Search results for "Embryogenesis"
showing 10 items of 187 documents
Piwi Proteins and piRNAs in Mammalian Oocytes and Early Embryos
2015
SummaryGerm cells of most animals critically depend on piRNAs and Piwi proteins. Surprisingly, piRNAs in mouse oocytes are relatively rare and dispensable. We present compelling evidence for strong Piwi and piRNA expression in oocytes of other mammals. Human fetal oocytes express PIWIL2 and transposon-enriched piRNAs. Oocytes in adult human ovary express PIWIL1 and PIWIL2, whereas those in bovine ovary only express PIWIL1. In human, macaque, and bovine ovaries, we find piRNAs that resemble testis-borne pachytene piRNAs. Isolated bovine follicular oocytes were shown to contain abundant, relatively short piRNAs that preferentially target transposable elements. Using label-free quantitative pr…
Structure and function of prothoracic glands and oenocytes in embryos and last larval instars of Oncopeltus fasciatus Dallas (Insecta, Heteroptera).
1976
1. Active prothoracic glands and oenocytes of last larval stage are both characteristized by well-developed smooth and rough endoplasmic reticulum (ER). Prothoracic glands also show plasma membrane infoldings, but not oenocytes which contain a large number of pleomorphic vesicles. 2. The fine structure of embryonic oenocytes corresponds after blastokinesis with that of active larval and adult cells. Thus, an activity in the late embryo can be assumed. Embryonic prothoracic glands reveal no signs of activity: smooth and rough ER are absent. The subcellular structure resembles that of organ anlagen, i.e. not yet fully differentiated tissue. Hormone synthesis is not likely. 3. Ecdysone titer w…
The impact of ovarian stimulation on the expression of candidate reprogramming genes in mouse preimplantation embryos.
2012
Ovarian stimulation with gonadotrophins is an integral part of assisted reproductive technologies in human subfertility/infertility treatment. Recent findings have associated ovarian stimulation with the increased incidence of imprinting disorders in humans as well as defects in genome-wide methylation reprogramming and, in particular, imprinting in mice. Here, we present the first study that determined the impact of ovarian stimulation on the expression of developmentally important reprogramming genes <i>(Apex1, Lig1, Lig3, Mbd2, Mbd3, Mbd4, </i>and<i> Polb)</i> in single early mouse morula embryos (16-cell stage). Using absolute quantification of mRNA by quantitati…
FIRST STAGES OF MICROSPORE REPROGRAMMING TO EMBRYOGENESIS THROUGH ISOLATED MICROSPORE CULTURE IN LOQUAT
2011
The current experiments were undertaken to develop a method for regenerating doubled haploid (DH) plants of Eriobotrya japonica (Thunb.), Rosaceae, subfamily Maloideae through isolated microspore culture of nine loquat cultivars. Protocols were developed for isolation and culture of loquat microspores. Isolated microspores in vitro cultured started dividing and developing multicellular, globular and irregular structures. After 4 weeks of culture, the responding microspores produced yellowish/white callus. The embryogenic response of microspores was highly dependent on the cultivar and on the medium composition.
Holm Oak Quercus ilex L.
2018
The holm oak is an evergreen tree species representative of Mediterranean forests. The largest populations of this species are in the Iberian Peninsula, forming the tree cover of an agro-silvo-pastoral system called “dehesa” in Spain and “montado” in Portugal. The high ecological and economic value of the species is of interest for rural development. The main current product are the acorns used for feeding Iberian black pigs, which are the basis of an important gastronomic industry. In addition, several bioactive compounds with new potential industrial applications in nutrition, pharmacology and cosmetics have been identified in acorns of oak species. Plantations with holm oak seedlings myc…
On the Establishment of Polarity in Polychaete Eggs
1990
The study of Spiralian development began about a hundred years ago when Whitman (1878) published a description of the development of the leech, Clepsine marginata. Subsequently, Spiralian development became popular because the developmental fate of each individual blastomere can be determined precisely from the cell lineage. About the turn of the century several extensive papers describing the cell lineages of various molluscs (e.g. Blochmann, 1881, 1883; Kofoid, 1895; Conklin, 1897; Wierzejski 1905) and annelids (e.g. Wilson, 1892; Mead, 1897; Woltereck, 1904) appeared. From these studies it became clear that the general principles of mollusc and annelid development (and to a much lesser d…
Ultrastructure of differentiating hemocytes in the embryo of Oncopeltus fasciatus dallas (insecta, heteroptera).
1978
The hemocytes of Oncopeltus differentiate rather early during embryogenesis. They are segregated by the mesoderm soon after its formation (about 50h after egg deposition). Newly segregated hemocytes show the “typical” features of “embryonic” cells: many free ribosomes, a few strands of rough ER, the cisternae of which are considerably distended, electron lucent vacuoles around the periphery, and glycogen deposits. A few hours thereafter the hemocytes undergo striking subcellular changes. First, glycogen, electron lucent vacuoles and rough ER disappear and phagocytotic activity can be observed. Golgi complexes become well expressed and give rise to electron dense vesicles which fuse to large…
Quantitative analysis of cellular differentiation during early embryogenesis ofPlatynereis dumerilii.
1990
As in many spiralian embryos with unequal cleavage, cleavage inPlatynereis follows an invariant pattern. Preceding each cleavage the cytoplasm is reorganized, allowing the spiral cleavage mode to produce cells with different cytoplasmic composition. The fertilized egg undergoes a dramatic ooplasmic segregation after the completion of the cortical reaction. As a consequence, a plug of clear cytoplasm becomes located at the animal pole. Once the four quadrants of the embryo have been established, the cleavage sequence of the D quadrant differs clearly from that of the other three quadrants. The results presented here suggest that differential distribution of the clear cytoplasm governs this s…
Early embryo achievement through isolated microspore culture in citrus clementina hort. Ex tan., cvs. 'Monreal Rosso' and 'nules'
2015
10 p.-5 fig.-3 tab.
Expression of en and wg in the embryonic head and brain of Drosophila indicates a refolded band of seven segment remnants
1992
ABSTRACT Based on the expression pattern of the segment polarity genes engrailed and wingless during the embryonic development of the larval head, we found evidence that the head of Drosophila consists of remnants of seven segments (4 pregnathal and 3 gnathal) all of which contribute cells to neuromeres in the central nervous system. Until completion of germ band retraction, the four pregnathal segment remnants and their corresponding neuromeres become arranged in an S-shape. We discuss published evidence for seven head segments and morphogenetic movements during head formation in various insects (and crustaceans).