A liquid crystal pixel array for signal discrimination in array biosensors.

A new optical design uses a liquid crystal pixel array (LCPA) to discriminate multiple fluorescence signals on a two-dimensional biosensor array. The LCPA can selectively control the transmission of fluorescence generated from multiple biosensing elements on a planar waveguide. This device sequentially acquires the fluorescence data from the substrate by making multiple individual measurements of the sensing elements on the waveguide. The biosensing elements are patterned according to the pixel layout of the LCPA and optically aligned so that each electronically driven pixel can either transmit or filter out the fluorescence signal as specified by the user. The primary advantage of this system is that a single detection channel (i.e. photomultiplier tube (PMT)) can be used to measure multiple fluorescence signals from a two-dimensional substrate while the LCPA provides for spatial resolution. We evaluate the performance of the LCPA by testing the optical homogeneity of the liquid crystal pixels and linear dynamic range for transmitting light. The LCPA is also used with well-developed biosensing chemistry modified for this optical format.

[Pre- and postsynaptic action of the ATP-dependent K+-channel-(K+ATP)-opener pinacidil in rabbit pulmonary artery]. / Az ATP-függó K(+)-csatorna-(K+ATP)-aktiváló pinacidil pre- és poszt-szinaptikus hatása nyúl pulmonáris artérián.

Low frequency (2 Hz) of electrical depolarisation induced [3H]noradrenaline ([3H]NA) release has been measured from the isolated main pulmonary artery of the rabbit in the presence of uptake blockers (cocaine, 3x10(-5)M and corticosterone, 5x10(-5)M), with parallel measurements of post-junctional contractile responses. The K+ATP-channel opener pinacidil (10(-6)-10(-4)M), slightly potentiated the nerve-evoked release of [3H]NA which failed to show close concentration-dependency. Large concentration of pinacidil (10(-4)M) increased the ratio of [3H]NA release from 0.99 +/- 0.02 to 1.28 +/- 0.05 (P < 0.0005). On the other hand, pinacidil inhibited the nerve-evoked contractions in a concentration-dependent manner. 10(-4)M caused nearly 70% inhibition of contractile response. The pre- and post-junctional effects of pinacidil were studied under the following experimental conditions: 1) exogenously applied 1-NA; 2) excess K+; 3) 'L-type' Ca(2+)-channel activation (BAY K 8644); K(+)-channel inhibition (4-AP); and 5) Na(+)-pump inhibition/reactivation. Pinacidil (10(-4)M) retained its marginal NA-release stimulatory effect in all cases. However, pinacidil inhibited the contraction of smooth muscle, although to a different extent, in all of the experimental conditions used in our study.

Pre-junctional stimulatory and post-junctional inhibitory effects of pinacidil in the isolated main pulmonary artery of the rabbit under different experimental conditions.

Low frequency (2Hz) nerve-stimulation induced [3H]noradrenaline ([3H]NA) release has been measured from the isolated main pulmonary artery of the rabbit in the presence of uptake blockers (cocaine, 3 x 10(-5)M; corticosterone, 5 x 10(-5), with parallel measurements of post-junctional contractile responses. The K+ ATP-channel opener pinacidil (10(-6)-10(-4)M), slightly potentiated the nerve-evoked release of [3H]NA which failed to show close concentration-dependency. Large concentration of pinacidil (10(-4)M) increased the ratio of [3H]NA release from 0.99 +/- 0.02 to 1.29 +/- 0.05; P < 0.0005). On the other hand, pinacidil inhibited the nerve-evoked contractions in a concentration-dependent manner. 10(-4)M caused nearly 70% inhibition of contractile response. The pre- and post-junctional effects of pinacidil were studied under the following experimental conditions: (1) exogenously applied I-NA; (2) excess K+; (3) 'L-type' Ca(2+)-channel activation (BAY K 8644); (4) K(+)-channel inhibition (4-AP); and (5) Na(+)-pump inhibition/reactivation. Pinacidil (10(-4)M) retained its marginal NA-release stimulatory effect in all cases. However, pinacidil inhibited the contraction of smooth muscle, although to a different extent, in all of the experimental conditions used in our study.

Phenylethylamine and tyramine are mixed-acting sympathomimetic amines in the brain.

On the helical strip of a capacitance vessel, the pulmonary artery of the rabbit, phenylethylamine (PEA) and tyramine act solely via displacement of noradrenaline from their storage sites and this effect is inhibited by desmethylimipramine (DMI). In contrast, on a resistance vessel, the perfused central ear artery of the rabbit, PEA enhances stimulation induced contractions in 0.2-0.8 microgram/ml concentration [catecholaminergic activity enhancer (CAE) effect], and increases smooth muscle tone (noradrenaline displacing effect) in 4-6 micrograms/ml concentration. This latter effect only is blocked by DMI. Tyramine acts similarly and is more potent than PEA. On the isolated brain stem PEA, tyramine and (-)methamphetamine are, in the presence of cocaine and DMI, highly potent enhancers of stimulation induced release of 3H-noradrenaline, 3H-dopamine and 3H-serotonin. Compounds with specific CAE effect in the brain, (-)deprenyl and 1-phenyl-2-propylaminopentane [(-)PPAP], antagonize tetrabenazine-induced depression of performance of rats in the shuttle box. PEA and tyramine, which are rapidly metabolized in vivo, are ineffective in this test up to 40 mg/kg, whereas (-)methamphetamine, the stable PEA derivative, is highly effective. Compounds with CAE effect enhance at low concentrations the slow inward Ca2+ current in the sino-auricular fibers of the frog heart and inhibit it in high concentration. PEA and tyramine enhance Ca2+ influx from 0.05 to 4 micrograms/ml and inhibit it in 8 micrograms/ml. In conclusion, PEA and tyramine stimulate primarily coupling of action potential to transmitter release in the catecholaminergic neurons in the brain and displace catecholamines in higher concentration only.

A-23187 evoked transmitter release from rabbit pulmonary artery and its inhibition by reactivation of sodium-pump.

1. The spontaneous [3H]-release has been measured from the isolated main pulmonary artery of the rabbit preloaded with [3H]noradrenaline in the presence of uptake blockers (cocaine, 3 x 10(-5) M; corticosterone, 5 x 10(-5) M). 2. The Ca-ionophore A-23187 (3 x 10(-7)-3 x 10(-5) M) increased the outflow of [3H] by a concentration dependent manner. 3. Inhibition of Na+-pump by removal of K+ from the external medium also increased the release of labelled noradrenaline. 4. In the absence of external K+, the applied A-23187 (3 x 10(-6) M; EC50) further increased the release of [3H]. 5. Reactivation of Na+-pump by readmission of K+ (5.9 mM) to the external medium abolished the [3H]-release which had previously been increased in "K+-free" solution. 6. The reactivated Na+-pump significantly inhibited the transmitter releasing action of A-23187. 7. This latter was antagonized by an increase of external Ca2+ (7.5 mM). 8. It is concluded that the reactivated Na+-pump caused re-establishment of Na+-gradient is capable to counteract the Ca-ionophore facilitated Ca2+-influx and release from internal stores, which can be antagonized by excess Ca2+.

The role of internal calcium-stores in the termination of noradrenaline release during sodium-pump reactivation in peripheral nerves.

The release of [(3)H]noradrenaline has been measured from the isolated main pulmonary artery of the rabbit in the presence of uptake blockers (cocaine, 3 x 10(?5) M; corticosterone, 5 x 10(?5) M). K(+)-removal from Krebs solution increased the release of [(3)H]NA even in the absence of external calcium. K(+)-readmission to the external medium terminated the transmitter release. The rate of recovery was much faster than the rate of rise of transmitter release both in the presence and absence of external Ca(2+). The main aim of the present study was to examine whether the reactivated Na(+)-pump per se or the Na(+)-gradient dependent Ca(2+)-extrusion and -uptake into the internal calcium-stores is responsible for the termination of transmitter release. In Ca(2+)-free, 1 mM EGTA containing solution the "K-free" stimulated [(3)H]NA release was further enhanced by calcium-store releasers (CCCP, 10(?5) M; A23187, 3 x 10(?6) M). External K(+)-readmission was effective in abolishing the transmitter release evoked by CCCP and A23187. However when veratrine (10(?4) g/ml) was also present the readmitted K(+) was ineffective in inhibiting the [(3)H]NA release although the Na(+)-pump was fully activated by the elevated level of Na(+) inside. The results suggest that the Na(+)-gradient dependent Ca(2+)-metabolism of the nerves is responsible for the abolition of transmitter release rather than the Na(+)-pump reactivation per se.