Influence of nitrogen on the behaviour of nickel in wheat

A glasshouse experiment was conducted to study the effect of Ni on the growth and nutrients concentration in wheat (Triticum aestivum Cv. WH 291) in the presence and absence of applied N as urea. Responses to N application were observed up to 120 g N g^–1 soil. No response to Ni was observed in the dry matter yield of wheat tops (leaves + stem) in the absence of applied N while in the presence of applied N, significant yield increases were obtained at 12.5g Ni g^–1 soil. Nickel was not toxic to wheat up to 50g Ni g^–1 soil in the presence of 120g N g^–1 soil. Nitrogen and Ni concentration in wheat tops and roots increased with increasing levels of applied N and Ni, respectively. Applied Ni had an antagonistic effect on N concentration. Similarly, N reduced the Ni concentration in the wheat tissues. Positive growth responses to Ni were associated with 22 and 15g Ni g^–1 in wheat tops, in the presence of applied N at 60 and 120g N g^–1 soil, while Ni toxicity was associated with 63, 92.5 and 112.5g Ni g^–1 in wheat tops, in the absence and presence of applied N at 60 and 120g N g^–1 soil, respectively.     

Architecture of the media of the arterial vessels in the dog brain: A scanning electron-microscopic study

Summary The architecture of the media of arterial vessels in dog brain was investigated using scanning electron microscopy. The arrangement and shape of the circularly-oriented smooth muscle cells varied with vessel diameter: The arteries (>100 m in diameter) had 4–10 layers of spindle-shaped smooth muscle cells; the muscular arterioles (30–100 m), 2–3 layers of spindle-shaped smooth muscle cells; the terminal arterioles (10–30 m), a compact layer of spindle-shaped smooth muscle cells with more dominant nodular or rod-like processes and thin lateral processes; and the precapillary arterioles (5–15 m), a less compact layer of branched smooth muscle cells.Longitudinally-oriented muscles were observed in the medio-adventitial border. The distribution and arrangement of these muscles varied with vessel size: in the large arteries (> 300 m in diameter), at the branching sites only; in the small arteries (100–300 m), at both the branching and non-branching sites; in the muscular arterioles, at both the branching and non-branching sites in a reticular arrangement with some muscle cells having an asteroid appearance; in the terminal aterioles, only asteroid-like muscle cells were found at the branching and non-branching sites.     

Tissue culture ofKarwinskia humboldtiana—a plant producing toxins with antitumoural effects

Isolated embryos ofKarwinskia humboldtiana were cultured in vitro. The growth of embryos and development to plantlets on woody plant medium supplemented with indole-3-acetic acid 6.10^-2 mol l^–1, gibberellic acid (GA₃) 3.10^-2 mol l^–1, and 6-benzylaminopurine (BA) 2 mol l^–1 was obtained. Multiplication of shoots and rooting of excised shoots has been achieved. Callus formation on modified Murashige-Skoog medium supplemented with 1-naphthaleneacetic acid 10 mol l^–1, GA₃ 14 mol l^–1, and kinetin 5 mol l^–1 on hypocotyls, or on root cultures on medium supplemented with 2.4-dichlorophenoxyacetic acid 10 mol l^–1 and BA 10 mol l^–1 was induced.Abbreviations BA 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - TEM transmission electron microscopy     

Contribution of flow cytometry to estimate picoplankton biomass in estuarine systems

Picoplankton (plankton 3 m) biomass was determined by flow cytometry in three European estuarine systems (Krka Estuary in Croatia, Rhône Delta in France, and Lena Delta and Laptev Sea in Russia). The size of natural phytoplankton groups was obtained by a calibration curve, with different picoplankton's strains (from 1.6 to 3.4 m), measured by a Coulter counter (size) and a flow cytometer (light-scattering). Two natural groups of picoplankton were identified by flow cytometry in the three systems: Synechococcus sp and picoeukaryotes. Picoplankton cells abundance ranged between: 2800 and 42000, 5000 and 37000, 1000 and 50000 cells ml^–1 in the Krka estuary, in the Rhône delta and in the Lena-Laptev system, respectively. In the Krka estuary, picoplankton biomass ranges between 11 and 68 gC l^–1. It can make up as much as 88% of the total photosynthetic plankton population and 50% of total organic particulate carbon. Picoplankton biomass was greater in the summer than in the autumn. At the halocline layer this biomass can attempt ca. 390 gC l^–1during the summer cruise. In the Rhône delta, a lower picoplankton biomass (6–39 gC l^–1) was observed at the end of the winter. These biomass represented between 0.4 and 22% of the particulate organic carbon, which could reach 71% of the total photosynthetic plankton biomass at the marine station. In the Lena-Laptev system, picoplankton biomass varied between 6 and 56 gC l^–1 in surface waters. Picoplankton biomass decreased with depth, but picoeukaryotes were still observed in deep samples (20, 30 m) in the Laptev Sea, showing a considerable autotrophic activity in spite of low temperatures (0–1 °C). Although the widely dispersed estuary geographic distribution and their different estuarine characteristics, the data point out that these small organisms can also play an important role in the transfer of organic carbon from rivers to oceans and that flow cytometry can be able to detect these small cells in turbid systems.     

Asymmetric diffusion into the postsynaptic neuron: An extremely efficient mechanism for removing excess GABA from synaptic clefts on the Deiters' neurone plasma membrane

Microdissected Deiters' neuron plasma membranes have been used for studying the passage of GABA through the membrane both in the inward and outward direction. Working with 0.2 mM GABA in the compartment simulating the outside of the neurone and with 2.0 mM GABA in the one simulating the inside we found a net transport of GABA towards the inside. This mechanism does not require a Na⁺ ion gradient across the membrane. The nature of the transport process involved was studied by determining the rate of [³H]-GABA inward passage as a function of GABA concentration (1 nM–800 M) on the outward side of the membrane. The results have shown that until 50 M a diffusion process (v=D₁×C, where D₁=3.1×10^–11 1/m²×sec) is the sole mechanism involved. Above 50 M a second diffusion process is activated v=D₂×(C–50×10^–6), where D₂=2.8×10^–11 1/m²×sec. Taking in account both inward and outward directed diffusion, one can calculate 16 M as the equilibrium concentration of GABA on the outward side of the membrane. From a kinetic point of view, these diffusion processes are able to reduce GABA concentration in a synaptic cleft from 3 mM to 20 M within 3 sec. These diffusion systems are discussed as extremely efficient in removing the excess of released GABA in the synaptic cleft.     

New expanded bed adsorbents for the recovery of DNA

A 20–40 m pellicular high density (3.7 g cm^–3) expanded bed material has been designed for the capture of DNA and other large macromolecules. Anion exchangers fashioned out of these supports exhibited dramatically enhanced DNA binding capacities over commercial anion exchange adsorbents (6 mg ml^–1, c.f. 50 g ml^–1 at 10% breakthrough), due to a combination of small particle and fuzzy surface architecture created through the coupling of polyethylene imine chains.     

The uptake of copper ions by cell suspension cultures of Agave amaniensis,and its effect on the growth,amino acids and hecogenin content

Cell suspension cultures of Agave amaniensiswere able to grow in media containing 10 – 240 M copper ions, and could remove more than 67% copper ions from the media. The cells accumulated up to 106 mg g^–1 copper ions in the biomass. Copper ions at 240 M caused a decrease in growth index and packed cell volume of the cultures of 61.5 and 53.3%, respectively. The presence of copper ions caused the cell walls to thicken and to be more wrinkled. Certain amino acids were released in high concentration into the media. The hecogenin content in the biomass increased up to 157.9% at 20 M copper ions.     

Uptake of sewage derived nitrogen by<Emphasis Type="Italic"> Ulva rigida</Emphasis> (Chlorophyceae) in Bahía Nueva (Golfo Nuevo,Patagonia, Argentine)

Uptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3M of ammonium and between 0.77 and 6.21M of nitrate+nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: V_max = 591.2molg^–1h^–1, K _s=262.3M, nitrate+nitrite: V _max=12.9molg^–1h^–1, K _s=3.5M). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source.     

Clonal propagation of Callistemon by tissue culture techniques

Callus development in Callistemon viminalis was readily achieved when axillary buds derived from nodal tissue were placed in a medium containing macro- and micro-nutrients, sucrose (0.06 M), inositol (300 M), nicotinic acid (20 M), pyridoxine hydrochloride (3 M), thiamine hydrochloride (2 M), riboflavin (10 M), cytokinins (5 M) and auxins (0.1 M). The presence of benzylaminopurine (5 M) and p-chlorophenoxyacetic acid (0.1 M) promoted the most vigorous callus development and sprout formation. Rooting of nodal material was rare but occurred readily following the transference of sprouts developed on callus to a basal medium containing sucrose and salts. Root initiation was stimulated, however, by the presence of auxins. Chlorophenoxyacetic acid while stimulating root initiation repressed root growth. Indole butyric acid stimulated both root initiation and shoot growth at concentrations of 0.005 to 0.1 M. The treatment of choice for rooting and shoot growth was the addition of indole butyric acid at a concentration of 0.01 M.     

A lyophilized aqueous extract of<Emphasis Type="Italic"> Maytenus ilicifolia</Emphasis> leaves inhibits histamine-mediated acid secretion in isolated frog gastric mucosa

Lyophilized aqueous extract of Maytenus ilicifolia leaves (LAEMIL) is commonly used in Brazilian folk medicine in the treatment of dyspepsia as well as gastric ulcers. We have investigated the effect and the possible mechanism of action of the LAEMIL on acid secretion in isolated frog gastric mucosa incubated in an Ussing chamber. It was observed that LAEMIL (7–28 mg%) as well as cimetidine (125–4,000 M), a well-known histamine H₂ receptor antagonist, decreased basal acid secretion in a concentration-dependent manner. Similarly to cimetidine (190 M), LAEMIL (21 mg%) also inhibited gastric acid secretion induced by increasing concentrations of histamine (50–800 M). The EC₅₀ values for histamine alone and histamine in the presence of LAEMIL or cimetidine were 94.6 M (71.1–125.9 M), 244.9 M (209.4–286.4 M) and 142.2 M (23.6–855.0 M), respectively. LAEMIL, histamine and cimetidine were effective on acid secretion only when added to the serosal surface of the mucosa. Furthermore, simultaneous addition of LAEMIL and cimetidine at concentrations, per se, ineffective, caused a 16% reduction in the basal acid secretion [from 8.3±0.3 to 6.9±0.2 Eq g^–1 (15 min)^–1, n=4]. Although effects such as inhibition of histamine biosynthesis and/or histamine release can not be ruled out, our data suggest that LAEMIL, like cimetidine, reduces acid secretion in the isolated frog gastric mucosa by antagonising histamine H₂ receptors.Abbreviations LAEMIL Lyophilized aqueous extract of Maytenus ilicifolia leaves - Hist Histamine - Cim Cimetidine     

In vitro meristem cloning of Eucalyptus tereticornis Sm.

Rapid multiplication of axillary meristems and direct shoot development occurred from nodal explants of mature Eucalyptus tereticornis Sm. with 5.3 M NAA, 1.1 M IAA and 4.4 M BA in Murashige-Skoog medium. Repeated subcultures of the second generation shoot cultures into low cytokinin-auxin containing media (0.44–0.88 M BA+0.1 M NAA) yielded axillary microshoots in large numbers. Half-strength MS liquid medium with 4.9 M IBA, 5.5 M IAA and 5.3 M NAA for four days, half-strength semi-solid hormonefree MS medium with charcoal, and MS liquid medium without charcoal and hormones, in sequence, induced rooting of shoots in the dark. This system is suitable for the mass propagation of this difficult-to-root eucalypt.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - IBA -indole-3-butyric acid - 2-iP isopentyl adenine - Kn kinetin - MS Murashige-Skoog - NAA -naphthalene acetic acid - PVP polyvinylpyrrolidone     

Fine structure of abscission zones

Summary Electron micrographs of the zone of separation in flower pedicels of Lycopersicon esculentum and Nicotiana tabacum are presented with particular reference to the indentation of epidermal tissue in the abscission zone, subcellular organelles, and the cell wall. The indentation or groove which delineates the abscission zone extends some distance into the pedicel with branchings off the main groove. These branches are approximately 20 m in width while the main groove averages approximately 200 m in width. Invaginations of the plasmalemma are observed with considerable frequency. within these invaginations one observes a material of about the same density as the cell wall except that it is more fibrillar. Plasmodesmata are also observed, with considerable branching into middle lamellae of cells comprising the abscission zones. Microbodies with crystalloid cores appear with considerable frequency in cells of the abscission zone. The crystalloids appear to be cubical in shape and are composed of parallel sheets of osmiophilic material. The sheets average about 6 m in thickness and are spaced at 4 m intervals. The microbodies with crystalloid cores are observed to be characteristically of two size groupings. In tobacco the microbodies average 900 m and 1,500 m in profile. In tomato they average 300 m and 500 m. Chloroplasts contain a granular component which is membrane-enclosed. The component is large in comparison with the plastid in which it occurs, averaging 1.2–1.4 in diameter in chloroplasts ranging from 1.6 to 2.2 in diameter. The inner membrane of the chloroplast is highly invaginated, and DNA- and phytoferritin-like materials are observed within the plastids. Microtubules with an average diameter of 20 m are observed adjacent and parallel to the plasmalemma, primarily in the corners of the cells. Micrographs of other normally occurring cytoplasmic inclusions are also presented.     

Scanning electron-microscopic study on the three-dimensional structure of motor endplates of the slow (tonic) muscle fibers in the frog,Rana n. nigromaculata

Summary The three-dimensional organization of the motor endplates of the slow fibers of the rectus abdominis muscle in the Japanese meadow frog (Rana nigromaculata nigromaculata Hallowell) is visualized by use of a field-emission scanning electron microscope after removal of connective tissue components by HCl hydrolysis. Clusters of shallow oval depressions 1–3 m in diameter are seen in the postsynaptic membrane at intervals of about 150 m. On the surface of these depressions, a few low bulges of postsynaptic membrane are irregularly arranged. Terminal boutons, 1–3 m in diameter, occur along the length of nerve branches and terminals and fit into the shallow oval depressions of the postsynaptic membrane. The Schwann cells covering the terminal branches exhibit a simpler organization than those in twitch fibers.     

Developmental aspects of long-term callus culture ofVicia faba L.

Summary Vicia faba callus line (VFS 1), isolated from expiants of immature embryo, grew satisfactorily onMurashige andSkoog complete medium with 1.38 M 2,4-D, or with 0.92 M 2,4-D to which 1.0 M kinetin was added. It also grew well on the B 5 modified medium containing 2.3 M 2,4-D and 25.0 M kinetin. On the last of these media the cultures grew more uniformly and without necrosis. They also showed diminishing variation in polyploidy in favour of diploids and corresponding aneuploids (hypodiploids).After being cultured for nearly three years on MS containing 1.38 M 2,4-D, 8–33% of cultures of VFS 1 were able to regenerate roots when transferred to either MS half strength with 5.37 M NAA, or to a medium without 2,4-D, or else to media with the addition of kinetin only (in various concentrations).     

Fabrication of Stable Packed Capillary Reversed-Phase Columns for Protein Structural Analysis

Capillary column (320-m ID) liquid chromatography is an essential tool for the separation and concentration of low-picomole amounts of proteins and peptides for mass-spectrometric based structural analysis. We describe a detailed procedure for the fabrication of stable and efficient 50- to 180-m ID polyimide fused-silica columns. Columns were packed by conventional slurry packing with reversed-phase silica-based supports followed by column bed consolidation with acetonitrile and sonication. PVDF membrane or internal fused-silica particles were employed for column end-frit construction. The ability of these columns to withstand high back pressures (300–400 bar) enabled their use for rapid chromatography (>3400 cm/hr; i.e., 40 l/min for 200-m ID columns) and the loading of large sample volumes (up to 500 l). The accurate low flow rates (0.4–4.0 l/min) and precise gradient formation necessary to operate these columns were achieved by a simple modification of conventional HPLC systems [Moritz et al. (1992), J. Chromatogr. 599, 119–130]. Column performance was evaluated for ability to resolve low-fmol amounts of all components of a mixture of PTH-amino acids and to separate peptides for on-line LC/MS analysis of peptide mixtures derived from in situ digestion of 2-DE resolved protein spots.     

Adventitious shoot formation and plant regeneration from tissues of tomatillo (Physalis ixocarpa Brot.)

Cultured hypocotyl explants of tomatillo (Physalis ixocarpa Brot.), were evaluated with regard to their morphogenic responses to combinations of benzyladenine (BA, 0–5 M) with either naphthaleneacetic acid (NAA, 0–50 M) or 2,4-dichlorophenoxyacetic acid (2,4-D, 0–50 M). The induction of shoots or roots was dependent on the cytokinin/auxin combination.Hypocotyl explants failed to form shoots when they were grown on media containing either a cytokinin or an auxin alone. The highest frequency of shoot formation was observed on media containing 12.5–25 M BA and 5 M NAA. Likewise the highest frequency of root formation was observed on media supplemented with 1 M BA and 1 M NAA. Complete plants were regenerated and transferred to soil, where they reached maturity.     

Grazing by a dominant rotifer Conochilus unicornis Rousselet in a mountain lake: in situ measurements with synthetic microspheres

Grazing rates of zooplankton were analysed in the summer of 1999 in Yellow Belly Lake, an oligotrophic system in the Sawtooth Mountains of Idaho (U.S.A.). The colonial rotifer Conochilus unicornis was a dominant species in the epilimnion, with densities reaching 20 colonies l^–1 (ca. 400 ind. l^–1). Clearance rates were measured with an in situ Haney Grazing chamber and synthetic microspheres 5, 9 and 23m in diameter. At epilimnetic temperatures of around 14 °C, mean clearance rates for 5m particles ranged from 30 to 65 l ind.^–1 h ^–1. Clearance rates were 2–9 times higher on the 5m spheres than on the 9 m spheres, and C. unicornis almost never fed on the 23 m spheres. Grazing rates did not change over the diel cycle. Clearance rates declined more than 10-fold as temperatures declined from 14 °C in the epilimnion to 7 °C in the metalimnion. In the epilimnion, grazing by C. unicornis was more important than grazing by crustaceans in the community, at least on particles 9m. The results show the importance of grazing by rotifers in lakes, and the significance of spatial variations that influence grazing rates.     

Haematological effects of apholate in the red cotton bug,Dysdercus koenigii

Topical application of sterilizing doses of apholate causes haematological changes in the adults ofDysdercus koenigii. The normal males have less haemolymph (13–16 l) than females (18–37 l) for the first 120 hr of adult life. Apholate treatment significantly reduces the haemolymph volume of both the sexes. There are significantly more haemocytes in circulation in adult females than in males. The total haemocyte count shows an initial increase up to 48 hr, but later indicates a drastic reduction in the treated males and females. The plasmatocytes of the treated insects are found to reduce in numbers and the prohaemocytes become the predominant type, while in controls the plasmatocytes are the major type of haemocytes.

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Zusammenfassung Topicale Anwendung von sterilisierenden Dosen von Apholat verursacht hämatologische Änderungen bei den Adulten vonDysdercus koenigii. Die normalen Männchen haben weniger Hämolymphe (13–16 l) als Weibchen (18–37 l) in den ersten 120 h des adulten Lebens. Apholatbehandlung reduziert signifikant das Hämolymphvolumen beider Geschlechter. Es sind signifikant mehr Hämocyten im Umlauf bei adulten Weibchen als bei Männchen. Zählung der Gesamthämocyten zeigt bei behandelten Männchen und Weibchen ein anfängliches Anwachsen bis zu 48 h, später aber eine drastische Reduktion. Die Zahl der Plasmatocyten der behandelten Insekten erwies sich als abnehmend und die Prohämocyten werden der überwiegende Typ, während in der Kontrolle die Plasmatocyten der Haupttyp der Hämocyten sind.

     

Gangliosides Attenuate Ethanol-Induced Apoptosis in Rat Cerebellar Granule Neurons

Ethanol significantly enhances cell death of differentiated rat cerebellar granule neurons on culture in a serum-free medium containing a depolarizing concentration of KCl (25 mM), 5 M MK-801 (an NMDA receptor antagonist), and 20–200 mM ethanol for 1–4 days. Cell death augmented by ethanol was concentration- and time-dependent with neurons displaying hallmark apoptotic morphology and DNA fragmentation that correlated with the activation of cytosolic caspase-3. Inclusion of 5 M MK-801 or 100 M glycine in culture media did not alter rates of cell death indicating ethanol toxicity is mediated via an NMDA receptor-independent pathway. Preincubation with 50 M gangliosides GM1, GD1a, GD1b or GT1b for 2 h, or preincubation with 10 M LIGA₂₀ (a semisynthetic GM1 with N-dichloroacetylsphingosine) for 10 min, attenuated caspase-3 activity and ethanol-induced cell death. Data show native gangliosides and a synthetic derivative are potently neuroprotective in this model of ethanol toxicity, and potentially serve as useful probes to further unravel the mechanisms relevant to neuronal apoptosis.     

Development of high frequency multiple shoot formation in Persian clover (<Emphasis Type="Italic">Trifolium resupinatum</Emphasis> L.)

An efficient and reliable micropropagation system for Persian clover (Trifolium resupinatum L.) was developed using different explants and media. Node, hypocotyl and cotyledonary node explants were cultured on Murashige and Skoog (MS) medium supplemented with combinations of either 6-benzyladenine (BA) and indole-3-butyric acid (IBA) or BA, Kinetin (KIN) and IBA. Direct multiple shoots developed within 6weeks in all explants in most media tested. The best shoot multiplication capacity was obtained from cotyledonary node explants on MS medium containing 7.1M BA and 1M IBA or 14.1M BA and 1M IBA. Elongated shoots were rooted on either MS medium alone or combination with different concentrations of indole-3-butyric acid (IBA), indole-3-acetic acid (IAA) and -naphthaleneacetic acid (NAA). High rooting was achieved in half strength MS medium containing 8M IBA.