Calcium Regulation in Intermoult Gammarus Pulex

1979 ◽  
Vol 83 (1) ◽  
pp. 131-144
Author(s):  
D. A. WRIGHT
Keyword(s):  
Calcium Concentration ◽  
Regulatory Mechanism ◽  
Specific Activity ◽  
Calcium Influx ◽  
Gammarus Pulex ◽  
Whole Body ◽  
Metabolic Inhibitor ◽  
Calcium Balance ◽  
Similar Time ◽  
Total Body Calcium

The compartmentation of calcium was studied in adult intermoult Gammarus pulex. The total body calcium concentration was 547 μmol g. wet wt.−1, which is weight for weight approximately one half of the calcium concentration found in decapod crustaceans. Over 96% of whole body calcium in G. pulex was found in the exoskeleton. 45Ca exchange curves for haemolymph and hepatopancreas had similar time constants indicative of a comparatively large pool of freely exchangeable calcium. The parallel exchange of calcium between the haemolymph and other soft tissue compartments confounded the satisfactory use of analgebraic model for indirect calcium influx measurement using haemolymph specific activity. All calcium influx was subsequently measured on a whole bodybasis. Passive absorption of calcium on to the cuticle was eliminated as a significant factor as the metabolic inhibitor 2:4-DNP almost completely inhibited any form of calcium uptake. The active nature of the calcium regulatory mechanism was further illustrated by potential difference measurements indicating that calcium is accumulated against an electrochemical gradient from media having a calcium activity less than 1 mmol l−1. When placed in calcium-free media, intermoult Gammarus pulex areable to achieve at least a tenuous calcium balance between 12 and 50μmol Ca l−1 at a density of 1 animal per 10 ml medium. Some specimens showa slow calcium loss. The calcium regulatory mechanism is saturated at an external calcium concentration of 2 mmol l1, which is the normal field calcium concentration for this population, and has a half saturation valueof 0.3 mmol l−1.

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 Parathyroid hormone-related protein and calcium regulation in vitamin D-deficient sea bream (Sparus auratus)

2007 ◽  
Vol 193 (3) ◽  
pp. 473-480 ◽  
Author(s):  
W Abbink ◽  
X M Hang ◽  
P M Guerreiro ◽  
F A T Spanings ◽  
H A Ross ◽  
...  
Keyword(s):  
Vitamin D ◽  
Parathyroid Hormone ◽  
Calcium Influx ◽  
Sea Bream ◽  
Whole Body ◽  
Calcium Balance ◽  
Related Protein ◽  
Deficient Diet ◽  
Parathyroid Hormone Related Protein ◽  
Sparus Auratus

Gilthead sea bream (Sparus auratus L.) were fed a vitamin D-deficient diet for 22 weeks. Growth rate, whole body mineral pools and calcium balance were determined. Plasma parathyroid hormone-related protein (PTHrP) and calcitriol levels were assessed. Expression of mRNA for pthrp and pth1r was quantified in gills and hypophysis. Fish on vitamin D-deficient diet (D− fish) showed reduced growth and lower calcium turnover (calcium influx, efflux and accumulation rates decreased) and unaltered plasma calcium levels. Plasma calcitriol levels became undetectable, PTHrP levels decreased in the D− fish. In controls, a significant increase in plasma PTHrP level over time was seen, i.e. it increased with body mass. Relationships were found between plasma PTHrP and the whole body pools of calcium, phosphorus and magnesium, indicative of a role for PTHrP in bone development. Expression of pthrp and pth1r mRNA was down-regulated in the hypophysis of D−fish, whereas in gill tissue, pthrp and pth1r mRNA were up-regulated. We conclude that lower pthrp mRNA expression and plasma values in D− fish reflect lower turnover of PTHrP under conditions of hampered growth; up-regulation of pthrp mRNA in gills indicate compensatory paracrine activity of PTHrP during calcitriol deficiency to guarantee well-regulated branchial calcium uptake. This is the first report to document a relation between PTHrP and calcitriol in fish.

scholarly journals Significant artefactual noise in 90Y TOF-PET imaging of low specific activity phantoms arises despite increased acquisition time

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Michel Hesse ◽  
Stephan Walrand
Keyword(s):  
Pet Imaging ◽  
Specific Activity ◽  
Whole Body ◽  
Acquisition Time ◽  
Random Coincidence ◽  
Natural Crystal ◽  
Phantom Studies ◽  
Pet Reconstruction ◽  
Very High ◽  
Tof Pet

AbstractVolumes of usual PET phantoms are about four to sixfold that of a human liver. In order to avoid count rate saturation and handling of very high 90Y activity, reported TOF-PET phantom studies are performed using specific activities lower than those observed in liver radioembolization.However, due to the constant random coincidence rate induced by the natural crystal radioactivity, reduction of 90Y specific activity in TOF-PET imaging cannot be counterbalanced by increasing the acquisition time. As a result, most 90Y phantom studies reported images noisier than those obtained in whole-body 18F-FDG, and thus advised to use dedicated noise control in TOF-PET imaging post 90Y liver radioembolization.We performed acquisitions of the Jaszczak Deluxe phantom in which the hot rod insert was only partially filled with 2.6 GBq of 90Y. Standard reconstruction parameters recommended by the manufacturer for whole-body 18F-FDG PET were used.Low specific activity setups, although exactly compensated by increasing the acquisition time in order to get the same number of detected true coincidences per millilitre, were impacted by significant noise. On the other hand, specific activity and acquisition time setup similar to that used in post 90Y liver radioembolization provided image quality very close to that of whole-body 18F-FDG.This result clearly discards the use of low specific activity phantoms intended to TOF-PET reconstruction parameter optimization. Volume reduction of large phantoms can be achieved by vertically setting the phantoms or by adding Styrofoam inserts.

Trends in Trabecular and Cortical Bone in the Radius Compared with Whole Body Calcium Balance in Osteoporosis

1984 ◽  
Vol 66 (1) ◽  
pp. 109-112 ◽  
Author(s):  
R. Hesp ◽  
A. C. Deacon ◽  
Patricia Hulme ◽  
J. Reeve
Keyword(s):  
Trabecular Bone ◽  
Cortical Bone ◽  
Distal Radius ◽  
Rate Of Change ◽  
Whole Body ◽  
Calcium Balance ◽  
Total Absorption ◽  
Balance Study ◽  
Attenuation Coefficients ◽  
Change Trend

1. Mean linear attenuation coefficients for trabecular bone (T) in the distal radius and total absorption coefficients (TA) in the radial mid-shafts of 22 patients with crush fracture osteoporosis were measured serially for a year by using computed tomography. After approximately 6 months, each patient was admitted to a metabolic ward for an 18-day calcium balance study. 2. The rate of change (trend) in trabecular bone (T) in the distal radius was a better predictor of calcium balance than the trend in mid-shaft cortical bone (TA). 3. The scatter in the regressions of the trends of T and TA on calcium balance could be accounted for by known methodological uncertainties.

The Regulation of Calcium and Magnesium in the Brackish Water Polychaete Nereis Diversicolor O.F.M

1970 ◽  
Vol 53 (2) ◽  
pp. 425-443
Author(s):  
C. R. FLETCHER
Keyword(s):  
Brackish Water ◽  
Calcium Concentration ◽  
Sea Water ◽  
Calcium Influx ◽  
Coelomic Fluid ◽  
Nereis Diversicolor ◽  
Active Uptake ◽  
Calcium And Magnesium ◽  
Electrochemical Potentials

1. Nereis diversicolor tolerates changes in the concentration of calcium and magnesium in its coelomic fluid proportional to the concentrations in the medium between chlorosities of 100-1000 mM/kg of water. 2. In lower salinities both ions are maintained relatively constant providing that the ratios of these ions to chloride in the medium are similar to the ratios in sea water. 3. The ratio of the concentration of calcium in the coelomic fluid to the concentration in the medium is a function of the salinity of the medium but not of the calcium concentration. 4. Both calcium and magnesium are at lower electrochemical potentials in the coelomic fluid than in the medium, indicating that it is not necessary to invoke active uptake. 5. The rate of calcium influx is substantial. 6. In salinities below to mM of chloride/kg of water the urine must contain less calcium than the coelomic fluid. 7. The significance of these results is discussed.

Changes in total body calcium balance with exercise in the rat

1983 ◽  
Vol 55 (1) ◽  
pp. 201-204 ◽  
Author(s):  
A. D. LeBlanc ◽  
H. J. Evans ◽  
P. C. Johnson ◽  
S. Jhingran
Keyword(s):  
Least Squares ◽  
Voluntary Exercise ◽  
Calcium Balance ◽  
Sprague Dawley ◽  
Total Body Calcium ◽  
Sprague Dawley Rats ◽  
Least Squares Fit ◽  
Significant Change ◽  
Total Body ◽  
And Control

The purpose of this study was to evaluate the effect of deconditioning on the total body calcium in rats. Two separate experiments were performed using female Sprague-Dawley rats, 187-266 days of age. Total body calcium was measured in experimental and control rats during and following several weeks of voluntary exercise. The slope from the least-squares fit of total body calcium with time was used to obtain an average calcium balance for each animal during each study period. In both groups the exercised rats had a significantly decreased calcium balance after cessation of exercise, whereas no significant change was seen in nonexercised controls. In both groups, the exercised animals gained calcium at a significantly greater rate than controls. Our findings indicate that while exercised rats may gain calcium at a faster rate compared with nonexercising controls, the rate of gain following cessation of exercise is less than the controls.

Selectivity and Response Characteristics of Human Olfactory Neurons

1997 ◽  
Vol 77 (3) ◽  
pp. 1606-1613 ◽  
Author(s):  
N. E. Rawson ◽  
G. Gomez ◽  
B. Cowart ◽  
J. G. Brand ◽  
L. D. Lowry ◽  
...  
Keyword(s):  
Calcium Concentration ◽  
Calcium Influx ◽  
Olfactory Neuron ◽  
Olfactory Neurons ◽  
Response Characteristics ◽  
Inositol 1,4,5 Trisphosphate ◽  
Transduction Mechanisms ◽  
Individual Odors ◽  
Second Messenger Pathways ◽  
Induced Changes

Rawson, N. E., G. Gomez, B. Cowart, J. G. Brand, L. D. Lowry, E. A. Pribitkin, and D. Restrepo. Selectivity and response characteristics of human olfactory neurons. J. Neurophysiol. 77: 1606–1613, 1997. Transduction mechanisms were investigated in human olfactory neurons by determining characteristics of odorant-induced changes in intracellular calcium concentration ([Ca2+]i). Olfactory neurons were freshly isolated from nasal biopsies, allowed to attach to coverslips, and loaded with the calcium-sensitive indicator fura-2. Changes in [Ca2+]i were studied in response to exposure to individual odors, or odorant mixtures composed to distinguish between transduction pathways mediated by adenosine 3′5′-monophosphate (cAMP; mix A) or inositol 1,4,5-trisphosphate (InsP3; mix B). Overall, 52% of biopsies produced one or more odorant-responsive olfactory neurons, whereas 24% of all olfactory neurons tested responded to odorant exposure with a change in [Ca2+]i. As in olfactory neurons from other species, the data suggest that odorant exposure elicited calcium influx via second-messenger pathways involving cAMP or InsP3. Unlike olfactory neurons from other species that have been tested, some human olfactory neurons responded to odorants with decreases in [Ca2+]i. Also in contrast with olfactory neurons from other species, human olfactory neurons were better able to discriminate between odorant mixtures in that no neuron responded to more than one type of odor or mixture. These results suggest the presence of a previously unreported type of olfactory transduction mechanism, and raise the possibility that coding of odor qualities in humans may be accomplished to some degree differently than in other vertebrates, with the olfactory neuron itself making a greater contribution to the discrimination process.

Depolarization modulates endothelial cell calcium influx and microvessel permeability

1991 ◽  
Vol 261 (4) ◽  
pp. H1246-H1254 ◽  
Author(s):  
P. He ◽  
F. E. Curry
Keyword(s):  
Membrane Potential ◽  
Calcium Concentration ◽  
Calcium Influx ◽  
Ringer Solution ◽  
Initial Increase ◽  
High Potassium ◽  
Microvessel Permeability ◽  
Microvessel Wall ◽  
Initial Peak ◽  
Peak Value

We investigated the mechanisms whereby high-potassium (57.9 mM) Ringer solutions attenuate the increase in permeability caused when microvessels are exposed to the calcium ionophores ionomycin and A23187 (5 microM). In single perfused microvessels we measured cytoplasmic calcium concentration, [Ca2+]i, in the cells forming the microvessel wall and the hydraulic conductivity, Lp, to follow changes in the permeability of the microvessel walls. In normal Ringer solution, [Ca2+]i was increased to an initial peak value of 226 +/- 12 nM after exposure to calcium ionophores; the corresponding increase in microvessel Lp was 10.3 +/- 2.6 times control. With high-potassium solutions, the peak value of [Ca2+]i was 133 +/- 12 nM and Lp was increased to only 2.5 +/- 0.7 times control. Increasing extracellular calcium from 1.1 to 5 mM with high potassium restored the initial peak value of [Ca2+]i to 303 +/- 38 nM. The increases in both [Ca2+]i and Lp were abolished in calcium-free solutions. If high-potassium solutions depolarize the cells forming the microvessel wall as indicated by the membrane potential-sensitive dye bisoxonol, then the magnitude of the initial increase in [Ca2+]i could be accounted for by changes in the electrochemical driving force through conductive channels for calcium ion. Our results conform to the hypothesis that the permeability properties of microvessels are modulated by changes in the membrane potential of the endothelial cells and/or pericytes forming the microvessel wall.

Regulation of calcium balance in the sturgeon Acipenser naccarii: a role for PTHrP

2007 ◽  
Vol 293 (2) ◽  
pp. R884-R893 ◽  
Author(s):  
Juan Fuentes ◽  
Christophe Haond ◽  
Pedro M. Guerreiro ◽  
Nádia Silva ◽  
Deborah M. Power ◽  
...  
Keyword(s):  
Calcium Transport ◽  
Calcium Uptake ◽  
Dietary Calcium ◽  
Calcium Deficiency ◽  
Cell Number ◽  
The Body ◽  
Whole Body ◽  
Calcium Balance ◽  
Parathyroid Hormone Related Protein ◽  
Juvenile Sturgeon

Calcium regulation in sturgeon is of special interest because they are a representative of the ancient fishes possessing mainly cartilaginous skeletons and a supposedly low calcium demand. The present study aimed to characterize the effect of a chronic absence of dietary calcium and the effect of parathyroid hormone-related protein (PTHrPA) (1-34) ( 7 ) on calcium balance in juvenile sturgeon ( Acipenser naccarii). At rest, sturgeon juveniles are in net positive calcium balance, since whole body calcium uptake is significantly higher than efflux and calcium accumulates in the body. To study the importance of dietary calcium, the sturgeon were kept on a calcium-free diet for 8 wk. This manipulation impaired growth as measured by failure to gain weight or increase in length and indicates that dietary calcium is important for growth in sturgeon. An increased whole body calcium uptake partially compensated dietary calcium deficiency and was associated with increased gill chloride cell number in lamellae and filaments in parallel with increased gill Na+K+-ATPase activity. In addition, a single injection of piscine PTHrP(1-34) significantly increased whole body calcium uptake and decreased whole body calcium efflux. Administration of PTHrP significantly increased circulating plasma calcium 4–24 h postinjection. The increase in net calcium transport and increased plasma levels of calcium is consistent with the actions of a hypercalcemic factor. It would appear that the sturgeon rely on calcium for growth and tightly regulate calcium transport. The action in calcium balance is consistent with PTHrP acting as a hypercalcemic factor in sturgeon.

V-A and A-V modes in whole body and regional kinetics: domain of validity from a physiological model

1992 ◽  
Vol 263 (4) ◽  
pp. E597-E606 ◽  
Author(s):  
L. Sacca ◽  
G. Toffolo ◽  
C. Cobelli
Keyword(s):  
Specific Activity ◽  
Venous Blood ◽  
Physiological Model ◽  
Regional Level ◽  
Whole Body ◽  
Distributed Model ◽  
Mixed Venous Blood ◽  
Tissue System ◽  
Mixed Venous ◽  
Domain Of Validity

In turnover studies, both at whole body and regional level, sources of tracer and tracee are in general nonidentical thus resulting in nonuniformity of specific activity (SA). Guidelines are available in literature to deal with the heterogeneous SA problem, and either the V-A or A-V modes, based on the arterial and mixed venous blood SA, respectively, have been recommended for different substrates. In particular, the A-V mode is considered the method of choice for studying lactate, amino acids, free fatty acid, etc. Guidelines are based on specific models chosen to describe kinetic and circulatory events of the substance under study but are often conflicting. A unitary physiological framework to understand assumptions of various models is also lacking. In this paper, we first review these models to assess their domain of validity. In particular, we point out major drawbacks that relate to the tissue compartment being treated as a lumped well-mixed pool with a single SA value. We then attempt to handle the nonuniform tissue SA by employing a more physiological model. The tissue system is thought to be made up of elementary units connected in parallel and categorized according to their functional ability to affect incoming SA. Potential changes of SA within individual units are examined. Thus each tissue unit may provide a different contribution to the overall change in SA, as measured in mixed venous blood. A spatial profile of SA is also identified both along the direction of blood flow and transversely toward the inner cellular space. This distributed model allows assessment of the domain of validity of V-A and A-V modes. We show that, in general, the V-A mode underestimates the production rate both at whole body and regional level, whereas the A-V mode can either under- or overestimate it.

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