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At least 19 recordsLinked to original sources
PubMed1977

Myocardial imaging with thallium-201 at rest and during exercise. Comparison with coronary arteriography and resting and stress electrocardiography.

Myocardial imaging with intravenous thallium-201 (201Tl) was performed at rest and following maximal treadmill exercise in 101 patients with suspected coronary artery disease. Results were interpreted from Polaroid scintiphotos by three independent observers with complete interobserver agreement in 79%. Of 25 patients with no or insignificant coronary artery disease (less than 50% diameter stenosis), one (4%) had a resting 201Tl image defect, one (4%) had an exercise 201Tl defect, none had an ECG Q wave, and four (16%) had exercise ST-segment depression. Among 76 patients with coronary artery disease (greater than or equal to 50% diameter stenosis), 58 (76%) had a defect on either the rest or exercise 201Tl image. The proportion of patients with an exercise image defect (50/76, 66%) was greater than the proportion with exercise ST depression alone (34/76, 45%; P less than 0.02). Overall, 69 of the 76 (91%) patients with coronary artery disease had either a positive rest or exercise myocardial image and/or a positive rest (ECG Q waves) or exercise (ST depression) electrocardiogram. This exceeded the proportion with only rest or exercise electrocardiographic abnormalities (50/76, 65%; P less than 0.001). We conclude that rest and exercise myocardial imaging with 201Tl is easily accomplished with readily available imaging equipment. The image data enhanced the diagnostic sensitivity of stress electrocardiography, and provided spatial identification of the abnormal segment(s) of myocardium.

Adult↗
PubMed1978

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↗
PubMed1976

Effects of clomiphene citrate and progesterone on resting and proliferative cell-populations in resting and proliferative cell-populations in mouse uterine epithelium.

Resting cells (GO cells) of the uterine surface epithelium in castrated mice began to synthesize DNA with high synchrony from 10 hr after the injection of 50 ng of estradiol-17beta with or without 5.5 mug of clomiphene citrate. Highly synchronized DNA synthesis in GO cells elicited with estradiol was delayed approximately 5 hr when the simultaneous administration of 0.5 mg of progesterone was given. In GO cells of castrated mice which received 5.5 mug of clomiphene or 55 mug of clomiphene plus 50 ng of estradiol, DNA synthesis with partial synchrony began 15 hr after the injection. The effects of estradiol were completely suppressed by the administration of 55 mug of clomiphene. It is suggested that the inhibitory action of clomiphene may be due to the competitive blocking of estrogen binding, while progesterone suppresses the estrogen-induced DNA synthesis of the surface epithelium and transfers them to the GO cell-compartment.

Animals↗
PubMed2026

Reliability of resting heart rate measurements in atrial fibrillation.

BACKGROUND: Heart rate (HR) control in atrial fibrillation (AF) is commonly guided by resting HR measurements, usually with 12&#x2011;lead ECG or in-office pulse palpation. OBJECTIVES: We aimed to assess the reliability of resting HR measurements in AF patients with long-term ambulatory ECG and activity monitoring. METHODS: We included patients who had recorded a full-disclosure ambulatory ECG with a mobile cardiac telemetry device equipped with an accelerometer (PocketECG, MEDICALgorithmics, Poland), with at least 95% AF. Resting HR samples (&#x2264;20 per individual/day) were collected as 10-s daytime (8&#xa0;am to 8&#xa0;pm) measurements after &#x2265;10&#xa0;min of rest. These samples were compared to each individual's mean daytime resting HR. RESULTS: In 832 patients (median age 77 (interquartile range (IQR) 69-83) years, 42% women) with a median registration duration of 13&#xa0;days (IQR 7-22), the population mean daytime resting HR was 85 (&#xb1;15) beats per minute (bpm). A single resting HR differed from the mean daytime resting HR by a mean of &#xb1;10.4% (IQR 3.6-14.4%). When the mean daytime resting HR was &#x2265;110&#xa0;bpm, 29% of resting HR samples were&#xa0;<&#xa0;110&#xa0;bpm, and when the mean daytime resting HR was 80-109&#xa0;bpm,11% of samples were&#xa0;&#x2265;&#xa0;110&#xa0;bpm. Resting HR measurement variability decreased to 5.3% (IQR 1.9-7.5%) when four resting HR samples were averaged. CONCLUSION: In patients with AF, a single resting HR measurement often differs substantially from the mean daytime resting HR. When a precise measurement is clinically relevant, repeated resting HR sampling or ambulatory monitoring can address this measurement imprecision.

Humans↗
PubMed1992

Mechanisms underlying the genesis of post-rest contractions in cardiac muscle.

1. Post-rest potentiation reflects basic cellular mechanisms that control cardiac muscle contraction. Transmembrane calcium influx, the Na+/Ca2+ exchange and the function of intracellular stores that liberate activator calcium upon activation are some of the mechanisms involved. 2. Three aspects of the post-rest potentiated phenomenon were investigated, using isometrically contracting rat papillary muscles and toad ventricle strips: dependence on 1) inotropic state of steady-state contractions, 2) pause duration and Na+/Ca2+ exchange activity, and 3) the extent of transmembrane calcium influx. 3. The results suggest that the potentiated state of post-rest contractions increases linearly with the inotropic state of preceding steady-state control contractions. As the pause duration increases from 5 to 240 s, the post-rest potentiation also increases, attaining a steady level after 30-s pauses. During the pause, the Na+/Ca2+ exchange mechanism operates at an activity level that can alter the amount of activator calcium used for post-rest contractions. Interventions that increase intracellular Na+, such as the increase of the stimulation rate from 0.5 to 1 Hz or the increase of extracellular NaCl concentration to 160 mM, reduce the Na+/Ca2+ activity, increasing intracellular Ca2+ and post-rest potentiation. The decrease of transmembrane Ca2+ influx during activation increases the relative participation of the sarcoplasmic reticulum in the development of post-rest potentiation. Reduction of extracellular Ca2+ concentration from 1.25 mM to 0.25 mM or the use of 1 microM verapamil and 2 mM manganese increases the relative potentiation of post-rest contractions. This is particularly observed in toad ventricle strips since post-rest potentiation, which does not develop under control conditions, is observed after verapamil or manganese treatment. The results suggest that the excitation-contraction coupling process operating for post-rest contraction activation, unlike that operating for steady-state contraction activation, depends more on the calcium stored at intracellular sites than on transmembrane calcium influx.

Animals↗
PubMed1975

Haemodynamic effect of atrail triggered versus fixed rate pacing at rest and during exercise in complete heart block.

The central haemodynamics at rest and during exercise have been studied in 25 patients with complete AV block who were treated with fixed rate (FRP) and atrial triggered pacemakers (ATP). The aim of the investigation has been to study the effect of a synchronized atrial contraction for the filling of the ventricles and for the cardiac output (Q). Pressures and Q have been determined during heart catheterization. The P wave for triggering the atrial synchronized pacemaker has been obtained with an electrode in close contact with the atria, introduced by means of mediastinoscopy. The study consists of two series. In the first series (12 patients) the central haemodynamics were recorded with each patient connected first the FRP (about 70 impulses/min) and later to the ATP. Most patients were studied both at rest and during exercise, the work loads being identical with both types of pacemakers. Q at rest is 10% higher with ATP (p less than 0.02) than with FRP and during exercise 20% higher with ATP (p less than 0.01). Stroke volume (SV) at rest is equal with both types of pacemakers, but significantly larger with FRP during work (p less 0.001). The left ventricular (LV) filling pressure is significantly lower (p less than 0.01) with ATP at rest, but not during exercise (p less than 0.8). In the second series 13 patients were studied at rest and during exercise. The recordings of pressures and Q were first performed with the patient on ATP. After 30 min rest an identical study was performed with the patient connected to FRP, the rate of which was matched (FRPm) to that previously recorded with ATP. Q at rest is 18% higher (p less than 0.01) with ATP than with FRPm and during work 8% higher (p less than 0.05) with ATP. SV at rest is significantly larger (p less than 0.01) with ATP than with FRPm, whereas during exercise no significant difference is observed between the two types of pacemakers. LV filling pressure at rest is significantly lower on the 5% level with ATP; during exercise no significant difference is observed. The investigation shows that in many patients, especially younger ones, treatment with ATP makes it possible to obtain a larger Q during exercise, and thus to increase the oxygen transporting capacity of the circulation. This benefical effect may be more pronounced in patients with low compliance of the ventricular myocardium.

Adult↗
PubMed1976

Plasma vasopressin and renin activity in women exposed to bed rest and +Gz acceleration.

To study the effect of prolonged recumbency on plasma vasopressin and renin activity, eight women (23-34 yr) were subjected to 17 days of absolute bed rest. The +3 Gz tolerance of the subjects was tested before and after 14 days of bed rest. From day 2 and through day 17 of bed rest, plasma arginine vasopressin (AVP) levels were reduced 33%. Plasma renin activity (PRA) increased 91% (P less than 0.05) above ambulatory control values from days 10 through 15 of bed rest. When compared to precentrifuge values, exposure to +3 Gz prior to bed rest provoked a 20-fold rise (P less than 0.05) in mean plasma AVP but resulted in only a slight increase in PRA. After bed rest, acceleration increased plasma AVP 7-fold (P less than 0.02); however, the magnitude of this increase was less than the post +3Gz value obtained prior to bed rest. After bed rest, no significant rise was noted in PRA following +3 Gz. This study demonstrates that prolonged bed rest leads to a significant rise in the PRA of female subjects, while exposure to +Gz acceleration provokes a marked rise in plasma AVP.

Adult↗
PubMed1979

Phosphate efflux and oxygen consumption in small non-myelinated nerve fibres at rest and during activity.

1. The oxygen consumption and the movements of labelled phosphate were measured in garfish olfactory nerve at rest and during activity.2. In solutions with 2.5 mM-K and 0.2 mM-phosphate the resting oxygen consumption was 0.206 m-mole/kg.min; activity at 2 sec(-1) produced an extra oxygen consumption of 2.46 mumole/kg.impulse. The extra oxygen consumption declined exponentially with a time constant of 2.62 min at 22-26 degrees C.3. The phosphate efflux, measured simultaneously, had a resting efflux rate constant of 1.24 x 10(-3) min(-1); activity at 2 sec(-1) produced an extra fractional loss of 9.38 x 10(-6) impulse(-1). The increase in phosphate efflux followed almost the same time course as the increase in oxygen consumption.4. Increasing the frequency of stimulation from 2 sec(-1) to 3 or 5 sec(-1) decreased both the extra oxygen consumption and the extra fractional loss of phosphate. When the frequency was decreased to 0.5 or 1 sec(-1) the extra oxygen consumption per impulse increased, while the extra phosphate liberation was lowered.5. Changing the phosphate concentration did not much affect the extra oxygen consumption; on the other hand, lowering or increasing the phosphate from the standard 0.2 mM decreased both the resting and the stimulated phosphate efflux.6. Lowering the K from the standard 2.5 mM did not affect the extra oxygen consumption, but increased both the resting and the extra loss of phosphate. At higher K concentrations the extra oxygen consumption and the extra fractional loss of phosphate decreased without much change in the resting phosphate efflux.7. Application of 1-20 muM-strophanthidin produced a transient decrease in the resting phosphate efflux without much change in resting oxygen consumption. With 10 or 20 muM-strophanthidin the extra fractional loss of phosphate and the extra oxygen consumption were both lowered in approximately the same proportions.8. The findings are consistent with the hypothesis that the increase in intracellular inorganic phosphate that results from increased break-down of ATP after activity, is the main cause for the increased phosphate efflux. A fraction of the increase in intracellular phosphate only appears to be liberated to the outside, the value of the fraction depending on the resting phosphate efflux before activity.9. The initial increase in intracellular inorganic phosphate after an impulse, estimated from the oxygen consumption or the phosphate fluxes, appears to be about 12-19 mumole/kg nerve, remarkably close to the value known from chemical analysis.

Animals↗
PubMed1975

Physiologic characteristics of vestibular first-order canal neurons in the cat. I. Response plane determination and resting discharge characteristics.

The response plane and resting rate characteristics of first-order, vestibular, semicircular canal neurons were studied in 67 cats under sodium pentobarbital anesthesia using single-unit recording techniques in the eighth nerve. Five hundred fifty-nine units were classified as to the canal they were associated with by employing an identification technique based on physiologic response patterns to brief, high-level (up to 250 degrees/S2) angular accelerations delivered in various head positions. All horizontal canal neurons had increased firing rates to ampullopetal and all vertical canal units to ampullofugal endolymph flow. The average observed roll and pitch null points for each canal were used to determine the average sensitivity vectors for the right horizontal, anterior, and posterior canals. These sensitivity vectors were at a variance of 4.6-10.2 degrees from those predicted by anatomical measurements (3). The mean resting discharge characteristics of 318 first-order neurons was 36.0 spikes/s (range 0.50-114 spikes/s). No significant difference was noted between horizontal and anterior canal neurons on horizontal and anterior canal neurons on the basis of resting rate. The resting rate of the posterior canal neuron population was significantly lower. The regularity of the resting discharge varied in all three canals and the average coefficient of variation was 0.238 for the population, with a range of 0.298-1.030. The population distribution of all resting-rate statistical parameters appeared to be unimodal, indicating that first-order canal neurons may not be broken into discrete populations on the basis of resting-rate characteristics. Of 47 adequately examined first-order canal neurons, 25 demonstrated a repeatable and predictable alteration in their resting discharge as their position to gravity was reoriented. This alteration was usually nonadapting and varied in magnitude according to the degree of tilt and original starting position. Of 25 canal gravity units, 4 had nearby units from the same canal which were unresponsive to gravity, suggesting the effect was due to a limited distortion of the crista or cupula rather than an overall displacement of the cupula.

Acceleration↗
PubMedDate not supplied

Cumulative dose-response curves for gallamine: effect of altered resting thumb tension and mode of stimulation.

Neuromuscular blockade studies often use the thumb adductor twitch response to ulna nerve stimulation. Two factors that may influence the results are the resting muscle tension (initial fiber length) and the pattern of the stimulus wave form. This study was undertaken to improve understanding of the effect of these factors and lead to better controlled study conditions and more consistent data. During nitrous oxide-barbiturate-narcotic anesthesia in 10 normal adult patients, as the resting thumb tension was increased from 50 to 200 g, the evoked thumb adductor twitch response (Grass stimulator, 0.25 Hz) was augmented by 28%. There was only a 2.5% increase in the evoked (developed) tension when the resting tension was further increased from 200 to 300 g. Developed tension at 50 g was significantly (p less than 0.001) less than at the other resting tensions. The developed tension at 100 g was also significantly (p less than 0.05) less than at resting tensions of 200 or 300 g. Cumulative dose-response curves for gallamine in nine patients were not significantly altered by increasing resting tension from 50 to 200 g. Biphasic (Block-Aide monitor) or single square wave (Grass stimulator) stimuli wave forms in nine normal adult patients yielded gallamine dose-response curves that were not statistically different. The muscle response to biphasic stimulation during a non-depolarizing blockade was not affected by the average muscle refractory period. Because of the significantly lower developed tension at resting tension settings of 50 to 100 g, a practical consideration during neuromuscular function studies would be to have the resting thumb tension adjusted and rechecked for each patient and kept within the 200-300-g range to ensure maximum uniform developed tension. The type of stimulus wave form selected will not affect results as long as it is used consistently throughout the study.

Adjuvants, Anesthesia↗
PubMed1976

[Pulmonary artery pressure and left ventricular late diastolic pressure in rest and during dynamic load. Comparative studies on pressure transmission in the pulmonary circulation during simultaneous determination].

Left ventricular enddiastolic pressure (LVEDP), mean pulmonary artery pressure (PAPM) and enddiastolic pulmonary artery pressure (PADP) were simultaneously recorded in 19 subjects with normal left ventricular (LV) function, and in 109 patients with LV-dysfunction, 83 of whom were also studied during exercise. Patients with valvular heart disease or atrial fibrillation were excluded from this study. LVEDP and mean pulmonary capillary wedge (PCW) pressure were simultaneously recorded in 81 patients at rest, andin 16 patients also during exercise; the LV diastolic pressure prior to atrial contraction (LVPpreA) could accurately be identified in 45 patients at rest and in 23 patients with exercise. In contrast to the widely accepted opinion of others, the PADP (mean 8.2 +/- 2.2 mm Hg at rest and 12.3 +/- 3.4 mm Hg with exercise) showed a close approximation of LVEDP (10.0 +/- mm Hg at rest and 16.2 +/- 3.5 mm Hg with exercise) only in normal subjects at rest (p less than 0.05 and p less than 0.01 respectively). In patients with LV dysfunction there was no significant difference between PADP (11.7 +/- 4.5 mm Hg and 23.0 +/- 8.9 mm Hg), PCW (11.6 +/- 5.1 mm Hg and 24.1 +/- 11.9 mm Hg) and LVPpreA (12.5 +/- 5.5 and 21.5 +/- 7.7 mm Hg) at rest and during exercise. LVEDP could be estimated with sufficient accuracy only from the PAPM (18.9 +/- 6.5 and 35.7 +/- 10.8 mm Hg). The increase in LVEDP (14.7 +/- 7.7 mm Hg) with exercise was not significantly different from the increase in PAPM (16.8 +/- 7.1 mm Hg). There were highly significant correlations (p less than 0.001) between LVEDP and PADP (r = 0.85) as well as PAPM (r = 0.86) at rest and during exercise with the regressionline being closest to the line of identity for LVEDP and PAPM. The pressure gradient between LVEDP and PADP (LVEDP - PADP = 6.3 mm Hg with exercise) equaled the pressure increase in LV by atrial contraction (LVEDP - LVPpreA = 6.3 and 13.3 mm Hg). The pressure difference between PADP or PAPM and LVEDP remained constant despite marked variation of other hemodynamic parameters, e.g. stroke volume index (SVI), heart rate (HR) and cardiac index(CI). These data suggest that an elevated LVEDP is caused mainly by an augmented atrial contraction in patients with LV dysfunction at rest and with exercise. This mechanism precludes an enddiastolic pressure equilibrium between pulmonary artery and left ventricel. PAPM allows the best estimation of LVEDP independent from other hemodynamic variables.

Adult↗
PubMed1979

Noninvasive assessment of hemodynamic effects of mitral valve commissurotomy during rest and exercise in patients with mitral stenosis.

Noninvasive radionuclide angiocardiography (RNA) provides simple and accurate assessment of parameters of cardiac function during rest and during maximal exercise. Left ventricular function was assessed by RNA in nine patients with isolated mitral stenosis before and approximately 6 months after mitral commissurotomy. Before operation, the mean mitral valve gradient was 14.0 +/- 2.8 mm Hg, and the mean mitral valve area was 1.20 +/- 0.3 cm2. Each patient was evaluated at rest and during maximal exercise on an isokinetic bicycle ergometer before and after commissurotomy. Heart rate, ejection fraction, end-diastolic volume, stroke volume, pulmonary transit time, cardiac output, and diastolic ventricular filling rate were determined by the radionuclide technique. Before operation, patients with mitral stenosis had characteristic changes from rest to exercise which supported restriction to diastolic ventricular filling as the primary limitation in generating a cardiac output during exercise. The stroke volume was unchanged from rest to exercise. Thus the cardiac output during exercise was heart rate dependent. However, after commissurotomy the stroke volume increased from rest to exercise. Therefore, cardiac output during exercise was achieved by heart rate and an augmented stroke volume. Moreover, the pulmonary transit time was reduced during rest and exercise after operation. The maximum ventricular ejection and filling rates were markedly increased during rest and exercise after commissurotomy. These differences in hemodynamic parameters at rest and during exercise document the mechanics of increased exercise tolerance in patients with mitral stenosis after mitral commissurotomy.

Adult↗
PubMed1992

Raised resting energy expenditure in Parkinson's disease and its relationship to muscle rigidity.

1. Resting energy expenditure was measured, by indirect calorimetry, in 12 patients with Parkinson's disease and in eight healthy age-matched control subjects. In the patients with Parkinson's disease measurements were made in both the untreated state and after an injection of the dopamine agonist apomorphine (treated state). In each state muscle rigidity was recorded. 2. Resting energy expenditure was higher in patients with Parkinson's disease in both the treated and untreated states than in the control subjects. Of the patients with Parkinson's disease, seven showed no difference in resting energy expenditure between the two treatment states, whereas four showed markedly increased resting energy expenditure in the untreated state. The change in resting energy expenditure in the untreated state, as compared with the treated state, was significantly related to the development of muscle rigidity in the untreated state. 3. In Parkinson's disease, even in optimally treated patients, resting energy expenditure is raised and this may contribute to the weight loss seen in this disease. Severe muscle rigidity occurring during untreated periods results in a further increase in resting energy expenditure.

Apomorphine↗
PubMed1976

Resting and stimulated values of model parameters governing transmitter release at a synapse in Aplysia californica.

Transmitter release (R) at a synpase in Aplysia californica can be analyzed in terms of a model with the following parameters: A, the available pool of transmitter; F, the fraction of available pool released by a presynaptic action potential; M, the rate of transmitter mobilization into the available pool; D, the rate constant of demobilization of transmitter from the available pool. In the present paper we show that: (1) beginning with an analysis of the recovery from depression of the second of a pair of disolated EPSPs separated by a series of intervals of about 10-60 sec, and assuming that the recovery is due to refilling of a depleted A, it is possible to estimate resting equilibrium values of these parameters; (2) changes in these parameters when a new equilbrium state is reached after prolonged stimulation (e.g., 300 stimuli at 1/sec) can then be quantitatively determined; (3) the increased rate of transmitter release observed during and after repetitive stimulation is the consequence of increases in F and M with changes in A passively following; and (4) there are significant correlations among certain resting parameters and between the values of certain resting parameters and these parameters upon stimulation. Preparations with a large resting F tend to have a relatively small resting A. Preparations with a large resting F or M tend to increase these less with stimulation than preparations with smaller resting values of these parameters. Preparations with large stimulus-dependent increases in F tend to have large stimulus-dependent increases in M.

Animals↗