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PubMedDate not supplied

Digestive enzyme activities in herbivorous and carnivorous prickleback fishes (Teleostei: Stichaeidae): ontogenetic, dietary, and phylogenetic effects.

We measured the activities of eight digestive enzymes in four species of herbivorous and carnivorous prickleback fishes and determined the effects of ontogeny, diet, and phylogeny on these enzyme activities. Of the four species, Cebidichthys violaceus and Xiphister mucosus shift to a more herbivorous diet as they grow (> or =45 mm SL [standard length]), whereas Xiphister atropurpureus and Anoplarchus purpurescens remain carnivores throughout life. Digestive enzyme activities of small (30-40 mm SL) carnivorous juveniles were compared with those of larger (60-75 mm SL) wild-caught juveniles that had consumed a natural diet and larger (60-75 mm SL) juveniles raised on a high-protein animal diet. Cebidichthys violaceus and both species of Xiphister showed ontogenetic changes in digestive enzyme activities, whereas A. purpurescens did not. Despite dietary differences between X. atropurpureus and X. mucosus, these sister taxa displayed the most similar digestive enzyme activities from ontogenetic and dietary perspectives (high alpha-amylase and lipase and low trypsin and aminopeptidase activities), and both were more similar to C. violaceus, a member of the same largely herbivorous clade, than either was to A. purpurescens, a member of an adjacent, carnivorous clade. The results support the hypothesis that phylogeny influences digestive enzyme activities in these fishes. Anoplarchus purpurescens, a carnivore with a diverse diet, showed great plasticity in enzyme activity, especially trypsin and aminopeptidase, which were elevated in this species to the highest level among the four species after consuming the high-protein diet. These results support the hypothesis that fishes with relatively broad diets can modulate digestive enzyme activities in response to changes in dietary composition.

Animals↗
PubMed1985

Effects of sodium bicarbonate on nitrogen balance, bacterial protein synthesis and sites of nutrient digestion in sheep.

Two experiments were conducted to determine effects of sodium bicarbonate (NaHCO3) on nitrogen (N) balance, ruminal N metabolism and site and extent of nutrient digestion in sheep fed 75% concentrate diets. A 2 X 2 factorial arrangement of treatments was employed in both trials with experimental diets balanced for 10.5 or 12.0% crude protein and containing 0 or 3.5% NaHCO3. In experiment 1, 12 lambs were allotted to four diets for two periods in a randomized complete-block design. Dry matter (DM) digestibility was increased (P less than .10) by NaHCO3 supplementation, but organic matter (OM) digestibility was unaffected by treatment. Apparent N digestibility was not affected by NaHCO3 addition but was increased (P less than .0001) at the higher level of protein. Ruminal pH (4 h postfeeding) was increased (P less than .01) by NaHCO3 supplementation. Sodium bicarbonate had no effect on molar proportions of acetate or propionate, but increased molar proportion of butyrate (P less than .10) in ruminal fluid. Mean N retention (g/d) was increased (P less than .05) at the higher protein level, but was not affected by NaHCO3. In experiment 2, four ruminal- and duodenal-cannulated wethers were utilized in a 4 X 4 Latin square design. Sodium bicarbonate addition increased ruminal pH (P less than .05) 2 h postfeeding but did not affect ruminal ammonia (NH3) levels, total VFA concentration or ruminal fluid dilution rates. Molar proportion of acetate was increased (P less than .01) by NaHCO3 at the lower protein level. Ruminal particulate dilution rates were increased (P less than .05) by NaHCO3 addition. Ruminal, postruminal and apparent total tract digestibilities of OM and neutral detergent fiber (NDF) were unaffected by NaHCO3 supplementation. Sodium bicarbonate decreased (P less than .05) ruminal starch digestion at the lower protein level but increased (P less than .05) it at the higher protein level. Bacterial N flow (g/d) at the duodenum and efficiency of bacterial protein synthesis were increased (P less than .10) by NaHCO3 additions.

Animal Nutritional Physiological Phenomena↗
PubMed1994

Inhibition of bloodmeal digestion in glossina morsitans fed on rabbits immunized with tsetse midgut homogenate.

The efficacy of bloodmeal digestion in teneral Glossina morsitans centralis fed on rabbits immunized with tsetse fly midgut extracts was progressively monitored over a period of 96 hours. Flies fed on immunized rabbits showed reduced rate of bloodmeal digestion as compared to the controls. Although there was insignificant difference in the rate of bloodmeal digestion upto 24 hours post-feeding in later stages of digestion there was quite a significant difference. Polyacrylamide gel electrophoretic patterns of bloodmeal drawn from the posterior sections of the midgut demonstrated that, bloodmeal is completely degraded in the midgut after 96 hours in the control flies, while substantial amount is still undigested in the experimental flies. However, not much difference in the rates of digestion was observed with bloodmeal drawn from the anterior section of the midgut. These results suggests that when flies are fed on rabbits immunized with tsetse fly midgut extract, there is an impairment on the efficiency of digestion. The anti-midgut antibodies could be interfering with either the induction or proteolytic activity of the midgut enzymes.

Animals↗
PubMed2001

Starch and protein digestibility of newly released moth bean cultivars: Effect of soaking, dehulling, germination and pressure cooking.

Effect of soaking (12 h), soaking (12 h) dehulling, germination (60 h) and pressure cooking on starch and protein digestibility of four varieties of moth bean, one Local commonly used by the farmers of the area and three newly released high yielding varieties, Jwala, RMO 225 and RMO 257, was studied. The starch digestibility of raw unprocessed moth bean cultivars differed significantly (P < 0.05) from 25.4-28.2 mg maltose released/g flour being the highest and lowest in RMO 257 and RMO 225, respectively. The protein digestibility differed significantly from 70.3-74.6 per cent among all the unprocessed varieties of moth bean. All the processing treatments namely soaking, dehulling, germination and pressure cooking brought about appreciable enhancement in protein digestibility (1-19%) over the control and starch digestibility (19-115%) of all the four moth bean cultivars. However, out of all the processing treatments, germination (60 h) of soaked seeds (12 h) was the most effective in bringing about improvement in digestibility of starch and protein followed by dehulling and soaking (12 h).

Cooking↗
PubMed1995

Histocytochemical and immunohistochemical studies related to the role of glycogen in human developing digestive organs.

To elucidate the role of glycogen in the epithelium of developing digestive organs, we investigated the appearance of glycogen and glycogen phosphorylase (GP) in these organs. We studied 64 externally normal human embryos at Carnegie stages 13-23 (5.1-28.0 mm in crown-rump length, 4-8 weeks of gestation) by histocytochemical staining for glycogen and immunohistochemical staining with antibodies against two isoenzymes of GP: brain-type (BGP) and muscle-brain-type (MBGP) GP. At stage 13, glycogen appeared in the epithelium of the digestive tract and the parenchyma of the pancreas. As development advanced, glycogen granules increased in number and size in these tissues, and they became evenly distributed in the epithelium of the digestive tract as either single particles or aggregates, as deduced by electron microscopy at late embryonic stages. Immunoreactivity specific both for BGP and for MBGP was detected in the digestive tract and the pancreas from stage 13. As development advanced, both BGP- and MBGP-immunoreactive cells increased in number and in immunoreactivity, and the number of MBGP-immunoreactive cells became larger than that of BGP-immunoreactive cells. By contrast, in hepatic cells, which serve as a major storage site for glycogen in adults, glycogen was detected only from stage 20, in smaller amounts, without formation of aggregates, and no immunoreactivity specific for BGP or MBGP was apparent throughout the embryonic stages examined. Thus, in the epithelium of the digestive tract and the parenchyma of the pancreas, but not in hepatic cells, the appearance and localization of GP coincided almost exactly with that of glycogen. These observations suggest that glycogen in the epithelium of the digestive tract and the parenchyma of the pancreas has not only been synthesized but also degraded from an early embryonic period and may, thus, be related to active cellular metabolism that is specific for embryonic development, including proliferation of the epithelium and interactions between epithelium and mesenchyme.

Digestive System↗
PubMed1994

The lysozyme locus in Drosophila melanogaster: an expanded gene family adapted for expression in the digestive tract.

Lysozyme has been studied in insects as part of the system of inducible antibacterial defence in the haemolymph. We recently found two Drosophila lysozyme genes that are constitutively expressed in the digestive tract, and are probably involved in the digestion of bacteria in the food. To obtain an overview of the lysozyme genes in this species and their possible roles in immunity and digestion, we have now characterized all six lysozyme genes in the cloned part of the lysozyme locus at 61F, and a seventh gene that maps to the same chromosomal location. The expression of the genes follows four different patterns: firstly, four closely related genes, LysB, C, D and E, are all strongly expressed in the midgut of larvae and adults; secondly, LysP is expressed in the adult salivary gland; thirdly, LysS is expressed mainly in the gastric caecae of larvae; and finally, LysX is primarily expressed in the metamorphosing midgut of late larvae and early pupae. The LysD-like genes and LysS are strongly repressed in artificially infected animals, possibly reflecting a malaise reaction in the digestive tract. None of the genes is expressed in the fat body or haemocytes. Thus rather than being a component of the haemolymph, the Drosophila lysozymes are found mainly in the digestive tract where they are expressed at a high level. Furthermore all genes, except LysP, encode acidic proteins, in contrast to the strongly basic "typical" lysozymes. This is highly reminiscent of the situation in ruminants, where the lysozymes have been recruited for the digestion of symbiotic bacteria in the stomach.

Adaptation, Physiological↗
PubMed1989

Digestibility of protein and amino acids in selected foods as determined by a rat balance method.

Values (%) for true digestibility of crude protein and individual amino acids in 20 selected foods were determined by the rat balance (fecal) method. The products were fed as the sole source of protein in diets containing 8% crude protein (N x 6.25). Lowest true protein digestibility values (79-84) were obtained for pinto beans, kidney beans and lentils; intermediate values (89-92) were obtained for chick peas, beef stew, skim milk (over heated), rolled oats, whole wheat cereal, and pea protein concentrate; and highest values (94-100) were obtained for sausage, macaroni-cheese, rice-wheat gluten cereal, skim milk, tuna, soy isolate, peanut butter, chicken frankfurters, beef salami, casein and casein + methionine. In animal foods, peanut butter and soy isolate, the differences between true digestibility of crude protein and most individual amino acids were less than 5%. However, the values for true digestibility of methionine and cystine were up to 44% lower than those of crude protein in pinto beans, kidney beans, lentils, chick peas and pea concentrate. In these legumes, digestibility of crude protein was not a good predictor of digestibility of the limiting amino acids.

Amino Acids, Essential↗
PubMed1991

[Digestibility, intestinal passage time and energy value of wheat bran in model studies in sows].

An energy metabolism trial was conducted with four sows allocated to each of four levels of wheat bran (7, 14, 21 or 28 g/kg body weight 0.75.day). During 2-week experimental periods half the number of animals received increasing levels of the wheat bran supplementation, the other sows were fed in decreasing order. The basal diet was given constantly at a level of 36 g/kg Bw 0.75. Total digestibility of energy was determined by the collection method. For partioning the digestible energy into a prececal and postileal component the diet was supplemented with 0.3% Cr2O3, and samples of digesta taken by means of a cecum cannula were analyzed for this marker. The rate of passage of food was evaluated by using plastic pellets fed orally as well as inserted into the cecum. During each experimental period a complete energy balance was performed according to the methods of indirect calorimetry. The digestibility and metabolizability of wheat bran energy over the total alimentary tract was 60% and 57%, respectively. As a percentage of the total digestible energy, 70% were found in the prececal site of the digestive tract, and 30% in the hindgut fermentation. The efficiency of utilization of metabolizable energy (ME) for energy retention was 66.2%. Utilization of hindgut energy was lower by about a quarter than utilization of energy digested in the small intestine. The mean contents of ME of wheat bran amounted to 10.1 kJ/g dry matter. The ME of the wheat bran fiber (non-starch poly-saccharides) was calculated to be 5 kJ/g. The excretion of short-chain fatty acids in the feces was only 1-2% of fecal energy. The rate of passage of food decreased from 78 h (basal diet alone) to 52 h with the highest wheat bran supplementation. The prececal retention time was only 20% of the total rate of passage through the alimentary tract.

Animals↗
PubMed1992

Digestibility of proteins and starch (in vitro) of amphidiploids (black gram x mung bean) as affected by domestic processing and cooking.

The effects of different domestic processing and cooking methods on starch digestibility (in vitro) and protein digestibility (in vitro) of four strains of amphidiploids (black gram x mung bean) were investigated. An increase of 35 to 48% and 22 to 25% was observed in starch digestibility and protein digestibility, respectively, when the seed of amphidiploids were soaked for 18 h. Cooking (both of unsoaked and soaked seeds) and germination improved significantly the starch digestibility and protein digestibility of all the varieties.

Amylases↗
PubMed1997

Microspectrophotometric evaluation of digestibility of pollen grains.

Digestibility of pollen grains of poppy (Papaver rhoeas) and hazelnut (Corylus avellana) subjected to a human-like in vitro digestion with pancreatic enzymes was evaluated. Pollens showed different types of walls. Digestibility was determined for total protein and insoluble carbohydrate contents by means of a new application of microspectrophotometry. Results demonstrated that pollen grains of both species were only partly digested; after 24 h treatment, only 26% of carbohydrates and 48% of proteins were digested in poppy and only 3% and 59% in hazelnut. This is probably due to the difficulty of enzymes to penetrate the intine of pollen grains. The degree of digestion of insoluble carbohydrates varied in the studied species according to their chemical nature and their storage sites.

Carbohydrate Metabolism↗
PubMed1998

Effects of vertebrate growth factors on digestive gland cells from the mollusc Pecten maximus L.: an in vitro study.

In relation with the digestive cycle, the digestive gland cells of bivalve molluscs undergo a sequence of cytological changes which is controlled by external and internal effectors such as putative gastrointestinal hormones and growth differentiation factors. A tissue dissociation method was developed to investigate the in vitro effect of the vertebrate growth and differentiation factors: insulin, insulin growth factor I (IGF-I), basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) on the digestive gland cells of the scallop Pecten maximus. All these vertebrate peptides induced a dose-dependent increased incorporation of 3H-leucine and 14C-uridine in whole digestive gland cell suspensions. However, after Percoll density gradient purification of the digestive cells, only stem and undifferentiated enriched cell fractions were responsive to the different peptides. In addition, insulin and IGF-I, but not EGF and bFGF, stimulated 3H-leucine incorporation in control dispersed mantle edge cells. These results suggest that insulin-related peptides could work as general growth promoting factors in molluscs. On the other hand, EGF and bFGF, or at least their molluscan counterparts, may be efficient growth differentiation factors in the regenerative processes occurring in the digestive gland of molluscs.

Animals↗
PubMed1999

Comparative analysis of the digestive efficiency and nitrogen and energy requirements of the phyllostomid fruit-bat (Artibeus jamaicensis) and the pteropodid fruit-bat (Rousettus aegyptiacus).

Nitrogen (N) and energy (E) requirements of the phyllostomid fruit bat, Artibeus jamaicensis, and the pteropodid fruit bat Rousettus aegyptiacus, were measured in adults that were fed on four experimental diets. Mean daily food intake by A. jamaicensis and R. aegyptiacus ranged from 1.1-1.6 times body mass and 0.8-1.0 times body mass, respectively. Dry matter digestibility and metabolizable E coefficient were high (81.1% and 82.4%, respectively) for A. jamaicensis and (77.5% and 78.0%, respectively) for R. aegyptiacus. Across the four diets, bats maintained constant body mass with mean metabolizable E intakes ranging from 1357.3 kJ.kg-0.75.day-1 to 1767.3 kJ.kg-0.75.day-1 for A. jamaicensis and 1282.6-1545.2 kJ.kg-0.75.day-1 for R. aegyptiacus. Maintenance E costs were high, in the order of 3.6-5.4 times the basal metabolic rate (BMR). It is unlikely that the E intakes that we observed represent a true measure of maintenance E requirements. All evidence seems to indicate that fruit bats are E maximizers, ingesting more E than required and regulating storage by adjusting metabolic output. We suggest that true maintenance E requirements are substantially lower than what we observed. If it follows the eutherian norm of two times the BMR, fruit bats must necessarily over-ingest E on low-N fruit diet. Dietary E content did affect N metabolism of A. jamaicensis. On respective low- and high-E diets, metabolic fecal N were 0.492 mg N.g-1 and 0.756 mg N.g-1 dry matter intake and endogenous urinary N losses were 163.31 mg N.kg-0.75.day-1 and 71.54 mg N.kg-0.75.day-1. A. jamaicensis required 332.3 mg.kg-0.75.day-1 and 885.3 mg.kg-0.75.day-1 of total N on high- and low-E diets, respectively, and 213.7 mg.kg-0.75.day-1 of truly digestible N to achieve N balance. True N digestibilities were low (29% and 49%) for low- and high-E diets, respectively. For R. aegyptiacus, metabolic fecal N and endogenous urinary N losses were 1.27 mg N.g-1 dry matter intake and 96.0 mg N.kg-0.75.day-1, respectively, and bats required 529.8 mg.kg-0.75.day-1 (total N) or 284.0 mg.kg-0.75.day-1 (truly digestible N). True N digestibility was relatively low (50%). Based on direct comparison, we found no evidence that R. aegyptiacus exhibits a greater degree of specialization in digestive function and N retention than A. jamaicensis. When combined with results from previous studies, our results indicate that all fruit bats appear to be specialized in their ability to retain N when faced with low N diet.

Animals↗
PubMed2004

Energy value of a low-digestible carbohydrate, NUTRIOSE FB, and its impact on magnesium, calcium and zinc apparent absorption and retention in healthy young men.

BACKGROUND: Long-term consumption of imbalanced diets, poor in dietary fibres, resulted in the prevalence of several nutritional pathologies. However, low digestible carbohydrates (LDC) have many beneficial effects, especially on energy intake, digestive physiology, and mineral absorption. AIM OF THE STUDY: To determine the digestive effects of a LDC, called NUTRIOSE FB, its metabolisable energy (ME) value, and its effects on mineral absorption in humans. METHODS: Ten healthy young men were fed for 31 d periods a maintenance diet supplemented with either dextrose or the LDC at a level of 100 g DM/d, in six equal doses per d according to a cross-over design. After a 20 d adaptation period, food intake was determined for 11 days using the duplicate meal method, and faeces and urine were collected for 10 d for further analyses. RESULTS: Ingestion of the LDC did not cause severe digestive disorders, except excessive gas emission, and flatulence and slight abdominal pain in some subjects for intakes above 50 g DM/d. Wet and dry stool outputs increased by 45 and 70%, respectively (P<0.02). In vitro enzymatic digestibility of the LDC was 15 (SD 1.5) %, and 9.2 (SD 8.3) % of the LDC was excreted in faeces (P<0.001). The ME value of the LDC was 14.1 (SD 2.3) kJ/g DM, that is 14 % less than the tabulated values of sucrose and starch. Its net energy value (NEV), estimated using three prediction equations, was 8.7, 8.9, and 11.4 kJ/g DM. Ingestion of the LDC significantly increased the relative apparent absorption of Mg, and Mg retention by 67% and 31 mg/d, respectively, tended to increase Ca apparent absorption (P=0.110) and Ca retention (P=0.059), but did not significantly alter Zn parameters. CONCLUSION: NUTRIOSE FB can be used as a "bulking" agent, and substituted up to 50 g/d for usual maltodextrins without causing digestive disorders in healthy subjects. It would reduce intestinal transit disorders and energy intake, and improve magnesium and calcium absorption and retention.

Adult↗
PubMed2006

Organic potassium salts or fibers effects on mineral balance and digestive fermentations in rats adapted to an acidogenic diet.

BACKGROUND: Fibers and potassium (K) organic salts in plant foods are liable to affect Ca and Mg balance at digestive and renal levels, respectively. K organic salts could counteract the acidifying effects of western diets and consequences of excess NaCl. AIM OF THE STUDY: To study this question, male rats were adapted to a basal acidifying low-K (LK) diet, or to diets supplemented with a fiber mix (LK/F), or K citrate (HK) or both (HK/F). RESULTS: HK and HK/F diets displayed a marked alkalinizing effect in urine and promoted citraturia, but this effect was not modulated by fibers. The effect of fibers on Ca digestive absorption was more potent than K citrate effect on Ca renal excretion. In contrast, K citrate effect on kidney Mg excretion was more effective than that of fibers on Mg digestive absorption, a maximal effect on Mg balance was observed in rats fed the HK/F diet. Digestive fermentations in rats fed the LK/F diet were characterized by high-propionic acid fermentations and succinate accumulation. In rats adapted to the HK/F diet, K citrate supplementation depressed succinate and increased butyrate concentrations. CONCLUSION: Organic anions arising from digestive fermentations seem to be not directly involved in the alkalinizing effects of plant foods. Fibers and organic K salts exert distinct effects on Ca and Mg metabolism, but with interesting interactions as to Mg balance, digestive fermentations and urine pH.

Acid-Base Equilibrium↗
PubMed2004

Aquaporins in the digestive system.

Fluid transfer such as secretion and absorption is one of the major functions of the digestive system. Aquaporins are water channel proteins providing water transfer across the cellular membrane. At least six aquaporin isoforms are expressed in the digestive system. Aquaporin-1 (AQP1) is widely distributed in endothelial cells of capillaries and small vessels as well as in the central lacteals in the small intestine. AQP1 is also present in the duct system in the pancreas, liver, and bile duct. AQP3 is mainly expressed in the epithelia of the upper digestive tract from the oral cavity to the stomach and of the lower digestive tract from the distal colon to the anus. AQP4 is present in the parietal cells of the stomach and in the intestinal epithelia. AQP5 is expressed in acinar cells of the salivary, pyloric, and duodenal glands. AQP8 is expressed in the intestinal epithelia, salivary glands, pancreas, and liver. AQP9 is present in the liver and intestinal goblet cells. Aquaporins have important roles in the digestive system, such as AQP5 in saliva secretion, as shown by the studies on AQP5-null mice. In addition, water transfer across the digestive epithelia seems to occur not only via aquaporins but also via other transporter or channel systems.

Animals↗
PubMed1985

Partially purified white bean amylase inhibitor reduces starch digestion in vitro and inactivates intraduodenal amylase in humans.

Whether commercial, bean-derived alpha-amylase inhibitor preparations failed to decrease starch digestion in humans because of insufficient antiamylase activity, destruction by gastrointestinal secretions, or decreased activity in the presence of starch is unknown. We used a simple partial purification procedure to markedly concentrate the inhibitor (sixfold to eightfold by total protein content, and 30-40-fold by dry weight). Compared with a commercial preparation and crude bean extract, this partially purified inhibitor inactivated intraduodenal, intraileal, and salivary amylase in vitro faster and more completely (p less than 0.001); its specific activity was not affected by exposure to gastric juice and was only minimally reduced by duodenal juice. Whereas the rate of amylase inhibition by inhibitor was markedly slowed in the presence of nondietary liquid starch, dietary solid starch had only a minimal effect. Consequently, the partially purified inhibitor had no effect on liquid starch digestion, but decreased in vitro digestion of dietary starch in a dose-dependent manner (p less than 0.001). Perfusion of the partially purified inhibitor (2.0, 3.5, or 5.0 mg/ml at 5 ml/min) into the duodenum of humans rapidly inhibited greater than 94%, greater than 99%, or greater than 99.9% of intraluminal amylase activity. We conclude that commercial amylase inhibitors failed to decrease starch digestion in vivo mainly because they have insufficient antiamylase activity. However, a partially purified inhibitor with increased specific activity is stable in human gastrointestinal secretions, slows dietary starch digestion in vitro, rapidly inactivates amylase in the human intestinal lumen, and, at acceptable oral doses, may decrease intraluminal digestion of starch in humans. Such an inhibitor therefore deserves study.

Adult↗
PubMed1986

Relationship between dietary proteins, their in vitro digestion products, and serum cholesterol in rats.

A relationship was assessed between the amino acid composition of 9 protein sources or of their in vitro digestion products and total serum cholesterol in rats. Three animal proteins (casein, beef, fish) and 6 vegetable proteins (soy, pea, peanut meal, rapeseed, oatmeal, wheat gluten) were tested. The intact protein sources were submitted to an enzymatic proteolysis according to a new in vitro digestion method. Each protein source was hydrolyzed for 30 min with pepsin at pH 1.9, then with 10 mg pancreatin at basic pH in a dialysis cell. The digestion products diffused through the dialysis membrane of the cell and were collected by a circulating sodium phosphate buffer over a 6-h period. They were likely to correspond to end products luminal in vivo digestion. The aromatic and the basic amino acids were present in higher proportions in the digestion products than in the intact protein sources, reflecting the specificity of the proteolytic enzymes. Total serum cholesterol was measured on male Sprague-Dawley rats fed cholesterol-free or cholesterol-enriched (1% cholesterol, 0.5% cholic acid) semipurified diets containing protein sources. Total serum cholesterol ranged from 70 mg/dl with the pea diet to 98 mg/dl with the peanut meal diet in rats fed cholesterol-free diets and from 163 mg/dl with the wheat gluten diet to 313 mg/dl with the casein diet in rats fed the cholesterol-enriched diets. These results suggested no specific effect of protein from animal or vegetable origin on total serum cholesterol in rats. In rats fed cholesterol-enriched diets, significant correlations were observed between total serum cholesterol and tyrosine content or leucine/isoleucine ratio of digestion products. These correlations were stronger than those observed with intact protein sources.

Amino Acids↗
PubMed1989

The quantification of dietary intake, digestion and metabolism in farm livestock and its relevance to the study of radionuclide uptake.

The transfer coefficient and biological half-life have been widely used to describe the uptake of radionuclides by farm animals. However, these parameters may be inadequate, for they take little account of the effects of the processes occurring in the animal upon the behaviour of a radionuclide. The aim of this paper is to review techniques which could be used to study the uptake of dietary radionuclides by farm animals. The main factors affecting uptake can be categorised in terms of intake, digestion and absorption, and metabolism. The estimation of the intake of a radionuclide by grazing animals is difficult. Intake estimation by determining amounts of standing herbage before and after grazing is rarely a valid method because of herbage growth. Methods based on animal measurements have wider application. Many intake methods give short-term estimates (measured over a few hours), whereas for most radionuclide studies, longer-term estimates (over days or weeks) are required. The most suitable methods use indigestible markers to determine the output of faeces and the digestibility of grazed herbage. Considerable variability in the distribution of radionuclides may exist among different plant species. To accurately estimate radionuclide intake on mixed pastures it is necessary to determine the plant species composition of the diet of animals; present methods may be inadequate and new techniques may be required. If contaminated, the drinking-water intake by animals would need to be determined. The processes of digestion (the physical disintegration and chemical breakdown by gut microbes and secreted enzymes) may affect the radionuclide uptake by an animal. Other factors, including the chemical form of the radionuclide, rate of passage of material along the gut, degree of incorporation into microbial tissue, and the absorption mechanism might also affect the degree to which the radionuclide can cross the gut wall. The apparent absorption coefficient (apparent digestibility) has been widely used in nutritional studies to quantify net uptake of a component from the gut. However, as this parameter does not adequately indicate the ability of a substance to cross the gut wall, its value in radionuclide uptake studies is rather limited. More useful, since it gives an indication of transfer across the wall of the gut, is the true absorption coefficient. The use of animals with cannulae in the digestive tract, allows the quantitative measurement of digestion and absorption in the different functional parts of the gut. The metabolism of absorbed substances by an animal involves transport (through the circulatory system), uptake into tissue cells, modification by biochemical reactions, and excretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗