Socioeconomic position and cardiovascular and neuroendocrine responses following cognitive challenge in old age

Social disparities in health persist into old age, and differences in psychophysiological responsivity may contribute to this pattern. We assessed whether higher socioeconomic status (SES) is associated with attenuated cardiovascular and neuroendocrine responses elicited by cognitive tasks in old age. We tested 132 community-dwelling men and women aged 65-80 years, divided on the basis of educational attainment into higher and lower SES groups, and compared them with 26 higher educated participants aged 27-42 years. Blood pressure, hemodynamic variables and salivary cortisol were assessed in response to the performance of three cognitive tasks, and then during recovery. Older groups showed smaller heart rate and larger cortisol changes than younger participants. Post-task recovery in heart rate, stroke volume, pre-ejection period, and systolic blood pressure was greatest in the younger group, least in the older/lower education group, and intermediate in the older/higher education group. SES did not influence the increased cortisol responsivity of older participants. The results are consistent with the notion that higher SES protects against age-related changes in cardiovascular response profiles, particularly during recovery.     

Lactic dehydrogenase virus (LDV) impairs the antigen-presenting capacity of macrophages yet fails to affect their phagocytic activity

The effect of acute infection of mice with lactic dehydrogenase virus (LDV) on two major functions of peritoneal macrophages was tested. Using a macrophage-dependent T cell proliferative assay to test the antigen-presenting capacity of LDV-infected macrophages we found that LDV impairs the capacity of antigen-presenting cells to trigger memory T lymphocytes. Endocytosis of antigen by LDV-infected macrophages was similar to that of uninfected cells. In addition, the proportion of intracellular antigen versus membrane-bound antigen in LDV-infected cells were similar to that observed in uninfected mice. It appears therefore, that the impaired immunogenic effect of LDV-infected macrophages results from reduced immunogenicity of the membrane-bound antigen.Testing the phagocytic activity of peritoneal macrophages we found that the uptake of radiolabeled antibody-coated sheep erythrocytes or bacteria (E. coli) by infected cells was similar to that by uninfected macrophages. In addition, LDV failed to affect the ability of peritoneal macrophages in a nitroblue tetrazolium reduction reaction which serves as an alternative parameter for measuring phagocytic activity. Our results support the assumption that LDV, which probably propagates in the cells of the reticuloendothelial system, impairs some of the immunogenic functions of macrophages and thereby affects macrophage-dependent immune responses.     

Latent Pneumocystis carinii infection in commercial rat colonies: comparison of inductive immunosuppressants plus histopathology, PCR, and serology as detection methods

Histopathologic evaluation combined with a period of immunosuppression has been the standard procedure for detection of Pneumocystis carinii in commercial rat colonies. Variation in induction regimens and in the sensitivity of detection methods may result in underreporting of the presence of P. carinii in breeding colonies or delay its detection. In the present study, methylprednisolone and cyclophosphamide were evaluated for the ability to induce P. carinii infection in rats from an enzootically infected commercial barrier colony. The presence of P. carinii was detected by histopathologic methods and by amplification of a targeted region of the P. carinii thymidylate synthase gene by PCR over the 8-week study period. Sera taken from rats prior to either induction regimen were evaluated for the presence of P. carinii-specific antibodies by the immunoblotting technique. Few significant differences in ability to induce organism burden or in histopathology were observed between the two immunosuppressive regimens. However, a dramatic loss of weight over the study period was observed in rats treated with methylprednisolone but not in rats treated with cyclophosphamide. Although histopathologic changes attributable to P. carinii did not appear before 2 weeks with either immunosuppressant, the presence of the organism in these animals was detected by immunoblotting and PCR. Cyst scores and the intensities of the histopathologic lesions increased during the study period, but the number of rats exhibiting evidence of P. carinii infection did not change after week 3. These results suggest that use of the PCR method on postmortem lung tissue of rats without prior induction regimens or identification of anti-P. carinii antibodies in antemortem serum samples is a sufficiently sensitive method for detection of the presence of a P. carinii carrier state in rodent breeding colonies.     

The alpha-L-(1----2)-trirhamnopyranoside epitope on the group-specific polysaccharide of group B streptococci.

A number of epitope specificities associated with the group antigen (group B polysaccharide) of group B streptococci have been identified in a polyclonal antiserum induced in rabbits by a nonencapsulated variant strain of group B streptococci. This was achieved by using a series of oligosaccharide inhibitors, obtained by both synthetic and degradative procedures, to inhibit the binding of the group B polysaccharide to the polyclonal antiserum. While the dominant epitope expressed in the antiserum was alpha-L-Rhap(1----2)alpha-L-Rhap(1----2)alpha-L-Rhap, specificities associated with alpha-L-Rhap and alpha-L-Rhap(1----3)alpha-D-Galp(1----3)beta-D-Glcp-NAc(1----4)alp ha-L-Rhap were also identified. The dominant expression of the former epitope is consistent with its terminal location on the group antigen and also with highly branched multiantennary structure of this antigen. Antibodies specific for the alpha-L-trirhamnopyranoside epitope were purified by affinity chromatography, using the synthetic trisaccharide glucitol as the hapten. Oligosaccharide inhibition studies indicate that the specificity of these antibodies is identical to that of a murine monoclonal antibody induced by the same nonencapsulated strain of group B streptococci.     

Inter-agency referrals and the establishment of a community-based treatment program

Based upon a treatment program involving the referral of more than 400 "antisocial" children to a community agency, common problems associated with inter-agency referral processes are discussed. The efficacy of selected inter-agency referral processes (computation, bargaining, judgment, and inspiration) are examined. Causes of misreferrals also are discussed. These include those generated separately by the host agency and by the donor agency and those additionally generated by their mutual interaction. Suggested means for preventing dysfunctions are presented.     

Pneumolysin induces the salient histologic features of pneumococcal infection in the rat lung in vivo.

Streptococcus pneumoniae infections are common, but how they cause host tissue injury and death is incompletely understood. Immunization with pneumolysin, a thiol-activated toxin produced by the pneumococcus, partially protects animals during subsequent infection. The mechanism by which pneumolysin contributes to disease is not known. The aim of the present investigation was to determine the histologic changes induced by recombinant pneumolysin in the rat lung and to compare them with the changes induced by live organisms. Injection of either toxin (200 or 800 ng) or bacteria into the apical lobe bronchus was associated with the development of a severe lobar pneumonia restricted to the apical lobe. The changes induced by the toxin were greater at the higher concentration, and changes were most severe in those animals in which there was partial ligation of the apical lobe bronchus. The pneumonitis was less severe following injection of a modified toxin with decreased hemolytic activity, generated by site-directed mutagenesis of the cloned pneumolysin gene, indicating that this property of the toxin was important in generating pulmonary inflammation. There was still considerable pneumonitis after injection of a modified toxin with decreased capacity to activate complement.     

Pseudomonas aeruginosa cell-to-cell signaling is required for virulence in a model of acute pulmonary infection

Cell-to-cell signaling controls many virulence genes in Pseudomonas aeruginosa. We tested the virulence of las and rhl quorum-sensing mutants in neonatal mice. A lasI rhlI double mutant was nearly avirulent, and the respective single mutant strains were reduced in virulence compared with the wild-type strain. Quorum sensing plays a role in P. aeruginosa pneumonia in neonatal mice.     

Surveillance of resistance in bacteria causing community-acquired respiratory tract infections

Bacterial resistance to antibiotics in community-acquired respiratory tract infections is a serious problem and is increasing in prevalence world-wide at an alarming rate. Streptococcus pneumoniae , one of the main organisms implicated in respiratory tract infections, has developed multiple resistance mechanisms to combat the effects of most commonly used classes of antibiotics, particularly the β -lactams (penicillin, aminopenicillins and cephalosporins) and macrolides. Furthermore, multidrug-resistant strains of S. pneumoniae have spread to all regions of the world, often via resistant genetic clones. A similar spread of resistance has been reported for other major respiratory tract pathogens, including Haemophilus influenzae , Moraxella catarrhalis and Streptococcus pyogenes . To develop and support resistance control strategies it is imperative to obtain accurate data on the prevalence, geographic distribution and antibiotic susceptibility of respiratory tract pathogens and how this relates to antibiotic prescribing patterns. In recent years, significant progress has been made in developing longitudinal national and international surveillance programs to monitor antibiotic resistance, such that the prevalence of resistance and underlying trends over time are now well documented for most parts of Europe, and many parts of Asia and the Americas. However, resistance surveillance data from parts of the developing world (regions of Central America, Africa, Asia and Central/Eastern Europe) remain poor. The quantity and quality of surveillance data is very heterogeneous; thus there is a clear need to standardize or validate the data collection, analysis and interpretative criteria used across studies. If disseminated effectively these data can be used to guide empiric antibiotic therapy, and to support—and monitor the impact of—interventions on antibiotic resistance.     

Electrophysiology of supraoptico-paraventricular nucleus connections in the rat

Summary In an attempt to clarify the mechanisms involved during synchronous discharge of magnocellular neurosecretory cells of the supraoptic and paraventricular nuclei, extracellular action potentials were recorded from 149 single units located in the rat paraventricular nucleus. Responses of the cells to stimulation of the ipsilateral supraoptic nucleus were recorded and it was observed that 7% of paraventricular nucleus neurones could be antidromically identified as projecting to the supraoptic nucleus. Excitatory responses were recorded from 40% of cells tested and were probably mediated by an interneurone population. Inhibitory responses were recorded from 37% of the cells and may have been mediated by direct projections from the supraoptic nucleus. No differences in responses were recorded from cells identified as projecting to the median eminence or neurohypophysis as compared with the rest of the population tested. However, more of the phasically firing putative vasopressin-secreting cells, (58%) were excited than were continuously active cells (38%). Delivery of short trains of high-frequency stimulation induced bursts of discharge from 93% of cells so tested, regardless of response to single shock stimulation. These burst discharges showed a late onset as compared with responses following single shock stimulation. The results suggest that a complex of intra- and internuclear interactions serve to regulate the neurosecretory activity of magnocellular cells within the supraoptic and paraventricular nuclei.