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PubMed1991

Suicide, stressors, and the life cycle.

OBJECTIVE: Relationships between stressors and suicide might be expected to vary with stages of the life cycle. The purpose of this study was to examine this possibility. METHOD: The authors examined the first 204 consecutive cases from the San Diego Suicide Study, a federally funded investigation of 283 suicides, for possible relationships between suicide and age and the frequency of specific stressors. Information was gathered from family members, spouses, acquaintances, employers, other witnesses, physicians, and other professionals by trained interviewers using a structured format. Hospital, physician, therapist, school, and police records were also included when available. DSM-III diagnoses were made by consensus of two investigators. Life events information was also reviewed independently by the investigators to determine stressors (if any) for each case. RESULTS: Of the 202 subjects for whom data were available, 195 (97%) had one or more stressors; 137 male subjects had a total of 272 stressors, and 58 female subjects had a total of 115 stressors. The authors found predictable patterns of the three most common stressor groups--conflict-separation-rejection, economic problems, and medical illness. The majority of the stressors among subjects 80 years old or older were illnesses. The only significant difference between the sexes was that more men than women had economic problems as a stressor. CONCLUSIONS: The variations in the patterns of stressors found in this study of suicides coincide with adult development theory. The lack of population comparison subjects and stressor scoring validation, however, limits the predictive value of these data in assessing suicidal persons.

Adolescent↗
PubMed2006

The management of metabolic energy storage during the life cycle of mayflies: a comparative field investigation of the collector-gatherer Ephemera danica and the scraper Rhithrogena semicolorata.

The concentration and seasonal dynamics of the major energy storage components, triglycerides and glycogen, were measured in two species of mayfly (Rhithrogena semicolorata and Ephemera danica) with contrasting life cycle strategies living in a small mountain stream. E. danica is a burrowing, semivoltine collector-gatherer; R. semicolorata is univoltine and scrapes periphyton from stones. This is the first publication which focuses on the role of metabolic energy sources during the larval life span of two mayfly species until the larvae emerge. Although triglycerides are the major energy reserve in both species (>84% of total energy storage) throughout the whole larval development their seasonal dynamic differed considerably. In R. semicolorata the triglyceride concentration declined during the last weeks prior to emergence in both sexes. The same pattern was found in female larvae of E. danica, but not in male E. danica. It is suggested that females use triglycerides in the last larval stages for egg maturation, which is completed in the last larval instar. In male E. danica the triglyceride concentrations remained high until emergence, presumably due to their high energy demands as adults for their swarming flights. Glycogen concentrations did not show such a difference between species and sexes. Its significance as a storage substrate for energy is rather low; however, concentrations decreased in both species and sexes prior to emergence.

Animals↗
PubMed2001

Genome ploidy in different stages of the Giardia lamblia life cycle.

The early diverging eukaryotic parasite Giardia lamblia is unusual in that it contains two apparently identical nuclei in the vegetative trophozoite stage. We have determined the nuclear and cellular genome ploidy of G. lamblia cells during all stages of the life cycle. During vegetative growth, the nuclei cycle between a diploid (2N) and tetraploid (4N) genome content and the cell, consequently, cycles between 4N and 8N. Stationary phase trophozoites arrest in the G2 phase with a ploidy of 8N (two nuclei, each with a 4N ploidy). On its way to cyst formation, a G1 trophozoite goes through two successive rounds of chromosome replication without an intervening cell division event. Fully differentiated cysts contain four nuclei, each with a ploidy of 4N, resulting in a cyst ploidy of 16N. The newly excysted cell, for which we suggest the term 'excyzoite', contains four nuclei (cellular ploidy 16N). In a reversal of the events occurring during encystation, the excyzoite divides twice to form four trophozoites containing two diploid nuclei each. The formation of multiple cells from a single cyst is likely to be one of the main reasons for the low infectious doses of G. lamblia.

Animals↗
PubMed1996

Expression of different forms of the heat-shock factor during the life cycle of the parasitic helminth Schistosoma mansoni.

HSE-HSF complexes from different stages of the life cycle of schistosome were analyzed by pore exclusion electrophoresis (estimates the size of the native DNA-protein complex), and by U.V.-cross-linking followed by SDS-PAGE (estimates the size of the monomeric heat shock factor, HSF). The apparent M(r) values of the native and monomeric HSE-HSF complexes from schistosomula were 80,000 and 60,000, respectively. In adult worms M(r) values were 70,000 for the native HSE-HSF complex, 60,000 and 80,000 for the monomeric form. These findings indicate that: (1) schistosome express two (maybe three) forms of HSF, (2) different forms of HSF are expressed at different developmental stages. The findings that the native HSE-HSF complex and the monomeric HSF are of a similar size indicates that the complex contains a single HSF, or that the complex is a labile oligomer of HSF that decomposes into monomers during electrophoresis in a nondenaturing gel.

Animals↗
PubMed2005

The vegetative life-cycle of the clover pathogen Cymadothea trifolii as revealed by transmission electron microscopy.

The vegetative life-cycle of Cymadothea trifolii (anamorph Polythrincium trifolii), causing sooty blotch of clover, is described using chemically as well as cryofixed and freeze-substituted samples. The pathogen enters the leaf through stomata and proliferates intercellularly. Nutrients are assumedly obtained via an interaction apparatus produced within the pathogen's hyphae, opposite to which the host cell is triggered to invaginate its plasmalemma. Rare attempts of 'self-parasitism' were also seen. Entering the conidial stage, stromata are laid down under the lower epidermis. The dying tissue above may explain the necrotic spots observed on infected leaflets. Foot cells in the conidial stromata produce thick-walled conidiophores, which grow sympodially. New conidiophores may grow into empty shells of old ones. Conidia are detached after pores between them and conidiophores have become plugged by organelles resembling Woronin bodies. Conidia are usually two-celled and their walls contain chitin and beta-1,3-glucans as indicated by labelling with gold-conjugated wheat germ agglutinin and anti-beta-1,3-glucan antibodies. Both conidiophores and conidia contain a structure which we regard as a new organelle with as yet unknown function.

Ascomycota↗
PubMed1999

Differential expression of translational elements by life cycle variants of Coxiella burnetii.

Coxiella burnetii replicates as distinct morphological forms, which may allow potential life cycle variants to survive the harsh environment of the phagolysosome. Monoclonal antibodies (MAbs) were compared by Western blotting for reactivity with large cell variant (LCV) and small cell variant (SCV) antigens to characterize proteins differentially expressed by C. burnetii. MAb NM7.3 reacted with a approximately 32-kDa LCV-upregulated antigen, and MAb NM183 reacted with a approximately 45-kDa LCV-specific antigen. MAb NM7.3 was used to screen a lambdaZapII C. burnetii DNA expression library, and an immunoreactive clone was identified with sequence similarity to the Escherichia coli tsf gene, which encodes elongation factor Ts (EF-Ts). Since a similar screen with MAb NM183 did not identify immunoreactive clones, an alternate strategy was devised to clone the reactive antigen based on observations of cross-reactivity with the 45-kDa elongation factor Tu (EF-Tu) protein from Chlamydia trachomatis. The highly conserved nature of EF-Tu among eubacteria allowed PCR amplification of a tuf gene fragment (encoding approximately 95% of the predicted EF-Tu open reading frame) from C. burnetii using degenerate primers. The product of the cloned tuf gene fragment reacted with MAb NM183 in Western blot analysis, confirming the identity of the 45-kDa LCV-specific antigen. Identification of two proteins differentially expressed by C. burnetii, EF-Tu and EF-Ts, both essential components of the translational machinery of the cell, supports the hypothesis that LCVs are metabolically more active than SCVs.

Amino Acid Sequence↗
PubMed1991

Subcellular distribution and life cycle of Epstein-Barr virus in keratinocytes of oral hairy leukoplakia.

The authors investigated the life cycle of Epstein-Barr virus (EBV) in keratinocytes of oral hairy leukoplakia by combining immunohistochemistry. DNA in situ hybridization, and lectin histochemistry with electron microscopy. Diffuse-staining components of the EBV early antigen complex (EA-D), EBV 150-kd capsid antigen (VCA), EBV membrane antigen (gp350/220), and double-stranded DNA were labeled with monoclonal antibodies. An EBV-DNA probe was used to locate EBV DNA. Wheat-germ agglutinin (WGA) was employed to distinguish Golgi-associated compartments. The authors found EBV proteins and EBV DNA only in keratinocytes with apparent viral assembly. In situ hybridization showed EBV DNA in free corelike material and in electron-dense cores of mature nucleocapsids. Monoclonal antibodies to nonspecific double-stranded DNA attached to the same structures and to marginated chromatin. Components of EA-D were dispersed throughout the nuclei but accumulated near condensed chromatin and in 'punched-out' regions of the chromatin. Epstein-Barr virus 150-kd capsid antigen was found only in the nuclei, where it appeared preferentially on mature nucleocapsids. As yet unexplained arrays of intranuclear particles that remained unlabeled with all EBV-specific probes reacted intensely with an antiserum against common papillomavirus antigen. Gp350/220 was detectable in various cellular membrane compartments and was highly concentrated on EBV envelopes in peripheral Golgi-associated secretory vesicles. It was less abundant on the extracellular EBV, indicating that viral membrane antigen partly dissociates from the mature virus. Combined lectin-binding histochemistry and electron microscopy demonstrated for the first time that EBV is processed in the Golgi apparatus, which eventually releases the virus by fusion with the plasma membrane. These results provide insight into the biologic events that occur during complete EBV replication in vivo.

Adult↗
PubMed1989

Life-cycle effects of alcoholism on education, earnings, and occupation.

In this article we examine the life-cycle effects of alcoholism on human capital formation and labor market outcomes. We attempt empirically to unravel some of the complicated structural relationships among family background, educational attainment, labor force participation, earnings, and current as well as past alcoholism. Access to a new data set allows us to study some of these relationships. The Epidemiological Catchment Area data set contains not only the standard socioeconomic and demographic variables but also information on family background and age of onset of symptoms and current alcoholism. Thus, when estimating models of occupational choice and earnings, we can assess both the indirect and the direct effects of alcoholism. We find that early onset of alcoholism significantly retards educational attainment.

Adult↗
PubMed1989

Re-establishing a life cycle of Schistosoma mansoni from cryopreserved larvae.

To study the feasibility of re-establishing a life cycle of Schistosoma mansoni (NMRI strain) from cryopreserved larvae, schistosomules were suspended in the cryoprotectant 1,2-ethanediol and cryopreserved in liquid nitrogen. Mice were injected intramuscularly with samples thawed after 3 days, 3 wk, or 6 mo in liquid nitrogen storage. Two to 5% of the cryopreserved larvae and approximately 18% of corresponding unfrozen control larvae developed into adult worms. Infectivity did not decrease as a function of storage time. The adult worms showed no structural damage or changes in overall size and morphology when examined by light and transmission electron microscopy. Female worms derived from cryopreserved larvae had the same or slightly elevated egg production as controls, but tissue egg distributions were comparable. Subsequent passages through Biomphalaria glabrata snails and mice revealed no difference in snail prepatent death rate, percentage of snails infected, cercarial production per snail, or cercarial infectivity.

Animals↗
PubMed2003

[Calodium hepaticum (Bancroft, 1893) Moravec, 1982--capillaria with an atypical life cycle].

Calodium hepaticum (Bancroft, 1893)--commonly known as Capillaria hepatica is a nematode parasitising in liver of rodents, some domestic and wild mammals: Insectivora, Carnivora, Artiodactyla and Primates including human as well. C. hepaticum is the only nematode--geohelminth, which for the continuity of the life cycle needs the death of the host being the intermediate and final host at the same time. The eggs of the parasite deposited by female worms in liver of the host became entrapped in fibrotic tissue. C. hepaticum is a cosmopolitic nematode. Rats and mice (domestic and field) are the main hosts of this parasite, the prevalence of infection can be very high e.g. Rattus norvegicus--100% in the Baltimore Zoo (Farhang-Azad 1977) as well as from the urban area of Milan (Italy)--the prevalence of infection was 36% (Ceruti et al. 2001). Hepatic capillariasis was not recorded in our country but its existence seems to be very probable.

Animals↗
PubMed2002

Natural history of Ctenus medius Keyserling, 1891 (Araneae, Ctenidae). II: Life cycle and aspects of reproductive behavior under laboratory conditions.

Ctenus medius Keyserling, 1891 is a wandering spider common in the Brazilian Atlantic Forest. It has been the subject of few studies. Thus, this work aims to elucidate aspects of its natural history, such as the life cycle and reproductive behavior of this species, through laboratory and field observations. Two females with egg sacs were observed in the laboratory and one was observed in field (Barra Mansa, 22 degrees 32'S and 44 degrees 10'W) until the emergence of the spiderlings. For observation of the immature stage development, a portion of the spiderlings from the same hatch were taken to the laboratory and watched until sexual maturity. In the field, the period between the oviposition and the emergence of spiderlings was of 36 days. The female selects a site for egg sac deposition and stays there until the spiderlings emerge. Seven days after the emergence, the female abandoned the site where the egg sac was made, concomitant to the spiderlings dispersion from observation's place and until the moment that the spiderlings started to eat. For the spiderlings kept under laboratory conditions, cannibalism was not observed in the first instars (1-4th) when sufficient food was offered. Sexual maturity happened in the 14th or 15th instars, with an average of 309.2 to 344.5 days until the last/sexual molt, respectively. Until the date of sexual maturity, there was a mortality rate of 85%. This species is very fragile in captivity. This hampered deductions concerning longevity. Both females and males collected in the field were induced to mate in the laboratory. Courtship movements of males were registered, but the females did not permit the mating. These data may assist in initial biological studies of Ctenus genus and offer comparative parameters for studies of other related species.

Animals↗
PubMedDate not supplied

[Evolutionary complication of life cycles in Coccidea (Sporozoa: Coccidea)].

Similar strategies to preserve a species were evolved independently in different groups of Coccidea. Polyenergid oocysts and tissue cysts are found in representatives of the orders Protococcidiida and Eimeriida. Hypnozoits are found in Karyolysus lacerate and Plasmodium vivax; transovarial transmission of parasites occurs in life cycles of Coccidea of the genera Karyolysis and Babesia. Formation of heteroxenity in groups of Coccidea apparently was developed by different ways and in different periods. In some groups (Cystoisospora, Toxoplasma, Aggregata, Atoxoplasma, Schelackia, Lankesterella, and Calyptospora), recent definitive hosts were initial hosts; in other groups (Sarcocystis, Karyolysus, Haemogregarina, Hepatozoon, Plasmodium, Haemoproteus, Leucytozoon, Babesiosoma, Theileria, and Babesia), intermediate hosts were initial hosts.

Animals↗
PubMed2004

EtCRK2, a cyclin-dependent kinase gene expressed during the sexual and asexual phases of the Eimeria tenella life cycle.

EtCRK2, a cyclin-dependent kinase from the coccidian parasite, Eimeria tenella is closely related to eukaryotic cyclin-dependent kinases that regulate progression of the cell cycle and to several cyclin-dependent kinases identified in the Apicomplexa. Northern blot analyses revealed that EtCRK2 is transcribed during both asexual (first-generation schizogony) and sexual (oocyst sporulation) replicative phases of the parasite life cycle. In addition, it appears to be transcriptionally regulated during meiosis. Recombinant EtCRK2 produced in Escherichia coli has kinase activity which is significantly stimulated by the addition of vertebrate cyclin A. This cyclin-dependent kinase may play a significant role in regulating critical cell cycle events during both asexual proliferation and sexual development of the parasite.

Amino Acid Sequence↗
PubMed1999

Life cycle of the mammalian germ cell: implication for spontaneous mutation frequencies.

A brief history of the developmental life cycle of the mammalian germ cell, from fertilization to gametogenesis in the mature gonad, is presented. The differences between gametogenesis in the mature gonad of males and females are also described with regard to properties that may affect their susceptibilities to mutation. It is emphasized that any historical control background rate of necessity will include mutations that occur in germinal tissue at all stages of development and differentiation, although it is not always possible to determine at what stage of germline development a spontaneous mutation has occurred. Studies of induced mutations suggest that the impact on the molecular level and the distribution of mutations among the F1 and F2 progeny may be partly determined by the stage and sex of germ cells in which spontaneous mutations occur. In summary, historical control rates should only be considered the sum total of mutations that occur during the entire life of the individual and cannot represent the control values of any individual germ cell stage. Nonetheless, it is certainly important and valid to use historical control data for calculating human risk, because the primary use of the estimation of mutant frequencies is to access the potential impact of agents in increasing the genetic load in the human population.

Cell Cycle↗
PubMed2006

Risk assessment of the National Institute of Standards and Technology petroleum crude oil standard water accommodated fraction: further application of a copepod-based, full life-cycle bioassay.

The U.S. National Institute of Standards and Technology (NIST) petroleum crude oil was used to generate NIST water-accommodated hydrocarbon fractions (WAFs) for standardized assessment of crude oil effects on the copepod Amphiascus tenuiremis. Effects were assessed using a 96-well microplate, full life-cycle test. Briefly, nauplii (age, 24 h) were reared individually to adults (n > or =120 nauplii/treatment) in microplate wells containing 200 microl of treatment solution (seawater control [0%] or 10, 30, 50, or 100% NIST-WAF). Nauplii were monitored through development to adulthood, and mature virgin male:female pairs mated in wells containing original treatments (<30 d). A second bioassay using 0, 10, 30, and 50% WAFs (n > or =60 nauplii/treatment) was conducted to assess the effects of ultraviolet (UV) light on naupliar endpoints (<16 d). In the first experiment, nauplius-to-copepodite survival in exposures to 100% WAF was 27% +/- 6% lower than in controls (92% +/- 1%), but copepodite-to-adult survival was greater than 90% across all treatments. Analysis of development curves showed that nauplii in the 10% WAF developed into copepodites 25% faster, whereas nauplii in the 50 and 100% WAFs developed 17% slower, than controls. Copepodite development into male and female copepods was significantly delayed (2 and 4 d, respectively) in the 100% WAF compared to controls. Although none of the WAF exposures had significant effects on fertilization success or total viable production (p > 0.05), embryo hatching in the 100% WAF was significantly less (70.0% +/- 21.2%) than that in controls (87.0% +/- 19.4%). Results from the UV bioassay showed that relatively short exposures (<14 d) to 30 and 50% WAFs in the presence of UV light caused negative effects on copepod survival and development. Naupliar-stage survival and developmental endpoints were the most sensitive indicators of exposure to the NIST crude oil WAF

Animals↗
PubMed2006

Service utilization and the life cycle of youth homelessness.

The study sought to describe service utilization patterns of homeless youth based on their life cycle stage. Ninety-nine percent of participants accessed services. Medical service utilization was highest among youth who were attempting to leave the street. Drug-related service utilization was lowest among youth most entrenched in street life.

Adolescent↗
PubMed1994

Divorce in the family life cycle.

"We present the results of [a] study conducted in the years 1986-1988 in three big cities in Poland.... The sample population consisted of persons who divorced in the years 1983-1984....[The focus is on] a detailed evaluation of the sources of divorce and a discussion of the determinants, in relation to the family life cycle. The paper constitutes an attempt at an interdisciplinary approach to the phenomenon of divorce; the approach combines demographic and sociological perspectives."

Developed Countries↗
PubMed2000

The HOX-like gene Cnox2-Pc is expressed at the anterior region in all life cycle stages of the jellyfish Podocoryne carnea.

The marine jellyfish Podocoryne carnea (Cnidaria, Hydrozoa) has a metagenic life cycle consisting of a larva, a colonial polyp and a free-swimming jellyfish (medusa). To study the function of HOX genes in primitive diploblastic animals we screened a library of P. carnea cDNA using PCR primers derived from the most conserved regions in helix 1 and helix 3 of the homeobox. A novel gene, Cnox2-Pc, has been isolated and characterized. Cnox2-Pc is a HOX cluster-like gene, and its homeodomain shows similarity to the Deformed subfamily of HOM-C/HOX genes. In situ hybridization revealed that Cnox2-Pc is expressed in the anterior region of the larva, the polyp head, and the most apical ectoderm of the differentiating bud during medusa development. In adult medusa expression is restricted to the gastrovascular entoderm. The results suggest that Cnox2-Pc is involved in establishment of an anterior-posterior axis during development in primitive metazoans.

Amino Acid Sequence↗