Local cerebral blood volume (CBV) and capillary flow changes in regions of depolarizing neurons during K þ -induced cortical spreading depression (CSD) in the cerebral cortex of a-chloraloseurethane-anesthetized rats were examined employing a transillumination (550 nm) video system. Capillary flow was calculated as the reciprocal of mean transit times of blood in pixels of 40 lm  40 lm, each of which contains a few capillaries. Potassium microinjection into the cortex evoked repetitive wave-ring spreads of oligemia at a speed of ca. 2.3370.48 mm/min. During the spread of CSD, tracer (either saline or carbon black) was injected into the internal carotid artery. Colocated with the oligemic wave, we detected capillary flow stop as evidenced by disappearance of the hemodilution curves. At any location in the region of interest within the cerebral cortex, we observed cyclic changes of capillary flow stop/hyperperfusion in synchrony with oligemia/ hyperemia fluctuations. The initial flow stop and oligemia were ascribed to capillary compression by astroglial cell swelling, presumably at the pericapillary endfeet, since the oligemia occurred before larger vessel changes. We conclude that local depolarizing neurons can decrease adjacent capillary flow directly and immediately, most likely via astroglial cell swelling, and that the flow stop triggers upstream arteriolar dilatation for capillary hyperperfusion.
Mobile phones have been used to monitor mobility changes during the COVID-19 pandemic but surprisingly few studies addressed in detail the implementation of practical applications involving whole populations. We report a method of generating a “mobility-index” and a “stay-at-home/resting-index” based on aggregated anonymous Call Detail Records of almost all subscribers in Hungary, which tracks all phones, examining their strengths and weaknesses, comparing it with Community Mobility Reports from Google, limited to smartphone data. The impact of policy changes, such as school closures, could be identified with sufficient granularity to capture a rush to shops prior to imposition of restrictions. Anecdotal reports of large scale movement of Hungarians to holiday homes were confirmed. At the national level, our results correlated well with Google mobility data, but there were some differences at weekends and national holidays, which can be explained by methodological differences. Mobile phones offer a means to analyse population movement but there are several technical and privacy issues. Overcoming these, our method is a practical and inexpensive way forward, achieving high levels of accuracy and resolution, especially where uptake of smartphones is modest, although it is not an alternative to smartphone-based solutions used for contact tracing and quarantine monitoring.
In pentobarbital-anesthetized male Sprague-Dawley rats, a small cranial window was trephined, and the cortex was transilluminated with a fine glass fiber inserted into the brain parenchyma. The light intensity at the surface area of 2 x 2 mm was recorded during intracarotid injection of 25 microl of carbon black (CB) solution. The region of interest (ROI) was divided into a 50 x 50 matrix, and the mean transit time of CB transport was calculated in each matrix element. We found rapid transits of CB along the microvasculature, with considerable heterogeneity in the avascular area, and heterogeneous efficiency in autoregulatory capacity in the ROI during hypotension. The method was validated by comparison with laser-Doppler flowmetry. The average mean difference was 0.03 +/- 0. 05%. Five percent CO(2) inhalation increased the flow by 85%, but heterogeneously. We concluded that the technique is exclusively sensitive to indicator transits in a very small area on the brain surface with potential usefulness in detecting regional heterogeneity in blood flow.
High-speed camera investigation of rapidly moving red blood cells (RBCs) in the microvasculature has been limited by an inability to handle the vast volume of data. We have developed a novel method to analyze large numbers of RBC images captured by a high-resolution, high-speed camera fitted on a confocal fluorescence microscope, to determine the velocities of individual RBCs in capillaries in vivo. Fluorescein isothiocyanate (FITC)-labeled RBCs flowing in the microvasculature of the cerebral cortex of urethane-anesthetized Wistar rats were recorded through the skull window on video clips during specified periods at high frame rates (500 fps). Sequential frames of moving RBCs in the video clips for a specified period were analyzed offline with in-house software (KEIO-IS2). Images of RBCs acquired were numbered automatically in order of appearance and displayed in a two-dimensional (2-D) RBC tracking map. The velocities of individual RBCs were automatically computed based on the RBC displacement per frame multiplied by the frame rate (fps), and the results were displayed in a 2-D velocity map and a 2-D RBC number map. Single capillaries were identified by staining with FITC-dextran. The mean capillary velocity of RBCs was evaluated as 2.05 +/- 1.59 mm/second in video clips obtained at 500 fps. This method is considered to have wide potential applicability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.