92 research outputs found
Estrogen-Receptor Expression and Function in Thymocytes in Relation to Gender and Age
The expression of estrogen receptor (ER) in thymocytes was studied in young, middle-aged, and
old (2, 12, and 24 months, respectively) female and male C57BL/6J mice. Western immunoblots
prepared from the thymocytes of females of all age groups showed the presence of a 67-kD
protein band, which has been associated with the apparent MW of denatured ER. Flow cytometry
analysis o,f cells stained with a monoclonal anti-ER antibody (clone 13H2) disclosed ER
expression in both females and males of all age groups. In vivo treatment with estradiol (E2) led
to an increase in the specific activity of thymic creatine kinase (CK) in the female mice, whereas
the male thymocytes responded with an increase in CK activity only on treatment with
dihydrotestosterone (DHT). The data show no differences in ER expression between male and
females, but the receptor appears not to be functional in males. Interestingly, when estradiol was
applied to co-cultures of lymphoid-depleted fetal thymus (FT) explants and bone-marrow cells,
or thymocytes, from young and old females, it resulted in increased cellularity of cultures
containing cells of the young, and not those of the old. The proportion of CD4/CD8 phenotypes
of the developing cells in these cultures was not affected by E2 treatment. These observations
provide a new insight into ER expression and function in T-cell development in relation to
gender and age
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Commissioning results from the recently upgraded RHIC LLRF system
During RHIC Run 10, the first phase of the LLRF Upgrade was successfully completed. This involved replacing the aging VME based system with a modern digital system based on the recently developed RHIC LLRF Upgrade Platform, and commissioning the system as part of the normal RHIC start up process. At the start of Run 11, the second phase of the upgrade is underway, involving a significant expansion of both hardware and functionality. This paper will review the commissioning effort and provide examples of improvements in system performance, flexibility and scalability afforded by the new platform. The RHIC LLRF upgrade is based on the recently developed RHIC LLRF Upgrade Platform. The major design goals of the platform are: (1) Design a stand alone, generic, digital, modular control architecture which can be configured to satisfy all of the application demands we currently have, and which will be supportable and upgradeable into the foreseeable future; and (2) It should integrate seamlessly into existing controls infrastructure, be easy to deploy, provide access to all relevant control parameters (eliminate knobs), provide vastly improved diagnostic data capabilities, and permit remote reconfiguration. Although the system is still in its infancy, we think the initial commissioning results from RHIC indicate that these goals have been achieved, and that we've only begun to realize the benefits the platform provides
Higher order mode damper for low energy RHIC electron cooler SRF booster cavity
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon,
the Low Energy RHIC electron Cooler (LEReC) is currently under commissioning at
BNL. The Linac of LEReC is designed to deliver a 1.6 MeV to 2.6 MeV electron
beam, with rms dp/p less than 5e-4. A 704 MHz superconducting radio frequency
(SRF) booster cavity in this Linac provides up to 2.2 MeV accelerating voltage.
With such a low energy and very demanding energy spread requirement, control of
Higher Order Modes (HOMs) in the cavities becomes critical and needs to be
carefully evaluated to ensure minimum impact on the beam. In this paper, we
report the multiphysics design of the HOM damper for this cavity to meet the
energy spread requirement, as well as experimental results of the cavity with
and without the HOM damper.Comment: 9 pages, 7 figure
The Hetero-Hexameric Nature of a Chloroplast AAA+ FtsH Protease Contributes to Its Thermodynamic Stability
FtsH is an evolutionary conserved membrane-bound metalloprotease complex. While in most prokaryotes FtsH is encoded by a single gene, multiple FtsH genes are found in eukaryotes. Genetic and biochemical data suggest that the Arabidopsis chloroplast FtsH is a hetero-hexamer. This raises the question why photosynthetic organisms require a heteromeric complex, whereas in most bacteria a homomeric one is sufficient. To gain structural information of the possible complexes, the Arabidopsis FtsH2 (type B) and FtsH5 (type A) were modeled. An in silico study with mixed models of FtsH2/5 suggests that heteromeric hexamer structure with ratio of 4â¶2 is more likely to exists. Specifically, calculation of the buried surface area at the interfaces between neighboring subunits revealed that a hetero-complex should be thermodynamically more stable than a homo-hexamer, due to the presence of additional hydrophobic and hydrophilic interactions. To biochemically assess this model, we generated Arabidopsis transgenic plants, expressing epitope-tagged FtsH2 and immuno-purified the protein. Mass-spectrometry analysis showed that FtsH2 is associated with FtsH1, FtsH5 and FtsH8. Interestingly, we found that âtype Bâ subunits (FtsH2 and FtsH8) were 2â3 fold more abundant than âtype Aâ (FtsH1 and FtsH5). The biochemical data corroborate the in silico model and suggest that the thylakoid FtsH hexamer is composed of two âtype Aâ and four âtype Bâ subunits
Design of a High-bunch-charge 112-MHz Superconducting RF Photoemission Electron Source
High-bunch-charge photoemission electron-sources operating in a continuous
wave (CW) mode are required for many advanced applications of particle
accelerators, such as electron coolers for hadron beams, electron-ion
colliders, and free-electron lasers (FELs). Superconducting RF (SRF) has
several advantages over other electron-gun technologies in CW mode as it offers
higher acceleration rate and potentially can generate higher bunch charges and
average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed
at Brookhaven National Laboratory (BNL) to produce high-brightness and
high-bunch-charge bunches for the Coherent electron Cooling Proof-of-Principle
(CeC PoP) experiment. The gun utilizes a quarter-wave resonator (QWR) geometry
for assuring beam dynamics, and uses high quantum efficiency (QE) multi-alkali
photocathodes for generating electrons
Essential versus accessory aspects of cell death: recommendations of the NCCD 2015
Cells exposed to extreme physicochemical or mechanical stimuli die in an uncontrollable manner, as a result of their immediate structural breakdown. Such an unavoidable variant of cellular demise is generally referred to as âaccidental cell deathâ (ACD). In most settings, however, cell death is initiated by a genetically encoded apparatus, correlating with the fact that its course can be altered by pharmacologic or genetic interventions. âRegulated cell deathâ (RCD) can occur as part of physiologic programs or can be activated once adaptive responses to perturbations of the extracellular or intracellular microenvironment fail. The biochemical phenomena that accompany RCD may be harnessed to classify it into a few subtypes, which often (but not always) exhibit stereotyped morphologic features. Nonetheless, efficiently inhibiting the processes that are commonly thought to cause RCD, such as the activation of executioner caspases in the course of apoptosis, does not exert true cytoprotective effects in the mammalian system, but simply alters the kinetics of cellular demise as it shifts its morphologic and biochemical correlates. Conversely, bona fide cytoprotection can be achieved by inhibiting the transduction of lethal signals in the early phases of the process, when adaptive responses are still operational. Thus, the mechanisms that truly execute RCD may be less understood, less inhibitable and perhaps more homogeneous than previously thought. Here, the Nomenclature Committee on Cell Death formulates a set of recommendations to help scientists and researchers to discriminate between essential and accessory aspects of cell death
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FPC conditioning cart at BNL
The 703 MHz superconducting gun for the BNL Energy Recovery Linac (ERL) prototype has two fundamental power couplers (FPCs), and each of them will deliver up to 500 kW of CW RF power. In order to prepare the couplers for high power RF service and process multipacting, the FPCs should be conditioned prior to installation into the gun cryomodule. A conditioning cart based test stand, which includes a vacuum pumping system, controllable bake-out system, diagnostics, interlocks and data log system has been designed, constructed and commissioned by collaboration of BNL and AES. This paper presents FPC conditioning cart systems and the conditioning process
Interaction of Temperature and Light in the Development of Freezing Tolerance in Plants
Abstract Freezing tolerance is the result of a wide range
of physical and biochemical processes, such as the induction
of antifreeze proteins, changes in membrane composition,
the accumulation of osmoprotectants, and changes
in the redox status, which allow plants to function at low
temperatures. Even in frost-tolerant species, a certain period
of growth at low but nonfreezing temperatures, known
as frost or cold hardening, is required for the development
of a high level of frost hardiness. It has long been known
that frost hardening at low temperature under low light
intensity is much less effective than under normal light
conditions; it has also been shown that elevated light
intensity at normal temperatures may partly replace the
cold-hardening period. Earlier results indicated that cold
acclimation reflects a response to a chloroplastic redox
signal while the effects of excitation pressure extend
beyond photosynthetic acclimation, influencing plant
morphology and the expression of certain nuclear genes
involved in cold acclimation. Recent results have shown
that not only are parameters closely linked to the photosynthetic
electron transport processes affected by light
during hardening at low temperature, but light may also
have an influence on the expression level of several other
cold-related genes; several cold-acclimation processes can
function efficiently only in the presence of light. The
present review provides an overview of mechanisms that
may explain how light improves the freezing tolerance of
plants during the cold-hardening period
Dynamic Interaction of cBid with Detergents, Liposomes and Mitochondria
The BH3-only protein Bid plays a key role in the induction of mitochondrial apoptosis, but its mechanism of action is still not completely understood. Here we studied the two main activation events of Bid: Caspase-8 cleavage and interaction with the membrane bilayer. We found a striking reversible behaviour of the dissociation-association events between the Bid fragments p15 and p7. Caspase-8 cleavage does not induce per se separation of the two Bid fragments, which remain in a stable complex resembling the full length Bid. Detergents trigger a complete dissociation, which can be fully reversed by detergent removal in a range of protein concentrations from 100 ”M down to 500 nM. Incubation of cBid with cardiolipin-containing liposomes leads to partial dissociation of the complex. Only p15 (tBid) fragments are found at the membrane, while p7 shows no tendency to interact with the bilayer, but complete removal of p7 strongly increases the propensity of tBid to become membrane-associated. Despite the striking structural similarities of inactive Bid and Bax, Bid does not form oligomers and reacts differently in the presence of detergents and membranes, highlighting clear differences in the modes of action of the two proteins. The partial dissociation of cBid triggered by the membrane is suggested to depend on the strong and specific interaction between p15 and p7. The reversible disassembly and re-assembly of the cBid molecules at the membrane was as well proven by EPR using spin labeled cBid in the presence of isolated mitochondria. The observed dynamic dissociation of the two Bid fragments could allow the assistance to the pore-forming Bax to occur repeatedly and may explain the proposed âhit-and-run" mode of action of Bid at the bilayer
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