Nitrogen in global animal production and management options for improving nitrogen use efficiency

Animal production systems convert plant protein into animal protein. Depending on animal species, ration and management, between 5% and 45 % of the nitrogen (N) in plant protein is converted to and deposited in animal protein. The other 55%-95% is excreted via urine and feces, and can be used as nutrient source for plant (= often animal feed) production. The estimated global amount of N voided by animals ranges between 80 and 130 Tg N per year, and is as large as or larger than the global annual N fertilizer consumption. Cattle (60%), sheep (12%) and pigs (6%) have the largest share in animal manure N production. The conversion of plant N into animal N is on average more efficient in poultry and pork production than in dairy production, which is higher than in beef and sheep production. However, differences within a type of animal production system can be as large as differences between types of animal production systems, due to large effects of the genetic potential of animals, animal feed and management. The management of animals and animal feed, together with the genetic potential of the animals, are key factors to a high efficiency of conversion of plant protein into animal protein. The efficiency of the conversion of N from animal manure, following application to land, into plant protein ranges between 0 and 60%, while the estimated global mean is about 15%. The other 40%-100% is lost to the wider environment via NH3 volatilization, denitrification, leaching and run-off in pastures or during storage and/or following application of the animal manure to land. On a global scale, only 40%-50% of the amount of N voided is collected in barns, stables and paddocks, and only half of this amount is recycled to crop land. The N losses from animal manure collected in barns, stables and paddocks depend on the animal manure management system. Relative large losses occur in confined animal feeding operations, as these often lack the land base to utilize the N from animal manure effectively. Losses will be relatively low when all manure are collected rapidly in water-tight and covered basins, and when they are subsequently applied to the land in proper amounts and at the proper time, and using the proper method (low-emission techniques). There is opportunity for improving the N conversion in animal production systems by improving the genetic production potential of the herd, the composition of the animal feed, and the management of the animal manure. Coupling of crop and animal production systems, at least at a regional scale, is one way to high N use efficiency in the whole system. Clustering of confined animal production systems with other intensive agricultural production systems on the basis of concepts from industrial ecology with manure processing is another possible way to improve N use efficiency.     

Peculiarities of the Mechanism of Interactions of Catalytic Antibodies with Organophosphorus Substrates

Catalytic antibodies are a promising model for creating highly specific biocatalysts with predetermined activity. However, in order to realize the directed change or improve their properties, it is necessary to understand the basics of catalysis and the specificity of interactions with substrates. In the present work, a structural and functional study of the Fab fragment of antibody A5 and a comparative analysis of its properties with antibody A17 have been carried out. These antibodies were previously selected for their ability to interact with organophosphorus compounds via covalent catalysis. It has been established that antibody A5 has exceptional specificity for phosphonate X with bimolecular reaction rate constants of 510 ± 20 and 390 ± 20 min^–1M^–1 for kappa and lambda variants, respectively. 3D-Modeling of antibody A5 structure made it possible to establish that the reaction residue L-Y33 is located on the surface of the active site, in contrast to the A17 antibody, in which the reaction residue L-Y37 is located at the bottom of a deep hydrophobic pocket. To investigate a detailed mechanism of the reaction, A5 antibody mutants with replacements L-R51W and H-F100W were created, which made it possible to perform stopped-flow kinetics. Tryptophan mutants were obtained as Fab fragments in the expression system of the methylotrophic yeast species Pichia pastoris. It has been established that the effectiveness of their interaction with phosphonate X is comparable to the wild-type antibody. Using the data of the stopped-flow kinetics method, significant conformational changes were established in the phosphonate modification process. The reaction was found to proceed using the induced-fit mechanism; the kinetic parameters of the elementary stages of the process have been calculated. The results present the prospects for the further improvement of antibody-based biocatalysts.     

Identification of structural DNA variations in human cell cultures after long-term passage

Random amplified polymorphic DNA (RAPD) analysis was adapted for genomic identification of cell cultures and evaluation of DNA stability in cells of different origin at different culture passages. DNA stability was observed in cultures after no more than 5 passages. Adipose-derived stromal cells demonstrated increased DNA instability. RAPD fragments from different cell lines after different number of passages were cloned and sequenced. The chromosomal localization of these fragments was identified and single-nucleotide variations in RAPD fragments isolated from cell lines after 8–12 passages were revealed. Some of them had permanent localization, while most variations demonstrated random distribution and can be considered as de novo mutations.     

Situation of mycotoxins in milk, dairy products and human milk in Egypt

Abstact  Milk and dairy products purchased at Egyptian markets and breast milk from lactating mothers in Cairo and Giza governorates were analyzed for some mycotoxins. Three of 15 cows’ milk samples were found positive for Afl. M₁ with mean value 6.3 ppb. Only one sample of dried milk was positive (5 ppb). Two of 10 hard cheese samples contained detectable levels of Afl. M₁ (3and 6 ppb), whereas one sample containing Afl. B₁ and G₁ (10 and 4 ppb resp.). For soft cheese one sample of 10 was positive for Afl. M₁ (0.5 ppb). Blue veined cheeses were free of Afl. M₁ and PR-toxins. For breast milk two of 10 samples were positive for Afl. M₁ (20%) with mean value 2.75 ppb, while 3 of 10 samples were positive for Ochratoxin A (30 %).     

Investigation of activation of phosphate groups in mono- and oligonucleotides with mesitoyl chloride.

It has been demonstrated with the use of 31P NMR pulsed spectroscopy that the reaction of mesitoyl chloride (MsCOCl) both with terminal and internucleotide phosphate groups pA, d(MeOTr)TpT and dpTpT (Ac) proceeds in a quantitative fashion within less than 2 min at 0 degrees C with the respective mixed anhydrides being thereby formed. The anhydrides of phosphomonoesters are resistant, unlike those of phosphodiesters which may be readily split by water, alcohol or amine without the internucleotide bonds being broken. Treatment of poly(U) with an excess of MsCOCl leads to rapid cyclization followed by formation of phosphotriesters. A comparatively easy hydrolysis leads to partial cleavage and isomerization of internucleotide bonds. A similar treatment of UpC showed that about 20% of the internucleotide bonds are cleaved, the remaining UpC being a mixture of approximately equal amounts of 3'-5'- and 2'-5'-isomers.     

Modification of DNA with dihydrazide of succinic acid for preparation of hybridization probes

A two-step chemical method of introduction of nonradioactive labels in DNA was proposed. At first step DNA is modified by succinic dihydrazide at pH 5.0 and 95 degrees C, or at pH 4.5 and 37 degrees C in presence of sodium bisulfite. Then FITC or biotin are joined to the hydrazide groups. DNA modified in this way were shown to be effective hybridisation probes.