Biomedical subjects

M Osmak

Publications and source records attributed to M Osmak.

At least 55 records · Page 3Linked to original sources

PubMed1991

Mechanisms involved in resistance of preirradiated Chinese hamster V79 cells to cytotoxic drugs are multifactoral.

We found previously that Chinese hamster V79 cells irradiated with multiple fractions of gamma rays (0.3 Gy of gamma rays daily, five times per week over 12 weeks) become resistant to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and vincristine sulfate (VCR), sensitive to methotrexate and cis-dichlorodiammineplatinum (II), but exhibit no change in their sensitivity to gamma rays and ultraviolet light. The aim of this study was to elucidate the mechanisms by which these cells acquire the resistance to MNNG and VCR. Flow cytometric analysis shows this induced resistance is not the result of parasynchronization, i.e. the selective killing of the cells in the sensitive part of the cell cycle. The levels of protective molecules, glutathione, and metallothioneins were significantly increased in V79 cells irradiated with multiple fractions of gamma rays. Addition of verapamil reverses the resistance of these cells to VCR, suggesting the involvement of plasma membrane-associated P-glycoprotein in acquiring resistance to VCR. We infer that mechanisms of resistance to MNNG and VCR are multifactoral, involving changes in the plasma membrane as well as an increase in the cellular levels of glutathione and metallothioneins. Both mechanisms may be responsible for the non-effectiveness of the treatment for cancer, in which radiotherapy is used during or before chemotherapy.

Animals↗

PubMed1991

The influence of mouse sera, regenerating liver extracts and bacterial products on the abilities of different cells in vitro.

In the complexity of host tumor relations, the regeneration of the tissue in which the tumor is growing, or in some other tissue in the organism, could influence the maturation of tumor cells, i.e. tumor reversion. Clinical observations and experiments on plants, lower animals, or animal embryos, performed by several authors, and our results on the influence of regenerating mouse liver on the abilities of tumor transplanted there or elsewhere in the organism led us to study the in vitro growth of different cells or bacteria exposed to the extracts of normal or regenerating liver and/or sera from these animals. Further, sterile used bacterial media were added to bacterial or cell cultures, respectively. Depending on the model, liver extracts-particularly extracts and sera from mice with regenerating liver-were shown to inhibit radioactive thymidine incorporation in the cells. In these experiments, the number of bacteria or cells per culture was lower than in otherwise treated corresponding cultures. Further, used sterile media of bacterial cultures stimulated the growth of bacteria but inhibited thymidine incorporation into fibrosarcoma cells in vitro. Whether this means that one or several common regulators exist in nature appears as an intriguing, but still completely open question. The idea of controlling tumor growth by using such regulatory growth factors seems very provocative.

Animals↗

PubMed1990

6-Deoxy-6-bromo-ascorbic acid inhibits growth of mouse melanoma cells.

The influence of 6-deoxy-6-bromo-ascorbic acid (6-Br-AA) and ascorbic acid (AA) on the growth of mouse melanoma cell line B16, mouse fibroblasts (L929), and human cervical carcinoma HeLa cells was examined by in vitro experiments. 6-Br-AA was added in concentrations 10(-1) to 10(-8)M and for incubation periods of 2, 18, 24 and 72 h. The present results indicate that 6-Br-AA exhibits a highly pronounced inhibiting effect on growth and DNA synthesis of melanoma cells. Inhibitory effect of 6-Br-AA was confirmed by the in vivo experiments. The tumor-suppressing effect on solid melanoma B16 was attained with 9 mg per mouse given three times daily for 16 days. Our preliminary results indicate that 6-Br-AA could serve as a potential antitumor agent.

Animals↗

PubMed1990

Opposing influence of age on the growth and colony-forming ability of mouse melanoma B16 and mammary adenocarcinoma: correlation with natural killer activity.

C57B1 and CBA mice of different ages (6, 12, 26 or 35 weeks) received intramuscular inocula of melanoma B16 or mammary adenocarcinoma (MCa), respectively. Median survival time was shorter, the younger the recipients. Tumor enlargement was correspondingly retarded in older mice. This was associated with decrease of natural killer (NK) activity in the spleens. However, the cytotoxicity against fresh syngeneic tumor cells, increased with age in CBA mice. In contrast to the growth of intramuscular tumors, the ability of intravenously injected B16 or MCa cells to form nodules in the lungs was significantly superior in old animals (35 weeks or more), with low levels of NK activity, than in young ones (6 weeks) with high levels of NK activity. Stimulation of NK activity by poly(I).poly(C) reduced the number of MCa colonies by 50% in the lungs of old mice, but had no effect on colony-forming ability in young animals. The observed association of tumor growth with age and NK activity levels may reflect (a) an interplay of tumor-inhibiting and tumor-promoting effects of NK cells, changing with age, and (b) the accessibility of tumor cells, inoculated intramuscularly or captured in the lungs, to these influences.

Adenocarcinoma↗

PubMed1990

Multiple small exposures of filtered mid-UV radiation increase the resistance of Chinese hamster cells to far-UV, mid-UV and filtered mid-UV radiation.

The response of Chinese hamster cells (V79-MI2G) to multiple, low doses of filtered mid-UV radiation (wavelengths longer than 300 nm) were examined over an exposure period of 30 days. Cell survival and the induction of mutation at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus using resistance to 6-thioguanine (TG) were the endpoints in this study. With increasing total accumulated dose given at 500 J/m2/day as a single short exposure, an increased resistance to cell killing was observed. This increase in resistance to cell killing was accompanied by a gradual decrease in sensitivity to the induction of mutants resistant to 6-TG. Above total accumulated doses of 5000 J/m2 the frequency of 6-TG resistance did not increase. After multiple doses of filtered mid-UV radiation the cells became more resistant to subsequent challenges with acute doses of far-UV, mid-UV or filtered mid-UV. The increased resistance to the cell killing action and to the mutation induction by UV suggests that during exposure to low, multiple doses of filtered mid-UV radiation the cells become adapted to the damaging effects of filtered mid-UV radiation.

Adaptation, Physiological↗

PubMed1990

Dynamics of postirradiation intracellular cysteine and aspartic proteinases profiles in proliferating and nonproliferating mammalian cells.

Dynamics of postirradiation intracellular cysteine and aspartic proteinases profiles were examined in proliferating and nonproliferating Chinese hamster fibroblasts (V79). The results show that there are significant alterations in cysteine and aspartic intracellular proteinases activity already in the early postirradiation period, which are different in proliferating and nonproliferating cells. Irradiation of the cells examined to low doses and up to 15 Gy induced an increase in cysteine proteinases activity in the early postexposure period, while at higher irradiation doses applied, the activity of these proteinases was decreased. These observations suggest that intracellular proteinases are actively participating in process involving recovery from radiation injury or cell killing.

Animals↗

PubMed1989

In vivo and in vitro modulation of NK and ADCC activities of mouse spleen cells by peptidoglycan monomer (PGM).

The ability of peptidoglycan monomer (PGM), an immunomodulator obtained from Brevibacterium divaricatum, to modulate NK and ADCC activities of spleen cells was tested in mice with constitutively weak (C57B1) or strong NK activity (CBA, C3H). In weak reactors, i.v. injection of PGM enhanced the NK and ADCC activity as effectively as a known stimulator, poly I.C, and the dynamics of the response was comparable. In strong reactors, PGM caused two peaks of the ADCC response, and one peak of NK stimulation (after an initial decline), whereas poly I.C caused more or less persistent stimulation of both activities. Incubation of spleen cells with PGM was generally less effective than the treatment in vivo. No alteration of NK activity was recorded at high effector-to-target ratio (E:T), and at low ones, PGM caused suppression. This was true both for weakly and strongly reactive cells. ADCC was either unchanged (CBA spleen cells), stimulated (C3H), or suppressed at high E:T and enhanced at low E:T (C57B1). PGM apparently activates an interlocked regulatory mechanism, and the final outcome probably depends on relative concentrations of regulatory and effector cells and on their per cell activities. Hence the effect varied with the time interval between treatment and assay, with strain-related constitutive reactivity, and with the E:T ratio.

Acetylmuramyl-Alanyl-Isoglutamine↗

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

Multiple fractions of gamma rays induced resistance to cis-dichloro-diammineplatinum (II) and methotrexate in human HeLa cells.

Previous irradiation could induce changes in the cell-sensitivity to additional cytotoxic agents. In this study we examined whether the sensitivity to additional cytotoxic agents was affected in cells irradiated with multiple fractions of gamma rays if these agents were given at the time when the lesions induced in DNA by radiation have already been repaired. Human cervix carcinoma HeLa cells were irradiated daily with 0.5 Gy of gamma rays five times a week for 6 weeks. When the fractionation regimen was completed, that is when the cells had accumulated the total dose of 15 Gy of gamma rays, the sensitivity of these cells to gamma rays, UV light, cis-dichlorodiammineplatinum (II) (cis-DDP), methotrexate (MTX), and hydroxyurea (HU) was examined and compared to control cells. Results revealed that preirradiated cells did not change sensitivity to gamma rays and UV light, but that they increased the resistance to cis-DDP, and MTX (especially for higher concentrations of MTX), and increased sensitivity to HU (for lower concentrations of HU). The increased resistance to cis-DDP was also measurable up to 30 days after the last dose of gamma rays. The results indicate that preirradiation of HeLa cells with multiple fractions of gamma rays could change their sensitivity to additional cytotoxic agents, and that this is a relatively long-lasting effect. Our results suggest that caution is needed in medical application of radiation combined with chemical treatment.

Cell Survival↗

PubMed1989

Resistance of human and mouse myeloid leukemia cells to UV radiation.

Sensitivity of mouse bone marrow and myeloid leukemia cells as well as the sensitivity of human myeloid leukemia cells to UV light was tested. Criteria were the in vivo colony-forming ability of UV exposed cells and the inhibition of DNA synthesis during post-irradiation incubation for 24 h in vitro. Mouse bone marrow cells irradiated with a small dose of UV light (5 J/m2) and injected into x-irradiated animals did not form hemopoietic colonies on the recipients' spleens, and the recipients died. However, mouse leukemia cells, after irradiation with higher doses of UV light, retained the ability to form colonies on the spleens, and all recipient mice died with typical symptoms of leukemia. In vitro, mouse bone marrow cells exhibited high sensitivity to UV light as compared to mouse myeloid leukemia cells. Human leukemia cells were also resistant to UV light, but more sensitive than mouse leukemia cells. These results indicate that myeloid leukemia cells are resistant to UV light as compared with normal bone marrow cells.

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

Defect of NK activity in children with untreated acute lymphocytic leukemia (ALL). I. Dependence on the blast count and phenotype, and response to exogenous and endogenous alpha-interferon.

Endogenous NK-activity (eNK) against K-562 cells was determined in peripheral blood of 68 children with acute lymphocytic leukemia (ALL) before treatment. In 53% of them it was depressed, and in 47% it was within the range of control children (27) and adults (104). There was a significant negative correlation between blast contamination of peripheral blood and the level of eNK-activity. In spite of this general trend, 8 patients with high blast count have had normal eNK-activity, and 10 patients with relatively low blast count (below 50%) have had depressed eNK-activity. Examples of T ALL showed significantly lower eNK-activity than CALLA ALL. The ability of exogenous alpha-interferon (IFN) to stimulate eNK-activity was impaired in 18 of 40 examples of ALL and preserved in 22. The IFN-induced NK-response was also negatively correlated to the blast burden, but again with exceptions: Six nonresponders in spite of low blast count, and six responders in spite of high blast count in peripheral blood. IFN-inducer, poly-IC, stimulated eNK-activity only in 6 of 26 ALL samples. Surprisingly, positive correlation was found between poly-IC-induced NK-stimulation and blast count in peripheral blood. Poly-IC induced significant IFN production only in one of six cultures of ALL. Impaired eNK-activity has been attributed, in part, to "dilution" of NK cells by the blasts. Defects in production of IFN, and in response to it, may be additional reasons for depressed NK-activity in about 50% of children with untreated ALL.

Adolescent↗

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

NK cell activity and estrogen hormone levels during normal human pregnancy.

NK cell activity was determined in peripheral blood of 24 women during pregnancy, and compared to NK activity of 40 healthy nonpregnant women in generative age. An increase in the first trimester was followed by a significant decline of NK activity in the second trimester, and a further fall in the third trimester of pregnancy. The initial rise of NK activity was predominantly due to primigravidas, whereas the fall in the second trimester was mainly due to multigravidas. There was a significant negative correlation between NK activity and the increasing levels of estrogen hormones (beta-estradiol, estriol and estrone) in the sera of pregnant women. However, when analyzed for each trimester of pregnancy separately, a significant (p less than 0.02) negative correlation was only found with beta-estradiol, suggesting that high doses of this hormone could contribute to pregnancy-associated NK suppression.

Adolescent↗

PubMed1988

Repeated doses of gamma rays induce resistance to N-methyl-N'-nitro-N-nitrosoguanidine in Chinese hamster cells.

Chinese hamster V79 cells were preirradiated repeatedly with gamma rays and then exposed to ultraviolet (uv) light or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The cell killing and induction of mutation at the hypoxanthine-guanine phosphoribosyltransferase locus were examined following these treatments. Cells preirradiated with multiple fractions of gamma rays exhibit the same sensitivity to uv light as the control cells with respect to cell survival and mutation induction. Following treatment with MNNG, resistance to cell killing was observed along with a decreased frequency of mutations induced. These results indicate that the progeny of cells irradiated with multiple fractions of gamma rays could display subsequent changes in sensitivity to lethal and mutagenic effects of additional treatment with DNA-damaging agents.

Animals↗

PubMed1988

Multiple, small exposures of far-ultraviolet or mid-ultraviolet light change the sensitivity to acute ultraviolet exposures measured by cell lethality and mutagenesis in V79 Chinese hamster cells.

Chinese hamster V79 cells (subline MI2G) were exposed repeatedly to fractionated doses of germicidal 254 nm light (far-uv) at 6 J.m-2/fraction/day or sunlight-simulating 290-330 nm (mid-uv) at 150 J.m-2/fraction/day and sensitivities to cell killing action and mutation of far-uv and mid-uv were examined. As the number of exposure fractions increased, the cell cultures became resistant to cell killing induced by both far-uv and mid-uv. Increases in both Do and Dq were observed. Treatment with exposures of 6 J.m-2 far-uv is more efficient in yielding cell cultures that are resistant than exposures of 150 J.m-2 mid-uv. In contrast to the cells exposed to repeated far-uv, the cells exposed to repeated mid-uv were relatively more resistant to cell killing effects of mid-uv than far-uv, suggesting a possible role of photolesions other than pyrimidine dimers. When mutants resistant to 6-thioguanine were assayed during repeated exposure to far- or mid-uv light, the yield was initially linear with accumulating dose. At high total accumulated doses, the frequency decreased gradually (6 J.m-2 mid-uv) or reached a plateau (150 J.m-2 mid-uv). The sensitivity of N80 cells (exposed to 80 fractions of mid-uv) to mutation induction by uv light is higher than that of the original MI2G cells, whereas U81 cells (exposed to 81 fractions of far-uv) have a sensitivity similar to that of the original cells. Although an initial decrease in resistance to cell killing was observed, resistant cells retained their characteristics after 100 days in culture without further exposure. Cross-resistance to X rays was not shown. The data in this paper suggest that the capacity for repair of photolesions in DNA by repair processes was enhanced in cell cultures by repeated exposure to far-uv or mid-uv and that this altered the cells' ability to cope with lethal and mutagenic lesions. It remains to be seen if these changes in cell sensitivity were brought about by selective or inductive processes or a combination of both.

Animals↗

PubMed1985

Estramustine phosphate-reduced proliferation of murine and human cell lines and murine transplantable tumors.

The effect of estramustine phosphate (Estracyt) on the growth of murine aplastic mammary carcinoma, Ehrlich carcinoma, melanoma B-16, and five cell lines: L929 (mouse fibroblasts), BHK (baby hamster kidney), HeLa (human cervical carcinoma), HEp-2 (human laryngeal carcinoma), and K562 (human granulocytic leukemia) was investigated. In vivo, estramustine phosphate inhibits the growth of aplastic mammary carcinoma and Ehrlich carcinoma, but has no effect on melanoma B-16. In cultured aplastic mammary carcinoma, estramustine phosphate decreased the incorporation of 3H-thymidine into DNA. This drug inhibits the population growth of L929, BHK, HEp-2, and K562 cultures, but stimulates the growth of HeLa cells. We conclude that estramustine phosphate retards the growth of various cells, and that studies of other potential fields of application of the drug (aside from prostatic carcinoma) is justified.

Animals↗

PubMed1983

In vivo and in vitro effect of progesterone on the growth of some mouse and human tumours.

The effect of progesterone on the growth of tumours of different morphological and cytokinetic characteristics and origin has been investigated, such as mammary aplastic carcinoma, Ehrlich ascitic and solid tumour, fibrosarcoma, melanoma B-16, myeloid leukaemia and three cell lines, HeLa, HEp-2 and L929. The administration of progesterone has been proved to stimulate the growth of aplastic carcinoma of the breast in vivo. Directly implemented into cell culture of the same tumour it increased the incorporation of 3H-thymidine into DNA. In HeLa and HEp-2 cell cultures progesterone stimulated the population growth of these cells. However, progesterone has shown no effect at all on the growth of fibrosarcoma, melanoma, Ehrlich tumour, myeloid leukaemia and L929 cells, fibroblasts of C3H mice.

Animals↗