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1.
D K Martin  H Maclean  F H Lowy  J I Williams  E V Dunn 《CMAJ》1995,153(5):545-552
OBJECTIVE: To describe women''s attitudes and predicted behaviour regarding the potential for fetal tissue transplantation (FTT) to influence abortion decisions. DESIGNS: Self-administered questionnaire survey by mail. SETTING: Academic family practice in Toronto. PARTICIPANTS: Random sample of 475 women 18 to 40 years of age selected from the family practice registry of an urban teaching hospital. Family physicians were blind to their patients'' participation, and investigators were blind to the subjects'' identity. Forty questionnaires were undeliverable. Of the remaining 435, 272 (62.5%) were completed. Six of the women were over 40 years of age or did not indicate their age and were excluded, which left 266 (61.1%) questionnaires for analysis. OUTCOME MEASURES: Number of women who would (a) be more likely to have an abortion if they could donate tissue for FTT and (b) feel better or worse about choosing abortion if FTT were an option, and open-ended comments about the potential for FTT to influence abortion decisions. RESULTS: Of the 266 respondents 32 (12.0%) reported that they would be more likely to have an abortion if they could donate tissue for FTT, 178 (66.9%) stated that they would not be more likely to do so, and 56 (21.1%) were uncertain. Of the 122 who indicated that they would consider an abortion if they were pregnant, 21 (17.2%) stated that they would be more likely to have an abortion if they could donate tissue for FTT, 77 (63.1%) replied that they would not be more likely to do so, and 24 (19.7%) were uncertain. The women 25 to 33 years of age were more likely to be influenced by FTT than the younger or older women, and the women 18 to 24 years were more uncertain about the influence of FTT on abortion decisions than the older women. In written responses some of the women felt that FTT might make abortion decisions easier; many were troubled that FTT might be used to justify a morally problematic abortion decision and felt that FTT should not be used to justify abortion. CONCLUSION: The data, the first of their kind gathered from from women, suggest that some women''s abortion decisions may be influenced by the option to donate tissue for FTT. Further research is necessary to explore the mechanism of influence.  相似文献   

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3.
Fruit and seed abortion in plants have been traditionally attributed to limiting factors such as resources or to chemically mediated dominance hierarchy among the developing sinks. These hypotheses however do not satisfactorily explain the observed patterns of seed and fruit abortion and have also not withstood the test of critical experimentation. In this paper, we propose an alternative model based on the process of self organization used in physics to explain the flow of liquids etc. As proposed here, the model assumes one simple rule, that the probability of any given sink getting a resource molecule is a function of (a) the sink-drawing ability of each unit of the tissue and (b) the amount of resource molecules already moved to that sink. Accordingly, any resource molecule moving to a sink, autocatalytically increases the probability of the latter getting further resources.
We show that starting from a set of identical sinks, all with equal sink-drawing ability, the differential development of sinks and thence their abortion might occur purely as a consequence of the autocatalytic or feedback movement of the resource molecules to the developing sinks. We also show that, such a process can lead to abortion even under resource-abundant conditions, though resource limitation aggravates the extent of abortion. Further, the extent of abortion is shown to be highly dependent on the sink-drawing ability of the species. We offer the test of this prediction in two ways: (a) in Derris indica the extent of abortion increases with the sink drawing ability of the fertilized ovules and (b) treatments involving growth regulators that increase the sink-drawing ability result in increased abortion of seeds and fruits. Based on these, we argue that self organization could be the basic process regulating resource flow to sinks and factors such as resource limitation and chemical inhibition might be additionally aggravating the asymmetry among the developing sinks.  相似文献   

4.
Paternal care in humans is facultative, with investment decisions responsive to socioecological context. In particular, paternity confidence is thought to have a significant impact on men's provisioning. However, various aspects of the relationship a man has with his partner can also influence the way he provides for his children. Previous papers have tended to focus either on these kinds of relationship dynamics or on the impact of paternity confidence. However, these categories are often intertwined and parsing their contributions can be conceptually and methodologically difficult. To better understand how paternity confidence and relationship dynamics impact men's investment decisions, we used a series of pictorial vignettes to assess the resource allocation strategies of Himba men. We focus on three traits: mate fidelity, partner type (marital or non-marital), and relationship status (current or former). Results suggest that men prioritize mate fidelity and current reproductive partners in investment decisions, but social obligations to past and current partners and the presence of other male investors also influence decisions. Himba men appear to be balancing social norms related to marriage and fatherhood with individually-driven incentives to invest in current and more faithful partners.  相似文献   

5.
Females of many species can gain benefits from being choosy about their mates and even exhibit context-dependent investment in reproduction in response to the quality of their breeding situation. Here, we show that if a male house wren is provided with surplus nest boxes in his territory, his mate lays a larger clutch with a significantly higher proportion of sons. This response to a territory characteristic directly associated with male competitive ability, and ultimately to male reproductive success, suggests that male competition over access to high-quality territories with surplus nest boxes (i.e. those able to support polygyny) may influence female reproductive investment decisions. The results of this study have interesting implications, particularly considering the important role that studies of cavity nesting birds utilizing nest boxes have played in advancing our understanding of behaviour, ecology and evolution.  相似文献   

6.
Current research on seabirds suggests a key role of hormones in the trade-off between self-maintenance and parental investment through their influence on foraging decisions during the breeding period. Although prolactin is known to have major effects on parental care, its role in foraging behavior has rarely been investigated in seabirds to date.  相似文献   

7.
The evolution of matrotrophy introduces the potential for genomic conflicts between mothers and embryos. These conflicts are hypothesized to accelerate the evolution of reproductive isolation and to influence the evolution of life-history traits, reproductive structures, and genomic imprinting. These hypotheses assume offspring can influence the amount of maternal investment they receive and that there is a trade-off between maternal investment into individual offspring and maternal survival or fecundity. We used field data and laboratory crosses to test whether these assumptions are met in the matrotrophic poeciliid fish Heterandria formosa . Comparisons of life histories between two natural populations demonstrated a trade-off between the level of maternal investment into individual embryos and maternal fecundity. Laboratory crosses between individuals from these populations revealed that offspring genotype exerts an influence on the level of maternal investment and affects maternal fecundity through higher rates of embryo abortion and lower numbers of full-term offspring. Our results show that the prerequisites for parent–offspring conflict to be a potent evolutionary force in poeciliid fish are present in H. formosa. However, determining whether this conflict has shaped maternal investment in nature will require disentangling any effects of conflict from those of several ecological factors that are themselves correlated with the expected intensity of conflict.  相似文献   

8.
The interests of evolutionary anthropologists, behavioral ecologists, and demographers converge on the ecology of human fertility. Ecological conditions influence the optimum pattern of maternal effort. Patterns of abortion, neglect, and infanticide vary with mothers' ability to invest in their children and children's ability to use that investment. As in most other mammals, the ecology of human fertility varies between the sexes: status and resource control are important for males, whereas reproductive value is crucial for females. In pre-industrial societies, and even in monogamous societies in demographic transition, wealthy men had more children than did poorer men. This correlation, often assumed to have disappeared, persists today, with richer men still having more sexual access than others. Sex differences in the ecology of fertility mean that sex of the offspring, as well as birth order, influences parental investment. Because individual fertility varies with environment, it is not surprising that “natural” (uncontrolled) fertility varies across societies or that demographic transitions proceed locally, with occasional reverses, as individuals strive to maximize their lifetime reproductive success in changing, competitive, conditions.  相似文献   

9.
The Catholic Hierarchy unequivocally bans abortion, defining it as a mortal sin. In Mexico City, where the Catholic Church wields considerable political and popular power, abortion was recently decriminalized in a historic vote. Of the roughly 170,000 abortions that have been carried out in Mexico City's new public sector abortion program to date, more than 60% were among self-reported Catholic women. Drawing on eighteen months of fieldwork, including interviews with 34 Catholic patients, this article examines how Catholic women in Mexico City grapple with abortion decisions that contravene Church teachings in the context of recent abortion reform. Catholic women consistently leveraged the local cultural, economic, and legal context to morally justify their abortion decisions against church condemnation. I argue that Catholic women seeking abortion resist religious injunctions on their reproductive behavior by articulating and asserting their own moral agency grounded in the contextual dimensions of their lives. My analysis informs conversations in medical anthropology on moral decision-making around reproduction and on local dynamics of resistance to reproductive governance. Moreover, my findings speak to the deficiencies of a feminist vision focused narrowly on fertility limitation, versus an expanded framework of reproductive justice that considers as well the need for conditions of income equality and structural supports to facilitate reproduction and parenting among women who desire to keep their pregnancies.  相似文献   

10.
Abortion storms in 50 dairy herds in The Netherlands were reported in which there was a strong association with Neospora caninum-infection. The duration of the abortion storms ranged from 6 to 65 d (mean 41.5 d). The cumulative proportion of aborting cows ranged from 0.11 to 0.57 (mean 0.26) of the animals at risk. An apparent seasonal influence was noted as most abortion storms occurred during the summer and early autumn. The prevalence of antibodies to N. caninum in 50 herds which had had an abortion storm was compared with that of 100 control herds which had no history of an abortion storm. Seroprevalence was estimated by testing a 20% cross sectional herd sample using a tachyzoite lysate-based ELISA method. Seroprevalence in case herds (range 17 to 87%, mean 51.5%) was significantly higher than that in control herds (range 0 to 53%, mean 13.9%). For most herds the seroprevalence levels were equal across all age groups, which suggests that the infection had been perpetuated by vertical transmission. In these herds, the abortion storms appeared to be induced by factors causing recrudescence of a N. caninum-infection in chronically infected animals rather than being the result of a recent introduction. In 6 case herds the seroprevalence in the dairy cows was significantly higher than in the young stock, which may have been attributable to superimposed postnatal infection.  相似文献   

11.
Life cycle cost (LCC) computations are a well-established instrument for the evaluation of intertemporal choices in organizations, but they have not been widely adopted by private consumers yet. Consumer investment decisions for products and services with higher initial costs and lower operating costs are potentially subject to numerous cognitive biases, such as present-biased preferences or framing effects. This article suggests a classification for categorizing different cost profiles for eco-innovation and a conceptual model for the influence of LCC information on consumer decisions regarding eco-innovation. It derives hypotheses on the decision-making process for eco-innovation from a theoretical perspective. To verify the hypotheses, the publication reviews empirical studies evaluating the effects of LCC information on consumer investment decisions. It can be concluded that rather than finding ways to make customers pay more for environmentally sound products, the marketing challenge for eco-innovation should be reconceptualized as one of lowering customers' perceived initial cost and increasing awareness of LCC. Most existing studies report a positive effect of LCC information on the purchase likelihood of eco-innovations. Disclosing LCC information provides an important base for long-term thinking on the individual, corporate, and policy levels.  相似文献   

12.
Effect of defoliation on grass growth. A quantitative review   总被引:13,自引:0,他引:13  
This study describes the seasonal patterns of seed and cone abortion in natural Pinus halepensis trees and assesses the effects of pollen quantity, tree size and cone location on seed and cone abortion. The cone-set ratio was similar to the expected value, based on literature on woody perennials. The seed-ovule ratio, however, was almost twice as high as its expected value. The investment in protective cone elements was high and did not vary with the seed-ovule ratio of a cone. Pollination factors influenced cone abortion, as indicated by the high abortion rate at the end of the pollination period. Furthermore, abortive cones had lower pollination rates and lower pollen loads than well developed cones. Effects of resource availability were assessed as effects of tree size and cone position on twigs. Small trees aborted more cones than big trees and cone abortion was higher in apical cones than in basal cones. Abortion in P. halepensis is selective, mediated by both pollen quantity and resource availability. The relative importance of pollen and resources is suggested to be flexible, probably varying between trees and years. The high seed-ovule ratio of P. halepensis is the result of high pollination rate and selective abortion. The selective abortion might be due to the high allocation to protective cone elements relative to the allocation to seeds.  相似文献   

13.
Optimal investment in offspring is important in maximizing lifetime reproductive success. Yet, very little is known how animals gather and integrate information about environmental factors to fine tune investment. Observing the decisions and success of other individuals, particularly when those individuals initiate breeding earlier, may provide a way for animals to quickly arrive at better breeding investment decisions. Here we show, with a field experiment using artificial nests appearing similar to resident tit nests with completed clutches, that a migratory bird can use the observed high and low clutch size of a resident competing bird species to increase and decrease clutch size and egg mass, accordingly. Our results demonstrate that songbirds can discriminate between high and low quantity of heterospecific eggs, and that social information can have long-term physiological consequences affecting reproductive strategies. Such behaviour may help animals to better adapt to changing environments and lead to convergent traits with competitors.  相似文献   

14.
A key prediction of theories of differential allocation and sexual conflict is that male phenotype will affect resource allocation by females. Females may adaptively increase investment in offspring when mated to high quality males to enhance the quality of their offspring, or males may vary in their ability to manipulate female investment post-mating. Males are known to be able to influence female reproductive investment, but the male traits underlying this ability have been little studied in taxa other than birds. We investigated the relationship between male dominance and female oviposition rate in two separate experiments using the field cricket, Gryllus bimaculatus. In both experiments, females mated to more dominant (but not larger) males laid more eggs. This reveals that either females allocate more effort to reproduction after mating with a dominant male or that dominance status is associated with male ability to manipulate their mates. This is the first evidence that dominance, rather than male attractiveness, has a post-copulatory effect on reproductive investment by females.  相似文献   

15.
The role of past investment in parental-care behaviour has often been controversial. Some researchers have argued that organisms basing present investment on past investment are committing the 'Concorde fallacy'. Others have incorporated life history theory to suggest that investing according to past investment is one component of investing according to expected future reproductive success: a parent can use past investment as well as other information, such as brood size, to make its optimal parental-investment decisions. Although parental-investment research is still in its infancy, the incorporation of life history theory suggests that the Concorde fallacy is a misleading concept.  相似文献   

16.
This article presents a case study in a Nigerian firm of how waste costing can be applied to pollution prevention (P2) investment decisions. This case is informed by the priority accorded to P2 as a preferred alternative to end‐of‐pipe pollution control. It demonstrates that even in the absence of effective regulations in a developing country, cost accounting can spur P2 decisions by management through the system of waste cost allocation. The case used standard cost data from the Wonder Beauty Care Company and applied the activity‐based costing (ABC) system to waste cost allocation using waste cost drivers, which yielded another genre of waste costs—waste‐induced overhead. Subsequently, the waste‐induced overhead was applied to P2 investment analysis. This analysis indicated that the P2 investment alternative that incorporates the waste‐induced overhead produced a preferred alternative choice. The case further revealed that managers’ knowledge of waste costs in a Nigerian firm may influence their P2 decisions. The case illustrates practically a possible dual advantage of an improved costing system for Nigerian firms—cost reduction and cleaner production.  相似文献   

17.
Policy makers face a number of difficult choices as they develop policies to ensure maintenance of a polio-free world following global eradication and certification. These policy decisions include choices about immunization, outbreak response (including whether to create a vaccine stockpile), surveillance, containment, management of chronic excretors, and investment in future research. This paper focuses on identifying the categories of decisions and characterizing the actual factors that country-level policy makers must weigh to manage polio risks during the first 5 years after certification. Building on a comprehensive literature review, we report the results of the first qualitative analysis to: (1) systematically characterize each type of decision and the relevant options during the first 5 years after certification, (2) clearly identify critical factors that influence the choices, and (3) specifically demonstrate the interdependence among the decisions to produce a reduced set of decision options. This paper explicitly focuses on the different perspectives of developed and developing countries in characterizing the options. While the management of polio risk in the postcertification period presents important challenges, this comprehensive approach helps simplify the process by focusing on critical decisions.  相似文献   

18.
Models of small clutch sizes predict a number of invariant relationships between means and variances of measures of reproductive investment. However, empirical tests of the models have been lagging behind theoretical work. We tested the predictions using data on the mallee dragon, Ctenophorus fordi, a species where the basic assumptions of the models are likely to be fulfilled. Some, but not all, qualitative predictions of the models were shown to hold true, but the data fitted poorly to quantitative predictions. The patterns of deviation from theory may suggest the presence of a lower, and potentially an upper, limit on egg mass. We also argue that multiple and non-independent allocation decisions between total reproductive effort, growth and maintenance, and offspring size-number allocation could be important factors in the evolution of size-number strategies in lizards and thus need to be taken into account in theoretical models. The present study shows the potential to use small clutch size models to gain further insights into reproductive investment and allocation decisions in squamates.  相似文献   

19.
Selective Embryo Abortion Hypothesis Revisited - A Molecular Approach   总被引:1,自引:0,他引:1  
Abstract: Many plant species abort a large fraction of their embryos. It has often been suggested that embryos of genotypes that would perform worse later in life are preferentially aborted. Such selective embryo abortion would lead to investment of resources only in the offspring with the highest potential fitness. Many studies have shown that otherwise viable embryos are aborted. However, only few manipulative studies have indeed shown a correlation between the level of abortion and offspring quality and these studies have been challenged for their experimental design. Molecular techniques open new opportunities to study selective embryo abortion. Non-random abortion at the level of molecular markers can be observed as a deviation from Mendelian segregation: over- or under-representation of markers in the offspring. Subsequently, the over- or under-represented markers can be related to offspring quality later in life. We reviewed the literature on the genetic maps of intraspecific crosses of wild plant species and the selection of cultivated species. The level of non-Mendelian segregation we found in these maps is high. On average, 11.5 % of the tested markers in the genetic maps of wild species and 14.6 % in the cultivated ones, show a departure from Mendelian segregation. From six studies, providing sufficient data, it was calculated that in 68 % of loci segregating in non-Mendelian fashion post-fertilization selection is involved. We propose that the deviation from Mendelian segregation can be partly explained by selective embryo abortion. We describe an experimental design that allows for attributing selective embryo abortion to the non-Mendelian segregation that is found in a genetic map.  相似文献   

20.
Accurate data on dispersal ability are vital to the understanding of how species are affected by fragmented landscapes. However, three factors may limit the ability of field studies to detect a representative sample of dispersal events: (1) the number of individuals monitored, (2) the area over which the study is conducted and (3) the time over which the study is conducted. Using sub-sampling of mark-release-recapture data from a study on the endangered damselfly Coenagrion mercuriale (Charpentier), we show that maximum dispersal distance is strongly related to the number of recaptured individuals in the mark-release-recapture study and the length of time over which the study is conducted. Median dispersal distance is only related significantly to the length of the study. Spatial extent is not associated with either dispersal measure in our analysis. Previously consideration has been given to the spatial scale of dispersal experiments but we demonstrated conclusively that temporal scale and the number of marked individuals also have the potential to affect the measurement of dispersal. Based on quadratic relationships between the maximum dispersal distance, recapture number and length of study, we conclude that a previous study was of sufficient scale to characterise the dispersal kernel of C. mercuriale. Our method of analysis could be used to ensure that the results of mark-release-recapture studies are independent of levels of spatial and temporal investment. Improved confidence in dispersal estimates will enable better management decisions to be made for endangered species.  相似文献   

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