Leena N. Shoemaker
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View article: Two paths to one destination: altered low-frequency oscillations of cerebral perfusion and oxygenation but not oxygen metabolism in mild cognitive impairment
Two paths to one destination: altered low-frequency oscillations of cerebral perfusion and oxygenation but not oxygen metabolism in mild cognitive impairment Open
We used a novel, depth-enhanced optical monitoring system to investigate low-frequency hemodynamic oscillations (0.02–0.16 Hz) in cerebral microvascular perfusion, oxygenation, and relative metabolic rate of oxygen in patients with MCI and…
View article: Blood pressure in human large cerebral arteries: a feasibility study
Blood pressure in human large cerebral arteries: a feasibility study Open
We explored the feasibility of making direct measures of blood pressure in the large arteries at the base of the brain in humans. Measures were made with an optical sensor positioned in the aorta, common carotid, internal carotid artery ex…
View article: Cerebrovascular compliance during progressive hypotension in patients with autonomic failure
Cerebrovascular compliance during progressive hypotension in patients with autonomic failure Open
We identify a threshold effect for the increase in cerebrovascular compliance (Ci) during progressive hypotension (baseline vs. end-tilt: 86 ± 18 vs. 50 ± 8 mmHg) in individuals with autonomic failure, such that Ci began to increase progre…
View article: Short-term estradiol administration does not restore endothelin‐B receptor‐mediated vasodilation in postmenopausal women
Short-term estradiol administration does not restore endothelin‐B receptor‐mediated vasodilation in postmenopausal women Open
The vascular endothelial endothelin-B receptor (ET B R) mediates vasodilation in premenopausal women, an effect modulated by estradiol. ET B R-mediated vasodilation is lost in postmenopausal women, but the effect of exogenous estradiol adm…
View article: Effect of insulin on indices of cerebral blood flow and cerebrovascular compliance in young adults
Effect of insulin on indices of cerebral blood flow and cerebrovascular compliance in young adults Open
Insulin has important vasodilatory effects in the peripheral circulation, but less is known about the role of insulin in cerebrovascular control. Contrary to our hypothesis, there was no effect of systemic (intravenous) nor local (intranas…
View article: All-optics technique for monitoring absolute cerebral blood flow: validation against magnetic resonance imaging perfusion
All-optics technique for monitoring absolute cerebral blood flow: validation against magnetic resonance imaging perfusion Open
Results demonstrated the feasibility of an all-optics approach that can both quantify CBF and perform continuous perfusion monitoring.
View article: Assessing changes in regional cerebral hemodynamics in adults with a high-density full-head coverage time-resolved near-infrared spectroscopy device
Assessing changes in regional cerebral hemodynamics in adults with a high-density full-head coverage time-resolved near-infrared spectroscopy device Open
The Kernel Flow has promise as an intraoperative neuromonitoring device. Although regional sensitivity was affected by hair color and density, enhanced depth sensitivity of trNIRS was able to resolve differences in scalp and brain oxygenat…
View article: Characterization of cerebral macro- and microvascular hemodynamics during transient hypotension
Characterization of cerebral macro- and microvascular hemodynamics during transient hypotension Open
To characterize the relationship between cerebrovascular patterns within the large middle cerebral artery (MCA) and a downstream microvascular segment, we used a novel combination of transcranial Doppler ultrasound of the MCA and optical m…
View article: Using depth-enhanced diffuse correlation spectroscopy and near-infrared spectroscopy to isolate cerebral hemodynamics during transient hypotension
Using depth-enhanced diffuse correlation spectroscopy and near-infrared spectroscopy to isolate cerebral hemodynamics during transient hypotension Open
Transient hypotension caused significantly larger blood flow and oxygenation changes in the extracerebral tissue compared to the brain. We demonstrate the importance of accounting for extracerebral signal contamination within optical measu…
View article: Assessing the Sensitivity of Multi-Distance Hyperspectral NIRS to Changes in the Oxidation State of Cytochrome C Oxidase in the Brain
Assessing the Sensitivity of Multi-Distance Hyperspectral NIRS to Changes in the Oxidation State of Cytochrome C Oxidase in the Brain Open
Near-infrared spectroscopy (NIRS) measurements of tissue oxygen saturation (StO2) are frequently used during vascular and cardiac surgeries as a non-invasive means of assessing brain health; however, signal contamination from extracerebral…
View article: Assessing the relationship between the cerebral metabolic rate of oxygen and the oxidation state of cytochrome-c-oxidase
Assessing the relationship between the cerebral metabolic rate of oxygen and the oxidation state of cytochrome-c-oxidase Open
Significance: Hyperspectral near-infrared spectroscopy (hsNIRS) combined with diffuse correlation spectroscopy (DCS) provides a noninvasive approach for monitoring cerebral blood flow (CBF), the cerebral metabolic rate of oxygen ( …
View article: ET<sub>B</sub> receptor-mediated vasodilation is regulated by estradiol in young women
ET<sub>B</sub> receptor-mediated vasodilation is regulated by estradiol in young women Open
The endothelin-B (ETB) receptor mediates vasodilation in young women, an effect lost following menopause. It is unclear whether these alterations are due to aging or changes in estradiol (E2). During endogenous hormone suppression (GnRH an…
View article: Indomethacin markedly blunts cerebral perfusion and reactivity, with little cognitive consequence in healthy young and older adults
Indomethacin markedly blunts cerebral perfusion and reactivity, with little cognitive consequence in healthy young and older adults Open
Key points Cognitive function depends on adequate cerebrovascular perfusion and control. However, it is unknown whether acutely‐reduced cerebral blood flow (CBF) impairs cognition in healthy adults. In the present study, we used a placebo‐…
View article: Altered endothelial ET<sub>B</sub> receptor expression in postmenopausal women
Altered endothelial ET<sub>B</sub> receptor expression in postmenopausal women Open
Our study provides novel data demonstrating attenuated endothelial ET B R expression in postmenopausal women. Furthermore, our data extend current knowledge by demonstrating a positive relation between ET B R expression and brachial artery…
View article: Fine‐tuning our understanding of the baroreflex: size‐dependent regulation of action potential subpopulations
Fine‐tuning our understanding of the baroreflex: size‐dependent regulation of action potential subpopulations Open
The sympathetic arm of the arterial baroreflex is a homeostatic mechanism which rapidly regulates blood pressure (BP) via changes in sympathetic outflow. The use of microneurography has catalysed our understanding of the baroreflex by prov…
View article: The cerebrovascular role in cognition during physiological stress
The cerebrovascular role in cognition during physiological stress Open
Cognition may depend in part on cerebral blood flow (CBF) and its regulation. All are affected in similar directions by stress acutely (e.g., mental and exercise-related) and chronically (e.g., fitness and age). For example, cognition, CBF…
View article: Swimming‐related effects on cerebrovascular and cognitive function
Swimming‐related effects on cerebrovascular and cognitive function Open
Both acute and regular exercise influence vascular and cognitive function. Upright aquatic exercise increases mean middle cerebral artery blood velocity (MCAvmean ) and has been suggested as favorable for cerebrovascular adaptat…
View article: Reactivity of larger intracranial arteries using 7 T MRI in young adults
Reactivity of larger intracranial arteries using 7 T MRI in young adults Open
The larger intracranial conduit vessels contribute to the total cerebral vascular resistance, and understanding their vasoreactivity to physiological stimuli is required when attempting to understand regional brain perfusion. Reactivity of…
View article: Ventilation inhibits sympathetic action potential recruitment even during severe chemoreflex stress
Ventilation inhibits sympathetic action potential recruitment even during severe chemoreflex stress Open
This study investigated the influence of ventilation on sympathetic action potential (AP) discharge patterns during varying levels of high chemoreflex stress. In seven trained breath-hold divers (age 33 ± 12 yr), we measured muscle sympath…