Calcium metabolism modeling

In attempting to reconcile these findings, it should be pointed out that rats may not be appropriate models for the study of calcium metabolism in humans. Unlike humans, the rat does not undergo epiphyseal plate closure and does not have a significant haversian remodeling sequence (21) Furthermore, rats excrete only l-270 of their calcium intake in their urine whereas humans excrete approximately 20-30% or more. This fact is especially significant, since most of the known effects of phosphates on calcium retention in humans are effected by alterations in urinary calcium. 

Matkovic, V. (1991). Calcium metabolism and calcium requirements during skeletal modeling and consolidation of bone mass. Am. J. Clin. Nutr. 54, 245S-260S. 

The power of this modeling technique might be better appreciated by considering a case of abnormal calcium metabolism, such as fibroplasia ossificans progressiva (FOP) The shape of the isotope dilution curves for this subject are notably different in the period of 1-2 days into the study as Figure 5 shows They have a flattening in the first 20 hours that is not... 

Figure 6. Four internal compartment serial model used to calculate calcium metabolic parameters for FOP subject.

The studies of calcium metabolism in normal children are underway with 15-20 children to be studied in the near future The data generated from these studies will be used as the basis for studies of diseases of calcium metabolism in children We anticipate being able to study a number of children with FOP and possibly contribute to innovative therapies for these children by monitoring changes in calcium kinetics Improvements in the thermal ionization source for the quadrupole mass spectrometer are underway a substantial improvement in sesitivity is expected from this effort The model used for data analysis is under continuing investigation in order to improve its predictive and experimental design capabilities ... 

A simple two-variable theoretical model is proposed. It exhibits most of the temporal dynamical behaviours reported for nonlinear chemical systems [1] oscillations, excitability, multi stability. This autocatalytic model, part of our nonlinear model of calcium metabolism [2], has been associated with bone calcification processes (nucleation and crystal growth). It is described by the differential system ... 

E.J. O Flaherty, Modeling bone mineral metabolism, with special reference to calcium and lead. Neurotoxicology 13 (1992) 789-797. 

Dimercaprol is FDA-approved as single-agent treatment of acute poisoning by arsenic and inorganic mercury and for the treatment of severe lead poisoning when used in conjunction with edetate calcium disodium (EDTA see below). Although studies of its metabolism in humans are limited, intramuscularly administered dimercaprol appears to be readily absorbed, metabolized, and excreted by the kidney within 4-8 hours. Animal models indicate that it may also undergo biliary excretion, but the role of this excretory route in humans and other details of its biotransformation are uncertain. 

Levy, J., Zhu, Z., and Dunbar, J. C., 1998, The effect of glucose and calcium on Ca2+-adenosine triphosphatase in pancreatic islets isolated from a normal and a non-insulin-dependent diabetes mellitus rat model. Metabolism, 47 185-9. 

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