Biology subjects

Bao, M.

Publications and source records attributed to Bao, M..

26 records · Page 2Linked to original sources

bioRxiv2020

Eye-specific voluntary attention can induce a shift of perceptual ocular dominance

Ocular dominance plasticity in adults has been extensively studied in the recent decade. An interocular imbalance of visual input, e.g. monocular deprivation, has been proved to markedly reshape ocular dominance. As visual attention can be eye-specific, dissimilar visual inputs from the two eyes during monocular deprivation inevitably lead attention to be more allocated to the monocular input that conveys relatively intact information. Does the imbalanced attention across the eyes also contribute to reshaping ocular dominance? Here, using a novel "backwards-movie" adaptation paradigm, we showed that prolonged attention to the input in one eye was sufficient to shift perceptual ocular dominance in favor of the unattended eye. Furthermore, the effect was stronger when eye-specific attention was directed to the dominant eye, possibly due to fewer disturbances from the other eye during the adaptation. Taken together, these findings suggest that top-down attention plays an important role in short-term ocular dominance plasticity. Statement of RelevanceAn important goal in neuroscience is to understand and take advantage of adaptive neural plasticity. Ocular dominance plasticity resulting from imbalanced visual input signals across the two eyes has been intensively investigated. By developing a novel "backwards-movie" paradigm in which movie images played normally were presented to one eye while movie images of the same episode but played backwards were presented to the other eye, the current study for the first time demonstrates the non-negligible contributions of selective attention in reshaping ocular dominance. These findings expand the homeostatic compensation theory of monocular deprivation by highlighting the contributions of feedback signals. Furthermore, our method could be applied in future work to explore new possibilities in treating adults with amblyopia.

neuroscience↗

bioRxiv2020

Quantifying synergy in the bioassay-guided fractionation of natural product extracts

Mixtures of drugs often have greater therapeutic value than any of their constituent drugs alone, and such combination therapies are widely used to treat diseases such as cancer, malaria, and viral infections. However, developing useful drug mixtures is challenging due to complex interactions between drugs. Natural substances can be fruitful sources of useful drug mixtures because secondary metabolites produced by living organisms do not often act in isolation in vivo. In order to facilitate the study of interactions within natural substances, a new analytical method to quantify interactions using data generated in the process of bioassay-guided fractionation is presented here: the extract fractional inhibitory concentration index (EFICI). The EFICI method uses the framework of Loewe additivity to calculate fractional inhibitory concentration values by which interactions can be determined for any combination of fractions that make up a parent extract. The EFICI method was applied to data on the bioassay-guided fractionation of Lechea mucronata and Schinus terebinthifolia for growth inhibition of the pathogenic bacterium Acinetobacter baumannii. The L. mucronata extract contained synergistic interactions (EFICI = 0.4181) and the S. terebinthifolia extract was non-interactive overall (EFICI = 0.9129). Quantifying interactions in the bioassay-guided fractionation of natural substances does not require additional experiments and can be useful to guide the experimental process and to support the development of standardized extracts as botanical drugs.View Full Text

pharmacology and toxicology↗

bioRxiv2020

Magnetic Bead-Quantum Dot (MB-Qdot) CRISPR Assay for Instrument-Free Viral DNA Detection

We have developed a novel detection system which couples CRISPR-Cas recognition of target sequences, Cas mediated nucleic acid probe cleavage, and quantum dots as highly sensitive reporter molecules for instrument-free detection of viral nucleic acid targets. After target recognition and Cas mediated cleavage of biotinylated ssDNA probe molecules, the probe molecules are bound to magnetic particles. A complimentary ssDNA oligonucleotide quantum dot conjugate is then added, which only hybridizes to un-cleaved probes on the magnetic beads. After separation of hybridized from unhybridized quantum dot conjugates by magnetic sequestration, the signal is measured fluorometrically to provide a signal proportional to the cleaved probes and therefore the amount of target nucleic acid. To demonstrate the power of this assay, a 250 bp DNA target sequence matching a portion of the African swine fever virus (ASFV) genome is used and a detection limit of ~0.5 nM is achieved without target amplification using a simple portable ultraviolet flashlight. The positive samples are readily confirmed by visual inspection, completely avoiding the need for complicated devices and instruments. This work establishes the feasibility of a simple, instrument free assay for rapid nucleic acid screening in both hospitals and point-of-care settings.

biochemistry↗

bioRxiv2020

Integrated Micropillar Polydimethylsiloxane Accurate CRISPR Detection (IMPACT) System for Rapid Viral DNA Sensing

A fully Integrated Micropillar Polydimethylsiloxane Accurate CRISPR Detection (IMPACT) system is developed for viral DNA detection. This powerful system is patterned with high-aspect ratio micropillars to enhance reporter probe binding. After surface modification and probe immobilization, CRISPR Cas12a/crRNA complex is injected into the fully enclosed system. With the presence of double-stranded DNA target, the CRISPR enzyme is activated and non-specifically cleaves the ssDNA reporters initially immobilized on the micropillars. This collateral cleavage releases fluorescence dyes into the assay, and the intensity is linearly proportional to the target DNA concentration ranging from 0.1 to 10 nM. Importantly, this system does not rely on traditional dye-quencher labeled probe thus eliminating the fluorescence background presented in the assay. Furthermore, our one-step detection protocol is performed at isothermal conditions (37{degrees}C) without using complicated and time-consuming off-chip probe hybridization and denaturation. This miniaturized and fully packed IMPACT chip demonstrates rapid, sensitive, and simple nucleic acid detection and is an ideal candidate for the next generation molecular diagnostic platform for point-of-care (POC) applications, responding to emerging and deadly pathogen outbreaks.

bioengineering↗

bioRxiv2020

Single Chlamydomonas reinhardi (C. reinhardtii) cell separation from bacterial cells and auto-fluorescence tracking with a nano-sieve device

A planar, transparent, and adaptable nano-sieve device is developed for efficient microalgae/bacteria separation. In our strategy, a sacrificial layer is applied in the dual photolithography patterning to achieve a one-dimensional channel with a very low aspect ratio (1:10,000). Microalgae/bacteria mixture is then introduced into the deformable polydimethylsiloxane (PDMS) nano-channel. The hydrodynamic deformation of the nano-channel is regulated to allow the bacteria cells to pass through while leaving the microalgae cells trapped in the device. At a flow rate of 4 l/min, ~100% of the microalgae cells are trapped in the device. Additionally, this device is capable of immobilizing single cells in a transparent channel for auto-fluorescence tracking. These microalgae cells demonstrate minimal photo-bleaching over 250 s laser exposure and can be used to monitor hazardous compounds in the sample with a continuous flow fashion. Our method will be valuable to purify microalgae samples containing contaminations and study single cell heterogeneity.

bioengineering↗

bioRxiv2019

Reward produces learning of a consciously inaccessible feature

Reward has significant impacts on behavior and perception. Most past work in associative reward learning has used distinct visual cues to associate with different reward values. Thus, it remains unknown to what extent the learned associations depend on the consciousness. Here we resolved this issue by using an inter-ocular suppression paradigm with the monetary rewarding and non-rewarding cues identical to each other except for the eye-of-origin. Thus, the reward coding system cannot rely on the consciousness to select the reward-associated cue. Surprisingly, the targets in the rewarded eye broke into awareness faster than those in the non-rewarded eye. We further revealed that producing this effect required both attention and inter-ocular suppression. These findings suggest that the humans reward coding system can produce two different types of reward-based learning. One is independent of the consciousness yet fairly consuming attentional resource. The other one results from volitional selections guided by top-down attention.

neuroscience↗

bioRxiv2019

Energy Expenditure during Cell Spreading Induces AMPK Activation and Regulates the Mechanoresponse of Stem Cells

Cells respond to the mechanical properties of the extracellular matrix (ECM) through formation of focal adhesions (FAs), re-organization of the actin cytoskeleton and adjustment of cell contractility. These are energy-demanding processes, but a potential causality between mechanical cues (matrix stiffness) and cellular (energy) metabolism remains largely unexplored. Here, we culture human mesenchymal stem cells (hMSCs) on stiff (20 kPa) or soft (1 kPa) substrate and demonstrate that cytoskeletal reorganization and FA formation spreading on stiff substrates lead to a drop in intracellular ATP levels, correlates with the activation of AMP-activated protein kinase (AMPK). The resulting increase in ATP levels further facilitates cell spreading and reinforces cell tension of the steady state, and coincides with nuclear localization of YAP/TAZ and Runx2. While on soft substrates (1 kPa), lowered ATP levels limit these cellular mechanoresponses. Furthermore, genetic ablation of AMPK lowered cellular ATP levels on stiff substrate and strongly reduced responses to substrate stiffness. Together, these findings reveal a hitherto unidentified relationship between energy expenditure and the cellular mechanoresponse, and point to AMPK as a key mediator of stem cell fate in response to ECM mechanics.

cell biology↗

bioRxiv2019

High-throughput and all-solution phase African Swine Fever Virus (ASFV) detection using CRISPR-Cas12a and fluorescence based point-of-care system

Here we report the development of a high throughput, all-solution phase, and isothermal detection system to detect African Swine Fever Virus (ASFV). CRISPR-Cas12a programmed with a CRISPR RNA (crRNA) is used to detect ASFV target DNA. Upon ASFV DNA binding, the Cas12a/crRNA/ASFV DNA complex becomes activated and degrades a fluorescent single stranded DNA (ssDNA) reporter present in the assay. We combine this powerful CRISPR-Cas assay with fluorescence-based point-of-care (POC) system we developed for rapid and accurate virus detection. Without nucleic acid amplification, a detection limit of 1 pM is achieved within 2 hrs. In addition, the ternary Cas12a/crRNA/ASFV DNA complex is highly stable at physiological temperature and continues to cleave the ssDNA reporter even after 24 hrs of incubation, resulting in an improvement of the detection limit to 100 fM. We show that this system is very specific and can differentiate nucleic acid targets with closely matched sequences. The high sensitivity and selectivity of our system enables the detection of ASFV in femtomolar range. Importantly, this system features a disposable cartridge and a sensitive custom designed fluorometer, enabling compact, multiplexing, and simple ASFV detection, intended for low resource settings.

bioengineering↗