Substrate Induced Movement of the Metal Cofactor between Active and Resting State.

Regulation of enzyme activity is vital for living organisms. In metalloenzymes, far-reaching rearrangements of the protein scaffold are generally required to tune the metal cofactor's properties by allosteric regulation. Here structural analysis of hydroxyketoacid aldolase from Sphingomonas wittichii RW1 (SwHKA) revealed a dynamic movement of the metal cofactor between two coordination spheres without protein scaffold rearrangements. In its resting state configuration (M2+ R ), the metal constitutes an integral part of the dimer interface within the overall hexameric assembly, but sterical constraints do not allow for substrate binding. Conversely, a second coordination sphere constitutes the catalytically active state (M2+ A ) at 2.4 Šdistance. Bidentate coordination of a ketoacid substrate to M2+ A affords the overall lowest energy complex, which drives the transition from M2+ R to M2+ A . While not described earlier, this type of regulation may be widespread and largely overlooked due to low occupancy of some of its states in protein crystal structures.

Anomeric Selectivity of Trehalose Transferase with Rare l-Sugars.

Retaining LeLoir glycosyltransferases catalyze the formation of glycosidic bonds between nucleotide sugar donors and carbohydrate acceptors. The anomeric selectivity of trehalose transferase from Thermoproteus uzoniensis was investigated for both d- and l-glycopyranose acceptors. The enzyme couples a wide range of carbohydrates, yielding trehalose analogues with conversion and enantioselectivity of >98%. The anomeric selectivity inverts from α,α-(1 → 1)-glycosidic bonds for d-glycopyranose acceptors to α,ß-(1 → 1)-glycosidic bonds for l-glycopyranose acceptors, while (S)-selectivity was retained for both types of sugar acceptors. Comparison of protein crystal structures of trehalose transferase in complex with α,α-trehalose and an unnatural α,ß-trehalose analogue highlighted the mechanistic rationale for the observed inversion of anomeric selectivity.

Laparoscopic appendectomy during pregnancy is safe for both the mother and the fetus.

INTRODUCTION: The diagnosis and treatment of acute appendicitis during pregnancy is still debated. While laparoscopic appendectomy in general has become the gold standard, this procedure has not generally been implemented for pregnant women. METHODS: We retrospectively reviewed the patient charts of all patients who underwent appendectomy during pregnancy in the period from 2000 to 2012. Open appendectomy (OA) was performed in 25 cases and laparoscopic (LA) in 19. RESULTS: We observed a significantly longer operation time (69 versus 49 min., p = 0.002), but fewer complications, a shorter hospital stay (2.6 versus 5.5 days, p = 0.004) and a lower rate of negative appendectomies (16% versus 52%, p = 0.02) in the LA group compared with the OA group. The mean gestation age at appendectomy was significantly lower in the LA group. There were no significant differences in gestational age at birth, Apgar score, birth weight or height between the two groups. Five births (11%) were categorised as mildly to moderately preterm. There were no cases of fetal loss. CONCLUSION: Laparoscopic appendectomy is safe for both the mother and the fetus during pregnancy irrespective of gestational age, and the procedure is associated with a low risk of post-operative complications. FUNDING: none. TRIAL REGISTRATION: not relevant.

ApoA-I/HDL-C levels are inversely associated with abdominal aortic aneurysm progression.

Abdominal aortic aneurysm (AAA) evolution is unpredictable, and there is no therapy except surgery for patients with an aortic size> 5 cm (large AAA). We aimed to identify new potential biomarkers that could facilitate prognosis and treatment of patients with AAA. A differential quantitative proteomic analysis of plasma proteins was performed in AAA patients at different stages of evolution [small AAA (aortic size=3-5 cm) vs large AAA] using iTRAQ labelling, high-throughput nano-LC-MS/MS and a novel multi-layered statistical model. Among the proteins identified, ApoA-I was decreased in patients with large AAA compared to those with small AAA. These results were validated by ELISA on plasma samples from small (n=90) and large AAA (n=26) patients (150± 3 vs 133± 5 mg/dl, respectively, p< 0.001). ApoA-I levels strongly correlated with HDL-Cholesterol (HDL-C) concentration (r=0.9, p< 0.001) and showed a negative correlation with aortic size (r=-0.4, p< 0.01) and thrombus volume (r=-0.3, p< 0.01), which remained significant after adjusting for traditional risk factors. In a prospective study, HDL-C independently predicted aneurysmal growth rate in multiple linear regression analysis (n=122, p=0.008) and was inversely associated with need for surgical repair (Adjusted hazard ratio: 0.18, 95 % confidence interval: 0.04-0.74, p=0.018). In a nation-wide Danish registry, we found lower mean HDL-C concentration in large AAA patients (n=6,560) compared with patients with aorto-iliac occlusive disease (n=23,496) (0.89± 2.99 vs 1.59± 5.74 mmol/l, p< 0.001). Finally, reduced mean aortic AAA diameter was observed in AngII-infused mice treated with ApoA-I mimetic peptide compared with saline-injected controls. In conclusion, ApoA-I/HDL-C systemic levels are negatively associated with AAA evolution. Therapies targeting HDL functionality could halt AAA formation.

[Lower benefit and higher total costs because of unrestricted use of endovascular repair procedures for treatment of abdominal aortic aneurysms]. / Nedsat gevinst og højere omkostninger ved ukritisk endovaskulær behandling af abdominalt aortaaneurisme.

A rapid increase in endovascular aortic repair (EVAR) procedures for treatment of asymptomatic abdominal aortic aneurysms has occurred in Denmark. However, the newest level 1A evidence suggests that unrestricted use of EVAR in patients suitable for open repair lead to lower benefit and higher total costs as compared with open surgery. Amongst cases with relative and absolute contraindications for open surgery, use of EVAR is likely to lead to more benefit, however at a relatively high cost per quality-adjusted life year (QALY). This calls for a more restrictive use.

Femoral vein repair of arterial infections: technical tips to reduce procedure time.

INTRODUCTION: Success with the neoaortoiliac system (NAIS) bypass has previously been reported. Drawbacks to this procedure include prolonged operative times and significant morbidity. The aim of this study was to evaluate whether a 2-team approach in addition to a consistent anastomosis technique reduces the operative time of the NAIS procedure. METHODS: A single-center retrospective review was performed for operations using femoral vein in arterial reconstruction from 2003 to 2012. RESULTS: A total of 40 patients, 25 men and 15 women, were included for analysis. Median operative time for all operations was 300 minutes (interquartile range). Thirty-day mortality was 7.5% (n = 3). Assisted primary patency at 1 year was 100%. CONCLUSION: A 2-surgical team approach can reduce the operative time by up to 50%. This improves the attractiveness of this procedure, particularly when recalling that the treatment is definitive by virtue of its eradication of the source of infection.

The value of routine flexible sigmoidoscopy within 48 hours after surgical repair of ruptured abdominal aortic aneurysms.

BACKGROUND: Left-sided colonic and rectal ischemia is commonly seen after surgery for ruptured abdominal aortic aneurysms (rAAAs) and is associated with increased mortality. Earlier studies have shown that flexible sigmoidoscopy (FS) may detect ischemia when performed postoperatively, and suggestions have been made that patients can be selected for FS based on clinical and biochemical parameters. We sought to perform FS in all patients surviving the first 24 hours after surgery for rAAA and to compare the findings of FS to clinical and biochemical parameters. METHODS: All patients undergoing emergency surgery for rAAA and surviving the first 24 hours underwent FS to assess any degree of ischemia. RESULTS: During the study period, 41 patients survived the first 24 hours after surgery. In 9 (22%) patients, some degree of colonic ischemia was found. Segmental necrosis was only shown in 5% at first FS. Patients with ischemia received more blood transfusions intraoperatively than those with normal findings at FS. They also had longer periods with mean blood pressure <60 mm Hg postoperatively, and lower arterial pH on the first postoperative day. Blood lactate levels did not differ between the groups. None of the parameters were sufficiently discriminative to be used for distinguishing between patients with and without ischemia. CONCLUSIONS: Severe colonic ischemia was less common than previously reported. All cases of colonic ischemia were identified by early FS, but none of the clinical and biochemical parameters were sufficiently reliable to distinguish between patients with and without ischemia. It is suggested that all patients initially surviving surgery for rAAA should be offered FS to screen for colonic ischemia.

Cost effectiveness of abdominal aortic aneurysm screening and rescreening in men in a modern context: evaluation of a hypothetical cohort using a decision analytical model.

OBJECTIVE: To assess the cost effectiveness of different screening strategies for abdominal aortic aneurysm in men, from the perspective of a national health service. SETTING: Screening units at regional hospitals. PARTICIPANTS: Hypothetical cohort of 65 year old men from the general population. MAIN OUTCOME MEASURES: Costs (£ in 2010) and effect on health outcomes (quality adjusted life years (QALYs)). RESULTS: Screening seems to be highly cost effective compared with not screening. The model estimated a 92% probability that some form of screening would be cost effective at a threshold of £20,000 (€24,790; $31,460). If men with an aortic diameter of 25-29 mm at the initial screening were rescreened once after five years, 452 men per 100,000 initially screened would benefit from early detection, whereas lifetime rescreening every five years would detect 794 men per 100,000. We estimated the associated incremental cost effectiveness ratios for rescreening once and lifetime rescreening to be £10,013 and £29,680 per QALY, respectively. The individual probability of being the most cost effective strategy was higher for each rescreening strategy than for the screening once strategy (in view of the £20,000 threshold). CONCLUSIONS: This study confirms the cost effectiveness of screening versus no screening and lends further support to considerations of rescreening men at least once for abdominal aortic aneurysm.

Prognosis of ruptured abdominal aortic aneurysms in Denmark from 1994-2008.

INTRODUCTION: Few modern population-based estimates of the prognosis of ruptured abdominal aortic aneurysm (rAAA) exist. METHODS AND MATERIALS: From 1994-2008, a total of 6954 rAAA cases were identified in Danish nationwide population-based registries. RESULTS: Of 3148 (45%) surgery cases, 1454 (46%) died within 30 days of surgery. The overall mortality risk of rAAA was 76%. The proportion of patients who received surgery increased from 44%, in the first study period, to 47% in the last study period; the 30-day postoperative mortality rate decreased from 51% to 42%; and the overall mortality risk declined significantly from 77% to 74% (odds ratio: 0.86: 95% confidence interval: 0.77-0.97). However, the age-adjusted mortality rate remained unchanged, due to the increased incidence of rAAA.

Long-term incidence of myocardial infarct, stroke, and mortality in patients operated on for abdominal aortic aneurysms.

OBJECTIVE: The risks of myocardial infarction (MI) and stroke after abdominal aortic aneurysm (AAA) resection are not known. Prophylaxis with aspirin and statins is not generally recommended, although patients with AAAs have an increased prevalence of cardiovascular atherosclerosis. We report the incidences of MI, stroke, and death in an unselected national cohort of patients operated on for AAAs, with the general population as the control group. METHODS: In a matched cohort study, 11,094 Danish patients who underwent acute or elective open AAA repair from January 1986 through June 2009 were compared with four randomly chosen age- and sex-matched individuals (controls) from the general population (n = 44,364). Data were collected retrospectively from the Danish Vascular Registry (Karbase), the National Population Registry, and the National Inpatient Registry. The groups were analyzed for the incidences of MI, stroke, and death, with up to 20 years of follow-up. RESULTS: AAA patients had an annual MI incidence of 2.5% (hazard ratio, 2.1; 95% confidence interval [CI], 1.9-2.2) compared with the general population. The annual incidence of stroke was 2.9% (hazard ratio, 1.8; 95% CI, 1.6-1.9), and there was a 2.4-fold (95% CI, 2.3-2.4) increase in the hazard of all-cause mortality compared with the general population. CONCLUSION: AAA patients of both sexes have a high risk of atherosclerotic events (MI, stroke) and death, so lifelong prophylaxis must be considered from our epidemiologic data. Randomized trials investigating the potential benefit of aspirin and statin therapy in AAA patients are needed.

Hemodynamic effects of closure of residual arteriovenous fistulae during in situ graft procedures.

The objective was to study the intraoperative hemodynamic effects of closure of residual arteriovenous fistulae during in situ saphenous vein graft procedures. Data on 60 residual arteriovenous fistulae in nine patients (five men) with a median age of 74 years (range 64-83 years) with critical lower limb ischemia were obtained. Direct measurements of proximal and distal blood pressures in the graft were taken and simultaneous determinations of volume blood flow proximally and distally in the graft with ultrasound transit time technique before and after closure of residual fistulae were made. Closure of a fistula with blood flow around or below 100 mL/min did not increase distal outflow, whereas closure of fistulae with higher blood flow resulted in unpredictable changes in distal outflow. Only fistulae with a blood flow above approximately 100 mL/min may be of hemodynamic significance.

[Autologous reconstruction with a femoral vein in cases of infection in synthetic prosthetic vascular grafts]. / Autolog rekonstruktion med dybe vener ved infektion i syntetiske karproteser.

Infection in central prosthetic vascular grafts is a serious threat to both life and limb of the patient. Replacement of the infected material with autologous graft material is the logical treatment. Only recently, however, has it been demonstrated that it is possible to remove the patient's own femoral vein and use it as an arterial conduit. We report our initial experience with the first three operations performed in this country.