Utilisation of electrospray time-of-flight mass spectrometry for solving complex fragmentation patterns: application to benzoxazinone derivatives.

In this paper we describe the application of electrospray time-of-flight mass spectrometry (ESI-TOFMS) to structural elucidation of the fragment ions formed from a range of natural and synthetic allelochemical derivatives. The extensive mass spectrometric characterisation of ten non-glucosylated benzoxazinone derivatives using this method is described here for the first time. The analytes include six naturally occurring 1,4-benzoxazin-3(4H)-one derivatives, including the hydroxamic acids DIMBOA [2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one] and DIBOA [2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one], lactams HBOA [2-hydroxy-2H-1,4-benzoxazin-3(4H)-one] and HMBOA [2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one], benzoxazolinones BOA [benzoxazolin-2(3H)-one] and MBOA [6-methoxy-benzoxazolin-2(3H)-one] and four synthetic variations, 2'H-DIBOA [4-hydroxy-2H-1,4-benzoxazin-3(4H)-one], 2'OMe-DIBOA [2-methoxy-4-hydroxy-2H-1,4-benzoxazin-3(4H)-one], 2'H-HBOA [2H-1,4-benzoxazin-3(4H)-one] and 2'OMe-HBOA [2-methoxy-2H-1,4-benzoxazin-3(4H)-one]. Assignments of the mass spectral fragments were aided by elemental composition calculation results, comparison of structural analogues and background literature, and acquired knowledge regarding feasible structures for the compounds. The influence of substituents on the chemical reactivity of the compounds with respect to the observed MS behaviour over varying nozzle potentials is addressed and, through comparison of the structural analogues, generic fragmentation patterns have also been identified.

The exposed cardiac pacemaker. Treatment by subfascial pocket relocation.

Ten patients were treated for skin erosion and exposure of chronically implanted pacemakers. The pulse generators had been implanted either subcutaneously or in the subpectoral, submammary location. All patients were treated either by primary or secondary relocation of the pulse generator to deeper subfascial planes. Pacemakers relocated primarily to subfacial planes healed without resurfacing. Those pacemakers relocated to other superficial planes resurfaced but healed in a second subfascial translocation. Bacteriologic studies on these patients revealed that the organisms cultured or antibiotics utilized did not influence the fate of the relocated pulse generator. The subfascial location was the only determinant of the ultimate healing of the exposed pacemaker. We conclude that subfascial relocation of well-functioning pacemaker generators should be considered as an alternative to complete replacement of the unit.

The Ionescu-Shiley valve: a solution for the small aortic root.

Valve replacement in patients with a small aortic anulus can cause difficult technical problems or leave the patient with a significant residual transvalvular gradient. Between August, 1977, and June, 1983, 35 patients with a small aortic root (21 mm or less) underwent aortic valve replacement with Ionescu-Shiley pericardial xenograft valves. They ranged in age from 29 to 76 years (mean 52.8 years) and in weight from 64 to 91 kg (mean 76.3 +/- 3.6 kg). Preoperatively, 26 patients were in New York Heart Association Functional Class III-IV. The valve sizes used were 17 mm in three cases, 19 mm in 16 cases, and 21 mm in 16 cases. There were four hospital deaths (11.4%) resulting from sepsis or low cardiac output. There were no late deaths. Cumulative duration of follow-up was 819.4 patient-months. Twenty-four (78%) of the 31 surviving patients are asymptomatic. Up to the time of review, there have been no episodes of thromboembolism, infective endocarditis, perivalvular leak, valve thrombosis, or primary tissue valve failure. Fifteen patients were hemodynamically evaluated 2 to 47 months (mean 14.3 months) after operation. The average resting transvalvular gradients for 19 and 21 mm valves were 15.1 and 10.8 mm Hg, respectively. Our experience suggests that the Ionescu-Shiley pericardial xenograft valve is a valid alternative in the surgical treatment of patients with a small aortic root.