Extended states in random dimer gated graphene superlattices.

Ordered and disordered semiconductor superlattices represent structures with completely opposed properties. For instance, ordered superlattices exhibit extended Bloch-like states, while disordered superlattices present localized states. These characteristics lead to higher conductance in ordered superlattices compared to disordered ones. Surprisingly, disordered dimer superlattices, which consist of two types of quantum wells with one type always appearing in pairs, exhibit extended states. The percentage of dissimilar wells does not need to be large to have extended states. Furthermore, the conductance is intermediate between ordered and disordered superlattices. In this work, we explore disordered dimer superlattices in graphene. We calculate the transmission and transport properties using the transfer matrix method and the Landauer-Büttiker formalism, respectively. We identify and discuss the main energy regions where the conductance of random dimer superlattices in graphene is intermediate to that of ordered and disordered superlattices. We also analyze the resonant energies of the double quantum well cavity and the electronic structure of the host gated graphene superlattice (GGSL), finding that the coupling between the resonant energies and the superlattice energy minibands gives rise to the extended states in random dimer GGSLs.

Gaussian and Gaussian-pulsed-like Fermi velocity graphene structures.

Gaussian and Gaussian-related structures are quite attractive due to its versatility to modulate the electronic transport, including its possibility as electron filters. Here, we show that these non-conventional profiles are not the exception when dealing with Fermi velocity barriers in monolayer graphene. In particular, we show that Gaussian Fermi velocity graphene barriers (G-FVGBs) and Gaussian-pulsed-like Fermi velocity graphene superlattices (GPL-FVGSLs) can serve as electron band-pass filters and oscillating conductance structures. We reach this conclusion by theoretically studying the transmission and transport properties of the mentioned structures. The study is based on the continuum model, the transfer matrix method and the Landauer-Büttiker formalism. We find nearly flat transmission bands or pass bands for G-FVGBs modulable through the system parameters. The pass bands improve as the maximum ratio of Fermi velocities (ξmax) increases, however its omnidirectional range is reduced. These characteristics result in a decaying conductance (integrated transmission) withξmax. The integrated transmission remains practically unaltered with the size of the system due to the saturation of the electron pass band filtering. In the case of GPL-FVGSLs the GPL profile results in regions of high transmission probability that can merge as flat transmission minibands if the pulse fraction and the superlattice parameters are appropriately tuned. The GPL profile also results in conductance (integrated transmission) oscillations that can be multiplied or reduced in number by adjusting the pulse fraction as well as the superlattice parameters.

Self-similar conductance patterns in graphene Cantor-like structures.

Graphene has proven to be an ideal system for exotic transport phenomena. In this work, we report another exotic characteristic of the electron transport in graphene. Namely, we show that the linear-regime conductance can present self-similar patterns with well-defined scaling rules, once the graphene sheet is subjected to Cantor-like nanostructuring. As far as we know the mentioned system is one of the few in which a self-similar structure produces self-similar patterns on a physical property. These patterns are analysed quantitatively, by obtaining the scaling rules that underlie them. It is worth noting that the transport properties are an average of the dispersion channels, which makes the existence of scale factors quite surprising. In addition, that self-similarity be manifested in the conductance opens an excellent opportunity to test this fundamental property experimentally.

Performance and anticoccidial effects of nicarbazin-fed broilers reared at standard or reduced environmental temperatures.

A series of 4 floor pen studies was conducted to evaluate the effects of environmental temperature modification on nicarbazin (NIC) responses in broiler chickens raised to 28 d of age. Birds were reared at either standard temperatures (recommended by the primary breeder for ages zero to 28 d) or at 3°C below this level. From placement to 28 d, birds were provided feeds containing zero, 100, or 125 ppm NIC, comprising a 2 × 3 factorial arrangement in each test. Two of the trials were conducted in the presence of an imposed coccidial challenge and 2 were conducted in healthy animals. At 18 and 28 d of age, performance was recorded; cloacal temperatures were measured at 7, 14, 21, and 26 days. Mortality data were collected daily and coccidial lesions were scored at 6 d post challenge. Results of these studies revealed that NIC improved coccidial lesion scores regardless of environmental temperature. In the absence of coccidial challenge, NIC depressed performance, but reductions in environmental temperature diminished the magnitude of these responses. Under conditions of coccidial challenge, NIC significantly improved body weight gains in both temperature environments. Compared to standard temperature conditions, lower environmental temperatures exerted a positive effect on feed conversion rates of NIC-fed broilers. Birds reared in the low temperature environment exhibited lower cloacal temperatures than standard environment groups throughout the test period. Irrespective of coccidial challenge, lower environmental temperatures significantly reduced nicarbazin mortality compared to standard temperature groups, resulting in a significant nicarbazin x temperature interaction. This finding indicates that temperature modification is a practical method for minimizing mortality over the course of 28-day nicarbazin usage.

Evidencias de la utilidad del ácido láctico como marcador pronóstico de morbimortalidad en pacientes politraumatizados. Importancia bioquímica / Evidence of the utility of lactic acid as a marker prognosis of morbidity and mortality in polytraumatized patients. Biochemical importance

El trauma es una de las principales causas de muerte en los países desarrollados y está dentro de las primeras causas de muerte en el mundo. Según la Organización Mundial de la Salud, afecta fundamentalmente a jóvenes de entre 15 y 29 años de edad. Es importante que los profesionales del equipo de salud, tanto médicos como bioquímicos o de otras especialidades, que trabajan con este tipo de enfermos conozcan la importancia de la determinación del ácido láctico en pacientes politraumatizados, hemodiná- micamente estables o no, así como también la fisiopatología de esta clase de cuadro. El objetivo del presente trabajo fue realizar una revisión bibliográfica para evaluar la utilidad del ácido láctico como marcador de hipoperfusión oculta en pacientes politraumatizados, y su relación con la falla multiorgánica y la morbimortalidad. En los trabajos evaluados, se observaron diferencias significativas en los porcentajes de mortalidad y de falla multiorgánica respecto de los valores altos o bajos de ácido láctico tanto al ingreso como a diferentes tiempos posingreso y al margen de si los pacientes se presentaban hemodinámicamente estables o no.(AU)

Trauma is one of the leading causes of death in developed countries and it is one of the first causes of death in the world. According to the World Health Organization, trauma mainly affects young people between 15 and 19 years old. It is very important that health professionals, such as doctors, biochemist, and another health specialists who work with that kind of patients, know the importance of lactic acid measurements in multiple trauma patients whether normotensive or not, as well as the physiopathology of that kind of condition. The aim of this review was to evaluate the usefulness of lactic acid measurements as an indicator of occult hypoperfusion in multiple trauma and its relationship with multiple system organ failure and morbidity and mortality. This review shows the significant difference between the rate of mortality and multiple system organ failure with high or low lactic acid blood levels at hospital admission, as well as at different times after admission independently if the patients were suffering hypoperfusion or not(AU)

Effect of oral nutritional supplementation on wound healing in diabetic foot ulcers: a prospective randomized controlled trial.

AIMS: Among people with diabetes, 10-25% will experience a foot ulcer. Research has shown that supplementation with arginine, glutamine and ß-hydroxy-ß-methylbutyrate may improve wound repair. This study tested whether such supplementation would improve healing of foot ulcers in persons with diabetes. METHODS: Along with standard of care, 270 subjects received, in a double-blinded fashion, (twice per day) either arginine, glutamine and ß-hydroxy-ß-methylbutyrate or a control drink for 16 weeks. The proportion of subjects with total wound closure and time to complete healing was assessed. In a post-hoc analysis, the interaction of serum albumin or limb perfusion, as measured by ankle-brachial index, and supplementation on healing was investigated. RESULTS: Overall, there were no group differences in wound closure or time to wound healing at week 16. However, in subjects with an albumin level of ≤ 40 g/l and/or an ankle-brachial index of < 1.0, a significantly greater proportion of subjects in the arginine, glutamine and ß-hydroxy-ß-methylbutyrate group healed at week 16 compared with control subjects (P = 0.03 and 0.008, respectively). Those with low albumin or decreased limb perfusion in the supplementation group were 1.70 (95% CI 1.04-2.79) and 1.66 (95% CI 1.15-2.38) times more likely to heal. CONCLUSIONS: While no differences in healing were identified with supplementation in non-ischaemic patients or those with normal albumin, addition of arginine, glutamine and ß-hydroxy-ß-methylbutyrate as an adjunct to standard of care may improve healing of diabetic foot ulcers in patients with risk of poor limb perfusion and/or low albumin levels. Further investigation involving arginine, glutamine and ß-hydroxy-ß-methylbutyrate in these high-risk subgroups might prove clinically valuable.

Broiler performance, hatching egg, and age relationships of progeny from standard and dwarf broiler dams.

The relationship of egg and chick weights to the performance of broiler chickens from two 42-wk-old flocks (standard and dwarf dams) having male parents from the same genetic stock was investigated in this study. Fertility (91.7 vs. 94.7%) and hatchability (95.2 vs. 96.3%) were not significantly (P > 0.10) different for eggs from standard and dwarf dams, respectively. Egg weight contributed significantly to the variation in BW [BW = ß(0) + ß(i) (egg weight) + ß(i) (dam) + ß(i) (sex)]. Body weight as a function of chick weight was not significant. However, chick weight was significant when included in a model with egg weight, suggesting that significant differences in BW at 50 d could be attributed to both egg and chick weights. The negative coefficient for chick weight indicated that between the 2 broilers of the same egg weight, the one with the greater chick weight would have the smaller 50-d BW. Chick weight was a linear function of egg weight. Similarly, the effect of egg or chick weight on broiler BW at 35 or 50 d was best represented by a single linear function. Dam genotype did not contribute significantly to variation in 50-d BW after variation attributable to egg weight was removed from the model. Differences in BW attributable to egg weight increased with broiler age. The coefficients of egg weight and chick weight showed that the differences in BW per gram of egg were 1.43, 3.06, 6.24, and 7.61 g and those per gram of chick were 1.87, 3.99, 8.14, and 9.93 g, respectively, at 7, 21, 35, and 50 d. Body weight increased by 0.1563 times egg weight (and 0.2092 times chick weight) with each additional day of age for both sexes and genotypes. Clearly, both egg and chick weights are important for modeling or predicting market-age broiler BW and economic returns. The relatively small relationship between BW and egg weight demonstrates that genetic selection over the past 3 decades has decreased the influence of egg weight on broiler growth. The present dwarf broiler breeder dams may produce progeny comparable in performance with standard dams.

The effects of anticalcification treatments and hydration on the molecular dynamics of bovine pericardium collagen as revealed by 13C solid-state NMR.

This article describes a solid-state NMR (SSNMR) investigation of the influence of hydration and chemical cross-linking on the molecular dynamics of the constituents of the bovine pericardium (BP) tissues and its relation to the mechanical properties of the tissue. Samples of natural phenethylamine-diepoxide (DE)- and glutaraldehyde (GL)-fixed BP were investigated by (13)C cross-polarization SSNMR to probe the dynamics of the collagen, and the results were correlated to the mechanical properties of the tissues, probed by dynamical mechanical analysis. For samples of natural BP, the NMR results show that the higher the hydration level the more pronounced the molecular dynamics of the collagen backbone and sidechains, decreasing the tissue's elastic modulus. In contrast, in DE- and GL-treated samples, the collagen molecules are more rigid, and the hydration seems to be less effective in increasing the collagen molecular dynamics and reducing the mechanical strength of the samples. This is mostly attributed to the presence of cross-links between the collagen plates, which renders the collagen mobility less dependent on the water absorption in chemically treated samples.

Sensitivity of Eimeria field isolates in the United States: responses of nicarbazin-containing anticoccidials.

A series of studies were conducted to assess the drug sensitivity of 26 coccidial field isolates to the anticoccidial effects of nicarbazin (NIC) and narasin + NIC (NAR + NIC). Isolates were collected from typical broiler farms in the United States from 2003 to 2006, propagated once in the absence of anticoccidial medication, and then used to inoculate broilers that were fed nonmedicated rations or those containing NIC 125 ppm or NAR + NIC 80 ppm. Results of these sensitivity trials indicated that 81% of these coccidial isolates were sensitive to the effects of NIC, but only 22% of these coccidia were controlled by NAR + NIC. Studies conducted to evaluate performance responses to these drugs demonstrated that birds fed NIC gained more weight and utilized feed more efficiently than those receiving NAR + NIC. The results of 2 floor pen tests, conducted to confirm the results of the above sensitivity trials, demonstrated that NIC provided a greater level of protection from coccidiosis than NAR + NIC. Lower lesion scores and improved performance were recorded for birds receiving NIC compared with NAR + NIC. Results of these studies revealed that changes in the susceptibility of Eimeria spp. to the activity of NAR + NIC are evident. These changes appear to be associated with the reduction in ionophore sensitivity that has been documented in most areas of the world.

The influence of withdrawal time on the performance of broiler chickens fed semduramicin.

Three 49-d experiments, with a total of 6,528 male broiler chicks in floor pens, were conducted to test the hypothesis that Semduramicin feeding-time affects the body weight gain, feed consumption, and feed conversion ratio of broilers. Semduramicin ionophore was added to corn and soybean meal-based diets at the recommended level, 25 mg/kg for 0,34,39, or 42 d. Thus, three withdrawal times were employed (7, 10, and 15 d) during each experiment. Significant differences among experiments were observed for body weight gain, feed intake, and feed conversion ratio, but no significant differences due to Semduramicin were noted in body weight or feed intake. There was only one treatment by experiment interaction found for 0-to-34-d feed intake (P = 0.028), but it was not evident for 0 to 39 d (P = 0.818) or any other times. Feeding Semduramicin with a 10- or 15-d withdrawal period resulted in an improvement in feed conversion of about 0.04 units.

Isolation and hypoglycemic activity of 5, 7,3'-trihydroxy-3,6,4'-trimethoxyflavone from Brickellia veronicaefolia.

Hypoglycemic activity-guided fractionation together with chemical analysis led to the isolation of one flavone (5, 7,3'-trihydroxy-3,6,4'-trimethoxyflavone) from the chloroform extract of the leaves of Brikkellia veronicaefolia. Identification was based on spectroscopic methods. The isolated flavone was tested for hypoglycemic activity in normal and alloxan-diabetic CD1 mice (25-30 g) were administered in doses of 10, 25 and 50 mg/kg body weight. The blood glucose levels were determined before and 1.5, 3, 4.5 and 24 hours after drug administration. The results showed that the flavone produces a significant hypoglycemic effect in normal as well as in diabetic mice. Comparison was made between the action of the flavone and a known hypoglycemic drug as tolbutamide (50 mg/kg). The flavone was found to be slow and less effective than tolbutamide.

Studies on semduramicin and nutritional responses: 3. Electrolyte balance.

Four experiments were conducted to determine whether fluctuations in dietary electrolyte level (milliequivalents Na+K-Cl per kilogram) or different dietary sodium chloride levels would affect performance, water intake, or excreta moisture of chickens fed semduramicin vs nonmedicated controls. In all experiments, male commercial broiler chicks were used, and all diets were fed with and without 25 mg semduramicin/kg diet. The basal diets were based on corn, soybean meal, and poultry oil. Experiments 1, 3, and 4 were conducted using male broiler chicks in battery brooders to 18 d of age. In Experiment 1, six electrolyte levels were fed [basal (0.2% Na, 0.33% Cl, 1.10% K); basal plus 0.1% Na (from sodium chloride); basal plus 0.1% K (from potassium chloride); basal plus 0.2% Na (from sodium carbonate); basal plus 0.34% K (from potassium chloride); basal plus 0.15% Cl (from ammonium chloride)]. There were no significant changes in BW gain, feed consumption, or feed conversion ratio caused by any dietary treatment. Water consumption was not affected by the inclusion of Na, Cl, K, or electrolyte levels, but excreta moisture was affected. The highest and lowest excreta moisture levels came from chicks fed the lowest chloride levels. There were no significant dietary effects on serum Na, Cl, or K by dietary electrolytes or semduramicin. Experiment 2 was conducted with triplicate floor pens of 33 male broilers each for 42 d with four electrolyte levels [basal (0.2% Na, 0.34% Cl, 1.03% K); basal plus 0.1% Na (from sodium carbonate); basal plus 0.1% Cl (from ammonium chloride); basal plus 0.18% K (from potassium carbonate)]. Increasing electrolyte level had a significant effect on BW gain at 35 d but not at 42 d [mainly because of differences in K (1.943 kg at 35 d) vs Cl (2.013 kg at 35 d)]. At 42 d, there were no differences in growth because of N, K, Cl, or semduramicin. Potassium supplementation caused a significant increase in litter moisture (P = 0.031). Semduramicin did not affect litter moisture (P = 0.892), nor were there significant semduramicin interactions with Na, K, Cl, or semduramicin. The basal diets in Experiments 3 and 4 were identical to the basal diet in Experiment 1 except there was no sodium chloride added. The diets fed in Experiment 3 contained 0, 0.1, 0.2, 0.3, or 0.4% added sodium chloride. The diets fed in Experiment 4 contained 0.1, 0.3, 0.5, 0.7, and 0.9% added sodium chloride. The results of Experiments 3 and 4 show that about 0.4% added sodium chloride is necessary to achieve maximum growth and feed conversion. It is clear that semduramicin had no significant effect upon the variation observed in any of the variables measured.

Studies on semduramicin and nutritional responses: 2. methionine levels.

Three experiments were conducted to determine whether feeding semduramicin at recommended levels would affect the broiler chicken's response to dietary methionine. In Experiment 1, three levels of methionine (0, 0.15, 0.30%) were fed to chicks in battery brooders. In Experiment 2, two levels of protein (18 and 22%) and three levels of methionine (0, 0.15, 0.30%) were fed to chicks in floor pens from 18 to 44 d. In Experiment 3, two methionine supplements were fed during each of the starter (0 and 0.21%, 0 to 18 d) and grower (0 and 0.10%, 18 to 35 d) periods to chicks in floor pens. In all experiments, male commercial broiler chicks were used, and all diets were fed with and without 25 mg/kg diet of semduramicin. The basal diets were based on corn, soybean meal, and poultry oil. In Experiment 1, there was a growth and feed conversion ratio response to methionine supplements, but there was no effect of semduramicin on growth nor any semduramicin by methionine supplement interaction. In Experiment 2, at 44 d, protein and methionine levels both influenced feed conversion ratios, but semduramicin did not. Feeding 22 vs 18% protein increased carcass and breast muscle yields and decreased abdominal fat pad weights. The results of Experiments 2 and 3 were very similar. Overall, the effects of semduramicin on growth and processing parameters were small and not significant, but considerable benefits in performance and carcass parameters could be realized by feeding the higher levels of protein or methionine.

Studies on semduramicin and nutritional responses. 1. Level and source of protein.

An experiment was conducted to determine whether feeding semduramicin at recommended levels (25 mg/kg) would affect the broiler chicken's response to dietary protein; and to determine whether protein source (all vegetable, corn and soybean meal, vs 12% high animal protein ingredients) would affect the response to semduramicin. Semduramicin was fed to half of 1,584 male Ross x Ross broilers in floor pens during the growing phase (18 to 35 d). Three protein fortification levels were also fed with protein and amino acid minimum restrictions at 80, 100, and 120% of NRC (1994) recommendations. At 35 d, semduramicin was found to cause a slight growth depression in body weight gain only when low protein levels were fed (P = 0.051). After a 7-d withdrawal period, compensatory gains occurred (P = 0.006) such that there was no interaction effect of semduramicin by protein level for 42-d body weight (P = 0.75). Birds fed the diets containing high animal protein were slightly heavier than those fed control diets containing all-vegetable protein (2.40+/-0.02 vs 2.36+/-0.01 kg/bird; P = 0.059). Semduramicin feeding did not affect feed consumption (2.43+/-0.03 vs 2.40+/-0.02 kg per bird during the growing period when it was fed) so that overall feed conversion ratios were identical to two decimal places (1.90+/-0.02 vs 1.90+0.02). Neither did semduramicin affect feathering score or weight of the No. 8 primary feather, except that feather weight tended to be improved by semduramicin feeding with the diets containing ingredients high in animal protein (P = 0.067).

Effect of increasing dietary threonine intakes on amino acid metabolism of the central nervous system and peripheral tissues in growing rats.

The threonine content of most of the infant formulas currently on the market is approximately 20% higher than the threonine concentration in human milk. Due to this high threonine content the plasma threonine concentrations are up to twice as high in premature infants fed these formulas than in infants fed human milk. To study the effect of different threonine intakes on plasma and tissue amino acid concentrations, 24 young male Wistar rats were fed three experimental diets based on a mixture of bovine proteins with a whey protein/casein ratio of 60/40 with different threonine contents [group A, 0.86 g of threonine/100 g (n = 8); group B, 1.03 g of threonine/100 g (n = 8); group C, 2.21 g of threonine/100 g (n = 8)]. Eight animals were fed a typical rat diet based on bovine casein as controls. After a feeding period of 15 d, amino acids were measured in plasma and in homogenates of the cerebral cortex, brain stem, liver, and muscle. There was a significant correlation between threonine intake and plasma threonine levels (r = 0.687, p < 0.001). The plasma threonine concentration correlated significantly with the threonine concentration in the cortex (r = 0.821, p < 0.01) and the brain stem (r = 0.882, p < 0.01). There was a positive significant correlation between threonine and glycine concentrations in the cortex (r = 0.673, p < 0.01), and the brain stem (r = 0.575, p < 0.01), whereas the glycine concentration decreased with increasing threonine intakes in the liver and muscle. The presented data indicate that increasing the threonine in plasma leads to increasing brain glycine and thereby affects the neurotransmitter balance in the brain. This may have consequences for brain development during early postnatal life. Therefore, excessive threonine intake during infant feeding should be avoided.

Citrus Blight Found in Yucatan, Mexico.

Citrus blight, a serious tree decline problem of unknown cause in humid citrus-growing areas such as Florida and Louisiana, South America, South Africa, and the Caribbean, has never been reported from Mexico. Citrus blight has no reliable visual symptoms, and physical and chemical tests have to be used for diagnosis. We used water injection into the trunk (2), zinc and potassium analysis of the outer trunk wood (3), and an immunological test for specific blight proteins in the leaves (1). Low uptake when water is injected into the trunk, and high zinc and potassium in the wood, compared with healthy trees, are characteristic of citrus blight (3). Water injection tests and wood analysis of four healthy and four declining trees in the Dzan, Yucatan, Mexico, area in August 1995, showed highly significant differences in water uptake (healthy trees 44.3 ml/min, declining trees 1.0 ml/min), little difference in wood zinc (healthy 2.8 µg/g, declining 3.0 µg/g) and 39% more potassium in the wood (healthy 0.147%, declining 0.204%). No leaf protein tests were done at this location. Tests on eight declining and five healthy trees in Seye, Yucatan, Mexico, in June 1996, showed significant (P = 0.01 to 0.05) differences in water uptake (healthy 12.9 ml/min, declining 0.6 ml/min), in wood zinc (healthy 2.0 µg/g, declining 7.0 µg/g) and potassium in the wood (healthy 0.156%, declining 0.251%). Leaf samples from all eight declining trees were positive for blight in a specific protein test (1). The visual symptoms of all declining trees tested were the same as those of blight-affected trees in Florida and Cuba: zinc deficiency symptoms in the leaves, thin foliage, wilt, and sprouting from the trunk and the main branches. The reasons for the lack of earlier reports of citrus blight from Mexico are apparently climatic and rootstock related. Many of Mexico's citrus-producing areas are dry and blight does not occur in dry areas such as the Mediterranean countries and California. Most of Mexico's citrus is grown on sour orange (Citrus aurantium L.) rootstock that is highly resistant to citrus blight, but very susceptible to tristeza virus disease. In response to warnings that tristeza disease might appear in Yucatan, growers planted Valencia orange (C. sinensis (L.) Osbeck) on Cleopatra mandarin (C. reticulata Blanco) rootstock in Dzan and on Volkamer lemon (C. limon (L.) N. L. Burm.) in Seye, both highly susceptible to citrus blight (4). Changes in rootstock to avoid one disease led to problems with another. References: (1) K. S. Derrick et al. Proc. Fla. State Hortic. Soc. 105:26, 1993. (2) R. F. Lee et al. Plant Dis. 68:511, 1984. (3) H. K. Wutscher and C. J. Hardesty. J. Am. Soc. Hortic. Sci. 104:9, 1979. (4) R. H. Young et al. Proc. Fla. State Hortic. Soc. 91:56, 1978.

Tyrosine uptake and regional brain monoamine metabolites in a rat model resembling congenital hyperammonemia.

Hyperammonemia found in congenital disorders has a toxic effect on the central nervous system. Disturbances of brain neurotransmitter metabolism have been proposed, such as an increased transport of tryptophan into the brain and an increased flux through the serotonin pathway. Results concerning the catecholamine pathway are, however, contradictory. We therefore studied whether hyperammonermia increases brain uptake of the neurotransmitter precursor amino acid tyrosine and whether these changes affect the concentration of neurotransmitters and their metabolites in different brain areas (frontal cortex, caudatus-putamen, thalamus, hypothalamus, hippocampus/substantia nigra, brainstem) of rats made hyperammonemic with urease. The brain uptake of tyrosine was measured in the forebrain, brainstem, and cerebellum. The brain areas were analyzed for dopamine, 3,4-hydroxyphenylacetic acid; homovanillic acid, norepinephrine, and vanillylmandelic acid. The brain uptake index of tyrosine was increased in the forebrain and brainstem of the hyperammonemic rats with concomitantly elevated concentrations in the forebrain of tyrosine, phenylalanine, and tryptophan. The homovanillic acid content was significantly increased in the hypothalamus, hippocampus/substantia nigra and brainstem. The concentrations of norepinephrine, dopamine, and 3, 4-hydroxyphenylacetic acid were not significantly changed. Vanillylmandellic acid was decreased in the caudatus-putamen, thalamus, and hypothalamus. The data indicate an undisturbed neurotransmitter synthesis and, taken with the augmented tyrosine uptake at the blood-brain barrier, an increased flux through the dopamine pathway. These changes observed in the hyperammonemic animal model could contribute to the understanding of the pathogenic mechanisms and offer an explanation for the neuropsychiatric disturbances observed in children with congenital hyperammonemia.

Effect of different protein diets on the distribution of amino acids in plasma, liver and brain in the rat.

The distribution of amino acids between plasma, liver and brain was studied in adult male rats, fed a diet containing 8.7, 17 (control animals), 32 and 51% of protein during 15 days. The caloric intake was nearly equal in all groups. The highest food intake was observed in the animals on the low protein diet. Changes in plasma amino acids were variable. In contrast to the behavior of most amino acids in plasma, the branched chain amino acids were highest in the animals fed the 51% protein diet. Despite the low protein intake in the animals fed a 8.7% protein diet, the concentration of serine, glutamic acid, glutamine, glycine, alanine, methionine, isoleucine, leucine, phenylalanine and ornithine were significantly higher compared to control animals, whereas in those receiving a high protein diet, valine, leucine, tyrosine, tryptophan and histidine increased in relation to the increased protein and amino acid intake. The plasma amino acid patterns are not greatly influenced by the amino acid distribution in the food and the amount ingested. Alanine aminotransferase, aspartate aminotransferase, glutamate dehydrogenase and cholinesterase showed a two- to fivefold increased activity in the liver of animals consuming a high protein diet. In the brain, the concentration of valine, leucine, isoleucine, phenylalanine and tyrosine in animals receiving the low protein diet was higher than in controls and increased further with increasing protein content of the diet. Glutamine was increased in all dietary groups. The predicted influx of amino acids showed increasing influx rates in dependence of the plasma amino acid concentration. The entry of tyrosine and tryptophan and their brain concentration was inversely proportional to the protein content of the diet. In the present study which considers long-term adaptation to an increasing protein and amino acid intake in comparison to a balanced control protein diet, the levels of the indispensable amino acids were maintained within narrow limits in the brain and liver. The results indicate that inspite of a variable protein intake, the body tends to keep organ amino acids in relatively narrow limits favoring in this way amino acid homeostasis.

The regulation of N-acetylglutamate synthetase in rat liver by protein intake.

Urea cycle enzymes are subjected to regulation by dietary proteins. We have shown that this is also the case for N-acetylglutamate synthetase (EC 2.3.1.1.) (NAGS). Four different groups (n = 7) of male Wistar rats received either a low protein (8.7%) or a high (32% and 51%) protein diet and a control diet of 17% protein. The NAGS-activity in the liver, assayed after 15 days of feeding the different diets, increased from 25 +/- 7 (controls, 17% protein) to 31 +/- 5 (32% protein) and to 52 +/- 17 (51% protein) nmoles.min-1.g-1 wet weight. It decreased in the group with low protein diet (8.7%) to 5 +/- 3. The ratio of the arginine stimulated to the unstimulated enzyme activity remained constant over the range of protein intake. Similar changes were observed for carbamylphosphate synthetase, ornithine carbamyltransferase and arginase. As it is known for these enzymes adaptive mechanisms in relation to variations in dietary protein consumption also could be demonstrated for the enzyme NAGS.

Dietary and monensin effects on activity of hepatic microsomal mixed function oxidase system in chickens.

Four experiments were conducted to investigate if the degree of activation of the microsomal mixed-function oxidase (MFO) system was related to the degree of growth depression associated with the addition of monensin to the diet. The experiments were conducted with broiler chicks in battery brooders in which the chicks were fed diets of various composition and containing monensin at 0 to 160 ppm. In all experiments, the activity of the MFO system was estimated by the change in the content of cytochrome P-450 in the hepatic microsomes. Activities of some microsomal enzymes were also measured in some of the experiments. Feeding a diet with 24% protein containing fish meal, alfalfa meal, and torula yeast significantly increased the activity of the MFO system in comparison with feeding an isonitrogenous and isoenergetic corn and soybean diet, but there was no difference between the diets in the toxicity of monensin as measured by growth rate. Supplementing a 16% protein but not a 24% protein diet with monensin significantly reduced growth rate. In none of the four experiments was there a statistically significant change in the hepatic content of cytochrome P-450 as a result of feeding monensin. Thus, variation in the magnitude of growth depression caused by monensin in diets of different protein concentration or ingredient composition does not appear to be explained on the relative degree of the activation of the MFO system.