The accumulation of endogenous adenosine 3':5'-cyclic phosphate (cAMP) and of [(14)C]cAMP, derived from nucleotides labeled by prior incubation of cells with [(14)C]adenine, has been investigated in four glial cell lines from rats. The following results are similar to data reported for brain slices: (i) rat glial cells contain a system that readily incorporates [(14)C]adenine into nucleotides that serve as precursors for cAMP. (ii) norepinephrine stimulates accumulation of both [(14)C]cAMP and endogenous cAMP, and (iii) the phosphodiesterase inhibitors, papaverine and isobutylmethylxanthine, are effective in enhancing the stimulatory effect of norepinephrine. In contrast to results reported for brain slices, histamine, veratridine, and adenosine, the purine either alone or with a biogenic amine, do not cause an enhanced accumulation of cAMP in rat glial cells, and repetitive accumulations of cAMP can be elicited during a series of restimulations of the cells with norepinephrine. The magnitude of the accumulation of cAMP elicited by the catecholamine decreases markedly by the fifth restimulation in the absence of, but only slightly in the presence of, papaverine. In glial cells, a large portion of the [(14)C]adenine is incorporated into intracellular compounds that do not serve as precursors of [(14)C]cAMP.

Adenine↗

PubMed1972

Characterization of the DNA in Drosophila melanogaster.

DNA has been quantitatively extracted from Drosophila melanogaster at various stages of embryonic development and analyzed by isopycnic centrifugation in CsCl and by fractionation on methylated albumin columns. The DNA is composed of three main classes of DNA, as defined by their buoyant density, rho, in CsCl: a bulk DNA, rho = 1.699 g cm(-3), and two satellite DNAs, rho = 1.685 g cm(-3) and rho = 1.669 g cm(-3). These three types of DNA persist throughout the development of the insect. In the unfertilized egg, 80% of the total DNA consists of the satellite DNAs; this amount decreases to 18% during the first three hours after fertilization and then remains constant through embryogenesis. There is a concomitant increase of the satellite DNA's with the bulk DNA after blastoderm formation.

Animals↗

PubMed1972

Satellite DNAs in the embryos of various species of the genus Drosophila.

A tentative evolutionary pattern has been found for two classes of the multiple satellite DNA's found in the genus Drosophila. The satellite DNA's from five Drosophila species (D. melanogaster, D. simulans, D. nasuta, D. virilis and D. hydei) were analyzed and found to fall into three arbitrary CsCl buoyant density classes: Class I, rho = 1.661-1.669 g cm(-3), DNA molecules composed of primarily dA and dT moieties; Class II, rho = 1.685 and rho = 1.692, DNA molecules of low GC content; and Class III, rho = 1.711, a DNA of high GC composition. The dAT satellite DNA's appear in all the species studied except D. hydei, the species of most recent evolutionary divergence, whereas the heavy satellite appears only in the two species of most recent divergence, D. virilis and D. hydei.

Animals↗