An improved detection system applied to the study of serum lipoproteins after single-step density gradient ultracentrifugation

Starting from a single-spin ultracentrifugation procedure described previously (Foreman et al., J. Lipid Res. 18, 759, 1977), we have improved the system for detection of the fractions eluted from the gradient by monitoring them continuously at 280 nm. A graphic display readily permits assessment of the distribution of the lipoproteins and their quantification with the aid of a computer program. By the use of appropriate factors, one can convert absorbance readings into actual lipoprotein values which correspond well (±7% for low-density lipoproteins and ±5% for high-density lipoproteins) to those obtained by means of chemical analyses. The examples provided indicate the versatility of the method and its sensitivity (down to 0.1 ml of serum).     

Evaluation of technetium-99m decay on Escherichia coli inactivation: effects of physical or chemical agents.

Technetium-99m (99mTc) has been used in nuclear medicine and in biomedical research to label molecular and cellular structures employed as radiotracers. Here, we have evaluated, on a DNA repair proficient Escherichia coli strain, the 99mTc decay inactivation and the influence of the (i) pre-treatment with metal ion chelators or of the (ii) treatment with a free radical scavenger on the protection of the cells against the lethal effect of the 99mTc. As SnCl2 is frequently used as a reducing agent in the 99mTc-labeling process, we have also studied the capability of SnCl2 to alter the biological effects induced by the 99mTc decay. As we are exposed to either chemical or physical agents in the nature, we have decided to study a possible influence of the ultraviolet solar radiation in the biological phenomena induced by the 99mTc decay. Our data point out (i) a very important role of the Auger and/or conversion electrons in the cytotoxicity induced by the 99mTc decay; (ii) SnCl2, the metal ion chelators and the free radical scavenger protect the cells against the lethal effect of the 99mTc; and (iii) near-UV does not alter the lethal effect of the 99mTc decay.     

Evaluation of the cytotoxic and mutagenic potentiality of technetium-99m in Escherichi coli.

Since technetium-99m (99mTc) was introduced in medical research it has become one of the most employed radionuclides in nuclear medicine. 99mTc is ideal for routine use on the labeling of different radiopharmaceuticals due to its favorable characteristics. However, some biological effects have been described. These effects may be related to internal conversion electron and/or Auger electron emissions from 99mTc decay that present high linear energy transfer and can generate reactive oxygen species (ROS) in the medium. We evaluated in Escherichia coli K12S and Salmonella typhimurium TA102, both proficient in DNA repair, contribution of those decay emissions on the cytotoxicity induced by 99mTc, both either by generating lesions on DNA or by inducing alterations at membrane. We also studied the genotoxic and/or mutagenic potentiality of 99mTc, in Salmonella typhimurium, using the Ames test. The results showed that: i/ 99mTc is cytotoxic to the Escherichia coli K12S strains; ii/ this effect is related to the electrons (Auger and internal conversion) emissions, and iii/ the 99mTc is not mutagenic and/or genotoxic, when measured by Ames test.