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At least 109 records · Page 6Linked to original sources
PubMed1999

Abnormal capacity to induce cholesterol efflux and a new LpA-I pre-beta particle in type 2 diabetic patients.

In this study, we first characterized the lipoprotein components of serum samples obtained from a group of well-controlled diabetic patients and from healthy subjects in fasting and postprandial states. We then explored some aspects of reverse cholesterol transport in the same population. Patients showed high levels of fasting triglycerides, postprandial triglyceride responses and LpC-III levels (3.18+/-0.86 vs 2.17+/-0.54 mg/dl, P < 0.001). There were also positive correlations between LpC-III and fasting triglycerides (r = 0.82, P < 0.001), total triglyceride area (r = 0.75, P < 0.001) and incremental triglyceride area (r = 0.54, P < 0.001). HDL-C and apo A-I were significantly decreased in diabetic patients due to a selective reduction in LpA-I subfraction, whose antiatherogenic role is generally accepted (37.4+/-8.0 vs 49.2+/-12.5 mg/dl, P < 0.001). In addition, HDL from patients proved to be triglyceride enriched and cholesteryl ester depleted, alterations which were further amplified in the postprandial state. The molar ratio HDL-C/apo A-I + apo A-II, already defined as a predictor of apo A-I fractional catabolic rate, was significantly diminished in the patient group (15.1+/-2.2 vs 20.8+/-3.3, P < 0.001), thus suggesting an accelerated catabolism of apo A-I. For the first time, we describe here the presence of a small apo A-I-containing particle, isolated by two-dimensional electrophoresis and characterized by immunoblotting, only in samples from diabetic patients. This particle that we named pre-beta0, has an apparent molecular weight of 40 kDa. As regards the capacity of serum samples to promote cholesterol efflux from [3H]cholesterol-labeled Fu5AH rat hepatoma cells, patient samples were found to induce significantly lower cholesterol efflux than controls only in the postprandial state (21.2+/-3.3 vs 23.8+/-1.8%, P = 0.012). The presence of pre-beta0 in samples from diabetic patients might therefore be associated to an altered capacity of these serum samples to promote cellular cholesterol efflux. Overall, these abnormalities may contribute to a delay in the reverse cholesterol transport pathway in type 2 diabetic patients.

Adult↗
PubMed2000

Radiation protection by cysteamine against the lethal effects of intracellularly localized Auger electron, alpha- and beta-particle emitting radionuclides.

The mechanisms by which DNA-incorporated radionuclides impart lethal damage to mammalian cells were investigated by examining the capacity of cysteamine (MEA) to protect against lethal damage to V79 cells caused by unbound tritium (3H2O), DNA-incorporated 131/125I-iododeoxyuridine (IdU) and the alpha-particle emitter 210Po-citrate. Radiolabeled cells were maintained at 10.5 degrees C for 72 h in the absence or presence of MEA (0.65-2.6 mM) and the surviving fraction was determined. Protection against lethal damage caused by 3H2O, 131IdU or 125IdU and 210Po-citrate depended on the concentration of MEA with maximum protection at 1.3-1.9 mM. The dose modification factors obtained at 1.3 mM for the radiochemicals were 2.5 +/- 0.3, 1.8 +/- 0.2, 1.7 +/- 0.1 and 1.4 +/- 0.1, respectively. MEA provides more protection against indirect than direct effects of ionizing radiation, and indirect effects play a role in the radiotoxicity of Auger electron emitters incorporated into the DNA of mammalian cells.

Animals↗
PubMed2001

The water-equivalence of phantom materials for 90Sr-90Y beta particles.

Intravascular brachytherapy requires that the dose be specified within millimeters of the source. High dose gradients near brachytherapy sources require that the source-detector distance be accurately known for dosimetry purposes. Solid phantoms can be designed to accommodate these stringent requirements. This study reports dosimeter readings from 90Sr-90Y sources measured in water, A150, polystyrene and in an epoxy-based water-equivalent plastic. Measurements showed that while A150 and the epoxy-based plastic agreed well with water when the surface of the source contacted the detector housing, the relative response in the phantoms decreased with increasing depth in phantom, falling to approximately 0.55 those of water at a depth of 5 mm. Readings in polystyrene were within 4% of those in water between 1 and 2 mm depth. However, while polystyrene followed water more closely than the other two materials, at greater depths the relative response in polystyrene to water varied from 0.65 to 1.34. When the density of the materials is accounted for, the relative response in A150 is nearly constant with increasing areal density. Furthermore, the response in A150 shows the closest agreement with that in water of any of the solid materials for higher areal densities. For values below 0.3 g/cm2, polystyrene shows the closest agreement with water.

Angioplasty↗
PubMed2001

Beta-particle dosimetry of the trabecular skeleton using Monte Carlo transport within 3D digital images.

Presently, skeletal dosimetry models utilized in clinical medicine simulate electron path lengths through skeletal regions based upon distributions of linear chords measured across bone trabeculae and marrow cavities. In this work, a human thoracic vertebra has been imaged via nuclear magnetic resonance (NMR) spectroscopy yielding a three-dimensional voxelized representation of this skeletal site. The image was then coupled to the radiation transport code EGS4 allowing for 3D tracing of electron paths within its true 3D structure. The macroscopic boundaries of the trabecular regions, as well as the cortex of cortical bone surrounding the bone site, were explicitly considered in the voxelized transport model. For the case of a thoracic vertebra, energy escape to the cortical bone became significant at source energies exceeding approximately 2 MeV. Chord-length distributions were acquired from the same NMR image, and subsequently used as input for a chord-based dosimetry model. Differences were observed in the absorbed fractions given by the chord-based model and the voxel transport model, suggesting that some of the input chord distributions for the chord-based models may not be accurate. Finally, this work shows that skeletal mass estimates can be made from the same NMR image in which particle transport is performed. This feature allows one to determine a skeletal S-value using absorbed fraction and mass data taken from the same anatomical tissue sample. The techniques developed in this work may be applied to a variety of skeletal sites, thus allowing for the development of skeletal dosimetry models at all skeletal sites for both males and females and as a function of subject age.

Age Factors↗