Production, purification, and properties of an endoglucanase produced by the hyphomycete Chalara (Syn. Thielaviopsis) paradoxa CH32     

Lucas R  Robles A  García MT  Alvarez De Cienfuegos G  Gálvez A 《Journal of agricultural and food chemistry》2001,49(1):79-85

The hyphomycete Chalara (syn. Thielaviopsis) paradoxa produces endoglucanase activity during the late trophophase. The low molecular mass (35 kDa) endoglucanase purified from cultured broths works optimally at 37 degrees C and pH 5.0. The enzyme inactivates at pH below 3.0 and also at temperatures of 50 degrees C or higher, but it is stable at lower temperatures, including refrigeration temperature and freezing. The enzyme is inhibited by detergents, by EDTA, and by the divalent cations Hg(2+) and Ag(2+). It is also inhibited to some extent by 10 mM Zn(2+), Fe(2+), and Mg(2+), but it is stimulated by Mn(2+). Enzyme activity is not affected by reducing agents. In the presence of low concentrations of water miscible organic solvents (20%) endoglucanase activity is inhibited by 7% (for methanol) to 50% (for acetonitrile), and it is totally inhibited at higher solvent concentrations (50%). Enzyme activity is not affected by the water immiscible solvent ethyl acetate. Carboxymethylcellulose is the preferred substrate (K(m(app)) = 8.3 g/L; V(max(app)) = 1.1 microM/min). Hydrolysis of crystalline cellulosic substrates is very limited, but it is greatly enhanced by phosphoric acid swelling. The purified enzyme shows no activity toward disaccharides or aryl-glucosides. Its activity is inhibited by cellobiose.  相似文献   

Genetic diversity of Musa diploid and triploid accessions from the Brazilian banana breeding program estimated by microsatellite markers     

Silvana Creste  Augusto Tulmann Neto  Roland Vencovsky  Sebastião de Oliveira Silva  Antonio Figueira 《Genetic Resources and Crop Evolution》2004,51(7):723-733

Banana (Musa spp.) is one of the most consumed fruits worldwide. Production is based mainly on triploid cultivars, and most genetic improvement programs aim to generate tetraploid hybrids obtained from the crossing of established triploid cultivars with a diploid parent genotype, improved or wild, exhibiting the trait of interest, normally resistance to biotic factors. Microsatellites were used to investigate the genetic variability and relationships between 58 Musa genotypes, including 49 diploids and nine triploid cultivars maintained at the Musa germplasm collection of the Brazilian dessert banana breeding program. Thirty-three primer pairs developed for banana were tested, and nine amplified reproducible and discrete fragments, producing a total of 115 alleles. The average number of alleles amplified per primer was 12.8, ranging from 10 to 15. The diploid genotypes presented the largest genetic variability, demonstrated by the large number of alleles detected, and the low similarity between the clones. The phenetic analysis clustered the triploid cultivars in a separated group, with the exception of the Nanica and Gros Michel cultivars, which showed high similarity with the diploid cultivar Mambee Thu. It was not possible to separate the wild diploid genotypes from the cultivated ones, indicating a common origin of these genotypes. A high proportion of duplicated alleles and/or loci was observed for diploid and triploid genotypes. The information gathered about the similarity between diploid and triploid accessions will help to define potential crosses to maximize the recovery of the typical fruit qualities required in Brazil (AAB, Pome and Silk dessert banana).  相似文献   

Improving minimum detectable differences in the assessment of soil organic matter change in short‐term field experiments          下载免费PDF全文

Lucas Knebl  Günter Leithold  Christopher Brock 《植物养料与土壤学杂志》2015,178(1):35-42

The demand for information on cropping system impact on soil organic matter (SOM) calls for efforts to improve the utilization of short‐term field experiments (e.g., to evaluate the parameterization of cropping systems in models). Those approaches have coped with the problem of determining small SOM changes within a large background mass. Thus, objectives of this survey are (1) the improvement of the minimum detectable difference (MDD) in SOM in the hudycrop short‐term field experiment by methods of sampling design and data treatment, (2) the verification to what extend the hudycrop short‐term field experiment allows for the determination of management induced effects on SOM, and (3) the investigation to what extent the obtained results may be suitable to evaluate the parameterization of a SOM balance model. The design of the hudycrop is suitable for excluding outliers plotwise. The estimation of plot means can be improved by the sampling design. Instead of determining a single plot mean in a mixed sampling procedure, the design provides multiple values for each plot, allowing for the identification of extreme values before calculating plot means. In consequence, minimum detectable differences decrease by a factor of 0.53 for soil organic C (SOC) and 0.63 for soil total N (STN) masses, allowing for detection of changes in the magnitude of 3.7 and 2.6% of background SOC and STN levels, respectively. Differences between treatments, however, are significant with corrected values (after outlier exclusion) for the crop production systems with the highest impact (potatoes and mulched red clover). Determining outliers based on Student's t‐test gives the lowest MDD and is therefore considered to be the most suitable method in this case. Correlations between apparent changes and SOM balances according to the HU‐MOD–2 model, used in this survey, indicate that the experimental design, in principal, is suitable for the evaluation of the parameterization of crop production systems in models. Still, an improved precision in SOM change detection is necessary. Reasonable options for that purpose are discussed in the paper.  相似文献   

To compare the incubation period following intratracheal and subcutaneous inoculation of bovine leukosis virus infected lymphocytes and to study their clearance from the circulation   总被引：1，自引：0，他引：1  

D H Roberts  M H Lucas  G Wibberley 《Veterinary immunology and immunopathology》1986,11(4):351-359

The migration of fluorescein isothiocyanate labelled lymphocytes through the tracheobronchial mucosa has been studied in cattle. Following intratracheal inoculation of labelled non-infected autologous lymphocytes and bovine leukosis virus (BLV) infected heterologous (presumed allogeneic) lymphocytes, the labelled lymphocytes appeared in the blood circulation between 4 and 7 days post inoculation. Following intravenous inoculation of labelled autologous lymphocytes, the cells could be detected in the circulation for 10 days post inoculation whereas BLV infected and non-infected heterologous lymphocytes could be detected for only 2 days. The migration of BLV-infected heterologous lymphocytes through the tracheobronchial mucosa caused a delay in the appearance of labelled lymphocytes in the circulation and a corresponding delay in the appearance of BLV antibodies. Comparison was made of the effect of two different routes of inoculation, subcutaneous and intratracheal on the incubation period as indicated by the detection of antibody. Subcutaneous inoculation of 1 X 10(4), 5 X 10(3), 1 X 10(3) of lymphocytes from a BLV infected cow caused seroconversion whereas 5 X 10(2) cells did not. Intratracheal inoculation of 5 X 10(3) cells caused sero-conversion. One animal did not develop BLV antibody until 30 weeks after inoculation although BLV could be isolated from the blood at 24 and 26 weeks post inoculation.  相似文献   

Protection against bovine leukosis virus infection in sheep with the BL 20 bovine lymphoblastoid cell line   总被引：2，自引：0，他引：2  

D H Roberts  M H Lucas  J Sands  G Wibberley 《Veterinary immunology and immunopathology》1982,3(6):635-642

The bovine lymphoblastoid BL 20 cell line derived from a case of sporadic bovine leukosis when inoculated into sheep did not induce an antibody response directed against bovine leukosis virus (BLV) structural proteins. Sheep were inoculated twice with the BL 20 cell line and then challenged with BLV infected lymphocytes. Three out of four sheep challenged four weeks after BL 20 inoculation did not develop BLV antibodies. Of the 12 sheep challenged later, three sheep did not develop BLV antibodies. BLV was isolated from all the seropositive animals and from none of the seronegative animals.  相似文献   

Effect of salicylates on intestinal secretion in calves given (intestinal loops) Escherichia coli heat-stable enterotoxin     

C M Wise  A P Knight  M J Lucas  C J Morris  R P Ellis  R W Phillips 《American journal of veterinary research》1983,44(12):2221-2225

The inhibitory effect of salicylates on intestinal secretion in 1- to 5-day-old calves given Escherichia coli heat-stable enterotoxin (ST)-induced intestinal fluid response was investigated. Purified ST was diluted in isotonic saline solution to obtain 1:10, 1:25, 1:50, 1:75, and 1:100 dilutions. Each dilution (1 ml) was inoculated into ligated loops in the distal part of the jejunum of each calf. Acetylsalicylic acid (aspirin) given orally (100 mg/kg) at 4 hours before ST was inoculated did not substantially alter the intestinal fluid response to ST. Sodium salicylate (IV) infusion, begun simultaneously when, or at 1 hour after, ST was inoculated, significantly (P less than 0.05) decreased fluid accumulation in those loops inoculated with ST dilutions of 1:25 or greater. The sodium and potassium concentrations of the accumulated fluid did not differ significantly between or within treatment groups. These results indicate that sodium salicylate infusion may be beneficial in treating enterotoxic colibacillosis in calves. Aspirin given orally at the dose used in the present study, would not have any beneficial effect.  相似文献   

Factors associated with an epizootic of peracute coliform mastitis in cows     

E M Huffman  M Lucas 《Journal of the American Veterinary Medical Association》1983,183(5):570-572

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Survival of infectious bovine rhinotracheitis virus in stored bovine semen     

M. S. Chapman  M. H. Lucas  C. N. Hebert  R. G. Goodey 《Veterinary research communications》1979,3(1):137-139

No loss in the titre of infectious bovine rhinotracheitis virus was found during storage in semen at –196°C for 1 year.  相似文献   

Comparison of the agar gel immunodiffusion test and ELISA in the detection of bovine leukosis virus antibody in cattle persistently infected with bovine virus diarrhoea virus   总被引：1，自引：0，他引：1  

D H Roberts  M H Lucas  C Swallow 《Veterinary immunology and immunopathology》1989,22(3):275-281

When six cattle persistently infected with bovine virus diarrhoea virus (BVDV) were inoculated with lymphocytes infected with bovine leukosis virus (BLV), a depressed antibody response to BLV was observed by ELISA which was due to a decrease in IgG1 synthesis. The ELISA was more sensitive and more reliable than the agar gel immunodiffusion (AGID) test in detecting BLV infection in cattle persistently infected with BVDV. Decreased antibody responses were manifested in the AGID test by negative, inconclusive or weakly positive reactions: only two of the six cattle developed antibodies that generated positive AGID reactions.  相似文献   

Aujeszky's disease in France: isolation of the virus from 2 cats     

T Metianu  A Lucas  A Vallee  R Laurent 《Bulletin de l'Académie vétérinaire de France》1971,44(5):221-228

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