Showing papers on "Ciliogenesis published in 1979"

Species specific pattern of ciliogenesis in developing sea urchin embryos

Abstract: The events of cell division and ciliogenesis in individual blastomeres of developing embryos of the sea urchins Temnopleurus toreumaticus and Hemicentrotus pulcherrimus were followed with a Nomarski differential interference microscope. The number of cell divisions before initiation of ciliogenesis was determined with respect to species. In T. toreumaticus, ciliogenesis began about 4 hr after fertilization at 25°C. The sequence of ciliogenesis was as follows: cilia appeared first on smaller micromeres, followed in order by blastomeres derived from larger micromeres, those from mesomeres and finally those derived from macromeres. Blastomeres originating from mesomeres, macromeres, larger micromeres and smaller micromeres had completed the 8th, 9th, 7th and 5th divisions respectively, before they generated cilia. In H. pulcherrimus, embryos started to form cilia about 9 hr after fertilization at 18°C. Cilia appeared first on blastomeres of mesomere origin and, then on those of macromere origin. Before initiation of ciliogenesis, descendants of mesomeres and macromeres completed 9 and 10 rounds of cell division. Descendants of larger micromeres and the majority of cells derived from smaller micromeres did not acquired cilia even when the embryo began to rotate within the fertilization membrane. At this stage, the former had completed the 6th division and the latter the 8th division. Cell counts of blastomeres per embryo at the blastula stage also supported this observation.

An ultrastructural study of morphogenesis of fibrogranular complex and centriole in ductuli efferentes of Chinese hamster.

Abstract: An ultrastructural study of ciliated epithelial cells in the ductuli efferentes of young and adult hamsters has revealed that these cells possess dense granules, dense granule clusters, dense bodies and fibrogranular complexes as reservoirs or precursors for ciliogenesis. The dense granules are first seen in the centrosomal region. Later, many dense granules and dense granule clusters appear in the apical portion of the epithelial cells where, subsequently, dense bodies are also found. Finally, the fibrogranular complexes are formed in adults. Morphological evidence strongly suggests that cilia are formed from diplosomal centrioles, de novo centrioles, dense body centrioles, and fibrogranular complex centrioles. Ciliogenesis begins in the fourth day after birth and increases rapidly in the fifth day. After the sixth day, cilia appear to be generated mostly from dense bodies and the total ciliogenesis activities gradually decrease as the animal ages.

Ultrastructural investigation on the cell membranes of the vomeronasal organ in the rat: a freeze-etching study.

Abstract: The free surfaces and cell contacts in the epithelia of the vomeronasal organ of the rat were investigated by freeze-etching. The microvilli of receptor cells show a lower density of intramembranous particles (IMP) than the microvilli in the receptor-free epithelium. The ratio between the IMP on P and E-face is approximately 11∶1 in the receptor terminals, and 3.5∶1 in the cilia and microvilli of the receptor-free epithelium. Although atypical in length and only poorly equipped with rootlet fibers, the cilia of the receptor-free epithelium are furnished with typical ciliary necklace structures of up to 10 rows of membrane particles. Differences in the density of IMP on the P-faces of different cilia are probably due to continual ciliogenesis and also due to the different age of cilia in the receptor-free epithelium. Zonulae occludentes show different configurations in the neuroepithelium and in the receptor-free epithelium. In the former, they show a tendency to cross-link and form facet-like patterns, reflecting a constant morphology and relative stability for this apical region. In the receptor-free epithelium the junctional rows of zonulae occludentes display only loosely interconnected networks and a tendency to orient parallel to each other and to the free surface. In addition to zonulae occludentes, typical square aggregations of IMP are observed in the receptor-free epithelium. They are not exclusively restricted to the zone of intensive cell contacts by means of fine interdigitating cell processes, and their function has yet to be identified experimentally.

Centriologenesis and ciliogenesis in rat pituicytes

Abstract: A study of pituicytes in young and adult rats, under various experimental conditions, shows that these cells have normally two centrioles, one of which often acts as a basal body for the growth of a single cilium. Moreover, pituicytes displaying an active multiplication of centrioles, leading to the formation of numerous cilia, have been found in normal and experimental animals, in particular after injection of microtubule poisons. While this ciliogenesis is apparently more evident in pituicytes in conditions of hyperactivity of the posterior pituitary, no quantitative conclusions are possible at this moment about the relations between cell activity, the action of antitubulins, and the numbers of multiciliated cells.

Origin of necklace particles in thymic ciliating cells

Abstract: The formation of ciliary necklaces during ciliogenesis in a thymic cyst was observed in freeze-etched replicas. The necklaces first appear as clusters of particles arranged in concentric circles on a flat area of the cell membrane. As soon as the cilium begins to grow, the particles move to the periphery.

Selection of nonmotile Tetrahymena with Ficoll underlayers.

Abstract: SYNOPSIS The mechanisms regulating the development of cilia in Tetrahymena are poorly understood but might be revealed through the study of ciliogenesis mutants. Failure to regenerate cilia after dibucaine deciliation results in continued absence of motility. Therefore, to isolate ciliogenesis mutants efficiently, methods for separating motile and nonmotile cells are essential. We examined the efficacy of Ficoll underlayers for these separations. Ciliates of T. thermophila strain mpr-/mpr (6 mp sens IV) (6-methyl purine-sensitive; mating type IV) were mixed with Ficoll and added as underlayers to separatory funnels containing growth medium. At 27 C most of the cells remained motile and were found in the top layer; at 37 C, there was a time-dependent increase in the number of nonmotile cells and the number of cells in the Ficoll layer. After 150 min at 37 C, most of the cells became nonmotile and were found in the Ficoll layer. Other studies indicated that at 37 C, the cells remained alive and capable of regenerating cilia when deciliated. Thus, it is clear that the Ficoll underlayer effectively separates the majority of nonmotile cells from the majority of motile cells. Evidently, however, at 37 C wild-type T. thermophila exhibit temperature-sensitive phenotypic variability with regard to motility which should be minimized when selecting for mutations affecting motility and ciliogenesis.