Optogenetics revolutionizes basic research in neuroscience and cell biology and bears potential for medical applications. We develop mutants leading to a unifying concept for the construction of ...various channelrhodopsins with fast closing kinetics. Due to different absorption maxima these channelrhodopsins allow fast neural photoactivation over the whole range of the visible spectrum. We focus our functional analysis on the fast-switching, red light-activated Chrimson variants, because red light has lower light scattering and marginal phototoxicity in tissues. We show paradigmatically for neurons of the cerebral cortex and the auditory nerve that the fast Chrimson mutants enable neural stimulation with firing frequencies of several hundred Hz. They drive spiking at high rates and temporal fidelity with low thresholds for stimulus intensity and duration. Optical cochlear implants restore auditory nerve activity in deaf mice. This demonstrates that the mutants facilitate neuroscience research and future medical applications such as hearing restoration.
Optogenetic tools, providing non‐invasive control over selected cells, have the potential to revolutionize sensory prostheses for humans. Optogenetic stimulation of spiral ganglion neurons (SGNs) in ...the ear provides a future alternative to electrical stimulation used in cochlear implants. However, most channelrhodopsins do not support the high temporal fidelity pertinent to auditory coding because they require milliseconds to close after light‐off. Here, we biophysically characterized the fast channelrhodopsin Chronos and revealed a deactivation time constant of less than a millisecond at body temperature. In order to enhance neural expression, we improved its trafficking to the plasma membrane (Chronos‐ES/TS). Following efficient transduction of SGNs using early postnatal injection of the adeno‐associated virus AAV‐PHP.B into the mouse cochlea, fiber‐based optical stimulation elicited optical auditory brainstem responses (oABR) with minimal latencies of 1 ms, thresholds of 5 μJ and 100 μs per pulse, and sizable amplitudes even at 1,000 Hz of stimulation. Recordings from single SGNs demonstrated good temporal precision of light‐evoked spiking. In conclusion, efficient virus‐mediated expression of targeting‐optimized Chronos‐ES/TS achieves ultrafast optogenetic control of neurons.
Synopsis
Here we biophysically characterized and molecularly improved the fast gating blue‐light activated channelrhodopsin Chronos. Employing the potent viral vector AAV‐PHP.B we postnatally expressed the improved Chronos in cochlear neurons and achieved ultrafast neural control.
Biophysical characterization of the fast channelrhodopsin Chronos revealed a deactivation time constant of less than a millisecond at body temperature.
Molecular engineering of Chronos via adding trafficking sequences enhanced plasma membrane abundance of the opsin and use of postnatal AAV‐PHP.B carrying Chronos into the mouse cochlea enabled efficient expression in spiral ganglion neurons.
Chronos enabled synchronized optically driven firing in spiral ganglion neurons for stimulation rates of up to hundreds of Hz as required for future optical cochlear implants.
Biophysical characterization and molecular engineering of the fast channelrhodopsin Chronos results in a new optogentics tool for controlling fast neural circuitries with high temporal fidelity.
We studied the role of the synaptic ribbon for sound encoding at the synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) in mice lacking RIBEYE (RBE
). Electron and ...immunofluorescence microscopy revealed a lack of synaptic ribbons and an assembly of several small active zones (AZs) at each synaptic contact. Spontaneous and sound-evoked firing rates of SGNs and their compound action potential were reduced, indicating impaired transmission at ribbonless IHC-SGN synapses. The temporal precision of sound encoding was impaired and the recovery of SGN-firing from adaptation indicated slowed synaptic vesicle (SV) replenishment. Activation of Ca
-channels was shifted to more depolarized potentials and exocytosis was reduced for weak depolarizations. Presynaptic Ca
-signals showed a broader spread, compatible with the altered Ca
-channel clustering observed by super-resolution immunofluorescence microscopy. We postulate that RIBEYE disruption is partially compensated by multi-AZ organization. The remaining synaptic deficit indicates ribbon function in SV-replenishment and Ca
-channel regulation.
Optogenetic stimulation of spiral ganglion neurons (SGNs) in the ear provides a future alternative to electrical stimulation used in current cochlear implants. Here, we employed fast and very fast ...variants of the red‐light‐activated channelrhodopsin (ChR) Chrimson (f‐Chrimson and vf‐Chrimson) to study their utility for optogenetic stimulation of SGNs in mice. The light requirements were higher for vf‐Chrimson than for f‐Chrimson, even when optimizing membrane expression of vf‐Chrimson by adding potassium channel trafficking sequences. Optogenetic time and intensity coding by single putative SGNs were compared with coding of acoustic clicks. vf‐Chrimson enabled putative SGNs to fire at near‐physiological rates with good temporal precision up to 250 Hz of stimulation. The dynamic range of SGN spike rate coding upon optogenetic stimulation was narrower than for acoustic clicks but larger than reported for electrical stimulation. The dynamic range of spike timing, on the other hand, was more comparable for optogenetic and acoustic stimulation. In conclusion, f‐Chrimson and vf‐Chrimson are promising candidates for optogenetic stimulation of SGNs in auditory research and future cochlear implants.
Synopsis
Identifying suitable channelrhodopsins is crucial for future optogenetic restoration of sound encoding by optical cochlear implants. Here, fast and very fast light‐activated Chrimsons were compared for their utility to optogenetically encode timing and intensity information in the auditory nerve.
Very fast Chrimson increases temporal fidelity but confers lower light sensitivity of optogenetic auditory nerve fiber stimulation compared with fast Chrimson.
Adding trafficking sequences of the inwardly rectifying potassium channel 2.1 improved plasma membrane expression of very fast Chrimson enabling shorter stimulus durations
The dynamic range, based on the discharge rate, of optogenetic auditory nerve fiber stimulation was narrower than that of acoustic stimulation.
The dynamic range, based on temporal precision of spiking, of optogenetic auditory nerve fiber stimulation was broader than that based on discharge rate.
Identifying suitable channelrhodopsins is crucial for future optogenetic restoration of sound encoding by optical cochlear implants. Here, fast and very fast light‐activated Chrimson were compared for their utility to optogenetically encode timing and intensity information in the auditory nerve.
Aims
Availability of normative reference values for cardiac chamber quantitation is a prerequisite for accurate clinical application of echocardiography. In this study, we report normal reference ...ranges for cardiac chambers size obtained in a large group of healthy volunteers accounting for gender and age. Echocardiographic data were acquired using state-of-the-art cardiac ultrasound equipment following chamber quantitation protocols approved by the European Association of Cardiovascular Imaging.
Methods
A total of 734 (mean age: 45.8 ± 13.3 years) healthy volunteers (320 men and 414 women) were enrolled at 22 collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study. A comprehensive echocardiographic examination was performed on all subjects following pre-defined protocols. There were no gender differences in age or cholesterol levels. Compared with men, women had significantly smaller body surface areas, and lower blood pressure. Quality of echocardiographic data sets was good to excellent in the majority of patients. Upper and lower reference limits were higher in men than in women. The reference values varied with age. These age-related changes persisted for most parameters after normalization for the body surface area.
Conclusion
The NORRE study provides useful two-dimensional echocardiographic reference ranges for cardiac chamber quantification. These data highlight the need for body size normalization that should be performed together with age-and gender-specific assessment for the most echocardiographic parameters.
Reference values for Doppler parameters according to age and gender are recommended for the assessment of heart physiology, specifically for left ventricular (LV) diastolic function. In this study, ...we report normal reference ranges for Doppler parameters obtained in a large group of healthy volunteers. Echocardiographic data were acquired using state-of-the-art cardiac ultrasound equipment following Doppler acquisition and measurement protocols approved by the European Association of Cardiovascular Imaging.
A total of 449 (mean age: 45.8 ± 13.7 years) healthy volunteers (198 men and 251 women) were enrolled at the collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study. A comprehensive echocardiographic examination was obtained from all subjects following predefined protocols. The majority of the Doppler diastolic parameters (e', E/e') as well as right ventricle systolic s' wave velocity were similar in men and women. Left ventricle s' wave velocity was higher in men than in women. E wave and e' were higher in younger subjects and decreased progressively in the older ones. E/e' ratio increased with ageing. Septal e' <8 cm/s was present in 19.7% of the subjects in the 40-60 year group and in 55% of those in the ≥60 year group. However, the cut-off value of average E/e' or lateral E/e' remained <15 or 13, respectively, in the majority of patients.
The NORRE study provides the reference values for the most useful Doppler parameters in the evaluation of heart physiology. These data highlight the need of using age-specific reference values especially for the diagnosis of LV systolic and diastolic dysfunction and for the estimation of LV filling pressures.
Aim
To obtain the normal ranges for 3D echocardiography (3DE) measurement of left ventricular (LV) volumes, function, and strain from a large group of healthy volunteers.
Methods and results
A total ...of 440 (mean age: 45 ± 13 years) out of the 734 healthy subjects enrolled at 22 collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study had good-quality 3DE data sets that have been analysed with a vendor-independent software package allowing homogeneous measurements regardless of the echocardiographic machine used to acquire the data sets. Upper limits of LV end-diastolic and end-systolic volumes were larger in men (97 and 42 mL/m2) than in women (82 and 35 mL/m2; P < 0.0001). Conversely, lower limits of LV ejection fraction were higher in women than in men (51% vs. 50%; P < 0.01). Similarly, all strain components were higher in women than in men. Lower range was −18.6% in men and −19.5% in women for 3D longitudinal strain, −27.0% and −27.6% for 3D circumferential strain, −33.2% and −34.4% for 3D tangential strain and 38.8% and 40.7% for 3D radial strain, respectively. LV volumes decreased with age in both genders (P < 0.0001), whereas LV ejection fraction increased with age only in men. Among 3DE LV strain components, the only one, which did not change with age was longitudinal strain.
Conclusion
The NORRE study provides applicable 3D echocardiographic reference ranges for LV function assessment. Our data highlight the importance of age- and gender-specific reference values for both LV volumes and strain.
Abstract
Aims
To obtain the normal ranges for 2D echocardiographic (2DE) measurements of left ventricular (LV) strain from a large group of healthy volunteers accounting for age and gender.
Methods ...and results
A total of 549 (mean age: 45.6 ± 13.3 years) healthy subjects were enrolled at 22 collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study. 2DE data sets have been analysed with a vendor-independent software package allowing homogeneous measurements irrespective of the echocardiographic equipment used to acquire the data sets. The lowest expected values of LV strains and twist calculated as ± 1.96 standard deviations from the mean were −16.7% in men and −17.8% in women for longitudinal strain, −22.3% and −23.6% for circumferential strain, 20.6% and 21.5% for radial strain, and 2.2 degrees and 1.9 degrees for twist, respectively. In multivariable analysis, longitudinal strain decreased with age whereas the opposite occurred with circumferential and radial strain. Male gender was associated with lower strain for longitudinal, circumferential, and radial strain. Inter-vendor differences were observed for circumferential and radial strain despite the use of vendor-independent software. Importantly, no intervendor differences were noted in longitudinal strain.
Conclusion
The NORRE study provides contemporary, applicable 2D echocardiographic reference ranges for LV longitudinal, radial, and circumferential strain. Our data highlight the importance of age- and gender-specific reference values for LV strain.
Aims
To report normal reference ranges for echocardiographic dimensions of the proximal aorta obtained in a large group of healthy volunteers recruited using state-of-the-art cardiac ultrasound ...equipment, considering different measurement conventions, and taking into account gender, age, and body size of individuals.
Methods and Results
A total of 704 (mean age: 46.0 ± 13.5 years) healthy volunteers (310 men and 394 women) were prospectively recruited from the collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study. A comprehensive echocardiographic examination was obtained in all subjects following pre-defined protocols. Aortic dimensions were obtained in systole and diastole, following both the leading-edge to leading-edge and the inner-edge to inner-edge conventions. Diameters were measured at four levels: ventricular-arterial junction, sinuses of Valsalva, sino-tubular junction, and proximal tubular ascending aorta. Measures of aortic root in the short-axis view following the orientation of each of the three sinuses were also performed. Men had significantly larger body sizes when compared with women, and showed larger aortic dimensions independently of the measurement method used. Dimensions indexed by height and body surface area are provided, and stratification by age ranges is also displayed. In multivariable analysis, the independent predictors of aortic dimensions were age, gender, and height or body surface area.
Conclusion
The NORRE study provides normal values of proximal aorta dimensions as assessed by echocardiography. Reference ranges for different anatomical levels using different (i) measurement conventions and (ii) at different times of the cardiac cycle (i.e. mid-systole and end-diastole) are provided. Age, gender, and body size were significant determinants of aortic dimensions.
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