scholarly journals Adaptations in the calcium and phosphorus metabolism of sheep in response to an intravenous infusion of Ca

1978 ◽  
Vol 40 (1) ◽  
pp. 17-21 ◽  
Author(s):  
G. D. Braithwaite
Keyword(s):  
Intravenous Infusion ◽  
High Rate ◽  
Phosphorus Metabolism ◽  
Active Absorption ◽  
Rate Of Absorption ◽  
Calcium And Phosphorus ◽  
Maximum Retention ◽  
P Retention ◽  
Low Rate

1. The effect on calcium and phosphorus metabolism of a high rate of Ca infused directly into the blood of Ca-deficient wethers, already receiving an adequate Ca intake, has been studied by a combination of balance and radioisotope techniques.2. The rate of Ca retention, which was already high, increased only slightly during the infusion before it reached a maximum. The surplus Ca was compensated for by a decrease in the rate of absorption and an increase in the rate of urinary Ca excretion.3. These findings support the theory that at maximum retention the rate of Ca absorption becomes regulated according to the rate at which Ca can be stored in bone.4. Results suggest that the decreased absorption was due to a decrease in the rate of active absorption and that the low rate remaining was due to diffusion.5. The rate of P retention was increased by the Ca infusion, possibly as a result of the increased Ca retention.

Changes in phosphorus metabolism of sheep in response to the increased demands for P associated with an intravenous infusion of calcium

1984 ◽  
Vol 102 (1) ◽  
pp. 135-139 ◽  
Author(s):  
G. D. Braithwaite
Keyword(s):  
Intravenous Infusion ◽  
Calcium Metabolism ◽  
Research Council ◽  
Agricultural Research ◽  
Close Association ◽  
High Rate ◽  
Phosphorus Metabolism ◽  
Agricultural Research Council ◽  
P Absorption ◽  
P Retention

SummaryThe effect on phosphorus and calcium metabolism of a high rate of Ca infused directly into the blood of 10-month-old sheep, already receiving an adequate Ca and P intake, has been studied by a combination of balance and radioisotope techniques. Ca retention was significantly increased during the infusion and most of the extra Ca was retained in bone. Urinary Ca excretion also showed a small but significant increase and the efficiency of Ca absorption a small but significant decrease. Because of the close association of Ca and P in bone, the increased skeletal retention of Ca resulted in an increased skeletal P retention and hence an increased demand for P. This increased P demand was met partly by a decrease in the rate of endogenous faecal loss of P and partly by an increase in the rate and efficiency of P absorption. Because the increase in P demand was relatively small, it was not possible to decide whether the endogenous faecal loss of P can be reduced in response to increased demands to the level found at zero P intake as suggested by the Agricultural Research Council (1980) or whether higher losses at normal P intakes are inevitable.

scholarly journals Studies on the absorption and retention of calcium and phosphorus by young and mature Ca-deficient sheep

1975 ◽  
Vol 34 (2) ◽  
pp. 311-324 ◽  
Author(s):  
G. D. Braithwaite
Keyword(s):  
Bone Resorption ◽  
Absorption Maximum ◽  
Deficient Diet ◽  
Mineral Balance ◽  
Rate Of Absorption ◽  
Lower Maximum ◽  
Calcium And Phosphorus ◽  
P Absorption ◽  
Maximum Retention ◽  
P Retention

1. A combination of a mineral balance and a radioactive technique has been used to study the effects of increased levels of dietary calcium and phosphorus on the Ca and P metabolism of young and mature wether sheep previously made Ca-deficient.2. Ca absorption was directly related to Ca intake until an absorption maximum was reached. Young animals absorbed dietary Ca more efficiently than mature animals and had a much higher maximum rate of absorption. Apparent P absorption was directly related to P intake and maximum P absorption was also higher for the young animals.3. Excretion of Ca in the urine and into the intestine was not altered by changes in Ca intake. Excretion of P in the urine, however, varied considerably and it is suggested that this process may be largely responsible for P homoeostasis.4. Ca retention was directly related to Ca absorption. Maximum retention was considerably higher for the young animals than for the mature animals and occurred for each group of animals at exactly the same dietary intake as maximum Ca absorption.5. Ca and P were retained in a constant ratio of 1.25:1 and the results suggested that P retention was controlled by the rate of Ca retention.6. Bone turnover was higher for the young than for the mature animals. Animals mobilized skeletal Ca when receiving the Ca-deficient diet and replaced their Ca losses when the dietary Ca was plentiful by changing the relative rates of bone resorption and bone accretion. Although bone resorption was mainly responsible for Ca homoeostasis, bone accretion appeared to play some part in the young animals.7. Maximum retention of Ca occurred just as the rate of bone resorption become zero and was equal to the rate of bone accretion. The lower maximum retention of Ca for mature animals was due to a lower rate of bone accretion.8. Results suggested that when bone resorption ceased, Ca absorption was regulated by homoeostatic mechanisms at a level just sufficient to maintain maximum retention, and that the maximum rates of absorption measured may not have been true maximum rates.9. The consequences of a relationship between bone accretion and maximum Ca retention are discussed with reference to older, pregnant and lactating animals.

The effect of dietary intake of calcium and phosphorus on their absorption and retention by mature Ca-replete sheep

1979 ◽  
Vol 92 (2) ◽  
pp. 337-342 ◽  
Author(s):  
G. D. Braithwaite
Keyword(s):  
Body Weight ◽  
Bone Resorption ◽  
Dietary Manipulation ◽  
Mineral Balance ◽  
Milk Fever ◽  
Calcium And Phosphorus ◽  
Maintenance Requirements ◽  
Constant Maximum ◽  
Maximum Retention ◽  
P Retention

SummaryA combination of a mineral balance and a radioisotope technique has been used to study the effect of increased intakes of dietary calcium and phosphorus on the Ca and P metabolism of mature, Ca-replete wether sheep. Between Ca intakes of 40 and 100 mg/ day per kg body weight Ca absorption remained constant at a level just sufficient to supply maintenance requirements. Above 100 mg/day per kg body weight, however, absorption increased in direct relation to intake. It is suggested that the increased absorption occurred by diffusion and that at lower Ca intakes, increased diffusion was offset by a corresponding decrease, until it reached a negligible level, in the rate of active absorption.In spite of the fact that the wethers were already Ca-replete, the increased Ca absorption resulted in increased Ca retention and not as might have been expected in increased excretion. Increased retention was brought about by a decrease in the rate of bone resorption and bone accretion remained constant. Maximum retention occurred when bone resorption ceased and it was equal to the rate of bone accretion. It was only when retention of Ca reached a maximum that further increases in absorption resulted in increased excretion of Ca into urine and intestine. P retention was also increased with increased Ca and P intakes and probably occurred as a result of the increased Ca retention.The relevence of these findings to the control of parturient paresis (milk fever) in the dairy cow by dietary manipulation is discussed.

Effect of lα-hydroxycholecalciferol on calcium and phosphorus metabolism in sheep given high or low calcium diets

1981 ◽  
Vol 96 (2) ◽  
pp. 291-299 ◽  
Author(s):  
G. D. Braithwaite
Keyword(s):  
Body Weight ◽  
Urinary Excretion ◽  
Soft Tissues ◽  
Phosphorus Metabolism ◽  
Mineral Balance ◽  
A Value ◽  
Calcium And Phosphorus ◽  
The Relationship ◽  
P Absorption ◽  
P Retention

SUMMARYThe relationship between calcium and phosphorus metabolism in wether sheep given high or low Ca diets, with or without 1α-hydroxycholecalciferol (1α-0H-D3) has been studied by a mineral balance and radioactive technique.Ca absorption was not related to Ca intake but was stimulated by 1α-OH-D3. More Ca was absorbed by treated animals from the high Ca diet than from the low diet and all the extra Ca absorbed was retained, increased retention being brought about largely by an increase in the rate of bone accretion.P absorption was increased to approximately the same extent from both diets suggesting that stimulation was due to the 1 α-0H-D3 treatment rather than increased Ca absorption. Whereas the extra P absorbed from the high Ca diet was retained, together with Ca, in bone and soft tissues, that absorbed from the low Ca diet was largely excreted in the urine. It is suggested that this difference in P retention reflects a difference in availability of Ca for retention in bone and P retention was in fact found to be directly related to Ca retention.The roles of secretion of P into the gut, absorption of P from the gut and urinary excretion of P are discussed in relation to P homoeostasis.As absorption of P from the intestine and loss of P to bone, soft tissues and urine increased, so endogenous faecal loss decreased until it reached a value of approximately 35 mg/day per kg body weight when it remained constant. It is suggested that this value may represent the inevitable loss of endogenous P in the faeces from a hay and concentrates diet and that this minimum value may have a bearing on the calculation of P requirements.

CHANGES IN THE METABOLISM OF CALCIUM AND PHOSPHORUS IN THE VARIOUS PHASES OF ACROMEGALY AND FOLLOWING THE IMPLANTATION OF THE PITUITARY GLAND WITH 90Y

1961 ◽  
Vol 36 (2) ◽  
pp. 161-179 ◽  
Author(s):  
G. M. Molinatti ◽  
F. Camanni ◽  
O. Losana ◽  
M. Olivetti
Keyword(s):  
Pituitary Gland ◽  
Marked Decrease ◽  
Active Phase ◽  
Tolerance Test ◽  
Urinary Calcium ◽  
Phosphorus Metabolism ◽  
Blood Calcium ◽  
X Ray ◽  
Calcium Retention ◽  
Calcium And Phosphorus

ABSTRACT A study of calcium and phosphorus metabolism has been carried out on 13 acromegalic patients, in various stages of the disease. This study was repeated in nine patients following implantation of the pituitary gland with 90Y and in another two patients after deep X-ray therapy and suction removal of a pituitary adenoma respectively. Increased urinary calcium and phosphorus excretion was found in all the patients in whom the disease was in an active phase of evolution. The calcium tolerance test revealed a marked decrease of calcium retention in certain subjects, while in others, calcium retention was found to be increased. Such changes were not found in patients in whom the disease was in a quiescent phase. The blood calcium, phosphorus and alkaline phosphatase were found to be either normal or slightly increased. The implantation of the pituitary gland with 90Y and deep X-ray therapy induced a marked decrease of hypercalciuria, both spontaneous and induced, and of hyperphosphaturia, together with a definite improvement, of the clinical picture and glucose metabolism. It is concluded that the changes in calcium and phosphorus metabolism described above depend either directly or indirectly on a pituitary factor. They may therefore prove a reliable index for assessing pituitary growth hormone activity.

A Note on Groove Depth Changes Without Wear

1980 ◽  
Vol 8 (1) ◽  
pp. 10-12
Author(s):  
F. C. Brenner
Keyword(s):  
Weight Loss ◽  
Wear Test ◽  
Groove Depth ◽  
High Rate ◽  
Weight Changes ◽  
Wear Rates ◽  
Weight Loss Method ◽  
Loss Method ◽  
And Storage ◽  
Low Rate

Abstract Tread wear rates during first wear measured by groove depth and weight changes do not always agree. Sometimes, the groove depth method shows a high rate and the weight loss method a low rate. Reported here are experiments designed to determine if grooves show depth changes without wear. Four tires were measured before mounting on a wheel, after mounting and inflation, and after inflation and storage. The mounted and inflated tires showed shallower shoulder grooves and deeper center grooves than the unmounted tires. In a second experiment, tires were measured immediately after a tread wear test and then stored mounted for two weeks before remeasuring. Each groove became deeper, and there was no change in the crown radius of any tire.

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