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At least 127 records · Page 7Linked to original sources

Contingency contracting with delinquents: effects of a brief training manual on staff contract negotiation and writing skills.

A brief training manual was developed for the purpose of teaching child-care workers to contingency contract with delinquent youths living in residential care facilities. The manual was designed to require minimal supplementary training by a professional. In Experiment 1 a multiple baseline design was used to assess the effect of the manual on 4 child-care workers' contract negotiation and writing behaviors. Experiment 2 consisted of four A-B systematic replications. Behaviors were assessed within the context of analogue training simulations and generalization tests with delinquent youths. Results from the analogue simulations indicated that the manual was successful in increasing both types of behaviors to a level of proficiency that equaled or surpassed that of behaviorally trained graduate students, and results from the generalization tests indicated that the child-care workers were able to apply their newly acquired contracting skills with delinquent youths. Procedural reliability varied across child-care workers, but was usually high.

Adolescent↗

[Cationic regulation of myocardial contraction and relaxation when contraction frequency is increased].

During augmentation of frequency of contractions or Ca2+ perfusate concentration the velocity of isotonic relaxation increased much more than the velocity or amplitude of contraction. The phenomenon of predominant activation of relaxation ( PPAR ) was less prominent at decreased Ca2+ concentration acidosis (pH 6,85), under action of calmodulin inhibitor, trifluoperazine, or replacement of Ca2+ ions by Sr2+. Diminution of Na2+ concentration to 25 mM was followed by apparent signs of cellular Ca2+--overload and elimination of PPAR . The results coincide with the suggestion that PPAR is caused by activation of calmodulin-dependent Ca2+ removal from the myoplasma and myofibrils.

Animals↗

Effect of inhibitors of slow calcium current on rested state contraction of papillary muscles and post rest contractions of atrial muscle of the cat and rabbit hearts.

Effect of Ni, Co and Mn ions and of D-600 on rested state contractions (RSCs) of cat and rabbit papillary muscles and on post rest contractions (PRCs) of cat and rabbit atrial muscle was investigated. Ni and Co in concentration 2 mmol/l reduced the force of RSCs in papillary muscles by 78%, increased the dip between the phase 1 and 2 of respective action potentials (APs), lowered the level of plateau and decreased the total duration of AP. Strong PRCs in atrial muscle were reduced by Ni only by 25%, while the subsequent beats were strongly inhibited. Ni completely inhibited RSCs in papillary muscles increased by caffeine (10 mmol/1) or by reduction in Na concentration by 50%. Mn ions in concentration 1--2 mmol/l inhibited strongly both RSCs in papillary muscles and strong PRCs in atrial muscle, increased the dip between phase 1 and 2 and increased total duration of AP. Mn ions stimulated 45Ca efflux from papillary muscles and atrial strips. D-600 did not affect RSCs nor the shape of respective APs. It is concluded that RSCs in papillary muscles are directly activated by Ca inflow during the respective excitation while strong PRCs in atrial muscle are activated mostly by Ca released from intracellular stores.

Action Potentials↗

A comparison of perinatal outcome in patients undergoing contraction stress testing performed by nipple stimulation versus spontaneously occurring contractions.

Perinatal outcomes were analyzed in 848 high-risk pregnancies managed with a prospective weekly contraction stress testing protocol. In 615 patients the last test was performed by a nipple stimulation protocol whereas 233 patients had sufficient spontaneous contractions for performance of the test. All patients were either delivered of their infants or admitted for delivery within 7 days of the last test. The results of the last test were compared to various perinatal outcome parameters. There was no significant difference in perinatal outcomes between the two groups.

Breast↗

Effect of Ca2+ modulators on acetylcholine-induced phasic and tonic contractions and A23187-induced contractions in ileal longitudinal muscle and IP3 production.

The influence of different sources of Ca2+ on the Emax and ED50 values of acetylcholine (ACh)-induced phasic and tonic contractions and on A23187-induced contractions was studied using different extracellular Ca2+ concentrations ([Ca2+]o) and the Ca2+ modulators TMB-8 and D600. IP3 production induced by both stimulants was also studied. The results are compatible with: (a) the mobilization of Ca2+ from an intracellular source as a primary event in the phasic response. (b) The primary involvement of a D600-sensitive inward Ca2+ current in the ACh-tonic response. (c) An inward D600-sensitive Ca2+ current associated with the ionophore transported ion. (d) The involvement of an IP3 independent, TMB-8 sensitive mechanism of Ca2+ mobilization involved in the A23187-induced responses.

Acetylcholine↗

Electromyographic assessment of the activity of the masticatory using the agonist contract-antagonist relax technique (AC) and contract-relax technique (CR).

Proprioceptive neuromuscular facilitation (PNF) techniques are a group of therapeutic procedures that may be used to cause relaxation of muscles. Studies have found controversial results when applying these techniques. The aim of the present study was to evaluate the effectiveness of masticatory muscle relaxation through the use of the contract-relax technique (CR) when compared with the agonist contract-antagonist relax technique (AC). A convenience sample of 30 students was recruited for this study. The CR and the AC techniques were applied to the subjects in order to cause relaxation of the masticatory muscles. Electromyography activity of all muscles was registered. Two way ANOVA with repeated measures analysis demonstrated that both the AC technique and the CR technique did not decrease the EMG activity of masticatory muscles (P>0.05). Instead, both techniques caused an increase in electromyographic activity of the masticatory muscles. Based on the results obtained from this study, both the CR and the AC techniques were not effective in causing relaxation of the masticatory muscles. The purported physiological mechanisms of PNF techniques, which stated that they act through reciprocal inhibition and autogenic inhibition causing muscular relaxation, are not supported by this study.

Adult↗

Phorbol esters inhibit alpha 1-adrenergic receptor-stimulated phosphoinositide hydrolysis and contraction in rat aorta: evidence for a link between vascular contraction and phosphoinositide turnover.

We investigated the actions of two biologically active phorbol esters, phorbol dibutyrate (PDB) and phorbol myristate acetate (PMA), on receptor-stimulated phosphoinositide hydrolysis in rat aorta. We found both PDB and PMA potently inhibited norepinephrine (NE) stimulated PI hydrolysis in rat aortic rings. The biologically inactive phorbol, 4-alpha-phorbol was ineffective. In the presence of the calcium channel antagonist nitrendipine, PDB potently inhibited both the phasic and tonic components of NE-induced contraction. These results suggest a functional coupling between receptor-stimulated PI turnover and vascular contraction. They also suggest a mode of feed-back regulation in vascular tissue involving phorbol esters in receptor-stimulated PI hydrolysis.

Animals↗

Biomimetic model of skeletal muscle isometric contraction: II. A phenomenological model of the skeletal muscle excitation-contraction coupling process.

This paper describes a new macroscopic, phenomenological model of the skeletal muscle excitation-contraction coupling process, as represented by four principal and consecutive compartments (biophysical, biochemical, and biomechanical phases) characteristic of isometric excitation-contraction coupling in mammalian skeletal muscle, and coupled by a system of simultaneous, first-order linear ordinary differential equations. The model is based upon biological compartmental transport kinetics and irreversible thermodynamic energy transformation, and represents a distinct improvement over other biomimetic models. The model was derived using physiological parameter data published in the literature, and validated using MATLAB R12.

Calcium↗

Effects of ryanodine on cardiac contraction, excitation-contraction coupling and "Treppe" in the conscious dog.

The effects of ryanodine on left ventricular (LV) function and hemodynamics were studied in 16 conscious dogs, chronically instrumented for measurements of LV pressures and dimensions. Systemic infusion of ryanodine (0.5-4 micrograms/kg i.v.) resulted in a dose-dependent depression of cardiac contraction. For example, ryanodine, 4 micrograms/kg i.v., decreased LV fractional shortening by 30.5 +/- 4.1%, LV dP/dt by 41.5 +/- 4.0% and Vcfc by 37.8 +/- 4.1%, while increasing the isovolumic relaxation time constant, tau, from 23.1 +/- 1.4 to 34.1 +/- 3.6 ms without a major effect on preload or afterload. Ryanodine also depressed (P < 0.05) the plateau phase of the mechanical restitution and post-extrasystolic potentiation responses, indicating a direct effect on excitation-contraction coupling. The heart rate dependent positive staircase ("Treppe") was significantly enhanced (P < 0.05) after ryanodine infusion, i.e. LV dP/dt rose by 43.1 +/- 4.7% with an increase in heart rate from 150 to 240 beats/min in the presence of ryanodine 4 micrograms/kg, but by only 7.5 +/- 2.1% without ryanodine. The more pronounced "Treppe" in the conscious dog under the condition of impaired SR calcium release caused by ryanodine, supports the concept that the classical Bowditch "Treppe" reflects either a state of myocardial depression due to alteration in SR calcium handling, or enhanced availability of trans-sarcolemmal Ca2+ influx. This finding may help to understand the discrepancy in the importance of the "Treppe" between conscious animals and more isolated preparations.

Animals↗

Some effects of hypertonic solutions on contraction and excitation-contraction coupling in frog skeletal muscles.

In frog fast skeletal muscle, we find a decline of twitch, tetanus, and maximum K and caffeine contracture tensions as tonicity of the bathing solution is increased. The decline of tension independent of the method of producing contraction indicates that the major effect of hypertonicity is directly on contractile tension probably because of the increased internal ionic strength. However, there is some apparent disruption of excitation-contraction (E-C) coupling in solutions made three times the normal tonicity (3T solutions) since: (a) in 3T solutions tetanic and K contracture tensions decline to zero from a value near the average maximum caffeine contracture tension at this tonicity (10% of 1T tetanic tension). At this time, caffeine contractures of 10% of 1T tetanic tension can be elicited; (b) once the K contracture tension has declined, elevated [Ca(++)](o), 19.8 mM, restores K contracture tension to 13% of 1T tetanic tension. This probable disruption is not caused by changes in mechanical threshold since in 2T solutions the mechanical threshold is shifted by 12 mv in the hyperpolarizing direction. This is consistent with neutralization of fixed negative charges on the inside of the membrane. The repriming curve is also shifted in the hyperpolarizing direction in 2T solutions. Shifts of the repriming curve coupled with membrane depolarizations in 3T solutions (about 20 mv) may produce loss of repriming ability at the resting potential and disruption of E-C coupling.

Amidines↗

Excitation-contraction uncoupling: major role in contraction-induced muscle injury.

The mechanisms that account for the strength loss after contraction-induced muscle injury remain controversial. We present data showing that (1) most of the early strength loss results from a failure of excitation-contraction coupling and (2) a slow loss of contractile protein in the days after injury prolongs the recovery time.

Animals↗

Relaxation following contraction in tonically contracted smooth muscle from the bovine trachea.

Isometric tension was recorded from strips of bovine tracheal smooth muscle in which the tone had been artificially raised by agonist drugs such as histamine and carbachol. Application of exogenous acetylcholine produced a biphasic response consisting of an initial contraction followed by a more prolonged relaxation before tone was restored to normal. Atropine blocked both components of the biphasic response to exogenous acetylcholine. Tetrodotoxin blocked neither phase of the response to exogenous acetylcholine even though a similar biphasic response to electrical stimulation was severely disrupted. Application of exogenous substance P produced a biphasic response of similar magnitude and form to that produced by acetylcholine. Application of exogenous histamine (tone raised by carbachol) also produced a biphasic response although higher concentrations were required to produce a relaxation of equal magnitude to that produced by acetylcholine. It is concluded that the inhibitory component of the biphasic response to exogenous acetylcholine occurs as a non-specific sequel to contraction.

Acetylcholine↗

Role of atrial contraction and synchrony of ventricular contraction in the optimisation of ventriculoarterial coupling in humans.

OBJECTIVE: To examine the effects of pacing modes on the interaction between the left ventricle and arterial system in humans. DESIGN: The slope of the end systolic pressure-volume relation (end systolic elastance), effective arterial elastance, the ratio of effective arterial elastance to end systolic elastance, and mechanical energy efficiency were compared under different pacing modes (atrial, atrioventricular, and ventricular). PATIENTS: Nine male patients with sick sinus syndrome who had cardiac catheterisation for diagnosis and to see whether they needed a pacemaker. INTERVENTIONS: A conductance catheter with tip-manometer was inserted into the left ventricle to obtain pressure-volume loops, and two pacing catheters were inserted into the right atrium and into the right ventricle respectively. RESULTS: End systolic elastance was lower in atrioventricular pacing than in atrial pacing, but effective arterial elastance was not significantly different. End systolic elastance was lower in ventricular pacing than in atrioventricular pacing, and effective arterial elastance was higher in ventricular pacing than in atrioventricular pacing. Consequently the ratio of effective arterial elastance to end systolic elastance was lowest in atrial pacing and highest in ventricular pacing, and mechanical energy efficiency was highest in atrial pacing and lowest in ventricular pacing. CONCLUSIONS: Atrial contraction and synchronous ventricular contraction independently optimise ventriculoarterial coupling in terms of a transfer of energy. Thus atrial pacing gives the best ventriculo-arterial coupling among these pacing modes.

Adult↗

Decreased contraction economy in mouse EDL muscle injured by eccentric contractions.

The objective of this study was to find out whether basal and/or active energy metabolism are altered in isolated mouse extensor digitorum longus muscle injured by eccentric (Ecc) contractions. Measurements of basal O2 consumption and isometric tetanus O2 recovery cost were made at 25 degrees C on muscles that had done either 10 Ecc, 10 isometric (Iso), or no contractions (No). In parallel experiments, rates of lactate and pyruvate production were measured to estimate the anaerobic contribution. Basal O2 consumption was unaffected by the type of protocol performed (P = 0.07). However, the tetanus O2 cost per force-time integral was elevated by 30-36% for the Ecc protocol muscles over that for the Iso and No protocol muscles. When including the increased lactate production by the Ecc protocol muscles, the total energetic cost per force-time integral was 53% higher than that for the Iso protocol muscles [2.35 +/- 0.17 vs. 1.54 +/- 0.18 mumol O2/(N.m.s)]. The decreased economy was attributed to two factors. First, in skinned fibers isolated from the injured muscles, the ratio of maximal actomyosin adenosinetriphosphatase activity to force production was up by 37.5%, suggesting uncoupling of ATP hydrolysis from force production. Second, increased reliance on anaerobic metabolism along with the fluorescent microscopic study of mitochondrial membrane potential and histochemical study of ATP synthase suggested an uncoupling of oxidative phosphorylation in the injured muscles.

Animals↗

Ultrastructure of the contractile system of striated skeletal muscle and the processes of muscular contraction. II. Releasing system and mechanisms of muscular contraction.

The tropomyosin-troponin system of the thin filaments acts as a regulator of the interaction of myosin with actin by a process of inhibition. This inhibition is released by Ca2+ ions. Muscle contraction occurs when Ca+2 ions are released from the sarcoplasmic reticulum into the myofibril, where they interact with the troponin of the thin filaments. Muscular contraction is due to the sliding of the two kinds of filaments past each other in the hexagonal network of the myofibril. Many hypotheses have been formulated concerning the intimate molecular mechanisms responsible for the sliding of the filaments past each other, but none of these can be considered to be entirely satisfactory.

Actins↗

Uterine contraction frequency before and after successful tocolytic therapy for preterm uterine contractions.

OBJECTIVE: To examine the association between prelabor uterine contraction frequency (UCF) and the success of tocolytic therapy for preterm labor (PTL). STUDY DESIGN: Eleven centers conducted a prospective, observational study of UCF recorded between 22(0/7) and 36(6/7) weeks' gestational age or until delivery > or = 2 times/d on > or = 2 d/wk in women with singleton pregnancies with and without risk factors for preterm birth. Uterine contraction data obtained from patients diagnosed with PTL allowed comparison of mean UCF both before and after an acute episode of PTL treated with either intravenous, subcutaneous or oral tocolysis. The signed rank test was used to analyze differences in UCF before and after tocolytic therapy and between women who were or were not successfully treated with a labor-inhibiting agent. RESULTS: Of 454 enrolled women, 128 were diagnosed with PTL, and 74 were successfully treated with a labor-inhibiting agent. The mean UCF preceding PTL was not different between those women successfully treated and those who delivered as a consequence of the PTL episode. There was no difference (P = .653) in mean UCF between the week before PTL (UCF 0.60 +/- 0.8, median 0.30) and the first week of monitoring after successful tocolysis (UCF 0.82 +/- 1.4, median 0.27). CONCLUSION: The mean UCF immediately preceding PTL does not predict tocolytic success or failure.

Adult↗

Contracting with limited commitment: evidence from employment-based health insurance contracts.

Impediments to worker mobility serve to mitigate the attrition of healthy individuals from employer-sponsored insurance pools, thereby creating a de facto commitment mechanism that allows for more complete insurance of health risks than would be possible in the absence of such frictions. Using data on health insurance contracts obtained from the 1987 National Medical Expenditure Survey, we find that the quantity of insurance provided is positively related to the degree of worker commitment. These results illustrate the importance of commitment in the design of long-term contracts, and provide an additional rationale for the bundling of health insurance with employment.

Career Mobility↗

What issues should be considered when negotiating an employment contract? Employment contracts for CRNAs: protecting yourself amid the new economic realities.

Severe imbalances in the supply and demand for nurse anesthesia services are giving CRNAs a new and substantial economic worth in the health care provider marketplace. As a result, CRNAs are using written employment contracts increasingly to delineate their scope of practice, limit their liability, and protect their new economic value. This article discusses basic points that every anesthetist should consider in negotiating such contracts. Practical suggestions are offered for conducting negotiations as both an employee and independent contractor.

Contract Services↗