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Biomedical subjects

P Grossman

Publications and source records attributed to P Grossman.

At least 19 recordsLinked to original sources
PubMed2004

Respiratory sinus arrhythmia, cardiac vagal control, and daily activity.

Ambulatory respiratory sinus arrhythmia (RSA) or high-frequency heart rate (HR) variability is frequently employed as an index of cardiac parasympathetic control and related to risk or severity of cardiovascular disease. However, laboratory studies indicate variations in physical activity and respiratory parameters of rate and tidal volume may confound estimation of vagal activity. Because little is known about these relations outside the laboratory, we examined ambulatory relations among RSA, respiration, physical activity, and HR during waking hours by employing a multichannel monitoring system. Forty healthy young-to-middle aged adults underwent daytime monitoring that included continuous registration of the ECG, respiration (inductance plethysmography), and accelerometry motion activity. Within-individual regression analyses were performed to examine minute-to-minute relations between RSA and respiration, HR, and indexes of physical activity (minute ventilation and motion). HR changes were assumed to be strongly related to within-individual variations of vagal tone. RSA adjusted for respiratory parameters and unadjusted RSA were compared for strength of prediction of other measures. Unadjusted RSA was related to respiratory parameters (R = 0.80) and moderately predicted minute-to-minute HR and activity variances (means = 56%, HR; 48%, minute ventilation; and 37%, motion). Adjusted RSA predicted significantly more HR and activity variance (means = 75%, 76%, and 57%, respectively) with narrower confidence intervals. We conclude that ambulatory RSA magnitude is associated with respiratory variations and physical activity. Adjustment for respiratory parameters substantially improves relations between RSA and significantly vagally mediated HR and physical activity. Concurrent monitoring of respiration and physical activity may enhance HR variability accuracy to predict autonomic control.

Adult↗
PubMed2001

Simplified catechin-gallate inhibitors of HIV-1 reverse transcriptase.

Systematic simplification of the molecular structures of epicatechin gallate and epigallocatechin gallate to determine the minimum structural characteristics necessary for HIV-1 reverse transcriptase inhibition in vitro resulted in several compounds that strongly inhibited the native as well as the A17 double mutant (K103N Y181C) enzyme, which is normally insensitive to most known nonnucleoside inhibitors.

Catechin↗
PubMed2000

Is there a glycemic threshold for impaired autonomic control?

OBJECTIVE: Although hyperglycemia has been recognized as a predictor of cardiovascular autonomic neuropathy in diabetic patients, the glucose threshold at which autonomic control begins to become impaired has not been evaluated. This study examined whether fasting plasma glucose (FPG) or fasting plasma insulin (FPI) is associated with reductions in baroreflex sensitivity (BRS) in healthy volunteers. RESEARCH DESIGN AND METHODS: FPG and FPI were measured after an overnight fast in 162 healthy volunteers (91 men, 71 women) who were 25-44 years of age. BRS was measured with power spectral analysis. RESULTS: Univariate analyses showed that FPG was negatively correlated with BRS (r = -0.25, P < or = 0.001) with significant reductions observed in volunteers with FPG in the upper 2 quintiles (i.e., 93-124 mg/dl). However, after adjustment for other predictors of BRS (e.g., age, blood pressure, and BMI), the relationship between FPG and BRS was no longer significant. In contrast, FPI was negatively correlated with BRS in univariate analyses (r = -0.32, P < 0.0001) as well as after covariate adjustment, with close to a 50% reduction in BRS observed in the volunteers with insulin values in the highest quintile (i.e., 16-36 microU/ml). CONCLUSIONS: These findings suggest that high normal levels of FPG are associated with reduced autonomic control secondary to the effects of aging, obesity, and elevated blood pressure on FPG levels and that elevations in FPI are associated with substantial reductions in autonomic cardiac control independent of other covariates.

Adult↗
PubMed1999

Association of depressive symptoms with reduced baroreflex cardiac control in coronary artery disease.

BACKGROUND: Although depression has been associated with cardiac death in coronary artery disease (CAD), little is known about the effects of depression on autonomic nervous system control of heart rate. This study evaluated whether depressive symptomatology is associated with impaired baroreflex sensitivity (BRS) in patients with CAD. METHODS AND RESULTS: BRS was assessed in 66 patients with stable CAD by using cross-spectral analysis to measure baroreceptor-mediated R-R interval oscillations. Depressive symptomatology was determined with the Beck Depression Inventory, with lower (scores <3, n = 14) and upper (scores >9, n = 16) quartiles of scores used to define groups with low and high depressive symptomatology, respectively. Comparison of the two groups showed that age-adjusted BRS was reduced in the patients with high depressive symptomatology when compared with patients with low depressive symptomatology (4.5 +/- 2.7 vs 6.5 +/- 2.8 ms/mm Hg; P <. 05). CONCLUSIONS: The current findings show that patients with CAD and depressive symptomatology have reduced BRS. Future studies are needed to examine whether reduced baroreflex cardiac control predicts cardiac risk in patients with CAD and depressive symptomatology.

Age Factors↗
PubMed1999

Analysis of cardiovascular regulation.

Adequate characterization of hemodynamic and autonomic responses to physical and mental stress can elucidate underlying mechanisms of cardiovascular disease or anxiety disorders. We developed a physiological signal processing system for analysis of continuously recorded ECG, arterial blood pressure (BP), and respiratory signals using the programming language Matlab. Data collection devices are a 16-channel digital, physiological recorder (Vitaport), a finger arterial pressure transducer (Finapres), and a respiratory inductance plethysmograph (Respitrace). Besides the conventional analysis of the physiological channels, power spectral density and transfer functions of respiration, heart rate, and blood pressure variability are used to characterize respiratory sinus arrhythmia (RSA), 0.10-Hz BP oscillatory activity (Mayer-waves), and baroreflex sensitivity. The arterial pressure transducer waveforms permit noninvasive estimation of stroke volume, cardiac output, and systemic vascular resistance. Time trends in spectral composition of indices are assessed using complex demodulation. Transient dynamic changes of cardiovascular parameters at the onset of stress and recovery periods are quantified using a regression breakpoint model that optimizes piecewise linear curve fitting. Approximate entropy (ApEn) is computed to quantify the degree of chaos in heartbeat dynamics. Using our signal processing system we found distinct response patterns in subgroups of patients with coronary artery disease or anxiety disorders, which were related to specific pharmacological and behavioral factors.

Autonomic Nervous System↗
PubMed1998

Influence of drive and timing mechanisms on breathing pattern and ventilation during mental task performance.

Assessment of multiple respiratory measures may provide insight into how behavioral demands affect the breathing pattern. This is illustrated by data from a study among 44 subjects, in which tidal volume, respiration rate, minute ventilation and indices of central drive and timing mechanisms were assessed via inductive plethysmography, in addition to end-tidal PCO2. After a baseline, three conditions of a memory comparison task were presented. The first two conditions differed only with regard to the presence or absence of feedback of performance (NFB and FB). In the third 'all-or-nothing' (AON) condition, subjects only received a monetary bonus, if their performance exceeded that of the previous two conditions. Minute ventilation increased from baseline to all task conditions, and from NFB and FB to AON. Respiration rate increased in all task conditions, but there were no differences between task conditions. Tidal volume decreased during NFB, but was equal to baseline during FB and AON. Of the respiratory control indices, inspiratory flow rate covaried much more closely with minute ventilation than duty cycle. The task performance induced a minor degree of hyperventilation. The discussion focusses on how behavioral demands affect respiratory control processes to produce alterations in breathing pattern and ventilation.

Adult↗
PubMed1997

Blood pressure responses to mental stress in emotionally defensive patients with stable coronary artery disease.

Emotional defensiveness, defined by concealment of both negative emotions and personal vulnerability, was substantially and consistently correlated with the magnitude of blood pressure reactions to 2 types of mental stress among coronary patients, independently of clinical status. Given recent studies denoting stress-related blood pressure surges as triggers of dangerous cardiovascular events, exaggerated vasomotor reactions among defensive patients may be of clinical significance.

Blood Pressure↗
PubMed1997

Heart rate variability: origins, methods, and interpretive caveats.

Components of heart rate variability have attracted considerable attention in psychology and medicine and have become important dependent measures in psychophysiology and behavioral medicine. Quantification and interpretation of heart rate variability, however, remain complex issues and are fraught with pitfalls. The present report (a) examines the physiological origins and mechanisms of heart rate variability, (b) considers quantitative approaches to measurement, and (c) highlights important caveats in the interpretation of heart rate variability. Summary guidelines for research in this area are outlined, and suggestions and prospects for future developments are considered.

Animals↗
PubMed1997

Incremental bias in Finapres estimation of baseline blood pressure levels over time.

Finapres finger blood pressure monitoring appears to provide a reliable alternative to intra-arterial blood pressure measurement under many circumstances. However, few studies have focused on the limitations of Finapres assessment. In a previous pilot investigation, we observed that Finapres pressure following mental stressors failed to return to initial resting levels. Our objectives in the present study were to (1) replicate earlier findings, (2) examine whether local changes in the measured finger were responsible for the observed drift, and (3) test a method to facilitate the return of pressure to systemic baseline levels. We studied two groups of healthy subjects who underwent a protocol consisting of two mental stressors preceded and followed by baseline periods. In the control group, the Finapres continuously monitored pressure on a single finger for the entire protocol. The intervention group periodically had the Finapres cuff removed and the measured finger exercised to prevent local changes that might influence Finapres estimation of blood pressure. Comparisons indicated a group x baseline interaction effect for systolic and diastolic pressures (P < .0004 and P < .003, respectively). The group with the exercise intervention showed much greater recover during the final baseline than the control group. Recovery of pressures in the control group but not the intervention group was inversely related to the stress level of blood pressure (r = .86, P < .0002), indicating a relationship between blood pressure rise and the degree of distortion of subsequent baseline values. On the basis of our results, we propose that in prolonged protocols, the measurement finger be exercised to facilitate accurate measurements of finger pressure with the Finapres.

Adult↗
PubMed1996

Noninvasive assessment of baroreflex control in borderline hypertension. Comparison with the phenylephrine method.

In this study, we examined the sensitivity of two recently developed noninvasive baroreflex measurement techniques to assess baroreflex control in hypertension. We assessed baroreflex sensitivity noninvasively from covariations of systolic pressure and RR interval using spectral analysis and sequence detection. The noninvasive estimates of baroreflex control were compared with estimates derived from phenylephrine-induced increases in systolic pressure and RR interval in normotensive subjects (n = 27) and borderline hypertensive subjects (n = 15). Baroreflex sensitivity was significantly reduced in the borderline hypertensive group relative to the normotensive group when assessed with the use of either the noninvasive or invasive methods to index baroreflex control. In addition, estimates obtained from the noninvasive methods were significantly correlated with baroreflex sensitivity assessed with the phenylephrine method (spectral: r = .48, P < .001; sequence: r = .50, P < .001). These findings suggest that spectral analysis and the sequence method provide viable alternatives to the pharmacological approach for estimation of baroreflex sensitivity in hypertension.

Adult↗
PubMed1996

Post-traumatic apallic syndrome following head injury. Part 2: Treatment.

There is no doubt that vegetative patients need the appropriate medical and nursing procedures as well as family involvement, education and counselling. Additional structured stimulation programmes are used for the treatment of coma and vegetative state. The theoretical foundation is derived from animal studies. The relevance of the results for the rehabilitation of head-injured human patients remains questionable, because all animal studies involve the use of cerebral lesions different from those found in human head-injured patients. The studies of human sensory stimulation give more an orientation than a definitive statement. Very recently, hypotheses concerning sensory regulation have begun to be evaluated. Further investigations are required to provide a more definite conclusion.

Animals↗
PubMed1996

Post-traumatic apallic syndrome following head injury. Part 1: clinical characteristics.

Epidemiological studies made within the western countries indicate an incidence of 200-300 traumatic head injuries per 100 000 residents each year. Severe head injuries account for 5-25% of all head injuries; 10-14% of all severe head-injured patients develop into a vegetative state, in which a sleep-wake rhythm is apparent, but however in which there is no evidence of awakeness or reactivity to the environment. The most commonly used labels, in the German and international literature, for these patients are 'vegetative state', 'apallic syndrome' and 'coma vigile'. This clinical characterization is not sufficient. It is necessary to employ additional criteria to distinguish subsets of vegetative patients e.g. computerized tomography, magnetic resonance imaging, single photon emission tomography, electroencephalography, brainstem reflexes, evoked potentials, assessment scales, age, premorbid brain disorders. Diagnostic and prognostic parameters must form the basis for various decisions relating to patients' care and intervention.

Brain Injuries↗
PubMed1995

Fluorescence-based oligonucleotide ligation assay for analysis of cystic fibrosis transmembrane conductance regulator gene mutations.

Isolation of the gene for cystic fibrosis (CF), the cystic fibrosis transmembrane conductance regulator (CFTR), provided a basis for analyzing its molecular pathology and resulted in the identification of > 400 mutations associated with disease. Except for the delta F508 mutation, no other single mutation accounts for > 5% of CF chromosomes in most populations, and most mutation frequencies are < 1%. A strategy based on multiplex PCR followed by multiplex allele-specific oligonucleotide probe ligation was used to detect 30 mutations, distributed throughout ten exons and seven introns of the CFTR gene, that together account for > 96% of CF mutant chromosomes worldwide. Mutations were detected by competitive oligonucleotide probe ligation to detect normal and/or mutant genotypes in one reaction. Three probes (one common and two allelic probes) were needed for analysis of each mutation. Probes hybridized to target DNA were joined by a thermostable ligase if there were no mismatches at their junctions; temperature cycling resulted in a linear increase in product. Common probes were labeled with fluorochromes, and allelic probes each had different lengths. Ligation products were analyzed electrophoretically on a fluorescent DNA sequencer. The results show that combined PCR and probe ligation amplification rapidly and reliably screen for CF homozygotes and carriers.

Alleles↗
PubMed1993

Respiratory sinus arrhythmia, cardiac vagal tone, and respiration: within- and between-individual relations.

Respiratory sinus arrhythmia (RSA) is frequently employed as an intra- and interindividual index of cardiac parasympathetic tone, although the relationship of RSA to interindividual differences in cardiac vagal tone remains questionable. Our study examined between- and within-subject relations among RSA, cardiac vagal tone, and respiratory parameters. Twenty-nine young adults performed two sessions of tasks under no medication and single and double autonomic blockade (intravenously administered propranolol and atropine). Parasympathetic tone was determined from heart period responses to complete vagal blockade. Results indicated the following. Resting RSA does not accurately predict individual differences in cardiac vagal tone. However, RSA and heart period together do predict such individual differences reasonably well. The relationship between individual variations in RSA and vagal tone is not improved by controlling respiratory parameters. Substantial cardiac vagal activity occurs during inspiration, and intraindividual variations in respiratory measures confound the association between RSA and cardiac vagal tone.

Adolescent↗
PubMed1992

Respiratory and cardiac rhythms as windows to central and autonomic biobehavioral regulation: selection of window frames, keeping the panes clean and viewing the neural topography.

Respiratory and cardiovascular processes figure importantly in biobehavioral regulation. Various cardiac and respiratory measures may, furthermore, index the activity of relatively distinct central and autonomic mechanisms. In this regard, I consider ventilatory indices of central drive and timing of respiration, and rhythmic cardiac-interval fluctuations as reflections of parasympathetic and sympathetic cardiac influences. Particular emphasis is placed upon the phenomenon of respiratory sinus arrhythmia (RSA). A number of conceptual and methodological questions are addressed concerning quantification and inference. Among others, these include the following issues: (1) What is the evidence that the three cardiac periodicities slower than heart rate reflect distinct autonomic mechanisms? (2) Does RSA reflect tonic or phasic parasympathetic regulation of heart rate? (3) Do specific quantification procedures for measuring these rhythms provide superior estimates? (4) What are some potential pitfalls for quantification and inference.

Arousal↗