[The formation of stable aggrregates of human platelets induced by lectin from Solanum tuberosum].

It has been demonstrated for the first time that GlcNAc-specific lectin from Solanum tuberosum induces the formation of haptenic sugar-resistant intercellular contacts (HSR-contacts) in platelet aggregation and does not induce stable neutrophil and lymphocyte aggregation. The formation of HSR-contacts in platelets was significantly impaired by the inhibitors of cAMP phosphodiesterase (papaverine) and arachidonic acid methabolism (indomethacin, aristolochic acid, and MK-886) as well as by the sulfhydryl reagent N-ethylmaleimide. The results obtained indicate that STA can be used to study the mechanisms of stable platelet aggregation, to screen drugs with potential antithrombotic activity, and to develop new cell engineering techniques.

Metabolic inhibitors as tools to delineate participation of distinct intracellular pathways in enhancement of lactose-induced dissociation of neutrophil and thymocyte aggregates formed by mediation of a plant lectin.

Signaling processes in the course of the formation of the lectin-mediated aggregates may partake in conveying enhanced stability to the cell clusters. To prove the validity of this reasoning in a model, we have studied the impact of addition of three metabolic inhibitors (N-ethylmaleimide, nordihydroguaiaretic acid, and trifluoperazine) on lactose-dependent dissociation of cell aggregates, formed in the presence of the galactoside-binding mistletoe lectin. Using both human neutrophils and rat thymocytes to avoid measurement of responses restricted to a single cell type, an enhanced dissociation of lectin-formed cell aggregates was observed, when lactose and an inhibitor were present. Among the tested inhibitors, nordihydroguaiaretic acid and N-ethylmaleimide were more potent enhancers of cell dissociation than trifluoperazine. These results suggest that biosignalling pathways connected with lipoxygenase activity as well as the level of intracellular sulfhydryl groups confer further stability to lectin-dependent cell aggregates. The systematic evaluation of inhibitors for defined activities is thus suggested as a tool to disclose the nature and the contribution of individual signaling mechanisms to post-binding effects following lectin-initiated cell contact formation.

Viscum album agglutinin-induced aggregation of blood cells and the lectin effects on neutrophil function.

Extracts from mistletoe enjoy a large popularity in central Europe as an unconventional treatment modality for cancer, warranting scientific efforts with defined components to delineate any potential benefit. The galactose-specific lectin from Viscum album (VAA), known to exhibit immunomodulatory and ensuing antitumoral capacities in animal model systems, was shown to aggregate human blood cells in the following order: neutrophils, mononuclear cells--thrombocytes and erythrocytes. To contribute to the analysis of lectin effects on individual aspects of the host defence system, two parameters of neutrophils were quantitatively assessed, namely the aggregating activity of VAA as a measure of strength of interaction with cell surface ligands and the effect of lectin on oxidative metabolism (H2O2 release) of these cells. It was found that whole lectin and its carbohydrate-binding B-subunit possessed the capacity to induce cell aggregation and H2O2 release, which were blocked by D-galactose and lactose. Both effects displayed similar dependence on the lectin concentration in the range 0.1-25 micrograms/ml. The toxic A-subunit displayed detectable activity only in high doses (50 micrograms/ml) while the bovine heart galaptin (14 kDa; galectin-1) failed to affect neutrophils. The role of oxidative metabolism in regulation of neutrophil aggregation induced by VAA was studied using metabolic inhibitors and controlled heating at 46 degrees C leading to inhibition of plasma membrane NADPH-oxidase system. Trifluoperazine and menadione inhibited the neutrophil aggregation in a dose-dependent manner in comparison with such inhibitors as amiloride and theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of hyperthermia (45 C) on lymphoid cell aggregation]. / Vliianie gipertermii (45 C) na agregatsiiu limfoidnykh kletok.

Hyperthermia (45 degrees C) has found to decrease the rate of rat thymocytes as well as splenocytes aggregation induced by lectins (concanavalin A, wheat germ agglutinin) and sulphated polysaccharides (heparin, dextran sulphate-500) and to increase those induced by cationic dye alcian blue. Shedding of plasma membrane glycoproteins and changes of surface charge are supposed to affect the aggregation.

Photodynamic activity of chlorin e6 and chlorin e6 ethylenediamide in vitro and in vivo.

Several parameters of chlorin e6 and its derivative chlorin e6 ethylenediamide have been investigated as these compound are potential sensitizers for photodynamic therapy. A study carried out to compare the cellular uptake of the pigments indicates that chlorin e6 ethylenediamide possesses an enhanced affinity for tumour cells and cellular membranes. Comparison of the uptake in induced sarcoma shows that chlorin e6 ethylenediamide is a much better tumour localizer than chlorin e6. The efficiency of phototherapy with chlorin e6 ethylenediamide is higher than that with chlorin e6. These data show the influence of the substitution of the carboxyl groups in chlorin e6 by ester and amide groups on the photosensitizing properties of the pigments.

[The distribution of chlorine e6 and its derivatives in HeLa cells studied using luminescence microscopy]. / Issledovanie raspredelenie khlorina e6 i ego proizvodnykh v kletkakh HeLa metodom liuminestsentnoi mikroskopii.

The influence of the chemical structure of porphyrin pigments on their accumulation and localization in HeLa cells has been examined by the scanning fluorescence microphotometry. It has been found that the replacement of carboxyl groups of chlorine e6 for methyl and amino groups has no influence on the pigment distributions in cells. All the pigments are bound by cell membrane structures. The chemical modification of chlorine e6 structure is essential for the ability of pigment to be accumulated by cells that can be used to increase the efficiency of cancer phototherapy. The charge and hydrophobic properties of pigment molecules are of great importance for accumulating porphyrin sensitizers by cells.