Age-dependent changes in rat brain mitochondria of synaptic and non-synaptic origins

Synaptic and non-synaptic mitochondria were isolated from the brains of 3- 12-and 28-30-month-old female Fisher 344 rats. Total oxygen consumption and oxygen consumption due to mitochondrial respiration decreases 83% with increasing age in synaptic mitochondria using malate plus glutamate as substrate, but only 33% in non-synaptic mitochondria; succinate-driven activity is not affected. Succinate-driven superoxide generation decreases over 90% in both fractions; malate plus glutamate-driven superoxide generation decreases 50% in synaptic mitochondria only. The amount of c- and a-type cytochromes decreases approximately 50% in synaptic mitochondria. The absorbance wavelength maximum of cytochrome b decreases 2.6 nm in synaptic mitochondria from senescent brains but only 1.6 nm in non-synaptic mitochondria.     

Age-dependent changes in glutamate oxidation by non-synaptic and synaptic mitochondria from rat brain

The oxidation of glutamate by non-synaptic and synaptic mitochondria from brains of 3-, 12- and 24-month-old rats was studied. With glutamate plus malate as substrates, non-synaptic mitochondria showed higher respiration rates than synaptic mitochondria in all the three age groups studied. The rate of oxidation of L-[1-¹⁴C] glutamate and the activities of NAD-glutamate dehydrogenase and aspartate aminotransferase were also higher in non-synaptic mitochondria compared with synaptic mitochondria in three age groups. With glutamate plus malate as substrates, a significant reduction in state 3 respiration was observed in both mitochondrial populations from 12- and 24-month-old rats compared with 3-month-old animals. Although an age-dependent decrease in the oxidation of L-[1-¹⁴C] glutamate was observed in both non-synaptic and synaptic mitochondria from aging rats, the oxidation of [1-¹⁴C]-2-oxoglutarate was unaltered in non-synaptic and synaptic mitochondria from senescent rats. The activity of NAD-glutamate dehydrogenase was decreased with age in both mitochondrial populations, whereas aspartate aminotransferase was not altered with age. The results indicate that the oxidation rate of glutamate in rat brain mitochondria is decreased during aging.     

Biochemical effects of carbon monoxide poisoning in rat brain with special reference to blood carboxyhemoglobin and cerebral cytochrome oxidase activity

Male Wistar rats exposed to 1000 ppm carbon monoxide for 3 h showed a rapid removal of carbon monoxide from the blood, and a cerebral cytochrome oxidase activity within the control range immediately after the end of the exposure. The cytochrome oxidase activity decreased while carboxyhemoglobin concentration diminished during the reoxygenation period. The effect might have been caused through a loss of mitochondria by increased lipid peroxidation as cerebral glutathione concentration decreased and lysosomal acid proteinase activity increased in glial cell fractions. The present results seem to indicate that the cerebral cytochrome oxidase may not be specifically inhibited in non-lethal carbon monoxide poisoning despite its proven interactions in vitro.     

Age-related changes in glutathione and lipid peroxide content in mouse synaptic mitochondria: Relationship to cytochrome c oxidase decline

To elucidate the contribution of lipid peroxides and glutathione to brain aging, we have carried out a comparative study of their contents in synaptic mitochondria from young (10-week-old), adult (24-week-old), and senescent (72-week-old) mice. In synaptic mitochondria, there is a significant decline in lipid peroxide content (P < 0.01) and cytochrome c oxidase activity (P < 0.001) in senescent as compared to adult and young mice. By contrast, glutathione concentration showed an increase in senescent (P < 0.05) in comparison to the other age groups. Moreover, there was a significant inverse correlation between age and lipid peroxide content (r = -0.5, P < 0.001) or cytochrome c oxidase-specific activity (r = -0.58, P < 0.001). We suggest that this age-dependent decrease in lipid peroxide content in synaptic mitochondria may be the result of an age-related decline in the activity of the electron transport chain, with concomitant decrease in oxyradical production, in the senescent organelles.     

Lack of age-dependent changes in CO binding to cardiac mitochondrial cytochrome oxidase

The rates of CO binding to cytochrome oxidase at low temperatures were studied in mitochondria isolated from the hearts of 3- and 30-32-month-old male F344/N rats. A single apparent energy of activation of 9.6 kcal/mol is observed in mitochondria from 3-month-old rats in the presence of 1% CO. In the presence of 100% CO, the energy of activation is 10.1 kcal/mol and the rate constants of CO recombination following flash photolysis are approximately twice the rate constants in the presence of 1% CO at warm temperatures indicating that an intermediate region near the heme iron can hold a maximum of two CO molecules. In 30-month-old cardiac mitochondria, recombination in the presence of 1% and 100% CO requires crossing barriers of 9.4 kcal/mol and 10.3 kcal/mol height, respectively. The approximate doubling of the values of k at warm temperatures (above 225 K) indicates, as in mitochondria from young animals, that CO migration from solvent to the heme iron involves migration across two similarly sized barriers separating the Fe from an innermost intermediate region I (capable of holding only one CO) and separating region I from intermediate region I2 (capable of holding two CO). The kinetics of CO binding to cytochrome oxidase do not change with increasing age.     

CO对局灶性缺血脑组织血脑屏障通透性的影响

目的:研究一氧化碳及其限速酶(血红素氧合酶-1)对局灶性缺血脑组织血脑屏障通透性的影响。方法:将SD大鼠随机分为3组(n=6),使用血红素氧合酶诱导剂及抑制剂腹腔注射,用等量生理盐水腹腔注射作为对照组,12h后复制MCAO模型。梗塞后24h后检测血液中一氧化碳浓度、血脑屏障通透性。结果:诱导剂组一氧化碳浓度明显高于对照组(P＜0.01),血脑屏障通透性明显低于对照组(P＜0.05),而抑制剂组一氧化碳浓度明显低于对照组(P＜0.01),血脑屏障通透性明显高于对照组(P＜0.05)。血红素氧合酶诱导剂、抑制剂对非梗塞侧的血脑屏障通透性没有影响(P＞0.05)。结论:一氧化碳作为一种信使分子,脑缺血时浓度升高具有保护血脑屏障的作用。     

Aggregations of synaptic vesicles on the exposed inner membrane of presynaptic mitochondria in brain

Summary Fragments of rat cerebral cortex have been incubated under various conditions. When divalent cations are present, patches of the external membrane of some mitochondria are disassembled leaving the inner mitochondrial membrane exposed to the cytoplasm. Sometimes the entire external membrane is missing. In presynaptic bulbs the synaptic vesicles are attracted and adhere to the exposed outer face of the inner mitochondrial membrane. The mode of attraction and adhesion of the vesicles is discussed. Possibly this could serve as a model for further investigation of the attraction of vesicles to the active zone of the presynaptic membrane.     

Changes in protein content of developing brain synaptic membranes,mitochondria and myelin

The development of myelin, synaptosomal plasma membranes (SPM) and mitochondria in neonatal rat cortex has been followed by examining the electrophoretic profiles of protein in brain subcellular fractions. The appearance of the myelin proteins parallels the time course of myelination and confirms previous reports of the order of appearance of the proteins. Few changes occur in mitochondria during the developmental period. Plasma membranes in the SPM fraction show a progressive change from an ante-synaptogenesis profile to that characteristic of adult SPM. Tubulin, which is the major synaptic junctional protein, reaches its adult level in the developing SPM earlier than other SPM proteins, indicating that it may be involved in establishing the basic framework of the junction.     

Comparison of carbon monoxide and nitrogen induced effects on synaptic transmission in the rat hippocampal slice.

A comparison has been made of the effects of carbon monoxide (CO) or nitrogen (N2) exposure on synaptic transmission in the hippocampal slice. CA1 field potentials, evoked by Schaffer collateral stimulation, were unaffected by superfusion of slices with artificial cerebral spinal fluid (ACSF) equilibrated with either 15% CO or 15% N2 for 120 min. However, superfusion with hypoxic ACSF equilibrated with either 85% CO or 85% N2 caused a rapid depression of synaptic transmission. Reperfusion with control ACSF following 30 min hypoxia led to recovery of evoked responses and a slight hyperexcitability. In the hippocampal slice, synaptic transmission, as assessed by input/output curves, was not different during or following hypoxia induced by exposure to CO or N2. In the short term, CO is not toxic.     

Regional brain variations of cytochrome oxidase activity in spontaneously hypertensive mice

To explore the central disturbances resulting from blood pressure changes, spontaneously hypertensive mice (SHM) were compared to normotensive controls for cytochrome oxidase (CO) activity, an index of oxidative capacity in the central nervous system and a marker of long-term regional brain metabolism and neuronal activity. In all brain areas presenting significant enzymatic variations, only increases in CO activity were found in SHM, particularly the central autonomic network. However, only specific regions were affected, namely the insular cortex and the hypothalamic nuclei principally involved in high-order autonomic control. Altered limbic structures included the lateral septum, various hippocampal subregions, as well as prelimbic cortex. CO activity was also elevated in several forebrain regions, including those directly connected to the limbic system, such as the nucleus accumbens, the claustrum, and dorsomedial and reticular thalamic nuclei, as well as subthalamic and ventrolateral thalamic nuclei. In the brainstem, the only regions affected were the locus coeruleus, site of noradrenergic cell bodies, the trigeminal system, and four interconnected regions: the inferior colliculus, the paramedial reticular formation, the medial vestibular, and the cerebellar fastigial nuclei. These data show that specific regions modulating sympathetic nerve discharge are activated in young adult SHM, possibly due to mitochondrial dysfunction and excitotoxicity.     

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).     

Age-dependent changes in pyruvate uptake by nonsynaptic and synaptic mitochondria from rat brain

Changes in the uptake of pyruvate by nonsynaptic and synaptic mitochondria from brains of young adult and old rats were investigated. An age-dependent decrease in State 3 respiration in the presence of pyruvate plus malate as substrate was observed in cerebral mitochondrial populations but not in liver mitochondria. Addition of exogenous cytochrome c to nonsynaptic and synaptic mitochondria enhanced the rate of State 3 respiration but the age-dependent decrease in State 3 respiration persisted in both types of mitochondria. A decrease in the uptake of pyruvate as measured by the inhibitor-stop and rapid centrifugation techniques was observed in both nonsynaptic and synaptic mitochondria from 24-month-old rats compared to 3-month-old rats. The results suggest that the decrease in the uptake of pyruvate may be one of the factors responsible for the observed reduction in State 3 respiration in the presence of pyruvate plus malate by both nonsynaptic and synaptic mitochondria from brains of senescent rats compared to young adults.     

Effect of doxorubicin on oxidative phosphorylation in brain mitochondria

Inin vitro experiments, antineoplastic anthracycline antibiotic doxorubicine caused deenergization of rat brain mitochondria due to oxidation-phosphorylation uncoupling and inhibition of succinate oxidase system. Reduced production and oxidation of succinic acid is the most early effect of doxorubicin on mitochondrial oxidation. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 128, No. 10, pp. 445–447, October, 1999