Gill Na(+),K(+)-ATPase and osmoregulation in the estuarine crab, Chasmagnathus granulata Dana, 1851 (Decapoda, Grapsidae)

Some kinetic properties of gill Na(+),K(+)-ATPase of the estuarine crab, Chasmagnathus granulata, and its involvement in osmotic adaptation were analyzed. Results suggest the presence of different Na(+),K(+)-ATPase isoforms in anterior and posterior gills. They have different affinities for Na(+), but similar affinity values for K(+), Mg(2+), ATP and similar enzymatic profiles as a function of temperature of the incubation medium. Ouabain concentrations which inhibit 50% of enzyme activity were also similar in the two types of gills. Enzyme activity and affinity for Na(+) are higher in posterior gills than in anterior ones. Furthermore, affinities of Na(+),K(+)-ATPase of posterior gills for Na(+) and K(+) were similar to or higher than those of gills or other structures involved in the osmoregulation in several euryaline decapod crustaceans. Acclimation to low salinity was related to a significant increase in the maximum Na(+), K(+)-ATPase activity, mainly in posterior gills. On the other hand, crab acclimation to high salinity induced a significant decrease in maximum enzyme activity, both in anterior and posterior gills. These results are in accordance to the osmoregulatory performance showed by C. granulata in diluted media, and point out the major role of posterior gills in the osmoregulation of this species.     

Copper effects on key metabolic enzymes and mitochondrial membrane potential in gills of the estuarine crab Neohelice granulata at different salinities

The estuarine crab Neohelice granulata was exposed (96h) to a sublethal copper concentration under two different physiological conditions (hyperosmoregulating crabs: 2ppt salinity, 1mg Cu/L; isosmotic crabs: 30ppt salinity, 5mg Cu/L). After exposure, gills (anterior and posterior) were dissected and activities of enzymes involved in glycolysis (hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase), Krebs cycle (citrate synthase), and mitochondrial electron transport chain (cytochrome c oxidase) were analyzed. Membrane potential of mitochondria isolated from anterior and posterior gill cells was also evaluated. In anterior gills of crabs acclimated to 2ppt salinity, copper exposure inhibited hexokinase, phosphofructokinase, pyruvate kinase, and citrate synthase activity, increased lactate dehydrogenase activity, and reduced the mitochondrial membrane potential. In posterior gills, copper inhibited hexokinase and pyruvate kinase activity, and increased citrate synthase activity. In anterior gills of crabs acclimated to 30ppt salinity, copper exposure inhibited phosphofructokinase and citrate synthase activity, and increased hexokinase activity. In posterior gills, copper inhibited phosphofructokinase and pyruvate kinase activity, and increased hexokinase and lactate dehydrogenase activity. Copper did not affect cytochrome c oxidase activity in either anterior or posterior gills of crabs acclimated to 2 and 30ppt salinity. These findings indicate that exposure to a sublethal copper concentration affects the activity of enzymes involved in glycolysis and Krebs cycle, especially in anterior (respiratory) gills of hyperosmoregulating crabs. Changes observed indicate a switch from aerobic to anaerobic metabolism, characterizing a situation of functional hypoxia. In this case, reduced mitochondrial membrane potential would suggest a decrease in ATP production. Although gills of isosmotic crabs were also affected by copper exposure, changes observed suggest no impact in the overall tissue ATP production. Also, findings suggest that copper exposure would stimulate the pentose phosphate pathway to support the antioxidant system requirements. Although N. granulata is very tolerant to copper, acute exposure to this metal can disrupt the energy balance by affecting biochemical systems involved in carbohydrate metabolism.     

Repeated Restraint Stress Induces Oxidative Damage in Rat Hippocampus

It has been shown that emotional stress may induce oxidative damage, and considerably change the balance between pro-oxidant and antioxidant factors in the brain. The aim of this study was to verify the effect of repeated restraint stress (RRS; 1 h/day during 40 days) on several parameters of oxidative stress in the hippocampus of adult Wistar rats. We evaluated the lipid peroxide levels (assessed by TBARS levels), the production of free radicals (evaluated by the DCF test), the total radical-trapping potential (TRAP) and the total antioxidant reactivity (TAR) levels, and antioxidant enzyme activities (SOD, GPx and CAT) in hippocampus of rats. The results showed that RRS induced an increase in TBARS levels and in GPx activity, while TAR was reduced. We concluded that RRS induces oxidative stress in the rat hippocampus, and that these alterations may contribute to the deleterious effects observed after prolonged stress.     

Branchial carbonic anhydrase (CA) of gills of Chasmagnathus granulata (Crustacea Decapoda)

The occurrence, localization and response to environmental salinity of carbonic anhydrase (CA) activity were studied in all of the gills of the euryhaline crab Chasmagnathus granulata from Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina). CA activity in all gills appeared to be dependent on salinity. The pattern of distribution of CA activity among gills was different upon transition of C. granulata from osmoionoconformity (more uniform distribution) to hyperregulation (highest activity in posterior gills 6-8). Upon abrupt salinity change a differential response of CA activity occurred among gills which could suggest a differential role of CA in ion transport process in different gills of this crab. Furthermore, CA activity in anterior and posterior gills was found in cytosolic and microsomal fractions, although highest activity appeared to be membrane-associated. Both pools of CA were also strongly influenced by salinity and very sensitive to sulfonamide acetazolamide. The results suggest a differential participation of branchial CA in ionoregulatory mechanisms of C. granulata.     

Effects of hypo- or hyperosmotic stress on lipid synthesis and gluconeogenic activity in tissues of the crab Neohelice granulata

The present study assesses the effects of osmotic stress on phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-bisphosphatase (FBPase) and glucose 6-phosphatase (G6Pase) activities and (14)C-total lipid synthesis from (14)C-glycine in the anterior and posterior gills, jaw muscle, and hepatopancreas of Neohelice granulata. In posterior gills, 24-h exposure to hyperosmotic stress increased PEPCK, FBPase and G6Pase activities. Increase in (14)C-lipid synthesis was associated to the decrease in PEPCK activity after 72-h exposure to hyperosmotic stress. Hypo-osmotic stress decreased PEPCK and G6Pase activities in posterior gills; however, (14)C-lipids increased after 72-h exposure to stress. In anterior gills, decreases in the G6Pase activity after 72-h of hyperosmotic stress and in (14)C-lipogenesis after 144-h were observed, while PEPCK activity increased after 144 h. Exposure to hypo-osmotic stress increased (14)C-lipid synthesis and PEPCK activity in anterior gills. Muscle G6Pase activity increased after 72-h exposure to hypo-osmotic stress; however, no significant change was observed in the lipogenesis. PEPCK decreased in muscle after 144-h exposure to hyperosmotic, coinciding with increased (14)C-lipid synthesis. In the hepatopancreas, a decrease in the (14)C-lipogenesis occurred after 24-h exposure to hyperosmotic stress, accompanied by increase in (14)C-lipid synthesis. Additionally, PEPCK activity returned to control levels. The hepatopancreatic lipogenesis from amino acids was not involved in the metabolic adjustment during hypo-osmotic stress. However, gluconeogenesis is one of the pathways involved in the adjustment of the intracellular concentration of nitrogenated compounds.     

Effects of photoperiod on gluconeogenic activity and total lipid concentration in organs of crabs, Neohelice granulata, challenged by salinity changes

Abstract. This study assessed the effects of long (LD) or short (SD) days on the conversion of [¹⁴C]-glycerol to [¹⁴C]-glucose and total lipid concentration in organs of the crab Neohelice granulata challenged by a change in external salinity. In the 20‰-acclimated crabs, no difference was found in the concentration of total lipids in the muscle, hepatopancreas, gills, or hemolymph between crabs acclimated to SD or LD. In SD crabs, the total lipid levels in the anterior and posterior gills did not decrease during an osmotic challenge. Only in the posterior gills did the total lipid levels decrease during acclimation to the 34‰ medium in LD animals. The total lipid concentration in the hemolymph decreased after 1 d of osmotic stress in SD, and increased in the hepatopancreas. In LD crabs, the lipid contents decreased gradually in muscle, and in the hepatopancreas on day 3 after transfer to 34‰ medium. In 20‰-acclimated crabs, the gluconeogenesis activity in both sets of gills was higher in LD than in SD animals. The gluconeogenesis capacity decreased in both sets of gills on the first day of osmotic challenge in SD, and in the posterior gills on the third day in LD crabs. These results suggest that in organs of N. granulata , photoperiod affects the metabolic adjustments to an osmotic challenge.     

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.     

Effect of microcystin on ion regulation and antioxidant system in gills of the estuarine crab Chasmagnathus granulatus (Decapoda,Grapsidae)

The objective of this work was to evaluate mechanisms of microcystin toxicity on crustacean species. Adult male crabs of Chasmagnathus granulatus (13.97+/-0.35 g) acclimated to low salinity (2 per thousand ) were injected with saline (control) or Microcystis aeruginosa aqueous extract (39.2 microg/l) at 24 h intervals for 48 h. After the exposure period, the anterior and posterior gills were dissected, measuring Na(+),K(+)-ATPase and glutathione-S-transferase (GST) activity. Total oxyradical scavenging capacity (TOSC) and lipid peroxides (LPO) content were also determined. Na(+),K(+)-ATPase activity in anterior gills was significantly lower in crabs injected with toxin than in control crabs, while no significant difference in the enzyme activity was detected in posterior gills. Both sodium and chloride concentration in the hemolymph were not affected by toxin exposure. Significant changes in GST activity were detected in posterior gills, with higher values being observed in the toxin-injected crabs. Crabs exposed to microcystin also showed a significant increase in the TOSC value against peroxyl radicals, for both anterior and posterior gills. Lipid peroxides level did not change in both gill types after exposure to the toxin. The increased levels of TOSC suggest the occurrence of a crab response against oxidative stress induced by toxin injection, which prevents lipid peroxidation.     

Salinity dependent Na+-K+ATPase activity in gills of the euryhaline crab Chasmagnathus granulata

The occurrence and response of Na+-K+ATPase specific activity to environmental salinity changes were studied in gill extracts of all of the gills of the euryhaline crab Chasmagnathus granulata from Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina). All of the gills exhibited a salinity dependent Na+-K+ATPase activity, although the pattern of response to environmental salinity was different among gills. As described in other euryhaline crabs highest Na+-K+ATPase specific activity was found in posterior gills (6 to 8), which, with exception of gill 6, increased upon acclimation to reduced salinity. However, a high increase of activity also occurred in anterior gills (1 to 5) in diluted media. Furthermore, both short and long term differential changes of Na+-K+ATPase activity occurred among the gills after the transfer of crabs to reduced salinity. The fact that variations of Na+-K+ATPase activity in the gills were concomitant with the transition from osmoconformity to ionoregulation suggests that this enzyme is a component of the branchial ionoregulatory mechanisms at the biochemical level in this crab.     

Lymphocyte enzymatic antioxidant responses to oxidative stress following high-intensity interval exercise

The purposes of this study were to 1) examine the immune and oxidative stress responses following high-intensity interval training (HIIT); 2) determine changes in antioxidant enzyme gene expression and enzyme activity in lymphocytes following HIIT; and 3) assess pre-HIIT, 3-h post-HIIT, and 24-h post-HIIT lymphocyte cell viability following hydrogen peroxide exposure in vitro. Eight recreationally active males completed three identical HIIT protocols. Blood samples were obtained at preexercise, immediately postexercise, 3 h postexercise, and 24 h postexercise. Total number of circulating leukocytes, lymphocytes, and neutrophils, as well as lymphocyte antioxidant enzyme activities, gene expression, cell viability (CV), and plasma thiobarbituric acid-reactive substance (TBARS) levels, were measured. Analytes were compared using a three (day) × four (time) ANOVA with repeated measures on both day and time. The a priori significance level for all analyses was P < 0.05. Significant increases in superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities were observed in lymphocytes following HIIT. No significant increases in lymphocyte SOD, CAT, or GPX gene expression were found. A significant increase in TBARS was found immediately post-HIIT on days 1 and 2. Lymphocyte CV in vitro significantly increased on days 2 and 3 compared with day 1. Additionally, there was a significant decrease in CV at 3 h compared with pre- and 24 h postexercise. These findings indicate lymphocytes respond to oxidative stress by increasing antioxidant enzyme activity. Additionally, HIIT causes oxidative stress but did not induce a significant postexercise lymphocytopenia. Analyses in vitro suggest that lymphocytes may become more resistant to subsequent episodes of oxidative stress. Furthermore, the analysis in vitro confirms that lymphocytes are more vulnerable to cytotoxic molecules during recovery from exercise.     

Antioxidant levels from different Antarctic fish caught around South Georgia Island and Shag Rocks

Antarctic fish have been isolated for over several million years in an environment with a very low and constant temperature and high oxygen concentration. In such conditions the oxidative stress might be an important factor affecting their metabolic adaptive strategies. Activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), vitamin E levels and total antioxidant capacity (TRAP) were measured in liver, gill, heart and muscle homogenates of red-blooded (Nototheniidae) and white-blooded (Channichthyidae) Antarctic fish. SOD activity was also measured in blood samples. Gill SOD activity was threefold higher in channichthyids than in nototheniids while CAT and GPx were significantly higher in the gills of channichthyids. The increased SOD activity of channichthyids probably reflects the large PO₂ gradient across their gills. The H₂O₂ produced seems to be preferentially eliminated by diffusion, according to the low levels of CAT and GPx found in the gills of these species. In contrast, blood SOD was about fivefold higher in the latter group, which possesses erythrocytes and thus a much higher oxygen-carrying capacity. CAT activity was always higher in nototheniids except in muscle. However, vitamin E did not show clear differences between families except for the pattern observed in muscle. The higher content of vitamin E in this tissue shown in channichthyids is related to the higher volume density of mitochondria reported for this group, since vitamin E is responsible for preventing membrane lipid peroxidation. Accordingly, TRAP (representative of hydrosoluble antioxidant capacity) was also higher in muscle of channichthyids. This is probably related to the role of ascorbic (a hydrosoluble compound) acid in regenerating vitamin E. Accepted: 4 September 1999     

Effects of extracts from the cyanobacterium Microcystis aeruginosa on ion regulation and gill Na+,K+-ATPase and K+-dependent phosphatase activities of the estuarine crab Chasmagnathus granulata (Decapoda,Grapsidae)

Recent discoveries indicate that microcystins affect enzymes, such as Na(+),K(+)-ATPase, involved in ion regulation of aquatic animals, through K(+)-dependent phosphatase inhibition. In vitro studies showed the inhibitory effect of Microcystis aeruginosa extracts on Na(+),K(+)-ATPase and K(+)-dependent phosphatase activities in gills of Chasmagnathus granulata (Decapoda, Grapsidae). Extracts of M. aeruginosa were prepared from lyophilized or cultures cells of the cyanobacterium. For lyophilized cells, IC(50) values were estimated as 0.46 microg/L (95% confidence interval [CI]=0.40-0.52 microg/L) and 1.31 microg/L (95% CI=1.14-1.51 microg/L) for Na(+),K(+)-ATPase and K(+)-dependent phosphatase, respectively. However, extracts prepared from cultured cells presented a much lower inhibitory potency against both enzymes. Gas chromatography revealed long-chain fatty acids in the lyophilized cell extracts, indicating that they are in part responsible for the enzyme inhibition. In vivo studies showed that the toxin inhibited Na(+),K(+)-ATPase activity in anterior gills, whereas an increased augmented activity of glutathione-S-transferase was observed in both kind of gills, indicating that the crab has increased its ability to conjugate the toxin. No significant differences in hemolymph sodium or chloride concentration were detected. This result is in agreement with the lack of effects of microcystin on Na(+),K(+)-ATPase activity of posterior (osmoregulating) gills.     

Does a relationship exist between the urate pool in the body and lipid peroxidation during exercise?

In this study, we investigated whether a relationship exists between the levels of urate in vivo and lipid peroxidation during exercise. Seven healthy male subjects performed exhaustive cycling exercise under the following three conditions. The levels of urate, thiobarbituric acid reactive substances (TBARS) and allantoin in plasma and urine were examined before exercise and during a 3h recovery period. (1) Benzbromarone administration experiment: benzbromarone (an uricosuric agent) was administered orally the day before exercise. (2) IMP administration experiment: inosine 5'-monophosphate disodium salt (a precursor of urate) was administered orally the day before exercise. (3) Control experiment: no test substance was administered. The main results obtained were as follows. Plasma urate levels and total peroxyl radical-trapping antioxidant parameter (TRAP) for deproteinized plasma in the resting period significantly decreased depending on the treatment, in the order of IMP> control > benzbromarone. A significant positive correlation was evident between plasma urate levels and TRAP values for deproteinized plasma. The increase in plasma levels of allantoin was observed only in the case of IMP treatment. A significant negative correlation between plasma levels of urate in the resting period and the amounts of urinary TBARS excreted during the recovery period was recognized. These results suggest that the urate level in vivo before exercise is a factor influencing lipid peroxidation during exhaustive exercise. Furthermore, these findings support the view that urate may serve as an important freeradical scavenger in vivo.     

Hymenolepis diminuta: experimental studies on the antioxidant system with short and long term infection periods in the rats

Many helminths cause long-lasting infections, living for several years in mammalian hosts reflecting a well balanced coexistence between host and parasite. There are many possible explanations as to how they can survive for lengthy periods. One possibility is their antioxidant systems, which can serve as defence mechanisms against host-generated oxygen radicals. Therefore, the aim of this experimental study was to examine the antioxidant system in Hymenolepisdiminuta during short (1.5 months young tapeworms) and long (1.5 years old tapeworms) term infection in the rat small intestine.The strobilae of H. diminuta tapeworms (14 young and three old) were divided into three pieces: the anterior part, containing the genital primordiae in the immature segments; the medial part, containing the early uterus in the mature, hermaphroditic proglottids and the terminal part with the mature gravid uterus in the gravid segments. Supernatants of these fragments were used for determination of markers of oxidative stress: concentration of thiobarbiturate reactive substances (TBARS) and of reduced glutathione (GSH), and the activity of antioxidant enzymes: superoxide dismutase (SOD1 and SOD2), catalase (CAT), glutathione peroxidases (GSHPxs), glutathione transferase (GST) and glutathione reductase (GSHR).The results indicated changes in levels of oxidative stress markers and antioxidant enzyme activity in both the young and old forms of H. diminuta. Relatively high activity of SOD (particularly in the anterior part of young tapeworms) was observed, as was increased activity of total GSHPx and a relatively high concentration of GSH in all parts of the tapeworms. These are caused by exposure to increased amount of ROS, which are produced during the inflammatory state. Due to the high activity of antioxidant enzymes, the anterior section of young and old tapeworms is equipped with a very effective antioxidant system. Old organisms also effectively resist oxidative stress due to reduced levels of lipid peroxidation and the high activity of GST, all of which suggest good adaptation to the hostile environment in the host’s intestine.     

Pretreatment with methylprednisolone protects the isolated rat heart against ischaemic and oxidative damage

In this study, we investigated whether a relationship exists between the levels of urate in vivo and lipid peroxidation during exercise. Seven healthy male subjects performed exhaustive cycling exercise under the following three conditions. The levels of urate, thiobarbituric acid reactive substances (TBARS) and allantoin in plasma and urine were examined before exercise and during a 3 h recovery period. (1) Benzbromarone administration experiment: benzbromarone (an uricosuric agent) was administered orally the day before exercise. (2) IMP administration experiment: inosine 5′-monophosphate disodium salt (a precursor of urate) was administered orally the day before exercise. (3) Control experiment: no test substance was administered. The main results obtained were as follows. Plasma urate levels and total peroxyl radical-trapping antioxidant parameter (TRAP) for deproteinized plasma in the resting period significantly decreased depending on the treatment, in the order of IMP > control > benzbromarone. A significant positive correlation was evident between plasma urate levels and TRAP values for deproteinized plasma. The increase in plasma levels of allantoin was observed only in the case of IMP treatment. A significant negative correlation between plasma levels of urate in the resting period and the amounts of urinary TBARS excreted during the recovery period was recognized. These results suggest that the urate level in vivo before exercise is a factor influencing lipid peroxidation during exhaustive exercise. Furthermore, these findings support the view that urate may serve as an important free-radical scavenger in vivo.     

Oxidative stress and antioxidant defenses in goldfish Carassius auratus during anoxia and reoxygenation

The purpose of this work was to evaluate the response of the antioxidant system of goldfish Carassius auratus during anoxia and reoxygenation. The exposure of goldfish to 8 h of anoxia induced a 14% decrease in total glutathione levels in the kidney, although the liver, brain, and muscle were unaffected. Anoxia also resulted in increases in the activities of liver catalase, brain glucose-6-phosphate dehydrogenase, and brain glutathione peroxidase (by 38, 26, and 79%, respectively) and a decrease in kidney catalase activity (by 17.5%). After 14 h of reoxygenation, liver catalase and brain glutathione peroxidase activities remained higher than controls and several other tissue-specific changes occurred in enzyme activities. Superoxide dismutase activity was unaffected by anoxia and reoxygenation. The levels of conjugated dienes, as indicators of lipid peroxidation, increased by 114% in liver after 1 h of reoxygenation and by 75% in brain after 14 h of reoxygenation. Lipid peroxidation was unaffected in kidney and depressed during anoxia and reoxygenation (by 44-61%) in muscle. Regulation of the goldfish antioxidant system during anoxia may constitute a biochemical mechanism that minimizes oxidative stress following reoxygenation.     

Enzymatic antioxidant system in the cestode Hymenolepis diminuta after chronic infection of the rat

Background

The aim of the present paper was to describe the enzymatic antioxidant system in Hymenolepis diminuta collected from rats exposed to chronic cestode invasion.

Methodology

We dissected different tissues of H. diminuta (immature proglottids, genital primordia, hermaphroditic proglottids, early uterus, and gravid uterus) and studied activity of: superoxide dismutases (SOD1 and SOD2), catalase (CAT), glutathione peroxidases (non-Se-dependent GSHPx and Se-dependent GSHPx), glutathione-S-transferase (GST) and glutathione reductase (GSHR), and oxidative stress markers ?? reduced glutathione (GSH), and the lipid peroxidation level (TBARS).

Results

We demonstrated changes in antioxidant enzyme activities and levels of oxidative stress markers in different tissues of the parasite. The levels of TBARS and GSH indicate that oxidative stress occurred in tissues located proximal to the intestine wall. Activity of SOD1 was high in all parts of H. diminuta, but the GST activity was the highest of all studied antioxidant enzymes. SOD2 activity differed significantly in various parts of H. diminuta. Significant differences were observed for nonSeGSHPx and activity of other GSH-dependent enzymes was generally similar in all the tissues.

Conclusions

Our results show that the enzymatic antioxidant system of H. diminuta, allows the parasite to adapt and live under conditions of chronic oxidative stress. It suggests an oxidative-antioxidative balance during interactions between parasite and host.     

Effect of aerial exposure on the antioxidant status in the subantarctic stone crab Paralomis granulosa (Decapoda: Anomura)

In Tierra del Fuego (Southern South America), the stone or false king crab, Paralomis granulosa represents one of the most important crab fisheries. After capture, animals are kept in baskets and exposed to dryness for several hours, when the water flow through the gills is interrupted. As a consequence a concomitant increase of reactive oxygen species begins, triggering oxidative stress. The aim of this study was to determine oxidative stress and antioxidant enzyme activities due to air exposure in different tissues of P. granulosa. Fifty crabs (carapace length >82 mm) were captured in Beagle Channel (54 degrees 50'S, 68 degrees 20'W) during winter 2004. Five groups of 10 crabs each were exposed to dryness at 6 degrees C for 0, 3, 6, 12 or 24 h, respectively. Activity of superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST) protein and lipid oxidation were measured in gills, muscle, hepatopancreas and haemolymph samples. Almost all analyzed tissues showed antioxidant enzymes activity, which varied with time of air exposure. The maximum enzyme activity was measured after 6 h of air exposure. Protein oxidation levels varied significantly in gills. Lipid peroxidation levels increased significantly in muscle and hepatopancreas. The critical time of air exposure probably occurs at 6 h. Thereafter animals were unable to induce the synthesis of antioxidant enzymes or proteins. This should be taken into account to minimize the stress generated by the commercial capture process.     

Uric acid deposits and estivation in the invasive apple-snail, Pomacea canaliculata

The physiological ability to estivate is relevant for the maintenance of population size in the invasive Pomacea canaliculata. However, tissue reoxygenation during arousal from estivation poses the problem of acute oxidative stress. Uric acid is a potent antioxidant in several systems and it is stored in specialized tissues of P. canaliculata. Changes in tissue concentration of thiobarbituric acid reactive substances (TBARS), uric acid and allantoin were measured during estivation and arousal in P. canaliculata. Both TBARS and uric acid increased two-fold during 45 days estivation, probably as a consequence of concomitant oxyradical production during uric acid synthesis by xanthine oxidase. However, after arousal was induced, uric acid and TBARS dropped to or near baseline levels within 20 min and remained low up to 24h after arousal induction, while the urate oxidation product allantoin continuously rose to a maximum at 24h after induction, indicating the participation of uric acid as an antioxidant during reoxygenation. Neither uric acid nor allantoin was detected in the excreta during this 24h period. Urate oxidase activity was also found in organs of active snails, but activity shut down during estivation and only a partial and sustained recovery was observed in the midgut gland.     

Vascular redox imbalance in rats submitted to chronic exercise

Exercise training has been used for treatment/prevention of many cardiovascular diseases, but the mechanisms need to be clarified. Thus, our aim was to compare oxidative stress parameters between rats submitted to a swimming training and sedentary rats (control). Twelve male rats were divided into two groups: control and exercise training. The exercise training had daily 1 h swimming sessions for 8 weeks and a load (5% of its body mass) was placed in rat's tail. Thereafter the animals were killed, aorta and heart were surgically removed and blood was collected. Body mass gain, thiobarbituric acid reactive species (TBARS), carbonyl content, total reactive antioxidant potential (TRAP), total antioxidant reactivity (TAR), superoxide dismutase (SOD) activity and catalase (CAT) activity were evaluted. The trained rats showed a lower body mass gain and no modifications on heart. An increased SOD activity was observed on aorta after the training, but no changes were seen for CAT activity, which led to an increased SOD/CAT ratio. The arterial TBARS was also increased for trained rats. The decrease in TRAP in exercise training was the single modification on plasma. Our findings suggest that the increased SOD activity could play a role in vascular adaptations to exercise training. Copyright © 2010 John Wiley & Sons, Ltd.