911 research outputs found
Leukotrienes B 4 , C 4 and D 4 stimulate DNA synthesis in cultured human epidermal keratinocytes
Leukotrienes in psoriatic skin lesions are potent mediators of inflammation. We have studied the capacity of leukotrienes to stimulate the DNA synthesis of cultured human epidermal keratinocytes. At concentrations ranging from 10 −12 to 10 −8 M, LTB 4 produced a 100% increase of DNA synthesis determined both as the incorporation of [ 3 H] thymidine and as the labelling index. In comparison, LTB 4 had no effect on the DNA synthesis of dermal fibroblast cultures. 5S, 12S-LTB 4 and 5S, 12S-all-trans-LTB 4 did not change the DNA synthesis of keratinocytes, but the effect of LTB 4 was abolished in the presence of 5S, 12S-all- trans HLTB 4 . Being less potent than LTB 4 the peptidoleukotrienes (LTC 4 , LTD 4 ) also stimulated keratinocyte DNA synthesis. The effect of the peptidoleukotrienes, but not of LTB 4 , was antagonized by EPL 55712. These results show that leukotrienes B 4 , C 4 and D 4 exert potent and stereospecific mitogenic effects on cultured human keratinocytes. The presence of these arachidonic acid metabolites in psoriatic skin lesions may be pertinent to both inflammation and aberrant epidermal growth in psoriasis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74813/1/j.1365-2133.1985.tb02043.x.pd
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Investigation of Nitro-Organic Compounds in Diesel Engine Exhaust: Final Report, February 2007 - April 2008
The National Renewable Energy Laboratory upgraded its ReFUEL engine and vehicle testing facility to speciate unregulated gas-phase emissions. To complement this capability, the laboratory contracted with the Colorado School of Mines (CSM) to study the effects of soy biodiesel fuel and a diesel particle filter (DPF) on emissions of polycyclic aromatic hydrocarbons (PAH) and nitro-polycyclic aromatic hydrocarbons (NPAH). CSM developed procedures to sample diesel particulate matter (PM) emissions from raw and diluted exhaust, with and without a DPF. They also developed improved procedures for extracting PAH and NPAH from the PM and quantifying them with a gas chromatograph-electron monochromator mass spectrometer. The study found the DPF generally reduced PAH emissions by 1 to 3 orders of magnitude. PAH conversion was lowest for B100, suggesting that PAHs were forming in the DPF. Orders of magnitude reductions were also found for NPAH emissions exiting the DPF
The Energy of the Gamma Metric in the M{\o}ller Prescription
We obtain the energy distribution of the gamma metric using the
energy-momentum complex of M{\o}ller. The result is the same as obtained by
Virbhadra in the Weinberg prescription
Histological and immunocytological changes in psoriasis after 7 days of cyclosporin therapy
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75545/1/j.1365-2133.1987.tb12012.x.pd
Coarse-graining of cellular automata, emergence, and the predictability of complex systems
We study the predictability of emergent phenomena in complex systems. Using
nearest neighbor, one-dimensional Cellular Automata (CA) as an example, we show
how to construct local coarse-grained descriptions of CA in all classes of
Wolfram's classification. The resulting coarse-grained CA that we construct are
capable of emulating the large-scale behavior of the original systems without
accounting for small-scale details. Several CA that can be coarse-grained by
this construction are known to be universal Turing machines; they can emulate
any CA or other computing devices and are therefore undecidable. We thus show
that because in practice one only seeks coarse-grained information, complex
physical systems can be predictable and even decidable at some level of
description. The renormalization group flows that we construct induce a
hierarchy of CA rules. This hierarchy agrees well with apparent rule complexity
and is therefore a good candidate for a complexity measure and a classification
method. Finally we argue that the large scale dynamics of CA can be very
simple, at least when measured by the Kolmogorov complexity of the large scale
update rule, and moreover exhibits a novel scaling law. We show that because of
this large-scale simplicity, the probability of finding a coarse-grained
description of CA approaches unity as one goes to increasingly coarser scales.
We interpret this large scale simplicity as a pattern formation mechanism in
which large scale patterns are forced upon the system by the simplicity of the
rules that govern the large scale dynamics.Comment: 18 pages, 9 figure
Quantum dot formation on a strain-patterned epitaxial thin film
We model the effect of substrate strain patterning on the self-assembly of quantum dots (QDs). When the surface energy is isotropic, we demonstrate that strain patterning via embedded substrate inclusions may result in ordered, self-organized QD arrays. However, for systems with strong cubic surface energy anisotropy, the same patterning does not readily lead to an ordered array of pyramids at long times. We conclude that the form of the surface energy anisotropy strongly influences the manner in which QDs self-assemble into regular arrays.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87827/2/133102_1.pd
Double-blind, placebo-controlled study to evaluate the efficacy of fish oil and low-dose UVB in the treatment of psoriasis
Since eicosanoids have been implicated in the pathogenesis of psoriasis, less potent eicosanoid mediators derived from fish oil might improve psoriasis. Using a double-blind, randomized, parallel design, 18 patients with stable, plaque psoriasis received capsules of either fish oil or identical-appearing placebo olive oil for 15 weeks, with concomitant sub-erythemal UVB in weeks 3 to 11. At the conclusion of phototherapy, and 4 weeks later, patients in the fish oil group had a greater decrease in the total body surface area of psoriasis and more improvement compared to patients in the olive oil group. The improvement in the fish oil group was statistically significantly greater for all parameters compared to the change in the olive oil group. The apparent safety and general health-promoting features of fish oil could provide an ideal adjunctive therapy for psoriasis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73035/1/j.1365-2133.1989.tb01378.x.pd
Controlling crystal symmetries in phase-field crystal models
We investigate the possibility to control the symmetry of ordered states in
phase-field crystal models by tuning nonlinear resonances. In two dimensions,
we find that a state of square symmetry as well as coexistence between squares
and hexagons can be easily obtained. In contrast, it is delicate to obtain
coexistence of squares and liquid. We develop a general method for constructing
free energy functionals that exhibit solid-liquid coexistence with desired
crystal symmetries. As an example, we develop a free energy functional for
square-liquid coexistence in two dimensions. A systematic analysis for
determining the parameters of the necessary nonlinear terms is provided. The
implications of our findings for simulations of materials with simple cubic
symmetry are discussed.Comment: 19 pages, 6 figure
Surface Layers in General Relativity and Their Relation to Surface Tensions
For a thin shell, the intrinsic 3-pressure will be shown to be analogous to
-A, where A is the classical surface tension: First, interior and exterior
Schwarzschild solutions will be matched together such that the surface layer
generated at the common boundary has no gravitational mass; then its intrinsic
3-pressure represents a surface tension fulfilling Kelvin's relation between
mean curvature and pressure difference in the Newtonian limit. Second, after a
suitable definition of mean curvature, the general relativistic analogue to
Kelvin's relation will be proven to be contained in the equation of motion of
the surface layer.Comment: 12 pages, LaTeX, no figur
Electromigration of Single-Layer Clusters
Single-layer atom or vacancy clusters in the presence of electromigration are
studied theoretically assuming an isotropic medium. A variety of distinctive
behaviors distinguish the response in the three standard limiting cases of
periphery diffusion (PD), terrace diffusion (TD), and evaporation-condensation
(EC). A general model provides power laws describing the size dependence of the
drift velocity in these limits, consistent with established results in the case
of PD. The validity of the widely used quasistatic limit is calculated. Atom
and vacancy clusters drift in opposite directions in the PD limit but in the
same direction otherwise. In absence of PD, linear stability analysis reveals a
new type of morphological instability, not leading to island break-down. For
strong electromigration, Monte Carlo simulations show that clusters then
destabilize into slits, in contrast to splitting in the PD limit.
Electromigration affects the diffusion coefficient of the cluster and
morphological fluctuations, the latter diverging at the instability threshold.
An instrinsic attachment-detachment bias displays the same scaling signature as
PD in the drift velocity.Comment: 11 pages, 4 figure
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