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.     

Specific Cd2+ uptake of encapsulated Aureobasidium pullulans biosorbents

Calcium alginate capsules containing Aureobasidium pullulans cells were prepared by an in-situ one-step method. The Cd²⁺uptakes of free biosorbent and capsule biosorbent were described well by the Freundlich isotherms. The Cd²⁺ uptake of capsule biosorbent was lower than that of free biosorbent with Cd^{2 +}at 100 mg l^–1. The total cadmium uptake of capsule biosorbent increased with the increase in encapsulated cell density and plateaued at a value of 23 g Cd²⁺/capsule with 150 g dry biosorbent l^–1 core volume of a capsule. The specific cadmium uptake of encapsulated biosorbent was 85% to that of free biosorbent at 35 g biosorbent dry weight l^–1 core volume of a capsule, decreased to 35% at 176 g biosorbent dry weight l^–1.     

Purification of theN-acetylglucosaminide α(1–3/4) fucosyltransferase of human milk

TheN-acetylglucosaminide (1–3/4)fucosyltransferase has been purified 1.8×10⁶-fold from human milk by ion-exchange chromatography, affinity chromatography of GDP-agarose and HPLC. The (1–3/4)fucosyltransferase behaves in gel filtration-HPLC as a molecule of M_r 98 000, and differs from the (1–3)fucosyltransferase which behaves like a molecule of about M_r 47 000. The enzyme is a glycoprotein, and the purified preparation appears in SDS polyacrylamide gel electrophoresis as a band of M_r 44 000. The results present the first purification of human milk (1–3/4)fucosyltransferase to apparent homogeneity, and suggest that the (1–3/4)- and (1–3)fucosyltransferases of human milk differ in their native molecular sizes, the former being a dimer of two subunits.     

Laboratory culture studies of Trichodesmium isolated from the Great Barrier Reef Lagoon, Australia

Cultures of Trichodesmium from the Northern and Southern Great Barrier Reef Lagoon (GBRL) have been established in enriched seawater and artificial seawater media. Some cultures have been maintained with active growth for over 6years. Actively growing cultures in an artificial seawater medium containing organic phosphorus (glycerophosphate) as the principal source of phosphorus have also been established. Key factors that contributed to the successful establishment of cultures were firstly, the seed samples were collected from depth, secondly, samples were thoroughly washed and thirdly, incubations were conducted under relatively low light intensities (PAR 40–50molquantam^–2s^–1). N₂ fixation rates of the cultured Trichodesmium were found to be similar to those measured in the GBRL. Specific growth rates of the cultures during the exponential growth phase in all enriched media were in the range 0.2–0.3day^–1 and growth during this phase was characterised by individual trichomes (filaments) or small aggregations of two to three trichomes. Characteristic bundle formation tended to occur following the exponential growth phase, which suggests that the bundle formation was induced by a lack of a necessary nutrient e.g. Fe. Results from some exploratory studies showed that filament-dominated cultures of Trichodesmium grew over a range of relatively low irradiances (PAR 5–120molquantam^–2s^–1) with the maximum growth occurring at 40–50molquantam^–2s^–1. These results suggest that filaments of the tested strain are well adapted for growth at depth in marine waters. Other studies showed that growth yields were dependent on salinity, with maximum growth occurring between 30 and 37psu. Also the cell yields decreased by an order of magnitude with the reduction of Fe additions from 450 to 45nM. No active growth was observed with the 4.5nM Fe addition.     

Sialyltransferases of developing rat brain

The activity of four different sialyltransferases acting on N- or O-linked chains of glycoproteins was studied in brains of 19 days-old embryos, 1 day-old newborns and adult rats. By using asialofetuin, fetuin andN-acetyllactosamine as acceptors, it has been possible to measure independently the following enzyme activities: CMP-NeuAc:Gal1-3GalNac (2–3)-sialyltransferase (EC 2.4.99.4), CMP-NeuAc:Gal1-4GlcNAc (2–3)-sialyltransferase (EC 2.4.99.6), CMP-NeuAc:Gal1-4GlcNAc (2–6)-sialyltransferase (EC 2.4.99.1) and CMP-NeuAc:NeuAc2-3Gal1-3GalNac (2–6)-sialyltransferase (EC 2.4.99.7). The specific activity of the first three enzymes which act on asialylated acceptors showed a 2.6-fold decrease in a parallel manner after ontogenic development, while the activity of NeuAc2-3Gal1-3GalNac (2–6)-sialyltransferase was four times lower in adult than in embryonic brain, showing a stronger dependence on ontogenic development. Despite the higher level of sialyltransferases able to act on glycoproteins, in fetal brain these glycoproteins do not contain a higher amount of sialic acid.Abbreviations HPLC high performance liquid chromatography - N-CAM neural cell adhesion molecule     

New ganglioside analogs that inhibit influenze virus sialidase

Synthetic thioglycoside-analogs of gangliosides such as Neu5Ac)2-S-6)Glc-(1-1)Ceramide (1) and the GM3 analog Neu5Ac(2-S-6)Gal-(1–4)Glc(1-1)Ceramide (2), competitively inhibited GM3 hydrolysis by the sialidase of different subtypes of human and animal influenza viruses with an apparent K_i value of 2.8×10^–6 and 1.5×10^–5 M, respectively. The inhibitory activity of the ganglioside GM4 analog [Neu5Ac-(2-S-6)Gal-(1-1)Ceramide (3)], in which the glucose of 1 was substituted by galactose, was lower than that of 1 (K_i =1.0×10^–4 M). The thioglycoside-analogs (1, 2, 3) of the gangliosides were nonhydrolyzable substrates for influenza virus sialidase. The inhibitory activity of 1 to bacterial sialidases fromClostridium perfringens andArthrobacter ureafaciens was considerably lower than that to influenza virus sialidase, indicating that the structure of the active site in bacterial and influenza virus sialidase may be different and the analogs may be useful to determine the orientation of the substrate to the active site of sialidases, especially of influenza viruses.Abbreviations Cer ceramide - GM3 Neu5Ac(2–3)Gal(1–4)Glc(1-1)Cer - GM4 Neu5Ac(2–3)Gal(1-1)Cer Gangliosides were abbreviated according to Svennerholm [1] and the recommendation of the IUPAC-IUB Commission on Biochemical Nomenclature [2].     

The Use of the [13C]/[12C] Ratio for the Assay of the Microbial Oxidation of Hydrocarbons

The study deals with a comparative analysis of the relative abundances of the carbon isotopes ¹²C and ¹³C in the metabolites and biomass of the Burkholderia sp. BS3702 and Pseudomonas putida BS202-p strains capable of utilizing aliphatic (n-hexadecane) and aromatic (naphthalene) hydrocarbons as sources of carbon and energy. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of Burkholderia sp. BS3702 on n-hexadecane (¹³C = –44.6 ± 0.2) were characterized by the values of ¹³C_{CO 2} = –50.2 ± 0.4, ¹³C_biom = –46.6 ± 0.4, and ¹³C_exo = –41.5 ± 0.4, respectively. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of the same bacterial strain on naphthalene (¹³C = –21 ± 0.4) were characterized by the isotope effects ¹³C_{CO 2} = –24.1 ± 0.4, ¹³C_biom = –19.2 ± 0.4, and ¹³C_exo = –19.1 ± 0.4, respectively. The possibility of using the isotope composition of metabolic carbon dioxide for the rapid monitoring of the microbial degradation of petroleum hydrocarbons in the environment is discussed.     

Amino acid deletions in loop C of the chlorophyll a-binding protein CP47 alter the chloride requirement and/or prevent the assembly of photosystem II

The chlorophyll a-binding protein CP47 directs excitation energy to the reaction center of photosystem II (PSII) during oxygenic photosynthesis and has additional structural and functional roles associated with the PSII water-oxidizing complex. Oligonucleotide-directed mutagenesis was employed to study loop C of CP47 (approximately Trp-162 to Gly-197) which faces the thylakoid lumen. Five short amino acid deletion strains, (S169–P171), (Y172–G176), (G176–P180), (E184–A188) and (F190–N194), were created that span this domain. The deletion between Gly-176 and Pro-180, located around the middle of loop C, produced an obligate photoheterotroph that could not assemble functional PSII centers. The deletions in mutants (S169–P171) and (Y172–G176) reduced PSII levels to 20% of the control and thus impaired photoautotrophic growth. In contrast, mutants (E184-A188) and (F190–N194) were photoautotrophic even though the number of photosystems was decreased by 50%. All PSII complexes assembled in the deletion strains had an increased susceptibility to photoinactivation and deletion of Glu-184 to Ala-188 prevented photoautotrophic growth under chloride-limiting conditions. Furthermore, the removal of the extrinsic PSII-O, PSII-U and PSII-V proteins from mutants (E184–A188) and (F190–N194) reduced the rates of oxygen evolution and, in the strains lacking either the PSII-O or PSII-V proteins, also increased the photoautotrophic doubling times. These effects were greater in mutant (E184–A188) than in mutant (F190–N194) and the order of importance for the removal of the extrinsic proteins was found to be PSII-V PSII-O > PSII-U.     

Use of15N/14N rations to evaluate the food source of the mysid,Neomysis intermedia Czerniawsky,in a eutrophic lake in Japan

The stable isotope ratios of nitrogen were measured in the mysid,Neomysis intermedia, together with various biogenic materials in a eutrophic lake, Lake Kasumigaura, in Japan throughout a year of 1984/85. The mysid, particulate organic matter (POM, mostly phytoplankton), and zooplankton showed a clear seasonal change in ¹⁵N with high values in spring and fall, but the surface bottom mud did not. A year to year variation as well as seasonal change in ¹⁵N was found in the mysid. The annual averages of ¹⁵N of each material collected in 1984/85 are as follows: surface bottom mud, 6.3 (range: 5.7–6.9); POM, 7.9 (5.8–11.8); large sized mysid, 11.6 (7.7–14.3); zooplankton, 12.5 (10.0–16.4); prawn, 13.2 (9.9–15.4); goby, 15.1 (13.8–16.7). The degree of¹⁵N enrichment by the mysid was determined as 3.2 by the laboratory rearing experiments. The apparent parallel relationship between the POM and the mysid in the temporal patterns of ¹⁵N with about 3 difference suggests the POM (mostly phytoplankton) as a possible food source ofN. intermedia in this lake through the year.     

Benzyl-N-acetyl-α-d-galactosaminide inhibits the sialylation and the secretion of mucins by a mucin secreting HT-29 cell subpopulation

We have analysed the mucins synthesized by the HT-29 MTX cell subpopulation, derived from the HT-29 human colon carcinoma cells through a selective pressure with methotrexate (Lesuffleuret al., 1990,Cancer Res 50: 6334–43), in the presence of benzyl-N-acetyl--galactosaminide (GalNAc-O-benzyl), which is a potential competitive inhibitor of the 1,3-galactosyltransferase that synthesizes the T-antigen. The main observation was a 13-fold decrease in the sialic acid content of mucins after 24 h of exposure to 5mm GalNAc-O-benzyl. This effect was accompanied by an increased reactivity of these mucins to peanut lectin, testifying to the higher amount of T-antigen. The second observation was a decrease in the secretion of the mucins by GalNAc-O-benzyl treated cells. The decrease in mucin sialyation was achieved through thein situ -galactosylation of GalNAc-O-benzyl into Gal1–3GalNAc-O-benzyl, which acts as a competitive substrate of Gal1–3GalNAc 2,3-sialyltransferase, as shown by the intracellular accumulation of NeuAc2–3Gal1–3GalNAc-O-benzyl in treated cells.Abbreviations BSM bovine submaxillary mucin - MTX methotrexate - PBS sodium phosphate 10mm, NaCl 0.15m, pH 7.4 buffer - pNp p-nitrophenol - TBS Tris/HCl 10mm, NaCl 0.15m, pH 7.4 buffer Enzymes: CMP-NeuAc: Gal1–3/4GlcNAc 2,3-sialyltransferase, ST3(N), EC 2.4.99.6; CMP-NeuAc: Gal1–4GlcNAc 2,6-sialyltransferase, ST6(N), EC 2.4.99.1; CMP-NeuAc: Gal1–3GalNAc 2,3-sialyltransferase, ST3(O), EC 2.4.99.4; CMP-NeuAc: R-GalNAc1-O-Ser 2,6-sialyltransferase, ST6(O)-I, EC 2.4.99.3; CMP-NeuAc: NeuAc2–3Gal1–3GalNAc 2,6-sialyltransferase, ST6(O)-II, EC 2.4.99.7; UDP-GlcNAc: Gal1–3GalNAc-R·(GlcNAc to GalNAc) 1,6-N-acetylglucosaminyltransferase, EC 2.4.1.102; UDP-GlcNAc: GalNAc-R 1,3-N-acetylglucosaminyltransferase, EC 2.4.1.147; UDP-Gal: GalNAc-R 1,3-galactosyltransferase, EC 2.4.1.122.     

Arsenic concentrations in water and fish from Chautauqua Lake,New York

Synopsis Arsenic persists in Chautauqua Lake, New York waters 13 years after cessation of herbicide (sodium arsenite) application and continues to cycle within the lake. Arsenic concentrations in lake water ranged from 22.4–114.81 g l^–1, = 49.0 ag l^–1. Well water samples generally contained less than 10 g l^–1 arsenic. Arsenic concentrations in lake water exceeded U.S. Public Health Service recommended maximum concentrations (10 g l^–1) and many samples exceeded the maximum permissible limit (50 g l^–1). Fish accumulated arsenic from water but did not magnify it. Fish to water arsenic ratios ranged from 0.4–41.6. Black crappie (Pomoxis nigromaculatus) contained the highest arsenic concentrations (0.14–2.04 g g^–1 ), X = 0.7 g g^–1) while perch (Perca flavescens), muskellunge (Esox masquinongy) and largemouth bass (Micropterus salmoides) contained the lowest concentrations (0.02–0.13 g g^–1). Arsenic concentrations in fish do not appear to pose a health hazard for human consumers.     

Elucidation of Structure of Lipid A from the Marine Gram-Negative Bacterium Pseudoalteromonas haloplanktis ATCC 14393T

The chemical structure of lipid A, from the marine -proteobacterium Pseudoalteromonas haloplanktis 14393, a main product of lipopolysaccharide hydrolysis (1% AcOH), was determined using chemical methods and NMR spectroscopy. The lipid A was shown to be -1,6-glucosaminobiose 1,4-diphosphate acylated with two (R)-3-hydroxyalkanoic acid residues at C3 and C3 and amidated with one (R)-3-hydroxydodecanoyl and one (R)-3-dodecanoyloxydodecanoyl residue at N2 and N2, respectively.     

Larvae of <Emphasis Type="Italic">Arnoglossus elongatus</Emphasis> (Pleuronectiformes: Bothidae) from northwestern Australia

Eleven postflexion larvae (9.1–23.9mm standard length: SL) of a bothid, Arnoglossus elongatus, from northwestern Australian waters were described. These specimens were characterized by vertebral numbers of 11–12+32–34=43–45, slender body, remarkably elongated second dorsal fin ray, and presence of melanophores on and slightly above midlateral line of body, plus on dorsal wall of abdominal cavity and air bladder (specimens >12.6mm SL), proximally on caudal fin rays (>16.5mm SL), and on pterygiophore zones of dorsal fin and anal fin (>23.8mm SL).     

Lysine Dendrimers and Their Starburst Polymer Derivatives: Possible Application for DNA Compaction and in vitro Delivery of Genetic Constructs

We attempted to find some compounds for the effective delivery of gene constructs into cells and obtained two trispherical dendrimers on the basis of lysine, (Lys)₈-(,-Lys)₄-(,-Lys)₂-(,-Lys)-Ala-NH₂ (D1) and ((Lys)₈-(,-Lys)₄-(,-Lys)₂-,-Lys)-Ala-[Lys(Plm)]₂-Ala-NH₂ (D2), as well as the starburst polymeric derivatives of D1, (pVIm) ₈ -D1 and (pLys) _n -D1, containing poly(N-vinylimidazole) and polylysine chains single-point bound to the dendrimer amino groups. The conditions of dendrimer–plasmid DNA complex formation were studied. The intracellular localization of these complexes and the expression of gene constructs delivered with their help were analyzed in transfection experiments on the HeLa cell cultures of human epithelial carcinoma and on mouse C2C12 myoblasts. It was found that the chemical structure of dendrimer D1 and its derivatives significantly affected the structure and properties of complex.     

The nutritional status of Picea abies (L.) Karst. across Europe,and implications for ‘forest decline’

Summary During the summer of 1986, three year-classes of foliage were sampled from approximately 30-year-old Norway spruce [Picea abies (L.) Karst.] trees at 12 sites from S. W. Germany to N. Scotland. At sites in Germany, where trees were showing symptoms of decline, samples were taken from trees with good crown condition and poor crown conditon. The distinction between good and poor was made on the basis of international protocols for defining crown density and foliar discoloration. There was a wide range in nutrient content (percent dry weight) in apparently healthy trees. Current year foliage had ranges of mean values per site: S(0.07–0.13%), N(0.9–1.4%), K(0.5–0.9%), Ca(0.2–0.7%), and Mg (0.05–0.1%). Ranges were greater for 2-year-old foliage: S(0.09–0.18%), N(1.0–1.8%), K(0.4–0.7%), Ca(0.2–1.4%), and Mg(0.03–0.09%). At sites with trees having poor crown condition, there were significantly smaller concentrations of Mg and Ca, and larger concentrations of K in 2-year-old foliage from poor trees, compared with adjacent good trees. Ratios of nutrient content were more significantly related to crown condition within sites than individual nutrients, especially in older needles. Poor crowns were associated with larger ratios of NMg, KMg, SMg, KCa and smaller ratios of SK and NK. A risk index is defined for trees showing no visible decline symptoms, based upon nutrient content and nutrient ratios, which may be useful in identifying sites liable to experience deterioration in crown condition.With the exception of one German site, where few poor trees were observed, the index increases from Scottish sites to English sites to Dutch sites to German sites. The index is empirical, and not necessarily related to potential effects of air pollution. The time dependence of foliar nutrient content may also be useful in diagnosis. At sites with trees having poor crown condition, even apparently healthy trees showed a lack of increase in calcium content with needle age, decreases in nitrogen content and very large decreases in magnesium content with needle age. The results show the importance of sampling several year classes of foliage from Norway spruce trees in determining the nutrient status of the tree.     

Diel Movements of Bat Rays, Myliobatis californica, in Tomales Bay, California: Evidence for Behavioral Thermoregulation?

We used ultrasonic telemetry to examine movement patterns of 11 bat rays, Myliobatis californica, in Tomales Bay, California. Tomales Bay is long (20km) and narrow (1.4km), and is hydrographically separated into outer and inner bay regions. The outer bay (the outermost 8km) is characterized by oceanic conditions while the shallow inner bay (the innermost 12km) features wide seasonal temperature shifts. Five rays were tracked monthly from October 1990 to November 1991 and six rays (four of which carried temperature-sensing transmitters) were tracked daily from 30 June to 16 July 1992. Mean bat ray movement rate was 8.84mmin^–1 (range 4.49 to 13.40mmin^–1) and was not significantly affected by size (p=0.592), tidal stage (p=0.610), or time of day (p=0.327). Movement direction was unrelated to tidal stage (p=0.472) but showed a highly significant diel pattern (p<0.001). From 2:50–14:50h, rays moved toward the warmer and shallower inner bay, while from 14:50–2:50h they moved toward the cooler and deeper outer bay. These telemetry data, along with known bat ray foraging patterns and respiratory temperature-sensitivity, argue for behavioral thermoregulation as the primary influence on this movement pattern.     

Synthesis of β(1–2)glucan in Rhizobium loti

Fast growing strains of Rhizobium loti isolated from nodules of Lotus tenuis of the flooding Pampas of Argentina produced cellular (1–2)glucans having a higher degree of polymerization and more anionic substituents than (1–2)glucans accumulated by Agrobacterium tumefaciens cells. Inner membranes of R. loti contained a 235 kDa (1–2)glucan intermediate protein indistinguishable by polyacrylamide gel electrophoresis from the intermediate protein present in A. tumefaciens inner membranes. Incubation of inner membrannes of R. loti with UDP-Gle led to the formation of neutral (1–2)glucans with a higher degree of polymerization than glucans formed by A. tumefaciens inner membranes.Introduction in R. loti strains of plasmid pCD523 containing A. tumefaciens chvA and chvB virulence regions yielded strains that accumulated 4 times more cellular (1–2)glucans than wild type cells. This glucan was, regarding anionic substitution and degree of polymerization, indistinguishable from A. tumefaciens (1–2)glucans. Furthermore inner membranes of these R. loti exoconjugant cells contained higher levels of the 235 kDa (1–2)glucan intermediate protein and formed in vitro 8 times more neutral (1–2)glucan with a degree of polymerization corresponding to A. tumefaciens (1–2)glucan than inner membranes isolated from wild type cells.It was concluded that A. tumefaciens chvB gene is expressed in R. loti and determined the degree of polymerization of (1–2)glucan.Abbreviations Nod⁺ effective nodulation - Vir⁺ virulent - Vir^- avirulent - Trp^r trimethoprim resistence - Tc^r tetracycline resistence - TCA trichloroacetic acid - PMSF phenyl methyl sulfonyl fluoride     

Preferred conformations and dynamics of five core structures of mucin typeO-glycans determined by NMR spectroscopy and force field calculations

Glycosyltransferases acting onO-glycans have been shown to exhibit distinct specificity for the carbohydrate and the peptide moiety of their substrates. As an approach to study the 3-dimensional interactions between enzymes andO-glycan substrates, we determined the preferred conformations of five oligosaccharide-core structures of mucin type glycoproteins by NMR spectroscopy and by static and dynamic force field calculations. Seven oligosaccharides, representing five basic core structures, were investigated: Gal(1–3)GalNAcBzl (1, core 1), GlcNAc(1–6)[Gal(1–3)]GalNAcBzl (2, core 2), GlcNAc(1–3)GalNacBzl (3, core 3), GlcNAc(1–6)[GlcNAc(1–3)]GalNAcBzl (4, core 4), GlcNAc(1–6)GalNAcBzl (5, core 6), the elongated core 2, Gal(1–4)GlcNAc(1–6)[Gal(1–3)]GalNAcpNp (6) and GalNAc-Bzl (7). The dynamic behaviour of the molecules was studied by Metropolis Monte Carlo (MMC) simulations. Experimental coupling constants, chemical shift changes, and NOEs were compared with results from static energy minimizations and dynamic MMC simulations and show a good agreement. MMC simulations show that the (1–6) linkage is much more flexible than the (1–3) or the (1–4) linkages. The preferred conformations of the disaccharides (1) and (3) show only slight differences due to the additionalN-acetyl group in (3). The conformational equilibrium of (1–3) glycosidic bonds of1 and3 was not affected by attaching a (1–6) linked GlcNAc unit to the GalNAc residue in2 and4. However, experimental and theoretical data show that the (1–6) linkages of the trisaccharides2 and4, which carry an additional (1–3) linked glycosyl residue, change their preferred conformations when compared with (5). The 6-branch also shows significant interactions with the benzyl aglycon altering the preferred conformation of the hydroxymethyl group of the GalNAc to a higher proportion of the gt conformer. The (1–6) linkage of2, 4, and6 can have two different families of conformations of which the lower energy state is populated only to about 20% of the time whereas the other state with a relative enthalpy of 4 kcal mol^–1 is populated to 80%. This fact demonstrates that the two conformational states have different entropy contents. Entropy is implicitly included in MMC simulations but cannot be derived from energy minimizations.Abbreviations Bzl benzyl - COSY correlation spectroscopy - Gal d-galactose - GalNAc N-acetyl-d-galactosamine - GalNAc-ol N-acetylgalactosaminitol - GlcNAc N-acetyl-d-glucosamine - HOHAHA homonuclear Hartmann-Hahn-spectroscopy - MMC metropolis Monte Carlo - NOE nuclear Overhauser enhancement - pNp p-nitrophenyl - ROESY rotating frame Overhauser enhancement spectroscopy - TOCSY totally correlated spectroscopy     

Patterns of direct and indirect embryogenesis from mesophyll protoplasts of Medicago sativa

Clones of three cultivars of Medicago sativa (Rambler, Regen S and Rangelander) were used as sources of mesophyll protoplasts. Although all three clones readily produced protoplasts, the subsequent development patterns in culture varied greatly among genotypes, with protoplasts from Regen S and Rambler forming calli which could be induced to form embryos, and protoplasts from Rangelander undergoing direct embryogenesis. Protoplasts of Regen S exhibited high rates of division while those of Rangelander tended to aggregate with only a few cells per aggregate surviving. The surviving cells gave rise to proembryos within the aggregates; these proembryos developed into differentiated embryos after 5–7 weeks of culture. Based on the initial protoplast population, the efficiency of embryo formation averaged 0.13% and ranged from 0.001–0.4%. Observations during the early stages of culture indicated that cell aggregation was a prerequisite for direct embryogenesis.     

Ecotoxicity of lead to the zebra musselDreissena Polymorpha,Pallas

The effect of lead on the filtration rate of the zebra musselDreissena polymorpha was investigated, together with the accumulation of Pb in the soft tissues of the mussels. The NOEC-filtration was 116 g.l^–1 (0,56 mol.l^–1) and the EC₅₀-filtration was 370 g.l^–1 (1.79 mol.l^–1). The NOEC-accumulation was the concentration found in the control water (1.4g.l^–1). These experiments show that the EC₅₀-filtration for Pb is similar to that for Cd, higher than that for Cu and lower than that for Zn. The water quality criteria for lead allow 25 g Pb.l^–1 in surface water. This will not cause short-term effects. Long-term effects may, however, occur, since an accumulation of Pb as low as 16 g.l^–1 was recorded in this study.