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  • 1
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Allergic squirrel monkeys when exposed to an aerosol ofAscaris suum either develop a reproducible, immediate bronchoconstriction or an immediate bronchoconstriction followed by a reproducible late response. Pretreatment of ascaris-challenged squirrel monkeys with a potent, selective, orally active 5-lipoxygenase inhibitor, L-651,392 (4-bromo-2,7-dimethoxy-3,4-phenothizin-3-one), at a dose of 5 mg/kg p.o. resulted in near complete inhibition of the increases in pulmonary resistance (R L) and decreases in dynamic compliance (Cdyn) normally observed following exposure to the antigen. A lower dose (1 mg/kg p.o.) of L-651-392 produced only a significant inhibition of the decreases in Cdyn. In monkeys known to develop dual responses to antigen, L-651,392 (5 mg/kg p.o.) significantly attenuated the immediate response and markedly inhibited the late response. These results suggest an important role for leukotrienes in primary and late phase allergen-induced bronchoconstriction.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1536
    Keywords: Key words Disruption ; Aggregates ; Size ; Fractal dimension ; Capillary flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Disruption of polystyrene latex aggregates, formed in 1 M citric acid/phosphate buffer solution at pH 3.8 through diffusion-limited colloid aggregation (DLCA) and in 0.2 M NaCl solution at pH 5.5 through reaction-limited colloid aggregation (RLCA), was studied with respect to aggregate size and fractal nature. This was achieved using small-angle laser scattering in conjunction with a specially designed sampling method, which brought about the elimination of the disruption of the aggregates caused by a commercial stirrer sample unit. Aggregations were carried out in a mixture of deuterium oxide and water instead of water alone as a solvent to minimise sedimentation resulting from the differences in density between the latex particles and the electrolytes. An initial “steady state” in terms of aggregate size and fractal dimension was found to occur after around 20 min and 2 days for DLCA and RLCA aggregates, respectively, at 25 °C. No aggregate disruption was detected for DLCA and RLCA aggregates after their passing through a capillary tube for shear rates up to 1584 and 2694 s−1, respectively. At higher shear rates, significant decreases in the aggregate volume-mean diameter, D[4, 3], occurred after shearing. The degree of reduction in D[4, 3] was larger for DLCA aggregates in comparison to RLCA aggregates. The results would suggest that DLCA aggregates were more subject to disruption during shearing. A high degree of disruption was observed in turbulent flow for both aggregates.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1536
    Keywords: Key words Latex particles ; Aggregates ; Fractal dimensions ; Image analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fractal nature of latex particles and their aggregates was characterised by image analysis in terms of fractal dimensions. The one- and two-dimensional fractal dimensions, D 1 and D 2, were estimated for polystyrene latex aggregates formed by flocculation in citric acid/phosphate buffer solutions. The dimensional analysis method was used, which is based on power law correlations between aggregate perimeter, projected area and maximum length. These aggregate characteristics were measured by image analysis. A two-slopes method using cumulative size distributions of aggregate length and solid volume has been developed to determine the three-dimensional fractal dimension (D 3) for the latex aggregates. The fractal dimensions D 1, D 2 and D 3 measured for single latex particles in distilled water agreed well with D 1 = 1, D 2 = 2 and D 3 = 3 expected for Euclidean spherical objects. For the aggregates, the fractal dimension D 2 of about 1.67 ± 0.04 (±standard deviation) was comparable to the fractal dimension D 3 of approximately 1.72 ± 0.13 (±standard deviation), taking the standard deviations into account. The measured three-dimensional fractal dimension for latex aggregates is within the fractal dimension range 1.6–2.2 expected for aggregates formed through a cluster-cluster mechanism, and is close to the D 3 value of about 1.8 indicated for cluster formation via diffusion-limited colloidal aggregation.
    Type of Medium: Electronic Resource
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