1,515 research outputs found
Sperm repository for a breeding program of the eastern oyster crassostrea virginica: Sample collection, processing, cryopreservation, and data management plan
The Eastern oyster Crassostrea virginica (Family Ostreidae) is one of the most important fishery and aquaculture species in the U.S. and is a keystone species for coastal reefs. A breeding program was initiated in 2019 to support the fastâgrowing aquaculture industry culturing this species in the Gulf of Mexico. Oysters from 17 wild populations in embayment along the U.S. Gulf of Mexico coast from southwest Florida to the Matagorda Bay, Texas were used as broodstock for the program to maximize genetic diversity in the base population. A sperm repository of the broodstock was established to support the breeding project. The goal of this study was to demonstrate the sperm sample collection, processing, cryopreservation, and the data management plan involved in the establishment of a sperm germplasm repository of base populations. The supporting objectives were to: (1) develop a data management plan for the sperm repository; (2) streamline the procedure for sample collection, processing, and cryopreservation; (3) incorporate sperm quality analysis into the procedure, and (4) archive the cryopreserved samples as a repository for future use in the breeding program. This sperm repository included a total of 102 male oysters from the 17 collection sites (six oysters per site). A data management plan was developed with six categories, including sample collection, phenotype, fresh sperm, genotype, cryopreservation, and postâthaw sperm, as guide for data collection. Sperm collection was accomplished by strip spawn, and fresh sperm production, motility, and fertility were recorded for quality analysis. Cryopreserved sperm samples were sorted, labelled, archived, and stored in liquid nitrogen for future use. Postâthaw motility (1â30%) and plasm membrane integrity (15.34â70.36%) were recorded as postâthaw quality parameters. Overall, this study demonstrated a streamlined procedure of oyster sperm collection, processing, and cryopreservation for establishing a sperm repository that can serve as a template for construction of oyster germplasm repositories for breeding programs
Age structure, dispersion and diet of a population of stoats (Mustela erminea) in southern Fiordland during the decline phase of the beechmast cycle
The dispersion, age structure and diet of stoats (Mustela erminea) in beech forest in the Borland and Grebe Valleys, Fiordland National Park, were examined during December and January 2000/01, 20 months after a heavy seed-fall in 1999. Thirty trap stations were set along a 38-km transect through almost continuous beech forest, at least 1 km apart. Mice were very scarce (nights, C/100TN) along two standard index lines placed at either end of the transect, compared with November 1999 (>60/100TN), but mice were detected (from footprints in stoat tunnels) along an 8 km central section of the transect (stations 14-22). Live trapping with one trap per station (total 317.5 trap nights) in December 2000 caught 2 female and 23 male stoats, of which 10 (including both females) were radio collared. The minimum range lengths of the two females along the transect represented by the trap line were 2.2 and 6.0 km; those of eight radio-tracked males averaged 2.9 ± 1.7 km. Stations 14-22 tended to be visited more often, by more marked individual stoats, than the other 21 stations.
Fenn trapping at the same 30 sites, but with multiple traps per station (1333.5 trap nights), in late January 2001 collected carcasses of 35 males and 28 females (including 12 of the marked live-trapped ones). Another two marked males were recovered dead. The stoat population showed no sign of chronic nutritional stress (average fat reserve index = 2.8 on a scale of 1-4 where 4 = highest fat content); and only one of 63 guts analysed was empty. Nevertheless, all 76 stoats handled were adults with 1-3 cementum annuli in their teeth, showing that reproduction had failed that season. Prey categories recorded in descending frequency of occurrence were birds, carabid beetle (ground beetle), weta, possum, rat, and mouse. The frequencies of occurrence of mice and birds in the diet of these stoats (10% and 48%, respectively) were quite different from those in stoats collected in Pig Creek, a tributary of the Borland River (87%, 5%), 12 months previously when mice were still abundant. Five of the six stoat guts containing mice were collected within 1 km of stations 14-22
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Radionuclides in a deciduous forest surrounding a shallow-land-burial site in the eastern United States
The objective of this study was to determine if radioactive materials buried in trenches at the Maxey Flats burial ground in eastern Kentucky have migrated into the surrounding oak-hickory forest. Forest floor litter, minearl soil, and tree leaves were sampled and the radionuclide content measured. (ACR
The CRI v2.2 reduced degradation scheme for isoprene
The reduced representation of isoprene degradation in the Common Representative Intermediates (CRI) mechanism has been systematically updated, using the Master Chemical Mechanism (MCM v3.3.1) as a reference benchmark, with the updated mechanism being released as CRI v2.2. The complete isoprene degradation mechanism in CRI v2.2 consists of 186 reactions of 56 closed shell and free radical species, this being an order of magnitude reduction in size compared with MCM v3.3.1. The chemistry initiated by reaction with OH radicals, NO3 radicals and ozone (O3) is treated. An overview of the updates is provided, within the context of reported kinetic and mechanistic information. The revisions mainly relate to the OH-initiated chemistry, which tends to dominate under atmospheric conditions, although these include updates to the chemistry of products that are also generated from the O3- and NO3-initiated oxidation. The revisions have impacts in a number of key areas, including recycling of HOx and NOx. The performance of the CRI v2.2 isoprene mechanism has been compared with those of the preceding version (CRI v2.1) and the reference MCM v3.3.1 over a range of relevant conditions, using a box model of the tropical forested boundary layer. In addition, tests are carried out to ensure that the performance of MCM v3.3.1 remains robust to more recently reported information. CRI v2.2 has also been implemented into the STOCHEM chemistry-transport model, with a customized close-variant of CRI v2.2 implemented into the EMEP MSC-W chemistry-transport model. The results of these studies are presented and used to illustrate the global-scale impacts of the mechanistic updates on HOx radical concentrations
Critical roles of arginine in growth and biofilm development by Streptococcus gordonii
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112199/1/mmi13023.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112199/2/mmi13023-sup-0001-si.pd
Support varieties for selfinjective algebras
Support varieties for any finite dimensional algebra over a field were
introduced by Snashall-Solberg using graded subalgebras of the Hochschild
cohomology. We mainly study these varieties for selfinjective algebras under
appropriate finite generation hypotheses. Then many of the standard results
from the theory of support varieties for finite groups generalize to this
situation. In particular, the complexity of the module equals the dimension of
its corresponding variety, all closed homogeneous varieties occur as the
variety of some module, the variety of an indecomposable module is connected,
periodic modules are lines and for symmetric algebras a generalization of
Webb's theorem is true
Stellar wind properties of the nearly complete sample of O stars in the low metallicity young star cluster NGC346 in the SMC galaxy
Massive stars are among the main cosmic engines driving the evolution of
star-forming galaxies. Their powerful ionising radiation and stellar winds
inject a large amount of energy in the interstellar medium. Furthermore,
mass-loss () through radiatively driven winds plays a key role in the
evolution of massive stars. Even so, the wind mass-loss prescriptions used in
stellar evolution models, population synthesis, and stellar feedback models
often disagree with mass-loss rates empirically measured from the UV spectra of
low metallicity massive stars. The most massive young star cluster in the low
metallicity Small Magellanic Cloud galaxy is NGC346. This cluster contains more
than half of all O stars discovered in this galaxy so far. A similar age,
metallicity (), and extinction, the O stars in the NGC346 cluster are
uniquely suited for a comparative study of stellar winds in O stars of
different subtypes. We aim to use a sample of O stars within NGC346 to study
stellar winds at low metallicity. We mapped the central 1" of NGC346 with the
long-slit UV observations performed by the Space Telescope Imaging Spectrograph
(STIS) on board of the {\em Hubble Space Telescope} and complemented these new
datasets with archival observations. Multi-epoch observations allowed for the
detection of wind variability. The UV dataset was supplemented by optical
spectroscopy and photometry. The resulting spectra were analysed using a
non-local thermal equilibrium model atmosphere code (PoWR) to determine wind
parameters and ionising fluxes. The effective mapping technique allowed us to
obtain a mosaic of almost the full extent of the cluster and resolve stars in
its core. Among hundreds of extracted stellar spectra, 21 belong to O stars.
Nine of them are classified as O stars for the first time. We analyse, in
detail, the UV spectra of 19 O stars... (continued)Comment: 33 pages, 40 figure
Accounting for aboveground carbon storage in shrubland and woodland ecosystems in the Great Basin
Improving the accuracy of carbon accounting in terrestrial ecosystems is critical for understanding carbon fluxes associated with land cover change, with significant implications for global carbon cycling and climate change. Semiâarid ecosystems account for an estimated 45% of global terrestrial ecosystem area and are in many locations experiencing high degrees of degradation. However, aboveground carbon accounting has largely focused on tropical and forested ecosystems, while drylands have been relatively neglected. Here, we used a combination of field estimates, remotely sensed data, and existing land cover maps to create a spatially explicit estimate of aboveground carbon storage within the Great Basin, a semiâarid region of the western United States encompassing 643,500 km2 of shrubland and woodland vegetation. We classified the region into seven distinct land cover categories: pinyonâjuniper woodland, sagebrush steppe, salt desert shrub, low sagebrush, forest, nonâforest, and other/excluded, each with an associated carbon estimate. Aboveground carbon estimates for pinyonâjuniper woodland were continuous values based on tree canopy cover. Carbon estimates for other land cover categories were based on a mean value for the land cover type. The Great Basin ecosystems contain an estimated 295.4 Tg in aboveground carbon, which is almost double the previous estimates that only accounted for forested ecosystems in the same area. Aboveground carbon was disproportionately stored in pinyonâjuniper woodland (43.7% carbon, 16.9% land area), while the shrubland systems accounted for roughly half of the total land area (49.1%) and oneâthird of the total carbon. Our results emphasize the importance of distinguishing and accounting for the distinctive contributions of shrubland and woodland ecosystems when creating carbon storage estimates for dryland regions
Neural feedback strategies to improve grasping coordination in neuromusculoskeletal prostheses
Conventional prosthetic arms suffer from poor controllability and lack of sensory feedback. Owing to the absence of tactile sensory information, prosthetic users must rely on incidental visual and auditory cues. In this study, we investigated the effect of providing tactile perception on motor coordination during routine grasping and grasping under uncertainty. Three transhumeral amputees were implanted with an osseointegrated percutaneous implant system for direct skeletal attachment and bidirectional communication with implanted neuromuscular electrodes. This neuromusculoskeletal prosthesis is a novel concept of artificial limb replacement that allows to extract control signals from electrodes implanted on viable muscle tissue, and to stimulate severed afferent nerve fibers to provide somatosensory feedback. Subjects received tactile feedback using three biologically inspired stimulation paradigms while performing a pick and lift test. The grasped object was instrumented to record grasping and lifting forces and its weight was either constant or unexpectedly changed in between trials. The results were also compared to the no-feedback control condition. Our findings confirm, in line with the neuroscientific literature, that somatosensory feedback is necessary for motor coordination during grasping. Our results also indicate that feedback is more relevant under uncertainty, and its effectiveness can be influenced by the selected neuromodulation paradigm and arguably also the prior experience of the prosthesis user
Dual roles for LUBAC signaling in thymic epithelial cell development and survival
Thymic epithelial cells (TECs) form a unique microenvironment that orchestrates T cell differentiation and immunological tolerance. Despite the importance of TECs for adaptive immunity, there is an incomplete understanding of the signalling networks that support their differentiation and survival. We report that the linear ubiquitin chain assembly complex (LUBAC) is essential for medullary TEC (mTEC) differentiation, cortical TEC survival and prevention of premature thymic atrophy. TEC-specific loss of LUBAC proteins, HOIL-1 or HOIP, severely impaired expansion of the thymic medulla and AIRE-expressing cells. Furthermore, HOIL-1-deficiency caused early thymic atrophy due to Caspase-8/MLKL-dependent apoptosis/necroptosis of cortical TECs. By contrast, deficiency in the LUBAC component, SHARPIN, caused relatively mild defects only in mTECs. These distinct roles for LUBAC components in TECs correlate with their function in linear ubiquitination, NFÎșB activation and cell survival. Thus, our findings reveal dual roles for LUBAC signaling in TEC differentiation and survival
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