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Biomedical subjects

B T Engel

Publications and source records attributed to B T Engel.

At least 55 records · Page 3Linked to original sources
PubMed1989

Learned control of systolic blood pressure raising and lowering in rhesus monkeys.

Three male monkeys (Macaca mulatta) were operantly conditioned to raise and lower systolic blood pressure (SP). All animals were trained in three stages: first to lower, then to raise systolic pressure, and finally to alternate these two behaviors. All monkeys learned the task and performed reliably in all stages. Diastolic pressure (DP) usually paralleled systolic pressure but changed much less than SP. Heart rate (HR) always fell below baseline in lowering sessions, and in two of the three animals during raising sessions as well. These findings support our earlier results which showed that monkeys could learn to control heart rate. This animal model should permit detailed studies of the hemodynamic mechanisms mediating learned control of systolic pressure.

Animals↗
PubMed1988

The use of successive blood-pressure measurements to estimate blood-pressure variability.

Multiple daily, self-determined blood-pressure measurements were obtained from 254 hypertensive patients for 1 month. In an effort to establish a practical and reliable technique for estimating blood-pressure variability, standard deviations from three (at one time of day) or nine (throughout the day) successive self-determinations were compared with a reference value, taken to be the standard deviation for the entire month (252 determinations per subject). Neither the standard deviation of three measures taken on one occasion nor that of nine measures taken throughout the day correlated well with the reference value (average R3 = .21 for SBP, .20 for DBP; average R9 = .39 for SBP, .38 for DBP). However, when a sample consisting of 12 measures (taken three at a time, at the same time of day, weekly for 4 weeks) was used, the average correlation rose to .60 for SBP and .54 for DBP. Thus, it appears that 12 samples taken in this way provide a reliable estimate of the standard deviation for an entire month, and it is suggested that this sampling technique also would enhance the reliability of conclusions drawn from assessments of the prognostic value of blood-pressure variability.

Age Factors↗
PubMed1988

Habituation and dishabituation to repeated mild cold exposures in C57BL/6J mice.

Every two weeks for 12 weeks four groups of C57BL/6J male mice, initially 12 months old, were subjected to three-hour cold stress tests, which consisted of a partial physical restraint at an ambient temperature of 10 degrees C. The control group experienced six consecutive tests; one experimental group skipped the cold exposure during test No. 4 but was physically restrained at room temperature; the other two experimental groups omitted test No. 4. One of these groups spent the four weeks between test No. 3 and test No. 5 in their home cages, while the other was subjected to daily, 30-minute sessions of electrical stimulation of the hypothalamus through electrodes implanted in the "rewarding" area of the medial forebrain bundle. All animals in this group showed self-stimulating behavior in the test session which preceded cold stress test No. 1. During test No. 3, all four groups showed an improvement of cold tolerance relative to their first tests; body mass and colonic temperature prior to cold exposure remained unchanged. The two experimental groups that were not exposed to cold during test No. 4 and did not receive brain stimulation, demonstrated a significant worsening of cold tolerance during the subsequent test. Their body mass and baseline colonic temperatures did not change. The control group and the group which was subjected to brain stimulation during the interval between tests No. 3 and No. 5 did not demonstrate any changes in cold tolerance. These data demonstrated habituation to repeated mild cold exposures and dishabituation after interruption of cold exposures.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1988

Behavioral training for urinary incontinence in elderly ambulatory patients.

Research questions addressed by this study were: 1) Is the treatment of chronic urinary incontinence (UI) in elderly, nondemented ambulatory patients using bladder-sphincter biofeedback as effective when performed by an internist/geriatrician and a nurse practitioner as that reported by behavioral scientists?; and 2) how does bladder-sphincter biofeedback compare to a program of behavioral training that does not utilize biofeedback? Twenty-seven patients with UI were assigned based on the number of baseline accidents documented in a self-maintained log, their sex, and the predominant pattern of symptoms (urge or stress) to one of two treatment groups: biofeedback (13 patients) or behavioral training not utilizing biofeedback (14 patients). Patients were given up to six treatments. Patients in both groups achieved a highly significant (P less than .001) reduction in urinary accidents 1 month following treatments compared with their baseline number of accidents. The average reduction of accidents over this time period was 79% for the biofeedback group and 82% for the group receiving behavioral training without biofeedback. All patients showed improvement and no patient experienced any side effect. A internist/geriatrician and a geriatric nurse practitioner may achieve success utilizing behavioral therapy with or without biofeedback for the treatment of chronic urinary incontinence for ambulatory elderly patients.

Aged↗
PubMed1987

Cardiovascular reactivity as behavior.

The word, behavior, means action or reaction. Thus, all physiologic responses meet this definition and are behavior. Furthermore, if the response is neurally mediated, then there are only 3 possible behavioral mechanisms that can be operating to determine it: (1) The response is part of a reflex, elicited by an adequate stimulus. In this case, in an intact animal the expression of the response will be modulated by a variety of situational factors. (2) The response is part of a reflex. However, the capacity of the stimulus to elicit the response is acquired through association with an adequate stimulus. Thus, the reflex is learned rather than innate. (3) The response is part of a "central command" and is emitted in anticipation of a consequence whose likelihood of occurrence has been learned. Neurally mediated responses of the circulation meet all these criteria. Thus, circulatory responses not only are passive reflexes, they also are reactive and proactive behaviors, which permit animals to interact effectively with their environments, and which change with practice. These principles explain a variety of cardiovascular effects observed in experimental or clinical settings. Furthermore, by applying well-established behavioral principles to circulatory responses, it is possible to achieve clinically significant effects. This presentation will characterize the way in which behavioral mechanisms are expressed in the circulation, it will describe a number of clinically significant findings that illustrate the importance of these mechanisms, and it will propose a number of applications of behavioral principles that can be used in clinical practice.

Animals↗
PubMed1987

Diurnal patterns of hemodynamic performance in nonhuman primates.

Heart rate, stroke volume, and intra-arterial blood pressures were monitored continuously in each of four monkeys for 18 consecutive hours, 5 days/wk, for several weeks. Mean heart rate, stroke volume, cardiac output, systolic and diastolic pressure, and total peripheral resistance were calculated each minute, and these averages were analyzed further to yield hourly means and intercorrelations. The main findings from the analyses of mean levels were that cardiac output fell throughout the night and that peripheral resistance rose during the same interval so that arterial pressure fell only slightly; the highest levels of peripheral resistance and lowest levels of cardiac output were recorded between 0500 and 0700. Furthermore, the levels of these responses during the remainder of the morning were higher (peripheral resistance) and lower (cardiac output) than those recorded in the evening.

Animals↗
PubMed1986

The role of biofeedback in Kegel exercise training for stress urinary incontinence.

This study examined the effectiveness of teaching pelvic floor exercises with use of bladder-sphincter biofeedback compared to training with verbal feedback based on vaginal palpation in 24 women with stress urinary incontinence. Verbal feedback training consisted of instructing the patient to squeeze the vaginal muscles around the examiner's fingers and providing her with verbal performance feedback. Biofeedback patients received visual feedback of bladder pressure, abdominal (rectal) pressure, and external anal sphincter activity. The biofeedback group improved the strength and selective control of pelvic floor muscles; the verbal feedback group did not. Both groups significantly reduced the frequency of incontinence. The biofeedback group averaged 75.9% reduction in incontinence, significantly greater than the 51.0% reduction shown by the verbal feedback group. Twelve of 13 patients in the biofeedback group improved by 60% or better. Six patients in the verbal feedback group improved by 68% or better, and five were less than 30% improved.

Adult↗
PubMed1986

Temporal decrease of body temperature in middle-aged C57BL/6J mice.

Colonic temperature of C57BL/6J mice of both sexes between 12 and 19 months was measured at normal ambient temperature in four independent studies. One study was cross-sectional and the others were longitudinal. In all samples, colonic temperature at about 14 months was always lower than temperature at earlier ages. Furthermore, temperature always returned to earlier levels within 2 weeks; however, it remained unstable up to the age of 18 months after which it returned to the pre-14-month level until finally it fell late in life (after 23 months). Additionally, parametric studies showed that there were differences in the reliability of temperature probes made by different manufacturers to measure absolute temperature. These differences, however, did not affect relative differences among temperatures. Further parametric studies showed that colonic temperature in restrained mice rises 1.2 degrees C within the first 5 min after restraint indicating that duration of restraint is an important factor in studies such as these.

Aging↗
PubMed1986

Diurnal variations in cardiovascular integration.

Beat-to-beat heart periods and intra-arterial blood pressures were monitored continuously for 18 h in each of six monkeys over periods of several weeks. Means, based on 128-s averages of these functions, were highly correlated during early evening and daytime periods; however, heart period was poorly correlated with blood pressure during the evening hours, although systolic and diastolic pressures were highly correlated, and the standard deviations of heart period also were highly correlated with the pressures. These shifts in cardiovascular integration were unexpected and suggest that the circulation is relatively sensitive to the conditions under which it is being assessed, and they suggest further that response relationships observed under one set of conditions may not be comparable to those measured under another set of conditions.

Animals↗
PubMed1986

Learned control of heart rate during dynamic exercise in nonhuman primates.

The purpose of this study was to describe an animal model to test the relationships among the cardiovascular, pulmonary, and somatomotor command systems during exercise. Using operant conditioning, three chronically chaired monkeys (Macaca mulatta) were trained to exercise (to lift weights repeatedly), to attenuate their heart rate responses, and finally, both conditions were combined so that the animals were required to exercise and attenuate their heart rates. Heart rate, systolic and diastolic blood pressure, rate-pressure product, O2 and CO2 concentration in expired air, and number of weight lifts were recorded and compared between the two conditions, i.e., exercise only and combined exercise and heart rate slowing. In all animals heart rate increases in response to exercise were significantly less (P less than 0.05) during combined conditions than during exercise only: the mean heart rate increase was 41 beats/min less during combined sessions than during exercise only sessions for monkey 1, 13.5 beats/min less for monkey 2, and 9 beats/min less for monkey 3. Rate-pressure product showed a consistent difference across animals paralleling the heart rate differences. This acquired response did not involve other cardiovascular and pulmonary parameters, which did not change systematically across animals. However, the pattern of cardiovascular reactivity in relation to O2 consumption (linear regression of heart rate and systolic or diastolic blood pressure on change in O2 consumption over many experiments) was attenuated during combined sessions relative to exercise only experiments. The relative attenuation of heart rate during combined sessions also remained significant when both experimental conditions were equated on the basis of work done. Therefore, this animal model shows a dissociation of cardiovascular, somatomotor, and pulmonary effects of central command.

Animals↗
PubMed1986

Increasing distance and independence of ambulation in elderly nursing home residents.

We tested the effectiveness of a prompt-and-praise procedure for increasing walking distance and independence in eight nursing home residents. Walking distance and method of ambulation were observed just prior to mealtimes; in addition, mobility and social interaction were time-sampled in the living areas throughout the day. Treatment was lagged in a multiple baseline design across lunch and dinner meals within subjects, and across subjects within each of three units. In the mealtime setting, two subjects began walking the maximum scored distance during baseline; the other six subjects showed a marked increase in walking beginning with the first meal in which the intervention was applied. Six of the eight subjects also progressed to more independent means of ambulation. Generalization of walking to the second meal was observed in all four of the subjects in whom this could be assessed. Generalization across subjects was not observed nor was generalization to the living areas. Staff successfully implemented the procedures in the mealtime settings and the effects were maintained at the 4-month follow-up.

Aged↗
PubMed1985

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

Twelve patients with borderline hypertension [less than or equal to 21 X 33/12.6, greater than or equal to 18 X 6/12.0 kPa (less than or equal to 160/95; greater than or equal to 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.

Adult↗
PubMed1985

Cardiovascular and electrodermal adjustments during a vigilance task in patients with borderline and established hypertension.

We studied cardiovascular and noncardiovascular sympathetic nervous system (SNS) responses to a vigilance task in patients with borderline (BT) or established hypertension (HT). Twelve patients in each group and twelve normotensive controls (NT) were subjected to a signalled reaction-time (RT) task which included the presentation of a noxious 110 dB white noise contingent upon RT-performance at the end of a 30 sec foreperiod. During this foreperiod recordings were made of: systolic and diastolic blood pressures, heart rate, skin- and muscle-blood flows. Skin and muscle vascular resistances were calculated from mean blood pressure and regional blood flows. Skin conductance level, fluctuations and responses were recorded as noncardiovascular SNS-responses. Compared to NT both HT and BT had higher resting blood pressures, heart rate, skin- and muscle-vascular resistances. BT showed higher resting skin conductance levels than HT and NT who were not different from one another. During stimulation HT and BT evidenced pressor hyperreactivity compared to NT. The electrodermal effects did not parallel the cardiovascular ones. Skin conductance and cardiovascular variables were more closely related in NT than HT or BT. The presence of cardiovascular hyperreactivity together with the absence of noncardiovascular hyperreactivity in HT indicates heightened SNS-activity specific to the cardiovascular system and not part of generalized SNS-arousal. The similarity between HT and BT is consistent with the notion that the differences between BT and HT are quantitative rather than qualitative.

Adult↗