323,117 research outputs found
Plasma L-ergothioneine measurement by high-performance liquid chromatography and capillary electrophoresis after a pre-column derivatization with 5-iodoacetamidofluorescein (5-IAF) and fluorescence detection
No full textTwo sensitive and reproducible capillary electrophoresis and high-performance liquid chromatography-fluorescence procedures were established for quantitative determination of L-egothioneine in plasma. After derivatization of L-ergothioneine with 5-iodoacetamidofluorescein, the separation was carried out by HPLC on an ODS-2 C-18 sperisorb column by using a linear gradient elution and by HPCE on an uncoated fused silica capillary, 50 µm id, and 60 cm length. The methods were validated and found to be linear in the range of 0.3 to 10 µmol/l. The limit of quantification was 0.27 µmol/l for HPCE and 0.15 µmol/l for HPLC. The variations for intra- and inter-assay precision were around 6 RSD%, and the mean recovery accuracy close to 100% (96.11%)
Experimental investigation of three phase oil/water/air flow
No full textThree-phase flow of oil, water and air is investigated in a horizontal pipe of inner diameter 40 mm. The mineral oil used in the experiments is similar to crude oil transported in industrial pipelines with a viscosity of μo = 0.919 Pa s and ro = 889 kg/m3 at 20◦C. Careful measurements of pressure drop are performed at different flow rates of the liquids and with the air superficial velocity being varied in steps between Jg = 0.0 m/s and Jg ≈ 6.5 m/s. The pressure drop behaviour depends upon the initial two-phase flow regime of the two liquids, and in most cases it shows a progressive increase caused by the injection of air. A wide variety of flow patterns is observed: pictures of flow configurations obtained by starting with the two liquids in core-annular and wavy-annular regimes are provided together with full descriptions
Reverse injection capillary electrophoresis UV detection for serotonin quantification in human whole blood
No full textWe describe the first capillary electrophoresis UV detection method to measure serotonin in human whole blood (WB). Procedural parameters such as concentration and pH of run buffer and injection mode were investigated. The reverse injection allows to decrease the analysis time by injecting samples at the outlet end of the silica capillary close to the detection window, so reducing the migration distance. Thus, when a capillary with an effective length of 10 cm and a 400 mmol/L Tris phosphate as background electrolyte at pH 3.25 was used, the migration time of the serotonin peak was 2.6 min. These conditions gave a good reproducibility of migration times (CV, 0.77%) and peak areas (CV, 2.44%). Intra- and inter-assay CV were 3.85% and 7.32%, respectively, and the analytical recovery was between 96.8% and 99.4%
Experimental Analysis of Flow Regime Trasnitions and Pressure Drop Reductions in Oil-Water Mixtures
No full textThe present work reports an experimental and theoretical analysis of the fluid dynamic behavior of oil-water systems flowing through horizontal ducts. In the frame of an ongoing research program, new experimental tests are conducted on smooth, horizontal tubes of Pyrex and Plexiglas. Tap water and mineral oil are used, with a viscosity ratio of about 800 and a density ratio of about 0.9. The resulting database, which includes previous test findings, covers a tube diameter range spanning from 21 to 40 mm. The influence of different parameters on the pressure drop in oil-water flows is evaluated, and some particular behaviors of the pressure drop reduction as a function of the water volume fraction are observed. Flow pattern maps are obtained, which report consistent results of the experimental campaign in terms of flow regimes and transitions. A theoretical analysis based on both Froude and Reynolds numbers is also proposed
S-homocysteinylated LDL apolipoprotein B adversely affects human endothelial cells in vitro
No full textObjective: In recent years elevated homocysteine (Hcy) levels have been widely recognized as a risk factor for cardiovascular diseases (CVDs) and a connection between hyperhomocysteinemia and lipid metabolism has been suggested to have a possible role in endothelial vascular damage as lipoprotein fractions contain higher Hcy levels in hypercholesterolemia, compared to normolipidemic individuals. However, the biochemical events underlying the interaction between Hcy and LDL are still poorly understood. Methods and results: Herein we have investigated the interaction of LDL with Hcy by measuring thiols S-linked to apoprotein using capillary electrophoresis and have evaluated the effect of S-homocysteinylated LDL on human endothelial cells (HECs). We found that Hcy binds to LDL in a dose dependent manner and the saturation binding is achieved at 100 mu mol/L. Hcy in about 5 h. Addition of Hcy resulted in a rapid displacement of other thiols bound to apoprotein and this was dependent on the concentration of Hcy added. For the first time we also demonstrated that treatment of HECs with homocysteine-S-LDL (Hcy-S-LDL) resulted in the induction of significantly higher levels of reactive oxygen species (ROS) compared to N-LDL (native LDL). Furthermore, the Hcy-S-LDL-induced a rise in intracellular ROS production was followed by a marked reduction of HECs proliferation and viability. Conclusions: Although the mechanism by which Hcy-S-LDL elicits the current cellular effects needs further investigation, our data suggest that intracellular ROS production induced by Hcy-S-LDL might be responsible for the observed HECs damage and indicate that Hcy-S-LDL may have some role in CVD. (C) 2009 Elsevier Ireland Ltd. All rights reserved
Endothelial cell injury due to post-translational LDL apoprotein B modification by S-homocysteinylation
No full textOBJECTIVE: In recent years elevated homocysteine (Hcy) levels have been widely recognized as a risk factor for cardiovascular diseases (CVDs) and a connection between hyperhomocysteinemia and lipid metabolism has been suggested to have a possible role in endothelial vascular damage as lipoprotein fractions contain higher Hcy levels in hypercholesterolemia, compared to normolipidemic individuals. However, the biochemical events underlying the interaction between Hcy and LDL are still poorly understood.
METHODS AND RESULTS: Herein we have investigated the interaction of LDL with Hcy by measuring thiols S-linked to apoprotein using capillary electrophoresis and have evaluated the effect of S-homocysteinylated LDL on human endothelial cells (HECs). We found that Hcy binds to LDL in a dose dependent manner and the saturation binding is achieved at 100 micromol/L Hcy in about 5h. Addition of Hcy resulted in a rapid displacement of other thiols bound to apoprotein and this was dependent on the concentration of Hcy added. For the first time we also demonstrated that treatment of HECs with homocysteine-S-LDL (Hcy-S-LDL) resulted in the induction of significantly higher levels of reactive oxygen species (ROS) compared to N-LDL (native LDL). Furthermore, the Hcy-S-LDL-induced a rise in intracellular ROS production was followed by a marked reduction of HECs proliferation and viability.
CONCLUSIONS: Although the mechanism by which Hcy-S-LDL elicits the current cellular effects needs further investigation, our data suggest that intracellular ROS production induced by Hcy-S-LDL might be responsible for the observed HECs damage and indicate that Hcy-S-LDL may have some role in CVD
Low density lipoprotein S-homocysteinylation is increased in acute myocardial infarction patients
No full textOBJECTIVES: We have investigated on the levels of homocysteine linked to LDL in acute myocardial infarction patients.
DESIGN AND METHODS: We used capillary electrophoresis to measure LDL-bound thiols in 16 AMI individuals and 32 healthy volunteers.
RESULTS: We found a significant increase of apo-B homocysteine and cysteine levels in LDL fraction of AMI subjects.
CONCLUSIONS: Our findings suggest that also LDL S-homocysteinylation may be considered among the markers for the CVD risk evaluation
Field-amplified online sample stacking capillary electrophoresis UV detection for plasma malondialdehyde measurement
No full textMalondialdehyde (MDA) determination is the most widely used method for monitoring lipid peroxidation. Here, we describe an easy field-amplified sample injection (FASI) CE
method with UV detection for the detection of free plasma MDA. MDA was detected within 8 min by using 200 mmol/L Tris phosphate pH 5.0 as running buffer. Plasma samples treated with ACN for protein elimination were directly injected on capillary without complex cleanup and/or sample derivatization procedures. Using electrokinetic
injection, the detection limit in real sample was 3 nmol/L, thus improving of about 100-fold the LOD of the previous described methods based on CE. Precision tests indicate a good repeatability of our method both for migration times (CV=1.11%) and for areas (CV=2.05%). Moreover, a good reproducibility of intra- and inter-assay tests was obtained (CV=2.55% and CV=5.14%, respectively). Suitability of the method was tested by measuring MDA levels in 44 healthy volunteers
Factors affecting S-homocysteinylation of LDL apoprotein B
No full textBACKGROUND: Hyperhomocysteinemia is an important risk factor for vascular disease and atherosclerosis, but the mechanisms by which homocysteine exerts its deleterious effects are not known. Because oxidation and/or homocysteinylation may increase atherogenicity of LDL, we investigated S-homocysteinylation of LDL as a possible contributor to atherosclerosis pathogenesis.
METHODS: We used capillary electrophoresis to measure LDL-bound thiols [homocysteine, cysteine (Cys), cysteinylglycine, glutathione, and glutamylcysteine] in 104 healthy study participants We also assessed total plasma thiol concentrations and lipid profiles.
RESULTS: Our data suggest that apoprotein B (apoB)-cysteinylglycine (CysGly), apoB-Hcy, and apoB-Cys concentrations are markedly higher in men than in women. The percentage of CysGly and glutathione on apoB was higher than that of the same thiols in plasma, whereas the other thiols were markedly less prevalent in lipoprotein than in plasma. Pearson correlation showed that among all thiols, only total plasma Hcy is related to apoB-Hcy concentrations. Multiple correlation analysis confirmed that total Hcy was the most important determinant of apoB-Hcy. Age and LDL cholesterol also showed positive associations, but Cys and, mainly, CysGly were negatively associated with apoB-Hcy concentrations.
CONCLUSIONS: apoB-Hcy derivative formation is mainly dependent on total homocysteine concentration. Increased cholesterol concentrations are related to increased apoB-Hcy. CysGly seems to compete with Hcy for binding to LDL apoprotein, suggesting that CysGly may protect against atherosclerosis by decreasing the concentrations of Hcy transferred by LDL from plasma to endothelial and subendothelial spaces
Field-amplified sample injection combined with pressure-assisted capillary electrophoresis UV detection for the simultaneous analysis of allantoin, uric acid, and malondialdehyde in human plasma
No full textThe allantoin/uric acid (All/UA) ratio and malondialdehyde
(MDA) plasma levels have been proposed as important markers for monitoring oxidation triggered by the action of free radicals (FR). Here, we describe an easy field
amplified sample injection capillary electrophoresis method
with UV detection for the separation and quantification of All, UA, and free MDA in human plasma. The plasma samples
were simply filtered through centrifugation membrane tubes
for protein elimination and directly injected on a capillary without complex cleanup and/or sample derivatization procedures. The use of a run buffer composed of 300 mmol/L sodium borate at pH 10 with 50 mmol/L of N-methyl-Dglucamine and an overimposed pressure/voltage of 0.1 psi during the electrophoretic run allows basline resolution of the analytes within 17 min. The electrokinetic injection allows a detection limit of 15 nmol/L for All, 20 nmol/L for UA and 10 nmol/L for MDA in a plasma sample, thus significantly improving the LOD of previous described methods based on capillary electrophoresis. Precision tests indicate a good repeatability of our method both for migration times (CV=1.85%) and areas (CV=2.87%). Moreover, a good reproducibility of intra- and inter-assay tests was obtained (CV=4.63%and CV=6.59%respectively). The suitability of the method was tested by measuring analyte
levels in 40 healthy volunteers
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