Development of a formulation that enhances gene expression and efficacy following intraperitoneal administration in rabbits and mice

We conducted a series of experiments to determine if intraperitoneal (IP) delivery of recombinant adenovirus (rAd)-based therapies is improved through carrier vehicle selection, and compared an icodextrin solution (a high molecular weight dextrin with a prolonged peritoneal cavity residence time) with a standardized phosphate buffered saline (PBS) delivery solution. In vitro, comparative adenovirus particle concentration determination (27 h) and bioactivity assay (24h) indicated equivalent compatibility with icodextrin or PBS. In vivo, rabbits treated IP (100 ml) with rAd-betagal 1 x 10(9) P/ml in icodextrin showed improved transgene expression throughout the peritoneal wall compared to rAd-betagal in PBS. In PC-3 tumor-bearing mice treated IP with 5 x 10(9) P/0.5 ml or 1 x 10(10) P/0.5 ml rAd-betagal, transgene expression was significantly enhanced (p < 0.01) with icodextrin compared to PBS in both tumor specimens and peritoneal wall. In subsequent studies we compared prolongation of survival in intraperitoneal PC-3 and MDAH-2774 human xenograft tumor models in nude mice using rAd-p53 in icodextrin or PBS in multi-dose ranging (1 x 10(8) to 1 x 10(10) P) experiments. The icodextrin formulation alone significantly increased rAd-p53 mediated survival (p < 0.05). In animals, these results show that IP rAd gene therapy can be improved with the use of icodextrin, and suggest that prolonged retention and distribution in the peritoneal cavity is an important factor.

Design, development and performance of a novel multidose dry-powder inhaler

The authors describe the design and development of a breath-actuated multidose dry-powder inhaler and summarize the in vitro and in vivo data demonstrating its robustness and performance in the laboratory and during clinical use. Drugs for the treatment of asthma--including budesonide, beclomethasone dipropionate and salbutamol--when formulated with lactose powder as a carrier and dispensed via this device, have exhibited clinical efficacy and safety profiles comparable with standard pressurized metered-dose inhalers and dry-powder formulations.

Compliance with nedocromil sodium and a nedocromil sodium/salbutamol combination. Compliance Working Group

Nonadherence to prescribed preventive medication is common in asthma. We wanted to assess whether the combination of a beta 2-bronchodilator with an anti-inflammatory treatment in the same metered-dose inhaler (MDI) with a regular dosing schedule might improve compliance. A double-blind study was used to compare use (two actuations four times daily for 12 weeks) of 2 mg nedocromil sodium (n = 101) with a combination of 2 mg nedocromil sodium and 100 micrograms salbutamol (n = 100) in mild-to-moderate asthma patients (mean age 42 +/- 14 yrs; 98 males and 103 females). Compliance was measured using the electronic Nebulizer Chronolog (NC) device, change in MDI canister weight, patient questionnaire and physician assessment. The mean +/- SD number of actuations per day for nedocromil sodium and the combination during the primary period of assessment (Weeks 11-12) was 4.2 +/- 2.6 and 4.6 +/- 2.5 (NC), 5.3 +/- 2.1 and 5.3 +/- 2.0 (canister weight), and 7.5 +/- 1.3 and 7.4 +/- 1.3 (questionnaire), respectively. Physician assessment rated compliance as "good" to "excellent". The first and final days of the period were not used in the NC analysis to exclude part-days of treatment and drug-dumping (repeated actuations without inhalation), and may account for the difference between NC and canister weight results. The mean number of two-actuation doses per day determined from the NC was 2.1 +/- 1.3 for nedocromil sodium and 2.4 +/- 2.1 for the combination. Thirty five percent (nedocromil sodium) and 34% (combination) of the patients were compliant (6-10 actuations per day for > or = 60% of the days). We conclude that compliance is poor in asthma, electronic recording revealed the dumping phenomenon and, in this study, the combination of an inhaled beta 2-bronchodilator with a preventive treatment did not improve compliance over a three month period in patients with mild-to-moderate asthma.

Dietary guidelines in perspective

To assess whether dietary guidelines for Americans are appropriate for young children, the evolution of dietary guidance, the nature of the guidelines, evidence used to support the concept of diet modification to prevent heart disease and the rationale for extending application of the guidelines to children have been examined. As health improved during this century, life expectancy lengthened, and diseases associated with aging became major causes of death. As a consequence, emphasis on dietary advice for selecting a nutritionally adequate diet--the primary need of children--declined, whereas emphasis on dietary advice for preventing chronic and degenerative diseases increased. It is clear from reading the text accompanying the guidelines that they were proposed to prevent diseases of aging by reducing consumption of animal products. Critical evaluation of evidence bearing on the concept of the guidelines reveals that there are grounds for skepticism about claims for the effectiveness of diet modification as a measure for reducing the incidence of heart disease. Also, the rationale for extending the guidelines to young children is based on inferences from observations on adults, not on direct evidence that children will benefit from following them. There is, thus, ample justification for proposing separate dietary guidelines for children.

Leucine affects the metabolism of valine by isolated perfused rat hearts: relation to branched-chain amino acid antagonism

This study was conducted to determine the effects of different concentrations of leucine on the transport, transamination and oxidation of valine and on incorporation of valine into heart proteins in the isolated perfused rat heart. Valine metabolism was studied in rat hearts perfused with medium containing glucose and graded levels of L-leucine. In transport studies L-phenylalanine was also tested. Uptake of L-[1-14C]valine (0.2 mmol/L) was significantly reduced (-50%) by inclusion of 0.2 mmol/L phenylalanine or leucine, and by -70% by inclusion of 1.0 mmol/L phenylalanine or leucine in the perfusate. Transamination of valine decreased by 37 and 48%, and oxidation of valine by 53 and 71%, respectively, when 0.2 or 1.0 mmol/L leucine was included in the perfusate. Tissue concentrations of valine decreased by 43, 48 and 62% in the presence of 0.2, 0.5 and 1.0 mmol/L leucine, respectively; tissue concentrations of leucine, glutamate and alanine increased approximately 11-fold, 1.2-fold and 0.5-fold, respectively, when 1.0 mmol/L leucine was present in the perfusate. Addition of 0.2-1.0 mmol/L leucine did not affect incorporation of valine into heart proteins. We conclude that 1) competition among large neutral amino acids for transport into heart occurs at physiological concentrations of these amino acids in plasma; 2) inhibition of valine uptake by leucine can limit the rate of valine catabolism in heart; and 3) depletion of tissue valine concentration by an excess of leucine did not affect the rate of protein synthesis.

Protein quality, amino acid balance, utilization, and evaluation of diets containing amino acids as therapeutic agents

Basic concepts of amino acid nutrition are summarized and quantitative amino acid requirements of different age-groups based on current knowledge are presented. The newer concepts of "conditionally indispensable" amino acids and organ-specific requirements for amino acids are discussed. The concepts of nitrogen balance, limiting amino acid, protein utilization, protein efficiency ratio, and amino acid score for determining protein quality are reviewed, and examples of low-, intermediate-, and high-quality proteins are provided. Problems in assessing efficiency of nitrogen utilization when single amino acids or amino acids in combination with balanced diets are used as therapeutic agents are discussed in relation to the potential roles of the branched-chain amino acids, arginine, and glutamine in trauma and as immunostimulators.

Transport of amino acids into rat erythrocytes and its potential physiological role

Previous studies have proposed the possibility that erythrocytes (RBC) are involved in the interorgan transport of amino acids; however, this role has not been confirmed. In order to study the likelihood that erythrocytes are involved in the interorgan transport, rates of influx and efflux of glycine, threonine, lysine, histidine and leucine were measured in rat red blood cells. Time course of influx of leucine, a large neutral amino acid, was very rapid (319 mumoles/L RBC. min), and a steady state was reached between 5 to 10 min of incubation, whereas glycine influx was very slow (5.04 mumoles/L RBC. min). Threonine influx was similar to leucine although the rate was slower (41.4 mumoles/L RBC. min); however, the steady state was reached in 30 minutes and its uptake showed less capacity. Histidine and lysine showed a continuous influx, and did not reach a steady state after 60 min of incubation. Efflux of leucine was extremely rapid indicating a rapid equilibration between the incubation medium and the intracellular space of the erythrocytes. Threonine efflux had a half life (t1/2) of between two to three min, independently of the medium used. Histidine showed a t1/2 of around six min, whereas for the small neutral amino acid glycine it was of 14 to 17 min. These results indicate that some large neutral amino acids are not involved in the potential interorgan transport by red blood cells due to the rapid equilibration of the concentration of amino acid between cells and the medium.

Competition for transport of amino acids into rat heart: effect of competitors on protein synthesis and degradation

Transport of the neutral amino acids, 2-(methylamino)isobutyrate (MeAIB) and Phe, was examined in isolated rat hearts perfused by the Langendorff method. Hearts were perfused by recirculating for various time periods buffer containing [14C]-MeAIB or [14C]-Phe plus desired additions. Uptake of MeAIB was linear for approximately 30 minutes; Phe uptake was linear for a maximum of 5 minutes, and reached a steady state after 15 minutes. Km and Vmax for MeAIB were 1.1 +/- 0.03 mmol/L and 37.7 +/- 0.4 pmol/microL intracellular fluid (ICF)/min; values for Phe were 1.8 +/- 0.02 mmol/L and 364 +/- 5 pmol/microL ICF/minute. Uptake of MeAIB (0.2 mmol/L) was reduced 95% in the presence of Ser (10 mmol/L), and less severely by large neutral amino acids ([LNAA], 10 mmol/L) such as Phe and Leu (by 46% and 54%, respectively). Uptake of Phe (0.2 mmol/L) was reduced by LNAA such as Val, Leu, and Ile (by 51%, 78%, and 81%, respectively), or by commercial preparations used in parenteral nutrition, eg, Travasol or Travasol plus extra branched-chain amino acids (BCAA) (Branchamin); Ser had little effect (8% reduction). Insulin in the perfusion medium increased the fractional rate of protein synthesis. Individual BCAA at physiological concentrations (0.2 mmol/L) did not alter the rate of protein synthesis. Branchamin or Travasol plus Branchamin also had no effect on the rate of protein synthesis in heart, but did depress the rate of degradation. These studies suggest that amino acid transport into heart may be affected by normal levels of plasma amino acids, whereas protein synthesis is not.

A feather-sexed strain of laying hens was more responsive to dietary supplements of choline and methionine than a vent-sexed strain

A response surface design was used to study Cho and Met interactions with corn and soybean diets, using two strains of hens. The strains were a feather-sexed line (FS strain), and a vent-sexed line (SS strain). The diets contained 3% meat and bone meal and, on chemical analysis, 15.1% crude protein, .29% Met, .225% Cys, and 1,041 ppm of Cho. Nine diets were fed from 20 to 68 wk of age, using added Met levels ranging from 0 to 500 ppm and added Cho levels ranging from 0 to 1,500 ppm, to fix the design points. The FS strain consumed significantly more feed per day (117 versus 108 g) than the SS strain, but there were no significant differences for the 24 to 68 wk period in egg production, egg weight, or feed per dozen eggs. Three and five combinations of Met and Cho were significant in improving egg production (P less than .05) out of the eight combinations for the SS and FS strains, respectively. The best egg production for the FS strain for the period 24 to 68 wk was observed at 250 ppm Met and 1,500 ppm Cho, or 427 ppm Met and 220 ppm added Cho. The SS strain showed no significant (P greater than .05) dietary responses in egg production between 250 ppm Met and no Cho, or 427 ppm Met and either 220 or 1,280 ppm Cho. The SS strain showed no significant (P greater than .05) dietary response in egg weight to either Cho or Met.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein selection by rats adapted to high or moderately low levels of dietary protein

After preliminary studies on flavor acceptability, patterns and indices of subsequent feeding behavior were monitored by computer in young rats which were adapted to 15% or 70% casein diets before being offered, sequentially, choices between flavored diet pairs in which the proportions of percentage casein were 5/65, 5/55, 5/45, 5/35 and 5/25. Similarly adapted rats received these choices in the reverse sequence. Rats adapted to 15% casein usually ate randomly from the diet pairs and selected approximately 15-30% casein; individual behaviors were prominent. The 70% casein groups avoided the higher casein diet, often within minutes (except for the first-offered 5/25 choice), and seldom selected more than 10% casein; individual differences were infrequent. Such rats also distinguished between flavored 70% and 65% casein diets. Sizes and numbers of meals and rates of eating differed for the paired diets, especially for rats adapted to 70% casein. A flavor added to the 70% casein adaptation diet was not avoided when present only in the 5% casein diet of a 5/65 choice. Rats adapted to 70% soy protein before receiving flavored 5/65 to 5/25 choices selected 20-28% soy protein, a level far above those of casein selections by rats adapted to 70% casein. Dietary adaptation and type of protein thus affect subsequent diet selection and feeding patterns and indices.

Three-day dietary intake of incarcerated and nonincarcerated adolescent males

We collected 3-day dietary intake information from both incarcerated (n = 137) and nonincarcerated (n = 42) adolescent males to provide an objective assessment of diets of residents of a juvenile correctional facility. Average daily intake of energy, protein, 13 indicator micronutrients and of macronutrients as percent of energy were calculated. Average intakes of the total group of adolescents (n = 179) were greater than 90% of the 1980 recommended dietary allowance (RDA) for energy, protein, and 10 micronutrients. There were no statistically significant differences between black (n = 63) and white (n = 63) incarcerated subgroups and white (n = 41) nonincarcerated subjects on average measures of energy, protein, macronutrients as percent of energy, and seven micronutrients. Cumulative intakes (as a proportion of the 1980 RDA) of nonincarcerated subjects and at least one group of incarcerated subjects were significantly different for vitamin B6, folate, vitamin C, iron, sodium, and thiamin. However, average intakes of vitamin C, sodium, and iron by all groups exceeded the RDA. Overall, the total group of adolescents did not appear to be at significant nutritional risk. Folate, copper, and magnesium intakes were consistently below RDA in all groups. We suggest that these findings are not indicative of nutritional inadequacy but are, rather, cues that some RDAs may be inappropriately high.

Relationship between protein intake and hepatic protein synthesis in rats

Protein synthesis has been measured in vitro in postmitochondrial extracts from livers of rats fed levels of casein ranging from 0 to 40% by weight. The maximal capacity for protein synthesis per milligram of RNA, measured with each amino acid added at 250 mumol/L, was 40-60% higher in rats fed a protein-free diet than in those fed 6 or 15% casein. Our results suggest that the livers of rats fed a protein-free diet are primed for the synthesis of tissue proteins and, given an adequate supply of amino acids, the rate of protein synthesis would be as high as or higher than the rate in protein-replete animals. When amino acids were added to the in vitro system at concentrations found in plasma of rats fed 0, 6, 15 or 40% casein the rate of protein synthesis increased by three- to fourfold over this range, with the highest rate observed for the 15% dietary casein level. We conclude that when protein intake is below the requirement level, the rate of liver protein synthesis may be limited by amino acid supply, by the capacity of the system for protein synthesis or by both.

Thiamin status of incarcerated and nonincarcerated adolescent males: dietary intake and thiamin pyrophosphate response

We measured thiamin status in 137 incarcerated and 42 nonincarcerated adolescent males by use of both dietary intake data and a standard biochemical assay, thiamin pyrophosphate (TPP) response. Average thiamin intake of the total group was greater than 120% of the age-specific recommended dietary allowance (RDA). Ninety-two percent of incarcerated subjects and 93% of nonincarcerated subjects were consuming greater than or equal to 70% of RDA. Although average daily thiamin intake of nonincarcerated subjects was significantly higher than that of incarcerated subjects, both groups appeared to be at minimal risk for marginal thiamin status. Comparison of TPP response values indicated that there was no significant difference between groups. However, approximately 24% of the total population appeared to have less than adequate RBC thiamin on the basis of current standards for TPP response. Neither dietary intake nor reported previous alcohol intake was correlated with TPP response. These discrepant findings raise questions about the usefulness of the TPP response as the sole indicator of marginal thiamin status.

High levels of dietary amino and branched-chain alpha-keto acids alter plasma and brain amino acid concentrations in rats

Plasma and brain amino acid and plasma branched-chain alpha-keto acid (BCKA) concentrations were measured in rats fed diets containing high levels of individual amino and alpha-keto acids. Consumption of a low-protein (9% casein) diet high in leucine or alpha-ketoisocaproate depressed plasma concentrations of isoleucine and valine and their respective keto acids, alpha-keto-beta-methylvalerate and alpha-ketoisovalerate. High dietary levels of alpha-keto-beta-methylvalerate or alpha-ketoisovalerate (but not of isoleucine or valine) depressed plasma concentrations of the other BCKA and their respective branched-chain amino acids (BCAA). Consumption of a low protein, high phenylalanine diet depressed plasma concentrations of both BCAA and BCKA. Brain large neutral amino acid pools of rats fed all low-protein, high-amino acid diets were depleted. Consumption of diets high in individual BCKA increased brain concentrations of aromatic amino acids. In this study of rats allowed to feed for only 6 h/d, elevated brain phenylalanine concentration was associated with a significant depression of food intake, whereas elevated brain BCAA concentrations were not. Also, elevated plasma BCKA concentrations, comparable with those observed in maple syrup urine disease, were accompanied by elevations in concentrations of aromatic amino acids in brain but not in plasma.

Neutral amino acid transport into rat skeletal muscle: competition, adaptive regulation, and effects of insulin

Amino acid (AA) transport systems A and L, which transfer preferentially small neutral AA (SNAA) and large neutral AA (LNAA), respectively, were studied in the isolated soleus muscle with the specific models, 2-(methylamino)isobutyrate (MeAIB) and 2-aminobicyclo[2,2,1]heptane-2-carboxylate (BCH). Affinity for MeAIB was greater than for BCH (Km = 3.2 +/- 0.2 and 8.7 +/- 0.2 mm, respectively). Rate of transport of MeAIB (Vmax = 104 +/- 3 pmol/microL/min) was slower than for BCH (970 +/- 12 pmol/microL/min), but accumulation was far more concentrative; transport of BCH, but not MeAIB, rapidly reached a steady-state level. MeAIB transport was reduced in the presence of SNAA; BCH transport was reduced to a lesser extent only by LNAA. Mixtures of AA at concentrations resembling those in plasmas of rats fed either a 6% or 50% casein diet reduced transport of MeAIB, whereas BCH transport was low only with the latter mixture. Only MeAIB transport was stimulated by insulin. Preincubation of muscles for 5 hours in a AA-free medium stimulated subsequent MeAIB uptake by about twofold to fourfold; this effect was suppressed by inhibitors of protein synthesis. Selective differences were thus observed in transport by skeletal muscle of model AA for the A and L systems: increased transport resulting from various stimuli was limited to the model for the A system, and transport of either model was depressed with mixtures containing physiological levels of AA. Changes in dietary protein or AA intake may thus alter transport of certain neutral AA into skeletal muscle via changes in plasma AA pools.

Branched-chain and other amino acids in tissues of rats fed leucine-limiting amino acid diets containing norleucine

Amino acid concentrations were measured in plasma, brain, muscle and liver from rats fed leucine-limiting diets containing varying proportions of other indispensable amino acids (IAA), the branched-chain amino acids (BCAA) and norleucine, a BCAA analog known to compete with large neutral amino acids (LNAA) for transport into tissues. Leucine was low and other IAA were high when dietary IAA were 125% and leucine was 65% of requirements; higher leucine and lower IAA concentrations occurred when dietary IAA were 75% of requirements. Tissue leucine was high and isoleucine and valine were low in rats fed excess leucine. Norleucine induced dose-dependent reductions in BCAA, especially in brain and muscle in which isoleucine or valine were sometimes undetectable. Leucine was not depressed further when control values were low as in the rats fed 125% IAA. Norleucine frequently prevented the high BCAA found after feeding additional BCAA. Other LNAA tended to be low in the brain and muscle of rats fed norleucine. Lysine was high only in the tissues of rats fed 75% IAA and norleucine; this effect was prevented when added leucine was given. Brain tryptophan, but not always serotonin, was low in rats fed norleucine. The results show transport-related, selective and usually marked depletions of tissue BCAA in rats fed norleucine; this suggests norleucine may be an aid in the treatment of clinical conditions involving excesses of BCAA.

Altered phosphorylation state of branched-chain 2-oxo acid dehydrogenase in a branched-chain acyltransferase deficient human fibroblast cell line

The abundance and phosphorylation state of the polypeptide constituents of the human branched-chain 2-oxo acid dehydrogenase complex were examined in mitochondria from normal and maple syrup urine disease (MSUD) fibroblasts. In normal fibroblast mitochondria two forms of the E1 alpha subunit were observed: non-phosphorylated (E1 alpha) and phosphorylated (E1 alpha-P). About 40-50% of E1 alpha was present as E1 alpha-P. The ability to quantitate the two forms of E1 alpha permitted examination of the association between decreased capacity of oxidize branched-chain 2-oxo acids and the phosphorylation state of E1 alpha. Changes in phosphorylation state of E1 alpha were observed in MSUD fibroblasts as compared to control cells. Of particular interest was the absence of E1 alpha-P in an MSUD fibroblast line which lacked the dihydrolipoyl acyltransferase (E2) subunit of the dehydrogenase complex. In two MSUD cell lines deficient in E1 alpha, the abundance of E1 alpha-P appeared to be preferentially reduced. A fourth MSUD cell line contained normal quantities of E3, E2 and both forms of the E1 alpha polypeptide. Our results indicate that alterations in the abundance of dehydrogenase complex polypeptides in MSUD fibroblasts may influence the phosphorylation state of the E1 alpha polypeptide. They demonstrate the potential for examining simultaneously mutations which affect both the catalytic and regulatory components of the dehydrogenase complex.

Sucrose and delinquency: behavioral assessment

In this study, a double-blind challenge design was used to evaluate the hypothesis that sucrose ingestion may compromise the behavioral performance of juvenile delinquents. Subjects were 58 white delinquents, 57 black delinquents, and 39 white nondelinquents. The behavioral assessment included tasks that are relevant to delinquency and that might be expected to be disrupted following sucrose ingestion. The results provide no evidence that sucrose ingestion impairs the performance of juvenile delinquents. In fact, the results of several analyses indicated that the sucrose breakfast was associated with improved performance. In additional analyses the effect of sucrose on particular subgroups of juvenile delinquents was evaluated. Statistical interactions indicated that the performance of delinquents rated as more behaviorally disturbed benefited from sucrose ingestion, whereas those delinquents with less pronounced behavior problems tended to show impaired performance following a sucrose-loaded breakfast. These results indicate that simple statements regarding the effects of sucrose ingestion on behavior are likely to be misleading and highlight the need to consider individual difference variables when investigating the effects of sucrose on juvenile delinquents.

Sucrose and delinquency: oral sucrose tolerance test and nutritional assessment

Claims that juvenile delinquency may be associated with reactive hypoglycemia or nutritional deficiencies have received widespread attention but little objective evaluation. To assess the validity of these claims, nutritional and psychological indices of juvenile delinquents have been measured. Serum glucose and insulin profiles during an oral sucrose tolerance test were measured in 137 delinquent and 41 nondelinquent male adolescents aged 14 to 19. In addition, nutritional status of both populations was assessed by anthropometry (height, weight, arm circumference, triceps skin fold) and biochemical measures (hematocrit, red-blood cell thiamin, and serum copper, ferritin, and zinc). Delinquent subjects had slightly but significantly lower serum glucose values at four of six time points (fasting, 60 minutes, 120 minutes, 180 minutes) and higher serum insulin values at one time point (30 minutes) compared with nondelinquent subjects. Changes in glucose from fasting levels indicate that these subjects were regulating serum glucose adequately, but doing so at lower values; changes in insulin from fasting levels indicate that black delinquents initially secreted more insulin than either white subject group. There were no significant associations between excursions in serum glucose or insulin and any adrenergic signs or symptoms of low blood glucose levels. Nutritional status of incarcerated delinquents did not differ from that of nonincarcerated subjects on most measures. Although the significantly lower serum glucose levels and higher serum insulin levels are intriguing, no support is offered by results of this study for allegations that sucrose ingestion causes reactive hypoglycemia in juvenile delinquents or that delinquent male adolescents are at greater risk nutritionally than male adolescents of the same age who are not delinquent.(ABSTRACT TRUNCATED AT 250 WORDS)

High branched-chain alpha-keto acid intake, branched-chain alpha-keto acid dehydrogenase activity, and plasma and brain amino acid and plasma keto acid concentrations in rats

Diets containing high quantities of individual branched-chain alpha-keto acids (BCKAs) or a combination of BCKAs as used for treatment of renal disease were fed to rats. When the diet contained a single BCKA, its concentration was high in plasma and the concentration of its corresponding amino acid was high in plasma and brain. Liver BCKA dehydrogenase (BCKD) was 42% active in control rats. Consumption of diets containing 0.38 mol/kg diet of alpha-ketoisocaproate (KIC), alpha-keto-beta-methylvalerate (KMV), or alpha-ketoisovalerate (KIV) resulted in complete activation of liver BCKD. Consumption of the diet containing the combination of BCKAs increased basal BCKD activity of liver twofold. Muscle BCKD was activated after feeding the KIV diet (2-fold), the KIC diet (3-fold), and the KMV diet (15-fold). Total BCKD activity of liver and muscle was unaffected by dietary treatments. Activation of liver and muscle BCKD by dietary BCKA is consistent with their ability to inhibit BCKD kinase in vitro.

Dietary disproportions of amino acids in the rat: effects on food intake, plasma and brain amino acids and brain serotonin

Food intake, growth, plasma and brain amino acid, and brain serotonin and 5-hydroxyindole-3-acetic acid (5-HIAA) concentrations were measured in rats fed low protein diets containing disproportionate amounts of large neutral amino acids (LNAA) devoid of tryptophan or histidine (tryptophan or histidine imbalance). Five-day food intakes and weight gains of rats fed the imbalanced diets were depressed. The concentration of the limiting amino acid was low in brains of rats fed diets containing LNAA that compete with either tryptophan or histidine for entry into brain. Correlations were observed between the brain concentrations of most individual LNAA and either the ratios of the plasma concentration of that LNAA to the sum of the other LNAA, or the predicted rates of influx of that LNAA. Cumulative food intakes were correlated with brain concentrations of the limiting amino acid, tryptophan or histidine. Food intakes were not consistently correlated with concentrations of serotonin and 5-HIAA because these compounds were altered only in brains of rats in the tryptophan study. Competition among amino acids for uptake into brain appears to be involved in the feeding response of the rat to dietary disproportions of amino acids, but this response is not directly related to changes in brain concentrations of serotonin and 5-HIAA.

Norleucine: a branched-chain amino acid analog affecting feeding behavior of rats

Norleucine, an isomer of leucine and isoleucine and a potent competitor of large neutral amino acid transport into brain, thereby depleting certain amino acid pools, was tested for its effects on growth and feeding behavior of rats fed an amino acid diet limiting in leucine. Growth and food intake were depressed in proportion to the dietary level of norleucine (0.2 to 1.1% of the diet). With suboptimal amounts of indispensable amino acids, leucine at 150% of the requirement reversed the effects of 0.2 and 0.5% norleucine; slight excesses of the other indispensable amino acids were required with extra leucine for maximum growth with 1.1% norleucine. Rats almost exclusively preferred the control to the norleucine diet, but not if the latter diet also contained leucine. Rats also strongly selected a nonprotein rather than norleucine diet when this was the first available choice. If the first choice was between the nonprotein and control diets, rats later almost exclusively selected the norleucine-containing rather than the nonprotein diet for varying periods (2 to 6 days). These studies suggest that amino acid analogs may be useful agents in the study of animal behavior associated with changes in brain amino acid pools.

Dietary branched-chain amino acids and protein selection by rats

Consumption by rats of high protein diets is associated with elevated plasma and brain concentrations of branched-chain amino acids (BCAA). We examined the possibility that changes in BCAA concentrations in blood and brain might serve as modulators of protein consumption. After young rats had adjusted to selecting between a 10% or 25% casein diet and a 50% casein diet, a mixture of BCAA was included in the diet containing the lower amount of protein (10% + BCAA, 25% + BCAA). Supplementation of the 10% or 25% casein diets with BCAA and subsequent elevation of BCAA concentrations in plasma and brain were associated with increased selection of protein in rats given the 10% + BCAA/50% casein diet choice, but not in rats offered the 25% + BCAA/50% casein diets. When no alternative diet was available, addition of BCAA to a 15% casein diet depressed food intake, and rats given a choice between a 15% casein diet with or without added BCAA selected almost exclusively the diet without added BCAA. Although BCAA concentrations were high in plasma and brain in all experiments, concentrations of methionine, tyrosine, phenylalanine, tryptophan and histidine were low in brain in experiments in which rats altered their diet or protein selection after BCAA addition. High concentrations of BCAA in plasma and brain were not consistently associated with changes in protein selection.

Phylogenetic comparisons of the branched-chain alpha-ketoacid dehydrogenase complex

1. Antibodies against the E1b and E2b components of bovine branched-chain alpha-ketoacid (BCKA) dehydrogenase (BCKAD) complex completely inhibited BCKA oxidation in mammalian and avian mitochondria. BCKA oxidation by salmonid mitochondria was less affected and the enzyme from Pseudomonas putida was unaffected. 2. In rodents, anti-E1b E2b IgG inhibited oxidation of all three BCKA in a similar dose-dependent manner: oxidation of alpha-ketobutyrate and alpha-keto-y-methiolbutyrate was also partially inhibited. 3. Except for the salmonid BCKAD, a similar Mr for the E2b and E1b alpha proteins was observed in these species. 4. After digestion with V-8 protease similar immunoreactive peptides were observed for the human and rodent complex.

Activities of branched-chain amino acid--degrading enzymes in liver from rats fed different dietary levels of protein

The relationships among dietary protein intake, plasma branched-chain amino acid (BCAA) and keto acid (BCKA) concentrations, and liver BCAA-degrading enzyme activities were investigated in rats fed, for 5 h/d for 2, 6 or 9 d, diets containing from 0 to 50% casein. Plasma, liver and muscle BCAA concentrations were proportional to protein intake over the entire range tested; plasma BCKA concentration, however, was proportional only in the range from 0 to 20% casein, after which a plateau was reached. By d 2, liver cytosolic BCAA aminotransferase activity had increased in rats fed 50% casein; by d 9, activity had increased in rats fed 0 or 5% casein as well. Liver mitochondrial BCAA aminotransferase activity was unresponsive to dietary treatment. Basal liver BCKA dehydrogenase activity and the percent active complex were proportional to protein intake on d 2 and 6. On d 2, total BCKA dehydrogenase activity was the same in all groups; by d 6, total activity had increased in rats fed 30 or 50% casein. We conclude that although the adaptive changes in BCAA-degrading enzyme activities are small, they are sufficient to compensate for excessively high or low protein intakes, so that tolerable concentrations of BCAA and BCKA are maintained.

Protein intake, brain amino acid and serotonin concentrations and protein self-selection

Analysis of evidence of associations among dietary protein content, brain amino acid and serotonin concentrations, and protein self-selection by rats suggests that 1) protein intake is not regulated precisely, although rats will select between low and high protein diets to obtain an adequate, but not excessive, amount of protein; 2) associations between brain serotonin concentration and protein intake are weak, although consumption of single meals of protein-deficient diets will elevate brain serotonin concentration; 3) the nature of signals that drive rats to avoid diets containing inadequate or excessive amounts of protein remains obscure; (4) whole brain amino acid and serotonin concentrations are quite stable over the usual range of protein intakes, owing to competition among amino acids for uptake across the blood-brain barrier and effective metabolic regulation of blood amino acid concentrations; 5) protein intake and preference are not in themselves regulated, but what appears to be regulation of intake and preference is a reflection of the responses of systems for control of plasma amino acid concentrations; and (6) the relative stability of the average protein intake of groups of self-selecting rats (which gives the appearance of regulation) results from averaging the variable behavioral responses--learned aversions and preferences--of rats to the variety of sensory cues arising from diets that differ in protein content.

Distribution of alpha-aminoisobutyric acid in tissues of lean and genetically obese mice

Distribution of tracer amounts of the nonmetabolizable neutral amino acid alpha-[1-14C]aminoisobutyric acid (AIB) between blood and several tissues was measured in lean and ob/ob mice over an 8-hr period. As AIB was injected on the basis of body weight and as ob/ob mice have a relatively low blood volume, absolute concentrations of AIB in blood and tissues were almost always higher in the obese than the lean mice. However, the ratio of AIB concentration in the tissues to that in the blood was clearly higher in skeletal muscle, diaphragm, and brain, and possibly higher in liver of the lean than of the obese animals. Ratios in heart were similar. The results suggest that lean and genetically obese mice differ in their capacity to transport amino acids between blood and various tissues.

Alterations in phospholipid composition of egg yolks from laying hens fed choline and methionine-supplemented diets

A trial was conducted to assess the effects of choline and methionine supplementation of the diets of hens on phospholipid composition of egg yolk. By chemical analysis, the basal diet contained 16.6% protein, 1,041 parts per million (ppm) of choline, and .53% TSAA. The energy level was 2,899 kcal ME/kg diet, with no added fat. A rapid isocratic HPLC procedure using a Waters mu Bond-NH2 column (Waters Associates, Milford, MA) was developed to quantify phospholipid components. Analysis of egg samples at peak production (36 wk of age) showed significant (P less than .05) elevations in total phospholipids, phosphatidylcholine (PC), and the ratio of PC to phosphatidylethanolamine (PE), when choline was added at 500 or 1,000 ppm. Phosphatidylethanolamine, in contrast, showed a decline with choline supplementation. Methionine supplementation (125 to 250 ppm) also caused elevations in the total phospholipid composition of the egg yolk but had only modest effects on PC and PE. There was a significant (P less than .05) correlation between the yolk weight and total phospholipid concentration, PC, and the PC:PE ratio. There was a relationship between phospholipid content and weight of eggs when diets of laying hens were supplemented with choline.

Regulation of valine and alpha-ketoisocaproate metabolism in rat kidney mitochondria

Activities of branched-chain amino acid (BCAA) aminotransferase (BCAT) and alpha-keto acid dehydrogenase (BCKD) were assayed in mitochondria isolated from kidneys of rats. Rates of transamination of valine and oxidation of keto acids alpha-ketoisocaproate (KIC) or alpha-ketoisovalerate (KIV) were estimated using radioactive tracers of the appropriate substrate from amounts of 14C-labeled products formed (14CO2 or [1-14C]-keto acid). Because of the high mitochondrial BCAT activity, an amino acceptor for BCAT, alpha-ketoglutarate (alpha-KG) or KIC, was added to the assay medium when valine was the substrate. Rates of valine transamination and subsequent oxidation of the KIV formed were determined with 0.5 mM alpha-KG as the amino acceptor; these rates were 5- to 50-fold those without added alpha-KG. Rates of CO2 evolution from valine also increased when KIC (0.01-0.10 mM) was present; however, with KIC concentrations above 0.2 mM, rates of CO2 evolution from valine declined although rates of transamination continued to rise. When 0.05 mM KIC was added to the assay medium, oxidation of KIC was suppressed by inclusion of valine or glutamate in the medium. When valine was present KIC was not oxidized preferentially, presumably because it was also serving as an amino acceptor for BCAT. These results indicate that as the supply of amino acceptor, alpha-KG or KIC, is increased in mitochondria not only is the rate of valine transamination stimulated but also the rate of oxidation of the KIV formed from valine.(ABSTRACT TRUNCATED AT 250 WORDS)

Some characteristics of threonine transport across the blood-brain barrier of the rat

Threonine entry into brain is altered by diet-induced changes in concentrations of plasma amino acids, especially the small neutrals. To study this finding further, we compared effects of various amino acids (large and small neutrals, analogues, and transport models) on transport of threonine and phenylalanine across the blood-brain barrier. Threonine transport was saturable and was usually depressed more by natural large than small neutrals. Norvaline and 2-amino-n-butyrate (AABA) were stronger competitors than norleucine. 2-Aminobicyclo[2.2.1]heptane-2-carboxylate (BCH), a model in other preparations for the large neutral (L) system, and cysteine, a proposed model for the ASC system only in certain preparations, reduced threonine transport; 2-(methylamino)isobutyrate (MeAIB; a model for the A system for small neutrals) did not. Phenylalanine transport was most depressed by cold phenylalanine and other large neutrals; threonine and other small neutrals had little effect. Norleucine, but not AABA, was a strong competitor; BCH was more competitive than cysteine or MeAIB. Absence of sodium did not affect phenylalanine transport, but decreased threonine uptake by 25% (p less than 0.001). Our results with natural, analogue, and model amino acids, and especially with sodium, suggest that threonine, but not phenylalanine, may enter the brain partly by the sodium-dependent ASC system.

Dietary amino acid analogues and transport of lysine or valine across the blood-brain barrier in rats

Studies were undertaken to determine if dietary disproportions of amino acids would alter flux into brain of the amino acid present in the diet in a growth-limiting concentration. Rats were adapted to a lysine-limiting diet before receiving a meal of this control diet, alone or with added lysine or homoarginine (a competitor for lysine transport) or both, before intravenous infusion of [14C]lysine. The brain-to-plasma radioactivity ratio was lower in rats fed extra lysine or homoarginine than in rats fed the control diet, whereas lysine flux and brain lysine concentration were high in rats fed extra lysine alone. Flux and concentration were lower in rats fed homoarginine + lysine than in rats fed extra lysine alone. Other rats were fed a valine-limiting diet containing added valine, norleucine (a competitor for valine transport) or both, before [14C]valine was infused. Valine flux and brain valine concentrations were higher in rats fed extra valine than in control rats, whereas flux was lower in the group fed norleucine alone. Valine flux was higher in rats fed norleucine + valine than in the rats fed norleucine alone. Our studies show that dietary disproportions of amino acids can alter the flux of specific amino acids across the blood-brain barrier.

Influence of dietary leucine content on the activities of branched-chain amino acid aminotransferase (EC 2.6.1.42) and branched-chain alpha-keto acid dehydrogenase (EC 1.2.4.4) complex in tissues of preruminant lambs

1. Branched-chain amino acid aminotransferase (EC 2.6.1.42; BCAAT) and branched-chain alpha-keto acid dehydrogenase (EC 1.2.4.4; BCKDH) activities were measured preruminant lamb liver, longissimus dorsi muscle, kidney, jejunum and adipose tissue, 2 h after a meal with or without an excess of leucine. 2. Skeletal muscle contained about 70% of the total basal BCAAT activities of the tissues studied whereas liver contained about 60% of the total BCKDH activities of these tissues. 3. BCAAT activities were very low in preruminant lamb tissues. BCKDH was more phosphorylated in tissues of preruminant lambs than in rats, especially in liver. These low catalytic potentialities might contribute to a low rate of branched-chain amino acid catabolism in sheep. 4. Ingestion of an excess of leucine led to an increase in liver and jejunum BCAAT activities and activation of BCKDH in jejunum.

Effects of dietary protein intake on branched-chain keto acid dehydrogenase activity of the rat. Immunochemical analysis of the enzyme complex

Polyclonal antibodies directed against the dihydrolipoyl transacylase (E2) and alpha subunit of branched-chain alpha-keto acid decarboxylase (E1 alpha) components of the bovine branched-chain keto acid dehydrogenase complex were shown to cross-react with the E2 and E1 alpha polypeptides of the enzyme complex of different rat tissues. Phosphorylation of the branched-chain keto acid dehydrogenase complex resulted in inhibition of enzyme activity concomitant with phosphate incorporation into the E1 alpha polypeptide. Phosphorylation of E1 alpha slowed its rate of migration through sodium dodecyl sulfate-polyacrylamide gels. This permitted resolution of the phosphorylated and unphosphorylated forms of E1 alpha on immunoblots. Liver and skeletal muscle mitochondria were prepared from rats consuming 6, 20, or 50% casein diets. The enzyme complex in mitochondria was measured by radioisotopic enzyme assay and immunoassay. Liver branched-chain keto acid dehydrogenase was 25% active in rats consuming 6% casein diets; whereas in rats consuming 20 or 50% casein diets, the liver enzyme was 82 or 100% active, respectively. Branched-chain keto acid dehydrogenase of muscle was 10, 13, and 22% active, respectively, in rats consuming 6, 20, and 50% casein diets. The amount of protein consumed by rats did not affect the total amount of the enzyme complex per unit of mitochondrial protein as measured by either the radioisotopic assay (enzyme activity) or the immunoassay. However, the protein intake of rats did affect activity of the enzyme kinase in liver. Liver branched-chain keto acid dehydrogenase kinase was more active in rats consuming 6% casein than in those fed chow or 50% casein diets. The amount of protein consumed by rats thus influences the enzyme activity in liver and muscle by affecting the reversible phosphorylation mechanism and not by induction of branched-chain keto acid dehydrogenase.

Induction of conditioned taste aversion in rats by GABA or other amino acids

GABA included in the diet is known to reduce food intake and growth of rats fed a low protein diet. Experiments were designed to determine if GABA or other small neutral amino acids would affect food intake if they were administered separately from the diet, and if such amino acids could induce a conditioned taste aversion (CTA) to saccharin. Intubated or injected GABA or alpha-aminoisobutyric acid (AIB), a non-metabolizable isomer of GABA, reduced food intake. When rats were fed a low protein diet, IP injection of threonine (2 mmoles/200 g rat) induced CTA but did not depress food intake; serine (3 mmoles/200 g rat) induced CTA and caused only a small reduction in food intake. Another isomer, alpha-amino-n-butyric acid did not affect food intake or induce CTA at the tested concentrations. Adaptation to a high protein diet, which increases enzymatic degradation of many amino acids including GABA and serine, lessened severity of GABA-induced CTA and eliminated that caused by serine. CTA to saccharin can be induced by certain amino acids; the mechanism is unknown but may involve malaise or other adverse sensations.

Acceptability by rats of aqueous solutions of amino acid analogues

Preferences differed widely when rats were offered choices between water and solutions of various natural amino acids and structurally related analogues. They avoided the branched-chain amino acid valine but preferred solutions of its isomer norvaline and of norleucine. The hydrochloride forms of ornithine and arginine were preferred to water at concentrations up to about 100 mM and avoided at 410 mM; homoarginine.HCl was never preferred and was avoided at 39 and 78 mM. Rats were indifferent to taurine and beta-alanine at most concentrations but refused these amino acids at high concentrations (205 and 410 mM, respectively). In conjunction with earlier observations on feeding behavior in response to dietary additions of amino acids, the results show that selections by rats between water and amino acid solutions cannot be used to predict choices among amino acid-containing diets.

Critical vitamin supplementation of broiler diets high in alfalfa juice protein

Three trials were conducted to identify the critical vitamins in the diets of broiler-strain chicks fed alfalfa juice protein concentrate (AJPC) corn-soy diets from 0 to 3 wk of age. Vitamin supplements were added to AJPC diets. Diets were formulated to contain, parts 30/121, 40/128, 50/135, and 60/142 parts AJPC/parts total diet. Parts were used to permit usage of wet materials and still maintain about 90% dry matter. All diets were formulated to contain 20% crude protein, .93% total sulfur-containing amino acids, and 2,940 kcal metabolizable energy/kg diet. Propionic acid was added at .2% to all diets. Feeds were refrigerated (7 C) and fed out daily. The addition of choline, riboflavin, vitamin B12, vitamin A or E, folic acid, or biotin did not increase weight gains. Addition of 3 mg/kg vitamin B6 completely overcame the growth depression caused by the 50-parts AJPC diet and significant (P less than .05) growth increases (13 to 29%) were achieved with vitamin-B6 supplementation to the 60-parts AJPC diet. Depressed immune responses were completely prevented by the addition of 3 mg/kg of vitamin B6. The significant (P less than .05) increases in leg deformities observed in birds fed the 60-parts AJPC diet were also brought back to more typical values in birds fed the diet supplemented with 3 mg/kg vitamin B6. Vitamin K supplementation (.53 mg/kg) to the 60-parts AJPC diet resulted in significant decreases from 15 min in blood clotting times to 3 to 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of volatile sulfur derivatives released from feathers of chicks fed diets with various levels of sulfur-containing amino acids

Physical changes are observed in the feathers of chickens fed diets with high levels of methionine or cysteine. Chicks were fed diets chemically analyzed to contain 21% crude protein, 0.35% methionine and 0.37% cystine (basal) supplemented with DL-methionine [0.063 (control), 0.25 or 1.45%] or L-cysteine (0.203%). At 3 wk of age, the birds were weighed and the feathers scored for softness. Feather strength (i.e., force-displacement curves) was determined on feathers from the pectoral tract. A significant (P less than 0.05) reduction in body weight and an increase in feather softness were seen when chicks fed the control diet and those fed the diet with 1.45% added methionine were compared. Chicks fed the diet supplemented with 0.203% L-cysteine produced the strongest feathers; those fed diets supplemented with 1.45% DL-methionine produced the weakest feathers. Volatile sulfur compounds released from the feathers were trapped as dinitrophenyl (DNP) thioethers and were analyzed by thin-layer chromatography, high pressure liquid chromatography and mass spectrometry. More bound sulfide (P less than 0.05) was recovered from feathers of chickens fed the diet supplemented with 1.45% methionine than from feathers of chickens fed the other diets. The feather softness score was correlated (r = 0.5; P less than 0.05) with bound sulfide. Thus, consumption of a diet with a level of methionine that is approximately three times the requirement resulted in decreased growth, elevated sulfide bound to the feathers and soft, weak feathers.

Assessment of softness properties of feathers

An instrument to be called the "Crimp Meter" was designed and used with a conventional balance to enable the plotting of a force-displacement curve for individual feathers. A comparison of the curves described by different feathers was made by regression analysis. The type of curve described by a feather is characteristic of its tensile properties and its degree of softness. This procedure was employed to objectively confirm the observation that chicks fed toxic levels of methionine (1.45% added) in corn-soybean diets had significantly softer (P less than .001) feathers than those fed nontoxic levels of cysteine (.203% added). The basal diet was analyzed and found to contain .35% methionine and .37% cystine. This device had potential for the down-feather, wool, and fabric industries.

Efficacy of cysteine in replacing methionine in the immune responses of broiler chicks

Two trials were conducted to compare the effects of supplements of methionine and cysteine on the growth and immune responses of broiler chicks fed corn-soy diets. The basal diet contained 21% crude protein, 3,255 kcal metabolizable energy/kg diet, .35% methionine, .37% cysteine, and .13% choline. Additions to the basal diet were methionine (.063, .25, .85, and 1.45%), or cysteine (.203%), or a combination of methionine (.063%) and cysteine (.153%). Total antibody and 2-mercaptoethanol-resistant antibodies, immunoglobulin G (IgG), were determined in chicks inoculated intraperitoneally at 14 days of age and serially bled at 4, 7, and 10 days postinoculation. Thymus-derived (T)-cell-dependent in vivo mitogen response to phytohemagglutinin-P (PHA-P) was assessed via wing web swelling. The methionine requirement for growth (0 to 3 wk of age) was found to be no more than .413% of the diet (.35% in the basal diet plus .063% added). Addition of 1.45% methionine to the basal diet resulted in significant depression (P less than .05) in growth. The antibody responses generally peaked at 7 days postprimary inoculation. Both methionine and cystine supplementation at low levels resulted in improvement in the cell mediated PHA-P responses as well as in the IgG (T-cell-dependent) responses. High supplemental methionine (1.45%), however, caused significant (P less than .05) depressions in both responses. Equimolar additions of methionine and cysteine (16.8 mmol/kg diet) showed that cysteine was about 84 and 70% as efficacious as methionine in the IgG and the PHA-P stimulation (PHA-I), respectively, in healthy chicks.(ABSTRACT TRUNCATED AT 250 WORDS)