Search PubMed⌕ Search

Biomedical subjects

M Korbelik

Publications and source records attributed to M Korbelik.

53 records · Page 3Linked to original sources
PubMed1989

The influence of cathepsin B and leupeptin on potentially lethal damage repair in mammalian cells.

Cell response to irradiation depends on many micro-environmental and intracellular factors. It is known that proteinases control many physiological functions and are also involved in progression of the cell cycle. They also could be involved in cell response to irradiation. In this work the influence of cathepsin B, which is one of the important lysosomal proteinases, and one of its inhibitors, leupeptin, on the potentially lethal damage repair (PLDR) was studied. Chinese hamster V79 cells were irradiated with gamma rays in the plateau-phase of growth. Immediately after irradiation cathepsin B or leupeptin were added to the growth medium. Four hours later, a determined sufficient period of time for maximal PLDR, the cells were replated to assess survival and mutation induction. Mutation frequency was determined at the hypoxanthine-guanine phosphoribosyltransferase (HGPRT) locus using resistance to 6-thioguanine (6-TG). Simultaneously, the activity of cysteine, aspartic and serine proteinases were determined at different postirradiation intervals. The results show that when plateau-phase cells were incubated with cathepsin B during the postirradiation interval strong inhibition of PLDR was observed, accompanied with a reduced number of 6-TG resistant mutants. If leupeptin was added, more modest inhibition of PLDR was observed, accompanied with only slight reduction in the mutation frequency. The addition of cathepsin B or leupeptin to irradiated cells modified the activities of intracellular proteinases. As the highest alterations in proteinase activities were observed at the time when maximum repair of DNA lesions occurred, the biological consequences could involve a series of sequential steps in intracellular proteinase activities.

Animals↗
PubMed1989

Substance immunologically cross-reactive with insulin (SICRI) stimulates cell division.

A substance immunologically cross-reactive with insulin (SICRI) was isolated and purified from murine melanoma B16. Biochemical and biological data provide evidence that SICRI and insulin are two distinct biologically active agents. In vitro, SICRI has stimulated the DNA and protein synthesis, cell growth or colony-forming ability of 19 normal and transformed cell lines of human and rodent origin. It indicates that SICRI is a potent nonspecific growth factor. The most pronounced stimulatory effect of SICRI on proliferative capacity of cells is observed with cells at G0/G1 point of the cell cycle.

Animals↗
PubMed1989

Inactivation of hypoxic cells by cisplatin and radiation at clinically relevant doses.

We have examined the effects of exposure to cisplatin (cis-diamminedichloroplatinum(II] on the response of exponentially growing V79 cells to low (0-4 Gy) and high (up to 30 Gy) doses of X rays under hypoxic and aerobic conditions. Survival in both dose regions was assessed by clonogenic assays; the low-dose studies were facilitated by a Cell Analyser (B. Palcic and B. Jaggi, Int. J. Radiat. Biol. 50, 345-352 (1986]. The results show that cisplatin, like its isomer trans-DDP, exhibits greater interaction with low than with high radiation doses in hypoxic cells. This increased interaction could be seen even with subtoxic exposures to cisplatin as low as 1 mumol dm-3. In contrast, with cells irradiated in air in the presence of either complex, the interaction seen with high doses of radiation is completely lost or greatly diminished in the low radiation dose region. Further experiments showed that enhanced interaction of hypoxic cells with low doses of radiation could be equally effective with cisplatin pretreatments in air or in hypoxia, even if the cells are exposed to cisplatin only after irradiation. In experiments with nonproliferating plateau-phase cultures, the same enhanced interaction was observed in the low-dose region. These results, for example enhancement ratios of 2.3 and 1.2 at low- and high-dose regions, respectively, for 5 mumol dm-3 cisplatin, are contrasted with those for nitroimidazoles which are better sensitizers in the high-dose region.

Aerobiosis↗
PubMed1989

Oxygen enhancement ratio of fractionated regimens in vitro.

The oxygen enhancement ratio (OER) of proliferating and nonproliferating cells grown in vitro was measured using accelerated fractionated regimens. Irradiations were performed either twice daily or three times per day, with a minimum of 6 h between the consecutive fractions. The dose delivered was 2.3 Gy per fraction. Two significant observations were made: (i) the OER of accelerated fractionation regimens for proliferating cells is lower than that obtained from single-exposure experiments at 2.3 Gy (approximately 1.4 vs 2.4, respectively), while for nonproliferating cells it is approximately the same (2.3); (ii) the fractionated regimen does not spare proliferating cells irradiated under hypoxic conditions, and thus the fractionated survival curve lies below the single-exposure curve. For cells irradiated under aerobic conditions or for nonproliferating cells, irradiated under either hypoxic or aerobic conditions, the fractionated survival curve lies above the single-exposure curves as expected.

Animals↗
PubMed1988

Modification of potentially lethal damage repair by some intrinsic intra- and extracellular agents: I. Proteinases and proteinase inhibitors.

The effects of nine intra- and extracellular proteinases and six proteinase inhibitors on the repair of potentially lethal damage (PLDR) induced by gamma-rays in plateau-phase V79 cells were examined. It was demonstrated that these agents, which are intrinsic factors produced within mammalian cells, can modify PLDR activity. A stimulatory effect on PLDR was seen with calf liver neutral proteinase, and to a lesser extent, with inhibitor pepstatin A. Other proteinases which belong to serine, cysteine and aspartic superfamilies, as well as proteinase inhibitors, inhibited PLDR to different degrees. The effects of some of these agents, present during the PLDR period, on the rate of tritiated thymidine incorporation into the acid-insoluble cell fraction was also examined. They can modify the DNA synthesis of cells when subcultured from plateau phase for the assessment of colony-forming ability. There is no clear evidence that the effects observed are entirely attributed to the alteration of cellular proliferative processes. It seems more likely that many serine and cysteine proteinases and their inhibitors can adversely affect the PLDR process by modulating the activity of proteinase(s) and other enzymes involved more directly in PLDR because of interrelationships of the entire intracellular proteinase system.

Animals↗
PubMed1988

The role of proteinases, interferons and hormones in proliferative activities of nonmalignant and malignant cells.

Proliferative responses, in form of colony forming ability, of nonmalignant Chinese hamster fibroblasts (V79) and malignant human laryngeal carcinoma cells (HEp) were examined after treatment with proteinases, proteinase inhibitors, interferons or hormones, in G0-phase, early G1-phase and G1/S point of the cell cycle. These phases of the cell cycle are of particular importance from the point of control and regulation of the proliferative activity of cells, and the effects of proteinases and other agents examined in this study occurred predominantly at these points. Among the agents tested, cysteine proteinase inhibitor (CPI) and calf liver neutral proteinase acted differently on malignant cells as compared to nonmalignant cells: they inhibited the proliferative commitment of malignant HEp cells in early G1-phase, while stimulated colony formation of V79 cells at the same point of the cell cycle.

Animals↗
PubMed1986

The effect of intracellular proteinases on transformation of human lymphocytes.

The effect of two intracellular proteinases, calf liver chymotrypsin-like neutral proteinase and human brain cathepsin H, and of two proteinase inhibitors, leupeptin and endogenous cysteine proteinases inhibitor, was studied on unstimulated and mitogen-stimulated peripheral human blood lymphocytes. Classification of blood samples into four types, on the basis of their potential for spontaneous and mitogen-stimulated transformation, helped in analyzing the results. Within some of these types, at least, there appears certain uniformity of response to proteinase action. Lymphocytes most susceptible to proteinase action were those that were insensitive to phytohemagglutinin mitogenic stimulus. The maximal effect of proteinases or their inhibitors was obtained most often when these agents were added to lymphocyte cultures 24 hours before mitogen. Both proteinases, although of quite different specificities, gave very often results of similar trend on the same lymphocyte culture. Moreover, this was followed also by the two inhibitors, which showed not only inhibitory, but also potentiating power of action on lymphocyte transformation. The regulatory nature of the action of proteinases within lymphocytes and other cells is underlined.

Animals↗
PubMed1985

Bleomycin and misonidazole cytotoxicity.

Chinese hamster ovary (CHO) cells were exposed in vitro to combinations of bleomycin and misonidazole under hypoxic conditions. Only one drug was present at any given time and cells were washed before being exposed to the second drug. Both drugs induced potentially lethal damage (PLD). This damage was repaired under hypoxic conditions very rapidly, and bleomycin-induced PLD was repaired more rapidly than misonidazole-induced PLD. If, after the combined treatment, cells are kept in hypoxia, much of the damage can be repaired.

Animals↗
PubMed1982

Biochemical and biological characteristics of leucocyte proteinase inhibitors.

Pig leucocytes contain inhibitors of neutral and thiol proteinases. These proteins could be isolated from post-granule supernatant fraction as well as from nuclear extract using ion exchange chromatography, gel chromatography and affinity chromatography. Inhibitors differ in molecular weight, isoelectric point, immunologically and their inhibition ability against tested enzymes.

Animals↗
PubMed1980

The mutagenicity of nitroaromatic drugs: effect of metronidazole after incubation in hypoxia in vitro.

The analysis of induction of chromosomal aberration after incubation of V79-379A cells with 10 mM metronidazole in aerobic and hypoxic conditions has shown that, in concordance with cytotoxic effect, this drug exhibits a significant clastogenic action i hypoxic, but not in oxic cells. The duration of the post-incubation period after incubation with drug is important for expression of chromosomal damage. It is probable that other nitroaromatic drugs showing enhanced cytoxicity in hypoxia, which are widely used in medicine, could also belong to such specific class mutagens.

Animals↗
PubMed1975

DNA-to-protein cross-linking in synchronized HeLa cells exposed to ultra-violet light.

The U.V.-induced DNA-to-protein cross-linking in synchronously growing HeLa cells exhibits age-dependent variations. The maximum yield of cross-linking is observed during S-phase and exposure of mid-S cells to 250 ergs/mm2 renders about 22 per cent of DNA unextractable owing to cross-linking with proteins. Cells irradiated in G1 or G2 exhibit much smaller amount of cross-linking. The unextracted DNA was recovered from the protein fraction, and the addition of 0-5 per cent trypsin solution rendered all the DNA extractable. Fluctuations in the age-response pattern for the yield of DNA-protein cross-links varies throughout the cell-cycle in the same way as the efficiency for cell-killing, i.e. cells are resistant in G1, sensitive as they move into and through the S phase, and resistant again in G2. Dose-response curves determined at different times in the cycle reveal that up to about 500 ergs/mm2 the amount of DNA recovered from S cells decreased for about 8 per cent for every 100 ergs/mm2 of U.V. light. The amount of recovered DNA remained unchanged for cells exposed to 500 ergs/mm2 in the middle of S, for as long as 8 hours after exposure, i.e. for as long as the experiments were carried out no recovery from this damage was observed.

DNA↗
PubMedDate not supplied

Misonidazole and potentially lethal damage.

The existence of potentially lethal damage (PLD) is demonstrated in exponentially growing CHO cells exposed to misonidazole in hypoxia. The method of hypertonic post-treatment of cells was used in these studies. Misonidazole-induced PLD differs in many characteristics from radiation-induced PLD. The repair kinetics of misonidazole-induced PLD are much slower than for the repair of radiation-induced PLD (hours vs. minutes). No significant repair of misonidazole-induced PLD took place at 25 degrees C. Other differences are discussed. Hypertonic post-treatment of irradiated cells which had been pre-incubated with misonidazole to non-toxic levels, gave survival data consistent with the interpretation that no radiation PLD can be induced in such cells.

Aerobiosis↗
PubMedDate not supplied

Energy and misonidazole toxicity: the effects of 5-thio-D-glucose.

Cell inactivation and DNA damage (single-strand breaks) were used to study the effects of inhibitors of anaerobic glucose oxidation on the toxicity of misonidazole to hypoxic Chinese hamster cells. Citrate and 2-deoxyglucose produced no effects on the toxicity. 5-thio-D-glucose (5-TG) protected cells of the CH2B2 line to some extent (SSB decreased by about 30%). In the CHO lines used (wild, and ethylmethanesulfonate-sensitive mutants), 5-TG had varied effects. Non-protein sulfhydryl (NPSH) levels were measured in all lines. Cells with lower NPSH levels are more sensitive to misonidazole; these are the cells which are protected by 5-TG. Cell line variations must be considered when studying interactions between a drug and other forms of treatment as possible treatments of cancer.

Animals↗