scholarly journals Effect of Increased Oxygen Tension on Flicker-Induced Vasodilatation in the Human Retina

2014 ◽  
Vol 34 (12) ◽  
pp. 1914-1918 ◽  
Author(s):  
Stefan Palkovits ◽  
Reinhard Told ◽  
Agnes Boltz ◽  
Doreen Schmidl ◽  
Alina Popa Cherecheanu ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Tension ◽  
Neural Activity ◽  
Retinal Vessel ◽  
Human Retina ◽  
Flicker Response ◽  
Tightly Coupled ◽  
Hyperemic Response ◽  
Retinal Vessel Diameters ◽  
Stimulation Of

In the retina, blood flow and neural activity are tightly coupled. Stimulation of the retina with flickering light is accompanied by an increase in blood flow. The current study seeks to investigate whether an increase in oxygen tension modulates flicker (FL)-induced vasodilatation in the human retina. A total of 52 healthy volunteers were included. Via a breathing mask, 100% oxygen (O2) was administered in one, a mixture of 8% carbon dioxide and 92% oxygen (C/O) in a second cohort. Retinal vessel diameters were measured with a Vessel Analyzer and FL responses were assessed before and during the breathing periods. At baseline, FL stimulation increased retinal vessel diameters by +3.7 ± 2.3% in arteries and by +5.1 ± 3.7% in veins. Breathing of C/O led to a decrease in arterial (−9.0 ±,6.9%) and venous (−11.3 ± 5.9%) vessel calibers. Flicker response was increased to 5.7 ± 2.5% in arteries and to 8.6 ± 4.1% in veins. Breathing of pure O2 induced a vasoconstriction of vessel diameters by −14.0 ± 5.3% in arteries and −18.4 ± 7.0% in veins and increased FL responses in arteries (+6.2 ± 2.8%) and veins (+7.2 ± 3.1%). Systemic hyperoxia increases FL-induced retinal vasodilatation in the retina. The mechanism by which oxygen modulates the hyperemic response to FL stimulation remains to be elucidated.

scholarly journals Imaging Single–Cell Blood Flow in the Smallest to Largest Vessels in the Living Retina

2019 ◽  
Author(s):  
Aby Joseph ◽  
Andrés Guevara–Torres ◽  
Jesse B. Schallek
Keyword(s):  
Blood Flow ◽  
Single Cell ◽  
Adaptive Optics ◽  
Blood Cells ◽  
Retinal Vessel ◽  
Full Spectrum ◽  
Early Evaluation ◽  
The Central Nervous System ◽  
Data Collection Approach ◽  
Retinal Vessel Diameters

Impact StatementUsing a specialized camera that corrects for eye blur, millions of single blood cells are imaged and their speed measured, as they travel through the largest-to-smallest vessels of the retina.AbstractTissue light scatter limits the visualization of the microvascular network deep inside the living mammal. The transparency of the mammalian eye provides a noninvasive view of the microvessels of the retina, a part of the central nervous system. Despite its clarity, imperfections in the optics of the eye blur microscopic retinal capillaries, and single blood cells flowing within. This limits early evaluation of microvascular diseases that originate in capillaries. To break this barrier, we use adaptive optics to noninvasively measure single–cell blood flow, in one of the most widely used research animals: the C57BL/6J mouse. Flow ranged four orders of magnitude (0.0002–1.55 µL min−1) across the full spectrum of retinal vessel diameters (3.2–45.8 µm), without requiring surgery or contrast dye. Here we describe the data collection approach using adaptive optics and provide an analysis pipeline that can measure millions of blood cell speeds automatically.

Arteriolar Oxygen Saturation, Cerebral Blood Flow, and Retinal Vessel Diameters

Ophthalmology ◽  
2008 ◽  
Vol 115 (5) ◽  
pp. 887-892 ◽  
Author(s):  
Frank Jan de Jong ◽  
Meike W. Vernooij ◽  
M. Kamran Ikram ◽  
M. Arfan Ikram ◽  
Albert Hofman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Oxygen Saturation ◽  
Retinal Vessel ◽  
Retinal Vessel Diameters

Role of endothelium-pericyte signaling in capillary blood flow response to neuronal activity

2021 ◽  
pp. 0271678X2110079
Author(s):  
Wenri Zhang ◽  
Catherine M Davis ◽  
Douglas M Zeppenfeld ◽  
Kirsti Golgotiu ◽  
Marie X Wang ◽  
...  
Keyword(s):  
Blood Flow ◽  
Neuronal Activity ◽  
Functional Hyperemia ◽  
Neuronal Activation ◽  
Two Photon Microscopy ◽  
Tightly Coupled ◽  
Whisker Stimulation ◽  
Optical Microangiography ◽  
Hyperemic Response

Local blood flow in the brain is tightly coupled to metabolic demands, a phenomenon termed functional hyperemia. Both capillaries and arterioles contribute to the hyperemic response to neuronal activity via different mechanisms and timescales. The nature and specific signaling involved in the hyperemic response of capillaries versus arterioles, and their temporal relationship are not fully defined. We determined the time-dependent changes in capillary flux and diameter versus arteriolar velocity and flow following whisker stimulation using optical microangiography (OMAG) and two-photon microscopy. We further characterized depth-resolved responses of individual capillaries versus capillary networks. We hypothesized that capillaries respond first to neuronal activation, and that they exhibit a coordinated response mediated via endothelial-derived epoxyeicosatrienoates (EETs) acting on pericytes. To visualize peri-capillary pericytes, we used Tie2-GFP/NG2-DsRed mice, and to determine the role of endothelial-derived EETs, we compared cerebrovascular responses to whisker stimulation between wild-type mice and mice with lower endothelial EETs (Tie2-hsEH). We found that capillaries respond immediately to neuronal activation in an orchestrated network-level manner, a response attenuated in Tie2-hsEH and inhibited by blocking EETs action on pericytes. These results demonstrate that capillaries are first responders during functional hyperemia, and that they exhibit a network-level response mediated via endothelial-derived EETs’ action on peri-capillary pericytes.

scholarly journals ETa-receptor blockade, but not ACE inhibition, blunts retinal vessel response during isometric exercise

2006 ◽  
Vol 290 (4) ◽  
pp. H1693-H1698 ◽  
Author(s):  
Alexandra Luksch ◽  
Barbara Wimpissinger ◽  
Kaija Polak ◽  
Kerstin Jandrasits ◽  
Leopold Schmetterer
Keyword(s):  
Blood Flow ◽  
Intraocular Pressure ◽  
Angiotensin Ii ◽  
Isometric Exercise ◽  
Retinal Vessel ◽  
Flow Regulation ◽  
Retinal Blood Flow ◽  
Receptor Blockade ◽  
Converting Enzyme ◽  
Retinal Vessel Diameters

Angiotensin II and endothelin-1 are potent vasoconstrictors that appear to play a role in retinal blood flow regulation. In the present study, we investigated the possible role of the angiotensin and the endothelin system in the regulation of retinal vessel diameters during isometric exercise in healthy humans. The study design was randomized, double-masked, placebo-controlled, and three-way cross over. Twelve healthy subjects performed squatting exercises for 6 min during infusion of either an angiotensin-converting enzyme inhibitor (enalapril), an ETA-receptor antagonist (BQ-123), or placebo. Retinal vessel diameters were measured continuously with the Zeiss retinal vessel analyzer. Systemic hemodynamics were assessed noninvasively, and intraocular pressure was measured with applanation tonometry. Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a vasoconstriction in retinal arteries and veins. Intraocular pressure was only slightly increased during the squatting periods. BQ-123 significantly blunted the exercise-induced decrease in venous ( P < 0.01) and arterial ( P < 0.02, ANOVA) vessel diameters but had no effect on basal retinal diameters. By contrast, enalapril did neither influence vessel diameter at baseline conditions nor in response to isometric exercise. The data of the present study indicate that retinal vasoconstriction during isometric exercise is modified by ETA-receptor blockade, whereas it is not altered by angiotensin-converting enzyme inhibition. Hence, the present data indicate that endothelin-1, but not angiotensin II, is involved in retinal blood flow regulation during isometric exercise.

Using reactive hyperemia to investigate the effect of cupping sizes of cupping therapy on skin blood flow responses

2021 ◽  
pp. 1-7
Author(s):  
Xiangfeng He ◽  
Xueyan Zhang ◽  
Fuyuan Liao ◽  
Li He ◽  
Xin Xu ◽  
...  
Keyword(s):  
Blood Flow ◽  
Laser Doppler Flowmetry ◽  
Skin Blood Flow ◽  
Repeated Measures ◽  
Recovery Time ◽  
Reactive Hyperemia ◽  
Cupping Therapy ◽  
Doppler Flowmetry ◽  
Healthy Participants ◽  
Hyperemic Response

BACKGROUND: Various cupping sizes of cupping therapy have been used in managing musculoskeletal conditions; however, the effect of cupping sizes on skin blood flow (SBF) responses is largely unknown. OBJECTIVE: The objective of this study was to compare the effect of three cupping sizes of cupping therapy on SBF responses. METHODS: Laser Doppler flowmetry (LDF) was used to measure SBF on the triceps in 12 healthy participants in this repeated measures study. Three cup sizes (35, 40 and 45 mm in diameter) were blinded to the participants and were tested at -300 mmHg for 5 minutes. Reactive hyperemic response to cupping therapy was expressed as a ratio of baseline SBF. RESULTS: All three sizes of cupping cups resulted in a significant increase in peak SBF (p< 0.001). Peak SBF of the 45 mm cup (9.41 ± 1.32 times) was significantly higher than the 35 mm cup (5.62 ± 1.42 times, p< 0.05). Total SBF of the 45 mm cup ((24.33 ± 8.72) × 103 times) was significantly higher than the 35 mm cup ((8.05 ± 1.63) × 103 times, p< 0.05). Recovery time of the 45 mm cup (287.46 ± 39.54 seconds) was significantly longer than the 35 mm cup (180.12 ± 1.42 seconds, p< 0.05). CONCLUSIONS: Our results show that all three cup sizes can significantly increase SBF. The 45 mm cup is more effective in increasing SBF compared to the 35 mm cup.

Exercise-induced alterations of retinal vessel diameters and cardiovascular risk reduction in obesity

2011 ◽  
Vol 216 (2) ◽  
pp. 433-439 ◽  
Author(s):  
H. Hanssen ◽  
T. Nickel ◽  
V. Drexel ◽  
G. Hertel ◽  
I. Emslander ◽  
...  
Keyword(s):  
Cardiovascular Risk ◽  
Risk Reduction ◽  
Retinal Vessel ◽  
Cardiovascular Risk Reduction ◽  
Exercise Induced ◽  
Retinal Vessel Diameters

DA1 dopamine receptors in renal cortical collecting duct

1991 ◽  
Vol 261 (5) ◽  
pp. F890-F895 ◽  
Author(s):  
K. Ohbu ◽  
R. A. Felder
Keyword(s):  
Adenylate Cyclase ◽  
Specific Binding ◽  
Collecting Duct ◽  
Sch 23390 ◽  
Receptor Density ◽  
Cortical Collecting Duct ◽  
Tightly Coupled ◽  
Renal Dopamine ◽  
Dissociation Constant Kd ◽  
Stimulation Of

Renal dopamine DA1 receptors are linked to the regulation of sodium transport. We have previously reported the presence of DA1 receptors in the proximal convoluted tubule (PCT) but not in the distal convoluted tubule. However, the DA1 receptor in the collecting duct, the final determinant of electrolyte transport, has not been studied. DA1 receptors were studied in the microdissected cortical collecting duct (CCD) of rats by autoradiography with use of the selective DA1 radioligand 125I-Sch 23982 and by measurement of adenylate cyclase (AC) activity. Specific binding of 125I-Sch 23982 to CCD was saturable with radioligand concentration. The dissociation constant (Kd) was 0.46 +/- 0.08 nM (n = 5), and the maximum receptor density (Bmax) was 1.41 +/- 0.43 fmol/mg protein (n = 5). The DA1 antagonist Sch 23390 was more effective than the DA1 agonist fenoldopam in competing for specific 125I-Sch 23982 binding. Fenoldopam stimulated AC activity in CCD in a concentration-dependent (10(-9)-10(-6) M) manner. The ability of fenoldopam to stimulate AC activity was similar in CCD and PCT even though DA1 receptor density was 1,000 times greater in the CCD than in the PCT. In additional studies, fenoldopam stimulation of AC activity did not influence vasopressin-stimulated AC activity. We conclude that the DA1 receptor in rat CCD is tightly coupled to AC stimulation and that there is no interaction between DA1 agonist-stimulated and vasopressin-stimulated AC activity in the CCD.

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