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The gut associated lymphoid tissue is responsible for specific responses to intestinal antigens. During HIV infection, mucosal immune deficiency may account for the gastrointestinal infections. In this review we describe the humoral and cellular mucosal immune responses in normal and HIV-infected subjects.

The mucosa associated lymphoid tissue regulates and coordinates immune responses against mucosal pathogens. Mucosal tissues are the major targets exposed to HIV during transmission. In this paper we describe in vitro models of HIV mucosal infection using human explants to investigate target cells within this tissue.

Understanding the physiological processes in aging and how neurodegenerative disorders affect cognitive function is a high priority for advancing human health. One specific area of recently enabled research is the in vivo biomechanical state of the brain. This study utilized reverberant optical coherence elastography, a high-resolution elasticity imaging method, to investigate stiffness changes during the sleep/wake cycle, aging, and Alzheimer's disease in murine models. Four-dimensional scans of 44 wildtype mice, 13 mice with deletion of aquaporin-4 water channel, and 12 mice with Alzheimer-related pathology (APP/PS1) demonstrated that (1) cortical tissue became softer (on the order of a 10% decrease in shear wave speed) when young wildtype mice transitioned from wake to anesthetized, yet this effect was lost in aging and with mice overexpressing amyloid-β or lacking the water channel AQP4. (2) Cortical stiffness increased with age in all mice lines, but wildtype mice exhibited the most prominent changes as a function of aging. The study provides novel insight into the brain's biomechanics, the constraints of fluid flow, and how the state of brain activity affects basic properties of cortical tissues., Competing Interests: Declaration of competing interest Authors declare that they have no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: A decreased autophagic capacity of bone marrow mesenchymal stromal cells (BMSCs) has been suggested to be an important cause of decreased osteogenic differentiation. A pharmacological increase in autophagy of BMSCs is a potential therapeutic option to increase osteoblast viability and ameliorate osteoporosis., Aim: To explore the effects of sinomenine (SIN) on the osteogenic differentiation of BMSCs and the underlying mechanisms., Methods: For in vitro experiments, BMSCs were extracted from sham-treated mice and ovariectomized mice, and the levels of autophagy markers and osteogenic differentiation were examined after treatment with the appropriate concentrations of SIN and the autophagy inhibitor 3-methyladenine. In vivo , the therapeutic effect of SIN was verified by establishing an ovariectomy-induced mouse model and by morphological and histological assays of the mouse femur., Results: SIN reduced the levels of AKT and mammalian target of the rapamycin (mTOR) phosphorylation in the phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR signaling pathway, inhibited mTOR activity, and increased autophagy ability of BMSCs, thereby promoting the osteogenic differentiation of BMSCs and effectively alleviating bone loss in ovariectomized mice in vivo ., Conclusion: The Chinese medicine SIN has potential for the treatment of various types of osteoporosis, bone homeostasis disorders, and autophagy-related diseases., Competing Interests: Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article., (©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.)

Objective . Elastography of the brain has the potential to reveal subtle but clinically important changes in the structure and composition as a function of age, disease, and injury. Approach . In order to quantify the specific effects of aging on mouse brain elastography, and to determine the key factors influencing observed changes, we applied optical coherence tomography reverberant shear wave elastography at 2000 Hz to a group of wild-type healthy mice ranging from young to old age. Main results . We found a strong trend towards increasing stiffness with age, with an approximately 30% increase in shear wave speed from 2 months to 30 months within this sampled group. Furthermore, this appears to be strongly correlated with decreasing measures of whole brain fluid content, so older brains have less water and are stiffer. Rheological models are applied, and the strong effect is captured by specific assignment of changes to the glymphatic compartment of the brain fluid structures along with a correlated change in the parenchymal stiffness. Significance . Short-term and longer-term changes in elastography measures may provide a sensitive biomarker of progressive and fine-scale changes in the glymphatic fluid channels and parenchymal components of the brain., (Creative Commons Attribution license.)

As elastography of the brain finds increasing clinical applications, fundamental questions remain about baseline viscoelastic properties of the brain in vivo . Furthermore, the underlying mechanisms of how and why elastographic measures can change over time are still not well understood. To study these issues, reverberant shear wave elastography using an optical coherence tomography scanner is implemented on a mouse model, both under awake conditions and in a sleep state where there are known changes in the glymphatic fluid flow system in the brain. We find that shear wave speed, a measure of stiffness, changes by approximately 12% between the two states, sleep versus awake, in the entire cortical brain imaging volume. Our microchannel flow model of biphasic (fluid plus solid) tissue provides a plausible rheological model based on the fractal branching vascular and perivascular system, plus a second parallel system representing the finer scale glymphatic fluid microchannels. By adjusting the glymphatic system fluid volume proportional to the known sleep/wake changes, we are able to approximately predict the measured shear wave speeds and their change with the state of the glymphatic system. The advantages of this model are that its main parameters are derived from anatomical measures and are linked to other major derivations of branching fluid structures including Murray's Law. The implications for clinical studies are that elastography of the brain is strongly influenced by the regulation or dysregulation of the vascular, perivascular, and glymphatic systems., (© 2022 Institute of Physics and Engineering in Medicine.)

Elastography researchers have utilized several rheological models to characterize soft tissue viscoelasticity over the past thirty years. Due to the frequency-dependent behavior of viscoelastic parameters as well as the different techniques and frequencies employed in various studies of soft tissues, rheological models have value in standardizing disparate techniques via explicit mathematical representations. However, the important question remains: which of the several available models should be considered for widespread adoption within a theoretical framework? We address this by evaluating the performance of three well established rheological models to characterize ex vivo bovine liver tissues: the Kelvin-Voigt (KV) model as a 2-parameter model, and the standard linear solid (SLS) and Kelvin-Voigt fractional derivative (KVFD) models as 3-parameter models. The assessments were based on the analysis of time domain behavior (using stress relaxation tests) and frequency domain behavior (by measuring shear wave speed (SWS) dispersion). SWS was measured over a wide range of frequency from 1 Hz to 1 kHz using three different tests: (i) harmonic shear tests using a rheometer, (ii) reverberant shear wave (RSW) ultrasound elastography scans, and (iii) RSW optical coherence elastography scans, with each test targeting a distinct frequency range. Our results demonstrated that the KVFD model produces the only mutually consistent rendering of time and frequency domain data for liver. Furthermore, it reduces to a 2-parameter model for liver (correspondingly to a 2-parameter "spring-pot" or power-law model for SWS dispersion) and provides the most accurate predictions of the material viscoelastic behavior in time (>98% accuracy) and frequency (>96% accuracy) domains. STATEMENT OF SIGNIFICANCE: Rheological models are applied in quantifying tissues viscoelastic properties. This study is unique in presenting comprehensive assessments of rheological models., Competing Interests: Declaration of Competing Interest The authors declare no potential conflicts of interest with respect to this article., (Copyright © 2022. Published by Elsevier Ltd.)

Speckle statistics in ultrasound and optical coherence tomography have been studied using various distributions, including the Rayleigh, the K, and the more recently proposed Burr distribution. In this paper, we expand on the utility of the Burr distribution by first validating its theoretical framework with numerical simulations and then introducing a new local estimator to characterize sample tissues of liver, brain, and skin using optical coherence tomography. The spatially local estimates of the Burr distribution's power-law or exponent parameter enable a new type of parametric image. The simulation and experimental results confirm the potential for various applications of the Burr distribution in both basic science and clinical realms., Competing Interests: The authors declare no conflicts of interest., (© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.)

Significance: Corneal cross-linking (CXL) is a well-known procedure for treating certain eye disorders such as keratoconus. However, characterization of the biomechanical changes in the cornea as a result of this procedure is still under active research. Specifically, there is a clinical need for high-resolution characterization of individual corneal layers., Aim: A high-resolution elastography method in conjunction with a custom optical coherence tomography system is used to track these biomechanical changes in individual corneal layers. Pre- and post-treatment analysis for both low-dose and high-dose CXL experiments are performed., Approach: A recently developed elastography technique that utilizes the theory of reverberant shear wave fields, with optical coherence tomography as the modality, is applied to pig corneas ex vivo to evaluate elasticity changes associated with corneal CXL. Sets of low-dose and high-dose CXL treatments are evaluated before and after treatments with three pairs of pig corneas per experiment., Results: The reverberant three-dimensional (3D) optical coherence elastography (OCE) technique can identify increases in elasticity associated with both low-dose and high-dose CXL treatments. There is a notable graphical difference between low-dose and high-dose treatments. In addition, the technique is able to identify which layers of the cornea are potentially affected by the CXL procedure and provides insight into the nonlinearity of the elasticity changes., Conclusions: The reverberant 3D OCE technique can identify depth-resolved changes in elasticity of the cornea associated with CXL procedures. This method could be translated to assess and monitor CXL efficacy in various clinical settings.

The speckle statistics of optical coherence tomography images of biological tissue have been studied using several historical probability density functions. Here, we propose a new theoretical framework based on power-law functions, where we hypothesize that an underlying power-law distribution governs scattering from tissues. Thus, multi-scale scattering sites including the fractal branching vasculature will contribute to power-law probability distributions of speckle statistics. Specifically, these are the Burr type XII distribution for speckle amplitude, the Lomax distribution for intensity, and the generalized logistic distribution for log amplitude. Experimentally, these three distributions are fitted to histogram data from nine optical coherence tomography scans of various samples and biological tissues, in vivo and ex vivo . The distributions are also compared with classical models such as the Rayleigh, K, and gamma distributions. The results indicate that across OCT datasets of various tissue types, the proposed power-law distributions are more appropriate models yielding novel parameters for characterizing the physics of scattering from biological tissue. Thus, the overall framework brings to the field new biomarkers from OCT measures of speckle in tissues, grounded in basic biophysics and with wide applications to diagnostic imaging in clinical use., Competing Interests: The authors declare no conflicts of interest., (© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

In dynamic optical coherence elastography (OCE), surface acoustic waves are the predominant perturbations. They constrain the quantification of elastic modulus to the direction of wave propagation only along the surface of tissues, and disregard elasticity gradients along depth. Longitudinal shear waves (LSW), on the other hand, can be generated at the surface of the tissue and propagate through depth with desirable properties for OCE: (1) LSW travel at the shear wave speed and can discriminate elasticity gradients along depth, and (2) the displacement of LSW is longitudinally polarized along the direction of propagation; therefore, it can be measured by a phase-sensitive optical coherence tomography system. In this study, we explore the capabilities of LSW generated by a circular glass plate in contact with a sample using numerical simulations and tissue-mimicking phantom experiments. Results demonstrate the potential of LSW in detecting an elasticity gradient along axial and lateral directions simultaneously. Finally, LSW are used for the elastography of ex vivo mouse brain and demonstrate important implications in in vivo and in situ measurements of local elasticity changes in brain and how they might correlate with the onset and progression of degenerative brain diseases., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

Test disk electrodes were fabricated from carbon nanotubes (CNT) using the Carbon Nanotube Templated Microfabrication (CNT-M) technique. The CNT-M process uses patterned growth of carbon nanotube forests from surfaces to form complex patterns, enabling electrode sizing and shaping. The additional carbon infiltration process stabilizes these structures for further processing and handling. At a macroscopic scale, the electrochemical, electrical and magnetic properties, and magnetic resonance imaging (MRI) characteristics of the disk electrodes were investigated; their microstructure was also assessed. CNT disk electrodes showed electrical resistivity around 1 Ω·cm, charge storage capacity between 3.4 and 38.4 mC/cm 2 , low electrochemical impedance and magnetic susceptibility of -5.9 to -8.1 ppm, closely matched to that of tissue (∼-9 ppm). Phantom MR imaging experiments showed almost no distortion caused by these electrodes compared with Cu and Pt-Ir reference electrodes, indicating the potential for significant improvement in accurate tip visualization., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Microelectrode arrays of carbon nanotube (CNT)/carbon composite posts with high aspect ratio and millimeter-length were fabricated using carbon-nanotube-templated microfabrication with a sacrificial "hedge". The high aspect ratio, mechanical robustness, and electrical conductivity of these electrodes make them a potential candidate for next-generation neural interfacing. Electrochemical measurements were also demonstrated using an individual CNT post microelectrode with a diameter of 25 μm and a length of 1 mm to perform cyclic voltammetry on both methyl viologen and dopamine in a phosphate-buffered saline solution. In addition to detection of the characteristic peaks, the CNT post microelectrodes show a fast electrochemical response, which may be enabling for in vivo and/or in vitro measurements. The CNT post electrode fabrication process was also integrated with other microfabrication techniques, resulting in individually addressable electrodes.

The H-scan analysis of ultrasound images is a matched-filter approach derived from analysis of scattering from incident pulses in the form of Gaussian-weighted Hermite polynomial functions. This framework is applied in a preliminary study of thyroid lesions to examine the H-scan outputs for three categories: normal thyroid, benign lesions, and cancerous lesions within a total group size of 46 patients. In addition, phantoms comprised of spherical scatterers are analyzed to establish independent reference values for comparison. The results demonstrate a small but significant difference in some measures of the H-scan channel outputs between the different groups.