285 resultados para Embryology


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Event report following a multidisciplinary workshop at the Economic and Social Research Council's Genomics Policy and Research Forum, which took place at the University of Edinburgh on 20 January 2011.

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This paper provides an overview of the regulatory developments in the UK which impact on the use of in vitro fertilization (IVF) and embryo screening techniques for the creation of “saviour siblings.” Prior to the changes implemented under the Human Fertilisation and Embryology Act 2008, this specific use of IVF was not addressed by the legislative framework and regulated only by way of policy issued by the Human Fertilisation and Embryology Authority (HFEA). Following the implementation of the statutory reforms, a number of restrictive conditions are now imposed on the face of the legislation. This paper considers whether there is any justification for restricting access to IVF and pre-implantation tissue typing for the creation of “saviour siblings.” The analysis is undertaken by examining the normative factors that have guided the development of the UK regulatory approach prior to the 2008 legislative reforms. The approach adopted in relation to the “saviour sibling” issue is compared to more general HFEA policy, which has prioritized the notion of reproductive choice and determined that restrictions on access are only justified on the basis of harm considerations.

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Section 14(4) of the Human Fertilisation and Embryology Act 2008 imposes – within the general licensing conditions listed in the Human Fertilisation and Embryology Act 1990 – a prohibition to prevent the selection and implantation of embryos for the purpose of creating a child who will be born with a “serious disability.” This article offers a perspective that demonstrates the problematic nature of the consultation, review, and legislative reform process surrounding s 14(4). The term “serious disability” is not defined within the legislation, but we highlight the fact that s 14(4) was passed with the case of selecting deaf children in mind. We consider some of the literature on the topic of disability and deafness, which, we think, casts some doubt on the view that deafness is a “serious disability.” The main position we advance is that the lack of serious engagement with alternative viewpoints during the legislative process was unsatisfactory. We argue that the contested nature of deafness necessitates a more robust consultation process and a clearer explanation and defence of the normative position that underpins s 14(4).

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This editorial first describes the workshop out of which the present special issue arose. The editors then identify the need for a multidisciplinary collection examining the Human Fertilisation and Embryology Act 2008 from both legal and political perspectives, including the consultation process, campaigning and parliamentary debates leading to its passage, and the concluded legislation and its effects. The editorial provides an overview of the legislative reform process, key legislative changes, and the various contributions to the special issue. Cross-cutting themes include the value of a qualitative, discourse-based approach to research in this area; the need to understand the 2008 Act in historical context; unforeseen practical implications of the legislative provisions; and silences and missed opportunities in the legislation. Finally, a postscript covers the changing landscape of hybrid embryo research since the passage of the Act, and the uncertain future of the Human Fertilisation and Embryology Authority at the time of writing.

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This paper reports the mega-, micro-sporogenesis and female-, male-gametogenesis of Swertia cincta for the first time, with the aim of discussing the systematic position of section Platynema and section Ophelia of Swertia. Anthers are tetrasporangiate. The development of anther walls conforms to the dicotyledonous type. The tapetum cells have dual origin and are similar to the glandular type. There are two middle layers. The endothecium and epidermis persist. Cytokinesis in the microsporrocyte meiosis is simultaneous type and the microscpore teads are tetrahedral. Pollen grains are 3-celled. The ovary is bicarpellum and unilocular. The placentation is of suparietal placentation with 12 series of ovules. The ovules. The ovule is unitegmic, tenuinucellar and ana-campylotropous, The embryo sac orignates from the single-archesporial cell. The one chalazal megaspore in lienar tetrad become the functional megasore. The development of embryo sac is of the polygonum type. Before fertilization, two polar nuclei fuse into one secondary nucleus. Three antipodal cells persisted and divided into 5-8 cells. A comparison between two sections indicates that section Plathnema is better treated as distinct section and is more advanced than section Ophelia according to the evolutionary trends of embryological characters.

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The embryological features of three species of Swertia (s.l.) - S. erythrosticta, S. franchetiana, and S. tetraptera were characterized, and the observations were used, together with previously gathered data on other species, to evaluate a recently proposed polyphyly, based on molecular data, of Swertia s.l. Comparisons of species within the genus showed that they have diversified embryologically, and there are significant between-species differences. Notable features that vary between species include the number of cell layers that form the anther locule wall, the construction of the wall of the mature anther, tapetum origin, the cell number in mature pollen grains, the structure of the fused margins of the two carpels, the ovule numbers in placental cross-sections, the shape of the mature embryo sac, the degree of ovule curvature, antipodal variation and the presence of a hypostase, and seed appendages. They share characters that are widely distributed in the tribe Gentianeae, such as a dicotyledonous type of anther wall formation, a glandular tapetum with uninucleate cells, simultaneous cytokinesis following the meiosis of the microsporocytes, tetrahedral microspore tetrads, superior, bicarpellary and unilocular ovaries, unitegmic and tenuinucellar ovules, Polygonum-type megagametophytes, progamous fertilization, nuclear endosperm, and Solanad-type embryogeny. The presence of variation in embryological characters amongst the species of Swertia s.l. strongly supports the view that Swertia s.l. is not a monophyletic group. Frasera is better separated from Swertia s.l. as an independent genus, and is only distantly related to Swertia s. s. judging from the numerous differences in embryology. Swertia tetraptera is very closely related to Halenia, as they show identical embryology. (C) 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 383-400.

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The embryological characters of Crawfurdia delavayi Frabnch. are described and the systematic relationships of Crawfurdia discussed. Anthers are tetrasporangiate. The development of anther walls conforms to the Dicotyledonous type. The tapetum is of single origin. The development of the tapetum with uninucleate cells is of the glandular type. The tapetal cells on the connective side show radial elongation or periclinal division and intrude into the anther locule. The epidermis of anther walls persists and its cells become pillar and fibrous, and the endothecium degenerates. The ovary is bicarpellary and unilocular. The placentation is typically parietal with 8 rows of anatropous ovules. The development of embryo sac is of the polygonum type. Before fertilization, two polar nuclei fuse into a secondary nucleus. Three antipodal cells persist. Flowers are protandrous. Fertilization is porogamous. The development of the endosperm is of the nuclear type. The embryogeny corresponds to the solanad type physalis II variation. The embryological data indicate that it is better to separate Crawfurdia from Gentiana as an independent genus.

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