Biology subjects

Denisov, P.

Publications and source records attributed to Denisov, P..

3 recordsLinked to original sources

bioRxiv2024

Rapid Raman spectroscopy-based test for antimicrobial resistance

Antimicrobial resistance is one of the top global health threats. In 2019, antimicrobial resistance was associated with 4.95 million deaths, of which 1.97 million were caused by drug resistant infections directly. The main subset of AMR is the antibiotic resistance, that is resistance of bacteria to antibiotic treatment. Traditional and most commonly used antibiotic susceptibility tests are based on detection of bacterial growth and its inhibition in the presence of an antimicrobial. These tests typically take over 1-2 days to perform, so empirical therapy schemes are often administered before the proper testing. Rapid tests for antimicrobial resistance are necessary to optimize the treatment of bacterial infection. Here we combine MTT test with Raman spectroscopy to provide 1.5-hour long test for minimal inhibitory concentrations determination. Several E.coli and K.pneumoniae strains were tested with three types antibiotics, including ampicillin from penicillin family, kanamycin from aminoglycoside family and levofloxacin from fluoroquinolone family. The test provided the same minimal inhibitory concentrations as traditional Etest confirming its robustness.

molecular biology↗

bioRxiv2020

Astrocytes dystrophy in ageing brain parallels impaired synaptic plasticity

Little is known about age-dependent changes in structure and function of astrocytes and of the impact of these into the cognitive decline in the senescent brain. The prevalent view on age-dependent increase in reactive astrogliosis and astrocytic hypertrophy requires scrutiny and detailed analysis. Using two-photon microscopy in conjunction with 3D reconstruction, Sholl and volume fraction analysis we demonstrate a significant reduction in the number and the length of astrocytic processes, in astrocytic territorial domains and in astrocyte-to-astrocyte coupling in the aged brain. Probing physiology of astrocytes with patch-clamp and Ca2+ imaging revealed deficits in K+ and glutamate clearance, and spatiotemporal reorganization of Ca2+ events in old astrocytes. These changes paralleled impaired synaptic long-term potentiation (LTP) in hippocampal CA1 in old mice. Our findings may explain astroglial mechanisms of age-dependent decline in learning and memory.

neuroscience↗

bioRxiv2019

An astrocytic basis of caloric restriction action on the brain plasticity

One month of calorically restricted diet (CR) induced morphological plasticity of astrocytes in the stratum (str.) radiatum of hippocampal CA1 in three-months old mice: the volume fraction of distal perisynaptic astrocytic processes increased whereas the number of gap-junction coupled astrocytes decreased. The uncoupling was not associated with a decrease in the expression of connexin 43. Uncoupling and morphological remodeling affected spontaneous Ca2+ activity in the astrocytic network: Ca2+ events became longer, whereas their spread was reduced. The change in the pattern of astrocytic Ca2+ activity may increase the spatial resolution of the information encoding in the astroglial network. Consistent with expanded synaptic enwrapping by the astroglial processes, the spillover of synaptically released K+ and glutamate was diminished after CR. However, no significant changes in the expression of astrocytic glutamate transporter (GLT-1/EAAT2) were observed, although the level of glutamine synthetase was decreased. Glutamate uptake is known to regulate the synaptic plasticity. Indeed, the magnitude of long-term potentiation (LTP) in the glutamatergic CA3-CA1 synapses was significantly enhanced after CR. Our findings highlight an astroglial basis for improved learning and memory reported in various species subjected to CR.

neuroscience↗