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A Froese

Publications and source records attributed to A Froese.

At least 37 records · Page 2Linked to original sources
PubMed1986

Disulphide-linked receptors for IgE on rat basophilic leukaemia cells.

Rat basophilic leukaemia (RBL) cells are known to possess three different kinds of receptors capable of interacting with IgE, which have been named R, H and 71K and which differ in apparent molecular weight (MW) as determined by SDS-PAGE. Reduction of receptors isolated from surface-iodinated RBL cells reduced the MW of 71K to a value corresponding to the MW of R without altering significantly the MW of H or R. Only a single reduction product of 71K could be detected when either surface-iodinated or 3H-leucine labelled RBL cells were used. Analysis of one- and two-dimensional tryptic peptide maps derived from surface-iodinated receptors revealed a similarity between R and 71K. The tryptic peptides of H exhibited an entirely different pattern. These results suggest that 71K consists either of two disulphide-linked R-like molecules, or of one such molecule linked to another as yet undetected polypeptide chain.

Animals↗
PubMed1982

The cross-reactivity of rat IgE and IgG with solubilized receptors of rat basophilic leukemia cells.

Normal rat IgG-Sepharose binds the same two receptors from solubilized rat basophilic leukemia (RBL) cells as are bound by rat IgE-Sepharose. These receptors have previously been designated R and H, and have apparent mol. wts of 45,000 and 55,000, respectively. Inhibition studies indicate that, although soluble deaggregated IgG is capable of interacting with both receptors, its affinity is higher for H than for R. Conversely, soluble IgE preferentially interacts with R, but its affinity for H is somewhat higher than that of rat IgG. Control studies show that IgG receptor interaction to be specific in that it is significantly stronger than that obtained with F(ab')2 fragments or a variety of proteins having pIs approximating that of IgG.

Animals↗
PubMed1982

Proteolytic fragments of the receptors for IgE.

Partially purified IgE receptor(s) of rat basophilic leukemia cells (RBL) designated R and H and having apparent molecular weight of 45,000 and 55,000 daltons, respectively, were subjected to proteolysis with papain. Polyacrylamide gel electrophoresis of the digests in the presence of sodium dodecyl sulfate revealed a difference in the size and number of the fragments produced. These results suggest that these two receptor molecules are different with respect to amino acid composition and sequence. Whole Nonidet P-40 extracts of RBL cells were also subjected to digestions with papain, trypsin and chymotrypsin in an attempt to obtain receptor fragments still capable of binding to IgE-Sepharose. Treatment with papain produced a 38,000 dalton fragment of H but no fragments of R which retained the ability to bind to IgE. Tryptic and chymotryptic treatment produced a 41,000 dalton fragment of H with affinity for IgE. The IgE-binding site of R was either destroyed or not affected at all.

Animals↗
PubMed1982

Suicide attempts in children and adolescents.

In a review of pediatric hospital emergency room admissions over 7 years, the authors found 505 children and adolescents who had attempted suicide. There were three times as many girls as boys, and the boys were significantly younger. Features that distinguished them from matched controls were religion, living situation, substance abuse, current psychiatric illness, prior psychotherapy, and current medical illness. Their families had more psychiatric illness (primarily drug or alcohol abuse), suicide, paternal unemployment, and paternal and maternal absence than the controls' families. The suicide attempts usually occurred in the winter, after school or in the evening, at home with someone nearby, and by drug overdose.

Adolescent↗
PubMed1982

Comparison of the receptors for IgE of various rat basophilic leukaemia cell lines. I. Receptors isolated by IgE-sepharose and IgE and anti-IgE.

REceptors for IgE of rat basophilic leukaemia (RBL) cells, maintained in different laboratories were isolated by means of IgE-Sepharose or IgE and anti-IgE, and characterized by SDS-polyacrylamide gel electrophoresis. All cell lines were found to be associated with a receptor molecule (R) which could be isolated either with IgE-Sepharose or IgE and anti-IgE and a second receptor (H) which could only be isolated with the aid of IgE-Sepharose. The relative amounts of these two molecules, as isolated from surface iodinated cells, varied from the RBL cell line to the other and their apparent molecular weights were not identical on all cell lines. Since comparisons were made on the same gel using receptors isolated from cells labelled with different isotopes of iodine, differences in molecular weight must be considered as being intrinsic and not due to methodological variations. These results provide an explanation why differences were observed among receptors for IgE as characterized in various laboratories. In spite of the fact that the various RBL cell lines originated from the same chemically-induced tumour they have, over the years, undergone changes which are reflected in the receptors for IgE.

Animals↗
PubMed1982

Comparison of the receptors for IgE of various rat basophilic leukaemia cell lines. II. Studies with different anti-receptor antisera.

Receptors for IgE of rat basophilic leukaemia (RBL) cells, maintained in different laboratories were isolated by means of various anti-receptor antisera, and characterized by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis. Most antisera were shown to react with a receptor designated H and which, as shown previously, could be isolated by IgE-Sepharose but not by a combination of IgE and anti-IgE. Only two highly purified anti-receptor antibody preparations, which had been purified by adsorption to and elution from rat basophilic leukaemia cells, reacted primarily with a second kind of receptor molecule which had previously been designated R. Some indirect evidence was obtained which suggests that H is a highly immunogenic molecule. It was confirmed that the apparent molecular weight of H-like molecules varied on different RBL cell lines.

Animals↗
PubMed1981

Binding of the receptors for IgE by various lectins.

Two receptors for IgE, having apparent molecular weights of 55,000 and 45,000 daltons were isolated from rat basophilic leukaemia cells by means of IgE-Sepharose. Both molecules were bound by concanavalin A, wheat germ agglutinin and Ricinus communis agglutinin (castor bean lectin). The lectins of pea and gorse origin only bound the 45,000 dalton receptor.

Animals↗
PubMed1981

The incorporation of tritiated precursors into receptors for IgE of rat basophilic leukemia cells.

It has previously been shown that two receptors, H and R, having apparent mol. wt of 55,000 and 45,000 daltons, can be isolated from surface iodinated RBL cells. In addition, small amounts of a third molecule of 71,000 daltons (71 K) can now be detected in receptor preparations isolated by means of IgE-Sepharose. The SDS-PAGE patterns show that the three surface molecules were not significantly altered when cell solubilization was carried out in the presence of protease inhibitors. The same three molecules were also observed when cells were biosynthetically labelled with [3H]-fucose of [3H]-galactose. When cells were labelled with [3H]-leucine or [3H]-tyrosine, several additional molecules were observed in IgE-Sepharose purified preparations. When cells were exposed to free IgE- before solubilization, significant inhibition of binding to IgE-Sepharose could only be seen among molecules corresponding to H, R and 71 K. When receptors were isolated by means of DNP-IgE and anti-DNP-Sepharose, fewer molecules were found. One, which was frequently observed, had a mol. wt of 26,000 daltons. This molecule may be non-covalently associated with receptors for IgE.

Amino Acids↗
PubMed1980

The presence of two kinds of receptors for IgE on rat mast cells.

Receptors for IgE from peritoneal mast cells (RMC) of six strains of rats were studied and compared with those of rat basophilic leukemia cells (RBL). Receptors were isolated from surface iodinated and detergent solubilized cells by means of IgE-Sepharose, IgE and anti-IgE, and a rabbit antiserum specific for the receptors of RBL cells (RAR). Like RBL cells, RMC from all rate strains were shown to be associated with two receptor molecules H and R, having apparent m.w. of about 55,000 and 45,000, respectively. THe presence of both molecules could be clearly demonstrated with RAR. When IgE-Sepharose was used, the presence of H could only be unequivocally shown if large numbers of IgE molecules were bound to the RMC.

Animals↗
PubMed1979

Lentil-lectin affinity chromatography of surface glycoproteins and the receptor for IgE from rat basophilic leukemia cells.

Surface proteins and glycoproteins of RBL cells were labelled enzymatically with 125I and then solubilized with Nonidet P-40. Analysis by polyacrylamide-gel electrophoresis in SDS on 10% gel revealed 10 distinctive peaks ranging in molecular weights from 17,000 to 200,000 daltons. Mainly components of higher molecular weights were bound by lentil-lectin Sepharose and could be eluted with alpha-methyl mannoside. The receptor for IgE was clearly shown to bind to the lentil-lectin. A second cell surface component which previously had been shown to bind to IgE-Sepharose as well, was found to bind only slightly to lentil-lectin. Thus, it can be concluded that the receptor for IgE is a glycoprotein with mannose and/or N-acetylglucosamine in the carbohydrate moiety(s).

Animals↗
PubMed1978

A new concept of triggering mechanisms of IgE-mediated histamine release.

It is generally accepted that an initial step of reaginic hypersensitivity reactions is a bridging of mast cell--bound IgE antibody molecules by antigen. Since IgE molecules are firmly bound to receptors on mast cells, bridging of cell-bound IgE molecules probably brings receptor molecules into close proximity. A hypothesis was therefore presented that such a local change in membrane structure and/or possible interaction between adjacent receptor molecules may be triggering mechanisms of IgE-mediated histamine release. The hypothesis was tested by use of antibodies against "exposed portion" of receptor molecules on rat basophilic leukemia cells. It was found that antireceptor antibodies and its F(ab')2fragments induced noncytotoxic histamine release from normal rat mast cells without participation of IgE, while the monovalent Fab' fragments of the antibody failed to do so. However, sensitization of normal rat skin with the Fab' fragments followed by an intravenous injection of antirabbit IgG induced skin reactions. These findings support the concept that bridging of receptors rather than polymerization of IgE molecules is responsible for the activation of membrane-associated enzymes which in turn leads to histamine release.

Animals↗