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Biomedical subjects

M Grote

Publications and source records attributed to M Grote.

At least 55 records · Page 3Linked to original sources

Annexin proteins PP4 and PP4-X. Comparative characterization of biological activities of placental and recombinant proteins.

The human placental proteins PP4 and PP4-X, belonging to the annexin protein family, were expressed in Escherichia coli at high yield. The proteins were purified to homogeneity. The physicochemical parameters of the recombinant proteins were determined and compared with those of their natural placental counterparts. Except for a minor change in the pI, the proteins appeared to be indistinguishable by several criteria. Both recombinant PP4 and recombinant PP4-X were biologically active in a thromboplastin inhibition test and in a phospholipase A2 inhibition test.

Annexin A5↗

Techniques to preserve soluble surface components in birch pollen wall: a scanning and transmission electron microscopic study.

The exine of birch pollen was examined by scanning and transmission electron microscopy in the native state and after fixation in different aqueous fixatives: glutaraldehyde + OsO4; glutaraldehyde + cetylpyridinium chloride (CPC) + OsO4; glutaraldehyde + cuprolinic blue (CB); and periodate + lysine + paraformaldehyde (PLP). The native pollen exine showed a thin (3-5-nm) border of electron-dense material lining the tectum and electron-dense material within microchannels and bacula cavities. Fixation with the addition of CPC resulted in a voluminous surface coat surrounding the pollen grain, but empty microchannels and bacula cavities. After fixation with the addition of CB, there was a thin surface coat, whereas microchannels and bacula cavities were partially filled with electron-dense material. The other fixatives led to empty microchannels and bacula cavities. There was no surface coat on the pollen grain. However, after all fixation procedures, a thin electron-dense border of the tectum remained visible. Concerning the electron-dense material filling microchannels and bacula cavities in the native pollen grain, the results obtained in the present study suggest that it is either completely lost (after conventional and PLP fixation) or, after fixation with a precipitating additive, partially (CB) or completely (CPC) solubilized and precipitated on the surface of the pollen grain as a surface coat.

Cetylpyridinium↗

Binding of antibodies against birch pollen antigens/allergens to various parts of apples as studied by immuno-gold electron microscopy.

The clinically and biochemically observed correlation between birch pollen allergy and hypersensitivity to apples was investigated by immunocytochemical techniques. For this purpose, apple tissue was fixed in p-formaldehyde and embedded in Lowicryl K4M resin at -35 degrees C. Ultrathin sections were cut and successively incubated with rabbit antibodies against birch pollen antigens/allergens and protein A/gold. Specific antibody binding sites were detected throughout the apple fruit (peel, fruit flesh, seed). Control sections incubated with normal rabbit IgG antibodies and protein A/gold showed minimal background staining. It was concluded from the results of immunocytochemical labelling that apple tissue and birch pollen contain similar molecular structures which lead to the observed cross-reactions. The present immunocytochemical results confirm biochemical investigations reporting partial structural identity of antigens/allergens in birch and apple.

Allergens↗

Immuno-electronmicroscopic identification and localization of the antigenic proteins of tree pollen grains.

The localization of antigenic proteins on ultrathin sections of pollen grains represents an interesting approach to understanding the release mechanisms of these antigens when the pollen grains come in contact with various physiological fluids. Using different rabbit antibodies we have demonstrated the locations of these antigens in the various structures of pollen grains. We further demonstrated the cross-reactivities between alder (Alnus incana), birch (Betula verrucosa) and hazel (Corylus avellana) pollen allergens. Ultrathin sections of the pollen grains were prepared and allowed to react with two individually raised rabbit antibodies, (Ab-BV and Ab-ALK), against birch pollen. The sites of the Ag/Ab complex on the sections were labelled by protein A/gold, and identified in a transmission electron microscope. The two birch antibodies showed either quantitative or qualitative differences regarding their binding to various structures on the pollen sections. Using Ab-BV, the antigen-binding sites were located in the apertural region of the pollen grain and in the cytoplasm, while almost no gold labelling could be seen on the pollen surface. With the other antibodies (Ab-ALK), we could visualize the antigen-binding locations on the surface material of the pollen grains, particularly in the exine part of the wall and in the cytoplasm. A few gold particles could also be seen in the apertural region of the pollen. In hazel and alder pollen the exine part of the wall was the most densely labelled, whereas the cytoplasm and the aperture bound smaller numbers of gold particles. Cross-incubations: birch pollen incubated with antibodies against hazel (Ab-CA), or alder (Ab-AI), showed various intensities of gold labelling for each of the three species. Statistically, the differences in the number of gold particles bound per micron 2 grain section between birch, hazel and alder, were highly significant. The cross-reactivities between these antigens from the three pollen species were further tested using house-produced rabbit antisera against antigens of the three species by means of electrophoretic and autoradiographic techniques (CIE and CRIE). The three antibodies could precipitate the major IgE-binding antigen from all three pollen species.

Animals↗

Immunocytochemical mapping of IgE/IgG binding sites within the birch pollen grain using serum from a patient undergoing hyposensitization therapy. Comparison with biochemically determined data.

Serum from an atopic patient undergoing a hyposensitization therapy to birch pollen allergens was used to carry out immunocytochemical mapping of specific IgE/IgG binding sites within ultrathin sections of birch pollen grains. There was a distinct rise in the density of specific IgG labelling in the course of therapy, whereas the density of IgE labelling remained fairly constant. However, the patterns of IgG and IgE binding in the pollen grain did not completely coincide since there was only IgE binding to certain pollen structures such as the apertural region. If the widely accepted concept of specific antibodies as 'blocking antibodies' is taken as a basis, the success of therapy must be questioned in this case because no IgG antibodies were formed to some of the allergens localized in the pollen grain and relevant to this patient. Very probably this result must be attributed to an incomplete pollen extract used in hyposensitization therapy. The results of the biochemical measurements (RAST, ELISA) agreed well with the immunocytochemical observations.

Binding Sites, Antibody↗

Electron microscopic study of DNA complexes with proteins from the Archaebacterium Sulfolobus acidocaldarius.

DNA-protein complexes formed in vitro with isolated DNA-binding proteins from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius were analyzed by electron microscopy. Two of the proteins (10a and 10b) formed specific structures after incubation with DNA. Protein 10a, at low protein concentrations, showed individual small spots on the DNA and at high concentrations evenly covered doublestranded DNA. Protein 10b showed three different types of regular structures: one with single-stranded and two with double-stranded DNA. Using double-stranded DNA, 10b first bound cooperatively to two strands forming long, plait-like structures only slightly shorter than respective free DNA. The complex consists of two right-handed, interwound fibers, with a helical pitch of 26 nm and a diameter of approximately 10-11 nm. At higher protein concentration than needed to package all DNA into the complex with two double-stranded DNAs, the two DNAs were separated again and a new structure was formed evenly covering only one DNA strand. Both structures showed no significant contraction of the length of the DNA covered in the complex. Nucleoprotein formed with single-stranded PhiX174 DNA had a diameter of approximately 11 nm and could form circles with a contour length of 0.5 mum.

Journal Article↗

Visualization of birch pollen allergens using IgE-containing sera from human atopic individuals in immunogold labelling experiments.

Pollen from birch trees (Betula pendula) was fixed in paraformaldehyde with or without the addition of 0.5% cetylpyridinium chloride, dehydrated and embedded in Lowicryl K4M in the cold. Ultrathin sections were incubated using the following sequence of antibodies and antisera: IgE-containing serum from an atopic human individual allergic to birch pollen allergens, rabbit anti-human IgE antibodies, and colloidal gold-labelled goat anti-rabbit antibodies. Controls were performed by replacing the specific human antiserum by serum from an atopic person with a similar level of IgE antibodies directed against allergens other than birch pollen allergens, or by omitting the human antiserum or the anti-IgE antibody or both. In test experiments, there was a dense specific labelling of the exine and the cytoplasmic matrix of the pollen grain. There was moderate labelling of the apertural regions (poral plugs). There was no labelling of the intine. In pollen grains fixed with the addition of cetylpyridinium chloride, an electron-dense surface coat was precipitated on the outside of the pollen wall. This surface material also remained completely unlabelled.

Antibodies, Anti-Idiotypic↗

Cross-reactivity of birch anthers and leaves with birch pollen antigens and allergens. A fine-structural immunocytochemical study using the post-embedding protein-A-gold technique.

Ultra-thin sections of vegetative tissues from birch (anthers and leaves) were labeled for pollen antigens and allergens using a commercial rabbit IgG antibody preparation directed against birch pollen antigens and allergens. Antibody binding sites were visualized using the protein A-gold technique. Specific labeling occurred in anther tissue (tape-tum cells, anther wall cells) as well as in the birch leaf (assimilation parenchyma). In both types of tissue, antigens and allergens were detected throughout the living protoplast (including cell organelles such as nuclei, mitochondria, and plastids). The cellulose cell walls were always free from anti-birch-pollen IgG-binding sites. The immunological controls (normal rabbit IgG) showed a low degree of nonspecific labeling. In plant tissues belonging to genera quite different from birch (tulip anther, rhododendron leaves), after incubation with the specific IgG weak labeling was observed. The immunological basis for these results is discussed.

Allergens↗

Immunoautoradiographic and protein-A/gold labelling experiments for localization of pollen allergens using antisera from atopic human individuals.

Using serum from human atopic individuals with a sufficiently high titre of IgE and IgG antibodies to birch- or hazel-pollen allergens and antigens, the localization of IgE binding sites in birch- and hazel-pollen grains was determined by pre- and post-embedding electron microscopic immunoautoradiography with 125I-anti-IgE, whereas the IgG binding sites were localized in ultrathin sections of birch-pollen grains by the protein-A/gold technique. Concerning the distribution patterns of both IgE/IgG binding sites within the pollen grains, no difference could be observed in the dormant pollen grain: Labelling was found in the exine part of the pollen wall and throughout the highly condensed cytoplasm except for starch grains and lipid droplets. The intine part and the germination pores were almost completely unlabelled. In pollen grains which had been soaked in a hypotonic buffer for 15 min, however, IgE binding sites were predominantly localized within the intine and the germination pores. The specificity of the labelling reactions and the observed differences in the localization patterns are discussed.

Antibodies, Anti-Idiotypic↗

Immunoelectron-microscopic localization of diffusible birch-pollen antigens in ultrathin sections using the protein-A/gold technique.

Pollen grains from Betula pendula were fixed in a mixture of p-formaldehyde and cetylpyridinium chloride (CPC) for the precipitation of soluble pollen glycoproteins. After dehydration and embedding at low temperatures in the water-soluble resin, Lowicryl K4M, ultrathin sections of the pollen grains were incubated using specific antibodies against birch-pollen extract and protein-A/gold complexes. Antigen activity was found in the CPC-precipitated surface material and within the exine (bacular cavities) and the cytoplasm (except for starch grains and lipidic droplets). There was no labelling within the intine. The region of the germinal aperture also showed a very low degree of antigen activity. The control sections were almost completely free of background staining.

Antigens↗

Ultrastructural demonstration of a glycoproteinic surface coat in allergenic pollen grains by combined cetylpyridinium chloride precipitation and silver proteinate staining.

In allergenic birch pollen grains, highly watersoluble surface substances were precipitated by the cationic detergent cetylpyridinium chloride (CPC) during aqueous fixation. After processing the pollen for electron microscopy, ultrathin sections of pollen grains were subjected to the periodic acid - thiocarbohydrazide - silver proteinate (PA-TCH-SP) procedure according to Thiery (1967) for the detection of vicinal glycol groups. It was found that the material precipitated by CPC on the surface and within the exine cavities of the pollen wall strongly reacted with the PA-TCH-SP reagent thus indicating the presence of polysaccharides on the surface of birch pollen grains. In samples which had not been treated with the cationic detergent, PA-TCH-SP reactivity was reduced to thin linings on the surface and within the exine cavities. In both cases the exine proper did not stain whereas the intine showed moderate staining. Within the aperture region of the intine, PA-TCH-SP reactivity is preferably associated with fibrillar or reticular structures. The results are discussed with special reference to biochemical findings on allergenic birch pollen proteins.

Cetylpyridinium↗

Electron microscopic localization of concanavalin A receptor sites in pollen surface material after fixation with glutaraldehyde-cetylpyridinium chloride.

Pollen from birch trees (Betula pendula) was fixed in glutaraldehyde containing 0.5% cetylpyridinium chloride (CPC), incubated with concanavalin A (Con A)-ferritin, postfixed in osmium, dehydrated, and embedded in Epon. On ultrathin sections, ferritin particles were observed closely associated with the electron-dense material precipitated by CPC on the surface of the pollen grains. Controls for CPC, which were fixed in glutaraldehyde alone, showed no electron-dense material on the surface. In controls for Con A, which were incubated in Con A-ferritin in the presence of the inhibitory sugar (alpha-methyl-D-mannopyranoside), no ferritin particles were observed. The above-described procedure thus allows the localization of sugar residues in highly soluble pollen wall glycoproteins.

Cetylpyridinium↗

[Element standards for quantitative X-ray microanalysis of biological specimens in the scanning transmission electron microscope].

Quantitation in biological X-ray microanalysis usually depends on the reference to one or more element standards. This paper deals with the general characteristics of such standards and gives a survey of the various methods of standard preparation reported in literature. Their advantages and disadvantages are briefly discussed. Practical experiments were carried out to prepare a potassium, calcium, and sulfur standard for X-ray microanalysis in the scanning transmission electron microscope.

Calcium↗