Biology subjects

Watson, G.

Publications and source records attributed to Watson, G..

10 recordsLinked to original sources

bioRxiv2026

Synchrotron phase contrast micro-CT of prostate tissue

Formalin-fixed prostate tissue samples were imaged by propagation-based synchrotron phase contrast micro computed tomography ({micro}CT) with a 3D spatial resolution of ca. 3 {micro}m. Post-{micro}CT, samples were prepared for histology with sections close to coplanar with the transverse {micro}CT image planes. Haematoxylin and eosin stained sections were examined by an expert prostate histopathologist and compared qualitatively with corresponding {micro}CT-visible microstructure features. There is potential for {micro}CT to provide complimentary information to conventional histology and light microscopy without the need for preparation of stained thin sections. For the imaging conditions and spatial resolution of our study, {micro}CT may provide tissue architectural features similar to those used in Gleason grading, albeit without clear subcellular microstructure detail. At the spatial resolution of our study {micro}CT may provide novel 3D microstructure information for validation of diffusion weighted magnetic resonance imaging (MRI) methods. As an example, we demonstrate a qualitative correlation between {micro}CT-derived stromal fibre orientation and preferential water diffusion direction measured by diffusion tensor MRI microscopy of the same sample.

cancer biology↗

bioRxiv2022

Elucidating a locus coeruleus-hippocampal dopamine pathway for operant reinforcement

Animals can learn to repeat behaviors to earn desired rewards, a process commonly known as reinforcement learning. While previous work has implicated the ascending dopaminergic projections to the basal ganglia in reinforcement learning, little is known about the role of the hippocampus. Here we report that a specific population of hippocampal neurons and their dopaminergic innervation contribute to operant self-stimulation. These neurons are located in the dentate gyrus, receive dopaminergic projections from the locus coeruleus, and express D1 dopamine receptors. Activation of D1+ dentate neurons is sufficient for self-stimulation: mice will press a lever to earn optogenetic activation of these neurons. A similar effect is also observed with selective activation of the locus coeruleus projections to the dentate gyrus, and blocked by D1 receptor antagonism. Calcium imaging of D1+ dentate neurons revealed significant activity at the time of action selection, but not during passive reward delivery. These results reveal the role of dopaminergic innervation of the hippocampus in supporting operant reinforcement.

neuroscience↗

bioRxiv2022

Identifying opportunities for high resolution pesticide usage data to improve the efficiency of endangered species pesticide risk assessment

The US pesticide registration and review process requires regular re-assessment of the risk of pesticide use, including risk to species listed under the Endangered Species Act (ESA). Yet, current methods for assessment were not designed to assess threats that could involve hundreds of pesticides potentially impacting multiple species across a continent. Thus, many pesticides remain on the market without complete review under ESA. A promising approach to address this challenge calls for the use of high-resolution data in the spatial analyses used to determine the likelihood of adverse effect. However, such data are rare, and implementing data collection initiatives are difficult and expensive. Here we examine the extent to which increased data resolution could result in significant gains in efficiency to the pesticide risk assessment process. To do so, we employ a modified value-of-information (VOI) approach. By using data available only in California, we found that high resolution data increased the number of species deemed not likely to be adversely affected by pesticides from less than 5% to nearly 50%. Across the contiguous US, we predicted that 48% of species would be deemed not likely to be adversely affected using high resolution data, compared to 20% without. However, if such data were available in just 11 states, 68% of the available gains in efficiency could be obtained. Therefore, a focused collection or release of high-resolution pesticide usage data could expedite pesticide risk assessment and reduce endangered species risk of pesticide impacts. SignificanceRegulation of environmental risk must balance avoidance of harm with assessment efficiency. The current pesticide registration and review process in the U.S. is generally considered ineffective in assessing impact on species listed under the Endangered Species Act, due to the vast scale of the problem. We assessed the value of using high resolution pesticide usage data in the risk assessment process to identify cost-effective opportunities to rapidly improve this assessment process and ensure that ESA listed species are protected while accounting for agricultural production. Our results suggest that using existing high-resolution data in California and collection of such information from 11 other states could reduce the risk assessment burden across the contiguous U.S. by one-quarter.

ecology↗

bioRxiv2020

A nucleoid-associated protein bends and bridges DNA in a multiplicity of topological states with varying specificity

Nucleoid-associated proteins (NAPs) are crucial in organizing prokaryotic DNA and regulating genes. Vital to these activities are complex nucleoprotein structures, however, how these form remains unclear. Integration host factor (IHF) is an Escherichia coli NAP that creates very sharp bends in DNA at sequences relevant to several functions including transcription and recombination, and is also responsible for general DNA compaction when bound non-specifically. We show that IHF-DNA structural multimodality is more elaborate than previously thought, and provide insights into how this drives mechanical switching towards strongly bent DNA. Using single-molecule atomic force microscopy and atomic molecular dynamics simulations we find three binding modes in roughly equal proportions: "associated" (73{degrees} of DNA bend), "half-wrapped" (107{degrees}) and "fully-wrapped" (147{degrees}), only the latter occurring with sequence specificity. We show IHF bridges two DNA double helices through non-specific recognition that gives IHF a stoichiometry greater than one and enables DNA mesh assembly. We observe that IHF-DNA structural multiplicity is driven through non-specific electrostatic interactions that we anticipate to be a general NAP feature for physical organization of chromosomes.

biophysics↗

bioRxiv2020

Ventral tegmental dopamine neurons control the impulse vector during motivated behavior

The Ventral Tegmental Area (VTA) is a major source of dopamine, especially to the limbic brain regions. Despite decades of research, the function of VTA dopamine neurons remains controversial. Here, using a novel head-fixed behavioral system with five orthogonal force sensors, we show for the first time that distinct populations of VTA dopamine activity precisely represent the impulse vector (force exerted over time) generated by the animal. Optogenetic excitation of VTA dopamine neurons quantitatively determines impulse in the forward direction, and optogenetic inhibition produces impulse in the backward direction. At the same time, these neurons also regulate the initiation and execution of anticipatory licking. Our results indicate that VTA controls the magnitude, direction, and duration of force used to move towards or away from any motivationally relevant stimuli. One Sentence SummaryVTA dopamine bidirectionally controls impulse vector and anticipatory behavior

neuroscience↗

bioRxiv2019

Opponent regulation of action performance and timing by striatonigral and striatopallidal pathways

The basal ganglia have been implicated in action selection and timing, but the relative contributions of the striatonigral (direct) and striatopallidal (indirect) pathways to these functions remain unclear. We investigated the effects of optogenetic stimulation of D1+ (direct) and A2A+ (indirect) neurons in the ventrolateral striatum in head-fixed mice on a fixed time reinforcement schedule. Direct pathway stimulation initiates licking, whereas indirect pathway stimulation suppresses licking and results in rebound licking after stimulation. Moreover, direct and indirect pathways also play distinct roles in timing. Direct pathway stimulation produced a resetting of the internal timing process, whereas indirect pathway stimulation transiently paused timing, and proportionally delayed the next bout of licking. Our results provide evidence for the continuous and opposing contributions of the direct and indirect pathways in the production and timing of reward-guided behavior.

neuroscience↗

bioRxiv2019

Successful field performance in dry-warm environments of soybean expressing the sunflower transcription factor HaHB4

Soybean yield is limited primarily by abiotic constraints. No transgenic soybean with improved abiotic-stress tolerance is available in the market. We transformed soybean plants with genetic constructs able to express the sunflower transcription factor HaHB4, which confers drought tolerance to Arabidopsis and wheat plants. One line (b10H) carrying the sunflower promoter was chosen among three independent lines because it exhibited the best performance in seed yield (SY). Such line was evaluated in the greenhouse and in twenty-seven field trials developed in different environments of Argentina. In greenhouse experiments, transgenic plants showed increased SY under stress conditions together with wider epycotyl diameter, enlarged xylem area and enhanced water use efficiency than controls. They also exhibited enhanced SY in warm-dry field conditions. This response was accompanied by the increased in seed number that was not compensated by the decreased in individual seed weight. The transcriptome analysis of plants from a field trial with maximum SY difference between genotypes indicated an induction of genes encoding redox and heat shock proteins in b10H. Collectively, our results indicate that soybeans transformed with HaHB4 are expected to have reduced SY penalization when cropped in warm-dry conditions, which constitute the best target environments for this technology. HighlightSoybean transformed with the sunflower gene encoding the transcription factor HaHB4 was evaluated in greenhouse and field trials. Transgenic plants significantly outyielded controls in drought-warm environments due to, at least in part, increased seed number, xylem area, and water use efficiency as well as to the induction of genes encoding redox and heat shock proteins.

plant biology↗

bioRxiv2019

Structure-guided design of a synthetic mimic of an EPCR-binding PfEMP1 protein

Structure-guided vaccine design provides a route to elicit a focused immune response against the most functionally important regions of a pathogen surface. This can be achieved by identifying epitopes for neutralizing antibodies through structural methods and recapitulating these epitopes by grafting their core structural features onto smaller scaffolds. In this study, we have conducted a modified version of this protocol. We focused on the PfEMP1 protein family found on the surfaces of erythrocytes infected with Plasmodium falciparum. A subset of PfEMP1 proteins bind to endothelial protein C receptor (EPCR), and their expression correlates with development of the symptoms of severe malaria. Structural studies revealed the PfEMP1 to present a helix-kinked-helix motif which forms the core of the EPCR binding site. Using Rosetta-based design we successfully grafted this motif onto a three-helical bundle scaffold. We show that this synthetic binder interacts with EPCR with nanomolar affinity and adopts the expected structure. We also assessed its ability to bind to antibodies found in immunized animals and in humans from malaria endemic regions. Finally, we tested its capacity to effectively elicit antibodies that prevent EPCR binding and analysed the degree of cross-reactivity of these antibodies across a diverse repertoire of EPCR-binding PfEMP1. This provides a case study of immunogen design, assessing the effect of designing a focused immunogen that contains the core features of a ligand binding site, rather than those of a neutralizing antibody epitope.

microbiology↗

bioRxiv2019

Precise Coordination of 3-dimensional Rotational Kinematics by Ventral Tegmental Area GABAergic Neurons

The Ventral Tegmental Area (VTA) is a midbrain region implicated in a variety of motivated behaviors. However, the function of VTA GABAergic (Vgat+) neurons remains poorly understood. Here, using 3D motion capture, in vivo electrophysiology and calcium imaging, and optogenetics, we demonstrate a novel function of VTAVgat+ neurons. We found three distinct populations of neurons, each representing head angle about a principal axis of rotation: pitch, roll, and yaw. For each axis, opponent cell groups were found that increase firing when the head moves in one direction, and decrease firing in the opposite direction. Selective excitation and inhibition of VTAVgat+ neurons generate opposite rotational movements. The relationship between these neurons and head angle is degraded only at the time of reward consumption, at which point all head-angle related neuronal subpopulations show indistinguishable reward-related responses. Thus, VTAVgat+ neurons serve a critical role in the control of rotational kinematics while pursuing a moving target. This general-purpose steering function can guide animals toward desired spatial targets in any motivated behavior.

neuroscience↗

bioRxiv2019

Hypothalamic-extended amygdala circuit regulates temporal discounting

Choice behavior is characterized by temporal discounting, i.e., preference for immediate rewards over delayed rewards. Temporal discounting is often dysfunctional in psychiatric disorders, addiction, and eating disorders. However, the underlying neural mechanisms governing temporal discounting are still poorly understood. We found that food deprivation resulted in steep temporal discounting of food rewards, whereas satiation abolished discounting. In addition, optogenetic activation of AgRP-expressing neurons in the arcuate nucleus or their axon terminals in the posterior bed nucleus of stria terminalis (BNST) restored temporal discounting in sated mice. Activation of postsynaptic neuropeptide Y receptors (Y1Rs) within the BNST, which is influenced by neuropeptide released by AgRP neurons, was sufficient to restore temporal discounting. These results demonstrate for the first time a profound effect of motivational signals from hypothalamic feeding circuits on temporal discounting and reveal a novel neural circuit that regulates choice behavior.

neuroscience↗