bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of the changes in systemic copper metabolism and excretion produced by the intravenous administration of trithiomolybdate in sheep
Authors: Mason J. , Lamand M. , Tressol J. C. , Mulryan G. 
Published: May 2005

1. The effects of intravenous trithiomolybdate administration on the fate of 64Cu and on stable Cu metabolism were examined in sheep held in metabolism cages and fed on a low-Cu diet supplying 2·95 mg Cu/animal per d.2. In Expt 1 the injection of trithiomolybdate, 30 mg molybdenum/sheep per d for 5 d, greatly increased plasma Cu levels and more than doubled the faecal Cu excretion. Urinary Cu excretion was unaffected. The disappearance from plasma of 64Cu injected during the trithiomolybdate administration was slowed although faecal 64Cu excretion was increased more than threefold.3. In Expt 2 trithiomolybdate, 10 and 30 mg Mo/sheep per d for 3 d, was administered 22 h after the injection of 64Cu. Radioactivity reappeared immediately in plasma and faecal 64Cu excretion was increased.4. In both experiments the 64Cu and the increased stable Cu in plasma were associated with albumin.5. The experiments explain the effectiveness of thiomolybdates as ‘decoppering’ agents and provide a model for some of the systemic effects seen in ruminants exposed to increased dietary Mo. The experiments support the view that the thiomolybdates, by causing the appearance of new ligands, alter the distribution of Cu in tissues and cause an overall depletion.
Effect of nitrate and its reduction products on the growth and activity of the rumen microbial population
Authors: Marais J. P. , Therion Joha J. , Mackie R. I. , Kistner A. , Dennison C. 
Published: May 2005

1. The nature of the digestion-inhibiting substance in Kikuyu grass (Pennisetum clandestinum, Hochst), containing high levels of nitrate, was investigated using in vitro digestibility techniques.2. Nitrite, which accumulated during the reduction of nitrate to ammonia, seemed to be the primary factor reducing digestibility. Nitrate and ammonia did not affect digestion in vitro.3. Nitrite caused a reduction in the cellulolytic, xylanolytic and total microbial population, with a concomitant reduction in cellulase and xylanase activity of the digesta.4. The mode of action of nitrite on rumen microbial growth was investigated.5. The possibility that the growth of cellulolytic rumen microbes was depressed by a reduction in concentration of essential branched-chain volatile fatty acids by nitrite was discounted.6. Although nitrite caused a marked increase in the redox potential, due to its oxidizing properties, the more-positive redox potential did not reduce the digestibility of the grass.7. The growth of three of the four major cellulolytic bacteria commonly found in the rumen was severely depressed by nitrite, while some rumen bacteria were relatively insensitive to nitrite.8. Growth inhibition seemed to depend primarily on the extent to which these microbes derive their energy from electron-transport-mediated processes.9. It was suggested that, due to the sensitivity of some rumen bacteria to nitrite, digestibility and therefore animal performance could be affected long before clinical symptoms of nitrite toxicity become apparent.
Fetal growth, glucose tolerance and plasma insulin concentration in rats given a marginal-zinc diet in the latter stages of pregnancy
Authors: Southon Susan , Fairweather-Tait Susan J. , Williams Christine M. 
Published: May 2005

1. Wistar rats were fed on a control semi-synthetic diet throughout pregnancy, or a control diet in the first 2 weeks and a marginal-zinc diet in the 3rd week of pregnancy. On day 20, after an overnight fast, half the animals in each group were given glucose by gavage and the 0–30 min rise in blood glucose measured in tail blood. After 60 min blood was taken by cardiac puncture for glucose and insulin assay. Maternal pancreases were removed and the Zn contents measured. Fetuses from each litter were combined for wet/dry weights, protein and DNA determinations.2. Plasma insulin concentration was higher, and glucose concentration and pancreatic Zn content lower, in pregnantv. non-pregnant animals of similar age, fed on the same diet. Pancreatic Zn content was lowest in the marginal-Zn group of pregnant rats. Fetuses from mothers fed on the marginal-Zn diet during the last week of pregnancy were slightly heavier than controls and had a significantly higher protein: DNA ratio. The 0–30 min rise in blood glucose was significantly greater in the marginal-Zn animals.3. In a second experiment, pregnant rats were given similar diets to those used in the first study, but the marginal-Zn diet was given for a shorter period (days 15–19 of pregnancy). On day 19 the rats were meal-fed and on day 20, after an overnight fast, an oral glucose dose was administered. Tail-blood was taken at timed intervals up to 60 min post-dosing for glucose assay. Both maternal and fetal blood glucose and insulin concentration was measured 70 min post-dosing.4. Values for maternal and fetal blood glucose and plasma insulin, measured 70 min after the administration of a glucose dose, were similar in the two groups, but the initial rise in blood glucose concentration was again significantly higher in pregnant rats given the marginal-Zn diet towards term.5. It is suggested that the change in growth and composition, observed in fetuses from rats given a marginal-Zn diet in later pregnancy, is associated with altered maternal carbohydrate metabolism.
Leucine degradation in sheep
Authors: Bergen W. G. , Busboom J. R. , Merkel R. A. 
Published: May 2005

1. In vitro leucine catabolism in adipose tissue, skeletal muscle, kidney and liver homogenates was studied in sheep.2. In Expt 1, Suffolk × Targhee ram lambs were slaughtered at 1, 28, 56, 84, 112, 140, 168, 196, 224 and 365 d of age. In Expt 2, 5-month-old crossbred wethers were fed on 80, 120 or 180 g crude protein (nitrogen × 6·25) /kg diets for 4 weeks or fed on 120 g crude protein/kg for 4 weeks and then fasted for 48 or 96 h before slaughter. Leucine catabolism was assayed in tissue homogenates for Expts 1 and 2.3. Leucine deamination (per unit protein) was highest in skeletal muscle at day 1 and then declined; liver exhibited an activity pattern akin to muscle while kidney activity tended to rise over the duration of the study. Adipose tissue in vitro leucine deamination was higher at all ages studied and 9- to 50-fold higher than all other tissues at 365 d. Leucine decarboxylation (per unit protein) was highest at day 1 in muscle and declined to low levels (P< 0·01) after 28 d; liver and kidney decarboxylation activities were higher than muscle at all ages with kidney showing the highest activity. Whilst adipose had high initial activity it declined significantly (P< 0·01) by day 28 and remained low.4. Dietary protein intake had no effect on leucine deamination in any tissue. Leucine decarboxylation tended to increase with protein intake for all tissues except kidney. Length of fast (96 h) resulted in a variable decline in leucine deamination; leucine decarboxylation was significantly lower in kidney, liver and adipose tissue after a 96 h fast.5. When these in vitro enzyme activity results are related to questions concerning the role of skeletal muscle in leucine catabolism in sheep, the present findings indicate that in grown sheep, skeletal muscle has a small to moderate role in total body leucine deamination but plays a very minor role in leucine decarboxylation. Adipose tissue appears to be a major site of leucine deamination in grown sheep. These results are not in agreement with the idea that during fasting leucine becomes an important energy substrate and is oxidized in skeletal muscle as has been shown in rodents.
Nutrient sensitivity of gastric emptying of digesta in the preruminant calf
Authors: Sissons J. W. , Bell F. R. , Girard C. L. , Wass J. A. H. 
Published: May 2005

1. Studies of gastric function were made in preruminant calves fitted with a single abomasal cannula, re-entrant cannulas in the duodenum close to the pylorus and recording electrodes on the pyloric antrum and proximal duodenum.2. Simultaneous measurements were made of gastric emptying of a saline (9 g sodium chloride/1) meal, myoelectric activity of antral muscle and plasma concentration of somatostatin in jugular blood whilst infusing the duodenum with different solutions. The duodenal infusates were isotonic sodium bicarbonate (300 mosmol/kg), hyperosmolar solutions of NaCl (1000 mosmol/kg), sodium carbonate (500 mosmol/kg), sucrose (1000 mosmol/kg), 41 g emulsified butterfat/kg or 60 mM-hydrochloric acid.3. Infusing the duodenum with isotonic NaHCO3 stimulated intense myoelectric activity of the antral smooth muscle and rapid emptying of the test meal. In contrast, infusions of 60 mM-HCl reduced antral motility and inhibited gastric emptying of digesta. This inhibitory response to HCl infusion was related to a significant (P < 0·05) increase of somatostatin in peripheral venous blood.4. The Na2CO3 infusate, like HC1, inhibited gastric motor activity and digesta emptying, but the concentration of circulating somatostatin was only slightly elevated above pre-infusion levels.5. Compared with the effects of infusing HCl, infusions of emulsified butterfat or hyperosmolar NaCl and sucrose induced a greater intensity of antral motor activity and faster outflow of gastric effluent, although not to the same extent as with isotonic NaHCO3. However, as with isotonic NaHCO3, these infusates did not evoke the release of somatostatin.6. The results support the concept of duodenal receptors which, in response to a variety of stimuli in gastric chyme, modulate stomach emptying of digesta through actions on contractile processes of antral smooth muscle. Activation of such receptors by fat or osmotic stimuli, both ionic and non-ionic, do not appear to involve the release of somatostatin. However, the hormone appears to have an entero-gastrone role in mediating the inhibitory action of HCI on gastric motor function.
Circadian variation in fat concentration of breast-milk in a rural northern Thai population
Authors: Jackson Dorothy A. , Imong Stella M. , Silprasert A. , Ruckphaopunt S. , Woolridge M. W. , Baum J. D. , Amatayakul K. 
Published: May 2005

1. Twenty-five northern Thai mothers, breast-feeding their infants on demand, were studied in their homes for 24 h. All breast-feeds were test-weighed and pre- and post-feed expressed breast-milk samples (0·5 ml) taken at each feed.2. The fat concentration of milk taken during a feed showed significant circadian variation, with maximum values between 16.00 and 20.00 hours and minimum values between 04.00 and 08.00 hours. Fat concentration at the start and at the end of a feed also varied significantly over 24 h.3. Multiple regression analysis showed that the most important predictor of fat concentration at a feed was the length of time elapsed since the previous feed – the longer this interval, the lower the subsequent fat concentration. Other significant predictors were the fat concentration at the end of the previous feed, and the milk intake at the previous and at the current feed.4. Fat concentration declined between feeds in proportion to the length of time between feeds, but the decline was less between sleep feeds than between waking feeds. This would appear to be a reflection of the lower post-feed fat concentration and higher pre-feed fat concentration of sleep feeds compared with waking feeds, when other variables relating to feeding pattern are taken into account.5. The larger the milk intake at a feed, the greater was the increase in fat concentration from the start to the end of the feed. The change in fat concentration was less in feeds taking place during the sleep period than in daytime feeds.
Estimation of 24 h breast-milk fat concentration and fat intake in rural northern Thailand
Authors: Jackson Dorothy A. , Imong Stella M. , Silprasert A. , Preunglumpoo S. , Leelapat P. , Yootabootr Y. , Amatayakul K. , Baum J. D. 
Published: May 2005

1. The present study assesses the accuracy with which mean 24 h breast-milk composition can be estimated if milk samples can only be collected during the daytime.2. Twenty-five northern Thai mothers, feeding their infants on demand, were studied in their homes for 24 h. All feeds were test-weighed and 0·5 ml pre- and post-feed expressed milk samples taken at each feed.3. If daytime sampling was restricted to two breast-feeds, it was found that the best estimate of 24 h fat concentration was given by two randomly chosen daytime feeds, predicting 24 h fat concentration with 95% confidence limits of ±7·0 g/l (equivalent to 21% of mean 24 h fat concentration).4. Alternative sampling methods using the mean fat concentration of the feed after 08·00 hours and after 18·00 hours, or the first two feeds after 12·00 hours, predicted fat concentration with 95% confidence limits of ±9·7 g/l and ±8·9 g/l (28 and 26% of mean 24 h fat concentration) respectively.5. If well-tolerated by mothers, it would be preferable to sample all daytime feeds, since this reduces the 95% confidence limits to ±3·3 g/l, equivalent to 10% of the mean 24 h fat concentration.
Modifications of gastric inhibitory polypeptide (GIP) secretion in man by a high-fat diet
Authors: Morgan L. M. , Hampton S. M. , Tredger J. A. , Cramb R. , Marks V. 
Published: May 2005

1. Five healthy volunteers (usual fat intake 103) (SE 9) g/d and energy intake 9855 (SE 937) kJ/d were given on two separate occasions (a) 100 g oral glucose and (b) sufficient intravenous (IV) glucose to obtain similar arterialized plasma glucose levels to those after oral glucose.2. Subjects increased their fat intake by 68 (SE 9·6) % for 28 d by supplementing their diet with 146 ml double cream/d (fat intake on high-fat diet (HFD) 170 (SE 8) g/d; energy intake 12347 (SE 770)).3. The 100 g oral glucose load was repeated and IV glucose again given in quantities sufficient to obtain similar arterialized blood glucose levels. Immunoreactive plasma insulin, C-peptide and gastric inhibitory polypeptide (GIP) were measured.4. Plasma GIP levels were higher following oral glucose after the HFD (area under plasma GIP curve 0–180 min 1660 (SE 592) v. 2642 (SE 750) ng/l.h for control and HFD respectively; P < 0·05). Both insulin and C-peptide levels were significantly higher after oral than after IV glucose (P < 0·01) but neither were affected by the HFD. Glucose levels were lower following the HFD after both oral and IV glucose (area under plasma glucose curve 0–180 min, following oral glucose 6·7 (SE 0·3) mmol/l.h for control and 4·2 (SE 0·6) mmol/l.h for HFD; P < 0·01).5. Glucose-stimulated GIP secretion was thus enhanced by the HFD. Insulin secretion in response to oral glucose was unchanged, in spite of an improvement in glucose tolerance.6. The improvement in glucose tolerance post-HFD could possibly be due to a GIP-mediated inhibition of hepatic glycogenolysis, or a decreased rate of glucose uptake from the small intestine.
The effect of riboflavin deficiency in rats on the absorption and distribution of iron
Authors: Powers Hilary J. , Wright A. J. A. , Fairweather-tait Susan J. 
Published: May 2005

1. Riboflavin may play a part in the transport of iron across the gastrointestinal mucosa. Fe absorption was measured in the rat by monitoring whole-body retention of a dose of 59Fe using a small-animal γ-counter.2. Female Norwegian Hooded rats were fed on a diet deficient in riboflavin (B2−) from 5 weeks of age. Control animals, fed on a complete diet (B2+), were weight-matched to rats fed on the B2− diet. After 7 weeks all rats were fed on a test meal extrinsically labelled with 59Fe and whole-body radioactivity measured for 15 d.3. Riboflavin deficiency was associated with a reduction in the percentage of the dose absorbed and an increase in the rate of loss of Fe post absorption.4. A smaller percentage of the absorbed dose was present in the livers of the riboflavin-deficient animals.
The effect of three types of saponin on iron and zinc absorption from a single meal in the rat
Authors: Southon Susan , Wright A. J. A. , Price K. R. , Fairweather-Tait S. J. , Fenwick G. R. 
Published: May 2005

1. Iron and zinc retentions in young male rats, given 3 g starch–sucrose paste containing 120 μg Fe as FeSO4or 139 μg Zn as ZnC12(extrinsically labelled with59Fe or65Zn) and increasing amounts ofGypsophilasaponins, were measured by whole-body counting. The results were compared with whole-body Fe and Zn retention from a meal containing crude or purified saponin fractions. In a separate experiment Fe retention from a meal containingGypsophilasaponins, soyasaponin I, or saponins extracted from lucerne (Medicago sativa) plant tops, was measured in older rats.2. Results indicated that Fe absorption decreased with increasing concentration ofGypsophilasaponins. This was significant at a saponin: Fe molar value of approximately 1, with maximum effect occurring at molar ratios of 4 and above, when Fe absorption was reduced by approximately 17%.Gypsophilasaponins had no effect on Zn absorption from a test meal.3. Fe absorption was similar in groups given purified or crudeGypsophilasaponins at the same saponin: mineral molar value of 8, demonstrating that the ‘non-saponin’ fraction of the commercial preparation does not affect the absorption of this mineral.4. Saponins extracted from lucerne plant tops, fed at a saponin:Fe value of approximately 8, also reduced Fe absorption from a single meal. Fe absorption from a meal containing a similar amount of soyasaponin I was not significantly different from controls.5. These results indicate that some dietary saponins may reduce Fe absorption and hence have an adverse effect on Fe status in man and simple-stomached animals.
Influence of prostaglandins on unidirectional zinc fluxes across the small intestine of the rat
Authors: Song Moon K. , Lee David B. N. , Adham Nabeel F. 
Published: May 2005

1. The regulatory role of prostaglandins (PGs) E2and F2aon the zinc transport rate across the jejunal segments of rats was examined by employing the Ussing chamber technique. The Zn flux rate from mucosa to serosa across jejunal segments (Jms) was 5·24 (SE 1·54) nmol/h per cm2(n48) and that from serosa to mucosa (Jsm) was 15·16 (SE 2·38) nmol/h per cm2(n48) when both sides of the segment were bathed with Ringer's bicarbonate solution containing 0·5 mM-zinc chloride and 3 mM-L-histidine.2. When 5·0 or 50 μM of either PGE2or PGF2αwere added to the serosal side of the tissue,Jsmgenerally decreased andJmsgenerally increased, compared with controls. On the other hand, when PGE2or PGF2αwas added to the mucosal side of the tissue,Jmseither did not change or increased whileJsmhad a tendency to decrease.3. The Zn uptake capacity of tissue increased significantly when PG was added to the serosal side of the tissuebathing medium, but not when PG was added to the mucosal side. The uptake capacity of mucosal Zn by jejunal segments was approximately twice that of serosal Zn.4. When PG was included in the tissue-bathing medium, the short-circuit current, potential difference and conductance between the mucosa- and serosa-bathing media generally decreased.5. These results suggest that (a) PGs influence Zn flux rate not by chelating Zn and carrying it across the mucosal cell membrane but by interacting with the cytosolic components, (b) it is the serosal PGs which control the Zn flux rate and (c) PGs play a part in triggering a transduction mechanism in the intestinal Zn transport process.
Dynamics of protozoa in the rumen of cattle
Authors: Ffoulkes D. , Leng R. A. 
Published: May 2005

1. The dynamics of protozoa were studied in two groups of rumen-fistulated cattle fed on a basal diet of molassesad lib., with oaten chaff given at 6 or 18 g/kg live weight. This diet resulted in different mixtures of protozoal species in the populations in the rumen.2. The rumen protozoa were studied by intrarumen injections of protozoa labelled in vitro with [14CH3]choline. An indication of protozoal death and fermentation of protozoal cell residues was obtained by measuring14C loss via the methane pool.3. After a single injection of labelled protozoa, the decline in the specific radioactivity (μCi/g nitrogen) of the protozoal pool in the rumen indicated that first-order kinetic processes applied. Conversely the specific radioactivity of protozoa, incubated in rumen fluid, remained constant indicating no growth in vitro, presumably owing to a rapid exhaustion of essential nutrients.4. The protozoal populations in the rumen of cattle fed on the diet with the low level of oaten chaff were mainly small ciliates; but on the higher level of chaff in the diet, the large ciliates were a higher proportion of the total protozoal population present.5. The mean pool size of protozoa in the rumen was significantly larger and the protozoal half-life tended to be longer for cattle fed on the higher level of chaff in the diet. The apparent production rate of protozoa in cattle fed on each diet was not significantly different and there were no differences in the production rate of methane. The percentage losses of label from protozoa in the rumen via the methane pool were not significantly different on the two diets and indicated that 74% of the protozoa that were apparently irreversibly lost from the rumen could be accounted for by death and lysis in the rumen and therefore only 26% of protozoa apparently entered the lower digestive tract.
A possible relation between dietary zinc and cAMP in the regulation of tumour cell proliferation in the rat
Authors: Skeef Noel S. , Duncan John R. 
Published: May 2005

1. The possibility of an effect of zinc on the rate of tumour cell division, mediated through a regulation of cellular cAMP concentration, was investigated in the present study in rats.2. Dietary Zn deficiency (< 1·5 mg Zn/kg) but not Zn excess (500 mg Zn/kg) resulted in an increased cAMP concentration in transplanted hepatoma cells. Neither treatment had any effect on the cAMP concentration in regenerating liver or normal resting liver. Both the deficient and excess Zn diets resulted in a small reduction in tumour growth (not statistically significant).3. The results seem to indicate that the relation investigated in the present study does not apply in the cell line used.
The β-carotene-rich alga Dunaliella bardawil as a source of retinol in a rat diet
Authors: Ben-Amotz A. , Mokady S. , Avron M. 
Published: May 2005

1. Dunaliella bardawil, a β-carotene-accumulating alga, has been tested as a source of retinol and β-carotene in a diet given to rats. The β-carotene in this alga is composed of about equal amounts of the 9-cis and all-trans isomers. Male weanling rats were fed on a retinol-deficient diet for 60 d. Thereafter, the rats were divided into groups and fed on a diet deficient in retinol or supplemented with retinol, synthetic β-carotene, dry alga or an algal oil-extract. Following further growth for 7 d, samples were taken for liver analyses of retinol, retinol isomers and β-carotene.2. Liver analyses revealed a comparable content of retinol and normal conversion rates in the rats grown on the diets supplemented with synthetic or natural β-carotene. Rats fed on the alga and the algal-oil-supplemented diets accumulated 9-cis retinol in addition to the all-trans isomer. Rats fed on synthetic β-carotene, alga and algal oil had a liver retinol: β-carotene value of about 3:1.3. These studies demonstrate the possibility of using dried D. bardawil or an oil extract of the alga as a dietary natural β-carotene supplement which satisfies the total requirement of retinol in rats.4. Rats fed on alga or on algal oil, accumulated in the liver 9-cis β-carotene and all-trans β-carotene in a ratio similar to that present in the alga.