3'5'-Cyclic AMP phosphodiesterase activity in the internal and external layers of human myometrium at the end of pregnancy]

The hydrolysis of cAMP by phosphodiesterase was studied in whole homogenate from human myometrium at the end of the pregnancy before onset of labour. Tissue samples were taken from outer and inner layers of placental and anti-placental sites. Kinetic analysis shows in every case two apparent Km values for low and high cAMP concentrations in the order of 1 x 10(-5) M and 1 x 10(-4) M. On the other hand Vmax values are lower for the enzyme isolated from the placental site than for the one isolated from the anti-placental area. In the 4 zones studied, an appreciable proportion of the low Km enzyme is present.     

Interconvertibility of molecular forms of 3'5' cyclic AMP phosphodiesterase of human platelets]

Three forms of cyclic AMP phosphodiesterase from human platelets are resolved upon sucrose gradient centrifugation : 2.5S (monomer), 4.8S (dimer) and 7S (tetramer). They are interconvertible and form an association-dissociation equilibrium depending on the concentration of enzyme. The dissociated form has a high Km for cyclic AMP (Km : 3-5.10(-4) M) whereas the associated form has a low Km (Km : 3-5.10(-5) M).     

Demonstration of fructose 1,6-bisphosphatase in human term placenta

Summary A proteolysed form of fructose 1,6-bisphosphatase (Fru-P₂ase) has been detected and characterized in human term placenta. The extract was found to contain very low levels of activity with an alkaline pH optimum. Western blotting demonstrated a polypeptide of Mr 26,000, instead of the subunit of Mr 36,000 observed in native mammalian Fru-P₂ases.     

Demonstration of fructose 1,6-bisphosphatase in human term placenta.

A proteolysed form of fructose 1,6-bisphosphatase (Fru-P2ase) has been detected and characterized in human term placenta. The extract was found to contain very low levels of activity with an alkaline pH optimum. Western blotting demonstrated a polypeptide of Mr 26,000, instead of the subunit of Mr 36,000 observed in native mammalian Fru-P2ases.     

Renal effects of 8-substituted derivatives of adenosine 3',5'-cyclic monophosphate in dogs

The renal effects of nine, 8-substituted derivatives of 3',5'-cyclic monophosphate were studied in anesthetized mongrel dogs. Infusion of the compounds into a renal artery resulted in an increase of renal blood flow without any effect on blood pressure. Diuretic and natriuretic effects are evident with 6 of the 9 derivatives. As these 8-substituted analogues exert renal effects in a manner similar to that seen with the parent nucleotide, cyclic adenosine 3',5'-monophosphate, they may serve as useful pharmacological agents in vivo.     

Lack of effect of neurotransmitters on cyclic AMP phosphodiesterase activity in an insect CNS

Summary The inhibition of cyclic nucleotide phosphodiesterase from the nerve cord ofManduca sexta was studied using theophylline as a model compound. 11 putative neurotransmitters had no effect on enzyme activity.Supported in part by NIH grant NS-09161-20 to R. W. Newburgh     

Phosphorylase activity of human placenta perfused in vitro: effect of gonadotropins, dibutyryl cyclic AMP and prostaglandins]

The gonadotropic hormones stimulate the glycogen phosphorylase activity of human full-term placenta perfused in vitro. This effect is reproduced by dibutyryl cAMP and PG F2alpha and accompanied by an increased glucose liberation in the perfusion fluid.     

Lack of effect of neurotransmitters on cyclic AMP phosphodiesterase activity in an insect CNS.

The inhibition of cyclic nucleotide phosphodiesterase from the nerve cord of Manduca sexta was studied using theophylline as a model compound. 11 putative neurotransmitters had no effect on enzyme activity.     

Inhibition of the 3' to 5' exonuclease activity of the DNA polymerase I of Escherichia coli by deoxyribonucleotides

The 3' à 5' exonuclease activity of E. coli DNA-polymerase I is inhibited by nucleotides and deoxynucleotides at concentrations (< 1 mM) where polymerase activity is not affected. This inhibitory effect depends on the nature of the excised deoxynucleotide, excision of purines being much less inhibited than that of pyrimidines. It does not depend on the purine or pyrimidine nature of the inhibitor.     

Inhibition of cyclic 3′, 5′-nucleotide phosphodiesterase activity by diuretics and other agents

Résumé Différent composés organo-mercuriels ainsi que l'acide éthacrinique inhibent les phosphodiestérases de l'AMP cyclique, du cur de cobaye, de buf et de rat, des plaquettes de rat et de l'homme ainsi que du cerveau de rat.