Effect of Increasing Concentrations of Lead and Cadmium on Cucumber Seedlings

The effect of lead and cadmium on biomass accumulation of cucumber seedlings (Cucumis sativus L.) as well as the contents of abscisic acid (ABA), free proline and soluble proteins in leaves were studied. Seedlings were subjected to lead nitrate or cadmium bromide in low concentrations (1 – 5 µM) for 1, 4 or 7 d, and then to the action of the same substances in high concentrations (500 – 1000 µM). The pretreatments of the seedlings with heavy metals in low concentrations enabled them to tolerate the subsequent high concentrations of cadmium and lead without injury. The plant responses to heavy metal treatment were accompanied by the accumulation of ABA, free proline and soluble proteins in leaf tissues.     

Antioxidant capacity of <Emphasis Type="Italic">Brassica juncea</Emphasis> plants exposed to elevated levels of copper

Brassica juncea L. eight-day-old seedlings treated with various concentrations (50–200 µM) of copper for 48 h accumulated Cu more in the roots than in leaves. Accumulation of copper resulted in more active lipid peroxidation and depletion of glutathione (GSH) pools in both roots and shoots, which was attributed to copper-induced additional oxidative stress. Activities of ascorbate peroxidase and superoxide dismutase were higher in both roots and shoots while catalase activity increased in leaves but remained unchanged in roots in response to copper accumulation. Changes in lipid peroxidation, GSH content, and antioxidant enzyme activities suggest that oxidative damage may be involved in copper toxicity.From Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 233–237.Original English Text Copyright © 2005 by Devi, Prasad.This article was submitted by the authors in English.This revised version was published online in April 2005 with a corrected cover date.     

Phytochelatin synthesis and cadmium localization in wild type of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

AlthoughArabidopsis thaliana is known as a model plant, in molecular studies, as well as heavy metal tolerance of higher plants, there have been no detailed studies of its cadmium accumulation, tolerance and cellular distribution in a wild type of this species. In hydroponic experiments the wild type of A. thaliana (L.) Heynh cv. Columbia plants grew at cadmium concentrations varying from 5 to 100 M with phytotoxicity symptoms depending on the concentration and time of application. The concentration of cadmium in roots and shoots increased from 0.28 and 0.08 mg g^–1 d.wt at 5 M Cd treatment after 7 days to 0.82 and 0.85 mg g^–1 d.wt at 100 M Cd treatment after 14 days, respectively. Most of the cadmium (69–88% of its total pool) was found in shoot. Cd application induced the biosynthesis of phytochelatins (PCs) in root and shoot tissues. Studies with buthionine sulfoximine [BSO, specific inhibitor of glutathione (GSH) synthesis] supported the presence of Cd–phytochelatin complexes and their role in Cd detoxification and tolerance in wild type of A. thaliana. Cellular distribution of cadmium was examined using energy-dispersive X-ray micro-analysis. Particularly interesting was the observation of cadmium localized in the root pericycle.     

Multiplicity of chemical mechanisms of regulation of muscle contractions in <Emphasis Type="Italic">Lymnaea stagnalis</Emphasis> L.

Effects of acetylcholine, octopamine, and their antagonists, as well as of glutamic acid were studied on contractions of dorsal longitudinal muscle of the mollusc Lymnaea stagnalis L., evoked by electrical stimulation of n. cervicalis inferior. Acetylcholine and octopamine increased amplitude of contractions evoked by applications at concentrations about 10^–8 M and decreased at concentrations higher than 10^–7 M. Glutamic acid produced only inhibitory effect on the contraction amplitude, which appeared at concentrations beginning from 10^–9 M and higher. The acetylcholine antagonists atropine and d-tubocurarine also decreased amplitude of evoked contractions. Their blocking effect rose with increase of their concentrations in the range from 10^–9 M to 10^–5 M. Specificity of the effect of the studied substances was established in experiments with a combined application of the transmitters and their antagonists. The obtained results indicate multiplicity of chemical mechanisms of regulation of contractions of the dorsal longitudinal muscle in L. stagnalis.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 44–50.Original Russian Text Copyright © 2005 by Kononenko, Zhukov.     

Sensitivity of hippocampal interneurons and pyramidal cells to GABA and some of its agonists:in vitro experiments

Effects of GABA and its agonists baclofen and muscimol on the background spike activity of single hippocampal neurons were studied in rat brain slices using an intracellular recording technique. Interneurons localized in thestratum alveus-oriens and pyramidal neurons of thestratum pyramidale showed high sensitivity to GABA (mean ID₅₀=65 µM and 40 µM, ranges 10–140 µM and 3–200 µM), baclofen (ID₅₀=2.6 µM and 3.5 µM, ranges 0.6–20.0 µM and 0.4–30.0 µM), and muscimol (ID₅₀=0.85 µM and 0.21 µM, ranges 0.11–4.0 µM and 0.05–0.45 µM, respectively). Responses of hippocampal neurons to application of GABA or either of its agonists were predominantly inhibitory. A part of interneurons (30%) differed from pyramidal neurons in their irresponsivity or low sensitivity to baclofen applications. GABA- or muscimol-induced inhibition of spike activity in many pyramidal cells was preceded by a short-lasting excitation. Our findings indicate that a part of hippocampal interneurons are very poorly supplied with GABAb receptors. Inhibition of pyramidal cells evoked by activation of GABAa receptors probably develops against the background of accompanying depolarization, which in some cases can result in a provisional excitation of these neurons. The excitatory effects of GABA on the pyramidal cells are mediated by GABAa receptors.Neirofiziologiya/Neurophysiology, Vol. 27, No. 1, pp. 36–44, January–February, 1995.     

Heavy metals (Cu,Zn, Pb,Cd) in sediment,zooplankton and epibenthic invertebrates from the area of the continental slope of the Banc d'Arguin (Mauritania)

The concentrations of copper, zinc, lead and cadmium in the surface sediment (upper 5 mm) were generally higher in the silt fraction than in the bulk sediment. No significant geographical trend in the metal concentrations of the surface sediments was found, nor a correlation between concentrations in bulk sediment as well as in the silt fraction and the % silt could be established. In general, the metal concentrations in both bulk sediment and silt are lower, when compared to marine environments in other climatological regions.In zooplankton, the metal concentrations were relatively high: expressed in µg g^–1 on a dry weight (D.W.) basis, they ranged from 15–90 for copper, 70–580 for zinc, 12–55 for lead and 4–10 for cadmium.In epibenthic invertebrate species, both in crustaceans and bivalve molluscs, the concentrations of copper, zinc, and lead were in the same order of magnitude as compared to corresponding species from other geographical latitudes. Cadmium concentrations were relatively low, ranging from 0.13–0.42 µg g^–1 D.W. in the bivalve molluscs Pitaria tumens and from 0.04–0.27 µg g^–1 D.W. in the shrimp Processa elegantula. Also in the crab species Ilia spinosa, Inachus sp. and Pagurus sp., the cadmium concentrations were low, varying between 0.1 and 0.2 µg g^–1 D.W.No significant relation between the metal concentration in whole-body samples and sediment (either bulk or silt) was present. Also no gradient was apparent in concentrations in organisms sampled at different depths (5 to 200 m) along two off-shore transects perpendicular to the Banc d'Arguin. Data indicated lower metal concentration in epibenthic organisms from sampling stations along a northern transect (southwest of Cap Blanc) than in organisms from the southern transect, off Cap Timiris.Evidence was obtained for a considerable atmospheric input of heavy metals, in particular zinc and lead, in a certain area along the continental slope of the Banc d'Arguin.     

Effect of Nitrogen Limitation on the Growth and Lipid Composition of the Green Alga <Emphasis Type="Italic">Botryococcus braunii</Emphasis> Kutz IPPAS H-252

The effect of nitrogen limitation in a medium on the composition of intracellular lipids in the alga Botryococcus braunii Kutz IPPAS H-252 in the course of culture development was investigated. Under the conditions of nitrogen limitation, the alga under investigation accumulated lipids as triacylglycerols, and this process was accompanied by substantial changes in the total fatty acid (FA) composition, which were manifested in a decrease in trienoic acids (from 52.8–57.2 to 19.5–24.7% of total FAs) and an increase in the content of oleic (from 1.1–1.2 to 17.1–24.4%) and saturated (from 23.7–26.0 to 32.9–46.1%) acids. In the control culture, the directionality of FA redistribution was less marked, and these changes were noticed at the later stages of culture development. Under nitrogen limitation, marked changes in the FA composition of polar lipids occurred by the 13th day, and they were characterized by an increase in the content of saturated acids (up to 76.8%) and a dramatic decrease in the content of all polyenoic acids (up to 6.8%). The changes in the FA composition of triacylglycerols were noticed as early as by the 7th day; these changes consisted in an increase in the content of oleic acid, and its high content (28.4–38.4%) was maintained up to the end of culturing. In the control culture, triacylglycerols with a high content of oleic acid were found by the 13th day, although, by this time, the content of total lipids and triacylglycerols did not change.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 3, 2005, pp. 357–365.Original Russian Text Copyright © 2005 by Zhila, Kalacheva, Volova.     

The effect of phosphate concentration on growth and agar content of Gelidium robustum (Gelidiaceae,Rhodophyta) in culture

Phosphate concentration of the growth medium was found to affect the growth rate and agar yield of a clone of Gelidium robustum grown in the laboratory. To study differences in growth we used phosphate concentrations from 0 to 200 µM. To determine the effect of phosphate on agar yield and its properties we used concentrations from 0 to 20 µM. Growth rates generally increased with increasing phosphate concentration, with the highest growth rate (21% d^–1) obtained at 150 µM. Agar yield as percentage of fresh weight was highest (10%) in the algae grown with low phosphate concentrations, but agar yield as percentage of dry weight was highest(43%) at 20 µM of phosphate. Gel strength increased with phosphate concentration with a maximum of 160 g m^–2 for 0.75% gels for the cultures at 20 µM. Melting and gelling temperatures of the gels were also affected by phosphate concentration of the growth medium. Starch yield was highest in algae grown in low phosphate concentrations.     

Enteromorpha as a monitor of heavy metals in estuaries

An account is given of the use of Enteromorpha to monitor zinc, cadmium, mercury and lead pollution in six estuaries and the British North Sea coast. The ranges for each element were: Zn, 19–437 µg g^–1; µg g^–1 Cd, 0.07–4.8 µg g^–1; Hg, 0.02–0.23 µg g^–1. It is suggested that tissue analysis of Enteromorpha is one of the most useful biological techniques available in estuaries for pin-pointing aqueous (as opposed to sediment) metal contamination, and also for providing data suitable for world-wide comparisons. Provisional values are given for concentrations corresponding to moderate and high pollution.Deceased     

Chronic effects of cadmium on two species of mysid shrimp:Mysidopsis bahia andMysidopsis bigelowi

Two species of mysid shrimp, the sub-tropicalMysidopsis bahia and the northern temperateMysidopsis bigelowi, were exposed simultaneously to cadmium (as CdCl₂) in a continuous-flow bioassay system to determine the effect on survival and reproductive success. Temperature and salinity were maintained at 21 ± 1°C and 30,respectively. The 96-h LC50 was 110 µg ^–1 for both species. The 23-day life cycle LC50 forM. bahia was 19.5 µg ^–1 and forM. bigelowi the 27-day LC-50 was 14.8 µg ^–1. At 10 µg ^–1 a series of morphological aberrations were observed in both species at the onset of sexual maturity. Carapace malformations apparently prevented molting after the release of the initial brood and resulted in death of brooding females. As a result, although the initial reproductive rate at this concentration was successful, successive broods could not be produced. For both species in this study the no observed effect concentration was 5.1 µg ^–1; the effect concentration was 10.0 µg ^–1. Mechanisms were postulated in this study to explain the effect of cadmium on the molting process and on calcification and enzymatic reactions of osmosis.Contribution No. 257 of the U.S. Environmental Protection Agency.Contribution No. 257 of the U.S. Environmental Protection Agency.     

Translocation of cadmium and mercury into the fruiting bodies ofAgrocybe aegerita in a model system using agar platelets as substrate

Summary Growth of Tetrahymena pyriformis (Gl) was studied in axenic culture in the presence of cadmium. The maximum growth rate is not affected by concentrations of cadmium below 1.5 mg/l (1.3×10^–5 M). The concentration reducing the growth rate to 50% of its initial value is 2.6 mg/l (2.3×10^–5 M) and the lethal dose is 5 mg/l (4.5×10^–5 M).The mean cell volume, mean cell dry weight, mean cell protein content, yield and respiration rate were compared at 0, 0.2 and 2.0 mg/l Cd. No significant differences were detected for these parameters between control and treated groups.     

Alteration in growth and thylakoid membrane lipid composition of <Emphasis Type="Italic">Azolla caroliniana</Emphasis> under phosphate deficiency

The changes in the fresh biomass accumulation, photosynthetic and anthocyanin pigments, photosystem 2 (PS 2) activity, ultrastructure of chloroplast, total lipids and fatty acid composition of thylakoid membrane were followed in the aquatic fern Azolla caroliniana grown on medium either deficient or supplied with various phosphorus concentrations. The content of photosynthetic pigments and the anthocyanin/chlorophyll ratio increased significantly with increasing PO₄ ³⁻ concentration. Phosphate deficiency inhibited growth and PS 2 activity and decreased content of total lipids and phospholipids in isolated thylakoids. This was accompanied with a significant increase in the percentage of galalactolipids.     

Cumulative effect of low and high atrazine concentrations on <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> plants

Atrazine belongs to the widely used herbicides blocking the electron transport chain in chloroplasts, thus resulting in the generation of active oxygen species. In the present work, we demonstrated that, at low concentrations mimicking residual amounts, atrazine enhanced the susceptibility of Arabidopsis plants to further treatments with the same herbicide applied at the recommended field rate. Arabidopsis thaliana plants were treated three times (at five-day intervals) with 1 µM atrazine. Five days after the last treatment, the plants were sprayed with 5 mM atrazine. Atrazine increased the levels of lipid peroxidation products, hydrogen peroxide, and ion leakage, and caused changes in the activities of antioxidant enzymes, such as superoxide dismutase, guaiacol peroxidase, and catalase.From Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 243–249.Original English Text Copyright © 2005 by Ivanov, Alexieva, Karanov.This article was submitted by the authors in English.This revised version was published online in April 2005 with a corrected cover date.     

ATP-induced currents in submucous plexus neurons of the guinea pig small intestine

ATP-induced membrane durrents in the submucous neurons of the guinea pig small intestine were studied using the whole-cell patch-clamp recording technique. Being applied at –50 mV. ATP activated an inward non-selective cationic current in 68.3% of the investigated neurons. An increase in ATP concentration within the 1–1,000 µM range resulted in the s-like increase in the amplitude of ATP-induced current. The EC₅₀ was 150.0±18.5 µM, while the Hill number was 1.6. The current was selectively activated by ATP and was not blocked by P2 purinoreceptor antagonist suramin (50–300 µM).,-Methylene-ATP (100–200 µM) and,-methylene-ATP (100–200µM), which are P2-purinoreceptor agonists, as well as adenosine (100–300 µM), exerted no effects. Reactive blue 2, if applied up to 4 min, enhanced ATP-induced current, while its longer application partially suppressed this current. In most submucous neurons, acetylcholine (ACh) likewise activated an inward cationic current. The amplitude of ACh-induced current was lower if ACh was applied during a long-lasting application of ATP than if ACh only was applied. Hexamethonium (50 µM), d-tubocurarine (20–40 µM), and trimethaphan (30 µM) completely and reversibly blocked ACh-induced currents, regardless of the presence of ATP, and did not affect ATP-induced currents. The results suggest that ATP-induced currents in submucous neurons are due to activation of a unique type of P2 purinoreceptors, which function in connection with nicotinic ACh receptors.Neirofiziologiya/Neurophysiology, Vol. 28, No. 2/3, pp. 100–110, March–June, 1996.     

Solubility of cadmium and cobalt in a post-oxic or sub-oxic sediment suspension

A sediment sample with high organic matter and trace metal content was suspended in synthetic river water for four weeks under an inert gas atmosphere. Subsequently, the anaerobic suspension was reoxidized by bubbling air through it. The concentrations of dissolved oxygen, sulfide, ferrous iron, manganese, cadmium, cobalt and the pH-value were measured at close time intervals during the anaerobic incubation. The anaerobic suspension was a post-oxic or sub-oxic environment with oxygen and total sulfide concentrations less than 1 µmole 1^–1. Concentrations of dissolved ferrous iron and manganese were 50–150 µmole 1^–1 and 5–30 µmole 1^–1, respectively. The total sulfide concentration was measured using a sensitive voltammetric technique, with a detection limit of 1 nmole 1^–1. A sequential extraction procedure was applied to two sediment samples taken at the end of the anaerobic incubation and after one week of reoxidation. The extractions indicated that cadmium was bound in sulfide minerals under post-oxic conditions. Thermodynamic equilibrium calculations revealed that the concentrations of dissolved cobalt in the post-oxic suspension were limited by the precipitation of cobalt sulfide minerals.     

In vitro culture of adult and juvenile bud explants of Passiflora species

Cultivar E23, an F1 hybrid of P. edulis and P. edulis f. flavicarpa is usually propagated by shoot-tip grafting. Various media were tested to evaluate the potential of E23 for in vitro propagation. Adult tissue was difficult to culture and did not respond to media containing low (<10 µM) concentrations of growth regulators. Growth of adult buds on intact stem sections was promoted by 1 week of dark incubation on MS basal medium plus 150 µM 2iP, 200 µM adenine sulphate and 17.1 µM IAA (3 mg l^–1), and further developed into shoots on MS medium plus 4.9 µM 2iP (1 mg l^–1) and 5.7 µM IAA (1 mg l^–1). By contrast, juvenile shoots of E23, and Passiflora species: edulis f. flavicarpa, edulis, alata, caerulea, mollissima, coccinea, herbertiana and suberosa grew rapidly on MS medium plus 10 µM kinetin and 5 µM IAA. Rapid multiplication was achieved on MS plus 20 µM BA, 10 µM kinetin, 5 µM IAA, and roots initiated on MS plus 5 µM IAA.Abbreviations IAA indole-3-acetic acid - 2iP N6-iso pentenyl adenine - BA N6-benzyl adenine     

Effect of light intensity and ammonium-N on carotenogenesis ofTrentepohlia odorata andDunaliella bardawil

AxenicTrentepohlia odorata was cultured at three different NH₄Cl levels (3.5 × 10^–2, 3.5 × 10^–3, 3.5 × 10^–4 M) and three different light intensities (48, 76, 122 µmol m^–2 s^–1). Chloride had no effect on growth over this range of concentration. High light intensity and high NH₄Cl concentration enhanced the specific growth rate. The carotenoid content increased under a combination of high light intensity and low N concentration. WhenD. bardawil was exposed to the same combination of growth conditions, there was an increase in its carotenoid content. The light saturation and the light inhibition constants (K _s andK _i, respectively) for growth, and the saturation constant (K _m) for NH₄Cl were determined. TheK _s andK _i values were higher inT. odorata (66.7 and> 122 mol m^–2 s^–1, respectively) than inD. bardawil (5.1 and 14.7 µmol m^–2 s^–1, respectively). TheK _m value determined at 122 µmol m^–2 s^–1, however, was lower inT. odorata (0.048 µM) than inD. bardawil (0.062 µM).Author for correspondence     

Effects of Nitrendipine and Nimodipine on Low-Threshold Ca<Superscript>2+</Superscript> Channels in Thalamic Neurons of the Rat

We compared the effects of two dihydropyridines extensively used in clinical medicine, nimodipine and nitrendipine, on Ca²⁺ channels of two subtypes providing the fast and slow components of low-threshold Ca²⁺ currents in isolated neurons of the nucl. lateralis dorsalis of the thalamus of the rat; a patch-clamp technique in the whole-cell configuration was used. The fast component of the Ca²⁺ current demonstrated a higher sensitivity to nimodipine and nitrendipine (IC₅₀ = 0.6 and 0.1 µM, respectively) than the slow component (IC₅₀ = =1.09 and 0.18 µM, respectively). Maximum decreases in the current amplitude, A _max, caused by nimodipine and nitrendipine were 74 and 94% for the fast component and 55 and 80% for the slow component, respectively. Both tested agents evoked a shift of the inactivation curves of the fast component toward more negative potentials, whereas they did not significantly modify the inactivation characteristics of the slow component. Both dihydropyridines weakly influenced the characteristics of stationary activation of low-threshold Ca²⁺ channels and the blocking intensity demonstrated a voltage dependence.Neirofiziologiya/Neurophysiology, Vol. 37, No. 1, pp. 3–10, January–February, 2005.     

Effects of heavy metals on growth and ultrastructure ofChara vulgaris

Summary The toxicity of some heavy metals to the common macrophytic freshwater algaChara vulgaris was studied under laboratory conditions. For experiments, apical tips of algae containing two internodes were cultivated for fourteen days in the presence of various concentrations of cadmium, mercury or lead (as triethyl lead or lead nitrate). Fifty percent growth inhibition occurred with concentrations of 8.5×10^–8 M (9.5 ppb) cadmium, 7.5×10^–7M (150ppb) mercury, 1.6×10^–6 M (330ppb) organic lead or 4× 10^–5 M (8000 ppb) inorganic lead. Sublethal concentrations of these metals caused alterations in the fine structure of internodal cells which turned out to be at least partly metal-specific or in the case of lead, the effects depended on whether the lead was ionic or organically bound. Cadmium and inorganic lead induced disorders of cell wall microfibrils which resulted in local wall protuberances. Mercury affected the chloroplasts which mostly showed considerably increased grana stacks. In addition, mercury caused a dilation of the endoplasmic reticulum and of the mitochondrial tubuli. Organic lead damaged the membrane system of chloroplasts; sheet- or tubule-like thylakoids were disarranged and showed whorl-like structures. At higher concentrations of organic lead, tubular invaginations of the plasmalemma (charasomes) disappeared. The fine structure of nuclei was not altered by any of the metals.     

UV-B radiation and cadmium induced changes in growth,photosynthesis, and antioxidant enzymes of cyanobacterium <Emphasis Type="Italic">Plectonema boryanum</Emphasis>

UV-B (0.4 W m^–2) irradiation and cadmium (2 and 8 M) treatments separately inhibited the survival, growth, pigment content, and photosynthetic electron transport in Plectonema boryanum. Phycocyanin was the main target to UV-B and Cd and it was followed by chlorophyll a and carotenoids. UV-B and Cd caused strong inhibition on activities of photosystem 2 (PS2) and the whole electron transport chain, whereas photosystem 1 (PS1) was the least affected. UV-B and Cd treatment accelerated respiration, lipid peroxidation, and the activities of superoxide dismutase and catalase. However, enhancement in catalase activity was considerably less (5 – 50 %) as compared to SOD activity. As compared to individual treatment, the effect of their combination (UV-B + Cd) was more detrimental to the above parameters. A synergistic interaction of UV-B and Cd is probably due to increased cadmium uptake as a result of increased membrane permeability caused by lipid peroxidation in P. boryanum after UV-B exposure.