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Biomedical subjects

H Rau

Publications and source records attributed to H Rau.

At least 73 records · Page 4Linked to original sources
PubMed1994

Central effects of baroreceptor activation in humans: attenuation of skeletal reflexes and pain perception.

Activating the arterial baroreceptors blunts pain sensation and produces other forms of central nervous system inhibition in animals. These effects may be important to blood pressure regulation but have not been rigorously verified in humans. We describe (i) a noninvasive behaviorally unbiased method for baroreceptor stimulation and (ii) the application of this method to measurement of baroreceptor-mediated attenuation of pain perception and of the Achilles tendon reflex. The findings are relevant to basic mechanisms of blood pressure stabilization and cardiovascular reactivity and may also have implications for noncompliance with antihypertensive medications and for the pathophysiology of essential hypertension.

Achilles Tendon↗
PubMed1994

Speaking from the heart: cardiovascular components of stress rating changes and the relative reactivity of physiological and psychological variables.

The first part of the experiment compared the relative reactivity of various cardiovascular measurements and self-reported assessment of mental arithmetic, an active coping stress task. It was found that the self-reported stress rating was more responsive (student's t = 9.4) than the physiological measurements. Among the cardiovascular indices, heart rate was the most responsive (student's t = 6.5), followed by the interval between R-wave and the maximal systolic pressure (student's t = 5.0). The second part of the study used a multiple regression to examine the cardiovascular components of change in stress rating following mental arithmetic. Both resting (psychophysiological "trait" variables) and change under stress (psychophysiological "state" variables) were used to predict change in stress rating. Stress rating increase were associated with greater maximal systolic pressure rate of rise (finger dP/dt) at baseline and less heart rate increase during mental arithmetic, yielding a multiple r of 0.67. The dual autonomic nature of active coping stress response is discussed. The shortcomings of using a correlate of a correlate are noted.

Adult↗
PubMed1994

Slow cortical potential biofeedback and the startle reflex.

The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Self-control of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP. The current study used a modified feedback methodology, and found a positive relationship between negativity and magnitude of EMG startle response (a measure of cortical and subcortical arousal, particularly aversive response disposition). Greater success in SCP differentiation was associated with self-report of less relaxation during negativity training.

Adult↗
PubMed1994

Positive shifts of event-related potentials: a state of cortical disfacilitation as reflected by the startle reflex probe.

Cortical positivity as measured by slow event-related potentials is assumed to represent a decreased excitability of cortical networks and suppression of their behavioral-cognitive output. The blink reflex probe is a commonly used defensive electromyographic response whose amplitude was shown to be modulated by emotional and attentional orientation. It was used here as an indicator of cortico-subcortical excitation. In study 1, 33 healthy subjects took part in a continuous performance test (CPT). Event-related potentials were recorded from 15 standard scalp locations. Acoustic startling noise bursts were delivered during conditions that required either performance of prepared motor responses (Go), inhibition of prepared motor responses (NoGo), or had no motor significance (Irrelevant condition). During the NoGo condition, EEG surface potentials showed a widespread P300-like positivity with a central maximum. Startle responses were inhibited during the NoGo condition as compared to the Irrelevant condition. In study 2 (21 subjects) the same format was used, except that the startle reflex was elicited visually. Startle reflexes again showed smaller magnitude during the NoGo condition, which evoked larger positivity at central sites in comparison to the Irrelevant condition. The relationship between positivity in the EEG and inhibited startle responses is in line with the hypothesis that positive EEG shifts reflect a state of cortical disfacilitation.

Acoustic Stimulation↗
PubMed1994

Behavioral and psychophysiological predictors of self-monitored 19 month blood pressure change in normotensives.

Selected demographic, behavioral and psychophysiological variables (sex of the subject, exercise, coffee and cigarette consumption, baroreceptor stimulation-dependent pain dampening, initial blood pressure, body mass index, daily stress rating, reactivity to mental stress as measured by change in stress rating and heart rate and blood pressure from resting to mental arithmetic conditions) were entered into a stepwise multiple-regression equation to predict changes of oscillometrically self-measured tonic blood pressure in 80 normotensives over a 19 month period. The prediction equation (r = 0.55) associated increases in diastolic blood pressure with baseline diastolic blood pressure, more baroreceptor stimulation-dependent pain inhibition, and less heart rate change during mental arithmetic. There were no significant predictors of systolic changes, and no sex differences. Results are discussed in terms of the learned model of hypertension.

Adult↗
PubMed1994

Mapping P300 waves onto inhibition: Go/No-Go discrimination.

Subjects viewed letters presented at 2 sec intervals and prepared a fast button press whenever an "O" appeared. If the next letter was an "X" the button press was executed (Go signal), but if the letter was a non-X character (T, H, Z) suppression of the response was required (No-Go cue). No-Go signals elicited a P300-like wave that was larger at central and frontal scalp sites contralateral to the prepared movement, compared to P300s elicited by Go cues which were symmetric about the sagittal midline and dominant at parietal sites. Subtraction of preparatory CNVs from the No-Go P300 did not remove differences in scalp topography, or reduce the amplitude of the No-Go P300 to that seen following control letters that required perceptual identification but did not call for suppression of prepared motor responses. Principal components analysis identified a middle positive wave following X-alone control stimuli whose topography resembled the No-Go P300. These findings suggest that the source of augmented No-Go P300s is a generator involved with sensorimotor inhibition. We discuss the mechanism of P300 waves and evidence linking these waves with inhibition in other task arrangements.

Adult↗
PubMed1994

Baroreceptor stimulation: pain perception and sensory thresholds.

Baroreceptor activity has been implicated in the modulation of pain. Sensory detection thresholds and pain ratings were measured in a group of 28 men during carotid baroreceptor manipulation with the PRES (phase-related external suction) neck suction technique. Brief, cardiac phase-related electrical impulses were delivered intracutaneously to the finger. The results indicate that minimum baroreceptor activity was associated with more severe pain, but had no effect on sensory detection threshold. The results are discussed in terms of the learned model of hypertension.

Adult↗
PubMed1994

Brain potentials during mental arithmetic: effects of extensive practice and problem difficulty.

Recent behavioral investigations indicate that the processes underlying mental arithmetic change systematically with practice from deliberate, conscious calculation to automatic, direct retrieval of answers from memory [Bourne, L.E.Jr. and Rickard, T.C., Mental calculation: The development of a cognitive skill, Paper presented at the Interamerican Congress of Psychology, San Jose, Costa Rica, 1991: Psychol. Rev., 95 (1988) 492-527]. Results reviewed by Moscovitch and Winocur [In: The handbook of aging and cognition, Erlbaum, Hillsdale, NJ, 1992, pp. 315-372] suggest that consciously controlled processes are more dependent on frontal lobe function than are automatic processes. It is appropriate, therefore to determine whether transitions in the locus of primary brain activity occur with practice on mental calculation. In this experiment, we examine the relationship between characteristics of event-related brain potentials (ERPs) and mental arithmetic. Single-digit mental multiplication problems varying in difficulty (problem size) were used, and subjects were trained on these problems for four sessions. Problem-size and practice effects were reliably found in behavioral measures (RT). The ERP was characterized by a pronounced late positivity after task presentation followed by a slow wave, and a negativity during response indication. These components responded differentially to the practice and problem-size manipulations. Practice mainly affected topography of the amplitude of positivity and offset latency of slow wave, and problem-size mainly offset latency of slow wave and pre-response negativity. Fronto-central positivity diminished from session to session, and the focus of positivity centered finally at centro-parietal regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

DNA ploidy in carcinoma of the gallbladder. Prognostic significance and comparison of flow and image cytometry on archival tumor material.

The aim of this investigation was to determine whether the cytometrically assessed DNA ploidy is a parameter of prognostic significance in gallbladder carcinomas. For this purpose the DNA content of tumor cells from archival tumor material from 80 patients with cholecystic cancer was analysed retrospectively by using comparatively different cytometrical methods, namely flow cytometry (FCM) and image cytometry, using tissue sections (ICM-S) and nuclear suspensions (ICM-N). Conventional tumor classifications (according to pTNM and Nevin) were able to predict the further clinical course. DNA ploidy showed a statistically significant correlation only to histological grade (P < 0.001), but not to tumor stage and survival. Only a trend towards a poorer outcome for patients harboring non-diploid tumors became evident especially when no residual tumor was present postoperatively (R 0-stage; P = 0.08). The different cytometrical methods discussed in detail, showed a highly significant concordance in the determination of DNA index values (DI) and in the classification of the tumors as either diploid or non-diploid. In conclusion, our results indicate that cytometrical determination of DNA ploidy provides no further prognostic informations in gallbladder carcinomas as compared to conventional tumor staging.

Aged↗
PubMed1994

Reduced pain during baroreceptor stimulation in patients with symptomatic and silent myocardial ischaemia.

OBJECTIVE: Baroreceptor activation has been shown to reduce pain, and the accumulation of such pain reduction has been implicated in the operant learning (under certain circumstances) of hypertension. The current study is an examination of differences in the pain dampening effects of baroreceptor activity in patients with symptomatic and asymptomatic myocardial ischaemia. The objective was to determine whether there are differences between patients with symptomatic and silent myocardial ischaemia with respect to their antinociceptive response to baroreceptor stimulation, and, if so, whether these differences could be related to the absence of angina pectoris pain in patients with silent myocardial ischaemia. METHODS: Sensory detection and electrical pain thresholds were compared in nine symptomatic and 10 asymptomatic patients with replicable myocardial ischaemia during PRES (phase related external suction) carotid baroreceptor manipulation in which the pressure inside a neck cuff was phase locked in time to the R wave of the ECG and negative pressure was applied during either systole or diastole. Tourniquet pain thresholds were also determined. RESULTS: It was found that (1) external baroreceptor manipulation had no effect on detection thresholds; (2) painful stimuli were judged by both symptomatic and asymptomatic patients as less intense when delivered during maximum baroreceptor activity; (3) symptomatic and asymptomatic patients did not differ in their sensory detection thresholds; and (4) asymptomatic patients had significantly higher ischaemic (tourniquet) pain thresholds than symptomatic patients. CONCLUSIONS: The results indicate that baroreceptor activity can modify the intensity of painful stimuli. The degree to which baroreceptor manipulation affects pain does not appear to differ between patients with painful and silent myocardial ischaemia. Thus the baroreceptor dependent pain inhibition effects seems not to be responsible for the higher ischaemic pain threshold found in the silent myocardial ischaemia group.

Electric Stimulation↗
PubMed1994

Effects of PRES baroreceptor stimulation on thermal and mechanical pain threshold in borderline hypertensives and normotensives.

Prior studies have noted a pain relieving effect of baroreceptor stimulation and of higher tonic blood pressure in animals and humans. The present study used a new technique for the controlled, noninvasive stimulation of human carotid baroreceptors (PRES). PRES baroreceptor manipulation was delivered to both normotensive subjects (n = 11) and medication-free labile hypertensive subjects (n = 10) during both thermal and mechanical pain. Consistent with prior research, hypertensives had a higher threshold for thermal pain than did normotensives. PRES baroreceptor manipulation had no significant effect on thermal pain threshold for either group. For the mechanical pain model, the opposite results were obtained; group pain thresholds did not differ, but there was a significant PRES baroreceptor stimulation effect of increasing pain threshold for both groups. Results are discussed in terms of specific features of the stimuli, dampening of pain in hypertensives, and adaptation to pain.

Adult↗
PubMed1994

Sensory effects of baroreceptor activation and perceived stress together predict long-term blood pressure elevations.

Activating the arterial baroreceptors in animals has been shown to blunt pain sensation and provide other forms of central nervous system inhibition. This study tested the hypothesis that, among human subjects, a tonic increase in blood pressure (BP) could be a learned response to environmental stressors among subjects in whom the baroreceptor inhibitory mechanism is active. In a sample of 96 healthy, normotensive men and women, amount of pain-reduction produced by baroreceptor stimulation predicted an increase in resting BP 20 months later: the increase was proportional to self-assessed daily life stress. Among the subjects reporting the greatest amount of stress, the pain inhibition effect accounted for more than 80% of the BP variance. These results support the hypothesis that the reduction in perceived stress produced by baroreceptor stimulation may reward learned increases in BP.

Journal Article↗
PubMed1993

Bromocriptine treatment over 12 years in acromegaly: effect on glucose tolerance and insulin secretion.

It is not known whether the beneficial effect of bromocriptine on glucose homeostasis in acromegaly is limited by a certain duration of therapy. To elucidate this problem, oral glucose tolerance tests were performed in 12 acromegaly patients before bromocriptine medication, under therapy (15.0 +/- 6.8 mg/day for 12 +/- 3 years), and during a 2-week drug withdrawal after long-term treatment. Initially altered glucose tolerance was normalized in 4 of 5 patients under bromocriptine therapy. During drug withdrawal the mean fasting glucose level and the mean glucose concentration at 120 min after oral glucose load increased from 5.05 +/- 0.61 to 5.77 +/- 0.78 mmol/l and from 5.61 +/- 2.05 to 7.55 +/- 3.05 mmol/l, respectively. A deterioration in glucose homeostasis was observed in 9 patients, and impaired glucose tolerance was ameliorated (but not to normal range) in 2 when bromocriptine was withdrawn. The proportion of alterations in glucose tolerance during drug withdrawal corresponded to that before the beginning of long-term bromocriptine treatment. Impaired glucose tolerance, observed in 2 patients under bromocriptine treatment, seemed to be compensated because a distinct elevation of glycosylated hemoglobin A1c was not observed. Bromocriptine led to a significant decrease in basal as well as glucose-stimulated insulin levels, and growth hormone secretion during oral glucose load was reduced in all 12 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1993

Blood pressure changes validate phase related external suction, a controlled method for stimulation of human baroreceptors.

Phase related external suction (PRES), a new controlled method for manipulating activity in human baroreceptors, applies precisely timed bursts of suction and pressure within the cardiac cycle through an external neck cuff. Seven healthy adult men participated in 32 pseudo-random trials of baroreceptor stimulation and inhibition. Blood pressure was assessed both intra-arterially and with a noninvasive device. In the present study, PRES baroreceptor stimulation elicited invasively measured blood pressure decreases of about 2.5 mmHg (0.33 kPa) and heart rate decreases of about 5 beats,min-1, while baroreceptor inhibition increased invasively measured blood pressure by about 1.5 mmHg (0.20 kPa) and heart rate about 2.5 beats.min-1. It was concluded that PRES is an effective method for baroreceptor manipulation with weaker size effect but better control of nonspecific factors in human subjects than other baroreceptor manipulation techniques. The noninvasive blood pressure measurement device was less sensitive to experimental variation than was the invasive device.

Adult↗
PubMed1993

Cigarette smoking, blood lipids, and baroreceptor-modulated nociception.

Activation of arterial blood pressure has been shown to influence higher central nervous activity. In animals, induction of sleep-like states and increases of seizure and pain thresholds in response to baroreceptor stimulation have been reported. In certain human groups, mechanical stimulation of the carotid baroreceptors also increases pain thresholds. The present paper examines the hypothesis that smokers show baroreceptor dependent antinociception as compared to non-smokers. It is speculated that one effect which rewards smoking is the nicotine induced phasic blood pressure increase which leads to baroreceptor stimulation and dampens pain perception. One hundred and twenty subjects were investigated using a recently developed mechanical baroreceptor stimulation technique and an electrical pain stimulus. The group of heavy smokers showed the predicted effect: their pain thresholds were enhanced during conditions of increased baroreceptor activity as compared to the control condition. The group of medium, light and non-smokers, however, did not show this effect. Neither blood lipid levels nor diastolic or systolic blood pressure paralleled the group differences on baroreceptor dependent antinociception. In heavy smokers, the nicotine induced phasic blood pressure increases might have baroreceptor dependent pain dampening effects, which might be among the reinforcing qualities of smoking.

Adult↗
PubMed1993

Effects of smoking on thermal pain threshold in deprived and minimally-deprived habitual smokers.

This study examined the antinociceptive effects of smoking in nine habitual smokers under deprived (12 h) and minimally-deprived (< 30 min) conditions. Pain threshold for thermal stimuli, heart rate, blood pressure and ratings of mood, arousal, dominance and well-being were assessed before and after smoking a cigarette. Over-all, smoking affected all measured variables in the expected direction, leading to increased physiological activity, elevated pain threshold and improved mood. However, most of these effects depended on the deprivation status of the subjects, such that smoking after deprivation increased pain threshold whereas smoking after minimal deprivation did not. Pain threshold before smoking was the same for both groups. Deprived subjects had lower pre-smoke diastolic blood pressure, heart rate, and arousal levels, which rose to equal minimally-deprived subjects' scores after smoking.

Adult↗
PubMed1993

Hypochondriacal attitudes, pain sensitivity, and attentional bias.

The relation between hypochondriacal attitudes, thermal pain threshold, and attentional bias toward pain was examined in a non-clinical population (N = 28). Attentional bias was operationalized with a concentration-performance test, which subjects performed while connected to a pain stimulator. Subjects were informed that they would receive a painful stimulus during the second part of the test, while the first part was introduced as pain-free. The pain stimulus was never applied during the test phase. The expectancy of a forthcoming pain stimulus reduced the performance of high hypochondriacal subjects in both parts of the test. Low hypochondriacal subjects, on the other hand, displayed significantly better performance in the first, pain-free compared to the second, pain-related part of the test. Thermal pain thresholds were assessed at four measuring sites (thenar, neck, collar-bone, abdomen), but no relations with hypochondriasis sum scores and locus of pain stimulation were found. A stepwise multiple regression of pain threshold by individual Illness Attitude Scales (IAS) led to 66% of the variance being explained by the scales 'concern about pain', 'worry about illness', and 'disease phobia'. Results are discussed in terms of amplifying somatic style, preoccupation with or attentional bias toward bodily symptoms, and experimental induction of a hypochondriacal state.

Adult↗