bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Visualization by Confocal Fluorescent Microscopy of the Permeation of Myristoylated Peptides Through the Cell Membrane
Authors: Enseñat‐Waser Roberto , Martin Franz , Barahona Fernando , Vazquez Jesús , Soria Bernat , Reig Juan A. 
Published: September 2003

AbstractTo study the permeability through the cellular membrane of synthetic peptides containing an hydrofobic moiety, we used a 13‐mer myristoylated peptide labeled with a N ‐terminal fluorescent probe. After 2 h of incubation, the subcellular distribution was analyzed in intact chromaffin cells by confocal fluorescent microscopy. Our results demonstrate that myristoylated peptides diffuse into intact cells, showing an heterogeneous distribution, but they do not reach the cellular nucleous, at least during the time range used.
Serpins: Finely Balanced Conformational Traps
Authors: Pike Robert N. , Bottomley Stephen P. , Irving James A. , Bird Phillip I. , Whisstock James C. 
Published: September 2003

AbstractSerine protease (serpins) play very important roles in the maintenance of various physiologically important systems. As knowledge of the workings of proteins of this family grows, new understanding is gained of the mechanisms by which they inhibit target proteases, using conformational changes for which the structure of serpins is uniquely adapted. This finely balanced system is utilized to healthy benefit in the control of serpin function by modulators, arguably the most striking examples of which occur in the control of proteolytic cascades, such as the coagulation system. Serpins also play very important intracellular roles: one example is the protection of immune cells from their own cytotoxic proteases. The finely balanced serpin mechanism also means that it is prone to disastrous consequences if mutations should occur in vital positions in the serpin structure. Many examples of disease‐associated mutations have been shown, which has the dual effect of highlighting how important these molecules are in the maintenance of health and the fine balance that must be maintained in order to preserve their active, inhibitory conformation.
Isolation and Characterization of a Porin‐Like Outer Membrane Protein from Xanthomonas campestris pv. campestris
Authors: Wang Lingyun , Zheng Ying , Zhang Xujia 
Published: September 2003

AbstractXanthomonas campestris pv. campestris, a plant‐associated pathogenic bacterium, is the causal agent of foliar spots and blights in crucifers. The major outer membrane protein, Omp37, of 37 kDa, has been identified, purified to homogeneity, and its characterization has also been carried out. Native Omp37 behaved as a trimer, as revealed by gel filtration and SDS‐PAGE. FTIR measurements revealed a high β‐structure content. The pore‐forming ability of the purified Omp37 was studied by the liposome swelling assay. Omp37, to our knowledge, is the first porin that has been isolated from Xanthomonas . This study clearly demonstrates that Omp37 is related to the family of trimeric bacterial porins.
A Resurgent Phoenix‐‐A Hypothesis for the Origin of Meiosis
Authors: Li Wei , Zheng Guo‐Chang 
Published: September 2003

AbstractThe origin and evolution of sex is a great puzzle in biology, and meiosis is the core of sex. Here, we propose a new hypothesis that meiosis may have evolved by blending features of two responses that cells have to deal with double‐strand‐DNA breaks, recombinational repair and apoptosis. This hypothesis can explain some unsolved problems and is in agreement with some known molecular mechanisms, cytological phenomena, and the fossil records. Furthermore, it can predict some testable features of meiosis.
Selection of Peptide Ligands Binding to Fibroblast Growth Factor Receptor 1
Authors: Fan Hongkuan , Duan Yanfen , Zhou Hui , Li Wei , Li Fei , Guo Lili , Roeske Roger W. 
Published: September 2003

AbstractInappropriate expression of fibroblast growth factors (FGFs) or activation of FGF receptors (FGFRs) could contribute to several human angiogenic pathologies. In an attempt to design antagonists of FGF, we developed a screening procedure for identifying peptide ligands binding to FGFR1. To retain the natural conformation of FGFR1 during screening, we expressed recombinant FGFR1 on the surface of Sf9 insect cells. A 6‐mer phage display peptide library was then screened on the cell surface and a group of hydrophobic peptide sequences were identified. Further experiments demonstrated that the phages displaying these sequences can specifically bind to FGFR1. The docking analysis suggests that the peptide ValTyrMetSerProPhe can specifically bind to the hydrophobic surface of FGFR1. The synthetic peptide Ac‐ValTyrMetSerProPhe‐NH 2 can inhibit mitogenic activity of aFGF and has the potential to become a therapeutic agent as an aFGF antagonist.
Gene and Cell Therapy for Heart Disease
Authors: Graham Regina M. , Bishopric Nanette H. , Webster Keith A. 
Published: September 2003

AbstractHeart disease is the most common cause of morbidity and mortality in Western society and the incidence is projected to increase significantly over the next few decades as our population ages. Heart failure occurs when the heart is unable to pump blood at a rate to commensurate with tissue metabolic requirements and represents the end stage of a variety of pathological conditions. Causes of heart failure include ischemia, hypertension, coronary artery disease, and idiopathic dilated cardiomyopathy. Hypertension and ischemia both cause infarction with loss of function and a consequent contractile deficit that promotes ventricular remodeling. Remodeling results in dramatic alterations in the size, shape, and composition of the walls and chambers of the heart and can have both positive and negative effects on function. In 30‐40% of patients with heart failure, left ventricular systolic function is relatively unaffected while diastolic dysfunction predominates. Recent progress in our understanding of the molecular and cellular bases of heart disease has provided new therapeutic targets and led to novel approaches including the delivery of proteins, genes, and cells to replace defective or deficient components and restore function to the diseased heart. This review focuses on three such strategies that are currently under development: (a) gene transfer to modulate contractility, (b) therapeutic angiogenesis for the treatment of ischemia, and (c) embryonic and adult stem cell transfer to replace damaged myocardium.
Identification of Modified Proteins by Mass Spectrometry
Authors: Sickmann Albert , Mreyen Marcus , Meyer Helmut E. 
Published: September 2003

AbstractBecause it is obvious that high‐throughput genomics do not lead to a molecular description or even a prediction of protein function, modern techniques for protein analysis become increasingly more important. Sequence analysis of proteins and peptides is not limited to the elucidation of the primary structure of a protein. The analysis of posttranslational modifications is an important task of protein chemistry in proteome research. Increased sensitivity in mass spectrometry as a result of more efficient ionization techniques and better detection systems has allowed the stepwise reduction of protein quantity for analysis. Protein spots of 2D‐PAGE separated samples are now sufficient for an unequivocal identification of a protein by mass spectrometry. In addition to protein identification, a closer look at posttranslational modifications is now also possible. It is assumed that modifications such as phosphorylation or glycosylation exist on every second protein and that they are important for the protein function.
Tocotrienols Inhibit Human Glutathione S‐Transferase P1‐1
Authors: van Haaften Rachel I. M. , Haenen Guido R. M. M. , Evelo Chris T. A. , Bast Aalt 
Published: September 2003

AbstractTocopherols and tocotrienols are food ingredients that are believed to have a positive effect on health. The most studied property of both groups of compounds is their antioxidant action. Previously, we found that tocopherols and diverse tocopherol derivatives can inhibit the activity of human glutathione S‐transferase P1‐1 (GST P1‐1). In this study we found that GST P1‐1 is also inhibited, in a concentration‐dependent manner, by α‐ and γ‐tocotrienol. The concentration giving 50% inhibition of GST P1‐1 is 1.8 ±0.1 μM for α‐tocotrienol and 0.7 ±0.1 μM for γ‐tocotrienol. This inhibition of GST P1‐1 is noncompetitive with respect to both substrates CDNB and GSH. We also examined the 3D structure of GST P1‐1 for a possible tocopherol/tocotrienol binding site. The enzyme contains a very hydrophobic pit‐like structure where the phytyl tail of tocopherols and tocotrienols could fit in. Binding of tocopherol and tocotrienol to this hydrophobic region might lead to bending of the 3D structure. In this way tocopherols and tocotrienols can inhibit the activity of the enzyme; this inhibition can have far‐reaching implications for humans.
Down‐Regulation of Organic Anion Transporter 2 mRNA Expression by Nitric Oxide in Primary Cultured Rat Hepatocytes
Authors: Cha Seok Ho , Kim Hong Pyo , Jung Nam‐Hee , Lee Woon Ki , Kim Ju Young , Cha Young‐Nam 
Published: September 2003

AbstractRole of nitric oxide (NO) 1 on the expression of organic anion transporter 2 (OAT2) located in sinusoidal domain of hepatocytes has been investigated. Effect of NO generated in vivo in rat and delivered in vitro to hepatocytes was determined. Lipopolysaccharide (LPS) and spermine NONOate (SPER/NO) were selected as the NO donors for in vivo and in vitro experiments, respectively. Constitutive basal expression of rOAT2 mRNA was detected in the normal rat liver and the level of its expression was decreased by intraperitoneal administration of LPS. This LPS‐induced decrement did not occur when aminoguanidine (AG), an inhibitor of iNOS, was co‐administered with LPS. The expression of rOAT2 mRNA was detected in hepatocytes, but not in the nonparenchymal cells. In the primary cultured hepatocytes obtained from normal rats (normal hepatocytes), a time‐dependent decline of rOAT2 mRNA expression was observed, but not in the hepatocytes obtained from rats pretreated with gadolinium chloride (GdCl 3, Gd‐hepatocytes), an inhibitor of Kupffer cell activation. The decline of rOAT2 mRNA expression observed in the normal hepatocytes was enhanced by LPS treatment, but not in the Gd‐hepatocytes. The LPS‐dependent enhancement in the decline of rOAT2 mRNA expression did not occur when the normal hepatocytes were treated with AG or actinomycin D. When the Gd‐hepatocytes were treated with SPER/NO, an NO donor, the rOAT2 mRNA expression declined markedly. Combined, our results suggest that rOAT2 mRNA expression in hepatocytes is down‐regulated by NO at least at the transcriptional step.
Unification for the Expression of the Monophenolase and Diphenolase Activities of Tyrosinase
Authors: Fenoll L. G. , Rodríguez‐López J. N. , García‐Molina F. , García‐Cánovas F. , Tudela J. 
Published: September 2003

AbstractIn order to unify and generalize, we define the International Units used to express the monophenolase and diphenolase activity of mushroom tyrosinase acting on different monophenol/diphenol pairs and establish a quantitative relation. Similarly, the activity units to express tyrosinase activity proposed by suppliers are discussed and compared with the above International Units. Lastly, we study the relation between International Units of diphenolase activity and of monophenolase activity for other biological sources of tyrosinase.
In Vivo Studies on Mouse Erythrocytes Linked to Transferrin
Authors: Pérez M. Teresa , García‐Pérez Ana Isabel , Pinilla Montserrat , Sancho Pilar 
Published: September 2003

AbstractTransferrin (Tf), a plasma protein with numerous, highly specific receptors in proliferating and differentiating cells was already discussed as a targeting ligand for drugs and liposomes in previous studies. In this paper, we deal with erythrocytes linked to Tf as possible physiological targeting carrier systems for delivering anticancer drugs. For that purpose we have used glutaraldehyde (0.1%) as a coupling agent between Tf and erythrocytes. The highest amount of Tf linked to erythrocytes turned out to be 0.76 ±0.13 μg Tf/10 6 cells, while reaching 65% of cell recovery. After 13 days, the Tf‐erythrocytes hemolysis reached 50%, with transferrin still coupled to erythrocytes. The in vivo kinetic behaviour of intravenously injected 51 Cr‐Tf‐erythrocytes showed a reduced half‐life to hours as compared to days of controls. However, a considerable percentage of Tf‐erythrocytes (close to 20%) remained circulating for a relatively long period (around 2 days), which made possible the specific targeting by these carrier systems. In vivo biodistribution studies indicated that 51 Cr‐Tf‐erythrocytes rapidly accumulated in the different studied organs (liver, spleen, lungs, kidneys, femur‐tibia, and heart), suggesting a selective removal of Tf‐erythrocytes by the cells of the mononuclear phagocytic system present mainly in liver and spleen. On the other hand, Tf‐erythrocytes showed a poor targeting of heart tissue, therefore a reduced cardiac toxicity should be expected after administration of erythrocyte‐encapsulated drugs. The presence of Tf‐erythrocytes in femur‐tibia and spleen could be related to the Tf‐specific binding to the hematopoietic cells containing Tf receptors. The final results of this study encourage additional research on Tf‐erythrocyte to investigate the relationship between transferrin‐mediated targeting by carrier erythrocytes and uptake of different erythrocyte‐encapsulated drugs. Consequently, the current study showed possible use of these carriers as a potential therapeutic tool for drug targeting in animal models with alterations affecting mononuclear phagocytic system or carcinomas of various origins whose cells show elevated number of Tf receptors.
The Complementary Membranes Forming the Blood‐Brain Barrier
Authors: Hawkins Richard A. , Peterson Darryl R. , Viña Juan R. 
Published: September 2003

AbstractBrain capillary endothelial cells form the blood‐brain barrier. They are connected by extensive tight junctions, and are polarized into luminal (blood‐facing) and abluminal (brain‐facing) plasma membrane domains. The polar distribution of transport proteins allows for active regulation of brain extracellular fluid. Experiments on isolated membrane vesicles from capillary endothelial cells of bovine brain demonstrated the polar arrangement of amino acid and glucose transporters, and the utility of such arrangements have been proposed. For instance, passive carriers for glutamine and glutamate have been found only in the luminal membrane of blood‐brain barrier cells, while Na‐dependent secondary active transporters are at the abluminal membrane. This organization could promote the net removal of nitrogen‐rich amino acids from brain, and account for the low level of glutamate penetration into the central nervous system. Furthermore, the presence of a γ‐glutamyl cycle at the luminal membrane and Na‐dependent amino acid transporters at the abluminal membrane may serve to modulate movement of amino acids from blood‐to‐brain. Passive carriers facilitate amino acid transport into brain. However, activation of the γ‐glutamyl cycle by increased plasma amino acids is expected to generate oxoproline within the blood‐brain barrier. Oxoproline stimulates secondary active amino acid transporters (Systems A and B o,+ ) at the abluminal membrane, thereby reducing net influx of amino acids to brain. Finally, passive glucose transporters are present in both the luminal and abluminal membranes of the blood‐brain barrier. Interestingly, a high affinity Na‐dependent glucose carrier has been described only in the abluminal membrane. This raises the question whether glucose entry may be regulated to some extent. Immunoblotting studies suggest more than one type of passive glucose transporter exist in the blood‐brain barrier, each with an asymmetrical distribution. In conclusion, it is now clear that the blood‐brain barrier participates in the active regulation of brain extracellular fluid, and that the diverse functions of each plasma membrane domain contributes to these regulatory functions.
Nitric Oxide and Mycobacterium leprae Pathogenicity
Authors: Visca Paolo , Fabozzi Giulia , Milani Mario , Bolognesi Martino , Ascenzi Paolo 
Published: September 2003

AbstractLeprosy is an old, still dreaded infectious disease caused by the obligate intracellular bacterium Mycobacterium leprae . During the infectious process, M. leprae is faced with the host macrophagic environment, where the oxidative stress and NO release, combined with low pH, low pO 2, and high pCO 2, contribute to limit the growth of the bacilli. Comparative genomics has unraveled massive gene decay in M. leprae, linking the strictly parasitic lifestyle with the reductive genome evolution. Compared with Mycobacterium tuberculosis and Mycobacterium bovis, the leprosy bacillus has lost most of the genes involved in the detoxification of reactive oxygen and nitrogen species. The very low reactivity of the unique truncated hemoglobin retained by M. leprae could account for the susceptibility of this exceptionally slow‐growing microbe to NO.
Phenomenological Perspectives on the Folding of β/α‐Barrel Domains Through the Modular Formation and Assembly of Smaller Structural Elements
Authors: Maiti Sankar , Luthra‐Guptasarma Manni , Guptasarma Purnananda 
Published: September 2003

AbstractThe β/α‐barrel motif was once considered to be a single protein domain. In recent years, however, it has been shown to consist of smaller substructures displaying the ability to fold autonomously. Here we review the current status of experimental findings concerning the motif's folding behavior in the light of what is currently known about (a) the relative rates of formation of helices and sheets in proteins, in general, and (b) the peculiarities of topology and architecture of the motif, in particular, to develop a detailed phenomenological understanding of how β/α‐barrels might form through the modular folding and assembly of substructures.
Heparin and Heparan Sulfate Biosynthesis
Authors: Sugahara Kazuyuki , Kitagawa Hiroshi 
Published: September 2003

AbstractHeparan sulfate is one of the most informationally rich biopolymers in Nature. Its simple sugar backbone is variously modified to different degrees depending on the cellular conditions. Thus, it matures to have an enormously complicated structure, which most likely exhibits a considerable number of unique overlapping sequences with peculiar sulfation profiles. Such sequences are recognized by specific complementary proteins, which form a huge group of “heparin‐binding proteins,” and the sugar sequences in turn support unique functions of the respective proteins through specific interactions. The heparan sulfate sequences are not directly encoded by genes, but are created by elaborate biosynthetic mechanisms, which ensure the generation of these indispensable sequences. In heparan sulfate biosynthesis, the tetrasaccharide sequence (GlcA‐Gal‐Gal‐Xyl‐), designated the protein linkage region, is first assembled on a specific Ser residue at the glycosaminoglycan attachment site of a core protein. A heparan sulfate chain is then polymerized on this fragment by alternate additions of GlcNAc and GlcA through the actions of glycosyltransferases with overlapping specificities encoded by the tumor suppressor EXT family genes. Then follow various modifications by N ‐deacetylation and N ‐sulfation of glucosamine, C5‐epimerization of GlcA and multiple O ‐sulfations of the component sugars. Recent studies have achieved purification of several, and molecular cloning of most, of the enzymes responsible for these reactions. Some of these enzymes are bifunctional. The availability of cDNA probes has facilitated elucidation of the crystal structures for two of the biosynthetic enzymes, demonstration of their intracellular location, and their occurrence in complexes to achieve rapid and efficient synthesis of complex sugar sequences. Genomic structure and transcript analysis have shown the existence of multiple isoforms for most of the sulfotransferases. Many aspects of the heparan sulfate biosynthetic scheme are shared by the structural analog heparin, which is synthesized in mast cells and some other mammalian cells and is several‐fold higher degree of polymerization and more extensive modification than heparan sulfate.
Mammalian Hyaluronan Synthases
Authors: Itano Naoki , Kimata Koji 
Published: September 2003

AbstractThree mammalian hyaluronan (HA) synthase genes, HAS1, HAS2, and HAS3, have been cloned and expressed, allowing the mechanisms for regulation of HA biosynthesis and function to be studied. The hyaluronan synthase (HAS) isoforms differ in kinetic characteristics and product size. The expression of each HAS isoform is controlled in a different fashion when mammalian cells are stimulated by various cytokines and the expression patterns are both spatially and temporally regulated during embryonic development. The existence of three different HAS isoforms with different characteristics implies that the broad range of biological and physiological roles performed by HA are regulated by controlling the activities and expression of the HAS isoforms. This review focuses on recent findings on the regulatory mechanisms for controlling HA biosynthesis and provides new insights into the enzymic basis for the functional regulation of HA.
Clonidine Displacement from Type 1 Imidazoline Receptor by p ‐Aminobenzamidine, the Prototype of Trypsin‐Like Serine Protease Inhibitors
Authors: Pallottini Valentina , Marino Maria , Ascenzi Paolo 
Published: September 2003

Abstractp ‐Aminobenzamidine inhibits competitively the catalytic activity of enzymes that recognize preferentially the L ‐arginyl side chain and related structures. Notably, p ‐aminobenzamidine is considered as the prototype of trypsin‐like serine protease inhibitors. Furthermore, p ‐aminobenzamidine inhibits the catalytic activity of nitric oxide synthase type I and type II as well as copper amine oxidase. Taking into account the structural similarity between p ‐aminobenzamidine, agmatine (the putative endogenous ligand of the membrane type 1 imidazoline receptor (I 1 ‐R)), and N ‐amidino‐2‐hydroxypyrrolidine (the product of agmatine oxidation by copper amine oxidase), the [ 3 H]clonidine displacement from I 1 ‐R in rat heart membranes by p ‐aminobenzamidine was investigated. p ‐Aminobenzamidine is as effective as agmatine and N ‐amidino‐2‐hydroxypyrrolidine and more effective than the antihypertensive drug clonidine to displace [ 3 H]clonidine from I 1 ‐R. Therefore, trypsin‐like serine protease inhibitors structurally related to p ‐aminobenzamidine should be administrated under careful control.
Inhibitors of Apoptosis Proteins in Injury and Disease
Authors: Lotocki George , Keane Robert W. 
Published: September 2003

AbstractThe inhibitor of apoptosis (IAP) gene family prevents cell death by binding to and inhibiting caspases. In addition to negatively regulating apoptosis, IAPs bind to signaling intermediates and receptors, and participate in diverse cellular functions. Here, we describe the physiological functions of IAPs and their participation in injury and disease processes.