Schwermetalle in Auenböden der Vereinigten Mulde: Methodische Untersuchungen zur Ablagerung und räumlichen Verteilung von Schwermetallen in Auenböden der Vereinigten Mulde

Der Bericht informiert über die räumliche Verteilung und Ablagerung von Schadstoffen in Auenböden der Vereinigten Mulde am Beispiel von Arsen, Blei und Cadmium. Auf der Grundlage von drei Testgebieten und anhand von Raumeinheiten wird versucht eine Vorhersage über die zu erwartenden Schadstoffgehalte zu treffen und diese in Karten darzustellen. Der Bericht richtet sich an Fachleute und die interessierte Öffentlichkeit. Redaktionsschluss: 02.02.202

Optogenetics and electron tomography for structure-function analysis of cochlear ribbon synapses

Ribbon synapses of cochlear inner hair cells (IHCs) are specialized to indefatigably transmit sound information at high rates. To understand the underlying mechanisms, structure-function analysis of the active zone (AZ) of these synapses is essential. Previous electron microscopy studies of synaptic vesicle (SV) dynamics at the IHC AZ used potassium stimulation, which limited the temporal resolution to minutes. Here, we established optogenetic IHC stimulation followed by quick freezing within milliseconds and electron tomography to study the ultrastructure of functional synapse states with good temporal resolution in mice. We characterized optogenetic IHC stimulation by patch-clamp recordings from IHCs and postsynaptic boutons revealing robust IHC depolarization and neurotransmitter release. Ultrastructurally, the number of docked SVs increased upon short (17–25 ms) and long (48–76 ms) light stimulation paradigms. We did not observe enlarged SVs or other morphological correlates of homotypic fusion events. Our results indicate a rapid recruitment of SVs to the docked state upon stimulation and suggest that univesicular release prevails as the quantal mechanism of exocytosis at IHC ribbon synapses

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Schwermetalle in Auenböden der Vereinigten Mulde: Methodische Untersuchungen zur Ablagerung und räumlichen Verteilung von Schwermetallen in Auenböden der Vereinigten Mulde

Der Bericht informiert über die räumliche Verteilung und Ablagerung von Schadstoffen in Auenböden der Vereinigten Mulde am Beispiel von Arsen, Blei und Cadmium. Auf der Grundlage von drei Testgebieten und anhand von Raumeinheiten wird versucht eine Vorhersage über die zu erwartenden Schadstoffgehalte zu treffen und diese in Karten darzustellen. Der Bericht richtet sich an Fachleute und die interessierte Öffentlichkeit. Redaktionsschluss: 02.02.202

Schwermetalle in Auenböden der Vereinigten Mulde: Methodische Untersuchungen zur Ablagerung und räumlichen Verteilung von Schwermetallen in Auenböden der Vereinigten Mulde

Der Bericht informiert über die räumliche Verteilung und Ablagerung von Schadstoffen in Auenböden der Vereinigten Mulde am Beispiel von Arsen, Blei und Cadmium. Auf der Grundlage von drei Testgebieten und anhand von Raumeinheiten wird versucht eine Vorhersage über die zu erwartenden Schadstoffgehalte zu treffen und diese in Karten darzustellen. Der Bericht richtet sich an Fachleute und die interessierte Öffentlichkeit. Redaktionsschluss: 02.02.202

Exocytosis at the hair cell ribbon synapse apparently operates without neuronal SNARE proteins

International audienceSNARE proteins mediate membrane fusion. Neurosecretion depends on neuronal SNAREs (SNAP-25, syntaxin-1, and synaptobrevin-1 or 2) and is blocked by neurotoxin-mediated cleavage or genetic ablation. We report that exocytosis in mouse inner hair cells (IHCs) is insensitive to neurotoxins and genetic ablation of neuronal SNAREs. We found mRNA but no synaptically localized protein of neuronal SNAREs in IHCs. Thus, IHC exocytosis is unconventional and may operate independently of neuronal SNAREs

Modes and Regulation of Endocytic Membrane Retrieval in Mouse Auditory Hair Cells

Synaptic vesicle recycling sustains high rates of neurotransmission at the ribbon-type active zones (AZs) of mouse auditory inner hair cells (IHCs), but its modes and molecular regulation are poorly understood. Electron microscopy indicated the presence of clathrin-mediated endocytosis (CME) and bulk endocytosis. The endocytic proteins dynamin, clathrin, and amphiphysin are expressed and broadly distributed in IHCs. We used confocal vglut1–pHluorin imaging and membrane capacitance (C(m)) measurements to study the spatial organization and dynamics of IHC exocytosis and endocytosis. Viral gene transfer expressed vglut1–pHluorin in IHCs and targeted it to synaptic vesicles. The intravesicular pH was ∼6.5, supporting only a modest increase of vglut1–pHluorin fluorescence during exocytosis and pH neutralization. Ca(2+) influx triggered an exocytic increase of vglut1–pHluorin fluorescence at the AZs, around which it remained for several seconds. The endocytic C(m) decline proceeded with constant rate (linear component) after exocytosis of the readily releasable pool (RRP). When exocytosis exceeded three to four RRP equivalents, IHCs additionally recruited a faster C(m) decline (exponential component) that increased with the amount of preceding exocytosis and likely reflects bulk endocytosis. The dynamin inhibitor Dyngo-4a and the clathrin blocker pitstop 2 selectively impaired the linear component of endocytic C(m) decline. A missense mutation of dynamin 1 (fitful) inhibited endocytosis to a similar extent as Dyngo-4a. We propose that IHCs use dynamin-dependent endocytosis via CME to support vesicle cycling during mild stimulation but recruit bulk endocytosis to balance massive exocytosis

Modes and regulation of endocytic membrane retrieval in mouse auditory hair cells.

Synaptic vesicle recycling sustains high rates of neurotransmission at the ribbon-type active zones (AZs) of mouse auditory inner hair cells (IHCs), but its modes and molecular regulation are poorly understood. Electron microscopy indicated the presence of clathrin-mediated endocytosis (CME) and bulk endocytosis. The endocytic proteins dynamin, clathrin, and amphiphysin are expressed and broadly distributed in IHCs. We used confocal vglut1-pHluorin imaging and membrane capacitance (Cm) measurements to study the spatial organization and dynamics of IHC exocytosis and endocytosis. Viral gene transfer expressed vglut1-pHluorin in IHCs and targeted it to synaptic vesicles. The intravesicular pH was ∼6.5, supporting only a modest increase of vglut1-pHluorin fluorescence during exocytosis and pH neutralization. Ca(2+) influx triggered an exocytic increase of vglut1-pHluorin fluorescence at the AZs, around which it remained for several seconds. The endocytic Cm decline proceeded with constant rate (linear component) after exocytosis of the readily releasable pool (RRP). When exocytosis exceeded three to four RRP equivalents, IHCs additionally recruited a faster Cm decline (exponential component) that increased with the amount of preceding exocytosis and likely reflects bulk endocytosis. The dynamin inhibitor Dyngo-4a and the clathrin blocker pitstop 2 selectively impaired the linear component of endocytic Cm decline. A missense mutation of dynamin 1 (fitful) inhibited endocytosis to a similar extent as Dyngo-4a. We propose that IHCs use dynamin-dependent endocytosis via CME to support vesicle cycling during mild stimulation but recruit bulk endocytosis to balance massive exocytosis. J Neurosci 2014 Jan 15; 34(3):705-16