Life Cycle (life + cycle)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Life Cycle

  • complete life cycle
  • complex life cycle
  • entire life cycle
  • family life cycle
  • knowledge life cycle
  • parasite life cycle
  • plant life cycle
  • product life cycle
  • short life cycle
  • viral life cycle
  • virus life cycle
  • whole life cycle

  • Terms modified by Life Cycle

  • life cycle analysis
  • life cycle assessment
  • life cycle cost
  • life cycle inventory
  • life cycle model
  • life cycle stage

  • Selected Abstracts


    JOURNAL OF PHYCOLOGY, Issue 5 2010
    Karina M. Michetti
    The diplobiontic,haplodiplontic life cycle with alternating isomorphic generations in Stigeoclonium tenue (C. Agardh) Kütz. is described for the first time. Sporophytes (2n = 10) arise from tetraflagellate zoospores that are produced by meiosis. Sporic meiosis might be inferred from the cruciform divisions formed during zoosporogenesis and is confirmed through observations of prophase I substages. Zoospores do not germinate directly but produce a haploid cyst that germinates to give rise to a gametophyte (n = 5). Gametophytes produce biflagellate isogametes, which fuse to produce zygotes that germinate by mitosis into the sporophytic stage. Gametophytes and sporophytes reproduce asexually both via mitotic tetraflagellate zoospores and by thallus fragmentation. Results from this study indicate that both the cosmopolitan distribution and dominance of S. tenue in many periphytic communities might be due to its multiple reproductive strategies. [source]


    JOURNAL OF PHYCOLOGY, Issue 5 2010
    Steffi Gaebler-Schwarz
    Few members of the well-studied marine phytoplankton taxa have such a complex and polymorphic life cycle as the genus Phaeocystis. However, despite the ecological and biogeochemical importance of Phaeocystis blooms, the life cycle of the major bloom-forming species of this genus remains illusive and poorly resolved. At least six different life stages and up to 15 different functional components of the life cycle have been proposed. Our culture and field observations indicate that there is a previously unrecognized stage in the life cycle of P. antarctica G. Karst. This stage comprises nonmotile cells that range in size from ,4.2 to 9.8 ,m in diameter and form aggregates in which interstitial spaces between cells are small or absent. The aggregates (hereafter called attached aggregates, AAs) adhere to available surfaces. In field samples, small AAs, surrounded by a colony skin, adopt an epiphytic lifestyle and adhere in most cases to setae or spines of diatoms. These AAs, either directly or via other life stages, produce the colonial life stage. Culture studies indicate that bloom-forming, colonial stages release flagellates (microzoospores) that fuse and form AAs, which can proliferate on the bottom of culture vessels and can eventually reform free-floating colonies. We propose that these AAs are a new stage in the life cycle of P. antarctica, which we believe to be the zygote, thus documenting sexual reproduction in this species for the first time. [source]


    JOURNAL OF PHYCOLOGY, Issue 1 2008
    Naoji Yubuki
    Life cycle and perennation of a colorless chrysophyte, Spumella sp., isolated from an ephemeral ditch were investigated. From a single resting cyst (statospore), only one nonmotile cell germinated. Shortly after germination, the cell generated flagella, started to swim, and formed a gelatinous sphere. The cell itself retained the ability to swim within the sphere. Cells fed on bacteria inhabiting the sphere and grew by longitudinal binary cell division very rapidly. The gelatinous sphere gradually enlarged as the number of cells increased. When it reached maximum size (,500 ,m in diameter), the gelatinous substance of the sphere weakened, and the sphere gradually broke into several pieces, forming cleavages between them. Cells swam away through the cleavages. Five to ,40 swimming cells soon gathered and formed a swarm. In the swarm, some cells cannibalized other sibling cells and enlarged, resulting in giant cells that were two to three times larger in diameter than ordinary cells. The giant cells soon started statospore formation. Statospore formation was independent of any changes of environmental factors, such as increase or decrease in temperature or changes in nutrient or light levels, which are known to induce resting-cyst formation in other groups of algae and protists. Statospore formation started when cells divided 15 to 16 times after germination. This is congruent with the idea that statospore formation in planktonic chrysophytes directly depends on cell density. An extraordinarily high growth rate and cannibalism involved in the initiation of statospore formation are interpreted as adaptations to achieve the perennation in ephemeral aquatic environments. [source]


    JOURNAL OF PHYCOLOGY, Issue 4 2002
    A new species of Gonyaulax, here named Gonyaulax baltica sp. nov., has been isolated from sediment samples from the southeastern Baltic. Culture strains were established from individually isolated cysts, and cyst formation was induced in a nitrogen-depleted medium. Although G. baltica cysts are similar to some forms attributed to Spiniferites bulloideus and the motile stage of G. baltica has affinities with G. spinifera, the combination of features of cyst and motile stage of G. baltica is unique. The culture strains were able to grow at salinity levels from 5 to 55 psu and formed cysts from 10 to 50 psu. Cultures at each salinity level were grown at 12, 16, and 20° C. Temperature- and salinity-controlled morphological variability was found in the resting cysts. Central body size varied with temperature and salinity, and process length varied with salinity. Cysts that formed at extreme salinity levels displayed lower average process length than cysts formed at intermediate salinity levels, and central body length and width were lowest at higher temperature and lower salinity. Models for the relationship between central body size and temperature/salinity and process length and salinity have been developed and may be used to determine relative paleosalinity and paleotemperature levels. Our results on salinity-dependent process length confirm earlier reports on short-spined cysts of this species found in low salinity environments, and the model makes it possible to attempt to quantify past salinity levels. [source]

    Knowledge Life Cycle, Knowledge Inventory, and Knowledge Acquisition Strategies,

    DECISION SCIENCES, Issue 1 2010
    Andrew N. K. Chen
    ABSTRACT For a knowledge- and skill-centric organization, the process of knowledge management encompasses three important and closely related elements: (i) task assignments, (ii) knowledge acquisition through training, and (iii) maintaining a proper level of knowledge inventory among the existing workforce. Trade-off on choices between profit maximization in the short run and agility and flexibility in the long term is a vexing problem in knowledge management. In this study, we examine the effects of different training strategies on short-term operational efficiency and long-term workforce flexibility. We address our research objective by developing a computational model for task and training assignment in a dynamic knowledge environment consisting of multiple distinct knowledge dimensions. Overall, we find that organizational slack is an important variable in determining the effectiveness of training strategies. Training strategies focused on the most recent skills are found to be the preferred option in most of the considered scenarios. Interestingly, increased efficiencies in training can actually create preference conflict between employees and the firm. Our findings indicate that firms facing longer knowledge life cycles, higher slack in workforce capacity, and better training efficiencies actually face more difficult challenges in knowledge management. [source]

    Consumption Over the Life Cycle

    ECONOMETRICA, Issue 1 2002
    Pierre-Olivier Gourinchas
    This paper estimates a structural model of optimal life-cycle consumption expenditures in the presence of realistic labor income uncertainty. We employ synthetic cohort techniques and Consumer Expenditure Survey data to construct average age-profiles of consumption and income over the working lives of typical households across different education and occupation groups. The model fits the profiles quite well. In addition to providing reasonable estimates of the discount rate and risk aversion, we find that consumer behavior changes strikingly over the life cycle. Young consumers behave as buffer-stock agents. Around age 40, the typical household starts accumulating liquid assets for retirement and its behavior mimics more closely that of a certainty equivalent consumer. Our methodology provides a natural decomposition of saving and wealth into its precautionary and life-cycle components. [source]

    Life Cycle and Cohort Productivity in Economic Research: The Case of Germany

    Michael Rauber
    Research productivity; life cycles; cohort effects Abstract. We examine the research productivity of German academic economists over their life cycles. It turns out that the career patterns of research productivity as measured by journal publications are characterized by marked cohort effects. Moreover, the life cycles of younger German economists are hump shaped and resemble the life cycles identified for US economists, whereas the life cycles of older German economists are much flatter. Finally, we find that not only productivity, but also research quality follows distinct life cycles. Our study employs econometric techniques that are likely to produce estimates that are more trustworthy than previous estimates. [source]

    Life Cycle, Feeding and Production of Isoptena serricornis(Pictet, 1841) (Plecoptera, Chloroperlidae)

    Abstract Some aspects of the biology and ecology (life cycle, feeding and production) of a population of Isoptena serricornis in the Rudava River (Slovakia) are studied, reported and discussed. The life cycle is annual, with slow growth in autumn-winter and fast growth in late summer and spring. The growth decreased two weeks before the Fall Equinox and increased two weeks after the Spring Equinox. The flight period spans from the end of May to the beginning of July. The presence of large sand particles in the gut of all studied nymphs is of note, and indicates that I. serricornis acts as a deposit-collector species. Nymphal food is principally composed of detritus, unicellular organisms and, in nymphs of intermediate or large size, Chironomidae larvae. Adult food is composed fundamentally of different types of pollen grains. Males usually have lower food content than females. Annual production of this species (,694,750 mg · m,2) is very high in relation to other previously studied Chloroperlidae. This is probably largely responsible for I. serricornis being one of the most abundant components of the macroinvertebrate community in its habitat in the Rudava River. A negative correlation between production and temperature was observed. [source]

    Psychosocial Stages and the Accessibility of Autobiographical Memories Across the Life Cycle

    Martin A. Conway
    Memories were classified in terms of the psychosocial stages to which their content corresponded. For the majority of memories it was found that age at encoding corresponded to when specific psychosocial stages would have been most likely to have occurred. In a second experiment older adults recalled memories to cues drawn from psychosocial stages and the same pattern of findings was observed. These findings demonstrate that the goals of the self play a major role in both the encoding and accessibility of autobiographical memories, and they also provide support for Erikson's psychosocial theory of development (1950, 1997). [source]

    Are There Differences in the Health, Socio-economic Status Relationship over the Life Cycle?

    LABOUR, Issue 1 2008
    Evidence from Germany
    This paper, however, examines the effect of SES on health across different age groups. Using data from the German Socio-Economic Panel and controlling for health,SES endogeneity, we find that the health,income relationship does vary across the life cycle and between genders and different labor force status, with the impact of income on health relatively more pronounced for younger cohorts. The unemployed also have lower levels of health at all levels of income. [source]

    Children's Economic Roles in the Maya Family Life Cycle: Cain, Caldwell, and Chayanov Revisited

    Ronald D. Lee
    This article examines the relationship between household demographic pressure and interage transfers for a group of Maya subsistence agriculturists in Yucatán, Mexico. The authors use data from a field study conducted in 1992,93 on individual time allocation, relative productivity by age and sex, and caloric costs of activities to estimate age schedules of average consumption and production. Using these, they investigate the net costs of children to their parents and find that children have a negative net asset value up to the time they leave home. The direction of net wealth flows in this group is downward, from older to younger, and in economic terms the internal rate of return to children is highly negative up to the time they leave home. Nonetheless, children play a critically important role in the family's economic life cycle. On average, girls offset 76 percent of their consumption costs before leaving home at age 19, and boys offset 82 percent before leaving home at 22. Without the contributions from children as a group, parents would have to double or triple their work effort during part of the family life cycle if they were to raise the same number of children. By the thirteenth year of the family life cycle, children as a group produce more than half of what they consume in every year, and after the twentieth year children produce more than 80 percent of what they as a group consume. The authors also find that the elderly in the sample, ages 50 to 65, produce more than they consume. Thus while children have a negative net asset value to parents, the timing of their children's economic contribution across the family life cycle plays a key role in underwriting the cost of large families. [source]

    Order Beyond Crisis: Organizing Considerations Across the Public Service Configuration Life Cycle

    Eva M. Witesman
    This article responds to the preceding paper by Stephanie Moulton and Charles Wise, critiquing the dimensions that those authors use as organizing guides in the delivery of public services through public,private institutional configurations, including the evaluation of the Troubled Asset Relief Program (TARP). In this essay, Eva M. Witesman proposes a modification to the framework and provides suggestions for future research. [source]

    A journey along the 21 CFR Part 11 Life Cycle,

    Richard M. Siconolfi
    Abstract The Food and Drug Administration's (FDA) Guidance to Industry on 21 Code of Federal Regulations (CFR) Part 11 attempts to explain how industry can develop work processes that allow flexibility with this regulation without compromising compliance. However, to take advantage of this flexibility, our company needed to clearly understand the impact this guidance could have on our current work processes. We focused our attention on two specific areas: (1) developing and deploying a risk assessment and management process, and (2) revising our Part 11 Life Cycle for computerized systems. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Paranucleospora theridion n. gen., n. sp. (Microsporidia, Enterocytozoonidae) with a Life Cycle in the Salmon Louse (Lepeophtheirus salmonis, Copepoda) and Atlantic Salmon (Salmo salar)

    ABSTRACT. Paranucleospora theridion n. gen, n. sp., infecting both Atlantic salmon (Salmo salar) and its copepod parasite Lepeophtheirus salmonis is described. The microsporidian exhibits nuclei in diplokaryotic arrangement during all known life-cycle stages in salmon, but only in the merogonal stages and early sporogonal stage in salmon lice. All developmental stages of P. theridion are in direct contact with the host cell cytoplasm or nucleoplasm. In salmon, two developmental cycles were observed, producing spores in the cytoplasm of phagocytes or epidermal cells (Cycle-I) and in the nuclei of epidermal cells (Cycle-II), respectively. Cycle-I spores are small and thin walled with a short polar tube, and are believed to be autoinfective. The larger oval intranuclear Cycle-II spores have a thick endospore and a longer polar tube, and are probably responsible for transmission from salmon to L. salmonis. Parasite development in the salmon louse occurs in several different cell types that may be extremely hypertrophied due to P. theridion proliferation. Diplokaryotic merogony precedes monokaryotic sporogony. The rounded spores produced are comparable to the intranuclear spores in the salmon in most aspects, and likely transmit the infection to salmon. Phylogenetic analysis of P. theridion partial rDNA sequences place the parasite in a position between Nucleospora salmonis and Enterocytozoon bieneusi. Based on characteristics of the morphology, unique development involving a vertebrate fish as well as a crustacean ectoparasite host, and the results of the phylogenetic analyses it is suggested that P. theridion should be given status as a new species in a new genus. [source]

    The Unique Adaptation of the Life Cycle of the Coelomic Gregarine Diplauxis hatti to its Host Perinereis cultrifera (Annelida, Polychaeta): an Experimental and Ultrastructural Study

    ABSTRACT. The coelomic gregarine Diplauxis hatti exhibits a unique adaptation of its life cycle to its polychaete host Perinereis cultrifera. Experimental and ultrastructural observations on natural populations from the English Channel showed that release of parasite spores is concomitant with the polychaete spawning. As the development of P. cultrifera is direct, the notochete larva ingest parts of the jelly coat covered with numerous sporocysts of D. hatti during hatching. Transepithelial migration of the sporozoites takes place in the gut of three- or four-segment notochete larvae and syzygies of about 20 ,m are observed in the coelom. Growth of these young syzygies is slow: after 18,24 mo they reach only 60,70 ,m. They exhibit active pendular movements. In the English Channel, female and male gametogenesis of P. cultrifera begins at 19 mo and 2 yr, respectively; the somatic transformations (epitoky) in the last 4 mo of their 3-year life. During epitoky, the syzygies undergo an impressive growth and reach 700,800 ,m within a few weeks. A shift from pendular to active peristaltic motility is observed when the syzygies reach 200,250 ,m. When gamogony occurs, syncytial nuclear divisions are initiated and cellularization produces hundred to thousands of male and female gametes of similar size. The male gametes exhibit a flagellum with 3+0 axoneme. The mixing of the gametes ("danse des gametes") and fertilization are observed during 4,5 h. Zygotes differentiate sporoblasts with eight sporozoites. The sporozoites exhibit the canonical structure of Apicomplexa, a polarized cell with micronemes and rhoptries. [source]

    Managing the Political Life Cycle of Regulation in the UK and German Telecommunication Sectors

    David Coen
    This article investigates how the relationship between regulators and stakeholders evolves as a function of market developments and political learning. Drawing on a comparative case study of the UK and German telecommunication sector, the paper illustrates how regulators constrained by administrative and business traditions have asserted their discretion over politicians by developing sophisticated political relationship with a wide range of stakeholders. The paper concludes that while regulators have undoubtedly diverged from the initial delegation of powers, there is little evidence to suggest that European regulators will converge on a single regulatory model. [source]

    Life cycle of Phacellophora camtschatica (Cnidaria: Scyphozoa)

    Chad L. Widmer
    Abstract. Gelatinous zooplankton play important roles in marine ecosystems and at times can have significant impacts on human activities. Many scyphozoans have enigmatic life cycles and the specific habitat for benthic life history stages is unknown. This is especially true for many of the large surface-cruising scyphomedusae of the northeast Pacific Ocean. Phacellophora camtschatica belongs to the family Ulmaridae and is known to have scyphistomae in the life history. However, the life cycle of P. camtschatica has not been formally described. Here the life cycle of members of P. camtschatica is described based on laboratory observations and compared with early life history stages in the scyphomedusa Aurelia labiata. [source]


    JOURNAL OF PHYCOLOGY, Issue 1 2008
    Naoji Yubuki
    Life cycle and perennation of a colorless chrysophyte, Spumella sp., isolated from an ephemeral ditch were investigated. From a single resting cyst (statospore), only one nonmotile cell germinated. Shortly after germination, the cell generated flagella, started to swim, and formed a gelatinous sphere. The cell itself retained the ability to swim within the sphere. Cells fed on bacteria inhabiting the sphere and grew by longitudinal binary cell division very rapidly. The gelatinous sphere gradually enlarged as the number of cells increased. When it reached maximum size (,500 ,m in diameter), the gelatinous substance of the sphere weakened, and the sphere gradually broke into several pieces, forming cleavages between them. Cells swam away through the cleavages. Five to ,40 swimming cells soon gathered and formed a swarm. In the swarm, some cells cannibalized other sibling cells and enlarged, resulting in giant cells that were two to three times larger in diameter than ordinary cells. The giant cells soon started statospore formation. Statospore formation was independent of any changes of environmental factors, such as increase or decrease in temperature or changes in nutrient or light levels, which are known to induce resting-cyst formation in other groups of algae and protists. Statospore formation started when cells divided 15 to 16 times after germination. This is congruent with the idea that statospore formation in planktonic chrysophytes directly depends on cell density. An extraordinarily high growth rate and cannibalism involved in the initiation of statospore formation are interpreted as adaptations to achieve the perennation in ephemeral aquatic environments. [source]

    Macrosiphum on Knautia in Europe: biology, morphology and systematics, including new synonymy (Hemiptera, Aphididae)

    Rimantas Rakauskas
    Abstract Life cycle, host specificity and biogeografical data revealed only two species of the genus Macrosiphum L. living on Knautia spp. in Europe: M. rosae (L.) and M. knautiae Holman. Morphological analysis of all morphs of both species was performed and modified key to summer morphs and males presented. Macrosiphum silvaticum Meier, 1985 is synonymized with M. knautiae Holman, 1972. Separation of the Moravian, Alpine or Baltic populations of M. knautiae as a separate subspecies is not reasonable for the present. [source]

    Life cycle of the QBO-modulated 11-year solar cycle signals in the Northern Hemispheric winter

    Hua Lu
    Abstract This paper provides some insights on the quasi-biennial oscillation (QBO) modulated 11-year solar cycle (11-yr SC) signals in Northern Hemisphere (NH) winter temperature and zonal wind. Daily ERA-40 Reanalysis and ECMWF Operational data for the period of 1958,2006 were used to examine the seasonal evolution of the QBO-solar cycle relationship at various pressure levels up to the stratopause. The results show that the solar signals in the NH winter extratropics are indeed QBO-phase dependent, moving poleward and downward as winter progresses with a faster descent rate under westerly QBO than under easterly QBO. In the stratosphere, the signals are highly significant in late January to early March and have a life span of ,30,50 days. Under westerly QBO, the stratospheric solar signals clearly lead and connect to those in the troposphere in late March and early April where they have a life span of ,10 days. As the structure changes considerably from the upper stratosphere to the lower troposphere, the exact month when the maximum solar signals occur depends largely on the altitude chosen. For the low-latitude stratosphere, our analysis supports a vertical double-peaked structure of positive signature of the 11-yr SC in temperature, and demonstrates that this structure is further modulated by the QBO. These solar signals have a longer life span (,3,4 months) in comparison to those in the extratropics. The solar signals in the lower stratosphere are stronger in early winter but weaker in late winter, while the reverse holds in the upper stratosphere. Copyright © 2009 Royal Meteorological Society [source]

    Life histories of Eucalanus bungii and Neocalanus cristatus (Copepoda: Calanoida) in the western subarctic Pacific Ocean

    Abstract Life cycles of the large suspension-feeding copepods, Eucalanus bungii and Neocalanus cristatus were investigated by seasonal sampling in the western subarctic Pacific. Eucalanus bungii has a diapause from August to March at copepodite stages between copepodite 3 (C3) and C6 female. We propose that individuals with early birth dates are young of overwintering C5 and C6-females that develop to C4 in their birth year, while individuals with late birth dates are young of overwintering C4 that develop to C3 in their birth year. Thus, a majority of the population has annual generations alternating with biennial generations. Neocalanus cristatus showed life history almost identical to the population in the Alaskan gyre. Timing of the life cycle in N. cristatus is very close to that in the eastern subarctic gyre, but that of E. bungii is 2 months earlier than in the eastern subarctic. This difference is probably caused by the timing difference in the maximum primary production in the two areas and the plasticity of the life cycle strategy in E. bungii. [source]

    Association with host mitochondrial haplotypes suggests that feminizing microsporidia lack horizontal transmission

    J. E. Ironside
    Abstract The amphipod crustacean Gammarus duebeni hosts two feminizing microsporidian parasites, Nosema granulosis and Microsporidium sp. Samples of G. duebeni were collected from three sites on the Scottish island of Great Cumbrae and screened for microsporidia using polymerase chain reaction. Associations between the prevalence of the two feminizing parasites and haplotypes of the host mitochondrial gene cytochrome oxidase I (COI) were investigated. The prevalence of both parasites varied significantly among the host's COI haplotypes, suggesting that horizontal transmission is rare or absent in the life cycles of the feminizing microsporidia and that all transmission must therefore be vertical. Life cycles in which all transmission is vertical are common among bacterial parasites but have never before been demonstrated in Eukaryotic parasites. [source]

    Trust-based robust scheduling and runtime adaptation of scientific workflow

    Mingzhong Wang
    Abstract Robustness and reliability with respect to the successful completion of a schedule are crucial requirements for scheduling in scientific workflow management systems because service providers are becoming autonomous. We introduce a model to incorporate trust, which indicates the probability that a service agent will comply with its commitments to improve the predictability and stability of the schedule. To deal with exceptions during the execution of a schedule, we adapt and evolve the schedule at runtime by interleaving the processes of evaluating, scheduling, executing and monitoring in the life cycle of the workflow management. Experiments show that schedules maximizing participants' trust are more likely to survive and succeed in open and dynamic environments. The results also prove that the proposed approach of workflow evaluation can find the most robust execution flow efficiently, thus avoiding the need of scheduling every possible execution path in the workflow definition. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Necessity to establish new risk assessment and risk communication for human fetal exposure to multiple endocrine disruptors in Japan

    Emiko Todaka
    ABSTRACT, Our recent study clearly shows that fetuses are exposed to multiple chemicals including endocrine disruptors in Japan. Although the embryo and fetus stages are the most sensitive period to chemicals in humans' life cycle, the health effects of the chemicals such as endocrine disruptors to them are largely unknown. The conventional risk assessment method cannot assess the risk to fetuses precisely. Now we need a new risk assessment, in which the target is fetuses and not the adults, in addition to the conventional risk assessment At the same time, we also need a new strategy to practically eliminate the risk for the future generations. To make the strategy effective, we suggest a new approach to reduce the risk and avoid the possible adverse health effects, using primary, secondary and tertiary preventions as they are used in public health. We also suggest a new concept of "pre-primary prevention" to reduce the risk for fetuses. Furthermore, to make this method even more practical, we suggest a new risk communication method. In this paper, we present a framework of risk avoidance of multiple chemical exposure to fetuses. [source]

    Effects of Human Exclusion on Parasitism in Intertidal Food Webs of Central Chile

    Fissurella crassa; intermareal rocoso; parasitismo; Proctoeces lintoni; reservas marinas Abstract:,Numerous ecological studies have demonstrated the dramatic effects that humans have on coastal marine ecosystems. Consequently, marine reserves have been established to preserve biodiversity. Recent reviews show that this strategy has paid off because inside reserves, most species have rapidly increased in size and abundance. Even though these studies focused on free-living organisms and paid little attention to parasite populations, numerous authors support the hypothesis that parasitism levels could be good indicators of ecosystem stability. We examined harvesting effects on the dynamics of a parasitic trematode ( Proctoeces lintoni) that completes its life cycle in intertidal mussels ( Perumytilus purpuratus), keyhole limpets (Fissurella crassa), and clingfish ( Sicyases sanguineus). All of these species are directly or indirectly affected by humans. Prevalence and abundance of the trematode P. lintoni in the three host species were compared in four study sites that differed in the intensity of human harvest. Parasitism infection in limpets and mussels was significantly higher in areas protected from human harvesting than in open-access areas, which suggests a significant change in parasite dynamics inside reserves. Yet the average parasitic biomass found in the gonads of F. crassa did not differ between protected and open-access areas. These results show, then, that the parasite system responded by increasing infection rates in marine protected areas without implication for reproductive success of the intermediate host. Our findings show that the indirect effects of harvesting by humans on the embedded parasite communities of littoral ecosystems require further scientific investigation. Resumen:,Numerosos estudios ecológicos han demostrado los efectos dramáticos de la actividad humana sobre ecosistemas marinos costeros. Consecuentemente, se han establecido las reservas marinas para preservar la biodiversidad. Revisiones recientes muestran que esta estrategia es adecuada porque la mayoría de las especies dentro de las reservas han incrementado en tamaño y abundancia rápidamente. Aunque, estos estudios se han concentrado en organismos de vida libre y han puesto poca atención a poblaciones de parásitos, numerosos autores apoyan la hipótesis de que los niveles de parasitismo pueden ser buenos indicadores de la estabilidad del ecosistema. Examinamos los efectos de pesquería artesanal sobre la dinámica de un trematodo parásito ( Proctoeces lintoni) que completa su ciclo de vida en mitíldos intermareales ( Perumytilus purpuratus), lapas ( Fissurella crassa) y Sicyases sanguineus, los cuales son afectados por humanos directa o indirectamente. La prevalencia y abundancia del trematodo P. lintoni en las tres especies de hospedadores fueron comparadas en cuatro sitios de estudio que difieren en la intensidad de recolecta por humanos. La infección parasitaria en lapas y mitíldos fue significativamente mayor en áreas protegidas que en áreas de libre acceso, lo que sugiere un cambio significativo en la dinámica del parásito dentro de las reservas, pero, la biomasa promedio de parásitos en gónadas de F. crassa no fue diferente entre áreas protegidas y de libre acceso. Por lo tanto, los resultados muestran que el sistema parásito respondió incrementando tasas de infección en áreas marinas protegidas sin consecuencias sobre el éxito reproductivo del ho spedador intermediario. Nuestros hallazgos muestran que se requiere más investigación científica de los efectos indirectos de los humanos sobre las comunidades de parásitos en ecosistemas litorales. [source]

    Evaluation of the skin sensitizing potency of chemicals by using the existing methods and considerations of relevance for elicitation

    CONTACT DERMATITIS, Issue 1 2005
    David A. Basketter
    The Technical Committee of Classification and Labelling dealing with harmonized classification of substances and classification criteria under Directive 67/548/EEC on behalf of the European Commission nominated an expert group on skin sensitization in order to investigate further the possibility for potency consideration of skin sensitizers for future development of the classification criteria. All substances and preparations should be classified on the basis of their intrinsic properties and should be labelled accordingly with the rules set up in the Directive 67/548/EEC. The classification should be the same under their full life cycle and in the case that there is no harmonized classification the substance or preparation should be self-classified by the manufacturer in accordance with the same criteria. The Directive does not apply to certain preparations in the finished state, such as medical products, cosmetics, food and feeding stuffs, which are subject to specific community legislation. The main questions that are answered in this report are whether it would be possible to give detailed guidance on how to grade allergen potency based on the existing methods, whether such grading could be translated into practical thresholds and whether these could be set for both induction and elicitation. Examples are given for substances falling into various potency groups for skin sensitization relating to results from the local lymph node assay, the guinea pig maximization test, the Buehler method and human experience. [source]

    Managing stakeholders or the environment?

    The challenge of relating indicators in practice
    Abstract Many organizations present their environmental work in the form of annual reports and use the indicators in them for follow-up. However, internal communication and management is needed for environmental improvements. The indicators found in reports may be suitable for external communication, but are they also suitable internally and operationally? This article reviews the existing literature on environmental indicators. With the help of an operational approach, from organisation theory, and a life-cycle approach, indicators are analysed. The analysis shows that formulating indicators for internal management is not an easy task; available guidelines are of little help. It is concluded that the environment can be managed internally by relating indicators. Therefore, an additional set of indicators for internal management and a wider responsibility for the life cycle are recommended. The analysis and recommendations are illustrated with examples drawn from the field of property management. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment. [source]

    Limited LCAs of pharmaceutical products: merits and limitations of an environmental management tool

    Anne Marie de Jonge
    This article explores both the merits and the limitations of life cycle analysis (LCA) as an environmental management tool in the framework of the pharmaceutical industry. In this study, limited LCAs in the form of product lifecycle-oriented energy balances were established for two rather different pharmaceutical products. Primary energy requirements served as the single indicator for the products' direct and indirect environmental impacts. The functional units of the products were defined as the one year treatments of average patients. The results of the case studies indicate that the portion of the active substance in the pharmaceutical end product is an important predictor for the breakdown of energy requirements and thus environmental impacts over the life cycle. Despite its limitations, the energy balances provide first-hand indications of where eco-efficiency measures should be taken. In this sense, the limited LCAs served as a useful environmental management tool. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment [source]

    Branch-and-Price Methods for Prescribing Profitable Upgrades of High-Technology Products with Stochastic Demands*

    DECISION SCIENCES, Issue 1 2004
    Purushothaman Damodaran
    ABSTRACT This paper develops a model that can be used as a decision support aid, helping manufacturers make profitable decisions in upgrading the features of a family of high-technology products over its life cycle. The model integrates various organizations in the enterprise: product design, marketing, manufacturing, production planning, and supply chain management. Customer demand is assumed random and this uncertainty is addressed using scenario analysis. A branch-and-price (B&P) solution approach is devised to optimize the stochastic problem effectively. Sets of random instances are generated to evaluate the effectiveness of our solution approach in comparison with that of commercial software on the basis of run time. Computational results indicate that our approach outperforms commercial software on all of our test problems and is capable of solving practical problems in reasonable run time. We present several examples to demonstrate how managers can use our models to answer "what if" questions. [source]

    Muscle stem cells and model systems for their investigation

    Nicolas Figeac
    Abstract Stem cells are characterized by their clonal ability both to generate differentiated progeny and to undergo self-renewal. Studies of adult mammalian organs have revealed stem cells in practically every tissue. In the adult skeletal muscle, satellite cells are the primary muscle stem cells, responsible for postnatal muscle growth, hypertrophy, and regeneration. In the past decade, several molecular markers have been found that identify satellite cells in quiescent and activated states. However, despite their prime importance, surprisingly little is known about the biology of satellite cells, as their analysis was for a long time hampered by a lack of genetically amenable experimental models where their properties can be dissected. Here, we review how the embryonic origin of satellite cells was discovered using chick and mouse model systems and discuss how cells from other sources can contribute to muscle regeneration. We present evidence for evolutionarily conserved properties of muscle stem cells and their identification in lower vertebrates and in the fruit fly. In Drosophila, muscle stem cells called adult muscle precursors (AMP) can be identified in embryos and in larvae by persistent expression of a myogenic basic helix,loop,helix factor Twist. AMP cells play a crucial role in the Drosophila life cycle, allowing de novo formation and regeneration of adult musculature during metamorphosis. Based on the premise that AMPs represent satellite-like cells of the fruit fly, important insight into the biology of vertebrate muscle stem cells can be gained from genetic analysis in Drosophila. Developmental Dynamics 236:3332,3342, 2007. © 2007 Wiley-Liss, Inc. [source]