Visualization of different anatomical parts of the enucleated human eye using X-ray micro-CT imaging.

Micro-CT visualization allows reconstruction of eye structures with the resolution of light microscopy and estimation of tissue densities. Moreover, this method excludes damaging procedures and allows further histological staining due to the similar steps in the beginning. We have shown the feasibility of the lab-based micro-CT machine usage for visualization of clinically important compartments of human eye such as trabecular outflow pathway, retina, iris and ciliary body after pre-treatment with iodine in ethanol. We also identified the challenges of applying this contrasting technique to lens, cornea, and retina and proposed alternative staining methods for these tissues. Thereby this work provides a starting point for other studies for imaging of human eyes in normal and pathological conditions using lab-based micro-CT systems.

Influence of porous titanium-based jaw implant structure on osseointegration mechanisms.

The reconstruction of maxillofacial defects caused by anomalies, fractures, or cancer is challenging for dentofacial surgeons. To produce efficient, patient-specific implants with long-term performance and biological suitability, numerous methods of manufacturing are utilized. Because additive manufacturing makes it possible to fabricate complex pore structure samples, it is now recognized as an acceptable option to design customized implants. It is well recognized that a porous structure with proper design promotes accelerated cell proliferation, which enhances bone remodeling. Porosity can also be employed to modify the mechanical characteristics of fabricated implants. Thus, design and choice of rational lattice structure is an important task. The influence of the structure of jaw implants made of highly porous titanium-based materials on their mechanical properties and bone tissue growth was studied. Based on a 3D computer model of Wigner-Seitz lattice structure, the model samples were fabricated from Ti6Al4V powder by selective laser melting to characterize the mechanical properties of the samples depending on their macroporosity. Then two types of jaw bone implants were manufactured to conduct studies of bone tissue ingrowth when implanted in laboratory animals. The research was carried out in several stages: design and production of the implants for replacing incomplete defects of the lower jaw; implantation of SLM-printed implants in laboratory animals into an artificially produced defect of the lower jaw; analysis of the degree of fixation of the "implant - bone" connection (for implantation periods from 2 weeks to 9 months). During the research, Ti-alloy structures with cell diameters of 2-3 mm and macroporosity of 90-97% mimicking the spongy structure of trabecular bone tissue, were characterized by a compressive strength of 12.47-37.5 MPa and an elastic modulus of 0.19-1.23 GPa, corresponding to the mechanical properties of bone tissue. Active processes of tissue growth into implant cells were detected 2 weeks after implantation, the significant differences in the volume and types of filling tissue depending on the size of the cell were described. Recommendations for choosing the cell size depending on the type of bone tissue damage were given. When using SLM-printed implants with lattice structure (cell sizes from 1 to 3 mm), an active osteosynthesis processes occurred, which culminated in the formation of bone tissue inside the implant cells 9 months after implantation, with 68% of the samples characterized by the maximum degree of implant fixation. Implants with 3 mm cells with macropores diameters of 850 µm were recommended for replacing cavities after removal of perihilar cysts. To replace complete and partial defects, it was recommended to use implants with a cell size of 2 and 3 mm.

Mathematical tools for recovery of the load on the fissure according to the micro-CT results.

In the present paper X-ray microtomographic research of a molar tooth was conducted. The study revealed regions with a reduced mineral density in the vicinity of the fissure tip. The basic assumption investigated is that corrosion induced enamel mineral density decrease is enhanced by high tensile stresses generated by mechanical load on the occlusal surface of the tooth during crushing of food. Magnitude and location of tensile stress concentration occurs at the fissure tip and may be determined by solving the problem of the stress-strain state of the tooth crown enamel with a wedge-shaped notch. The study of stresses in the vicinity of fissure tip make it possible to construct the boundaries of enhanced enamel virtual fracture. Comparison of the sizes and locations of areas with a reduced enamel mineral density with the sizes and locations of areas of virtual enamel fracture made it possible to establish their approximate congruence. This circumstance made it possible to recreate by mathematical means the nature and magnitude of the force load on the lateral surface of the fissure. Degree of influence of the main parameters of the fissure on the geometrical characteristics of the virtual fracture, such as its area and diameters, were determined.

A new millipede genus and species of the tribe Pachyiulini from the Caucasus (Diplopoda, Julida, Julidae).

A new genus and species of the millipede tribe Pachyiulini, Bellatoiulusgolovatchi gen. et sp. nov., is described from the Lesser Caucasus, Azerbaijan. Cybertypes of the new species are created from the physical holotype male and from a paratype female. The distribution and ecological features of the new species, and the position of the new genus within Pachyiulini are discussed.

Structure and Properties of ZrON Coatings Synthesized by Cathodic Arc Evaporation.

The transition metal oxynitrides are a coating material with decorative features due to their adjustable color and good mechanical properties. The purpose of the research was to study the effect of the relative oxygen concentration O2(x) = O2/(N2 + O2) in particular on adhesion, but also on the color, structural and mechanical properties of ZrON coatings synthesized by cathodic arc evaporation on HS6-5-2 steel substrates. The surface morphology, phase and chemical composition and mechanical properties were determined using scanning electron microscopy, X-ray diffraction, wavelength dispersive X-ray spectroscopy, nanoindentation and scratch test. It was found that color of the coatings changed from light yellow for ZrN first to gold and then to graphite for Zr-O phase with increase of oxygen concentration. X-ray diffraction patterns showed that the phase separation of ZrN and ZrO2 occurred for about 35 at.% of oxygen in the coating. Increase in oxygen concentration in the coatings led to decrease in crystallite size from about 20 nm for ZrN to about 5 nm for coatings with about 35 at.% of oxygen and about 25 at.% of nitrogen. An increase in hardness from about 26 GPa for ZrN to about 30 GPa for coating with small concentration of oxygen (about 9 at.%) and then decrease to about 15 GPa was observed. Adhesion of Zr-O-N coatings demonstrated strong dependence on oxygen concentration. Critical load for ZrN is about 80 N and decreases with oxygen concentration increase to about 30 N for ZrO2.

X-ray micro-computed tomography in the assessment of penile cavernous fibrosis in a rabbit castration model.

BACKGROUND: Current assessment methods of penile cavernous fibrosis in animal models have limitations due to the inability to provide complex and volume analysis of fibrotic alterations. OBJECTIVE: The aim was to evaluate micro-computed tomography for assessment of cavernous fibrosis and compare it with histological, histochemical, immunohistochemical, and RT-PCR analysis. MATERIALS AND METHODS: A controlled trial was performed involving 25 New Zealand male rabbits with induced testosterone deficiency by orchidectomy. Penile samples were obtained before and after 7, 14, 21, and 84 days from orchidectomy. We consistently performed (a) gray value analysis of corpora cavernosa 3D models reconstructed after micro-computed tomography, (b) morphometry of smooth muscles/connective tissue ratio, collagen type I/III ratio, and area of TGF-beta-1 expression in corpora cavernosa, and (c) RT-PCR of TGF-beta-1 expression. RESULTS: Micro-computed tomography allowed visualization of penile structures at a resolution comparable to light microscopy. Gray values of corpora cavernosa decreased from 1673 (1512-1773) on the initial day to 1184 (1089-1232) on the 21st day (p < 0.005). However, on the 84th day, it increased to 1610 (1551-1768). On 21st and 84th days, there was observed a significant decrease in smooth muscle/connective tissue ratio and a significant increase in collagen type I/III ratio (p < 0.05). TGF-beta1 expression increased on the 84th day according to immunohistochemistry (p < 0.005). RT-PCR was impossible to conduct due to the absence of RNA in obtained samples after micro-CT. DISCUSSION AND CONCLUSIONS: Micro-computed tomography provided 3D visualization of entire corpora cavernosa and assessment of radiodensity alterations by gray value analysis in fibrosis progression. We speculate that gray value changes at early and late fibrosis stages could be related to tissue reorganization. RT-PCR is impossible to conduct on tissue samples studied by micro-CT due to RNA destruction. We also suggest that micro-computed tomography could negatively affect the immunohistochemical outcome, as a significant increase of TGF-beta-1 expression occurs later than histological fibrotic signs.