Protein fractionation byproduct from canola meal for dairy cattle.

Fiber-protein is a byproduct arising from a process for fractionating high-quality protein from canola meal. The objective of this study was to evaluate the fiber-protein fraction by examining the chemical profiles, rumen degradation, and intestinal digestive characteristics and determining the nutritive value of the fiber-protein fraction as dietary components for dairy cattle in comparison with commercial canola meal and soybean meal. Available energy values were estimated based on National Research Council guidelines, whereas total true protein content potentially absorbable in the small intestine (DVE) were predicted using the predicted DVE/degraded protein balance (OEB) model.

Transport of putrescine across duodenal, jejunal and ileal brush-border membrane of chicks (Gallus domesticus).

Luminal polyamines and their absorption are essential for proliferation of the enterocytes and, therefore, nutrition, health and development of the animal. The transport systems that facilitate the uptake of putrescine were characterized in chick duodenal, jejunal and ileal brush-border membrane vesicles prepared by MgCl2 precipitation from three-week-old chicks. An inwardly-directed Na+ gradient did not stimulate putrescine uptake and, therefore, putrescine transport in chick intestine.

Absorption of methionine and 2-hydroxy-4-methylthiobutoanic acid in conventional and germ-free chickens.

The apparent absorption of 3H-labeled L-Met and L-2-hydroxy-4-methylthiobutoanic acid (MHA-FA) was compared in germ-free and conventional broiler chickens to determine the effect of intestinal bacteria on the absorption of Met and MHA-FA. The two diets contained 0.236% of added Met or MHA-FA.

Enzymic release of reducing sugars from oat hulls by cellulase, as influenced by Aspergillus ferulic acid esterase and trichoderma xylanase.

Hydroxycinnamic acids, mainly ferulic and p-coumaric acids, are believed to be inhibitory to ruminal biodegradability of complex cell wall materials such as oat hulls. Previous studies have shown that a novel enzyme, Aspergillus ferulic acid esterase, and Trichoderma xylanase act synergistically to break the ester linkage between ferulic acid and the attached sugar of feruloyl polysaccharides, releasing ferulic acid from oat hulls. In this paper, we examined the enzymic release of reducing sugars from oat hulls by the actions of individual enzymes (Aspergillus ferulic acid esterase at 13 mU, 6.

Release of ferulic acid from oat hulls by Aspergillus ferulic acid esterase and trichoderma xylanase.

Oat hulls, an agricultural byproduct, contain a relatively high amount of ferulic acid (FA; 4-hydroxy-3-methoxycinnamic acid), which is believed to be inhibitory to oat hull biodegradability by rumen microorganisms. In this paper, Aspergillus ferulic acid esterase (FAE) was investigated for its ability to release FA from oat hulls. The objectives were to determine the effects of particle size of oat hulls (ground to pass through 1 mm and 250 microm screens and a 100 microm sieve) on release of FA by FAE both in the presence and in the absence of Trichoderma xylanase.

Stability of porcine and microbial lipases to conditions that approximate the small intestine of young birds.

In vitro experiments were conducted to study the stability of lipase activities from bacterial, fungal, and animal sources under conditions that approximate the small intestine. In the first experiment, the effects of preincubation with trypsin (500, 1,000, and 2,000 U/mL), chymotrypsin (200, 400, and 800 U/mL), and trypsin plus chymotrypsin (TC; 2,000 U/mL trypsin + 800 U/inL chymotrypsin) for 30 min at 40 C, on lipase activities from sources of Pseudomonas spp. (PL1, PL2), Chromobacterium viscosum (CVL), and Aspergillus niger (ANL) were determined.

Stability of porcine and microbial lipases to conditions that approximate the proventriculus of young birds.

In vitro experiments were conducted to characterize the activity and the stability of lipase from animal (crude porcine, CPL; lyophilized porcine, LPL), fungal (Rhizopus arrhizus, RAL; Aspergillus niger, ANL), and bacterial (two Pseudomonas spp., PL1, PL2; and Chromobacterium viscosum, CVL) sources when exposed to conditions associated with the glandular stomach. Activity was measured at pH 3 to 8, 40 C and then monitored in response to temperature (40 C), time of exposure (0 and 30 min), pH (3 and 7), and pepsin level (5, 50, and 500 U/mL).

Phytase activity in the small intestinal brush border membrane of the chicken.

The kinetics, mineral dependency, and pH dependency of phytate hydrolysis by preparations of chicken small intestinal brush border membrane vesicles were determined. Substantial phytate hydrolysis occurred over the pH range from 5 to 6.5 with a maximum hydrolysis at pH of 6.

Pre-steady-state and steady-state function of the ileal brush border SO4(2-)-OH- exchanger.

Rapid-sampling analysis of the detailed time course of 35SO4(2-) uptake under pH-gradient (pHin = 7.5; pHout = 5.5) conditions converged to a model of an initial burstlike pre-steady-state with relaxation to linear steady-state uptake across pig ileal brush border vesicles.

Methionine and 2-hydroxy-4-methylthiobutanoic acid are partially converted to nonabsorbed compounds during passage through the small intestine and heat exposure does not affect small intestinal absorption of methionine sources in broiler chicks.

Broiler chicks were fed diets supplemented with DL-methionine or DL-2-hydroxy-4-methyl-thiobutanoic acid. At 4 wk of age the chicks were subdivided into thermoneutral (22 degrees C) and heat-exposed (32 degrees C) groups and maintained under these conditions for 48 h. Highly purified 3H-L-methionine (3H-L-Met) and 3H-L-2-hydroxy-4-methyl-thiobutanoic acid (3H-L-HMB) were used to evaluate treatment effects on the small intestinal passage of sources of supplemental methionine and on the transport of methionine sources across purified small intestinal brush border vesicles.

Methionine and 2-hydroxy-4-methylthiobutanoic acid are transported by distinct Na(+)-dependent and H(+)-dependent systems in the brush border membrane of the chick intestinal epithelium.

The pathways that facilitate the uptake of L-methionine (L-Met), D-methionine (D-Met) and L-2-hydroxy-4-methylthiobutanoic acid (L-HMB) were characterized in chick intestinal brush border membrane vesicles. A model of high affinity transport (Km approximating 0.1 mmol/L) converged to the data obtained for 35S-L-Met uptake under Na(+)-gradient and Na(+)-free conditions.

The influence of the mineral level in drinking water and the thermal environment on the performance and intestinal fluid flux of newly-weaned pigs.

The effects of drinking water containing high levels of dissolved minerals including sulphate (HMW) and a chilled environment on the performance of newly-weaned pigs were evaluated in three replicate 10-d trials. In each trial, 12, 28-d-old pigs were taken from the sow and allocated by weight and litter to treatment groups following a 2 x 2 factorial arrangement of HMW vs low-mineral drinking water (LMW) and normal (heat lamp) vs chilled (21 degrees C) pen temperature. No interactive effects of water mineral level and pen temperature on any of the measurements of health and productivity were found.

Heterotropic effects of dipolar amino acids on the activity of the anionic amino acid transport system X-AG in rabbit jejunal brush-border membrane vesicles.

D-Aspartic acid was used as a specific substrate to evaluate the effects of dipolar amino acids on the high affinity anionic amino acid transport system X-AG in rabbit jejunal brush-border membrane vesicles. At pH 6, increasing L-phenylalanine concentrations caused a saturable activation of 0.05 mM D-aspartic acid uptake (Ka = 2.

L-threonine transport in pig jejunal brush border membrane vesicles. Functional characterization of the unique system B in the intestinal epithelium.

Uptake and inhibitory kinetics of [3H]L-threonine were evaluated in preparations of pig jejunal brush border membrane vesicles. Uptake of [3H]L-threonine under O-trans, Na+ gradient, and O-trans, Na(+)-free conditions was best described by high affinity transport (Km < 0.01 mM) plus a nonsaturable component.

pH-dependent heterogeneity of acidic amino acid transport in rabbit jejunal brush border membrane vesicles.

Initial rates of Na(+)-dependent L-glutamic and D-aspartic acid uptake were determined at various substrate concentrations using a fast sampling, rapid filtration apparatus, and the resulting data were analyzed by nonlinear computer fitting to various transport models. At pH 6.0, L-glutamic acid transport was best accounted for by the presence of both high (Km = 61 microM) and low (Km = 7.

Improved stability of rabbit and rat intestinal brush border membrane vesicles using phospholipase inhibitors.

The initial rates of Na(+)-dependent D-aspartate and D-glucose uptakes were shown to decline from the time of resuspension of brush border membrane vesicles isolated from rabbit and rat jejunum by standard divalent cation precipitation procedures. The former were however more stable than the latter and followed quite closely the decrease in the intravesicular volume, thus suggesting that the loss of transport activity may involve both nonspecific opening of the vesicles and either direct or indirect specific inactivation of the transporters. Uptake rates for both substrates did tend to stabilize at 6-24 h from resuspension, however this final 'next day' uptake activity was too low to be of practical use in kinetic studies.

Rapid regulation of D-glucose transport in basolateral membrane of rat jejunum.

D-Glucose transport and D-glucose inhibitable [3H]cytochalasin B binding to jejunal basolateral membrane vesicles were measured to investigate the possible association between changes in transport activity seen in hyperglycemia and density of transporter sites. Comparison was made between hyperglycemic animals, noninfused rats, and a group infused with sorbitol. Vascular infusion of D-glucose produced a rapid increase in D-glucose transport followed by a delayed and smaller increase in [3H]cytochalasin B binding.

Is leucine an allosteric modulator of the lysine transporter in the intestinal basolateral membrane?

The transport of the dibasic amino acid L-lysine was investigated using basolateral membrane vesicles prepared from rat jejunal mucosal scrapings. The majority of the carrier-mediated transport was unaffected by the presence of sodium in the incubation medium, but voltage clamping of the vesicles did increase lysine uptake, indicating an associated movement of charge. Kinetic analysis of lysine influx and efflux showed the system to be symmetrical, but although the Vmax was comparable to other amino acid transport systems in this membrane, the dissociation constant for the overall reaction (KT) was an order of magnitude larger.

A novel imino-acid carrier in the enterocyte basolateral membrane.

Basolateral membrane vesicles prepared from rat small intestinal epithelial cells were used to study the sodium-independent transport of L-proline. The uptake of L-proline was unaffected by the presence of sodium and showed saturation kinetics (Kt = 0.5 mM and Vmax = 23.

The Na+-independent D-glucose transporter in the enterocyte basolateral membrane: orientation and cytochalasin B binding characteristics.

Phloridzin-insensitive, Na+-independent D-glucose uptake into isolated small intestinal epithelial cells was shown to be only partially inhibited by trypsin treatment (maximum 20%). In contrast, chymotrypsin almost completely abolished hexose transport. Basolateral membrane vesicles prepared from rat small intestine by a Percoll gradient procedure showed almost identical susceptibility to treatment by these proteolytic enzymes, indicating that the vesicles are predominantly oriented outside-out.

Calcium transport affinity, ion competition and cholera toxin effects on cytosolic Ca concentration.

The physiological relevance of an apparent ionophore activity of cholera toxin towards Ca2+ has been examined in several different systems designed to measure affinity, specificity, rates of ion transfer, and effects on intracellular ion concentrations. Half-maximal transfer rates across porcine jejunal brush-border vesicles were obtained at a concentration of 0.20 microM Ca2+.

Use of calcium depletion and chlorpromazine to study calcium dependence of secretory detergent action in the colon.

The role of Ca2+ in the in situ secretory response of rat colon and pig ileum was studied by chelation depletion of Ca2+ and by treatment with chlorpromazine. The effect of depleting lumenal Ca2+ by chelation and the effect of intraperitoneal administration of chlorpromazine were determined relative to colonic permeability and net fluid flux measured across the rat colon or pig ileum. Replacement of Ca2+ in the perfusate by 1.

Effect of hyperglycemia on D-glucose transport across the brush-border and basolateral membrane of rat small intestine.

Experimental hyperglycemia leads to an increase in the capacity of the rat small intestine to absorb glucose. This effect occurs within hours from the onset of hyperglycemia and is thought to involve an induction of glucose transport in the brush-border and/or basolateral membrane of the intestinal epithelium. We devised a protocol for the simultaneous preparation of brush-border vesicles and basolateral vesicles from rat small intestine to determine the locus for the induction of glucose transporter in hyperglycemic rats.

Cholera toxin facilitates calcium transport in jejunal brush border vesicles.

Cholera toxin is very well characterized in terms of the activation of adenylate cyclase. In some systems, however, this cyclase activation does not seem to account for all of the physiological responses to the toxin. On the premise that cholera toxin may also exert effects through other second messenger compounds we have studied the effect of cholera toxin on the rate of Ca2+ movement across the membrane of intestinal brush border vesicles.

Calcium mediation of the pig jejunal secretory response.

The involvement of Ca++ ions as secretory mediators in pig jejunal epithelia has been investigated with an in vitro system. Omission of Ca++ from the Ringer-HCO3 bathing media on both sides of the tissue had minor effects on the basal electrical activity of pig jejunal mucosa. There were only slight decreases in transepithelial potential difference and increases in conductance with Ca++ free media.