Changes in binding of JH-III in hemolymph of adult femaleLocusta migratoria

Summary Hemolymph from adult femaleLocusta migratoria migratorioides was analyzed for binding of juvenile hormone III (JH-III) after allatectomy and transection of thenervus corporis allati 1 (NCA-I). These operations did not affect the apparent dissociation constant of the binding (Kd=3.3 10^–8 M). The concentration of binding sites exhibited fluctuations in relation to age and type of operation: an increased concentration of binding sites in females with disconnected corpora allata and a decreased concentration in allatectomized females. The changes in concentration of binding sites was not due to differences in water content or hemolymph volume in operated animals. The hemolymph protein concentration was reduced after NCA-I transection and even more after allatectomy. However, variations in protein concentration did not correlate with changes in concentration of JH-III binding sites. The changes in binding site concentration were related to changes in JH-titer.     

The oxidation of cystamine and other sulfur-diamines by diamine-oxidase preparations

Riassunto Le diamine solforate cistamina e lantionamina sono ossidate con velocità comparabile a quella della cadaverina dalla diamino-ossidasi. Il solfone della lantionamina è ossidato più lentamente ed il disolfossido della cistamina non è ossidato affatto. Benchè dall'ossidazione della cistamina si produca una mole di ammoniaca per mole di substrato, il consumo di ossigeno è due volte più elevato del teorico, indicante una ulteriore ossidazione del prodotto metabolico della reazione. Tuttavia taurina, ipotaurina e solfati, non sono determinabili nel deproteinizzato finale.     

Hydra vulgaris ω10-lipoxygenase is used in vivo to synthesize new α-linolenic acid metabolites

Previous studies conducted in cytosolic extracts of the freshwater hydrozoanHydra vulgaris led to the finding of an abundant 11(R)-lipoxygenase catalyzing the peroxidation of polyunsaturated fatty acid (PUFAs) on the tenth carbon atom from the aliphatic end (10 peroxidation). Here we describe experiments aimed at identifying the actual metabolites generated in vivo by such enzymic activity. Homogenates ofH. vulgaris polyps were analyzed by HPLC. This showed the presence of three major components chromatographically identical to three metabolites obtained when incubating the homogenates with exogenous -linolenic acid (-LA). The presence, in extracts of polyps prelabelled with [¹⁴C]--linolenic acid, of radioactive metabolites displaying the same chromatographic properties, substantiated the hypothesis that the natural products isolated in vivo are derived from -LA. Gas chromatographic analyses revealed that this was the most abundant PUFA in both free and phosphoglyceride-bound fatty acid pools. [¹H]-NMR analysis of the endogenous substances, carried out in comparison with products obtained from exogenously incubated -LA, indicated that their structures were those of 9-hydroxy-, 9-hydroperoxy- and 9-keto-octadeca-10E-12Z-15Z-trienoic acids (9--HOTrE,-HPOTrE and-KOTrE).Hydra homogenates transformed 9--HPOTrE partly into 9--HOTrE and partly into 9--KOTrE. Chiral phase HPLC conducted on 9--HOTrE established that this metabolite was composed mostly of theR anantiomer. These observations, and the finding that the presence of exogenous arachidonic acid in incubated homogenates significantly reduces the production of -LA metabolites, provide strong evidence that these compounds are produced by an enzymic activity identical to the previously-describedH. vulgaris (R)-10-lipoxygenase. Further experiments suggested that -LA, acting as the native substrate for this enzyme, is mainly esterified on the 2 position ofHydra phosphoglycerides, and that the production of the -LA metabolites described here for the first time from natural sources, can be potentially enhanced in vivo by stimuli activating phospholipase A₂.     

Ammonia photoproduction byCyanospira rippkae cells ‘entrapped’ in dialysis tube

Summary The photoproduction of ammonia by cells of the heterocystous cyanobacteriumCyanospira rippkae in the presence of the glutamine synthetase inhibitor, L-methionine D,L-sulfoximine (MSX), was investigated. The time course of changes in protein, pigment and carbohydrate concentrations and the C₂H₂-reducing activity of nitrogenase in MSX treated and untreated filament suspensions was also determined. The results show that nearly 40 h after MSX addition the cells are able to recover from the nitrogen starvation induced by the inhibitor by themselves, without the removal of MSX or the addition of nitrogenous compounds. Biliproteins, mobilized as a consequence of MSX addition, seem to play a key role in the process of cell recovery. These findings were exploited in a semicontinuous ammonia producing process with cells immobilized in a dialysis tube photobioreactor.