Biology subjects

Kwon, H.

Publications and source records attributed to Kwon, H..

49 records · Page 3Linked to original sources

bioRxiv2021

Detection of the 40-Hz Auditory Steady-state Response with Optically Pumped Magnetometers

Magnetoencephalography (MEG) is a functional neuroimaging technique that noninvasively detects the brain magnetic field from neuronal activations. Conventional MEG measures brain signals using superconducting quantum interference devices (SQUIDs). SQUID-MEG requires a cryogenic environment involving a bulky non-magnetic dewar and the consumption of liquid helium, which restricts the variability of the sensor array and the gap between the cortical sources and sensors. Recently, miniature optically pumped magnetometers (OPMs) have been developed and commercialized. OPMs do not require cryogenic cooling and can be placed within millimeters from the scalp. In the present study, we arranged six OPM sensors on the temporal area to detect auditory-related brain responses in a two-layer magnetically shielded room. We presented the auditory stimuli of 1-kHz pure-tone bursts with 200-ms duration and obtained the M50 and M100 components of auditory evoked fields. We delivered the periodic stimuli with a 40-Hz repetition rate and observed the gamma-band power changes and inter-trial phase coherence of auditory steady-state responses at 40 Hz. We found that the OPM sensors have a performance comparable to that of conventional SQUID-MEG sensors, and our results suggest the feasibility of using OPM sensors for functional neuroimaging and brain-computer interface applications.

neuroscience↗

bioRxiv2021

Neuronal glucose metabolism sets cholinergic tone and controls thermo-regulated signaling at the neuromuscular junction

Cholinergic and sympathetic counter-regulatory networks control numerous physiologic functions including learning/memory/cognition, stress responsiveness, blood pressure, heart rate and energy balance. As neurons primarily utilize glucose as their primary metabolic energy source, we generated mice with increased glycolysis in cholinergic neurons by specific deletion of the fructose-2,6-phosphatase protein TIGAR. Steady-state and stable isotope flux analyses demonstrated increased rates of glycolysis, acetyl-CoA production, acetylcholine levels and density of neuromuscular synaptic junction clusters with enhanced acetylcholine release. The increase in cholinergic signaling reduced blood pressure and heart rate with a remarkable resistance to cold-induced hypothermia. These data directly demonstrate that increased cholinergic signaling through the modulation of glycolysis has several metabolic benefits particularly to increase energy expenditure and heat production upon cold exposure. HighlightsO_LIDeficiency of a negative regulator of glycolysis (TIGAR) in cholinergic neurons increases the biosynthesis and content of the neurotransmitter acetylcholine. C_LIO_LIIncreased cholinergic tone reduces blood pressure and heart rate while enhancing signaling at neuromuscular junction. C_LIO_LIUpregulation of neuromuscular junction activation provides protection against the paralytic curare and cold-induced hypothermia. C_LIO_LIModulation of cholinergic neuron glycolysis may provide a novel therapeutic approach for treatment of diseases stemming from reduced acetylcholine signaling such as myasthenia gravis and sarcopenic pre-synaptic dysfunction. C_LI

cell biology↗

bioRxiv2020

Identification of a prostaglandin E2 receptor that regulates mosquito oenocytoid immune cell function in limiting bacteria and parasite infection

Lipid-derived signaling molecules known as eicosanoids have integral roles in mediating immune and inflammatory processes across metazoans. This includes the function of prostaglandins and their cognate G protein-coupled receptors (GPCRs) to employ their immunological actions. In insects, prostaglandins have been implicated in the regulation of both cellular and humoral immune responses, yet studies have been limited by the absence of a described prostaglandin receptor. Here, we characterize a prostaglandin E2 receptor (AgPGE2R) in the mosquito Anopheles gambiae and examine its contributions to innate immunity. AgPGE2R expression is most abundant in circulating hemocytes where it is primarily localized to oenocytoid immune cell populations. Through the administration of prostaglandin E2 (PGE2) and AgPGE2R-silencing by RNAi, we demonstrate that PGE2 signaling regulates the expression of a subset of prophenoloxidases (PPOs) and antimicrobial peptides (AMPs). PGE2 priming via the AgPGE2R significantly limited bacterial replication and suppressed Plasmodium oocyst survival. Additional experiments establish that PGE2 priming increases phenoloxidase (PO) activity through the increased expression of PPO1 and PPO3, which significantly influence Plasmodium oocyst survival. We also provide evidence that PGE2 priming is concentration-dependent, where high concentrations of PGE2 promote oenocytoid lysis, negating the protective effects of PGE2 priming on anti-Plasmodium immunity. Taken together, our results characterize the AgPGE2R and the role of prostaglandin signaling on immune cell function, providing new insights into the role of PGE2 on anti-bacterial and anti-Plasmodium immune responses in the mosquito host.

immunology↗

bioRxiv2020

Aspirin inhibition of prostaglandin synthesis impairs egg development across mosquito taxa

Several endocrine signals are known to mediate mosquito egg development including insulin-like peptide, 20-hydroxyecdysone, and juvenile hormone. The objective of this study was to determine the effects of prostaglandin E2 (PGE2) as an additional mediator of oogenesis in the mosquitoes, Aedes albopictus and Anopheles gambiae. The injection of aspirin (an inhibitor of cyclooxygenase) shortly after blood-feeding significantly inhibited egg development at choriogenesis in a dose-dependent manner in Ae. albopictus. Moreover, oral administration of aspirin to An. albopictus and An. gambiae also inhibited egg production. The aspirin treatment suppressed expression of the genes (Yellow-g and Yellow-g2) associated with exochorion darkening and led to the production of a malformed egg shell in Ae. albopictus. These inhibitory effects of aspirin on egg development were rescued by the addition of PGE2, confirming the specificity of aspirin in inhibiting prostaglandin production. To validate these results, we identified a putative PGE2 receptor (Aa-PGE2R) in Ae. albopictus. Aa-PGE2R expression was highly inducible in adult ovary after blood-feeding. RNA interference of Aa-PGE2R expression resulted in the significant suppression of choriogenesis similar to aspirin treatment, where the addition of PGE2 to Aa-PGE2R-silenced females failed to rescue egg production. Together, these results suggest that PG synthesis and signaling are required for egg development across diverse mosquito taxa. Author SummaryProgstaglandins (PGs) play crucial roles in mediating various physiological processes in insects. Aspirin (ASP) inhibits PG biosynthesis and has been used as an anti-inflammatory drug. ASP injection or feeding to mosquitoes of Aedes albopictus or Anopheles gambiae significantly inhibits egg production at chorion formation. This led to significant reduction in fecundity and egg hatchability. PG signal is interrupted by RNA interference (RNAi) of PGE2 receptor. The RNAi treatment also gave a similar damage to females in egg production as seen in ASP treatment. Thus, PG signal is required for egg production of these mosquitoes. Data Availability StatementAll relevant data are within the manuscript and its Supporting Information file.

developmental biology↗

bioRxiv2020

Optimized residue analysis method for broflanilide and its metabolites in agricultural produce using the QuEChERS method and LC-MS/MS

Since broflanilide is a newly developed pesticide, analytical methods are required to determine the corresponding pesticide residues in diverse crops and foods. In this study, a pesticide residue analysis method was optimized for the detection and quantification of broflanilide and its two metabolites, DM-8007 and S(PFH-OH)-8007, in brown rice, soybean, apple, green pepper, mandarin, and kimchi cabbage. Residue samples were extracted from the produce using QuEChERS acetate and citrate buffering methods and were purified by dispersive solid-phase extraction (d-SPE) using six different adsorbent compositions with varying amounts of primary secondary amine (PSA), C18, and graphitized carbon black. All the sample preparation methods gave low-to-medium matrix effects, as confirmed by liquid chromatography-tandem mass spectrometry using standard solutions and matrix-matched standards. In particular, the use of the citrate buffering method, in combination with purification by d-SPE using 25 mg of PSA and a mixture of other adsorbents, consistently gave low matrix effects that in the range from -18.3 to 18.8%. Pesticide recoveries within the valid recovery range 70-120% were obtained both with and without d-SPE purification using 25 mg of PSA and other adsorbents. Thus, the developed residue analysis method is viable for the determination of broflanilide and its metabolites in various crops.

plant biology↗

bioRxiv2020

Distinct CD8+ T Cell Programming in the Tumor Microenvironment Contributes to Sex Bias in Bladder Cancer Outcome

Men and women show striking yet unexplained discrepancies in incidence, clinical presentation, and therapeutic response across different types of infectious/autoimmune diseases and malignancies1,2. For instance, bladder cancer shows a 4-fold male-biased incidence that persists after adjustment for known risk factors3,4. Here, we utilize murine bladder cancer models to establish that male-biased tumor burden is driven by sex differences in endogenous T cell immunity. Notably, sex differences exist in early fate decisions by intratumoral CD8+ T cells following their activation. While female CD8+ T cells retain their effector function, male counterparts readily adopt a Tcf1lowTim3- progenitor state that becomes exhausted over tumor progression. Human cancers show an analogous male-biased frequency of exhausted CD8+ T cells. Mechanistically, we describe an opposing interplay between CD8+ T cell intrinsic androgen and type I interferon5,6 signaling in Tcf1/Tcf7 regulation and formation of the progenitor exhausted T cell subset. Consistent with female-biased interferon response7, testosterone-dependent stimulation of Tcf1/Tcf7 and resistance to interferon occurs to a greater magnitude in male CD8+ T cells. Male-biased predisposition for CD8+ T cell exhaustion suggests that spontaneous rejection of early immunogenic bladder tumors is less common in males and carries implications for therapeutic efficacy of immune checkpoint inhibitors8,9.

immunology↗

bioRxiv2019

20-hydroxyecdysone (20E) primes innate immune responses that limit bacteria and malaria parasite survival in Anopheles gambiae

Blood-feeding is an integral behavior of mosquitoes to acquire nutritional resources needed for reproduction. This requirement also enables mosquitoes to serve as efficient vectors to acquire and potentially transmit a multitude of mosquito-borne diseases, most notably malaria. Recent studies suggest that mosquito immunity is stimulated following a blood meal, independent of infection status. Since blood-feeding results in the increased production of the hormone 20-hydroxyecdysone (20E), we hypothesized that 20E may play an important role in priming the immune response for pathogen challenge. Herein, we examine the immunological effects of priming in Anopheles gambiae with 20E prior to pathogen infection, demonstrating a significant reduction in bacteria and Plasmodium berghei survival in the mosquito host. RNA-seq analysis following 20E treatment identifies several known 20E-regulated genes, as well as several immune genes with previously reported function in anti-pathogen defense. This includes the anti-microbial peptide cecropin 3, which we demonstrate its role as an antagonist of bacteria and Plasmodium in Anopheles gambiae and provide support that these responses are under temporal regulation. Together, these data demonstrate that 20E influences cellular immune function and anti-pathogen immunity following mosquito blood-feeding, arguing the importance of hormones in the regulation of mosquito innate immune function.

immunology↗

bioRxiv2019

Malaria parasite immune evasion and adaptation to its mosquito host is influenced by the acquisition of multiple blood meals

A minimum of two blood meals are required for a mosquito to acquire and transmit malaria, yet Anopheles mosquitoes frequently obtain additional blood meals during their adult lifespan. To determine the impact of subsequent blood-feeding on parasite development in Anopheles gambiae, we examined rodent and human Plasmodium parasite infection with or without an additional non-infected blood meal. We find that an additional blood meal significantly reduces P. berghei immature oocyst numbers, yet does not influence mature oocysts that have already begun sporogony. This is in contrast to experiments performed with the human parasite, P. falciparum, where an additional blood meal does not affect oocyst numbers. These observations are reproduced when mosquitoes were similarly challenged with an artificial protein meal, suggesting that parasite losses are due to the physical distension of the mosquito midgut. We provide evidence that feeding compromises the integrity of the midgut basal lamina, enabling the recognition and lysis of immature P. berghei oocysts by the mosquito complement system. Moreover, we demonstrate that additional feeding promotes P. falciparum oocyst growth, suggesting that human malaria parasites exploit host resources provided with blood-feeding to accelerate their growth. This contrasts experiments with P. berghei, where the size of surviving oocysts is independent of an additional blood meal. Together, these data demonstrate differences in the ability of Plasmodium species to evade immune detection and adapt to utilize host resources at the oocyst stage, representing an additional, yet unexplored component of vectorial capacity that has important implications for transmission of malaria.

microbiology↗

bioRxiv2019

Fluorescent Sp3 Defect-Tailored Carbon Nanotubes Enable NIR-II Single Particle Imaging in Live Brain Slices at Ultra-Low Excitation Doses

Cellular and tissue imaging in the second near-infrared window (NIR-II, [~]1000 - 1350 nm) is advantageous for in vivo studies because of low light extinction by biological constituents at these wavelengths. However, deep tissue imaging at the single molecule sensitivity has not been achieved in the NIR-II window due to lack of suitable bio-probes. Single-walled carbon nanotubes have emerged as promising near-infrared luminescent molecular bio-probes; yet, their inefficient photoluminescence (quantum yield [~]1%) drives requirements for sizeable excitation doses ([~]1-10 kW/cm2) that are significantly blue-shifted from the NIR-II region (<850 nm) and may thus ultimately compromise live tissue. Here, we show that single nanotube imaging can be achieved in live brain tissue using ultralow excitation doses ([~]100 W/cm2), an order of magnitude lower than those currently used. To accomplish this, we synthesized fluorescent sp3-defect tailored (6,5) carbon nanotubes which, when excited at their first order excitonic transition fluoresce brightly at [~]1160 nm. The biocompatibility of these functionalized nanotubes, which are wrapped by state-of-the-art encapsulation agents (phospholipid-polyethylene glycol), is demonstrated using standard cytotoxicity assays. Single molecule photophysical studies of these biocompatible nanotubes allowed us to identify the optimal luminescence properties in the context of biological imaging.

biophysics↗

bioRxiv2019

Ultra-widefield fluorescein angiography findings in patients with multiple retinal holes.

PurposeTo evaluate the ultra-widefield fluorescein angiography (UWFA) findings in patients with multiple retinal holes.\n\nMethodsSeventy-five eyes, each with more than two retinal holes, underwent a comprehensive ophthalmologic examination, including UWFA, along with 77 age-matched control eyes with no retinal holes. The UWFA was scored according to a system suggested by the Angiography Scoring for Uveitis Working Group (ASUWG). UWFA findings from the patients with retinal holes were compared with those of the control group without retinal holes. Factors associated with a high ASUWG score were also evaluated.\n\nResultsPatients with multiple retinal holes showed a significantly higher prevalence of retinal vascular staining/leakage, capillary leakage at the posterior pole, and capillary leakage at the periphery when compared to the control group (p<0.001, for each of them). Univariate analysis revealed that logMAR BCVA (r=0.271, p=0.027), spherical equivalent (r= -0.275, p=0.021), and number of retinal holes (r=0.271, p=0.027) were associated with a higher ASUWG score. After adjustments for age, gender, and logMAR BCVA, multivariate regression analysis revealed that the spherical equivalent was independently associated with a higher ASUWG score (r2=0.161, p=0.001).\n\nConclusionsPatients with multiple retinal holes showed profound peripheral vascular leakages on UWFA findings, suggesting the presence of chronic retinal traction induced by equatorial scleral elongation.

neuroscience↗

bioRxiv2018

Loop-mediated isothermal amplification assay for Enterococcus sp., E. coli and S. aureus in chicken

Bacterial chondronecrosis with osteomyelitis (BCO) is a major cause of lameness in broiler chicken, and results in serious economic losses worldwide. Although the pathogenesis mechanism leading to lameness is not entirely understood, some strains of Enterococcus sp., avian pathogenic Escherichia coli, or Staphylococcus aureus have been long recognized as important causative pathogens. To prevent the progression of Enterococcus sp., avian pathogenic E. coli, or S. aureus infections, we developed rapid, sensitive, and convenient diagnostic assays using loop-mediated isothermal amplification (LAMP). Entero-Common-LAMP assays were developed for a simultaneous detection of eight Enterococcus species. To target specific microorganisms, seven Entero-Specific-LAMP assays for E. faecalis, E. faecium, E. hirae, E. gallinarum, E. avium, E. durans and E. cecorum, and E. coli-LAMP and S. aureus-LAMP assays, were developed. Considering the prevalence and economic impact of Enterococcus sp., E. coli, and S. aureus, the developed ten different LAMP assays have a considerable potential as routine diagnostic methods in the field or in resource-limited environments.

microbiology↗

bioRxiv2017

Heartfelt Face Perception via the Interoceptive Pathway - a MEG study

The somatic marker hypothesis proposes that the cortical representation of visceral signals is a crucial component of emotion processing. No previous study has investigated the causal relationships among brain regions that process visceral information during emotional perception. In this magnetoencephalography study of 32 healthy subjects, heartbeat-evoked potentials (HEPs), which reflect the cortical processing of heartbeats, were modulated by the perception of a sad face. The modulation effect was localized to the prefrontal cortices, the globus pallidus, and an interoceptive network including the right anterior insula (RAI) and anterior cingulate cortex (RACC). Importantly, our Granger causality analysis provides the first evidence for increased causal flow of heartbeat information from the RAI to the RACC during sad face perception. Moreover, this HEP modulation effect was neither an artefact nor an effect of visual-evoked potentials. These findings provide important progress in the understanding of brain-body interactions during emotion processing.

neuroscience↗

bioRxiv2017

Comparison of Principal Component Analysis and t-Stochastic Neighbor Embedding with Distance Metric Modifications for Single-cell RNA-sequencing Data Analysis

Recent developments in technological tools such as next generation sequencing along with peaking interest in the study of single cells has enabled single-cell RNA-sequencing, in which whole transcriptomes are analyzed on a single-cell level. Studies, however, have been hindered by the ability to effectively analyze these single cell RNA-seq datasets, due to the high-dimensional nature and intrinsic noise in the data. While many techniques have been introduced to reduce dimensionality of such data for visualization and subpopulation identification, the utility to identify new cellular subtypes in a reliable and robust manner remains unclear. Here, we compare dimensionality reduction visualization methods including principle component analysis and t-stochastic neighbor embedding along with various distance metric modifications to visualize single-cell RNA-seq datasets, and assess their performance in identifying known cellular subtypes. Our results suggest that selecting variable genes prior to analysis on single-cell RNA-seq data is vital to yield reliable classification, and that when variable genes are used, the choice of distance metric modification does not particularly influence the quality of classification. Still, in order to take advantage of all the gene expression information, alternative methods must be used for a reliable classification.

bioinformatics↗