Influence of ouabain of electrolyte and water transport in the rabbit ileum and colon in vitro and in vivo.

We studied the influence of the Na(+)-K+ pump inhibitor ouabain on water and electrolyte transport in the rabbit distal ileum and proximal colon in vitro and in vivo. Under in vitro conditions, ouabain markedly reduced the absorption of water, sodium, chloride and bicarbonate, and reduced potassium secretion in both the ileum and the colon. In vivo results were similar but less marked than those obtained in vitro, with significant differences only at the level of the distal ileum.     

Segmental distribution and expression of two heterodimeric amino acid transporter mRNAs in the intestine of pigs during different ages

BACKGROUND: Segmental distribution and expression of two heterodimeric amino acid transporter mRNAs during different ages were evaluated in pigs along the horizontal axis of the intestine. RESULTS: The intestinal distribution of b^{0, +} AT and y⁺LAT1 mRNA at day 90 showed that for b^{0, +} AT the mRNA levels were increased from the proximal to distal part of the small intestine (P < 0.05) and dropped dramatically in colon (P < 0.05). The ileum had the highest b^{0, +} AT mRNA abundance and the ileum had the lowest. Compared to b^{0, +} AT, the y⁺ LAT1 mRNA levels were decreased from the proximal to distal part of the small intestine (P < 0.05). The duodenum has the highest y⁺ LAT1 mRNA abundance. The mRNA abundance of b^{0, +} AT mRNA increased linearly (P < 0.0001) from day 1 to day 150 in ileum. CONCLUSION: The mRNA expression of heterodimeric amino acid transporters (b^{0, +} AT and y⁺LAT1) was not only differentially regulated by age but also differentially distributed along the intestine of piglets at early stages and growing stages of life, which may be related to luminal substrate concentration as well as amino acid requirement and hormones. Copyright © 2008 Society of Chemical Industry     

Effect of method of delivery of sodium butyrate on maturation of the small intestine in newborn calves

The effect of sodium butyrate (SB) supplementation in milk replacer (MR), starter mixture (SM), or both on small intestine maturation in newborn calves was investigated. Twenty-eight male calves with a mean age of 5 (±1) d were randomly allocated into 1 of 4 groups (7 animals per group) and fed (1) MR and SM, without SB (MR⁻ and SM⁻, respectively; MR⁻/SM⁻); (2) MR⁻ and SM supplemented with SB encapsulated within triglyceride matrix (SM⁺, 0.6% as fed; MR⁻/SM⁺); (3) MR supplemented with crystalline SB (MR⁺, 0.3% as fed) and SM⁻ (MR⁺/SM⁻); or (4) MR⁺ and SM⁺ (MR⁺/SM⁺). The MR was offered in amounts equal to 10% of initial body weight of the calf. The SM was blended with whole corn grain (50/50; wt/wt) and offered ad libitum as a starter diet. Calves were slaughtered at 26 d (±1) of age and small intestine development was investigated. Treatment with MR⁺ decreased villus height in the proximal jejunum and decreased villus height, crypt depth, and tunica mucosa thickness in the middle jejunum, whereas treatment with SM⁺ tended to increase small intestine weight and crypt depth in the proximal jejunum, and increased villus height in the distal jejunum. In the duodenum, crypt depth and tunica mucosa thickness were greater for the MR⁻/SM⁺ group compared with MR⁻/SM⁻, MR⁺/SM⁻, and MR⁺/SM⁺ groups. In the ileum, crypt depth was less for MR⁻/SM⁺ compared with MR⁻/SM⁻. Supplementation with SB in both MR and SM enhanced cell proliferation and decreased apoptosis in the middle jejunum mucosa. Regarding brush border enzyme activities, addition of SB to MR increased lactase activity in the middle jejunum and maltase activity in the distal jejunum, and tended to increase lactase activity in the distal jejunum, aminopeptidase A activity in the middle jejunum and ileum, and aminopeptidase N activity in the ileum. In contrast, SM⁺ increased dipeptidylpeptidase IV activity in the distal jejunum and tended to increase aminopeptidase N in the distal jejunum. In conclusion, both MR⁺ and SM⁺ affected small intestine development in newborn calves. This effect depended on the method of SB delivery but MR⁺ generally had a more pronounced effect. No synergistic effect of SB supplementation into MR and SM was found.     

Potassium and insulin affect the contractility of abomasal smooth muscle

Abomasal displacement is a frequent and important disease of high yielding dairy cows. Although several factors are related to its occurrence, the pathogenesis of the condition is still inadequately understood, particularly in regard to K⁺ and insulin homeostasis. For this reason the aim was to investigate the effects of K⁺ and insulin concentrations on in vitro motility of abomasal smooth muscle. The second aim was to determine whether the in vivo change in K⁺ and insulin levels might be sufficient to induce reduced abomasal motility. Muscle strips were isolated from the abomasum of slaughtered cows and incubated in buffer solution under isometric conditions. Results show that a decrease in extracellular K⁺ (between 5 and 1 mmol/L) or an increase in extracellular insulin concentrations (to 21 mU/L or higher) were able to affect the contraction activity of abomasal muscles. Contraction activity given as median (25th, 75th percentiles) changed from 28.1 mN/min (2.5, 49.9) at 5 mmol/L of K⁺ to 9.4 mN/min (0.6, 35.7) at 1 mmol/L of K⁺, and from 34.5 mN/min (10.8, 112.4) at 0 mU/L of insulin to 12.0 mN/min (7.6, 49.8) at 120 mU/L of insulin. Because the effect of insulin could be abolished by barium, glybenclamide, or ouabain, the underlying mechanisms of the insulin action could be an increased K⁺ conductance or an increased Na/K-ATPase activity or both. Low K⁺ or high insulin concentrations both reduced the activity of the circular muscle of the abomasal corpus (i.e., of the part that is responsible for the propulsion of abomasal chymus) and might play an important role in the pathogenesis of abomasal displacement.     

Evaluation of allergenicity of cow milk treated with enzymatic hydrolysis through a mouse model of allergy

Cow milk (CM) allergy is a worldwide concern. Currently, few studies have been performed on the immunoreactivity of CM and fewer still on the antigenicity of CM in vivo and in vitro. In this study, we assessed the potential allergenicity of enzymatically hydrolyzed CM using in vitro ELISA and oral sensitization and challenge of BALB/c mice. Alcalase-, Protamex-, and Flavourzyme-treated CM (all from Novozymes) diminished IgE binding capacity, with greatest reductions of 56.31%, 50.62%, and 56.45%, respectively. Allergic symptoms and levels of total IgG₁ were reduced, and allergic inflammation of the lung, jejunum, and spleen was relieved. Moreover, the numbers of CD8⁺ T and B220⁺ cells decreased, and the balance of CD4⁺ T/CD8⁺ T cells was effectively regulated. These findings suggest that the potential allergenicity of CM was reduced by enzymatic hydrolysis, and our research will lay a solid foundation for developing high-quality hypoallergenic CM products.     

Yogurt starter cultures of Streptococcus thermophilus and Lactobacillus bulgaricus ameliorate symptoms and modulate the immune response in a mouse model of dextran sulfate sodium-induced colitis

We investigated the yogurt starter cultures of Lactobacillus bulgaricus 151 and Streptococcus thermophilus MK-10 for their effect on the severity of experimental colitis, lymphocyte profile, and regulatory T-cell response. Colitis was induced in BALB/c mice via the administration of 3.5% dextran sulfate sodium salt (DSS) in drinking water for 6 d. Next, the mice were gavaged intragastrically with an active yogurt cultures (YC) mixture (～5 × 10⁹ cfu/mouse per day) or saline (vehicle) for 8 d. Mice receiving DSS or saline alone served as positive and negative controls, respectively. The length of the colon, disease activity index, histological scores, myeloperoxidase activity, epithelium-associated microbes, short-chain fatty acid profile, total IgA antibody-forming cells, CD3⁺CD8⁺, CD3⁺CD4⁺, CD3⁺CD4⁺CD25⁺, CD3⁺CD4⁺CD25⁺Foxp3⁺ T-cell subsets, and cytokine profiles (IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ, and tumor necrosis factor) were examined after termination of the mice. Feeding mice with YC mixture reduced disease symptoms and modified intestinal microbiota and host inflammatory responsiveness to DSS. We observed limited weight loss and a decreased disease activity index score, lowered myeloperoxidase activity, and somewhat reduced damage of the intestine. The YC mixture upregulated the colon length, increased the amount and diversity of mucosa-associated microbes (enterobacteria, enterococci, and yeast), and decreased the concentration of putrefactive short-chain fatty acids in the cecal contents. It downregulated the input of cytotoxic CD3⁺CD8⁺ T cells and CD3⁺CD4⁺CD25⁺FoxP3⁺ regulatory T cells in Peyer's patches and enhanced CD3⁺CD4⁺CD25⁺ T cells in spleens and CD3⁺CD4⁺CD25⁺FoxP3⁺ cells in peripheral blood mononuclear cells. Simultaneously, IgA antibody-forming cells were downregulated in mesenteric lymph nodes (MLN) and enhanced in spleens (SPL). The cultures mostly enhanced the production of cytokines tested in MLN and SPL, except for IL-6, which was downregulated in MLN. Interleukin-2 and IL-4 were the most upregulated in MLN, whereas IL-10, IL-4, IL-2, IFN-γ, and tumor necrosis factor were most upregulated in SPL. In serum, the YC mixture downregulated IFN-γ and clearly increased IL-2. Based on these results, we recognize the high anti-inflammatory and immunomodulatory potential of the L. bulgaricus 151 and S. thermophilus MK-10 set. The strains possess the ability to modulate the intestinal mucosal and systemic immune system toward both IgA production and induction of regulatory T cells, shifting Th1/Th2 balance.     

桑叶水提物改善肠肌运动及缓解便秘的作用

目的:研究桑叶水提物对豚鼠离体回肠收缩活动及对便秘大鼠的影响,探讨其改善便秘的作用及相关机制。方法:通过离体肠肌张力测定手段,观察桑叶水提物对豚鼠离体回肠运动的影响。采用洛哌丁胺（10 mg/kg/d）构建3 d及7 d便秘大鼠模型,并以桑叶水提物（5 g/kg/d）同期灌胃给药进行干预,观察大鼠第一白便时间、24 h粪便粒数和小肠推进率等,以及卡巴胆碱（carbachol,CCh）诱发各组大鼠回肠收缩反应的情况;通过石蜡切片HE染色观察大鼠结肠组织形态学变化,免疫组化检测结肠组织水通道蛋白3（aquaporin 3,AQP3）的表达。结果:桑叶水提物能促进豚鼠回肠的自主运动,表现为收缩幅度增强,平均张力升高。桑叶水提物对造模3 d和造膜7 d大鼠的第一白便时间、24 h粪便粒数（造模7 d,P<0.05）及小肠推进率（造模7 d, P<0.05）等指标均有不同程度改善;桑叶水提物明显改善卡巴胆碱诱发的便秘大鼠离体回肠平均张力的降低（P<0.05）;桑叶水提物对洛哌丁胺引起的大鼠结肠组织肌层变薄有改善作用,并显著降低洛哌丁胺引起的结肠AQP3表达的增加（P<0.05）。结论:桑叶水提物明显促进豚鼠回肠运动,并可能通过降低AQP3的表达,抑制结肠水分过度吸收,使粪便含水量增加,促进肠肌运动而改善便秘。     

Factors influencing permeability of the cell membrane of the osmotolerant yeast Saccharomyces rouxii grown in the presence and absence of 18% NaCl. I. Na+/K+-activated Mg2+-dependent ATPase

It was found that cells of Saccharomyces rouxii contain an ouabain-inhibited ATPase, assumed to be an Na⁺/K⁺-activated Mg²⁺-dependent ATPase, which could serve as a sodium pump protecting the cells in a high salt environment. Twenty-two cell homogenates or supernatants (centrifuged at 3000 × g) grown without added salt in the medium contained sufficient total ATPase activity to liberate (on average) 0.225 μM P_i min^?1 mg^?1 protein. The percentage of total ATPase inhibited by the addition of ouabain (1 × 10^?4 M) varied from 7 to 100%. Cell homogenates or supernatants from cells grown in the presence of 18% NaCl in the media contained sufficient ATPase activity to liberate (on average) 0.114 μM P_i min^?1 mg^?1 protein, about 50% of the total ATPase activity found in the non-salt grown cells. The percentage of total ATPase activity inhibited by ouabain ranged from 16 to 100%. Although the non-salt-grown cells contained approximately double the total ATPase activity of the salt-grown cells. there was evidence that the percentage of total ATPase that is ouabain sensitive (Na⁺/K⁺-activated ATPase) is higher in the salt-grown cells. Also, cells of S. rouxii grown in media without added NaCl, recovered by centrifugation and transferred to media containing 18% NaCl for 16 h and again recovered by centrifugation, homogenized and centrifuged at 10 000 × g contained 61.2% ouabain-sensitive ATPase compared with 21.3% ouabain-sensitive ATPase in the cells before adaptation to the high salt environment.     

Altered mucosa-associated microbiota in the ileum and colon of neonatal calves in response to delayed first colostrum feeding

The present study investigated whether delaying the first feeding of colostrum affected ileum and colon mucosa-associated microbiota in calves. Twenty-seven male Holstein calves were randomly assigned to 1 of 3 groups, fed colostrum at 45 min, 6 h, and 12 h after birth, respectively. Ileum and colon mucosa were collected at 51 h after birth, and their associated microbial profiles were assessed using amplicon sequencing. Both ileum and colon mucosa-associated microbiota were predominated by genus Escherichia-Shigella. The negative correlation between the molar proportion of short-chain fatty acids (SCFA) and ileum mucosa-associated opportunistic pathogens, and the positive correlation between the molar proportion of SCFA and colon mucosa-associated beneficial bacteria, suggest that SCFA might play an important role in maintaining the gut health of 2-d-old calves. A higher relative abundance of ileum mucosa-associated Enterococcus and Streptococcus was detected when the first colostrum feeding was delayed for 12 h. The relative abundance of colon mucosa-associated Lactobacillus tended to be lower in calves fed colostrum 12 h than those under the other 2 treatments, whereas that of Faecalibacterium tended to be lower in calves fed colostrum immediately after birth than those fed colostrum 6 and 12 h after birth, respectively. Our findings suggest that delayed first colostrum feeding affects the establishment of ileum and colon mucosa-associated bacteria, which may have long-term effects on gut health of calves.     

Evaluation of survival and release of encapsulated bacteria in ex vivo porcine gastrointestinal contents using a green fluorescent protein gene-labelled E. coli

A gfp-labelled E. coli strain K 12 was used to study the survival and release of calcium alginate encapsulated bacteria in ex vivo porcine intestinal contents. Encapsulated bacteria survived better in ex vivo porcine gastric conditions compared to non-encapsulated free bacterial cells. There was 2 log decrease in viable cells of encapsulated E. coli GFP⁺ after 3 h incubation in gastric contents compared to 4 log decrease in the free non-encapsulated cells. There was a complete release of encapsulated bacteria (E. coli GFP⁺) within 1 h of incubation in small intestinal contents at 37°C, while it took 8 h to nearly completely release the encapsulated bacteria in colon content under similar conditions. There was only a partial release of encapsulated bacteria incubated in duodenal content even after 10 h of incubation. Using gfp labelled E. coli, the efficacy of alginate capsule in protecting the bacterial cells from gastric environment and releasing the encapsulated bacteria in the intestine (desired site) was demonstrated.     

Effects of probiotic,prebiotic and synbiotic follow‐up infant formulas on large intestine morphology and bone mineralisation in rats

The effects of powder functional follow‐up infant formulas on the morphology of the large intestine and the bone mineral content in rats were investigated. Infant formulas were supplemented with probiotics (Bifidobacterium bifidum and Bifidobacterium longum), prebiotics (galacto‐oligosaccharides (4′‐GOS) at 12, 50 and 100 g kg^?1) or synbiotics (bifidobacteria and 4′‐GOS) and administered to seven groups of weanling rats over 30 days. After sacrificing the animals, the caecum and colon were removed and the luminal content pH and the crypt depth and cell density within the epithelial layer were measured. Results showed that groups fed synbiotic diets had significantly (P < 0.05) lower caecal and colonic content pH values compared with the control group. However, no test diet significantly modified the crypt depth or cell density in the caecum. In contrast, all seven test diets significantly increased (P < 0.05) the crypt depth in both the proximal and distal portions of the colon. There was a high correlation (Pearson correlation coefficient 0.870) between caecal and colonic content pH values. On the other hand, colonic content pH was negatively correlated with crypt depth in both the proximal and distal colon and with cell density in the distal colon. The authors previously reported increases in calcium, magnesium and phosphorus absorption using the same infant formulas. In the present study it was concluded that the increase in calcium absorption took place in the distal colon whereas magnesium absorption increased in both the proximal and distal colon, and their contents (especially that of calcium) increased in both the femur and tibia. Copyright © 2007 Society of Chemical Industry     

Long‐term effects on the digestive tract of feeding large amounts of resistant starch: A study in pigs

The present study aimed to assess the digestive consequences of the long‐term intake of two starches providing different amounts of resistant starch. Growing pigs were used as the animal model and meal‐fed for 14 weeks on a diet containing a high amount of either raw potato starch (RPS) or corn starch (CS). Digestive adaptation was chronologically evaluated by measuring organic matter (OM), crude protein (CP), neutral detergent fibre (NDF) and starch digestibility. After 97 days, whole‐tract digestibility of OM, CP and NDF was lower for RPS‐ compared to CS‐fed pigs, whereas no differences were observed in faecal starch digestibility. In contrast, starch digestibility was reduced in the proximal compartments (ileum, caecum and proximal colon) of animals fed the RPS diet. The concentration of short‐chain fatty acids (SCFAs; P < 0.05), and purine bases (PBs; P < 0.01) was also higher in distal colon and rectum of animals fed the RPS diet. Changes in bacterial community structure (dendogram analyses) were seen in the rectum. Biodiversity tends to increase more in RPS compared to CS fed animals (34.1 vs. 28.8; P = 0.07). Among SCFAs, the proportion of butyrate was two‐fold higher in proximal colon digesta of RPS compared to CS fed pigs (0.20 vs. 0.11; P < 0.05). Increased butyrate formation in the colon reduced the number of apoptosis per crypt in the proximal colonic mucosa (0.38 vs. 0.62; P < 0.05). RPS fermentation reduced indices associated with damage to intestinal epithelial cells, such as crypt cell hyperproliferation and magnesium excretion. Long‐term ingestion of RPS induces pronounced changes of the digestive tract and their microflora, modifying mineral absorption and colonic morphology for which health benefits are likely to be associated. Copyright © 2007 Society of Chemical Industry     

Short‐chain fatty acid content in the hindgut of rats fed various composite foods and commercial dietary fibre fractions from similar sources

The fermentability of indigestible carbohydrates and content of short‐chain fatty acids along the hindgut of rats were investigated using plant materials of importance in the Swedish diet (instant potato powder, apples and oat flakes). Results with the composite food products were compared with commercial fibre fractions obtained from similar sources, ie potato fibre, apple pectin and β‐glucan‐enriched oat fibre. The materials were incorporated into diets yielding a concentration of 60 or 70 g kg^?1 indigestible carbohydrates. The fermentability of indigestible carbohydrates was high with all diets, between 79 and 90%. All substrates except the pure apple pectin generated intermediate to high proportions of butyric acid in the caecum (15–22 vs 8%). The potato products gave high concentrations of butyric acid in the distal colon. The potato powder, ie the diet with the highest content of resistant starch (22 g kg^?1), also gave the highest proportion of butyric acid in the distal colon (19%), which was higher than the proportion in the caecum with the same substrate (15%) (P < 0.005). The composite foods promoted a higher proportion of butyric acid in the distal colon as compared with the commercial fibre fractions (P < 0.05). © 2002 Society of Chemical Industry     

The effect of dietary Laminaria‐derived laminarin and fucoidan on nutrient digestibility,nitrogen utilisation,intestinal microflora and volatile fatty acid concentration in pigs

BACKGROUND: In experiment 1, 30 boars were assigned to one of five treatments (n = 6): T1, 0 g kg^?1 seaweed extract (SWE); T2, 0.7 g kg^?1 SWE; T3, 1.4 g kg^?1 SWE; T4, 2.8 g kg^?1 SWE and T5, 5.6 g kg^?1 SWE. The extract contained laminarin and fucoidan only and was extracted from Laminaria spp. In experiment 2, 28 boars were assigned, in a 2 × 2 factorial to one of four treatments (n = 7): T1, control; T2, control plus 300 mg laminarin; T3, control plus 240 mg fucoidan; T4, control plus 300 mg laminarin and 240 mg fucoidan kg^?1 diet. RESULTS: In experiment 1 there was a response to SWE on colonic Bifidobacterium spp. (P < 0.01 quadratic), Enterobacterium spp. (quadratic P < 0.05) and on caecal Enterobacterium spp. (quadratic P < 0.05). In experiment 2 there was an interaction (P < 0.05) between laminarin and fucoidan supplementation on Enterobacterium spp. in the proximal and distal colon. Pigs offered laminarin had reduced Enterobacterium spp. compared with pigs offered the control diet. However, the combination of laminarin and fucoidan had increased Enterobacterium spp. compared with alone. Pigs offered diets containing fucoidan had increased Lactobacilli spp. in the proximal colon (P < 0.05) and distal colon (P < 0.001) compared with non‐fucoidan diets. CONCLUSION: Overall, the reductions in intestinal Enterobacterium spp. and increases in Lactobacilli spp. obtained suggest that laminarin and fucoidan may provide a dietary means to improve gut health in pigs. Copyright © 2009 Society of Chemical Industry     

Dietary modulation of the expression of genes involved in short-chain fatty acid absorption in the rumen epithelium is related to short-chain fatty acid concentration and pH in the rumen of goats

We have tested the hypothesis that increased concentrate intake induces mRNA abundance alterations of genes involved in short-chain fatty acid (SCFA) absorption in the rumen epithelium of goats and these changes of mRNA abundance are probably related to ruminal SCFA concentration and ruminal pH. Goats (n = 12) were randomly allocated to 2 groups and fed either a low-concentrate (LC) diet (10% concentrate; n = 6) or a medium-concentrate (MC) diet (35% concentrate; n = 6) in 2 equal portions daily. Goats were fed separately with their respective diet for 3 wk. The goats were slaughtered 6 h after the morning feeding on d 22. In vivo, goats in the MC treatment exhibited a greater ruminal SCFA concentration (81.9 mM) compared with those in the LC treatment (58.0 mM), and the pH decreased from 7.03 to 6.63. Correspondingly, mRNA expression of candidates for SCFA⁻/HCO₃⁻ exchangers, namely downregulated in adenoma (DRA), putative anion transporter 1 (PAT1), and anion exchanger 2 (AE2) were increased in the MC group. Further, upregulation in monocarboxylate transporter 1 (MCT1) and monocarboxylate transporter 4 (MCT4) mRNA abundances was observed in the MC group. The expression of genes that help the rumen epithelial cells to maintain intracellular pH, including Na⁺/H⁺ exchanger 1 (NHE1), NHE2, NHE3, vacuolar H⁺ ATPase subunit B (vH⁺ATPase), and Na⁺/K⁺ ATPase pump subunit α1 (Na⁺/K⁺ATPase) were also enhanced in the MC group relative to the LC group. During in vitro studies with isolated rumen epithelial cells from goats, exposure to a pH of 6.8 increased MCT1 mRNA expression after 24 h of culture, whereas the mRNA expression of AE2 was downregulated. The presence of SCFA (20 mM) in the medium increased DRA, PAT1, AE2, MCT1, and Na⁺/K⁺ATPase mRNA expression. The expression of vH⁺ATPase was decreased by increased SCFA concentration. The mRNA expression of MCT4 did not vary in vitro with pH (6.8) or SCFA (20 mM). The expression of DRA was increased by synergistic effects of higher SCFA concentration and lower pH, similar to that of MCT1. Thus, diet-dependent rumen epithelial mRNA expression changes in genes involved in SCFA absorption are probably related to ruminal SCFA concentration and pH.     

In Vitro and In Vivo Digestibility of Recrystallized Amylose and Its Application for Low Glycemic Foods

ABSTRACT: To predict physiologic functions of recrystallized amylose (RCA), the true resistant starch (RS) content of RCA in the small intestine was directly measured using ileorectostomized rats where the distal ileum was anastomosed to the rectum (the cecum and colon were surgically resected together). The estimated in vivo resistant starch content of RCA was the same as the value obtained from the in vitro enzymatic RS determination (∼50%). RCA resistance to amylolytic enzymes in the small intestine was retained even after RCA incorporation into processed foods, and a bread containing 20% RCA showed a significantly lower glycemic response in rats compared with that of a control bread. Also, RCA ingestion significantly and dose-dependently decreased the body fat accretion and lowered serum concentrations of cholesterol and triglycerides in rats compared with cornstarch. These lipid-lowering effects of RCA were comparable to those obtained with high-amylose cornstarch. The restricted energy value as well as suppressed insulin response with RCA ingestion might be related to preferable changes in lipid metabolism. These nutritional properties of RCA may suggest a possible benefit as an alternative source of resistant starch for preventing diabetes, hyperlipidemia and obesity, and so on.     

Monitoring the effects of divalent ions (Mn and Ca) in heat-set whey protein gels

Exploring the effects of cations in whey protein-based gels (WPG) is of importance when these gels are used for controlled release applications in food systems. The objective of this study was to evaluate both water uptake and cation release from heat-set WPGs. Magnetic Resonance Imaging and NMR relaxometry were employed to study the uptake and release. A non-paramagnetic (Ca⁺²) and a paramagnetic cation (Mn⁺²) were incorporated into the WPG as model divalent cations. Cylindrical pieces of WPGs with manganese were immersed in water (pH 2.40, 7.00, 10.40) or in EDTA solution whereas WPGs with calcium were immersed in water at pH 2.40. Water uptake by the gels was influenced by both ionic environment and pH. The release of Mn⁺² from WPG was enhanced by the presence of EDTA. Relaxation spectra of Mn⁺²-loaded gels were significantly influenced by pH of the suspending fluid and by the presence of EDTA. Results of relaxometry experiments, obtained with Ca⁺²-loaded gels immersed in water at pH 2.40, indicated a strong correlation (R² > 0.99) between relative areas of the proton pools and the amount of calcium released to the medium. Results support the use of MRI and NMR to monitor cation release and water uptake in WPG, non-destructively.     

The role of K+ and H+ transport systems during glucose‐ and H2O2‐induced cell death in Saccharomyces cerevisiae

Glucose, in the absence of additional nutrients, induces programmed cell death in yeast. This phenomenon is independent of yeast metacaspase (Mca1/Yca1) and of calcineurin, requires ROS production and it is concomitant with loss of cellular K⁺ and vacuolar collapse. K⁺ is a key nutrient protecting the cells and this effect depends on the Trk1 uptake system and is associated with reduced ROS production. Mutants with decreased activity of plasma membrane H⁺‐ATPase are more tolerant to glucose‐induced cell death and exhibit less ROS production. A triple mutant ena1‐4 tok1 nha1, devoid of K⁺ efflux systems, is more tolerant to both glucose‐ and H₂O₂‐induced cell death. We hypothesize that ROS production, activated by glucose and H⁺‐ATPase and inhibited by K⁺ uptake, triggers leakage of K⁺, a process favoured by K⁺ efflux systems. Loss of cytosolic K⁺ probably causes osmotic lysis of vacuoles. The nature of the ROS‐producing system sensitive to K⁺ and H⁺ transport is unknown. Copyright © 2010 John Wiley & Sons, Ltd.     

Sodium Retention in Prerigor and Postrigor Ground Pork

Sodium retention in pre- and postrigor ground pork was studied. Pork of different ionic strengths was prepared by mixing meat with various amounts of water and NaCl, and was separated into two fractions: supernatants and pellets. Na⁺ retention in supernatants increased with increasing percent NaCl (0–5%). Supernatants of prerigor ground pork contained less Na⁺ than those of postrigor ground meat. Na⁺ retention in pellets also increased with increasing percent NaCl (0–5%). Na⁺ retention was higher in pellets of prerigor ground pork than in those of postrigor ground meat. Muscle proteins were not able to bind added Na⁺, as demonstrated by a dialysis method, regardless of rigor state and fraction.