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At least 793 records · Page 44Linked to original sources
PubMed1975

Implications of dinoflagellate life cycles on initiation of Gymnodinium breve red tides.

Florida Gymnodinium breve red tides are initiated in off-shore (approx. 18 to 74 km) coastal waters primarily in late summer-fall months. Past culture studies by W. B. Wilson suggested that this species could have a sexual cycle, inferring the possibility of an alternation of cytological and/or morphological generations. This possibility is further supported by numerous recent advances in dinoflagellate life cycle work which are reviewed in detail. If G. breve has a benthic resting stage (hypnozygote), as is suggested, then seed populations or seed "beds" can possibly be pinpointed and mapped.

Animals↗
PubMed2003

Life cycle assessment of automobile/fuel options.

We examine the possibilities for a "greener" car that would use less material and fuel, be less polluting, and would have a well-managed end-of-life. Light-duty vehicles are fundamental to our economy and will continue to be for the indefinite future. Any redesign to make these vehicles greener requires consumer acceptance. Consumer desires for large, powerful vehicles have been the major stumbling block in achieving a "green car". The other major barrier is inherent contradictions among social goals such as fuel economy, safety, low emissions of pollutants, and low emissions of greenhouse gases, which has led to conflicting regulations such as emissions regulations blocking sales of direct injection diesels in California, which would save fuel. In evaluating fuel/vehicle options with the potential to improve the greenness of cars [diesel (direct injection) and ethanol in internal combustion engines, battery-powered, gasoline hybrid electric, and hydrogen fuel cells], we find no option dominates the others on all dimensions. The principles of green design developed by Anastas and Zimmerman (Environ. Sci. Technol. 2003, 37, 94A-101A) and the use of a life cycle approach provide insights on the key sustainability issues associated with the various options.

Air Pollutants↗
PubMed1987

The two gene pairs encoding H2A and H2B play different roles in the Saccharomyces cerevisiae life cycle.

We have isolated Saccharomyces cerevisiae mutants bearing deletions of one or the other of the two divergently transcribed gene pairs encoding H2A and H2B. The deletions produced diverse effects on the yeast life cycle. Deletion of TRT1, one of the H2A-H2B gene pair sets, affected mitotic growth, sporulation, spore germination, the heat shock response, and exit from the stationary phase; deletion of TRT2, the other H2A-H2B gene pair set, had negligible effects on these same processes. Using a genetic complementation assay, we found that the differential effects of the deletions could be attributed to two features of the gene sets: first, the expression of the TRT1 gene pair, but not the TRT2 gene pair, could compensate for the absence of its partner; second, the protein subtypes encoded by the two gene pairs appear to have different functions in the heat shock response.

Cell Cycle↗
PubMedDate not supplied

[Systematic position and life cycle of Asymphylotrema macracetabulum comb. Nov. (Trematoda, Monorchidae)].

Asymphylotrema macracetabulum (Belous, 1953) c. n. is described and diagnosis of the new genus Asymphylotrema in the subfamily Asymphylodorinae (the fam. Monorchidae) is given. The life cycle is studied and morphological characteristics of larval stages of this trematode in intermediate (freshwater molluscs Valvata sibirica and V. amurensis) and additional (Planaria sp.) hosts is given.

Animals↗
PubMed2006

Gene expression of arachidonate cyclooxygenase pathway leading to the delayed synthesis of prostaglandins E2 and F2alpha in response to phorbol 12-myristate 13-acetate and action of these prostanoids during life cycle of adipocytes.

Several types of prostaglandin (PG)s are synthesized in adipocytes and involved differently in the control of adipogenesis. To elucidate how the PG synthesis is regulated at different stages in the life cycle of adipocytes, we examined the gene expression of arachidonate cyclooxygenase (COX) pathway leading to the delayed synthesis of PGE2 and PGF2alpha and their roles in adipogenesis after exposure of cultured cells to phorbol 12-myristate 13-acetate (PMA), which is a useful system for monitoring mitogen-induced changes. While the expression of COX-1 remained constitutive, mRNA and protein levels of COX-2 were up-regulated by treatment with PMA. Preadipocytes exhibited higher gene expression of cytosolic phospholipase A2alpha (cPLA2alpha) and PGF synthase. In contrast, three isoforms of PGE synthase are expressed constitutively during all phases. The delayed synthesis of PGE2 and PGF2alpha following the stimulation for 24 with a mixture of PMA and calcium ionophore A23187 was the highest in preadipocytes, reflecting the increased expression levels of cPLA2alpha and COX-2. Cultured cells treated with PMA during the differentiation phase and then exposed to the maturation medium, or cells treated with PMA in the maturation medium after the differentiation phase showed the suppression of adipogenesis in adipocytes. The attenuating effect of PMA was additionally enhanced when the cell were treated along with A32187 during the differentiation phase, suggesting the involvement of endogenous PGs. The cells at the stages of the differentiation and maturation phases were highly sensitive to exogenous PGE2 and PGF2alpha, respectively, resulting in the marked suppression of the stored fats in adipocytes. Taken together, these results provided the evidence for the distinct gene expression of isoformic enzymes in the COX pathway leading to the synthesis of PGE2 and PGF2alpha and the specific action of these prostanoids at different cycle stages of adipocytes.

3T3-L1 Cells↗
PubMed2006

Life cycle assessment of the waste hierarchy--a Danish case study on waste paper.

The waste hierarchy is being widely discussed these days, not only by cost-benefit analysts, but a growing number of life cycle assessments (LCA) have also begun to question it. In this article, we investigate the handling of waste paper in Denmark and compare the present situation with scenarios of more waste being recycled, incinerated or consigned to landfill. The investigations are made in accordance with ISO 14040-43 and based on the newly launched methodology of consequential LCA and following the recent guidelines of the European Centre on Waste and Material Flows. The LCA concerns the Danish consumption of paper in 1999, totalling 1.2 million tons. The results of the investigation indicate that the waste hierarchy is reliable; from an environmental point of view recycling of paper is better than incineration and landfilling. For incineration, the reason for the advantage of landfilling mainly comes from the substitution of fossil fuels, when incinerators provide heat and electricity. For recycling, the advantage is related to the saved wood resources, which can be used for generating energy from wood, i.e., from renewable fuel which does not contribute to global warming.

Conservation of Energy Resources↗
PubMed1983

A proposed life cycle for the Reiter treponeme.

Direct microscopical observations of single developing cysts in sealed slide microcultures prepared from 5-days-old tube cultures of the Reiter treponeme revealed two distinct phases in the life cycle. In one phase transverse fission was the main method of multiplication while in a second phase, occurring when conditions in the medium became unfavourable for propagation, cysts developed. These could release large numbers of actively motile treponemes when returned to optimum growth conditions. These observations, together with results of the dilution method for the calculation of the Most Probable Number and the absence of a response in treponemes killed by high temperature (45 degrees C) or abnormal pH (10), showed that the cysts were viable and a mode of propagation for the Reiter treponeme.

Anaerobiosis↗
PubMed1991

Behavioral manifestations of prolonged lead exposure initiated at different stages of the life cycle: I. Schedule-controlled responding.

While early development represents a period of particular sensitivity to the neurotoxic effects of lead (Pb), much less is known about CNS effects at later stages of the life cycle. It is conceivable that old age represents an additional period of vulnerability given the neurodegenerative processes that are the inevitable accompaniment of advanced age. The experiments described here examined that possibility. The effects of prolonged low-level Pb exposures were assessed in young (21 day old), adult (8 mon old) and old (16 mon old) F-344 rats performing on Fixed-Interval (F1) and Variable-Interval (VI) schedules of reinforcement, two behavioral baselines previously shown to be sensitive to Pb exposure in young rats. The profile of Pb effects within each age group was remarkably uniform across both reinforcement schedules, while the direction of effect differed by age group. Pb exposure was associated with shifts toward increased VI and FI response rates in both young and old rats. In contrast, adult rats exposed to Pb exhibited decreased rates of responding on both FI and VI schedules. Both patterns of response rate changes can be indicative of less efficient performance. Of the two reinforcement schedules, the FI appeared to be the more sensitive, as marginally significant behavioral effects were observed at both the 2 and 10 mg Pb/kg/day doses on the FI, while only occurring in response to the 10 mg/kg dose of Pb on the VI. The differential pattern of Pb effects across age groups does not appear to reflect a rate-dependency phenomenon, but its exact basis awaits further investigation. The detection of primarily marginally significant response rate changes here as compared to previous studies using similar Pb exposure levels suggests that the F-344 strain of rats is less sensitive to Pb than is the Long-Evans rat strain.

Aging↗
PubMed1998

Estimation of duration of separation, widowhood, and family life cycle.

This is the second of two reports on a study of the durations related to marriage. Divorce and death of one's spouse, the main causes of dissolution of marriage, are two of the most important events in a person's life. In the United States in 1994, 30.7 million, or 16.2%, of the adult population were either divorced or widowed. Among the widowed, the female to male ratio was 5 to 1! In this paper duration of separation due to divorce and duration of widowhood are the main variables under study. Algebraic formulas are derived and computer programs are written for estimating these durations for husbands and wives, and for living couples of any age. Relations with the duration of marriage, the expectation of life, and the family life cycle are also presented.

Adult↗
PubMed1992

Morphological characteristics of the life cycle of resting cartilage cells in mouse rib investigated in intrasplenic isografts.

Resting cartilages taken from 2-day-old mouse ribs were transplanted into spleens in order to carry out morphological investigations of the life cycles of their chondrocytes. The explants were isografted for periods of up to 60 days and examined at light and electron microscopic levels, using von Kossa's reaction or osmium-potassium ferrocyanide (OPF) fixation. By day 3 after transplantation, resting cartilage containing immature chondrocytes was well adapted to splenic tissue and by 7 days after transplantation these chondrocytes had changed into early hypertrophic chondrocytes containing large vacuoles, glycogen aggregates and abundant secretory organelles. It was also demonstrated by von Kossa's reaction that the initial calcification occurred in the territorial matrix during this period. In spite of the hypertrophic chondrocytes in the central zone being surrounded by an extensively calcified matrix during days 14-21 after transplantation, these cells had well-preserved organized organelles, except that Golgi-associated elements and endoplasmic reticulum revealed a tendency toward degenerative changes. With increased duration of the grafting period, from 30-60 days, the calcification zone progressed gradually, and the number of hypertrophic chondrocytes embedded in the calcified matrix decreased considerably. By day 60, degenerating hypertrophic chondrocytes of two types were distinguished:flattened cells containing large vacuoles, poorly developed Golgi apparatuses, and rough endoplasmic reticulum; and shrunken dark cells displaying terminal hypertrophy. During the present study, we observed no vascular invasion into the calcified matrix, or appearance of bone-related cells, and the morphological changes from the resting chondrocytes to cellular hypertrophy accompanied by the formation of a calcified matrix were observed at day 60. These findings indicate that resting cartilage cells of the mouse have the capacity for terminal differentiation when transplanted into the spleen.

Animals↗
PubMed1978

Developmental biology of Pneumocystis carinii, and alternative view on the life cycle of the parasite.

In this paper we present, based on elaborate ultrastructural studies, data on the existence of both intracellular and extracellular stages of Pneumocystis carinii, which result in a proposal of a new life cycle of the parasite. Up to now the formation of daughter cells in thick-walled pneumocysts is supposed to be the only way of multiplication. The present study shows that in rats treated with cortisone acetate the formation of daughter cells also takes place within thin-walled pneumocysts. In our opinion this way of multiplication is important for the understanding of the rapid increase in number of the parasites in an infected lung. The presence of pneumocysts inside the alveolar epithelial cells suggests that intracellular development of the parasites can occur, but the method of cell penetration, intracellular multiplication and parasite liberation is still unknown. Moreover our observations for the first time indicate a direct pathogenicity of the parasites in host cells.

Animals↗
PubMed2004

On the relevance of genotoxicity for fish populations I: effects of a model genotoxicant on zebrafish (Danio rerio) in a complete life-cycle test.

Genotoxicity may be detected in surface waters by means of various genotoxicity assays. In order to enable an ecotoxicological assessment of the consequences of such genotoxic potential for fish populations, a complete life-cycle test with zebrafish (Danio rerio) and the model genotoxicant 4-nitroquinoline-1-oxide (NQO) was conducted. Zebrafish (f1) were continuously exposed to NQO (i.e. 0.1, 0.3, 1.1, 2.9, and 14.6 microg/l, respectively) from fertilised eggs until sexual maturity. In addition to reproduction studies in the f1-generation, f2-fish were exposed to NQO during the first 6 weeks of development. Up to 2.9 microg/l NQO, fish did not display differences in survival and growth (P < 0.05). A NQO concentration of 14.6 microg/l, however, was lethal. Female fish exposed to all NQO concentrations up to 2.9 microg/l displayed a significant reduction in egg production (P < 0.05). A mathematical simulation revealed that exposure to weak concentrations of NQO is leading to an elevated extinction risk.

4-Nitroquinoline-1-oxide↗
PubMed2000

Overwintering strategy in Pyrrhocoris apterus (Heteroptera): the relations between life-cycle, chill tolerance and physiological adjustments.

Seasonal dynamics of ecophysiological parameters are described which are relevant to overwintering in field-collected adults of a Czech population of the red firebug, Pyrrhocoris apterus. Five life-cycle phases were distinguished using the duration of pre-oviposition period as a criterion: reproductive activity (spring-early summer), intensification of reproductive diapause (RD) (peak of summer), maintenance of RD (late summer-early autumn), termination of RD (late autumn-early winter), and low temperature quiescence (LTQ) (winter). The supercooling capacity and chill tolerance (c.t.) increased simultaneously with the termination of RD and all three processes were triggered/conditioned by autumnal decrease in ambient temperatures. Maximum supercooling capacity and c.t. 'outlived' the end of diapause and persisted throughout the LTQ state. The limits of c.t. were estimated as -15 degrees C/1-2 weeks for 50% survival. Ribitol, sorbitol, arabinitol, and mannitol were accumulated in the winter-sampled insects. Relatively low concentrations of polyols (dominating ribitol reached ca. 1% FW) indicate that they do not function as colligative cryoprotectants. However, because their seasonal occurrence coincided with the highest c.t., their non-colligative cryoprotectant effects would merit further study. Although the overwintering microhabitat of P. apterus is buffered, the temperatures may fall to -13 degrees C during exceptionally cold winters and thus, the parameters of c.t. seem to be just appropriately tuned to the local overwintering conditions.

Journal Article↗
PubMed2005

Gender differences and dynamics shaping the adoption life cycle: review of the literature and recommendations.

The role of gender in the experiences of adoptive family members has received little systematic attention. Gender differences in response to different tasks and phases of the adoption life cycle are described. Gendered dynamics within the adoptive family, for birth parents, and in the field of adoption are highlighted. Birth fathers and adoptive fathers are typically marginalized, which leaves women to address emotion, connection, and communication, and family dialogues about adoption may engage daughters more successfully than sons. The article reviews reasons why differential rates of problem behavior for adopted boys and girls may result from gender differences in emotional expressiveness, social support seeking, and identity formation. Implications of the feminization of adoption are explored, and recommendations for practice and research are proposed.

Adolescent↗
PubMed2003

Correlated clustering and virtual display of gene expression patterns in the wheat life cycle by large-scale statistical analyses of expressed sequence tags.

Compared to rice, wheat exhibits characteristic growth habits and contains complex genome constituents. To assess global changes in gene expression patterns in the wheat life cycle, we conducted large-scale analysis of expressed sequence tags (ESTs) in common wheat. Ten wheat tissues were used to construct cDNA libraries: crown and root from 14-day-old seedlings; spikelet from early and late flowering stages; spike at the booting stage, heading date and flowering date; pistil at the heading date; and seeds at 10 and 30 days post-anthesis. Several thousand colonies were randomly selected from each of these 10 cDNA libraries and sequenced from both 5' and 3' ends. Consequently, a total of 116 232 sequences were accumulated and classified into 25 971 contigs based on sequence homology. By computing abundantly expressed ESTs, correlated expression patterns of genes across the tissues were identified. Furthermore, relationships of gene expression profiles among the 10 wheat tissues were inferred from global gene expression patterns. Genes with similar functions were grouped with one another by clustering gene expression profiles. This technique might enable estimation of the functions of anonymous genes. Multidimensional analysis of EST data that is analogous to the microarray experiments may offer new approaches to functional genomics of plants.

Contig Mapping↗