scholarly journals Assessment of flow within developing chicken vasculature and biofabricated vascularized tissues using multimodal imaging techniques

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Prasanna Padmanaban ◽  
Ata Chizari ◽  
Tom Knop ◽  
Jiena Zhang ◽  
Vasileios D. Trikalitis ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Imaging Techniques ◽  
Dark Field ◽  
Flow Dynamics ◽  
Laser Speckle ◽  
Shear Stresses ◽  
Imaging Data ◽  
Contrast Imaging ◽  
Flow Shear ◽  
Engineered Tissues

AbstractFluid flow shear stresses are strong regulators for directing the organization of vascular networks. Knowledge of structural and flow dynamics information within complex vasculature is essential for tuning the vascular organization within engineered tissues, by manipulating flows. However, reported investigations of vascular organization and their associated flow dynamics within complex vasculature over time are limited, due to limitations in the available physiological pre-clinical models, and the optical inaccessibility and aseptic nature of these models. Here, we developed laser speckle contrast imaging (LSCI) and side-stream dark field microscopy (SDF) systems to map the vascular organization, spatio-temporal blood flow fluctuations as well as erythrocytes movements within individual blood vessels of developing chick embryo, cultured within an artificial eggshell system. By combining imaging data and computational simulations, we estimated fluid flow shear stresses within multiscale vasculature of varying complexity. Furthermore, we demonstrated the LSCI compatibility with bioengineered perfusable muscle tissue constructs, fabricated via molding techniques. The presented application of LSCI and SDF on perfusable tissues enables us to study the flow perfusion effects in a non-invasive fashion. The gained knowledge can help to use fluid perfusion in order to tune and control multiscale vascular organization within engineered tissues.

scholarly journals Nephron blood flow dynamics measured by laser speckle contrast imaging

2011 ◽  
Vol 300 (2) ◽  
pp. F319-F329 ◽  
Author(s):  
Niels-Henrik Holstein-Rathlou ◽  
Olga V. Sosnovtseva ◽  
Alexey N. Pavlov ◽  
William A. Cupples ◽  
Charlotte Mehlin Sorensen ◽  
...  
Keyword(s):  
Blood Flow ◽  
Signal Transmission ◽  
Experimental Studies ◽  
Flow Dynamics ◽  
Laser Speckle ◽  
Tubuloglomerular Feedback ◽  
Contrast Imaging ◽  
Laser Speckle Contrast Imaging ◽  
Speckle Contrast ◽  
Blood Flow Dynamics

Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50–100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney.

scholarly journals Titanium-Based Microbolometers: Control of Spatial Profile of Terahertz Emission in Weak Power Sources

2020 ◽  
Vol 10 (10) ◽  
pp. 3400
Author(s):  
Linas Minkevičius ◽  
Liang Qi ◽  
Agnieszka Siemion ◽  
Domas Jokubauskis ◽  
Aleksander Sešek ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Dark Field ◽  
Spatial Mode ◽  
Contrast Imaging ◽  
Optical Components ◽  
Broadband Antenna ◽  
Power Sources ◽  
Precise Control ◽  
Imaging And Spectroscopy ◽  
And Control

Terahertz (THz) imaging and spectroscopy set-ups require fine optical alignment or precise control of spatial mode profile. We demonstrate universal, convenient and easy-to-use imaging—resonant and broadband antenna coupled ultrasensitive titanium-based—dedicated to accurately adjust and control spatial mode profiles without additional focusing optical components of weak power THz sources. Versatile operation of the devices is shown using different kinds of THz—electronic multiplier sources, optical THz mixer-based frequency domain and femtosecond optoelectronic THz time-domain spectrometers as well as optically pumped molecular THz laser. Features of the microbolometers within 0.15–0.6 THz range are exposed and discussed, their ability to detect spatial mode profiles beyond the antennas resonances, up to 2.52 THz, are explored. Polarization-sensitive mode control possibilities are examined in details. The suitability of the resonant antenna-coupled microbolometers to resolve low-absorbing objects at 0.3 THz is revealed via direct, dark field and phase contrast imaging techniques as well.

scholarly journals Characterization of cerebral blood flow dynamics with multiscale entropy

2017 ◽  
Vol 10 (05) ◽  
pp. 1743005 ◽  
Author(s):  
Alexey N. Pavlov ◽  
Arkady S. Abdurashitov ◽  
Olga N. Pavlova ◽  
Maria V. Ulanova ◽  
Anastasia A. Bodrova ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Dynamics ◽  
Laser Speckle ◽  
Multiscale Entropy ◽  
Cerebral Veins ◽  
Contrast Imaging ◽  
Speckle Contrast ◽  
Sound Exposure ◽  
Blood Flow Dynamics

Based on the laser speckle contrast imaging (LSCI) and the multiscale entropy (MSE), we study in this work the blood flow dynamics at the levels of cerebral veins and the surrounding network of microcerebral vessels. We discuss how the phenylephrine-related acute peripheral hypertension is reflected in the cerebral circulation and show that the observed changes are scale-dependent, and they are significantly more pronounced in microcerebral vessels, while the macrocerebral dynamics does not demonstrate authentic inter-group distinctions. We also consider the permeability of blood–brain barrier (BBB) and study its opening caused by sound exposure. We show that alterations associated with the BBB opening can be revealed by the analysis of blood flow at the level of macrocerebral vessels.

scholarly journals Computer simulations of blood flow with mass transport through the carotid artery bifurcation

2004 ◽  
Vol 31 (1) ◽  
pp. 1-33 ◽  
Author(s):  
Nenad Filipovic ◽  
Milos Kojic
Keyword(s):  
Mass Transport ◽  
Computer Simulations ◽  
Stokes Equations ◽  
Computational Simulation ◽  
Flow Dynamics ◽  
Shear Stresses ◽  
Separation Flow ◽  
Imaging Data ◽  
Element Analysis ◽  
Comparison Results

The current paradigm for clinical diagnostic for the treatment of vascular disease relies exclusively on diagnostic imaging data to define the present state of the patient, empirical data to evaluate the efficacy of prior treatments for similar patients. These techniques are insufficient to predict the outcome of a given treatment for an individual patient. We here propose a new paradigm of predictive medicine where physician could use computational simulation to construct and evaluate a specific geometrical/anatomical model to predict the outcome for an individual patient. For this purpose it is necessary to develop a complex software system which combines user friendly interface, automatic solid modeling, automatic finite mesh generation, computational fluid dynamics and post-processing visualization. The flow dynamics is defined according to the incompressible Navier-Stokes equations for Newtonian and non-Newtonian fluids. Mass transport of oxygen and macromolecules is modeled by the convection diffusion equation and coupled with flow dynamics. The computer simulations are based upon finite element analysis where the new computer methods for coupling oxygen transport and fluid flow are described. The comparison results shows a good agreement between clinical observation for critical zones of flow separation, flow recirculation, low wall shear stresses which may contribute to the development of atherosclerotic diseases.

scholarly journals Hard X-ray omnidirectional differential phase and dark-field imaging

2021 ◽  
Vol 118 (9) ◽  
pp. e2022319118
Author(s):  
Hongchang Wang ◽  
Kawal Sawhney
Keyword(s):  
Imaging Techniques ◽  
Dark Field ◽  
X Rays ◽  
Contrast Imaging ◽  
X Ray ◽  
Differential Phase ◽  
Dark Field Imaging ◽  
Spiral Path ◽  
Wide Range ◽  
Phase Images

Ever since the discovery of X-rays, tremendous efforts have been made to develop new imaging techniques for unlocking the hidden secrets of our world and enriching our understanding of it. X-ray differential phase contrast imaging, which measures the gradient of a sample’s phase shift, can reveal more detail in a weakly absorbing sample than conventional absorption contrast. However, normally only the gradient’s component in two mutually orthogonal directions is measurable. In this article, omnidirectional differential phase images, which record the gradient of phase shifts in all directions of the imaging plane, are efficiently generated by scanning an easily obtainable, randomly structured modulator along a spiral path. The retrieved amplitude and main orientation images for differential phase yield more information than the existing imaging methods. Importantly, the omnidirectional dark-field images can be simultaneously extracted to study strongly ordered scattering structures. The proposed method can open up new possibilities for studying a wide range of complicated samples composed of both heavy, strongly scattering atoms and light, weakly scattering atoms.

Response of human osteoblast-like cells to fluid flow shear: A potential role for the microtubule network and primary ciliums

2007 ◽  
Vol 30 (4) ◽  
pp. 90 ◽  
Author(s):  
Kenneth A. Myers ◽  
Jerome B. Rattner ◽  
Nigel G. Shrive ◽  
David A. Hart
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Cellular Response ◽  
Primary Cilia ◽  
Cytochalasin D ◽  
Shear Stresses ◽  
Human Osteoblast ◽  
Flow Shear ◽  
Microtubule Network

Introduction: A limited understanding of the cellular mechanisms governing bone mechanotransduction has inhibited the development of clinical treatments for a variety of bone disorders, including osteoporosis, osteoarthritis and microgravity-associated bone atrophy. The cytoskeleton is thought to play a role in cellular mechanotransduction, however the exact mechanism in bone cells has not yet been clearly elucidated. Studies involving cytoskeletal inhibitors have not generally considered secondary effects on cellular organelles such as the primary cilia. These cellular projections could account for the disparity between shear stresses predicted to occur in vivo and the minimum threshold of membrane deformation required to elicit a cellular response in vitro. Methods: MG-63 (human osteoblast-like) cells were cultured in vitro. Cultures were exposed to intermittent cyclic fluid flow shear stress (1 Pa amplitude), for 8 or 12 hrs. Some cultures were loaded in the presence of nocodazole (a microtubule inhibitor) or cytochalasin D (an actin filament inhibitor). The cellular response was analyzed through RT-PCR assessment of messenger RNA levels for specific molecules related to matrix metabolism. The effects of drug treatments on cytoskeletal disorganization and the primary cilia were assessed with immunocytochemistry and electron microscopy. Results: In untreated cultures, shear stress was associated with significant increases in mRNA levels for collagen I and matrix metalloproteinases 1 and 3, for both time points assessed. These increases were maintained in cultures loaded in the presence of cytochalasin D, but were almost completely abrogated in nocodazole-treated cultures. Cytoskeletal inhibitors exerted some dose-dependent effects on length and structure of primary cilia in MG-63 cells. Conclusions: The microtubule network appears to be necessary for some shear-induced responses of osteoblast-like cells. MG-63 cells possess primary cilia, organelles that could amplify fluid flow shear, accounting for some apparent contradictions between studies related to osteoblast mechanosensitivity. Since these structures are composed of microtubules, the observation that microtubule disruptors inhibit the shear response of osteoblast-like cells suggests the primary cilium may have a role in osteoblast mechanotransduction. The effects of cytoskeletal inhibitors on cilium structure may explain the conflicting results of earlier mechanotransduction studies.

scholarly journals A Modified Mini-Stroke Model with Region-Directed Reperfusion in Rat Cortex

2007 ◽  
Vol 28 (5) ◽  
pp. 973-983 ◽  
Author(s):  
Weihua Luo ◽  
Zhen Wang ◽  
Pengcheng Li ◽  
Shaoqun Zeng ◽  
Qingming Luo
Keyword(s):  
Imaging Techniques ◽  
Brain Area ◽  
Laser Speckle ◽  
Stroke Model ◽  
Contrast Imaging ◽  
Control Groups ◽  
Triphenyltetrazolium Chloride ◽  
Cranial Window ◽  
Brain Recovery ◽  
Ischemic Core

Mini-ischemia localized into a specific brain area has promoted understanding of the mechanisms underlying brain recovery in stroke. However, the conventional mini-stroke model adopted permanent arterial ligations but lacked controllable reperfusion, which is crucial for the outcome of delayed functional recovery. In this study, we devised a new rat mini-stroke model in which the vascular ligations can be easily reversed to induce targeted reperfusion. Specifically, a flexible ring was incorporated into the conventional small arterial ligations to tighten the ligating loops and facilitate cutting the ligatures for sufficient reperfusion afterwards. The distribution of cerebral blood flow was explored directly through a cranial window using laser speckle contrast imaging. A distinct ischemic core, which well fits the profile of the ligated ring, was bordered by a penumbral zone and then together surrounded by nonischemic tissue immediately after the arterial ligations involving the ring. After cutting the ligatures, post-recanalization hyperperfusion occurred in the previous ischemic core and to a greater extent at 24 h after reperfusion. In contrast, recirculation of common carotid artery in the conventional mini-stroke model hardly altered hypoperfusion status within the ischemic core. Evidence from two kinds of control groups indicated that the ring might produce a compression effect on the underlying cortex and then contribute to the more highly localized infarct that was identified by triphenyltetrazolium chloride staining. Our data suggest that this model provides opportunities for investigating the neurovascular dynamics in acute stroke and rehabilitation, especially with emerging optical imaging techniques.

A medium throughput device to study the effects of combinations of surface strains and fluid-flow shear stresses on cells

Lab on a Chip ◽  
2015 ◽  
Vol 15 (2) ◽  
pp. 429-439 ◽  
Author(s):  
R. Sinha ◽  
S. Le Gac ◽  
N. Verdonschot ◽  
A. van den Berg ◽  
B. Koopman ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Shear Stresses ◽  
Flow Shear

A device is reported to screen for the effects on cells of all combinations of five surface strains and five fluid-flow shear stresses, each with four replicates (total 100 units).

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