Changes in brain protease activity in aging.

We measured changes in protease activity with aging, conducting assays of cathepsin D and calpain II activities and the rate of degradation of cytoskeletal proteins, preparing the enzymes and substrates from young and aged brains. Calpain preparations added to the young and to the aged substrates were standardized with casein as substrate so that age-related changes in calpain specificity and substrate susceptibility were measured. Several age-related differences were observed in substrate susceptibility and in enzyme activity.

Amino acid distribution in immature rat brain.

We compared the levels of amino acids in the free pool in 6 regions (cerebral cortex, olfactory bulb, substantia nigra, globus pallidus, caudate nucleus, and spinal cord) in the newborn rat brain. The amino acid distribution was heterogeneous, with the area of highest concentration containing 2-3 fold as much as the lowest area. These differences were considerably less than those previously found for adult brain.

Effect of food deprivation on glutathione and amino acid levels in brain and liver of young and aged rats.

The effect of short-term food deprivation on glutathione (GSH) and amino acid levels in brain regions of young and aged rats was compared with changes observed in liver. Animals aged 3 months and 24 months were deprived of food for 48 h. GSH and amino acid levels from cerebral cortex, cerebellum, pons medulla, and liver were assayed and compared with levels in animals of the same age fed normal diets.

Effect of diet on tissue protease activity.

Rats 1, 3, 12, and 24 months old were fed diets low in protein (8% casein), and proteolytic activity in tissue from brain, liver, and lung was determined. After a low-protein diet was fed for 4 weeks to 1-month-old rats, there was a significant increase in cathepsin D activity in liver, and calpain activity was increased in lung. Little change was seen in proteolytic activity in brain.

Calpain activity in adult and aged human brain regions.

We assayed calpain activity in 27 human brain regions from adult (43-65 years of age) and aged (66-83 years of age) postmortem tissue samples. Calpain I (microM Ca-requiring) activity was 10% or less of the total activity; it was below detectable levels in a number of areas, and so data are are expressed as total (microM + mM Ca-dependent) calpain activity. The distribution of the enzyme was regionally heterogeneous.

L-tyrosine pharmacotherapy of schizophrenia: preliminary data.

The utility of L-tyrosine (10 g/day in four divided doses) as an adjuvant to molindone (150 mg/day) in the treatment of schizophrenia was investigated using a placebo-controlled, double-blind crossover design (3 weeks on L-tyrosine, 3 weeks on placebo). The objective of this inpatient study was to increase dopaminergic neural transmission along mesocortical projections in patients by increasing the precursor availability of L-tyrosine for dopamine biosynthesis. Theoretically, this approach might lessen both negative and positive symptoms of schizophrenia and improve frontal lobe-mediated neuropsychological performance.

Levels of amino acids in 52 discrete areas of postmortem brain of adult and aged humans.

In a series of studies we have analyzed the regional distribution of the free amino acid pool in 52 discrete areas of postmortem brain of adult and aged humans. Here we show the distribution of eleven amino acids: alanine, methionine, valine, leucine, isoleucine, glutamine, asparagine, lysine, arginine, ornithine, and histidine. As found previously for other amino acids, the distribution of these amino acids was seen to be heterogeneous, the level of the area of highest level being 3.

Heterogeneous distribution of functionally important amino acids in brain areas of adult and aging humans.

The regional distribution of seven amino acids thought to have inhibitory neurotransmitter or neurotransmitter precursor function--GABA, glycine, taurine, serine, threonine, phenylalanine, and tyrosine--was determined in 52 discrete areas from brain of adult and old humans. Significant heterogeneity was found, with 3- to 16-fold differences in levels in the various regions analyzed. The patterns of distribution were somewhat different from those in the adult or old rat brain.

Proteolytic activity is altered in brain tissue of rats upon chronic exposure to ozone.

Tissue from pons medulla of rats exposed in vivo to various levels of ozone was assayed for calpain and cathepsin D activity. Chronic exposure to ozone increased calpain activity, which was 35% to 46% higher in the homogenates of animals exposed to 1.0 ppm ozone than in those of animals exposed to 0.

Peroxidative stress effects on calpain activity in brain of young and adult rats.

Three hours after administration of the pro-oxidant 2-cyclohexen-1-one, calpain activity was significantly reduced in the brain of young rats, but not in the brain of adult rats, and cathepsin D activity remained unchanged. Addition of isovalerylcarnitine to the incubation medium increased calpain activity 5-7-fold, counteracting the effect of the pro-oxidant.

Regional distribution of glutamate and aspartate in adult and old human brain.

In previous studies on rat brain we found that the observed heterogeneity of the regional distribution of amino acids was much greater when small well-defined anatomical structures were assayed. We therefore reinvestigated the distribution of glutamate and aspartate in 50 discrete areas from adult and old human brain. The concentration of glutamate in the area of highest level was 4.

The distribution of cathepsin D activity in adult and aging human brain regions.

We measured the activity of cathepsin D, the major cerebral protease, in 50 separate areas of the central nervous system of adult and aged humans, using hemoglobin as the substrate. The activity showed significant regional heterogeneity, with average differences of 50-100% between the lower and higher level areas, and a more than threefold difference between the lowest and highest levels. The forebrain, midbrain, and hindbrain each had areas of high and low activity; cerebellum and cord areas were among those with low activity.

Effect of a low-tryptophan diet as an adjuvant to conventional neuroleptic therapy in schizophrenia.

Eleven patients with DSM-III-R schizophrenia were entered into a 4-day tryptophan (TRP)-deficient diet. The diet lowered total plasma TRP levels in all patients; during the diet phase, there was a greater than 50% reduction in mean total plasma TRP levels from the pre-diet phase. The low-TRP diet improved performance on the Stroop Color and Word Test.

Effect of acetyl-L-carnitine on the dopaminergic system in aging brain.

We studied the effect of acetyl-L-carnitine (ALCAR) on dopamine release and the effect of long-term acetyl-L-carnitine treatment on age-related changes in striatal dopamine receptors and brain amino acid levels. In striatal tissue that had been incubated with [3H]dopamine, acetyl-L-carnitine increased the release of [3H]dopamine evoked by electrical stimulation. In striatal tissue from aged mice administered acetyl-L-carnitine for 3 months, the release of [3H]dopamine evoked by electrical stimulation was higher than that of its aged control; the release after a second stimulation was similar in the two groups.

Effects of brief starvation on brain protease activity.

Changes in the activity of proteases (cathepsin D and calpains) caused by 48-h food withdrawal were studied in the brain, liver, kidney, spleen, and heart of 3-, 12-, and 24-month-old Fischer rats. Cathepsin D activity was similar in brain, liver, and heart of control animals; in kidney it was 5-fold higher and in spleen about 10-fold higher. With age, activity increased in all organs tested except spleen.

Changes with aging in the levels of amino acids in rat CNS structural elements: IV. Methionine and basic amino acids.

This paper reports the distribution of methionine, histidine, lysine, arginine, and ornithine in 53 discrete brain areas of 3- and 29-month-old male Fischer 344 rats microdissected by the punch technique. Like that of the other amino acids were reported in previous papers of this series, the distribution of methionine and the basic amino acids was regionally highly heterogeneous. The ratios of levels in the areas of highest concentrations to levels in the areas of lowest concentration varied from 10 to 15 for these amino acids, except that it was 23 for arginine.

Changes with aging in the levels of amino acids in rat CNS structural elements: III. Large neutral amino acids.

This paper reports the concentrations of valine, leucine, isoleucine, phenylalanine, and tyrosine as determined in 53 discrete brain areas of 3- and 29-month-old male Fischer 344 rats microdissected by the punch technique. The levels of other amino acids in the same areas are reported in other papers of this series. The essential amino acids reported in this paper showed great regional heterogeneity, with concentrations in areas of the highest content being 9 to 12 times higher than levels in areas of the lowest content.

Plasma tryptophan to large neutral amino acid ratios in depressed and normal subjects.

The ratios of total and free plasma tryptophan to the sum of five large neutral amino acids (LNAAs) were found to be significantly lower in a group of 16 depressed inpatients compared to nine normal subjects after oral loading with L-tryptophan. The group differences in these ratios were significant before, and 2 weeks after starting treatment with a tricyclic antidepressant. Plasma tryptophan ratios and severity of depression were not significantly correlated.

Calpain II activity and calpastatin content in brain regions of 3- and 24-month-old rats.

In previous studies, we found a significantly higher (100% or more) content of cathepsin D in the aging brain. In the present study, we determined activity of Ca2(+)-activated neutral protease requiring millimolar Ca2+ (calpain II, CANP II) and amount of its endogenous inhibitor, calpastatin, in extracts of various brain regions of 3-month-old and 24-month-old male Fischer-344 rats. Calpain II was separated from calpastatin in a single step (chromatography) and its activity was tested using as substrates [methyl-14C]alpha-casein, the cytoskeletal proteins desmin and actin, and a mixture of neurofilament triplet proteins and glial fibrillary acidic proteins (GFAP).

Glycine adjuvant therapy to conventional neuroleptic treatment in schizophrenia: an open-label, pilot study.

In an open-label study, glycine was administered orally (10.8 g/day in three divided doses) to six chronically psychotic patients, as an adjunct to conventional neuroleptic therapy, for periods extending from 4 days to 8 weeks. Glycine was administered in an effort to facilitate endogenous glutamatergic transmission at the level of the N-methyl-D-aspartate (NMDA) receptor complex, since a glutamatergic deficiency in the pathophysiology of schizophrenia has been postulated.

The presence of ATP + ubiquitin-dependent proteinase and multicatalytic proteinase complex in bovine brain.

The presence of two distinct high-molecular-weight proteases with similar pH optima in the weakly alkaline region was shown in cytosol of the bovine brain cortex. They were separated by ammonium sulfate fractionation and each was further purified by DEAE-Sephacel, Sephacryl S-300, DEAE-Cibacron Blue 3GA-agarose, heparin-agarose, and Sepharose 6B chromatography. The larger enzyme (Mr 1,400 kDa), which precipitates at 0-38% ammonium sulfate saturation, seems to be active in ATP + ubiquitin (Ub)-dependent proteolysis; it has low basal caseinolytic activity that is stimulated 3-fold by ATP, and when Ub is present ATP causes a 4.

Amino acid analysis using 1-naphthylisocyanate as a precolumn high performance liquid chromatography derivatization reagent.

A method which uses 1-naphthylisocyanate as an HPLC precolumn derivatization reagent for amino acid analysis is described. Derivatization is carried out by adding the isocyanate dissolved in dry acetone to a buffered amino acid solution followed by extraction of the excess reagent with cyclohexane. The resulting naphthylcarbamoyl amino acids are stable and highly fluorescent, with excitation maxima at 238 and 305 nm and an emission maximum at 385 nm, for most amino acids.