Comparison of polymerase chain reaction and flow cytometry for measuring telomere length of human leukocytes.

Telomere length can be measured by polymerase chain reaction (PCR), allowing to obtain the absolute length of telomeres (ALT) in base pair, and by flow cytometry, which can only estimate the relative telomere length. The aim of the study was to compare the results of the two methods and to develop an accurate and reliable way of converting the relative telomere length to absolute. The peripheral blood from 21 donors was analyzed. Measurement of leukocyte telomere length by flow cytometry was carried out using a commercial Telomere PNA Kit / FITC (Dako, Denmark) with two CytoFLEX flow cytometers (Beckman Coulter, China) and BD FACSCanto II (Becton Dickinson, USA), obtaining the molecular equivalent of fluorescence (MEF). To measure telomere length by real-time PCR, calibrators with a known number of telomeric repeats were prepared. Two quantitative PCRs were carried out: one for telomeric repeats, the other for determining the number of genome-equivalents of DNA, three times for each sample, which made it possible to calculate ALT. A strong direct relationship was found between the MEF obtained with BD FACSCanto II and CytoFLEX (r = 0.97). Analysis of PCR and flow cytometry results showed a significant correlation between ALT and MEF. We calculated the regression equations of ALT and MEF for CytoFLEX - y = 0.0043x (r = 0.84) and for BD FACSCanto II - y = 0.0051x (r = 0.82). Correlation analysis showed a high comparability of telomere lengths measured by two methods. The obtained regression equations allow converting the results of flow cytometry into absolute values, allowing the comparison of the results of different research groups and the use of this method in clinical trials.

Taylor column instability in the problem of a vibrational hydrodynamic top.

The object of experimental study is a fluid flow generated by differential rotation of a free light spherical body in a rotating cylindrical cavity. The body stays near the axis under the action of centrifugal force. The body rotation is generated by a force field oscillating in the cavity reference system (vibrational hydrodynamic top). It was found that the Taylor-Proudman column that forms undergoes instability, which manifests itself in the formation of a two-dimensional azimuthal wave at the column boundary, in a Stewartson layer. The experimental results are summarized on a plane of dimensionless parameters, i.e., the dimensionless velocity of the cavity rotation and Rossby number. The bounds of the Stewartson layer stability were found and the supercritical structures and transition sequences were studied. Systematic research into that problem in its classical formulation--when a sphere is fixed on the axis and its differential rotation is imposed--was done for comparison. It was demonstrated that in conditions of vibratory differential rotation of a free sphere the stability threshold of the Stewartson layer was reduced by more than one order of magnitude, in comparison with the classical case. A qualitative change was also found in the wave phase velocity which for a free sphere exceeds the lagging differential rotation velocity of the body. It was concluded that the uncovered specifics are related to the difference in the mechanism of the Taylor-Proudman column formation and of the flow generation in it. For a vibrational hydrodynamic top, streams in the column will not be defined by Ekman pumping but by steady streaming, which is also responsible for the free-sphere differential rotation.