Harold P. Cohen

Patterns of clinical response and plasma dopa levels in Parkinson's disease

Serial determinations of plasma dihydroxyphenylalanine (dopa) in 16 Parkinsons disease patients receiving levodopa showed a negative correlation between plasma dopa levels and disability scores among patients who exhibited daily fluctuations of signs and symptoms. This suggests that the amount of levodopa delivered to the brain from the periphery is of major importance in the production of the “on-off” phenomenon. A close relationship between plasma dopa levels and abnormal involuntary movements was present in six patients. In three a striking dissociation between control of Parkinsons disease and abnormal involuntary movements was present, suggesting that in some patients these two effects are mediated through different underlying mechanisms. Administration of levodopa in such a way as to prevent both high and low levels of dopa in plasma minimizes disability in Parkinsons disease and may lessen abnormal involuntary movements in patients with the “on-off” effect.

Measurement of adenosine triphosphate content of crayfish stretch receptor cell preparations

Abstract A sensitive and rapid method for the assay of ATP down to 2× 10−14 mole was presented. This was achieved by the use of firefly luciferase-luciferin reaction and a scintillation spectrometer operated on single channel at high voltage. The ATP content of single resting orayfish stretch receptor cell preparations was determined. It was found to be 4.24 picomoles in the absence, and 5.02 picomoles in the presence, of 1 mM glucose.

Crayfish ventral nerve cord and hemolymph: Content of free amino acids and other metabolites☆

Abstract 1. 1. Non-protein amino acids and related compounds in the ventral nerve cord (VNC) and the hemolymph of the fresh-water crayfish Orconectes immunis have been determined by ion-exchange chromatography. Some other metabolites have also been measured. 2. 2. A total of twenty-six and twenty-seven amino compounds has been found in the VNC and the hemolymph, respectively. 3. 3. The VNC contained over ten times as much total amino compounds as the hemolymph. 4. 4. Some pharmacologically active amino acids such as GABA, glutamate and aspartate existed in even higher content in the VNC than in the hemolymph. 5. 5. The significance of such disparity in distribution has been discussed.

The effect of topical application of diethyl- -fluoroglutarate on the metabolism and electrical activity in vivo of cat cerebral cortex.

Abstract— The effect of topical application of diethyl‐α‐fluoroglutarate on the primary response of cat cerebral cortex to thalamic stimulation was investigated, and samples of the involved tissue and of homologous contralateral control tissue were removed at appropriate times for biochemical analyses. Changes in electrocortical response were first noted 30–40 min after topical application of 10 μ1 (52.7 μmol) of the drug to the pericruciate gyrus. A rapid reduction in amplitude of the surface negative component of the primary response was observed initially, followed by amplitude reduction and rapid disappearance of the primary response throughout the cortical field within a few minutes after the change first observed at the surface. The effects were interpreted either as a direct action of the drug on the somadendritic membrane or an inhibition of the excitatory synaptic impingement.

The effect of diethyl- -fluoroglutarate on phosphates and glutamate in slices of rabbit cerebral cortex.

Abstract— The diethyl ester of α‐fluoroglutarate (DEFG), an inhibitor of glutamate dehydrogenase, was prepared, and its effect on glutamate and phosphates in slices of rabbit cerebral cortex was examined. The primary effect of the drug on cortical slices incubating in a Krebs‐Ringer glucose medium was to decrease the tissue levels of glutamate in association with decreased levels and turnover of high‐energy phosphates. Assimilation of exogenous glutamate by the slices was partially blocked in the presence of the drug and severely depressed oxidative phosphorylation resulted when glutamate and DEFG were both present in the incubation mixture. The results suggested a significant relationship between the activity of cerebral glutamate dehydrogenase and oxidative phosphorylation.

THE EFFECT OF GLUTAMIC ACID ON PHOSPHORUS METABOLISM IN CEREBRAL TISSUE PREPARATIONS

THE oxidation of glutamate by cerebral mitochondrial preparations has been reported to be efficiently coupled to phosphorylation (BRODY and BAIN, 1952; MCKHANN and TOWER, 1959). However, when cerebral cortex slices were employed, glutamate as substrate did not support steady-state concentrations of phosphocreatine (PC)

Phosphorylation coupled to glycolytic and oxidative metabolism in cerebral mitochondrial systems

comparable to those obtained with glucose (MCILWAIN, 1952). The possibility that increased potassium ion transport may play a role in this phenomenon was suggested by the studies of TERNER, ECGLESTON and KREBS (1950). Demonstration that addition of glutamate to the incubation medium did not produce an increase in intracellular potassium (PAPPIUS and ELLIOTT, 1956) made this possibility unlikely. Increased formation of glutamine from glutamate has been suggested as responsible for the lowered concentration of ATP (Acs, BALAZS and STRAUB, 1953) as well as PC (WOODMAN and MCILWAIN, 1961). The present studies were undertaken to re-examine this problem with techniques capable of determining the effect of glutamate on cerebral mitochondria1 as well as cortex slice metabolism, in the presence of glucose. The effect of glutamate on glycolysis and on the turnover of ATP was of special interest.

The effect of scorbutus and pentobarbital on the in vivo levels of "energy-rich" phosphates and their turnover in guinea pig cerebral tissue.

Abstract Two cerebral mitochondrial preparations capable of coupling the metabolism of glucose (or fructose) to net phosphorylative processes are described. The first (P-1) requires the addition of crude yeast hexokinase for net phosphorylation. The second carries out an active aerobic glycolysis without the crude yeast material. In its presence, however, aerobic glycolysis is inhibited and phosphorylative efficiency is increased. It is suggested that this represents a shunt from a less efficient glycolytic to a more efficient, oxidatively linked phosphate-transfer system. A large portion of the phosphorylative yield of these systems is coupled to oxidative metabolism. This is indicated by the inhibitory action of cyanide, pentobarbital, dinitrophenol, and anaerobiosis and by the ability of the P-2 system consistently to provide P O ratios above 1. In the P-2 system oxygen consumption, in the presence of DPNH and fluoride, is equivalent to the amount of DPNH added, and some net phosphorylation is obtained. This is considered a reflection of the ability of cerebral as well as liver mitochondria to couple the oxidation of DPNH to phosphorylative processes.

EFFECT OF GLUTAMIC ACID ON PHOSPHORYLATIVE ACTIVITY IN CEREBRAL TISSUE IN VITRO

Abstract The in vivo cerebral levels of ascorbic acid and “energy-rich” phosphates and turnover of the phosphates were measured in young guinea pigs under different experimental conditions. Pentobarbital-treated scorbutic animals show a cerebral ascorbic acid level twice that of the untreated scorbutic guinea pig. The results also indicate that the combination of scorbutus plus pentobarbital treatment raises the in vivo creatine phosphate level and interferes with the turnover of creatine phosphate and adenosine triphosphate. Boiling water and cold perchloric acid were compared as extracting agents for cerebral organic phosphates. Boiling water results in considerably less creatine phosphate and adenosine triphosphate isolation than does cold perchloric acid, although total creatine and adenine nucleotides extracted by the two remain the same.

Column chromatographic separation of acidic and neutral and basic metabolites of tyrosine and dihydroxyphenylalanine

Although glutamate is unable to maintain concentrations of phosphocreatine in cerebral cortex slices it has been reported to support active phosphorylation in mitochondria1 preparations. This report is concerned with further investigation of this apparent discrepancy. I n cortical slice studies glucose supported concentrations of phosphocreatine of 1.40 and of ATP of 0 . 7 8 pmoleslg. The relative specific activity (R.S.A.) of ATP (S.A. tissue inorganic phosphate = 1) approximated 1, and of phosphoethanolamine 0.0s . All these values were markedly lower when glutamate alone was employed as substrate and approximated to those obtained in the absence of any added substrate. When glutamate in equimolar concentrations was added to a medium containing a glucose substrate, phosphocreatine concentrations fell to 0.84 pmoles/g. The decrease in the R.S.A. of ATP to 0 . 6 9 with glutamate as substrate would suggest decreased phosphorylation of ADP to ATP rather than an increased utilization (e.g. in the synthesis of glutamine) as has been suggested. In a glucose medium 27 mM K+ did not produce as low concentrations of phosphocreatine as did media containing 6 . 3 mM K+ with glutamate