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PubMed1989

Cognitive versus motivational significance of the cardiac response to intense auditory stimulation.

This paper reports on an investigation to examine the psychological significance of the heart rate response to intense auditory stimulation--the cardiac defense response (CDR) - by studying its relationship with cognitive tasks related to Lacey's intake/rejection hypothesis (simple reaction time and mental arithmetic) and motivational tasks related to Obrist's cardiosomatic hypothesis (avoidance reaction time and cold pressor). Eight subjects who consistently evoked the CDR pattern (pattern 1) and 8 subjects who consistently did not (pattern 2) underwent the 4 cognitive/motivational tasks balancing the order of task presentation. Results showed that CDR does not bear any relation to mental arithmetic or cold pressor. Significant relationships were found with both simple and avoidance reaction time tasks. During the foreperiod of both tasks, pattern 1 showed a greater initial acceleration followed by a greater final deceleration. In addition, in the avoidance reaction time task pattern 1 showed a greater acceleration after initial greater deceleration during the period prior to the expected shock. It is concluded that CDR is sequentially related to both cognitive processes of input intake (Lacey's hypothesis) and motivational processes of active coping (Obrist's hypothesis).

Acoustic Stimulation↗
PubMed1989

Human Pavlovian HR decelerative conditioning with negative tilt as US: a review of some S-R, stimulus-substitution evidence.

Interest in human Pavlovian heart rate (HR) conditioning with conventional shock and loud noise unconditional stimuli has declined, as measured by reports in the literature. Accompanying this decline have been the following views: (a) that HR should be abandoned as a psychophysiological index of the psychological (learning) process of Pavlovian conditioning; (b) that, following psychology's shift to a more cognitive emphasis, the self-regulation (S-R), stimulus-substitution view of pavlovian conditioning is wrong, because there is no equivalence in direction between shock- and loud noise-induced HR-accelerative unconditional response and the conditional response. This paper reviews recent reports of human Pavlovian conditioning of HR deceleration with negative tilt as the unconditional stimulus. The results support an S-R, stimulus-substitution interpretation of conditioning. In addition, these studies have potential therapeutic application in the teaching of (medically desirable) HR deceleration, especially when Pavlovian procedures are combined with instrumental (biofeedback) ones. However, such physiological aspects of the decelerative unconditioned response as the degree of vagal involvement are difficult to investigate in the human preparation.

Arousal↗
PubMed1989

Human Pavlovian HR-decelerative conditioning with negative tilt as US: evidence of vagal and sympathetic influences on the UR in dogs.

Following a review of studies employing negative tilt in human Pavlovian conditioning of heart rate (HR) deceleration (Furedy et al, in press), this paper reports data based on animal subjects on such physiological aspects of the decelerative unconditioned response (UR) as the degree of vagal involvement. Five anesthetized dogs underwent 90 degrees negative body tilts pre- and postbilateral vagotomy, while interbeat interval (IBI), left ventricular pressure (LVP) and its first derivative, d(LVP)/dt, which is a measure of sympathetic cardiac drive, were recorded. Consistent with the vagal interpretation of the tilt-induced decelerative UR, the results indicated that vagotomy markedly changed the tilt-induced bradycardic reflex from a fast-recruiting, large-magnitude (over 45%), and sustained (throughout the 20-27-s tilt) IBI increase, to slower-recruiting, and markedly smaller (less than 5%) IBI increase. However, there was also evidence of an initial sympathetic excitation of about 5 s, as indicated by a 45% increase in d(LVP)/dt, which returned to baseline level by 9 s following tilt onset. Vagotomy increased this tilt-induced sympathetic excitation to about 100%, and it remained at above 70% throughout the tilt. Prevagotomy LVP showed a slight (about 10%) and delayed (about 6 s following tilt onset) depressor response, which was eliminated by vagotomy. Finally, unaveraged data from individual dogs suggested that prevagotomy, LVP changes preceded IBI changes. Regarding implications of these results for human HR deceleration-inducing preparations, we conclude that the different physiological mechanisms that accompany and/or produce a given change in HR need continuing investigation with multiple dependent physiological variables (which are assessed for topographical differences), and in both human and animal preparations.

Animals↗
PubMed1991

Restrained eating, obesity, and cumulative food intake curves during four-course meals.

A four-course meal was presented to six obese and 18 normal weight women in which the second course was eaten ad libitum and the other three courses were fixed in amount. Eating behaviour was observed directly and intake was monitored via an electronic scale built into the table under the plate. Intake deceleration was observed in the normal weight women who scored low on the Herman-Polivy (1980) restraint questionnaire and on the cognitive restraint factor (F1) of Stunkard and Messick's (1985) questionnaire, whereas the normal weight and obese restrained women displayed linear cumulative food intake. In all groups, if deceleration occurred in the second course it was usually identical in the third and fourth courses, and constant eating rate persisted from the second course to the later courses. Food-specific eating rates were positively correlated to relative palatability, and removed deviation from linearity in cumulative intake over the four courses.

Body Mass Index↗
PubMedDate not supplied

Kinematics of arm movements in elderly humans.

Changes in the kinematics of arm movements with age were studied. "Young" (aged 21-23) and "elderly" (aged 68-95) subjects performed a visually guided, step tracking task. Each subject performed movements of eight different amplitudes (10-80 deg) at two volitionally determined speeds ("own speed," "fast and accurate"). Movement durations and maximum velocities were similar for both groups and increased with movement amplitude under all conditions. The young subjects made movements in which approximately the same length of time was spent in accelerating as in decelerating the movement. In contrast, movements by the elderly subjects were temporally asymmetrical, the deceleration phase being longer than the acceleration phase. The ratio of maximum to average velocities (Vm/Vav) was markedly different between the young and elderly subjects, particularly in the smaller amplitude movements (less than 40 deg). Values of this parameter ranged from 1.5 to 6 in the elderly subjects. Movements made by the elderly subjects were more variable than those of the young subjects, particularly so at smaller amplitudes. Variability was most apparent in the deceleratory phase of movement where the elderly subjects often showed hypermetria. Some elderly subjects also showed movement decomposition, the movements being made as a series of discrete submovements. Thus, the elderly subjects displayed some of the characteristics classically described as arising from cerebellar dysfunction.

Adult↗
PubMed1994

Long-term modulation of Galactic Cosmic Radiation and its model for space exploration.

As the human exploration of space has received new attention in the United States, studies find that exposure to space radiation could adversely impact the mission design. Galactic Cosmic Radiation (GCR), with its very wide range of charges and energies, is particularly important for a mission to Mars, because it imposes a stiff mass penalty for spacecraft shielding. Dose equivalent versus shielding thickness calculations, show a rapid initial drop in exposure with thickness, but an asymptotic behavior at a higher shielding thickness. Uncertainties in the radiobiology are largely unknown. For a fixed radiation risk, this leads to large uncertain ties in shielding thickness for small uncertainties in estimated dose. In this paper we investigate the application of steady-state, spherically-symmetric diffusion-convection theory of solar modulation to individual measurements of differential energy spectra from 1954 to 1989 in order to estimate the diffusion coefficient, kappa (r,t), as a function of time. We have correlated the diffusion coefficient to the Climax neutron monitor rates and show that, if the diffusion coefficient can be separated into independent functions of space and time: kappa (-r,t)=K(t)kappa 0 beta P kappa 1(r), where beta is the particle velocity and P the rigidity, then (i) The time dependent quantity 1/K(t), which is proportional to the deceleration potential, phi(r,t), is linearly related to the Climax neutron monitor counting rate. (ii) The coefficients obtained from hydrogen or helium intensity measurements are the same. (iii) There are different correlation functions for odd and even solar cycles. (iv) The correlation function for the Climax neutron monitor counting rate for given time, t, can be used to estimate mean deceleration parameter phi(t) to within +/- 15% with 90% confidence. We have shown that kappa(r,t) determined from hydrogen and/or helium data, can be used to fit the oxygen and iron differential energy spectra with a root mean square error of about +/- 10%, and essentially independent of the particle charge or energy. We have also examined the ion chamber and 14C measurements which allow the analysis to be extended from the year 1906 to 1990. Using this model we have defined reference GCR spectra at solar minimum and solar maximum. These can be used for space exploration studies and provide a quantitative estimate of the error in dose due to changes in GCR intensities.

Carbon Radioisotopes↗
PubMed1976

Heart-rate decelerative Pavlovian conditioning with tilt as UCS: towards behavioural control of cardiac dysfunction.

As part of a programme the ultimate goal of which is to teach behavioural control of stress-induced maladaptive cardiac accelerations through Pavlovian decelerative conditioning, this study was directed at examining the feasibility of using tilting of the body from a head-up to a head-down position as the unconditional stimulus (UCS) to elicit phasic cardiac deceleration as the unconditional response (UCR). Experiment I assessed the reflexive features of the cardiac response to 32 tilt UCS trials delivered at mean intervals of 75 sec. The results yielded a large-magnitude (over 30 BsPM) cardiac decelerative UCR with fast recruitment and complete resistance to habituation. Experiment II examined the feasibility of using the tilt UCS to demonstrate associative control over decelerative responding to a tone as the conditional stimulus (CS). Relative to a control 'backward' UCS-CS group with an interstimulus interval (ISI) of 14.5 sec, a 0.5 sec ISI CS-UCS experimental group demonstrated both orderly acquisition and extinction performance. The magnitude of the conditional deceleration of some 4 BsPM is greater than the extent of control generally achieved with biofeedback, but still constitutes a problem for theoretical accounts of classical conditioning framed in terms of stimulus substitution, and is still only of borderline clinical significance.

Acoustic Stimulation↗
PubMed1979

Differential effects of state and trait anxiety on heart rate responses and reaction time.

College students were tested on 10 trials of a reaction time task, using a variable interval warning signal, while heart rate was recorded. Subjects were divided into high and low anxiety groups using a median split based on their scores on a modification of the trait scale of the State-Trait Anxiety Inventory. The low anxiety group exhibited faster reaction times, shorter latency heart rate deceleration following warning signal onset, and a more consistent deceleration immediately prior to the respond signal than the high anxiety group. When the same subjects were divided into groups according to state anxiety, no group differences were found in either heart rate or reaction time. In Part II of the study, subjects listened to six 15 s presentations of a 70 dbA, 250 Hz tone. No group differences in heart rate responses to the tones were found for either state or trait anxiety groups.

Adolescent↗
PubMed1996

Amnioinfusion.

Abnormal amniotic fluid volume may be both the result and the cause of complications at various stages of pregnancy. This review focuses on evidence from randomised trials of the effectiveness of amnioinfusion. Attempts to prevent the development of pulmonary hypoplasia by means of transabdominal amnioinfusion to correct severe oligohydramnios in the middle trimester of pregnancy have not been evaluated by randomised trials. Long-term transcervical amnioinfusion for prelabour rupture of the membranes has shown promising results in prospective studies, but has also not been subjected to randomised evaluation. Transcervical amnioinfusion during labour is a relatively simple procedure. Normal saline is infused through an intrauterine catheter, preferably one with a catheter-tip pressure transducer. Once an adequate volume of amniotic fluid has been achieved, it is maintained by means of a slow continuous infusion or repeated bolus infusions. Amnioinfusion has been used to prevent or treat fetal heart rate (FHR) decelerations thought to be due to oligohydramnios. In several rather small randomised trials, amnioinfusion has been associated with a reduction in FHR decelerations, caesarean sections, low Apgar scores, low umbilical arterial pH values and postpartum endometritis. Amnioinfusion has also been used to dilute thick meconium-staining of the amniotic fluid. In trials for this indication, amnioinfusion has been associated with similar benefits, and in addition a reduction in meconium presence below the vocal cords, meconium aspiration syndrome and the need for neonatal ventilation. Larger trials are needed to determine whether amnioinfusion is associated with an effect on perinatal mortality, and whether complications such as umbilical cord prolapse are increased.

Amnion↗
PubMed1996

Dynamic and steady state response of heart rate to orthostatic stress in normotensive and hypertensive pregnant women.

We determined the dynamic and steady state responses of heart rate (HR) to orthostatic stress (standing up) in normotensive and hypertensive pregnant women. Using a continuous recording with servo-photosphygmography, HR response to change in posture from left lateral recumbent position to standing was analysed. The subjects were divided into five groups comprising: Groups I, II and III: normotensive pregnant women in each of the three trimesters of pregnancy (total n = 77); Group IV: women with gestational proteinuric hypertension (GPH) in the third trimester (n = 16); Group V: age-matched non-pregnant normotensive controls (n = 15). The HR reacted with a typical overshoot response to this orthostatic change with HR rising to a peak and then settling to a new but higher steady state. Change in steady state HR from lying to standing (delta HR), rate of rise of HR in response to standing (i.e. the acceleration slope (HRon)), and rate of fall of HR after reaching the peak (i.e. deceleration slope (HRoff)) were evaluated from standing heart rate time curves. HRon in response to standing showed a downward trend with gestation (ANOVA, P < 0.05) in normotensive gravida. The deceleration slope (HRoff) showed a distinct gestational age-related decrease from first to third trimester in normotensive women (ANOVA, P < 0.01). The most striking observation was that the slope of HRoff for the GPH group was significantly steeper than that of normotensive women of comparable gestational age (unpaired t-test P < 0.01) and approximated to that of the non-pregnant group. The difference in HR response between normotensive women and those with GPH in the third trimester suggests it may have potential as a new marker for pre-eclampsia.

Adult↗
PubMed1989

Hemodynamic effects of innominate artery occlusive disease. Evaluation by Doppler ultrasound.

Between 1976 and 1987 we saw 20 patients presenting with stenosis or occlusion of the innominate artery with a measurable hemodynamic effect. This corresponds to less than 0.1% of our patients subjected to noninvasive vascular testing. The hemodynamic sequelae involved the vertebral as well as the carotid arteries. The majority of the cases (n = 17) showed a vertebral steal and only minor concomitant alterations of carotid artery flow. Only three patients had a carotid steal in addition to the vertebral steal. In general, the vertebral steal is predominant over the carotid steal and precedes the latter. We propose a phenomenological classification of innominate artery disease following the severity of hemodynamic changes. Type I shows systolic deceleration or alternating flow in the right vertebral artery and only minor changes in the carotid arteries. Type II is characterized by reversed flow in the ipsilateral vertebral artery and systolic deceleration in the carotid arteries and type III by alternating flow or even complete steal in the carotid arteries in addition to vertebral artery steal. Continuous wave Doppler ultrasound is a valuable noninvasive method for examinating innominate artery occlusive disease and its hemodynamic sequelae. In special cases the additional use of duplex- and transcranial sonography is useful.

Adult↗
PubMed1993

Experimentally induced changes in heart rate alter umbilicoplacental hemodynamics in fetal sheep.

In the anesthetized sheep fetus, we have accelerated heart rate by atrial pacing (n = 6) or caused decelerations by stimulating the vagus nerve (n = 7). Alterations in heart rate were linearly related to changes in the ratio of the diastolic minimum (D) to systolic maximum (S) of flow and velocity, and to changes in the flow pulsatility index in the umbilical artery. Decelerations slightly increased vascular resistance, and decreased blood flow and mean arterial pressure, but accelerations had no significant effect. The index of impedance was unaltered by either intervention. The major factor mediating the influence of heart rate on blood flow pulsatility in the umbilical artery was the aortic blood pressure pulsatility. An equation was derived to adjust flow D/S to a standardized heart rate. Results showed that heart rate correction can affect the interpretation of experimental data.

Animals↗
PubMed1982

Effects of fructose on synthesis and degradation of purine nucleotides in isolated rat hepatocytes.

The effects of fructose on purine nucleotide synthesis and degradation were studied in isolated rat hepatocytes. Incubation of the hepatocytes with fructose resulted in deceleration of the rate of de novo purine synthesis, gauged by the rate of incorporation of precusor [14C]formate into total purines produced, and in acceleration of purine nucleotide degradation, as measured by the rate of conversion of prelabelled purine nucleotides into end-product allantoin. These effects were found to be associated with decreases in cellular content of ATP and Pi and in the metabolic availability of 5-phosphoribosyl 1-pyrophosphate. The results support the suggestion that the fructose-induced acceleration of purine degradation is mediated through activation of AMP deaminase. However, the results also suggest that decreased reutilization of hypoxanthine for IMP synthesis, due to the decreased PP-Rib-P availability, is an additional mechanism for the acceleration of purine degradation. The decreased PP-Rib-P availability is also suggested to be the main mechanism for the fructose-induced deceleration of purine synthesis.

Animals↗
PubMed1985

Mechanism of desensitization of neutrophil response to N-formylmethionylleucylphenylalanine by slow rate of receptor occupancy. Studies on changes in Ca2+ concentration and phosphatidylinositol turnover.

Previous studies on the regulation of responses of neutrophils to fMet-Leu-Phe have demonstrated the relevance of the role of the rate of occupation of the receptors by the stimulant. When this rate is decreased by presenting the peptide to neutrophils over a period of time by means of an infusion pump, the activation of the respiratory burst and of the secretion is greatly depressed or is absent. This paper deals with further investigations on the mechanisms of this desensitization, which previous results have shown to consist of an uncoupling between the ligand-receptor complexes and the target for cell responses, caused by the deceleration of the initial rate of occupation of the receptors. The data presented here demonstrate that this desensitization is not linked to the formation of a negative intermediate such as cAMP, but is associated with: (i) a depression of the rate and magnitude of the phosphatidylinositol response (activation of phosphatidylinositol turnover measured as modification of incorporation of [32P]Pi and [3H]glycerol into phosphatidylinositol and phosphatidic acid); (ii) a deceleration of the rate of the release of bound Ca2+, without a decrease in the total quantity of Ca2+ liberated (measured as fluorescence changes of chlorotetracycline treated neutrophils); (iii) a slower rise of cytosolic free Ca2+ concentration [Ca2+]i, without a decrease in the magnitude of the final increase of [Ca2+]i (monitored with Quin 2). These findings, which are discussed in relation to the recent hypotheses on the transduction reactions of receptor-mediated stimuli for neutrophil responses, are consistent with a mechanism of desensitization involving decreased production of diacylglycerol by the hydrolysis of phosphatidylinositol and deficient activation of Ca2+-phospholipid-dependent protein kinase C.

Adult↗
PubMed1996

Severe hypoglycaemia unawareness is associated with an early decrease in vigilance during hypoglycaemia.

To elucidate neurophysiological characteristics in hypoglycaemia unawareness, we investigated the relationship between electroencephalography (EEG) parameters of vigilance and awareness of various symptom categories early in response to hypoglycaemia in intensively treated diabetic patients with different degrees of hypoglycaemia unawareness. Hypoglycaemia (venous plasma glucose below 2.2 mmol/1) was induced with an intravenous insulin bolus in seven patients with insulin-dependent diabetes mellitus (IDDM) with a history of hypoglycaemia unawareness and repeated severe hypoglycaemia, as well as in a group of seven IDDM patients with good awareness of hypoglycaemia. Both groups were comparable in age, treatment strategy, glycaemic control and level of late complications. Basic cognitive performance and other symptom categories were estimated serially during a period of 2 h following the insulin bolus. A vigilance-controlled EEG was recorded continuously; its automatic analysis included the evaluation of vigilance indices. In the baseline prehypoglycaemic state, hypoglycaemia unaware patients showed higher initial vigilance (p = .05) than the aware group. Unaware patients reported fewer neurogenic (p = .002, mainly cholinergic, p = .009) hypoglycaemia symptoms during hypoglycaemia, and developed an impairment in cognitive performance over time (p = .002). EEG analysis indicated a more rapid decrease in vigilance after the hypoglycaemic stimulus for unaware patients than for aware patients. The lowering of plasma glucose to 3.06-3.89 mmol/l already induced a significant increase in delta and theta, as well as a decrease in alpha relative power only in the unaware group. Differences between groups with regards to the degree of deceleration were most pronounced early, during only slight hypoglycaemia, and topographically spread over central and parietal brain regions. Further lowering of plasma glucose induced an even more pronounced, abrupt increase in slow waves in unaware patients at higher plasma glucose levels than in hypoglycaemia aware subjects (for delta waves at 2.41 +/- 0.16 vs. 1.96 +/- 0.1 mmol/l, p = .04). This preceded the worsening of cognitive performance during hypoglycaemia in unaware patients by 19 +/- 3 min. Hypoglycaemia unawareness associated with previous unconsciousness is associated with- and may be the result of-an early hypoglycaemia-induced reduction in vigilance and an early EEG deceleration, which seems to be a teleologically effective measure for delaying eventual cerebral energy failure in hypoglycaemia.

Adult↗
PubMed1989

Responses to smoking-related stimuli and early relapse to smoking.

Prior to engaging in treatment for smoking cessation, subjects were tested for their responsiveness to cigarette smoking cues. Subjects performed a role-play with a confederate who lit their preferred brand of cigarette. Heart rate (HR) and galvanic skin conductance were assessed continuously, while urge to smoke and anxiety were rated subjectively after the role-play. Three months after treatment ended, subjects were divided into groups of continuous quitters, verified by expired carbon monoxide measurement, and relapsers. The results showed a significant difference between the groups in the pattern of pretreatment HR response to the lighting of the cigarette; relapsers displayed a sharp HR deceleration in response to the stimulus, while quitters' HR did not decelerate. The theoretical and clinical significance of these results is discussed.

Adult↗
PubMed1988

Radiotherapy of the rhabdomyosarcoma R1H of the rat: kinetics of cellular inactivation by fractionated irradiation.

The kinetics of cellular inactivation by fractionated irradiation in the R1H rhabdomyosarcoma of the rat was studied in the dose range of 1.07 to 12.50 Gy per fraction. Regimens of 1, 3, 5, 7, and 10 fractions per week for several weeks were compared. The number of clonogenic tumor cells per tumor in the course of the different treatment schedules was determined using an in vitro colony assay. The results show that the proliferation of clonogenic tumor cells is decelerated in the course of a fractionated radiotherapy. The deceleration persists for several days after end of treatment, until accelerated repopulation is initiated. The fraction of tumor cells inactivated per week was only dependent on the total dose per week, that is the cellular response was the same whether the weekly dose was applied in 1,3,5,7, or 10 fractions. Thus, the fractionation regimens were considerably more effective than expected from calculations based on single-dose in situ survival curves.

Algorithms↗
PubMed1987

Diurnal and other variations in fetal movement and heart rate patterns at 20-22 weeks.

It was investigated when diurnal and other variations in fetal movements and in heart rate pattern emerge during the course of pregnancy. Real-time ultrasound observations were made at 13 weeks of gestation in 7 nulliparous women and at 20-22 weeks in 10 nulliparous women. The observations took place at 0800, 1300 and 2200 and lasted 60 min/session at 13 weeks and 120 min at 20-22 weeks. The fetal heart rate was recorded for 24 h at 20-22 weeks using electrocardiographic electrodes. No diurnal variations were found for any of the movement patterns at 13 weeks. At 20-22 weeks, however, significant diurnal changes were observed in the total activity, the incidence of general movements and the breathing movements, with the lowest values in the morning and the highest during the evening. Fetal breathing movements already appeared to be related to maternal meals at 20-22 weeks as their incidence was significantly lower during the third hour after meals compared to the second hour. The rank order of the incidence of movements (from high to low incidence) was fairly constant over the course of the day both at 13 and at 20-22 weeks. This confirms earlier findings that the rank order of movements is strictly age dependent. Diurnal rhythms were observed for both the fetal heart rate and its variation. The fetal heart rate was lowest between 2400 and 0600 and the heart rate variation was lowest between 0600 and 1100. The incidence of accelerations and decelerations showed no systematic fluctuations over the 24-h period. Decelerations occurred more frequently than accelerations. Episodes of high heart rate variation were associated with an increased incidence of general movements. The various diurnal variations over 24 h at 20-22 weeks generally followed the same temporal sequence as those found near term, although the changes were considerably smaller.

Circadian Rhythm↗