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PubMed1983

Evidence for central alpha-adrenergic transmission in a cardio-inhibitory response from the rabbit hypothalamus.

The heart rate of the anaesthetized rabbit was slowed by electrical stimulation of the hypothalamus with 7-9 sec trains of 250-330 microA pulses, duration 1 msec, frequency 60 Hz. This vagally-mediated cardio-decelerator response was attenuated in a dose-dependent manner after intravenous administration of phenoxybenzamine (0.01-5 mg/kg), phentolamine (0.01-3 mg/kg) or yohimbine (0.1-5 mg/kg). The attenuation of the cardio-decelerator response was not due to any vagolytic action of these drugs nor to block of the baroreceptor reflex, but appeared to be due to a central block of pathways descending from the hypothalamus. Propranolol, haloperidol, pimozide and spiperone did not show this central blocking action except in very large doses when there was evidence of some alpha-adrenoceptor blockade.

Adrenergic alpha-Antagonists↗
PubMed1992

Prehension movements directed to approaching objects: influence of stimulus velocity on the transport and the grasp components.

In this investigation we studied the influence of object velocity on the transport and on the grasp components of prehension movements directed to approaching objects. Three experiments were carried out. In the first experiment six subjects were required to reach and grasp a sphere that approached them with a constant velocity. The effects of four velocities were studied. The results showed that the end point of the arm movement changed with object velocity: nearer the body with higher than with lower object velocities. Transport velocity increased with movement amplitude and the deceleration phase decreased in duration with higher object velocities. On the contrary the grasp component was not affected by object velocity. The second experiment was a control experiment carried out in order to verify whether a possible influence of object velocity on the grasp could be revealed in an experimental condition in which grasp planning relies without doubt on visual computation of all object features. In this experiment object velocity and object size were randomly varied. The results showed that the grasp was not influenced by object velocity, whereas it was sensitive to changes of object size. The third experiment had the two-fold aim of establishing (1) whether transport velocity was influenced by object velocity once the location in space at which the object had to be grasped was fixed and (2) whether the grasp kinematics differed for prehension movements directed respectively to stationary or to moving objects. Results showed that the first part of the transport is affected only by distance, whereas the deceleration phase decreased with increasing object velocity. This last result suggests that subjects minimized object displacements in order to grasp the sphere correctly. The grasp component differed between the conditions of stationary and moving stimuli only in the relative timing between finger aperture and closure phases. The closure phase decreased in the condition of moving stimuli. The results of the three experiments indicate the dependence of transport parameters on object velocity, whereas grasp parameters appear to be unaffected.

Acceleration↗
PubMed1995

Umbilical plasma concentration of endothelin-1 in intrapartum fetal stress: effect of fetal heart rate abnormalities.

OBJECTIVE: To measure the umbilical plasma concentration of endothelin (ET)-1 in the presence of labor, fetal heart rate (FHR) abnormalities, and fetal hypoxia. METHODS: Umbilical and maternal plasma concentrations of ET-1 were measured in 100 pregnant women at full-term deliveries (60 with vaginal delivery without induction and 40 with elective cesarean delivery without labor). We assessed the FHR pattern, measured umbilical blood gases and plasma concentration of vasopressin, and investigated the relationships between the umbilical vein-artery ET-1 concentration difference and these variables. RESULTS: The concentration of ET-1 in the umbilical vein was higher than in the umbilical artery and the maternal vein in all cases. The umbilical vein-artery ET-1 concentration difference (mean +/- standard error of the mean) was significantly greater in the vaginal delivery group (4.5 +/- 2.0 pmol/L) than in those delivered by elective cesarean (1.7 +/- 1.5 pmol/L) (P < .05). The umbilical vein-artery ET-1 concentration difference was significantly greater when more than three episodes of severe variable decelerations occurred during the 30-minute period before delivery (7.0 +/- 2.0 pmol/L) than in the absence of any decelerations (1.6 +/- 1.5 pmol/L) (P < .05). The umbilical vein-artery ET-1 concentration difference correlated positively with the umbilical arterial concentration of vasopressin (r = 0.45, P < .05) and negatively with the umbilical arterial oxygen pressure (r = -0.47, P < .05). CONCLUSION: In cases of vaginal delivery with FHR abnormalities and with fetal hypoxia, the fetoplacental concentration of ET-1 was increased.

Adult↗
PubMed1996

Doppler study of the fetal cardiac function in prolonged pregnancies.

OBJECTIVE: To evaluate the association between fetal cardiac function and amniotic fluid index (AFI) in postterm fetuses, and to determine if changes in fetal cardiac function precede the occurrence of nonreassuring intrapartum fetal heart rate (FHR) patterns. METHODS: Forty-five otherwise low-risk pregnant women between 41 and 43 weeks' gestation were studied longitudinally. Gestational age was confirmed in all patients by ultrasound before 20 weeks' gestation. Each subject had two or three tests performed every 3-4 days, including a non-stress test, a biophysical profile, and Doppler studies of the aortic and pulmonic outflow tracts. Aortic and pulmonic artery flow velocity waveforms were recorded slightly distal to the valves. Peak velocity, velocity time integral, and heart rate were calculated from the flow velocity waveforms we obtained. The change in AFI and aortic and pulmonic peak velocity and [velocity time integral] x [heart rate] were calculated for each fetus. RESULTS: Labor was induced at 42 weeks' gestation in 20 patients, and 17 entered labor spontaneously. Changes in AFI, observed during the follow-up period, correlated significantly with changes in aortic peak velocity (r = 0.54, P < .01) and with aortic outflow [velocity time integral] x [heart rate] (r = 0.60, P < .001) but not with pulmonic peak velocity and [velocity time integral] x [heart rate]. The decrease in aortic peak velocity and aortic and pulmonic [velocity time integral] x [heart rate] was significantly higher (P < .01) in eight fetuses that developed a nonreassuring intrapartum FHR (reduced FHR variability, late decelerations, and severe variable decelerations) than in those who had an uneventful labor. CONCLUSION: In prolonged pregnancies, cardiac function deteriorates in fetuses that develop a nonreassuring intrapartum FHR, and the changes in the left cardiac function correlate with changes in AFI.

Adult↗
PubMed1975

Effects of prior aversive stimulation on heart rate responses to open field exposure in the rat.

Heart rate (HR) responses to open field (OF) exposure were compared between rats previously exposed to intense, inescapable electric shock (preshock, PS) and Controls. Results indicated that (1) Control animals showed a steady increase in HR across a 3 min exposure on each of 4 days of testing, while PS animals showed an initial HR deceleration followed by partial recovery on each day; (2) the HR response of PS animals in the OF was not related to any HR response to shock during treatment; and (3) the HR responses of both PS and Control animals were specific to the OF situation, with both groups showing steady HR deceleration across 3 min after being placed in their home cages. Results were discussed in terms of (1) the apparently altered perception of environmental change produced by PS, and (2) the possible role of HR acceleration in Controls in terms of minimizing the impact of aversive stimulation.

Animals↗
PubMed1987

Summation and saturation properties in the rewarding effect of brain stimulation.

We used a two-lever self-stimulation chamber and rats with central grey and hypothalamic electrodes to obtain a choice-frequency (C/F) function, which plots the relative choice of an electrical stimulus of fixed pulse frequency (the standard stimulus) as a function of the frequency of a second competing stimulus (the alternative stimulus). A family of C/F functions was obtained using increasing frequencies for the standard. A choice index, varying from -1.0 (exclusive choice of the fixed stimulus) to 1.0 (exclusive choice of the alternative stimulus) was computed by using the barpressing rates on the two levers. Reward saturation was assumed to occur when the C/F function obtained with the largest standard reached an asymptote below the value of 1.0. For the hypothalamic subjects, the pulse frequency at the point of reward saturation was twice as high as the frequency required for the maximum rate of self-stimulation in the usual single-lever chamber. Decreasing the pulse intensity always increased the saturation frequency, indicating that the saturation was not due to a frequency blocking effect in the directly activated neurons. Reward saturation occurred with a considerably higher frequency in the central grey than in the hypothalamus. Thus, the asymptotic rate of self-stimulation in the usual single-lever chamber is not conditioned by the processes that summate the central grey and hypothalamic rewarding effects. From the central grey data we obtained the relation between the slope and the position of the C/F function on the frequency axis. We used the slope/frequency profile to delimit the most probable profile of summation rate in the rewarding process. We found that the slope/frequency function has an early plateau followed by a rapidly decelerating phase. We proposed that these two distinct phases reflect an early accelerating rate of summation, followed by a decelerating rate of summation. In other words, reward summation would be predicted by a sigmoid growth model.

Animals↗
PubMed1992

Diet-induced thermogenesis and cumulative food intake curves as a function of familiarity with food and dietary restraint in humans.

Cumulative food intake curves and diet-induced thermogenesis were recorded in women during four-course solid-food lunches, consisting of familiar and unfamiliar food, offered in ad lib or restricted portions, in order to assess a possible relation between eating behaviour on the one hand and a reflection of internal processes and subject characteristics on the other. The subjects were characterized as normal weight restrained, normal weight unrestrained, and overweight restrained. A negative relation was found between degree of restraint and deceleration of the cumulative food intake curve during the ad lib courses of any menu, and between degree of restraint and diet-induced thermogenesis (p less than 0.001). Consequently, a positive relation was found between deceleration of the cumulative food intake curves during the ad lib courses of any menu and diet-induced thermogenesis (p less than 0.001). Diet-induced thermogenesis during the first serving of a meal consisting of unfamiliar food was significantly higher in all groups than during the other two times, when meals consisting of more familiar food were served (+0.98%; 0.71%, p less than 0.05).

Adult↗
PubMed1992

Visual suppression of torsional vestibular nystagmus in rhesus monkeys.

Juvenile rhesus monkeys, placed on a motorized turntable, were rotated at constant velocity and then decelerated about an Earth-vertical axis. The animals were implanted with dual search coils to measure eye movements in three dimensions. By changing the monkey's body position (upright, ear-down, supine), postrotatory nystagmus was elicited in the horizontal, vertical, or torsional direction. Peak slow phase eye velocity and time constant of velocity decay were compared between decelerations in the dark and in the light. In all nystagmus directions, illumination reduced the time constant (Tc) to values around 5 sec. Peak velocity (Vp) was markedly attenuated in the horizontal and vertical directions (around 50%), but the effect of light on Vp in the torsional direction was small (less than 20%). These findings were independent of the velocity step size. Our hypothesis is that the two dynamic components of optokinetic nystagmus, as they interact with postrotatory nystagmus during visual suppression, differ in their dimensionality: the early component (fast component, direct pathway, pursuit system) is mainly activated in the horizontal and vertical directions, while the late component (slow component, indirect pathway, optokinetic system) effectively operates in all three dimensions.

Animals↗
PubMed1983

Abolition of conditioned heart-rate responses in rabbits following central administration of [N-MePhe3, D-Pro4] morphiceptin.

Rabbits were initially habituated to a tone and then give 15-20 paired trials where the tone was followed by periorbital shock resulting in conditioned heart-rate decelerations to tone onset and an acceleration of heart-rate following shock offset. The animals were matched for learning performance and divided into two groups. Each animal received a microinfusion into the region of the fourth ventricle of either the opiate [N-MePhe3,D-Pro4] morphiceptin, a highly selective mu receptor agonist, or a mixture of the morphiceptin analogue and the opiate antagonist naltrexone. Administration of the morphiceptin analogue eliminated the conditioned bradycardia to the tone but not the acceleration to the shock. Rabbits given the mixture continued to show conditioned heart-rate decelerations. Previous studies have shown that opiates abolish a recently learned conditioned nictitating membrane response. These effects are consistent with the hypothesis that the opiate effect on conditioning is due to an attenuation of conditioned fear.

Acoustic Stimulation↗
PubMed1989

Cardiotocography in cows: A method for monitoring calves during delivery.

Fetal ECG-electrodes and an intrauterine catheter were inserted into 15 Holstein-Friesian cows during their first stage of labor to make a cardiotocogram. Simultaneously, fetal heart rate and intrauterine pressure were recorded until completion of fetal expulsion. Immediatly post partum the viability of the calf was assessed by clinical evaluation and measurements of blood pH, base excess (BE) and pCO(2). Fetal heart rate patterns and their changes were evaluated according to standards used in human medicine. Basal fetal heart rate (90 to 120) in 10 calves gradually increased towards the end of parturition, with a marked loss of variability. Decelerations, coinciding with periods of increased intrauterine pressure, occurred in all cows. When decelerations occurred beyond the end of a contraction the calf was born in a poor condition. Accelerations were only recorded in two cows. Many of the fetal heart rate changes observed were similar to those which in human cardiotocography are considered to be signs of fetal distress. Further investigation is needed to establish the predictive value of fetal heart rate patterns in cows, which would be a welcome addition to improved fetal diagnostics during parturition.

Journal Article↗
PubMed1985

Limitations of a histologic assay for syn-, allo-, and xenogeneic H-Y antigen.

In view of the potential significance of the H-Y antigen in the etiology of cases of sexual ambiguity we have attempted to develop a clinically useful test for the presence of H-Y on the cells of such patients. The attempts were directed at the detection of accelerated or decelerated rejection of syngeneic skin grafts on H-Y-incompatible mice previously exposed to H-Y positive syngeneic, allogeneic, or xenogeneic cells. Using a simple and rapid histologic assay after exposure to syn- or allogeneic cells, acceleration (sensitization) as well as deceleration (tolerance) was readily demonstrable. However, the assay was not helpful with the use of xenogeneic (rabbit, human) cells.

Animals↗
PubMed1986

Autonomic correlates of alimentary conditioned and unconditioned reactions in the dog.

Analysis of changes in cardiac action and the secretion of saliva during unconditioned alimentary activity in 6 dogs revealed that the beginning of food consumption was accompanied by acceleration of the heart rate (HR) without an increase in salivation. In the course of eating, the heart rate decelerated and salivation increased. Alimentary conditioned stimuli of excitatory (CS+) and inhibitory (CS-) character always produced cardiac acceleration, which in the case of CS+ was accompanied by secretion of saliva. The findings indicate that during food consumption activation of the autonomic system depends upon the contents of motivational processes. In the course of an alimentary act the parasympathetic withdrawal (heart rate acceleration and decrease in salivation) seems to reflect the drive component of the act, while the following parasympathetic activation (heart rate deceleration and increase in salivation) is probably associated with an hedonic component of the consummatory reaction. In our study alimentary conditioned stimuli evoked both drive and hedonic components of alimentary motivation.

Animals↗
PubMed1991

Constrictive pericarditis versus restrictive cardiomyopathy: the role of Doppler echocardiography in differential diagnosis.

Doppler ultrasound recordings of velocities of flow across the mitral and tricuspid valves and in the hepatic veins, and their variation with respiration, were recorded in seven patients with constrictive pericarditis and in six patients with restrictive cardiomyopathy. Deceleration of mitral and tricuspid flow was also evaluated during apnea. Color flow Doppler was performed in order to evaluate mitral and tricuspid regurgitation. Eight healthy adults served as controls. The patients with constrictive pericarditis showed higher peak diastolic velocities of mitral flow, as well as marked increase of velocity of flow at the onset of expiration and decrease at the onset of inspiration. Reciprocal respiratory variation of the velocities were also observed across the tricuspid valve. The patients with restrictive cardiomyopathy showed moderate or severe mitral and tricuspid regurgitation. They also showed shorter deceleration of flow across the mitral and tricuspid valves during apnea. The pattern of flow in the hepatic veins showed reversal during systole with accentuated reversion during inspiration. These results suggest that patient with constrictive pericarditis and restrictive cardiomyopathy can be differentiated by comparing Doppler echocardiographic data, along with changes induced by respiration.

Adult↗
PubMed1994

Effect of 24-h blood pressure levels and circadian blood pressure rhythm on left ventricular structure and function in isolated systolic hypertension.

Forty-one participants (mean age 69 +/- 5.6 years) were examined by fully automatic blood pressure monitor and Doppler echocardiography to gain information on the ambulatory blood pressure and the left ventricular structure and function in isolated systolic hypertension. Cumulative sum (cusum)-derived statistics was used to quantify circadian blood pressure rhythm and 24-h blood pressure levels were defined as mean blood pressure values during 24 h, waking (06:00-22:00 h) and sleeping (22:00-06:00 h) periods, respectively. Most of the derivatives of ambulatory blood pressure, including cusum-derived statistics and 24-h blood pressure levels, were significantly related with the left ventricular structural (left ventricular posterior wall and interventricular septum thickness) and functional (acceleration time in the left ventricular outflow tract and early diastolic deceleration time) indexes. Among the left ventricular structural and functional indexes, interventricular septum thickness at end diastole had the strongest correlation with sleeping diastolic mean blood pressure (r = 0.41, P < 0.01), left ventricular posterior wall at end diastole, the best with 24-h systolic mean blood pressure (r = 0.41, P < 0.01), acceleration time the strongest with systolic cusum-derived circadian alteration magnitude (r = 0.49, P < 0.01) and early diastolic deceleration time the greatest with diastolic cusum-derived trough blood pressure (r = 0.45, P < 0.01). We conclude that left ventricular structural changes rely on 24-h systolic and diastolic blood pressure levels, whereas left ventricular functional variations may be more dependent upon circadian blood pressure rhythm in elderly patients with isolated systolic hypertension.

Aged↗
PubMed1994

Variability of changes in Doppler transmitral filling pattern during stress echocardiography in patients with stable angina pectoris.

Stress electrocardiography and echocardiography using atrial pacing together with the right-sided heart catheterization were performed in 21 patients with stable angina pectoris. Peak velocity of transmitral flow in early diastole (E) and in atrial contraction (A), deceleration time of early filling, and pulmonary artery wedge pressure were measured simultaneously at rest and immediately after each pacing frequency. Patients were divided according to their stress pulmonary artery wedge pressure changes into Group A (14 patients with an increase in pulmonary artery wedge pressure > or = 3 mmHg during stress) and into Group B (6 patients with a change in pulmonary artery wedge pressure < or = 2 mmHg during stress). One patient, T.L., with an increase in pulmonary artery wedge pressure > or = 5 mmHg after each pacing frequency was evaluated separately. In Group A patients, the non-linear course of the E/A ratio changes (from 0.78 +/- 0.06 to 0.66 +/- 0.05, P < 0.01; to 0.72 +/- 0.05, P = NS; and to 0.93 +/- 0.06, P < 0.01) and deceleration time changes (from 188.9 +/- 7.2 ms to 195.3 +/- 8.9 ms, P = NS; to 188.8 +/- 9.9 ms, P = NS; and to 154.2 +/- 6.7 ms, P < 0.01) was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

'Abnormal' diastolic Doppler patterns in patients over age 65 with severe left ventricular systolic dysfunction.

OBJECTIVE: The purpose of this study was to determine whether Doppler diastolic filling patterns of the left ventricle are altered in patients over age 65 with poor left ventricular function, compared to patients with normal left ventricular systolic function. BACKGROUND: In elderly, healthy subjects, the mitral valve Doppler inflow pattern exhibits an increase in atrial contribution to left ventricular filling. Myocardial disease, which results in stiffness, may also cause an increase in A wave velocity. METHODS: Twenty-seven patients over age 65, with left ventricular systolic dysfunction, were age and sex-matched with 19 patients with normal left ventricular systolic function. Patients with significant mitral or aortic valvular disease were excluded. Maximal early inflow velocity, maximal atrial inflow velocity, heart rate, acceleration time and deceleration time were calculated. RESULTS: Comparing the group with normal left ventricular systolic function, the group with decreased left ventricular systolic function had pseudonormalization of the maximal early flow/atrial flow velocity ratio (1.7 +/- 1.3 vs. 0.9 +/- 0.3; P = 0.003), E wave velocity was similar (82 +/- 28 vs. 70 +/- 24 cm/s; P = n.s.), and A wave velocity was diminished (66 +/- 30 vs. 84 +/- 20 cm/s; P = 0.02). The acceleration time was similar for the groups (53 +/- 17 vs. 46 +/- 21 ms), but the deceleration time was shorter in patients with left ventricular systolic dysfunction (122 +/- 33 vs. 192 +/- 80 ms; P < 0.001). CONCLUSION: Such differences may relate to increased left atrial pressure, increased left ventricular diastolic pressure and/or decreased atrial systolic function. These findings are important when interpreting left ventricular filling indices by Doppler echocardiography in elderly patients.

Aged↗
PubMed1996

Effects of cardiac output on Doppler transmitral and transtricuspid flow velocity patterns in very low birth weight infants.

We studied effects of cardiac output on Doppler transmitral and transtricuspid flow velocities in 24 appropriate for gestational age premature infants. We measured peak flow velocity of early diastole (peak E) and atrial contraction (peak A), ratio of peak flow velocity of early diastole to atrial contraction (peak E/A), total flow velocity-time integral, the first third filling fraction, peak filling rate normalized to stroke volume, and deceleration time (DT). Cardiac output was calculated as the product of the aortic flow velocity-time integral, aortic valve area, and heart rate. The cardiac output increased significantly with advancing gestational age and body weight (r = 0.78 and 0.86, P < 0.01, respectively). With increasing cardiac output, the transmitral as well as transtricuspid peak E, peak E/A, and total flow velocity-time integral increased significantly without any change in the peak filling rate normalized to stroke volume, peak A, and deceleration time. The transmitral as well as transtricuspid peak E did not correlate with the heart rate. Although these results do not establish whether changes in ventricular relaxation process or in cardiac output is responsible for the progressive increase in the peak E and peak E/A. Unchanged peak filling rate normalized to stroke volume of the left and right ventricles suggest that changes in cardiac output with maturity is, in fact, one of the important contributory factors. This evidence should be borne in mind in interpreting ventricular diastolic filling as an index of ventricular diastolic function in premature infants.

Blood Flow Velocity↗
PubMed1986

Effects of photic stimulation on heart rate of infant rats.

We present the results of three experiments which characterize the heart rate (HR) response of infant rats at a number of different ages to the onset, or the offset, of a bright light. Experiment 1 demonstrated that at ages 5, 8, 11, 14, 17 and 21 days, a sudden increase in ambient illumination caused a HR deceleration, whereas a sudden decrease in ambient illumination caused a HR acceleration. At each age, the HR acceleration did not habituate over 60 stimulus presentations, whereas at all ages beginning at 8 days, the HR deceleration did habituate. By varying the intensity of either the visual or thermal component of the stimulus at ages 8 and 17 days, Experiment 2 revealed that the directional effects were a result of the visual and not the thermal component of the stimulus, thereby ruling out any account of the findings in terms of local adaptational reflexes. Finally, Experiment 3 varied the rate of stimulation, tested for spontaneous recovery, and demonstrated that the decrement in response magnitude observed across trials conformed to several of the accepted parametric characteristics of habituation, and could not be accounted for by changes in baseline HR across trials. These results are discussed in terms of traditional interpretations of HR changes as orienting and defensive reactions.

Age Factors↗