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PubMed1989

Professional life cycle changes and their effect on knowledge level of dental practitioners.

Utilizing a national data set (U.S.A.), the effect of age and age-related professional characteristics on dentists' knowledge with regard to prevention of infective endocarditis was examined. The following research questions were addressed: (1) Do age-related characteristics produce different effects on knowledge level at various stages of professional careers?; (2) What are the key changes in these age-related characteristics and what processes are suggested by these changes? Multiple regression analysis assessed the influence of potential predictors of variation in knowledge level with regard to prevention of infective endocarditis for the entire sample. Using these findings as a guide, variation in the effect of significant predictor variables was then analyzed for three time segments of approximately equal duration: early professional life less than 40, mid-professional life 40-54, and older professional life 55 or greater than. Age had a profoundly negative effect on knowledge level, i.e. the level progressively declines as clinicians grow older. The impact of the age-related characteristics on knowledge level of infective endocarditis prevention also varied according to the stage of the professional life cycle. Indices measuring the size or extent of theoretical understanding, in-office networks, institutional affiliations, and consulting networks were significant predictors of endocarditis prevention knowledge for younger clinicians. For those 40-54, only practice organization (office business and staff size and diversity) was a significant predictor, while for older clinicians theoretical understanding was the only significant predictor. Differences in the mean levels of these predictor (independent) variables across age groups were also examined via ANOVA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2000

The role of virion membrane protein endocytosis in the herpesvirus life cycle.

Endocytosis of cellular surface membrane proteins is a well-characterized, common occurrence. Internalization of cell surface receptors, often with bound ligands, aid in global events, such as cellular metabolism, as well as in specific, directed functions, such as the induction of signal transduction cascades or immune function. Some, but not all, herpesvirus membrane proteins are internalized from the plasma membrane by a process similar to receptor-mediated endocytosis. No known functions, however, have been ascribed to endocytosis of these proteins. In this review, we consider the function of herpesvirus membrane protein endocytosis. We compare and contrast the endocytosis and intracellular trafficking of two pseudorabies virus membrane proteins, the type I glycoprotein, gE, and the type II, tail-anchored membrane protein, Us9, and discuss the possible function of their internalization during the virus life cycle.

Amino Acid Sequence↗
PubMed1983

An active intermediate host role for man in the life cycle of Echinococcus granulosus in Turkana, Kenya.

Hydatid material removed at operation from 97 Turkana was compared for fertility and viability with hydatid material removed from camels, cattle, sheep, and goats. The results showed that the human material was extremely fertile and viable, as was material from the camels, goats, and sheep. Cattle cysts were invariably sterile, and the protoscoleces, when present, were comparatively less viable. The high incidence and fertility of hydatid cysts in the Turkana, together with the lack of burial customs thus allowing dogs to have ready access to infected human corpses, means that the Turkana are potential biological participants in the cyclic transmission of Echinococcus granulosus in this region. This is a unique situation, for elsewhere in the world man is regarded as an accidental host who plays no role in the parasite's life cycle.

Adolescent↗
PubMed1986

Eimerian life cycles: the patency of eimeria vermiformis, but not Eimeria pragensis, is subject to host (Mus musculus) influence.

The ability of Eimeria vermiformis and Eimeria pragensis to produce oocysts in primary infections is influenced by host factors. Oocyst production and the duration of patency were determined for each species in: NIH mice, normal or immunosuppressed (by X-irradiation or injection of cortisone acetate), and strains of mice: nu/+, nu/nu; BALB/c, C57BL/6 known (E. vermiformis), or suspected (E. pragensis), to be of contrasting susceptibility to infection. The effect of induced or genetic susceptibility on the reproduction of E. vermiformis resulted in increases in both oocyst production and the duration of patency. Eimeria pragensis was less affected, with smaller increases in the numbers of oocysts produced and no significant prolongation of patency. The implications of these findings with respect to eimerian life cycles are discussed.

Animals↗
PubMed1998

Amblyospora salinaria n. sp. (Microsporidia: amblyosporidae), parasite of Culex salinarius (Diptera: culicidae): its life cycle stages in an intermediate host.

Horizontal transmission testing with an Amblyospora species from the mosquito Culex salinarius has documented the involvement of a copepod intermediate host. Meiospores (one type of uninucleate spore) of the Amblyospora sp. were infectious per os to female Macrocyclops albidus adults. All developmental stages in the copepod had unpaired nuclei (were haplophasic), starting with the sporoplasms from the meiospore, continuing as a succession of schizonts undergoing binary division and ending with sporulation, producing a second type of uninucleate spore. These spores, formed in the ovaries of M. albidus, were lanceolate, slightly curved and measured 13.23 x 3.85 microm. They infected C. salinarius larvae, both male and female, when ingested. In addition, cross-infectivity testing was conducted and demonstrated that while A. californica from C. tarsalis will infect C. salinarius, it does not complete its life cycle in this host. Based on these findings, we conclude that Amblyospora sp. from Culex salinarius is a distinct species and assign it the name Amblyospora salinaria n. sp.

Animals↗
PubMed2004

Variability assessment of groundwater exposure to pesticides and its consideration in life-cycle assessment.

Pesticide leaching from agricultural fields to groundwater is an environmentally relevant and highly variable process. In the present paper, leaching scenarios typical in European agriculture are defined. These scenarios consider important sources of pesticide leaching variability, namely site factors, farming practice, and substance properties. The logic-tree method was used to structure these scenarios. For each scenario, leached fractions of pesticide applied in agriculture were calculated with data and models used in the registration process of the European Union (EU). Contributions of all parameters to variability were calculated for 11 pesticides. Substance properties (Koc and DT50,soil) contributed the mostto variability, followed by site, weather, season of application, crop, and macropore flow. The results of the variability assessment may be directly applied in policy making or they may be used in the environmental assessment of pesticides, e.g. with the life-cycle assessment (LCA) method. Several approaches are suggested for howthe variability assessment presented in this paper may be incorporated in LCA. The application of these approaches is illustrated by a case study on atrazine.

Europe↗
PubMed1994

Life cycle, cytology, and morphology of Polypodium hydriforme, a coelenterate parasite of the eggs of acipenseriform fishes.

Polypodium hydriforme is the only coelenterate adapted to intracellular parasitism in oocytes of acipenserid and polyodontid fishes. It occurs in both the Old and the New worlds, being parasitic in 12 species of Acipenseridae and in 1 species of Polyodontidae. Its earliest parasitic stages are binucleate cells that occur in previtellogenic oocytes. All embryonic and postembryonic development (which seems to be parthenogenetic) up to the budding stolon stage takes place inside fish oocytes and lasts several years. The planula and stolon have inverted germ layers. All parasitic stages are encircled with a highly polyploid unicellular trophamnion that is homologous to the second polar body. Before spawning, eversion of the stolon takes place inside the oocyte. At spawning, the everted stolons get into water and the free-living phase of the life cycle begins. The stolon fragments into individual specimens that can move and feed. They multiply by longitudinal fission (paratomy). In mid-summer they form 2 kinds of endodermal gonads. The so-called "female" gonads (2 ovaria, each with a gonoduct encircled with a common envelope) produce diploid cells that display no meiotic phenomena. The so-called "male" gonads have no gonoducts, but their sex cells undergo 2 meiotic divisions, giving rise to binucleate cells with unequal nuclei. The entire gonad becomes a gametophore with an ectodermal lid carrying nematocysts and containing many binucleate cells. Gametophores can be deposited onto the skin of prelarvae of fishes. How the parasite gets into young fish oocytes is not known.

Animals↗
PubMed1998

Adenomatous polyposis coli protein is expressed in alternate stages of the ameloblast life cycle.

Mutations of the adenomatous polyposis coli gene protein (APC) are associated with familial polyposis and also sporadic colon adenomas, both preconditions to cancer formation. Some familial polyposis patients also develop Gardner's syndrome, a condition characterized by supernumerary teeth, mandibular osteomas, and other maladies. We investigated participation of APC in normal tooth development. Using a monoclonal antibody to study APC expression in the forming rat incisor, we found no APC staining in differentiating ameloblasts, then strong staining in secreting ameloblasts and stratum intermedium cells, followed by cells in the transition stage which did not stain. Intense APC staining resumes in maturation-stage ameloblasts and proximal papillary cells. APC staining disappears again in reduced ameloblasts at the conclusion of amelogenesis. APC staining was not seen in any other odontogenic cells. We report a unique system in which APC expression is upregulated and downregulated twice during the normal life cycle of ameloblasts. APC, therefore, is important in the normal maturation of both colonic epithelium and odontogenic epithelium. At this point, we cannot rule out any of the known functions of APC, which include: modulation of cell adhesion by binding to catenin, regulation of beta-catenin as a differentiative signaling molecule, and promotion of microtubule assembly. In this respect, the rat incisor enamel organ provides a unique tissue for studying the regulation and functions of APC.

Adenomatous Polyposis Coli↗
PubMed2002

Expression analysis of a family of nsLTP genes tissue specifically expressed throughout the plant and during potato tuber life cycle.

Non-specific lipid-transfer proteins (nsLTPs) are capable of binding lipid compounds in plant tissues and are coded by the nsLTP genes. Here, we present the analysis of expression of a family of potato (Solanum tuberosum) nsLTP genes that express throughout the developing plant in a highly tissue-specific manner. Three transcript-derived fragments were isolated using an amplified restriction fragment polymorphism-derived technique for RNA fingerprinting that show homology to plant nsLTP genes. These transcript-derived fragments displayed modulated expression profiles related to the development of new tissues, with a peak of transcription around the time of tuberization and just prior to sprout development, at dormancy breakage. In addition, a homologous family of expressed sequence tags was identified whose individual members could be classified according to their tissue specificity. Two subgroups of expressed sequence tags were found to express during tuber life cycle. To study the regulation of potato nsLTP genes, two putative potato nsLTP promoters were isolated and their expression was studied using promoter-marker-gene fusions. The results showed that one of the two promoters directed a highly specific pattern of expression detected in the phloem surrounding the nodes of young plants and in the same tissue of tuber related organs, whereas the second putative promoter showed little tissue or organ specificity. This difference in expression is likely due to a 331-bp insertion present in the tissue-specific promoter.

Amino Acid Sequence↗
PubMed1998

Experimental analysis of character coupling across a complex life cycle: pigment pattern metamorphosis in the tiger salamander, Ambystoma tigrinum tigrinum.

Developmental relationships among characters are expected to bias patterns of morphological variation at the population level. Studies of character development thus can provide insights into processes of adaptation and the evolutionary diversification of morphologies. Here I use experimental manipulations to test whether larval and adult pigment patterns are coupled across metamorphosis in the tiger salamander, Ambystoma tigrinum tigrinum (Ambystomatidae). Previous investigations showed that the early larval pigment pattern depends on interactions between pigment cells and the lateral line sensory system. In contrast, the results of this study demonstrate that the major features of the adult pigment pattern develop largely independently of both the early larval pattern and the lateral lines. These results suggest that ontogenetic changes that occur across metamorphosis decouple larval and adult pigment patterns and could thereby facilitate independent evolutionary modifications to the patterns during different stages of the life cycle.

Ambystoma↗
PubMed1995

DNA measurements and ploidy determination of developmental stages in the life cycles of Theileria annulata and T. parva.

The relative DNA levels of different developmental stages of Theileria annulata and T. parva in the cow and the tick were measured by the cytophotometric DNA technique using the fluorochrome Hoechst 33258 as a staining dye. The results revealed that sporozoites, merozoites, gamonts, and gametes were haploid, whereas multinucleated intralymphocytic schizonts were polyploid. No difference was observed between T. parva and T. annulata in these stages. For both Theileria species, the DNA measurements revealed that fusion of gametes occurred in the gut of the final host, thus providing evidence of sexual reproduction. However, differences were observed between the two parasites in the tick. Whereas T. parva zygotes underwent a two-step meiotic division, a comparable reduction division could not be unequivocally detected in T. annulata. Differences could also be detected in the further development of kinetes, indicating that Theileria species are not characterized by only one life cycle, which is specific for this genus.

Animals↗
PubMed1987

Pleurotus mushrooms. Part I A. Morphology, life cycle, taxonomy, breeding, and cultivation.

Pleurotus species represent a well-defined group of Basidiomyceteous fungi of the order Agaricales and family Tricholomataceae. They are characterized by the production of fruit bodies with an eccentric stalk and a wide cap shaped like an oyster shell, with the widest portion of the cap being away from the stalk. They grow over a wide range of temperatures and are able to colonize a wide spectrum of unfermented, natural, lignino-cellulosic wastes. Because of their fast mycelial growth rate, they colonize the substrates rapidly; the yield of fruit bodies is also high. The bifactorial inheritance, observed in many of the species, suggests the likelihood of a high degree of genetic variability, and, hence, considerable breeding potential. Pleurotus species can be grown on a commercial scale, without the need for composting and artificial conditioning of the ambient temperature. Aspects of basic and applied research--such as morphology, life cycle, taxonomy, breeding, and cultivation--leading to development of a "Pleurotus Technology" are dealt with here.

Basidiomycota↗
PubMed1994

Cytogenetic analysis and morphology of malignant nuclear vlimata. The life cycle of malignant cells.

The karyotype of malignant nuclear vlimata (NVs) was investigated with the in situ and chromosomal spreading techniques. NV metaphases were recognised by the head with tail morphology, kept in situ and evaluated by the chromosomal spreading technique. It was shown that malignant NVs were produced by random, uncontrolled meiosis. NVs contain and carry single, hypodiploid, haploid, hypohaploid, hyperdiploid and atypical sets of chromosomes. NVs are unstable parasitic cellular elements, invading the cytoplasm or the nucleus of host cells, extruding and implanting their chromosomes in the host cell upon contact. Within a malignant cell culture, NVs play the role of chromosomal donors and host cells of chromosomal recipients. NVs were identified as episomatic on host cell nuclei or incorporated into host cell metaphases. The observations are discussed in terms of fertilization, viral infection and apoptosis. Comparison of malignant NVs with phytohaemagglutinin (PHA)-activated lymphocytic NVs is provided, as well as the life cycle of the malignant cells as follows: [Formula see text] cells (Logothetou-Rella, 1993). Phytohaemagglutinin (PHA)-activated lymphocytes also produced NVs by meiosis, carrying hypodiploid, haploid and hypohaploid sets of chromosomes (Logothetou-Rella, 1994a). In this study the cytogenetic analysis and morphology of malignant NVs are investigated, using a) the in situ cytogenetic technique, and b) the chromosomal spreading technique.

Aneuploidy↗
PubMed1995

Trypanosoma brucei: characterisation of a life cycle stage-specific G-protein.

G-proteins have important and diverse roles in cellular signaling in higher eukaryotes but as yet little is known about the involvement of these GTP-binding proteins in protozoan parasites. Bacterial toxin-catalysed ADP-ribosylation, routinely used in the characterisation of G-proteins in higher eukaryotes, was used to determine whether functional G-protein homologues could be detected in Trypanosoma brucei. A 43-kDa polypeptide that was ADP-ribosylated in the presence of pertussis toxin was identified in membrane fractions. This polypeptide was also recognised by an antibody generated against a peptide sequence representing a mammalian GO alpha G-protein subunit. GTP and GTP gamma S (a nonhydrolysable analogue of GTP) abolished the ADP-ribosylation reaction, indicating that the 43-kDa polypeptide also binds GTP. Furthermore, this T. brucei G-protein is present in bloodstream but not procyclic life cycle stages. Using an in situ GTP binding assay, a further group of small-molecular-size GTP-binding proteins which are present in both bloodstream and procyclic stages have been identified. This demonstration of G-proteins in T. brucei suggests possible intracellular mechanisms that may be involved in the transduction of host or other parasite signals.

Adenosine Diphosphate Ribose↗
PubMed2006

Maintenance of DNA methylation during the Arabidopsis life cycle is essential for parental imprinting.

Imprinted genes are expressed predominantly from either their paternal or their maternal allele. To date, all imprinted genes identified in plants are expressed in the endosperm. In Arabidopsis thaliana, maternal imprinting has been clearly demonstrated for the Polycomb group gene MEDEA (MEA) and for FWA. Direct repeats upstream of FWA are subject to DNA methylation. However, it is still not clear to what extent similar cis-acting elements may be part of a conserved molecular mechanism controlling maternally imprinted genes. In this work, we show that the Polycomb group gene FERTILIZATION-INDEPENDENT SEED2 (FIS2) is imprinted. Maintenance of FIS2 imprinting depends on DNA methylation, whereas loss of DNA methylation does not affect MEA imprinting. DNA methylation targets a small region upstream of FIS2 distinct from the target of DNA methylation associated with FWA. We show that FWA and FIS2 imprinting requires the maintenance of DNA methylation throughout the plant life cycle, including male gametogenesis and endosperm development. Our data thus demonstrate that parental genomic imprinting in plants depends on diverse cis-elements and mechanisms dependent or independent of DNA methylation. We propose that imprinting has evolved under constraints linked to the evolution of plant reproduction and not by the selection of a specific molecular mechanism.

Alleles↗
PubMed1989

Phylogenetic analysis of the class Sporozoea (phylum Apicomplexa Levine, 1970): evidence for the independent evolution of heteroxenous life cycles.

A phylogenetic analysis of representative genera in the class Sporozoea was undertaken using biological and morphological features to infer evolutionary relationships among the widely recognized groups in the class. Gregarines were used as a functional outgroup to the remaining sporozoa (adeleids, eimeriorins, haemosporinids, and piroplasms). The piroplasms were shown to be closely related to the adeleid parasites. Species of Babesia and Theileria were shown not to form a sister group to the haemosporinids as has been frequently suggested. The data indicate that the biologically diverse family Haemogregarinidae should be divided into at least 3 families (Haemogregarinidae Neveu-Lemaire, 1901, containing the genera Haemogregarina and Cyrilia; Karyolysidae Wenyon, 1926, containing the genus Karyolysus; Hepatozoidae Wenyon, 1926, containing the genus Hepatozoon) because the 4 genera currently within the family do not form a monophyletic group. Correlation between parasite phylogeny and taxonomic affinities of their definitive hosts suggests that the definitive hosts of heteroxenous sporozoa are their ancestral hosts. Heteroxenous sporozoan life cycles apparently have evolved independently to adapt to changes in the feeding behaviors of their definitive hosts.

Animals↗
PubMed2002

TNT, RDX, and HMX decrease earthworm (Eisenia andrei) life-cycle responses in a spiked natural forest soil.

Sublethal and chronic toxicities of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) on earthworm Eisenia andrei in a sandy forest soil were assessed. Various reproduction parameters of fecundity (total and hatched number of cocoons, number of juveniles, and their biomass) were significantly decreased by TNT (> or = 58.8 +/- 5.1 mg/kg dry soil), RDX (> or = 46.7 +/- 2.6 mg/kg), and HMX (> or = 15.6 +/- 4.6 mg/kg). These effects occurred at much lower concentrations than those reported earlier using artificial soil preparations. Growth of adults was significantly decreased in the TNT-spiked natural soils at 136.2 +/- 25.6 mg/kg dry soil, the highest concentration having no significant mortality. In contrast, survival and growth were not significantly reduced at relatively high measured concentrations of RDX (167.3 mg/kg) and HMX (711.0 mg/kg). Although TNT, RDX, and HMX share a common life-cycle response ( i.e., decreased juvenile counts), a number of differences related to other reproduction parameters (e.g., productivity of cocoons) was observed. These results indicate that the tested explosives do not support a common mechanism of toxicity, at least in the earthworm, probably due to differences in their physical-chemical properties as well as metabolites formed during exposure.

Animals↗
PubMed1986

Modeling the supply of nurse labor. Life-cycle activity patterns of registered nurses in one Canadian delivery system.

Using 1980 membership data made available by the provincial nurses' association, a simple, age-specific projection model was developed that comprised two submodels: a Markovian one to monitor yearly movements from one membership state to another and a linear submodel for the infusion of new members. The model assumes that the likelihood of moving to any membership state depends only on the nurse's current age and membership state. A comparison of actual/projected data for 1981-1984 indicates a fairly high level of accuracy, despite the oscillatory pattern of the nurse labor market in the Province of British Columbia since 1982. The details of the projections of labor force over time show a particular age cohort's characteristic behavior and delineate the effect of childbearing and aging on the supply of nurses. As well as projecting future manpower, the age-specific transition matrices were used to estimate the professional life expectancy of registered nurses. This information includes the average number of continuous years of practice for each age, as well as the average total number of years of practice until being deleted from the system at the age of 75. The forecasting capability developed from this work attempts to address two questions central to manpower planning: how many nurses will there be in the province in the next 5 years? and what is the time-frame involved in nurses' life-cycle activity patterns?

Age Factors↗