Unitary Behavior Research Articles

Unitary behavior of skeletal, cardiac, and chimeric L-type Ca2+ channels expressed in dysgenic myotubes.

Skeletal and cardiac dihydropyridine receptors function both as voltage-dependent L-type calcium channels (L-channels) and as critical proteins that trigger calcium release from the sarcoplasmic reticulum in muscle. In spite of these similarities, skeletal L-channels exhibit a markedly slower activation rate than cardiac L-channels. We investigated the mechanisms underlying this difference by comparing the unitary behavior of L-channels in cell-attached patches of dysgenic myotubes expressing skeletal, cardiac, or chimeric dihydropyridine receptors. Our results demonstrate that ensemble averages activate rapidly for the purely cardiac dihydropyridine receptor and approximately five times more slowly for L-channels attributable to the purely skeletal dihydropyridine receptor or a chimeric dihydropyridine receptor in which only the first internal repeat and all of the putative intracellular loops are of skeletal origin. All of the constructs studied similarly exhibit a brief (2-ms) and a long (> or = 15-ms) open time in the presence of Bay K 8644, neither of which depend significantly on voltage. In the absence of Bay K 8644, the fraction of total open events is markedly shifted to the briefer open time without altering the rate of ensemble activation. Closed time analysis of L-channels with cardiac-like, rapid activation (recorded in the presence of dihydropyridine agonist) reveals both a brief (approximately 1-ms) closed time and a second, voltage-dependent, long-lasting closed time. The time until first opening after depolarization is three to six times faster for rapidly activating L-channels than for slowly activating L-channels and depends strongly on voltage for both types of channels. The results suggest that a voltage-dependent, closed-closed transition that is fast in cardiac L-channels and slow in skeletal L-channels can account for the difference in activation rate between these two channels.

Single calcium channel behavior in native skeletal muscle.

The purpose of this study was to use whole-cell and cell-attached patches of cultured skeletal muscle myotubes to study the macroscopic and unitary behavior of voltage-dependent calcium channels under similar conditions. With 110 mM BaCl2 as the charge carrier, two types of calcium channels with markedly different single-channel and macroscopic properties were found. One class was DHP-insensitive, had a single-channel conductance of approximately 9 pS, yielded ensembles that displayed an activation threshold near -40 mV, and activated and inactivated rapidly in a voltage-dependent manner (T current). The second class could only be well resolved in the presence of the DHP agonist Bay K 8644 (5 microM) and had a single-channel conductance of approximately 14 pS (L current). The 14-pS channel produced ensembles exhibiting a threshold of approximately -10 mV that activated slowly (tau act approximately 20 ms) and displayed little inactivation. Moreover, the DHP antagonist, (+)-PN 200-110 (10 microM), greatly increased the percentage of null sweeps seen with the 14-pS channel. The open probability versus voltage relationship of the 14-pS channel was fitted by a Boltzmann distribution with a VP0.5 = 6.2 mV and kp = 5.3 mV. L current recorded from whole-cell experiments in the presence of 110 mM BaCl2 + 5 microM Bay K 8644 displayed similar time- and voltage-dependent properties as ensembles of the 14-pS channel. Thus, these data are the first comparison under similar conditions of the single-channel and macroscopic properties of T current and L current in native skeletal muscle, and identify the 9- and 14-pS channels as the single-channel correlates of T current and L current, respectively.

Eigenvector statistics for the transitions from the orthogonal to the unitary ensemble

A description for the eigenvector statistics of classical chaotic systems with a time reversal destroying part of the Hamilton operator is proposed in closed form. We have checked our form by a numerical simulation of a model system capable to show all intermediate stages between orthogonal and unitary behaviour, and proved the superiority to a chi-square distribution.

Rib cage distortion during voluntary and involuntary breathing acts.

We examined chest wall and rib cage configuration in seven normal subjects during a variety of breathing maneuvers. Magnetometers were used to measure lower rib cage anteroposterior, lower rib cage transverse, upper rib cage anteroposterior, and abdomen anteroposterior diameters. Changes of these diameters were recorded during voluntary maneuvers, rebreathing, reading, and "natural" breathing. Relative motion of the rib cage and abdomen was displayed with the rib cage represented by the product of its lower anteroposterior and transverse diameters. During spontaneous breathing the rib cage and chest wall are near their relaxation configuration. During chemically driven ventilation the chest wall and rib cage progressively depart from this configuration. Much greater distortions of the chest wall and rib cage occurred during some voluntary maneuvers. Additionally, esophageal pressure and gastric pressure were measured during voluntary distortion of the rib cage. Substantial changes in lower rib cage shape occurred during voluntary maneuvers when compared with spontaneous breaths at the same transmural pressure. We conclude that the unitary behavior of the rib cage in normal subjects requires muscle coordination.

The Unitary Approach and Behaviour Modification within the Social Work Repertoire

I'm going to describe the unitary approach, a recent model for social work, and then use the model to pinpoint the place of behavioural procedures.Social Work is — or aspires to be — a profession that carries out a planned change process aimed at helping people who are having difficulty with life tasks. These tasks range from coping emotionally and practically with the birth of a handicapped child, to keeping within the rules of society, to obtaining the basic supplies: food, shelter and satisfying personal relationships, and they require emotional, cognitive and material resources.

Simultaneous recording of steady potential, extracellular potassium activity and unitary behavior on penicillin-focus in cats.

Simultaneous recording of steady potential, extracellular potassium activity and unitary behavior on penicillin-focus in cats.

Command neurons and unitary behavior

Command neurons and unitary behavior

Crossing-symmetric model for ππ scattering with some unitary aspects

A class of functions are devised which incorporate some of the properties thought to be appropriate to the S-matrix for ππ scattering from considerations of unitary, crossing symmetry, Lorentz invariance and analyticity. The imposition of Regge asymptotics limits the acceptability of some of these functions. Further elimination is obtained by demanding unitary threshold behaviour in all partial waves. Examples of some simple functions containing most of the desired properties save exact elastic unitarity are presented.