Search PubMed⌕ Search

Biomedical subjects

P C Tai

Publications and source records attributed to P C Tai.

At least 73 records · Page 4Linked to original sources
PubMed1986

Role of inflammatory cells in Chagas' disease. III. Kinetics of human eosinophil activation upon interaction with parasites (Trypanosoma cruzi).

The kinetics of human eosinophil activation and granule secretion initiated by interaction with Trypanosoma cruzi amastigotes was studied by using a monoclonal IgG1 antibody (termed EG2) that is specific for an epitope present only in the secreted forms of both eosinophil cationic protein (ECP) and the eosinophil protein X (EP-X), and hence not detectable in unstimulated resting eosinophils. Studies were carried out by using electron microscopy and indirect immunofluorescence. In the electron microscopy studies, deposits of protein A-gold particles in parasite-containing eosinophils that had been incubated previously with EG2 antibody were first detected 4 hr after initiation of the eosinophil-amastigote interaction. Control tests performed with a monoclonal IgG1 unreactive with eosinophils showed no deposition of protein A-gold particles. EG2 antibody binding was confined to the crystalloid granule matrix, where ECP and EP-X are known to be stored. A similar kinetic pattern of ECP/EP-X solubilization and secretion was confirmed by the results of the indirect immunofluorescence experiments also showing the binding of EG2 antibody after 4 hr of cell-parasite interaction. The kinetics of ECP/EP-X solubilization and secretion paralleled the kinetics of destruction of internalized amastigotes, suggesting a role for these basic proteins in parasite killing. Consistent with this notion was the detection of ECP/EP-X in the fluid of phagocytic vacuoles containing amastigotes and associated with the ingested organisms at the same time as the parasites began to show structural alterations. These results outlined the kinetics of eosinophil activation in terms of the time required for mobilization of two basic proteins associated with eosinophil secretion that are known to be biologically active.

Antigens, Protozoan↗
PubMed1986

Monoclonal antibodies to human eosinophil plasma membrane antigens enhance the secretion of eosinophil cationic protein.

This study was done to examine the nature of the membrane constituents involved in the secretion of eosinophil cationic protein (ECP) from human blood eosinophils. Three mouse monoclonal antibodies were used, which showed greater binding to membrane antigens on activated, and light density eosinophils from patients with an eosinophilia, than on nonactivated or normal density eosinophils. All three antibodies (EoN4, EoN5 & EoN6) stimulated normal density human eosinophils to secrete ECP, either alone or in association with sepharose-C3b. The antibodies bound to at least two separate sites on the membrane, which were distinct from the receptors for immunoglobulins, C3b, and eosinophil activating factor. One combination of antibodies increased the amount of ECP which was secreted. The membrane antigen recognized by antibody EoN4 was a glycoprotein, molecular weight 75 kD. These findings showed that ECP secretion may be induced by a wider range of stimuli than has been previously recognized, and that the antigens recognized by these monoclonal antibodies may play an important role in the induction of eosinophil degranulation.

Antibodies, Monoclonal↗
PubMed1985

Partial purification and biological properties of an eosinophil-activating factor.

A protein (eosinophil-activating factor, EAF), which enhances the capacity of human peripheral blood eosinophils to kill antibody-coated schistosomula of Schistosoma mansoni, has been partially purified from supernatants of cultured peripheral blood mononuclear cells by sequential chromatography on Sephacryl S200 and DEAE-cellulose. This protein is acidic with a molecular mass on gel filtration of 40 +/- 7 kDa. It not only enhances the activity of eosinophils against schistosomula but also increases their ability to lyse antibody-coated, herpes simplex virus-infected Chang liver cells. It enhances the production of superoxide and hydrogen peroxide by eosinophils that occurs both spontaneously and in response to opsonized zymosan. However, increased respiratory burst activity does not appear to be responsible for the enhancement of eosinophil-mediated killing of schistosomula, since a comparable or greater increase in hydrogen peroxide production is induced by column fractions that have little or no effect on schistosomulum killing. EAF enhances eosinophil degranulation, both spontaneously and after incubation with opsonized zymosan. Enhanced degranulation is associated with release of eosinophil peroxidase and eosinophil cationic protein. These findings suggest that EAF enhances the capacity of eosinophils to kill parasites by increasing the extent of eosinophil degranulation and the amount of toxic granule proteins that are secreted.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1985

The pathogenesis of eosinophilic endomyocardial disease in patients with carcinomas of the lung.

Studies were done on a patient with a carcinoma of the lung induced by hypereosinophilia who was thought to be at risk from developing eosinophilic endomyocardial disease to see whether the development of heart disease could be related to abnormalities in the morphology or kinetics of blood eosinophils. The patient was a 61-year-old man who had a partial resection of a squamous cell bronchial carcinoma of anaplastic large cell type which has spread locally. Seven months later, he developed a blood eosinophil count of 33.9 x 10(9)/1. There were only transient responses to treatment with steroids and tumor irradiation, and he died 15 weeks later. Up to 3 x 10(9)/1 blood eosinophils were degranulated, correlating with serum levels of eosinophil cationic protein. The blood half-life of 111indium-labeled eosinophils was prolonged to 53 h, but their distribution was normal. Although an unsuccessful search was made during life for the development of endomyocardial damage, at postmortem the left ventricle had features of eosinophilic endomyocardial disease in the acute necrotic stage. Among 13 other reported patients with carcinoma of the lung and hypereosinophilia, three also had endomyocardial disease or myocardial lesions. These findings confirm the suggestion that the presence in the blood of greater than 1 x 10(9)/1 degranulated eosinophils can be used to predict the development of eosinophilic endomyocardial disease before it becomes apparent clinically, and they also add weight to the hypothesis that blood eosinophil degranulation causes this complication of hypereosinophilic states.

Blood Proteins↗
PubMed1985

Eosinophilic disorders affecting the myocardium and endocardium: a review.

A wide range of disorders give rise to eosinophil counts greater than 1.5 X 10(9)/l (hypereosinophilia) and cardiac injury. The best known of these is eosinophilic endomyocardial disease (Löffler's endomyocardial fibrosis), which occurs as a major complication of the idiopathic hypereosinophilic syndrome. Here the heart damage appears to be a direct result of tissue injury produced by toxic eosinophil granule proteins within the heart. However, it is not known what causes the eosinophilia in these patients, why the eosinophils degranulate, or why the endocardium is especially susceptible to this type of injury. A number of parasitic infections may give rise to eosinophilic myocarditis. This is usually the result of the presence of the parasites within the myocardium where they die within inflammatory lesions, which may be extensive. Occasionally, drug reactions and rejection of a transplanted heart may produce eosinophilic myocarditis. Allergic granulomatosis and vasculitis (the Churg-Strauss syndrome), which gives rise to granulomas involving the myocardium, and eosinophilic (hypersensitivity) myocarditis usually respond rapidly to treatment with steroids. However, diffuse myocardial involvement may lead to heart failure, and some of these patients may later develop dilated cardiomyopathy. It is concluded that the heart may be affected by a variety of diseases in which eosinophils are a prominent component in the inflammatory cell infiltrates. Eosinophils themselves may contribute to some of the myocardial cell injury which occurs in these diseases, and attempts to limit this with steroids may be worthwhile in some patients.

Cardiomyopathies↗
PubMed1985

In situ detection of beta-lactamase activity in sodium dodecyl sulfate-polyacrylamide gels.

After beta-lactamase had been denatured by boiling in the presence of sodium dodecyl sulfate (SDS) and then electrophoresed in SDS-polyacrylamide gels, activity could be restored and could be detected in situ as specific molecular species. Renaturation was simple and facilitated by the presence of a carrier protein. The assay was sensitive, detecting 0.8 ng beta-lactamase activity in the gel.

Bacillus↗
PubMed1985

Orientation and expression of the cloned hemolysin gene of Pseudomonas aeruginosa.

The structural gene for Pseudomonas aeruginosa hemolysin, carried on recombinant plasmid pSL2 and cloned in Escherichia coli, was analyzed by insertional and deletional mutagenesis. Expression of the hemolysin was blocked by insertion of transposon Tn5 into different locations. Two of the mutants allowed detectable synthesis of truncated hemolysin polypeptides of two different sizes and thus defined the structural gene. The location of the hemolysin gene in the recombinant plasmid, and the direction of transcription, were further established by nuclease BAL 31 digestion, and by construction of gene fusions between hemolysin and beta-galactosidase. Evidently, the tet promoter contributed to the majority of the expression of cloned hemolysin gene, but the Pseudomonas promoter was present in the cloned DNA and was functional in E. coli since inactivation of the tet promoter either by Tn5 insertion or by deletion decreased synthesis of the 80-kDal hemolysin but did not fully abolish it.

Chromosome Mapping↗
PubMed1985

Activated eosinophils in familial eosinophilic gastroenteritis.

Two siblings with eosinophilic gastroenteritis who presented with severe iron deficiency anemia and hypoalbuminemia associated with varying degrees of mucosal damage are described. Using a monoclonal antibody to the secreted form of eosinophil cationic protein, we demonstrated activated degranulating eosinophils in the gastrointestinal mucosa that correlated with the degree of histologic damage. This finding suggests that eosinophils may have a primary role in the tissue damage in this condition. Oral disodium cromoglycate (Nalcrom) failed to alter the clinical, radiologic, and histologic abnormalities. Prednisolone, however, was beneficial in 1 case but did not completely reverse the abnormalities.

Adolescent↗
PubMed1985

Secretory S complex of Bacillus subtilis forms a large, organized structure when released from ribosomes.

The S complex of Bacillus subtilis, a set of four proteins that appears to be involved in protein secretion, is shown to be attached to 70S ribosomes: antibody to its 64-kDa component can aggregate these ribosomes, and the complex can be chemically crosslinked to ribosomal proteins. Low Mg2+ or prolonged high-speed centrifugation in a sucrose gradient releases the S complex from the ribosomes, and it is recovered as an aggregate with an S value of 76. Electron microscopy shows that these aggregates have a regular structure, somewhat resembling clathrin cages, with a diameter of about 45 nm. If these aggregates are physiological, their function would differ significantly from that of the signal recognition particle of eukaryotes.

Bacillus subtilis↗
PubMed1985

ATP is essential for protein translocation into Escherichia coli membrane vesicles.

The energy requirement for translocation of alkaline phosphatase and the outer membrane protein OmpA into Escherichia coli membrane vesicles was studied under conditions that permit posttranslational translocation and, hence, prior removal of various components necessary for protein synthesis. Translocation could be supported by an ATP-generating system or, less well, by the protonmotive force generated by D-lactate oxidation; the latter might act by generating ATP from residual bound nucleotides. However, when protonmotive force inhibitors were used or when ATP was further depleted by E. coli glycerol kinase, D-lactate no longer supported the translocation. Furthermore, ATP could still support protein translocation in the presence of proton uncouplers or with membranes defective in the F1 fraction of the H+-ATPase. We conclude that ATP is required for protein translocation in this posttranslational system (and probably also in cotranslational translocation); the protonmotive force may contribute but does not appear to be essential.

Adenosine Diphosphate↗
PubMed1985

Alkaline phosphatase and OmpA protein can be translocated posttranslationally into membrane vesicles of Escherichia coli.

We previously described a system for translocating the periplasmic enzyme alkaline phosphatase and the outer membrane protein OmpA into inverted membrane vesicles of Escherichia coli. We have now optimized and substantially improved the translocation system by including polyamines and by reducing the amount of membrane used. Under these conditions, efficient translocation was seen even posttranslationally, i.e., when vesicles were not added until after protein synthesis was stopped. This was the case not only with the OmpA protein, which is synthesized by free polysomes and hence is presumably exported posttranslationally in the cell, but also with alkaline phosphatase, which is synthesized only by membrane-bound polysomes and has been shown to be secreted cotranslationally in the cells. Prolonged incubation rendered the precursors inactive for subsequent translocation. Posttranslational translocation was impaired, like cotranslational translocation, by inhibitors of the proton motive force and by treatment of the vesicles with protease. Since it appears that E. coli can translocate the same proteins either cotranslationally or posttranslationally, the cotranslational mode may perhaps be more efficient, but not obligatory, for the secretion of bacterial proteins.

Alkaline Phosphatase↗
PubMed1985

Eosinophil membrane antigens: phenotypic frequencies in normal individuals and patients with the hypereosinophilic syndrome.

The membrane antigen phenotype of eosinophils from six normal individuals and eight patients with the hypereosinophilic syndrome (HES) were examined to see whether subpopulations of eosinophils exist. Experiments were done with a panel of 6 monoclonal antibodies, using the fluorescent activated cell sorter, and immunocytochemistry. All six antibodies bound eosinophils and neutrophils, but not lymphocytes, monocytes, platelets or erythrocytes. The phenotypic frequencies of five of the six antibodies were increased in patients' eosinophils (p less than 0.005). This increase was associated with the intermediate-density eosinophils, while the antigen detected by antibody Eon 7 was associated with the light-density eosinophils. Normal eosinophils could be induced to increase their expression of these membrane antigens by incubation with mononuclear cell supernatants which are known to increase the cytotoxic capacities of eosinophil, 'activation'. It was concluded that there is a single eosinophil which undergoes post-mitotic differentiation in the blood, leading to activation and degranulation. The heterogeneity seen in patients' eosinophils reflect different stages of cell maturation and activation.

Antibodies, Monoclonal↗
PubMed1985

Tissue localization of human eosinophil cationic proteins in allergic diseases.

Mouse monoclonal antibodies were raised to the storage and secreted forms of eosinophil cationic protein (ECP), and were used to study the presence of activated eosinophils and secreted ECP in the tissues of patients with a variety of allergic diseases. Immunocytochemical localization was shown with alkaline phosphatase-linked second antibodies, and fast-red substrate. Deposition of a red reaction product indicated sites in tissues where eosinophils had become activated, and where secreted ECP was present. Activated eosinophils and secreted ECP were found together in (1) skin lesions of patients with chronic urticaria, (2) gut lesions of patients with eosinophilic gastroenteritis and ulcerative colitis, and (3) tissues containing granulomas in patients with allergic granulomatosis and vasculitis - the Churg and Strauss syndrome. These results show the value of these techniques for determining the sites of eosinophil activation and secretion in allergic diseases. They support the suggestion that ECP may be involved in the development of these tissue lesions.

Blood Proteins↗
PubMed1985

Purification of eosinophil peroxidase and studies of biosynthesis and processing in human marrow cells.

Human eosinophil peroxidase (EPO) was purified from leukocytes obtained from a patient with hypereosinophilia. EPO was extracted from the granule fraction using 0.2 mol/L sodium acetate pH 4.0, and the extract was subjected to gel chromatography on Sephadex G-75 and ion exchange chromatography on Biorex 70. The mol wt calculated from gel chromatography was approximately 50,000. However, under reducing and denaturing conditions, polyacrylamide gel electrophoresis revealed two subunits with mol wt of 50,000 and 15,000. The biosynthesis of EPO was studied in marrow cells from patients with eosinophilia using labeling with (14C)-leucine, followed by immunoprecipitation with anti-EPO, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and fluorography for visualization of labeled EPO. Biosynthesis of an Mr 53,000 subunit was demonstrated. Biosynthetic labeling of the Mr 15,000 subunit was not demonstrated. A labeled Mr 25,000 chain was detected and may represent a degradation product or a chain that, after further modification, produces the Mr 15,000 subunit. Labeling was also detected in two polypeptides with mol wt of 78,000 and 72,000. These forms of EPO seem to represent precursor polypeptides subjected to proteolytic processing in a similar manner as has been reported for myeloperoxidase (MPO). However, Monensin, a proton ionophore, which blocks the processing of MPO, did not inhibit processing of EPO, indicating separate mechanisms by which MPO and EPO are directed to granules.

Antibodies, Monoclonal↗
PubMed1985

Plasma membrane antigens on light density and activated human blood eosinophils.

In order to study the membrane events which lead to human blood eosinophil activation and degranulation, six clone of mouse monoclonal antibodies were made to isolated blood eosinophils from a patient with the hypereosinophilic syndrome (HES). The antibodies were specific for the plasma membranes of blood eosinophils and neutrophils, eosinophil myelocytes and haemopoietic cell lines. A higher proportion of blood eosinophils from eight patients with the HES bound these antibodies compared to normal individuals. Five antibodies stained intermediate density eosinophils preferentially, and one stained the light density eosinophils most strongly. Normal blood eosinophils were induced to express more of these antigens either by culture alone (two antibodies) or culture with monocyte culture supernatant which activates eosinophils for increased cytotoxic capacity (four antibodies). It was concluded that several of the principal antigens on the eosinophil plasma membrane are also present on neutrophils and immature haemopoietic cells, and that their expression in mature blood eosinophils is related to the extent of eosinophil activation and degranulation. It is suggested that these antigens may be useful in studying the ways in which eosinophils alter their plasma membrane during activation and degranulation in vitro, and in the blood of patients with an eosinophilia.

Adult↗
PubMed1984

Deposition of eosinophil cationic protein in granulomas in allergic granulomatosis and vasculitis: the Churg-Strauss syndrome.

Biopsy specimens and tissues obtained at necropsy from two women who died after developing the Churg-Strauss syndrome were analysed to see whether granulomas in these patients contained activated eosinophils or secreted eosinophil cationic proteins, or both. Immunocytochemical studies with monoclonal antibody EG2 showed large amounts of eosinophil cationic protein and eosinophil protein-X (which are toxic for heart cells and other tissues) in the granulomas. Many activated and degranulating eosinophils were seen to be migrating from the blood into these areas. Eosinophils may play a central part in the development of lesions in the heart and other tissues in the Churg-Strauss syndrome.

Adolescent↗
PubMed1984

The 64-kilodalton membrane protein of Bacillus subtilis is also present as a multiprotein complex on membrane-free ribosomes.

The 64-kDa membrane protein of Bacillus subtilis is evidently involved in the attachment of secreting ribosomes to membrane. On immunoprecipitation with antibody to this protein, the solubilized particulate fraction, with or without prior chemical cross-linking, yields a complex of four proteins (64, 60, 41, and 36 kDa). This "S complex" was found to be associated with membrane-free ribosomes rather than with membrane, but the 64-kDa protein is also present, without the other proteins of the S complex, in the membrane-ribosome fraction and in the cytosol. Only the form present in the membrane-ribosome fraction is protected from protease. These findings suggest a cycle in which the complex participates in initiation of secretion but not in the later stages. It is not yet clear whether the 64-kDa protein found in the membrane-ribosome complexes is retained from the S complex after initiation and later recycled via the cytosol or whether it is a separate pool.

Bacillus subtilis↗