Bay K 8644 increases resting Ca2+ spark frequency in ferret ventricular myocytes independent of Ca influx: contrast with caffeine and ryanodine effects

Bay K 8644, an L-type Ca2+ channel agonist, was shown previously to increase resting sarcoplasmic reticulum (SR) Ca2+ loss and convert post-rest potentiation to decay in dog and ferret ventricular muscle. Here, the effects of Bay K 8644 on local SR Ca2+ release events (Ca2+ sparks) were measured in isolated ferret ventricular myocytes, using laser scanning confocal microscopy and the fluorescent Ca2+ indicator fluo-3. The spark frequency under control conditions was fairly constant during 20 s of rest after interruption of electrical stimulation. Bay K 8644 (100 nmol/L) increased the spark frequency by 466+/-90% of control at constant SR Ca2+ load but did not change the spatial and temporal characteristics of individual sparks. The increase in spark frequency was maintained throughout the period of rest. The increase in Ca2+ spark frequency induced by Bay K 8644 was not affected by superfusion with Ca2+-free solution (with 10 mmol/L EGTA) but was suppressed by the addition of 10 micromol/L nifedipine (which by itself did not alter resting Ca2+ spark frequency). This suggests that the effect of Bay K 8644 on Ca2+ sparks is mediated by the sarcolemmal dihydropyridine receptor but is also independent of Ca2+ influx. Low concentrations of caffeine (0.5 mmol/L) increased both the average frequency and duration of sparks. Ryanodine (50 nmol/L) increased the spark frequency and also induced long-lasting Ca2+ signals. This may indicate long-lasting openings of SR Ca2+ release channels and a lack of local SR Ca2+ depletion. In lipid bilayers, Bay K 8644 had no effect on either single-channel current amplitude or open probability of the cardiac ryanodine receptor. It is concluded that Bay K 8644 activates SR Ca2+ release at rest, independent of Ca2+ influx and perhaps through a functional linkage between the sarcolemmal dihydropyridine receptor and the SR ryanodine receptor. In contrast, caffeine and ryanodine modulate Ca2+ sparks by a direct action on the SR Ca2+ release channels.     

An automatic measurement device for the evaluation of the print quality of printed characters

When using OCR equipment (OCR = Optical Character Recognition) it is necessary to define shape and print quality of the characters in national and international standards.The paper gives a review of the standardization of the character fonts OCR A and OCR B for optical character recognition. All relevant parameters are discussed which define the print quality of printed characters. A critical review of two measurement methods used so far for the evaluation of print quality parameters is given. The improvement of the measurement methods led to the development of an automatic measurement device which is described in detail.The automatic measurement device consists of a high precision scanning device to digitize the printed characters and a computer program for the evaluation of the data. The mechanical construction and the properties of the scanning device are explained. The computer program consists of two main parts for preprocessing of the scanned data and for the evaluation of the different print parameters.Test results are reported and possible applications of the measurement device are discussed.     

Cyclic stretch down-regulates calcium transporter gene expression in neonatal rat ventricular myocytes

Abnormal intracellular Ca2+ handling in hypertrophied and failing hearts is partly due to changes in Ca2+ transporter gene expression, but the mechanisms responsible for these alterations remain largely unknown. We previously showed that intrinsic mechanical load (i.e. spontaneous contractile activity) induced myocyte hypertrophy, and down-regulated SR Ca2+ ATPase (SERCA2) gene expression in cultured neonatal rat ventricular myocytes (NRVM). In the present study, we examined whether extrinsic mechanical load (i.e. cyclic stretch) also induced NRVM hypertrophy, and led to down-regulation of SERCA2 and other Ca2+ transporter genes which have been associated with cardiac hypertrophy and failure in vivo. NRVM were maintained in serum-free culture medium under control conditions, or subjected to cyclic mechanical deformation (1.0 Hz, 20% maximal strain, 48 h). Under these conditions, cyclic stretch induced NRVM hypertrophy, as evidenced by significant increases in total protein/DNA ratio, myosin heavy chain (MHC) content, and atrial natriuretic factor (ANF) secretion. Cyclic stretch also induced the MHC isoenzyme "switch" which is characteristic of hemodynamic overload of the rat heart in vivo. Cyclic stretch significantly down-regulated SERCA2 and ryanodine receptor (RyR) mRNA and protein levels, while simultaneously increasing ANF mRNA. In contrast, Na+-Ca2+ exchanger and phospholamban mRNA levels were unaffected. Load-dependent SERCA2 and RyR down-regulation was independent of Ca2+ influx via voltage-gated, L-type Ca2+ channels, as cyclic stretch down-regulated SERCA2 and RyR mRNA levels in both control and verapamil-treated NRVM. These results indicate that extrinsic mechanical load (in the absence of other exogenous stimuli) induces NRVM hypertrophy and causes down-regulation of Ca2+ transporter gene expression. This in vitro model system should prove useful to dissect the intracellular signaling pathways responsible for transducing this phenotype during cardiac hypertrophy and heart failure in vivo.     

Social-comparison jealousy: A developmental and motivational study.

72 6–11 yr olds were read 12 stories in which the protagonists failed to excel or attain something in each of 6 areas: possessions, sports, art, appearance, mathematics, and reading. In 6 stories, one child failed, whereas another excelled; in 6 stories no other child was involved. Ss rated the importance of the 6 areas to themselves and completed the PPVT-R and the Piers-Harris Self-Concept Scale. Measures from the responses to the stories were grouped into 3 components of social-comparison jealousy—spontaneous comparisons, affect, and thoughts about jealous behavior. Jealousy was a common response to comparison failure situations. Older Ss revealed more social-comparison jealousy in areas of greater importance to themselves, whereas younger Ss did not show this differentiation as clearly. No sex differences in the experience of social-comparison jealousy were found. Results are discussed in terms of social-comparison theory, and a stage model of jealousy development is proposed. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accumulation-layer surface-wave convolver

A new type of coupled silicon?lithium-niobate convolver is reported, in which a known accumulation layer of electrons was produced at the silicon surface. By applying a normal electric field, the electron density was varied, and the convolution signal was a strong function of this surface charge density.     

A body model server for human motion capture and representation

This paper presents a body model server (BMS) that provides real-time access to the position and posture of a person's torso, arms, hands, head, and eyes. It can be accessed by clients over a network. The BMS is designed to function as a device-independent data-layer between the sensing devices and client applications that require real-time human motion data, such as animation control. It can provide clients with accurate information at up to 40 Hz. For data collection, the model uses four magnetic position/orientation sensors, two data-gloves, and an eye-tracker. The BMS combines the data-streams from the sensors and transforms them into snapshots of the user's upper-body pose. A geometric model made up of joints and segments structures the input. Posture of the body is represented by joint angles. Two unique characteristics of our approach are the use of the implicit, geometric constraints of the sensed body to simplify the computation of the unmeasured joint angles, and the use of time-stamped data that allow synchronization with other data streams, e.g., speech input. This paper describes the architecture of the BMS, including the management of multiple input devices, the representation and computation of the position and joint angle data, and the client-server interface.     

A Venerable Tool for a New Application: Using Scenario Analysis for Formulating Strategies for Emerging Technologies in Emerging Markets

ABSTRACT

Scenario analysis appears to be an ideal strategic planning tool for emerging technologies in emerging markets, yet it is in its infancy in the business world. This article is one of the first reports on applying this powerful tool to emerging technology business planning. Scenario analysis was incorporated into a PC-based simulation model and was applied by 11 teams consisting of company presidents, managers, and technical professionals to formulate a business strategy for wireless communications prior to its commercial launch. By incorporating key concepts from finance, market and competitive analysis, and management of technology, the model guides the user through a series of assumptions and decisions to arrive at a resilient strategy that maximizes the technology's chance of commercial success under a range of scenarios.