Bibliothek

Notizen: Abstract: An in vitro model of ischemia was obtained by subjectingPC12 cells differentiated with nerve growth factor to a combination of glucosedeprivation plus anoxia. Immediately after the ischemic period, the proteinsynthesis rate was significantly inhibited (80%) and western blots of cellextracts revealed a significant accumulation of phosphorylated eukaryoticinitiation factor 2, α subunit, eIF2(αP) (42%). Upon recovery,eIF2(αP) levels returned to control values after 30 min, whereas proteinsynthesis was still partially inhibited (33%) and reached almost controlvalues within 2 h. The activities of the mammalian eIF2α kinases,double-stranded RNA-activated protein kinase, mammalian GCN2 homologue, andendoplasmic reticulum-resident kinase, were determined. None of theeIF2α kinases studied showed increased activity in ischemic cells ascompared with controls. Exposure of cells to cell-permeable inhibitors ofprotein phosphatases 1 and 2A, calyculin A or tautomycin, induced dose- andtime-dependent accumulation of eIF2(αP), mimicking an ischemic effect.Protein phosphatase activity, as measured with [32P]phosphorylasea as a substrate, diminished during ischemia and returned to controllevels upon 30-min recovery. In addition, the rate of eIF2(αP)dephosphorylation was significantly lower in ischemic cells, paralleling boththe greatest translational inhibition and the highest eIF2(αP) levels.The endogenous phosphatase activity from control and ischemic extracts showeddifferent sensitivity to inhibitor 2 and fostriecin in in vitro assays,inhibitor-2 effect in ischemic cells being lower than in control cells.Together these results indicate that an eIF2α phosphatase, probablyprotein phosphatase 1, is implicated in the ischemia-induced eIF2(αP)accumulation in PC12 cells.

Notizen: A Monte Carlo analysis of bipolar transport and voltage fluctuations in a p+-Si/n-Si0.7Ge0.3 heterojunction and in a p+n Si homojunction under different operation regimes is presented. Comparison of the spectral density of voltage fluctuations at low frequency, SV(x,0), between both structures reveals the strong effect of the SiGe layer on the noise behavior in the heterojunction. Alloy scattering hinders the electron mobility enhancement expected from the removal of valley degeneracy in the SiGe layer. Despite this mobility reduction, the greater accumulation of carriers in the low-doped region supported by the valence band discontinuity reduce SV(x,0) in the heterojunction for a given average voltage. This study also reveals the impact of hot carriers on noise performance in the quasisaturation regime of both diodes. © 2000 American Institute of Physics.

Notizen: Pregnant rats were treated throughout the gestational period with either caffeine or theophylline, and its effect on the metabotropic glutamate receptor (mGluRs) signal transduction pathway was studied in both maternal and fetal brain. In maternal brain, radioligand binding assays showed that chronic treatment with methylxanthines caused a significant decrease in the total number of mGluRs. This decrease was accompanied by an increase in receptor affinity. Immunodetection showed that mGluR1a and phospholipase C β1 (PLCβ1) were significantly decreased in response to chronic methylxanthine treatment, whereas αGq/11 was not affected. A loss was also detected of PLC stimulation mediated by (S)-3,5-dihydroxyphenylglycine (DHPG), a selective Group I mGluR agonist, suggesting desensitization of the mGluR/PLC pathway. In fetal brain, a loss in total mGluRs was observed in fetuses from mothers treated with caffeine or theophylline, without variation in receptor affinity. A decrease in mGluR1a, αGq/11 and PLCβ1 levels was also observed in response to treatment. However, changes detected in this immature tissue were not associated with variations in PLC activity. These results suggest that chronic caffeine or theophylline treatment down-regulates several mGluR/PLC transduction pathway components in both maternal and fetal brain, causing a loss of receptor responsiveness only in maternal brain.

Notizen: Translational repression induced during reperfusion of the ischaemic brain is significantly attenuated by ischaemic preconditioning. The present work was undertaken to identify the components of the translational machinery involved and to determine whether translational attenuation selectively modifies protein expression patterns during reperfusion. Wistar rats were preconditioned by 5-min sublethal ischaemia and 2 days later, 30-min lethal ischaemia was induced. Several parameters were studied after lethal ischaemia and reperfusion in rats with and without acquired ischaemic tolerance (IT). The phosphorylation pattern of the α subunit of eukaryotic initiation factor 2 (eIF2) in rats with IT was exactly the same as in rats without IT, reaching a peak after 30 min reperfusion and returning to control values within 4 h in both the cortex and hippocampus. The levels of phosphorylated eIF4E-binding protein after lethal ischaemia and eIF4E at 30 min reperfusion were higher in rats with IT, notably in the hippocampus. eIF4G levels diminished slightly after ischaemia and reperfusion, paralleling calpain-mediated α-spectrin proteolysis in rats with and without IT, but they did not show any further decrease after 30 min reperfusion in rats with IT. The phosphorylated levels of eIF4G, phosphatidylinositol 3-kinase-protein B (Akt) and extracellular signal-regulated kinases (ERKs) were very low after lethal ischaemia and increased following reperfusion. Ischaemic preconditioning did not modify the observed changes in eIF4G phosphorylation. All these results support that translation attenuation may occur through multiple targets. The levels of the glucose-regulated protein (78 kDa) remained unchanged in rats with and without IT. Conversely, our data establish a novel finding that ischaemia induces strong translation of growth arrest and DNA damage protein 34 (GADD34) after 4 h of reperfusion. GADD34 protein was slightly up-regulated after preconditioning, besides, as in rats without IT, GADD34 levels underwent a further clear-cut increase during reperfusion, this time as earlier as 30 min and coincident with translation attenuation.

Notizen: Objective  To assess whether infectious morbidity after total abdominal hysterectomy is decreased by the addition of 20 cc povidone–iodine gel at the vaginal apex after the usual vaginal preparation with povidone–iodine solution.Study design  Randomised controlled trial.Setting  Fifteen secondary and tertiary hospitals in Canada.Sample  A total of 1570 women undergoing planned total abdominal hysterectomy.Methods  Computer-generated randomisation using a centralised telephone service was stratified by study centre with variable block size. In the operating room, a swab for bacterial vaginosis was taken before vaginal antisepsis. Study group remained concealed until the standard surgical preparation in the operating room was complete. Then povidone-iodine gel 20 cc was placed at the vaginal apex in the intervention group only. Participants were followed for one month post-operative.Main outcome measures  The primary outcome was post-operative infectious morbidity during the 30 days after surgery, defined as: febrile morbidity with hospital stay greater than five days or antibiotic treatment, or infection requiring readmission to hospital or additional visit. Other outcomes included abdominal wound infection, pelvic abscess and other pelvic infections.Results  Post-operative infectious morbidity within 30 days occurred in 128/780 (16%) women receiving povidone–iodine gel preparation and 142/790 (18%) women not receiving gel (RR 0.9, 95% CI 0.7 to 1.1). Pelvic abscess was diagnosed in 0 patients in the gel group and in seven patients in the control group (P 〈 0.01). No significant difference was found in pelvic cellulitis (eight in each group) or abdominal wound infection (51 in the gel group and 58 in the control group, P= 0.5).Conclusion  Povidone–iodine vaginal gel antisepsis led to a 9% relative decrease in overall infectious morbidity after abdominal hysterectomy, which was not statistically significant. Povidone–iodine vaginal gel decreased the risk of pelvic abscess after total abdominal hysterectomy.

Notizen: Naevus lipomatosus cutaneous superficialis (NLCS) is an uncommon hamartomatous lesion with an exceptional presentation on the face. We report the case of an elderly patient who presented with a classic type of NLCS on the right nasal orifice. This patient was taking inhaled steroids for his allergic rhinitis during 35 years.

Notizen: We investigated the carrier and light trapping in GaInAs/AlGaAs single-quantum-well laser structures by means of time-resolved photoluminescence and Raman spectroscopy. The influence of the shape and depth of the confinement potential and of the cavity geometry was studied by using different AlGaAs/GaAs short-period superlattices as barriers. Our results show that grading the optical cavity improves considerably both carrier and light trapping in the quantum well, and that the trapping efficiency is enhanced by increasing the graded confining potential. © 2000 American Institute of Physics.