Cyclic nucleotides and cell growth.

Growth induction in resting fibroblast cultures by serum or growth factors induces a fast, transient cGMP peak which may constitute the intracellular signal for growth. A similar cGMP peak occurs when 3T3 cells arrested at the restriction point or in G0 by starvation for certain amino acids are induced for growth by readdition of the lacking nutrients. Both 3T3 and SV3T3 cells which are arrested randomly all around the cell cycle do not exhibit major changes in cyclic nucleotides after growth induction. Determination of intracellular cAMP and cGMP levels in normal and transformed fibroblasts under different growth conditions shows that the transition between growing and resting state (G0 arrest) is accompanied and probably induced by characteristic changes in cAMP to cGMP ratios. cGMP is decreased 2-5-fold in resting as compared to growing cultures, and increased 10-20-fold in activated cultures 20 min after serum induction. No major cGMP change was observed in growing, confluent, or serum-activated cultures of transformed cells. Measurement of guanylcyclase under unphysiological conditions (2 mM Mn++) in crude and purified membranes from 3T3 and SV3T3 cultures did not show increased enzyme activity in the transformed cells. Significant differences may only show up when synchronized cells pass through the restriction point in G1 phase. As a hypothesis it is proposed that transformed cells have an activated guanylcyclase system or a relaxed cGMP-pleiotypic response mechanism at the restriction point of their cell cycle.     

Field desorption mass spectrometry: I. Cyclic nucleotides

The FD spectra of nineteen 3′, 5′-cyclic nucleotides and their derivatives are reported. The principal features of spectra, the fragmentation mode, and the experimental techniques are described.     

Nonglycoside analogs of nucleotides

N¹-(2′,3′-Dihydroxypropyl)uracil, -thymine, -cytosine, and N⁹-(2′,3′-dihydroxypropyl)adenine were synthesized by alkylation of nucleic bases with 2,3-O-isopropylideneglycerol chlorohydrin, subsequent separation of the resulting mixtures, and removal of the protective groupings. Phosphorylation of these compounds or of their selectively substituted derivatives gave 2′(3′)-monophosphates, which were converted to 2′,3′-cyclophosphates by reaction with N,N′-dicyclohexylcarbodiimide. Thionation of the corresponding cytosine derivatives gave N¹-(2′,3′-dihydroxypropyl)-4-thiouracil and its 2′(3′) phosphate.     

Nonglycoside analogs of nucleotides

Conclusions We synthesized nine analogs of dinucleoside monophosphates that contain 9-(2-hydroxyethyl)adenine, 9-(3-hydroxypropyl)adenine, and 9-(4-hydroxybutyl)adenine as the 3 residue, and the natural nucleosides: uridine, cytidine, adenosine, guanosine, and inosine as the 5 residue.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 915–916, April, 1975.     

Assays of cyclic nucleotides

Cyclic nucleotides are recognized as important second messenger molecules, and many assay formats exist for their quantification. This article critically reviews these different approaches. For measurement of cAMP or cGMP in biological fluids or tissue extracts, immunoassay is effective. For other purposes, such as measurement of cyclic nucleotide phosphodiesterase activity, methods that separate nucleotides from their cyclic counterparts are best, and offer a variety of means of detection.