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PubMed1996

Immunization against Trichinella spiralis using antigens from different life-cycle stages experimental study in mice.

Crude antigen preparations from different life-cycle stages of T. spiralis using 10 micrograms and 100 micrograms antigen/dose, were tested for their ability to immunize mice against homologous challenge infection. Immunization was assessed by accelerated expulsion of adult worms, reduction in female worm fecundity and decreased yield of muscle larvae. The dose of 100 micrograms proved to be more protective in all antigen preparations. The AA provided highly significant protection against adult stages (89%) and muscle larvae (80%). NLA produced highly significant protection against muscle larvae only (76%). MLA provided highly significant protection against adult stages (74%), female fecundity (74%) and muscle larvae (80%). Combination of AA and MLA produced highly significant protection against adult stages (96%), female fecundity (73%) and muscle larvae (86). The results show that all antigen preparations provided variable, considerable but partial protection against challenge infection. The variations in immunization potential are discussed.

Animals↗
PubMed1977

The life cycle of the myofibroblast.

Myofibroblasts in pig granulating wounds have an identifiable life cycle that parallels the eight week span of contraction of the wounds. As seen by electron microscopy, fibroblasts with a contractile appearance became prominent within one week after wounding and persisted for 12 weeks, after which time they were not visible. Large tangled filaments, measuring 120 Angstrom units are prominent in fibroblasts in late contracted wounds and may be actin. Such filaments could preserve fibroblasts in a contracted state and allow time for the reorganization of collagen into a fixed rigid scar.

Animals↗
PubMedDate not supplied

[Life cycle of trematode Psilotrema acutilostris (Psilostomidae) from Primor'e region].

Brought description trematodes Psilotrema acutilostris Oschmarin, 1963 received as a result experimental studying a life cycle. Installed that in conditions of Primorye land a role of intermediate host trematodes execute snails of Parafossarulus spiridonovi and P. manjuricus. The most further development trematodes goes with formation adolescaria. Adult worms P. acutilostris were growing in the chicken.

Animals↗
PubMed2000

Completion of the life cycle of Sarcocystis neurona.

Sarcocystis neurona is the most important cause of a neurologic disease in horses, equine protozoal myeloencephalitis (EPM). The complete life cycle of S. neurona, including the description of sarcocysts and intermediate hosts, has not been completed until now. Opossums (Didelphis spp.) are definitive hosts, and horses and other mammals are aberrant hosts. In the present study, laboratory-raised domestic cats (Felis domesticus) were fed sporocysts from the intestine of a naturally infected opossum (Didelphis virginiana). Microscopic sarcocysts, with a maximum size of 700 x 50 microm, developed in the muscles of the cats. The DNA of bradyzoites released from sarcocysts was confirmed as S. neurona. Laboratory-raised opossums (D. virginiana) fed cat muscles containing the sarcocysts shed sporocysts in their feces. The sporocysts were approximately 10(-12) x 6.5-8.0 microm in size. Gamma interferon knockout mice fed sporocysts from experimentally infected opossums developed clinical sarcocystosis, and S. neurona was identified in their tissues using S. neurona-specific polyclonal rabbit serum. Two seronegative ponies fed sporocysts from an experimentally-infected opossum developed S. neurona-specific antibodies within 14 days.

Animals↗
PubMed2003

Morphological description and life cycle of Paragonimus sp. (Trematoda: Troglotrematidae): causal agent of human paragonimiasis in Colombia.

The first morphological description is made of all stages of the life cycle of a Paragonimus species infecting humans in Colombia. Larval stages were obtained both in vitro and from field collections. Adult Paragonimus spp. are described. The aquatic snail Aroapyrgus sp. serves as an intermediate host of this species, both naturally and experimentally, yielding rediae and cercariae. Crabs (Hypolobocera bouvieri monticola and H. emberarum) were found to be the natural second intermediate hosts, and individuals of another crab species (Strengeria sp.) were also infected in the laboratory.

Animals↗
PubMed2002

The life cycle of Gregarina ronderosi n. sp. (Apicomplexa: Gregarinidae) in the Argentine grasshopper Dichroplus elongatus (Orthoptera: Acrididae).

Gregarina ronderosi n. sp. is described based on life cycle observations conducted on nymphs and adults of its natural host, the grasshopper Dichroplus elongatus. Following ingestion of oocysts by the host, parasite development occurs between the epithelium and the food mass in the midgut and gastric caeca. Gametocysts are liberated in the faeces. Natural prevalence in the type locality, Girondo, northwestern Buenos Aires Province, was 39.7% (n=131). The earliest trophozoites seen were small (< or = 10 microm), somewhat ovoid, unsegmented bodies. Fully developed trophozoites (the body is divided into epimerite, protomerite, and deutomerite) were slender, with conical or globular epimerites in attached or unattached forms, respectively. Trophozoites varied greatly in size [total length: 10.4-275.1 microm; mean (+/-S.E.): 126.3+/-78.9]. Gamonts, which were the most common stages observed and filled the midgut and gastric caeca in grasshoppers kept in rearing rooms, had a stocky appearance and also varied greatly in size (total length: 80-348 microm; 205+/-13). Association of gamonts was precocious, biassociative, and caudofrontal. Gametocysts were spherical and highly variable in size (96-376 microm in diameter; 202.8+/-52.5), and normally have 14 sporoduct basal discs. Everted sporoducts were up to 60 microm long. Oocysts were uniformly doliform in shape, measured (5+/-0.08 by 3.2+/-0.06 microm) and contained eight sporozoites. Wall reinforcements (carinae) were present. No infection resulted in experimentally inoculated Locusta migratoria, which is a host of Gregarina acridiorum. G. ronderosi is strikingly similar to G. acridiorum, but has larger oocysts.

Animals↗
PubMed2006

Inteins, introns, and homing endonucleases: recent revelations about the life cycle of parasitic genetic elements.

Self splicing introns and inteins that rely on a homing endonuclease for propagation are parasitic genetic elements. Their life-cycle and evolutionary fate has been described through the homing cycle. According to this model the homing endonuclease is selected for function only during the spreading phase of the parasite. This phase ends when the parasitic element is fixed in the population. Upon fixation the homing endonuclease is no longer under selection, and its activity is lost through random processes. Recent analyses of these parasitic elements with functional homing endonucleases suggest that this model in its most simple form is not always applicable. Apparently, functioning homing endonuclease can persist over long evolutionary times in populations and species that are thought to be asexual or nearly asexual. Here we review these recent findings and discuss their implications. Reasons for the long-term persistence of a functional homing endonuclease include: More recombination (sexual and as a result of gene transfer) than previously assumed for these organisms; complex population structures that prevent the element from being fixed; a balance between active spreading of the homing endonuclease and a decrease in fitness caused by the parasite in the host organism; or a function of the homing endonuclease that increases the fitness of the host organism and results in purifying selection for the homing endonuclease activity, even after fixation in a local population. In the future, more detailed studies of the population dynamics of the activity and regulation of homing endonucleases are needed to decide between these possibilities, and to determine their relative contributions to the long term survival of parasitic genes within a population. Two outstanding publications on the amoeba Naegleria group I intron (Wikmark et al. BMC Evol Biol 2006, 6:39) and the PRP8 inteins in ascomycetes (Butler et al.BMC Evol Biol 2006, 6:42) provide important stepping stones towards integrated studies on how these parasitic elements evolve through time together with, or despite, their hosts.

Amoeba↗
PubMedDate not supplied

[Conditions favoring differentiation and stabilization of the life cycle of the yeast Pachysolen tannophilus].

Conditions favoring differentiation and stabilization of the life cycle of the yeast Pachysolen tannophilus have been studied. When concentrations of the carbon source in the medium were lower than 100 g/l, it was found to be favorable to the mating of vegetative cells, both haploid and diploid. The addition of nitrogen and sulfur sources to the medium influenced the life phases of haploid cells and partially stabilized the vegetative growth of diploid cells. Enrichment of the nutrient medium with potassium, vitamins, and microelements was shown to be necessary for the formation and maturation of conjugated ascospores. Microelements, vitamins, and phosphorus in excessive amounts activated conjugation but did not provide for the distinct phases of formation of unconjugated asci and spores in the diploid cells. Possible reasons for the unstable diplophase in the yeast P. tannophilus are discussed.

Cell Cycle↗
PubMed2005

Modelling of the life cycle of Chironomus species using an energy-based model.

Little is known about the differences between the species of the genus Chironomus relatively to their life cycle strategies. This knowledge is however crucial to fully understand the response of the Chironomus community to field perturbations. Here, we proposed to study four Chironomus species by using an energy-based model to describe growth, emergence and reproduction. We used data from the literature for two species (Chironomus plumosus and Chironomus tentans) and data from our experiments for two other species (Chironomus prasinus and Chironomus riparius). We showed that our model is able to accurately describe the life-history attributes for all the species tested, which suggests that Chironomus species have the same fundamental characteristics (low maintenance energetic costs, isomorphism), which makes possible the building of a common modelling framework to assess effects of toxicants at individual and population level. The species showed a few differences relatively to the parameters of the models with possible consequences when assessing effects of chemicals on Chironomus community. For instance, due to differences in growth parameters, C. riparius population dynamics should be more sensitive to effects on individual growth than C. prasinus or C. plumosus ones.

Animals↗
PubMedDate not supplied

Centripetal and centrifugal family life cycle factors in long-term outcome following traumatic brain injury.

The family life cycle model categorizes stresses on family systems in terms of their source and their effects on family members. Centripetal forces bring members together while centrifugal forces lead to loosened intrafamilial ties. This study examined the association of normative, developmental and centripetal illness-related family forces with patient outcome. Hypothesized centripetal and centrifugal forces acting on 65 families of married male TBI patients were used as independent variables in stepwise multiple regressions with criterion measures of quality of life outcome used as dependent measures. Centripetal variables included measures of family coping, marital adjustment, and number of years married. Centrifugal variables included number of children, age of oldest child, and amount of perceived financial strain. Regression equations obtained had multiple R's ranging from 0.623 to 0.407 (p values < 0.017). Results suggest that families normatively dealing with the developmental stage of the family with young children may face unique challenges when a husband sustains a TBI, particularly when financial strain exists. Stages in family development involving conflict between centripetal and centrifugal forces may be most problematic for families to resolve, and potentially the most effective periods for intervention.

Adaptation, Psychological↗
PubMed2000

Life cycle and parasitic interaction of the lizard-parasitizing mite Ophionyssus galloticolus (Acari: Gamasida: Macronyssidae), with remarks about the evolutionary consequences of parasitism in mites.

Wild-caught specimens of the lacertid lizard Gallotia galloti eisentrauti from the Canary Island of Tenerife were checked for ectoparasites. The parasitic gamasid mite Ophionyssus galloticolus Fain and Bannert (2000) was very abundant on these lizards. Additionally, parasitism by larvae of two species of Trombiculidae (Prostigmata: Parasitengona) was observed. O. galloticolus was reared in the laboratory on its natural host in order to investigate its life cycle, reproductive biology, and development. The life history of O. galloticolus is documented in detail and compared to literature data of other Ophionyssus species. O. galloticolus was found to be similar to other species of the same genus with respect to the duration of development, the precopulatory association of protonymphs, and the arrhenotokous development of eggs. However, it seems to be more tolerant towards low relative humidity and longer starvation periods than other Ophionyssus species. Evolutionary transformations of the life-history pattern of this genus and other parasitic mites in comparison to its predatory precursors involve a reduction or partial suppression of ontogenetic instars in order to decrease mortality during host-seeking phases, and a compensating increase in growth capacity of the remaining feeding instars facilitated by replacement of sclerites through elastic cuticle or by growth of new cuticle unrelated to a moult (neosomy).

Animals↗
PubMedDate not supplied

Nutrition and the life cycle 2: infancy and weaning.

The first article in this nutrition and the life cycle series discussed nutrition in pregnancy (Vol 9 (17): 1133-8). This second article will concentrate on infancy and weaning. Weaning infants is an area that causes concern for parents. Health professionals need to be well informed about this aspect of childcare, as practices have changed recently. Babies should usually begin weaning between 4 and 6 months of age. Infant diets need to be high in lipid for energy, and for essential long-chain fatty acids and fat-soluble vitamins. Their diets should also be rich in the micronutrients; infants are particularly at risk of deficiency for iron and zinc. Infants should be introduced to as many tastes and textures as reasonably possible, but foods likely to cause an allergic reaction should be avoided for as long as possible. Finally, all the family should enjoy mealtimes, and the pattern laid down for a life of healthy eating. The next article in this series will review nutrition in the school-age child.

Child, Preschool↗
PubMed2004

Predictors and characteristics of Erikson's life cycle model among men: a 32-year longitudinal study.

To assess Erikson's life cycle model, 86 men, initially selected for health, were prospectively studied at age 21, and reassessed 32 years later at age 53. Using the Vaillant and Milofsky (1980) modification of Erikson's model, 48 men (56%) achieved generativity, an advanced developmental stage, at follow-up. Results generally support Erikson's model and show that generativity was significantly associated with successful marriage, work achievements, close friendships, altruistic behaviors, and overall mental health. Successful young adult predictors of Erikson's model at midlife included a warm family environment, an absence of troubled parental discipline, a mentor relationship, and, most importantly, favorable peer group relationships. Significant predictors of Erikson's model were of moderate effect size and involve young adult social relationships rather than physical symptoms or parental social class standing.

Adaptation, Psychological↗
PubMed1989

The extraparasitic life cycle of Toxocara vitulorum in the village environment of Sri Lanka.

The extraparasitic life cycle of Toxocara vitulorum of buffalo in the villages of Sri Lanka is related to observations on buffalo behaviour, experimental studies on the development and persistence of the eggs in soil and in wallows and the presence of eggs in village locations. Calf faeces on soil were rapidly incorporated by insect activity and the eggs developed only slightly slower than in the laboratory. Some infective eggs persisted 3-4 cm deep for 17 months, finally dying during a prolonged hot, dry period. Eggs in a wallow developed intermittently over 16 months as it was flushed with rain water, and eventually died when the wallow dried out. When infected faeces were placed in water, decomposition caused some material to rise to the surface and eggs developed. In villages, eggs are ubiquitous where young calves are kept but survive best where there is moisture and shade around animal pens and wallows. Cows and calves acquire infection from infective eggs in wallow water, soil and pasture, while calves may also be infected from contamination on the udder and teats of the cow. The larvae resulting from this infection do not mature until the infection is passed to the calf through the milk of the cow. At least 72% of village calves have patent infections and current treatment procedures do not reduce the prevalence. The possibility that T. vitulorum is a cause of human visceral larva migrans is discussed.

Animal Husbandry↗
PubMedDate not supplied

[Life cycle of the trematode Echinostoma caproni Richard, 1964 (Echinostomatoidea) (author's transl)].

The life cycle of the Trematode Echinostomatoidea Echinostoma caproni Richard, 1964, develops under natural conditions in Madagascar in a bird Falco newtoni and in a Gastropod Biomphalaria pfeifferi. Metacercaries encyst in other Molluscs and in the kidney of an Amphibian Ptychadaena mascareniensis. The cycle has been reproduced experimentaly in France. The defivitive hosts are the white mouse, the rat and the chick. Biomphalaria galbrata is the first and the second intermediate host. Metacercaries encyst in different Molluscs and in the kidney of tadpoles of Rana esculenta. The larval stages are described. The cycle pattern and the morphology of larval stages are quite similar to those of Echinostoma liei Jeyarasasingam and coll., 1972.

Animals↗
PubMed2005

Break free from the product life cycle.

Most firms build their marketing strategies around the concept of the product life cycle--the idea that after introduction, products inevitably follow a course of growth, maturity, and decline. It doesn't have to be that way, says HBS marketing professor Youngme Moon. By positioning their products in unexpected ways, companies can change how customers mentally categorize them. In doing so, they can shift products lodged in the maturity phase back--and catapult new products forward--into the growth phase. The author describes three positioning strategies that marketers use to shift consumers' thinking. Reverse positioning strips away"sacred" product attributes while adding new ones (JetBlue, for example, withheld the expected first-class seating and in-flight meals on its planes while offering surprising perks like leather seats and extra legroom). Breakaway positioning associates the product with a radically different category (Swatch chose not to associate itself with fine jewelry and instead entered the fashion accessory category). And stealth positioning acclimates leery consumers to a new offering by cloaking the product's true nature (Sony positioned its less-than-perfect household robot as a quirky pet). Clayton Christensen described how new, simple technologies can upend a market. In an analogous way, these positioning strategies can exploit the vulnerability of established categories to new positioning. A company can use these techniques to go on the offensive and transform a category by demolishing its traditional boundaries. Companies that disrupt a category through positioning create a lucrative place to ply their wares--and can leave category incumbents scrambling.

Consumer Behavior↗
PubMed1987

The Afro-American life cycle: success, failure, and mental health.

The author examines the Afro-American life cycle from the period of the 1900s to the 1980s and discusses the psychosocial context for a three-generation Afro-American family living in America in the 1980s. The specific stresses and successful or maladaptive coping strategies of the members are presented as well as the potential mental health problems arising from ineffective mastery of developmental transitions.

Achievement↗