Torsional tension in metaphase chromosome DNA]

The torsional tension in DNA of isolated metaphase chromosomes from murine fibroblasts was measured by the microfluorescent method. The method is based on the ability of a fluorescent dye ethidium bromide to compensate for the negative torsional tension in topologically closed DNA by intercalation between DNA base pairs. The value of the relative twist difference delta Tw/Tw = -0.1 was found in a bulk (about 3/4) of unconstrained chromosomal DNA. In interphase nuclei, the torsionally stressed DNA comprises about 15%, with value of delta Tw/Tw = -0.075. We suppose that the tension in chromosomal DNA was created in the prophase stage of mitosis by condensines, the drivers of chromosomal condensation.     

Experience in isolating Campylobacter jejuni from patients with acute intestinal diseases

Erythrite agar, a commercial culture medium produced by the Research Institute for Culture Media (Makhachkala, USSR), is suitable for the cultivation of C. jejuni after the addition of hemolized sheep blood. The addition of antibiotics to the medium permits its use for the isolation of C. jejuni from feces. By means of this medium C. jejuni has been isolated from the feces of 10% of patients hospitalized on account of acute infectious intestinal diseases.     

Enzyme activity of adenosine metabolism in human natural killers (NK cells) during the activation and suppression of their cytotoxic activity

Experiments in vitro were made to study adenosine deaminase (ADA) and 5'-nucleotidase (5-N) activity in NK after their treatment with interferon inductor--Newcastle disease virus (NDV) or with prostaglandin E2 (PGE2). It has been established that treatment of human NK with NDV leads to increasing of their cytotoxic activity (CTA), which is accompanied by rising of ADA activity and reducing of 5-N activity in these cells. Decrease of CTA under the influence of PGE2 occurs together with reduction of ADA activity and increase of 5-N activity in human NK. Changes in NK activity under the influence of various exogenous or endogenous factors may be due to the modification of activity of adenosine metabolism enzymes in these cells.     

The Method of Transformation of Moroccan Toadflax (<Emphasis Type="Italic">Linaria maroccana</Emphasis> Hook. f.)

Plants of the genus Linaria are scientifically interesting owing to the presence of natural-transgenic forms containing a set of agrobacterial genes (so-called cT-DNA). Many Linaria species are valuable ornamental plants. However, until recently, the literature did not describe the method of genetic transformation of plants of the genus Linaria. In this paper, we present the method of in vitro agrobacterial transformation of plants of Moroccan toadflax (Linaria maroccana Hook. f.). Method of adaptation for in vivo conditions is also described. This technique will be used in further studies of the functioning of сT-DNA and can also be recommended for solving applied problems.     

Scheduled perturbation in DNA during in vitro differentiation of mouse embryo-derived cells

Studies of sister chromatid exchanges (SCE) and recombination rate of certain mini-satellite DNAs have demonstrated that their levels are considerably higher during the preimplantation stage than in latest developmental stages of embryos. It appeared likely that single-strand DNA breaks (SSB) may be relevant to both events during early development. With this in mind, we estimated SSB during in vitro retinoic acid (RA)-induced and spontaneous differentiation of mouse teratocarcinoma (EC) and embryonic stem (ES) cells. Using the method of nucleoid sedimentation and single-cell DNA electrophoresis, we have observed a dramatic increase in the SSB during the first 2–4 mitoses after beginning of differentiation of EC cells, followed by a gradual return to the basal level characteristic of undifferentiated cells. The increase in the SSB was manifested as the appearance of mass nucleoids with slow sedimentation rates, as well as the low-weight mass fragments in DNA patterns of most cells. We concluded that not less then half of genomic DNA has been nicked at the early steps of differentiation. The decrease in SSB level was observed in spite of continuing differentiation, as judged by embryonic antigens and morphological criteria. Also, the increase in the SCE level coincided with that of SSB, possibly being its consequence. The scheduled “surge” of SSB may be the earliest event in commencing differentiation at steps without a phenotypic manifestation. Mol. Reprod. Dev. 47:1–10, 1997. © 1997 Wiley-Liss, Inc.     

Dihydroquercetin (taxifolin) and other flavonoids as inhibitors of free radical formation at key stages of apoptosis

Formation of free radicals in mitochondria plays a key role in the development of apoptosis, which includes formation of superoxide by the respiratory chain, formation of radicals by cytochrome c-cardiolipin complex in the presence of hydrogen peroxide or lipids, and chain lipid peroxidation resulting in cytochrome c release from mitochondria and initiation of the apoptotic cascade. In this work the effect of taxifolin (dihydroquercetin) and some other antioxidants on these three radical-producing reactions was studied. Peroxidase activity of the complex of cytochrome c with dioleyl cardiolipin estimated by chemiluminescence with luminol decreased by 50% with quercetin, taxifolin, rutin, Trolox, and ionol at concentrations 0.7, 0.7, 0.8, 3, and 10 μM, respectively. The lipid radical production detected by coumarin C-525-activated chemiluminescence decreased under the action of rutin and taxifolin in a dose-dependent manner, so that a 50% inhibition of chemiluminescence was observed at the antioxidant concentrations of 3.7 and 10 μM, respectively. Thus, these two radical-producing reactions responsible for apoptosis onset are inhibited by antioxidants at rather low concentrations. Experiments performed on liver slices and mash showed that taxifolin, quercetin, naringenin, and Trolox have low inhibitory effect on the lucigenin-dependent chemiluminescence in the tissue only at concentrations higher than 100 μM.