Subcellular localization of cyclo-oxygenase-prostaglandin E2 synthetase complex in goat vesicular gland by catalytic activity analysis

The catalytic activity of he cyclo-oxygenase prostaglandin E₂ synthetase complex in subcellular organelles of goat vesicular gland was determined. The enzyme activity was found to be located mostly in the rough endoplasmic reticulum and partly in the nuclear membrane; comparatively very little activity could be detected in the smooth endoplasmic reticulum. There was no detectable activity of the enzyme in the plasma membrane.     

Levuglandin E2 crosslinks proteins

Levuglandin E₂ (LGE₂), a γ-ketoaldehyde produced by rearrangement of the prostaglandin endoperoxide PGH₂ under the aqueous conditions of its biosynthesis, causes extensive intermolecular crosslinking of ovalbumin at pH 6 or pH 7 and 37°C. The time dependence of protein oligomerization is monitored by SDS-PAGE. Effects of pH and concentration on the extent of LGE₂-induced crosslinking are examined. The efficacy of LGE₂ for inducing crosslinking is compared with other oxidative metabolites of arachidonic acid (AA), including the prostaglandins PGE₂, PGD₂, PGA₂, PGB₂, and PGF_2α, as well as malondialdehyde and E-4-hydroxy-non-2-enal. LGE₂ is orders of magnitude more effective in crosslinking protein than any other cyclooxygenase or lipoxygenase metabolite of AA tested.     

Sterols of some Clerodendrum species (Verbenaceae): occurrence of the 24 alpha- and 24 beta-epimers of 24-ethylsterols lacking a delta 25-bond

The configurations at C-24 of 24-alkylsterols of six samples of Clerodendrum species (Verbenaceae) - the aerial parts of C. fragrans, C. inerme, C. infortunatum, C. scandens, and C. siphonanthus, and the seeds of C. infortunatum - were examined by NMR. All samples contained 24 beta-ethylsterols possessing a delta 25-bond, clerosterol and 22-dehydroclerosterol, as the dominant sterol components. The other 24-ethylsterols lacking a delta 25-bond, 24-ethyl-22-dehydrocholestanol, 24-ethylcholesterol, and 24-ethyl-22-dehydrocholesterol, which were present as minor components, were shown to be mixtures of the 24 alpha- and 24 beta-epimers, with the 24 alpha-epimers predominating in all cases. Four minor 24-methyl-sterols, 24-methylcholestanol, 24-methylcholesterol, 24-methyl-22-dehydrocholesterol, and 24-methyllathosterol, were shown to be C-24 epimeric mixtures, whereas two others, 24-methyl-22,25-bisdehydrocholesterol and 24-methyl-22-dehydrolathosterol, were found to be present only as the 24 beta-epimers. This is the first report of the occurrence of 24 beta-ethyl-22-dehydrocholestanol in higher plants.     

Pharmacological and electrophysiological analysis of nicotine induced apnoea in the cat

Intravenous nicotine (20-60 micrograms/kg) produced an initial brief apnoea followed by hyperventilation in anaesthetized cats. The apneic response to nicotine remained uneffected by atropine, by phentolamine or propranolol. Hexamethonium and guanethedine sulphate antagonized the apneic response. In bilateral vagotomized cats, nicotine failed to produce respiratory apnoea. Veratridine and phenyldiguanide produced apnoea similar to that produced by nicotine within 2-3 sec. administered intraartrially. Nicotine failed to stimulate pulmonary stretch receptors as did veratridine in artificially ventilated cats. The alpha and gamma motoneurone activity of inspiratory and expiratory muscles and the phrenic efferent activity were inhibited during apnoea. These inhibitions were absent in vagotomized cats. In conclusion, these results suggest that the nicotine induced apneic response is mediated through pulmonary vagal afferents, probably through J-receptors, which in turn inhibit the motoneurone activity involving the respiratory muscles.     

Control of ornithine decarboxylase activity in jute seeds by antizyme

The control of ornithine decarboxylase activity by antizyme was studied during early germination of jute seeds(Corchorus olitorius). When 2 mM of putrescine and spermidine were applied to the germinating medium, the enzyme activity was markedly inhibited (1.7-fold) during 16 h imbibition. This inhibition could be attributed to the formation of an inhibitory protein termed antizyme. The antizyme was partially purified from jute and barley seedlings. The activity of jute ornithine decarboxylase antizyme was weaker than that of barley.