140 research outputs found
PF191012 Myszyniec - highest Orionid meteor ever recorded
On the night of Oct 18/19, 2012 at 00:23 UT a -14.7 mag Orionid fireball
occurred over northeastern Poland. The precise orbit and atmospheric trajectory
of the event is presented, based on the data collected by five video and one
photographic Polish Fireball Network (PFN) stations. The beginning height of
the meteor is 168.4 +\- 0.6 km which makes the PF191012 Myszyniec fireball the
highest ever observed, well documented meteor not belonging to the Leonid
shower. The ablation became the dominant source of light of the meteor at a
height of around 115 km. The thermalization of sputtered particles is suggested
to be the source of radiation above that value. The transition height of 115 km
is 10-15 km below the transition heights derived for Leonids and it might
suggest that the material of Leonids should be more fragile and have probably
smaller bulk density than in case of Orionids.Comment: 5 pages, 5 figures, accpeted for publication in Astronomy &
Astrophysic
Winter Bird Assemblages in Rural and Urban Environments: A National Survey
Urban development has a marked effect on the ecological and behavioural traits of many living
organisms, including birds. In this paper, we analysed differences in the numbers of wintering
birds between rural and urban areas in Poland. We also analysed species richness
and abundance in relation to longitude, latitude, human population size, and landscape
structure. All these parameters were analysed using modern statistical techniques incorporating
species detectability. We counted birds in 156 squares (0.25 km2 each) in December
2012 and again in January 2013 in locations in and around 26 urban areas across Poland
(in each urban area we surveyed 3 squares and 3 squares in nearby rural areas). The influence
of twelve potential environmental variables on species abundance and richness was
assessed with Generalized Linear Mixed Models, Principal Components and Detrended
Correspondence Analyses. Totals of 72 bird species and 89,710 individual birds were recorded
in this study. On average (±SE) 13.3 ± 0.3 species and 288 ± 14 individuals were recorded
in each square in each survey. A formal comparison of rural and urban areas
revealed that 27 species had a significant preference; 17 to rural areas and 10 to urban areas. Moreover, overall abundance in urban areas was more than double that of rural
areas. There was almost a complete separation of rural and urban bird communities. Significantly
more birds and more bird species were recorded in January compared to December.
We conclude that differences between rural and urban areas in terms of winter conditions
and the availability of resources are reflected in different bird communities in the two
environments
Expression of a protein involved in bone resorption, Dkk1, is activated by HTLV-1 bZIP factor through its activation domain
<p>Abstract</p> <p>Background</p> <p>Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia, a malignancy characterized by uncontrolled proliferation of virally-infected CD4+ T-cells. Hypercalcemia and bone lesions due to osteoclast-mediated bone resorption are frequently associated with more aggressive forms of the disease. The HTLV-1 provirus contains a unique antisense gene that expresses HTLV-1 basic leucine zipper (bZIP) factor (HBZ). HBZ is localized to the nucleus where it regulates levels of transcription by binding to certain cellular transcriptional regulators. Among its protein targets, HBZ forms a stable complex with the homologous cellular coactivators, p300 and CBP, which is modulated through two N-terminal LXXLL motifs in the viral protein and the conserved KIX domain in the coactivators.</p> <p>Results</p> <p>To determine the effects of these interactions on transcription, we performed a preliminary microarray analysis, comparing levels of gene expression in cells with wild-type HBZ versus cells with HBZ mutated in its LXXLL motifs. <it>DKK1</it>, which encodes the secreted Wnt signaling inhibitor, Dickkopf-1 (Dkk1), was confirmed to be transcriptionally activated by HBZ, but not its mutant. Dkk1 plays a major role in the development of bone lesions caused by multiple myeloma. In parallel with the initial findings, activation of Dkk1 expression by HBZ was abrogated by siRNA-mediated knockdown of p300/CBP or by a truncated form of p300 containing the KIX domain. Among HTLV-1-infected T-cell lines tested, the detection of Dkk1 mRNA partially correlated with a threshold level of HBZ mRNA. In addition, an uninfected and an HTLV-1-infected T-cell line transfected with an HBZ expression vector exhibited <it>de novo </it>and increased DKK1 transcription, respectively. In contrast to HBZ, The HTLV-1 Tax protein repressed Dkk1 expression.</p> <p>Conclusions</p> <p>These data indicate that HBZ activates Dkk1 expression through its interaction with p300/CBP. However, this effect is limited in HTLV-1-infected T-cell lines, which in part, may be due to suppression of Dkk1 expression by Tax. Consequently, the ability of HBZ to regulate expression of Dkk1 and possibly other cellular genes may only be significant during late stages of ATL, when Tax expression is repressed.</p
Riluzole Increases the Amount of Latent HSF1 for an Amplified Heat Shock Response and Cytoprotection
BDNF/TrkB Signaling as a Potential Novel Target in Pediatric Brain Tumors: Anticancer Activity of Selective TrkB Inhibition in Medulloblastoma Cells
Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Deregulation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) signaling has been associated with increased proliferative capabilities, invasiveness, and chemoresistance in several types of cancer. However, the relevance of this pathway in MB remains unknown. Here, we show that the selective TrkB inhibitor N-[2-[[(hexahydro-2-oxo-1H-azepin-3-yl)amino]carbonyl]phenyl]-benzo[b]thiophene-2-carboxamide (ANA-12) markedly reduced the viability and survival of human cell lines representative of different MB molecular subgroups. These findings provide the first evidence supporting further investigation of TrkB inhibition as a potential novel strategy for MB treatment
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