Journal of Neurochemistry

Trabucchi, M.; Cheney, D. L.; Susheela, A. K.; Costa, E.

doi: 10.1111/j.1471-4159.1975.tb07656.xpmid: 234516

Abstract— The cholinoacetyltransferase activity (CAT) in diaphragm of mice of Bar Harbor strain (129 ReJ dy/dy) with muscular dystrophy was significantly lower than that of phenotypically normal litter mates (129 ReJ dy/+). CAT, tyrosine hydroxylase (TH), dopamine‐β‐hydroxylase (DβH) activities were found identical in adrenal gland and brain homogenates of normal and dystrophic mice. Subacute injections of atropine (72 μmol/kg i. p., twice daily for 3 days) failed to increase the activity of adrenal CAT in dystrophic mice but increased this enzyme activity in adrenals of normal litter mates. The concentration in brain of dopamine, norepinephrine, serotonin, acetylcholine (ACh), γ‐aminobutyric acid (GABA) and some of their precursors were measured. Only the concentration of ACh was significantly lower in the brain of muscular dystrophic mice. The rate of accumulation of brain ACh concentration after the injection of oxotremorine (5μmol/kg i. p.) is slower in muscular dystrophic animals than in normal litter mates. Furthermore, the turnover rate of ACh in total brain was slower in muscular dystrophic mice than in phenotypically normal litter mates. The turnover rate of brain dopamine and norepinephrine in these 2 groups of animals was similar.

Aunis, D.; Miras‐portugal, M. T.; Mandel, P.

doi: 10.1111/j.1471-4159.1975.tb07657.xpmid: 234517

Abstract— Bovine adrenal medullary dopamine‐β‐hydroxylase binds with concanavalin A and forms an enzymically active precipitate. The formation of the insoluble complex is pH‐dependent and can be inhibited by α‐methyl‐D‐mannoside, D‐mannose and D‐glucose. The insoluble complex can be dissociated into two species with α‐methyl‐D‐mannoside. From the results, it appears that the interaction between dopamine‐β‐hydroxylase and concanavalin A is due to the carbohydrate moiety of dopamine‐β‐hydroxylase. This property was used to purify the enzyme from a soluble lysate of chromaffin granules. Of all the proteins contained in the soluble lysate, dopamine‐β‐hydroxylase was the only one to be retained on a column of concanavalin A covalently bound to Sepharose 4B. The preparation of pure dopamine‐β‐hydroxylase exhibits a very high specific activity of 320 μmol of octopamine formed per 30 min per mg of protein.

Fried, R.; Mandel, P.

doi: 10.1111/j.1471-4159.1975.tb07658.xpmid: 1113119

Abstract— Superoxide dismutase was assayed in portions of the nervous system (a) by inhibition of tetrazolium reduction by oxygen radicals, generated enzymically, and (b) by inhibition of tetrazolium reduction by oxygen radicals generated by oxidation of NADH in presence of phenazine methosulphate. Superoxide dismutase activity was found in beef brain, retina and adrenal medulla, as well as in brain, retina and lungs of adult and of newborn rats. Preliminary experiments with rats exposed to hyperbaric oxygen showed no alteration of enzyme activities in tissues of newborn and adult animals. The possible role of superoxide dismutase in the nervous system is discussed.

Pasquini, J. M.; Gomez, C. J.; Najle, R.; Soto, E. F.

doi: 10.1111/j.1471-4159.1975.tb07659.xpmid: 1113120

Abstract— The possible transport role of phospholipid‐protein complexes, present in the cell supernatant of rat brain was investigated using labelled choline as precursor of phosphatidyl choline. Results obtained after the intracranial injection of choline gave no indication of a sequence of events compatible with a transport of phospholipid molecules from the possible site of synthesis (microsomes) to the supernatant and subsequently to myelin. Chase experiments using rat brain slices incubated in vitro with radioactive choline agreed well with the above mentioned results. Contrariwise, when Na352SO4 was used as precursor, the results clearly indicated that synthesis of sulphatides takes place in microsomes, followed by transfer of the radioactive lipid to sulphatide‐containing lipoproteins in the supernatant and finally to myelin. Results presented in this paper seem to give further support to the idea that other subcellular fractions, besides microsomes, can autonomously synthesize part of their own provision of phospholipids. Possible reasons which might explain the marked differences between the mechanisms of addition of phospholipids and sulphatides to myelin are discussed in relation to results obtained by other investigators.

Harvey, J. A.; Scholfield, C. N.; Graham, L. T.; Aprison, M. H.

doi: 10.1111/j.1471-4159.1975.tb07660.xpmid: 1113121

Abstract— Olfactory bulb removal and the consequent degeneration of the lateral olfactory tract led to a selective change in putative synaptic transmitters of the denervated olfactory cortex of guinea‐pigs. Nine days after bulbectomy there was a significant decrease in content of aspartate (31%) and glutamate (20%) in olfactory cortex but no change in neocortex. The content of GABA, alanine and ACh in olfactory cortex was unchanged (± 3 per cent of control). The content of 5‐HT, dopamine, NE and glycine was increased by 10‐18 per cent. The decrease in aspartate and glutamate content of the olfactory cortex after bulbectomy suggests that these two amino acids have a high concentration in fibres of the lateral olfactory tract. This tissue may prove to be useful in determining the possible role of these acidic amino acids in neuronal function.

Skolnick, P.; Daly, J. W.

doi: 10.1111/j.1471-4159.1975.tb07661.xpmid: 163293

Abstract— Cyclic AMP accumulates in cerebral cortical slices from the C57B1/6J mouse incubated with the following stimulatory agents: norepinephrine, adenosine, veratridine and adenosine‐biogenic amine combinations. The results with slices labelled with radioactive adenine or adenosine provide evidence for the existence of distinct functional compartments of adenine nuclcotides which serve as precursors of cyclic AMP on stimulation with specific agents. Thus, in slices labelled with (14C)adenine or (3H)adenosine the ratio of (14C) to (3H)cyclic AMP was dependent on the stimulatory agent; with veratridinc the ratio was 1.4 while with adenosine the ratio was 3.0. In addition, a greater than 2‐fold difference in the ratio of endogenous/radioactive cyclic AMP was observed in adenine or adenosine‐labelled slices after incubation with veratridine, norepinephrine, adenosine or adenosine‐amine combinations; the lowest ratios after stimulation with veratridine and the highest after adenosine or adenosine‐amine combinations. The high ratio observed with adenosine was in part due to a quite marked incorporation of the stimulant, adenosine, into the accumulating cyclic AMP. Such distinct functional compartments of cyclic AMP precursors may represent different cell types and/or morphological entities within one cell type.

Berman, K.; Fishman, R. A.

doi: 10.1111/j.1471-4159.1975.tb07662.xpmid: 234518

Abstract— The effect of depolarization of rat brain cortex slices on the relative distribution of thiamine among its various phosphate esters and on the efflux of thiamine was studied as a probe of possible coenzyme‐independent neurophysiological functions of thiamine. Electrical pulses for 30 min increased lactate production but did not affect the levels of thiamine esters. Depolarization with 41 mM‐potassium decreased thiamine diphosphate by only 3 percent (P= 0.05). Thiamine triphosphate levels (TTP) were unaffected by depolarization but doubled during incubation for 1 h in which time efflux of 40 percent of the total thiamine from the slices as unesterified thiamine occurred. Depolarization by potassium released a small but highly variable portion of the thiamine content of superfused cortex slices above the basal rate of efflux. The basal efflux was partially sodium dependent. Thiamine efflux was unaffected by acetylcholine, ouabain, or tetrodotoxin, compounds previously reported to increase thiamine efflux. The incorporation of 32P1 into the endogenous thiamine phosphates of cortex slices was studied. Incorporation into thiamine diphosphate reached only 20 percent of the specific activity of its precursor, ATP, after 2h of incubation while the incorporation into TTP approached equilibrium with ATP in 15‐30 min indicating that the TTP pool was the most rapidly turning over of the thiamine phosphates. The data suggest that only a small portion of the TDP pool undergoes rapid turnover and serves as a precursor for TTP. The rapid turnover of TTP phosphoryl groups is consistent with specific functions for this compound related to its potential for phosphorylation reactions. An analog of TTP with the β, γ oxygen bridge replaced by a methylene group decreased TDP levels and increased thiamine when incubated with cortex slices, but did not effect thiamine monophosphate or triphosphate levels indicating inhibition of thiamine pyrophosphokinase.

Brown, F. C.; Harralson, J. D.

doi: 10.1111/j.1471-4159.1975.tb07663.xpmid: 1113122

Abstract— The activity of dopamine‐β‐hydroxylase is inhibited by copper. It is stimulated by a variety of substances, such as fumarate and sodium chloride, which exert salt‐like effects. Both phenomena are mediated indirectly through an interaction of ascorbate with catalase. The latter is converted to the inactive catalase II, by the autoxidation of ascorbate and other electron donors. Copper accelerates the autoxidation, thereby enhancing the inactivation of catalase. The activity of DβH, which requires catalase, is therefore inhibited. At high ionic strength, i. e. in the presence of high levels of salt, the conversion of catalase to catalase II is prevented, and the DβH reaction proceeds.

Kogure, K.; Busto, R.; Scheinberg, P.; Reinmuth, O.

doi: 10.1111/j.1471-4159.1975.tb07664.xpmid: 234519

Abstract— The effects of hypercapnia on the kinetics of cerebral energy metabolism were evaluated in adult rats by the closed system method of LOWRY et al. (1964). Moderate hypercapnia with a Paco2 of 61 torr sustained for 20 min resulted in intracellular brain acidosis (7.07‐6.97). During hypercapnia the tissue content of glucose increased whereas phosphocreatine, ADP, pyruvate and lactate contents, and the lactate/pyruvate ratio decreased. The ATP/ADP ratio increased from 7.7 to 9.0; the cytoplasmic NADH/NAD + ratio decreased from 2.06 × 10‐3 to 1.49 × 10‐3. There was no change in Energy Charge. Turnover rate of phosphocreatine increased from 3.84 to 4.62 mmol/kg/min, but the turnover rates of ATP, glucose and glycogen were reduced (from 1.98 to 1.86, 6.24 to 4.80, and 3.96 to 2.94 mmol/kg/min, respectively). The utilization rate of total high energy phosphate decreased from 30.6 to 25.4 mmol/kg/min while the post‐decapitation EEG during hypercapnia persisted longer than during normocapnia. These results indicate that moderate hypercapnia reduces the overall kinetic activity of cerebral energy metabolism. The steady Energy Charge suggests that the reduction in the rate of high energy phosphate use is proportionally balanced by a lowered production rate of ATP.

Clarke, D. D.; Greenfield, S.; Dicker, E.; Tirri, L. J.; Ronan, E. J.

doi: 10.1111/j.1471-4159.1975.tb07665.xpmid: 1113123

Abstract— A detailed time study of the incorporation of label from sodium‐(1‐14C)acetate, (1‐14C)ethanol, and (2‐14C)glucose into the aspartyl moiety of N‐acetylaspartic acid (NAA) was conducted. As expected the specific activity of aspartate increased rapidly with time and peaked within 15‐20 min after which it fell sharply; but significantly, that of the aspartyl moiety of NAA rose very slowly even after the specific activity of aspartate had fallen to less than 1 per cent of the peak values. A rat brain microsomal free supernatant preparation was shown enzymatically to incorporate label from sodium‐(1‐14C)acetate into the t‐RNA fraction from which was isolated N‐(1‐14C)acetylaspartic acid. From these observations we were inclined to speculate that NAA‐t‐RNA may serve as an initiator of neuronal protein synthesis.