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At least 19 recordsLinked to original sources
PubMed1989

Psychological issues affecting women throughout the life cycle.

Throughout life, some psychological issues facing women are shared with men, and some are unique to women. This article compares the traditional life cycle perspective with the complementary perspective of different lines of development that characterize women's lives. Traditionally, there was a concept, especially of the woman's life cycle, linking growth and reproduction to expected work, social status, and sources of self-esteem. Today, there is no single life cycle for women, but rather a number of predictable areas of growth and development. The article will explore the biologic-reproductive life cycle, the family-marital life cycle, and the educational-vocational life cycle, from before birth to old age. It will also review psychological problems most common at each stage, and it will discuss how societal changes in expectations of women may be changing women's growth and development today.

Aging↗
PubMed1977

The parasitic ecology of the rodent mite, Myobia musculi. IV. Life cycle.

The life cycle of Myobia musculi was determined by daily examination (under anesthesia) of experimentally infested mice. It was found that the larval period lasted 10 days followed by a 5-day nymphal period. Adult forms were seen on the 16th day. Adults produced fertile eggs within 24 hours of their appearance and eggs hatched in 7 days. Thus, the life cycle was completed in 23 days. Application of this information for a successful treatment regimen was discussed. Any treatment which does not kill embryonated eggs must be repeated subsequent to hatching of the eggs but prior to oviposition of fertile eggs by newly hatched females.

Animals↗
PubMed1991

Trypanosoma (Nannomonas) congolense: changes in respiratory metabolism during the life cycle.

All four life cycle stages (bloodstream, procyclic, epimastigote, and metacyclic) of Trypanosoma congolense IL 3000 were assayed with an oxygen electrode (polarograph) for the presence of terminal oxidases and carbon-source preference. In addition, these stages were used for histochemical analysis of mitochondrial activity using rhodamine 123, nitroblue tetrazolium, and diaminobenzidine. Morphometry was used to compare mitochondrial volumes and surface area among the different life cycle stages. It was found that in contrast to epimastigote forms, which were metabolically almost identical to procyclic forms, metacyclic forms showed characteristics of, and seemed preadapted to, differentiation into the bloodstream stage. While mitochondrial NAD+ diaphorase activity and an electrochemical potential were detected in all life cycle stages, metacyclic metabolism was glucose-based and terminal oxidase activity was primarily dependent upon the trypanosome alternative oxidase with the contribution of cyanide-sensitive respiration accounting for only 20-30% of the total respiratory capacity.

Adenosine Triphosphate↗
PubMedDate not supplied

Experimental life cycle of Lagochilascaris minor Leiper, 1909.

The life cycle of Lagochilascaris minor was studied using material collected from human lesion and applying the experimental model: rodents (mice, hamsters), and carnivores (cats, dogs). In mice given infective eggs, orally, hatch of the third stage larvae was noted in the gut wall, with migration to liver, lungs, skeletal musculature and subcutaneous tissue becoming, soon after, encysted. In cats infected with skinned carcasses of mice (60 to 235 days of infection) it was observed: hatch of third stage larvae from the nodules (cysts) in the stomach, migration through the oesophagus, pharynx, trachea, related tissues (rhino-oropharynx), and cervical lymph nodes developing to the mature stage in any of these sites on days 9-20 post inoculation (P.I.). There was no parasite development up to the mature stage in cats inoculated orally with infective eggs, which indicates that the life cycle of this parasite includes an obligatory intermediate host. In one of the cats (fed carcass of infected mice) necropsied on day 43 P.I., it was observed the occurrence of the self-infective cycle of L. minor in the lung tissues and in the cervical region which was characterized by the finding of eggs in different stages of development, third stage larvae and mature worms. It's believed that some component of the carnivore gastrointestinal tracts may preclude the development of third stage larvae from L. minor eggs what explains the interruption of the life cycle in animals fed infective eggs. It's also pointed out the role of the intermediate host in the first stages of the life cycle of this helminth.

Animals↗
PubMed1972

Protein and ribonucleic acid synthesis during the diploid life cycle of Allomyces arbuscula.

The diploid life cycle of Allomyces arbuscula may be divided into four parts: spore induction, germination, vegetative growth, and mitosporangium formation. Spore induction, germination, and mitosporangium formation are insensitive to inhibition of actinomycin D, probably indicating that stable, pre-existing messenger ribonucleic acid (RNA) is responsible for these developmental events. Protein synthesis is necessary during the entire life cycle except for cyst formation. A system for obtaining synchronous germination of mitospores is described. During germination there is a characteristic increase in the rate of synthesis of RNA and protein although none of the other morphogenetic changes occurring during the life cycle are necessarily accompanied by an appreciable change in the rate of macromolecular synthesis.

Adenine↗
PubMed1991

Endopeptidase variations among different life-cycle stages of African trypanosomes.

Lysates of different life-cycle stages of Trypanosoma congolense, Trypanosoma vivax and Trypanosoma brucei were analysed for endopeptidase activity, using reaction conditions which permitted a distinction to be made between lysosomal and non-lysosomal activity [Lonsdale-Eccles, J. D. & Grab, D. J. (1987) Eur. J. Biochem. 169, 467-475]. Hydrolysis of Z-Arg-Arg-NHMec (Z = benzyloxycarbonyl, NHMec = 7-amino-4-methylcoumaryl) and Z-Gly-Gly-Arg-NHMec occurred predominantly at alkaline pH and was observed in lysates of both insect and mammalian infective forms of T. brucei and T. congolense. Compared to their other life-cycle stages, procyclic forms of T. brucei and epimastigote forms of T. congolense exhibited enhanced hydrolysis of these substrates. Low levels of hydrolysis of Z-Arg-Arg-NHMec were observed in the bloodstream and epimastigote forms of T. vivax. The hydrolysis of Z-Gly-Gly-Arg-NHMec in each of the life-cycle stages of T. vivax was generally below detectable levels. In lysates of T. congolense, proteolytic and Z-Phe-Arg-NHMec-hydrolytic activity in bloodstream forms greater than metacyclic greater than epimastigote greater than procyclic forms. In T. vivax Z-Phe-Arg-NHMec-hydrolytic activity differed slightly according to the origin of the parasite but, in general, followed the same pattern (i.e. bloodstream forms greater than epimastigote forms, with metacyclic forms usually intermediate between these two). In T. brucei, Z-Phe-Arg-NHMec-hydrolytic activity in bloodstream forms greater than procyclic forms. Upon differentiation of the long, slender bloodstream forms into short, stumpy forms the Z-Phe-Arg-NHMec-hydrolytic activity was elevated even further. Thus, during their life cycle, each of these African trypanosomes exhibits complex changes of endopeptidase activity, suggestive of an induction of lysosomal activity between the insect and mammalian forms.

Amino Acid Sequence↗
PubMedDate not supplied

[Certain principles of the secondary simplication of the life cycles of helminths].

On the basis of the analysis of regularities accompanying the secondary simplification of the life cycles of helminths on account of the reduction in the number of the animals-hosts 8 rules have been formulated. They are based on the following important regularities. 1. At the secondary simplification of the life cycles of helminths never fall out the first intermediate host in Trematoda and the definitive host in Nematoda. This phenomenon is suggested to be called "the host stability in the life cycle". 2. Mostly often from the life cycles fall secondarily out those hosts which join in the life cycle at its first complication later. 3. The phase of the helminth having transformed into a parasitic form at the first complication of its life cycle remains the same at the secondary simplification of this cycle.

Adaptation, Physiological↗
PubMedDate not supplied

[Toxoplasmids, their life cycle and systematic position].

Recent evidence on the life cycles of the toxoplasmids (Toxoplasma, Besnoitia, Sarcocystis, Hammondia, Frenkelia) has been analysed. The availability of the complex life cycles, including the alternation of sexual and asexual reproduction, in addition to gametogenesis involving the independent development of gametes that produce unequal numbers of gametes, makes it possible to include the toxoplasmids into the family Eimeriidae within the order Coccidiida. A detailed evidence recently provided for Isospora has suggested a kinship of this typical coccidian genus with toxoplasmids. At the same time much similarity is obvious between Isospora and Eimeria in the general pattern of their life cycles. Hence, the family Eimeriidae is suggested to be divided into two subfamilies: Eimeriinae Wenyon, 1926 with Eimeria as the type genus and Isosporinae Wenyon, 1926 with Isospora, Toxoplasma, Besnoitia, Sarcocystis, Frenkelia and Hammondia. The main features of the former subfamily are: various oocyst structures, the lack of the extra-intestinal development, obligatory monoxeny. The main characters of the latter subfamily: oocysts of the same pattern, the involvement of extra-intestinal development, shifts from facultative to obligatory heteroxeny.

Animals↗
PubMed1985

Variations in interstate migration of men across the early stages of the life cycle.

The results reported here show that the stage of an individual's life cycle not only has direct effects on the likelihood of migration, but also establishes a context within which the motives to migrate are evaluated and acted upon. One contextual impact of the life cycle concerns the effects of length of residence on migration. The results show that the probability of migrating declines more rapidly over time for married males with children than for singles males--i.e., the difference between the likelihood of migration for single males and married males with children widens with increasing length of residence. Much of this difference may be due to the greater number and strength of community ties for individuals who are married with children. These ties are not well developed at the beginning of a residence but continue to strengthen over the course of a residence. In addition, there are variations in the levels of job rewards and location-specific resources across the life cycle and there are two variations across the early life cycle in the effects of independent variables on the initial rate of migration. One resource (self-employment) and one job reward (prestige) have different effects for single individuals than for either group of married males. If the span of the life cycle considered in this analysis were broadened to include older men, additional differences in the effects of independent variables might be uncovered. In research with cross-sectional data containing a wider range of ages than the data used here, Heaton et al. (1981) found that economic variables were more important in determining the migration of younger individuals than that of older individuals, whereas noneconomic factors were more important determinants of the migration of older than of younger individuals. The results of this paper and Heaton's results suggest that at different stages of life people use a somewhat different "subjective cost-benefit calculus" in making migration decisions. The importance of certain migration determinants may vary significantly depending on whether an individual is married, whether he or she has children, and/or whether he or she is in the labor force or retired. Additional research on these issues could greatly contribute to our understanding of migration.

Adult↗
PubMed1990

The use of computer-aided learning for teaching parasite life cycles.

The difficulty of presenting parasite life cycles in a textual or diagrammatic form is discussed and the use of computer-aided learning to solve this is described. The design and use of a Hypercard stack for teaching parasite life cycles on an Apple Macintosh microcomputer are outlined.

Animals↗
PubMed1991

Life cycle of Simulium jenningsi (Diptera: Simuliidae) in southern West Virginia.

The life cycle of Simulium jenningsi Malloch was compared at two study sites representing the largest and smallest streams (New River and Indian Creek, respectively) where this species is known to breed in southern West Virginia. Larvae first appeared in March, and the first generation emerged in April, followed by two to four more generations by September. A few larvae and adults persisted in autumn, then the population overwintered in the egg stage. There were considerable differences in life cycle at the two study sites. In the New River, emergence of the first generation was 2-3 wk earlier, there were five generations rather than three, and the last larvae of the season persisted 1 mo later as compared with Indian Creek. Warmer temperature and higher quality food in the New River are probable explanations for differences in life cycle. Effective pest management of this species will require larviciding at frequent intervals (1-2 wk) from April through September in many streams over a broad geographic area because of the species' nonsynchronous life cycle, occurrence in different size streams, and strong dispersal ability.

Animals↗
PubMed1978

Life cycle variation and regulation of macronuclear DNA content in Tetrahymena thermophila.

The mean DNA content of G2 macronuclei varies during the life cycle of the ciliate Tetrahymena thermophila. Early in the life cycle the mean is about 130 C; later it is about 94 C. In hybrids between strains A and B the decrease from 130 C to 94 C usually began after 60 fissions after conjugation. In B X B clones the decrease was complete by 50 fissions. The data suggest that there may be a genetic difference between strains A and B with respect to the onset of the decrease in DNA content. The downward regulation of the mean DNA content appears to be related to the mechanism which removes the variance in macronuclear DNA content which is added to macronuclei by unequal macronuclear division. Unequal macronuclear division regularly occurs at all stages of the life cycle, with larger macronuclei tending to divide more unequally. In the absence of regulation, unequal macronuclear division would constantly add variance to G1 macronuclei and their range would continue to increase. Analysis of the variances of G1 and G2 macronuclei suggests that at all stages of the life cycle the added variance is removed by acting upon nuclei which become too small or too large. According to this model, macronuclei with smaller amounts of DNA are regulated upward by an extra macronuclear S phase, while larger amounts are regulated downward by chromatin extrusion and the skipping of macronuclear S. The mean DNA content appears to change during the life cycle because the thresholds at which macronuclei become too small or too large are readjusted. It is postulated that these thresholds are a function of gene dosage.

Analysis of Variance↗