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PubMed2002

Life cycle, feeding and adaptive strategy implications on the co-occurrence of Argyrodiaptomus furcatus and Notodiaptomus iheringi in Lobo-Broa reservoir (SP, Brazil).

The population dynamics, life cycle and feeding of Argyrodiaptomus furcatus and Notodiaptomus iheringi, were studied in Broa reservoir from August 1988 to August 1989, period when a replacement of A. furcatus by N. iheringi was observed. Some abiotic factors such as temperature, dissolved oxygen, pH and conductivity were measured to characterize the limnological conditions of the reservoir. Also, phytoplankton composition was analyzed and related to the feeding of the two species. Experimental data on developmental time and reproduction of A. furcatus and N. iheringi under different temperatures showed that lower temperatures were responsible for density decreasing of both populations in the reservoir during the dry season. Chlorophyta and Chrysophyta smaller than 20 microns were the most abundant phytoplankton groups in the reservoir as well as in the gut content of A. furcatus and N. iheringi, representing an important food source for both species. The temporary disappearance of Argyrodiaptomus furcatus, observed between 1988 and 1989 and its replacement by Notodiaptomus iheringi was related to mining activities upstream, modifying the water turbidity, pH and conductivity. However, the reappearance and maintenance of A. furcatus for another ten years and a recent replacement re-incidence indicates that these two calanoids do not coexist in this environment. Adaptive strategies of both species, related to changes in environmental conditions, are discussed. Probably, Argyrodiaptomus furcatus is an indicator of less eutrophic environments, while Notodiaptomus iheringi of more eutrophic systems.

Animals↗
PubMed2002

Nonrandom association patterns in parasite infections caused by the host life cycle: empirical evidence from Kudoa camarguensis (Myxosporea) and Aphalloides coelomicola (Trematoda).

Pomatoschistus microps is 1 of the most common fish species inhabiting Mediterranean coastal lagoons. This small species uses an early maturation and a short life span to occupy sites subject to high variability in environmental factors. During monthly investigations on a P. microps population of the Vaccarès Lagoon from March 1993 to December 1997, 2 conspicuous parasites were noticed. The digenean Aphalloides coelomicola was harbored in the abdominal cavity of the fish, whereas the myxosporean Kudoa camarguensis was found in the muscle tissues. Monthly peaks of prevalence occurred at the same period for both parasites, and a positive correlation (permutation test and Janson and Vegelius correlation) was observed between their occurrences among sampled fish. These results suggest that this positive association is related to a third common factor, i.e., their host's life cycle.

Animals↗
PubMed2006

Effects of the antithyroid agent propylthiouracil in a partial life cycle assay with zebrafish.

Some ubiquitous pollutants of the aquatic environment, such as PCBs or other polyhalogenated aromatic hydrocarbons, may disrupt the thyroid hormone system. In a partial life cycle assay with zebrafish (Danio rerio), we studied the effects of the reference compound propylthiouracil (PTU) on reproduction, growth and development, histopathology of some target tissues, and plasma thyroid hormone levels. PTU induced a concentration-dependent increase of egg production with a concomitant decrease of mature oocyte size but had no effect on fertilization rate or hatching. In F1, serious dysmorphogenesis was found in 4 dph larvae at the highest PTU level tested (100 mg/L), and there was a dose-dependent decrease in body length and weight at 42 dph (significant at 100 mg/L PTU). At this time, there was also a decreased scale thickness, suggesting inhibited metamorphosis, detectable at 1 mg/L PTU and higher. PTU also induced activation of the thyroid follicles in a concentration-dependent way, in juveniles associated with hyperemia in the thyroid area, and depletion of liver glycogen. Effects in adults were associated with decreased circulating levels of the thyroid hormones T3 and T4. These observations indicate that disruption of the thyroid hormone system may affect the fitness of these aquatic organisms. The zebrafish model may contribute to the identification of thyroid hormone disrupting activity in water samples and also in the interpretation of histological observations in free-ranging fish species.

Animals↗
PubMed2005

An expressed sequence tag analysis of the life-cycle of the parasitic nematode Strongyloides ratti.

14,761 expressed sequence tags (ESTs) were generated, representing five stages during the parasitic and free-living phases of the life-cycle of the parasitic nematode Strongyloides ratti. These ESTs formed 4152 clusters, of which 97% contained 10 or fewer ESTs and 66% were singletons. These 4152 clusters are likely to represent approximately 20% of S. ratti's genes. The clusters' consensus sequences were used to assign each cluster to one of three databases: (i) Caenorhabditis elegans and C. briggsae sequences; (ii) other nematode sequences; (iii) non-nematode sequences. This approach has identified putative nematode-specific genes, that may be targets for developing approaches for parasitic nematode control. Approximately 25% of the clusters have no significant alignments and may therefore represent novel genes. The EST representation between the libraries was used to analyse stage-specific or -biased expression in silico. This showed that 81% of clusters are present in only one library and 12% are present in any two libraries, indicating substantial stage-specificity of gene expression. The 30-most abundantly expressed clusters were analysed in further detail. Many of these have significantly different parasitic- or free-living-specific or -biased expression. Many of the parasitic-specific genes are, as yet, uncharacterised: one of these represents 25% of all ESTs obtained from the parasitic stage.

Animals↗
PubMed2005

Calculating life-cycle assessment effect factors from potentially affected fraction-based ecotoxicological response functions.

A new multisubstance potentially affected fraction (msPAF)-based method for calculating ecotoxicological effect factors for life-cycle assessment is introduced and compared to two other available methods of calculation. The new method is based on marginal increase of the msPAF of species. The method follows concentration-additive rules for pollutants with the same toxic mode of action (TMoA) and response-additive calculation rules for pollutants with independent action, and it combines a TMoA-specific factor, which is calculated differently in different methods, and a substance-specific factor, which is common to all methods. For 261 substances in 22 toxic modes of action, ecotoxicological effect factors for freshwater ecosystems have been calculated by different methods. Method-related differences appear to be rather small. Intersubstance differences in effect factors stem from differences in substance-specific toxic potencies, which span eight orders of magnitude, rather than from differences in TMoA-specific factors, which span only three orders of magnitude. Based on these insights, the choice of a calculation method seems to be a matter of personal (scientific) preference. The new hybrid msPAF method was greatly sensitive to data that usually are not known with sufficient certainty. Its use is recommended, entirely for reasons of scientific consistency, under strict conditions. When such conditions are not met or if necessary parameter values are unavailable, use of a fixed value for the TMoA-specific component is recommended.

Adaptation, Physiological↗
PubMed2005

Role of the E1--E4 protein in the differentiation-dependent life cycle of human papillomavirus type 31.

The most highly expressed protein in the productive life cycle of human papillomaviruses (HPVs) is E1--E4, but its function is not well understood. To investigate the role of E1--E4, we undertook a genetic analysis in the context of the complete HPV type 31 (HPV31) genome. A mutant HPV31 genome (E4M9) was constructed that contained a stop codon in the E4 open reading frame at amino acid 9 and was silent in the overlapping E2 coding sequence. Wild-type and mutant genomes were transfected into normal human foreskin keratinocytes (HFKs) and selected for drug resistance, and pooled cultures were examined for effects of E1--E4 on viral functions. Southern blot analyses of transfected HFKs demonstrated that cells carrying the E4M9 mutant genomes were maintained as episomes at copy numbers similar to those in keratinocytes transfected with wild-type HPV31. Both sets of cells grew at similar rates, exhibited comparable extensions of life spans, and had equivalent levels of early transcripts. Following suspension of the cells in a semisolid medium, differentiation-dependent genome amplification and late gene expression were significantly decreased in cells maintaining the E4M9 mutant genome compared to those with wild-type HPV31. One explanation for these effects could be a reduction in the number of cells harboring mutant genomes that enter S phase upon differentiation. An analysis of cells containing E4M9 mutant genomes in organotypic raft cultures indicated a reduction in bromodeoxyuridine incorporation in differentiated suprabasal cells compared to that seen in wild-type rafts. Our results indicate that the HPV31 E1--E4 protein plays a significant role in promoting HPV genome amplification and S phase maintenance during differentiation.

Cell Differentiation↗
PubMed1995

Comparison of characteristics of life cycle in female ticks collected on N'Dama and zebu cattle.

Characteristics of the life cycle of female ticks (Amblyomma variegatum, Hyalomma truncatum and Boophilus geigyi) fed on N'Dama and zebu cattle were studied in the laboratory from pre-oviposition period to larval development. Percentage of A. variegatum eggs hatched and engorgement weight of H. truncatum were lower in ticks collected on N'Dama than on zebu cattle. Laboratory results confirmed field observations of species specific tick resistance in the N'Dama breed.

Animals↗
PubMed1975

Effects of antibiotics on the life cycle of Neurospora crassa.

Some antibiotics and synthetic inhibitors affect, in several ways, the life cycle of Neurospora crassa (germination of conidia leads to myceliar growth leads to formation of conidia). Bikaverin, cyanein, scopathricin and phenethyl alcohol retard the germination of conidia, without inhibiting it completely. 5-Fluorouracil, ramihyphin A and zygosporin A (cytochalasin D) do not inhibit the germination. Bikaverin brings about a thickening of the hyphae of growing mycelium. Ramihyphin A, cyanein, scopathricin and zygosporin A stimulate the ramification of hyphae while 5-fluorouracil and phenethyl alcohol do not affect the myceliar morphology apart from their inhibitory effect on growth. Actinomycin D, 5-fluorouracil, cycloheximide, ramihyphin A and partially also sodium iodoacetate inhibit to a different degree the photoinduced formation of conidia. The inhibition by 5-fluorouracil is very conspicuous when the agent is present during the photoinduction but considerably weaker when it is applied 2 h after the photoinduction.

Antifungal Agents↗
PubMed1987

Interaction of the plant toxin ricin with different life cycle stages of Schistosoma mansoni.

The binding of the plant toxin ricin to various life cycle stages of Schistosoma mansoni has been studied. Fluorescein isothiocyanate (FITC)-ricin exhibited binding to schistosomula and adult worms, but not to cercariae or to freshly transformed schistosomula. Binding was specifically inhibited by the presence of galactose in the medium. Analysis of protein synthesis in treated parasites illustrated that ricin failed to intoxicate schistosomula or adult worms. Indeed, fluorescence quenching studies suggested that the fluorescent toxin was confined to the outer bilayer and was not internalised.

Animals↗
PubMed2005

The papillomavirus life cycle.

Papillomaviruses infect epithelial cells, and depend on epithelial differentiation for completion of their life cycle. The expression of viral gene products is closely regulated as the infected basal cell migrates towards the epithelial surface. Expression of E6 and E7 in the lower epithelial layers drives cells into S-phase, which creates an environment that is conducive for viral genome replication and cell proliferation. Genome amplification, which is necessary for the production of infectious virions, is prevented until the levels of viral replication proteins rise, and depends on the co-expression of several viral proteins. Virus capsid proteins are expressed in cells that also express E4 as the infected cell enters the upper epithelial layers. The timing of these events varies depending on the infecting papillomavirus, and in the case of the high-risk human papillomaviruses (HPVs), on the severity of neoplasia. Viruses that are evolutionarily related, such as HPV1 and canine oral papillomavirus (COPV), generally organize their productive cycle in a similar way, despite infecting different hosts and epithelial sites. In some instances, such as following HPV16 infection of the cervix or cottontail rabbit papillomavirus (CRPV) infection of domestic rabbits, papillomaviruses can undergo abortive infections in which the productive cycle of the virus is not completed. As with other DNA tumour viruses, such abortive infections can predispose to cancer.

Epithelial Cells↗
PubMed2005

Retroviral matrix domains share electrostatic homology: models for membrane binding function throughout the viral life cycle.

The matrix domain (MA) of Gag polyproteins performs multiple functions throughout the retroviral life cycle. MA structures have an electropositive surface patch that is implicated in membrane association. Here, we use computational methods to demonstrate that electrostatic control of membrane binding is a central characteristic of all retroviruses. We are able to explain a wide range of experimental observations and provide a level of quantitative and molecular detail that has been inaccessible to experiment. We further predict that MA may exist in a variety of oligomerization states and propose mechanistic models for the effects of phosphoinositides and phosphorylation. The calculations provide a conceptual model for how non-myristoylated and myristoylated MAs behave similarly in assembly and disassembly. Hence, they provide a unified quantitative picture of the structural and energetic origins of the entire range of MA function and thus enhance, extend, and integrate previous observations on individual stages of the process.

Cell Membrane↗
PubMed1976

Observations on the life-cycle of the strigeoid trematode, Apatemon (Apatemon) gracilis (Rudolphi, 1819) Szidat, 1928.

The life-cycle of Apatemon (A.) gracilis was completed in the laboratory. The snail host is Lymnaea peregra (Muller). The cercaria is redescribed from a wide range of material. Metacercariae were found in naturally infected rainbow trout (Salmo gairdneri Richardson), three-spined sticklebacks (Gasterosteus aculeatus L.) and stone loach (Nemacheilus barbatulus (L.)) from Scotland and in three-spined sticklebacks from Iceland. In trout, most metacercariae were found in the pericardial cavity, in sticklebacks, the eye, and in loach, the body cavity. In infection experiments, cercariae from naturally infected Scottish snails developed in three-spined sticklebacks, rainbow trout and brown trout (Salmo trutta L.). Under experimental conditions cercariae did not penetrate stone loach, although this species is naturally infected with A. gracilis. The phenomenon of fish host specificity is briefly discussed. Development of the metacercaria is described. Excystation of metacercarial cysts with pepsin and trypsin solutions is unlike that reported for any other digenean; the contents of the cyst appear to be under pressure. In pepsin, layers of the cyst wall peel back from one end. When transferred to trypsin, one pole of the cyst ruptures and the worm is forcibly expelled.

Animals↗
PubMed2000

Life cycle of the tick Haemaphysalis leporis-palustris (Acari: Ixodidae) under laboratory conditions.

The life cycles of two separate populations (colonies A and B) of the rabbit tick, Haemaphysalis leporis-palustris, were studied under laboratory conditions. Domestic New Zealand rabbits, Oryctolagus cuniculus, and wild rabbits, Sylvilagus brasiliensis, were used as hosts for ticks from colony B and only O. cuniculus rabbits were used as hosts for ticks from colony A. Developmental periods were observed in an incubator at 27+/-1 degrees C and RH 90+/-5%. Larvae from colonies A and B fed for 8.0+/-3.7 days and 8.5+/-1.3 days, respectively, on O. cuniculus. On S. brasiliensis larvae from colony B fed for 7.2+/-1.3 days. Nymphs from colony A fed for 8.1+/-1.4 days on O. cuniculus and nymphs from colony B fed for 8.1+/-1.0 days on S. brasiliensis. Only one engorged nymph from colony B was recovered from O. cuniculus. Females from colony A fed for 20.9+/-5.9 days on O. cuniculus and females from colony B fed for 18.6+/-2.4 days on O. cuniculus and 18.7+/-3.7 days on S. brasiliensis. Engorged larvae from colony A required 13.7+/-3.7 days to molt while engorged larvae from colony B required 11.8+/-3.0 and 11.5+/-1.8 days to molt, after having fed on O. cuniculus and S. brasiliensis, respectively. Engorged nymphs from colonies A and B required 16.3+/-1.9 days and 14.7+/-1.4 days to molt, respectively. Engorged females from colonies A and B required 4-7 and 3-5 days, respectively, to start oviposition. Mean egg incubation periods lasted for 33-34 days. For ticks from colony B, host species accounted for significant differences (p < 0.05) in larval and nymphal feeding periods, oviposition weights and CEIs. Significant differences (p < 0.05) between the two colonies when ticks fed on O. cuniculus were observed for larval and nymphal feeding and premolt periods, engorged female and oviposition weights and conversion efficiency indexes (CEI). S. brasiliensis were always a more suitable host for H. leporis-palustris than O. cuniculus. Significantly more larvae and nymphs engorged and molted when fed on S. brasiliensis (p < 0.001). Females fed S. brasiliensis were more successful to lay fertile eggs and showed the highest engorged and egg mass weights, and the highest CEIs. Data of H. leporis-palustris fed on wild rabbits (one of its natural host species) are reported for the first time.

Animals↗
PubMedDate not supplied

[Adolescence and family life cycle. Role of the pediatrician].

Adolescence observed as one of the step of the life cycle from the point of view of changes in the family. The role of paediatricians in the conversation with the adolescent and his parents is to pay attention to the influence that the whole family system could have on producing symptoms.

Adolescent↗
PubMed1978

The life cycle of Eimeria falciformis var. pragensis (Sporozoa: Coccidia) in the mouse, Mus musculus.

The life cycle of Eimeria falciformis var. pragensis, established from a single oocyst, is described in experimentally infected mice (Mus musculus). The coccidium had a prepatent period of 7 days and a patent period of 10--16 days. Oocysts were spherical to ellipsoidal in shape and measured 21.2 x 18.3 micron. Sporulation time was 3 to 3.5 days. Sporocysts measured 12.2 x 7.2 micron and contained a circular to avoid granular sporocyst residuum measuring 5.5 X 5.0 micron. One, 2 or 3 circular to rectangular polar granules were observed within each sporulated oocyst. The endogenous stages developed primarily in the cecum and colon and only occasionally in the lower ileum. Four generations of schizonts were found. Mature 1st-generation schizonts, first observed 48 hr postinfection (PI), measured 17.8 x 12.3 micron and had 12 merozoites that measured 13.3 x 2.0 micron. Mature 2nd-generation schizonts appeared 78 hr PI. They measured 10.2 x 9.3 micron and had 8 merozoites measuring 5.0 x 1.6 micron. Mature 3rd-generation schizonts appeared first at 114 hr PI and measured 17.5 x 10.2 micron and had 10 merozoites that measured 12.4 x 1.8 micron. Mature 4th-generation schizonts appeared first at 144 hr PI. They measured 18.2 x 15.3 micron and had 18 merozoites. The merozoites of the 4th-generation schizont were 4.5 x 1.2 micron. Mature macrogamonts and microgamonts developed simultaneously appearing at 156 hr PI. Macrogamonts measured 16 x 14.5 micron and microgamonts were 18.2 x 15.3 micron. In experimentally infected rats (Rattus norvegicus), development of E. falciformis var. pragensis progressed only as far as mature 1st-generation schizonts.

Animals↗
PubMed1978

The life cycle of the tick Hyalomma marginatum rufipes Koch (Acarina: Ixodidae) under laboratory conditions.

The life cycle of Hyalomma marginatum rufipes Koch was studied under laboratory conditions at 26 +/- 1 C. The preoviposition period was 7.1 +/- 0.23 days. The mean (+/- SE) number of eggs was 6,867 +/- 2,609 (max. 13,180, min. 3,184). The greatest egg production was recorded on day 3 (avg 1,170 egg/female). The incubation period was 29.3 +/- 2.96 days. The feeding time of larvae and nymphs of this 2-host tick was 22.8 +/- 0.13 days. Nymphs producing males weighed less (23.1 +/- 0.748 mg) than those producing females (26.8 +/- 1.19 mg); the combined larval-nymphal feeding time of the former was shorter (21.9 +/- 0.1 days) than that of the latter (22.9 +/- 1.12 days). The premolting period of nymphs to adults of both sexes was similar.

Animals↗