Control of nitrification of fertilizer nitrogen: Effect of inhibitors,banding and nesting

Laboratory incubation and field experiments were conducted to evaluate thiourea, ATC (4-amino-1, 2, 4 triazole hydrochloride) and N-Serve 24 E (2-chloro-6-trichloromethyl-pyridine) as inhibitors of nitrification of fertilizer N. In the incubation experiment, most of the added aqueous NH₃ or urea was nitrified at 14 days on both soils, but addition of the inhibitors to fertilizer N decreased the conversion of NH₄−N to NO₃−N markedly. There was less nitrification for ATC and thiourea but not for N-Serve 24 E when the fertilizers and the inhibitors were placed at a point as opposed to when mixed into soil. After 28 days, ATC and N-Serve 24 E were more effective in inhibiting nitrification than thiourea. ATC and N-Serve 24 E also inhibited release of mineral N (NH₄−N+NO₃−N) from native soil N. In the uncropped field experiment, which received N fertilizers in the fall, nitrification of fall-applied N placed in the 15-cm bands was almost complete by early May in the Malmo soil, but not in the Breton soil. When ATC or thiourea had been applied with urea, nitrification of fall-applied N was depressed by May and the recovery of applied N as NH₄−N was greater with increasing band spacing to 60 cm or placing N fertilizer in nests (a method of application where urea prills were placed at a point in the soil in the center of 60×60 cm area). In late June, the percentage recovery of fall-applied N in soil as NH₄−N or mineral N increased with wide band spacing, or nest placement, or by adding ATC to fertilizer N on both soils. These results indicate that placing ammonium-based N fertilizers in widely-spaced bands or in nests with low rates of inhibitors slows nitrification enough to prevent much of the losses from fall-applied N. Scientific Paper No. 552, Lacombe Research Station, Research Branch, Agric, Can.     

Unsuccessful induction of low-zone tolerance to bovine serum albumin injected into the subarachnoid space

Introduction of T-dependent antigens into the subarachnoid space (isas) resulted in higher systemic antibody responses in mice than injections into the peritoneal cavity (ip) or other sites commonly used for immunization. Antibody production in isas immunized mice was not increased by treatment with cyclophosphamide (Cy) at doses known to abolish T-suppressor-cell activity, but such treatment increased antibody production in ip immunized mice toward the higher level which was observed in the isas immunized animals. Suppressor cell-dependent low zone tolerance (LZT) to TNP-BSA could not be induced by isas injections of deaggregated BSA (d-BSA). Conversely, mice which were unresponsive to ip injected d-BSA showed consistent systemic antibody responses when the antigen was injected isas. These observations indicate that immune responses initiated within the CNS are associated with relatively ineffective induction of systemic suppressor cell activity.     

Studies on the C-24 configurations of Δ7-sterols in theseeds of Cucurbita maxima

Uncertainties surrounding the structures of the Δ⁷-sterols in the seeds of Cucurbita maxima have been resolved. Seven components were found by TLC, GLC, HPLC, mass spectrometry and ¹H NMR. They were 24β-ethyl-5α-cholesta-7,22,25(27)-trien-3β-ol, 24β-ethyl-5α-cholesta-7,25(27)-dien-3gb-ol, avenasterol, spinasterol, 24-dihydrospinasterol, 24ζ-methyllathosterol and 25(27)-dehydrofungisterol. The ¹H NMR spectra indicated that the sterols with an ethyl substituent at C-24 occurred in the absence of their C-24 epimers. This seems to be the first instance of the detection of 25(27)-dehydrofungisterol in a higher plant.     

Changes in composition and function of thylakoid membranes as a result of photosynthetic adaptation of chloroplasts from pea plants grown under different light conditions

The hypothesis that chloroplasts having different light-saturated rates of photosynthesis will have different proportions of the intrinsic thylakoid complexes engaged in light-harvesting and electron transport (Anderson, J.M. (1982) Mol. Cell. Biochem. 46, 161–172) has been tested. Peas were grown in light regimes which varied in light intensity, quality and time of irradiance, and ranged from sunlight through red to blue-enriched light of very low radiation. The electron-transport capacity at saturating light of Photosystem I and Photosystem II of chloroplasts isolated from light-adapted peas was 2-fold and 5–6-fold lower, respectively, in the lowest radiation compared to sunlight. There was a marked increase in the amount of total chlorophyll associated with the main chlorophyll $\text{a}\text{b-}\text{proteins}$ (LHCP¹, LHCP² and LHCP³) and a 2-fold decrease in the core reaction centre complex of Photosystem II (CP a) as the radiation decreased; the $\text{LHCP}{}^{\mathrm{1–3}}\text{CP}$ a ratio changed from 3.5 to 9.0. The amount of chlorophyll associated with Photosystem I varied from 34% in sunlight to 27% in the lowest radiation, but the antenna size of Photosystem I was not markedly different; there was a 2-fold decrease in the amount of cytochrome f on a chlorophyll basis, which partly accounted for the decreased electron-transport capacity of Photosystem I. Since the increases or decreases in the levels of each of the components correlated with decreasing radiation, it is clear that the light-adaptation of both light-harvesting and electron-transport components is indeed closely co-ordinated.     

In vivo interactions of acrylonitrile with macromolecules in rats

The irreversible binding of [2,3-14C]acrylonitrile (VCN) to proteins, RNA and DNA of various tissues of male Sprague-Dawley rats after a single oral dose of 46.5 mg/kg (0.5 LD50) has been studied. Proteins were isolated by chloroform-isoamyl alcohol-phenol extraction. RNA and DNA were separated by hydroxyapatite chromatography. Binding of VCN to proteins was extensive and was time dependent. Radioactivity in nucleic acids was registered in the liver and the target organs, stomach and brain. DNA alkylation, which increased by time, was significantly higher in the target organs, brain and stomach (119 and 81 pmol/mg, respectively, at 24 h) than that in the liver. The covalent binding indices for the liver, stomach and brain at 24 h after dosing were, 5.9, 51.9 and 65.3, respectively. These results suggest that VCN is able to act as a multipotent carcinogen by alkylation of DNA in the extrahepatic target tissues, stomach and brain.     

Immunologic and clinical improvement of progressive coccidioidomycosis following administration of transfer factor

Three patients with progressive coccidioidomycosis were given preparations of transfer factor (TF). Adverse reactions to TF were minimal. Following TF administration two of these patients had prolonged clinical remissions in their coccidioidal disease. Cellular immune responses were sequentially evaluated by coccidioidininduced delayed-type skin tests, lymphocyte blast transformation and macrophage inhibition factor production (MIF). These three patients each exhibited different cellular immune patterns before and after TF administration. Two patients converted their coccidioidin skin tests, and one converted lymphocyte transformation response to coccidioidin. Also, TF apparently favorably affected the MIF response in all three patients.     

Cloning, nucleotide sequence, and expression of the Brucella melitensis bp26 gene coding for a protein immunogenic in infected sheep

Abstract We have previously identified a Brucella melitensis 28 kDa cytosoluble protein (CP28) which was highly immunogenic in infected sheep and which in addition made possible the serological differentiation between infected and B. melitensis Rev.l vaccinated sheep. Monoclonal antibodies against CP28 were used to screen a B. melitensis 16M genomic library and to clone the corresponding gene. DNA sequencing of the gene encoding CP28 of B. melitensis 16M revealed that it was nearly identical to that of the recently published bp26 gene of Brucella abortus vaccine strain S19 coding for a periplasmic protein. The differences between the B. melitensis 16M gene and that of B. abortus S19 consisted of single nucleotide substitutions, one or two codon deletions, one codon addition, and most importantly a 21-bp deletion. The corresponding region of B. abortus S19 contains two 10-bp direct repeats which could have been involved in the genesis of the deletion. Expression of the B. melitensis 16M bp26 gene in Escherichia coli studied by the use of the monoclonal antibodies showed the same characteristics as reported for the B. abortus S19 bp26 gene, i.e. the presence of a higher molecular mass preprotein and a lower molecular mass band which probably corresponds to the mature protein exported to the periplasm. Immunoblotting performed with sera from either naturally infected or B. melitensis H38 experimentally infected sheep confirmed the importance of the B. melitensis CP28/BP26 protein as diagnostic antigen.     

Site-directed mutagenesis of the CP 47 protein of photosystem II: 167W in the lumenally exposed loop C is required for photosystem II assembly and stability

The intrinsic chlorophyll-protein CP 47 is a component of photosystem II which functions in both light-harvesting and oxygen evolution. Using site-directed mutagenesis we have produced the mutant W167S which lies in loop C of CP 47. This strain exhibited a 75% loss in oxygen evolution activity and grew extremely slowly in the absence of glucose. Examination of normalized oxygen evolution traces indicated that the mutant was susceptible to photoinactivation. Analysis of the variable fluorescence yield indicated that the mutant accumulated very few functional PS II reaction centers. This was confirmed by immunoblotting experiments. Interestingly, when W167S was grown in the presence of 20 M DCMU, the mutant continued to exhibit these defects. These results indicate that tryptophan 167 in loop C of CP 47 is important for the assembly and stability of the PS II reaction center.     

The heterogeneous nature of microbial products as shown by solid-state13C CP/MAS NMR spectroscopy

Homoionic Na-, Ca-, and Al-clays were prepared from the <2 m fractions of Georgia kaolinite and Wyoming bentonite and mixed with sand to give artificial soils with 5, and 25% clay. The artificial soils were inoculated with microbes from a natural soil before incubation. Unlabelled and uniformly¹³C-labelled (99.9% atom) glucose were incorporated into the artificial soils to study the effects of clay types, exchangeable cations and clay contents on the mineralization of glucose-carbon and glucose-derived organic materials. Chemical transformation of glucose-carbon upon incorporation into microbial products and metabolites, was followed using solid-state¹³C CP/MAS NMR spectroscopy.There was a significant influence of exchangeable cations on the mineralization of glucose-carbon over a period of 33 days. At 25% clay content, mineralization of glucose-carbon was highest in Ca-soils and lowest in Al-soils. The influence of exchangeable cations on mineralization of glucose-carbon was more pronounced in soils with bentonite clay than those with kaolinite clay. Statistical analysis of data showed no overall effect of clay type on mineralization of glucose-carbon. However, the interactions of clay type with clay content and clay type with clay content and exchangeable cations were highly significant. At 25% clay content, the mineralization of glucose-carbon was significantly lower in Na- and Al-soils with Wyoming bentonite compared with Na- and Al-soils with Georgia kaolinite. For Ca-soils this difference was not significant. Due to the increased osmotic tension induced by the added glucose, mineralization of glucose-carbon was slower in soils with 5% clay than soils with 25% clay.Despite the differences in the chemical and physical characteristics of soils with Ca-, Na- and Al-clays, the chemical composition of organic materials synthesised in these soils were similar in nature. Assuming CP/MAS is quantitative, incorporation of uniformly¹³C-labelled glucose (99.9% atom) in these soils resulted in distribution of carbon in alkyl (24–25%), O-alkyl (56–63%), carbonyl (11–15%) and small amounts of aromatic and olefinic carbon (2–4%). However, as decomposition proceeded, the chemistry of synthesised material showed some changes with time. In the Ca- and Na-soils, the proportions of alkyl and carbonyl carbon decreased and that of O-alkyl carbon increased with time of incubation. However, the opposite trend was found for the Al-soil.Proton-spin relaxation editing (PSRE) subspectra clearly showed heterogeneity within the microbial products. Subspectra of the slowly-relaxing (long T₁(H)) domains were dominated by alkyl carbon in long- and short-chain structures. The signals due to N-alkyl (55 ppm) and carbonyl carbon were also strong in these subspectra. These subspectra were very similar to those obtained for microbial and fungal materials and were probably microbial tissues attached to clay surfaces by polysaccharide extracellular mucilage. Subspectra of fast-relaxing (short T₁(H)) domains comprised mostly O-alkyl and carbonyl carbon and were probably microbial metabolites released as neutral and acidic sugars into the extracellular environment, and strongly sorbed by clay surfaces.