Xenobiotic oxidation by cytochrome P-450-enriched extracts of Streptomyces griseus

Crude extracts of Streptomyces griseus grown on soybean flour-enriched medium contain high levels of cytochrome P-450. The cytochrome P-450-enriched fractions, obtained by ammonium sulfate fractionation (30-50% saturation), catalyze the NADPH-dependent oxidation of a variety of xenobiotics when complemented with both spinach ferredoxin:NADP+ oxidoreductase and spinach ferredoxin. Reactions observed are aromatic, benzylic and alicyclic hydroxylations, O-dealkylation, non-aromatic double bond epoxidation, N-oxidation and N-acetylation.     

25-Hydroxylation of 1 alpha-hydroxyvitamin D-3 in rat and human liver

1 alpha-Hydroxyvitamin D-3 25-hydroxylase activity was measured in subcellular fractions of rat and human liver. The formation of 1,25-dihydroxyvitamin D-3 was determined by high pressure liquid chromatography. In rat liver 1 alpha-hydroxyvitamin D-3 25-hydroxylase activities were found in the purified nuclei, the heavy mitochondrial fraction and the microsomal fraction. The enrichment of 25-hydroxylase activity was highest in the heavy mitochondrial fraction. With this fraction a minimum amount (about 0.5 mg) of protein was required before formation of 1,25-dihydroxyvitamin D-3 could be detected. Above this amount the reaction was linear with amount of protein up to at least 2 mg/ml. The reaction was also linear with time up to 60 min. An apparent Km value of 2 X 10(-5) M was found. The mitochondrial 25-hydroxylase was stimulated by addition of cytosolic protein or bovine serum albumin. The degree of stimulation was dependent on the amount of mitochondrial protein present in the incubation mixture. Maximal stimulation was seen with 0.2 mg/ml of either protein in the presence of 0.5 mg mitochondrial protein. The stimulating effect remained after heating the protein for 5 min at 100 degrees C. The cytosolic protein did not stimulate a reconstituted mitochondrial 1 alpha-hydroxyvitamin D-3 25-hydroxylase. The mitochondrial vitamin D-3 25-hydroxylase was inhibited both by cytosolic protein and by bovine serum albumin. Human liver revealed only one 1 alpha-hydroxyvitamin D-3 25-hydroxylase activity located to the heavy mitochondrial fraction. The results are in agreement with previous studies on the localization of vitamin D-3 25-hydroxylase in rat and human liver. The difference in localization of the 25-hydroxylase between rat and human liver implies that studies on the regulation of the microsomal 25-hydroxylase in rat liver may not be relevant to the situation in human liver.     

Host tree resistance against the polyphagous wood-boring beetle Anoplophora glabripennis

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae: Lamiini) is an invasive wood‐boring beetle with an unusually broad host range and a proven ability to increase its host range as it colonizes new areas and encounters new tree species. The beetle is native to eastern Asia and has become an invasive pest in North America and Europe, stimulating interest in delineating host and non‐host tree species more clearly. When offered a choice among four species of living trees in a greenhouse, adult A. glabripennis fed more on golden‐rain tree (Koelreuteria paniculata Laxmann) and river birch (Betula nigra L.) than on London planetree (Platanus × acerifolia (Aiton) Willdenow) or callery pear (Pyrus calleryana Decaisne). Oviposition rate was highest in golden‐rain tree, but larval mortality was also high and larval growth was slowest in this tree species. Oviposition rate was lowest in callery pear, and larvae failed to survive in this tree species, whether they eclosed from eggs laid in the trees or were manually inserted into the trees. Adult beetles feeding on callery pear had a reduced longevity and females feeding only on callery pear failed to develop any eggs. The resistance of golden‐rain tree against the larvae appears to operate primarily through the physical mechanism of abundant sap flow. The resistance of callery pear against both larvae and adults appears to operate through the chemical composition of the tree, which may include compounds that are toxic or which otherwise interfere with normal growth and development of the beetle. Unlike river birch or London planetree, both golden‐rain tree and callery pear are present in the native range of A. glabripennis and may therefore have developed resistance to the beetle by virtue of exposure to attack during their evolutionary history.     

Sucrose and application of Rhizobium on seed

Summary Studies on the effect of different levels of sucrose in the slurry of peat-based Rhizobium inoculant on germination, seedling growth, and rhizosphere fungi of peanut and soybean revealed that the limits of tolerance for good germination were 2.5 and 5 per cent of the sugar, respectively. Fusaria and aspergilli were invariably present at all levels of sucrose whereas species of Penicillium, Myrothecium, Cunninghamella and Curvularia were isolated only from the rhizosphere at higher levels of the sugar     

Measurements of intra-and extracellular pH in the liverwort Conocephalum conicum during action potentials

During action potentials triggered by electricity and light, measurements of intra- and extracellular pH in the liverwort Conocephalum conicum L. were carried out by the use of antimony-filled H⁺-sensitive microelectrodes. Intracellular pH increased transiently by about 0.05 unit in the course of an action potential, while extracellular pH, measured at the surface of the thallus, remained unchanged. Switching the light off caused a transient increase in intracellular pH by less than 0.1 unit. Turning the light on produced a fast pH decrease by about 0.15 unit followed by a slow increase. When the light was intensive enough, the action potential thus triggered caused a slight increase in intracellular pH superimposed on the phase of a slow pH increment.
The magnitude and time course of the intracellular pH changes seem insufficient for a role as messenger between action potential and the up to 100% increase in the rate of respiration that has been registered in Conocephalum conicum as a consequence of excitation.