Comparison of the smoking behaviour and attitudes of smokers who attribute respiratory symptoms to smoking with those who do not.

General practitioners' (GPs') advice against smoking helps smokers to stop; unfortunately, GPs cannot predict which patients will quit following advice. This postal questionnaire survey suggests that where smokers attribute their respiratory symptoms to smoking, they are eight times (95% confidence interval [CI] = 3.0-23.3) more likely to believe that their health will improve if they stop smoking and six times (95% CI = 1.4-23.3) more likely to intend to stop smoking.     

Staphylococci express a receptor for human transferrin: identification of a 42-kilodalton cell wall transferrin-binding protein.

Staphylococcus aureus and the coagulase-negative staphylococci are commonly responsible for peritonitis in renal patients undergoing continuous ambulatory peritoneal dialysis. To simulate growth conditions in vivo, staphylococci isolated from peritoneal infections were cultured in used human peritoneal dialysate (HPD). Immunoblotting experiments using cell wall preparations from these staphylococci revealed the presence of the host iron-binding glycoprotein transferrin bound to S. aureus, S. epidermidis, S. capitis, S. haemolyticus, and S. hominis but not to S. warneri or S. saprophyticus. Similar results were obtained by incubating broth-grown staphylococci with human transferrin, although, in contrast to S. aureus, the coagulase-negative staphylococci bound more transferrin after growth in iron-restricted broth. To determine whether the staphylococci express a saturable specific receptor for human transferrin, the interaction of human 125I-transferrin with the staphylococci was examined. Both S. aureus and S. epidermidis bound the radiolabelled iron-saturated ligand in a time- and concentration-dependent manner. From competition binding assays, the affinity (Kd) and number of receptors were estimated for S. epidermidis (Kd, 0.27 microM; 4,200 receptors per cell) and S. aureus (Kd, 0.28 microM; 4,200 receptors per cell). S. epidermidis but not S. aureus receptor activity was partially iron regulated. Human apotransferrin and iron-saturated transferrin and rabbit and rat transferrins competed equally well for the staphylococcal receptor. Bovine and porcine transferrins and ovotransferrin as well as human and bovine lactoferrins were much less effective at competing with human transferrin. Treatment of whole staphylococci with protease abolished transferrin binding, indicating the involvement of cell surface protein. Western blots (immunoblots) of cell wall preparations probed with human transferrin revealed the presence of a 42-kDa transferrin-binding protein common to both S. aureus and S. epidermidis. On Western strip blots, the binding of human transferrin to this protein was blocked by labelled human transferrin but not by albumin, immunoglobulin G, or bovine transferrin or ovotransferrin. To assess the conservation of the 42-kDa transferrin-binding protein, cell wall proteins of S. epidermidis, S. haemolyticus, S. capitis, S. hominis, S. warneri, and S. saprophyticus were Western blotted and probed with human transferrin. Only S. warneri and S. saprophyticus lacked the 42-kDa wall protein, consistent with their inability to bind transferrin. These data show that the staphylococci express a specific receptor for human transferrin based at least in part on a common 42-kDa cell wall protein.     

Differentiation of bursal secretory-dendritic cells studied with anti-vimentin monoclonal antibody

Embryonic and posthatched differentiation of bursal secretory dendritic cells, which express vimentin intermediate filaments, were studied with anti-vimentin (clone 3B4) and anti-cytokeratin (clone Lu5) monoclonal antibodies. Anti-cytokeratin staining revealed that medullary reticular epithelial cells formed a continuous network at every age, whereas the vimentin positive cells were single and showed dendritic appearance. On the basis of location, number, shape, polarized appearance, and Ia staining, the vimentin-positive cells and secretory dendritic cells appeared to be the same cell. Secretory dendritic cell precursors entered the bursal epithelium between 11 and 13 days of embryogenesis. The first vimentin positive cell appeared in the bud of 14-day embryos. Bud formation preceded the appearance of vimentin-positive cells. These observations suggested that the secretory dendritic cell precursor did not express vimentin when it entered the epithelium. Between 15 days of embryogenesis and 2 weeks of posthatch development, the changes in vimentin staining pattern revealed a cytological differentiation of the vimentin-positive cell. During rapid bursal growth, the number of secretory dendritic cells (vimentin-positive cells) increased about 18 times possibly by proliferation of vimentin-negative precursors in the epithelial arches of the corticomedullary border. © 1992 Wiley-Liss, Inc.     

Induction of B cell costimulatory function by recombinant murine CD40 ligand

T cell-dependent regulation of B cell growth and differentiation involves an interaction between CD40, a B cell surface molecule, and the CD40 ligand (CD40L) which is expressed on activated CD4⁺ T cells. In the current study, we show that recombinant membrane-bound murine CD40L induces B cells to express costimulatory function for the proliferation of CD4⁺ Tcells. CD40L- or lipopolysaccharide (LPS)-activated, but not control-cultured B cells were strong costimulators of anti-CD3 or alloantigen-dependent T cell responses. The molecular interactions responsible for the increased costimulatory functions were examined by analyzing the activated B cells for changes in the expression of two costimulatory molecules, B7 and heat-stable antigen (HSA), as well as by the use of antagonists of B7 and HSA (CTLA4.Fc and 20C9, respectively). The expression of both B7 and HSA was enhanced on B cells activated with LPS. As observed in previous studies, the costimulatory activity of the LPS-activated B cells was dependent on both B7 and HSA and was completely inhibited in the presence of a combination of CTLA4.Fc and 20C9. In contrast, activation of B cells with CD40L induced the expression of B7 but did not enhance the expression of HSA. In addition the costimulatory activity of the CD40L-activated B cells was partially, but not completely, inhibited by the combination of CTLA4.Fc and 20C9. These results demonstrate that CD40L regulates costimulatory function of B cells in part by inducing the expression of B7 and suggest that CD40L-activated B cells express an additional costimulatory activity that is not associated with LPS-activated B cells.     

Molecular Manipulations of Extracellular Superoxide Dismutase: Functional Importance for Learning

Extracellular superoxide dismutase (EC-SOD) controls the availability of extracellular superoxide (O ₂ ^- ), which is important for a variety of physiological pathways, including the primary means of inactivating nitric oxide (NO). The role of EC-SOD in neurobehavioral function has been until now unexplored. In the current studies, the phenotypic expression of genotypic alterations of EC-SOD production in mice were characterized for spatial learning and memory. Dramatic impairments in spatial learning in the win-shift 8-arm radial maze were seen in both EC-SOD knockout mice and EC-SOD overexpressing mice. The EC-SOD overexpressing mice were further characterized as having significant deficits in a repeated acquisition task in the radial-arm maze, which permitted the dissociation of long and short-term learning. Long-term learning was significantly impaired by EC-SOD overexpression, whereas short-term learning was not significantly affected by EC-SOD overexpression. NO systems have been shown to be importantly involved in learning and memory. This may be important in the current studies because EC-SOD has primary control over the inactivation of NO. We found that EC-SOD overexpressing mice were resistant to the cognitive effects of L-NAME (N^G-nitro-L-arginine methyl ester hydrochloride), an NO synthase inhibitor. Decreased NO catabolism in these mice may have served to counter the effects of NOS inhibition by L-NAME. The current finding that EC-SOD levels that were either higher or lower than controls impaired learning demonstrates that the proper control of brain extracellular (O ₂ ^- ) may be more vital than merely reduction of brain extracelluar (O ₂ ^- ) in maintaining adequate learning function.     

Oesophagostomum species in pigs in england: 2. Oesophagostomum quadrispinulatum: Resistance to reinfection

Under experimental conditions, repeated infection with 500 larvae of Oesophagostomum quadrispinulatum induced a solid resistance in about 50 days, this being manifested by a failure of third-stage larvae to develop. An apparently stable population of a few hundred adult worms remained in the pigs for at least 200 days.     

Wheat streak mosaic virus--structural parameters for a Potyvirus

Wheat streak mosaic virus is a Tritimovirus, a member of the Potyviridae family, which includes the very large Potyvirus genus. We have examined wheat streak mosaic virus by electron microscopy and fiber diffraction from partially oriented sols, and analyzed the results to estimate the symmetry and structural parameters of the viral helix. The virions have an apparent radius of 63 +/- 5 A. The viral helix has a pitch of 33.4 A +/- 0.6 A. There appear to be 6.9 subunits per turn of the helix, although we cannot completely eliminate values of 5.9 or 7.9 for this parameter.