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At least 919 records · Page 51Linked to original sources
PubMed1983

Biochemical mapping of the simian rotavirus SA11 genome.

Biochemical mapping experiments of the simian rotavirus SA11 genome were performed to determine which double-stranded RNA segment coded for each of the viral polypeptides. Viral RNA transcripts were synthesized in vitro by using the endogenous viral RNA polymerase and fractionated by electrophoresis in acid-urea agarose gels. The fractionated transcripts were translated in two cell-free systems: micrococcal nuclease-treated reticulocyte lysates and wheat germ extracts. The polypeptide products were identified by polyacrylamide gel electrophoresis and partial peptide analysis and compared with polypeptides synthesized in infected cells or found in purified virus. The RNA segment that coded for each transcript was determined by hybridization of the fractionated transcripts to the double-stranded RNA genome and analysis of the hybrids by electrophoresis in polyacrylamide gels. Primary gene products were assigned for 10 of the rotavirus transcripts and 10 of the double-stranded RNA segments. The coding assignments are as follows: the inner-capsid polypeptides, VP1, VP2, and VP6, were assigned to segments 1, 2, and 6, respectively; the major outer-capsid polypeptides, VP3 and VP7, were assigned to segments 4 and 9, respectively; segments 5, 7, and 8 coded for nonstructural polypeptides with molecular weights of 53,000, 34,000, and 35,000, respectively; segment 10 coded for the 20,000-molecular-weight precursor to the 29,000-molecular-weight glycosylated nonstructural polypeptide; and segment 11 coded for a 26,000-molecular-weight polypeptide that may be the precursor to the minor outer-capsid polypeptide VP9. Several methods were used to determine the product of gene segment 3, and the problems associated with the identification of this gene product are discussed.

Animals↗
PubMed1959

A quantitative study of the kinetics of blood clearance of P32-labelled Escherichia coli and Staphylococci by the reticuloendothelial system.

1. The clearance of P(32)-labelled heat-killed E. coli and staphylococci from the blood follows an exponential function of the time, and the bacteria are phagocytized principally by the RES of the liver and spleen. 2. The rates of clearance of equivalent number of E. coli from the blood is rapid in rabbits and slow in mice and appears to be related to the level of antibodies in the serum of these animals. 3. Unlike E. coli, staphylococci are cleared rapidly and efficiently by the RES from the blood of mice which have a sufficient level of serum antibody against these bacteria. 4. The numbers of bacteria, phagocytized by the liver or the spleen respectively, depend upon the rate of clearance and the extent of opsonization of the bacteria. Rapidly cleared, well opsonized E. coli are removed almost exclusively by the liver, while less efficiently phagocytized bacteria are also cleared by the spleen in large numbers. 5. The rate of clearance of E. coli and the efficiency with which they are phagocyted by the RES in mice have been shown to be directly related to the level of antibody in the serum. 6. Treatment of mice with S. typhi or Serratia marcescens endotoxins increases the rate of clearance of E. coli from the blood and the level of antibody against E. coli in the serum. The enhanced clearance of E. coli can be transferred to normal mice by the serum of endotoxin-treated mice.

Animals↗
PubMed1995

Direct identification of Staphylococcus aureus in blood cultures by detection of the gene encoding the thermostable nuclease or the gene product.

This study compares methods for direct identification of S. aureus in blood cultures by detection of the thermonuclease (TNase) of this bacterium or the nuc gene encoding it. The protein was detected by an enzyme diffusion test in o-toluidine blue DNA agar with a test time of at least 4 h, by a monoclonal antibody (MAb)-based sandwich enzyme-linked immunosorbent assay (sELISA) with a test time of approximately 4 h, and by a MAb-based sandwich enzyme-linked immunofiltration assay (sELIFA) with a test time of 25-30 min (sample preparation included). The nuc gene was amplified by a polymerase chain reaction (PCR) with a test time (amplification plus detection) of approximately 3.5 h. The tests were optimized for direct examination of blood-containing cultures. All tests were positive with 67/67 blood cultures which grew S. aureus, negative with 35/35 cultures which grew coagulase-negative staphylococci, and negative with 37/37 cultures with various other bacteria. These results showed positive agreement with those of the commercial AccuProbe test but not with the StaphAurex agglutination kit. With an artificially seeded blood culture, minimum total times required (incubation plus testing) were as follows: nuc-PCR, 9.5 h; sELIFA, 12.5 h; enzymatic test, 16-36 h; AccuProbe, 14 h. Direct examination of both the nuc gene and the mecA gene encoding methicillin resistance demonstrated the mecA gene in all the coagulase-negative staphylococci (48.6%) which showed oxacillin resistance. The sELIFA had the particular advantage of its short test time, the PCR its high sensitivity and the possibility of simultaneous detection of the species-specific nuc gene and genes encoding other clinically important characters of the bacteria. These tests offer the prospect of direct application to a variety of clinical specimens for rapid diagnosis of S. aureus infection.

Bacteriological Techniques↗
PubMed2003

Ability of Lactococcus lactis to export viral capsid antigens: a crucial step for development of live vaccines.

The food grade bacterium Lactococcus lactis is a potential vehicle for protein delivery in the gastrointestinal tract. As a model, we constructed lactococcal strains producing antigens of infectious bursal disease virus (IBDV). IBDV infects chickens and causes depletion of B-lymphoid cells in the bursa of Fabricius and subsequent immunosuppression, morbidity, or acute mortality. The two major IBDV antigens, i.e., VP2 and VP3, that form the viral capsid were expressed and targeted to the cytoplasm, the cell wall, or the extracellular compartment of L. lactis. Whereas VP3 was successfully targeted to the three compartments by the use of relevant expression and export vectors, VP2 was recalcitrant to export, thus confirming the difficulty of translocating naturally nonsecreted proteins across the bacterial membrane. This defect could be partly overcome by fusing VP2 to a naturally secreted protein (the staphylococcal nuclease Nuc) that carried VP2 through the membrane. Lactococcal strains producing Nuc-VP2 and VP3 in various bacterial compartments were administered orally to chickens. The chickens did not develop any detectable immune response against VP2 and VP3 but did exhibit an immune response against Nuc when Nuc-VP2 was anchored to the cell wall of lactococci.

Animals↗
PubMed2000

Evidence for nucleic acid binding ability and nucleosome association of Bombyx mori nucleopolyhedrovirus BRO proteins.

The Bombyx mori nucleopolyhedrovirus (BmNPV) genome contains five related members of the bro gene family, all of which are actively expressed in infected BmN cells. Although their functions are unknown, their amino acid sequences contain a motif found in all known viral and prokaryotic single-stranded DNA binding proteins. To determine if they bind to nucleic acids, we fractionated the nuclei of BmNPV-infected BmN cells using a histone extraction protocol. We detected BRO-A, BRO-C, and BRO-D in the histone H1 fraction using anti-BRO antibodies. Micrococcal nuclease treatment released these BRO proteins from the chromatin fraction, suggesting their involvement in nucleosome structures. Chromatographic fractionation showed that BRO-A and/or BRO-C interacted with core histones. Expression of partial sequences of BRO-A proved that the N-terminal 80 amino acid residues were required for DNA binding activity. We also demonstrated that BmNPV BRO proteins underwent phosphorylation and ubiquitination followed by proteasome degradation, which may explain their distribution in the cytoplasm as well as the nucleus. We propose that BRO-A and BRO-C may function as DNA binding proteins that influence host DNA replication and/or transcription.

Animals↗
PubMed1982

A transcriptionally active, covalently closed minichromosome of cauliflower mosaic virus DNA isolated from infected turnip leaves.

Purified nuclei from turnip leaves infected by cauliflower mosaic virus (CaMV) have been shown to contain a fraction of CaMV DNA that consists of covalently closed circular molecules; possesses a nucleosome structure, based on sensitivity to micrococcal nuclease; and contains nuclear RNA polymerase II that selectively transcribes the coding strand of CaMV DNA in vitro. Our results suggest that the transcriptionally active CaMV DNA is in the form of a minichromosome and that this DNA does not contain the site-specific discontinuities characteristic of the virion.

Chromosomes↗
PubMed2001

Variant chromatin structure of the oriP region of Epstein-Barr virus and regulation of EBER1 expression by upstream sequences and oriP.

Most of the Epstein-Barr virus genome in latently infected cells is in a standard nucleosomal structure, but the region encompassing oriP and the Epstein-Barr virus-encoded small RNA (EBER) genes shows a distinctive pattern when digested with micrococcal nuclease. This pattern corresponds to a previously mapped nuclear matrix attachment region. Although the EBER genes are adjacent to oriP, there is only a two- to fourfold effect of oriP on EBER expression. However, sequences containing a consensus ATF site upstream of EBER1 are important for EBER1 expression.

Chromatin↗
PubMed1976

Specific herpes simplex virus-induced incorporation of 5-iodo-5'-amino-2',5'-dideoxyuridine into deoxyribonucleic acid.

5-Iodo-5'-amino-2',5'-dideoxyuridine (AIdUrd) is a novel thymidine analog which inhibits herpes simplex virus, type 1 (HS-1 virus) replication in the absence of detectable host toxicity. When murine, simian, or human cells in culture are treated with [125I]AIdUrd for up to 24 hours essentially none of the nucleoside becomes cell-associated. In contrast, upon HS-1 virus infection significant radiolabel is detected in both nucleotide pools and in DNA. The major acid-soluble metabolite has been shown by enzymic and chromatographic analysis to be the 5'-triphosphate of AIdUrd. DNA from HS-1 virus-infected Vero cells labeled with [14C]thymidine, 5-[125I]iodo-2'-deoxyuridine (IdUrd), or [125I]AIdUrd was isolated by buoyant density centrifugation and subjected to digestion by pancreatic DNase I, spleen DNase II, micrococcal nuclease, spleen, and venom phosphodiesterases. Analysis of the digestion products clearly indicate that AIdUrd is incorporated internally into the DNA structure. DNA containing AIdUrd therefore contains phosphoramidate (P-N) bonds, known to be extremely acid-labile. The selective HS-1 virus-induced phosphorylation of AIdUrd and its subsequent incorporation into DNA may account for the unique biological activity of the AIdUrd nucleoside.

DNA Replication↗