385 research outputs found
Enhanced human papillomavirus type 8 oncogene expression levels are crucial for skin tumorigenesis in transgenic mice
AbstractHuman papillomavirus 8 (HPV8) is involved in skin cancer development in epidermodysplasia verruciformis patients. Transgenic mice expressing HPV8 early genes (HPV8-CER) developed papillomas, dysplasias and squamous cell carcinomas. UVA/B-irradiation and mechanical wounding of HPV8-CER mouse skin led to prompt papilloma induction in about 3weeks. The aim of this study was to analyze the kinetics and level of transgene expression in response to skin irritations. Transgene expression was already enhanced 1 to 2days after UVA/B-irradiation or tape-stripping and maintained during papilloma development. The enhanced transgene expression could be assigned to UVB and not to UVA. Papilloma development was thus always paralleled by an increased transgene expression irrespective of the type of skin irritation. A knock-down of E6 mRNA by tattooing HPV8-E6-specific siRNA led to a delay and a lower incidence of papilloma development. This indicates that the early increase of viral oncogene expression is crucial for induction of papillomatosis
Human papillomavirus mediated inhibition of DNA damage sensing and repair drives skin carcinogenesis
Background: The failure to mount an effective DNA damage response to repair UV induced cyclobutane pyrimidine dimers (CPDs) results in an increased propensity to develop cutaneous squamous cell carcinoma (cSCC). High-risk patient groups, such as organ transplant recipients (OTRs) frequently exhibit field cancerization at UV exposed body sites from which multiple human papillomavirus (HPV)-associated cSCCs develop rapidly, leading to profound morbidity and increased mortality. In vitro molecular evidence indicates that HPV of genus beta-papillomavirus (β-PV) play an important role in accelerating the early stages of skin tumorigenesis. Methods: We investigated the effects of UV induced DNA damage in murine models of β-PV E6 oncoprotein driven skin tumorigenesis by crossing K14-HPV8-E6wt mice (developing skin tumors after UV treatment) with K14-CPD-photolyase animals and by generating the K14-HPV8-E6-K136N mutant mouse strain. Thymine dimers (marker for CPDs) and γH2AX (a marker for DNA double strand breaks) levels were determined in the murine skin and organotypic skin cultures of E6 expressing primary human keratinocytes after UV-irradiation by immunohistochemistry and in cell lines by In Cell Western blotting. Phosphorylation of ATR/Chk1 and ATM were assessed in cell lines and organotypic skin cultures by Western blots and immunohistochemistry. Results: Skin tumor development after UV-irradiation in K14-HPV8-E6wt mice could completely be blocked through expression of CPD-photolyase. Through quantification of thymine dimers after UV irradiation in cells expressing E6 proteins with point mutations at conserved residues we identified a critical lysine in the
Decomposing the misery index: A dynamic approach
YesThe misery index (the unweighted sum of unemployment and inflation
rates) was probably the first attempt to develop a single statistic to measure the level
of a population’s economic malaise. In this letter, we develop a dynamic approach to
decompose the misery index using two basic relations of modern macroeconomics:
the expectations-augmented Phillips curve and Okun’s law. Our reformulation of the
misery index is closer in spirit to Okun’s idea. However, we are able to offer an improved
version of the index, mainly based on output and unemployment. Specifically,
this new Okun’s index measures the level of economic discomfort as a function of
three key factors: (1) the misery index in the previous period; (2) the output gap in
growth rate terms; and (3) cyclical unemployment. This dynamic approach differs
substantially from the standard one utilised to develop the misery index, and allow
us to obtain an index with five main interesting features: (1) it focuses on output,
unemployment and inflation; (2) it considers only objective variables; (3) it allows
a distinction
between short-run and long-run phenomena; (4) it places more
importance
on output and unemployment rather than inflation; and (5) it weights
recessions
more than expansions
Testing the paradox of enrichment along a land use gradient in a multitrophic aboveground and belowground community
In the light of ongoing land use changes, it is important to understand how multitrophic communities perform at different land use intensities. The paradox of enrichment predicts that fertilization leads to destabilization and extinction of predator-prey systems. We tested this prediction for a land use intensity gradient from natural to highly fertilized agricultural ecosystems. We included multiple aboveground and belowground trophic levels and land use-dependent searching efficiencies of insects. To overcome logistic constraints of field experiments, we used a successfully validated simulation model to investigate plant responses to removal of herbivores and their enemies. Consistent with our predictions, instability measured by herbivore-induced plant mortality increased with increasing land use intensity. Simultaneously, the balance between herbivores and natural enemies turned increasingly towards herbivore dominance and natural enemy failure. Under natural conditions, there were more frequently significant effects of belowground herbivores and their natural enemies on plant performance, whereas there were more aboveground effects in agroecosystems. This result was partly due to the “boom-bust” behavior of the shoot herbivore population. Plant responses to herbivore or natural enemy removal were much more abrupt than the imposed smooth land use intensity gradient. This may be due to the presence of multiple trophic levels aboveground and belowground. Our model suggests that destabilization and extinction are more likely to occur in agroecosystems than in natural communities, but the shape of the relationship is nonlinear under the influence of multiple trophic interactions.
Stellar structure and compact objects before 1940: Towards relativistic astrophysics
Since the mid-1920s, different strands of research used stars as "physics
laboratories" for investigating the nature of matter under extreme densities
and pressures, impossible to realize on Earth. To trace this process this paper
is following the evolution of the concept of a dense core in stars, which was
important both for an understanding of stellar evolution and as a testing
ground for the fast-evolving field of nuclear physics. In spite of the divide
between physicists and astrophysicists, some key actors working in the
cross-fertilized soil of overlapping but different scientific cultures
formulated models and tentative theories that gradually evolved into more
realistic and structured astrophysical objects. These investigations culminated
in the first contact with general relativity in 1939, when J. Robert
Oppenheimer and his students George Volkoff and Hartland Snyder systematically
applied the theory to the dense core of a collapsing neutron star. This
pioneering application of Einstein's theory to an astrophysical compact object
can be regarded as a milestone in the path eventually leading to the emergence
of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal
75th Anniversary of ‘Existence of Electromagnetic-Hydrodynamic Waves’
We have recently passed the 75th anniversary of one of the most important
results in solar and space physics: Hannes Alfv\'en's discovery of Alfv\'en
waves and the Alfv\'en speed. To celebrate the anniversary, this article
recounts some major episodes in the history of MHD waves. Following an
initially cool reception, Alfv\'en's ideas were propelled into the spotlight by
Fermi's work on cosmic rays, the new mystery of coronal heating and, as
scientific perception of interplanetary space shifted dramatically and the
space race started, detection of Alfv\'en waves in the solar wind. From then
on, interest in MHD waves boomed, laying the foundations for modern remote
observations of MHD waves in the Sun, coronal seismology and some of today's
leading theories of coronal heating and solar wind acceleration. In 1970,
Alfv\'en received the Nobel Prize for his work in MHD, including these
discoveries. The article concludes with some reflection about what the history
implies about the way we do science, especially the advantages and pitfalls of
idealised mathematical models.Comment: 10 pages, accepted by Solar Physic
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