Amino acid-mediated stimulation of renal phospholipid biosynthesis after acute tubular necrosis

Amino acid-mediated stimulation of renal phospholipid biosynthesis after acute tubular necrosis. The mechanism by which amino acid infusion stimulates membrane phospholipid biosynthesis during renal regeneration after mercuric-chloride-induced acute tubular necrosis was studied in the rat. Amino acids can act directly on regenerating renal tissue to enhance net phospholipid synthesis because preincubation of cortical slices with amino acids induced an increase in [14C]-choline incorporation into phospholipid without altering the rate of breakdown. This amino acid stimulation of phospholipid biosynthesis was studied further by measuring [14C]-choline accumulation and its sequential conversion to phosphorylcholine, cytidine diphosphocholine (CDP-choline), and phosphatidylcholine via the Kennedy pathway in regenerating renal tissue. [14C]-Choline accumulation was increased after amino acid infusion, compared to glucose infusion. There were also increments in the Vmax of the choline kinase reaction, which converts entering [14C]-choline into [14C]-phosphorylcholine, and of the cholinephosphotransferase reaction in which [14C]-CDP-choline is incorporated into [14C]-phosphatidylcholine, whereas the apparent Km of each reaction was unchanged. Thus, amino acids infused after tubular necrosis can act directly on regenerating renal cells to increase precursor availability and augment two reactions of the phospholipid bio-synthetic pathway.Stimulation par les acides aminés de la biosynthèse rénale de phospholipides après nécrose tubulaire aiguë. Le mécanisme par lequel la perfusion d'acides aminés stimule la biosynthèse de phospholipides membranaires au cours de la régénération rénale consécutive à la nécrose tubulaire aiguë déterminée par le chlorure mercurique a été étudié chez le rat. Les acides aminés peuvent agir directement sur le tissu rénal en régénération pour accroître la synthèse nette de phospholipides puisque la pré-incubation de tranches de cortex avec des acides aminés détermine une augmentation de l'incorporation de [14C]-choline dans les phospholipides sans modification du catabolisme. Cette stimulation par les acides aminés de la synthèse des phospholipides a été étudiée par la mesure de l'accumulation de [14C]-choline et de sa conversion séquentielle en phosphorylcholine, cytidine diphosphocholine (CDP-choline) et phosphatidylcholine, selon la voie de Kennedy, dans le tissu rénal en cours de régénération. L'accumulation de [14C]-choline est augmentée après perfusion d'acides aminés, par comparaison avec celle de glucose. On observe aussi des augmentations des Vmax de la réaction de la choline kinase, qui transforme la [14C]-choline entrante en [14C]-phosphorylcholine, et de la réaction de la cholinephosphotransferase, dans laquelle la [14C]-CDP-choline est incorporée dans la [14C]-phosphatidylcholine, alors que le Km de ces réactions est inchangé. Ainsi les acides aminés perfusés après une nécrose tubulaire peuvent agir directement sur les cellules rénales en régénération pour augmenter la disponibilité en précurseur et accélérer deux réactions de la voie de biosynthèse des phospholipides

Prospects for Searching for Excited Leptons during RunII of the Fermilab Tevatron

This letter presents a study of prospects of searching for excited leptons during RunII of the Fermilab Tevatron. We concentrate on single and pair production of excited electrons in the photonic decay channel in one CDF/DO detector equivalent for 2 fb^{-1}. By the end of RunIIa, the limits should be easily extended beyond those set by LEP and HERA for excited leptons with mass above about 190 GeV.Comment: 4 pages, 8 figure

The CDF Calorimetry Upgrade for Run IIb

The physics program at the Fermilab Tevatron Collider will continue to explore the high energy frontier of particle physics until the commissioning of the LHC at CERN. The luminosity increase provided by the Main Injector will require upgrades beyond those implemented for the first stage (Run IIa) of the Tevatron's Run II physics program. The upgrade of the CDF calorimetry includes: 1) the replacement of the slow gas detectors on the front face of the Central Calorimeter with a faster scintillator version which has a better segmentation, and 2) the addition of timing information to both the Central and EndPlug Electromagnetic Calorimeters to filter out cosmic ray and beam related backgrounds.Comment: Presented at `Frontier Detectors for Frontier Physics; 9th Pisa Meeting on Advanced Detectors', Biodola, Italy, 25-31 May 2003. 2 page

Long-Lived Neutralino NLSPs

We investigate the collider signatures of heavy, long-lived, neutral particles that decay to charged particles plus missing energy. Specifically, we focus on the case of a neutralino NLSP decaying to Z and gravitino within the context of General Gauge Mediation. We show that a combination of searches using the inner detector and the muon spectrometer yields a wide range of potential early LHC discoveries for NLSP lifetimes ranging from 10^(-1)-10^5 mm. We further show that events from Z(l+l-) can be used for detailed kinematic reconstruction, leading to accurate determinations of the neutralino mass and lifetime. In particular, we examine the prospects for detailed event study at ATLAS using the ECAL (making use of its timing and pointing capabilities) together with the TRT, or using the muon spectrometer alone. Finally, we also demonstrate that there is a region in parameter space where the Tevatron could potentially discover new physics in the delayed Z(l+l-)+MET channel. While our discussion centers on gauge mediation, many of the results apply to any scenario with a long-lived neutral particle decaying to charged particles.Comment: 31 pages, 12 figure

The level-1 trigger for the SuperCDMS experiment at SNOLAB

The SuperCDMS SNOLAB dark matter search experiment aims to be sensitive to energy depositions down to Script O(1 eV). This imposes requirements on the resolution, signal efficiency, and noise rejection of the trigger system. To accomplish this, the SuperCDMS level-1 trigger system is implemented in an FPGA on a custom PCB. A time-domain optimal filter algorithm realized as a finite impulse response filter provides a baseline resolution of 0.38 times the standard deviation of the noise, $σ_{n}$, and a 99.9% trigger efficiency for signal amplitudes of 1.1 $σ_{n}$ in typical noise conditions. Embedded in a modular architecture, flexible trigger logic enables reliable triggering and vetoing in a dead-time-free manner for a variety of purposes and run conditions. The trigger architecture and performance are detailed in this article

Results from the Super Cryogenic Dark Matter Search (SuperCDMS) experiment at Soudan

We report the result of a blinded search for Weakly Interacting Massive Particles (WIMPs) using the majority of the SuperCDMS Soudan dataset. With an exposure of 1690 kg days, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP--nucleon cross section of $1.4 \times 10^{-44}$ ($1.0 \times 10^{-44}$) cm$^2$ at 46 GeV/$c^2$. These results set the strongest limits for WIMP--germanium-nucleus interactions for masses $>$12 GeV/$c^2$