Charles Knapp

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Healthy young people may become syncopal during standing, head up tilt (HUT) or lower body negative pressure (LBNP). To evaluate why this happens we measured hormonal indices of autonomic activity along with arterial pressure (AP), heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR) and measures of plasma volume.(More)
We studied 15 men (8 treatment, 7 control) before and after 21 days of 6º head-down tilt to determine whether daily, 1-h exposures to 1.0 Gz (at the heart) artificial gravity (AG) would prevent bed rest-induced cardiovascular deconditioning. Testing included echocardiographic analysis of cardiac function, plasma volume (PV), aerobic power (VO2pk) and(More)
Variations in respiratory pattern influence the heart rate spectrum. It has been suggested, hence, that metronomic respiration should be used to correctly assess vagal modulation of heart rate by using spectral analysis. On the other hand, breathing to a metronome has been reported to increase heart rate spectral power in the high- or respiratory frequency(More)
The autonomic nervous system drives variability in heart rate, vascular tone, cardiac ejection, and arterial pressure, but gender differences in autonomic regulation of the latter three parameters are not well documented. In addition to mean values, we used spectral analysis to calculate variability in arterial pressure, heart rate (R-R interval, RRI),(More)
Mycosis fungoides (MF) is a primary cutaneous lymphoma characterized by atypical T-lymphocytes that usually presents as patches and plaques on photoprotected areas of the body, such as the groin and buttocks. Classically, the atypical lymphocytes in MF are CD3/CD4 positive with loss of CD7 and less often loss of CD5. In a minority of cases, the atypical(More)
This study describes alterations in skin perfusion in response to step increases in surface pressure, before and after long-term (5 hr) exposure to pressure-induced ischemia. A provocative test was developed in which surface pressure was increased in increments of 3.7 mmHg until perfusion reached an apparent minimum by a computer-controlled plunger that(More)
Key Points Summary We report how blood pressure, cardiac output and vascular resistance are related to height, weight, body surface area (BSA), and body mass index (BMI) in healthy young adults at supine rest and standing.Much inter-subject variability in young adult's blood pressure, currently attributed to health status, may actually result from(More)
BACKGROUND Intermittent artificial gravity (AG) training over days and weeks has been shown to improve the human orthostatic tolerance limit (OTL) and improve cardiovascular regulation in response to orthostatic stress. Effects of a single AG exposure are currently unknown. METHODS We tested cardiovascular responses to orthostatic stress in 16 hypovolemic(More)
Atypical complete DiGeorge syndrome (DGS) is an extremely rare congenital disease characterized by an eczematous dermatitis, lymphadenopathy, and an oligoclonal T-cell proliferation. Because its initial presentation may be confused with other types of eczematous dermatitis, diagnosis and treatment are usually delayed. We describe herein a case of an infant(More)
T lymphocytes belong to 2 distinct sublineages that express either αβ or γδ T-cell receptor (TCR) complex. Although malignancy is a great instigator of lineage infidelity, as exemplified by aberrant expression of numerous lineage markers in lymphoma cells, malignant T cells rarely coexpress αβ and γδ TCR complexes. Similarly, only rare cases of CD4/CD8(More)