julilili42/papers huggingface dataset:
Preservation of intraalveolar surfactant in a rat lung ischaemia/reperfusion injury model
2000-03-01

Ischaemia/reperfusion (I/R) injury, a major problem in clinical lung transplantation, is associated with surfactant dysfunction. The present study aimed to test the hypothesis that preservation related improvements in post-ischaemic lung function are associated with improved ultrastructural preservation of pulmonary surfactant. Rat lungs were flush perfused with modified Euro-Collins solutions (ECS), stored for 2 h at 4 degrees C, and reperfused for 40 min. Lungs were preserved with conventional (ECS 115: 115 mmol x L(-1) K+), medium-K+ (ECS 40: 40 mmol x L(-1) K+), or low-K+ (ECS 10: 10 mmol x L(-1) K+) ECS. Functional parameters were monitored during reperfusion (n=10 per group). After reperfusion, left lungs were prepared for electron microscopical and stereological analysis of surfactant (n=5 per group). In all three experimental groups notable I/R injury developed which was lowest in ECS 40 as indicated by significantly less intraalveolar oedema, higher perfusate oxygenation, and lower peak inspiratory pressure. This was associated with a significantly superior preservation of the ultrastructure of the surface active surfactant subtype tubular myelin in ECS 40 compared with ECS 115 and ECS 10. Stereological analysis revealed that the relative amount of tubular myelin was highest in ECS 40 (mean+/-SEM; 6.2+/-0.8%) compared with ECS 115 (3.0+/-1.0%) and ECS 10 (2.7+/-1.6%). Analysis of surfactant in its natural location within the organ showed that the severity of ischaemia/reperfusion injury correlates with differences in intraalveolar surfactant composition. Improved post-ischaemic respiratory function achieved by medium-K+ Euro-Collins solution is associated with superior ultrastructural preservation of tubular myelin. It is concluded that the integrity of surface active tubular myelin represents an important criterion for the assessment of lung preservation quality.
Synthesis and release ofL-serine by rat astroglia-rich primary cultures
2000-03-01

L-serine is known to have important functions in the mammalian CNS other than being a constituent of proteins. It is the metabolic precursor of the neuroactive substances D-serine and glycine, serves as a building block for phospholipid biosynthesis and is likely to be a neurotrophic factor. Based on the observation that rat astroglia-rich primary cultures release L-serine into their culture medium, the biosynthesis and release of L-serine in these cultures has been investigated. Release of L-serine is due to both biosynthesis from glucose and to proteolysis. Amino groups for L-serine synthesis originate from transamination of amino acids that are either taken up from the extracellular space or produced intracellularly by proteolysis. The enzymes of the "phosphorylated pathway" of serine biosynthesis, i.e., 3-phosphoglycerate dehydrogenase, phosphoserine aminotransferase and phosphoserine phosphatase are present in rat brain as well as in rat astroglia-rich primary cultures and their specific activities have been determined. The presence of these enzymes indicates the operation of the "phosphorylated pathway" of L-serine biosynthesis in brain.
Isotope effect in the presence of a pseudogap
2000-03-01

We investigate the question whether the unusual doping dependence of the\\nisotope exponent observed in underdoped high-Tc superconductors might be\\nrelated to another unusual phenomenon observed in these systems: the pseudogap\\nphenomenon. Within different approximations we study the influence of a\\nphenomenological pseudogap on the isotope exponent and find that it generally\\nstrongly increases the isotope exponent, in qualitative agreement with\\nexperiments on underdoped high-Tc compounds. This result is stable against\\nstrong-coupling self-energy corrections and also holds for recently proposed\\nspinfluctuation exchange models, if a weak additional electron-phonon coupling\\nis considered.\\n
Double Butterfly Suture for High Tension: A Broadly Anchored, Horizontal, Buried Interrupted Suture
2000-03-01

The double butterfly suture described here has the advantages of withstanding tension better while everting wound margins and requiring fewer stitches for wound closure. However, it is important that the suture knot be deeply anchored beneath the corium.
Molecular characterization of two genes from Streptomyces tendae Tü901 required for the formation of the 4‐formyl‐4‐imidazolin‐2‐one‐containing nucleoside moiety of the peptidyl nucleoside antibiotic nikkomycin
2000-03-01

The genes nikQ and nikR were identified by sequencing DNA of the nikkomycin biosynthetic gene cluster from Streptomyces tendae Tü901/8c. The nikQ gene encodes a P450 cytochrome, and the predicted NikR gene product shows 48–56% sequence identity with uracil phosphoribosyltransferases from eukaryotic organisms. The nikQ and nikR genes were inactivated separately by insertion of a kanamycin‐resistance cassette. Inactivation of the nikQ gene abolished synthesis of nikkomycins containing 4‐formyl‐4‐imidazolin‐2‐one as the base (nikkomycins X and I), whereas production of nikkomycins containing uracil (nikkomycins Z and J) was not affected. Nikkomycin X and I production could be restored by feeding 4‐formyl‐4‐imidazolin‐2‐one to the nikQ mutants, indicating that NikQ is responsible for its formation from l ‐histidine. Disruption of the nikR gene resulted in formation of decreased amounts of nikkomycins X and I, whereas nikkomycins Z and J were synthesized at wild‐type levels. A fluorouracil‐resistant nikR mutant lacking uracil phosphoribosyltransferase (UPRTase) activity did not synthesize nikkomycins X and I and accumulated 4‐formyl‐4‐imidazolin‐2‐one in its culture filtrate, whereas formation of nikkomycins Z and J was unimpaired. The mutant was complemented to nikkomycin X and I production by nikR expressed from the mel promoter of plasmid pIJ702. The nikR gene expressed in Escherichia coli led to the production of UPRTase activity. Our results indicate that NikR converts 4‐formyl‐4‐imidazolin‐2‐one to yield 5′‐phosphoribosyl‐4‐formyl‐4‐imidazolin‐2‐one, the precursor of nikkomycins containing this base.
A clinical evaluation of some factors affecting image quality in panoramic radiography
2000-03-01

AIM To evaluate the suitability of panoramic radiographs obtained with two different machines for clinical use. MATERIAL AND METHODS Three observers assessed 111 pairs of panoramic radiographs taken with the Scanora (Soredex, Orion Corp., Helsinki, Finland) programme 001, and the Orthophos Plus (Sirona, Bensheim, Germany), programme P1 respectively, for visualisation of seven anatomical structures on each side, on a 5-point scale where 1 = very good. The median values were computed and a descriptive analysis performed. Interrater and intrarater agreement were expressed as weighted kappa. RESULTS The median values of both Scanora and Orthophos radiographs were the same, scoring 2. The intra- and inter-observer agreement was generally poor and similar for both machines. CONCLUSIONS The two panoramic machines were both given good ratings for evaluation of anatomical structures. The differences were very small and suggest that both machines are suitable for clinical use.
Immunocytochemical Localization of β‐Methylcrotonyl‐CoA Carboxylase in Astroglial Cells and Neurons in Culture
2000-03-01

Abstract: Astroglia‐rich primary cultures and brain slices rapidly metabolize branched‐chain amino acids (BCAAs), in particular leucine, as energy substrates. To allocate the capacity to degrade leucine oxidatively in neural cells, we have purified β‐methylcrotonyl‐CoA carboxylase (β‐MCC) from rat liver as one of the enzymes unique for the irreversible catabolic pathway of leucine. Polyclonal antibodies raised against β‐MCC specifically cross‐reacted with both enzyme subunits in liver and brain homogenates. Immunocytochemical examination of astroglia‐rich rat primary cultures demonstrated the presence of β‐MCC in astroglial cells, where the enzyme was found to be located in the mitochondria, the same organelle that the mitochondrial isoform of the BCAA aminotransferase (BCAT) is located in. This colocalization of the two enzymes supports the hypothesis that mitochondrial BCAT is the isoenzyme that in brain energy metabolism prepares the carbon skeleton of leucine for irreversible degradation in astrocytes. Analysis of neuron‐rich primary cultures revealed also that the majority of neurons contained β‐MCC. The presence of β‐MCC in most neurons demonstrates their ability to degrade the α‐ketoisocaproate that could be provided by neighboring astrocytes or could be generated locally from leucine by the action of the cytosolic isoform of BCAT that is known to occur in neurons.
Generation of LR parsers by partial evaluation
2000-03-01

The combination of modern programming languages and partial evaluation yields new approaches to old problems. In particular, the combination of functional programming and partial evaluation can turn a general parser into a parser generator. We use an inherently functional approach to implement general LR( k ) parsers and specialize them with respect to the input grammars using offline partial evaluation. The functional specification of LR parsing yields a concise implementation of the algorithms themselves. Furthermore, we demonstrate the elegance of the functional approach by incorporating on-the-fly attribute evaluation for S-attributed grammars and two schemes for error recovery, which lend themselves to natural and elegant implementation. The parser require only minor changes to achieve good specialization results. The generated parsers have production quality and match those produced by traditional parser generators in sped and compactness
Altered expression of calcium- and apoptosis-regulating proteins in multiple system atrophy purkinje cells
2000-03-01

The expression patterns of the calcium binding proteins calbindin and parvalbumin and of the apoptosis modulating proteins Bcl-2, Bax, and Bcl-x were studied in the cerebellum of patients with multiple system atrophy (MSA). Calbindin and parvalbumin immunoreactivity was markedly decreased in MSA Purkinje cells whereas Bax and Bcl-x protein expression was increased. Bcl-2 expression was restricted to a subpopulation of granule neurons, but no decrease of Bcl-2 was evident in MSA. Additional DNA end-labeling (ISEL) studies revealed only one possible apoptotic Purkinje cell nucleus, but nuclei in the cerebellar white matter, probably oligodendrocytes, in the cerebellum of patients with MSA. The present results suggest that a diminished calcium binding capacity of MSA Purkinje cells might lead to a change in the regulation of proteins of the bcl-2 family that could favor the pathologic initiation of apoptosis.
Neutralization of measles virus wild-type isolates after immunization with a synthetic peptide vaccine which is not recognized by neutralizing passive antibodies
2000-03-01

The sequence H379-410 of the measles virus haemagglutinin (MV-H) protein forms a surface-exposed loop and contains three cysteine residues (Cys-381, Cys-386 and Cys-394) which are conserved among all measles isolates. It comprises the minimal sequential B cell epitope (BCE) (H386-400) of the neutralizing and protective MAb BH6 that neutralizes all wild-type viruses tested. The aim of this study was to design synthetic peptides which induce neutralizing antibodies against MV wild-type isolates. Peptides containing one or two copies of T cell epitopes (TCE) and BCEs of different lengths (H386-400, B(CC); H379-400, B(CCC)), in different combinations and orientations were produced and iteratively optimized for inducing neutralizing antibodies. Peptides with the shorter BCE induced sera that cross-reacted with MV but did not neutralize. The longer BCE containing the three cysteines (B(CCC)) and two homologous TCE were required for neutralization activity. These sera neutralized wild-type strains of different clades and geographic origins. Neutralizing serum was also obtained after immunization with human promiscuous TCEs. Furthermore B(CCC)-based peptides were fully immunogenic even in the presence of pre-existing MV-specific antibodies. The results suggest that subunit vaccines based on such peptides could potentially be used to actively protect infants against wild-type viruses irrespective of persisting maternal antibodies.
Rationally designed inhibitors as tools for comparing the mechanism of squalene‐hopene cyclase with oxidosqualene cyclase
2000-03-01

Abstract The inhibition of squalene‐hopene cyclase (SHC) (E.C. 5.4.99.‐), an enzyme of bacterial membranes catalyzing the formation of pentacyclic sterol‐like triterpenes, was studied by using different classes of compounds originally developed as inhibitors of oxidosqualene cyclase (OCS) (E.C. 5.4.99.7), the enzyme of eukaryotes responsible for the formation of tetracyclic precursors of sterols. The mechanism of cyclization of squalene by SHC, beginning with a protonation of the 2,3 double bond by an acidic residue of the enzyme, followed by a series of electrophilic additions of the carbocationic intermediates to the double bonds, is similar to the mechanism of cyclization of 2,3‐oxidosqualene by OSC. The inhibitors studied included: (i) analogs of the carbocationic intermediates formed during cyclization, such as aza‐analogs of squalene and 2,3‐oxidosqualene; (ii) affinity‐labeling inhibitors bearing a methylidene reactive group; and (iii) vinyldioxidosqualenes and vinylsulfide derivatives of the substrates. Comparison of the results obtained with the two enzymes, SHC and OSC, showed that many of the most effective inhibitors of OSC were also able to inhibit SHC, while some derivatives acted as specific inhibitors. Differences could be easily explained on the basis of the different substrate specificity of the two enzymes.
Independent magnetotransport in parallel InGaAs double quantum wells with strongly different properties
2000-03-01

A double quantum well system consisting of two asymmetric In 0.53 Ga 0.47 As quantum wells, of 9 nm and 7 nm width. Respectively, separated by a 4.5 nm In 0.52 Al 0.48 As barrier, has been studied using magnetotransport measurements over a wide range of different total electron densities as well as different ratios of the electron densities in the two quantum wells ns1:ns2. The Hall measurements reveal planteaus for even and odd integer filling factors v. depending on the electron density. SdH and Hall measurements for an electron density ratio ns1:ns2 = 1:2 show integer filling factors V = 3i (i integer). This can be understood by treating transport in both quantum wells as independent. Therefore filling factors v = v1 + v2, with v1 and v2 filling factors of the two quantum wells respectively, are observed. From SdH measurements other basic quantities, such as electron densities, transport and quantum lifetimes and g-factor, were obtained for both quantum wells separately. This leads to the conclusion that the upper quantum well is always less than half as populated as the lower one. it also exhibits a longer quantum lifetime and therfore shows a very pronounced g-factor enhancement, more than four times as large as for the lower quantum well. The pronounced appearance of odd filling factors is therefore understood by means of this very strong g-factor enhancement for the less populated upper quantum well for magnetic fields larger than 4 T.
Jean Goubault-Larrecq and Ian Mackie. Proof theory and automated deduction. Applied logic series, vol. 6. Kluwer Academic Publishers, Dordrecht, Boston, and London, 1997, xv + 424 pp.
2000-03-01

Jean Goubault-Larrecq and Ian Mackie. Proof theory and automated deduction. Applied logic series, vol. 6. Kluwer Academic Publishers, Dordrecht, Boston, and London, 1997, xv + 424 pp. - Volume 6 Issue 1
Towards generative components
2000-03-01

On September, 28 - 30, 1999, the First International Symposium on Generative and Component-based Software Engineering (GCSE'1999) took place at Erfurt, Germany. This was the origin of a new international forum bundling the research on all generative techniques within the software development process, especially those focused on components. The next Symposium GCSE'2000 is intended to take place on October, 10 - 12, 2000, Erfurt. This time co-hosted with NET.OBJECTDAYS'2000.
Tissue Concentrations of Endothelial Cell Adhesion Molecules in the Lower Uterine Segment During Term Parturition
2000-03-01

In Brief Objective To determine the concentration of endothelial cell adhesion molecules in the lower uterine segment during parturition at term. Methods We analyzed protein extracts from the lower uterine segments of 38 women who had nonelective cesareans at term. We measured concentrations of intercellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and platelet endothelial cell adhesion molecule-1 by enzyme-linked immunosorbent assay. Subjects were grouped according to cervical dilatation (less than 2 cm, n = 10; 2 to less than 4 cm, n = 9; 4–6 cm, n = 9; more than 6 cm, n = 10) and duration of labor (up to 6 hours, n = 14; 6–12 hours, n = 10; 12–24 hours, n = 9; longer than 24 hours, n = 5) at the time of cesarean. Results The median concentration of intercellular adhesion molecule-1 increased significantly with increasing dilatation (from 2.24 ng/mg total protein at less than 2 cm to 6.73 ng/mg at 4–6 cm) and increasing duration of labor (from 2.53 ng/mg up to 6 hours to 5.90 ng/mg at 12–24 hours). However, this study did not have adequate statistical power to identify differences in concentrations of the other endothelial adhesion molecules. Conclusion The results indicate that parturition at term is associated with expression of intercellular adhesion molecule-1. The concentration of intercellular adhesion molecule-1 in the lower uterine segment increases during parturition at term.
Reduced Loading of Intracellular Ca2+ Stores and Downregulation of Capacitative Ca2+Influx in Bcl-2–Overexpressing Cells
2000-03-06

The mechanism of action of the oncogene bcl-2, a key regulator of the apoptotic process, is still debated. We have employed organelle-targeted chimeras of the Ca2+-sensitive photoprotein, aequorin, to investigate in detail the effect of Bcl-2 overexpression on intracellular Ca2+ homeostasis. In the ER and the Golgi apparatus, Bcl-2 overexpression increases the Ca2+ leak (while leaving Ca2+ accumulation unaffected), hence reducing the steady-state [Ca2+] levels. As a direct consequence, the [Ca2+] increases caused by inositol 1,4,5 trisphosphate (IP3)-generating agonists were reduced in amplitude in both the cytosol and the mitochondria. Bcl-2 overexpression also reduced the rate of Ca2+ influx activated by Ca2+ store depletion, possibly by an adaptive downregulation of this pathway. By interfering with Ca2+-dependent events at multiple intracellular sites, these effects of Bcl-2 on intracellular Ca2+ homeostasis may contribute to the protective role of this oncogene against programed cell death.
The Role of Peptides in T Cell Alloreactivity Is Determined by Self–Major Histocompatibility Complex Molecules
2000-03-06

By analyzing T cell responses against foreign major histocompatibility complex (MHC) molecules loaded with peptide libraries and defined self- and viral peptides, we demonstrate a profound influence of self-MHC molecules on the repertoire of alloreactive T cells: the closer the foreign MHC molecule is related to the T cell's MHC, the higher is the proportion of peptide-specific, alloreactive (“allorestricted”) T cells versus T cells recognizing the foreign MHC molecule without regard to the peptide in the groove. Thus, the peptide repertoire of alloreactive T cells must be influenced by self-MHC molecules during positive or negative thymic selection or peripheral survival, much like the repertoire of the self-restricted T cells. In consequence, allorestricted, peptide-specific T cells (that are of interest for clinical applications) are easier to obtain if T cells and target cells express related MHC molecules.
Neutral amino acid transporter ASCT2 displays substrate-induced Na+ exchange and a substrate-gated anion conductance
2000-03-07

The neutral amino acid transporter ASCT2 mediates electroneutral obligatory antiport but at the same time requires Na+ for its function. To elucidate the mechanism, ASCT2 was expressed in Xenopus laevis oocytes and transport was analysed by flux studies and two-electrode voltage clamp recordings. Flux studies with 22NaCl indicated that the uptake of one molecule of glutamine or alanine is accompanied by the uptake of four to seven Na+ ions. Similarly to the transport of amino acids, the Na+ uptake was mediated by an obligatory Na+ exchange mechanism that depended on the presence of amino acids but was not stoichiometrically coupled to the amino acid transport. Other cations could not replace Na+ in this transport mechanism. When NaCl was replaced by NaSCN in the transport buffer, the superfusion of oocytes with amino acid substrates resulted in large inward currents, indicating the presence of a substrate-gated anion channel in the ASCT2 transporter. The Km for glutamine derived from these experiments is in good agreement with the Km derived from flux studies; it varied between 40 and 90 μM at holding potentials of -60 and -20 mV respectively. The permeability of the substrate-gated anion conductance decreased in the order SCN- NO3- &amp;gt; I- &amp;gt; Cl- and also required the presence of Na+.
The α1/2 helical backbone of the prodomains defines the intrinsic inhibitory specificity in the cathepsin L‐like cysteine protease subfamily
2000-03-08

Proregions of papain‐like cysteine proteases are potent and often highly selective inhibitors of their parental enzymes. The molecular basis of their selectivity is poorly understood. For two closely related members of the cathepsin L‐like subfamily we established strong selectivity differences. The propeptide of cathepsin S was observed to inhibit cathepsin L with a K i of 0.08 nM, yet cathepsin L propeptide inhibited cathepsin S only poorly. To identify the respective structural correlates we engineered chimeric propeptides and compared their inhibitory specificity with the wild‐types. Specificity resided in the N‐terminal part, strongly suggesting that the backbone of the prodomain was the underlying structure.
Smoothed Particle Hydrodynamics Simulations of Ultrarelativistic Shocks with Artificial Viscosity
2000-03-10

We present a fully Lagrangian conservation form of the general relativistic hydrodynamic equations for perfect fluids with artificial viscosity in a given arbitrary background spacetime. This conservation formulation is achieved by choosing suitable Lagrangian time evolution variables, from which the generic fluid variables rest-mass density, 3-velocity, and thermodynamic pressure have to be determined. We present the corresponding equations for an ideal gas and show the existence and uniqueness of the solution. On the basis of the Lagrangian formulation we have developed a three-dimensional general relativistic Smoothed Particle Hydrodynamics (SPH) code using the standard SPH formalism as known from non-relativistic fluid dynamics. One-dimensional simulations of a shock tube and a wall shock are presented. With our method we can model ultra-relativistic fluid flows including shocks with relativistic gamma-factors of even 1000.