Gastrointestinal Morphology Research Articles

Changes in gastrointestinal morphology associated with obstructive jaundice.

Bacterial translocation has been consistently demonstrated in experimental models of obstructive jaundice. An important factor which promotes this phenomenon is physical injury of the intestinal mucosa. Some previous studies have presented suggestive evidence of this, following bile duct ligation. The aims of this study were to analyse objectively intestinal mucosal morphometric characteristics, to examine for evidence of bacterial translocation, and to assess enterocytes for ultrastructural abnormalities. Adult female Wistar rats were assigned to one of three groups: control (n=8), bile duct ligation (BDL; n=11), or sham operation (n=10). One week later, portal blood, mesenteric lymph nodes, liver, and spleen were harvested and cultured aerobically and anaerobically for evidence of bacterial translocation. Segments of jejunum, ileum, caecum, and large bowel were examined histologically, using light microscopy and morphometrically, using an image analysis system. Electron microscopy was performed on regions of the gastrointestinal tract where significant morphometric alterations had been identified. Significant bacterial translocation was identified following BDL (63. 6% BDL vs. 0% sham vs. 0% control, p<0.01, Fisher's exact test). There was a significant reduction in total mucosal thickness (standard error) [650 microm (23) BDL vs. 731 microm (27) sham vs. 744 microm (95) control] and villous height [451 microm (20) BDL vs. 515 microm (18) sham vs. 559 microm (79) control] in jaundiced animals, compared with sham-operated and control animals (p<0.02, Mann-Whitney U-test). Electron microscopy revealed oedematous change associated with mild inflammation, disruption of desmosomes, and the formation of lateral spaces between enterocytes. In addition, enterocytes showed vacuolation of their cytoplasm and mitochondrial swelling. Increased numbers of bacteria appeared to be attached to the mucosa. These data provide evidence of physical disruption of intestinal mucosa in jaundiced animals, most marked in the distal ileum. Significant bacterial translocation occurs following bile duct ligation and this supports the hypothesis of gut barrier dysfunction with obstructive jaundice.

From blackbirds and thrushes...to the gut-loaded cricket: a new approach to zoo animal nutrition

Zoo animal nutritionists need to make decisions about diet composition for a wide variety of vertebrate species, including those with very specialized diets (dietary specialists). For some zoo species it is common to refer to the published literature on the nutrient requirements of analogous domestic animals, such as cattle, horses and cats, as well as human beings (Allen &amp; Oftedal, 1996). When this information is combined with knowledge of natural history, feeding patterns, composition of foods consumed in the wild and gastrointestinal tract morphology, it is possible to develop a sound foundation for a successful feeding programme for many zoo animals.

Gastric Na +K +ATPase activity and intestinal urea hydrolysis of the common vampire bat, Desmodus rotundus

The blood diet of the vampire bat represents an extraordinarily high ratio of protein to other nutrients and the highest water consumption per body weight of any other mammal. This bat has a unique gastrointestinal morphology that is characterized by a reduced small intestine, absence of a large intestine and intestinal cecum and the presence of a water-absorptive gastric fundus. The present study demonstrates that the gastric fundus has a greater Na +K +ATPase activity for active ion transport compared with other equally sized mammals. This activity is believed to be necessary to establish a gradient favoring water absorption across what would otherwise be an osmotic disequilibrium. The absence of a large intestine and intestinal cecum may reflect a reduced urea hydrolysis by the vampire bat. The present study demonstrated that the vampire bat does not hydrolyze urea as does an equally sized non-sanguinivorous mammal. These data suggest that the blood diet and the relocation of water-absorptive tissue from the lower intestinal tract to the stomach is associated with an active ion transport mechanism in the gastric tissue and a reduced capacity for ureolytic microbes to hydrolyze urea in the intestine. Both processes are specializations for a diet high in protein and water.

Gastrointestinal Morphology and Motility in American Kestrels Receiving High or Low Fat Diets

Fifteen yearling, male American Kestrels (Falco sparverius) were fed either intact day-old chicks (Gallus domesticus) (high-fat diet) or chicks with the yolk removed plus a piece of lean turkey meat approximately equivalent in volume to the yolk (low-fat diet). This was done for 33-37 days to determine the influence of dietary fat on the gastrointestinal gross anatomy and contractile activity of the kestrels. Fat content of the diet appeared to have little effect on either anatomy or contractions. Observations of contractile activity, via Image Intensification Radiology, revealed a unique reflux of duodenal contents associated with every duodenal flux in every gastroduodenal contraction cycle (approximately 3-4 min-1). This presumably improved mixing of ingesta with digestive secretions and hastened digestion of ingested nutrients which would be advantageous to a small bird with a high mass-specific metabolic rate. The duodenum was enlarged relative to the size of this organ in other raptors, possibly to accommodate to this process. The colon also was relatively larger in this species, perhaps to permit final processing of the diet and water absorption from the greater quantity of digesta passed from the small intestine.

Effect of L-Arginine and L-Name on visceral blood flow in ovine endotoxaemia

Excess production of the endogenous vasodilator nitric oxide is thought to contribute to the refractory hypotension of septic shock. Nitric oxide synthase blockers (e.g. NG-nitro-L-arginine-methyl-ester, L-Name) have been shown to increase arterial blood pressure and systemic vascular resistance but with an uncertain effect on visceral blood supply. The amino acid precursor of nitric oxide, L-Arginine, has been shown to have a beneficial effect on gastrointestinal morphology [1] and also survival in gut-derived sepsis [2]. The study was undertaken to assess the effects of nitric oxide modulation on visceral blood suppy in ovine endotoxaemia. The study was performed under UK Government regulations concerning animal experimentation. Eighteen Soay sheep (10-18 kg) were anaesthetized with thiopentone, fentanyl and halothane 1.5% in oxygen enriched air. Systemic and pulmonary arterial thermodilution catheters were inserted and electromagnetic flow probes placed around the cranialmesenteric and left renal arteries. Escherichia coli endotoxin 2 μg kg−1 was administered followed 2 h later by either L-Arginine (0.575 g kg−1), L-Name (25 mg kg−1) or N.Saline (6 per group). This was followed by an infusion of the same dose over 8 h. Mesenteric and renal conductance (flow/meanBP) and cardiac output (CO) were measured serially. Results are shown in Figs. 4 and 5. There were no differences in CO or renal conductance between the three groups, whereas mesenteric conductance increased significantly in the arginine group (P=0.0299 vs. controls, P=0.0166 vs. L-Name: two factor ANOVA).Fig. 4: (abstract 4). Percentage change in renal conductance (mean:SEM).Fig. 5: (abstract 4). Percentage change in mesenteric conductance (mean:SEM).The administration of L-arginine in this model of ovine endotoxaemia caused a significant (three fold) increase in mesenteric conductance. Nitric oxide enhancement may improve mesenteric blood flow in sepsis.

Convergence in community structure and dietary adaptation in Australian possums and gliders and Malagasy lemurs

Abstract The possums and gliders of Australia and the lemurs of Madagascar are ideally suited for investigation of radiation and convergence in arboreal mammal communities because of their long history of independent radiation in similar biophysical environments. Possum and glider communities at 22 sites in Australia and lemur communities at 18 sites in Madagascar were compared to evaluate patterns of community and species convergence in two shared habitats (evergreen and deciduous monsoon rainforests) and three derived habitats (Australian eucalypt forests and heaths, and Malagasy thorn scrubs). Arboreal mammals were classified into five dietary guilds for comparison of community structure and species adaptation. There is little evidence of convergence in trophic structure at the community level, but strong evidence of convergence in dietary adaptation at the species and niche level. Malagasy rainforest communities were characterized by a higher proportion of frugivore‐folivores, and Australian rainforest and moist eucalypt communities by a higher proportion of folivores and folivore‐frugivores. Possum and glider communities in temperate eucalypt forests and heaths supported a higher proportion of nectarivores and exudivores. Overall species richness was significantly higher in Madagascar. Four hypotheses are erected to account for these differences. The relative scarcity of frugivores in Australian evergreen rainforests is accounted for by the predominance of bird‐dispersed fruits, and fruiting phenologies unsuitable for mammal exploitation and dispersal. Higher folivore diversity in Australian evergreen rainforests is associated with a more pronounced seasonal shortage of edible fruits and new leaf, which has increased dependence on mature leaf. Folivore species richness is greatest in Australian moist eucalypt forests where structural complexity, sustained by serai responses to wildfire, permits a high level of vertical segregation. Increased nectarivory and exudivory in Australian temperate eucalypt forests and heaths is associated with Mediterranean winter rainfall regimes, which permit year round exudate production, and not with the absence of nectar feeding bats as previously supposed. A lower overall species richness in Australian rainforests is attributed to a longer history of contraction and fragmentation by anthropogenic fires (monsoon rainforests) and Pleistocene climatic change (tropical evergreen rainforests). A high degree of convergence is apparent between genera occupying folivore and wood gouging niches, in terms of gastrointestinal morphology (e.g. Pseudocheirus‐Lepilemur) and dental morphology (e.g. Dactylopsila‐Daubentonia). Divergences are most apparent in adaptations associated with frugivory, including larger body size, diurnality, and bipedal suspension and leaping modes of locomotion (in Eulemur spp.). This study highlights the importance of founding effects, competition from other vertebrate taxa, coevolution between animals and their food plants, and differences in biophysical environments, as determinants of mammalian radiation and convergence.

Differential Diagnosis of Cyclic Vomiting Syndrome

Summary:Vomiting is a nonspecific symptom and cyclic vomiting is a symptom complex that may result from a disorder of any major organ system. Children with cyclic vomiting syndrome (CVS) need careful review and investigation at their earliest presentations to exclude potentially lethal abnormalities such as intestinal volvulus, metabolic disorders, and neurologic space‐occupying lesions. The range of abnormalities that may present with features consistent with CVS includes gastrointestinal obstructive, inflammatory and motility abnormalities, pancreatic disease, metabolic disease (particularly the amino acidopathies, organic acidurias, fatty acid oxidation defects, and acute intermittent porphyria), renal disease, epilepsy, migraine, and psychiatric disorders. Careful history taking will usually provide clues to these uncommon problems, but all children should undergo baseline assessment of gastrointestinal morphology and screening tests for renal and metabolic disease.

Somatotropin Transgenic Mice Have Reduced Jejunal Active Glucose Transport Rates

Small intestinal glucose absorption and gastrointestinal morphology were compared in adult bovine somatotropin transgenic (MT-bGH) and control mice. The MT-bGH mice were 57% heavier than controls, although both groups consumed comparable amounts of food during the 5 d before transport measurements were made. Stomach, cecum and colon were 98, 53, and 81% heavier (P < 0.001), and small intestinal tract 52% heavier and 27% longer in MT-bGH than in control mice (P < 0.001). As a proportion of live weight, MT-bGH mice tended to have a shorter small intestine than controls (P < 0.07), whereas there was no difference for either small or large bowel relative weights. Villus dimensions, crypt depth and thickness of external muscle layers in the jejunum were not significantly different in control and MT-bGH mice. Active glucose transport rate per milligram of jejunum was 24% less than in control mice (P < 0.05). Jejunal active glucose transport rate per gram of live weight in MT-bGH mice was approximately half that of control mice. The larger small intestinal mass of MT-bGH mice compensated for the reduced rate of glucose transport per unit weight of intestine such that there was no significant difference in total small intestinal tract glucose transport between control and MT-bGH mice. These results suggest that there are substantial differences in nutrient absorptive efficiency between intestinal tract from MT-bGH and control mice.

Gastrointestinal morphology and absorption of monosaccharides in fowls conditioned to different types and levels of dietary fibre.

To test a possible influence of dietary fibre on intestinal sugar uptake, rates of absorption of 10 mM-D-[U-14C] glucose and 10 mM-D-[U-14C] xylose were measured in either jejunum or (distal) caecum, by in vivo lumen perfusion, in immature female fowls preconditioned to a standard diet containing (g/kg) either 0, 100, 200 or 400 added dried grass, 200 powdered cellulose, or 200 grass with a polysaccharidase enzyme supplement. When birds were killed after perfusion, dimensions of (unperfused) parts of their alimentary tracts were determined, and recoveries of 14C radioactivity in some body tissues were compared with measured activities absorbed. On average, absorption of glucose was 1.9 and 1.2 times faster than xylose in jejunum and caecum respectively, although these differences varied with dietary treatment and order of perfusion. Increasing grass in the diet caused significant changes in xylose absorption rate in both jejunum and caecum, but only when it was perfused before glucose. With any one sugar and intestinal segment, mean rates of absorption were correlated positively with corresponding mean rates of fluid loss from perfusate. Although their influence on sugar absorption was not well defined, the dietary fibre treatments had more pronounced effects on gross dimensions of parts of the alimentary tract and, hence, potentially on total rates of absorption. Compared with the basal diet, addition of 100, 200 or 400 g grass/kg or 200 g cellulose/kg caused significant increases in small intestine length while 200 g grass/kg with supplementary enzyme did not, and combined caecal length increased with the 400 g grass/kg and the supplementary enzyme treatments. Absorbed 14C activity was recovered in plasma after jejunal perfusions but not caecal ones, whereas it was recovered in liver and in the flushed perfused segment after both types of perfusion. Since there was overlap in absorption rates between jejunum and caecum, this result suggests that the liver may be able to distinguish and treat differently compounds absorbed in the two regions.

Seasonal Changes in Energy Expenditure and Digestive Tract of Abrothrix andinus (Cricetidae) in the Andes Range

The South American field mouse Abrothrix andinus (Rodentia: Cricetidae) is a small mammal active throughout the year in the Andes, despite substantial seasonal environmental changes. Body mass exhibited a significant decrease during winter, and maximum metabolic rate for thermoregulation increased by 36.6%. In absolute terms, the maximum thermal differential between body and environmental temperatures increased 44° C during winter. On the other hand, body temperature and thermal conductance did not show significant changes through the year; however, mass-independent conductance decreased in winter. Parallel to these changes, the length and dry mass of the total digestive tract changed significantly with wintertime; at the same time the length and mass of the small intestine and the length of the large intestine also showed significance. Significant differences in gastrointestinal morphology between males andfemales were found only during the reproductive season (summer).

Physiological Basis of Stomach Oil Formation in Leach's Storm-Petrel (Oceanodroma leucorhoa)

We describe the mechanisms and kinetics of stomach oil formation in a representative procellariiform, Leach's Storm-Petrel. We relate the mechanics of stomach oil formation to the process by which procellariiforms are able to use the dietary lipids. We show how birds concentrate food into a store, the composition of which is determined largely by properties of the meals, the lipids, and a specialized gastrointestinal morphology

Digestive tract of the African giant rat, Cricetomys gambianus

The study of gastrointestinal morphology, anatomy, passage rates and pH in the African giant rat, Cricetomys gambianus, were undertaken to elucidate the relationship between feeding habits and gut structure. The relatively slow transit times of digesta, suggested to be advantageous in digestion, probably resulted from a complex gastrointestinal tract. The prime function of the large papillated corpus and fornix ventriculi is thought to be starch digestion, while the caecum enhances the utilization of undigested food. Gut structure appears to be a result of a multitude of selective forces, not only dietary habits.

Comparative gastrointestinal morphology of the Kori bustard and secretary bird

AbstractTwo secretary birds and three Kori bustards were studied to determine differences between their body size and gastrointestinal morphology. Body measurements were made on captive, live birds and gastrointestinal measurements on fresh postmortem specimens. For predator species, such as the Kori bustard and secretary bird, body size is a function of their ability to capture and destroy prey. While the secretary bird was clearly the taller of the two species, superior body weight, wing length, and therefore body size was noted for the Kori bustard. The size and length of the gastrointestinal tract varied between species. The secretary bird had the shorter, less complex digestive tract, with a foregut well adapted for consumption of large quantities of flesh. The large intestine was devoid of ceca. The gastrointestinal tract of the Kori bustard was markedly different from that of the secretary bird. The foregut was less complex and the large intestine possessed large, voluminous ceca.