Showing papers in "Developmental Biology in 1974"

TL;DR: It appears that preferential pathways located at precise levels of the embryo lead crest cells to their definitive sites and mesenchymal derivatives of the cephalic neural crest appear to be early determined since they differentiate according to their presumptive fate when transplanted into the trunk.

TL;DR: A method is described which permits the growth of chicken embryos in petri dishes from the third to the 20th day of incubation, providing ready access to the embryo and its membranes for tissue grafting, for introduction of teratogenic agents, and for microscopic observation of morphogenesis and growth.

TL;DR: The present data are consistent with those proposals that relate the cessation of mitotic activity of neuroepithelial cells to the determination of neuronal size, axon length, and the specification of neuronal connections on the mouse, killifish, and toad.

TL;DR: The retina of a mouse embryo on day 13 of gestation, the first day when ganglion cells with axons are detectable, has been studied both qualitatively and quantitatively by reconstructing a large number of cells from an electron microscopic serial section series to construct a simple hypothesis explaining some of the apparently contradictory results of neuronal development.

TL;DR: The immaturity of endothelial cells in the young chorioallantois, or conversely their high rate of cell division, may influence the ability of this membrane to support grafted tissue prior to day 11, which suggests the capillary network of the growing chorio allantoic membrane is expanding by an overall proliferation of endothelium in existing capillaries, rather than by formation of new capillary sprouts.

TL;DR: Ovarian teratomas developed spontaneously in about half of the females of the inbred strain LT, and the incidence rose to about 50% in animals 90 days old, and originated from ovarian eggs that began to develop parthenogenetically.

TL;DR: The morphological events that occur when the vitelline envelope of an unfertilized egg of Xenopus laevis is transformed into the fertilization envelope (FE) surrounding the zygote are reported.

TL;DR: The experiments reported here were designed to test whether or not the collagen of the lens basement lamina is capable of stimulating corneal epithelium to produce primary stroma, and found that purified chondrosarcoma collagen is as effective as lens capsule, and the stimulatory effect on collagen and GAG synthesis by cornean epithelia is not specific for basal lamina (lens capsule) collagen.

TL;DR: The postnatal development of acetylcholinesterase activity in the hippocampal formation of the developing rat brain, as demonstrated histochemically by the copper-thiocholine technique, serves as a marker for the ingrowing cholinergic afferent fibers.

TL;DR: For most, but possibly not for all, myogenic cells in typical primary muscle cell cultures, fusion is a prerequisite for the parallel differentiative changes in CPK and aldolase isoenzymes, and the possibility is discussed that a “cluster” of proteins, including CPK, may be coordinately regulated during myogenesis.

TL;DR: Clonal analysis of myoblast populations within regions of the developing limb have indicated that, between stages 21 and 27, the dorsal and ventral segments of the myogenic region contain appreciably more clonable muscle cells than the anterior and posterior segments.

TL;DR: It is found that ammonia activation does not result in the early respiratory burst and also does not initiate the late activation of Na+-dependent amino acid transport, indicating that augmentation of protein synthesis is causally linked neither to the earlier Na-influx, cortical reactions, and respiratory burst nor to the later activation of amino acid Transport.

TL;DR: Less-detailed data on development of ChAc and AChE activities in the hippocampal region as a whole suggest a similar sequence in divisions other than the dentate gyrus, and this finding is interpreted as a correlate of cholinergic synaptogenesis.

TL;DR: Microscopical observations of UV irradiated eggs with and without transplanted polar cytoplasm revealed that UV irradiation delays the migration of cleavage nuclei into the posterior periplasm and prevents cy toplasmic protrusions at the posterior pole from becoming isolated from the periplasms to form pole cells.

TL;DR: These results show clearly that embryonic ectoderm exercises a significant role in differentiation of the dorsoventral organization of limb parts in the chick embryo.

TL;DR: Judged by polysome content, the stage 42 tadpole seems to make protein about 20 times faster than the unfertilized egg, though it contains very few more ribosomes, and the relationship betweenpolysome content and the synthesis of various types of RNA is discussed.

TL;DR: This activity appeared within 4 hr after hormone treatment in Rana pipiens and Xenopus laevis and represents the earliest detectable, specific response of the oocyte yet observed, suggesting the presence of both a minimum and threshold level of cytoplasmic factor.

TL;DR: Examination of cytodifferentiation of the acinar exocrine cells of the rat submandibular gland at the ultrastructural level concluded that different developmental pathways are followed to attain a similar functional capacity in the three organs.

TL;DR: Silver-stained whole mounts of the tectal surface were used to study the developing retinotectal fiber pathway in the chick embryo, weakening previous support for specificity in the guidance of developing optic axons.

TL;DR: The amount of β -ecdysone found at the time of puparium formation is comparable to the amount required to induce morphogenesis of imaginal discs cultured in vitro.

TL;DR: There is no evidence that cells actually withdraw from the cycle prior to fusion, and it seems reasonable to assume that some preparation for fusion occurs during this phase and the probability of fusion increases with protraction of G 1.

TL;DR: For example, when RNA synthesis is blocked by actinomycin D, maternal mRNA alone can direct a quantitatively and qualitatively changing pattern of histone synthesis as cleavage proceeds as discussed by the authors.

TL;DR: Under the influence of juvenile hormone, the pattern by which the various areas of the epidermis become committed to make larval cuticle is very similar to the larval pattern of independence from the prothoracic glands.

TL;DR: Whether, when a differentiated vertebrate cell divides, its daughter cells inherit the parental cell-type determination is investigated in the regenerating limb of the axolotl by grafting differentiated cells carrying the triploid cell marker into the limbs of diploid X-irradiated host animals.

TL;DR: It is concluded that the wing-bud mesoderm, appropriately combined with flank ectoderman, has the property of morphological and axial self-differentiation by stage 12 and the apical ectodermal ridge is induced in flank ectODerm by prospective wing- bud mesderm.

TL;DR: It is proposed that the cell-lethal action of the mutant is sufficient to account for phenotypic effects described, and it was found that in gynandromorphs, pattern duplications can be found in wild-type tissue in the presence of lethal tissueIn the same disc, a cell-autonomous lethal may affect the process of pattern formation in a nonautonomous way.

TL;DR: It is shown that hyaluronic acid inhibits chondroitin sulfate synthesis and the accumulation of newly synthesized proteoglycan in the cell layer, indicating that specific glycosaminoglycans, such as hyaluonic acid, can affect the synthesis and accumulation of other glycosaminecans and should be considered as possible regulators of specific cellular activities.

TL;DR: It is suggested that there is a correlation between sulfated polysaccharide synthesis, cell surface morphology and cell movement, and the greatest sulfation activity, being found at the early mesenchyme blastula stage.

TL;DR: Embryonic chick leg bud mesoderms from stages 17 through 25 were cultured from 1 to 3 weeks as explants or as monolayers (1×104 to 2×106 cells per 35 mm dish) and differentiation of muscle and cartilage was exmained in living and fixed cultures.

TL;DR: An investigation of the pacemaker regions which organize cell aggregation in the cellular slime mold Dictyostelium discoideum shows that circular waves are initiated by spontaneous periodic signals and by spontaneous nonperiodic signals, each of which interact with a periodic signal relaying response in the responding cells.