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At least 1,441 records · Page 80Linked to original sources

PubMed1999

Protective cultures inhibit growth of Listeria monocytogenes and Escherichia coli O157:H7 in cooked, sliced, vacuum- and gas-packaged meat.

Contamination of cooked meat products with Listeria monocytogenes poses a constant threat to the meat industry. The aim of this study was therefore to investigate the use of indigenous lactic acid bacteria (LAB) as protective cultures in cooked meat products. Cooked, sliced, vacuum- or gas-packaged ham and servelat sausage from nine meat factories in Norway were inoculated with 10(3) cfu/g of a mixture of three rifampicin resistant (rif-mutant) strains of L. monocytogenes and stored at 8 degrees C for four weeks. Growth of L. monocytogenes and indigenous lactic acid flora was followed throughout the storage period. LAB were isolated from samples where L. monocytogenes failed to grow. Five different strains growing well at 3 degrees C. pH 6.2, with 3% NaCl, and producing moderate amounts of acid were selected for challenge experiments with the rif-resistant strains of L. monocytogenes. a nalidixic acid/streptomycin sulphate-resistant strain of Escherichia coli O157:H7 and a mixture of three rif-resistant strains of Yersinia enterocolitica O:3. All five LAB strains inhibited growth of both L. monocytogenes and E. coli O157:H7. No inhibition of Y. enterocolitica O:3 was observed. A professional taste panel evaluated cooked, sliced, vacuum-packaged ham inoculated with each of the five test strains after storage for 21 days at 8 degrees C. All samples had acceptable sensory properties. The five LAB strains hybridised to a 23S rRNA oligonucleotide probe specific for Lactobacillus sakei. These indigenous LAB may be used as protective cultures to inhibit growth of L. monocytogenes and E. coli O157:H7 in cooked meat products.

Animals↗

PubMed1998

Truncation of the nuclear localization signal of polyomavirus VP1 results in a loss of DNA packaging when expressed in the baculovirus system.

Using the pBlueBacIII baculovirus transfer vector, N11-VP1, a truncated form of the polyomavirus major capsid protein VP1, was cloned for expression in the baculovirus-insect cell expression system. The N11-VP1 protein is virtually identical to full-length, wild-type VP1, except that the first 11 amino acids have been deleted from the amino terminus of the protein. The N-terminal region of VP1 has previously been shown to contain the nuclear localization signal (NLS) of the protein and contains residues essential for both nuclear transport as well as DNA-binding functions. The 5-day infected Sf9 cellular lysate from the recombinant N11-VP1 preparation was purified by cesium chloride density gradient centrifugation. Capsid-like particles were observed in the resulting preparation. The purified particle preparation was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as well as Western blotting and was shown to have accurately expressed the N11-VP1 as cloned. Examination of the Coomassie-stained gels revealed that the capsid-like particles composed of the N11-VP1 protein did not contain any host-derived histones. The absence of the histones in the N11-VP1 capsid-like particles is indicative of the inability of these particles to package DNA, a feature which is observed when wild-type VP1 is treated in this manner. Electron microscopy of these particles substantiated this observation. To determine if the deletion of the NLS exhibited true in vivo characteristics, Sf9 insect cells were infected with the recombinant baculovirus carrying the N11-VP1 gene and examined early in infection (30 h post-infection) by indirect immunofluorescence. The N11-VP1 protein was not transported to the nucleus and remained in the cytoplasm. When the Sf9 cells were coinfected with N11-VP1 and polyomavirus VP2 and VP3 carrying baculoviruses, the N11-VP1 was transported to the nucleus by cooperation with the minor capsid proteins. These studies demonstrate that the N-terminal region of VP1, which contains the NLS and DNA-binding domains, is essential for VP1 nuclear transport and its ability to package Sf9 cellular DNA.

Baculoviridae↗

PubMed2003

Gene packaging with lipids, peptides and viruses inhibits transfection by electroporation in vitro.

To develop improved methods of gene delivery, packaging DNA in chemical or viral vectors could increase electroporation-mediated transfection. To test this hypothesis, electroporation was applied to DU145 prostate cancer cells incubated with green fluorescent protein-encoded DNA plasmid either naked or packaged with cationic lipid (Lipofectin), polycationic peptide (salmon protamine) or retroviral vectors (Moloney murine leukemia viruses) and then assayed for gene expression and cell viability. Cationic lipid or electroporation alone each significantly increased transfection, but their combination was less effective. Addition of protamine peptide during electroporation was also less effective than electroporation alone. The combination of retroviral vectors and electroporation transfected fewer cells than retrovirus alone. We conclude that the combination of electroporation with chemical or viral vectors does not improve gene transfection in vitro.

Animals↗

PubMedDate not supplied

[The definition of benefits: from the benefit package to the supply of services].

The definition of a "benefit package" of services covered by the National Health System of Spain--NHSS--raises technical and political problems. This article examines six relevant issues related with the implementation of this strategy: the instrument to define the services covered by the public system; health care expenditures; access to the services; quality; and the decision making-process. The definition of a comprehensive package of--broadly defined--services covered by the NHSS seems to be the most appropriate strategy, instead of a very detailed "catalog" of medical practices.

Decision Making, Organizational↗

PubMed2003

Pyrolysis kinetics of electronic packaging material in a nitrogen atmosphere.

The kinetics of pyrolysis of electronic packaging material are investigated under various heating rates (5, 10, 15, 20 K/min) in an inert atmosphere using a thermogravimetric analysis (TGA) technique. The pyrolysis characteristics of samples are examined by SEM, XRD, FTIR, ICP-MS and EA. The effect of heating condition on the surface area and pore structure of samples is discussed. Two reaction stages are involved for the pyrolysis of electronic packaging material when nitrogen is present in the carrier gas. The corresponding kinetic parameters, including activation energy, pre-exponential factor and reaction order are presented. The apparent activation energies can be divided into three groups. The results will be useful in developing pyrolysis or incineration systems for plastic waste from electronic components.

Electronics↗

PubMed1997

Evaluation of the presence of porcine reproductive and respiratory syndrome virus in packaged pig meat using virus isolation and polymerase chain reaction (PCR) method.

An investigation was carried out to assess the potential presence of porcine reproductive and respiratory syndrome virus (PRRSV) in packaged pig meat. Samples of meat were collected at the processing plants and were sent to the laboratory for testing by virus isolation and reverse transcription-polymerase chain reaction (RT-PCR). Samples collected at four plants were randomly selected from lots of packaged pig meat from different slaughtering days and were sent frozen to the laboratory. Homogenates of meat were prepared and were inoculated onto MARC-145 cells and after two passages the presence of PRRSV was monitored by indirect immunofluorescence staining using PRRSV specific monoclonal antibody. All pig meat samples (six pools of meat samples from 73 different lots = 438 total homogenates) tested were found negative by virus isolation. Primers from open reading frames 6 and 7 were designed and a RT-PCR assay was developed and was demonstrated to detect both North American and European PRRSV isolates. Using this assay virus was detected at a concentration as low as 0.355 infectious virions per ml in supernatant of PRRSV infected cells. This RT-PCR assay could detect PRRS viral nucleic acid from various tissue samples of experimentally infected pigs including muscle tissue, thus demonstrating its applicability on tissue samples. All meat sample homogenates tested by RT-PCR (one sample pool from the 73 lots) were also found negative for PRRS viral nucleic acid. The results suggest that pig meat does not retain detectable amounts of PRRSV and further support that the transmission of PRRSV through pig meat is unlikely.

Abattoirs↗

PubMed1998

Misleading nutrition claims on cracker packages prior to and following implementation of the Nutrition Labeling and Education Act of 1990.

OBJECTIVES: This study compared patterns in selected health claims on snack cracker packaging and fat content prior to and following enforcement of the Nutrition Labeling and Education Act of 1990 (NLEA). METHODS: Through observations at supermarkets in 1991 and 1995, the prevalence on packages of health claims that consumers associate with heart disease prevention was evaluated. The fat content of each product also was recorded. Criteria for potentially misleading claims were developed. RESULTS: Analysis of both cross-sectional data and products that were available in both years showed that fat content, as well as the number of products containing target claims, had significantly decreased by 1995. The prevalence of potentially misleading claims also declined significantly, from 77% in 1991 to 49% in 1995. CONCLUSIONS: Although the data regarding the changes from 1991 to 1995 are encouraging, the prevalence of potentially misleading health claims for this food category continues to be high.

Adult↗

PubMedDate not supplied

Estrogenic effects of food wrap packaging xenoestrogens and flavonoids in female Wistar rats: a comparative study.

The objective of this study was to compare the estrogenicity of xenoestrogens found in food wrap packaging and phytoestrogen flavonoids. Uterotrophic and vaginal cornification assays were performed on immature and ovariectomized rats. Genistein, bisphenol F, and octylphenol were identified as estrogenic only in immature rats. Using vaginal cornification as a more specific estrogenic parameter, all tested compounds except tangeretin were active in immature rats. While apigenin and kaempferol appeared to have low estrogenic activity, they potentialized the uterotrophic effect of 17beta-estradiol in immature rats. These data showed that (i) phytoestrogens like genistein can be as potent or even more estrogenic than compounds found in food wrap packaging, (ii) immature rats appear to be a more sensitive in vivo model than ovariectomized rats in term of estrogenicity, (iii) the vaginal cornification assay could be a sensitive and useful test to detect weak estrogenic compounds to which humans can be exposed via food.

Animals↗

PubMed2000

A comprehensive package of support to facilitate the treatment of problem drug users in primary care: an evaluation of the training component.

Since the early 1980s, government policy documents and specialist reports have encouraged the involvement of general practitioners (GPs) in the treatment of problem drug users. In spite of such policy initiatives, their involvement has been patchy and slow. In response to this apparent reluctance, the London Boroughs of Brent and Harrow established the substance misuse management project (SMP) to support and train GPs in the management of substance misuse. The SMP is a GP-led project that provides ongoing support, shared-care protocol, primary care team training, treatment audits and financial reimbursements. In 1996, the SMP worked with GPs who were not currently involved in treating problem drug users, and those who were providing only minimal interventions. This paper evaluates the training and support given to these GPs and examines changes in their practice. A pre- and post-test survey was undertaken of GP knowledge, attitudes and levels of activity. A structured questionnaire was administered to all GPs before training (n=40) and re-administered between 6 and 9 months following training. SMP audit data were also reviewed to validate any reported changes in practice. All GPs initially reported insufficient knowledge to manage problem drug users. One-fifth were unaware they could prescribe methadone, and nearly half believed drug problems should be treated by specialist services. Post-training, the GPs had increased their levels of treatment activity and reported greater confidence and willingness to treat. This study demonstrates the potential to involve GPs in the treatment of problem drug users. The training was part of a package that included ongoing support sessions, team training, audits of treatment and financial reimbursements. It is proposed that, whilst training is a necessary condition, a more comprehensive package of support is needed to facilitate the treatment of problem drug users in primary care.

Journal Article↗

PubMed2001

Chromosome condensation: packaging the genome.

The packaging of centimetre long DNA molecules into compact metaphase chromosomes is essential for genome segregation in anaphase. The chromosomal condensin complex plays a crucial part in this packaging, and important new insight into condensin action in vitro and in vivo has recently been gained.

Adenosine Triphosphatases↗

PubMed2002

DNA packaging: a new class of molecular motors.

DNA is packaged into preformed bacteriophage capsids to liquid crystalline density by the action of a portal protein complex. Single molecule packaging studies indicate that this is a new and extremely powerful class of molecular motors.

Capsid↗

PubMed2003

Models of bacteriophage DNA packaging motors.

An ATP-dependent motor drives a DNA genome into a bacteriophage capsid during morphogenesis of double-stranded DNA bacteriophages both in vivo and in vitro. The DNA molecule enters the capsid through a channel in the center of a symmetric protein ring called a connector. Mechanisms in two classes have been proposed for this motor: (1) An ATP-driven rotating connector pulls a DNA molecule via serial power strokes. (2) The connector rectifies DNA motion that is either thermal, biased thermal, or oscillating electrical field-induced (motor-ratchet hypothesis). Mechanisms in the first class have previously been proposed to explain the detailed structure of DNA packaging motors. The present study demonstrates that the motor-ratchet hypothesis also explains the current data, including data in the following categories: biochemical genetics, energetics, structure, and packaging dynamics.

Adenosine Triphosphate↗

PubMed2002

Insights into specific DNA recognition during the assembly of a viral genome packaging machine.

Terminase enzymes mediate genome "packaging" during the reproduction of DNA viruses. In lambda, the gpNu1 subunit guides site-specific assembly of terminase onto DNA. The structure of the dimeric DNA binding domain of gpNu1 was solved using nuclear magnetic resonance spectroscopy. Its fold contains a unique winged helix-turn-helix (wHTH) motif within a novel scaffold. Surprisingly, a predicted P loop ATP binding motif is in fact the wing of the DNA binding motif. Structural and genetic analysis has identified determinants of DNA recognition specificity within the wHTH motif and the DNA recognition sequence. The structure reveals an unexpected DNA binding mode and provides a mechanistic basis for the concerted action of gpNu1 and Escherichia coli integration host factor during assembly of the packaging machinery.

Adenosine Triphosphate↗

PubMed1993

Kinetic characterization of the ATPase activity of the DNA packaging enzyme from bacteriophage lambda.

Terminases are enzymes common to all of the complex double-stranded DNA viruses and are required for viral assembly. These enzymes function to excise a single viral genome from a concatemeric DNA precursor and package it into a preformed protective protein shell or capsid. ATP hydrolysis by these enzymes has been described and appears to be critical to the packaging process. We have previously characterized the endonuclease activity of purified terminase from bacteriophage lambda [Tomka, M. A., & Catalano, C. E. (1993) J. Biol. Chem. 268, 3056-3065], and we describe here a kinetic characterization of the ATPase activity of the enzyme. lambda Terminase possesses a DNA-stimulated ATPase activity and hydrolyzes ATP to ADP and Pi. This activity requires divalent metal and is supported by all of the group IIa metals examined, as well as Mn2+. The reaction is also stimulated by NaCl, GTP, and dGTP. Of note is that neither of the guanosine nucleotides is hydrolyzed by the enzyme, while dATP is hydrolyzed at a rate comparable to that of ATP. Kinetic analysis of the ATPase activity revealed two apparent binding sites for ATP hydrolysis. The high-affinity site (Km = 5 microM) and low-affinity site (Km approximately 1.3 mM) hydrolyze ATP with kcat = 3 and 16 min-1, respectively. While the high-affinity site is unaffected by the presence of DNA, ATP hydrolysis at the low-affinity site is stimulated by DNA, which results from both a decrease in the Km and a concomitant increase in the kcat of the reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗

PubMed2001

The functional asymmetry of cosN, the nicking site for bacteriophage lambda DNA packaging, is dependent on the terminase binding site, cosB.

cosN is the site at which terminase, the DNA packaging enzyme of phage lambda, introduces staggered nicks into viral concatemeric DNA to initiate genome packaging. Although the nick positions and many of the base pairs of cosN show 2-fold rotational symmetry, cosN is functionally asymmetric. That is, the cosN G2C mutation in the left half-site (cosNL) causes a strong virus growth defect whereas the symmetrically disposed cosN C11G mutation in the right half-site (cosNR) does not affect virus growth. The experiments reported here test the proposal that the genetic asymmetry of cosN results from terminase interactions with cosB, a binding site to the right of cosN. In the presence of cosB, the left half-site mutation, cosN G2C, strongly affected the cos cleavage reaction, while the symmetric right half-site mutation, cosN C11G, had little effect. In the absence of cosB, the two mutations moderately reduced the rate of cos cleavage by the same amount. The results indicated that the functional asymmetry of cosNdepends on the presence of cosB. A model is discussed in which terminase-cosN interactions in the nicking complex are assisted by anchoring of terminase to cosB.

Bacteriophage lambda↗

PubMed1997

Kinetic characterization of the strand separation ("helicase") activity of the DNA packaging enzyme from bacteriophage lambda.

Bacteriophage lambda is assembled from preformed viral capsids (proheads), tails, and genomes that are excised from a concatemeric DNA precursor. The enzyme responsible for insertion of the genome into the precapsid is known as terminase. This enzyme possesses site-specific endonuclease, ATPase, and DNA strand separation ("helicase") catalytic activities, which work in concert to excise and package a single viral genome during phage assembly. We have previously characterized the endonuclease [Tomka, M. A., & Catalano, C. E. (1993) J. Biol. Chem. 268, 3056-3065] and ATPase [Tomka, M. A., & Catalano, C. E. (1993) Biochemistry 32, 11992-11997] catalytic activities of lambda terminase and present here similar studies on the strand separation activity of the enzyme. Strand separation requires terminase, divalent metal, and adenosine nucleotides with a hydrolyzable beta,gamma-phosphate bond. Two apparent binding sites for ATP-mediated strand separation were identified, one of which appears to be distinct from the high- and low-affinity sites previously observed for ATP hydrolysis [Hwang, Y., Catalano, C. E., & Feiss, M. (1995) Biochemistry 35, 2796-2803]. Salt stimulates the reaction at low concentrations but is strongly inhibitory at elevated concentrations, presumably due to impaired DNA binding. The above results are identical with either a complex DNA mixture (a nicked, annealed DNA duplex in the presence of excess nonspecific DNA) or a purified DNA substrate; however, a kinetic analysis of the reaction revealed that the observed rate was approximately 5-fold greater with the purified DNA substrate. Moreover, while Escherichia coli integration host factor (IHF) stimulates terminase-mediated strand separation with both substrates, the observed stimulation is more pronounced with the complex DNA mixture (10-fold rate increase) than the purified DNA substrate (5-fold rate increase). Our data are consistent with a model where IHF binding to the terminase assembly site forms a binary protein.DNA complex readily distinguishable from bulk DNA. The implications of these results to the process of DNA packaging in bacteriophage lambda are discussed.

Adenosine Triphosphatases↗

PubMed1999

Cloning, expression, and characterization of a DNA binding domain of gpNu1, a phage lambda DNA packaging protein.

Terminase is an enzyme from bacteriophage lambda that is required for insertion of the viral genome into an empty pro-capsid. This enzyme is composed of the viral proteins gpNu1 (20.4 kDa) and gpA (73.3 kDa) in a holoenzyme complex. Current models for terminase assembly onto DNA suggest that gpNu1 binds to three repeating elements within a region of the lambda genome known as cosB which, in turn, stimulates the assembly of a gpA dimer at the cosN subsite. This prenicking complex is the first of several stable nucleoprotein intermediates required for DNA packaging. We have noted a hydrophobic region within the primary amino acid sequence of the terminase gpNu1 subunit and hypothesized that this region constitutes a protein-protein interaction domain required for cooperative assembly at cosB and that is also responsible for the observed aggregation behavior of the isolated protein. We therefore constructed a mutant of gpNu1 in which this hydrophobic "domain" has been deleted in order to test these hypotheses. The deletion mutant protein, gpNu1DeltaK, is fully soluble and, unlike full-length protein, shows no tendency toward aggregation; However, the protein is a dimer under all experimental conditions examined as determined by gel permeation and sedimentation equilibrium analysis. The truncated protein is folded with evidence of secondary and tertiary structural elements by circular dichroism and NMR spectroscopy. While physical and biological assays demonstrate that gpNu1DeltaK does not interact with the terminase gpA subunit, the deletion mutant binds with specificity to cos-containing DNA. We have thus constructed a deletion mutant of the phage lambda terminase gpNu1 subunit which constitutes a highly soluble DNA binding domain of the protein. We further propose that the hydrophobic amino acids found between Lys100 and Pro141 define a self-association domain that is required for the assembly of stable nucleoprotein packaging complexes and that the C-terminal tail of the protein defines a distinct gpA-binding site that is responsible for terminase holoenzyme formation.

Bacteriophage lambda↗

PubMed2002

Rotavirus protein involved in genome replication and packaging exhibits a HIT-like fold.

Rotavirus, the major cause of life-threatening infantile gastroenteritis, is a member of the Reoviridae. Although the structures of rotavirus and other members of the Reoviridae have been extensively studied, little is known about the structures of virus-encoded non-structural proteins that are essential for genome replication and packaging. The non-structural protein NSP2 of rotavirus, which exhibits nucleoside triphosphatase, single-stranded RNA binding, and nucleic-acid helix-destabilizing activities, is a major component of viral replicase complexes. We present here the X-ray structure of the functional octamer of NSP2 determined to a resolution of 2.6 A. The NSP2 monomer has two distinct domains. The amino-terminal domain has a new fold. The carboxy-terminal domain resembles the ubiquitous cellular histidine triad (HIT) group of nucleotidyl hydrolases. This structural similarity suggests that the nucleotide-binding site is located inside the cleft between the two domains. Prominent grooves that run diagonally across the doughnut-shaped octamer are probable locations for RNA binding. Several RNA binding sites, resulting from the quaternary organization of NSP2 monomers, may be required for the helix destabilizing activity of NSP2 and its function during genome replication and packaging.

Amino Acid Sequence↗