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PubMedDate not supplied

[The life form concept and the use in the analysis of life cycle evolutionary strategies].

The life form is a generalized morphoecological characteristic of an animal giving an idea of the organism as a whole, its position and function and functional role in the ecosystem. This characteristic is inherent to a species or to a group of congeneric species (for applied goal it is better to use a genus, not species) considered in the framework of higher taxon (from family to type). The principal contradiction of life form concept is determined by the existence of ontogenetic stages and changes of life forms during the whole life of individual. It is usually assumed that the concept of life form should be applied only to the adult stage, thus ignoring the integral character of the life cycle as indivisible unit of selection, evolution and functioning in ecosystem. We propose that a morphologically specific ontogenetic of a given species should be used as an elementary lowest unit in the classification of life forms. Thus it can be considered as integrated internally structured morphoecological unit in time and multidimensional space of abiotic and biotic environmental factors. As an example we describe the types of reproductive strategies and classification of elementary (ontogenetic) life forms in cephalopods. We present characteristics of the life cycle of some typical cephalopod species inhabiting different biotopes and having different models of locomotion, feeding, reproduction and development.

Animals↗
PubMed2002

Tricarboxylic acid cycle aconitase activity during the life cycle of Streptomyces viridochromogenesTü494.

Previously, it was shown that inactivation of the tricarboxylic acid cycle aconitase gene acnA impairs the morphological and physiological differentiation of Streptomyces viridochromogenes Tü494, which produces the herbicide phosphinothricin tripeptide (PTT). In order to further characterize the role of the aconitase in the Streptomyces life cycle, aconitase activity was analyzed during growth of S. viridochromogenes in liquid culture. Two prominent maxima were measured in cell-free crude extracts. The first maximum was found at an early stage of growth, which is correlated with a decrease in pH when rapid glucose consumption is initiated. The second, lower maximum was detected at the beginning of the expression of the PTT-specific biosynthetic gene phsA,implying the onset of secondary metabolism. These results were confirmed by examining transcription of the acnA promoter in time-course experiments. The highest transcription rate was found during the early growth phases. In order to identify putative regulatory mechanisms, the transcriptional start site of the acnA transcript and subsequently the promoter were identified. Several putative, regulatory protein binding sites (e.g. regulators of oxygen stress or iron metabolism) were detected in the promoter region of acnA, which suggested complex regulation of acnA.

Aconitate Hydratase↗
PubMed1995

Life cycle of Ornithodoros (Alectorobius) talaje (Acari: Argasidae) in laboratory.

Specimens of Ornithodoros (Alectorobius) talaje (Guérin-Mèneville) collected in the state of Minas Gerais, Brazil, were used to start a laboratory colony. Larvae were fed on chicks and nymphs and adults were fed on adult chickens. From the specimens that emerged after the third molt, 97.6% were nymphs and 2.4% were males. After the fourth molt, 41.6% were nymphs, 37.6% were males, and 20.8% were females. After the fifth molt, 24% were males and 60% were females; the remainder were nymphs. The number of eggs per female per gonotrophic cycle and the mean duration of preoviposition, oviposition, and incubation periods were recorded. At the first gonotrophic cycle, duration of preoviposition period was longer and the number of eggs was smaller than any other studied gonotrophic cycle. The life cycle was completed within 849 d (maximum). The O. (A.) talaje first-instar nymphal population failed to molt without having a blood meal, which differs from other Alectorobius species. Parthenogenesis was not observed. Larval morphology was studied by optical microscopy. Unengorged specimens were larger, with smaller dorsal plate and fewer dorsal setae than those previously described.

Animals↗
PubMed2000

Re-validation of Echinostoma miyagawai Ishii, 1932 (Digenea: Echinostomatidae) on the basis of the experimental completion of its life-cycle.

The life-cycle of Echinostoma miyagawai, a Eurasian species closely related to E. revolutum, was completed in the laboratory, and the morphology of the larval stages and the adults obtained experimentally was studied. Planorbis planorbis and Anisus vortex were the first intermediate hosts in the brackish Lake Durankulak on the Bulgarian Black Sea coast. Characteristic features of the cercaria include: a prominent collar with 37 spines; a tail as long as the body and with seven conspicuous fin-folds, the two ventral fin-folds being very close to each other; and a specific number and distribution of both the para-oesophageal gland-cell outlets and sensilla. The adult is characterised by: a very elongate body with a constriction at the posterior border of the ventral sucker; a large head collar with relatively small spines; a spherical ventral sucker which is only about half the maximum body width; a long cirrus-sac reaching posteriorly dorsal to the middle of the ventral sucker; indented subglobular testes; and a vitellarium forming two lateral fields of follicles which are almost confluent in the post-testicular space. The species described in this study resembles E. miyagawai, as described by Kosupko, in the morphology of larval stages and both the site and the general morphology of the adults. It differs from both E. revolutum, as described by both Kanev and Nasincová, and E. echinatum (also referred to as E. lindoense and E. barbosai by Kanev). The re-examination of Kanev's voucher specimens from his experimental studies used in his delimitation of E. revolutum and E. echinatum showed that the specimens identified by him as E. revolutum represent two distinct forms which consistently differ both from each other and from the redescription of E. revolutum which was based upon them. It also revealed that a number of specimens were wrongly identified and erroneously treated as E. echinatum by Kanev and co-workers; these include members of different genera (Hypoderaeum and Echinoparyphium) and an Echinostoma species of the group possessing 47 collar spines. The relative merits of the features used by Kanev and co-workers in discriminating the closely related Echinostoma spp. are discussed in detail with respect to the experimental evidence provided by these authors.

Animals↗
PubMed2005

Evaluation of environmental burdens associated with sewage treatment processes using life cycle assessment techniques.

Life cycle assessments of a range of wastewater treatment processes have been undertaken. At lower consent standards rotating biological contactors and biological filters exhibit lower environmental burdens for the required functionality than other process options. However, at tighter consents this distinction becomes less clear. Attempts to reduce environmental burdens should focus on operational energy requirements (which dominate burden profiles and, where appropriate, on synthetic materials used for bio-mass growth). However, differences between dry and operational weight, and the consequent size of necessary foundation structures are likely to limit opportunities for reducing overall burden profiles through material substitution. Comparison of processes across population equivalents suggests economies of scale may favour adopting larger scale plant, although there are additional factors yet to be included in this analysis. Furthermore, adopting different waste disposal routes during the demolition phase is unlikely to have a distinct impact on burden profiles.

Biodegradation, Environmental↗
PubMed2005

[Life cycle assessment on oxygen biofuels].

Life Cycle Assessment (LCA) was used to compare energy consumption and pollutant emissions of two oxygen biofuels, ethanol and methyl ester, which were mixed with gasoline and diesel oil at levels of 10% and 30% of the biofuel. The future of oxygen-containing biofuels was analyzed and forecasted. The results show that the mixture of biofuels and petroleum products can reduce crude oil consumption, but only methyl ester alternative fuel can reduce fossil fuel consumption. Use of methyl ester mixtures would reduce NOx by 50% compared to gasoline or diesel on a life cycle basis; however, NOx would increase using ethanol. Each alternative fuel mixture reduced PM10 emissions from the vehicle and methyl ester decreased VOCs. The SO2 emissions from the fuel production processes, which account for about 80% of SO2 life cycle emissions, must be strictly controlled.

Energy-Generating Resources↗
PubMed2005

Using an immortalized cell line to study the HPV life cycle in organotypic "raft" cultures.

The papillomavirus life cycle is tied to the differentiation of the stratified squamous epithelium that this virus infects. The ability to study the papillomavirus life cycle is facilitated by organotypic culturing techniques that allow one to closely recapitulate this terminal differentiation process in the laboratory. Current techniques allow for the establishment of recombinant wild-type or mutant human papillomavirus (HPV) genomes in transfected early-passage human foreskin keratinocytes (HFKs). These cells can then be used in organotypic culture to investigate the role of individual viral genes in different aspects of the viral life cycle. When using early-passage HFKs, there is a need for the transfected HPV genome to extend the life span of the cells in order to have sufficient cell generations in which to carry out organotypic culturing. The recent isolation of a spontaneously immortalized HFK cell line that supports the complete HPV life cycle has further allowed investigators to study wild-type or mutant papillomaviral genomes that do not confer immortalization. In this chapter, we describe the methodologies that permit the study of the HPV life cycle in this HFK cell line.

Animals↗
PubMed1993

Selection and the evolution of genetic life cycles.

The evolution of haploid and diploid phases of the life cycle is investigated theoretically, using a model where the relative length of haploid and diploid phases is under genetic control. The model assumes that selection occurs in both phases and that fitness in each phase is a function of the time spent in that phase. The equilibrium and stability conditions that allow for all-haploid, all-diploid, or polyphasic life cycles are considered for general survivorship functions. Types of stable life cycles possible depend on the form of the viability selection. If mortality rates are constant, either haploidy or diploidy is the only stable life cycle possible. Departures from constant mortality can give qualitatively different results. For example, when survivorship in each phase is a linear, decreasing function of the time spent in the phase, stable haploid, diploid or polyphasic life cycles are possible. The addition of genetic variation at a coevolving viability locus does not qualitatively affect the outcome with respect to the maintenance of polyphasic cycles but can lead to situations where more than one life cycle is concurrently stable. These results show that trade-offs between the advantages of being diploid and of being haploid may help explain the patterns of life cycles found in nature and that the type of selection may be critical to determining the results.

Biological Evolution↗
PubMedDate not supplied

Experimental life cycle of Lagochilascaris minor Leiper, 1909.

The life cycle of Lagochilascaris minor was studied using material collected from human lesion and applying the experimental model: rodents (mice, hamsters), and carnivores (cats, dogs). In mice given infective eggs, orally, hatch of the third stage larvae was noted in the gut wall, with migration to liver, lungs, skeletal musculature and subcutaneous tissue becoming, soon after, encysted. In cats infected with skinned carcasses of mice (60 to 235 days of infection) it was observed: hatch of third stage larvae from the nodules (cysts) in the stomach, migration through the oesophagus, pharynx, trachea, related tissues (rhino-oropharynx), and cervical lymph nodes developing to the mature stage in any of these sites on days 9-20 post inoculation (P.I.). There was no parasite development up to the mature stage in cats inoculated orally with infective eggs, which indicates that the life cycle of this parasite includes an obligatory intermediate host. In one of the cats (fed carcass of infected mice) necropsied on day 43 P.I., it was observed the occurrence of the self-infective cycle of L. minor in the lung tissues and in the cervical region which was characterized by the finding of eggs in different stages of development, third stage larvae and mature worms. It's believed that some component of the carnivore gastrointestinal tracts may preclude the development of third stage larvae from L. minor eggs what explains the interruption of the life cycle in animals fed infective eggs. It's also pointed out the role of the intermediate host in the first stages of the life cycle of this helminth.

Animals↗
PubMed1972

Protein and ribonucleic acid synthesis during the diploid life cycle of Allomyces arbuscula.

The diploid life cycle of Allomyces arbuscula may be divided into four parts: spore induction, germination, vegetative growth, and mitosporangium formation. Spore induction, germination, and mitosporangium formation are insensitive to inhibition of actinomycin D, probably indicating that stable, pre-existing messenger ribonucleic acid (RNA) is responsible for these developmental events. Protein synthesis is necessary during the entire life cycle except for cyst formation. A system for obtaining synchronous germination of mitospores is described. During germination there is a characteristic increase in the rate of synthesis of RNA and protein although none of the other morphogenetic changes occurring during the life cycle are necessarily accompanied by an appreciable change in the rate of macromolecular synthesis.

Adenine↗
PubMed1983

[2 rules for the life cycles of cestodes in the ecosystem].

Rule I: The more advanced in its primary evolution the life cycle of a cestode is, the greater is the participation of the animal component of the ecosystem in it. The direct influence of the non-living component of the ecosystem on the course of the cycle is one and the same with both the primarily evolved 2-host and 3-host life cycles within the separate orders. Rule II: In the secondarily evolved life cycles of cestodes, when compared with their initial life cycles, the following things are observed: a) either a decrease of both the participation of the animal component of the ecosystem in the life cycle and the direct influence of the non-living component of the ecosystem on the course of the cycle; b) or a decrease only of the participation of the animal component of the ecosystem in the life cycle, without any change in the direct influence of the non-living component of the ecosystem on the course of the cycle; c) or, quite rarely, a decrease only of the direct influence of the non-living component of the ecosystem on the course of the life cycle, without any change in the participation of the animal component of the ecosystem in the life cycle.

Animals↗
PubMed2006

A life cycle for Borrelia spirochetes?

Subsequent to Schaudinn and Hoffman's visualization of Treponema pallidum in 1905, many distinguished syphilologists proposed that spirochetes have a life cycle. What is the "essence" of a life cycle? Simply put, life cycles are diverse arrays of life forms, which emerge in an ordered sequence; which are "connected" to one another across primary and secondary hosts, and constitute a cycle with "circular" relationship between hosts. Fecal-oral life cycles and blood-to-blood life cycles are exemplary of host parasite relationships in this realm. The "blood-to-blood" begins and ends with an insect taking a blood "meal". In this operatic scenario, a "blood-less" insect functions simultaneously as a hypodermic needle and as an incubator for some of the infectious components. The initial phase is inside the body fluid compartment of an insect. The second phase is in the blood or body fluid of a warm-blooded mammal. Third, is the phase inside the cell of a mammalian host. And a final portion of the "life" marked by "death" of the parasitized mammalian cells and the release of infectious parasites which return to the "warm" blood where the "cold blooded" vector again takes a blood meal. The cycle then begins again. In each phase of a blood to blood life cycle, the infectious agent changes its shape. Blood phase "profiles" look different from "tissue phase" profiles. Some of the tissue phase profiles may be "invisible". Borrelia spirochetes offer an excellent example of a life cycle, by virtue of the insect vector to mammalian "piece", the blood and intracellular residence "pieces" and the morphologic diversity "piece". Stereotypes of what a spirochete "should " look like, have actually produced a state of "perseveration" in spirochetal pathobiology. We have been "stuck" like a broken record, on the corkscrew form, and have failed to see the rest of the life cycle. Cystic, granular, and cell wall deficient spirochetal profiles, which were well known in the 19th and 20th centuries by such titans as Schaudinn, Hoffman, Noguchi, Delamater, Steiner, and Mattman, have been repudiated by professional microbiologists, and by pathologists who practice and who confer the status of 21st century truths in microbiology matters. Proper microscopic study, as is required by Dr. Robert Koch's second postulate, for establishing links between microbes and disease, presupposes that the microscopist be aware of the complete array of morphologic repertoires of the alleged pathogen. (Morphologies, which are herein introduced.).

Animals↗
PubMed2005

The priming of periodical cicada life cycles.

Periodical cicadas in the genus Magicicada have unusually long life cycles for insects, with periodicities of either 13 or 17 years. Biologists have explained the evolution of these prime number period lengths in terms of resource limitation, enemy avoidance, hybridization and climate change. Here, I question two aspects of these explanations: that the origin of the life cycles was associated with Pleistocene ice age events, and that they evolved from shorter life cycles through the lengthening of nymphal stages in annual increments. Instead, I suggest that these life cycles evolved earlier than the Pleistocene and involved an abrupt transition from a nine-year to a 13-year life cycle, driven, in part, by interspecific competition.

Journal Article↗
PubMed2004

Sleep Problems Across the Life Cycle in Women.

Across the life cycle of women, the quality and quantity of sleep can be markedly impacted by internal (eg, hormonal changes and vasomotor symptoms) and external (financial and child-care responsibilities; marital issue) factors. This paper will outline some of the major phases of the life cycle in women that have been associated with sleep problems. The main messages from this paper include 1) that very little systematic, large-scale research has been performed in virtually every area reviewed; and 2) once identified, the sleep problem is generally best addressed by the standard therapeutic approach, except in the case of pregnant and lactating women in which concern for the fetus and child must be considered in the treatment decision. This paper is organized into sections that address sleep problems associated with the menstrual cycle, pregnancy, postpartum, and perimenopause. Anecdotal reports recommend treatment that addresses the specific physical discomfort experienced by the woman (eg, analgesics for premenstrual pain, pregnancy pillows for backache, and hormone replacement therapy for hot flashes). The importance of developing standard treatment recommendations is stressed because the development of chronic insomnia has been linked to precipitating events. In addition, primary sleep disorders (eg, sleep apnea or restless legs syndrome) have been shown to increase during pregnancy and menopause, but treatment recommendations may be contraindicated or are not specific for women.

Journal Article↗
PubMed1996

[New details of the life cycle of Myxobolus cerebralis according to the literature].

The article comprises new details of the life cycle of Myxobolus cerebralis, the parasite of the skeleton of salmonids. Although this species has been known since 1903, its complete life cycle has remained unknown till now or it has comprised mistaken details. Recently EL Matbouli et al. (1995) have described the life cycle of this parasite with numerous new data. M. cerebralis provokes in salmonids (especially in rainbow trouts) the whirling disease and heavy economical losses. Therefore the article may be useful for Polish ichthyopathologists. Besides the new description of the life cycle of M. cerebralis the authoress of the article gives her own considerations on some topics connected with this life cycle, which still remain insufficiently explained. The considerations concern the mechanism of the specificity of the invasive stages of the parasite to two species of its hosts (Tubifex tubifex and Oncorhynchus mykiss) and also to tissue specificity, the possibility of better and more effective control of whirling disease in breeding conditions through the knowledge of the complete life cycle of the parasite, the pathogenic activity of the parasite on fish central nervous system in spite of the lack of its lesions noted by EL Matbouli et al. (1995). The authoress pays attention to the necessity of future studies on the mitotic and meiotic cleavages of the developmental stages of the parasite. She considers also if the very complicated life cycle of M. cerebralis determined during the long evolution of this species may be recognized as favourable feature for it.

Animals↗
PubMed1997

Brugia pahangi: differential induction and regulation of jird inflammatory responses by life-cycle stages.

It has been hypothesized that different life-cycle stages of filarial nematodes induce different host responses. This concept was examined in the Brugia pahangi-jird model of lymphatic filariasis by measuring the kinetics of inflammatory responses to parasite antigens following intraperitoneal inoculation of different life-cycle stages. For this purpose, viable female or male worms, L3, L4, or microfilarial stage, were used. Dead worms served as controls. Worm and microfilarial burdens, pulmonary granulomatous inflammation (PGRN) to soluble adult worm antigen (SAWA)-coated beads, and peritoneal eosinophil and macrophage numbers were assessed at different days post-inoculation. All jirds inoculated with any of these life-cycle stages developed an early PGRN to SAWA which was later significantly reduced. Only viable worms induced down-regulation of the PGRN response. These results indicate that the hyporesponsive state is induced and maintained by all life-cycle stages. Also, the degree of granulomatous response was influenced by worm burden, with larger worm burdens inducing lower initial levels of PGRN to SAWA. Peritoneal inflammatory responses differed from the systemic response in that numbers of macrophages increased with time and microfilarial accumulation. No correlation was observed between peritoneal inflammatory responses measured by eosinophil and macrophage numbers and PGRN to SAWA.

Animals↗
PubMedDate not supplied

Comparative life-cycle assessments for biomass-to-ethanol production from different regional feedstocks.

This study compares life-cycle (cradle-to-gate) energy consumption and environmental impacts for producing ethanol via fermentation-based processes starting with two lignocellulosic feedstocks: virgin timber resources or recycled newsprint from an urban area. The life-cycle assessment in this study employed a novel combination of computer-aided tools. These tools include fermentation process simulation coupled with an impact assessment software tool for the manufacturing process life-cycle stage impacts. The process simulation file was provided by the National Renewable Energy Laboratory (NREL) and was modified slightly to accommodate these different feedstocks. For the premanufacturing process life-cycle stage impacts, such as the fuels and process chemicals used, transportation, and some preparatory steps (wood chipping, etc.), a life-cycle inventory database (the Boustead Model) coupled with an impact assessment software tool were used (the Environmental Fate and Risk Assessment Tool). The Newsprint process has a slightly lower overall composite environmental index (created from eight impact categories) compared to the Timber process. However, the Timber process consumes less electricity, produces fewer emissions in total, and has less of a human health impact. The amount of life-cycle fossil energy required to produce ethanol is 14% of the energy content of the product, making the overall efficiency 86%. Process improvement strategies were evaluated for both feedstock processes, including recycle of reactor vent air and heat integration. Heat integration has the greatest potential to reduce fossil-derived energy consumption, to an extent that fossil-derived energy over the life cycle is actually saved per unit of ethanol produced. These energy efficiency values are superior to those observed in conventional fossil-based transportation fuels.

Biotechnology↗