黏膜超微结构变化.结果 模型组胃黏膜的损伤评分与对照组的差异无统计学意义.模型组第1天小肠黏膜可见散在红斑、糜烂和溃疡,溃疡沿肠系膜侧分布;第5天小肠黏膜可见出血、穿孔和窦道形成,其大体损伤评分均高于对照组(P＜0.05).模型组第1天和第5大Chiu氏病理评分分别为3.5分和5.0分,与对照组相比差异有统计学意义(P＜0.05).造模第1天大鼠空、回肠绒毛高度分别为(126.9±32.0)μm和(118.6±22.9)μm,较对照组显著降低(P＜O.05);而空、回肠黏膜厚度、黏膜截面积和对照组相比差异无统计学意义,但有下降趋势;第5大大鼠空、回肠绒毛高度[(73.4±25.4)μm和(109.3±17.6)μm]显著降低、黏膜厚度[(123.8±51.6)μm和(165.7±37.4)μm]变薄、黏膜截而积[(2.48±1.01)mm2和(3.27±0.76)mm2]变小,与对照组相比差异均有统计学意义(P＜0.05).透射电镜下见模型组第1天大鼠小肠黏膜微绒毛水肿、排列紊乱,线粒体肿胀,部分峪减少,内质网出现不同程度扩张,细胞问连接开始出现部分增宽;第5天小肠黏膜上皮微绒毛脱落更为明显,细胞连接断裂破坏严重.结论 双氯芬酸可导致大鼠小肠黏膜屏障功能受损.绒毛变短、黏膜厚度变薄、微绒毛脱落和细胞间紧密连接增宽可能是其形态学基础.