[Mosaic forms of ataxia-telangiectasia].

Ataxia-telangiectasia (AT) is a severe hereditary autosomal recessive neurodegenerative disease associated with accelerated aging and caused by mutation in both alleles of atm gene. This gene encodes a key protein of cell response to DNA damage--an ATM protein kinase. Normally, upon formation of DNA double strand breaks ATM is autophosphorylated and its active form phospho-ATM (P-ATM) appears. Here we describe a mosaic form of AT in which cells of the same patient with normal atm gene demonstrated the accumulation of P-ATM in response to DNA double-strand breaks-inducing factors whereas in cells bearing a mutant form of atm P-ATM was not detected. The epigenetic markers such as histone deacetylases SIRT1 and SIRT6, and trimethylated forms of histone H3 - H3K9me3 and H3K27me3--were studied in the nuclei of primary fibroblasts derived from patients with different forms of AT and the increase of SIRT6 level was revealed.

[The influence of age of donors on the ability of cells to homologous recombination DNA repair].

Old and young donors cells show different ability to homologous recombination (shown on the first stage--the chromosome transference) in vitro, that we suppose could be the reasons of the genome instability in aging. Homologous recombination, induced by X-radiation, is limited in cells taken from donors older than 70 years. Alpha-amanitin, the RNA-polymerize II repressor, in toxic doze, could induce the chromosome transference in the cells from all studied groups: from old and young donors and donors with repair process defect (with BRCA 1, 2 mutations). Summarized effect of X-radiation and alpha-amanitin does not increase the induction of the chromosome transference.

[Diagnostics of ataxia-telangiectasia by the express-test found on the method of indirect immunofluorescence].

Ataxia-telangiectasia (AT) is a hereditary severe neurodegenerative disease developing, when mutations take place in both alleles of the atm gene, which encodes the key protein of the cellular response to DNA damage (DDR)--ATM proteinkinase. In response to the occurrence of double-strand DNA breaks, the ATM proteinkinase pass the autophosphorylation, and its active form--the phospho-ATM (P-ATM) appears in cells. In the nuclei of cells having the atm gene, P-ATM is revealed, being absent in cells with mutated forms of this gene, by means of the application of the modified method of indirect immunofluorescence. This peculiarity may be applied in the clinic, in order to confirm the diagnosis of AT.

[Telomere length in the population of long-lived persons of North-West region of Russia].

Interdisciplinary study of telomere length, polymorphism of genes of renin-angiotensin (ACE) and serotonin (5HTR2A and 5HTTPR) systems in population of aged and old inhabitants of the North-West of Russia was conducted, in their relations to data from clinical and geriatric anamnesis, and psychological functioning. Regular link between telomere length and respondent's age was demonstrated in subgroups of old respondents and long-livers, by method of factor analysis.

[Metformin slows down ageing processes at the cellular level in SHR mice].

It has been shown recently that metformin, the indirect mTOR-kinase inhibitor, significantly increases medium (by 37.8%) and maximum (by 10.3%) life span of SHR mice (Anisimov et al., 2008). We obtained fibroblasts from skin of 11-, 16-, 19- and 23-months-old SHR mice treated with metformin since the third and ninth day of life. We studied markers of cellular senescence in these fibroblasts. Significant differences were observed between the average number of senescence-associated heterochromatic foci (SAHF), the average of area nuclei and fluorescence intensity of nucleus after staining for gamma-H2AX in control and experimental animals. Also, we showed that metformin prevented the accumulation of fibroblasts with large area of nuclei; high activity of senescence-associated beta-galactosidase (SA-beta-gal), and high fluorescence intensity after staining for gamma-H2AX. It appears that accumulation of large quantity of senescence markers within a cell triggers it to enter the aging process. It appears that the increase of "old" cell population above the threshold disrupts the normal function of certain tissues, organs, and finally, the whole organism. It appears that metformin delays the "old" cells accumulation and prolongs the organism youth.

[Telomere shortening is the main mechanism of natural and radiation aging].

Adduced proofs of the telomere shortening are the main or even the sole mechanism of the natural and radiation aging. All apparent contradictions, primary, the absence of exact inverse correlation between residual telomere length and the donor age are explained within the frames of the telomere theory. We try to explain in what way telomere shortening might be the cause of aging and longevity restriction. We also show the inability of the oxidative theory to explain a number of indisputable facts easily explained by the telomere theory, such as unlimited growth of tumor sells or why a new-born child starts to age from zero level rather than the level reached by the cells of his parents at the moment of conception. We postulate that if oxidative damage was entirely absent, telomeres would, nevertheless, shorten with each mitotic cycle because such is the mechanism of DNA replication, and aging would be in progress, which we invariantly observe in the presence of any antioxidants. But if telomeres do not shorten, as happens in transformed cells because telomerase works there, aging does cease and the transformed cells show no senescence. We also observe it in spite of the damaging effect of reactive oxygen species which may be even more than in normal cells.

[Telomere length of cord blood cells chromosomes as additional quality characteristic of sample for transplantation].

Telomeres are the ends of the chromosomes and represent repeated DNA sequence and protein complex. Telomeres shorten with each cell division, which limits proliferative potential of cells. There is a great progress in clinical application of telomere length now. Additional characteristic of stem cell proliferation activity estimated by telomere length can be an informative indicator of transplant quality. In this work, we analyzed 14 cord blood samples by flow-FISH, ELISA and gematologycal analisator, and also the number of CD34 + CD45dim cells. Average telomere length of leukocytes fraction CB cells was 20.4-4.9 % respectively the control cells 1301 (T-cell lymphoblastic leukemia).

[Syndrome of premature ageing in ataxia-telangiectasia patients].

Ataxia-telangiectasia (AT), a genetic disorder due to mutation of gene atm characterized by progressive neurological abnormalities in combination with oculocutaneous telangiectasias, immunodeficiency, and increased frequency of malignant formations, is inherited according to autosome recessive mechanism. Cells of the patients with AT show increased radio sensitivity and some markers of premature ageing. The telomere lengths are sharply shortened in these cells already from the birth. We studied radio sensitivity (at the dose 2 Gy) and manifestations of premature ageing markers in cultured skin fibroblasts obtained from two unrelated AT patients and their heterozygous parents. We have shown that all the markers studied, that is HP1-gamma, phosphorylation of the histone variant H2AX (gamma-H2AX), and focuses 53BP1, indicate premature ageing of both the patients' and their blood relatives' cells. However, cells of the heterozygous carriers express premature ageing to a less extent. Investigation of the repair process characteristics (the amount of gamma-H2AX and the deal of cells with focuses 53BP1 in their nuclei) after X-ray irradiation has given following results: the patients' cells complete repair only half even in 24 after irradiation, while the healthy donor's cells complete repair in 24 h. Heterozygous cells also reliably differ from healthy donor's cells. Only in the case of apoptosis marker, p21, heterozygous cells do not differ from normal cells, whereas the patients' cells differ significantly. It has been noted that the mutation of gene atm is related to suppression of DNA double-strand breaks (DSBs) repair systems, which, in its turn, is in accordance with the increased radio sensitivity and premature ageing at the cell level in the AT families.

[Cellular repair potential in families of ataxia-telangiectasia patients].

The key protein of the global cellular response to DNA damage is proteinkinase ATM. Ataxia-telangiectasia (AT), a genetic disorder due to mutations in both alleles of ATM gene, is characterized by numerous neurological abnormalities, increased frequency of malignant tumors, premature ageing and increased radio sensitivity. AT is the most frequently found disease displaying inherited radio sensitivity. The data accumulated by this time on the role of the protein ATM in regulation of cellular response to DNA damage and detailed description of its proteins-targets allows to analyze repair potential and manifestation of premature ageing markers both in the cells obtained from AT patients and in the cells of their heterozygous parents. Primary skin fibroblasts obtained from AT patients and their heterozygous parents were analyzed by the flow cytometry and comet assay. It has been shown that cells of the patient AT8SP do not initiate cell cycle blockade after ionizing irradiation during all the experiment, unlike the healthy donor cells where cell cycle blockade is observed. Irradiated cells of the heterozygous parents demonstrated less brightly expressed changes in cell cycle parameters than healthy donor's cells did. The ability to repair DNA double-strand breaks (DSBs) after irradiation is reduced in the cells of AT patients and their heterozygous parents in comparison with the healthy donor's cells. Cells of the healthy donor were capable to repair not less than 90 % of DNA damage for 2.5 h. The repair efficiency in the cells of AT patients came only to about 30 % of DNA damage and in the cells of heterozygous carries of the disease was approximately 50 %. The difference in the dynamics of DNA damage repair process in different proband's families is in accordance with the reports about great phenotypic variety of the given disease.

[The atypical of Werner syndrome: effect of laminopathy].

A case of adult progeria has been described. During detailed studies of the cells from this patient the nuclear lamina and cytoskeleton aberrations were detected. It has been suggested that this case is an atypical form of Werner syndrome with laminopathy--not the WRN helicase-nuclease defect.

[An atypical case of Werner syndrome: epigenetic control and DNA damage response alterations].

A case of adult progeria has been described. It has been suggested that this case is an atypical form of Werner syndrome with laminopathy--not WRN helicase-nuclease defect. During detailed studies of the patient's cells, epigenetic control and DNA damage response alterations were detected.

[Discrimination of heterozygote currency of ataxia-telangiectasia by indirect immunofluorescent analysis].

The qualitative differences in P53 protein stabilization after ionizing irradiation in different doses were found in cells of members of ataxia-telangiectasia (AT) family--proband AT6SP, her sister AT(S)6SP and father AT(F)6SP. The method of indirect immunofluorescence with confocal microscopy was used.

[Characteristics of p53 protein stabilization in cells of patients with ataxia-telangiectasia after gamma-irradiation].

Stabilization of P53 protein in cells isolated from patients with a grave hereditary disease ataxia-telangiectasia (AT), characterized by strongly enhanced sensitivity to ionizing radiation and impairment of cell cycle control after DNA damage, was studied. The level of expression of these reactions by patients may vary, and it tends to be linked with the severity of the disease. In all AT strains studied, both acquired by the authors and obtained from foreign colleagues, we observed the alteration of timing and character of stabilization of P53 protein, after the action of ionizing radiation in sublethal dosage, as compared to that in cells from healthy donor.

[The results of a cytogenetic examination performed in different years on those who worked in the cleanup of the aftermath of the accident at the Chernobyl Atomic Electric Power Station]. / Rezul'taty tsitogeneticheskogo obsledovaniia likvidatorov posledstvii avarii na ChAES, provedennogo v raznye gody.

Persons participated in the Chernobyl accident amelioration in the years of 1986-1987 were examined cytogenetically either in 1987 (group 1) or in 1990-1992 (group 2). The frequency of chromosome aberrations in cultured peripheral lymphocytes is found to be significantly lower in group 2 in comparison with group 1, being increased in both exposed groups as compared to the control one. The data are obtained in favour of hypothesis on chromosome instability of exposed individuals. On the base of cytogenetic data the collective dose received by amelioraters was calculated.

[Reorganization of DNA replicating system induced by 5-fluorodeoxyuridine and caffeine as the basis for radiosensitivity in human calls]. / Reorganizatsiia DNK-replitsiruiushchei sistemy, indutsiruemaia 5-flordesoksiuridinom i kofeinom, kak osnova radiochuvsvitel'nosti kletok cheloveka.

Treatment of diploid human fibroblasts with 5-fluorodeoryuridine (FUdR) and caffeine results in the increase in cellular radiosensitivity in terms of survival and chromosomal aberrations, on the one hand, and in radioresistant DNA synthesis (RDS), on the other hand, i.e. rather mimics those in mutant cells from patients with AT, XPII, Down syndrome, and others. A study was made of the autoradiographic length of simultaneously active adjacent replicon clusters. After incubation of diploid human cells with FUdR (10(-6) M, 6 h), this parameter was shown to reduce by two-fold, remaining unchanged upon 5 Gy irradiation. In contrast, after incubation of the cells with caffeine (2 mM, 30 min), this parameter was longer, compared to that in intact cells; upon 5 Gy irradiation the values remained almost the same as in the control. A possible relation of the data to the cellular radiosensitivity and RDS in the cells incubated with FUdR and caffeine is discussed.

[UV-induced unscheduled DNA synthesis in differentiated and dedifferentiated lymphocytes from human peripheral blood under the action of DNA-repair and -replication inhibitors]. / UF-indutsirovannyi vneplanovyi sintez DNK v differentsirovannykh i dedifferentsirovannykh limfotsitakh perifericheskoi krovi cheloveka pri deistvii ingibitorov reparatsii i replikatsii DNK.

The UV-stimulated unscheduled synthesis (US) of DNA has been investigated in lymphocytes of human peripheral blood in correlation with the extent of differentiation under the action of inhibitors of DNA synthesis and repair: caffeine, hydroxyurea (HU), cytosine arabinoside (ara-C) and 3-methoxybenzamide (3-MB). The US of DNA was investigated in dedifferentiated (PGA-stimulated) and in differentiated (PGA-unstimulated) lymphocytes. Caffeine and HU inhibited US of DNA more intensely in PGA-stimulated cells, and ara-C and ara-C in combination with HU--in unstimulated cells. 3-MB enhanced US of DNA in PGA-stimulated (but not in PGA-unstimulated) lymphocytes.

[Unscheduled DNA synthesis in human peripheral blood lymphocytes undergoing combined exposure to gamma irradiation and methylmethane sulfonate]. / Vneplanovyi sintez DNK v limfotsitakh perifericheskoi krovi cheloveka pri kombinirovannom deistvii gamma-oblucheniia i metilmetansul'fonata.

The value of the unscheduled DNA synthesis by exposure to combined action of damaging agents--gamma-irradiation and methyl methanesulfonate--does not exceed its value after separate actions of each particular agent in lymphocytes from healthy subjects as well as in those with Xeroderma pigmentosum in form II (XP2LE). This result is due to inhibiting effects of alkylating agents on DNA-polymerases.

[The determination of the complementation groups for the cells of patients with xeroderma pigmentosum and the Cockayne syndrome found in Russia]. / Opredelenie grupp komplementatsii dlia kletok bol'nykh pigmentnoi kserodermoi i sindromom Kokkeina, obnaruzhennykh v Rossii.

Complementation groups for xeroderma pigmentosum (XP) and Cockayne's syndrome (CS) cells have been first determined for patients encountered in the former Soviet Union. The determination was carried out using fusion of fibroblasts to be examined with those of already known complementation groups, and subsequently registering the level of DNA unscheduled synthesis (for XP cells) and RNA synthesis recovery (for CS cells) after UV-irradiation. The evidence of the complementation was normalization of these indexes. Cells of XP2SP and XP4SP patients are shown to fall under the XPC complementation group, whereas CS1SP cells are classified within the CSA complementation group.

[Repair of DNA damaged by methylmethane sulfonate in normal human lymphocytes and in xeroderma pigmentosum]. / Reparatsiia DNK, povrezhdennoi metilmetansul'fonatom, v limfotsitakh cheloveka v norme i pri pigmentnoi kseroderme.

Methylmethanesulphonate has been shown to stimulate an intensive unscheduled DNA synthesis in lymphocytes derived from normal donors as well as in those from patients with xeroderma pigmentosum of the classical form. Somewhat less intensive unscheduled DNA synthesis was observed in cells of a patient suffering from xeroderma pigmentosum. In the case of XPII unscheduled DNA synthesis was greatly reduced which supports the peculiarity of this form of xeroderma pigmentosum.