Protein S-nitrosylation in photosynthetic organisms: A comprehensive overview with future perspectives.

BACKGROUND: The free radical nitric oxide (NO) and derivative reactive nitrogen species (RNS) play essential roles in cellular redox regulation mainly through protein S-nitrosylation, a redox post-translational modification in which specific cysteines are converted to nitrosothiols. SCOPE OF VIEW: This review aims to discuss the current state of knowledge, as well as future perspectives, regarding protein S-nitrosylation in photosynthetic organisms. MAJOR CONCLUSIONS: NO, synthesized by plants from different sources (nitrite, arginine), provides directly or indirectly the nitroso moiety of nitrosothiols. Biosynthesis, reactivity and scavenging systems of NO/RNS, determine the NO-based signaling including the rate of protein nitrosylation. Denitrosylation reactions compete with nitrosylation in setting the levels of nitrosylated proteins in vivo. GENERAL SIGNIFICANCE: Based on a combination of proteomic, biochemical and genetic approaches, protein nitrosylation is emerging as a pervasive player in cell signaling networks. Specificity of protein nitrosylation and integration among different post-translational modifications are among the major challenges for future experimental studies in the redox biology field. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock.

CT and MRI imaging at the acute phase of inaugural non-traumatic hepatic haemorrhages.

PURPOSE: Although rare, non-traumatic hepatic haemorrhage is a known complication of liver tumors. In cases where the haemorrhage is the first clinical event, diagnostic work-up is critical. MATERIAL AND METHODS: This retrospective study was conducted between July 2001 and March 2011. Acute phase CT-scan and MRI imaging in patients diagnosed with non-traumatic liver hematomas were interpreted with particular attention to the radio-semiotic characteristics of hematomas and liver lesions. Those findings were then confronted to the patients' final diagnoses. RESULTS: Twelve patients were included (mean age of 42 years). In seven of them a suspect liver lesion was discovered in the acute CT-Scan or MRI imaging. All lesions were strongly hyper vascular.The haemorrhage revealed hepatocarcinoma in four patients, liver adenoma in two and focal nodular hyperplasia in an other. CONCLUSION: It is important in spontaneous liver haemorrhage to consider the high probability of hepatocarcinoma or potentially malignant lesions even when the patient has no known hepatic disorders, and especially in young patients. The results of this study show that imaging is a key issue at the acute phase of inaugural non-traumatic hepatic haemorrhages and requires a simple but complete triphasic injected protocol.

Computed tomography of the parathyroids: the value of density measurements to distinguish between parathyroid adenomas of the lymph nodes and the thyroid parenchyma.

PURPOSE: To compare the densities of parathyroid adenomas, lymph nodes and the thyroid parenchyma during multi-phase cervico-thoracic computed tomography to determine the differentiating threshold values. MATERIALS AND METHODS: This study comprises 30 patients operated for a parathyroid adenoma after computed tomography without injection and then 45 and 70 seconds after the injection of an iodine based contrast product (350 mgI/mL, 150 mL, 3 mL/s). The density of the adenomas, lymph nodes and thyroid was measured during the three phases (D0, D45, D70). The relative enhancement (RE) at 45 seconds was calculated: RE=(D45-D0)/D0. RESULTS: A significant difference was found in the spontaneous density of the parathyroid adenomas of the thyroid (P<0.01) with a threshold value of 75 HU. A significant difference is found in the enhancement after injection of the adenomas and lymph nodes (P<0.01). The adenomas present an enhancement peak at 45 seconds while the maximum enhancement of the lymph nodes is at 70 seconds. At 45 seconds, a threshold value of 114 HU and an RE 125% allows them to be distinguished (sensitivity and specificity 0.96). CONCLUSION: Measurement of the densities can differentiate between the parathyroid adenomas, lymph nodes and thyroid.

Pharmacodynamic evaluation of the activity of antibiotics against hemin- and menadione-dependent small-colony variants of Staphylococcus aureus in models of extracellular (broth) and intracellular (THP-1 monocytes) infections.

Staphylococcus aureus small-colony variants (SCVs) persist intracellularly, which may contribute to persistence/recurrence of infections and antibiotic failure. We have studied the intracellular fate of menD and hemB mutants (corresponding to menadione- and hemin-dependent SCVs, respectively) of the COL methicillin-resistant S. aureus (MRSA) strain and the antibiotic pharmacodynamic profile against extracellular (broth) and intracellular (human THP-1 monocytes) bacteria. Compared to the parental strain, SCVs showed slower extracellular growth (restored upon medium supplementation with menadione or hemin), reduced phagocytosis, and, for the menD SCV, lower intracellular counts at 24 h postinfection. Against extracellular bacteria, daptomycin, gentamicin, rifampin, moxifloxacin, and oritavancin showed similar profiles of activity against all strains, with a static effect obtained at concentrations close to their MICs and complete eradication as maximal effect. In contrast, vancomycin was not bactericidal against SCVs. Against intracellular bacteria, concentration-effect curves fitted sigmoidal regressions for vancomycin, daptomycin, gentamicin, and rifampin (with maximal effects lower than a 2-log decrease in CFU) but biphasic regressions (with a maximal effect greater than a 3-log decrease in CFU) for moxifloxacin and oritavancin, suggesting a dual mode of action against intracellular bacteria. For all antibiotics, these curves were indistinguishable between the strains investigated, except for the menD mutant, which systematically showed a lower amplitude of the concentration-effect response, with markedly reduced minimal efficacy (due to slower growth) but no change in maximal efficacy. The data therefore show that the maximal efficacies of antibiotics are similar against normal-phenotype and menadione- and hemin-dependent strains despite their different intracellular fates, with oritavancin, and to some extent moxifloxacin, being the most effective.

Quality assessment in open surgical repair of thoracic aortic disease.

Risk-prediction and quality-assurance models facilitate comparison of surgeons, institutions, and emerging alternative technologies. With comparative context, the most meaningful outcomes for thoracic aortic (TA) repair can be identified, evaluated, and adopted to improve open TA repair among a variety of providers; moreover, open TA repair can be more accurately compared to endovascular TA repair. Although the EuroSCORE risk-stratification model was not specifically designed for TA repair, it is largely suitable for this purpose despite the aged dataset from which it was developed. However, such prediction models could be improved by expanding their end points to include not only mortality but other life-altering adverse events, such as paraplegia, stroke, and renal failure. Population-based studies may be useful in establishing trends and should be conducted in a fashion that will enhance their external applicability; procedure-volume studies are often limited as comparative benchmarks. Additionally, experienced centers have great value because they can report the outcomes of large numbers of cases. Despite a tendency to take on challenging cases, centers of excellence consistently report better outcomes than those observed in population studies. Stratifying reported outcomes for risk level and urgency of repair may have value, because it would avoid penalizing surgeons for taking on complex repairs. For the average patient with few comorbidities, the most durable and established repair should be offered, and the best contemporary success rates should be presented to facilitate that choice.

Analysis of multigenerational families with thoracic aortic aneurysms and dissections due to TGFBR1 or TGFBR2 mutations.

BACKGROUND: Mutations in the transforming growth factor beta receptor type I and II genes (TGFBR1 and TGFBR2) cause Loeys-Dietz syndrome (LDS), characterised by thoracic aortic aneurysms and dissections (TAAD), aneurysms and dissections of other arteries, craniosynostosis, cleft palate/bifid uvula, hypertelorism, congenital heart defects, arterial tortuosity, and mental retardation. TGFBR2 mutations can also cause TAAD in the absence of features of LDS in large multigenerational families, yet only sporadic LDS cases or parent-child pairs with TGFBR1 mutations have been reported to date. METHODS: The authors identified TGFBR1 missense mutations in multigenerational families with TAAD by DNA sequencing. Clinical features of affected individuals were assessed and compared with clinical features of previously described TGFBR2 families. RESULTS: Statistical analyses of the clinical features of the TGFBR1 cohort (n = 30) were compared with clinical features of TGFBR2 cohort (n = 77). Significant differences were identified in clinical presentation and survival based on gender in TGFBR1 families but not in TGFBR2 families. In families with TGFBR1 mutations, men died younger than women based on Kaplan-Meier survival curves. In addition, men presented with TAAD and women often presented with dissections and aneurysms of arteries other than the ascending thoracic aorta. The data also suggest that individuals with TGFBR2 mutations are more likely to dissect at aortic diameters <5.0 cm than individuals with TGFBR1 mutations. CONCLUSION: This study is the first to demonstrate clinical differences between patients with TGFBR1 and TGFBR2 mutations. These differences are important for the clinical management and outcome of vascular diseases in these patients.

Dielectric spectroscopy of normal and malignant human lung cells at ultra-high frequencies.

Microwave techniques for biomedical applications aimed at cancer treatment or diagnosis, either by imaging or spectroscopy, are promising. Their use relies on knowledge of the dielectric properties of tissues, especially on a detectable difference between malignant and normal tissues. As most studies investigated the dielectric properties of ex vivo tissues, there is a need for better biophysical understanding of human tissues in their living state. As an essential component of tissues, cells represent valuable objects of analysis. The approach developed in this study is an investigation at cell level. Its aim was to compare human lung normal and malignant cells by dielectric spectroscopy in the beginning of the microwave range, where such information is of substantial biomedical importance. These cells were embedded in small and low-conductivity agarose hydrogels and laid on an open-ended coaxial probe connected to a vector network analyser operated from 200 MHz to 2 GHz. The comparison between normal and malignant cells was drawn using the variation of measured dielectric properties and fitting the measurements using the Maxwell-Wagner equation. Both methods revealed slight differences between the two cell lines, which were statistically significant regarding conductivities of composite gels and cells.

Activities of antistaphylococcal antibiotics towards the extracellular and intraphagocytic forms of Staphylococcus aureus isolates from a patient with persistent bacteraemia and endocarditis.

Decreased susceptibility of Staphylococcus aureus to antistaphylococcal agents may be associated with inability to eradicate intracellular forms, which could explain therapeutic failures. This hypothesis was tested using clinical isolates obtained from a patient with persistent staphylococcal bacteraemia under therapy. Four isogenic isolates (three from tissue, one from blood) with increased MICs for vancomycin (1-4 mg/L) and for daptomycin (1-4 mg/L) were collected after an initial 16-day treatment with vancomycin-rifampicin-gentamicin, followed by 13-20 days of treatment with daptomycin-rifampicin-gentamicin. Isolates were tested for MICs and for: (i) vancomycin (BODIPY-FL-vancomycin) and daptomycin binding; (ii) cell wall turnover (loss of N-acetyl-d-[1-(14)C]glucosamine in 30 min after 1 h of labelling); and (iii) Triton X-100-induced autolysis. Extracellular (broth) and intracellular (THP-1 macrophages) activities of rifampicin, linezolid and fusidic acid at C(max), and of vancomycin, daptomycin, quinupristin-dalfopristin and oritavancin over a wide range of extracellular concentrations (with pharmacological modelling to determine E(max)), were measured at 24 h. Increases in vancomycin MICs correlated with increased drug binding, and decreased cell wall turnover and detergent-induced autolysis. Increases in daptomycin MICs correlated with decreased daptomycin binding. Intracellular activity was weak (E(max) <1 log(10) CFU decrease) for vancomycin against all isolates, and for daptomycin against isolates with MICs >1 mg/L. Among all antibiotics tested, only quinupristin-dalfopristin and oritavancin provided close to bactericidal intracellular activities (1.6-2.5 log(10) CFU decreases at C(max)). Determination of the intracellular susceptibility of S. aureus, combined with improved methods of diagnosis, could be useful when dealing with persistent staphylococcal infections and could improve therapy.

[Fluoroscopy guided L5-S1 transforaminal injection as a treatement for s1 radiculopathy]. / Infiltration foraminale L5-S1 radioguidée dans le traitement de la lombosciatique S1.

OBJECTIVE: To assess the efficacy of fluoroscopy guided L5-S1 transforaminal steroid injections for the treatment of S1 radiculopathy secondary to intervertebral disk disorder. METHOD: 41 patients were included: prospective study (20 patients) and retrospective study (21 patients). All patients suffered from S1 radiculopathy secondary to nerve root compression by intervertebral disk material, as demonstrated by lumbar spine CT. The patients underwent 2 fluoroscopy guided L5-S1 transforaminal injections of steroid (Hydrocotancyl 125 mg), at 8 days interval. RESULTS: 60% of patients showed significant improvement of their painful radiculopathy at day 8 (n:41), 60-67% at day 30 (n:41) and 67% at day 90 (n:18). CONCLUSION: Fluoroscopy guided L5-S1 transforaminal injection showed good efficacy in the treatment of S1 radiculopathy.

Biochemical and histological responses in mussel (Mytilus edulis) exposed to North Sea oil and to a mixture of North Sea oil and alkylphenols.

Several environmental chemicals are suspected to be responsible for adverse health effects on the reproductive system in various organisms. During this work, environmentally relevant concentrations of North Sea oil were used alone or in combination with alkylphenols and additional PAH to study the effect on vitellogenin-like protein expression and gonadal development in mussels. North Sea oil (0.5 ppm) induced the expression of phospho-proteins in both sexes indicating that some compounds are oestrogen-mimics. This induction was not seen in samples dosed with the mixture but signs of toxic effects were observed in the gonads. Indeed, numerous degenerating ovarian follicles in females and foci, similar to vertebrate melanomacrophage centres, were observed in testes.

Characterization of thioredoxin y, a new type of thioredoxin identified in the genome of Chlamydomonas reinhardtii.

The sequencing of the Arabidopsis genome revealed a multiplicity of thioredoxins (TRX), ubiquitous protein disulfide oxido-reductases. We have analyzed the TRX family in the genome of the unicellular green alga Chlamydomonas reinhardtii and identified eight different thioredoxins for which we have cloned and sequenced the corresponding cDNAs. One of these TRXs represents a new type that we named TRX y. This most probably chloroplastic TRX is highly conserved in photosynthetic organisms. The biochemical characterization of the recombinant protein shows that it exhibits a thermal stability profile and specificity toward target enzymes completely different from those of TRXs characterized so far.

Target-controlled infusion of propofol and remifentanil in cardiac anaesthesia: influence of age on predicted effect-site concentrations.

BACKGROUND: Propofol-anaesthesia administrated via target-controlled infusion (TCI) has been proposed for cardiac surgery. Age-related changes in pharmacology explain why propofol dose requirement is reduced in elderly patients. However, the Marsh pharmacokinetic model incorporated in the Diprifusor propofol device does not take age into account as a covariable. In the absence of depth of anaesthesia monitoring, this limitation could cause adverse cardiovascular effects resulting from propofol overdose in older patients. We assessed the influence of age on effect-site propofol concentrations predicted by the Diprifusor and titrated to the bispectral index score (BIS) during cardiac anaesthesia. METHODS: Forty-five patients received propofol by Diprifusor and remifentanil by software including Minto model. Propofol and remifentanil effect-site concentrations were adapted to BIS (40-60) and haemodynamic profile, respectively. The influence of age on effect-site concentrations was assessed by dividing patients into two groups: young (<65 yr) and elderly (> or =65 yr). RESULTS: For a similar depth of anaesthesia, effect-site propofol concentrations were significantly lower in elderly patients at the different stages of cardiac surgery. The mean dose of propofol required to perform tracheal intubation was significantly lower in elderly patients. However, the overall doses of propofol were comparable in both groups. Neither effect-site remifentanil concentrations nor overall doses of remifentanil were significantly different between the two groups. CONCLUSIONS: In cardiac anaesthesia, target concentrations of propofol must be reduced in elderly patients. Although this probably contributes to improving intraoperative haemodynamic stability, the absence of decrease in overall dose requirement of propofol suggests that this adjustment is relatively moderate.

Early evaluation of dressage ability in different breeds.

Dressage is one of the Olympic equestrian sports practiced in several countries using different horse breeds. Specific characteristics of the walk, trot and canter are required for dressage. It has been assumed that some of these traits could be selected for genetically and contribute to dressage performance. The purpose of this study was to compare the walk, trot and conformation characteristics in young horses of different breeds used for dressage. A total of 142 horses age 3 years were classified into 3 groups of breeds (German, French and Spanish saddle horses) and tested using the same procedure. The skeletal conformation measurements were made by image analysis. Gait variables of the walk and trot were measured by the accelerometric gait analysis system Equimetrix. Discriminant analysis could explain the variability between the groups by taking into account the walk (P<0.0003), trot (P<0.0001) and conformation variables (P<0.0001). Many gait and conformation variables were significantly different between the breeds. In summary, the German horses had gait characteristics more adapted for dressage competition, and the results of this group could be used as a reference for early evaluation in dressage. Purebred Spanish horses could be considered as a reference for collected gaits used for farm work and old academic dressage. The gait and conformation tests could be applied in a breeding or crossing plan to detect more accurately young horses with good dressage ability.

The effect of reins on kinetic variables of locomotion.

The equestrian literature and reports of experienced riders indicated that attitude of a horse's head and neck is related to the equine locomotion characteristics. The purpose of this study was to quantify the effects of 3 types of reins on locomotion at walk and trot. Eight saddle horses were tested in an automatic walker without reins, with rubber bands, Chambons and Back lift, using the same procedure. The rubber bands closed the head-neck angle, whereas the Chambons and the Back lift opened it. The gait characteristics were measured with the Equimetrix gait analysis system. Two accelerometric devices were fixed on the sternum and sacrum to measure the kinetic characteristics of the fore- and hindlimbs at walk and trot. Analysis of variance was used to test the effects of reins on the fore- and hindlimbs. All 3 types of reins significantly (P<0.05) modified walk and trot, with increased forelimb propulsion at the trot (P<0.05). Chambons increased the dorsoventral activity of the hindlimbs at the trot and hindlimb propulsion at the walk (P<0.05). Back lift increased forelimb dorsoventral activity both at the trot and walk (P<0.05). It was concluded that the Chambons increased the activity of the hindlimbs while Back lift increased that of the forelimbs. The use of reins modified the head placement and the fore- and hindlimbs activity. The specific effect of each type of rein can be used for training, rehabilitation or management of locomotor's injury.

Quality of life in multiple sclerosis: influence of interferon-beta1 a (Avonex) treatment.

BACKGROUND: Numerous data argue for initiating treatment with interferon-beta (IFN-beta) at an early stage in multiple sderosis (MS). The consequences of its use may negatively influence the MS patient's quality of life (QoL). OBJECTIVE: To evaluate the QoL of MS patients before and after a one-year period of treatment with IFN-beta1a (Avonex). PATIENTS AND METHODS: QoL was assessed using the SF-36 in 121 relapsing-remitting MS patients. We compared QoL before and after treatment and with data from a normal population. We also studied the possible influence of disease progression on the SF-36 scores. RESULTS: One hundred six patients completed the study (87%). Compared to a normal population, patients were, at baseline, worse off for all QoL scales, varying from a minimum decrease of 0.73 SD in mental health, to a maximum decrease of 1.55 SD in general health. After treatment, we found no significant changes in any of the QoL scores, except for physical function, where we noted a slight but significant decrease (p = 0.03). Furthermore, there was no significant change either in the physical component summary (PCS) or mental component summary (MCS). The 'reported health transition' item was significantly improved compared to baseline (p = 0.001). At indusion, significant correlations were found between EDSS scores and scores of physical function (p < 0.001), role - physical (p < 0.01), general health and social function (both p < 0.01), and with the PCS (p < 0.01). Patients with dinical relapses and/or disability progression had a more significant decease in physical function (p < 0.05) and also in social function (p < 0.05). CONCLUSION: The QoL, assessed by the SF-36 scale, is correlated with disability in MS. IFN-beta1a treatment (Avonex) has no negative effect on MS patient's QoL.

Derivatives of (2R,3R,4S)-2-aminomethylpyrrolidine-3,4-diol are selective alpha-mannosidase inhibitors.

A collection of (2R,3R,4S)-3,4-dihydroxypyrrolidin-2-yl derivatives have been tested for their inhibitory activities toward 25 glycosidases. Competitive (K(i)=7.4 microM) and selective inhibition of alpha-mannosidase from jack bean has been found for (2R,3R,4S)-2-[(benzylamino)methyl]pyrrolidine-3,4-diol and other derivatives.

Genetic diversity of Bacillus thuringiensis serovars revealed by RFLP using random DNA probes.

EcoRI and HindIII restriction fragment length polymorphism (RFLP) profiles using 2 random DNA probes, named 104 and 106, were generated for 85 B. thuringiensis strains. These include 80 serovars, 4 intra-serovar strains: kurstaki HD-1, dendrolimus, tenebrionis and sandiego, and a non-serotypeable strain B. thuringiensis var. wuhanensis. A total of 47 EcoRI and 65 HindIII restriction patterns were generated when hybridization results from both probes were combined. Seventy-seven B. thuringiensis strains showed distinctive hybridization profiles. The dendrogram resulting from the numerical analysis of the distance matrix revealed fourteen distinct phylogenetic groups at the 96% banding patterns similarity. The intra-serovar strains showed higher similarity with their respective type serovars. However, different serovars from a common H-serotype did not always cluster in the same phylogenetic group. Alternatively, several mosquitocidal serovars clustered in a single phylogenetic group. The correlation between serotyping and banding pattern similarity is discussed.

S100beta correlates with neurologic complications after aortic operation using circulatory arrest.

BACKGROUND: Astrocyte protein S100beta is a potential serum marker for neurologic injury. The goals of this study were to determine whether elevated serum S100beta correlates with neurologic complications in patients requiring hypothermic circulatory arrest (HCA) during thoracic aortic repair, and to determine the impact of retrograde cerebral perfusion (RCP) on S100beta release in this setting. METHODS: Thirty-nine consecutive patients underwent thoracic aortic repairs during HCA; RCP was used in 25 patients. Serum S100beta was measured preoperatively, after cardiopulmonary bypass, and 24 hours postoperatively. RESULTS: Neurologic complications occurred in 3 patients (8%). These patients had higher postbypass S100beta levels (7.17 +/- 1.01 microg/L) than those without neurologic complications (3.63 +/- 2.31 microg/L, p = 0.013). Patients with S100beta levels of 6.0 microg/L or more had a higher incidence of neurologic complications (3 of 7, 43%) compared with those who had levels less than 6.0 microg/L (0 of 30, p = 0.005). Retrograde cerebral perfusion did not affect S100beta release. CONCLUSIONS: Serum S100beta levels of 6.0 microg/L or higher after HCA correlates with postoperative neurologic complications. Using serum S100beta as a marker for brain injury, RCP does not provide improved cerebral protection over HCA alone.

A new predictive model for adverse outcomes after elective thoracoabdominal aortic aneurysm repair.

BACKGROUND: Recent recommendations have emphasized individualized treatment based on balancing a patient's risk of thoracoabdominal aortic aneurysm rupture with the risk of an adverse outcome after surgical repair. The purpose of this study was to determine which preoperative risk factors currently predict an adverse outcome after elective thoracoabdominal aortic aneurysm repair. METHODS: A single, composite end point termed adverse outcome was defined as the occurrence of any of the following: death within 30 days, death before discharge from the hospital, paraplegia, paraparesis, stroke, or acute renal failure requiring dialysis. A risk factor analysis was performed using data from 1,108 consecutive elective thoracoabdominal aortic aneurysm repairs. RESULTS: The incidence of an adverse outcome was 13.0% (144 of 1,108 patients); predictors included preoperative renal insufficiency (p = 0.0001), increasing age (p = 0.0035), symptomatic aneurysms (p = 0.020), and extent II aneurysms (p = 0.0001). These risk factors were used to construct an equation that estimates the probability of an adverse outcome for an individual patient. CONCLUSIONS: This new predictive model may assist in decisions regarding elective thoracoabdominal aortic aneurysm operations. For patients who are acceptable candidates, contemporary surgical management provides favorable results.

Ceramide generation occurring during 7beta-hydroxycholesterol- and 7-ketocholesterol-induced apoptosis is caspase independent and is not required to trigger cell death.

Biological activities of oxysterols seem tightly regulated. Therefore, the ability to induce cell death of structurally related oxysterols, such as those oxidized at C7(7alpha-, 7beta-hydroxycholesterol, and 7-ketocholesterol), was investigated on U937 cells at different times of treatment in a concentration range of 5-80 microg/ml. Whereas all oxysterols accumulate inside the cells, strong inhibition of cell growth and increased permeability to propidium iodide were observed only with 7beta-hydroxycholesterol and 7-ketocholesterol, which trigger an apoptotic process characterized by the occurrence of cells with fragmented and/or condensed nuclei, and by various cellular dysfunctions: loss of mitochondrial transmembrane potential, cytosolic release of cytochrome c, activation of caspase-9 and -3 with subsequent enhanced activity of caspase-3, degradation of poly(ADP-ribose) polymerase, and increased accumulation of cellular C16 : 0 and C24 : 1 ceramide species. This ceramide generation is not attributed to caspase activation since inhibition of 7beta-hydroxycholesterol- and 7-ketocholesterol-induced apoptosis by Z-VAD-fmk (100 microM), a broad spectrum caspase inhibitor, did not reduce C16 : 0 and C24 : 1 ceramide species accumulation. Conversely, when U937 cells were treated with 7beta-hydroxycholesterol and 7-ketocholesterol in the presence of fumonisin B1 (100 microM), a specific inhibitor of ceramide synthase, C16 : 0 and C24 : 1 ceramide species production was completely abrogated whereas apoptosis was not prevented. Noteworthy, 7alpha-hydroxycholesterol induced only a slight inhibition of cell growth. Collectively, these results are consistent with the notion that the alpha or beta hydroxyl radical position of oxysterols oxidized at C7 plays a key role in the induction of the apoptotic process. In addition, our findings demonstrate that 7beta-hydroxycholesterol- and 7-ketocholesterol-induced apoptosis involve the mitochondrial signal transduction pathway and they suggest that C16 : 0 and C24 : 1 ceramide species generated through ceramide synthase play a minor role in the commitment of 7beta-hydroxycholesterol- and 7-ketocholesterol-induced cell death.