In phosphoinositid

Other enzymes present in myelin include those involved in phosphoinositide metabolism phosphatidylinositol kinase, diphosphoinositide kinase, the corresponding phosphatases and diglyceride kinases. These are of interest because of the high concentration of polyphosphoinositides of myelin and the rapid turnover of their phosphate groups. This area of research has expanded towards characterization of signal transduction system(s), with evidence of G proteins and phospholipases C and D in myelin. 

Measurement of Phosphoinositide Turnover. As a result of these labeling experiments, two analytical procedures can be used to assess the involvement of the phosphoinositides in stimulus-induced activation of platelets by the agonist, PAF. One uses the measurement of the change in phosphoinositide levels per se as determined by [32P]phosphate labeling, and the other uses an assay to determine the accumulation of [3H]inositol phosphates through myo-[3H]inositol labeling. 

The increase in phosphoinositide hydrolysis appears to occur during the G0 and early G[ phases of the cell cycle. Cells will not tolerate a sustained increase in intracellular Ca2+ and actively extrude the ion. Recent evidence in B lymphocytes, using calcium probes and image intensifies, shows that when surface immunoglobulin is crosslinked the rise of intracellular Ca2+ occurs in repeated short bursts [37]. 

Changes in Phosphoinositide Signaling System in the Brains of AD Patients... 

Romero G, Perez MP, Carceller A, Monroy X, Farre AJ, et al. 2000. Changes in phosphoinositide signalling activity and levels of the alpha subunit of G(q/ll) protein in rat brain induced by E-5842, a sigma(l) receptor ligand and potential atypical antipsychotic. Neurosci Lett 290 189-192. 

Heilmann, I., Perera, I.Y., Gross, W. and Boss, W.F., 1999, Changes in phosphoinositide metabolism with days in culture affect signal transduction pathways in Galderia sulphuraria. Plant Physiol. 119 1331-1339. 

In animal systems, it is well documented that phosphoinositides and inositol phosphates participate in various signal transduction processes. One of the most studied signaling events involved in phosphoinositide turnover is the generation... 

Carlton JG, Cullen PJ. Coincidence detection in phosphoinositide signaling. Trends Cell Biol. 2005 15 540-547. 

Schwertz D.W., Halverson J. Changes in phosphoinositide-specific phospholipase C and phospholipase A2 activity in ischemic and reperfused rat heart. Basic Res. Cardiol. 87... 

Stimulation of P 2 Turnover in Phosphoinositide and Phosphatidic Acid of Tissue Slices... 

Logothetis D, Nilius B (2007) Dynamic changes in phosphoinositide levels control ion channel activity. Pfliigers Archiv European Journal of Physiology... 

Klein RM, Ufret-Vincenty CA, Hua L, Gordon SE (2008) Determinants of Molecular Specificity in Phosphoinositide Regulation PHOSPHATIDYLINOSI-... 

Lithium selectively interferes with the inositol lipid cycle [42,43] and this is the basis for a proposal of a unifying hypothesis for lithium actions [44,45]. Administration of lithium to rats (10 mmol/kg) resulted in a reduction in brain myoinositol and an increase in the reaction substrate inositol-1 -phosphate [46]. The magnesium-dependent enzyme inositol monophosphate phosphatase was inhibited in rat mammary gland by lithium [47]. Lithium has been shown to inhibit inositol monophosphate phosphatase in bovine brain ( (j = 0.8 mM) by substituting noncompetitively for magnesium ions [48]. Lithium may also affect other enzymes involved in phosphoinositide metabolism [43,49]. Lithium reduces the cell concentrations of myoinositol, which would otherwise be converted to phosphatidylinositol, and this attenuates the response to external stimuli [43,50]. 

Naslavsky, N., Weigert, R., and Donaldson, J. G. (2003). Convergence of non-clathrin and clathrin-derived endosomes involves Arf6 inactivation and changes in phosphoinositides. Mol. Biol. Cell 14, 417 31. 

Table 1 Distribution of P label between individual phosphate groups in phosphoinositides.

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