Lens culinaris lectin receptors in the plasma membrane of rat liver cells: comparative electron microscopic studies on normal cells, on cells in vivo transformed by diethylnitrosamine and on Zajdela ascites hepatoma cells

The distribution of the Lens culinaris lectin receptors on normal rat liver cells, on rat liver cells in vivo transformed by diethylnitrosamine and on Zajdela ascites hepatoma cells of the rat is investigated by means of the Lens culinaris lectin-peroxidase method and by ferritin conjugated Lens culinaris lectin. The normal rat liver cells show a continuous labeling at the outer membrane surface by the lectin complexes, whereas the transformed rat liver cells exhibit a strong tendency for patchy distribution of the cell surface label. The discontinuous cell surface label in the transformed rat liver cells is obviously caused by an internalization of plasma membrane areas. The importance of these morphological findings in their relationship to Lens culinaris lectin mediated agglutination of rat liver cells and the membrane fluidity in general are discussed. In the experiments no hints to a rotation of the Lens culinaris lectin receptors from the outer membrane surface to the inner membrane surface of rat liver cells can be found.

Interaction of Lens culinaris lectin, concanavalin A, Ricinus communis agglutinin and wheat germ agglutinin with the cell surface of normal and transformed rat liver cells

The observation of BOREK et al. (1973) on nonagglutinability of transformed rat liver cells by Lens culinaris lectin and our ultrastructural findings of a greater mobility of the Lens culinaris lectin receptors on transformed rat liver cells as compared to normal rat liver cells (ROTH 1975) initiated the present agglutination experiments on liver cells with lectins. For agglutination assay the microhemadsorption technique after FURMANSKI et al. (1973) was used with exception of several tests on EDTA-detached cells. The transformed rat liver cells exhibited, in contrast to the findings of BOREK et al. (1973), a positive microhemadsorption with Lens culinaris lectin as well as with Concanavalin A, Ricinus communis lectin and wheat germ agglutinin whereas the normal rat liver cells became positive only after a brief trypsin treatment. The significance of the difference in agglutinability of rat liver cells with Lens culinaris lectin and the other lectins used is discussed with regard to the cell-cell interaction mediated by lectins.

Defect in insulin binding to receptors in obese man. Amelioration with calorie restriction

With insulin at 0.1 ng/ml, the binding of (125I)insulin in vitro to circulating lymphocytes from 11 obese patients was less than that observed with cells from 10 thin volunteers. Furthermore, with obese cells, unlabeled insulin was less effective in competing with labeled hormone for binding, both at low and high concentrations of unlabeled insulin. These differences were not accounted for by the high concentrations of insulin in the circulation of the obese patients at the time fthe blood was drawn, or by differences in degradation of hormone, or in the characteristics of the cell population. The decrease in binding appears to be due to a lowering of the receptor concentration, but some loss of affinity has not been excluded. Institution of a calorie restricted diet (nine patients) which ameliorated the hyperinsulinemia, produced an improvement in hormone binding. Since the insulin receptors of lymphocytes in metabolic disorders seem to reflect the state of insulin receptors or target cells such as liver and fat, the lymphocytes or other leukocytes appear to be ideal for studies of impaired cell responsiveness to hormones in man.

[Studies on the Concanavalin A-receptors of rabbit erythrocytes and of erythyrocyte shadows using immunoelectron microscopy]

The authors report on the immuno electron microscopic demonstration of Concanavalin A-receptors on the erythrocyte membrane. Immuno freeze-etching studies evidenced a focal arrangement of Concanavalin A-receptors on intact erythrocytes as well as on erythrocyte ghosts. Obviously hemolysis by distilled water does not produce changes in the pattern of distribution of Concanavalin A-receptors whereas slight aggregation of plasma membrane intramembraneous particles occured. No unambigous spatial relationship between Concanavalin A-receptors and the plasma membrane intramembraneous particles (intrinsic proteins) of erythrocytes could be observed.

Ultrastructural detection of lectin receptors by cytochemical affinity reaction using mannan-iron complex

A two-step affinity reaction is described for electron microscopic demonstration of the Concanavalin A as well as the Lens culinaris lectin receptors by means of the yeast mannan-iron complex. First the tissue was incubated in the lectin. Afterwards the incubation in the yeast mannan-iron complex was performed and reaction takes place between the still free second sugar binding site of membrane bound lectin molecules and the polysaccharides. This membrane receptor-lectin-polysaccharide complex is revealed by the electron dense iron core of the yeast mannan-iron complex. The specificity of the reactions could be demonstrated by addition of the hapten or by incubation in the yeast mannan-iron complex only. The proposed technique has proved useful for demonstration of lectin receptors in the small intestine.

The use of fluorescein isothiocyanate labelled lectins for immunohistochemical demonstration of saccharides

Cryostat sections of various tissues from man, rat, mice, hamster, rabbit, guinea pig, sparrow and carp were examined by fluorescence microscopy after incubation with fluorescein isothiocyanate labelled Concanavalin A and Lens culinaris lectin. In the same tissue of various species no basic differences in the pattern of fluorescence were observed. In general, connective tissue structures were stained by both lectins in the same degree, whereas by fluorescein isothiocyanate labelled Concanavalin A additionally a varying staining of the cell surface and of cytoplasmic structures occurred. The results show the general presence of Concanavalin A and Lens culinaris lectin receptors in normal animal tissues.

Concanavalin A receptors on normal rat liver cells, on rat liver cells in vivo transformed by diethylnitrosamine and on Zajdela ascites hepatoma cells of the rat: morphokinetic analysis of cell surface dynamics

Comparative electron microscopic investigations were performed in living cultures of normal rat liver cells, of rat liver cells in vivo transformed by diethylnitrosamine and on Zajdela ascites hepatoma cells of the rat concerning the mobility of the Concanavalin A cell surface receptors. The cells were incubated in Concanavalin A and peroxidase and subsequently washed. They were then reincubated for various periods at +37 degrees C in PBS prior to fixation. In the case of the Zajdela ascites hepatoma cells the cells were reincubated after Concanavalin A incubation followed by fixation and peroxidase incubation. The cytochemical procedure allowed us to show differences in the mobility of Concanavalin A surface receptors between normal and transformed rat liver cells. The cell surface label disappeared completely within 15 min of reincubation in the transformed cells, whereas in normal cells the same degree of loss in surface label was visible after 120 min reincubation. In both cases an internalization of labelled plasma membrane areas occurred. After complete disappearance of cell surface label in diethylnitrosamine transformed cells a complete relabelling of the cell surface occurred after 60 min reincubation caused by an exocytosis.

[Significance of the acetylcholin-test in screening and evaluation of recurrent and chronic bronchitis (author's transl)]

156 healthy persons, 198 patients with recurrent bronchitis and 112 patients with chronic bronchitis showed different reaction to the acetylcholin test. Frequency of cough-reaction (bronchosensorial hyperreactivity) was high-significant lower in healthy persons (17,3%) than in patients with recurrent (30,8%) or chronic bronchitis (54,5%). Frequency of obstructive reaction (bronchomotorial hyperreactivity) was less but still significant different in these 3 groups (32,7%; 39,4%; 52,7%). The author proposes to pay more attention to acetylcholin-cough-test.

Distribution of concanavalin a receptors on normal rat liver cells and zajdela ascites hepatoma cells

The distribution of Concanavalin A receptors in cultures of normal rat liver cells and of Zajdela ascites hepatoma cells of the rat was investigated by the Con A-po technique (Bernhard and Avrameas, 1971). Con A-po labelling of the cell surface showed a patchy distribution of Concanavalin A receptors in ascites hepatoma cells, whereas continuous Con A-po labelling was seen at the surface of normal rat liver cells. The different distribution of Concanavalin A receptors was caused by rapid internalization of Con A-po labelled material and not by a simple rearrangement of the receptors. The significance of this process is discussed with respect to Concanavalin A receptor mobility and membrane stability after cell transformation.

Isolation of P22 specialized transducing phage followong F'-episome fusion

A P22 specialized transducing phage has been constructed which carries the structural gene for aspartate transcarbamylase (ATCase). This gene (pyrB) was first brought close to the P22 attachment site by fusing an F' pyrB(+) episome to an F' prolac episome which carries a P22 prophage attachment site. A prophage was added to these fused F' episomes and the lysogen was UV-induced. The specialized transducing phage was isolated from the resulting lysate. The phage also carries argI, the structure gene for ornithine transcarbamylase.

Specialized transducing phages derived from salmonella phage P22

Salmonella phage P22 has been used in the construction of three sorts of specialized transducing phage: P22 proAB, P22 proABlac and P22 argF. The bacterial genes carried are derived from E. coli K12. Since E. coli and Salmonella chromosomes recombine very poorly, E. coli genes cannot be transduced into Salmonella recipients by P22's generalized transduction mechanism. Therefore, stable inheritance of E. coli material provides a means of detecting specialized transduction. Formation of these phages was possible because the P22 prophage recognizes an attachment site in the E. coli F' prolac episome. Salmonella strains carrying the F' prolac episome can be lysogenized by P22 so as to leave the prophage inserted into the E. coli material of the F' factor. Improper prophage excision can then lead to formation of P22 specialized phages carrying E. coli genetic material.