Factors involved in the age-related alteration in the efficiency of the brain bioenergetics

The synaptic energy state may be defined by the redox state of the intramitochondrial NAD-couple (delta Gox-red) and the phosphorylation state of adenine nucleotide system (delta GATP). The biological energy 'lost' by the system during the coupled reactions is calculated as delta delta G = delta Gox-red-delta GATP. These evaluations are performed in synaptosomes isolated from the forebrain of rats of different ages (20, 60 and 100 weeks of age) and incubated in Krebs-Henseleit-Hepes (pH 7.4) buffer, for 10 min at 24 degrees C. The animals are submitted for 10 min to different degrees of in vivo hypoxia. To better elucidate the mechanism of action, the effects of the pretreatment with agents inducing vasodilation (papaverine), or acting on cerebral carbohydrate metabolism (hopanthenate), or on neurotransmission and cerebral metabolism (theniloxazine) are tested. In synaptosomes isolated from the forebrain of animals submitted to moderate degree of hypoxia (PaO2 = 32-29 mmHg) the efficiency of the system is quite similar to that observed in normoxia, with the exception of the older rats. In synaptosomes isolated from the forebrain of rats submitted to severe degree of hypoxia (PaO2 = 20-18 mmHg) the efficiency is altered as a function of both aging and severity of hypoxemia. Drug pretreatment may partially interfere with the delta delta G by hypoxemia, the action being related to the rat age and hypoxic degrees. The age-related decrease in the efficiency of the coupled states seems to be related to alteration in the phosphorylation state of adenine nucleotides.

Evaluation of prevalence of "doping" among Italian athletes

To evaluate knowledge of, attitudes to, and use of illegal drugs and other forms of "doping" in sport 1015 Italian athletes and 216 coaches, doctors, and managers (technicians) were interviewed after selection on a quota basis. Overall, 30% of athletes, managers, and coaches and 21% of doctors indicated that athletic performance can be enhanced by drugs or other doping practices. Over 10% of athletes indicated a frequent use of amphetamines or anabolic steroids at national or international level, fewer athletes mentioning blood doping (7%) and beta-blockers (2%) or other classes of drugs. These proportions were 2-3 times higher for occasional use than for frequent use. Estimates by managers and coaches were much the same as those of athletes when allowance was made for larger random variation. 62% of athletes who acknowledged doping reported pressure to do so from coaches and managers. According to over 70% of athletes access to illegal substances was not difficult. Both athletes and technicians awarded higher scores to risk than to efficacy for any substance, although 42-67% of athletes and technicians regarded amphetamines and anabolic steroids as efficacious. 82% wanted stricter controls not only during competitions but also during training.

Age-related modifications of cytochrome C oxidase activity in discrete brain regions

The apparent Km for cytochrome c of cytochrome oxidase does not change but the Vmax decreases in synaptosomes and non-synaptic mitochondria isolated from the cerebral cortex as a whole of 30-month-old rats compared with 4-month-old ones. When the subcellular organelles are submitted to stressful conditions, namely incubation in media of altered osmolality, the percentage of cytochrome oxidase activity released is much higher in senescent rats. The activity of cytochrome oxidase evaluated in non-synaptic mitochondria and synaptosomes isolated from cortical and subcortical regions and cerebellum of rats aged 4 and 30 months shows a highly significant decrease (P less than 0.001) in the parietotemporal cortex of senescent rats (both in non-synaptic mitochondria and synaptosomes) and in the cerebellum (in synaptosomes).

Relationship between alpha-fetoprotein serum levels, tumour volume and growth rate of hepatocellular carcinoma in a western population

In order to detect a possible relationship between alpha-fetoprotein (AFP) levels, total tumour volume at the moment of the discovery and the tumour volume doubling time, we studied a population of 138 patients, affected by Hepatocellular Carcinoma (HCC) discovered at abdominal ultrasound (US) examination and confirmed by liver biopsy in all cases. In each patient the serum AFP level was determined within a week before or after the US examination. A small therapy-free subgroup of 23 patients, was also serially observed for a mean period of 4 months, so making possible the evaluation of the tumour volume doubling time and its relationship with the initial value of AFP. In 81 patients (58.7%) the serum AFP resulted less than 20 ngr/ml in 21 (15.2%), between 20 and 200 and in 36 (26.1%) greater than 200ngr/ml. No statistical correlation was found between the tumour volume calculated on the basis of the US image at the moment of the discovery and the AFP level, even though very high levels (greater than 3000) were found only in large tumours. Furthermore the tumour doubling time was not correlated with the initial value of AFP.

Influence of aging and drug treatment on the bioenergetics of hypoxic brain

Synaptosomes isolated from the forebrain of rats of different ages (20, 60 and 100 weeks of age) were incubated in Krebs-Henseleit-Hepes (pH 7.4) buffer, for 10 min at 24 degrees C. The energetic state was defined by the redox state of the intramitochondrial NAD-couple (delta Gox-red) and the phosphorylation state of adenine nucleotide system (delta GATP). The biological energy "lost" by the system during the coupled reactions was estimated by the delta delta G = delta Gox-red - delta GATP. The animals were submitted for 10 min to different degrees of in vivo hypoxia. To elucidate the mechanism of action, the effect of the pretreatment with drugs acting on oxygen availability (almitrine) or on microcirculation and metabolism (delta-yohimbine) was tested. In synaptosomes isolated from the forebrain of animals submitted to moderate degree of hypoxia (oxygen arterial partial pressure ranging between 32 and 29 mmHg) the efficiency of the system was quite similar to that observed in normoxia, with the exception of the older rats. In synaptosomes isolated from the forebrain of rats submitted to severe degree of hypoxia (oxygen arterial partial pressure ranging between 20 and 18 mmHg) the efficiency of the system was markedly altered as a function of both aging and severity of hypoxemia. The pretreatment with the agent increasing the oxygen availability partially modified the efficiency of the system, the alpha-blocking agent being less important. The drug action was markedly related to both the age and the degree of hypoxia.

Influence of oxidative stress on the age-linked alterations of the cerebral glutathione system

The glutathione system (reduced and oxidized glutathione; redox index) was studied in the forebrain of male Wistar rats of 5, 15, and 25 months of age following the administration for 2 months in drinking water of chemicals that induce oxidative stress: paraquat and diethyldithiocarbamate (DDC) to increase superoxide radical formation, aminotriazole and hydrogen peroxide to increase hydroxyl radical generation, as well as diamide and ferrous chloride to decrease the glutathione cycle activity. Chronic oral administration of phosphatidylcholine for 2 months was evaluated in 25-month-old rats. Aging accentuated the changes produced by chemicals that induce oxidative stress; i.e., the changes in the glutathione redox index were most pronounced in the forebrains of the older paraquat-, DDC-, H2O2-, and diamide-treated rats. Markedly different adaptative changes occurred within the various drug groups. The reduced glutathione was increased (by paraquat, DDC and aminotrazole), decreased (by H2O2) or unchanged (by iron and diamide). Furthermore, in older rats, paraquat and DDC increased the glutathione redox index, whereas H2O2 and diamide decreased the glutathione redox index or were ineffective (i.e., aminotriazole, iron). The glutathione redox index altered by chronic drug administration was modified by the concomitant administration of phosphatidylcholine.

Arachidonic acid metabolism and pathophysiologic aspects of subarachnoid hemorrhage in rats

We studied the ex vivo production of prostaglandin D2, prostaglandin E2, 6-ketoprostaglandin F1 alpha, and leukotriene C4 in the brain tissue of rats subjected to experimental subarachnoid hemorrhage. The ex vivo method allows the study of arachidonic acid metabolites released from brain slices at different times after subarachnoid hemorrhage induction and reflects the residual capacity for arachidonic acid metabolism after the pathologic event. The rats were sacrificed 30 minutes, 1 and 6 hours, and 2 days after subarachnoid hemorrhage was induced by the injection of 0.30 ml autologous arterial blood into the cisterna magna. Concentration of prostaglandin D2 and 6-ketoprostaglandin F1 alpha was increased significantly relative to control 2 days after induction. The concentration of prostaglandin E2 was increased significantly 6 hours after induction, while ex vivo production of leukotriene C4 was increased significantly at 1 and 6 hours and 2 days. The correlation between these results and the occurrence of vasospasm after subarachnoid hemorrhage is discussed. The results obtained from the ex vivo incubation of brain tissue slices after experimental subarachnoid hemorrhage suggest that after the hemorrhage there is a significant modification of brain eicosanoid metabolism, which could be of great importance in interpreting the pathogenesis of subarachnoid hemorrhage-related neuronal impairment.

Role of synaptosomal enzymatic alterations and drug treatment in brain aging

The activity patterns of enzyme linked to energy transduction are measured as an estimate of the energy potential capacity of the brain during aging. Early investigations provided information on age-related modifications in the apparent activity of these enzymes in the brain as a whole without taking into account the anatomical, morphological, and functional heterogeneity of the discrete brain regions, the metabolic compartments, and their different time course of aging processes. These considerations prompted the investigators to focus their efforts on subcellular organelles, representative of metabolic compartments, isolated from selected brain regions. In the present study, to better elucidate the role of the synaptic compartment during aging, the maximum rate (Vmax) of enzymes involved in energy metabolic pathways is evaluated in synaptosomes isolated from the cerebral cortex of rats aged 4, 12, and 24 months. The potential catalytic activity of phosphofructokinase and citrate synthase is not affected by aging. In contrast, the Vmax of pyruvate dehydrogenase and particularly of cytochrome oxidase decreases in aged rats. A marked increase is found in the Vmax of glucose-6-phosphate dehydrogenase in 24-month-old rats and could support the availability of nicotinamide adenine dinucleotide phosphate (NADPH) for antiperoxidative processes. Pretreatments of the animals with certain drugs are performed in order to check the responsiveness of the tissue and the plasticity of enzyme proteins during aging. Papaverine (acting on macrocirculation) is ineffective, but raubasine (acting on microcirculation and metabolism) and almitrine (acting on oxygen availability) both interfere with the potential activity of some of the enzymes tested. Their influence differs with the age of the animal and are in agreement with their action on brain carbohydrate and phospholipid metabolism.

Effects of nicardipine on the ex vivo release of eicosanoids after experimental subarachnoid hemorrhage

The activation of lipid peroxidation and the enhancement of arachidonic acid metabolism have been demonstrated as indicators of brain damage after subarachnoid hemorrhage (SAH). Meanwhile, the final common pathway of neuronal damage seems to be related to the impaired homeostasis of Ca++. The present study evaluated the effect of the calcium-antagonist nicardipine on arachidonate metabolism after experimental induction of SAH. The ex vivo release of four eicosanoids (prostaglandin (PG)D2, PGE2, 6-keto-PGF1 alpha, and leukotriene (LT)C4) was measured at different intervals after SAH induction. Rats were separated into the following three groups: a sham-operated group, an SAH group (rats were injected with 0.3 ml autologous arterial blood), and an SAH-treated group (after SAH induction, rats were treated with nicardipine 1.2 mg/kg intraperitoneally). Nicardipine significantly decreased the ex vivo release of PGD2 at 48 hours after SAH (p less than 0.01). The release of PGE2 was significantly enhanced at 6 hours after SAH, while in the nicardipine-treated group PGE2 release is significantly reduced. Nicardipine also affects the lipoxygenase pathway, reducing the release of LTC4 at 1, 6, and 48 hours after SAH induction. The results of the present study show that nicardipine treatment exerts an inhibitory effect on both biochemical pathways of arachidonic acid metabolism; aside from vascular effects, nicardipine could exert a protective role against the release of arachidonate metabolites, which could play a significant role in the pathogenesis of brain damage after SAH.

Experimental subarachnoid hemorrhage. Lipid peroxidation and Na+,K(+)-ATPase in different rat brain areas

Subarachnoid hemorrhage (SAH) was produced in Sprague Dawley rats by injection of 0.30 mL of autologous arterial blood into the cisterna magna. Tissue lipid peroxide, quantified as thiobarbituric acid reactive material (TBAR), and Na+,K(+)-ATPase activity were assayed in three different rat brain areas (cerebral cortex, hippocampus, and brain stem) of sham-operated rats and in four hemorrhagic rat groups at 30 min, 1 h, 6 h, and 2 d after SAH. Na+,K(+)-ATPase activity decreased in the cerebral cortex at 30 min, 1 h, and 6 h and in the brain stem at 1 h after SAH induction, whereas enzymatic activity was unchanged in the hippocampus. There was no evident difference in lipid peroxide content between sham-operated animals and hemorrhagic animals. These results indicate that little modifications in lipid peroxidative process (as expressed in TBAR) are not responsible for changes in the ATPase activity.

Cerebral enzyme antioxidant system. Influence of aging and phosphatidylcholine

To obtain a comprehensive profile of the age-related changes of the antioxidant enzyme system in discrete brain regions (cortex, caudate-putamen, substantia nigra, thalamus), the present study involved practically the total life span of male Wistar rats (from 5 to 35 months of age). The activities of both glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase increase from 5 to 25 months of life and remain relatively constant or decrease scantily thereafter. In thalamus, the activity of total superoxide dismutase (SOD) increases from 5 to 20 months of rat life and decreases thereafter. Conversely, in both substantia nigra and caudate-putamen, enzyme activity declines steadily with age, while in parietotemporal cortex enzyme activity deteriorates from the 25th month onward. In both caudate-putamen and parietotemporal cortex, the activity of glutathione peroxidase increases from 5 to 20 months of life and remains relatively constant thereafter, while in substantia nigra the enzyme activity is practically unmodified during the life span. Furthermore, the activity of glutathione reductase in parietotemporal cortex declines from the 20th month onward, while in caudate-putamen and thalamus, enzyme activity deteriorates after an increase from 5 to 20 months of life. The interference of phosphatidylcholine and/or its metabolite(s) with the cerebral enzyme antioxidant system shows a characteristic specificity as regards both the time of onset and the enzyme activities involved, namely, SOD and glutathione reductase. The interference with SOD is related to the cytosolic form of the enzyme and affects the cortex only of 5-month-old animals and also extends to the thalamus of 15-month-old rats and all regions in 25-month-old ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related effect induced by oxidative stress on the cerebral glutathione system

In the forebrain from male Wistar rats aged 5, 15 and 25 months, age-related putative alterations in the glutathione system (reduced and oxidized glutathione; redox index) were chronically induced by the administration in drinking water of free radical generators (hydrogen peroxide, ferrous chloride) or of inhibitors of endogenous free radical defenses (diethyl-dithio-carbamate, an inhibitor of superoxide dismutase activity). In hydrogen peroxide administered rats, both reduced glutathione and the cerebral glutathione redox index markedly declined as a function of aging, whereas oxidized glutathione consistently increased. In contrast, chronic iron intake failed to modify the reduced glutathione in forebrain from the rats of the different ages tested, whereas the oxidized glutathione was increased in the older brains. The chronic intake of diethyl-dithio-carbamate enhanced the concentrations of reduced glutathione in the forebrains from the rats of the different ages tested, the oxidized glutathione being unchanged. In 15-month-old rats submitted to chronic oxidative stress, ergot alkaloids (and particularly dihydroergocriptine) interfered with cerebral glutathione system, while papaverine was always ineffective. The comprehensive analysis of the data indicates that: (a) both the type of oxidative stress and the age of the animals modulate the cerebral responsiveness to the putative modifiers in the level of tissue free radicals; (b) aging magnifies the cerebral alterations induced by oxidative stress; the (c) cerebral glutathione system may be modified by metabolic rather than by circulatory interferences; (d) a balance between the various cerebral antioxidant defenses is present, the perturbation of an antioxidant system resulting in the compensatory modified activity of component(s) of another system.

Age-related modification of enzyme activities in synaptosomes isolated from rat cerebral cortex

In synaptosomes from rat cerebral cortex, the potential catalytic activity of some enzymes related to energy metabolism--namely, phosphofructokinase and citrate synthase--is not affected by aging. In contrast, the maximum velocity (Vmax) of cytochrome oxidase and of pyruvate dehydrogenase decreases in aged rats. A marked increase is found in the Vmax of glucose 6-phosphate dehydrogenase in aged rats and could be related to the availability of NADPH for antiperoxidative processes. Pretreatments of experimental animals with certain drugs were done to investigate the plasticity of enzyme proteins during aging. Papaverine, which acts on macrocirculation, is ineffective, but delta-yohimbine acting on microcirculation and metabolism and almitrine acting on oxygen availability both could interfere with the potential activity of some enzymes. However, their influence differs with the age of the rats.

Relationship between aging, drug treatment and the cerebral enzymatic antioxidant system

Four different brain regions (parieto-temporal cortex, caudate-putamen, substantia nigra, and thalamus) were examined in rats aged 5, 10, 15, 20, 25, 30, and 35 months. The following enzyme activities related to the antioxidant system were measured: glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione peroxidase, glutathione reductase, and superoxide dismutase (as total). Specific enzyme activities vary markedly with age, according to the various regions studied, indicating nonhomogenous vulnerability of different brain regions to aging. In general, both superoxide dismutase and glutathione reductase tended to decline during the last half of life, while glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase tended to increase slightly with age. In rats of 10, 20, or 30 months, chronic treatment for two months with a vasodilator (papaverine) or a calcium-blocker (nicardipine) indicated that the antioxidant enzyme activities are partially influenced according to the exogenous agent used, the brain region tested, and the age of the animals.

Action of L-acetylcarnitine on age-dependent modifications of mitochondrial membrane proteins from rat cerebellum

Protein patterns of mitochondrial outer membrane, inner membrane, and matrix from non-synaptic (free) mitochondria from rat cerebellum at different ages (4, 8, 12, 16, 20, and 24 months) were analyzed by gel electrophoresis. Acute L-acetylcarnitine treatment was performed by a single i.p. injection (100 mg/kg body weight) of the substance 60 min before the sacrifice of the animals. Different age-dependent changes were obtained for the proteins of the three fractions. The amount of some protein subunits increased and/or decreased after drug treatment. In particular, protein composition of the inner mitochondrial membrane showed significant age-related modifications. This result probably indicates differences in protein synthesis and/or turnover rates in the various mitochondrial compartments during aging. Acute L-acetylcarnitine treatment caused: a high increase in the amount of one inner membrane protein with Mw 16 kDa, at all the ages studied; a decrease in the amount of many other inner membrane proteins; modifications of some matrix proteins. Our results show that in vivo administration of L-acetylcarnitine affects mainly the inner membrane protein composition of cerebellar mitochondria.

Influence of aging and drug treatment on the cerebral glutathione system

Age-related changes of the components of the glutathione system (reduced and oxidized glutathione) were evaluated in forebrains from male Wistar rats aged 5, 10, 15, 20, 25, 30 and 35 months. The trend of both forms of glutathione and the glutathione redox index markedly differs with age. Reduced glutathione increases during the first third of a rat's life and decreases thereafter. In contrast, oxidized glutathione remains relatively constant during the first half of the life-span and increases thereafter. Thus, the glutathione redox index steadily declines with age after an increase during the first third of the rat's life-span. In rats aged 10, 20 or 30 months, chronic IP treatment for two months with drugs known to modify cerebral circulation (papaverine) or the cerebral metabolism (ergot alkaloids dihydroergocristine, dihydroergocriptine) indicates that, according to the age, the cerebral glutathione system may be modified by metabolic changes rather than by circulatory events.

Changes induced by aging and drug treatment on cerebral enzymatic antioxidant system

The age-related modifications of the participants to the cerebral enzymatic antioxidant system (superoxide dismutase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase) were evaluated in four brain regions from male Wistar rats aged 5, 10, 15, 20, 25, 30, and 35 months. Both the specific enzyme activity and the profile of any enzyme tested markedly differ with age according to the region examined: parieto-temporal cortex, caudate-putamen, substantia nigra and thalamus. This inhomogeneous age-related profile of enzyme activities could explain both the controversial data of literature and the different regional vulnerability of the brain tissue to damage with aging. In rats aged 10, 20, or 30 months, the chronic i.p. treatment for two months with papaverine or ergot alkaloids (dihydroergocristine, dihydroergocornine, dehydroergocriptine) suggests that the antioxidant enzyme activities may be influenced according to the agent utilized, the brain region tested, and the age of the animal. In any case, small differences in the drug structure support marked differences in the type and extent of the intervention on the antioxidant enzymatic system.

Bioenergetics of different brain areas after experimental subarachnoid hemorrhage in rats

We studied energy metabolism after experimental subarachnoid hemorrhage in rats. Four different cerebral areas were tested: frontal cortex, occipital cortex, hippocampus, and brainstem. Vmax of the following enzymatic activities was evaluated: in the homogenate: hexokinase, phosphofructokinase, and lactate dehydrogenase for the glycolytic pathway, and glucose-6-phosphate dehydrogenase for the hexose monophosphate shunt; in the purified nonsynaptic mitochondria: NAD+-isocitrate dehydrogenase, citrate synthase, and succinate dehydrogenase for the Krebs cycle, and cytochrome oxidase for the electron transfer chain. We also evaluated some parameters related to the respiration of nonsynaptic mitochondria (State 3, State 4, uncoupled state, respiratory control ratio, and ADP:O ratio). Subarachnoid hemorrhage did not significantly affect Vmax of the enzymatic activities related to anaerobic and aerobic metabolism; however, mitochondrial respiration was affected, particularly in the presence of NADH-producing substrates (glutamate + malate).

Modifications in cerebral lipid metabolism by severe glucose deprivation during aging

Severe glucose deprivation causes extensive derangement of phospholipids, fatty acids and free fatty acids in cerebral cortex of rats of different ages. The hypoglycemia-induced cerebral loss of phospholipids and fatty acids persists after 60 min recovery. Changes in individual classes of lipids are largely affected by aging. In fact, during glucose deprivation and recovery, in adult animals no preferential loss of polyunsaturated fatty acids and ethanolamine phosphoglycerides occurs, suggesting that the loss could be related to oxidative rather than to peroxidative degradation. On the contrary, in senescent rats the quoted events occur, suggesting the hypothesis of a possible peroxidation of cerebral lipids. Pretreatment with some agents is performed to elucidate the aging mode of action. Papaverine (acting on macrocirculation) is uneffective, while raubasine (acting on microcirculation and metabolism) and almitrine (acting on oxygen availability) interfere with the phospholipid and fatty acid metabolism, their action being different according to the rat age.