bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Immunodeficiency Virus Type 1 Central DNA Flap: Dynamic Terminal Product of Plus-Strand Displacement DNA Synthesis Catalyzed by Reverse Transcriptase Assisted by Nucleocapsid Protein
Authors: Hameau Laurence , Jeusset Josette , Lafosse Sophie , Coulaud Dominique , Delain Etienne , Unge Torsten , Restle Tobias , Le Cam Eric , Mirambeau Gilles
Published: July 2002

To terminate the reverse transcription of the human immunodeficiency virus type 1 (HIV-1) genome, a final step occurs within the center of the proviral DNA generating a 99-nucleotide DNA flap (6). This step, catalyzed by reverse transcriptase (RT), is defined as a discrete strand displacement (SD) synthesis between the first nucleotide after the central priming (cPPT) site and the final position of the central termination sequence (CTS) site. Using recombinant HIV-1 RT and a circular single-stranded DNA template harboring the cPPT-CTS sequence, we have developed an SD synthesis-directed in vitro termination assay. Elongation, strand displacement, and complete central flap behavior were analyzed using electrophoresis and electron microscopy approaches. Optimal conditions to obtain complete central flap, which ended at the CTS site, have been defined in using nucleocapsid protein (NCp), the main accessory protein of the reverse transcription complex. A full-length HIV-1 central DNA flap was then carried out in vitro. Its synthesis appears faster in the presence of the HIV-1 NCp or the T4-encoded SSB protein (gp32). Finally, a high frequency of strand transfer was shown during the SD synthesis along the cPPT-CTS site with RT alone. This reveals a local and efficient 3′-5′ branch migration which emphasizes some important structural fluctuations within the flap. These fluctuations may be stabilized by the NCp chaperone activity. The biological implications of the RT-directed NCp-assisted flap synthesis are discussed within the context of reverse transcription complexes, assembly of the preintegration complexes, and nuclear import of the HIV-1 proviral DNA to the nucleus toward their chromatin targets.
Frequencies of Virus-Specific CD4+and CD8+T Lymphocytes Secreting Gamma Interferon after Acute Natural Rotavirus Infection in Children and Adults
Authors: Jaimes María C. , Rojas Olga Lucía , González Ana María , Cajiao Isabela , Charpilienne Annie , Pothier Pierre , Kohli Evelyne , Greenberg Harry B. , Franco Manuel A. , Angel Juana
Published: July 2002

Human rotavirus-specific CD4+and CD8+T-cell responses in peripheral blood lymphocytes were studied using a flow cytometric assay that detects the intracellular accumulation of cytokines after short-term in vitro antigen stimulation. The frequencies of virus-specific T cells that secrete gamma interferon and interleukin-13 (IL-13) were determined in adults and children during the acute or convalescent phase of rotavirus-induced diarrhea, in asymptomatically infected adults and laboratory workers who worked with human stool samples containing rotavirus, and in healthy adults. Significantly higher frequencies of rotavirus-specific interferon gamma-secreting CD8+and CD4+T cells, but not IL-13-secreting T cells, were detected in symptomatically infected adults and exposed laboratory workers than in healthy adults and children with acute rotavirus diarrhea. The levels of rotavirus-specific T cells returned to levels found in healthy adults by 32 days after the onset of rotavirus diarrhea in most adult subjects. Children with rotavirus diarrhea had undetectable or very low levels of CD4+and CD8+T cells that secrete gamma interferon. Adult cytomegalovirus-seropositive individuals had frequencies of cytomegalovirus-specific T cells that secrete gamma interferon that were approximately 20 times the level of rotavirus-specific T cells. This result suggests that rotavirus is a relatively poor inducer of circulating memory T cells that secrete gamma interferon. The frequencies of gamma interferon-secreting CD4+and CD8+T cells and the frequencies of IL-13-secreting CD4+T cells responding to the T-cell superantigen staphylococcal enterotoxin B (SEB) were lower in children than in adults. In both adults and children, the frequencies of CD4+cells secreting gamma interferon in response to SEB were higher than the frequencies of cells secreting IL-13.
Mutations in the Yellow Fever Virus Nonstructural Protein NS2A Selectively Block Production of Infectious Particles
Authors: Kümmerer Beate M. , Rice Charles M.
Published: July 2002

Little is known about the function of flavivirus nonstructural protein NS2A. Two forms of NS2A are found in yellow fever virus-infected cells. Full-length NS2A (224 amino acids) is the product of cleavage at the NS1/2A and NS2A/2B sites. NS2Aα, a C-terminally truncated form of 190 amino acids, results from partial cleavage by the viral NS2B-3 serine protease at the sequence QK↓T within NS2A. Exchange of serine for lysine at this site (QKT→QST) blocks the production of both NS2Aα and infectious virus. The present study reveals that this defect is not at the level of RNA replication. Despite normal structural region processing, infectious particles containing genome RNA and capsid protein were not released from cells transfected with the mutant RNA. Nevertheless, production of subviral prM/M- and E-containing particles was unimpaired. The NS2A defect could be complemented in
trans
by providing NS1-2A or NS1-2Aα. However,
trans
complementation was not observed when the C-terminal lysine of NS1-2Aα was replaced with serine. In addition to true reversions, NS2Aα cleavage site mutations could be suppressed by two classes of second-site changes. The first class consisted of insertions at the NS2Aα cleavage site that restored its basic character and cleavability. A second class of suppressors occurred in the NS3 helicase domain, in which NS3 aspartate 343 was replaced with an uncharged residue (either valine, alanine, or glycine). These mutations in NS3 restored infectious-virus production in the absence of cleavage at the mutant NS2Aα site. Taken together, our results reveal an unexpected role for NS2A and NS3 in the assembly and/or release of infectious flavivirus particles.
Transcriptional Profiling of Interferon Regulatory Factor 3 Target Genes: Direct Involvement in the Regulation of Interferon-Stimulated Genes
Authors: Grandvaux Nathalie , Servant Marc J. , tenOever Benjamin , Sen Ganes C. , Balachandran Siddarth , Barber Glen N. , Lin Rongtuan , Hiscott John
Published: July 2002

Ubiquitously expressed interferon regulatory factor 3 (IRF-3) is directly activated after virus infection and functions as a key activator of the immediate-early alpha/beta interferon (IFN) genes, as well as the RANTES chemokine gene. In the present study, a tetracycline-inducible expression system expressing a constitutively active form of IRF-3 (IRF-3 5D) was combined with DNA microarray analysis to identify target genes regulated by IRF-3. Changes in mRNA expression profiles of 8,556 genes were monitored after Tet-inducible expression of IRF-3 5D. Among the genes upregulated by IRF-3 were transcripts for several known IFN-stimulated genes (ISGs). Subsequent analysis revealed that IRF-3 directly induced the expression of ISG56 in an IFN-independent manner through the IFN-stimulated responsive elements (ISREs) of the ISG56 promoter. These results demonstrate that, in addition to its role in the formation of a functional immediate-early IFN-β enhanceosome, IRF-3 is able to discriminate among ISRE-containing genes involved in the establishment of the antiviral state as a direct response to virus infection.
Overcoming the Phage Replication Threshold: a Mathematical Model with Implications for Phage Therapy
Authors: Kasman Laura M. , Kasman Alex , Westwater Caroline , Dolan Joseph , Schmidt Michael G. , Norris James S.
Published: July 2002

Prior observations of phage-host systems in vitro have led to the conclusion that susceptible host cell populations must reach a critical density before phage replication can occur. Such a replication threshold density would have broad implications for the therapeutic use of phage. In this report, we demonstrate experimentally that no such replication threshold exists and explain the previous data used to support the existence of the threshold in terms of a classical model of the kinetics of colloidal particle interactions in solution. This result leads us to conclude that the frequently used measure of multiplicity of infection (MOI), computed as the ratio of the number of phage to the number of cells, is generally inappropriate for situations in which cell concentrations are less than 10
7
/ml. In its place, we propose an alternative measure, MOI
actual
, that takes into account the cell concentration and adsorption time. Properties of this function are elucidated that explain the demonstrated usefulness of MOI at high cell densities, as well as some unexpected consequences at low concentrations. In addition, the concept of MOI
actual
allows us to write simple formulas for computing practical quantities, such as the number of phage sufficient to infect 99.99% of host cells at arbitrary concentrations.
Formation of a Human Immunodeficiency Virus Type 1 Core of Optimal Stability Is Crucial for Viral Replication
Authors: Forshey Brett M. , von Schwedler Uta , Sundquist Wesley I. , Aiken Christopher
Published: July 2002

Virions of human immunodeficiency virus type 1 (HIV-1) and other lentiviruses contain conical cores consisting of a protein shell composed of the viral capsid protein (CA) surrounding an internal viral ribonucleoprotein complex. Although genetic studies have implicated CA in both early and late stages of the virus replication cycle, the mechanism of core disassembly following penetration of target cells remains undefined. Using quantitative assays for analyzing HIV-1 core stability in vitro, we identified point mutations in CA that either reduce or increase the stability of the HIV-1 core without impairing conical core formation in virions. Alterations in core stability resulted in severely attenuated HIV-1 replication and impaired reverse transcription in target cells with only minimal effects on viral DNA synthesis in permeabilized virions in vitro. We conclude that formation of a viral core of optimal stability is a prerequisite for efficient HIV-1 infection and suggest that disassembly of the HIV-1 core is a regulated step in infection that may be an attractive target for pharmacologic intervention.
Infectious cDNA Clone of the Epidemic West Nile Virus from New York City
Authors: Shi Pei-Yong , Tilgner Mark , Lo Michael K. , Kent Kim A. , Bernard Kristen A.
Published: July 2002

We report the first full-length infectious clone of the current epidemic, lineage I, strain of West Nile virus (WNV). The full-length cDNA was constructed from reverse transcription-PCR products of viral RNA from an isolate collected during the year 2000 outbreak in New York City. It was cloned into plasmid pBR322 under the control of a T7 promoter and stably amplified in
Escherichia coli
HB101. RNA transcribed from the full-length cDNA clone was highly infectious upon transfection into BHK-21 cells, resulting in progeny virus with titers of 1 × 10
9
to 5 × 10
9
PFU/ml. The cDNA clone was engineered to contain three silent nucleotide changes to create a
Sty
I site (C to A and A to G at nucleotides [nt] 8859 and 8862, respectively) and to knock out an
Eco
RI site (A to G at nt 8880). These genetic markers were retained in the recovered progeny virus. Deletion of the 3′-terminal 199 nt of the cDNA transcript abolished the infectivity of the RNA. The plaque morphology, in vitro growth characteristics in mammalian and insect cells, and virulence in adult mice were indistinguishable for the parental and recombinant viruses. The stable infectious cDNA clone of the epidemic lineage I strain will provide a valuable experimental system to study the pathogenesis and replication of WNV.
Probing the Sialic Acid Binding Site of the Hemagglutinin-Neuraminidase of Newcastle Disease Virus: Identification of Key Amino Acids Involved in Cell Binding, Catalysis, and Fusion
Authors: Connaris Helen , Takimoto Toru , Russell Rupert , Crennell Susan , Moustafa Ibrahim , Portner Allen , Taylor Garry
Published: July 2002

We recently reported the first crystal structure of a paramyxovirus hemagglutinin-neuraminidase (HN) from Newcastle disease virus. This multifunctional protein is responsible for binding to cellular sialyl-glycoconjugate receptors, promotion of fusion through interaction with the second viral surface fusion (F) glycoprotein, and processing progeny virions by removal of sialic acid from newly synthesized viral coat proteins. Our structural studies suggest that HN possesses a single sialic acid recognition site that can be switched between being a binding site and a catalytic site. Here we examine the effect of mutation of several conserved amino acids around the binding site on the hemagglutination, neuraminidase, and fusion functions of HN. Most mutations around the binding site result in loss of neuraminidase activity, whereas the effect on receptor binding is more variable. Residues E401, R416, and Y526 appear to be key for receptor binding. The increase in fusion promotion seen in some mutants that lack receptor binding activity presents a conundrum. We propose that in these cases HN may be switched into a fusion-promoting state through a series of conformational changes that propagate from the sialic acid binding site through to the HN dimer interface. These results further support the single-site model and suggest certain residues to be important for the triggering of fusion.
Feasibility of Generating Adeno-Associated Virus Packaging Cell Lines Containing Inducible Adenovirus Helper Genes
Authors: Qiao Chunping , Li Juan , Skold Anna , Zhang Xudong , Xiao Xiao
Published: July 2002

The adeno-associated virus (AAV) vector system is based on nonpathogenic and helper-virus-dependent parvoviruses. The vector system offers safe, efficient, and long-term in vivo gene transfer in numerous tissues. Clinical trials using AAV vectors have demonstrated vector safety as well as efficiency. The increasing interest in the use of AAV for clinical studies demands large quantities of vectors and hence a need for improvement in vector production. The commonly used transient-transfection method, although versatile and free of adenovirus (Ad), is not cost-effective for large-scale production. While the wild-type-Ad-dependent AAV producer cell lines seem to be cost-effective, this method faces the problem of wild-type Ad contamination. To overcome these shortcomings, we have explored the feasibility of creating inducible AAV packaging cell lines that require neither transfection nor helper virus infection. As a first step toward that goal, we have created a cell line containing highly inducible Ad E1A and E1B genes, which are essential for AAV production. Subsequently, the AAV Rep and Cap genes and an AAV vector containing a green fluorescent protein (GFP) reporter gene were stably introduced into the E1A-E1B cell line, generating inducible AAV-GFP packaging cell lines. Upon induction of E1A and E1B genes and infection with replication-defective Ad with E1A, E1B, and E3 deleted, the packaging cells yielded high-titer AAV-GFP vectors. Finally, the E2, E4, and VA genes of Ad, under the control of their endogenous promoters, were also introduced into these cells. A few producer cell lines were obtained, which could produce AAV-GFP vectors upon simple drug induction. Although future improvement is necessary to increase the stability and vector yield of the cells, our study has nonetheless demonstrated the feasibility of generating helper-virus-free inducible AAV producer cell lines.
The Capsid of Infectious Bursal Disease Virus Contains Several Small Peptides Arising from the Maturation Process of pVP2
Authors: Da Costa Bruno , Chevalier Christophe , Henry Celine , Huet Jean-Claude , Petit Stéphanie , Lepault Jean , Boot Hein , Delmas Bernard
Published: July 2002

The capsid proteins VP2 and VP3 of infectious bursal disease virus, a birnavirus, are derived from the processing of a large polyprotein: NH2-pVP2-VP4-VP3-COOH. Although the primary cleavage sites at the pVP2-VP4 and VP4-VP3 junctions have been identified, the proteolytic cascade involved in the processing of this polyprotein is not yet fully understood, particularly the maturation of pVP2. By using different approaches, we showed that the processing of pVP2 (residues 1 to 512) generated VP2 and four small peptides (residues 442 to 487, 488 to 494, 495 to 501, and 502 to 512). We also showed that in addition to VP2, at least three of these peptides (residues 442 to 487, 488 to 494, and 502 to 512) were associated with the viral particles. The importance of the small peptides in the virus cycle was assessed by reverse genetics. Our results showed that the mutants lacking the two smaller peptides were viable, although the virus growth was affected. In contrast, deletions of the domain 442 to 487 or 502 to 512 did not allow virus recovery. Several amino acids of the peptide 502 to 512 appeared essential for virus viability. Substitutions of the P1 and/or P1" position were engineered at each of the cleavage sites (P1-P1": 441-442, 487-488, 494-495, 501-502, and 512-513). Most substitutions at the pVP2-VP4 junction (512-513) and at the final VP2 maturation cleavage site (441-442) were lethal. Mutations of intermediate cleavage sites (487-488, 494-495, and 501-502) led to viable viruses showing different but efficient pVP2 processing. Our data suggested that while peptides 488 to 494 and 495 to 501 play an accessory role, peptides 442 to 487 and 502 to 512 have an unknown but important function within the virus cycle.
Human Immunodeficiency Virus Type 1 Nef Binds to Tumor Suppressor p53 and Protects Cells against p53-Mediated Apoptosis
Authors: Greenway Alison L. , McPhee Dale A. , Allen Kelly , Johnstone Ricky , Holloway Gavan , Mills John , Azad Ahmed , Sankovich Sonia , Lambert Paul
Published: July 2002

The
nef
gene product of human immunodeficiency virus type 1 (HIV-1) is important for the induction of AIDS, and key to its function is its ability to manipulate T-cell function by targeting cellular signal transduction proteins. We reported that Nef coprecipitates a multiprotein complex from cells which contains tumor suppressor protein p53. We now show that Nef interacts directly with p53. Binding assays showed that an N-terminal, 57-residue fragment of Nef (Nef 1-57) contains the p53-binding domain. Nef also interacted with p53 during HIV-1 infection in vitro. As p53 plays a critical role in the regulation of apoptosis, we hypothesized that Nef may alter this process. Nef inhibited UV light-induced, p53-dependent apoptosis in MOLT-4 cells, with Nef 1-57 being as effective as its full-length counterpart. The inhibition by Nef of p53 apoptotic function is most likely due its observed ability to decrease p53 protein half-life and, consequently, p53 DNA binding activity and transcriptional activation. These data show that HIV-1 Nef may augment HIV replication by prolonging the viability of infected cells by blocking p53-mediated apoptosis.
Absence of IE1 p72 Protein Function during Low-Multiplicity Infection by Human Cytomegalovirus Results in a Broad Block to Viral Delayed-Early Gene Expression
Authors: Gawn Jonathan M. , Greaves Richard F.
Published: July 2002

Human cytomegalovirus (HCMV)
ie1
deletion mutant CR208 is profoundly growth deficient after low-multiplicity infection of primary fibroblasts. Previously, we showed that many fewer cells infected with CR208 at low multiplicity accumulated the delayed-early (DE) protein ppUL44 than accumulated the immediate-early 2 (IE2) p86 protein, indicating a high frequency of abortive infections. We now demonstrate that accumulation of all DE proteins tested was defective after low-multiplicity infection in the absence of IE1 p72. Accumulation of the DE proteins pUL57, pUL98, and pUL69 followed a pattern very similar to that of ppUL44 during low-multiplicity CR208 infection. Accumulation of the ppUL112-113 proteins occurred in a greater proportion of cells than other DE proteins during low-multiplicity CR208 infection, but was still deficient relative to wild-type virus. We also show for the first time that steady-state levels of many DE RNAs were reduced during low-multiplicity CR208 infection and that by in situ hybridization of the abundant cytoplasmic 2.7-kb TRL4 DE (β2.7) RNA, a viral DE RNA followed a defective pattern of accumulation similar to that of ppUL44. Furthermore, transfected DE promoter-reporter constructs were found in transient assays to be considerably less responsive to CR208 infection than to infection by wild-type Towne virus. Our results indicate a general defect in DE gene expression following low-multiplicity HCMV infection in the absence of functional IE1 p72, most probably mediated by reduced transcription of DE genes and by the reduced accumulation of DE RNAs.
Gene Expression Pattern in Caco-2 Cells following Rotavirus Infection
Authors: Cuadras Mariela A. , Feigelstock Dino A. , An Sungwhan , Greenberg Harry B.
Published: July 2002

Rotaviruses are recognized as the leading cause of severe dehydrating diarrhea in infants and young children worldwide. Preventive and therapeutic strategies are urgently needed to fight this pathogen. In tissue culture and in vivo, rotavirus induces structural and functional alterations in the host cell. In order to better understand the molecular mechanisms involved in the events after rotavirus infection, we identified host cellular genes whose mRNA levels changed after infection. For this analysis, we used microarrays containing more than 38,000 human cDNAs to study the transcriptional response of the human intestinal cell line Caco-2 to rotavirus infection. We found that 508 genes were differentially regulated >2-fold at 16 h after rotavirus infection, and only one gene was similarly regulated at 1 h postinfection. Of these transcriptional changes, 73% corresponded to the upregulation of genes, with the majority of them occurring late, at 12 or more hours postinfection. Some of the regulated genes were classified according to known biological function and included genes encoding integral membrane proteins, interferon-regulated genes, transcriptional and translational regulators, and calcium metabolism-related genes. A new picture of global transcriptional regulation in the infected cell is presented and families of genes which may be involved in viral pathogenesis are discussed.
Solvent Extraction of Mercury Complexes with Diisopropylaminoethanethiol and Other Substances Accompanying Agent VX
Authors: Navrátil Oldřich , Kobliha Zbyněk , Halámek Emil
Published: July 2002

The distribution of 2-diisopropylaminoethanethiol (RSH) between aqueous phase containing picric acid at various pH values (ionic strength 0.1) and toluene as the organic phase was investigated. The protonation constant of the reagent is Ka = 106.27. The constants characterizing the formation of the ion-associate with the picrate anion were also determined. The distribution of mercury was also examined between solutions of RSH and its derivatives in low-polar organic solvents and aqueous phases containing mineral acids and/or their sodium salts. The composition of the extractable chelating complexes formed in neutral and alkaline aqueous phases is Hg : reagent = 1 : 3.
Photoelectrochemical Characteristics of n-InSe Single Crystals
Authors: Poulios Ioannis , Farmakis Kostantinos , Paraskevopoulos Kostantinos
Published: July 2002

The photoelectrochemical behaviour of n-InSe single crystals in aqueous solutions has been studied in the presence and absence of several redox systems. Among them, Ce3+/4+ and KI/I2 yielded the highest photocurrents, photovoltages and show the highest stability. The semiconductor energy gap Eg = 1.2 eV, has been calculated from transmittance measurements. The flat band potential UFB = -0.40 V vs NHE and the donor density have been calculated from differential capacity measurements.
Pyrolysis of Hexadecane
Authors: Barteková Elena , Bajus Martin
Published: July 2002

The kinetics of thermal decomposition of hexadecane was studied in a flow tubular reactor from stainless steel. The experiments were performed in the temperature range of 700 to 780 °C for the mass ratio of steam to hydrocarbon 3 : 1. The hexadecane pyrolysis took place according to the first-order reaction with a frequency factor of 3.5 . 109 s-1 and an activation energy of 162 kJ mol-1. In the pyrolysis products there were above all 1-alkenes. From alkanes, methane and ethane and less propane were formed in a higher degree. The prevailing compounds are ethene and propene whose amount increases with increasing temperature and residence time. The content of 1-alkenes higher than 1-pentene decreases with increasing conversion which gives evidence of their decomposition owing to their lower stability in comparison with the lighter 1-alkenes. The formation of dienes (1,3-butadiene and propadiene) and benzene also confirmed the course of secondary reactions. The observed higher formation of hydrogen results from the reaction of steam with coke deposited on the walls of the reactor or with hydrocarbon radicals. The evidence of the coke formation is given also by the presence of carbon oxides whose amount grew with the pyrolysis severity. The high content of 1-hexene in comparison with the other higher 1-alkenes is probably caused by the isomerization of alkyl radicals by 1,5-hydrogen transfer.
Humic Substances - Excited States, Quenching by Metal Ions, and Photosensitized Degradation of Chlorophenols
Authors: Lang Kamil , Wagnerová Dana M. , Klementová Šárka , Kubát Pavel
Published: July 2002

Alteration of photochemical properties of humic substances (HS) by the addition of metals abundant in natural waters has been investigated. Excited HS states have been characterized by fluorescence spectra and by laser kinetic spectroscopy. The effect of Cu2+, Fe2+, and Mn2+ has been explained in terms of static quenching of the HS excited states. In agreement with this, the metal ions were found to inhibit HS sensitized photooxidative degradation of chlorophenols.
119Sn, 13C and 1H NMR Spectra of Tris(1-butyl)stannyl D-Glucuronate
Authors: Lyčka Antonín , Holeček Jaroslav , Micák David
Published: July 2002

The 119Sn, 13C and 1H NMR spectra of tris(1-butyl)stannyl D-glucuronate have been measured in hexadeuteriodimethyl sulfoxide, tetradeuteriomethanol and deuteriochloroform. The chemical shift values have been assigned unambiguously with the help of H,H-COSY, TOCSY, H,C-COSY and 1H-13C HMQC-RELAY. From the analysis of parameters of 119Sn, 13C and 1H NMR spectra of the title compound and their comparison with the corresponding spectra of tris(1-butyl)stannyl acetate and other carboxylates it follows that in solutions of non-coordinating solvents (deuteriochloroform) the title compound is present in the form of more or less isolated individual molecules with pseudotetrahedral environment around the central tin atom and with monodentately bound carboxylic group. The interaction of tin atom with oxygen atoms of carbonyl group and hydroxyl groups of the saccharide residue - if they are present at all - are very weak. In solutions in coordinating solvents (hexadeuteriodimethyl sulfoxide or tetradeuteriomethanol), the title compound forms complexes with one molecule of the solvent. Particles of these complexes have a shape of trigonal bipyramid with the 1-butyl substituents in equatorial plane and the oxygen atoms of monodentate carboxylic group and coordinating solvent in axial positions.
Niobocene Dichloride and Niobocene Diiodide: Electronic Absorption Spectra and Electron Spin Resonance
Authors: Holubová Jana , Černošek Zdeněk , Pavlík Ivan
Published: July 2002

The effect of the halide ligand on the bonding of niobium in niobocene dichloride and niobocene diiodide was investigated. The electronic absorption spectra of the two compounds in the range of d-d transitions were resolved into four bands corresponding to transitions of the d1 electron between five frontier orbitals in a molecule of symmetry point group C2v. The energies of the frontier molecular orbitals were determined relatively to the energy of the orbitals in the spherically symmetric ligand field formed by the appropriate halide ligands. The effect of the halide ligands on the spin-orbital interaction of the HOMO orbital is discussed qualitatively on the basis the ESR spectra.
Adsorption of Gaseous Propylamine on Films of Polypyrrole in Different Oxidation States
Authors: Papež Vítězslav , Brodská Šárka , Langmaier Jan , Samec Zdeněk , Potje-Kamloth Karin
Published: July 2002

Quartz crystal microbalance and Kelvin probe were used to investigate the interaction between propylamine (PrNH2) vapour and polypyrrole (PPy) films. The films were prepared by oxidative electropolymerization of pyrrole on a platinum electrode in acetonitrile solution. The nature of interaction is strongly influenced by the oxidation state of the film and co-adsorption of water. On the surface of the oxidized PPy, water adsorbs to form a multilayer. The work function increase of the Pt/PPy electrode exposed to both water and PrNH2 vapoures was attributed to the PrNH2 dissolution and dissociation within the water layer followed by the formatted PrNH3+ cation adsorption on the liquid surface with the alkyl group facing the gas phase. On the contrary, the water adsorption on the reduced PPy is rather weak and the work function decrease observed at the PrNH2 exposure might be connected with the neutral molecules adsorption directly on the polymer surface. The water co-adsorption is documented by a drop in the adsorption of PrNH2 upon lowering the water vapour pressure in the gas phase.
Nano-Organized Structures in a Field: Equilibrium and Steady-State Gradient Focusing in Multicomponent Colloidal Systems
Authors: Janča Josef
Published: July 2002

Focusing behaviour appearing in multicomponent colloidal systems exposed to the action of a field can be considered as a special case of the formation of the organized structures on a nanosize scale. The emergence of such structures was observed under the thermodynamic equilibrium conditions as well as at a steady state characterized by an entropy production due to an energy flux. It has already been proven that a complex liquid forming a primary concentration gradient should not necessarily behave as a continuum with respect to the focused species but the focusing effect can appear as well. Two theoretical models predicting equilibrium or steady-state gradient focusing under various conditions were published recently. The first model is based on a macroscopic dynamic mechanism and the other on a microscopic kinetic mechanism. Although seemingly complementary, they bring along some paradoxes. The dynamic model describes correctly the focusing of the large species in a continuum or pseudocontinuum gradient. Nevertheless, its application to the description of the focusing emerging in a bidisperse or multicomponent mixture of the colloidal particles of commensurable sizes does not seem to be physically adequate. The kinetic model provides a coherent physical image of the focusing in such a bidisperse or multicomponent mixture but, on the other hand, it gives rise to the mentioned paradoxes. In this study, both models were compared with the former theoretical approaches dealing with equilibrium or steady states established in multicomponent and/or concentrated colloidal systems interacting with a field. Moreover, computer simulation was carried out to elucidate the consequences of the mentioned paradoxes and to discuss the domain of the prevailing contribution of the macroscopic and microscopic mechanisms to the resulting focusing phenomenon.
An Equation for Viscosity of Binary Liquid Mixtures
Authors: Moumouzias George , Ritzoulis George
Published: July 2002

An equation for the viscosity of binary liquid mixtures is presented. The equation is based on McAllister's four-body model by taking into account the viscosity dependence on temperature suggested by Goletz and Tassios.
Electrochemical Analysis of Solids. A Review
Authors: Grygar Tomáš , Marken Frank , Schröder Uwe , Scholz Fritz
Published: July 2002

The topic of the review is the electrochemical analysis of solids aimed to identify or determine their phase or elemental composition, analyse the composition of solid mixtures, characterise their electrochemistry-related properties and analyse the redox state of the constituent elements. The ways of the electrode preparation are discussed with a special attention paid to compact and composite electrodes including carbon-paste electrodes, and direct immobilisation of powders on a working electrode. Examples are given of simultaneous electrochemical measurements combined with X-ray diffraction, optical or atomic force microscopy, and mass measurement by quartz microbalance. The state-of-art of voltammetric analysis of inorganic and organic solids achieved in the last two decades is systematically reviewed with the aim to find cases, when electrochemistry can compete successfully with other analytical techniques as for sensitivity, specificity, and sample consumption. Electrochemical methods are shown to be a perspective tool for redox analysis of catalysts, combined elemental and phase analysis of inorganic pigments and minerals, characterisation of solid solutions, metalloorganic and organic solids. A review with 196 references.
The risk and outcome of cerebral oedema developing during diabetic ketoacidosis
Authors: Edge J A , Hawkins M M , Winter D L , Dunger D B
Published: July 2002

BACKGROUND

Cerebral oedema is a major cause of morbidity and mortality in children with insulin dependent diabetes.

AIMS

To determine the risk and outcome of cerebral oedema complicating diabetic ketoacidosis (DKA).

METHODS

All cases of cerebral oedema in England, Scotland, and Wales were reported through the British Paediatric Surveillance Unit between October 1995 and September 1998. All episodes of DKA were reported by 225 paediatricians identified as involved in the care of children with diabetes through a separate reporting system between March 1996 and February 1998. Further information about presentation, management, and outcome was requested about the cases of cerebral oedema. The risk of cerebral oedema was investigated in relation to age, sex, seasonality, and whether diabetes was newly or previously diagnosed.

RESULTS

A total of 34 cases of cerebral oedema and 2940 episodes of DKA were identified. The calculated risk of developing cerebral oedema was 6.8 per 1000 episodes of DKA. This was higher in new (11.9 per 1000 episodes) as opposed to established (3.8 per 1000) diabetes. There was no sex or age difference. Cerebral oedema was associated with a significant mortality (24%) and morbidity (35% of survivors).

CONCLUSIONS

This first large population based study of cerebral oedema complicating DKA has produced risk estimates which are more reliable and less susceptible to bias than those from previous studies. Our study indicates that cerebral oedema remains an important complication of DKA during childhood and is associated with significant morbidity and mortality. Little is known of the aetiology of cerebral oedema in this condition and we are currently undertaking a case control study to address this issue.
Do high impact exercises produce higher tibial strains than running?
Authors: Milgrom Charles , Finestone Aharon , Levi Yael , Simkin Ariel , Ekenman Ingrid , Mendelson Stephen , Millgram Michael , Nyska Meir , Benjuya Nissim , Burr David
Published: July 2002

Background—Bone must have sufficient strength to withstand both instantaneous forces and lower repetitive forces. Repetitive loading, especially when bone strain and/or strain rates are high, can create microdamage and result in stress fractureAim—To measure in vivo strains and strain rates in human tibia during high impact and moderate impact exercises.

Methods—Three strain gauged bone staples were mounted percutaneously in a rosette pattern in the mid diaphysis of the medial tibia in six normal subjects, and in vivo tibial strains were measured during running at 17 km/h and drop jumping from heights of 26, 39, and 52 cm.

Results—Complete data for all three drop jumps were obtained for four of the six subjects. No statistically significant differences were found in compression, tension, or shear strains with increasing drop jump height, but, at the 52 cm height, shear strain rate was reduced by one third (p = 0.03). No relation was found between peak compression strain and calculated drop jump energy, indicating that subjects were able to dissipate part of the potential energy of successively higher drop jumps by increasing the range of motion of their knee and ankle joints and not transmitting the energy to their tibia. No statistically significant differences were found between the principal strains during running and drop jumping from 52 cm, but compression (p = 0.01) and tension (p = 0.004) strain rates were significantly higher during running.

Conclusions—High impact exercises, as represented by drop jumping in this experiment, do not cause higher tibial strains and strain rates than running and therefore are unlikely to place an athlete who is accustomed to fast running at higher risk for bone fatigue.
Bone mineral density and serum testosterone in chronically trained, high mileage 40–55 year old male runners
Authors: MacKelvie K J , Taunton J E , McKay H A , Khan K M
Published: July 2002

Objectives—To identify physical activity that is beneficial for the maintenance of bone strength with increasing age by examining the relation between bone mineral density (BMD) and chronic endurance training in men. BMD at the proximal femur, its subregions, and the lumbar spine, and serum testosterone were compared between two groups of long distance runners with more than 20 years of training experience and non-athletic controls.

Methods—Runners (n = 12) were divided into (a) high volume runners (n = 7), running 64–80 km a week, and (b) very high volume runners (n = 5), running more than 95 km a week, and compared with non-athletic male controls, exercising in non-endurance oriented activities two to four times a week. BMD (g/cm2) at the total proximal femur, femoral neck, trochanteric region, and lumbar spine was measured by dual energyxray absorptiometry. Total testosterone (nmol/l) and free testosterone (pmol/l) in serum were measured by radioimmunoassay from single fasting blood samples.

Results—Height, weight, and age (range = 40–55 years) were not significantly different between groups. The high volume runners had significantly higher BMD at the total proximal femur (1.09 (0.17)v0.94 (0.056)), femoral neck (0.91 (0.16)v0.78 (0.071)), and trochanteric region (0.85 (0.14)v0.73 (0.053)) than controls (p<0.05). The differences in BMD for the proximal femur between the very high volume runners and the other two groups were not significant. There was no difference in lumbar spine BMD, total testosterone, or free testosterone between groups. However, there was a significant negative correlation between total testosterone (r= −0.73, p<0.01) and free testosterone (r= −0.79, p<0.005) and running volume in the distance runners.

Conclusions—Long term distance running with training volumes less than 80 km a week had a positive effect on BMD of the proximal femur. With running volumes greater than 64 km a week, training was inversely related to testosterone levels, but levels remained within the normal range.
Epidemiology of injuries in the Australian Football League, seasons 1997–2000
Authors: Orchard J , Seward H
Published: July 2002

Objective: To describe the epidemiology of injuries in the Australian Football League (AFL) over four seasons.

Methods: An injury was defined as “any physical or medical condition that caused a player to miss a match in the regular season.” The rationale for this definition was to eliminate a previously noted tendency of team recorders to interpret injury definitions subjectively. Administrative records of injury payments to players who did not play matches determined the occurrence of an injury.

Results: The seasonal incidence of new injuries was 39 per club (of 40 players) per season (of 22 matches). The match injury incidence for AFL games was 25.7 injuries per 1000 player hours. The injury prevalence (percentage of players missing through injury in an average week) was 16%. The recurrence rate of injuries was 17%. The most common and prevalent injury was hamstring strain (six injuries per club per season, resulting in 21 missed matches per club per season), followed in prevalence by anterior cruciate ligament and groin injuries.

Conclusions: The injury definition of this study does not produce incidence rates that are complete for all minor injuries. However, the determination of an injury is made by a single entity in exactly the same manner for all teams, which overcomes a significant methodological flaw present in other multiteam injury surveillance systems.
Stress fracture of the hook of the hamate
Authors: Guha A R , Marynissen H
Published: July 2002

Fractures of the hook of the hamate have rarely been reported. They have usually resulted from blunt trauma or a sharp strike against the hamate hook while swinging a golf club, baseball bat, or tennis racquet. Patients present with acute onset of pain localised over the ulnar aspect of the wrist and reduction in grip strength. In the case reported here, the patient complained of gradual onset of pain on the ulnar aspect of the wrist after altering his grip for serving in tennis. Once the diagnosis was made, the fracture was treated conservatively and the patient made a complete recovery.
Functional results and visceral perception after ileo neo-rectal anastomosis in patients: a pilot study
Authors: Andriesse G I , Gooszen H G , Schipper M E I , Akkermans L M A , van Vroonhoven T J M V , van Laarhoven C J H M
Published: July 2002

INTRODUCTION

To reduce pouch related complications after restorative proctocolectomy, an alternative procedure was developed, the ileo neo-rectal anastomosis (INRA). This technique consists of rectal mucosa replacement by ileal mucosa and straight ileorectal anastomosis. Our study provides a detailed description of the functional results after INRA.

PATIENTS AND METHODS

Eleven patients underwent an INRA procedure with a temporary ileostomy. Anorectal function tests were performed two months prior to and six and 12 months after closure of the ileostomy and comprised: anal manometry, ultrasound examination, rectal balloon distension, and transmucosal electrical nerve stimulation (TENS). Function was subsequently related to the histopathology of rectal biopsy samples.

RESULTS

Median stool frequency decreased from 15/24 hours (10–25) to 6/24 hours (4–11) at one year. All patients reported full continence. Anal sensibility, and resting and squeeze pressures did not change after INRA. Rectal compliance decreased (2.1 (0.7–2.8) v 1.5 (0.4–2.2) and 1.4 (0.8–3.7) ml/mm Hg (p=0.03)) but the maximum tolerated volume increased (70 (50–118) v96 (39–176) (NS) and 122 (56–185) ml (p=0.03)). Decreasing rectal sensitivity was found: the maximum tolerated pressure increased (14 (8–24) v 22 (8–34) (NS) and 26 (14–40) (p=0.02)) and the rectal threshold for TENS displayed a similar tendency. All patients displayed a low grade chronic inflammatory infiltrate in neorectal biopsy samples before closure of the ileostomy, with no change during follow up.

CONCLUSIONS

The technique of INRA provides a safe alternative for restorative surgery. Stool frequency after INRA improves with time and seems to be related to decreasing sensitivity and not to histopathological changes in the neorectum. Furthermore, after the INRA procedure, all patients reported full continence.
Arginine induced acute pancreatitis alters the actin cytoskeleton and increases heat shock protein expression in rat pancreatic acinar cells
Authors: Tashiro M , Schäfer C , Yao H , Ernst S A , Williams J A
Published: July 2002

Arginine induced acute pancreatitis was evaluated as a novel and distinct form of experimental pancreatitis with particular attention to the actin cytoskeleton and expression of heat shock or stress proteins. Arginine induced a dose related necrotising pancreatitis in rats, as shown by histological evaluation, and an increase in serum amylase. Severe pancreatitis induced by 4.5 g/kg arginine was accompanied by dramatic changes in the actin cytoskeleton, as visualised with rhodamine phallodin. Intermediate filaments were also disrupted, as visualised by cytokeratin 8/18 immunocytochemistry. Arginine pancreatitis was accompanied by a stress response with a large increase in the small heat shock protein HSP27, as well as HSP70, peaking at 24 hours and localised to acinar cells. There was a lower increase in HSP60 and HSP90 and no effect on GRP78. HSP27 was also shifted to phosphorylated forms during pancreatitis. A lower dose of arginine (3.0 g/kg) induced less pancreatitis but a larger increase in HSP70 and HSP27 expression and phosphorylation of HSP27. Thus HSP expression can be overwhelmed by severe damage. The present work in conjunction with earlier work on caerulein induced pancreatitis indicates that changes in the actin cytoskeleton are an early component in experimental pancreatitis.
Quantitation ofHelicobacter pyloriin dental plaque samples by competitive polymerase chain reaction
Authors: Song Q , Haller B , Ulrich D , Wichelhaus A , Adler G , Bode G
Published: July 2002

Aim—To establish a competitive PCR (cPCR) assay for quantitation ofH pyloriorganisms in dental plaque samples.

Methods—The cPCR coamplified targetH pyloriDNA and a known amount of internal standard template in the same tube with the same primers directed to 0.86 kb DNA of H pylori. The internal standard was a synthesised DNA bearing the same primer recognition sites at two ends and a non-homologous core sequence as the target DNA fragment. Quantitation was based on determination of the relative, not absolute, amounts of the differently sized and [32P]-dCTP labelled products derived fromH pyloriDNA and the competitive internal standard after gel electrophoresis separation.

Results—A significant correlation between known amounts ofH pyloriadded to dental plaque samples and the results of the cPCR was found, and a standard line was developed which allowed quantitation ofH pyloriin the plaque samples. cPCR was performed on supragingival plaque samples from 10 adult patients with H pylori infection in the stomach, and from five adults and six children withoutH pyloriinfection in the stomach. The ranges ofH pylorinumbers were 1–213 (median 25), 6–76 (10), and 4–94 (14) cells/mg of dental plaque in the three groups, respectively.

Conclusions—cPCR is useful for quantitation ofH pyloriin supragingival dental plaque samples; however, the number of the organisms in dental plaque samples seems very low.