Effect of age of growing turkeys on digesta viscosity and nutrient digestibility of maize,wheat, barley and oats fed as such or with enzyme supplementation

The effects of age of growing turkeys and β-glucanase-xylanase activity-containing feed enzyme supplementation on digestibility and feeding value of pelleted maize, wheat, barley and oats were investigated in growing turkeys using excreta collection and ileal sampling by slaughter. Excreta were collected and turkeys were slaughtered at 4, 8 and 12 weeks of age. Viscosity of jejuno-duodenal digesta, caecal volatile fatty acid concentration, ileal crude protein digestibility, total tract fat digestibility and AME_N were assayed using titanium dioxide as an indigestible marker. The highest viscosities were observed in barley and wheat. Viscosity of wheat, barley and oats digesta decreased while caecal volatile fatty acid concentration, fat digestibility and AME_N increased with age. Ileal crude protein digestibility was highest in wheat and lowest in barley. Ileal crude protein digestibility significantly declined with age in most feeding treatments. Enzyme reduced digesta viscosity most efficiently in wheat and barley and improved ileal crude protein digestibility, total tract fat digestibility and AME_N in wheat, barley and oats, but interactions occurred, the effect of enzyme on viscosity being the most remarkable for wheat and barley and for the young birds.     

Using the dual isotope method to assess cecal amino acid absorption of goat whey protein in rats,a pilot study

Measurement of ileal amino acids (AA) bioavailability is recommended to evaluate protein quality. A dual isotope tracer method, based on plasma isotopic enrichment ratios, has been proposed to determine true digestibility in humans. In a pilot study, we aimed to evaluate whether this method could be implemented in rats to determine AA bioavailability based on isotopic enrichment ratios measured in cecal digesta or plasma samples. Goat milk proteins were intrinsically labeled with ¹⁵N and ²H. Wistar rats were fed a meal containing the doubly labeled goat whey proteins and a tracer dose of ¹³C-spirulina. Blood samples were collected 0, 1 h and 3 h after meal ingestion from the tail vein. The rats were euthanized 4 h (n?=?6) or 6 h (n?=?6) after meal to collect plasma and intestinal contents. True orocecal protein digestibility and AA bioavailability were assessed by means of ¹⁵N and ²H enrichment in cecum content and compared with absorption indexes determined at the plasma or cecum level using isotopic ratios. Plasma kinetics of isotopic enrichment could not be completed due to the limited quantity of plasma obtained with sequential blood collection. However, the absorption indexes determined from cecal ¹⁵N or ²H/¹³C ratios gave coherent values with true orocecal AA bioavailability. This dual isotope approach with measurements of isotopic ratios in digestive content could be an interesting strategy to determine true AA bioavailability in ileal digesta of rats.

     

Effect of age of growing turkeys on digesta viscosity and nutrient digestibility of maize, wheat, barley and oats fed as such or with enzyme supplementation

The effects of age of growing turkeys and beta-glucanase-xylanase activity-containing feed enzyme supplementation on digestibility and feeding value of pelleted maize, wheat, barley and oats were investigated in growing turkeys using excreta collection and ileal sampling by slaughter. Excreta were collected and turkeys were slaughtered at 4, 8 and 12 weeks of age. Viscosity of jejuno-duodenal digesta, caecal volatile fatty acid concentration, ileal crude protein digestibility, total tract fat digestibility and AMEN were assayed using titanium dioxide as an indigestible marker. The highest viscosities were observed in barley and wheat. Viscosity of wheat, barley and oats digesta decreased while caecal volatile fatty acid concentration, fat digestibility and AMEN increased with age. Ileal crude protein digestibility was highest in wheat and lowest in barley. Ileal crude protein digestibility significantly declined with age in most feeding treatments. Enzyme reduced digesta viscosity most efficiently in wheat and barley and improved ileal crude protein digestibility, total tract fat digestibility and AMEN in wheat, barley and oats, but interactions occurred, the effect of enzyme on viscosity being the most remarkable for wheat and barley and for the young birds.     

Concomitant changes in high temperature tolerance and heat-shock proteins in desert succulents

Raising the day/night air temperatures from 30°C/20°C to 50°C/40°C increases the high temperature tolerated by Agave deserti, Carnegiea gigantea, and Ferocactus acanthodes by 6°C to 8°C; the increase is about half completed in 3 days and fully completed in 10 days. A 25 to 27 kilodalton protein concomitantly accumulates for all three desert succulents upon transfer to 50°C/40°C, while accumulation of other heat “heat-shock” proteins is species specific. Some of the induced proteins are more abundant at 3 days, while others (including the 25-27 kilodalton protein) remain after completion of high temperature acclimation.     

Effect of substitution of wheat starch by potato starch on the performance,digestive physiology and health of growing rabbits

The goal of this research was to study the effect of the substitution of wheat starch by potato starch (PS) on the performance, health and digestion of growing rabbits. Three experimental diets were formulated with 0%, 7% and 14% PS (PS0, PS7 and PS14, respectively) and similar starch contents (22% dry matter basis), proteins and fibre. The three diets were administered to three groups of 48 rabbits from weaning (28 days) to slaughter (70 days), and growth and health measurements were made. Another 10 rabbits per diet (30 rabbits at each age), reared under similar conditions, were slaughtered at 6 to 10 weeks of age, and the digesta were collected to analyse the caecal microbial activity (pH, volatile fatty acids (VFA) levels, fibrolytic activity) and the starch concentration in the ileal digesta. At the same ages, the whole tract digestibility coefficients were measured in 10 other rabbits for each treatment (30 rabbits). The feed intake between 28 and 42 days of age (days) increased by 11% (P < 0.05) in PS0 v. PS14. Over the whole growth period (28 to 70 days), weight gain was similar among diets (40.5 g/day), whereas the feed intake and feed conversion increased (8.5% and 5.2%, respectively; P < 0.05) with the PS14 diet. Mortality and morbidity were not affected by the diets. The starch concentration of the ileal contents increased (P < 0.01) with the addition of PS to the diet (0.39%, 0.77% and 1.08% for diets PS0, PS7 and PS14, respectively). Starch digestibility was 0.8 percentage units higher (99.8% v. 99.0%) with the PS0 diet than the PS14 diet (P = 0.04). The bacterial cellulolytic activity in the caecum tended to be higher with the PS14 diet (P = 0.07). The total VFA caecal concentration increased (P < 0.01) only in 6-week-old rabbits with PS7 compared with PS0 (54.7 v. 74.5 mmol/l). Protein digestibility and ileal starch concentration decreased (P < 0.05) with age (6 v. 10 weeks), and hemicelluloses digestibility increased (P < 0.05). At 10 weeks of age, rabbits showed a higher VFA pool (6.25 mol) and proportion of butyrate (15.9%) and a lower proportion of acetate (79.3%), ammonia level (7.5 mmol/l) and C3/C4 ratio (0.31) than at 6 weeks of age. The intake of potato starch had no effect on the performance, caecal microbial activity or digestive health of growing rabbits.     

Effects of Temperature and Carbon-Nitrogen (C/N) Ratio on the Performance of Anaerobic Co-Digestion of Dairy Manure,Chicken Manure and Rice Straw: Focusing on Ammonia Inhibition

Anaerobic digestion is a promising alternative to disposal organic waste and co-digestion of mixed organic wastes has recently attracted more interest. This study investigated the effects of temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure (DM), chicken manure (CM) and rice straw (RS). We found that increased temperature improved the methane potential, but the rate was reduced from mesophilic (30∼40°C) to thermophilic conditions (50∼60°C), due to the accumulation of ammonium nitrogen and free ammonia and the occurrence of ammonia inhibition. Significant ammonia inhibition was observed with a C/N ratio of 15 at 35°C and at a C/N ratio of 20 at 55°C. The increase of C/N ratios reduced the negative effects of ammonia and maximum methane potentials were achieved with C/N ratios of 25 and 30 at 35°C and 55°C, respectively. When temperature increased, an increase was required in the feed C/N ratio, in order to reduce the risk of ammonia inhibition. Our results revealed an interactive effect between temperature and C/N on digestion performance.     

CRYSTALLINE TRYPSIN : IV. REVERSIBILITY OF THE INACTIVATION AND DENATURATION OF TRYPSIN BY HEAT

1. If dilute solutions of purified trypsin of low salt concentration at pH from 1 to 7 are heated to 100°C. for 1 to 5 minutes and then cooled to 20°C. there is no loss of activity or formation of denatured protein. If the hot trypsin solution is added directly to cold salt solution, on the other hand, all the protein precipitates and the supernatant solution is inactive. 2. The per cent of the total protein and activity present in the soluble form decreases from 100 per cent to zero as the temperature is raised from 20°C. to 60°C. and increases again from zero to 100 per cent as the solution is cooled from 60°C. to 20°C. The per cent of the total protein present in the soluble (native) form at any one temperature is nearly the same whether the temperature is reached from above or below. 3. If trypsin solutions at pH 7 are heated for increasing lengths of time at various temperatures and analyzed for total activity and total protein nitrogen after cooling, and for soluble activity and soluble (native) protein nitrogen, it is found that the soluble activity and soluble protein nitrogen decrease more and more rapidly as the temperature is raised, in agreement with the usual effects of temperature on the denaturation of protein. The total protein and total activity, on the other hand, decrease more and more rapidly up to about 70°C. but as the temperature is raised above this there is less rapid change in the total protein or total activity and at 92°C. the solutions are much more stable than at 42°C. 4. Casein and peptone are not digested by trypsin at 100°C. but when this digestion mixture is cooled to 35°C. rapid digestion occurs. A solution of trypsin at 100°C. added to peptone solution at zero degree digests the peptone much less rapidly than it does if the trypsin solution is allowed to cool slowly before adding it to the peptone solution. 5. The precipitate of insoluble protein obtained from adding hot trypsin solutions to cold salt solutions contains the S-S groups in free form as is usual for denatured protein. 6. The results show that there is an equilibrium between native and denatured trypsin protein the extent of which is determined by the temperature. Above 60°C. the protein is in the denatured and inactive form and below 20°C. it is in the native and active form. The equilibrium is attained rapidly. The results also show that the formation of denatured protein is proportional to the loss in activity and that the re-formation of native protein is proportional to the recovery of activity of the enzyme. This is strong evidence for the conclusion that the proteolytic activity of the preparation is a property of the native protein molecule.     

Impact of Inoculum Preparation and Storage Conditions on the Response of Escherichia coli O157:H7 Populations to Undercooking and Simulated Exposure to Gastric Fluid

This study evaluated the impact of inoculum preparation and storage conditions on the response of Escherichia coli O157:H7 exposed to consumer-induced stresses simulating undercooking and digestion. Lean beef tissue samples were inoculated with E. coli O157:H7 cultures prepared in tryptic soy broth or meat decontamination runoff fluids (WASH) or detached from moist biofilms or dried biofilms formed on stainless steel coupons immersed in inoculated WASH. After inoculation, the samples were left untreated or dipped for 30 s each in hot (75°C) water followed by lactic acid (2%, 55°C), vacuum packaged, stored at 4 (28 days) or 12°C (16 days), and periodically transferred to aerobic storage (7°C for 5 days). During storage, samples were exposed to sequential heat (55°C; 20 min) and simulated gastric fluid (adjusted to pH 1.0 with HCl; 90 min) stresses simulating consumption of undercooked beef. Under the conditions of this study, cells originating from inocula of planktonic cells were, in general, more resistant to heat and acid than cells from cultures grown as biofilms and detached prior to meat inoculation. Heat and acid tolerance of cells on meat stored at 4°C was lower than that of cells on nondecontaminated meat stored at 12°C, where growth occurred during storage. Decontamination of fresh beef resulted in injury that inhibited subsequent growth of surviving cells at 12°C, as well as in decreases in resistance to subsequent heat and acid stresses. The shift of pathogen cells on beef stored under vacuum at 4°C to aerobic storage did not affect cell populations or subsequent survival after sequential exposure to heat and simulated gastric fluid. However, the transfer of meat stored under vacuum at 12°C to aerobic storage resulted in reduction in pathogen counts during aerobic storage and sensitization of survivors to the effects of sequential heat and acid exposure.     

Protein Synthesis in Bromegrass (Bromus inermis Leyss) Cultured Cells during the Induction of Frost Tolerance by Abscisic Acid or Low Temperature

Bromus inermis Leyss cell cultures treated with 75 micromolar abscisic acid (ABA) at both 23 and 3°C developed more freezing resistance than cells cultured at 3°C. Protein synthesis in cells induced to become freezing tolerant by ABA and low temperature was monitored by [¹⁴C]leucine incorporation. Protein synthesis continued at 3°C, but net cell growth was stopped. Most of the major proteins detected at 23°C were synthesized at 3°C. However, some proteins were synthesized only at low temperatures, whereas others were inhibited. ABA showed similar effects on protein synthesis at both 23 and 3°C. Comparative electrophoretic analysis of [¹⁴C]leucine labeled protein detected the synthesis of 19, 21 and 47 kilodalton proteins in less than 8 hours after exposure to exogenous ABA. Proteins in the 20 kilodalton range were also synthesized at 3°C. In addition, a 31 kilodalton protein band showed increased expression in freezing resistant ABA treated cultures after 36 hours growth at both 3 and 23°C. Quantitative analysis of [¹⁴C]leucine labeled polypeptides in two-dimensional gels confirmed the increased expression of the 31 kilodalton protein. Two-dimensional analysis also resolved a 72 kilodalton protein enriched in ABA treated cultures and identified three proteins (24.5, 47, and 48 kilodaltons) induced by low temperature growth.     

THE INFLUENCE OF ENVIRONMENTAL TEMPERATURE ON THE UTILIZATION OF FOOD ENERGY IN BABY CHICKS

1. An optimum of environmental temperature is to be expected for the utilization of food energy in warm blooded animals if their food intake is determined by their appetite. 2. Baby chicks were kept in groups of five chicks in a climatic cabinet at environmental temperatures of 21°, 27°, 32°, 38°, and 40°C. during the period of 6 to 15 days of age. The intake of qualitatively complete food was determined by their appetite. Food intake, excretion, and respiratory exchange were measured. Control chicks from the same hatch as the experimental groups were raised in a brooder and were given the same food as the experimental chicks. The basal metabolism of each experimental group was determined from 24 to 36 hours without food at the age of 16 days. 3. The daily rate of growth increased with decreasing environmental temperature from 2.74 gm. at 40°C. to 4.88 gm. at 21°C. This was 4.2 to 6.5 per cent of their body weight. 4. The amount of food consumed increased in proportion to the decrease in temperature. 5. The availability of the food, used for birds instead of the digestibility and defined as See PDF for Structure showed an optimum at 38°C. 6. The CO₂ production increased from 2.95 liters CO₂ per day per chick at 40°C. to 6.25 liters at 21°C. Per unit of the 3/4 power of the body weight, 23.0 liters CO₂ per kilo^3/4 was produced at 40°C. and 43.4 liters per kilo^3/4 at 21°C. The CO₂ production per unit of 3/4 power of the weight increased at an average rate of approximately 1 per cent per day increase in age. The R.Q. was, on the average, 1.04 during the day and 0.92 during the night. 7. The net energy is calculated on the basis of C and N balances. A maximum of 11.8 Cal. net energy per chick per day was found at 32°C. At 21°C. only 6.9 Cal. net per day per chick was produced and at 40°C. an average of 6.7 Cal. 8. The composition of the gained body substance changed according to the environmental temperature. The protein stored per gram increase in body weight varied from 0.217 to 0.266 gm. protein and seemed unrelated to the temperature. The amount of fat per gram gain in weight dropped from a maximum of 0.153 gm. at 32°C. to 0.012 gm. at 21°C. and an average of 0.107 gm. at 40°C. The energy content per gram of gain in weight had its maximum of 2.95 Cal. per gm. at 38°C. and its minimum of 1.41 Cal. per gm. at 21°C. at which temperature the largest amount of water (0.763 gm. per gm. increase in body weight) was stored. 9. The basal metabolism increased from an average of 60 Cal. per kilo^3/4 at an environmental temperature of 40°C. to 128 Cal. per kilo^3/4 at 21°C. No indication of a critical temperature was found. 10. The partial efficiency, i.e. the increase in net energy per unit of the corresponding increase in food energy, seemed dependent on the environmental temperature, reaching a maximum of 72 per cent of the available energy at 38°C. and decreasing to 57 per cent at 21°C. and to an average of 60 per cent at 40°C. 11. The total efficiency, i.e. the total net energy produced per unit of food energy taken in, was maximum (34 per cent of the available energy) at 32°C., dropped to 16 per cent at 21°C., and to an average of 29 per cent at 40°C.     

Seedling growth, mitochondrial characteristics, and alternative respiratory capacity of corn genotypes differing in cold tolerance

Four maize (Zea mays L.) inbreds representing genetic differences in seedling cold tolerance were used to determine the effect of growth temperatures on dry weight accumulation and mitochondrial properties, especially the alternative oxidase capacity. Seedlings were grown in darkness at 30°C (constant), 14°C (constant), and 15°C for 16 hours and 8°C for 8 hours. Inbreds B73 and B49 were characterized as cold tolerant while G50 and G84 were cold sensitive. Shoot growth rate of cold-sensitive inbreds in the lower temperatures was slower relative to the tolerant inbreds. Mesocotyl tissue was particularly sensitive to low temperatures during growth after germination. There were no significant differences in relative rates of mitochondrial respiration in the cold-tolerant compared to cold-sensitive inbreds measured at 25°C. Mitochondria from all seedlings grown at all temperatures had the ability to phosphorylate as indicated by the observation of respiratory control. This result indicated that differences in low temperature growth were probably not related to mitochondrial function at low temperatures. Alternative oxidase capacity was higher in mitochondria from seedlings of all inbreds grown at 14°C compared to 30°C. Capacities in seedlings of 14°C-grown B73 and G50 were higher than in B49 and G84. Capacities in seedlings grown for 16 hours at 15°C and 8 hours at 8°C were similar to those from 14°C-grown except in G50 which was lower and similar to those grown at 30°C. Mesocotyl tissue was the most responsive tissue to low growth temperature. Coleoptile plus leaf tissue responded similarly but contained lower capacities. Antibody probing of western blots of mitochondrial proteins confirmed that differences in alternative oxidase capacities were due to differences in levels of the alternative oxidase protein. Male sterile lines of B73 were also grown under the three different temperature regimes. These lines grew equally as well as the normal B73 at all temperatures and the response of alternative oxidase capacity and protein to low growth temperature was similar to normal B73.     

Comparative Proteomic Analysis of the Hepatic Response to Heat Stress in Muscovy and Pekin Ducks: Insight into Thermal Tolerance Related to Energy Metabolism

The Pekin duck, bred from the mallard (Anas platyrhynchos) in china, is one of the most famous meat duck species in the world. However, it is more sensitive to heat stress than Muscovy duck, which is believed to have originated in South America. With temperature raising, mortality, laying performance, and meat quality of the Pekin duck are severely affected. This study aims to uncover the temperature-dependent proteins of two duck species using comparative proteomic approach. Duck was cultured under 39°C ± 0.5°C for 1 h, and then immediately returned to 20°C for a 3 h recovery period, the liver proteins were extracted and electrophoresed in two-dimensional mode. After analysis of gel images, 61 differentially expressed proteins were detected, 54 were clearly identified by MALDI TOF/TOF MS. Of the 54 differentially expressed protein spots identified, 7 were found in both species, whereas 47 were species specific (25 in Muscovy duck and 22 in Pekin duck). As is well known, chaperone proteins, such as heat shock protein (HSP) 70 and HSP10, were abundantly up-regulated in both species in response to heat stress. However, we also found that several proteins, such as α-enolase, and S-adenosylmethionine synthetase, showed different expression patterns in the 2 duck species. The enriched biological processes were grouped into 3 main categories according to gene ontology analysis: cell death and apoptosis (20.93%), amino acid metabolism (13.95%) and oxidation reduction (20.93%). The mRNA levels of several differentially expressed protein were investigated by real-time RT-PCR. To our knowledge, this study is the first to provide insights into the differential expression of proteins following heat stress in ducks and enables better understanding of possible heat stress response mechanisms in animals.     

Temperature-Induced Protein Conformational Changes in Barley Root Plasma Membrane-Enriched Microsomes: II. Intrinsic Protein Fluorescence

The membrane-bound proteins of barley (Hordeum vulgare L. cv Conquest) root plasma membrane-enriched microsomes displayed fluorescence typical of protein-associated trytophan residues. The protein fluorescence intensity was sensitive to variations in sample temperature. The temperature-induced decline in protein fluorescence intensity was nonlinear with slope discontinuities at about 12 and 32°C. Detergents at levels above their critical micelle concentration enhanced protein fluorescence. Glutaraldehyde reduced protein fluorescence. Protein fluorescence polarization increased at temperatures above 30°C. Both the rate of tryptophan photoionization and the fluorescence intensity of the photoionization products suggested alterations in membrane protein conformation between 12 and 32°C. The quenching of the intrinsic protein fluorescence by acrylamide and potassium iodide indicated changes in accessibility of the extrinsic agents to the protein tryptophan residues beginning at about 14°C. The results indicate thermally induced changes in the dynamics of the membrane proteins over the temperature range of 12 to 32°C which could account for the complex temperature dependence of the barley root plasma membrane ATPase.     

Response of Lactobacillus helveticus PR4 to Heat Stress during Propagation in Cheese Whey with a Gradient of Decreasing Temperatures

The heat stress response was studied in Lactobacillus helveticus PR4 during propagation in cheese whey with a gradient of naturally decreasing temperature (55 to 20°C). Growth under a gradient of decreasing temperature was compared to growth at a constant temperature of 42°C. Proteinase, peptidase, and acidification activities of L. helveticus PR4 were found to be higher in cells harvested when 40°C was reached by a gradient of decreasing temperature than in cells grown at constant temperature of 42°C. When cells grown under a temperature gradient were harvested after an initial exposure of 35 min to 55°C followed by decreases in temperature to 40 (3 h), 30 (5 h 30 min), or 20°C (13 h 30 min) and were then compared with cells grown for the same time at a constant temperature of 42°C, a frequently transient induction of the levels of expression of 48 proteins was found by two-dimensional electrophoresis analysis. Expression of most of these proteins increased following cooling from 55 to 40°C (3 h). Sixteen of these proteins were subjected to N-terminal and matrix-assisted laser desorption ionization-time of flight mass spectrometry analyses. They were identified as stress proteins (e.g., DnaK and GroEL), glycolysis-related machinery (e.g., enolase and glyceraldehyde-3-phosphate dehydrogenase), and other regulatory proteins or factors (e.g., DNA-binding protein II and ATP-dependent protease). Most of these proteins have been found to play a role in the mechanisms of heat stress adaptation in other bacteria.     

Acquisition of Thermotolerance in Soybean Seedlings : Synthesis and Accumulation of Heat Shock Proteins and their Cellular Localization

When soybean Glycine max var Wayne seedlings are shifted from a normal growth temperature of 28°C up to 40°C (heat shock or HS), there is a dramatic change in protein synthesis. A new set of proteins known as heat shock proteins (HSPs) is produced and normal protein synthesis is greatly reduced. A brief 10-minute exposure to 45°C followed by incubation at 28°C also results in the synthesis of HSPs. Prolonged incubation (e.g. 1-2 hours) at 45°C results in greatly impaired protein synthesis and seedling death. However, a pretreatment at 40°C or a brief (10-minute) pulse treatment at 45°C followed by a 28°C incubation provide protection (thermal tolerance) to a subsequent exposure at 45°C. Maximum thermoprotection is achieved by a 2-hour 40°C pretreatment or after 2 hours at 28°C with a prior 10-minute 45°C exposure. Arsenite treatment (50 micromolar for 3 hours) also induces the synthesis of HSP-like proteins, and also provides thermoprotection to a 45°C HS; thus, there is a strong positive correlation between the accumulation of HSPs and the acquisition of thermal tolerance under a range of conditions.

During 40°C HS, some HSPs become localized and stably associated with purified organelle fractions (e.g. nuclei, mitochondria, and ribosomes) while others do not. A chase at 28°C results in the gradual loss over a 4-hour period of the HSPs from the organelle fractions, but the HSPs remain selectively localized during a 40°C chase period. If the seedlings are subjected to a second HS after a 28°C chase, the HSPs rapidly (complete within 15 minute) relocalize in the organelle fractions. The relative amount of the HSPs which relocalize during a second HS increases with higher temperatures from 40°C to 45°C. Proteins induced by arsenite treatment are not selectively localized with organelle fractions at 28°C but become organelle-associated during a subsequent HS at 40°C.

     

Effective lipid lowering diets including lean meat

The plasma lipid and lipoprotein responses to two modified isoenergetic diets including meat were studied in 15 free living men with hyperlipidaemia (mean plasma cholesterol and triglyceride concentrations 8·1 and 3·4 mmol/l). A reference diet (diet A, 42% energy from fat, ratio of polyunsaturated to saturated fatty acids (P:S ratio) 0·2) was compared with a fat reduced diet (diet B, 35% energy from fat, P:S ratio 0·5) and with a further fat modified diet supplemented with fibre (diet C, 27% energy from fat, P:S ratio 1·0). Daily intake of meat and meat products (180 g/day) was the same in each dietary period; that in diet A had a fat content typical of the average British diet, whereas that in diets B and C was based on very lean meat and meat products. During consumption of diet B the plasma cholesterol concentration fell by 8·6% and low density lipoprotein cholesterol by 11%. During consumption of diet C plasma cholesterol fell by 18·5% and low density lipoprotein cholesterol by 23·8%. Triglyceride and high density lipoprotein cholesterol concentrations and body weight did not change appreciably during the study.A modified diet including a moderate amount of lean meat and meat products is compatible with a reduced lipoprotein mediated risk of atherosclerotic heart disease.     

Effect of dietary nutrients on ileal endogenous losses of threonine,cysteine, methionine,lysine, leucine and protein in broiler chicks

An isotope dose technique was utilized (i) to determine endogenous amino acid (AA) and protein losses and (ii) to propose adjusted values for AA requirements. The endogenous flow rate was calculated from the pool of enrichment in plasma AA, assuming similitude to enrichment of endogenous AA. In experiment 1, chicks were orally administered D4-lysine at 2% of estimated lysine intake from 16 to 24 days to find the isotopic steady state of the atom percent excess (APE) of lysine for plasma and jejunal and ileal digesta. The APE of D4-lysine in plasma, jejunal digesta and ileal digesta reached the isotopic steady state at 5.5, 3.4 and 2.0 days, respectively, by using the broken-line model. It was assumed that the isotopic steady state at 5 days identified for D4-lysine is also representative for the ¹⁵N-labeled AA. In experiment 2, chicks were fed diets from 1 to 21 days with increasing levels of fat (6%, 8%, 12%, 13% extract ether), protein (26%, 28.5%, 31% CP) or fiber (14%, 16%, 18% NDF) by adding poultry fat, soybean meal, blended animal protein or barley. Chicks were orally administered ¹⁵N-threonine, ¹⁵N-cysteine, ¹⁵N-methionine, ¹⁵N-lysine and ¹⁵N-leucine at 2% of estimated daily intake for 5 days from 17 to 21 days of age. Dietary nutrients influenced endogenous losses (EL), where dietary fat stimulated EL of lysine (P=0.06), leucine and protein (P=0.07); dietary protein enhanced EL of leucine and protein; and finally the dietary fiber increased EL of leucine. Dietary nutrients also affected apparent ileal digestibility (AID). Dietary fat increased AID of cysteine but decreased AID of lysine. Dietary protein reduced AID of protein, threonine, lysine and leucine, and similarly dietary fiber decreased AID of protein, threonine, methionine, lysine and leucine. In contrast, dietary fat or protein did not affect real ileal digestibility (RID) of protein and AA except threonine and leucine. The dietary fiber reduced the RID of protein, threonine and leucine. This indicate that variations of some endogenous AA and protein losses due to dietary nutrients almost eliminates the effects of RID, and thus the EL coming from the body should be utilized to adjust the AA requirement instead of changing the true digestible nutrients of ingredients. The present data suggest that 5 days’ feeding labeled AA was enough to reach the isotopic steady state and AA requirements should be adjusted when additional dietary protein, fat or fiber is fed.     

Synthesis, transport and localization of a nuclear coded 22-kd heat-shock protein in the chloroplast membranes of peas and Chlamydomonas reinhardi

The synthesis, transport and localization of a nuclear coded 22-kd heat-shock protein (HSP) in the chloroplast membranes was studied in pea plants and Chlamydomonas reinhardi. HSPs were detected in both systems by in vivo labeling and in vitro translation of poly(A)⁺RNA, using the wheat-germ and reticulocyte lysate systems. Heat-shock treatment of pea plants for 2 h at 42-45°C induces the expression of ˜10 nuclear coded proteins, among which several (18 kd, 19 kd, 22 kd) are predominant. A 22-kd protein is synthesized as a 26-kd precursor protein and is localized in a chloroplast membrane fraction in vivo. Following post-translational transport into intact chloroplasts in vitro of the 26-kd precursor, the protein is processed but the resulting 22-kd mature protein is localized in the chloroplast stroma. If, however, the in vitro transport is carried out with chloroplasts from heat-shocked plants, the 22-kd protein is preferentially transported to the chloroplast membrane fraction. In C. reinhardi the synthesis of poly(A)⁺RNAs coding for several HSPs is progressively and sequentially induced when raising the temperature for 1.5 h from 36°C to 42°C, while that of several preexisting RNAs is reduced. Various pre-existing poly(A)⁺RNAs endure in the cells at 42°C up to 5 h but are no longer translated in vivo, whereas some poly(A)⁻RNAs persist and are translated. As in pea, a poly(A)⁺RNA coded 22-kd HSP is localized in the chloroplast membranes in vivo, although it is translated as a 22-kd protein in vitro. The in vitro translated protein is not transported in isolated pea chloroplast which, however, processes and transports other nuclear coded chloroplast proteins of Chlamydomonas. The poly(A)⁺RNA coding for the 22-kd HSP appears after 1 h at 36°C. Its synthesis increases with the temperature of incubation up to 42°C, although it decreases after ˜2 h of heat treatment and the already synthesized RNA is rapidly degraded. The degradation is faster upon return of the cells to 26°C. None of the heat-induced proteins is identical to the light-inducible proteins of the chloroplast membranes.     

The Role of Semidisorder in Temperature Adaptation of Bacterial FlgM Proteins

Probabilities of disorder for FlgM proteins of 39 species whose optimal growth temperature ranges from 273 K (0°C) to 368 K (95°C) were predicted by a newly developed method called Sequence-based Prediction with Integrated NEural networks for Disorder (SPINE-D). We showed that the temperature-dependent behavior of FlgM proteins could be separated into two subgroups according to their sequence lengths. Only shorter sequences evolved to adapt to high temperatures (>318 K or 45°C). Their ability to adapt to high temperatures was achieved through a transition from a fully disordered state with little secondary structure to a semidisordered state with high predicted helical probability at the N-terminal region. The predicted results are consistent with available experimental data. An analysis of all orthologous protein families in 39 species suggests that such a transition from a fully disordered state to semidisordered and/or ordered states is one of the strategies employed by nature for adaptation to high temperatures.