A point mutation in influenza B neuraminidase confers resistance to peramivir and loss of slow binding

The influenza neuraminidase (NA) inhibitors peramivir, oseltamivir, and zanamivir are potent inhibitors of NAs from both influenza A and B strains. In general, these inhibitors are slow, tight binders of NA, exhibiting time-dependent inhibition. A mutant of influenza virus B/Yamagata/16/88 which was resistant to peramivir was generated by passage of the virus in tissue culture, in the presence of increasing concentrations (0.1-120 microM over 15 passages) of the compound. Whereas the wild type (WT) virus was inhibited by peramivir with an EC(50) value of 0.10 microM, virus isolated at passages 3 and 15 displayed EC(50) values of 10 and >50 microM, respectively. Passage 3 virus contained 3 hemagglutinin (HA) mutations, but no NA mutation. Passage 15 (P15R) virus contained an additional 3 HA mutations, plus the NA mutation His273Tyr. The mechanism of inhibition of WT and P15R NA by peramivir was examined in enzyme assays. The WT and P15R NAs displayed IC(50) values of 8.4+/-0.4 and 127+/-16 nM, respectively, for peramivir. Peramivir inhibited the WT enzyme in a time-dependent fashion, with a K(i) value of 0.066+/-0.002nM. In contrast, the P15R enzyme did not display the property of slow binding and was inhibited competitively with a K(i) value of 4.69+/-0.44nM. Molecular modeling suggested that His273 was relatively distant from peramivir (>5A) in the NA active site, but that Tyr273 introduced a repulsive interaction between the enzyme and inhibitor, which may have been responsible for peramivir resistance.     

Endovascular management of a ruptured mycotic aneurysm of the innominate artery

Mycotic aneurysms of the innominate artery are infrequent lesions and, as such, represent challenging surgical problems. We describe herein a case of a ruptured mycotic innominate artery aneurysm, which developed after radical neck dissection and radiation therapy for tonsillar carcinoma. The aneurysm was successfully excluded from the systemic circulation with endoluminal placement of a covered stent, with efficacy confirmed by vascular imaging at 6 months follow-up. The patient suffered no permanent neurologic sequelae. Long-term follow-up and chronic antibiotic therapy will be necessary to avoid infection of the covered stent in this high-risk surgical patient.     

Conservatism and new technology: the impact on abdominal aortic aneurysm repair

The last decade has represented a time of fundamental change in the treatment of abdominal aortic aneurysms (AAAs). Potentially, vascular surgeons will either acquire catheter-based skills or relinquish the care for many patients with infrarenal AAA. We investigated AAA referral patterns and method of AAA repair after the establishment of an endovascular AAA program at our institution. We conducted a retrospective review of elective AAA repairs after the initiation of an endovascular AAA program in April 1994. Six vascular surgeons performed all procedures with a clear distinction between the surgeons (n=3) who performed traditional AAA repair only and those (n=3) who managed AAAs by means of either endovascular or traditional treatment. From April 1994 through December 2000, 740 elective AAA repairs were performed. During this time the mean number of AAA repairs has been 106/year ranging from 75 to 155/year. More notable however is the steady increase in the percentage of endovascular AAA repairs from 6 per cent of all AAA repairs in 1994 to 61 per cent in 2000. During this time traditional surgeons have experienced a plateau in total AAA repairs performed per year with their number of open repairs decreasing by 36 per cent. At the same time endovascular surgeons have seen a progressive rise in total AAA cases including an increase of 200 per cent in open repairs and of 1367 per cent in endovascular repairs. Our vascular surgeons who repair AAA utilizing both endovascular and open techniques have experienced an increase in aneurysm referrals since the advent of an endovascular AAA program. Those who have not adopted endovascular skills have seen a decline in their aneurysm practice. The larger question about whether or not to embrace new technology before the availability of long-term follow-up remains unanswered.     

A prospective evaluation of hypogastric artery embolization in endovascular aortoiliac aneurysm repair

PURPOSE: Hypogastric artery embolization (HAE) is often performed in endovascular aortoiliac aneurysm repair to prevent potential endoleak, and this can be associated with pelvic ischemic sequelae. This prospective study was performed to evaluate the clinical outcome of HAE in patients who underwent endovascular aortoiliac aneurysm repair. METHODS: During a 15-month period, 12 patients who underwent either unilateral or bilateral HAE for endovascular aortoiliac aneurysm repair were prospectively evaluated. All patients underwent preoperative and postoperative penile pressure measurement and pulse-volume recording evaluation. Angiographic features relating to pelvic collaterals and clinical outcomes relating to pelvic ischemia were evaluated. RESULTS: Unilateral HAE was performed in eight patients (67%), and bilateral HAE was performed in four patients (33%). Mean reductions in penile brachial index (PBI) after unilateral and bilateral HAE were 13 +/- 6% (not significant) and 39 +/- 14% (P <.05), respectively. Erectile dysfunction occurred in three patients for unilateral HAE (38%) and in two patients for bilateral HAE (50%), with an overall PBI reduction of 36 +/- 12% (P <.01). No significant change in thigh brachial or ankle brachial index occurred after HAE. Hip and buttock claudication occurred in four patients for unilateral HAE (50%) and in two patients for bilateral HAE (50%), with an overall PBI reduction of 18 +/- 9% (P <.05). Other associated pelvic ischemic complications after bilateral HAE included one scrotal skin sloughing (25%) that occurred 3 days after aortic endografting and one sacral decubitus (25%) that occurred 4 months after aortic endografting. With analysis of angiographic collateral patterns, diseased profunda femoral artery (PFA; >50% stenosis) was noted in four patients, all in whom post-HAE pelvic ischemic symptoms developed (P <.05). In contrast, only four of the remaining eight patients with normal or mild PFA disease had pelvic ischemic sequelae after HAE. CONCLUSION: Erectile dysfunction after HAE correlates with significant reduction in PBI. Severe pelvic ischemic symptoms are more likely to occur after bilateral HAE, which should be avoided if possible. Moreover, patients with diseased PFA are at risk of development of pelvic ischemia after HAE. Our data suggest a potential role of concomitant profundapalsty at the time of aortic endografting to improve pelvic collateral flow and reduce pelvic ischemia in this subset of patients with HAE.     

A strategy for in vitro propagation of rat nephrons

BACKGROUND: Recent advances in the understanding of the molecular biology of rodent renal development have lead to the ability to culture the components of the developing rat kidney-the ureteric bud (UB) and the metanephric mesenchyme (MM)-in isolation from one another. Here we here describe a method for subculturing and propagating either whole rat metanephric rudiments or isolated rat UBs. Exploiting the branching program intrinsic to the UB, propagated rat UBs can be recombined with fresh rat mesenchyme to form a large number of rat "neokidneys" derived from a single progenitor that may be amenable to site-specific modulation of function. METHODS: Whole rat metanephric rudiments or isolated rat UBs were cultured and subdivided through several generations. Both cultured progenitor and subsequent generations of isolated rat UBs were recombined with freshly isolated rat metanephric mesenchyme. The tubules of these rat neokidneys were examined for expression of epithelial markers. RESULTS: Isolated rat UBs and whole rat metanephric rudiments could be propagated through several generations and appeared morphologically identical to their progenitors. Generations of isolated rat UB could be recombined with fresh rat mesenchyme and the resultant neokidney displayed the same morphologic appearance as the whole rat kidney rudiment. The UB-derived and MM-derived portions of the tubules of these rat neokidneys appear contiguous. CONCLUSIONS: The recombination of cultured and propagated rat UB with rat mesenchyme yielded rat neokidneys with tubular structures that appeared morphologically identical to whole rat kidney. In vitro propagation of rat metanephric rudiments and recombination of rat UB and MM suggest the possibility of designing nephrons that possess specific desirable functions that can be propagated in vitro.