High-Throughput Platform for Optoacoustic Probing of Genetically Encoded Calcium Ion Indicators

Functional optoacoustic (OA) imaging assisted with genetically encoded calcium ion indicators (GECIs) holds promise for imaging large-scale neuronal activity at depths and spatiotemporal resolutions not attainable with existing optical microscopic techniques. However, currently available GECIs optimized for fluorescence (FL) imaging lack sufficient contrast for OA imaging and respond at wavelengths having limited penetration into the mammalian brain. Here we present an imaging platform capable of rapid assessment and cross-validation between OA and FL responses of sensor proteins expressed in Escherichia coli colonies. The screening system features optimized pulsed light excitation combined with ultrasensitive ultrasound detection to mitigate photobleaching while further allowing the dynamic characterization of calcium ion responses with millisecond precision. Targeted probing of up to six individual colonies per second in both calcium-loaded and calcium-unloaded states was possible with the system. The new platform greatly facilitates optimization of absorption-based labels, thus setting the stage for directed evolution of OA GECIs

Early Imaging Prediction of Malignant Cerebellar Edema Development in Acute Ischemic Stroke

Background and Purpose-Malignant cerebellar edema (MCE) is a life-threatening complication of acute ischemic stroke that requires timely diagnosis and management. Aim of this study was to identify imaging predictors in initial multiparametric computed tomography (CT), including whole-brain CT perfusion (WB-CTP). Methods-We consecutively selected all subjects with cerebellar ischemic WB-CTP deficits and follow-up-confirmed cerebellar infarction from an initial cohort of 2635 patients who had undergone multiparametric CT because of suspected stroke. Follow-up imaging was assessed for the presence of MCE, measured using an established 10-point scale, of which scores >= 4 are considered malignant. Posterior circulation-Acute Stroke Prognosis Early CT Score (pc-ASPECTS) was determined to assess ischemic changes on noncontrast CT, CT angiography (CTA), and parametric WB-CTP maps (cerebellar blood flow [CBF];cerebellar blood volume;mean transit time;time to drain). Fisher's exact tests, Mann-Whitney U tests, and receiver operating characteristics analyses were performed for statistical analyses. Results-Out of a total of 51 patients who matched the inclusion criteria, 42 patients (82.4%) were categorized as MCE-and 9 (17.6%) as MCE+. MCE+ patients had larger CBF, cerebellar blood volume, mean transit time, and time to drain deficit volumes (all with P0.05). Receiver operating characteristics analyses yielded the largest area under the curve values for the prediction of MCE development for CBF (0.979) and cerebellar blood volume deficit volumes (0.956) and pc-ASPECTS on CBF (0.935), whereas pc-ASPECTS on noncontrast CT (0.648) and CTA (0.684) had less diagnostic value. The optimal cutoff value for CBF deficit volume was 22 mL, yielding 100% sensitivity and 90% specificity for MCE classification. Conclusions-WB-CTP provides added diagnostic value for the early identification of patients at risk for MCE development in acute cerebellar stroke

Correlation of composition and structure of shark teeth

In contrast to mammalian teeth with the biomineral phase hydroxyapatite, the shark teeth contain harder mineral phase fluoroapatite with partial substitutions of phosphate by carbonate and of fluoride by hydroxide [1]. Their excellent mechanical properties are due to a special hierarchical structure of the constituting fluoroapatite crystals and organic matrix [2]. The two main structural elements of teeth, i.e. hard and mineral-rich enameloid on the outside and softer and less mineralized dentin on the inside, were structurally, chemically and mechanically characterized [3]. The teeth of two different shark species mako shark (Isurus oxyrinchus) and tiger shark (Galeocerdo cuvier) were investigated and their hierarchical structure by high-resolution scanning electron microscopy presented (Fig.1). X-ray diffraction showed that the inorganic matrix of both enameloid and dentin consisted of fluoroapatite, with a high crystalline phase in enameloid and nanocrystalline phase in dentin. FTIR-spectra of the shark teeth showed the characteristic bands of biological apatite. It was found by thermogravimetry that dentin had a higher content of water, organic matrix and carbonate than enameloid. To investigate the mechanical properties of the teeth in longitudinal and cross sections, nanoindentation and Vickers microhardness were carried out. Both methods gave comparable results: the enameloid of both shark teeth was approximately six times harder than the dentin with an isotropic hardness (longitudinal or cross section)