Effect of lithium ions on the growth of wheat roots and the role of phosphoinositide cycle in growth regulation]

The influence of lithium ions (LiCl in concentrations of 0.5, 1.0, and 5.0 mM) on the growth processes of roots of 2-5-day old wheat seedlings was studied. It was shown that the inhibition of the root growth increased with the increase of LiCl concentration and seedling age. The membrane potential of root cells was lower and the loss of K+ by cells was greater when roots were treated with 5 mM LiCl, compared with the control. The growth inhibition by lithium was decreased by univalent ions, partially by potassium at the beginning of growth and completely by sodium throughout the experimental period. The divalent ions calcium and barium decreased the Li(+)-induced inhibition of root growth by reducing the rate of lithium uptake by cells. Myoinositol, controlled by Li-sensitive inositolmonophosphatase, reversed the Li-induced root growth inhibition in 2-day old seedlings, but did not prevent the inhibition during subsequent elongation. It can be concluded that lithium effects on wheat root growth are mediated by a partial blockage of signal transduction for proliferation (via the phosphoinositide cycle), because of calcium deficiency and caused by modification of ion transporting systems of the plasmalemma, and by disturbance of ion gradients, primarily H+ and K+.     

Fatty acid composition of microsomal phospholipids and H+-ATPase activity in the roots of Scots pine seedlings grown at different root temperatures during flushing

The fatty acid composition of phospholipids in the microsomesand the vanadate-sensitive H⁺-ATPase activity of the roots ofone-year-old Scots pine (Pinus sylvestris L.) seedlings werestudied during flushing in spring. The seedlings in hydroponiccultures were subjected to different root temperatures (5, 12or 20°C). The shoot was maintained at 20/15° C (day/night)during the 35 d experiment. After 35 d at 5° C, root growthwas totally inhibited and shoot growth partly inhibited. In roots grown at 5° C the fatty acid composition of themicrosomal phospholipids and the degree of fatty acid unsaturation(bond index) were unchanged, while in roots grown at 12 and20° C the fatty acid composition changed and bond indexdecreased. At those root temperatures, the most obvious changewas a decline in the proportion of linolenic acid (C18:3). Inthe new white roots grown either at 12°C or 20°C theproportion of C18:2 was higher and the proportion of C18:3 lowerthan in 1-year-old roots. Independently of root temperature,H⁺-ATPase activity, determined on a fresh weight basis, declinedto half of the original activity during the experiment. Thedecline in H⁺ -ATPase activity was most rapid during the firstweek. In the old roots the decline in H⁺-ATPase activity followedclosely the decline in amount of membrane protein. In new rootsH⁺-ATPase activity was high and increased with increasing roottemperature. These results suggest that in the roots of Scotspine seedlings, vanadate-sensitive H⁺-ATPase activity is dependenton age, while changes in the microsomal fatty acid compositionof phospholipids are regulated mainly by root temperature. Key words: Fatty acids of phospholipids, microsomes, H⁺-ATPase, root temperature, Scots pine     

Lithium Stimulation of Membrane-Bound Phospholipase C from PC 12 Cells Exposed to Nerve Growth Factor

LiCl stimulated the formation of inositol monophosphate in PC12 cells that had been exposed to nerve growth factor (NGF) for 4-5 days. Half-maximal accumulation was observed at approximately 8 mM LiCl. Stimulation of formation of inositol bisphosphate plus inositol trisphosphate was half-maximal at approximately 1 mM LiCl. With membranes isolated from PC12 cells differentiated with NGF, the hydrolysis of added phosphatidylinositol 4,5-bisphosphate (PIP2) was stimulated by LiCl in a biphasic manner, with the first stimulation half-maximal at approximately 0.7 mM and the second half-maximal at approximately 15 mM LiCl. The apparent Km for PIP2 was lowered in the presence of 1.1 mM LiCl from approximately 200 to approximately 70 microM. Membranes from cells grown in the absence of NGF did not respond to LiCl. Although observations with intact cells are difficult to interpret without ambiguity, the results obtained with isolated membranes support our interpretation of the stimulatory action of lithium in the intact PC12 cells.     

Characterisation of the wheat phospholipid fraction in the presence of nickel and/or selenium

The influence of nickel (Ni) and/or selenium (Se) on phospholipid composition was studied in shoots and roots of wheat seedlings. Phospholipid differences between samples were analysed using liquid chromatography/electrospray ionization–MS coupled. A total of 39 lipid species were identified. Individual phospholipids were then quantified using a multiple reaction monitoring method. In the roots, Ni toxicity was associated with an elevated level of phosphatidic acid species. In the shoots, the phosphatidylcholine/phosphatidylethanolamine ratio was about fivefold higher than in roots and decreased in Ni-treated samples. Additionally, the concentrations of phospholipid species containing C 18:3 fatty acid were reduced. Lipidome data were then analyzed using principal component analysis, which confirmed the compositional changes in phospholipids in response to Ni and Ni + Se. In contrast, the phospholipid profiles of wheat seedlings exposed to Se alone showed more similarities with the control. Together, our results suggested that the presence of Se, despite a considerable improvement of growth of Ni-treated wheat, did not counterbalance negative effect of Ni on the phospholipid composition in wheat roots and shoots.     

Biological effects of lithium chloride on Herpetomonas muscarum muscarum and Blastocrithidia culicis (kinetoplastida: trypanosomatidae).

Lithium is widely used in medicine as an antidepressive drug and for myelosuppression attenuation during chemotherapy. In spite of abundant literature, questions on the biological action of lithium ions are far from being answered. We have here examined the effects of lithium (10-200 mM) on culture forms of the trypanosomatid protozoa Herpetornonas muscarum muscarum and Blastocrithidia culicis. Incubation of these parasites with LiCl inhibited cell growth in a concentration-dependent manner, but growth could be restored when the drug was removed from the medium. Furthermore, Li+ induced cell differentiation in H. m. muscarum. Light microscopy examination of cell viability, using erythrosin B staining, showed that all treated parasites remained viable with all drug concentrations used. Ultrastructural analysis by transmission electron microscopy showed that the cells presented no signs of degeneration. However, in H. m. muscarum the nuclei lost their peripheral heterochromatin and appeared filled with a homogeneous matrix, whereas in B. culicis an increased amount of lipid droplets was present in the cytoplasm. Our data show that LiCl treatment arrested the cell division process, stimulated cell differentiation, and affected the metabolism of these parasites.     

Age-Related Differences in Synaptosomal Peroxidative Damage and Membrane Properties

Young, adult, and old rats were used to study the effect of age on the integrity and functioning of brain synaptosomes. An evaluation was made of the differences in lipid composition, membrane fluidity, Na+, K(+)-ATPase activity, and susceptibility to in vitro lipid peroxidation. There was an age-related increase in synaptosomal free fatty acids, with no modification in acyl chain composition, and a decrease in membrane phospholipids which increased the cholesterol/phospholipid mole ratio. With altered lipid composition, there was a corresponding age-dependent decrease in membrane fluidity, a reduction of Na+, K(+)-ATPase activity, and an overall greater susceptibility to in vitro lipid peroxidation. Furthermore, lipid peroxidation promoted strong modifications of the membrane fluidity, lipid composition, and Na+,K(+)-ATPase activity just as aging did, thus indicating a possible contribution of oxidative damage to ageing processes. The cases studied revealed that the greater responsiveness of old membranes to in vitro lipid peroxidation resulted in the highest degree of membrane alteration, indicating that all pathological states known to promote a peroxidative injury can have even more dramatic consequences when they take place in old brain.     

Energy metabolism in wheat root cells under modification of plasma membrane permeability by antibiotic nystatin

This paper reports changes in ion transport and energy metabolism of plant cells during short- and long-term expositions, resp., to antibiotic nystatin, which is known to specifically bind with plasma membrane sterols to form channels. The excised roots of 5 days old wheat seedlings were used as a model system in this research. It has been shown that treatment of excised roots with nystatin leads to activation of energy metabolism expressed as an increase of respiration and heat production by root cells. Furthermore, in the presence of nystatin increased pH of incubation medium, plasma membrane depolarization and a significant loss of potassium ions were observed. Nystatin-induced stimulation of respiration was prevented by malonate, an inhibitor of succinate dehydrogenase, electron acceptor dichlorophenolindophenol, and AgNO3, an inhibitor of H(+)-ATPase. Based on the data obtained it can be suggested that nystatin-induced stimulation of respiration is related to electron transport activation via mitochondrial respiratory chain, and is connected with activation of plasmalemma proton pump. Moreover, nystatin-induced increase of oxygen consumption was prevented by cerulenin, an inhibitor of fatty acid and sterol synthesis. This indicates that additional sterols and phospholipids may be synthesized in root cells to "heal" nystatin-caused damage of plasma membrane. A supposed chain of events of cell response to nystatin action may by as following: formation of nystatin channels-influx of protons--depolarization of plasmalemma-efflux of potassium ions-disturbance of ion homeostasis--activation of H(+)-ATPase work-increase in energy "requests" for H(+)-ATPase function--increase in the rate of oxygen consumption and heat production. The increased energy production under the action of nystatin, may provide the work of proton pump and synthesis of sterols and phospholipids, which are necessary for membrane regeneration.     

Phospholipid metabolism in roots and microsomes of sunflower seedlings: Inhibition of choline phosphotransferase activity by boron

The action of boron on phospholipid composition and synthesis in roots and microsomes from sunflower seedlings has been studied. The fatty acid composition and relative amounts of individual molecular species of phospholipids in roots and microsomes were very similar. In both the content of phospholipids was decreased and the relative levels of their component fatty acids changed by treatment with 50 ppm of boron. This concentration of boron in the culture medium was found to inhibit the in vivo [1-^14C] acetate incorporation into root lipids and that of [Me-¹⁴C] choline into phosphatidylcholine of root microsomes. Cytidine-5-diphospho (CDP)-[Me-¹⁴C] choline incorporation into phosphatidylcholine of isolated microsomes was also inhibited by 50 ppm of boron when present in the growth medium of seedlings. These results indicate that the decrease in phosphatidylcholine labelling from [¹⁴C] choline observed when root microsomes were treated with boron would be caused by a decrease in CDP-choline phosphotransferase activity.     

Lithium inhibits hepatic gluconeogenesis and phosphoenolpyruvate carboxykinase gene expression.

Incubation of isolated hepatocytes from fasted rats with 20 mM LiCl for 1 h decreased glucose production from lactate, pyruvate, and alanine. In addition, phosphoenolpyruvate carboxykinase (PEPCK) gene expression in FTO-2B rat hepatoma cells was inhibited by treatment with LiCl. Lithium was also able to counteract the increased PEPCK mRNA levels caused by both Bt2cAMP and dexamethasone, in a concentration-dependent manner. A chimeric gene containing the PEPCK promoter (-550 to +73) linked to the amino-3-glycosyl phosphotransferase (neo) structural gene was transduced into FTO-2B cells using a Moloney murine leukemia virus-based retrovirus. In these infected cells, 20 mM LiCl decreased both the concentration of neo mRNA transcribed from the PEPCK-neo chimeric gene and mRNA from the endogenous PEPCK gene. Lithium also inhibited the stimulatory effect of Bt2cAMP and dexamethasone on both genes. The stability of neo mRNA was not altered by lithium, since in cells infected with retrovirus containing only the neo gene transcribed via the retroviral 5'-LTR and treated with 20 mM LiCl, no change in neo mRNA levels was observed. The intraperitoneal administration of LiCl to rats caused a decrease in hepatic PEPCK mRNA, indicating that lithium could also modify gene expression in vivo. The effects of lithium were not due to an increase in the concentration of insulin in the blood but were correlated with an increase in hepatic glycogen and fructose 2,6-bisphosphate levels. These results indicate that lithium ions, at concentrations normally used therapeutically for depression in humans, can inhibit glucose synthesis in the liver by a mechanism which can selectively modify the expression of hepatic phosphoenolpyruvate carboxykinase.     

Differences in lipid and in fatty acid composition of taproots and lateral roots of faba bean plants (Vicia faba L.) grown in saline media

Abstract

The content and composition of lipids and fatty acids of taproots and lateral roots of Vicia faba were investigated with plants grown under saline (80 mM NaCl) and non-saline conditions. Lipids of both types of faba bean roots are constituted of ～80% phospholipids, of ～15% glycolipids and of some 5% of wax-esters. Phosphatidylethanolamine (PE) and phosphatidylcholine are the main constituents of both root types. Di-phosphatyidylglycerol and phosphatidylinositol are present in medium concentrations, whereas phosphatidylglycerol and phosphatidylserine are present only in trace amounts. The content of sulpholipids was much lower in salt-treated roots as compared with that of the controls. The content of cardiolipins and PE was higher in lateral roots than in the taproots. Roots of salt-treated plants had some 18% lower ether-soluble lipid content in the lateral roots, and approximately 28% lower than the taproots. Less than 25% of the fatty acids of the extracted phospholipids were saturated, with palmitic acid as the main constituent (13 – 18%). Linoleic acid comprised 65 – 70% of the unsaturated acids. Differences in the composition of some fatty acids were found between taproots and lateral roots of salt-treated plants. The observed differences in composition between root types suggests that the reported physiological differences between such roots could be based, at least in part, on structural or compositional differences in their lipids.     

Zinc-alleviating effects on iron-induced phytotoxicity in roots of <Emphasis Type="Italic">Triticum aestivum</Emphasis>

The mechanisms of growth inhibition and antioxidative response were investigated in wheat roots exposed to 300 μM iron together with different zinc concentrations (0, 50, and 250 μM). All Zn concentrations decreased Fe content but increased Zn content in the roots and leaves of Fe-treated seedlings. Compared with Fe stress alone, 50 or 250 μM Zn + Fe treatment stimulated root growth, and increased cell viability but decreased malondialdehyde content, which were correlated with the decreases of total and apoplastic hydrogen peroxide and superoxide anion radical (O₂ ^·?) content along with apoplastic hydroxyl radical content. Generation of O₂ ^·? in response to 10 μM diphenylene iodonium suggested that NADPH oxidase activity was lower in Zn + Fe-treated roots than in other roots. In addition, cell wallbound peroxidase, diamine oxidase, and polyamine oxidase in Fe-treated roots were insensitive to Zn addition. Further study showed the stimulation of total superoxide dismutase and glutathione reductase (GR) activities as well as apoplastic catalase, ascorbate peroxidase, and GR in Zn + Fe-stressed roots in comparison with Fe-alone-treated ones. Taken together, Zn could alleviate iron-inhibitory effect on root growth, which might be associated with the decrease of lipid peroxidation, the increase of cell viability and the reductions of reactive oxygen species generation.     

Drought acclimation reduces O2*- accumulation and lipid peroxidation in wheat seedlings

Abiotic stresses cause ROS accumulation, which is detrimental to plant growth. It is well known that acclimation of plants under mild or sub-lethal stress condition leads to development of resistance in plants to severe or lethal stress condition. The generation of ROS and subsequent oxidative damage during drought stress is well documented in the crop plants. However, the effect of drought acclimation treatment on ROS accumulation and lipid peroxidation has not been examined so far. In this study, the effect of water stress acclimation treatment on superoxide radical (O(2)(-z.rad;)) accumulation and membrane lipid peroxidation was studied in leaves and roots of wheat (Triticum aestivum) cv. C306. EPR quantification of superoxide radicals revealed that drought acclimation treatment led to 2-fold increase in superoxide radical accumulation in leaf and roots with no apparent membrane damage. However under subsequent severe water stress condition, the leaf and roots of non-acclimated plants accumulated significantly higher amount of superoxide radicals and showed higher membrane damage than that of acclimated plants. Thus, acclimation-induced restriction of superoxide radical accumulation is one of the cellular processes that confers enhanced water stress tolerance to the acclimated wheat seedlings.     

Effect of Temperature and BASF 13 338 on the Lipid Composition and Respiration of Wheat Roots

The fatty acid composition of wheat seedling roots changed in response to temperature. As temperature declined, the level of linolenic acid increased and the level of linoleic acid decreased. The distribution of phospholipid classes was not influenced by temperature. Phosphatidyl choline and phosphatidyl ethanolamine were the predominant phospholipids isolated and comprised 85% of the total lipid phosphorus. Smaller quantities of phosphatidyl glycerol, phosphatidyl inositol, phosphatidic acid, and phosphatidyl serine were isolated. The fatty acid composition of phosphatidyl choline and phosphatidyl ethanolamine were the same and temperature affected the fatty acid composition of both phospholipids in the same manner.Growth in the presence of the substituted pyridazinone, BASF 13 338 (4-chloro-5-dimethylamino-2-phenyl-3(2H)pyridazinone), reduced the level of linolenic acid and increased the level of linoleic acid in the phosphatidyl choline, phosphatidyl ethanolamine, and total polar lipid fractions. BASF 13 338 did not affect the levels of palmitate, stearate, and oleate or the distribution of phospholipid classes.Respiration rates of wheat root tips were measured over a range of temperatures. The respiration rate declined as the temperature decreased. Neither the temperature at which the tissue was grown nor BASF 13 338 treatment influenced the ability of root tips to respire at any temperature from 4 to 30 C. The results indicated that the relative proportion of linolenic acid to linoleic acid did not influence the plants ability to grow and respire over the range of temperatures tested.     

Binding of sterols affects membrane functioning and sphingolipid composition in wheat roots

The present work was devoted to the exploration of the role of sterols in the functioning of membranes in root cells. Membrane characteristics and composition of the membrane lipids in the roots of wheat (Triticum aestivum L.) seedlings treated with exogenous cholesterol and antibiotic nystatin, which specifically binds with endogenous sterols, were analyzed. Cholesterol caused a fall of membrane potential, acidification of the incubation medium, decrease in potassium leakage of roots, and increase in the level of exogenous superoxide radical. Similarly to cholesterol, the application of nystatin also induced the depolarization of the plasma membrane, but in contrast with cholesterol it was accompanied by alkalinization of the incubation medium and decrease in the level of exogenous superoxide radical. Analysis of membrane lipids showed that following nystatin treatment the total sterol content in roots did not change, while the level of complex sphingolipids represented mainly by glycoceramides became higher. Using mass spectrometry with electrospray ionization (+ESI-MS) for the analysis of the glycoceramide composition, we showed that nystatin induced changes in the ratios of molecular species of glycoceramides. It was suggested that the modification of the sterol component of plasma membrane could influence membrane functioning by changing the sphingolipid composition of lipid rafts.     

Role of the nonspecific modification of erythrocyte membrane lipids during hibernation in the suslik Citellus parryi

Studies have been made on the content of cholesterol, phospholipids, fatty acid composition, the intensity of lipid peroxidation, the activity of Na+, K+-ATPase, as well as on the peroxide hemolysis in the erythrocytes in prehibernating and hibernating ground squirrels. Changes in partial content of cholesterol and in fatty acid composition of membranes are presumably due to the excessive lipid peroxidation during hibernation resulting from the decrease in the activity of antioxidative enzymes, which also accounts for the increase in peroxide hemolysis of erythrocytes.     

Effect of fungal infection on the composition of acyl lipids in wheat seedlings

Infection of etiolated wheat seedlings with a root rot fungus Bipolaris sorokiniana caused a strong deviation in the fatty acid composition of their total lipids from the control. The deviation occurred at the expense of that lipid group, which predominates in a given plant organ (shoots or roots), and peak deviation coincided with the onset of a severe inhibition of growth.     

The role of iron in oxygen radical mediated lipid peroxidation

The role of iron in the peroxidation of polyunsaturated fatty acids is reviewed, especially with respect to the involvement of oxygen radicals. The hydroxyl radical can be generated by a superoxide-driven Haber-Weiss reaction or by Fenton's reaction; and the hydroxyl radical can initiate lipid peroxidation. However, lipid peroxidation is frequently insensitive to hydroxyl radical scavengers or superoxide dismutase. We propose that the hydroxyl radical may not be involved in the peroxidation of membrane lipids, but instead lipid peroxidation requires both Fe2+ and Fe3+. The inability of superoxide dismutase to affect lipid peroxidation can be explained by the fact that the direct reduction of iron can occur, exemplified by rat liver microsomal NADPH-dependent lipid peroxidation. Catalase can be stimulatory, inhibitory or without affect because H2O2 may oxidize some Fe2+ to form the required Fe3+, or, alternatively, excess H2O2 may inhibit by excessive oxidation of the Fe2+. In an analogous manner reductants can form the initiating complex by reduction of Fe3+, but complete reduction would inhibit lipid peroxidation. All of these redox reactions would be influenced by iron chelation.     

Characteristics of the ionic composition and ultrastructure of Bordetella pertussis in controlled regulation of the mineral element content in a growth medium

The content of trace elements necessary for the normal growth of bacteria was found to have no effect on the intracellular concentration of Ca2+ and Al3+. The content of Cu2+, Fe3+, Mn2+, Mg2+ was considerably reduced. The addition of Mg2+ at different concentrations to this culture medium stimulated the capacity of cells for accumulating not only Mg2+, but also some other ions. Their maximum intracellular concentration was observed when the concentration of Mg2+ in the culture medium was 41 mM. The growth of microbial cells in the standard culture medium containing Mg2+ at a concentration of 4 mM was accompanied by the increased consumption of elements actively participating in redox reactions (Cu2+, Fe3+, Mn2+). Shifts in the ionic composition of microbial cells were manifested by the morphological features of B. pertussis, linked with the increased synthesis of crystalloid structures. The influence of Mn2+, Al3+, Zn2+ at different concentrations on the ionic composition and morphology of B. pertussis was studied.     

Production of 1,2-Diacylglycerol in PC12 Cells by Nerve Growth Factor and Basic Fibroblast Growth Factor

The addition of nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) to PC12 cells prelabeled with [3H]inositol and preincubated for 15 min in the presence of 10 mM LiCl stimulated the production of inositol phosphates with maximal increases of 120-180% in inositol monophosphate (IP), 130-200% in inositol bisphosphate (IP2), and 45-50% in inositol trisphosphate (IP3) within 30 min. The majority of the overall increase (approximately 85%) was in IP; the remainder was recovered as IP2 and IP3 (approximately 10% as IP2 and 5% as IP3). Under similar conditions, carbachol (0.5 mM) stimulated about a 10-fold increase in IP, a sixfold increase in IP2, and a fourfold increase in IP3. The mass level of 1,2-diacylglycerol (DG) in PC12 cells was found to be dependent on the incubation conditions; in growth medium [Dulbecco's modified Eagle's medium (DME) plus serum], it was around 6.2 mol %, in DME without serum, 2.5 mol %, and after a 15-min incubation in Dulbecco's phosphate-buffered saline, 0.62 mol %. The addition of NGF and bFGF induced an increase in the mass level of DG of about twofold within 1-2 min, often rising to two- to threefold by 15 min, and then decreasing slightly by 30 min. This increase was dependent on the presence of extracellular Ca2+, and was inhibited by both phenylarsine oxide (25 microM) and 5'-deoxy-5'-methylthioadenosine (3 mM). Under similar conditions, 0.5 mM carbachol stimulated the production of DG to the same extent as 200 ng/ml NGF and 50 ng/ml bFGF. Because carbachol is much more effective in stimulating the production of inositol phosphates, the results suggest that both NGF and bFGF stimulate the production of DG primarily from phospholipids other than the phosphoinositides.     

Lipid biochemistry of echinochloa crus-galli during anaerobic germination

Seven day old seedlings of Echinochloa crus-galli var. oryzicola (Vasing) had a higher total lipid content when germinated under N₂ than in air, although ungerminated seeds contained more lipid than either seedling. The triacylglycerol pool was not depleted under anaerobiosis as it was in air and only air-grown seedlings showed a net increase in free fatty acids and polar lipids. Concentrations of most of the individual acids of the total fatty acid profile declined during germination in air and in the free acid and polar lipid fractions of these seedlings the relative proportion of polyunsaturated fatty acids increased. Compared to air-grown seedlings, ungerminated seeds and N₂-grown seedlings had a similar qualitative and quantitative lipid composition. Our results show that mobilization of storage lipids was apparently severely inhibited under anoxia. The importance of lipid metabolism to the germination and growth of Echinochloa during anoxia is discussed in terms of maintaining membrane integrity and serving (indirectly) to reoxidize pyridine nucleotides.