177 research outputs found
The Emerging Role of Lamin C as an Important LMNA Isoform in Mechanophenotype
Lamin A and lamin C isoforms of the gene LMNA are major structural and mechanotransductive components of the nuclear lamina. Previous reports have proposed lamin A as the isoform with the most dominant contributions to cellular mechanophenotype. Recently, expression of lamin C has also been shown to strongly correlate to cellular elastic and viscoelastic properties. Nevertheless, LMNA isoforms exist as part of a network that collectively provides structural integrity to the nucleus and their expression is ultimately regulated in a cell-specific manner. Thus, they have importance in mechanotransduction and structural integrity of the nucleus as well as potential candidates for biomarkers of whole-cell mechanophenotype. Therefore, a fuller discussion of lamin isoforms as mechanophenotypic biomarkers should compare both individual and ratiometric isoform contributions toward whole-cell mechanophenotype across different cell types. In this perspective, we discuss the distinctions between the mechanophenotypic correlations of individual and ratiometric lamins A:B1, C:B1, (A + C):B1, and C:A across cells from different lineages, demonstrating that the collective contribution of ratiometric lamin (A + C):B1 isoforms exhibited the strongest correlation to whole-cell stiffness. Additionally, we highlight the potential roles of lamin isoform ratios as indicators of mechanophenotypic change in differentiation and disease to demonstrate that the contributions of individual and collective lamin isoforms can occur as both static and dynamic biomarkers of mechanophenotype
Inbred Strain-Specific Effects of Exercise in Wild Type and Biglycan Deficient Mice
Biglycan (bgn)-deficient mice (KO) have defective osteoblasts which lead to changes in the amount and quality of bone. Altered tissue strength in C57BL6/129 (B6;129) KO mice, a property which is independent of tissue quantity, suggests that deficiencies in tissue quality are responsible. However, the response to bgn-deficiency is inbred strain-specific. Mechanical loading influences bone matrix quality in addition to any increase in bone mass or change in bone formation activity. Since many diseases influence the mechanical integrity of bone through altered tissue quality, loading may be a way to prevent and treat extracellular matrix deficiencies. C3H/He (C3H) mice consistently have a less vigorous response to mechanical loading vs. other inbred strains. It was therefore hypothesized that the bones from both wild type (WT) and KO B6;129 mice would be more responsive to exercise than the bones from C3H mice. To test these hypotheses at 11 weeks of age, following 21 consecutive days of exercise, we investigated cross-sectional geometry, mechanical properties, and tissue composition in the tibiae of male mice bred on B6;129 and C3H backgrounds. This study demonstrated inbred strain-specific compositional and mechanical changes following exercise in WT and KO mice, and showed evidence of genotype-specific changes in bone in response to loading in a gene disruption model. This study further shows that exercise can influence bone tissue composition and/or mechanical integrity without changes in bone geometry. Together, these data suggest that exercise may represent a possible means to alter tissue quality and mechanical deficiencies caused by many diseases of bone
Plug-Based Microfluidics with Defined Surface Chemistry to Miniaturize and Control Aggregation of Amyloidogenic Peptides
Small with control: For miniaturization of protein aggregation experiments the interfacial chemistry must be controlled to avoid protein aggregation caused by interfacial adsorption. Plug-based microfluidics with defined surface chemistry (see schematic picture) can then be used to perform hundreds of aggregation experiments with volume-limited samples, such as cerebrospinal fluid from mice
Lessons learned from synthetic research projects based on the ostrom workshop frameworks
A generalized knowledge of social-ecological relationships is needed to address current environmental challenges. Broadly comparative and synthetic research is a key method for establishing this type of knowledge. To date, however, most work on social-ecological systems has applied idiosyncratic methods to specific systems. Several projects, each based on the frameworks developed by Elinor Ostrom and colleagues, stand out for their application of consistent methods across a broad range of cases. In this paper we compare seven of these projects and draw conclusions regarding their potential benefits and the challenges that scholars can expect in conducting this type of research. The two main challenges that we identified are (1) the collective-action dilemmas that collaborators face in producing and maintaining the social and technical infrastructure that is needed for such projects; and (2) balancing complexity and comparability in the structure of the databases used and the associated methods for characterizing complex social-ecological cases. We discuss approaches for meeting these challenges, and present a guiding checklist of questions for project design and implementation to provide guidance for future broadly comparative research
Role of primary motor cortex in the control of manual dexterity assessed via sequential bilateral lesion in the adult macaque monkey: A case study
From a case study, we describe the impact of unilateral lesion of the hand area in the primary motor cortex (M1) on manual dexterity and the role of the intact contralesional M1 in long-term functional recovery. An adult macaque monkey performed two manual dexterity tasks: (i) “modified Brinkman board” task, assessed simple precision grip versus complex precision grip, the latter involved a hand postural adjustment; (ii) “modified Klüver board” task, assessed movements ranging from power grip to precision grip, pre-shaping and grasping. Two consecutive unilateral M1 lesions targeted the hand area of each hemisphere, the second lesion was performed after stable, though incomplete, functional recovery from the primary lesion. Following each lesion, the manual dexterity of the contralesional hand was affected in a comparable manner, effects being progressively more deleterious from power grip to simple and then complex precision grips. Both tasks yielded consistent data, namely that the secondary M1 lesion did not have a significant impact on the recovered performance from the primary M1 lesion, which took place 5 months earlier. In conclusion, the intact contralesional M1 did not play a major role in the long-term functional recovery from a primary M1 lesion targeted to the hand area
Mechanical Properties and Gene Expression of Chondrocytes on Micropatterned Substrates Following Dedifferentiation in Monolayer
Chondrocytes in articular cartilage normally exhibit high expression of collagen II and aggrecan but rapidly dedifferentiate to a fibroblastic phenotype if passaged in culture. Previous studies have suggested that the loss of chondrocyte phenotype is associated with changes in the structure of the F-actin cytoskeleton, which also controls cell mechanical properties. In this study, we examined how dedifferentiation in monolayer influences the mechanical properties of chondrocytes isolated from different zones of articular cartilage. Atomic force microscopy was used to measure the mechanical properties of superficial and middle/deep zone chondrocytes as they underwent serial passaging and subsequent growth on fibronectin-coated, micropatterned self-assembled monolayers (MSAMs) that restored a rounded cell shape in 2D culture. Chondrocytes exhibited significant increases in elastic and viscoelastic moduli with dedifferentiation in culture. These changes were only partially ameliorated by the restoration of a rounded shape on micropatterned surfaces. Furthermore, intrinsic zonal differences in cell mechanical properties were rapidly lost with passage. These findings indicate that cell mechanical properties may provide additional measures of phenotypic expression of chondrocytes as they undergo dedifferentiation and possibly redifferentiation in culture
Darwin’s wind hypothesis: does it work for plant dispersal in fragmented habitats?
Using the wind-dispersed plant Mycelis muralis, we examined how landscape fragmentation affects variation in seed traits contributing to dispersal.
Inverse terminal velocity (Vt−1) of field-collected achenes was used as a proxy for individual seed dispersal ability. We related this measure to different metrics of landscape connectivity, at two spatial scales: in a detailed analysis of eight landscapes in Spain and along a latitudinal gradient using 29 landscapes across three European regions.
In the highly patchy Spanish landscapes, seed Vt−1 increased significantly with increasing connectivity. A common garden experiment suggested that differences in Vt−1 may be in part genetically based. The Vt−1 was also found to increase with landscape occupancy, a coarser measure of connectivity, on a much broader (European) scale. Finally, Vt−1 was found to increase along a south–north latitudinal gradient.
Our results for M. muralis are consistent with ‘Darwin’s wind dispersal hypothesis’ that high cost of dispersal may select for lower dispersal ability in fragmented landscapes, as well as with the ‘leading edge hypothesis’ that most recently colonized populations harbour more dispersive phenotypes.
The Arecibo Legacy Fast ALFA Survey: The alpha.40 HI Source Catalog, its Characteristics and their Impact on the Derivation of the HI Mass Function
We present a current catalog of 21 cm HI line sources extracted from the
Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800
square degrees of sky: the alpha.40 catalog. Covering 40% of the final survey
area, the alpha.40 catalog contains 15855 sources in the regions 07h30m < R.A.
< 16h30m, +04 deg < Dec. < +16 deg and +24 deg < Dec. < +28 deg and 22h < R.A.
< 03h, +14 deg < Dec. < +16 deg and +24 deg < Dec. < +32 deg. Of those, 15041
are certainly extragalactic, yielding a source density of 5.3 galaxies per
square degree, a factor of 29 improvement over the catalog extracted from the
HI Parkes All Sky Survey. In addition to the source centroid positions, HI line
flux densities, recessional velocities and line widths, the catalog includes
the coordinates of the most probable optical counterpart of each HI line
detection, and a separate compilation provides a crossmatch to identifications
given in the photometric and spectroscopic catalogs associated with the Sloan
Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line
sources cannot be identified with a feasible optical counterpart; some of those
may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented
of the completeness, width dependent sensitivity function and bias inherent in
the current alpha.40 catalog. The impact of survey selection, distance errors,
current volume coverage and local large scale structure on the derivation of
the HI mass function is assessed. While alpha.40 does not yet provide a
completely representative sampling of cosmological volume, derivations of the
HI mass function using future data releases from ALFALFA will further improve
both statistical and systematic uncertainties.Comment: 62 pages, 28 figures. See http://egg.astro.cornell.edu/alfalfa/data
for ASCII and CSV datafiles corresponding to Tables 1, 2 and 3. A higher
resolution PDF version can be found at
http://egg.astro.cornell.edu/alfalfa/pubs.php. To appear in Nov 2011 Astron.
Where do stars explode in the ISM? -- The distribution of dense gas around massive stars and supernova remnants in M33
Star formation in galaxies is regulated by turbulence, outflows, gas heating
and cloud dispersal -- processes which depend sensitively on the properties of
the interstellar medium (ISM) into which supernovae (SNe) explode.
Unfortunately, direct measurements of ISM environments around SNe remain
scarce, as SNe are rare and often distant. Here we demonstrate a new approach:
mapping the ISM around the massive stars that are soon to explode. This
provides a much larger census of explosion sites than possible with only SNe,
and allows comparison with sensitive, high-resolution maps of the atomic and
molecular gas from the Jansky VLA and ALMA. In the well-resolved Local Group
spiral M33, we specifically observe the environments of red supergiants (RSGs,
progenitors of Type II SNe), Wolf-Rayet stars (WRs, tracing stars 30
M, and possibly future stripped-envelope SNe), and supernova remnants
(SNRs, locations where SNe have exploded). We find that massive stars evolve
not only in dense, molecular-dominated gas (with younger stars in denser gas),
but also a substantial fraction (45\% of WRs; higher for RSGs) evolve in
lower-density, atomic-gas-dominated, inter-cloud media. We show that these
measurements are consistent with expectations from different stellar-age tracer
maps, and can be useful for validating SN feedback models in numerical
simulations of galaxies. Along with the discovery of a 20-pc diameter molecular
gas cavity around a WR, these findings re-emphasize the importance of
pre-SN/correlated-SN feedback evacuating the dense gas around massive stars
before explosion, and the need for high-resolution (down to pc-scale) surveys
of the multi-phase ISM in nearby galaxies.Comment: 34 pages, 14 figures. Submitted to ApJ. Comments welcome! The density
distributions will be made publicly available after journal acceptance of
manuscript. Please feel free to contact us in the meantime if you would like
to use the
Conjugative Botulinum Neurotoxin-Encoding Plasmids in Clostridium botulinum
Clostridium botulinum produces seven distinct serotypes of botulinum neurotoxins (BoNTs). The genes encoding different subtype neurotoxins of serotypes A, B, F and several dual neurotoxin-producing strains have been shown to reside on plasmids, suggesting that intra- and interspecies transfer of BoNT-encoding plasmids may occur. The objective of the present study was to determine whether these C. botulinum BoNT-encoding plasmids are conjugative.C. botulinum BoNT-encoding plasmids pBotCDC-A3 (strain CDC-A3), pCLJ (strain 657Ba) and pCLL (strain Eklund 17B) were tagged with the erythromycin resistance marker (Erm) using the ClosTron mutagenesis system by inserting a group II intron into the neurotoxin genes carried on these plasmids. Transfer of the tagged plasmids from the donor strains CDC-A3, 657Ba and Eklund 17B to tetracycline-resistant recipient C. botulinum strains was evaluated in mating experiments. Erythromycin and tetracycline resistant transconjugants were isolated from donor:recipient mating pairs tested. Transfer of the plasmids to the transconjugants was confirmed by pulsed-field gel electrophoresis (PFGE) and Southern hybridizations. Transfer required cell-to-cell contact and was DNase resistant. This indicates that transfer of these plasmids occurs via a conjugation mechanism.This is the first evidence supporting conjugal transfer of native botulinum neurotoxin-encoding plasmids in C. botulinum, and provides a probable mechanism for the lateral distribution of BoNT-encoding plasmids to other C. botulinum strains. The potential transfer of C. botulinum BoNT-encoding plasmids to other bacterial hosts in the environment or within the human intestine is of great concern for human pathogenicity and necessitates further characterization of these plasmids
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