The rate of free radical production as a determinant of the rate of aging: evidence from the comparative approach

The relationship of oxidative stress with maximum life span (MLSP) in different vertebrate species is reviewed. In all animal groups the endogenous levels of enzymatic and non-enzymatic antioxidants in tissues negatively correlate with MLSP and the most longevous animals studied in each group, pigeon or man, show the minimum levels of antioxidants. A possible evolutionary reason for this is that longevous animals produce oxygen radicals at a low rate. This has been analysed at the place where more than 90% of oxygen is consumed in the cell, the mitochondria. All available work agrees that, across species, the longer the life span, the lower the rate of mitochondrial oxygen radical production. This is true even in animal groups that do not conform to the rate of living theory of aging, such as birds. Birds have low rates of mitochondrial oxygen radical production, frequently due to a low free radical leak in their respiratory chain. Possibly the low rate of mitochondrial oxygen radical production of longevous species can decrease oxidative damage at targets important for aging (like mitochondrial DNA) that are situated near the places of free radical generation. A low rate of free radical production can contribute to a low aging rate both in animals that conform to the rate of living (metabolic) theory of aging and in animals with exceptional longevities, like birds and primates. Available research indicates there are at least two main characteristics of longevous species: a high rate of DNA repair together with a low rate of free radical production near DNA. Simultaneous consideration of these two characteristics can explain part of the quantitative differences in longevity between animal species. Accepted: 12 December 1997     

Oxygen measurements in the burrows of freshwater insects

1. Thin-tipped micro-electrodes were used to measure oxygen concentrations in the burrows of two common aquatic insects, the mayfly Hexagenia limbata and the alderfly Sialis velata . Both species maintain their surroundings oxygenated by drawing water from above the sediment surface into their tubes. 2. The temporal pattern of oxygen in the burrows differed between the species. The constant high oxygen concentration (>75% of air saturation) measured in the tubes of the mayfly suggest that this animal pumps water almost continuously, which is consistent with its high oxygen requirements. In contrast, oxygen concentration in burrows of the alderfly fluctuated widely over time, suggesting that this animal irrigates only irregularly, probably because it can tolerate short periods of low oxygen concentration in its burrow. 3. The interval between pumping episodes by the alderfly decreased with increasing temperature, a result of increased oxygen consumption by the animal and by sediment at high temperature. 4. Based on the tube dimensions, oxygen penetration depth and animal density in lakes, we estimate that Hexagenia could create an oxic micro-environment equivalent to 3–35% of the volume of the surface oxidized sediment layer created by molecular diffusion. The mosaic of oxic micro-environments created by the burrowing and irrigation of freshwater animals could influence chemical and biological processes in sediments, the fluxes of materials between the sediment and the overlying water column, and the exposure of benthic animals to sedimentary contaminants.     

Chemiluminescence Emission during Reactions between Superoxide and Selected Aliphatic and Aromatic Halocarbons in Aprotic Media

The reactions between superoxide free radical anion (.O⁻₂) with the halocarbons CCl₄, CHCl₃, BrCH₂CH₂Br(EDB), decachloro-biphenyl (DCBP), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in dimethyl sulphoxide (DMSO) results in the emission of chemiluminescence (CL). The chemiluminescence reactions are characterized as having biphasic second order kinetics, CL wavelengths between 350 nm and 650 nm, and exhibiting perturbation by chemicals reactive with singlet oxygen. These data suggest that singlet oxygen species are the excited state responsible for the light emissions. Polarographic studies confirm .O⁻₂ consumption and halide release in the reactions, while gas liquid chromatography and NBT reduction demonstrate the decomposition of the halocarbons into products. A chemiluminescent reaction mechanism is proposed involving reductive dehalogenation of the halocarbons and the generation of singlet oxygen. The significance of singlet oxygen generation is discussed with respect to a general mechanism for explaining the rapid initiation of lipid peroxidative membrane damage in halocarbon toxigenicity in animal and plant tissues.     

Estimation of free radical formation by beta-ray irradiation in rat liver

In vivo free radical reactions in rat liver as a result of exposure to low-dose beta-radiation was evaluated with electron paramagnetic resonance (EPR) spectroscopy by monitoring the reduction of the nitroxyl spin probe after intravenous administration. The EPR signal intensity of a nitroxyl probe as a function of time in bile flow was monitored by cannulating the bile duct through the cavity of an X-band EPR spectrometer. The results show that the rate of nitroxyl signal loss was higher in rats whose livers were exposed to beta-rays compared to unexposed rats. However, the rate of signal loss was lower in animals whose organs were exposed to air by opening the abdominal cavity. In vitro experiments also showed that the nitroxyl EPR signal loss was greater in an atmosphere of nitrogen than in air. Results suggest that under low levels of tissue oxygen, exposure to beta-rays results in nitroxyl signal loss, which may be mediated by free radical dependent pathways. When tissue oxygen were higher, hydrogen peroxide mediated oxidation of hydroxylamine may predominate resulting in a signal loss of smaller magnitudes. This study shows possible evidence of reactive oxygen species formation by low-dose beta-ray irradiation in a living animal.     

Chemicals in the Environment

Synthetic chemicals are now being incorporated into the earth''s ecosystems at a rate and in such manners as to alarm environmentalists. These chemicals are the uncontrolled waste products of a technological society. Most prominent among them at the present time are organochlorine, organomercurial and lead compounds. Persistent members of these groups disperse in water, air and animal tissues. Also they have the capacity for concentration in animal food chains, thereby reversing the historical expectation of the dilution and degradation of wastes.Examples of damage from environmental residues to man are at this stage speculative but documentation from effects on wild species is abundant. Already several species of birds seem on their way to extinction. These wild species constitute a gratuitous monitoring system which already has signaled clear warnings for the welfare of man.     

Comparison of various approaches to calculating the optimal hematocrit in vertebrates

An interesting problem in hemorheology is to calculate that volume fraction of erythrocytes (hematocrit) that is optimal for transporting a maximum amount of oxygen. If the hematocrit is too low, too few erythrocytes are present to transport oxygen. If it is too high, the blood is very viscous and cannot flow quickly, so that oxygen supply to the tissues is again reduced. These considerations are very important, since oxygen transport is an important factor for physical performance. Here, we derive theoretical optimal values of hematocrit in vertebrates and collect, from the literature, experimentally observed values for 57 animal species. It is an interesting question whether optimal hematocrit theory allows one to calculate hematocrit values that are in agreement with the observed values in various vertebrate species. For this, we first briefly review previous approaches in that theory. Then we check which empirical or theoretically derived formulas describing the dependence of viscosity on concentration in a suspension lead to the best agreement between the theoretical and observed values. We consider both spatially homogeneous and heterogeneous distributions of erythrocytes in the blood and also possible extensions, like the influence of defective erythrocytes and cases where some substances are transported in the plasma. By discussing the results, we critically assess the power and limitations of optimal hematocrit theory. One of our goals is to provide a systematic overview of different approaches in optimal hematocrit theory.     

Oxygen and carbon monoxide kinetics of Glycera dibranchiata monomeric hemoglobin.

Oxygen and carbon monoxide kinetics of Glycera dibranchiata monomeric hemoglobin have been studied using laser photolysis, air flash, and stopped flow techniques. The reactions of this hemoglobin with both ligands were found to be more rapid than the corresponding reactions involving myoglobin and were also biphasic in nature, the rate constants being approximately an order of magnitude different for the fast and slow phases in each case. No pH or hemoglobin concentration dependence of the pseudo-first order rate constants was apparent between pH 6 and 9 and in the concentration range of 1.25 to 40 muM heme. Both fast and slow pseudo-first order oxygen combination rate constants varied linearly with oxygen concentration between 16 and 1300 muM. A first order slow relaxation was also noted which was linearly dependent on heme concentration and inversely dependent on oxygen concentration. This reaction has been shown to be due to a replacement of oxygen by carbon monoxide. The presence of this reaction is a result of the high affinity of Glycera monomer for carbon monoxide as shown by the partition coefficient Mr = approximately 20,000 ana an equilibrium dissociation constant of the order L = 1.1 X 10(-9) M.     

Effect of low-frequency alternating magnetic fields on the rate of biochemical reactions proceeding with formation of reactive oxygen species

It is (theoretically) shown by an example of the reaction of a radical with an oxygen molecule that the alternating component of a combined weak magnetic field affects the rate constants of chemical reactions. The mechanism of transduction of a weak magnetic perturbation from the primary receptor of the field to experimentally observed biological effects is followed. It is stated that the external magnetic field alters the initial population of energy levels. The magnitude of these changes depends on the field parameters. The exposure to an alternating field with proper parameters can substantially increase the concentration of reactive oxygen species in biological systems. By controlling their concentration by means of weak magnetic field, it is possible to affect the key links of metabolism.     

Potential roles of myoglobin autoxidation in myocardial ischemia-reperfusion injury.

The source(s) of reactive partially reduced oxygen species associated with myocardial ischemia/reperfusion injury remain unclear and controversial. Myoglobin has not been viewed as a participant but is present in relatively high concentrations in heart muscle and, even under normal conditions, undergoes reactions that generate met (Fe3+) species and also superoxide, hydrogen peroxide, and other oxidants, albeit slowly. The degree to which the decrease in pH and the freeing of copper ions, as well as the variations in pO2 associated with ischemia and reperfusion increase the rates of such myoglobin reactions has been investigated. Solutions of extensively purified myoglobin from bovine heart in 50 mM sodium phosphate buffer were examined at 37 degrees C. Sufficiently marked rate increases were observed to indicate that reactions of myoglobin can indeed contribute substantially to the oxidant stress associated with ischemia/reperfusion injury in myocardial tissues. These findings provide additional targets for therapeutic interventions.     

Cardiac metabolism in high performance fish

In aerobic tissues, such as cardiac and skeletal muscle, short term increases in energy demand are met primarily by acute regulation of mitochondrial pathways. Chronic increases in time-average metabolic rate of an individual or tissue can lead to modest “physiological adaptations” that may result in increased metabolic capacities and more efficient energy production and utilization. These physiological adaptations differ fundamentally from those which alter metabolic rate acutely. Analysis of the metabolic strategies used by an individual to chronically elevate cardiac metabolic rates may help identify the components of cardiac metabolism which may be constrained or malleable over evolutionary time. While pronounced physiological differences in cardiac energy transduction are apparent across species, the evolutionary origins of such differences are difficult to assess. However, the functional consequences of such differences in homologous tissues across species can be discussed with more certainty. Both chronic hypermetabolic challenges and interspecies comparisons suggest highly oxidative tissues such as heart are restricted to strategies which a) elevate the functional mass b) make more efficient use of intracellular space devoted to mitochondria and c) shift toward more efficient metabolic fuels, primarily fatty acids if oxygen delivery is not a factor.     

Up-regulation of alpha1-microglobulin by hemoglobin and reactive oxygen species in hepatoma and blood cell lines

alpha(1)-Microglobulin is a 26-kDa glycoprotein synthesized in the liver, secreted to the blood, and rapidly distributed to the extravascular compartment of all tissues. Recent results show that alpha(1)-microglobulin has heme-binding and heme-degrading properties and it has been suggested that the protein is involved in the defense against oxidation by heme and reactive oxygen species. In the present study the influence of hemoglobin and reactive oxygen species (ROS) on the cellular expression of alpha(1)-microglobulin was investigated. Oxy- and methemoglobin, free heme, and Fenton reaction-induced hydroxyl radicals induced a dose-dependent up-regulation of alpha(1)-microglobulin on both mRNA and protein levels in hepatoma cells and an increased secretion of alpha(1)-microglobulin. The up-regulation was reversed by the addition of catalase and ascorbate, and by reacting hemoglobin with cyanide which prevents redox reactions. Furthermore, the blood cell lines U937 and K562 expressed alpha(1)-microglobulin at low levels, and this expression increased up to 11-fold by the addition of hemoglobin. These results suggest that alpha(1)-microglobulin expression is induced by ROS, arising from redox reactions of hemoglobin or from other sources and are consistent with the hypothesis that alpha(1)-microglobulin participates in the defense against oxidation by hemoglobin, heme, and reactive oxygen species.     

Effect of black snake (Walterinnesia aegyptia) venom on the respiratory activity of some tissues of the rabbit

Conclusion As the venom was found to activate all the tissues of the body and it has no specific effect on certain tissues, one can deduce that it must contain factors which affect the respiratory enzyme systems of the body stimulating them and causing increase in their oxygen consumption. As a result of this activation the animal when injected with the venom is subjected to both hypoglycaemia and oxygen lack.In the present experiments, one concentration of the venom was uesd, the effect of different concentrations, the nature of the active principle in the venom causing this activation, and the way of its action on the tissues are under investigation.     

Iron and its sensitive balance in the cell

Iron is vital in life because it is an important component of molecules that undergoes redox reactions or transport oxygen. However, the existence of two stable and inter-convertible forms of iron, iron(III) and iron(II), makes possible one electron being transferred to or captured from other species to form radicals. In particular, superoxide and hydroxyl radicals may be formed in these reactions, both with capacity of attacking other molecules. DNA is one important target and a vast literature exists showing that attack of hydroxyl radical to DNA leads to cell death cellular necrosis, apoptosis, mutation and malignant transformation. Therefore, a fine balance must exist at various levels of an organism to maintain iron concentration in a narrow range, above and below which deleterious effects of distinct nature occur. This review will deal with the formation of oxygen reactive species in iron participating reactions, defenses in the organism against these species, the different mechanisms of iron homeostasis and iron deficiency and iron overload related diseases.     

Lung oxygen consumption and mitochondria of alveolar epithelial and endothelial cells.

We examined oxygen consumption by lung slices and measured the volume density of mitochondria of granular pneumocytes, alveolar type I cells, and alveolar capillary endothelial cells in several species. We found that lung oxygen consumption (mu-1 02 times h-1 times mg DNA-1) varies inversely with the log of animal body weight and with the species alveolar diameter and directly with the species respiratory rate. The volume density of granular pneumocyte mitochondria show a direct linear correlation with the lung's oxygen consumption and the species respiratory rate, and an inverse linear correlation with the species alveolar diameter. The volume density of mitochondria in type I alveolar epithelial cells and capillary endothelial cells, considered together, did not differ in the two species studied (mouse and rat). We conclude that there are interspecies differences in oxygen consumption by lung cells and that granular pneumocytes contribute to these differences. We suggest that, at least part of these differences, are related to interspecies differences in surfactant secretory activity.     

The Significance of Oxygen Transport and of Metabolic Adaptation in Flood-Tolerance of Senecio Species

Experiments were designed to provide information about the physiological basis of flood-tolerance in Senecio species. The oxygen concentration in roots of S. jacobaea L., S. viscosus L. and S. vulgaris L. became almost zero after transplantation to a solution of low oxygen concentration, and it was concluded that the flood-sensitivity of these Senecio species could be due to insufficient oxygen transport from the shoots to the roots. The oxygen concentration in the roots of the flood-tolerant S. congestus (R.Br.) DC., growing in a solution of low oxygen tension, was almost sufficient to maintain oxygen utilization at the rate observed in roots of plants, grown in an air-saturated solution. Oxygen utilization by roots of the flood-tolerant S. aquaticus Hill, growing in a solution of low oxygen tension, was inhibited 50%. However, the oxygen concentration in the roots of this species remained high enough to maintain cytochrome oxidase activity and oxidative phosphorylation at the rate observed in roots from an air-saturated environment. The activity of a second (“alternative”) oxidase must have been drastically reduced. Alternative NADH-oxidizing enzymes, like nitrate reductase which was induced by anaerobiosis in roots of S. aquaticus, might replace the regulatory function of the alternative oxidase. — Thus, in S. aquaticus root porosity and root length contributed to the maintenance of an oxygen concentration which was sufficient for uninhibited cytochrome oxidase activity and oxidative phosphorylation rate in roots growing in a solution of low oxygen tension.     

Protein synthesis and specific dynamic action in crustaceans: effects of temperature

Temperature influences the specific dynamic action (SDA), or rise in oxygen uptake rate after feeding, in eurythermal and stenothermal crustaceans by changing the timing and the magnitude of the response. Intra-specific studies on the eurythermal crab, Carcinus maenas, show that a reduction in acclimation temperature is associated with a decrease in SDA magnitude, resulting from an increase in SDA duration but a decrease in peak factorial scope (the factorial rise in peak SDA over prefeeding values). Inter-specific feeding studies on stenothermal polar isopods revealed marked differences in SDA response between the Antarctic species, Glyptonotus antarcticus and the Arctic species, Saduria entomon. Compared to S. entomon held at 4 and 13 degrees C, the SDA response in G. antarcticus held at 1 degrees C was characterised by a lower absolute oxygen uptake rate at peak SDA and an extended SDA duration. At peak SDA, whole animal rates of protein synthesis increased in proportion to the postprandial increase in oxygen uptake rate in the Antarctic and the Arctic species. Rates of oxygen uptake plotted against whole animal rates of protein synthesis gave similar relationships in both isopod species, indicating similar costs of protein synthesis after a meal, despite their differences in SDA response and thermal habitat.     

EXPERIMENTS ON THE HERBICIDAL ACTION OF 1,1'-ETHYLENE-2,2'-DIPYRIDYLIUM DIBROMIDE

Light was shown to increase the rate of kill obtained with 1,1'-ethylene-2,2'-dipyridylium dibromide, without being essential for herbicidal action. The light effect, which was observed only in green tissues, increased with intensity up to about 10 k-lux, and was inhibited by N -(4-chlorophenyl)- N,N '-dimethyl urea or the absence of oxygen, but not by potassium cyanide or in a carbon-dioxide-free atmosphere. The herbicide was also shown to stimulate and inhibit respiration. The stimulation was transitory, and appeared to depend on a continuous supply to the tissues, while the inhibition did not.
These observations are interpreted, consistently with chemical evidence, to show that the reduction of the herbicide to its free radical form is an essential step in the sequence of toxic reactions. It is supposed that energy for reduction comes from the photolysis of water in the light, and from respiration in the dark. Once formed, the radical may initiate chain reactions in the presence of oxygen which end in the degradation of essential cytoplasmic components.     

Rate of generation of oxidative stress-related damage and animal longevity

Comparative studies about the relationship between endogenous antioxidant and pro-oxidant factors and maximum longevity of different animal species are reviewed. The majority of studies on antioxidant supplementation indicate that it can increase mean survival without changing maximum longevity. On the other hand, endogenous antioxidants are negatively correlated with maximum longevity. The same is true for the rates of mitochondrial oxygen radical generation, oxidative damage to mitochondrial DNA, and the degree of fatty acid unsaturation of cellular membranes in postmitotic tissues. The lower rate of mitochondrial oxygen radical generation of long-lived animals in relation to that of short-lived ones can be a primary cause of their slow aging rate. This is secondarily complemented in long-lived animals with low rates of lipid peroxidation due to their low degrees of fatty acid unsaturation. These two traits suggest that the rate of generation of endogenous oxidative damage determines, at least in part, the rate of aging in animals.     

植物抗氧化动态平衡研究进展

植物在生长发育的过程中会产生代谢副产物活性氧,其含量在植物生长过程中起双重作用。适量的活性氧可提高植物对逆境胁迫的耐受性,但是过量的活性氧会诱发氧化猝发反应,严重影响植物的生长发育。因此,提高植物的抗氧化能力对于提高植物的抗逆能力来说显得尤为重要,该方面的研究也成为近年来逆境生物学的一大热点。植物体为了应对逆境环境造成的活性氧动态失衡,进化出了含酶和非酶组分的抗氧化系统。本文主要介绍了参与高等植物活性氧代谢的相关物质,对近年来国内外报道的代谢途径进行了综述,为提高植物的抗逆能力提供参考依据。