Prominent publications by Julian M Stewart

KOL Index score: 16516

Recent investigations suggest a role for neurally mediated hypotension (NMH) in the symptomatology of chronic fatigue syndrome (CFS) in adults. Our previous observations in children with NMH and syncope (S) unrelated to CFS indicate that the modulation of sympathetic and parasympathetic tone measured by indices of heart rate variability (HRV) is abnormal in children who faint during head-up tilt (HUT). In order to determine mine the effects of autonomic tone on HUT in children with CFS ...

Also Ranks for: Heart Rate |  hut cfs |  chronic fatigue |  autonomic dysfunction |  neurally mediated hypotension
KOL Index score: 15591

POTS (postural tachycardia syndrome) is associated with low blood volume and reduced renin and aldosterone; however, the role of Ang (angiotensin) II has not been investigated. Previous studies have suggested that a subset of POTS patients with increased vasoconstriction related to decreased bioavailable NO (nitric oxide) have decreased blood volume. Ang II reduces bioavailable NO and is integral to the renin-Ang system. Thus, in the present study, we investigated the relationship ...

Also Ranks for: Blood Volume |  postural tachycardia syndrome |  plasma angiotensin |  flow pots |  upright tilt
KOL Index score: 14146

Low-flow postural tachycardia syndrome (POTS) is associated with increased plasma angiotensin II (ANG II) and reduced neuronal nitric oxide (NO), which decreases NO-dependent vasodilation. We tested whether the ANG II type 1 receptor (AT(1)R) antagonist losartan would improve NO-dependent vasodilation in POTS patients. Furthermore, if the action of ANG II is dependent on NO, then the NO synthase inhibitor nitro-L-arginine (NLA) would reverse this improvement. We used local heating of the ...

Also Ranks for: Nitric Oxide |  tachycardia syndrome |  nla losartan |  type 1 |  receptor blockade
KOL Index score: 14057

The objective was to determine the nature of autonomic and vasomotor changes in adolescent patients with orthostatic tachycardia associated with the chronic fatigue syndrome (CFS) and the postural orthostatic tachycardia syndrome (POTS). Continuous electrocardiography and arterial tonometry was used to investigate the heart rate and blood pressure responses before and 3–5 min after head-up tilt in 22 adolescents with POTS and 14 adolescents with CFS, compared with control subjects ...

Also Ranks for: Tachycardia Syndrome |  autonomic nervous |  chronic fatigue |  heart rate |  cfs patients
KOL Index score: 13842

The contribution of endothelium-derived relaxing factor (EDRF) to the regulation of regional vascular resistance and tissue blood flow at rest and during acute moderate exercise was studied in chronically instrumented conscious dogs. Radioactive microspheres were injected before and during exercise to measure regional blood flow. An infusion of nitro-L-arginine (L-NA), an analogue of L-arginine, was used to inhibit the synthesis of EDRF and resulted in a significant increase in mean ...

Also Ranks for: Blood Flow |  vascular resistance |  conscious dogs |  rest exercise |  skeletal muscles
KOL Index score: 13583

Local cutaneous heating produces vasodilation that is largely nitric oxide (NO) dependent. We showed that angiotensin II (ANG II) attenuates this by an ANG II receptor, type 1 (AT1R)-dependent mechanism that is reversible with the antioxidant ascorbate, indicating oxidative stress. Reactive oxygen species (ROS) produced by ANG II employ NADPH and xanthine oxidase pathways. To determine whether these mechanisms pertain to skin, we measured cutaneous local heating with 10 μM ANG II, using ...

Also Ranks for: Xanthine Oxidase |  reactive oxygen species |  local heating |  apocynin tempol |  cutaneous blood
KOL Index score: 12963

Variants of postural tachycardia syndrome (POTS) are associated with increased ["high-flow" POTS (HFP)], decreased ["low-flow" POTS (LFP)], and normal ["normal-flow" POTS (NFP)] blood flow measured in the lower extremities while subjects were in the supine position. We propose that postural tachycardia is related to thoracic hypovolemia during orthostasis but that the patterns of peripheral blood flow relate to different mechanisms for thoracic hypovolemia. We studied 37 POTS patients ...

Also Ranks for: Blood Volume |  postural tachycardia |  supine position |  lfp control subjects |  upright tilt
KOL Index score: 12768

Postural tachycardia syndrome (POTS), a chronic form of orthostatic intolerance, has signs and symptoms of lightheadedness, loss of vision, headache, fatigue, and neurocognitive deficits consistent with reductions in cerebrovascular perfusion. We hypothesized that young, normocapnic POTS patients exhibit abnormal cerebral autoregulation (CA) that results in decreased static and dynamic cerebral blood flow (CBF) autoregulation. All subjects had continuous recordings of mean arterial ...

Also Ranks for: Pots Patients |  cerebral autoregulation |  tachycardia syndrome |  cbfv tilt |  supine position
KOL Index score: 12352

Chronic fatigue syndrome (CFS) is a complex illness, which is often misdiagnosed as a psychiatric illness. In two previous reports, using (1)H MRSI, we found significantly higher levels of ventricular cerebrospinal fluid (CSF) lactate in patients with CFS relative to those with generalized anxiety disorder and healthy volunteers (HV), but not relative to those with major depressive disorder (MDD). In this third independent cross-sectional neuroimaging study, we investigated a ...

Also Ranks for: Oxidative Stress |  cortical glutathione |  ventricular lactate |  chronic fatigue syndrome |  patients cfs
KOL Index score: 11821

Previous investigations have allowed for stratification of patients with postural tachycardia syndrome (POTS) on the basis of peripheral blood flow. One such subset, comprising "normal-flow POTS" patients, is characterized by normal peripheral resistance and blood volume in the supine position but thoracic hypovolemia and splanchnic blood pooling in the upright position. We studied 32 consecutive 14- to 22-yr-old POTS patients comprising 13 with low-flow POTS, 14 with normal-flow POTS, ...

Also Ranks for: Upright Tilt |  blood flow |  splanchnic hyperemia |  supine position |  postural tachycardia
KOL Index score: 11562

OBJECTIVES: To describe the orthostatic tachycardia syndrome (OTS) in adolescents, similarities to and differences from chronic fatigue syndrome (CFS), and patterns of orthostatic intolerance during head-up tilt (HUT).

STUDY DESIGN: Using electrocardiography and arterial tonometry, we investigated the heart rate and blood pressure responses during HUT in 20 adolescents with OTS compared with 25 adolescents with CFS, 13 healthy control subjects, and 20 patients with simple faint.


Also Ranks for: Orthostatic Intolerance |  chronic fatigue |  tachycardia syndrome |  patients cfs |  blood pressure
KOL Index score: 10859

Low flow postural tachycardia syndrome (POTS), is associated with reduced nitric oxide (NO) activity assumed to be of endothelial origin. We tested the hypothesis that cutaneous microvascular neuronal NO (nNO) is impaired, rather than endothelial NO (eNO), in POTS. We performed three sets of experiments on subjects aged 22.5 +/- 2 yr. We used laser-Doppler flowmetry response to sequentially increase acetylcholine (ACh) doses and the local cutaneous heating response of the calf as ...

Also Ranks for: Nitric Oxide |  tachycardia syndrome |  10 mm |  drug endothelium |  local heating
KOL Index score: 10786

We hypothesize that upright cognitive impairment in patients with postural tachycardia syndrome (POTS) is caused by reduced cerebral blood flow (CBF). The CBF velocity (CBF(v)) measured by transcranial Doppler ultrasound decreased excessively during 70° tilt in a minority of patients with intermittent hyperpnea/hypocapnia. Incremental tilt showed no difference in mean CBF(v). But N-back memory tasking indicated progressive compromised memory, reduced functional hyperemia, and reduced ...

Also Ranks for: Functional Hyperemia |  postural tachycardia syndrome |  patients pots |  blood flow |  neurovascular coupling
KOL Index score: 10471

CFS (chronic fatigue syndrome) is commonly co-morbid with POTS (postural tachycardia syndrome). Individuals with CFS/POTS experience unrelenting fatigue, tachycardia during orthostatic stress and ill-defined neurocognitive impairment, often described as 'mental fog'. We hypothesized that orthostatic stress causes neurocognitive impairment in CFS/POTS related to decreased CBFV (cerebral blood flow velocity). A total of 16 CFS/POTS and 20 control subjects underwent graded tilt table ...

Also Ranks for: Orthostatic Stress |  postural tachycardia syndrome |  cfs pots |  cbfv groups |  cognitive challenge
KOL Index score: 10346

The vasodilation response to local cutaneous heating is nitric oxide (NO) dependent and blunted in postural tachycardia but reversed by angiotensin II (ANG II) type 1 receptor (AT(1)R) blockade. We tested the hypothesis that a localized infusion of ANG II attenuates vasodilation to local heating in healthy volunteers. We heated the skin of a calf to 42 degrees C and measured local blood flow to assess the percentage of maximum cutaneous vascular conductance (%CVC(max)) in eight healthy ...

Also Ranks for: Local Heating |  nitric oxide |  heat response |  10 mm |  angiotensin type

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Julian M Stewart:Expert Impact

Concepts for whichJulian M Stewarthas direct influence:Postural tachycardia syndrome,  Orthostatic intolerance,  Blood flow,  Blood volume,  Vasovagal syncope,  Blood pressure,  Fontan procedure,  Tachycardia syndrome.

Julian M Stewart:KOL impact

Concepts related to the work of other authors for whichfor which Julian M Stewart has influence:Blood pressure,  Orthostatic intolerance,  Vasovagal syncope,  Heart rate,  Postural tachycardia syndrome,  Chronic fatigue,  Nitric oxide.



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From the Department of Pediatrics (J.M.S., I.A.W., C.T., M.S.M.), New York Medical College, Valhalla | Departments of Physiology (J.M.S., M.S.M.), New York Medical College, Valhalla | Department of Pediatrics, New York Medical College, Valhalla, NY,