[Contamination of exosome preparations, isolated from biological fluids]

The aim of our study was to attract the attention of researchers at the problem of contamination of exosome preparations. Using a transmission electron microscope JEM-1400 ("JEOL", Japan) we have examined exosome preparations, isolated according to the conventional scheme of sequential centrifugation from different biological fluids: plasma and urine of healthy persons and patients with oncologic diseases, bovine serum, and culture fluid (MDCK, MDA-MB и MCF-7 cells). All exosome preparations (over 200) contained exosomes, which were identified by immuno-electron microscopy using antibodies to tetraspanins CD63 or CD9. Besides exosomes, all the studied preparations contained contaminating structures: distinct particles of low electron density without limiting membrane ("non-vesicles"). Two main kinds of the "non-vesicles" species were found in exosome preparations: 20-40 nm in size, representing 10-40% of all structures in the preparations; and 40-100 nm in size (identical to exosomes by size). Morphology of the "non-vesicles" allowed to identify them as lipoproteins of intermediate and low density (20-40 nm), and very low density (40-100 nm). The highest level of the contamination was detected in exosome preparations, isolated from blood samples. The results of our study indicate the need to control the composition of exosome preparation by electron microscopy and take into account the presence of contaminating structures in analysis of experimental data.

[Pro-aggressive effect of diazepam in male mice with repeated experience of aggression]

Previous studies have reported that repeated experience of aggression is attended with the development of increased anxiety in male mice. The paper aimed to investigate effect of anxiolytic, diazepam, on the level of anxiety and aggression in these animals. The drug was chronically administrated for two weeks at the process of aggression experience acquisition. It was shown that diazepam decreased anxiety but didn't influence aggression level assessed by total time of attacks. However, diazepam decreased demonstration of aggressive grooming in part of aggressive males. Group of diazepam-treated aggressive males which displayed aggressive grooming didn't differ in level of anxiety and aggression in saline-treated male mice. Diazepam had anxiolytic and pro-aggressive effects in male mice without demonstrating aggressive grooming. Thus, we can conclude that anxiolytic effect of diazepam is accompanied with increased aggression as side effect in some male mice which have repeated experience of aggression.