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Biomedical subjects

D H Copp

Publications and source records attributed to D H Copp.

At least 37 records · Page 2Linked to original sources
PubMed1975

Net uptake and release of calcium and phosphate by bone in vitro: effects of medium calcium and phosphate concentrations.

The effects of varying the initial calcium and phosphate concentrations of the culture media on bone calcium and phosphate release were examined, using whole calvaria from 3-day-old mice in 48-hour cultures. The initial calcium and phosphate concentrations of the culture media were varied in the range 3-10 mg/100 ml; either calcium or phosphate alone was changed while the other ion was held constant, or the concentrations of both were varied while the Ca:P ratio was held constant. For all combinations, 3 treatment groups were used: i) control (no added hormone); ii) 0.5 U/ml PTH; iii) 50 mU/ml CT. The release of calcium and phosphate from the bones was greatest at low initial calcium or phosphate concentrations in the media, and least at high initial concentrations. High concentrations of both ions together abolished hormonal responses and resulted in extensive uptake of calcium and phosphate by the bones. The response to PTH was lost at a high concentration of either ion alone, while a response to CT was observed under all experimental conditions except simultaneously high calcium and phosphate concentrations.

Animals↗
PubMed1975

Calcium uptake by placental plasma membrane vesicles.

The placental plasma membrane vesicles are capable of accumulating up to 190 mM Ca2+. This is 24-fold higher than the external Ca2+ concentration. This process is dependent on ATP hydrolysis by the placental Ca2+-ATPase. The Pi/Ca ratio is dependent on the external Ca2+ concentration, and reaches the value of 2 at 10 mM Ca2+. Phosphate (5 mM) can double Ca2+ uptake when measured in the presence of 5 mM Ca2+. Mg2+ increased Ca2+ uptake only at low Ca2+ concentrations, and had no significant effect at 5 mM Ca2+.

Adenosine Triphosphatases↗
PubMed1975

Stimulation by ATP of alkaline phosphatase in placental plasma membranes.

1. ATP stimulated the p-nitrophenyl phosphatase activity of placental plasma membranes, with an increase in activity of approximately 100% at 5 mM ATP. The stimulation was not dependent on the presence of Mg-2-+. 2. The K-m for p-nitrophenyl phosphate was not changed by the presence of 5 mM ATP. 3. ATP hydrolysis by the plasma membrane preparation under the same assay conditions as for alkaline phosphatase was not influenced by the presence of 5 mM p-nitrophenyl phosphate. 4. Extraction of the plasma membrane preparation with n-butanol abolished the stimulatory effect of ATP, as well as Ca-2-+-activated ATPase activity.

4-Nitrophenylphosphatase↗
PubMed1975

Changes in plasma calcitonin and calcium during the migration of salmon.

The levels of immunoassayable calcitonin and of calcium were measured in the preblood of sockeye salmon during their migration from sea water to fresh water to spawn. Plasma calcitonin was higher in the females than in the males during all stages of migration as was plasma calcium except during spawning. In both sexes calcium decreased progressively throughout migration. In the male, calcitonin decreased as the fish arrived in fresh water but increased again at the spawning. These observations suggest that calcitonin may play an important role in the reproductive cycle of fish.

Animals↗