RESUMO
Aquatic animals often display physiological adjustments to improve their biological performance and hydrosaline balance in saline environments. In addition to energetic costs associated with osmoregulation, oxidative stress, and the activation of the antioxidant system are common cellular responses to salt stress in many species, but the knowledge of osmoregulation-linked oxidative homeostasis in amphibians is scarce. Here we studied the biochemical responses and oxidative responses of Xenopus laevis females exposed for 40 days to two contrasting salinities: hypo-osmotic (150 mOsm·kg-1 ·H2 O NaCl, HYPO group) and hyper-osmotic environments (340 mOsm·kg-1 ·H2 O NaCl, HYPER group). We found an increase of plasma osmolality and plasma urea concentration in the animals incubated in the HYPER treatment. Increases in electrolyte concentration were paralleled with an increase of both citrate synthase and cytochrome c oxidase activities in liver and heart. Interestingly, HYPO group had higher catabolic activity of the skin and liver total antioxidant capacity (TAC), compared with animals from the HYPER group. Moreover, there was an inverse relationship between liver TAC and plasma osmolality; and with the metabolic enzymes from liver. These findings suggest that salinity induces changes in urea metabolism and specific activity of metabolic enzymes, which appears to be tissue-dependent in X. laevis. Contrary to our expectations, we also found a moderate change in the oxidative status as revealed by the increase in TAC activity in the animals acclimated to low salinity medium, but constancy in the lipid peroxidation of membranes.
Assuntos
Espécies Introduzidas , Osmorregulação/fisiologia , Estresse Oxidativo/fisiologia , Salinidade , Xenopus laevis , Aclimatação , Animais , Peso Corporal , FemininoRESUMO
Life in saline environments represents a major physiological challenge for birds, particularly for passerines that lack nasal salt glands and hence are forced to live in environments that do not contain salty resources. Increased energy costs associated with increased salt intake, which in turn increases the production of reactive oxygen species, is likely a major selection pressure for why passerines are largely absent from brackish and marine environments. Here we measured basal metabolic rates (BMR) and oxidative status of free-ranging individuals of three species of Cinclodes, a group of passerine birds that inhabit marine and freshwater habitats in Chile. We used a combination of carbon, nitrogen, and hydrogen isotope data from metabolically active (blood) and inert (feathers) tissues to estimate seasonal changes in marine resource use and infer altitudinal migration. Contrary to our expectations, the consumption of marine resources did not result in higher BMR values and higher oxidative stress. Specifically, the marine specialist C. nigrofumosus had lower BMR than the other two species (C. fuscus and C. oustaleti), which seasonally switch between terrestrial and marine resources. C. fuscus had significantly higher total antioxidant capacity than the other two species (C. nigrofumosus and C. oustaleti) that consumed a relatively high proportion of marine resources. Nearly all studies examining the effects of salt consumption have focused on intraspecific acclimation via controlled experiments in the laboratory. The mixed results obtained from field- and lab-based studies reflect our poor understanding of the mechanistic link among hydric-salt balance, BMR, and oxidative stress in birds.
Assuntos
Passeriformes , Animais , Metabolismo Basal , Chile , Ecossistema , Estresse OxidativoRESUMO
The purpose of this paper is to explore the firing rate of the caudal photoreceptors (CPRs) from the sixth abdominal ganglion of the crayfish Cherax quadricarinatus. We use simultaneous extracellular recordings on left and right CPR in the isolated ganglion (n = 10). The CPRs showed an asymmetry in the spontaneous activity and light-induced response. In darkness, we observed one subgroup (70%) in which the left CPR (CPR-L) and right CPR (CPR-R) had spontaneous firing rates with a median of 18 impulses/s and 6 impulses/s, respectively. In another subgroup (20%), the CPR-R had a median of 15 impulses/s and the CPR-L had 8 impulses/s. In both groups, the differences were significant. Furthermore, the CPRs showed an asymmetrical photoresponse induced by a pulse of white light (700 Lux, 4 s). In one subgroup (30%), the CPR-L showed light-induced activity with a median of 73%, (interquartile range, IQR = 51), while the CPR-R had a median of 41%, (IQR = 47). In another subgroup (70%), the CPR-R showed a median of 56%, (IQR = 51) and the CPR-L had a median of 42%, (IQR = 46). In both groups, the differences were significant. Moreover, we observed a differential effect of temperature on CPR activity. These results suggest a functional asymmetry in both activities from left and right CPRs. These CPR activity fluctuations may modulate the processing of information by the nervous system.
Assuntos
Potenciais de Ação/fisiologia , Astacoidea/fisiologia , Lateralidade Funcional/fisiologia , Gânglios dos Invertebrados/fisiologia , Transdução de Sinal Luminoso/fisiologia , Células Fotorreceptoras de Invertebrados/fisiologia , Potenciais de Ação/efeitos da radiação , Animais , Astacoidea/efeitos da radiação , Relação Dose-Resposta à Radiação , Lateralidade Funcional/efeitos da radiação , Gânglios dos Invertebrados/efeitos da radiação , Luz , Transdução de Sinal Luminoso/efeitos da radiação , Estimulação Luminosa/métodos , Células Fotorreceptoras de Invertebrados/efeitos da radiação , Doses de RadiaçãoRESUMO
Many physiological adjustments occur in response to salt intake in several marine taxa, which manifest at different scales from changes in the concentration of individual molecules to physical traits of whole organisms. Little is known about the influence of salinity on the distribution, physiological performance, and ecology of passerines; specifically, the impact of drinking water salinity on the oxidative status of birds has been largely ignored. In this study, we evaluated whether experimental variations in the salt intake of a widely-distributed passerine (Zontotrichia capensis) could generate differences in basal (BMR) and maximum metabolic rates (Msum), as well as affect metabolic enzyme activity and oxidative status. We measured rates of energy expenditure of birds after 30-d acclimation to drink salt (SW) or tap (fresh) water (TW) and assessed changes in the activity of mitochondrial enzymes (cytochrome c oxidase and citrate synthase) in skeletal muscle, heart, and kidney. Finally, we evaluated the oxidative status of bird tissues by means of total antioxidant capacity (TAC) and superoxide dismutase activities and lipid oxidative damage (Malondialdehyde, MDA). The results revealed a significant increase in BMR but not Msum, which resulted in a reduction in factorial aerobic scope in SW- vs. TW-acclimated birds. These changes were paralleled with increased kidney and intestine masses and catabolic activities in tissues, especially in pectoralis muscle. We also found that TAC and MDA concentrations were ~120 and ~400% higher, respectively in the liver of animals acclimated to the SW- vs. TW-treatment. Our study is the first to document changes in the oxidative status in birds that persistently drink saltwater, and shows that they undergo several physiological adjustments that range that range in scale from biochemical capacities (e.g., TAC and MDA) to whole organism traits (e.g., metabolic rates). We propose that the physiological changes observed in Z. capensis acclimated to saltwater could be common phenomena in birds and likely explain selection of prey containing little salt and habitats associated with low salinity.
RESUMO
Effects of pesticides on non-target organisms have been studied in several taxa at different levels of biological organization, from enzymatic to behavioral responses. Although the physiological responses may be associated with higher energy costs, little is known about metabolic costs of pesticide detoxification in birds. To fill this gap, we exposed orally (diet) 15-d old Coturnix coturnix japonica individuals to sublethal doses of chlorpyrifos (10 and 20 mg active ingredient/kg dry food) for four weeks. Carboxylesterase (CbE), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities were periodically measured in multiple tissues along with measurements of resting (RMR) and maximum metabolic rates (M(sum)). Furthermore, glucuronic acid in bird excreta was also assessed at the end of the trial. While CbE and BChE activities were inhibited by chlorpyrifos in all tissues during the third and fourth weeks following pesticide treatment, AChE activity was unaffected. At this sampling times, both M(sum) and RMR expansibility decreased. These results suggest that the exposure to chlorpyrifos caused a negative effect on aerobic performance. Additionally, excretion rate of glucuronic acid was up to 2-fold higher in the 20-mg/kg group than in the control and 10-mg/kg chlorpyrifos groups. The inhibition of CbE and BChE activities corroborated that these enzymes are fulfilling their role as bioscavengers for organophosphate pesticides, decreasing its concentration and thus protecting AChE activity against inhibition by chlorpyrifos.
Assuntos
Clorpirifos/toxicidade , Coturnix/metabolismo , Ecotoxicologia , Metabolismo Energético/efeitos dos fármacos , Poluentes Ambientais/toxicidade , Animais , Butirilcolinesterase/metabolismo , Carboxilesterase/metabolismo , Colinesterases/metabolismo , Fatores de TempoRESUMO
Inhibition of blood esterase activities by organophosphate (OP) pesticides has been used as a sensitive biomarker in birds. Furthermore, compared to mammalian vertebrates, less is known about the role of these enzyme activities in the digestive tracts of non-mammalian vertebrates, as well as the environmental and biological stressors that contribute to their natural variation. To fill this gap, we examined butyrylcholinesterase (BChE) and carboxylesterases (CbE) in the digestive tracts of sixteen passerine species from central Chile. Whole intestine enzyme activities were positively and significantly correlated with body mass. After correcting for body mass and phylogenetic effect, we found only a marginal effect of dietary category on BChE activity, but a positive and significant association between the percentage of dietary nitrogen and the mass-corrected lipase activity. Our results suggest that observed differences may be due to the dietary composition in the case of lipases and BChE, and also we predict that all model species belonging to the same order will probably respond differently to pesticide exposure, in light of differences in the activity levels of esterase activities.
Assuntos
Aves/fisiologia , Monitoramento Ambiental , Poluentes Ambientais/toxicidade , Animais , Biomarcadores/sangue , Aves/classificação , Butirilcolinesterase , Chile , Esterases , Inseticidas/toxicidade , Intestinos , Compostos Organofosforados/toxicidade , Praguicidas/toxicidade , Filogenia , Especificidade da EspécieRESUMO
Exposure and effect assessment of organophosphate (OP) pesticides generally involves the use of cholinesterase (ChE) inhibition. In earthworm, this enzyme activity is often measured in homogenates from the whole organism. Here we examine the tissue-specific response of ChE and carboxylesterase (CE) activities in Lumbricus terrestris experimentally exposed to chlorpyrifos-spiked field soils. Esterases were measured in different gut segments and in the seminal vesicles of earthworms following acute exposure (2 d) to the OP and during 35d of a recovery period. We found that inhibition of both esterase activities was dependent on the tissue. Cholinesterase activity decreased in the pharynx, crop, foregut and seminal vesicles in a concentration-dependent way, whereas CE activity (4-nitrophenyl valerate) was strongly inhibited in these tissues. Gizzard CE activity was not inhibited by the OP, even an increase of enzyme activity was evident during the recovery period. These results suggest that both esterases should be determined jointly in selected tissues of earthworms. Moreover, the high levels of gut CE activity and its inhibition and recovery dynamic following OP exposure suggest that this esterase could play an important role as an enzymatic barrier against OP uptake from the ingested contaminated soil.
Assuntos
Clorpirifos/toxicidade , Inibidores da Colinesterase/toxicidade , Inseticidas/toxicidade , Oligoquetos/efeitos dos fármacos , Oligoquetos/enzimologia , Animais , Relação Dose-Resposta a Droga , Trato Gastrointestinal/efeitos dos fármacos , Trato Gastrointestinal/enzimologia , Cinética , Masculino , Glândulas Seminais/efeitos dos fármacos , Glândulas Seminais/enzimologia , Testes de Toxicidade AgudaRESUMO
To test the hypothesis that eutrophication ponds modulate some aspects of the health responses and survival of anuran tadpoles, we conducted field experiments using Scinax nasicus as sentinel organism to evaluate the quality of two ponds filled with agricultural runoff in a dominant agricultural landscape of Mid-Western Entre Ríos Province (Argentina). The survival, growth and development rates, erythrocytes nuclei aberrations, parasite infection, and brain cholinesterase activity were monitored after seven days of exposure. Water samples from the ponds were also analyzed for physico-chemical variables and levels of pesticide residues. Residues of organochlorine pesticides and nutrients were higher in the agricultural ponds with respect to those from the control pond. We suggest that the interactions among washed-off nutrients and pesticides from agriculture and environmental factors account for deleterious effects on S. nasicus survival, growth and development rate, thereby compromising their health status. These effects can lead, in turn, to an increase in tadpole vulnerability to opportunistic parasites, erythrocytes nuclei aberrations or hemolysis.
Assuntos
Agricultura , Anuros/fisiologia , Eutrofização , Poluentes Químicos da Água/toxicidade , Animais , Anuros/sangue , Anuros/parasitologia , Argentina , Biomarcadores/metabolismo , Encéfalo/enzimologia , Colinesterases/metabolismo , Monitoramento Ambiental , Monitoramento Epidemiológico , Eritrócitos/efeitos dos fármacos , Eritrócitos/patologia , Larva/efeitos dos fármacos , Larva/parasitologia , Larva/fisiologia , Testes para Micronúcleos , Doenças Parasitárias em Animais/epidemiologia , Doenças Parasitárias em Animais/metabolismo , Resíduos de Praguicidas/análise , Resíduos de Praguicidas/toxicidade , Praguicidas/análise , Praguicidas/toxicidade , Movimentos da Água , Poluentes Químicos da Água/análiseRESUMO
Semi-volatile organochlorine compounds (OC) were analyzed in remote Andean soils and lake sediments. The sampling sites covered a wide latitudinal gradient from 18 degrees S to 46 degrees S along Chile and an altitudinal gradient (10-4500 m). The concentrations were in the order of background levels, involving absence of major pollution sources in the high mountain areas. Significant correlations were found between log-transformed concentrations of hexachlorobenzene, alpha- and gamma-hexachlorocyclohexane in soils and total organic content (TOC). In addition, TOC-normalized concentrations of the most volatile OC showed a significant linear dependence with air temperature. This good agreement points to temperature as a significant factor for the retention of long range transported OC in remote ecosystems such as the Andean mountains, although other variables should not be totally excluded. The highest concentrations of OCs were achieved in the sites located at highest altitude and lowest temperature of the dataset.
Assuntos
Monitoramento Ambiental/métodos , Sedimentos Geológicos/análise , Hidrocarbonetos Clorados/análise , Poluentes do Solo/análise , Altitude , Chile , Água Doce , TemperaturaRESUMO
Organochlorine compounds (OC), namely pentachlorobenzene, hexachlorobenzene, hexachlorocyclohexanes, polychlorobiphenyls (PCBs), and DDTs, have been studied in mosses distributed over three altitude gradients of the Andean mountains in Chile at 18 degrees S (3200-4500 m above sea level), 37 degrees S (345-1330 m), and 45 degrees S (10-700 m). The observed concentrations range among the lowestvalues ever reported in remote sites, but they are still higher than those found in previously studied Antarctic areas. The log transformed OC concentrations show a significant linear dependence from reciprocal of temperature independently of the origin of the compounds, e.g. industrial, agricultural, or mixed. In the case of the more volatile OC these correlations involve variance percentages higher than 50%. This good agreement gives further ground to temperature as the driving factor for the retention of long-range transported OC in remote ecosystems, including those in the southern hemisphere such as the Andean mountains. In the context of the samples selected for study, the temperature dependences in the areas of similar latitude are related to altitude. Thus, all OC in the highest altitude gradient (18 degrees S) and most compounds in the other two profiles (37 degrees S and 45 degrees S) exhibit higher concentrations with decreasing annual average temperature and thus increase with elevation above sea level. However, theoretical examination of the exponential equation relating OC concentrations to reciprocal of absolute temperatures shows that besides the temperature differences between highest and lowest elevation, the most relevant factor determining the OC concentration gradients is the lowest temperature value of each altitudinal series. That is, the point at highest elevation.