Lipopolysaccharide, also known as endotoxin (ET), is a major constituent of the outer membrane of the cell wall of most gram negative bacteria. ET is known to cause a number of pathophysiological ...changes associated with illness including inflammatory pain. The aim of this study is to characterize the peripheral hyperalgesia induced by ET in rats and mice. Different groups of rats and mice received different doses of ET ranging from 0.6 microgram to 40 micrograms dissolved in 50 microliters saline and injected in the plantar area of the left hind legs. All animals were subjected to tail immersion (TF), hot plate (HP) and paw pressure (PP) tests, 2-3 days prior to ET injection and during the following 1-2 days. ET injections produced a dose-dependent decrease in the latencies of the HP and PP tests of the injected leg reaching a maximum decrease of 50-60% of the control with 20-40 micrograms ET at 9 h (rats) and 24 h (mice) after the injection. Almost complete recovery was observed after 24 h in rats and 48 h in mice. TF latencies showed a less but a significant decrease while PP of the opposite leg and all tests in saline-injected animals did not elicit significant variations and served as additional controls. Our results indicate that the use of ET-produced hyperalgesia is a valid model for local and reversible inflammatory pain, with minimal distress to the animal. This model can also be used to study the efficacy of various anti-inflammatory and analgesic drugs and the molecular mechanisms of inflammation induced by bacterial invasion.
Exposure to midrange ultraviolet radiation (UVB) is known to produce skin inflammation similar to sunburn. The aim of this study was to characterize the hyperalgesia and cytokine upregulation induced ...by UVB and their modulation by antiinflammatory cytokines.
Acute exposure of the dorsal skin of mice to UVB (200, 250 and 300 mJ cm2) resulted in a dose‐dependent decrease in the latencies of the hot plate and tail flick tests, without evident signs of skin lesions.
The observed hyperalgesia displayed a biphasic temporal evolution with an acute phase (3–6 h) and a late (48–96 h) phase.
Exposure to UVB (300 mJ cm2) elicited significant upregulation of interleukin (IL)‐1β, tumour necrosis factor (TNF)‐α and nerve growth factor (NGF), determined by ELISA in the exposed skin. This upregulation was more important during the acute phase of hyperalgesia.
Daily treatment of mice, with i.p. injections of either IL‐10 or IL‐13 (1.5, 7.5 and 15 ng in 100 μl saline) produced a dose‐dependent attenuation of the UVB‐induced hyperalgesia.
Treatment with the highest doses of either IL‐10 or IL‐13, produced significant attenuation of the levels of the cytokines and NGF by UVB, with relatively more pronounced effects by IL‐13.
Acute exposure to moderate amounts of UVB results in a systemic hyperalgesia related to the upregulation of cytokine and NGF levels, since both were prevented by treatment with antiinflammatory cytokines.
British Journal of Pharmacology (2000) 131, 1317–1324; doi:10.1038/sj.bjp.0703699
Context.
Variable B supergiants (BSGs) constitute a heterogeneous group of stars with complex photometric and spectroscopic behaviours. They exhibit mass-loss variations and experience different ...types of oscillation modes, and there is growing evidence that variable stellar winds and photospheric pulsations are closely related.
Aims.
To discuss the wind properties and variability of evolved B-type stars, we derive new stellar and wind parameters for a sample of 19 Galactic BSGs by fitting theoretical line profiles of H, He, and Si to the observed ones and compare them with previous determinations.
Methods.
The synthetic line profiles are computed with the non-local thermodynamic equilibrium (NLTE) atmosphere code FASTWIND, with a
β
-law for hydrodynamics.
Results.
The mass-loss rate of three stars has been obtained for the first time. The global properties of stellar winds of mid/late B supergiants are well represented by a
β
-law with
β
> 2. All stars follow the known empirical wind momentum–luminosity relationships, and the late BSGs show the trend of the mid BSGs. HD 75149 and HD 99953 display significant changes in the shape and intensity of the H
α
line (from a pure absorption to a P Cygni profile, and vice versa). These stars have mass-loss variations of almost a factor of 2.8. A comparison among mass-loss rates from the literature reveals discrepancies of a factor of 1 to 7. This large variation is a consequence of the uncertainties in the determination of the stellar radius. Therefore, for a reliable comparison of these values we used the invariant parameter
Q
r
. Based on this parameter, we find an empirical relationship that associates the amplitude of mass-loss variations with photometric/spectroscopic variability on timescales of tens of days. We find that stars located on the cool side of the bi-stability jump show a decrease in the ratio
V
∞
∕
V
esc
, while their corresponding mass-loss rates are similar to or lower than the values found for stars on the hot side. Particularly, for those variable stars a decrease in
V
∞
∕
V
esc
is accompanied by a decrease in
Ṁ
.
Conclusions.
Our results also suggest that radial pulsation modes with periods longer than 6 days might be responsible for the wind variability in the mid/late-type. These radial modes might be identified with strange modes, which are known to facilitate (enhanced) mass loss. On the other hand, we propose that the wind behaviour of stars on the cool side of the bi-stability jump could fit with predictions of the
δ
−slow hydrodynamics solution for radiation-driven winds with highly variable ionization.
Context.
Be stars are rapid rotators surrounded by a gaseous disk envelope whose origin is still under debate. This envelope is responsible for observed emission lines and large infrared excess.
...Aims.
To progress in the understanding of the physical processes involved in the disk formation, we estimate the disk parameters for a sample of Be stars and search for correlations between these parameters and stellar properties.
Methods.
We performed spectro-interferometric observations of 26 Be stars in the region of the Br
γ
line to study the kinematical properties of their disks through the Doppler effect. Observations were performed at the Paranal observatory with the VLTI/AMBER interferometer. This instrument provides high spectral (
R
≃ 12 000) and high spatial (
θ
min
= 4 mas) resolutions.
Results.
We modeled 18 Be stars with emission in the Br
γ
line. The disk kinematic is described by a quasi-Keplerian rotation law, with the exception of HD 28497 that presents a one-arm density-wave structure. Using a combined sample, we derived a mean value for the velocity ratio
V
̅/
V
̅
c
= 0.75 (where
V
c
is the critical velocity), and found that rotation axes are probably randomly distributed in the sky. Disk sizes in the line component model are in the range of 2
–
13 stellar radii and do not correlate with the effective temperature or spectral type. However, we found that the maximum size of a stable disk correlates with the rotation velocity at the inner part of the disk and the stellar mass.
Conclusions.
We found that, on average, the Be stars of our combined sample do not rotate at their critical velocity. However, the centrifugal force and mass of the star defines an upper limit size for a stable disk configuration. For a given rotation, high-mass Be stars tend to have more compact disks than their low-mass counterparts. It would be interesting to follow up the evolution of the disk size in variable stars to better understand the formation and dissipation processes of their circumstellar disks.
Summary Objectives To estimate familial aggregation and the heritability of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and high density lipoprotein-cholesterol (HDL-C) in ...families assisted by the Family Doctor Program in a Brazilian city, and to evaluate associations between some environmental factors and familial aggregation of these lipids. Study design Cross-sectional familial study. Methods The association of lipids with sociodemographic factors, lifestyle factors and comorbidities (e.g. physical activity, alcohol consumption, smoking, hypertension, impaired glucose tolerance, body mass index) was estimated using linear models and generalized estimating equations. Correlation of TC, LDL-C and HDL-C between pairs of relatives was estimated with the familial correlation procedure, and heritability was estimated with the ASSOC procedure. Results All associations were statistically significant. There was familial aggregation of TC (parent/offspring, r = 0.33; sibling/sibling, r = 0.37), LDL-C (parent/offspring, r = 0.29; sibling/sibling, r = 0.37) and HDL-C (parent/offspring, r = 0.25; sibling/sibling, r = 0.48), but less than 3%, 6% and 14%, respectively, which was explained by lifestyle factors. Correlation between pairs with genetic sharing (parent/offspring and sibling/sibling) was higher than that observed between father and mother. Heritability estimates ranged between 0.32 (HDL-C) and 0.50 (TC). Similar results were found for the two approaches used to estimate the contribution of genetic and environmental factors in the correlation of TC, LDL-C and HDL-C between the family pairs. Conclusion The results showed that there is familial aggregation of TC, LDL-C and HDL-C, and point to the predominance of genetic factors because little influence of environmental variables was found.
AbstractThe Be phenomenon is present in about 20 per cent of B-type stars. Be stars show variability on a broad range of time-scales, which in most cases is related to the presence of a circumstellar ...disc of variable size and structure. For this reason, a time-resolved survey is highly desirable in order to understand the mechanisms of disc formation, which are still poorly understood. In addition, a complete observational sample would improve the statistical significance of the study of stellar and disc parameters. The 'Be Stars Observation Survey' (BeSOS) is a survey containing reduced spectra obtained using the Pontifica Universidad Católica High Echelle Resolution Optical Spectrograph (PUCHEROS) with a spectral resolution of 17 000 in the range 4260-7300 Å. BeSOS's main objective is to offer consistent spectroscopic and time-resolved data obtained with one instrument. The user can download or plot the data and obtain stellar parameters directly from the website. We also provide a star-by-star analysis based on photometric, spectroscopic and interferometric data, as well as general information about the whole BeSOS sample. Recently, BeSOS led to the discovery of a new Be star HD 42167 and facilitated study of the V/R variation of HD 35165 and HD 120324, the steady disc of HD 110335 and the Be shell status of HD 127972. Optical spectra used in this work, as well as the stellar parameters derived, are available online at http://besos.ifa.uv.cl.
A method for enhancing electronic performance of single-walled carbon nanotube (SWCNT) thin films through enhanced dispersion of SWCNTs in aqueous solutions is presented. The best dispersion ...enhancement is obtained by covalent attachment of urea to the acid functionalized SWCNTs. Dispersion properties of urea treatment are compared to conventional chemical and physical treatment techniques, such as surfactants. The treatment type and time significantly influence SWCNT surface functionalization, which determines the dispersion effectiveness as described by the SWCNT aggregate size, morphology and stability. The findings suggest that urea-SWCNTs, as compared to surfactant dispersed-SWCNTs, resulted in the most effective dispersion method among chemical treatments, yielding the smallest monodispersed aggregates with the most rod-like morphology that were stable over the greatest range in pH. Thin films prepared with SWCNT samples were evaluated for their transparency and resistance, two metrics that are important for electronics device applications. The urea-SWCNT films exhibited superior optoelectrical properties compared to SWCNT films prepared with conventional chemicals as well as surfactants. This indicates a correlation between degree of dispersibility and optoelectrical properties.
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