In vitro plant regeneration methods in alfalfa breeding     

Paul Varga  Elena Marcela Badea 《Euphytica》1992,59(2-3):119-123

  相似文献   

In-depth mechanistic study on the formation of acrylamide and other vinylogous compounds by the maillard reaction   总被引：2，自引：0，他引：2  

Stadler RH  Robert F  Riediker S  Varga N  Davidek T  Devaud S  Goldmann T  Hau J  Blank I 《Journal of agricultural and food chemistry》2004,52(17):5550-5558

The formation of acrylamide was studied in low-moisture Maillard model systems (180 degrees C, 5 min) based on asparagine, reducing sugars, Maillard intermediates, and sugar degradation products. We show evidence that certain glycoconjugates play a major role in acrylamide formation. The N-glycosyl of asparagine generated about 2.4 mmol/mol acrylamide, compared to 0.1-0.2 mmol/mol obtained with alpha-dicarbonyls and the Amadori compound of asparagine. 3-Hydroxypropanamide, the Strecker alcohol of asparagine, generated only low amounts of acrylamide ( approximately 0.23 mmol/mol), while hydroxyacetone increased the acrylamide yields to more than 4 mmol/mol, indicating that alpha-hydroxy carbonyls are much more efficient than alpha-dicarbonyls in converting asparagine into acrylamide. The experimental results are consistent with the reaction mechanism based on (i) a Strecker type degradation of the Schiff base leading to azomethine ylides, followed by (ii) a beta-elimination reaction of the decarboxylated Amadori compound to afford acrylamide. The beta-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in beta-position to the nitrogen atom. The beta-elimination step in the amino acid moiety was demonstrated by reacting under low moisture conditions decarboxylated model Amadori compounds obtained by synthesis. The corresponding vinylogous compounds were only generated if a beta-proton was available, for example, styrene from the decarboxylated Amadori compound of phenylalanine. Therefore, it is suggested that this thermal pathway may be common to other amino acids, resulting under certain conditions in their respective vinylogous reaction products.  相似文献   

Rapid and sensitive determination of phenol in honey by high-performance liquid chromatography with fluorescence detection     

Gyorik M  Herpai Z  Szécsényi I  Varga L  Szigeti J 《Journal of agricultural and food chemistry》2003,51(18):5222-5225

The objective of this research was to develop a novel high-performance liquid chromatographic (HPLC) method involving a simple sample preparation procedure for the rapid, low-cost, and sensitive quantitation of phenol in honey at levels of regulatory and practical importance. After proper dilution of honey with water, the samples were analyzed by a gradient HPLC system, using a reversed-phase column with fluorescence detection at excitation and emission wavelengths of 270 and 300 nm, respectively. The eluents applied were water-acetonitrile-85% orthophosphoric acid (10:10:0.01, v/v/v) and water-85% orthophosphoric acid (20:0.01, v/v). The retention time of phenol was found to be 14.1 min, and the limit of quantitation for phenol in honey was set at 5 microg/kg. Overall recovery was 98%. The proposed method has been successfully applied to real sample analysis.  相似文献   

Validity limits of Kubelka–Munk theory for DRIFT spectra of photodegraded solid wood     

L. Tolvaj  K. Mitsui  D. Varga 《Wood Science and Technology》2011,45(1):135-146

The validity of the Kubelka–Munk (K-M) theory was investigated to determine the IR absorption spectra of wood based on diffuse reflection infrared Fourier transform (DRIFT) measurements taken on photodegraded samples. After analysing plenty of DRIFT spectra of wood and examining the shape of the K-M equation, it can be concluded that the measured K-M function can be used as an absorption spectrum if the values of the function are below 14 K-M units. Above this limit, the K-M theory, which was created for poorly absorbing materials, does not give the absorption of wood properly. If a matt aluminium plate is used as a background material and the values are between 14 and 40, absorption changes can be calculated after normalisation of the spectra. This normalising manipulation is only successful if there is an absorption peak close to the examined one which does not change its absorption during the photodegradation.  相似文献   

Serogroups of Campylobacter jejuni from man and animals   总被引：1，自引：0，他引：1  

J Varga  B Mézes  L Fodor 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1990,37(6):407-411

A total of 186 campylobacter strains from aborted calf and sheep fetuses, from scouring dogs, rabbits and man, and from retailed poultry were isolated and examined biochemically and serologically for heat stable antigens. Immune sera were produced in rabbits against Penner reference strains from 1 to 60, and against two field isolates. Out of 186 biochemically tested strains 179 (96.2%) proved C. jejuni and only 6 (3.2%) C. coli. One strain has been identified as C. laridis. In cattle and sheep 3.2 and 21.7% respectively of all campylobacter abortions were due to C. jejuni infection. The same agent caused 12.7% of diarrhoea of dogs. The campylobacter infection rate of freshly slaughtered and dressed chicken varied between 25 and 64.3%. Out of the serologically examined 140 C. jejuni strains 118 (84.3%) could be assigned to 16 Penner serogroups and 13 (9.3%) to 2 further serogroups. Serogroups 8 (31.4%), 1 (19.3%) and 2 (12.1%) occurred most frequently. The human isolates represented the widest serotype distribution, as 32 tested strains belonged to 12 serogroups. All those serogroups which caused abortion or diarrhoea in animals or were isolated from poultry carcases were isolated also from man with diarrhoea, but some serogroups were found only in man.  相似文献   

Atomic-scale structure and catalytic reactivity of the RuO(2)(110) surface     

Over H  Kim YD  Seitsonen AP  Wendt S  Lundgren E  Schmid M  Varga P  Morgante A  Ertl G 《Science (New York, N.Y.)》2000,287(5457):1474-1476

The structure of RuO(2)(110) and the mechanism for catalytic carbon monoxide oxidation on this surface were studied by low-energy electron diffraction, scanning tunneling microscopy, and density-functional calculations. The RuO(2)(110) surface exposes bridging oxygen atoms and ruthenium atoms not capped by oxygen. The latter act as coordinatively unsaturated sites-a hypothesis introduced long ago to account for the catalytic activity of oxide surfaces-onto which carbon monoxide can chemisorb and from where it can react with neighboring lattice-oxygen to carbon dioxide. Under steady-state conditions, the consumed lattice-oxygen is continuously restored by oxygen uptake from the gas phase. The results provide atomic-scale verification of a general mechanism originally proposed by Mars and van Krevelen in 1954 and are likely to be of general relevance for the mechanism of catalytic reactions at oxide surfaces.  相似文献   

Efficacy evaluations of the use of oral tilmicosin in pneumonic calves   总被引：6，自引：0，他引：6  

Fodor L  Reeve-Johnson L  Hodge A  Varga J 《Veterinary journal (London, England : 1997)》2000,159(2):194-200

The therapeutic effect of oral tilmicosin was compared with enrofloxacin, and the efficacy of three doses of the drug was examined in two fully randomized blinded field trials. Pneumonic milk-fed calves between 3 days and 2.5 months of age were allocated into two groups in trial 1 (50 animals) and into three groups in trial 2 (69 calves). In the first trial, the animals were treated with 25 mg/kg/day tilmicosin or 2.5 mg/kg/day enrofloxacin in milk for 5 days. In the second trial, the calves received either 25 mg/kg/day tilmicosin for 5 days or 3 days, or else 12.5 mg/kg tilmicosin for 5 days. All calves were clinically examined for 10 days. In the first trial, oral tilmicosin at a dose of 25 mg/kg/day for 5 days proved to be effective for the treatment of endemic pasteurellosis of milk-fed calves. The efficacy was the same as that of enrofloxacin. All three doses in the second trial were effective and were statistically equivalent to the original dose tested.  相似文献   

Effect of lead treatment on the distribution of essential elements in cucumber     

Edit Cseh  Ferenc Fodor  Anita Varga  Gyula Záray 《Journal of plant nutrition》2013,36(8):1095-1105

Changes in the fresh and dry weight of leaf blades, petioles, internodes, and their ion concentrations as well as rates of root exudation were investigated in cucumber grown in hydroponic culture and treated with physiological concentrations of lead (Pb). The growth of flowering cucumber supplied with FeCl₃ shows a typical bell‐shaped curve derived from leaf dry weights, where the 4th, 5th, and 6th leaves are the largest ones. Lead inhibited growth up to 20% (except the youngest leaves which were stimulated), but did not cause morphological changes. Whereas root growth was also retarded by about 20%, exudation was inhibited to 50%, that is, the root resistance to water transport was increased by Pb. In spite of that the dry matter yield of internodes and petioles hardly reached 10 and 5% of that of leaf blades, respectively, their calcium (Ca), magnesium (Mg), and zinc (Zn) concentrations were almost the same. Similarly, the concentrations of these metals in the specific leaf blades are equal despite their different growth characteristics but the concentration of Mn is independent of the growth of the examined tissues. Lead was the only cation to accumulate in the largest leaves. The inhibitory effect of Pb on ion uptake was proportional to the growth inhibition of the tissues except manganese (Mn), the accumulation of which was stimulated by Pb in all the analyzed tissues and copper (Cu) which increased only in the internodes. We could not explain the extremely different ion distributions observed during the growth of cucumber. However, it is evident that the measurement of ion concentrations at whole shoot level is not enough to characterize ion interactions because only some ions accumulate at the same rate as tissues grow. These ions maintain stable concentration levels in shoot parts whereas others decrease or increase independently from growth.  相似文献   

Farmers’ reasoning behind the uptake of agroforestry practices: evidence from multiple case-studies across Europe     

M. Rois-Díaz  N. Lovric  M. Lovric  N. Ferreiro-Domínguez  M. R. Mosquera-Losada  M. den Herder  A. Graves  J. H. N. Palma  J. A. Paulo  A. Pisanelli  J. Smith  G. Moreno  S. García  A. Varga  A. Pantera  J. Mirck  P. Burgess 《Agroforestry Systems》2018,92(4):811-828

Potential benefits and costs of agroforestry practices have been analysed by experts, but few studies have captured farmers’ perspectives on why agroforestry might be adopted on a European scale. This study provides answers to this question, through an analysis of 183 farmer interviews in 14 case study systems in eight European countries. The study systems included high natural and cultural value agroforestry systems, silvoarable systems, high value tree systems, and silvopasture systems, as well as systems where no agroforestry practices were occurring. A mixed method approach combining quantitative and qualitative approaches was taken throughout the interviews. Narrative thematic data analysis was performed. Data collection proceeded until no new themes emerged. Within a given case study, i.e. the different systems in different European regions, this sampling was performed both for farmers who practice agroforestry and farmers who did not. Results point to a great diversity of agroforestry practices, although many of the farmers are not aware of the term or concept of agroforestry, despite implementing the practice in their own farms. While only a few farmers mentioned eligibility for direct payments in the CAP as the main reason to remove trees from their land, to avoid the reduction of the funded area, the tradition in the family or the region, learning from others, and increasing the diversification of products play the most important role in adopting or not agroforestry systems.  相似文献   

Serological and Some Pathological Characteristics of Escherichia coli Strains Isolated from Rabbits*     

J. Varga  L. Pesti 《Zoonoses and public health》1982,29(2):145-152

  相似文献