Showing papers in "British Journal of Nutrition in 1974"
TL;DR: Skinfold thicknesses at four sites – biceps, triceps, subscapular and supra-iliac – and total body density were measured on 209 males and 272 females aged from 16 to 72 years, finding it necessary to use the logarithm of skinfold measurements in order to achieve a linear relationship with body density.
Abstract: The fat content of the human body has physiological and medical importance. It may influence morbidity and mortality, it may aIter the effectiveness of drugs and anaesthetics, and it may affect the ability to withstand exposure to cold and starvation. Thus the measurement of the total body fat provides useful information. In many people, but by no means everyone, a moderately satisfactory estimate of the body fat content can be obtained from the height and weight. However, for more precise evaluation several methods are available which give a reasonably accurate measure of body fat both in normal subjects and in individuals with unusual body builds. Most of these methods are based on the assumption that the body can be considered to consist of two compartments of relatively constant composition but which are distinctly different; these compartments are: (I) the body fat, which includes the entire content of chemical fat or lipids in the body, and (2) the fat-free mass (FFM), which includes all the rest of the body apart from fat. The body fat compartment is anhydrous, contains no potassium and has a fairly constant density of about 0.90 x 103 kg/m3. The fat-free compartment on the other hand probably has a fairly constant density of about 1.10 x 103 kg/m3, a potassium content of about 68 mequiv./kg in males (about 10% less in females) and a water content of about 720 g/kg. Thus measurement of body density or of total body K or of total body water allows a calculation of the relative proportion of these two compartments in the body and therefore also of the total fat content. The accuracy of these measures, however, is limited by the variability of the composition and density of the fat-free compartment in different individuals. In particular, individuals with a relatively high or
6,287 citations
TL;DR: The results suggest that addition of non-protein N supplements to ruminant rations are warranted only if the prevailing concentration of ruminal ammonia is less than 50 mg NH3-N/l ruminal fluid.
Abstract: 1. The effect of ammonia concentration on microbial protein production was determined in continuous-culture fermentors charged with ruminal contents obtained from steers fed on either a protein-free purified diet, a maize-based all-concentrate diet, or a forage–concentrate (23:77) diet. Urea was infused into the fermentors to maintain various concentrations of ammonia in the incubating mixtures.2. Under nitrogen-limiting conditions, microbial protein yield measured as tungstic acid-precipitable N (TAPN) increased linearly with supplementary urea until ammonia started to accumulate in the incubating ingesta. Increasing the ammonia concentration beyond 50 mg NH3-N/l had no effect on microbial protein production.3. The molar proportions of volatile acids produced were not affected by the level of urea supplementation. Total acid production was decreased slightly under N-limiting conditions, but not to the same extent as microbial protein production.4. Estimated yield of microbial dry matter/mol ATP produced averaged 15·6 when non-limiting N as urea was provided with the purified diet.5. These results suggest that addition of non-protein N supplements to ruminant rations are warranted only if the prevailing concentration of ruminal ammonia is less than 50 mg NH3-N/l ruminal fluid.
1,731 citations
TL;DR: A continuous, in vitro fermentation system was developed, in which outputs of protozoa were comparable with in vivo outputs, and it was estimated that the amount of protozoal nitrogen leaving the rumen represented less than 2% of dietary N.
Abstract: 1 A procedure for sampling digesta from within the omasal canal of sheep given a variety of roughage diets was used to enable comparison to be made of the composition of effluent from the reticulo-rumen with that of rumen fluid2 Concentrations of protozoa in effluents, relative to a soluble marker continuously infused intraruminally, were usually less than 20% of corresponding rumen fluid concentrations It was estimated that the amount of protozoal nitrogen leaving the rumen represented less than 2% of dietary N3 Passage of volatile fatty acids (VFA) from the rumen in effluent was less than 75% of that indicated by rumen concentrations4 A continuous, in vitro fermentation system was developed, in which outputs of protozoa were comparable with in vivo outputs
329 citations
TL;DR: Significant differences were found between all diets in the concentration of some amino acids in ileal and faecal amino-N, and endogenous protein secretions did not mask the differences between diets.
Abstract: 1. Six 45 kg pigs with re-entrant ileal cannulas were used in two 3 × 3 Latin-square design experiments to study the site of absorption of protein and amino acids. Semi-purified diets containing soya-bean meal (SBM), rapeseed meal (RSM) or no protein source (protein-free) were offered at the rate of 1 kg dry matter/d.2. Flow-rates of ileal contents for 24 h collection periods, corrected for recovery of marker, were 3135, 3127 and 1243 ml (SE 390) for SBM, RSM and protein-free diets respectively.3. Amounts of dry matter digested in the small intestine were 730, 669 and 809 g/d for SBM, RSM and protein-free diets respectively, all values being significantly different (P < 0·001).4. Nitrogen intakes were 32·6, 29·9 and 5·9 g/d, and amounts digested in the small intestine were 25·7, 20·2 and 1·6 g/d for SBM, RSM and protein-free diets respectively, all values being significantly different (P < 0·001). Amounts digested in the large intestine were 2·6, 3·7 and 0·7 g/d.5. Total amino acid intakes and amounts collected at the ileum and in the faeces were (g/d): SBM, 177, 24 and 18; RSM, 149, 28 and 22; protein-free 3, 9 and 12. Digestibility in the small intestine was higher for SBM than RSM for seventeen of the eighteen amino acids estimated. Greater quantities of arginine, methionine, cystine and tyrosine were voided in the faeces than passed through the ileal cannulas for pigs receiving the SBM and RSM diets. For those receiving the protein-free diet this was true for each amino acid except proline.6. Significant differences were found between all diets in the concentration of some amino acids in ileal and faecal amino-N, and endogenous protein secretions did not mask the differences between diets.7. Differences in digestibility between SBM and RSM were greater at the ileum than in the faeces. Amino acid fermentation in the large intestine obscured or reduced differences between SBM and RSM.
153 citations
TL;DR: The results suggest that the activity of the urea cycle enzymes depends in part on the amount of N available for excretion after the demands for synthesis have been met.
Abstract: 1. Measurements were made, at 6 h intervals, of urinary nitrogen output and of the activity of some hepatic enzymes in the rat during adaptation from one level of dietary protein to another. The enzymes measured were arginase (EC 3.5.3.1), argininosuccinate lyase (EC 4.3.2.1), argininosuccinate synthetase (EC 6.3.4.5), glutamate dehydrogenase (EC 1.4.1.2) and alanine and aspartate aminotransferases (EC 2.6.1.2 and EC 2.6.1.1).2. Completeness of urine collection, which was essential for these experiments, was checked by recovery of injected [131I]iodide.3. When the dietary protein content was reduced from 135 to 45 g casein/kg, the urinary N output and the activities of the hepatic enzymes reached their new steady-state levels in 30 h. The reverse adaptation, from 45 to 135 g casein/kg, was also complete in 30 h.4. The rate of change of enzyme activity and the final activity as percentage of initial activity were very similar for all six enzymes, suggesting a common control mechanism. The calculated half-lives of the enzymes were of the order of 7 h, which is very much shorter than those found by previous workers.5. There was no simple relationship between the activity of the urea cycle enzymes and the amount of N excreted. When an equal amount of gelatin was substituted for casein the N output was doubled but there was no change in the activity of the liver enzymes.6. The results suggest that the activity of the urea cycle enzymes depends in part on the amount of N available for excretion after the demands for synthesis have been met. The enzymes, however, appear to be present in excess so that an increased N load was not necessarily accompanied by an increase in enzyme activity.
126 citations
TL;DR: Bacteria taken 4–6 h after a feed from calves which were kept in an experimental calf-house with no contact with adult animals (environment A) contained more α-dextran, less total N and higher nucleic acid:total N ratios than similar bacteria from calves reared in contact withadult sheep (environment C) but otherwise treated in an identical way.
Abstract: 1. Sheep, cows and calves fitted with rumen cannulas were given diets mostly containing 10–16 g nitrogen/kg dry matter and consisting of roughage and cereals. Mixed bacteria were separated from samples of their rumen contents.2. Bacteria taken 4–6 h after a feed from calves which were kept in an experimental calf-house with no contact with adult animals (environment A) contained more α-dextran, less total N and higher nucleic acid:total N ratios than similar bacteria from calves reared in contact with adult sheep (environment C) but otherwise treated in an identical way.3. Mixed bacteria taken 4–6 h after a feed from sheep and cows were similar in composition, with respect to nitrogenous components, to those from the ‘environment C’ calves. This composition did not vary significantly when diets containing differing proportions of roughage were given.4. The ‘environment A’ calves were free of ciliate protozoa. When they were placed in contact with, and were inoculated with rumen contents from, adult cattle (environment B), they rapidly developed a normal protozoal population and the chemical composition of their rumen bacteria became like that of the bacteria from the ‘environment C’ calves.5. Mixed bacteria taken just before a feed, from either cows or ‘environment A’ calves, showed significantly lower RNA-N:total N ratios and slightly (but not usually significantly) higher DNA-N:total N ratios than bacteria taken 4–6 h after feeding. Total N contents of the bacteria did not change consistently with time after feeding.6. The possible significance of these differences in relation to the nutrition of the host animal is discussed.
126 citations
TL;DR: It was concluded that variations in dietary S within the normal range for herbage exert an independent effect on Cu metabolism, possibly through the formation of insoluble CuS at sites beyond the rumen.
Abstract: 1. The effects of dietary sulphur on the availability of dietary copper were estimated by means of a repletion technique. The responses of initially hypocupraemic ewes to repletion with Cu-supplemented diets containing supplements of organic S, as methionine, and of inorganic S, as Na 2 SO 4 , were compared with those obtained with a diet low in S. 2. The two forms of S had similar effects. Responses in plasma Cu were reduced by 39–56 % when S was increased from 1.0 to 3.0 or 4.0 g/kg diet and the availability of dietary Cu was estimated to have decreased from 0.062 to 0.041. Both S supplements produced marked increases in rumen sulphide concentrations. 3. Dietary S had no effect on plasma Cu when added to the low-Cu diet of hypocupraemic ewes being repleted by a continuous intravenous infusion of Cu. 4. The addition of CuS, providing 5 mg Cu/kg, to the diet of hypocupraemic ewes produced no response in plasma Cu or haemoglobin. The same amount of Cu, given as CuSO 4 , increased plasma Cu by 0.46±0.15 mg/l and haemoglobin by 33±3.8 g/l after 36 d: the subsequent replacement of CuSO 4 by CuS induced hypocupraemia again but had no effect on haemoglobin. 5. It was concluded that variations in dietary S within the normal range for herbage exert an independent effect on Cu metabolism, possibly through the formation of insoluble CuS at sites beyond the rumen.
123 citations
TL;DR: Comparisons are made with the changes which occurred in the fatty acid compositions of rumen free fatty acids and plasma triglycerides of sheep given intraruminal infusions of linoleic acid or maize oil to suggest the possibility that biohydrogenation of 18:2 derived from the triglyceride proceeds by a different pathway from that of18:2 presented as the free acid.
Abstract: 1. Studies have been made of the effects of different concentrations of either free or esterified linoleic acid on the biohydrogenation of linoleic acid by rumen micro-organisms in vitro. A comparison has been made with the changes which occurred in the fatty acid compositions of rumen free fatty acids and plasma triglycerides of sheep given intraruminal infusions of linoleic acid or maize oil.2. In the in vitro experiments, with increasing concentrations of 18:2 added as the free fatty acid, a decreasing proportion of this 18:2 was hydrogenated to 18:0 and trans-11-octadecenoic acid accumulated. The accumulation of large amounts of trans-11-octadecenoic acid was accompanied in all instances by the accumulation of a conjugated diene identified as cis-9, trans-11-octadecadienoic acid. There appeared to be a product–precursor relationship between the conjugated diene and the trans-11 monoene.3. When linoleic acid was presented in vitro as the triglyceride, the extent to which hydrogenation occurred was, in all instances, greater than when equivalent amounts of 18:2 were presented as the free acid. Only small amounts of the cis-9, trans-11 diene were detected, and there was no apparent product–precursor relationship between this conjugated diene and the C18 monoenoic acids. The C18 monoenoic acids that accumulated consisted of both cis and trans isomers; the cis isomers consisted largely of cis-9- and cis-11-octadecenoic acids, which together comprised about 30% of the C18 monoenoic acids present.4. The infusion of free linoleic acid into the rumen of sheep resulted in an increase in the proportion of total 18:1 and a decrease in the proportions of 16:0 and 18:0 in the total rumen free fatty acids. This increase which occurred in the concentration of 18:1 consisted predominantly of the trans-11 isomer. A concomitant increase in the concentration of the C18trans-11 acid was observed to occur in the fatty acids of the plasma triglycerides. Infusion of maize oil into the rumen of sheep resulted in little change in the fatty acid compositions of either the free fatty acids in the rumen or the triglycerides of the plasma.5. The findings in vitro and in vivo are discussed with reference to each other and with reference to the possibility that biohydrogenation of 18:2 derived from the triglyceride proceeds by a different pathway from that of 18:2 presented as the free acid.
116 citations
TL;DR: It is concluded that the binders might well influence the vitamin economy in the neonatal period, and the ecology of the gut microflora, by preventing their uptake by intestinal micro-organisms.
Abstract: 1. The folate and vitamin B12 in milk are strongly bound to minor whey proteins. These binder proteins are present in excess, and so milk has capacity – which varies between milks of different mammalian species – to sequester added cyanocobalamin and folic acid.2. A study was made of the influence of different milks on uptake of [3H]cyanocobalamin and [3H]folic acid in selected bacteria, mostly of types that are commonly found in the intestine.3. None of the test cultures required exogenous vitamin B12. Nevertheless, when free cyanocobalamin was added, in seven of nine cultures it was rapidly taken up into the cells, though there were large differences between the different bacterial species in their absorptive capacity. In presence of sow's milk, little or none of the added cyanocobalamin was taken up, even after incubation of the test mixture for 1 h at 37°. The avidity of sow's milk for cyanocobalamin, as judged from its retention of the vitamin against competition by bacterial cells, was greater than that of a preparation of porcine Intrinsic Factor of similar binding capacity.4. Of ten cultures of bacteria representing seven species, only the five cultures that required exogenous folate took up added folic acid into the cells. Uptake was severely depressed by the simultaneous addition of goat's colostrum, even after incubation of the test mixture for 1 h at 37°.5. The physiological role of the binders is discussed. It is postulated that they may act in the mammary gland as trapping mechanisms to accumulate the vitamins from blood plasma into milk and in the gut to facilitate their absorption, both directly, and indirectly by preventing their uptake by intestinal micro-organisms. It is concluded that the binders might well influence the vitamin economy in the neonatal period, and the ecology of the gut microflora.
111 citations
TL;DR: The interactions between appetite, growth and activity in the development of obesity in the Zucker rat are discussed and marked discrepancies existed between the different estimates of N retention.
Abstract: 1. Heat losses associated with the utilization of metabolizable energy for synthesis of protein and of fat during growth were studied in Zucker rats selected for normal leanness or congenital obesity.2. Measurements of energy and nitrogen balance were made on groups of four lean and four fat rats offered food ad lib. and kept at 22°. Balance trials were also conducted on groups of fat or lean rats offered restricted amounts of food at two levels and kept at 22° or 28°. The medium rations offered to fat and lean rats were the same. The energy and N contents of fat and lean rats were determined by carcass analysis at 35 d and at about 90 d of age.3. At ad lib. intake, fat rats ate 38% more than lean rats. Heat losses and N balance were similar. When fat and lean rats were pair-fed, heat loss and N retention were lower in fat rats. Absolute values and changes during growth of heat loss (kJ/rat per 24 h) were closely correlated with values obtained for N balance.4. Carcass analysis showed that energy retention in protein was, on average, 75% in lean rats but only 14% in fat rats. Estimates of energy retention from slaughter experiments and balance trials agreed well, but marked discrepancies existed between the different estimates of N retention.5. The net efficiencies of utilization of metabolizable energy for growth in lean and fat rats were 0.485 and 0.614 respectively. The energetic efficiencies of net protein synthesis and net fat synthesis were estimated to be 43 and 65% respectively.6. The interactions between appetite, growth and activity in the development of obesity in the Zucker rat are discussed.
106 citations
TL;DR: In this article, an analysis of materials in which proteins were caused to react with sugars so as to cause a severe fall in their nutritionally available lysine content as assayed with both rats and chicks was made.
Abstract: 1. Analyses have been made of materials in which proteins were caused to react with sugars so as to cause a severe fall in their nutritionally available lysine content as assayed with both rats and chicks.2. With materials in which the reactions had proceeded under mild conditions (37°), the direct use of either fluorodinitrobenzene (FDNB), o-methylisourea or sodium borohydride to measure selectively those lysine units which had not engaged in Maillard reactions gave similar values which, in turn, appeared to reflect the full extent of the nutritional damage.3. Analysis by a procedure using trinitrobenzenesulphonic acid (TNBS), or the use of FDNB indirectly to measure ‘bound lysine’ failed to indicate the full extent of the Maillard reaction in mildly heated materials, although the same procedures did appear to do so when applied to materials in which sugar and proteins had been allowed to react at a higher temperature.4. With a pure protein and with fat-extracted, dried muscle that had been severely heated, all the procedures for measuring reactive lysine gave similar results, with the exception of the procedure using sodium borohydride which proved ineffective in measuring the type of damage that had occurred in these materials.5. The findings are discussed in relation to the nature of the reactions believed to take place in different types of heat damage.6. Suggestions are made of the types of materials with which different procedures can be satisfactorily used. The direct FDNB procedure and that using o-methylisourea appeared to be applicable to all our samples.
TL;DR: Feeding diets containing loose whole barley increased the firmness of the subcutaneous fat, and this was associated with a decrease in the proportion of propionic acid in the rumen fluid.
Abstract: 1. The effects of processing cereals on aspects of rumen metabolism, physiology and pathology were investigated in five experiments with lambs. Three experiments studied the effects of diets containing loose whole, pelleted whole or pelleted rolled barley on rumen volatile fatty acid ratios, rumen pH and digestibility. In a 4th experiment the effects, on the same measurements, of pelleting whole barley, maize, oats or wheat compared to feeding the whole grains in the loose form were studied. The firmness of subcutaneous fat was measured in two of these experiments when injections of cyanocobalamin or hydroxycobalamin were given and in one experiment when the diets were supplemented with two levels of cobalt. In a 5th experiment, the effect on rumination time of pelleting whole barley compared to feeding loose whole grain was assessed.2. When the diet contained whole barley in a loose mix and also when it contained whole maize, oats or wheat, the proportion of acetic acid in the rumen fluid was significantly increased and that of propionic acid decreased in comparison with the proportions observed when the pelleted diets were offered.3. The pH of the rumen liquor was not significantly changed by feeding pellets based on rolled or whole barley, but when barley, maize, oats or wheat was given in loose form, there was an increase in the pH by about 1 unit in comparison with the pelleted diets. This increase in pH was, for all cereals, associated with complete elimination of ruminitis which, except for the oat diet, was always apparent with the pelleted feeds.4. In general the digestibilities were not affected greatly by processing and in two experiments there were no significant differences. In one experiment pelleted whole barley was better digested than pelleted rolled barley. In another experiment the digestibility of barley was slightly greater when it was fed whole and loose compared to pelleted, while the digestibility of whole wheat was less than that of pelleted wheat. The mean digestibilities of organic matter for barley, maize, oats and wheat were 0.791, 0.832, 0.687 and 0.846 respectively.5. Neither injections of vitamin B12 nor cobalt supplementation of the diet had any effect on the firmness of subcutaneous fat. Feeding diets containing loose whole barley increased the firmness of the subcutaneous fat, and this was associated with a decrease in the proportion of propionic acid in the rumen fluid.6. The feeding of loose whole barley instead of pelleted whole barley caused an increase in time of rumination from 3.6 to 6.6 h/24 h.
TL;DR: In this article, a comparison of the compositions of rumen bacteria and duodenal contents was made, and it was estimated that the rhamnose, ribose and mannose came mainly from the bacteria, the arabinose, xylose and cellulose-glucose mainly from both sources.
Abstract: 1. Samples of mixed bacteria were separated from rumen digesta taken from calves, kept out of contact with adult animals, and from sheep and cows.2. For calves receiving a diet made up of equal amounts of roughage and cereals with 13–16 g nitrogen/kg dry matter, samples of mixed bacteria taken 4–6 h after feeding contained, on average, 140 g glucose in α-linked polymers (α-dextran), 25 g galactose and a total of 25 g other non-glucose, non-galactose sugars (mainly rhamnose, ribose and mannose) in combined forms per kg dry matter.3. The α-dextran content of similar bacteria samples from sheep or cows receiving diets of similar composition was 70 g/kg dry matter. Samples from animals receiving all-roughage diets contained only 25 g α-dextran/kg dry matter, but those from cows given more than 70% of their ration as concentrates (mainly cereal) contained 150 g α-dextran/kg dry matter.4. Addition of supplementary protein or urea to cereal–roughage diets given to calves greatly depressed the amount of α-dextran in the rumen bacterial samples to an average value of 60 g/kg dry matter.5. Samples taken before a morning feed (i.e. after 16 h fasting) contained less α-dextran than samples taken 4–6 h after feeding for both calves and cows.6. Under different conditions, variations in the amounts of galactose in rumen bacteria sometimes paralleled variations in α-dextran. Amounts of other non-glucose sugars did not vary greatly.7. It was estimated, from a comparison of the compositions of rumen bacteria and duodenal contents, that, in the latter, the rhamnose, ribose and mannose came mainly from the bacteria, the arabinose, xylose and cellulose-glucose mainly from the diet and the galactose and α-dextran-glucose from both sources.
TL;DR: The results show that the food-induced thermogenesis, for a moderate energy intake, is less dependent on the nature of the nutrients than was classically admitted and this increased heat production mainly induces changes in heat storage rather than in heat losses during the first hours following ingestion of a meal.
Abstract: 1. In order to reinvestigate the classical concept of specific dynamic action of food, the thermic effect of ingested glucose (50 g) or essential amino acids (50 g) or both was measured in seven healthy male subjects dressed in shorts, by using both direct and indirect calorimetry simultaneously. Experiments were performed under conditions of thermal comfort at 28°. 2. Energy ‘balance’ (heat production minus heat losses) was negative during the control period (mean heat deficit: −16.0 ± 0.8 kJ/m 2 per h. 3. Metabolic rate increased 13.6 ± 1.8% after the glucose load, 17.2 ± 1.4% after amino acids, and 17.3 ± 2.9% after both glucose and amino acids: thus there was no additive thermic effect when both nutrients were given together. 4. In contrast to the metabolic rate, heat losses were not significantly altered after nutrient ingestion; consequently, the energy ‘balance’ became rapidly positive. 5. These results show that: (a) the food-induced thermogenesis, for a moderate energy intake, is less dependent on the nature of the nutrients than was classically admitted; (b) this increased heat production mainly induces changes in heat storage rather than in heat losses during the first hours following ingestion of a meal.
TL;DR: A study by gel-filtration techniques of the soluble copper- and zinc-binding proteins in livers from calves and sheep of widely differing Cu and Zn status found that Zn was usually absent from the low-molecular-weight fraction in Zn-deficient or high-Cu livers, with Cu also being absent in the former instance.
Abstract: 1. A study has been made by gel-filtration techniques of the soluble copper- and zinc-binding proteins in livers from calves and sheep of widely differing Cu and Zn status. 2. Cu and Zn generally occurred together in three main fractions, with approximate molecular weights of > 75000, 35000 and 12000, and Zn also in one other fraction with molecular weight about 65000. The distribution of the metals between these fractions was variable and dependent on both the Cu and Zn status of the animals. 3. Zn was usually absent from the low-molecular-weight fraction in Zn-deficient or high-Cu livers, with Cu also being absent in the former instance. 4. The fraction with molecular weight of 35000 was tentatively identified as hepatocuprein. It generally accounted for only 4% of the total hepatic Cu except in Cu-deficient livers. 5. The possible relationship of these findings to the mutual antagonism between Cu and Zn is discussed.
TL;DR: The rapid changes in muscle RNA concentrations following food intake demonstrate that the minimum turnover rate of RNA in this tissue must be considerably faster than has been previously reported, and must be similar to that in liver.
Abstract: 1. This study set out to measure the sensitivity of muscle RNA content to food intake and food restriction, and to relate this to plasma insulin and intracellular amino acid concentrations.2. Young rats were trained for 2 weeks to consume their daily food ration in a single 4 h period. After this time they had resumed normal growth. The rats were killed at intervals over 24 h and subsequently at daily intervals. One group was given a protein-free meal in place of the stock diet and a similar procedure was followed. Measurements were made of plasma insulin, concentration of nucleic acids and protein in liver, heart and skeletal muscle, and free amino acids in the gastrocnemius muscle.3. Following the meal there was a fivefold increase in plasma insulin, which was accompanied by small increases in the concentrations of the intracellular amino acids in muscle. In all the tissues, after feeding, the RNA:DNA ratio increased by (%) 20, 19 and 12 in liver, skeletal and heart muscle respectively.4. During the fasting period the plasma insulin decreased, and this decrease was accompanied by rapid losses of RNA from liver, muscle and heart at similar rates. There were increases in the concentrations of the essential amino acids, especially methionine and the branched-chain amino acids, but decreases, in general, in those of the non-essential amino acids. When the protein-free meal was given, there was a small increase in the plasma insulin, but the RNA was lost from the three tissues at the same rate as in the starved rats. There was, however, a transient fall in the concentrations of the essential amino acids.5. The rapid changes in muscle RNA concentrations following food intake demonstrate that the minimum turnover rate of RNA in this tissue must be considerably faster than has been previously reported, and must be similar to that in liver. There is a direct correlation between tissue RNA concentration and that of plasma insulin, but little correlation between tissue RNA concentration and that of the intracellular essential amino acids.
TL;DR: After an initial phase in which radioactivity decreased rapidly, whole-body retention of 75Se diminished exponentially with a half-time of 96–144 d, Radioactivity in the liver, heart and plasma decreased more rapidly than that in the whole body, but radioactivity in skeletal muscle and bone decreased more slowly.
Abstract: I. The long-term fate of an oral dose of ['sSe]selenite was studied in three young women. 2. Urinary and faecal excretion, respiratory and dermal losses and whole-body retention of W e were measured, and also 75Se turnover in whole body, blood and tissues during a period of 16-20 weeks. 3. Intestinal absorption of [75Se]selenite by the three subjects was 70, 64 and 44 % of the dose. 4. Urinary excretion accounted for 14-20% of absorbed W e in the 1st week. There were only trace amounts of radioactivity in expired air and no dermal loss was detected. 5 . After an initial phase in which radioactivity decreased rapidly, whole-body retention of W e diminished exponentially with a half-time of 96-144 d. Radioactivity in the liver, heart and plasma decreased more rapidly than that in the whole body, but radioactivity in skeletal muscle and bone decreased more slowly.
TL;DR: It is concluded that the gut microflora has little influence on the utilization of dietary protein by chicks, although it may modify the route of excretion of the N which survives digestion and reaches the lower gut.
Abstract: 1. The influence of the gut microflora on protein utilization has been investigated with a series of good- and poor-quality protein diets in germ-free (GF) and conventional (CV) chicks by the measurement of net protein utilization (NPU) and uric acid excretion.2. The diets used were: 280 g protein per kg diet containing unheated or heat-damaged albumen (100 g/kg), casein (80 g/kg) and gelatin (100 g/kg); sesame protein (220 g/kg); sesame protein (220 g/kg) supplemented with lysine (5 g/kg); freeze-dried cod muscle (160 g/kg); heat-damaged cod muscle (160 g/kg); mildly-steamed egg albumen (100g/kg); heat-damaged egg albumen (100 g/kg).3. No significant differences in NPU values for the proteins measured in GF and CV chicks were found, with the exception of unsupplemented sesame protein, for which the NPU value was slightly higher in GF chicks.4. The replacement of unheated egg albumen by heat-damaged egg albumen in the 280 g protein/kg diet resulted in a decrease in uric acid excretion. With the cod-muscle diets, heat-damaging the protein caused an increase in uric acid excretion. Supplementing the sesame protein with lysine resulted in a decrease in uric acid excretion.5. Excretion of uric acid tended to be higher in CV chicks than in GF chicks with all proteins except sesame protein, with which uric acid excretion was a little higher in GF chicks.6. Endogenous nitrogen excretion was higher in GF than in CV chicks.7. It is concluded that the gut microflora has little influence on the utilization of dietary protein by chicks, although it may modify the route of excretion of the N which survives digestion and reaches the lower gut.
TL;DR: Results suggest that the national (UK) recommended energy requirements for boys and girls, aged 14 years, attending Glasgow schools in 1964 and 1971 are too high.
Abstract: 1. A study of the food intake, during a period of 7 consecutive days, was made on 192 boys and girls, aged 14 years, attending Glasgow schools in 1964. A similar study was done in 1971 on 419 boys and girls of the same age. The children came from all the various socio-economic backgrounds and were subdivided into four social groups.2. The heights and body-weights of the groups studied in 1964 and 1971 were similar but the percentage contribution of fat to the body-weight had increased in the boys.3. Between 1964 and 1971 there had been a decrease in the mean energy intake of both boys and girls of between 0.8 and 1.0 MJ (200–250 kcal)/d. A similar proportionate decrease had also occurred in the protein, fat, carbohydrate, calcium and iron contents of the diet. However, no individual had a very low intake of protein.4. Only the boys of the poorest social group (4) showed a lower intake of nutrients than the other groups. There were almost no differences between the girls from the different socio-economic groups.5. Eating school meals did not affect levels of total energy and nutrient intake.6. The proportion of energy and nutrients derived from different food groups did not appear to have appreciably altered in the two surveys, although the amount of milk drunk had become less. Fish, eggs and cheese contributed surprisingly little to the diet.7. The combination, in both sexes, of a reduction in energy intake in 1971 compared to 1964, together with, for the boys, an increased body fat content, could be accounted for by a marked reduction in physical activity.8. Although a comparison of the energy intake of the fattest and of the thinnest boys showed no clear differentiation, there was a consistently lower energy intake, in all social groups, by the fattest girls (‘fattest’ 7.07 MJ (1690 kcal)/d; ‘thinnest’ 9.23 MJ (2207 kcal)/d).9. These and other recent results suggest that the national (UK) recommended energy requirements, at least for this group, are too high.
TL;DR: The method was finally adapted to situations with either frequent or infrequent feeding patterns, and the need for a priming infusion period of 16 h before the collection and sampling of duodenal digesta was established.
Abstract: I. A method is described for the estimation of the microbial and dietary protein entering the small intestine of sheep, based on an intraruminal infusion of [s5S]sulphate, and isolation of the labelled microbial protein. 2. Samples of the microbial fraction contained in duodenal digesta were isolated by highspeed centrifugation and a scheme of analysis was devised for the determination of the specific activity of the methionine in the microbial fraction and the duodenal digesta. 3. In the absence of dietary methionine in duodenal digesta, it was postulated that the ratio of the specific activities of microbial methionine (M) and digesta methionine (D) should equal I. Using two purified diets containing urea as the sole source of nitrogen, the M : D ratio was found to vary from 0.94 to 1.08 (mean 1.01 4. Addition of known quantities of dietary protein to labelled duodenal digesta obtained from one sheep fed on a non-protein diet increased the M:D ratio. Prediction of the dietary protein present from changes in the M : D ratio gave satisfactory agreement with the amounts of dietary protein known to be present (96-101 % of known value, mean 98-4 i1.24 %). 5. When animals were fed hourly the M:D ratio remained reasonably constant throughout 24 h. In contrast, with twice-daily feeding the M : D ratio varied markedly throughout the 24 h. However, summation of the estimates made of the flow of microbial and dietary protein into the duodenum in each z h period throughout 24 h agreed closely with the estimates made from samples withdrawn from the accumulated flow of digesta over the whole 24 h period. 6. The method was finally adapted to situations with either frequent or infrequent feeding patterns, and the need for a priming infusion period of 16 h before the collection and sampling of duodenal digesta was established. 0.01).
TL;DR: The supply of essential amino acids to the tissues of sheep is improved, compared with the amino acid composition of the diet, as the result of ruminal biosynthesis of essential Amino acids and ruminal degradation of non-essential amino acids and preferential absorption of Essential amino acids through the intestinal wall.
Abstract: 1. The rate of flow of digesta along the intestinal tract, and particularly the changes occurring in proteins during their passage through the intestine were determined in six rams; each animal was fistulated with three cannulas which involved six different sites of the intestine. Cr2O3 was used as a marker substance to measure the rate of flow of the digesta.2. In the sections of the intestine from 1 to 15 m posterior to the pylorus the amounts of water, dry matter and total nitrogen decreased gradually as a result of their absorption through the intestinal wall. The region of the intestine situated at a distance of 7–15 m from the pylorus was more active with respect to the absorption of N, whereas water and dry matter were adsorbed to a greater extent in the region from 1 to 7 m from the pylorus.3. The only part of the intestine in which substantial increases of water, dry matter and total N were found was the section immediately distal to the pylorus, and these increases were caused by the inflow of bile, and pancreatic and duodenal juices. The net increase found beyond the entry of the common bile duct was 2.7 g protein N and 2.0 g non-protein N (NPN)/24 h.4. The activities of trypsin, chymotrypsin and carboxypeptidase A and the ratio α-NH2 NPN: protein N increased from the pylorus up to a distance of 7 m and decreased again from this point to a distance of 15 m from the pylorus.5. In the sections of the intestine between 1 and 3 and between 3 and 7 m distant from the pylorus the extent of proteolysis exceeded considerably that of absorption of amino acids through the intestinal wall. This was concluded from the decrease in the rate of flow of protein amino acids (by 31% between 1 and 3 m distant from the pylorus and by 34% between 3 and 7 m) and the simultaneous increase in non-protein amino acids (by 20% in the region between 1 and 3 m) or no change in non-protein amino acids (between 3 and 7 m).6. The relatively greater decrease in non-protein amino acids (by 57%) compared with that of protein amino acids (by 41%) occurring in the section 7 to 15 m distant from the pylorus showed that this is an area of most intensive absorption of amino acids.7. In the lower section of the intestine, from 15 to 25 m distant from the pylorus, the total amount of amino acids showed almost no change; probably a net effect of loss and gain of amino acids mainly due to microbial activities. Increases in the dehydrogenase activity suggested enhancement of bacterial activity in this lower region of the intestine.8. The supply of essential amino acids to the tissues of sheep is improved, compared with the amino acid composition of the diet, as the result of ruminal biosynthesis of essential amino acids and ruminal degradation of non-essential amino acids and preferential absorption of essential amino acids through the intestinal wall, particularly in the section of most intensive absorption, 7–15 m distant from the pylorus.
TL;DR: A method was developed for the estimation of tryptophan in purified proteins or in feeding-stuffs and results agreed fairly well with published values for purified proteins, though rather less well for the samples analysed by other workers.
Abstract: 1. A method was developed for the estimation of tryptophan in purified proteins or in feeding-stuffs. Samples were hydrolysed by autoclaving them with barium hydroxide in polypropylene flasks or tubes. Excess Ba was precipitated as the hydroxide by cooling, and hydrogen sulphide formed during hydrolysis was removed under reduced pressure. Tryptophan was assayed colorimetrically with dimethylaminobenzaldehyde by comparison with tryptophan standards carried through the complete procedure.2. The method was applied to purified proteins, to analysed materials and to a wide range of samples. Results agreed fairly well with published values for purified proteins, though rather less well for the samples analysed by other workers. Reasons are discussed. The samples examined gave results in the expected range.
TL;DR: It was concluded that the gut microflora of the chick had little influence on the digestion of the proteins in the diets tested, but may serve an important role in the degradation of endogenous proteins and the recycling of N.
Abstract: 1. To assess the part played by the microflora in the digestion of proteins, the amino acid composition of the excreta and the apparent and true digestibilities of individual amino acids were measured in germ-free (GF) and conventional (CV) chicks.2. Three diets were used: diet 1, nitrogen-free; diet 2,280 g protein/kg as (g/kg): casein 80, gelatin 100 and freeze-dried egg albumen 100 and diet 3,280 g protein/kg as diet 2 but with heat-damaged instead of freeze-dried egg albumen. Half of the GF and half of the CV chicks received the N-free diet in the first 7 d of test and the other half of each group received either diet 2 or diet 3. In the second 7 d test period those chicks which had been given the N-free diet received either diet 2 or diet 3 while those which had been given protein diets received the N-free diet. Total amino acids were measured in hydrolysates of the soluble and insoluble fractions of the excreta collected in the last 3 d of each test period.3. The amino acid composition of the soluble fraction of the excreta of chicks given either diet 2 or diet 3 differed markedly from that of chicks given the N-free diet. The amino acid composition of the insoluble fraction of the excreta of chicks given diet 2 was similar to that of chicks given the N-free diet, whereas that of chicks given diet 3 was markedly different and resembled egg albumen in composition.4. In the soluble fraction of excreta from CV chicks given diets 1 and 2 the proportions of threonine, serine and glucosamine were lower and those of methionine, leucine, isoleucine and phenylalanine were higher than in those from GF chicks, particularly on diet 1. In the insoluble fraction of excreta from CV chicks given these two diets, compared with GF chicks, there were lower proportions of serine and proline and higher proportions of cysteic acid and lysine, the latter particularly with diet 1.5. Lower proportions of threonine, serine and glucosamine were also observed in the soluble fractions of excreta from the CV chicks given diets 1 and 3, compared with GF chicks, whereas the proportion of glutamic acid was higher. With these two diets the insoluble fraction from CV chicks contained a higher proportion of alanine. In each instance the environmental effect was greater with diet 1.6. No effect of environment on either apparent or true digestibility of individual dietary protein amino acids was demonstrated, with the exception of threonine in diet 2, the true digestibility of which was higher in GF than in CV chicks.7. It was concluded that the gut microflora of the chick had little influence on the digestion of the proteins in the diets tested, but may serve an important role in the degradation of endogenous proteins and the recycling of N.
TL;DR: The high serum concentration of Cu with diets high in Mo indicates that Mo either mobilizes tissue Cu or inhibits Cu uptake, or both, and that Mo had no effect on Cu absorption.
Abstract: I. The effect of various dietary levels of molybdenum on uric acid and copper excretion was studied in experiments with four adult men given diets based on two sorghum varieties (Sorghum vulgure Pers.) differing widely in Mo content. 2. With a Mo intake of 160, 540 or I j40 pg/d the urinary excretion of uric acid was unaltered. 3. The excretion of Cu in urine increased with increasing Ma intake. 4. Cu-balance studied with high- and low-Mo diets showed that with a high-Mo diet urinary Cu excretion increased but faecal Cu was unaffected. This indicates that dietary Mo had no effect on Cu absorption. 5. The high serum concentration of Cu with diets high in Mo indicates that Mo either mobilizes tissue Cu or inhibits Cu uptake, or both. In populations subsisting on plant foods, the principle sources of dietary molybdenum are cereals, millets and pulses. Mo is an integral part of xanthine oxidase (Xanthine: oxygen oxidoreductase; EC I. 2.3.2), an enzyme concerned in uric acid synthesis. Tissue concentrations of this enzyme in experimental animals are related to the dietary intake of Mo (Hart & Bray, 1967; Underwood, 1971). In regions with soil rich in Mo, prevalence of gout is reported to be high (Kovalsky & Vorotnitskaya, 1970) and uric acid production is shown to be affected by very high intakes of Mo (Kovalsky, Yarovaya & Shmavonyan, 1961). In certain parts of India, urolithiasis is common in millet-eating populations (Patwardhan, 1961). The millet sorghum (Sorghum vulgare Pers.), one of the important staple foods in these regions, is relatively rich in Mo when compared with rice (Deosthale, unpublished). However, there is no direct evidence of the role of dietary Mo in uric acid synthesis in man, especially in relation to renal-stone formation. Dietary Mo also affects copper metabolism in various animal species. High intake of Mo apparently hastens Cu deficiency, especially in cattle and sheep ; other species are apparently less affected (Underwood, 1971). The mechanism underlying the effect of high Mo intake on Cu deficiency is unknown. Two sorghum grain samples differing widely in their Mo content were available in large quantities. We are able, therefore, to study the effect of diets based on the high- and low-Mo varieties of sorghum on uric acid and Cu excretion in human subjects.
TL;DR: It is concluded that the repletion technique provides a sensitive means of assessing the availability of Cu in ruminant diets and was used to assess the biological availability of the added Cu.
Abstract: 1. Ewes were made hypocupraemic by feeding a copper-deficient diet and the subsequent responses in plasma Cu obtained when Cu was added to the diet were used to assess the biological availability of the added Cu.2. The uniformity of responses was investigated by repleting thirty-six ewes for 33 d on two occasions with a standard diet containing 5.0 mg Cu/kg dry matter (DM). The mean responses were 0.36 and 0.33 mg/l and the coefficient of variation was approximately 53% on each occasion. The marked individual differences were largely repeatable, the correlation coefficient (r) within individuals being 0.68 (P < 0.001).3. A dose: response relationship was investigated by giving five groups of seven ewes diets containing 2.7, 4.2, 5.7, 7.2 or 8.7 mg Cu/kg DM for 33 d. Each increment in dietary Cu above 4.2 mg/kg significantly increased the response in plasma Cu. The relationship between plasma Cu response (y, mg/l) and Cu intake (x, mg/d) after 21 d was y = 0.0871x−0.250 (r = 0.99; 3 df).4. The source of individual variation was investigated by comparing the responses of three ‘slow’ and three ‘fast’ responding ewes from Expt 1 to Cu given as a continuous intravenous infusion at rates of 0.05–0.3 mg/d. The relationship between plasma Cu response (y) and infusion rate (x, mg/d) after 17 d, was y = 2.135x –0.156 (r = 0.86; P < 0 .001). The regression coefficients for ‘slow’ and ‘fast’ responding ewes were similar, as was their metabolism of intravenous 64Cu, suggesting that the individual differences were due to differences in absorption rather than in the metabolism of absorbed Cu. Faecal endogenous Cu excretion was estimated to be 0.127 ± 0.019 (mean ± SE) mg/d.5. The relative responses to oral and intravenous Cu were used to estimate the true availability of dietary Cu; in one experiment it was 4.1% and for individual ewes in another experiment, availabilities ranged from 4.5 to 11.4%. The figures are compared with assessments by conventional techniques.6. It is concluded that the repletion technique provides a sensitive means of assessing the availability of Cu in ruminant diets.
TL;DR: It is concluded that the Fe nutrition of rice-eating communities could be improved significantly by the addition of ascorbic acid to the diet.
Abstract: 1. Iron absorption from rice-containing meals was measured by red cell utilization of radioactive Fe in sixty-six volunteer multiparous Indian women.2. In all the studies salt added during the cooking process was used as the carrier for supplemental inorganic Fe and ascorbic acid.3. Intrinsic Fe in the rice and supplementary inorganic Fe were absorbed to the same extent, with a wide range of absorption values.4. There was a striking difference between the mean absorption of a 3 mg dose of ferrous Fe given to fasting subjects in a solution containing 30 mg ascorbic acid and that of Fe in a rice meal (48.7 and 3.5% respectively).5. When ascorbic acid was added during cooking there was a threefold increase in the absorption of both intrinsic Fe and supplementary Fe when a sufficient quantity (60 mg) was present.6. It is concluded that the Fe nutrition of rice-eating communities could be improved significantly by the addition of ascorbic acid to the diet.
TL;DR: A metal-binding fraction with a molecular weight of about 12000 in calf and sheep liver has been characterized as a metallothionein-like protein and the relative proportions of Cu and Zn in the fraction are dependent on the Cu: Zn ratio in the liver.
Abstract: 1. A metal-binding fraction with a molecular weight of about 12000 in calf and sheep liver has been characterized as a metallothionein-like protein. 2. The combined concentrations of copper and zinc in the fraction (as μg/g liver) are a direct function of liver Zn concentration. 3. The relative proportions of Cu and Zn in the fraction are dependent on the Cu: Zn ratio in the liver. 4. These findings may be relevant to the mutual interaction between Cu and Zn.
TL;DR: It was concluded that rumen micro-organisms are mainly responsible for this degradation of grass lipids and pigments in the rumen of the sheep, although grass itself also contains enzymes which can degrade galactolipids.
Abstract: 1. Digestion of grass lipids and pigments in the rumen of the sheep has been studied during starvation and following the administration of 14C-labelled grass.2. Both galactolipids contained in chloroplasts are rapidly degraded, although mono-galactosyldiglycerides disappear faster than digalactosyldiglycerides. It was concluded that rumen micro-organisms are mainly responsible for this degradation, although grass itself also contains enzymes which can degrade galactolipids.3. Rumen contents can degrade added 14C-labelled mono- and digalactosyldiglycerides in vitro at a rate sufficient to account for the disappearance of galactolipids in the intact rumen. The initial enzyme attack is probably a successive deacylation to give monogalactosylglycerol and digalactosylglycerol.4. Most of the chlorophyll pigments are rapidly converted into phaeophytins by loss of magnesium. A small proportion of chlorophyll a and more of chlorophyll b remains intact even after 24 h starvation. On the other hand, about half the phaeophytin undergoes further rapid decomposition to yield phylloerythrin.5. Although the grass phospholipids are extensively degraded, β-carotenes and many non-polar compounds, e.g. steroids, appear to undergo little change in the rumen.
TL;DR: Frequency of feeding had no effect on the response of pigs given the control diet and the addition of lysine at both levels significantly increased the significance of a significant interaction.
Abstract: 1. Pigs from 20 to 47 kg live weight were given a wheat–safflower diet supplemented with either 0, 2 or 4 g L-lysine/kg either once daily or in six equal portions at intervals of 3 h.2. The addition of lysine at both levels significantly (P < 0.001) increased growth rate, feed conversion and lean content of the ham.3. Frequency of feeding had no effect on the response of pigs given the control diet.4. A significant interaction (P < 0.05) between frequency of feeding and lysine supplementation occurred for growth rate. Growth responses to the supplements of 2 and 4 g L-lysine/ kg with once-daily feeding were only 43 and 69% of those achieved under the frequent-feeding regimen.
TL;DR: The over-all secretion of digestive enzymes increased parallel to the increase in food consumption, and specific activities were the same in the force-fed and ad lib.-fed groups, except for a higher activity in intestinal amylase.
Abstract: 1. Force-feeding of young chicks for 15 d increased kidney arginase (EC 3·5·3·1) activity threefold. Fasting for 30 h decreased this activity by 50%.2. Liver xanthine dehydrogenase was slightly increased after force-feeding and decreased following fasting.3. The specific activities of two pentose-phosphate-cycle enzymes were not significantly affected by force-feeding, but glucose-6-phosphate dehydrogenase (EC 1.1.1.49) decreased following fasting.4. The over-all secretion of digestive enzymes increased parallel to the increase in food consumption. Therefore, despite an increased absolute weight of the pancreas and intestinal chyme, specific activities were the same in the force-fed and ad lib.-fed groups, except for a higher activity in intestinal amylase.5. Fasting did not affect the pancreatic enzymic activities.