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Biomedical subjects

G Markus

Publications and source records attributed to G Markus.

At least 37 records · Page 2Linked to original sources
PubMed1982

Interference with dimethylhydrazine induction of colon tumors in mice by epsilon-aminocaproic acid.

The antifibrinolytic agent epsilon-aminocaproic acid given in the drinking water to Swiss ICR/Ha mice significantly counteracted the appearance of colorectal tumors induced by 21 weekly infections of 1,2-dimethylhydrazine. The drug affected both the number and the location of the tumors and, in some animals, altogether prevented their appearance. The low concentrations of epsilon-aminocaproic acid in the plasma of four control mice given the agent labeled with carbon-14 for 3 days suggest that the effect may depend not on inhibition of plasminogen activator activity, but on interference with the binding of some substance to the strong lysine binding site of plasminogen.

Adenocarcinoma↗
PubMed1982

Urokinase-like plasminogen activators of unusually high molecular weight secreted by a cell line derived from a human lung cancer case.

The HPL-SK-1 cell line derived from the pleural exudate of a lung cancer patient has been shown to secrete plasminogen activators of very high molecular weights (greater than or equal to 2 and 1 million), as shown by gel filtration on Sepharose 6B or CL-6B. The size of these activators could not be reduced by chromatography in buffers containing 2% sodium dodecyl sulfate, 8 M urea, or 1 M KSCN. Goat anti-urokinase antibody inhibited these activators only partially. Trypsin digestion of the 2 million-dalton species yielded several active fragments including one of the size of urokinase, 55,000 daltons. These large activators could be purified only by a double antibody immunoadsorption technique which consisted of the formation of a soluble immune complex between the activators and goat anti-urokinase IgG, followed by the adsorption of this complex to rabbit anti-goat IgG coupled to Affi-Gel 10. The eluted activators were purified 50-fold (2 million daltons) and 130-fold (1 million daltons), respectively. Reduction of the two largest species in the presence of sodium dodecyl sulfate resulted in the appearance of smaller molecular weight active fragments of differing size, indicating that these activators are disulfide-linked oligomers. Among the fragments of the 2 million-dalton species was found a 10,000-dalton enzyme which had lost activator and antigenic specificity and retained only a non-specific protease activity. A similar fragment was also isolated from reduced, purified 55,000-dalton urinary urokinase.

Antigen-Antibody Complex↗
PubMed1981

Plasminogen activator content of neoplastic and benign human prostate tissues; fibrin augmentation of an activator activity.

The plasminogen activator content of the extracts of excise prostate cancers (25 specimens) was determined with an azocasein assay and found to be on the average 1.7 times higher than that of extracts of excised prostate benign hyperplasias (29 specimens). Both groups contained the same average percentage of human urokinase type activator (approximately 45%) as determined by the inhibition of activity when anti-human urokinase antibody was included in the assay system. The two types of activators were partially purified and found to have distinctly different properties. The most striking difference was the large augmentation of activity o the non-urokinase enzyme in fibrinolysis. The implications of an enhanced fibrinolysis relative to azocaseinolysis (or other) is discussed, particularly with respect to its importance in the quantitation and characterization of activators by different investigators. Highly purified urokinase-like activator was found to be similar to commercial urokinase preparation with respect to molecular weight, isoelectric point, inhibition by the antibody, and inhibition by placenta inhibitor.

Fibrin↗
PubMed1980

Plasminogen activator content of human colon tumors and normal mucosae: separation of enzymes and partial purification.

Plasminogen activator content was determined quantitatively in extracts of 23 pairs of surgically removed colon tumors and adjacent normal mucosa specimens. The activator content averaged 4.4 times higher in the tumor samples than in the corresponding normal tissue. Polyps removed with the adenocarcinomas gave values intermediate between those for tumors and those for the normal mucosae. The enzyme content of the group of tumors that showed invasive propagation or metastatic spread was significantly higher (P < 0.05) than was the enzyme content of the group not manifesting these conditions. Activator activity of the tumor extracts was completely inhibited by rabbit antibody formed against human urokinse. The activity of the normal mucosae was variably inhibited, suggesting the presence of several kinds of activator in normal tissues. The activator from the normal tissues could be separated into a completely refractory fraction and a completely inhibitable fraction by means of an affinity column made of Sepharose-linked, rabbit antiurokinase antibody. The activator, eluted from this column with 1 M acetic acid in 0.5 M NaCl (pH 2.2), was highly purified and had an isoelectric point of 8.6, as does authentic urokinase. The details of the isoelectric profile of the two, however, differed. The data are discussed in relation to earlier studies on the fibrinolytic system in colon cancer.

Adenocarcinoma↗
PubMed1980

Content and characterization of plasminogen activators in human lung tumors and normal lung tissue.

The plasminogen activator content of surgically removed lung cancers, as well as that of adjacent normal lung tissue has been determined quantitatively. Optimum conditions for the quantitative extraction have been worked out using a modification of the technique described by Nagy et al. (Int. J. Cancer, 19:614-620, 1977) which utilizes a buffered solution of the non-ionic detergent Triton X-100. Plasminogen activator was significantly elevated in the tumors (2.5- to 4.3-fold over the normal lung, depending on sample selection and other criteria), although individual variations between tumors were extremely large. No significant correlation was found between the histopathological character of the tumors and the activator content, or between invasiveness and activator content. Using rabbit antibody formed against purified urokinase as an inhibitor of activator action, it was found that lung tumors contain a urokinase-like enzyme as the predominant plasminogen activator, while the activator content of the adjacent normal lung tissue consists of some urokinase-like enzyme, but mostly of an enzyme which is not inhibited by the antibody. The urokinase-like activator has been purified approximately 20,000-fold from lung tumors by the combination of two affinity chromatographic procedures, and was compared with purified urokinase with a molecular weight of 55,000 on all criteria used, the lung tumor activator was identical to urokinase.

Adenocarcinoma↗
PubMed1978

Quantitative determination of the binding of epsilon-aminocaproic acid to native plasminogen.

The binding of epsilon-amino[14C]caproic acid (6-aminohexanoic acid, EACA) to native human plasminogen was determined using the ultrafiltration technique of Paulus (Paulus, H. (1969) Anal. Biochem. 32, 91-100) at free ligand concentrations ranging from 2 micrometer to 16 mM. One strong binding site (Kd = 0.009 mM) and approximately five weaker ones (Kd = 5 mM) were found. The constants were obtained by fitting the experimental points to the simple assumption of two sets of noninteracting sites. The distinct separation of the two kinds of sites allowed the correlation of the well known epsilon-aminocaproic acid-induced conformational transition in plasminogen with the saturation of the weaker group of binding sites by this ligand. The conformational transition was monitored by measurements of the sedimentation coefficient, as was done by others earlier. The midpoint of the transition occurred at approximately 3.3 mM free ligand. A dissociation constant of 0.32 mM was also obtained for L-lysine by measurements of the competition between this compound and labeled epsilon-aminocaproic acid for the strong binding site. The correlation between epsilon-aminocaproic acid binding and effects of the compound on various physical and functional properties is discussed. A discussion of the possible sources of error encountered in the technique used is also included.

Aminocaproates↗
PubMed1976

Activator activities of the transient forms of the human plasminogen-streptokinase complex during its proteolytic conversion to the stable activator complex.

When human plasminogen and the bacterial protein streptokinase are mixed, a tight equimolar complex is formed in which an active center of well defined hydrolytic activity developes; this event precedes the cleavage of the plasminogen chain, i.e. the conversion to plasmin. Immediately after the formation of the complex, a series of proteolytic transformations occurs which, within a few minutes, results in at least two cleavages in the plasminogen, and at least five cleavages in the streptokinase peptide chains. None of the fragments so created seem to dissociate from the main body of the complex, but the activator activity, when measured by a rapid bovine clot-lysis system, undergoes a characteristic pattern of fluctuation coincident with the fragmentation of the two components. When the latter process is followed by sodium dodecyl sulfate gel electrophoresis, the state of fragmentation of the activator can be correlated with the measured activator activities. By manipulating the temperature, and by the introduction of inhibitors, it was possible to slow down, or temporarily arrest, the fragmentation at certain stages, allowing the identification in a number of cases of the predominant activator species, and the determination of a characteristic relative activator activity for it. By the use of such relative activities, it was possible to carry out a calculation, based on electrophoretic analysis alone, which predicted reasonably successfully the kinetics of activator fluctuation.

Electrophoresis, Polyacrylamide Gel↗
PubMed1976

Affinity chromatography of thymidine kinase from a rat colon adenocarcinoma.

Thymidine kinase from a transplantable colon adenocarcinoma, induced by 1,2-dimethylhydrazine and maintained in CDF rats, was purified by affinity chromatography using thymidine-3'(4-aminophenylphosphate) coupled to carboxyhexyl-Sepharose. Most of the contaminating protein passed through the column; non-specifically adsorbed protein was washed from the column by 0.1 M KC1 in 0.01 M Tris-HC1, 7.5. Thymidine kinase was eluted with 0.1 mM thymidine, 0.1 M KC1 in 0.01 M Tris-HC1, pH 7.5. The purified enzyme accounted for about 26% of the applied activity; the specific activity of the purified material (peak fraction) was 3,500 moles TMP formed per mg protein per 10 min., a 1,800-fold purification of the applied extract. The preparation is free of nucleoside phosphotransferase, but contains other protein impurities. Purification was completed in less than 1 hour, making this a useful procedure for isolation of this unstable enzyme.

Adenocarcinoma↗