The isolation and specificity of alfalfa lipoxygenase

Partial purification of the lipoxygenase from alfalfa seed was accomplished by fractionation of the protein with (NH4)2SO4, phosphate, heavy metal salts and ultracentrifugation. About 24% of the original activity was recovered. The partially‐purified alfalfa lipoxygenase enzyme was free of hydroperoxide‐decomposing activity and was used to determine the positional specificity of linoleic acid oxidation by alfalfa lipoxygenase. Combined gas liquid chromatography‐mass spectrometry was used to analyze known mixtures of 10‐ and 12‐hydroxystearic acid derivatives and was satisfactory for the quantitative determination of the ratio of each component. This combination was used to analyze mixtures containing position isomers of hydroxy fatty acids without separation of each individual compound by other methods. Hydroperoxides produced from linoleic acid oxidation catalyzed by alfalfa lipoxygenase were converted by sodium borohydride reduction, catalytic hydrogenation and bis(trimethylsilyl)acetamide silylation to their corresponding trimethylsilyl either esters and the positional distribution was studied. The 9‐ and 13‐linoleate hydroperoxides produced by alfalfa lipoxygenase were in equal concentrations (50∶50) whereas the distribution for soybean lipoxygenase was 70% 13‐ and 30% 9‐hydroperoxides.

Effects of antigonadotrophins on ovarian function

Immunologic techniques have proven to be useful tools in characterizing the action of pituitary protein hormones on the target organs. Specifically, an antibody to luteinizing hormone can prevent ovulation, delay implantation, or cause fetal resorption depending on the time of administration of the antiserum to female rats. The immunologic interference with ovarian function appears to be associated with the steroidogenesis process during early pregnancy, and with fetal placental function during mid pregnancy in the rat. Progesterone synthesis is diminished, probably by the prevention of luteinizing hormone from stimulating the <i>&#916;</i>⁵&#914; hydroxysteroid dehadrogenase within the interstitial tissue of the ovary. In later pregnancy, the antibody combines with specific cells within the placenta, thereby eliminating any placental influence on the ovarian steroidogenic process.

Modulation of noradrenaline incorporation by nerve activities in the rat submaxillary gland

1. Rats were anaesthetized with chloralose and prepared for electrical stimulation of the cervical sympathetic trunk. The effect of such stimulation was studied on the incorporation of intravenously infused [(3)H]noradrenaline, [(3)H]adrenaline or [(3)H]dopamine by the submaxillary gland.2. A train of 200 stimuli every min for 30 min at 20/sec increased the total incorporation of [(3)H]noradrenaline by 92% over the unstimulated side of the gland, at 50/sec by about 200% and at 3.3/sec by about 30%. The incorporation of [(3)H]adrenaline and of [(3)H]dopamine was also increased by sympathetic stimulation.3. The increases in unaltered [(3)H]noradrenaline and its metabolites were proportional to the increase in total radioactivity.4. Mean venous outflow from the gland was decreased by 15-30% by the sympathetic stimulation.5. After elimination of extraneuronal binding of noradrenaline by ligation of the common excretory ducts, nerve stimulation still increased incorporation.6. Inhibition of normetanephrine production by pyrogallol did not antagonize the nerve impulse-mediated increase of [(3)H]noradrenaline incorporation. alpha-Methyltyrosine was also without effect.7. Desmethylimipramine and bretylium completely abolished the nerve impulse-mediated increase of [(3)H]noradrenaline incorporation in concentrations which did not affect the control uptake or abolish adrenergic transmission.8. Reserpine, guanethidine and phenoxybenzamine antagonized both the control and nerve impulse-mediated incorporations of [(3)H]noradrenaline.9. The results indicate that nerve impulses modulate the incorporation of transmitter amine at the neuronal membrane. Possible mechanisms for this modulation are discussed.

Biogenesis of oxalate in plant tissues

Red beet root discs aerated in potassium phosphate for 2 to 3 days and young spinach leaves actively produce oxalate. A series of labeled compounds was supplied to each of these tissues to determine the extent of conversion to oxalate. Similar results were obtained with the 2 tissues except that in the leaf tissue glyoxylate and glycolate were outstandingly good precursors. Carbon from glucose, acetate, and particularly from some acids of the tricarboxylic acid cycle was recovered in oxalate. Extracts from both tissues were found to contain an enzyme which converts oxaloacetate to oxalate and acetate. The enzyme was partially purified and some of its properties are described. A pathway of oxalate synthesis which does not include glycolate or its oxidase is therefore proposed.