Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Life Cycle”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed1966

The distribution of nicotinamide nucleotides during the life cycle of the blowfly Lucilia cuprina Wied.

1. Variations in the amounts and distribution of the nicotinamide coenzymes during the life cycle of the blowfly Lucilia cuprina have been investigated. 2. The concentrations of NAD and NADP declined to a minimum in mid-pupal life, then increased threefold from this to about 600 and 40mmumoles/g. fresh wt. respectively in the adult. 3. The NADH/NAD ratio was relatively constant (0.15) except in mid-pupal life (0.09); the NADPH/NADP ratio was lower (0.6) in larvae and mated adults than at other stages (0.90). 4. The increase in NAD content during development was greatest in the thorax, which finally contained about 75% of the total coenzyme. 5. Incorporation of NAD into the thoracic sarcosomes began about 2 days before ecdysis. Initially, most (77%) of the coenzyme was in particles 0.2-1mu in diameter, at a concentration of 11.1mmumoles/mg. of protein. During development there was a gradual appearance of NAD in larger particles (1-10mu) containing 2.8mmumoles/mg. of protein. 6. Similar but less marked changes occurred with NADP, which had a final concentration in the large particles of 0.01mmumole/mg. of protein.

Abdomen↗
PubMed2002

A proteomic view of the Plasmodium falciparum life cycle.

The completion of the Plasmodium falciparum clone 3D7 genome provides a basis on which to conduct comparative proteomics studies of this human pathogen. Here, we applied a high-throughput proteomics approach to identify new potential drug and vaccine targets and to better understand the biology of this complex protozoan parasite. We characterized four stages of the parasite life cycle (sporozoites, merozoites, trophozoites and gametocytes) by multidimensional protein identification technology. Functional profiling of over 2,400 proteins agreed with the physiology of each stage. Unexpectedly, the antigenically variant proteins of var and rif genes, defined as molecules on the surface of infected erythrocytes, were also largely expressed in sporozoites. The detection of chromosomal clusters encoding co-expressed proteins suggested a potential mechanism for controlling gene expression.

Animals↗
PubMed1998

Taxonomy, genetic organization, and life cycle of Pneumocystis carinii.

Pneumocystis carinii was initially misidentified as a protozoan parasite. Recent molecular and biochemical analyses provide unequivocal evidence for placement of P. carinii with the fungi, and that P. carinii is most likely an ascomycete. Genetic investigations further show that P. carinii derived from different mammalian hosts (human, rat, mouse, and ferret) exhibit considerable chromosomal and gene sequence divergence indicating that they are likely of different species. The life cycle of P. carinii has not been definitively established, but available evidence is reviewed in light of classification of this organism as a fungus.

Animals↗
PubMed2006

Identification of new morphological and life-cycle stages of Cochlosoma anatis and experimental transmission using pseudocyst.

Cochlosoma anatis is a flagellated intestinal parasite that infects a variety of avian species. C. anatis infections have been associated with decreased weight gain and increased morbidity and mortality. Conditions favoring the growth of this organism in birds are current pathogenic intestinal infections and/or young age. There is little data describing the life cycle of this parasite. In this study, electron microscopy images are presented that document longitudinal binary fission of the trophozoite stage and outline the events of pseudocyst formation, which includes a rounding stage. Evidence provided here indicates that the pseudocyst stage may be a mechanism for transmission of this organism. The observations reported here provide additional evidence of homology between Cochlosoma and members of the trichomonad order.

Animals↗
PubMed2000

The kidney form of Trypanosoma musculi: A distinct stage in the life cycle?

Trypanosoma musculi is a parasite specific to mice, which resides in the blood and lacks intracellular stages. After immune clearance of the flagellates from the general circulation, mice are resistant to reinfection. Yet, long after parasites are no longer detected in the peripheral blood, they persist in the vasa recta of the kidneys and it has been proposed that this is an immunologically privileged site for T. musculi. This relationship provides a useful model for studies of latent or chronic infections in immune hosts. Here, Fernando Monroy and Donald Dusanic consider the immune responses of mice to T. musculi and compare characteristics of the parasites from the vasa recta (kidney forms, KFs) of mice with latent infections to trypanosomes from the peripheral blood (bloodstream forms, BSFs) of animals during active infections. They consider how KFs evade immune destruction and suggest that these sequestered parasites represent a distinct stage in the life cycle.

Animals↗
PubMed2000

[Cell biology and life cycle of the testate amoeba Corythion delamarei].

Corythion delamarei Bonnet, Thomas, 1960, a typical testate amoeba with hyaline, filiform pseudopodia (Filosea Leidy, 1879), is a mass and widely spread species in the forest soil of Leningrad district. This species has been studied in natural and experimental conditions by means of morphological, cytochemical and morphometrical methods, including original culturing in vitro. The complex life cycle of C. delamarei involves the number of phases: trophozoites, precysts, resting cysts, copulating trophozoits, cystozygotes, cells with spores inside the shell, small amoeboid cells producing spores after germination. Different stages display structural peculiarities reflecting adaptation to exogenous environment. In C. delamarei sexual process has been first discovered. It represents a primitive form of isogamic copulation of morphologically similar trophozoites copulation and results in uninuclear cystozygote formation. The zygote nucleus is a synkaryon meiosis is zygotic, and is accomplished in two steps. Copulation occurs only between two trophozoites of one and the same species. Further zygote development includes its excystation that eventually gives rise to a trophozoite which then undergoes several metagamic divisions resulting in spore formation, thus starting a new generation of trophozoites.

Amoeba↗
PubMed1994

A search for an essential function of the replication origin ARS1 in the life cycle of Saccharomyces cerevisiae.

We have investigated the significance of the chromosomal replication origin, ARS1, during the entire life cycle of yeast. This was done by substituting the chromosomal copy with a series of ars1 deletion mutants. It was shown that the ARS1 replication origin is not essential for mitotic or premeiotic DNA replication since no effect on growth, chromosomal loss rate and spore viability was observed in the ars1 mutant strains. We conclude that replication origins are abundantly, present in the yeast genome and that the removal of a single replication origin is compensated for by replication forks emanating from neighbouring origins.

Chromosomes, Fungal↗
PubMed1994

The life cycle of Asymphylodora tincae (Modeer 1790) (Trematoda: Monorchiidae): a unique development in monorchiid trematodes.

A study on the life cycle of the trematode Asymphylodora tincae (Modeer 1790) (family Monorchiidae), carried out under both natural and laboratory conditions, revealed as its most remarkable characteristics the absence of a metacercarial stage. The definitive host, the tench [Tinca tinca (L.)], became directly infected after the ingestion of snails harbouring rediae with mature cercariae. With the exception of the sporocyst, all developmental stages from both naturally and experimentally infected pulmonate snails as well as adults from experimental fish hosts were described and illustrated, including the surface morphology of the cercariae, studied by scanning electron microscopy. Confusion in the identification of larval stages from pulmonate snails and the prosobranchiate genus Bithynia, hitherto identified as A. tincae by other authors, are briefly discussed with regard to the present results.

Animals↗
PubMed2001

Priority assessment of toxic substances in life cycle assessment. III: Export of potential impact over time and space.

Toxicity potentials are scaling factors used in life cycle assessment (LCA) indicating their relative importance in terms of potential toxic impacts. This paper presents the results of an uncertainty assessment of toxicity potentials for 181 substances that were calculated with the global nested multi-media fate, exposure and effects model USES-LCA. The variance in toxicity potentials resulting from choices in the modelling procedure was quantified by means of scenario analysis. A first scenario analysis showed to what extent potential impacts in the relatively short term are obscured by the inclusion of impacts on the very long term. Toxicity potentials representing potential impacts over time horizons of 20, 100 and 500 years were compared with toxicity potentials representing potential impacts over an infinite time horizon. Time horizon dependent differences up to 6.5 orders of magnitude were found for metal toxicity potentials, while for toxicity potentials of organic substances under study, differences remain within 0.5 orders of magnitude. The second scenario analysis addressed to what extent potential impacts on the continental scale are obscured by the inclusion of impacts on the global scale. Exclusion of potential impacts on the global scale changed the toxicity potentials of metals and volatile persistent halogenated organics up to 2.3 orders of magnitude. These scenario analyses also provide the basis for determining exports to future generations and outside the emission area.

Animals↗
PubMed1997

Toxoplasma gondii expresses two distinct lactate dehydrogenase homologous genes during its life cycle in intermediate hosts.

Two Toxoplasma gondii genes were characterized that are differentially expressed during the parasite's life cycle. The genes named LDH1 and LDH2, respectively, encode polypeptides similar to the enzyme lactate dehydrogenase (LDH; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) from a variety of organisms. They show 64.0% nucleotide identity in the coding region and both have an intron at the same relative position. The deduced amino acid sequences of LDH1 and LDH2 share 71.1% identity. LDH1 and LDH2 are most similar to an LDH of Plasmodium falciparum (46.5% and 48.5% amino acid identities, respectively). The mRNA of LDH2 was only detected in the bradyzoite stage, while the mRNA of LDH1 was detected in both the bradyzoite and tachyzoite stages. However, by isoelectric focusing and immunoblot analysis, only one LDH isoform was found to be expressed in each stage. Furthermore, the expression of a reporter gene carrying chloramphenicol acetyltransferase (CAT) coding sequence and the putative LDH2 promoter sequence was significantly up-regulated by growing parasites in tissue culture in media with alkaline pH (pH 8.2, a condition known to induce the expression of bradyzoite-specific antigens), while the expression of a CAT reporter construct carrying the putative LDH1 promoter sequence was down-regulated by similar treatment. These results indicate that LDH expression is developmentally regulated in T. gondii and suggest a possible correlation between stage conversion and alteration in carbohydrate or energy metabolism in this parasite.

Amino Acid Sequence↗
PubMed1986

Observations on the life-cycle and larval morphogenesis of Cooperia fuelleborni (Nematoda: Trichostrongyloidea) parasitic in impala, Aepyceros melampus.

The previously unknown life-cycle of Cooperia fuelleborni, parasitic in impala, is described. The morphology of the developmental stages are compared to those of other Cooperia spp. The similarity between C. fuelleborni and C. curticei is discussed as well as the differences between those two species. The morphological studies showed that C. fuelleborni is closely related to C. curticei of sheep, but also has some affinity with the cattle parasite C. punctata and C. oncophora.

Animals↗
PubMed1975

An experimental investigation of a direct life-cycle in Reighardia sternae (Diesing, 1864), a pentastomid parasite of the herring gull (Larus argentatus).

A direct life-cycle in Reighardia sternae, a cephalobaenid pentastomid of gulls was investigated: the work was prompted by a report of eggs and larvae recovered from the stomach and intestine of a naturally infected gull. Infective pentastomid eggs were obtained by surgically transplanting maturing female Reighardia, taken from freshly shot wild gulls, into captive recipients. Faecal material from birds thus artificially infected was collected daily and examined for eggs. Eggs were force fed to 33 hand-reared (from eggs or nestlings) juvenile gulls which were selected at random and sacrificed at intervals thereafter and examined for pentastomids. One hour after infection, primary larvae appear in the body cavity where they moult immediately. They grow steadily and by 27-35 days are sexually differentiated, and by 66 days have copulated. Fertilized females take a further 116 days to produce eggs by which time they are 7-6 cm long. The complex migrations undertaken by developing larvae in the gull, and the problems of the mechanism of direct transmission, are discussed.

Air Sacs↗
PubMed1966

Analysis of the life cycle of Mycoplasma gallisepticum.

Morowitz, Harold J. (Yale University, New Haven, Conn.), and Jack Maniloff. Analysis of the life cycle of Mycoplasma gallisepticum. J. Bacteriol. 91:1638-1644. 1966.-A series of electron microscope observations on Mycoplasma gallisepticum strain A5969 have been made by use of thin-section techniques and negative staining. The methods presented a consistent picture of a postdivision cell, which contains a fibrillar nuclear region, surrounding ribosomal region, highly organized bleb at one end of the cell, granular infrableb region, and bounding unit membrane. Cell division commenced with the appearance of a second infrableb area at the end of the cell opposite the original bleb. A new bleb grew in this area, and the cell then elongated. The nuclear material segregated into two parts separated by a band of ribosomes. A constriction appeared, in this central ribosome-packed area, leading to the formation of two daughter cells. The following was noted: the cells were very small (volume, 5 x 10(-14) cm(3)); each cell was highly structured and strongly ordered; and the replication appeared to be a very precisely programmed series of events.

Cell Division↗
PubMed1980

Numerical, morphological and topographical heterogeneity of the chondriome during the vegetative life cycle of Polytoma papillatum.

Numerical, morphological, and topographical changes in the mitochondrial inventory (= chondriome) during the vegetative (= asexual) life cycle of Polytoma papillatum were examined by means of the serial-sectioning technique. At the onset of interphase the chondriome consists of primarily of one highly reticulated basket-shaped complex, which lines the periphery of the cell. Up to 3 additional fragments could be analysed, which, however, were much smaller and either spherical to ovoid, or elongated and poorly branched. During interphase growth both the size of the mitochondrial basket and the number of additional fragments (ca. 40) increases. During mitosis I (I. division cycle) the multiplication of the number of mitochondria gradually continues; the maximum (ca. 250) was counted at late telephase I and early cytokinesis I, but it cannot be excluded that the sparser short-lived meta- and anaphase cells, which were unfortunately missed, contain an even higher number of mitochondrial units. Concomitant with mitosis I, the mitochondrial basket is subdivided into several fragments; at the same time the mitochondria tend to form clusters and to occupy no longer merely peripheral but also more central regions. An irregular distribution of the chondriome results, with either local accumulations or local absence of mitochondria within definite regions of the cell. After completion of cytokinesis I the total number of mitochondria (ca. 80) is drastically reduced but it seems to increase again during the 2. division cycle. Irrespective of the number of preceding division cycles, the chondriome of young daughter cells enclosed in the sporangium usually resembles that of young interphase cells. Our results are discussed in relation to some of the current problems on mitochondriogenesis.

Animals↗
PubMedDate not supplied

Nutrition and the life cycle 5: nutritional needs of older adults.

The previous four articles in this series on nutrition and the life cycle reviewed the nutritional needs during pregnancy (Vol 9(17): 1133-8), infancy (Vol 9(21): 2205-16), childhood (Vol 10(1): 26-31) and adulthood (Vol 10(6): 362-9). This article, the last in the series, will review the special nutritional needs of the older person. Older adults form an increasing proportion of our society, and it is important that nurses appreciate their special needs. The article concentrates on the health older adult, and reviews what nutritional advice nurses should be providing order to help them achieve maximal health.

Age Factors↗
PubMed1982

A Hammondia-like coccidian with a mink-muskrat life cycle.

A tissue cyst-forming coccidian morphologically resembling the known species Hammondia has a mink-muskrat life cycle. Cysts are found in skeletal muscle of muskrats (Ondatra zibetheca). Mink (Mustela vison) fed infected muskrat carcasses shed oocysts for 4 to 6 days after a prepatent period of 6 to 8 days. The oocysts, 99% of which are unsporulated in mink feces, measure 11.5 to 12 microns X 10 to 11 microns. Sporulated oocysts have 2 sporocysts, each with 4 sporozoites. The present work was insufficient to establish whether this Hammondia-like parasite is identical to the known Hammondia spp. or is a new parasite, although the evidence gathered supports the hypothesis that this parasite is a new member of the genus Hammondia.

Animals↗
PubMed2003

Life-cycle management: a long-term challenge.

With some electronics components being withdrawn after only two years, life-cycle management is becoming a key strategic issue for users and manufacturers of electromedical equipment. This article describes some approaches to tackling the challenge.

Cost-Benefit Analysis↗