Biology subjects

Huynh, S.

Publications and source records attributed to Huynh, S..

7 recordsLinked to original sources

bioRxiv2026

BBB-Permeable Near-Infrared Oxazine Fluorophores for White Matter Tract Imaging

Preserving critical functional tissue remains a major challenge in fluorescence-guided surgery (FGS), particularly in neurosurgery where injury to white matter tracts can lead to lasting neurological deficits. Probes for preventing iatrogenic injury of the peripheral nervous system have highlighted the potential of real-time intraoperative guidance for nerve-sparing surgery, supporting improved preservation of critical functional tissue, but analogous tools for the central nervous system remain limited. While there are some awake mapping and MRI based techniques that try to minimize the resection of white matter tracts (WMTs), they do not provide surgeons with real-time visualization. To address this gap, we rationally translated a peripheral nerve targeted oxazine fluorophore platform into a library of novel oxazine dyes that can penetrate the blood-brain barrier (BBB), exhibit specificity for white matter tissue and maintain spectral compatibility with clinically relevant imaging systems. Guided by our fluorophore medicinal chemistry platform, this work includes library design, photophysical property characterization, in vivo WMTs specificity screening, and in vivo imaging window assessment of the lead candidates to evaluate neurosurgical workflow compatibility. The lead candidate identified from this library demonstrated strong in vivo WMTs-specific fluorescence intensity, contrast and imaging window compatible with neurosurgical workflows, establishing BBB-permeable oxazine fluorophores as a promising scaffold for future structure-sparing neurosurgical FGS.

bioengineering↗

bioRxiv2025

A line attractor maintains aggressiveness during feeding in hangry mice

Aggression evolved to protect resources such as food from competitors, but animals must balance fighting and feeding so that they facilitate rather than hinder re-establishment of energy homeostasis. How this balancing is computed is not well understood. We have approached this problem at the level of neural population-coding by examining the effect of progressive starvation on a hypothalamic line attractor that encodes an internal state of aggressiveness. Moderate fasting yielded "hangry" mice, decreasing attack latency and increasing attack frequency. In parallel, line attractor ramping rate and stability were increased, suggesting that hunger enhances aggressiveness by modifying neural dynamics. In contrast, prolonged starvation inhibited aggression and eliminated the line attractor. In satiated mice, titrated acute chemogenetic activation of arcuate AgRP neurons recapitulated the biphasic effects of progressive starvation, suggesting that a continuous increase in hunger exerts bi-directional influences at different intensities. When confronted with food and an intruder, hangry mice alternated between feeding and fighting. During eating, population neural activity moved out of the line attractor while activity in the attractor dimension remained unchanged. Following feeding, activity rapidly relaxed back into the attractor and aggression resumed. Thus, the line attractor may serve to keep hungry animals primed for aggression during intermittent feeding bouts.

animal behavior and cognition↗

bioRxiv2025

American black bear (Ursus americanus) as a potential host for Campylobacter jejuni

The Gram-negative bacterium Campylobacter jejuni is part of the commensal gut microbiota of numerous animal species and a leading cause of bacterial foodborne illness in humans. Most complete genomes of C. jejuni are from strains isolated from human clinical, poultry, and ruminant samples. Here, we characterized and compared the genomes of C. jejuni that were isolated from American black bears in three states in the southeastern United States. Despite the limited sample size (n=9), the isolates displayed substantial genotypic variability, including eight distinct sequence types (STs) and variable gene content encoding surface glycan structures such as capsular polysaccharides (CPS) and lipooligosaccharides (LOS). Phylogenetic analysis identified several C. jejuni host generalist strains among the isolates from bears that clustered with isolates from domestic poultry, cattle, and environmental sources. Three isolates (SKBC94, SKBC3, SKBC5) clustered with wildlife-associated strains, exhibiting mutations or deletions in loci associated with cytolethal distending toxin production and oxidative stress resistance, potentially influencing host-specific colonization. Additionally, strains SKBC3 and SKBC5 harbored distinct Entner-Doudoroff (E-D) loci, suggesting a potential evolutionary fitness advantage. This study provides the first evidence of C. jejuni colonization in American black bears, highlighting their potential role as reservoirs for diverse C. jejuni lineages from both anthropogenic and environmental sources. Further research is needed to determine the prevalence and host specificity of C. jejuni strains in black bears and their potential implications for public and wildlife health.

microbiology↗

bioRxiv2023

Bacterial diversity and composition on the rinds of specific melon cultivars and hybrids from across different growing regions in the United States

The goal of this study was to characterize the bacterial diversity on different melon varieties grown in different regions of the US, and determine the influence that region, rind netting, and variety of melon has on the composition of the melon microbiome. Assessing the bacterial diversity of the microbiome on the melon rind can identify antagonistic and protagonistic bacteria for foodborne pathogens and spoilage organisms to improve melon safety, prolong shelf-life, and/or improve overall plant health. Bacterial community composition of melons (n = 603) grown in seven locations over a four-year period were used for 16S rRNA gene amplicon sequencing and analysis to identify bacterial diversity and constituents. Statistically significant differences in alpha diversity based on the rind netting and growing region (p < 0.01) were found among the melon samples. Principal Coordinate Analysis based on the Bray-Curtis dissimilarity distance matrix found that the melon bacterial communities clustered more by region rather than melon variety (R2 value: 0.09 & R2 value: 0.02 respectively). Taxonomic profiling among the growing regions found Enterobacteriaceae, Bacillaceae, Microbacteriaceae, and Pseudomonadaceae present on the different melon rinds at an abundance of [≥] 0.1%, but no specific core microbiome was found for netted melons. However, a core of Pseudomonadaceae, Bacillaceae, and Exiguobacteraceae were found for non-netted melons. The results of this study indicate that bacterial diversity is driven more by the region that the melons were grown in compared to rind netting or melon type. Establishing the foundation for regional differences could improve melon safety, shelf-life, and quality as well as the consumers health.

microbiology↗

bioRxiv2022

G protein βγ subunits bind to and inhibit the function of multiple Qa- and Qb,c-SNARE isoforms.

While the ability of G protein {beta}{gamma} subunits (G{beta}{gamma}) to bind to and functionally inhibit the neuronal SNARE proteins Stx1A, SNAP25, and synaptobrevin in the presence of the calcium sensor synaptotagmin I is well documented, these three SNARE proteins, which form the core SNARE complex for synchronous evoked release in neurons, are but a subset of the larger family of SNARE proteins, which participate in many other exocytic processes within the cell and in other populations of secretory cells throughout the body, from which the release of neurotransmitters, hormones, and other factors is regulated by Gi/o-coupled GPCRs. The ability of G{beta}{gamma} to regulate these processes is unknown. To investigate the feasibility of this mechanism to inhibit SNARE function more broadly, we utilized a series of biochemical assays of binding and function with four Qa-SNAREs (Stx1A, Stx2, Stx3, and Stx4) and four Qb,c-SNAREs (SNAP25, SNAP23, SNAP29, and SNAP47) in tandem with the R-SNARE synaptobrevin, synaptotagmin I, and G{beta}{gamma}. G{beta}{gamma} was found to bind to multiple Qa-SNARE isoforms as well as SNAP23, and inhibit the lipid mixing function of these SNAREs, as well as SNAP29. Together, this data suggests a more broad role for the G{beta}{gamma}-SNARE pathway in the regulation of exocytosis beyond cells that express Stx1A or SNAP25.

biochemistry↗

bioRxiv2021

Utilization efficiency of human milk oligosaccharides by human-associated Akkermansia is strain-dependent

Akkermansia muciniphila are mucin degrading bacteria found in the human gut and are often associated with positive human health. However, despite being detected as early as one month of age, little is known about the role of Akkermansia in the infant gut. Human milk oligosaccharides (HMOs) are abundant components of human milk and are structurally similar to the oligosaccharides that comprise mucin, the preferred growth substrate of human-associated Akkermansia. A limited subset of intestinal bacteria has been shown to grow well on HMOs and mucin. We therefore examined the ability of genomically diverse strains of Akkermansia to grow on HMOs. First, we screened 85 genomes representing the four known Akkermansia phylogroups to examine their metabolic potential to degrade HMOs. Furthermore, we examined the ability of representative isolates to grow on individual HMOs in a mucin background and analyzed the resulting metabolites. All Akkermansia genomes were equipped with an array of glycoside hydrolases associated with HMO-deconstruction. Representative strains were all able to grow on HMOs with varying efficiency and growth yield. Strain CSUN-19 belonging to the AmIV phylogroup, grew to the highest level in the presence of fucosylated and sialylated HMOs. This activity may be partially related to the increased copy numbers and/or the enzyme activities of the -fucosidases, -sialidases, and {beta}-galactosidases. Utilization of HMOs by strains of Akkermansia suggests that ingestion of HMOs by an infant may enrich for these potentially beneficial bacteria. Further studies are required to realize this opportunity and deliver long-lasting metabolic benefits to the human host. ImportanceHuman milk oligosaccharides (HMOs) are utilized by a limited subset of bacteria in the infant gut. Akkermansia are detected in infants as young as one month of age and are thought to contribute to the HMO deconstruction capacity of the infant. Here, using phylogenomics, we examined the genomic capacity of different Akkermansia phylogroups to potentially deconstruct HMOs. Furthermore, we experimentally showed that strains from all the currently known phylogroups of Akkermansia can deconstruct all the major types of HMOs, albeit with different utilization efficiencies. This study thus examines Akkermansia-HMO interactions that can potentially influence the gut microbial ecology during the first 1,000 days of life - a critical phase for the development of the gut microbiome and infant health. This study will be of interest to a wide range of scientists from microbiologists, glycochemists/glycobiologists, to functional food developers investigating Akkermansia as probiotics or functional foods containing milk oligosaccharides as prebiotics.

microbiology↗

bioRxiv2019

Hybridization preceded radiation in diploid wheats

Evolutionary relationships among the Aegilops-Triticum relatives of cultivated wheats have been difficult to resolve owing to incomplete lineage sorting and reticulate evolution. Recent studies have suggested that the wheat D-genome lineage (progenitor of Ae. tauschii) originated through homoploid hybridization between the A-genome lineage (progenitor of Triticum s.str.) and the B-genome lineage (progenitor of Ae. speltoides). Scenarios of reticulation have been debated, calling for adequate phylogenetic analyses based on comprehensive sampling. To reconstruct the evolution of Aegilops-Triticum diploids, we here combined high-throughput sequencing of 38 nuclear low-copy loci of multiple accessions of all 13 species with inferences of the species phylogeny using the full-parameterized MCMC_SEQ method. Phylogenies recovered a monophyletic Aegilops-Triticum lineage that began diversifying ~6.5 Ma ago and gave rise to four sublineages, i.e. the A- (2 species), B- (1 species), D- (9 species) and T- (Ae. mutica) genome lineage. Full-parameterized phylogenies as well as patterns of tree dilation and tree compression supported a hybrid origin of the D-genome lineage from A and B ~4.1 Ma ago, and did not indicate additional hybridization events. This comprehensive and dated phylogeny of wheat relatives indicates that the origin of the hybrid D-genome was followed by intense diversification into almost all diploid as well as allopolyploid wild wheats.

evolutionary biology↗