Circadian variation of adrenocortical cyclic nucleotides (cyclic AMP and cyclic GMP) in hypophysectomized rats

The existence of a circadian variation in the adrenocortical concentrations of cyclic AMP and cyclic GMP in male adult Wistar rats examined 10 days after hypophysectomy is demonstrated. The results suggest that the circadian variations of adrenocortical cyclic nucleotides observed previously in intact rats might not entirely depend upon pituitary corticotrophin.     

Circadian variation of adrenocortical cyclic nucleotides (cyclic AMP and cyclic GMP) in hypophysectomized rats

Summary The existence of a circadian variation in the adrenocortical concentrations of cyclic AMP and cyclic GMP in male adult Wistar rats examined 10 days after hypophysectomy is demonstrated. The results suggest that the circadian variations of adrenocortical cyclic nucleotides observed previously in intact rats might not entirely depend upon pituitary corticotrophin.Acknowledgment. Thanks are due to Prof. J. M. Racadot and Dr Y. Drouet for their assistance with the histological examinations.     

Ontogenetic changes in relative levels of cyclic AMP-dependent and cyclic GMP-dependent protein kinases in prostates,epididymides and testes from guinea-pigs

Summary Changes in realtive levels of cyclic AMP-dependent protein kinase (A-PK) and cyclic GMP-dependent protein kinase (G-PK) in prostates, epididymides and testes from guinea-pigs were examined at 3 different ages. During postnatal development, a decrease in the ratio of the 2 classes of protein kinases was seen in prostates, whereas increases of the ratios of the enzymes were found in epididymides and testes.Acknowledgments. This work was supported by grant RR-08199 from the National Institutes of Health, USA. The authors thank Dr J.F. Kuo, in whose laboratory part of this work was performed, for his great advice.Undergraduate trainee of Minority Biomedical Support.     

Ontogenetic changes in relative levels of cyclic AMP-dependent and cyclic GMP-dependent protein kinases in prostates, epididymides and testes from guinea-pigs.

Changes in relative levels of cyclic AMP-dependent protein kinase (A-PK) and cyclic GMP-dependent protein kinase (G-PK) in prostates, epidymides and testes from guinea-pigs were examined at 3 different ages. During postnatal development, a decrease in the ratio of the 2 classes of protein kinases was seen in prostates, whereas increases of the ratios of the enzymes were found in epididymides and testes.     

Plasma cyclic 3',5'-guanosine monophosphate and cyclic 3',5'-adenosine monophosphate response to methacholine in man

Cholinergic agents are known to induce increases in tissue and plasma levels of cyclic GMP in experimental animals. We observed that i.m. injection of methacholine, a cholinergic agent, caused significant increases in plasma cyclic GMP and cyclic AMP in man.     

Plasma cyclic 3′,5′-guanosine monophosphate and cyclic 3′,5′-adenosine monophosphate response to methacholine in man

Summary Cholinergic agents are known to induce increases in tissue and plasma levels of cyclic GMP in experimental animals. We observed that i.m. injection of methacholine, a cholinergic agent, caused significant increases in plasma cyclic GMP and cyclic AMP in man.     

Ionic effects on cyclic nucleotide accumulation in a phytophagous insect

Summary Incubation in solutions containing high potassium levels reduces specific accumulation of cyclic AMP in larval nerve cords ofManduca, sexta in vitro with or without serotonin or theophylline.Supported in part by NIH grant NS-09161-20 to R.W.N.     

Altered brain cyclic AMP-responses in rats reared in enriched or impoverished environments

Summary The accumulation of radioactive cyclic AMP elicited by various neurohormones has been examined in adenine-labeled telencephalon slices from rats raised in enriched or impoverished environments. Basal levels of cyclic AMP and responses of the brain slice cyclic AMP-generating systems to norepinephrine, isoproterenol and adenosine did not differe between the two group of rats, while responses to prostaglandin E₁ were significantly greater with the impoverished group and responses to histamine appeared to be greater with the enriched group.     

Are there cyclic variations in estradiol secretion in the non-pregnant rabbit?

Plasma estradiol-17 beta (E2) concentration was measured in 5 adult non-pregnant rabbits each in 3 different seasons (January, April and September). Blood samples were taken from each rabbit every other day. There was a considerable variation in plasma E2 levels from one sampling day to another, irrespective of the season. The pattern of variation in E2 levels in individual rabbits tended to be cyclic and this cycle was roughly of the order of 8 days. There was no correlation between changes in E2 levels and those in the vaginal appearance.     

Pineal-related changes in cyclic AMP levels of rat medial basal hypothalamus

Summary Pinealectomy (Px) in adult male rats resulted in increased cyclic AMP accumulation by medial basal hypothalamic (MBH) explants 3 and 7 days after surgery. 24 h after superior cervical ganglionectomy (Gx) an augmented MBH cyclic AMP accumulation was observed. The effects of Px and Gx were additive, as revealed in animals subjected to Gx 3 days after Px.This study was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (N^o 6638) and from the Fundación Alberto J. Roemmers, Argentina.     

Influence of cyclic nucleotides on protein synthesis in vascular smooth muscle

Summary The incorporation of leucice-¹⁴C into protein in bovine mesenteric arteries was augmented by cyclic GMP (10^–3 M) and decreased by cyclic AMP (10^–3 M). There was no effect of 5 AMP (10^–3 M). The phosphodiesterase inhibiting drugs theophylline (10^–3 M) and papaverine (5×10^–5 g/ml) both decreased the leucine-¹⁴C incorporation.We are indebted to Mrs.Lena Burlin for hear assistance. Finacial support has been provided by the Swedish State Medical Research Council (No. 04X-101X-4498).