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Papers by Lewis Marks
Journal of Clinical Investigation, 1975
Previous studies have demonstrated an increase in blood flow to extremities involved by Paget&... more Previous studies have demonstrated an increase in blood flow to extremities involved by Paget's disease of bone. It has been assumed that the increase in blood flow is through bone, but warmth of skin overlying Pagetic bone suggests that cutaneous blood flow might be increased. In three patients with Paget's disease involving one extremity, we compared blood flow in "Pagetic" extremities with flow in the contralateral normal extremities. Resting blood flow (measured with water plethysmographs) was 14.2plus or minus2.9 (meanplus or minusSE) ml/min times 100 ml extremity in the Pagetic limbs. The contribution of cutaneous flow to the increase in extremity blood flow was evaluated with epinephrine iontophoresis, which suppresses flow to skin but not to underlying tissue. Epinephrine iontophoresis of the Pagetic extremities decreased blood flow from 14.2plus or minus2.9 to 3.6plus or minus1.5 ml/min. Local heating (which increases cutaneous flow only) failed to increase blood flow in the Pagetic extremities as much as it did in the normal extremities. This suggests that cutaneous vessels in the Pagetic extremities were already dilated. During heating, blood flow in the normal extremities was similar to resting flow in the Pagetic extremities; this indicates that increases in cutaneous flow could account for most of the increase in total blood flow in the Pagetic extremities. Adrenergic control of blood flow to the Pagetic extremities was compared with that of the normal extremities. Vasoconstrictor responses to reflex stimuli in the Pagetic extremities were reduced; when vasoconstriction occurred it was gradual and sustained after termination of the stimuli, which suggests an exaggerated humoral response but reduced neural response to the stimuli. Intravenous epinephrine produced vasoconstriction in the Pagetic extremities and vasodilatation in the normal extremities. In summary, responses to epinephrine iontophoresis and heating suggest that the increase in blood flow in Pagetic extremities is primarily the result of cutaneous vasodilatation.
Journal of The American College of Cardiology, 1990
To determine if circulating levels of atrial natriuretic factor comparable with those seen in pat... more To determine if circulating levels of atrial natriuretic factor comparable with those seen in pathophysiologic states alter autonomic control of the circulation, direct recordings of hemodynamic variables and efferent sympathetic nerve activity to muscle (microneurography) were obtained during two separate protocols in a total of 21 normal men (age 25 ± 1 years). In protocol 1, the responses of 10 men were compared during incremental mechanical unloading of cardiopulmonary baroreceptors with lower body negative pressure versus responses to comparable unloading during infusion of alpha-human atrial natriuretic factor. Lower body negative pressure decreased pulmonary artery diastolic and right atrial pressures, did not alter arterial pressure or heart rate and increased muscle sympathetic nerve activity from 205.2 ± 36.3 to 438.7 ± 100.2 units/min (p < 0.01). Intravenous infusion of atrial natriuretic factor (25 ng/kg per min) increased plasma levels of the hormone from 24 ± 4 to 322 ± 34 pg/ml (p < 0.01, n =6), produced similar decreases in pulmonary artery diastolic and right atrial pressures, did not alter arterial pressure, increased heart rate and increased sympathetic nerve activity from 233.1 ± 35.6 to 387.2 ± 64.9 units/min (p < 0.05). Thus, during similar hemodynamic perturbations produced by lower body negative pressure or infusion of atrial natriuretic factor at the dose used in this study, these subjects exhibited comparable sympathoexcitatory responses, with a 109 ± 23% increase in sympathetic activity during lower body negative pressure and a 76 ± 19% increase during atrial natriuretic factor infusion (p =NS).
Journal of Clinical Investigation, 1975
Previous studies have demonstrated an increase in blood flow to extremities involved by Paget&... more Previous studies have demonstrated an increase in blood flow to extremities involved by Paget&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease of bone. It has been assumed that the increase in blood flow is through bone, but warmth of skin overlying Pagetic bone suggests that cutaneous blood flow might be increased. In three patients with Paget&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease involving one extremity, we compared blood flow in &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Pagetic&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; extremities with flow in the contralateral normal extremities. Resting blood flow (measured with water plethysmographs) was 14.2plus or minus2.9 (meanplus or minusSE) ml/min times 100 ml extremity in the Pagetic limbs. The contribution of cutaneous flow to the increase in extremity blood flow was evaluated with epinephrine iontophoresis, which suppresses flow to skin but not to underlying tissue. Epinephrine iontophoresis of the Pagetic extremities decreased blood flow from 14.2plus or minus2.9 to 3.6plus or minus1.5 ml/min. Local heating (which increases cutaneous flow only) failed to increase blood flow in the Pagetic extremities as much as it did in the normal extremities. This suggests that cutaneous vessels in the Pagetic extremities were already dilated. During heating, blood flow in the normal extremities was similar to resting flow in the Pagetic extremities; this indicates that increases in cutaneous flow could account for most of the increase in total blood flow in the Pagetic extremities. Adrenergic control of blood flow to the Pagetic extremities was compared with that of the normal extremities. Vasoconstrictor responses to reflex stimuli in the Pagetic extremities were reduced; when vasoconstriction occurred it was gradual and sustained after termination of the stimuli, which suggests an exaggerated humoral response but reduced neural response to the stimuli. Intravenous epinephrine produced vasoconstriction in the Pagetic extremities and vasodilatation in the normal extremities. In summary, responses to epinephrine iontophoresis and heating suggest that the increase in blood flow in Pagetic extremities is primarily the result of cutaneous vasodilatation.
Journal of The American College of Cardiology, 1990
To determine if circulating levels of atrial natriuretic factor comparable with those seen in pat... more To determine if circulating levels of atrial natriuretic factor comparable with those seen in pathophysiologic states alter autonomic control of the circulation, direct recordings of hemodynamic variables and efferent sympathetic nerve activity to muscle (microneurography) were obtained during two separate protocols in a total of 21 normal men (age 25 ± 1 years). In protocol 1, the responses of 10 men were compared during incremental mechanical unloading of cardiopulmonary baroreceptors with lower body negative pressure versus responses to comparable unloading during infusion of alpha-human atrial natriuretic factor. Lower body negative pressure decreased pulmonary artery diastolic and right atrial pressures, did not alter arterial pressure or heart rate and increased muscle sympathetic nerve activity from 205.2 ± 36.3 to 438.7 ± 100.2 units/min (p < 0.01). Intravenous infusion of atrial natriuretic factor (25 ng/kg per min) increased plasma levels of the hormone from 24 ± 4 to 322 ± 34 pg/ml (p < 0.01, n =6), produced similar decreases in pulmonary artery diastolic and right atrial pressures, did not alter arterial pressure, increased heart rate and increased sympathetic nerve activity from 233.1 ± 35.6 to 387.2 ± 64.9 units/min (p < 0.05). Thus, during similar hemodynamic perturbations produced by lower body negative pressure or infusion of atrial natriuretic factor at the dose used in this study, these subjects exhibited comparable sympathoexcitatory responses, with a 109 ± 23% increase in sympathetic activity during lower body negative pressure and a 76 ± 19% increase during atrial natriuretic factor infusion (p =NS).