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Topic: Embryonic cleavage

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	Embryogenesis - Wikipedia, the free encyclopedia
		Holoblastic cleavage occurs in animals with little yolk in their eggs, such as humans and other mammals who receive nourishment as embryos from the mother via placenta or milk.
		Cleavage thus creates a very uneven distribution of cells concentrating at the animal pole of the zygote.
		In holoblastic eggs the first cleavage always occurs along the vegetal-animal axis of the egg, the second cleavage is perpendicular to the first.
	en.wikipedia.org /wiki/Embryonic_development (616 words)

	ScienceWeek
		When viewed from the embryonic pole, the inner cell mass does not form a perfectly round shape, but acquires an oblong one with a short and a long diameter; the latter defines an axis of bilateral symmetry that is orthogonal to the embryonic-abembryonic axis.
		Gardner, R.L. The early blastocyst is bilaterally symmetrical and its axis of symmetry is aligned with the animal-vegetal axis of the zygote in the mouse.
		Smith, L.J. Embryonic axis orientation in the mouse and its correlation with blastocyst relationships to the uterus.
	scienceweek.com /2004/sb040528-4.htm (1670 words)

	Cleavage
		There are two major consequences of cleavage: production of a multicellular organism from a single-celled zygote and acquisition by individual cells or groups of cells of differences that will facilitate their later development into different cell types.
		Thus, blastomere volume is decreased during cleavage to produce the small, individual cellular units that participate in the subsequent morphogenic events that mold the embryo.
		Cleavage also increases the number of nuclei, which amplifies the number of templates that will facilitate the later production of specialized proteins needed for formation of a functional organism.
	www.ucalgary.ca /UofC/eduweb/virtualembryo/cleavage.html (595 words)

	The Anatomy of the Embryonic Disc
		The embryonic disc is the mass of cells that sits on the surface of the yolk and gives rise to the chick and its extra-embryonic membranes.
		The embryonic disc is also called the blastoderm, the blastodisc, the disc of blastomeres or, at later stages, the blastula.
		cleavage is incomplete (meroblastic) and is restricted to the small portion of yolk-free cytoplasm called the germinal disc.
	www.uoguelph.ca /zoology/devobio/210labs/embryodisc1.html (493 words)

	Morula - Wikipedia, the free encyclopedia
		A morula (Latin "morus", mulberry) is an embryo at an early stage of embryonic development, consisting of approximately 12-32 cells (called blastomeres).
		The morula is produced by embryonic cleavage, the rapid cell division of the zygote.
		The morula is a solid ball of cells; the inner blastomeres are called the "inner cell mass" and the blastomeres on the surface are called the "outer cell mass." The blastomeres change their shape and tightly align themselves against each other to form a compact ball of cells.
	en.wikipedia.org /wiki/Morula (172 words)

	Morula
		Morula is a stage of embryonic development in animals, including the 16-cell phase, the 32-cell phase, and the 64-cell phase.
		The morula is produced by embryonic cleavage[?], the rapid cell division of the zygote with virtually no growth.
		The morula is a solid ball; after the 64-cell phase, it develops into a hollow ball, the blastula.
	www.ebroadcast.com.au /lookup/encyclopedia/mo/Morula.html (56 words)

	The Development-associated Cleavage of Lens Connexin 45.6 by Caspase-3-like Protease Is Regulated by Casein Kinase ...
		A, in vitro cleavage of Cx45.6 by calpain.
		Embryonic lens membranes were incubated with and without caspase-3 for 2 (lanes 1 and 2) and 16 h (lanes 3 and 4) and compared with Cx45.6 in newborn chick lens membranes (lane 5).
		Phosphorylation of Cx45.6 by CKII inhibited its cleavage by caspase-3.
	www.jbc.org /cgi/content/full/276/37/34567 (4816 words)

	Embryonic Development: Getting Started
		The activities of cleavage are controlled by the mother's genome; that is, by mRNAs and proteins she deposited in the unfertilized egg.
		Like other protostomes, cleavage of the zygote produces daughter cells that are already committed to their fate.
		As cleavage continued, the mRNAs moved from the centrosome to a spot on the inner surface of the plasma membrane.
	home.comcast.net /~john.kimball1/BiologyPages/E/EmbryonicDevelopment.html (1807 words)

	NOVA \| scienceNOW \| Stem Cells: Ask the Expert \| PBS
		Embryonic stem cells develop that carry all the mutations in the DNA that causes the Alzheimer's disease.
		If one now wants to differentiate the human embryonic stem cells, all one has to do is to change the culture conditions by withdrawing the molecules that maintain the human embryonic stem cells in an undifferentiated state, and add in some other molecules, depending on what cell type one wants to obtain.
		Embryonic stem cells are derived from embryos during the blastocyst stage.
	www.pbs.org /wgbh/nova/sciencenow/3209/04-ask.html (3943 words)

	Revista Brasileira de Zoologia - Embryonic development of four species of palaemonid prawns (Crustacea, Decapoda): ... (Site not responding. Last check: 2007-09-30)
		The aim of this study was to characterize the embryonic development of four brackish and freshwater palaemonid species, and to establish a relationship between the appearance of the embryonic structures and the total development time.
		The cleavage process observed in stage II indicates that development follows a holoblastic pattern, since cleavage furrows can be seen in the surface of the whole egg, individualizing the blastomeres.
		Cleavage and gastrulation in the shrimp Sicyonia ingentis: invagination is accompanied by oriented cell division.
	www.scielo.br /scielo.php?pid=S0101-81752004000100005&script=sci_arttext&tlng=en (2893 words)

	Animal Developmental Biology
		Typically, the pattern of cleavage is significantly impacted upon by the amount and distribution of yolk.
		That is, embryonic cells typically may become more specialized, but similarly typically more specialized (differentiated) cells are not well equipped to become less specialized.
		Embryonic development basically takes the basically rudimentary organism found at the end of pre-embryonic development, and produces and a recognizable organism complete with all of its developing organ sytem.
	www.mansfield.ohio-state.edu /~sabedon/biol1130.htm (1894 words)

	Physiology of Metazoa - Developmental biology (Site not responding. Last check: 2007-09-30)
		However, it is not known whether the embryonic—abembryonic axis is set up by the first cleavage itself, by polarity in the oocyte that then sets the first cleavage plane with respect to the animal pole, or indeed whether it can be divorced entirely from the first cleavage and established in relation to the animal pole.
		The importance of the orientation of the first cleavage was tested by imposing an elongated shape on the zygote so that the division no longer passes close to the animal pole, marked by the second polar body.
		Seessel's pouch : a transient outpouching of the embryonic pharynx rostrad of the oropharyngeal membrane and caudal to Rathke's pouch.
	focosi.altervista.org /development.htm (12198 words)

	ScienceWeek
		Evidence suggests that the cleavage pattern of normal development may be involved in specifying the future embryonic axis, but how and when this pattern becomes established is unclear.
		In animals, "epithelial cells" compose the cell layers that form the interface between a tissue and the external environment, for example, the cells of the skin, the lining of the intestinal tract, the lung airway passages, and the lining of various ducts.
		In general, all embryonic organs consist of an epithelium and an associated mesenchyme, and epithelial-mesenchyme interactions are apparently of great importance in development.
	scienceweek.com /2001/sw010309.htm (14185 words)

	System and sequential culture media for in vitro fertilization patent invention (Site not responding. Last check: 2007-09-30)
		The cleavage stage embryo must then undergo further development in a non-homologous environment to reach the blastocyst stage, in which the embryo has trophectoderm cells capable of implanting in the uterine lining.
		The zygote and cleavage stage embryo (up to the eight-cell stage) are characterized by low levels of biosynthesis, low respiratory rates, only limited ability to metabolize glucose, and a capacity to utilize pyruvate.
		Cleavage stage embryos, like the oocyte, are susceptible to loss of amino acids through their cell membranes when surrounded by an environment having a low concentration of such factors.
	www.freshpatents.com /System-and-sequential-culture-media-for-in-vitro-fertilization-dt20051124ptan20050262581.php (3455 words)

	AMA (CSAPH) Report 7 of the Council on Scientific Affairs (A-99) Full Text
		In human subjects, scientists have succeeded in increasing the number of pre-implantation embryos produced per oocyte in preparation for in vitro fertilization in cases where oocyte availability is a limiting factor.
		It is, therefore, not surprising that the first successfully cloned mammalian farm animal (a sheep) was derived from a cell of the inner cell mass of an embryo.
		A simpler way of producing matched tissues and organs would be to use a clone at its early embryonic stages as a source of cells.
	www.ama-assn.org /ama/pub/category/13564.html (7347 words)

	[No title]
		Cleavage beyond the eightcell stage was obtained in the parthenogeneticactivated eggs, and blastocoele cav ities were observed in six.
		protocol for parthenogenetic activation of human eggs, embryonic cleavage, and the formation of a blasto coele cavity.
		Rather, the goal is to derive pri mordial stem cells in vitro, such as embryonic stem cells from the inner cell masses of blastocysts as a source of cells for regenerative therapy (3).
	earthops.org /human-clones1.txt (2783 words)

	Fetal Development Presentation
		Early in the embryonic phase, the cells of the embryo begin to differentiate into three layers of cells; the endoderm and the ectoderm form first, and the mesoderm forms in between shortly thereafter.
		In the third week of embryonic development, a slight depression, the primitive groove, forms on the ectodermal surface of the embryonic disk.
		In the fourth week of development, the flat disk becomes cylindrical in structure-as the human body is cylindrical, with the skin on the outside, skeletal muscles in the middle, and the gastrointestinal tract in the center (Hole, 1994).
	www.uky.edu /Classes/PHI/305.002/fd.htm (4208 words)

	Polarity of the mouse embryo is established at blastocyst and is not prepatterned -- Motosugi et al. 19 (9): 1081 -- ...
		Davies, T.J. and Gardner, R.L. The plane of first cleavage is not related to the distribution of sperm components in the mouse.
		The early blastocyst is bilaterally symmetrical and its axis of symmetry is aligned with the animal–vegetal axis of the zygote in the mouse.
		Hiiragi, T. and Solter, D. First cleavage plane of the mouse egg is not predetermined but defined by the topology of the two apposing pronuclei.
	www.genesdev.org /cgi/content/full/19/9/1081 (6606 words)

	Grzimeks Animal Life Encyclopedia
		Cleavage pattern refers to the process of cell division from one fertilized cell, the zygote, into hundreds of cells, the embryo.
		Radial cleavage is also known as indeterminate cleavage, because the fate of the cells is not fixed early in development.
		The eggs of amphibians lack a shell and the embryonic membranes (e.g., amnion, allantois, and chorion) of reptiles, birds, and mammals.
	www.wordtrade.com /science/lifescience/grzimeksanimallifeencyclopedi.htm (16285 words)

	Rab-protein 11 (Site not responding. Last check: 2007-09-30)
		Embryonic cleavage leads to the formation of an epithelial layer during development.
		Although the processes are different, the columnerization of flat squamous epithelial cells and embryonic cleavage are both accompanied by the growth of a basal lateral membrane domain.
		Drosophila cellularization, a specialized form of embryonic cleavage, is a very good system for addressing this problem, although the process may in part rely on specific mechanisms that may not apply to other cases of epithelial morphogenesis.
	www.sdbonline.org /fly/torstoll/rab11-4.htm (8212 words)

	CSIRO PUBLISHING - Reproduction, Fertility and Development
		Higher cleavage rates were observed in infertile females as well as numbers of TE per session.
		Embryonic development rates were mainly influenced by donor breed and parity.
		To conclude, cleavage and development rates were mainly influenced by donor characteristics (breed, parity, physiological status).
	www.publish.csiro.au /view/journals/dsp_journal_fulltext.cfm?nid=44&f=RDv18n2Ab285 (415 words)

	NEST: Nonsurgical Embryonic Selective Thinning and Transfer - The National Fertility Directory
		It is a technique for the active management of early embryonic growth and development.
		The combination of embryonic thinning and selective transfer results in an increase in implantation rates, cycle fecundity rates, and overall pregnancy rates.
		Selective thinning can be performed on the 2nd day of embryonic culture, or even on the 3rd day, if assisted hatching is not clinically indicated.
	www.fertilitydirectory.org /what-is-nest.html (300 words)

	eMedicine - Holoprosencephaly : Article by David H Tegay, DO, FACMG
		This variant denotes incomplete cleavage of the posterior frontal and parietal lobes, with varying degrees of incomplete cleavage of the basal ganglia and thalami and an absent body of the corpus callosum.
		Semilobar holoprosencephaly is detected by identifying the partial cleavage of the occipital horns and the presence of a posterior falx and a posterior portion of the corpus callosum.
		Sonograms of the middle interhemispheric fusion variant demonstrate normal cleavage anteriorly and posteriorly, with fusion of the hemispheres and absence of body of the corpus callosum in the posterior, frontal and parietal region.
	www.emedicine.com /RADIO/topic347.htm (3579 words)

	Grace Wyngaard Research Page
		Classic model of embryonic chromatin diminution using the example of Diacyclops navus.
		embryonic cleavage division DNA is excised from the presomatic line, resulting in dramatically reduced somatic nuclear DNA contents and a reorganized somatic genome.
		Analysis of DNA levels during gonomery in early cleavage divisions of the freshwater copepod Mesocyclops edax.Microscopy and Microanalysis 3, Suppl.
	csm.jmu.edu /biology/wyngaaga/research.html (494 words)

	Advanced Cell Technology Clones Human Embryos
		Cleavage beyond the eight-cell stage was obtained in the parthenogenetic-activated eggs, and blastocoele cavities were observed in six.
		Ultimately, the nucleus of the donor somatic cell must render itself to be reprogrammed by the egg, which in turn must be capable to induce all the epigenetic changes to down-regulate somatic genes and up-regulate embryonic ones.
		Rather, the goal is to derive primordial stem cells in vitro, such as embryonic stem cells from the inner cell masses of blastocysts as a source of cells for regenerative therapy (3).
	earthops.org /cloning/human-clones1.html (2702 words)

	World Aquaculture Society abstract data (Site not responding. Last check: 2007-09-30)
		Morphometric parameters, e.g., delayed cleavage and embryonic developments were monitored to establish indicators of polyploidy induction.
		On numerous occasions heat shock inductions prior to the first cleavage resulted in tetraploid and polyploid embryos and nauplii.
		Control samples yielded normal number (2n=88) of chromosomes in their embryonic cells while the treated batch yielded mosaic of cells containing 2n, 3n and 4n chromosomes.
	www.was.org /meetings/AbstractData.asp?AbstractId=7857 (400 words)

	Andrology - Advanced Institute of Fertility Andrology Lab
		Still, even if fertilization and initial embryonic cleavage proceed normally, the embryo must continue to develop normally.
		The formulation of new laboratory media-the liquid in which the embryos are grown in vitro--has made it possible to safely grow embryos in vitro beyond the typical 2-3 day stage of development.
		A blastocyst is the final stage of embryonic development before it hatches out of its shell, or zona pellucida, and implants in the uterine wall.
	aiof.com /html/blastocyst.htm (679 words)

	Zebrafish mitotic kinesin-like protein 1 (Mklp1) functions in embryonic cytokinesis -- Chen et al. 8 (1): 51 -- ...
		Hauptmann G and Gerster T. Pou-2: a zebrafish gene active during cleavage stages and in the early hindbrain.
		Cleavage of structural proteins during the assembly of the head of bacteriophage T4.
		Establishment of cleavage furrows by the mitotic spindle.
	physiolgenomics.physiology.org /cgi/content/full/8/1/51 (7283 words)

	Oral &&38; Poster Presentations (Site not responding. Last check: 2007-09-30)
		This study was conducted to determine the role of active management of embryonic growth and development utilizing newly defined growth media for embryo culture and selective thinning.
		Conclusion: Nonsurgical embryonic selective thinning and transfer is a technique for the active management of early embryonic growth and development.
		It utilizes newly defined growth media which facilitates embryonic cleavage so that selective thinning and transfer can be performed on the third day post ovum pickup when genetic competence may be more easily assessed on morphologic grounds.
	www.fertilitydocs.com /abstracts/fert02.html (647 words)

	Cleavage in Sea Urhcins - Intro (Site not responding. Last check: 2007-09-30)
		Sea urchins undergo radial cleavage, as do "typical" deuterstomes, such as chordates, ascidians, and other echinoderms.
		Like embryonic cleavages in other organisms, sea urchin cleavage divisions are reductive, i.e., the cleavages result in more cells, but without an increase in the total cellular volume of the embryo.
		The next few pages provide representative pictures of cleavage stage embryos, and discuss the mechanisms and consequences of cleavage in sea urchin embryos.
	worms.zoology.wisc.edu /urchins/SUcleavage_intro.html (79 words)

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