bluuebunny/crossref_metadata_2025 huggingface dataset:
The caspase family in urochordates: distinct evolutionary fates in ascidians and larvaceans
Authors: Weill Mylène , Philips Alexandre , Chourrout Daniel , Fort Philippe
Published: October 2005

Background information. Caspases are cysteine proteases that mediate apoptosis (programmed cell death) initiation and execution. Apoptosis is a conserved mechanism shared by all metazoans, although its physiological function and complexity show considerable taxon‐dependent variations. To gain insight into the caspase repertoire of putative ancestors to vertebrates, we performed exhaustive genomic searches in urochordates, a sister taxon to vertebrates in which ascidians and appendicularians display chordate characters at early stages of their development.

Results. We identified the complete caspase families of two ascidians (Ciona intestinalis and C. savignyi) and one larvacean (Oikopleura dioica). We found in ascidian species an extremely high number of caspase genes (17 for C. intestinalis and 22 for C. savignyi), deriving from five founder gene orthologues to human pro‐inflammatory, initiator and executioner caspases. Although considered to be sibling species, C. intestinalis and C. savignyi only share 11 orthologues, most of the additional genes resulting from recent mass duplications. A sharply contrasted picture was found in O. dioica, which displayed only three caspase genes deriving from a single founder gene distantly related to caspase 3/7. The difference between ascidian and larvacean caspase repertoires is discussed in the light of their developmental patterns and life cycles.

Conclusions. The identification of caspase members in two ascidian species delineates five founder genes that bridge the gap between vertebrates and Ecdysozoa (arthropods and nematodes). Given the amazing diversity among urochordates, determination and comparison of the caspase repertoires in species from orders additional to Enterogona (ascidians) and Oikopleuridae might be highly informative on the evolution of caspase‐dependent physiological processes.
Mn2+-adenosine nucleotide complexes in the presence of the nitrogenase iron-protein: detection of conformational rearrangements directly at the nucleotide binding site by EPR and 2D-ESEEM (two-dimensional electron spin-echo envelope modulation spectroscopy)
Authors: Petersen Jan , Gessner Christof , Fisher Karl , Mitchell Claire J. , Lowe David J. , Lubitz Wolfgang
Published: October 2005

Both ATP and a bivalent nucleotide-bound metal activator, normally Mg2+, are required for nitrogenase activity. EPR and ESEEM (electron spin-echo envelope modulation) measurements have been carried out on adenosine nucleotides in which the Mg2+ ion that is usually bound is replaced by Mn2+ in the presence of Kp2 (nitrogenase Fe-protein from Klebsiella pneumoniae). The Mn2+ zero-field splitting parameters have been determined from the EPR-spectrum to be |D|=0.0125 cm−1 with a rhombicity λ=E/D=0.31 by direct diagonalization of the complete spin Hamiltonian. ESEEM spectra of the Fe-protein with MnADP and MnATP both show an ESEEM line pair with one signal component at about 3.6 MHz and a relatively broad resonance at 8 MHz originating from a superhyperfine coupling to a 31P nuclear spin from one or more directly co-ordinated phospho group(s) of the nucleotide. A pronounced resonance overlapping the low-frequency component of the 31P-signal at about 3.5 MHz is attributed to an interaction of Mn2+ with univalent 23Na nuclei. ESEEM lines at frequencies <3.5 MHz have been ascribed to interactions with 14N nuclei. Differences in the 14N features that depend on the type of nucleotide are consistent with substantial conformational rearrangements at the nucleotide-binding site upon hydrolysis. In addition, four-pulse HYSCORE (hyperfine sublevel correlation spectroscopy) experiments not only confirm the three-pulse ESEEM results, but also achieve significantly better spectral deconvolution, especially of the 31P-couplings, and demonstrate that the nucleotide is at least a unidentate ligand of Mn2+. Moreover it was also possible to identify peaks from an 14N interaction more clearly; these most probably arise from outer-sphere interactions with nitrogen atom(s) of non-co-ordinated residues which are affected by conformational rearrangements upon nucleotide hydrolysis. In addition, different redox states of the [4Fe-4S] cluster of the Fe-protein show disparate conformations of the metal–nucleotide co-ordination environment, demonstrating that also the cluster site communicates with the nucleotide binding site.
N-glycans of core2 β(1,6)-N-acetylglucosaminyltransferase-I (C2GnT-I) but not those of α(1,3)-fucosyltransferase-VII (FucT-VII) are required for the synthesis of functional P-selectin glycoprotein ligand-1 (PSGL-1): effects on P-, L- and E-selectin binding
Authors: Prorok-Hamon Maëlle , Notel Frédéric , Mathieu Sylvie , Langlet Claire , Fukuda Minoru , El-Battari Assou
Published: October 2005

C2GnT-I [core2 β(1,6)-N-acetyglucosaminyltransferase-I] and FucT-VII [α(1,3)-fucosyltransferase-VII] are the key enzymes for the biosynthesis of sialyl-Lewis x determinants on selectin ligands and therefore they represent good drug targets for the treatment of inflammatory disorders and other pathologies involving selectins. In the present study, we examined the importance of N-glycosylation for the ability of C2GnT-I and FucT-VII to generate functional selectin ligands, particularly the PSGL-1 (P-selectin glycoprotein ligand-1). We found that (i) both enzymes have their two N-glycosylation sites occupied, (ii) for C2GnT-I, the N-glycan chain linked to Asn-95 significantly contributes to the synthesis of functional PSGL-1 and is required to localize the enzyme to the cis/medial-Golgi compartment, (iii) all N-glycosylation-deficient proteins of FucT-VII displayr a dramatic impairment of their in vitro enzymatic activities, but retain their ability to fucosylate the core2-modified PSGL-I and to generate P- and L-selectin binding, and (iv) the glycomutants of FucT-VII fail to synthesize sialyl-Lewis x or to generate E-selectin binding unless core2-modified PSGL-1 is present. All combined, our results show a differential functional impact of N-glycosylation on C2GnT-1 and FucT-VII and disclose that a strongly reduced FucT-VII activity retains the ability to fucosylate PSGL-1 on the core2-based binding site(s) for the three selectins.
The Rab27a-binding protein, JFC1, regulates androgen-dependent secretion of prostate-specific antigen and prostatic-specific acid phosphatase
Authors: Johnson Jennifer L. , Ellis Beverly A. , Noack Deborah , Seabra Miguel C. , Catz Sergio D.
Published: October 2005

Two of the major proteins secreted by the prostate epithelium secretory cells are PSA (prostate-specific antigen) and PSAP (prostatic-specific acid phosphatase). The molecules involved in the secretory machinery of PSA and PSAP, and the regulation of this machinery, remain unknown. In the present paper, we provide evidence that JFC1 [synaptotagmin-like protein (slp1)], a Rab27a- and PtdIns(3,4,5)P3-binding protein, regulates the androgen-dependent secretion of PSAP and PSA in human LNCaP prostate carcinoma cells. Androgen-dependent PSAP secretion was significantly inhibited in cells that expressed the C2A domain of JFC1 [PtdIns(3,4,5)P3-binding-domain], but was unaffected by JFC1 overexpression. Conversely, PSA secretion was not inhibited by the C2A domain of JFC1. We show, using immunofluorescence analysis, that JFC1 co-localizes with PSAP, but rarely with PSA, in prostate granules, suggesting that JFC1 is part of the PSAP secretory machinery. However, PSA secretion was significantly increased in LNCaP cells that overexpressed JFC1, indicating that the secretion of PSA is susceptible to variations in the intracellular concentration of JFC1. Both PSAP and PSA secretion was increased by overexpression of wild-type Rab27a or the constitutively active Rab27aQ78L. The secretion of PSA was partially inhibited in the presence of LY294002, while the secretion of PSAP was completely abolished by the PI3K (phosphoinositide 3-kinase) inhibitor. This supports the view that PI3K plays a differential role in the secretion of prostate secretory markers. In conclusion, we present evidence that JFC1 differentially regulates the secretion of PSAP and PSA, and that Rab27a and PI3K play a central role in the exocytosis of prostate-specific markers.
Rat liver betaine–homocysteine S-methyltransferase equilibrium unfolding: insights into intermediate structure through tryptophan substitutions
Authors: Garrido Francisco , Gasset María , Sanz-Aparicio Juliana , Alfonso Carlos , Pajares María A.
Published: October 2005

Equilibrium folding of rat liver BHMT (betaine–homocysteine methyltransferase), a TIM (triosephosphate isomerase)-barrel tetrameric protein, has been studied using urea as denaturant. A combination of activity measurements, tryptophan fluorescence, CD and sedimentation-velocity studies suggested a multiphasic process including two intermediates, a tetramer (I4) and a monomer (J). Analysis of denaturation curves for single- and six-tryptophan mutants indicated that the main changes leading to the tetrameric intermediate are related to alterations in the helix α4 of the barrel, as well as in the dimerization arm. Further dissociation to intermediate J included changes in the loop connecting the C-terminal α-helix of contact between dimers, disruption of helix α4, and initial alterations in helix α7 of the barrel, as well as in the dimerization arm. Evolution of the monomeric intermediate continued through additional perturbations in helix α7 of the barrel and the C-terminal loop. Our data highlight the essential role of the C-terminal helix in dimer–dimer binding through its contribution to the increased stability shown by BHMT as compared with other TIM barrel proteins. The results are discussed in the light of the high sequence conservation shown by betaine–homocysteine methyltransferases and the knowledge available for other TIM-barrel proteins.
FoxO6 transcriptional activity is regulated by Thr26 and Ser184, independent of nucleo-cytoplasmic shuttling
Authors: van der Heide Lars P. , Jacobs Frank M. J. , Burbach J. Peter H. , Hoekman Marco F. M. , Smidt Marten P.
Published: October 2005

Forkhead members of the ‘O’ class (FoxO) are transcription factors crucial for the regulation of metabolism, cell cycle, cell death and cell survival. FoxO factors are regulated by insulin-mediated activation of PI3K (phosphoinositide 3-kinase)–PKB (protein kinase B) signalling. Activation of PI3K–PKB signalling results in the phosphorylation of FoxO factors on three conserved phosphorylation motifs, which are essential for the translocation of FoxO factors from the nucleus to the cytosol. FoxO6, however, remains mostly nuclear due to the fact that its shuttling ability is dramatically impaired. FoxO1, FoxO3 and FoxO4 all contain an N- and C-terminal PKB motif and a motif located in the forkhead domain. FoxO6 lacks the conserved C-terminal PKB motif, which is the cause of the shuttling impairment. Since FoxO6 can be considered constitutively nuclear, we investigated whether it is also a constitutively active transcription factor. Our results show that FoxO6 transcriptional activity is inhibited by growth factors, independent of shuttling, indicating that it is not constitutively active. The PKB site in the forkhead domain (Ser184) regulated the DNA binding characteristics and the N-terminal PKB site acted as a growth factor sensor. In summary, FoxO6 is not a constitutively active transcription factor and can be regulated by growth factors in a Thr26- and Ser184-dependent manner, independent of shuttling to the cytosol.
Cancer cells activate p53 in response to 10-formyltetrahydrofolate dehydrogenase expression
Authors: Oleinik Natalia V. , Krupenko Natalia I. , Priest David G. , Krupenko Sergey A.
Published: October 2005

A folate enzyme, FDH (10-formyltetrahydrofolate dehydrogenase; EC 1.5.1.6), is not a typical tumour suppressor, but it has two basic characteristics of one, i.e. it is down-regulated in tumours and its expression is selectively cytotoxic to cancer cells. We have recently shown that ectopic expression of FDH in A549 lung cancer cells induces G1 arrest and apoptosis that was accompanied by elevation of p53 and its downstream target, p21. It was not known, however, whether FDH-induced apoptosis is p53-dependent or not. In the present study, we report that FDH-induced suppressor effects are strictly p53-dependent in A549 cells. Both knockdown of p53 using an RNAi (RNA interference) approach and disabling of p53 function by dominant-negative inhibition with R175H mutant p53 prevented FDH-induced cytotoxicity in these cells. Ablation of the FDH-suppressor effect is associated with an inability to activate apoptosis in the absence of functional p53. We have also shown that FDH elevation results in p53 phosphorylation at Ser-6 and Ser-20 in the p53 transactivation domain, and Ser-392 in the C-terminal domain, but only Ser-6 is strictly required to mediate FDH effects. Also, translocation of p53 to the nuclei and expression of the pro-apoptotic protein PUMA (Bcl2 binding component 3) was observed after induction of FDH expression. Elevation of FDH in p53 functional HCT116 cells induced strong growth inhibition, while growth of p53-deficient HCT116 cells was unaffected. This implies that activation of p53-dependent pathways is a general downstream mechanism in response to induction of FDH expression in p53 functional cancer cells.
Role of peroxisome proliferator-activated receptor γ in amyloid precursor protein processing and amyloid β-mediated cell death
Authors: d'Abramo Cristina , Massone Sara , Zingg Jean-Marc , Pizzuti Antonio , Marambaud Philippe , Dalla Piccola Bruno , Azzi Angelo , Marinari Umberto M. , Pronzato Maria A. , Ricciarelli Roberta
Published: October 2005

Recent data indicate that PPARγ (peroxisome proliferator-activated receptor γ) could be involved in the modulation of the amyloid cascade causing Alzheimer's disease. In the present study we show that PPARγ overexpression in cultured cells dramatically reduced Aβ (amyloid-β) secretion, affecting the expression of the APP (Aβ precursor protein) at a post-transcriptional level. APP down-regulation did not involve the pathway of the secretases and correlated with a significant induction of APP ubiquitination. Additionally, we demonstrate that PPARγ was able to protect the cells from H2O2-induced necrosis by decreasing Aβ secretion. Taken together, our results indicate a novel mechanism at the basis of the neuroprotection shown by PPARγ agonists and an additional pathogenic role for Aβ accumulation.
Functional analysis of the promoter of the mitochondrial phosphate carrier human gene: identification of activator and repressor elements and their transcription factors
Authors: Iacobazzi Vito , Infantino Vittoria , Costanzo Paola , Izzo Paola , Palmieri Ferdinando
Published: October 2005

The phosphate carrier (PiC) catalyses the import of phosphate into mitochondria where it is needed for ATP synthesis. We have analysed the 5′-flanking region of the human PiC gene and found that it has a single transcriptional initiation site and lacks a TATA box. Through deletion analysis of the −1213/−25 nt region, we identified an activation domain (−223/−25) and an inhibition domain (−1017/−814). The most effective promoter activity in transfected HeLa cells corresponded to the region containing putative binding sites for Sp1 (−163/−142; where Sp1 stands for stimulating protein-1) and CREB (−138/−116; where CREB stands for cAMP-response-element-binding protein). These DNA sequences were active in gel-shift assays in the presence of HeLa cell nuclear extracts or recombinant Sp1 and CREB respectively. Forskolin increased PiC promoter activity via the CREB site. Both footprinting and transfection of deletion constructs of the inhibition region (−1017/−814) showed that PiC silencer activity extends over 25 nt (−943/−919), which specifically binds two proteins present in HeLa cell nuclear extracts. These transcription factors were purified by DNA affinity, analysed by MS and identified as p54nrb/NonO (nuclear RNA binding protein) and PSF (protein-associated splicing factor). The PiC silencer region cloned in front of the ferritin promoter conferred a strong inhibition to the heterologous promoter. These findings may provide insight into control of PiC gene expression in different cell types and under different growth conditions. To our knowledge, this is the first study to analyse the regulation of the PiC gene expression in any cell.
Synaptic vesicle chips to assay botulinum neurotoxins
Authors: Ferracci Géraldine , Miquelis Raymond , Kozaki Shunji , Seagar Michael , Lévêque Christian
Published: October 2005

BoNTs (botulinum neurotoxins), considered to be the most toxic of all biological substances, inhibit neurotransmission through proteolytic cleavage of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins [VAMP (vesicle-associated membrane protein, or synaptobrevin), SNAP-25 (25 kDa synaptosome-associated protein) or syntaxin]. Expansion in the use of BoNTs as therapeutic and cosmetic agents, and the potential threat they constitute as biological weapons, underlines the need for rapid and sensitive in vitro assays. Here, we present new automatized bioassays to detect VAMP cleavage by BoNT/B and F. Western blotting and SPR (surface plasmon resonance) methods revealed that BoNT/B and F totally cleave their substrate on immunoisolated SVs (synaptic vesicles). Real-time monitoring of the immunocapture of native SVs from crude lysates on SPR sensor chips enabled the detection of picogram amounts of different SV proteins. Pre-incubation of a membrane fraction containing SVs with BoNT specifically inhibited capture by anti-VAMP antibodies, and amounts as low as 0.1 pg of BoNT/B were detected. This automated SPR assay is approx. 200 times more sensitive, and 25 times more rapid, than the in vivo BoNT/B test currently used. Moreover, the method can be performed using a few thousand cultured neurons and constitutes a new screening assay for inhibitors. Our data indicate that native VAMP is an optimal substrate for in vitro BoNT assays that can be monitored by SPR.
Structure and function of steroid receptor AF1 transactivation domains: induction of active conformations
Authors: Lavery Derek N. , Mcewan Iain J.
Published: October 2005

Steroid hormones are important endocrine signalling molecules controlling reproduction, development, metabolism, salt balance and specialized cellular responses, such as inflammation and immunity. They are lipophilic in character and act by binding to intracellular receptor proteins. These receptors function as ligand-activated transcription factors, switching on or off networks of genes in response to a specific hormone signal. The receptor proteins have a conserved domain organization, comprising a C-terminal LBD (ligand-binding domain), a hinge region, a central DBD (DNA-binding domain) and a highly variable NTD (N-terminal domain). The NTD is structurally flexible and contains surfaces for both activation and repression of gene transcription, and the strength of the transactivation response has been correlated with protein length. Recent evidence supports a structural and functional model for the NTD that involves induced folding, possibly involving α-helix structure, in response to protein–protein interactions and structure-stabilizing solutes.
Amino-acid limitation induces transcription from the human C/EBPβ gene via an enhancer activity located downstream of the protein coding sequence
Authors: Chen Chin , Dudenhausen Elizabeth , Chen Hong , Pan Yuan-Xiang , Gjymishka Altin , Kilberg Michael S.
Published: October 2005

For animals, dietary protein is critical for the nutrition of the organism and, at the cellular level, protein nutrition translates into amino acid availability. Amino acid deprivation triggers the AAR (amino acid response) pathway, which causes enhanced transcription from specific target genes. The present results show that C/EBPβ (CCAAT/enhancer-binding protein β) mRNA and protein content were increased following the deprivation of HepG2 human hepatoma cells of a single amino acid. Although there was a modest increase in mRNA half-life following histidine limitation, the primary mechanism for the elevated steady-state mRNA was increased transcription. Transient transfection documented that C/EBPβ genomic fragments containing the 8451 bp 5′ upstream of the transcription start site did not contain amino-acid-responsive elements. However, deletion analysis of the genomic region located 3′ downstream of the protein coding sequence revealed that a 93 bp fragment contained an amino-acid-responsive activity that functioned as an enhancer. Exogenous expression of ATF4 (activating transcription factor 4), known to activate other genes through amino acid response elements, caused increased transcription from reporter constructs containing the C/EBPβ enhancer in cells maintained in complete amino acid medium. Chromatin immunoprecipitation demonstrated that RNA polymerase II is bound at the C/EBPβ promoter and at the 93 bp regulatory region in vivo, whereas ATF4 binds to the enhancer region only. Immediately following amino acid removal, the kinetics of binding for ATF4, ATF3, and C/EBPβ itself to the 93 bp regulatory region were similar to those observed for the amino-acid-responsive asparagine synthetase gene. Collectively the findings show that expression of C/EBPβ, which contributes to the regulation of amino-acid-responsive genes, is itself controlled by amino acid availability through transcription.
Attempts to characterize the NBD heterodimer of MRP1: transient complex formation involves Gly771 of the ABC signature sequence but does not enhance the intrinsic ATPase activity
Authors: Ramaen Odile , Sizun Christina , Pamlard Olivier , Jacquet Eric , Lallemand Jean-Yves
Published: October 2005

MRP1 (multidrug-resistance-associated protein 1; also known as ABCC1) is a member of the human ABC (ATP-binding cassette) transporter superfamily that confers cell resistance to chemotherapeutic agents. Considering the structural and functional similarities to the other ABC proteins, the interaction between its two NBDs (nucleotide-binding domains), NBD1 (N-terminal NBD) and NBD2 (C-terminal NBD), is proposed to be essential for the regulation of the ATP-binding/ATP-hydrolysis cycle of MRP1. We were interested in the ability of recombinant NBD1 and NBD2 to interact with each other and to influence ATPase activity. We purified NBD1 (Asn642–Ser871) and NBD2 (Ser1286–Val1531) as soluble monomers under native conditions. We measured extremely low intrinsic ATPase activity of NBD1 (10−5 s−1) and NBD2 (6×10−6 s−1) and no increase in the ATP-hydrolysis rate could be detected in an NBD1+NBD2 mixture, with concentrations up to 200 μM. Despite the fact that both monomers bind ATP, no stable NBD1·NBD2 heterodimer could be isolated by gel-filtration chromatography or native-PAGE, but we observed some significant modifications of the heteronuclear single-quantum correlation NMR spectrum of 15N-NBD1 in the presence of NBD2. This apparent NBD1·NBD2 interaction only occurred in the presence of Mg2+ and ATP. Partial sequential assignment of the NBD1 backbone resonances shows that residue Gly771 of the LSGGQ sequence is involved in NBD1·NBD2 complex formation. This is the first NMR observation of a direct interaction between the ABC signature and the opposite NBD. Our study also reveals that the NBD1·NBD2 heterodimer of MRP1 is a transient complex. This labile interaction is not sufficient to induce an ATPase co-operativity of the NBDs and suggests that other structures are required for the ATPase activation mechanism.
The caspase-3 cleavage product of the plasma membrane Ca2+-ATPase 4b is activated and appropriately targeted
Authors: Pászty Katalin , Antalffy Géza , Penheiter Alan R. , Homolya László , Padányi Rita , Iliás Attila , Filoteo Adelaida G. , Penniston John T. , Enyedi Ágnes
Published: October 2005

The calmodulin-activated transporter hPMCA4 (human plasma membrane Ca2+-ATPase isoform 4) is a target for cleavage by caspase-3 during apoptosis. We have demonstrated that caspase-3 generates a 120 kDa fragment of this pump which lacks the complete autoinhibitory sequence [Paszty, Verma, Padanyi, Filoteo, Penniston and Enyedi (2002) J. Biol. Chem. 277, 6822–6829]. In the present study we analysed further the characteristics of the fragment of hPMCA4b produced by caspase-3. We did this by overexpressing the caspase-3 cleavage product of hPMCA4b in COS-7 and MDCKII (Madin–Darby canine kidney II) cells. This technique made it possible to clearly define the properties of this fragment, and we showed that it is constitutively active, as it forms a phosphoenzyme intermediate and has high Ca2+ transport activity in the absence of calmodulin. When this fragment of hPMCA4b was stably expressed in MDCKII cell clones, it was targeted without degradation to the basolateral plasma membrane. In summary, our studies emphasize that the caspase-3 cleavage product of hPMCA4b is constitutively active, and that the C-terminus is not required for proper targeting of hPMCA4b to the plasma membrane. Also, for the first time, we have generated cell clones that stably express a constitutively active PMCA.
Towards the application of proteomics in renal disease diagnosis
Authors: Vidal Bernardo C. , Bonventre Joseph V. , I-Hong Hsu Stephen
Published: October 2005

Proteomics is widely envisioned as playing a significant role in the translation of genomics to clinically useful applications, especially in the areas of diagnostics and prognostics. In the diagnosis and treatment of kidney disease, a major priority is the identification of disease-associated biomarkers. Proteomics, with its high-throughput and unbiased approach to the analysis of variations in protein expression patterns (actual phenotypic expression of genetic variation), promises to be the most suitable platform for biomarker discovery. Combining such classic analytical techniques as two-dimensional gel electrophoresis with more sophisticated techniques, such as MS, has enabled considerable progress to be made in cataloguing and quantifying proteins present in urine and various kidney tissue compartments in both normal and diseased physiological states. Despite these accomplishments, there remain a number of important challenges that will need to be addressed in order to pave the way for the universal acceptance of proteomics as a clinically relevant diagnostic tool. We discuss issues related to three such critical developmental tasks as follows: (i) completely defining the proteome in the various biological compartments (e.g. tissues, serum and urine) in both health and disease, which presents a major challenge given the dynamic range and complexity of such proteomes; (ii) achieving the routine ability to accurately and reproducibly quantify proteomic expression profiles; and (iii) developing diagnostic platforms that are readily applicable and technically feasible for use in the clinical setting that depend on the fruits of the preceding two tasks to profile multiple disease biomarkers.
Endothelial nitric oxide synthase Glu298→Asp polymorphism, carotid atherosclerosis and intima-media thickness in a general population sample
Authors: Wolff Birger , Braun Claudia , Schlüter Christina , Grabe Hans J. , Popowski Katrin , Völzke Henry , Lüdemann Jan , John Ulrich , Cascorbi Ingolf
Published: October 2005

The Glu298→Asp (E298D; 894G→T) polymorphism of eNOS (endothelial nitric oxide synthase) has been related with cardiovascular disease. In the present study, we investigated the association of Glu298→Asp with atherosclerotic plaques in different carotid vessel segments and with carotid IMT (intima-media thickness). The Glu298→Asp eNOS polymorphism was determined by 5′-exonuclease assay among 2448 participants of the SHIP (Study of Health in Pomerania). Mean and maximum common carotid IMT, as well as carotid atherosclerosis, were measured by high-resolution ultrasound. The Asp/Asp298 genotype was associated with an increased risk of atherosclerotic plaques at the level of the common carotid arteries [multivariate odds ratio, 1.57 and 95% CI (confidence interval), 1.05–2.34; P=0.025], but not in the carotid bifurcations or internal or external carotid arteries. Glu298→Asp genotype was not associated with carotid IMT in the whole sample. However, the Asp/Asp298 genotype was independently associated with both higher mean [adjusted increase by 0.046 mm (95% CI, 0.013–0.078); P=0.006] and maximum carotid IMT [0.137 mm (95% CI, 0.064–0.209); P<0.001] in the low-risk group of subjects without carotid atherosclerosis. In conclusion, the Asp/Asp298 genotype is associated with atherosclerosis in the common carotid arteries and, in a low-risk group, also with carotid IMT. This suggests that the association of the Glu298→Asp genotype with atherosclerosis in the carotid arteries is site-specific and is modified by overall cardiovascular risk.
α2-Adrenergic receptor signalling in hypertension
Authors: Kanagy Nancy L.
Published: October 2005

Cardiovascular regulation by the sympathetic nervous system is mediated by activation of one or more of the nine known subtypes of the adrenergic receptor family; α1A-, α1B-, α1D-, α2A-, α2B-, α2C-, β1-, β2- and β3-ARs (adrenoceptors). The role of the α2-AR family has long been known to include presynaptic inhibition of neurotransmitter release, diminished sympathetic efferent traffic, vasodilation and vasoconstriction. This complex response is mediated by one of three subtypes which all uniquely affect blood pressure and blood flow. All three subtypes are present in the brain, kidney, heart and vasculature. However, each differentially influences blood pressure and sympathetic transmission. Activation of α2A-ARs in cardiovascular control centres of the brain lowers blood pressure and decreases plasma noradrenaline (norepinephrine), activation of peripheral α2B-ARs causes sodium retention and vasoconstriction, whereas activation of peripheral α2C-ARs causes cold-induced vasoconstriction. In addition, non-selective agonists elicit endothelium-dependent vasodilation and presynaptic inhibition of noradrenaline release. The evidence that each of these receptor subtypes uniquely participates in cardiovascular control is discussed in this review.
Inhibition of human endothelial cell nitric oxide synthesis by advanced glycation end-products but not glucose: relevance to diabetes
Authors: Xu Biao , Ji Yong , Yao Kang , Cao Yue-Xin , Ferro Albert
Published: October 2005

Endothelial dysfunction, with decreased NO (nitric oxide) biosynthesis, may play a pathophysiological role in diabetic vasculopathy. The aim of the present study was to determine the relative contributions of glucose and AGE (advanced glycation end-product) accumulation in suppressing NOS-3 (the endothelial isoform of NO synthase). Cultured HUVECs (human umbilical vein endothelial cells) were incubated with different concentrations of glucose, unmodified albumin or AGE-modified albumin for different times. NOS activity was measured from the conversion of L-[3H]arginine into L-[3H]citrulline, and the expression, serine phosphorylation and O-glycosylation of NOS-3 were determined by Western blotting. High (25 mmol/l) glucose, for up to 12 days of incubation, had no effect on the activity or expression of NOS-3, nor on its degree of serine phosphorylation or O-glycosylation, compared with physiological (5 mmol/l) glucose. By contrast, AGE-modified albumin exerted a concentration- and time-dependent suppression of NOS-3 expression in HUVECs at a range of concentrations (0–200 mg/l) found in diabetic plasma; this was evident after 24 h, whereas inhibition of NOS activity was seen after only 3 h incubation with AGE-modified albumin, consistent with our previous observations of rapid suppression of NOS-3 serine phosphorylation and NOS-3 activity by AGE-modified albumin. In conclusion, AGE-modified albumin suppresses NOS-3 activity in HUVECs through two mechanisms: one rapid, involving suppression of its serine phosphorylation, and another slower, involving a decrease in its expression. We also conclude that, in the context of the chronic hyperglycaemia in diabetes, the effects of AGEs on endothelial NO biosynthesis are considerably more important than those of glucose.
IUPAC-NIST Solubility Data Series. 81. Hydrocarbons with Water and Seawater—Revised and Updated. Part 6. C8H8–C8H10 Hydrocarbons with Water
Authors: Goral Marian , Wisniewska-Goclowska Barbara , Skrzecz Adam , Owczarek Iwona , Blazej Krystyna , Haulait-Pirson Marie-Claire , Hefter Glenn T. , Maczynska Zofia , Szafranski Andrzej
Published: October 2005

The mutual solubility and related liquid-liquid equilibria of C8H8–C8H10 hydrocarbons with water are exhaustively and critically reviewed. Reports of experimental determination of solubility in 5 chemically distinct binary systems that appeared in the primary literature prior to the end of 2002 are compiled. For all the systems sufficient data are available to allow critical evaluation. All data are expressed as mass percent and mole fraction as well as the originally reported units. In addition to the standard evaluation criteria used throughout the Solubility Data Series, a new method based on the evaluation of all experimental data for a given homologous series of aliphatic and aromatic hydrocarbons was used.
IUPAC-NIST Solubility Data Series. 81. Hydrocarbons with Water and Seawater-Revised and Updated. Part 5. C7 Hydrocarbons with Water and Heavy Water
Authors: Goral Marian , Wisniewska-Goclowska Barbara , Skrzecz Adam , Owczarek Iwona , Blazej Krystyna , Haulait-Pirson Marie-Claire , Hefter Glenn T. , Kapuku F. , Maczynska Zofia , Szafranski Andrzej , Young Colin L.
Published: October 2005

The mutual solubility and related liquid-liquid equilibria of C7 hydrocarbons with water and heavy water are exhaustively and critically reviewed. Reports of experimental determination of solubility in 23 chemically distinct binary systems that appeared in the primary literature prior to end of 2002 are compiled. For 9 systems sufficient data are available to allow critical evaluation. All data are expressed as mass percent and mole fraction as well as the originally reported units. In addition to the standard evaluation criteria used throughout the Solubility Data Series, a new method based on the evaluation of the all experimental data for a given homologous series of aliphatic and aromatic hydrocarbons was used.
Fields of accelerated sources: Born in de Sitter
Authors: Bičák Jiří , Krtouš Pavel
Published: October 2005

This paper deals thoroughly with the scalar and electromagnetic fields of uniformly accelerated charges in de Sitter space–time. It gives details and makes various extensions of our Physical Review Letter from 2002. The basic properties of the classical Born solutions representing two uniformly accelerated charges in flat space–time are first summarized. The worldlines of uniformly accelerated particles in de Sitter universe are defined and described in a number of coordinate frames, some of them being of cosmological significance, the others are tied naturally to the particles. The scalar and electromagnetic fields due to the accelerated charges are constructed by using conformal relations between Minkowski and de Sitter space. The properties of the generalized “cosmological” Born solutions are analyzed and elucidated in various coordinate systems. In particular, a limiting procedure is demonstrated which brings the cosmological Born fields in de Sitter space back to the classical Born solutions in Minkowski space. In an extensive Appendix, which can be used independently of the main text, nine families of coordinate systems in de Sitter space–time are described analytically and illustrated graphically in a number of conformal diagrams.
Convective polymerase chain reaction around micro immersion heater
Authors: Hennig Martin , Braun Dieter
Published: October 2005

Polymerase chain reaction (PCR) is performed in the thermal convection created by a micro immersion heater. Instead of repetitive heating and cooling, the temperature gradient induces thermal convection which drives the reaction liquid between hot and cold parts of the chamber. The convection triggers DNA amplification as the DNA melts into two single strands in the hot region and replicates with the use of proteins into twice the amount in the cold region. The constant heater is simply dipped into the reaction solution. Compared to previous experiments, we demonstrate that convective PCR is possible in a robotically accessible open vessel. Our approach compares well with fast PCR cyclers and replicates DNA 500 000 fold within 20minutes. We reduce the necessary components for PCR to cheap, single-use components and therefore increasing the prospects of bringing PCR to point of care applications—even in third world countries.
The structure and crystallization of thin water films on Pt(111)
Authors: Zimbitas G. , Haq S. , Hodgson A.
Published: October 2005

When water is adsorbed on Pt(111) above 135K several different ice structures crystallize, depending on the thickness of the ice layer. At low coverage water forms extended islands of ice with a (√37×√37)R25° unit cell, which compresses as the monolayer saturates to form a (√39×√39)R16° structure. The √39 low-energy electron diffraction (LEED) pattern becomes more intense as the second layer grows, remaining bright for films up of 10–15 layers and then fading and disappearing for films more than ca. 40 layers thick. The ice multilayer consists of an ordered √39 wetting layer, on which ice grows as a crystalline film which progressively loses its registry to the wetting layer. Ice films more than ca. 50 layers thick develop a hexagonal LEED pattern, the entire film and wetting layer reorienting to form an incommensurate bulk ice. These changes are reflected in the vibrational spectra which show changes in line shape and intensity associated with the different ice structures. Thin amorphous solid water films crystallize to form the same phases observed during growth, implying that these structures are thermodynamically stable and not kinetic phases formed during growth. The change from a √39 registry to incommensurate bulk ice at ca. 50 layers is associated with a change in crystallization kinetics from nucleation at the Pt(111) interface in thin films to nucleation of incommensurate bulk ice in amorphous solid water films more than 50 layers thick.
Microscopic investigations of homogeneous nucleation in charged sphere suspensions
Authors: Wette Patrick , Schöpe Hans Joachim , Palberg Thomas
Published: October 2005

We studied the homogeneous nucleation kinetics of an aqueous suspension of charged colloidal spheres under de-ionized conditions. Samples of equilibrium crystalline structure were shear molten and the metastable melt left to solidify after cessation of shear. At low particle number densities n, corresponding to low metastability of the melt, nucleation was monitored directly via video microscopy. We determined the nucleation rates Γ(t) by counting the number of newly appearing crystals in the observation volume per unit time. Using a suitable discrete adaptation of Avrami's [J. Chem. Phys. 7, 1003 (1939); J. Chem. Phys.8, 212 (1940); J. Chem. Phys.9, 177 (1941)] model for solidification via homogeneous nucleation and subsequent growth, we calculate the remaining free volume VF(t) to obtain the rate densities J(t)=Γ(t)∕VF(t). We observe J(t) to rise steeply, display a plateau at a maximum rate density Jmax, and to decrease again. With increased n the plateau duration shrinks while Jmax increases. At low to moderate number densities fully solidified samples were analyzed by microscopy to obtain the grain-size distribution and the average crystallite size ⟨L⟩. Under the assumption of stationarity, we obtained the nucleation rate density JAvr, which increased strongly with increasing n. Interestingly, JAvr agrees quantitatively to Jmax and to JAvr as obtained previously from scattering data taken on the same sample at large n. Thus, by combination of different methods, reliable nucleation rate densities are now available over roughly one order of magnitude in n and eight orders of magnitude in J.
Shape transition of InAs quantum dots on GaAs(001)
Authors: Xu M. C. , Temko Y. , Suzuki T. , Jacobi K.
Published: October 2005

InAs quantum dots (QD’s) grown by molecular-beam epitaxy on GaAs(001) substrates were studied by atomically resolved in situ (without breaking a ultrahigh vacuum) scanning tunneling microscopy. A detailed sequence of shapes, appearing during the growth process, is evaluated: The smallest QD is terminated by {137}A bounding facets with a rhombic base. With increasing size, {1¯3¯5¯}B and {1¯1¯2¯}B facets appear in succession besides {137}A, making the QD more rounded. At a critical diameter of the base, the QD undergoes a shape transition from flat to steep by the formation of steeper {110} and {111} facets at the sides and gradually achieves a squared base. For all QD’s the {137}A facets remain on top. Almost all shapes that have been observed for InAs QD’s on GaAs(001) in earlier publications are covered.
Density-functional calculations of relativistic spin-orbit effects on nuclear magnetic shielding in paramagnetic molecules
Authors: Pennanen Teemu O. , Vaara Juha
Published: October 2005

Terms arising from the relativistic spin-orbit effect on both hyperfine and Zeeman interactions are introduced to density-functional theory calculation of nuclear magnetic shielding in paramagnetic molecules. The theory is a generalization of the former nonrelativistic formulation for doublet systems and is consistent to O(α4), the fourth power of the fine structure constant, for the spin-orbit terms. The new temperature-dependent terms arise from the deviation of the electronic g tensor from the free-electron g value as well as spin-orbit corrections to hyperfine coupling tensor A, the latter introduced in the present work. In particular, the new contributions include a redefined isotropic pseudocontact contribution that consists of effects due to both the g tensor and spin-orbit corrections to hyperfine coupling. The implementation of the spin-orbit terms makes use of all-electron atomic mean-field operators and/or spin-orbit pseudopotentials. Sample results are given for group-9 metallocenes and a nitroxide radical. The new O(α4) corrections are found significant for the metallocene systems while they obtain small values for the nitroxide radical. For the isotropic shifts, none of the three beyond-leading-order hyperfine contributions are negligible.
A computer simulation study of the segregation of amphiphiles in binary immiscible matrices: Short asymmetric copolymers in short homopolymers
Authors: Guo Hongxia , Olvera de la Cruz Monica
Published: October 2005

The bulk and interfacial properties of ternary mixtures with asymmetric amphiphiles (A2B8) in A2 and B2 matrices and in A2 and B10 matrices are investigated by the dissipative particle dynamics type of molecular-dynamics simulations. The monomer concentrations of A2B8(φA2B8) studied are below the critical micelle concentration (φA2B8cmc) for the formation of micelles in the presence of an adsorbed amphiphilic monolayer at the interface. Macrophase separation from the mixed phase to the segregated state with A-rich and B-rich coexisting phases and the segregation of A2B8 at the interface are thermodynamically gradual but are accompanied by a pronounced stretching and orientation of the constituent chains. The segregation of A2B8 at the interface broadens the interfacial region and reduces the interfacial tension. The chain conformation of the asymmetric amphiphilic molecules and the interfacial properties are dominated by the majority block in the amphiphilic chain and dependent on the composition of the matrix in contact with the majority block. In the A2 and B2 matrices, the B8 blocks in A2B8 chains at the interface resemble a wet brush swollen by short B2 chains. Swelling is responsible for the pronounced stretching and orienting of the amphiphilic chains and the reduced interfacial amphiphile enrichment. At the same interfacial amphiphile excess, however, swollen amphiphiles are more efficient in reducing the interfacial tension than nonswollen amphiphiles.
Lifetime and yield of metastable Ar2+ ions
Authors: Lepère V. , Ismail I. M. , Barat M. , Fayeton J. A. , Picard Y. J. , Wohrer K. , Jouvet C. , Martrenchard S.
Published: October 2005

Ar 2 + ions produced in a cooled supersonic expansion by electron-impact ionization are accelerated at 2.5 keV and kept during few milliseconds inside a linear electrostatic trap. The lifetime of the metastable Ar2+ ion is determined from the measurement of the rate of the argon atoms escaping the trap. The lifetime and the relative metastable populations are measured as a function of the pressure and temperature in the supersonic expansion, i.e., of the mean cluster size. Possible mechanisms responsible for the metastable formation are discussed.
Ab initio surface reaction energetics of SiH4 and Si2H6 on Si(001)-(2×2)
Authors: Smardon R. D. , Srivastava G. P.
Published: October 2005

First-principles pseudopotential calculations, within a simple dynamically constrained scheme, have been performed to investigate the reaction of 0.25 ML coverage of SiH4 and Si2H6 with the Si(001)-(2×2) surface. The silane molecule (SiH4) is adsorbed on to the surface at a number of different sites (on dimer, interrow, or intrarow) with varying barrier heights. Two distinct structures, which are similar in energy, arise from the initial dissociative reaction SiH4→SiH3(silyl)+H, where the dissociated species are adsorbed either on the same dimer components or on adjacent dimer components. Several further decays of silyl from SiH4 are presented in two separate regimes of high and low ambient hydrogen coverages. The decomposition of silyl can form two different bridging structures: an on top or an intrarow bridging structure in both of the two hydrogen coverage regimes. The disilane molecule (Si2H6) is also adsorbed upon this surface with varying energy barriers, resulting in a dissociation reaction where two SiH3 species are adsorbed on one dimer or in an adjacent dimer configuration. Plausible energy reaction paths for the above models are presented. The stability of the SiH2 species is also discussed.
Si
H
2
Cl
2
: Ab initio anharmonic force field, dipole moments, and infrared vibrational transitions
Authors: Liu An-Wen , Hu Shui-Ming , Zhu Qing-Shi
Published: October 2005

The vibrational spectra of SiH2Cl2 have been recorded in the 1000–13000cm−1 region, utilizing the Fourier-transform spectroscopy and Fourier-transform intracavity laser absorption spectroscopy. Totally 61 band centers and intensities are derived from the infrared spectra. An ab initio quartic force field is obtained by applying the second-order Møller-Plesset perturbation theory and correlation-consistent polarized valence triplet-zeta basis sets [J. Chem. Phys. 90, 1007 (1989); 98, 1358 (1993)]. Most observed bands are assigned by the vibration analysis based on the second-order perturbation theory. Reduced-dimensional ab initio dipole moment functions (two dimensional and three dimensional) have also been calculated to investigate the absolute band intensities of the SiH2 chromophore. The calculated values agree reasonably with the observed ones.