Ganglioside lactones:1H-NMR determination of the inner ester position of GD1b-ganglioside lactone naturally occurring in human brain or produced by chemical synthesis

The complete definition of the chemical structure of G_D1b-ganglioside (G_D1b) lactone isolated from human brain has been given by means of spectrometric and spectroscopic analyses. G_D1h lactone contains a single ester linkage involving the external sialic acid carboxyl group and the C-9 hydroxyl group of the internal sialic acid unit. A synthetic lactone of G_D1b prepared treating G_D1b with glacial acetic acid characterized in the same way showed an identical chemical structure.Abbreviations: Ganglioside nomenclature is according to Svennerholm [16] and the IUPAC-IUB Recommendations [17] G_M1 G_M1-ganglioside, II³NeuAc-GgOse₄Cer, Gal1-3GalNac1-4[NeuAc2-3]Gal1-4Glc1-1Cer - G_D1b G_D1b-ganglioside, II³(NeuAc)₂GgOse₄Cer, Gal1-3GalNAc1-4[NeuAc2-8NeuAc2-3]Gal1-4Glc1-1Cer - G_D1b lactone G_D1b-L, Gal1-3GalNAc1-4[NeuAc(1-9)2-8NeuAc2-3]Gal1-4Glc1-1Cer - Cer ceramide - FAB-MS fast atom bombardment-mass spectrometry - ¹H-NMR proteon nuclear magnetic resonance - 1D-NMR one dimensional NMR - 2D-COSY two dimensional correlated spectroscopy - DMSO-d₆ deuterated dimethylsulfoxide     

Effect of dissolved inorganic carbon on oxygen evolution and uptake by Chlamydomonas reinhardtii suspensions adapted to ambient and CO2-enriched air

Mass spectrometric measurements of ¹⁶O₂ and ¹⁸O₂ isotopes were used to compare the rates of gross O₂ evolution (E₀), O₂ uptake (U₀) and net O₂ evolution (NET) in relation to different concentrations of dissolved inorganic carbon (DIC) by Chlamydomonas reinhardtii cells grown in air (air-grown), in air enriched with 5% CO₂ (CO₂-grown) and by cells grown in 5% CO₂ and then adapted to air for 6h (air-adapted).At a photon fluence rate (PFR) saturating for photosynthesis (700 mol photons m^-2 s^-1), pH=7.0 and 28°C, U₀ equalled E₀ at the DIC compensation point which was 10M DIC for CO₂-grown and zero for air-grown cells. Both E₀ and U₀ were strongly dependent on DIC and reached DIC saturation at 480 M and 70 M for CO₂-grown and air-grown algae respectively. U₀ increased from DIC compensation to DIC saturation. The U₀ values were about 40 (CO₂-grown), 165 (air-adapted) and 60 mol O₂ mg Chl^-1 h^-1 (air-grown). Above DIC compensation the U₀/E₀ ratios of air-adapted and air-grown algae were always higher than those of CO₂-grown cells. These differences in O₂ exchange between CO₂- and air-grown algae seem to be inducable since air-adapted algae respond similarly to air-grown cells.For all algae, the rates of dark respiratory O₂ uptake measured 5 min after darkening were considerably lower than the rates of O₂ uptake just before darkening. The contribution of dark respiration, photorespiration and the Mehler reaction to U₀ is discussed and the energy requirement of the inducable CO₂/HCO₃ ^- concentrating mechanism present in air-adapted and air-grown C. reinhardtii cells is considered.Abbreviations DIC dissolved inorganic carbon - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - E₀ rate of photosynthetic gross O₂ evolution - PCO photosynthetic carbon oxidation - PFR photon fluence rate - PS I photosystem I - PS II photosystem II - U₀ rate of O₂ uptake in the light - MS mass spectrometer     

A light-enhanced metabolism of sulfite in cells of Cucumis sativus L. cotyledons

The effects of light and several photosynthetic inhibitors on the rate of sulfite metabolism in cells obtained from Cucumis sativus L. cotyledons was studied. The cells were treated with 200 M Na₂SO₃ and the disappearance of sulfite was monitored using either dithiobisnitrobenzoic acid or fuchsin. The rate of sulfite disappearance in light was double the dark rate. Disalicylidene propanediamine at 1 mM increased this light-enhanced metabolism approx. 50%; neither 1 M 3,4-dichlorophenyl-N,N-dimethylurea nor 0.1 mM cyanazine, which completely inhibited CO₂-dependent oxygen evolution, affected the rate of sulfite metabolism. Addition of 200 M Na₂SO₃ to the cells partially inhibited ¹⁴CO₂ fixation. The rate of sulfite consumption by the cells did not affect this inhibition. We conclude that light-dependent sulfite metabolism is cucumber cells may utilize reduced ferredoxin generated as a result of photosynthetic electron transport. An injurious interaction between CO₂ fixation and sulfite appears to occur independently of the sulfite-metabolism process.Abbreviations DCMU 3,4-dichlorophenyl-N,N-dimethylurea - DSPD disalicylidene propanediamine - DTNB 5,5-dithiobis-(2-nitrobenzoic acid)     

Different Ks values for hydrogen of methanogenic bacteria and sulfate reducing bacteria: An explanation for the apparent inhibition of methanogenesis by sulfate

Desulfovibrio vulgaris (Marburg) and Methanobrevibacter arboriphilus (AZ) are anaerobic sewage sludge bacteria which grow on H₂ plus sulfate and H₂ plus CO₂ as sole energy sources, respectively. Their apparent K_s values for H₂ were determined and found to be approximately 1 M for the sulfate reducing bacterium and 6 M for the methanogenic bacterium. In mixed cell suspensions of the two bacteria (adjusted to equal V _max) the rate of H₂ consumption by D. vulgaris was five times that of M. arboriphilus, when the hydrogen supply was rate limiting. The apparent inhibition of methanogenesis was of the same order as expected from the different K_s values for H₂. Difference in substrate affinities can thus account for the inhibition of methanogenesis from H₂ and CO₂ in sulfate rich environments, where the H₂ concentration is well below 5 M.     

Photosynthesis and apparent affinity for dissolved inorganic carbon by cells and chloroplasts of Chlamydomonas reinhardtii grown at high and low CO2 concentrations

Chloroplasts with high rates of photosynthetic O₂ evolution (up to 120 mol O₂· (mg Chl)^-1·h^-1 compared with 130 mol O₂· (mg Chl)^-1·h^-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO₂ concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O₂ uptake could be observed in the dark by high- and low-CO₂ adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m^-2·s^-1 for high- and low-CO₂ adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO₂ adapted chloroplasts, whereas high-CO₂ adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O₂ evolution (K_m(DIC)) was 31.1 and 156 M DIC for low- and high-CO₂ adapted chloroplasts, respectively. These results demonstrate that the CO₂ concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl chlorophyll - DIC dissolved inorganic carbon - K_m(DIC) coneentration of dissolved inorganic carbon required for the rate of half maximal net O₂ evolution - PFR photon fluence rate - SPGM silicasol-PVP-gradient medium     

Growth,acetylene reduction activity and localization of nitrogenase in relation to vesicle formation in Frankia strains Cc1.17 and Cp1.2

A comparative study was conducted on the effect of NH₄Cl on growth, vesicle formation and formation of nitrogenase of Frankia strains Cc1.17 and Cp1.2, derived from root nodules of Colletia cruciata and Comptonia peregrina, respectively. On a medium without combined nitrogen (P-N), both strains formed spherical cells, called vesicles, like many other Frankia strains. Data are presented on the number of vesicles per mg protein, after cultivation in media with sodium propionate as C-source without combined nitrogen (P-N) or with 0.2 g NH₄Cl/l (P+N). Strain Cp1.2 as may other Frankia strains, showed on P+N medium a very strong reduction of vesicle formation of 99% relative to the number of vesicles formed on P-N medium, after 11 days growth. However, in strain Cc11.17 this reduction was only 70%. The occurence of relatively large numbers of vesicles in P+N media has not yet been reported for other Frankia strains. No acetylene reduction activity was found in NH ₄ ⁺ -grown cells. The regulation of induction of nitrogenase in Frankia by NH₄Cl was tested by immuno-gelectrophoresis using antisera against nitrogenase of Rhizobium leguminosarum PRE. The component I of the enzyme showed crossreactivity while the component II had only a weak crossreaction. The experiments indicated that no nitrogenase was detectable in the NH ₄ ⁺ -grown cells. For the localization of nitrogenase, relative amounts of the enzyme were compared in whole cells and vesicle-enriched fractions. Western blots showed a significant enrichment of nitrogenase in the vesicle fractions, which indicated that most of the nitrogenase was localized in the vesicle.     

Electrical characteristics of stomatal guard cells: The ionic basis of the membrane potential and the consequence of potassium chlorides leakage from microelectrodes

The membrane electrical characteristics of stomatal guard cells in epidermal strips from Vicia faba L. and Commelina communis L. were explored using conventional electrophysiological methods, but with double-barrelled microelectrodes containing dilute electrolyte solutions. When electrodes were filled with the customary 1–3 M KCl solutions, membrane potentials and resistances were low, typically decaying over 2–5 min to near-30 mV and <0.2 k·cm² in cells bathed in 0.1 mM KCl and 1 mM Ca²⁺, pH 7.4. By contrast, cells impaled with electrodes containing 50 or 200 mM K⁺-acetate gave values of-182±7 mV and 16±2 k·cm² (input resistances 0.8–3.1 G, n=54). Potentials as high as (-) 282 mV (inside negative) were recorded, and impalement were held for up to 2 h without appreciable decline in either membrane parameter. Comparison of results obtained with several electrolytes indicated that Cl^- leakage from the microelectrode was primarily responsible for the decline in potential and resistance recorded with the molar KCl electrolytes. Guard cells loaded with salt from the electrodes also acquired marked potential and conductance responses to external Ca²⁺, which are tentatively ascribed to a K⁺ conductance (channel) at the guard cell plasma membrane.Measurements using dilute K⁺-acetate-filled electrodes revealed, in the guard cells, electrical properties common to plant and fungal cell membranes. The cells showed a high selectivity for K⁺ over Na⁺ (permeability ratio P_Na/P_K=0.006) and a near-Nernstian potential response to external pH over the range 4.5–7.4 (apparent P_H/P_K=500–600). Little response to external Ca²⁺ was observed, and the cells were virtually insensitive to CO₂. These results are discussed in the context of primary, charge-carrying transport at the guard cell plasma membrane, and with reference to possible mechanisms for K⁺ transport during stomatal movements. They discount previous notions of Ca²⁺-and CO₂-mediated transport control. It is argued, also, that passive (diffusional) mechanisms are unlikely to contribute to K⁺ uptake during stomatal opening, despite membrane potentials which, under certain, well-defined conditions, lie negative of the potassium equilibrium potential likely prevailing.Abbreviations and symbols EGTA ethylene glycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - Mes 2-(N-morpholino) propanesulfornic acid - E equilibrium potential - G_m membrane conductance - R_in input resistance - V_m membrane potential     

Evaluation of the role of State transitions in determining the efficiency of light utilisation for CO2 assimilation in leaves

Wheat leaves were exposed to light treatments that excite preferentially Photosystem I (PS I) or Photosystem II (PS II) and induce State 1 or State 2, respectively. Simultaneous measurements of CO₂ assimilation, chlorophyll fluorescence and absorbance at 820 nm were used to estimate the quantum efficiencies of CO₂ assimilation and PS II and PS I photochemistry during State transitions. State transitions were found to be associated with changes in the efficiency with which an absorbed photon is transferred to an open PS II reaction centre, but did not correlate with changes in the quantum efficiencies of PS II photochemistry or CO₂ assimilation. Studies of the phosphorylation status of the light harvesting chlorophyll protein complex associated with PS II (LHC II) in wheat leaves and using chlorina mutants of barley which are deficient in this complex demonstrate that the changes in the effective antennae size of Photosystem II occurring during State transitions require LHC II and correlate with the phosphorylation status of LHC II. However, such correlations were not found in maize leaves. It is concluded that State transitions in C₃ leaves are associated with phosphorylation-induced modifications of the PS II antennae, but these changes do not serve to optimise the use of light absorbed by the leaf for CO₂ assimilation.Abbreviations Fm, Fo, Fv maximal, minimal and variable fluorescence yields - Fm, Fv maximal and variable fluorescence yields in a light adapted state - LHC II light harvesting chlorophyll a/b protein complex associated with PS II - q_P photochemical quenching - A₈₂₀ light-induced absorbance change at 820 nm - _{PS I}, _{PS II} relative quantum efficiencies of PS I and PS II photochemistry - _{CO 2} quantum yield of CO₂ assimilation     

The photosynthetic F1-α3β3 and α1β1 catalytic core complexes

Minimal photosynthetic catalytic F₁() core complexes, containing equimolar ratios of the and subunits, were isolated from membrane-bound spinach chloroplast CF₁ and Rhodospirillum rubrum chromatophore RrF₁. A CF₁-₃₃ hexamer and RrF₁-₁₁ dimer, which were purified from the respective F₁() complexes, exhibit lower rates and different properties from their parent F₁-ATPases. Most interesting is their complete resistance to inhibition by the general F₁ inhibitor azide and the specific CF₁ inhibitor tentoxin. These inhibitors were earlier reported to inhibit multisite, but not unisite, catalysis in all sensitive F₁-ATPases and were therefore suggested to block catalytic site cooperativity. The absence of this typical property of all F₁-ATPases in the ₁₁ dimer is consistant with the view that the dimer contains only a single catalytic site. The ₃₃ hexamer contains however all F₁ catalytic sites. Therefore the observation that CF₁-₃₃ can bind tentoxin and is stimulated by it suggests that the F₁ subunit, which is required for obtaining inhibition by tentoxin as well as azide, plays an important role in the cooperative interactions between the F₁-catalytic sites.Abbreviations CF₀F₁ chloroplast F₀F₁ - CF₁ chloroplast F₁ - CF₁ chloroplast F₁ subunit - CF₁ chloroplast F₁ subunit - CF₁() a complex containing equal amounts of the CF₁ and subunits - MF₁ mitochondrial F₁ - RrF₀F₁ Rhodospirillum rubrum F₀F₁ - RrF₁ R. rubrum F₁ - RrF₁ R. rubrum F₁ subunit - RrF₁ R. rubrum F₁ subunit - RrF₁() a complex containing equal amounts of the RrF₁ and subunits - Rubisco Ribulose-1,5-bisphosphate carboxylase - TF₁ thermophilic bacterium PS3 F₁     

Ultrastructural analysis ofSpinacia oleracea sperm cells isolated from mature pollen grains

Summary In isolated condition, the sperm cells ofSpinacia oleracea are no longer arranged in pairs as in the pollen grain. The vegetative membrane, which surrounds a sperm cell pair in a mature pollen grain, is lost during the isolation procedure. The sperm cells become spherical in shape.The isolated sperm cell is surrounded by an intact plasma membrane. The heterochromatic or euchromatic sperm cell nucleus is located in the cell center. Mitochondria are round to oval and have distinct cristae. Often they are clustered in groups of 5 to 10 mitochondria. Dictyosomes are present in the cytoplasm and consist of 4 to 5 cisterns. Endoplasmatic reticulum is mostly situated at the sperm cell periphery, as single cisterns very near the plasma membrane.From diameters of sectioned sperm cells in electron micrographs, it is possible to calculate the average diameter of the whole sperm cell. This average diameter is 3.66 m with a variation of 3.0 m to 4.2 m, resulting in an average volume of 25.6 m³. The nuclear volume is 12.8 m³ (50.0% of the whole cell) and the mitochondrial volume is 0.7 m³ (2.5% of the whole cell). The frequency distribution of the isolated sperm cells diameters shows only one peak with a normal distribution, indicating that there is no dimorphism in volume.     

Calculation of leaf photosynthetic parameters from light-response curves for ecophysiological applications

Measurement of the light response of photosynthetic CO₂ uptake is often used as an implement in ecophysiological studies. A method is described to calculate photosynthetic parameters, such as the maximum rate of whole electron transport and dissimilative respiration in the light, from the light response of CO₂ uptake. Examples of the light-response curves of flag leaves and ears of wheat (Triticum aestivum cv. ARKAS) are shown.Abbreviations and symbols A net photosynthesis rate - D ¹ rate of dissimilative respiration occurring in the light - f loss factor - I incident PPFD - I effective absorbed PPFD - J rate of whole electron transport - J _m maximum rate of whole electron transport - p ^c intercellular CO₂ partial pressure - PPFD photosynthetic photon flux density - q effectivity factor for the use of light (electrons/quanta) - absorption coefficient - I ^* CO₂ compensation point in the absence of dissimilative respiration (bar) - II conversion factor for calculation of CO₂ uptake from the rate of whole electron transport - convexity factor Gas-exchange rates relate to the projective area and are given in mol·m^-2·s^-1. Electron-transport rates are given in mol electrons·m^-2·s^-1; PPFD is given in mol quanta·m^-2·s^-1.     

(T2AG3)n Telomeric Sequence Hybridization Indicating Centric Fusion Rearrangements in the Karyotype of the Rodent Oryzomys Subflavus

Chromosome preparations of 30 specimens of Oryzomys subflavus trapped in eight Brazilian localities were C-, and G-banded and analyzed by fluorescence in situ hybridization (FISH). Two karyotypes were found, 2n=50/FN=64, at three coastal localities of the Atlantic Forest domain, and 2n=58/FN=70 at two sites located in the Cerrado biome, Brazil Central. Two fluorescence in situ hybridization (FISH) patterns of the telomeric sequence (T₂AG₃)_n were observed: in both karyotypes the probes hybridized to the telomeres of all chromosomes and also a hybridization signal in the centromeric regions of two autosome pairs was seen in the 2n=50 karyotype. These results, together with the occurrence of other diploid numbers described in the literature, suggest that O. subflavus is a complex species, bearing fusion/fission rearrangements proper to the different biomes which it inhabits.     

Subcellular distribution of terminal α-D- and β-D-galactosyl residues in Ehrlich tumour cells studied by lectin-gold techniques

We have studied by high resolutionin situ light and electron microscopic lectin-gold techniques the subcellular distribution of -d-Gal residues using theGriffonia simplicifolia I-B₄ isolectin and compared it with that of -d-Gal residues as detected with theDatura stramonium lectin in Ehrlich tumour cells grown as ascites or monolayer. The microvillar but not the smooth plasma membrane regions were labelled with theGriffonia simplicifolia I-B₄ isolectin whereas both plasma membrane regions were equally well labelled with theDatura stramonium lectin. Elements of the endocytotic/lysosomal system such as coated membrane invaginations and vesicles, early and late endosomes and secondary lysosomes were positive for both -d-Gal and -d-Gal residues. A particular feature of Ehrlich tumour cells is an elaborate tubular membrane system located in the pericentriolar region which is labelled throughout by both lectins and represents part of the endosomal system. In the Golgi apparatus labelling with both lectins was observed to commence in trans cisternae which is indirect evidence for a joint distribution of the sequentially acting 1,4 and 1,3-galactosyl-transferases.     

Inorganic-carbon uptake by a small-celled strain of Stichococcus bacillaris

Air-grown cells of a marine, small-celled (2 m diameter) strain of Stichococcus bacillaris contained appreciable carbonic-anhydrase activity but this was repressed when cells were grown on air enriched with 5% (v/v) CO₂. Assay of carbonic-anhydrase activity using intact cells and cell extracts showed all activity was intracellular in this Stichococcus strain. Measurement of inorganic-carbon-dependent photosynthetic O₂ evolution at pH 5.0, where CO₂ is the predominant form of inorganic carbon, showed that the concentration of inorganic carbon required for half-maximal rate of photosynthetic O₂ evolution [K_0.5(CO₂)] was 4.0 M for both air- and CO₂-grown cells. At pH 8.3 the K_0.5(CO₂) was 0.3 mM for air-grown and 0.6 mM for CO₂-grown cells. Sodium ions did not enhance bicarbonate utilization. Measurement of the internal inorganic-carbon pool (HCO ₃ ^– +CO₂) by the silicone-oil-layer centrifugal filtering technique showed that air- and CO₂-grown cells were able to concentrate inorganic carbon up to 20-fold in relation to the external medium at pH 5.0 but not at pH 8.3. In this alga the high affinity for CO₂ and inorganic-carbon accumulation in CO₂- and air-grown cells results from active CO₂ transport that is not dependent on carbonic-anhydrase activity.Abbreviation Hepes 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid     

Proton translocation in corn coleoptiles: ATPase or redox chain?

The O₂ dependence of net H⁺ efflux of maize coleoptiles has been investigated. Below 100 M O₂, H⁺ efflux in young (1 cm long) coleoptiles is markedly decreased while old (7 cm long) coleoptiles show a decline only at 10 M O₂. Old coleoptiles show the same decrease in net H⁺ efflux as young ones if treated with fusicoccin. The ratio of alteration of CO₂ production to the change in net proton efflux is about 1:1 at 40–80 M O₂ but not at 10 M O₂. An influx can be observed at 10 M O₂ in young as well as in old coleoptiles if the H⁺ concentration is held at values below pH 6.5. Lower O₂ concentrations lead to an increase of net H⁺ efflux, which might be caused by leaching of organic acids resulting from anaerobic processes, but CO₂ production is not significantly changed at these values. It is proposed that more than one system is responsible for proton translocation across the plasmalemma. One of the systems has a high sensitivity to reduced O₂ concentration which is within the same range as the high K_m of the alternative path.Abbreviation FC fusicoccin     

Oxygen inhibition of photosynthesis in the C4 species Amaranthus graecizans L.

In the C₄ plant, Amaranthus graecizans, increasing [O₂] from 2% up to 100% inhibited photosynthesis, quantum yield, and the carboxylation efficiency, and increased the CO₂ compensation point () from 2 to about 12 l/l. The O₂ inhibition of photosynthesis was fully reversible. When changing from 2.5 to 40% O₂ and vice versa, about 1 h was required for full equilibration with an O₂ inhibition of 18%; whereas in wheat, a C₃ species, inhibition of photosynthesis and its reversal occurs within minutes after changing [O₂], resulting in 63% inhibition of photosynthesis by 45% O₂. These differences in O₂ inhibition between a C₄ and C₃ species can be explained by high diffusive resistance across bundle-sheath cells of C₄ plants and the increased CO₂/O₂ ratio in bundle-sheath cells which is the consequence of the C₄ cycle. In A. graecizans, increased with increasing [O₂] but tended to reach a maximum at relatively high O₂ levels. The lack of a linear increase in as previously observed for C₃ species indicates that a considerable amount of photorespired CO₂ may be re-fixed with increasing levels of O₂. In comparison to previous reports with other C₄ species, photosynthesis of A. graecizans shows greater sensitivity to O₂, with a noticeable inhibition occurring with shifts from 2 to 21% O₂. A. graecizans has characteristics of other C₄ species with respect to Kranz anatomy, localization of PEP carboxylase in mesophyll cells and RuBP carboxylase in bundle-sheath cells, and little fractionation among carbon isotopes during CO₂ fixation. The basis for the higher sensitivity of photosynthesis of A. graecizans to O₂ may be based upon a lower diffusive resistance of gases across bundle-sheath cells than in some other C₄ species.Abbreviations CE carboxylation efficiency - RuBP ribulose-1,5-bisphosphate - CO₂ compensation point     

Photosynthesis and the intracellular inorganic carbon pool in the bluegreen alga Anabaena variabilis: Response to external CO2 concentration

The apparent photosynthetic affinity of A. variabilis to CO₂ is greatly affected by the CO₂ concentration in the medium during growth. Halfmaximal rate of photosynthetic O₂ evolution is achieved at 10 M and 100 M inorganic carbon (C_inorg) in cells grown at low-CO₂ (air) and high CO₂ (5% v/v CO₂ in air), respectively, whilst the maximum rate of photosynthesis is similar in both cases. Both high- and low-CO₂-grown Anabaena accumulate C_inorg within the cell; however, the rate of accumulation and the steady-state internal C_inorg concentration reached is much higher in low as compared with high-CO₂-grown cells. It is suggested that Anabaena cells actively accumulate C_inorg. Measurements of the kinetics of C_inorg transport indicate that the affinity of the transport mechanism for C_inorg is similar (K_m(C_inorg(150 M) in both high- and low-CO₂-grown cells. However, V _max is 10-fold higher in the latter case. It is suggested that this higher V _max for transport is the basis of the superior capability to accumulate C_inorg and the higher apparent photosynthetic affinity for external C_inorg in low-CO₂-grown Anabaena. Carbonic anhydrase activity was not detectable in Anabaena, yet both photosynthetic affinity to C_inorg in the medium (but not V _max) and the rate of accumulation of C_inorg were inhibited by the carbonic-anhydrase inhibitor ethoxyzolamide.Abbreviations C_inorg inorganic carbon - PEP phosphoenol pyruvate - RuBP ribulose-1,5-bisphosphate CIW-DPB Publication No. 682     

Rates of glycolate synthesis and metabolism during photosynthesis of Euglena and microalgae grown on low CO2

The rate of glycolate excretion in Euglena gracilis Z and some microalgae grown at the atmospheric level of CO₂ was determined using amino-oxyacetate (AOA). The extracellular O₂ concentration was kept at 240 M by bubbling the incubation medium with air. Glycolate, the main excretion product, was excreted by Euglena at 6 mol·h^-1·(mg chlorophyll (Chl))^-1. Excretion depended on the presence of AOA, and was saturated at 1 mM AOA. A substituted oxime formed from glyoxylate and AOA was also excreted. Bicarbonate added at 0.1 mM did not prevent the excretion of glycolate. The excretion of glycolate increased with higher O₂ concentrations in the medium, and was competitively inhibited by much higher concentrations of bicarbonate. Aminooxyacetate also caused excretion of glycolate from the green algae, Chlorella pyrenoidosa, Scenedesmus obliquus and Chlamydomonas reinhardtii grown on air, at the rates of 2–7 mol·h^-1·(mg Chl)^-1 in the presence of 0.2–0.6 mM dissolved inorganic carbon, but the cyanobacterium, Anacystis nidulans, grown in the same way did not excrete glycolate. The efficiency of the CO₂-concentrating mechanism to suppress glycolate formation is discussed on the basis of the magnitude of glycolate formation in these low-CO₂-grown cells.Abbreviations AOA aminooxyacetate - Chl chlorophyll - DIC dissolved inorganic carbon - HPLC high-pressure liquid chromatography - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase This is the 16th paper in a series on the metabolism of glycolate in Euglena gracilis. The 15th paper is Yokota et al. (1985c)     

Effect of the triacontanol formulation ‘Miraculan’ on photosynthesis,growth, nutrient uptake,and essential oil yield of Lemongrass (Cymbopogon flexuosus) Steud. Watts

The influence of different foliar applications of the triacontanol (Tria.) based plant grow regulator-Miraculan, on growth, CO₂ exchange and essential oil accumulation in Lemongrass (Cymbopogon flexuosus L.) Steud. Watts. was studied in glass-house conditions. The yield components, viz., plant height, tillers per plant, biomass yield, accumulation of essential oil, net CO₂ exchange and transpiration rates increased with Miraculan treatment of 0.4 g/ml compared to the untreated control, but the number of leaves per tiller remained unaffected. Application of Miraculan at 0.4 g/ml increased micronutrient uptake, total chlorophyll and citral content but decreased chlorophyll a/b ratio and stomatal resistance. Increase in shoot biomass, photosynthesis and chlorophyll were significantly correlated with essential oil content.     

Nuclear Overhauser effect investigation on GM1 ganglioside containingN-glycolyl-neuraminic acid (II3Neu5GcGgOse4Cer)

The conformational properties of the oligosaccharide chain of GM1 ganglioside containingN-glycolyl-neuraminic acid, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer, were studied through NMR nuclear Overhauser effect investigations on the monomeric ganglioside in dimethylsulfoxide, and on mixed micelles of ganglioside and dodecylphosphocholine in water. Several interresidual contacts for the trisaccharide core--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-were found to fix the relative orientitation of the three saccharides, while the glycosidic linkage of the terminal -Gal-was found to be quite mobile as the -Gal-(1-3)--GalNAc-disaccharide exists in different conformations. These results are similar to those found for two GM1 gangliosides containingN-acetyl-neuraminic acid and neuraminic acid [1].Abbreviations Ganglioside nomenclature is in accordance with Svennerholm [23] and the IUPAC-IUB Recommendations [24] GM3(Neu5Ac) II³Neu5AcLacCer, -Neu5Ac-(2-3)--Gal-(1-4)--Glc-(1-1)-Cer - GM3(Neu5Gc) II³Neu5GcLacCer, -Neu5Gc-(2-3)--Gal-(1-4)--Glc-(1-1)-Cer - GM1(Neu5Ac) II³Neu5AcGgOse₄Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer - GM1(Neu5Gc) II³Neu5GcGgOse₄Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer - GM1(Neu) II³NeuGgOse₄Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu-(2-3)]--Glc-(1-1)-Cer - GD1a IV³Neu5AcII³Neu5AcGgOse₄Cer, -Neu5Ac-(2-3)--Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer - GalNAc-GD1a IV⁴GalNAcIV³Neu5AcII³Neu5AcGgOse₄Cer, -GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer - Neu neuraminic acid - Neu5Ac N-acetyl-neuraminic acid - Neu5Gc N-glycolyl-neuraminic acid - Cer ceramide