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1.
Artigo em Inglês | MEDLINE | ID: mdl-28764991

RESUMO

Palaemonid shrimps exhibit numerous adaptive strategies, both in their life cycles and in biochemical, physiological, morphological and behavioral characteristics that reflect the wide variety of habitats in which they occur, including species that are of particular interest when analyzing adaptive osmoregulatory strategies. The present investigation evaluates the short- (hours) and long-term (days) time courses of responses of two palaemonid shrimps from separate yet overlapping osmotic niches, Palaemon northropi (marine) and Macrobrachium acanthurus (diadromous, fresh water), to differential salinity challenges at distinct levels of structural organization: (i) transcriptional, analyzing quantitative expression of gill mRNAs that encode for subunits of the Na+/K+-ATPase and V(H+)-ATPase ion transporters; (ii) translational, examining the kinetic behavior of gill Na+/K+-ATPase specific activity; and (iii) systemic, accompanying consequent adjustment of hemolymph osmolality. Palaemon northropi is an excellent hyper-hypo-osmoregulator in dilute and concentrated seawater, respectively. Macrobrachium acanthurus is a strong hyper-regulator in fresh water and hypo-regulates hemolymph osmolality and particularly [Cl-] in brackish water. Hemolymph hyper-regulation in fresh water (Macrobrachium acanthurus) and dilute seawater (Palaemon northropi) is underlain by augmented expression of both the gill Na+/K+-ATPase and V(H+)-ATPase. In contrast, in neither species is hypo-regulation sustained by changes in Na+/K+-ATPase mRNA expression levels, but rather by regulating enzyme specific activity. The integrated time course of Na+/K+- and V(H+)-ATPase expression and Na+/K+-ATPase activity in the gills of these palaemonid shrimps during acclimation to different salinities reveals versatility in their levels of regulation, and in the roles of these ion transporting pumps in sustaining processes of hyper- and hypo-osmotic and chloride regulation.


Assuntos
Concentração Osmolar , Palaemonidae/fisiologia , Biossíntese de Proteínas , Transcrição Gênica , Adenosina Trifosfatases/metabolismo , Animais , Brânquias/metabolismo , Reação em Cadeia da Polimerase
2.
Aquat Toxicol ; 170: 13-23, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26571214

RESUMO

We evaluate the effects of total ammonia nitrogen-N (TAN) exposure for 72h on (Na(+),K(+))- and V(H(+))-ATPase activities and on their subunit expressions in gills of the diadromous freshwater shrimp Macrobrachium amazonicum. Specific (Na(+),K(+))- and V(H(+))-ATPase activities increased roughly 1.5- to 2-fold, respectively, after exposure to 2.0mmolL(-1) TAN. Quantitative RT-PCR analyses revealed a 2.5-fold increase in V(H(+))-ATPase B subunit mRNA expression while (Na(+),K(+))-ATPase α-subunit expression was unchanged. Immunohistochemical analyses of the gill lamellae located the (Na(+),K(+))-ATPase throughout the intralamellar septal cells, independently of TAN concentration, while the V(H(+))-ATPase was located in both the apical pillar cell flanges and pillar cell bodies. Systemic stress parameters like total hemocyte count decreased by 30% after exposure to 2.0mmolL(-1) TAN, accompanied by increased activities of the oxidative stress enzymes superoxide dismutase, glutathione reductase and glucose-6-phosphate dehydrogenase in the gills. The stress responses of M. amazonicum to elevated TAN include increases in gill (Na(+),K(+))- and V(H(+))-ATPase activities that are accompanied by changes in oxidative stress enzyme activities, immune system effects and an increase in gill V(H(+))-ATPase gene expression. These findings likely underpin physiological effects in a crustacean like M. amazonicum that exploits multiple ecosystems during its life cycle, as well as under culture conditions that may significantly impact shrimp production by the aquaculture industry.


Assuntos
Amônia/toxicidade , Palaemonidae/efeitos dos fármacos , Rios , Trifosfato de Adenosina/farmacologia , Animais , Contagem de Células , Exposição Ambiental/análise , Brânquias/efeitos dos fármacos , Brânquias/enzimologia , Hemócitos/citologia , Hemócitos/efeitos dos fármacos , Cinética , Microssomos/efeitos dos fármacos , Microssomos/enzimologia , Oxirredução , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , ATPases Vacuolares Próton-Translocadoras/metabolismo , Poluentes Químicos da Água/toxicidade
3.
J Exp Biol ; 213(Pt 22): 3894-905, 2010 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-21037069

RESUMO

We evaluate osmotic and chloride (Cl(-)) regulatory capability in the diadromous shrimp Macrobrachium amazonicum, and the accompanying alterations in hemolymph osmolality and [Cl(-)], gill Na(+)/K(+)-ATPase activity, and expression of gill Na(+)/K(+)-ATPase α-subunit and V-ATPase B subunit mRNA during salinity (S) acclimation. We also characterize V-ATPase kinetics and the organization of transport-related membrane systems in the gill epithelium. Macrobrachium amazonicum strongly hyper-regulates hemolymph osmolality and [Cl(-)] in freshwater and in salinities up to 25‰ S. During a 10-day acclimation period to 25‰ S, hemolymph became isosmotic and hypo-chloremic after 5 days, [Cl(-)] alone remaining hyporegulated thereafter. Gill Na(+)/K(+)-ATPase α-subunit mRNA expression increased 6.5 times initial values after 1 h, then decreased to 3 to 4 times initial values by 24 h and to 1.5 times initial values after 10 days at 25‰ S. This increased expression was accompanied by a sharp decrease at 5 h then recovery of initial Na(+)/K(+)-ATPase activity within 24 h, declining again after 5 days, which suggests transient Cl(-) secretion. V-ATPase B-subunit mRNA expression increased 1.5-fold within 1 h, then reduced sharply to 0.3 times initial values by 5 h, and remained unchanged for the remainder of the 10-day period. V-ATPase activity dropped sharply and was negligible after a 10-day acclimation period to 21‰ S, revealing a marked downregulation of ion uptake mechanisms. The gill epithelium consists of thick, apical pillar cell flanges, the perikarya of which are coupled to an intralamellar septum. These two cell types respectively exhibit extensive apical evaginations and deep membrane invaginations, both of which are associated with numerous mitochondria, characterizing an ion transporting epithelium. These changes in Na(+)/K(+)- and V-ATPase activities and in mRNA expression during salinity acclimation appear to underpin ion uptake and Cl(-) secretion by the palaemonid shrimp gill.


Assuntos
Brânquias/metabolismo , Palaemonidae/genética , Palaemonidae/metabolismo , ATPase Trocadora de Sódio-Potássio/genética , ATPase Trocadora de Sódio-Potássio/metabolismo , ATPases Vacuolares Próton-Translocadoras/genética , ATPases Vacuolares Próton-Translocadoras/metabolismo , Aclimatação/genética , Aclimatação/fisiologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Cloretos/metabolismo , Primers do DNA/genética , Expressão Gênica , Brânquias/ultraestrutura , Hemolinfa/metabolismo , Microscopia Eletrônica de Transmissão , Dados de Sequência Molecular , Palaemonidae/anatomia & histologia , RNA Mensageiro/química , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Salinidade , Homologia de Sequência de Aminoácidos , ATPases Vacuolares Próton-Translocadoras/química , Equilíbrio Hidroeletrolítico/genética , Equilíbrio Hidroeletrolítico/fisiologia
4.
J Exp Zool A Ecol Genet Physiol ; 313(8): 508-23, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20878750

RESUMO

To better comprehend the structural and biochemical underpinnings of ion uptake across the gills of true freshwater crabs, we performed an ultrastructural, ultracytochemical and morphometric investigation, and kinetically characterized the Na(+),K(+)-ATPase, in posterior gill lamellae of Dilocarcinus pagei. Ultrastructurally, the lamellar epithelia are markedly asymmetrical: the thick, mushroom-shaped, proximal ionocytes contain elongate mitochondria (41% cell volume) associated with numerous (≈14 µm² membrane per µm³cytoplasm), deep invaginations that house the Na(+),K(+)-ATPase, revealed ultracytochemically. Their apical surface is amplified (7.5 µm² µm⁻²)) by stubby evaginations whose bases adjoin mitochondria below the subcuticular space. The apical membrane of the thin, distal ionocytes shows few evaginations (1.6 µm² µm⁻²), each surrounding a mitochondrion, abundant in the cytoplasm below the subcuticular space; basolateral invaginations and mitochondria are few. Fine basal cytoplasmic bridges project across the hemolymph space, penetrating into the thick ionocytes, suggesting ion movement between the epithelia. Microsomal Na(+),K(+)-ATPase specific activity resembles marine crabs but is ≈5-fold less than in species from fluctuating salinities, and freshwater shrimps, suggesting ion loss compensation by strategies other than Na(+) uptake. Enzyme apparent K(+) affinity attains 14-fold that of marine crabs, emphasizing the relevance of elevated K(+) affinity to the conquest of fresh water. Western blotting and biphasic ouabain inhibition disclose two α-subunit isoforms comprising distinct functional isoenzymes. While enzyme activity is not synergistically stimulated by NH(4) (+) and K(+), each increases affinity for the other, possibly assuring appropriate intracellular K(+) concentrations. These findings reveal specific structural and biochemical adaptations that may have allowed the establishment of the Brachyura in fresh water.


Assuntos
Braquiúros/metabolismo , Brânquias/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Animais , Western Blotting , Braquiúros/enzimologia , Braquiúros/ultraestrutura , Inibidores Enzimáticos/farmacologia , Epitélio/enzimologia , Epitélio/metabolismo , Epitélio/ultraestrutura , Água Doce , Brânquias/enzimologia , Brânquias/ultraestrutura , Transporte de Íons , Isoenzimas , Cinética , Microscopia Eletrônica de Transmissão , Mitocôndrias/enzimologia , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Ouabaína/farmacologia , ATPase Trocadora de Sódio-Potássio/antagonistas & inibidores
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