RESUMO
Upwelling oceanographic phenomenon is associated with increased food availability, low seawater temperature and pH. These conditions could significantly affect food quality and, in consequence, the growth of marine species. One of the most important organismal traits is somatic growth, which is highly related to skeletal muscle. In fish, skeletal muscle growth is highly influenced by environmental factors (i.e. temperature and nutrient availability) that showed differences between upwelling and downwelling zones. Nevertheless, there are no available field studies regarding the impact of those conditions on fish muscle physiology. This work aimed to evaluate the muscle fibers size, protein content, gene expression of growth and atrophy-related genes in fish sampled from upwelling and downwelling zones. Seawater and fish food items (seaweeds) samples were collected from upwelling and downwelling zones to determine the habitat's physical-chemical variations and the abundance of biomolecules in seaweed tissue. In addition, white skeletal muscle samples were collected from an intertidal fish to analyze muscular histology, the growth pathways of protein kinase B and the extracellular signal-regulated kinase; and the gene expression of growth- (insulin-like growth factor 1 and myosin heavy-chain) and atrophy-related genes (F-box only protein 32 and muscle RING-finger protein-1). Upwelling zones revealed higher nutrients in seawater and higher protein content in seaweed than samples from downwelling zones. Moreover, fish from upwelling zones presented a greater size of muscle fibers and protein content compared to downwelling fish, associated with lower protein ubiquitination and gene expression of F-box only protein 32. Our data indicate an attenuated use of proteins as energy source in upwelling conditions favoring protein synthesis and muscle growth. This report shed lights of how oceanographic conditions may modulate food quality and fish muscle physiology in an integrated way, with high implications for marine conservation and sustainable fisheries management.
Assuntos
Ecossistema , Alga Marinha , Animais , Peixes , Água do Mar/química , Músculo Esquelético , Atrofia/metabolismoRESUMO
In the past two decades, Chile has developed intense mining activity in the Andes mountain range, whose altitude is over 4,000 meters above sea level. It is estimated that a workforce population of over 55,000 is exposed to high altitude hypobaric hypoxia. The miners work under shift systems which vary from 4 to 20 days at the worksite followed by rest days at sea level, in a cycle repeated for several years. This Chronic Intermittent Hypoxia (CIH) constitutes an unusual condition for workers involving a series of changes at the physiological, cellular and molecular levels attempting to compensate for the decrease in the environmental partial pressure of oxygen (PO2). The mine worker must become acclimatized to CIH, and consequently undergoes an acute acclimatization process when he reaches the worksite and an acute reverse process when he reaches sea level. We have observed that after a period of 3 to 8 years of CIH exposure workers acclimatize well, and evidence from our studies and those of others indicates that CIH induces acute and chronic multisystem adjustments which are effective in offsetting the reduced availability of oxygen at high altitudes. The aims of this review are to summarize findings of the physiological responses to CIH exposure, highlighting outstanding issues in the field.
Assuntos
Aclimatação/fisiologia , Altitude , Pressão Atmosférica , Mineração , Estresse Oxidativo/fisiologia , Medicina Selvagem/métodos , Antioxidantes/metabolismo , Chile , Humanos , Hipertensão Pulmonar/fisiopatologia , Policitemia/fisiopatologiaRESUMO
Reactive oxygen species such as superoxide anion radicals (O2 (-) ) and hydrogen peroxide (H2 O2 ) have for long time been recognized as undesirable by-products of the oxidative mitochondrial generation of adenosine triphosphate (ATP). Recently, these highly reactive species have been associated to important signaling pathways in diverse physiological conditions such as those activated in hypoxic microenvironments. The molecular response to hypoxia requires fast-acting mechanisms acting within a wide range of partial pressures of oxygen (O2 ). Intracellular O2 sensing is an evolutionary preserved feature, and the best characterized molecular responses to hypoxia are mediated through transcriptional activation. The transcription factor, hypoxia-inducible factor 1 (HIF-1), is a critical mediator of these adaptive responses, and its activation by hypoxia involves O2 -dependent posttranslational modifications and nuclear translocation. Through the induction of the expression of its target genes, HIF-1 coordinately regulates tissue O2 supply and energetic metabolism. Other transcription factors such as nuclear factor κB are also redox sensitive and are activated in pro-oxidant and hypoxic conditions. The purpose of this review is to summarize new developments in HIF-mediated O2 sensing mechanisms and their interactions with reactive oxygen species-generating pathways in normal and abnormal physiology.
Assuntos
Trifosfato de Adenosina/metabolismo , Metabolismo Energético/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Espécies Reativas de Oxigênio/metabolismo , Regulação da Expressão Gênica , Humanos , Peróxido de Hidrogênio/metabolismo , Hipóxia , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Mitocôndrias/metabolismo , Oxigênio/metabolismo , Transdução de SinaisRESUMO
In the past two decades, Chile has developed intense mining activity in the Andes mountain range, whose altitude is over 4,000 meters above sea level. It is estimated that a workforce population of over 55,000 is exposed to high altitude hypobaric hypoxia. The miners work under shift systems which vary from 4 to 20 days at the worksite followed by rest days at sea level, in a cycle repeated for several years. This Chronic Intermittent Hypoxia (CIH) constitutes an unusual condition for workers involving a series of changes at the physiological, cellular and molecular levels attempting to compensate for the decrease in the environmental partial pressure of oxygen (PO2). The mine worker must become acclimatized to CIH, and consequently undergoes an acute acclimatization process when he reaches the worksite and an acute reverse process when he reaches sea level. We have observed that after a period of 3 to 8 years of CIH exposure workers acclimatize well, and evidence from our studies and those of others indicates that CIH induces acute and chronic multisystem adjustments which are effective in offsetting the reduced availability of oxygen at high altitudes. The aims of this review are to summarize findings of the physiological responses to CIH exposure, highlighting outstanding issues in the field.
Assuntos
Humanos , Altitude , Pressão Atmosférica , Aclimatação/fisiologia , Mineração , Estresse Oxidativo/fisiologia , Medicina Selvagem/métodos , Antioxidantes/metabolismo , Chile , Hipertensão Pulmonar/fisiopatologia , Policitemia/fisiopatologiaRESUMO
Using an integrative approach at the whole animal, isolated vessels, and molecular levels, we tested the hypothesis that the llama, a species that undergoes pregnancy under the influence of the chronic hypoxia of high altitude, delivers offspring with an increased α-adrenergic peripheral vascular reactivity compared with neonates from lowland species. We studied the femoral vascular response to acute hypoxia in vivo, the reactivity of femoral vessels ex vivo, and the expression of femoral α(1)-adrenergic receptor subtypes using RT-PCR in vitro. The increase in femoral resistance during hypoxia was 3.6 times greater in newborn llamas than newborn sheep (P < 0.05). The sensitivity of the contractile response to noradrenaline (pD(2) = 5.18 ± 0.06 vs. 4.84 ± 0.05, P < 0.05) and the maximal response (R(max) = 101.3 ± 1.4 vs. 52.4 ± 1.4% K(+)(max), P < 0.05) and sensitivity (pD(2) = 5.47 ± 0.03 vs. 4.57 ± 0.05, P < 0.05) to phenylephrine were higher in femoral vessels from newborn llamas than newborn sheep. Competitive inhibition with prazosin of noradrenaline-induced contraction followed by Schild analysis showed higher affinity in the llama than the sheep (pA(2) = 10.08 ± 0.093 vs. 8.98 ± 0.263, respectively, P < 0.05), consistent with greater α(1B)-adrenergic receptor transcript expression observed in small femoral arteries from neonatal llama. The llama newborn demonstrates significantly greater α-adrenergic peripheral vascular reactivity compared with neonates from lowland species that could be partially explained by preferential expression of α(1B)-adrenergic receptor subtype.
Assuntos
Altitude , Animais Recém-Nascidos/fisiologia , Camelídeos Americanos/fisiologia , Artéria Femoral/fisiologia , Receptores Adrenérgicos alfa/fisiologia , Ovinos/fisiologia , Animais , Gasometria , Sistema Cardiovascular/fisiopatologia , Feminino , Concentração de Íons de Hidrogênio , Hipóxia/fisiopatologia , Modelos Animais , GravidezRESUMO
AIMS: To study the nitric oxide (NO) and carbon monoxide roles in the regulation of the pulmonary circulation in lowland and highland newborn sheep and llamas. METHODS AND RESULTS: We used neonatal sheep (Ovis aries) and llamas (Lama glama) whose gestation and delivery took place at low (580 m) or high (3600 m) altitude. In vivo, we measured the cardiopulmonary function basally and with a NO synthase (NOS) blockade and calculated the production of carbon monoxide by the lung. In vitro, we determined NOS and soluble guanylate cyclase (sGC) expression, NOS activity, and haemoxygenase (HO) expression in the lung. Pulmonary arterial pressure was elevated at high altitude in sheep but not in llamas. Sheep at high altitude relative to sea level had significantly greater total lung NOS activity and eNOS protein, but reduced sGC and HO expression and carbon monoxide production. In contrast, llamas showed no difference in NO function between altitudes, but a pronounced increase in pulmonary carbon monoxide production and HO expression at high altitude. CONCLUSIONS: In the llama, enhanced pulmonary carbon monoxide, rather than NO, protects against pulmonary hypertension in the newborn period at high altitude. This shift in pulmonary dilator strategy from NO to carbon monoxide has not been previously described, and it may give insight into new treatments for excessive pulmonary vasoconstriction.
Assuntos
Camelídeos Americanos/fisiologia , Monóxido de Carbono/fisiologia , Artéria Pulmonar/fisiologia , Vasodilatação , Altitude , Animais , Animais Recém-Nascidos , Pressão Sanguínea , Heme Oxigenase-1/análise , Óxido Nítrico/fisiologia , Oxigênio/sangue , OvinosRESUMO
Compared with lowland species, fetal life for mammalian species whose mothers live in high altitude is demanding. For instance, fetal llamas have to cope with the low fetal arterial PO2 of all species, but also the likely superimposition of hypoxia as a result of the decreased oxygen environment in which the mother lives in the Andean altiplano. When subjected to acute hypoxia the llama fetus responds with an intense peripheral vasoconstriction mediated by alpha-adrenergic mechanisms plus high plasma concentrations of catecholamines and neuropeptide Y (NPY). Endothelial factors such as NO and endothelin-1 also play a role in the regulation of local blood flows. Unlike fetuses of lowland species such as the sheep, the llama fetus shows a profound cerebral hypometabolic response to hypoxia, decreasing cerebral oxygen consumption, Na-K-ATPase activity and temperature, and resulting in an absence of seizures and apoptosis in neural cells. These strategies may have evolved to prevent hypoxic injury to the brain or other organs in the face of the persistent hypobaric hypoxia of life in the Andean altiplano.
Assuntos
Aclimatação/fisiologia , Altitude , Camelídeos Americanos/fisiologia , Desenvolvimento Fetal/fisiologia , Consumo de Oxigênio/fisiologia , Animais , Feminino , Hipóxia/sangue , Troca Materno-Fetal/fisiologia , Oxigênio/sangue , GravidezRESUMO
Perinatal exposure to chronic hypoxia induces sustained pulmonary hypertension and structural and functional changes in both pulmonary and systemic vascular beds. The aim of this study was to analyze consequences of high-altitude chronic hypoxia during gestation and early after birth in pulmonary and femoral vascular responses in newborn sheep. Lowland (LLNB; 580 m) and highland (HLNB; 3,600 m) newborn lambs were cathetherized under general anesthesia and submitted to acute sustained or stepwise hypoxic episodes. Contractile and dilator responses of isolated pulmonary and femoral small arteries were analyzed in a wire myograph. Under basal conditions, HLNB had a higher pulmonary arterial pressure (PAP; 20.2 +/- 2.4 vs. 13.6 +/- 0.5 mmHg, P < 0.05) and cardiac output (342 +/- 23 vs. 279 +/- 13 ml x min(-1) x kg(-1), P < 0.05) compared with LLNB. In small pulmonary arteries, HLNB showed greater contractile capacity and higher sensitivity to nitric oxide. In small femoral arteries, HLNB had lower maximal contraction than LLNB with higher maximal response and sensitivity to noradrenaline and phenylephrine. In acute superimposed hypoxia, HLNB reached higher PAP and femoral vascular resistance than LLNB. Graded hypoxia showed that average PAP was always higher in HLNB compared with LLNB at any Po2. Newborn lambs from pregnancies at high altitude have stronger pulmonary vascular responses to acute hypoxia associated with higher arterial contractile status. In addition, systemic vascular response to acute hypoxia is increased in high-altitude newborns, associated with higher arterial adrenergic responses. These responses determined in intrauterine life and early after birth could be adaptive to chronic hypoxia in the Andean altiplano.
Assuntos
Doença da Altitude/fisiopatologia , Altitude , Débito Cardíaco , Hipóxia Fetal/fisiopatologia , Consumo de Oxigênio , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Troca Gasosa Pulmonar , Adaptação Fisiológica , Animais , Animais Recém-Nascidos , Doença Crônica , Feminino , Gravidez , OvinosRESUMO
The pregnant llama (Lama glama) has walked for millions of years through the thin oxygen trail of the Andean altiplano. We hypothesize that a pool of genes has been selected in the llama that express efficient mechanisms to withstand this low-oxygen milieu. The llama fetus responds to acute hypoxia with an intense peripheral vasoconstriction that is not affected by bilateral section of the carotid sinus nerves. Moreover, the increase in fetal plasma concentrations of vasoconstrictor hormones, such as catecholamines, neuropeptide Y, and vasopressin, is much greater in the llama than in the sheep fetus. Furthermore, treatment of fetal llamas with an alpha-adrenergic antagonist abolished the peripheral vasoconstriction and resulted in fetal cardiovascular collapse and death during acute hypoxia, suggesting an indispensable upregulation of alpha-adrenergic mechanisms in this high altitude species. Local endothelial factors such as nitric oxide (NO) also play a key role in the regulation of fetal adrenal blood flow and in the adrenal secretion of catecholamines and cortisol. Interestingly, in contrast to the human or sheep fetus, the llama fetus showed a small increase in brain blood flow during acute hypoxia, with no increase in oxygen extraction across the brain, and thereby a decrease in brain oxygen consumption. These results suggest that the llama fetus responds to acute hypoxia with hypometabolism. How this reduction in metabolism is produced and how the cells are preserved during this condition remain to be elucidated.