Preferential inhibition of phorbol ester-induced hydrolysis of phosphatidylethanolamine by N-acetylsphingosine in NIH 3T3 fibroblasts

AbstractIt has been reported that in rat fibroblasts cell-permeable ceramide analogs inhibit agonist-induced phospholipase D (PLD)-mediated hydrolysis of phosphatidylcholine (PtdCho). Here we demonstrate that relatively short (30 min) treatments of NIH 3T3 fibroblasts with 15–60 μM concentrations of N-acetylsphingosine result in preferential, although not exclusive, inhibition of phorbol 12-myristate 13-acetate-induced PLD-mediated hydrolysis of phosphatidylethanolamine (PtdEtn). The results suggest that in different cell types the PtdEtn- and PtdCho-hydrolyzing PLD activities are differentially sensitive to the inhibitory effect of ceramide

Ha-Ras stimulates uptake and phosphorylation of ethanolamine: inhibition by wortmannin

AbstractTransformation of NIH 3T3 fibroblasts by Ha-Ras resulted in large increases in the phosphorylation of both [14C]ethanolamine (Etn) and [14C]choline (Cho) when these precursors were added to the medium. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase (P13K), preferentially decreased phosphorylation of externally added Etn in the Ha-Ras transformed, but not in the untransformed, fibroblasts. However, wortmannin had no effect on the phosphorylation of Etn formed endogenously by phorbol ester-stimulated hydrolysis of phosphatidylethanolamine. Data suggest that interaction of mutated Ras with PI3K leads to specific stimulation of Etn uptake, followed by nearly quantitative phosphorylation of Etn by a Ras-activated Cho/Etn kinase

Neutralisation and contrast preservation: Voicing assimilation in Hungarian three-consonant clusters

This paper studies the contextual variation in the voicing properties of three-consonant clusters (CC#C) in Hungarian. We investigate the velar–alveolar stop clusters /kt/ and /ɡd/, and the alveolar fricative–stop clusters /st/ and /zd/ in potentially voicing-neutralising and assimilating contexts. We show that in these contexts, regressive voicing assimilation in Hungarian is categorical, but partially contrast preserving, and that stops and fricatives are not affected in the same way. Fricatives resist voicing before a voiced obstruent and are devoiced utterance-finally. This is a phonetically unfavourable position, therefore other duration-related cues step up to prevent complete laryngeal neutralisation

The laryngeal properties of Slovak three-consonant clusters

In this paper, we study the phonetic properties of three-consonant clusters (CC#C) in Slovak. More precisely, we will investigate the laryngeal properties of the velar–alveolar stop clusters /kt/ and /ɡd/, and the alveolar fricative– stop clusters /st/ and /zd/ in word-final position when followed by a voiced or a voiceless obstruent, or a sonorant consonant. This topic is of interest for two reasons: (i) there are not many studies dealing with the laryngeal characteristics of three-consonant clusters, and (ii) the study of consonant clusters can shed further light on the issue whether or not regressive voicing assimilation (RVA) in general, including pre-sonorant voicing, is a neutralizing process in Slovak. We will seek to answer the following research questions: (i) Is voicing assimilation in Slovak (with obstruent and sonorant consonants as triggers) neutralizing or incomplete? (ii) Does pre-sonorant voicing in Slovak differ from pre-obstruent voicing? (iii) Is the word-final devoicing of obstruent clusters a completely neutralizing process in Slovak, or is it an example of incomplete laryngeal neutralization

Herschel-PACS photometry of faint stars

Our aims are to determine flux densities and their photometric accuracy for a set of seventeen stars that range in flux from intermediately bright (<2.5 Jy) to faint (>5 mJy) in the far-infrared (FIR). We also aim to derive signal-to-noise dependence with flux and time, and compare the results with predictions from the Herschel exposure-time calculation tool. The PACS faint star sample has allowed a comprehensive sensitivity assessment of the PACS photometer. Accurate photometry allows us to establish a set of five FIR primary standard candidates, namely alpha Ari, epsilon Lep, omega,Cap, HD41047 and 42Dra, which are 2 -- 20 times fainter than the faintest PACS fiducial standard (gamma Dra) with absolute accuracy of <6%. For three of these primary standard candidates, essential stellar parameters are known, meaning that a dedicated flux model code may be run.Comment: 42 pages, 12 figure

Search for signatures of dust in the Pluto-Charon system using Herschel/PACS observations

In this letter we explore the environment of Pluto and Charon in the far infrared with the main aim to identify the signs of any possible dust ring, should it exist in the system. Our study is based on observations performed at 70 um with the PACS instrument onboard the Herschel Space Observatory at 9 epochs between March 14 and 19, 2012. The far-infrared images of the Pluto-Charon system are compared to those of the point spread function (PSF) reference quasar 3C454.3. The deviation between the observed Pluto-Charon and reference PSFs are less then 1 sigma indicating that clear evidence for an extended dust ring around the system was not found. Our method is capable of detecting a hypothetical ring with a total flux of ~3.3 mJy at a distance of ~153 000 km (~8.2 Pluto-Charon distances) from the system barycentre. We place upper limits on the total disk mass and on the column density in a reasonable disk configuration and analyse the hazard during the flyby of NASAs New Horizons in July 2015. This realistic model configuration predicts a column density of 8.7x10^(-10) gcm^(-2) along the path of the probe and an impactor mass of 8.7x10^(-5) g.Comment: 10 pages, 4 figures, 2 table

Cooperative interactions of protein kinase C and cAMP-dependent protein kinase systems in human promyelocytic leukemia HL60 cells

AbstractInteractions of protein kinase C (PKC) and cAMP-dependent protein kinase (PKA) systems were investigated in HL60 cells. It was found that the differentiating effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) were potentiated by dibutyryl cAMP (dbcAMP) or prostaglandin E2 (PGE2). In addition, dbcAMP or PGE2 inhibited TPA-induced binding of PKC to plasma membrane, leading to decreased protein phosphorylation, and promoted subsequent redistribution of enzyme to the nuclear membrane region. The findings are consistent with the hypothesis that PKC and PKA systems regulate cooperatively the phenotypical differentiation of leukemic cells

The Polysialylated Neural Cell Adhesion Molecule Promotes Neurogenesis in vitro

A characteristic feature of neurogenic sites in the postnatal brain is the expression of the polysialylated forms of the neural cell adhesion molecule (PSA-NCAM). To investigate the role of PSA-NCAM in generation of neuronal populations, we developed an in vitro model where neurogenesis occurs in primary cortical cultures following serum withdrawal. We show that removal or inactivation of the PSA tail of NCAM in these cultures leads to a significant decrease in the number of newly generated neurons. Similarly, cultures prepared from NCAM knock-out mice exhibit a significantly reduced neurogenesis. Pulse-chase experiments using the proliferation marker BrdU reveal that the lack of PSA does not affect the mitotic rate of neural progenitors but rather, it reduces the early survival of newly generated neurons. These results suggest that, in addition to its role in the migration of neuronal progenitors, PSA-NCAM is required for the adequate survival of these cell