399 research outputs found
MiR-888: A newly identified miRNA significantly over-expressed in endometrial cancers
Endometrial cancer is the most common gynecological malignancy and the fourth most common cancer in women. With accumulating evidence, microRNAs have emerged as significant players in the development and progression of cancers. The data points to miR-888 playing an important functional role in the development of aggressive endometrial tumors. Future research will focus on identifying and validating the targets of miR-888 to elucidate its mechanism of action and support this hypothesi
Sequestered Alkaloid Defenses in the Dendrobatid Poison Frog Oophaga pumilio Provide Variable Protection from Microbial Pathogens
Most amphibians produce their own defensive chemicals; however, poison frogs sequester their alkaloid-based defenses from dietary arthropods. Alkaloids function as a defense against predators, and certain types appear to inhibit microbial growth. Alkaloid defenses vary considerably among populations of poison frogs, reflecting geographic differences in availability of dietary arthropods. Consequently, environmentally driven differences in frog defenses may have significant implications regarding their protection against pathogens. While natural alkaloid mixtures in dendrobatid poison frogs have recently been shown to inhibit growth of non-pathogenic microbes, no studies have examined the effectiveness of alkaloids against microbes that infect these frogs. Herein, we examined how alkaloid defenses in the dendrobatid poison frog, Oophaga pumilio, affect growth of the known anuran pathogens Aeromonas hydrophila and Klebsiella pneumoniae. Frogs were collected from five locations throughout Costa Rica that are known to vary in their alkaloid profiles. Alkaloids were isolated from individual skins, and extracts were assayed against both pathogens. Microbe subcultures were inoculated with extracted alkaloids to create dose-response curves. Subsequent spectrophotometry and cell counting assays were used to assess growth inhibition. GC-MS was used to characterize and quantify alkaloids in frog extracts, and our results suggest that variation in alkaloid defenses lead to differences in inhibition of these pathogens. The present study provides the first evidence that alkaloid variation in a dendrobatid poison frog is associated with differences in inhibition of anuran pathogens, and offers further support that alkaloid defenses in poison frogs confer protection against both pathogens and predators
Modelling Deep Water Habitats to Develop a Spatially Explicit, Fine Scale Understanding of the Distribution of the Western Rock Lobster, Panulirus cygnus
Background: The western rock lobster, Panulirus cygnus, is endemic to Western Australia and supports substantial commercial and recreational fisheries. Due to and its wide distribution and the commercial and recreational importance of the species a key component of managing western rock lobster is understanding the ecological processes and interactions that may influence lobster abundance and distribution. Using terrain analyses and distribution models of substrate and benthic biota, we assess the physical drivers that influence the distribution of lobsters at a key fishery site. Methods and Findings: Using data collected from hydroacoustic and towed video surveys, 20 variables (including geophysical, substrate and biota variables) were developed to predict the distributions of substrate type (three classes of reef, rhodoliths and sand) and dominant biota (kelp, sessile invertebrates and macroalgae) within a 40 km 2 area about 30 km off the west Australian coast. Lobster presence/absence data were collected within this area using georeferenced pots. These datasets were used to develop a classification tree model for predicting the distribution of the western rock lobster. Interestingly, kelp and reef were not selected as predictors. Instead, the model selected geophysical and geomorphic scalar variables, which emphasise a mix of terrain within limited distances. The model of lobster presence had an adjusted D 2 of 64 and an 80 % correct classification. Conclusions: Species distribution models indicate that juxtaposition in fine scale terrain is most important to the wester
Rotation Measure Synthesis of Galactic Polarized Emission with the DRAO 26-m Telescope
Radio polarimetry at decimetre wavelengths is the principal source of
information on the Galactic magnetic field. The diffuse polarized emission is
strongly influenced by Faraday rotation in the magneto-ionic medium and
rotation measure is the prime quantity of interest, implying that all Stokes
parameters must be measured over wide frequency bands with many frequency
channels. The DRAO 26-m Telescope has been equipped with a wideband feed, a
polarization transducer to deliver both hands of circular polarization, and a
receiver, all operating from 1277 to 1762 MHz. Half-power beamwidth is between
40 and 30 arcminutes. A digital FPGA spectrometer, based on commercially
available components, produces all Stokes parameters in 2048 frequency channels
over a 485-MHz bandwidth. Signals are digitized to 8 bits and a Fast Fourier
Transform is applied to each data stream. Stokes parameters are then generated
in each frequency channel. This instrument is in use at DRAO for a Northern sky
polarization survey. Observations consist of scans up and down the Meridian at
a drive rate of 0.9 degree per minute to give complete coverage of the sky
between declinations -30 degree and 90 degree. This paper presents a complete
description of the receiver and data acquisition system. Only a small fraction
of the frequency band of operation is allocated for radio astronomy, and about
20 percent of the data are lost to interference. The first 8 percent of data
from the survey are used for a proof-of-concept study, which has led to the
first application of Rotation Measure Synthesis to the diffuse Galactic
emission obtained with a single-antenna telescope. We find rotation measure
values for the diffuse emission as high as approximately 100 rad per square
metre, much higher than recorded in earlier work.Comment: Accepted for publication in The Astronomical Journa
Editorial: The Mammary Stroma in Normal Development and Function
The mammary gland can no longer be simply viewed as an organ composed of epithelial cells within a passive stromal microenvironment. Many lines of evidence have evolved to reinforce the notion that mammary epithelial cell growth, differentiation, lactation and progression to cancer involves bidirectional interactions between the epithelial population and its surrounding stroma. Within this stroma are numerous systems that are all capable of modulating epithelial function. In this context, the mammary stroma is not simply a depot of adipose tissue in which mammary epithelial cells undertake a unique growth and differentiation process, although adipocytes can impart numerous modulatory signals to epithelial cells, and vice versa. Rather, the stromal environment constitutes and supports a critical vasculature that supplies nutrients and endocrine cues, a lymphatic system that not only removes metabolites but also provides an intimate interface with the immune system, and an extracellular matrix scaffold in which epithelial cells grow, differentiate and regress. Ultimately all of these components play a critical role in directing the epithelial phenotype during normal mammary gland growth and function. An increasing appreciation for these different systems demands a view of mammary epithelial cells in a much different light, and further necessitates the development of model systems that incorporate and integrate increasing complexity
On the Whitehead spectrum of the circle
The seminal work of Waldhausen, Farrell and Jones, Igusa, and Weiss and
Williams shows that the homotopy groups in low degrees of the space of
homeomorphisms of a closed Riemannian manifold of negative sectional curvature
can be expressed as a functor of the fundamental group of the manifold. To
determine this functor, however, it remains to determine the homotopy groups of
the topological Whitehead spectrum of the circle. The cyclotomic trace of B
okstedt, Hsiang, and Madsen and a theorem of Dundas, in turn, lead to an
expression for these homotopy groups in terms of the equivariant homotopy
groups of the homotopy fiber of the map from the topological Hochschild
T-spectrum of the sphere spectrum to that of the ring of integers induced by
the Hurewicz map. We evaluate the latter homotopy groups, and hence, the
homotopy groups of the topological Whitehead spectrum of the circle in low
degrees. The result extends earlier work by Anderson and Hsiang and by Igusa
and complements recent work by Grunewald, Klein, and Macko.Comment: 52 page
Gorenstein homological algebra and universal coefficient theorems
We study criteria for a ringâor more generally, for a small categoryâto be Gorenstein and for a module over it to be of finite projective dimension. The goal is to unify the universal coefficient theorems found in the literature and to develop machinery for proving new ones. Among the universal coefficient theorems covered by our methods we find, besides all the classic examples, several exotic examples arising from the KK-theory of C*-algebras and also Neemanâs BrownâAdams representability theorem for compactly generated categories
Association of Plasma 25â Hydroxyvitamin D Concentrations and Pathogenic Oral Bacteria in Postmenopausal Females
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141146/1/jper0944.pd
Brown representability for space-valued functors
In this paper we prove two theorems which resemble the classical
cohomological and homological Brown representability theorems. The main
difference is that our results classify small contravariant functors from
spaces to spaces up to weak equivalence of functors.
In more detail, we show that every small contravariant functor from spaces to
spaces which takes coproducts to products up to homotopy and takes homotopy
pushouts to homotopy pullbacks is naturally weekly equivalent to a
representable functor.
The second representability theorem states: every contravariant continuous
functor from the category of finite simplicial sets to simplicial sets taking
homotopy pushouts to homotopy pullbacks is equivalent to the restriction of a
representable functor. This theorem may be considered as a contravariant analog
of Goodwillie's classification of linear functors.Comment: 19 pages, final version, accepted by the Israel Journal of
Mathematic
DG-algebras and derived A-infinity algebras
A differential graded algebra can be viewed as an A-infinity algebra. By a
theorem of Kadeishvili, a dga over a field admits a quasi-isomorphism from a
minimal A-infinity algebra. We introduce the notion of a derived A-infinity
algebra and show that any dga A over an arbitrary commutative ground ring k is
equivalent to a minimal derived A-infinity algebra. Such a minimal derived
A-infinity algebra model for A is a k-projective resolution of the homology
algebra of A together with a family of maps satisfying appropriate relations.
As in the case of A-infinity algebras, it is possible to recover the dga up
to quasi-isomorphism from a minimal derived A-infinity algebra model. Hence the
structure we are describing provides a complete description of the
quasi-isomorphism type of the dga.Comment: v3: 27 pages. Minor corrections, to appear in Crelle's Journa
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