Calcium channels measurement

Smith, J.S., Coronado, R., Meissner, G. (1986). Single channel measurements of the calcium release charmel from skeletal muscle sarcoplasmic reticulum. J. Gen. Physiol. 88, 573-588. 

Another popular assay for GPCR activation is to measure the increase in intracellular Ca2+ that occurs upon activation. GPCRs on the cell surface produce inositol triphosphate (IP3) via the action of Phospholipase C (PLC). IP3 stimulates calcium channels called IP3 receptors on the endoplasmic reticulum, which raise... 

Selected entries from Methods in Enzymology [vol, page(s)] Analysis, software for, 207, 717 barrier models, 207, 818 closed and open time estimation, 207, 755 data acquisition, 207, 747 modal behavior analysis, 207, 757 multiple channel problem, 207, 756 single-channel [extraction of kinetic information, 207, 765 measurement in tissue slices, 207, 220] synaptic, resolution improvement in patch clamp recording, 207, 216 whole-cell recording in calcium channel, 207, 181 fluctuation analysis, 207, 192. 

A next-level assay is usually an isolated heart/cardiac tissue preparation. The canine Purkinje fiber assay (GLP) measures several action potential parameters, like resting membrane potential, upstroke velocity, action potential duration and shape, but also if a drug acts reverse-use dependently [72]. Based on changes of the action potential shape it is possible to conclude which ion channels are modulated (e.g., L-type calcium channel block would abolish the plateau phase). The papillary muscle assay (e.g., guinea pigs) determines similar parameters [73]. 

The side effects of typical neuroleptics are extensively discussed in Chapters 26 and 41 in this volume. Given its potent calcium channel blocking properties, additional considerations apply to the use of pimozide. The use of pimozide requires caution regarding the possibility of QT prolongation, and we typically obtain an electrocardiogram (EKG) to measure the QTc interval at baseline, and obtain a repeat EKG during the dose... 

Turner TJ, Dunlap K (1995) Pharmacological characterization of presynaptic calcium channels using subsecond biochemical measurements of synaptosomal neurosecretion. Neuropharmacology 34 1469-78... 

Adherent cells have also been patterned using cell-adhesive and non-cell-adhesive microdomains created on a glass coverslip. This coverslip was then bonded with a PDMS channel layer for cell patterning [857]. For instance, endothelia or astrocyte-neuron cocultures were plated only on the cell-adhesive poly-L-lysine microdomains, but not on the non-adhesive agarose (1%) microdomains. Subsequently, calcium wave measurements were made to study calcium signaling of cells in two modes (1) within confluent cell microdomains, and (2) across neighboring, but spatially disconnected, microdomains [857]. 

It is possible to measure the formation of various radicals such as reactive oxygen species in cells. Reactive oxygen species (ROS) activate the nuclear factor of activated T cell transcription factor (NFAT), which is associated with its dephosphorylation, nuclear translocation, and increased affinity for DNA binding. Vanadium activation of nuclear factor of activated T cells (NFAT) was found to correlate with formation of the ROS H202 and was dependent upon the activity of calcium channels [39], In activated human neutrophiles, vanadium(II), (III), and (IV) increased hydroxyl radical formation and attenuation of myeloperoxidase activity, whereas V(V) did not show these effects. Similar results were seen in a cell-free system [40], Increased lipid peroxidation in liver but not in kidneys was found in normal rats treated with vanadate [41]. 

Glyceryl trinitrate overdose should be treated with the patient s head lowered. Other measures include respiration maintenance, use of plasma expanders, and electrolyte balance. Withdrawal of heparin treatment or dose reduction should be performed with the overdose of heparin. Protamine sulfate may be used to reduce severe bleeding. Heparin should be used with caution with glyceryl trinitrate, aprotinine, alcohol, tobacco, and ACE inhibitors. Nifedipine should be used with care when coadministering with immunosuppressants, magnesium salts, tobacco, digoxin, antineoplastics, calcium channel blockers, antihistamines, antifungals, antiepileptics, antiarrhythmics, and alcohol. 

Medications such as P-blockers, calcium channel blockers, digoxin, and amiodarone can be used to control cardiac conduction abnormalities (arrhythmias), and a pacemaker may be inserted to combat heart failure. The general supportive care measures used in acute stroke syndromes also should be followed. Death in patients with MELAS is usually the result of cardiac failure, pulmonary embolus, or renal failure. 

High throughput flash luminescence readers such as the FDS6000 and 7000, as well as the Lumax Flash HT, enable functional GPCR and calcium channel testing. A sensitive photon-counting CCD camera enables aequorin and luciferase activity to be measured by flash luminescence. Thus, these advances allow fluorescence-based assays to be replaced by luminescence-based assays,... 

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