Radioimmunoassay of free plasma metanephrines for the diagnosis of catecholamine-producing tumors.

BACKGROUND: The determination of plasma metanephrines (MNs) provides a highly sensitive test for the diagnosis of catecholamine producing tumors. Chromatographic determinations with electrochemical or mass spectrometric detections are the methods of choice, but immunological assays have been developed. This study evaluated the clinical performances of a radioimmunoassay for free MNs in plasma. METHODS: MNs, normetanephrine (NMN) and metanephrine (MN) and catecholamines, norepinephrine (NE) and epinephrine (E) were determined in plasma and urine of 533 patients suspected of catecholamine producing tumor. Urinary and plasma catecholamines and urinary MNs were determined by HPLC using amperometric detection. Plasma MNs were purified by solid phase chromatography and quantified by a specific radioimmunoassay. RESULTS: Fifty-nine patients had tumors (13 paraganglioma and 46 pheochromocytoma) and the diagnosis was excluded in 474 patients. Receiver operator characteristic curves have identified optimal thresholds at 100 pg/mL for plasma NMN (sensitivity 96.6% and specificity 95.8%) and 70 pg/mL for plasma MN (sensitivity 61.0% and specificity 96.8%). These cut-off values were lower than those suggested by the manufacturer (170 and 100 pg/mL, respectively). The sensitivity of combined MNs was similar in plasma (100%) and urine (98%) but higher than that of urinary catecholamines (85%, p<0.001). The specificity of combined MNs in plasma (95%) was higher than urinary MNs (85%, p<0.001) and plasma catecholamines (75%, p<0.001). CONCLUSIONS: Plasma-free and urinary-total MNs have a better discriminative power than catecholamines in the diagnosis of catecholamines producing tumors. Using these established cut-offs, measurement of plasma-free MN by radioimmunoassay represents an effective alternative to chromatographic methods.

Effects of vegetable oils on biochemical and biophysical properties of membrane retinal pigment epithelium cells.

The aim of this study was to investigate the effect of vegetable oil enrichment of retinal pigment epithelial (RPE) cells on their biochemical and biophysical properties. For this, RPE cells were incubated with 4 different vegetables oils (olive oil, corn oil, argan oil, and camelina oil). The cytotoxicity of these vegetable oils was assessed in vivo on 8-week-old mice and in vitro by using the neutral red and YO-PRO-1 tests. Membrane fluidity was evaluated by fluorescence anisotropy using the fluorescent probe diphenylhexatriene, and membrane fatty acid composition was assessed by gas chromatography. None of the oils tested displayed cytotoxic effects. In vitro, omega-3 rich oils improved membrane fluidity by 47% compared with the control cells. The omega-3 PUFA content within membranes decreased by 38% to 55% when cells were incubated separately with olive oil, corn oil, or argan oil, and increased when cells were incubated with a mixture of those oils, or with camelina oil alone (50% and 103% increase, respectively). Our results show that the fatty acids in vegetable oil incorporate into retinal cells and increase the plasma membrane fluidity.

Ocular burn: rinsing and healing with ionic marine solutions and vegetable oils.

PURPOSE: We investigated the effects of various rinsing and healing protocols on corneal wound repair and inflammation following alkali burn in rabbits. METHODS: We conducted in vitro, in vivo and ex vivo studies. First, different rinse solutions were tested in vitro after incubation of ocular cells with methanol or NaOH. Cell viability was then assessed using the neutral red test (cytofluorometry). Second, NaOH was applied to rabbit corneas and associations of rinse solutions (NaCl 0.9% or controlled ionization marine solutions) with N-acetylcysteine or vegetable oils (from Calophyllum inophyllum and Aleurites moluccana) were tested in vivo. The regeneration of the corneal epithelium and the infiltration of inflammatory cells were evaluated using in vivo confocal microscopy and ex vivo histological cuts. RESULTS: The association of a controlled ionization marine solution with 10% C. inophyllum oil and 90% A. moluccana oil induced regeneration of the corneal epithelium and a decrease in inflammatory cells. CONCLUSIONS: Irrigation with marine solution followed by treatment with a mixture of C. inophyllum and A. moluccana oils is a promising treatment for ocular burns.

Benefits and side effects of different vegetable oil vectors on apoptosis, oxidative stress, and P2X7 cell death receptor activation.

PURPOSE: Ocular side effects in patients using eye drops may be due to intolerance to the vector used in eye drops. Castor oil is the commonly used lipophilic vector but has been shown to be cytotoxic. Effects on cells of four oils (olive, camelina, Aleurites moluccana, maize) were compared with those of castor oil in human conjunctival cells. METHODS: Human conjunctival cells were incubated with the oils for 15 minutes. After a 24-hour recovery period, cells were tested for viability, proliferation, apoptosis (P2X7 cell death receptor and caspase 3 activation), intracellular redox potential, and reactive oxygen species production. Fatty acid incorporation in cell membranes was also analyzed. In vivo ocular irritation was assessed using the Draize test. RESULTS: Compared to the four other oils, castor oil was shown to induce significant necrosis and P2X7 cell death receptor and caspase 3 activation and to enhance intracellular reactive oxygen species production. Aleurites moluccana and camelina oils were not cytotoxic and increased cell membrane omega-3 fatty acid content. None of the five tested oils showed any in vivo ocular irritation. CONCLUSIONS: The results demonstrated that castor oil exerts cytotoxic effects on conjunctival cells. This cytotoxicity could explain the side effects observed in some patients using eye drops containing castor oil as a vehicle. The lack of cytotoxic effects observed with the four other oils, Aleurites, camelina, maize, and olive, suggest that they could be chosen to replace castor oil in ophthalmic formulations.

Activation of PAF receptor by oxidised LDL in human monocytes stimulates chemokine releases but not urokinase-type plasminogen activator expression.

BACKGROUND: We investigated whether the increase of urokinase-type plasminogen activator (uPA) monocyte expression and chemokine releases induced by oxidised low density lipoproteins (LDL), which participate to vascular tissue remodeling and to atherosclerotic plaque rupture, involved proinflammatory phospholipid products having platelet-activating factor (PAF)-like activity via the PAF-receptor pathway. METHODS: uPA monocyte expression was stimulated by either copper ions-oxidised or O2*-/HO* free radical-oxidised LDL. The effects of PAF and oxidised LDL on the production of monocyte chemoattractant protein-1 and interleukin-8 were also examined. RESULTS: Synthetic PAF significantly enhanced chemokine releases (P<0.001) without modifying uPA expression. Copper-oxidised LDL, which exhibit a higher content in lysophosphatidylcholines than free radical-oxidised LDL, induced a significantly higher enhancement in uPA expression (P<0.05). By contrast, free radical-oxidised LDL were more efficient than copper-oxidised LDL to increase chemokine releases (P<0.01). Oxidised LDL-enhanced uPA expressions were not altered by the PAF-receptor antagonist SR27417, whereas increases in chemokine releases induced by oxidised LDL and by PAF were abolished. PAF-acetylhydrolase activity was rapidly and largely inhibited in free radical-oxidised LDL when compared to copper-oxidised LDL, suggesting that free radical-oxidised LDL would contain a higher content in PAF-like products than copper-oxidised LDL. CONCLUSION: Our results indicated that PAF-like oxidation products are responsible for the monocyte chemokine releases, but did not contribute to the enhanced monocyte uPA expression by oxidised LDL.