Major Portion (major + portion)

Distribution by Scientific Domains

Selected Abstracts

The most C-terminal tri-glycine segment within the polyglycine stretch of the pea Toc75 transit peptide plays a critical role for targeting the protein to the chloroplast outer envelope membrane

FEBS JOURNAL, Issue 7 2006
Amy J. Baldwin
The protein translocation channel at the outer envelope membrane of chloroplasts (Toc75) is synthesized as a larger precursor with an N-terminal transit peptide. Within the transit peptide of the pea Toc75, a major portion of the 10 amino acid long stretch that contains nine glycine residues was shown to be necessary for directing the protein to the chloroplast outer membrane in vitro[Inoue K & Keegstra K (2003) Plant J34, 661,669]. In order to get insights into the mechanism by which the polyglycine stretch mediates correct targeting, we divided it into three tri-glycine segments and examined the importance of each domain in targeting specificity in vitro. Replacement of the most C-terminal segment with alanine residues resulted in mistargeting the protein to the stroma, while exchange of either of the other two tri-glycine regions had no effect on correct targeting. Furthermore, simultaneous replacement of the N-terminal and middle tri-glycine segments with alanine repeats did not cause mistargeting of the protein as much as those of the N- and C-terminal, or the middle and C-terminal segments. These results indicate that the most C-terminal tri-glycine segment is important for correct targeting. Exchanging this portion with a repeat of leucine or glutamic acid also caused missorting of Toc75 to the stroma. By contrast, its replacement with repeats of asparagine, aspartic acid, serine, and proline did not largely affect correct targeting. These data suggest that relatively compact and nonhydrophobic side chains in this particular region play a crucial role in correct sorting of Toc75. [source]

A Closer Look Inside Nanotubes: Pore Structure Evaluation of Anodized Alumina Templated Carbon Nanotube Membranes Through Adsorption and Permeability Studies

Georgios Pilatos
Abstract Although hollow nanostructures, such as nanotubes, represent a major portion of nanoscaled materials with a tremendously large application range, a detailed evaluation of their internal characteristics still remains elusive. Transmission electron microscopy is the most common analytical technique to examine the internal configuration of these structures, yet it can only provide evidence of a minimal portion of the overall material, thus, it cannot be accurately generalized. In the present paper, in addition to electron microscopy and other spot-size analysis methods (X-ray diffraction, Raman spectroscopy, etc.), a combination of techniques including adsorption, permeability, and relative permeability are employed in order to provide important insights into various crucial details of the overall internal surface and hollow-space characteristics of carbon nanotube (CNT) arrays and membranes. The CNT arrays are fabricated using anodized alumina as a template in a flow-through chemical vapor deposition (CVD) reactor. This is the first systematic approach for investigating the internal configuration of template-based CNT arrays in detail. Key findings are made for the customized optimization of the resulting nanotube membranes for a variety of applications, including separations, nanofluidics and nanoreactors, biological capturing and purification, and controlled drug delivery and release. [source]

Climate change causes rapid changes in the distribution and site abundance of birds in winter

Abstract Detecting coherent signals of climate change is best achieved by conducting expansive, long-term studies. Here, using counts of waders (Charadrii) collected from ca. 3500 sites over 30 years and covering a major portion of western Europe, we present the largest-scale study to show that faunal abundance is influenced by climate in winter. We demonstrate that the ,weighted centroids' of populations of seven species of wader occurring in internationally important numbers have undergone substantial shifts of up to 115 km, generally in a northeasterly direction. To our knowledge, this shift is greater than that recorded in any other study, but closer to what would be expected as a result of the spatial distribution of ecological zones. We establish that year-to-year changes in site abundance have been positively correlated with concurrent changes in temperature, but that this relationship is most marked towards the colder extremities of the birds' range, suggesting that shifts have occurred as a result of range expansion and that responses to climate change are temperature dependent. Many attempts to model the future impacts of climate change on the distribution of organisms, assume uniform responses or shifts throughout a species' range or with temperature, but our results suggest that this may not be a valid approach. We propose that, with warming temperatures, hitherto unsuitable sites in northeastern Europe will host increasingly important wader numbers, but that this may not be matched by declines elsewhere within the study area. The need to establish that such changes are occurring is accentuated by the statutory importance of this taxon in the designation of protected areas. [source]

Specialized morphology for a generalist diet: evidence for Liem's Paradox in a cichlid fish

S. A. Binning
The stable isotope ratio and seasonal changes in diet of Alluaud's haplo Astatoreochromis alluaudi, a cichlid fish with massive pharyngeal jaws well known for its ability to process hard-bodied prey, are described. The diet of A. alluaudi was quantified in Lake Saka, Uganda, over a period of 30 months. Variation in physico-chemical variables (mean monthly rainfall, water temperature, turbidity and dissolved oxygen), as well as potential competitor density and food abundance, was measured throughout the second half of the study (14 months). Stomach contents and isotope analysis revealed a diet comprised mainly of fishes and insects, with a low contribution of molluscs (0,33%) in any given month. No correlation was detected between diet and either macroinvertebrate abundance or competitor abundance. The running average rainfall was positively related to the percentage of fish consumed per month. Although A. alluaudi exhibits an apparent molluscivorous trophic morphology in Lake Saka, molluscs did not appear to compose a major portion of its diet. Gradients of rainfall seemed to be the most important environmental predictor of diet choice in Lake Saka. These results are discussed with reference to Liem's Paradox that apparently morphologically specialized fishes often function as generalist feeders in the wild. [source]

Performance of the invasive weevil Polydrusus sericeus is influenced by atmospheric CO2 and host species

Michael L. Hillstrom
1Natural forest systems constitute a major portion of the world's land area, and are subject to the potentially negative effects of both global climate change and invasion by exotic insects. A suite of invasive weevils has become established in the northern hardwood forests of North America. How these insects will respond to increasing CO2 or O3 is unknown. 2The present study examined the effects of elevated atmospheric CO2 and O3 on the invasive weevil Polydrusus sericeus Schaller at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, Wisconsin. A performance assay was conducted in the laboratory during the summer of 2007 using mated pairs of P. sericeus fed a combination of aspen, birch and maple foliage. We recorded leaf area consumption, oviposition and adult longevity. We also conducted visual abundance surveys in the field from 2004 to 2007 on aspen and birch at Aspen FACE. 3Elevated CO2, but not O3, significantly affected P. sericeus performance. Female, but not male, longevity was reduced under elevated CO2. Polydrusus sericeus also produced fewer eggs under elevated CO2 conditions compared with ambient conditions. Adult P. sericeus strongly preferred birch over both aspen and maple, regardless of fumigation treatment. 4The effects of elevated CO2 on P. sericeus populations at Aspen FACE were minimal, and varied among years and host tree species. Polydrusus sericeus abundance was significantly greater on birch than aspen. Over the long term, elevated CO2 may reduce adult female longevity and fecundity of P. sericeus. Further studies are needed to evaluate how this information may scale to ecosystem impacts. [source]

Neuronal pigmented autophagic vacuoles: lipofuscin, neuromelanin, and ceroid as macroautophagic responses during aging and disease

David Sulzer
Abstract The most striking morphologic change in neurons during normal aging is the accumulation of autophagic vacuoles filled with lipofuscin or neuromelanin pigments. These organelles are similar to those containing the ceroid pigments associated with neurologic disorders, particularly in diseases caused by lysosomal dysfunction. The pigments arise from incompletely degraded proteins and lipids principally derived from the breakdown of mitochondria or products of oxidized catecholamines. Pigmented autophagic vacuoles may eventually occupy a major portion of the neuronal cell body volume because of resistance of the pigments to lysosomal degradation and/or inadequate fusion of the vacuoles with lysosomes. Although the formation of autophagic vacuoles via macroautophagy protects the neuron from cellular stress, accumulation of pigmented autophagic vacuoles may eventually interfere with normal degradative pathways and endocytic/secretory tasks such as appropriate response to growth factors. [source]


ABSTRACT:,Banks are considered key actors in affordable housing and community development in the United States. Their involvement in such activities may be due partly to their dependence on economic rents generated from development. In the United States, however, banks are encouraged to support such activities by the federal 1977 Community Reinvestment Act (CRA). I examine how different factors explain the CRA-qualified investments by banks. Qualified investments are essentially nondebt financial resources provided as an equity investment or grant with a community development purpose. I find that the identity of the regulator (the United States has four banking regulators) has a major impact on the level of qualified investments. Other things equal, a difference in regulators can cause a bank's qualified investments to more than double. Besides suggesting that some regulators may be enforcing a major portion of CRA regulations more vigorously than others, this also suggests that the CRA plays a major role in bank investment in community development. This has policy implications not just in the United States but also in other countries that might consider replicating the CRA. [source]

Trophic state, fish community and intensive production of salmonids in Alicura Reservoir (Patagonia, Argentina)

P. F. Temporetti
Abstract The Governments of the Provinces located in Patagonia, Argentina, promote the intensive breeding of salmonids in the Andean Patagonian region. Although annual production is low (450 ton ha,1 year,1), some effects are significant. Waste produced by salmonid breeding (feed losses, faeces and excretion) increases nutrient and organic matter concentrations, which cause modifications of water quality, sediments and biota. A consequent risk is the elevation of eutrophication levels. Possible changes in water composition, sediments, algae and wild fish populations were studied. Sites affected by fish farming showed increased nutrient concentration, and phytoplankton and periphyton biomass. Chlorophyll a was similar at both sites (affected and unaffected by fish farm sites). Sediments clearly reflect fish farm waste inputs: total phosphorus and organic matter increased 12-fold and fourfold, respectively. The species present in the gill-net catches were the autochthonous Percichthys trucha, Odontesthes hatcheri, Diplomystes viedmensis, and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, Salmo salar sebago and Salvelinus fontinalis. About 50% of the total catch was salmonids. A major portion of the catch per unit weight was composed of rainbow trout, followed by perch. The catch per unit weight obtained for this reservoir agrees with the range of values previously determined (Quiros 1990) for Patagonian reservoirs. Compared with previous studies by Freyre et al. (1991), a variation in catch composition exists. This consists mainly of an increase in the numbers and condition of O. mykiss and a decrease in P. trucha. Presence of fish that escaped from hatcheries, recognizable by their eroded fins, was observed; particularly in a sampling station near the fish cage systems. Variations in catches could be caused by cyclical changes in fish populations (Wooton 1991), by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long-term studies of catch variation. [source]

Proceedings of the International Consensus Conference on Breast Cancer Risk, Genetics, & Risk Management, April, 2007

Gordon F. Schwartz MD
Abstract:, A consensus conference including thirty experts was held in April, 2007, to discuss risk factors for breast cancer and their management. Four categories of risk were outlined, from breast cancer "average" through "very high" risk, the latter including individuals with high penetrance BRCA1/2 gene mutations. Guidelines for management of patients in each of these categories were discussed, with the major portion of the conference being devoted to individuals with BRCA1/2 mutations. Prevalence of these mutations in the general populations was estimated to be 1 in 250,500 individuals, with an increased prevalence in Ashkenazic Jews and other founder groups. Risk reduction strategies for these individuals include surveillance, with or without chemoprevention drugs, or surgical procedures to remove the organs at risk, i.e., bilateral mastectomy and/or bilateral salpingo-oophorectomy. These risk reduction strategies were evaluated fully, and recommendations were made for the care of patients in each of the risk categories. These guidelines for patient care were approved by the entire group of experts. [source]

Cholinergic axons in the rat ventral tegmental area synapse preferentially onto mesoaccumbens dopamine neurons

Natalia Omelchenko
Abstract Cholinergic afferents to the ventral tegmental area (VTA) contribute substantially to the regulation of motivated behaviors and the rewarding properties of nicotine. These actions are believed to involve connections with dopamine (DA) neurons projecting to the nucleus accumbens (NAc). However, this direct synaptic link has never been investigated, nor is it known whether cholinergic inputs innervate other populations of DA and ,-aminobutyric acid (GABA) neurons, including those projecting to the prefrontal cortex (PFC). We addressed these questions by using electron microscopic analysis of retrograde tract-tracing and immunocytochemistry for the vesicular acetylcholine transporter (VAChT) and for tyrosine hydroxylase (TH) and GABA. In tissue labeled for TH, VAChT+ terminals frequently synapsed onto DA mesoaccumbens neurons but only seldom contacted DA mesoprefrontal cells. In tissue labeled for GABA, one-third of VAChT+ terminals innervated GABA-labeled dendrites, including both mesoaccumbens and mesoprefrontal populations. VAChT+ synapses onto DA and mesoaccumbens neurons were more commonly of the asymmetric (presumed excitatory) morphological type, whereas VAChT+ synapses onto GABA cells were more frequently symmetric (presumed inhibitory or modulatory). These findings suggest that cholinergic inputs to the VTA mediate complex synaptic actions, with a major portion of this effect likely to involve an excitatory influence on DA mesoaccumbens neurons. As such, the results suggest that natural and drug rewards operating through cholinergic afferents to the VTA have a direct synaptic link to the mesoaccumbens DA neurons that modulate approach behaviors. J. Comp. Neurol. 494:863,875, 2006. 2005 Wiley-Liss, Inc. [source]

Free will in context: a contemporary philosophical perspective

Patrick Grim B.Phil., Ph.D.
Philosophical work on free will is inevitably framed by the problem of free will and determinism. This paper offers an overview of the current state of the philosophical art. Early sections focus on quantum indeterminism, an outline of the most influential logical argument for incompatibilism between free will and determinism, and telling problems that face incompatibilism. A major portion of the paper focuses on the compatiblist alternative, favored by many working philosophers. The conditional account of free will offered by classical compatibilism can be shown to be inadequate. A number of compatibilist options remain open, however, and seem promising for future research. These include ,hierarchical' or ,mesh' accounts of free will, normative perspectives and an approach to free will in terms of an emphasis on context. Final sections draw out the implications of contemporary compatibilism for the brain and behavioral sciences and for the law. Copyright 2007 John Wiley & Sons, Ltd. [source]

Metabolic Carbon Fluxes and Biosynthesis of Polyhydroxyalkanoates in Ralstonia eutropha on Short Chain Fatty Acids

Jian Yu
Short chain fatty acids such as acetic, propionic, and butyric acids can be synthesized into polyhydroxyalkanoates (PHAs) by Ralstonia eutropha. Metabolic carbon fluxes of the acids in living cells have significant effect on the yield, composition, and thermomechanical properties of PHA bioplastics. Based on the general knowledge of central metabolism pathways and the unusual metabolic pathways in R. eutropha,a metabolic network of 41 bioreactions is constructed to analyze the carbon fluxes on utilization of the short chain fatty acids. In fed-batch cultures with constant feeding of acid media, carbon metabolism and distribution in R. eutropha were measured involving CO2, PHA biopolymers, and residual cell mass. As the cells underwent unsteady state metabolism and PHA biosynthesis under nitrogen-limited conditions, accumulative carbon balance was applied for pseudo-steady-state analysis of the metabolic carbon fluxes. Cofactor NADP/NADPH balanced between PHA synthesis and the C3/C4 pathway provided an independent constraint for solution of the underdetermined metabolic network. A major portion of propionyl-CoA was directed to pyruvate via the 2-methylcitrate cycle and further decarboxylated to acetyl-CoA. Only a small amount of propionate carbon (<15% carbon) was directly condensed with acetyl-CoA for 3-hydroxyvalerate. The ratio of glyoxylate shunt to TCA cycle varies from 0 to 0.25, depending on the intracellular acetyl-CoA level and acetic acid in the medium. Malate is the node of the C3/C4 pathway and TCA cycle and its decarboxylation to dehydrogenation ranges from 0.33 to 1.28 in response to the demands on NADPH and oxaloacetate for short chain fatty acids utilization. [source]

Oily calcium hydroxide suspension (Osteoinductal) used as an adjunct to guided bone regeneration: an experimental study in rats

Andreas Stavropoulos
Abstract Objectives: To evaluate whether an oily calcium hydroxide suspension (OCHS) promotes bone healing when used as an adjunct to guided bone regeneration (GBR). Material and methods: Rigid, hemispherical, teflon capsules were placed with their open part facing the lateral surface of the ramus on both sides of the mandible in 10 adult Wistar rats. In each animal, one capsule was filled out with an OCHS (test) before placement, while the capsule on the other side was left empty (control). After 4 months of healing, the animals were sacrificed and histological sections containing the capsules and the neighboring soft and hard tissues were prepared. On three to four sections taken by uniformly random sampling from each specimen, the relative volumes of (1) the newly formed bone (mineralized bone and marrow), (2) the soft connective tissue, (3) the residual OCHS, and (4) the acellular (empty) space inside the capsule were estimated by a point-counting technique, and expressed as percentage of the space originally created by the capsule. Results: There was no new bone formation inside the capsules in all but one test specimen, where only a minimal amount of newly formed bone could be observed in continuation with the lateral surface of the ramus. OCHS had a homogenous appearance and occupied the major portion (79.4%) of the space created by the capsule. No signs of active resorption of the material could be observed. On the contrary, 31.5% of the space provided by the capsule was filled out with newly formed bone in the control group. The new bone had a trabecular appearance with large marrow spaces filled with hematopoietic and fatty marrow. The rest of the capsule space in the controls appeared empty. Conclusion: OCHS may hamper bone healing when used as an adjunct to GBR. [source]

Examining the role of the forest industry in collaborative ecosystem management: implications for corporate strategy

Jennifer Dyke
Abstract The North American timber industry owns or controls a substantial amount of commercial timberland, and it is within this privately held acreage that major portions of critical natural habitat and areas of biodiversity are found. Because significant ecosystem components and processes lie within the ownership of forestry operations, industry participation in collaborative ecosystem management initiatives is vital to protect the integrity of ecological units at the landscape scale. This article analyzes and identifies the role of industry in ecosystem management projects, industry's willingness to participate in collaborative ecosystem management and the motivations behind company participation. Companies indicated active involvement in collaborative ecosystem management as both project initiators and collaborators. Motivations for participating in collaborative ecosystem management initiatives include the desires to decrease governmental regulations, collect data, develop relationships and improve current practices. Many companies also feel that participation is financially beneficial because it positively impacts corporate public relations. We discuss the implications of these results for developing an effective corporate environmental strategy associated with resource-based industries. Copyright 2005 John Wiley & Sons, Ltd and ERP Environment. [source]

Myogenesis in Aplysia californica (Cooper, 1863) (Mollusca, Gastropoda, Opisthobranchia) with special focus on muscular remodeling during metamorphosis

Tim Wollesen
Abstract To date only few comparative approaches tried to reconstruct the ontogeny of the musculature in invertebrates. This may be due to the difficulties involved in reconstructing three dimensionally arranged muscle systems by means of classical histological techniques combined with light or transmission electron microscopy. Within the scope of the present study we investigated the myogenesis of premetamorphic, metamorphic, and juvenile developmental stages of the anaspidean opisthobranch Aplysia californica using fluorescence F-actin-labeling in conjunction with modern confocal laser scanning microscopy. We categorized muscles with respect to their differentiation and degeneration and found three true larval muscles that differentiate during the embryonic and veliger phase and degenerate during or slightly after metamorphosis. These are the larval retractor, the accessory larval retractor, and the metapodial retractor muscle. While the pedal retractor muscle, some transversal mantle fibers and major portions of the cephalopedal musculature are continued and elaborated during juvenile and adult life, the buccal musculature and the anterior retractor muscle constitute juvenile/adult muscles which differentiate during or after metamorphosis. The metapodial retractor muscle has never been reported for any other gastropod taxon. Our findings indicate that the late veliger larva of A. californica shares some common traits with veligers of other gastropods, such as a larval retractor muscle. However, the postmetamorphic stages exhibit only few congruencies with other gastropod taxa investigated to date, which is probably due to common larval but different adult life styles within gastropods. Accordingly, this study provides further evidence for morphological plasticity in gastropod myogenesis and stresses the importance of ontogenetic approaches to understand adult conditions and life history patterns. J. Morphol., 2008. 2007 Wiley-Liss, Inc. [source]

A Holistically Deweyan Feminism

Jane Duran
The argument that a holistic analysis of Dewey's work, drawing not only on the major portions subject to extensive commentary (such as Experience and Nature) but also on his aesthetics, provides fuel for feminist theorizing is sustained by advertence to the standard commentary and also to new work in aesthetic feminism itself. Sleeper, Rorty, Hickman and Russell are cited, and the recent resurgence of interest in developing the intersection between analytic aesthetics and feminist aesthetics is alluded to. It is concluded that the enterprising feminist theorist may suffer from an embarrassment of riches in attempting to approach Dewey but that such an approach is well worth the effort. [source]