... cleavage patterns. Data from the mouse suggest that cellular morphogenesis and molecular signaling at the cleavage stage play important roles in lineage specification at later (blastula and gastrula) stages. Very little is known, however, about cleavage-stage chick embryos, owing to their poor...

...Karolina Piotrowska; Magdalena Zernicka-Goetz The first cleavage of the fertilised mouse egg divides the zygote into two cells that have a tendency to follow distinguishable fates. One divides first and contributes its progeny predominantly to the embryonic part of the blastocyst, while the other...

... of constituents ( Dalcq, 1957 ; Mulnard, 1965 ) (reviewed by Denker, 1983 ). They proposed that such constituents were partitioned to different blastomeres by cleavage divisions as in other model systems with visible constituents. This proposal was based on histochemical analysis of acid phosphatases and other...

... cleavages. During these divisions, the nuclear-centrosome complex appears unstable in position. In addition, in almost half of the mutant embryos, there are reversals of the normal pattern of spindle orientations at second cleavage: the spindle of the anterior cell is aligned with the long axis...

...Dmitrii A. Voronov; Yuri V. Panchin ABSTRACT Early cleavages of the marine nematode Enoplus brevis are symmetrical and occur in synchrony. At the 2- to 16-cell stages, blastomeres are indistinguishable. The progeny of blastomeres was investigated by intracellular injections of fluorescent dyes...

... a description of the zebrafish PGCs for the first time. Furthermore, vas transcript was detected in a novel pattern, localized to the cleavage planes in 2- and 4-cell-stage embryos. During subsequent cleavages, the RNA is segregated as subcellular clumps to a small number of cells that may be the future germ...

... equatorial cleavage produces two tiers of sister cells called ‘veg1’ and ‘veg2,’ which were projected by early studies to be allocated to the ectoderm and endoderm, respectively. Recent in vitro studies have proposed that the segregation of veg1 and veg2 cells to distinct fates involves signaling between...

... zygotes by the injection of antisense oligodeoxynucleotides arrests development prior to the first cell division. We show that single-stranded antisense oligodeoxynucleotides specifically block cleavage, and that injection of SpOct mRNA overcomes this block. The accumulation of [ 35 S]methionine...

... the ‘MBT period’. The water-activated eggs do not actually cleave, but periodically they commence cytokinesis with bizarre, unpredictably located cleavage furrows ( Fig. 7A-C ) that then abort. There is a nuclear cycle marked by the disappearance of the nuclear membrane during each ‘mitosis’ ( Fig. 7D,E...

...Evelyn Houliston; Danièle Carré; Jennifer A. Johnston; Christian Sardet ABSTRACT The single axis (oral-aboral) and two planes of symme-try of the ctenophore Beroe ovata become established with respect to the position of zygote nucleus formation and the orientation of first cleavage. Bisection...

... 1 -integrin of the embryo. Until late blastula only small amounts of precursor are processed into the mature form. Starting with the formation of the first cleavage membrane, mature β 1 -integrin is inserted into the newly formed plasma membranes of all cells. The membrane domains forming the outer...

... is initially most evident near the egg’s equator or marginal zone, extensive rearrangements associated with cleavage furrowing (cytoplasmic ingression) relocate portions of the swirl to vegetal blastomeres on the prospective dorsal side. References Ancel , P. and Vintemberger , P. ( 1948...

...Eugenia M. del Pino; Sandra Loor-Vela Comparison of early development of the marsupial frog Gastrotheca riobambae with Xenopus laevis suggests that the cleavage pattern of Xenopus and the tight coupling of events at the midblastula transition are features of the accelerated development of small...

...) but was possible throughout most of the first egg cycle. The cytoplasmic components required for cytokinesis seem to increase progressively during the first division cycle. Nuclear transfer experiments indicated that the timing of cleavage was normal only when the nucleus and egg cytoplasm were reassociated...

... occurs in the ovisacs, presumably around the time of egg laying. Opposition may be postponed for hours or days, but the eggs in the ovisacs remain blocked at first meiotic metaphase. Development of the uncleaved egg, from the time of oviposition to completion of the first cleavage division, has been sub...

... of actin remain anterior as the zygote generates an asymmetric mitotic spindle and undergoes mitosis. As mitosis is being completed, actin fibres align circumferentially around the zygote where the cleavage furrow will form ( Fig. 3E ; Strome, 1986 b ). During cytokinesis the cleavage furrow is very...

...Lynne Selwood ABSTRACT The effect of destruction of some blastomeres on subsequent cleavage in vitro was investigated in the marsupial Antechinus stuartii . Blastomeres were killed by puncturing with a fine glass needle. The positions of the punctured and surviving blastomeres were recorded...

...Richard P. Elinson; Eugenia M. Del Pino ABSTRACT The marsupial frog Gastrotheca riobambae has several reproductive adaptations, most prominent of which is the incubation of the embryo in a pouch on the mother’s back. We have followed cleavage and gastrulation by microscopical observation...

... polypeptide and DNA synthesis cleavage mouse In the mouse egg, as in other animal species, the early events that take place following fertilization are largely, if not exclusively, under maternal control (reviewed by Davidson, 1976 , and Johnson, 1981 ; Woodland, Flynn & Wylie, 1979...

...Hiromasa Ohshima; Tomoyuki Kubota ABSTRACT Scanning electron microscopic studies were carried out on changes of the cell surface during the first cleavage of eggs of the newt, Cynopus (Triturus) pyrrhogaster . A dense population of elongated microvilli, which initially covered a double line...