bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Replication-Competent Molecular Clones of Porcine Endogenous Retrovirus Class A and Class B Derived from Pig and Human Cells
Authors: Krach Ulrich , Fischer Nicole , Czauderna Frank , Tönjes Ralf R.
Published: July 2002

Vertically transmitted endogenous retroviruses pose an infectious risk in the course of pig-to-human transplantation of cells, tissues, and organs. Two classes of polytropic type C porcine endogenous retroviruses (PERV) which are infectious for human cells in vitro are known. Recently, we described the cloning and characterization of replication-competent PERV-B sequences from productively infected human cells (F. Czauderna, N. Fischer, K. Boller, R. Kurth, and R. R. Tönjes, J. Virol. 74:4028–4038, 2000). Here, we report the isolation of infectious molecular PERV-A and PERV-B clones from pig cells and compare these proviruses with clones derived from infected human 293 cells. In addition to clone PERV-A(42) derived from 293 cells, four “native” full-length proviral PERV sequences derived from a genomic library of the porcine cell line PK15 were isolated. Three identical class A clones, designated PK15-PERV-A(42), PK15-PERV-A(45), and PK15-PERV-A(58), and one class B clone, PK15-PERV-B(213), were characterized. PK15-PERV-B(213) is highly homologous but distinct from the previously described clone PERV-B(43). PK15-PERV-A(58) demonstrates close homology to PERV-A(42) in
env
and to PERV-C in long terminal repeat,
gag
, and
pro
/
pol
sequences. All three PERV clones described here were replication competent upon infection of susceptible cell lines. The findings suggest that the pig genome harbors a limited number of infectious PERV-A and -B sequences.
p21cip1 Degradation in Differentiated Keratinocytes Is Abrogated by Costabilization with Cyclin E Induced by Human Papillomavirus E7
Authors: Noya Francisco , Chien Wei-Ming , Broker Thomas R. , Chow Louise T.
Published: July 2002

The human papillomavirus (HPV) E7 protein promotes S-phase reentry in a fraction of postmitotic, differentiated keratinocytes. Here we report that these cells contain an inherent mechanism that opposes E7-induced DNA replication. In organotypic raft cultures of primary human keratinocytes, neither cyclin E nor p21cip1 is detectable in situ. However, E7-transduced differentiated cells not in S phase accumulate abundant cyclin E and p21cip1. We show that normally p21cip1 protein is rapidly degraded by proteasomes. In the presence of E7 or E6/E7, p21cip1, cyclin E, and cyclin E2 proteins were all up-regulated. The accumulation of p21cip1 protein is a posttranscriptional event, and ectopic cyclin E expression was sufficient to trigger it. In constract, cdk2 and p27kip1 were abundant in normal differentiated cells and were not significantly affected by E7. Cyclin E, cdk2, and p21cip1 or p27kip1 formed complexes, and relatively little kinase activity was found associated with cyclin E or cdk2. In patient papillomas and E7 raft cultures, all p27kip1-positive cells were negative for bromodeoxyuridine (BrdU) incorporation, but only some also contained cyclin E and p21cip1. In contrast, all cyclin E-positive cells also contained p27kip1. When the expression of p21cip1 was reduced by rottlerin, a PKC δ inhibitor, p27kip1- and BrdU-positive cells remained unchanged. These observations show that high levels of endogenous p27kip1 can prevent E7-induced S-phase reentry. This inhibition then leads to the stabilization of cyclin E and p21cip1. Since efficient initiation of viral DNA replication requires cyclin E and cdk2, its inhibition accounts for heterogeneous viral activities in productively infected lesions.
Intrahepatic Genetic Inoculation of Hepatitis C Virus RNA Confers Cross-Protective Immunity
Authors: Weiner Amy J. , Paliard Xavier , Selby Mark J. , Medina-Selby Angelica , Coit Doris , Nguyen Steve , Kansopon Joe , Arian Christopher L. , Ng Philip , Tucker Jeffery , Lee Chun-Ting , Polakos Noelle K. , Han Jang , Wong Shirley , Lu Hui-Hua , Rosenberg Steve , Brasky Kathy M. , Chien David , Kuo George , Houghton Michael
Published: July 2002

Naturally occurring hepatitis C virus (HCV) infection has long been thought to induce a weak immunity which is insufficient to protect an individual from subsequent infections and has cast doubt on the ability to develop effective vaccines. A series of intrahepatic genetic inoculations (IHGI) with type 1a HCV RNA were performed in a chimpanzee to determine whether a form of genetic immunization might stimulate protective immunity. We demonstrate that the chimpanzee not only developed protective immunity to the homologous type 1a RNA after rechallenge by IHGI but was also protected from chronic HCV infection after sequential rechallenge with 100 50% chimpanzee infectious doses of a heterologous type 1a (H77) and 1b (HC-J4) whole-virus inoculum. These results offer encouragement to pursue the development of HCV vaccines.
E1B 19K Blocks Bax Oligomerization and Tumor Necrosis Factor Alpha-Mediated Apoptosis
Authors: Sundararajan Ramya , White Eileen
Published: July 2002

Tumor necrosis factor alpha (TNF-α)-mediated death signaling causes the recruitment of monomeric pro- apoptotic Bax into a 500-kDa protein complex. The adenovirus Bcl-2 homologue, E1B 19K, inhibits TNF-α-mediated apoptosis, interacts with Bax, and blocked the formation of the 500-kDa Bax complex. TNF-α and truncated Bid induced Bax-Bax cross-linking, indicative of oligomerization, and E1B 19K expression during infection inhibited this TNF-α-mediated Bax oligomerization. TNF-α signaled conformation changes at the Bax amino and carboxy termini. Exposure of the Bax amino terminus facilitates E1B 19K-Bax binding, which prevented exposure of the carboxy-terminal Bax Bcl-2 homology region 2 epitope. Inhibition of Bax oligomerization by E1B 19K is an activity that bears striking similarity to the means by which bacterial immunity proteins block pore formation by bacterial toxins which have structural homology to Bax.
Activation of NF-κB by the Human Herpesvirus 8 Chemokine Receptor ORF74: Evidence for a Paracrine Model of Kaposi's Sarcoma Pathogenesis
Authors: Pati Shibani , Cavrois Marielle , Guo Hong-Guang , Foulke James S. , Kim Jynho , Feldman Ricardo A. , Reitz Marvin
Published: July 2002

Infection with human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma (KS)-associated herpesvirus, is necessary for the development of KS. The HHV-8 lytic-phase gene ORF74 is related to G protein-coupled receptors, particularly interleukin-8 (IL-8) receptors. ORF74 activates the inositol phosphate/phospholipase C pathway and the downstream mitogen-activated protein kinases, JNK/SAPK and p38. We show here that ORF74 also activates NF-κB independent of ligand when expressed in KS-derived HHV-8-negative endothelial cells or primary vascular endothelial cells. NF-κB activation was enhanced by the chemokine GROα, but not by IL-8. Mutation of Val to Asp in the ORF74 second cytoplasmic loop did not affect ligand-independent signaling activity, but it greatly increased the response to GROα. ORF74 upregulated the expression of NF-κB-dependent inflammatory cytokines (RANTES, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor) and adhesion molecules (VCAM-1, ICAM-1, and E-selectin). Supernatants from transfected KS cells activated NF-κB signaling in untransfected cells and elicited the chemotaxis of monocytoid and T-lymphoid cells. Expression of ORF74 conferred on primary endothelial cells a morphology that was strikingly similar to that of spindle cells present in KS lesions. Taken together, these data, demonstrating that ORF74 activates NF-κB and induces the expression of proangiogenic and proinflammatory factors, suggest that expression of ORF74 in a minority of cells in KS lesions could influence uninfected cells or latently infected cells via autocrine and paracrine mechanisms, thereby contributing to KS pathogenesis.
Polymorphisms in HLA Class I Genes Associated with both Favorable Prognosis of Human Immunodeficiency Virus (HIV) Type 1 Infection and Positive Cytotoxic T-Lymphocyte Responses to ALVAC-HIV Recombinant Canarypox Vaccines
Authors: Kaslow Richard A. , Rivers Charles , Tang Jianming , Bender Thomas J. , Goepfert Paul A. , El Habib Raphaelle , Weinhold Kent , Mulligan Mark J. ,   the NIAID Aids Vaccine Evaluation Group
Published: July 2002

Carriers of certain human leukocyte antigen class I alleles show favorable prognosis of human immunodeficiency virus type 1 (HIV-1) infection, presumably due to effective CD8+cytotoxic T-lymphocyte responses, but close relationships between class I variants mediating such responses to natural and to vaccine HIV-1 antigen have not been established. During 6 to 30 months of administration and follow-up in trials of ALVAC-HIV recombinant canarypox vaccines, cells from 42% of 291 HIV-1-negative vaccinated subjects typed at class I loci responded to an HIV-1 protein in a lytic bulk CD8+cytotoxic T-lymphocyte assay. By 2 weeks after the second dose, higher proportions of vaccinees carrying one of two alleles consistently associated with slower progression of natural HIV-1 infection reacted at least once: B∗27 carriers reacted to Gag (64%; odds ratio [OR] = 10.3,P= 0.001) and Env (36%; OR = 4.6,P= 0.04), and B∗57 carriers reacted to Env (44%; OR = 6.6,P< 0.05). By 2 weeks after the third or fourth dose, B∗27 carriers had responded (two or more reactions) to Gag (33%; OR = 4.4,P< 0.05) and B∗57 carriers had responded to both Gag (39%; OR = 5.3,P= 0.013) and Env (39%; OR = 9.5,P= 0.002). Homozygosity at class I loci, although conferring an unfavorable prognosis following natural infection, showed no such disadvantage for vaccine response. Individual class I alleles have not previously demonstrated such clear and consistent relationship with both the clinical course of an infection and cellular immunity to a vaccine against the infectious agent. This proof of principle that class I an alleles modulate both processes has implications for development of HIV-1 and presumably other vaccines.
Virus-Cell Interactions Regulating Induction of Tumor Necrosis Factor Alpha Production in Macrophages Infected with Herpes Simplex Virus
Authors: Paludan Søren R. , Mogensen Søren C.
Published: July 2002

Macrophages respond to virus infections by rapidly secreting proinflammatory cytokines, which play an important role in the first line of defense. Tumor necrosis factor alpha (TNF-α) is one of the major macrophage-produced cytokines. In this study we have investigated the virus-cell interactions responsible for induction of TNF-α expression in herpes simplex virus (HSV)-infected macrophages. Both HSV type 1 (HSV-1) and HSV-2 induced TNF-α expression in macrophages activated with gamma interferon (IFN-γ). This induction was to some extent sensitive to UV treatment of the virus. Virus particles unable to enter the cells displayed reduced capacity to stimulate TNF-α expression but retained a significant portion which was abolished by HSV-specific antibodies. Recombinant HSV-1 glycoprotein D was able to trigger TNF-α secretion in concert with IFN-γ. Sugar moieties of HSV glycoproteins have been reported to be involved in induction of IFN-α but did not contribute to TNF-α expression in macrophages. Moreover, the entry-dependent portion of the TNF-α induction was investigated with HSV-1 mutants and found to be independent of the tegument proteins VP16 and UL13 and partly dependent on nuclear translocation of the viral DNA. Finally, we found that macrophages expressing an inactive mutant of the double-stranded RNA (dsRNA)-activated protein kinase (PKR) produced less TNF-α in response to infectious HSV infection than the empty-vector control cell line but displayed the same responsiveness to UV-inactivated virus. These results indicate that HSV induces TNF-α expression in macrophages through mechanisms involving (i) viral glycoproteins, (ii) early postentry events occurring prior to nuclear translocation of viral DNA, and (iii) viral dsRNA-PKR.
Internal Ribosome Entry Site Regulates Translation of Kaposi's Sarcoma-Associated Herpesvirus FLICE Inhibitory Protein
Authors: Low Walter , Harries Mark , Ye Hongtao , Du Ming-Qing , Boshoff Chris , Collins Mary
Published: July 2002

The gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV) (or human herpesvirus 8) is associated with the endothelial tumor Kaposi's sarcoma (KS) and lymphoproliferative disorders in immunocompromised individuals. Only a small number of viral proteins are expressed in B cells latently infected with KSHV; here we characterize the mechanism of expression of one of these, the viral FLICE inhibitory protein v-FLIP (K13, ORF71). The v-FLIP coding region is present in a bicistronic message, following the v-cyclin coding region. Using both in vitro translation and cell transfection assays, we have identified an internal ribosome entry site (IRES) preceding the v-FLIP start codon and overlapping the v-cyclin (ORF 72) coding region, which allows v-FLIP translation. Using an antibody against v-FLIP we have detected expression of the endogenous protein in latently infected KSHV-positive primary effusion lymphoma (PEL) cell lines. Induction of apoptosis by serum withdrawal from PEL cells results in a relative increase in v-FLIP synthesis, as previously described for some cellular proteins translated from IRES.
JC Virus-Specific Cytotoxic T Lymphocytes in Individuals with Progressive Multifocal Leukoencephalopathy
Authors: Koralnik Igor J. , Du Pasquier Renaud A. , Letvin Norman L.
Published: July 2002

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by a reactivation of the polyomavirus JC (JCV) within a setting of immunosuppression. The nature of the immune response that contains replication of this virus is unknown. We have explored JCV-specific cellular immune responses in patients with PML and control subjects. JCV antigen-stimulated peripheral blood mononuclear cells (PBMC) of four human immunodeficiency virus (HIV)-infected patients who were survivors of PML and one HIV-uninfected patient recently diagnosed with PML lysed autologous B-lymphoblastoid cell lines expressing either the JCV T regulatory protein or the VP1 major capsid protein. This lysis was mediated by CD8+T lymphocytes and was major histocompatibility complex class I restricted. These cells were therefore cytotoxic T lymphocytes (CTL). JCV-specific CTL could not be detected in PBMC of three HIV-infected PML patients who had progressive neurologic disease and an eventual fatal outcome. These data suggest that the JCV-specific cellular immune response may play a crucial role in the containment of PML. This finding may also prove useful as a favorable prognostic marker in the clinical management of these patients.
Role of Alpha/Beta Interferon in Venezuelan Equine Encephalitis Virus Pathogenesis: Effect of an Attenuating Mutation in the 5′ Untranslated Region
Authors: White Laura J. , Wang Jia-Gang , Davis Nancy L. , Johnston Robert E.
Published: July 2002

Venezuelan equine encephalitis virus (VEE) is an important equine and human pathogen of the Americas. In the adult mouse model, cDNA-derived, virulent V3000 inoculated subcutaneously (s.c.) causes high-titer peripheral replication followed by neuroinvasion and lethal encephalitis. A single change (G to A) at nucleotide 3 (nt 3) of the 5′ untranslated region (UTR) of the V3000 genome resulted in a virus (V3043) that was avirulent in mice. The mechanism of attenuation by the V3043 mutation was studied in vivo and in vitro. Kinetic studies of virus spread in adult mice following s.c. inoculation showed that V3043 replication was reduced in peripheral organs compared to that of V3000, titers in serum also were lower, and V3043 was cleared more rapidly from the periphery than V3000. Because clearance of V3043 from serum began 1 to 2 days prior to clearance of V3000, we examined the involvement of alpha/beta interferon (IFN-α/β) activity in VEE pathogenesis. In IFN-α/βR
−/−
mice, the course of the wild-type disease was extremely rapid, with all animals dying within 48 h (average survival time of 30 h compared to 7.7 days in the wild-type mice). The mutant V3043 was as virulent as the wild type (100% mortality, average survival time of 30 h). Virus titers in serum, peripheral organs, and the brain were similar in V3000- and V3043-infected IFN-α/βR
−/−
mice at all time points up until the death of the animals. Consistent with the in vivo data, the mutant virus exhibited reduced growth in vitro in several cell types except in cells that lacked a functional IFN-α/β pathway. In cells derived from IFN-α/βR
−/−
mice, the mutant virus showed no growth disadvantage compared to the wild-type virus, suggesting that IFN-α/β plays a major role in the attenuation of V3043 compared to V3000. There were no differences in the induction of IFN-α/β between V3000 and V3043, but the mutant virus was more sensitive than V3000 to the antiviral actions of IFN-α/β in two separate in vitro assays, suggesting that the increased sensitivity to IFN-α/β plays a major role in the in vivo attenuation of V3043.
Cytokine-Sensitive Replication of Hepatitis B Virus in Immortalized Mouse Hepatocyte Cultures
Authors: Pasquetto Valérie , Wieland Stefan F. , Uprichard Susan L. , Tripodi Marco , Chisari Francis V.
Published: July 2002

We have previously shown that alpha/beta interferon (IFN-α/β) and gamma interferon (IFN-γ) inhibit hepatitis B virus (HBV) replication by eliminating pregenomic RNA containing viral capsids from the hepatocyte. We have also shown that HBV-specific cytotoxic T lymphocytes that induce IFN-γ and tumor necrosis factor alpha (TNF-α) in the liver can inhibit HBV gene expression by destabilizing preformed viral mRNA. In order to further study the antiviral activity of IFN-α/β, IFN-γ, and TNF-α at the molecular level, we sought to reproduce these observations in an in vitro system. Accordingly, hepatocytes were derived from the livers of HBV-transgenic mice that also expressed the constitutively active cytoplasmic domain of the human hepatocyte growth factor receptor (c-Met). Here, we show that the resultant well-differentiated, continuous hepatocyte cell lines (HBV-Met) replicate HBV and that viral replication in these cells is efficiently controlled by IFN-α/β or IFN-γ, which eliminate pregenomic RNA-containing capsids from the cells as they do in the liver. Furthermore, we demonstrate that IFN-γ, but not IFN-α/β, is capable of inhibiting HBV gene expression in this system, especially when it acts synergistically with TNF-α. These cells should facilitate the analysis of the intracellular signaling pathways and effector mechanisms responsible for these antiviral effects.
Ionic Strength- and Temperature-Induced K
Ca
Shifts in the Uncoating Reaction of Rotavirus Strains RF and SA11: Correlation with Membrane Permeabilization
Authors: Martin Sandra , Lorrot Mathie , El Azher Mounia Alaoui , Vasseur Monique
Published: July 2002

The hydrodynamic diameters of native rotavirus particles, bovine RF and simian SA11 strains, were determined by quasielastic light scattering. By using this method and agarose gel electrophoresis, the Ca
2+
dissociation constant, K
Ca
, governing the transition from triple-layer particles (TLPs) to double-layer particles (DLPs), was shown to increase, at constant pH, as the temperature and/or the ionic strength of the incubation medium increased. We report the novel observation that, under physiological conditions, K
Ca
values for both RF and SA11 rotaviruses were well above the intracytoplasmic Ca
2+
concentrations of various cells, which may explain why TLP uncoating takes place within vesicles (possibly endosomes) during the entry process. A correlation between TLP uncoating and cell membrane permeabilization was found, as shown by the release of carboxyfluorescein (CF) from CF-loaded intestinal brush-border membrane vesicles. Conditions stabilizing the virion in the TLP form inhibited CF release, whereas conditions favoring the TLP-to-DLP transformation activated this process. We conclude that membrane permeabilization must be preceded by the loss of the outer-capsid proteins from trypsinized TLP and that physiological ionic strength is required for permeabilization to take place. Finally, the paper develops an alternative explanation for the mechanism of rotavirus entry, compatible with the Ca
2+
-dependent endocytic pathway. We propose that there must be an iterative process involving tight coupling in time between the lowering of endosomal Ca
2+
concentration, virion decapsidation, and membrane permeabilization, which would cause the transcriptionally active DLPs to enter the cytoplasm of cells.
The Solitary Long Terminal Repeats of ERV-9 Endogenous Retrovirus Are Conserved during Primate Evolution and Possess Enhancer Activities in Embryonic and Hematopoietic Cells
Authors: Ling Jianhua , Pi Wenhu , Bollag Roni , Zeng Shan , Keskintepe Meral , Saliman Hatem , Krantz Sanford , Whitney Barry , Tuan Dorothy
Published: July 2002

The solitary long terminal repeats (LTRs) of ERV-9 endogenous retrovirus contain the U3, R, and U5 regions but no internal viral genes. They are middle repetitive DNAs present at 2,000 to 4,000 copies in primate genomes. Sequence analyses of the 5" boundary area of the erythroid β-globin locus control region (β-LCR) and the intron of the embryonic axin gene show that a solitary ERV-9 LTR has been stably integrated in the respective loci for at least 15 million years in the higher primates from orangutan to human. Functional studies utilizing the green fluorescent protein (GFP) gene as the reporter in transfection experiments show that the U3 region of the LTRs possesses strong enhancer activity in embryonic cells of widely different tissue origins and in adult cells of blood lineages. In both the genomic LTRs of embryonic placental cells and erythroid K562 cells and transfected LTRs of recombinant GFP plasmids in K562 cells, the U3 enhancer activates synthesis of RNAs that are initiated from a specific site 25 bases downstream of the AATAAA (TATA) motif in the U3 promoter. A second AATAAA motif in the R region does not serve as the TATA box or as the polyadenylation signal. The LTR-initiated RNAs extend through the R and U5 regions into the downstream genomic DNA. The results suggest that the ERV-9 LTR-initiated transcription process may modulate transcription of the associated gene loci in embryonic and hematopoietic cells.
The Distribution Coefficients of Bis(2-chloroethyl) Sulfide Between Some Organic Solvents and Water
Authors: Lukovic Zoran T. , Jovanovic Bratislav Ž. , Skala Dejan U.
Published: July 2002

The results of determining the distribution coefficients of bis(2-chloroethyl) sulfide between some organic solvents and water at 25 °C are presented in this paper. Two original methods for determining the distribution coefficients were applied: the kinetic method and the method of hydrolysis blocking. Values of the obtained distribution coefficients are discussed from the aspect of the calculated solubility parameters. The denoted methods can also be applied in a similar fashion to determine the distribution coefficients of other substances of similar properties.
X-Ray Structural Study of Terguride SolvatesTerguride Methanol Solvate
Authors: Kratochvíl Bohumil , Novotný Jiří , Hušák Michal , Had Jiří , Stuchlík Josef , Jegorov Alexandr
Published: July 2002

The structure of the unstable solvate of the semisynthetic ergot derivate terguride methanol solvate C20H28N4O .CH3OH, was solved by direct methods and refined to an R value of 0.093 for 1 462 unique observed reflections. The title alkaloid crystallizes in the orthorhombic space group P212121 with lattice parameters a = 10.438(1), b = 13.200(4), c = 15.495(5) Å, V = 2 134.8(9) Å3, Z = 4. An indole moiety of the terguride molecule is almost perfect planar, ring C has an E6 envelope conformation and ring D adopts a 1C4 chair shape. As found from X-ray powder diffraction study, terguride methanol solvate completely transforms to terguride monohydrate in air during several hours.
Effects of Substituents and Medium on Acidity of α,α-Bis(butylsulfonyl)toluenes
Authors: Ludwig Miroslav , Petržílek Jan , Kulhánek Jiří , Pytela Oldřich
Published: July 2002

Seven substituted α,α-bis(butylsulfonyl)toluenes and three 2-aryl-1,1,3,3-tetraoxo-1,3-dithiolanes have been prepared and their 1H NMR, IR, and MS spectra measured. The pKHA values of the substituted α,α-bis(butylsulfonyl)toluenes have been determined by potentiometric titration in dimethyl sulfoxide, dimethylformamide, and 80% (v/v) mixture of dimethyl sulfoxide and water. The results are interpreted by the Yukawa-Tsuno relationship (parameter r = 0.43 - 0.49) and classified in relation to analogous N- and O-acids by the methods with latent variables (the method of conjugated deviations).
Quaternary Heteroarenium Aldoximes as Catalysts for Cleavage of Phosphate Esters
Authors: Hampl František , Mazáč Jiří , Liška František , Šrogl Jiří , Kábrt Lubomír , Suchánek Miloslav
Published: July 2002

1-Methyl- (Ia - Id) and 1-dodecyl-2-, 3- and 4-hydroxyiminomethylpyridinium salts (Ie - Ih), as well as 1-methyl- (IIa) and 1-dodecyl-3-hydroxyiminomethylpyridazinium salts (IIb, IIc), were synthesized as catalysts for hydrolytic cleavage of organophosphates. The activities of the prepared catalysts were evaluated by measuring rate constants of hydrolysis of 4-nitrophenyl diphenyl phosphate (PNPDPP) under conditions of a pseudo-first-order reaction. The observed reactivity of pyridinium aldoximes Ia - Ih towards PNPDPP in neutral or slightly basic aqueous solutions (pH 7.2 and 7.8) depends on the acidity of the hydroxyimino group. The cleavage of PNPDPP is strongly accelerated in solutions of 1-dodecylhydroxyiminomethylpyridinium salts Ie - Ih above their critical micellar concentration (CMC). Considerable effect on the velocity of PNPDPP cleavage was observed when quaternary pyridinium aldoximes Ie - Ih were comicellized with inert cationic tenside hexadecyltrimethylammonium bromide (CTAB). 1-Dodecyl-3-hydroxyiminomethylpyridazinium salts IIb and IIc were unstable in aqueous solutions under the above-mentioned conditions.
Self-Degradable Hydrogel with Covalently Bound Proteolytic Enzyme
Authors: Rypáček František , Škarda Václav
Published: July 2002

Biodegradable hydrogel as a self-degradable system for controlled release of biologically active macromolecules was prepared from the biodegradable poly[N5-(2-hydroxyethyl)-L-glutamine-stat -N5-(2-methacryloyloxyethyl)-L-glutamine -stat-L-glutamic acid], to which a proteolytic enzyme, papain, was covalently bound. The polymer-enzyme conjugate was crosslinked by radical copolymerization with acrylamide. Significantly improved thermal stability and increased pH optimum of the catalytic activity of conjugated papain was observed. Self-degradation of the hydrogel by the action of encapsulated papain could be triggered by the addition of a low-molecular-weight enzyme activator, such as dithioerythritol.
The First Examples of Metallatricarbollides. Isomeric Twelve-Vertex Cyclopentadienyl Ferratricarbadodecaboranes [(η5-C5H5)-closo-FeC3B8H11]
Authors: Štíbr Bohumil , Holub Josef , Teixidor Francesc , Viñas Clara
Published: July 2002

The first metallatricarbollides, six isomeric twelve-vertex metallatricarbaboranes of general structure [(η5-C5H5)-closo-FeC3B8H11], are formed in the reaction between TI[nido-7,8,9-C3B8H11] and [(η5-C5H5)- Fe(CO)2I] in toluene at reflux. Two of them have so far been satisfactorily identified as [3-(η5-C5H5)-closo-3,1,2,4-FeC3B8H11] and [2-(η5-C5H5)-closo-2,1,8,11-FeC3B8H11] by NMR spectroscopy.
Assessing the Effect of Ligand Proximity on Chiroptical and Other Properties in Cobalt(III) Model, Tyrosine-Like Complexes
Authors: Jursík František , Archer Ronald D.
Published: July 2002

A series of new cobalt(III) octahedral complexes of the general formula Na[Co(ohb-aa)2] (ohb-aa = N-(o-hydroxybenzyl)amino acid anion); amino acid = glycine, (S)-α-alanine, α-aminoisobutyric acid, (S)-valine, (S)-norvaline and (S)-leucine) were prepared by the charcoal catalyzed reaction of the appropriate ligand with [Co(NH3)6]3+ in alkaline aqueous solution. Complexes obtained have, regardless of the amino acid used, the same facial all-trans symmetry (CoN2O4 chromophore) with the vicinal effects as the entire source of the optical activity. 13C NMR spectra reveal that the leucine derivative has, due to the steric reasons, a different ground state structure. Absorption maxima reflect a positive inductive effect from the amino acid side chain carbon atoms. Complexes of the ligands bearing electrophobic alkyl groups exhibit more negative E1/2 in comparison with the glycine derivative, reduction of which occurs at a more positive potential. Reduction potentials do not correlate with cobalt(III) Lewis acidity modulated by ligands.
Synthesis and Antituberculotic Properties of Some Substituted Pyrazinecarbothioamides
Authors: Doležal Martin , Hartl Jiří , Lyčka Antonín , Buchta Vladimír , Odlerová Želmíra
Published: July 2002

A series of N-substituted 3-amino-5-thiocarbamoyl-2-pyrazinecarboxamides was prepared. The structure of compounds was confirmed by elemental analysis, IR and 1H NMR spectra. The results of in vitro antifugal and antimycobacterial susceptibility testing shown no activity against pathogenic fungi and some effect on mycobacteria. The highest antituberculotic activity (MIC within 25-50 mg ml-1) against Mycobacterium tuberculosis and other mycobacterial strains in this series was shown by 3-(3-hydroxyphenylamino)-5-thiocarbamoyl-2-pyrazinecarboxamide. The antituberculotic activity of these compounds is mostly influenced by the presence of the thioamide moiety.
Extremes in Dependences of Enthalpy and Entropy of Saturated Vapour on Temperature
Authors: Novák Josef P. , Malijevský Anatol , Dědek Jaroslav , Oldřich Jiří
Published: July 2002

It was proved that the enthalpy of saturated vapour as a function of temperature has a maximum for all substances. The dependence of the entropy of saturated vapour on temperature can be monotonous, has a minimum and a maximum, or has only a maximum. The thermodynamic relations were derived for the existence of the extremes which enable their computation from the knowledge of dependence of the ideal-gas heat capacity on temperature and an equation of state. A method based on the theorem of corresponding states was proposed for estimating the extremes, and its results were compared with literature data. The agreement between the literature and estimated temperatures corresponding to the extremes is very good. The procedure proposed can serve for giving precision to the H-p and T-S diagrams commonly used in applied thermodynamics.
Equilibrium Studies of Alkyltin(IV) Complexes with D-Glucosamine
Authors: Shoukry Mohamed M. , El-Medani Samir M.
Published: July 2002

The acid-base and complex-formation equilibria involving glucosamine and its complexes with alkyltin(IV) chlorides have been studied by potentiometric technique. The results prove to a formation of 1 : 1 complex with trialkyltin(IV) and both 1 : 1 and 1 : 2 complexes with dialkyltin(IV) species. The stability constants in water were determined, the effects of temperature (from 15 to 35 °C) and ethanol (up to 88 vol.%) was studied and the speciation of the complexes was resolved.
Complexes of Mercury(II) with Tetraethyl 2,2'-Bipyridyl-4,4'-diphosphonate
Authors: Vojtíšek Pavel , Rohovec Jan , Lukeš Ivan
Published: July 2002

Complexes [Hg(bipyP2)Br2] (2), [Hg(bipyP2)BrCl] (3), and [Hg(bipyP2)Cl2] (4), where bipyP2 is tetraethyl 2,2'-bipyridyl-4,4'-diphosphonate (1), were prepared and their crystal structures were determined. Coordination of the phosphonate group was only found in 4. In this compound, the coordination sphere of Hg(II) contains two Cl atoms, two N atoms from the bipyridine chelate and O atom from phosphonate group and thus, the coordination number is five. The presence of Br atoms in the coordination sphere of complexes 2 and 3 results in the formation of tetrahedral environment (coordination number four) without any interaction with phosphonate. The coordination of the phosphonate group in 4 was also confirmed by IR spectroscopy.
Synthesis, Characterization and Theoretical Evaluation of [Ti(NC4Me4)(NMe2)3] - A Complex with N-Bonded 2,3,4,5-Tetramethylpyrrolyl Ligand
Authors: Dias Alberto R. , Galvão Adelino M. , Galvão Ana C.
Published: July 2002

The complex [Ti(NC4Me4)(NMe2)3] has been synthesized, characterized by mass spectrometry, 1H and 13C NMR and theoretically studied by ab initio molecular orbital calculations. The N-σ-coordination mode of the heterocyclic ring was predicted by the 13C NMR data and confirmed by the optimized geometry of the model complex [Ti(NC4H4)(NMe2)3]. The different bonding modes of the 2,3,4,5-tetramethylpyrrolyl ligand are discussed.
Synthesis of Some 6-Substituted 5-Azacytidines
Authors: Hanna Naeem B. , Masojídková Milena , Fiedler Pavel , Pískala Alois
Published: July 2002

Protected 6-substituted benzyl, phenyl and chloromethyl derivatives of 5-azacytidine 8-10 have been prepared by addition of phenylacetyl- (2), benzoyl- (3) or (chloroacetyl)guanidine (4) to 2,3,5-tri-O-benzoyl-β-D-ribosyl isocyanate (1) and subsequent silylation-mediated cyclization of the obtained acyl(carbamoyl)guanidines 5-7. 4-Amino-6-phenyl-1,3,5-triazin-2(1H)-one (12) was obtained by condensation of carbamoylguanidine (13) with methyl benzoate in presence of methanolic sodium methoxide or by condensation of 13 with triethyl orthobenzoate in N,N-dimethylformamide. Stannic chloride catalyzed condensation of silylated 6-phenyl derivative 11 with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribose (14) in 1,2-dichloroethane afforded a 1.2 : 1 mixture of N1 and N3 nucleosides 9 and 15, respectively. Methanolysis of the protected compounds 8-10 and 15 gave the respective free nucleosides 16-19. The latter compounds inhibited the growth of bacteria E. coli B to a much lower extent than the unsubstituted 5-azacytidine.
Solubility and Thermodynamic Transfer Functions of Cesium Dianilinetetraisothiocyanatochromate(III)
Authors: Holba Vladislav
Published: July 2002

The solubilities of cesium dianilinetetraisothiocyanatochromate(III) in water as well as in aqueous methanol, isopropyl alcohol, tert-butyl alcohol and acetonitrile were measured as a function of temperature and solvent composition. The Gibbs energies, enthalpies and entropies of transfer of the salt from water to the given solvents have been evaluated from experimental data. The contribution of [Cr(C6H5NH2)2(NCS)4]- ion to the Gibbs energy of transfer of the investigated salt has been calculated using the tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption.
Single-Root Multireference Brillouin-Wigner Coupled-Cluster Theory. Rotational Barrier of the Ethylene Molecule
Authors: Mášik Jozef , Mach Pavel , Urban Ján , Polášek Martin , Babinec Peter , Hubač Ivan
Published: July 2002

Recently developed single-root multireference Brillouin-Wigner coupled cluster (MR BWCC) theory is applied to study the rotational barrier of the ethylene molecule. The method belongs to a broad family of state-selective coupled-cluster (CC) methods and may be considered as a bridge connecting the single-reference and multireference CC theories. In a highly nondegenerate case, it becomes identical with the standard single-reference CC method while in a quasi-degenerate case gives results very close to the Hilbert space MR CC method. The method switches between the two cases in a continuous way, providing thus smooth potential energy surfaces, not plagued by intruder states. The rotation about the double bond in ethylene represents a typical two-state problem. To demonstrate abilities of our approach, we study the rotation barrier using the single-root MR BWCC theory at the CCSD level of approximation and the results are compared with other CC methods.
Dendrimers Based on Electroactive Metal Complexes. A Review of Recent Advances
Authors: Juris Alberto , Venturi Margherita , Ceroni Paola , Balzani Vincenzo , Campagna Sebastiano , Serroni Scolastica
Published: July 2002

Recent studies in the field of dendrimers based on electroactive metal complexes are reviewed. The electroactive units may be present (i) in the core, (ii) in the branches, (iii) in the surface, (iv) in the core and in the branches, (v) in the core and in the surface, (vi) in the branches and in the surface, and (vii) in the core, branches and surface. Depending on the dendrimer structure, the electroactive units can either interact or behave independently. The most interesting features are the shielding of electroactive cores by non electroactive branches, the great number of electrons that can be exchanged in a very narrow potential region by high generation surface-functionalized dendrimers, and the tailor-made redox patterns that can be obtained by dendrimers based on metal complexes at each branching centre. A review with 42 references.
Experimental and Theoretical Studies of Rotational Barriers in Aceto-, N-Methylaceto- and N-Phenylacetohydroxamic Acid
Authors: Brown David A. , Cuffe Laurence P. , Fitzpatrick Geraldine M. , Fitzpatrick Noel J. , Glass William K. , Herlihy Kara M.
Published: July 2002

Experimental and theoretical calculations for the E and Z forms of aceto-, N-methylaceto- and N-phenylacetohydroxamic acid are reported. The experimental method was NMR spectroscopy, while the computational methods included Hartree-Fock, Møller-Plesset and density functional theory calculations, with and without solvation, using either the Onsager or Tomasi's PCM method. In all calculations zero point energy corrections were included. The computed results when compared with the experimental ones show that, irrespective of the method used, the differences in the rotational barriers, ∆(E-TS) and ∆(Z-TS), are slight and below the 3 kcal mol-1 limit of the theoretical methods. In general the results using the PCM method were worse than the ones obtained from gas phase calculations or using the Onsager method, even though the PCM method is computationally most expensive. The calculations show, using either the Hartree-Fock or the B3LYP approach, that considering solvation using the Onsager method improves agreement with the experiment results. The calculated barrier heights, excluding the PCM method, agree broadly with the experimental results. Thus using the Onsager approach or gas phase calculations adequate results for barrier heights, but not for relative differences, were obtained.
Giant retinal tears resulting from eye gouging in rugby football
Authors: Duguid I G M , Leaver P K
Published: July 2002

A 29 year old myopic man sustained two separate giant retinal tears in his right eye following deliberate eye gouging during a rugby tackle. These were successfully repaired by vitrectomy and intraocular silicone oil injection. Although the postoperative course was complicated by pupil block glaucoma, he regained corrected visual acuity of 6/5 after oil removal. This injury highlights the potentially sight threatening nature of this type of rugby injury and the importance of early referral for specialist treatment.
Decreasing landing forces: effect of instruction
Authors: McNair Peter J , Prapavessis Harry , Callender Karen
Published: July 2002

Objective—To examine the effects of instructions related to joint kinematics, auditory stimuli, and imagery on lowering the vertical ground reaction forces associated with landing from a jump.

Study Design—Randomised controlled trial.

Setting—A laboratory in an educational institution.

Subjects—Eighty asymptomatic subjects (27 men) with a mean age of 24 years.

Intervention—Subjects were randomly assigned to the following groups: (1) instruction (limb position instructions); (2) auditory cue (listen to impact sounds); (3) imagery (metaphorical); (4) control. Subjects were required to jump from a box 300 mm in height and land on a force plate. Measures of the ground reaction force were recorded before and after the intervention.

Main Outcome Measure—The peak vertical ground reaction force recorded at footstrike.

Results—The peak vertical ground reaction forces in the technical instruction and auditory groups were significantly less than those of the control group. There was no significant difference between the auditory and technical instruction groups. There was no significant difference between the imagery and control groups.

Conclusions—When an aim of a rehabilitation programme is to minimise forces on the lower limb during landing type activities, the findings support the use of instructions related to kinematics as well as instructions that draw the patient's attention to the sound at impact.
Tai chi: physiological characteristics and beneficial effects on health
Authors: Li J X , Hong Y , Chan K M
Published: July 2002

Objectives—To assess the characteristic effects of Tai Chi Chuan (TCC) exercise on metabolism and cardiorespiratory response, and to measure its effect on cardiorespiratory function, mental control, immune capacity, and the prevention of falls in elderly people.

Design—A review of controlled experimental studies and clinical trials designed with one of two aims: either to assess physiological responses during the performance of TCC or to assess the impact of this exercise on general health and fitness.

Main outcome measures—Metabolic rate, heart rate, blood pressure, ventilation, maximal oxygen uptake (V̇o2max), immune capacity, falls, and fall related factors.

Subjects—A total of 2216 men and women.

Results—Under review were 31 original studies, published in Chinese or English journals, that met the criteria for inclusion. Most of the papers written in Chinese had not been introduced into the Western literature. Nine of these studies showed that TCC can be classified as moderate exercise, as its does not demand more than 55% of maximal oxygen intake. When this form of exercise and others conducted at equal intensity were compared, TCC showed a significantly lower ventilatory equivalent (V̇e/V̇o2max). Evidence provided by cross sectional and longitudinal studies suggests that TCC exercise has beneficial effects on cardiorespiratory and musculoskeletal function, posture control capacity, and the reduction of falls experienced by the elderly.

Conclusions—TCC is a moderate intensity exercise that is beneficial to cardiorespiratory function, immune capacity, mental control, flexibility, and balance control; it improves muscle strength and reduces the risk of falls in the elderly.
Dependence of the maximal lactate steady state on the motor pattern of exercise
Authors: Beneke R , Leithäuser R M , Hütler M
Published: July 2002

Background—Blood lactate concentration (BLC) can be used to monitor relative exercise intensity. The highest BLC representing an equilibrium between lactate production and elimination is termed maximal lactate steady state (MLSS). MLSS is used to discriminate qualitatively between continuous exercise, which is limited by stored energy, from other types of exercise terminated because of disturbance of cellular homoeostasis.

Aim—To investigate the hypothesis that MLSS intraindividually depends on the mode of exercise.

Methods—Six junior male rowers (16.5 (1.4) years, 181.7 (3.1) cm, 69.8 (3.3) kg) performed incremental and constant load tests on rowing and cycle ergometers. Measurements included BLC, sampled from the hyperaemic ear flap, heart rate, and oxygen uptake. MLSS was defined as the highest BLC that increased by no more than 1.0 mmol/l during the final 20 minutes of constant workload.

Results—In all subjects, MLSS was lower (p≤0.05) during rowing (2.7 (0.6) mmol/l) than during cycling (4.5 (1.0) mmol/l). No differences between rowing and cycling were found with respect to MLSS heart rate (169.2 (9.3)v172.3 (6.7) beats/min), MLSS workload (178.7 (29.8)v205.0 (20.7) W), MLSS intensity expressed as a percentage (63.3 (6.6)%v68.6 (3.8)%) of peak workload (280.8 (15.9)v299.2 (28.4) W) or percentage (76.4 (3.4)%v75.1 (3.0)%) of peak oxygen uptake (60.4 (3.4)v57.2 (8.6) ml/kg/min).

Conclusions—In rowing and cycling, the MLSS but not MLSS workload and MLSS intensity intraindividually depends on the motor pattern of exercise. MLSS seems to decrease with increasing mass of the primarily engaged muscle. This indicates that task specific levels of MLSS occur at distinct levels of power output per unit of primarily engaged muscle mass.
Syncopal episodes in a young amateur body builder
Authors: Manoharan G , Campbell N P S , O'Brien C J
Published: July 2002

A 36 year old male weight training enthusiast suffered several syncopal episodes. An electrocardiogram confirmed atrial fibrillation with normal ventricular response. The patient admitted to taking anabolic steroids and bromocriptine. The atrial fibrillation was considered to be due to bromocriptine misuse.
Lactic acidosis, potassium, and the heart rate deflection point in professional road cyclists
Authors: Lucía A , Hoyos J , Santalla A , Pérez M , Carvajal A , Chicharro J L
Published: July 2002

Objective: To determine the influence of lactic acidosis, the Bohr effect, and exercise induced hyperkalaemia on the occurrence of the heart rate deflection point (HRDP) in elite (professional) cyclists.

Methods: Sixteen professional male road cyclists (mean (SD) age 26 (1) years) performed a ramp test on a cycle ergometer (workload increases of 5 W/12 s, averaging 25 W/min). Heart rate (HR), gas exchange parameters, and blood variables (lactate, pH, P50of the oxyhaemoglobin dissociation curve, and K+) were measured during the tests.

Results: A HRDP was shown in 56% of subjects at about 88% of their maximal HR (HRDP group; n = 9) but was linear in the rest (No-HRDP group; n = 7). In the HRDP group, the slope of the HR-workload regression line above the HRDP correlated inversely with levels of K+at the maximal power output (r= −0.67; p<0.05).

Conclusions: The HRDP phenomenon is associated, at least partly, with exercise induced hyperkalaemia.
Background electroencephalographic (EEG) activities of very preterm infants born at less than 27 weeks gestation: a study on the degree of continuity
Authors: Hayakawa M , Okumura A , Hayakawa F , Watanabe K , Ohshiro M , Kato Y , Takahashi R , Tauchi N
Published: July 2002

AIMS

To clarify the features of the background electroencephalographic (EEG) activities in clinically well preterm infants born at less than 27 weeks gestation and to outline their chronological changes with increasing postconceptional age (PCA).

METHODS

EEGs of clinically well premature infants born at less than 27 weeks gestation were recorded during the early postnatal period. The infants were separated into three groups according to their PCA at the time of EEG recording (21–22 weeks PCA, 23–24 weeks PCA, and 25–26 weeks PCA). The mean and maximum duration of interburst intervals (IBIs), the mean duration of bursts, and the percentage of continuous and discontinuous patterns in each PCA group were evaluated.

RESULTS

There were three infants at 21–22 weeks PCA, seven at 23–24 weeks PCA, and five at 25–26 weeks PCA. Eighteen EEG recordings were obtained. The mean and maximum IBI duration decreased with increasing PCA. The percentage of continuous patterns increased with increasing PCA. Conversely, the percentage of discontinuous patterns decreased with increasing PCA.

CONCLUSIONS

In premature infants born at less than 27 weeks gestation, the characteristics of the background EEG activities were similar to those of older premature infants. These changes reflect the development of the central nervous system in this period.

Key messages

At less than 27 weeks gestational age, the characteristics of background EEG activities were found to be as follows:

the mean and maximum IBI duration decreased with increasing PCA

the percentage of continuous patterns increased with increasing PCA

the percentage of discontinuous patterns increased with increasing PCA

the mean burst duration during discontinuous patterns increased as PCA increased