The properties of three baculoviruses from closely related hosts.

The baculoviruses of three important and closely related pest insects, Spodoptera littoralis, S. exempta and S. frugiperda, were purified and several of their properties were compared. These include data on virus morphology, physical properties of the virus particle, serological properties, structural polypeptides, and viral DNA. The effect of the endogenous polyhedron alkaline protease on the polyhedron and virus particle proteins was also investigated. Biochemical and biophysical differences between the viruses were found which were reflected in their serological properties. The feasibility of using a simple serological technique for specific identification of each virus has been demonstrated.     

An observational study of variation in GPs' out-of-hours emergency referrals.

Out-of-hours organisations are responsible for the care of patients 70% of the time, and their GPs act as gatekeepers to secondary care services. This observational study identifies the variations in GPs' out-of-hours referral rates to secondary care and factors that could explain these variations. One hundred and forty-nine GPs who worked in one UK general practice out-of-hours cooperative which served 19 practices with 167 000 registered patients. Data on patients who accessed the out-of-hours service over 3 years (2001-2004) were examined. Factors thought to be predictors of variation in referral rates were investigated using logistic regression analysis. There was a fivefold difference in referral rates between the lowest and highest referring quartiles of GPs (OR [odds ratio] = 4.56, CI [confidence interval] = 3.86 to 5.38). The sex (female) of the clinician, the time of the consultation (11 pm to 7 am), and the place of the consultation (home visit) accounted for some, but not all, of the increased referral rates. A doctor working out-of-hours disproportionately influences the fate of the patient, the number of hospital admissions, and extra costs to the health service. There is a need for follow-up studies to investigate the factors associated with referral behaviour, and how the variation relates to patient factors and the resources available. These findings could be used when planning the staffing of out-of-hours services to optimise appropriate care and minimise patients' exposure to unnecessary intrusive and expensive hospital care.     

Iron and fur regulation in Vibrio cholerae and the role of fur in virulence

Regulation of iron uptake and utilization is critical for bacterial growth and for prevention of iron toxicity. In many bacterial species, this regulation depends on the iron-responsive master regulator Fur. In this study we report the effects of iron and Fur on gene expression in Vibrio cholerae. We show that Fur has both positive and negative regulatory functions, and we demonstrate Fur-independent regulation of gene expression by iron. Nearly all of the known iron acquisition genes were repressed by Fur under iron-replete conditions. In addition, genes for two newly identified iron transport systems, Feo and Fbp, were found to be negatively regulated by iron and Fur. Other genes identified in this study as being induced in low iron and in the fur mutant include those encoding superoxide dismutase (sodA), fumarate dehydratase (fumC), bacterioferritin (bfr), bacterioferritin-associated ferredoxin (bfd), and multiple genes of unknown function. Several genes encoding iron-containing proteins were repressed in low iron and in the fur mutant, possibly reflecting the need to reserve available iron for the most critical functions. Also repressed in the fur mutant, but independently of iron, were genes located in the V. cholerae pathogenicity island, encoding the toxin-coregulated pilus (TCP), and genes within the V. cholerae mega-integron. The fur mutant exhibited very weak autoagglutination, indicating a possible defect in expression or assembly of the TCP, a major virulence factor of V. cholerae. Consistent with this observation, the fur mutant competed poorly with its wild-type parental strain for colonization of the infant mouse gut.     

Iron-vibriobactin transport system is not required for virulence of Vibrio cholerae.

The possible requirement of a functional siderophore (vibriobactin)-mediated iron transport system in the pathogenicity of Vibrio cholerae was determined. Two mutants of V. cholerae defective in the iron-vibriobactin transport system were examined for their ability to multiply and elicit diarrhea in infant mice. One mutant, 40130, was unable to synthesize vibriobactin. The second mutant, 1510, was able to synthesize, but not transport, the siderophore. Both mutants retained the ability to multiply and produce disease in the infant mouse, and virulence was indistinguishable from the parent strains. This indicates that a functional iron-vibriobactin transport system is not essential for cholera pathogenesis. These mutants, like the wild-type strains, were found to have a ferric citrate iron uptake system and could utilize citrate or asparagine for growth in low-iron medium. Compounds of this type may increase the availability of iron to V. cholerae in the host.     

Cloning the gene for Congo red binding in Shigella flexneri.

The ability to bind the dye Congo red from agar medium is associated with virulence of Shigella species. DNA sequences conferring this property have been cloned from a large, 140-kilobase plasmid of Shigella flexneri into a plasmid vector. This recombinant plasmid does not fully restore virulence to S. flexneri isolates which have lost the large plasmid. This indicates that other genes present on the 140-kilobase plasmid must also be required for virulence of S. flexneri. The cloned fragment contains a copy of the insertion sequence IS1 closely linked to the gene for Congo red binding.     

Effect of differences in antibody and complement requirements on phagocytic uptake and intracellular killing of "c" protein-positive and -negative strains of type II group B streptococci

The influence of antibody and complement on the polymorphonuclear leukocytic uptake and killing of type II group B streptococci (GBS) was examined with 11 adult sera and three type II strains possessing the trypsin-resistant and trypsin-sensitive components (II/TR+TS) of the "c" (formerly Ibc) protein or two type II strains lacking both components (II/no c) of the c protein. All tested sera mediated a greater than 1 log10 reduction in colony-forming units (CFUR) of a type II/no c strain, even in the absence of measurable type-specific antibody (less than 1.08 micrograms/ml), but only 5 of 11 mediated a greater than 1 log10 CFUR of any type II/TR/TS strain, even in the presence of moderate levels of type-specific antibody. The classical pathway of complement activation appeared to be more important than the alternative pathway, and even absorbed or immunoglobulin G (IgG)-depleted serum (IgG, 10 mg/dl) mediated a greater than 1 log10 CFUR without magnesium ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (magnesium EGTA) chelation. Chelation with magnesium EGTA reduced the CFUR in 4 of 11 test sera and greatly reduced the CFUR in absorbed or IgG-depleted sera for type II/no c strains. Despite variation in the phagocytic killing of two representative strains of type II GBS, both strains were well phagocytized, as measured by radiolabeled bacterial uptake or electron microscopy. This study suggested that poorly killed type II/TR+TS GBS were easily phagocytized but apparently resisted intracellular killing.     

Three-dimensional modeling of the anatomy of the heart and great vessels

Summary The anatomic constraints imposed on a total artificial heart (TAH) require specific anatomic studies. A thoracic anatomic study was performed with a scanning device equipped with three-dimensional (3-D) reconstruction software on 15 male patients, between the ages of 41 to 63 years (52 ± 6 years). All were candidates for heart transplantation. The 3-D reconstructions of the cardiovascular structures obtained from surgical anatomy data specific to TAH implantation allowed a volumetric measurement of these structures. A modeling diagram of these structures permitted reproducible quantitative measurements of the 35 geometrical parameters which characterized shape, orientation, and position of these structures within the thorax. Most of the measured parameters were characterized by low variability (coefficient of variation from 10 to 25%).

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Modélisation tridimensionnelle de l'anatomie du cur et des gros vaisseaux

Résumé Les contraintes anatomiques imposées au cur artificiel total (CAT) nécessitent des études anatomiques spécifiques. Une étude anatomique thoracique a été réalisée avec un scanner doté d'un logiciel de reconstruction tridimensionnelle (3-D) chez 15 patients, tous de sexe masculin, agés de 41 à 63 ans (52 ± 6 ans), et candidats à une transplantation cardiaque. Les reconstructions 3-D des structures cardio-vasculaires réalisées selon les données de l'anatomie chirurgicale propre à l'implantation du CAT ont permis la mesure volumétrique de ces structures. Un schéma de modélisation de ces structures a permis des mesures quantitatives reproductibles de 35 paramètres géométriques caractéristiques de la forme, de l'orientation, de la position de ces structures dans le thorax. Les résultats de ces mesures ont pu être exprimés en termes statistiques. La plupart des paramètres mesurés étaient caractérisés par une faible variabilité (coefficients de variations de 10 à 25%).

     

The effect of steroids on peripheral blood lymphocytes containing parallel tubular arrays.

The response of lymphocytes containing cytoplasmic inclusions called parallel tubular arrays (PTA) was determined after the administration of the glucocorticoid dexamethasone to 10 healthy volunteers. The percentage of these lymphocytes was found to increase during the lymphopenia induced by steroid administration. The size and number of parallel tubular arrays per cell showed no differences before and after steroid administration, indicating that the increase was a result of a change in the proportion of whole cells. This indicates, for the first time, that a morphologically defined population of lymphocytes from the normal peripheral circulation has been linked to a specific response, ie, steroid resistance. The possible mechanism of steroid resistance is discussed.