Showing papers in "British Journal of Nutrition in 1981"

The effect of dietary supplements of omega 3 polyunsaturated fatty acids on the fatty acid composition of platelets and plasma choline phosphoglycerides.

Abstract: 1. The effects of dietary supplements of omega 3 polyunsaturated fatty acids on the fatty acid composition of platelets and plasma choline phosphoglycerides were studied in vegans and in omnivores. 2. A supplement of 18:3 omega 3 led to an increase in 20:5 omega 3 but was less effective than one of 20:5 omega 3 + 22:6 omega 3.

Characteristics of the rumen proteolysis of fraction I (18S) leaf protein from lucerne (Medicago sativa L)

Abstract: 1. The rate of proteolysis of fraction I (18S) leaf protein in the rumen of sheep of cattle was affected by diet ans the rate on fresh lucerne (medicago sativa L) was three to nine times the rate on a hay + concentrate diet. 2. Simultaneous rumen fermentations in vivo and in an artificial rumen showed that the rates of proteolysis of fraction I in vitro was approximately 30% of the rates in sheep. 3. Using 14 C uniformly-labelled fraction I protein at low concentrations, proteolysis exhibited 1st-order kinetics. Over a wide range of protein concentrations the velocity v. substrate concentration curve showed Michaelis-Menten characteristics typical of an enzyme-catalysed reaction. With rumen fluid from a hay + concentrate-fed sheep the maximum velocity was 2.6 mg protein nitrogen/1 per min and the Michaelis constant was 75 mg nitrogen/l. 4. Rapid absorption of 14C-labelled fraction I protein onto bacterial cells preceded proteolysis. 5. Sucrose-density-gradient analysis showed initial incorporation of 14C from protein into rumen bacteria followed by partial transfer to rumen protozoa. 6. No peptides were detected during proteolysis showing that the rate-limiting step occurred during the initial stages of proteolysis. Only small amounts of free amino acids were released except for leucine, isoleucine, valine and ornithine, which showed significantly increased levels. 7. Volatile fatty acids were the main 14C-labelled end products and were rapidly produced in descending concentrations: acetate greater than propionate greater than 3-methyl + 2-methyl butyrate greater than butyrate greater than isobutyrate greater than valerate.

Experimental model for in vivo determination of dietary fibre and its effect on the absorption of nutrients in the small intestine

Abstract: 1. An experimental model for the determination of dietary fibre according to the definition of Trowell et al. (1976) is described. Food was subjected to in vivo digestion in ileostomy patients, and the ileostomy contents were collected quantitatively, the polysaccharide components of which were analysed by gas--liquid chromatography and the Klason lignin by gravimetric determination. The model was used for the determination of dietary fibre in AACC (American Association of Cereal Chemists), wheat bran and for studies on the extent of hydrolysis of wheat-bran fibre in the stomach and small intestine. The effect of wheat bran on ileostomy losses of nitrogen, starch and electrolytes was also investigated. 2. Nine patients with established ileostomies were studied during two periods while on a constant low-fibre diet. In the second period 16 g AACC wheat bran/d was added to the diet. The ileostomy contents and duplicate portions of the diet were subjected to determinations of wet weight, dry weight, water content, fibre components, starch, N, sodium and potassium. 3. The wet weight of ileostomy contents increased by 94 g/24 h and dry weight by 10 g/24 h after consumption of bran. The dietary fibre of AACC bran, determined as the increase in polysaccharides and lignin of ileostomy contents after consumption of bran, was 280 g/kg fresh weight (310 g/kg dry matter). Direct analysis of polysaccharides and lignin in bran gave a value of 306 g/kg fresh weight. Of the added bran hemicellulose and cellulose 80--100% and 75--100% respectively were recovered in ileostomy contents. There was no significant difference between the two periods in amount of N, starch and K found in the ileostomy contents. The Na excretion increased during the 'bran' period and correlated well with the wet weight of ileostomy contents. 4. In conclusion, it seems probable that determination of dietary fibre by in vivo digestion in ileostomy patients comes very close to the theoretical definition of dietary fibre, as the influence of bacteria in the ileum seems small. Bacterial growth should be avoided by using a technique involving the change of ileostomy bags every 2 h and immediate deep-freezing of the ileostomy contents. True dietary fibre can be determined by direct analysis of polysaccharides and lignin in the food, at least in bran. Very little digestion of hemicellulose and cellulose from bran occurs in the stomach and small bowel. The 10--20% loss in some patients may be due to digestion by the gastric juice or to bacterial fermentation in the ileum, or both. The extra amount of faecal N after consumption of bran, reported by others, is probably produced in the large bowel.

An examination of factors which may affect the water holding capacity of dietary fibre.

Abstract: 1. Dietary fibre has a water holding capacity (WHC) and this is a function of the fibre source and method of measurement. Water can be associated with fibre either as trapped water or bound water. This makes it difficult to predict the ability of fibre to influence stool weight in humans. 2. Examination of various fibre concentrates for chemical composition, as neutral detergent fibre (NDF), acid detergent fiber (ADF) and lignin; structure, by scanning electron microscopy; WHC, by centrifugation, suggests that WHC is more a function of fibre structure than chemical composition. Cereal fibre and vegetable fibre have a different chemical composition and are structurally very distinct. Structure is also dependent on the method of fibre preparation. 3. Measurement of WHC by centrifugation gives an estimate of the water which can be bound and also trapped by the fibre. The amount of trapped water will depend on the structure of the fibre whereas bound water will depend on the chemical composition.

Acetate supply and utilization by the tissues of sheep in vivo.

Abstract: 1. The supply and utilisation of acetate has been estimated simultaneously in the whole animal and tissues of sheep using a combination is isotope-dilution and arteriovenous-difference techniques. Animals were made alloxani-diabetic and acetate metabolism was compared when stabilized to normal metabolite levels with insulin (ITA sheep) and when food and insulin had been withdrawn for 36 h (fasted, diabetic sheep). 2. Acetate was simultaneously produced and utilized by all tissues. The exogenous (or gut) supply of acetate was the most important determinant of circulating acetate level. Endogenous acetate was produced mainly in the liver; 77 and 94% in fasted, diabetic and ITA sheep respectively. The production of endogenous acetate remained fairly constant and was not related to ketogenesis, which supports the idea that circulating acetate is largely a produce of fermentation. The liver, gut and muscle utilized 17, 25 and 54% respectively (96% total) of the acetate entry rate in ITA sheep; a similar percentage utilization was found in fasted, diabetic sheep. 3. Acetate is largely oxidized to carbon dioxide in the gut and muscles of sheep and may account for 30-40% of their oxidative metabolism. This figure is similar to that for the whole animal. The total acetate taken up by the liver could account for 30% of the oxygen consumption; however, the liver may not directly oxidize all the utilized acetate. 4. The over-all conclusion from this study is that acetate is largely of dietary origin and the major factor determining its rate of utilization is the arterial concentration.

Availability to pigs of amino acids in cereal grains. 1. Endogenous levels of amino acids in ileal digesta and faeces of pigs given cereal diets.

Abstract: 1. Endogenous levels of amino acids in ileal digesta were determined as the output from pigs given protein-free diets and by extrapolation to zero intake of linear regressions of ileal amino acid output v. dietary amino acid intake. The protein-free diets included 0 or 50 g cellulose/kg and extrapolations were made from two series of four diets which contained graded levels of wheat or barley as the only source of protein. Within each series, dietary fibre level (mg/g) was maintained at approximately 140 or 190 neutral-detergent fibre (NDF) respectively. Endogenous amino acid levels in faeces were also determined. 2. Endogenous amino acid output in faeces was linearly related to dietary fibre level; endogenous ileal output increased with dietary fibre up to approximately 100 mg NDF/g, after which endogenous output no longer increased. 3. The amino acid composition of endogenous ileal protein varied little among levels of output and among different experiments. The composition appears to be determined by the predominance of mucin protein, the slow absorption of some acids and the methods commonly used to measure output. The very high levels of proline and glycine in ileal digesta seemed characteristic only of protein-free and low-protein diets. 4. The amino acid composition of endogenous faecal protein also varied little among different estimates, but was considerably different from that of endogenous ileal protein. Furthermore, the similarity of bacterial and faecal proteins suggested that much of the endogenous faecal protein was of bacterial origin.

Quantitative studies of food protein degradation and the energetic efficiency of microbial protein synthesis in the rumen of sheep given chopped lucerne and rolled barley

Abstract: 1. In a randomized block design, four sheep were given 800 g daily of diets containing: chopped lucerne (L), chopped lucerne-rolled barley (2:1; LB), rolled barley-chopped lucerne (2:1; BL), rolled barley (B); each diet was supplemented with minerals, vitamins and urea as considered necessary. Chronic oxide was included in the diets as a flow marker. 2. Flows of organic matter (OM) and non-ammonia-nitrogen (NAN) to the small intestine (SI) were measured and microbial protein was identified by a 35S-incorporation procedure. 3. OM disappearance in the rumen increased linearly with increasing inclusion of barley in the diet but there was no significant change in microbial NAN flow to the SI so that the yield of microbial NAN (g)/kg fermented OM (FOM) decreased from 29.6 (diet L) to 22.7 (diet B). Changes in the energetic efficiency of microbial protein synthesis appeared to be unrelated to alterations in rumen fluid volatile fatty acid (VFA) proportions or in rumen fluid dilution rate (D). 4. The degradability of dietary protein (non-urea-N), estimated using the 35S procedure, was 0.72, 0.76, 0.86 and 0.86 for diets L, LB, BL and B respectively. Similar values were obtained from concurrent polyester-bag experiments when the fractional outflow rate of undegraded protein from the rumen (k) was assumed to be 0.046.

Influence of mild cold on 24 h energy expenditure, resting metabolism and diet-induced thermogenesis

Abstract: UNLABELLED 1. It has been suggested previously that people in developed countries do not expose themselves to cold severe enough to induce a metabolic response. The energy expenditure, at both heat production and total heat loss, of nine women was therefore measured continuously while each lived for 30 h in a whole-body calorimeter on two occasions, one at 28 degrees and the other at 22 degrees. All subjects followed a predetermined pattern of activity and food intake. The environmental conditions were judged by the subjects to be within those encountered in everyday life. In the standard clothing worn, 28 degrees was considered to be comfortably warm but not too hot, while 22 degrees was judged to be cool but not too cold. 2. Heat production for 24 h was significantly greater at the lower temperature, by (mean +/- SE) 7 . 0 +/- 1 . 1%. The range was between 2 and 12%. Total heat loss was also significantly greater, by 6%, and there was a large change in the partition of heat loss. At the lower temperature sensible heat loss increased by 29% while evaporative heat loss decreased by 39%. 3. Resting metabolism measured in the morning 12--13 h after the last meal was significantly greater at 22 degrees than at 28 degrees, whereas there was no difference when the resting measurement was made for 2 . 5 h following a meal. 4. IN CONCLUSION (a) environmental temperature may play a more important role than was previously recognized in the energy balance of those living in this country, and (b) there is an indication of at least a partial replacement of cold-induced by diet-induced thermogenesis in man.

The diet of individuals: a study of a randomly-chosen cross section of British adults in a Cambridgeshire village

Abstract: 1. The dietary intakes of sixty-three adults, randomly-selected from the electoral role of a large village near Cambridge, have been measured using the weighed-intake technique for 7 d. 2. Mean (+/- SD) daily intakes (g) for men and women respectively were: energy (MJ) 10.0 +/0 2.4, 8.2 +/- 2.1; fat 104 +/- 27, 90 +/- 27; protein 77 +/- 20, 67 +/- 16; carbohydrate 285 +/- 81, 229 +/- 74; sucrose 91 +/- 47, 57 +/- 33. 3. When interviewed at the end of the study 40% of subjects said they were watching their weight. 4. Women ate less food over all than men, and proportionately less potato and bread, and used only one-third as much sugar in drinks, probably in an attempt to control their weight. Men took considerably more alcohol than the women. In the age-group 20-39 years alcohol provided 9% (1.0 MJ/d) of the total energy intake in the men. 5. Wide variation in the intake of nutrients was observed amongst the individuals. For vitamin C and fibre intake this was partly partly explained by seasonal variation but for most nutrients total energy intake and food choice were the main determinants. The range of intakes of nutrients such as fat was similar in these individuals to that seen amongst countries internationally. It is suggested that if differences in nutrient intake amongst the various populations of the world can be associated with disease risk, then the same interpretation should be possible in individuals.

Availability to pigs of amino acids in cereal grains: 3. A comparison of ileal availability values with faecal, chemical and enzymic estimates

Abstract: 1. Availability values for amino acids in nine cereal grains determined by faecal analyses with pigs and by the Silcock available lysine test (Roach et al. 1967) and an in vitro digestibility assay were compared with ileal availability values for the same grains determined with pigs by Taverner et al. (1981 b). 2. There was a significant canonical correlation of ileal and faecal availability values. On average, apparent faecal availability of the indispensable amino acids was 4.2% greater than apparent ileal availability, but the difference was up to 12.6% for threonine. Furthermore, the difference appeared to increase as the digestibility of the grain decreased. 3. Silcock available-lysine values for the cereal grains were unrelated to the lysine truly absorbed by the pig. 4. There were close relationships of ileal protein and lysine availability values of nitrogen digestibility determined by an in vitro assay using pronase enzyme.

The effect of guar gum on the viscosity of the gastrointestinal contents and on glucose uptake from the perfused jejunum in the rat.

Abstract: 1. Male Wistar rats were meal-fed for at least 10 d a control semi-synthetic diet containing no guar gum, or one of three similar test diets containing 3, 10 or 20 g dry guar gum/kg. 2. Rats were killed 6 h after feeding, and contents of stomach, small and large intestine were collected separately. The apparent viscosities of stomach and small intestine contents from animals fed on diets containing 10 and 20 g guar gum/kg were increased relative to control animals, but large intestine contents were unchanged. 3. In the second part of this study, male Wistar rats were anaesthetized and two consecutive lengths of jejunum were perfused, initially with Ringer only (control) or Ringer plus 5 or 6 g guar gum/1 (test). Following this pre-perfusion, both segments were perfused with Ringer containing glucose (10 mM), [3H]glucose and [14C]inulin, and the rate of glucose absorption was determined. 4. The rate of glucose absorption was decreased relative to control values in segments pre-perfused with both 5 and 6 g guar gum/1 solution, but this reduction was significant only in the instance of the 6 g/l solution (P less than 0.001). 5. These results provide evidence to support previous assumptions that ingestion of guar gum will increase the apparent viscosity of the contents of the stomach and small intestine. We propose that a possible mechanism by which guar reduces post-prandial glycaemia is a reduction of glucose absorption from the small intestine, resulting from an increase in viscosity of the contents.

The digestive capacity of the caecum-colon and the value of the nitrogen absorbed from the hind gut for protein synthesis in pigs.

Abstract: 1. The aim of the investigation was to study the effects of lysine, methionine, crude protein, a complete balanced diet, maize starch and potato starch infused continuously into the caecum on the digestibility of the nutrients, urinary nitrogen excretion and N balance in the presence of a normal or a depressed (modified) microflora. 2. The effects of the the infused nutrients on digestibility differed when diets supplemented with antibiotics were compared with unsupplemented diets. 3. Infused lysine improved the digestibility of crude protein (0.004/g lysine), crude fibre (0.01/g lysine), gross energy (0.003/g lysine) and lysine (0.03/g lysine) when the diets were not supplemented with antibiotics. 4. Infused lysine, methionine and crude protein seemed to be of very little value for protein synthesis in the pigs, as the effects on N balance, although positive, were very small. 5. Despite the fact that a part of the infused lysine passed through the caecum-colon and into the faeces intact, the effect of N balance was negligible, indicating that the ability to absorb amino acids through the gut wall in the caecum-colon was very poor. 6. Crude protein, a complete balanced diet, maize starch and potato starch infused into the caecum were digested almost as well as if they had been given orally, thus demonstrating the large digestive capacity of the caecum-colon.

Effect of monensin on the fermentation of basal rations in the Rumen Simulation Technique (Rusitec)

Abstract: 1. A long-term experiment was made with the Rumen Simulation Technique (Rusitec), in which the fermentation of a mixed ration of hay (10 g/d) and bruised barley (5 g/d) was compared with the fermentation of the same diet in the presence of 2, 10 and 50 mg monensin/d. 2. Monensin depressed the production of acetic and butyric acids, markedly increased the production of propionic acid and virtually, eliminated the production of isovaleric acid. The production of methane was decreased in the presence of monensin, but this decrease could be accounted for entirely by the changes in the production of volatile fatty acids and redistribution of metabolic hydrogen. 3. The digestibility of dry matter (DM) in the rations declined in the presence of monensin. Determinations of the rates of digestion showed that the digestion of the readily-fermented food in the initial stages was not affected by monensin, but that at 24 h digestion had been inhibited by monensin. The inhibition was due entirely to its effect on the digestion of the fibrous components. Digestion of non-fibrous material was not affected. 4. The efficiency of microbial growth, expressed as g dry weight/mol ATP formed (YATP) and in terms of DM digested, tended to be increased by monensin. This however occurred only at high, non-practical doses. 5. Urease (EC 3. 5. 1. 5) was induced by the addition of urea of the fermentation, but monensin had no effect on urease activity. Although monensin increased the activity of protease in washed suspensions, more food protein apparently escaped degradation. This may have been due to decreased deaminative activity. 6. Monensin altered the microscopic appearance of the fermentation fluid, and changed the activity of some enzymes in sonicated extracts, including alkaline phosphatase (EC 3. 1. 3. 1), acetate kinase (EC 2. 7. 2. 1) and succinate dehydrogenase (EC 1. 3. 99. 1). These results are discussed in terms of known sensitivities of rumen microbes to monensin and their contribution to the fermentation as a whole.

The effects of protein degradability and food intake on milk yield and composition in cows in early lactation.

Abstract: 1. In two experiments measurements were made of food intake, live-weight change, milk yield and milk composition in early lactation when dairy cows were given diets containing varying proportions of protein as fish meal (low rumen degradability) or as groundnut meal (high rumen degradability). In a preliminary trial measurements were also made with cows given supplements of either fish meal or barley and fed at a restricted level of feeding. 2. When metabolizable energy (ME) intake exceeded 160 MJ/d there was no evidence of responses to changes in protein degradability, ut at ME intakes below 135 MJ/d increases in the supply of undegradable protein led to increases in fat-corrected milk yield, protein content and live-weight loss. 3. The interaction between energy intake and protein degradability is unexpected because net protein:net energy requirement increases as milk yield increases, but may be explained in terms of differential effects of changing rumen outflow rates on degradabilities.

A method to measure the water-holding properties of dietary fibre using suction pressure.

Abstract: 1. Water-holding capacity (WHC) of dietary fibre is usually considered as the amount of water held but the manner in which water is held by the fibre matrix may be more relevant in understanding the role of fibre in nutrition. 2. A method used to determine WHC under physiological conditions has been adapted to determine how strongly water is held by fibre. Solutions of compounds, such as polyethylene glycol, of known osmotic potential are used to generate a suction pressure across a dialysis membrane containing a fibre sample. The WHC at each suction pressure can then be determined. 3. The method can be applied to water-soluble and water-insoluble sources of fibre. Fibre sources studied included potato fibre concentrate, bran and gum arabic. 4. Results are comparable to other similar systems of WHC measurement for gels and suggest that vegetable fibre has water-holding properties more akin to a true gel than bran. Bran has very poor water-holding properties. 5. Differences in WHC between fibre sources are more apparent if WHC is considered as fibre concentration (g fibre/g water). 6. Differences in the water-holding properties could be important in determining fibre activity in the gut.

Effects of changes in the intakes of protein and non-protein energy on whole-body protein turnover in growing pigs.

Abstract: 1. The relationships between the intakes of protein and of non-protein energy (NPE), nitrogcn retention and body protein synthesis have been studied in female pigs weighing 30 and 35 kg.2. Four animals were assigned to three regimens and given a conventional (basal) diet supplemented with fat, carbohydrate or protein. After 1 week, measurements of N excretion in urine and faeces (7 d collection) and gaseous exchange (3–4 d) were made. At the end of the balance period a solution of [l-14C]leucine was infused at a constant rate. Body protein synthesis was then calculated as the difference between the apparent irreversible loss of blood leucine and the loss of 14C in expired air.The animals were then offered the basal diet without supplement for 10 d and the measurements of N retention, energy retention and protein synthesis were repeated.3. The intakes of metabolizable energy (ME; MJ/kg body-weight (W)0.75per d) were 1.75 for fat, 1.58 for carbohydrate, 1–25for protein and 1.18 for the basal diet; corresponding intakes of apparently digestible N (ADN; g N/kgW0.75 per d) were 2.30,2.31,4.35 and 2–17. Daily N retention, which during the period of basal feeding was 13.6 g was increased by between 3.4 and 7.2 g by the supplements. Daily fat deposition was also increased in the animals that received the diets supplemented with carbohydrate and fat.4. The rate of leucine catabolism was significantly reduced in the animals receiving the diets that were supplemented with W Eand increased by the addition of protein to the diet.5. When based on the specfic radioactivity of blood leucine both the synthesis and breakdown of body protein (per unit metabolic body-weight) were increased by 30% in the animals receiving the high-protein diet but the increases in protein synthesis associated with the addition of carbohydrate (+14%) and fat (+12%) were much less marked. Consideration of these results together with previous observations (Reeds et al. 1980) suggested that body protein synthesis(g N/d) increased by 0.88 for each g increase in daily ADN and by 0.93 for each MJ increase in daily ME intake.6. Comparison of the results obtained with the animals given high-carbohydrate diets and those given high-protein diets suggested an increase in heat production of 14 KJ/g of additional fat deposition. A similar comparison of animals receiving the high-protein and basal diets suggested a heat increment of 23.5KJ/g additional protein deposition. The changes in heat production and protein synthesis in the animals given the protein supplement were compatible with a heat increment of 5.3 KJ/g additional protein synthesized. Because of the large proportion of heat production associated with the deposition of fat this could not be confirmed with either of the other supplements, but it is possible that the energy cost of protein accretion varies with the relative proportions of protein and NPE in the diet.

Breast-milk fat concentrations of rural African women. 2. Long-term variations within a community.

Abstract: 1. Long-term variations in breast-milk fat concentration of mothers feeding on demand were studied in 120 rural West African women over a 12-month period. 2. The over-all mean 12 h breast-milk fat concentration was 39.3 g/l. 3. Mean breast-milk fat concentrations were affected by season in a manner which was correlated with seasonal changes in maternal subcutaneous fat stores (P less than 0.05) but which was unrelated to seasonal variations in maternal energy intake and breast-milk output. 4. Breast-milk fat concentrations were highest in early lactation, decreasing to a constant level during the first year. 5. There was significantly greater between-mother than within-mother variation in breast-milk fat concentrations measured in successive months, after correcting for season and stage of lactation (P less than 0.001). 6. Breast-milk fat concentrations were highest for primiparous mothers, decreasing to a constant level at parity 4 and higher. 7. A mother's relative breast-milk fat concentration was not correlated with her levels of dietary energy intake and breast-milk output but was positively correlated with her relative subcutaneous fat deposits (P less than 0.01).

The urinary excretion of N tau-methyl histidine by cattle: validation as an index of muscle protein breakdown.

Abstract: 1. The recoveries of radioactivity in cattle urine following the intravenous administration of N tau-[14CH3]methyl histidine were essentially quantitative in 5--7 d in non-lactating cows, bulls and steers and did not change with age. 2. The N tau-methyl histidine was excreted unchanged in urine. 3. N tau-methyl histidine occurred in muscle extracts both in the free form and as a perchloric acid-soluble, acid-labile form which accounted for approximately 85% of the total non-bound N tau-methyl histidine in muscle and appeared identical to a similar component identified in muscle extracts of sheep and pigs. 4. There was probably an age-related decrease in the concentration of the acid-labile component in muscle but which did not produce a measurable change in recovery of radioactivity in urine. 5. The daily excretion of N tau-methyl histidine (E, mumol) by male cattle was highly correlated with live weight (W, kg) by the equation: E = 50 . 4 + 3 . 536 (+/- 0 . 044)W (r 0. 997). The excretions progressively decreased from 4 . 04 mumol/d per kg at 100 kg weight to 3 . 62 mumol/d per kg at 600 kg. 6. By the criterion of the rate of clearance of labelled N tau-methyl histidine from the body, the excretion of N tau-methyl histidine in urine appears to be a valid index of muscle protein breakdown in cattle.

The maximum capacity of the liver of the adult dairy cow to metabolize ammonia

Abstract: 1. Three adult dairy cows were fitted with cannulas in a mesenteric, portal, hepatic and jugular vein and a carotid artery. They received infusions of step-wise increasing amounts of ammonia as ammonium acetate via a mesenteric vein until NH3 intoxication occurred. Sodium acetate was used in control infusions. The maximum rate of uptake of NH3 by the liver and the concentrations of glucose, urea, lactate, acetate and bilirubin in blood were measured.2. During the infusions of ammonium acetate the liver extracted almost all the NH3 present in the portal vein until an infusion rate of approximately 15·0 mmol/min was reached. The maximum capacity of the liver to remove NH3 during its first pass was on average 1·84 mmol/min per kg wet weight. The cows became intoxicated when arterial plasma ammonia concentrations reached 0·8 mmol/1. Concentrations of NH3 in jugular venous blood were between 66 and 74% of those in the carotid.

Metabolism of zinc and copper in the neonate: accumulation and function of (Zn, Cu)-metallothionein in the liver of the newborn rat.

Abstract: 1. Measurements were made of the hepatic concentrations and contents of total and thionein-bound zinc and copper in late foetal and newborn rats and of the distribution of these metals between the particulate and soluble components of the liver. 2. The decrease in the hepatic concentration of thionein-bound Zn, which occurred with age after birth, was proportional to the increase in liver weight until the 16th day post partum; thereafter it was greater. 3. Throughout the period from birth to 25 d of age the Zn concentration remained constant in the cytosolic non-thionein fraction (i.e. total cytoplasmic Zn – thionein-bound Zn). but decreased in other compartments of the liver. 4. The same constant concentration of cytoplasmic non-thionein-bound Zn also was observed in animals with reduced total hepatic Zn contents, but normal body-weights, and in 20-d-old Zn-deficient pups. 5. The concentration of thionein-bound Cu exhibited two maxima, one at 2 d of age and the second at 14 d. 6. The total hepatic content of Cu increased significantly only between the 6th and 14th day post partum. The age-related variations in Cu contents of the particulate components closely paralleled those in the whole liver, whereas the Cu contents of the cytosolic thionein and non-thionein fractions did not increase appreciably until after the 10th day. 7. It is concluded that the cytosolic non-thionein fraction of newborn rat liver may contain particularly important metabolic sites that require Zn and a major function of Zn-thionein is to regulate is to regulate the supply of the metal to these sites. As, from birth to 26 d of age, the sum of the concentrations of thionein-bound Zn and Cu was correlated with whole liver Zn, the accumulation of Cu as a soluble metallothionein seems to be a secondary event, dependent on the hepatic Zn concentration.

Intravenous administration of thiomolybdate for the prevention and treatment of chronic copper poisoning in sheep

Abstract: 1. Twenty-six sheep were used in experiments designed to test the effectiveness of ammonium tetrathiomolybdate in the prevention and treatment of chronic copper poisoning. 2. Intravenous injections of 100 mg ammonium tetrathiomolybdate twice weekly (a) prevented the occurrence of haemolytic crisis in sheep repeatedly dosed with copper sulphate and (b) minimized tissue damage and prevented further haemolytic crisis when given to sheep already in haemolysis. 3. Thiomolybdate prevented excessive deposition of Cu in the liver of sheep receiving orally large amounts of Cu and decreased liver Cu levels in sheep that were not given additional Cu. In the latter sheep, 50 mg ammonium tetrathiomolybdate given twice weekly did not produce histologically-detectable tissue damage even though liver and kidneys contained high levels of molybdenum, and kidneys contained elevated levels of Cu. 4. It is concluded that chronic Cu poisoning can be successfully prevented or treated by intravenous injection of appropriate doses of ammonium tetrathiomolybdate.

Breast-milk fat concentrations of rural African women. 1. Short-term variations within individuals.

Abstract: The study purpose was to establish the pattern of breast milk fat concentration changes that occurs during the day among underprivileged African women feeding on demand and thereby to devise a rational sampling procedure for the estimation of daily mean fat concentrations. The creamatocrit method was used in detailed studies of variations in breast-milk fat concentrations performed over 12 or 24 hour periods on 60 rural Gambian women. The complex pattern of within-feed and between-feed changes in fat concentration was largely explained by differences in volume per feed and time interval between feeds. There were no consistent differences in fat production between the breasts of each individual despite the local custom of beginning all feedings on the right breast. A marked diurnal variation in the mean fat concentration was noted. On average the values were highest in the early morning and lowest in the late afternoon. There was significantly greater between-individual variation in the mean fat concentration per feed over 12 hours. A simple rational and non-intrusive sampling procedure was devised for the estimation of whole day mean fat levels. It was based on the finding that the mean fat concentration of small samples of milk (0.25 ml) taken from both breasts before and after 1 specific feed of the day was closely correlated with 12 hour and 24 hour mean fat concentrations.

Protein synthesis in tissues of growing lambs.

Abstract: 1. The fractional rate of protein synthesis (FSR) in tissues of nine growing lambs (4-5 months of age) was estimated following continuous infusion of L-[4,5-3H]leucine for a period of 7 h. Minimum and upper estimates of FSR were obtained assuming that the specific radioactivity (SRA) of leucine in blood plasma and tissue homogenate respectively defined that of leucyl tRNA. 2. Mean upper estimates of tissue protein FSR (/d) were skin 0.35, longissimus dorsi muscle 0.05 biceps femoris muscle 0.04, liver 0.54, rumen 0.79, cardiac muscle 0.09. Minimum estimates of tissue protein FSR ranged from 0.03 (muscle) to 0.15 (liver). 3. Plasma leucine flux was closely related to body protein content and dietary leucine absorption (r 0.94). 4. The rate of whole-body protein synthesis (WBS) derived from plasma leucine flux corrected for oxidation and localized recycling of leucine into protein was similar to that calculated from the sum of daily protein synthesis in individual tissues using the upper estimate of FSR, i.e. 610 g/d v. 581 g/d. 5. The estimate of WBS derived from plasma leucine flux directly (241 g/d) was similar to that calculated from the sum of minimum estimates of daily protein synthesis in individual tissues (214 g/d). 6. The ratio, intracellular leucine SRA:plasma leucine SRA tended to increase with increasing dietary leucine absorption in all tissues although these factors were only significantly correlated (P less than 0.05) in cardiac muscle, skin and rumen. Such relationships suggest an increased exchange of plasma leucine with intracellular leucine with increased food intake. 7. It was estimated that the energy cost of protein synthesis accounted for approximately 42% of daily heat production.

Further studies on the hypocholesterolaemic effect of soya-bean protein in rats.

Abstract: 1. The hypocholesterolaemic effect of soya-bean protein compared with that of casein, when fed at 200 g/kg diet for 3 weeks, was studied in rats. 2. Using a cholesterol-free low-fat (10 g maize oil/kg) diet, the hypocholesterolaemic effect was demonstrated not only with soya-bean protein but also with an amino acid mixture simulating this protein. The addition of lysine to these diets did not modify their intrinsic effects on serum cholesterol. 3. By feeding the vegetable protein or its amino acid mixture, both high-density-lipoprotein-and very-low-density-lipoprotein plus low-density-lipoprotein-cholesterol decreased to a similar extent, and the concentration of serum apolipoprotein A--I decreased and that of apolipoprotein B increased. 4. Although rats given soya-bean protein excreted more neutral and acidic steroids, the difference disappeared when the amino acid mixture was fed, indicating that the hypocholesterolaemic effect of the vegetable protein is not ascribed only to the increased elimination of steroids. 5. It is likely that the difference in the amino acid composition between animal and vegetable proteins is in fact responsible for the different response of serum cholesterol.

Breast-milk production in Australian women.

Abstract: 1. Milk productions and 7 d dietary records were determined on twenty-seven mothers who had been breast-feeding for 1, 3, 6, 9, 12 or 15 months. 2. The mean milk productions for each group of mothers was 1 . 87, 1 . 238, 0 . 884, 0 . 880 and 0 . 951 kg/24 h at 1, 3, 6, 9, 12 and 15 months of lactation respectively. There was no significant difference between two milk determination 3--7 d apart on each mother or between the mean milk production of each group of mothers. 3. Energy intakes of the infants was found to be higher than the usually-accepted values at 1 and 3 months of age but by 6 months were similar to the accepted normal values. 4. Energy intakes of the mothers although greater than those recommended for similar non-lactating women were not sufficient to take into account the energy content of the milk.

Factors affecting the voluntary intake of food by sheep. 3. The effect of intravenous infusions of gastrin, cholecystokinin and secretin on motility of the reticulo-rumen and intake.

Abstract: 1. Sheep given ground and pelleted lucerne hay (Medicago sativa) ad lib. were infused intravenously with pentagastrin, secretin, cholecystokinin (CCK) and its analogues to assess their effects on motility of the reticulo-rumen and on food intake. In the latter experiments the animals were deprived of their diet for periods of up to 6 h to induce hunger and the infusions were made before and during 3-10 min periods of feeding. 2. Pentagastrin, and analogue of gastrin, depressed intake by 35-50% (P less than 0.05) when it was infused at 9 microgram/kg per h during 30 min of feeding. The threshold may however be below 1 microgram/kg per h as this dose decreased intake of 12-17%. The frequency of reticular contractions decreased by 13, 35, 39 and 44% when 1, 3, 9, and 27 microgram pentagastrin/kg per h respectively was infused (P less than 0.025). 3. Secretin depressed food intake 38% after 30 min (P less than 0.025) when 8 Clinical Units (CU)/kg per h was infused but the threshold could be less than this dose since 0.5 CU/kg per h depressed intake by 12%. Contraction amplitude but not frequency decreased at 8 CU/kg per h. 4. CCK produced a 39% decrease in intake during the first 10 min of feeding (P less than 0.05) and the threshold was between 5 and 15 Ivy Dog Units (IDU) or 425 and 1276 pmol/kg per h. The frequency of reticular contractions was not affected by 1.7 IDU/kg per h but it was depressed 21 and 63% by 5 and 15 IDU/kg per h. Octapeptide at 1.5 and 3 microgram (1312 and 2624 pmol) kg per h depressed intake by 11 and 43% respectively after 10 min (not significant) and 1.5 microgram/kg per h depressed motility by 39% (P less than 0.01). Ceruletide at 810 ng (599 pmol)/kg per h depressed intake by 31% (not significant) after 10 min and decreased motility by 52% (P less than 0.05). The threshold dose for ceruletide on intake appeared to be about 90 ng or 66 pmol/kg per h which is considerably less than that for CCK or octapeptide. 5. The biological significance of gastrointestinal hormones as signals of satiety in normal sheep is not known since doses of pentagastrin and CCK that suppressed intake also interfered quite markedly with motility. However there is good reason to suspect that elevated concentrations of gastrin and CCK in blood of parasitized sheep may account at least in part for their symptoms of rumen atony and reduced food intakes.

Factors affecting the absorption of iron from Fe(III)EDTA.

Abstract: 1. The modification of iron absorption from Fe(III)EDTA by agents known to promote or inhibit absorption was examined in 101 volunteer multiparous Indian women. Fe absorption from Fe(III)EDTA was compared with absorption of intrinsic food Fe in a further twenty-eight subjects. Finally the urinary excretion of radio-Fe after oral administration of 59Fe(III)EDTA was studied in twenty-four subjects and evidence of intraluminal exchange of Fe was examined. 2. Fe absorption from maize porridge fortified with Fe(III)EDTA was more than twice that from porridge fortified with FeSO4 . 7H2O. 3. Although bran decreased Fe absorption from FeSO4 . 7H2O approximately 11-fold, it had no significant effect on Fe absorption from Fe(III)EDTA. Nevertheless tea, which is a more potent inhibitor of Fe absorption, decreased absorption from Fe(III)EDTA 7-fold. 4. Fe absorption from Fe(III)EDTA given in water was only increased 40% by addition of 3 mol ascorbic acid/mol Fe but by 7-fold when the relative proportions were increased to 6:1. This enhancing effect was blunted when the Fe(III)EDTA was given with maize porridge. In these circumstances, an ascorbate:iron value of 3:1 (which doubles absorption from FeSO4 . 7H2O) produced no significant increase in Fe absorption, while a value of 6:1 produced only a 2 . 5-fold increase. 5. Fe absorption from Fe(III)EDTA was not altered by addition of maize porridge unless ascorbic acid was present. 6. Less than 1% of 59Fe administered as 59Fe(III)EDTA was excreted in the urine and there was no inverse relationship between Fe absorption and the amounts excreted (r 0 . 58, P less than 0 . 05). 7. Isotope exchange between 59Fe(III)EDTA and 59FeSO4 . 7H2O was demonstrated by finding a similar relative value for the two isotopes in urine and erythrocytes when the two labelled compounds were given together orally. This finding was confirmed by in vitro studies, which showed enhanced 59Fe solubilization from 59FeSO4 . 7H2O in maize porridge when unlabelled Fe(III)EDTA was added. 8. Although Fe absorption from Fe(III)EDTA was marginally higher it appeared to form a common pool with intrinsic food iron in most studies. It is postulated that the mechanism whereby Fe(III)EDTA forms a common pool with intrinsic food Fe differs from that occurring with simple Fe salts. When Fe is present in the chelated form it remains in solution and is relatively well absorbed because it is protected from inhibitory ligands. Simple Fe salts, however, are not similarly protected and are absorbed as poorly as the intrinsic food Fe. 9. It is concluded that Fe(III)EDTA may be a useful compound for food fortification of cereals because the Fe is well absorbed and utilized for haemoglobin synthesis. The substances in cereals which inhibit absorption of simple Fe salts do not appear to inhibit absorption of Fe from Fe(III)EDTA.

The effect of type and level of protein, fibre and starch on nitrogen excretion patterns in rats.

Abstract: 1. Three series of nitrogen balance experiments were performed with growing rats to test the effect of type and level of protein, fibre and starch on N excretion patterns. The design involved eighteen treatments in a 3 X 3 X 2 factorial experiment with five rats per dietary treatment. The eighteen treatments resulted from a combination of three protein treatments, three fibre treatments and two starch treatments. Protein treatments consisted of one level (15 g N/kg DM) of casein fortified with methionine, a protein of high digestibility, and two levels (15 and 20 g N/kg DM) of autoclaved brown beans (Phaseolus vulgaris), a protein source of low digestibility. The fibre treatments were two levels of cellulose powder and one level of barley hulls. The two starch treatments were autoclaved potato starch and autoclaved and raw potato starch (1:1, w/w). 2. The inclusion of raw potato starch reduced true protein digestibility markedly when the protein source was casein, but the corresponding biological values were increased significantly with this treatment. This strongly indicated a movement of urea from the blood to the intestines. This assumption was also supported by significantly lower blood urea concentrations in animals given raw starch. The influence of raw starch on true protein digestibility was, however, significantly less when cellulose and barley hulls were included. This is probably due to reduced transit time from fibre inclusion. The nature of the gut contents also supported this hypothesis. 3. The inclusion of raw potato starch when brown beans were the source of protein had much less effect on true protein digestibility and biological value than when casein was the protein source. This was probably due to the low digestibility of DM and protein in this food leaving sufficient energy and protein for maximum microbial growth. The inclusion of fibre also had little effect on N excretion patterns with the brown-bean diets. 4. An increase in the level of brown bean inclusion reduced true protein digestibility only on the diets containing raw starch whereas the biological value was consistently reduced regardless of starch treatment. The lower biological values were associated with significantly higher blood urea concentrations. Increasing the level of brown bean inclusion also resulted in higher fresh weights of caecum, colon and contents. 5. The present work proves that, through dietary manipulation, it is possible to affect nitrogen excretion patterns in rats.

An investigation of the effects of intravenous administration of thiomolybdate on copper metabolism in chronic Cu-poisoned sheep

Abstract: 1. Fourteen sheep were dosed repeatedly with a solution of copper sulphate (2 g/l) in order to induce chronic copper poisoning and four similar undosed animals acted as controls. 2. Thiomolybdate (TM) was intravenously administered to all control sheep and to all except two of the test sheep. A variety of biochemical factors were studied before and after injections of TM. 3. The direct-reacting Cu, whole-blood Cu and plasma Cu concentrations were elevated in animals given TM injections and at the ‘haemolytic crisis’ of untreated chronic Cu-poisoned animals. But most of the increased Cu observed on injecting TM was insoluble in trichloroacetic acid (TCA) and did not enter erythrocytes. The results indicate that uptake of Cu by erythrocytes is essential for haemolysis to occur and that for this to happen the Cu must be in a direct reacting, TCA-soluble form. 4. Increased amounts of Cu were excreted in the urine at haemolysis and at the commencement of TM injections. High levels of direct-reacting Cu were found in plasma at these times. 5. Marked changes were not found in caeruloplasmin activity, packed cell volume or the osmotic fragility of erythrocytes except at haemolysis. TM injections did not alter these factors in any of the sheep studied.

Energy expenditure of male farmers in dry and rainy seasons in Upper-Volta.

Abstract: 1. Thirty Mossi male farmers from Upper-Volta were investigated, twenty-three in the dry season (March-April) and sixteen in the rainy season (July-August), eight of them being studied twice. A 48 h time-and-motion study was carried out and the daily energy expenditure was computed. 2. The mean height was 1.70 m and the mean weight 58.5 kg. The averaged percentage of body fat calculated from skinfold thickness was 10. 3. During the dry season the subjects could be classified as very moderately active with an energy output of 10.0 MJ (2410 kcal)/d. By contrast, with an energy expenditure of 14.4 MJ (3460 kcal)/d, they were considered as exceptionally active in July-August when performing the agricultural work. 4. In this study we measured the intensity of physical work in a society where human labour is still the main tool of production. The determination of seasonal variations in energy expenditure may be useful to assess the nutritional requirements in arid zones of West Africa.