1,507 research outputs found
Assessing Sandhill Crane Roosting Habitat along the Platte River, Nebraska
Each spring approximately 500,000 sandhill cranes and some endangered whooping cranes use the Central Platte River Valley in Nebraska as a staging habitat during their migration north to breeding and nesting grounds in Canada, Alaska, and the Siberian Arctic. Over the last century changes in the flow of the river have altered the river channels and the distribution of roost sites. USGS researchers studied linkages between water flow, sediment supply, channel morphology, and preferred sites for crane roosting. These results are useful for estimating crane populations and for providing resource managers with techniques to understand crane habitats
Effect of Ammonium Enrichment on Animal and Algal Biomass of the Coral Pocillopora damicornis
Algal and animal biomass parameters of colonies of the Pacific
coral Pocillopora damicornis (Linnaeus) were measured as a function of time of
exposure to elevated concentrations of seawater ammonium (20 and 50 uM
[(NH4)2S04]) ranging from 2 to 8 weeks. Areal concentrations of zooxanthellae,
chlorophyll, and protein increased with 20 uM ammonium addition. During
the 8-week period of exposure to 20 uM ammonium, the population density
of zooxanthellae increased from 3.5 to 7.5 x 105 cells cm-2, chlorophyll a
content of zooxanthellae increased from 5.7 to 8.6 pg, and animal protein
concentration doubled (from 0.74 to 1.38 mg cm-2). These data indicate that
both the coral animal and the zooxanthellae respond to the addition of exogenous
dissolved inorganic nitrogen provided as 20 uM ammonium. Growth of
the symbiotic association in response to the addition of 20 uM ammonium adds
further evidence to support the argument that growth of tropical symbioses is
limited by the availability of nitrogen. However, the coral response is likely to
depend on the concentration of ammonium provided, because the biomass
parameters of corals held at 50 uM ammonium did not change significantly
with time of exposure to the added nutrient
Multiple sclerosis and the microbiota:Progress in understanding the contribution of the gut microbiome to disease
Multiple sclerosis (MS), a neurological autoimmune disorder, has recently been linked to neuro-inflammatory influences from the gut. In this review, we address the idea that evolutionary mismatches could affect the pathogenesis of MS via the gut microbiota. The evolution of symbiosis as well as the recent introduction of evolutionary mismatches is considered, and evidence regarding the impact of diet on the MS-associated microbiota is evaluated. Distinctive microbial community compositions associated with the gut microbiota of MS patients are difficult to identify, and substantial study-to-study variation and even larger variations between individual profiles of MS patients are observed. Furthermore, although some dietary changes impact the progression of MS, MS-associated features of microbiota were found to be not necessarily associated with diet per se. In addition, immune function in MS patients potentially drives changes in microbial composition directly, in at least some individuals. Finally, assessment of evolutionary histories of animals with their gut symbionts suggests that the impact of evolutionary mismatch on the microbiota is less concerning than mismatches affecting helminths and protists. These observations suggest that the benefits of an anti-inflammatory diet for patients with MS may not be mediated by the microbiota per se. Furthermore, any alteration of the microbiota found in association with MS may be an effect rather than a cause. This conclusion is consistent with other studies indicating that a loss of complex eukaryotic symbionts, including helminths and protists, is a pivotal evolutionary mismatch that potentiates the increased prevalence of autoimmunity within a population
Control of atypical PKCĪ¹ membrane dissociation by tyrosine phosphorylation within a PB1-C1 interdomain interface
Atypical PKCs are cell polarity kinases that operate at the plasma membrane where they function within multiple molecular complexes to contribute to the establishment and maintenance of polarity. In contrast to the classical and novel PKCs, atypical PKCs do not respond to diacylglycerol cues to bind the membrane compartment. Until recently it was not clear how aPKCs are recruited; whether aPKCs can directly interact with membranes or whether they are dependent on other protein interactors to do so. Two recent studies identified the pseudo-substrate region and the C1 domain as direct membrane interaction modules, however their relative importance and coupling are unknown. We combined molecular modelling and functional assays to show that the regulatory module of aPKCĪ¹, comprising the PB1 pseudo-substrate and C1 domains, forms a cooperative and spatially continuous invariant membrane interaction platform. Furthermore, we show the coordinated orientation of membrane-binding elements within the regulatory module requires a key PB1-C1 interfacial Ī²-strand (BSL). We show this element contains a highly conserved Tyr residue that can be phosphorylated and that negatively regulates the integrity of the regulatory module, leading to membrane release. We thus expose a novel regulatory mechanism of aPKCĪ¹ membrane binding and release during cell polarization
DNA induces conformational changes in a recombinant human minichromosome maintenance complex
ATP-dependent DNA unwinding activity has been demonstrated for recombinant archaeal homohexameric minichromosome maintenance (MCM) complexes and their yeast heterohexameric counterparts, but in higher eukaryotes such as Drosophila, MCM-associated DNA helicase activity has only been observed in the context of a co-purified Cdc45-MCM-GINS (CMG) complex. Here we describe the production of recombinant human MCM complex (hMCM) in E. coli. This protein displays ATP hydrolysis activity and is capable of unwinding duplex DNA. Using single particle asymmetric electron microscopy reconstruction, we demonstrate recombinant hMCM forms a hexamer that undergoes a conformational change when bound to DNA. Recombinant hMCM produced without post-translational modifications is functional in vitro and provides an important tool for the biochemical reconstitution of the human replicative helicase
Into the fold: advances in understanding aPKC membrane dynamics
Atypical protein kinase Cs (aPKCs) are part of the PKC family of protein kinases and are atypical because they donāt respond to the canonical PKC activators diacylglycerol (DAG) and Ca2+. They are central to the organization of polarized cells and are deregulated in several cancers. aPKC recruitment to the plasma membrane compartment is crucial to their encounter with substrates associated with polarizing functions. However, in contrast
with other PKCs, the mechanism by which atypical PKCs are recruited there has remained elusive until recently. Here, we bring aPKC into the fold, summarizing recent reports on the direct recruitment of aPKC to membranes, providing insight into seemingly discrepant findings and integrating them with existing literature
Photodissociation of the OD radical at 226 and 243 nm
The photodissociation dynamics of state selected OD radicals has been examined at 243 and 226 nm using velocity map imaging to probe the angleāspeed distributions of theD(2S) and O(3P2) products. Both experiment and complementary first principle calculations demonstrate that photodissociation occurs by promotion of OD from high vibrational levels of the ground Xā2Ī state to the repulsive 1ā2Ī£ā state
Cosmology with a long range repulsive force
We consider a class of cosmological models in which the universe is filled
with a (non-electric) charge density that repels itself by means of a force
carried by a vector boson with a tiny mass. When the vector's mass depends upon
other fields, the repulsive interaction gives rise to an electromagnetic
barrier which prevents these fields from driving the mass to zero. This can
modify the cosmology dramatically. We present a very simple realization of this
idea in which the vector's mass arises from a scalar field. The electromagnetic
barrier prevents this field from rolling down its potential and thereby leads
to accelerated expansion.Comment: 15 pages, 8 figures, LaTeX (version accepted for publication in PRD).
3 new figures, extended discussion of observational consequence
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