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Multicellular Organisms (multicellular + organism)
Selected AbstractsEpigenetic reprogramming: Enforcer or enabler of developmental fate?DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 6 2010Alexander N. Combes A single fertilized egg is programmed to differentiate into a multitude of distinct cell types that comprise a multicellular organism. Epigenetic mechanisms such as DNA methylation and histone modifications are intricately involved in regulating developmental potential and cellular identity by establishing permissive or repressive chromatin states that are mitotically heritable. Here, we review the dynamics of major epigenetic marks during early mammalian development, and explore the question of whether DNA methylation and chromatin modifications enable or enforce changes that lead to the first cell fate decision. [source] Paternal sex in parthenogenetic planarians: a tool to investigate the accumulation of deleterious mutationsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2000Storhas Clonally reproducing organisms are expected to accumulate slightly deleterious mutations, and this has been demonstrated in RNA viruses, bacteria and unicellular algae. In this paper we present evidence for increased embryo mortality in obligate parthenogenetic strains of the freshwater flatworm Schmidtea polychroa, possibly indicating the action of deleterious mutations. The inheritance of this fitness defect was tested by crossing parthenogens with sexuals. This is possible because both forms are simultaneous hermaphrodites that produce fertile sperm. The resulting sexual offspring showed significantly increased embryo mortality in comparison to offspring of a sexual × sexual cross. Alternatives to a mutation explanation of these results, like the degeneration of male traits in parthenogens, are being discussed. In conclusion, these results lend support to the hypothesis that sex is advantageous to a multicellular organism because it prevents the accumulation of deleterious mutations. [source] A conserved mechanism of autoinhibition for the AMPK kinase domain: ATP-binding site and catalytic loop refolding as a means of regulationACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Dene R. Littler The AMP-activated protein kinase (AMPK) is a highly conserved trimeric protein complex that is responsible for energy homeostasis in eukaryotic cells. Here, a 1.9,Å resolution crystal structure of the isolated kinase domain from the ,2 subunit of human AMPK, the first from a multicellular organism, is presented. This human form adopts a catalytically inactive state with distorted ATP-binding and substrate-binding sites. The ATP site is affected by changes in the base of the activation loop, which has moved into an inhibited DFG-out conformation. The substrate-binding site is disturbed by changes within the AMPK,2 catalytic loop that further distort the enzyme from a catalytically active form. Similar structural rearrangements have been observed in a yeast AMPK homologue in response to the binding of its auto-inhibitory domain; restructuring of the kinase catalytic loop is therefore a conserved feature of the AMPK protein family and is likely to represent an inhibitory mechanism that is utilized during function. [source] Symmetry-breaking in mammalian cell cohort migration during tissue pattern formation: Role of random-walk persistenceCYTOSKELETON, Issue 4 2005S. Huang Abstract Coordinated, cohort cell migration plays an important role in the morphogenesis of tissue patterns in metazoa. However, individual cells intrinsically move in a random walk-like fashion when studied in vitro. Hence, in the absence of an external orchestrating influence or template, the emergence of cohort cell migration must involve a symmetry-breaking event. To study this process, we used a novel experimental system in which multiple capillary endothelial cells exhibit spontaneous and robust cohort migration in the absence of chemical gradients when cultured on micrometer-scale extracellular matrix islands fabricated using microcontact printing. A computational model suggested that directional persistence of random-walk and dynamic mechanical coupling of adjacent cells are the critical control parameters for this symmetry-breaking behavior that is induced in spatially-constrained cell ensembles. The model predicted our finding that fibroblasts, which exhibit a much shorter motility persistence time than endothelial cells, failed to undergo symmetry breaking or produce cohort migration on the matrix islands. These findings suggest that cells have intrinsic motility characteristics that are tuned to match their role in tissue patterning. Our results underscore the importance of studying cell motility in the context of cell populations, and the need to address emergent features in multicellular organisms that arise not only from cell-cell and cell-matrix interactions, but also from properties that are intrinsic to individual cells. Cell Motil. Cytoskeleton 61:201,213, 2005. © 2005 Wiley-Liss, Inc. [source] Primer and interviews: Gene regulation in Arabidopsis thalianaDEVELOPMENTAL DYNAMICS, Issue 9 2009Julie C. Kiefer Abstract The animal and plant kingdoms use many of the same molecular tools to build decidedly different multicellular organisms. Learning how plants approach challenges common to both kingdoms can inspire new ways of thinking in the animal biologist. This primer introduces how a weed from the mustard family, Arabidopsis thaliana, has been used to work through developmental problems. It also compares and contrasts gene regulation tools in animals and plants. Accompanying the primer is a discussion of current topics in root development with Arabidopsis researchers Philip N. Benfey, Ph.D., and Kenneth D. Birnbaum, Ph.D. Developmental Dynamics 238:2449,2458, 2009. © 2009 Wiley-Liss, Inc. [source] Phenotypic analysis of deflated/Ints7 function in Drosophila developmentDEVELOPMENTAL DYNAMICS, Issue 5 2009Rachael J. Rutkowski Abstract The Drosophila gene deflated (CG18176; renamed after the pupal lethal abdominal phenotype of mutant individuals) is a member of a conserved gene family found in all multicellular organisms. The human orthologue of deflated (Ints7) encodes a subunit of the Integrator complex that associates with RNA polymerase II and has been implicated in snRNA processing. Since loss-of-function analyses of deflated have not yet been reported, we undertook to investigate deflated expression patterns and mutant phenotypes. deflated mRNA was detected at low levels in proliferating cells in postblastoderm embryos and GFP tagged protein is predominately nuclear. Generation and analysis of four mutant alleles revealed deflated is essential for normal development, as mutant individuals displayed pleiotropic defects affecting many stages of development, consistent with perturbation of cell signalling or cell proliferation. Our data demonstrate multiple roles in development for an Ints7 homologue and to demonstrate its requirement for normal cell signalling and proliferation. Developmental Dynamics 238:1131,1139, 2009. © 2009 Wiley-Liss, Inc. [source] Multiple sites of L-histidine decarboxylase expression in mouse suggest novel developmental functions for histamineDEVELOPMENTAL DYNAMICS, Issue 1 2001Kaj Karlstedt Abstract Histamine mediates many types of physiologic signals in multicellular organisms. To clarify the developmental role of histamine, we have examined the developmental expression of L-histidine decarboxylase (HDC) mRNA and the production of histamine during mouse development. The predominant expression of HDC in mouse development was seen in mast cells. The HDC expression was evident from embryonal day 13 (Ed13) until birth, and the mast cells were seen in most peripheral tissues. Several novel sites with a prominent HDC mRNA expression were revealed. In the brain, the choroid plexus showed HDC expression at Ed14 and the raphe neurons at Ed15. Close to the parturition, at Ed19, the neurons in the tuberomammillary (TM) area and the ventricular neuroepithelia also displayed a clear HDC mRNA expression and histamine immunoreactivity (HA-ir). From Ed14 until birth, the olfactory and nasopharyngeal epithelia showed an intense HDC mRNA expression and HA-ir. In the olfactory epithelia, the olfactory receptor neurons (ORN) were shown to have very prominent histamine immunoreactivity. The bipolar nerve cells in the epithelium extended both to the epithelial surface and into the subepithelial layers to be collected into thick nerve bundles extending caudally toward the olfactory bulbs. Also, in the nasopharynx, an extensive subepithelial network of histamine-immunoreactive nerve fibers were seen. Furthermore, in the peripheral tissues, the degenerating mesonephros (Ed14) and the convoluted tubules in the developing kidneys (Ed15) showed HDC expression, as did the prostate gland (Ed15). In adult mouse brain, the HDC expression resembled the neuronal pattern observed in rat brain. The expression was restricted to the TM area in the ventral hypothalamus, with the main expression in the five TM subgroups called E1,E5. A distinct mouse HDC mRNA expression was also seen in the ependymal wall of the third ventricle, which has not been reported in the rat. The tissue- and cell-specific expression patterns of HDC and histamine presented in this work indicate that histamine could have cell guidance or regulatory roles in development. © 2001 Wiley-Liss, Inc. [source] Effect of volatile hydrocarbon fractions on mobility and earthworm uptake of polycyclic aromatic hydrocarbons from soils and soil/lampblack mixturesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2005Bill W. Bogan Abstract Studies were conducted to examine the mobility and bioavailability to earthworms (Eisenia fetida) of priority pollutant polycyclic aromatic hydrocarbons (PAH) in a suite of 11 soils and soil/lampblack mixtures obtained from former manufactured-gas plant sites. Contaminant mobility was assessed using XAD4 resins encapsulated in dialysis tubing, which were exposed to slurried soils for 15 d. These experiments showed that mobility of PAH in the different soils strongly correlated to the levels of volatile hydrocarbons (namely, gasoline- and diesel-range organics [GRO and DRO]) that existed in the soils as co-contaminants. Actual PAH bioavailability (as measured by earthworm PAH concentrations) also appeared to depend on GRO + DRO levels, although this was most evident at high levels of these contaminants. These findings are discussed in view of the effects of diesel-range organics on oil viscosity, assuming that the hydrocarbon contaminants in these soils exist in the form of distinct adsorbed oil phases. This study, therefore, extends correlations between carrier-oil viscosity and dissolved solute bioavailability, previously observed in a number of other in vitro and whole-organism tests (and in bacterial mutagenicity studies in soil), to multicellular organisms inhabiting contaminated-soil systems. [source] ON THE EVOLUTION OF DIFFERENTIATED MULTICELLULARITYEVOLUTION, Issue 2 2009Martin Willensdorfer Most conspicuous organisms are multicellular and most multicellular organisms develop somatic cells to perform specific, nonreproductive tasks. The ubiquity of this division of labor suggests that it is highly advantageous. In this article I present a model to study the evolution of specialized cells. The model allows for unicellular and multicellular organisms that may contain somatic (terminally differentiated) cells. Cells contribute additively to a quantitative trait. The fitness of the organism depends on this quantitative trait (via a benefit function), the size of the organism, and the number of somatic cells. The model allows one to determine when somatic cells are advantageous and to calculate the optimum number (or fraction) of reproductive cells. I show that the fraction of reproductive cells is always surprisingly high. If somatic cells are very small, they can outnumber reproductive cells but their biomass is still less than the biomass of reproductive cells. I discuss the biology of primitive multicellular organisms with respect to the model predictions. I find a good agreement and outline how this work can be used to guide further quantitative studies of multicellularity. [source] THE LOCI OF EVOLUTION: HOW PREDICTABLE IS GENETIC EVOLUTION?EVOLUTION, Issue 9 2008David L. Stern Is genetic evolution predictable? Evolutionary developmental biologists have argued that, at least for morphological traits, the answer is a resounding yes. Most mutations causing morphological variation are expected to reside in the cis -regulatory, rather than the coding, regions of developmental genes. This "cis -regulatory hypothesis" has recently come under attack. In this review, we first describe and critique the arguments that have been proposed in support of the cis -regulatory hypothesis. We then test the empirical support for the cis -regulatory hypothesis with a comprehensive survey of mutations responsible for phenotypic evolution in multicellular organisms. Cis -regulatory mutations currently represent approximately 22% of 331 identified genetic changes although the number of cis -regulatory changes published annually is rapidly increasing. Above the species level, cis -regulatory mutations altering morphology are more common than coding changes. Also, above the species level cis -regulatory mutations predominate for genes not involved in terminal differentiation. These patterns imply that the simple question "Do coding or cis -regulatory mutations cause more phenotypic evolution?" hides more interesting phenomena. Evolution in different kinds of populations and over different durations may result in selection of different kinds of mutations. Predicting the genetic basis of evolution requires a comprehensive synthesis of molecular developmental biology and population genetics. [source] PERSPECTIVE: THE SIZE-COMPLEXITY RULEEVOLUTION, Issue 9 2004J. T. Bonner Abstract It is widely accepted that bigger entities have a greater division of labor than smaller ones and this is reflected in the fact that larger multicellular organisms have a corresponding increase in the number of their cell types. This rule is examined in some detail from very small organisms to large animals, and plants, and societies. Compared to other size-related rules, the size-complexity rule is relatively rough and approximate, yet clearly it holds throughout the whole range of living organisms, as well as for societies. The relationship between size and complexity is analyzed by examining the effects of size increase and decrease: size increase requires an increase in complexity, whereas size decrease permits, and sometimes requires, a decrease in complexity. Conversely, an increase or decrease in complexity permits, but does not require changes in size. An especially compelling argument for the close relation between size and complexity can be found in size quorum sensing in very small multicellular organisms. [source] The sociobiology of biofilmsFEMS MICROBIOLOGY REVIEWS, Issue 1 2009Carey D. Nadell Abstract Biofilms are densely packed communities of microbial cells that grow on surfaces and surround themselves with secreted polymers. Many bacterial species form biofilms, and their study has revealed them to be complex and diverse. The structural and physiological complexity of biofilms has led to the idea that they are coordinated and cooperative groups, analogous to multicellular organisms. We evaluate this idea by addressing the findings of microbiologists from the perspective of sociobiology, including theories of collective behavior (self-organization) and social evolution. This yields two main conclusions. First, the appearance of organization in biofilms can emerge without active coordination. That is, biofilm properties such as phenotypic differentiation, species stratification and channel formation do not necessarily require that cells communicate with one another using specialized signaling molecules. Second, while local cooperation among bacteria may often occur, the evolution of cooperation among all cells is unlikely for most biofilms. Strong conflict can arise among multiple species and strains in a biofilm, and spontaneous mutation can generate conflict even within biofilms initiated by genetically identical cells. Biofilms will typically result from a balance between competition and cooperation, and we argue that understanding this balance is central to building a complete and predictive model of biofilm formation. [source] Assembly rules and community models for unicellular organisms: patterns in diatoms of boreal streamsFRESHWATER BIOLOGY, Issue 4 2005JANI HEINO Summary 1. Many studies have addressed either community models (e.g. Clementsian versus Gleasonian gradients) or assembly rules (e.g. nestedness, checkerboards) for higher plant and animal communities, but very few studies have examined different non-random distribution patterns simultaneously with the same data set. Even fewer studies have addressed generalities in the distribution patterns of unicellular organisms, such as diatoms. 2. We studied non-randomness in the spatial distribution and community composition of stream diatoms. Our data consisted of diatom surveys from 47 boreal headwater streams and small rivers in northern Finland. Our analytical approaches included ordinations, cluster analysis, null model analyses, and associated randomisation tests. 3. Stream diatom communities did not follow discrete Clementsian community types, where multiple species occur exclusively in a single community type. Rather, diatom species showed rather individualistic responses, leading to continuous Gleasonian variability in community composition. 4. Although continuous variability was the dominating pattern in the data, diatoms also showed significant nestedness and less overlap in species distribution than expected by chance. However, these patterns were probably only secondary signals from species' individualistic responses to the environment. 5. Although unicellular organisms, such as diatoms, differ from multicellular organisms in several biological characteristics, they nevertheless appear to show largely similar non-random distribution patterns previously found for higher plants and metazoans. [source] In Vivo Function of a Differentiation Inhibitor, Id2IUBMB LIFE, Issue 4 2001Yoshifumi Yokota Abstract Cell differentiation is an essential process for the development of various cell types that constitute multicellular organisms. During development, the large family of factors bearing a helix-loop-helix (HLH) motif participates profoundly in this process and these factors serve as good experimental tools for investigating mechanisms underlying tissue-specific differentiation. The HLH family includes both positive and negative regulators of cell differentiation: basic HLH (bHLH)-type transcription factors and Id proteins, respectively. Following an exciting decade focusing on bHLH factors, advances achieved in studies of the inhibitory factors in the last couple of years have placed them in the front line of the research on differentiation and proliferation control. Here, we present and discuss recent results obtained using Id2 -deficient mice, which manifest intriguing phenotypes in various systems. [source] Relationships between local population persistence, local abundance and regional occupancy of species: distribution patterns of diatoms in boreal streamsJOURNAL OF BIOGEOGRAPHY, Issue 11 2005Janne Soininen Abstract Aims, We have two aims: (1) to examine the relationship between local population persistence, local abundance and regional occupancy of stream diatoms and (2) to characterize the form of the species,occupancy frequency distribution of stream diatoms. Location, Boreal streams in Finland. There were three spatial extents: (1) across ecoregions in Finland, (2) within ecoregions in Finland, and (3) within a single drainage system in southern Finland. Methods, Diatoms were sampled from stones (epilithon), sediment (epipelon) and aquatic plants (epiphyton) in streams using standardized sampling methods. To assess population persistence, diatom sampling was conducted monthly at four stream sites from June to October. The relationships between local population persistence, local abundance and regional occupancy were examined using correlation analyses. Results, There was a significant positive relationship between local persistence and abundance of diatoms in epilithon, epipelon and epiphyton. Furthermore, local abundance and regional occupancy showed a significant positive relationship at multiple spatial extents; that is, across ecoregions, within ecoregions and within a drainage system. The relationships between occupancy and abundance did not differ appreciably among impacted and near pristine-reference sites. The occupancy,frequency distribution was characterized by a large number of satellite species which occurred at only a few sites, whereas core species that occurred at most sites were virtually absent. Main conclusions, The positive relationship between local population persistence and abundance suggested that a high local abundance may prevent local extinction or that high persistence is facilitated by a high local cell density. High local persistence and local abundance may also positively affect the degree of regional occupancy in stream diatoms. The results further showed that anthropogenic effects were probably too weak to bias the relationship between occupancy and abundance, or that the effects have already modified the distribution patterns of stream diatoms. The small number of core species in the species,occupancy frequency distribution suggested that the regional distribution patterns of stream diatoms, or perhaps unicellular microbial organisms in general, may not be fundamentally different from those described previously for multicellular organisms, mainly in terrestrial environments, although average global range sizes may differ sharply between these two broad groups of organisms. [source] Epigenetic pre-patterning and dynamics during initial stages of mammalian preimplantation developmentJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010Theodore P. Rasmussen Mammals, like all multicellular organisms, develop from a single cell,the totipotent zygote. During preimplantation development and subsequent development in utero, over 200 distinct cell types are established and integrated into the organ systems and tissues of the developing organism. Much of the field of mammalian developmental biology is devoted to investigation of mechanisms that govern the formation of complete organs and tissues. In contrast to later development, which consumes the vast majority of time associated with development in utero, preimplantation development and germ layer specification occur rapidly. Yet knowledge is limited regarding the regulatory mechanisms that specify the transient, but pluripotent, cellular lineages that form during the initial stages of mammalian development. Gametogenesis and preimplantation development are marked by dramatic and pervasive epigenetic changes rooted in chromatin dynamics. The fundamental mechanisms that specify subsequent cellular lineages of the conceptus are only now becoming understood, and tend to rely relatively heavily upon broad epigenetic mechanisms in addition to master transcription factors. This review considers epigenetic regulation in the very earliest stages of preimplantation development. In addition, recent advances which indicate that some epigenetic coding is imposed during gametogenesis and maintained during preimplantation development are considered. J. Cell. Physiol. 225: 333,336, 2010. © 2010 Wiley-Liss, Inc. [source] Zinc regulates the ability of Cdc25C to activate MPF/cdk1JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2007Lu Sun Zn2+ is an essential micronutrient for the growth and development of multicellular organisms, as Zn2+ deficiencies lead to growth retardation and congenital malformations (Vallee, BL, Falchuk, KH. 1993. Physiol Rev., 73:79,118). At the cellular level Zn2+ depravation results in proliferation defects in many cell types (Vallee, BL, Falchuk, KH. 1993. Physiol Rev., 73:79,118), however the molecular pathways involved remain poorly defined. Here we show that the transition metal chelator TPEN (N,N,N,,N,-tetrakis(2-pyridylmethyl) ethylene diamine) blocks the G2/M transition of the meiotic cell cycle by inhibiting Cdc25C-cdk1 activation. ICP-MS analyses reveal that Cdc25C is a Zn2+ -binding metalloprotein, and that TPEN effectively strips Zn2+ away from the enzyme. Interestingly, although apo-Cdc25C (Zn2+ -deficient) remains fully catalytically active, it is compromised in its ability to dephosphorylate and activate MPF/cdk1. Thus, Zn2+ is an important regulator of Cdc25C function in vivo. Because of the conserved essential role of the Cdc25C-cdk1 module in the eukaryotic cell cycle, these studies provide fundamental insights into cell cycle regulation. J. Cell. Physiol. 213: 98,104, 2007. © 2007 Wiley-Liss, Inc. [source] Synthetic retinoids as inducers of apoptosis in ovarian carcinoma cell linesJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2004William F. Holmes Apoptosis is also known as programmed cell death. Apoptosis plays an essential role in maintaining normal tissue and cell physiology in multicellular organisms. Clearance of aberrant or pre-cancerous cells occurs through the induction of apoptosis. It has been reported that many tumors and tumor cell lines have dysfunctional apoptosis signaling, causing these tumors to escape immune monitoring and internal cellular control mechanisms. One potential cause of this dysfunctional apoptosis is the tumor suppressor p53, an important regulator of growth arrest and apoptosis that is mutated in over 50% of all cancers. Retinoids have great potential in the areas of cancer therapy and chemoprevention. While some tumor cells are sensitive to the growth inhibitory effects of natural retinoids such as all- trans -retinoic acid (ATRA), many ovarian tumor cells are not. 6-[3-(1-Admantyl)]-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) and fenretinide N -[4-hydroxyphenyl] retinamide (4-HPR) are conformationally restricted synthetic retinoids that induce growth arrest and apoptosis in both ATRA-sensitive and ATRA-resistant ovarian tumor cell lines. Recently, we have identified the molecular pathways of apoptosis induced by treatment of ovarian carcinoma cells with mutated p53 by CD437 and 4-HPR. © 2004 Wiley-Liss, Inc. [source] Myogenesis and molecules, insights from zebrafish Danio rerioJOURNAL OF FISH BIOLOGY, Issue 8 2009S.-W. Chong Myogenesis is a fundamental process governing the formation of muscle in multicellular organisms. Recent studies in zebrafish Danio rerio have described the molecular events occurring during embryonic morphogenesis and have thus greatly clarified this process, helping to distinguish between the events that give rise to fast v. slow muscle. Coupled with the well-known Hedgehog signalling cascade and a wide variety of cellular processes during early development, the continual research on D. rerio slow muscle precursors has provided novel insights into their cellular behaviours in this organism. Similarly, analyses on fast muscle precursors have provided knowledge of the behaviour of a sub-set of epitheloid cells residing in the anterior domain of somites. Additionally, the findings by various groups on the roles of several molecules in somitic myogenesis have been clarified in the past year. In this study, the authors briefly review the current trends in the field of research of D. rerio trunk myogenesis. [source] Caspases and apoptosis in fishJOURNAL OF FISH BIOLOGY, Issue 2007H. Takle Apoptosis has a vital impact on the development and homeostasis of all multicellular organisms. Hence, all metazoan species seem to possess the necessary components of the apoptotic machinery, but in general, their numbers and complexity have increased during evolution. The key apoptotic factors are a cascade of cysteine proteases known as caspases. The fish homologous of almost all the mammalian caspases have also been identified, but several fish-specific caspases with putative distinct functions have also been reported. Despite these differences, the extrinsic and intrinsic pathways have been remarkably well conserved throughout 500 million years of vertebrate evolution. Here, the authors review what is currently known about fish caspases and apoptosis and demonstrate the huge amount of sequence information available from a range of fish species by screening Atlantic salmon genome databases for apoptotic homologous. [source] Melatonin induces apoptotic death in LNCaP cells via p38 and JNK pathways: therapeutic implications for prostate cancerJOURNAL OF PINEAL RESEARCH, Issue 1 2009Seong Soo Joo Abstract:, Apoptosis, a form of cell death, is a fundamental process for the development and maintenance of multicellular organisms that promotes the removal of damaged, senescent or unwanted cells. Induction of cancer cell apoptosis is an important strategy of anticancer therapy. In this study, we examined if melatonin, the main secretory product of the pineal gland, inhibited the growth of prostate cancer cells (LNCaP) and promoted apoptosis via mitogen-activated protein kinases (MAPKs), which are closely associated with apoptosis and survival. Melatonin treatment significantly inhibited the growth of LNCaP cells in a dose- and time-dependent manner. It clearly induced both an early stage of apoptosis (propidium iodide,, FITC Annexin-V+) and a late apoptosis/secondary necrosis (propidium iodide+ and FITC Annexin-V+), which indicated induction of serial stages of apoptosis in cells. Moreover, melatonin markedly activated c-JUN N-terminal kinase (JNK) and p38 kinase, whereas extracellular signal-regulated kinase (ERK) was not responsive to melatonin. Treatment with MAPK inhibitors, PD98059 (ERK inhibitor), SP600125 (JNK inhibitor) and SB202190 (p38 inhibitor), confirmed that melatonin-induced apoptosis was JNK- and p38-dependent, but ERK-independent. In the presence of PD98059, caspase-3 activity increased, while levels of Bax/cytochrome c (Cyt c) and Bcl-2 decreased. These effects were opposite to those observed with SP600125 and SB202190 treatments. Together, these results strongly suggest that JNK and p38 activation directly participate in apoptosis induced by melatonin. Thus, melatonin may be of promise for anti-prostate cancer strategies. [source] Enterobacteria-mediated nitrogen fixation in natural populations of the fruit fly Ceratitis capitataMOLECULAR ECOLOGY, Issue 9 2005A. BEHAR Abstract Nitrogen, although abundant in the atmosphere, is paradoxically a limited resource for multicellular organisms. In the Animalia, biological nitrogen fixation has solely been demonstrated in termites. We found that all individuals of field-collected Mediterranean fruit flies (Ceratitis capitata) harbour large diazotrophic enterobacterial populations that express dinitrogen reductase in the gut. Moreover, nitrogen fixation was demonstrated in isolated guts and in live flies and may significantly contribute to the fly's nitrogen intake. The presence of similar bacterial consortia in additional insect orders suggests that nitrogen fixation occurs in vast pools of terrestrial insects. On such a large scale, this phenomenon may have a considerable impact on the nitrogen cycle. [source] Co-occurrence in nature of different clones of the social amoeba, Dictyostelium discoideumMOLECULAR ECOLOGY, Issue 4 2003A. Fortunato Abstract The social amoeba, Dictyostelium discoideum, produces a multicellular fruiting body and has become a model system for cell,cell interactions such as signalling, adhesion and development. However, unlike most multicellular organisms, it forms by aggregation of cells and, in the laboratory, forms genetic chimeras where there may be competition among clones. Here we show that chimera formation is also likely in nature, because different clones commonly co-occur on a very small scale. This suggests that D. discoideum will likely have evolved strategies for competing in chimeras, and that the function of some developmental genes will be competitive. Natural chimerism also makes D. discoideum a good model organism for the investigation of issues relating to coexistence and conflict between cells. [source] Structure, function and evolution of microbial adenylyl and guanylyl cyclasesMOLECULAR MICROBIOLOGY, Issue 5 2004David A. Baker Summary Cells respond to signals of both environmental and biological origin. Responses are often receptor mediated and result in the synthesis of so-called second messengers that then provide a link between extracellular signals and downstream events, including changes in gene expression. Cyclic nucleotides (cAMP and cGMP) are among the most widely studied of this class of molecule. Research on their function and mode of action has been a paradigm for signal transduction systems and has shaped our understanding of this important area of biology. Cyclic nucleotides have diverse regulatory roles in both unicellular and multicellular organisms, highlighting the utility and success of this system of molecular communication. This review will examine the structural diversity of microbial adenylyl and guanylyl cyclases, the enzymes that synthesize cAMP and cGMP respectively. We will address the relationship of structure to biological function and speculate on the complex origin of these crucial regulatory molecules. A review is timely because the explosion of data from the various genome projects is providing new and exciting insights into protein function and evolution. [source] Death's toolbox: examining the molecular components of bacterial programmed cell deathMOLECULAR MICROBIOLOGY, Issue 3 2003Kelly C. Rice Summary Programmed cell death (PCD) is a genetically determined process of cellular suicide that is activated in response to cellular stress or damage, as well as in response to the developmental signals in multicellular organisms. Although historically studied in eukaryotes, it has been proposed that PCD also functions in prokaryotes, either during the developmental life cycle of certain bacteria or to remove damaged cells from a population in response to a wide variety of stresses. This review will examine several putative examples of bacterial PCD and summarize what is known about the molecular components of these systems. [source] New tools for labeling silica in living diatomsNEW PHYTOLOGIST, Issue 3 2008Julien Desclés Summary ,,Silicon biomineralization is a widespread mechanism found in several kingdoms that concerns both unicellular and multicellular organisms. As a result of genomic and molecular tools, diatoms have emerged as a good model for biomineralization studies and have provided most of the current knowledge on this process. However, the number of techniques available to study its dynamics at the cellular level is still rather limited. ,,Here, new probes were developed specifically to label the pre-existing or the newly synthesized silica frustule of several diatoms species. ,,It is shown that the LysoTracker Yellow HCK-123, which can be used to visualize silica frustules with common filter sets, presents an enhanced signal-to-noise ratio and allows details of the frustules to be imaged without of the use of ionophores. It is also demonstrated that methoxysilane derivatives can be coupled to fluorescein-5-isothiocyanate (FITC) to preferentially label the silica components of living cells. ,,The coupling of labeling procedures might help to address the challenging question of the process of frustule exocytosis. [source] Underground Vendobionta From NamibiaPALAEONTOLOGY, Issue 1 2002Dmitri Grazhdankin The late Precambrian fossils from Namibia have generally been regarded as soft-bodied organisms whose three-dimensional preservation resulted from smothering in fluidized sand. The sedimentological context of Pteridinium and Namalia within a sandstone bed, however, allows us to distinguish between two taphocoenoses: (1) winnowed, laterally collapsed, current-transported specimens accumulated as a lag deposit of turbidite-like flows, and (2) specimens ,floating' in the top part of an event bed with their vanes extending upwards to the upper bedding surface. The second taphocoenosis is interpreted as an in situ preserved ,infaunal' community. The immobile underground life habit and the bizarre modes of growth of Pteridinium and Namalia do not fit any extinct or modern group of multicellular organisms. Similar statements can be made for Ernietta and Rangea, thus reviving the Vendobionta hypothesis. [source] Tissue-specific mechanical microdissection of higher plantsPHYSIOLOGIA PLANTARUM, Issue 3 2006Marco Thome Higher plants are multicellular organisms, which exhibit a high degree of differentiation with respect to their anatomy, metabolism and gene expression. Analysing entire plants or organs results in an average of information of all tissues and cells included in the sample. In this way neither physiological processes nor gene expression can be attributed to particular tissues. For revealing the contributions of specific tissues to the overall metabolism and the gene expression, highly spatially resoluted cell sampling is a prerequisite. Here, mechanical microdissection (MMD), a low cost and easy to handle alternative to existing sampling techniques (e.g. laser-assisted microdissection or glass capillary,based sampling) was tested on several plant species (Arabidopsis thaliana L., Cucurbita maxima Duch., Hordeum vulgare L. and Pelargonium hybrid cultivar ,Graveolens'). The applicability and potential of MMD for separating tissues from different organs of these plants was demonstrated. Furthermore, A. thaliana samples were, as examples, tested for their RNA quality by reverse transcription,PCR and for tissue specificity by amplifying messenger RNA of tissue marker genes. [source] Phylogenetic and transcriptional analysis of a strictosidine synthase-like gene family in Arabidopsis thaliana reveals involvement in plant defence responsesPLANT BIOLOGY, Issue 1 2009M. M. Sohani Abstract Protein domains with similarity to plant strictosidine synthase-like (SSL) sequences have been uncovered in the genomes of all multicellular organisms sequenced so far and are known to play a role in animal immune responses. Among several distinct groups of Arabidopsis thaliana SSL sequences, four genes (AtSSL4,AtSSL7) arranged in tandem on chromosome 3 show more similarity to SSL genes from Drosophila melanogaster and Caenorhabditis elegans than to other Arabidopsis SSL genes. To examine whether any of the four AtSSL genes are immune-inducible, we analysed the expression of each of the four AtSSL genes after exposure to microbial pathogens, wounding and plant defence elicitors using real-time quantitative RT-PCR, Northern blot hybridisation and Western blot analysis with antibodies raised against recombinant AtSSL proteins. While the AtSSL4 gene was constitutively expressed and not significantly induced by any treatment, the other three AtSSL genes were induced to various degrees by plant defence signalling compounds, such as salicylic acid, methyl jasmonate and ethylene, as well as by wounding and exposure to the plant pathogens Alternaria brassicicola and cucumber mosaic virus. Our data demonstrate that the four SSL-coding genes are regulated individually, suggesting specific roles in basal (SSL4) and inducible (SSL5-7) plant defence mechanisms. [source] Two novel neuropeptides in innervation of the salivary glands of the black-legged tick, Ixodes scapularis: Myoinhibitory peptide and SIFamideTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2009Ladislav The peptidergic signaling system is an ancient cell,cell communication mechanism that is involved in numerous behavioral and physiological events in multicellular organisms. We identified two novel neuropeptides in the neuronal projections innervating the salivary glands of the black-legged tick, Ixodes scapularis (Say, 1821). Myoinhibitory peptide (MIP) and SIFamide immunoreactivities were colocalized in the protocerebral cells and their projections terminating on specific cells of salivary gland acini (types II and III). Immunoreactive substances were identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis: a 1,321.6-Da peptide with the sequence typical for MIP (ASDWNRLSGMWamide) and a 1,395.7-Da SIFamide (AYRKPPFNGSIFamide), which are highly conserved among arthropods. Genes encoding these peptides were identified in the available Ixodes genome and expressed sequence tag (EST) database. In addition, the cDNA encoding the MIP prepropeptide was isolated by rapid amplification of cDNA ends (RACE). In this report, we describe the anatomical structure of specific central neurons innervating salivary gland acini and identify different neuropeptides and their precursors expressed by these neurons. Our data provide evidence for neural control of salivary gland by MIP and SIFamide from the synganglion, thus lending a basis for functional studies of these two distinct classes of neuropeptides. J. Comp. Neurol. 517:551,563, 2009. © 2009 Wiley-Liss, Inc. 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