The distribution and density of Clostridium difficile toxin receptors on the intestinal mucosa of neonatal pigs

Clostridium difficile is an enteric pathogen affecting a variety of mammals, but it has only recently been diagnosed as a cause of neonatal typhlocolitis in pigs. The most important virulence factors of C. difficile are 2 large exotoxins, toxin A (TcdA) and toxin B (TcdB). TcdA is a potent enterotoxin with effects on host tissues that are dependent upon receptor-mediated endocytosis of the intact toxin. TcdB is an effective cytotoxin, but it apparently does not bind receptors on intact mucosal epithelium. TcdB is much less toxic in vivo unless there is underlying damage to the mucosa, and it is not essential for the virulence of C. difficile. One hypothesis to explain the resistance of most species as neonates (e.g., humans and hamsters) is that they may lack significant numbers of TcdA receptors. The susceptibility of neonatal pigs suggests cells of the gastrointestinal mucosa express sufficient numbers of toxin receptors for lesion development. Immunohistochemical (IHC) assays documented specific binding of TcdA, but not TcdB, to the epithelium of the small and large intestine. The carbohydrate Galalpha1-3beta1-4GlcNAc-R has been described as an important receptor for TcdA. However, IHC indicated a distribution on cell surfaces much different from that of TcdA binding, suggesting a specific interaction of toxin with an alternative receptor.     

The quantitative assessment of mucosa in canine small intestinal malabsorption.

Histological sections from the small intestines of dogs showing clinical signs of small intestinal malabsorption have been examined using morphometric techniques. Weibel graticule measurements appear to be a useful adjunct to the subjective assessment of villus atrophy. Severe clinical signs of small intestinal malabsorption may be associated with a patchy distribution of lesions throughout the small bowel.     

The quantitative assessment of normal canine small intestinal mucosa.

Quanitative methods of assessing the architecture of small intestinal mucosa have been applied to biopsy material from normal dogs. Mucosal samples taken from four predetermined sites show that there are significant quantitative differences between the various levels of the small bowel. Animals of one year of age and older show no correlation between age or weight and mucosal dimensions. The significance of these findings, in relation to examination of biopsy material from cases of clinical small intestinal disease, is discussed.     

Chronic small intestinal disease in the dog

New approaches to the investigation of chronic small intestinal disease have facilitated the identification and characterization of three enteropathies in the dog. The main features of these diseases are presented and diagnostic problems are discussed.     

Histological development of the small intestinal mucosa in the ovine fetus.

Histological changes in the small intestine of 85 ovine fetuses were studied, with particular reference to the mucosa. In 24-day-old fetuses the endoderm of the intestine consisted of a single layer of epithelium. By the 26th day the epithelium was flattened and stratified. The first evidence of rudimentary villus formation was noted in 39-day-old fetuses. Intestinal glands were first observed at 56 days. Other mucosal structures were present by 101 days. At birth the intestinal mucosa was fully mature.     

Characterization of xenobiotic metabolizing enzymes in bovine small intestinal mucosa

Virkel, G., Carletti, M., Cantiello, M., Della Donna, L., Gardini, G., Girolami, F., Nebbia, C. Characterization of xenobiotic metabolizing enzymes in bovine small intestinal mucosa. J. vet. Pharmacol. Therap. 33 , 295–303. The intestinal mucosa plays a capital role in dictating the bioavailability of a large array of orally ingested drugs and toxicants. The activity and the expression of several xenobiotic metabolizing enzymes were measured in subcellular fractions from the duodenal mucosa of male veal calves and beef cattle displaying a functional rumen but differing in both age (about 8 months vs. 18 to 24 months) and dietary regimens (i.e., milk replacer plus hay and straw vs. corn and concentrated meal). Intestinal microsomes showed cytochrome P450 (CYP) 2B, 2C‐ and 3A‐mediated activities and the presence of the corresponding immunorelated proteins, but no proof of CYP1A expression and/or functions could be provided. Intestinal microsomes were also active in performing reactions typically mediated by carboxylesterases (indophenylacetate hydrolysis), flavin‐containing monooxygenases (methimazole S‐oxidation), and uridindiphosphoglucuronyltransferases (1‐naphthol glucuronidation), respectively. Cytosolic fractions displayed the glutathione S‐transferase (GST)‐dependent conjugation of 1‐chloro‐2,4‐dinitrobenzene; besides, the GST‐mediated conjugation of ethacrinic acid (GSTπ) or cumene hydroperoxide (GSTα) was matched by the presence of the corresponding immunorelated proteins. Conversely, despite the lack of measurable activity with 3,4‐dichloronitrobenzene, a protein cross reacting with anti‐rat GSTμ antibodies could be clearly detected. Although, as detected by densitometry, CYPs and GST isoenzymes tended to be more expressed in beef cattle than in veal calf preparations, there was a general poor correlation with the rate of the in vitro metabolism of the selected diagnostic probes.     

Recurrent intestinal intussusceptions in the dog.

Intestinal intussusceptions in 2 young dogs recurred within 3 days of initial surgical reduction. Subsequent recurrence was prevented by intestinal resection and creation of multiple intestinal adhesions in 1 dog and by creation of adhesions alone in the other.     

Normal and abnormal ultrasonographic findings that mimic small intestinal intussusception in the dog

On ultrasonographic examination of the abdomen, the appearance of healthy intestine, enteritis secondary to an intestinal foreign body, and postpartum involution of the uterus may be visualized in some imaging planes as a target-like structure that is subsequently misinterpreted as intestinal intussusception. To avoid misdiagnosis, the ultrasonographer should ensure multi-plane scanning of the lesion, paying particular attention to the completeness of the lesion's peripheral ring structure and the overall width of the concentric rings of the target-like lesion. The presence of a semilunar or G-shaped hyperechoic center and the visualization of the inner intussusceptum (extending into the intussusception lumen) can be useful ultrasonographic findings that distinguish an intussusception from other lesions or from healthy tissues. These principles are illustrated through the following case presentations.     

Synthesis of citrulline from ornithine by the small intestinal mucosa of cattle

Three segments of cattle small intestine (duodenum, upper jejuno‐ileum and lower jejuno‐ileum) were examined in an in vitro system for activity of ornithine carbamoyltransferase (OCT; EC 2.1.3.3) which is involved in the synthesis of citrulline (Cit) from ornithine (Orn). The mucosa of the three segments of small intestine was collected from Japanese black cattle, homogenized and then centrifuged. The supernatant fraction was used as the crude OCT enzyme solution. The OCT activity was assayed by the production of Cit from Orn determined directly by HPLC. The optimal pH and temperature for OCT activities in the duodenum, upper jejuno‐ileum and lower jejuno‐ileum of cattle small intestine were 7.47 and 39°C. Little difference was observed between the three segments. The OCT activity in cattle kidney was also examined for comparison, and almost no activity was found. The OCT activities in crude enzyme solutions of the three segments of small intestine were stable for up to one month of storage at ?20°C in Tris HCl buffer solution. Finally, the role of the small intestine in supplying Cit as a precursor for arginine synthesis in cattle kidney was discussed.     

The use of porcine small intestinal submucosa as a biomaterial for perineal herniorrhaphy in the dog

OBJECTIVES: To develop an in vivo perineal hernia model, to develop a technique for using small intestinal submucosa (SIS) in perineal hernia repair, to further elucidate the biological behavior of SIS, and to compare SIS herniorrhaphy with the internal obturator muscle transposition (IOT) technique. STUDY DESIGN: Prospective evaluation comparing SIS herniorrhaphy with IOT. ANIMALS: Twelve adult castrated male, large-breed dogs. METHODS: All dogs had bilateral pelvic diaphragm defects created by complete excision of the levator ani muscle. Each dog had one side repaired using SIS and the other by IOT. Pain and inflammation were subjectively scored. Dogs were killed 2 weeks (n = 4), 12 weeks (n = 4), or 16 weeks (n = 4) after surgery. Each pelvic diaphragm was biomechanically tested to failure. The pelvic diaphragms from 2 normal dogs (n = 4 sides) were also biomechanically tested. Failure site, maximum pressure, displacement at failure, and initial linear stiffness values were determined. Histologic assessment was performed. Statistical analysis was performed with significance set at P <.05 RESULTS: No significant postoperative complications were noted. There were no significant differences in maximum pressure to failure, displacement, or stiffness when comparing normal, SIS, and IOT at any time point. The SIS group had significantly less displacement (P =.004) at 2 weeks than at weeks 12 or 16. For all herniorrhaphy techniques, the failure site was central (n = 22) or at the suture line (n = 2). At 2 weeks, histologic evaluation of tissues from the IOT group showed inflammation, mineralization, and necrosis, which were not present in tissues from the SIS group. Histologic examination at 12 and 16 weeks showed no microscopic differences in cell population or tissue characteristics between the IOT and SIS groups. CONCLUSIONS: SIS herniorrhaphy was successfully performed in this in vivo model of perineal hernia in the dog. CLINICAL RELEVANCE: This study suggests that SIS can be used as a primary means of repair, as augmentation when the internal obturator muscle is thin and friable, or as a salvage procedure in cases of recurrence in dogs with perineal hernia.     

The effects of Strongylus vulgaris parasitism on eosinophil distribution and accumulation in equine large intestinal mucosa

REASONS FOR PERFORMING STUDY: Eosinophilic granulocytes have been associated with parasite or immune-mediated diseases, but their functions in other disease processes remain unclear. Cause and timing of eosinophil migration into the equine gastrointestinal mucosa are also unknown. OBJECTIVE: To determine the effects of intestinal parasitism on eosinophils in equine large intestinal mucosa. METHODS: Large intestinal mucosal samples were collected from horses and ponies (n = 16) from the general veterinary hospital population, ponies (n = 3) raised in a parasite-free environment, ponies experimentally infected with 500 infective Strongylus vulgaris larvae and treated with a proprietary anthelmintic drug (n = 14), and a similar group of ponies (n = 7) that received no anthelmintic treatment. Total eosinophil counts and eosinophil distribution in the mucosa were determined by histological examination. A mixed model analysis was performed and appropriate Bonferroni adjusted P values used for each family of comparisons. P<0.05 was considered significant. RESULTS: There was no difference in large intestinal mucosal eosinophil counts and eosinophil distribution between ponies infected with S. vulgaris and those raised in a parasite-free environment. Experimental infection with S. vulgaris, with or without subsequent anthelmintic treatment, did not change eosinophil counts, and counts were similar to those for horses from the general population. CONCLUSIONS: Migration of eosinophils to the equine large intestinal mucosa appears to be independent of exposure to parasites. Large intestinal mucosal eosinophils may have more functions in addition to their role in defence against parasites.     

The presence of EGF- and IGF-1-receptors in the small intestine of fetal, neonatal and weaned piglets

During development, gut morphology and functions change. Some of these are mediated by milk-borne factors, e.g. insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF), of which the effects are in part dictated by the distribution of their receptors (R).

EGFR- and IGF-1R-immunoreactivity (IR) was evaluated in samples of the fetal, neonatal and weaned porcine small intestine.

EGFR-IR first appeared in the neonatal duodenum and was located basolaterally in villar and to a lesser extent in cryptal enterocytes. In weaned pigs, EGFR appeared apically in enterocytes with a region-dependent distribution along the villus–crypt axis. IGF-1R-IR was observed in smooth muscle cells in each age group. From the last trimester of gestation onward IGF-1R-IR was seen at the apical and basolateral side of villar enterocytes and in submucosal arterioles.

Thus, the age- and region-dependent presence of EGFR and IGF-1R has to be taken into account when evaluating effects of EGF and IGF-1 on growth or repair.     

荣昌乳仔猪小肠黏膜二糖酶活性发育规律及影响因素的研究

为了系统研究荣昌乳仔猪二糖酶的发育规律,为荣昌乳仔猪饲养工艺研究及产业化示范优化补料技术提供理论依据,试验选择30窝胎次、产仔数一致的荣昌乳仔猪随机分为补饲(A)组和非补饲(B)组,A组从6日龄开始补饲,B组不补饲,分别在第0,2,5,8,11,15,19,23,28,30,35天取仔猪十二指肠、空肠(前、中、后各段)、回肠测定麦芽糖酶、乳糖酶、蔗糖酶的活性。结果表明:补饲对小肠中3种二糖酶活性有一定的影响,补饲组乳糖酶活性在空肠段8,11,15天显著高于其他各天(P<0.05),蔗糖酶活性在空肠前段和中段11,15天显著高于其他各天(P<0.05);非补饲组麦芽糖酶在十二指肠19天、空肠前段19,15,28天显著高于其他各天(P<0.05),乳糖酶活性在十二指肠15天、空肠前段和中段15,11天显著高于其他各天(P<0.05)。说明乳仔猪进行补饲能提前二糖酶发挥高活性的时间;21日龄断奶二糖酶活性对补饲仔猪的影响小于非补饲组;21日龄断奶仔猪比28日龄断奶仔猪酶活性的波动更大;乳仔猪乳糖酶活性在8,11,15日龄达到较高水平。     

6-羟多巴胺对小鼠体重及其小肠黏膜结构的影响

采用组织学和图像分析技术，研究了小鼠经腹腔注射交感神经损毁剂6-羟多巴胺后小鼠体重和小肠绒毛长度、V／C比值、绒毛宽度以及黏膜厚度的变化。结果表明，注射6-羟多巴胺组与对照组小鼠相比，体重下降（约3．4％）；小肠绒毛变短（5．6％～19．4％），V／C比值减少（0．88％～24．1％），绒毛变窄（8．8％～24．7％）、黏膜厚度变薄（4．4％～16．9％），其中空肠的绒毛长度和黏膜厚度减少较明显，而十二指肠和回肠的V／C比值和绒毛宽度减少较明显。提示交感神经的活动可影响小肠的黏膜结构，从而影响肠道的消化吸收功能。     

Duodenal Brunner's gland adenoma causing chronic small intestinal obstruction in a dog

An eight-year-old, neutered, female English springer spaniel was presented with a 14-month history of vomiting, marked weight loss and lethargy, all of which were non-responsive to medical therapy. Abdominal radiographs and ultrasonography showed an intraluminal soft tissue mass extending from the pyloric antrum to the proximal duodenum. Two spherical masses both approximately 8 cm in diameter were removed via a duodenotomy. Histopathological examination showed the first mass to be a trichobezoar and the aboral mass to be a Brunner's gland adenoma. Surgery resulted in a complete resolution of the clinical signs.     

Uptake of Mycobacterium avium subsp. paratuberculosis through the distal small intestinal mucosa in goats: an ultrastructural study

Various pathogens gain access to the intestinal wall via specialized cells, the M cells, found among the follicle-associated epithelial cells overlying the domes of the Peyer's patches. The present study was undertaken to examine the uptake of live Mycobacterium avium subsp. paratuberculosis in the distal small intestine of goat kids. Following laparotomy, distal small intestinal segments of five goats were ligated and injected with bacterial suspension. After 1 hour, the intestinal segments were excised and fixed for light and electron microscopic studies. M. a. paratuberculosis organisms were observed by transmission electron microscopy at locations in the intestinal wall, suggesting transcellular transportation through the M cells. The organisms were present both in the cytoplasm of the M cells and in the cytoplasm of intraepithelial leukocytes found in M-cell pockets. Intercellular bacteria between M cells were occasionally seen. Bacteria were not observed in association with the absorptive epithelium. This study indicates that in goat kids, M. a. paratuberculosis enters the intestinal wall primarily through the M cells in the follicle-associated epithelium of the Peyer's patches.