Understanding Na uptake mechanisms in vertebrates has been a research priority since vertebrate ancestors were thought to originate from hyperosmotic marine habitats to the hypoosmotic freshwater system. Given the evolutionary success of osmoregulator teleosts, these freshwater conquerors from the marine habitats are reasonably considered to develop the traits of absorbing Na from the Na-poor circumstances for ionic homeostasis. However, in teleosts, the loss of epithelial Na channel (ENaC) has long been a mystery and an issue under debate in the evolution of vertebrates.
View Article and Find Full Text PDFRelatively warm environments caused by global warming enhance the productivity of aquaculture activities in tropical/subtropical regions; however, the intermittent cold stress (ICS) caused by negative Arctic Oscillation can still result in major economic losses. In contrast to endotherms, ectothermic fishes experience ambient temperature as an abiotic factor that is central to performance and survival. Therefore, the occurrence of extreme temperatures caused by climate change has ignited a surge of scientific interest from ecologists, economists and physiologists.
View Article and Find Full Text PDFThe neuroplastic mechanisms in the fish brain that underlie sex reversal remain unknown. Gonadotropin-releasing hormone 3 (GnRH3) neurons control male reproductive behaviours in Mozambique tilapia and show sexual dimorphism, with males having a greater number of GnRH3 neurons. Treatment with androgens such as 11-ketotestosterone (KT), but not 17β-estradiol, increases the number of GnRH3 neurons in mature females to a level similar to that observed in mature males.
View Article and Find Full Text PDFThe body temperatures of teleost species fluctuate following changes in the aquatic environment. As such, decreased water temperature lowers the rates of biochemical reactions and affects many physiological processes, including active transport-dependent ion absorption. Previous studies have focused on the impacts of low temperature on the plasma ion concentrations or membrane transporters in fishes.
View Article and Find Full Text PDFThe unusual rate and extent of environmental changes due to human activities may exceed the capacity of marine organisms to deal with this phenomenon. The identification of physiological systems that set the tolerance limits and their potential for phenotypic buffering in the most vulnerable ontogenetic stages become increasingly important to make large-scale projections. Here, we demonstrate that the differential sensitivity of non-calcifying Ambulacraria (echinoderms and hemichordates) larvae towards simulated ocean acidification is dictated by the physiology of their digestive systems.
View Article and Find Full Text PDFIn contrast to terrestrial animals most aquatic species can be characterized by relatively higher blood [Formula: see text] concentrations despite its potential toxicity to the central nervous system. Although many aquatic species excrete [Formula: see text] via specialized epithelia little information is available regarding the mechanistic basis for NH/[Formula: see text] homeostasis in molluscs. Using perfused gills of we studied acid-base regulation and ammonia excretion pathways in this cephalopod species.
View Article and Find Full Text PDFHydrothermal vent organisms have evolved physiological adaptations to cope with extreme abiotic conditions including temperature and pH. To date, acid-base regulatory abilities of vent organisms are poorly investigated, although this physiological feature is essential for survival in low pH environments. We report the acid-base regulatory mechanisms of a hydrothermal vent crab, Xenograpsus testudinatus, endemic to highly acidic shallow-water vent habitats with average environment pH-values ranging between 5.
View Article and Find Full Text PDFBackground: Regulation of pH homeostasis is a central feature of all animals to cope with acid-base disturbances caused by respiratory CO2. Although a large body of knowledge is available for vertebrate and mammalian pH regulatory systems, the mechanisms of pH regulation in marine invertebrates remain largely unexplored.
Results: We used squid (Sepioteuthis lessoniana), which are known as powerful acid-base regulators to investigate the pH regulatory machinery with a special focus on proton secretion pathways during environmental hypercapnia.
Am J Physiol Regul Integr Comp Physiol
February 2011
The hexose supply and subsequent metabolism are crucial for the operations of the iono- and osmoregulatory mechanisms in fish, but how hexose is transported and supplied to cells of the ionoregulatory epithelia is unknown. Three zebrafish glucose transporters (zGLUTs), zGLUT1a, -13.1, and -6, were previously found to respectively be expressed by ionocytes (Na(+)-K(+)-ATPase-rich, Na(+)-Cl(-) cotransporter-expressing, and H(+)-ATPase-rich cells) and adjacent energy-depositing cells [glycogen-rich (GR) cells] in zebrafish skin and gills (32).
View Article and Find Full Text PDFIt has been known for more than three decades that outward Kir currents (I(K1)) increase with increasing extracellular K(+) concentration ([K(+)](o)). Although this increase in I(K1) can have significant impacts under pathophysiological cardiac conditions, where [K(+)](o) can be as high as 18 mm and thus predispose the heart to re-entrant ventricular arrhythmias, the underlying mechanism has remained unclear. Here, we show that the steep [K(+)](o) dependence of Kir2.
View Article and Find Full Text PDFHeme oxygenase-1 (HO-1), a stress-inducible enzyme anchored in the endoplasmic reticulum (ER) by a single transmembrane segment (TMS) located at the C terminus, interacts with NADPH cytochrome P450 reductase and biliverdin reductase to catalyze heme degradation to biliverdin and its metabolite, bilirubin. Previous studies suggested that HO-1 functions as a monomer. Using chemical cross-linking, co-immunoprecipitation, and fluorescence resonance energy transfer (FRET) experiments, here we showed that HO-1 forms dimers/oligomers in the ER.
View Article and Find Full Text PDFAm J Physiol Regul Integr Comp Physiol
August 2009
Glucose, a carbohydrate metabolite, plays a major role in the energy supply for fish iono- and osmoregulation, and the way that glucose is transported in ionocytes is a critical process related to the functional operations of ionocytes. Eighteen members of glucose transporters (GLUTs, SLC2A) were cloned and identified from zebrafish. Previously, Na(+),K(+)-ATPase-rich (NaR), Na(+)-Cl(-) cotransporter-expressing (NCC), H(+)-ATPase-rich (HR), and glycogen-rich (GR) cells have been identified to be responsible for Ca(2+) uptake, Cl(-) uptake, Na(+) uptake, and the energy deposition, respectively, in zebrafish skin/gills.
View Article and Find Full Text PDFKir1.1 channels are important in maintaining K+ homeostasis in the kidney. Intracellular acidification reversibly closes the Kir1.
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