Disorders of Consciousness: An Embedded Ethnographic Approach to Uncovering the Specific Influence of Functional Neurodiagnostics of Consciousness in Surrogate Decision Making

A recent qualitative study published in Neuroethics by Schembs and colleagues explores how functional neurodiagnostics of consciousness inform surrogate decision making in cases of disorders of consciousness. In this commentary, we argue that the chosen methodology significantly limits the scope of the potential conclusions and suggest an embedded ethnographic approach of co-presence as an alternative.

     

Effects of a new calcium sensitizer, levosimendan, on haemodynamics, coronary blood flow and myocardial substrate utilization early after coronary artery bypass grafting

Aims The aim of the study was to evaluate the effects on systemicand coronary haemodynamics and myocar-dial substrate utilizationof a new calcium sensitizer, levosimendan, after coronary arterybypass grafting. Methods and Results Twenty-three low-risk patients were included in this randomizedand double-blind study. They received placebo (n=8), 8 (n=8)or 24 (n=7) µg.kg^–1of levosimendan after coronaryartery bypass operation. Systemic and coronary sinus haemodynamicswith thermodilution and myocardial substrate utilization weremeasured. The heart rate increased 11 beats.min^–1afterthe higher dose (P<0·05). Cardiac output increasedby 0·7 and 1·6l.min^–1(P<0·05 forboth) after 8 and 24µg.kg^–1of levosimendan, respectively.Systemic and pulmonary vascular resistance decreased significantlyafter both doses. Coronary sinus blood flow increased by 28and 42ml/(P=0·054 for the combined effect) after thelower and higher dose, respectively. Myocardial oxygen consumptionor substrate extractions did not change statistically significantly. Conclusion Despite improved cardiac performance, levosimendan did not increasemyocardial oxygen con-sumption or change myocardial substrateutilization. Thus levosimendan has the potential to treat lowcardiac output states after cardiopulmonary bypass surgery.     

From the Cover: Breaking the diffraction limit of light-sheet fluorescence microscopy by RESOLFT

We present a plane-scanning RESOLFT [reversible saturable/switchable optical (fluorescence) transitions] light-sheet (LS) nanoscope, which fundamentally overcomes the diffraction barrier in the axial direction via confinement of the fluorescent molecular state to a sheet of subdiffraction thickness around the focal plane. To this end, reversibly switchable fluorophores located right above and below the focal plane are transferred to a nonfluorescent state at each scanning step. LS-RESOLFT nanoscopy offers wide-field 3D imaging of living biological specimens with low light dose and axial resolution far beyond the diffraction barrier. We demonstrate optical sections that are thinner by 5–12-fold compared with their conventional diffraction-limited LS analogs.Far-field nanoscopy (1, 2) methods discern features within subdiffraction distances by briefly forcing their molecules to two distinguishable states for the time period of detection. Typically, fluorophores are switched between a signaling “on” and a nonsignaling (i.e., dark) “off” state. Depending on the switching and fluorescence registration strategy used, these superresolution techniques can be categorized into coordinate-stochastic and coordinate-targeted approaches (2). The latter group of methods, comprising the so-called RESOLFT [reversible saturable/switchable optical (fluorescence) transitions] (1, 3–7) approaches, have been realized using patterns of switch-off light with one or more zero-intensity points or lines, to single out target point (zero-dimensional) or line (1D) coordinates in space where the fluorophores are allowed to assume the on state. The RESOLFT idea can also be implemented in the inverse mode, by using switch-on light and confining the off state. In any case, probing the presence of molecules in new sets of points or lines at every scanning step produces images.Owing to the nature of the on and off states involved––first excited electronic and ground state––stimulated emission depletion (STED) (3) and saturated structured illumination microscopy (SSIM) (8), which both qualify as variants of the RESOLFT principle, typically apply light intensities in the range of MW/cm² and above. Especially when imaging sensitive samples where photoinduced changes must be avoided, RESOLFT is preferably realized with fluorophores which lead to the same factor of resolution improvement at much lower intensities of state-switching light. Reversibly switchable fluorescent proteins (RSFPs) are highly suitable for this purpose (4–7, 9), as transitions between their metastable on and off states require 5 orders of magnitude lower threshold intensities than STED/SSIM to guarantee switch-off. Suitable spectral properties, relatively fast millisecond switching kinetics, and high photostability of recently developed yellow-green-emitting RSFPs like rsEGFP (5), rsEGFP2 (7), and rsEGFP(N205S) (10) compared with early RSFPs have indeed enabled RESOLFT nanoscopy in living cells and tissues. To date, RSFP-based RESOLFT has achieved resolution improvements by factors of 4–5 in rsEGFP2-labeled samples (7). To further reduce the imaging time, massive parallelization of scanning has been reported (10). However, the diffraction-limited axial resolution and lack of background suppression restrict applications to thin samples.Imaging applications typically require careful tuning of imaging parameters including speed, contrast, photosensitivity, and spatial resolution, depending on the information that is sought. Light-sheet fluorescence microscopy (LSFM) (11–15) stands out by its ability to balance most of these parameters for 3D imaging of living specimens. Recently reenacted as the selective plane illumination microscope (13), this microscopy mode has sparked increasing interest notably because of its short acquisition times in 3D imaging and low phototoxicity in living specimens. It excites fluorophores only in a thin diffraction-limited slice of the sample, perpendicular to the direction of fluorescence detection. The LS is generated by a cylindrical lens which focuses an expanded laser beam in only one direction onto the specimen or into the back-focal plane of an illumination objective. Alternatively, a single beam is quickly moved as a “virtual” LS (16) across a specimen section.In such conventional LSFM imaging, the lateral resolution is determined by the numerical aperture (N.A.) of the detection objective (17), whereas axial resolution is given by the LS thickness, provided the latter is thinner than the axial extent of the point-spread function describing the imaging process from the focal plane of the detecting lens to the camera. In a previous study, the axial resolution of LSFM was pushed to the diffraction limit by using the full aperture of the illumination objective with Gaussian beams; this was carried out for practically useful combinations of N.A. (e.g., 0.8 for both illumination and detection objectives) permissible in light of the geometrical constraints given by the objective lens dimensions (18). High-N.A. illumination comes with short Rayleigh ranges of Gaussian beams, which inherently limit the field of view (FOV) along the direction of illumination. Scanned Bessel beams for diffraction-limited excitation with a virtual LS (19–21) typically offer larger FOVs (22), but side lobes broaden the scanned LS in the axial direction and contribute to phototoxicity outside of the focal plane of detection (20). A more complex approach has used Bessel-beam excitation in combination with structured illumination to obtain near-isotropic (but still diffraction-limited) resolution as measured on fluorescent beads (20), albeit at the cost of acquisition time and reduced contrast due to fluorescence generated by the side lobes. In different work, axial resolution has also been improved about fourfold by acquiring two complementary orthogonal views of the sample using two alternating LSs, followed by computationally fusing image information with a deconvolution incorporating both views (23). LS approaches have also helped suppress out-of-focus background for single-molecule imaging in biological situations (e.g., in ref. 24), including at superresolution (25–27).Slight axial resolution improvement beyond the diffraction barrier has been demonstrated by overlapping a Gaussian excitation LS with a STED LS featuring a zero-intensity plane (28). Due to scattering and possibly additional aberrations caused by the wavelength difference between excitation and STED light, the maximal achievable resolution in biological specimens was severely limited. This was the case even in fixed samples. A successful application of LS-STED to living cells or organisms has not been reported. The relatively high average STED laser power required for high resolution gains calls for developing a coordinate-targeted superresolution LS approach with low-power operation, meaning a concept that does not solely rely on changing the way the light is directed to––or collected from––the sample, but a concept that harnesses an “on–off” transition for improved feature separation.     

Evidence for Risk Reduction Among Amphetamine-Injecting Men Who have Sex with Men; Results from National HIV Behavioral Surveillance Surveys in the Seattle Area 2008–2012

In the Seattle area men who have sex with men and also inject amphetamines (amphetamine-injecting MSM/IDU) are disproportionately likely to be infected with HIV. To characterize their distinctive characteristics, we combined data from two Seattle-area surveys of men who have sex with men (MSM) and two surveys of injection drug users (IDU). Amphetamine-injecting MSM/IDU were compared with: male IDU, MSM and other MSM/IDU. Amphetamine-injecting MSM/IDU were older than MSM but younger than IDU, more likely to be white than either group, and had an educational level higher than IDU but below MSM. They had the highest HIV prevalence (56 vs. 4–19 %). However, reported HIV cases among them fell from 92 in 1990 to 25 in 2012. They were most likely to report ten or more sex partners (49 vs. 4–26 %), an STD diagnosis (22 vs. 1–7 %) and be tested for HIV (odds ratio 1.00 vs. 0.34–0.52), and least likely to share needles (odds ratio 1.00 vs. 6.80–10.50). While sexual risk remains high, these data suggest measurable and effective risk reduction with respect to sharing injection equipment and HIV testing among Seattle-area amphetamine-injecting MSM/IDU.