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Calcium-binding calmyrin forms stable covalent dimers in vitro, but in vivo is found in monomeric form.

100%
Sobczak A., Blazejczyk M., Piszczek G., Zhao G., Kuznicki J., Wojda U.
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2005
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vol. 52
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issue 2
469-476
EN
The EF-hand Ca^(2+)-binding protein calmyrin is expressed in many tissues and can interact with multiple effector proteins, probably as a sensor transferring Ca^(2+) signals. As oligomerization may represent one of Ca^(2+)-signal transduction mechanisms, we characterised recombinant calmyrin forms using non-reducing SDS/PAGE, analytical ultracentrifugation and gel filtration. We also aimed at identification of biologically active calmyrin forms. Non-reducing SDS/PAGE showed that in vitro apo- and Ca^(2+)-bound calmyrin oligomerizes forming stable intermolecular disulfide bridges. Ultracentrifugation indicated that at a 220 µM initial protein concentration apo-calmyrin existed in an equilibrium of a 21.9 kDa monomer and a 43.8 kDa dimer (trimeric or tetrameric species were not detected). The dimerization constant was calculated as Ka = 1.78 × 103 M^(-1) at 6oC. Gel filtration of apo- and Ca^(2+)-bound calmyrin at a 100 µM protein concentration confirmed an equilibrium of a monomer and a covalent dimer state. Importantly, both monomer and dimer underwent significant conformational changes in response to binding of Ca^(2+). However, when calmyrin forms were analyzed under non-reducing conditions in cell extracts by Western blotting, only monomeric calmyrin was detected in human platelets and lymphocytes, and in rat brain. Moreover, in contrast to recombinant calmyrin, crosslinking did not preserve any dimeric species of calmyrin regardless of Ca^(2+) concentrations. In summary, our data indicate that although calmyrin forms stable covalent dimers in vitro, it most probably functions as a monomer in vivo.
2
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Detection of damage-recognition proteins from human lymphocytes.

100%
Łanuszewska J., Cudak A., Rzeszowska-Wolny J., Widłak P.
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2000
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vol. 47
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issue 2
443-450
EN
Proteins recognizing and binding to damaged DNA (DDB-proteins) were analyzed in human lymphocytes obtained from healthy donors. Using an electrophoretic mobility shift assay several complexes between nuclear extract proteins and damaged DNA were detected: a complex specific for DNA damaged by N-acetoxy-N-acetylaminofluorene, another complex specific for UV-irradiated DNA, and two complexes specific for DNA damaged by cis-dichlorodiammine platinum. All the detected complexes differed in electrophoretic mobility and possibly contained different proteins. Complexes specific for free DNA ends were also detected in protein extracts from lymphocytes.
3
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The rapid interphase chromosome assay (RICA) implementation: comparison with other PCC methods

100%
Sommer S., Buraczewska I., Sikorska K., Bartłomiejczyk T., Szumiel I., Kruszewski M.
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issue 4
933-941
EN
A report is presented on the advantages of the rapid interphase chromosome assay (RICA) and the difficulties that may be met while implementing this method for application in biological dosimetry. The RICA test can be applied on unstimulated human lymphocytes; this is an advantage in comparison with the dicentric chromosomes or micronucleus tests. In the former two tests, stimulated lymphocytes are examined and hence, 48 h more are needed to obtain cells traversing the cell cycle. Due to the use of unstimulated nondividing cells, higher numbers of cells are available for RICA analysis than for dicentric chromosomes or micronuclei tests. Moreover, the method can be applied after exposure to ionizing radiation doses in excess of 5 Gy. Such doses cause a significant cell cycle delay or result in the loss of G2 phase and mitotic cells because of apoptosis. Therefore, the traditional biodosimetry based on the evaluation of the incidence of damage to chromosomes is very difficult to carry out. This is due to the lack of an adequate number of mitotic cells for analysis. RICA is free of this disadvantage. An automatic microscope can be used to retrieve cell images; automatic image analysis can also be used.
4
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Apoptosis induced by membrane damage in human lymphocytes; effects of arachidonic acid and its photoproducts.

88%
Zarębska Z., Zielińska J., Zhukov I., Maśliński W.
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2005
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vol. 52
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issue 1
179-194
EN
The effect of arachidonic acid (AA) combined with UVA irradiation was studied in a model system mimicking phototherapy PUVA (psoralen+UVA) ex vivo in vitro. The contribution of damage to the plasma membrane by PUVA was tested on human lymphocytes derived from healthy donors. The effect of arachidonic acid (AA) combined with UVA irradiation was compared with that of a psoralen photoadduct to AA added to the culture. The adduct, obtained photochemically and purified, was characterized by NMR and MS spectrometry as a cycloadduct of psoralen to the vinylene bond of the acid (AA<>PSO). The reactions of cultured cells, manifested 20 h after treatment by changes in apoptosis and mitochondrial depolarization, were monitored by flow cytometry by tagging lymphocytes with appropriate fluorescent probes. Treatment of lymphocyte suspension within AA doses from 40 to 100 μM gradually induced a shift from Anx-V+ (single positive cells) to late apoptotic, Anx-V+PI+ (double positive cells) in a dose dependent manner. The adduct, AA<>PSO, induced apoptotic changes at a concentration 2-3 times higher than free AA. Combination of psoralen (1 μM ) or arachidonic acid (20-120 μM) with UVA irradiation (2-6 J/cm2) accelerated the plasma membrane changes in a synergic way. Preliminary studies indicated that changes in the transmembrane potential of mitochondria paralleled the apoptosis when cells were treated by AA alone. Our findings showed that UVA radiation of lymphocytes in the presence of arachidonic acid, as in the presence of psoralen, enhanced apoptosis of cells in a synergic manner. Thus, PUVA-induced apoptosis may proceed in part by a still undefined signaling pathway(s) triggered in lymphocyte membranes.
5
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DNA damage and repair in lymphocytes of normal individuals and cancer patients: studies by the comet assay and micronucleus tests.

75%
Palyvoda O., Polańska J., Wygoda A., Rzeszowska-Wolny J.
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2003
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vol. 50
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issue 1
181-190
EN
A population study is reported in which the DNA damage induced by γ-radiation (2 Gy) and the kinetics of the subsequent repair were estimated by the comet and micronucleus assays in isolated lymphocytes of 82 healthy donors and patients with head and neck cancer before radiotherapy. The parameters of background and radiation-induced DNA damage, rate of repair, and residual non-repaired damage were measured by comet assay, and the repair kinetics for every donor were computer-fitted to an exponential curve. The level of background DNA damage before irradiation measured by comet assay as well as the level of micronuclei were significantly higher in the head and neck cancer patient group than in the healthy donors, while the parameters of repair were widely scattered in both groups. Cancer patient group contained significantly more individuals, whose irradiated lymphocytes showed high DNA damage, low repair rate and high non-repaired DNA damage level. Lymphocytes of donors belonging to this subgroup showed significantly lower inhibition of cell cycle after irradiation.
6
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Thiamine prevents X-ray induction of genetic changes in human lymphocytes in vitro.

75%
Konopacka M., Rogoliński J.
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vol. 51
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issue 3
839-843
EN
The effects of thiamine (vitamin B1) on the level of spontaneous or radiation-induced genetic changes in human lymphocytes in vitro were studied. Cultured lymphocytes were exposed to increasing concentrations of thiamine (0-500 μg/ml) and irradiated with X-rays. The DNA damage was estimated as the frequency of micronuclei and apoptotic or necrotic morphological changes in fixed cells. The results show that thiamine alone did not induce genetic changes. A significant decrease in the fraction of apoptotic and necrotic cells was observed in lymphocytes irradiated in the presence of vitamin B1 at concentrations between 1-100 μg/ml compared to those irradiated in the absence of thiamine. Vitamin B1 at 1 and 10 μg/ml decreased also the extent of radiation-induced formation of micronuclei. Vitamin B1 had no effect on radiation-induced cytotoxicity as measured by nuclear division index. The results indicate that vitamin B1 protects human cells from radiation-induced genetic changes.
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