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The genus Acavus from Sri Lanka includes three species, Acavushaemastoma (Linnaeus), Acavus superbus (L. Pfeiffer) and Acavusphoenix (L. Pfeiffer) with two subspecies, Acavus phoenix phoenix(L. Pfeiffer) and Acavus phoenix castaneus new subspecies.The conchological and anatomical differences between these species,as well as their intraspecific variation are described. Theirdistribution is shown on maps and all locality records are listed.The presence of extensive intraspecific polymorphism, the developmentof geographical subspecies and the presumable hybridizationbetween some species show that the Acavus species are not isolatedrelict species, but that speciation is in progress and thatthe radiation of the Acavus species is probably much youngerthan the radiation of the acavid genera. The three Acavus speciesare not acutely endangered at present. In contrast to manyother land snails, there is no risk of a rapid decline of theAcavus species due to deforestation, because these species alsooccur in synanthropic habitats. (Received 22 December 1998; accepted 2 October 1999)  相似文献   

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In establishing National Bioethics Organisations (NBOs), liberal democracies seek to acknowledge the diversity of strongly held ethical positions and the imperative to engage in public debate about important bioethical decisions. NBOs are typically given a range of responsibilities, including contributing to and stimulating public debate; providing expert opinion on relevant issues for policy deliberations; and developing public policy. The state is now found to have an interest in areas previously thought to be a matter of individual choice. NBOs can provide one way of opening up public debate to allow the diversity of views to be heard in a manner that is well‐informed, articulate and responsive to both expert and ‘lay’ public views. We draw on debates in political theory about democratic decision‐making and on the policy making roles of some key NBOs. We are particularly interested in examining the capacity of NBOs to meet the democratic ideal of effective participation by the public, or citizenry, especially by those who are directly affected by the policies, in the development of effective public policy. We provide a basic framework for policy development involving NBOs that can begin to meet this ideal, a process of ‘contested deliberation’.  相似文献   

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Research ethics is the most developed aspect of bioethics in Africa. Most African countries have set up Institutional Review Boards (IRBs) to provide guidelines for research and to comply with international norms. However, bioethics has not been responsive to local needs and values in the rest of the continent. A new direction is needed in African bioethics. This new direction promotes the development of a locally‐grounded bioethics, shaped by a dynamic understanding of local cultures and informed by structural and institutional problems that impact the public's health, as well as cognisant of the salient contribution of social sciences and social epidemiology which can bring a lasting impact on African local communities. In today's post‐Structural Adjustment Africa, where healthcare has been liberalized and its cost increased, a bioethics agenda that focuses essentially on disease management and clinical work remains blind in the face of a structural marginalization of the masses of poor. Instead, the multidimensional public health crisis, with which most African countries are confronted, calls for a bioethics agenda that focuses primarily, but not exclusively, on health promotion and advocacy. Such an approach to bioethics reckons with the macro‐determinants of health and well‐being and places clinical and research ethics in the broader context of population's health. The same approach underscores the need to become political, not only by addressing health policymaking processes and procedures, but also by becoming an advocacy forum that includes other constituencies equipped with the potentialities to impact the population's health.  相似文献   

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JAMES DWYER 《Bioethics》2009,23(9):497-502
In this paper, I explore one way to bring bioethics and environmental ethics closer together. I focus on a question at the interface of health, sustainability, and justice: How well does a society promote health with the use of no more than a just share of environmental capacity? To address this question, I propose and discuss a mode of assessment that combines a measurement of population health, an estimate of environmental sustainability, and an assumption about what constitutes a fair or just share. This mode of assessment provides an estimate of the just and sustainable life expectancy of a population. It could be used to monitor how well a particular society promotes health within just environmental limits. It could also serve as a source of information that stakeholders use when they deliberate about programs, policies, and technologies. The purpose of this work is to focus attention on an ethical task: the need to fashion institutions and forms of life that promote health in ways that recognize the claims of sustainability and justice.  相似文献   

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描述了斯里兰卡步甲总科直角步甲属3新种:斯直角步甲O.srilankaicus sp.nov.,贝氏直角步甲O.batesi sp.nov.和卵形直角步甲O.ovatulus sp.nov.。股直角步甲O.femoralis Chaudoir为斯里兰卡新纪录种。  相似文献   

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The function of nuptial gifts has generated longstanding debate. Nuptial gifts consumed during ejaculate transfer may allow males to transfer more ejaculate than is optimal for females. However, gifts may simultaneously represent male investment in offspring. Evolutionary loss of nuptial gifts can help elucidate pressures driving their evolution. In most katydids (Orthoptera: Tettigoniidae), males transfer a spermatophore comprising two parts: the ejaculate‐containing ampulla and the spermatophylax—a gelatinous gift that females eat during ejaculate transfer. Many species, however, have reduced or no spermatophylaces and many have prolonged copulation. Across 44 katydid species, we tested whether spermatophylaces and prolonged copulation following spermatophore transfer are alternative adaptations to protect the ejaculate. We also tested whether prolonged copulation was associated with (i) male cercal adaptations, helping prevent female disengagement, and (ii) female resistance behavior. As predicted, prolonged copulation following (but not before) spermatophore transfer was associated with reduced nuptial gifts, differences in the functional morphology of male cerci, and behavioral resistance by females during copulation. Furthermore, longer copulation following spermatophore transfer was associated with larger ejaculates, across species with reduced nuptial gifts. Our results demonstrate that nuptial gifts and the use of grasping cerci to prolong ejaculate transfer are functionally equivalent.  相似文献   

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Correlative data are presented here on the developmental history, dynamics, histochemistry, and fine structure of intranuclear rodlets in chicken sympathetic neurons from in vivo material and long-term organized tissue cultures. The rodlets consist of bundles of ~70 ± 10 A proteinaceous filaments closely associated with ~0.4–0.8 µ spheroidal, granulofibrillar (gf) bodies of a related nature. These bodies are already present in the developing embryo a week or more in advance of the rodlets. In early formative stages rodlets consist of small clusters of aligned filaments contiguous with the gf-bodies. As neuronal differentiation progresses these filaments increase in number and become organized into well-ordered polyhedral arrays. Time-lapse cinemicrography reveals transient changes in rodlet contour associated with intrinsic factors, changes in form and position of the nucleolus with respect to the rodlet, and activity of the gf-bodies. With the electron microscope filaments may be seen extending between the nucleolus, gf-bodies, and rodlets; nucleoli display circumscribed regions with fine structural features and staining reactions reminiscent of those of gf-bodies, We suggest that the latter may be derivatives of the nucleolus and that the two may act together in the assemblage and functional dynamics of the rodlet. The egress of rodlet filaments into the cytoplasm raises the possibility that these might represent a source of the cell's filamentous constituents.  相似文献   

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Since its origin bioethics has been a specialized, academic discipline, focussing on moral issues, using a vast set of globalized principles and rational techniques to evaluate and guide healthcare practices. With the emergence of a plural society, the loss of faith in experts and authorities and the decline of overarching grand narratives and shared moralities, a new approach to bioethics is needed. This approach implies a shift from an external critique of practices towards embedded ethics and interactive practice improvement, and from a legal defence of rights towards fostering interdependent practices of responsibility. This article describes these transitions within bioethics in relation to the broader societal and cultural dynamics within Western societies, and traces the implications for the methodologies and changing roles of the bioethicist. The bioethicist we foresee is not just a clever expert but also a relationally sensitive person who engages stakeholders in reciprocal dialogues about their practice of responsibility and helps to integrate various sorts of knowledge (embodied, experiential, visual, and cognitive‐scientific). In order to illustrate this new approach, we present a case study. It concerns a project focusing on an innovation in elderly care, based on the participation of various stakeholders, especially older people themselves.  相似文献   

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Spherical, golden bodies, 0.5 to 25 μm in diameter, were noted in outer bundle sheath and mesophyll of cells of fresh sections of Spartina alterniflora leaves. Attempts to further characterize these structures with light and electron microscope (EM) techniques after dehydration failed initially because these bodies were soluble in organic solvents such as alcohol. Subsequently, it was found that certain heavy metals would stabilize the structure so that dehydration techniques could be used. The resultant stabilized bodies as viewed with EM were found to reside in the cell vacuole. Two major structural components were recognized: (1) a granular matrix and (2) a non-electron dense internal vesicle. Internal vesicles were not always present. No membranes were visible with this technique. These vacuolar bodies also were found to occur in parenchyma cells of roots, peduncles, glumes, and rhizomes of S. alterniflora. The material which forms the vacuolar body matrix is probably produced in the cytoplasm and gradually accumulates in the vacuole, forming larger and more numerous vacuolar bodies during the growing season. The matrix material remains in the leaf cells following their senescence.  相似文献   

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束丝藻(Aphanizomenon Morr. ex Born. et Flah)是我国水华蓝藻的重要种类, 由其产生的束丝藻水华已经引起了许多的环境问题。水华束丝藻、柔细束丝藻和依沙束丝藻是我国淡水水体常见的三种束丝藻种类,然而, 国内外对它们的生理学研究却相对较少。基此, 文章对水华束丝藻、柔细束丝藻和依沙束丝藻的形态特性、色素含量、生长及光合作用进行了比较研究, 结果表明丝状体的营养细胞、异形胞和厚壁孢子的长宽比具有一定的差异性, 揭示了厚壁孢子的长宽比可作为三种束丝藻分类的一个参数; 同时, 种间的差异性也体现在三种束丝藻的生理特性上, 相比水华束丝藻和依沙束丝藻, 柔细束丝藻的藻蓝素含量较高, 而叶绿素a、类胡萝卜素含量、最大光合作用(Pm)、表观光合作用效率(α)和最大电子传递速率(ETRmax)显著偏低。此外, 水华束丝藻和依沙束丝藻生理特性基本一致, 表明了形态不同的三种束丝藻在生理上可被分为两种类型, 暗示了依沙束丝藻可能具有像水华束丝藻一样形成水华的生理潜能且由于它的产毒性所以应该倍加关注    相似文献   

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THE DEVELOPMENT OF BASAL BODIES AND FLAGELLA IN ALLOMYCES ARBUSCULUS   总被引:3,自引:26,他引:3       下载免费PDF全文
The development of basal bodies and flagella in the water mold Allomyces arbusculus has been studied with the electron microscope. A small pre-existing centriole, about 160 mµ in length, was found in an inpocketing of the nuclear membrane in the vegetative hypha. Thus, formation of a basal body does not occur de novo. When the hyphal tip started to differentiate into gametangia, the centrioles were found to exist in pairs. One of the members of the pair then grew distally to more than three times its original length, whereas the other remained the same size. The larger centriole would correspond to the basal body of a future gamete. Gametogenesis was usually induced by transferring a "ripe" culture to distilled water. Shortly after this was done, a few vesicles were pinched off from the cell membrane of the gametangium and came in contact with the basal body. Apparently, they fused and formed a large primary vesicle. The flagellum then started to grow by invaginating into it. Flagellar fibers were evident from the very beginning. As the flagellum grew so did the vesicle by fusion with secondary vesicles, thus coming to form the flagellar sheath. The different stages of flagellar morphogenesis are described and the possible interrelationships with other processes are discussed.  相似文献   

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