John W. Brown

Behavioral and neurochemical effects of dietary tyrosine in young and aged mice following cold-swim stress.

Abstract The effects of dietary supplements of L-tyrosine on aggressive behavior, locomotor activity, and brain neurochemical changes were assessed in young and aged mice following cold-swim stress. Male CF-1 mice, ages 3 months and 21 months, were maintained on a semi-synthetic basal diet for one week, pretested for aggressive behavior and locomotor activity, then switched to diets modified by the addition of tyrosine or casein (control). After one week on the diet supplements, half of the mice were stressed by cold water swim and all were again subjected to behavioral testing. Members of each group were sacrificed for analysis of amino acids and monoamines in brain tissue and corticosterones in blood. It was found that tyrosine supplementation induced a marked increase in aggressive behavior in young, nonstressed mice but not in aged mice. Stress decreased the aggressiveness of both young and aged mice, and tyrosine prevented this stress-induced decrease in both groups. Young mice exhibited no changes in locomotion as a function of stress or diet. However, tyrosine prevented decreases in locomotion observed on second testing of both stressed and nonstressed older mice. The effect of stress was to lower levels of brain norepinephrine (NE) and dopamine (DA) in both young and aged mice. Tyrosine supplementation increased brain tyrosine and DA in both groups. Brain serotonin levels were lower in the aged mice compared to the younger ones, and this was associated with relatively higher concentrations of 5-hydroxyindoleacetic acid. It appears that tyrosine supplementation was effective in reducing the effects of stress in the aged animals, possibly by virtue of its relationship to catecholamine metabolism.

Effects of dietary tyrosine, phenylalanine, and tryptophan on aggression in mice

Dietary amino acid regimens designed to enhance catecholaminergic and serotonergic functioning were found to differentially affect territorial-induced attacks in mice. Male albino mice were maintained on a semi-synthetic 12% casein protein diet for 2 weeks, then switched to diets modified by the addition of a 4% L-amino acid supplement, or 4% casein (control). Measures of aggressive behavior and open-field locomotor activity were obtained before and after the dietary supplements were administered. Resident mice fed supplements of L-tyrosine displayed a marked increase in the number of attacks on intruders and shorter attack latencies, but their locomotor activity was unaffected. L-phenylalanine supplements alone or in combination with L-tyrosine reduced the latency to attack and increased motility but did not affect the number of attacks. As a whole, the group of animals fed L-tryptophan showed no changes in aggression or motility.

Dietary amino acid precursors: Effects on central monoamines, aggression, and locomotor activity in the mouse

Abstract Behavioral and brain neurochemical changes were assessed in mice maintained on amino acid supplemented 12% protein diets for two and six weeks. Addition of 1,2, or 4% L-phenylalanine increased aggression but only the 1% supplement increased locomotion. Addition of 0.25 or 0.5% L-tryptophan of the basal diet also increased aggression. All behavioral effects were noted after two weeks but not after six weeks on the diets, suggesting the development of behavioral tolerance. All groups of mice gained the same amount of weight on the various diets over a seven-week period and no ill effects were observed. Mice on 16% protein diets displayed only marginal differences in brain concentrations of phenylalanine, tyrosine, tryptophan, dopamine, norepinephrine, serotonin or 5-hydroxyindoleacetic acid. Brain concentrations of tyrosine, phenylalanine and tryptophan were significantly reduced in animals receiving supplements of leucine for two and six weeks. L-phenylalamine supplementation caused marked increases in brain phenylalanine and tyrosine concentrations after two and six weeks. Changes in brain dopamine and 5-hydroxyindoleacetic acid also were noted. Supplements of 0.25, 0.5, and 1.0% L-tryptophan increased brain indoles, and these changes also appeared to be sustained over the six-week period.

Effect of brain monoamine precursors on stress-induced behavioral and neurochemical changes in aged mice.

Male CF-1 mice aged 22 months showed approximately the same level of motor activity and aggressive behavior as 3-month-old mice under control (no stress) conditions, or 45 min following cold swim stress. Increasing brain catecholamine activity by dietary L-tyrosine treatment had no effect on these two age groups either under control conditions or after stress. In contrast, 30-month-old mice showed lower motor activity under control conditions which was raised significantly by supplementation of the diet with L-tyrosine. However, marked reductions in activity and aggression following stress were observed in the 30-month-old animals and these deficits were not reversed by L-tyrosine treatment prior to stress. Reduction in motor activity was greatest in stressed, 30-month-old mice on L-tyrosine supplemented diets. Compared to 3-month-old mice, the 30-month-old animals had lower brain tyrosine following dietary L-tyrosine treatment, lower brain tryptophan, norepinephrine (NE), dopamine (DA) and DOPAC, but higher HVA, serotonin (5-HT) and 5-HIAA levels. Under both control (no stress) and stress conditions, L-tyrosine pretreatment decreased brain 5-HT in the young animals, but increased 5-HT in the old mice. After stress the 30-month-old animals evidenced only slight increases in levels of blood corticosterone. Brain tyrosine was reduced by stress in the young animals but increased by stress in the old animals. Stress-induced decreases in brain NE and increases in serotonin and 5-HIAA levels were observed in both age groups. These results are consistent with hypotheses concerning age-related alterations in brain monoamine functions and adrenocortical control mechanisms.

Composition of fractions prepared from Sarcina lutea protoplasts

Abstract The composition of “particulate” and “cytoplasmic” fractions from lysates of Sarcina lutea protoplasts has been investigated. The particulate material contained primarily protein and lipid, but its composition was, at least in part, a function of the method by which it was prepared. The particulate fraction contained essentially all of the carotenoid and respiratory pigments of the cell. The cytoplasmic material contained protein, lipid and almost all of the nucleic acid of the protoplast. By ultracentrifugal analysis of this fraction, 4 boundaries were obtained, with sedimentation coefficients of approx. 37, 26, 8 and 4 S.

Properties of a methionyl-tRNA systhetase from Sarcina lutea☆

Abstract Methionyl-tRNA synthetase was purified from sonic extracts of Sarcina lutea by successive elution from calcium phosphate gel followed by (NH4)2SO4 fractionation and DEAE-cellulose chromatography. When methionine activation was measured by hydroxamate formation, ATP-32PPi exchange and attachment to tRNA, the ratio of activities determined by these methods remained constant throughout the purification. The kinetics of the enzymatic reaction were determined using all three assay. The reaction was inhibited by various salts at high ionic strength, certain nucleotides and RNA from several sources. Reduced glutathione and mercaptoethanol also were inhibitory. Selenomethionine and methionine analogues with alkyl-substituted thiol groups stimulated both ATP 32PPi exchange and hydroxamate formation. Of the other methionine analogues tested, homocysteine was the most potent inhibitor.

Differential tolerance to dietary amino acid-induced changes in aggressive behavior and locomotor activity in mice

Male albino mice were maintained on a semisynthetic 12% casein protein diet for 2 weeks, then switched to diets modified by the addition of a 4% L-amino acid supplement (L-tyrosine, L-phenylalanine, and L-tryptophan) or 4% casein (control). Territorial-induced aggressive behavior increased following 1 week on the amino acid supplements, especially after tyrosine, but an apparent tolerance developed to these effects after 5 weeks on the amino acid supplements. Locomotor activity also increased following 1 week on the supplements, most notably after phenylalanine alone or in combination with tyrosine, and these effects tended to persist after 5 weeks on the supplements. Endogenous whole brain levels of dopamine, norepinephrine, serotonin, 5-hydroxyindoleacetic acid, tyrosine, phenylalanine, and tryptophan showed no tolerance to increased concentrations of brain catecholamines and indoleamines over the 5-week period, and no clear relation between the concentrations of these monoamines and the behavioral changes.

Evidence for a magnesium-dependent dissociation of bacterial cytoplasmic membrane particles

Abstract 1. 1. A preparation of the bacterial cytoplasmic membrane was obtained by osmotic disruption of protoplasts prepared from Sarcina lutea . 2. 2. Sonification of the membrane preparation in the presence of Mg 2+ resulted in its conversion to particles which sedimented on ultracentrifugation as two boundaries having sedimentation coefficients of 5 S and 70 S. Dialysis of the sonified preparation against buffer solutions containing no Mg 2+ resulted in conversion of the 70-S particles to 5-S particles. A partial re-association into larger aggregate particles was obtained by dialyzing 5-S particles in the presence of Mg 2+ . 3. 3. Although quite different in chemical composition, membrane particles exhibit strong similarities in sedimentation behavior to cytoplasmic ribosomal nucleoproteins.

Effect of fusaric acid on aggression, motor activity, and brain monoamines in mice

The effects of fusaric acid (FA), a dopamine-beta-hydroxylase (D beta H) inhibitor, were determined on aggression, motor activity, and brain monoamines at doses of 3.2 to 60 mg/kg following administration of dietary supplements of L-tyrosine or balanced protein to male albino mice. Compared to saline injected control animals, both aggression and motor activity were reduced by the highest doses of FA. Somewhat more reduction in aggression was observed in animals administered dietary supplements of casein compared to those given the tyrosine supplement. Treatment with FA at doses of 30 to 60 mg/kg decreased brain norepinephrine and dopamine, and decreased brain tyrosine in animals fed the tyrosine supplement. In contrast, FA increased 5-hydroxytryptamine, and caused marked increases in 5-hydroxyindoleacetic acid at the highest doses. The data suggest that the neurochemical effects of FA may not be the same in rats and mice.

Aminoacyl-tRNA synthetases from Sarcina lutea

Extracts from Sarcina lutea were assayed for aminoacyl-tRNA synthetase activity by determining amino acid-stimulated ATP-32PPi exchange or hydroxamate formation. Extracts from logarithmically growing cells exhibited a higher specific activity than those from stationary cultures. When amino acid activation was measured both by hydroxamate formation and ATP-32PPi exchange, the ratio of activities determined by these methods varied with each amino acid tested. This is explained by the finding that hydroxylamine at higher concentrations is an inhibitor of the exchange reaction.