2,709 research outputs found
Epigenetic regulation of osteogenesis: human embryonic palatal mesenchymal cells.
Mesenchymal stem cells (MSCs) provide an appropriate model to study epigenetic changes during osteogenesis and bone regeneration due to their differentiation potential. Since there are no unique markers for MSCs, methods of identification are limited. The complex morphology of human embryonic palatal mesenchyme stem cell (HEPM) requires analysis of fractal dimensions to provide an objective quantification of self-similarity, a statistical transformation of cellular shape and border complexity. We propose the hypothesis of a study to compare and contrast sequential steps of osteogenic differentiation in HEPMs both phenotypically using immunocytochemistry, and morphometrically using fractal analysis from undifferentiated passage 1 (P1) to passage 7 (P7) cells. The proof-of-concept is provided by results we present here that identify and compare the modulation of expression of certain epigenetic biomarkers (alkaline phosphatase, ALP; stromal interaction molecule-1, STRO-1; runt-related transcription factor-2, RUNX2), which are established markers of osteogenesis in bone marrow studies, of osteoblastic/skeletal morphogenesis, and of osteoblast maturation. We show that Osteoinductive medium (OIM) modulates the rate of differentiation of HEPM into Run-2+ cells, the most differentiated subpopulation, followed by ALP+ and STRO-1+ cells. Taken together, our phenotypical and morphometric data demonstrate the feasibility of using HEPM to assess osteogenic differentiation from an early undifferentiated to a differentiated stage. This research model may lay the foundation for future studies aimed at characterizing the epigenetic characteristics of osteoimmunological disorders and dysfunctions (e.g., osteoarthritis, temporomandibular joint disorders), so that proteomic profiling can aid the diagnosis and monitor the prognosis of these and other osteoimmunopathologies
On the origin of variable structures in the winds of hot luminous stars
Examination of the temporal variability properties of several strong optical
recombination lines in a large sample of Galactic Wolf-Rayet (WR) stars reveals
possible trends, especially in the more homogeneous WC than the diverse WN
subtypes, of increasing wind variability with cooler subtypes. This could imply
that a serious contender for the driver of the variations is stochastic,
magnetic subsurface convection associated with the 170 kK partial-ionization
zone of iron, which should occupy a deeper and larger zone of greater mass in
cooler WR subtypes. This empirical evidence suggests that the heretofore
proposed ubiquitous driver of wind variability, radiative instabilities, may
not be the only mechanism playing a role in the stochastic multiple
small-scaled structures seen in the winds of hot luminous stars. In addition to
small-scale stochastic behaviour, subsurface convection guided by a global
magnetic field with localized emerging loops may also be at the origin of the
large-scale corotating interaction regions as seen frequently in O stars and
occasionally in the winds of their descendant WR stars.Comment: 8 pages, 2 figures and 2 tables. Monthly Notices of the Royal
Astronomical Society 201
Diagnostic of the unstable envelopes of Wolf-Rayet stars
The envelopes of stars near the Eddington limit are prone to various
instabilities. A high Eddington factor in connection with the Fe opacity peak
leads to convective instability, and a corresponding envelope inflation may
induce pulsational instability. Here, we investigate the occurrence and
consequences of both instabilities in models of Wolf-Rayet stars. We determine
the convective velocities in the sub-surface convective zones to estimate the
amplitude of the turbulent velocity at the base of the wind that potentially
leads to the formation of small-scale wind structures, as observed in several
WR stars. We also investigate the effect of mass loss on the pulsations of our
models. We approximated solar metallicity WR stars by models of mass-losing
helium stars, and we characterized the properties of convection in the envelope
adopting the standard MLT. Our results show the occurrence of sub-surface
convective regions in all studied models. Small surface velocity amplitudes are
predicted for models with masses below 10Msun. For models with M>10Msun, the
surface velocity amplitudes are of the order of 10km/s. Moreover we find the
occurrence of pulsations for stars in the mass range 9-14Msun, while mass loss
appears to stabilize the more massive WR stars. We confront our results with
observationally derived line variabilities of 17 WN stars. The data suggest
variability to occur for stars above 10Msun, which is increasing linearly with
mass above this value, in agreement with our results. We further find some of
our models to be unstable to radial pulsations, and predict local magnetic
fields of the order of hundreds of Gauss in WR stars more massive than 10Msun.
Our study relates the surface velocity fluctuations induced by sub-surface
convection to the formation of clumping in the inner part of the wind. From
this mechanism, we expect a stronger variability in more massive WR stars.Comment: A&A, accepte
Vermont Adolescent Perception of Barriers to Smoking and Cessation
Introduction: Despite a decline in youth smoking rates over the past decade, thirteen percent of Vermont high school students still smoke (Vermont Youth Risk Behavior Survey, YRBS, 2013). Smoking and nicotine exposure at an early age can have detrimental effects on brain development and lead to long term, sustained tobacco use (Arrazola et. al 2015). It was our goal to characterize the barriers to cessation for these adolescents. Some important factors suggested by the literature include living with someone who smokes (50% of VT teen smokers report a parent or guardian who smokes) and having a close friend who smokes (70% of VT teen smokers) (American Lung Association 2015). Nationally, while teen smoking rates continue to decline, the decrease is being offset by a significant increase in electronic vapor products (e-cigs) (12% increase from 2011-2014) (Arrazola et. al 2015). The 2013 Vermont YRBS data may therefore be misleading, and not capture this increase in tobacco and e-cig use. Therefore, we were particularly interested in further characterizing the link, if any, between e-cig use and smoking initiation or successful smoking cessation.https://scholarworks.uvm.edu/comphp_gallery/1222/thumbnail.jp
Nachhaltig stabile Bahnlaufprozesse – Fehlerursachenanalyse und Reaktion
Der Herstellung von Kunststoffen, deren Weiterverarbeitung zu Halbzeugen wie Folien und Platten sowie Produkten wie Verpackungen oder Bauteilen wird in der deutschen Industrie, nicht zuletzt aufgrund der hohen Exportquoten, eine große Bedeutung zugesprochen [STAT2016]. Dabei müssen Halbzeugprodukte immer höheren Funktionsanforderungen bei zugleich geringerem Rohstoffeinsatz gerecht werden [DAUN2014]. Unter diesem Gesichtspunkt werden heute hohe Anforderungen an eine stabile Prozessführung mit zunehmend weniger Toleranz gegenüber Qualitätsschwankungen (z.B. fehlerhafte Druckbilder oder Siegelnähte) bei der Verarbeitung gestellt [VÄTH2011]. [... aus der Einleitung
Binding Specificities of the Telomere Phage ϕKO2 Prophage Repressor CB and Lytic Repressor Cro
Temperate bacteriophages possess a genetic switch which regulates the lytic
and lysogenic cycle. The genomes of the temperate telomere phages N15, PY54,
and ϕKO2 harbor a primary immunity region (immB) comprising genes for the
prophage repressor (cI or cB), the lytic repressor (cro) and a putative
antiterminator (q). The roles of these products are thought to be similar to
those of the lambda proteins CI (CI prophage repressor), Cro (Cro repressor),
and Q (antiterminator Q), respectively. Moreover, the gene order and the
location of several operator sites in the prototype telomere phage N15 and in
ϕKO2 are reminiscent of lambda-like phages. We determined binding sites of the
ϕKO2 prophage repressor CB and lytic repressor Cro on the ϕKO2 genome in
detail by electrophoretic mobility shift assay (EMSA) studies. Unexpectedly,
ϕKO2 CB and Cro revealed different binding specificities. CB was bound to
three OR operators in the intergenic region between cB and cro, two OL
operators between cB and the replication gene repA and even to operators of
N15. Cro bound exclusively to the 16 bp operator site OR3 upstream of the ϕKO2
prophage repressor gene. The ϕKO2 genes cB and cro are regulated by several
strong promoters overlapping with the OR operators. The data suggest that Cro
represses cB transcription but not its own synthesis, as already reported for
PY54 Cro. Thus, not only PY54, but also phage ϕKO2 possesses a genetic switch
that diverges significantly from the switch of lambda-like phages
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