Reduced reactivation rate in mutant CuZnSOD and progression rate of amyotrophic lateral sclerosis

Mutations in the SOD1 gene are associated with familial amyotrophic lateral sclerosis (fALS). The mechanisms by which these mutations lead to anterior horn cell loss are unknown, however, increased binding of Hsps on the demetallated mutant SOD1 has been described which would make the HSPs unavailable for other purposes, and reduce the SOD1 concentration in mitochondria, thereby creating a proapoptotic situation finally leading to motor neuron death. Here we report the recombinant expression of four human copper/zinc superoxide dismutase (CuZnSOD) variants, including the wild-type enzyme and mutant proteins associated with familial ALS. The bacterial expression level of soluble mutated proteins was influenced by the mutations leading to drastically reduced levels of soluble CuZnSOD. Simultaneously, increasing levels of insoluble and probably aggregated mutated CuZnSOD were identified in bacterial cell pellets. In addition, altered reactivation kinetics of the purified mutant apoproteins after expression in bacterial culture was shown. Biophysical and biochemical analysis showed that zinc incorporation is severely reduced in the CuZnSOD proteins associated with the most severely forms of fALS (A4V, G93A). These data indicate that a reduced holoenzyme formation rate of mutant enzymes may be a critical factor in the etiopathology of fALS.

Leukoencephalopathy and chronic pancreatitis as concomitant manifestations of systemic lupus erythematosus related to anticardiolipin antibodies

Symptoms of leukoencephalopathy led to hospital admission of a 59-year-old woman. In addition, a tumor of unknown nature in the pancreas was identified by abdominal ultrasound and CT scan. Following explorative laparotomy and pancreas tail resection, histopathologic analysis revealed a pancreatic pseudotumor with chronic fibrotic pancreatitis. Systemic lupus erythematosus (SLE) was diagnosed due to the presence of antinuclear antibodies (ANA) in serum, antiphospholipid antibodies, and involvement of the central nervous system. Leukoencephalopathy related to anticardiolipin antibodies in serum is a known but rare manifestation of SLE. The concomitant occurrence of chronic pancreatitis can be caused by the development of SLE-induced vasculitis in the pancreas. Subsequent complications of pancreatitis are responsible for the critical, life-threatening state of these patients and may be prevented by early identification of anticardiolipin antibodies and therapy for SLE.

High-resolution contrast-enhanced magnetic resonance angiography of the carotid arteries using fluoroscopic monitoring of contrast arrival: diagnostic accuracy and interobserver variability

PURPOSE

To evaluate the diagnostic accuracy of high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) of the supra-aortic arteries using the CareBolus technique. Digital subtraction angiography was the standard of reference.

MATERIAL AND METHODS

Fifty consecutive patients with suspected internal carotid artery stenosis underwent CE-MRA and digital subtraction angiography. CE-MRA was performed on a 1.5-T superconducting scanner with the CareBolus technique. CareBolus combines a nearly real-time 2D-FLASH (fast low angle shot) sequence for fluoroscopic triggering and a high-resolution 3D-FLASH with elliptical centric view order for the angiographic pulse sequence (6.0/2.16 ms [TR/TE], 30 degrees flip angle, 30.98 s acquisition time, 0.88 mm effective (interpolated) partition thickness and a 160 x 512 matrix). Intra-arterial digital subtraction angiography and CE-MRA studies were evaluated independently by four blinded readers. Internal carotid artery stenoses were graded according to the NASCET criteria.

RESULTS

CE-MRA had an accuracy of 92.53%, a sensitivity of 95.64%, and a specificity of 90.39% for the identification of carotid artery stenoses > or = 70% (grade 3). Image quality for suppression of stationary tissue and venous contrast was good, but was reduced in five cases due to patient motion.

CONCLUSION

The CareBolus technique is a useful non-invasive method for high-resolution imaging of the supra-aortic vessels because of its easy application and high sensitivity and specificity. Limitations can occur in non-compliant patients due to motion artifacts during the measurement time.

Selective intraarterial fibrinolysis of acute central retinal artery occlusion

PURPOSE

To evaluate the outcome of our patients with central retinal artery occlusion after local fibrinolysis and to compare these data with results reported in the literature.

MATERIAL AND METHODS

Over a period of 7 years, 22 patients (11 male, 11 female, mean age 64.6 +/- 12.1 years) were treated with super-selective local fibrinolysis. In 1 case, treatment was carried out via the maxillary-ophthalmic anastomoses due to preexisting occlusion of the ipsilateral internal carotid artery. The latency period from the onset of symptoms to the beginning of therapy was 7.6 +/- 1.8 h. Urokinase was used in 7 cases (300,000-1.1 million units) and recombinant tissue plasminogen activator (20-40 mg) was applied in 15 patients. Visual acuity and fundus were examined before and after treatment.

RESULTS

One patient (1/22 = 4.6%) recovered completely and regained a visual acuity of 20/20. Six patients (6/22 = 27.3%) showed a marked improvement with a range of visual outcome from 20/800 to 20/320. In 2 cases (2/22 = 9.1%) only a slight improvement was observed, with a visual outcome allowing detection of hand movements. In 13 cases (13/22 = 59.1%) no change in visual acuity as a result of treatment was observed. In 2/22 cases (9.2%) reversible neurological side-effects occurred, in 1 case suffered a stroke, and in another case intracerebral bleeding was observed.

CONCLUSION

In our study, the recovery of visual acuity and the complication rate were not as positive as reported in the literature.

[Evaluation of a hemostatic device with percutaneous collagen application (VasoSeal) compared to a mechanical compression system (Compressar) after transfemoral catheterization of patients suffering from arterial occlusive disease]

PURPOSE

Comparison of the efficacy of VasoSeal and a mechanical compression system (Compressar) for percutaneous hemostasis after femoral arterial catheterization of patients with arterial occlusive disease.

MATERIALS AND METHODS

60 patients underwent either diagnostic angiography or interventional procedures. The level of anticoagulation, blood pressure, and activation clotting time were recorded, and the time to hemostasis after sheath removal was measured. VasoSeal application was considered "successful" if the compression time was less than two minutes. On the subsequent day as well as 4 months later, color coded Doppler ultrasound was performed to register treatment success and potential (late) complications.

RESULTS

57 patients qualified for inclusion in this study. In 21 of the 26 patients who underwent the procedure with the VasoSeal, immediate hemostasis was achieved within 1.75 minutes. In all 31 patients who had the Compressar applied, hemostasis was successful with a mean compression time of 17.4 minutes. Thus, VasoSeal significantly reduced hemostasis time irrespective of anticoagulation status, but it had a much higher incidence of minor local complications (bleeding, hematoma) compared to the control group (34.6 % vs. 5.8 %). The technical success was lower with VasoSeal than with Compressar (81 % vs. 100 %). Both groups had no severe or late complications.

CONCLUSION

According to our results, VasoSeal does not provide a suitable alternative compared to the effective, safe and cheap application of Compressar as a hemostatic device.

Bolus-chasing contrast-enhanced 3D MRA of the lower extremity. Comparison with intraarterial DSA

PURPOSE

To evaluate step-table 3D contrast-enhanced (CE) MRA with bolus chasing for the detection and grading of stenoses in patients with peripheral vascular disease (PVD) of the lower extremities.

MATERIAL AND METHODS

Fifty patients were studied by step-table bolus-chasing 3D-CE-MRA and i.a. DSA within 24 h. After determination of the individual circulation time, CE-MRA was performed during power injection of 40 ml of Gd-DTPA. To cover the whole range between the renal arteries and the feet with three slab locations, the scanner table was manually advanced twice for 350 mm. Total imaging time was 1 min 23 s. The degree of stenosis and image quality of the images were evaluated by 2 observers. In addition, a treatment plan was established based on the 3D-CE-MRA and DSA investigations.

RESULTS

In 44 of 50 patients (88%), the visualization of the arterial tree from the renal arteries to the foot was possible. Forty-six of 50 patients (92%) had good or very good image quality. In the calf, 3D-CE-MRA was superior to DSA in 6 patients. For the detection of stenosis >50%, sensitivity was 99.5%, specificity 98.8%, positive predictive value 95.6% and the negative predictive value 99.8%. Cohen's kappa for 3D-CE-MRA vs. DSA was 0.926; for interobserver agreement it was 0.96.

CONCLUSION

Bolus-chasing 3D-CE-MRA with manual table movement is a simple, robust and easy to perform technique which provides high quality angiograms of the lower extremity arterial system and is comparable to, i.a., DSA for the diagnosis of PVD.

Bolus-chasing contrast-enhanced 3D MRA of the lower extremity. Comparison with intraarterial DSA

PURPOSE

To evaluate step-table 3D contrast-enhanced (CE) MRA with bolus chasing for the detection and grading of stenoses in patients with peripheral vascular disease (PVD) of the lower extremities.

MATERIAL AND METHODS

Fifty patients were studied by step-table bolus-chasing 3D-CE-MRA and i.a. DSA within 24 h. After determination of the individual circulation time, CE-MRA was performed during power injection of 40 ml of Gd-DTPA. To cover the whole range between the renal arteries and the feet with three slab locations, the scanner table was manually advanced twice for 350 mm. Total imaging time was 1 min 23 s. The degree of stenosis and image quality of the images were evaluated by 2 observers. In addition, a treatment plan was established based on the 3D-CE-MRA and DSA investigations.

RESULTS

In 44 of 50 patients (88%), the visualization of the arterial tree from the renal arteries to the foot was possible. Forty-six of 50 patients (92%) had good or very good image quality. In the calf, 3D-CE-MRA was superior to DSA in 6 patients. For the detection of stenosis >50%, sensitivity was 99.5%, specificity 98.8%, positive predictive value 95.6% and the negative predictive value 99.8%. Cohen's kappa for 3D-CE-MRA vs. DSA was 0.926; for interobserver agreement it was 0.96.

CONCLUSION

Bolus-chasing 3D-CE-MRA with manual table movement is a simple, robust and easy to perform technique which provides high quality angiograms of the lower extremity arterial system and is comparable to, i.a., DSA for the diagnosis of PVD.

[Percutaneous therapy of inoperable biliary stenoses and occlusions with a new self-expanding nitinol stent (SMART)]

OBJECTIVE

To evaluate the treatment of malignant biliary stenoses and occlusions using a new stent.

METHODS

In a prospective study, 25 patients with malignant obstructive jaundice were treated with SMART(R) stents. The handling and the quality of stent expansion were documented. Stent function was assessed 2 - 4 days after intervention by cholangiography and laboratory tests. A follow-up was performed three months, after stent placement.

RESULTS

All lesions were treated successfully, with a total of 35 stents implanted. In 14 patients a further balloon dilatation was performed after stent placement (8 - 10 mm diameter/ 40 - 80 mm length). The mean serum bilirubin level decreased significantly from 11.6 mg/dl to 4.6 mg/dl after intervention (p < 0.05). The follow-up showed a mean serum bilirubin level at 4.0 mg/dl. In 4 cases (16 %) a further intervention (PTCD or stent) was performed. Six patients died due to tumor progression. The stents proved to be patent in 79 % (n = 15) of patients alive at the time of follow-up.

CONCLUSIONS

Placement of the SMART stent for the therapy of malignant biliary lesions yields good technical and clinical results.

[Contrast-enhanced MR angiography in the routine work-up of the lower extremity arteries]

PURPOSE

Prospective evaluation of the effectiveness of contrast-enhanced moving-table magnetic resonance angiography (CE-MRA) as the sole routine tool for the diagnosis of peripheral arterial occlusive disease and determination whether it can replace catheter arteriography.

SUBJECTS AND METHODS

In a time period of 23 weeks, 100 consecutive patients were evaluated. A total of 112 contrast-enhanced moving-table MR angiograms were performed at 1.5 Tesla. A dedicated vascular coil system was used. It was evaluated in which cases MR angiography was sufficient to determine the treatment plan and in which cases limited quality required additional examinations.

RESULTS

In 93.75 % (105/112) of all examinations, the treatment plan was determined by MRA as the sole diagnostic tool. Twenty-two patients underwent surgery or percutaneous angioplasty based on MRA findings. Additional examinations due to impaired quality were performed in seven (6.25 %) cases: two MR angiographies of the pelvic arteries, one MR angiography of the calf, and four selective arteriographies because of venous overlay at the calf.

CONCLUSION

Contrast-enhanced MR angiography can take the place of catheter angiography in the routine work-up of patients with peripheral arterial occlusive disease. Further assessment might be necessary in five to ten percent of the cases when the diagnostic quality is inadequate, mostly due to venous overlay in the lower leg.

[Extracorporeal lung support and endovascular stent in traumatic aortic rupture and severe lung failure]

Blunt thoracic injury in association with aortic rupture represents a life-threatening situation. Surgical repair used to be the preferred method of treatment. Because most patients are multiple trauma patients including head injuries, bone fractures and respiratory failure, urgent surgical procedures portend excessively high morbidity and mortality rates. Delay in operative management bears the risk of exsanguinating hemorrhage, secondary complications, prolonged hospital stay with increased costs. We present here an alternative treatment protocol including pumpless extracorporal lung assist and endovascular aortic stent graft placement in a 20-year old traffic accident victim. This procedure may be an especially useful treatment option in managing patients with complex lung and aortic pathology primarily not suitable for transportation or surgery.

Evaluation of arterial bypass grafts of the pelvic and lower extremities with gadolinium-enhanced magnetic resonance angiography: comparison with digital subtraction angiography

RATIONALE AND OBJECTIVES

The aim of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) with digital subtraction angiography (DSA) in the assessment of patency and stenoses in bypass grafts.

METHODS

Fifteen patients were examined with both CE MRA and DSA. Fifteen bypass grafts were evaluated by four readers for potential stenosis in five locations. The stenoses were classified in five types: 1 (0% to 24% stenosis), 2 (25% to 49%), 3 (50% to 74%), 4 (75% to 99%), and 5 (occlusion).

RESULTS

Using both techniques, 70 of 75 evaluated locations (93.3%) were classified identically. This included six stenoses < 50% and six stenoses > 50%, respectively. Four of five overestimations of stenoses were scaled in DSA as stenoses type 1. One stenosis was categorized as type 3 in DSA. Sensitivity for CE MRA for detecting stenoses >or= 25% was 100% and the specificity 90%. Interobserver agreement for all evaluations was 0.77 (Spearman rank correlation test).

CONCLUSION

In the assessment of low-grade stenosis in bypass grafts, CE MRA overestimates stenoses slightly but yields good results in comparison with DSA.

[Indirect MR Arthrography of the wrist in the diagnosis of TFCC-Lesions]

PURPOSE

The objective of this prospective study was to assess the value of the indirect MR arthrography (MR-AR) of the wrist in the detection of lesions of the TFCC.

MATERIAL AND METHODS

Indirect MR-AR was performed in 45 patients (23 f/22 m) with unclear ulnar wrist pain. After i. v. injection of 0.1 mmol/kg Gd-DTPA and after a motion-phase of the wrist (15 minutes) MRI was performed in a coronal plane. We used a STIR-, a fatsaturated (fs) T1-SE and a 3D-DESS sequence. The images were evaluated by two radiologists using a consensus score. The lesions were assigned to the system of Palmer and correlated with arthroscopy.

RESULTS

Indirect MR-AR showed in 35 of 45 patients a lesion of the TFCC, but arthroscopy only revealed a defect in 32 cases. This means three false positive but no false negative assessments by MRI. Using this MRI protocol sensitivity and specificity in the detection of TFCC lesions were calculated as 100 % and 77 %. The accuracy was 93 %. Small degenerative changes of the fibres were most common (Palmer type II A). In trauma patients the ligaments usually showed tears near the insertion at the ulna (Palmer type I B). The sensitivity and specificity was 88 % and 95 % for evaluation of the scapho-lunate (SL) ligament, the accuracy was 93 %. Arthroscopy and MRI did not diagnose any rupture of the lunate-triquetral (LT) ligament.

CONCLUSION

Indirect MR-AR is a non-invasive method with a high sensitivity in the evaluation of the TFCC and associated injuries. Therefore, it is an excellent screening procedure to assess the indication for therapeutic arthroscopy.

[CT-guided thoracal sympathicolysis for the treatment of peripheral arterial occlusive disease and chronic thoracal pain syndromes in 6 patients]

CT-guided thoracal sympathicolysis for the treatment of peripheral arterial occlusive disease and chronic thoracal pain syndromes in 6 patients.

PURPOSE

Retrospective evaluation of the safety and effectivity of CT-guided percutaneous thoracal sympathicolysis (CT-TSL) in the treatment of patients with peripheral arterial occlusive disease (PAOD) of the upper limb and chronic thoracal pain syndromes. Comparison of our own experience with literature reports.

MATERIAL AND METHODS

Between 6/96 and 12/99, 4 patients with PAOD of the upper limb and two with chronic thoracal pain syndromes caused by herpes zoster were treated by unilateral CT-TSL.

RESULTS

18, 21 and 32 months after the intervention 3 out of 4 patients treated for PAOD reported subjective improvements, and one remained unchanged. Two patients treated for pain syndromes showed no long-term benefit of the procedure. There were no serious complications.

CONCLUSION

The CT-TSL is an alternative method in the treatment of PAOD in patients who are unsuitable for treatment by revascularization.

[The endoleak problem in endoluminal therapy]

Endovascular treatment of aortic aneurysms with stent grafts was performed increasingly in recent years. The most frequent complication after endovascular therapy of aortic aneurysms is an endoleak. In case of a persistent endoleak, diameter of the aneurysm is increasing with a high risk of aneurysm ruptur. Diagnostic tools are spiral computed tomography and angiography. Spiral computed tomography is the most sensitive method for the diagnosis of an endoleak ad should be performed with a biphasic acquisition. In- and outflow of sidebranches can be identified correctly with selective angiography in 86%. Perigraft endoleaks should be treated in any case. Patent side branches generally are observed over a period of 6 months. After 6 months approximately half of these endoleaks are thrombosed. Is there an increasing of the diameter of the aneurysm or any changing in the morphology of the aneurysm there is an indication for embolisation of these sidebranches of the aneurysmal sac. Preinterventional embolisation of patent sidebranches is under discussion. Type I endoleaks can be managed by additional stent-graft implantation or coil embolisation. In case of type II endoleaks in- ad outflow vessels should be embolised with coils. Therapy of type III endoleak is performed mostly by additional stent-graft placement. The total incidence of secondary interventions in the Eurostar-study was nearly 10% per year.

Superoxide dismutase mutations of familial amyotrophic lateral sclerosis and the oxidative inactivation of calcineurin

Approximately 10% of all familial cases of amyotrophic lateral sclerosis (fALS) are linked to mutations in the SOD1 gene, which encodes the copper/zinc superoxide dismutase (CuZnSOD). Recently, wild-type CuZnSOD was shown to protect calcineurin, a calcium/calmodulin-regulated phosphoprotein phosphatase, from inactivation by reactive oxygen species. We asked whether the protective effect of CuZnSOD on calcineurin is affected by mutations associated with fALS. For this, we monitored calcineurin activity in the presence of mutant and wild-type SOD. We found that the degree of protection against inactivation of calcineurin by different SOD mutants correlates with the severity of the phenotype associated with the different mutations, suggesting a potential role for calcineurin-SOD1 interaction in the etiology of fALS.

[The problem with endoleakage in endoluminal therapy]

Endovascular treatment of aortic aneurysms with stent grafts was performed increasingly in recent years. The most frequent complication after endovascular therapy of aortic aneurysms is an endoleak. In case of a persistent endoleak, diameter of the aneurysm is increasing with a high risk of aneurysm rupture. Diagnostic tools are spiral computed tomography and angiography. Spiral computed tomography is the most sensitive method for the diagnosis of an endoleak ad should be performed with a biphasic acquisition. In- and outflow of sidebranches can be identified correctly with selective angiography in 86%. Perigraft endoleaks should be treated in any case. Patent side branches generally are observed over a period of 6 months. After 6 months approximately half of these endoleaks are thrombosed. Is there an increasing of the diameter of the aneurysm or any changing in the morphology of the aneurysm there is an indication for embolisation of these sidebranches of the aneurysmal sac. Preinterventional embolisation of patent sidebranches is under discussion. Type I endoleaks can be managed by additional stent-graft implantation or coil embolisation. In case of type II endoleaks in- ad outflow vessles should be embolised with coils. Therapy of type III endoleak is performed mostly by additional stent-graft placement. The total incidence of secondary interventions in the Eurostar-study was nearly 10% per year.

Renal time-resolved MR angiography: quantitative comparison of gadobenate dimeglumine and gadopentetate dimeglumine with different doses

PURPOSE

Results with different doses of gadobenate dimeglumine and gadopentetate dimeglumine were compared at magnetic resonance (MR) angiography of the renal arteries. The signal-to-noise ratio (SNR) was evaluated as a quantitative measure of image quality.

MATERIALS AND METHODS

Sixty consecutive patients (age range, 24-81 years; mean age, 65 years) underwent intraarterial digital subtraction angiography (DSA) and contrast material-enhanced time-resolved MR angiography. DSA was the standard of reference. Fifteen patients received gadopentetate dimeglumine at doses of 0.2 or 0.1 mmol per kilogram of body weight. Fifteen patients received gadobenate dimeglumine at doses of 0.05 or 0.1 mmol/kg. The SNR was calculated in the aorta and both main renal arteries. The number and degree of stenoses of the renal arteries and accessory vessels were evaluated by four observers.

RESULTS

SNRs with gadobenate dimeglumine at a dose of 0.1 mmol/kg were significantly superior to those with gadopentetate dimeglumine at a dose of 0.1 mmol/kg. Differences were not statistically significant between the SNRs in the other groups. Eleven (85%) of 13 hemodynamically significant renal artery stenoses were detected correctly with MR angiography as were 22 (85%) of 26 accessory renal arteries.

CONCLUSION

SNRs with gadobenate dimeglumine were higher than those with gadopentetate dimeglumine, but in most cases the differences in SNRs were not statistically significant.

[Central retinal artery occlusion. Importance of selective intra-arterial fibrinolysis]

BACKGROUND

Conventional treatment of a central retinal artery occlusion usually has a poor prognosis but intra-arterial fibrinolysis (IF) of the ophthalmic artery is an invasive treatment option. The importance of IF was evaluated in 62 patients with central retinal artery occlusion and in addition the risk spectrum for this disease was considered.

MATERIAL AND METHODS

Data from charts of 62 patients were retrospectively analysed. Visual recovery after IF (n = 17) was compared to conventional treatment (e.g. decrease of IOP, improvement of rheological conditions, n = 45). Patients were excluded from IF if the occlusion was present for more than 8 h, if there was a history of bleeding and previous operations, or if they were older than 85 years. IF was performed using either urokinase (n = 7) or tPA (n = 10).

RESULTS

Out of 62 patients, 22 (35%) with central retinal artery occlusion underwent catheterisation. Stenosis of the carotid artery excluded IF in 5 out of these 22 cases, therefore only 17 patients were treated by IF. Of the patients, 40 (65%) were excluded from IF for various reasons: 47% (19/40) arrived later than 8 h after occlusion, 17% (7/40) did not consent to IF, 15% (6/40) had medical contraindications and 13% (5/40) were over 85 years of age. Two patients required no IF because of a cilioretinal anastomosis with moderate visual acuity and another patient showed spontaneous visual recovery during ophthalmic examination. Of the 17 patients treated with IF, 4 achieved an improvement of visual acuity by more than 2 lines, no change of visual acuity was observed in 12/17 patients and 1/17 lost more than 2 lines after treatment. Of the 45 conservatively treated patients, 16 achieved improvement by more than 2 lines and no change occurred in 29/45 patients. Three patients treated with IF suffered from a stroke during treatment. The main risk factor for central retinal artery occlusion was high blood pressure in 32% of all cases and nicotine abuse in 16%.

CONCLUSIONS

Many patients presented too late for IF. However, there was no statistical difference between patients with IF and conventional treatment with regards to the improvement of visual acuity. Additionally there is an increased risk of a stroke from IF, therefore a prospective study is necessary to evaluate the importance of IF. Stabilisation of high blood pressure may be the best prophylaxis for preventing a central retinal artery occlusion.

[Treatment of para-ostium renal artery stenoses with a new, solidly premounted balloon expandable stent]

PURPOSE

Evaluation of the handling, technical success rate, and six-months patency rate of a new, premounted balloon-expandable stent in ostial renal artery stenoses.

MATERIAL AND METHODS

In a prospective study, 27 ostial renal artery stenoses in 20 patients were primarily treated with the new "Renal Bridge Stent" (Medtronic AVE, Düsseldorf). All patients had a history of hypertension and 8 patients had renal dysfunction. The handling and visibility of the stent was scored on a three grade scale by the operators. Follow-up angiography including intra-arterial trans-stenotic pressure measurements was performed in 23 out of 27 stenoses (17 patients).

RESULTS

Handling and visibility were scored as good by all operators. 26 of 27 stenoses were treated with technical success by implantation of 28 stents. The mean degree of stenosis was reduced from 74.2% to less than 5%. At 6 months, 8 stents out of 23 (35%) showed a significant in-stent stenosis (stenosis degree > 50% and intra-arterial pressure gradient > 10 mmHg). The stenosis rates were 63% using 5-mm stents, 30% using 6-mm stents, and 0% using 7-mm stents.

CONCLUSION

Endovascular treatment of ostial renal artery stenosis with the used stent is safe and effective. The new stent shows a good handling and visibility. The high rate of in-stent stenoses might be explained by the rigid follow-up protocol including angiography, trans-stenotic pressure measurements, and the high number of 5-mm vessels in our study.

[Percutaneous transfemoral implantation of a new, flexible thoracic aorta endoprosthesis using a percutaneous suture system for vascular suture--initial experiences]

PURPOSE

To evaluate the transfemoral placement of a new, flexible stent-graft into the thoracic aorta and the suture-mediated closure of the femoral access.

PATIENTS AND METHODS

Five patients were treated endovascularly with a stent-graft for an aneurysm (n = 3) or acute dissection (n = 2) of the thoracic aorta via a femoral 24 F sheath. The femoral access site was closed with two suture-mediated closure devices after placement of the stent-graft.

RESULTS

The aneurysm or the false lumen was excluded from perfusion by the placement of the stent-graft in all patients. Hemostasis at the femoral access site was successful in all patients with the percutaneous suture device. A minor stenosis of the femoral artery was found angiographically in four patients after suture-mediated closure. Besides a reversible renal failure due to the medically induced hypotension for the treatment of an acutely ruptured aneurysm, no complications resulted from the stent-graft placement or the percutaneous suture.

CONCLUSION

The percutaneous transfemoral placement of stent-grafts in the thoracic aorta using a suture-mediated closure of the access site is technically feasible. Long-term results of the technique have to be awaited.

MR imaging-guided stent placement in iliac arterial stenoses: a feasibility study

PURPOSE

To assess the feasibility of magnetic resonance (MR) imaging-guided stent placement in iliac arterial stenoses.

MATERIALS AND METHODS

Thirteen patients with 14 iliac arterial stenoses were examined prospectively. Angioplasty was performed through a femoral sheath by using a conventional 1.5-T MR imaging system. Stents and catheters were visualized on the basis of their artifacts. Nitinol stents were placed with gradient-echo MR imaging guidance. Angioplasty balloons were inflated with gadolinium-based contrast material. Results were evaluated clinically and with both digital subtraction angiography (DSA) and contrast material-enhanced MR angiography.

RESULTS

Ten of 13 patients were treated with technical success by using MR imaging-guided intervention alone. Three patients were treated with additional fluoroscopic guidance, because complications (ie, panic attack, subintimal recanalization, and stent misplacement) occurred with MR guidance. The quality of the postinterventional contrast-enhanced MR angiograms of three of 12 lesions with stents was limited owing to stent-induced signal loss of the lumen. The mean stenosis degree after stent placement was significantly higher at contrast-enhanced MR angiography than at DSA (24.6% vs 6.2%). The mean MR imaging-guided procedure time was 74 minutes.

CONCLUSION

MR imaging-guided stent placement in iliac arteries is feasible in select patients. The presented technique has limitations-that is, long procedure times, lack of real-time monitoring, and stent artifacts-that necessitate further modifications before it can be recommended for clinical use.

A novel serine protease inhibition motif involving a multi-centered short hydrogen bonding network at the active site

We describe a new serine protease inhibition motif in which binding is mediated by a cluster of very short hydrogen bonds (<2.3 A) at the active site. This protease-inhibitor binding paradigm is observed at high resolution in a large set of crystal structures of trypsin, thrombin, and urokinase-type plasminogen activator (uPA) bound with a series of small molecule inhibitors (2-(2-phenol)indoles and 2-(2-phenol)benzimidazoles). In each complex there are eight enzyme-inhibitor or enzyme-water-inhibitor hydrogen bonds at the active site, three of which are very short. These short hydrogen bonds connect a triangle of oxygen atoms comprising O(gamma)(Ser195), a water molecule co-bound in the oxyanion hole (H(2)O(oxy)), and the phenolate oxygen atom of the inhibitor (O6'). Two of the other hydrogen bonds between the inhibitor and active site of the trypsin and uPA complexes become short in the thrombin counterparts, extending the three-centered short hydrogen-bonding array into a tetrahedral array of atoms (three oxygen and one nitrogen) involved in short hydrogen bonds. In the uPA complexes, the extensive hydrogen-bonding interactions at the active site prevent the inhibitor S1 amidine from forming direct hydrogen bonds with Asp189 because the S1 site is deeper in uPA than in trypsin or thrombin. Ionization equilibria at the active site associated with inhibitor binding are probed through determination and comparison of structures over a wide range of pH (3.5 to 11.4) of thrombin complexes and of trypsin complexes in three different crystal forms. The high-pH trypsin-inhibitor structures suggest that His57 is protonated at pH values as high as 9.5. The pH-dependent inhibition of trypsin, thrombin, uPA and factor Xa by 2-(2-phenol)benzimidazole analogs in which the pK(a) of the phenol group is modulated is shown to be consistent with a binding process involving ionization of both the inhibitor and the enzyme. These data further suggest that the pK(a) of His57 of each protease in the unbound state in solution is about the same, approximately 6.8. By comparing inhibition constants (K(i) values), inhibitor solubilities, inhibitor conformational energies and corresponding structures of short and normal hydrogen bond-mediated complexes, we have estimated the contribution of the short hydrogen bond networks to inhibitor affinity ( approximately 1.7 kcal/mol). The structures and K(i) values associated with the short hydrogen-bonding motif are compared with those corresponding to an alternate, Zn(2+)-mediated inhibition motif at the active site. Structural differences among apo-enzymes, enzyme-inhibitor and enzyme-inhibitor-Zn(2+) complexes are discussed in the context of affinity determinants, selectivity development, and structure-based inhibitor design.