Ultrastructure and Morphological Variability of Non-Culturable Forms of Yersinia pseudotuberculosis Bacteria.

One of the mechanisms underlying the appearance of chronic infections is transition of pathogens into a non-culturable state, which is largely associated with the use of antibiotics. We studied ultrastructure of dormant bacteria Yersinia pseudotuberculosis obtained from the vegetative form of strain 512 by inhibition with kanamycin. On the model of the causative agent of pseudotuberculosis we showed that transition of prokaryotes to a dormant state occurs through apoptosis of bacteria. Fragmentation and condensation of chromatin with the formation of electron-dense fibrils, clumps and large conglomerates characteristic of apoptosis were found in the nucleoid zone of the cytoplasm of inhibited bacterial cells. These results are of great importance for understanding the mechanisms of the existence of pathogens in different conditions, as well as for identifying the causative agents of infectious diseases.

An approach to growth of Fe-Si multilayers with controlled composition profile-a way to exchange coupled thin films.

The growth, composition and structure of sandwich structures (Fe-rich layer/Si-rich layer/Fe-rich silicide layer) grown on a Si(111) surface were studied by a few complementary microscopic and spectroscopic techniques with high spatial resolution. Intermixing at the Fe/Si and Si/Fe interfaces is demonstrated. Fe-rich layers grown directly on the Si(111) surface are crystalline and have abrupt but rough interfaces at both sides. The succeeding layers are disordered and their interfaces are fuzzy. The distributions of Fe and Si within the layers are laterally non-uniform. The reproducible fabrication of thin non-magnetic silicide spacers of predetermined thickness is demonstrated. Sandwich structures with such spacers exhibit exchange coupling between ferromagnetic Fe-rich layers.

THE STRUCTURAL CHANGES OF MACROPHAGES INFECTED WITH TICK-BORNE ENCEPHALITIS VIRUS.

Macrophages belong to the innate immune cells and play a key role in the pathogenesis of viral infections. The results of ultrastructural study of macrophages infected with tick-borne encephalitis virus (TBEV), the Flavivirus family, pathogens of human infections, affecting the nervous system, were presented. With the assistance of virological methods was found that the TBEV are absorbed by macrophages and replication in them. An ultrastructural study has shown that the virus enters into the cytoplasm by local destruction of plasmalemma and newly synthesized virus particles exited from the cell by same. Simultaneously there is a seal of perinuclear cytoplasm space, where found in a large number of ribosomes, microfilaments, ribonucleoprotein fibers and viral special structure: nucleocapsids, tubular formations and viral layers (fabrics). On the surface of last structures the newly synthesized virus particles were visualized. Thus, the evidence shows that macrophages play a role in the spread of TBEV, being for their the target cell. As active antigen presenting cells the macrophages can modulate the protective response of the body and influence on the pathogenesis of tick-borne encephalitis.

Cavity-based Fabry-Perot probe with protruding subwavelength aperture.

We investigate numerically and experimentally the possibility of development of a cavity-based probe for near-field optical microscopy systems based on a fiber Fabry-Perot interferometer with a subwavelength protruding aperture. It was shown that the probe provides a spatial resolution of no worse than λ/37 for λ=1550 nm.

Plasmonic Nanolenses Produced by Cylindrical Vector Beam Printing for Sensing Applications.

Interaction of complex-shaped light fields with specially designed plasmonic nanostructures gives rise to various intriguing optical phenomena like nanofocusing of surface waves, enhanced nonlinear optical response and appearance of specific low-loss modes, which can not be excited with ordinary Gaussian-shaped beams. Related complex-shaped nanostructures are commonly fabricated using rather expensive and time-consuming electron- and ion-beam lithography techniques limiting real-life applicability of such an approach. In this respect, plasmonic nanostructures designed to benefit from their excitation with complex-shaped light fields, as well as high-performing techniques allowing inexpensive and flexible fabrication of such structures, are of great demand for various applications. Here, we demonstrate a simple direct maskless laser-based approach for fabrication of back-reflector-coupled plasmonic nanorings arrays. The approach is based on delicate ablation of an upper metal film of a metal-insulator-metal (MIM) sandwich with donut-shaped laser pulses followed by argon ion-beam polishing. After being excited with a radially polarized beam, the MIM configuration of the nanorings permitted to realize efficient nanofocusing of constructively interfering plasmonic waves excited in the gap area between the nanoring and back-reflector mirror. For optimized MIM geometry excited by radially polarized CVB, substantial enhancement of the electromagnetic near-fields at the center of the ring within a single focal spot with the size of 0.37λ2 can be achieved, which is confirmed by Finite Difference Time Domain calculations, as well as by detection of 100-fold enhanced photoluminescent signal from adsorbed organic dye molecules. Simple large-scale and cost-efficient fabrication procedure offering also a freedom in the choice of materials to design MIM structures, along with remarkable optical and plasmonic characteristics of the produced structures make them promising for realization of various nanophotonic and biosensing platforms that utilize cylindrical vector beam as a pump source.

[Infection of macrophages with tick-borne encephalitis virus].

Virological and morphological studies have established that tick-borne encephalitis (TBE) from virus-containing liquid is able to adhere to the surface of macrophages, to penetrate, and to multiple in them. Viral particles come into and out through local macrophageal plasmolemma lysis. The type of macrophageal infection is considered to be autonomic as genomic activation and TBE reproduction occurred in the cell cytoplasm. Productive acute lytic infection in the macrophages was due to the appearance of reproduction-induced adequate TBE with a pronounced cytopathic effect on cultured porcine embryo kidney cells and to the synthesis of virus-specific and virus-induced cytoplasmic organelles that caused cell deaths upon toxic and mechanical exposure.

Composite topological structure of domain walls in synthetic antiferromagnets.

We experimentally study the structure and dynamics of magnetic domains in synthetic antiferromagnets based on Co/Ru/Co films. Dramatic effects arise from the interaction among the topological defects comprising the dual domain walls in these structures. Under applied magnetic fields, the dual domain walls propagate following the dynamics of bi-meronic (bi-vortex/bi-antivortex) topological defects built in the walls. Application of an external field triggers a rich dynamical response: The propagation depends on mutual orientation and chirality of bi-vortices and bi-antivortices in the domain walls. For certain configurations, we observe sudden jumps of composite domain walls in increasing field, which are associated with the decay of composite skyrmions. These features allow for the enhanced control of domain-wall motion in synthetic antiferromagnets with the potential of employing them as information carriers in future logic and storage devices.

[Mechanism of viral infection of macrophages by an agent of hemorrhagic fever with renal syndrome: ultrastructural aspects]. / Mekhanizm infitsirovaniia makrofagov vozbuditelem gemorragicheskoi likhoradki s pochechnym sindromom: ul'trastrukturnye aspekty.

Monocytes/macrophages are one of the first cells subjected to the infectious effect of viruses. The present paper analyses for the first time the ultrastructural changes in macrophages caused by an agent of hemorrhagic fever with renal syndrome (HERS)--hantavirus (HV). After a local fusion with the host cell plasmalemma and its adsorption on the cell surface, the HV penetrates through the macrophage membrane. This process occurred without destruction of cell plasmalemma. HV viral particles were observe within the macrophage cytoplasm mostly on the smooth granular endoplasmic reticulum vesicles. Viroplasts were defined in macrophages after a 2 h incubation, with synthesis of viral nucleoproteins and primary covers being observed on the surface of viroplasts. Viral particles left macrophages in the process of budding on the phagocyte surface. Thereby HV, similar to other enveloped viruses, realizes entrance and egress from the target cell without damaging its plasmalemma. This accounts for the viral ability to reproduce in macrophages for a long time without any cytopathological effect. Consequently, in the absence of obvious destruction changes, mononuclear phagocytes can serve as a long-term storage of viruses, and thus being involved in HV dissemination during HERS.

Ultrastructure of Yersinia pseudotuberculosis inhabiting the soil for a long time.

Ultrastructural changes in the population of pathogenic Yersinia pseudotuberculosis inhabiting a model soil ecosystem for a long time were studied. Changes in the bacteria were mainly adaptive until the 8th month of the experiment, their capacity to binary division was preserved. After 9 months cell structure changed: extracellular amorphous matrix appeared, probably due to increased mucus production.