Biology subjects

Amaral, M. M.

Publications and source records attributed to Amaral, M. M..

5 recordsLinked to original sources

bioRxiv2025

Application of Spectral Domain Optical Coherence Tomography To Guide Cochlear Implant Electrode Array

HypothesisA custom spectral domain optical coherence tomography (SD-OCT) platform can be used for real-time guidance of a cochlear implant electrode array (EA). BackgroundWith current cochlear implant surgical techniques, placement of the EA is a blind maneuver in which the surgeon relies on tactile feedback as the EA advances through the cochlear lumen. Cochlear implant trauma is a leading factor for poor speech performance outcomes and loss of residual hearing following surgery. Optical coherence tomography (OCT) is a non-invasive imaging modality that provides real-time visualization of tissue microstructure at higher spatial resolutions compared to clinical CT and MRI. Already adopted as standard of care in ophthalmology, OCT has the potential to assist the surgeon in real-time visualization of the EA trajectory. Unlike commercial systems, our custom OCT system allows tailored wavelength, scanning geometry, and real-time processing, which are critical factors for navigating the compact anatomy of the facial recess to image the cochlea. MethodsA custom-built SD-OCT system was used to image cochlear microanatomy in mice and human cadaveric temporal bones. The OCT system was then used to guide a mock EA in human cadaveric temporal bones in real-time using individual B scans that were reviewed sequentially as the EA was being advanced through the round window. ResultsUsing our OCT system, high-resolution (< 5.0 m) images of cochlear microanatomy were obtained in both mice and cadaveric human temporal bones with an image sensitivity of [~]104 dB. Following cochleostomy in cadaveric temporal bones, real-time sequential OCT B-scans were used to reliably guide placement of the EA through the scala tympani. ConclusionOur custom-built SD-OCT platform can generate high-resolution real-time visualization and orientation of mammalian cochlear microanatomy that can be used to assist with real time guidance of a CI EA. This technology has the potential to serve as a real-time surgical image guidance tool to minimize EA trauma and further our understanding of human cochlear pathophysiology.

bioengineering↗

bioRxiv2024

Label free, capillary-scale blood flow mapping in vivo reveals that low intensity focused ultrasound evokes persistent dilation in cortical microvasculature

Non-invasive, low intensity focused ultrasound (FUS) is an emerging neuromodulation technique that offers the potential for precision, personalized therapy. An increasing body of research has identified mechanosensitive ion channels that can be modulated by FUS and support acute electrical activity in neurons. However, neuromodulatory effects that persist from hours to days have also been reported. The brains ability to provide targeted blood flow to electrically active regions involve a multitude of non-neuronal cell types and signaling pathways in the cerebral vasculature; an open question is whether persistent effects can be attributed, at least partly, to vascular mechanisms. Using a novel in vivo optical approach, we found that microvascular responses, unlike larger vessels which prior investigations have explored, exhibit persistent dilation following sonication without the use of microbubbles. This finding and approach offers a heretofore unseen aspect of the effects of FUS in vivo and indicate that concurrent changes in neurovascular function may partially underly persistent neuromodulatory effects.

neuroscience↗

bioRxiv2023

Three-dimensional imaging and quantification of mouse ovarian follicles via optical coherence tomography

Ovarian tissue cryopreservation has been successfully applied worldwide for fertility preservation. Correctly selecting the ovarian tissue with high follicle loading for freezing and reimplantation increases the likelihood of restoring ovarian function, but it is a challenging process. In this work, we explore the use of three-dimensional spectral-domain optical coherence tomography (SD-OCT) to identify different follicular stages, especially primary follicles, compare the identifications with H&E images, and measure the size and age-related follicular density distribution differences in mice ovaries. We use the thickness of the layers of granulosa cells to differentiate primordial and primary follicles from secondary follicles. The measured dimensions and age-related follicular distribution agree well with histological images and physiological aging. Finally, we apply attenuation coefficient map analyses to significantly improve the image contrast and the contrast-to-noise ratio (p < 0.001), facilitating follicle identification and quantification. We conclude that SD-OCT is a promising method to noninvasively evaluate ovarian follicles.

bioengineering↗

bioRxiv2022

Detection and characterization of circulating microvesicles containing Shiga toxin type 2 (Stx2) in a rat model of Hemolytic Uremic Syndrome

Shiga toxin (Stx) producing Escherichia coli (STEC) are foodborne pathogens that release Stx and may develop Hemolytic Uremic Syndrome (HUS). Stx causes endothelial cell damage and leads to platelets deposition and thrombi formation within the microvasculature. It has been described that Stx activates blood cells and induces the shedding of proinflammatory and prothrombotic microvesicles (MVs) containing the toxin. In this sense, it has been postulated that MVs containing Stx2 (MVs-Stx2+) can contribute to the physiopathology of HUS, allowing Stx to reach the target organs and evading the immune system. In this work, we propose that circulating MVs-Stx2+ can be a potential biomarker for the diagnosis and prognosis of STEC infections and HUS progression. In this regard, we developed a rat HUS model by the intreperitoneal injection of a sublethal dose of Stx2 and observed: decrease in body weight, increase of creatinine and urea levels, decrease of creatinine clearance and histological renal damages. After characterization of renal damages we investigated circulating total MVs and MVs-Stx2+ by flow cytometry at different times after Stx2 injection. Additionally, we evaluated the correlation of biochemical parameters such as creatinine and urea in plasma with MVs-Stx2+. As a result, we found a significant circulation of Mvs-Stx2+ at 96 hours after Stx2 injection, nevertheless no correlation with creatinine and urea plasma levels were detected. Our results suggest that MVs-Stx2+ may be an additional biomarker for the characterization and diagnosis of HUS progression. Further analysis is required in order to validate MVs-Stx2+ as biomarker of the disease.

pathology↗

bioRxiv2021

Effects of bacterial lipopolysaccharide and Shiga Toxin on induced Pluripotent Stem Cell-derived Mesenchymal Stem Cells

BackgroundMesenchymal Stem Cells can be activated and respond to different bacterial toxins. Lipopolysaccharides (LPS) and Shiga Toxin (Stx) are the two main bacterial toxins present in Hemolytic Uremic Syndrome (HUS) that cause endothelial damage. In this work we aimed to study the response of iPSC-MSC to LPS and/or Stx and its effect on the restoration of injured endothelial cells. MethodsiPSC-MSC were used as a source of mesenchymal stem cells (MSC) and Human Microvascular Endothelial Cells-1 (HMEC-1) as a source of endothelial cells. iPSC-MSC were treated or not with LPS and/or Stx. For some experiments, Conditioned Media (CM) were collected from each plate and incubated with an anti-Stx antibody to block the direct effect of Stx, or Polymyxin to block the direct effect of LPS. In CM from both treatments, anti-Stx and Polymyxin were used. Results are expressed as mean {+/-} S.E.M. Significant differences (p<0.05) were identified using one way analysis of variance (ANOVA) and Bonferronis Multiple comparison test. ResultsThe results obtained showed that LPS induced a pro-inflammatory profile on iPSC-MSC, but not Stx, even though they expressed Gb3 receptor. Moreover, LPS induced on iPSC-MSC an increment in migration and adhesion to gelatin substrate. Also, the addition of CM of iPSC-MSC treated with LPS+Stx, decreased the capacity of HMEC-1 to close a wound, and did not favor the formation of new tubes. Proteomic analysis of iPSC-MSC treated with LPS and/or Stx revealed specific protein secretion patterns that support many of the functional results described here. ConclusionsIn conclusion, these results suggest that iPSC-MSC activated by LPS acquired a pro-inflammatory profile that induces migration and adhesion to extracellular matrix proteins (ECM), but the combination LPS+Stx decreased the repair of endothelial damage. The importance of this work is that it provides knowledge to understand the context in which iPSC-MSC could benefit or not the restoration of tissue injury, taking into account that the inflammatory context in response to a particular bacterial toxin is relevant for iPSC-MSC immunomodulation.

immunology↗