E. Arrigoni

Influence of some biological pyrimidines on the succinate cycle during and after cerebral ischemia.

Abstract Some cortical metabolites (glycogen, glucose, glucose-6-phosphate, pyruvate, lactate, α-ketoglutarate, succinate, fumarate. malate, citrate, glutamate, glutamine, alanine, NH 4 + ) were studied in rat brain after 5 min of complete compression ischemia, as well as after 15 min of recirculation following 5 min of ischemia. These two conditions (ischemia and post ischemia restitution) were induced in control animals and in rats pretreated 1 hr before by an intraperitoneal injection of 120 mg·kg −1 of some biological pyrimidines (uridine, cytidine and uridine disphosphate glucose). At the cerebral level total complete ischemia induced the: (a) drop of substrates and of glycolytic intermediates, consistent with the increase of lactate and redox state; (b) increase of succinate and alanine; (c) decrease of malate and fumarate; and (d) depletion of α-ketoglutarate. Some of these events may be regarded as the expression of the activation of the succinate cycle which contributed by approx. 10 per cent to the release of anaerobic energy during cerebral ischemia. Pretreatment with the tested pyrimidines did not modify this cerebral biochemical pattern. During post-ischemic recovery, cerebral parameters tended to normalize, except for a further increase in alanine production (as an expression of the activation of the alanine aminotransferase reaction) with conversion of pyruvate into α-ketoglutarate available for the ammonia-detoxicating processes (amination to glutamate and amidation to glutamine). During post-ischemic recovery, pretreatment with cytidine was poorly active. Pretreatment with uridine decreased glucose, glucose-6-phosphate and pyruvate cerebral concentrations, while succinate and alanine were increased. This latter effect was also present in the case of pretreatment with uridine diphosphate glucose. However, this substance increased the cerebral concentration of glycogen and decreased those of fumarate and malate. The different biochemical actions of uracyl derivatives are discussed with regard to their biological effects.

Drug Action on the Metabolic Changes Induced by Acute Hypoxia on Synaptosomes from the Cerebral Cortex

The synaptosomal fractions obtained from the motor area of the cerebral cortex of normocapnic, normoxic, or hypoxic, untreated beagle dogs and of pentobarbital (Nembutal®)- or cytidine diphosphate (CDP)-choline-treated dogs were incubated and analyzed for ATP, ADP, AMP, creatine phosphate, pyruvate, and lactate. The data were compared with data obtained by the surface freezing technique from the whole contralateral cortical area. The in vivo intracarotid perfusion of the drug differentially affected the content of the metabolites and their ratio. This occurred whether the evaluations were performed in the incubated synaptosomal preparations or in whole cerebral tissue, both during normoxia and after hypoxia (15 min; Pao2 = 17–19 mm Hg). Thus intracarotid perfusion of nembutal increased the synaptosomal phosphorylation state both in normoxic and in hypoxic animals, whereas the effect on the metabolism of the contralateral cortical motor area as a whole was in all cases less than that observed in the synaptosomal fraction. Perfusion with CDP-choline increased synaptosomal phosphorylation after the hypoxic condition, but had no effect in normoxia or on the whole cortical tissue of the motor area. The possibility of obtaining a cerebral sparing action by utilizing molecules devoid of anesthetic action is suggested.

Effect of chronic treatment with some drugs on the enzymatic activities of the rat brain

Abstract In untreated and treated rats, age-dependent changes of some cerebral enzymatic activities (lactate dehydrogenase; citrate synthase and malate dehydrogenase; total NADH-cytocrome c reductase and cytochrome oxidase) were studied in the homogenate in toto and in the crude mitochondrial fraction of the brain from the 16th to the 28th week of age, at 4-week intervals. All the activities studied exhibited a natural peak around the 20th week of life, and subsequently they decreased to lower values. The tested drugs (medibazine. trimetazidine, (−)eburnamonine, papaverine, suloctidil, bamethan, inositol niacinate, and UDP-glucose) were administered daily for periods of 4, 8 or 12 weeks each (16–20, 16–24. 16–28 or 24–28 weeks of life) by intraperitoneal route and at one dose level (1 or 5 mg/kg). The drugs tested exerted different effects in the various administration periods, thus enabling us to differentiate drug action on some important cerebral enzymatic activities after chronic treatment.

Metabolism and cerebral energy state: Effect of acute hyperammonemia in beagle dog

Abstract The acute effect of hyperammonemia (NH4+ blood level 0.2 mM) was evaluated in the isolated dog brain in situ. The interference of the transmethylating system of S- adenosyl- L -methionine was also studied by means of infusion with S- adenosyl- L -methionine or adenosine (blood level 0.4 mM). The changes induced by hyperammonemia on the cerebral glutamate-ammonia system (pyruvate, α-oxoglutarate, oxaloacetate, l -alanine, l -glutamate, l -aspartate, l -glutamine, NH4+) were evaluated. Cerebral detoxication of ammonia is connected with the formation of glutamine and. to a lesser extent. of alanine, and is balanced by a decrease in aspartate; glutamate, oxaloacetate, pyruvate and α-oxoglutarate are unmodified or slightly modified. Cerebral intermediate metabolism of glucides was largely activated by acute hyperammonemia. a marked increase in Gibbs free energy being observed. A fraction of this energy not exceeding 10 per cent can be ascribed to the synthesis of glutamine. Hyperammonemia induced a variation of the resting transmembrane potential (as indirectly obtained by applying the Nernst equation), which becomes less negative.

The Early Phase of Cryogenic Lesions: An Experimental Model of Seizures Updated

Summary: : Following cryogenic lesions in 64 rabbits, epileptic activity and gray matter edema were correlatively investigated during the initial phase (23 h). Indexes were developed to allow a quantitative assessment of epileptic activity. The indexes demonstrated that the early phase of cryogenic epilepsy is a very rapid phenomenon during the first 4 h postlesion. Epileptic activity precedes brain edema, and in individual animals, there is a significant positive correlation between the total amount of epileptic activity and the total amount of edema. The relationship between epileptic activity and brain edema are most likely interrelated at the level of pathophysiological mechanisms and several mechanisms can be postulated.

Metabolic Changes Induced by Acute Hypoxia on the Synaptosomes from Dog Brain

Synaptosomal preparations from the motor area of the cerebral cortex of normocapnic, normoxic or hypoxic untreated beagle dogs and phenobarbital-, papaverine-, and (-) eburnamonine-treated dogs were incubated for 10 min at 24 degrees C and analyzed for ATP, ADP, AMP creatine phosphate, pyruvate, and lactate. The data were compared with those obtained from the whole controlateral cortical motor area, by the surface-freezing technique. Both during normoxia and after hypoxic hypoxia (15 min, at PaO2 equal to 17-19 mm Hg) the metabolite contents and ratios were very different in the incubated synaptosomal preparations and in the whole cerebral tissues. As concerns the drug treatment, papaverine was always inactive, while (1) eburnamonine increased the synaptosomal phosphorylation state in hypoxic dogs, being ineffective on the glycolytic metabolites evaluated. Phenobarbital increased the synaptosomal phosphorylation state both in normoxic and in hypoxic animals, and was effective also on the glycolytic metabolites studied.

Calcium-activated neutral protease activities in brain trauma

This paper investigates the level of cytosolic and synaptosomal forms of calcium activated neutral protease activities in the normal brain and their changes following a freezing lesion in the rabbit. From 1 to 24 hours post lesion we observe a progressive disappearing of the enzyme activities from the cytosolic compartment and concurrently their increase in the membranal fraction. These changes are likely to be due to a rise in intracellular calcium concentration, a well documented consequence of many cellular insults. The specific role of the activation of calpain activities in the pathophysiology of trauma is discussed, an enhancement of excitotoxic mechanisms is proposed.

Acetylcholine esterase sensitivity to chronic administration of diphenylhydantoin and effects on cerebral enzymatic activities related to energy metabolism

The effect of chronic treatment (8 months) with diphenylhydantoin (DPH) on rat brain was studied. The activity of some enzymes related to energy transduction (lactate dehydrogenase, citrate synthase, and malate dehydrogenase; NADH-cytochromec reductase and cytochrome oxidase) and neurotransmission (acetylcholine esterase) was evaluated both in the whole brain homogenate and/or in the crude mitochondrial fraction. A clear-cut decrease of acetylcholine esterase activity was observed, the decrease continuing even after treatment was discontinued. Effects on energy metabolism and on lactate dehydrogenase, malate dehydrogenase, and cytochrome oxidase are discussed.

Effect of some drugs on cerebral energy state during and after hypoxia and complete or incomplete ischemia.

Abstract The effect of caffeine, nicergoline and medibazine was evaluated in the brain of beagle dogs during various experimental conditions of cerebral damage (hypoxia, hypoxia plus incomplete ischemia, hypoxia plus complete ischemia), and during post-hypoxic recovery and restoration of circulation. The behavior of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), as well as the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge potential were evaluated in the motor area of the cerebral cortex. The drugs tested proved unable to improve the deranged brain metabolism and the energy charge potential under these various hypoxemic conditions. On the contrary, a certain pharmacological effect of nicergoline and medibazine could be observed both in the post-hypoxic recovery and in the recovery following hypoxia plus complete ischemia, caffeine being totally ineffective. As for the recovery subsequent to hypoxia plus incomplete ischemia, none of the drugs tested was able to trigger restoration.

Acute Model for the Estimation of the Cerebral Energy State during or after Hypoxia and Complete or Incomplete Ischaemia

The behaviour of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), as well as the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge of the brain were studied in the motor area of the cerebral cortex of beagle dogs in hypovolaemic hypotension. These parameters were evaluated after acute hypoxia (obtained by altering the composition of the inhalation mixture), after acute hypoxia plus incomplete ischaemia, after acute hypoxia plus complete ischaemia, during post-hypoxic recovery (3, 15 or 30 min after the restoration of normal ventilation), during post-hypoxic recovery and recirculation. A comparative examination of the different conditions showed that the most dramatic fall in the cerebral energy state took place in hypoxia plus complete ischaemia followed, in the order, by hypoxia plus incomplete ischaemia and simple hypoxia. However, reversal was most difficult in hypoxia plus incomplete ischaemia. The different situations are discussed in this paper with regard to the changes taking place in cerebral biochemical events.