Radiobiological experiments with plant seeds aboard the biosatellite Cosmos 1887

The effects of spaceflight factors on the seeds of Arabidopsis thaliana and Crepis capillaris were studied. The seeds were located inside the satellite in an open space, protected with aluminum foil and also exposed without the foil cover. When the seeds were in open space without any protection, their viability was found to be suppressed; the survival rate and fertility of plants grown from these seeds were also diminished. An increase in the frequency of chromosome aberrations (CA) and in the number of multiple injuries was registered in this case. Experiments with the aluminum foil shielding showed a decrease in the suppression of the seeds' viability, but mutational changes were found to be even more increased, while the survival rate and fertility of the plants decreased. An increase in the thickness of shielding resulted in a decrease in the effects up to the level of the control, except for the effects connected with CA and fertility of the plants. Analysis of the results shows that these impairments can be ascribed to the action of single heavy charged particles (HCP). The seeds can thus be regarded as an integral biological 'dosimeter' which allows estimation of the total effects of radiation, ecological and biological factors

Potential of machine learning methods in operational risk stratification in patients with coronary artery disease scheduled for coronary bypass surgery

Aim. To develop and evaluate the effectiveness of models for predicting mortality after coronary bypass surgery, obtained using machine learning analysis of preoperative data.Material and methods. As part of a cohort study, a retrospective prediction of in-hospital mortality after coronary artery bypass grafting (CABG) was performed in 2182 patients with stable coronary artery disease. Patients were divided into 2 following samples: learning (80%, n=1745) and training (20%, n=437). The initial ratio of surviving (n=2153) and deceased (n=29) patients in the total sample indicated a pronounced class imbalance, and therefore the resampling method was used in the training sample. Five machine learning (ML) algorithms were used to build predictive risk models: Logistic regression, Random Forrest, CatBoost, LightGBM, XGBoost. For each of these algorithms, cross-validation and hyperparameter search were performed on the training sample. As a result, five predictive models with the best parameters were obtained. The resulting predictive models were applied to the learning sample, after which their performance was compared in order to determine the most effective model.Results. Predictive models implemented on ensemble classifiers (CatBoost, LightGBM, XGBoost) showed better results compared to models based on logistic regression and random forest. The best quality metrics were obtained for CatBoost and LightGBM based models (Precision — 0,667, Recall — 0,333, F1-score — 0,444, ROC AUC — 0,666 for both models). There were following common high-ranking parameters for deciding on the outcome for both models: creatinine and blood glucose levels, left ventricular ejection fraction, age, critical stenosis (>70%) of carotid arteries and main lower limb arteries.Conclusion. Ensemble machine learning methods demonstrate higher predictive power compared to traditional methods such as logistic regression. The prognostic models obtained in the study for preoperative prediction of in-hospital mortality in patients referred for CABG can serve as a basis for developing systems to support medical decision-making in patients with coronary artery disease

A 6-year experience of the Ross procedure in children with congenital aortic valve disease

Background: The choice of an optimal method for correction of aortic valve stenosis or insufficiency remains the matter of debate. Some clinicians prefer transluminal balloon angioplasty, some would perform an open type commissurotomy, or aortic valve replacement, or to valve leaflets repair with various materials, while others opt for the Ross procedure. Each of these techniques has its advantages and disadvantages both in the early postoperative period and in the long-term.Aim: To assess the results of the Ross procedure, its complications, survival, and probability of reoperations in the long-term.Materials and methods: We retrospectively analyzed the results of 32 Ross procedures performed from the end of 2012 to the beginning of 2019 in children aged from 3 days to 18 years. Eight children were below 1 year of age, including one newborn. A pulmonary autograft was placed into the aortic position in all children. In 31 children, a homograft was placed into the pulmonary artery. In one patient, an aortic autograft was implanted instead of the pulmonary artery valve. The mean patient age was 6.8 years, mean bodyweight 27.7 kg (range, 3.9–74.6 kg).Results: Two patients died in the early postoperative period (mortality 6.25%). We examined 26 patients at the follow-up, with its mean duration of 2.5 years. There were no indications for replacement of the homograft during the follow-up. One patient, in whom we had implanted an aortic autograft into the pulmonary position, required its replacement after 4.5 years. We have no data on death rates in the long-term.Conclusion: The Ross procedure provides satisfactory results in the early and intermediate postoperative period. Continuous follow-up is needed to determine the time points and the proportion of repeated interventions with a pulmonary homograft and aortic valve

Reoperations after the correction of partial abnormal venous return: a clinical case series

Rationale: The surgical procedure for partial abnormal pulmonary venous return (PAPV) implies the formation of a tunnel between the orifices of the right pulmonary veins and the left atrial cavity with the interatrial septum repair. To avoid any obstruction of the tunnel, a direct anastomosis between the superior vena cava (SVC) and the right atrial appendage is placed in a number of cases. However, the reparative procedure is potentially associated with such complications as SVC stenosis and/or pulmonary vein stenosis. Aim: To present our experience of reoperations for stenosis of systemic and pulmonary veins after primary PAPV repair. Materials and methods: From 2014 to 2018, seven patients (boys, 4) with SVC stenosis and/or with stenosis of the right pulmonary veins have been admitted to the FCHMT (Kaliningrad). Their mean bodyweight was 29.1 kg (± 12.5 kg), mean age 9.3 years (± 3.6 years). Three patients had an isolated SVC stenosis. In two patients, there was a combination of SVC stenosis and pulmonary vein obstruction (from stenosis to complete occlusion); in one patient the right pulmonary vein stenosis had been caused by thrombosis. SVC stenosis with subaortal obstruction after the repair of double-outlet right ventricle was diagnosed in one case. In six patients, various procedures for correction of SVC and/or pulmonary vein stenosis were performed. Only in one case the obstruction of systemic veins, confirmed by cardiac catheterization, turned out to be non-significant, making a reoperation unnecessary. Results: There were no deaths in this patient group. Endovascular procedures were performed in two patients. In one case, there was an unsuccessful attempt of transluminal balloon angioplasty for SVC stenosis, with subsequent Warden procedure. In another case, a 16-year old patient with SVC stenosis and high pulmonary hypertension was admitted after two previous surgeries had failed. We used a homograft as SVC prosthesis; however, after one year, a re-stenosis was identified. In this case, a SVC stent placement was successful. Due to sick sinus syndrome at one year after the Warden procedure and the repair of pulmonary veins by a homograft, an implantation of electric cardiac pacemaker was necessary in one patient. Conclusion: The curative repair of partial abnormal venous return is a well-established surgical technique with satisfactory shortand long-term results. A potential complication of the procedure is an obstruction of systemic and pulmonary veins. To prevent such complications during primary defect repair, as well as with reoperations for vein stenosis, the Warden procedure seems effective and highly reproducible technique associated with lower surgical risks

INCREASE OF DRUG RESISTANCE OF ACUTE MYELOID LEUKEMIA CELLS IN MULTICELLULAR AGGREGATES IN VITRO

Background: Therapeutic efficiency in treatment of acute myeloid leukemia (AML) ranges from 20 to 45%. One of the causes of the latter is a drug resistance acquired by leukemic cells under the influence of treatment with antitumor medicines. More important cause is a development of the primary resistance of myeloid leukemic cells to induction of cellular death associated with elemental microenvironment within the bone marrow. Studying primary resistance is very important, and first of all, to prevent development of drug resistance of leukemic cells and, correspondingly, to increase the efficiency of medicamental therapy. Aim: To study the mechanisms of primary resistance of AML cells to induction of cellular death. Materials and methods: Human AML cells of THP-1 line and mononuclear cells of the bone marrow were used in the study of patients with diagnosed AML. Multicellular aggregates were formed during cell cultivating on the 1.5% agarose. To cut off intercellular adhesion, the cells were cultivated in the medium with methylcellulose (0.9%). The viability of the cells was assessed by reduction of Alamar Blue indicator. Results: Within multicellular aggregates, about 75±5% of THP-1 cells were resistant to the activity of recombinant protein izTRAIL, 70±5% – to etoposide, and 40±7% – to sorafenib. Cutting off intercellular contacts decreased the resistance to them. Within multicellular aggregates of primary mononuclear cells, 45±5% of cells were resistant to sorafenib, 57±4% – to etoposide, and all cells were resistant to izTRAIL. Cutting off intracellular adhesion reduced the resistance to sorafenib and etoposide but not to izTRAIL. Conclusion: In multicellular aggregates, AML cells of THP-1 line and mononuclear cells of the bone marrow showed increased resistance to activity of recombinant protein izTRAIL, etoposide, and sorafenib. Diminishing intracellular adhesion in the medium including methylcellulose decreases cellular resistance to cytotoxic agents