Effect of T-activin on thymocyte reproduction and migration

Forty seven F1 (CBA X C57Bl) mice were used for quantitative morphologic examination of the thymus on 1, 5, 10 and 15 days after a single injection of 0.5 microgram T-activin, and injections of 0.1 microgram of T-activin once a day during 5 days. The number of transformed thymocytes and mitoses figures in cortex was found to be increased reaching a maximum at the 5th day as regards the magnitude and spreading. By the end of the research the number of transformed thymocytes and mitoses returned to initial values. There was a periodical (at the 5th and 10th days) 1 mm2 reduction in the number of thymocytes, an increase in the proportion of medullary thymocytes, reaching maximum at the 5th day, and a tendency towards the reduction of a relative area of the parenchyma. These indicators did not return to the initial values by the 15th days. However there was a tendency towards normalization. The conclusion is made about the stimulatory effect of T-activin on reproduction and migration of thymocytes.     

Biophysical characterization of the interaction of high-density lipoprotein (HDL) with endotoxins.

The interaction of bacterial endotoxins [lipopolysaccharide (LPS) and the 'endotoxic principle' lipid A], with high-density lipoprotein (HDL) from serum was investigated with a variety of physical techniques and biological assays. HDL exhibited an increase in the gel to liquid crystalline phase transition temperature Tc and a rigidification of the acyl chains of the endotoxins as measured by Fourier-transform infrared spectroscopy and differential scanning calorimetry. The functional groups of the endotoxins interacting with HDL are the phosphates and the diglucosamine backbone. The finding of phosphates as target groups is in accordance to measurements of the electrophoretic mobility showing that the zeta potential decreases from -50 to -60 mV to -20 mV at binding saturation. The importance of the sugar backbone as further target structure is in accordance with the remaining negative potential and competition experiments with polymyxin B (PMB) and phase transition data of the system PMB/dephosphorylated LPS. Furthermore, endotoxin binding to HDL influences the secondary structure of the latter manifesting in a change from a mixed alpha-helical/beta-sheet structure to a predominantly alpha-helical structure. The aggregate structure of the lipid A moiety of the endotoxins as determined by small-angle X-ray scattering shows a change of a unilamellar/inverted cubic into a multilamellar structure in the presence of HDL. Fluorescence resonance energy transfer data indicate an intercalation of pure HDL, and of [LPS]-[HDL] complexes into phospholipid liposomes. Furthermore, HDL may enhance the lipopolysaccharide-binding protein-induced intercalation of LPS into phospholipid liposomes. Parallel to these observations, the LPS-induced cytokine production of human mononuclear cells and the reactivity in the Limulus test are strongly reduced by the addition of HDL. These data allow to develop a model of the [endotoxin]/[HDL] interaction.