Hormonal influence on experimental infections by a toxic shock strain of Staphylococcus aureus.

Subcutaneous infection chambers in rabbits were infected with a strain of Staphylococcus aureus isolated from a patient with toxic shock syndrome. Estrogens (mestranol and 17-beta-estradiol) protected male rabbits and prolonged survival. Neither androgens (testosterone and dihydrotestosterone) nor progesterone affected the susceptibility of intact or ovarihysterectomized female rabbits.     

Factors influencing the sensitivity of herpes simplex virus detection in clinical specimens in a simultaneous enzyme-linked immunosorbent assay using monoclonal antibodies

A rapid simultaneous enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies was investigated for herpes simplex virus (HSV) detection. All HSV isolated (n = 127) were detected, whereas no response was obtained with HSV negative preparations. Equivalent results were obtained from 275 of 277 clinical specimens in the monoclonal ELISA and in an ELISA using polyclonal antibodies, confirming that appropriately selected monoclonal antibodies may be as efficacious as polyclonal antibodies in antibody-based assays. In clinical specimens, the rate of HSV detection (sensitivity) relative to tissue culture isolation was low for both assays, and the major factor responsible for this was the low concentration of virus present in some specimens. The sensitivity of ELISA obtained in routine use varied with different panels of unselected specimens and was related to the speed of development of the cytopathic effect. These results emphasise the need for caution in assigning a definitive sensitivity level to ELISA tests evaluated on different panels of specimens.     

Synergistic induction of interleukin-1 by endotoxin and toxic shock syndrome toxin-1 using rat macrophages.

We studied interleukin-1 (IL-1) secretion by rat peritoneal exudate macrophages stimulated with purified toxic shock syndrome toxin-1 (TSST-1). TSST-1 was observed to be a more potent inducer of IL-1 than was endotoxin. The induction of IL-1 secretion by TSST-1 was not blocked by polymyxin B but could be blocked by monoclonal antibodies directed against TSST-1. Synergistic induction of IL-1 was observed when the cells were stimulated with TSST-1 and endotoxin. The sequence of addition was found to be important for the synergistic response. Enhanced IL-1 production was observed only when macrophages were exposed to endotoxin before or simultaneously with TSST-1. Prior exposure of macrophages to TSST-1 had no enhancing effect on endotoxin-induced IL-1 secretion. We conclude that stimulation of the macrophage by endotoxin enhances the responsiveness of the cells to TSST-1 and may thereby play a role in the pathogenesis of toxic shock syndrome.     

Setting characteristics and mechanical behaviour of a calcium phosphate bone cement containing tetracycline

Calcium phosphate cements are used for bone defect filling and they may also be used as delivery systems for active agents. The physicochemical behaviour of an ionic cement, with a final composition of hydroxyapatite, containing tetracycline hydrochloride was investigated. Chemical characterisation, X-ray diffraction analysis, compressive strength and tensile strength were performed. It is known that the antibiotic can be adsorbed on calcium phosphate compounds and the presence of chloride ions can strongly influence the behaviour of the cement. Adding more than 1% (w/w) of 95% pure tetracycline hydrochloride in the solid phase led to a cement with poor mechanical properties, but which, in addition to hydroxyapatite, contained residual starting reagents. For this reason, experiments were also performed with tetracycline previously treated with a calcium sulphate solution. Using a treated tetracycline, it was possible to introduce at least 7% (w/w) of active ingredient whilst still allowing the reaction to proceed to completion i.e. the formation of hydroxyapatite with good mechanical properties. Therefore, treating the tetracycline HCI with calcium sulphate solution prior to reaction conserved the activity of the antibiotic, limited the influence of the antibiotic on the cement evolution and retained the physical properties of the cement.     

JC virus genomes in progressive multifocal leukoencephalopathy: detection using a sensitive non-radioisotopic in situ hybridization method

JC virus genomes have been localized in formalin-fixed, paraffin-embedded brain tissues of two cases of known progressive multifocal leukoencephalopathy by in situ hybridization utilizing a biotinylated JC virus DNA probe. A three-stage immunoperoxidase system with gold-silver amplification of the diaminobenzidine substrate was used to visualize biotinylated nucleic acid hybrids. Dot-blot quantification of this visualization system indicates that subpicogramme amounts of biotinylated DNA can be detected. Optimal detection of the virus genomes in the brain tissues required a microwave irradiation step prior to hybridization. JC virus genomes were observed in the nuclei of enlarged oligodendrocytes and of some bizarre astrocytes. No other cell types were found to harbour the genomes.     

A method for two dimensional multi-segmental kinematic and kinetic analysis of normal and pathological human gait

The application of an integrated gait analysis system in clinical research is described. With this system it is possible to analyse the walking pattern of various groups of patients with regard to foot-floor contact, kinematics and kinetics, using a Selspot system. In order to study various groups of patients an extensive body-segment model adapted to the variety in patient groups is dealt with and is related to data from the literature. Special attention has been paid to the analysis or errors in the quantities used in kinematics and kinetics. The various sources of errors leading to inaccuracy of the data describing the walking pattern are discussed.     

Mediodorsal thalamic lesions impair "reference" and "working" memory in rats

The present experiment evaluated the ability of rats with lesions in the thalamic mediodorsal nucleus (MD) to perform a task which differentiates between "reference" and "working" memory. In this task, only four of the arms of an 8-arm radial maze were baited, and animals were to restrict their entries to arms which were baited and to avoid never-baited arms. Despite several postoperative acquisition trials, rats with MD lesions did not acquire the task to a degree comparable to control subjects. Subjects with lesions continued to enter never-baited arms (reference memory errors) and to reenter baited arms (working memory errors). Given the lack of specificity in the behavioural impairment, the reference-working memory distinction seems to be an inappropriate one for characterizing the MD lesion deficit in rats. This deficit may involve an inability to use environmental stimuli to distinguish among arms of the maze, or an alteration in motor mechanisms.     

Assays for HIV with improved sensitivity and specificity

Increased knowledge of the human immunodeficiency virus (HIV) and the infection it causes in humans has resulted in an enormous expansion in the understanding of viral parameters and host changes. HIV is a virus which mutates readily and rapidly, presenting many challenges to assay developers, and monitors of therapy and drug-resistance. Prolific viral replication at all the stages of the disease means that an accurate assessment of viral burden, viral load and changes to immune system markers is essential for effective clinical management and treatment. In the present review we have summarised current opinion on the kinetics of HIV infection and the pathogenesis of the disease it causes, and have provided a background to the evolution of HIV assays. Sensitivities and specificities of assays used for anti-HIV and HIV detection have improved, and new assays have been developed employing novel molecular techniques, which are being applied to meet continually evolving demands for more sensitive measurement of an increasing number of parameters. The future of HIV testing is also considered in the light of new knowledge concerning virus dynamics in vivo, the likelihood of the emergence of new subtypes and the changing approach to therapy. Assays will be, on the whole, used to quantify virus and to measure the host reactions to infection, often in the presence of antivirals. Thus, extreme sensitivity and specificity will be required.     

Measurement of basal tear turnover using a standardized protocol

Background: The aim of this study was to compare basal tear turnover values of healthy volunteers in different countries. Methods: Healthy volunteers aged between 20 and 70 years were selected in three European cities. Basal tear turnover values were calculated according to a standardized protocol from the decay of the fluorescein concentration in tears after instillation of 1-l drop of fluorescein in the conjunctival sac. Fluorescein concentration was measured with identical commercial fluorophotometers. A monoexponential decay of fluorescein was assumed to represent basal tear flow. Results: The mean tear turnover values were 13.1%/ min ± 4.6 SD (n=4), 16.0%/ min ± 5.2 SD (n=24) and 17.5%/ min ± 3.4 SD (n = 20) in Clermont-Ferrand (France), Leiden (The Netherlands) and Madrid (Spain), respectively. The differences between the values were not significant (Mann-Whitney test P > 0.09). Conclusions: The tear turnover in the different cities was similar. The methods used were simple and the software easy to use.Concerted Action, supported in part by the European Commission, on Ocular Fluorometry: Standardization and Instrumentation Development of the 4th European Community Medical and Health Research Programme (No. MR 4*/0314/P).