Scattering of high energy particles from nucleons probes their structure, as was done in the experiments that established the non-zero size of the proton using electron beams1. The use of charged leptons as scattering probes enables measuring the distribution of electric charges, which is encoded in the vector form factors of the nucleon2. Scattering weakly interacting neutrinos gives the opportunity to measure both vector and axial vector form factors of the nucleon, providing an additional, complementary probe of their structure. The nucleon transition axial form factor, FA, can be measured from neutrino scattering from free nucleons, νμn → μ−p and $${\bar{\nu }}_{\mu }p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n , as a function of the negative four-momentum transfer squared (Q2). Up to now, FA(Q2) has been extracted from the bound nucleons in neutrino–deuterium scattering3–9, which requires uncertain nuclear corrections10. Here we report the first high-statistics measurement, to our knowledge, of the $${\bar{\nu }}_{\mu }\,p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n cross-section from the hydrogen atom, using the plastic scintillator target of the MINERvA11 experiment, extracting FA from free proton targets and measuring the nucleon axial charge radius, rA, to be 0.73 ± 0.17 fm. The antineutrino–hydrogen scattering presented here can access the axial form factor without the need for nuclear theory corrections, and enables direct comparisons with the increasingly precise lattice quantum chromodynamics computations12–15. Finally, the tools developed for this analysis and the result presented are substantial advancements in our capabilities to understand the nucleon structure in the weak sector, and also help the current and future neutrino oscillation experiments16–20 to better constrain neutrino interaction models.

Keywords: blood-retinal barrier, VEGFA165b, MAPK, AKT, Endothelial blood-retinal barrier, diabetic retinopathy, image analysis, optical coherence tomography, retinal cell culture, retinal vasculature 2 ABSTRACT Purpose: Studies show that the b-isoform of Vascular Endothelial Growth Factor-A-165 (VEGFA 165 b) is predominant in normal human vitreous, switching to the a-isoform (VEGFA 165 a) in the vitreous of eyes with active diabetic retinopathy or ROP. The potential of this isoformswitching to impact the retinal vasculature is not clear, particularly in primary human retinal endothelial cells, which are important targets of VEGFA. We do not know how these two isoforms compare in their ability to activate key intracellular signalling pathways (MAPK, AKT) or alter VEGFA-target gene expression in primary human endothelial cells from the neural retina. Methods: Effects of saturating amounts of both VEGFA 165 isoforms (a/b) on the rat retinal vasculature were compared using intravitreal injection, fluorescein-angiography and Optical Coherence Tomography to monitor primary vein dilation and retinal edema. Full dose-response curves for the activation of MAPK (ERK1/2), AKT and VEGFR2 were determined using direct in-cell western assays of primary Human Retinal Microvascular Endothelial Cells (HRMECs). Differences in dose-response effects on gene expression markers related to endothelial cell / leukocyte adhesion (ICAM1, VCAM1 and SELE ) and tight-junctions (CLDN5 and OCLN ) were tested by quantitative-PCR. Results: In rats, dilation of primary retinal veins and edema could be induced within 24 hours by intravitreal injection of a saturating dose of either isoform. In HRMECs, activation dose-response analysis revealed much stronger activation of MAPK, AKT and VEGFR2 by the a-isoform at lower doses. While similar maximum activation of VEGFR2 and MAPK could be achieved by both isoforms at higher doses, maximum activation of AKT by the b-isoform was only half that observed for the a-isoform. At the level of gene expression, VEGFA 165 a was also more effective 3 at increasing expression of ICAM1, VCAM1 and SELE and decreasing expression of CLDN5 and OCLN at intermediate and high doses in primary HRMECs. Conclusions: VEGFA 165 a maximally activated MAPK and AKT in HRMECs at lower concentrations where VEGFA 165 b had little effect. The timing for maximal activation of MAPK was similar for both isoforms in HRMECs, which is different from non-retinal endothelial cells. While the dose-responses for VEGFR2 and MAPK activation had similar maximums with both isoforms, there were large differences between the isoforms in their effects on endothelial cell gene expression even at a high dose. The shifts of VEGFA 165 expression from mostly b-isoform to mostly a-isoform, as reported in some human retinal vascular diseases, could potentially impact the activation of intracellular signalling and VEGFA target gene expression in endothelial cells of the human neural retina. Receptor-2 (VEGFR2). A seminal analysis of the vitreous fluids of pati...

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