Exploring the mechanical properties of single vimentin intermediate filaments by atomic force microscopy.

Intermediate filaments (IFs), together with actin filaments and microtubules, compose the cytoskeleton. Among other functions, IFs impart mechanical stability to cells when exposed to mechanical stress and act as a support when the other cytoskeletal filaments cannot keep the structural integrity of the cells. Here we present a study on the bending properties of single vimentin IFs in which we used an atomic force microscopy (AFM) tip to elastically deform single filaments hanging over a porous membrane. We obtained a value for the bending modulus of non-stabilized IFs between 300 MPa and 400 MPa. Our results together with previous ones suggest that IFs present axial sliding between their constitutive building blocks and therefore have a bending modulus that depends on the filament length. Measurements of glutaraldehyde-stabilized filaments were also performed to reduce the axial sliding between subunits and therefore provide a lower limit estimate of the Young's modulus of the filaments. The results show an increment of two to three times in the bending modulus for the stabilized IFs with respect to the non-stabilized ones, suggesting that the Young's modulus of vimentin IFs should be around 900 MPa or higher.

[The effect of different regimens of artificial ventilation on the pulmonary microcirculation during the development of experimental edema]. / Vliianie razlichnykh rezhimov iskusstvennoi ventiliatsii na mikrotsirkuliatsiiu legkikh pri razvitii ikh éksperimental'nogo oteka.

Acute experiments were conducted on male cats with a closed chest by the biomicroscopic method to study the effect of artificial ventilation (AV) of increased frequency and volume on the diameter and length of the pulmonary microvessels and the character of blood flow in them during the development of pulmonary edema induced by intravenous infusion of a fatty acid mixture. It is shown that AV of increased frequency inhibits the reduction of the length of the functioning narrow capillaries and dilatation of the wide capillaries of the lungs as compared to the initial ventilation parameters and prevents a change in the directions of the blood flow in the pulmonary arterioles after exposure to the edematogenic effect. The diameter of the arterioles and venules reduces and that of the wide capillaries increases at the beginning of edema more in AV of increased volume than in ventilation of the initial parameters. It is assumed that AV of increased frequency is more effective than ventilation of increased volume in preventing pulmonary microcirculatory disorders in edema of the lungs.