Transcranial Doppler and diffusion-weighted magnetic resonance evaluation of cerebral embolization occurring during transfemoral carotid stenting with proximal flow blockage

AIM: Transfemoral carotid artery stenting (CAS) with endovascular proximal flow blockage is deemed able to reduce the cerebral embolization observed during filter-protected CAS. We evaluated clinical outcome and intraoperative embolization rates, measured by diffusion-weighted magnetic resonance imaging (DW-MRI) and transcranial Doppler monitoring, in a series of patients undergoing CAS with proximal flow blockage. METHODS: A series of 35 consecutive patients with symptomatic or asymptomatic internal carotid artery stenosis ≥70% were included to undergo CAS with proximal flow blockage, obtained with the Mo.Ma system. All patients underwent preoperative and postoperative DW-MRI in order to detect new ischemic lesions. Of the 35 patients, 31 (89%) underwent intraoperative transcranial Doppler monitoring to record the microembolic signals (MES) produced during each procedure. RESULTS: The MoMa system was successfully used in 34 patients (technical success: 97%). Intolerance to balloon occlusion was observed in 4 patients (12%), but never compromised the completion of the procedure. No deaths or neurological events occurred in the postoperative period. DW-MRI disclosed 74 new ischemic lesions in 8 patients (8/34, 23.5%). All lesions except one were ipsilateral to the treated carotid artery. MES were detected in all procedures, with a mean number of 33.2±23.2 (range 3-103). In 20 procedures (20/31, 65%), MES were detected also during flow blockage (mean: 9.1±7; range 2-28). CONCLUSION: While achieving good technical and clinical results, CAS with proximal flow blockage is still accompanied by a non-negligible cerebral embolization. The detection of MES during ICA flow blockage suggests the need for a better selection of patients.

Aortic arch catheterization during transfemoral carotid artery stenting: an underestimated source of cerebral emboli

Cerebral embolization is still a major concern in patients undergoing transfemoral carotid artery stenting. Intraoperative transcranial Doppler (TCD) monitoring and diffusion-weighted magnetic resonance imaging (DW-MRI), two techniques currently used to study this phenomenon, have provided data suggesting the importance of aortic arch catheterization in determining the overall embolic load observed during this procedure. In order to reduce this cerebral embolization, some Authors have proposed the performance of carotid artery stenting through a cervical access, either surgical or percutaneous. We review in this article the available TCD and DW-MRI data supporting transcervical CAS, along with its clinical results.

Safety and effectiveness of combining carotid artery stenting with cardiac surgery: preliminary results of a single-center experience

AIM

Optimal strategy (staged or combined) for the treatment of patients with concurrent severe carotid and cardiac disease is still controversial. Moreover, carotid artery stenting (CAS), has become a valid alternative to carotid endarterectomy (CEA) and has been proposed for the treatment of cardiac patients. The authors report the preliminary results of a new therapeutic strategy consisting in combined CAS and cardiac surgery.

METHODS

An initial series of 22 patients underwent combined CAS and cardiac surgery in the same operating room and under general anesthesia. All filter-protected CAS procedures were performed under only heparin and aspirin. A cervical approach (3-cm cervicotomy) was used in patients with documented vessel tortuosity or severe aorto-iliac occlusive arteriopathy. In all the other cases a femoral access was used. A double antiplatelet regimen was initiated in the early postoperative period, once major bleedings were excluded.

RESULTS

Among the 22 patients who underwent this combined procedure, no deaths, no myocardial infarctions and one controlateral stroke (overall complication rate: 4.5%) were observed. This stroke was observed after transcervical CAS, coronary artery bypass and mitral valve replacement. No major postoperative bleedings nor stent thrombosis were observed.

CONCLUSIONS

Combined carotid stenting and cardiac surgery, performed in the same operating room under only heparin and aspirin, seems a safe and effective strategy for the treatment of patients with concomitant carotid and cardiac disease.

High-dose calcitriol therapy and progression of cardiac vascular calcifications

BACKGROUND

Dialysis patients show a very high prevalence of cardiovascular complications, affected as they are with abnormal and accelerated vascular calcifications and, eventually, calcium and phosphorous metabolism disorders. Multislice computed tomography (MSCT) provides a reproducible, high-resolution imaging of calcium contained in cardiac arteries, measured by Agatston score. The aim of the present study was to evaluate the influence of high-dose and low-dose calcitriol therapy on the progression of cardiac vascular calcifications in dialyzed patients.

METHODS

We enrolled 36 dialyzed patients in a prospective study, including an interventional period of 12 months and a follow-up period of 12 months. Eighteen protocol patients received intravenous pulses of high-doses calcitriol at the end of dialytic treatment and sevelamer hydrochloride therapy. Control patients received low-dose calcitriol and sevelamer hydrochloride as well. Two MSCT scans were performed: 1 at the start of the study and 1 at the end of follow-up, and Agatston score was calculated at both examinations.

RESULTS

At first examination, protocol patients showed almost the same level of cardiac vascular calcification as control patients. At the second MSCT, statistically significantly higher values of Agatston score were recorded for all patients. Indeed, patients who showed higher baseline values developed worse calcifications as recorded at the end of follow-up, both in the protocol and control group.

CONCLUSIONS

Our data show that baseline level is strongly predictive of vascular calcification progression, and, moreover, there is no association between calcitriol administered doses and the progression of cardiac vascular calcification.

Late evaluation of silent cerebral ischemia detected by diffusion-weighted MR imaging after filter-protected carotid artery stenting

BACKGROUND AND PURPOSE

Postoperative diffusion-weighted MR imaging (DWI) often discloses new lesions after carotid artery stent placement (CAS), most of them asymptomatic. Our aim was to investigate the fate of these silent ischemic lesions.

MATERIALS AND METHODS

We prospectively studied 110 patients undergoing protected transfemoral CAS, 98 of whom underwent DWI before and after the intervention. Patients in whom DWI disclosed silent postoperative lesions also had delayed MR imaging. Preoperative, postoperative, and delayed scans were compared.

RESULTS

Of the 92 patients without postoperative symptoms, DWI disclosed 33 new silent ischemic lesions in 14 patients (15.2%), 13 of whom (30 lesions) underwent delayed MR imaging after a mean follow-up of 6.2 months. In 8 of these 13 patients (61%), MR imaging disclosed 12 persistent lesions (12/30, 40%). The reversibility rate depended significantly on the location (cortical versus subcortical) and size (0-5 versus 5-10 mm) of the lesions (P < .05 by chi(2) test).

CONCLUSIONS

Because many silent ischemic lesions seen on postoperative DWI after CAS reverse within months, the extent of permanent CAS-related cerebral damage may be overestimated.

Cerebral embolization in patients undergoing protected carotid-artery stenting and carotid surgery

AIM

Intraoperative cerebral embolization is a greater concern in patients undergoing carotid-artery stenting (CAS) than in those undergoing the reference standard treatment carotid endarterectomy (CEA). We evaluated cerebral embolism with diffusion-weighted magnetic resonance imaging (DW-MRI) and transcranial Doppler monitoring during CAS and CEA.

METHODS

A series of 75 patients with carotid stenosis, 40 undergoing CEA and 35 transfemoral protected CAS, underwent preoperative and postoperative cerebral DW-MRI. Of the 75 patients, 64 (85%) underwent intraoperative transcranial Doppler monitoring to evaluate the mean number of microembolic signals (MES) recorded in each procedure.

RESULTS

None of the patients died. No patient in the CEA but two in the CAS group had strokes (5.7%, P=NS). The mean MES count on transcranial Doppler monitoring was higher in the CAS than in the CEA group (330.0 MES, range 2754 vs 13.2, range 0-49 MES; P<0.01). DW-MRI disclosed a significantly larger number of new ischemic lesions in the CAS than in the CEA group (40 lesions in 12/35 patients, 34.3% vs 4 lesions in 3/40 patients, 7.5%; P<0.01). In the CEA group, all patients with ischemic lesions were asymptomatic whereas in the CAS group 5 were symptomatic (14.3%) and 7 asymptomatic (20%). The cerebral distribution also differed in the two groups: no CEA but 20% of CAS lesions were contralateral.

CONCLUSION

CAS is associated with a significantly higher rate of cerebral embolization than CEA. Even though the clinical meaning of new postoperative ischemic lesions remains debatable, it seems prudent to reduce the embolic load by improving procedural techniques and cerebral protection devices.

Improved Tumor Targeting by Combined Use of Two Antitenascin Antibodies

PURPOSE

In the pretargeted antibody-guided radioimmunotherapy (PAGRIT) system, the combined use of two different antibodies directed against the same tumor antigen could represent a valid approach for improving tumor targeting and therapeutic efficacy. We developed a novel monoclonal antitenascin antibody, ST2485, and studied its biochemical and functional properties by in vitro and in vivo assays. We then investigated the first of the three-step therapy combining ST2485 with another antitenascin antibody, ST2146, previously described, to increase accumulation of biotinylated antibodies at the tumor site.

EXPERIMENTAL DESIGN

Studies of immunoreactivity, affinity, immunohistochemistry, and biodistribution in xenograft model were carried out on ST2485. Analysis of the ST2485 and ST2146 combination was preliminary carried out by ELISA and BiaCore tests and then by in vivo distribution studies after administration of the radiolabeled biotinylated antibodies, followed by a chase with avidin as clearing agent.

RESULTS

ST2485 was found to be a suitable antibody for therapeutic applications. Indeed, for its behavior in all tests, it was comparable with ST2146 and better than BC2, an antibody already used for clinical trials. The additivity of ST2146 and ST2485 in tenascin C binding, shown by in vitro tests, was confirmed by biodistribution studies in a xenograft model where tumor localization of the antibodies was near the sum of each antibody alone, with a tumor-to-blood ratio higher than 24.

CONCLUSION

The results reported in this study suggest that a monoclonal antitenascin antibody mixture can improve tumor targeting. This strategy could represent progress for therapeutic approaches such as PAGRIT.

Novel ligands for the affinity-chromatographic purification of antibodies

Affinity chromatography represents one of the most powerful fractionation techniques for the large-scale purification of biotechnological products. Despite its potential, the use of this methodology is limited by the availability of specific ligands for each target. Combinatorial chemistry and molecular modeling, often combined, have become interesting and innovative methods for generating novel ligands, tailored to specific biotechnological needs. One of the greatest area of application has been the discovery of novel ligands for the purification of antibodies, which represent an emerging but very important class of innovative therapeutic agents for the treatment of a vast array of diseases. Naturally available affinity ligands, such as Protein A or G for IgG purification or lectins for IgA and IgM purification, which are obtained from microorganisms or genetically modified bacteria through complex and expensive procedures, are not well suited for large-scale purification and require moreover time-consuming analytical controls to check for the presence of contaminants which may affect the safety of the purified antibody for clinical purposes. Recent results suggest that the application of combinatorial technologies and molecular modeling for the discovery of synthetic ligands may open new avenues for the development of more efficient, less expensive and--more importantly--safer procedures for antibody purification at the industrial level.

Cardiac function and oxygen balance in septic patients during continuous hemofiltration

The aim of this work was to study hemodynamic, oximetric and metabolic parameters in septic patients during continuous hemofiltration, in order to determine whether the changes in hemodynamic parameters can influence the oxygen utilization in peripheral tissues. 29 multiple organ failure patients with septic shock were studied during the first 48 h of continuous hemofiltration: 18 were submitted to CAVH and 11 patients were treated with CAVHD to correct ARF and fluid overload. Our data show that RVEF improves and REDVI reduces progressively during treatment, together with a significant reduction of the cardiac index after 48 h of CAVH(D). There were no significant variations in oxygen tissue parameters, while plasma lactate was reduced significantly. In conclusion, our data confirm that continuous hemofiltration may be useful in septic patients to correct fluid overload and ARF, without affecting hemodynamic stability and oxygen balance. Moreover, in septic patients, this technique improves hemodynamics, reduces the filling pressure in the right heart and reduces hyperdynamic response as CI and SVRI, without any negative effects on O2 balance.

A synthetic ligand for IgA affinity purification

We reported previously that TG19318, a synthetic ligand deduced from the screening of combinatorial libraries, displays specific and selective recognition properties for immunoglobulins of the G class and can be used conveniently for affinity chromatography purification of monoclonal and polyclonal antibodies. In this study we have extended the ligand characterization, examining its ability to bind IgA from cell culture supernatants and from IgG-deprived serum. Affinity columns prepared by immobilizing TG19318 on Sepharose allowed convenient one-step purification of monoclonal IgA directly from crude feedstocks, in high yield and with full recovery of immunoreactivity. Optimal column adsorption occurred with phosphate buffer at neutral pH, while elution of adsorbed IgA could be accomplished by a buffer pH change to acidic or basic conditions. Column capacity was close to 7 mg IgA/ml support.

Immunoglobulin specificity of TG19318: a novel synthetic ligand for antibody affinity purification

A synthetic ligand [TG19318], able to mimic protein A in the recognition of the immunoglobulin Fc portion, has been previously identified in our laboratory through the synthesis and screening of multimeric combinatorial peptide libraries. In this study we have fully characterized its applicability in affinity chromatography for the downstream processing of antibodies, examining the specificity and selectivity for polyclonal and monoclonal immunoglobulins derived from different sources. Ligand specificity was broader than protein A, since IgG deriving from human, cow, horse, pig, mouse, rat, rabbit, goat and sheep sera, IgY obtained from egg yolk, and IgM, IgA and IgE were efficiently purified on TG19318 affinity columns. Adsorbed antibodies were conveniently eluted by a buffer change to 0.1 M acetic acid or 0.1 M sodium bicarbonate pH 9, with full retention of immunological properties. Monoclonal antibodies deriving from cell culture supernatants or ascitic fluids were also conveniently purified on TG19318 affinity columns, even from very diluted samples. The affinity constant for the TG19318-IgG interaction was 0.3 microM, as determined by optical biosensor measurements. Under optimized conditions, antibody purity after affinity purification was close to 95%, as determined by densitometric scanning of SDS-PAGE gels of purified fractions, and maximal column capacity reached 25 mg Ig/ml support. In vivo toxicity studies in mice indicated a ligand oral toxicity greater than 2000 mg kg-1 while intravenous toxicity was close to 150 mg kg-1. Validation of antibody affinity purification processes for therapeutic use, a very complex, laborious and costly procedure, is going to be simplified by the use of TG19318, which could reduce considerably the presence of biological contaminants in the purified preparation, a very recurrent problem when using recombinant or extractive biomolecules as affinity ligands.

Affinity purification of mouse monoclonal IgE using a protein A mimetic ligand (TG19318) immobilized on solid supports

A synthetic ligand (TG19318), deduced from the screening of a combinatorial peptide library, has been previously characterized by our group for its applicability in affinity chromatography for polyclonal and monoclonal IgG purification from crude sources. In this study we have extended the characterization of its recognition properties for other immunoglobulin classes, evaluating its ability to purify mouse monoclonal IgE from ascitic fluid. TG19318 affinity columns proved useful for a very convenient one-step purification of IgE directly from crude ascites, by loading the samples on the columns equilibrated with 50 mM sodium phosphate at pH 7 and eluting and adsorbed IgE by a buffer change to 0.1 M acetic acid. Antibody purity after affinity purification was very high and no albumin traces were detected, as determined by SDS-PAGE analysis. Antibody activity was fully recovered after purification, as determined by immunoassays on antigen-coated plates, and up to 5 mg of IgEs could be purified on a 1 ml column in a single run.

Red blood cell membrane lipid peroxidation and resistance to erythropoietin therapy in hemodialysis patients

BACKGROUND

Chronic hemolysis, inadequate production of erythropoietin (EPO) or an impaired response of erythroid stem cells to EPO are the main factors of anemia in end-stage renal disease (ESRD) patients. Oxidative damage of red blood cell (RBC) membrane is a well-established cause of chronic hemolysis in hemodialysis (HD) patients. Administration of high-dose recombinant human EPO (rHuEPO) fails to correct anemia in 5 to 10% HD patients although all established factors of resistance to rHuEPO therapy have been previously ruled out or corrected.

PATIENTS AND METHODS

We investigated the degree of RBC membrane oxidative damage in 9 HD patients who failed to respond to maximal rHuEPO administration (more than 200 UI/Kg weekly for 4 months consecutively, group A), compared to 10 patients who showed a good response to standard rHuEPO therapy (group B) and to 10 patients who needed no treatment (group C). RBC malondialdehyde (MDA) was assumed as the index of oxidative stress in erythrocyte membrane.

RESULTS

No significant difference in erythrocyte MCV and MCHC, iron status, parathyroid function, aluminum and dialysis-related blood loss was observed between patients of group A, B and C. RBC MDA, reticulocyte count, plasma-free hemoglobin (fhb) and serum lactate dehydrogenase (LDH) were significantly higher while plasma haptoglobin was significantly lower in patients of group A compared to patients of groups B and C. Moreover, a significant inverse relationship was observed between RBC MDA and either plasma hemoglobin, RBC count and hematocrit when all patients were evaluated together.

CONCLUSION

In conclusion, increased oxidative damage of RBC membrane is often detectable in HD patients who fail to respond to rHuEPO administration even in the absence of all established factors of resistance to EPO. Peripheral response to rHuEPO may be normal in these patients and persistent anemia may be related to enhanced hemolysis due to oxidative stress. Oxidative damage itself may therefore be considered a factor of resistance to EPO.

Selection of Peptide Ligands for A-1 Antitrypsin from a Phage Display Library

Abstract:

An eptapeptide phage library was used to isolate peptides interacting specifically with a-1 antitrypsin through a subtractive biopanning procedure. The peptide ligand identified after three selection cycles [SITPLVH] was chemically synthesized in a tetrameric form and analyzed for its capacity to recognize a-1 antitrypsin by ELISA assays. Multimeric ligand immobilization on solid supports for the preparation of a'°ffinity columns proved useful for the purification of a-1 antitrypsin in the presence of large amounts of albumin.

Affinity purification of immunoglobulin M using a novel synthetic ligand

While monoclonal antibodies of the G class can be conveniently purified by affinity chromatography using immobilized protein A or G, even on a large scale, scaling up IgM purification still presents several problems, since specific and cost-effective ligands for IgM are not available. A synthetic peptide (TG19318), deduced from the screening of a combinatorial peptide library, was characterized previously by our group for its binding properties for immunoglobulins of the G class and its applicability as a synthetic ligand for polyclonal and monoclonal IgG purification, from sera or cell culture supernatants. In this study, we have examined the ligand recognition properties for IgM, immobilizing the synthetic peptide on different affinity supports and examining its ability to purify IgMs from serum, ascitic fluid and cell culture supernatants. TG19318 affinity columns proved useful for a very convenient one-step purification of monoclonal IgMs directly from crude sources, loading the samples on the columns equilibrated with saline buffers at pH values ranging from 5 to 7, and eluting adsorbed IgM by a buffer change to 0.1 M acetic acid or 0.05-0.1 M sodium bicarbonate, pH 9.0. Antibody purity after affinity purification was very high, close to 85-95%, as determined by densitometric scanning of sodium dodecyl sulfate-polyacrylamide gels of purified fractions, and by gel permeation analysis. Antibody activity was fully recovered after purification, as determined by immunoassays. Column capacity was related to the type of support used for ligand immobilization, and ranged from 2 to 8 mg of IgM/ml of support.

Plasmapheresis in severe forms of myasthenia gravis

In this study we introduce a new combination treatment of plasma exchange (PE) and high daily doses of prednisone for severe forms of myasthenia gravis (MG). The clinical efficacy of the combined therapy has been tested in 18 patients suffering from severe forms of MG. The protocol included 5 sessions of PE, performed in a range of 15 days, 1 session every 3 days, with concurrent administration of oral prednisone (1 mg/kg of body weight), starting at the first session of PE and given daily for at least 3 months. At the end of the entire cycle of PE, almost complete recovery (more than 90% of the initial clinical score) was obtained in 8 of 18 patients while an improvement between 60 and 90% of the initial score was achieved in 9 of 18 patients. An early improvement was noted 24 h after the beginning of plasmapheresis in 11 of 18 patients. No recurrence of symptoms was reported after 36 months of follow-up for 17 patients. The administration of steroid therapy was never followed by an early exacerbation of myasthenic symptoms as reported when it is administered in the absence of concomitant PE. According to our results, we can conclude that high doses of oral prednisone therapy in simultaneous association with PE lead to successful control of severe forms of MG, significantly superior to the therapeutic strategies until now adopted and reported in literature.

Blood purification procedures for acute renal failure: convenient strategy related to clinical conditions

The choice in the renal replacement therapy of acute renal failure (ARF) should match the patients' individual needs and the characteristics of available therapies. 141 ARF patients, 65 with "isolated' ARF (group I) and 76 with ARF in multiorgan failure (group II), have been treated. In 33 patients of group I standard bicarbonate hemodialysis was used, while acetate-free biofiltration was used for the others. In group II, 42 patients have been treated by continuous arteriovenous hemofiltration and 34 patients by daily recycled bicarbonate hemodialysis. Our data show that acetate-free biofiltration and bicarbonate dialysis were both highly dependable, but acetate-free biofiltration was better tolerated. Continuous arteriovenous hemofiltration is the method of choice in high-risk patients; daily bicarbonate hemodialysis is preferable only in patients with hemorrhagic diathesis. The average survival time is 55.2% with a statistically significant difference between groups I and II, while no difference has been observed within the same group according to the procedure.

Plasmapheresis versus plasma perfusion in acute Guillain-Barré syndrome

Guillain-Barré Syndrome (GBS) is an acute post infectious or disimmune illness that affects nerve roots and peripheral nerves. Multicenter studies have clearly shown that plasma exchange (PE) provides valuable amelioration of GBS. It was recently suggested that plasma perfusion (PP) on phenylalanine columns displays the same therapeutic effects of PE in neuroimmunologic disorders, without the infectious risks linked with plasma replacement. In this study, the authors compared the efficacy of PE versus that of PP in two groups of patients suffering from GBS by investigating the clinical outcomes and the electrophysiologic and cerebrospinal fluid findings. Of 22 patients suffering from GBS, 16 underwent seven sessions of PE in a mean time of 15 days (Group A). Six patients, showing the same clinical pattern, underwent three sessions of PP in a mean time of 10 days (Group B). Data reported in Group A show that PE: 1) stops the progressive worsening of the disease, 2) prevents the development of acute respiratory failure, 3) allows an early and significant clinical improvement with change in disability grade, and 4) improves motor conduction velocities and motor action potentials when recorded 45 days after the end of treatment. Data in Group B show that PP allows a slower and later improvement in disability grade, and electrophysiologic data recorded at the end of treatment was worse after 45 days. Finally, it may be concluded that PE has beneficial effects on GBS in terms of time of recovery, complication rate, and relapses. Plasma perfusion did not show the same results.

Pharmacokinetics of amoxicillin in subjects with normal and impaired renal function

The pharmacokinetics of amoxicillin was investigated in 4 healthy volunteers and in 16 patients with varying degrees of renal impairment, 4 of whom were on regular hemodialysis. Amoxicillin was administered both in a 1-g single intravenous injection and two 500-mg capsules per os. The kinetics of the antibiotic followed an open two-compartment model. In the patients with renal failure there was a significant decrease in beta, kappa10, and total body clearance. A linear relationship between beta of amoxicillin and creatinine clearance was found. This relationship allows dosage regimen adjustment for patients with renal impairment. A significant increase in the absorption half-life of the antibiotic was also observed in patients with renal impairment. The half-life of the antibiotic during hemodialysis was 2.3 h.

[Advantages of spectrophotometric reading of ELISA plates for determination of the HBs/anti-HB system]

It has been tested some diluted HBsAg and anti-HBs positive sera by modified ELISA test. We have found a correlation between HBsAg titer and spectrophotometric reading value and we have shown it in a curve. On the other hand, by neutralization of different dilutions of a RIA anti-HBs positive serum with different dilutions of a HBsAg positive serum we have carried out a checkboard and we have found that the best titer for neutralizing HBsAg is 30 ng/ml. This HBsAg has been called "standard". Using HBsAg "standard" we have tested 50 sera of hemophiliacs and we have found 1 HBsAg positive (2%) and 38 anti-HBs positive patients (76%).