ABSTRACT
Lipoxygenase (LOX) is an important contributor to the formation of aroma-active C6 aldehydes in apple (Malus × domestica) fruit upon tissue disruption but little is known about its role in autonomously produced aroma volatiles from intact tissue. We explored the expression of 22 putative LOX genes in apple throughout ripening, but only six LOXs were expressed in a ripening-dependent manner. Recombinant LOX1:Md:1a, LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b proteins showed 13/9-LOX, 9-LOX, 13/9-LOX and 13-LOX activity with linoleic acid, respectively. While products of LOX1:Md:1c and LOX2:Md:2b were S-configured, LOX1:Md:1a and LOX2:Md:2a formed 13(R)-hydroperoxides as major products. Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation. The high expression level of the corresponding MdLOX1a gene in stored apple fruit, the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio- and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits, suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples. While LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.
ABSTRACT
BACKGROUND: Simultaneous pancreas-kidney transplantation (SPK) has a higher rate of surgical complications compared with other whole organ transplantations. Graft thrombosis and intra-abdominal infections are the most frequent causes for relaparotomy. We evaluated risk factors for abdominal infections after SPK, with emphasis on the value of the routinely taken intraoperative swabs. METHODS: Between June 1994 and December 2000, 177 SPK were performed. Immunosuppression consisted of antithymocyte globulin induction and triple-drug maintenance therapy. Routine swabs were taken from the graft perfusion solutions, from the donors' duodenum, and from the recipients' bladder and jejunum (in case of enteric drainage). RESULTS: A total of 19 (10.7%) of 177 patients underwent 41 relaparotomies as a result of intra-abdominal infections. Positive microbial results from any donor site and positive duodenal swabs were significant risk factors for intra-abdominal infections after SPK (P=0.01, P=0.02). There was a significantly higher incidence of abdominal infections when Candida was found in the donor duodenal swab (P=0.0048). Patient survival was significantly lower in cases with abdominal infection (P=0.02). Survival rates of patients with and without abdominal infection were 89.5% and 97.4% at 1 year and 72.3% and 92.8% at 5 years, respectively. CONCLUSIONS: The results of this study confirm that abdominal infections significantly reduce patient survival and thus jeopardize the success of SPK. Positive donor duodenal swabs have been revealed to be a significant risk factor for a subsequent intra-abdominal infection, especially when Candida was found.
