bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct Requirement for Two Stages of Protein-Primed Initiation of Reverse Transcription in Hepadnaviruses
Authors: Wang Xingtai , Hu Jianming
Published: July 2002

Reverse transcription in hepadnaviruses is primed by the viral reverse transcriptase (RT) (protein priming) and requires the specific interaction between the RT and a viral RNA signal termed ε, which bears the specific template sequence for protein priming. The product of protein priming is a short oligodeoxynucleotide which represents the 5′ end of the viral minus-strand DNA and is covalently attached to the RT. We have now identified truncated RT variants from the duck hepatitis B virus that were fully active in the initial step of protein priming, i.e., the covalent attachment of the first nucleotide to the protein (RT deoxynucleotidylation), but defective in any subsequent DNA polymerization. A short sequence in the RT domain was localized that was dispensable for RT deoxynucleotidylation but essential for the subsequent DNA polymerization. These results have thus revealed two distinct stages of protein priming, i.e., the initial attachment of the first nucleotide to the RT (RT deoxynucleotidylation or initiation of protein priming) and the subsequent DNA synthesis (polymerization) to complete protein priming, with the second step entailing additional RT sequences. Two models are proposed to explain the observed differential sequence requirement for the two distinct stages of the protein priming reaction.
The 2-Kilobase Intron of the Herpes Simplex Virus Type 1 Latency-Associated Transcript Has a Half-Life of Approximately 24 Hours in SY5Y and COS-1 Cells
Authors: Thomas Darby L. , Lock Martin , Zabolotny Janice M. , Mohan Bangalore R. , Fraser Nigel W.
Published: July 2002

The herpes simplex virus type 1 (HSV-1) 2-kb latency-associated transcript (LAT) is a stable intron, which accumulates in cells both lytically and latently infected with HSV-1. We have used a tetracycline-repressible expression system to determine the half-life of the 2-kb LAT RNA intron in the human neuroblastoma cell line SY5Y. Using Northern hybridization analyses of RNA isolated from transiently transfected SY5Y cells over time after repression of LAT expression, we measured the half-life of the 2-kb LAT to be approximately 24 h. Thus, unlike typical introns that are rapidly degraded in a matter of seconds following excision, the 2-kb LAT intron has a half-life similar to those of some of the more stable cellular mRNAs. Furthermore, a similar half-life was measured for the 2-kb LAT in transiently transfected nonneuronal monkey COS-1 cells, suggesting that the stability of the 2-kb LAT is neither cell type nor species specific. Previously, we found that the determinant responsible for the unusual stability of the 2-kb LAT maps to the 3′ terminus of the intron. At this site is a nonconsensus intron branch point located adjacent to a predicted stem-loop structure that is hypothesized to prevent debranching by cellular enzymes. Here we show that mutations which alter the predicted stem-loop structure, such that branching is redirected, either reduce or abolish the stability of the 2-kb LAT intron.
Critical Role for Perforin-, Fas/FasL-, and TNFR1-Mediated Cytotoxic Pathways in Down-Regulation of Antigen-Specific T Cells during Persistent Viral Infection
Authors: Zhou Shenghua , Ou Rong , Huang Lei , Moskophidis Demetrius
Published: July 2002

Viral persistence following infection with invasive strains of lymphocytic choriomeningitis virus (LCMV) can be achieved by selective down-regulation of virus-specific T lymphocytes. High viral burden in the onset of infection drives responding cells into functional unresponsiveness (anergy) that can be followed by their physical elimination. In this report, we studied down-regulation of the virus-specific CD8+-T-cell response during persistent infection of adult mice with LCMV, with emphasis on the role of perforin-, Fas/FasL-, or tumor necrosis factor receptor 1 (TNFR1)-mediated cytolysis in regulating T-cell homeostasis. The results reveal that the absence of perforin, Fas-ligand, or TNFR1 has no significant effect on the kinetics of proliferation and functional inactivation of virus-specific CD8+T cells in the onset of chronic LCMV infection. However, these molecules play a critical role in the homeostatic regulation of T cells, influencing the longevity of the virus-specific CD8+-T-cell population once it has become anergic. Thus, CD8+T cells specific to the dominant LCMV NP396–404epitope persist in an anergic state for at least 70 days in perforin-, FasL-, or TNFR1-deficient mice, but they were eliminated by day 30 in C57BL/6 controls. These effects were additive as shown by a deficit of apoptotic death of NP396–404peptide-specific CD8+T cells in mice lacking both perforin and TNFR1. This suggests a role for perforin-, FasL-, and TNFR1-mediated pathways in down-regulation of the antiviral T cell response during persistent viral infection by determining the fate of antigen-specific T cells. Moreover, virus-specific anergic CD8+T cells in persistently infected C57BL/6 mice contain higher levels of Bcl-2 and Bcl-XL than functionally intact T cells generated during acute LCMV infection. In the case of proapoptotic factors, Bax expression did not differ between T-cell populations and Bad was below the limit of detection in all samples. As expression of the Bcl-2 family members controls susceptibility to apoptosis, this finding may provide a molecular basis for the survival of anergic cells under conditions of prolonged antigen stimulation.
Structure of Equine Infectious Anemia Virus Matrix Protein
Authors: Hatanaka Hideki , Iourin Oleg , Rao Zihe , Fry Elizabeth , Kingsman Alan , Stuart David I.
Published: July 2002

The Gag polyprotein is key to the budding of retroviruses from host cells and is cleaved upon virion maturation, the N-terminal membrane-binding domain forming the matrix protein (MA). The 2.8-Å resolution crystal structure of MA of equine infectious anemia virus (EIAV), a lentivirus, reveals that, despite showing no sequence similarity, more than half of the molecule can be superimposed on the MAs of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV). However, unlike the structures formed by HIV-1 and SIV MAs, the oligomerization state observed is not trimeric. We discuss the potential of this molecule for membrane binding in the light of conformational differences between EIAV MA and HIV or SIV MA.
Nuclear Interactions Are Necessary for Translational Enhancement by Spleen Necrosis Virus RU5
Authors: Dangel Andrew W. , Hull Stacey , Roberts Tiffiney M. , Boris-Lawrie Kathleen
Published: July 2002

The 5′ long terminal repeat of spleen necrosis virus (SNV) facilitates Rev/Rev-responsive element (RRE)-independent expression of intron-containing human immunodeficiency virus type 1 (HIV-1)
gag
. The SNV RU5 region, which corresponds to the 165-nucleotide 5′ RNA terminus, functions in a position- and orientation-dependent manner to enhance polysome association of intron-containing HIV-1
gag
RNA and also nonviral
luc
RNA. Evidence is mounting that association with nuclear factors during intron removal licenses mRNAs for nuclear export, efficient translation, and nonsense-mediated decay. This project addressed the relationship between the nuclear export pathway of SNV RU5-reporter RNA and translational enhancement. Results of RNA transfection experiments suggest that cytoplasmic proteins are insufficient for SNV RU5 translational enhancement of
gag
or
luc
RNA. Reporter gene assays, leptomycin B (LMB) sensitivity experiments, and RNase protection assays indicate that RU5
gag
RNA accesses a nuclear export pathway that is distinct from the LMB-inhibited leucine-rich nuclear export sequence-dependent CRM1 pathway, which is used by the HIV-1 RRE. As a unique tool with which to investigate the relationship between different RNA trafficking routes and translational enhancement, SNV RU5 and Rev/RRE were combined on a single
gag
RNA. We observed a less-than-synergistic effect on cytoplasmic mRNA utilization. Instead, Rev/RRE diverts RU5
gag
RNA to the CRM1-dependent, LMB-inhibited pathway and abrogates translational enhancement by SNV RU5. Our study is the first to show that a nuclear factor(s) directs SNV RU5-containing RNAs to a distinct export pathway that is not inhibited by LMB and programs the intron-containing transcript for translational enhancement.
Effects of Mutations in the Adenoviral E1B 55-Kilodalton Protein Coding Sequence on Viral Late mRNA Metabolism
Authors: Gonzalez Ramon A. , Flint S. J.
Published: July 2002

The human subgroup C adenoviral E1B 55-kDa protein cooperates with the viral E4 Orf6 protein to induce selective export of viral, late mRNAs from the nucleus to the cytoplasm. Previous studies have suggested that such preferential transport of viral mRNA and the concomitant inhibition of export of cellular mRNAs are the result of viral colonization of specialized microenvironments within the nucleus. However, neither the molecular basis of this phenomenon nor the mechanism by which the E1B 55-kDa protein acts has been elucidated. We therefore examined viral late mRNA metabolism in HeLa cells infected with a series of mutant viruses that carry insertions at various positions in the E1B protein coding sequence (P. R. Yew, C. C. Kao, and A. J. Berk, Virology 179:795-805, 1990). All the mutations examined impaired cytoplasmic accumulation of viral L2 mRNAs and reduced L2 mRNA export efficiency. However, in most cases these defects could be ascribed to reduced E1B 55-kDa protein concentration or the unexpected failure of the altered E1B proteins to enter the nucleus efficiently. The latter property, the pleiotropic defects associated with all the mutations that impaired nuclear entry of the E1B protein, and consideration of its primary sequence suggest that these insertions result in misfolding of the protein. Insertion of four amino acids at residue 143 also inhibited viral mRNA export but resulted in increased rather than decreased accumulation of the E1B 55-kDa protein in the nucleus. This mutation specifically impaired the previously described association of the E1B protein with intranuclear structures that correspond to sites of adenoviral DNA replication and transcription (D. Ornelles and T. Shenk, J. Virol. 65:424-439, 1991) and the colocalization of the E1B and E4 Orf6 proteins. As this insertion has been shown to inhibit the interaction of the E1B with the E4 Orf6 protein in infected cell extracts (S. Rubenwolf, H. Schütt, M. Nevels, H. Wolf, and T. Dobner, J. Virol. 71:1115-1123, 1997), these phenotypes provide direct support for the hypothesis that selective viral mRNA export is determined by the functional organization of the infected cell nucleus.
Mechanism of the Facilitated Ion Transfer Across a Liquid/Liquid Interface
Authors: Sabela Alfréd , Mareček Vladimír , Koryta Jiří , Samec Zdeněk
Published: July 2002

The facilitated transfer of sodium ion across the water/nitrobenzene interface was examined by faradaic impedance measurements at the thermodynamic equilibrium potential. Kinetic data for the interfacial reaction Na+(w) + L(n) ↔ NaL+(n) (L = dibenzo-18-crown-6, w = water, n = nitrobenzene) were confronted with the theoretical predictions for three possible reaction mechanisms, and a conclusion was reached that the reaction occurs via a single electrochemical step. Its pseudo-first order rate constant depends on the interfacial potential difference and falls between 0.01 and 1 cm s-1, i.e. it is comparable with the first order rate constant for a simple ion transfer.
Effect of Triton X100 on Tetramethylammonium Ion Transport Kinetics Through the Water/Nitrobenzene Interface
Authors: Wawrzynczak Wojciech S. , Figaszewski Zbigniew
Published: July 2002

The tetramethylammonium cation (TMA+) transport through the water/nitrobenzene interface modified by the Triton X100 (TX100) adsorption has been investigated using cyclic voltammetry and interfacial tension measurements. Obtained results indicate the strong adsorption of TX100 and its responsible effect on the TMA+ ion transfer. Adsorption data have been fitted to six theoretical adsorption isotherm equations with the best fitting for the Frumkin isotherm. The mechanism of facilitating effect of TX100 on the TMA+ transfer has been proposed. The suggested mechanism is different from that developed by other authors.
Electrochemical Dissolution of Iron(III) Hydroxy-Oxides: More Information About the Particles
Authors: Grygar Tomáš
Published: July 2002

The process of reductive dissolution of α-Fe2O3, Ba-hexaferrite, α-FeOOH, γ-Fe2O3, γ-FeOOH, and ferrihydrite can be monitored continuously by abrasive stripping voltammetry and chronoamperometry to obtain information about homogeneity of reactivity and about the particle size of the pure phases and mixtures. Phase parameters (rate constant and charge transfer coefficient) and the geometrical factor γ, which is independent on the specific surface area, can be assigned to a phase-pure sample in the given medium. Differences in reactivity of the hydroxy-oxides are documented, and the dependence of reactivity of the α-Fe2O3 samples on the preparation procedure is characterized. The electrochemical techniques can also be employed to investigate changes in the particles during phase transformations.
Pitzer Model Based Study of CsX-NiX2-H2O (X = Cl, Br) Systems at 298.15 K
Authors: Christov Christomir
Published: July 2002

The Pitzer ion-interaction model was used for simulating the CsX-NiX2-H2O (X = Cl, Br) systems at 298.15 K. The necessary thermodynamic functions (binary and ternary parameters, thermodynamic solubility products) were calculated and the theoretical solubility diagrams plotted. A very good agreement was found between the calculated and observed data.
Chemometric Analysis of Substituent Effects. XII. Application of Relationship Between 2- and 4-Substitution of Benzene Ring to Study ortho Effect in Selected Compounds with Different Reaction Centres
Authors: Pytela Oldřich , Prusek Ondřej
Published: July 2002

Three model compounds have been selected to study the relationship between ortho and para substitution: benzoic acid, phenol, and aniline. Sixteen substituents have been chosen involving also those capable of potential interaction between ortho substituent and the reaction centre. For the combinations given, literature presents 25 pairs of data obtained by measuring a particular process for both the ortho and para substituted derivatives. The missing dissociation constants of 16 ortho substituted benzoic acids in water and ethanol and 16 para substituted benzoic acids in dimethyl sulfoxide and pyridine have been measured by potentiometric titration. The data matrices were submitted to analysis by the methods of projection of latent structures (PLS) and principal component analysis (PCA). It has been found that the substituent effects from ortho and para positions have the same character unless the ortho substituents interact with the reaction centre. Such interactions can change the experimentally found value by as much as 20% of its magnitude. The most significant interaction is a hydrogen bond formation. Out of the three models studied the most extensive interactions are present in benzoic acid, whereas almost none were observed in aniline. The capability of donation of electron pair to a hydrogen bond decreases in the substituent series COCH3 > SO2CH3 > NO2. The capability of donation of proton to a hydrogen bond with electron-pair donor decreases in the substituent series OH > NHCOCH3 ≈ SH > NH2 > SO2NH2.
Theory of Second- and Third-Order Reciprocal Derivative Chronopotentiometry for a Reversible Reaction
Authors: Bi Shuping , Chen Jian , Xing Xiaolan , Yu Jiong
Published: July 2002

Equations describing the second- and third-order reciprocal derivative chronopotentiometric curves, dt/dE vs E are deduced for a reversible reaction. Theoretical calculated values are verified experimentally.
Investigation on Cyclic Reciprocal Derivative Chronopotentiometry. Part II. Theoretical Equation for an Irreversible Reaction
Authors: Bi Shuping , Chen Jian , Chen Tao
Published: July 2002

A rigorous mathematical analysis is presented for an irreversible electrode process in the cyclic reciprocal derivative chronopotentiometry. Influences of basic electrochemical parameters, such as transfer coefficient α, rate constant ks, current density j, number of the electrons involved in the electrode reaction n and reactant concentration c0• on the properties of the dt/dE-E chronopotentiogram are described.
Viscosities of Binary and Ternary Aqueous Solutions of 2-Amino-2-methylpropan-1-ol, 2-Amino-2-methylpropane-1,3-diol, and 2-Amino-2-methylpropan-1-ol Hydrochloride
Authors: Chenlo Francisco , Moreira Ramón , Pereira Gerardo , Vázquez María-José
Published: July 2002

Kinematic viscosities of aqueous solutions of 2-amino-2-methylpropan-1-ol (AMP), 2-amino-2-methylpropane-1,3-diol (AMPD), or 2-amino-2-methylpropan-1-ol hydrochloride (AMP-HCl) and aqueous ternary solutions (AMP and AMPD) and (AMP and AMP-HCl) were measured in the molality range from 0 to 2.5 mol kg-1 (0.5 mol kg-1 intervals) and temperatures from 293.1 to 323.1 K (5.0 K intervals). The viscosity data were correlated with concentration and temperature by empirical equations with deviations up to 1.4 and 3.3% for binary and ternary aqueous solutions, respectively.
Necropsies in African children: consent dilemmas for parents and guardians
Authors: Lishimpi K , Chintu C , Lucas S , Mudenda V , Kaluwaji J , Story A , Maswahu D , Bhat G , Nunn A J , Zumla A
Published: July 2002

BACKGROUND

Necropsy examination provides a good index of the accuracy of clinical diagnosis and the quality of treatment, but its use in sub-Saharan Africa is limited.

AIMS

To identify the main reasons for parents'/guardians' refusal of consent for necropsy and to explore the issues affecting their decision.

METHODS

A sequential necropsy study of Zambian children between 2 months and 15 years dying of respiratory disease. When the parent/guardian refused permission for necropsy, the main reason given was recorded, after encouragement to express their specific concerns in their own words.

RESULTS

Parents/guardians of 891 of 1181 children (75.4%) refused to give permission, and 290 (24.6%) consented. Of those who refused, 43% did so on the grounds that it would be a “waste of time,” as the diagnosis should have been made in life and the findings would now be of no benefit to them. More than one quarter of those who refused did so because a death certificate had already been issued and arrangements to transport the body had been made and could not be delayed. Traditional beliefs that ancestral spirits forbade the mutilation of dead bodies were cited by 77 (8.6%). Other reasons included the child not being their own or that they must seek permission from other family members who were not available (6%). Religious beliefs were not a major cause of refusal.

CONCLUSIONS

It is possible to achieve a rate of necropsy consent sufficient to undertake valuable clinical pathology studies on children in sub-Saharan Africa. The wide range of reasons cited for refusal points to the diverse and complex interaction of social and cultural factors affecting attitudes to necropsy examination. Medical staff need training and support to improve the uptake of clinical pathology services.

Key messages

Worldwide necropsy rates are declining in both adults and children

Even in conditions where trained counsellors and rapid access to necropsy examination exist, rates of consent remain low

In Zambia, necropsy examination of children is most commonly perceived by parents/guardians as a waste of time and an inconvenience to arrangements for burial
Delayed union stress fractures of the anterior tibia: conservative management
Authors: Batt M E , Kemp S , Kerslake R
Published: July 2002

Introduction—A conservative method of treating four delayed union stress fractures of the anterior mid-tibia is described, with an illustrative case history.

Methods—Once diagnosed each of the patients was treated in a pneumatic lower leg brace with modified rest. The mean (range) age of the patients was 28 (24–32) years and all were involved in professional or amateur sports. The mean (range) duration of symptoms before diagnosis and definitive treatment of the four fractures was 9 (3–14) months.

Results—Use of this technique avoided the need for surgery in this group of patients and allowed return to unrestricted activity an average of 12 months from presentation.

Conclusion—The treatment is cost effective and avoids the often uncertain results and morbidity associated with surgery for these difficult stress fractures.
Abnormal regulation of the oestrogen receptor in benign breast lesions
Authors: Shoker B S , Jarvis C , Clarke R B , Anderson E , Munro C , Davies M P A , Sibson D R , Sloane J P
Published: July 2002

Background—In normal breast tissue the oestrogen receptor (ER) and the proliferation associated antigen Ki67 are negatively associated, indicating that ER+ cells are non-dividing, or that the receptor is downregulated as cells enter cycle. This relation is completely or partially lost in many ER+ breast cancers and in in situ proliferations associated with an increased cancer risk, where coexpression of the two markers is often found.

Aims—To determine whether similar changes can be identified in other risk associated breast lesions.

Patients/Methods—Paraffin wax blocks from 12 cases of lactational change, 21 apocrine metaplasias, 22 duct ectasias, 20 sclerosing adenosis, 20 fibroadenomas, 19 phyllodes tumours, 20 radial scars, 21 papillomas (15 solitary and six multiple), 15 gynaecomastias, and nine postmortem male breast tissues were retrieved. Immunohistochemistry was used to determine the expression of ER and dual labelling immunofluorescence was used to detect cells expressing both ER and Ki67.

Results—Increased numbers of ER+ cells were seen in sclerosing adenosis, radial scars, papillomas, fibroadenomas, and phyllodes tumours but not in apocrine cysts (where no ER+ cells were detected) or duct ectasia (where normal numbers were found). As in the normal breast, the proportion of ER+ cells increased with age in all lesions with the exception of fibroadenomas. Coexpression of ER and Ki67 was found in an increased proportion of cells of all risk associated lesions studied. ER+ cells were less likely to be dividing than ER− cells in all cases, although this was significant only for sclerosing adenosis. The data on sclerosing adenosis, radial scars, papillomas, and fibroadenomas are comparable with those reported previously in hyperplasia of usual type, whereas those in duct ectasia are similar to those of the normal breast. The findings in all lesions, however, differed from those in ductal carcinoma in situ, where proportions of ER+ and ER+/Ki67+ cells are higher and the relation between ER+ cell numbers and age is lost. Thus, the nature and degree of dysregulation of ER in benign breast lesions is broadly in accordance with the degree of risk of developing breast cancer with which they are associated. In gynaecomastia, the proportions of ER+ and ER+/Ki67+ cells were comparable with those seen in benign female breast lesions, but changes with age were not observed. However, the changes in gynaecomastia were similar to those seen in normal male breast.

Conclusion—These findings are in keeping with the contention that the dissociation of ER and Ki67 expression is a very early change in the pathway to many breast cancers. However, this change might only have preneoplastic importance in the hormonal milieu of the female breast.
Recurrence of Kikuchi's lymphadenitis after 12 years
Authors: Blewitt R W , Kumar S N , Abraham J S
Published: July 2002

A 40 year old woman developed recurrent Kikuchi's disease 12 years after the original episode. The recurrence affected the same site (axilla) and occurred after the longest delay so far recorded in a European resident. Care must be taken to avoid misdiagnosis of Kikuchi's disease as lymphoma.
A molecular linkage map of tomato displaying chromosomal locations of resistance gene analogs based on aLycopersicon esculentum×Lycopersicon hirsutumcross
Authors: Zhang L P , Khan A , Niño-Liu D , Foolad M R
Published: July 2002

A molecular linkage map of tomato was constructed based on a BC1population (N = 145) of a cross between Lycopersicon esculentum Mill. line NC84173 (maternal and recurrent parent) and Lycopersicon hirsutum Humb. and Bonpl. accession PI126445. NC84173 is an advanced breeding line that is resistant to several tomato diseases, not including early blight (EB) and late blight (LB). PI126445 is a self-incompatible accession that is resistant to many tomato diseases, including EB and LB. The map included 142 restriction fragment length polymorphism (RFLP) markers and 29 resistance gene analogs (RGAs). RGA loci were identified by PCR amplification of genomic DNA from the BC1population, using ten pairs of degenerate oligonucleotide primers designed based on conserved leucine-rich repeat (LRR), nucleotide binding site (NBS), and serine (threonine) protein kinase (PtoKin) domains of known resistance genes (R genes). The PCR-amplified DNAs were separated by denaturing polyacrylamide gel electrophoresis (PAGE), which allowed separation of heterogeneous products and identification and mapping of individual RGA loci. The map spanned 1469 cM of the 12 tomato chromosomes with an average marker distance of 8.6 cM. The RGA loci were mapped to 9 of the 12 tomato chromosomes. Locations of some RGAs coincided with locations of several known tomato R genes or quantitative resistance loci (QRLs), including Cf-1, Cf-4, Cf-9, Cf-ECP2, rx-1, and Cm1.1 (chromosome 1); Tm-1 (chromosome 2); Asc (chrromosme 3); Pto, Fen, and Prf (chromosome 5); OI-1, Mi, Ty-1, Cm6.1, Cf-2, CF-5, Bw-5, and Bw-1 (chromosome 6); I-1, I-3, and Ph-1 (chromosome 7); Tm-2a and Fr1 (chromosome 9); and Lv (chromosome 12). These co-localizations indicate that the RGA loci were either linked to or part of the known R genes. Furthermore, similar to that for many R gene families, several RGA loci were found in clusters, suggesting their potential evolutionary relationship with R genes. Comparisons of the present map with other molecular linkage maps of tomato, including the high density L. esculentum × Lycopersicon pennellii map, indicated that the lengths of the maps and linear order of RFLP markers were in good agreement, though certain chromosomal regions were less consistent than others in terms of the frequency of recombination. The present map provides a basis for identification and mapping of genes and QTLs for disease resistance and other desirable traits in PI126445 and other L. hirsutum accessions, and will be useful for marker-assisted selection and map-based gene cloning in tomato.Key words: disease resistance, genetic marker, molecular map, quantitative trait locus (QTL), restriction fragment length polymorphism (RFLP), RGAs.
Kinetic analysis of histone acetylation turnover and Trichostatin A induced hyper- and hypoacetylation in alfalfa
Authors: Waterborg Jakob H , Kapros Tamás
Published: July 2002

Dynamic histone acetylation is a characteristic of chromatin transcription. The first estimates for the rate of acetylation turnover of plants are reported, measured in alfalfa cells by pulse, pulse-chase, and steady-state acetylation labeling. Acetylation turnover half-lives of about 0.5 h were observed by all methods used for histones H3, H4, and H2B. This is consistent with the rate at which changes in gene expression occur in plants. Treatment with histone deacetylase inhibitor Trichostatin A (TSA) induced hyperacetylation at a similar rate. Replacement histone variant H3.2, preferentially localized in highly acetylated chromatin, displayed faster acetyl turnover. Histone H2A with a low level of acetylation was not subject to rapid turnover or hyperacetylation. Patterns of acetate labeling revealed fundamental differences between histone H3 versus histones H4 and H2B. In H3, acetylation of all molecules, limited by lysine methylation, had similar rates, independent of the level of lysine acetylation. Acetylation of histones H4 and H2B was seen in only a fraction of all molecules and involved multiacetylation. Acetylation turnover rates increased from mono- to penta- and hexaacetylated forms, respectively. TSA was an effective inhibitor of alfalfa histone deacetylases in vivo and caused a doubling in steady-state acetylation levels by 46 h after addition. However, hyperacetylation was transient due to loss of TSA inhibition. TSA-induced overexpression of cellular deacetylase activity produced hypoacetylation by 18 h treatment with enhanced acetate turnover labeling of alfalfa histones. Thus, application of TSA to change gene expression in vivo in plants may have unexpected consequences.
The promyelocytic leukemia nuclear body: sites of activity?
Authors: Eskiw Christopher H , Bazett-Jones David P
Published: July 2002

The promyelocytic leukemia (PML) nuclear body is one of many subnuclear domains in the eukaryotic cell nucleus. It has received much attention in the past few years because it accumulates the promyelocytic leukemia protein called PML. This protein is implicated in many nuclear events and is found as a fusion with the retinoic acid receptor RARα in leukemic cells. The importance of PML bodies in cell differentiation and growth is implicated in acute promyelocitic leukemia cells, which do not contain PML bodies. Treatment of patients with drugs that reverse the disease phenotype also causes PML bodies to reform. In this review, we discuss the structure, composition, and dynamics that may provide insights into the function of PML bodies. We also discuss the repsonse of PML bodies to cellular stresses, such as virus infection and heat shock. We interpret the changes that occur as evidence for a role of these structures in gene transcription. We also examine the role of the posttranslational modification, SUMO-1 addition, in directing proteins to this nuclear body. Characterization of the mobility of PML body associated proteins further supports a role in specific nuclear events, rather than the bodies resulting from random accumulations of proteins.Key words: promyelocytic leukemia, nucleus, transcription, nuclear bodies.
Finite element assessment of the effects of seismic loading rate on soil liquefaction
Authors: Popescu Radu
Published: July 2002

The influence of frequency content of seismic excitation on the extent and pattern of pore-water pressure build-up in saturated soil deposits is addressed. Seismic acceleration time histories are generated as uniformly modulated nonstationary stochastic processes, in accordance with prescribed response spectra and prescribed modulating functions. Based on numerical examples, it is shown that the interplay between the frequency content of seismic excitation and the dynamic characteristics of the soil system and their evolution during and after the earthquake have important implications on the dynamic response.Key words: seismic motion, frequency content, finite elements, soil dynamics.
Inhibition of rat lipoprotein lipid peroxidation by the oral administration of D003, a mixture of very long-chain saturated fatty acids
Authors: Menéndez R , Más R , Amor A M , Ledón N , Pérez J , González R M , Rodeiro I , Zayas M , Jiménez S
Published: July 2002

Previous results have demonstrated that policosanol, a mixture of aliphatic primary alcohols isolated and purified from sugar cane wax, whose main component is octacosanol, inhibited lipid peroxidation in experimental models and human beings. D003 is a defined mixture of very long-chain saturated fatty acids, also isolated and purified from sugar cane wax, whose main component is octacosanoic acid followed by traicontanoic, dotriacontanoic, and tetracontanoic acids. Since very long-chain fatty acids are structurally related to their corresponding alcohols, we investigated the effect of oral treatment with D003 (0.5, 5, 50, and 100 mg/kg) over 4 weeks in reducing the susceptibility of rat lipoprotein to oxidative modification. The combined rat lipoprotein fraction VLDL + LDL was subjected to several oxidation systems, including those containing metal ions (CuSO4), those having the capacity to generate free radicals 2,2-azobis-2-amidinopropane hydrochloride (AAPH), and a more physiological system (resident macrophages). D003 (5, 50, and 100 mg/kg) significantly inhibited copper-mediated conjugated-diene generation in a concentration-dependent manner. D003 increased lag phase by 53.1, 115.3, and 119.3%, respectively, and decreased the rate of conjugate-diene generation by 16.6, 21.5, and 19.6%, respectively. D003 also inhibited azo-compound initiated and macrophage-mediated lipid peroxidation as judged by the significant decrease in thiobarbituric acid reactive substance (TBARS) generation. In all the systems the maximum effect was attained at 50 mg/kg. There was also a parallel attenuation in the reduction of lysine amino groups and a significant reduction of carbonyl content after oxidation of lipoprotein samples. Taken together, the present results indicate that oral administration of D003 protects lipoprotein fractions against lipid peroxidation in the lipid as well in the protein moiety.Key words: D003, very long-chain saturated fatty acids, lipoprotein lipid peroxidation.
AN EFFICIENT JOB SCHEDULING ALGORITHM IN PARTITIONABLE MESH CONNECTED SYSTEMS
Authors: LI KEQIN
Published: July 2002

In this paper, we consider the problem of scheduling independent jobs in partitionable mesh connected systems. The problem is NP-hard, since it includes the multiprocessor scheduling problem as a special case when all jobs request for one processor. We analyze a simple approximation algorithm called A m. In particular, we show that if the sizes of submeshes requested by jobs are independent and identically distributed (i.i.d.) random variables uniformly distributed in the range [1..M1]×[1..M2], where M1×M2 is the size of a partitionable mesh connected system, and task execution times are i.i.d. random variables with finite mean and variance, then the average-case performance ratio E( A m(L))/E( OPT (L)) is asymptotically bounded from above by 1.6637594…. The average-case performance ratio improves significantly when jobs request for square submeshes or small submeshes.
RICCATI EQUATION, FACTORIZATION METHOD AND SHAPE INVARIANCE
Authors: CARIÑENA JOSÉ F. , RAMOS ARTURO
Published: July 2002

The basic concepts of factorizable problems in one-dimensional Quantum Mechanics, as well as the theory of Shape Invariant potentials are reviewed. The relation of this last theory with a generalization of the classical Factorization Method presented by Infeld and Hull is analyzed in detail. By the use of some properties of the Riccati equation the solutions of Infeld and Hull are generalized in a simple way.
COUPLING INTERACTING PARTICLE SYSTEMS
Authors: MAES CHRISTIAN
Published: July 2002

We consider random processes (probabilistic cellular automata or interacting particle systems) defined through the interaction of an infinite number of components. We show how coupling arguments yield simple yet quite general ergodicity theorems. The relation between discrete time and continuous time versions is analyzed via similar techniques and the explicit convergence rate of discrete time approximations to the continuous time process is obtained.
QUANTUM SUPERGROUPS AND LINK POLYNOMIALS
Authors: GOULD M. D. , TSOHANTJIS I. , BRACKEN A. J.
Published: July 2002

A general method for constructing invariants for quantum supergroups is applied to obtain a closed formula for link polynomials. For type I quantum supergroups, a realization of the braid group and corresponding link polynomial is determined, for each irreducible representation of the quantum supergroup in a certain class. Although these realizations are not matrix representations in the usual sense, nevertheless link polynomials are defined which are generalizations of those previously obtained from quantum groups. To illustrate the theory, link polynomials corresponding to the defining representations of the quantum supergroups Uq [gl(m|n)], Uq [C (m + 1)] are determined explicitly.
HAMILTONIAN STRUCTURES FOR THE GENERALIZED DISPERSIONLESS KdV HIERARCHY
Authors: BRUNELLI J.C.
Published: July 2002

We study from a Hamiltonian point of view the generalized dispersionless KdV hierarchy of equations. From the so-called dispersionless Lax representation of these equations we obtain three compatible Hamiltonian structures. The second and third Hamiltonian structures are calculated directly from the r-matrix approach. Since the third structure is not related recursively with the first two the generalized dispersionless KdV hierarchy can be characterized as a truly tri-Hamiltonian system.
Symmetry, Integrable Chain Models and Stochastic Processes
Authors: Albeverio Sergio , Fei Shao-Ming
Published: July 2002

A general way to construct chain models with certain Lie algebraic or quantum Lie algebraic symmetries is presented. These symmetric models give rise to series of integrable systems. As an example the chain models with An symmetry and the related Temperley–Lieb algebraic structures and representations are discussed. It is shown that corresponding to these An symmetric integrable chain models there are exactly solvable stationary discrete-time (resp. continuous-time) Markov chains with transition matrices (resp. intensity matrices) having spectra which coincide with the ones of the corresponding integrable models.
LOCAL CHARACTERIZATION OF APPROXIMATELY FINITE OPERATOR ALGEBRAS
Authors: HAWORTH P. A.
Published: July 2002

We show that the family of nest algebras with r non-zero nest projections is stable, in the sense that an approximate containment of one such algebra within another is close to an exact containment. We use this result to give a local characterization of limits formed from this family. We then consider quite general regular limit algebras and characterize these algebras using a local condition which reflects the assumed regularity of the system.
Misuse of Randomization: A Review of Chinese Randomized Trials of Herbal Medicines for Chronic Hepatitis B
Authors: Liu Jianping , Kjaergard Lise Lotte , Gluud Christian
Published: July 2002

The quality of randomization of Chinese randomized trials on herbal medicines for hepatitis B was assessed. Search strategy and inclusion criteria were based on the published protocol. One hundred and seventy-six randomized clinical trials (RCTs) involving 20,452 patients with chronic hepatitis B virus (HBV) infection were identified that tested Chinese medicinal herbs. They were published in 49 Chinese journals. Only 10% (18/176) of the studies reported the method by which they randomized patients. Only two reported allocation concealment and were considered as adequate. Twenty percent (30/150) of the studies were imbalanced at the 0.05 level of probability for the two treatments and 13.3% (20/150) imbalanced at the 0.01 level in the randomization. It is suggested that there may exist misunderstanding of the concept and the misuse of randomization based on the review.
ON THE EXISTENCE OF THE SUPERSTRING AXION MINI-STAR
Authors: POLLOCK M. D.
Published: July 2002

It is shown that the lasing mechanism of axion solitonic stars found by Tkachev is suppressed above a critical value of the QCD decay constant fa ≈ 1015 GeV . This means, in particular, that the heterotic superstring axion mini-star — for which theory [Formula: see text], where λ ≡ fB/fA is the ratio of the decay constants of the second and model-independent axions, respectively, and [Formula: see text] is the strong-interaction coupling — is allowed to form, the laser amplification being exp A, where [Formula: see text]. Relaxation may occur either by the "gravitational cooling" proposed by Seidel and Suen, and by Khlebnikov, and/or by the four-axion self-interaction studied by Tkachev.
CURRENT CORRELATORS AND DUAL DESCRIPTION OF LONG DISTANCE QCD
Authors: CHANDOLA H. C. , PANDEY H. C.
Published: July 2002

An attempt has been made to analyze the magnetic symmetry of the non-Abelian gauge theory associated with the strong interactions using the fibre bundle formulation. Utilizing the gauge field topology, the analysis of dual dynamics associated with the non-Abelian fields is shown to have important bearings on the nonperturbative hadronic effects like confinement of colored quarks and gluons inside hadrons. The state of dual superconductivity for the magnetically condensed vacuum has been analyzed to understand the bulk QCD magnetic properties by evaluating the current correlators in magnetic gauge in terms of the dielectric parameters. The dielectric behavior has been shown to lead to the p-4 confining nature to the dual gluon propagators and to provide an effective macroscopic description of the complicated nonperturbative microscopic interactions of charged particles in dual QCD. The p-4 behavior of dual gluon propagator has also been shown to confirm the linearly rising inter-quark confining potential with an explicit dual gluon mass dependency in dual QCD.
ON SOLITON SOLUTIONS OF NONLINEAR SIGMA MODELS OF SYMMETRIC SPACES
Authors: KARASU (KALKANLI) AYŞE
Published: July 2002

The inverse scattering transform technique of Belinskii–Zakharov for the integration of nonlinear σ model equations is reviewed. N-soliton solutions of the principal chiral field equations are given. The explicit two-complex pole soliton solutions of vacuum and electro-vacuum Ernst equations are constructed.
CRITICAL FLUCTUATIONS AND QUENCHED DISORDERED TWO-DIMENSIONAL CHARGE STRIPES IN LA5/3SR1/3NIO4
Authors: HATTON P. D. , GHAZI M. E. , BROWN S. , CHEONG S-W.
Published: July 2002

Using high-resolution x-ray scattering, we have demonstrated the existance of quenched disordered charge stripes in a single crystal of La 5/3 Sr 1/3 NiO 4 at low temperatures. Above the second-order transition critical scattering was observed due to fluctuations into the charge stripe phase. The charge stripes are shown to be two dimensional in nature both by measurements of their correlation lengths (ξ a ≈185 Å, ξ b ≈400 Å, ξ c ≈25 Å.) and by the critical exponents of the charge stripe transition. The charge stripes are disordered and that the length scale of the disorder is quenched. Detailed measurements of the correlation lengths at higher temperatures, just below the charge stripe melting temperature, display an anisotropic broadening indicative of an order-disorder transition. We ascribe these results to a smectic-nematic phase transition at approximately 225 K. Such electronic quantum liquid-crystal phase transitions have been theoretically predicted before, but these results provide the first experimental evidence for them in charge stripe nickelates.
PAIRING CORRELATIONS IN NUCLEAR SYSTEMS, FROM INFINITE MATTER TO FINITE NUCLEI
Authors: ELGARØY Ø. , ENGELAND T. , HJORTH-JENSEN M. , OSNES E.
Published: July 2002

Finite nuclei such as those found in the chain of even tin isotopes from 102 Sn to 130 Sn , exhibit a near constancy of the [Formula: see text] excitation energy, a constancy which can be related to strong pairing correlations and the near degeneracy in energy of the relevant single-particle orbits. Large shell-model calculations for these isotopes reveal that the major contribution to pairing correlations in the tin isotopes stems from the 1S0 partial wave in the nucleon-nucleon interaction. Omitting this partial wave and the 3P2 wave in the construction of an effective interaction, results in a spectrum which has essentially no correspondence with experiment. These partial wave are also of importance for infinite neutron matter and nuclear matter and give the largest contribution to the pairing interaction and energy gap in neutron star matter.
EXPECTED AND UNEXPECTED SOLUTIONS TO THE STATIONARY ONE-DIMENSIONAL NONLINEAR SCHRÖDINGER EQUATION
Authors: CARR LINCOLN D. , CLARK CHARLES W. , REINHARDT WILLIAM P.
Published: July 2002

We present all stationary solutions to the nonlinear Schrödinger equation in one dimension for box and periodic boundary conditions. For both repulsive and attractive nonlinearity we find expected and unexpected solutions. Expected solutions are those that are in direct analogy with those of the linear Schödinger equation under the same boundary conditions. Unexpected solutions are those that have no such analogy. We give a physical interpretation for the unexpected solutions. We discuss the properties of all solution types and briefly relate them to experiments on the dilute-gas Bose-Einstein condensate.
ON HEAT FLOW AND NON-RECIPROCITY
Authors: MONTES DE OCA ALEJANDRO CABO
Published: July 2002

Heat transfer properties in non-reciprocal systems are discussed. An ideal experiment employing microwave or optical isolators is considered in order to investigate the possibility for a spontaneous transfer of energy between two black-bodies at common temperatures. Under the validity of the adopted assumptions on the examined physical system, the effect appears to be weak but feasible. We consider that the relevance of detailed balance for thermal equilibrium and its close connections with reciprocity confer interest to the close inspection of these problems started here.
EFFECT OF CERAMIC COATING THICKNESS ON RESIDUAL STRESS AND FATIGUE CHARACTERISTIC OF 1Cr-1Mo-0.25V STEEL
Authors: SUH CHANG-MIN , HWANG BYUNG-WON , KIM KYUNG-RYUL
Published: July 2002

To evaluate the effect of coatings on the fatigue behaviors of turbine rotor steel, TiN and TiAlN films were deposited on the 1Cr-1Mo-0.25V steels by arc-ion plating (AIP) method with and wihtout screen ion filter. The coating thickness were varied with 2.5 μm, 3.5 μm, and 5.0 μm. A Cu-K α beam source was used as a characteristic X-ray and the crystal plane of (422) was selected to evaluate the residual stresses. In order to clear the relationship between fatigue behavior and residual stress of specimen coated with TiN and TiAlN films, the fatigue tests of specimens with and without coating were carried out at room temperatures respectively. It is shown that the fatigue life of the coated specimen was longer than that of uncoated specimen. The compressive residual stresses on the coatings were higher, and the fatigue crack initiated at an inclusion in the substrate near bond interface. It is known that compressive residual stress caused by hard coating would retard the fatigue crack initiation on the specimen surface, and then led to fatigue strength and fatigue life increasing.
CUPRATE SUPERCONDUCTIVITY ON INTERACTING ELECTRONIC COMPONENTS PREPARED BY DOPING
Authors: KRISTOFFEL N. , RUBIN P.
Published: July 2002

A model of a "defect" band which expands by doping above the itinerant hole band is used to describe the cuprate superconductivity by the interband scattering of pairs. Bands overlap reached by progressive doping determines the under/optimal-doping separation line and the reset of the Fermi-liquid behaviour. A two-band scheme with the interband scattering of intraband pairs reproduces the observed peculiar behaviour of gaps. A pseudogap appears as the minimal excitation energy of the itinerant band at underdoping. Doping forms the electronic structure of cuprates on which the interband superconductivity can occur.
BOSON JOSEPHSON JUNCTION WITH TRAPPED ATOMS
Authors: RAGHAVAN S. , SMERZI A. , FANTONI S. , SHENOY S. R.
Published: July 2002

We consider coherent atomic tunneling between two weakly coupled Bose-Einstein condensates at T =0 in a double-well trap. The condensate dynamics of the macroscopic amplitudes in the two wells is modeled by two Gross-Pitaevskii equations (GPE) coupled by a tunneling matrix element. Analytic elliptic function solutions are obtained for the time evolution of the inter-well fractional population imbalance z(t) (related to the condensate phase difference) of the Boson Josephson junction (BJJ). Surprisingly, the neutral-atom BJJ shows (non-sinusoidal generalizations of) effects seen in charged-electron superconductor Josephson junctions (SJJ). The BJJ elliptic-function behavior has a singular dependence on a GPE parameter ratio Λ at a critical ratio Λ=Λc, beyond which a novel 'macroscopic quantum self-trapping' effect sets in with a non-zero time-averaged imbalance ≠0.