bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA shuffling as a tool for protein crystallization
Authors: Keenan Robert J. , Siehl Daniel L. , Gorton Rebecca , Castle Linda A.
Published: June 2005

The success of structural studies performed on an individual target in small scale or on many targets in the systemwide scale of structural genomics depends critically on three parameters: (
i
) obtaining an expression system capable of producing large quantities of the macromolecule(s) of interest, (
ii
) purifying this material in soluble form, and (
iii
) obtaining diffraction-quality crystals suitable for x-ray analysis. The attrition rate caused by these constraints is often quite high. Here, we present a strategy that addresses each of these three parameters simultaneously. Using DNA shuffling to introduce functional sequence variability into a protein of interest, we screened crude lysate supernatants for soluble variants that retain enzymatic activity. Crystallization trials performed on three WT and eight shuffled enzymes revealed two variants that crystallized readily. One of these was used to determine the high-resolution structure of the enzyme by x-ray analysis. The sequence diversity introduced through shuffling efficiently samples crystal packing space by modifying the surface properties of the enzyme. The approach demonstrated here does not require guidance as to the type of mutation necessary for improvements in expression, solubility, or crystallization. The method is scaleable and can be applied in situations where a single protein is being studied or in high-throughput structural genomics programs. Furthermore, it should be readily applied to structural studies of soluble proteins, membrane proteins, and macromolecular complexes.
Effects of threshold choice on biological conclusions reached during analysis of gene expression by DNA microarrays
Authors: Pan Kuang-Hung , Lih Chih-Jian , Cohen Stanley N.
Published: June 2005

Global analysis of gene expression by using DNA microarrays is employed increasingly to search for differences in biological properties between normal and diseased tissue. In such studies, expression that deviates from defined thresholds commonly is used for creating genetic signatures that characterize disease vs. normality. Although it is axiomatic that the threshold parameters applied to microarray analysis will alter the contents of such genetic signatures, the extent to which threshold choice can affect the fundamental conclusions made from microarray-based studies has not been elucidated. We used
gabriel
(Genetic Analysis By Rules Incorporating Expert Logic), a platform of knowledge-based algorithms for the global analysis of gene expression, together with conventional statistical approaches, to examine the sensitivity of conclusions to threshold choice in recently published microarray-based studies. An analysis of the effects of threshold decisions in one of these studies [Ramaswamy, S., Ross, K. N., Lander, E. S. & Golub, T. R. (2003)
Nat. Genet.
33, 49–54], which arrived at the important conclusion that the metastatic potential of primary tumors is encoded by the bulk of cells in the tumor, is the focus of this article. We discovered that support for this conclusion highly depends on the threshold used to create gene expression signatures. We also found that threshold choice dramatically affected the gene function categories represented nonrandomly in signatures. Our results suggest that the robustness of biological conclusions made by using microarray analysis should be routinely assessed by examining the validity of the conclusions by using a range of threshold parameters.
Stem cells in the dog heart are self-renewing, clonogenic, and multipotent and regenerate infarcted myocardium, improving cardiac function
Authors: Linke Axel , Müller Patrick , Nurzynska Daria , Casarsa Claudia , Torella Daniele , Nascimbene Angelo , Castaldo Clotilde , Cascapera Stefano , Böhm Michael , Quaini Federico , Urbanek Konrad , Leri Annarosa , Hintze Thomas H. , Kajstura Jan , Anversa Piero
Published: June 2005

The purpose of this study was to determine whether the heart in large mammals contains cardiac progenitor cells that regulate organ homeostasis and regenerate dead myocardium after infarction. We report that the dog heart possesses a cardiac stem cell pool characterized by undifferentiated cells that are self-renewing, clonogenic, and multipotent. These clonogenic cells and early committed progeny possess a hepatocyte growth factor (HGF)–c-Met and an insulin-like growth factor 1 (IGF-1)-IGF-1 receptor system that can be activated to induce their migration, proliferation, and survival. Therefore, myocardial infarction was induced in chronically instrumented dogs implanted with sonomicrometric crystals in the region of the left ventricular wall supplied by the occluded left anterior descending coronary artery. After infarction, HGF and IGF-1 were injected intramyocardially to stimulate resident cardiac progenitor cells. This intervention led to the formation of myocytes and coronary vessels within the infarct. Newly generated myocytes expressed nuclear and cytoplasmic proteins specific of cardiomyocytes: MEF2C was detected in the nucleus, whereas α-sarcomeric actin, cardiac myosin heavy chain, troponin I, and α-actinin were identified in the cytoplasm. Connexin 43 and N-cadherin were also present. Myocardial reconstitution resulted in a marked recovery of contractile performance of the infarcted heart. In conclusion, the activation of resident primitive cells in the damaged dog heart can promote a significant restoration of dead tissue, which is paralleled by a progressive improvement in cardiac function. These results suggest that strategies capable of activating the growth reserve of the myocardium may be important in cardiac repair after ischemic injury.
The diet of the Tristan da Cunha Islanders
Authors: Taylor Elaine C. , Hollingsworth Dorothy F. , Chambers Margaret A.
Published: June 2005

1. An assessment of the Islanders' food consumption on Tristan da Cunha before the volcanic eruption of 1961 was made (Part 1). The mean daily intake of energy was 2030 kcal per person and the calories derived from protein, fat, carbohydrate and alcohol accounted for 21, 26, 50 and 3% respectively of the total calorie intake, the proportion of calories derived from protein being about twice that found in other types of diet. 2. The weekly food intake of thirty-seven families resident at Calshot, Hants, was measured in July 1963, 3–4 months before the Islanders left England to return to Tristan da Cunha (Part 2). The mean intake of energy was 1750 kcal per person per day and the calories derived from protein, fat and carbohydrate accounted for about 12, 41 and 47% respectively of total calorie intake, proportions similar to those found in present-day British diets. The proportion of other nutrients in relation to calories also resembled those in British diets, except for vitamin A and ascorbic acid, which were relatively low in the Tristan diet. 3. A comparison of the results for the Islanders with those for a sample of households surveyed for the National Food Survey was made. The Islanders consumed less of all nutrients, and the average energy value met only 65% of estimated requirements compared with 108% in the British sample. 4. Details of foods consumed and of the Islanders' food patterns and preferences are given. There is some evidence that the Tristanidns did not like their former staple foods, potatoes and fish, as available in England, though at the time of the survey they had not appreciably switched to the British staple, bread. 5. The relatively low food intake reported in this study conforms with that recorded in the Norwegian investigation of 1937–8 (Henriksen & Oeding, 1946) and with calculations of island food supplies before 1961 (Part 1). 6. Possible explanations for the low food intake are discussed. It is suggested that the Islanders may not be very active and that energy balance studies on individuals who have returned to Tristan da Cunha might throw some light on the results of this survey.
The heat of combustion of the urine of sheep and cattle in relation to its chemical composition and to diet
Authors: Blaxter K. L. , Clapperton J. L. , Martin A. K.
Published: June 2005

1. The results of over 500 determinations of the heat of combustion of the urine produced by cattle and sheep have been analysed statistically. 2. The analytical errors for nitrogen, carbon and heat of combustion were ±0.54, ±1.4 and ±2.2%. The error attached to an estimate of the heat of combustion of the urine produced by an individual sheep in 4 days was ± 10%.3. At the maintenance level of feeding, the heat of combustion of the urine (U kcal/ 100 kcal food) was related to the crude protein content of the diet (P%)by the equation

U = 0.25P+1.6

with a residual standard deviation of ±0.88 kcal/100 kcal.4. Regression analysis of the relation between the heat of combustion of urine and its N content showed significant differences with diet. The heat of combustion of the urine of sheep was 9.7 kcal/g C and of cattle 10.3 kcal/g C, and did not vary with diet. 5. It is shown that the variation in the heat of combustion of urine/g N and its relative constancy/g C arises largely from variation, from diet to diet, in the proportion of the N excreted as hippurate. 6. The results have been combined with the results of a similar analysis (Blaxter & Clapperton, 1965) of methane production by sheep to show that the ratio of metabolizable energy to digested energy varies very little from mean values of 0.82 for roughages, 0.85 for cereals and 0.79 for oilseed cakes and meals.
The effect of functional groups other than carboxyl on the metabolism of C18and C12alkyl compounds by sheep
Authors: Czerkawski J. W. , Blaxter K. L. , Wainman F. W.
Published: June 2005

1. Sixteen experiments were made with eight sheep to determine the effects of various compounds on methane production, digestion and metabolism. 2. Two experiments with two sheep given stearic acid incorporated in the diet showed that it depressed CH4production by 2.7 moles/mole stearic acid. The digestion of the basal diet was also depressed, the apparent digestibility of dietary cellulose falling from 61.7 to 55.0%. 3. Three experiments with two sheep given liquid paraffin (mainly the C18hydrocarbon) by infusion into the rumen showed that it had no effect on CH4production and that it increased the excretion of fatty acids in the faeces and the non-lipid energy of the faeces. 4. Oleyl alcohol infused into the rumen of one sheep had no effect on CH4production. It was excreted unchanged in large amounts in the faeces and increased the faecal excretion of fatty acids. 5. A preparation of sulphated C18and Cla alcohols infused into the rumen of one sheep reduced CH4production by 11.4 moles/mole sulphated alcohol. The preparation also caused a large increase in the excretion of non-lipid calories in the faeces and in the heat production of the animal. A larger amount of sulphated alcohols, given by infusion into the rumen of another sheep, reduced CH4production to 41% of the initial values in 5 days, but caused refusal of food. 6. Two experiments were made with two sheep in which lauric acid was given by infusion into the rumen: Food refusals occurred within 48 h of commencing the infusion. 7. Sodium lauryl sulphate given to two sheep by infusion into the rumen reduced CHI production by 8.4 moles/mole. It greatly increased the faecal loss of non-lipid energy and also increased the heat production of the animals. When two further sheep were given sodium lauryl sylphate incorporated in the diet, cellulose digestion was depressed. Evidence of hydrolysis of the sodium lauryl sulphate was obtained. 8. Lauryl alcohol had no effect on the CH4production of one sheep, but increased the faecal excretion of lipid. Inorganic sulphate had no effect on metabolism in an experiment with a further sheep. 9. The results, together with previous work with oleic, linoleic and linolenic acid (Czerkawski, Rlaxter & Wainman, 1966a), suggest that depression of CH4production is a function of molecules with both polar and non-polar activities, that is with surface-active properties, and that such compounds when given to ruminants have a greater affect on the CH4-producing organisms than on organisms concerned in cellulose digestion.
Effect of dietary phosphorus supplementation on the uptake of radioactive strontium in rats
Authors: Harrison G. E. , Howells G. R. , Pollard Jill , Kostial Krista , Manitaševi´c R.
Published: June 2005

1. After feeding radioactive markers 85Sr and 45Ca for 10 days to weanling and adult rats receiving basal diets all of which contained adequate calcium and phosphorus to support normal growth, the skeletal retention of the markers was compared with that in litter-mates receiving seven different P compounds as dietary supplements so that the P intake was increased 2 to 3½ times. 2. In weanling rats a dietary supplement of KH2PO4 decreased the skeletal retention of 85Sr by some 30% without affecting the retention of 46Ca. In adults on this supplement, the skeletal retention of 85Sr was reduced by over 40% compared with controls on the same basal diet. 3. When the supplement contained Ca as well as P the reduction in skeletal retention of 85Sr in young and adult rats was greater than when no Ca was present in the supplement. 4. It is concluded that there was no experimental evidence to show that supplements of P which also contained Ca induced any Ca deficiency in the rats. 5. In rats receiving P supplements which also contained Ca, the ratio of the skeletal retention of 85Sr, experimental to controls, was 0.45 for weanling rats and 0.52 in adults, 34 weeks old. These ratios were not significantly different for any of the seven supplements used. 6. From comparisons with previous experiments, it is concluded that supplementation with Ca plus P is more promising as a remedial measure for decreasing the uptake of radioactive Sr from the diet than supplementation with Ca alone.
Severe undernutrition in growing and adult animals
Authors: Lister D. , McCance R. A.
Published: June 2005

1. Ten pigs which had been undernourished for a year, and weighed about 5.5 kg at that time, were rehabilitated on an excellent dict. They grew fast, but no faster per kg body-weight than normal pigs, and they stopped growing at the same chronological age. Consequently, they did not attain the same adult size as the normally reared pigs.

2. The rehabilitated animals appeared to be fatter than the control animals, but the proportions of muscle to bone in the carcasses of the males and females were within the range to be expected in normal animals of the same fat-free weight, although the castrates may have been somewhat less muscular on this basis.

3. The weights of the organs per kg of fat-free body weight were within the limits found in normally reared animals of the same fat-free weight.
The effect of uncooked and roll-dried wheat starch, alone and mixed in equal quantity with sucrose, on dental caries in the albino rat
Authors: Green R. M. , Hartles R. L.
Published: June 2005

1. Eighty weanling albino rats, five from each of sixteen litters were distributed between five dietary groups in sixteen randomized blocks. Each block was formed from within a litter and each animal in the block received a different diet.

2. The main features of the diets were: group 1, 72% sucrose; group 2, 72% uncooked wheat starch; group 3, 72% roll-dried wheat starch; group 4, 36% sucrose and 36% uncooked starch; group 5, 36% sucrose and 36% roll-dried starch.

3. The rats were killed after 20 days on the diets and assessed for dental caries. The rats consuming diets containing sucrose (groups 1, 4 and 5) had significantly more caries than animals receiving diets in which starch was the sole carbohydrate. The diet containing roll-dried wheat starch produced significantly more caries than uncooked starch. The mixture of uncooked starch and sucrose was more cariogenic than the mixture of roll-dried starch and sucrose.
Transaminase activity in the rumen liquor of sheep
Authors: Rekib Abdur , Sadhu D. P.
Published: June 2005

1. The presence of transaminase activity in rumen contents has been demonstrated. The level of activity varied with time after feeding and was influenced by the nature of the diet.

2. Rumen contents from a sheep given a diet containing casein showed greater transaminase activity at 2 h than at 6 h after feeding. Conversely, with a diet containing urea and maize, the activity was higher at 6 h than at 2 h after feeding.

3. The greater part of the transaminase activity of rumen liquor was associated with the fraction containing protozoa and food residues while the cell-free fraction contained no transaminase activity under the experimental conditions.
An investigation of very low calorie intakes reported in Jamaica
Authors: Ashworth Ann
Published: June 2005

1. A previous dietary survey has reported some very low calorie intakes in a farming community in rural Jamaica. Subsequently, ten subjects were specially selected on the basis of being very poor and underfed and individual dietary surveys were carried out in their homes for 7 days.

2. The accuracy of the dietary surveys was tested in a metabolic ward by feeding the subjects with the same meals as were recorded in their homes. Body-weight, calorie and nitrogen intakes, and urinary and faecal N outputs were measured.

3. Basal metabolic rates and the calorie expenditure during sleep were measured to investigate whether any metabolic adaptations to the low calorie intakes had occurred. The calorie cost of performing a standard step-test was measured and compared with that of well-fed control subjects to find out if there were differences in physical efficiency.

4. Nine of the subjects were found to be thinner than the average person of the same age and sex in their district, and were considerably thinner than the average American.

5. Five of the dietary surveys were thought to have given a correct picture of the normal dietary pattern. The remaining five surveys were unsatisfactory.

6. In the five correct surveys, calorie intakes were 61, 69, 72, 78 and 98% of the FAO recommended requirements.

7. No clear-cut evidence of an adaptive change in basal metabolic rate was found.

8. Few calories were available for physical exertion and there was an apparent increase in the physical efficiency of work.
Severe undernutrition in growing and adult animals
Authors: McCance R. A. , Owens P. D. A. , Tonge C. H.
Published: June 2005

1. Pigs, held by undernutrition to a weight of about 5.5 kg till they were a year old, were then rehabilitated on an excellent growing ration, and killed when they were fully mature.

2. Undernutrition of this degree of severity delayed the growth and development of the teeth, but relatively less than that of the body or the jaws.

3. The teeth became abnormally sited and the shape of the mandible changed.

4. During rehabilitation, some of the crowns and most of the roots of the molar teeth failed to reach their proper size.

5. Some of the molar teeth remained permanently impacted and out of alignment.

6. The fine structure of the teeth, particularly of those parts formed during the period of undernutrition, was still abnormal when the animals were killed.
Iron metabolism during lactation in the rabbit
Authors: Tarvydas H. , Jordan Susan M. , Morgan E. H.
Published: June 2005

1. Iron metabolism was studied during lactation in the rabbit by the intravenous injection of59Fe in order to measure plasma Fe turnover, Fe transfer to the milk and Fe absorption by the suckling young.

2. Although the plasma and red cell volumes were elevated in the lactating animal a significant increase of plasma Fe turnover was not demonstrated.

3. Between 2.5 and 11.5% of the injected dose of59Fe appeared in the milk during the following 2–3 weeks. Secretion into the milk continued for at least 2 weeks, and the specific activity of Fe was higher in milk than in plasma, suggesting that the mammary gland contained a pool of Fe, with a low turnover rate from which milk Fe was derived. On the average, 150–315 μg Fe were secreted in the milk per day.

4. Almost all the59Fe ingested by suckling rabbits, either in milk or sodium chloride solution, was absorbed.

5. It is concluded that in the rabbit the relatively small increase of body Fe which occurs during suckling is entirely due to the limited supply of Fe available in the milk. The high concentration of Fe-binding protein present in rabbit milk did not appear to aid Fe transfer into the milk or to affect Fe absorption by the young.
The nutritive value of groundnut protein
Authors: Dawson R.
Published: June 2005

1. The effects of heat treatment on the proteins of the groundnut were studied by examining the electrophoretic patterns of the proteins extracted from samples of a laboratory-prepared groundnut flour after various heat treatments.

2. Marked changes in the electrophoretic pattern of the conarachin fraction were found and these changes correlated with changes in nutritive value.

3. Marked differences were found between the electrophoretic patterns of the conarachin fractions extracted from twenty commercial groundnut meals, and these differences could be correlated with nutritive value.

4. It is suggested that an examination of the electrophoretic pattern of the conarachin fraction could provide a useful and rapid means of determining the nutritive value of a groundnut meal.
The metabolic response of young women to changes in the frequency of meals
Authors: Swindells Yola E. , Holmes Susan A. , Robinson Marion F.
Published: June 2005

1. Six healthy young women residing in a metabolic unit, but continuing their normal activities, received a uniform diet for 27 days, subdivided into four periods of 6 days and a final collection period of 3 days.

2. The daily food was divided into equal-sized portions; the subjects ate their daily quota as three meals a day in periods 1, 3, and 5 (control), two meals in period 2 (gorging), and nine meals in period 4 (nibbling).

3. The metabolic response of each subject was investigated by measurements of energy expenditure, and by analysis of the food, the urine and the faeces.

4.The subjects showed distinct differences in response, but for most subjects the changes in body-weight and in the metabolism of nitrogen and fat appeared unrelated to the frequency of the meals.
Effects of protein and vitamin E on haemoglobin formation in rats
Authors: Bunyan J. , Green J. , Cawthorne M. A.
Published: June 2005

1. Young rats were given, for 9 weeks, vitamin E-deficient diets containing either 20% or 10% casein, with and without a dietary supplement of 350 ppm D-α-tocopheryl acetate. For the next 5 weeks the casein content of the low-protein diets was decreased to 7%.

2. The low-protein diets induced severe growth depression.

3. The dialuric acid-induced haemolysis test showed that the rats given the 20% casein vitamin E-deficient diet were depleted of vitamin E, but that the rate of depletion on the lowcasein diet was slower.

4. Haemoglobin levels were slightly decreased by the 10% casein diets after 9 weeks, but this difference was not found after 14 weeks, comparing 20% and 7% casein. Dietary vitamin E had no effect on haemoglobin levels or erythrocyte counts.
Assessment of the heart-rate method for determining energy expenditure in man, using a whole-body calorimeter
Authors: Dauncey M. J. , James W. P. T.
Published: June 2005

1. The heart-rate (HR) method for determining the energy expenditure of free-living subjects has been evaluated using a whole-body calorimete in which individuals lived continuously for 27 h while carrying out normal daily activities. Eight male volunteers each occupied the calorimeter on at least two occasions when HR and energy expenditure were measured continously.

2. After each session in the calorimeter a calibration was obtained using standard techniques by determining HR and heat production (HP) over periods of 10–15 min at several levels of activity. Energy expenditure in the calorimeter was then predicted, by each of five methods, from the mean HR in the calorimeter. Additionally, one session in the calorimeter was used to obtain a calibration and was used for predicting the subject's energy expenditure while in the calorimeter on other occasions.

3. Standard methods of prediction using one calibration point at rest and several points during activity were unreliable for predicting the energy expenditure of an individual. The 24 h HR was at the lower end of the calibration scale and there were considerable over-estimates or underestimates of energy expenditure, particularly during the night when the mean (±SD) difference between the actual and predicted HP was −66±38±6%. A linear regression fitted to points at the lower levels of activity improved the prediction of 24 h HP while a logistic plot reduced the error even further. The best estimate of energy expenditure was that obtained from a calibration over 24 h within the calorimeter; the mean (±SD) difference between the actual and predicted 24 h HP was +3+10.5% for light activity and −3±6.7% for moderate activity. Thus current procedures for calibrating subjects may lead to large errors which could be reduced by using a respiratory chamber.
The effect of intestinal coccidiosis (Eimeria acervulina) on blood and tissue ascorbic acid concentrations
Authors: Kechik Ishak T. , Sykes A. H.
Published: June 2005

1. Two experiments were conducted to investigate the effect of intestinal coccidiosis (Eimeria acervulina) on blood plasma and tissue ascorbic acid (AA) concentrations in chicks, and a third experiment was carried out to examine the role of dietary AA in this infection.

2. Experimental infection with intestinal coccidiosis (Eimeria acervulina) brought about a depletion in the concentration of AA in blood plasma, duodenum, jejunum, ileum, liver and the adrenal glands. Generally, these changes were obtained after the prepatent period of 4–5 d of the infection.

3. Dietary AA at 1000 mg/kg prevented the depletion in plasma and tissue AA levels but did not significantly affect adrenal weight.
Some factors associated with the difference in nutritive value of artificially dried red clover and perennial ryegrass for sheep
Authors: Moseley G. , Jones J. R.
Published: June 2005

1. Three sheep fitted with duodenal re-entrant cannulas and three with large rumen fistulas were given red clover, perennial ryegrass and a 2:1 (w/w) mixture of grass and clover in two Latin square arrangements. Measurements were made of voluntary intake, digestibility, flow of nutrients into the duodenum and the flow of Cr-EDTA marker through the reticulo-rumen.

2. Organic matter (OM) digestibility was similar for the three feeds but the voluntary intake decreased in the order mixture > red clover > perennial ryegrass. There was an increase in the rate of marker flow from the rumen and a decrease in retention time of the same order. Rumen volume did not change significantly.

3. There was a reduction in the mean particle size of rumen contents in the order perennial ryegrass > clover > mixture. The in vitro digestibility of particles decreased with size; the reduction being more rapid for clover than perennial ryegrass.

4. The proportion of ingested digestible OM appearing at the duodenum increased from 18.4% to 26.7% to 30.0% for perennial ryegrass, clover and the mixture respectively.

5. A higher proportion of digestible cellulose and hemicellulose disappeared over the stomach for the perennial ryegrass feed compared to the clover and the mixture but over 96% of water soluble carbohydrates and starch disappeared over the stomach for all three feeds.

6. The apparent digestibility of nitrogen was similar for all three feeds but the proportion of undigested feed N appearing at the duodenum was calculated to be greater by a factor of 1.71 and 2.52 for clover and mixture feeds compared to grass.

7. It was concluded that the higher nutritive value of red clover compared to perennial ryegrass was due to an increased rate of flow of nutrients througth the reticulo-rumen and an increase in the proportion of digestible OM digested post ruminally.
The effect of a low-protein ration on milk yield and plasma metabolites in Friesian heifers during early lactation
Authors: Oldham J. D. , Broster W. H. , Napper D. J. , Siviter J. W.
Published: June 2005

1. Sixteen first-calf Friesian heifers were used in a continuous treatment design experiment. For 2 weeks after calving they were given a 750 g concentrate, 250 g hay/kg ration with 169 g crude protein (nitrogen × 6.25; CP)/kg dry matter (DM). They were then divided into two groups of eight and given a high-protein (223 g CP/kg DM) or low-protein (107 g CP/kg DM) ration at the rate of 10.8 kg concentrates+3.6 kg hay for 8 weeks.

2. Milk yield and composition, live weight and blood composition were monitored throughout. A digestibility trial was carried out with six animals on each treatment.

3. The low protein ration reduced DM, organic matter, energy and fibre digestibility significantly (P < 0.001) so that intakes of digestible energy were not equal and the low-protein group lost more weight than the high-protein group.

4. Milk yield and the fat content of milk were lower in heifers given the low-protein ration (P < 0.01). The lactose content of the milk was not affected and protein content only slightly reduced (P < 0.1) by low-protein feeding. When the heifers were all changed onto an adequate protein (190 g CP/kg DM) ration in mid-lactation, those which had previously been under-fed protein appeared to recover in milk yield to the point they might have been expected to reach if given an adequate-protein ration throughout.

5. Concentrations of urea (P < 0.001) and albumin (P < 0.05) were reduced by underfeeding protein, but albumin concentration was affected less by diet than by stage of lactation. Blood concentrations of total protein, glucose, sodium, potassium, calcium, inorganic phosphate, iron, copper, haemoglobin and packed cell volume were unaffected by treatment. Blood magnesium concentration was slightly lower (P < 0.1) with low-protein feeding.
A new method for measuring the body density of obese adults
Authors: Garrow J. S. , Stalley Susan , Diethelm R. , Pittet Ph. , Hesp R. , Halliday D.
Published: June 2005

1. A new apparatus is described with which it is possible to measure the volume (and hence density) of obese patients without requiring them to immerse totally in water. Replicate measurements of subjects with 6, 23 and 38 kg body fat had a standard deviation not greater than 0.3 kg fat.

2. In nineteen obese women body fat was measured by density, total body water, and total body potassium at the beginning, and again at the end, of a period of 3–4 weeks on a reducing diet, during which they lost 5.43 (SD 1.83) kg in weight. The composition of weight loss was also estimated both by energy balance and nitrogen balance during the interval between the two measurements of body composition.

3. The estimates of fat content of the nineteen women at the start of the balance period were 45.63 (SD 14.50)kg by density, 48.07 (SD 13.88) kg by K and 47.09 (SD 13.85) kg by water. The correlation coefficient between the density and K estimate was 0–949, and for the density and water estimate it was 0.971.

4. It is concluded that measurement of density by the new method provides a convenient method for estimating body fatness, and change in fat content, which compares favourably with estimates based on total body water or total body K. However, these methods cannot be used to provide an accurate estimate of the composition of a small weight loss in an individual since deviations up to 4 kg fat occur between fat loss based on change in density and those based on the more reliable (but more tedious) energy balance method.
Experiments with the long-term rumen simulation technique (Rusitec); response to supplementation of basal rations
Authors: Czerkawski J. W. , Breckenridge Grace
Published: June 2005

1. It is shown that a basal roughage diet can be successfully supplemented with glucose, as long as nitrogen is not limiting. Lack of N depresses the digestibility of the basal ration, results in incomplete fermentation and the increased recoveries of N are consistent with fixation of atmospheric N2.

2. Using a complex, but soluble supplement (whey powder) it is shown that reproducible incremental measurements can be made and that the supplement used gives increases in production of characteristic end-products only (carbon dioxide, methane, acetic and butyric acids).

3. The location of the solid dietary components within the reaction vessel is not important and it is possible to measure changes in a particular component in the presence of others. It is shown that there is sequestration of bacteria and protozoa on the solid digesta.
Nτ-Methylhistidine content of organs and tissues of cattle and an attempt to estimate fractional catabolic and synthetic rates of myofibrillar proteins of skeletal muscle during growth by measuring urinary output of Nτ-methylhistidine
Authors: Nishizawa N. , Toyoda Y. , Noguchi T. , Hareyama S. , Itabashi H. , Funabiki R.
Published: June 2005

1. Distribution ofNτ-methylhistidine (3-methylhistidine; Me-His) among organs and tissues in cattle was determined. From the amount of Me-His in skeletal muscle protein and daily urinary output of Me-His, fractional catabolic and synthetic rates of myofibrillar proteins of skeletal muscle during growth were calculated.

2. More than 93.4% of the total Me-His (35.6 mg/kg body-weight) in the analysed cattle tissues occurred in skeletal muscle protein. The amount of Me-His in tissues other than skeletal muscle was relatively small. Daily urinary excretion of Me-His in the cattle which were fed on hay and concentrate was 135 mg at a growing stage of 217 kg body-weight and 145 mg at a stage of 312 kg. The Me-His content of foodstuffs was also carefully checked in the present investigation. Assuming that absorbed dietary Me-His in quantitatively excreted in the urine without delay, the contribution of Me-His in foodstuffs was calculated to be approximately 30 % of the urinary Me-His. Rumen protozoa and bacteria contained little Me-His.

3. From these results, fractional catabolic and synthetic rates of myofibrillar proteins of the cattle at a growing stage of 217 kg body-weight were calculated to be 1.22%/d (half-life 56 d) and 2.73%/d, while these rates at a stage of 312 kg body-weight were 1.02%/d (half-life 67 d) and 1.51%/d respectively. These values were calculated on the same assumptions as those for the rat (Younget al.1972; Funabikiet al.1976). Of the Me-His present in foodstuffs 94% was tentatively assumed to be excreted into urine.
Protein nutrition of growing lambs
Authors: Kempton T. J. , Nolan J. V. , Leng R. A.
Published: June 2005

1. Lambs with cannulas in the duodenum and ileum were allowed free access to one of four diets: a basal diet of oat hulls and solka floc, or the basal diet supplemented with either urea, urea plus casein or urea plus formaldehyde-treated (HCHO)-casein. Mean nitrogen intake was 1.9 g N/d for the basal diet and 15.0, 32.4 and 36.9 g N/d respectively for the other diets.

2. The rate of irreversible loss of ammonia from the rumen pool estimated using15NH+4was highest on the casein diet (33 g NH3-N/d) by comparison with 18 g NH3-N/d for the urea and HCHO-casein diets and 7 g NH3-N/d for the basal diet.

3. The proportions of bacterial and protozoal N in the rumen derived from rumen ammonia did not differ significantly between the supplemented diets and were 0.66 and 0.52 respectively.

4. Estimation of15N flowing to the duodenum during continuous infusions of15NH+4into the rumen indicated considerable ammonia absorption from the rumen on all the diets. Greatest absorption of ammonia (21 g N/d) apparently occurred in animals on the diet supplemented with urea and casein.

5. The estimated microbial non-ammonia-N (NAN) flowing out of the rumen per unit organic matter fermented in the rumen (FOM) was similar on all diets, i.e. 21.3 (±1.09) g N/kg FOM. The requirement for dietary fermentable N for microbial N production on these diets was 1.2 (±0.07) g N/MJ ME.

6. The flow of NAN into the duodenum and throught the ileum, and total N in the faeces was significantly influenced by the form of N supplementation. The flow of NAN into the duodenum for the HCHO-casein diet (27 g N/d) was more than twice that for the other diets (11 g N/d). The flow of NAN through the ileum and excretion of total N in the faeces was also greater with the HCHO-casein diet than with all other diets. The apparent digestibility of NAN in the small intestine ranged between 0.62–0.66 for all diets.

7. Urea and casein supplements were apparently completely degraded in the rumen. In contrast, the HCHO-casein was almost completely resistant to degradation in the rumen and only 65% of the HCHO-casein was digested in the small intestine.

8. Protein absorbed: energy absorbed (expressed as NAN digested in the small intestine/MJ ME) was calculated to be 5.5 (±0.70) for the basal, urea and urea-plus-casein diets, and 11.6 (±1.71) for the urea-plus-HCHO-casein diet.
The influence of protein nutrition in early life on growth and development of the pig
Authors: Campbell R. G. , Dunkin A. C.
Published: June 2005

1. The effects of feeding either a high-protein (HP) diet or a low-protein (LP) diet between 1·8 and 15 kg live weight (LW) and a low-energy (LE) or a high-energy (HE) intake but at the same protein intake subsequent to 15 kg LW on the performance and body composition of pigs growing to 75 kg LW were investigated.

2. During the LW period 1·8–15 kg, pigs given the LP diet exhibited poorer growth performance (P < 0·01) and at 15 kg contained more fat (P < 0·01) in their empty bodies than pigs given the HP diet.

3. On the LE treatment subsequent to 15 kg LW, pigs previously given the LP diet deposited protein at a faster rate and exhibited more rapid and efficient growth to 60 kg LW than those given the HP diet before 15 kg. However, on the HE treatment, pigs previously given the LP diet deposited protein at a slower rate and exhibited poorer growth performance (P < 0·05) between 15 and 45 kg LW but grew at a faster rate between 45 and 60 kg LW than pigs previously given the HP diet.

4. On the LE treatment subsequent to 15 kg LW the differences in body composition between the two protein groups were no longer significant at 45 kg. However, on the HE treatment, pigs previously given the LP diet remained fatter (P < 0·05) to 60 kg LW than those previously given the HP diet.

5. The results suggested that restricting protein intake between 1.8 and 15 kg LW reduced, temporarily, the upper limit of protein retention and growth performance during subsequent development. This finding is discussed in relation to the effects of protein nutrition in early life on the hyperplasic development of muscle tissue.
Hepatic iron accumulation in copper-deficient rats
Authors: Williams Darryl M. , Kennedy F. Scott , Green Brenda G.
Published: June 2005

1. Studies of anaemia and tissue iron distribution were carried out in copper-deficient rats and pair-fed control animals given Fe orally or parenterally in varying doses.

2. The anaemia of Cu deficiency was partially but incompletely corrected by oral Fe supplementation of one-to five-fold normal dietary levels or by intramuscular Fe supplementation.

3. Serum Fe increased in Cu-deficient animals as the dose of supplemental Fe was increased.

4. Hepatic Fe accumulation occurred in Cu-deficient rats which were administered with either oral Fe in two-to five-fold excess or low doses of intramuscular Fe. This difference was not seen in animals receiving high doses of intramuscular Fe, but similar relativedifferences were seen in Cu-deficient and Cu-replete rats which had been given no Fe supplementation.

5. Duodenal Fe was not increased in Cu deficiency. Bone marrow Fe was present in Cu-deficient animals receiving either parenteral or oral Fe supplementation.

6. Present studies suggest that a decrease in caeruloplasmin (EC1. 16. 3. 1) activity does not wholly explain the anaemia of Cu deficiency.Fe accumulation may be restricted to the liver, suggesting that Cu may be required for normal intracellular Fe metabolism.
The influence of dietary fibre on caecal metabolism in the rat
Authors: McKay Linda F. , Eastwood Martin A.
Published: June 2005

1. The influence of three diets ((1) high-fibre–low-fat, (2) low-fibre–high-fat, (3) commercial breeding diet) on the concentration of short chain fatty acids (SCFA) has been investigated in male and female rats up to 14 weeks of age.

2. Hydrogen was detected in respired gas in all rats with no significant differences between diets or sex. Methane was detected only in control-fed rats at 12 weeks of age and thereafter. Caecal contents contained higher concentrations of SCFA than were found in faeces. There were no significant differences in the total faecal SCFA excreted by rats on the three diets. The proportions of SCFA in the caecum and faeces were influenced by diet.

3. The production and excretion of hydrogen, methane and SCFA in the rat appeared to reflect different aspects of bacterial metabolism. Comparison of caecal and faecal SCFA may indicate differential absorption from the colon or differential metabolism by bacteria or colonic mucosa which may be influenced by diet.
Studies of the large intestine of sheep
Authors: Dixon R. M. , Nolan J. V.
Published: June 2005

1. A study was made of nitrogen kinetics in the large intestine of sheep given 800 g chopped lucerne (Medicago sativa) hay/d. Four sheepwere continuously infused with (15NH4)2SO4into the caecum and three other sheep were infused intravenously with [15N]urea. A digesta marker,51Cr complexed with EDTA (51Cr-EDTA), was infused into the rumen of each sheep to allow estimation of the rates of flow of digesta constituents. Infusions were continued until tracer concentrations reached plateaux in digesta and blood pools, after which the sheep were anaesthetized and slaughtered.

2. Pre-infusion samples and samples on plateau were obtained before slaughter for subsequent analysis to give plasma urea and rumen ammonia-N concentration and enrichment. At slaughter, digesta were obtained from the ileum and segments of the large intestine. These were analysed for51Cr-EDTA content and concentration and enrichment of ammonia-N, microbial N and non-urea non-ammonia-N (NU-NAN).

3. N flows in segments of the large intestine were calculated and represented in a quantitative eight-pool model.

4. Transfer of plasma urea across the wall of the caecum and proximal colon was negligible but there was an input of 0·8 g endogenous NU-NAN/d.

5. Flow of urea plus ammonia-N in digesta from the ileum into the caecum contributed 1·0 g N/d to the caecal ammonia pool.

6. Proteolysis and deamination produced a further 3·0 g ammonia-N/d in the caecum and proximal colon.

7. The net absorption of N between the ileum and the rectum was 2·8 g N/d but 3·0 g ammonia-N/d was absorbed from the caecum and proximal colon and, in addition, at least 0·9 g ammonia-N/d from the distal colon and rectum.

8. Ammonia-N was incorporated into caecal microbes (0·6 g N/d) and approximately 57% of the NU-NAN in caecal digesta was microbial N. The majority of the microbial N flowing from the caecum was excreted in faeces.

9. The rate of irreversible loss of urea-N from plasma, measured by intravenous infusion of [15N]urea, was 13·6 g/d. On average 83 (SE 6·8)% of the15NH3apparently absorbed from the caecum was incorporated into plasma urea; caecal ammonia contributed 9–19% of the N in plasma urea and 0·2–3·1% of the N in rumen ammonia.
Incorporation of nitrogen into rumen bacterial fractions of steers given protein- and urea-containing diets. Ammonia assimilation into intracellular bacterial amino acids
Authors: Blake J. S. , Salter D. N. , Smith R. H.
Published: June 2005

1. Experiments were carried out in vivo to investigate the pathways of ammonia incorporation into rumen bacteria, bacterial fractions and free amino acids within the bacteria.

2. Steers were alternately given two isoenergetic, isonitrogenous diets containing the nitrogen mainly as either urea or decorticated groundnut meal (DCGM). At the end of each period on a given diet, a solution of15NH4Cl was infused into the rumen and samples of rumen contents were removed at 2, 10, 20 and 90 min and 5, 10 and 24 h afterwards. Concentrations of ammonia and its15N enrichment were determined and samples of mixed rumen bacteria were prepared. Bacteria were disrupted ultrasonically and separated into bacterial protein, cell wall and protein-free cell supernatant fractions. Amino acids were separated after hydrolysis and their15N contents determined.

3. A rumen fluid circulation pump was developed so that representative samples could be taken at very short time intervals after the introduction of the15N label.

4. Rumen pH changes, rumen fluid dilution rates and patterns of rumen ammonia concentrations were consistent with normal rumen metabolism. Net bacterial synthesis (as calculated from the net outflow of bacteria from the rumen) was significantly (P< 0·05) greater with the DCGM diet (12·4 g bacterial N/d) than with the ureadiet (9·24 g bacterial N/d).

5. With both diets the15N label rapidly left the rumen ammonia pool and entered the rumen bacteria. Analysis of the bacterial fractions indicated that the label appeared rapidly in the protein-free cell supernatant fraction and more slowly in the bacterial protein and cell wall fractions.

6. With the DCGM diet bacteria apparently utilized intracellular label less efficiently than with the urea diet. The proportion of N in the protein-free cell supernatant was higher with the DCGM diet, suggesting increased levels of intracellular amino acids and peptides, following extracellular protein degradation.

7. Levels of enrichment of the amino acids alanine and glutamate in the protein-free cell supernatant fraction suggested that the enzymes alanine dehydrogenase (EC1. 4. 1. 1) and glutamate dehydrogenase (EC1. 4. 1. 2 and 1. 4. 1. 4) may be the major enzymes for assimilating ammonia when concentrations of soluble carbohydrate and rumen ammonia are high in the rumen.

8. The high levels of intracellular alanine are discussed with reference to publishedwork on the excretion of alanine by rumen bacteria.