scholarly journals Functional hyperemia drives fluid exchange in the paravascular space

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Ravi Teja Kedarasetti ◽  
Kevin L. Turner ◽  
Christina Echagarruga ◽  
Bruce J. Gluckman ◽  
Patrick J. Drew ◽  
...  
2020 ◽  
Author(s):  
Ravi Kedarasetti ◽  
Kevin L. Turner ◽  
Christina Echagarruga ◽  
Bruce J. Gluckman ◽  
Patrick J. Drew ◽  
...  

Abstract The brain lacks a conventional lymphatic system to remove metabolic waste. It has been proposed that fluid movement through the arteriolar paravascular space (PVS) promotes metabolite clearance. We performed simulations to understand how arteriolar pulsations and dilations, and brain deformability affect PVS fluid flow. In simulations with compliant brain tissue, arteriolar pulsations did not drive appreciable flows in the PVS. However, when the arteriole dilated as in functional hyperemia, there was a marked movement of fluid. Simulations suggest that functional hyperemia may also serve to increase fluid exchange between the PVS and the subarachnoid space. We measured blood vessels and brain tissue displacement simultaneously in awake, head-fixed mice using two-photon microscopy. These measurements showed that brain deforms in response to pressure changes in PVS, as predicted by simulations. Our results show that the deformability of the brain tissue needs to be accounted for when studying fluid flow and metabolite transport.Acknowledgements: This work was supported by NSF Grant CBET 1705854.


2020 ◽  
Author(s):  
Ravi Kedarasetti ◽  
Kevin L. Turner ◽  
Christina Echagarruga ◽  
Bruce J. Gluckman ◽  
Patrick J. Drew ◽  
...  

Abstract The brain lacks a conventional lymphatic system to remove metabolic waste. It has been proposed that fluid movement through the arterial paravascular space (PVS) promotes metabolite clearance. We performed simulations to understand how arterial pulsations and dilations, and brain deformability affect PVS fluid flow. In simulations with compliant brain tissue, arterial pulsations did not drive appreciable flows in the PVS. However, when the artery dilated as in functional hyperemia, there was a marked movement of fluid. Simulations suggest that functional hyperemia may also serve to increase fluid exchange between the PVS and the subarachnoid space. We measured blood vessels and brain tissue displacement simultaneously in awake, head-fixed mice using two-photon microscopy. Measurements show that brain deforms in response to fluid movement in PVS, as predicted by simulations. Our results show that the deformability of the brain tissue needs to be accounted for when studying fluid flow and metabolite transport.


2019 ◽  
Author(s):  
Ravi Teja Kedarasetti ◽  
Kevin L. Turner ◽  
Christina Echagarruga ◽  
Bruce G. Gluckman ◽  
Patrick J. Drew ◽  
...  

AbstractMaintaining the ionic and chemical composition of the extracellular spaces in the brain is extremely important for its health and function. However, the brain lacks a conventional lymphatic system to remove metabolic waste. It has been proposed that the fluid movement through the paravascular space (PVS) surrounding penetrating arteries can help remove metabolites from the brain. The dynamics of fluid movement in the PVS and its interaction with arterial dilation and brain mechanics are not well understood. Here, we performed simulations to understand how arterial pulsations and dilations interact with brain deformability to drive fluid flow in the PVS. In simulations with compliant brain tissue, arterial pulsations did not drive appreciable flows in the PVS. In contrast, when the artery dilated with dynamics like those seen during functional hyperemia, there was a marked movement of fluid through the PVS. Our simulations suggest that in addition to its other purposes, functional hyperemia may serve to increase fluid exchange between the PVS and the subarachnoid space, improving the clearance of metabolic waste. We measured displacement of the blood vessels and the brain tissue simultaneously in awake, head-fixed mice using two-photon microscopy. Our measurements show that brain tissue can deform in response to fluid movement in the PVS, as predicted by simulations. The results from our simulations and experiments show that the deformability of the soft brain tissue needs to be accounted for when studying fluid flow and metabolite transport in the brain.


2020 ◽  
Author(s):  
Ravi Kedarasetti ◽  
Kevin L. Turner ◽  
Christina Echagarruga ◽  
Bruce J. Gluckman ◽  
Patrick J. Drew ◽  
...  

Abstract The brain lacks a conventional lymphatic system to remove metabolic waste. It has been proposed that directional fluid movement through the arteriolar paravascular space (PVS) promotes metabolite clearance. We performed simulations to examine if arteriolar pulsations and dilations can drive directional CSF flow in the PVS and found that arteriolar wall movements do not drive directional CSF flow. We propose an alternative method of metabolite clearance from the PVS, namely fluid exchange between the PVS and the subarachnoid space (SAS). In simulations with compliant brain tissue, arteriolar pulsations did not drive appreciable fluid exchange between the PVS and the SAS. However, when the arteriole dilated, as seen during functional hyperemia, there was a marked exchange of fluid. Simulations suggest that functional hyperemia may serve to increase metabolite clearance from the PVS. We measured blood vessels and brain tissue displacement simultaneously in awake, head-fixed mice using two-photon microscopy. These measurements showed that brain deforms in response to pressure changes in PVS, consistent with our simulations. Our results show that the deformability of the brain tissue needs to be accounted for when studying fluid flow and metabolite transport.Acknowledgements: This work was supported by NSF Grant CBET 1705854.


2016 ◽  
Vol 33 (4) ◽  
pp. 522-568
Author(s):  
Cory M. Gavito

Among the roughly 150 Italian songbooks published between 1610 and 1665 with the guitar tablature known as alfabeto, about thirteen are anthologies. These anthologies often advertise the role of a compiler who has gathered together music by diverse authors. The extent to which compilers also functioned as authors and editors is not well understood. This essay considers the case of Giovanni Stefani, a compiler who, in the preface to his Scherzi amorosi of 1622, describes the anthology as a collection of his choosing that contains “varie compositioni de Virtuosi della prima classe” (various compositions of first-class virtuosos). Intriguingly, none of the settings Stefani prints (in both this alfabeto anthology and two others) include attributions. Since the 1880s, scholars have been preoccupied with matters of transmission and attribution, unearthing a network of textual and musical concordances. This article expands the nexus of Stefani’s songs and their concordant sources, revealing an array of examples that range from identical copies to “partial” concordances that take over motives, phrases, refrains, or harmonic schemes. These examples indicate that in preparing his anthologies, Stefani mined a corpus of existing prints and manuscripts while also relying heavily on oral transmission. The complex nature of Stefani’s approach, taken together with his complete avoidance of composer attributions, points toward an editorial process shaped by a fluid exchange between oral and written musical practices.


Eye ◽  
2021 ◽  
Author(s):  
Ting Zhang ◽  
Yantao Wei ◽  
Zhaotian Zhang ◽  
Wei Chi ◽  
Lujia Feng ◽  
...  

Abstract Introduction To investigate the incidence and causes of intraoperative choroidal detachment (CD) during small-gauge vitrectomy, as well as the anatomic and visual outcomes. Methods We retrospectively reviewed the medical records of 1026 consecutive patients who underwent small-gauge vitrectomy from June 2017 to December 2018 at Zhongshan Ophthalmic Centre, Guangzhou, China. Data on the presence, location, and extent of intraoperative CD and its relationship to the infusion cannula were collected. Patient demographic characteristics and postoperative anatomic and visual outcomes were also assessed. Results A total of six cases were found to have intraoperative CD, including two with serous CD, three with limited haemorrhagic CD, and one with CD caused by inadvertent perfusion of gas during air/fluid exchange. Retraction of the infusion cannula and acute ocular hypotony were found to be the main causes of intraoperative CD in five out of the six cases. The best-corrected visual acuity of all cases significantly improved after the surgery. Conclusion The incidence of intraoperative CD during small-gauge vitrectomy is low; the predominant causes are retraction of the infusion cannula and acute ocular hypotony. Immediate awareness and timely closure of the incision may contribute to a better surgical prognosis.


Lab on a Chip ◽  
2017 ◽  
Vol 17 (12) ◽  
pp. 2085-2094 ◽  
Author(s):  
Matthew D. Wehrman ◽  
Melissa J. Milstrey ◽  
Seth Lindberg ◽  
Kelly M. Schultz

A novel microfluidic design enables repeated phase transitions in a single sample by surrounding fluid exchange and microrheological characterization.


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