Showing papers in "Developmental Biology in 1968"

TL;DR: Evidence is presented for the existence of specific factors associated with the cell surface and intercellular spaces which function as cell ligands and mediate histogenetic attachment and aggregation of sponge cells and in relation to the ECM hypothesis.

TL;DR: The hypothesis is advanced of stepwise specification of progressively finer details of the pattern of neuronal connections; the initial steps occurring at an early stage of neuroblast differentiation before the outgrowth of neuronal processes.

TL;DR: Colchicine and thymidine-3H were used to determine the source and manner of distribution of the new cells added to the inner nuclear layer of the retina of Rana pipiens tadpoles.

TL;DR: It is suggested that collagen is essential for stabilization of epithelial morphology in cases where epithelial branching is occurring, but not where acini are forming; no evidence demonstrates any inductive properties for collagen in these systems.

TL;DR: Although no causal relationship has been shown, there appears to be a correlation between the cessation of DNA synthesis in ganglion cell neuroblasts at stages 28–29, and the specification of the central connections of theganglion cells at stages 29–31.

TL;DR: The hypothesis that steroids act directly on the oocyte to induce maturation whereas pituitary hormones act through the mediation of follicular tissue is supported.

TL;DR: The hemoglobin pattern of embryonic and adult mice was determined by a modified method of acrylamide gel electrophoresis and it was suggested that the environment at the site of hematopoiesis determines the type of hemoglobin produced.

TL;DR: An electron microscope study of palatal fusion in mouse embryos found evidence of true adhesion between epithelia of opposing processes, but no extracellular “sticky substance” was demonstrable.

TL;DR: Evidence suggests that the active component(s) in the supernatant is taken up onto the cell surface and that materials immunologically cross-reactive with it are normally present there.

TL;DR: In the postnatal maturation process of skeletal muscle, neuronal influences are necessary and more critical for the type II fibers in the rat and a possible neurogenic role in certain of human cases termed “myotubular myopathy” was suggested.

TL;DR: The data suggest a close temporal linkage between initial specific synthesis and initial organ morphogenesis, as well as correlations of structure that are discussed in light of the biochemical information.

TL;DR: Results indicated that the black-eyed white phenotype in Sl and W homozygotes was caused by gene action at different sites, and a general pigment reduction in these locations resulted from the action of both mutant genes.

TL;DR: It is concluded that nonselective adhesions occurred between freshly dissociated cells of different types more readily than between cells and heterotypic aggregates.

TL;DR: Observations and correlations indicate that one consequence of primary embryonic induction is a patterned change in the height of the cells in the forming neural plate with concomitant displacements of cell groups and regional changes in area that give the neural plate its characteristic shape.

TL;DR: Vital staining with trypan blue was found to provide a simple and reliable index to the stages of follicular development that sequester blood proteins in yolk spheres.

TL;DR: Nucleic acid synthesis in the 2-blastomere egg was undetectable by the methods used, which may imply that m-RNA is long lived in the early stages of cleavage.

TL;DR: The results imply that DNA replication and mitosis become less frequent and finally cease in the prospective primary and secondary fiber cells as they differentiate into definitive fibers, and that the cells of lens rudiment which are not participating in fiber differentiation retain a high level of cell-labeling and mitotic frequencies.

TL;DR: It is concluded that the Xenopus larva acquires a very early competence to exhibit biochemical and morphological responses to the metamorphic stimulus of thyroid hormones.

TL;DR: A collagenolytic enzyme capable of degrading reconstituted collagen fibrils at neutral pH and physiological temperature, not demonstrable in the intact forelimb of the adult newt ( Triturus viridescens) appears in cultures of healing and regenerating tissues of the amputation stump.

TL;DR: Microtubules, neurofilaments, and neurotubules have been studied in neural epithelial cells and differentiating motor neuroblasts in the spinal cord of chick embryos after glutaraldehyde fixation and possible roles of these structures in the differentiating neuroblast are discussed.

TL;DR: Control of cell death in a zone of necrosis (PNZ) which is visible near the posterior junction of the wing bud and body wall of the chick embryo at stage 24 indicates that a prolonged period is necessary for the PNZ cells to reach a stabilized condition leading to a pattern of growth and differentiation instead of death.

TL;DR: It has been concluded that the blastema, at least from the cone stage on, contains a pattern of discrete and separate parts which make up a wholly self-organizing system.

TL;DR: It has been concluded that by the time the blastema has reached the cone stage, it is not dependent upon inductive messages from the stump for differentiation, but is a self-differentiating system.

TL;DR: Embryonic chick otocysts with the associated mesenchyme and acoustic ganglion developed completely differentiated sensory epithelial membranes of the inner ear such as the organ of Corti and cristae, indicating that proximity of mesenchymal and epithelial tissue were essential for the histo-differentiation of the epithelium of the otocyst into sensory areas.

TL;DR: Analysis of the acid-soluble fraction during growth and development of the brine shrimp, Artemia salina, indicates diguanosine tetraphosphate (Gp 4 G) to be peculiar to the female and to be actively synthesized by the developing ovarian egg.

TL;DR: Evidence that the Spm system can preset a gene locus at one stage in development to give a particular pattern of gene expression at a later stage was obtained from studies of several different gene loci that came under the control of the system.

TL;DR: The failure of detergent or trypsin treatments to increase incorporation activity significantly in the nonincubated material led to the conclusion that the initiation of protein synthesis inArtemia is due not to the release of preprogrammed particles, but to a gradual programming of free monosomes.

TL;DR: Kinetics of amino acid incorporation have been studied in oocytes of Rana pipiens at all stages from the full-grown ovarian oocyte, through the period of pituitary-induced maturation and several hours beyond fertilization or artificial activation.

TL;DR: Observations indicate that the capacity for the complex changing pattern of cell differentiation is intrinsic to the epidermis, and it is suggested that the pattern of differentiation is regulated by a feedback mechanism effected via communication between epidermal cells of the different strata.

TL;DR: This chapter illustrates the developmental and control processes in the basal bodies and flagella of Chlamydomonasreinhardii as basal bodies persist in the vegetative cells, but not in the zygotes, after flagellar regression.