What transport adaptations enable mammals to absorb sugars and amino acids faster than reptiles?

What digestive adaptations enable mammals to process much more food in much less time with equal or higher digestive efficiency than reptiles and thus to sustain much higher metabolic rates? To answer this question, we measured glucose and proline uptake in small intestinal sleeves of three mammal and three reptile species of similar body size and natural diet. All species exhibit saturable, stereospecific uptake of D-glucose and Na+-dependent L-proline uptake. Passive permeability to glucose is high in hamsters and low in the other species. Uptake increases with temperature up to a maximum around 45–50 degrees C. This temperature dependence may help explain why reptiles bask after meals and why their digestion is impaired if basking is prevented. The total uptake capacity of the small intestine for glucose and proline is seven times higher in mammals than similar-sized reptiles, mainly because the area of mammalian intestine is 4–5.5 times greater. Minor reasons for the higher uptake capacity of mammals are that the transport activity of mammal intestine normalized to quantity of tissue is up to twofold higher and that reptile intestine operates at a lower temperature at night. Vmax for glucose transport varies 10-fold among species, but apparent differences in Km values may be unstirred-layer artifacts. Carrier-mediated uptake of glucose and proline is measurable in the colon of at least three species, but the uptake capacity of the colon is less than 10% of that of the small intestine. An appendix presents a method for measuring the microscopic area of intestines with ridges rather than villi, applies this method to desert iguana intestine, and measures area amplification due to villi in wood rat intestine.

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Ontogenetic development of monosaccharide and amino acid transporters in rabbit intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1990.259.4.g544 ◽

1990 ◽

Vol 259 (4) ◽

pp. G544-G555 ◽

Cited By ~ 6

Author(s):

R. K. Buddington ◽

J. M. Diamond

Keyword(s):

Amino Acids ◽

Small Intestine ◽

Metabolic Rate ◽

Direct Proportion ◽

Natural Diet ◽

Sugar Absorption ◽

Age Related ◽

Rabbit Intestine ◽

Small Intestinal ◽

Rabbit Milk

We measured brush-border uptakes of seven sugars and amino acids by rabbit intestine as a function of age from the day of birth to adulthood. Gut dimensions, especially those of the colon and cecum, increase more rapidly with body weight than would be true if rabbits maintained identical proportions as they grew. However, nominal small intestinal area increases in approximately direct proportion to the animal's basal metabolic rate. For all solutes except fructose, uptake per milligram of intestinal tissue is maximal at or near birth and declines to a level 2.5-5 times lower in the adult. Because of small intestinal growth, though, the total uptake capacity of the whole length of the small intestine increases in approximately direct proportion to metabolic rate. Fructose uptake per milligram is unique in increasing steeply at the time of weaning, correlated with the post-weaning first appearance of fructose in the natural diet. Age-related changes in uptake ratios among aldohexoses or amino acids suggest developmental sequences of related transporters. Correlated with the very high protein content of rabbit milk, the proline-to-glucose uptake ratio is higher in suckling rabbits than in other sucking mammals. Remarkably, the ratio for adult rabbits is higher than in other monogastric herbivores and is instead similar to values for carnivores. In explanation, although the transport capacity of the small intestine appears to account for proline absorption in rabbits of all ages and for sugar absorption in suckling rabbits, the hindgut may be a major site of carbohydrate digestion in adult rabbits.

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Magnitude of functional adaptation after intestinal resection

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1999.276.5.r1265 ◽

1999 ◽

Vol 276 (5) ◽

pp. R1265-R1275 ◽

Cited By ~ 12

Author(s):

Timothy P. O’Connor ◽

Mandy M. Lam ◽

Jared Diamond

Keyword(s):

Small Intestine ◽

Glucose Uptake ◽

Safety Factor ◽

Time Course ◽

Intestinal Adaptation ◽

Intestinal Resection ◽

Functional Adaptation ◽

Glucose Load ◽

Uptake Capacity ◽

Small Intestinal

Intestinal adaptation after resection has been much studied, but rarely examined in an integrative context. Hence we assessed the effects of resection and subsequent adaptation on the quantitative relationship between dietary glucose load and gut capacity to transport glucose. The ratio of capacity to load is termed the “safety factor.” Our objectives were to determine 1) the time course of intestinal adaptation after resection, 2) whether adaptation is quantitatively complete, 3) whether survival requires maintaining a safety factor of at least 1.0 for glucose transport, 4) the effect of altered energy demands on adaptation, and 5) the relationship between the amount of tissue removed and the magnitude of functional adaptation. We performed 80% resection of the small intestine on Sprague-Dawley rats and measured small intestinal glucose uptake capacity, dietary glucose load, and gut gross morphology at 1, 5, and 10 wk postsurgery. Nearly all aspects of adaptation were complete by 1 wk postsurgery. After resection, remnant small intestine mass increased by over fivefold within 1 wk, to reach 50–70% of its preresection value. However, mass-specific glucose uptake activity was reduced, so that intestinal regeneration restored uptake capacity to only 33% of control values. Increased energetic demands had only modest effects on intestinal adaptation. Although the safety factor for small intestinal glucose uptake remained <1.0 (i.e., capacity < load) after adaptation to resection, nearly all rats survived. Hindgut fermentation of nonabsorbed nutrients appeared to contribute to that survival, despite inadequate small intestinal capacity. After less massive resection surgeries (25, 50, and 75% resections), the percent increase in glucose uptake capacity increased with the amount of tissue removed.

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Application of a dynamic mechanistic model of small intestinal starch digestion in the dairy cow

Proceedings of the British Society of Animal Science ◽

10.1017/s1752756200007602 ◽

2002 ◽

Vol 2002 ◽

pp. 104-104

Author(s):

J. A. N. Mills ◽

E. Kebreab ◽

L. A. Crompton ◽

J. Dijkstra ◽

J. France

Keyword(s):

Experimental Data ◽

Small Intestine ◽

Dairy Cow ◽

Energy Recovery ◽

Mechanistic Model ◽

Biological Knowledge ◽

Dietary Energy ◽

Starch Digestion ◽

High Contribution ◽

Small Intestinal

The high contribution of postruminal starch digestion (>50%) to total tract starch digestion on certain energy dense diets (Mills et al. 1999) demands that limitations to small intestinal starch digestion are identified. Therefore, a dynamic mechanistic model of the small intestine was constructed and evaluated against published experimental data for abomasal carbohydrate infusions in the dairy cow. The mechanistic structure of the model allowed the current biological knowledge to be integrated into a system capable of identifying restrictions to dietary energy recovery from postruminal starch delivery.

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Influence of microbial species on small intestinal myoelectric activity and transit in germ-free rats

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.2001.280.3.g368 ◽

2001 ◽

Vol 280 (3) ◽

pp. G368-G380 ◽

Cited By ~ 157

Author(s):

Einar Husebye ◽

Per M. Hellström ◽

Frank Sundler ◽

Jie Chen ◽

Tore Midtvedt

Keyword(s):

Small Intestine ◽

Intestinal Microflora ◽

Burst Activity ◽

Intestinal Transit ◽

Myoelectric Activity ◽

Regular Spike ◽

Spike Burst ◽

Germ Free ◽

Microbial Species ◽

Small Intestinal

The effect of an intestinal microflora consisting of selected microbial species on myoelectric activity of small intestine was studied using germ-free rat models, with recording before and after specific intestinal colonization, in the unanesthetized state. Intestinal transit, neuropeptides in blood (RIA), and neuromessengers in the intestinal wall were determined. Clostridium tabificum vp 04 promoted regular spike burst activity, shown by a reduction of the migrating myoelectric complex (MMC) period from 30.5 ± 3.9 min in the germ-free state to 21.2 ± 0.14 min ( P < 0.01). Lactobacillus acidophilus A10 and Bifidobacterium bifidum B11 reduced the MMC period from 27.9 ± 4.5 to 21.5 ± 2.1 min ( P < 0.02) and accelerated small intestinal transit ( P < 0.05). Micrococcus luteus showed an inhibitory effect, with an MMC period of 35.9 ± 9.3 min compared with 27.7 ± 6.3 min in germ-free rats ( P < 0.01). Inhibition was indicated also for Escherichia coli X7gnotobiotic rats. No consistent changes in slow wave frequency were observed. The concentration of neuropeptide Y in blood decreased after introduction of conventional intestinal microflora, suggesting reduced inhibitory control. Intestinal bacteria promote or suppress the initiation and aboral migration of the MMC depending on the species involved. Bacteria with primitive fermenting metabolism (anaerobes) emerge as important promoters of regular spike burst activity in small intestine.

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Su1211 The Utility of Small Intestine Capsule Endoscopy and Balloon-Assisted Enteroscopy in the Diagnosis of Small Intestinal Tumors

Gastrointestinal Endoscopy ◽

10.1016/j.gie.2017.03.727 ◽

2017 ◽

Vol 85 (5) ◽

pp. AB316

Author(s):

Ryoichi Sawada ◽

Ryosuke Miyazaki ◽

Ayako Ishii ◽

Yusuke Nagata ◽

Makio Ogawa ◽

...

Keyword(s):

Small Intestine ◽

Capsule Endoscopy ◽

Intestinal Tumors ◽

Small Intestinal

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Serum cobalamin concentrations and small intestinal ultrasound changes in 75 cats with clinical signs of gastrointestinal disease: a retrospective study

Journal of Feline Medicine and Surgery ◽

10.1177/1098612x15598184 ◽

2016 ◽

Vol 19 (1) ◽

pp. 48-56 ◽

Cited By ~ 5

Author(s):

Maria C Jugan ◽

John R August

Keyword(s):

Small Intestine ◽

Gastrointestinal Disease ◽

Clinical Signs ◽

Small Animal ◽

Abdominal Ultrasound ◽

Wall Layer ◽

Normal Serum ◽

Definitive Diagnosis ◽

Albumin Concentration ◽

Small Intestinal

Objectives The aim of the study was to evaluate ultrasonographic changes in the small intestine of cats with clinical signs of gastrointestinal disease and low or low–normal serum cobalamin concentrations. Methods Records for client-owned cats presenting to the small animal hospital with signs of gastrointestinal disease and in which serum cobalamin concentrations were measured from 2000–2013 were reviewed. Inclusion criteria were cobalamin concentrations <500 ng/l, abdominal ultrasound within 1 month of cobalamin testing and definitive diagnosis. Results Of 751 serum cobalamin measurements, hypocobalaminemia or low–normal cobalamin was identified in 270 cats, abdominal ultrasound was performed in 207 of those cats and a diagnosis was available for 75 of them. Small intestinal ultrasound changes were detected in 49/75 (65%) cats. Abnormalities included thickening, loss of wall layer definition, echogenicity alterations and discrete masses. Serum cobalamin concentrations <500 ng/l were observed with diagnoses of inflammatory disease, neoplasia, infectious disease and normal histopathology. Cobalamin concentration was significantly lower in cats with lymphoma or inflammatory bowel disease compared with other gastrointestinal neoplasia ( P = 0.031). No difference was found between cobalamin concentration and the presence of ultrasound abnormalities, specific ultrasound changes or albumin concentration. Conclusions and relevance One-third of symptomatic cats with hypocobalaminemia or low–normal cobalamin concentrations may have an ultrasonographically normal small intestine. For the majority of cats in this study, histopathologic abnormalities were observed in the small intestine, regardless of ultrasound changes. These findings suggest gastrointestinal disease should not be excluded based on low–normal cobalamin concentrations, even with a concurrent normal ultrasound examination. Additional studies are needed in cats with low–normal serum cobalamin concentrations, as a definitive diagnosis was not pursued consistently in those cats. However, data from this study suggest that careful monitoring, histopathologic evaluation and future cobalamin supplementation may be warranted.

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A breakdown in communication? Understanding the effects of aging on the human small intestine epithelium

Clinical Science ◽

10.1042/cs20150364 ◽

2015 ◽

Vol 129 (7) ◽

pp. 529-531 ◽

Cited By ~ 14

Author(s):

Neil A. Mabbott

Keyword(s):

Small Intestine ◽

Barrier Function ◽

Intestinal Barrier ◽

Intestinal Barrier Function ◽

Human Small Intestine ◽

Small Intestinal ◽

Effects Of Aging ◽

Insight Into

A new study by Man and colleagues provides further insight into the effects of aging on small intestinal barrier function in humans. Here, their findings are briefly summarised and the wider implications discussed.

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Carbohydrase activity in the pancreatic tissue and small intestine mucosa of sheep fed dried-grass or ground maize-based diets

The Journal of Agricultural Science ◽

10.1017/s0021859600044142 ◽

1985 ◽

Vol 104 (2) ◽

pp. 435-443 ◽

Cited By ~ 17

Author(s):

A. N. Janes ◽

T. E. C. Weekes ◽

D. G. Armstrong

Keyword(s):

Small Intestine ◽

Amylase Activity ◽

Total Activity ◽

Pancreatic Tissue ◽

Proximal Region ◽

Small Intestinal Mucosa ◽

Intestine Mucosa ◽

Ruminant Animals ◽

Specific Activities ◽

Small Intestinal

SummaryTwo groups of six sheep were fed either dried-grass or ground maize-based diets for at least 4 weeks before slaughter. Samples of the small intestinal mucosa and spancreatic tissue were assayed for a-amylase, glucoamylase, maltase and oligo-l,6-glucosidase.The pancreatic tissue contained high activities of α-amylase and much lower activities of glucoamylase, maltase and oligo-1,6-glucosidase. There was no effect of diet on the specific activities of any of these enzymes in the pancreatic tissue.The activity of α-amylase adsorbed on to the mucosa of the small intestine was greatest in the proximal region of the small intestine, the activity generally declining with increasing distance away from the pylorus. There was no diet effect on the absorbed α-amylase activity.Similar patterns of distribution along the small intestine were observed for maltase, glucoamylase and oligo-1,6-glucosidase with the highest activities in t he jejunum. There was no overall effect of diet on glucoamylase or maltase specific activities and glucoamylase total activity, although the total activities of maltase and oligo-1,6-glucosidase were significantly greater for the sheep fed the ground maize-based diet (P < 0·05).It is suggested that ruminant animals may be capable of digesting large amounts of starch in the small intestine through an adaptation in the activity of the host carbohydrases.

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