bluuebunny/crossref_metadata_2025_split huggingface dataset:
Life cycle matters: DNA barcoding reveals contrasting community structure between fern sporophytes and gametophytes
Authors: Nitta Joel H. , Meyer Jean‐Yves , Taputuarai Ravahere , Davis Charles C. 
Published: December 2016

AbstractFerns are the only major lineage of vascular plants that have nutritionally independent sporophyte (diploid) and gametophyte (haploid) life stages. However, the implications of this unique life cycle for fern community ecology have rarely been considered. To compare patterns of community structure between fern sporophytes and gametophytes, we conducted a survey of the ferns of the islands of Moorea and Tahiti (French Polynesia). We first constructed a DNA barcode library (plastid rbcL and trnH‐psbA) for the two island floras including 145 fern species. We then used these DNA barcodes to identify more than 1300 field‐collected gametophytes from 25 plots spanning an elevational gradient from 200 to 2000 m. We found that species richness of fern sporophytes conforms to the well‐known unimodal (i.e., mid‐elevation peak) pattern, reaching a maximum at ~1000–1200 m. Moreover, we found that fern sporophyte communities become increasingly phylogenetically clustered at high elevations. In contrast, species richness of fern gametophytes was consistent across sites, and gametophytes showed no correlation of phylogenetic community structure with elevation. Turnover of sporophyte and gametophyte communities was closely linked with elevation at shallow phylogenetic levels, but not at deeper nodes in the tree. Finally, we found several species for which gametophytes had broader ranges than sporophytes, including a vittarioid fern with abundant gametophytes but extremely rare sporophytes. Our study highlights the importance of including diverse life history stages in surveys of community structure, and has implications for the possible impacts of climate change on the distribution of fern diversity.
Understanding and predicting physiological performance of organisms in fluctuating and multifactorial environments
Authors: Koussoroplis Apostolos‐Manuel , Pincebourde Sylvain , Wacker Alexander 
Published: December 2016

AbstractUnderstanding how variance in environmental factors affects physiological performance, population growth, and persistence is central in ecology. Despite recent interest in the effects of variance in single biological drivers, such as temperature, we have lacked a comprehensive framework for predicting how the variances and covariances between multiple environmental factors will affect physiological rates. Here, we integrate current theory on variance effects with co‐limitation theory into a single unified conceptual framework that has general applicability. We show how the framework can be applied (1) to generate mathematically tractable predictions of the physiological effects of multiple fluctuating co‐limiting factors, (2) to understand how each co‐limiting factor contributes to these effects, and (3) to detect mechanisms such as acclimation or physiological stress when they are at play. We show that the statistical covariance of co‐limiting factors, which has not been considered before, can be a strong driver of physiological performance in various ecological contexts. Our framework can provide powerful insights on how the global change‐induced shifts in multiple environmental factors affect the physiological performance of organisms.
Changes in community phylogenetic structure in a North American forest chronosequence
Authors: Pastore Abigail I. , Scherer Brendan P. 
Published: December 2016

AbstractSeveral studies of succession in tropical and subtropical climates include phylogenetic analyses of the plant communities; the majority of these studies find a shift from more closely related to less closely related assemblages over succession. It has been suggested that this pattern indicates a shift from abiotic to biotic filters structuring communities over time, but there is considerable debate surrounding this interpretation. Conducting analyses for multiple components of plant assemblages can provide insight into the processes structuring communities. Here, we present community phylogenetic analyses of a deciduous forest chronosequence for three community components: standing vegetation, seed bank, and vegetation regenerated after small‐scale disturbance. We constructed a phylogeny from 228 taxa present in the community data of a chronosequence obtained from previously published research. In the standing vegetation, we found a shift from more closely related to less closely related vegetation over the chronosequence. These results are consistent with other studies of chronosequences in tropical forests, lending support to the ubiquity of such shifts in relatedness over succession under different climatic conditions. However, the seed bank and vegetation regenerated after small‐scale disturbance showed no consistent pattern with stand age, suggesting recruits are experiencing different forces than surrounding vegetation. These phylogenetic analyses of seed banks and vegetation regenerated after small‐scale disturbance over a chronosequence provide additional evidence into the mechanisms driving forest succession.
Predicting conifer establishment post wildfire in mixed conifer forests of the North American Mediterranean‐climate zone
Authors: Welch Kevin R. , Safford Hugh D. , Young Truman P. 
Published: December 2016

AbstractDue to fire suppression policies, timber harvest, and other management practices over the last century, many low‐ to mid‐elevation forests in semiarid parts of the western United States have accumulated high fuel loads and dense, multi‐layered canopies that are dominated by shade‐tolerant and fire‐sensitive conifers. To a great extent, the future status of western US forests will depend on tree species’ responses to patterns and trends in fire activity and fire behavior and postfire management decisions. This is especially the case in the North American Mediterranean‐climate zone (NAMCZ), which supports the highest precipitation variability in North America and a 4‐ to 6‐month annual drought, and has seen greater‐than‐average increases in air temperature and fire activity over the last three decades. We established 1490 survey plots in 14 burned areas on 10 National Forests across a range of elevations, forest types, and fire severities in the central and northern NAMCZ to provide insight into factors that promote natural tree regeneration after wildfires and the differences in postfire responses of the most common conifer species. We measured site characteristics, seedling densities, woody shrub, and tree growth. We specified a zero‐inflated negative binomial mixed model with random effects to understand the importance of each measured variable in predicting conifer regeneration. Across all fires, 43% of all plots had no conifer regeneration. Ten of the 14 fires had median conifer seedling densities that did not meet Forest Service stocking density thresholds for mixed conifer forests. When regeneration did occur, it was dominated by shade‐tolerant but fire‐sensitive firs (Abies spp.), Douglas‐fir (Pseudotsuga menziesii) and incense cedar (Calocedrus decurrens). Seedling densities of conifer species were lowest in sites that burned at high severity, principally due to the biotic consequences of high severity fire, for example, increased distances to live seed trees and competition with fire‐following shrubs. We developed a second model specifically for forest managers and restoration practitioners who work in yellow pine and mixed conifer forests in the central NAMCZ to assess potential natural regeneration in the years immediately following a fire, allowing them to prioritize which areas may need active postfire forest restoration and supplemental planting.
Ecosystem resilience is evident 17 years after fire in Wyoming big sagebrush ecosystems
Authors: Ellsworth L. M. , Wrobleski D. W. , Kauffman J. B. , Reis S. A. 
Published: December 2016

AbstractRecent policy has focused on prevention of wildfire in the sagebrush steppe in an effort to protect habitat for the greater sage grouse (Centrocercus urophasianus). Historically, fire return intervals in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) ecosystems were 50–100 yr or more, but invasive species, climate change, and a legacy of intensive grazing practices have led to degraded rangeland condition, altered fire regimes and fire effects, and declines in sagebrush cover. Little is known about the long‐term impacts of fire in this ecosystem in areas where grazing pressure has been removed, few invasive species exist, and fire return intervals are maintained. In this study, we quantified vegetation composition prior to prescribed burning, 1 year following fire, and 17 years after fire in a native‐dominated Wyoming big sagebrush ecosystem at Hart Mountain National Antelope Refuge, Oregon, United States. Seventeen years following fire, the ecosystem was dominated by native herbaceous vegetation, with 8.3% cover of broad‐leaved forbs and bunchgrasses in the understory, compared to just 3.8% cover of native herbaceous vegetation in unburned controls. Invasive annual grass cover ranged from 0.2% to 8.4% across all treatments and years (P = 0.56). One year following fire, the distance from a randomly located point and the nearest mature sagebrush was 16.6 m, but by 17 years after the fire, that distance had decreased to 2.5 m. Seventeen years after fires, shrub cover was 0.4–4% in burned plots compared to 13–24% in unburned controls. Collectively, these data demonstrate that good condition ungrazed Wyoming big sagebrush plant communities exhibited resilience following fire and maintained a native‐dominated mosaic of shrubs, bunchgrasses, and forbs. Further, unburned control plots were dominated by woody vegetation and exhibited losses in herbaceous understory, possibly indicating that they are outside of their natural fire return interval. Our results illustrate that management of all habitat components, including natural disturbance and a mosaic of successional stages, is important for persistent resilience and that suppression of all fires in the sagebrush steppe may create long‐term losses of heterogeneity in good condition Wyoming big sagebrush ecosystems.
Growth rate and resource imbalance interactively control biomass stoichiometry and elemental quotas of aquatic bacteria
Authors: Godwin Casey M. , Whitaker Emily A. , Cotner James B. 
Published: December 2016

AbstractThe effects of resource stoichiometry and growth rate on the elemental composition of biomass have been examined in a wide variety of organisms, but the interaction among these effects is often overlooked. To determine how growth rate and resource imbalance affect bacterial carbon (C): nitrogen (N): phosphorus (P) stoichiometry and elemental content, we cultured two strains of aquatic heterotrophic bacteria in chemostats at a range of dilution rates and P supply levels (C:P of 100:1 to 10,000:1). When growing below 50% of their maximum growth rate, P availability and dilution rate had strong interactive effects on biomass C:N:P, elemental quotas, cell size, respiration rate, and growth efficiency. In contrast, at faster growth rates, biomass stoichiometry was strongly homeostatic in both strains (C:N:P of 70:13:1 and 73:14:1) and elemental quotas of C, N, and P were tightly coupled (but not constant). Respiration and cell size increased with both growth rate and P limitation, and P limitation induced C accumulation and excess respiration. These results show that bacterial biomass stoichiometry is relatively constrained when all resources are abundant and growth rates are high, but at low growth rates resource imbalance is relatively more important than growth rate in controlling bacterial biomass composition.
Polydatin and its derivatives inhibit fatty acid desaturases in microorganisms
Authors: Řezanka Tomáš , Vítová Milada , Kolouchová Irena , Nedbalová Linda , Doležalová Jana , Palyzová Andrea , Sigler Karel 
Published: December 2016

Antioxidant plant polyphenols resveratrol and its glycoside polydatin at 500 μg/L were found to have two distinct effects on yeasts and algae depending on the cell content of polyunsaturated fatty acids (PUFA). In yeasts that do not produce PUFA, resveratrol (0.5 mg/L) increased resistance to biosynthesized ethanol (an important property in winemaking) to 22% EtOH in Saccharomyces cerevisiae and 14% EtOH in Torulaspora delbrückii, the fatty acid content being changed only slightly, whereas in the PUFA‐producing algae Desmodesmus quadricauda and Euglena gracilis both compounds act as inhibitors of Δ4 desaturases blocking the formation of both even‐ and odd‐numbered PUFA having the first double‐bond in position 4. This leads to the biotechnologically desirable accumulation of the health‐beneficial polyunsaturated fatty acids (PUFAs), docosapentaenoic (DPA), and docosahexaenoic acid (DHA).Practical applications: Employing natural stilbene compounds has far‐reaching use in biotechnological applications such as the production of ethanol used for biofuels or production of wine and beer. It allows the production of beer with higher alcohol content, without resorting to the use of consumer‐unacceptable genetically modified yeast. In brewing, when the yeast is often repeatedly reused to ferment fresh wort, higher resistance of yeast in the presence of these compounds can lead to an increase in the number of yeast reuses and thereby reduce economic costs of the brewery needed for preparation of inocula. Using polydatin as inhibitor of Δ4 desaturase in Euglena and Desmodesmus algae blocks the biosynthesis of both even‐ and odd‐numbered PUFAs having a double bond in position 4. This leads to a change in the content of fatty acids and accumulation of biosynthetic precursors, e.g., 22:5n‐3 acid that has more favorable pharmacological effects than docosahexaenoic acid (22:6n‐3)Natural stilbenes such as polydatin and resveratrol have not yet been known as inhibitors of desaturases. We found that they alter the fatty acid composition in microorganisms containing PUFA (algae) by inhibiting Δ4 desaturase and thus blocking the biosynthesis of specific PUFAs. Inhibition of Δ4 desaturase produces oils with a higher proportion of DPA. Moreover, these compounds increase yeast resistance to ethanol.
Voltammetric and Spectrophotometric Studies on DNA Interacting with Daunorubicin and its Amidino Derivatives
Authors: Palinska‐Saadi Adriana , Lukasiewicz Magdalena , Oszczapowicz Janusz , Lukawska Malgorzata , Oszczapowicz Irena , Zwierkowska Elzbieta , Achmatowicz Selim , Maj‐Zurawska Magdalena 
Published: December 2016

AbstractDaunorubicin (DAU) is one of the anticancer drugs widely applied in therapy although it reveals high toxicity. As a result of the search for new derivatives of anthracyclines with better biological properties, amidino antracyclines were invented. They contain in the daunosamine moiety an amidine group, –N=CR–NR1R2 where −NR1R2 is the rest of the cyclic secondary amine, instead of the −NH2 group. DAU and its two formamidino derivatives, the one containing the rest of the morpholine in the formamidine group (DAU‐Fmor) and the other one containing the rest of the hexamethyleneimine (DAU‐Fhex) were selected for voltammetric and spectrophotometric investigation of their interactions with DNA. These interactions were investigated by monitoring the changes in the UV/Vis absorption spectra of the anthracyclines interacting with oligonucleotides in the solution, as well as by monitoring the changes in electrochemical properties of oligonucleotides interacting with anthracyclines on the surface of screen‐printed graphite electrodes (SPEs) using square wave voltammetry (SWV). The obtained results indicate that interactions between DNA and anthracyclines depend mainly on two factors: the DNA sequence and the detailed structure of the anthracycline. As a result of these interactions, the anthracycline absorbance and the oxidation current of both, guanine and adenine change. The relations between these changes and the structure of the investigated anthracyclines are discussed.
Deciding what is possible and impossible following hippocampal damage in humans
Authors: McCormick Cornelia , Rosenthal Clive R. , Miller Thomas D. , Maguire Eleanor A. 
Published: December 2016

ABSTRACTThere is currently much debate about whether the precise role of the hippocampus in scene processing is predominantly constructive, perceptual, or mnemonic. Here, we developed a novel experimental paradigm designed to control for general perceptual and mnemonic demands, thus enabling us to specifically vary the requirement for constructive processing. We tested the ability of patients with selective bilateral hippocampal damage and matched control participants to detect either semantic (e.g., an elephant with butterflies for ears) or constructive (e.g., an endless staircase) violations in realistic images of scenes. Thus, scenes could be semantically or constructively ‘possible’ or ‘impossible’. Importantly, general perceptual and memory requirements were similar for both types of scene. We found that the patients performed comparably to control participants when deciding whether scenes were semantically possible or impossible, but were selectively impaired at judging if scenes were constructively possible or impossible. Post‐task debriefing indicated that control participants constructed flexible mental representations of the scenes in order to make constructive judgements, whereas the patients were more constrained and typically focused on specific fragments of the scenes, with little indication of having constructed internal scene models. These results suggest that one contribution the hippocampus makes to scene processing is to construct internal representations of spatially coherent scenes, which may be vital for modelling the world during both perception and memory recall. © 2016 The Authors. Hippocampus Published by Wiley Periodicals, Inc.
Acute moderate exercise improves mnemonic discrimination in young adults
Authors: Suwabe Kazuya , Hyodo Kazuki , Byun Kyeongho , Ochi Genta , Yassa Michael A. , Soya Hideaki 
Published: December 2016

ABSTRACTIncreasing evidence suggests that regular moderate exercise increases neurogenesis in the dentate gyrus (DG) of the hippocampus and improves memory functions in both humans and animals. The DG is known to play a role in pattern separation, which is the ability to discriminate among similar experiences, a fundamental component of episodic memory. While long‐term voluntary exercise improves pattern separation, there is little evidence of alterations in DG function after an acute exercise session. Our previous studies showing acute moderate exercise‐enhanced DG activation in rats, and acute moderate exercise‐enhanced prefrontal activation and executive function in humans, led us to postulate that acute moderate exercise may also activate the hippocampus, including more specifically the DG, thus improving pattern separation. We thus investigated the effects of a 10‐min moderate exercise (50%
O2peak) session, the recommended intensity for health promotion, on mnemonic discrimination (a behavioral index of pattern separation) in young adults. An acute bout of moderate exercise improved mnemonic discrimination performance in high similarity lures. These results support our hypothesis that acute moderate exercise improves DG‐mediated pattern separation in humans, proposing a useful human acute‐exercise model for analyzing the neuronal substrate underlying acute and regular exercise‐enhanced episodic memory based on the hippocampus. © 2016 Wiley Periodicals, Inc.
Nanofluid Flow in a Porous Channel with Suction and Chemical Reaction using Tiwari and Das's Nanofluid Model
Authors: Chen Hui , Xiao Tianli , Shen Ming 
Published: December 2016

AbstractIn this paper, an analysis is made for a nanofluid flow in a porous channel by introducing the conservation equation of nanoparticle volume fraction into Tiwari and Das's nanofluid model. The suction and chemical reaction are also considered in this work. The governing partial differential equations are simplified by employing a new variable and transformed into a system of high‐order nonlinear ordinary differential equations by similarity transformations. The Keller box method is used to solve this problem numerically. In addition, the influences of significant physical parameters on the distributions of the velocity and temperature as well as nanoparticle concentration are graphically presented and discussed in detail. It is found that there exists a critical value of the permeable parameter which determines the influence law of nanoparticle volume fraction parameter on skin friction coefficient and local Sherwood number. The results also indicate that the concentration increases sharply with the Schmidt number and chemical reaction parameter.
Modulation of the anti‐inflammatory effects of phosphatidylserine‐containing liposomes by PEGylation
Authors: Quan Hongxuan , Park Hee Chul , Kim Yongjoon , Yang Hyeong‐Cheol 
Published: December 2016

AbstractInhibiting liposome uptake by macrophages using polyethylene glycol (PEG) surface modifications is a widely used approach for extending the half‐life of liposomes circulating in the blood. However, the biological effects of PEGylated liposomes on macrophages have not yet been thoroughly investigated. The purpose of this study was to examine the effects of PEGylated phosphatidylserine‐containing liposomes (PEG‐PSLs) on the expression of two inflammation‐associated cytokines, tumor necrosis factor‐α (TNF‐α) and transforming growth factor‐β (TGF‐β), in the murine macrophage‐like cell line RAW 264.7. Previous studies have demonstrated that PSLs inhibit TNF‐α secretion and enhance TGF‐β synthesis in macrophages by mimicking apoptotic cells. We found that PEGylation differentially affected the TNF‐α and TGF‐β levels. The PSL‐mediated inhibitory effect on TNF‐α secretion was enhanced by PEGylation, and PEG‐PSLs decreased TGF‐β levels compared with non‐PEGylated PSLs. Fluorescence‐activated cell sorting analysis demonstrated that 1% PEGylation disturbed the incorporation of PSLs into macrophages. The interference of uptake is thought to extend the binding interaction between PS to PS receptors for PSL‐mediated inhibition of TNF‐α expression. Together, these findings indicate that PEG‐PSLs can prevent TNF‐α secretion without increasing TGF‐β levels in macrophages, and they support the potential clinical use of PEG‐PSLs as anti‐inflammatory agents with a relatively low potential to induce tissue fibrosis. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1479–1486, 2017.