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1. Pollinator-mediated reproductive interactions among co-flowering plant species are prime examples of how species interactions may affect fitness and community assembly. Despite considerable interest in these issues, statistical methods for assessing signal of reproductive interactions in observational data on co-flowering species are currently lacking. 2. We propose a flexible method for quantifying potential reproductive interactions among co-flowering plant species using the hierarchical latent-variable joint models implemented in the Hierarchical Modelling of Species Communities (HMSC) framework. The method accommodates any measure of reproductive success, including pollinator visitation, stigma pollen loads, and seed set. We demonstrate the method by analysing a dataset on bumblebee visitation to a set of co-flowering plant species in a species-rich meadow in Norway, and provide R tutorials for this and additional data types. 3. The example analysis revealed both positive and negative effects of heterospecific flower abundances on visitation to co-flowering species, which we interpret as potential reproductive interactions. 4. Synthesis. Hierarchical joint models provide a flexible approach to analysing patterns of covariation in the reproductive success of co-flowering species, thus identifying potential species interactions. Important strengths include explicit consideration of community-level effects and the assessment of residual fitness correlations after controlling for covariates such as flower abundances and phenotypic traits, yielding more complete insights into pollinator-mediated reproductive interactions.

ABS TRACT Entry in new technological domains is essential for the long-term performance of firms. Therefore, it is important to understand the conditions that increase the likelihood that firms enter, and further explore, new technological domains. Some recent studies have started to unpack these issues by looking at the environmental conditions in a new technological domain that pull firms into it. In this paper, we complement these studies by looking at the environmental conditions in the firm's current technological domain that push firms into new domains. We do it from the perspective of technological ecology, by looking at how technological diversity and crowding in the firm's current technological niche, as well as firm's knowledge generalism, affect the likelihood that the firm enters, and further explores, new technological niches. To test our hypotheses, we rely on an empirical setting based on U.S. patents by 340 firms in the pharmaceutical industry. We propose a novel and advanced approach that, by leveraging a vast set of technological classifications, extracts technological niches from the patent system as they evolve over time.

Glioblastoma (GBM) is the most lethal brain tumor also due to malignant and therapy-resistant GBM stem cells (GSCs) that are localized in protecting hypoxic GSC niches. Some members of the cysteine cathepsin family of proteases have been found to be upregulated in GBM. Cathepsin K gene expression is highly elevated in GBM tissue versus normal brain and it has been suggested to regulate GSC migration out of the niches. Here, we investigated the cellular distribution of cathepsins B, X and K in GBM tissue and whether these cathepsins are co-localized in GSC niches. Therefore, we determined expression of these cathepsins in serial paraffin sections of 14 human GBM samples and serial cryostat sections of two samples using immunohistochemistry and metabolic mapping of cathepsin activity using selective fluorogenic substrates. We detected cathepsins B, X and K in peri-arteriolar GSC niches in 9 out of 16 GBM samples, which were defined by co-expression of the GSC marker CD133, the niche marker stromal-derived factor-1α (SDF-1α) and smooth muscle actin as a marker for arterioles. The expression of cathepsin B and X was detected in stromal cells and cancer cells throughout the GBM sections, whereas cathepsin K expression was more restricted to arteriole-rich regions in the GBM sections. Metabolic mapping showed that cathepsin B, but not cathepsin K is active in GSC niches. On the basis of these findings, it is concluded that cathepsins B, X and K have distinct functions in GBM and that cathepsin K is the most likely GSC niche-related cathepsin of the three cathepsins investigated.

In this paper, we aim to understand what ICT-related automobility experiments are initiated in the Netherlands, who is involved and what promises they make, in order to get a better understanding of the magnitude and direction of change. We show an example of how to study a large variety of experiments to understand the emergence of niches before predetermining these as analytical constructs. By analyzing 118 experiments, we can identify the emergence of two niches: an automated mobility niche and a mobility services niche. The automated niche is characterized by large involvement of incumbents and a strong technological orientation. The services niche focuses more on organizational innovations and involves many new entrants. The involvement of a third actor category, ‘mature entrants’, applies to both niches and concern those actors that fall more or less in-between the common ‘incumbent-new entrant’ dichotomy. In general, experiments in the automated niche seem to strengthen the dominant role of the car in the automobility system, while services niche experiments mainly portray an altered role of the car in an alternative mobility system. We conclude that we gained a better understanding of the experiments and emerging niches, but at this stage, developments can still head in different directions. Nevertheless, the involvement of mature entrants in both niches, we argue, can be an important indication that more substantial change is likely to occur.

International audience; The emergence of carbapenem-resistant enterobacterial species poses a serious threat to public health worldwide. OXA-48-type carbapenem-hydrolyzing class D β-lactamases are widely distributed among Enterobacteriaceae, with significant geographical differences. To date, 11 OXA-48-like variants have been identified, with classical OXA-48 being the most widespread. These enzymes show high-level hydrolytic activity against penicillins and low-level hydrolysis towards carbapenems. Since the first description of the OXA-48 carbapenemase in Turkey, bacterial strains producing the enzyme have been extensively reported in nosocomial and community outbreaks in many parts of the word, particularly in the Mediterranean area and European countries. The rapid spread of Enterobacteriaceae producing OXA-48-like enzymes in different ecosystems has become a serious issue recently. The number of reservoirs for such organisms is increasing, not only in hospitals, but also in the community, among animals (e.g., livestock, companion animals, and wildlife) and in the environment. This review aims to summarize the main characteristics of the OXA-48-type carbapenemases, covering genetic and enzymatic traits, their epidemiology, clonality and associated genes, correlation with extended-spectrum β-lactamases (ESBLs) or plasmidic AmpC (pAmpC) in different bacterial species worldwide.

Summary We earlier showed that outside-in integrin signaling through POSTN-ITGAV interaction plays an important role in regulating adult hematopoietic stem cell (HSC) quiescence. Here, we show that Itgav deletion results in increased frequency of phenotypic HSCs in fetal liver (FL) due to faster proliferation. Systemic deletion of Postn led to increased proliferation of FL HSCs, albeit without any loss of stemness, unlike Vav-Itgav−/− HSCs. Based on RNA sequencing analysis of FL and bone marrow HSCs, we predicted the involvement of DNA damage response pathways in this dichotomy. Indeed, proliferative HSCs from Postn-deficient FL tissues showed increased levels of DNA repair, resulting in lesser double-strand breaks. Thus POSTN, with its expression majorly localized in the vascular endothelium of FL tissue, acts as a regulator of stem cell pool size during development. Overall, we demonstrate that the duality of response to proliferation in HSCs is developmental stage dependent and can be correlated with DNA damage responses., Graphical Abstract, Highlights • Interruption of POSTN-ITGAV interaction leads to HSC expansion in fetal liver • HSC from fetal liver in comparison with adult BM excel in their DNA damage responses • POSTN is a potential component of the vascular niche for HSCs in the fetal liver, Khurana and colleagues demonstrate here a role of outside-in integrin signaling in regulating the size of hematopoietic stem cell (HSC) pool in mouse fetal liver. Using Postn−/− and Vav-Itgav−/− mice, they show that HSCs lacking POSTN-ITGAV interaction proliferate faster without any functional loss. The study proposes a possible role of increased levels of DNA damage responses in tolerating proliferation stress during fetal development.

Anthropogenic climate change ranks among the major global-scale threats to modern biodiversity. Extinction risks are known to increase via the interactions between rapid climatic alterations and environmentally-sensitive species traits that fail to adapt to those changes. Accumulating evidence reveals the influence of ecophysiological, ecological and phenological factors as drivers underlying demographic collapses that lead to population extinctions. However, the extent to which life-history traits influence population responses to climate change remains largely unexplored. The emerging 'cul-de-sac hypothesis' predicts that reptilian viviparity ('live-bearing' reproduction), a 'key innovation' facilitating historical invasions of cold climates, increases extinction risks under progressively warming climates compared to oviparous reproduction - as warming advances polewards/mountainwards, historically cold-climates shrink, leading viviparous species to face demographic collapses. We present the first large-scale test of this prediction based on multiple lizard radiations and on future projections of climate-based ecological niche models. Viviparous species were found to experience stronger elevational range shifts (and potentially increased extinctions) in coming decades, compared to oviparous lizards. Therefore, our analyses support the hypothesis's fundamental prediction that elevational shifts are more severe in viviparous species, and highlight the role that life-history adaptations play in the responses of biodiversity to ongoing climate change. University of Lincoln's School of Life Sciences University of Lincoln for a Research Investment Fund (RIF) Grant FPI [BES-2012-054387 (MICIIN-CGL2011-24150/BOS)] Global Change Center Seed Grant 2017-18 We thank A. Townsend Peterson for his valuable comments and suggestions to improve this manuscript. MJ thanks the University of Lincoln's School of Life Sciences for a PhD scholarship. DPD thanks the University of Lincoln for a Research Investment Fund (RIF) Grant that supported this paper. RGR benefited from an FPI grant number BES-2012-054387 (MICIIN-CGL2011-24150/BOS). LEE was supported by the Global Change Center Seed Grant 2017-18.

Islands have great potential for renewable energy, and several pilot and experimental projects have been set up on islands globally, aiming to promote clean energy and self-sufficiency. Many of these decentralized energy initiatives oppose the established regimes of centralized electricity generation and introduce new forms of organization and management. Thus, they can be considered social niches. The aim of the present study is to explore the transition potential of renewable energy projects on three islands located in southern Europe. The analysis mobilizes literature on the strategic niche management theory (SNM) with a focus on the role of the various actors and the different management models. Through a systematic analysis of policy documents and the literature, enriched by interviews, the paper identifies different types of renewable energy projects and discusses the potential for scale up. The paper concludes that these projects are currently in the inter-local phase, and decentralization is not only an important innovation for energy production, but also a new form of energy management often dominated by different actors than the established electricity system.

The role of dispersal in the assembly of microbial communities remains contentious. This study tested the importance of dispersal limitation for the structuring of local soil bacterial communities using an experimental approach of propagule addition. Microbes extracted from soil pooled from samples collected at 20 localities across ~ 400 km in a temperate steppe were added to microcosms of local soils at three sites; the microcosms were then incubated in situ for 3 months. We then assessed the composition and diversity of bacterial taxa in the soils using 16S rRNA gene amplicon sequencing. The addition of the regional microbial pool did not cause significant changes in the overall composition or diversity of the total bacterial community, although a very small number of individual taxa may have been affected by the addition treatment. Our results suggest a negligible role of dispersal limitation in structuring soil bacterial communities in our study area.

Cell-based tissue engineering offers great promise to regenerative therapy, but so far it has been restricted due to insufficient number of cells obtained from donors and the lack of efficient ways of delivering them to target sites. This study shows, for the first time, the ability of a composite scaffold of gelatin and poly(methyl vinyl ether- alt-maleic anhydride) (GP-2) as a niche for expansion and multilineage differentiation ability of human umbilical cord–derived mesenchymal stem cells. First, the in vivo biocompatibility of scaffolds was checked by subcutaneous implantation of scaffolds in male Wistar rats for up to 45 days. Hematological parameters and histology of skin near implanted region rule out the probability of any adverse effects due to the scaffolds. The isolated human umbilical cord–derived mesenchymal stem cells were seeded on to pre-optimized scaffolds and induced to differentiate into osteogenic and adipogenic lineages by culturing in respective induction media. The human umbilical cord–derived mesenchymal stem cells were found to be viable and proliferated well on scaffolds when assessed with live/dead and PicoGreen assay. The biochemical assays such as alkaline phosphatase activity and triglycerides estimation confirmed the differentiation of cells toward particular lineages when cultured on scaffolds with appropriate inductive media. The study exhibited the proficiency of scaffold GP-2 for mesenchymal stem cells’ adherence, proliferation, and differentiation and also showed its engraftment efficiency. Taken together, our study establishes the in vivo biocompatibility of composite scaffold and, importantly, indicates its potential for stem cell–based therapy.

Pigs are one of the most important economic livestock. Gut microbiota is not only critical to the health but also the production efficiency of pigs. Manipulating gut microbiota relies on the full view of gut microbiome and the understanding of drive forces shaping microbial communities. 16s rDNA sequencing was used to profile microbiota along the longitudinal and radical axes to obtain the topographical map of microbiome in different intestinal compartments in young pigs. Alpha and beta-diversities revealed distinct differences in microbial compositions between the distal ileum and cecum and colon, as well as between the lumen and mucosa. Firmicutes and Proteobacteria dominated in the ileum, constituting 95 and 80% of the luminal and mucosa-attached microbiome. Transitioning from the small intestine to the large intestine, luminal Bacteroidetes increased from 1.69 to 45.98% in the cecum and 40.09% in the colon, while mucosal Bacteroidetes raised from 9 to 35.36% and 27.96%. Concurrently, luminal Firmicutes and Proteobacteria and mucosal-attached Proteobacteria remarkably decreased. By co-occurrence network analyses, Prevotellaceae, Ruminococcaceae, Lachnospiraceae and Veillonellaceae were recognized as the central nodes of luminal microbial network, and Prevotellaceae and Enterobacteriaceae, Caulobacteraceae, Enterococcaceae, Xanthomonadaceae, Pseudomonadaceae were identified as mucosal central nodes. Co-abundance was uncovered among Prevotellaceae, Lachnospiraceae, and Veillonellaceae in the luminal and mucosal microbiome, while opportunistic pathogens from γ-Proteobacteria in the mucosa. Strong co-exclusion was shown between Enterobacteriaceae with Prevotellaceae-centered microbial groups in the lumen. Redundancy analysis found bile acids and short chain fatty acids explained 37.1 and 41% of variations in the luminal microbial composition, respectively. Primary bile acid, taurine- and glycine- conjugated bile acids were positively correlated with Lactobacillaceae, Enterobacteriaceae, Clostridiaceae_1, Peptostreptococcaceae, whereas secondary bile acids, acetate, propionate, butyrate, and valerate were positively correlated with Prevotellaceae, Acidaminococcaceae, Ruminococcaceae, Lachnospiraceae, Desulfovibronaceae, Veillonellaceae. Functional analyses demonstrated that Prevotella, Veillonellaceae, Lachnospiraceae, and Ruminococcaceae were positively correlated with gene functions related to amino acids, energy, cofactors and vitamins metabolism, which are indispensable for the hosts. These results suggested site specific colonization and co-occurrence of swine gut microbiome closely relate to the microenvironment in each niche. Interactions of core gut microbiome greatly contributed to metabolism and/or immunity in the swine intestine.

Background Estuaries are primary habitats that serve as feeding and nursery grounds for most juvenile marine fish. However, estuaries have been used as fishing grounds by the artisanal fishers in Tanzania. The slow-growing predatory fish at juvenile and sub-adult stages are among the most frequently caught species that functionally enhance multiple linkages of energy pathways within the food web. Stomach contents and stable isotopes (δ13C and δ15N) were used to describe the nutritional sources and trophic niches between the co-existing benthic, predatory species, Carangoides chrysophrys and Epinephelus malabaricus in the Pangani estuary, Tanzania. Results The findings indicated significant inter-specific variations in dietary composition (PERMANOVA, p = 0.001, pseudo-F = 15.81). The prey-specific index of relative importance (%PSIRI) indicated that juvenile shrimps (%PSIRI = 51.4) and Teleostei (%PSIRI = 26.5) were the main diets of C. chrysophrys while brachyura (%PSIRI = 38.8), juvenile shrimps (%PSIRI = 25.6) and Teleostei (%PSIRI = 23.3) were important diets of E. malabaricus. The isotope mixing models indicated that the predatory fish species accumulate nutrients derived from similar autotrophic sources, microphytobenthos, seagrass and macro-algae via consumption of small fish, including clupeids and mugilids. Yet, they significantly showed different isotopic niche width with varying degree of niche overlap across the longitudinal estuary gradient. This situation was justified by the presence of basal food sources among the estuarine zones that isotopically were different. Conclusion The reliance of both predators on clupeids and mugilid preys that are trophically linked with estuarine and marine basal food sources, is an indication of low estuarine food webs’ connectivity to the fresh water related food web. This situation is most likely threatening the stability of the estuarine food web structure. Management strategies and plans in place should be cautiously implemented to ensure the balanced anthropogenic freshwater use in the catchment and fishing activities, for the maintenance of the Pangani estuarine ecosystem health.

Dental pulp stem/progenitor cells guarantee tooth homeostasis, repair and regeneration throughout life. The decision between renewal and differentiation of these cells is influenced by physical and molecular interactions with stromal cells and extracellular matrix molecules forming the specialized microenvironment of dental pulp stem cell niches. Here we study the activation of putative pulp niches after tooth injury through the upregulation of Notch signaling pathway. Notch1, Notch2, and Notch3 molecules were used as markers of dental pulp stem/progenitor cells. Upon dental injury, Notch1 and Notch3 are detected in cells related to vascular structures suggesting a role of these proteins in the activation of specific pulpal perivascular niches. In contrast, a population of Notch2-positive cells that are actively proliferative is observed in the apical part of the pulp. Kinetics of these cells is followed up with a lipophilic DiI labeling, showing that apical pulp cells migrate toward the injury site where dynamic regenerative/repair events occur. The knowledge of the activation and regulation of dental pulp stem/progenitor cells within their niches in pathologic conditions may be helpful for the realization of innovative dental treatments in the near future.

We consider interacting population systems of predator-prey type, presenting four models of control strategies for epidemics among the prey. In particular to contain the transmissible disease, safety niches are considered, assuming they lessen the disease spread, but do not protect prey from predators. This represents a novelty with respect to standard ecosystems where the refuge prevents predators' attacks. The niche is assumed either to protect the healthy individuals, or to hinder the infected ones to get in contact with the susceptibles, or finally to reduce altogether contacts that might lead to new cases of the infection. In addition a standard culling procedure is also analysed. The effectiveness of the different strategies are compared. Probably the environments providing a place where disease carriers cannot come in contact with the healthy individuals, or where their contact rates are lowered, seem to preferable for disease containment.

Glioblastoma multiforme (GBM) harbors are not only rapidly dividing cells but also small populations of slowly dividing and dormant cells with tumorigenesity, self-renewal, and multi-lineage differentiation capabilities. Known as glioblastoma stem cells (GSCs), they are resistant to conventional chemo- and radiotherapy and may be a causative factor in recurrence. The treatment outcome in patients with GBM remains unsatisfactory and their mean survival time has not improved sufficiently. We studied clinical evidence and basic research findings to assess the possibility of new treatment strategies that target GSCs and their specific microenvironments (GBM niches) and raise the possibility of adding new treatments to eradicate GSCs and GBM niches.

A synthesis is presented highlighting the importance of hydrologic variables and dynamics to biodiversity patterns. The focus of this paper is the key hydrologic controls crucial towards quantifying the impacts of climate changes on the distribution of species. Specifically, we highlight the hydrologic controls operating on the carrying capacity, niche formation, and dispersal dynamics. This synthesis will facilitate avenues of future research and is connected to issues of major practical importance, such as the integration of the structure of river networks into conservation strategies and the evaluations of the impacts of climate change on biodiversity. (C) 2012 Elsevier Ltd. All rights reserved.

The complexity of stem cell niches poses a tremendous challenge to understanding mechanisms of extrinsic regulation of stem cell fate. In order to better understand niche signaling and its effect on stem cell fate choices, in vitro systems are being engineered which recapitulate, in a simplistic but increasingly sophisticated manner, native stem cell niches. New technologies or new combinations of existing technologies allow more systematic ways to probe niche signaling in high-throughput. Systems biology approaches in experimental design, data acquisition and analysis will be necessary to tackle the challenges that lie ahead.

Stem cells guarantee tissue repair and regeneration throughout life. The decision between cell self-renewal and differentiation is influenced by a specialized microenvironment called the ‘stem cell niche’. In the tooth, stem cell niches are formed at specific anatomic locations of the dental pulp. The microenvironment of these niches regulates how dental pulp stem cell populations participate in tissue maintenance, repair, and regeneration. Signaling molecules such as Notch proteins are important regulators of stem cell function, with various capacities to induce proliferation or differentiation. Dental injuries often lead to odontoblast apoptosis, which triggers activation of dental pulp stem cells followed by their proliferation, migration, and differentiation into odontoblast-like cells, which elaborate a reparative dentin. Better knowledge of the regulation of dental pulp stem cells within their niches in pathological conditions will aid in the development of novel treatments for dental tissue repair and regeneration.

The putative existence of a cancer stem cell niche consisting of bi-directional stromal and stem cell secreting factors that trigger cancer stem cell growth and proliferation has been hypothesized in the nervous and hematopoietic systems. In light of this theory, it has been proposed that embryonic stem cell microenvironments, upon interactions with cancer stem cells, may reprogram cancer cells resulting in a substantial inhibition of tumor cell properties. Here, we discuss emerging data that support this novel concept of cancer inhibitory factors produced in the context of embryonic microenvironments as well as by embryonic stem cells (ESCs).

The seasonal dynamics of Acartia tonsa and the invader Eurytemora americana were analysed in relation to the environ- mental variability occurring from April to November in the Bahia Rlanca Estuary. Twice a month, the abundance of eggs, nauplii, copepodites and adults was examined and some environmental variables were recorded. Multivariate statistics (CCA) was applied to analyse the data of variables. Acartia tonsa eggs and nauplii diminishedfrom April-May and they were almost absent between Tune and September, although a small larval peak cot~ld be detected from the end of July to October. All the stages of this species increased in number through spring. Eurytemora americana was registered as from June and only nauplii larvae were observed, with a peak increase during September. Copepodites and adults were observed as from July, increasing in number until peaking at the end ofSeptember. The number of all stages of this species decreased abruptly, the whole population disappearing from the plankton. The A. tonsa developmental stages were most positively correlated with temperature, photoperiod and other light variables whereas those of E. americana showedpositive correlations with chlorophyll-a and salinity. The gradients ofthe main environmental factors likelygive rise to a certain niche separation facilitating the coexistence of the two copepod populations within the period studied. Fil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional; Argentina Fil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina Fil: Beigt, Debora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina Fil: Piccolo, Maria Cintia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur; Argentina

The performance of firms depends not just on the structure of the industries in which they compete but also on their relative positioning within those industries, in terms of operating within particular niches. We propose that demand for these niches depends endogenously on the historical ecology of the products offered: Niches become saturatedreduced in their ability to support productsas a large number of previous offerings allows the audience to satisfy its desire for products of a particular type. Analyzing the survival rates of television series aired in the United States from 1946 to 2003, we found that the survival rates of future entrants fell with the extensiveness of recent offerings in the niche, and that the negative association between crowding and survival also weakened with this saturation. We gratefully acknowledge financial support from the Italian Ministry of University and Research (project CUP B41J12000160008), the Ministerio de Economia y Competitividad in Spain (Grant ECO2012-34734), and the Juan de la Cierva Fellowship Programme of the Ministry of Science and Innovation of Spain.

Several harpacticoid copepod species are adapted to an epiphytic lifestyle. Previous studies on tropical seagrass meiofauna mainly focussed on the epiphytic communities and neglected the benthic component. The present study aims to document the benthic harpacticoid copepod communities sampled from different sediment depth horizons adjacent to five seagrass species in the intertidal and subtidal zone of a tropical seagrass bed (Gazi Bay, Kenya). Two benthic copepod communities could be identified mainly based on the tidal position of the samples: a first community was collected near the intertidal seagrasses Halophila ovalis and Halodule wrightii; a second community occurred near the subtidal seagrasses Thalassia hemprichii, Syringodium isoetifolium and Halophila stipulacea. The first community was mainly determined by sediment characteristics (e.g. skewness), while the second community was split off based on organic matter content (% TOM), nutrient and pigment values. A subtle combination of horizontal and vertical niche segregation was reported for the dominant copepod families. Species of the families Thalestridae, Laophontidae and Diosaccidae were structured by tidal position and showed a strong preference for the subtidal zone. The opposite strategy, i.e. a clear preference for the intertidal zone, was found for copepods belonging to the families Paramesochridae and Canuellidae. In addition, Apodopsyllus africanus (Paramesochridae) was well-adapted to stress and was concentrated in the deeper sediment layers near the subtidal seagrasses. On the other hand, Canuellidae, as filter feeders, were concentrated in the upper centimetres of the sediment. The families Ectinosomatidae and Cletodidae did not show any vertical or horizontal segregation. On the species level, however, clear horizontal niche segregation was detected for the family Cletodidae. In addition to the reported ecological results, the study material was used to evaluate different niche definitions. We found tidal position to be the most important factor forcing harpacticoids to specialise. Sediment depth horizon was less powerful in dividing the families into different guilds (from specialists to generalists) based on standardised niche breadth. The present study documents the subtle habitat partitioning of co-existing species in a limited area and its role in sustaining high biodiversity in the community.

A great challenge when conducting ex vivo studies of leukaemia is the construction of an appropriate experimental platform that would recapitulate the bone marrow (BM) environment. Such a 3D scaffold system has been previously developed in our group [1]. Additionally to the BM architectural characteristics, parameters such as oxygen and glucose concentration are crucial as their value could differ between patients as well as within the same patient at different stages of treatment, consequently affecting the resistance of leukaemia to chemotherapy. The effect of oxidative and glucose stress—at levels close to human physiologic ones—on the proliferation and metabolic evolution of an AML model system (K-562 cell line) in conventional 2D cultures as well as in 3D scaffolds were studied. We observed that the K-562 cell line can proliferate and remain alive for 2 weeks in medium with glucose close to physiological levels both in 20 and 5 % O2. We report interesting differences on the cellular response to the environmental, i.e., oxidative and/or nutritional stress stimuli in 2D and 3D. Higher adaptation to oxidative stress under non-starving conditions is observed in the 3D system. The glucose level in the medium has more impact on the cellular proliferation in the 3D compared to the 2D system. These differences can be of significant importance both when applying chemotherapy in vitro and also when constructing mathematical tools for optimisation of disease treatment.

It has been shown that in Drosophila the germline stem cells (GSCs), similar to the germline and non-germline stem cells of other species, develop and function in specialized microenvironments formed by somatic cells, referred to as the niches. In the fruit fly ovaries, the female GSCs divide asymmetrically to produce new GSCs and the progenitor cells, the cystoblasts (Cbs). Each Cb then divides to generate the cyst composed of 16 interconnected sibling cells, the cystocytes. After cyst formation, specific molecules are transferred to one of the cystocytes which differentiates into the oocyte, whereas the other 15 cystocytes become the nurse cells. We have studied morphology and ultrastructure of the germaria in the ovarioles (ovaries) of a basal "apterygotous" insect, the firebrat (Thermobia domestica). Our analyses have revealed that in this insect, putative GSCs are present along the anterior apex of the germarium. These cells are separated from each other and from the basement lamina covering the ovariole by characteristic somatic cells, termed the apical somatic cells (ASCs), or their elongated processes. We believe that all the ASCs of a given ovariole constitute a "dispersed" niche in which putative GSCs are anchored. Our analyses have additionally shown that in Thermobia, both the Cbs and young (meiotic) oocytes are always individual and never form syncytial cysts. These findings indicate that in certain basal insects the syncytial phase of oogenesis has been eliminated during evolution. Finally, we show that in the early meiotic oocytes of Thermobia, during the so-called bouquet stage, prominent Balbiani bodies (Bbs) are formed. Analysis of serial micrographs indicates that the Bbs invariably arise next to the segment of the nuclear envelope to which the telomeres of the bouquet chromosomes are attached. We suggest, in the light of these data, that the localization of the Bb together with the polar attachment of the bouquet chromosomes play a crucial role in the early asymmetrization of Thermobia oocytes.

We review aspects of invertebrate biodiversity relevant to the management of Scots pine forests. At a landscape level, the area occupied by the host tree species, the length of time that species has been present, and the taxonomic relatedness of the host to other trees, all influence invertebrate biodiversity. At a stand level, tree size and above-ground architecture affect the number of niches available. Consideration needs to be given to the various feeding guilds since they exploit different components of these niches. Although there have been few published studies of invertebrate numbers in relation to niche availability in Scots pine, it would appear that the deadwood habitat is underrepresented in Scots pine forests and increasing the availability of this niche would enhance invertebrate biodiversity. An issue for managers is the need to distinguish between increasing total biodiversity and the encouragement of rare species with particular niche requirements which may also be dependent upon the continuity of that niche within a landscape. Se revisan distintos aspectos de la biodiversidad de invertebrados relevantes en la gestión de los bosques de Pino silvestre. A un nivel de paisaje, el área ocupada por la especie del árbol anfitrión, el tiempo que la especie ha estado presente, y la relación taxonómica del anfitrión con los otros árboles, influyen en la biodiversidad invertebrada. A un nivel de rodal, el tamaño del árbol y la arquitectura aérea afectan el número de nichos disponibles. Debe prestarse atención a los diversos grupos alimenticios de invertebrados, puesto que ellos explotan diferentes componentes de esos nichos. Aunque ha habido pocos estudios publicados sobre el número de invertebrados en relación con la disponibilidad del nicho en Pino silvestre, parece que el hábitat de la madera muerta está infrarrepresentada en los bosques de Pino silvestre y que el aumento de la disponibilidad de este nicho mejoraría la diversidad biológica de invertebrados. Un aspecto para los gestores es la necesidad de distinguir entre el aumento de la biodiversidad total y favorecer las especies raras con requisitos particulares del nicho que también pueden depender de la continuidad de ese nicho dentro de un paisaje.

Stem cells are characterized by their dual ability to reproduce themselves (self-renew) and specialize (differentiate), yielding a plethora of daughter cells that maintain and regenerate tissues. In contrast to their embryonic counterparts, adult stem cells retain their unique functions only if they are in intimate contact with an instructive microenvironment, termed stem cell niche. In these niches, stem cells integrate a complex array of molecular signals that, in concert with induced cell-intrinsic regulatory networks, control their function and balance their numbers in response to physiologic demands. This progress report provides a perspective on how advanced materials technologies could be used (i) to engineer and systematically analyze specific aspects of functional stem cells niches in a controlled fashion in vitro and (ii) to target stem cell niches in vivo. Such “artificial niches” constitute potent tools for elucidating stem cell regulatory mechanisms with the capacity to directly impact the development of novel therapeutic strategies for tissue regeneration.

Maintenance of the blood system is dependent on dormant haematopoietic stem cells (HSCs) with long-term self-renewal capacity. After injury these cells are induced to proliferate to quickly reestablish homeostasis(1). The signalling molecules promoting the exit of HSCs out of the dormant stage remain largely unknown. Here we show that in response to treatment of mice with interferon-alpha (IFN alpha), HSCs efficiently exit G(0) and enter an active cell cycle. HSCs respond to IFN alpha treatment by the increased phosphorylation of STAT1 and PKB/Akt (also known as AKT1), the expression of IFN alpha target genes, and the upregulation of stem cell antigen-1 (Sca-1, also known as LY6A). HSCs lacking the IFN alpha/beta receptor (IFNAR)(2), STAT1 (ref. 3) or Sca-1 (ref. 4) are insensitive to IFN alpha stimulation, demonstrating that STAT1 and Sca-1 mediate IFN alpha-induced HSC proliferation. Although dormant HSCs are resistant to the anti-proliferative chemotherapeutic agent 5-fluoro-uracil(1,5), HSCs pre-treated (primed) with IFN alpha and thus induced to proliferate are efficiently eliminated by 5-fluoro-uracil exposure in vivo. Conversely, HSCs chronically activated by IFN alpha are functionally compromised and are rapidly out-competed by non-activatable Ifnar(-/-) cells in competitive repopulation assays. Whereas chronic activation of the IFN alpha pathway in HSCs impairs their function, acute IFN alpha treatment promotes the proliferation of dormant HSCs in vivo. These data may help to clarify the so far unexplained clinical effects of IFN alpha on leukaemic cells(6,7), and raise the possibility for new applications of type I interferons to target cancer stem cells(8).

Stem cells are characterized by their dual ability to self- renew and differentiate, yielding essentially unlimited numbers of progeny that can replenish tissues with either high turnover such as blood and skin or contribute to the regeneration of organs with less frequent remodeling such as muscle. In contrast to their embryonic counterparts, adult stem cells can only preserve their unique functions if they are in intimate contact with an instructive microenvironment, termed niche. Stem cells integrate a complex array of niche signals that regulate their fate, keeping them in a relatively quiescent state during homeostasis, or controlling their numbers via symmetric or asymmetric divisions in response to the regenerative demands of a tissue. This chapter provides an overview of the current state of knowledge of structural and functional hallmarks of mammalian stem cell niches and offers a perspective on how bioengineering principles could be used to deconstruct the niche and providing novel insights into the role of its specific components in the regulation of stem cell fate. Such “artificial niches” constitute powerful tools for elucidating stem cell regulatory mechanisms that should fuel the development of novel therapeutic strategies for tissue regeneration.