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A Egorova

Publications and source records attributed to A Egorova.

10 recordsLinked to original sources
PubMed2001

Application of f--f luminescence of terbium ion for determination of non-steroidal anti-inflammatory drug-niflumic acid.

A simple, rapid and sensitive luminescence method for determination of niflumic acid (NFA) is described. The method is based on the intramolecular energy transfer from niflumic acid to terbium ion (Tb(3+)) in the presence of trioctylphosphine oxide (TOPO). Optimum conditions for the formation of the NFA-Tb(3+)-TOPO ternary complex have been investigated. The calibration graph is linear over the range 0.002--0.02 microg ml(-1). The relative standard deviation is close to 4%. The recoveries obtained by applying the method to the analysis of urine ranged from 94--102%.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Signal transduction from bradykinin, angiotensin, adrenergic and muscarinic receptors to effector enzymes, including ADP-ribosyl cyclase.

Muscarinic acetylcholine receptors in NG108-15 neuroblastoma x glioma cells, and beta-adrenergic or angiotensin II receptors in cortical astrocytes and/or ventricular myocytes, utilize the direct signaling pathway to ADP-ribosyl cyclase within cell membranes to produce cyclic ADP-ribose (cADPR) from beta-NAD+. This signal cascade is analogous to the previously established transduction pathways from bradykinin receptors to phospholipase Cbeta and beta-adrenoceptors to adenylyl cyclase via G proteins. Upon receptor stimulation, the newly-formed cADPR may coordinately function to upregulate the release of Ca2+ from the type II ryanodine receptors as well as to facilitate Ca2+ influx through voltage-dependent Ca2+ channels. cADPR interacts with FK506, an immunosuppressant, at FKBP12.6, FK506-binding-protein, and calcineurin, or ryanodine receptors. cADPR also functions through activating calcineurin released from A-kinase anchoring protein (AKAP79). Thus, some G(q/11)-coupled receptors can control cADPR-dependent modulation in Ca2+ signaling.

ADP-ribosyl Cyclase↗
PubMed1999

Sympathetic potentiation of cyclic ADP-ribose formation in rat cardiac myocytes.

We examined the role of cyclic ADP-ribose (cADP-ribose) as a second messenger downstream of adrenergic receptors in the heart after excitation of sympathetic neurons. To address this question, ADP-ribosyl cyclase activity was measured as the rate of [(3)H]cADP-ribose formation from [(3)H]NAD(+) in a crude membrane fraction of rat ventricular myocytes. Isoproterenol at 1 microM increased ADP-ribosyl cyclase activity by 1.7-fold in ventricular muscle; this increase was inhibited by propranolol. The stimulatory effect on the cyclase was mimicked by 10 nM GTP and 10 microM guanosine 5'-3-O-(thio)triphosphate, whereas 10 microM GTP inhibited the cyclase. Cholera toxin blocked the activation of the cyclase by isoproterenol and GTP. The above effects of isoproterenol and GTP in ventricular membranes were confirmed by cyclic GDP-ribose formation fluorometrically. These results demonstrate the existence of a signal pathway from beta-adrenergic receptors to membrane-bound ADP-ribosyl cyclase via G protein in the ventricular muscle cells and suggest that increased cADP-ribose synthesis is involved in up-regulation of cardiac function by sympathetic stimulation.

ADP-ribosyl Cyclase↗
PubMed1999

Fluorimetric determination of pipemidinic acid using the europium chelate.

The sensitized luminescence of europium ion in the complexes with pipemidinic acid is investigated. It was shown that in the result of intramolecular energy transfer from ligand to lanthanide ion the luminescence intensity of the latter increases by 10(10) times. The luminescence properties of the complex were studied and the high sensitive luminescence method for the determination of pipemidinic acid has been developed.

Anti-Infective Agents↗
PubMed1997

Sulfhydryl modification inhibits K+ (M) current with kinetics close to acetylcholine in rodent NG108-15 cells.

The effects of sulfhydryl reagents on M-type voltage-dependent potassium currents (IK(M)) were examined in NG108-15 cells transformed to express ml muscarinic acetylcholine receptors (mAChRs), a NGPM1-27 clone. Focal application of glutathione at millimolar concentrations dissolved in acidic solutions caused a transient inward current in NGPM1-27 cells at holding potentials of -30mV, associated with an inhibition of IK(M). The glutathione-induced response was mimicked by cysteine. These effects were also reproduced by superfusion with micromolar concentrations of HgCl2, AgNO3, N-methylmaleimide and p-chloromercuribenzoic acid (pCMB), agents which target protein thiols. Glutathione, HgCl2, AgNO3 and pCMB inhibited the peak conductance of IK(M) without shifting the half activating voltage (V1/2), which was comparable to the acetylcholine (ACh)-induced response. The voltage dependence of time constants for IK(M) deactivation in sulfhydryl reagent-, ACh- and non-treated cells resembled, but differed from that in Ba(2+)-treated cells. These results reveal that there is an accessible cysteine moiety, but not a disulfide bond, either on the M channel protein itself or on a protein directly involved in agonist-M channel coupling.

Acetylcholine↗
PubMed1996

Streptozotocin, an inducer of NAD+ decrease, attenuates M-potassium current inhibition by ATP, bradykinin, angiotensin II, endothelin 1 and acetylcholine in NG108-15 cells.

The M-potassium current was inhibited by bath application of 100 micron ATP, 10 nM bradykinin, 100 nM angiotensin II and 100 nM endothelin 1 as well as by 10 micron acetylcholine in an m1-muscarinic acetylcholine receptor-transformed NG108-15 cell line. The inhibition of M-current was attenuated in cells pretreated with 5 mM streptozotocin for 5-15 h and restored by simultaneous incubation with 5 mM nicotinamide. The results suggest that signal transduction from these five different receptors to M channels shares a common pathway which is susceptible to a streptozotocin-induced decrease in cellular NAD+ content.

Acetylcholine↗
PubMed1996

Inositol trisphosphate/Ca2+ as messengers of bradykinin B2 and muscarinic acetylcholine m1-m4 receptors in neuroblastoma-derived hybrid cells.

Neuroblastoma x glioma hybrid NG 108-15 and neuroblastoma x fibroblast hybrid NL308 cells possess endogenous bradykinin B2 receptors and m4 muscarinic acetylcholine receptors (mAChRs), which couple to phospholipase C and adenylate cyclase, respectively. Four genetic subtypes of mAChRs differed in their effects when stimulated in NG108-15 and NL308 cells overexpressing mAChRs. Broadly speaking, the principal effects fell into two categories: the odd-numbered receptors (m1 and m3) activated phospholipase C and increased inositol trisphosphate/Ca2+, as bradykinin did, whereas the even-numbered receptors (m2 and m4) inhibited adenylate cyclase via a pertussis toxin (PTx)-sensitive G-protein in NG108-15 cells. But all four types of NL308 cells overexpressing each m1, m2, m3 and m4 receptor activated phospholipase C, while keeping the PTx-sensitivity in m2/m4, but not in m1/m3 receptors. Coupling to ion channel effectors showed a comparable dichotomy in NG108-15 cells, while cross-activation occurred in NL308 cells.

Animals↗
PubMed1995

Nicotinamide-adenine dinucleotide regulates muscarinic receptor-coupled K+ (M) channels in rodent NG108-15 cells.

1. The possible role of nicotinamide-adenine dinucleotide (NAD+) and cyclic adenosine diphosphate ribose (cADPR) as regulators of M-type K+ currents (IK(M)) has been studied in whole-cell patch-clamped NG108-15 mouse neuroblastoma x rat glioma cells that had been transformed to express m1 muscarinic acetylcholine receptors (mAChRs). 2. Pre-incubation of NG108-15 cells for 6-8 h with streptozotocin (2-5 mM) reduced NAD+ levels by 40-50%. Nicotinamide (2-5 mM) increased NAD+ levels and prevented depletion by streptozotocin. 3. Streptozotocin pretreatment reduced the inhibition of IK(M) produced by 100 microM acetylcholine (ACh) from 51.6 +/- 7.0 to 29.1 +/- 7.5%. This was prevented by simultaneous pre-incubation with 2 mM nicotinamide or by adding 2 mM NAD+ to the pipette solution. Neither procedure significantly affected the initial amplitude of IK(M). 4. Inclusion of 2 microM cADPR in the pipette solution induced a slow loss of IK(M) with a time constant of about 20 min. 5. It is concluded that mAChR-induced inhibition of IK(M) requires intracellular NAD+. This might be needed for the formation of cADPR as a regulator or messenger for IK(M) inhibition.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

Cyclic ADP-ribose as a second messenger revisited from a new aspect of signal transduction from receptors to ADP-ribosyl cyclase.

Cyclic ADP-ribose (cADPR), an endogenous modulator of ryanodine receptor Ca(2+)-releasing channels, is found in various tissues. Cytosolic injection of cADPR induces an elevation of intracellular Ca(2+) concentrations or potentiates Ca(2+) increases. cADPR facilitates neurotransmitter or insulin release and modifies ionic currents. cADPR is synthesized by ADP-ribosyl cyclase and is metabolized by cADPR hydrolase. ADP-ribosyl cyclase activity is up-regulated by nitric oxide/cyclic GMP-dependent phosphorylation or receptor stimulation via G-proteins within membranes. These findings suggest that cADPR is a second messenger in cellular Ca(2+) signaling. However, many intriguing issues remain to be addressed before this identity is confirmed.

ADP-ribosyl Cyclase↗