Showing papers in "Developmental Biology in 1971"

TL;DR: It is suggested that the shape of the sperm head is probably not a consequence of external modeling by pressures applied to the condensing spermatid nucleus by microtubules in the surrounding cytoplasm or by filaments in the ectoplasm of the supporting cell.

TL;DR: The possibility that the messenger RNA molecules which specify the synthesis of proteins essential for cell fusion and increased enzymatic activity are formed at a developmental stage preceding cell fusion is suggested.

TL;DR: It is suggested that the steroid acts at or near the surface to cause the production of a second effector which, when accumulated to a sufficient level in the oocyte, induces the observable events associated with maturation.

TL;DR: Using X-ray-induced somatic crossing-over, a clonal analysis of the wing disc development of Drosophila melanogaster was carried out and indicated that the wing imaginal disc cells grow exponentially from the beginning of the larval period up to puparium formation.

TL;DR: Glycosaminoglycan (acid mucopolysaccharide) synthesis was studied during development of the embryonic chick cornea by the introduction of isotopically labeled precursors both in ovo and to excised corneas in culture.

TL;DR: It is concluded that hyaluronate is associated with blastema formation, and its possible role in the regulation of mesenchymal cell behavior is discussed.

TL;DR: Whenever fusion is experimentally delayed proliferation continues, at an undiminished rate, for a longer period of time generating a larger cell population, thus, although close proximity is a necessary condition for fusion it is not a sufficient condition.

TL;DR: When fragments of the foreleg disc are injected into old larval hosts, they differentiate structures according to the anlage plan as discussed by the authors, they can also duplicate patterns, regenerate, or form multiple copies of units of markers.

TL;DR: Neurite formation in a cloned tissue culture line of mouse neuroblastoma C1300 can be rapidly induced by plating cells in serum-free or conditioned media, and microtubule formation in neurites is dependent on protein synthesis.

TL;DR: Electron microscopy of presumptive neural cells has been carried out in an attempt to understand the mechanism of morphogenetic cell shape changes and several observations suggest that microtubules contribute to cell elongation by some form of transport mechanism.

TL;DR: The concurrent appearance of myofilaments and ACh sensitivity is discussed in relation to the early events and control mechanisms of myogenesis.

TL;DR: It is shown for the first time that collagens are produced by the neural tube and the appearance of the juxta-neural extracellular materials in situ at the time of “induction” is described.

TL;DR: In the case of various salt solutions used for testes maceration, inhibition of sperm motility was primarily a function of the ionic strength, however, there was some specificity in the salt employed as KCl and CaCl 2 solutions gave anomalous results in comparison with those obtained with other salt solutions.

TL;DR: Observations support the ideas of Rappaport that furrow initiation results from the interaction of pairs of asters with the egg surface, and present the possibility that there are at least two sources of membrane for furrow growth.

TL;DR: The polysomes do not change in size over the 2 hrs that more messenger RNA is becoming active, indicating that the messenger RNA molecules are released individually at various times over the2-hr period, which suggests that the translational control mechanism in the egg acts directly at the level of the messengerRNA molecules.

TL;DR: It has been found that the labeling index changes very little in the wing region between stage 16 and stage 20, but decreases rapidly in the flank region during the same period, which correlates very well with morphological changes.

TL;DR: During late larval stages of Xenopus laevis the neural retina increases in area in concert with the increase in diameter of the eye and there is an increase in thickness of the inner nuclear layer over the whole expanse of the retina.

TL;DR: The results revealed that acinar differentiation in the rat parotid gland is primarily postnatal, and suggests that substrates in the food and secretory stimulation may have inductive significance in the differentiation of the gland.

TL;DR: The results suggest that homoeotic leg cells and antennal cells can both respond to the same positional information or prepattern, and suggest that determination may be of two types—a clonally inherited determination and an environmental determination.

TL;DR: It is suggested that regeneration and duplication are identical phenomena, resulting from the properties of of the anlagen at the cut edge.

TL;DR: The proposed roles of microtubules and microfilaments in bringing about neurulation have been experimentally tested and are cited as evidence in support of parts of the model of Schroeder (1970) .

TL;DR: These findings indicate that the Gpi-1 paternal locus is expressed by day 5, and demonstrate the value of using electrophoretic variants to pinpoint synthesis of new enzyme which may not be reflected in changes in levels of activity.

TL;DR: The finding of effective hydroxyurea levels in the embryo strengthens the idea of a direct effect on embryonic cells as the cause of malformations and reveals that embryo cells respond to similar concentrations of hydroxyUREa as do other cell types.

TL;DR: The data on gynandromorphs, as well as those of somatic spots, indicate that the adult tergites have an indeterminate pattern of growth, corresponding with the constant number of imaginal cells during the larval development.

TL;DR: Observations on the germ plasm of Rana are remarkably similar to those seen in the formation of pole cells in the taxonomically distant Drosophila.

TL;DR: Clones of cells which were genetically marked at specific ages by X-ray induced somatic crossing-over were observed on the antenna of Drosophila melanogaster, which indicates that oriented cell divisions play a role in antennal morphogenesis.

TL;DR: The posterior intestinal portal develops by inversion of a circumscribed area of endoderm, forming the posterior gut, suggesting that gastrulation in the chick is similar to that of other chordates except that the archenteron is not completely formed until the most peripheral pregut cells in the hypoblast layer are drawn together ventrally like pursestring at the umbilicus.

TL;DR: On ae´tudie´la synthe-se du RNA durant l'oogene'se du crapaud sud-africain Xenopus laevis as discussed by the authors, provenant de 7 classes diffe´rentes d'oocytes obtenuesa'partir de femelles immatures and de femelle muˆres, ae'te´analyse´par filtration sur colonne de Sephadex G-100 and par centrifugation en gradient de saccharose.

TL;DR: Radioautographic evidence, together with the histological evidence for continuity of the iris epithelium and the regenerating lens, provides support for the concept that dorsal iris cells transform into lens cells.

TL;DR: Reaggregated cells from Xenopus laevis embryos in blastula through larval stages become electrically coupled within 20 min of the beginning of aggregation and some of these cells can exchange fluorescein injected intracellularly.