CALCIUM AND THE CONTROL OF CIRCADIAN MITOTIC ACTIVITY IN RAT BONE MARROW AND THYMUS

1974 ◽  
Vol 62 (3) ◽  
pp. 451-462 ◽  
Author(s):  
N. H. HUNT ◽  
A. D. PERRIS
Keyword(s):  
Bone Marrow ◽  
Mitotic Activity ◽  
Calcium Homeostasis ◽  
Calcium Concentration ◽  
Plasma Calcium ◽  
Ionized Calcium ◽  
Plasma Phosphate ◽  
Circadian Changes ◽  
Plasma Calcium Concentration ◽  
Rat Bone

SUMMARY Circadian changes in mitotic activity in rat bone marrow and thymus have been demonstrated to closely parallel variations in total and ionized calcium concentrations in plasma. These fluctuations in plasma calcium concentration and tissue mitosis were abolished by parathyroidectomy. Significant changes in plasma phosphate and magnesium concentrations were also observed over the 24 h period. The evidence suggests that hour-to-hour variations in the systems controlling calcium homeostasis determine the levels of mitosis in rat bone marrow and thymus.

Plasma Magnesium and Calcium Levels in Depressive Psychosis

1972 ◽  
Vol 120 (559) ◽  
pp. 683-684 ◽  
Author(s):  
G. J. Naylor ◽  
Laura W. Fleming ◽  
W. K. Stewart ◽  
H. B. McNamee ◽  
D. Le Poidevin
Keyword(s):  
Divalent Cation ◽  
Calcium Concentration ◽  
Depressive Illness ◽  
Plasma Calcium ◽  
Ionized Calcium ◽  
Total Plasma ◽  
Total Calcium ◽  
Before And After ◽  
Plasma Calcium Concentration ◽  
Plasma Magnesium

There have been reports of the association of alterations in the divalent cation content of plasma with depressive illness. Coirault and colleagues (1959) found increased ionized calcium levels despite decreased total plasma calcium concentration in patients recovered from depression. More recently, Frizel and colleagues (1969) have reported normal plasma ionized and total calcium levels both before and after recovery from depression.

The comparative in vitro release of calcium from dried and defatted eel and rat bone fragments, and its possible significance to calcium homeostasis in teleosts

1974 ◽  
Vol 52 (6) ◽  
pp. 755-764 ◽  
Author(s):  
James C. Fenwick
Keyword(s):  
Calcium Homeostasis ◽  
Calcium Concentration ◽  
In Vitro Release ◽  
Rat Plasma ◽  
Bone Fragments ◽  
Plasma Calcium Concentration ◽  
Vitro Release ◽  
Rat Bone

The in vitro release of calcium from dried and defatted fragments of eel bone and rat bone was examined in a number of inorganic solvents and in eel and rat plasma. In each inorganic solvent, the rate of withdrawal of calcium from eel bone exceeded the rate of withdrawal from rat bone; and at equilibrium, the eel bone supported a higher solvent-calcium concentration than did the rat bone. In eel plasma, fragments of eel bone supported a plasma calcium concentration greater than the concentration of calcium in normal plasma in vivo. These results are consistent with the view that in normal eels, the plasma is undersaturated with calcium with respect to the simple solubility of bone calcium.The hypothesis that the simple solubility of bone calcium plays a greater role in the maintenance of calcium homeostasis in fishes than it does in mammals is discussed in relation to the observations made.

THE EFFECT OF HYPOCALCAEMIA ON THE SECRETION OF CALCITONIN

1973 ◽  
Vol 56 (3) ◽  
pp. 463-470 ◽  
Author(s):  
T. E. T. WEST ◽  
J. L. H. O'RIORDAN ◽  
D. H. COPP ◽  
R. F. L. BATES ◽  
A. D. CARE
Keyword(s):  
Calcium Homeostasis ◽  
Calcium Concentration ◽  
Plasma Calcium ◽  
Secretion Rate ◽  
Previous Period ◽  
Plasma Calcium Concentration ◽  
Calcitonin Secretion

SUMMARY Hypocalcaemia was produced by i.v. infusion of EDTA into pigs from which the thyroid venous effluent could be quantitatively collected. Calcitonin in the effluent was measured by radioimmunoassay. Reduction of plasma calcium concentration rapidly suppressed the secretion of calcitonin. In contrast, as plasma calcium was raised slowly from hypocalcaemic levels by infusion of CaCl2, calcitonin secretion quickly returned and increased rapidly. The secretion rate observed when the plasma calcium concentration had been raised from hypocalcaemia to the initial normocalcaemic level was 3½–10 times greater than that observed during the normocalcaemia which pertained at the start of each experiment. A previous period of hypocalcaemia also produced an exaggerated response to a subsequent hypercalcaemic stimulus. It is suggested that the preconditioned response of calcitonin secretion increases the efficiency of the role of calcitonin in calcium homeostasis.

THYROCALCITONIN AND ITS ROLE IN CALCIUM HOMEOSTASIS

1967 ◽  
Vol 37 (2) ◽  
pp. 155-167 ◽  
Author(s):  
A. D. CARE ◽  
T. DUNCAN ◽  
D. WEBSTER
Keyword(s):  
Calcium Homeostasis ◽  
Calcium Level ◽  
Calcium Concentration ◽  
Feedback Mechanism ◽  
Plasma Calcium ◽  
Negative Feedback Mechanism ◽  
Initial Plasma ◽  
Plasma Calcium Concentration ◽  
Plasma Calcium Level

SUMMARY In pigs, the control of hypercalcaemia was significantly impaired by thyroidectomy. Hypercalcaemic perfusion of the pig thyroid (which contains no parathyroids) in situ produced a systemic hypocalcaemic response which reached its maximum after about 2 hr. perfusion and which persisted for as long as the hypercalcaemic stimulus was applied. Thyroid venous plasma from a gland so perfused, when cross-transfused into a second pig, caused a hypocalcaemic reaction similar to that produced by the intravenous injection of porcine thyrocalcitonin preparations. Hypermagnesaemia did not appear to influence the release of thyrocalcitonin. A hypocalcaemic response to hypercalcaemic perfusion of the thyroid, similar to that seen in intact pigs, occurred in parathyroidectomized pigs, provided that the initial plasma calcium level was maintained by suitable calcium supplement to the diet. Hypocalcaemic perfusion of the thyroid, in either intact or parathyroidectomized pigs, resulted in a rise in the systemic plasma calcium concentration, although this rise was only consistently observed when the systemic plasma calcium level was already low as a result of thyrocalcitonin secretion. It is suggested that the secretion of thyrocalcitonin is controlled by a negative feedback mechanism operating through the plasma calcium concentration, and that because of the rapidity of its release, action and elimination, relative to parathyroid hormone, thyrocalcitonin acts as a fine regulator of calcium homeostasis.

ABOLITION OF MAGNESIUM-INDUCED HYPOCALCAEMIA BY ACUTE THYRO-PARATHYROIDECTOMY IN THE CAT

1970 ◽  
Vol 64 (1) ◽  
pp. 150-158 ◽  
Author(s):  
S. Pors Nielsen
Keyword(s):  
Sodium Chloride ◽  
Flow Rate ◽  
Magnesium Chloride ◽  
Calcium Concentration ◽  
Plasma Calcium ◽  
Magnesium Concentration ◽  
Isotonic Sodium Chloride ◽  
Plasma Calcium Concentration ◽  
High Concentrations ◽  
Plasma Magnesium

ABSTRACT Intravenous infusion of isotonic magnesium chloride into young cats with a resultant mean plasma magnesium concentration of 7.7 meq./100 g protein was followed by a significant lowering of the plasma calcium concentration in 90 minutes. The rate of decrease of plasma calcium is consistent with the hypothesis that calcitonin is released by magnesium in high concentrations. There was no decrease in the plasma calcium concentration in cats of the same weight thyroparathyroidectomized 60 min before an identical magnesium chloride infusion or an infusion of isotonic sodium chloride at the same flow rate. The hypercalciuric effect of magnesium could not account for the hypocalcaemic effect of magnesium. Plasma magnesium concentration during magnesium infusion into cats with an intact thyroid-parathyroid gland complex was slightly, but not significantly higher than in acutely thyroparathyroidectomized cats.

Effect of Small Increments in Plasma Calcium Concentration on the Responsiveness of Forearm Resistance Vessels to Verapamil in Normal Subjects

1984 ◽  
Vol 67 (6) ◽  
pp. 613-618 ◽  
Author(s):  
B. F. Robinson ◽  
R. J. W. Phillips
Keyword(s):  
Calcium Concentration ◽  
Venous Blood ◽  
Normal Subjects ◽  
Plasma Calcium ◽  
Calcium Handling ◽  
Membrane Function ◽  
Resistance Vessels ◽  
Initial Control ◽  
Plasma Calcium Concentration ◽  
Small Increments

1. The effect of a small increase in local plasma calcium concentration on the responsiveness of the forearm resistance vessels to verapamil has been examined in normal subjects, by using a plethysmographic method with infusion of calcium and other agents into the brachial artery. 2. Infusion of calcium at a rate which increased the concentration in forearm venous blood by about 0.5 mmol/l caused basal blood flow to fall by 19% and the dilator response to verapamil to fall by 35% (n = 8; P<0.02). 3. When, after 46 min, the infusion of calcium was discontinued, the dilator response to verapamil increased to reach a level 53% higher than the initial control (n = 8; P<0.02). 4. Infusion of calcium had no effect on the dilator response to sodium nitroprusside. 5. Infusion of noradrenaline at a rate which caused a greater reduction in basal flow than that induced by calcium had no effect on the response to verapamil. 6. It is concluded that the dilator response to verapamil, which is thought to reflect activity of the potential operated system for calcium entry, is selectively depressed by a small elevation of plasma calcium concentration, but subsequently becomes elevated. These findings point to an important role for calcium in the regulation of membrane function in the resistance vessels and support the view that altered calcium handling may contribute to the development of primary hypertension.

Nature of calcemic effect of 1,25-dihydroxyvitamin D3 in experimental hypoparathyroidism

1983 ◽  
Vol 244 (4) ◽  
pp. E313-E316
Author(s):  
E. Hefti ◽  
U. Trechsel ◽  
H. Fleisch ◽  
J. P. Bonjour
Keyword(s):  
Calcium Concentration ◽  
Calcium Absorption ◽  
Single Injection ◽  
Plasma Calcium ◽  
Constant Infusion ◽  
Feeding Period ◽  
Daily Fluctuation ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Plasma Calcium Concentration

The influence of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] treatment on the daily fluctuation of plasma calcium concentration ( [Ca]P1) in relation to the feeding-fasting alternation has been studied in vitamin D-replete sham-operated (sham) and thyroparathyroidectomized (TPTX) rats fed a normal Ca diet. 1,25(OH)2D3 was given (26 or 39 pmol/day) intraperitoneally either by single injection or constant infusion using osmotic minipumps. After 7 days of treatment [Ca]P1 was measured at 4-h intervals for 24 h. Pair-fed, sham and TPTX animals received the solvent vehicle intraperitoneally. The results show that in sham rats the very moderate daily fluctuation of [Ca]P1 was not accentuated by 1,25(OH)2D3. A marked fluctuation of [Ca]P1 in relation to the food intake was observed in untreated TPTX as compared with sham rats. In TPTX rats 1,25(OH)2D3 increased the fasting [Ca]P1. In contrast the rise in [Ca]P1 during feeding was not significantly accentuated by 1,25(OH)2D3. The daily fluctuation of [Ca]P1 was the same whether the dose of 1,25(OH)2D3 was given in one single injection or by constant infusion, suggesting that this hormone is not involved in the hour-to-hour regulation of [Ca]P1. In conclusion, in the absence of parathyroid glands, 1,25(OH)2D3 given in doses that stimulate intestinal calcium absorption has a much more pronounced effect on the fasting calcemia than on the rise in calcemia observed during the feeding period. These results suggest that the mobilization of calcium from bone could play an important role in the calcemic effect of 1,25(OH)2D3 when given in the hypoparathyroid state.

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