Changes in oxidative processes and components of the antioxidant system during tomato fruit ripening

Analysis of the oxidative processes taking place during fruit ripening in a salad tomato variety (Lycopersicon esculentum Mill. cv. Ailsa Craig) revealed changes in oxidative and antioxidative parameters. Hydrogen peroxide content, lipid peroxidation and protein oxidation were measured as indices of oxidative processes and all were found to increase at the breaker stage. The levels of the aqueous-phase antioxidants, glutathione and ascorbate, increased during the ripening process and these increases were associated with significant changes in their redox status, becoming more reduced as ripening progressed. Changes in the activities of superoxide dismutase, catalase and the enzymes involved in the ascorbate-glutathione cycle during ripening indicated that the antioxidative system plays a fundamental role in the ripening of tomato fruits.     

Age-related and organ-tissue characteristics of the function of the antioxidant system in white rats

Various components of antioxidant system (concentration of the reduced and oxidated forms of non-protein thiol compounds and ascorbic acid, the activity of glucose-6-phosphate dehydrogenase, glutathione reductase, catalase, superoxide dismutase) have been investigated in the blood, brain and liver of growing albino rats. It was found that the specific condition of this system depends on the age of animals and on the source of the system. Disorganization of the antioxidant system in senile animals was noted which results from intensification of free radical oxidation.     

Hypoxia and recovery perturb free radical processes and antioxidant potential in common carp (Cyprinus carpio) tissues

The effects of hypoxia exposure and subsequent normoxic recovery on the levels of lipid peroxides (LOOH), thiobarbituric acid reactive substances (TBARS), carbonylproteins, total glutathione levels, and the activities of six antioxidant enzymes were measured in brain, liver, kidney and skeletal muscle of the common carp Cyprinus carpio. Hypoxia exposure (25% of normal oxygen level) for 5h generally decreased the levels of oxidative damage products, but in liver TBARS content were elevated. Hypoxia stimulated increases in the activities of catalase (by 1.7-fold) and glutathione peroxidase (GPx) (by 1.3-fold) in brain supporting the idea that anticipatory preparation takes place in order to deal with the oxidative stress that will occur during reoxygenation. In liver, only GPx activity was reduced under hypoxia and reoxygenation while other enzymes were unaffected. Kidney showed decreased activity of GPx under aerobic recovery but superoxide dismutase (SOD) and catalase responded with sharp increases in activities. Skeletal muscle showed minor changes with a reduction in GPx activity under hypoxia exposure and an increase in SOD activity under recovery. Responses by antioxidant defenses in carp organs appear to include preparatory increases during hypoxia by some antioxidant enzymes in brain but a more direct response to oxidative insult during recovery appears to trigger enzyme responses in kidney and skeletal muscle.     

Extended nights, sleep loss, and recovery sleep in adolescents

In summary, this study of sleep in adolescents on an atypical schedule of 18-hour nights showed marked but not unanticipated differences in sleep as function of prior sleep deprivation. Unanticipated was the evidence of "recovery" sleep in adolescents who not only were not sleep deprived, but who had been on a sleep "optimizing" schedule and had been awake for only 10 hours. Extended sleep beginning about 4 hours in advance of entrained sleep onset phase was not associated with a return of SWS, a finding coinciding with predictions from studies in adults. Finally, this study provides an indication that the homeostatic sleep/wake process becomes less robust or sleep responsive during adolescent development, a phenomenon that may influence the delay of sleep common in adolescents.     

Antioxidant defense responses to sleep loss and sleep recovery

Sleep deprivation in humans is widely believed to impair health, and sleep is thought to have powerful restorative properties. The specific physical and biochemical factors and processes mediating these outcomes, however, are poorly elucidated. Sleep deprivation in the animal model produces a condition that eventually becomes highly lethal, lacks specific localization, and is reversible with sleep, implying mediation by a biochemical abnormality. Metabolic and immunological consequences of sleep deprivation point to a high potential for antioxidant imbalance. The objective, therefore, was to study glutathione content in the liver, heart, and lung, because glutathione is considered a major free radical scavenger that reflects the degree to which a tissue has been oxidatively challenged. We also investigated major enzymatic antioxidants, including catalase and glutathione peroxidase, as well as indexes of glutathione recycling. Catalase activity and glutathione content, which normally are tightly regulated, were both decreased in liver by 23-36% by 5 and 10 days of sleep deprivation. Such levels are associated with impaired health in other animal models of oxidative stress-associated disease. The decreases were accompanied by markers of generalized cell injury and absence of responses by the other enzymatic antioxidants under study. Enzymatic activities in the heart indicated an increased rate of oxidative pentose phosphate pathway activity during sleep deprivation. Recovery sleep normalized antioxidant content in liver and enhanced enzymatic antioxidant activities in both the liver and the heart. The present results link uncompensated oxidative stress to health effects induced by sleep deprivation and provide evidence that restoration of antioxidant balance is a property of recovery sleep.     

Exogenous trehalose differentially modulate antioxidant defense system in wheat callus during water deficit and subsequent recovery

To elucidate the resistance mechanism of exogenous trehalose on water deficit further, we investigated the effect of exogenous trehalose (50 mM) in wheat callus during water deficit and subsequent recovery. Enhanced levels of endogenous trehalose were detected in calli exposed to water deficit (W) and trehalose (T) medium, moreover, W plus T treatment showed an additive effect. Water deficit elevated the accumulation of ROS (hydrogen peroxide and formation rate of O ₂ ^.? ) and the endogenous MDA (Malonaldehyde), and resulted in the decrease of cell viability and biomass. Exogenous trehalose (TW) could alleviate the damage induced by water deficit, which was involved in the decrease of MDA and the generation of ROS, and resulted in elevating cell viability and biomass. Additionally, water deficit induced activity of antioxidative enzymes (Peroxidase, POD; Catalase, CAT; Glutathione reductase, GR). Content of AsA (Reduced ascorbate) was also increased by water deficit, while the content of GSH (Glutathione) showed the opposite effect. The combined effect of T and W treatment led to a higher activity of enzymatic antioxidants including SOD (Superoxide dismutase) and GR, and elevated the content of nonenzymatic antioxidants including AsA and GSH, but had a negative effect on enzymatic antioxidants including POD and CAT in comparison to the water deficit treatment alone. During recovery, calli treated by TW showed a greater reduction in ROS resulted in enhancing a higher cell viability and biomass. The scavenging mechanism of ROS by exogenous trehalose is mainly dependent on nonenzymatic antioxidants, especially AsA-GSH cycle, rather than enzymatic mechanisms and trehalose itself.     

Free-radical crosslinking of specific proteins alters the function of the egg extracellular matrix at fertilization

All animal embryos begin development by modifying the egg extracellular matrix. This protein-rich matrix protects against polyspermy, microbes and mechanical stress via enzyme-dependent transformations that alter the organization of its constituents. Using the sea urchin fertilization envelope, a well-defined extracellular structure formed within minutes of fertilization, we examine the mechanisms whereby limited permeability is established within this matrix. We find that the fertilization envelope acquires a barrier filtration of 40,000 daltons within minutes of insemination via a peroxidase-dependent mechanism, with dynamics that parallel requisite production of hydrogen peroxide by the zygote. To identify the molecular targets of this free-radical modification, we developed an in vivo technique to label and isolate the modified matrix components for mass spectrometry. This method revealed that four of the six major extracellular matrix components are selectively crosslinked, discriminating even sibling proteins from the same gene. Thus, specific free-radical chemistry is essential for establishing the embryonic microenvironment of early development.     

Effect of L-arginine on age-dependent changes of lipid peroxidation processes and antioxidant system activity in rat tissues

The antioxidant system and lipid peroxidation processes under the L-arginine injection were investigated in experiments on the myocardium, liver and blood of rats of different age. Lipid peroxidation processes intensification and antioxidant system enzymes activity decrease in old rats was shown. A pro- and antioxidant property changes which had different specificity and depended on the tissue were investigated. It was concluded that NO-ergic link activated antioxidant protection in old rats, activates antioxidant enzymes but does not influence the antioxidant properties of tissues of young and adult rats.     

The antioxidant function of metallothionein in the heart

The antioxidant function of metallothionein (MT) was first suggested in the early 1980s. Studies in vitro have revealed that MT reacts directly with reactive oxygen species, including superoxide and hydroxyl radicals and hydrogen peroxide. These reactions have never been demonstrated in intact animal studies. Nevertheless, both pharmacologic and genetic studies have shown that MT functions in protection against oxidative injury in vivo. In particular, the antioxidant function of MT in the heart has been explored extensively. The data gathered from recent studies using a cardiac-specific, MT-overexpressing transgenic mouse model have provided direct evidence to support this physiological role of MT. Under acute and chronic oxidative stress conditions such as treatment with doxorubicin, ischemia-reperfusion, and dietary copper restriction, MT-overexpressing transgenic mouse hearts displayed a marked resistance to the injurious consequences, including biochemical, pathological, and functional alterations. This protective action of MT correlates with its inhibition of reactive oxygen species-induced lipid peroxidation. A critical elucidation of the mechanism of action of MT as an antioxidant in vivo remains to be achieved. However, the combination of recent understanding of the zinc cluster structure of MT and novel molecular genetic approaches has provided the basis for further advancement in this field.     

On the function of sleep.

It is proposed that sleep serves the function of maintaining immobility in animals at times when immobility is an optimum behavioural survival strategem. Sleep is of great evolutionary age and is always carefully tailored to the life-style of each animal; abundant in some species and absent from others. The survival advantages conferred on an animal by the power of sleep to schedule behaviour effectively may justify its existence and persistence in the evolution of species.