9 results on '"Paul J. Marc"'
Search Results
2. Near-lifespan longitudinal tracking of brain microvascular morphology, topology, and flow in male mice
- Author
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Konrad W. Walek, Sabina Stefan, Jang-Hoon Lee, Pooja Puttigampala, Anna H. Kim, Seong Wook Park, Paul J. Marchand, Frederic Lesage, Tao Liu, Yu-Wen Alvin Huang, David A. Boas, Christopher Moore, and Jonghwan Lee
- Subjects
Science - Abstract
Abstract In age-related neurodegenerative diseases, pathology often develops slowly across the lifespan. As one example, in diseases such as Alzheimer’s, vascular decline is believed to onset decades ahead of symptomology. However, challenges inherent in current microscopic methods make longitudinal tracking of such vascular decline difficult. Here, we describe a suite of methods for measuring brain vascular dynamics and anatomy in mice for over seven months in the same field of view. This approach is enabled by advances in optical coherence tomography (OCT) and image processing algorithms including deep learning. These integrated methods enabled us to simultaneously monitor distinct vascular properties spanning morphology, topology, and function of the microvasculature across all scales: large pial vessels, penetrating cortical vessels, and capillaries. We have demonstrated this technical capability in wild-type and 3xTg male mice. The capability will allow comprehensive and longitudinal study of a broad range of progressive vascular diseases, and normal aging, in key model systems.
- Published
- 2023
- Full Text
- View/download PDF
3. A simulation study investigating potential diffusion-based MRI signatures of microstrokes
- Author
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Rafat Damseh, Yuankang Lu, Xuecong Lu, Cong Zhang, Paul J. Marchand, Denis Corbin, Philippe Pouliot, Farida Cheriet, and Frederic Lesage
- Subjects
Medicine ,Science - Abstract
Abstract Recent studies suggested that cerebrovascular micro-occlusions, i.e. microstokes, could lead to ischemic tissue infarctions and cognitive deficits. Due to their small size, identifying measurable biomarkers of these microvascular lesions remains a major challenge. This work aims to simulate potential MRI signatures combining arterial spin labeling (ASL) and multi-directional diffusion-weighted imaging (DWI). Driving our hypothesis are recent observations demonstrating a radial reorientation of microvasculature around the micro-infarction locus during recovery in mice. Synthetic capillary beds, randomly- and radially-oriented, and optical coherence tomography (OCT) angiograms, acquired in the barrel cortex of mice (n = 5) before and after inducing targeted photothrombosis, were analyzed. Computational vascular graphs combined with a 3D Monte-Carlo simulator were used to characterize the magnetic resonance (MR) response, encompassing the effects of magnetic field perturbations caused by deoxyhemoglobin, and the advection and diffusion of the nuclear spins. We quantified the minimal intravoxel signal loss ratio when applying multiple gradient directions, at varying sequence parameters with and without ASL. With ASL, our results demonstrate a significant difference (p < 0.05) between the signal-ratios computed at baseline and 3 weeks after photothrombosis. The statistical power further increased (p < 0.005) using angiograms measured at week 4. Without ASL, no reliable signal change was found. We found that higher ratios, and accordingly improved significance, were achieved at lower magnetic field strengths (e.g., B0 = 3T) and shorter echo time TE (< 16 ms). Our simulations suggest that microstrokes might be characterized through ASL-DWI sequence, providing necessary insights for posterior experimental validations, and ultimately, future translational trials.
- Published
- 2021
- Full Text
- View/download PDF
4. Fast-lysis cell traps for chemical cytometry
- Author
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Nancy L. Allbritton, G. P. Li, Paul J. Marc, Christopher E. Sims, and Mark Bachman
- Subjects
Lysis ,Capillary action ,Surface Properties ,Biomedical Engineering ,Analytical chemistry ,Bioengineering ,Photoresist ,Biochemistry ,Sensitivity and Specificity ,Article ,Capillary electrophoresis ,Cell Line, Tumor ,Cell Adhesion ,Animals ,Electrodes ,Fluorescent Dyes ,Chemistry ,Electrophoresis, Capillary ,General Chemistry ,Equipment Design ,Flow Cytometry ,Indium tin oxide ,Rats ,Electrophoresis ,Electrode ,Fluorescein ,Cytometry - Abstract
Electrically addressable cell traps were integrated with capillary electrophoresis for the analysis of the contents of single adherent cells. Electrodes composed of indium tin oxide were patterned on a glass surface followed by formation of topographical cell traps using 1002F photoresist. Single cells trapped in the holes could be lysed in less than 66 ms by applying a brief electric field (10 ms) across the electrode beneath the cell and the ground electrode placed in the aqueous media above the cell traps. The gas formed during cell lysis remained localized within the cavity formed by the 1002F photoresist. The retention of the gas in the cell trap enabled the cell traps to be coupled to an overlying capillary without blockage of the capillary. Single cells cultured in the traps were loaded with fluorescein and Oregon Green and then electrically lysed. By simultaneous application of an electric field to the capillary, the cell's contents were loaded into the capillary and electrophoretically separated. Orgeon Green and fluorescein from a single cell were fully resolved in less than two minutes. The use of a single patterned electrode beneath the 1002F cell trap yielded a simple easily fabricated design that was robust when immersed in aqueous solutions. Moreover, the design can easily be scaled up to create arrays of adherent cells for serial analyses using a single capillary or for parallel analysis by mating to an array of capillaries. Enhancing the rate of analysis of single adherent cells would enable a greater understanding of cellular physiology.
- Published
- 2008
- Full Text
- View/download PDF
5. Coaxial Flow System for Chemical Cytometry
- Author
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Christopher E. Sims, Nancy L. Allbritton, and Paul J. Marc
- Subjects
Analyte ,Lysis ,Chromatography ,Capillary action ,Electrophoresis, Capillary ,Buffers ,Article ,Analytical Chemistry ,Electrophoresis ,chemistry.chemical_compound ,Capillary electrophoresis ,chemistry ,Spectrophotometry, Ultraviolet ,Coaxial ,Fluorescein ,Cytometry - Abstract
Over the past decade, chemical cytometry performed by capillary electrophoresis (CE) has become increasingly valuable as a bio-analytical tool to quantify analytes from single cells. However, extensive use of CE-based chemical cytometry has been hindered by the relatively low throughput for the analysis of single adherent cells. In order to overcome the low throughput of CE-based analysis of adherent cells and increase its utility in evaluating cellular attributes, new higher throughput methods are needed. Integration of a coaxial buffer exchange system with CE-based chemical cytometry increased the rate of serial analyses of cells. In the designed system, fluid flow through a tube coaxial to the separation capillary was used to supply electrophoretic buffer to the capillary. This sheath or coaxial fluid was turned off between analysis of cells and on during cell sampling and electrophoresis. Thus, living cells were not exposed to the nonphysiologic electrophoretic buffer prior to lysis. Key parameters of the system such as the relative capillary-sheath positions, buffer flow velocities, and the cell chamber design were optimized. To demonstrate the utility of the system, rat basophilic leukemic cells loaded with Oregon Green and fluorescein were serially lysed and loaded into a capillary. Separation of the contents of 20 cells at a rate of 0.5 cells/min was demonstrated.
- Published
- 2007
- Full Text
- View/download PDF
6. Soliton microcomb based spectral domain optical coherence tomography
- Author
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Paul J. Marchand, Johann Riemensberger, J. Connor Skehan, Jia-Jung Ho, Martin H. P. Pfeiffer, Junqiu Liu, Christoph Hauger, Theo Lasser, and Tobias J. Kippenberg
- Subjects
Science - Abstract
Superluminescent diodes, that provide a broadband spectrum are typically used in spectral domain coherence tomography. Here, the authors use chipscale silicon nitride resonators to generate soliton microcombs with a lower noise flor that could substitute the diode sources.
- Published
- 2021
- Full Text
- View/download PDF
7. Micropatterning of living cells on a heterogeneously wetted surface
- Author
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Christopher E. Sims, Nancy L. Allbritton, Yuli Wang, Mark Bachman, Paul J. Marc, and Guann-Pyng Li
- Subjects
Materials science ,Cell Survival ,Polymers ,Surface Properties ,Cell Culture Techniques ,Nanotechnology ,Virtual wall ,chemistry.chemical_compound ,Electrochemistry ,Cell Adhesion ,Humans ,General Materials Science ,Spectroscopy ,Cell Proliferation ,chemistry.chemical_classification ,Aqueous solution ,Aqueous medium ,Biomolecule ,Air ,Water ,Surfaces and Interfaces ,Condensed Matter Physics ,Silane ,Trapped air ,chemistry ,Chemical engineering ,Wettability ,Epoxy Compounds ,Wetting ,Glass ,Hydrophobic and Hydrophilic Interactions ,Porosity ,Micropatterning ,HeLa Cells - Abstract
We report a simple approach to fabricate heterogeneously wetted surfaces which can be used to pattern living cells or biomolecules. An array of pedestals composed of SU-8 was fabricated on a glass surface which was then derivatized with a hydrophobic silane. Upon addition of aqueous solutions to the array, air was trapped within the hydrophobic cavities between the pedestals. The trapped air formed a “virtual wall” blocking access to these cavities. Cells cultured on the array were forced to grow only on the tops of the pedestals, i.e., the surfaces wetted by aqueous media. The virtual walls were stable during manipulation of the array and over long time periods (months).
- Published
- 2006
8. Deep Learning and Simulation for the Estimation of Red Blood Cell Flux With Optical Coherence Tomography
- Author
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Sabina Stefan, Anna Kim, Paul J. Marchand, Frederic Lesage, and Jonghwan Lee
- Subjects
RBC flux ,deep learning ,simulation ,capillary flow ,microvascular network ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
We present a deep learning and simulation-based method to measure cortical capillary red blood cell (RBC) flux using Optical Coherence Tomography (OCT). This method is more accurate than the traditional peak-counting method and avoids any user parametrization, such as a threshold choice. We used data that was simultaneously acquired using OCT and two-photon microscopy to uncover the distribution of parameters governing the height, width, and inter-peak time of peaks in OCT intensity associated with the passage of RBCs. This allowed us to simulate thousands of time-series examples for different flux values and signal-to-noise ratios, which we then used to train a 1D convolutional neural network (CNN). The trained CNN enabled robust measurement of RBC flux across the entire network of hundreds of capillaries.
- Published
- 2022
- Full Text
- View/download PDF
9. Fast-lysis cell traps for chemical cytometry.
- Author
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Paul J. Marc, Christopher E. Sims, Mark Bachman, G. P. Li, and Nancy L. Allbritton
- Subjects
- *
CYTOMETRY , *ELECTROPHORESIS , *PHASE partition , *ELECTRIC resistors - Abstract
Electrically addressable cell traps were integrated with capillary electrophoresis for the analysis of the contents of single adherent cells. Electrodes composed of indium tin oxide were patterned on a glass surface followed by formation of topographical cell traps using 1002F photoresist. Single cells trapped in the holes could be lysed in less than 66 ms by applying a brief electric field (10 ms) across the electrode beneath the cell and the ground electrode placed in the aqueous media above the cell traps. The gas formed during cell lysis remained localized within the cavity formed by the 1002F photoresist. The retention of the gas in the cell trap enabled the cell traps to be coupled to an overlying capillary without blockage of the capillary. Single cells cultured in the traps were loaded with fluorescein and Oregon Green and then electrically lysed. By simultaneous application of an electric field to the capillary, the cell's contents were loaded into the capillary and electrophoretically separated. Orgeon Green and fluorescein from a single cell were fully resolved in less than two minutes. The use of a single patterned electrode beneath the 1002F cell trap yielded a simple easily fabricated design that was robust when immersed in aqueous solutions. Moreover, the design can easily be scaled up to create arrays of adherent cells for serial analyses using a single capillary or for parallel analysis by mating to an array of capillaries. Enhancing the rate of analysis of single adherent cells would enable a greater understanding of cellular physiology. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
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