Effects of Acute and Endurance Exercise on Cerebrovascular Function and Oxygen Metabolism: A Photoacoustic Microscopy Study.

Regular exercise improves the cerebrovascular function and has shown considerable therapeutic effects on a wide variety of brain diseases. However, the influence of exercise on different aspects of the cerebrovascular function remains to be comprehensively examined. In this study, we combined awake-brain photoacoustic microscopy (PAM) and a motorized treadmill to assess the effects of both acute exercise stimulation and endurance exercise training on the cerebrovascular function and cerebral oxygen metabolism under both physiological and pathological conditions.

Deep Learning-Powered Bessel-Beam Multiparametric Photoacoustic Microscopy.

Enabling simultaneous and high-resolution quantification of the total concentration of hemoglobin ( [Formula: see text]), oxygen saturation of hemoglobin (sO2), and cerebral blood flow (CBF), multi-parametric photoacoustic microscopy (PAM) has emerged as a promising tool for functional and metabolic imaging of the live mouse brain. However, due to the limited depth of focus imposed by the Gaussian-beam excitation, the quantitative measurements become inaccurate when the imaging object is out of focus. To address this problem, we have developed a hardware-software combined approach by integrating Bessel-beam excitation and conditional generative adversarial network (cGAN)-based deep learning.

Photoacoustic microscopy of vascular adaptation and tissue oxygen metabolism during cutaneous wound healing.

Cutaneous wounds affect millions of people every year. Vascularization and blood oxygen delivery are critical bottlenecks in wound healing, and understanding the spatiotemporal dynamics of these processes may lead to more effective therapeutic strategies to accelerate wound healing. In this work, we applied multi-parametric photoacoustic microscopy (PAM) to study vascular adaptation and the associated changes in blood oxygen delivery and tissue oxygen metabolism throughout the hemostasis, inflammatory, proliferation, and early remodeling phases of wound healing in mice with skin puncture wounds.

SOD1 mediates lysosome-to-mitochondria communication and its dysregulation by amyloid-β oligomers.

Altered mitochondrial DNA (mtDNA) occurs in neurodegenerative disorders like Alzheimer's disease (AD); how mtDNA synthesis is linked to neurodegeneration is poorly understood. We previously discovered Nutrient-induced Mitochondrial Activity (NiMA), an inter-organelle signaling pathway where nutrient-stimulated lysosomal mTORC1 activity regulates mtDNA replication in neurons by a mechanism sensitive to amyloid-β oligomers (AβOs), a primary factor in AD pathogenesis (Norambuena et al., 2018).

High-speed multi-parametric photoacoustic microscopy of cerebral hemodynamic and metabolic responses to acute hemodilution.

The ability of hemodilution to improve vascular circulatory impairment has been demonstrated. However, the effects of acute hemodilution on cerebral hemodynamics and oxygen metabolism have not been assessed at the microscopic level, due to technical limitations. To fill this void, we have developed a new, to the best of our knowledge, photoacoustic microscopy system, which enables high-speed imaging of blood hemoglobin concentration, oxygenation, flow, and oxygen metabolism in vivo.

Recovery of Blood Flow From Undersampled Photoacoustic Microscopy Data Using Sparse Modeling.

Photoacoustic microscopy (PAM) leverages the optical absorption contrast of blood hemoglobin for high-resolution, multi-parametric imaging of the microvasculature in vivo. However, to quantify the blood flow speed, dense spatial sampling is required to assess blood flow-induced loss of correlation of sequentially acquired A-line signals, resulting in increased laser pulse repetition rate and consequently optical fluence. To address this issue, we have developed a sparse modeling approach for blood flow quantification based on downsampled PAM data.

Longitudinal cortex-wide monitoring of cerebral hemodynamics and oxygen metabolism in awake mice using multi-parametric photoacoustic microscopy.

Multi-parametric photoacoustic microscopy (PAM) has emerged as a promising new technique for high-resolution quantification of hemodynamics and oxygen metabolism in the mouse brain. In this work, we have extended the scope of multi-parametric PAM to longitudinal, cortex-wide, awake-brain imaging with the use of a long-lifetime (24 weeks), wide-field (5 × 7 mm), light-weight (2 g), dual-transparency ( light and ultrasound) cranial window. Cerebrovascular responses to the window installation were examined , showing a complete recovery in 18 days.

Development of a photoacoustic microscopy technique to assess peritubular capillary function and oxygen metabolism in the mouse kidney.

Microcirculatory changes and oxidative stress have long been associated with acute kidney injury. Despite substantial progress made by two-photon microscopy of microvascular responses to acute kidney injury in rodent models, little is known about the underlying changes in blood oxygen delivery and tissue oxygen metabolism. To fill this gap, we developed a label-free kidney imaging technique based on photoacoustic microscopy, which enables simultaneous quantification of hemoglobin concentration, oxygen saturation of hemoglobin, and blood flow in peritubular capillaries in vivo.

Hemodynamic and oxygen-metabolic responses of the awake mouse brain to hypercapnia revealed by multi-parametric photoacoustic microscopy.

A widely used cerebrovascular stimulus and common pathophysiologic condition, hypercapnia is of great interest in brain research. However, it remains controversial how hypercapnia affects brain hemodynamics and energy metabolism. By using multi-parametric photoacoustic microscopy, the multifaceted responses of the awake mouse brain to different levels of hypercapnia are investigated.

Peritubular Capillary Oxygen Consumption in Sepsis-Induced AKI: Multi-Parametric Photoacoustic Microscopy.

Understanding and measuring parameters responsible for the pathogenesis of sepsis-induced AKI (SI-AKI) is critical in developing therapies. Blood flow to the kidney is heterogeneous, partly due to the existence of dynamic networks of capillaries in various regions, responding differentially to oxygen demand in cortex versus medulla. High energy demand regions, especially the outer medulla, are susceptible to hypoxia and subject to damage during SI-AKI.

The Biointegration of a Porcine Acellular Dermal Matrix in a Novel Radiated Breast Reconstruction Model.

Background: Ideal acellular dermal matrices (ADM) for breast reconstruction exhibit native extracellular matrix (ECM) structure to allow rapid biointegration and appropriate mechanical properties for desired clinical outcomes. In a novel in vivo model of irradiated breast reconstruction, we describe the cellular and vascular ingrowth of Artia, a porcine product chemically prepared to mimic the biomechanics of human ADM, with retained natural ECM structure to encourage cellular ingrowth.

Methods: Utilizing the murine dorsal skinfold model, Artia was implanted into 16 C57bl/6 mice.

In vivo imaging of hemodynamic redistribution and arteriogenesis across microvascular network.

Objective: Arteriogenesis is an important mechanism that contributes to restoration of oxygen supply in chronically ischemic tissues, but remains incompletely understood due to technical limitations. This study presents a novel approach for comprehensive assessment of the remodeling pattern in a complex microvascular network containing multiple collateral microvessels.

Methods: We have developed a hardware-software integrated platform for quantitative, longitudinal, and label-free imaging of network-wide hemodynamic changes and arteriogenesis at the single-vessel level.

Cortex-wide multiparametric photoacoustic microscopy based on real-time contour scanning.

Large-scale, high-resolution imaging of cerebral hemodynamics is essential for brain research. Uniquely capable of comprehensive quantification of cerebral hemodynamics and oxygen metabolism in rodents based on the endogenous hemoglobin contrast, multiparametric photoacoustic microscopy (PAM) is ideally suited for this purpose. However, the out-of-focus issue due to the uneven surface of the rodent brain results in inaccurate PAM measurements and presents a significant challenge to cortex-wide multiparametric recording.

Parallel Computing for Quantitative Blood Flow Imaging in Photoacoustic Microscopy.

Photoacoustic microscopy (PAM) is an emerging biomedical imaging technology capable of quantitative measurement of the microvascular blood flow by correlation analysis. However, the computational cost is high, limiting its applications. Here, we report a parallel computation design based on graphics processing unit (GPU) for high-speed quantification of blood flow in PAM.

Fenestration Improves Acellular Dermal Matrix Biointegration: An Investigation of Revascularization with Photoacoustic Microscopy.

Background: Acellular dermal matrices have revolutionized alloplastic breast reconstruction. Furthering our knowledge of their biointegration will allow for improved design of these biomaterials. The ideal acellular dermal matrix for breast reconstruction would provide durable soft-tissue augmentation while undergoing rapid biointegration to promote physiologic elasticity and reduced infectious complications.

Isotropic-resolution photoacoustic microscopy with multi-angle illumination.

We have developed photoacoustic microscopy (PAM) with three-dimensional (3D) micron-level spatial resolution. With multi-angle illumination, PAM images from different view angles can be simultaneously acquired for multi-view deconvolution, without the rotation of imaging targets. A side-by-side comparison of this multi-angle-illumination PAM (MAI-PAM) and conventional PAM, which share the same ultrasonic detector, was performed in phantoms and live mice.

Modified VEGF-A mRNA induces sustained multifaceted microvascular response and accelerates diabetic wound healing.

Capable of mediating efficient transfection and protein production without eliciting innate immune responses, chemically modified mRNA holds great potential to produce paracrine factors at a physiologically beneficial level, in a spatiotemporally controlled manner, and with low toxicity. Although highly promising in cardiovascular medicine and wound healing, effects of this emerging therapeutic on the microvasculature and its bioactivity in disease settings remain poorly understood. Here, we longitudinally and comprehensively characterize microvascular responses to AZD8601, a modified mRNA encoding vascular endothelial growth factor A (VEGF-A), in vivo.

[Variation of O Concentration in Different Regions of Beijing from 2006-2015].

O continuous monitoring data for the Dingling, Guanyuan, Liulihe, and Qianmen sites from 2006-2015 were analyzed to investigate concentration levels, variation trends, temporal variations, and relationships with precursors and meteorological factors. The results showed that the ten year average concentrations of O at the Dingling site were the highest at 65.2 μg·m, followed by concentrations at Liulihe (53.

Functional and oxygen-metabolic photoacoustic microscopy of the awake mouse brain.

A long-standing challenge in optical neuroimaging has been the assessment of hemodynamics and oxygen metabolism in the awake rodent brain at the microscopic level. Here, we report first-of-a-kind head-restrained photoacoustic microscopy (PAM), which enables simultaneous imaging of the cerebrovascular anatomy, total concentration and oxygen saturation of hemoglobin, and blood flow in awake mice. Combining these hemodynamic measurements allows us to derive two key metabolic parameters-oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO).

Multiparametric photoacoustic microscopy of the mouse brain with 300-kHz A-line rate.

Enabling simultaneous high-resolution imaging of the total concentration of hemoglobin ([Formula: see text]), oxygen saturation of hemoglobin ([Formula: see text]), and cerebral blood flow (CBF), multiparametric photoacoustic microscopy (PAM) holds the potential to quantify the cerebral metabolic rate of oxygen at the microscopic level. However, its imaging speed has been severely limited by the pulse repetition rate of the dual-wavelength photoacoustic excitation and the scanning mechanism. To address these limitations, we have developed a new generation of multiparametric PAM.

[Different Air Pollution Situations of O₃ and PM₂.₅ During Summer in Beijing].

Two different pollution situations of O₃ and PM₂.₅ during summer in Beijing were analyzed from theperspective of synoptic situations, meteorological elements, precursors, atmospheric oxidation, back-trajectories of air mass and chemical compositions of PM₂.₅.

[PM₂.₅ Background Concentration at Different Directions in Beijing in 2013].

PM₂.₅, background concentration at different directions in 2013 in Beijing was analyzed combining the techniques of mathematical statistics, physical identification and numerical simulation (CMAQ4.7.

Ultrasound-aided Multi-parametric Photoacoustic Microscopy of the Mouse Brain.

High-resolution quantitative imaging of cerebral oxygen metabolism in mice is crucial for understanding brain functions and formulating new strategies to treat neurological disorders, but remains a challenge. Here, we report on our newly developed ultrasound-aided multi-parametric photoacoustic microscopy (PAM), which enables simultaneous quantification of the total concentration of hemoglobin (CHb), the oxygen saturation of hemoglobin (sO2), and cerebral blood flow (CBF) at the microscopic level and through the intact mouse skull. The three-dimensional skull and vascular anatomies delineated by the dual-contrast (i.

[Temporal and spatial distribution characteristics of ozone in Beijing].

Ozone concentrations obtained from 35 automatic air monitoring stations in Beijing were analyzed to investigate their temporal and spatial distribution characteristics. A process with high ozone concentration in summer was analyzed. The results showed that ozone maintained relatively high concentration from May to August while in other months, the ozone concentration was at a low level.

Simultaneous photoacoustic microscopy of microvascular anatomy, oxygen saturation, and blood flow.

Capitalizing on the optical absorption of hemoglobin, photoacoustic microscopy (PAM) is uniquely capable of anatomical and functional characterization of the intact microcirculation in vivo. However, PAM of the metabolic rate of oxygen (MRO) at the microscopic level remains an unmet challenge, mainly due to the inability to simultaneously quantify microvascular diameter, oxygen saturation of hemoglobin (sO), and blood flow at the same spatial scale. To fill this technical gap, we have developed a multi-parametric PAM platform.