Biology subjects

Saulnier, R.

Publications and source records attributed to Saulnier, R..

3 recordsLinked to original sources

bioRxiv2024

Investigating the effects of protons versus x-rays on radiation-induced lymphopenia after brain irradiation

BackgroundConventional x-ray-based radiotherapy is a standard treatment for patients with brain tumors. However, is associated with systemic effects like lymphopenia that correlates with poor prognosis. Proton therapy has emerged as a new radiation strategy, given that the lower entry dose and absence of exit dose can be exploited to spare healthy brain tissues and reduce side-effects caused by systemic inflammation. We evaluated if brain irradiation with protons could spare circulating leukocytes along with other variables in rodent models. MethodsTumor-free C57BL/6 mice were irradiated with a total dose of 20Gy in 2.5Gy twice-daily sessions over four consecutive days with either x-rays or protons. Groups of mice were defined according to irradiation volume (whole-brain or hemisphere) and dose rate (1 or 2Gy/min). Blood was withdrawn at various time points and circulating lymphoid, with myeloid subpopulations analyzed using flow cytometry. Brain tissue histochemical analyses were performed late after irradiation. ResultsBlood sampling showed severe and acute radiation-induced lymphopenia after x-rays, with marked depletion of 50% CD4+ and CD8+, as well as B and NK cells. With protons, the decrease was 20% on average for whole-brain irradiations, suggesting a conservative effect on circulating lymphocytes. The data showed no effect in CD11b+ myeloid cells for both x-rays and protons. Histological analyses revealed a more intense expression level of CD68 and Iba1 immunostaining after x-ray irradiation. GFAP staining was well detected after both beams. ConclusionProton therapy for brain tumors differs from photon therapy in terms of its effects on circulating cells and tissues. Key pointsO_LIX-ray brain irradiation induced an acute severe lymphopenia, with a reduction of at least 50% lymphocytes. The whole-brain irradiation caused a more pronounced decrease in lymphocytes than hemisphere irradiation. Proton brain irradiation exhibited a conservative effect on circulating leukocytes. C_LIO_LIX-ray irradiation-induced lymphopenia is followed by a recovery of all lymphocyte subpopulations to control levels. However, this recovery is longer for CD3+ lymphocytes, and B and NK cells, depending on irradiation modalities. C_LIO_LILong-term brain tissue histochemical analyses demonstrated differences between the two beams, consisting of a macrophage/microglial activation seen mostly after x-rays while an astrocyte reaction was seen after brain exposure to the two beams. These differences may explain the disparities observed in leukocytes, thereby favoring a specific biological reaction between the brain and blood. C_LI Importance of the StudyOur study demonstrated that while whole-brain or hemispheric irradiation with x-rays resulted in lymphopenia, proton brain irradiation exhibited a conservative effect on circulating lymphocytes, which was paralleled by a less intense brain tissue reaction.

cell biology↗

bioRxiv2024

3D Transcranial ultrasound localization microscopy reveals major arteries in the sheep brain

ObjectiveStroke, a leading cause of mortality and disability globally, demands swift and accurate diagnosis for effective treatment. Although MRI and CT scans serve as conventional methods, their accessibility remains a challenge, prompting exploration into alternative, portable, and non-ionizing imaging solutions like ultrasound with reduced costs. While Ultrasound Localization Microscopy (ULM) displays potential in high-resolution vessel imaging, its 2D constraints limit its emergency utility. Materials and MethodsThis study delves into the feasibility of 3D ULM with multiplexed probe for transcranial vessel imaging in sheep brains, emulating human skull characteristics. Three sheep underwent 3D ULM imaging, compared with angiographic MRI, while skull characterization was conducted in vivo using ultrashort bone MRI sequences and ex vivo via micro CT. Results and conclusionsThe study showcased 3D ULMs ability to highlight vessels, down to the Circle of Willis, yet within a confined 3D field-of-view. Future enhancements in signal, aberration correction, and human trials hold promise for a portable, volumetric, transcranial ultrasound angiography system. Summary statement3D Ultrasound localization microscopy, using a low-frequency matrix probe, enables transcranial reconstruction of the main vessels in sheep brains.

physiology↗

bioRxiv2022

Validation of the EEG signal of the URGOnight neurofeedback device, associated with a new SMR detection method

Sensorimotor (SMR) neurofeedback is a promising therapy for several health disorders but is still not widely used due to the high cost of the equipment. URGOnight offers a low-cost solution to democratize these therapies by providing an at-home EEG headband with dry electrodes connected to a mobile application. The first aim of this study is both to validate the URGOnight EEG signal and to compare it to Enobio-20, a medical grade EEG device. The second aim of the study is to propose a new method to detect SMR rhythm based on its oscillatory properties and discriminate it from alpha oscillations. In our study, we compared the URGOnight headband EEG signal (C3/C4) to Enobio-20 (CP3/CP4), placed on subjects simultaneously equipped with the two headbands. All subjects (n=33) performed a dual blocking task inspired by Kulhman (1978) based on the blocking effect of movement and eyes opening on SMR and alpha respectively. This task was followed by SSVEP stimulations to evaluate the frequency response of the two EEG devices. The performance of the EEG headbands was statistically identical for most of the characteristics of the EEG signal, including the frequency response to SSVEP (from 4Hz to 20Hz). The main difference was a larger amplitude in the 8-15Hz due to the location of the reference in URGOnight that did not impair the detection of both alpha and SMR. In addition, we show that our new method allows to discriminate alpha and SMR rhythms based on their oscillatory properties with a single recording site (C3/C4). The method is fast enough to be used in real time. We show that the detected SMR rhythm is modulated by movement as opposed to the 12-15Hz frequency band often used as indicator of SMR in most neurofeedback studies. Altogether, our results validate the quality of the EEG recordings obtained with URGOnight since it gives similar results as the one obtained with Enobio-20, a validated EEG medical grade system. In addition, we provide a new method allowing the identification and the separation of the alpha and SMR with a single recording site C3/C4. This method opens up a new research lead to improve SMR neurofeedback efficiency and thus of its clinical possibilities by focusing on the reinforcement of the SMR oscillation strictly speaking. Highlights- Validation of the URGOnight EEG device suitable for neurofeedback at home - New method for the detection and the discrimination of alpha rhythm and SMR rhythm with a small number of recording sites - The oscillatory activity related to the SMR displays different properties compared to the 12-15Hz frequency band. - Description of a full validation procedure for wireless EEG devices usable at home for neurofeedback - Comparison of the signal of URGOnight (dry electrodes) with a wet electrode EEG device

neuroscience↗