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E C Raff

Publications and source records attributed to E C Raff.

42 records · Page 3Linked to original sources
PubMed1966

The effects of adenosine triphosphate and related compounds on some hydrodynamic properties of glycerinated cilia.

Cilia were isolated from Tetrahymena pyriformis by a glycerol method. The addition of low concentrations of ATP, but not of other nucleoside triphosphates, caused an increase of up to twofold in the amount of cilia pelleted in a low-speed centrifugation assay and decreased the density of the pellets compared to control pellets. Pellet size and density depend on pH, both in the absence and in the presence of low concentrations of ATP. High concentrations (5 mM and above) of ATP and of other nucleoside triphosphates tend to "dissolve" the cilia. Heating the cilia for 11 min at 40 degrees C abolishes the increase in pellet size and the decrease in pellet density caused by low ATP, but slightly increases the ATPase activity of the cilia. Heat treatment, however, does not prevent the dissolving effect of high ATP. There are, thus, two independent effects of ATP on the hydrodynamic properties of cilia suspensions.

Adenosine Triphosphatases↗
PubMedDate not supplied

Novel gene expression patterns in hybrid embryos between species with different modes of development.

Cross-species hybrids between eggs of the direct-developing sea urchin, Heliocidaris erythrogramma, and sperm from its congeneric indirect-developing species, Heliocidaris tuberculata, show restoration of features of the paternal feeding pluteus larva, including the gut, and pluteus spicular skeleton. Unlike other reported sea urchin cross-species hybrids, Heliocidaris hybrids express genes derived from both maternal and paternal species at high levels. Ectodermal cell types, which differ radically between the two parental species, are of intermediate form in the hybrids. Gene expression patterns in hybrid embryo tissues represent a number of combinations of parental gene expression patterns: genes that are not expressed in one paternal species, but are expressed in hybrids as in the expressing parent; genes that show additive expression patterns plus novel sites of expression; a gene that is misexpressed in the hybrids; and genes expressed identically in both parents and in hybrids. The results indicate that both conserved and novel gene regulatory interactions are present. Only one gene, CyIII actin, has lost cell-type-specific regulation in the hybrids. Hybrids thus reveal that disparate parental genomes, each with its own genic regulatory system, can produce in combination a novel gene expression entity with a unique ontogeny. This outcome may derive from conserved gene regulatory regions in downstream genes of both parental species responding in conserved ways to higher-level regulators that determine modular gene expression territories.

Animals↗