Sovremennye Tehnologii v Medicine最新文献

The aim of the investigation was to study the factors influencing the radial stiffness of the thoracic aorta stent-grafts with the stent elements made of nitinol tubes by laser cutting and thermal shape setting.

Materials and methods: The work used stent elements made by different technologies by two different manufacturers from a nitinol tube with a wall thickness of 0.5 mm (E1) and 0.4 mm (E2), with a final diameter of 20 mm. Height of cells E1 - 15 mm, E2 - 12.5 mm. The stents were manually attached to a tubular woven non-crimped base (PTGO Sever, Russia) with a 6/0 suture, resulting in either single or continuous stitches. In the RLU124 radial force tester (Blockwise Engineering LLC, USA), each of the four stent-grafts, as well as their individual stent elements, were compressed by 10 mm from the initial diameter. The dependence of the radial forces on deformation under loading and unloading was graphically presented. The temperature and enthalpy of phase transitions of nitinols into the austenite (Af) and martensitic (Mf) phases were studied using differential scanning calorimetry (DSC-3; Mettler Toledo, USA). All indicators were compared with the characteristics of two commercial models - Cronus (China) and E-vita Open Plus (Germany).

Results: Four prototypes of SibHybrid stent-grafts were tested; those differed in their stent elements, distances between them, and the type of sutures (single or continuous). The stent elements of the models studied differed in the values of Af, Mf, and the enthalpy of phase transitions of nitinols. The hardest stent was the E2 prototype. The fixation of stent elements to the woven fabric in the graft increased the radial force by 4.0-5.5 times. During compression by 50 and 20% of the original diameter, the SibHybrid models developed radial force 4.5-6.0 times greater compared with the E-vita Оpen Plus model. The radial force values of SibHybrid models were almost the same as for the Cronus and models at 20% compression. Using continuous twining round suturing increased the radial force by about 10 N; accordingly, SibHybrid E2 had the highest radial force because it was fixed by a continuous suture. The density of the stent elements fixed on the fabric did not affect the radial force of the stent-graft as a whole.

Conclusion: In the manufacture of stent elements from nitinol tubes, the main factor determining the radial stiffness is the technology of nitinol shape setting. With the standard technology of thermal shape setting, radial force can be changed by varying the height of the structure cell element and the cross-sectional area of the cell bars, as well as the suturing technique.

The aim of the investigation was to study the influence of pore size and the presence of a biologically active calcium phosphate coating in porous 3D printed titanium implants on the process of integration with the bone tissue.

Materials and methods: Samples of cylindrical implants with three different pore diameters (100, 200, and 400 μm) were fabricated from titanium powder on the Arcam 3D printer (Sweden) using electron beam melting technology. A calcium phosphate coating with a thickness of 20±4 μm was applied to some of the products by microarc oxidation. Cytotoxicity of the implants was determined in vitro on human dermal fibroblast cultures. The samples were implanted in the femoral bones of 36 rabbits in vivo. The animals were divided into 6 groups according to the bone implant samples. The prepared samples and peri-implant tissues were studied on days 90 and 180 after implantation using scanning electron microscopy and histological methods.

Results: All samples under study were found to be non-toxic and well biocompatible with the bone tissue. There were revealed no differences between coated and non-coated implants of 100 and 200 μm pore diameters in terms of their histological structure, intensity of vascularization in the early stages, and bone formation in the later stages. Samples with pore diameters of 100 and 200 μm were easily removed from the bone tissue, the depth of bone growth into the pores of the implant was lower than in the samples with pore diameter of 400 μm (p<0.001). There were differences between coated and non-coated samples of 400 μm pore diameter, which was expressed in a more intensive osseointegration of samples with calcium phosphate coating (p<0.05).

Conclusion: The optimal surface characteristics of the material for repairing bone defects are a pore diameter of 400 μm and the presence of a calcium phosphate coating.

The aim of the investigation was to study the biodegradation characteristics and rate of magnesium alloys in vitro.

Materials and methods: We studied the biodegradation of magnesium alloys Mg-Zn-Ca and WE43 (Mg-Y-Nd-Zr) in homogenized (initial) condition and after strengthening by mechanical processing using equal channel angular pressing (ECAP). The samples were incubated in a model system based on reference fetal calf serum (FCS) in the static and dynamic modes. The morphology of alloy surfaces was analyzed using light microscopy and computed tomography. Biodegradation was assessed by calculating weight loss within a certain incubation period. Cell adhesion and colonization stimulation were quantified in terms of a cell index (CI) using an analyzer xCELLigence RTCA Systems (ACEA Biosciences, Inc., USA) during the incubation of HEK 293 cells on WE43 specimens.

Results: Strengthening of magnesium alloys Mg-Zn-Ca and WE43 using ECAP and, consequently, the changed structure resulted in the biodegradation acceleration as high as eightfold. Among the specimens incubated in FCS in different modes, those incubated in liquid flow exhibited the biodegradation rate twice as high as that of the specimens tested under static conditions. The biodegradation process was accompanied by local corrosion, although the degradation was primarily concentrated along the specimen margins stimulating cell adhesion and colonization. Such nature of degradation, as a rule, does not lead to anisotropy of the strength characteristics, that is important for medical materials. Superficial degradation of the alloys with no X-ray density changes in the bulk of the specimens was confirmed by computed tomography.

Conclusion: The study of the biodegradation rate and further characteristics of magnesium alloys Mg-Zn-Ca and WE43 showed that the materials in both structural conditions are suitable for implants and can be used in bone implants and surgical fasteners.

The potential mechanisms of bronchial asthma (BA) negative modification under the influence of obesity are currently being actively studied. However, at present, the effect of nutritional status on bronchial obstruction in children with BA cannot be considered established. In this regard, the purpose of this work was to study the relationship of spirometric parameters reflecting bronchial patency with nutritional status in children with asthma.

Materials and methods: The study involved 54 patients with BA at the age of 8 to 17 years, 33 boys and 21 girls with different nutritional status. Assessment of nutritional status was carried out with the calculation of body mass index (BMI), relative body mass index (RBMI), and determination of body fat (% BF). Spirogram parameters were evaluated, including forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio, maximum expiratory flow at the point of 25% loop flow-volume (MEF 25).

Results: Among the children examined, taking into account the BMI Z-score, 9.3% (5/54) had low body weight (group 1), 33% (18/54) had normal body weight (group 2), 31.5% (17/54) overweight (group 3), 25.9% (14/54) obesity (group 4). As the body weight increased, a statistically significant decrease in the FEV1/FVC ratio was observed, amounting to 84.6 [79.3; 90.0], 79.4 [76.6; 82.2], 74.6 [71.7; 77.5], 70.2 [67.0; 73.4]%, respectively, p=0.003; as well as a decrease in MEF 25 (% pred.), which amounted, respectively, to 95.6 [76.1; 115.2], 81.7 [71.4; 92.0], 56.3 [45.7; 66.9], and 48.4 [36.7; 60.1]%, p=0.003. A statistically significant negative relationship was found between indicators of nutritional status, including BMI, RBMI, % BF, and spirometry parameters reflecting bronchial patency, including FEV1/FVC ratio and MEF 25 (% pred.); all p<0.01.

Conclusions: Overweight and obesity in children with BA, estimated both by calculated methods with determination of BMI and RBMI and direct determination of body fat content, are accompanied by a statistically significant decrease in bronchial patency.

The aim of the study was to assess the capabilities of combined application of dual-wavelength fluorescence visualization and contactless skin thermometry during photodynamic therapy monitoring (PDT) of basal cell cancer.

Materials and methods: The study was performed at the University Clinic of Privolzhsky Research Medical University (Nizhny Novgorod). Nine clinically, dermatoscopically, and histologically verified foci of basal cell skin cancer were exposed to PDT sessions (wavelength of 662 nm, light dose density of 150 J/cm²) with systemic application of chlorin-based photosensitizer Fotoditazin. A semiconductor laser system Latus-T (Russia) was employed for irradiation. Dual-wavelength fluorescence visualization and contactless thermometry with an IR pyrometer were used to monitor the PDT sessions.

Results: The PDT sessions of nine foci of basal cell cancer were carried out under the control of fluorescence imaging and contactless thermometry. Photosensitizer photobleaching in all foci amounted to 40% signifying a percent of photosensitizer involved in the photodynamic reaction. It has been shown that the combined employment of dual-wavelength fluorescence monitoring and contactless thermometry during the PDT of basal cell skin cancer allows oncologists to control simultaneously the degree of photosensitizer photobleaching and the depth of the photodynamic effect in tissues, the extent of involving the mechanisms associated with hyperthermia as well as the correctness of the procedure conducting. In the course of 9-month dynamic follow-up after the treatment, no clinical and dermatoscopic signs of recurrence were found.

Conclusion: A bimodal control of PDT enables the assessment of the correctness and efficacy of the procedure performance. The contactless control of tissue heating allows ensuring the temperature mode for hyperthermia realization, while the fluorescence monitoring makes it possible to evaluate the accumulation of the photosensitizer in the tumor and the depth of the PDT action as well as to predict the procedure efficacy based on the photobleaching data. The complementary use of these techniques allows the adjustment of the mode directly in the course of the PDT procedure. The acquisition of the sufficient statistical data on the combined monitoring will result in the development of a novel PDT protocol.

The aim of the study was to develop composite film materials derived from modified sodium carboxymethyl cellulose and to evaluate their anti-adhesive effects.

Materials and methods: The modified film materials were obtained by dissolving sodium carboxymethyl cellulose (Na-CMC) in an aqueous solution of a modifier (glycoluril) with subsequent homogenization and drying in a vacuum drying oven at room temperature. Physicomechanical parameters of the obtained films were determined using the Instron 3369 universal electromechanical testing machine (Great Britain) equipped with a climatic chamber (300-523 K), improved video extensometer, and the MKC-25 micrometer (Russia). Cytotoxicity of glycoluril-modified film materials derived from Na-CMC was studied by incubating cell cultures of 3T3-L1 mouse fibroblasts directly with extracts from films under study using a colorimetric test. Their anti-adhesion effect was investigated on 40 female Wistar rats by modeling a flat adhesion by inducing abrasion of the cecum and suturing the deserosed surface of the abdominal wall anatomically opposite the abrasion area. The presence of adhesions was assessed on day 8 after the operation. Commercial membrane Seprafilm (USA) was used as a reference sample.

Results: It was found that extracts obtained from film materials derived from Na-CMC modified with glycoluril at a concentration of 0.01 and 0.05 wt. % had no cytotoxic effect on the cell culture of mouse fibroblasts 3T3-L1. Flat adhesions were not detected when using Seprafilm. When film materials under study were placed in the abdominal cavity between the injured areas, formation of flat adhesions was not observed or observed in one case out of ten.

Conclusion: The obtained films are promising for preventing adhesions as a barrier-type agent. Modifying Na-CMC with glycoluril made it possible to create films that prevent formation of flat adhesions, have improved physical and mechanical properties and no cytotoxic effect.

The aim of the investigation was to study a systemic level of L-DOPA, dopamine, and norepinephrine, and assess their prognostic value in retinopathy of prematurity (ROP) development on an experimental disease model.

Materials and methods: The investigation was carried out on infant Wistar rats (n=36) divided into a study group (rat infants with experimental ROP, n=17) and a control group (n=19). The animals of both groups were sacrificed on days 14, 21-23, and on days 28-30. The choice of the indicated periods corresponded to the key stages of ROP development in an experiment and was based on the findings of our previous histological studies. Dopamine, L-DOPA, and norepinephrine levels in infant rat blood plasma samples were determined.

Results: On day 14 of the experiment (the period corresponds to the pathological neovascularization induction in the applied model and preclinical ROP in children), mean L-DOPA level in infant rats with ROP (0.31 ng/ml) was significantly decreased compared to that in the controls (0.42 ng/ml) (p≤0.01). On days 21-23 of the experiment (the period corresponds to the growth of pathological extraretinal neovascularization in the applied model and ROP stage 3 in children) the systemic level of L-DOPA was still statistically reduced in the study group (0.87 ng/ml) compared to the control group (1.53 ng/ml) (p≤0.01). On days 28-30 of the experiment (the period corresponds to the regress of neovasculature in the applied model and a spontaneous ROP regress stage in children) the L-DOPA level in blood plasma in the study group (0.33 ng/ml) showed an insignificant upward tendency in reference to the controls (0.21 ng/ml). Mean dopamine and norepinephrine levels had no difference in the groups under study of infant rats within all follow-up periods.

Conclusion: Low systemic level of L-DOPA at the preclinical stage of experimental ROP should be considered as a laboratory prognostic criterion of a developing pathological process; it will enable to use the criterion when working out the measures to optimize the existing screening system for the disease in children.

The aim of the study is to assess the gender-related specifics of the COVID-19 course in patients under 55 years of age.

Materials and methods: This pilot single-center continuous retrospective non-randomized study was carried out in the repurposed infectious diseases hospital of the Privolzhsky Research Medical University (Nizhny Novgorod, Russia). The study inclusion criterion was the age of patients (up to 55 years) and confirmed coronavirus infection. In the groups based on gender differences (25 men, average age 44.0±7.8 years and 32 women, average age 41.9±9.1 years), we monitored complications of COVID-19 such as the transfer of patients to the ICU and the volume of lung damage (determined with CT scans).

Results: The course of COVID-19 in male patients younger than 55 was aggravated by concomitant diseases (γ=0.36; p=0.043), among which IHD (γ=1.00; p=0.003) and liver disease (γ=0.58; p=0.007) dominated. Frequency analysis confirmed the high prevalence of coronary artery disease in men (p=0.044). Significant differences between the gender-related groups were noted in the volume of lung lesions: at admission (p=0.050), during hospital treatment (p=0.019), and at discharge (p=0.044). Using the logistic regression method, a relationship was found between the transfer of male patients to ICU and the Krebs index [y= -2.033 + 1.154 male gender + 1.539 Krebs index (χ²=5.68; p=0.059)] and comorbidity [y= -2.836 + 1.081 male gender + 2.052 comorbidity (χ²=7.03; p=0.030)]. The influence of the Krebs index and the male gender on the excess volume of lung lesions was shown [y= -1.962 + 0.575 male gender + 1.915 Krebs index (χ²=7.78; p=0.021)].

Conclusion: In individuals under the age of 55 diagnosed with COVID-19, gender is of significant importance: in men, there is a more pronounced lesion of the lung parenchyma and a more significant change in laboratory parameters. Risk factors for a severe course of COVID-19 in men are coronary artery disease and hepatobiliary disorder. Calculating the Krebs index can be used to assess the risk of disease progression.

The aim of the investigation was to study the clinical course of COVID-19 in the presence of diabetes mellitus (DM) and elucidate possible mechanisms of their mutual aggravation.

Materials and methods: The study included 64 patients with COVID-19; of them, 32 were with DM (main group) and 32 were DM-free (control group). The groups were formed according to the "case-control" principle. During hospitalization, the dynamics of clinical, glycemic, and coagulation parameters, markers of systemic inflammation, as well as kidney and liver functions were monitored and compared.

Results: Among patients with DM, the course of viral pneumonia was more severe, as evidenced by a 2.2-fold higher number of people with extensive (>50%) lung damage (p=0.05), an increased risk of death according to the CURB-65 algorithm (1.3-fold, p=0.043), and a longer duration of insufficient blood oxygen saturation (p=0.0004). With the combination of COVID-19 and DM, hyperglycemia is persistent, without pronounced variability (MAGE - 1.5±0.6 mmol/L), the levels of C-reactive protein (p=0.028), creatinine (p=0.035), and fibrinogen (p=0.013) are higher, manifestations of hypercoagulability persist longer, including slower normalization of antithrombin III (p=0.012), fibrinogen (p=0.037), and D-dimer (p=0.035).

Conclusion: The course of COVID-19 in patients with DM is associated with a high severity and extension of pneumonia, persistent decrease in oxygen supply, high hyperglycemia, accelerated renal dysfunction, systemic inflammation, and hypercoagulability.