Calcium ion homeostasis

Adults require 1-2 mg of copper per day, and eliminate excess copper in bile and feces. Most plasma copper is present in ceruloplasmin. In Wilson s disease, the diminished availability of ceruloplasmin interferes with the function of enzymes that rely on ceruloplasmin as a copper donor (e.g. cytochrome oxidase, tyrosinase and superoxide dismutase). In addition, loss of copper-binding capacity in the serum leads to copper deposition in liver, brain and other organs, resulting in tissue damage. The mechanisms of toxicity are not fully understood, but may involve the formation of hydroxyl radicals via the Fenton reaction, which, in turn initiates a cascade of cellular cytotoxic events, including mitochondrial dysfunction, lipid peroxidation, disruption of calcium ion homeostasis, and cell death. 

Jewell, S.A., Bellomo, G., Thor, H., Orrenius, S. and Smith, M.T. (1982). Bleb formation in hepatocytes during drug metabolism is caused by disturbances in thiol and calcium ion homeostasis. Science 217 1257-1258. 

PTH is a naturally occurring polypeptide with 84 amino acid residues that acts as the major regulator of calcium ion homeostasis [68]. The first two amino acids of PTH from the amino N-terminus are required for biological activity. Proteolytic fragments of PTH are inactive at the PTH-1 receptor, but may cross-react with an IA. The putative peptide PTH (7-84) fragment was reported to exist at 10- to 20-fold higher concentrations than the intact PTH (1-84), depending upon health status [69]. 

Osteocalcin is exclusively secreted by osteoblasts and thought to play a role in body s metabolic regulation and bone-building ability (Lee et al., 2007). It is also implicated in bone mineralisation and calcium ion homeostasis. As osteocalcin... 

Effects Hypoxia/Reoxygenation on Intracellular Calcium Ion Homeostasis in Ventricular Myocytes during Halothane Exposure Paui R. Knight, Mitchell D. Smith, and Bruce A. Davidson... 

Energy metabolism Energy metabolism Energy metabolism Energy metabolism Energy metabolism Structural integrity Calcium ion homeostasis Stress response... 

In regards to necrosis, it is clear that the old adage an ounce of prevention is worth a pound of cure applies. Agents that stabilize ion homeostasis have proved to be effective in preventing necrosis in cell culture studies. For example, drugs that activate plasma membrane potassium ion channels or chloride ion channels can prevent membrane depolarization and so inhibit sodium and calcium ion influx. Agents that prevent large sustained increases in intracellular free calcium levels can also prevent neuronal... 

In a series of studies, Dubovsky et al. ( 34) measured intracellular calcium ion concentrations in bipolar manic and depressed patients. They found decreases in mean concentrations in four bipolar, manic, and five bipolar, depressed, patients, in comparison with seven normothymic subjects without personal or first-degree relative histories of psychiatric disorders. Their findings were consistent with a diffuse abnormality in the mechanisms modulating intracellular calcium homeostasis. Further, this phenomenon s presence in both platelets and lymphocytes lends credence to a disruption in the cell membrane, the G-protein, or other mechanisms involved in the homeostasis of intracellular calcium ion concentrations. This may also support an extension of their findings from peripheral to neuronal tissue. 

C. Role of Calcium Ions in the Regulation of Skin Barrier Homeostasis... 

Among the former group, receptors that act as calcium ion or chloride ion channels play a crucial role in epidermal permeability barrier homeostasis. Topical application of calcium channel agonists delays the barrier recovery, while antagonists accelerate barrier repair.1,2,3 Topical application of chloride ion channel agonists accelerates the barrier recovery.2,4 The results of our studies are summarized in Table 15.1. 

Structure of SC and its lipid content affect the permeability barrier function. Visualization studies revealed that the penetration route across the SC resides in the intercellular tortuous pathway between the corneocytes. This implies that SC lipids play a key role in the skin barrier function.27 Another major controlling element in barrier homeostasis seems to be the epidermal Calcium ion.28... 

Calcium-binding Proteins Copper Enzymes in Denitrification Copper Proteins with Type 1 Sites Copper Proteins with Type 2 Sites Iron Heme Proteins Electron Transport Iron-Sulfin Proteins Metal-mediated Protein Modification Metallochaperones Metal Ion Homeostasis Molybdenum MPT-containing Enzymes Nickel Enzymes Cofactors, Nitrogenase Catalysis Assembly Zinc Enzymes. 

OC contains three specific glutamyl residues at amino acid positions 17, 21, and 24, which may be converted to y-carboxyglutamyl residues by a posttranslational, vitamin K-dependent enzymatic carboxylation. This unique car-boxylated amino acid binds calcium ions and is found in various proteins involved in blood coagulation and in calcium transport, deposition, and homeostasis. Undercar-boxylated OC, which has been reported in serum in some conditions, may be related to decreased bone density and may respond to administration of vitamin K. Although OC binds calcium and hydroxyapatite, its physiological role is unknown. 

The kidney plays a critical role in calcium homeostasis. PTH acts directly on the kidney to suppress calcium ion excretion in the urine by maximizing tubular calcium reabsorption. It increases phosphate ion excretion in the kidney (phosphaturic effect) to prevent excessive accumulation of this anion released during bone demineralization. 

Decay of Response Following Membrane Signal. If a rise in the Intracellular calcium ion concentration initiates the cellular events of exocytosls, it follows that there must be a means of limiting the rise in Intracellular calcium concentration and also a means of removing the calcium that is active, otherwise cellular homeostasis could not be maintained. 

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