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At least 217 records · Page 12Linked to original sources
PubMed1998

A DNA-based demonstration of a three-host life-cycle for the Bivesiculidae (Platyhelminthes: Digenea)

Immature bivesiculid trematodes collected from the intestine of Thlalassoma lunare (Labridae) are shown to be morphologically consistent with adults of Bivesicula claviformis from Epinephelus fasciatus (Serranidae). In addition, the immature bivesiculids have the same sequence for the second internal transcribed spacer of the ribosomal DNA. Comparison with three other species of Bivesiculidae showed differences of between 23% and 30%. These results show that bivesiculids may have three-host life-cycles in addition to the two-host life-cycles that have been demonstrated previously. The three-host life-cycle enables bivesiculids to infect large carnivorous fishes.

Animals↗
PubMed1984

Life cycle of Isospora suis in gnotobiotic and conventionalized piglets.

Isospora suis had 3 asexual and 1 sexual intra-intestinal conventional life cycle. The first asexual generation was most prominent at 2 days p.i. (post inoculation) and produced 2-7 merozoites. The second-generation meronts were prevalent at 3-4 days p.i. and produced 2-12 large merozoites. At 4-5 days p.i. the third generation meronts were prominent and produced 4-24 small crescent shaped merozoites. Mature sexual stages were most prominent at 5-6 days p.i. The stages were most numerous in the distal half of the small intestine. At 8-9 days p.i. stages morphologically similar to the second generation of meronts reappeared, followed by the further development into third generation merozoites and sexual stages. This was reflected in a prepatent period of 5 days and a biphasic patent period of 5-8 or 9, and 11-14 days p.i. Intraperitoneal injection of liver/spleen and intestinal lymph node homogenates, respectively, from piglets infected 24 and 48 h, previously with high doses of oocysts, resulted in a patent infection 10-12 days post inoculation of the donor piglets. No differences in the life cycle of I. suis were observed between conventionalized and germ-free piglets. An extra-intestinal life cycle of I. suis related to the second patent period was postulated.

Animals↗
PubMed1984

[Family life cycle in Quebec: comparative views, seventeenth to twentieth centuries].

A comparison of the family life cycle in Quebec at the end of the seventeenth century and in the middle of the twentieth century is presented. "For both periods, calculations of comparative indices were carried out in the absence of mortality and divorce. This allows the emphasizing of the outstanding features of the family life cycle....In particular, the considerable reduction in the duration of the extensive phase [is noted; this] is linked to the significant drop in fertility, and the emerging of a long phase of stabilization during which the parents are responsible for all their children. Finally, an examination of the proportion of undissolved families at each stage clearly shows the dramatic impact of mortality on family life in the past." (summary in ENG, SPA)

Americas↗
PubMed2001

Phylogenetic analysis of Alloglossidium (Digenea: Macroderoididae) and related genera: life-cycle evolution and taxonomic revision.

A phylogenetic analysis was performed on 13 species of digenetic trematodes in the Macroderoididae, including 10 species of Alloglossidium, 2 species of Alloglossoides, and Hirudicolotrema richardsoni. The evolution of the unusual life-cycle patterns in the group was assessed in light of the proposed phylogeny. The results support previous hypotheses that taxa with a 3-host life cycle involving catfish as definitive hosts are basal to taxa with a 2-host life cycle involving invertebrates such as crustaceans and leeches as definitive hosts. Our results also strongly suggest that species maturing in leeches evolved from an ancestor that matured in crustaceans. Our phylogeny places Alloglossoides and Hirudicolotrema within Alloglossidium, showing Alloglossidium to be paraphyletic. To achieve a natural classification, Alloglossoides and Hirudicolotrema are synonymized with Alloglossidium, and a revised generic diagnosis for Alloglossidium is given.

Animals↗
PubMed2004

Genetic and biochemical analysis of cis regulatory elements within the keratinocyte enhancer region of the human papillomavirus type 31 upstream regulatory region during different stages of the viral life cycle.

Using linker scanning mutational analysis, we recently identified potential cis regulatory elements contained within the 5' upstream regulatory region (URR) domain and auxiliary enhancer (AE) region of the human papillomavirus type 31 (HPV31) URR involved in the regulation of E6/E7 promoter activity at different stages of the viral life cycle. For the present study, we extended the linker scanning mutational analysis to identify potential cis elements located in the keratinocyte enhancer (KE) region (nucleotides 7511 to 7762) of the HPV31 URR and to characterize cellular factors that bind to these elements under conditions representing different stages of the viral life cycle. The linker scanning mutational analysis identified viral cis elements located in the KE region that regulate transcription in the presence and absence of any viral gene products or viral DNA replication and determine the role of host tissue differentiation on viral transcriptional regulation. Using electrophoretic mobility shift assays, we illustrated defined reorganization in the composition of cellular transcription factors binding to the same cis regulatory elements at different stages of the HPV differentiation-dependent life cycle. Our studies provide an extensive map of functional elements in the KE region of the HPV31 URR, identify cis regulatory elements that exhibit significant transcription regulatory potential, and illustrate changes in specific protein-DNA interactions at different stages of the viral life cycle. The variable recruitment of transcription factors to the same cis element under different cellular conditions may represent a mechanism underlying the tight link between keratinocyte differentiation and E6/E7 expression.

Base Sequence↗
PubMed2002

Mitochondrial development during life cycle differentiation of African trypanosomes: evidence for a kinetoplast-dependent differentiation control point.

Life cycle differentiation of African trypanosomes entails developmental regulation of mitochondrial activity. This requires regulation of the nuclear genome and the kinetoplast, the trypanosome's unusual mitochondrial genome. To investigate the potential cross talk between the nuclear and mitochondrial genome during the events of differentiation, we have 1) disrupted expression of a nuclear-encoded component of the cytochrome oxidase (COX) complex; and 2) generated dyskinetoplastid cells, which lack a mitochondrial genome. Using RNA interference (RNAi) and by disrupting the nuclear COX VI gene, we demonstrate independent regulation of COX component mRNAs encoded in the nucleus and kinetoplast. However, two independent approaches (acriflavine treatment and RNA interference ablation of mitochondrial topoisomerase II) failed to establish clonal lines of dyskinetoplastid bloodstream forms. Nevertheless, dyskinetoplastid forms generated in vivo could undergo two life cycle differentiation events: transition from bloodstream slender to stumpy forms and the initiation of transformation to procyclic forms. However, they subsequently arrested at a specific point in this developmental program before cell cycle reentry. These results provide strong evidence for a requirement for kinetoplast DNA in the bloodstream and for a kinetoplast-dependent control point during differentiation to procyclic forms.

Acriflavine↗
PubMed1999

Exploiting the life cycle of Strongyloides ratii.

The nematode Strongyloides ratti has a remarkable life cycle, which has both a parasitic and a free-living phase. The free-living phase includes a choice between two developmental routes. Here, Mark Viney discusses recent advances in understanding the biology of this developmental switch and shows how the life cycle of this nematode can be used to explore the lifestyle transitions common to all parasitic nematodes, as well as to address other basic biological questions.

Animals↗
PubMed1991

The mitochondrial ATP synthase of Trypanosoma brucei: developmental regulation through the life cycle.

The mitochondrial H(+)-ATPase of the parasitic protozoan Trypanosoma brucei is shown to be developmentally regulated through the T. brucei life cycle as has been shown for components of the mitochondrial electron transport chain. We have substantiated our results by assaying not only for oligomycin-sensitive ATPase activity but also by determining the level of ATP synthetic activity. These results show that the level of ATPase present in the procyclic form of T. brucei is increased by at least threefold from that of the early bloodstream form while the ATPase activity in the late bloodstream form is only about twofold higher than the early form. ATP synthesis activity shows these same results. We have determined the level of ATP synthase protein present in the life cycle stages by Western analysis employing the antibodies that we have raised against both the water soluble F1 and the membrane-associated F0 moieties which we have purified from T. brucei. The Western blots of the procyclic form show strong reactivity with both the F0 and F1 antibodies. The other two life cycle stages, the early and the late bloodstream forms, show considerably less reactivity, paralleling the activity results. Electron micrographs of the sonicated mitochondrial fraction show inverted vesicles which are studded with knobby H(+)-ATPase in the procyclic form. The early bloodstream vesicles show very few of these characteristic structures, while the late bloodstream form shows a range of vesicles from nearly nude to partially studded.

Adenosine Triphosphatases↗
PubMed2006

New details from the complete life cycle of the red-tide dinoflagellate Noctiluca scintillans (Ehrenberg) McCartney.

Noctilucid protozoans are among the dinoflagellates that cause red tides. Sexual reproduction may occur in this group, as they sometimes undergo gametogenesis. However, the life cycle, in particular the developmental process after gamete fusion, has not been fully elucidated. We have been able to maintain clonal cultures of Noctiluca scintillans throughout the whole life cycle and have revealed new details of various stages. In trophont populations, a small fraction of cells spontaneously transform into gametogenic cells, which undergo two successive nuclear divisions, without cellular division, probably corresponding to meiosis. The products of nuclear division migrate to the cell surface with a small amount of cytoplasm, and there further synchronously divide 6-8 times, during which the division products are connected by thin cytoplasmic bridges. Thus, numerous gametes with a semi-spindle body shape are released from the mother cell ghost. They retain two flagella that differ in length and motion, as is typical of dinoflagellates. The presence of longitudinal and transverse grooves indicates that dinoflagellate-like characteristics are conserved in the gametes, although they are not present in the specialized trophonts. Zygotes with four flagella result from the fusion of two isogametes. The zygotes change shape from spindle to spherical, with a reduction in flagellar number. The developing cell acquires a tentacle and crust, similar to large trophonts, and begins to develop a cytoplasmic network, thus completing the transformation into a miniscule trophont. These early trophonts grow to maturity as cell size increases. Our observations of the life cycle of N. scintillans may provide clues for understanding the evolutionary origin of noctilucae.

Animals↗
PubMed1989

Transpiration during life cycle in controlled wheat growth.

We use a previously-developed model of wheat growth, which was designed for convenient incorporation into system-level models of advanced space life support systems. We apply the model to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. We examine the adequacy of modeling the transpiration as proportional to the inedible biomass and an age factor, which varies during the life cycle. Results indicate that during the main phase of vegetative growth in the first half of the life cycle, the rate of transpiration per unit mass of inedible biomass is more than double the rate during the phase of grain development and maturation during latter half of the life cycle.

Biomass↗
PubMed2004

Life cycle and population dynamic of Armadillidium pelagicum Arcangeli, 1955 (Isopoda, Oniscidea) at Aouina.

Armadillidium pelagicum Arcangeli, 1955 is a terrestrial isopod endemic to the circum-Sicilian islands and the North of Tunisia. The life cycle and the population structure of this species were studied on a natural population at Aouina, in the surroundings of Tunis, over 16 months from, January 2000 to April 2001, by monthly or semi-monthly samplings. The ovigerous females were present from March/April to the end of August and absent from September to February/March. These observations indicate that A. pelagicum at Aouina has a seasonal reproduction, followed by a sexual rest. The recruitment period is spread from April/May to mid-September. The fecundity, estimated by the number of eggs in the marsupium of ovigerous females, exhibited a great variability, which is related to the weight of these females. The sex ratio underwent fluctuations throughout the sampling period. It was female-biased in most samplings. Mass frequency distribution was analysed and nine cohorts were identified during the sampling period. The field growth rates are high in the first life phase, decrease during winter and increase during spring. The characteristics of the life cycle of A. pelagicum at Aouina may be summarized as follows: (i) Semi-annual species, since females appear to produce up to five broods per year, (ii) iteroparous females, since females seem to reproduce twice or more in life; (iii) bivoltine life cycle, since the population produces two generations per year; (iv) variability of cohorts' life span.

Animals↗
PubMed1976

Immunity to coccidiosis: stages of the life-cycle of Eimeria maxima which induce, and are affected by, the response of the host.

An attempt was made to determine the relative importance of the different life-cycle stages of Eimeria maxima in the induction of immunity and also those stages most affected by the immune response of the host. In one experiment the life-cycle was controlled by chemotherapy but in all other experiments partial life-cycles were induced by transfers of infected mucosa between hosts. The results indicated that the second generation schizont stage is probably that most concerned in the induction of protective immunity and that sexual stages are most susceptible to immune inhibition. After initial inhibition in the immune host the earlier asexual stages were able to resume development when transferred to a susceptible host. The longer the period of exposure to the immune environment, the less able was the parasite to recover.

Animals↗
PubMed1984

Analysis by flow cytometry of DNA synthesis during the life cycle of African trypanosomes.

DNA content, at different stages in the life cycle of the hemoprotozoan parasite Trypanosoma brucei, has been analysed with a fluorescence activated cell sorter. It was observed that the long slender bloodstream form stage and procyclic culture forms (analogous to the tsetse fly midgut stage) are dividing cell populations with cells in G1, S, G2 and mitosis. Short stumpy bloodstream form and metacyclic fly salivary gland form populations are composed of non-dividing parasites stabilized in G1 or G0 of the cell cycle. Haploids, possible sexual forms, were not detected. In response to transfer to a culture system which mimics the fly midgut, short stumpy bloodstream form parasites were readily able to initiate DNA synthesis and differentiate into dividing procyclic culture forms. This supports the suggested role of the short stumpy form as a transitional stage between the mammalian host and the tsetse fly vector. Analysis of early and late bloodstream populations of another salivarian trypanosome, Trypanosoma vivax, revealed a transition from dividing to stationary cell population similar to that observed with T. brucei. A hitherto unrecognized morphological form of T. vivax, analogous to the T. brucei short stumpy form, was detected. It is suggested that the long slender to short stumpy morphological transformation, long known in T. brucei, reflects a physiological transition from dividing to nondividing parasite relevant to the life cycle of all the salivarian trypanosomes.

Animals↗
PubMed1998

Use of the ITS rDNA for elucidation of some life-cycles of Mesometridae (Trematoda, Digenea).

Identification of larval stages is crucial for elucidating the life-cycles of various Digenea. However, in many digenean species, the larvae lack distinctive morphological features and it is impossible to establish the affiliation between the larval and adult stages by using morphological criteria. Molecular methods, based on DNA sequencing or PCR-restriction fragment length polymorphism analysis, can offer a new tool for larval-stage identification. In this study, the sequences of internal transcribed spacer of the ribosomal DNA were used to identify the cercariae of three out of five species of the family Mesometridae (Centroderma spinosissima, Elstia stossichianum and Wardula capitellata). The three species differ from one another by number of repeats in the region of internal transcribed spacer 1. The phylogeny of Mesometridae was inferred from their internal transcribed spacer ribosomal DNA sequences. The PCR-linked restriction fragment length polymorphism approach was developed for future life-cycle and ecological studies of this family.

Animals↗
PubMed2000

The life cycles of the temperate lactococcal bacteriophage phiLC3 monitored by a quantitative PCR method.

We present here a new and general approach for monitoring the life cycles of temperate bacteriophages which establish lysogeny by inserting their genomes site-specifically into the bacterial host chromosome. The method is based on quantitative amplification of specific DNA sites involved in various cut-and-join events during the life cycles of the phages (i.e. the cos, attP, attB, attL and attR sites) with the use of sequence-specific primers. By comparing the amounts of these specific DNA sites at different intervals, we were able to follow the development of the lytic and lysogenic life cycles of the temperate lactococcal bacteriophage phiLC3 after infection of its bacterial host Lactococcus lactis ssp. cremoris IMN-C18.

Bacteriophages↗
PubMed2004

Simultaneous modeling of multiple end points in life-cycle toxicity tests.

Standard toxicity tests do not allow extrapolations to the population level, mainly because these tests apply a short, fixed exposure time and focus on a single end point only. These limitations can be overcome by (partial) life-cycle toxicity testing, although these test results are harder to analyze. DEBtox is an existing software tool for the process-based analysis of standardized bioassays, and this paper presents two extensions of this method, making it applicable to life-cycle tests: the simultaneous assessment of end points and the description of aging (senescence) of the animals. We demonstrate these adaptations by describing life-cycle tests with the springtail Folsomia candida, exposed to cadmium and triphenyltin in their food. The extended model is able to describe the data for all end points simultaneously overtime with few, physiologically relevant parameters. Furthermore, the analysis reveals these chemicals to have distinctly different modes of action: cadmium apparently decreases the assimilation of energy from the food whereas triphenyltin increases the maintenance costs. The model fit allows calculation of the intrinsic rate of population increase, integrating effects on survival and reproduction. As the analysis is process based, population responses under food limitation can be explored, which depends critically on the selected mode of action.

Aging↗
PubMed1980

Lipids of stages in the life-cycle of the cestode Spirometra mansonoides.

The kinds and amounts of the lipids of each stage (egg, coracidium, procercoid, plerocercoid, adult) in the life-cycle of the cestode Spirometra mansonoides, and of environmental lipids, have been examined by combinations of TEAE-cellulose and silicic acid column, silica gel thin-layer and SCOT column gas-liquid chromatography. Major lipids of all stages were triacylglycerols, cholesterol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and phosphatidylcholine. Minor lipids were sterol esters, fatty acids, benzoquinones, partial glycerides phosphatidic acid, sphingolipids and lysolipids. Triacylglycerols decreased and cholesterol and phospholipids, particularly diphosphatidylglycerol and phosphatidylcholine, increased during embryogenesis (egg to coracidium). Neutral and phosphoglycerides had characteristic fatty acyl group patterns irrespective of life-cycle stage, except for procercoid lipids, which were unique in their content of branched and odd-numbered forms. The patterns seen in the total lipids of the various life-cycle stages were qualitatively similar to those of the environments of those stages, but were often quantitatively dissimilar.

Animals↗
PubMed1998

Spatial and temporal distribution of proopiomelanotropin and proopiocortin mRNA during the life cycle of the sea lamprey: a qualitative and quantitative in situ hybridization study.

Two POMC-like pituitary prohormones proopiocortin (POC) and proopiomelanotropin (POM) have been characterized from adult sea lampreys (Petromyzon marinus). POC encodes a nasohypophysial factor (NHF), ACTH, an MSH, and beta-END; and POM encodes MSH-A, MSH-B, and beta-END. Two radiolabeled riboprobes, one encoding a unique portion of POC mRNA and the other encoding the MSH-B domain unique to POM mRNA, were generated in order to examine the expression of POC and POM during the life cycle of the sea lamprey by in situ hybridization. POC expression appears evenly distributed throughout most cells of the rostral pars distalis (RPD) during the entire life cycle. POC expression also occurs in scattered cells of the caudal (proximal) pars distalis (CPD) at stage 5 of metamorphosis. By the prespawner period, POC expression is mainly distributed in the dorsal aspect of this region. POM expression was completely confined to most cells of the pars intermedia (PI) at all periods examined. Quantitative, computer-assisted, image analysis of POM expression revealed high signal densities in all larvae which decreased by early metamorphosis, steadily increased and reached high levels by late metamorphosis (stages 6 and 7), and attained even higher levels in prespawners. Volumetric analysis revealed that the net volume of POM expressing cells is at its lowest in larvae and increases during subsequent development. Analysis of signal density and volumetric measurements of POC expression revealed that POC expression in the RPD is low in larvae and steadily increases during subsequent intervals of the life cycle reaching very high levels by the prespawning period. POC expression in the CPD, first visible at stage 5, increases steadily throughout the remainder of metamorphosis and reaches the highest levels of expression in prespawning animals. These results would implicate the role of POM and POC in some developmental processes but not in the initiation of metamorphosis. The very high levels of POM and POC expression in prespawner animals suggest that the two genes may have important roles at this time in the life cycle of lampreys.

Animals↗