Abstract-The feasibilities of the Kelvin probe mode were shown to estimate a surface potential of lympho cytes from the patients with leukemia. Having compared the values of the surface potential obtained by the traditional method of microelectrophoresis and by the Kelvin probe mode, it was established that the use of the atomic force microscope made it possible to obtain data which were of specified diagnostic importance while studying lymphocyte functional status at different stages in leucopoiesis and indicated progression of the pathological process.

Tapping mode-atomic force microscopy and force spectroscopy were used for studies of the topography of the cell surface and elastic properties of lymphocytes from healthy donors and patients with chronic lymphoblastic leukemia. It was demonstrated that the decrease in lymphocytes stiffness in patients with chronic lymphoblastic leukemia by 51.4% (p<0.05) was accompanied by spatial modification of the cell surface, in particular, increase in the number of globular protrusions and depressions by 247 and 122%, respectively (p<0.05), in comparison with normal lymphocytes.

Abstract. The aim of this paper was to study the elastic and electrical properties of lymphoid cells in patients with acute lymphoblastic leucosis (ALL, n = 15). The mechanical properties of the membrane of lymphoid cells was recorded by atomic force microscopy (AFM). The electrical properties of the lymphoid cell membranes were detected by the Kelvin method. The elastic and electrical membrane properties of lymphoid cells were recorded by incubation with doxorubicin, one of chemotherapy drugs. We used different concentrations and incubation time. It was shown that in the acute phase of the disease and the stage of stable remission the lymphoid cell clones with a reduced stiffness and increased cell surface charge were found. In the experiments in vitro was demonstrated that the increased cell membrane rigidity may be one of the factors determining the tumor cell resistance to the chemotherapy. It was found that if to use the highest concentration of drug in the incubation medium (0.5-1.0 mg/ml) and its longest time, then the surviving cells had more elastic membrane (0.25-1.0 Pa) and the positive potential of the membrane surface (15-29 mV). These obtained data may have a significant prognostic importance for the evaluation of drug resistance of tumor cells.

The influence of aqueous solution of pristine C60 fullerene (C60FAS) on functional activity of lymphocytes from a healthy person was studied for the first time. By means of atomic force microscopy, it was found that C60FAS in a concentration of 0.1 mg/ml increases the stiffness of the lymphocyte membrane by 41% (p < 0.05) and lowers the functional activity of the plasmalemma surface, thereby constraining the use of its membrane material in physiological reactions using a hypotonic model in vitro. However, a cell retains the ability to regulate its volume and demonstrates relative resistance to hypo-osmotic stress. The resistance of lymphocytes in hypo-osmotic medium is facilitated by activation of the nucleus by C60 fullerene particles, which regulates the implementation of two consistent phases of an increase and decrease of cell volume, thereby retaining cell viability. All these indicate the impact of C60 fullerene on the cellular nucleus.

Mitochondrial diseases (MD) are a heterogeneous group of multisystem disorders involving metabolic errors. MD are characterized by extremely heterogeneous symptoms, ranging from organ-specific to multisystem dysfunction with different clinical courses. Most primary MD are autosomal recessive but maternal inheritance (from mtDNA), autosomal dominant, and X-linked inheritance is also known. Mitochondria are unique energy-generating cellular organelles designed to survive and contain their own unique genetic coding material, a circular mtDNA fragment of approximately 16,000 base pairs. The mitochondrial genetic system incorporates closely interacting bi-genomic factors encoded by the nuclear and mitochondrial genomes. Understanding the dynamics of mitochondrial genetics supporting mitochondrial biogenesis is especially important for the development of strategies for the treatment of rare and difficult-to-diagnose diseases. Gene therapy is one of the methods for correcting mitochondrial disorders. Graphical Abstract

Alterations in function of hypoxanthine guanine phosphoribosyl transferase (HPRT), one of the major enzymes involved in purine nucleotide exchange, lead to overproduction of uric acid and produce various symptoms of Lesch-Nyhan syndrome (LNS). One of the hallmarks of LNS is maximal expression of HPRT in the central nervous system with the highest activity of this enzyme in the midbrain and basal ganglia. However, the nature of neurological symptoms has yet to be clarified in details. Here, we studied whether HPRT1 deficiency changes mitochondrial energy metabolism and redox balance in murine neurons from the cortex and midbrain. We found that HPRT1 deficiency inhibits complex I-dependent mitochondrial respiration resulting in increased levels of mitochondrial NADH, reduction of the mitochondrial membrane potential, and increased rate of reactive oxygen species (ROS) production in mitochondria and cytosol. However, increased ROS production did not induce oxidative stress and did not decrease the level of endogenous antioxidant glutathione (GSH). Thus, disruption of mitochondrial energy metabolism but not oxidative stress could play a role of potential trigger of brain pathology in LNS.

We propose and tested a method for studies of native blood cells by atomic-force microscopy in a humid chamber preserving viability, size, and shape of biological objects. The method has some advantages over scanning in a liquid cell: it allows studying non-fixed blood samples in the form of suspension of live cells and excludes mechanical and chemical influences on the cells.

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