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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Addition of subtoxic doses of the lectin concanavalin A to growing subconfluent monolayer cultures of pig kidney cells causes an increase in extra- and intracellular plasminogen activator activity which is reversibly inhibited by actinomycin D, cycloheximide and alpha-methyl-D-mannoside. These results suggest that cell surface events may play an important modulatory role in plasminogen activator production.
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PMID:Concanavalin A stimulation of plasminogen activator production in pig kidney cells in culture. 50 7

Primary cultures of peripheral lung lobes were grown in a highly supplemented medium. Human lung endothelial cells (HLE) were isolated from the mixed population by FACS. The cells proliferated rapidly and were serially cultivated for at least 16 passages. Both early and late passage cells were positive for the standard endothelial markers. Factor VIII related-antigen (Factor VIII R-Ag), angiotensin-converting enzyme, acetylated low-density lipoprotein labeled with 1,1'-dioctadecyl-1,3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI-Ac-LDL) uptake, and bound the lectin Ulex europaeus agglutinin (UEA). Prostaglandin E2 was the major cyclooxygenase product of HLE, in contrast to human umbilical vein endothelial cells (HUVE), which synthesized PGI2 in excess of PGE2. Factor VIII R-Ag exhibited a diffuse cytoplasmic as well as an extracellular fibrillar distribution in HLE, in contrast to a vesicular (Weibel-Palade body) cytoplasmic distribution in HUVE. The HUVE did demonstrate some extracellular fibrillar Factor VIII R-Ag as well. Urokinase was the predominant plasminogen activator (PA) secreted by HLE, whereas tissue PA was predominant in HUVE cultures. HLE formed tube-like structures within 2 h of plating on a Matrigel matrix whereas HUVE formed larger tube-like structures only after 1 or more days. The properties described here indicate that human lung microvessel endothelium can be isolated and continuously grown from small tissue segments and express a number of properties that differ from those of HUVE. These studies provide further support for the concept that endothelial cells from different sources can exhibit considerable heterogeneity relating to their phenotypic and biochemical properties.
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PMID:Isolation, cultivation, and partial characterization of microvascular endothelium derived from human lung. 133 46

A simple and sensitive chromogenic microtitre plate assay for glycoprotein enzymes is described, using melanoma tissue plasminogen activator (t-PA) as a model enzyme. The assay is based on the binding of t-PA to immobilised lectin and quantitating the bound enzyme with plasminogen, fibrinogen fragments and chromogenic substrate S-2251 on an ELISA plate reader. Seven different lectins were examined for the binding of t-PA, and of these, concanavalin A was chosen for subsequent studies. The specificity of this binding can be inhibited dose-dependently in the presence of D-mannose and methyl alpha-D-mannoside, but not by D-glucose and D-lactose. The lower limit of the sensitivity of this assay is about 0.5 IU/ml. Comparison of the dose-response curves indicates that the sensitivity of this assay method is very similar to that of bioimmunoassay using anti-t-PA IgG to capture the antigen. The applicability of this method to other glycoprotein enzymes was also evaluated using alkaline phosphatase from bovine mucosa. The specificity of this method was related to the choice of substrate and this was shown by analysis of a mixture of t-PA and alkaline phosphatase. It is suggested that this assay can be adapted for the analysis of complex glycoprotein mixtures with the appropriate choice of lectin and substrate.
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PMID:Lectin affinity bioassay: an assay method for glycoprotein enzyme. 249 37

The distribution of tissue plasminogen activator (t-PA) has been studied in a series of 38 human brain tumours and two specimens of cerebral cortex, using the monoclonal antibody ESP6. t-PA was localised in vascular endothelium in the majority of tumours and both the cortical specimens, confirmed by double staining with Ulex europaeus lectin (Uel) and Factor 8-related antigen. Nineteen out of 22 high grade astrocytomas showed strong endothelial staining whereas staining was weak or absent in the four low grade astrocytomas studied. No consistent relationship was found between the pattern of staining and tumour grade in the other tumours, although strong staining of the three metastatic lesions with Uel was observed. Among the astroglial tumours only one glioblastoma showed any tumour cell staining for t-PA, which raises questions concerning the origin of t-PA producing cells derived from human gliomas in vitro. Studies of t-PA in brain tumours should take account of this vascular localisation before concluding that the activity is derived from neoplastic cells.
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PMID:Immunohistochemical localisation of tissue plasminogen activator in human brain tumours. 253 81

Tissue-type plasminogen-activator antigenicity was immunohistochemically localized in the developing glomerulus of human embryonic kidneys using antibodies raised against a highly purified HeLa-cell activator [43]. At the very beginning of the S-shaped-body stage of glomerular differentiation, tissue-type activator antigenicity seemed to be co-distributed with a marker of invading endothelial cells, i.e., Ulex europaeus lectin. However, during further stages of glomerular remodelling and maturation, this plasminogen activator was also localized around developing and proliferating visceral epithelial cells (podocytes). Antibodies against the urokinase-type plasminogen activator did not react with any elements of developing glomeruli; rather, they stained the proximal tubules in more mature parts of the kidney, as revealed by double immunostaining using antibodies against the brush border. The present results suggest that the tissue-type plasminogen activator plays a role in the differentiation of glomerular structures during nephron morphogenesis.
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PMID:Plasminogen activators during differentiation of the human kidney. 311 29

Studies carried out by the authors on the rat mammary adenocarcinoma cell lines MAT 13762 and DMBA-8 are summarized. A series of variants and somatic cell hybrids have been prepared and partially characterized in terms of phenotypic properties which may correlate with metastatic potential. These include measurement of in vitro migration, lectin binding properties, expression of procoagulant activity and shedding of cell surface components. Particular emphasis has been placed on the production of enzymically-active plasminogen activator, as this seems to correlate with the ability of cells to metastasize. The finding has also been made that several of the cell types studied produce, in vitro, an inhibitor of plasminogen activator which may influence the metastatic behaviour of tumor cells. Results obtained are discussed in the context of the usefulness of these tumor systems for the study of spontaneous and experimental metastasis and the factors involved in these processes. Preliminary results of cloning and fluctuation analysis of metastatic potential together with discussion of the role of the metastatic heterogeneity and the formation of metastatic variants by mutation events are included.
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PMID:Studies on rat mammary adenocarcinomas: a model for metastasis. 390 19

In a series of 46 cases of primary mammary ductal carcinoma, immunohistochemical markers of differentiation (casein, human placental lactogen, alphalactalbumin, pregnancy specific beta-1 glycoprotein, secretory component, CEA, and peanut lectin agglutinins [PLA]), were quantitated via point-counting. An immunoperoxidase bridge (PAP) was used to identify all except the PLA, in which an avidin-biotin complex with alkaline phosphatase development was employed. For none of the markers was there any difference in the quantity present in tumors of patients who had recurred versus the tumors of patients who had enjoyed a minimum of five years disease-free survival. Nonneoplastic epithelium was only rarely positive for these markers. Although eventually surmounted, technical problems significantly hampered application of morphometry to this histochemical material. The authors conclude that these markers have little relationship to differentiation toward mammary duct epithelium and that they do not provide significant prognostic information in patients with breast cancer.
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PMID:Correlation of immunohistochemical markers with patient prognosis in breast carcinoma: a quantitative study. 609 96

Plasma membranes isolated from normal thymocytes of hamster and rats were found to exhibit neutral protease activity toward 125I-labeled casein. The plasma membrane-associated proteases were completely inhibited by the serine protease inhibitors, diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride and p-nitrophenyl-p-guanidinobenzoate, partially inhibited by soybean trypsin inhibitor and antipain, but were only weakly inhibited by L-1-tosylamino-2-phenylethyl chloromethyl ketone. The plasma membrane-associated proteases were also completely inhibited by ZnCl2 (75--100 mu M), but they were not affected by several other divalent cations. The plasma membrane fraction contained a plasminogen activator activity which was specifically localized in this fraction. The plasma membrane-associated plasminogen activator activity was inhibited by all of the inhibitors which inhibited plasma membrane-associated proteases except L-1-tosylamido-2-phenylethyl chloromethyl ketone. Labeling of plasma membrane-associated serine esterases with [3H] diisopropyl fluorophosphate followed by separation of the proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that this fraction contained a single major 3H-labeled protein of Mr 105 000. Both the plasminogen activator and the Mr 105 000 esterase were shown to be glycoproteins by affinity chromatography on lentil lectin-Sepharose. These results indicate that the plasminogen activator of thymocytes is a glycosylated serine protease with an active site-containing subunit of Mr 105 000 which is specifically localized in the plasma membrane.
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PMID:Characterization of a plasma membrane-associated plasminogen activator on thymocytes. 679 69

A human cell line has been established from a transplantable xenografted human testicular tumor, which, both in the original tumor and in the xenograft, exhibited the histological characteristics of an undifferentiated malignant teratoma (embryonal cell carcinoma). The cells in culture were undifferentiated by biochemical, morphological, and ultrastructural criteria, growing as small islands of cells that tended to form aggregates at high density. The cells showed some variation in chromosome number with 30 to 40% of the cells having a normal human karyotype. The cells expressed high levels of alkaline phosphatase, which by heat inactivation and inhibition studies was 40 to 50% placental type alkaline phosphatase. None of the cultures produced human chorionic gonadotrophin, alphafetoprotein, carcinoembryonic antigen, or fibronectin, although at high cell densities plasminogen activator could be detected at low levels. Cell surface studies showed that the cells shared antigens with the murine embryonal carcinoma cell line F9, expressed beta 2-microglobulin at very low and variable levels, and bound the lectin peanut agglutinin. These studies suggest that this cell line has some of the characteristics described for murine embryonal carcinoma cell lines.
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PMID:Characterization of a new human cell line derived from a xenografted embryonal carcinoma. 717 48

12-O-Tetradecanoylphorbol-13-acetate (TPA) modulates DNA synthesis in bovine lymph node lymphocytes in culture. Whether TPA enhances or depresses DNA synthesis depends on when the TPA is added with regard to time of mitogenic stimulation. We have previously reported that TPA acts as a comitogen when added with the lectins phytohemagglutinin or concanavalin A, but it inhibits DNA synthesis in these cells in mixed lymphocyte culture. We report in this study that pretreatment of bovine lymph node lymphocytes with TPA depressed their proliferative response to phytohemagglutinin, concanavalin A, or pokeweek mitogen. The extent of inhibition varied somewhat with each animal and particular lectin. The effect was reversible. Inhibition was not due to a shift in the kinetics of the response or to a change in the dose response. TPA may act directly by changing the lymphocyte surface properties and/or indirectly through a cell population or product to suppress the proliferative response. One cell product, plasminogen activator, was identified in culture medium, although we have no evidence at this time that it is responsible for the inhibitory effect of TPA.
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PMID:Suppression of lectin-stimulated DNA synthesis in bovine lymphocytes by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. 719 75


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