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Biomedical subjects

P Mignatti

Publications and source records attributed to P Mignatti.

50 records · Page 3Linked to original sources
PubMed1985

Degradation of human fibronectin by strains of E. coli K12 carrying R factors from Klebsiella pneumoniae.

We studied the ability to degrade human fibronectin by strains of E. coli K12 carrying R factors from Klebsiella pneumoniae, previously shown to possess a caseinolytic activity. The preliminary data obtained showed that at least two of these R+ strains are able to degrade fibronectin to small peptides retaining the gelatin-binding site of the molecule. We also found indications of non-fibronectin gelatin-binding polypeptides secreted by the strains tested into the culture broth. The possible significance of this bacterial property as a factor of pathogenicity is discussed.

Carrier Proteins↗
PubMed1985

R factor-mediated adhesiveness to mammalian cells in E. coli K12.

We checked the possible effects of the standard plasmids of known compatibility groups on the ability of three strains of E. coli K12, J62, J53 and C600, to agglutinate human and guinea pig erythrocytes and to adhere to cultures of human epithelial cells. The results obtained showed that under defined experimental conditions one plasmid, R478, from a clinical isolate of Serratia marcescens is able to modulate the adhesive properties of the strain J62 which lacks adhesiveness. On the contrary, the same factor did not alter the ability of strains J53 and C600 to agglutinate erythrocytes and to adhere to human epithelial cells in culture, nor did it induce adhesive properties in wild-type strains of E. coli from clinical isolates that lacked them. This would suggest a possible plasmidic control of chromosomally encoded surface structures that mediated adhesiveness of E. coli to mammalian cells.

Adhesiveness↗
PubMed1984

Plasminogen activators, activation inhibitors and alpha 2-macroglobulin produced by cultured normal and malignant human cells.

In the present paper we have characterized the plasminogen activators (PA) synthesized by 25 different human cell lines. Technically easy methods were adopted for concentration and immunological characterization of the activators even in the presence of PA inhibitors. Most cell lines produced u-PA (mol. wt 55,000), melanoma and HeLa cells t-PA (mol. wt 66,000) and two carcinoma cell lines and normal skin fibroblasts produced no detectable PA. The classical 125I-fibrin method was compared to a caseinolytic assay and some of the discrepancies between results obtained with the two methods were shown to be due to cell-derived NaDodSO4-sensitive proteinase inhibitors in culture media. Additionally, synthesis and uptake by the cells of the wide-spectrum proteinase inhibitor alpha-2-macroglobulin ( alpha 2M ) were studied by radioimmunoassay and immunofluorescence. No production of alpha 2M could be measured in any of the malignant cell lines. In normal cells no correlation existed between the production of alpha 2M and the observed inhibition of PA activity, which indicates that other proteinase inhibitors are produced by the cells.

Cells, Cultured↗
PubMed1984

Bovine leukemia virus inhibiting activity in fetal calf serum.

We have obtained a new cell line persistently infected with bovine leukemia virus (BLV). BLV-infected cells can be easily detected by indirect immunofluorescence or immunoperoxidase staining technique. The morphology and number of infected cells seem to be related to serum concentration in culture medium: fetal calf serum (FCS) showed a marked effect on virus growth and virus distribution in cell cultures. All of the commercial lots of FCS tested showed BLV inhibiting activity very similar to that previously described for other viruses.

Animals↗
PubMed1984

Relationship between beta-lactamases production and resistance to beta-lactam antibiotics in clinical isolates of Enterobacteriaceae.

288 clinical isolates of Enterobacteriaceae were assayed for beta-lactamase production in order to assess the role played by beta-lactamases in resistance to beta-lactam antibiotics. The data obtained showed that beta-lactamase production is undoubtedly a fundamental determinant for resistance. In fact, there was a significant correlation between the specific activity of the enzyme and the MIC of the strains considered. However, the role played by permeability barriers and/or other factors should be stressed, especially in determining resistance to cephalosporins. The validity of the nitrocefin test for detection of beta-lactamase production in Enterobacteriaeae from clinical isolates was also investigated.

Anti-Bacterial Agents↗
PubMed1983

A method for evaluating the statistical accuracy of in vitro virus titrations.

A method is proposed for evaluating the statistical accuracy of virus titrations based on formation of foci or plaques in monolayer cell cultures and of colonies in soft medium. It can be applied to experiments of enhancement or inhibition of virus replication and of cell transformation or lysis, even with effects of small amplitude. The method is based on simple formulae derived on the basis of Poisson's distribution of infectious particles in cell cultures. It can be used in determining the statistical significance of one result obtained in a single experiment, of the difference between two results obtained in a single experiment with the same control, and of two results obtained in two different experiments with two different controls. It offers moreover the possibility of planning experiments in order to get an expected result significant for a desired confidence limit.

Fibroblasts↗
PubMed1983

A plasmid-linked caseinolytic activity in Enterobacteriaceae.

We have tested for production of caseinolytic activity the strain of E. coli K12 J62 carrying different R factors from various Enterobacteriaceae of clinical isolates. The results obtained showed the presence of a caseinolytic activity in 7 out of 139 R factors tested. All of these positive (cas+) R factors derived from strains of Klebsiella pneumoniae and all were able to transfer a strong lac+ phenotype as well as multiple antibiotic resistances (R-lac factors). Another strain of E. coli K12, J53, which is plasmid-free, produced levels of caseinolytic activity comparable to those of the Klebsiella R factors; J62, on the contrary, appeared to possess an inhibitor specific for the caseinolytic activities of J53 and of the R factors but not of other cas+ Gram+ and Gram- organisms. The hypothesis that the expression of the cas+ phenotype in E. coli K12 may be due to the presence of plasmid-linked regulatory genes is discussed.

Caseins↗
PubMed1982

Enhancement of plasminogen activator activity by the culture medium of Rous sarcoma virus-transformed cells.

We have tested the effect of the culture medium of chicken embryo fibroblasts (CEF) transformed by Rous sarcoma virus (RSV) on plasminogen activator (PA) activity of normal and RSV-infected cells. The results obtained showed that fibrin digestion by cultures of normal uninfected and RSV-infected cells directly attached to a fibrin substrate was increased when the cells were exposed to the supernatant of an 18 h-culture of CEF transformed by RSV. Addition of cycloheximide to the supernatant completely abolished this effect. Similarly, exposure of both normal and RSV-infected cells to the culture medium of RSV-transformed CEF resulted in a marked increase of the soluble PA activity present in the supernatant. This effect, however, was not abolished by inhibition of protein synthesis. For both the cell-bound and soluble PA activities of normal and RSV-infected cells the stimulatory effect was transient, being maximal between 8 and 12 h of exposure to the transformed cell-conditioned medium and disappearing after 24 h. A possible correlation with transformation-enhancing factor(s), previously reported to be present in the culture medium of transformed cells, is discussed.

Animals↗
PubMed1980

Potential diagnostic and prognostic significance of the transformation-enhancing factor(s) in the plasma cryoprecipitate of tumor patients.

A biological activity which enhances cell transformation (TEF) in Rous sarcoma virus temperature-sensitive mutant-infected cultures has been evidenced in the plasma cryoprecipitate from patients affected with different types of neoplastic disease. In the present paper we report data on the analysis of TEF activity in the plasma cryoprecipitates from leukemic and tumor patients tested either before or during specific antineoplastic treatments. The screening of 57 cases of different neoplastic diseases and of 57 controls, healthy subjects or patients affected with other non-neoplastic diseases indicates that TEF activity is generally related to the presence of neoplasia. Furthermore, a follow-up of patients from the onset of the disease through its evolution during therapy suggests that variations of TEF activity in the plasma cryoprecipitate correlate well with the clinical and pathological conditions, thus indicating the TEF as a potential marker for monitoring cancer patients.

Animals↗
PubMed1980

Inhibition of Rous sarcoma-virus-induced transformation by proteins involved in blood coagulation.

Plasma, serum and the main proteins involved in the final steps of blood coagulation, fibrinogen, thrombin and plasma transglutaminase, have been tested for their ability to inhibit cell transformation and/or to induce reversion of the transformed to the normal phenotype in RSV-infected chicken embryo fibroblasts. The results obtained show that plasma, and not serum, fibrinogen, when converted to fibrin by thrombin, and activated transglutaminase alone prevent focus appearance and cause reversion of transformed to normal cell morphology.

Animals↗
PubMedDate not supplied

Properties and kinetics of development of Rous sarcoma virus-infected cells evidenced by methylene blue staining.

Three different kinds of areas of infected cells corresponding to different focus formation stages can be evidenced by methylene blue (MB) staining in cultures of chick embryo (CE) fibroblasts infected at low multiplicity with the temperature-sensitive (ts) mutant of Rous sarcoma virus (RSV), FU19, which transforms these fibroblasts at 37 degrees but not at 41 degrees. These are: (a) areas of MB-stainable cells with transformed phenotype (STP areas=foci); (b) areas of MB-stainable cells with normal phenotype (SNP areas), and (c) areas of MB-unstainable cells with normal phenotype (USNP areas). DNA and RNA synthesis and virus production were followed in these various stages at 37 degrees and at 41 degrees. The results show that when cultures are shifted from 37 degrees to 41 degrees, virus production in the SNP and USNP areas which arise by phenotypic reversion of STP foci remains comparable to that of the latter foci. On the contrary, DNA and RNA synthesis are markedly reduced in SNP and USNP areas, DNA synthesis falling down to the level of uninfected cells, and RNA synthesis remaining somewhat higher. The kinetics of development of SNP and STP areas in cultures infected with FU19 and with the parental virus SR4 were also compared. The results confirm that SNP areas are precursors of STP areas but that this passage occurs at a slower rate in cultures infected with FU19.

Animals↗
PubMedDate not supplied

Purification and biological activities of an angiogenesis factor from human placenta.

Several crude angiogenesis preparations, as well as a purified angiogenesis factor from human placenta, were tested for their ability to stimulate the production of plasminogen activator (PA) and collagenase activities, motility, chemotaxis, DNA synthesis and clonal growth in cultured endothelial cells. Treatment of capillary endothelial cells resulted in a stimulation of all the above activities, whereas endothelial cells derived from large vessels did not respond. These cellular activities are postulated to be responsible for capillary growth in vivo.

Angiogenesis Inducing Agents↗