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At least 469 records · Page 26Linked to original sources
PubMed1990

Antibody isotype responses to the Schistosoma mansoni schistosomulum in the CBA/N mouse induced by different stages of the parasite life cycle.

During infection with Schistosoma mansoni the extent and nature of immune reactions against schistosomula may be influenced by responses to cross-reactive antigens in eggs or adult worms, and there is now extensive evidence for cross-reactivity between the different stages of the parasite life cycle. In this study IgM and IgG subclass antibodies produced in (CBA/N x Balb/c) F1 male and female mice were measured over a period of time following exposure to a chronic infection, to unisexual male cercariae or to irradiated larvae. Antibody levels were also measured following immunization with antigen preparations derived from adult worms, schistosomula or eggs. (CBA/N x Balb/c) F1 male mice exhibit an X-linked immune deficiency which results in an inability to respond to T-independent (TI) type 2 polysaccharides. Isotype levels were measured by ELISA to detergent-soluble schistosomulum antigen. Results showed that antigens on the different stages of the parasite life cycle have a qualitative influence on the antibody response to the larval surface, and that T-independent type 2 polysaccharides, particularly abundant in egg, exhibit antigen-directed isotype restriction in the form of IgM and IgG3 antibodies.

Animals↗
PubMed2001

The cytoskeleton and spatial control of cytokinesis in the plant life cycle.

One of the intriguing aspects of development in plants is the precise control of division plane and subsequent placement of walls resulting in the specific architecture of tissues and organs. The placement of walls can be directed by either of two microtubule cycles. The better known microtubule cycle is associated with control of the future division plane in meristematic growth where new cells become part of tissues. The future daughter domains are determined before the nucleus enters prophase and the future site of cytokinesis is marked by a preprophase band (PPB) of cortical microtubules. The spindle axis is then organized in accordance with the PPB and, following chromosome movement, a phragmoplast is initiated in the interzone and expands to join with parental walls at the site previously occupied by the PPB. The alternative microtubule cycle lacks both the hooplike cortical microtubules of interphase and the PPB. Wall placement is determined by a radial microtubule system that defines a domain of cytoplasm either containing a nucleus or destined to contain a nucleus (the nuclear cytoplasmic domain) and controls wall placement at its perimeter. This more flexible system allows for cytoplasmic polarization and migration of nuclei in coenocytes prior to cellularization. The uncoupling of cytokinesis from karyokinesis is a regular feature of the reproductive phase in plants and results in specific, often unusual, patterns of cells which reflect the position of nuclei at the time of cellularization (e.g., the arrangement of spores in a tetrad, cells of the male and female gametophytes of angiosperms, and the distinctive cellularization of endosperm). Thus, both microtubule cycles are required for completion of plant life cycles from bryophytes to angiosperms. In angiosperm seed development, the two methods of determining the boundaries of domains where walls will be deposited are operative side by side. Whereas the PPB cycle drives embryo development, the radial-microtubule-system cycle drives the common nuclear type of endosperm development from the syncytial stage through cellularization. However, a switch to the PPB cycle can occur in endosperm, as it does in barley, when peripheral cells divide to produce a multilayered aleurone. The triggers for the switch between microtubule cycles, which are currently unknown, are key to understanding plant development.

Arabidopsis↗
PubMed1995

Cell adhesion in the life cycle of Dictyostelium.

Three forms of cell adhesion determine the life cycle of Dictyostelium: i) adhesion of bacteria to the surface of the growing amoebae, as the prerequisite for phagocytosis; ii) cell-substrate adhesion, necessary for both locomotion of the amoebae and migration of the slug; iii) cell-cell adhesion, essential for transition from the unicellular to the multicellular stage. Intercellular adhesion has received the most attention, and fruitful approaches have been developed over the past 25 years to identify, purify and characterize cell adhesion molecules. The csA glycoprotein, in particular, which mediates adhesion during the aggregation stage, is one of the best defined cell adhesion molecules. The molecular components involved in phagocytosis and cell-substratum adhesion are less well understood, but the basis has been laid for a systematic investigation of both topics in the near future.

Animals↗
PubMed2005

Quantifying and reducing uncertainty in life cycle assessment using the Bayesian Monte Carlo method.

The traditional life cycle assessment (LCA) does not perform quantitative uncertainty analysis. However, without characterizing the associated uncertainty, the reliability of assessment results cannot be understood or ascertained. In this study, the Bayesian method, in combination with the Monte Carlo technique, is used to quantify and update the uncertainty in LCA results. A case study of applying the method to comparison of alternative waste treatment options in terms of global warming potential due to greenhouse gas emissions is presented. In the case study, the prior distributions of the parameters used for estimating emission inventory and environmental impact in LCA were based on the expert judgment from the intergovernmental panel on climate change (IPCC) guideline and were subsequently updated using the likelihood distributions resulting from both national statistic and site-specific data. The posterior uncertainty distribution of the LCA results was generated using Monte Carlo simulations with posterior parameter probability distributions. The results indicated that the incorporation of quantitative uncertainty analysis into LCA revealed more information than the deterministic LCA method, and the resulting decision may thus be different. In addition, in combination with the Monte Carlo simulation, calculations of correlation coefficients facilitated the identification of important parameters that had major influence to LCA results. Finally, by using national statistic data and site-specific information to update the prior uncertainty distribution, the resultant uncertainty associated with the LCA results could be reduced. A better informed decision can therefore be made based on the clearer and more complete comparison of options.

Bayes Theorem↗
PubMed1998

When a family member has a schizophrenic disorder: practice issues across the family life cycle.

Viewing individuals with schizophrenic disorders within a family life-cycle context promotes recognition of the range of family roles, particularly partnership and parenting roles, in clients' lives. Knowledge of clients' stage of family development allows practitioners to view the client more holistically--as a family member with roles and responsibilities--instead of as an isolated, ill individual. Gender differences--in family roles and in manifestation of the illness--are considered.

Age of Onset↗
PubMed1993

[Psychosocial development and problems in early adulthood: developmental psychological characterization of an important segment of the life cycle].

Young adulthood represents a genuine developmental phase in the life cycle. In its transitional position it shares many traits with the developmental process in youth and adulthood. Among its central developmental problems are: establishing a secure personal identity, forming mature friendships and mature intimate relationships, reorientation of family ties, building up a core of ideological values, selecting a long-term vocation, finding one's bearings, looking to the future. The perspective of "normative crisis" vs "continuous transformation" is discussed. Ths significance of the patterns of adaptation found in young adulthood for further psychosocial development is emphasized.

Adolescent↗
PubMed2001

Experimental infection of Atlantic salmon (Salmo salar) with marine Eubothrium sp. (Cestoda: Pseudophyllidea): observations on the life cycle, aspects of development and growth of the parasite.

The life cycle of marine Eubothrium sp. (Cestoda: Pseudophyllidea), from Atlantic salmon (Salmo salar L.) was experimentally completed in one year and included only one intermediate host (Acartia tonsa Dana) (Copepoda: Calanoida). Adult cestodes were collected from farmed salmon, and ripe eggs released by the cestodes were fed to Acartia tonsa. Ingested eggs hatched in the gut and the larvae developed in the haemocoel of the copepod for 15 days at 16 degrees C. A total of 170 seawater-reared salmon were exposed to infected copepods and the total prevalence of Eubothrium sp. in the salmon after infection was 95.3%, with a mean intensity of 15.0 (range 1-87). The infected salmon were kept in the laboratory where the growth of the cestodes was studied for eleven months. Mean length of the cestodes increased with time, but a large variation among the cestodes was observed. Growth and maturation of the cestodes were dependent on host size and the number of worms present in the intestine. No evidence of mortality of Eubothrium sp. was observed during the experimental period.

Animals↗
PubMedDate not supplied

[The role of Cytograpsus angulatus (Crustacea; Brachyura) in the life cycles of Microphallus szidati (Digenea; Microphallidae) and Falsifilicollis chasmagnathi (Acanthocephala; Filicollidae): various aspects of their ecological parasitology].

Based on a study of the larvae from two helminth species parasitizing the crab Cyrtograpsus angulatus Dana, 1851 (Microphallus szidati Martorelli, 1986 and Falsifilicollis chasmagnathi Holcman-Spector et al., 1977), from Mar chiquita lagoom (Argentina) together with the analyses of their life cycles and rates of prevalence, intensity and association coefficient (compared in definitive and intermediate host) the following conclusions have been reached: a) C. angulatus suns to be an excellent intermediate host in the life-cycles of the studied helminths; b) the size of the crabs and the occurrence of natural amputations in the females (Spivak & Politis, in press) appeared correlated with prevalence; c) in the studied crabs the prevalence for F. chasmagnathi is higher in males than in females; d) the intensity did not appear correlated with size and sex of the intermediate host; e) M. szidati and F. chasmagnathi are closely associated with the intermediate host; f) C. angulatus and Himantopus melanurus Vieillot, 1817 (Aves; Recurvirostridae) are reported as new intermediate and definitive hosts, respectively, for F. chasmagnathi; g) Chasmagnathus granulata Dana, 1851 (Crustacea; Brachyura) is reported as a new intermediate host for M. szidati.

Animals↗
PubMed2002

Life cycle inventory for municipal solid waste management.

Evaluating the environmental performance of municipal solid waste management options is a complex task. Part 1 of this study presents the municipal solid waste management program of the Pamplona Region in Spain, exploring the institutional, operational and economic factors of the program. In Part 2, alternative waste management scenarios that include the selective collection of organic material and composting are illustrated. The use of a Life Cycle Inventory model for waste management allows for the comparison of the environmental burdens of the different scenarios. This use of a Life Cycle Inventory model for solid waste management lets program managers and decision makers include energy use, final solid waste, and Greenhouse gas emissions in the decision making process. Additionally, the different management scenarios are evaluated on their ability to fulfil Pamplona regional objectives and meet European Packaging and Landfill Directive targets.

Cities↗
PubMed1999

Temperature sensitivity of two different steps in the viral life cycle of feline immunodeficiency virus.

Feline immunodeficiency virus (FIV) multiplication is totally blocked by incubation of infected cells at 41 degrees. This inhibition does not take place with a thermoresistant strain of FIV, designated m41, indicating the role played by the viral genome in temperature sensitivity. We have investigated the steps in the life cycle of wild-type FIV that are thermosensitive and found that they depend on the host cells infected. In CrFK cells, FIV replication was inhibited after the penetration step at 41 degrees. Synthesis of viral RNA and DNA was barely detectable and no viral antigen appeared in the extracellular medium. Nevertheless, viral multiplication resumed on incubation at 37 degrees, suggesting a state of latency at the elevated temperature. In peripheral blood mononuclear cells (PBMCs), the FIV cycle was inhibited at 41 degrees after the synthesis of viral DNA. Several viral mRNAs failed to appear as fully spliced products and no viral antigen was found in the extracellular medium. As in CrFK cells, viral multiplication occurred in PBMCs after a shift to the permissive temperature. These results suggest that at least two steps in the viral life cycle are sensitive to 41 degrees and that two different viral functions of the thermoresistant mutant m41 are modified to overcome temperature sensitivity.

Animals↗
PubMed1997

Treatment of major depression in later life: a life cycle perspective.

The goal of this article is to provide a life-cycle perspective on the treatment of major depressive episodes in later life. Our studies have suggested that older patients appear to benefit as much, though perhaps more slowly, than mid-life patients from acute combined treatment (nortriptyline+interpersonal psychotherapy) of major depression. Given also the apparently higher relapse rate among the elderly, however, continuation treatment needs to be vigorous and closely monitored. The occurrence of severe life events prior to the index episode and the co-existence of an anxiety disorder both appear to prolong treatment response times, while chronic medical burden per se neither compromises response rates nor prolongs time to response. Self-rated perception of health improves with remission of depression in the elderly. As in mid-life patients, both antidepressant medication (nortriptyline) and interpersonal psychotherapy appear to possess chronic efficacy with respect to the prevention of recurrent episodes and prolongation of wellness. Finally, treatment of depression in the elderly results in improved quality of life, especially in domains of well being and coping. Particular challenges in the treatment of elderly patients are noncompliance and the prevention of suicide. The latter is closely linked to feelings of hopelessness, and these may be persistent in some patients.

Aged↗
PubMed2002

Life cycle inventory for municipal solid waste management. Part 2: MSW management scenarios and modeling.

Evaluating the environmental performance of municipal solid waste management options is a complex task. Part 1 of this study presents the municipal solid waste management program of the Pamplona Region in Spain and explores the operational, economic, and environmental factors of the program. In Part 2, alternative waste management scenarios that include the selective collection of organic material and composting are illustrated. The use of a Life Cycle Inventory model for waste management allows for the comparison of the environmental burdens of the different scenarios. This use of a Life Cycle Inventory model for solid waste management lets program managers and decision makers include energy use, final solid waste, and Greenhouse gas emissions in the decision making process. Additionally, the different management scenarios are evaluated on their ability to fulfil Pamplona regional objectives and meet European Packaging and Landfill Directive targets.

Cities↗
PubMed2003

Life cycle of the temporary fish parasite, Gnathia africana (Crustacea: Isopoda: Gnathiidae).

Laboratory work was conducted to elucidate the life cycle of the South African gnathiid isopod, Gnathia africana Barnard, 1914. The natural fish hosts of this temporary parasite, the super klipfish Clinus superciliosus (Linnaeus, 1758), were exposed to gnathiid larvae in the laboratory. It was found that G. africana has three larval stages, consisting of three unfed (zuphea) and three fed (praniza) stages. First-, second- and third-stage zuphea larvae took an average of 2 h 18 min, 2 h 43 min and 10 h 8 min respectively to complete their feeding and the first- and second-stage praniza moulted at 8 and 10 days respectively into the next zuphea stage. Three to six days after its last blood meal, the sex of the third and final praniza stage could be determined by the presence of either a testis or two ovaries in the dorsal pereon. Male larvae moulted into adult males between 8 and 10 days post feeding. Female larvae moulted at approximately 17 days into adult females. Fertilisation of the eggs by the male took place within 24 hours of completion of the female moult. The development of the embryos and subsequent release of the young larvae between 15 and 23 days post fertilisation completed the cycle. This entire cycle took approximately 62 days in water temperatures of 20-25 degrees C.

Animals↗
PubMed1984

[Haplodiploidy of Oxyurida. Effects of this phenomenon in the life cycle].

Chromosome behavior during gametogenesis and early cleavage is studied in two species of Thelastomatidae (Oxyurida), Hammerschmidtiella sp. and Thelastoma sp., parasites of diplopods. Both species are shown to be haplodiploid: male with 4 Thelastoma) or 5 (Hammerschmidtiella) chromosomes and double this number in the corresponding female. Haplodiploidy is now known in the 4 families of the Oxyurida and the author concludes that this form of reproduction is characteristic of the entire order. The Oxyuridan life cycle seems simple: 2 moults in the egg, no intermediate host, no extra-intestinal migration. However, several findings (some quite recent) indicate that this life cycle is often complicated by phenomena very closely adapted to host biology. The following particularities are analysed: 1) male progenesis; 2) laying of eggs in agglomerated packets; 3) peri-anal egg deposition; 4) poecilogony; 5) spanandry; 6) traumatic extra-genital insemination; 7) thelytoky. In a final chapter the author relates these adaptations to host biology and attempts to explain how they may have come to be favoured by natural selection during the course of evolution.

Animals↗
PubMed1996

The role of Gag in human immunodeficiency virus type 1 virion morphogenesis and early steps of the viral life cycle.

The phenotypes of a series of mutant human immunodeficiency virus type 1 proviruses with linker insertion and deletion mutations within the gag coding region were characterized. These mutants, with mutations in the matrix, capsid, and p2 coding regions, produced replication-defective virion particles with defects in the early steps of the viral life cycle. To investigate this phenotype further, the abilities of mutant virion particles to enter T cells, initiate and complete reverse transcription, and transport the newly transcribed proviral DNA were investigated. Only 4 of 10 of the mutants appeared to make wild-type levels of viral DNA. Biochemical analyses of the mutants revealed the middle region of CA as being important in determining virion particle density and sedimentation in velocity gradients. This region also appears to be critical in determining the morphology of mature virion particles by electron microscopy. Particles with aberrant morphology were uninfectious, and only those mutants which displayed cone-shaped cores were capable of carrying out the early steps of the viral life cycle. Thus, the normal morphology of human immunodeficiency virus type 1 appears to be critical to infectivity.

Animals↗
PubMed2006

An improved calculation of the exergy of natural resources for exergetic life cycle assessment (ELCA).

The focus in environmental research is shifting from emission abatement to critical process analysis, including assessment of resource consumption. The exergy theory offers a thermodynamic methodology to account for the consumption of natural resources. However, exergy data on mineral resources available in the literature are inadequate to apply to exergetic life cycle analysis, due to incompleteness, inconsistencies, and a dated thermochemical basis. An uncertainty assessment of the data has to be performed as well. In this work, three recent thermochemical databases were applied to evaluate the chemical exergy of 85 elements and 73 minerals, 21 of which had not yet been quantified in the literature. The process required the choice of a new reference species for aluminum. Muscovite was selected, giving rise to a chemical exergy of 809.4 kJ/mol for aluminum. The theory proved to be robust for the exergy of chemical elements, as exergy values differing by 1.2% on average from most recent literature were found. On the contrary, the exergy values for minerals differed by factors up to 14 from literature values, due to the application of recent thermochemical values and consistently selected reference species. The consistent dataset of this work will enable straightforward resource intake evaluation through an exergetic life cycle assessment.

Aluminum↗
PubMed2006

Reevaluation of the life cycle of Tuber magnatum.

Tuber spp. are ectomycorrhizal ascomycetes that produce ascocarps known as truffles. Basic aspects of Tuber biology have yet to be fully elucidated. In particular, there are conflicting hypotheses concerning the mating system and the ploidy level of the mycorrhizal and truffle hyphae. We used polymorphic microsatellites to compare the allelic configurations of asci with those from the network of the surrounding hyphae in single Tuber magnatum truffles. We then used these truffles to inoculate host plants and evaluated the microsatellite configurations of the resulting mycorrhizal root tips. These analyses provide direct evidence that T. magnatum outcrosses and that its life cycle is predominantly haploid. In addition to its scientific significance, this basic understanding of the T. magnatum life cycle may have practical importance in developing strategies to obtain and select nursery-produced mycorrhizal plants as well as in the management of artificial plantations of this and other Tuber spp.

Ascomycota↗
PubMed2006

The intestinal life cycle of Bacillus subtilis and close relatives.

Bacillus subtilis is considered a soil organism for which endospore formation provides a means to ensure long-term survival in the environment. We have addressed here the question of what happens to a spore when ingested. Spores displaying on their surface a heterologous antigen, tetanus toxin fragment C (TTFC), were shown to generate anti-TTFC responses not to the antigen contained in the primary oral inoculum but to those displayed on spores that had germinated and then resporulated. We then used reverse transcription-PCR to determine expression of vegetative genes and sporulation-specific genes in the mouse gut following oral dosing with spores. Significant levels of germination and sporulation were documented. Using natural isolates of B. subtilis that could form biofilms, we showed that these strains could persist in the mouse gut for significantly longer than the laboratory strain. Moreover, these isolates could grow and sporulate anaerobically and exhibited a novel phenomenon of being able to form spores in almost half the time required for the laboratory isolate. This suggests that spores are not transient passengers of the gastrointestinal tract but have adapted to carry out their entire life cycle within this environment. This is the first report showing an intestinal life cycle of B. subtilis and suggests that other Bacillus species could also be members of the gut microflora.

Adult↗