Infrarenal aortic stenosis: value of stent placement after percutaneous transluminal angioplasty failure.

PURPOSE: To evaluate the long-term clinical and hemodynamic effectiveness of aortic stent placement in cases of failure of intended infrarenal percutaneous transluminal aortic angioplasty (PTAA). MATERIALS AND METHODS: Fifty-three patients who underwent technically successful PTAA were compared with 24 patients who underwent aortic stent placement because of PTAA failure (19 patients) or ulcerated lesions (five patients) that otherwise would have been treated surgically because of the embolization hazard associated with PTAA alone. Clinical patency was defined as the absence or improvement of symptoms after the intervention. Hemodynamic patency was defined as a normal Doppler waveform in the common femoral arteries, an ankle-brachial index greater than 0.95, or the absence of a thigh-brachial pressure gradient. RESULTS: Three-year clinical and hemodynamic patency rates, respectively, were 85% and 79% for PTAA and 69% and 43% for aortic stent placement. No morbidity was encountered. With use of the Cox proportional hazards model, two significant risk factors were retained for restenosis: unchanged smoking habit (P =.04) and small dilatation diameter (P =.001). Aortic stent placement, performed in patients with a smaller aortic diameter (10.3 vs. 12.7 mm for PTAA), appeared to be a predictive factor for restenosis by using univariate analysis. By using the Cox proportional hazards model, however, the restenosis rates after PTAA and aortic stent placement were not significantly different. CONCLUSION: When aortic diameter is taken into consideration, there is no evidence that clinical outcome after secondary aortic stent placement would be poorer than technically successful PTAA.

Arterial embolotherapy for upper gastrointestinal hemorrhage: outcome assessment.

PURPOSE: To identify predictors of clinical outcome after arterial embolotherapy for upper gastrointestinal (UGI) hemorrhage. MATERIALS AND METHODS: Seventy-five consecutive patients (mean age, 62.5 y) underwent arterial embolization for acute UGI hemorrhage. Bleeding was detected at endoscopy and angiography in 22 patients, at endoscopy alone in 29 patients, and at angiography alone in 24 patients. As such, embolization was directed by angiography in 46 patients (61.3%) and by endoscopy (referred to as "blind" embolization) in 29 patients (38.7%). The embolic agents used were metallic coils, polyvinyl alcohol particles (size range, 355-710 microm), gelatin sponge, and tissue adhesive. Predictors of bleeding recurrence and mortality were analyzed with logistic regression and Cox models, respectively. RESULTS: The technical success rate of embolization was 98.7%. Primary clinical success was achieved in 57 patients (76%). Secondary clinical success occurred in five additional patients (82.5%) after repeat embolization. There were four (5.3%) complications: two cases of self-resolving duodenal ischemia, one hepatic infarct, and one inguinal hematoma. The periprocedural mortality rate was 34.6% (26 of 75), mostly related to underlying illness. Early recurrence of bleeding (within 30 days of embolization) was associated with coagulation disorders (international normalized ratio >1.5, partial thromboplastin time >45 seconds, or platelet count <80,000/microL; odds ratio, 19.46; P = .001) and with the use of coils as the only embolic agent (odds ratio, 7.73; P = .01). Cirrhosis and cancer shortened the overall survival of patients after embolic therapy. The mean patient follow-up time was 34.5 months. CONCLUSION: Arterial embolotherapy for UGI hemorrhage is safe, effective, and durable. Coagulopathy and the use of coils as the only embolic agent were associated with a higher risk of early bleeding recurrence.

Biosynthesis of biotin and lipoic acid.

The genetics and mechanistic enzymology of biotin biosynthesis have been the subject of much investigation in the last decade, owing to the interest for biotin production by fermentation, on the one hand, and for the design of inhibitors with potential herbicidal properties, on the other hand. Four enzymes are involved in the synthesis of biotin from its two precursors, alanine and pimeloyl-CoA. They are now well-characterized and the X-ray structures of the first three have been published. 8-Amino-7-oxopelargonic acid synthase is a pyridoxal 5'-phosphate (PLP) enzyme, very similar to other acyl-CoA alpha-oxoamine synthases, and its detailed mechanism has been determined. The origin of its specific substrate, pimeloyl-CoA, however, is not completely established. It could be produced by a modified fatty acid pathway involving a malonyl thioester as the starter. 7,8-Diaminopelargonic acid (DAPA) aminotransferase, although sharing sequence and folding homologies with other transaminases, is unique as it uses S-adenosylmethionine (AdoMet) as the NH2 donor. The mechanism of dethiobiotin synthethase is also now well understood. It catalyzes the formation of the ureido ring via a DAPA carbamate activated with ATP. On the other hand, the mechanism of the last enzyme, biotin synthase, which has long raised a very puzzling problem, is only starting to be unraveled and appears indeed to be very complex. Biotin synthase belongs to the family of AdoMet-dependent enzymes that reductively cleave AdoMet into a deoxyadenosyl radical, and it is responsible for the homolytic cleavage of C-H bonds. A first radical formed on dethiobiotin is trapped by the sulfur donor, which was found to be the iron-sulfur (Fe-S) center contained in the enzyme, and cyclization follows in a second step. Two important features come from these results: (1) a new role for an Fe-S center has been revealed, and (2) biotin synthase is not only a catalyst but also a substrate for the reaction. Lipoate synthase, which catalyzes the formation of two C-S bonds from octanoic acid, has a very high sequence similarity with biotin synthase. Although no in vitro enzymology has been carried out with lipoate synthase, the sequence homology as well as the results of in vivo studies support the conclusion that both enzymes are strongly mechanistically related.

Enzyme-mediated sulfide production for the reconstitution of [2Fe-2S] clusters into apo-biotin synthase of Escherichia coli. Sulfide transfer from cysteine to biotin.

We previously showed that biotin synthase in which the (Fe-S) cluster was labelled with 34S by reconstitution donates 34S to biotin [B. Tse Sum Bui, D. Florentin, F. Fournier, O. Ploux, A. Méjean & A. Marquet (1998) FEBS Lett. 440, 226-230]. We therefore proposed that the source of sulfur was very likely the (Fe-S) centre. This depletion of sulfur from the cluster during enzymatic reaction could explain the absence of turnover of the enzyme which means that to restore a catalytic activity, the clusters have to be regenerated. In this report, we show that the NifS protein from Azotobacter vinelandii and C-DES from Synechocystis as well as rhodanese from bovine liver can mobilize the sulfur, respectively, from cysteine and thiosulfate for the formation of a [2Fe-2S] cluster in the apoprotein of Escherichia coli biotin synthase. The reconstituted enzymes were as active as the native enzyme. When [35S]cysteine was used during the reconstitution experiments in the presence of NifS, labelled (Fe35S) biotin synthase was obtained. This enzyme produced [35S]biotin, confirming the results obtained with the 34S-reconstituted enzyme. NifS was also effective in mobilizing selenium from selenocystine to produce an (Fe-Se) cluster. However, though NifS could efficiently reconstitute holobiotin synthase from the apoform, starting from cysteine, these two effectors had no significant effect on the turnover of the enzyme in the in vitro assay.

Biotin synthase mechanism: on the origin of sulphur.

Biotin synthase catalyses the last step of the biosynthesis of biotin in microorganisms and plants. The active protein isolated from Bacillus sphaericus and Escherichia coli contains an iron-sulphur (FeS) cluster. The native enzymes were depleted of their iron and inorganic sulphide and the resulting apoenzymes were chemically reconstituted with FeCl3 and Na2[34S] to give labelled (Fe34S) enzymes. These enzymes were functional and when assayed in vitro produced labelled biotin containing about 65% of 34S. These data strongly support the hypothesis that the sulphur of biotin is derived from the (FeS) centre of the enzyme.

Infrarenal aortic stenosis: long-term clinical and hemodynamic results of percutaneous transluminal angioplasty.

PURPOSE: To evaluate the safety and long-term clinical and hemodynamic results of percutaneous transluminal angioplasty (PTA) of the infrarenal aorta. MATERIALS AND METHODS: During nearly 10 years, 102 patients with symptomatic infrarenal atherosclerotic aortic stenosis underwent PTA. Follow-up information was available in 92 patients (17 men, 75 women; mean age, 51.9 years). Stenosis involved the aortic bifurcation in 18 patients and only the infrarenal abdominal aorta in 74 patients. Technical success was defined as residual stenosis less than 50% or a pressure gradient less than 10 mm Hg after PTA. Clinical patency was defined as the absence or improvement of symptoms after PTA. Hemodynamic patency was defined as a normal Doppler waveform in the common femoral arteries, an ankle-brachial ratio greater than 0.95, or the absence of a thigh-brachial pressure gradient. RESULTS: Technical success was achieved in 78 patients after PTA. After 10 years, primary clinical and hemodynamic patency rates were 72% and 46%, respectively. After a mean follow-up of 51 months, 15 of the 22 symptomatic recurrences were due to aortic restenosis; 11 of these were treated with repeated PTA with or without stent placement, and three eventually required aortic surgery. No morbidity was encountered. CONCLUSION: Infrarenal aortic PTA proved to be safe and provided durable, long-term clinical improvement. In this group of relatively young patients, the clinical patency rate of PTA was equivalent to that of aortic surgery but with less morbidity.

Treatment of renal angioplasty failure by percutaneous renal artery stenting with Palmaz stents: midterm technical and clinical results.

OBJECTIVE: Renal artery stenting has recently been used to treat failures or complications of renal angioplasty. Although technical results and complication rates have been reported, clinical follow-up and long-term data are limited. The purpose of this study was to evaluate the midterm clinical efficacy and safety of Palmaz stents in rescuing renal artery angioplasty failures. MATERIALS AND METHODS: Palmaz stents were placed in 35 renal arteries of 33 patients (14 men and 19 women; 37-77 years old; mean age, 62.6 years old) for immediate angioplasty failure (29 arteries) or for recurrent stenosis after previous angioplasty (six arteries). Indications for treatment were hypertension alone (16 patients) or hypertension associated with renal failure (17 patients). Blood pressure, medication, and serum creatinine level were followed after stenting. RESULTS: No residual stenosis was found immediately after stenting. Mean clinical follow-up was 13.4 months (range, 1-34 months). Of the 33 patients, two (6%) were cured of their hypertension, 20 (61%) were improved, and 11 (33%) did not respond to renal artery stenting. Of the 17 patients whose serum creatinine level was greater than 132 mumol/dl (1.5 mg/dl), seven (41%) were improved by renal artery stenting, six (35%) were stabilized, and renal function deteriorated in four (24%). Of the 33 patients, seven developed complications including one renal artery thrombosis, four renal artery emboli, one cholesterol embolization to the lower limbs, and one femoral hematoma that required surgery. CONCLUSION: Midterm results of renal artery stenting with the Palmaz stent to treat immediate or late angioplasty failures reveal improvements in blood pressure and renal function similar to those of successful primary balloon angioplasty.

Highly purified biotin synthase can transform dethiobiotin into biotin in the absence of any other protein, in the presence of photoreduced deazaflavin.

Biotin synthase from Bacillus sphaericus has been purified to homogeneity from a recombinant strain. The UV-visible spectrum of the pure protein reveals the presence of a [2Fe-2S] cluster. The enzyme is active in the conversion of dethiobiotin to biotin in vitro, in the presence of NADPH, AdoMet and additional unidentified components from the crude extract of B. sphaericus wild type. We have also found that photoreduced deazaflavin can substitute for the crude extract and NADPH. In this system, biotin synthase is capable of transforming dethiobiotin into biotin in the absence of any other protein but at a substoichiometric level. When this assay was conducted in the presence of [35S]cysteine, no 35S was incorporated into biotin, contrary to what happens in the presence of the crude extract.

Renal artery stenosis: evaluation of Doppler US after inhibition of angiotensin-converting enzyme with captopril.

PURPOSE: To evaluate the modifications of Doppler ultrasound waveform morphology after inhibition of angiotensin-converting enzyme with captopril to increase the sensitivity of Doppler sonography in detecting renal artery stenosis. MATERIALS AND METHODS: Sixty-two renal arteries were studied in 31 hypertensive patients who underwent Doppler scanning before and 1 hour after administration of captopril prior to undergoing angiography. Pattern recognition criteria were applied to classify the Doppler waveforms as having a normal or pulsus tardus configuration. Doppler scanning results were compared with those of arteriography. RESULTS: On the basis of recognition of the pulsus tardus, precaptopril Doppler scanning showed 13 (68%) of 19 significant renal artery stenoses found at angiography (95% confidence interval, 0.43, 0.85), whereas 19 (100%) of 19 stenoses were detected with postcaptopril Doppler scanning (95% confidence interval, 0.85, 1.0). CONCLUSION: Captopril significantly (95% confidence intervals) increases Doppler scanning sensitivity in detecting renal artery stenoses by inducing or enhancing the pulsus tardus distal to a significant renal artery stenosis.

Stimulatory factors for enzymatic biotin synthesis from dethiobiotin in cell-free extracts of Escherichia coli.

The activity of biotin synthesis from dethiobiotin was found in cell-free extracts of an Escherichia coli bioB transformant. Among the sulfur compounds tested, only S-adenosyl-L-methionine (AdoMet) had a significant effect, while methionine and cysteine were inert. The activity was linearly stimulated by increasing protein concentration. When the dialyzed cell-free extracts were used for the reaction, NADP+, NADPH, and FAD among the well-known cofactors tested promoted the activity. Furthermore, in the presence of AdoMet, cysteine was apparently effective for biotin synthetic activity.

Percutaneous removal of a biliary stent after acute spontaneous duodenal perforation.

A 38-year-old woman was treated for malignant stricture by the endoscopic placement of a biliary endoprosthesis. She developed a large retroperitoneal biloma secondary to acute duodenal perforation by the stent. We describe the successful percutaneous retrieval of the biliary stent through a retroperitoneal approach which also permitted drainage of the biloma.

Renal artery aneurysm: treatment with percutaneous placement of a stent-graft.

A stent-graft was placed percutaneously in the right renal artery of a 50-year-old woman with hypertension and a fibromuscular dysplastic lesion consisting of severe stenoses and a 1.5-cm saccular aneurysm with a wide neck. At 1-year follow-up with arteriography, arterial luminal diameter was normal and no aneurysm was depicted. The patient's blood pressure was normal without blood pressure medication.

Correction of deteriorating renal function by superselective embolization of an arcuate renal artery pseudoaneurysm.

We performed superselective embolization of an iatrogenic pseudoaneurysm of the right kidney that was causing hematuria and deterioration of renal function in a patient with chronic renal failure. An arcuate artery was embolized with absorbable gelatin sponge and a straight embolization wire without significant loss of renal vascularization, thus restoring baseline renal function. To our knowledge the clinical and technical aspects of our case are unique. The technique is described.

Liver angiomyolipoma: classic and unusual presentations.

Two cases of liver angiomyolipoma (AML) are presented. The first case has the classical imaging findings previously reported. The second case has no fat content on the various imaging modalities. AML should probably be included in the differential diagnosis of any hypervascular lesion of the liver. Preoperative diagnosis with core biopsy is possible.

Enzymatic conversion of dethiobiotin to biotin in cell-free extracts of a Bacillus sphaericus bioB transformant.

The activity of biotin synthase, responsible for biotin synthesis from dethiobiotin, was demonstrated in a completely defined reaction mixture with cell-free extracts of a Bacillus sphaericus bioB transformant. Among the sulfur compounds tested, only S-adenosyl-L-methionine was active, while L-methionine and L-cysteine had no significant effect. Protein concentrations higher than 15 mg/ml in the reaction mixture were needed to detect biotin synthase activity. When dialyzed cell-free extracts were used for the reaction, NADH, NADPH, or FAD among the well-known cofactors tested enhanced the activity, and Fe2+, Mn2+, and Ca2+ among the metal ions tested also had some effects.

On the mechanism of biotin synthase of Bacillus sphaericus.

A cell-free system of a bioB transformant of Bacillus sphaericus, effecting the last step of biotin biosynthesis, namely the introduction of sulfur into dethiobiotin has been recently described. S-adenosyl methionine (SAM) is absolutely necessary for activity. We show here, through experiments with [35S]SAM and [35S]Cys, that the sulfur donor is not SAM but probably cysteine (Cys) or a derivative. This finding together with the fact that NADPH and FAD are required for activity leads us to postulate some analogy between the biotin synthase system and other systems which use SAM as a source of desoxyadenosyl radical.

Case report: primary mesenchymal chondrosarcoma of the brain.

We report an 11-year-old girl with a very rare tumour, mesenchymal chondrosarcoma of the brain, presenting as a haemorrhagic stroke, in whom angiography originally showed a distal arterial aneurysm. One month later MRI showed a solid tumour in addition to evidence of haemorrhage, and angiography then demonstrated pathological vascularity. The diagnosis was made following craniotomy.