[Neurophysiological peculiarities of cognitive activity in patients anxiety-depressive and hypochondriacal disorders]. / Neirofiziologicheskie osobennosti kognitivnoi deiatel'nosti u patsientov s trevozhno-depressivnymi i ipokhondricheskimi rasstroistvami.

AIM: To study neurophysiological features of the cognitive activity in patients with anxiety-depressive and hypochondriacal disorders. MATERIAL AND METHODS: The study included 65 people: 16 with hypochondriacal disorder, 23 with mixed anxiety and depressive disorder, and 26 control subjects. Heart rate variability method and electroencephalography were used. RESULTS AND CONCLUSION: There was a decrease in the beta-1 frequency range in EEG after performing cognitive test in patients with mixed anxiety and depressive disorder. Patients with hypochondriacal disorder had the reduced duration of RR intervals; increased beta-1 frequency range in the resting state; the increase in the dominant beta-2 frequency during the cognitive test, and in the standard deviation of theta-wave frequencies after the cognitive test.

[Functioning features of the mirror neuron system in patients with affective disorders]. / Osobennosti funktsionirovaniia sistemy zerkal'nykh neironov u bol'nykh s affektivnymi rasstroistvami.

AIM: To reveal EEG patterns and activation of neural network changes during perception and realization of a simple motor act in healthy subjects and patients with affective disorders. MATERIAL AND METHODS: The patient group consisted of 15 people with affective disorders, the control group included 11 normals. As task subjects were asked to observe the movement of the experimenter hand (clenching of the hand), then submit this motion and then repeat it by themselves. EEG recording and EEG analysis were conducted. To identify activation areas, sLORETA method was used for solving the inverse problem of EEG. RESULTS AND CONCLUSION: In patients with affective disorders, the activation of the brain mirror system occurred in the left temporal region, while in healthy people such activation was observed in the temporal lobes of the two hemispheres and in the frontal upper, middle and lower convolutions.

Advanced consumable-free morphological analysis of intact red blood cells by a compact scanning flow cytometer.

Whereas modern automated blood cell analyzers measure the volume of individual red blood cells (RBCs), leading to four RBC indices (mean corpuscular volume, MCV; mean corpuscular hemoglobin, MCH; mean corpuscular hemoglobin concentration, MCHC; red cell distribution width, and RDW), the RBC shape has not been assessed by clinical screening tools. We applied the scanning flow cytometer (SFC) for complete characterization of intact RBC morphology in terms of diameter, maximal and minimal thicknesses, volume, surface area, sphericity index, spontaneous curvature, hemoglobin concentration, and content. The above-mentioned individual RBC characteristics were measured without fluorescent markers and other chemicals by a SFC equipped only with 660 nm laser for RBC illumination and single detector for measurement of angle-resolved light scattering. The distributions over all RBC characteristics were constructed and processed statistically to form the novel 31 RBC indices for 22 donor samples. Our results confirm the possibility of precise, label-free, enhanced morphological analysis of individual intact RBCs with compact single-detector flow cytometer. Detailed characterization of RBCs with high statistics and precision can be used to increase the value of screening examinations and to reveal pathologies accompanied by abnormality of RBC shape. © 2017 International Society for Advancement of Cytometry.

Fluorescence-free flow cytometry for measurement of shape index distribution of resting, partially activated, and fully activated platelets.

Whereas commercially available hematological analyzers measure volume of individual platelets, angle-resolved light-scattering provides unique ability to additionally measure their shape index. We utilized the scanning flow cytometer to measure light-scattering profiles (LSPs) of individual platelets taken from 16 healthy donors and the solution of the inverse light-scattering problem to retrieve the volume and shape index of each platelet. In normal conditions, the platelet shape index distribution (PSID) demonstrates three peaks, which relate to resting, partially activated, and fully activated platelets. We developed an algorithm, based on fitting PSID by a sum of three peak functions, to determine the percentage, mean platelet shape index, and distribution width of each platelet fraction. In total, this method gives eight additional parameters of platelet morphology and function to be used in clinical hematological analysis. We also stimulated the platelets with adenosine diphosphate (ADP) and measured the dependence of equilibrium PSID, including the total percentage of activated platelets, on ADP concentration. © 2016 International Society for Advancement of Cytometry.

Eye-safe 1.55 µm passively Q-switched Er,Yb:GdAl3(BO3)4 diode-pumped laser.

We report for the first time, to the best of our knowledge, on a diode-pumped passively Q-switched Er,Yb:GdAl3(BO3)4 laser. By using a Co2+:MgAl2O4 crystal as a saturable absorber, Q-switched laser pulses with a duration of 12 ns and a maximum energy of 18.7 µJ at a repetition rate of 32 kHz corresponding to an average output power of 0.6 W were obtained at 1550 nm under continuous-wave pumping. In the burst mode of operation, Q-switched laser pulses with the highest energy up to 44 µJ were realized with a pulse repetition rate of 6.5 kHz.

Dynamic quantification of antigen molecules with flow cytometry.

Traditional methods for estimating the number of expressed molecules, based on the detection of target antigens bound with fluorescently labeled antibodies, assume that the antigen-antibody reaction reaches equilibrium. A calibration procedure is used to convert the intensity of the fluorescence signal to the number of target molecules. Along with the different limitations of every calibration system, this substantially limits the applicability of the traditional approaches especially in the case of low affinity antibodies. We address this problem here with studies in which we demonstrate a new approach to the antigen molecule quantification problem. Instead of using a static calibration system, we analyzed mean fluorescence values over time by flow cytometry during antibody-antigen binding. Experimental data obtained with an LSRII cytometer were fitted by a diffusion-reaction mathematical model using the Levenberg-Marquardt nonlinear least squares curve-fitting algorithm in order to obtain the number of target antigen molecules per cell. Results were compared with the Quanti-BRITE calibration system. We conclude that, instead of using experiment-specific calibration, the value of the binding rate constant for each particular antibody-antigen reaction can be used to quantify antigen molecules with flow cytometry. The radius of CD8 antibody molecule binding site was found, that allows recalculating the binding rate constant for other conditions (different sizes of reagent molecules, fluorescent label, medium viscosity and temperature). This approach is independent of specially prepared calibration beads, antibody reagents and the specific dye and can be applied to both low and high affinity antibodies, under both saturating and non-saturating binding conditions. The method was demonstrated on a human blood sample dataset investigating CD8α antigen on T cells in stable binding conditions.

Dynamic quantification of antigen molecules with flow cytometry.

Traditional methods for estimating the number of expressed molecules, based on the detection of target antigens bound with fluorescently labeled antibodies, assume that the antigen-antibody reaction reaches equilibrium. A calibration procedure is used to convert the intensity of the fluorescence signal to the number of target molecules. Along with the different limitations of every calibration system, this substantially limits the applicability of the traditional approaches especially in the case of low affinity antibodies. We address this problem here with studies in which we demonstrate a new approach to the antigen molecule quantification problem. Instead of using a static calibration system, we analyzed mean fluorescence values over time by flow cytometry during antibody-antigen binding. Experimental data obtained with an LSRII cytometer were fitted by a diffusion-reaction mathematical model using the Levenberg-Marquardt nonlinear least squares curve-fitting algorithm in order to obtain the number of target antigen molecules per cell. Results were compared with the Quanti-BRITE calibration system. We conclude that, instead of using experiment-specific calibration, the value of the binding rate constant for each particular antibody-antigen reaction can be used to quantify antigen molecules with flow cytometry. The radius of CD8 antibody molecule binding site was found, that allows recalculating the binding rate constant for other conditions (different sizes of reagent molecules, fluorescent label, medium viscosity and temperature). This approach is independent of specially prepared calibration beads, antibody reagents and the specific dye and can be applied to both low and high affinity antibodies, under both saturating and non-saturating binding conditions. The method was demonstrated on a human blood sample dataset investigating CD8α antigen on T cells in stable binding conditions.

Highly efficient continuous-wave diode-pumped Er, Yb:GdAl3(BO3)4 laser.

We report the highly efficient continuous-wave diode-pumped laser operation of Er, Yb:GdAl3(BO3)4 crystal. Absorption and stimulated emission spectra, emission lifetimes, and efficiencies of energy transfer from Yb3+ to Er3+ ions were determined. A maximal output power of 780 mW was obtained at 1531 nm at absorbed pump power of 4 W with slope efficiency of 26%.

Passively Q-switched microchip Er, Yb:YAl3(BO3)4 diode-pumped laser.

We report, for the first time to our knowledge, a diode-pumped cw and passively Q-switched microchip Er, Yb:YAl(3)(BO(3))(4) laser. A maximal output power of 800 mW at 1602 nm in the cw regime was obtained at an absorbed pump power of 7.7 W. By using Co(2+):MgAl(2)O(4) as a saturable absorber, a TEM(00)-mode Q-switched average output power of 315 mW was demonstrated at 1522 nm, with pulse duration of 5 ns and pulse energy of 5.25 µJ at a repetition rate of 60 kHz.

Down-regulation of sodium current in chronic heart failure: effect of long-term therapy with carvedilol.

Evidence has accumulated recently about the importance of alterations in Na+ channel function and slow myocardial conduction for arrhythmias in the infarcted and failing heart. The present study tested a hypothesis that Na+ current (INa/C) density decreases in chronic heart failure (HF) and that Na+ channel (NaCh) functional density can be restored by long-term therapy with carvedilol, a mixed alpha- and beta-adrenergic blocker. Studies were performed using a canine model of chronic HF produced in dogs by sequential intracoronary embolizations with microspheres. HF developed approximately 3 months after the last embolization (left ventricle, LV, ejection fraction = 28 +/- 1%). Ventricular cardiomyocytes (VCs) were isolated enzymatically from LV mid-myocardium, and INa was measured by whole-cell patch-clamp. The maximum INa/C was decreased in failing (n = 19) compared to normal (n = 12) hearts (33.1 +/- 1.6 vs 48.5 +/- 5.1 pA/pF, mean +/- SE, p < 0.001). The steady-state inactivation and activation of INa remained unchanged in failing compared to normal hearts. Long-term treatment with carvedilol (1 mg/kg, twice daily for 3 months) normalized INa/C in dogs with HF. INa/C in HF dogs (n = 6) treated with carvedilol was higher compared to that of non-treated HF dogs (n = 6) (49.4 +/- 0.9 vs 29 +/- 4.8 pA/pF, p < 0.007). In vitro culture of VCs of failing hearts for 24 h did not restore INa/C. However, INa/C was partially restored when VCs were incubated for 24 h with BAPTA-AM, an intracellular Ca2+ buffer. Thus, we conclude that experimental chronic HF in dogs results in down-regulation of the functional density of NaCh that can be restored by long-term therapy with carvedilol. The mechanism of NaCh down-regulation in HF may be linked to poor Ca2+ handling in this stage of disease.

Late sodium current is a novel target for amiodarone: studies in failing human myocardium.

V. A. Maltsev, H. N. Sabbah and A. I. Undrovinas. Late Sodium Current is a Novel Target for Amiodarone: Studies in Failing Human Myocardium. Journal of Molecular and Cellular Cardiology (2001) 33, 923-932. The authors recently reported the existence of a novel late Na(+)current (I(NaL)) in ventricular cardiomyocytes (VC) isolated from both normal and failing human hearts. Both in failing human and canine VC, partial block of I(NaL)normalized action potential (AP) duration and abolished early after depolarizations (EADs). The most recent computer simulation studies indicate a significant contribution of the persistent Na(+)current into the ion current balance on the plateau of VC AP as well as its important role in the dispersion of AP duration across the ventricular wall. The data thus indicate a possibility for I(NaL)to be a new therapeutic target. The present study tested a hypothesis that I(naL)could be a novel target for amiodarone (AMIO). Midmyocardial VC isolated from left ventricle of explanted failing human hearts were measured by a whole-cell clamp. I(NaL)was effectively blocked by AMIO in therapeutic concentrations, with IC(50)being 6.7+/-1.1 microM (mean+/-S.E.M., n=16 cells). At the same time, AMIO (5 microM ) produced almost no effect on the transient Na(+)current (IC(50)=87+/-28 microM, n=8). AMIO significantly shifted the steady-state inactivation (SSI) curve of I(NaL)towards more negative potentials and accelerated decay time course in a dose-dependent manner. At 5 microM, AMIO shifted SSI by 21+/-3 mV (n=7) and decreased the decay time constant from 0.67+/-0.05 s to 0.37+/-0.04 s (n=5, P<0.004). Evaluation of AMIO binding to different Na(+)channel (NaCh) states by means of mathematical models describing dose-dependent SSI shift and decay acceleration was consistent with an action that AMIO blocks NaCh preferentially in inactivated and activated states rather than in resting state. The authors conclude that the late Na(+)current is effectively blocked by AMIO and represents a new target for the drug in patients with chronic heart failure (HF).

Cardiac contractility modulation with the impulse dynamics signal: studies in dogs with chronic heart failure.

The intravenous use of positive inotropic agents, such as sympathomimetics and phosphodiesterase inhibitors, in heart failure is limited by pro-arrhythmic and positive chronotropic effects. Chronic use of these agents, while eliciting an improvement in the quality of life of patients with advanced heart failure, has been abandoned because of marked increase in mortality when compared to placebo. Nevertheless, patients with advanced heart failure can benefit from long-term positive inotropic support if the therapy can be delivered 'on demand' and in a manner that is both safe and effective. In this review, we will examine the use of a novel, non-stimulatory electrical signal that can acutely modulate left ventricular (LV) contractility in dogs with chronic heart failure in such a way as to elicit a positive inotropic support. Cardiac contractility modulation (CCM) with the Impulse Dynamic(trade mark) signal was examined in dogs with chronic heart failure produced by intracoronary microembolizations. Delivery of the CCM signal from a lead placed in the great coronary vein for periods up to 10 minutes resulted in significant improvements in cardiac output, LV peak+dP/dt, LV fractional area of shortening and LV ejection fraction measured angiographically. Discontinuation of the signal resulted in a return of all functional parameters to baseline values. In cardiomyocytes isolated from dogs with chronic heart failure, application of the CCM signal resulted in improved shortening, rate of change of shortening and rate of change of relengthening suggesting that CCM application is associated with intrinsic improvement of cardiomyocyte function. The improvement in isolated cardiomyocyte function after application of the CCM signal was accompanied by an increase in the peak and integral of the Ca(2+) transient suggesting modulation of calcium cycling by CCM application. In a limited number of normal dogs, intermittent chronic delivery of the CCM signal for up to 7 days showed chronic maintenance of LV functional improvement. In conclusion, pre-clinical results to date with the Impulse Dynamics CCM signal indicate that this non-pharmacologic therapeutic modality can provide short-term positive inotropic support to the failing heart and as such, may be a useful adjunct in the treatment of advanced heart failure. Additional, long-term studies in dogs with heart failure are needed to establish the safety and efficacy of this therapeutic modality for the chronic treatment of this disease syndrome.

Structural units of cuprates in natural Cu-oxysalts.

The structure of copper oxysalt minerals is analyzed on the basis of the classification scheme developed earlier for synthetic cuprates. The copper-oxygen compounds were considered as the salts of hypothetical copper acids with characteristic Cu-containing structural units of various dimensions formed by a polymerization of the CuO squares. The results of magnetic susceptibility measurements performed recently were analyzed from the viewpoint of the developed extended structural classification scheme. The dimerization of magnetic moments was considered as a property of cuprates which was strongly dependent on the type of Cu-containing structural unit. A further extension of the structural classification scheme for cuprates is also discussed.

Mathematical modeling the kinetics of cell distribution in the process of ligand-receptor binding.

A statistical approach is presented to model the kinetics of cell distribution in the process of ligand-receptor binding on cell surfaces. The approach takes into account the variation of the amount of receptors on cells assuming the homogeneity of monovalent binding sites and ligand molecules. The analytical expressions for the kinetics of cell distribution have been derived in the reaction-limited approximation. In order to demonstrate the applicability of the mathematical model, the kinetics of binding the rabbit, anti-mouse IgG with Ig-receptors of the murine hybridoma cells has been measured. Anti-mouse IgG was labeled with fluorescein isothiocyanate (FITC). The kinetics of cell distribution on ligand-receptor complexes was observed during the reaction process by real-time measuring of the fluorescence and light-scattering traces of individual cells with the scanning flow cytometer. The experimental data were fitted by the mathematical model in order to obtain the binding rate constant and the initial cell distribution on the amount of receptors.

Individual Escherichia coli cells studied from light scattering with the scanning flow cytometer.

BACKGROUND: Flow cytometry is a powerful tool for the analysis of individual particles in a flow. Differential light scattering (an indicatrix) was used for many years to obtain morphologic information about microorganisms. The indicatrices play the same role for individual particle recognition as a spectrum for substance characterization. We combined two techniques to analyze the indicatrix of the cells for the purpose of developing a database of light-scattering functions of cells. METHODS: The scanning flow cytometer (SFC) allows the measurement of the entire indicatrix of individual particles at polar angles ranging from 5 degrees to 100 degrees. In this work, light-scattering properties of Escherichia coli have been studied both experimentally and theoretically with the SFC and the T-matrix method, respectively. The T-matrix method was used because of the nonspherical shape of E. coli cells, which were modeled by a prolate spheroid. RESULTS: The indicatrices of E. coli cells were stimulated with T-matrix method at polar angles ranging from 10 degrees to 60 degrees. The absolute cross-section of light scattering of E. coli has been determined comparing the cross section of polystyrene particles modeled by a homogeneous sphere. The E. coli indicatrices were compared for logarithmic and stationary phases of cell growth. CONCLUSIONS: The indicatrices of E. coli were reproducible and could be used for identification of these cells in biologic suspensions. The angular location of the indicatrix minimum can be used in separation of cells in logarithmic and stationary phases. To use effectively the indicatrices for that purpose, the light-scattering properties of other microorganisms have to be studied.

New aspects in the crystal chemistry of (M2CU2O3)m(CuO2)n-type (M = Ca, Sr, Y, Bi) cuprates

The structural regularities of (M2Cu2O3)m(CuO2)n-type (M = Ca, Sr, Y, Bi) cuprates with ladder-type planes have been considered. On the basis of the structural studies of the samples grown by floating-zone and flux methods, it was concluded that the phase (M2Cu2O3)(CU1+deltaO2+gamma), described as the m/n = 1/1 member, with Cu-deficient Cu-O ribbons in the series (M2Cu2O3)m(CuO2)n can be treated as an individual structural type intermediate between SrCu2O3 and incommensurate-type phases (M2Cu2O3)m(CuO2)n with m not equal n. The deficiency of the Cu sites in CuO ribbons is a particular crystal-chemistry feature of this structural type, in addition to the geometrical feature (m = n). The structural type of the 'Cu-deficient ladder' can transform into the incommensurate-type phases (M2Cu2O3)m(CUO2)n (m/n = 5/7, 7/10, 9/13 etc.) in the presence of free [CuO4]6- radicals in the melt. A realization of the (M2Cu2O3)m(CuO2)n phase with a particular m/n value is caused by the type of M cation. On the basis of recent data, the role of trivalent ions in the chemical composition of the (M2Cu2O3)m(CuO2)n-type compounds was also analyzed. The occurrence of the superconductivity in (Sr,Ca)CuO2 samples is discussed by analogy with cuprates of the infinite-layer structure.

Calibration-free method to determine the size and hemoglobin concentration of individual red blood cells from light scattering.

At present, hemoglobin concentration and the volume of an erythrocyte can be determined from the intensities of light scattered by an individual cell at fixed angular intervals. This method is used in modern hemoglobin analyzers, but it requires calibration of optical and electronic units by certified particles of known size and refractive index. We describe a method that is based on the parametric solution of an inverse light-scattering problem and does not require a calibration procedure. The method is based on the use of parameters of the entire angular light-scattering pattern, called an indicatrix here. These parameters do not depend on the absolute intensity of light scattering. The indicatrix parameters form approximating equations that relate these parameters to the size and the phase-shift parameters of the particle. The applicability of the method is demonstrated by measurement of the indicatrices of individual sphered erythrocytes. The indicatrices of the individual erythrocytes were measured with a scanning flow cytometer at an angular range of from 15 to 55 deg. The volume and the hemoglobin concentration have been calculated by use of the developed method and by fitting of the experimental indicatrices to the indicatrices calculated from the Mie theory.

Particle classification from light scattering with the scanning flow cytometer.

BACKGROUND: The differential light-scattering pattern, an indicatrix, provides the most complete characterization of the optical properties of a particle. Particle classification can be performed on the basis of particle parameters retrieved from the indicatrices. This classification extends the ability of flow cytometry in particle recognition. METHODS: The scanning flow cytometer (SFC) permits an acquisition of traces of light scattering signals, i.e., native SFC traces, from single particles. The acquired native SFC traces are transformed into indicatrices. The performance of the SFC in measurements of indicatrices has been demonstrated for the following particles: lymphocytes, erythrocytes, polystyrene particles, and milk-fat particles. RESULTS: The structure and profile of the indicatrix for each particle type have been found to be unique. Classification of polystyrene particles has been performed on the basis of the map formed by particle refractive index and size. The polystyrene particles were classified using this map into different size categories ranging from 1.4-7 microm, with a size deviation of 0.07 microm. CONCLUSIONS: The method based on analysis of native SFC traces shows better performance in particle classification than the method based on the particle refractive index and size map. The classification performance of the SFC will be useful, for example, for particle sorting and particle identification, and with additional fluorescent measurements may have applications in multiparameter particle-based immunoassay.

Repolarization abnormalities in cardiomyocytes of dogs with chronic heart failure: role of sustained inward current.

We previously showed that a canine model of chronic heart failure (HF) produced by multiple coronary microembolizations manifests ventricular arrhythmias similar to those observed in patients with chronic HF. In the present study, we used single canine cardiomyocytes isolated from the left ventricle (LV) of normal dogs (n = 13) and dogs with HF (n = 15) to examine the cellular substrate of these arrhythmias. Action potentials (APs) and ion currents were measured by perforated and whole cell patch clamp, respectively. We found prolonged APs and alterations of AP duration resulting in early afterdepolarizations (EADs) at the low pacing rates of 0.5 Hz and 0.2 Hz. Na+ channel blockers saxitoxin (STX, 100 nM) and lidocaine (90 microM) reduced AP duration dispersion and abolished EADs in HF cardiomyocytes. The steady-state current (Iss)-voltage relation, in the voltage range from -25 mV to 25 mV analogous to the AP plateau level, was significantly shifted inward in HF cardiomyocytes. STX and lidocaine shifted the Iss-voltage relationship in an outward direction. The shifts produced by both drugs was significantly greater in cardiomyocytes of dogs with HF, indicating an increase in inward current. In the experimental configuration in which K+ currents were blocked, the density of the steady-state Ca2+ current (ICa) was found to decrease in HF cardiomyocytes by approximately 33%. In contrast, the density of the steady-state Na+ current (INa) significantly (P < 0.01) increased in HF cardiomyocytes (0.17 +/- 0.06 pA/pF) compared with normal cells (0.08 +/- 0.02 pA/pF). The relative contribution of INa to the net inward current was greater in HF cardiomyocytes, as evident from the increased ratio of INa/ICa (from 0.22 to 0.68). These observation support a hypothesis that anomalous repolarization of HF cardiomyocytes is due, at least in part, to an increased steady-state inward Na+ current.

Establishment of beta-adrenergic modulation of L-type Ca2+ current in the early stages of cardiomyocyte development.

beta-Adrenergic modulation of the L-type Ca2+ current (ICaL) was characterized for different developmental stages in murine embryonic stem cell-derived cardiomyocytes using the whole-cell patch-clamp technique at 37 degreesC. Cardiomyocytes first appeared in embryonic stem cell-derived embryoid bodies grown for 7 days (7d). ICaL was insensitive to isoproterenol, forskolin, and 8-bromo-cAMP in very early developmental stage (VEDS) cardiomyocytes (from 7+1d to 7+2d) but highly stimulated by these substances in late developmental stage (LDS) cardiomyocytes (from 7+9d to 7+12d), indicating that all signaling cascade components became functionally coupled during development. In early developmental stage (EDS) cells (from 7+3d to 7+5d), the stimulatory response to forskolin and 8-bromo-cAMP was relatively weak. The forskolin effect was strongly augmented by ATP-gamma-S. At this stage, basal ICaL was stimulated by the nonselective phosphodiesterase (PDE) inhibitor isobutylmethylxanthine, by PDE inhibitors selective for the PDE II, III, and IV isoforms, as well as by the phosphatase inhibitor okadaic acid. Stimulation of ICaL by the catalytic subunit of the cAMP-dependent protein kinase A (PKA) was found to be similar (about 3 times) throughout development and in adult mouse ventricular cardiomyocytes, indicating that no structural changes of the Ca2+ channel related to phosphorylation occurred during development. ICaL was stimulated by isoproterenol in the presence of a PKA inhibitor and GTP-gamma-S in LDS but not VEDS cardiomyocytes, suggesting the development of a membrane-delimited stimulatory pathway mediated through the stimulatory GTP binding protein, Gs. We conclude that uncoupling and/or low expression of Gs protein accounted for the ICaL insensitivity to beta-adrenergic stimulation in VEDS cardiomyocytes. Furthermore, in EDS cells at the 7+4d stage, the reduced beta-adrenergic response is due, at least in part, to high intrinsic PDE and phosphatase activities.