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PubMed2006

Transcriptional profiling of the Bacillus anthracis life cycle in vitro and an implied model for regulation of spore formation.

The life cycle of Bacillus anthracis includes both vegetative and endospore morphologies which alternate based on nutrient availability, and there is considerable evidence indicating that the ability of this organism to cause anthrax depends on its ability to progress through this life cycle in a regulated manner. Here we report the use of a custom B. anthracis GeneChip in defining the gene expression patterns that occur throughout the entire life cycle in vitro. Nearly 5,000 genes were expressed in five distinct waves of transcription as the bacteria progressed from germination through sporulation, and we identified a specific set of functions represented within each wave. We also used these data to define the temporal expression of the spore proteome, and in doing so we have demonstrated that much of the spore's protein content is not synthesized de novo during sporulation but rather is packaged from preexisting stocks. We explored several potential mechanisms by which the cell could control which proteins are packaged into the developing spore, and our analyses were most consistent with a model in which B. anthracis regulates the composition of the spore proteome based on protein stability. This study is by far the most comprehensive survey yet of the B. anthracis life cycle and serves as a useful resource in defining the growth-phase-dependent expression patterns of each gene. Additionally, the data and accompanying bioinformatics analyses suggest a model for sporulation that has broad implications for B. anthracis biology and offer new possibilities for microbial forensics and detection.

Bacillus anthracis↗
PubMed2005

Insect seasonality: circle map analysis of temperature-driven life cycles.

Maintaining an adaptive seasonality, with life cycle events occurring at appropriate times of year and in synchrony with cohorts and ephemeral resources, is a basic ecological requisite for many cold-blooded organisms. There are many mechanisms for synchronizing developmental milestones, such as egg laying (oviposition), egg hatching, cocoon opening, and the emergence of adults. These are often irreversible, specific to particular life stages, and include diapause, an altered physiological state which can be reversed by some synchronizing environmental cue (e.g. photoperiod). However, many successful organisms display none of these mechanisms for maintaining adaptive seasonality. In this paper, we briefly review the mathematical relationship between environmental temperatures and developmental timing and discuss the consequences of viewing these models as circle maps from the cycle of yearly oviposition dates and temperatures to oviposition dates for subsequent generations. Of particular interest biologically are life cycles which are timed to complete in exactly 1 year, or univoltine cycles. Univoltinism, associated with reproductive success for many temperate species, is related to stable fixed points of the developmental circle map. Univoltine fixed points are stable and robust in broad temperature bands, but lose stability suddenly to maladaptive cycles at the edges of these bands. Adaptive seasonality may therefore break down with little warning with constantly increasing or decreasing temperature change, as in scenarios for global warming. These ideas are illustrated and explored in the context of Mountain Pine Beetle (Dendroctonus ponderosae Hopkins) occurring in the marginal thermal habitat of central Idaho's Rocky Mountains. Applications of these techniques have not been widely explored by the applied math community, but are likely to provide great insight into the response of biological systems to climate change.

Animals↗
PubMed1984

Chromosome condensation and decondensation factors in the life cycle of eukaryotic cells.

In this chapter, we have attempted to review our recent work pertaining to the regulation of the chromosome condensation-decondensation cycle within the life cycle of mammalian cells. The results summarized here strongly suggest that this sequence of events may be regulated by different protein factors. Mitotic factors injected into fully grown X. laevis oocytes induce meiotic maturation, i.e., GVBD and chromosome condensation. These factors, which accumulate slowly in the beginning of G2 and reach a threshold at the G2-mitosis transition, have a great affinity for chromatin and are localized on metaphase chromosomes, as well as in the cytoplasm. They are nondialyzable, heat- and Ca2+-sensitive, Mg2+-dependent nonhistone proteins with an approximate molecular mass of 100,000 Da. At the telophase of mitosis, the mitotic factors are rapidly inactivated by another set of factors, IMF. IMF are also nondialyzable nonhistone proteins, but unlike mitotic factors, are heat-stable. They are also stable over a broad pH range, but are extremely sensitive to low pH. IMF are activated at telophase and remain active throughout the G1 period, thus coinciding with the process of chromosome decondensation. Although evidence implicating IMF in the regulation of chromosome decondensation is still largely circumstantial, data summarized here nevertheless suggest a strong correlation between these two phenomena. The way in which mitotic factors and IMF might bring about the condensation-decondensation of chromosomes has not been established. Our studies on the role of protein phosphorylation and the use of monoclonal antibodies specific for mitotic cells have provided some evidence implicating nonhistone protein phosphorylation-dephosphorylation in the regulation of mitosis. A causal link between these events is suggested, but remains to be established. Characterization of these factors will help us learn about their functions, as well as lead to a better understanding of the events regulating the chromosome condensation-decondensation cycle in eukaryotic cells.

Antibodies, Monoclonal↗
PubMed2005

Life cycle assessment of EPS and CPB inserts: design considerations and end of life scenarios.

Expanded polystyrene (EPS) and corrugated paperboard (CPB) are used in many industrial applications, such as containers, shock absorbers or simply as inserts. Both materials pose two different types of environmental problems. The first is the pollution and resource consumption that occur during the production of these materials; the second is the growing landfills that arise out of the excessive disposal of these packaging materials. Life cycle assessment or LCA will be introduced in this paper as a useful tool to compare the environmental performance of both EPS and CPB throughout their life cycle stages. This paper is divided into two main parts. The first part investigates the environmental impacts of the production of EPS and CPB from 'cradle-to-gate', comparing two inserts--both the original and proposed new designs. In the second part, LCA is applied to investigate various end-of-life cases for the same materials. The study will evaluate the environmental impacts of the present waste management practices in Singapore. Several 'what-if' cases are also discussed, including various percentages of landfilling and incineration. The SimaPro LCA Version 5.0 software's Eco-indicator 99 method is used to investigate the following five environmental impact categories: climate change, acidification/eutrophication, ecotoxicity, fossil fuels and respiratory inorganics.

Environmental Monitoring↗
PubMedDate not supplied

Isolation and characterization of glutathione reductase from Physarum polycephalum and stage-specific expression of the enzyme in life-cycle stages with different oxidation-reduction levels.

Physarum polycephalum has a life cycle with several distinct phases that have different oxidation-reduction requirements. To investigate the relationship between the life cycle and the oxidation-reduction state, we isolated glutathione reductase (GR; EC 1.6.4.2) from Physarum microplasmodia. The enzyme was found to be a homodimer with a subunit M(r) of 49,000, and K(m) values for oxidized glutathione and NADPH of 40 and 28.6 microM, respectively. We then constructed a cDNA library from microplasmodium mRNA and cloned GR cDNA from the library. The isolated cDNA consisted of 1,475 bp encoding a polypeptide of 452 amino acids. The amino acid sequence similarity was about 50% with GRs of other organisms, and several conserved sequence motifs thought to be necessary for activity are evident in the Physarum enzyme. Escherichia coli transformed with an expression vector containing the cDNA synthesized the active GR. Genomic Southern blot analysis indicated that the GR gene is present as a single copy in the Physarum genome. Immunoblot analysis and RT-PCR analysis detected GR mRNA expression in the microplasmodium, plasmodium, and sclerotium, but not in the spore or flagellate. GR activity was low in the spore and flagellate. These results suggest that the glutathione oxidation-reduction system relates to the Physarum life cycle.

Amino Acid Sequence↗
PubMed1995

The life-cycle of the bont tick Amblyomma hebraeum in vitro.

The life-cycle of the hard tick Amblyomma hebraeum was completed in vitro by feeding all life-stages of the tick through silicone membranes on bovine blood from an abattoir. Ticks were placed in a simple feeder membranes on bovine blood from an abattoir. Ticks were placed in a simple feeder consisting of a honey jar containing the blood with a glass tube insert (o.d. 42 mm) across the end of which the membrane was stretched. This feeding unit was held in a water bath (38 degrees C). Larvae and nymphs fed on a membrane (< 90 microns thick) made of silicone reinforced with Kodak lens cleaning paper, and adults on a silicone membrane (0.5 mm thick) reinforced with Terylene netting. To control microbial growth, gentamicin (5 micrograms/ml) and nystatin (100 i.u./ml) were added to the weekly open-collected blood, which was manually defibrinated. The blood was changed twice daily for nymphs and three times for adults and larvae. Attachment of ticks was induced with combinations of host hair, tick faeces, a bovine pelage extract and a synthetic aggregation-attachment pheromone mixture. The in vitro life-cycle started with unengorged "natural" adults, which had moulted from nymphs fed on steer. The life-cycle closed with unengorged, first in vitro generation adults which had moulted from nymphs fed in vitro. Although the feeding and development of larvae and nymphs were similar to in vivo controls, females fed and developed poorly in vitro. The toxicity of the systemic acaricide Ivermectin for nymphs of A. hebraeum was confirmed using the in vitro feeding method.

Animals↗
PubMed1988

The life cycle and larval development of Fibricola seoulensis (Trematoda: Diplostomatidae).

The life cycle of Fibricola seoulensis was studied in the laboratory and in the field, with special interests in the larval developments within the eggs and in the intermediate hosts. The first emergence of miracidia after incubation of eggs in 26C water began on the ninth day. The miracidia, elongate and cylindrical shape, had epidermal plates in the formula of 6, 9, 4 and 3, with two pairs of flame cells and lateral processes. A kind of fresh water snail, Hippeutis (H.) cantori, was found to shed furcocercous cercariae from the 13th day after experimental challenge with miracidia while Physa acuta failed to shed. The same kind of snail collected from the field also shed the same cercariae. The cercariae were equipped with 2 pairs of penetration glands and 5 pairs of flame cells. The tadpoles of Rana nigromaculata were found susceptible to experimental infection with the cercariae. The same kind of tadpoles collected from various areas were also found naturally infected. The metacercariae in the tadpoles which were infected experimentally became infective to the definitive host in 21 days. The metacercariae were located free in the body cavity of tadpoles, and attained sexual maturity in rats in 7 days. The present study successfully followed the complete life cycle of F. seoulenis and found that it is possible to maintain the life cycle in the laboratory.

Journal Article↗
PubMed1991

Life cycle savings and consumption constraints: theory, empirical evidence, and fiscal implications.

"Recent tests of both the pure and the extended life cycle hypothesis have generated inconclusive results on the life cycle behavior of the elderly. We extend the life cycle model by introducing a constraint on the physical consumption opportunities of the elderly which, if binding, imposes a consumption trajectory declining in age. This explains much of the received evidence on the elderly's consumption and savings behavior, in particular declining consumption, and increasing savings and wealth with increasing age. Our analysis of [Federal Republic of Germany] data gives additional support to our theory. We finally draw the implications of the theory on the incidence of consumption and income (wealth) taxes, and on the recent (inconclusive) tests of intergenerational altruism."

Adult↗
PubMed1979

Time, age, and the life cycle.

Psychologists are increasingly interested in the life cycle as the unit for study and in such questions as whether adult development, like child development, is to be perceived as a succession of stages. A stage theory of adult life seems oversimplified for several reasons. First, the timing of life events is becoming less regular, age is losing its customary social meanings, and the trends are toward the fluid life cycle and an age-irrelevant society. Second, the psychological themes and preoccupations reported by young, middle-aged, and older persons are recurrent ones that appear and reappear in new forms and do not follow in a single fixed order. Third, intrapsychic changes occur slowly with age and not in stepwise fashion. These factors may have implications for the psychiatrist who, in helping the patient make a meaningful life story from a life history, deals always with issues of time, timing, and aging.

Adaptation, Psychological↗
PubMed1994

Pleoanamorphic life cycle of Exophiala (Wangiella) dermatitidis.

The anamorph life cycle of the black yeast Exophiala (Wangiella) dermatitidis is described. The fungus is dimorphic, yeast cells being the prevalent form of propagation. The fungus is strongly hydrophilic, probably completing its anamorph life cycle in submersion. Adaptation to dry conditions is slow. Types of conidiogenesis comprise annellidic, phialidic and sympodial reproduction, in addition to isotropic development. Phialoconidia fail to germinate under the conditions tested, and thus may have a function other than dispersal. Sterile, multicellular bodies resembling a Capronia teleomorph are described.

Exophiala↗
PubMed1979

Family formation and the life cycle.

Mathematical expressions are developed for certain life cycles when only the age-specific birth and death rates are known. The probability at birth that a woman will have a specified number of children and the expected length of time spent before the first birth, between the first and the last child, and between the last child and the time of the woman's death are shown to be calculable. Expressions for the probability of at least one child outliving the mother and for the expected number of children outliving the mother are also developed and are evaluated for three selected countries with different birth and death rates to show how these life cycles depend on birth and death rates.

Birth Rate↗
PubMed2004

[Multi-objectives optimization on life cycle pollutants emission of cassava-based ethanol blended gasoline fuels].

An optimization model on life cycle pollutants emission of cassava-based ethanol blended gasoline fuels, including single and multi-objectives, was carried out in this paper. And, the single and multi-objectives optimization of cassava-based ethanol blended gasoline fuels were done, using the life cycle CO, NOx, PM, HC, SOx, CO2 emissions as objectives. Moreover, sensitivity analysis of design variables was done. The multi-objectives results shown that the blend ratio between cassava-based ethanol and gasoline was 63%. Compare with the initial value, multi-objective optimization of cassava-based ethanol blended gasoline fuels achieved a little more life cycle CO, NOx and PM emissions, about 1%, 15% and 19% respectively, and reduced life cycle HC, SOx and CO2 emissions, 8%, 50%, and 21% respectively.

Air Pollutants↗
PubMed1986

Population dynamics in echinococcosis and cysticercosis: mathematical model of the life-cycle of Echinococcus granulosus.

A mathematical model of the life-cycle of Echinococcus granulosus in dogs and sheep in New Zealand is constructed and used to discuss previously published experimental and survey data. The model is then used to describe the dynamics of transmission of the parasite, and the means by which it may be destabilized. It is found that under the conditions that prevailed in New Zealand during the late 1950s, at the time of surveys of this parasite, the dog-sheep life-cycle was not regulated by any effective density-dependent constraint. In contrast there was evidence for an effective acquisition of immunity to reinfection by cattle. The long time to maturity of the cyst in sheep, together with the practice of feeding aged sheep to dogs, provides a time delay in the intermediate host. By comparison, the time to maturity of the adult stage in dogs is short, but it is of sufficient magnitude to be a key factor in the destabilization of the system by a regular dog-dosing programme. The model used to describe the life-cycle is a linear integrodifferential equation of the Volterra type. Such equations are intrinsically unstable in that a small perturbation in parameters can drive a previous equilibrium solution to zero. At the time of the surveys, the value of the basic reproductive rate, R0, was close to 1, and it has since been reduced below 1 by control measures.

Age Factors↗
PubMed1999

Establishment of the human papillomavirus type 16 (HPV-16) life cycle in an immortalized human foreskin keratinocyte cell line.

The study of human papillomaviruses (HPVs) in cell culture has been hindered because of the difficulty in recreating the three-dimensional structure of the epithelium on which the virus depends to complete its life cycle. Additionally, the study of genetic mutations in the HPV genome and its effects on the viral life cycle are difficult using the current method of transfecting molecularly cloned HPV genomes into early-passage human foreskin keratinocytes (HFKs) because of the limited life span of these cells. Unless the HPV genome transfected into the early-passage HFK extends the life span of the cell, analysis of stable transfectants becomes difficult. In this study, we have used BC-1-Ep/SL cells, an immortalized human foreskin keratinocyte cell line, to recreate the HPV-16 life cycle. This cell line exhibits many characteristics of the early-passage HFKs including the ability to stratify and terminally differentiate in an organotypic raft culture system. Because of their similarity to early-passage HFKs, these cells were tested for their ability to support the HPV-16 life cycle. The BC-1-Ep/SL cells could stably maintain two HPV genotypes, HPV-16 and HPV-31b, episomally. Additionally, when the BC-1-Ep/SL cell line was stably transfected with HPV-16 and cultured using the organotypic raft culture system (rafts), it sustained the HPV-16 life cycle. Evidence for the productive stage of the HPV-16 life cycle was provided by: DNA in situ hybridization demonstrating HPV-16 DNA amplification in the suprabasal layers of the rafts, immunohistochemical staining for L1 showing the presence of capsid protein in the suprabasal layers of the rafts, and electron microscopy indicating the presence of virus like particles (VLPs) in nuclei from cells in the differentiated layers of the rafts.

Capsid Proteins↗
PubMed2006

Variation in the intensity of inbreeding depression among successive life-cycle stages and generations in gynodioecious Silene vulgaris (Caryophyllaceae).

Inbreeding depression is one of the hypotheses explaining the maintenance of females within gynodioecious plant populations. However, the measurement of fitness components in selfed and outcrossed progeny depends on life-cycle stage and the history of inbreeding. Comparative data indicate that strong inbreeding depression is more likely to occur at later life-cycle stages. We used hermaphrodite individuals of Silene vulgaris originating from three populations located in different valleys in the Swiss Alps to investigate the effect of two generations of self- and cross-fertilization on fitness components among successive stages of the life cycle in a glasshouse experiment. We detected significant inbreeding depression for most life-cycle stages including: the number of viable and aborted seeds per fruit, probability of germination, above ground biomass, probability of flowering, number of flowers per plant, flower size and pollen viability. Overall, the intensity of inbreeding depression increased among successive stages of the life cycle and cumulative inbreeding depression was significantly stronger in the first generation (delta approximately 0.5) compared with the second generation (delta approximately 0.35). We found no evidence for synergistic epistasis in our experiment. Our finding of more intense inbreeding depression during later stages of the life cycle may help to explain the maintenance of females in gynodioecious populations of S. vulgaris because purging of genetic load is less likely to occur.

Crosses, Genetic↗
PubMed2004

Life cycle assessment of mobile phone housing.

The life cycle assessment of the mobile phone housing in Motorola(China) Electronics Ltd. was carried out, in which materials flows and environmental emissions based on a basic production scheme were analyzed and assessed. In the manufacturing stage, such primary processes as polycarbonate molding and surface painting are included, whereas different surface finishing technologies like normal painting, electroplate, IMD and VDM etc. were assessed. The results showed that housing decoration plays a significant role within the housing life cycle. The most significant environmental impact from housing production is the photochemical ozone formation potential. Environmental impacts of different decoration techniques varied widely, for example, the electroplating technique is more environmentally friendly than VDM. VDM consumes much more energy and raw material. In addition, the results of two alternative scenarios of dematerialization showed that material flow analysis and assessment is very important and valuable in selecting an environmentally friendly process.

Conservation of Energy Resources↗
PubMed1990

A study of the life cycle of Eimeria praecox, Johnson 1930.

The life cycle of a strain of Eimeria praecox derived from a single oocyst which was obtained from litter removed from a broiler farm in West-Germany was examined. Four generations of schizonts were observed, maturing at 24 hpi, 40 hpi, 56 hpi and 68 hpi, respectively. Mature gamonts were seen at 80 hpi to 84 hpi, and oocysts were detected in the faeces at less than 84 hours postinfection in two of the five propagations of the strain. Results are compared with previous descriptions of the life cycle of E. praecox.

Animals↗
PubMed2002

The life cycle of Nematodiroides zembrae (Nematoda, Trichostrongylina) in the rabbit.

The morphogenesis and the chronology of the life cycle of Nematodiroides zembrae (Bernard, 1965), a parasite of Oryctolagus cuniculus from Spain, were studied in detail in its natural host. For each experiment a morphological description of the different stages of the life cycle is provided. The free-living larvae developed in eggs until infective stage. First hatching began at 10 days. Twenty-one, worm-free rabbits were each infected per os with N. zembrae larvae and killed 3 days after infection (DAI) and every day from 4 to 22 DAI. By 3 DAI all recovered larvae were exsheathed and present in the small intestine. The third moult occurred between 6 and 7 DAI. The last moult occurred between 11 and 19 DAI. The prepatent period lasted for 21-22 days. The distribution of N. zembrae along the small intestine of the rabbit is described. Significantly different distributions of the parasite along the small intestine indicated that migrations occurred during the development of N. zembrae in the rabbit. The life cycle of N. zembrae is compared with the 5 known life cycles of Nematodirus spp. in ruminants. The biological data are very similar in both groups except for the prepatent period.

Animals↗