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87 records · Page 5Linked to original sources
PubMed1984

Relationship between cycles in level of serotonin N-acetyltransferase activity and cyclic GMP content of cultured chick pineal glands.

We examined effects of supplements on cycles in cyclic GMP content and serotonin N-acetyltransferase (NAT) activity in cultured chick pineal glands. Increases in cyclic GMP content and NAT activity were stimulated by 1-ethyl-4(isopropylidene-hydrazino)-1H-pyrazolo[3,4-b]pyridene-5-c arboxylic acid, ethyl ester, hydrochloride and isobutylmethyl xanthine under diurnal illumination and in constant darkness, but subsequent decreases were not inhibited. Hypoxanthine had little effect on NAT activity under all lighting conditions, or on the content of cyclic GMP in glands cultured in the dark. However, it markedly stimulated accumulation of cyclic GMP in illuminated cultures. EGTA or additional Ca2+ had no effect on pineal NAT activity. However, EGTA markedly stimulated accumulation of cyclic GMP both in the light and in the dark. Supplementary Ca2+ slightly retarded accumulation of cyclic GMP in the dark but stimulated slightly in the light.

1-Methyl-3-isobutylxanthine↗
PubMedDate not supplied

Male pronuclei formation release of phosphorylation of histone H-3 during decondensation of human sperm nuclei activated in vitro by heparin.

The release and phosphorylation/dephosphorylation mechanisms of human spermatozoa histone during nuclei in vitro decondensation by heparin was studied. Washed sperm cells were incubated in the presence of 32P and in the absence or presence of heparin. The results showed an increase in the incorporation of 32P of 20 times greater in the presence of heparin than in the absence of heparin (the control sample). In some cases the incorporation of 32P into histones was confirmed by its isolation. To validate these results a phosphorylation kinetic of isolated sperm histone, used as a substrate, was performed. The amount of 32P was not a linear function of time, and maximal phosphorylation was reached in 60 min. A measurement of 32P incorporated as a function of the amount of histone, shows a linear relationship of up to 50 micrograms of protein, with a rapid saturation thereafter with the incorporation of 220 nm and with a KD = 442 x 10(-6) mol/L. 32P incorporation, independent of exogenous cAMP, was related to alkaline pH but was totally dependent on temperature--with a maximum of 37 degrees C. The only histone released was histone H-3. Phosphorylation/dephosphorylation is involved during male pronuclei formation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Dissociation of lipolysis from the levels of cyclic AMP in rat epididymal fat cells.

Two compounds, theophylline and 8-aza-9-furfuryl-adenine (SQ 4665), were found to maximally stimulate lipolysis in preparations of rat epididymal fat cells in the absence of exogenous hormones. Cyclic AMP levels in lipocytes maximally stimulated by either agent alone were unchanged from control levels. In contrast, lipolysis stimulated by either epinephrine alone or in combination with several cyclic nucleotide phosphodiesterase inhibitors correlated well with increases in the levels of cyclic AMP observed. These results suggest the presence of a non-cyclic AMP dependent pathway for the stimulation of lipolysis in rat epididymal fat cells.

Adenine↗
PubMed1977

Influence of cyclic nucleotides and a phosphodiesterase inhibitor on in vitro human blood neutrophil chemotaxis.

Cyclic AMP and dibutyryl cyclic AMP as well as several 8-substituted analogs of cyclic AMP inhibited in vitro human blood neutrophil chemotaxis. Cyclic GMP enhanced chemotaxis. 8-substitution on the cyclic GMP nucleus markedly dampened the cyclic GMP effect. SQ 20,009, a potent phosphodiesterase inhibitor when tested alone inhibited chemotaxis; it potentiated the inhibition or enhancement of chemotaxis when combined with cyclic AMP or cyclic GMP, respectively.

Chemotaxis, Leukocyte↗
PubMedDate not supplied

[Neuron membrane depolarization under the influence of cyclic-3',5'-adenosine monophosphate and its possible role in the neuronal molecular computer (MC)].

The separate fourth intracellular microelectrode was used for controlling the conditions of cyclic nucleotide injection in neurons of Helix pomatia. Ionoforetic increase in intracellular cyclic AMP concentration elicits membrane depolarization in many neurons. Phosphodiesterase inhibitors 3-isobutyl-1-methylxantine and SQ-20009 prolong this depolarization and raise its level. In cell F-1 of helix brain sometimes cAMP induces weak hyperpolarization, but this response turns to usual depolarization after 3-isobutyl-1-methylxantine application. It is suggested that cell molecular computer has an analog input, where diffusion of cAMP, cGMP and Ca++ being a modelling process. Adenylate cyclase and guanylate cyclase and ionic channels of membrane are regulated sources. Phosphodiesterases with Ca2+-binding activator proteins are molecular out flowers and protein kinases--detectors that transform the data about the concentrations of cAMP and cGMP into codes for MCC. Protein kinases control over the activity of proteins directly. The depolarization effect on neuron membrane seems to be associated with protein kinase activation or with direct action of cAMP on phospholipase.

Adenylyl Cyclases↗
PubMed1982

Biological substrates of anxiety: benzodiazepine receptors and endogenous ligands.

Benzodiazepines have been shown to produce most, if not all, of their pharmacological effects by directly interacting with specific recognition or receptor sites within the CNS. The presence of benzodiazepine receptors has prompted many studies as to their possible physiological significance, including attempts at isolating an endogenous ligand. To data a number of substances including the purines inosine and hypoxanthine, nicotinamide, beta-carbolines, and an unidentified peptide factor have been isolated and postulated as being endogenous ligands. A number of these compounds have also been shown to either mimic or antagonize the behavioral effects of benzodiazepines, although it is still unclear whether these occur under physiological conditions. More recent biochemical studies have established a functional (and perhaps structural) relationship between te benzodiazepine receptor and the receptor for gamma amino butyric acid (GABA), the major inhibitory neurotransmitter in brain. It now appears that the benzodiazepine receptor actually exists as a "supramolecular complex" consisting of a GABA receptor and an associated chloride channel. A number of anxiolytic drugs including the barbiturates and pyrazolopyridines appear to act through these associated "regulatory" sites rather than directly on the benzodiazepine recognition site.

Animals↗
PubMed1984

Physostigmine inhibition of 3',5'-cyclic AMP phosphodiesterase from cat sciatic nerve.

This study was designed to determine whether cholinergic drug interaction with cyclic (c) AMP phosphodiesterase (PDE) might account for part of the effects of this class of drugs at the neuromuscular junction. The activity levels of both high- and low-affinity forms of cAMP PDE from cat sciatic nerve were examined for drug inhibition or activation. Of the cholinergic drugs tested, only physostigmine and Tacrine produced significant cAMP PDE inhibition. Physostigmine was 10 times more potent than theophylline and half as potent as SQ 20,009 (known PDE inhibitors) in inhibiting motor nerve cAMP PDE. Tacrine inhibited this enzyme at concentrations comparable with theophylline. None of the other drugs tested (diisopropylfluorophosphate, edrophonium, neostigmine, ecothiophate, carbachol or d-tubocurarine) produced significant changes in cAMP PDE activity. The inhibitory effects of physostigmine were shown to be pH independent over a range of 7.0 to 8.5. Kinetic studies indicated a mixed form of inhibition for physostigmine and Tacrine comparable with that seen for theophylline. These data indicate that the anticholinesterase activity of physostigmine and Tacrine do not adequately describe the facilitatory actions of these drugs at the motor nerve ending.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Motor nerve terminal facilitatory action of SQ 20009: an inhibitor of cyclic nucleotide phosphodiesterase.

Facilitatory effects of SQ 20009 [1-ethyl-4-(isopropylidenehydrazine)-1H-pyrazolo-(3,4-b)-pyridine-5-carboxylic acid, ethyl ester, HCl] were investigated at the frog sartorious neuromuscular junction. A dose-dependent increase in miniature end-plate potential frequency occurred without changes in miniature end-plate potential amplitude. Significant increases in the amplitude and the rate of rise of the end-plate potential and reduction in the incidence of end-plate potential failures were observed in magnesium blocked muscle. The increase in end-plate potential amplitude and rate of rise appeared calcium dependent. No significant changes in passive membrane resistance or muscle membrane sensitivity to acetylcholine were observed. Twitch studies employing direct and indirect stimulation of the rat diaphragm preparation demonstrated a preferential facilitation of the indirect response rather than a direct action on the muscle fiber. The facilitatory effect of SQ 20009 on evoked and spontaneous release were of approximately equal orders of magnitude, suggesting that the drug may affect a common mechanism in the two release processes.

Acetylcholine↗