Ronald J. Quinn

The occurrence of prostaglandins PGE2 and PGF2α in a plant - the red alga Gracilaria Lichenoides.

Abstract Prostaglandins PGE2 and PGF2α were isolated from the aqueous extract of the red alga Gracilaria lichenoides , after an investigation of the extracts anti-hypertensive properties.

Characterization of the neurotoxic constituents of Conus geographus (L) venom.

Abstract The crude venom of the marine gastropod Conus geographus (L) has been separated into three lethal constituents and their actions at the mammalian neuromuscular junction examined. Chromatography of the venom of Sephadex G-50 gave one toxic fraction, which was resolved by ion exchange chromatography on SP-Sephadex into three toxic components. These components were individually purified by diafiltration and Sephadex G-15 chromatography to give Toxins I,II and III. Toxins I and II in concentrations greater than 5 ug/ml reduced the amplitude of end-plate potentials and miniature end-plate potentials; Toxin I also blocked the depolarization of muscle fibres produced by carbachol; neither toxin affected the generation of action potentials in muscle fibres. Toxin III in concentrations greater than 5 ug/ml rapidly and reversibly blocked the generation of action potentials in muscle fibres; it had no effect on resting membrane potential nor on the amplitude of epps or mepps. It also slowly blocked the compound action potential recorded from isolated sciatic nerves but this was not reversible in the experiments. The rate at which this toxin blocked action potentials was increased by stimulation of the preparation. It is suggested that Toxin III acts by blocking the inward movement of sodium during activity. Toxin III appeared to be a nonadeca or eicosa peptide possibly having a cystine residue in the N-terminal position.

Stimulation of guinea-pig brain adenylate cyclase by adenosine analogues with potent pharmacological activity in vivo

Abstract 1-Methylisoguanosine, a marine natural product with potent muscle-relaxant and cardiovascular actions in vivo , interacts directly with adenosine receptors in guinea-pig brain slices to stimulate adenylate cyclase. These effects are blocked by theophylline. Comparison of the in vivo pharmacological activity of a number of synthetic analogues of 1-methylisoguanosine with in vitro adenylate cyclase-stimulating ability indicates that compounds lacking the latter biochemical activity have little muscle-relaxant activity. Adenosine is a potent stimulator of adenylate cyclase but is inactive in vivo because of rapid removal from the extracellular environment by uptake and deamination. Unlike adenosine, 1-methylisoguanosine is resistant to deamination and is only poorly accumulated by brain tissue slices or homogenates containing synaptosomes. Since it is an extremely weak competitive inhibitor of adenosine deaminase and only a weak inhibitor of adenosine uptake, it is unlikely to act by potentiating the effects of adenosine itself at extracellular receptors. Thus, the pharmacological effects of 1-methylisoguanosine are apparently due to its actions as a long-lasting adenosine analogue.

13 C n.m.r. spin–lattice relaxation time measurements determining the major tautomer of 1-methylisoguanosine in solution

Analysis of the contributions of 13C–1H dipolar interactions to the 13C n.m.r. spin-lattice relaxation times of the quaternary carbons of 1-methylisoguanosine establishes that the predominant tautomer in solution is the 2-keto, 6-amino form.

3-Hydroxy-4-methoxyphenethylamine, the cardioactive constituent of a soft coral

Intravenous administration to rats of the aqueous extract of the soft coralNephthea sp. caused an increase in heart rate and blood pressure. The cardioactive constituent was isolated and shown to be 3-hydroxy-4-methoxyphenethylamine.

The occurrence of 5-hydroxytryptamine in the holothurian,Pentacter crassa

5-Hydroxytryptamine (5-HT) and hypoxanthine were isolated chromatographically from the holothurianPentacter crassa. This study was initiated as a result of the observed hypotensive activity of aP. crassa extract. This activity was also encountered in extracts of the holothuriansThelenota ananus andStichopus chloronatus and can be attributed to 5-HT.