Calcium Restriction Research Articles

Uterine calcium-binding protein in the laying fowl

1. 1. Intestinal and uterine calcium-binding protein (CaBP) in the fowl ( Gallus domesticus) were compared by the Chelex assay and gel electrophoresis; their response to physiological and nutritional stimuli was studied. 2. 2. Molecular weight of uterine CaBP was found to be slightly higher than that of intestinal CaBP. 3. 3. Uterine and intestinal CaBP increased within 24 hr of the onset of egg production; both decreased as egg production ceased. 4. 4. Uterine CaBP level was slightly higher during periods of uterine inactivity than during periods of egg shell formation. There was no difference in uterine CaBP between laying hens which secreted heavy or light shells. 5. 5. A long-term calcium restriction did not influence uterine CaBP level. 6. 6. The similarities and differences between uterine and intestinal CaBP, and the possible role of CaBP in uterine calcium transport are discussed.

Calcium absorption and brush border phosphatases following dietary calcium restriction.

Calcium absorption and brush border phosphatases following dietary calcium restriction.

Relationship of duodenal calcium-binding protein to calcium absorption in the laying fowl

1. 1. Changes in duodenal calcium-binding protein (CaBP) in the fowl ( Gallus domesticus) were followed by the Chelex assay and gel electrophoresis. 2. 2. CaBP increased at the onset of egg production; the high level was sustained as long as egg production continued. A decrease in CaBP due to arrest of egg production occurred within 3–5 days. 3. 3. A long-term (16–32 days) calcium restriction resulted in an elevation of the CaBP level. 4. 4. There was no change in CaBP during shell formation. 5. 5. It was concluded that only some of the regulatory changes in calcium absorption in the laying fowl could be explained on the basis of changes in the CaBP level.

Apparent Increase in Carrier Affinity for Intestinal Calcium Transport following Dietary Calcium Restriction

Abstract Rats fed a diet lacking calcium adapt to this deprivation by increased active transport of this ion across the intestine. When the characteristics of the transport system were analyzed in vitro by use of saturation kinetics, increased net absorptive calcium transport appeared to be the result of an increased affinity (decrease in Kt from 1.12 to 0.59 mm) rather than an increase in the capacity or Vmax of the transport process. Adaptation through substrate induction in yeast results in an analogous increase in carrier affinity for sugar transport by a linkage to metabolic energy. Such a mechanism could account for the lowered dietary calcium effect, however the authors suggest that rather than an actual change in carrier affinity a second molecule (such as intestinal calcium-binding protein) could also alter carrier-substrate equilibria and produce a decrease in the observed Kt if access to the carrier were rate limiting at low substrate concentrations and this second molecule increased access of substrate. This model is consistent with the changes in calcium transport system characteristics and calcium-binding protein levels under conditions of restricted dietary calcium levels.

Relation between the Lumen-Blood Electrochemical Potential Difference of Calcium, Calcium Absorption and Calcium-binding Protein in the Intestine of the Fowl

The mechanism of calcium absorption by the intestine in vivo was investigated in both chicks and laying hens. Calcium activity, measured in ultrafiltrates of intestinal contents and blood plasma, and the electrical potential (PD) between the intestinal lumen and circulation, were used to calculate the electrochemical potential difference of calcium (ECPD) between lumen and blood. The calcium level of the hens' diets was 3.94, 1.76, or 0.60%; that of the chicks' diets was 1.11, 0.71 or 0.31%. The same diets were also used to measure calcium absorption in laying hens with the aid of yttrium-91, and calcium retention in chicks by bone analysis. Included were also measurements of the calcium-binding protein (CaBP) in the duodenal mucosa. In hens, the ECPD in the calcium-absorbing intestinal segments, the duodenum and jejunum, decreased as dietary calcium decreased but remained always positive. Thus, absorption always proceeded in the direction of the driving forces (downward). The ECPD in the chick upper intestine was positive with the two higher calcium diets, but became negative in the entire intestine with the 0.31% calcium diet. Thus, absorption proceeded downward with the 1.11 and the 0.71% calcium diets, but upward (against the driving forces) with the 0.31% calcium diet. It was concluded that, under conditions of calcium restriction in chicks, active transport may assume an important role in the overall process of calcium absorption. The CaBP was higher in laying hens than in chicks; it was independent of dietary calcium in the hen for the range of intake studied, but in chicks it increased as dietary calcium was reduced below 0.71%. The possible association of the CaBP with the adaptation to low calcium intakes is discussed. A net inflow of calcium was observed in the ileum of the hens fed the 3.94% calcium diet but not with diets containing less calcium. Phosphate absorption decreased progressively with increased dietary calcium supplementation. The duodenum was identified as the major site of this antagonism.

Influence of sodium on calcium transport by the rat small intestine.

Influence of sodium on calcium transport by the rat small intestine.

The Effect of Calcium-Deficient Diet on the Reproductive Organs of the Hen (Gallus domesticus)

INTRODUCTIONTHE restriction of dietary calcium affects profoundly the reproductive performance of the laying hen. Earlier investigations on the subject are reviewed by Mehring and Titus (1964). When hens are fed on a calcium-deficient diet they normally stop laying after 10–14 days (Taylor et al., 1962). The cessation of egg production is due to the failure of gonadotrophin secretion by the anterior pituitary which causes the bird to stop ovulating. If exogenous gonadotrophins are administrated to calcium-deficient hens, they continue ovulating and laying soft shelled eggs. It is speculated that the hypothalamic stimulation of the pituitary is reduced by the fall in the diffusible calcium level of the blood of calcium-depleted hens. (Taylor, 1965).The egg shell calcium content declines progressively from about 2 gm. per egg shell to about 1 gm. per egg shell during the first 7 days in hens placed on calciumrestricted diets. The recovery of…

Congenital osteopetrosis--a failure of normal resorptive mechanisms of bone.

On a constant intake of milk providing a normal amount of calclum(500 mg Ca/d; 500 mg P/d) plus prophylactic vitamin D supplements (400 iu/d), the serum calcium magnesium, phosphorus and alkaline phosphatase levels were normal. Drastic reduction of the calcium intake to 30 mg/d by substitution of a meat-base formula resulted in hypocalcaemia within a few days, and after several weeks of calcium restriction and hypocalcaemia, prominent radio-lucent zones appeared at the metaphyses of the continuously growing long bones. On resumption of the initial milk diet, the serum calcium quickly returned to normal and the bones again became densely mineralized.

Calcium Depletion and Repletion in Laying Hens: 1. Effect on Calcium in Various Bone Segments, in Egg Shells and in Blood Plasma, and on Calcium Balance ,

IN THE femurs of young pullets, the ends were found to be the principal site of storage of available calcium which may be utilized during the early period of egg production (Hurwitz, 1965). The ends were found to lose calcium during the production of the first five eggs but the calcium content of the cortical and medullary segments did not change significantly, even under conditions of calcium restriction. It was of interest to identify the site of available calcium stores in older laying hens which had been producing eggs for several months.The reaction of birds to periodic calcium restriction and their ability to recover from it is of considerable importance since calcium restriction is used to facilitate the utilization of dietary antibiotics (Price et al., 1959). Antibiotic utilization was also found to be enhanced by the substitution of gypsum (calcium sulfate) for limestone (calcium carbonate) in poultry rations (Eoff …

Calcium Depletion and Repletion in Laying Hens: 2. The Effect on Radiocalcium and Radiostrontium Retention in Bone and Deposition in the Egg Shell ,

THE retention of radiocalcium or radiostrontium in bones of humans (Spencer et al., 1961), rats (Cohn et al., 1961) and non-laying pullets (Hurwitz, 1965a), following a single intravenous dose, is reduced by the feeding of high-calcium diets. However, in the laying hen, the severe calcium depletion from bone during calcium restriction (Taylor and Moore, 1954; Hurwitz and Griminger, 1961) would suggest the possibility of reducing the body burden of bone-seeking radiosotopes by calcium restriction.It was the purpose of the present study to investigate the effects of variation in dietary calcium level and sources, and the timing of this variation, on the retention of calcium-45 and strontium-85 in various bone segments, and the deposition of these nuclides in the egg shell.METHODS AND RESULTSGeneral procedure: The method for preparation of samples for analysis was given in detail in the preceding paper (Hurwitz and Bar, 1966). For calcium-45 determinations, calcium …

The retention of calcium-45 in the stable bone fraction during dietary calcium restriction

The right arms of rats were amputated 67 days after the animals had received radiocalcium, at which time, according to evidence, the radioisotope was situated only in the stable calcium compartment of the bones. Groups of animals were then fed either ( a) a high calcium diet, ( b) a low calcium diet without vitamin D, or ( c) a low calcium diet with vitamin D and sacrificed at periods of time up to 80 days after the operation. The identity of radiocalcium contents of the forearm bones of the left and right arms showed that the experimental dietary regimens employed did not accelerate the turnover of the fixed bone calcium fraction. Radioautographs of the humeri of the same animals also were not demonstrably different. The influence of skeletal accretion on bone calcium specific activity and the cautions necessary in interpretation of skeletal mineral specific activities in the rat are discussed.

Reversible metastatic calcification associated with excessive milk and alkali intake

A case of metastatic calcification secondary to a prolonged intake of milk and alkali is presented. Regression of ocular and subcutaneous lesions was noted following dietary restriction of calcium although the patient subsequently died in renal insufficiency. The pathogenesis of the various forms of metastatic calcification is reviewed.

The Effect of Different Calcium Intake Levels on Egg Production, Shell Strength, and Hatchability

IN THE computation of poultry rations, considerable attention has been directed towards not only the nutrients necessary and the form in which they will be incorporated but also to the amounts of each that are required. Although much has been gleaned from research work thus far, there is a definite need for still further information.Among the many factors to be considered in ration formulation is the question of mineral requirements. This encompasses a broad field in which the calcium needs are by no means the least important. Although it has been recognized that a restriction of calcium reduces hatchability as shown by the work of Buckner, Martin, and Peter (1) favorable calcium levels have not been determined. These same authors (2) have also indicated the modes of transmission of calcium from the shell to the embryo during incubation. It is therefore evident that the shell performs more of a .

STUDIES ON CALCIUM AND MAGNESIUM METABOLISM IN DISEASE

In the stabilized stage of exostosis calcium exchange differs little from that of a normal individual whether the abnormal subject is maintained upon a calcium-poor diet or upon one rich in this element. In the progressive stage of the disease calcium metabolism is markedly different from the normal in that calcium is lost from the body in large amounts when the subject is maintained upon a calcium-poor diet. This excessive elimination of calcium is by way of both the urine and feces in a normal ratio. When placed upon a calcium-rich diet calcium is retained to an extent not widely deviating from that obtained in normal subjects. A resumption to a calcium-poor diet again induces excessive calcium elimination. In the stabilized stage of exostosis magnesium excretion is two or three times greater than the intake whether the subject is maintained upon a diet poor or rich in magnesium. In the progressive stage of the disease the general type of magnesium excretion resembles that of the stabilized stage but the degree of elimination is not so marked. Magnesium added to the diet in the stabilized stage is promptly excreted. The same test applied to the progressive stage gives evidence of retention of some magnesium. The degree of retention, however, is much less than that shown by normal individuals. Absorption of both calcium and magnesium in exostosis is not inferior to that of normal subjects. The facts enumerated suggest that in the early stages of exostosis, that is during the proliferative cartilage changes, the progress of the disease may perhaps be checked by proper dietary procedure - restriction of calcium and magnesium intake.