Adenosine 3',5'-monophosphate: regional differences in chick embryos at the head process stage

Role of site-selective cAMP analogs in the control and reversal of malignancy

Two isoforms of cAMP receptor protein, RI and RII, the regulatory subunits of cAMP-dependent protein kinase, transduce opposite signals, the RI being stimulatory and the RII being inhibitory of cell proliferation. In normal cells RI and RII exist at a specific physiological ratio whereas in cancer cells such physiological balance of these receptor proteins is disrupted. Reversal and suppression of malignancy can be achieved when the physiologic ratio of these intracellular signal transducers of cAMP is restored as shown by the use of site-selective cAMP analogs, antisense oligodeoxynucleotides or gene transfer, suggesting new approaches to cancer control.

An hypothesis: phosphorylation fields as the source of positional information and cell differentiation--(cAMP, ATP) as the universal morphogenetic Turing couple

It is hypothesized that (cAMP, ATP) is the elusive, universal Turing morphogenetic couple, which defies the second law of thermodynamics, i.e. the inexorable march towards homogeneity. cAMP and ATP can be distributed nonhomogeneously because the whole of the intermediary metabolism is so organized that they mutually satisfy the Turing bifurcation conditions upon nonlocalized application of an extracellular ligand, in particular a soluble peptide growth factor, which is nature's distinguished universal bifurcation parameter, acting homogeneously in space and removing the substrate inhibition from adenylate cyclase and thus triggering embryonic induction by triggering the (cAMP, ATP) Turing system. The hypothesis predicts that although the extracellular signal, the growth factor, is applied homogeneously, an organized "dissipative structure" will emerge spontaneously in the responding tissue; this "symmetry breaking" in a reaction-diffusion system occurs precisely in the manner envisaged by Turing, where (cAMP, ATP) constitutes the "reaction-diffusion system". This Turing bifurcation explicates the recent experiments where a differentiated embryoid emerges from the mere immersion of frog animal caps in an homogeneous growth factor solution, and similar experiments on chicks. The "metabolic" patterns found by Child and colleagues also reflect dissipative structures arising in a (cAMP, ATP) reaction-diffusion system when interpreted in the light of modern biochemistry: in particular, the localized glycogen depletion reflects localized cAMP; localized redox, respiratory or susceptibility activity reflects localized ATP. The dramatic collapse of organized structure found by Child and colleagues, for example, when Planaria or a section of it is exposed to an homogeneous environment of a narcotic solution, and the reemergence of structure upon return to water, are explained on the basis of the violation or satisfaction of the Turing bifurcation conditions with respect to (cAMP, ATP), respectively. cAMP is the "activator", ATP is the "inhibitor", and together they mutually satisfy the four activator-inhibitor inequalities, including the all-important autocatalytic cAMP production, as well as the lateral inhibition condition. The functional significance of gap junctions is to generate a multicellular purely reaction-diffusion system for (cAMP, ATP) as envisaged by Turing. It is emphasized that localization and pattern formation occur intracellularly in gap junction-coupled cells and not, as often suggested, extracellularly, the latter localization being too fragile to be maintained for long enough, and soon succumbing to the mixing effect of convection and movement. The activator-inhibitor property of (cAMP, ATP) means that the spatial distribution of cAMP and ATP could be not only nonhomogeneous but also of the same shape.(ABSTRACT TRUNCATED AT 400 WORDS)

Ultrastructural cytochemical localization of adenylate cyclase in the early chick embryo

Adenylate cyclase activity was localized in various tissues of the early chick embryo using an ultrastructural histochemical technique. Reaction product was deposited on the lateral plasma membrane of all cells, but with a preferential localization at the apical terminal complex in the epiblast. There was no activity associated with the free surfaces of these or other cells in the embryo. Intracellular deposits were found in all cells associated with the endoplasmic reticulum, nuclear envelope and Golgi bodies. In the last organelle, the deposit was sometimes observed to be distributed through the stack in a non-uniform way, with the heaviest deposits occurring at the forming face. No clear difference could be detected between the cytochemical activity associated with cells in various regions of the embryo, or with embryos at different stages of early development.

Emergence of beta-adrenergic sensitivity in the developing chicken heart

Muscle cells dissociated from 5-day embryonic chicken hearts showed dose-dependent increases in both chronotropic rates of contraction and cyclic AMP (cAMP) levels in response to epinephrine (EPI), an effect that could be blocked by beta-adrenergic antagonists. However, 2- to 2.5-day embryonic chicken myocardial cells, although similar to 5-day heart cells with respect to the organization of myofibrils, failed to respond to EPI either by increased rates of contraction or by elevated levels of intracellular cAMP. Development of beta-adrenergic sensitivity in 2- to 2.5-day cells did not occur even after several days of growth in culture. However, addition of an extract prepared from 11-day chicken embryos to 2- to 2.5-day muscle cell cultures at any point during in vitro growth resulted in the development of sensitivity to EPI as measured by increases in both the beating frequency and cAMP levels after a 48-hr incubation in embryo extract (EE). The basal level of cAMP in cells unresponsive to EPI is 5 times that in EPI-sensitive muscle cells from older hearts (5 days). The high basal level of cAMP in these cells is reduced to a level characteristic of cells from older hearts when treated with the EE. Once sensitivity was acquired, it was retained as a stable trait of the muscle cells in culture. Furthermore, EE-treated 2- to 2.5-day cells showed less reduction of positive chronotropy in response to multiple doses of EPI than did cells prepared from 5-day hearts. Fractionation of EE on Sephadex G-200 showed that the activity was present in the large-molecule fractions. It is concluded that the development of beta-adrenergic sensitivity can be induced in unresponsive heart cells cultured from 2- to 2.5-day embryos by a factor(s) in the EE that is not adsorbed on Sephadex G-200.

Axial bending in the early chick embryo by a cyclic adenosine monophosphate source

A microelectrode continuously releasing cyclic adenosine monophosphate can divert the axis of the early chick embryo and attract cells on its ventral surface. Cell movement in the intact embryo may be controlled by a cyclic adenosine monophosphate signal.

Cyclic AMP binding proteins in early embryos of Drosophila melanogaster

A variety of effects of cyclic AMP on cellular and subcellular phenomena suggest that there may be other modes of action of cyclic AMP then activation of protein kinase. It is also known that developing embryos contain cyclic AMP and its related enzymes. In order to explore the role of cyclic AMP in embryogenesis, a survey of proteins capable of binding cyclic AMP in the embryonic supernatant of Drosophila melanogaster was carried out. As the result, two cyclic AMP-binding proteins were found and characterized. The one (L) is, as expected, associated with protein kinase and has a dissociation constant of about 10(-9) M. Its molecular weight of 21 000 daltons is extremely small when compared with similar proteins in other organisms. The other (H), whose function is yet to be found, has a molecular weight of about 200 000 daltons and has a dissociation constant of about 10-7 M. Some laxity in binding specificity of the latter protein among adenosine nucleotides was observed, but cyclic AMP is the strongest ligand among them.

Induction of neural differentiation in cultures of amphibian undetermined presumptive epidermis by cyclic AMP derivatives

Induction of neural differentiation in cultures of undetermined presumptive epidermis from three amphibian species was achieved by the addition of 1 millimolar dibutyryl adenosine 3',5'-monophosphate, 8-bromadenosine 3',5'-monophosphate, or adenosine C',E'-monophosphate together with theophylline. Adenosine 5'-monophosphate, adenosine 2',3'-monophosphate, dibutyryl guanosine 3',5'-monophosphate, and butyrate at 1 millimolar are ineffective. These results suggest that the action of the primary inductor or inductors may be mediated via adenosine 3',5'-monophosphate.