408 research outputs found
Robert Milton Zollinger, M.D., teacher, surgeon, soldier, and farmer.
From Humble roots, Dr. Robert Milton Zollinger worked his way to a position in history among the giants of American surgery. He was born on September 4, 1903, in the central Ohio town of Millersport, the son of Elmira and William Zollinger. Neither of his parents had a high school education, but they supported education and always expressed a confidence that young Robert would be successful at anything he attempted.1 He had aspirations of attending West Point, a dream that was never fulfilled when he decided to be a surgeon. On being informed of his son’s intentions, Zollinger’s father bestowed on him advice that he ostensibly adhered to throughout his career: ‘‘If you are going to be a doctor, be a good one.’
Tyrosine phosphorylation controls brassinosteroid receptor activation by triggering membrane release of its kinase inhibitor
Receptor tyrosine kinases control many critical processes in metazoans, but these enzymes appear to be absent in plants. Recently, two
Arabidopsis receptor kinases-BRASSINOSTEROID INSENSITIVE 1 (BRI1) and
BRI1-ASSOCIATED KINASE1 (BAK1), the receptor and coreceptor for
brassinosteroids-were shown to autophosphorylate on tyrosines. However,
the cellular roles for tyrosine phosphorylation in plants remain poorly
understood. Here, we report that the BRI1 KINASE INHIBITOR 1 (BKI1) is
tyrosine phosphorylated in response to brassinosteroid perception.
Phosphorylation occurs within a reiterated [KR][KR] membrane
targeting motif, releasing BKI1 into the cytosol and enabling formation
of an active signaling complex. Our work reveals that tyrosine
phosphorylation is a conserved mechanism controlling protein
localization in all higher organisms
Preferred Basis in a Measurement Process
The effect of decoherence is analysed for a free particle, interacting with
an environment via a dissipative coupling. The interaction between the particle
and the environment occurs by a coupling of the position operator of the
particle with the environmental degrees of freedom. By examining the exact
solution of the density matrix equation one finds that the density matrix
becomes completely diagonal in momentum with time while the position space
density matrix remains nonlocal. This establishes the momentum basis as the
emergent 'preferred basis' selected by the environment which is contrary to the
general expectation that position should emerge as the preferred basis since
the coupling with the environment is via the position coordinate.Comment: Standard REVTeX format, 10 pages of output. Accepted for publication
in Phys. Rev
Predicting essential components of signal transduction networks: a dynamic model of guard cell abscisic acid signaling
Plants both lose water and take in carbon dioxide through microscopic
stomatal pores, each of which is regulated by a surrounding pair of guard
cells. During drought, the plant hormone abscisic acid (ABA) inhibits stomatal
opening and promotes stomatal closure, thereby promoting water conservation.
Here we synthesize experimental results into a consistent guard cell signal
transduction network for ABA-induced stomatal closure, and develop a dynamic
model of this process. Our model captures the regulation of more than forty
identified network components, and accords well with previous experimental
results at both the pathway and whole cell physiological level. Our analysis
reveals the novel predictions that the disruption of membrane depolarizability,
anion efflux, actin cytoskeleton reorganization, cytosolic pH increase, the
phosphatidic acid pathway or of K+ efflux through slowly activating K+ channels
at the plasma membrane lead to the strongest reduction in ABA responsiveness.
Initial experimental analysis assessing ABA-induced stomatal closure in the
presence of cytosolic pH clamp imposed by the weak acid butyrate is consistent
with model prediction. Our method can be readily applied to other biological
signaling networks to identify key regulatory components in systems where
quantitative information is limited.Comment: 17 pages, 8 figure
Fishing For Food: Values and Benefits Associated With Coastal Infrastructure
While there is substantial literature about the socio-cultural characteristics and values associated with recreational and commercial fisheries in the U.S., studies directed at those who ‘fish for food’—those who depend on consuming their catch to various degrees—are relatively sparse. Using qualitative data collected through 80 semi-structured interviews with fishers in the summer and fall of 2018 in Carteret County, North Carolina, this study aims to better understand the group of recreational fishers who consume their catch by describing social and cultural dimensions and values associated with fishing for food, examining the role of infrastructure in facilitating access to benefits associated with this activity, and considering how knowledge of existing licensing regulations surrounding subsistence license waivers affect this fishing community. Interviews conducted at free public fishing structures in the region revealed that fishers derive a variety of values and benefits from fishing at these sites, including access to recreation, nutrition, a social community, and mental health benefits, which were found to be negatively impacted by Hurricane Florence in September 2018. We also found an informal economy of sharing catch on- and off-site that extends the reach and benefits facilitated by public infrastructure to people beyond those using it directly. Overall, we call for conceptualizations of ‘fishing for food’ that include aspects that go beyond traditional definitions of ‘subsistence’ or ‘recreational’ fishing such as food security, access, and less obvious social and cultural motivations behind the activity. These findings are a compelling rationalization for the creation and maintenance of formal and informal fishing places locally and, by extension, in other coastal areas, given the array of benefits provided by access to these types of locations
Structure du cofacteur GUN4 du complexe Mg-chélatase : Une nouvelle conformation pour la fixation de la porphyrine
Control structural interaction testbed: A model for multiple flexible body verification
Conventional end-to-end ground tests for verification of control system performance become increasingly complicated with the development of large, multiple flexible body spacecraft structures. The expense of accurately reproducing the on-orbit dynamic environment and the attendant difficulties in reducing and accounting for ground test effects limits the value of these tests. TRW has developed a building block approach whereby a combination of analysis, simulation, and test has replaced end-to-end performance verification by ground test. Tests are performed at the component, subsystem, and system level on engineering testbeds. These tests are aimed at authenticating models to be used in end-to-end performance verification simulations: component and subassembly engineering tests and analyses establish models and critical parameters, unit level engineering and acceptance tests refine models, and subsystem level tests confirm the models' overall behavior. The Precision Control of Agile Spacecraft (PCAS) project has developed a control structural interaction testbed with a multibody flexible structure to investigate new methods of precision control. This testbed is a model for TRW's approach to verifying control system performance. This approach has several advantages: (1) no allocation for test measurement errors is required, increasing flight hardware design allocations; (2) the approach permits greater latitude in investigating off-nominal conditions and parametric sensitivities; and (3) the simulation approach is cost effective, because the investment is in understanding the root behavior of the flight hardware and not in the ground test equipment and environment
A Pilot Study Testing a Novel 3D Printed Amphibious Lower Limb Prosthesis in a Recreational Pool Setting
Effects of brassinosteroid, auxin, and cytokinin on ethylene production in Arabidopsis thaliana plants
Inflorescence stalks produced the highest amount of ethylene in response to IAA as compared with other plant parts tested. Leaf age had an effect on IAA-induced ethylene with the youngest leaves showing the greatest stimulation. The highest amount of IAA-induced ethylene was produced in the root or inflorescence tip with regions below this producing less. Inflorescence stalks treated with IAA, 2,4-D, or NAA over a range of concentrations exhibited an increase in ethylene production starting at 1 μM with increasingly greater responses up to 100 μM, followed by a plateau at 500 μM and a significant decline at 1000 μM. Both 2,4-D and NAA elicited a greater response than IAA at all concentrations tested in inflorescence stalks. Inflorescence leaves treated with IAA, 2,4-D, or NAA exhibited the same trend as inflorescence stalks. However, they produced significantly less ethylene. Inflorescence stalks and leaves treated with 100 μM IAA exhibited a dramatic increase in ethylene production 2 h following treatment initiation. Inflorescence stalks showed a further increase 4 h following treatment initiation and no further increase at 6 h. However, there was a slight decline between 6 h and 24 h. Inflorescence leaves exhibited similar rates of IAA-induced ethylene between 2 h and 24 h. Light and high temperature caused a decrease in IAA-induced ethylene in both inflorescence stalks and leaves. Three auxin-insensitive mutants were evaluated for their inflorescence's responsiveness to IAA. aux2 did not produce ethylene in response to 100 μM IAA, while axr1-3 and axr1-12 showed reduced levels of IAA-induced ethylene as compared with Columbia wild type. Inflorescences treated with brassinolide alone had no effect on ethylene production. However, when brassinolide was used in combination with IAA there was a dramatic increase in ethylene production above the induction promoted by IAA alone
Dual role for ubiquitin in plant steroid hormone receptor endocytosis
Brassinosteroids are plant steroid hormones that control many aspects of plant growth and development, and are perceived at the cell surface by the plasma membrane-localized receptor kinase BRI1. Here we show that BRI1 is post-translationally modified by K63 polyubiquitin chains in vivo. Using both artificial ubiquitination of BRI1 and generation of an ubiquitination-defective BRI1 mutant form, we demonstrate that ubiquitination promotes BRI1 internalization from the cell surface and is essential for its recognition at the trans-Golgi network/early endosomes (TGN/EE) for vacuolar targeting. Finally, we demonstrate that the control of BRI1 protein dynamics by ubiquitination is an important control mechanism for brassinosteroid responses in plants. Altogether, our results identify ubiquitination and K63-linked polyubiquitin chain formation as a dual targeting signal for BRI1 internalization and sorting along the endocytic pathway, and highlight its role in hormonally controlled plant development
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