Learned control of heart rate during exercise in patients with borderline hypertension

Summary Twelve patients with borderline hypertension [⩽21.33/12.6, ⩾18.6/12.0 kPa (⩽160/ 95; ⩾ 140/90 mm Hg)] participated in an experiment aimed at testing whether they could learn to attenuate heart rate while exercising on a cycle ergometer. Six experimental (E) subjects received beat-to-beat heart-rate feedback and were asked to slow heart rate while exercising; six control (C) subjects received no feedback. Averaged over 5 days (25 training trials) the exercise heart-rate of the E group was 97.8 bt min⁻¹, whereas the C group averaged 107 bt min⁻¹ (P=0.03). Systolic blood pressure was unaffected by feedback training. Generally, changes in rate-pressure product reflected changes in heart-rate. Oxygen consumption was lower in the E than in the C group late in training. We conclude that neurally mediated changes associated with exercise in patients with borderline hypertension can be brought under behavioral control through feedback training.     

Electrodermal Responsivity in Young Hypotensive and Hypertensive Men

Electrodermal responses were recorded during the presentation of 16 moderately intense (1000 Hz, 90dB) tones in three groups of young men: borderline hypertensives (138/79 mmHg), normotensives (112/65 mmHg), and hypotensives (104/63 mmHg). Electrodermal response habituation was measured as a decline in response over trials, number of trials to a response criterion of three successive nonresponses, and number of inversions of response amplitude (larger responses following smaller responses) in the stimulus sequence. Habituation was fastest in hypotensives. Nonspecific electrodermal responses at rest and during tone presentations were most frequent in borderline hypertensives, least frequent in the hypotensive group, with the normotensive group falling in between. There were no significant differences in electrodermal level. The rapid habituation rate in hypotensives is discussed in terms of cursory information processing associated with impulsive behaviour. The higher nonspecific electrodermal activity in borderline hypertensives is interpreted to indicate increased sympathetic nervous system activity.     

Psychosocial work characteristics and perceived control in relation to cardiovascular rewind at night

This study examined the effects of psychosocial work characteristics on cardiovascular rewind at night. Ambulatory 24-hr recordings of blood pressure (BP) and heart rate (HR) of 75 borderline hypertensive and 74 normotensive men were related to diary ratings of perceived control (PC) and to scores of psychological demand (P), control (C), and social support (S) at work determined by an occupational classification system. Multiplicative interaction terms for job strain (P x C), isostrain (P x C x S), and Job Strain x Perceived Control (P x C x PC) were calculated. The P x C x PC interaction predicted diastolic BP at night but not at work. A delayed latency to attain the lowest systolic BP during the night was found for jobs with high job strain and isostrain. Low perceived control and social support were associated with higher HR at work and at night. A logistic regression analysis indicated that the interaction between P x C x PC and the body mass index was independently associated with borderline hypertension.     

A radio (51Cr) micro-tube leukocyte adherence inhibition assay: specific tumor-associated immunity in 3 murine tumor systems.

A radio (51Cr) micro-tube leukocyte adherence inhibition assay is described. In this study, murine mononuclear cells were labeled with 51Cr, plated into tissue culture plates with different tumor extracts and counts/min (cpm) of the non-adherent cells were used as a parameter of adherence inhibition. This assay was used to measure anti-tumor immunity, in vitro, in 3 murine tumor systems: MCA-38 colon adenocarcinoma, L1210 lymphoma and P815 mastocytoma. Tumor immunity was detected using 3 doses (0.01-0.001 mg/ml) of tumor extract in the MCA-38 tumor model, and using 2 doses (0.1-0.05 mg/ml) of tumor extract in both the L1210 and P815 tumor models. It was observed that specific tumor-associated adherence inhibition could be measured in the MCA-38 tumor model between days 7 and 22 of tumor growth and in the L1210 and P815 tumor models between days 7 and 17 of tumor growth. The radio-LAI assay described is an easy, specific and reproducible way to measure tumor-associated adherence inhibition, in vitro.     

Cardiac Orienting to Pulsed and Continuous Auditory Stimulation: A Developmental Study

Pulsed presentations of auditory stimulation have been shown to be particularly effective in eliciting cardiac deceleration (orienting) during earliest infancy. In the present study the processing of pulsed as compared to continuous stimulation was studied developmentally for two infant age groups (13–18 and 26–35 weeks) and one adult group. Ten habituation trials of either a pulsed or a continuous 10-sec tone were followed by 2 dishabituation trials, in which the temporal pattern (continuous vs pulsed) was shifted. The dishabituation data showed that the two kinds of stimulation were discriminated, but the only finding of differential processing relating to the relevance of pulsed stimulation for younger infants was a tendency for infant subjects, unlike adults, to show prolonged orienting to initial presentations of the pulsed tone. For rate of habituation there were no differential effects. Only in the adult group was the response during dishabituation influenced by the direction of change of temporal pattern. Orienting to stimulus offset was observed on initial presentations of the continuous stimulus for the older infant group.     

Comparison of disseminated and nondisseminated strains of Borrelia burgdorferi sensu stricto in mice naturally infected by tick bite

Clinical isolates of Borrelia burgdorferi sensu stricto have been categorized into disseminated and nondisseminated groups based on distinct ribosomal spacer restriction fragment length polymorphism genotypes (RSTs). In order to determine whether transmission by tick bite would alter the dissemination dynamics and disease produced by distinct genotypes, disseminated isolates (RST1), nondisseminated isolates (RST3), and a standard laboratory strain (B-31) were established in a murine cycle utilizing infections transmitted by ticks. B-31 spirochetes circulated in the blood of inbred C3H/HeJ mice longer than in the blood of outbred mice. The majority of C3H mice exposed to RST1-infected ticks contained cultivable spirochetes in their blood for up to 17 days; in contrast, mice exposed to RST3 isolates demonstrated a precipitous decline in infection after day 7 postexposure. A quantitative PCR (q-PCR) assay demonstrated that the densities of spirochetes in blood were similar for the RST1 and RST3 isolates, except during the 2nd week postexposure, when the RST1 isolates displayed a markedly higher density in blood. Spirochete load in the heart and bladder of infected mice was measured by q-PCR at 8 weeks postexposure; the numbers of spirochetes in these tissues were similar for mice infected with either disseminated or nondisseminated strains. Similarly, histopathology samples of heart, bladder, and joint tissue obtained at 8 weeks postexposure did not reveal greater pathology in mice infected with the disseminated isolates. We conclude that although the spirochetemia induced by tick-transmitted disseminated isolates was more intense and of longer duration than that induced by nondisseminated isolates, the resultant pathologies produced by these strains were ultimately similar.     

Neuroendocrine and Cardiovascular Stress Reactivity in Middle-Aged Normotensive Adults with Parental History of Cardiovascular Disease

Neuroendocrine and cardiovascular stress reactivity was studied in healthy middle-aged individuals whose parental history included essential hypertension and/or myocardial infarction and a control group without parental history of cardiovascular disease. All subjects completed a rest session (1 hour) and a stress session (1 hour). The stress session included behavioral (mirror image tracing, mental arithmetic, and the Stroop color word conflict test) and physical stressors (the cold pressor test and isometric exercise). Systolic and diastolic blood pressures and heart rate were recorded at baseline before and during all stressors. Specimens for determination of urinary catecholamines and cortisol were sampled after the rest and stress sessions respectively. Generally, a parental history of hypertension but not of myocardial infarction influenced neuroendocrine and cardiovascular stress reactivity. A family history of hypertension was associated with exaggerated epinephrine, norepinephrine, and cortisol excretion during stress and with enhanced heart-rate reactivity to behavioral (mental arithmetic and mirror image tracing) but not to physical stressors (isometric exercise or the cold pressor test). We conclude that individuals with a family history of hypertension tend to display exaggerated cardiovascular and neuroendocrine reactivity to stress.     

Selective Attention Effects on the Reflex Blink

Past work has shown that facilitation of reflex blinking accompanies cardiac deceleration when the attention of subjects is directed to a reflex-eliciting stimulus. The present studies showed that when warning stimuli directed attention instead to weak (tactile) stimuli presented simultaneously with reflex-eliciting (acoustic) stimuli, cardiac deceleration was still present but reflex magnitude was unchanged or inhibited. However, latency to reflex onset remained facilitated, i.e., latency and magnitude changes were discordant. The findings were interpreted as evidence for two independent processes: a process capable of selectively enhancing or attenuating sensory input and a non-selective process presumably facilitating motor pathways.