bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface micromechanics of ultrahigh molecular weight polyethylene: Microindentation testing, crosslinking, and material behavior
Authors: Gilbert Jeremy L. , Cumber Jeffrey , Butterfield Aaron 
Published: August 2002

AbstractThe wear behavior of ultrahigh molecular weight polyethylene (UHMWPE) is critical to the success of total joint replacements. Recent attempts to modify the wear behavior of UHMWPE by processing, in particular, crosslinking UHMWPE have shown promise to increase wear resistance, but concerns persist regarding other mechanical properties. It is also unclear what specific surface mechanical properties govern the wear resistance seen in these materials. The goal of this study was to demonstrate a custom‐built surface mechanical test system and method that measures the micromechanical response of microtomed UHMWPE surfaces to depth‐sensing microindentation tests. The surface structure of these UHMWPE materials was also examined using scanning electron microscopy and atomic force microscopy. A custom designed microindentation test system assessed the microindentation behavior of three UHMWPE resins: 1. Hylamer™, 2. GUR‐1020 CMS, and 3. Marathon™—a lightly crosslinked material. The effects of material and indentation depth were studied. Microindentation tests were performed with indentation depths ranging from 2 to 45 μm. Four different measurements of surface micromechanical behavior were obtained including the surface modulus, microhardness, hysteresis energy (irreversible work done to the sample per unit cycle) and its associated energy dissipation factor, and loading slope. Statistically significant differences in each of these parameters were found for each material. Generally, Hylamer had the largest values for these parameters, followed by the GUR resin and then the Marathon. Surface modulus was independent of depth of testing and found to be 651 MPa for Marathon, 738 MPa for GUR, and 1015 MPa for Hylamer (Modulus for bulk UHMWPE is 540 MPa for Hylamer, 620 for GUR, and 1380 for Hylamer). The microhardness varied between 67 and 162 MPa depending on material and depth of testing. Surface structural characterization shows that the microtoming process for surface preparation generated distinct surface features that varied between materials. Intermittent drawn ribbons of polymer with oriented crystals were observed in both scanning electron microscopy and atomic force microscopy. The surface density and size of these features were characteristic of the materials with the Hylamer having the fewest, but largest ribbons, followed by GUR and then Marathon. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 270–281, 2002
Quantitative analysis of mRNA expression of TIMPs in the periprosthetic interface tissue of loose hips by real‐time PCR system
Authors: Sasaki Kan , Takagi Michiaki , Mandelin Jami , Takei Isao , Santavirta Seppo , Ida Hideo , Ogino Toshihiko , Konttinen Yrjö T. 
Published: August 2002

AbstractMatrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs), have been reported to play a critical role in extracellular degradation around artificial hip joints. Although messenger ribonucleic acid (mRNA) expression patterns of several MMPs and TIMPs were reported, there is no report of quantitative mRNA analysis of TIMPs in periprosthetic tissues. In this study, mRNA expression of four different types of TIMPs in periprosthetic interface tissue of loose hips was analyzed by a quantitative polymerase chain reaction system. The mRNA expression level of TIMP‐1, ‐2, and ‐3 in periprosthetic interface tissue was significantly higher than that in control. In contrast, the mRNA expression level of TIMP‐4 in the periprosthetic interface tissue was lower. This study suggested that increased levels of TIMP‐1, ‐2, and ‐3, and decreased levels of TIMP‐4 may contribute to pathologic extracellular matrix degradation in combination with MMPs, thus leading to prosthetic loosening and osteolysis around artificial total hip joints. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 605–612, 2001
Peroxisome proliferator perfluorodecanoic acid alters glutathione and related enzymes
Authors: Chen Li‐Chuan , Tatum Vickie , Glauert Howard P. , Chow Ching K. 
Published: August 2002

AbstractPreviously we have shown that treatment with the peroxisome proliferator perfluorodecanoic acid (PFDA) significantly increased hepatic reduced glutathione (GSH) content without altering the activity of selenium‐glutathione peroxidase. In this study we examined some potential mechanisms by which PFDA treatment increases GSH levels. Male Sprague‐Dawley rats were given a single injection of 0, 8.8, 17.5, and 35 mg PFDA in corn oil per kg body weight.
Twelve days later the effects of PFDA on the activities of enzymes associated with GSH synthesis, utilization, and regeneration were assessed. The results showed that in a dose‐dependent manner, PFDA treatment significantly decreased the activity of γ‐glutamylcysteine synthetase, while the activities of NADPH‐generating enzymes, malic enzyme, glucose‐6‐phosphate dehydrogenase, and 6‐phosphogluconate
dehydrogenase were increased. PFDA treatment also dose dependently decreased cytosolic, but not microsomal, glutathione S‐transferase activity, and the activity of glutathione reductase was decreased by the
highest dose of PFDA. The data obtained suggest that increased hepatic GSH levels following PFDA treatment may result from increased regeneration and/or decreased utilization. © 2001 John Wiley & Sons, Inc. J Biochem Mol Toxicol 15:107–113, 2001
Patients with thrombotic thrombocytopenic purpura commonly develop metabolic alkalosis during therapeutic plasma exchange
Authors: Marques Marisa B. , Huang Shu T. 
Published: August 2002

AbstractThrombotic thrombocytopenic purpura (TTP) and myasthenia gravis (MG) are category I indications for therapeutic plasma exchange (TPE). This study was based on the hypothesis that the development of metabolic alkalosis during TPE is more common in TTP than in MG, based on our previous observations. In order to test it, we compared the levels of bicarbonate and potassium in both groups of patients undergoing plasmapheresis. Fifteen patients with TTP (190 procedures) and ten MG patients seen concurrently were studied. While baseline bicarbonate levels were similar among all patients, the post‐procedure bicarbonate levels in TTP patients were mostly elevated with a mean ± SD of 29.4 ± 3.5 mEq/L, as opposed to decreased or unchanged in MG patients 26.3 ± 3.1 mEq/L (mean ± SD) (P = 1.4 × 10−8). Furthermore, alkalosis in the TTP group persisted throughout subsequent daily treatments. There was also a significant decrease between pre‐ and post‐TPE potassium levels in TTP patients (P = 3 × 10−21) by paired Student's t test. Additionally, samples with levels <3.3 mEq/L were alkalotic 75% of the time. In the MG group, however, potassium was normal in 85% and 83% of the pre‐ and post‐TPE samples, respectively. Consequently, the hypokalemia was significantly more marked in the TTP group (P = 0.0008). These data confirm that plasmapheresis commonly induces metabolic alkalosis in TTP patients, probably due to high citrate in fresh frozen plasma, the frequency of treatments, and perhaps decreased renal clearance due to disease involvement of the kidneys. J. Clin. Apheresis. 16:120–124, 2001. © 2001 Wiley‐Liss, Inc.
Mapping of functional epitopes of osteopontin by monoclonal antibodies raised against defined internal sequences
Authors: Kon Shigeyuki , Yokosaki Yasuyuki , Maeda Masahiro , Segawa Tatsuya , Horikoshi Yuko , Tsukagoshi Hiroe , Rashid Mohammod M. , Morimoto Junko , Inobe Manabu , Shijubo Noriharu , Chambers Ann F. , Uede Toshimitsu 
Published: August 2002

AbstractOsteopontin (OPN) is a secreted protein that has been implicated in diverse physiological and pathological processes. OPN can bind to integrins, via GRGDS or SVVYGLR amino acid sequences, and to other cell surface receptors, and many of OPN's functions are likely mediated via cell adhesion and subsequent signaling. Here we developed and characterized a series of five monoclonal antibodies, raised to distinct internal peptide sequences of human OPN, and have used these sequence‐specific reagents, along with the previously described anti‐OPN monoclonal antibody mAb53, to map functional epitopes of OPN that are important to cell adhesion and migration. All antibodies were reactive with native as well as recombinant human OPN. One antibody (2K1) raised against the peptide VDTYDGRGDSVVYGLRS could inhibit RGD‐dependent cell binding to OPN, with an efficacy comparable to that of mAb53. Furthermore, 2K1 could inhibit α9 integrin‐dependent cell binding to OPN. The epitope recognized by 2K1 was not destroyed by thrombin digestion, whereas mAb53 has been shown to be unable to react with OPN following thrombin cleavage. The two distinct epitopes defined by 2K1 and mAb53 antibodies are closely related to the SVVYGLR cell‐binding domain and the GLRSKS containing thrombin cleavage site, respectively, and are involved in cell binding and cell migration. J. Cell. Biochem. 84: 420–432, 2002. © 2001 Wiley‐Liss, Inc.
Nucleolin is a calcium‐binding protein
Authors: Gilchrist James S.C. , Abrenica Bernard , DiMario Patrick J. , Czubryt Michael P. , Pierce Grant N. 
Published: August 2002

AbstractWe have purified a prominent 110‐kDa protein (p110) from 1.6 M NaCl extracts of rat liver nuclei that appears to bind Ca2+. p110 was originally identified by prominent blue staining with ‘Stains‐All’ in sodium dodecyl sulfate–polyacrylamide gels and was observed to specifically bind ruthenium red and 45Ca2+ in nitrocellulose blot overlays. In spin‐dialysis studies, purified p110 saturably bound approximately 75 nmol Ca2+/mg protein at a concentration of 1 mM total Ca2+ with half‐maximal binding observed at 105 μM Ca2+. With purification, p110 became increasingly susceptible to proteolytic (likely autolytic) fragmentation, although most intermediary peptides between 40 and 90 kDa retained “Stains‐All”, ruthenium red, and 45Ca2+ binding. N‐terminal sequencing of intact p110 and a 70‐kDa autolytic peptide fragment revealed a strong homology to nucleolin. Two‐dimensional sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE)/IEF revealed autolysis produced increasingly acidic peptide fragments ranging in apparent pI's from 5.5 for intact p110 to 3.5 for a 40 kDa peptide fragment. Intact p110 and several peptide fragments were immunostained with a highly specific anti‐nucleolin antibody, R2D2, thus confirming the identity of this protein with nucleolin. These annexin‐like Ca2+‐binding characteristics of nucleolin are likely contributed by its highly acidic argyrophilic N‐terminus with autolysis apparently resulting in largely selective removal of its basic C‐terminal domain. Although the Ca2+‐dependent functions of nucleolin are unknown, we discuss the possibility that like the structurally analogous HMG‐1, its Ca2+‐dependent actions may regulate chromatin structure, possibly during apoptosis. J. Cell. Biochem. 85: 268–278, 2002. © 2002 Wiley‐Liss, Inc.
Soluble osteopontin inhibits apoptosis of adherent endothelial cells deprived of growth factors*
Authors: Khan S.A. , Lopez‐Chua C.A. , Zhang J. , Fisher L.W. , Sørensen E.S. , Denhardt D.T. 
Published: August 2002

AbstractOsteopontin (OPN) is primarily an extracellular glycosylated phosphoprotein capable of stimulating cell migration and cell attachment, predominantly to mineralized surfaces. Found in moderate levels in plasma, it acts as a cytokine able to modify gene expression via integrins and certain CD44 isoforms. In this work we show that soluble OPN inhibits apoptosis of adherent human umbilical vein endothelial cells incubated in medium lacking critical growth factors and cytokines. In a dose‐dependent manner OPN reduced the formation of apoptotic bodies and suppressed DNA fragmentation. OPN also caused an increase in Bcl‐XL mRNA levels, suppressed the apparent dispersion of Bcl‐XL throughout the cytoplasm, and slightly enhanced IκB‐α protein degradation. These data suggest that a function of OPN in homeostatic processes is to facilitate the survival of stressed endothelial cells, possibly by occupying unligated integrins and suppressing integrin‐mediated death. J. Cell. Biochem. 85: 728–736, 2002. © 2002 Wiley‐Liss, Inc.
Small GTP‐binding proteins in the nuclei of human placenta
Authors: Phillips Phoebe , Thomson Murray 
Published: August 2002

AbstractMitochondria and crude nuclei containing fractions from human placenta have been shown to contain proteins which bind [α32P]‐GTP. Prior to this study the number of GTP‐binding proteins in placental nuclei and their nucleotide specificity was not known. Also unknown was the identity of any of the GTP‐binding proteins in mitochondria of human placenta. Nuclei and mitochondria were purified from human placental extracts by sedimentation. Proteins were separated by electrophoresis and transferred to nitrocellulose membranes. Overlay blot with [α32P]‐GTP identified two nuclei proteins with approximate molecular weights of 24 and 27 kDa. Binding of [α32P]‐GTP to the 27 and 24 kDa proteins was significantly displaced by guanine nucleotides but not by adenine, thymine or cytosine nucleotides or deoxy (d) GTP. Western blot with a specific antibody to Ran identified a band at 27 kDa in nuclei and in mitochondrial fractions. These data indicate that both nuclei and mitochondria contain 24 and 27 kDa GTP‐binding proteins. The GTP‐binding proteins in nuclei display binding specificity for guanine nucleotides and the hydroxylated carbon 2 on the ribose ring of GTP appears essential for binding. It will be important in future studies to determine the functions of these small GTP‐binding proteins in the development and physiology of the placenta. J. Cell. Biochem. 84: 100–107, 2002. © 2001 Wiley‐Liss, Inc.
Is there a unique melting temperature for two‐state proteins?
Authors: Klimov D. K. , Thirumalai D. 
Published: August 2002

AbstractThermal unfolding (or folding) in many proteins occurs in an apparent two‐state manner, suggesting that only two states, unfolded and folded, are populated. At the melting temperature, Tm, the two states coexist. Using lattice models with side chains we show that individual residues become structured at temperatures that deviate from Tm, which implies that partially folded conformations make substantial contribution to thermodynamic properties of two‐state proteins. We also find that the folding cooperativity for a given residue is linked to its accessible surface area. These results are consistent with the experiments on GCN4‐like zipper peptide, which showed that local melting temperatures differ from Tm. Analysis of thermal unfolding of six proteins shows that ΔT/Tm∼N−1, where ΔT is the transition width and N is the number of residues. This scaling allows us to conclude that, when corrected for finite size effects, folding cooperativity can be captured using coarse grained models. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 161–165, 2002
MM3 parameterization for the BN dative bond
Authors: Fisher Luke , Holme Thomas 
Published: August 2002

AbstractA number of compounds that contain the BN dative bond have been found to exhibit intriguing physiological activities. Although there is no proven mechanism for this activity, one hypothesis is that some form of borane transfer reaction occurs. In this scenario, the BN dative bond within the small molecule, putative pharmacore breaks, and the borane forms a new dative bond with a Lewis base site on some critical protein. For this hypothesis to be investigated further from a computational perspective, an improved MM3 parameter set for tetravalent Btetravalent N bonds has been developed and is reported here. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 913–922, 2001
Combined QM/MM study of the opsin shift in bacteriorhodopsin
Authors: Rajamani Ramkumar , Gao Jiali 
Published: August 2002

AbstractCombined quantum mechanical and molecular mechanical (QM/MM) calculations and molecular dynamics simulations of bacteriorhodopsin (bR) in the membrane matrix have been carried out to determine the factors that make significant contributions to the opsin shift. We found that both solvation and interactions with the protein significantly shifts the absorption maximum of the retinal protonated Schiff base, but the effects are much more pronounced in polar solvents such as methanol, acetonitrile, and water than in the protein environment. The differential solvatochromic shifts of PSB in methanol and in bR leads to a bathochromic shift of about 1800 cm−1. Because the combined QM/MM configuration interaction calculation is essentially a point charge model, this contribution is attributed to the extended point‐charge model of Honig and Nakanishi. The incorporation of retinal in bR is accompanied by a change in retinal conformation from the 6‐s‐cis form in solution to the 6‐s‐trans configuration in bR. The extension of the π‐conjugated system further increases the red‐shift by 2400 cm−1. The remaining factors are due to the change in dispersion interactions. Using an estimate of about 1000 cm−1 in the dispersion contribution by Houjou et al., we obtained a theoretical opsin shift of 5200 cm−1 in bR, which is in excellent agreement with the experimental value of 5100 cm−1. Structural analysis of the PSB binding site revealed the specific interactions that make contributions to the observed opsin shift. The combined QM/MM method used in the present study provides an opportunity to accurately model the photoisomerization and proton transfer reactions in bR. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 96–105, 2002
Comparison of non‐diglyceride‐ and diglyceride‐based assays for pancreatic lipase activity
Authors: Steinhauer Jon R. , Hardy Robert W. , Robinson C. Andrew , Daly Thomas M. , Chaffin Carolyn , Konrad Robert J. 
Published: August 2002

AbstractPancreatic lipase is produced and stored in pancreatic acinar cells, and is normally secreted into the duct system. In disorders that cause pancreatic damage, pancreatic lipase enters the circulation, and serum lipase activity becomes useful in the diagnosis and evaluation of pancreatitis. During the last decade, many lipase assays have used the Imamura method, in which a series of enzymatic reactions utilizing a diglyceride substrate leads to the formation of a colorimetrically detected product. Historically, this method has been prone to significant interference from various substances, including glycerol itself. In the light of these limitations, we evaluated an automated enzymatic rate assay that uses a non‐diglyceride‐based, pancreatic lipase‐specific substrate. Precision, linearity, and potential interference were assessed, and when compared to the Imamura method, the non‐diglyceride‐based assay exhibited a slope of 0.475, y‐intercept of 15.89, r‐value of 0.9516, and Sy,x of 12.96. Similar results were also observed when the two assays were compared using samples with markedly elevated creatinine levels. Between‐day coefficients of variance (CVs) ranged from 5.0% to 5.5%, which compared well with the diglyceride‐based method, and linearity spanned a range of 3–156 U/L. Evaluation of over 2,000 patient results collected during a 6‐month period suggested that the manufacturer’s upper reference limit of 51 U/L may be too conservative. No significant interference was identified with bilirubin, triglyceride, or glycerol itself, and significant interference from hemoglobin was observed only at concentrations of 116 mg/dL or greater. As a result, the non‐diglyceride‐based method provides an acceptable alternative for the routine laboratory measurement of lipase activity. J. Clin. Lab. Anal. 16:52–55, 2002. © 2002 Wiley‐Liss, Inc.
Increased sialylation of polymeric λ‐IgA1 in patients with IgA nephropathy
Authors: Leung Joseph C.K. , Tang Sydney C.W. , Chan Daniel T.M. , Lui Sing Leung , Lai Kar Neng 
Published: August 2002

AbstractThe mechanism of mesangial IgA deposition is poorly understood in IgA nephropathy (IgAN). Abnormal glycosylation of carbohydrate moieties in the hinge region of the IgA molecule has recently attracted much attention. In this report, we studied galactosylation and sialylation profiles in κ‐ and λ‐IgA1 from patients with IgAN. Total serum IgA1 was isolated from patients with IgAN or healthy controls by jacalin‐affinity chromatography. Six fractions of molecular weight (MW) 50–1,000 kDa were separated by fast protein liquid chromatography (FPLC). Four lectin‐binding assays were used to study the sialylation and the presence of terminal galactose or N‐acetylgalactosamine (GalNAc) in the O‐linked carbohydrate moieties of κ‐ or λ‐IgA1. Maackia amurensis agglutinin (MAA) and Sambucus nigra agglutinin (SNA) lectin recognize α(2,3)‐ and α(2,6)‐linked sialic acid, respectively. Peanut agglutinin (PNA) and Helix aspersa (HA) lectin recognize terminal galactose and GalNAc, respectively. Reduced HA was demonstrated in macromolecular κ or λ‐IgA1 (300–825 kDa) isolated from patients with IgAN (P < 0.05 compared with healthy controls). Lambda‐ but not κ‐IgA1 from patients with IgAN bound less to PNA (P < 0.05). The α(2,3)‐linked sialic acid content in λ‐ but not κ‐IgA1 of MW 150–610 kDa from patients was higher than that of controls (P < 0.005). The α(2,6)‐linked sialic acid content in λ‐IgA1 (300–825 kDa) and κ‐IgA1 (150–610 kDa) from patients was also higher than that of controls. This unusual glycosylation and sialylation pattern of the λ‐IgA1 may have important implications for the pathogenesis of IgAN, as both the masking effect of sialic acid on galactose and the reduced galactosylation will hinder the clearance of macromolecular λ‐IgA1 by asialoglycoprotein receptor of hepatocytes. The negative charge from sialic acid may also favor mesangial deposition of macromolecular λ‐IgA1 in IgAN. J. Clin. Lab. Anal. 16:11–19, 2002. © 2002 Wiley‐Liss, Inc.
The relationship between dissociative tendencies and schizotypy: An artifact of childhood trauma?
Authors: Irwin Harvey J. 
Published: August 2002

AbstractPrevious research has suggested a relationship between dissociative tendencies and schizotypy. This study sought to extend the previous work in two fundamental respects. First, explicit cognizance was taken of the multidimensionality of both dissociative tendencies and schizotypy. Second, the study examined the possibility that the observed correlation between dissociative tendencies and schizotypy is an artifact of the association between each of these personality domains and a history of childhood trauma. Australian adults (N = 116) were administered the Dissociative Experiences Scale, the Schizotypal Personality Questionnaire—Brief, and the Childhood Trauma Questionnaire. Hierarchical regression analysis revealed that both pathological and nonpathological dissociative tendencies were predicted by the dimensions of schizotypy, even after the contribution of childhood trauma had been removed. It is concluded that the relationship between dissociative tendencies and schizotypy is not an artifact of childhood abuse, but the clinical significance of this relationship remains to be established. © 2001 John Wiley & Sons, Inc. J Clin Psychol 57: 331–342, 2001.