Association of Objectively Measured Sedentary Behavior With Arterial Stiffness: Findings From the Nijmegen Exercise Study.

Sedentary behavior (SB) may affect arterial stiffness, preceding the development of cardiovascular disease. We investigated the association of objectively measured SB with arterial stiffness. We also investigated factors that affected this association. We recruited adult volunteers and measured SB with thigh-worn accelerometery for 24 hrs/day for eight consecutive days. Central (carotid-femoral pulse wave velocity, cfPWV, gold standard) and local carotid arterial stiffness (stiffness index Beta and pressure-strain elasticity EP) were measured with ultrasound. Linear regression was used and adjusted for demographics, cardiometabolic factors, and moderate-to-vigorous physical activity (MVPA) volume. Effect modification was studied with interaction terms. Participants (N = 664, 64 (standard deviation: 11, range: 23-89) years, 397 (59.8%) male) demonstrated 9.1 (1.6) hrs/day of SB, and arterial stiffness was 8.6 (3.0) m/s for cfPWV, 6.4 (2.9) for Beta, and 87 (43) kPa for EP. SB was not associated with cfPWV (ß = 0.04 95% CI (-0.11, 0.18), p = 0.60). The association of SB with local arterial stiffness was modified by systolic blood pressure (SBP) and MVPA volume. Stratified analyses revealed positive associations of SB with Beta (ß = 0.29 (0.05, 0.53), p = 0.016) and EP (ß = 4.83 (1.39, 8.27), p = 0.006) in participants with SBP > 134 mmHg or > 103 min/day of MVPA (ß = 0.23 (0.03, 0.42), p = 0.024 and ß = 3.55 (0.82, 6.29), p = 0.011, respectively). We found no association of objectively measured SB with central arterial stiffness. However, SB was positively associated with local carotid stiffness in participants with higher SBP or MVPA levels. In certain subgroups, SB may affect carotid arterial stiffening, reinforcing the relation between SB and cardiovascular disease.

Long-term cardiovascular health status and physical functioning of nonhospitalized patients with COVID-19 compared with non-COVID-19 controls.

Coronavirus disease 2019 (COVID-19) is reported to have long-term effects on cardiovascular health and physical functioning, even in the nonhospitalized population. The physiological mechanisms underlying these long-term consequences are however less well described. We compared cardiovascular risk factors, arterial stiffness, and physical functioning in nonhospitalized patients with COVID-19, at a median of 6 mo postinfection, versus age- and sex-matched controls. Cardiovascular risk was assessed using blood pressure and biomarker concentrations (amino-terminal pro-B-type-natriuretic-peptide, high-sensitive cardiac troponin I, C-reactive protein), and arterial stiffness was assessed using carotid-femoral pulse wave velocity. Physical functioning was evaluated using accelerometry, handgrip strength, gait speed and questionnaires on fatigue, perceived general health status, and health-related quality of life (hrQoL). We included 101 former patients with COVID-19 (aged 59 [interquartile range, 55-65] yr, 58% male) and 101 controls. At 175 [126-235] days postinfection, 32% of the COVID-19 group reported residual symptoms, notably fatigue, and 7% required post-COVID-19 care. We found no differences in blood pressure, biomarker concentrations, or arterial stiffness between both groups. Former patients with COVID-19 showed a higher handgrip strength (43 [33-52] vs. 38 [30-48] kg, P = 0.004) and less sleeping time (8.8 [7.7-9.4] vs. 9.8 [8.9-10.3] h/day, P < 0.001) and reported fatigue more often than controls. Accelerometry-based habitual physical activity levels, gait speed, perception of general health status, and hrQoL were not different between groups. In conclusion, one in three nonhospitalized patients with COVID-19 reports residual symptoms at a median of 6 mo postinfection, but we were unable to relate these symptoms to increases in cardiovascular risk factors, arterial stiffness, or physical dysfunction.NEW & NOTEWORTHY We examined cardiovascular and physical functioning outcomes in nonhospitalized patients with COVID-19, at a median of 6 mo postinfection. When compared with matched controls, minor differences in physical functioning were found, but objective measures of cardiovascular risk and arterial stiffness did not differ between groups. However, one in three former patients with COVID-19 reported residual symptoms, notably fatigue. Follow-up studies should investigate the origins of residual symptoms and their long-term consequences in former, nonhospitalized patients with COVID-19.

A Standardized Protocol for the Safe Retrieval of Infectious Postmortem Human Brain for Studying Whole-Brain Pathology.

ABSTRACT: We describe a safe and standardized perfusion protocol for studying brain pathology in high-risk autopsies using a custom-designed low-cost infection containment chamber and high-resolution histology. The output quality was studied using the histological data from the whole cerebellum and brain stem processed using a high-resolution cryohistology pipeline at 0.5 µm per pixel, in-plane resolution with serial sections at 20-µm thickness. To understand the pathophysiology of highly infectious diseases, it is necessary to have a safe and cost-effective method of performing high-risk autopsies and a standardized perfusion protocol for preparing high-quality tissues. Using the low-cost infection containment chamber, we detail the cranial autopsy protocol and ex situ perfusion-fixation of 4 highly infectious adult human brains. The digitized high-resolution histology images of the Nissl-stained series reveal that most of the sections were free of processing artifacts, such as fixation damage, freezing artifacts, and osmotic shock, at the macrocellular and microcellular level. The quality of our protocol was also tested with the highly sensitive immunohistochemistry staining for specific protein markers. Our protocol provides a safe and effective method in high-risk autopsies that allows for the evaluation of pathogen-host interaction, the underlying pathophysiology, and the extent of the infection across the whole brain at microscopic resolutions.

A Lateral Flow Assay for the Detection of Leptospira lipL32 Gene Using CRISPR Technology.

The clinical manifestation of leptospirosis is often misdiagnosed as other febrile illnesses such as dengue. Therefore, there is an urgent need for a precise diagnostic tool at the field level to detect the pathogenic Leptospira lipL32 gene at the molecular level for prompt therapeutic decisions. Quantitative polymerase chain reaction (qPCR) is widely used as the primary diagnostic tool, but its applicability is limited by high equipment cost and the lack of availability in every hospital, especially in rural areas where leptospirosis mainly occurs. Here, we report the development of a CRISPR dFnCas9-based quantitative lateral flow immunoassay to detect the lipL32 gene. The developed assay showed superior performance regarding the lowest detectable limit of 1 fg/mL. The test is highly sensitive and selective, showing that leptospirosis diagnosis can be achieved with a low-cost lateral flow device.

Development and Evaluation of Europium-Based Quantitative Lateral Flow Immunoassay for the Chronic Kidney Disease Marker Cystatin-C.

This study aimed to establish a Europium label time-resolved fluorescence immunoassay (TRFIA) to detect the chronic kidney disease (CKD) biomarker Cystatin-C. An Europium based Time resolved fluorescence immunoassay was developed to detect the concentration of Cystatin-C in a urine sample to increase the sensitivity with captured anti-Cystatin-C antibodies immobilized on nitrocellulose membrane and then bonded with detection anti-Cystatin-C labelled with CM-EU, followed by fluorescence measurement using time-resolved fluorometry in 15 min. The performance of this TRFIA was evaluated using the clinical urine serum and compared with the ELISA assays. The linear calibration range was 0.015-32 µg/ml, and the limit of detection (LOD) quantified was 0.0001 µg/ml. This current work has improved the LOD of our previous work from 0.013 µg/ml to 0.001 µg/ml. These results indicated that the CM-EU nanoparticle-based LFIA is rapid, more sensitive, reliable, and reproducible for point-of-care testing of Cys-C concentrations in urine.

High-frame-rate A-mode ultrasound for calibration-free cuffless carotid pressure: feasibility study using lower body negative pressure intervention.

PURPOSE: Existing technologies to measure central blood pressure (CBP) intrinsically depend on peripheral pressure or calibration models derived from it. Pharmacological or physiological interventions yielding different central and peripheral responses compromise the accuracy of such methods. We present a high-frame-rate ultrasound technology for cuffless and calibration-free evaluation of BP from the carotid artery. The system uses a pair of single-element ultrasound transducers to capture the arterial diameter and local pulse wave velocity (PWV) for the evaluation of beat-by-beat BP employing a novel biomechanical model. MATERIALS AND METHODS: System's functionality assessment was conducted on eight male subjects (26 ± 4 years, normotensive and no history of cardiovascular risks) by perturbing pressure via short-term moderate lower body negative pressure (LBNP) intervention (-40 mmHg for 1 min). The ability of the system to capture dynamic responses of carotid pressure to LBNP was investigated and compared against the responses of peripheral pressure measured using a continuous BP monitor. RESULTS: While the carotid pressure manifested trends similar to finger measurements during LBNP, the system also captured the differential carotid-to-peripheral pressure response, which corroborates the literature. The carotid diastolic and mean pressures agreed with the finger pressures (limits-of-agreement within ±7 mmHg) and exhibited acceptable uncertainty (mean absolute errors were 2.4 ± 3.5 and 2.6 ± 4.0 mmHg, respectively). Concurrent to the literature, the carotid systolic and pulse pressures (PPs) were significantly lower than those of the finger pressures by 11.1 ± 9.4 and 11.3 ± 8.2 mmHg, respectively (p < .0001). CONCLUSIONS: The study demonstrated the method's potential for providing cuffless and calibration-free pressure measurements while reliably capturing the physiological aspects, such as PP amplification and dynamic pressure responses to intervention.

Systematic development of immunohistochemistry protocol for large cryosections-specific to non-perfused fetal brain.

BACKGROUND: Immunohistochemistry (IHC) is an important technique in understanding the expression of neurochemical molecules in the developing human brain. Despite its routine application in the research and clinical setup, the IHC protocol specific for soft fragile fetal brains that are fixed using the non-perfusion method is still limited in studying the whole brain. NEW METHOD: This study shows that the IHC protocols, using a chromogenic detection system, used in animals and adult humans are not optimal in the fetal brains. We have optimized key steps from Antigen retrieval (AR) to chromogen visualization for formalin-fixed whole-brain cryosections (20 µm) mounted on glass slides. RESULTS: We show the results from six validated, commonly used antibodies to study the fetal brain. We achieved optimal antigen retrieval with 0.1 M Boric Acid, pH 9.0 at 70°C for 20 minutes. We also present the optimal incubation duration and temperature for protein blocking and the primary antibody that results in specific antigen labeling with minimal tissue damage. COMPARISON WITH EXISTING METHODS: The IHC protocol commonly used for adult human and animal brains results in significant tissue damage in the fetal brains with little or suboptimal antigen expression. Our new method with important modifications including the temperature, duration, and choice of the alkaline buffer for AR addresses these pitfalls and provides high-quality results. CONCLUSION: The optimized IHC protocol for the developing human brain (13-22 GW) provides a high-quality, repeatable, and reliable method for studying chemoarchitecture in neurotypical and pathological conditions across different gestational ages.

Histological characterization and development of mesial surface sulci in the human brain at 13-15 gestational weeks through high-resolution histology.

Cellular-level anatomical data from early fetal brain are sparse yet critical to the understanding of neurodevelopmental disorders. We characterize the organization of the human cerebral cortex between 13 and 15 gestational weeks using high-resolution whole-brain histological data sets complimented with multimodal imaging. We observed the heretofore underrecognized, reproducible presence of infolds on the mesial surface of the cerebral hemispheres. Of note at this stage, when most of the cerebrum is occupied by lateral ventricles and the corpus callosum is incompletely developed, we postulate that these mesial infolds represent the primordial stage of cingulate, callosal, and calcarine sulci, features of mesial cortical development. Our observations are based on the multimodal approach and further include histological three-dimensional reconstruction that highlights the importance of the plane of sectioning. We describe the laminar organization of the developing cortical mantle, including these infolds from the marginal to ventricular zone, with Nissl, hematoxylin and eosin, and glial fibrillary acidic protein (GFAP) immunohistochemistry. Despite the absence of major sulci on the dorsal surface, the boundaries among the orbital, frontal, parietal, and occipital cortex were very well demarcated, primarily by the cytoarchitecture differences in the organization of the subplate (SP) and intermediate zone (IZ) in these locations. The parietal region has the thickest cortical plate (CP), SP, and IZ, whereas the orbital region shows the thinnest CP and reveals an extra cell-sparse layer above the bilaminar SP. The subcortical structures show intensely GFAP-immunolabeled soma, absent in the cerebral mantle. Our findings establish a normative neurodevelopment baseline at the early stage.

Developing technologies to assess vascular ageing: a roadmap from VascAgeNet.

Vascular ageing is the deterioration of arterial structure and function which occurs naturally with age, and which can be accelerated with disease. Measurements of vascular ageing are emerging as markers of cardiovascular risk, with potential applications in disease diagnosis and prognosis, and for guiding treatments. However, vascular ageing is not yet routinely assessed in clinical practice. A key step towards this is the development of technologies to assess vascular ageing. In this Roadmap, experts discuss several aspects of this process, including: measurement technologies; the development pipeline; clinical applications; and future research directions. The Roadmap summarises the state of the art, outlines the major challenges to overcome, and identifies potential future research directions to address these challenges.

Face-Free Chest Detection Using Convolutional Neural Networks for Non-Contact Respiration Monitoring.

Non-contact methods for monitoring respiration face limitations when it comes to selecting the chest region of interest. The semi-automatic method, which requires the user to select the chest region in the first frame, is not suitable for real-time applications. The automatic method, which tracks the face first and then detects the chest region based on the face's position, can be inaccurate if the face is not visible or is rotated. Moreover, using the face region to track the chest region can under-utilize camera pixels since the face is not essential for monitoring respiration. This approach may adversely affect the quality of the respiration signal being measured. To address these issues, we propose a face-free chest detection model based on Convolutional Neural Networks. Our model enhances the measured non-contact respiration signal quality and utilizes more pixels for the chest region alone. In our quantitative study, we demonstrate that our method outperforms traditional methods that require the presence of the face. This approach offers potential benefits for real-time, non-contact respiration monitoring applicationsClinical relevance- This work enhances the performance of non-contact respiration monitoring techniques by precisely detecting the chest region without the need of face in it through a CNN-based model. The use of the CNN-based chest detection model also enhances the real-time monitoring capabilities of non-contact respiration monitoring techniques.

Plethysmograph-Based Self-Assessment Device for Carotid-Femoral Pulse Wave Velocity Measurement: A Pilot Usability Study.

Arterial stiffness, a proxy of vascular aging is an important marker of cardiovascular events and mortality, independent of traditional risk factors. The aortic or carotid-femoral pulse wave velocity (cf-PWV) is the gold standard for determining arterial stiffness. Measuring arterial stiffness can help identify people who are at risk early on. State-of-the-art devices, majorly employing applanation tonometry at the carotid site, demand extensive skill, are costly, and are not intended for out-of-clinic use. However, a device that is suitable for homecare and primary health settings would facilitate primordial care. To address this gap, we have developed a novel easy-to-use, fully automated, and affordable photoplethysmography-based device for measuring cf-PWV. An in-vivo study on 25 subjects was conducted to investigate the device's usability by comparing self and expert-performed measurements, and by quantifying the user experience (score out of 5). A strong correlation (r = 0.88) and a statistically insignificant bias indicated the measurement reproducibility in self-versus expert-performed measurements. An average usability score of 3.98 ± 0.83 given by the participants showed the convenience and ease of use of the device. The results demonstrate the feasibility and reliability of using the device by inexperienced operators, even when newly introduced. Future clinical studies are in progress to assess the device's accuracy in comparison to gold-standard reference equipment.Clinical Relevance-This pilot study revealed the device's potential to offer a user-friendly solution for home care and other non-hospital settings.

Ultrasound for Venous Local Pulse Wave Velocity: Comparison of Pulse Transit Time Methods.

Venous pulse wave velocity (vPWV) is a potential marker for determining the state of venous hemodynamics, venosclerosis, and vascular filling. Although there have been several studies on pulse wave velocity through blood vessels, the majority have focused on arteries, with only limited studies on veins. To our knowledge, this study is the first to compare the local vPWV estimation metrices. An in vivo study was conducted on 10 participants where the jugular venous pulses (JVP) from two proximal sites were simultaneously acquired using a dual-element high frame rate system. The local vPWV was computed using different transit time-based techniques. The study demonstrates the comparison between vPWV ranges computed using thresholding, fiduciary point (c and v) and correlation-based approaches indicated as vPWV|th, vPWV|c, vPWV|v and vPWV|Xcorr respectively. High fidelity echo frames were acquired from the jugular vein (JV) at a temporal resolution of 2 ms and an amplitude resolution of 10 µm. The study findings indicated that the vPWV computed using various transit time metrics were comparable without significant bias (p > 0.05). Among the VPWV metrices, vPWV|th had the lowest beat-to-beat variation (CoV = 18 %). The mean deviations in vPWV|c, vPWV|v and vPWV|Xcorr values from vPWV|th were 0.28, 0.17 and 0.22 m/s respectively, where the average beat-to-beat variation was minimal. The results suggested that the thresholding and cross-correlation metrices offered better performance in comparison with the fiduciary point techniques for vPWV estimation.Clinical Relevance- The study demonstrated the potential of direct transit time methods to reliably estimate the local vPWV on the internal jugular vein.

Arterial Wave Separation Analysis and Reflection Wave Transit Time Estimation using a Double Rayleigh Flow Rate Model.

Arterial pulse wave separation analysis (WSA) requires simultaneously measured pressure and flow rate waveform from the same arterial site. Modelling approaches to flow rate waveforms offers a methodological and instrumentational advantage. However, current techniques are limited to the aortic site. For non-aortic sites such as carotid artery, modelling methods that were developed for aortic sites are not likely to capture the intrinsic differences in the carotid flow rate. In this work, a double-Rayleigh flow rate model for the carotid artery is developed to separate the forward and backward pressure waves using WSA (DRMWSA). The model parameters are optimally found based on characteristic features - obtained from the pressure waveform. The DRMWSA was validated using a database of 4374 virtual (healthy) subjects, and its performance was compared with actual flow rate based WSA (REFWSA) at the carotid artery. An RMSE < 2 mmHg were obtained for forward and backward pressure waveforms. The reflection quantification indices (ΔPF, ΔPB), (RM, RI) obtained from DRMWSA demonstrated strong and statistically significant correlation (r > 0.96, p < 0.001) and (r > 0.80, p < 0.001) respectively, with insignificant bias (p > 0.05), upon comparing with counterparts in REFWSA. A moderate correlation (r = 0.64, p < 0.001) was obtained for reflection wave transit time between both methods. The proposed method minimises the measurements required for WSA and has the potential to widen the vascular screening procedures incorporating carotid pulse wave dynamics.Clinical Relevance-This methodology quantifies arterial pressure wave reflections in terms of pressure augmentation and reflection transit time. The methodological advantage of using only a single waveform helps easy translation to technological solutions for clinical research.

Assessment of Endothelial Reactivity by Measurement of Vascular Material Response to Shear Stress: A Feasibility Study.

Flow-mediated dilation (FMD) evaluates the relative change in arterial diameter during hyperemia to assess the endothelial response due to a shear stimulus. However, conventional FMD measures diameter response alone and the alterations in the arterial wall's material properties during reactive hyperemia, which also influence dilation, go unaddressed. In this work, we examine the material response (MR) of the artery during reactive hyperemia using clinically relevant stiffness markers for the assessment of endothelial reactivity (ER). For this, we have developed an in-house brachial cuff control (BCC) system to continuously acquire brachial pressure which can be integrated with simultaneous measurement of brachial diameter and used to quantify the relative changes in wall property during hyperemia non-invasively. The assessment of endothelial reactivity using material response (ERAMR) was conducted on 20 healthy participants (12M/8F) and the results were compared with conventional FMD (FMD%). The mean pressure response gave an inverse trend to that of diameter response with varying magnitudes during reactive hyperemia (18.71% from baseline for diameter and 2.45% for pressure), there was a significant difference in the measurement of FMD and ERAMR (P < 0.05). The larger distribution of ERAMR compared to FMD% in box-plots further implies the inclusion of within-subject variations. Hence, ERAMR can be a potential estimate of ER, given the need for intensive validations in this line on larger cohorts.Clinical Relevance- This study demonstrates the independent role of arterial wall material properties to quantify endothelial reactivity in response to a shear stimulus.

Automation of slide staining for large tissue sections.

Staining is a critical step in tissue analysis as it enhances the visibility and contrast of tissue structures for microscopic examination. Large tissue sections such as the human brain, heart, and liver are becoming increasingly important in studying complex tissue structures, providing critical information about the tissue's normal or abnormal development, function, and disease processes. Manual staining methods are still widely used and are prone to inconsistencies and inaccuracies, leading to unreliable results. Commercially available automated staining systems offer a more efficient alternative, but currently, these systems are only available for smaller 1" x 3" slides which are ill-suited for examining larger tissue sections. To address this challenge, we present a custom-designed Large format Automated Slide Stainer that can handle various glass slides, from the standard 1" x 3" slides to the custom-sized 2" x 3", 5" x 7", and 6" x 8" glass slides. The system uses a Cartesian robotic arm to stain the slides and has a user-friendly and intuitive interface for creating and modifying custom staining protocols. Safety features include chemical isolation, a ventilation system, an emergency shutdown, and a protective shield to minimize hazards from handling chemicals and biological materials. The automated stainer showed little variability in positioning with a mean offset error of 1.65 ± 0.65 mm and 1.73 ± 0.76 mm in the X and Y axes, respectively. In addition, the automated staining process showed better uniformity than manual staining. A pairwise distance was used to evaluate how well image histograms matched within a batch. The automated staining had a mean pairwise distance of 0.0070 ± 0.0017 (Nissl) and 0.0060 ± 0.0003 (Hematoxylin and Eosin(H&E)), which were far superior to the manual staining distances (Nissl: 0.0173 ± 0.0107 and H&E: 0.0185 ± 0.0067). This system represents a substantial advancement in tissue staining and has the potential to improve the reliability of tissue analysis significantly.Clinical relevance - Automated system for providing accurate, reproducible, and high-throughput staining of large tissue sections for use in histopathology and research.

Wearable Ambulatory Accelerometer System for Estimating Arterial Stiffness: A Pilot Study.

Given the gap between the crucial role of measuring arterial stiffness in cardiovascular disease prevention and the lack of a technology for frequent/continuous measurement to assess it without an operator, we have developed a wearable accelerometer-based system. It estimates local stiffness metrics (Ep, ß, and AC) by employing a one-point patient-specific calibration on the features of acceleration plethysmogram (APG) signal. An in-vivo study on 12 subjects was conducted (a) to select suitable ones from the host features on which the calibration could be applied and (b) to assess the feasibility of reliably estimating the stiffness metrics post-exercise when calibrated prior. The acquired APG signals were found to be reliable (SNR > 38 dB) and repeatable (CoV < 10 %). By examining a correlation matrix, it was found that (a-b)/(a"-b") is a potential feature of consideration for calibration against the stiffness. Due to exercise intervention, the local stiffness metrics have physiologically perturbed by a significant amount (p < 0.05), as observed from the reference measurements. Estimated Ep was found to have statistically significant and strong correlation (r = 0.761, p < 0.05) with actual Ep value, whereas statistically significant and moderate correlation were found with estimated ß (r = 0.682, p < 0.05) and estimated AC (r = 0.615, p < 0.05) with their respective actual measures. The system demonstrated its ability to estimate post-exercise stiffness metrics using the baseline calibration, even when subject to significant physiological changes.Clinical Relevance- This study reveals the potential of the developed wearable system to be used for continuous stiffness estimation even in the presence of hemodynamic perturbations.

Automation of slide coverslipping for large tissue sections.

Coverslipping is the process of placing a cover glass or coverslip over a glass slide mounted with a stained tissue specimen without forming air bubbles, which can negatively impact the microscopic examination. While manual coverslipping is still widely used, automated systems have made the process easier and more consistent. Commercially available automated cover-slippers are limited to handling only slides that are 1" x 3", suitable for processing smaller tissue specimens. However, for larger tissue specimens sectioned from organs like the brain, liver, etc., slides can reach sizes up to 6" x 8", exceeding the capabilities of these systems. We present SLIDE PROTEKT, a fully automated large format coverslipping system designed to efficiently coverslip large format slides. This system has multiple zones for slide and coverslip transportation, dispensing of mounting medium, and precise placement of the coverslip without air bubbles. The ability of the system to output quality coverslipped slides was validated by processing 50 large-format brain tissue slides. The results were found to be comparable to manual coverslipping. The system achieved a coverslip placement accuracy of 80% with a mean positional offset that was within a tolerance of ±3 millimeters. Additionally, 75% of the slides had no air bubbles, while the remaining slides had air bubbles that were less than 120 micrometers in size. These results demonstrate the potential impact of SLIDE PROTEKT in the field of histology.

Normalization of Flow-mediated Dilation to Brachial Artery Material Property: A Feasibility Study.

Endothelial reactivity (ER) is widely measured using flow-mediated dilation (FMD) of brachial artery. Conventional measurement of FMD is influenced by factors such as input shear stress, arterial transmural pressure, diameter and thereby arterial material properties (ε). Thus, for a reliable interpretation of FMD, it has to be normalized with respect to the above confounding factors. Normalization of FMD with shear stress at the time of measurement has been reported to reduce measurement variability. However, its widespread usage among the research community is limited. In this work, we examine the feasibility of normalizing the brachial FMD index (FMD%) to ε : extrema (εp), baseline (εb) and extrema change (∆ε) post-ischemia using its inter-day variability against FMD. In-vivo measurements were performed on 10 participants for 2 consecutive days and simultaneous pressure-diameter cycles were collected to estimate the material properties during reactive hyperemia (RH). The box-whisker plot reveals differences in the mean and deviation of FMD to FMD|εb. A significant value for repeatability (ICC ≥ 0.6) was obtained for normalized FMD (FMD|εb) for specific stiffness index (ß), pressure-strain elastic modulus (Ep), and local pulse wave velocity (PWV) as compared to FMD. Hence, normalization of FMD% to arterial ε can potentially improve the measurement reliability of ER assessment.Clinical Relevance- This pilot study demonstrates the feasibility of brachial artery stiffness assessment during FMD and its potential use for normalizing the standard FMD measurement.

Wide field block face imaging using deep ultraviolet induced autofluorescence of the human brain.

BACKGROUND: Imaging large volume human brains at cellular resolution involve histological methods that cause structural changes. A reference point prior to sectioning is needed to quantify these changes and is achieved by serial block face imaging (BFI) methods that have been applied to small volume tissue (∼1 cm3). NEW METHOD: We have developed a BFI uniquely designed for large volume tissues (∼1300 cm3) with a very large field of view (20 × 20 cm) at a resolution of 70 µm/pixel under deep ultraviolet (UV-C) illumination which highlights key features. RESULTS: The UV-C imaging ensures high contrast imaging of the brain tissue and highlights salient features of the brain. The system is designed to provide uniform and stable illumination across the entire surface area of the tissue and to work at low temperatures, which are required during cryosectioning. Most importantly, it has been designed to maintain its optical focus over the large depth of tissue and over long periods of time, without readjustments. The BFI was installed within a cryomacrotome, and was used to image a large cryoblock of an adult human cerebellum and brainstem (∼6 cm depth resulting in 2995 serial images) with precise optical focus and no loss during continuous serial acquisition. COMPARISON WITH EXISTING METHOD(S): The deep UV-C induced BFI highlights several large fibre tracts within the brain including the cerebellar peduncles, and the corticospinal tract providing important advantage over white light BFI. CONCLUSIONS: The 3D reconstructed serial BFI images can assist in the registration and alignment of the microscopic high-resolution histological tissue sections.

A Pilot Observational Cohort Study to Investigate the Effect of Valsalva Maneuver on Internal Jugular Venous Diameter.

Valsalva maneuver (VM) is a technique widely used for acute elevation of blood pressure in humans. It has potential applications in cardiac health prediction and is also a diagnostic tool in cardiovascular, neurology and ENT screening. The jugular venous (JV) diameter increases during the VM procedure and hence it has been widely used to aid central venous catheterization in medical units. In this pilot study, we have quantified the variation in JV diameter response to VM across young and middle-aged populations. The study was conducted on a cohort of 16 males and 11 females, where the JV diameter in baseline, during and post VM intervention were acquired using a B-mode imaging system. The JV diameter measurements were within the ranges specified in earlier literature. The beat-to-beat variability in baseline diameter measurements was found to be between 8% to 20%. In younger population, the average maximum JV diameter during baseline was found to be 9.25 ± 2.61 mm and in middle-aged population it was 12.49 ± 2.65 mm. The average maximum JV diameter in young and middle-aged population during VM was 11.66 ± 2.74 mm and 16.73 ± 3.28 mm respectively. The study findings suggested a statistically significant variation (p < 0.05) between the JV diameter responses from young and middle-aged populations. The JV distensibility decreased significantly during VM in younger cohort (-35%) in comparison with the minimal changes observed in middle-aged population. The study demonstrates the variation in JV diameter and distensibility to VM in young and middle-aged populations.Clinical Relevance- This pilot study reveals the variations in JV diameter in response to VM intervention in young and middle-aged groups which has potential utility in assessing age dependent changes in vasculature.