: The activation of phospholipase D (PLD) is a common
response to mitogenic stimuli in various cell types. As PLD‐mediated signaling
is known to be disrupted in the presence of ethanol, we tested ...whether PLD is
involved in the ethanol‐induced inhibition of cell proliferation in rat
cortical primary astrocytes. Readdition of fetal calf serum (FCS) to
serum‐deprived astroglial cultures caused a rapid, threefold increase of PLD
activity and a strong mitogenic response ; both effects were dependent on
tyrosine kinases but not on protein kinase C. Ethanol (0.1‐2%) suppressed the
FCS‐induced, PLD‐mediated formation of phosphatidic acid (PA) as well as
astroglial cell proliferation in a concentration‐dependent manner. Moreover,
exogenous bacterial PLD increased astroglial proliferation in an
ethanol‐sensitive manner, whereas exogenous PA or lysophosphatidic acid was
less effective. Formation of PA and astroglial proliferation were strongly
inhibited by 1‐butanol (0.1‐1%), a substrate of PLD, but were unaffected by
t‐butanol, a nonsubstrate ; 2‐butanol had intermediate effects.
Platelet‐derived growth factor and endothelin‐1 mimicked the mitogenic effect
of FCS ; their effects were also inhibited by the butanols in the potency
order 1‐butanol > 2‐butanol > tert‐butanol. Our results, in
particular, the differential effects of 1‐, 2‐, and tert‐butanol with respect to PA formation and astroglial proliferation, strongly suggest that the antiproliferative effects of ethanol in glial cells are due to the disruption of the PLD signaling pathway. This mechanism may also contribute to the inhibition of astroglial growth and brain development observed in alcoholic embryopathy.
For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the ...detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.
We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the ...LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.
Primary cultures of rat cortical astrocytes express phospholipase D (PLD) isoforms 1 and 2 as determined by RT-PCR and Western blot. Basal PLD activity was strongly (10-fold) increased by ...4β-phorbol-12β,13α-dibutyrate (PDB) (EC
50: 56 nM), an effect which was inhibited by Ro 31-8220 (0.1–1 μM), an inhibitor of protein kinase C (PKC), and by brefeldin A (10–100 μg/ml), an inhibitor of ADP-ribosylating factor (ARF) activation. Pretreatment of the cultures with
Clostridium difficile toxin B-10463 (0.1–1 ng/ml), which inactivates small G proteins of the Rho family, led to a breakdown of the astroglial cytoskeleton; concomitantly, PLD activation by PDB was reduced by up to 50%. In contrast, inactivation of proteins of the Ras family by
Clostridium sordellii lethal toxin 1522 did not affect PLD activation. In parallel experiments, serum-induced PLD activation was sensitive to brefeldin A, but not to Ro 31-8220 and not to clostridial toxins. We conclude that, in astrocytes, the PLD isoform which is activated by phorbol ester requires PKC, ARF and Rho proteins for full activity and probably represents PLD1.
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