bluuebunny/crossref_metadata_2025_split huggingface dataset:
Duan's fixed point theorem: Proof and generalization
Authors: Arkowitz Martin 
Published: April 2006

AbstractLet "Equation missing" be an H-space of the homotopy type of a connected, finite CW-complex, "Equation missing" any map and "Equation missing" the "Equation missing"th power map. Duan proved that "Equation missing" has a fixed point if "Equation missing". We give a new, short and elementary proof of this. We then use rational homotopy to generalize to spaces "Equation missing" whose rational cohomology is the tensor product of an exterior algebra on odd dimensional generators with the tensor product of truncated polynomial algebras on even dimensional generators. The role of the power map is played by a "Equation missing"-structure "Equation missing" as defined by Hemmi-Morisugi-Ooshima. The conclusion is that "Equation missing" and "Equation missing" each has a fixed point.
Epsilon Nielsen fixed point theory
Authors: Brown Robert F 
Published: April 2006

AbstractLet "Equation missing" be a map of a compact, connected Riemannian manifold, with or without boundary. For "Equation missing" sufficiently small, we introduce an "Equation missing"-Nielsen number "Equation missing" that is a lower bound for the number of fixed points of all self-maps of "Equation missing" that are "Equation missing"-homotopic to "Equation missing". We prove that there is always a map "Equation missing" that is "Equation missing"-homotopic to "Equation missing" such that "Equation missing" has exactly "Equation missing" fixed points. We describe procedures for calculating "Equation missing" for maps of "Equation missing"-manifolds.
A base-point-free definition of the Lefschetz invariant
Authors: Coufal Vesta 
Published: April 2006

AbstractIn classical Lefschetz-Nielsen theory, one defines the Lefschetz invariant "Equation missing" of an endomorphism "Equation missing" of a manifold "Equation missing". The definition depends on the fundamental group of "Equation missing", and hence on choosing a base point "Equation missing" and a base path from "Equation missing" to "Equation missing". At times, it is inconvenient or impossible to make these choices. In this paper, we use the fundamental groupoid to define a base-point-free version of the Lefschetz invariant.
Fixed point variational solutions for uniformly continuous pseudocontractions in Banach spaces
Authors: Udomene Aniefiok 
Published: April 2006

AbstractLet "Equation missing" be a reflexive Banach space with a uniformly Gâteaux differentiable norm, let "Equation missing" be a nonempty closed convex subset of "Equation missing", and let "Equation missing" be a uniformly continuous pseudocontraction. If "Equation missing" is any contraction map on "Equation missing" and if every nonempty closed convex and bounded subset of "Equation missing" has the fixed point property for nonexpansive self-mappings, then it is shown, under appropriate conditions on the sequences of real numbers "Equation missing", "Equation missing", that the iteration process "Equation missing", "Equation missing", "Equation missing", strongly converges to the fixed point of "Equation missing", which is the unique solution of some variational inequality, provided that "Equation missing" is bounded.
A monoclonal antibody against CD148, a receptor-like tyrosine phosphatase, inhibits endothelial-cell growth and angiogenesis
Authors: Takahashi Takamune , Takahashi Keiko , Mernaugh Raymond L. , Tsuboi Nobuo , Liu Hua , Daniel Thomas O. 
Published: April 2006

AbstractAngiogenesis contributes to a wide range of neoplastic, ischemic, and inflammatory disorders. Definition of the intrinsic molecular controls in angiogenic vessel growth promises novel therapeutic approaches for angiogenesis-related diseases. CD148 (also named DEP-1/PTPη) is a receptor-like protein tyrosine phosphatase that is abundantly expressed in vascular endothelial cells. To explore a role of CD148 in endothelial vessel formation, we generated a monoclonal antibody, Ab1, against the ectodomain sequence of CD148 and examined its effects on endothelial-cell growth and vessel formation. Here we report that a bivalent, but not a monovalent, form of the Ab1 antibody inhibits endothelial-cell growth and blocks angiogenesis in mouse cornea in vivo. We further demonstrate that (1) bivalent Ab1 arrests cell-cycle progression of CD148-transfected CHO cells at G0/G1 phase, (2) coexpression of catalytically inactive CD148 mutants attenuates the Ab1-cell growth inhibition, and (3) bivalent Ab1 suppresses phosphorylation of ERK1/2 kinases and Met tyrosine kinase as activated CD148 does, with an increase in CD148-associated tyrosine phosphatase activity. Taken together, these findings demonstrate that Ab1-induced ectodomain oligomerization arrests endothelial-cell growth through catalytic activity of the CD148 cytoplasmic domain. The present study defines CD148 as a valuable molecular target for antiangiogenesis therapy.
Kaposi sarcoma herpesvirus K5 removes CD31/PECAM from endothelial cells
Authors: Mansouri Mandana , Douglas Janet , Rose Patrick P. , Gouveia Kristine , Thomas Gary , Means Robert E. , Moses Ashlee V. , Früh Klaus 
Published: April 2006

AbstractThe transmembrane ubiquitin ligase K5/MIR2 of Kaposi sarcoma herpesvirus (KSHV) mediates internalization and lysosomal degradation of glycoproteins involved in antigen presentation and co-stimulation. In endothelial cells (ECs), K5 additionally reduced expression of CD31/platelet–endothelial cell adhesion molecule (PECAM), an adhesion molecule regulating cell-cell interactions of ECs, platelets, monocytes, and T cells. K5 also reduced EC migration, a CD31-dependent process. Unlike other K5 substrates, both newly synthesized and pre-existing CD31 molecules were targeted by K5. K5 was transported to the cell surface and ubiquitinated pre-existing CD31, resulting in endocytosis and lysosomal degradation. In the endoplasmic reticulum, newly synthesized CD31 was degraded by proteasomes, which required binding of phosphofurin acidic cluster sorting protein-2 (PACS-2) to acidic residues in the carboxyterminal tail of K5. Thus, CD31, a novel target of K5, is efficiently removed from ECs by a dual degradation mechanism that is regulated by the subcellular sorting of the ubiquitin ligase. K5-mediated degradation of CD31 is likely to affect EC function in KS tumors.
Replacing the Mouse Androgen Receptor with Human Alleles Demonstrates Glutamine Tract Length-Dependent Effects on Physiology and Tumorigenesis in Mice
Authors: Albertelli Megan A. , Scheller Arno , Brogley Michele , Robins Diane M. 
Published: April 2006

AbstractPolymorphism in the length of the N-terminal glutamine (Q) tract in the human androgen receptor (AR) has been implicated in affecting aspects of male health ranging from fertility to cancer. Extreme expansion of the tract underlies Kennedy disease, and in vitro the AR Q tract length correlates inversely with transactivation capacity. However, whether normal variation influences physiology or the etiology of disease has been controversial. To assess directly the functional significance of Q tract variation, we converted the mouse AR to the human sequence by germline gene targeting, introducing alleles with 12, 21, or 48 glutamines. These three “humanized” AR (h/mAR) mouse lines were grossly normal in growth, behavior, fertility, and reproductive tract morphology. Phenotypic analysis revealed traits that varied subtly with Q tract length, including body fat amount and, more notably, seminal vesicle weight. Upon molecular analysis, tissue-specific differences in AR levels and target gene expression were detected between mouse lines. In the prostate, probasin, Nkx3.1, and clusterin mRNAs trended in directions predicted for inverse correlation of Q tract length with AR activation. Remarkably, when crossed with transgenic adenocarcinoma of mouse prostate (TRAMP) mice, striking genotype-dependent differences in prostate cancer initiation and progression were revealed. This link between Q tract length and prostate cancer, likely due to differential activation of AR targets, corroborates human epidemiological studies. This h/mAR allelic series in a homogeneous mouse genetic background allows examination of numerous physiological traits for Q tract influences and provides an animal model to test novel drugs targeted specifically to human AR.
A Voltage-Induced Transition of Hemin in BIODE (Biomolecular Light-Emitting Diode)
Authors: Tajima Hiroyuki , Shimatani Kazuhiro , Komino Takeshi , Matsuda Masaki , Ikeda Shingo , Ando Yoriko , Akiyama Hidefumi 
Published: April 2006

Abstract
We fabricated biomolecular light-emitting diodes (BIODE) using hemin, and measured the electroluminescence (EL) spectra, current–voltage and EL intensity–voltage characteristics. The current–voltage and EL intensity–voltage characteristics revealed an irreversible transition of hemin for the applied voltage of V ≈ 4.5 V, above which drastic changes of the EL spectra occur. In order to clarify the origin of this voltage-induced transition, we determined the spin state of several compounds containing heme (hemin, myoglobin, and cytochrome c) using magnetic susceptibility and Raman spectra. We clarified the features of the EL spectra of heme compounds both in the oxidized low-spin state and in the oxidized high-spin state. Based on the spectral features thus obtained, we concluded that the voltage-induced transition in hemin is associated with the change of iron from the oxidized high-spin state (S = 5/2) to the oxidized low-spin state (S = 1/2).
Stepwise strategies in analysing haematuria and leukocyturia in screening
Authors: Steinmetz Josiane , Henny Joseph , Gueguen René 
Published: April 2006

AbstractThe aim of the present work was to compare in a supposed healthy population of 680 subjects several algorithms for positive selection of urine samples requiring microscopic examination for erythrocytes and leukocytes after screening by automated test-strip measurement and particle counting on a Sysmex UF-50™ flow cytometer. Four strategies have been formulated and the sensitivity, specificity, positive predictive value, negative predictive value, false positive rate, false negative rate, and microscopic review rate were measured. The strategy combining test strip analysis and automated counting on all samples, followed by microscopic examination of only discordant samples gave the best results. When the two methods of haematuria screening were in agreement (91% of samples), the false negative rate for microscopy was 1.1%, with a false positive rate of 0.8%, sensitivity of 66% and specificity of 99%, and the results are acceptable without any other examination. When the two methods of haematuria screening were discrepant, visual microscopic analysis was necessary to obtain definitive results. For leukocyturia screening, 80% of results were in agreement by test strip and automatic sediment urinalysis, with only ten results considered as false negatives (1.8%) and four as false positives (0.7%). Agreement was good and the other criteria were good (sensitivity 79%, specificity 99%). On conflicting samples, there was no agreement between methods and microscopic analysis was essential. The benefit of such an algorithm would be optimisation of the workflow without any loss of sensitivity and specificity at the expense of a two-fold increase in cost.
Matrix metalloproteinases and their inhibitors in different acute stroke subtypes
Authors: Vukasovic Ines , Tesija-Kuna Andrea , Topic Elizabeta , Supanc Visnja , Demarin Vida , Petrovcic Marija 
Published: April 2006

AbstractThe aim of the study was to determine serum levels of selected matrix metalloproteinases (MMPs) and their natural inhibitors (TIMPs) in the acute phase of different stroke types subdivided according to the Oxfordshire Community Stroke Project (OCSP) classification and the possibility of discriminating stroke types according to their levels. The study included 126 patients with acute stroke within the first 24h of symptom onset, and 124 healthy volunteers. The stroke group had lower MMP-2 concentrations and MMP-2/TIMP-2 ratios (p<0.001) but higher TIMP-2 (p<0.001) than controls. The level of MMP-9 and the MMP-9/TIMP-1 ratio were higher in patients with total anterior circulation infarct (TACI) than in patients with other stroke subtypes according to OCSP classification (p=0.0019, p=0.0065, respectively) or in controls (p<0.0001, p=0.0024, respectively). A negative correlation of MMP-2 levels with MMP-9 and MMP-9/TIMP-1 ratio was recorded in all stroke subtypes except for TACI. Receiver operating characteristic analysis showed similar discriminating power for MMP-9 levels and Barthel index in the differential diagnosis of TACI. High MMP-9/TIMP-1 ratio (odds ratio 3.263) was associated with TACI. Our results demonstrate that the MMP-9/TIMP-1 ratio may provide information to help in assessing stroke patients in the future as a baseline biomarker of infarct extent.
Rapid decrease in plasma D-lactate as an early potential predictor of diminished 28-day mortality in critically ill septic shock patients
Authors: Sapin Vincent , Nicolet Laurent , Aublet-Cuvelier Bruno , Sangline Fabienne , Roszyk Laurence , Dastugue Bernard , Gazuy Nicole , Deteix Patrice , Souweine Bertrand 
Published: April 2006

Abstract
The Effect of Residual Calcium in Decalcified Freeze-dried Bone Allograft in a Critical-sized Defect in the Rattus norvegicus Calvarium
Authors: Turonis James W. , McPherson James C. , Cuenin Michael F. , Hokett Steven D. , Peacock Mark E. , Sharawy Mohamed 
Published: April 2006

AbstractDemineralized freeze-dried bone allograft (DFDBA), a widely used graft material in periodontal regenerative procedures, is processed with hydrochloric acid in the attempt to expose proteins located within the bone matrixes that are capable of inducing new bone formation. However, the degree of DFDBA demineralization varies between tissue banks, which may have an effect on clinical regeneration. This study uses the critical-sized defect (CSD) model to evaluate the wound-healing response to the residual calcium of donor bone. If the percentage of residual calcium in a graft were demonstrated to significantly enhance wound healing, then periodontal patients may benefit from further standardization of human-allograft processing. Sixty adult, male, Harlan Sprague-Dawley rats (Rattus norvegicus) were randomly and equally divided into 4 test groups (ie, DFDBA at 1%, 2%, and 3% to 6% residual calcium levels and FDBA at 23% residual calcium) and a control group (no allograft). An 8-mm-diameter craniotomy was made in the rat calvarium, and polytetrafluoroethylene membranes with pore sizes of 0.50 μm were placed intracranially and ectocranially. Treatment materials were carefully placed into the CSD with a new sterilized dental amalgam carrier. Tetracycline hydrochloride was injected intraperitoneally for labeling new bone growth, and animals were euthanized 12 weeks postsurgery. As a result, histomorphometric bone fill at 12 weeks showed a statistically significant increase in the 2% DFDBA group as compared to all other groups. The authors conclude that a 2% residual calcium level in human DFDBA appears to significantly (P ≤ .05) enhance osseous wound healing in the rat calvarium.
Carbonic Anhydrases (β‐Class)
Authors: Yamashita Eiki , Mitsuhashi Satoshi , Tsukihara Tomitake 
Published: April 2006

Abstract

Carbonic anhydrase (CA) catalyzes the reversible hydration of CO
2
to HCO
3
−
in aqueous solution. CAs are divided into three distinct classes (α‐CAs, β‐CAs, and γ‐CAs) that have little sequence homology to one another. β‐CA plays an essential role in photosynthesis, by concentrating CO
2
in the proximity of ribulose bisphosphate carboxylase/oxygenase for CO
2
fixation. Little is known about the physiological roles performed by β‐CA in nonphotosynthetic organisms.

Two homologous motifs are repeated in the

Porphyridium purpureum

β‐CA polypeptide (55 kDa). Each motif is composed of two components: an α/β domain and an N‐terminal arm. The two motifs in a monomer are related by a pseudo twofold axis. The two monomers form a dimer with pseudo 222 symmetry.

Escherichia coli

β‐CA and

Pisum sativum

β‐CA are composed of a tetramer and an octamer respectively. The dimer of

P. purpureum

β‐CA resembles a tetramer of

E. coli

β‐CA. A dimer of

P. sativum

β‐CA, which resembles the monomer of

P. purpureum

β‐CA, is the basic building block of the octamer.

Both β‐CAs from

Methanobacterium thermoautotrophicum

and

E. coli

have one zinc atom per monomer, while β‐CA from

P. purpureum

contains two zinc atoms per monomer. The catalytic zinc atom at each catalytic site is coordinated by four ligands in a tetrahedral manner. A possible catalytic mechanism of β‐CA based on the structure of

P. purpureum

CA is proposed.
Carbonic Anhydrases (γ‐Class)
Authors: Kisker Caroline , Iverson Tina M 
Published: April 2006

AbstractThe γ‐class carbonic anhydrase from the thermophilic archaeonMethanosarcina thermophilais involved in the aceticlastic pathway in which energy for growth is derived from the conversion of the methyl group of actetate to methane. This γ‐class carbonic anhydrase is arranged as a tightly packed trimer with each monomer folded into a left‐handed β‐helix. The catalytic active site zinc is located at the interface between subunits and is coordinated by three histidines, two from one monomer and the other from a second monomer. Interestingly, the arrangement of the histidine side chains ligating the metal show clear structural similarity to their counterparts in the well‐characterized α‐class carbonic anhydrases, despite the difference in overall fold. The conversion of CO2to bicarbonate has a maximal turnover number of 6 × 104s−1, and this reaction is believed to proceed by utilizing the zinc‐hydroxide mechanism previously proposed for α‐class carbonic anhydrases.
GTP
Cyclohydrolase
I
Authors: Nar Herbert 
Published: April 2006

Abstract

GTP Cyclohydrolase I (GTP‐CH‐I) is a homodecameric protein complex of approximately 250 kDa molecular weight and it catalyzes the conversion of guanosine triphosphate (GTP) to dihydroneopterin triphosphate (H
2
NTP), the committing step in the biosynthesis of pteridines.

The GTP‐CH‐I monomer forms a compact single‐domain α + β structure containing a predominantly α‐helical N‐terminal subdomain and a sequential, four‐stranded, antiparallel β‐sheet in the C‐terminal subdomain. Association to dimers occurs along an antiparallel α‐helix pair. Decamers are formed by five dimers through the association of the respective four‐stranded, antiparallel β‐sheets to two 20‐stranded β‐barrel structures in each pentameric substructure of the active enzyme complex.
The active site is located at the interface of three monomers and is composed of a 12‐Å deep cavity that contains a guanine recognition motif at its bottom and a zinc binding site. The metal ion is coordinated by two cysteines and a histidine residue. A water molecule completes the coordination environment of the zinc in the resting state of the enzyme.
The role of the Zn(II) ion in catalysis is probably similar to its role in Zn(II)‐dependent proteinases and involves water activation in the guanine hydrolysis steps of the reaction sequence.
The product is formed by a subsequent Amadori rearrangement and ring closure. These steps involve acid–base catalysis and are probably performed by strictly conserved amino acid side chains in the vicinity of the zinc binding site.
Metallo β‐Lactamases
Authors: Herzberg Osnat , Fitzgerald Paula MD 
Published: April 2006

Abstract
The metallo‐β‐lactamases (class B β‐lactamases) confer bacterial resistance to β‐lactam antibiotics and are therefore targets for the development of clinical agents against resistant strains of bacteria. They are found in a wide variety of bacteria and act on a broad spectrum of substrates including penicillins, cephalosporins, and carbapenems, as well as on some inhibitors of serine‐β‐lactamases. These ∼25 000 Da zinc‐dependent enzymes have been studied extensively in recent years, and crystal structures have been determined for the enzymes from five different bacteria representing two different sequence subclasses (B1 and B3). The active site is located at the interface between two α/β domains where two zinc atoms bind. This review surveys the current understanding of these enzymes, with emphasis on structural studies, spectroscopy, kinetics, and proposals for the catalytic mechanism.
NucleaseP1
Authors: Volbeda Anne , Romier Christophe , Suck Dietrich 
Published: April 2006

AbstractNuclease P1 of the moldPenicillium citrinumis a zinc‐dependent enzyme that cleaves all PO3′ bonds in single‐stranded DNA and RNA substrates, independent of base sequence. Crystallographic studies of the native enzyme have shown that the trinuclear zinc active site is inaccessible for phosphate groups in regular A‐ and B‐DNA structures, whereas crystal structures of complexes with thio‐ and dithiophosphorylated oligonucleotides as substrate analogs show the importance of stacking and hydrogen‐bonding interactions with unpaired bases. These studies provide, in addition, a structural basis for the understanding of the low pH optimum of the enzyme and of its catalytic mechanism. This is most likely to be very similar to the three–metal ion mechanisms proposed forBacillus cereusphospholipase C andEscherichia coliendonuclease IV, although the latter enzyme has a completely different structure. In each case, the phosphate‐attacking nucleophile is a water or hydroxide molecule that is activated by two closely spaced zinc ions, assisted by hydrogen bonding to a nearby carboxylate group, and with stabilization of the leaving PO3′ anion by a third, more exposed zinc ion. Sequence comparisons with P1‐related nucleases confirm the importance of an invariant asparagine in the proper orientation of the substrate by hydrogen bonding to the O4′ atom of the ribose moiety that is situated next to the cleaved PO3′ bond.
Structural Zinc Sites
Authors: Auld David S 
Published: April 2006

AbstractStructural zinc binding sites in proteins have a combination of four nitrogen, oxygen, and sulfur ligands provided by the side chains of amino acids of the protein. In marked contrast to catalytic zinc sites, no metal‐coordinated water molecule is present. There are over seven dozen representatives of structural zinc sites. While the sulfur of a cysteine is by far the preferred ligand for such sites, it is also found in combination with an imidazole nitrogen of a histidine, and/or a carboxylate oxygen from aspartate or glutamate. Of the 22 possible permutations of these 4 ligands, 8 have been observed. The ligands to these metal sites are provided by protein sequences as small as 10 amino acids and as large as 210 amino acids but the majority fall within the range of 25 to 50 amino acids. The ligands are frequently supplied from within or just before or after a β‐sheet secondary structure. The role of a structural zinc site is probably twofold. It maintains the structure of the protein in the immediate vicinity of the metal site. In this manner, it may influence enzymatic activity by providing active site residues involved in catalysis and/or affecting the chemical environment of catalytic groups through interaction with amino acids originating from within its metal‐binding spacers. However, in many cases these metal sites also affect the overall stability of the protein as judged by temperature and pH criteria.