Rapamycin supplementation of Drosophila melanogaster larvae results in less viable adults with smaller cells.

The intrinsic sources of mortality relate to the ability to meet the metabolic demands of tissue maintenance and repair, ultimately shaping ageing patterns. Anti-ageing mechanisms compete for resources with other functions, including those involved in maintaining functional plasma membranes. Consequently, organisms with smaller cells and more plasma membranes should devote more resources to membrane maintenance, leading to accelerated intrinsic mortality and ageing. To investigate this unexplored trade-off, we reared Drosophila melanogaster larvae on food with or without rapamycin (a TOR pathway inhibitor) to produce small- and large-celled adult flies, respectively, and measured their mortality rates. Males showed higher mortality than females. As expected, small-celled flies (rapamycin) showed higher mortality than their large-celled counterparts (control), but only in early adulthood. Contrary to predictions, the median lifespan was similar between the groups. Rapamycin administered to adults prolongs life; thus, the known direct physiological effects of rapamycin cannot explain our results. Instead, we invoke indirect effects of rapamycin, manifested as reduced cell size, as a driver of increased early mortality. We conclude that cell size differences between organisms and the associated burdens of plasma membrane maintenance costs may be important but overlooked factors influencing mortality patterns in nature.

Global patterns of migration of scholars with economic development.

We leverage metadata on over 36 million journal articles and reviews indexed by Scopus in order to estimate migration of scholars based on information on changes in their institutional affiliations over time. We produce a database of yearly international migration flows of scholars, for all countries from 1998 to 2017. We use the open-access database to provide descriptive evidence on the relationship between economic development and the emigration propensity of scholars. Statistical analysis using generalized additive mixed models reveals that emigration rates initially decrease as GDP per capita increases. Then, starting from around 25,000 dollars (2017 constant international dollars at purchasing power parity), the trend reverses and emigration propensity increases as countries get richer. This U-shaped pattern contrasts with what has been found in the literature for emigration rates for the general population and calls for theoretical frameworks to understand the heterogeneous responses of migration to development.

Facilitating behavioral change: A comparative assessment of ASHA efficacy in rural Bihar.

Community health worker (CHW) programs are essential for expanding health services to many areas of the world and improving uptake of recommended behaviors. One of these programs, called Accredited Social Health Activists (ASHA), was initiated by the government of India in 2005 and now has a workforce of about 1 million. ASHAs primarily focus on improving maternal and child health but also support other health initiatives. Evaluations of ASHA efficacy have found a range of results, from negative, to mixed, to positive. Clarity in forming a general impression of ASHA efficacy is hindered by the use of a wide range of evaluation criteria across studies, a lack of comparison to other sources of behavioral influence, and a focus on a small number of behaviors per study. We analyze survey data for 1,166 mothers from Bihar, India, to assess the influence of ASHAs and eight other health influencers on the uptake of 12 perinatal health behaviors. We find that ASHAs are highly effective at increasing the probability that women self-report having practiced biomedically-recommended behaviors. The ASHA's overall positive effect is larger than any of the nine health influencer categories in our study (covering public, private, and community sources), but their reach needs to be more widely extended to mothers who lack sufficient contact with ASHAs. We conclude that interactions between ASHAs and mothers positively impact the uptake of recommended perinatal health behaviors. ASHA training and program evaluation need to distinguish between individual-level and program-level factors in seeking ways to remove barriers that affect the reach of ASHA services.

[The Polish physiotherapists' state of knowledge about the act on the profession of physiotherapist]. / Wiedza polskiego srodowiska fizjoterapeutycznego dotyczaca regulacji prawnych w swietle ustawy o zawodzie fizjoterapeuty.

BACKGROUND: Work on the Act on the Profession of Physiotherapist had been conducted since the 1990s. However, it was not until October 2015 that the legal regulations were eventually introduced, following which physiotherapists gained professional independence and became a profession of public trust. The aim of the study was to assess the factors influencing the knowledge of these legal regulations among physiotherapists. MATERIAL AND METHODS: The study involved 399 physiotherapists and physiotherapy students (28.8±5.9 years old) who completed an anonymous questionnaire, in the form of a knowledge test, consisting of 24 questions on the general aspects of the reference Act. RESULTS: Overall, 30.3% of the respondents proved to have a significant knowledge about the rights and obligations resulting from the Act. The physiotherapists who were entered into the National Register of Physiotherapists (2.6 times) and residents of large cities (1.8 times) had a greater knowledge of the Act. There was a correlation between seniority and gender, and the knowledge of legal regulations. CONCLUSIONS: The main factors influencing the state of knowledge about the Act are the entry to the National Register of Physiotherapists, the place of residence and seniority. This proves better access to up-to-date information in cities and a greater interest in the Act among those people who have obtained the right to practice their profession. Med Pr. 2021;72(4):407-14.

Joint modeling of interval counts of recurrent events and death.

When a recurrent event process is ended by death, this may imply dependent censoring if the two processes are associated. Such dependent censoring would have to be modeled to obtain a valid inference. Moreover, the dependence between the recurrence process and the terminal event may be the primary topic of interest. Joint frailty models for recurrent events and death, which include a separate dependence parameter, have been proposed for exactly observed recurrence times. However, in many situations, only the number of events experienced during consecutive time intervals are available. We propose a method for estimating a joint frailty model based on such interval counts and observed or independently censored terminal events. The baseline rates of the two processes are modeled by piecewise constant functions, and Gaussian quadrature is used to approximate the marginal likelihood. Covariates can be included in a proportional rates setting. The observation intervals for the recurrent event counts can differ between individuals. Furthermore, we adapt a score test for the association between recurrent events and death to the setting in which only individual interval counts are observed. We study the performance of both approaches via simulation studies, and exemplify the methodology in a biodemographic study of the dependence between budding rates and mortality in the species Eleutheria dichotoma.

Phenotypic plasticity of senescence in Daphnia under predation impact: no ageing acceleration when the perceived risk decreases with age.

Recognising the nature of the predation risk, and responding to it accurately, is crucial to fitness. Yet, even the most accurate adaptive responses to predation risk usually entail costs, both immediate and lifelong. Rooting in life-history theory, we hypothesize that an animal can perceive the nuances of prey size and age selectivity by the predator and modulate its life history accordingly. We test the prediction that-contrary to the faster or earlier senescence under predation risk that increases with prey size and age-under predation risk that decreases with prey size and age either no senescence acceleration or even its deceleration is to be observed. We use two species of indeterminate growers, small crustaceans of the genus Daphnia, Daphnia Pulex and Daphnia magna, as the model prey, and their respective gape-limited invertebrate predators, a dipteran, midge larva Chaoborus flavicans, and a notostracan, tadpole shrimp Triops cancriformis. We analyse age-specific survival, mortality and fertility rates, and find no senescence acceleration, as predicted. With this study, we complete the picture of the expected non-consumptive phenotypic effects of perceived predation pressure of different age-dependence patterns.

Is the story about sensitive women and stoical men true? Gender differences in health after adjustment for reporting behavior.

Research indicates that women have higher levels of physical disability and depression and lower scores on physical performance tests compared to men, while the evidence for gender differences in self-rated health is equivocal. Scholars note that these patterns may be related to women over-reporting and men under-reporting health problems, but gender differences in reporting behaviors have not been rigorously tested. Using Wave 1 of the Survey of Health, Ageing and Retirement in Europe (SHARE), the present study investigates the extent to which adjusting for differences in reporting behavior modifies gender differences in general health. We also examine whether men and women's reporting behaviors are consistent across different levels of education. After adjusting for reporting heterogeneity, gender differences in both poor and good health widened. However, we found no clear gender-specific patterns in reporting either poor or good health. Our findings also do not provide convincing evidence that education is an important determinant of general health reporting, although the female disadvantage in poor health and the male advantage in good health were more apparent in lower than higher education groups at all ages. The results challenge prevailing stereotypes that women over-report and men under-report health problems and highlight the importance of attending to health problems reported by women and men with equal care.

Extrinsic Mortality Can Shape Life-History Traits, Including Senescence.

The Williams' hypothesis is one of the most widely known ideas in life history evolution. It states that higher adult mortality should lead to faster and/or earlier senescence. Theoretically derived gradients, however, do not support this prediction. Increased awareness of this fact has caused a crisis of misinformation among theorists and empirical ecologists. We resolve this crisis by outlining key issues in the measurement of fitness, assumptions of density dependence, and their effect on extrinsic mortality. The classic gradients apply only to a narrow range of ecological contexts where density-dependence is either absent or present but with unrealistic stipulations. Re-deriving the classic gradients, using a more appropriate measure of fitness and incorporating density, shows that broad ecological contexts exist where Williams' hypothesis is supported.

Population density shapes patterns of survival and reproduction in Eleutheria dichotoma (Hydrozoa: Anthoathecata).

Budding hydromedusae have high reproductive rates due to asexual reproduction and can occur in high population densities along the coasts, specifically in tidal pools. In laboratory experiments, we investigated the effects of population density on the survival and reproductive strategies of a single clone of Eleutheria dichotoma. We found that sexual reproduction occurs with the highest rate at medium population densities. Increased sexual reproduction was associated with lower budding (asexual reproduction) and survival probability. Sexual reproduction results in the production of motile larvae that can, in contrast to medusae, seek to escape unfavorable conditions by actively looking for better environments. The successful settlement of a larva results in starting the polyp stage, which is probably more resistant to environmental conditions. This is the first study that has examined the life-history strategies of the budding hydromedusa E. dichotoma by conducting a long-term experiment with a relatively large sample size that allowed for the examination of age-specific mortality and reproductive rates. We found that most sexual and asexual reproduction occurred at the beginning of life following a very rapid process of maturation. The parametric models fitted to the mortality data showed that population density was associated with an increase in the rate of aging, an increase in the level of late-life mortality plateau, and a decrease in the hidden heterogeneity in individual mortality rates. The effects of population density on life-history traits are discussed in the context of resource allocation and the r/K-strategies' continuum concept.

Latitudinal and age-specific patterns of larval mortality in the damselfly Lestes sponsa: Senescence before maturity?

Latitudinal differences in life history traits driven by differences in seasonal time constraints have been widely documented. Yet, latitudinal patterns in (age-specific) mortality rates have been poorly studied. Here, we studied latitudinal differences in pre-adult age-specific mortality patterns in the strictly univoltine damselfly Lestes sponsa. We compared individuals from three latitudes reared from the egg stage in the laboratory at temperatures and photoperiods simulating those at the latitude of origin (main experiment) and under common-garden conditions at a fixed temperature and photoperiod (supplementary experiment). Results from the main experiment showed that the high-latitude population exhibited higher mortality rates than the central and southern populations, likely reflecting a cost of their faster development. Age-specific mortality patterns, also indicated higher ageing rates in the high-latitude compared to the low-latitude population, which likely had a genetic basis. The strong within-population variation in hatching dates in the low-latitude population caused variation in mortality rates; individuals that hatched later showed higher mortality rates presumably due to their shorter development times compared to larvae that hatched earlier. In both experiments, larvae from all three latitudes showed accelerated mortality rates with age, which is consistent with a pattern of senescence before adulthood.

Constant mortality and fertility over age in Hydra.

Senescence, the increase in mortality and decline in fertility with age after maturity, was thought to be inevitable for all multicellular species capable of repeated breeding. Recent theoretical advances and compilations of data suggest that mortality and fertility trajectories can go up or down, or remain constant with age, but the data are scanty and problematic. Here, we present compelling evidence for constant age-specific death and reproduction rates in Hydra, a basal metazoan, in a set of experiments comprising more than 3.9 million days of observations of individual Hydra. Our data show that 2,256 Hydra from two closely related species in two laboratories in 12 cohorts, with cohort age ranging from 0 to more than 41 y, have extremely low, constant rates of mortality. Fertility rates for Hydra did not systematically decline with advancing age. This falsifies the universality of the theories of the evolution of aging that posit that all species deteriorate with age after maturity. The nonsenescent life history of Hydra implies levels of maintenance and repair that are sufficient to prevent the accumulation of damage for at least decades after maturity, far longer than the short life expectancy of Hydra in the wild. A high proportion of stem cells, constant and rapid cell turnover, few cell types, a simple body plan, and the fact that the germ line is not segregated from the soma are characteristics of Hydra that may make nonsenescence feasible. Nonsenescence may be optimal because lifetime reproduction may be enhanced more by extending adult life spans than by increasing daily fertility.

Unraveling the non-senescence phenomenon in Hydra.

Unlike other metazoans, Hydra does not experience the distinctive rise in mortality with age known as senescence, which results from an increasing imbalance between cell damage and cell repair. We propose that the Hydra controls damage accumulation mainly through damage-dependent cell selection and cell sloughing. We examine our hypothesis with a model that combines cellular damage with stem cell renewal, differentiation, and elimination. The Hydra individual can be seen as a large single pool of three types of stem cells with some features of differentiated cells. This large stem cell community prevents "cellular damage drift," which is inevitable in complex conglomerate (differentiated) metazoans with numerous and generally isolated pools of stem cells. The process of cellular damage drift is based on changes in the distribution of damage among cells due to random events, and is thus similar to Muller's ratchet in asexual populations. Events in the model that are sources of randomness include budding, cellular death, and cellular damage and repair. Our results suggest that non-senescence is possible only in simple Hydra-like organisms which have a high proportion and number of stem cells, continuous cell divisions, an effective cell selection mechanism, and stem cells with the ability to undertake some roles of differentiated cells.

How perceived predation risk shapes patterns of aging in water fleas.

Predation is an important selection pressure which shapes aging patterns in natural populations, and it is also a significant factor in the life history decisions of individuals. Exposure to the perceived threat of size-dependent fish predation has been shown to trigger adaptive responses in animal life history including an increase in early reproductive output. In water fleas, this response to perceived predation risk appears to have a cost, as a lifespan in an environment free of predation cues is 20% longer. The aim of this study is to establish the biodemographic basis of phenotypic differences in the water flea lifespan which are induced by the cues of fish predation. We examined mortality by fitting the Gompertz-Makeham model of mortality to large cohorts of two cladoceran species, Daphnia longispina and Diaphanosoma brachyurum. Our findings indicate that perceived exposure to the threat of fish predation (induced through chemical cues) only accelerated the rate of aging in Diaphanosoma, and not in Daphnia where the treatment led to an earlier onset of aging. The second of these two phenotypic responses is consistent with the genetically based differences between Daphnia from habitats that differ with respect to predation risk. In contrast, the response of Diaphanosoma demonstrates that the cue of extrinsic mortality-in this case, fish predation-is a key factor in shaping these cladoceran life histories in the wild, and is one of the few interventions which has been shown to induce a plastic change in the rate of aging.