Uptake and metabolism of  15 N labelled cyanamide by cuttings of grapevine 15 N labelled cyanamide was taken up from nutrient solution by rooted grapevine cuttings. Precipitable N in shoots or roots contained up to 2/3 of total supplied 15 N. Arginine concentrations were higher during cyanamide feeding than in controls and declined to control levels after transfer into cyanamide free nutrient solution. In arginine extracted from shoots and roots after hydrolysis with 6 M HCl and column chromatography, 6-7 % of l5N originating from cyanamide was recovered.

The effect of nitrogen, molasses and low-grade rock phosphate enrichment on the production of organic acids and solubilization of phosphorus during wheat straw composting was studied. The presence of glycolic, oxaloacetic, succinic, fumaric, malic, tartaric and citric acids was detected in a water extract of the compost. Their occurrence was very high, resulting in higher solubilization of added insoluble P at the beginning of 30 days, but thereafter decreased drastically reaching negligible amounts at 120 days of composting. Nitrogen addition increased the production of all the above organic acids. Nitrogen + molasses addition also increased all except oxaloacetic acid at 30 days and glycolic acid at both 30 and 60 days of composting. However the incorporation of both Mussoorie phos and Hyper phos precipitated out oxaloacetic, tartaric and citric acids and hence their concentration decreased in the aqueous solution. (C) 1998 Published by Elsevier Science Ltd.

The influence of humic (HA) and fulvic acids (FA) from wheat Straw compost on the solubilization of Mussooriephos (MP) and Hyperphos (HP) was studied. Solubilization of P from both rock phosphates (RP) increased up to 4:1, RP to HA ratio and 6:1, RP to FA ratio and thereafter decreased drastically, becoming negligible when pH of the equilibrium reached 7.35 on increasing the ratios. P solubility from HP was higher at lower ratios in comparison to MP. Fulvic acids had 80% higher P solubilizing capacity than humic acids.The kinetic data indicated that the reaction was of first order and it was completed within 2.5 and 1.5 h respectively, for humic and fulvic acids.

Different genotypes were grown in Zn optimum and low Zn media. Growth characters, Zn concentration as well as CA activity were used as parameters. Low zinc slightly reduced plant height, number of leaves and dry weight of plants. In low zinc medium, marked effects were found in Zn concentrations. Giza-3 and Victor were less affected than other cultivars. The low zinc concentration in the growth media reduced CA activity at flowering stage. The effect on 1st. fully mature leaf was more pronounced than on 3rd old leaf. The used cultivars differed widely in their enzymatic activity. No correlation could be found between the effect of low Zn in the different genotypes on growth, Zn concentration and CA activity. However, Giza-3 cultivar produced highest dry matter with least Zn concentration.

AbstractWe evaluated the effect of compost enriched with rock phosphate on the yield and phosphate nutrition of rye grass in a calcareous clay loam soil. Enriched compost was prepared by composting either Mussoorie rock phosphate (MP) or Hyper rock phosphate (HP) separately with wheat straw for up to 120 days. A significant amount of insoluble P was solubilized from both kinds of rock phosphates and converted to water soluble, organic, and formic acid soluble P fractions during composting. MP-enriched compost (MPEC) and HP-enriched compost (HPEC) contain 0.30% and 0.34% water soluble P205, 1.94% and 1.42% organic P2O5 2.82% and 3.28% formic acid soluble P2O5, and 1.76% and 1.18% insoluble P2O5, respectively. In a greenhouse study, the yield of ryegrass (three cuttings) with both enriched composts was not significantly different from that of single superphosphate fertilizer (SSP). Phosphorus fractions of soil before sowing and after harvesting the rye grass showed that fixation of P with native soil calcium was much higher with SSP than with enriched composts. No significant differences were observed between MRP and HRP.

Vascularization and expression of blood-brain barrier (bbb)-associated morphological characteristics during the embryonic development of the mouse cnetral nervous system (CNS) was studied by ultrastructural analysis. At embryonic day 9 (E9) capillaries were only found in the perineural mesenchymal tissue. These capillaries showed fenestrations, and pericyte like cells (PC) were found joined to the vessel walls. Around E10 endothelial cells (EC) together with PC started invading the intraneural section. At this stage, the immigrating endothelial cells lost their fenestrations and exhibited numerous, partly extended junctional complexes, which appeared 'tight' in some places. A first intraneural anastomotic plexus was observed at E10, as evidenced by the presence of blood cells in all capillary lumens. While the number of junctional complexes remained constant in intraneural capillaries, the frequency of pinocytotic vesicles decreased significantly from E10 to E17. These findings indicate that from the first day of intraneural vascularization onwards, the morphological properties of the bbb are present in the early embryonic mouse cerebral cortex.

Protein expression patterns of morphologically different cloned capillary endothelial cells from porcine and murine brain cortices were examined. Type I cells, grown in medium containing heparin and endothelial cell growth factor (ECGF), exhibited a polygonal, cobblestone appearance and appeared to replicate the cells of the blood-brain barrier endothelium. Type II cells, grown in medium without heparin and ECGF, were elongated and appeared to replicate capillaries in central nervous system tissue.Cells of both phenotypes stained positive by the specific endothelial cell marker Bandeiraea simplicifolia lectin. The expression of alpha smooth-muscle actin (mRNA and protein) was taken as a marker for type II cells. By use of 2-D gel images and the GELLAB II system, a data base was created revealing that two proteins (90 kDa, pI 5.1, and 35 kDa, pI 5.7) were exclusively expressed in type I cells. Furthermore, the synergistic action of ECGF and heparin in respect to the phenotypic determination of cerebral endothelial cells was demonstrated.

Expression of smooth muscle alpha-actin and migratory behaviour of cloned cerebral endothelial cells (cEC) which exhibited two distinct phenotypes (type I, type II) were studied. Removal of mitogenic factors (alpha ECGF, ECGS) and heparin from the culture medium resulted in a smooth muscle-like appearance (type II) of the cells, expression of smooth muscle alpha-actin protein and smooth muscle actin mRNA and in an increased migratory activity. In contrast, addition of growth factors and heparin led to a cobblestone-like phenotype (type I) which lacked the expression of smooth muscle alpha-actin but expressed other proteins as determined by 2-D-gel electrophoresis.

The solubilization and availability of phosphorus were measured during decomposition of wheat straw and cattle urine with two types of low grade rock phosphate, Mussoorie rock phosphate (M. phos) and Hyperphos. The rate of solubilization of insoluble phosphorus from both M. phos and Hyperphos increased significantly up to 60 days and thereafter decreased with increasing decomposition time. Molasses incorporation enhanced solubilization throughout the decomposing period of 120 days; it reached a maximum of 24.5 and 14.7% of the added insoluble phosphate for both M. phos and Hyperphos, respectively. About 95 to 99% of the solubilized P was converted into organic forms. In view of very high turnover of organic P, the availability of solubilized P was measured by fractionating organic P (Po) substrates. In the presence of both rock phosphates, with or without addition of molasses, organic Po was redistributed between 4-6, 68-72, 12-16 and 10-12% in labile, moderately labile, moderately resistant and highly resistant fractions respectively at 120 days composting. M. phos solubilized more readily and retained a greater amount of labile and moderately labile Po than Hyperphos.

The expression of smooth muscle (sm) alpha-actin was studied in cloned capillary cerebral endothelial cells of two phenotypes. Type I cells were cultured in medium containing 10% FCS, heparin and ECGS (or alpha-ECGF) and stained positive for a specific endothelial cell marker (Bandeiraea simplicifolia). Depletion of heparin and ECGS resulted in a smooth muscle-like appearance after 2-3 days. Cells of this phenotype, (type II) stained positive for the endothelial cell marker and for sm alpha-actin. In contrast to type I cells, type II cells expressed sm alpha-actin protein and mRNA as evidenced by Immunoblots and Northern blots. This phenotypic switch was shown to be reversible and so was the expression of sm alpha-actin.

The nitrification inhibitor dicyandiamide [DCD] did not inhibit growth and respiration of N-fixing bacteria (Rhizobium leguminosarum andAzotobacter chroococcum) in cell suspensions with concentrations of 400 ppm DCD. Growth ofRhizobium leguminosarum was inhibited by 17% with 100 ppm nitrapyrin (N-Serve), but respiration was not affected. Growth ofAzotobacter chroococcum was inhibited by 10 ppm (10%) and 100 ppm nitrapyrin (50%); in the latter case, respiration was also impaired (36%). Thiourea only caused a minor growth inhibition ofAzotobacter chroococcum with 100 ppm (8%) and had no effect onRhizobium leguminosarum.

Effects of the inhibitors dicyandiamide (DCD), nitrapyrin (N-Serve, NS), and thiourea (TU) on growth and metabolism ofNitrosomonas europaea were tested under laboratory conditions. Growth of a pure culture was completely suppressed by 10 ppm NS and 0.5 ppm TU; inhibition by 300 ppm DCD was 83%. Ammonia oxidation and respiration of Nitrosomonas cell suspensions were reduced by 93% (10 ppm NS), 95% (0.5 ppm TU), and 73% (300 ppm DCD).

The efficiency of the nitrification inhibitors dicyandiamide (DCD) and 1-amidino-2-thiourea (or guanylthiourea = GTU) in reducing losses from N fertilizers was investigated in two greenhouse experiments where leaching of nitrate-N was induced by percolation at 3 and 5 weeks after fertilization.

The production of humic substances and their retention capacities for phosphorus and calcium released during composting of wheat straw with two types of low-grade rock phosphate were examined. Relative quantities of humic acids increased with increase of composting time, while fulvic acids production decreased after 30 days of composting. The addition of both Mussoorie and Hyperphos retarded humic acids production and enhanced fulvic acids production. Molasses incorporation had no effect on humic acids but increased fulvic acids production. The production of humic acids and their retention capacity for P and Ca were greater in the presence of Mussoorie phosphate than in the presence of Hyperphos, but fulvic acids formation was higher with Hyperphos. About 80–85% P and 90–95% Ca retained by the total humic substances were found in the fulvic acids fraction.