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.     

三个与agropine合成相关的基因在大肠杆菌微细胞中的表达

pTiAch 5 TR区与在植物中积累agropine相关的三个基因片段已导入pINIIA或pACYC184,在大肠杆菌微细胞中表达出杂合蛋白。三个基因片段的pINIIA重组质粒的表达得到稳定蛋白、不稳定蛋白和在两个相表达出相似蛋白的三种结果。基因2'HindⅢ片段上的UGAA序列是在两个相表达相似蛋白的原因。从产生的杂合蛋白分子量和读码方式看,pTiAch 5中基因2'和基因1'的结构与pTi 15955近似,但由基因0'片段产生的杂合蛋白分子量比根据pTi15955 DNA序列数据推测的稍大。从表达强度和微细胞操作看,这个系统还不适应从大肠杆菌中方便地纯化杂合蛋白的需要。     

配体对(Na~++K~+)-ATP酶E_2→E_1转变的影响

 本研究确定了在0℃条件下,(Na~++K~+)-ATP酶纯化制备物与5mmol/L Na~+或Mg~(2+)在5mmol/L咪唑(pH7.4)环境中预保温30分钟,然后进行磷酸化,可以获得最高磷酸化水平,Na~+或Mg~(2+)的K_(0.5)值分别为0.29mmol/L或0.35mmol/L;以ADP代替Na~+和Mg~(2+)与酶预保温,对E_2向E_1转变无任何影响,而与Na~+、Mg~(2+)一起存在时则能加强Na~+及Mg~2的预保温效果。     

Trolox C, a lipid-soluble membrane protective agent, attenuates myocardial injury from ischemia and reperfusion

The lipophilic antioxidant Trolox C, a vitamin E analog, was administered to isolated, buffer-perfused rabbit hearts subjected to 25 min of global stop-flow ischemia and 30 min of reperfusion. In six hearts, Trolox C (200 microM) was infused for 15 min immediately prior to ischemia and for the first 15 min of reperfusion. Six control hearts received only vehicle. Gas chromatography analysis confirmed that effective myocardial levels of Trolox were attained. At 30 min reperfusion, the recovery of left ventricular developed pressure was 56 +/- 3% of baseline in control hearts versus 70 +/- 4% in Trolox-treated hearts (p < .01). There was also significant improvement in recovery of Trolox-treated hearts in diastolic pressure and both maximum and minimum values of the first derivative of left ventricular pressure (dP/dt). Creatine phosphokinase release into the coronary effluent at 30 min of reperfusion was 16.5 +/- 8.4 IU/min in untreated and 6.3 +/- 1.0 IU/min (p < .05) in Trolox-treated hearts. Thus Trolox C, a lipophilic antioxidant, attenuated myocardial injury during stop-flow ischemia and reperfusion.     

Measurement of two-bond JCOHα coupling constants in proteins uniformly enriched with13C

Summary A simple E.COSY type technique is described for measurement of two-bond J_COH coupling constants in proteins that are uniformly enriched with¹³C. The method has been used to measure²J_COH for 132 residues in the proteins calmodulin and staphylococcal nuclease having non-overlapping H–C correlations. Measured²J_COH coupling constants fall in the 0 to –9.5 Hz range. A separate experiment, measuring the accuracy of these values, indicates a root-mean-square error of 1 Hz. Comparison of the J couplings with the dihedral back bone angles from crystallographic studies confirms a weak but statistically significant correlation between the dihedral angle and the magnitude of²J_COH, but also indicates that parameters other than have a significant effect on the value of the coupling.     

Inhibition of rat yolk sac tumour growth in vivo by a monoclonal antibody to the retroviral molecule P15E

Summary A monoclonal mouse IgG2b antibody 19F8, directed towards a determinant on the retroviral transmembranous molecule p15E, binds selectively to certain rat tumours, including all tested yolk sac tumours, one rat colon carcinoma, one spontaneous kidney carcinoma and an adenovirus-type-9-induced rat breast tumour, as tested by antibody-dependent cellular cytotoxicity (ADCC) and immunohistochemistry. Groups of rats receiving yolk sac tumour F56 isografts intraperitoneally (i.p.) or subperitoneally (s.p.) were treated with this monoclonal antibody (mAb), 19F8, inoculated twice a week in doses of 100 µg. Parallel control groups received analogous inoculations of an isotype-matched monoclonal antibody. A significant growth inhibitory effect was observed with 19F8. In 5/10 rats isografted i.p., tumour outgrowth was completely inhibited and in the other 5 rats the outgrowth was delayed compared to the 10 rats in the control group, which all developed tumours. All rats of the control group developed large volumes of ascites, whereas the 5 rats in the therapy group with eventual tumour outgrowth had little or no ascites. In two experiments with rats carrying subperitoneal isografts and treated with the 19F8 mAb, tumour grew out in 4/5 and 5/10 rats, though growth was delayed compared to the control groups, in which 5/5 and 9/9 rats developed tumours. The tumours grew significantly more slowly in the therapy groups compared to the controls. All rats that developed tumours in the therapy groups showed an anti-idiotypic response against mAb 19F8. The single tumour-free rat in the first experiment and 1/5 tumour-free rats in the other showed no such response. The draining lymph node cells from the tumour-free animals showed a specific proliferative response to yolk sac tumour F56 cells in a mixed lymphocyte tumour cell culture (MLTC), and the MLTC-induced cells were cytotoxic to F56 but not to the natural-killer-sensitive rat T cell lymphoma G1—Tc1. The cytotoxic cell population was more than 90% CD4⁺. It is concluded that the two test systems for identification of the epitope of p15E detected by mAb 19F8 correlated well in detection of the epitope in the cells (immunohistochemistry) and at the cell surface (ADCC). It is also concluded that mAb 19F8 has a growth-inhibitory effect on yolk sac tumour F56 and that, as a result of the treatment, T cells with specificity for F56 are appearing in draining lymph nodes of tumour-free animals.     

Effect of base substitutions in the colicin E1 gene on colicin E1 export and bacteriocin activity

Summary Base substitutions have been introduced into the segment of the colicin E1 gene corresponding to the polypeptide region between the 404th and the 502nd residues which was considered to participate in colicin E1 export and bacteriocin activity. The methods used were in vitro localized mutagenesis with sodium bisulphite and in vivo mutagenesis using either nitrosoguanidine or ethyl methane sulphonate. Cells carrying mutagenized plasmids were screened by their inability to form a clear zone on a lawn of colicin E1 sensitive cells. Mutation sites were determined from the nucleotide sequence analysis and the altered amino acid residues were reduced. The mutant proteins were analysed for their ability to be exported to the periplasmic space and for their bacteriocin activity. Out of eight mutants obtained, three had a single amino acid replacement. Mutant proteins that had Ser and Glu in place of Pro-462 and Gly-502, respectively, showed a decrease in both the export and the bacteriocin activity. A mutant protein having Arg in place of Gly-439 showed a decrease only in the bacteriocin activity. These results suggest that the target region of colicin E1 contributes to the export as well as the bacteriocin activity but the two functions are supported in part by different amino acid residues of the protein.     

Factors affecting the survival of E. coli in a river

The relationships between physical, chemical and microbial characteristics of an aquatic ecosystem and the survival of E. coli have been studied. Two conditions of the ecosystem (warm and cold) are considered. T₉₀ (time necessary for 90% of a bacterial population to die) in the warm situation shows an inverse exponential relationship with water temperature. Besides the direct relationship temperature-T₉₀, there is an indirect effect of temperature upon T₉₀ through the natural microflora of the water. The relationships between temperature and the heterotrophic population, and between the heterotrophic population and the bacterial consumers (P.F.U.), are exponential and linear, respectively.     

Effects of Hypoxia and Anoxia on the Ex Vivo Release of Prostaglandins from Mouse Cortical Slices

Arachidonic acid is transiently accumulated in the brain as a result of a variety of pathological conditions. The synthesis and release of some of its metabolites, namely, prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) from cortical slices of mice were studied following exposure to 6 min of hypoxia (7% O2), 45 s of anoxia, and 5 min-4 h of reoxygenation following anoxia. Hypoxia induced a slight increase in the rate of TXB2 release and a slight decrease in the rate of PGE2 release, whereas 6-keto-PGF1 alpha was unaffected. Anoxia (45 s) followed by reoxygenation induced a transient increase in the release of PGE2 and of 6-keto-PGF1 alpha with a return to the normal rate at 30 min and 2 h of recovery, respectively. However, the rate of TXB2 synthesis and release reached its peak (twofold increase) after 1 h and remained significantly higher than the control rate even after 4 h of normal air breathing. Our results demonstrate that hypoxia and anoxia, even of short duration, selectively trigger the activity of thromboxane synthetase and that this elevated rate of synthesis and release persists long after normal oxygen supply is restored. We suggest that enhanced thromboxane synthesis, with normal prostacyclin levels, might have a role in the pathophysiology of ischemic cell damage.     

Evolution of the lipoprotein gene in the enterobacteriaceae. Cloning and DNA sequence of the lpp gene from Proteus mirabilis

We cloned the lipoprotein gene from Proteus mirabilis and determined its DNA sequence. Comparison with the lpp genes from Escherichia coli, Serratia marcescens, Erwinia amylovora and Morganella morganii revealed several unique features of the evolution of the lpp gene in the Enterobacteriaceae and enabled us to establish phylogenetic relationships between these bacteria.