Genomic Expansion of Magnetotactic Bacteria Reveals an Early Common Origin of Magnetotaxis with Lineage-specific Evolution

The origin and evolution of magnetoreception, which in diverse prokaryotes and protozoa is known as magnetotaxis and enables these microorganisms to detect Earth’s magnetic field for orientation and navigation, is not well understood in evolutionary biology. The only known prokaryotes capable of sensing the geomagnetic field are magnetotactic bacteria (MTB), motile microorganisms that biomineralize intracellular, membrane-bounded magnetic single-domain crystals of either magnetite (Fe3O4) or greigite (Fe3S4) called magnetosomes. Magnetosomes are responsible for magnetotaxis in MTB. Here we report the first large-scale metagenomic survey of MTB from both northern and southern hemispheres combined with 28 genomes from uncultivated MTB. These genomes expand greatly the coverage of MTB in the Proteobacteria, Nitrospirae, and Omnitrophica phyla, and provide the first genomic evidence of MTB belonging to the Zetaproteobacteria and “Candidatus Lambdaproteobacteria” classes. The gene content and organization of magnetosome gene clusters, which are physically grouped genes that encode proteins for magnetosome biosynthesis and organization, are more conserved within phylogenetically similar groups than between different taxonomic lineages. Moreover, the phylogenies of core magnetosome proteins form monophyletic clades. Together, these results suggest a common ancient origin of iron-based (Fe3O4 and Fe3S4) magnetotaxis in the domain Bacteria that underwent lineage-specific evolution, shedding new light on the origin and evolution of biomineralization and magnetotaxis, and expanding significantly the phylogenomic representation of MTB

Warming alters food web-driven changes in the CO2 flux of experimental pond ecosystems

Evidence shows the important role biota play in the carbon cycle, and strategic management of plant and animal populations could enhance CO(2) uptake in aquatic ecosystems. However, it is currently unknown how management-driven changes to community structure may interact with climate warming and other anthropogenic perturbations to alter CO(2) fluxes. Here we showed that under ambient water temperatures, predators (three-spined stickleback) and nutrient enrichment synergistically increased primary producer biomass, resulting in increased CO(2) uptake by mesocosms in early dawn. However, a 3°C increase in water temperatures counteracted positive effects of predators and nutrients, leading to reduced primary producer biomass and a switch from CO(2) influx to efflux. This confounding effect of temperature demonstrates that climate scenarios must be accounted for when undertaking ecosystem management actions to increase biosequestration

Landscape heterogeneity strengthens the relationship between β-diversity and ecosystem function.

Consensus has emerged in the literature that increased biodiversity enhances the capacity of ecosystems to perform multiple functions. However, most biodiversity/ecosystem function studies focus on a single ecosystem, or on landscapes of homogenous ecosystems. Here, we investigate how increased landscape-level environmental dissimilarity may affect the relationship between different metrics of diversity (α, β, or γ) and ecosystem function. We produced a suite of simulated landscapes, each of which contained four experimental outdoor aquatic mesocosms. Differences in temperature and nutrient conditions of the mesocosms allowed us to simulate landscapes containing a range of within-landscape environmental heterogeneities. We found that the variation in ecosystem functions was primarily controlled by environmental conditions, with diversity metrics accounting for a smaller (but significant) amount of variation in function. When landscapes were more homogeneous, α, β, and γ diversity was not associated with differences in primary production, and only γ was associated with changes in decomposition. In these homogeneous landscapes, differences in these two ecosystem functions were most strongly related to nutrient and temperature conditions in the ecosystems. However, as landscape-level environmental dissimilarity increased, the relationship between α, β, or γ and ecosystem functions strengthened, with β being a greater predictor of variation in decomposition at the highest levels of environmental dissimilarity than α or γ. We propose that when all ecosystems in a landscape have similar environmental conditions, species sorting is likely to generate a single community composition that is well suited to those environmental conditions, β is low, and the efficiency of diversity-ecosystem function couplings is similar across communities. Under this low β, the effect of abiotic conditions on ecosystem function will be most apparent. However, when environmental conditions vary among ecosystems, species sorting pressures are different among ecosystems, producing different communities among locations in a landscape. These conditions lead to stronger relationships between β and the magnitude of ecosystem functions. Our results illustrate that abiotic conditions and the homogeneity of communities influence ecosystem function expressed at the landscape scale

Upregulation of P2Y2 receptors by retinoids in normal human epidermal keratinocytes

Retinoids, vitamin A derivatives, are important regulators of the growth and differentiation of skin cells. Although retinoids are therapeutically used for several skin ailments, little is known about their effects on P2 receptors, known to be involved in various functions in the skin. DNA array analysis showed that treatment of normal human epidermal keratinocytes (NHEKs) with all-trans-retinoic acid (ATRA), an agonist to RAR (retinoic acid receptor), enhanced the expression of mRNA for the P2Y2 receptor, a metabotropic P2 receptor that is known to be involved in the proliferation of the epidermis. The expression of other P2 receptors in NHEKs was not affected by ATRA. ATRA increased the mRNA for the P2Y2 receptor in a concentration-dependent fashion (1 nM to 1 μM). Am80, a synthesized agonist to RAR, showed a similar enhancement, whereas 9-cis-retinoic acid (9-cisRA), an agonist to RXR (retinoid X receptor), enhanced P2Y2 gene expression to a lesser extent. Ca2+ imaging analysis showed that ATRA also increased the function of P2Y2 receptors in NHEKs. Retinoids are known to enhance the turnover of the epidermis by increasing both proliferation and terminal differentiation. The DNA microarray analysis also revealed that ATRA upregulates various genes involved in the differentiation of NHEKs. Our present results suggest that retinoids, at least in part, exert their proliferative effects by upregulating P2Y2 receptors in NHEKs. This effect of retinoids may be closely related to their therapeutic effect against various ailments or aging events in skins such as over-keratinization, pigmentation and re-modeling

Choice-Disability and HIV Infection: A Cross Sectional Study of HIV Status in Botswana, Namibia and Swaziland

Interpersonal power gradients may prevent people implementing HIV prevention decisions. Among 7,464 youth aged 15–29 years in Botswana, Namibia and Swaziland we documented indicators of choice-disability (low education, educational disparity with partner, experience of sexual violence, experience of intimate partner violence (IPV), poverty, partner income disparity, willingness to have sex without a condom despite believing partner at risk of HIV), and risk behaviours like inconsistent use of condoms and multiple partners. In Botswana, Namibia and Swaziland, 22.9, 9.1, and 26.1% women, and 8.3, 2.8, and 9.3% men, were HIV positive. Among both women and men, experience of IPV, IPV interacted with age, and partner income disparity interacted with age were associated with HIV positivity in multivariate analysis. Additional factors were low education (for women) and poverty (for men). Choice disability may be an important driver of the AIDS epidemic. New strategies are needed that favour the choice-disabled

Effects of dietary Na+ deprivation on epithelial Na+ channel (ENaC), BDNF, and TrkB mRNA expression in the rat tongue

<p>Abstract</p> <p>Background</p> <p>In rodents, dietary Na⁺deprivation reduces gustatory responses of primary taste fibers and central taste neurons to lingual Na⁺stimulation. However, in the rat taste bud cells Na⁺deprivation increases the number of amiloride sensitive epithelial Na⁺channels (ENaC), which are considered as the "receptor" of the Na⁺component of salt taste. To explore the mechanisms, the expression of the three ENaC subunits (α, β and γ) in taste buds were observed from rats fed with diets containing either 0.03% (Na⁺deprivation) or 1% (control) NaCl for 15 days, by using <it>in situ </it>hybridization and real-time quantitative RT-PCR (qRT-PCR). Since BDNF/TrkB signaling is involved in the neural innervation of taste buds, the effects of Na⁺deprivation on BDNF and its receptor TrkB expression in the rat taste buds were also examined.</p> <p>Results</p> <p><it>In situ </it>hybridization analysis showed that all three ENaC subunit mRNAs were found in the rat fungiform taste buds and lingual epithelia, but in the vallate and foliate taste buds, only α ENaC mRNA was easily detected, while β and γ ENaC mRNAs were much less than those in the fungiform taste buds. Between control and low Na⁺fed animals, the numbers of taste bud cells expressing α, β and γ ENaC subunits were not significantly different in the fungiform, vallate and foliate taste buds, respectively. Similarly, qRT-PCR also indicated that Na⁺deprivation had no effect on any ENaC subunit expression in the three types of taste buds. However, Na⁺deprivation reduced BDNF mRNA expression by 50% in the fungiform taste buds, but not in the vallate and foliate taste buds. The expression of TrkB was not different between control and Na⁺deprived rats, irrespective of the taste papillae type.</p> <p>Conclusion</p> <p>The findings demonstrate that dietary Na⁺deprivation does not change ENaC mRNA expression in rat taste buds, but reduces BDNF mRNA expression in the fungiform taste buds. Given the roles of BDNF in survival of cells and target innervation, our results suggest that dietary Na⁺deprivation might lead to a loss of gustatory innervation in the mouse fungiform taste buds.</p

High Salt Intake Down-Regulates Colonic Mineralocorticoid Receptors, Epithelial Sodium Channels and 11β-Hydroxysteroid Dehydrogenase Type 2

Besides the kidneys, the gastrointestinal tract is the principal organ responsible for sodium homeostasis. For sodium transport across the cell membranes the epithelial sodium channel (ENaC) is of pivotal relevance. The ENaC is mainly regulated by mineralocorticoid receptor mediated actions. The MR activation by endogenous 11β-hydroxy-glucocorticoids is modulated by the 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Here we present evidence for intestinal segment specific 11β-HSD2 expression and hypothesize that a high salt intake and/or uninephrectomy (UNX) affects colonic 11β-HSD2, MR and ENaC expression. The 11β-HSD2 activity was measured by means of 3H-corticosterone conversion into 3H-11-dehydrocorticosterone in Sprague Dawley rats on a normal and high salt diet. The activity increased steadily from the ileum to the distal colon by a factor of about 3, an observation in line with the relevance of the distal colon for sodium handling. High salt intake diminished mRNA and protein of 11β-HSD2 by about 50% (p<0.001) and reduced the expression of the MR (p<0.01). The functionally relevant ENaC-β and ENaC-γ expression, a measure of mineralocorticoid action, diminished by more than 50% by high salt intake (p<0.001). The observed changes were present in rats with and without UNX. Thus, colonic epithelial cells appear to contribute to the protective armamentarium of the mammalian body against salt overload, a mechanism not modulated by UNX

Rutas tróficas en macrozooplancton del Lago de Tota - Boyacá, Colombia

1 recurso en línea (56 páginas) : ilustraciones, figuras, tablas.In aquatic ecosystems inputs of matter and energy present in greater or lesser extent depending on the basin, given the origin and quality of these resources, you can alter the balance in metabolism or interactions in the food web. Using stable isotopes of carbon and nitrogen, the link between potential sources of funds and use established by macrozooplankton species in Lake Big and Lake Fellow the Lake Tota sectors. Trophic possible ways the role of each species in the proposed network, as well. In general, most of this study, most species have a bond with the autotrophic pathway, being the phytoplankton the food resource base for the food web, commonly found impoverished carbon signals. Particularly, the analysis showed a variation in the source or resource for two species (Daphnia laevis and Bosmina (Bosmina) cf. longirostris), with an enrichment in its signal to 19.92 ‰ -20.34 ‰ δ13C, which can be given by plasticity in their food supply, and even if Boeckella gracilis having a signal indicating a specialization in its appeal with carbon impoverished -30 to -26 ‰ values δ13C while nitrogen values are enriched with an average value 20.21 ‰ in δ15N. To set the trophic fractionation means establishing three groups, the first (herbivores) consisting of (D. laevis, B. (Bosmina) and Ceriodaphnia pulchella cf. longirostris), the second (omnivore) which is (Daphnia pulex, Macrocyclops sp. and Cyclopoida), and a third group (secondary consumer) where is the only calanoido B. gracilis. In comparing the temporal variation is observed that there is a significant change in signals δ13C and δ15N of some species in relation to the influence of sources and allochthonous or autochthonous origin, spatial variation was not significant. It is concluded that the macrozooplanton Lake Tota, has a strong link with the autotrophic pathway and pelagic trophic levels have 3 sections, plus the primary producers and the food web in general tends to have an amplitude of trophic niche.En los ecosistemas acuáticos se presentan aportes de materia y energía, en mayor o menor proporción dependiendo de su cuenca, dado el origen y calidad de estos recursos, se puede alterar el balance en el metabolismo o las interacciones en la red trófica. Utilizando los isotopos estables de Carbono y Nitrógeno, se estableció el vínculo entre fuentes potenciales de recursos y el uso por las especies del macrozooplancton en los sectores Lago grande y Lago chico del lago de Tota (Boyacá). Así, se propusieron las posibles vías tróficas y el rol de cada especie en la red. En general, en la mayor parte de este estudio, las especies tuvieron un vínculo marcado con la vía autotrófica, siendo el fitoplancton el recurso alimenticio base para la red trófica, encontrando comúnmente señales empobrecidas de carbono. Particularmente, el análisis mostró una variación en la fuente o recurso para dos especies (Daphnia laevis y Bosmina (Bosmina) cf. longirostris), con un enriquecimiento en su señal de 19.92‰ δ13C a -20.34‰ δ13C, lo que se puede dar por una plasticidad en su fuente alimenticia, e incluso el caso de Boeckella gracilis que tiene una señal que indica una especialización en su recurso con valores empobrecidos de carbono -30 a -26‰ δ13C mientras que los valores de nitrógeno son enriquecidos con un valor promedio de 20.21‰ en δ15N. Para establecer el fraccionamiento trófico medio se formaron tres grupos, el primero (herbívoros) conformado por (D. laevis, B. (Bosmina) cf. longirostris y Ceriodaphnia pulchella), el segundo (omnívoro) en el que se encuentra (Daphnia pulex, Macrocyclops sp. y Cyclopoida), y un tercer grupo (Consumidor secundario) donde esta B. gracilis el único calanoido. En la comparación de la variación temporal, se observa que hay un cambio significativo en las señales de δ13C y δ15N de algunas especies en relación a la influencia de las fuentes y su origen alóctono o autóctono, la variación espacial no fue significativa. Se concluye que el macrozooplanton del lago de Tota, tiene un fuerte vínculo con la vía autotrófica y que los niveles tróficos pelágicos tienen 3 eslabones, más los productores primarios, y la red trófica en general tiende a tener una amplitud del nicho trófico. En los ecosistemas acuáticos se presentan aportes de materia y energía, en mayor o menor proporción dependiendo de su cuenca, dado el origen y calidad de estos recursos, se puede alterar el balance en el metabolismo o las interacciones en la red trófica. Utilizando los isotopos estables de Carbono y Nitrógeno, se estableció el vínculo entre fuentes potenciales de recursos y el uso por las especies del macrozooplancton en los sectores Lago grande y Lago chico del lago de Tota (Boyacá). Así, se propusieron las posibles vías tróficas y el rol de cada especie en la red. En general, en la mayor parte de este estudio, las especies tuvieron un vínculo marcado con la vía autotrófica, siendo el fitoplancton el recurso alimenticio base para la red trófica, encontrando comúnmente señales empobrecidas de carbono. Particularmente, el análisis mostró una variación en la fuente o recurso para dos especies (Daphnia laevis y Bosmina (Bosmina) cf. longirostris), con un enriquecimiento en su señal de 19.92‰ δ13C a -20.34‰ δ13C, lo que se puede dar por una plasticidad en su fuente alimenticia, e incluso el caso de Boeckella gracilis que tiene una señal que indica una especialización en su recurso con valores empobrecidos de carbono -30 a -26‰ δ13C mientras que los valores de nitrógeno son enriquecidos con un valor promedio de 20.21‰ en δ15N. Para establecer el fraccionamiento trófico medio se formaron tres grupos, el primero (herbívoros) conformado por (D. laevis, B. (Bosmina) cf. longirostris y Ceriodaphnia pulchella), el segundo (omnívoro) en el que se encuentra (Daphnia pulex, Macrocyclops sp. y Cyclopoida), y un tercer grupo (Consumidor secundario) donde esta B. gracilis el único calanoido. En la comparación de la variación temporal, se observa que hay un cambio significativo en las señales de δ13C y δ15N de algunas especies en relación a la influencia de las fuentes y su origen alóctono o autóctono, la variación espacial no fue significativa. Se concluye que el macrozooplanton del lago de Tota, tiene un fuerte vínculo con la vía autotrófica y que los niveles tróficos pelágicos tienen 3 eslabones, más los productores primarios, y la red trófica en general tiende a tener una amplitud del nicho trófico.Bibliografía: páginas 46-56.MaestríaMagíster en Ciencias Biológica

Recent progress towards development of effective systemic chemotherapy for the treatment of malignant brain tumors

Systemic chemotherapy has been relatively ineffective in the treatment of malignant brain tumors even though systemic chemotherapy drugs are small molecules that can readily extravasate across the porous blood-brain tumor barrier of malignant brain tumor microvasculature. Small molecule systemic chemotherapy drugs maintain peak blood concentrations for only minutes, and therefore, do not accumulate to therapeutic concentrations within individual brain tumor cells. The physiologic upper limit of pore size in the blood-brain tumor barrier of malignant brain tumor microvasculature is approximately 12 nanometers. Spherical nanoparticles ranging between 7 nm and 10 nm in diameter maintain peak blood concentrations for several hours and are sufficiently smaller than the 12 nm physiologic upper limit of pore size in the blood-brain tumor barrier to accumulate to therapeutic concentrations within individual brain tumor cells. Therefore, nanoparticles bearing chemotherapy that are within the 7 to 10 nm size range can be used to deliver therapeutic concentrations of small molecule chemotherapy drugs across the blood-brain tumor barrier into individual brain tumor cells. The initial therapeutic efficacy of the Gd-G5-doxorubicin dendrimer, an imageable nanoparticle bearing chemotherapy within the 7 to 10 nm size range, has been demonstrated in the orthotopic RG-2 rodent malignant glioma model. Herein I discuss this novel strategy to improve the effectiveness of systemic chemotherapy for the treatment of malignant brain tumors and the therapeutic implications thereof

Autoregulation in resistance training : addressing the inconsistencies

Autoregulation is a process that is used to manipulate training based primarily on the measurement of an individual's performance or their perceived capability to perform. Despite being established as a training framework since the 1940s, there has been limited systematic research investigating its broad utility. Instead, researchers have focused on disparate practices that can be considered specific examples of the broader autoregulation training framework. A primary limitation of previous research includes inconsistent use of key terminology (e.g., adaptation, readiness, fatigue, and response) and associated ambiguity of how to implement different autoregulation strategies. Crucially, this ambiguity in terminology and failure to provide a holistic overview of autoregulation limits the synthesis of existing research findings and their dissemination to practitioners working in both performance and health contexts. Therefore, the purpose of the current review was threefold: first, we provide a broad overview of various autoregulation strategies and their development in both research and practice whilst highlighting the inconsistencies in definitions and terminology that currently exist. Second, we present an overarching conceptual framework that can be used to generate operational definitions and contextualise autoregulation within broader training theory. Finally, we show how previous definitions of autoregulation fit within the proposed framework and provide specific examples of how common practices may be viewed, highlighting their individual subtleties