Расчет ГИН по схеме Аркадьева-Маркса

Объектом исследования является генератор импульсного напряжения по схеме Аркадьева-Маркса. Цель работы: спроектировать и рассчитать генератор импульсных напряжений. В процессе работы рассчитаны количественные значения элементов ГИНа: значения коэффициентов использования разрядной схемы и волны; емкость и индуктивность конденсатора; количество ступеней; фронтовое и разрядное сопротивления. Был выполнен расчет ресурсов, ставки налогов, отчислений. Так же было описаны рабочее место и законодательные и нормативные документы.The object of study is the generator of pulse voltage according to the scheme Arkadiev-Marx. Objective: to design and calculate the voltage impulse generator. In the process, the calculated quantitative values of the elements of a Hin: the coefficients of use of the discharge circuit and wave; the capacitance and inductance of the capacitor; number of steps; the front and discharge resistors. Calculated resources, tax rates, deductions. As described workplace and legislative and regulatory documents

Mesodermal fate decisions of a stem cell: the Wnt switch

Stem cells are a powerful resource for cell-based transplantation therapies in osteodegenerative disorders, but before some kinds of stem cells can be applied clinically, several aspects of their expansion and differentiation need to be better controlled. Wnt molecules and members of the Wnt signaling cascade have been ascribed a role in both these processes in vitro as well as normal development in vivo. However some results are controversial. In this review we will present the hypothesis that both canonical and non-canonical signaling are involved in mesenchymal cell fate regulation, such as adipogenesis, chondrogenesis and osteogenesis, and that in vitro it is a timely switch between the two that specifies the identity of the differentiating cell. We will specifically focus on the in vitro differentiation of adipocytes, chondrocytes and osteoblasts contrasting embryonic and mesenchymal stem cells as well as the role of Wnts in mesenchymal fate specification during embryogenesis

Identification and fate of a marker chromosome in methotrexate-resistant V79,B7 cells by flow karyotyping and sorting, metaphase analysis and in situ hybridization.

The chromosomes from a methotrexate (MTX)-resistant and its parental V79,B7 Chinese hamster cell line were analysed by the combined use of flow karyotyping and sorting, metaphase analysis and in situ hybridization with a probe for the dihydrofolate reductase (DHFR) gene responsible for methotrexate resistance. A marker chromosome with an elongated arm carrying the amplified DHFR gene was identified by in situ hybridization of metaphase cells of the methotrexate-resistant line. In the flow karyotype the marker chromosome was found as an additional peak with a higher DNA content compared with the largest chromosome of the sensitive line. This was additionally verified by G-banding of the chromosomes sorted from the marker peak. Several other chromosomal rearrangements not associated with the amplified gene could be identified in the methotrexate-resistant line by the combined use of flow karyotyping and metaphase analysis. The fate of the original marker chromosome was studied in cells growing several weeks in the absence of methotrexate, comparing flow karyotyping and metaphase analysis. The original marker chromosome was lost in about 50% of the cells after 5 weeks and in about 60% of the cells after 8 weeks; between 80 and 90% of the cells, however, contained marker chromosomes of various sizes. The MTX-resistance decreased in parallel during loss of the original marker chromosome. In conclusion, the study shows that the power of cytogenetic analysis is improved by the combined use of conventional cytogenetics, molecular cytogenetics and flow cytometry

Induction of kinetochore positive and negative micronuclei in V79 cells by the alkylating agent diethylsulphate.

The induction by diethylsulphate of micronuclei derived from acentric fragments or from whole chromosomes was studied in Chinese hamster V79 cells using autoantibodies from the serum of a scleroderma patient (CREST-syndrome) to detect centromere--kinetochore structures. Centromere-containing micronuclei appeared early after treatment and plateaued both earlier and at lower level than centromere-lacking micronuclei. The frequency of centromere-containing micronuclei was in good agreement with that of mitotic chromosome displacement, suggesting that a high proportion of displaced chromosomes were transmitted to the cytoplasm of one of the two daughter cells, where they gave rise to micronuclei. On the contrary, centromere-lacking micronuclei were more frequent than what could be expected from chromosome fragments observed in mitotic stage

Micronuclei induced by 2-chlorobenzylidene malonitrile contain single chromosomes as demonstrated by the combined use of flow cytometry and immunofluorescent staining with anti-kinetochore antibodies.

The effects of the tear gas 2-chlorobenzylidene malonitrile (CS) on micronucleus induction and cell cycle kinetics were studied in Chinese hamster and Ehrlich ascites tumour cells using flow cytometric analysis of micronuclei and nuclei in suspension, and indirect immunofluorescent staining of kinetochores in micronuclei. In both cell lines CS induced a concentration-dependent inhibition of the fraction of cells in mitosis as observed by simultaneous flow cytometric measurements of DNA content and side scatter intensities of cell nuclei. Micronucleus frequency increased during the delayed division of cells accumulated by CS in mitosis and reached a plateau when most of these cells have divided. The height of this plateau depended on the CS concentration. Results obtained by flow cytometric analysis of the frequency of CS-induced micronuclei did not agree quantitatively with results obtained by microscopic analysis due to cells showing CS-induced fragmented nuclei. Nearly all CS-induced micronuclei exhibited kinetochores, the majority of which (60-70%) showed one kinetochore per micronucleus implying the presence of a single metaphase chromosome in these micronuclei. DNA distributions of micronuclei measured by flow cytometry showed pronounced peaks corresponding to the DNA distribution of chromosomes measured by flow karyotyping. Even micronuclei containing two of the large chromosomes could be observed as distinct peaks in the distributions. The combined results of flow cytometric analysis of micronucleus distributions and immunofluorescence staining of kinetochores in micronuclei suggest that CS induces micronuclei mainly by damaging the spindle fibres of single chromosomes during mitosis, thus possibly leading to aneuploidy and polyploidy

Antikinetochore antibodies and flow karyotyping: New techniques to detect aneuploidy in mammalian cells induced by ionizing radiation and chemicals.

For a possible detection of aneuploidy induction by chemicals and ionizing radiation, fluorescein-bound antikinetochore antibodies (CREST-scleroderma antibodies) were used to discriminate between micronuclei deriving from acentric fragments or from chromosome loss induced in Chinese hamster cells. The cells were treated with aphidicolin, adriamycin, Hoechst 33258, colcemid, the alkylating agent diethyl sulfate, and ionizing radiation. The frequency of micronucleated cells, the fraction of kinetochore-positive and -negative micronuclei per cell, and the fraction of kinetochore-positive micronuclei was measured using immunofluorescence staining of kinetochores in micronuclei. Of the micronuclei and fragmented nuclei induced by colcemid, 99% contained kinetochores, whereas ionizing radiation induced only 4% of kinetochore-positive micronuclei. The other drugs induced variable, in some cases also cell-cycle-dependent, fractions of kinetochore positive micronuclei. With this technique a discrimination between clastogenic effects and effects that occur at the level of spindle formation of the agent studied seems to be possible. Flow karyotyping was used to study the induction of stable homogeneous and numerical aberrations in diploid Chinese hamster cell clones that had survived a dose of 15 Gy gamma-radiation. All analyzed clones showed deviations in their flow karyotypes: the mean number was 9.2 deviations per clone, compared to 1.1 deviations per clone in unirradiated control clones

Flow Cytometric Analysis of Bromodeoxyuridine (BrdU)-Induced Micronuclei.

The effects of DNA substitution by the thymidine analogue 5-bromodeoxyuridine (BrdU) on cell cycle progression and micronucleus induction were studied in different mammalian cell cultures. Simultaneous flow cytometric measurements of DNA content and side scatter of nuclei in Chinese hamster embryo (CHE) cells revealed a concentration-dependent temporary block in the G2/M phase of the first cell cycle. NTH 3T3 cells and human amniotic fluid fibroblast-like cells, on the contrary, did not show any cell cycle disturbances in the presence of BrdU. Micronucleus frequency increased as soon as CHE cells started to divide and reached a plateau when all cells have divided. The height of this plateau was almost equal for 60 and 100 μM BrdU. This saturation of micronucleus induction was due to a saturation of BrdU incorporation into DNA already at a dosis of 60 μM as shown by the BrdU/Hoechst quenching technique. Indirect immunofluorescent staining of kinetochores with CREST antibodies revealed that nearly all BrdU-induced micronuclei were kinetochore-negative suggesting the presence of acentric chromosome fragments in these micronuclei. DNA distributions of micronuclei measured by flow cytometry showed several peaks representing micronuclei which contain DNA fragments of defined sizes induced by non-random breakage of chromosomes 1 and X as verified by flow karyotyping and C-banding