Calcium and magnesium interactions in browning of ‘Golden Delicious’ apples with bitter pit

The role of Ca and Mg in the enzymatic browning of ‘Golden Delicious’ apples was explored. Enzymatic browning due to polyphenol oxidase (PPO) was stimulated with the addition of 0.8–10 mM MgCl₂ to the reaction mixture, whereas 0.8–10 mM CaCl₂ had little effect or decreased the rate of enzymatic browning. Within a week after vacuum infiltration with MgCl₂, treated fruits exhibited browning symptoms that were similar to bitter pit. Six months after vacuum infiltration, when analyzed for enzyme activity, MgCl₂-treated fruits exhibited higher rates of PPO activity, whereas CaCl₂-treated fruits had lower activity than the MgCl₂-treated fruits and the controls. A hypothesis is advanced that the initial visible symptoms of bitter pit, i.e. the localized browning, is caused by PPO, its activity being stimulated by the localized Mg/Ca imbalance present in the tissue. The results indicate that Ca is predominant in the prevention of this disorder, whereas a deficiency of Ca is involved in its induction.     

Reproducibility of a commercial in vitro allergen-specific assay for immunoglobulin E in dogs

Samples of serum taken from 42 dogs with clinical signs and histories indicating pruritic skin disease and/or diseases of the ear were tested in a commercial allergen-specific assay for immunoglobulin E. Dogs which had been treated with glucocorticoids and/or antihistamines were not excluded. The samples were separated into two equal aliquots, given different randomised numbers, and analysed in two batches on two separate days. The laboratory was blinded to the identification numbers and the history of each dog, but knew the purpose of the study. The results for 48 allergens were expressed in modified absorbance units (MAU). The overall median MAU was 29. For each allergen the mean difference between the MAU values of the paired duplicates was determined and the difference was compared to zero by a paired t test. The number of means that were not 0 (P<0.05) in each allergen group were: seven of 10 grasses, seven of nine weeds, two of 13 trees, six of 10 fungi, and three of six environmental allergens. A single 2 x 2 table for the 48 allergens was created with MAU > or = 60 defined as 'positive' and < 60 as 'negative'. There were 116 of 188 (62 per cent) pairs that were reproducibly 'positive' and 1756 of 1828 (96 per cent) pairs that were reproducibly 'negative'.     

Reporting standards for biofilter performance studies

The development of standardized rating and design procedures for biological filters will require that filter performance be evaluated and reported in a standardized manner. This article recommends draft reporting standards for biofilter performance studies. It is important that critical parameters are defined and reported in a standard manner, both in terms of definition, variable names, and units. Depending on the type and scale of an experiment, reporting of certain parameters will be either mandatory or optional. Basic principles of experimental design, statistical analysis, and randomization must be followed. Experimental protocols are recommended to ensure the accuracy of measured or computed parameters. The development of this reporting standard is being organized through the Standards and Reporting Committee of the Aquaculture Engineering Society (AES). It is anticipated that a revised version of these standards will be incorporated into the Guide to Authors for Aquacultural Engineering.     

Effects of 4,4'-dimethyldiphenyliodonium chloride on performance of growing cattle

Two 112-d studies were conducted to evaluate effects of the deaminase inhibitor, 4,4'-dimethyldiphenyliodonium chloride, on performance of growing cattle. With diets containing low levels of crude protein (i.e., 11%), 25 ppm of chemical in the diet increased (P less than .05) gain and improved (P less than .05) feed efficiency. Feed intake was not affected. Higher levels of chemical (50 and 100 ppm) produced equivalent responses. With a higher level of dietary crude protein (i.e., 14%) gain and feed efficiency were not improved and some decreases in feed intake were observed. Performance responses resulting from adjustments in ruminal nitrogen transactions to provide more alpha-amino-N depend upon whether the animal needs additional amino acids for maintenance and production. Our data demonstrated that the supply of amino acids can be increased either by adjustment of ruminal nitrogen transactions with a chemical agent or by increasing concentration of dietary protein.