Volume 60, Nº 2 (2024)

In this study, changes in all blood formed elements of long-tailed ground squirrel Urocitellus undulatus (n=100) during different periods of their life activity were investigated. The hematological analysis was performed on an automatic veterinary analyser: a indices of leukocytes, platelets and erythrocytes were measured in summer (normothermia, june-july), autumn (preparatory period, october), winter torpid (hypothermia, december-february) and winter active periods (IBA, euthermia, short awakenings between hypothermia stages, december-february). It was shown that the total counts of platelets and leukocytes of ground squirrel increased by ~40 % in autumn compared to summer. During the torpor period, thrombocytosis and leukocytosis were replaced by extreme thrombocytopenia (~90 %) and leukopenia (~80 %). On awakening, the indices reached “summer” values, except for a slightly increased mean platelets volume. In autumn, an insignificant erythrocytosis (~10 %) was observed, which, together with changes in other parameters, could indicate an unexpressed autumn hypoxia. In torpor and in winter euthermia, the erythrocyte indices were no difference with summer control values; however, the presence of atypical forms of erythrocytes was detected both in the autumn period of preparation for hibernation and during hibernation. The results are discussed in the context of the adaptation of the blood-forming elements of the ground squirrel to the extreme conditions of hibernation and are valuable for the study of the adaptive abilities of homoeothermic animals and humans.

The study is aimed at evaluating the influence of composition and size of micro- and nanoparticles (MPs and NPs) on the immunogenicity of protein antigen associated with them. For comparative analysis, MPs and NPs based on poly(lactic acid) (PLA) and block copolymer of poly(ethylene glycol) with poly(lactic acid) (PEG-b-PLA) were obtained. Recombinant human beta2-microglobulin fusion protein with superfolder green fluorescent protein (β2M-sfGFP) was used for covalent modification of all types of polymer particles. Immobilization of the model protein β2M-sfGFP was carried out on the surface of the particles through the reaction of activated esters with the amino groups of the protein. Immunization of mice using complex antigen (β2M-sfGFP protein immobilized on the surface of MPs and NPs of different compositions) was carried out in four steps. Immunogenicity was assessed by the level of specific antibodies to sfGFP using enzyme-linked immunoassay. The results showed a significant increase in antibody levels in the control groups, which were immunized with a mixture of model protein and particles of different nature and sizes, compared to the experimental groups, which were immunized with conjugates of the corresponding particles with model protein. In the experimental groups, the highest number of specific antibodies was detected in the case of immunization of mice with the conjugate of protein and PLA or PEG-b-PLA-based NPs. The introduction of PEG block into the PLA composition did not significantly affect the immunogenicity of the protein, while the particle size was of significant importance. PLA- or PEG-b-PLA-based NPs showed higher immunogenicity compared to MPs of the same compositions, which can be used for practical purposes to develop vaccines (NP-protein) or ” trapping systems” (MP-protein) that bind infiltrating viruses.

Analysis of responses on electrical stimulation is one of the experimental paradigms to study the excitability of the nervous system. In particular, the technique of recording muscle responses evoked by electrical epidural stimulation (ES) of the spinal cord (SC) in humans and animals is widely used. In rats decerebrated at the precollicular level, responses of mm. tibialis anterior (TA) and gastrocnemius medialis (GM) on ES of the L2, L4, L6 spinal segments and transvertebral stimulation (TS) of the VL2, VL4, VL6 vertebrae with single and double pulses were analyzed. The currents at which the amplitude of the sensory component of the response for a single pulse and one of the pulses of the pair was maximum were determined. At the minimum of these currents, the ratio of the amplitudes of the sensory component of the response to the first and second pulses to the amplitude of the sensory component of the response to a single pulse was analyzed. For both muscles, a weakening of the response to both pulses of the pair was obtained with TS VL2 and VL4, while when stimulating VL2, the TA response to the second pulse was lower than to the first. On the contrary, with ES of all segments of interest, a facilitation of the response to the second pulse was obtained for both muscles. A similar facilitation was qualitatively observed for two other muscles, mm. iliacus and vastus lateralis. Thus, the use of double pulses during stimulation made it possible to identify the dependence of the response of SC neural networks on the method of their activation (TS or ES). The facilitation of the response to the second pulse during ES is presumably explained by a decrease in presynaptic inhibition due to decerebration.