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Biomedical subjects

L Erdei

Publications and source records attributed to L Erdei.

11 recordsLinked to original sources
PubMed2000

Distribution of the Mo-enzymes aldehyde oxidase, xanthine dehydrogenase and nitrate reductase in maize (Zea mays L.) nodal roots as affected by nitrogen and salinity.

The distribution of the Mo-enzymes aldehyde oxidase (AO; EC 1.2.3.1) xanthine dehydrogenase (XDH; EC 1.2.1.37) and nitrate reductase (NAD(P)H NR; EC 1.6.6.1-2) was studied along the longitudinal and transversal axes of maize (Zea mays L. cv. Jubily) nodal roots as affected by nitrogen sources and salinity. Activities of the Mo-enzymes were considerably enhanced under mild saline conditions. The activities of AO and XDH increased following addition of ammonium to the nutrient solution. Immunoblot analysis with antibodies raised against maize AO protein revealed increased levels of AO proteins in root tips of ammonium fed plants. Application of salinity to nitrate fed plants did not affect the enzyme protein level, although it enhanced the activity of the Mo-hydroxylases. The specific activities of the Mo-enzymes were the highest in root tips (0-1 cm segments) while on the transversal axis maximal activity was observed in the stele or vascular cylinder. Activity staining of AO after native PAGE of root extracts revealed four bands of AO proteins (AO1-4) capable of oxidizing a number of aliphatic and aromatic aldehydes. Increased AO activity in maize nodal roots grown with ammonium, and salinity were observed mainly at the AO3 and AO4 bands. Tips and stele contained primarily AO3 and AO4, and only traces of AO1 and AO2. SDS-PAGE of root extracts followed by Western blots revealed, besides the major 150 kD subunit of AO, two polypeptides with molecular masses of 72 and 85 kD located specifically in the cortex. Part of the polymorphism of AO in plant roots may be related to the allocation of distinct isoforms to different regions of the root, although the specific metabolic roles of the different bands have not been established.

Journal Article↗
PubMed1998

Do Selye's mammalian "GAS" concept and "co-stress" response exist in plants?

Converging data indicate the possible existence of a general adaptation syndrome (GAS) in which different types of stress evoke identical coping mechanisms. In Selyean terms, this implies a "co-stress" response whereby one type of stress resistance may impart co-resistance to others. Common coping denominators may be physiological or morphological. The former include oxy-free radical scavenging, osmoregulation, ABA, jasmonates, chaperones, HSPs, and phytochelatins. Morphological GAS adaptations include leaf pubescence, movements and stance, and rooting characteristics. The feasibility, with certain reservations, of the GAS hypothesis is discussed here.

Abscisic Acid↗
PubMed1994

Morphological and physiological differences between aeroponically and hydroponically grown sunflower plants.

The effects of aeroponic (AP) and hydroponic (HP) conditions on growth rate, morphological traits, potassium uptake and redox activities were compared in sunflower seedlings. Higher growth rate was found under HP than AP conditions and morphological traits were also different. The thickness of AP grown roots increased and new lateral roots with thickened root hairs were formed while the length of AP roots was small. Microscopical studies on cross-sections of the embedded root segments showed that the diameter of cross-section, the diameter of stele and the width of cortex of AP grown roots were significantly higher than those of HP plants. The element composition of AP or HP grown plants also differed, due to the different ion uptake processes. Potassium (86Rb+) uptake of AP grown plants was low and it seemed to be a passive process, while in case of HP grown plants it was decreased by both dinitrophenol and ferricyanide suggesting that the uptake process was coupled to the proton gradient. Roots of AP grown plants showed high ferricyanide reductase activity and it was accompanied by an increased acidification of the medium.

2,4-Dinitrophenol↗
PubMed1989

Plasma membrane purification from roots of sunflower by phase partitioning.

Plasma membrane vesicles were purified from the roots of sunflower (Helianthus annuus L. cv. Topflor) by aqueous polymer two-phase partitioning. The optimal conditions for separation were determined by systematic variation of the polymer concentration and salt composition. The phase system containing 6% (w/w) dextran T-500, 6% (w/w) polyethylene glycol 3350, 250 mM sucrose, 5 mM potassium phosphate, pH 7.8, without added salts proved to be the best. The ATPase activity had a pH optimum at 6.5 and it was stimulated by Mg2+, but not by Ca2+. The plasma membrane MgATPase activity was inhibited by vanadate but not by nitrate, an inhibitor of tonoplast ATPase. Only 10% of the microsomal protein was responsible for 36% of the total MgATPase activity. Moreover IDPase activity, a Golgi marker, appeared to be very low indicating the high purity of the preparation.

Ca(2+) Mg(2+)-ATPase↗
PubMed1982

Isolation of a wheat cell line with altered membrane properties.

A spontaneous dimethylsulfoxide (DMSO)-tolerant cell line was isolated from a cell culture of wheat (Triticum monococcum L.). The tolerant cells were able to grow in the presence of 4% DMSO. Cells formed from protoplasts of the tolerant line required DMSO for division in culture medium of high osmotic value.Fatty acid composition and the molar ratio of phospholipids/sterols suggest a more ordered membrane structure in the tolerant line. Accordingly, a lower K(+) influx rate was detected in the tolerant cells in comparison with the original line. These characteristics were maintained after 6 months' cultivation of the cells in DMSO-free growth medium. This suggested that genetic changes could be responsible for differences between the two cell lines.

Journal Article↗
PubMed1978

Electric field induced defect-forming mechanisms in lipid bilayers.

The role of structural defects in the ionic conduction properties of unmodified bimolecular lipid membranes (BLMs) is discussed. Two mechanisms of defect forming processes are considered: the compressive effect of the electric field on the membrane, and the field-induced bending of lipid polar head groups. It is shown that the dependence of conductivity on both concentration and temperature, as well as the dielectric stability of lipid membranes can be explained in the terms of either mechanism suggested.

Cholesterol↗
PubMed1975

Simple, rapid method for detecting phase transititons of lipids.

A simple rapid method was worked out for studying the physical and structural state of lipids by measuring the refractive indices of a layered lipid film. Melting processes of n-paraffins and phase transitions of phospholipids and the lecithin-cholesterol system also can be followed as a function of temperature. In accordance with data from the relevant literature, the measured refractive indices show that cholesterol lowers the phase transition temperature of lecithin. By isorefraction curves, the most ordered structure of the layers is indicated to occur at the equimolar ratio of cholesterol and lecithin. The method may be applied to study the effect of lipid-soluble agents upon lipid structure and is applicable for routine investigations and industrial purposes as well.

Birefringence↗