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

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.

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Biophotonics Modalities for High-Resolution Imaging of Microcirculatory Tissue Beds Using Endogenous Contrast: A Review on Present Scenario and Prospects

International Journal of Optics ◽

10.1155/2011/293684 ◽

2011 ◽

Vol 2011 ◽

pp. 1-20 ◽

Cited By ~ 4

Author(s):

Hrebesh M. Subhash

Keyword(s):

High Resolution ◽

Optical Imaging ◽

Perfusion Imaging ◽

Imaging Techniques ◽

Laser Speckle ◽

Contrast Imaging ◽

Endogenous Contrast ◽

Contrast Mechanism ◽

Recent Developments ◽

Resolution Imaging

The microcirculation is a complex system, and the visualization of microcirculation has great significance in improving our understanding of pathophysiological processes in various disease conditions, in both clinical and fundamental studies. A range of techniques are available or emerging for investigating different aspect of the microcirculation in animals and humans. This paper reviews the recent developments in the field of high-resolution and high-sensitive optical imaging of microcirculatory tissue beds, emphasizing technologies that utilize the endogenous contrast mechanism. Optical imaging techniques such as intravital microscopy, Capillaroscopy, laser Doppler perfusion imaging, laser speckle perfusion imaging, polarization spectroscopy, photo-acoustic tomography, and various implementations of optical coherence tomography based on Doppler and speckle contrast imaging are presented together with their prospectives and challenges.

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Fusogenic Liposomes Deliver Resveratrol to Brain Microcirculation and Improve Neurovascular Coupling in Aged Mice

Innovation in Aging ◽

10.1093/geroni/igaa057.394 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

pp. 120-120

Author(s):

Adam Nyul Toth ◽

Tabea Wiedenhoeft ◽

Stefano Tarantini ◽

Tamas Csipo ◽

Priya Balasubramanian ◽

...

Keyword(s):

Oxidative Stress ◽

Neurovascular Unit ◽

Neurovascular Coupling ◽

Laser Speckle ◽

Protective Effects ◽

Contrast Imaging ◽

Aged Mice ◽

Cranial Window ◽

Age Related

Abstract Adjustment of cerebral blood flow (CBF) to the increased oxygen and nutrient demands of active brain regions via neurovascular coupling (NVC) has an essential role in maintenance of healthy cognitive function. In advanced age, cerebromicrovascular oxidative stress and endothelial dysfunction impair neurovascular coupling, contributing to age-related cognitive decline. Recently we developed a resveratrol (3,4′,5- trihydroxystilbene)-containing fusogenic liposome (FL-RSV)-based molecular delivery system that can effectively target cultured cerebromicrovascular endothelial cells, attenuating age-related oxidative stress. To assess the cerebromicrovascular protective effects of FL-RSV in vivo, aged (24-monthold) C57BL/6 mice were treated with FL-RSV for four days. To demonstrate effective cellular uptake of FL-RSV, accumulation of the lipophilic tracer dyes in cells of the neurovascular unit was confirmed using two-photon imaging (through a chronic cranial window). NVC was assessed by measuring CBF responses (laser speckle contrast imaging) evoked by contralateral whisker stimulation. We found that NVC responses were significantly impaired in aged mice. Treatment with FL-RSV significantly improved NVC responses by increasing NO-mediated vasodilation. These findings are paralleled by the protective effects of FL-RSV on endothelium-dependent relaxation in the aorta. Thus, treatment with FL-RSV rescues endothelial function and NVC responses in aged mice. We propose that resveratrol containing fusogenic liposomes could also be used for combined delivery of various anti-geronic factors, including proteins, small molecules, DNA vectors and mRNAs targeting key pathways involved in microvascular aging and neurovascular dysfunction for the prevention/treatment of age-related cerebromicrovascular pathologies and development of vascular cognitive impairment (VCI) in aging.

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

Scientific Reports ◽

10.1038/s41598-021-97008-w ◽

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.

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Applicability of quantitative optical imaging techniques for intraoperative perfusion diagnostics: a comparison of laser speckle contrast imaging, sidestream dark-field microscopy, and optical coherence tomography

Journal of Biomedical Optics ◽

10.1117/1.jbo.22.8.086004 ◽

2017 ◽

Vol 22 (08) ◽

pp. 1 ◽

Cited By ~ 9

Author(s):

Sanne M. Jansen ◽

Daniel M. de Bruin ◽

Dirk J. Faber ◽

Iwan J. G. G. Dobbe ◽

Erik Heeg ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Optical Imaging ◽

Imaging Techniques ◽

Dark Field ◽

Laser Speckle ◽

Optical Coherence ◽

Contrast Imaging ◽

Sidestream Dark Field ◽

Speckle Contrast ◽

Dark Field Microscopy

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Effect of cranial window type on monitoring neurovasculature using laser speckle contrast imaging

10.1117/12.2213989 ◽

2016 ◽

Author(s):

Hang Yu ◽

Janaka Senarathna ◽

Betty M. Tyler ◽

Syed Hossain ◽

Nitish V. Thakor ◽

...

Keyword(s):

Laser Speckle ◽

Contrast Imaging ◽

Laser Speckle Contrast Imaging ◽

Speckle Contrast ◽

Cranial Window

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Novel Optical Techniques for Imaging Microcirculation in the Diabetic Foot

Current Pharmaceutical Design ◽

10.2174/1381612824666180302141902 ◽

2018 ◽

Vol 24 (12) ◽

pp. 1304-1316 ◽

Cited By ~ 13

Author(s):

Onno A. Mennes ◽

Jaap J. van Netten ◽

Riemer H.J.A. Slart ◽

Wiendelt Steenbergen

Keyword(s):

Diabetic Foot ◽

Clinical Relevance ◽

Imaging Techniques ◽

Laser Speckle ◽

Foot Ulcers ◽

Future Research ◽

Diabetic Foot Ulcers ◽

Contrast Imaging ◽

Optical Techniques ◽

Advantages And Disadvantages

Background: The most severe diabetic foot ulcers are those related with critical ischemia, which is primarily diagnosed with non-invasive diagnostics. However, these diagnostics have several disadvantages. For example, they only provide global indications of the (macro)level of ischemia. A potential solution can be found in novel optical imaging techniques for local assessment of the microcirculation in diabetic foot ulcers. This review provides an overview of these imaging techniques (Laser Doppler Perfusion Imaging, Laser Speckle Contrast Imaging, Photoacoustic Imaging and Hyperspectral Imaging) and their applicability for the diagnostic assessment of microcirculation in diabetic foot ulcers. <p> Method: For each technique, the following parts are described: a) their technical background; b) general clinical applications; and, c) its application for microcirculation assessment in diabetic foot ulcers. Parts a-b are based on a narrative review of the literature, part c on a systematic review that was performed in the database Scopus, covering the period from January 1, 2000 to November 31, 2017. <p> Results: Each of these techniques has specific advantages and disadvantages for imaging microcirculation. Potential clinical use depends on measurement aims, and clinical relevance. However, none of the techniques has a strongly established clinical relevance yet: we found a limited number of publications describing clinical outcomes. Future research is needed to determine which technique is the most clinically relevant for the assessment of microcirculation in diabetic foot ulcers. Conclusion: Although promising, the currently available novel optical techniques need to be further improved technically and prospective trials are necessary to evaluate their clinical value.

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Recent applications of TEM to the study of interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100174679 ◽

1990 ◽

Vol 48 (4) ◽

pp. 308-309

Author(s):

C. Barry Carter

Keyword(s):

High Resolution ◽

Sample Preparation ◽

Grain Boundaries ◽

Diffuse Scattering ◽

Imaging Techniques ◽

Amorphous Material ◽

Contrast Imaging ◽

Current State ◽

Actual Nature ◽

High Resolution Images

This paper will review the current state of understanding of interface structure and highlight some of the future needs and problems which must be overcome. The study of this subject can be separated into three different topics: 1) the fundamental electron microscopy aspects, 2) material-specific features of the study and 3) the characteristics of the particular interfaces. The two topics which are relevant to most studies are the choice of imaging techniques and sample preparation. The techniques used to study interfaces in the TEM include high-resolution imaging, conventional diffraction-contrast imaging, and phase-contrast imaging (Fresnel fringe images, diffuse scattering). The material studied affects not only the characteristics of the interfaces (through changes in bonding, etc.) but also the method used for sample preparation which may in turn have a significant affect on the resulting image. Finally, the actual nature and geometry of the interface must be considered. For example, it has become increasingly clear that the plane of the interface is particularly important whenever at least one of the adjoining grains is crystalline.A particularly productive approach to the study of interfaces is to combine different imaging techniques as illustrated in the study of grain boundaries in alumina. In this case, the conventional imaging approach showed that most grain boundaries in ion-thinned samples are grooved at the grain boundary although the extent of this grooving clearly depends on the crystallography of the surface. The use of diffuse scattering (from amorphous regions) gives invaluable information here since it can be used to confirm directly that surface grooving does occur and that the grooves can fill with amorphous material during sample preparation (see Fig. 1). Extensive use of image simulation has shown that, although information concerning the interface can be obtained from Fresnel-fringe images, the introduction of artifacts through sample preparation cannot be lightly ignored. The Fresnel-fringe simulation has been carried out using a commercial multislice program (TEMPAS) which was intended for simulation of high-resolution images.

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Development of a photochemical thrombosis investigation system to obtain a rabbit ischemic stroke model

Scientific Reports ◽

10.1038/s41598-021-85348-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yoonhee Kim ◽

Yoon Bum Lee ◽

Seung Kuk Bae ◽

Sung Suk Oh ◽

Jong-ryul Choi

Keyword(s):

Ischemic Stroke ◽

Brain Damage ◽

Rabbit Model ◽

Specific Area ◽

Brain Atlas ◽

Rabbit Brain ◽

Stroke Model ◽

Triphenyltetrazolium Chloride ◽

Induction System

AbstractPhotochemical thrombosis is a method for the induction of ischemic stroke in the cerebral cortex. It can generate localized ischemic infarcts in the desired region; therefore, it has been actively employed in establishing an ischemic stroke animal model and in vivo assays of diagnostic and therapeutic techniques for stroke. To establish a rabbit ischemic stroke model and overcome the shortcoming of previous studies that were difficult to build a standardized photothrombotic rabbit model, we developed a photochemical thrombosis induction system that can produce consistent brain damage on a specific area. To verify the generation of photothrombotic brain damage using the system, longitudinal magnetic resonance imaging, 2,3,5-triphenyltetrazolium chloride staining, and histological staining were applied. These analytical methods have a high correlation for ischemic infarction and are appropriate for analyzing photothrombotic brain damage in the rabbit brain. The results indicated that the photothrombosis induction system has a main advantage of being accurately controlled a targeted region of photothrombosis and can produce cerebral hemisphere lesions on the target region of the rabbit brain. In conjugation with brain atlas, it can induce photochemical ischemic stroke locally in the part of the brain that is responsible for a particular brain function and the system can be used to develop animal models with degraded specific functions. Also, the photochemical thrombosis induction system and a standardized rabbit ischemic stroke model that uses this system have the potential to be used for verifications of biomedical techniques for ischemic stroke at a preclinical stage in parallel with further performance improvements.

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Nephron blood flow dynamics measured by laser speckle contrast imaging

AJP Renal Physiology ◽

10.1152/ajprenal.00417.2010 ◽

2011 ◽

Vol 300 (2) ◽

pp. F319-F329 ◽

Cited By ~ 34

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.

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