Moderate hypoxia (Pio2, = 50 mmHg) caused tachycardia in carp, Cyprinus curpio Linnaeus, whereas ... more Moderate hypoxia (Pio2, = 50 mmHg) caused tachycardia in carp, Cyprinus curpio Linnaeus, whereas severe hypoxia (Pio2, from 30 to 5 mmHg) coincided with bradycardia accompanied by alterations of the waveforms of the electrocardiogram. A cardio respiratory synchronization developed during hypoxia and was maintained during bradycardia. The data raised the question: Does hypoxic bradycardia in part result from myocardial dysfunction or only from regulatory adjustments?
Ecologically distinct species of Hoplias were studied as to the cardio-respiratory responses to g... more Ecologically distinct species of Hoplias were studied as to the cardio-respiratory responses to graded hypoxia. Hoplias malabaricus maintained a constant oxygen uptake down to a PiO2 of 20 mmHg. Oxygen uptake declined markedly at lower PiO2 and, concomitantly, cardiac frequency decreased. Concurrent reductions of oxygen uptake and heart rate also occurred in Hoplias lacerdae but at the considerably higher PiO2 of 35 mmHg. These species-specific differences are consistent with the respective habitats: H. malabaricus occurs in stagnant hypoxic water, whereas H. lacerdae inhabits well-oxygenated rivers.
... SOPORATOR, A TROPICAL MARINE TELEOST FT RANTIN,' H. GESSER,= AL KALININ,' C... more ... SOPORATOR, A TROPICAL MARINE TELEOST FT RANTIN,' H. GESSER,= AL KALININ,' CDR GUERRA,' JC DE FREITAS' and WR ... Rua do Matao, Travessa 14, Cidade Universitaria, 05508900, Sao Paulo, SP, Brazil and Biology Department, Mount Allison University, Sackville ...
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2004
We examined the cardiorespiratory responses to 6 h of acute hypercarbia (1, 2.5, and 5% CO2) in i... more We examined the cardiorespiratory responses to 6 h of acute hypercarbia (1, 2.5, and 5% CO2) in intact and gill-denervated (bilateral denervation of branchial branches of cranial nerves IX and X) tambaqui, Colossoma macropomum. Intact fish exposed to 1 and 2.5% CO2 increased respiratory frequency (f R) and ventilation amplitude (V AMP) slowly over a 1- to 3-h period. Denervated fish did not show this response, suggesting that tambaqui possess receptors in the gills that will produce excitatory responses to low levels of hypercarbia (1 and 2.5% CO2) if the exposure is prolonged. The cardiac response to stimulation of these receptors with this level of CO2 was a tachycardia and not a bradycardia. During exposure to 5% CO2, intact fish increased f R and V AMP, and showed a pronounced bradycardia after 1 h. After 2 h, the heart rate (f H) started to increase, but returned to control values after 6 h. In denervated fish, the increase in f R was abolished. The slow increase in V AMP and the bradycardia were not abolished, suggesting that these changes arose from extra-branchial receptors. Neither intact nor denervated fish developed the swelling of the lower lip or performed aquatic surface respiration, even after 6 h, suggesting that these are unique responses to hypoxia and not hypercarbia.
Oreochromis niloticus were acclimated to 35 (group I) and 15°C (group II). In group I, the temper... more Oreochromis niloticus were acclimated to 35 (group I) and 15°C (group II). In group I, the temperature was decreased from 35 to 15°C, followed by return to 35°C, while in group II, the temperature rose to 35 and returned to 15°C. For each temperature, oxygen uptake (V̇O2), gill ventilation (V̇G) and electrocardiograms were obtained. Curves were identical and for the
The cardio-respiratory function, oxidative stress and fish antioxidants were analyzed in juvenile... more The cardio-respiratory function, oxidative stress and fish antioxidants were analyzed in juvenile Nile tilapia exposed for 96 h to a sublethal trichlorfon (TRC-Neguvon, Bayer) concentration of 0.5 mg L(-1). The exposure to TRC induced oxidative stress in the heart, as manifested by the glutathione S-transferase depletion and hydroperoxide elevation, and was the most sensitive organ when compared to the liver and gills, in which the antioxidant mechanisms against TRC exposure were sufficient to remove reactive oxygen species (ROS), preventing the increase of lipid peroxidation. TRC exposure also reduced O(2) uptake (V O(2)) and increased the critical oxygen tension (PcO(2)), reducing the species capacity to survive prolonged hypoxic conditions. The heart rate and force contraction were significantly impaired, making the heart the most sensitive organ when exposed to the TRC.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2006
In some neotropical environments, fishes often experience periods of poor food supply, especially... more In some neotropical environments, fishes often experience periods of poor food supply, especially due to extreme fluctuations in rainfall regime. The fish species that experience periods of drought such as the traíra Hoplias malabaricus (Bloch 1794), may stand up to long-term food deprivation. In this study, experiments were performed in order to determine the dynamic of utilization of endogenous reserves in this species during starvation. Adult traíra were both fasted for 30–240 days and re-fed for 30 days following 90 and 240 days of fasting. Glycogen and perivisceral fat were primary energy substrates consumed. During the first 30 days, fish consumed hepatic and muscular glycogen, without exhausting these reserves, and used lipids from perivisceral fat. Hepatic lipids were an important energy source during the first 60 days of starvation and perivisceral fat were consumed gradually, being exhausted after 180 days. Protein mobilization was noticeable after 60 days of fasting, and became the major energy source as the lipid reserves were decreased (between 90 and 180 days). Following the longest periods of food deprivation, fish had utilized hepatic glycogen again. Fish re-fed for 30 days after 90 and 240 days of fasting were able to recover hepatic glycogen stores, but not the other energy reserves.
Oxidative stress biomarkers, in vivo heart rate (f H), and contraction dynamics of ventricle stri... more Oxidative stress biomarkers, in vivo heart rate (f H), and contraction dynamics of ventricle strips of bullfrog (Lithobates catesbeiana) tadpoles were evaluated after 48 h of exposure to a sub-lethal concentration (1 ppm) of the herbicide Roundup Original® (glyphosate 41%). The activities of the antioxidant enzymes superoxide dismutase and catalase were increased in the liver and decreased in muscle, while oxidative damage to lipids increased above control values in both tissues, showing that the generation of reactive oxygen species and oxidative stress are involved in the toxicity induced by Roundup®. Additionally, tadpoles’ hyperactivity was associated with tachycardia in vivo, probably due to a stress-induced adrenergic stimulation. Ventricle strips of Roundup®-exposed tadpoles (R-group) presented a faster relaxation and also a higher cardiac pumping capacity at the in vivo contraction frequency, indicating that bullfrog tadpoles were able to perform cardiac mechanistic adjustments to face Roundup®-exposure. However, the lower maximal in vitro contraction frequency of the R-group could limit its in vivo cardiac performance, when the adrenergic-stimulation is present. The association between the high energetic cost to counteract the harmful effects of this herbicide and the induction of oxidative stress suggest that low and realistic concentrations of Roundup® can have an impact on tadpoles’ performance and success, jeopardizing their survival and/or population establishment.
Oxygen uptake and ventilatory responses to environmental hypoxia were assessed for two groups of ... more Oxygen uptake and ventilatory responses to environmental hypoxia were assessed for two groups of Hoplias malabaricus of nearly tenfold different body weights (mean weights, group I = 39 g; group II = 365 g). The main purpose of the study was to evaluate the relationships between body weight and the critical O2 tension (PCO2) for maintenance of normal resting O2 uptake. The smaller specimens had a threefold larger weight-specific O2 uptake compared to that of the larger specimens. Moreover, smaller size coincided with a higher PCO2, i.e., a more limited range for maintenance of O2 uptake during hypoxia. Likewise, at any inspired PO2 the weight-specific gill ventilation was largest for group I. This was most pronounced during severe hypoxia where both tidal volume and respiratory frequency increased markedly. In addition, the oxygen cost of breathing tended to be highest in the smaller individuals. The results open questions as to correlations between development, weight-dependent O2 demands, and tolerance to hypoxia on an intraspecific level.
Predominantly, Hoplias malabaricus inhabits stagnant O2 poor environments, whereas Hoplias lacerd... more Predominantly, Hoplias malabaricus inhabits stagnant O2 poor environments, whereas Hoplias lacerdae occurs in well-aerated streams. The present study evaluates the influence of mode of life on O2 uptake and gill ventilation in equally-sized (300 g) specimens of this genus at 25° C. Comparing the species, H. lacerdae was characterized by the highest O2 uptake and gill ventilation combined with a relatively higher cost of breathing and a lower O2 extraction. Both species substantially increased ventilation in response to hypoxia with the difference that H. malabaricus exclusively augmented tidal volume, whereas H. lacerdae also increased breathing frequency.
Adult traíra (Hoplias malabaricus) were submitted to different periods of food deprivation (from ... more Adult traíra (Hoplias malabaricus) were submitted to different periods of food deprivation (from 30 to 240 days) and refed for 30 days after 90 and 240 days of starvation. Stomach length remained constant during all the experimental period. However, the intestine length was significantly reduced after 30 days of food deprivation. Normal length was not recovered after refeeding. The number of pyloric caeca did not change significantly. Conversely, caeca thickness decreased after 150 days of starvation and their length decreased after 180 days. After refeeding, however, the pyloric caeca recovered original thickness. In fish refed after 240 days of starvation the length of these structures seemed to present compensatory growth, becoming longer than in the control group.
Moderate hypoxia (Pio2, = 50 mmHg) caused tachycardia in carp, Cyprinus curpio Linnaeus, whereas ... more Moderate hypoxia (Pio2, = 50 mmHg) caused tachycardia in carp, Cyprinus curpio Linnaeus, whereas severe hypoxia (Pio2, from 30 to 5 mmHg) coincided with bradycardia accompanied by alterations of the waveforms of the electrocardiogram. A cardio respiratory synchronization developed during hypoxia and was maintained during bradycardia. The data raised the question: Does hypoxic bradycardia in part result from myocardial dysfunction or only from regulatory adjustments?
Ecologically distinct species of Hoplias were studied as to the cardio-respiratory responses to g... more Ecologically distinct species of Hoplias were studied as to the cardio-respiratory responses to graded hypoxia. Hoplias malabaricus maintained a constant oxygen uptake down to a PiO2 of 20 mmHg. Oxygen uptake declined markedly at lower PiO2 and, concomitantly, cardiac frequency decreased. Concurrent reductions of oxygen uptake and heart rate also occurred in Hoplias lacerdae but at the considerably higher PiO2 of 35 mmHg. These species-specific differences are consistent with the respective habitats: H. malabaricus occurs in stagnant hypoxic water, whereas H. lacerdae inhabits well-oxygenated rivers.
... SOPORATOR, A TROPICAL MARINE TELEOST FT RANTIN,' H. GESSER,= AL KALININ,' C... more ... SOPORATOR, A TROPICAL MARINE TELEOST FT RANTIN,' H. GESSER,= AL KALININ,' CDR GUERRA,' JC DE FREITAS' and WR ... Rua do Matao, Travessa 14, Cidade Universitaria, 05508900, Sao Paulo, SP, Brazil and Biology Department, Mount Allison University, Sackville ...
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2004
We examined the cardiorespiratory responses to 6 h of acute hypercarbia (1, 2.5, and 5% CO2) in i... more We examined the cardiorespiratory responses to 6 h of acute hypercarbia (1, 2.5, and 5% CO2) in intact and gill-denervated (bilateral denervation of branchial branches of cranial nerves IX and X) tambaqui, Colossoma macropomum. Intact fish exposed to 1 and 2.5% CO2 increased respiratory frequency (f R) and ventilation amplitude (V AMP) slowly over a 1- to 3-h period. Denervated fish did not show this response, suggesting that tambaqui possess receptors in the gills that will produce excitatory responses to low levels of hypercarbia (1 and 2.5% CO2) if the exposure is prolonged. The cardiac response to stimulation of these receptors with this level of CO2 was a tachycardia and not a bradycardia. During exposure to 5% CO2, intact fish increased f R and V AMP, and showed a pronounced bradycardia after 1 h. After 2 h, the heart rate (f H) started to increase, but returned to control values after 6 h. In denervated fish, the increase in f R was abolished. The slow increase in V AMP and the bradycardia were not abolished, suggesting that these changes arose from extra-branchial receptors. Neither intact nor denervated fish developed the swelling of the lower lip or performed aquatic surface respiration, even after 6 h, suggesting that these are unique responses to hypoxia and not hypercarbia.
Oreochromis niloticus were acclimated to 35 (group I) and 15°C (group II). In group I, the temper... more Oreochromis niloticus were acclimated to 35 (group I) and 15°C (group II). In group I, the temperature was decreased from 35 to 15°C, followed by return to 35°C, while in group II, the temperature rose to 35 and returned to 15°C. For each temperature, oxygen uptake (V̇O2), gill ventilation (V̇G) and electrocardiograms were obtained. Curves were identical and for the
The cardio-respiratory function, oxidative stress and fish antioxidants were analyzed in juvenile... more The cardio-respiratory function, oxidative stress and fish antioxidants were analyzed in juvenile Nile tilapia exposed for 96 h to a sublethal trichlorfon (TRC-Neguvon, Bayer) concentration of 0.5 mg L(-1). The exposure to TRC induced oxidative stress in the heart, as manifested by the glutathione S-transferase depletion and hydroperoxide elevation, and was the most sensitive organ when compared to the liver and gills, in which the antioxidant mechanisms against TRC exposure were sufficient to remove reactive oxygen species (ROS), preventing the increase of lipid peroxidation. TRC exposure also reduced O(2) uptake (V O(2)) and increased the critical oxygen tension (PcO(2)), reducing the species capacity to survive prolonged hypoxic conditions. The heart rate and force contraction were significantly impaired, making the heart the most sensitive organ when exposed to the TRC.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2006
In some neotropical environments, fishes often experience periods of poor food supply, especially... more In some neotropical environments, fishes often experience periods of poor food supply, especially due to extreme fluctuations in rainfall regime. The fish species that experience periods of drought such as the traíra Hoplias malabaricus (Bloch 1794), may stand up to long-term food deprivation. In this study, experiments were performed in order to determine the dynamic of utilization of endogenous reserves in this species during starvation. Adult traíra were both fasted for 30–240 days and re-fed for 30 days following 90 and 240 days of fasting. Glycogen and perivisceral fat were primary energy substrates consumed. During the first 30 days, fish consumed hepatic and muscular glycogen, without exhausting these reserves, and used lipids from perivisceral fat. Hepatic lipids were an important energy source during the first 60 days of starvation and perivisceral fat were consumed gradually, being exhausted after 180 days. Protein mobilization was noticeable after 60 days of fasting, and became the major energy source as the lipid reserves were decreased (between 90 and 180 days). Following the longest periods of food deprivation, fish had utilized hepatic glycogen again. Fish re-fed for 30 days after 90 and 240 days of fasting were able to recover hepatic glycogen stores, but not the other energy reserves.
Oxidative stress biomarkers, in vivo heart rate (f H), and contraction dynamics of ventricle stri... more Oxidative stress biomarkers, in vivo heart rate (f H), and contraction dynamics of ventricle strips of bullfrog (Lithobates catesbeiana) tadpoles were evaluated after 48 h of exposure to a sub-lethal concentration (1 ppm) of the herbicide Roundup Original® (glyphosate 41%). The activities of the antioxidant enzymes superoxide dismutase and catalase were increased in the liver and decreased in muscle, while oxidative damage to lipids increased above control values in both tissues, showing that the generation of reactive oxygen species and oxidative stress are involved in the toxicity induced by Roundup®. Additionally, tadpoles’ hyperactivity was associated with tachycardia in vivo, probably due to a stress-induced adrenergic stimulation. Ventricle strips of Roundup®-exposed tadpoles (R-group) presented a faster relaxation and also a higher cardiac pumping capacity at the in vivo contraction frequency, indicating that bullfrog tadpoles were able to perform cardiac mechanistic adjustments to face Roundup®-exposure. However, the lower maximal in vitro contraction frequency of the R-group could limit its in vivo cardiac performance, when the adrenergic-stimulation is present. The association between the high energetic cost to counteract the harmful effects of this herbicide and the induction of oxidative stress suggest that low and realistic concentrations of Roundup® can have an impact on tadpoles’ performance and success, jeopardizing their survival and/or population establishment.
Oxygen uptake and ventilatory responses to environmental hypoxia were assessed for two groups of ... more Oxygen uptake and ventilatory responses to environmental hypoxia were assessed for two groups of Hoplias malabaricus of nearly tenfold different body weights (mean weights, group I = 39 g; group II = 365 g). The main purpose of the study was to evaluate the relationships between body weight and the critical O2 tension (PCO2) for maintenance of normal resting O2 uptake. The smaller specimens had a threefold larger weight-specific O2 uptake compared to that of the larger specimens. Moreover, smaller size coincided with a higher PCO2, i.e., a more limited range for maintenance of O2 uptake during hypoxia. Likewise, at any inspired PO2 the weight-specific gill ventilation was largest for group I. This was most pronounced during severe hypoxia where both tidal volume and respiratory frequency increased markedly. In addition, the oxygen cost of breathing tended to be highest in the smaller individuals. The results open questions as to correlations between development, weight-dependent O2 demands, and tolerance to hypoxia on an intraspecific level.
Predominantly, Hoplias malabaricus inhabits stagnant O2 poor environments, whereas Hoplias lacerd... more Predominantly, Hoplias malabaricus inhabits stagnant O2 poor environments, whereas Hoplias lacerdae occurs in well-aerated streams. The present study evaluates the influence of mode of life on O2 uptake and gill ventilation in equally-sized (300 g) specimens of this genus at 25° C. Comparing the species, H. lacerdae was characterized by the highest O2 uptake and gill ventilation combined with a relatively higher cost of breathing and a lower O2 extraction. Both species substantially increased ventilation in response to hypoxia with the difference that H. malabaricus exclusively augmented tidal volume, whereas H. lacerdae also increased breathing frequency.
Adult traíra (Hoplias malabaricus) were submitted to different periods of food deprivation (from ... more Adult traíra (Hoplias malabaricus) were submitted to different periods of food deprivation (from 30 to 240 days) and refed for 30 days after 90 and 240 days of starvation. Stomach length remained constant during all the experimental period. However, the intestine length was significantly reduced after 30 days of food deprivation. Normal length was not recovered after refeeding. The number of pyloric caeca did not change significantly. Conversely, caeca thickness decreased after 150 days of starvation and their length decreased after 180 days. After refeeding, however, the pyloric caeca recovered original thickness. In fish refed after 240 days of starvation the length of these structures seemed to present compensatory growth, becoming longer than in the control group.
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