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At least 163 records · Page 9Linked to original sources
PubMed1987

Is Sindbis a simple picornavirus with an envelope?

A three-dimensional image reconstruction was performed from cryo-electron micrographs of isolated Sindbis (SNV) nucleocapsids. The isolated capsid is a smooth but fenestrated T = 3 structure. Comparison with the nucleocapsid seen within the whole virion indicated that the structure resembles the swollen forms which some non-enveloped viruses adopt after removal of divalent cations. A sensitive comparison method was used to align SNV capsid protein sequences with those of picornavirus vp3 capsid proteins whose high resolution structures display an eight-stranded beta-barrel fold found in many icosahedral viruses. The alignment predicted a similar folding for the Sindbis protein which juxtaposes several sets of residues known to be essential for its serine proteolytic activity. These results suggest that the capsid proteins of the enveloped alphaviruses and the non-enveloped picornaviruses may have arisen through divergent evolution from a simple, vp3-like ancestor.

Amino Acid Sequence↗
PubMed2001

Frequency of direct repeat deletion in a human immunodeficiency virus type 1 vector during reverse transcription in human cells.

Retroviral genetic rearrangements can result from reverse transcriptase template switching. Most published data suggest that errors such as base misincorporation occur at similar frequencies for HIV-1 and for simple retroviruses such as spleen necrosis virus (SNV) and murine leukemia virus (MuLV). However, previous reports have suggested that template switch-mediated recombination is much more frequent for HIV-1 than for simple retroviruses. In this report, direct repeat deletion vectors similar to those previously used for measuring template switching events for SNV and MuLV were developed for HIV-1. Forward mutation rates and the frequency of template switching during a single cycle of HIV-1 replication were determined. The frequency of HIV-1-mediated repeat deletion was measured for three separate internal repeats in lacZ and was compared to rates observed with identical repeats for MuLV. The results indicated that the error rate and the frequency of repeat deletion of HIV-1 were similar to those of MuLV.

Cell Line↗
PubMed1987

Sequence instability in the long terminal repeats of avian spleen necrosis virus and reticuloendotheliosis virus.

Sequence divergence between the 3' long terminal repeats (LTR) of avian reticuloendotheliosis virus (REV), deletion variant proviral clone 2-20-4, and spleen necrosis virus (SNV)-proviral clones 14-44, 60, and 70-was found to involve two classes of base substitutions: low-frequency interspersed and high-frequency clustered substitutions. Clones 2-20-4 and 14-44 have diverged 4.4% owing to low-frequency substitutions. In contrast, two high-frequency substitution segments have diverged by 30% and 29%, respectively. Clustered substitutions appear to be located either within or next to tandem repeats, suggesting their introduction concomitant with sequence deletions and duplications commonly associated with such repeats. A new 19-bp tandem repeat is found in clone 2-20-4. Its sequence could have evolved from the 26-bp repeats found in the SNV clones.

Base Composition↗
PubMed2002

High fidelity of homologous retroviral recombination in cell culture.

Genetic variation continues to be a major obstacle in the development of therapies and vaccines against retroviral infections and contributes extensively to viral pathogenesis and persistence. Recombination is one mechanism that increases retroviral variation by shuffling mutations from different genomes. Recent studies suggest that recombination not only shuffles the mutations but also generates them at high rates during reverse transcription. In contrast to these recent studies, this investigation shows that recombination does not generate mutations during recombination. A spleen necrosis virus (SNV)-based homologous recombination system was used to test the hypothesis that retroviral recombination is a high-fidelity process during replication of the virus in cell culture. The system consisted of a pair of SNV vectors expressing two drug resistance genes. The vectors were constructed so that cells containing recombinant proviruses could be selected by a double drug-resistant phenotype. Restriction enzyme digestion and agarose gel electrophoresis were used to map the location of recombination within 182 proviruses. Sequencing and single-strand conformation polymorphism techniques were then used to check for mutations within the recombinant proviruses. Since no mutations were detected among the 182 recombinants that were analyzed, homologous recombination is a high-fidelity process for retroviruses in cell culture.

Cells, Cultured↗
PubMed1999

Insertion of sequences into the 3' untranslated region of a replication-competent spleen necrosis virus vector disrupts env gene expression.

The genomes of all replication-competent retroviruses contain cis-acting elements that regulate gene expression. However, the identities of many of these elements remain to be characterized. Inserting sequences into the 3' untranslated region of a replication-competent spleen necrosis virus (SNV) vector disrupted its ability to replicate. Inserts varying in sequences and sizes (0.4-kb to 1.6-kb) all resulted in this defect. Genetic compensation experiments and immunostaining revealed that env gene expression was deficient. Northern analysis indicated the presence of spliced viral mRNA of the correct size although at a reduced level compared to a wildtype vector. It is likely that the block in env expression occurs at a post-transcriptional step. These results suggest that the function of a cis-acting element distinct from the constitutive transport element is disrupted by the inserted sequences into the 3' untranslated region of SNV.

3' Untranslated Regions↗
PubMed1985

Purification and chemical and immunological characterization of avian reticuloendotheliosis virus gag-gene-encoded structural proteins.

Five gag-gene-encoded structural proteins, designated p12, pp18, pp20, p30, and p10 were purified from replication-competent avian reticuloendotheliosis-associated virus (REV-A) by high-performance liquid chromatography complemented with chloroform-methanol extraction and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Based on amino acid composition and NH2- and COOH-terminal sequence analysis p12, pp18, p30, and p10 are distinct from one another, whereas pp20 is likely identical to pp18 in primary structure. The p12 was resistant to Edman degradation and was found to be myristylated at the NH2-terminal amino group. Sequence comparisons among the retrovirus family show that pp18/pp20 and p10 are, respectively, homologs of phospho-proteins and nucleic acid-binding proteins. A comparison of terminal sequences with the nucleotide sequence of spleen necrosis virus (SNV) revealed that the gag genes of SNV and REV-A are highly conserved; together with the identification of REV-A gag-precursor polyprotein, Pr60gag in immunoprecipitates of radiolabeled cell lysates, this comparison also led to the establishment of the organization of Pr60gag, viz., NH2-p12-pp18-p30-p10-OH. Sequence comparisons show that REV-A/SNV is related to mammalian type C viruses: the pp18-p30 region is most homologous to the macaque/colobus group and least to simian sarcoma virus (SSV), whereas both the 5'- and 3'-gag regions (i.e., p12 and p10) are clostest to SSV. Immunological studies using monospecific antisera and Western-blot analysis showed that antigenic determinants of REV-A p30 are conserved in most of mammalian type C and type D viruses, but those of REV-A p12 are shared only with simian sarcoma-associated virus (SSAV) and endogenous viruses of macaques.

Amino Acid Sequence↗
PubMed1996

The immunodominant proteins of reticuloendotheliosis virus.

The antigenic profiles of three REV prototype strains, CSV, SNV and REV-T and eight Israeli isolates were analysed by SDS-PAGE and immunoblotting with convalescent chicken serum, three mAbs, 11A25, 11C237 and 11C100, a rabbit antiserum to REV-T whole virus (Cui et al., 1986) and a rabbit antiserum to REV-A p30 gag protein (Tsai et al., 1985). Under both reducing (+DTT) and non-reducing conditions of SDS-PAGE, a major immunodominant 75-100 kDa band was shared by all strains examined. In contrast to the chicken serum that recognized both continuous and discontinuous epitopes on the 75-100 kDa band of all the isolates, the mAbs and the two rabbit sera behaved otherwise. Only the DTT-resistant epitopes on the 75-100 kDa band of REV-T were recognized by the rabbit antisera and the mAb 11C237, and only the DTT-labile epitopes of REV-T 75-100 kDa antigen were detected by mAb 11C100. The two mAbs 11A25 and 11C237 detected discontinuous epitopes of all the strains except SNV, while the rabbit antisera recognized the discontinuous epitopes on the 75-100 kDa band of all the 11 strains. The rabbit antisera and mAb 11C237 detected additional lower molecular weight proteins and the mAb 11C237 also detected three proteins of high molecular weight under non-reducing conditions only. The p30 antiserum detected the low molecular weight proteins demonstrating their gag gene-encoded identity. From these results we conclude that the major immunogen of REV is the 75-100 kDa protein that contains both continuous and discontinuous epitopes. With this panel of antibodies the eight new isolates appeared to belong antigenically to REV subtype 3 (Chen et al., 1987).

Animals↗
PubMed2005

Determination of compound aminopyrine phenacetin tablets by using artificial neural networks combined with principal components analysis.

A method for simultaneous, nondestructive analysis of aminopyrine and phenacetin in compound aminopyrine phenacetin tablets with different concentrations has been developed by principal component artificial neural networks (PC-ANNs) on near-infrared (NIR) spectroscopy. In PC-ANN models, the spectral data were initially analyzed by principal component analysis. Then the scores of the principal components were chosen as input nodes for the input layer instead of the spectral data. The artificial neural network models using the spectral data as input nodes were also established and compared with the PC-ANN models. Four different preprocessing methods (first-derivative, second-derivative, standard normal variate (SNV), and multiplicative scatter correction) were applied to three sets of NIR spectra of compound aminopyrine phenacetin tablets. The PC-ANNs approach with SNV preprocessing spectra was found to provide the best results. The degree of approximation was performed as the selective criterion of the optimum network parameters.

Aminopyrine↗
PubMed2004

Low flow promotes instent intimal hyperplasia. Comparison with lumen loss in balloon-injured and uninjured vessels and the effects of the antioxidant pyrrolidine dithiocarbamate.

Low flow (LF) promotes late lumen loss after angioplasty by exacerbating inward remodelling through redox-sensitive mechanisms. Stents eliminate inward remodelling and the effect of LF on in-stent restenosis is uncertain. We performed over-sized (1.3-1.5:1) stenting (S) and balloon injury (in the same vessel, B) to the carotid arteries of cholesterol-fed rabbits and compared 28-day late lumen loss with that in an uninjured segment in the same vessel (U). Vessels (n = 5 animals per group) were subjected to high (H), normal (N) and low (L) flow in animals fed either vehicle (V) or the antioxidant pyrrolidine dithiocarbamate, PDTC (P). LF significantly increased in-stent neointima formation relative to normal and high flow (SLV 0.72 +/- 0.07 mm(2) versus SNV 0.43 +/- 0.08 mm(2) versus SHV 0.28 +/- 0.04 mm(2), P < 0.05). However, LF resulted in greater lumen loss in segments from the same vessel subject to balloon injury (lumen SLV 5.18 +/- 0.40 mm(2) and SNV 5.32 +/- 0.40 mm(2) versus BLV 1.28 +/- 0.33 mm(2) and BNV 2.19 +/- 0.28 mm(2)), by greater enhancement of inward remodelling. In addition, inward remodelling and lumen loss due to LF were greater in balloon-injured segments than in adjacent uninjured segments where shear homeostatic remodelling occurs (lumen BLV 1.28 +/- 0.33 mm(2) versus ULV 1.52 +/- 0.22 mm(2)). Lastly, while PDTC effectively reduced intima formation and inward remodelling due to LF in balloon-injured vessels there was no effect on flow-dependent neointima formation in stented vessels. We conclude that LF accentuates in-stent neointima formation, but that flow-dependent lumen loss after stenting is less than that after balloon injury. When LF is present lumen loss can be minimised by antioxidants or stenting.

Angioplasty, Balloon↗
PubMed2006

Haemocyte reactions in WSSV immersion infected Penaeus monodon.

White spot syndrome virus (WSSV) has been a major cause of shrimp mortality in aquaculture worldwide in the past decades. In this study, WSSV infection (by immersion) and behaviour recruitment of haemocytes is investigated in gills and midgut, using an antiserum against the viral protein VP28 and a monoclonal antibody recognising haemocytes (WSH8) in a double immunohistochemical staining and in addition transmission electron microscopy was applied. More WSH 8(+) haemocytes were detected at 48 and 72 h post-infection in the gills of infected shrimp compared to uninfected animals. Haemocytes in the gills and midgut were not associated with VP28-immunoreactivity. In the gills many other cells showed virus replication in their nuclei, while infected nuclei in the gut cells were rare. Nevertheless, the epithelial cells in the midgut showed a clear uptake of VP28 and accumulation in supranuclear vacuoles (SNV) at 8h post-infection. However, epithelial nuclei were never VP28-immunoreactive and electron microscopy study suggests degradation of viral-like particles in the SNV. In contrast to the gills, the midgut connective tissue shows a clear increase in degranulation of haemocytes, resulting in the appearance of WSH8-immunoreactive thread-like material at 48 and 72 h post-infection. These results indicate recruitment of haemocytes upon immersion infection in the gills and degranulation of haemocytes in less infected organs, like the midgut.

Animals↗
PubMed2003

Analysis of synergy between divergent simple retrovirus posttranscriptional control elements.

Mason-Pfizer monkey virus (MPMV) and spleen necrosis virus (SNV) are simple retroviruses that encode functionally divergent cis-acting RNA elements that use cellular proteins to facilitate nuclear export and translation of unspliced viral RNA. We tested the hypothesis that a combination of MPMV constitutive transport element (CTE) and SNV or MPMV RU5 translational enhancer on unspliced HIV-1 gag-pol reporter RNA synergistically augments Gag production. Results of transient transfection assays validate the hypothesis of synergistic augmentation in COS cells, but not 293 cells. RNA targeting experiments verified comparable responsiveness to CTE-interactive proteins tethered by RRE and RevM10Tap in COS and 293 cells. Exogeneous expression of Tap and NXT1 was necessary and sufficient to rescue Gag augmentation in 293 cells. Overexpression experiments established that CTE, but not RU5, confers the responsiveness to Tap and NXT1 and that CTE in conjunction with Tap and NXT1 conferred a 30-fold increase in translational utilization of the cytoplasmic RNA. Our results uncovered a previously unidentified role of CTE in conjunction with Tap and NXT1 in commitment to efficient cytoplasmic RNA utilization.

5' Untranslated Regions↗
PubMed2006

Phylogenetic analyses indicate little variation among reticuloendotheliosis viruses infecting avian species, including the endangered Attwater's prairie chicken.

Reticuloendotheliosis virus infection, which typically causes systemic lymphomas and high mortality in the endangered Attwater's prairie chicken, has been described as a major obstacle in repopulation efforts of captive breeding facilities in Texas. Although antigenic relationships among reticuloendotheliosis virus (REV) strains have been previously determined, phylogenetic relationships have not been reported. The pol and env of REV proviral DNA from prairie chickens (PC-R92 and PC-2404), from poxvirus lesions in domestic chickens, the prototype poultry derived REV-A and chick syncytial virus (CSV), and duck derived spleen necrosis virus (SNV) were PCR amplified and sequenced. The 5032bp, that included the pol and most of env genes, of the PC-R92 and REV-A were 98% identical, and nucleotide sequence identities of smaller regions within the pol and env from REV strains examined ranged from 95 to 99% and 93 to 99%, respectively. The putative amino acid sequences were 97-99% identical in the polymerase and 90-98% in the envelope. Phylogenetic analyses of the nucleotide and amino acid sequences indicated the closest relationship among the recent fowl pox-associated chicken isolates, the prairie chicken isolates and the prototype CSV while only the SNV appeared to be distinctly divergent. While the origin of the naturally occurring viruses is not known, the avian poxvirus may be a critical component of transmission of these ubiquitous oncogenic viruses.

Amino Acid Sequence↗
PubMed2003

Cell-type-specific gene delivery into neuronal cells in vitro and in vivo.

The avian retroviruses reticuloendotheliosis virus strain A (REV-A) and spleen necrosis virus (SNV) are not naturally infectious in human cells. However, REV-A-derived viral vectors efficiently infect human cells when they are pseudotyped with envelope proteins displaying targeting ligands specific for human cell-surface receptors. Here we report that vectors containing the gag region of REV-A and pol of SNV can be pseudotyped with the envelope protein of vesicular stomatitis virus (VSV) and the glycoproteins of different rabies virus (RV) strains. Vectors pseudotyped with the envelope protein of the highly neurotropic RV strain CVS-N2c facilitated cell type-specific gene delivery into mouse and human neurons, but did not infect other human cell types. Moreover, when such vector particles were injected into the brain of newborn mice, only neuronal cells were infected in vivo. Cell-type-specific gene delivery into neurons may present quite specific gene therapy approaches for many degenerative diseases of the brain.

Animals↗
PubMed1998

Automated system for the on-line monitoring of powder blending processes using near-infrared spectroscopy. Part II. Qualitative approaches to blend evaluation.

Near Infrared (NIR) spectroscopy is seen as a very powerful tool in a variety of applications involving powder characterisation. Here we deal with a typical pharmaceutical application of powder blend monitoring. A D-optimal experimental design is used to cover the 85-115% range of the target formulation which is comprised of the active component at 3.5% w/w, Microcrystalline Cellulose (Avicel PH102) at 62%, Dibasic Calcium Phosphate Anhydrous at 31.5%, Sodium Starch Glycolate (Explotab) at 2%, and 1% Magnesium Stearate. A miniature Flobin blender has been modified to enable the use of a fibre optic probe for on-line NIR spectral data collection. The experiments were successful in detecting spectral changes which eventually converged to constant variance. While the NIR spectrum of a powdered sample is rich in information which is representative of both the physical and chemical characteristics of the sample, it is at times difficult to select the appropriate mathematical treatments in order to extract the desired information. This article investigates several possible pre-treatments (including detrending (DT), standard normal variates (SNV), second derivatives, and the combination of SNV and DT) together with several ways in establishing blend homogeneity, which includes the running block standard deviation, dissimilarity calculations and principal components analysis (PCA). The focus of this work is to investigate qualitative tools of analysis for blend homogeneity determinations, while future work will focus on quantitative data interpretation.

Algorithms↗
PubMed1999

The influence of data pre-processing in the pattern recognition of excipients near-infrared spectra.

The effect of data pre-processing (no pre-processing, offset correction, de-trending, standard normal variate transformation (SNV), SNV + de-trending, multiplicative scatter correction, first and second derivative transformation after smoothing) on the identification of ten pharmaceutical excipients is investigated. Four pattern recognition methods are tested in the study, namely the Mahalanobis distance method, the SIMCA residual variance method, the wavelength distance method and a method based on triangular potential functions. The performance of the 32 method combinations is evaluated on the basis of two NIR data sets. The first one, measured in 1994, is used to build the classification models, the second, measured from 1994-1997, is used to assess the quality of the models. The best approach for the given data sets is the wavelength distance method combined with de-trending, a simple baseline correction method. More general recommendations for pre-processing excipient NIR data and for choosing an appropriate classification method are given.

Excipients↗
PubMed2006

Measurement of soluble solids contents and pH in orange juice using chemometrics and vis-NIRS.

The potential of visible and near-infrared reflectance spectroscopy (vis-NIRS) was investigated for its ability to nondestructively detect soluble solids contents (SSC) and pH in orange juices. A total of 104 orange juice samples were used for vis-NIRS at 325-1075 nm using a field spectroradiometer. Wavelet packet transform, standard normal variate transformation (SNV), and Savitzky-Golay first-derivative transformation were applied for the preprocessing of spectral data. The chemometrics of partial least-squares (PLS) regression analysis was performed on the processed spectral data. The evaluation of SSC and pH in orange juices by PLS regression with SNV showed the highest accuracy of the three preprocessing methods. The correlation coefficient (r), standard error of prediction, and the root-mean-square error of prediction for SSC were 0.98, 0.68, and 0.73, respectively, whereas those values for pH were 0.96, 0.06, and 0.06, respectively. The "fingerprint" representing features of orange juices or reflecting sensitivity to some elements at a certain band was proposed on the basis of regression coefficients. It is very useful in the field of food chemistry and further research on other materials. It is concluded that the vis-NIRS technique combined with chemometrics is promising for the fast and nondestructive detection of chemical components in orange juices or other materials.

Beverages↗
PubMed2000

Spleen necrosis virus-derived C-type retroviral vectors for gene transfer to quiescent cells.

Gene therapy applications of retroviral vectors derived from C-type retroviruses have been limited to introducing genes into dividing target cells. Here, we report genetically engineered C-type retroviral vectors derived from spleen necrosis virus (SNV), which are capable of infecting nondividing cells. This has been achieved by introducing a nuclear localization signal (NLS) sequence into the matrix protein (MA) of SNV by site-directed mutagenesis. This increased the efficiency of infecting nondividing cells and was sufficient to endow the virus with the capability to efficiently infect growth-arrested human T lymphocytes and quiescent primary monocyte-derived macrophages. We demonstrate that this vector actively penetrates the nucleus of a target cell, and has potential use as a gene therapy vector to transfer genes into nondividing cells.

Amino Acid Sequence↗
PubMed2000

Systemic necrotizing vasculitis: a review, with the personal perspective of a nurse educator.

Although its definition is simple, systemic necrotizing vasculitis (SNV) is a complex, potentially life-threatening disease. By reviewing current published literature, this article provides an overview of vasculitis and focuses on what is common to the many individual systemic vascular diseases (vasculitides). A case history of a 10-year-old girl with SNV is included. Parse's Human Becoming theory is reviewed briefly as it applies to this case.

Child↗