Physical characteristics of digesta and their influence on flow and mixing in the mammalian intestine: a review

Lentle, Roger G.; Janssen, Patrick

doi:10.1007/s00360-008-0264-x

Cited by 180 publications

(141 citation statements)

References 95 publications

Supporting

Mentioning

138

Contrasting

Order By: Relevance

“…FimH allows E. coli to colonize the mouth where shear stress due to salivary flow is estimated at 0.08 Pa (38), and the intestines where shear stress due to peristalsis is estimated at 1 Pa (39,40). Our data showing the superior binding of wild-type K12 over activated FocH in this flow range (Fig.…”

Section: Discussionsupporting

confidence: 50%

Inactive conformation enhances binding function in physiological conditions

Yakovenko

Tchesnokova

Sokurenko

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Many receptors display conformational flexibility, in which the binding pocket has an open inactive conformation in the absence of ligand and a tight active conformation when bound to ligand. Here we study the bacterial adhesin FimH to address the role of the inactive conformation of the pocket for initiating binding by comparing two variants: a wild-type FimH variant that is in the inactive state when not bound to its target mannose, and an engineered activated variant that is always in the active state. Not surprisingly, activated FimH has a longer lifetime and higher affinity, and bacteria expressing activated FimH bound better in static conditions. However, bacteria expressing wild-type FimH bound better in flow. It is now known that few proteins recognize ligands through a lock and key mechanism, in which the binding pocket is in essentially the same conformation whether or not ligand is bound. Instead, the conformation of the binding pocket is usually dynamic. Conformational dynamics have many functions for receptors as well as enzymes, so for simplicity, we will use the term ligand to describe substrates and products as well as molecules that are not changed by binding. For allosteric proteins, an obvious function of conformational changes in the pocket is to allow regulation of ligand binding by an allosteric effector. For other proteins, flexibility in the binding pocket allows proteins to bind structurally distinct ligands (1), which may in turn facilitate evolution of new structures and functions (2, 3). In many cases, the inactive conformation of the pocket is relatively loose, and the active conformation tightens around the ligand, often due to the closing of a hinge (4) between two domains, or loops that are described as a gate (e.g., refs. 5-7) or a lid (e.g., refs. 8-11) because they close over the ligand in binding pocket. The ability of the pocket to close around different ligands can contribute to specificity (5). Switching to the inactive state of the receptor dramatically increases the dissociation rate, so pocket dynamics controls the residence time of ligands (4, 12), and thus the catalytic rate of most enzymes (3). The importance of the inactive state to association rates is less clear; inactive states have been shown have lower (4, 12), similar (13), or higher (14) association rates relative to the active state, and the functional importance of the differences is unclear.We hypothesize that inactive states can have faster ligand association rates, and that this is important for nonequilibrium processes, where the kinetics, or rates, of individual steps are more important than overall affinity because the process does not reach equilibrium. An example of a nonequilibrium process is cell adhesion. Because adhesive receptors bind to ligands that are anchored to other cells or surfaces, the adhesive bonds are subjected to tensile mechanical force due to cytoskeletal contraction, fluidflow-induced drag forces, or other stresses. This tensile force can only be applied between receptor and lig...

show abstract

Section: Discussionsupporting

confidence: 50%

Inactive conformation enhances binding function in physiological conditions

Yakovenko

Tchesnokova

Sokurenko

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Cellulose resulted in faster transit than CMC and HG (data not shown); thus, besides the retention time in the small intestine, the accessibility of dietary nutrients appeared to be a critical factor for bacterial growth. Increased digesta viscosity impairs intestinal contractions (21), thereby preventing mixing of digesta and bacteria and thus access of bacteria to new substrate. Low-viscosity CEL, in turn, likely did not impair intestinal contractions and hence digesta mixing.…”

Section: Discussionmentioning

confidence: 99%

Nonstarch Polysaccharides Modulate Bacterial Microbiota, Pathways for Butyrate Production, and Abundance of Pathogenic Escherichia coli in the Pig Gastrointestinal Tract

Metzler‐Zebeli

Hooda

Pieper

et al. 2010

Appl Environ Microbiol

122

103

View full text Add to dashboard Cite

The impact of nonstarch polysaccharides (NSP) differing in their functional properties on intestinal bacterial community composition, prevalence of butyrate production pathway genes, and occurrence of Escherichia coli virulence factors was studied for eight ileum-cannulated growing pigs by use of terminal restriction fragment length polymorphism (TRFLP) and quantitative PCR. A cornstarch-and casein-based diet was supplemented with low-viscosity, low-fermentability cellulose (CEL), with high-viscosity, low-fermentability carboxymethylcellulose (CMC), with low-viscosity, high-fermentability oat ␤-glucan (LG), and with highviscosity, high-fermentability oat ␤-glucan (HG). Only minor effects of NSP fractions on the ileal bacterial community were observed, but NSP clearly changed the digestion in the small intestine. Compared to what was observed for CMC, more fermentable substrate was transferred into the large intestine with CEL, LG, and HG, resulting in higher levels of postileal dry-matter disappearance. Linear discriminant analysis of NSP and TRFLP profiles and 16S rRNA gene copy numbers for major bacterial groups revealed that CMC resulted in a distinctive bacterial community in comparison to the other NSP, which was characterized by higher gene copy numbers for total bacteria, Bacteroides-Prevotella-Porphyromonas, Clostridium cluster XIVa, and Enterobacteriaceae and increased prevalences of E. coli virulence factors in feces. The numbers of butyryl-coenzyme A (CoA) CoA transferase gene copies were higher than those of butyrate kinase gene copies in feces, and these quantities were affected by NSP. The present results suggest that the NSP fractions clearly and distinctly affected the taxonomic composition and metabolic features of the fecal microbiota. However, the effects were more linked to the individual NSP and to their effect on nutrient flow into the large intestine than to their shared functional properties.

show abstract

“…The absence of both, a distinct gas dome and a distinct sludge layer, could 314 theoretically be explained by a higher viscosity of both the rumen contents and the rumen 315 fluid in the browsing ruminants, which leaves both gas bubbles and fine, high-density 316 particles suspended in the fluid rather than allowing them to rise or sink within the RR. Even though, as discussed above, ingesta from both species separated according to particle 339 size due to its buoyancy characteristics in vitro, the situation in the densely packed suspension 340 of the RR is different (Lentle and Janssen, 2008). Buoyancy and sedimentation will probably 341 occur at much slower rates in this medium.…”

Section: Rr Contents Characteristics 305mentioning

confidence: 99%

“…After thawing, the viscosity of the rumen fluid supernatant was measured at 37 °C using 16 179 ml in a Brookfield LVDVE230 viscosimeter (Serial Number E6536, Brookfield Engineering 180 Laboratories, Middleboro, MA, USA) with a UL/Y adapter and spindle (rotational system 181 with concentric cylinder as recommended by Lentle and Janssen, 2008). With this system, the 182 shear rate is calculated as 1.29 x revolutions s -1 ; the producer recommends not to measure a 183 water-like substance at more than 1.29 s -1 .…”

Section: Introductionmentioning

confidence: 99%

Physical characteristics of rumen contents in two small ruminants of different feeding type, the mouflon (Ovis ammon musimon) and the roe deer (Capreolus capreolus)

Clauß

Fritz

Bayer

et al. 2009

Zoology

View full text Add to dashboard Cite

Hatt, J M (2009). Physical characteristics of rumen contents in two small ruminants of different feeding type, the mouflon (Ovis ammon musimon) and the roe deer (Capreolus capreolus). Zoology,. Postprint available at: http://www.zora.uzh.ch Posted at the Zurich Open Repository and Archive, University of Zurich. http://www.zora.uzh.ch Originally published at: Zoology 2009, 112(3):195-205. Physical characteristics of rumen contents in two small ruminants of different feeding type, the mouflon (Ovis ammon musimon) and the roe deer (Capreolus capreolus) AbstractIn domestic ruminants, the stratification of forestomach contents -the results of flotation and sedimentation processes -is an important prerequisite for the selective particle retention in this organ. A series of anatomical and physiological measurements suggests that the degree of this stratification varies between browsing and grazing wild ruminants. We investigated the forestomach contents of free-ranging mouflon and roe deer shot during regular hunting procedures. There was no difference between the species in the degree by which forestomach ingesta separated according to size due to buoyancy characteristics in vitro. However, forestomach fluid of roe deer was more viscous than that of mouflon, and no difference in moisture content was evident between the dorsal and the ventral rumen in roe deer, in contrast to mouflon. Hence, the forestomach milieu in roe deer appears less favourable for gas or particle separation due to buoyancy characteristics. These findings are in accord with notable differences in forestomach papillation between the species. In roe deer, particle separation is most likely restricted to the reticulum, whereas in mouflon, the whole rumen may pre-sort particles to a higher degree. The results suggest that differences in forestomach physiology may occur across ruminant species. In domestic ruminants, the stratification of forestomach contents -the results of flotation and 24 sedimentation processes -is an important prerequisite for the selective particle retention in 25 this organ. A series of anatomical and physiological measurements suggests that the degree of 26 this stratification varies between browsing and grazing wild ruminants. We investigated the 27 forestomach contents of free-ranging mouflon and roe deer shot during regular hunting 28procedures. There was no difference between the species in the degree by which forestomach 29 ingesta separated according to size due to buoyancy characteristics in vitro. However, 30 forestomach fluid of roe deer was more viscous than that of mouflon, and no difference in 31 moisture content was evident between the dorsal and the ventral rumen in roe deer, in contrast 32 to mouflon. Hence, the forestomach milieu in roe deer appears less favourable for gas or 33 particle separation due to buoyancy characteristics. These findings are in accord with notable 34 differences in forestomach papillation between the species. In roe deer, particle separation is 35 most likely restricted to the reticu...

show abstract

Physical characteristics of digesta and their influence on flow and mixing in the mammalian intestine: a review

Cited by 180 publications

References 95 publications

Inactive conformation enhances binding function in physiological conditions

Inactive conformation enhances binding function in physiological conditions

Nonstarch Polysaccharides Modulate Bacterial Microbiota, Pathways for Butyrate Production, and Abundance of Pathogenic Escherichia coli in the Pig Gastrointestinal Tract

Physical characteristics of rumen contents in two small ruminants of different feeding type, the mouflon (Ovis ammon musimon) and the roe deer (Capreolus capreolus)

Contact Info

Product

Resources

About