Biology subjects

Bowman, A.

Publications and source records attributed to Bowman, A..

8 recordsLinked to original sources

bioRxiv2026

Rapid Electro-optic Two-photon Bessel Light Sheet Fluorescence Lifetime Imaging for Tissue Volume Interrogation

We report a two-photon light sheet electro-optic fluorescence lifetime imaging microscopy (TPLS-EO-FLIM) technique based on an electro-optic (EO) modulation detection module. Scanning two-photon Bessel light sheet excitation was used to achieve in-depth volumetric imaging. The low cross-section of multiphoton excitation requires high detection efficiency, and electro-optic detection enables fast wide-field FLIM with a scientific complementary metal-oxide-semiconductor (sCMOS) detector. Phototoxicity is minimized by utilizing signal from the entire illuminated sample area in a wide field camera exposure, and time-resolved volume acquisitions are feasible in minutes, with cross-sectional field of view and light sheet length over 300 microns. The method has sub-nanosecond lifetime resolution and is capable of accurate FLIM images in 10 ms exposures with as low as a few hundred photons per pixel. The technique was demonstrated through volumetric FLIM of a green fluorescent protein (GFP) labeled zebrafish embryo heart, of multi-fluorescent protein (multi-FP) labeled plant root structures and of dynamic cardiac cycles in live zebrafish embryos. For the latter, we recorded the cardiac cycle dynamics of a zebrafish embryo at 50 frames per second and measured biomechanical parameters such as heart rate, ventricle/atrium areas, atrioventricular valve dynamics, and fractional area change. Taken together, these studies show the capability of the system for rapid, high resolution, and functional imaging in diverse biological contexts.

bioengineering↗

bioRxiv2026

Natural H5N1 immunity in dairy cows is durable and cross-protective but non-sterilizing

Ongoing transmission of influenza A virus (H5N1) in U.S. dairy cattle threatens both animal and human health, underscoring the need to understand the durability of host immunity against reinfection with evolving genotypes. We challenged naive and convalescent cows, infected one year prior with H5N1 genotype B3.13, with either homologous B3.13 or heterologous D1.1 genotype virus. Homologous rechallenge resulted in complete clinical protection with no infectious viral shedding. Conversely, heterologous rechallenge led to transient clinical disease and limited infectious viral shedding. Convalescent cows experienced significantly milder disease than naive cows, which developed severe illness with high viral shedding and required early euthanasia, regardless of the strain. These findings indicate that naturally acquired immunity offers strong protection against severe illness but may allow silent transmission of divergent strains. Therefore, natural herd immunity alone is unlikely to eliminate the virus; controlling H5N1 in cattle will likely require vaccination strategies that address viral evolution.

immunology↗

bioRxiv2025

Vertical Transmission of Bovine H5N1 during Pregnancy and Lactation in Mice

Avian influenza H5N1 has pandemic potential and historically has caused more severe disease in pregnant women than the general population. With increasing transmission of H5N1 detected among placental mammals, animal models are necessary for testing countermeasures, including during pregnancy. Pregnant outbred mice were infected with a contemporary strain of bovine H5N1 during the second or third trimester equivalent. Second trimester infection caused in utero transmission, with infectious virus detected in the uterus, placenta, and fetus. Birth following third trimester infection resulted in offspring with decreased size, neurodevelopmental delays, and adolescent behavioral impairments, with infectious virus detected in the neonatal milk ring and lungs, as well as mammary tissues. H5N1 viral protein colocalized with trophoblast cells in the placenta and epithelial cells in mammary tissue that spatially overlapped with lectins for 2,3-linked SA. With the pandemic potential of H5N1, our vertical transmission model in placental mammals is essential for understanding viral spread and evaluating treatments during pregnancy.

microbiology↗

bioRxiv2023

Genetic drift and purifying selection shape within-host influenza A virus populations during natural swine infections

Patterns of within-host influenza A virus (IAV) diversity and evolution have been described in natural human infections, but these patterns remain poorly characterized in non-human hosts. Elucidating these dynamics is important to better understand IAV biology and the evolutionary processes that govern spillover into humans. Here, we sampled an IAV outbreak in pigs during a week-long county fair to characterize viral diversity and evolution in this important reservoir host. Nasal wipes were collected on a daily basis from all pigs present at the fair, yielding up to 421 samples per day. Subtyping of PCR-positive samples revealed the co-circulation of H1N1 and H3N2 subtype IAVs. PCR-positive samples with robust Ct values were deep-sequenced, yielding 506 sequenced samples from a total of 253 pigs. Based on higher-depth re-sequenced data from a subset of these initially sequenced samples (260 samples from 168 pigs), we characterized patterns of within-host IAV genetic diversity and evolution. We find that IAV genetic diversity in single-subtype infected pigs is low, with the majority of intra-host single nucleotide variants (iSNVs) present at frequencies of <10%. The ratio of the number of nonsynonymous to the number of synonymous iSNVs is significantly lower than under the neutral expectation, indicating that purifying selection shapes patterns of within-host viral diversity in swine. The dynamic turnover of iSNVs and their pronounced frequency changes further indicate that genetic drift also plays an important role in shaping IAV populations within pigs. Taken together, our results highlight similarities in patterns of IAV genetic diversity and evolution between humans and swine, including the role of stochastic processes in shaping within-host IAV dynamics.

evolutionary biology↗

bioRxiv2021

Identifying target sites for placental therapeutics through the comparison of normal term pregnancies and intrauterine growth restricted proteomes

A variety of pathologies, including intrauterine growth restriction (IUGR), have been linked to placental insufficiencies as important causal factors, however, little has been done to develop therapeutics that may improve placental development, structure and function. The placenta offers the opportunity to manipulate the in-utero environment without directly intervening with the fetus, accessible from the maternal circulation, a vital but temporary organ, the placenta is no longer required after birth. Developing therapeutics must involve multiple aspects of targeting and safety to ensure no off-target impact on the pregnant person or fetus as well as enhance efficiency of delivery. In addition to our studies on nanoparticle delivery to the placenta [1] we are developing targeting strategies to allow peripheral delivery via the maternal circulation. In this study we have performed the isolation of the microvillous membrane from human placental syncytiotrophoblast (the targeting cell) and via proteomic analysis identified potential targeting moieties, we have then compared this to publicly available data from pregnancies complicated by fetal growth restriction to ensure that we do not identify targets which would be reduced in FGR, resulting in less efficient targeting. HighlightsO_LIProteomic analysis detected key genes, proteins, and pathways present in the syncytiotrophoblast membrane of normal placentas. C_LIO_LISpecific membrane proteins identified show promise for future characterization of placental pathologies, such as IUGR. C_LIO_LIProteomes of normal and diseased placentas require further study to better understand the etiology of certain conditions. C_LI

bioinformatics↗

bioRxiv2021

SARS-CoV-2 infection in free-ranging white-tailed deer (Odocoileus virginianus)

Human-to-animal spillover of SARS-CoV-2 virus has occurred in a wide range of animals, but thus far, the establishment of a new natural animal reservoir has not been detected. Here, we detected SARS-CoV-2 virus using rRT-PCR in 129 out of 360 (35.8%) free-ranging white-tailed deer (Odocoileus virginianus) from northeast Ohio (USA) sampled between January-March 2021. Deer in 6 locations were infected with at least 3 lineages of SARS-CoV-2 (B.1.2, B.1.596, B.1.582). The B.1.2 viruses, dominant in Ohio at the time, spilled over multiple times into deer populations in different locations. Deer-to-deer transmission may have occurred in three locations. The establishment of a natural reservoir of SARS-CoV-2 in white-tailed deer could facilitate divergent evolutionary trajectories and future spillback to humans, further complicating long-term COVID-19 control strategies. One-Sentence SummaryA significant proportion of SARS-CoV-2 infection in free-ranging US white-tailed deer reveals a potential new reservoir.

molecular biology↗

bioRxiv2020

Tissue tropisms of avian influenza A viruses affect their spillovers from wild birds to pigs

Wild aquatic birds maintain a large genetically diverse pool of influenza A viruses (IAVs), which can be transmitted to lower mammals and ultimately humans. Through phenotypic analyses, only a small set of avian IAVs replicated well in the epithelial cells of swine upper respiratory tracts, and these viruses were shown to infect and cause virus shedding in pigs. Such a phenotypic trait appears to emerge randomly and are distributed among IAVs across multiple avian species, geographic and temporal orders, and is determined not by receptor binding preference but other markers across genomic segments, such as those in the ribonucleoprotein complex. This study demonstrates that phenotypic variants exist among avian IAVs, only a few of which may result in viral shedding in pigs upon infection, providing opportunities for these viruses to become pig adapted, thus posing a higher potential risk for creating novel variants or detrimental reassortants within pig populations. Author SummaryHaving both avian-like receptors and human-like 2,6-linked sialic acid receptors, swine serve as a "mixing vessel" for generating human influenza pandemic strains. All HA subtypes of IAVs can infect swine; however, only sporadic cases of avian IAVs are reported in domestic swine. The molecular mechanisms affecting avian IAVs ability to infect swine are still not fully understood. Through phenotypic analyses, this study suggested that tissue tropisms (i.e., in swine upper respiratory tracts) of avian IAVs affect their spillovers from wild birds to pigs, and this phenotype was determined not by receptor binding preference but by other markers across genomic segments, such as those in the ribonucleoprotein complex. In addition, our results showed that such a phenotypic trait was sporadically and randomly distributed among IAVs across multiple avian species, geographic and temporal orders. This study suggested an efficient way for risk assessment of avian IAVs, such as in evaluating their potentials to be transmitted from avian to pigs.

microbiology↗

bioRxiv2019

Size-dependent increase in RNA Polymerase II initiation rates mediates gene expression scaling with cell size

Cell size varies during the cell cycle and in response to external stimuli. This requires the tight coordination, or \"scaling\", of mRNA and protein quantities with the cell volume in order to maintain biomolecules concentrations and cell density. Evidence in cell populations and single cells indicates that scaling relies on the coordination of mRNA transcription rates with cell size. Here we use a combination of single-molecule fluorescence in situ hybridisation (smFISH), time-lapse microscopy and mathematical modelling in single fission yeast cells to uncover the precise molecular mechanisms that control transcription rates scaling with cell size. Linear scaling of mRNA quantities is apparent in single fission yeast cells during a normal cell cycle. Transcription rates of both constitutive and regulated genes scale with cell size without evidence for transcriptional bursting. Modelling and experimental data indicate that scaling relies on the coordination of RNAPII transcription initiation rates with cell size and that RNAPII is a limiting factor. We show using real-time quantitative imaging that size increase is accompanied by a rapid concentration independent recruitment of RNAPII onto chromatin. Finally, we find that in multinucleated cells, scaling is set at the level of single nuclei and not the entire cell, making the nucleus the transcriptional scaling unit. Integrating our observations in a mechanistic model of RNAPII mediated transcription, we propose that scaling of gene expression with cell size is the consequence of competition between genes for limiting RNAPII.

molecular biology↗