Assessment of the excretion time of electronic capsules placed in the intestinal lumen of cows with cecal dilatation-dislocation, healthy control cows, and cows with left displacement of the abomasum

OBJECTIVE To analyze the transit time from various locations in the intestines of cows with cecal dilatation-dislocation (CDD), healthy control cows, and cows with left displacement of the abomasum (LDA). ANIMALS 15 cows with naturally occurring CDD (group 1), 14 healthy control cows (group 2), and 18 cows with LDA (group 3). PROCEDURES 5 electronic transmitters were encased in capsules and placed in the lumen of the ileum, cecum, proximal portion of the colon, and 2 locations in the spiral colon (colon 1 and colon 2) and used to measure the transit time (ie, time between placement in the lumen and excretion of the capsules from the rectum). Excretion time of the capsules from each intestinal segment was compared among groups. RESULTS Cows recovered well from surgery, except for 1 cow with relapse of CDD 4 days after surgery and 2 cows with incisional infection. High variability in capsule excretion times was observed for all examined intestinal segments in all groups. Significant differences were detected for the excretion time from the colon (greater in cows with CDD than in healthy control cows) and cecum (less in cows with LDA than in cows of the other 2 groups). CONCLUSIONS AND CLINICAL RELEVANCE The technique developed to measure excretion time of capsules from bovine intestines was safe and reliable; however, the large variability observed for all intestinal segments and all groups would appear to be a limitation for its use in assessment of intestinal transit time of cattle in future studies.

Adaptations of intestinal macrophages to an antigen-rich environment

Intestinal macrophages, preferentially located in the subepithelial lamina propria, represent in humans the largest pool of tissue macrophages. To comply with their main task, i.e. the efficient removal of microbes and particulate matter that might have gained access to the mucosa from the intestinal lumen while maintaining local tissue homeostasis, several phenotypic and functional adaptations evolved. Most notably, microbe-associated molecular pattern (MAMP) receptors, including the lipopolysaccharide receptors CD14 and TLR4, but also the Fc receptors for IgA and IgG are absent on most intestinal Mø. Here we review recent findings on the phenotypic and functional adaptations of intestinal Mø and their implications for the pathogenesis of inflammatory bowel diseases.

Stratification and compartmentalisation of immunoglobulin responses to commensal intestinal microbes

The gastrointestinal tract is heavily colonized with commensal microbes with the concentration of bacteria increasing longitudinally down the length of the intestine. Bacteria are also spatially distributed transversely from the epithelial surface to the intestinal lumen with the inner mucus layer normally void of bacteria. Maintenance of this equilibrium is extremely important for human health and, as the dominant immunoglobulin at mucosal sites, IgA influences mutualism between the host and its normal microbiota. In this review we focus on the links between immune and microbial geography of the mammalian intestinal tract.

The outer mucus layer hosts a distinct intestinal microbial niche

The overall composition of the mammalian intestinal microbiota varies between individuals: within each individual there are differences along the length of the intestinal tract related to host nutrition, intestinal motility and secretions. Mucus is a highly regenerative protective lubricant glycoprotein sheet secreted by host intestinal goblet cells; the inner mucus layer is nearly sterile. Here we show that the outer mucus of the large intestine forms a unique microbial niche with distinct communities, including bacteria without specialized mucolytic capability. Bacterial species present in the mucus show differential proliferation and resource utilization compared with the same species in the intestinal lumen, with high recovery of bioavailable iron and consumption of epithelial-derived carbon sources according to their genome-encoded metabolic repertoire. Functional competition for existence in this intimate layer is likely to be a major determinant of microbiota composition and microbial molecular exchange with the host.

Homeland security: IgA immunity at the frontiers of the body

IgA is the most abundant immunoglobulin produced in mammals, and is mostly secreted across mucous membranes. At these frontiers, which are constantly assaulted by pathogenic and commensal microbes, IgA provides part of a layered system of immune protection. In this review, we describe how IgA induction occurs through both T-dependent and T-independent mechanisms, and how IgA is generated against the prodigious load of commensal microbes after mucosal dendritic cells (DCs) have sampled a tiny fraction of the microbial consortia in the intestinal lumen. To function in this hostile environment, IgA must be induced behind the 'firewall' of the mesenteric lymph nodes to generate responses that integrate microbial stimuli, rather than the classical prime-boost effects characteristic of systemic immunity.

Insulin-like growth factors (IGFs), IGF binding proteins, and other endocrine factors in milk: role in the newborn

The role of colostrum and milk in the neonate has been chiefly recognized as a comprehensive nutrient foodstuff. In addition, the provision of colostrum-the first milk-for early immune capacity has been well documented for several species. Colostrum is additionally a rich and concentrated source of various factors that demonstrate biological activity in vitro. Three hypotheses have been proposed for the phenotypic function of these secreted bioactive components: (1) only mammary disposal, (2) mammary cell regulation, and (3) neonatal function [gastrointestinal tract (GIT) or systemic]. Traditionally, it was assumed that the development of the GIT is preprogrammed and not influenced by events occurring in the intestinal lumen. However, a large volume of research has demonstrated that colostrum (or milk-borne) bioactive components can basically contribute to the regulation of GIT growth and differentiation, while their role in postnatal development at physiological concentrations has remained elusive. Much of our current understanding is derived from cell culture and laboratory animals, but experimentation with agriculturally important species is taking place. This chapter provides an overview of work conducted primarily in neonatal calves and secondarily in other species on the effects on neonates of selected peptide endocrine factors (hormones, growth factors, in part cytokines) in colostrum. The primary focus will be on insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) and other bioactive peptides, but new interest and concern about steroids (especially estrogens) in milk are considered as well.

The immune geography of IgA induction and function

The production of immunoglobulin A (IgA) in mammals exceeds all other isotypes, and it is mostly exported across mucous membranes. The discovery of IgA and the realization that it dominates humoral mucosal immunity, in contrast to the IgG dominance of the systemic immune system, was early evidence for the distinct nature of mucosal immunology. It is now clear that IgA can function in high-affinity modes for neutralization of toxins and pathogenic microbes, and as a low-affinity system to contain the dense commensal microbiota within the intestinal lumen. The basic map of induction of IgA B cells in the Peyer's patches, which then circulate through the lymph and bloodstream to seed the mucosa with precursors of plasma cells that produce dimeric IgA for export through the intestinal epithelium, has been known for more than 30 years. In this review, we discuss the mechanisms underlying selective IgA induction of mucosal B cells for IgA production and the immune geography of their homing characteristics. We also review the functionality of secretory IgA directed against both commensal organisms and pathogens.

Compartmentalised expression of meprin in small intestinal mucosa: enhanced expression in lamina propria in coeliac disease

Epithelial cells in the human small intestine express meprin, an astacin-like metalloprotease, which accumulates normally at the brush border membrane and in the gut lumen. Therefore, meprin is targeted towards luminal components. In coeliac disease patients, peptides from ingested cereals trigger mucosal inflammation in the small intestine, disrupting epithelial cell differentiation and function. Using in situ hybridisation on duodenal tissue sections, we observed a marked shift of meprin mRNA expression from epithelial cells, the predominant expression site in normal mucosa, to lamina propria leukocytes in coeliac disease. Meprin thereby gains access to the substrate repertoire present beneath the epithelium.

Percutaneous vein occlusion with small intestinal submucosa: an experimental pilot study in Swine and sheep

PURPOSE: The objective of this study was to investigate the feasibility, outcomes, and amount of small intestinal submucosa (SIS) material needed for embolization of jugular vein (JV) in a swine and sheep model. Our hypothesis was that SIS would cause vein occlusion. MATERIALS AND METHODS: The external JVs (EJV) in swine (n = 6) and JVs in sheep (n = 6) were occluded with SIS fan-folded compressed strips. After percutaneous puncture of the peripheral portion of the EJV or JV, a TIPS set was used to exit their lumen centrally through the skin. The SIS strips were delivered into the isolated venous segment with a pull-through technique via a 10-Fr sheath. Follow-up venograms were done immediately after placement and at the time of sacrifice at 1 or 3 months. Gross examinations focused on the EJV or JV and their surrounding structures. Specimens were evaluated by histology. RESULTS: SIS strip(s) placement was successful in all cases, with immediate vein occlusion seen in 23 of 24 veins (95.8%). All EJVs treated with two strips and all JVs treated with three or four strips remained closed on 1- and 3-month follow-up venograms. Two EJVs treated with one strip and one JV treated with two strips were partially patent on venograms at 1 and 3 months. There has been one skin inflammatory reaction. Necropsies revealed excluded EJV or JV segments with SIS incorporation into the vein wall. Histology demonstrated various stages of SIS remodeling with fibrocytes, fibroblasts, endothelial cells, capillaries, and inflammatory cells. CONCLUSION: We conclude that EJV and JV ablation with SIS strips using percutaneous exit catheterization is feasible and effective in animal models. Further exploration of SIS as vein ablation material is recommended.

TNF suppresses acute intestinal inflammation by inducing local glucocorticoid synthesis

Although tumor necrosis factor (alpha) (TNF) exerts proinflammatory activities in a variety of diseases, including inflammatory bowel disease, there is increasing evidence for antiinflammatory actions of TNF. In contrast, glucocorticoids (GCs) are steroid hormones that suppress inflammation, at least in part by regulating the expression and action of TNF. We report that TNF induces extraadrenal production of immunoregulatory GCs in the intestinal mucosa during acute intestinal inflammation. The absence of TNF results in a lack of colonic GC synthesis and exacerbation of dextran sodium sulfate-induced colitis. TNF seems to promote local steroidogenesis by directly inducing steroidogenic enzymes in intestinal epithelial cells. Therapeutic administration of TNF induces GC synthesis in oxazolone-induced colitis and ameliorates intestinal inflammation, whereas inhibition of intestinal GC synthesis abrogates the therapeutic effect of TNF. These data show that TNF suppresses the pathogenesis of acute intestinal inflammation by promoting local steroidogenesis.

Lipopolysaccharide induces intestinal glucocorticoid synthesis in a TNFalpha-dependent manner

Stringent control of immune responses in the intestinal mucosa is critical for the maintenance of immune homeostasis and prevention of tissue damage, such as observed during inflammatory bowel disease. Intestinal epithelial cells, primarily thought to form a simple physical barrier, critically regulate intestinal immune cell functions by producing immunoregulatory glucocorticoids on T-cell activation. In this study we investigated whether stimulation of cells of the innate immune system results in the induction of intestinal glucocorticoids synthesis and what role TNF-alpha plays in this process. Stimulation of the innate immune system with lipopolysaccharide (LPS) led to an up-regulation of colonic steroidogenic enzymes and the induction of intestinal glucocorticoid synthesis. The observed induction was dependent on macrophage effector functions, as depletion of macrophages using clodronate-containing liposomes, but not absence of T and B cells, inhibited intestinal glucocorticoid synthesis. LPS-induced glucocorticoid synthesis was critically dependent on TNF-alpha as it was significantly decreased in TNF-alpha-deficient animals. Both TNF receptor-1 and -2 were found to be equally involved in LPS- and T-cell-induced intestinal GC synthesis. These results describe a novel and critical role of TNF-alpha in immune cell-induced intestinal glucocorticoid synthesis.

Immune adaptations that maintain homeostasis with the intestinal microbiota

Humans harbour nearly 100 trillion intestinal bacteria that are essential for health. Millions of years of co-evolution have moulded this human-microorganism interaction into a symbiotic relationship in which gut bacteria make essential contributions to human nutrient metabolism and in return occupy a nutrient-rich environment. Although intestinal microorganisms carry out essential functions for their hosts, they pose a constant threat of invasion owing to their sheer numbers and the large intestinal surface area. In this Review, we discuss the unique adaptations of the intestinal immune system that maintain homeostatic interactions with a diverse resident microbiota.

Like will to like: abundances of closely related species can predict susceptibility to intestinal colonization by pathogenic and commensal bacteria

The intestinal ecosystem is formed by a complex, yet highly characteristic microbial community. The parameters defining whether this community permits invasion of a new bacterial species are unclear. In particular, inhibition of enteropathogen infection by the gut microbiota ( = colonization resistance) is poorly understood. To analyze the mechanisms of microbiota-mediated protection from Salmonella enterica induced enterocolitis, we used a mouse infection model and large scale high-throughput pyrosequencing. In contrast to conventional mice (CON), mice with a gut microbiota of low complexity (LCM) were highly susceptible to S. enterica induced colonization and enterocolitis. Colonization resistance was partially restored in LCM-animals by co-housing with conventional mice for 21 days (LCM(con21)). 16S rRNA sequence analysis comparing LCM, LCM(con21) and CON gut microbiota revealed that gut microbiota complexity increased upon conventionalization and correlated with increased resistance to S. enterica infection. Comparative microbiota analysis of mice with varying degrees of colonization resistance allowed us to identify intestinal ecosystem characteristics associated with susceptibility to S. enterica infection. Moreover, this system enabled us to gain further insights into the general principles of gut ecosystem invasion by non-pathogenic, commensal bacteria. Mice harboring high commensal E. coli densities were more susceptible to S. enterica induced gut inflammation. Similarly, mice with high titers of Lactobacilli were more efficiently colonized by a commensal Lactobacillus reuteri(RR) strain after oral inoculation. Upon examination of 16S rRNA sequence data from 9 CON mice we found that closely related phylotypes generally display significantly correlated abundances (co-occurrence), more so than distantly related phylotypes. Thus, in essence, the presence of closely related species can increase the chance of invasion of newly incoming species into the gut ecosystem. We provide evidence that this principle might be of general validity for invasion of bacteria in preformed gut ecosystems. This might be of relevance for human enteropathogen infections as well as therapeutic use of probiotic commensal bacteria.

In remembrance of commensal intestinal microbes

Mammals contain an enormous load of commensal microbes in the lower intestine, which induce adaptive responses in the host immune system that ensure mutual coexistence of the host and its microbial passengers. The main way of studying how the host responds to commensal colonization has been to compare animals kept in entirely germ-free conditions and their colonized counterparts. We present an overview of our development of a reversible colonization system, whereby germ free animals can be treated with live commensal bacteria that do not persist in the host, so it becomes germ free again. We describe how this system has been used to demonstrate that there is little or no immune memory for specific IgA induction in the intestinal mucosal immune system by commensal intestinal bacteria.

Garlic extract induces intestinal P-glycoprotein, but exhibits no effect on intestinal and hepatic CYP3A4 in humans

Garlic extracts have been shown to decrease drug exposure for saquinavir, a P-glycoprotein and cytochrome P450 3A4 substrate. In order to explore the underlying mechanisms and to study the effects of garlic on pre-systemic drug elimination, healthy volunteers were administered garlic extract for 21 days. Prior to and at the end of this period, expression of duodenal P-glycoprotein and cytochrome P450 3A4 protein were assayed and normalized to villin, while hepatic cytochrome P450 3A4 function and simvastatin, pravastatin and saquinavir pharmacokinetics were also evaluated. Ingestion of garlic extract increased expression of duodenal P-glycoprotein to 131% (95% CI, 105-163%), without increasing the expression of cytochrome P450 3A4 which amounted to 87% (95% CI, 67-112%), relative to baseline in both cases. For the erythromycin breath test performed, the average result was 96% (95% CI, 83-112%). Ingestion of garlic extract had no effect on drug and metabolite AUCs following a single dose of simvastatin or pravastatin, although the average area under the plasma concentration curve (AUC) of saquinavir decreased to 85% (95% CI, 66-109%), and changes in intestinal P-glycoprotein expression negatively correlated with this change. In conclusion, garlic extract induces intestinal expression of P-glycoprotein independent of cytochrome P450 3A4 in human intestine and liver.