Ion Transport and the Effects of Moulting in the Freshwater Crayfish Cherax destructor (Decapoda : Parastacidae)

1997 ◽  
Vol 45 (5) ◽  
pp. 539 ◽  
Author(s):  
Samad Zare ◽  
Peter Greenaway
Keyword(s):  
Atpase Activity ◽  
Calcium Flux ◽  
Freshwater Crayfish ◽  
Transport Mechanisms ◽  
Transport Capacity ◽  
Apparent Affinity ◽  
High Affinity ◽  
Cherax Destructor ◽  
Net Uptake ◽  
Moulting Cycle

Sodium and chloride were maintained in approximate equilibrium by intermoult Cherax destructor but net uptake from the water began the day before ecdysis and continued for several days in postmoult. Sodium transport in postmoult was four times as much as that during the intermoult. The apparent affinities of the Na and Cl transport mechanisms, 0.5 ± 0.12 and 0.3 ± 0.04 mmol L-1, respectively, were relatively low compared with other reported values for freshwater crustaceans. Calcium flux was negligible in intermoult animals and net efflux was evident in premoult as calcium resorbed from the skeleton was excreted. Following ecdysis, calcium net influx was high and persisted for many days into postmoult as the new exosketon was calcified. An apparent affinity (Km) of 0.3 ± 0.04 mmol L-1 Ca and a maximal net transport rate (Jmax) of 1.8 ± 0.29 µmol Ca g-1 h-1 were measured in postmoult animals. The gills contained a high-affinity Ca2+ ATPase (K m= 0.040.05 µmol L-1) with a low transport capacity (Jmax = 5.6 nmol mg-1 protein min -1) that did not change during the moulting cycle. It is suggested that postmoult Ca transport was facilitated by Na–Ca exchange driven by elevated branchial Na + K+ -ATPase activity.

scholarly journals Differential reactivity of lysine residues of the red blood cell Ca2+ pump involved in the E1-E2 conformational equilibrium

1991 ◽  
Vol 279 (1) ◽  
pp. 121-127 ◽  
Author(s):  
C Donnet ◽  
A J Caride ◽  
H N Fernández ◽  
J P F C Rossi
Keyword(s):  
Atpase Activity ◽  
Blood Cells ◽  
Conformational Equilibrium ◽  
The Other ◽  
Apparent Dissociation Constant ◽  
Apparent Affinity ◽  
High Affinity ◽  
Human Red Blood Cells ◽  
Differential Reactivity ◽  
Lysine Residues

1. Modification of Lys residues of the Ca(2+)-ATPase from human red blood cells with methyl acetimidate (MA) inhibited up to 70% of the Ca(2+)-ATPase activity. Furthermore, calmodulin-activated p-nitrophenyl phosphatase activity was fully inhibited at non-limiting concentrations of MA. 2. Treatment with MA inhibited phosphorylation of the Ca(2+)-ATPase. 3. When the enzyme was treated with 7.2 mM-MA in the presence of 100 microM-Ca2+, Ca(2+)-ATPase activity was decreased by 33%, whereas when the membranes were treated with MA in the presence of 50 microM-VO4(3-), this activity was decreased by only 8%. 4. When membranes were either proteolysed or preincubated with 1 mM-Ca2+, MA quickly inactivated the Ca(2+)-ATPase (k = 1.2 min-1). On the other hand, inactivation of membranes preincubated in the absence of Ca2+ and Mg2+ was slow (k = 0.08 min-1). 5. When the activity was measured in the absence of calmodulin, MA decreased to the same extent the values of KCa (the apparent dissociation constant for Ca2+) and Vmax, but in the presence of calmodulin the treatment decreased Vmax. only. 6. The results are consistent with the idea that MA reacts readily with the Ca(2+)-ATPase when the enzyme is in an E1 conformation, but not an E2 conformation, and that, reciprocally, treatment of the enzyme with MA shifts the enzyme to E1. 7. Provided that Ca2+ is present, ATP, with low apparent affinity (K0.5 = 195 microM), protected against inactivation by MA. However, MA treatment did not change the Km values of either the high-affinity or the low-affinity site for ATP, suggesting that protection results from a shift to a conformation in which the Lys residues are inaccessible to MA.

Phylogeny of the Australian freshwater crayfish Cherax destructor-complex (Decapoda : Parastacidae) inferred from four mitochondrial gene regions

2005 ◽  
Vol 19 (3) ◽  
pp. 209 ◽  
Author(s):  
Thuy T. T. Nguyen ◽  
Christopher M. Austin
Keyword(s):  
16S Rrna ◽  
Cytochrome Oxidase ◽  
Mitochondrial Gene ◽  
Large Subunit ◽  
Strong Support ◽  
Interspecific Variation ◽  
Rrna Gene ◽  
Freshwater Crayfish ◽  
Cherax Destructor ◽  
Australian Freshwater

The phylogenetic relationships among 32 individuals of Australian freshwater crayfish belonging to the Cherax destructor-complex were investigated using a dataset comprising sequences from four mitochondrial gene regions: the large subunit rRNA (16S rRNA), cytochrome oxidase I (COI), adenosine triphosphatase 6 (ATPase 6), and cytochrome oxidase III (COIII). A total of 1602 bp was obtained, and a combined analysis of the data produced a tree with strong support (bootstrap values 94–100%) for three divergent lineages, verifying the phylogenetic hypotheses of relationships within the C. destructor species-complex suggested in previous studies. Overall, sequences from the 16S rRNA gene showed the least variation compared to those generated from protein coding genes, which presented considerably greater levels of divergence. The level of divergence within C. destructor was found to be greater than that observed in other species of freshwater crayfish, but interspecific variation among species examined in the present study was similar to that reported previously.

Assessment of transport capacity of plasmalemmal Ca2+ pump in smooth muscle

1988 ◽  
Vol 255 (2) ◽  
pp. C226-C236 ◽  
Author(s):  
P. A. Lucchesi ◽  
R. A. Cooney ◽  
C. Mangsen-Baker ◽  
T. W. Honeyman ◽  
C. R. Scheid
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Reliable Estimate ◽  
Flux Rate ◽  
Transport Capacity ◽  
High Affinity ◽  
Transmembrane Flux ◽  
Inositol 1,4,5 Trisphosphate ◽  
Biochemical Studies

In resting smooth muscle, a variety of Ca2+ extrusion processes offset the inward Ca2+ leak. Biochemical studies suggest that the plasmalemmal Ca2+ pump dominates this process; however, this contention could not be proven without a reliable estimate of the inward Ca2+ leak that must be opposed by active transport. Recent studies using dispersed cells from the toad stomach provided such an estimate; thus we examined the capacity of the plasmalemmal Ca2+ pump in this tissue. Membranes were prepared using nitrogen cavitation, high-salt extraction, and flotation on discontinuous sucrose gradients. These membrane vesicles were enriched 16- to 24-fold for plasma membrane markers and exhibited an ATP-dependent uptake of 45Ca that was insensitive to azide or oxalate but sensitive to orthovanadate inhibition and calmodulin stimulation. 45Ca accumulated in the presence of ATP was rapidly released by Ca2+ ionophore but not by caffeine, inositol 1,4,5-trisphosphate, or GTP. Uptake exhibited a high affinity for Ca2+ (Km 0.2 microM) and a high-transport capacity, producing greater than 12,000-fold gradient for Ca2+ and a transmembrane flux rate greater than that observed in resting smooth muscle cells. Thus this enzyme is capable of maintaining steady-state Ca2+ levels in smooth muscle.

Basolateral membrane H-OH-HCO3 transport in the proximal tubule

1989 ◽  
Vol 256 (5) ◽  
pp. F751-F765
Author(s):  
P. A. Preisig ◽  
R. J. Alpern
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Respiratory Acidosis ◽  
Cell Voltage ◽  
Transport Mechanisms ◽  
Transport Capacity ◽  
Chronic Metabolic Acidosis

This review focuses on the basolateral membrane mechanisms of H-OH-HCO3 transport in the proximal tubule. The mechanism that has the greatest transport capacity and mediates most of transepithelial H-HCO3 transport is the electrogenic, Na-3HCO3 cotransporter. This transporter has been extensively characterized in the salamander, rat, and rabbit proximal tubule, and has now been found in a number of other epithelia that effect transepithelial NaHCO3 transport. Transporter rate is sensitive to intra- and extracellular [Na], intra- and extracellular [HCO3]/pH, and cell voltage. Adaptations in transporter activity have been demonstrated in chronic metabolic acidosis and alkalosis, chronic respiratory acidosis and alkalosis, and chronic hyperfiltration. In addition to the Na-3HCO3 cotransporter, the basolateral membrane possesses both Na-dependent and -independent Cl-HCO3 exchangers, a H leak, and in the S3 proximal tubule an Na-H antiporter. The role of these H-OH-HCO3 transport mechanisms in transcellular HCO3 and Cl absorption and pHi defense is discussed.

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