Evaluation of three different microbial inhibition tests for the detection of sulphamethazine residues in the edible tissues of rabbit

The aim of the present study was to evaluate three microbial inhibition tests (MIT) based on inhibition of growth of the test organisms: (a) four plate test (FPT) containing Bacillus subtilis BGA, (b) screening test for antibiotic residues (STAR) containing Bacillus stearothermophilus var. calidolactis_ATCC 10149 and (c) the Premi®Test containing Bacillus stearothermophilus var. calidolactis. The tests were used to determine sulphamethazine (SMZ) residues in edible tissues of rabbit after oral administration up to day 15 of the withdrawal period (WP). A solvent extraction procedure was used to enhance the capability of the tests to detect SMZ residues at or below the maximum residue limit (MRL). Para-aminobenzoic acid (PABA) was employed to previously identify SMZ residues in the first stage of the residue screening. The presence of SMZ residues in the samples was confirmed and quantified by a validated HPLC method. The Premi®Test detected SMZ residues in the muscle and heart tissue up to day 9 of the WP, and in the liver, lungs and kidneys up to day 10 of the WP. The STAR detected SMZ residues in the edible organs of rabbits up to day 8 of the WP. The kidneys were positive up to day 5 of the WP, the liver until day 4 of the WP and the lungs until day 3 of the WP. No SMZ residues were detected in the muscle and heart. By using the solvent extraction procedure, SMZ residues were detected in the muscle extract up to day 10 of the WP and the muscle was positive until day 6 of the WP. No detection sensitivity was observed using the FPT. After solvent extraction, SMZ residues were detected in the muscle extract until day 8 of the WP and the muscle was positive until day 3 of the WP. No positive results were detected after the addition of PABA into/onto the agar medium. PABA at a concentration of 10 µg ml^?1 completely reversed the inhibitory activity of SMZ and enabled reliable identification of SMZ in the examined samples. Using HPLC, SMZ was detected in the muscle samples until day 10 of WP (0.02 mg kg^?1) and in the liver until day 12 of the WP (0.09 mg kg^?1). The results obtained by the HPLC method and the limit of detection (LOD) of screening tests for SMZ (FPT 0.4 µg ml^?1, STAR 0.2 µg ml^?1, Premi® Test 0.05 µg ml^?1) allowed us to state that the most suitable screening tests for the detection of SMZ residues in the edible tissues of rabbits at level corresponding to the MRL of 0.1 mg kg^?1, established for sulphonamides, are the Premi®Test and STAR in conjunction with the solvent-extraction procedure.     

Possibilities of enhancing the colour of egg yolk

BACKGROUND: This study attempts to compare two possibilities of enhancing the colour of egg yolk. One of them is based on the ecological rearing of laying hens on natural green grass whereas the other uses a feeding dose supplemented with natural pigments in laying hens reared in individual cages. Is it possible to distinguish these two technologies using yolk colour determination in the CIELAB system? RESULTS: Yolk colour parameters such as L*, a*, and b* in the group of grazed hens are significantly different (α = 0.001) from those observed in hens reared in cages. The yolk colour shows a darker, redder and more yellow colour. The greatest difference was seen in the red colour parameter, a*, that increased more than twice. Visually, this means a shift towards a more orange colour. Compared to grazing in the meadow (ΔE* = 13.257), the addition of artificial pigments in the feed resulted in a more significant increase in the parameter ΔE* (CIE total colour difference), with the greatest value of ΔE* being observed with the use of both pigments (ΔE* = 24.265). CONCLUSION: Grazing increases the parameter a* whereas the values of the parameter C*_ab remain relatively low. The parameter ΔE* is significantly lower in the case of grazing as compared to the supplementation of the feed with pigments. However, colourity parameters cannot be used as a specific standard to identify a particular grazing technology as their values vary during the laying period. Copyright © 2011 Society of Chemical Industry     

Calculation of countercurrent separation processes—III. Computation of two interlinked columns.

The relaxation procedure is used for solution of two interlinked distillation columns. Both approaches-sequential iterative method and the block relaxation technique are compared. A new algorithm making use of simultaneous solution of all equations is proposed.     

Propheromones derived from codlemone

Tricarbonyl [(8,9,10,11--8,10-dodecadien-l-ol] iron and the corresponding acetate prepared from 8,10-dodecadien-1-ol or its acetate, comprise the protected double-bond system of the molecule. After coming in contact with ambient oxygen, the iron complexes in question slowly release the corresponding pheromones of, for example, the codling moth,Cydia pomonella, and the pea moth,Cydia nigricana in highE,E purity and amounts that are sufficient for pest monitoring. A simple dispenser for propheromone application is proposed. Results of release rates in laboratory conditions and field trials are given.     

Are natural antioxidants better – and safer – than synthetic antioxidants?

Antioxidants are necessary in the Western diet as it is rich in polyenoic fatty acids, which are easily oxidized with formation of free radicals that are harmful if present in higher amounts. Consumers prefer natural antioxidants to synthetic antioxidants, mainly for emotional reasons. The common Western daily diet contains about 1 g natural antioxidants even if no natural antioxidants have been added for lipid stabilization. Their main sources are cereals, fruits, vegetables, and beverages. Only a part of the natural antioxidants is absorbed and used as free‐radical scavengers in vivo. Natural antioxidants should be added to food in larger amounts than synthetic antioxidants as they are less active, but the actual activity depends very much on particular conditions and food composition. Nevertheless, the addition of additional antioxidants is still negligible in comparison with the dietary supply of native antioxidants. The safety limits of natural antioxidants are mostly not known, but they are hardly safer than synthetic antioxidants. The best protection would be to replace high‐polyenoic oils in the diet with high‐oleic oils, and to use alternative methods of food protection against autoxidation.     

Synthesis of poly[methyl(phenyl)silanediyl] containing 1,3,4-oxadiazole electron-transporting moieties

Summary The new oxadiazole derivative containing amino group, 2-(4-aminophenyl)-5-(biphenyl-4-y1)- 1,3,4-oxadiazole (Oxad-NH₂), was synthesized and attached to formylated poly[methyl(phenyl)silanediyl] (PMPSi) by acid-catalyzed condensation of the aldehyde with the amino group yielding a Schiff base. The aldehyde groups were incorporated into the parent PMPSi by the reaction with dichloromethyl methyl ether in the presence of Lewis acid (SnCl₄). GPC analyses before and after modification reaction revealed that the attachment of Oxad-NH₂ proceeded without degradation of the silicon backbone. We reached 75 % conversion of aldehyde groups to oxadiazole Schiff base. The condensation reaction was followed and the prepared compounds and polymers were characterized by ¹H NMR, UV-vis, FT IR, GPC and elemental analyses. Fluorescence behavior of oxadiazole-modified PMPSi was studied in tetrahydrofuran. Broad emission band with maximum at 440 nm was observed. Fluorescence quantum yield of modified polysilanes increases with the increasing content of the attached oxadiazole moiety. Received: 10 February 2003/Revised version: 8 April 2003/Accepted: 8 April 2003 Correspondence to Drahomír Vyprachticky     

Polymerase Synthesis of DNA Containing Iodinated Pyrimidine or 7-Deazapurine Nucleobases and Their Post-synthetic Modifications through the Suzuki-Miyaura Cross-Coupling Reactions

All four iodinated 2′-deoxyribonucleoside triphosphates (dNTPs) derived from 5-iodouracil, 5-iodocytosine, 7-iodo-7-deazaadenine and 7-iodo-7-deazaguanine were prepared and studied as substrates for KOD XL DNA polymerase. All of the nucleotides were readily incorporated by primer extension and by PCR amplification to form DNA containing iodinated nucleobases. Systematic study of the Suzuki-Miyaura cross-coupling reactions with two bulkier arylboronic acids revealed that the 5-iodopyrimidines were more reactive and gave cross-coupling products both in the terminal or internal position in single-stranded oligonucleotides (ssONs) and in the terminal position of double-stranded DNA (dsDNA), whereas the 7-iodo-7-deazapurines were less reactive and gave cross-coupling products only in the terminal position. None of the four iodinated bases reacted in an internal position of dsDNA. These findings are useful for the use of the iodinated nucleobases for post-synthetic modification of DNA with functional groups for various applications.     

Isothermal and adiabatic Young's moduli of alumina and zirconia ceramics at elevated temperatures

The elastic moduli (Young's moduli) of alumina and zirconia ceramics with porosities ranging from almost dense (2–3%) to highly porous (46–52%), the latter prepared with starch as a pore-forming agent, have been measured via impulse excitation and four-point bending tests from room temperature up to more than 1200 °C. It is shown that, independent of the temperature and the material, the porosity dependence of the Young's modulus is well predicted by our exponential relation and that, irrespective of porosity, the temperature dependence follows a master curve that is characteristic of the material (for alumina exhibiting a decrease with a gradually growing tangent slope and for zirconia exhibiting a steep decrease with an inflection point at moderately elevated temperatures below 400 °C). Differences between isothermal (static) and adiabatic (dynamic) values are negligible as long as the materials are purely elastic (i.e. at temperatures below approximately 1000 °C).     

Phase structure in segmented polyurethanes having fatty acid-based soft segments

Structural studies on two segmented polyurethanes prepared from modified oleic acid soft segments and butane diol/diphenylmethane diisocyanate hard segments, were performed. Polyurethanes were thermoplastic elastomers with 50% and 70% soft segment concentration (SSC) for TPU-50 and TPU-70, respectively. DMA revealed the co-continuous morphology in TPU-50 and dispersed hard domains in the soft matrix in TPU-70. AFM showed micron size globules in TPU-70 ascribed to hard segment-rich superstructures. Alternating small soft and hard domains were present in TPU-50, with ～15 nm lateral dimensions and local modulus deviations from 40 to 50 MPa, consistent with co-continuous morphology. The dispersed hard domains in the soft matrix of TPU-70, and co-continuous phases in TPU-50 morphology was confirmed. USAXS showed the domain spacing of TPU-50 was about 13.3 nm. TPU-70 demonstrated domain spacing of about 11.3 nm. USAXS revealed that the interface between phase-separated domains exhibited surface-fractal-like behavior.