Calcium uncertain

DIGOXIN CALCIUM Risk of cardiac arrhythmias with large intravenous doses of calcium Uncertain it is known that calcium levels directly correlate with the action of digoxin therefore, high levels, even if transient, may t the chance of toxicity It is recommended that parenteral administration of calcium should be avoided in patients taking digoxin. If this is not possible, administer calcium slowly and in small aliquots... 

Calcium has a face-centered cubic crystal stmcture (a = 0.5582 nm) at room temperature but transforms into a body-centered cubic (a = 0.4477 nm) form at 428 2° C (3). Some of the more important physical properties of calcium are given in Table 1. For additional physical properties, see references 7—12. Measurements of the physical properties of calcium are usually somewhat uncertain owing to the effects that small levels of impurities can exert. 

Parvalbumin is a muscle protein with a single polypeptide chain of 109 amino acids. Its function is uncertain, but calcium binding to this protein probably plays a role in muscle relaxation. The helix-loop-helix motif appears three times in this structure, in two of the cases there is a calcium-binding site. Figure 2.13 shows this motif which is called an EF hand because the fifth and sixth helices from the amino terminus in the structure of parvalbumin, which were labeled E and F, are the parts of the structure that were originally used to illustrate calcium binding by this motif. Despite this trivial origin, the name has remained in the literature. 

Protein kinase A (PKA) is a cyclic AMP-dependent protein kinase, a member of a family of protein kinases that are activated by binding of cAMP to their two regulatory subunits, which results in the release of two active catalytic subunits. Targets of PKA include L-type calcium channels (the relevant subunit and site of phosphorylation is still uncertain), phospholam-ban (the regulator of the sarcoplasmic calcium ATPase, SERCA) and key enzymes of glucose and lipid metabolism. 

Equation (60) was used earlier125 for bubbles (of uncertain composition) introduced in pure aluminum wires by plunging these from 650 °C into a saturated solution of calcium chloride kept at 100 °C. The bubbles were up to 500 angstroms across. They were characterized as octahedral but treated (in calculations) as spheres. The 7S appeared to be at 150 °C, 175 °C, and 200 °C, respectively, 1160,930, and 960 erg/cm2. 

When 1,25 DHCC provision is adequate or when plasma calcium concentration is above approximately 2.20mmol/l, la hydroxylase activity is suppressed and 25-hydroxy vitamin D3 is converted by 24-hydroxylase into 24,25 dihydroxy vitamin D3 a metabolite whose true role is uncertain but one which seems to have little if any physiological activity. Renal 24-hydroxylase does have a role to play in the deactivation of 1,25 dihydroxy vitamin D the major metabolite of the vitamin being 1,24,25 trihydroxy vitamin D. 

The cellular mechanism of cannabinoid analgesia is uncertain. Although cAMP and adenylate cyclase mediate other effects of cannabinoids, they do not appear to be involved in cannabinoid-induced analgesia (Cook et al. 1995). Instead, other mechanisms such as cannabinoid receptor-coupled calcium or potassium channels may be responsible. 

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. 

Because the drug and the mobilized metals are excreted via the urine, the drug is relatively contraindicated in anuric patients. In such instances, the use of low doses of EDTA in combination with hemodialysis or hemofiltration has been described. Nephrotoxicity from EDTA has been reported, but in most cases can be prevented by maintenance of adequate urine flow, avoidance of excessive doses, and limitation of a treatment course to 5 or fewer consecutive days. EDTA may result in temporary zinc depletion that is of uncertain clinical significance. Analogs of EDTA, the calcium and zinc disodium... 

When preparing the cesium- and barium-saturated clays, the 1.0 M solutions used were decanted (after centrifuging) and analyzed semiquantitatively by emission spectroscopy. From those analyses, it appears that the following species were desorbed sodium, potassium, calcium, magnesium, and strontium. It further appeared that desorption of potassium was almost unique to cesium sorption whereas, desorption of the other species appeared to be common to both cesium and barium sorption. Small amounts of other elements such as nickel and copper were also detected by the analyses. However, to what extent the observed concentrations may represent desorption and to what extent they may represent the dissolution of sparingly soluble substances (particularly hydroxide species) is as yet-uncertain. The apparent concentrations of the desorbed species per gram of clay are given in Table III. 

It was long thought that boron was not required by human beings, but more recent studies suggest that we may need 30 pg / day.d Tire possible functions are uncertain. Animals deprived of boron show effects on bone, kidney, and brain as well as a relationship to the metabolism of calcium, copper, and nitrogen. Nielson proposed a signaling function, perhaps via phosphoinositides, in animals.b... 

Valproic acid. Although its exact mechanism of action remains uncertain, valproic acid (also valproate sodium, or valproate) may inhibit sodium and/or calcium channel function and perhaps thereby boost GABA inhibitory action as well as reduce glutamate excitatory action (Fig. 7—23). A unique and patented pharmaceutical formulation of valproic acid, called Depakote, reduces gastrointestinal side effects. 

The secondary mineralocorticoid activity of glucocorticoids can lead to salt and water retention, which can cause hypertension. Although the detailed mechanisms are as yet uncertain, glucocorticoid-induced hypertension often occurs in elderly patients and is more common in patients with total serum calcium concentrations below the reference range and/or in those with a family history of essential hypertension (SEDA-20, 368 19). 

There was a slight but significant increase in calcium excretion in 15 girls and 17 boys, median age 9.8 years, who received desmopressin 30 micrograms by intranasal spray for 4 weeks, withdrawn for 2 weeks, and then continued for at least 3 further weeks (47). This is unlikely to be significant in the short term and whether it would have any significance in the long term is uncertain. 

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