1,488 research outputs found
CREB is a critical regulator of normal hematopoiesis and leukemogenesis
The cAMP-responsive element binding protein (CREB) is a 43-kDa nuclear transcription factor that regulates cell growth, memory, and glucose homeostasis. We showed previously that CREB is amplified in myeloid leukemia blasts and expressed at higher levels in leukemia stem cells from patients with myeloid leukemia. CREB transgenic mice develop myeloproliferative disease after 1 year, but not leukemia, suggesting that CREB contributes to but is not sufficient for leukemogenesis. Here, we show that CREB is most highly expressed in lineage negative hematopoietic stem cells (HSCs). To understand the role of CREB in hematopoietic progenitors and leukemia cells, we examined the effects of RNA interference (RNAi) to knock down CREB expression in vitro and in vivo. Transduction of primary HSCs or myeloid leukemia cells with lentiviral CREB shRNAs resulted in decreased proliferation of stem cells, cell- cycle abnormalities, and inhibition of CREB transcription. Mice that received transplants of bone marrow transduced with CREB shRNA had decreased committed progenitors compared with control mice. Mice injected with Ba/F3 cells expressing either Bcr-Abl wild-type or T315I mutation with CREB shRNA had delayed leukemic infiltration by bioluminescence imaging and prolonged median survival. Our results suggest that CREB is critical for normal myelopoiesis and leukemia cell proliferation
Search for Light Gluinos via the Spontaneous Appearance of pi+pi- Pairs with an 800 GeV/c Proton Beam at Fermilab
We searched for the appearance of pi+pi- pairs with invariant mass greater
than 648 MeV in a neutral beam. Such an observation could signify the decay of
a long-lived light neutral particle. We find no evidence for this decay. Our
null result severely constrains the existence of an R0 hadron, which is the
lightest bound state of a gluon and a light gluino, and thereby also the
possibility of a light gluino. Depending on the photino mass, we exclude the R0
in the mass and lifetime ranges of 1.2 -- 4.6 GeV and 2E-10 -- 7E-4 seconds,
respectively. (To Appear in Phys. Rev. Lett.)Comment: Documentstyle aps,epsfig,prl (revtex), 6 pages, 7 figure
Search for the Decay K_L -> pi^0 nu nubar using pi^0 -> e^+ e^- gamma
We report on a search for the decay K_L -> pi^0 nu nubar, carried out as a
part of E799-II, a rare K_L decay experiment at Fermilab. Within the Standard
Model, the K_L -> pi^0 nu nubar decay is dominated by direct CP violating
processes, and thus an observation of the decay implies confirmation of direct
CP violation. Due to theoretically clean calculations, a measurement of B(K_L
-> pi^0 nu nubar) is one of the best ways to determine the CKM parameter eta.
No events were observed, and we set an upper limit B(K_L -> pi^0 nu nubar) <
5.9 times 10^-7 at the 90% confidence level.Comment: 5 pages, 4 figure
Measurement of the branching ratio of pi^0 -> e^+e^- using K_L -> 3 pi^0 decays in flight
The branching ratio of the rare decay pi^0 -> e^+e^- has been measured in
E799-II, a rare kaon decay experiment using the KTeV detector at Fermilab. The
pi^0's were produced in fully-reconstructed K_L -> 3 pi^0 decays in flight. We
observed 275 candidate pi^0 -> e^+e^- events, with an expected background of
21.4 +- 6.2 events which includes the contribution from Dalitz decays. We
measured BR(pi^0 -> e^+e^-, x>0.95) = (6.09 +- 0.40 +- 0.24) times 10^{-8},
where the first error is statistical and the second systematic. This result is
the first significant observation of the excess rate for this decay above the
unitarity lower bound.Comment: New version shortened to PRL length limit. 5 pages, 4 figures.
Published in Phys. Rev. Let
Measurement of the Decay KL -> Pi0 Gamma Gamma
We report on a new measurement of the decay KL -> pi0 gamma gamma by the KTeV
experiment at Fermilab. We determine the KL -> pi0 gamma gamma branching ratio
to be (1.68 +/- 0.07 +/- 0.08)x10**-6. Our data shows the first evidence for a
low-mass gamma gamma signal as predicted by recent O(p**6) chiral perturbation
calculations that include vector meson exchange contributions. From our data,
we extract a value for the effective vector coupling aV = -0.72 +/- 0.05 +/-
0.06.Comment: 5 pages, 4 figure
Light Gluino Search for Decays Containing pi+pi- or pi0 from a Neutral Hadron Beam at Fermilab
We report on two null searches, one for the spontaneous appearance of
pairs, another for a single , consistent with the decay of
a long-lived neutral particle into hadrons and an unseen neutral particle. For
the lowest level gluon-gluino bound state, known as the , we exclude the
decays and for
the masses of and in the theoretically allowed range. In
the most interesting mass range, , we exclude
lifetimes from seconds to as high as seconds,
assuming perturbative QCD production for the .Comment: 15 pages, 7 figure
Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System
We present a series of measurements based on K -> pi+pi- and K -> pi0pi0
decays collected in 1996-1997 by the KTeV experiment (E832) at Fermilab. We
compare these four K -> pipi decay rates to measure the direct CP violation
parameter Re(e'/e) = (20.7 +- 2.8) x 10^-4. We also test CPT symmetry by
measuring the relative phase between the CP violating and CP conserving decay
amplitudes for K->pi+pi- (phi+-) and for K -> pi0pi0 (phi00). We find the
difference between the relative phases to be Delta-phi = phi00 - phi+- = (+0.39
+- 0.50) degrees and the deviation of phi+- from the superweak phase to be
phi+- - phi_SW =(+0.61 +- 1.19) degrees; both results are consistent with CPT
symmetry. In addition, we present new measurements of the KL-KS mass difference
and KS lifetime: Delta-m = (5261 +- 15) x 10^6 hbar/s and tauS = (89.65 +-
0.07) x 10^-12 s.Comment: Submitted to Phys. Rev. D, August 6, 2002; 37 pages, 32 figure
Observation of CP Violation in K(L)->pi+pi-e+e- Decays
We report the first observation of a manifestly CP violating effect in the
K(L)->pi+pi-e+e- decay mode. A large asymmetry was observed in the distribution
of these decays in the CP-odd and T-odd angle phi between the decay planes of
the e+e- and pi+pi- pairs in the K(L) center of mass system. After acceptance
corrections, the overall asymmetry is found to be 13.6+-2.5 (stat) +-1.2
(syst)%. This is the largest CP-violating effect yet observed integrating over
the entire phase space of a mode and the first such effect observed in an
angular variable.Comment: 4 pages 4 figures submitted to pr
Diamond nitrogen-vacancy centers created by scanning focused helium ion beam and annealing
We demonstrate a method to create nitrogen-vacancy (NV) centers in diamond using focused helium ion microscopy. Near-surface NV centers can be created with spatial resolution below 0.6 μm. We studied the density, creation efficiency, and spectral linewidths at optical and microwave frequencies for NV centers produced using various helium ion implantation doses. The optical linewidths are narrower than those of similar nitrogen-vacancy centers produced using nitrogen ion implantation
Diet and Cell Size Both Affect Queen-Worker Differentiation through DNA Methylation in Honey Bees (Apis mellifera, Apidae)
Young larvae of the honey bee (Apis mellifera) are totipotent; they can become either queens (reproductives) or workers (largely sterile helpers). DNA methylation has been shown to play an important role in this differentiation. In this study, we examine the contributions of diet and cell size to caste differentiation.We measured the activity and gene expression of one key enzyme involved in methylation, Dnmt3; the rates of methylation in the gene dynactin p62; as well as morphological characteristics of adult bees developed either from larvae fed with worker jelly or royal jelly; and larvae raised in either queen or worker cells. We show that both diet type and cell size contributed to the queen-worker differentiation, and that the two factors affected different methylation sites inside the same gene dynactin p62.We confirm previous findings that Dnmt3 plays a critical role in honey bee caste differentiation. Further, we show for the first time that cell size also plays a role in influencing larval development when diet is kept the same
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