Effect of stage of lactation and dietary starch content on endocrine-metabolic status, blood amino acid concentrations, milk yield, and composition in Holstein dairy cows.

Milk yield and composition are modified by level and chemical characteristics of dietary energy and protein. Those factors determine nutrient availability from a given diet, and once absorbed, they interact with the endocrine system and together determine availability of metabolites to the mammary gland. Four multiparous dairy cows in early lactation and subsequently in late lactation were fed 2 diets for 28 d in a changeover design that provided, within the same stage of lactation, similar amounts of rumen fermentable feed with either high (HS) or low starch (LS). All diets had similar dietary crude protein (15.5% dry matter) and rumen-undegradable protein (∼40% of crude protein) content. Profiles of AA were calculated to be similar to that of casein. On d 28, [1-13C] Leu was infused into one jugular vein with blood samples taken at 0, 2, 4, 6, and 8 h, and cows milked at 0, 2, 4, 5, 6, 7, and 8 h from start of infusion. Isotopic enrichments of plasma Leu, keto-isocaproic acid, and milk casein were determined for calculation of Leu kinetics. Data were subjected to ANOVA using the MIXED procedure of SAS (SAS Institute Inc.), with time as repeated factor and cow as the random effect. Dry matter intake within each stage of lactation was similar between groups. Feeding LS resulted in lower blood glucose and greater ratio of bovine somatotropin to insulin. This response was associated with greater blood concentrations of nonesterified fatty acids and ß-hydroxybutyrate, which might have contributed to greater milk fat content in LS-fed cows. Except for His, average concentrations of all AA in blood were higher in late than early lactation. Diet did not alter average plasma concentrations of AA. However, for most of the essential AA (particularly branched-chain), the HS diet led to a marked decrease in concentrations after the forage meal, resulting in significant differences between dietary groups in early lactation. In early-lactating cows fed HS, a greater reduction in plasma concentrations at 8 h relative to pre-feeding values (time zero) was observed for Met, Lys, and His, resulting in decreases of 27.9%, 33.6%, and 38.5%, respectively. A higher bovine somatotropin/insulin ratio in early lactation and in cows fed LS could possibly have led to greater breakdown and, consequently, higher AA flux from peripheral tissues. In LS-fed cows, higher mobilization of body fat and protein was confirmed by the greater body weight loss in both stages of lactation. Higher irreversible loss of [1-13C] Leu in early lactation suggested lower protein retention in peripheral tissues during early compared with late lactation. Milk yield, protein output, and composition were similar between groups at both stages of lactation, whereas milk coagulation was faster (lower curd firming rate) and with higher curd firmness in response to feeding HS in late lactation. Overall, data indicated that rate of carbohydrate fermentability in the rumen can modify the availability of metabolites to the mammary gland and consequently modify milk protein coagulation.

Impact of a customised dietary intervention on antioxidant status, dietary intakes and periodontal indices in patients with adult periodontitis.

BACKGROUND: Dietary modification may be important in the prevention and control of chronic adult periodontitis. The role of promoting an adequate consumption of fruits, vegetables and whole grains in chronic periodontitis has not been thoroughly investigated. The main aim of this dietary intervention study was to assess the influence of a customised dietary intervention (aiming to increase the consumption of fruits, vegetables and whole grains) on antioxidant status in adults with chronic periodontitis. METHODS: Fifty-one participants, aged 30-65 years, were recruited from a U.K. Dental Hospital and randomly allocated to an intervention or control group. Both groups received normal clinical treatment but customised dietary advice was delivered to the intervention group by a community nutrition assistant. Dietary intakes, anthropometric parameters and biochemical indices with respect to blood and saliva and periodontal indices were evaluated at baseline, as well as at 3 and 6 months post-dietary intervention. RESULTS: At 3 and 6 months post-intervention, the intervention group showed a significant (P < 0.05) increase in plasma total antioxidant capacity measured by Trolox equivalent antioxidant capacity assay compared to the control group. At 3 and 6 months after dietary intervention, the intervention group had significantly higher intakes of fruits and vegetables compared to the control group. The intake of whole grain was significantly higher in the intervention group than in the control group, 6 months post-intervention. No significant differences were observed with respect to periodontal indices between groups. CONCLUSIONS: It is suggested that dietary advice may help to improve dietary habits and, consequently, the antioxidant status of patients with chronic periodontitis. However, the impact of such intervention on periodontal indices needs further investigation.

Effect of dietary starch level and high rumen-undegradable protein on endocrine-metabolic status, milk yield, and milk composition in dairy cows during early and late lactation.

Diet composition defines the amount and type of nutrients absorbed by dairy cows. Endocrine-metabolic interactions can influence these parameters, and so nutrient availability for the mammary gland can significantly vary and affect milk yield and its composition. Six dairy cows in early and then late lactation received, for 28 d in a changeover design, 2 diets designed to provide, within the same stage of lactation, similar amounts of rumen fermentable material but either high starch plus sugar (HS) content or low starch plus sugar content (LS). All diets had similar dietary crude protein and calculated supply of essential amino acids. Dry matter intake within each stage of lactation was similar between groups. Milk yield was similar between groups in early lactation, whereas a higher milk yield was observed in late lactation when feeding HS. At the metabolic level, the main difference observed between the diets in both stages of lactation was lower blood glucose in cows fed LS. The lower glucose availability during consumption of LS caused substantial modifications in the circulating and postprandial pattern of metabolic hormones. Feeding LS versus HS resulted in an increase in the ratio of bovine somatotropin to insulin. This increased mobilization of lipid reserves resulted in higher blood concentrations of nonesterified fatty acids and ß-hydroxybutyrate, which contributed to the higher milk fat content in both stages of lactation in the LS group. This greater recourse to body fat stores was confirmed by the greater loss of body weight during early lactation and the slower recovery of body weight in late lactation in cows fed LS. The lower insulin to glucagon ratio observed in cows fed LS in early and late lactation likely caused an increase in hepatic uptake and catabolism of amino acids, as confirmed by the higher blood urea concentrations. Despite the higher catabolism of amino acids in LS in early lactation, similar milk protein output was observed for both diets, suggesting similar availability of amino acids for peripheral tissue and mammary gland. The latter could be the result of sparing of amino acids at the gut level due to starch that escaped from the rumen, and to the balanced amino acid profile of digestible protein. This last aspect appears worthy of further research, with the aim to enhance the efficiency of protein metabolism of dairy cows, reducing environmental nitrogen pollution without affecting milk yield potential.

Randomized clinical trial of omega-3 fatty acid-supplemented enteral nutrition versus standard enteral nutrition in patients undergoing oesophagogastric cancer surgery.

BACKGROUND: Oesophagogastric cancer surgery is immunosuppressive. This may be modulated by omega-3 fatty acids (O-3FAs). The aim of this study was to assess the effect of perioperative O-3FAs on clinical outcome and immune function after oesophagogastric cancer surgery. METHODS: Patients undergoing subtotal oesophagectomy and total gastrectomy were recruited and allocated randomly to an O-3FA enteral immunoenhancing diet (IED) or standard enteral nutrition (SEN) for 7 days before and after surgery, or to postoperative supplementation alone (control group). Clinical outcome, fatty acid concentrations, and HLA-DR expression on monocytes and activated T lymphocytes were determined before and after operation. RESULTS: Of 221 patients recruited, 26 were excluded. Groups (IED, 66; SEN, 63; control, 66) were matched for age, malnutrition and co-morbidity. There were no differences in morbidity (P = 0·646), mortality (P = 1·000) or hospital stay (P = 0·701) between the groups. O-3FA concentrations were higher in the IED group after supplementation (P < 0·001). The ratio of omega-6 fatty acid to O-3FA was 1·9:1, 4·1:1 and 4·8:1 on the day before surgery in the IED, SEN and control groups (P < 0·001). There were no differences between the groups in HLA-DR expression in either monocytes (P = 0·538) or activated T lymphocytes (P = 0·204). CONCLUSION: Despite a significant increase in plasma concentrations of O-3FA, immunonutrition with O-3FA did not affect overall HLA-DR expression on leucocytes or clinical outcome following oesophagogastric cancer surgery. REGISTRATION NUMBER: ISRCTN43730758 (http://www.controlled-trials.com).

Impacts of operating conditions on efficiency of electrokinetically enhanced filtration for de-watering of orange juice and malt extract.

The effects of operational factors an on an electrokinetic-enhanced filtration (EKEF) application to dewater orange juice (OJ) and malt extract (ME) was investigated. EKEF improved dewatering of both foodstuffs and resulted in net dewatering efficiencies of 7.4% and 4.9% for OJ and 10.7% and 6.3% for ME after 5.5 h processing under 30 V and 15 V, respectively. Dry matter content was increased by 19.2% and 15.6% for OJ after 5.5 h and 14.8% and 12.8% for ME after 3.5 h under 30 V and 15 V, respectively, compared with 14.9% and 10.3% under the control conditions for OJ and ME, respectively. The EKEF process effectively improved dewatering of high moisture-content foods with positive impacts on process efficiency by increased voltage, pressure, and the pore size of filters. The initial distance between electrodes had a negative impact as the distance increased. EKEF is a useful adjunct to improve high pressure filtration of foodstuffs.

In vitro protective effects of Withania somnifera (L.) dunal root extract against hydrogen peroxide and ß-amyloid(1-42)-induced cytotoxicity in differentiated PC12 cells.

Withania somnifera L. Dunal (Solanaceae), also known as 'ashwagandha' in Sanskrit and as 'Indian ginseng', is used widely in Ayurvedic medicine as a nerve tonic and memory enhancer, with antiaging, antistress, immunomodulatory and antioxidant properties. There is a paucity of data on the potential neuroprotective effects of W. somnifera root, as traditionally used, against H(2)O(2)- and Aß((1-42))-induced cytotoxicity which are current targets for novel approaches to treat dementia, especially dementia of the Alzheimer's type (AD). In this study, an aqueous extract prepared from the dried roots of W. somnifera was assessed for potential protective effects against H(2)O(2)- and Aß((1-42))-aggregated fibril cytotoxicity by an MTT assay using a differentiated rat pheochromocytoma PC12 cell line. The results suggest that pretreatments of differentiated PC12 cells with aqueous extracts of W. somnifera root significantly protect differentiated PC12 cells against both H(2)O(2)- and Aß((1-42))-induced cytotoxicity, in a concentration dependent manner. To investigate the compounds that could explain the observed effects, the W. somnifera extract was analysed by liquid chromatography-serial mass spectrometry and numerous withanolide derivatives, including withaferin A, were detected. These results demonstrate the neuroprotective properties of an aqueous extract of W. somnifera root and may provide some explanation for the putative ethnopharmacological uses of W. somnifera for cognitive and other neurodegenerative disorders that are associated with oxidative stress.

Discharged filtrate movement in food materials under application of electrokinetics.

Orange juice (OJ) and malt extract (ME) samples were treated using an electrokinetic (EK) application to investigate the impact of the pH/Lowest conductivity point (LCP) ratio of experimental materials on the water profile direction and the anolyte to catholyte filtrate ratio. After applying the electric field through samples between two electrodes, filtrate was discharged mainly towards the anode in OJ samples (acidic medium, pH/LCP < 1) and towards the cathode in ME samples (alkaline medium, pH/LCP > 1). Adjusting the orientation of electrodes depending on the results maximised dewatering efficiency under EK by 7.8% in OJ and 11.8% in ME. Changing the pH/LCP ratio by adjusting the starting pH improved dewatering efficiency under EK by 25.7%. The results are used to develop theoretical guidelines to help determine the water profile direction and filtrate outlets for different food materials based on their pH and LCP values. EK is an effective method for dewatering food materials.

Effect of intraruminal propionic acid infusion on metabolism of mesenteric- and portal-drained viscera in growing steers fed a forage diet: I. Volatile fatty acids, glucose, and lactate.

This experiment investigated the effect of intraruminal infusion of propionic acid on ruminal VFA metabolism and the absorption of nutrients by the mesenteric- and portal-drained viscera of seven Friesian steers, average BW 127 kg, fed a dried grass-pellet diet. Each received by random allocation 0 (control), .5, or 1.0 mol of propionic acid/d for 7 d. Ruminal acetate and propionate irreversible loss rates and carbon exchange between VFA and CO2 were measured during continuous intraruminal infusions of 2-14C-acetic acid and 2-14C-propionic acid. Ruminal acetate irreversible loss rate was not affected by propionic acid infusion (overall mean 8.09, error mean square [EMS] 2.68 mol/d), whereas propionate irreversible loss increased incrementally with PA supply (3.22 vs 4.16, EMS .61 mol/d, for control and 1.0 mol of propionic acid/d, respectively, P = .09). Glucose irreversible loss rate was increased at the highest level of PA infusion (2.84, 2.83, and 3.22, EMS .06 mol/d, for control, .5, and 1.0 mol of propionic acid/d, respectively; P = .02 for control vs .5 + 1.0), although the proportion of glucose irreversible loss derived from propionate remained constant (.6). Net absorption into venous blood showed that propionate was extensively metabolized in the rumen wall and that the tissues of the small intestine utilized acetate. Utilization of glucose was reduced in portal tissues as a result of intraruminal infusion, and the data were used to derive a model of glucose and lactate interrelationships in gut tissues.

Effect of intraruminal propionic acid infusion on metabolism of mesenteric- and portal-drained viscera in growing steers fed a forage diet: II. Ammonia, urea, amino acids, and peptides.

This experiment investigated the effect of intraruminal infusion of propionic acid on the net flux of nitrogenous compounds across the mesenteric- (MDV) and portal-(PDV) drained viscera of seven Friesian steers, average BW 127 kg (SEM 4.6), fed a grass-pellet diet. Each received by random allocation 0 (control), .5, or 1.0 mol of propionic acid/d for 7 d. Blood flow in mesenteric and portal veins was determined by downstream dilution of p-aminohippuric acid in order to determine net appearance rates across the gastrointestinal tissues. Net urea and ammonia flux was unaffected by propionic acid supply. Circulating plasma free amino acid concentrations were increased (P < .05) by propionic acid infusion (2,235, 2,428, and 2,427, error mean square [EMS] 44,370 microM, for control, .5, and 1.0 mol of propionic acid/d, respectively). Net amino acid flux rates were increased at the highest rate of propionic acid infusion across MDV and PDV (4.66, 3.69, and 6.11, EMS 2.98 mol/d for MDV [P < .05] and 2.98, 2.45, and 3.73, EMS 1.69 mol/d for PDV [P < .10] for control, .5, and 1.0 mol of propionic acid/d respectively). Positive venous-arterio concentration differences for peptide-bound amino acids (PBAA) across the MDV and PDV indicated net appearance across the gastrointestinal tissues, but this was not affected by propionic acid infusion. The data show that amino acid flux across postruminal tissues can be influenced by ruminal propionic acid supply and that this does not affect PBAA appearance.

Effect of intravenous glucose infusion on metabolism of portal-drained viscera in sheep fed a cereal/straw-based diet.

This experiment investigated the effect of intrajugular infusion of glucose on whole-body glucose metabolism and the absorption of nutrients by the portal-drained viscera of four Suffolk-cross sheep, average BW 46 +/- 7 kg, fed a cereal/straw-based pelleted diet. Each sheep received by random allocation 0 (control), 1.0, or 2.0 mg of glucose.kg BW-1.min-1 for 8 h infused into the jugular vein. Glucose irreversible loss rate, measured by simultaneous infusion of 6-[3H]-glucose, increased approximately stoichiometrically during glucose infusion (.51, .75, and 1.09 error mean square [EMS] .032 mmol/min for control, 1.0, and 2.0 mg of glucose infused.kg BW-1.min-1, respectively). Utilization of glucose increased in portal tissues (P = .089) as a result of glucose infusion (.17, .18, and .33 EMS .008 mmol/min) and was a constant proportion of glucose irreversible loss (.28). Portal blood flow was not affected by glucose infusion (overall mean 1.13 L/min EMS .034). Net portal absorption of acetate increased during glucose infusion although ruminal VFA concentrations were not affected. In contrast, net free amino acid absorption by portal-drained tissues was reduced during glucose infusion (291, 115, and 4 EMS 33,816 mumol/min, P = .054). These results show that metabolism of nutrients across the gut wall is influenced by glucose availability to gastrointestinal tissues and affects the pattern of nutrients available to the liver and peripheral tissues.

Improving the fatty acid profile of winter milk from housed cows with contrasting feeding regimes by oilseed supplementation.

Many studies show concentrations of nutritionally desirable fatty acids in bovine milk are lower when cows have no access to grazing, leading to seasonal fluctuations in milk quality if cows are housed for part of the year. This study investigated the potential to improve the fatty acid profiles of bovine milk by oilseed supplementation (rolled linseed and rapeseed) during a period of indoor feeding in both organic and conventional production systems. Both linseed and rapeseed increased the concentrations of total monounsaturated fatty acids, vaccenic acid, oleic acid and rumenic acid in milk, but decreased the concentration of the total and certain individual saturated fatty acids. Linseed resulted in greater changes than rapeseed, and also significantly increased the concentrations of α-linolenic acid, total polyunsaturated fatty acids and total omega-3 fatty acids. The response to oilseed supplementation, with respect to increasing concentrations of vaccenic acid and omega-3 fatty acids, appeared more efficient for organic compared with conventional diets.

Variation in nutritionally relevant components in retail Jersey and Guernsey whole milk.

This study investigates the quality of retail milk labelled as Jersey & Guernsey (JG) when compared with milk without breed specifications (NS) and repeatability of differences over seasons and years. 16 different brands of milk (4 Jersey & Guernsey, 12 non specified breed) were sampled over 2 years on 4 occasions. JG milk was associated with both favourable traits for human health, such as the higher total protein, total casein, α-casein, ß-casein, κ-casein and α-tocopherol contents, and unfavourable traits, such as the higher concentrations of saturated fat, C12:0, C14:0 and lower concentrations of monounsaturated fatty acids. In summer, JG milk had a higher omega-3:omega-6 ratio than had NS milk. Also, the relative increase in omega-3 fatty acids and α-tocopherol, from winter to summer, was greater in JG milk. The latter characteristic could be of use in breeding schemes and farming systems producing niche dairy products. Seasonality had a more marked impact on the fatty acid composition of JG milk than had NS milk, while the opposite was found for protein composition. Potential implication for the findings in human health, producers, industry and consumers are considered.

Do implant-supported dentures facilitate efficacy of eating more healthily?

UNLABELLED: Edentulous persons have poor diet quality demonstrating a need for dietary intervention. Implant-supported mandibular overdentures (IODs) have functional advantages over conventional dentures (CD), but whether they enhance the ability to eat more healthily following dietary advice is unknown. OBJECTIVES: This study aimed to compare the effectiveness of dietary intervention between IODs and CD patients. METHODS: Edentulous adults (28 IOD and 26 CD) received customised dietary advice. The percentage contribution of dietary fats, carbohydrate and protein to energy (kcal) intake, dietary intakes of fibre, fruits, vegetables and antioxidants, and plasma antioxidants were assessed pre- and at 3 and 6 months post-dietary intervention. RESULTS: Both groups increased fruit and vegetable intake at 3 and 6 months following dietary intervention but intakes between groups did not differ. The IOD group had reduced % energy from total fat at 3 and 6 months and from saturated fat at 3 months. The CD group had reduced % energy from saturated by 6 months. The IOD group had a significantly lower % energy intake from saturated fat at 3 months and higher intake of non-starch polysaccharide (NSP) compared with the CD group. Both groups showed improvements in serum antioxidant status but the IOD group had significantly higher plasma antioxidant capacity post intervention compared with the CD group. CONCLUSIONS: Dietary intervention benefits denture patients. IOD patients showed moderately greater dietary improvements compared with conventional denture patients.

In vitro protective effects of colon-available extract of Camellia sinensis (tea) against hydrogen peroxide and beta-amyloid (Aß((1-42))) induced cytotoxicity in differentiated PC12 cells.

There is mounting evidence that the deposition and aggregation of ß-amyloid peptides (Aß) in the brain play a significant role in the development and pathogenesis of Alzheimer's disease. There is further evidence that free radical species such as hydrogen peroxide (H(2)O(2)) mediate Aß induced toxicity. Previous studies have demonstrated that green tea polyphenols possess neuroprotective properties through their ability to ameliorate oxidative stress induced by free radical species. Green tea polyphenols have also been shown to enhance cognition in various animal models of induced cognitive impairment. Upon ingestion, green tea polyphenols are metabolised and undergo bio-transformation which affects their bioavailability and therefore efficacy. In this study, a green tea extract was subjected to a simulated gastrointestinal digestion and a 'colon-available' extract (CAGTE) prepared and assessed for its potential protective effects against H(2)O(2) and Aß((1-42)) induced cytotoxicity using differentiated PC12 cells (dPC12) as a model for neuronal cells. CAGTE represents green tea phytochemicals potentially available after upper gastrointestinal digestion. CAGTE which was depleted in flavan-3-ols, as shown by LC-MS analysis, protected dPC12 cells at concentration ranges of 0.3-10 µg/ml and 0.03-0.125 µg/ml for H(2)O(2) and Aß((1-42)), induced cytotoxicity, respectively. At high concentrations, CAGTE exhibited direct anti-proliferative effects, in line with the reputed anti-cancer properties of green tea polyphenols. These results demonstrate that potentially bioavailable green tea metabolites are able to ameliorate both H(2)O(2) and Aß((1-42)) induced cytotoxicity.

Neonatal lamb vigour is improved by feeding docosahexaenoic acid in the form of algal biomass during late gestation.

To determine whether feeding a sustainable, algal source of docosahexaenoic acid (DHA) to sheep during late pregnancy would improve neonatal lamb vigour, 48 English mule ewes, of known conception date, were divided into four treatment groups. For the last 9 weeks of gestation, ewes received one of two dietary supplements: either a DHA-rich algal biomass providing 12 g DHA/ewe per day, or a control supplement based on vegetable oil. The four dietary treatment groups (n = 12) were: control supplement for the duration of the trial (C), DHA supplement from 9 to 6 weeks before parturition (3 week), DHA supplement from 9 to 3 weeks before parturition (6 week) and DHA supplement for the duration of the trial (9 week). Dietary supplements were fed alongside grass silage and commercial concentrate. There was a tendency for gestation length to be extended with increased duration of DHA supplementation (P = 0.08). After parturition, the concentrations of eicosapentaenoic acid (EPA) and DHA in ewe and lamb plasma and colostrum were elevated in line with increased periods of DHA supplementation. Lambs from the 6-week and 9-week groups stood significantly sooner after birth than lambs from the C group (P < 0.05). These data show that neonatal vigour may be improved by the supplementation of maternal diets with DHA-rich algal biomass and that this beneficial effect depends upon the timing and/or duration of DHA allocation.

Whole-grain intake of British young people aged 4-18 years.

Inverse associations between whole-grain food consumption and risk of CVD, some cancers and type 2 diabetes have been reported. However, there are few reports of whole-grain intake, particularly among young people. The objective of the present study was to estimate whole-grain intake in a nationally representative sample of young people aged 4-18 years living in Great Britain. Whole-grain intake was estimated using 7 d weighed dietary records from 1583 young people who participated in the cross-sectional National Diet and Nutrition Survey in 1997. Whole-grain intake was quantified from the consumption of all foods containing > or =10 % whole-grain content. Median whole-grain intake was 7 g/d (interquartile range 0-19 g/d), with a corresponding mean of 13 (sd 18) g/d. Intake was significantly lower among young people whose head of household had a manual occupation, but did not differ significantly by sex, age, region or season. There was no whole-grain intake for 27 % of participants. The percentages for less than one and less than three 16 g amounts of whole-grain intake per d were 70 and 94, respectively, while corresponding percentages based on 20 g amounts were 76 and 97. Foods with <51 % whole-grain content provided 28 % of whole-grain intake overall, with a higher percentage in older adolescents. The main sources of whole-grain intake were breakfast cereals (56 %) and bread (25 %). The present study provides the first quantification of absolute whole-grain intake from all significant food sources in any representative age group in the UK. Although there is some debate regarding the quantity of whole grains required for good health, whole-grain intake among British young people is low.

Influence of dietary picolinic acid on mineral metabolism in the rat.

Male rats were fed isonitrogenous, isocaloric diets containing different amounts of dietary zinc and picolinic acid (PA) (25, 60, 120 ppm Zn, 0, 20, 40, 60 mmol PA/kg diet) and balance collections of urine and faeces made over a 4-day period. Rats fed 25 ppm Zn were in negative Zn and Cu balance during the experiment. Faecal Zn, but not urinary Zn excretion was elevated with increasing dietary Zn supply. Urinary Zn, Cu and Mg excretion increased with increasing intakes of dietary PA, regardless of Zn intake. Tissue Zn levels were unaffected by dietary Zn or PA. It is concluded that dietary PA forms soluble complexes with metal ions which are rapidly absorbed but are then re-excreted in urine and may not be available for metabolism or incorporation into tissues.

Zinc transfer among proteins in rat duodenum mucosa.

Duodenums from freshly killed stock colony rats were incubated in Krebs buffer containing carrier-free 65ZnCl2 for periods of time between 5 and 60 s. Mucosa cytosol was separated and fractionated by gel filtration on Sephadex G-75. 65Zn was present in two main bands of protein with molecular weights of about 45,000 and 6,500, but the ratio between them rose progressively with time of exposure to the isotope. Addition of metabolic inhibitors greatly lowered the 45,000/6,500 ratio for 65Zn. It is concluded that when zinc enters the mucosal cytoplasm during absorption, it rapidly binds to the 6,500 protein in a passive way and is then transferred to the protein of molecular weight 45,000 by an active process.

Intestinal zinc transfer by everted gut sacs from rats given diets containing different amounts and types of dietary fibre.

Two experiments were carried out in which rats were offered diets containing different amounts and types of dietary fibre, i.e. commercial stock diet and three semi-purified diets containing no fibre, 200 g wheat bran or 200 g pectin/kg. Dietary inclusion of fibre, and especially pectin, stimulated large bowel fermentation, as indicated by caecal hypertrophy and reduced caecal pH. After 3 weeks, mucosal:serosal zinc transfer and Zn accumulation by tissue were measured using the everted-gut-sac technique. In Expt 2, incubations were carried out in the presence and absence of 0.25 mM-ouabain to assess the importance of transfer by Na+,K+-ATPase-dependent mechanisms, and some observations on glucose transport were also made. Ouabain reduced rates of transfer of both Zn and glucose and also tissue Zn accumulation. There were no significant differences in rates of Zn transfer by everted sacs from duodenal, ileal and colonic sites, but accumulation of Zn by tissue was a more important fate than transfer across the serosal surface, and accumulation by duodenal tissue was approximately twice as great as by other tissues. Mucosal:serosal transfer of glucose by ileal tissue was much more sensitive to ouabain than was Zn transfer. Previous diet appeared to alter the capacity of the intestinal tissue to transfer Zn, with the highest rates of transfer being by colonic tissue from pectin-fed rats.