Is elastography actually useful in the presurgical selection of thyroid nodules with indeterminate cytology?

BACKGROUND: Although fine-needle aspiration cytology remains the mainstay of the preoperative workup of thyroid nodules, those with follicular proliferation still represent a diagnostic challenge. Real-time elastography (RTE) estimates the stiffness/elasticity of lesions and is regarded as a promising technique for the presurgical selection of thyroid nodules (including those with indeterminate cytology). AIM: Our aim was to verify the potential role of RTE in the presurgical diagnosis of cancer in a large cohort of consecutive patients with follicular thyroid nodules. PATIENTS AND METHODS: One hundred two patients were submitted to conventional ultrasonography and RTE evaluation before being operated on for thyroid nodule with indeterminate cytology (54% single nodules). Tissue stiffness on RTE was scored from 1 (greatest elasticity) to 4 (no elasticity). RESULTS: At conventional ultrasonography examination, the nodules (median diameter 2.2 cm) were solid (cystic areas < 10%); microcalcifications were detected in 56% of them and a hypoechoic pattern in 64%. Elasticity was high in eight cases only (score 1-2) although low in 94 (score 3-4). Cancer was diagnosed in 36 nodules (35%), being associated with microcalcifications (P < 0.0001) and inversely related to nodule diameter (P < 0.01). Malignancy was detected in 50% of the nodules with RTE score 1-2 and in 34% of those with score 3-4. Therefore, either the positive (34%) or the negative predictive value (50%) was clinically negligible. CONCLUSIONS: The current study does not confirm the recently reported usefulness of RTE in presurgical selection of nodules with indeterminate cytology and suggest the need for quantitative analytical assessment of nodule stiffness to improve RTE efficacy.

Ultrasound findings guided a successful hemicolectomy in a leukemic patient with neutropenic enterocolitis.

INTRODUCTION: Neutropenic enterocolitis (NEC) can be a life-threatening complication of chemotherapy in leukemic patients. Early diagnosis and treatment is therefore crucial. METHODS: A 38-year-old woman with acute lymphoblastic leukemia and chemotherapy-induced neutropenia suddenly developed symptoms suspicious of NEC. Transabdominal ultrasound showed features consistent with NEC, later confirmed by computed tomography (CT) scan. RESULTS: The patient was scanned using portable ultrasound (US) equipment (Esaote My Lab 25). US findings showed involvement of the cecum, appendix, ascending colon and proximal middle transverse colon, with features resembling gas containing fissures within the colon wall itself. The risk of colon rupture was confirmed by CT scan. The patient underwent successful hemicolectomy after intravenous treatment with broad spectrum antibiotics, granulocyte-colony stimulating factor (G-CSF), platelets and fresh frozen plasma transfusion. DISCUSSION: A prompt bedside US examination upon development of symptoms allowed an early diagnosis of NEC and identified features consistent with imminent colon wall rupture, shifting the management of this life-threatening complication from medical to surgical. Multidisciplinary intervention was crucial for a successful hemicolectomy in a severely affected neutropenic patient.

Laparoscopic treatment of pancreatic insulinoma.

Laparoscopy and laparoscopic ultrasonography (LUS) have been proposed for the diagnosis and treatment of pancreatic insulinoma. We present for cases of pancreatic insulinoma approached by laparoscopy guided by LUS. In three cases, insulinomas were in the pancreatic body and in one case in the pancreatic head. All lesions were detected preoperatively by abdominal US and confirmed by computed tomography. Laparoscopy was performed under general anesthesia. LUS was performed using a 10-mm flexible probe. In two cases the adenoma was enucleated using scissors and electrocoagulation, major vessels were controlled using clips, and enucleation was completed using a 30-mm endo-GIA. In one case a laparoscopic distal pancreatectomy with spleen preservation was performed. In one case the adenoma was deep in the pancreatic head; minilaparotomy was performed and the adenoma enucleated. Patients were discharged in good health 5-7 days after surgery. The postoperative course was complicated in one case of enucleation by peripancreatic fluid collection that was treated percutaneously. Our experience confirms that accurate localization followed by excision of tumors via the laparoscopic approach constitute a significant advance in the management of insulinoma.

Restoration of fecal continence with chronic electrostimulation of gracilis muscle 17 years after a Pickrell's operation.

A 27-year-old woman who had undergone a Pickrell's operation at the age of 10 years, was observed for severe incontinence to solid and liquid stools. Physical examination and physiological tests revealed poor resting anal tone but a very good response of the transposed gracilis to percutaneous electrostimulation, which showed that the gracilis ability to contract was maintained in spite of 17 years of only occasional and unplanned muscular activity. Examination also demonstrated that the muscle had followed body growth during the patient's development. Restoration of continence by continuous electrostimulation of the gracilis muscle was then planned. To allow muscular resistance to this stimulation a fast-to-slow twitch fiber conversion was first obtained by low-frequency electrostimulation. A subcutaneous abdominal implant of a pulse generator connected to the gracilis by intramuscular platinum-iridium electrodes was carried out. After a period of muscular training, fiber conversion was achieved, and continuous electrostimulation led to complete restoration of continence with stable results at the 36 month follow-up evaluation. This case demonstrates that even such a long period of muscular inactivity does not affect the possibility of recovering a failed Pickrell's operation using electrostimulation. This easy and safe procedure can be applied to all previously failed graciloplasties provided that muscle contractility is maintained.

Safety and efficacy of dynamic graciloplasty for fecal incontinence: report of a prospective, multicenter trial. Dynamic Graciloplasty Therapy Study Group.

PURPOSE: Dynamic graciloplasty has been used for intractable fecal incontinence, and good results have been reported. The aim of this study was to assess prospectively the safety and efficacy of dynamic graciloplasty for intractable fecal incontinence in a prospective, multicenter trial. METHODS: A total of 123 adults were treated with dynamic graciloplasty at 20 institutions. Continence was assessed preoperatively and postoperatively by use of 14-day diaries. RESULTS: There was one treatment-related death. One hundred eighty-nine adverse events occurred in 91 patients (74 percent). Forty-nine patients (40 percent) required one or more operations to treat complications. One hundred seventy (90 percent) events were resolved. Sixty-three percent of patients without pre-existing stomas recorded a 50 percent or greater decrease in incontinent events 12 months after dynamic graciloplasty, and an additional 11 percent experienced lesser degrees of improvement. Twenty-six percent were not improved, worsened, or exited. In patients with pre-existing stomas, 33 percent achieved successful outcomes at 12 months. This number increased to 60 percent at 18 months. Seventy-eight percent of patients had increased enema retention time, and mean anal canal pressures improved significantly at 12 months. Significant changes in quality of life were also observed. CONCLUSIONS: Objective improvement can be demonstrated in the majority of patients with end-stage fecal incontinence treated with dynamic graciloplasty. Reduction in incontinence episodes can be correlated with improved quality of life. Adverse events are frequently encountered, but most resolve with treatment.

Standards for anal sphincter replacement.

PURPOSE: Anal sphincter replacement offers a new treatment option for patients with severe refractory fecal incontinence or for those who require abdominoperineal resection for localized malignancy. The purpose of this study was to review the current status of anal sphincter replacement, formulate a consensus statement regarding its current use, and outline suggestions for future development. METHODS: Four areas of interests were selected: indications for sphincter replacement, continence scoring and quality of life, choice of therapy, and dissemination of new technology. A questionnaire regarding these issues was developed and circulated to working party members; its results served as the basis for this consensus document. RESULTS: Both electrically stimulated skeletal muscle neosphincter and artificial anal sphincter are options for patients with end-stage fecal incontinence. Electrically stimulated skeletal muscle neosphincter is also appropriate for reconstruction after surgical excision of the anorectum in selected cases. Avoidance of complications requires strict attention to sterile technique, prophylactic antibiotics, and deep venous thrombus prophylaxis. A standardized scoring system is proposed that evaluates both continence and evacuation. Quality of life is a critical endpoint for assessing sphincter replacement, and use of The American Society of Colon and Rectal Surgeons incontinence-specific quality-of-life instrument is recommended. As the efficacy of sphincter replacement becomes proven, dissemination of the technique should occur in a controlled manner to ensure adequate surgeon training, minimization of complications, and optimization of results. CONCLUSIONS: Sphincter replacement by electrically stimulated skeletal muscle neosphincter and artificial anal sphincter provide a continent option for patients with end-stage fecal incontinence and those requiring abdominoperineal resection. The guidelines offered in this document are intended to facilitate the controlled and safe development and acceptance of these new techniques.

Quality of life after total anorectal reconstruction: long-term results.

The aim of the study was to assess the long-term quality of life (minimum 8 years after surgery) of patients undergoing total anorectal reconstruction for low rectal cancer. The quality of life of 27 patients undergoing total anorectal reconstruction (mean age: 73.07 years) and 27 healthy subjects (mean age: 73.50 years) randomly chosen from the population was analysed and compared using general standardized questionnaires and specific fecal continence scales. Twenty-one out of 27 patients were clinically evaluated and personally interviewed by the same surgeon who had performed the reconstruction some years before. Quality of life analysis yielded good global results, also in the light of the mean age of the patients. Fecal continence was obtained in 81% of patients. All of them report a good physical, psychological and social situation. There was no statistically significant difference (P = ns) in quality of life between these 27 total anorectal reconstruction patients and the control population. In adequately selected patients, total anorectal reconstruction is proposed as a technique capable of guaranteeing good quality of life as well as being a safe technique for the treatment of low rectal cancer.

Laparoscopic treatment of appendico-cecal intussusception.

Laparoscopy is a therapeutic possibility in pediatric surgery. A case of appendiceal intussusception treated laparoscopically in a 27-month-old girl is presented. The postoperative course was normal.

Different mechanisms are progressively recruited to promote Cu(II) reduction by isolated human low-density lipoprotein undergoing oxidation.

The kinetics of Cu(II) reduction and its relationship to the process of low density lipoprotein (LDL) oxidation were investigated in isolated human LDL incubated with CuSO4 by using the Cu(I) chelator and indicator dye bathocuproine disulfonate (BC). The inclusion of BC in the incubation medium containing isolated LDL and different concentrations of CuSO4 revealed a biphasic kinetics of Cu(II) reduction consisting of an early phase followed by a plateau phase and a subsequent extensive reduction phase. The amount of Cu(I) formed during the early phase, as well as the rate of its generation, were strictly dependent on both the level of Cu(II) available (saturation was observed at 20 and 50 microM CuSO4) and the concentration of alpha-tocopherol within native LDL particles. Artificial enrichment of LDL with different concentrations of alpha-tocopherol led to a parallel increase of both the amount of Cu(II) reduced and the rate of reduction. The late phase of Cu(II) reduction was strictly related to the availability of copper but was largely independent from alpha-tocopherol. Neither the amount of Cu(I) generated nor the rate of generation were saturated at concentrations of copper up to 100 microM. Comparable results were obtained by adding BC at different time-points to the LDL-copper mixture, in order to measure at the same time-points both the true rate of Cu(II) reduction and the generation of TBARS during the dynamic process of LDL oxidation. The rate of Cu(II) reduction was already high during the lag-phase of the LDL oxidation profile and progressively decreased as alpha-tocopherol concentration decreased. The subsequent increase in the rate of Cu(II) reduction paralleled the formation of TBARS during the extensive LDL oxidation phase. These results suggest that different mechanisms of Cu(II) reduction, namely alpha-tocopherol-dependent and independent (likely lipid peroxide-dependent), are progressively recruited during copper-promoted LDL oxidation.

Anorectal reconstruction after abdominoperineal resection. Experience with double-wrap graciloplasty supported by low-frequency electrostimulation.

PURPOSE: The aims of the study contained herein were to analyze the efficacy and safety of a chronically electrostimulated double-wrap graciloplasty for restoration of continence after a curative abdominoperineal resection for rectal carcinoma and to evaluate late results of a stimulation protocol that was begun early. METHODS: During the last six years, 31 consecutive patients underwent this procedure: in 24 patients, electrostimulated double-wrap graciloplasty was performed simultaneously with abdominoperineal resection for lower rectal cancer, 7 strictly selected patients underwent conversion to an abdominal stoma following previous abdominoperineal resection (mean length of time from stoma creation, 71.4 months) Anorectal reconstruction was performed following a surgical scheme already standarized since 1985 in 102 patients: after abdominoperineal resection, the distal colon was pulled through to the perineum and surrounded by both gracilis muscles following an "alfa and new-sling" configuration; using platinumiridium electrodes, both muscles were then connected to pulse generator, which was implanted subcutaneously in the abdomen. All surgical steps were performed during the same surgical session to allow early postoperative stimulation of the transposed muscles. A contemporary covering stoma was abandoned as a standard procedure; the distal colon was left closed for a few postoperative days, then it was resected and sutured to the perineum under local anesthesia. Eighteen patients underwent preoperative or postoperative radiotherapy or both, without any significant adverse outcome. To increase gracilis resistance to prolonged "tonic" contraction, patients underwent a chronic, low-frequency stimulation protocol. In the last 11 patients, a new "over-the-nerve and intramuscular" implant was adopted to optimize fiber recruitment and to reduce electrostimulation thresholds. At regular intervals, all patients were evaluated using continence scores and questionnaires, electromanometry, endoluminal ultrasound study, and defecography. RESULTS: Twenty-six of 31 patients were evaluated for continence, with a mean length of follow-up of 37.8 (range, 4-68) months; 3 patients died because of cancer recurrence, 1 underwent conversion to an abdominal stoma, and 1 is waiting for stoma closure. Continence to liquid and solid stools was achieved in 22 patients (85 percent), and electromanometry findings confirmed a good muscular contraction postoperatively and during follow-up intervals. No postoperative mortality (40 days) was observed; the postoperative complication rate was high 22-percent), but early treatment (drainage and temporary diversion in 7 patients) led to favorable outcomes (4 resolutions, 3 partial muscular impairments). Four stimulators had to be temporarily explanted because of late complications, and two stimulators had to be replaced because of battery exhaustion after three years of use with high stimulation parameters. A significant difference was observed comparing full-contracting threshold after intramuscular (14 patients) and the new over-the-nerve and intramuscular implant technique. CONCLUSIONS: The study contained herein confirms the efficacy of the surgical scheme we have adopted since 1985 to reconstruct sphincteric apparatus after abdominoperineal resection of the rectum. The "one-step" timing of surgical and electrostimulation-related procedures and the early start of stimulation did not show a significant increase in the complication rate and did not produce noticeable muscular or nerve damage. Adoption of chronic electrostimulation protocols using implantable devices increased the rate of fully continent patients; nevertheless, the overall cost for devices and medical staff duties was high, and a small increase of late morbidity was observed. Finally, the preliminary experience with our new technique of electrode implants encourages further application.

Total anorectal reconstruction supported by electrostimulation gracilis neosphincter.

PURPOSE: To review and to update the results of Total Anorectal Reconstruction with Electrostimulated Graciloplasty (ES-TAR) at the same time as or following abdominoperineal resection (APR). SETTING: A university hospital in Italy. METHODS: Retrospective study. POPULATION: A series of 98 consecutive anorectal cancer patients who had undergone ES-TAR (in 88 cases at the same time as APR; in 10 cases following APR), 61 of whom are still evaluable in respect of continence (median follow-up period 55 months). RESULTS: There was no mortality. Thirty-seven percent of patients had postoperative complications with no impact on survival or functional outcome. The 5-year survival rate in 50 patients was 61% and the 5-year estimated cumulative probability of survival in 81 patients was 65%. Local recurrence rate was 16%. Continence was achieved in 87% of patients with a chronically stimulated TAR, and in 69% of patients with short-term stimulation. CONCLUSION: ES-TAR is a safe and effective method for both curing anorectal cancer and restoring continence. It may be considered a reliable alternative to sphincter-saving procedures in lower rectal cancer patients.

Laparoscopically assisted abdominoperineal resection and simultaneous total anorectal reconstruction with electrostimulated static-dynamic graciloplasty.

Bilateral electrostimulated graciloplasty, performed in a "static-dynamic" configuration around a perineal colostomy (total anorectal reconstruction-TAR), has been proven a reliable way to restore continence in patients who undergo to abdomino perineal resection (A.Pe.R.) of the anorectum for lower rectal cancer. In selected cases, laparoscopically assisted TAR can significantly improve body-image preservation and aesthetic results. A 33-year-old woman affected by lower rectal cancer was submitted to laparoscopic-assisted A.Pe.R and TAR with simultaneous bilateral graciloplasty; a suprapubic median mini-access was adopted to fully mobilize the mesorectum in absence of pneumoperitoneum. A subcutaneous pulse generator and special electrodes were also implanted to chronically electrostimulate the graciloplasty. In spite of postoperative bleeding which required a blood transfusion, postoperative outcome was satisfactory; electrostimulation was started on the 10th postoperative (p.o.) day and the patient was discharged on the 17th p.o. day. Two months after TAR, level II continence (N.S. Williams Scale) was achieved. In selected cases, laparoscopically assisted A.Pe.R. and TAR can be safely adopted to preserve body image and quality of life, avoiding at the same time a large abdominal approach and a "permanent" abdominal colostomy.

The dynamic reduction of Cu(II) to Cu(I) and not Cu(I) availability is a sufficient trigger for low density lipoprotein oxidation.

Copper (II) is one of the most widely employed experimental models to induce in vitro low density lipoprotein (LDL) oxidation. It is generally assumed that Cu(I), generated from active reduction of Cu(II), is the real trigger for the peroxidation of polyunsaturated fatty acids in LDL. We have employed isolated human LDL challenged with Cu(II) and the Cu(I) chelator bathocuproine disulfonic acid (BC) to test the validity of this hypothesis. At lower Cu(II)/LDL molar ratios, BC completely inhibited copper-mediated LDL oxidation evaluated either as thiobarbituric acid reactive substances (TBARS) production or changes in apo B100 electrophoretic mobility. On the contrary, at higher Cu(II)/LDL molar ratios, BC did not prevent LDL oxidation but rather markedly stimulated both the generation of TBARS and the increase of apo B100 electronegativity. These oxidative modifications were completely prevented by the Cu(II) chelator EDTA. Furthermore, the BC-Cu(I) complex alone was neither redox active nor active inducer of TBARS generation. These findings indicate that, under these experimental conditions, [1] Cu(I) is not necessary to promote LDL oxidation, [2] the availability of Cu(II) is a prerequisite and [3] some of the reaction(s) involved in Cu(II) reduction may play an essential role in initiating LDL oxidation.

Suitability of chemical in vitro models to investigate LDL oxidation: study with different initiating conditions in native and alpha-tocopherol-supplemented LDL.

Isolated human LDL, used in the native form or supplemented with alpha-tocopherol (alpha T), were oxidized with Cu2+, 2,2'-azobis-(2-amidino propane) hydrochloride (AAPH), and H2O2 plus horseradish peroxidase (HRP). The oxidation kinetics were measured spectrophotometrically at 234 nm to follow the formation of conjugated dienes and evaluated as resistance to oxidation (lag phase, LP) and maximal oxidation rate (propagation rate, PR). The duration of LP in nonsupplemented LDL was different with the three prooxidant stimuli (LP, in min: 96 +/- 19 for Cu2+, 28.7 +/- 6.7 for HRP, and 67.1 +/- 11.2 for AAPH). No correlation was found between the values obtained with Cu2+ and AAPH or HRP, but a significant correlation was found with AAPH and HRP (r = 0.798, P < 0.002). In vitro alpha T supplementation prolonged the LP and decreased the PR with all the stimuli. The extent of increase in LP was highly correlated (r = 0.872, P < 0.001 for Cu2+ and HRP; r = 0.603, P < 0.03 for Cu2+ and AAPH; r = 0.749, P < 0.005 for AAPH and HRP). Although the evaluation of ex vivo LDL oxidation is dependent on the prooxidant stimulus, the three prooxidant conditions used detect equally well the efficiency of alpha T supplementation in preventing LDL oxidation.

The formation of some antigenic epitopes in oxidized human low-density lipoprotein is inhibited by nitric oxide.

NO and NO-donors are able to inhibit the peroxidation of polyunsaturated fatty acids in human low-density lipoproteins (LDL) exposed to Cu+2. Here we report that 1-hydroxy-2-oxo-3,3-bis(3-aminoethyl)-1-triazene (NOC-18), a compound which releases NO at low rate in aqueous solutions, powerfully inhibits the peroxidation of polyunsaturated fatty acids, tryptophan loss, the formation of fluorescent aldehydic adducts in apo B100 and the increase of electrophoretic mobility in isolated LDL undergoing oxidation. The inhibitory effect is not restricted to Cu+2-induced peroxidation but is also detectable with other oxidizing conditions such as the free radical generator 2,2'-azobis-(2-amidino propane) hydrochloride (AAPH), the combination of horseradish peroxidase and H2O2 (HRP), and peroxynitrite (ONOO-). The recognition of Cu+2-, AAPH-, and ONOO(-)-modified LDL by specific autoantibodies present in serum of atherosclerotic patients is almost completely inhibited when the oxidation procedure is performed in the presence of NOC-18. However, NOC-18 is completely ineffective in preventing the formation of recognizable antigens in HRP-modified LDL. These findings suggest that NO may efficiently prevent the formation of some, but not all, the antigenic epitopes recognized by human autoantibodies and thus likely formed during in vivo LDL oxidation.

Protective effect of dehydroepiandrosterone against copper-induced lipid peroxidation in the rat.

This study investigates the effectiveness and multitargeted activity of dehydroepiandrosterone (DHEA) as antioxidant in vivo. A single dose of DHEA was given IP to male rats. Liver and brain microsomes, and plasma low density lipoprotein (LDL), were isolated from rats sacrificed 17 h later. Liver and brain microsomes were challenged with CuSO(4) and, as index of lipid peroxidation, the production of thiobarbituric acid reactive substances (TBARS) was measaured. Also, plasma low-density lipoprotein (LDL) were challenged with copper and the time course of lipid peroxidation was evaluated following the formation of conjugated dienes. The onset of TBARS generation induced by copper was marked delayed in both liver and brain microsomes from DHEA-treated animals. Also, the resistance of LDL to oxidation, expressed by the duration of the lag-phase of the kinetic curve, was significantly enhanced in DHEA-treated rats. Results indicate that in vivo DHEA supplementation makes subcellular fractions isolated from different tissues and plasma constituents (LDL) more resistant to lipid peroxidation triggered by copper. The antioxidant effect on plasma LDL might be of special relevance to the proposed antiatherogenic activity of DHEA. Moreover, multitargeted antioxidant activity of DHEA might protect tissues from oxygen radicals damage.

Circulating autoantibodies recognizing peroxidase-oxidized low density lipoprotein. Evidence for new antigenic epitopes formed in vivo independently from lipid peroxidation.

Oxidatively modified LDLs are antigenic and elicit the generation of autoantibodies often detected in plasma and within plaques of atherosclerotic patients. Although Cu(2+)-oxidized LDL and malondialdehyde (MDA)-modified LDL are usually used as antigens in immunoassays, other, still unrecognized epitopes may be formed in vivo during LDL oxidation and may induce antibody production. Antibodies recognizing LDL oxidatively modified by Cu2+, 2,2'-azobis-(2-amidino propane) hydrochloride (AAPH), and the combination of horseradish peroxidase and H2O2 (HRP) were detected in serum of a group of 90 unselected patients. HRP-oxidized LDL was the antigen that revealed the highest IgG titers, although the extent of LDL oxidation (evaluated as conjugated diene formation, loss of tryptophan fluorescence, production of fluorescent aldehydic adducts, and change in electrophoretic mobility) was comparable to that obtained with Cu2+ and AAPH. There was a highly statistically significant correlation between the IgG titers detected using Cu(2+)- and AAPH-oxidized LDLs as antigens, but no correlation was found between the IgG titers revealed by HRP and Cu2+ or AAPH. In addition, the antibody titers against MDA-modified LDL exhibited a significant correlation with those against Cu(2+)- or AAPH-oxidized LDL but did not correlate with those against HRP-oxidized LDL. Finally, immunocompetition experiments revealed that IgG recognizing HRP-oxidized LDL did not cross-react with Cu(2+)-oxidized LDL and vice versa. The possibility that lipid peroxidation-independent modifications could play a role in HRP-induced formation of antigenic epitopes in LDL was supported by two lines of evidence. First, in probucol-enriched LDL, despite the complete inhibition of lipid peroxidation, HRP, but not Cu2+ and AAPH, was still able to generate epitopes that were recognized by the same sera reacting with HRP-oxidized native (not probucol-enriched) LDL. In addition, the presence of autoantibodies against Cu(2+)- and AAPH-oxidized LDLs was negatively correlated with serum alpha-tocopherol concentration, whereas the titers against HRP-oxidized LDL did not exhibit any statistically relevant correlation with alpha-tocopherol levels. Together, these findings indicate that peroxidase(s)-dependent mechanisms can trigger peculiar lipid peroxidation-independent modifications of LDL in vivo.

Inhibition of Cu2+-induced LDL oxidation by nitric oxide: a study using donors with different half-time of NO release.

The incubation of low density lipoproteins with Cu++ promotes oxidative modifications that make them atherogenic. Comparable alterations occur in vivo and are modulated by the generation of nitric oxide by endothelial cells or macrophages. Here we report that two donors (NOC-9 and NOC-18) with different half times of NO release (2.7 and >500 min, respectively) inhibit in vitro lipoprotein oxidation promoted by Cu++. Both donors increase the duration of the lag-phase and decrease the maximum rate of conjugated diene formation, prevent the loss of tryptophan in Apo B100, and decrease the formation of fluorescent adducts. The protective effect of NOC-9 was rapidly exhausted and its overall efficacy in preventing LDL oxidation was two orders of magnitude lower than that exhibited by NOC-18. These findings suggest that a continuous flux of NO generation, even at lower concentrations, is more efficient than considerably higher doses released as a burst in protecting both the lipid and the protein moiety of LDL from oxidation.