Prevalence of latex hypersensitivity among health care workers in Malaysia.
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Health care workers have been reported to constitute one of the few high-risk groups related to IgE-mediated hypersensitivity associated with the use of latex products. This paper describes the first ever study of prevalence carried out in Malaysia among these workers. One hundred and thirty health care personnel from Hospital Kuala Lumpur were skin tested. Extracts used were prepared from seven different brands of natural rubber latex gloves with varying levels of extractable protein (EPRRIM). Out of the 130 volunteers, 4 (3.1%) had positive skin test to latex with extracts with high levels of EPRRIM (> 0.7 mg/g). The prevalence among the Malaysian health care workers can be considered to be low in comparison to that of some consumer countries as the USA which reported a prevalence of as high as 16.9%. (+info)
Quantification of DNA using the luminescent oxygen channeling assay.
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BACKGROUND: Simplified and cost-effective methods for the detection and quantification of nucleic acid targets are still a challenge in molecular diagnostics. METHODS: Luminescent oxygen channeling assay (LOCI(TM)) latex particles can be conjugated to synthetic oligodeoxynucleotides and hybridized, via linking probes, to different DNA targets. These oligomer-conjugated LOCI particles survive thermocycling in a PCR reaction and allow quantified detection of DNA targets in both real-time and endpoint formats. The endpoint DNA quantification format utilized two sensitizer bead types that are sensitive to separate illumination wavelengths. These two bead types were uniquely annealed to target or control amplicons, and separate illuminations generated time-resolved chemiluminescence, which distinguished the two amplicon types. RESULTS: In the endpoint method, ratios of the two signals allowed determination of the target DNA concentration over a three-log range. The real-time format allowed quantification of the DNA target over a six-log range with a linear relationship between threshold cycle and log of the number of DNA targets. CONCLUSIONS: This is the first report of the use of an oligomer-labeled latex particle assay capable of producing DNA quantification and sequence-specific chemiluminescent signals in a homogeneous format. It is also the first report of the generation of two signals from a LOCI assay. The methods described here have been shown to be easily adaptable to new DNA targets because of the generic nature of the oligomer-labeled LOCI particles. (+info)
Microbial degradation of the multiply branched alkane 2,6,10,15,19, 23-hexamethyltetracosane (Squalane) by Mycobacterium fortuitum and Mycobacterium ratisbonense.
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Among several bacterial species belonging to the general Gordonia, Mycobacterium, Micromonospora, Pseudomonas, and Rhodococcus, only two mycobacterial isolates, Mycobacterium fortuitum strain NF4 and the new isolate Mycobacterium ratisbonense strain SD4, which was isolated from a sewage treatment plant, were capable of utilizing the multiply branched hydrocarbon squalane (2,6,10,15,19, 23-hexamethyltetracosane) and its analogous unsaturated hydrocarbon squalene as the sole carbon source for growth. Detailed degradation studies and high-pressure liquid chromatography analysis showed a clear decrease of the concentrations of squalane and squalene during biomass increase. These results were supported by resting-cell experiments using strain SD4 and squalane or squalene as the substrate. The degradation of acyclic isoprenoids and alkanes as well as of acids derived from these compounds was also investigated. Inhibition of squalane and squalene degradation by acrylic acid indicated the possible involvement of beta-oxidation in the degradation route. To our knowledge, this is the first report demonstrating the biodegradation of squalane by using defined axenic cultures. (+info)
Survival for immunity: the price of immune system activation for bumblebee workers.
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Parasites do not always harm their hosts because the immune system keeps an infection at bay. Ironically, the cost of using immune defenses could itself reduce host fitness. This indirect cost of parasitism is often not visible because of compensatory resource intake. Here, workers of the bumblebee, Bombus terrestris, were challenged with lipopolysaccharides and micro-latex beads to induce their immune system under starvation (i.e., not allowing compensatory intake). Compared with controls, survival of induced workers was significantly reduced (by 50 to 70%). (+info)
Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections.
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BACKGROUND: Peribulbar and retrobulbar anesthesia have long been opposed on the basis of the existence of an intermuscular membrane, which is supposed to separate the intraconal from the extraconal spaces in a water-tight fashion. A local anesthetic injected outside the cone should spread through this septum to reach the nerves to be blocked. The existence of this septum is questioned. The aim of this study was to compare the spread of a colored latex dye injected intraconally or extraconally to simulate both retrobulbar and peribulbar anesthesia. METHODS: The authors used 10 heads from human cadavers. For each head, one eye was injected intraconally, and the other eye was injected extraconally. The heads were then frozen and sectioned into thin slices following various planes. They were then photographed and observed. RESULTS: There was no evidence of the existence of an intermuscular septum separating the intraconal and extraconal spaces. Those two spaces appeared to be part of a common spreading space, the corpus adiposum of the orbit. CONCLUSIONS: These results are in accord with the fact that clinical studies were not able to clearly demonstrate that retrobulbar anesthesia is more efficient than peribulbar anesthesia. On the basis of a similar clinical efficacy of the two techniques as a result of similar spreading of the local anesthetic injected, and a potentially higher risk of introducing the needle into the muscular cone, the authors recommend replacing retrobulbar anesthesia with peribulbar anesthesia. (+info)
Correlating the kinetics of cytokine-induced E-selectin adhesion and expression on endothelial cells.
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Many human diseases are mediated through the immune system. In chronic inflammatory disorders, the processes ordinarily involved in tissue healing become destructive. Endothelial cells normally recruit leukocytes to inflamed tissue using cytokine-induced adhesion receptors on the surfaces of interacting cells. Leukocyte capture depends on specialized characteristics of these receptors, particularly the binding kinetics. This study is designed to clarify the relationship between cytokine-induced changes in cell properties and binding kinetics. Here, we measure the kinetics of expression and monoclonal antibody binding for E-selectin in interleukin-1alpha-stimulated microvascular endothelium in vitro and incorporate the data into kinetic models. Quantitative flow cytometry is used to determine molecular density (expression), and micropipette assays are used to find the probability of adhesion (function). Within five hours of interleukin-1alpha stimulation, E-selectin density increases from 0 to 742 sites/microm(2), and antibody-E-selectin adhesion probability increases from a baseline of 6.3% to 64%. A kinetic model is applied to find an apparent association rate constant, k(f), of 3.7 x 10(-14) cm(2)/sec for antibody-E-selectin binding. Although the model successfully predicts experimental results, the rate constant is undervalued for a diffusion-limited process, suggesting that functional adhesion may be modified through cytokine-induced changes in microtopology and receptor localization. (+info)
A microcantilever device to assess the effect of force on the lifetime of selectin-carbohydrate bonds.
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A microcantilever technique was used to apply force to receptor-ligand molecules involved in leukocyte rolling on blood vessel walls. E-selectin was adsorbed onto 3-microm-diameter, 4-mm-long glass fibers, and the selectin ligand, sialyl Lewis(x), was coupled to latex microspheres. After binding, the microsphere and bound fiber were retracted using a computerized loading protocol that combines hydrodynamic and Hookean forces on the fiber to produce a range of force loading rates (force/time), r(f). From the distribution of forces at failure, the average force was determined and plotted as a function of ln r(f). The slope and intercept of the plot yield the unstressed reverse reaction rate, k(r)(o), and a parameter that describes the force dependence of reverse reaction rates, r(o). The ligand was titrated so adhesion occurred in approximately 30% of tests, implying that >80% of adhesive events involve single bonds. Monte Carlo simulations show that this level of multiple bonding has little effect on parameter estimation. The estimates are r(o) = 0.048 and 0.016 nm and k(r)(o) = 0.72 and 2.2 s(-1) for loading rates in the ranges 200-1000 and 1000-5000 pN s(-1), respectively. Levenberg-Marquardt fitting across all values of r(f) gives r(o) = 0.034 nm and k(r)(o) = 0.82 s(-1). The values of these parameters are in the range required for rolling, as suggested by adhesive dynamics simulations. (+info)
Some factors affecting fibrinogen precipitation by ristocetin: ultrastructure of precipitates.
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Fibrinogen in aqueous solution is precipitated by the antibiotic ristocetin. This reaction is inhibited by albumin and facilitated by low temperature. Resolubilized fibrinogen clots in the presence of thrombin. Ristocetin-precipitated fibrinogen takes the form of fibrils or clumps, composed of irregularly spaced, structure-less particles. The addition of ristocetin to washed platelets suspended in fibrinogen-containing media produces fibrinogen clumps in both the media and in the surface cannalicular system of the platelets. The changes in light transmission (aggregation curves) are due to both platelet aggregation and fibrinogen clumping. The role of the latter is confirmed by the observation that the addition of ristocetin to inert latex particles suspended in fibrinogen solution produces typical aggregation curves. This phenomenon is prevented by the addition of albumin to the media. We conclude that (1) if fibrinogen is present in any artificial system, albumin should be included in the media to prevent fibrinogen precipitation; and (2) statements about aggregation of any particulated materials by ristocetin should not be based solely on light-transmission changes, but should also include a description of the morphologic appearance. (+info)