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Biomedical subjects

J Skrk

Publications and source records attributed to J Skrk.

At least 37 records · Page 2Linked to original sources
PubMed1992

Cathepsins B, H and L in human breast carcinoma.

We have measured the activity of the cysteine proteinase cathepsin B, the inhibitory activity of cysteine proteinase inhibitors and the amounts of cathepsins B, H and L in normal sera and sera from patients with breast cancer, as well as in tissue homogenates of tumorous and non-tumorous samples. The amounts of cathepsin B, determined by ELISA in tumour sera (n = 17) were significantly higher than the amounts determined in normal sera (n = 20). On the other hand, the differences in the amounts measured in tumour sera were not significant when compared with the known histopathological characteristics. In cytosols of breast cancer tumour tissue in general, the level of cathepsin H was higher than those of cathepsins B and L in all samples tested. In the same samples, at least a 10-fold increase of cathepsin B (activity and quantity) was detected in matched pairs (n = 20) of carcinoma and normal tissue of the same breast (p less than 0.01). The amount of cathepsin B correlated with the degree of malignancy inside the histological subtypes of invasive ductal carcinoma (n = 90, p less than 0.01). In addition, a negative correlation of values for cathepsin B with the involvement of regional lymph nodes (n = 75, p less than 0.01) was found inside the same group. In contrast, the activities of cysteine proteinase inhibitors did not correlate with any of the known clinical data. Our data provide further indirect evidence for the involvement of cathepsin B in the processes of tumour growth and metastasis in breast carcinoma. The follow-up studies will verify the prognostic value of these findings.

Breast Neoplasms↗
PubMed1992

Determination of cathepsins B, H, L and kininogen in breast cancer patients.

In 20 matched pairs, an increase of all cathepsins was measured in carcinoma tissue compared with normal tissue of the same breast. On contrary, the mean value for kininogen was almost 2 fold lower than mean value determined in normal cytosols. From all proteins tested, the amount of cathepsin B correlated mostly with the degree of malignancy inside the group of invasive ductal carcinoma (n = 90, p < 0.01).

Biomarkers, Tumor↗
PubMed1991

Chromosome aberrations induced in human lymphocytes by U-235 fission neutrons: I. Irradiation of human blood samples in the "dry cell" of the TRIGA Mark II nuclear reactor.

A set-up for irradiation of biological samples in the TRIGA Mark II research reactor in Ljubljana is described. Threshold activation detectors were used for characterisation of the neutron flux, and the accompanying gamma dose was measured by TLDs. Human peripheral blood samples were irradiated "in vitro" and biological effects evaluated according to the unstable chromosomal aberrations induced. Biological effects of two types of cultivation of irradiated blood samples, the first immediately after irradiation and the second after 96 h storage, were studied. A significant difference in the incidence of chromosomal aberrations between these two types of samples was obtained, while our dose-response curve fitting coefficients alpha 1 = (7.71 +/- 0.09) x 10(-2) Gy-1 (immediate cultivation) and alpha 2 = (11.03 +/- 0.08) x 10(-2) Gy-1 (96 h delayed cultivation) are in both cases lower than could be found in the literature.

Chromosome Aberrations↗
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

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↗
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↗
PubMed1983

Effect of homologous and heterologous interferons on proteolytic activity of normal and transformed cells.

The authors investigated the effect of various types of interferons (INF) on the activity of intracellular neutral and cysteine proteinases (cathepsin B and H) in normal and transformed rat embryonic fibroblasts. A substantially stronger inhibitory effect was observed with all three types of IFN on the proteolytic enzymes in transformed cells if compared to that on normal cells. Heterologous IFN reduces the activity of cysteine proteinases by 33% and neutral proteinases by 79%. Homologous IFN strongly reduced the activity of cysteine proteinases in transformed cells (59%) used in the experiments, but the inhibition of neutral proteinases remained nearly unchanged if compared with normal cells (18%).

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↗
PubMed1982

Carcinogenesis after sublethal ionizing irradiation and regular avoidance irritation.

160 mice of the BALB/C strain of both sexes, aged 3 months, were divided into four equal groups out of which two were regularly irritated by a combination of an optical signal and electrical stroke. After one month of irritation one nonirritated and one irritated group were whole body irradiated with a single dose of 6.65 Gy (1.83 Gy/min), the other two groups were sham irradiated. The mice lived until their spontaneous death or one year after irradiation, respectively, when the rest of the animals were sacrificed. The appearance of malignant tumors was noted. Irradiation shortened the survival time while the irritation had an appeasing, compensatory effect, more expressed in the males than in the females. After irradiation the number and assortment of the tumors increased and the latent period essentially shortened. In the irritated animals the number and assortment of the malignant tumors were reduced and a tendency for lengthening of the latent time period was seen; these differences, however, were not statistically significant. In spite of some differences the response in both sexes to irradiation and irritation or their combination was similar.

Animals↗
PubMed1981

Stress and radiation carcinogenesis in mice.

In the present experiment irritation consisting of a combination of an optic signal followed by a mild electroshock administered at regular intervals was started in 2 groups of animals at the age of 3 months. At 4 months of age, one of the irritated and one of the nonirritated groups were exposed to whole-body gamma irradiation at 20 daily doses of 0.5 Gy (50 rad(, 1.4 Gy/min (140 rad/min), while the other 2 groups were sham-irradiated. The animals were autopsied and the specimens were microscopically studied for the presence of malignant tumors. Malignant tumors involving particularly the testes and lungs and leukosis were found in 29% of males, whereas in females the tumor incidence with mammary, pulmonary and ovarian involvement and leukosis was 39%. The irradiation decreased the minimum latency time in the irritated males and both female groups. In males, the irritation lowered the cumulative prevalence of malignant tumors, a significant decrease being noted at the age of 15 months. In females, it was increased, with a significant rise observed to occur at the end of the experiment. The opposite effects of irritation on the radiation carcinogenesis in males and females can be attributed to the irradiation-induced specific alterations of the gonads in females and, in part, to a longer survival time observed in the irradiated females.

Animals↗
PubMed1980

Tumor cell repopulation in the rest interval of split-course radiation treatment.

Fifty-two patients who were treated for laryngeal carcinoma stage I and II by either continuous or split-course irradiation were analysed. The 5-year cure by irradiation was the same in both groups. An isoeffect line was drawn for cured tumours and used to estimate the dose necessary to kill the regrowth of tumour cells which survived the first part of the split-course treatment. The estimated dose was 40 +/- 4 cGy per day of the rest interval. The doubling time was then calculated by means of schematic survival curves for fractionated irradiation. It was found that the tumor cells which survive the first part of the split-course treatment have the doubling times 3.5 +/- 0.5 days.

Adult↗
PubMed1976

Proteolytic activity in liver cells from mouse, rat, Ehrlich ascites carcinoma bearing mouse and in Ehrlich ascites carcinoma cells.

The activity of intracellular proteinases from Ehrlich ascites carcinoma bearing mice were compared with that from liver cells of normal mice and rats. The activity of intracellular proteinases was measured in the supernatant of Ehrlich ascites carcinoma cells homogenate. The activity of intracellular proteinases in normal mouse and normal rat liver were different at pH 3.5, pH 6.0 and pH 7.5. The activity in liver cells from Ehlrich ascites carcinoma bearing mouse at pH 3.5 was not significantly changed from normal mouse or rat liver cells, however at pH 6.0 and pH 7.5 the activity in the affected liver significantly decreased. The proteolytic activity in the supernatant of Ehrlich ascites tumor cell homogenate was 0.110 E750 mmu/mgN at pH 7.5, 0.154 E750 mmu/mgN at pH 3.5. The proteolytic activity at pH 6.0 was not detected in any experiment.

Animals↗