ISSN:1059-910X    

DOI:10.1002/jemt.1070220102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe apical extracellular matrix of the sea urchin embryo, known as the hyaline layer (HL), is a multi‐laminate organelle composed of at least 10 polypeptides. Although integrated into one ECM, HL proteins exhibit individual temporal and spatial dynamics throughout development. These molecules are stockpiled in the oocyte during vitellogenesis in at least four distinct vesicle populations. They are released onto the cell surface at fertilization in a specific order, and interact differentially with embryonic cells as development proceeds. Many experiments have suggested that the HL is vital for embryogenesis, but relatively little is known about the functions and interactions of its constituent molecules. The purpose of the present review has been to gather information on the basic characteristics of the known HL proteins together with data on their expression in the embryo, and where possible, their biological activities. Compiled, these observations may provide some insight into the workings of a uniquely embryonic organelle. © 1992 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070220103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractSeveral methods were utilized to visualize the structure and orientation of the blastocoelic extracellular matrix (ECM) inStrongylocentrotus purpuratusembryos at the mesenchyme blastula stage. Rapid freezing in liquid propane cooled to LN2temperatures followed by freeze substitution was used to preserve the ECM without shrinkage due to dehydration. Scanning, transmission, and light microscopy were employed to elucidate the ECMs' structure. The blastocoelic ECM consisted of parallel fibrillar sheets that were interconnected by finer filaments and oriented along the animal‐vegetal axis. The ECM completely filled the blastocoelic cavity as viewed by scanning electron microscopy. The basal lamina could be distinguished from the blastocoelic ECM as a thin coat on the plasma membrane of epithelial cells; the ECM was in contact with this coat. In contrast, the blastocoelic ECM attached directly to the plasma membrane of primary mesenchyme cells (PMC) which did not possess a basal lamina. The blastocoelic ECM was isolated as an intact “bag” and probed in a hydrated state with Con A and alcian blue. Confocal microscopy confirmed that the entire blastocoel was filled with a fibrillar ECM. These approaches offer advantages for future studies of the ECMs of sea urchin embryos and their roles in gastrulation. © 1992 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070220104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractOocytes, eggs, and embryos from a diverse array of species have evolved cytoskeletal specializations which allow them to meet the needs of early embryogenesis. While each species studied possesses one or more specializations which are unique, several cytoskeletal features are widely conserved across different animal phyla. These features include highly‐developed cortical cytoskeletal domains associated with developmental information, microtubule‐mediated pronuclear transport, and rapid intracellular signal‐regulated control of cytoskeletal organization. © 1992 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070220105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractInsect eggs are giant and very complex cells covered by an extremely resistant shell. Both the egg cell and surrounding eggshell express anteroposterior and ventrodorsal polarity. The molecular and cytoplasmic organization of both axes originates during oogenesis and leads to the production of an ooplasmic system which consists of euplasm and deutoplasm (yolk) and contains a nucleus as well as extranuclear determinants of maternal origin. Both are part of the store of information for early embryogenesis. In addition, the deutoplasm serves as raw material and early nutrient supply for building the embryo. The insect egg cell, which is arrested in the first maturation division when released from the ovary during oviposition, will be activated by different stimuli among different species to complete meiosis and start embryogenesis. The zygote nucleus undergoes a number of synchronous mitotic divisions leading to cleavage energids which initially form a syncytial blastoderm and subsequently the cellular blastoderm. In many insects, prior to blastoderm formation, polar granules (or oosome material) are incorporated in a single cell or a small number of cells which bud off at the posterior pole. These so called pole cells give rise to the primordial germ cells. Therefore, polar granules or the oosome material mark the germ line, and while structural counterparts of determinants of body pattern formation have so far not been found, the polar granules or oosome serve as an autonomous ooplasmic determinant for the pole or germ cells. Anteroposterior body polarity can arise independent of the germ plasm. © 1992 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070220106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractCell lineage specification in molluscs is brought about by two mechanisms: the segregation of morphogenetic plasms and inductive cell interactions. The evidence for the existence of morphogenetic plasms is largely circumstantial, but in one species,Bithynia, such a plasm has been identified in the polar lobe that forms at first cleavage. Inductive cell interactions are thought to be a prerequisite for the development of a large number of tissues and organs. The most extensively studied example is the specification of the mesodermal stem cell inLymnaeaandPatella, which occurs between 5th and 6th cleavage through an interaction between one macromere and a large number of micromeres.Both segregation and induction are tuned to the animal‐vegetal polarity of the egg, at least during early development. This polarity probably arises during oogenesis and is manifest in regional differentiations of the surface architecture of the egg, in the distribution of inner membrane particles in the plasma membrane, in membrane fluidity characteristics, in ionic conductance properties of the plasma membrane, etc. All these phenomena have in common that they represent properties of the egg surface, suggesting that the polarity of the egg is somehow imprinted into the plasma membrane and the cortex of the egg during oogenesis. © 1992 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070220107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractUltrastructural studies have contributed significantly to our understanding of cell lineage differentiation in the mammalian pre‐implantation embryo. Such studies have documented, and continue to document, morphological, biochemical, and physiological characteristics of the cell lineages established during the pre‐implantation period in eutherian embryos, principally that of the mouse. This review evaluates these contributions and identifies areas of study in which ultrastructural analysis is most likely to have an important role in the future. © 1992 Wiley‐Lis

ISSN:1059-910X    

DOI:10.1002/jemt.1070220108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:1059-910X    

DOI:10.1002/jemt.1070220109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:1059-910X    

DOI:10.1002/jemt.1070220101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY