Pathological features of the colonic tumours induced in rats by the administration of 1,2-dimethylhydrazine.

The parenteral administration of 1,2-dimethylhydrazine to rats caused the development of colonic neoplasms in about 90% of animals by 24--30 weeks of treatment. Usually there were multiple tumours with a mean of 2.7 per rat. The lesions have been classified histologically into adenomata (26% of all tumours) and carcinomata, the latter showing varying degrees of differentiation. No completely anaplastic tumours were seen, and there were none originating in connective tissue. The distributions of the different tumour types along the length of the colon varied. The more benign lesions were situated predominantly in the distal half of the colon, while the poorly differentiated adenocarcinomata were concentrated in the proximal third of the colon. There was good evidence to suggest that adenomata often progressed to frank malignancy in the distal colon. In the proximal part, however, it appeared that tumours frequently developed de novo as poorly differentiated carcinomata. Perhaps regional variations in the kinetic organisation of the normal colonic mucosa somehow influence the nature of the neoplastic change induced by DMH, thus accounting for the differences in tumor distribution. After 24 weeks of DMH treatment there was only a small increase in the mean number of tumours per rat.     

Superoxide Dismutase Activity During Dimethylhydrazine Colon Carcinogenesis and the Effects of Cholic Acid and Indole

Copper, zinc superoxide dismutase (Cu, ZnSOD) and manganese superoxide dismutase (MnSOD) activities were measured in mouse large intestinal mucosa during dimethylhydrazine (DMH) carcinogenesis. Mice were divided into five groups. Group A was subcutaneously injected with DMH (20mg/kg) weekly and fed with a diet containing 0.2% cholic acid (C) and 0.8% indole (I). Group B was injected with DMH and given indole feeding. Group C was treated with DMH injection and cholic acid feeding. Group D was given DMH injection alone. Group E was an age-matched control group given 0.9% NaCl injection. The experiment last 21 weeks. The Cu, ZnSOD activity of intestinal mucosa in group A animals began to increase significantly at the 7th week of the experiment. In groups B, C and D, however, this enzyme was not elevated statistically until the 16th week, and then each of these groups kept an increased Cu, ZnSOD level the rest of the experimental period. MnSOD activity was elevated statistically in group C animals at the 7th week. The enzyme activity in group A and D animals increased at the 9th week, but the enzyme activity did not increase statistically until the 11th week in group B. After the 16th week of the experiment the increased activity of MnSOD in all experimental groups returned to the level of the control group. Large intestinal cancer tissues had increased Cu, ZnSOD activity and decreased MnSOD activity.     

Superoxide Dismutase Activity During Dimethylhydrazine Colon Carcinogenesis and the Effects of Cholic Acid and Indole

Copper, zinc superoxide dismutase (Cu, ZnSOD) and manganese superoxide dismutase (MnSOD) activities were measured in mouse large intestinal mucosa during dimethylhydrazine (DMH) carcinogenesis. Mice were divided into five groups. Group A was subcutaneously injected with DMH (20mg/kg) weekly and fed with a diet containing 0.2% cholic acid (C) and 0.8% indole (I). Group B was injected with DMH and given indole feeding. Group C was treated with DMH injection and cholic acid feeding. Group D was given DMH injection alone. Group E was an age-matched control group given 0.9% NaCl injection. The experiment last 21 weeks. The Cu, ZnSOD activity of intestinal mucosa in group A animals began to increase significantly at the 7th week of the experiment. In groups B, C and D, however, this enzyme was not elevated statistically until the 16th week, and then each of these groups kept an increased Cu, ZnSOD level the rest of the experimental period. MnSOD activity was elevated statistically in group C animals at the 7th week. The enzyme activity in group A and D animals increased at the 9th week, but the enzyme activity did not increase statistically until the 11th week in group B. After the 16th week of the experiment the increased activity of MnSOD in all experimental groups returned to the level of the control group. Large intestinal cancer tissues had increased Cu, ZnSOD activity and decreased MnSOD activity.     

Effect of age, castration and pregnancy on carcinogenesis, induced by 1,2-dimethylhydrazine, in CBA mice]

Subcutaneous injection of 1,2-dimethylhydrazine into female CBA mice once a week resulted in the development of tumours of the colon, anal region, uterus and liver. In 12-13-month-old mice treated with DMH an earlier appearance (week 8) of uterine sarcomas and more rapid increase in the incidence of tumours of the anal region were noted as compared to 3-month-old mice. In pregnant females treated with DMH a statistically significant decrease in the uterine sarcoma incidence was observed (10.3% versus 48.3% in nonpregnant). Pregnancy exerted no effect on the incidence of tumours at other sites. Castration did not affect the time of appearance and the incidence of tumours of any site.     

Sulindac enhances cell proliferation in DMH-treated mouse colonic mucosa

In a previous study we reported that the NSAID sulindac had a marked inhibitory effect on the development of colonic tumours in mice treated with the carcinogen 1,2-dimethylhydrazine (DMH). In this study we examined the effects of sulindac in respect of cell-kinetic changes in mouse colonic mucosa as determined by flash labelling with the thymidine analogue bromodeoxyuridine (BrdUrd) at varying intervals during the process of colonic carcinogenesis. We also investigated the possibility that these changes may be modulated by misoprostol a prostaglandin E₁ analogue. Four groups of 36 mice each were treated for 18 weeks with the following drug/s respectively: (1) DMH; (2) DMH and sulindac; (3) DMH, sulindac and misoprostol; and (4) DMH and misoprostol. Three animals from each group were killed each week between the sixth week and the eighteenth week after the start of the experiment. A 1-h flash label technique was employed and paraffin sections of colonic mucosa were examined. For each animal a total of 50 perfect axially cut crypts were chosen and the following parameters determined: crypt length, labelling index and labelling index distribution: the data were analysed using the computer program GLIM. For each of the four groups, crypt lengths increased significantly with the duration of treatment with no significant difference between the groups. In sulindac-treated animals the labelling index for all positions increased with duration of treatment whereas for animals not treated with sulindac there was no significant difference in labelling index with respect to duration of treatment. The administration of misoprostol did not appear to significantly alter the effects of sulindac. It is postulated that the observed increase in cell proliferation could be a compensatory phenomenon occurring secondary to loss of crypt epithelial cells by apoptosis induced by sulindac. Also the finding of an increase in labelling index mediated by a chemopreventive agent indirectly questions the rationale behind the therapeutic manipulation of crypt cell proliferation in order to reduce the risk of colon cancer.     

Failure to induce tumors in the large intestine of Capuchin mokeys (Cebus apella) by using 1,2-dimethylhydrazine

The purpose of this study was to produce tumors in the large intestine of Capuchin Monkeys (Cebus apella) by the administration of the colonotropic carcinogen 1,2-dimethylhydrazine (DMH). The subjects were 12 monkeys, all males, age 30 months, with a mean weight of 2.858 kg. The DMH was administered subcutaneously to six of the monkeys at a dosage of 25 mg/kg of body weight once a week for 16 weeks; control monkeys received an equivalent volume of the stock solution without DMH. Twenty months after administration of the first dose, the animals were sacrificed. None of the monkeys showed intestinal tumors. Samples of the gastrointestinal tract were removed, fixed, and stained according to standard histological techniques. Histological changes were seen in all of the DMH-treated animals; these consisted of glandular hyperplasia and hyperplasia of the epithelium overlying the lymphoid nodules. In addition, foci of dysplasia were found in three of the animals. Our results suggest that the DMH induced pre-neoplastic changes, characterized by hyperplasia and dysplasia, in the mucosa of the large intestine.     

优势菌群失衡对肠黏膜上皮结构的损害

目的通过观察小鼠肠道优势菌群失衡肠黏膜上皮结构的变化以探讨肠道优势菌群失衡对黏膜机械屏障的影响。方法利用光镜及电镜技术观察轻度、重度菌群失衡小鼠肠道黏膜绒毛形态变化及上皮细胞超微结构的变化。结果菌群失衡小鼠肠黏膜绒毛出现肿胀、断裂,绒毛顶端肠上皮细胞坏死、脱落,重度菌群失衡与轻度菌群失衡小鼠比较绒毛结构受损加重。超微结构观察发现上皮细胞间隙增宽,胞浆内出现空泡结构,黏膜及黏膜下层有淋巴细胞浸润。结论抗生素干扰肠道优势菌群,可导致肠道机械屏障黏膜绒毛及超微结构受损且重度优势菌群失衡的损害大于轻度优势菌群失衡的损害。     

Apoptotic differences in experimentally induced colorectal rat tumours

The presence of apoptotic bodies and of intraepithelial lymphocytes (IELs) were assessed in colorectal adenomas and adenocarcinomas induced in 158 rats by two different carcinogens: 1,2 dimethylhydrazine (DMH) and glutamic acid pyrolysate (GLU-P-1 and 2). Apoptotic granules were present in 97.5% ( n=40) of the 41 GLU-induced adenomas and adenocarcinomas, but only in 20.5% ( n=24) of the 117 DMH-induced tumours. IELs were found in 95.1% ( n=39) of the 41 GLU-induced tumours but only in 21.4% (n=25) of the 117 DMH-induced neoplasias. The differences were significant ( p< 0.001). The presence of IELs and apoptotic granules in GLU tumours (and their absence in the majority of the DMH tumours) is new evidence that IELs are the cells from which many of the apoptotic granules — seen in colorectal neoplasias — derive. GLU neoplasias were induced following daily treatment, for 24 months (about half the life span of the animals) and DMH neoplasias by weekly doses, for a period of only 2.8-6 months. It would appear that 'slowly growing' colorectal GLU neoplasias often attract IELs and trigger lymphocytic apoptosis whereas 'quickly growing' DMH tumours seldom evoke those reactions.     

Endocrine profile in gastric carcinomas. An immunohistochemical study.

22 gastric carcinomas (13 intestinal type and nine diffuse type) were immunostained for neuron specific enolase, chromogranin, Leu-7 and a panel of fifteen different peptide hormones. Five out of the 13 tumours of intestinal type and four out of the nine diffuse carcinomas expressed immunoreactivity for one or more of the pan endocrine markers. Seven out of the 13 tumours of intestinal type and five out of the nine diffuse carcinomas also expressed immunoreactivity for gastrin (3), ACTH (3), serotonin (7) and calcitonin (7). Immunoreactivity for somatostatin (1) and substance P (1) were also seen in two tumours of intestinal type. Seven out of 18 cases with benign mucosa adjacent to the tumours expressed a focal immunoreactivity for chromogranin (6), serotonin (6), gastrin (5) and calcitonin (1). All hormone-producing tumours also expressed immunoreactivity for carcino-embryonic antigen. Our results confirm that a high proportion of gastric carcinomas are hormone producing.     

Involvement of CD36 and intestinal alkaline phosphatases in fatty acid transport in enterocytes, and the response to a high-fat diet

The vertebrate intestine is notable for its plasticity in response to environmental, pathologic, reproductive, and dietary challenges. The molecular mechanisms of intestinal adaptations typically involve both morphologic and functional changes. In response to chronic ingestion of a high-fat diet, for example, the mammalian small intestine quickly adapts to efficiently accommodate increased transport of long-chain fatty acids across the mucosa. Whereas this may be adaptive in the short term, in the long term it may contribute to the pathologies associated with chronic high-fat diets in humans and other mammals. This review focuses on some of the known and putative mechanisms by which fatty acids are transported across the intestinal epithelium in addition to simple diffusion, and how these mechanisms may be regulated in part by a high-fat diet. A model is proposed in which two key proteins, CD36 and the enzyme intestinal alkaline phosphatase, work in a coordinated manner to optimize fatty acid transport across enterocytes in mice.     

Intestinal and splenic T cell responses to enteric Listeria monocytogenes infection: distinct repertoires of responding CD8 T lymphocytes

Listeria monocytogenes is an intracellular bacterium that causes systemic infections after traversing the intestinal mucosa. Clearance of infection and long term protective immunity are mediated by L. monocytogenes-specific CD8 T lymphocytes. In this report, we characterize the murine CD8 T cell response in the lamina propria and intestinal epithelium after enteric L. monocytogenes infection. We find that the frequency of MHC class Ia-restricted, L. monocytogenes-specific T cells is approximately 4- to 5-fold greater in the lamina propria than in the spleen of mice after oral or i.v. infection. Although the kinetics of T cell expansion and contraction are similar in spleen, lamina propria, and intestinal epithelium, high frequencies of Ag-specific T cells are detected only in the lamina propria 1 mo after infection. In contrast to MHC class Ia-restricted T cells, the frequency of H2-M3-restricted, L. monocytogenes-specific T cells is decreased in the intestinal mucosa relative to that found in the spleen. In addition to this disparity, we find that MHC class Ia-restricted CD8 T cells specific for a dominant L. monocytogenes epitope have different TCR V beta repertoires in the spleen and intestinal mucosa of individual mice. These findings indicate that the intestinal mucosa is a depot where L. monocytogenes-specific effector CD8 T cells accumulate during and after infection irrespective of immunization route. Furthermore, our results demonstrate that CD8 T cell populations in these two sites, although overlapping in Ag specificity, are distinct in terms of their repertoire.     

不同液体复苏对失血性休克大鼠肠粘膜的影响

目的：观察不同液体复苏对失血性休克大鼠肠粘膜的影响以及肠粘膜的变化。方法：利用大鼠失血性休克模型以及不同的补液方式,在复苏后120分钟时处死大鼠,取回肠4cm,做病理切片并根据Chiu等方法评估回肠黏膜上皮损伤指数。结果：液体复苏组的肠粘膜损伤程度小于休克不补液组（p〈0.05）,而限制型液体复苏组的肠粘膜损伤程度小于充分液体复苏组（p〈0.05）。结论：通过本实验对肠粘膜的观察可以得出,对于失血性休克,液体复苏时有效的抗休克方式,而对于复苏的方式来说,从肠黏膜的保护方面来说,限制型液体复苏是优于传统的充分液体复苏的。     

不同液体复苏对失血性休克大鼠肠粘膜的影响

目的:观察不同液体复苏对失血性休克大鼠肠粘膜的影响以及肠粘膜的变化。方法:利用大鼠失血性休克模型以及不同的补液方式,在复苏后120分钟时处死大鼠,取回肠4cm,做病理切片并根据Chiu等方法评估回肠黏膜上皮损伤指数。结果:液体复苏组的肠粘膜损伤程度小于休克不补液组(p<0.05),而限制型液体复苏组的肠粘膜损伤程度小于充分液体复苏组(p<0.05)。结论:通过本实验对肠粘膜的观察可以得出,对于失血性休克,液体复苏时有效的抗休克方式,而对于复苏的方式来说,从肠黏膜的保护方面来说,限制型液体复苏是优于传统的充分液体复苏的。     

SCID小鼠肠道菌群失调对深部白色念珠菌感染的影响研究

目的建立重度联合免疫缺陷（SCID）小鼠白色念珠菌感染模型,探讨肠道菌群失调与深部白色念珠菌感染的联系。方法SCID小鼠随机口服万古霉素水溶液7d,饥饿24h后给予白色念珠菌灌胃,建立小鼠白色念珠菌感染模型,观察小鼠死亡情况。荧光定量PCR检测肠道细菌总量、基质辅助激光解析电离飞行时间质谱仪鉴定肠道菌群种类,并应用扫描电镜观察肠壁黏膜组织超微结构的改变。结果应用万古霉素可致肠道菌群失调,肠道黏膜完整性受损。在万古霉素致肠道菌群失调的基础上,外源性白色念珠菌攻击可加重肠道菌群失调和肠壁黏膜损伤程度,促进深部白色念珠菌感染的发生。结论肠道菌群失衡可以导致深部白色念珠菌感染的发生,肠壁黏膜的完整性可能参与了肠道白色念珠菌播散过程。     

哺乳动物肠上皮屏障中非编码RNAs的调控作用

哺乳动物肠上皮是一种拥有快速自我更新能力的组织,在维持机体免疫稳态与肠道应激后的损伤修复中发挥重要作用。源于隐窝底部的多能肠干细胞不断进行增殖、迁移与分化,并沿隐窝 绒毛轴向上移动,从而维持肠上皮完整性。该过程受严格而复杂的基因调控网络参与。越来越多的数据表明,肠上皮完整性受到广泛的非编码RNA的调控,主要包括肠黏膜再生、保护与上皮屏障功能等方面。本文重点讨论了两类非编码RNA(包括microRNAs和lncRNAs)转录后调控肠上皮屏障功能的研究进展。其中,miR-503、miR-146和lnc-uc.173、lnc-SPRY4-IT1、lnc-plncRNA1、lnc-Gata6等,能够促进肠黏膜的更新,增强上皮屏障功能;相反,miR-222、miR-29b、miR-195和lnc-H19与lnc-BC012900等,抑制肠上皮再生并破坏肠上皮屏障功能。miRNAs、mRNAs与lncRNAs间构成复杂的分子网络,共同调控肠上皮稳态。深入研究与肠上皮相关的miRNAs和IncRNAs分子及其作用机制,探寻引起肠黏膜炎症的关键分子靶标,为肠道炎症临床诊治提供新方向与新方法。     

哺乳动物肠上皮屏障中非编码RNAs的调控作用

哺乳动物肠上皮是一种拥有快速自我更新能力的组织,在维持机体免疫稳态与肠道应激后的损伤修复中发挥重要作用。源于隐窝底部的多能肠干细胞不断进行增殖、迁移与分化,并沿隐窝 绒毛轴向上移动,从而维持肠上皮完整性。该过程受严格而复杂的基因调控网络参与。越来越多的数据表明,肠上皮完整性受到广泛的非编码RNA的调控,主要包括肠黏膜再生、保护与上皮屏障功能等方面。本文重点讨论了两类非编码RNA(包括microRNAs和lncRNAs)转录后调控肠上皮屏障功能的研究进展。其中,miR-503、miR-146和lnc-uc.173、lnc-SPRY4-IT1、lnc-plncRNA1、lnc-Gata6等,能够促进肠黏膜的更新,增强上皮屏障功能;相反,miR-222、miR-29b、miR-195和lnc-H19与lnc-BC012900等,抑制肠上皮再生并破坏肠上皮屏障功能。miRNAs、mRNAs与lncRNAs间构成复杂的分子网络,共同调控肠上皮稳态。深入研究与肠上皮相关的miRNAs和IncRNAs分子及其作用机制,探寻引起肠黏膜炎症的关键分子靶标,为肠道炎症临床诊治提供新方向与新方法。     

The role of mitochondria-derived reactive oxygen species in the pathogenesis of non-steroidal anti-inflammatory drug-induced small intestinal injury

Abstract

Non-steroidal anti-inflammatory drugs (NSAIDs) have been implemented in clinical settings for a long time for their anti-inflammatory effects. With the number of NSAID users increasing, gastroenterological physicians and researchers have worked hard to prevent and treat NSAID-induced gastric mucosal injury, an effort that has for the large part being successful. However, the struggle against NSAID-induced mucosal damage has taken on a new urgency due to the discovery of NSAID-induced small intestinal mucosal injury. Although the main mechanism by which NSAIDs induce small intestinal mucosal injury has been thought to depend on the inhibitory effect of NSAIDs on cyclooxygenase (COX) activity, recent studies have revealed the importance of mitochondria-derived reactive oxygen species (ROS) production, which occurs independently of COX-inhibition. ROS production is an especially important factor in the increase of small intestinal epithelial cell permeability, an early stage in the process of small intestinal mucosal injury. By clarifying the precise mechanism, together with its clinical features using novel endoscopy, effective strategies for preventing NSAID-induced small intestinal damage, especially targeting mitochondria-derived ROS production, may be developed.     

Resistance of germfree rats to indomethacin-induced intestinal lesions.

Indomethacin given orally to conventional rats produced in three days a syndrome, often fatal, of intestinal lesions characterized by multiple ulcers and peritonitis. Male germfree rats were found to be resistant to this effect of indomethacin, while female germfree rats developed very mild lesions. Germfree rats became sensitive again to such lesions when monocontaminated with E. coli. In such animals, however, the lesions were less severe than in conventional animals, presumably because more than one microorganism is necessary for the full syndrome to develop. These results suggest that microorganisms are necessary for the development of indomethacin-induced intestinal lesions. Secondary bile acids, absent in germfree animals, may also be necessary. The prostaglandin deficiency caused by indomethacin appears to weaken the resistance of the intestinal mucosa to microorganisms and/or their toxins. The latter may then penetrate the mucosa, damage the cells and produce ulcers and perforations. Since several prostaglandins also protect against indomethacin-induced lesions, the hypothesis is advanced that certain prostaglandins may protect the mucosa ("cytoprotection") by preventing the spread of microorganisms and/or their toxin through the intestinal wall.     

Inhibition of 1,2-dimethylhydrazine induced colon genotoxicity in rats by the administration of probiotic curd

Epidemiologic and experimental studies suggest that the probiotic organisms are effective in preventing colon carcinogenesis, which is the major cause of mortality and morbidity in western countries. Keeping this in view, a curd (a common Indian fermented milk product) was prepared by the addition of probiotic cultures Lactobacillus acidophilus, Lactobacillus casei and curd culture Lactococcus lactis biovar. diacetylactis. In present study, we have evaluated the anti tumor effect of probiotic curd by monitoring the DNA damage through comet assay. The rats were allocated to four groups, first group was DMH control group, second group was probiotic curd group in which probiotic curd was given along with DMH (1,2-dimethylhydrazine) injection, third group was normal curd group in which normal curd was given along with DMH injection and fourth group was normal control group. Animals received subcutaneous injection of DMH dissolved in normal saline at a dose rate of 20 mg/kg body weight, once weekly for 15 weeks. The rats were dissected at 40th week of experiment and comet assay was done in colonic cells to assess the DNA damage. A significant reduction in DNA damage (54.7%) was observed in probiotic curd group as compared to DMH control group (88.1%). The probiotic curd was effective to significantly reduce the L:W ratio in comparison to DMH control group and normal curd. The results of present study show the protective effects of probiotic curd against DMH induced genotoxicity in colonic cells.     

Changes of E-cadherin and β-catenin in Human and Mouse Intestinal Tumours

An immunohistochemical analysis of E-cadherin and β-catenin was performed in human colorectal cancer as well as in surrounding normal intestinal tissue. We also analysed the expression of these two cell adhesion proteins in transgenic Apc1638N mice as a model of human familial adenometous polyposis syndrome. In the normal intestinal mucosa of both species, E-cadherin and β-catenin were localized along the lateral plasma membrances of epithelial cells. In intestinal tumour cells, however, they were also present in the cytoplasm. The expression of both proteins was reduced in human and mouse tumours. The pattern of their distribution was frequently heterogenous with strongly positive cells in a mosaic of negative ones. Further, E-cadherin and β-catenin expression did not correlate to the Duke's staging of tumours and therefore neither can be used as prognostic criteria.