Biomedical subjects

D Egger

Publications and source records attributed to D Egger.

At least 37 records · Page 2Linked to original sources

PubMed1995

IL-4 renders mast cells functionally responsive to endothelin-1.

It has previously been shown that mouse bone marrow-derived mast cells (BMMC) synthesize and secrete endothelin-1 (ET-1) and express ETA-type endothelin receptors (ETA-R). The study presented here was designed to elucidate the influence of different cytokine conditions for cellular differentiation and maturation on the ability of primary mouse BMMC to respond to exogenous ET-1. BMMC were grown for 2 wk in IL-3 alone and then cultured for 2 to 3 wk with kit ligand (KL) and/or IL-3 in the presence or absence of IL-4. ET-1 induced a very rapid (< or = 1 min) and dose-dependent release of histamine and serotonin from BMMC cultured in the presence of both IL-3 and IL-4. The effect of ET-1 was quantitatively comparable with IgE/Ag-induced mediator release and comprised up to 20% and 16% of total cellular histamine and serotonin, respectively. In BMMC grown with KL or KL plus IL-3, a substantial effect of ET-1 on amine release was only observed when IL-4 had been included in the culture medium. These IL-4 effects could not be observed if BMMC grown in IL-3 and/or KL were preincubated for 1 or 24 h with IL-4 before activation with ET-1, suggesting that a differentiation process rather than a functional priming effect had been initiated by IL-4. In BMMC, the histamine and serotonin release induced by ET-1 (10(-6) M) was inhibited by an ETA-R-specific antagonist (cyclic [D-Asp-Pro-D-Val-Leu-D-Trp]) in a dose-dependent manner, with complete inhibition at an antagonist concentration of 10(-8) M. ET-1 stimulated leukotriene C4 biosynthesis up to 4.5-fold in BMMC cultured in the presence of IL-4. No such ET-1 effect was observed in BMMC cultured in media containing IL-3, KL, or a combination of both cytokines. Peritoneal cells (containing 2 to 3% serosal mast cells) obtained from BALB/c mice released 87 +/- 2% of histamine within 1 min after challenge with ET-1. Our results demonstrate that ET-1 can directly act as a histamine and serotonin secretagogue and as a stimulator of leukotriene C4 production in mast cells. IL-4 appears to be critically involved in the differentiation of immature mast cell precursors to an ET-1-reactive phenotype.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1995

Immunocytochemistry and in situ hybridization in the electron microscope: combined application in the study of virus-infected cells.

The present review evaluates methods for electron microscopic immunocytochemistry and in situ hybridization, using post-embedding techniques and colloidal gold as a label. Special emphasis is given to double labeling immunocytochemistry and double in situ hybridization and to their combined application on the same specimen. Brief guidelines are presented for fixation, embedding media, the use of polyclonal and monoclonal antibodies and nucleic acid probes. Conditions for labeling and binding of antibody and nucleic acid probes to the target and protocols for direct and indirect immunodetection are discussed. Combinations of direct and indirect immunodetections in multiple labeling experiments are summarized.

Antibodies↗

PubMed1995

Poliovirus subviral particles associated with progeny RNA in the replication complex.

The poliovirus replication complex (RC), the site of genomic 36S RNA synthesis, was previously shown to contain subviral particles of 5S protomer and 14S pentamer antigenicity. The present investigation demonstrates that 5S/14S antigenic subviral particles can be cross-linked to viral RNA by UV irradiation of a subcellular fraction containing the poliovirus RC. Each capsid protein of the subviral particles, i.e. VP0, VP1 and VP3, was cross-linked to viral RNA. SDS-PAGE analysis of the cross-linked capsid proteins revealed a bandshift for VP1, whereas VP0 migrated in several bands, which were interpreted to be multimers of VP0 linked by short stretches of RNA. It was found that 36S RNA rather than replicative intermediate RNA was cross-linked to capsid proteins. Our results indicate that encapsidation of poliovirus RNA starts in the RC and is initiated by 14S pentamers.

Capsid↗

PubMed1995

Reverse transcription multiplex PCR for differentiation between polio- and enteroviruses from clinical and environmental samples.

For the rapid detection of polioviruses and their differentiation from nonpoliovirus enteroviruses, we developed a protocol in which clinical or environmental specimens are first inoculated onto cell cultures in tubes. After overnight incubation, the cultures are subjected to reverse transcription multiplex PCR with a primer pair which detects all enteroviruses (T. Hyypiä, P. Auvinen, and M. Maaronen, J. Gen. Virol. 70:3261-3268 1989) and two newly designed primer pairs specific for all 36 poliovirus strains tested. The PCR products can unequivocally be identified by their lengths in agarose gels, whereas the genetic heterogeneity of the poliovirus strains precludes identification by back-hybridization with internal probes. The proposed protocol is highly insensitive to the inhibitory effects of substances in the sample (stool, sewage). It allows for the detection of polioviruses and for polioviruses to be distinguished from nonpoliovirus enteroviruses within 24 h, and it allows for the concomitant isolation of a viable strain suitable for further typing.

Base Sequence↗

PubMed1994

Simultaneous determination of histamine and serotonin in mast cells by high-performance liquid chromatography.

A sensitive and rapid high-performance liquid chromatographic method for the simultaneous determination of histamine and 5-hydroxytryptamine (serotonin) in supernatants and cellular extracts from mouse bone marrow-derived mast cells was developed. The described method is based on a precolumn derivatization of histamine and serotonin with o-phthaldialdehyde (OPA) and subsequent separation of the amine-OPA adducts with an analytical reversed-phase C18 column combined with fluorometric detection (excitation wavelength 360 nm, emission at 455 nm). The mobile phase was 0.02 M sodiumacetate buffer (pH 8) including 5 mM 1-octanesulfonic acid and 50% methanol. The detection limits for histamine and serotonin were 3.3 pmol and 6.9 pmol, respectively (signal-to-noise ratio 2:1). The variations of peak areas of repeatedly injected low or high amounts of amine standards were 23.3% or 6.9% (for 0.5 ng or 12.5 ng histamine) and 26.4% or 4.0% (for 5.0 ng or 250 ng serotonin) during an experimental period of 4 weeks. The variation of retention times over 2 days was 1.1% for histamine and 1.7% for serotonin. A perfect linear relationship of amine concentrations and peak areas was documented by correlation coefficients of r > 0.999 for both histamine (0.1-125 ng) and serotonin (0.5-250 ng).

Animals↗

PubMed1994

Membrane rearrangement and vesicle induction by recombinant poliovirus 2C and 2BC in human cells.

Poliovirus (PV)-infected cells undergo extensive proliferation and rearrangement of intracellular smooth membranes to generate vesicles on which viral RNA replication occurs. PV proteins 2C and 2BC are known to be tightly associated with these membranous replication complexes and have been proposed to be involved in the formation of these virus-induced vesicles. We have expressed these proteins, and proteins with mutations in the putative nucleotide (NTP) binding motifs, in human cells using recombinant vaccinia viruses and T7 RNA polymerase-directed transcription. To ascertain the subcellular localization properties of these proteins in the absence of other PV proteins and to determine whether they induced ultrastructural changes, cells expressing 2C and 2BC proteins were examined by immunofluorescence (IF) microscopy, electron microscopy (EM), and immuno-EM (IEM). The cytoplasm of cells expressing either 2C or 2BC exhibited vesicles of 50-350 nm in diameter, which resembled those found in PV-infected cells. Both 2C and 2BC were associated with these vesicles. Mutations in the putative NTP binding motif did not affect vesicle induction by 2C or 2BC. Despite the membrane reorganization and vesicle formation induced by 2C and 2BC proteins, no enhanced synthesis of lipid was observed. Guanidine hydrochloride at a concentration that inhibits PV replication, did not have significant effects on the IF patterns of either 2C or 2BC. An additional prominent alteration in cells expressing 2C, but not 2BC, was the formation of extensive tubular membrane structures with a myelin-like arrangement in the lumen of the rough endoplasmic reticulum. IEM analyses showed that 2C was associated with these structures. In the presence of other PV proteins, the tubular membrane structures induced by 2C were not detected. These structures are not observed in poliovirus-infected cells, but likely indicate a novel property of 2C that induces a complex interaction with intracellular membranes.

Amino Acid Sequence↗

PubMed1994

Characteristics of the poliovirus replication complex.

In the infected cell, the poliovirus replication complex (RC) is found in the center of a rosette formed by many virus-induced vesicles. The RC is attached to the vesicular membranes and contains a compact central part which encloses the replication forks of the replicative intermediate and all proteins necessary for strand elongation. The growing plus strands of the replicative intermediate protrude from the central part of the RC, but are still enclosed by membraneous structures of the rosette. After completion, progeny 36S RNA is set free at the surface of the rosette. In an in vitro transcription system, isolated replication complex-containing rosettes are active in initiation, elongation and maturation (release) of plus strand progeny RNA. Full functionality of the RC depends on an intact structural framework of all membraneous components of the rosette.

Capsid↗

PubMed1994

Protein (western) blotting.

The different steps involved in protein (Western) blotting and subsequent analysis of the proteins are reviewed. Electrophoretic separation of proteins, procedures of transfer to membranes, immunological and nonimmunological protein detection systems, and characterization of protein-nucleic acid and protein-protein interactions are described. Emphasis is on the sensitivity of the methods described and on possible variations that allow the individual steps of Western blotting to be adapted to specific questions.

Antibodies↗

PubMed1994

Light and electron microscopic in situ hybridization: non-radioactive labeling and detection, double hybridization, and combined hybridization-immunocytochemistry.

We performed light and electron microscopic in situ hybridization, according to the same protocol and without pretreatment of sections, on Lowicryl- and LR Gold-embedded cells. Digoxigenin (DIG)- or biotin-labeled riboprobes were visualized by direct or indirect immunodetection using commercially available gold-antibody conjugates with 0.8-10-nm gold grains. At the ultrastructural level, the main findings were that DIG-labeled probes gave a slightly higher labeling intensity (grains per signal) than biotin. The direct detection method produced a more compact signal, which led to better resolution at medium and high magnifications. Labeling intensities of all gold grain sizes were essentially equal. Grain sizes of 5 nm and larger were highly preferable because available enhancement methods are unsatisfactory for ultrasmall grains. The optimized immunodetection protocols are suitable for double hybridization with two different probes and for combined hybridization and immunocytochemistry.

Antibodies↗

PubMed1993

In a concerted action kit ligand and interleukin 3 control the synthesis of serotonin in murine bone marrow-derived mast cells. Up-regulation of GTP cyclohydrolase I and tryptophan 5-monooxygenase activity by the kit ligand.

Mouse bone marrow-derived mast cells (BMMC) store and release serotonin whose synthesis is initiated by tryptophan 5-monooxygenase. (6R)-H4biopterin serves as the natural cofactor for this reaction. GTP cyclohydrolase I catalyzes the first and rate-limiting step of its synthesis. In this study we demonstrate that among a panel of growth-promoting cytokines including kit ligand (KL), interleukin 3 (IL-3), IL-4, IL-9, and nerve growth factor, KL selectively enhances the synthesis of H4biopterin through up-regulation of GTP cyclohydrolase I activity to 6.2-fold levels. The activities of the subsequent enzymes 6-pyruvoyl-H4pterin synthase and sepiapterin reductase remain unaffected. The activity of tryptophan 5-monooxygenase was selectively enhanced 4.5-fold by the combination of IL-3 with KL. All other factors could not substitute for KL. The constitutive high activity of aromatic L-amino acid decarboxylase is not different in cells cultured in IL-3 and/or KL. In consequence, the concerted action of IL-3 and KL on the GTP cyclohydrolase I and the tryptophan 5-monooxygenase reaction enhances the production of serotonin to about 20-fold levels. Additionally, KL specifically causes the release of about half of total serotonin produced. Hence, our data demonstrate a novel role of these cytokines for the function of mouse BMMC and provide a coherent view of the regulation of serotonin synthesis in this cell type.

5-Hydroxytryptophan↗

PubMed1992

Intracellular localization of poliovirus RNA by in situ hybridization at the ultrastructural level using single-stranded riboprobes.

Polioviral RNA was localized by electron microscopic in situ hybridization on sections of poliovirus-infected HEp-2 cells. Viral plus-strand RNA was found accumulated in the close surroundings of the membrane-bound replication complex. Two different regions of the viral genome were detected with the same frequency, which indicates the predominant presence of full-length genomic RNA. Viral proteins of the P2 and the P3 genomic region were detected mainly over the core of the replication complex, whereas the hybridization signal was present rather at the peripheral parts of the complex. A more than 100-fold excess of viral plus- over minus-strand RNA was found by strand-specific hybridization to RNA extracted from isolated replication complexes. These findings support the idea of a pool of viral plus-strand RNA set free from the replication complex and accumulating in the close vicinity of the replication complex possibly before encapsidation.

Cells, Cultured↗

PubMed1992

Immunocytochemical localization of capsid-related particles in subcellular fractions of poliovirus-infected cells.

The structural proteins of poliovirus can assemble into a series of different configurations (capsid-related particles, CRP). Only some seem to be true capsid precursors and the role of most CRP in morphogenesis is unclear. We used electron microscopic immunocytochemistry with monoclonal antibodies recognizing different CRP [protomers, pentamers, 65S empty capsids (EC), 74S-EC, and virions] to locate CRP in subcellular fractions containing virus-induced vesicles associated with the viral replication complex. We found pentamer antigenic CRP to be associated with the replication complex. The same pentamer antigenicity was exhibited by novel, "capsid-like" structures attached to the surface of the virus-induced vesicles. Upon solubilization of the vesicular fraction, mainly 65S-EC and only negligible amounts of pentamers were found by sucrose gradient analysis and by immunoprecipitation. We show that the pentamer antigenic particles are converted into 65S-EC when their membranous support is dissolved. We propose that the vesicular membrane prevents the assembly of 65S-EC and keeps the pentamer antigenic CRP in the appropriate concentration and configuration for association with the nascent progeny RNA.

Antibodies, Monoclonal↗

PubMed1992

Structural and functional characterization of the poliovirus replication complex.

Two populations of membrane-bound replication complexes were isolated from poliovirus-infected HEp-2 cells by sucrose gradient centrifugation. The two fractions show similar ultrastructural features: the replication complex is enclosed in a rosettelike shell of virus-induced vesicles and contains a very tightly packed second membrane system (compact membranes). The vesicular fraction, which bands in 30% sucrose, contains replicative intermediate (RI) and 36S RNA. The fraction banding in 45% sucrose contains only minute amounts of RI and contains mainly 36S RNA, two-thirds of which is encapsidated. In vitro, the two fractions show similar RNA synthesizing capacities and produce 36S plus-strand RNA. Dissolving the membranes within and around synthetically active replication complexes with sodium deoxycholate abolishes the completion of 36S RNA but still allows elongation in the RI. Our findings suggest an architecture of the replication complex that has the nascent plus strands on the RI enclosed in the compact membranes and the replication forks wrapped additionally in protein. Plus-strand RNA can be localized by in situ hybridization with a biotinylated riboprobe between the replication complex and the rosette of the virus-induced vesicles. It was found that the progeny RNA strands are set free soon after completion from the replication complex at the sites where the compact membranes within the replication complex are in close contact with the surrounding virus-induced vesicles.

Cells, Cultured↗

PubMed1990

In situ hybridization for light and electron microscopy: a comparison of methods for the localization of viral RNA using biotinylated DNA and RNA probes.

We report procedures for in situ hybridization at the light and electron microscopic level for localization of viral RNA in poliovirus-infected, Lowicryl-embedded cells. We compare specificity and signal intensity of biotinylated, double-stranded DNA and single-stranded, strand-specific RNA probes, both corresponding to the same region of the poliovirus genome. The hybrids were detected with antibiotin antibodies or streptavidin with colloidal gold as a marker. Hybridization with the RNA probe was more sensitive and gave lower background than with DNA. Detection with immunogold proved to be by far more sensitive than with streptavidin. The hybridization and detection protocols for the DNA and the RNA probes could be applied without modification to light microscopic semi-thick sections as well as to electron microscopic ultrathin sections.

Biotin↗

PubMed1990

Structural organization of poliovirus RNA replication is mediated by viral proteins of the P2 genomic region.

Transcriptionally active replication complexes bound to smooth membrane vesicles were isolated from poliovirus-infected cells. In electron microscopic, negatively stained preparations, the replication complex appeared as an irregularly shaped, oblong structure attached to several virus-induced vesicles of a rosettelike arrangement. Electron microscopic immunocytochemistry of such preparations demonstrated that the poliovirus replication complex contains the proteins coded by the P2 genomic region (P2 proteins) in a membrane-associated form. In addition, the P2 proteins are also associated with viral RNA, and they can be cross-linked to viral RNA by UV irradiation. Guanidine hydrochloride prevented the P2 proteins from becoming membrane bound but did not change their association with viral RNA. The findings allow the conclusion that the protein 2C or 2C-containing precursor(s) is responsible for the attachment of the viral RNA to the vesicular membrane and for the spatial organization of the replication complex necessary for its proper functioning in viral transcription. A model for the structure of the viral replication complex and for the function of the 2C-containing P2 protein(s) and the vesicular membranes is proposed.

Antibodies, Monoclonal↗

PubMed1987

Colloidal gold staining and immunoprobing of proteins on the same nitrocellulose blot.

Proteins blotted onto nitrocellulose can be stained with colloidal gold. They retain their immunoreactivity so that the stained blot can be probed with appropriate antibodies. The resulting antigen-antibody reaction is made visible by a peroxidase-coupled antispecies antibody. The blue peroxidase reaction product contrasts well with the red-stained protein pattern and allows an easy documentation by black-and-white photography.

Collodion↗

PubMed1987

Association of polioviral proteins of the P2 genomic region with the viral replication complex and virus-induced membrane synthesis as visualized by electron microscopic immunocytochemistry and autoradiography.

Using high resolution electron microscopic autoradiography and immunocytochemistry with monoclonal antibodies against poliovirus proteins of the P2 genomic region, the location of these proteins in respect to the virus-induced vesicle formation and the viral RNA synthesis was followed during the viral replication cycle. It was found that P2 proteins become rER associated soon after their synthesis. At the site of protein and rER interaction, electron-dense patches appear. Simultaneously, membrane protrusions grow and form vesicles which finally budd off, carrying the patches on their outer surface. As shown by autoradiography, these patches are the site of viral RNA replication and, therefore, they represent the poliovirus replication complex. The vesicles with the replication complex, including replicating and replicated viral RNA, move away from the rER to form a continuously growing vesiculated area in the center of the infected cell, where virus maturation takes place. A likely function of the 2C protein is to attach the replication complex, or some of its components, to the vesicular membranes.

Antibodies, Monoclonal↗

PubMed1986

Experimental eosinophilia and inflammation--the effect of various inflammatory mediators and chemoattractants.

An experimental subcutaneous inflammation was produced in guinea pigs with peripheral blood eosinophilia. The eosinophilia resulted from two subsequent infections with Trichinella spiralis larvae. One group of guinea pigs served as non-infected control. Inflammation was induced by carrageenan, bradykinin, histamine, platelet activating factor and eosinophilotactic factors of lymphocytic or neutrophilic origin. Whereas in the control group no eosinophil granulocytic response was observed, this response was seen in the group with peripheral blood eosinophilia. The inflammatory substances and mediators (carrageenan, bradykinin, histamine, platelet activating factor) did not attract eosinophils alone, but also neutrophils. Under peripheral blood eosinophilia within the time course of the inflammatory reaction a second emigration with a shifted neutrophil/eosinophil ratio in favour of eosinophils was found. This could be due to a generation of chemoattractants by the injected substances themselves or more probably, by already emigrated granulocytes. Neither histamine, bradykinin, carrageenan, nor the eosinophilotactic factors (ECF's) in the concentrations used did release the cytotoxic major basic protein from eosinophils. Platelet activating factor exhibited a release of major basic protein from some eosinophils but no release of the peroxidase under our experimental conditions. The immigration of sufficient numbers of eosinophils into inflammatory areas might be one cause of the reduction of the inflammatory edema found in a previous investigation under similar conditions.

Acid Phosphatase↗