Role of mycorrhizal fungi and phosphorus in the arsenic tolerance of basin wildrye.

Revegetation of arsenic (As)-rich mine spoils is often impeded by the lack of plant species tolerant of high As concentrations and low nutrient availability. Basin wildrye [Leymus cinereus (Scribner & Merr.) A. Löve] has been observed to establish naturally in soils with elevated As content and thus may be useful for the stabilization of As-contaminated soils. An experiment was conducted to evaluate how variable phosphorus (P) concentrations and inoculation with site-specific arbuscular mycorrhizal fungi influence As tolerance of basin wildrye. Basin wildrye was grown in sterile sand in the greenhouse for 16 weeks. Pots of sterile sand were amended to create one of four rates of As (0, 3, 15, or 50 mg As kg(-1)), two rates of P (3 or 15 mg P kg(-1)), and +/-mycorrhizal inoculation in a 2 x 4 x 2 factorial arrangement. After 16 weeks of growth, plants were harvested, shoots and roots thoroughly washed, and the tissue analyzed for total shoot biomass, total root and shoot As and P concentrations, and degree of mycorrhizal infection. Basin wildrye was found to be tolerant of high As concentrations allowing for vigorous plant growth at application levels of 3 or 15 mg As kg(-1). Arsenic was sequestered in the roots, with 30 to 50 times more As in the roots than shoots under low P conditions. Mycorrhizal infection did not confer As tolerance in basin wildrye nor did mycorrhizal fungi influence biomass production. Phosphorus concentrations of 15 mg kg(-1) effectively inhibited As accumulation in basin wildrye. Basin wildrye has the potential to be used for stabilization of As-rich soils while minimizing exposure to grazing animals following reclamation.

Reoperation following failure of aortoiliofemoral arterial reconstruction.

Over a 19-year period, 729 primary arterial reconstructions for aneurysmal and occlusive disease of the aortoiliac arterial system were performed at the Health Sciences Centre, Winnipeg. During the same interval 49 of these reconstructions required reoperation and 6 additional cases were referred for secondary repair from other institutions. The authors reviewed these 55 cases to determine the reasons for reoperation and the cumulative results of secondary repair. Secondary arterial repair was performed in 11.5% of cases of occlusive disease and in 1.2% of cases of aneurysmal disease. The overall frequency of reoperation was 6.7%. The mean interval between primary and secondary operation was 31.5 months. Perioperative failure, false aneurysm, graft infection, progression of disease and late technical problems were the major reasons for reoperation. Of the secondary repairs the results in 83.6% were satisfactory at 30 days. At 5 years, 57% of secondary repairs at risk remained satisfactory. The operative mortality for secondary arterial repair was 5.4%. The authors believe that continued aggressive management of failed primary aortoiliac reconstructions is justified.