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PubMed2006

Myxozoan genera: definition and notes on taxonomy, life-cycle terminology and pathogenic species.

A list of myxozoan genera is presented in the current taxonomical scheme. These genera are defined; their type species and most important pathogens along with their hosts are listed. Simultaneously, definitions of actinospore stages representing sexual stages of the myxosporean life cycle are given; altogether, 17 actinospore collective groups with 180 types have been described. Life cycles of the two classes of the phylum Myxozoa, Malacosporea and Myxosporea, are briefly outlined with specification of the appropriate terms. Up to now, 4 malacosporean and 2,180 myxosporean species assigned to a total of 62 genera, have been established. The surviving classification of myxosporeans, based on spore morphology, is discussed in the context of the still fragmentary data resulting from SSU rDNA sequence analyses. The main task for the future is a rigorous, detailed morphological description combined with molecular techniques in establishment of new species and in revision of the existing ones. Establishment of a classification acceptable from morphological, biological and phylogenetical viewpoints is necessary.

Animals↗
PubMed1995

The life-cycle of Amblyomma variegatum (Acari: Ixodidae): a literature synthesis with a view to modelling.

All available information on the life-cycle of Amblyomma variegatum is collated. Data for each parameter are analysed to derive mathematical descriptions, which may now be used to construct a model of the life-cycle of this tick. Areas for future research are identified. These include the collection of data for most parameters around threshold conditions to clarify discrepancies reported in the literature and to better quantify the relationships described, examination of the effects of photoperiod and host type on various parameters, and assessment of feeding success of each instar on natural hosts.

Animals↗
PubMed2003

[Life cycle assessment of the infrastructure for hydrogen sources of fuel cell vehicles].

In order to promote the application of life cycle assessment and provide references for China to make the project of infrastructure for hydrogen sources of fuel cell vehicles in the near future, 10 feasible plans of infrastructure for hydrogen sources of fuel cell vehicles were designed according to the current technologies of producing, storing and transporting hydrogen. Then life cycle assessment was used as a tool to evaluate the environmental performances of the 10 plans. The standard indexes of classified environmental impacts of every plan were gotten and sensitivity analysis for several parameters were carried out. The results showed that the best plan was that hydrogen will be produced by natural gas steam reforming in central factory, then transported to refuelling stations through pipelines, and filled to fuel cell vehicles using hydrogen gas at last.

Automobiles↗
PubMed1991

Somatostatin concentrations in the pancreatic-intestinal tissues of the sea lamprey, Petromyzon marinus L., at various periods of its life cycle.

1. Somatostatin concentrations were measured in homogenates of the pancreas-intestinal tissues from each period of the life cycle of Petromyzon marinus using radioimmunoassay. 2. Levels were very low in larva (4.0 pg/mg wet weight) and in the first three stages of metamorphosis, but increased from stage 4 onwards and reached a high in upstream-migrating adults (210.0 ng/mg). 3. These data correlate well with our previous morphological and immunohistochemical observations on the morphogenesis of somatostatin-containing D-cells during the life cycle and indicate that the increased concentration of hormone accompanies the development of the endocrine pancreas in lampreys.

Animals↗
PubMed1979

Redescription of the life cycle of Haemogregarina simondi (Laveran and Mesnil, 1901) in its vertebrate host the marine fish Solea solea (Linnaeus).

The life cycle of Haemogregarina simondi is described in its vertebrate host the marine flatfish Solea solea. An intraleucocytic schizogony is followed by an intraerythrocytic schizogony giving rise to eight gametocytes. A differentiation into micro- and macro-gametocytes was also observed and thus confirms the results of other authors for H. aeglefini, H. bigemina, and H. sachai. It is postulated that most if not all of the haemogregarines of marine fish undergo similar life cycles as the one described here.

Animals↗
PubMed2006

One of the most complex life-cycles among trematodes: a description of Parvatrema margaritense (Ching, 1982) n. comb. (Gymnophallidae) possessing parthenogenetic metacercariae.

This study used light and electron microscopy to provide observations and morphometric details of the life-cycle of the gymnophallids (Trematoda, Digenea), Parvatrema margaritense (Ching, 1982) n. comb., the parthenogenetic metacercariae ('germinal sacs') of which were previously described by Ching (1982) as Cercaria margaritensis. The research was instigated by the discovery, on the Barents Sea coast, of a high prevalence of gymnophallid sporocysts and cercariae in the bivalve Turtonia minuta and an equivalent presence of distinctive gymnophallid metacercariae in the gastropod Margarites helicinus. Experiments and data obtained from naturally infected M. helicinus demonstrated that cercariae released from the bivalves invaded the gastropods to give rise to the metacercariae. Two generations (M1 and M2) of these parthenogenetic metacercariae were formed in the extrapallial cavities of their bivalve hosts and they, in turn, gave rise to a third generation (M3) which was shown to infect marine ducks such as the eider (Somateria mollissima). As only small numbers of cercariae are released from T. minuta, it was concluded that the inclusion of parthenogenetic metacercariae in the life-cycle is particularly significant. It allows each cercaria that infects M. helicinus to give rise to over 2000 invasive metacercariae. Evidence suggests that the parthenogenetic metacercariae are commensal rather that parasitic in the pallial cavities of their hosts. Implications of this for theories of early digenean evolution are discussed.

Animals↗
PubMed2004

Equipment life cycle costs minimised.

With the cost of energy now a major component of building operating costs, NHS Trust managers increasingly focus on estimating total life cycle costs of equipment such as boiler room and heat, steam and incineration plant. "Life cycle costing" is a broad term and encompasses a wide range of techniques that take into account both initial and future costs as well as the savings of an investment over a period of time.

Conservation of Energy Resources↗
PubMed1965

HELA CELLS: EFFECTS OF TEMPERATURE ON THE LIFE CYCLE.

After a shift in temperature, the population kinetics of HeLa cells does not immediately reach a steady state characteristic of the new temperature. During the transition period the duration of each period of the life cycle (period before DNA synthesis, of DNA synthesis, after DNA synthesis, and the period of mitosis) increases toward its steady-state value. Of the four periods, the period before DNA synthesis reaches its steady-state value fastest. Exponential growth can be maintained only from 33 degrees C through 40 degrees C. The period of mitosis is the most temperature-sensitive period of the life cycle of the cell. At subnormal temperatures (26 degrees C through 31 degrees C) there is an accumulation of cells in mitosis, and mitotic indices as high as 0.44 can be obtained. The duration of mitosis is a function both of the temperature and of the time which the cell has spent at this temperature.

Animals↗
PubMed1998

A developmental line of time sense. In late adulthood and throughout the life cycle.

This is the sixth and final paper in a series by the author on the normative, intrapsychic experience of time throughout the life cycle. Time sense is understood to be shaped by the primary forces that influence development at all points in the life cycle: an amalgam of past temporal conceptualizations, current developmental themes, and environmental influences. After a summary of the development of time sense in infancy, childhood, adolescence, and young and middle adulthood, this paper focuses on the experience of time after age sixty. The effect of death awareness and death anticipation, life reviews, reminiscence, and object relationships is discussed, as is the emergence of late-life generativity and wisdom. These concepts are illustrated by clinical material from the analysis of seventy-year-old woman.

Adolescent↗
PubMed1991

Testing life-cycle theory by computer simulation--I. Introduction of genetical structure.

Computer simulation was used to relax assumptions of analytical life-cycle theory about the eventual outcome of evolution in a constant environment. The computer simulation models, of diploid one-locus genetic systems, are described in detail. Good agreement was obtained between the analytical and simulation outcomes, except in some cases of discrepancy between the male and female life cycles.

Animals↗
PubMed1998

Advances in the life cycle of Toxoplasma gondii.

This paper reviews recent studies on the life cycle of Toxoplasma gondii. Tachyzoites, bradyzoites, and sporozoites are the three infectious stages of T. gondii. Humans and animals become infected mainly by ingesting bradyzoites or oocytes. After ingestion, both bradyzoites and sporozoites convert to tachyzoites inside tissues. The conversion of tachyzoites to bradyzoites and bradyzoites to tachyzoites is of biological and clinical significance because bradyzoites are less susceptible to chemotherapy and reactivation of bradyzoites to tachyzoites is considered the cause of fatal toxoplasmosis in AIDS patients. Of all the methods currently available to assess stage conversion of T. gondii, feeding infective stages to cats is the most reliable method. Felidae, the definitive hosts of T. gondii excrete oocysts 3-10 days after ingesting tissue cysts/bradyzoites, > or = 18 days after ingesting oocysts, and > or = 13 days after ingesting tachyzoites.

Animals↗
PubMed2005

Life cycle and reproductive patterns of Triatoma rubrovaria (Blanchard, 1843) (Hemiptera: Reduviidae) under constant and fluctuating conditions of temperature and humidity.

The aim of this study was to evaluate the temperature and relative humidity influence in the life cycle, mortality and fecundity patterns of Triatoma rubrovaria. Four cohorts with 60 recently laid eggs each were conformed. The cohorts were divided into two groups. In the controlled conditions group insects were maintained in a dark climatic chamber under constant temperature and humidity, whereas triatomines of the ambiental temperature group were maintained at room temperature. Average incubation time was 15.6 days in the controlled conditions group and 19.1 days in the ambiental temperature. In group controlled conditions the time from egg to adult development lasted 10 months while group ambiental temperature took four months longer. Egg eclosion rate was 99.1% and 98.3% in controlled conditions and ambiental temperature, respectively. Total nymphal mortality in controlled conditions was 52.6% whereas in ambiental temperature was 51.8%. Mean number of eggs/female was 817.6 controlled conditions and 837.1 ambiental temperature. Fluctuating temperature and humidity promoted changes in the life cycle duration and in the reproductive performance of this species, although not in the species mortality.

Animals↗
PubMed1997

Life-cycle of Bothriocephalus claviceps, a specific parasite of eels.

The life-cycle of the tapeworm Bothriocephalus claviceps (Goeze, 1782) (Cestoda: Pseudophyllidea), a specific parasite of eels (Anguilla spp.), was studied under experimental conditions. It was demonstrated that the parasite completed its development within 4 months at the temperature range of 22-24 degrees C. Embryonic development was finished in 2 days at this temperature, when coracidia spontaneously hatched. The rate of their development was controlled by water temperature, with delayed formation of coracidia at lower temperatures (8 days at 10-12 degrees C). At 2-4 and 6 degrees C, development did not take place but the eggs remained viable; at 33 degrees C the eggs died. The procercoids developed in copepods of the species Macrocyclops albidus, M. fuscus, Megacyclops viridis, Cyclops strenuus, C. vicinus and Acanthocyclops vernalis (Copepoda: Cyclopidae); their development was finished after 8-12 days at 22-24 degrees C. The definitive hosts, eels, acquired infection after ingestion of infected copepods; the prepatent period of the parasite was more than three months. Perch (Perca fluviatilis) and guppies (Poecilia reticulata) were shown to serve as paratenic hosts of the parasite; in guppies, the tapeworms survived up to 14 days after exposure and they developed similarly to tapeworms in the definitive host.

Anguilla↗
PubMed2001

Effects of the synthetic estrogen 17 alpha-ethinylestradiol on the life-cycle of the fathead minnow (Pimephales promelas).

A fish full life-cycle (FFLC) study was conducted for 17 alpha-ethinylestradiol (EE2) using the fathead minnow, Pimephales promelas. Newly fertilized embryos (< 24 h old) were exposed to five concentrations of EE2 (0.2, 1.0, 4.0, 16, and 64 ng/L nominal) in continuous flow-through conditions for 305 d at 25 +/- 1 degrees C. Exposure concentrations were verified by 14C-EE2 radiochemistry, supported by radioimmunoassay, and mean measured values were > or = 70% of nominal. For the F0 adult phase until 301 d posthatch, the no-observed-effect concentrations (NOECs) for growth, survival, and reproduction (as egg production) were all > or = 1.0 ng/L. The NOEC values for F1 embryo hatching success and larval survival (at 28 d posthatch) were both > or = 1.0 ng/L. While statistically detectable changes in F1 growth were evident at 0.2 ng/L, these were not considered to be biologically significant when compared with historical control data. Male fish exposed to EE2 at 4.0 ng/L failed to develop normal secondary sexual characteristics; on the other hand, assumed females exposed to this level of EE2 were able to breed when paired with males that had not been exposed to EE2. Histology of F0 control, 0.2-, and 1-ng/L exposed fish at 56 d posthatch indicated an approximate female-to-male (F:M) sex ratio of 50:50 (with no ovatestes observed in the control), while fish exposed to EE2 at 4.0 ng/L for 56 d posthatch had a F:M sex ratio of 84:5 (with ovatestes in 11% of fish). After 172 d posthatch, no testicular tissue was observed in any fish exposed to EE2 at 4.0 ng/L. At the same time point, plasma vitellogenin levels were significantly higher in fish exposed to EE2 at 16 ng/L. A lack of sexual differentiation occurred in males at concentrations > or = 4.0 ng/L. Taking into account these data, the overall no-observed-adverse-effect concentration was considered to be 1.0 ng/L.

Animals↗
PubMedDate not supplied

[Life cycles of ground beetles (Coleoptera, Carabidae) from the mountain taiga and mountain forest-steppe in the Eastern Sayan].

Seasonal dynamics and demographic structure was studied in 15 dominant ground beetle species in the mountain taiga and mountain forest-steppe belts of the Eastern Sayan (Okinskoe Plateau). Life cycles of the dominant ground beetle species were classified by developmental time, seasonal dynamics, and intrapopulation groups with different reproduction timing. The strategies of carabid life cycles adapted to severe mountain conditions of the Eastern Sayan were revealed.

Acclimatization↗
PubMed2002

The role of the cytoskeleton in the life cycle of viruses and intracellular bacteria: tracks, motors, and polymerization machines.

Recent advances in microbiology implicate the cytoskeleton in the life cycle of some pathogens, such as intracellular bacteria, Rickettsia and viruses. The cellular cytoskeleton provides the basis for intracellular movements such as those that transport the pathogen to and from the cell surface to the nuclear region, or those that produce cortical protrusions that project the pathogen outwards from the cell surface towards an adjacent cell. Transport in both directions within the neuron is required for pathogens such as the herpesviruses to travel to and from the nucleus and perinuclear region where replication takes place. This trafficking is likely to depend on cellular motors moving on a combination of microtubule and actin filament tracks. Recently, Bearer et al. reconstituted retrograde transport of herpes simplex virus (HSV) in the giant axon of the squid. These studies identified the tegument proteins as the viral proteins most likely to recruit retrograde motors for the transport of HSV to the neuronal nucleus. Similar microtubule-based intracellular movements are part of the biological behavior of vaccinia, a poxvirus, and of adenovirus. Pathogen-induced surface projections and motility within the cortical cytoplasm also play a role in the life cycle of intracellular pathogens. Such motility is driven by pathogen-mediated actin polymerization. Virulence depends on this actin-based motility, since virulence is reduced in Listeria ActA mutants that lack the ability to recruit Arp2/3 and polymerize actin and in vaccinia virus mutants that cannot stimulate actin polymerization. Inhibition of intracellular movements provides a potential strategy to limit pathogenicity. The host cell motors and tracks, as well as the pathogen factors that interact with them, are potential targets for novel antimicrobial therapy.

Actins↗
PubMed1982

Phasic secretion by follicular cells of the bat adenohypophysis during the prearousal period of their annual life cycle.

The fine structure of the follicular (nongranulated) cells of the adenohypophysis of the bat was examined at different periods of the annual life cycle. Follicular cells were found in all regions of the pars distalis of both active and hibernating bats. Throughout the active phase of the life cycle and during most of the hibernating period, the structure of follicular cells is unchanged. Toward the end of hibernation, however, striking ultrastructural changes occur. The most obvious of these alterations is the appearance in follicles of dense rod-shaped bodies within the follicular luminal space. Just prior to arousal, the rodlike bodies become much wider and appear more as paracrystalline aggregates of dense material. Images indicate that the dense rod-shaped bodies are packaged in vesicles in the cytoplasm of the follicular cells. The fusion of the membrane of filled vesicles with the plasma membrane of the follicular cell results in the release of their dense rod-shaped bodies into the follicular lumen by exocytosis. These cyclic ultrastructural changes indicate that follicular cells have a phasic secretory activity.

Animals↗
PubMed2000

SCID mice as a tool for evaluation of heteroxenous life cycle pattern of Caryospora (Apicomplexa, Eimeriidae) species.

Adult severe combined immunodeficient (SCID) mice were inoculated with oocysts of 13 different Caryospora (Protozoa, Apicomplexa) species isolated from the faeces of 10 reptilian and three raptorial bird hosts in attempt to test heteroxenous life cycle pattern. Only three reptilian isolates originated from viperid snakes, namely from Calloselasma rhodostoma, Atheris nitschei and Vipera ursinii induced lethal dermal caryosporosis in SCID mice. Neither clinical signs nor developmental stages were observed in mice infected with further nine caryosporan isolates originated from other reptilian and raptorial bird hosts. Results of this study confirmed that SCID mice represent a useful tool for evaluation of heteroxenous life cycle pattern of caryosporan coccidia and that only the Caryospora species from viperid and crotalid snakes produce dermal caryosporosis in mice

Animals↗