Neural Coding and Organization Principles in the Drosophila Olfactory System

Sensory systems receive and process external stimuli to allow an organism to perceive and react to the environment. How is sensory information subsequently represented, transformed, and interpreted in the neural system? In this dissertation, I have investigated this fundamental question using the fruit fly (Drosophila melanogaster) olfactory system.Chemical cues are transduced into neural signals in the insect antenna by the olfactory receptor neurons (ORNs). The ORNs send their axons to the antennal lobe (AL), with each ORN type innervating a specific neuropil (glomerulus), where they synapse onto excitatory and inhibitory projection neurons (ePNs and iPNs). The ePNs project their axons to the 3rd order stages, the calyx (CL) and lateral horn (LH). On the other hand, the iPNs only innervate the LH. In this dissertation, I first examined how well the peripheral neural activities evoked by an odorant could predict the final behavioral output. As the stimulus intensity increases, a fly’s preference for some odorants switch from attraction to aversion. Behavior assay suggested this phenomenon may help the fly evade harmful environment. Our results indicate that at the level of ORNs, increases in stimulus intensity could result in oscillatory extracellular field potentials that arise entirely due to abrupt changes in cell excitability. Notably, combining the activity of a few ORNs was sufficient to predict intensity-dependent preference changes with odor intensity. How is the sensory input organized in the downstream neural circuit, the insect antennal lobe? Odor-evoked signals from sensory neurons (ORNs) triggered neural responses that were patterned over space and time in cholinergic ePNs and GABAergic iPNs within the antennal lobe. The dendritic-axonal (I/O) response mapping was complex and diverse, and the axonal organization was region-specific (mushroom body vs. lateral horn). In the lateral horn, feed-forward excitatory and inhibitory axonal projections matched ‘odor tuning’ in a stereotyped, dorsal-lateral locus, but mismatched in most other locations. In the temporal dimension, ORN, ePN, and iPN odor-evoked responses had similar encoding features, such as information refinement over time and divergent ON and OFF responses. Notably, analogous spatial and temporal coding principles were observed in all flies, and the latter emerged from idiosyncratic neural processing approaches. In sum, these results provide key insights necessary for understanding how sensory information is organized along spatial and temporal dimensions

In vivo photoacoustic neuronal imaging of odor-evoked calcium signals in the drosophila brain

Neural scientists can benefit greatly from imaging tools that can penetrate thick brain tissue. Compared with traditional optical microscopy methods, photoacoustic imaging can beat the optical diffusion limit and achieve such deep tissue imaging with high spatial resolution. In this study, we used an optical-resolution photoacoustic microscope to image the odor-evoked neuronal activities in a drosophila model. Drosophila brain neurons stably express GCaMP5G, a calcium-sensitive fluorescent protein whose optical absorption coefficient changes with calcium influx during action potentials. We recorded an ~20% odor-evoked fractional photoacoustic signal increase at all depths of the drosophila brain in vivo, with and without removal of the brain cuticle, at a recording rate of 1 kHz. Our results were confirmed by concurrent fluorescent recordings. Furthermore, by performing fast 2D scanning, we imaged the antenna lobe region, which is of particular interest in neuroscience, at a volumetric rate of ~1 Hz with a sub-neuron resolution of 3 m. Unlike optical imaging, which requires surgical removal of the scattering brain cuticle, our photoacoustic system can image through the cuticle and measure neuronal signals of the whole drosophila brain without invasive surgery, enabling minimal disturbance to the animal’s behaviors. In conclusion, we have demonstrated photoacoustic imaging of calcium signals in drosophila brains for the first time. Utilizing the deep imaging capability of photoacoustic tomography, our methods could potentially be extended to in vivo imaging of neuronal activities from deep brains in other animal models

In vivo photoacoustic neuronal imaging of odor-evoked calcium signals in the drosophila brain

Neural scientists can benefit greatly from imaging tools that can penetrate thick brain tissue. Compared with traditional optical microscopy methods, photoacoustic imaging can beat the optical diffusion limit and achieve such deep tissue imaging with high spatial resolution. In this study, we used an optical-resolution photoacoustic microscope to image the odor-evoked neuronal activities in a drosophila model. Drosophila brain neurons stably express GCaMP5G, a calcium-sensitive fluorescent protein whose optical absorption coefficient changes with calcium influx during action potentials. We recorded an ~20% odor-evoked fractional photoacoustic signal increase at all depths of the drosophila brain in vivo, with and without removal of the brain cuticle, at a recording rate of 1 kHz. Our results were confirmed by concurrent fluorescent recordings. Furthermore, by performing fast 2D scanning, we imaged the antenna lobe region, which is of particular interest in neuroscience, at a volumetric rate of ~1 Hz with a sub-neuron resolution of 3 m. Unlike optical imaging, which requires surgical removal of the scattering brain cuticle, our photoacoustic system can image through the cuticle and measure neuronal signals of the whole drosophila brain without invasive surgery, enabling minimal disturbance to the animal’s behaviors. In conclusion, we have demonstrated photoacoustic imaging of calcium signals in drosophila brains for the first time. Utilizing the deep imaging capability of photoacoustic tomography, our methods could potentially be extended to in vivo imaging of neuronal activities from deep brains in other animal models

Comparison of novel oncology drugs that received dual approval from the US accelerated approval and EU conditional marketing authorisation pathways, 2006–2021: a cross-sectional study

Objective We aimed to provide insight into differences in drug review decisions made by the US Food and Drug Administration’s (FDA) accelerated approval (AA) pathway and the European Medicines Agency’s (EMA) conditional marketing authorisation (CMA) pathway, and to add to the current knowledge base of drug approval processes.Design, setting, participants This cross-sectional study thoroughly examines novel oncology drugs with dual approval through FDA AA and EMA CMA between 2006 and 2021. Statistical analysis was performed from June to July 2022.Primary and secondary outcome measures The study examined the regulatory differences between regions for dually approved novel oncology drugs, including approval decisions, pivotal efficacy clinical trials, speed of review and postmarketing obligations.Results During this time period, there was a difference in the use of the FDA AA and the EMA CMA (FDA: EMA: 41.2%: 70.0%, p<0.05). Of the 25 drugs approved by both the FDA AA and the EMA CMA, 22 (88.0%) of the regulatory decisions were based on the same pivotal clinical trials. But there were more differences in the requirements for postmarketing obligations, with the EMA’s postmarketing obligations focusing on the efficacy and safety of the drug (EMA: FDA: 63.0%: 27.0%, p＜0.05) and the FDA’s postmarketing obligations focusing more on the efficacy (FDA: EMA: 73.0%: 23.9%, p＜0.05). In addition, both the USA and EU had some postmarketing obligations completed beyond the schedule (30.4% and 19.2% in the USA and EU, respectively), with the longest delays lasting 3.7 years (0.2–3.7 years) and 3.3 years (0.04–3.3 years) in the USA and EU, respectively.Conclusions The FDA and EMA have different orientations and benefit–risk balance considerations in the use of AA or CMA. It is also the case that the shortcomings in the design and implementation of postmarketing studies have made it a challenge to obtain the evidence needed to confirm a drug’s benefits

Modified Robert Jones bandage can not reduce postoperative swelling in enhanced-recovery after primary total knee arthroplasty without intraoperative tourniquet: a randomized controlled trial

Abstract Background Compression therapy is commonly used to reduce lower limb swelling and blood loss after knee surgery. This study was performed to investigate whether modified Robert Jones bandage (MRJB) as a postoperative compression therapy is necessary for enhanced-recovery primary total knee arthroplasty without the tourniquet application. Methods In this prospective randomized controlled trial, 90 patients were grouped into 2 groups randomly. The experimental group received compression therapy with MRJB from toes to thigh for 24 h and the control group received no compression therapy. Knee swelling, blood loss, range of motion (ROM), pain, patient reported comfort level and complications were recorded. Results No significant differences were observed between the two groups when we compared knee swelling. Similarly, no significant difference on postoperative blood loss, pain, ROM, complications was found. However, patients in control group had significantly higher comfort ratings than compression group during the first 24 h. Conclusions MRJB is not routinely indicated in enhanced-recovery primary total knee arthroplasty without tourniquet application. Trial registration The trial was registered in the Chinese Clinical Trial Registry (ChiCTR-INR-16010177) dated 18th December 2016

Evaluation of Toxicity Ranking for Metal Oxide Nanoparticles via an in Vitro Dosimetry Model.

It has been argued that in vitro toxicity testing of engineered nanoparticles (NPs) should consider delivered dose (i.e., NP mass settled per suspension volume) rather than relying exclusively on administered dose (initial NP mass concentration). Delivered dose calculations require quantification of NP sedimentation in tissue cell culture media, taking into consideration fundamental suspension properties. In this article, we calculate delivered dose using a first-principles "particles in a box" sedimentation model, which accounts for the particle size distribution, fractal dimension, and permeability of agglomerated NPs. The sedimentation model was evaluated against external and our own experimental sedimentation data for metal oxide NPs. We then utilized the model to construct delivered dose-response analysis for a library of metal oxide NPs (previously used for hazard ranking and prediction making) in different cell culture media. Hierarchical hazard ranking of the seven (out of 24) toxic metal oxide NPs in our library, using EC50 calculated on the basis of delivered dose, did not measurably differ from our ranking based on administered dose. In contrast, simplified sedimentation calculations based on the assumption of impermeable NP agglomerates of a single average size significantly underestimated the settled NPs' mass, resulting in misinterpretation of toxicity ranking. It is acknowledged that in vitro dose-response outcomes are likely to be shaped by complex toxicodynamics, which include NP/cellular association, triggering of dynamic cell response pathways involved in NP uptake, and multiple physicochemical parameters that influence NP sedimentation and internalization

Evaluation of Toxicity Ranking for Metal Oxide Nanoparticles via an in Vitro Dosimetry Model.

It has been argued that in vitro toxicity testing of engineered nanoparticles (NPs) should consider delivered dose (i.e., NP mass settled per suspension volume) rather than relying exclusively on administered dose (initial NP mass concentration). Delivered dose calculations require quantification of NP sedimentation in tissue cell culture media, taking into consideration fundamental suspension properties. In this article, we calculate delivered dose using a first-principles "particles in a box" sedimentation model, which accounts for the particle size distribution, fractal dimension, and permeability of agglomerated NPs. The sedimentation model was evaluated against external and our own experimental sedimentation data for metal oxide NPs. We then utilized the model to construct delivered dose-response analysis for a library of metal oxide NPs (previously used for hazard ranking and prediction making) in different cell culture media. Hierarchical hazard ranking of the seven (out of 24) toxic metal oxide NPs in our library, using EC50 calculated on the basis of delivered dose, did not measurably differ from our ranking based on administered dose. In contrast, simplified sedimentation calculations based on the assumption of impermeable NP agglomerates of a single average size significantly underestimated the settled NPs' mass, resulting in misinterpretation of toxicity ranking. It is acknowledged that in vitro dose-response outcomes are likely to be shaped by complex toxicodynamics, which include NP/cellular association, triggering of dynamic cell response pathways involved in NP uptake, and multiple physicochemical parameters that influence NP sedimentation and internalization

Grid impedance detection based on complex coefficient filter and full-order capacitor current observer for three-phase grid-connected inverters

This article proposes a new grid impedance detection method incorporating the complex coefficient filter (CCF) with full-order capacitor current observer for a T-type three-level grid-connected inverter controlled by the inverter output current feedback. Compared with conventional CCF impedance detection algorithms, the proposed method reduces the number of current sensors and detects the grid impedance accurately. First, based on the sampled inverter output current and grid-connected voltage signals, the grid-connected current is estimated. Then, the CCF method is used to extract harmonics from the grid-connected current and voltage signals to calculate the grid impedance. Finally, the correctness of the full-order capacitor current observer is verified by simulation and the feasibility and effectiveness of the proposed algorithm are verified experimentally based on a laboratory prototype. © 1986-2012 IEEE

Characterization of tangeretin as an activator of nuclear factor erythroid 2-related factor 2/antioxidant response element pathway in HEK293T cells

Numerous studies have reported that tangeretin is a polymethoxylated flavone with a variety of biological activates, but little research has been done on the antioxidant mechanism of tangeretin. Hence, we investigated the effect of tangeretin on the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway and its potential molecular mechanisms by in vitro and in silico research. The results of molecular docking suggested that tangeretin bound at the top of the central pore of Kelch-like ECH-associated protein 1 (Keap1) Kelch domain, and the hydrophobic and hydrogen bond interactions contributed to their stable binding. Herein, the regulation of Nrf2-ARE pathway by tangeretin was explored in the human embryonic kidney cell line HEK293T, which is relatively easy to be transfected. Upon binding to tangeretin, Nrf2 translocated to the nucleus of HEK293T cells, which in turn activated the Nrf2-ARE pathway. Luciferase reporter gene analysis showed that tangeretin significantly induced ARE-mediated transcriptional activation. Real-time PCR and Western blot assays showed that tangeretin induced the gene and protein expressions of Nrf2-mediated targets, including heme oxygenase 1 (HO-1), nicotinamide adenine dinucleotide phosphate (NADPH) quinone dehydrogenase 1 (NQO1), and glutamate-cysteine ligase (GCLM). In addition, tangeretin could effectively scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. In summary, tangeretin may be a potential antioxidant via activating the Nrf2-ARE pathway