Fluorescent reagents for the labeling of glycoconjugates in solution and on cell surfaces

Rhodamine and fluoresceine containing hydrazides were synthesized and used for fluorescent labeling of glycoconjugates on cell surface or in solution. The procedure involves the oxidation of the glycoconjugates with sodium metaperiodate or galactose oxidase to form an aldehyde group which reacts with the respective hydrazides. The method was applied for the modification of cell surface sialic acid and galactose residues on thymocytes and nematodes as well as for the labeling of glycoproteins and gangliosides in solution. The many possible application of these highly fluorescent compounds in the study of cell surface events is considered.     

The influence of phosphate concentration on the kinetics of uptake by maize roots

In an experiment with native maize roots depending on different phosphorus concentration in the external solution (0.001 … 50 mM P), the multiphasic character of the kinetics of phosphate uptake has been stated. The single phases are characterized by the different values of K_m and V_max. In the wide range of concentrations the isotherm of the phosphate uptake has five evident phases. The character of kinetics for the uptake of phosphate is analogical to the kinetics of the enzymatic reactions described by the Michaelis-Menten equation. On the other hand the linear dependence for the inactivated root was determined,i.e. the uptake of phosphate versus different phosphorus concentration in the external solution. The graphic representation of the logarithmic values for the phosphorus taken up versus the different phosphorus concentration in the external solution gives the biphasic course including concentration less than 1.0 mM P and more than 1.0 mM P. Within the framework of the concentration range the following values of V_max, K_m and ϕ_in were calculated under the conditions if the concentration of phosphorus is less than 1.0mMP: V_max = 1.705 μmol P × g^-1h^-1, K_m = 0.057 mM P and ϕ_in = 0.83,i.e. if the concentration of phosphorus is more than 1.0mM P: V_max = 40 μmol P × g^-1 h^-1, K_m = 16.66 mM and ϕ_in = 20. According to these results, the phosphate concentration in the external solution influences the activity of the transport mechanisms concerning their conformative changes which discretely change their working regime of membrane transport. This is also demonstrated in the change of values V_max, K_m and ϕ_in.     

A new approach (cyano-transfer) for cyanogen bromide activation of Sepharose at neutral pH,which yields activated resins,free of interfering nitrogen derivatives

A new approach for the reaction of Sepharose with cyanogen bromide is described, using triethylamine as a “cyano-transfer” reagent. An optimized procedure for activation at neutral pH was developed. This procedure requires only about 5% of the usual amount of cyanogen bromide. Activated resins are free of imidocarbonates and carbamates, containing only active cyanate esters. Extremely high coupling capacities (75 μmol ligand/g wet Sepharose 4B) can be obtained using this method.     

Mechanisms of the filtering area adaptation in Daphnia

The changes of selected parameters of the filtering comb of the third thoracic limb were studied in a natural population of Daphnia pulicaria Forbes, as well as in experimental enclosures and in lab cultures, including individual life history. Two hypotheses were tested: 1. either these changes are related to the succession of clones coexisting within one population, or 2. the size of the filtering area changes gradually as an individual adaptation during the moulting. No evidence supporting the clonal hypothesis was found. On the contrary, the adaptability of the filtering comb is the same in a natural population as it is in a clone and in individuals.     

Construction and properties of K1 type killer wine yeasts

Summary With the use of a protoplast fusion technique the killer character of K1 type was transferred into four industrial Saccharomyces wine yeasts. The prototrophic yeast strains active against standard sensitive and K2 killer Saccharomyces strains, resistant to K1 killer toxin were constructed with no changes in technological properties.     

Correlation between cell density,membrane fluidity,and the availability of transferrin receptors in friend erythroleukemic cells

Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity ( ), in accord with the culture cell density. At low cell density poise, whereas at confluency it increases to poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the erythropoiesis pathway.     

Increase in sialic acids removable by neuraminidase during the shape change of platelets.

Human or rabbit platelets were activated by ADP or 5-hydroxytrypatamine and rapidly fixed with glutaraldehyde. The shape change associated with activation gave rise to an increase in sialic acids removable by neuraminidase. This increase, like the shape change, was prevented by adenosine or methysergide added before ADP or 5-hydroxytryptamine respectively. The results indicate the exposure of additional glycoprotein(s) on the platelet surface.     

Accelerated uptake of 5-hydroxytryptamine by human blood platelets enriched in a sialic acid.

The enzymically catalysed incorporation of N-acetylneuraminic acid into human platelets, whether suspended in their own citrated plasma or in buffered saline containing 0.17 mM-sucrose, accelerated the uptake of 5-hydroxytryptamine. This acceleration decreased with time. The observations may be explained by assuming that N-acetylneuraminic acid is a component of a transport receptor for 5-hydroxytryptamine.     

Rapid in vitro activation of corpora allata by extracted locust brain allatotropic factor

Brains of young (newly emerged) adult female locusts (Locusta migratoria migratorioides) and of mature (> 9 days old) locusts contain an extractable allatotropic factor, soluble in 100% methanol and in distilled water. This factor stimulates juvenile hormone III (JH III) synthesis and release from corpora allata (CA) that have been excised from donor locusts and then incubated with (radiolabeled methyl)-methionine in vitro in its presence. In addition to JH III, which is the major product synthesized by the CA, other hexanesoluble, radiolabeled compounds–-more polar than JH III–-are also released when CA are incubated in vitro. The activation of CA by the allatotropic factor is rapid and quickly declines when the factor is removed from the medium. Corpora allata excised from young females are marginally active and can be activated by brain allatotropic factor to less of an extent than CA of mature locusts. The content of allatotropic factor in brains of mature locusts is higher than that ascertained in brains of young females. Allatotropic factor is also present in the corpora cardiaca.