8,298 research outputs found
Complexity in cancer stem cells and tumor evolution: towards precision medicine
In this review, we discuss recent advances on the plasticity of cancer stem
cells and highlight their relevance to understand the metastatic process and to
guide therapeutic interventions. Recent results suggest that the strict
hierarchical structure of cancer cell populations advocated by the cancer stem
cell model must be reconsidered since the depletion of cancer stem cells leads
the other tumor cells to switch back into the cancer stem cell phenotype. This
plasticity has important implications for metastasis since migrating cells do
not need to be cancer stem cells in order to seed a metastasis. We also discuss
the important role of the immune system and the microenvironment in modulating
phenotypic switching and suggest possible avenues to exploit our understanding
of this process to develop an effective strategy for precision medicine.Comment: 2 Figures, to appear in Seminars in Cancer Biology, Available online
23 February 201
What Moves the Discount on Country Equity Funds?
The paper characterizes several empirical regularities of closed- end fund prices and examines the extent to which a 'sentiment' model of asset prices is consistent with the empirical regularities. We find that after controlling for the effect of cross-border investment restrictions, country funds trade at an average discount. Discounts vary substantially and contribute to a variance in country fund weekly returns which is generally three times greater than the returns on the net asset value (NAV). Regression analysis suggests that discounts have predictive power for fund returns but not for NAV returns, suggesting that investor 'sentiment' is a component of the price of a fund and not its NAV. Estimation of an unobserved components model on the discounts of the funds reveals a significant and strongly persistent common component across fund discounts. Regressions of fund and NAV returns on financial variables reveal that fund prices are 'sticky' with respect to movements in the host country's stock market and overly sensitive to variation in the U.S. and world stock markets. This relation is unaffected when we consider separately funds whose host countries restrict cross-border investment and funds which invest in emerging stock markets.
Protein accumulation in the endoplasmic reticulum as a non-equilibrium phase transition
Several neurological disorders are associated with the aggregation of
aberrant proteins, often localized in intracellular organelles such as the
endoplasmic reticulum. Here we study protein aggregation kinetics by mean-field
reactions and three dimensional Monte carlo simulations of diffusion-limited
aggregation of linear polymers in a confined space, representing the
endoplasmic reticulum. By tuning the rates of protein production and
degradation, we show that the system undergoes a non-equilibrium phase
transition from a physiological phase with little or no polymer accumulation to
a pathological phase characterized by persistent polymerization. A combination
of external factors accumulating during the lifetime of a patient can thus
slightly modify the phase transition control parameters, tipping the balance
from a long symptomless lag phase to an accelerated pathological development.
The model can be successfully used to interpret experimental data on
amyloid-\b{eta} clearance from the central nervous system
Conformational mechanism for the stability of microtubule-kinetochore attachments
Regulating the stability of microtubule(MT)-kinetochore attachments is
fundamental to avoiding mitotic errors and ensure proper chromosome segregation
during cell division. While biochemical factors involved in this process have
been identified, its mechanics still needs to be better understood. Here we
introduce and simulate a mechanical model of MT-kinetochore interactions in
which the stability of the attachment is ruled by the geometrical conformations
of curling MT-protofilaments entangled in kinetochore fibrils. The model allows
us to reproduce with good accuracy in vitro experimental measurements of the
detachment times of yeast kinetochores from MTs under external pulling forces.
Numerical simulations suggest that geometrical features of MT-protofilaments
may play an important role in the switch between stable and unstable
attachments
Investigation of a generalized Obukhov Model for Turbulence
We introduce a generalization of Obukhov's model [A.M. Obukhov, Adv. Geophys.
6, 113 (1959)] for the description of the joint position-velocity statistics of
a single fluid particle in fully developed turbulence. In the presented model
the velocity is assumed to undergo a continuous time random walk. This takes
into account long time correlations. As a consequence the evolution equation
for the joint position-velocity probability distribution is a Fokker-Planck
equation with a fractional time derivative. We determine the solution of this
equation in the form of an integral transform and derive a relation for
arbitrary single time moments. Analytical solutions for the joint probability
distribution and its moments are given.Comment: 10 page
Legal determinants of external finance revisited : the inverse relationship between investor protection and societal well-being
This paper investigates relationships between corporate governance traditions and quality of life as measured by a number of widely reported indicators. It provides an empirical analysis of indicators of societal health in developed economies using a classification based on legal traditions. Arguably the most widely cited work in the corporate governance literature has been the collection of papers by La Porta et al. which has shown, inter alia, statistically significant relationships between legal traditions and various proxies for investor protection. We show statistically significant relationships between legal traditions and various proxies for societal health. Our comparative evidence suggests that the interests of investors may not be congruent with the interests of wider society, and that the criteria for judging the effectiveness of approaches to corporate governance should not be restricted to financial metrics
Mechanical Properties of Growing Melanocytic Nevi and the Progression to Melanoma
Melanocytic nevi are benign proliferations that sometimes turn into malignant
melanoma in a way that is still unclear from the biochemical and genetic point
of view. Diagnostic and prognostic tools are then mostly based on dermoscopic
examination and morphological analysis of histological tissues. To investigate
the role of mechanics and geometry in the morpholgical dynamics of melanocytic
nevi, we study a computation model for cell proliferation in a layered
non-linear elastic tissue. Numerical simulations suggest that the morphology of
the nevus is correlated to the initial location of the proliferating cell
starting the growth process and to the mechanical properties of the tissue. Our
results also support that melanocytes are subject to compressive stresses that
fluctuate widely in the nevus and depend on the growth stage. Numerical
simulations of cells in the epidermis releasing matrix metalloproteinases
display an accelerated invasion of the dermis by destroying the basal membrane.
Moreover, we suggest experimentally that osmotic stress and collagen inhibit
growth in primary melanoma cells while the effect is much weaker in metastatic
cells. Knowing that morphological features of nevi might also reflect geometry
and mechanics rather than malignancy could be relevant for diagnostic purpose
The Future is Now
No abstract available DOI: http://dx.doi.org/10.5564/mjia.v0i5.361 The Mongolian Journal of International Affairs; Number 5, 1998, Pages 3-1
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