Calcium Regulation in the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)

1972 ◽  
Vol 57 (2) ◽  
pp. 471-487
Author(s):  
PETET GREENAWAY
Keyword(s):  
Active Transport ◽  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Regulation ◽  
Freshwater Crayfish ◽  
Calcium Balance ◽  
Electrochemical Gradient ◽  
Austropotamobius Pallipes ◽  
Calcium Loss ◽  
Normal Calcium

1. Calcium regulation in normal and in calcium-depleted specimens of Austropotamobius pallipes in the intermoult condition has been investigated. 2. Calcium turnover was very low and the normal calcium balance was negative for much of the winter intermoult stage. 3. Calcium uptake was against a small electrochemical gradient, at least part of the influx occurring by active transport. 4. Most of the calcium loss occurred across the gills, and the urine contribution was small. 5. Calcium-depleted animals showed only a small fall in haemolymph calcium concentration and calcium uptake was not significantly increased by depletion.

Calcium Balance at the Postmoult Stage of the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)

1974 ◽  
Vol 61 (1) ◽  
pp. 35-45
Author(s):  
PETER GREENAWAY
Keyword(s):  
Calcium Uptake ◽  
Maximum Level ◽  
Freshwater Crayfish ◽  
Calcium Balance ◽  
Electrochemical Gradient ◽  
Uptake Mechanism ◽  
Austropotamobius Pallipes ◽  
Ionised Calcium ◽  
Net Uptake ◽  
Level 2

Net uptake of calcium by Austropotamobius begins 15-30 min after the moult and rapidly reaches a maximum level (2 µmoles/g/h at 10°C) which is maintained throughout stages A and B. At stage C1 the rate of net uptake falls sharply to a lower level which is gradually reduced until equilibrium is reached at C4. The uptake mechanism is near-saturated at 0.4 mM-Ca/l and half-saturated at 0.13 mM-Ca/l. In the absence of external HCO3- net uptake is reduced. Calcium uptake is against an electrochemical gradient. The concentration of ionised calcium in the haemolymph remains unchanged during the intermoult cycle.

Calcium Balance at the Premoult Stage of the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)

1974 ◽  
Vol 61 (1) ◽  
pp. 27-34
Author(s):  
PETER GREENAWAY
Keyword(s):  
Body Surface ◽  
The Body ◽  
Ionized Calcium ◽  
Freshwater Crayfish ◽  
Calcium Balance ◽  
Electrochemical Gradient ◽  
Austropotamobius Pallipes

The premoult stage in Austropotamobius pallipes is characterized by a net loss of calcium which increases from D0 to a maximum of 0.83 µmoles/g/h at D4. The concentration of ionized calcium in the haemolymph does not increase during the premoult stage although there is an increase in complexed calcium. The electrochemical gradient across the body surface is similar to that at the intermoult stage and favours calcium outflux. Possible routes for calcium net loss have been discussed and a mechanism for elimination of calcium has been proposed.

Calcium Regulation in the Freshwater Mollusc Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)

1971 ◽  
Vol 54 (3) ◽  
pp. 609-620 ◽  
Author(s):  
PETER GREENAWAY
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Regulation ◽  
Fresh Tissue ◽  
Blood Calcium ◽  
Freshwater Mollusc ◽  
Net Uptake ◽  
Tissue Calcium ◽  
Limnaea Stagnalis ◽  
Calcium Loss

1. Three major calcium compartments have been identified in L. stagnalis: the shell, the blood and the fresh tissues. 2. The distribution of 45Ca, absorbed from the medium, in the tissues of L. stagnalis has been studied. Absorbed calcium appears first in the blood and then in the shell and other tissues. 3. 30% of the total fresh tissue calcium and about 20% of mantle calcium exchanges with blood calcium. A continual exchange between shell and blood calcium occurs. 4. During net calcium loss from L. stagnalis a net movement of calcium from shell to blood occurs at a rate similar to the rate of net loss. During net calcium uptake, the reverse movement from blood to shell at a rate similar to the rate of net uptake occurs. 5. A simple mechanism which might account for the control of blood calcium concentration has been proposed.

Characterization of branchial transepithelial calcium fluxes in freshwater trout, Salmo gairdneri

1988 ◽  
Vol 254 (3) ◽  
pp. R491-R498 ◽  
Author(s):  
S. F. Perry ◽  
G. Flik
Keyword(s):  
Active Transport ◽  
Calcium Uptake ◽  
Chloride Cells ◽  
Salmo Gairdneri ◽  
Apical Surface ◽  
Electrochemical Gradient ◽  
Plasma Membrane Vesicles ◽  
Pavement Cells ◽  
Calcium Fluxes

Experiments were performed to determine whether gill transepithelial calcium fluxes in the freshwater trout (Salmo gairdneri) are passive or require active transport and to characterize the mechanisms involved. A comparison of the in vivo unidirectional flux ratios with the flux ratios calculated according to the transepithelial electrochemical gradients revealed that calcium uptake from the water requires active transport of Ca2+. The inhibition of calcium uptake by external lanthanum, the specific deposition of lanthanum on the apical surface of chloride cells, and the favorable electrochemical gradient for calcium across the apical membrane suggest that the initial step in branchial calcium uptake is the passive entry of calcium into the cytosol of chloride cells through apical channels that are permeable to calcium. The study of gill basolateral plasma membrane vesicles demonstrated the existence of a high-affinity calmodulin-dependent calcium-transporting system [half-maximal Ca2+ concentration (K0.5) = 160 nM, Vmax = 1.86 nmol.min-1.mg protein-1]. This system actively transports calcium from the cytosol of chloride cells into the plasma against a sizeable electrochemical gradient, thereby completing the transepithelial uptake of calcium. Calcium efflux occurs passively through paracellular pathways between chloride cells and adjacent pavement cells or between neighboring pavement cells.

Transepithelial movement of calcium in crustaceans

1993 ◽  
Vol 184 (1) ◽  
pp. 1-16 ◽  
Author(s):  
D. S. Neufeld ◽  
J. N. Cameron
Keyword(s):  
Active Transport ◽  
Calcium Concentration ◽  
Cellular Mechanism ◽  
The Body ◽  
High Rate ◽  
Calcium Flux ◽  
Moult Cycle ◽  
Electrochemical Gradient ◽  
Low Concentration ◽  
Low Concentrations

The regulation of calcium in most crustaceans is especially challenging owing to the highly mineralized cuticle that must be recalcified after each moult, a process that often occurs in environments with low concentrations of calcium. The gill and carapace epithelia separate the major calcium-containing compartments of the body and therefore see large changes in the rate of calcium flux through the moult cycle. Large changes in the ultrastructure of these cells do not, however, correlate well with the periods of calcium movement and probably reflect other physiological events. Despite the challenges to regulating calcium levels at various acclimation salinities and moult stages, the calcium concentration in the blood is maintained relatively constant. There is a rapid increase to a high rate of calcium flux across both the gill and carapace epithelium shortly after the moult; on an area-specific basis these fluxes are among the highest reported for calcium-transporting epithelia. When in water with a very low concentration of calcium, the electrochemical gradient for calcium is directed outwards and net influx must occur by active transport. Evidence suggests that changes in the electrochemical gradient, permeability and active transport are all important in the ability of crustaceans to take up calcium from water with a low concentration of this ion. Although an enzyme transporter is presumably involved in the active transport of calcium across epithelia, very little is known about the cellular mechanism of the transepithelial movement of calcium in crustaceans.

The regulation of haemolymph calcium concentration of the crab Carcinus maenas (L.)

1976 ◽  
Vol 64 (1) ◽  
pp. 149-157
Author(s):  
P. Greenaway
Keyword(s):  
Body Weight ◽  
Calcium Concentration ◽  
Calcium Uptake ◽  
Sea Water ◽  
Calcium Influx ◽  
Carcinus Maenas ◽  
Ionic Form ◽  
Calcium Balance ◽  
Active Calcium ◽  
The Difference

After acclimation, Carcinus can maintain calcium balance in dilute (35–100%) but not in low calcium sea water. 71% of total haemolymph calcium (9–54 +/− 0–42 mM) was in ionic form as compared with 90–9%(9–9mM) in sea water. On acclimation to dilute sea water the calcium activity of the haemolymph was greater than that of the medium, the difference being maintained by active calcium uptake. Carcinus is highly permeable to Ca2+, influx from sea water being 0–513 +/− 0–07 mumoles g-1 h-1 and the time constant for calcium influx 4-3 +/− 0–48 h. Calcium space represented ca. 25% wet body weight independent of body size or salinity of acclimation medium.

scholarly journals CALCIUM METABOLISM IN HELA CELLS AND THE EFFECTS OF PARATHYROID HORMONE

1968 ◽  
Vol 36 (3) ◽  
pp. 567-582 ◽  
Author(s):  
André Bernard Borle
Keyword(s):  
Parathyroid Hormone ◽  
Hela Cells ◽  
Calcium Metabolism ◽  
Calcium Concentration ◽  
Calcium Uptake ◽  
Cell Monolayer ◽  
Metabolic Inhibitors ◽  
Calcium Balance ◽  
Cell Coat ◽  
Cellular Calcium

Calcium metabolism was investigated in HeLa cells. 90% of the calcium of the cell monolayer is bound to an extracellular cell coat and can be removed by trypsin-EDTA. The calcium concentration of the naked cell, freed from its coat, is 0.47 mM. The calcium concentration of the medium does not affect the concentration of the naked cell calcium. However, the calcium of the cell coat is proportional to the calcium concentration in the medium. Calcium uptake into the cell coat increases with increasing calcium concentration of the medium, whereas uptake by the naked cell is independent of the calcium of the medium. Anaerobic conditions and metabolic inhibitors do not inhibit calcium uptake by the cell, a fact suggesting that this transfer is a passive phenomenon. The calcium in the extracellular cell coat, was not affected by parathyroid hormone. In contrast, the hormone increased the cellular calcium concentration by stimulating calcium uptake or by enhancing calcium binding to some cell components. These results suggest that, contrary to current thinking, parathyroid hormone influences the cellular calcium balance by mobilizing calcium from the extracellular fluids in order to increase its concentration in some cellular compartment. It is proposed that these effects can enhance calcium transport.

EFFECT OF THE EXTERNAL CONCENTRATION OF CALCIUM ON THE POSTMOULT UPTAKE OF CALCIUM IN BLUE CRABS (CALLINECTES SAPIDUS)

1994 ◽  
Vol 188 (1) ◽  
pp. 1-9
Author(s):  
D Neufeld ◽  
J Cameron
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Callinectes Sapidus ◽  
Free Calcium ◽  
Blue Crabs ◽  
Electrochemical Gradient ◽  
External Concentration ◽  
High Calcium ◽  
Reduced Rate ◽  
Active Transport System

The rate of calcium uptake in blue crabs (Callinectes sapidus Rathbun) acclimated to 2 sea water with a calcium concentration of 1.4 mmol l-1 was dependent on the magnitude and direction of the electrochemical gradient for calcium. When transferred to water with a high calcium concentration (6 mmol l-1), the electrochemical gradient for calcium favoured diffusive influx, and calcium uptake and apparent H+ excretion increased by approximately 50 %. When transferred to water with a low calcium concentration (0.10 mmol l-1), where the electrochemical gradient for calcium strongly favoured diffusive efflux, calcium uptake ceased but apparent H+ excretion continued at a reduced rate. Crabs regulated the free calcium concentration in their blood at approximately 8 mmol l-1 when the external concentration of calcium was 1.4 mmol l-1 or higher, but the concentration of free calcium in the blood decreased to 5.6 and 4.6 mmol l-1, respectively, at external concentrations of calcium of 0.25 and 0.10 mmol l-1. Crabs transferred to water with 0.10 mmol l-1 calcium for the first 2 days after moult accumulated only 2.5 g calcium kg-1 wet mass, about one-quarter of the mass normally accumulated. Seawater-acclimated crabs transferred to 2 salinity at 1 day postmoult took up calcium at a reduced rate, indicating that a period of acclimation is necessary for a component of the active transport system to increase its capacity, for diffusive efflux to be reduced, or for both to occur.

Prescription of Calcium Concentration and Pth Control

1996 ◽  
Vol 16 (1_suppl) ◽  
pp. 300-305 ◽  
Author(s):  
Eberhard Ritz ◽  
Jutta Passlick-Deetjen ◽  
Martin Zeier ◽  
Adam Stefanski
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Content ◽  
Phosphate Binders ◽  
Calcium Balance ◽  
Frequent Episodes ◽  
Prospective Trials ◽  
Term Maintenance ◽  
Stimulation Of

The use of calcium-containing oral phosphate binders, introduced in an effort to avoid aluminum-containing compounds, has led to more frequent episodes of hypercalcemia. This prompted the introduction of continuous ambulatory peritoneal dialysis (CAPD) solutions with diminished calcium content. The problems raised by such solutions included stimulation of parathyroid hormone (PTH) secretion and long-term maintenance of calcium balance. Some of these issues can today be answered on the basis of controlled prospective trials. Variability of the rate of intestinal calcium uptake of bone turnover, of baseline parathyroid activity, and other factors make it necessary to individualize the indication for the use of CAPD solutions with low calcium content.

scholarly journals Calcium Regulation in the Freshwater Mollusc, Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)

1971 ◽  
Vol 54 (1) ◽  
pp. 199-214 ◽  
Author(s):  
PETER GREENAWAY
Keyword(s):  
Calcium Concentration ◽  
Calcium Regulation ◽  
Calcium Balance ◽  
Calcium Depletion ◽  
Uptake Mechanism ◽  
Freshwater Mollusc ◽  
Net Uptake ◽  
Limnaea Stagnalis ◽  
Sodium Regulation ◽  
Linear Manner

1. Calcium regulation in normal and calcium-depleted snails has been investigated. 2. L. stagnalis has an uptake mechanism with a high affinity for calcium ions and shows a positive calcium balance in media containing more than 0.062 mM Ca/l. 3. Influx and net uptake of calcium are related to external calcium concentration in a non-linear manner. The uptake mechanism is half-saturated and near-saturated in external media containing 0.3 and 1.0-1.5 mM Ca/l respectively. 4. Calcium uptake from external concentrations of less than 0.5 mM Ca/l is against a small electrochemical gradient whereas from external concentrations greater than 0.5 mM Ca/l there is no adverse gradient. 5. Calcium depletion does not significantly alter the normal influx or net uptake rate of calcium from 1.0 mM Ca/l. 6. The calcium concentration in the blood remains constant during net uptake from, and net loss to, the medium. 7. A comparison is made between the mechanisms of sodium regulation and calcium regulation in L. stagnalis.

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