Showing papers in "Zeitschrift für Naturforschung C in 1982"

Carotenoid Composition of Chlorophyll-Carotenoid-Proteins from Radish Chloroplasts

Abstract: The uneven distribution of carotenoids and chlorophylls between several chlorophyll- carotenoid-proteins isolated from radish chloroplasts by SDS-polyacrylamide-gel electrophoresis is described. Lutein and neoxanthin are enriched in the light-harvesting chlorophyll a/b-protein LHCP3, which exhibits low chlorophyll a/b ratios (1.1-1.3) and high values for the ratio chlorophyll a/β-carotene (a/c = 60-180). β-carotene is bound not only to the chlorophyll a-protein CPI + CPIa of photosystem I, but also to the chlorophyll a-protein CPa. Both chlorophyll a-proteins are characterized by high values for the ratio a/b and low values for the ratio a/c.

Isolation and synthesis of a hemoregulatory peptide.

Abstract: A peptide was isolated in pure form from human leukocytes which strongly inhibits the proliferation of immature myeloid cells in vitro (committed stem cells). Structural investigations yielded pGlu-Asp or Glu-Asp or Glu-Cys-Lys-OH as the probable sequence of this peptide. The Glu2, Asp3-analog, prepared synthetically, displayed similar activities and when applied in vivo showed effects on the hemopoietic system ranging from an inhibition of pluripotent and committed stem cells to variations in the bone marrow proliferation and alterations in peripheral blood counts.

Ca entry and contraction as studied in isolated bovine ventricular myocytes.

Abstract: Single bovine ventricular myocytes were superfused with Tyrode solution containing 1.8 mM CaCl2. The cells did not bear external load and contracted isotonically. Contraction and relaxation were characterized by the shortening and relengthening of the sarcomeres which resembled in their time course the isometric twitches of bovine papillary muscles. Resemblance was also found in regard to positive inotropic interventions as increase in the stimulation frequency, exposure to elevated [Ca]0 or to adrenaline. A two-microelectrode voltage-clamp technique was applied to the single myocyte. The transmembrane Ca inward current ICa was defined as difference current sensitive to 5 mM Ni or to 2 microM D600. During a voltage step from -45 to +5 mV, ICa peaked within 3 ms to -6 nA, afterwards it decayed to 15% of peak amplitude (incomplete inactivation with a 2 exponential time course). Experiments in Na-free media suggested that Na entry does not significantly contaminate ICa. Therefore, Ca entry could be calculated from ICa. The increment in total intracellular Ca concentration (delta[Ca]Ti) was estimated by referring Ca entry to the cell volume (50 pl). Within 100 ms delta[Ca]Ti came to 25 microM at control conditions, to 55 microM at [Ca]0 = 3.6 mM and to 88 microM when 0.1 microM adrenaline were present. The delta[Ca]Ti values were sufficient to activate contraction without the necessity of Ca-release from SR. Despite the new data, the relationship between Ca entry and activation of contraction was complex: during the "positive Herztreppe" ICa slightly attenuated but contractility doubled. Therefore, the old EC-model (M. Morad and Y. Goldman, Progr. Biophys. Mol. Biol. 27, 257 (1973)) was adapted. The Ca-entry's capability to load and to overload the intracellular Ca store (SR) is discussed.

Separation, Partial Purification and Characterization of a Fatty Acid Hydroperoxide Cleaving Enzyme from Apple and Tomato Fruits

Abstract: Abstract A membrane-bound enzyme catalysing the cleavage of 13-hydroperoxy-(Z)-9,(E)-11-oc-tadecadienoic acid (13-LHPO) and 13-hydroperoxy-(Z)-9,(E)-11,(Z)-15-octadecadienoic acid (13-LnHPO) to C6-aldehydes was isolated and partially purified from apples and tomatoes. Attempts to employ Ultrogel AcA 34 and AcA 22 in a gel chromatographic purification step were partially frustrated by reaggregation phenomena. However, by using Sepharose CL-4 B an enzyme fraction (MW 200 000 Da) with lipoxygenase and fatty acid hydroperoxide cleaving activity could be separated from a high molecular-weight active eluate. By applying preparative isoelec tric focussing to the tomato protein we succeeded in separating the fatty acid cleaving activity from the lipoxygenase, because o f their different isoelectric points of pH 5.8 -6 .1 and pH 5.0, respectively, An 8.4-fold purification of the fatty acid cleaving activity was achieved. A pH-optimum of 5.5 and a Km-value of 2.6 × 10-5 м/1 for the 13-hydroperoxide of linoleic acid were measured. p-Chloromercuribenzoic acid (1 mм) showed significant inhibitory effect on the fatty acid hydroperoxide cleaving enzyme, but no evidence o f inhibition was found with 1 mм H2O2, KCN, DABCO and EDTA or superoxide dismutase (270 U). The maximum amount of fatty acid hydroperoxide decomposition (C6-aldehyde formation) was determined to be 59%.

Release of K+ and H+ from Poly U in Aqueous Solution upon γ and Electron Irradiation.Rate of Strand Break Formation in Poly U

Abstract: Conductivity changes were found which followed the reaction of radiolytically generated OH radicals with the potassium salt of polyuridylic acid (poly U) in aqueous solution. After 60Co-gamma-irradiation the observed increase of conductivity at pH = 6.8 was shown to consist of the liberation of K+ ions from the stock of K+ ions electrostatically bound to the polyanion. The initial G(K+) is 36 and hence 6 times higher than the G value of OH radicals in N2O saturated solutions. At a poly U concentration of 60 mg l-1 half of the ion release occurred at 12 J kg-1 and nearly all ions are released at 40 J kg-1. The liberation of K+ is explained to be a consequence of the formation of chain breaks leading to an increase of the degree of dissociation. The rate of the ion release was studied under pulse radiolysis conditions. Because of the high G-value of counterion liberation and the use of conductivity as analytical quantity the method is very sensitive. With 6 mg l-1 poly U the rate could be measured even at a dose per pulse of 0.25 J kg-1. The kinetics of the ion release can be described in terms of two parallel first order reactions of comparable contribution with an average rate constant of 0.8 s-1 at 20 degrees C, 60 mg l-1 poly U and pH = 6.8 with a small contribution of slower components. In more acidic solutions, besides K+ ions H+ are also liberated since at low pH values bound K+ is replaced by H+. The rate of the ion release was found to increase with increasing replacement of K+ by H+ (kobs = 100 s-1 at pH = 3.4, 60 mg l-1 poly U and T = 18 degrees C). With potassium ion free polyuridylic acid the corresponding rate constant amounted to 220 s-1, nearly independent of pH. From the temperature dependence activation parameters for the ion release were derived (Ea = 57 kJ mol-1, A = 1.0 X 10(10) s-1 at pH = 6.8). Addition of p-benzoquinone at pH = 3.7 and dithiothreitol (DTT) at pH 6.8 were found to decrease the size of the conductivity changes and to increase the rate. The results show that p-benzoquinone and DTT react with poly U radicals and that these reactions prevent chain breaks and ion liberation. It is concluded that the rate determining step of the conductivity increase is the formation of strand breaks by a cleavage of poly U radicals and that this reaction is pH dependent. The pH dependence and the observed value for the activation energy was found to be in agreement with the behaviour of a model system for the earlier postulated C-4' mechanism for strand break formation of polynucleotides and DNA.

Mevinolin: a highly specific inhibitor of microsomal 3-hydroxy-3-methylglutaryl-coenzyme A reductase of radish plants.

Abstract: The fungal metabolite mevinolin, known to be a potent hypocholesterolemic agent, exerts in vitro a strong inhibitory effect on microsomal HMG-CoA reductase from etiolated radish seedlings at a concentration of about three magnitudes lower than the Km towards the natural substrate (S)-HMG-CoA (I50 = 2.5 x 10(-9)M). Beside this, mevinolin significantly inhibits the root elongation of radish as well as of wheat seedlings already at low concentrations of 10 to 100 ppb (= 2.5 x 10(-8) to 2.5 x 10(-7)M).

Coupled Gas Chromatography — Single Cell Recording: a New Technique for Use in the Analysis of Insect Pheromones

Abstract: Abstract A method is described for the continuous biological monitoring of the effluent from a high resolution gas chromatographic column using a single cell recording technique. The system can be used to provide precise information on the retention times of compounds with olfactory activity that are not detected with a coupled gas chromatograph - electroantennogram system.

Specific Localization of β-ᴅ-Glucoside Conjugates of 2,4-Dichlorophenoxyacetic Acid in Soybean Vacuoles

Abstract: Cell suspension cultures of soybean (Glycine max L.) were incubated with [¹⁴C]-2,4- dichlorophenoxyacetic acid (62 h, 27 °C). The cells were converted to protoplasts by use of the cell-wall degrading enzymes, Driselase and pectinase. This procedure resulted in the release of the cellular amino acid conjugates as well as part of the free 2,4-dichlorophenoxyacetic acid and of the β-ᴅ- glucoside conjugates. A vacuole fraction was obtained by mild osmotic shock in 10% yield, and was characterized by its polypeptide composition. The purified vacuoles were enriched in β-ᴅ-glucoside conjugates, free 2,4-dichlorophenoxyacetic acid being only a minor vacuolar constituent, and amino acid conjugates not being detectable.

The reversibility of the vitamin C redox system: electrochemical reasons and biological aspects.

Abstract: The biological efficacy of vitamin C depends on its redox abilities as given by the relations between ascorbic acid, semidehydroascorbic acid, and dehydroascorbic acid. It is shown by means of proton magnetic resonance spectroscopy that the enzymatic (by ascorbate oxidase) as well as non-enzymatic (by iodine) oxidation of ascorbic acid is, in principle, reversible despite the hydration and structural changes during the formation of dehydroascorbic acid. The strong redox activity of semidehydroascorbic acid which results in a fast disproportionation to ascorbic acid and dehydroascorbic acid is inferred from an inversion of the electrochemical potentials of the vitamin C redox system. The capacity of this is maintained by a fast reduction of dehydroascorbic acid e.g. by reduced glutathione, preventing its delactonization and further degradation.

Hydroxylation of the B-Ring of Flavonoids in the 3′-and 5′-Position with Enzyme Extracts from Flowers of Verbena hybrida

Abstract: Enzyme preparations from flowers of Verbena hybrida do not only catalyse hydroxylation of the B-ring of flavanones and dihydroflavonols in the 3'-position but also in the 5'-position. Enzyme activity for 3',5'-hydroxylation was found to be localized in the microsomal fraction and required NADPH as cofactor. Evidence is provided that the formation of the 3',4',5'- hydroxylated flavanone (5,7,3',4',5'-pentahydroxyflavanone) and dihydroflavonol (dihydromy- ricetin), respectively, proceeds via the corresponding 3',4'-hydroxylated compounds eriodictyol and dihydroquercetin, respectively, which are most probably formed by action of the same enzyme. Enzyme activity for 3',5'-hydroxylation was found to be strictly correlated with the prescence of 3',4',5'-hydroxylated flavonoid compounds in the flowers.

Adult T-cell leukemia-associated antigen (ATLA): detection of a glycoprotein in cell- and virus-free supernatant.

Abstract: A glycoprotein of an apparent molecular mass of 46,000, gp 46, was enriched by affinity chromatography from the virus- and cell-free culture medium of adult T-cell leukemia virus (ATLV) infected cells. gp 46 was specifically precipitated with sera from patients with adult T-cell leukemia associated antigen (ATLA). Thus, gp 46 is a novel component of the ATLA antigen complex.

A Cyanobacterial ATPase Distinct from the Coupling Factor of Photophosphorylation

Abstract: Abstract A particle-bound, Mg2+ -dependent ATPase activity is investigated in cell-free extracts of the tyanobacterium Anabaena variabilis. The enzyme can be clearly distinguished from the cyanobacterial coupling factor of photophosphorylation and from the alkaline phosphatase. It requires low concentrations of Ca2+ for maximal activity and is inhibited by ortho-vanadate, indicating that the enzyme may form a phosphorylated intermediate in its catalytic cycle. The distribution of the ATPase in sucrose density gradients does not follow that of thylakoids. It is concluded from these characteristics that the enzyme is bound to the plasma membrane. The cytochrome oxidase activity of the extracts appears to be restricted to the thylakoids.

Model Reactions for the Degradation of DNA-4′ Radicals in Aqueous Solution. Fast Hydrolysis of α-Alkoxyalkyl Radicals with a Leaving Group in β-Position Followed by Radical Rearrangement and Elimination Reactions

Abstract: α-Alkoxyalkyl radicals with a leaving group L = Cl or OCOCH₃ in β-position are produced by H-abstraction from the corresponding saturated substrates by ·OH, SO·₄⁻ or (CH₃)₃CO· radicals. From ESR spectroscopic observations it is concluded that in aqueous solution at pH 5 -9 the following fast hydrolysis reactions take place:The rate constants of these reactions and for the hydrolysis of CH₃O-ĊH-CH₂Cl are k ≥ 10⁶ s⁻¹, whereas the rate constant for CH3O-ĊH-CH₂OCOCH₃ was determined to be ≈ 2 × 10³ s⁻¹ at room temperature. The radicals with L = Cl cannot be scavenged by O₂ which fact leads to a value of k ≥ 2 × 10⁻⁷ s⁻¹. α-Alkoxyalkene radical cations are assumed as intermediates in the hydrolysis reactions. The radicals with L = OCOCH₃ and the radical CH₃O--ĊH-CH₂Cl are observable in acetone solution ESR spectroscopically.In aqueous solution at pH below 3 proton catalyzed reactions are observed by ESR spectroscopy:Radicals resulting from H-abstraction at the CH₃O-groups of the substrates or at the 5-positions of the cyclic ethers are also observed. The ESR parameters and the pH-ranges of existence of the above radicals are given. Support of the reported reactions comes from quantitative analysis of stable products such as H⁺, Cl⁻ or CH₃OH after ⁶⁰Co-γ-irradiation of N₂O saturated aqueous solutions of the substrates.The behaviour of the radicals is used as a model to describe a modified version of the degradation of DNA-4′ radicals in aqueous solution in the absence of oxygen.

Exogenous and Endogenous Control of Swimming Activity in Astyanax mexicanus (Characidae, Pisces) by Direct Light Response and by a Circadian Oscillator II. Features of Time-Controlled Behaviour of a Cave Population and their Comparison to a Epigean Ancestral Form

Abstract: 1. The swimming activity of 6 specimens of the Pachon cave form of Astyanax mexicanus was tested with regard to its time control under various light-dark(LD)cycles and constant conditions, and it is compared to that of a river form. 2. In general, activity is entrainable by all applied LDs, but even if the amplitude of a forcing signal increases the signal energies are lower than in the river fish. 3. In case of entrainment the maximum values of surface activity correspond to the dark phases, those of bottom activity to the light phases of a LD. Flexible patterns -as often observed in the river form in the range of resonance about 24 h - are very seldom. Furthermore, disturbances of­ ten occur in the entrainment of one activity form, or one form runs arrhythmic while the other is still entrained. 4. The activity answers to changing environmental conditions are not as uniformly quick as in the river fish. But the system hardly needs a swing-in time to become entrained when a LD starts. 5. After transition from LD to DD (= constant darkness) the entrained rhythms disappear immediately. 6. In no LD with a period length differing from 24 h a circadian rhythm can be observed in addition to the entrained frequency. 7. These results show that the passive system of the river form has developped into an extremely passive one being unable to oscillate and thus has become simplified during regressive evolution. Concerning the circadian oscillator of the epigean ancestor, it was also subjected to regression, but it has not been completely lost. After a LD with a period length about 24 h the circadian oscillator is able to act as a stable system, clearly shown by the freerunning circadian rhythms of surface activity. But out of this range the oscillator is unable to control activity. In DD after all other LDs activity patterns are arrhythmic.

Investigation of large intramolecular movement within metmyoglobin by Rayleigh scattering of Mössbauer radiation (RSMR).

Abstract: This paper reports Rayleigh scattering experiments on metmyoglobin crystals and freeze dried myoglobin which was exposed to air with different parital pressure of water vapor. While dry myoglobin shows no fluctuations between conformational substates such "breathing modes" are rarely seen in water covered myoglobin. Larger amounts of water increase the average mean square displacements. In crystals the dynamic behaviour is hindered by the crystal packing. The results are analysed by a theory describing the motion within the molecule by a Langevin equation with restoring forces corresponding to a square well potential.

Osmoregulation in Dunaliella. Intracellular Distribution of Enzymes of Glycerol Metabolism

Abstract: Dunaliella tertiolecta was disrupted mechanically and resolved by centrifugation into chloro­plast- and cytosol-enriched fractions. Intact chloroplasts could not be isolated because peripheral extensions of the single large chloroplast reached almost to the flagellar pole of the cell. The chloroplast envelope was closely appressed to the plasmalemma and, because of this and its dimensions, was vulnerable to mechanical damage to the cell.Distribution of enzymes of the glycerol cycle between the two fractions was compared with that of two marker enzymes, phosphoenolpyruvate carboxylase (cytosol) and ribulose bisphosphate carboxylase (chloroplast). The two reversible steps of the cycle were found to be spatially separated; glycerol-3-phosphate dehydrogenase (NAD-specific) was located in the chloroplast whereas glycerol dehydrogenase (NADP-specific) was located in the cytosol. The distribution of the two irreversible enzymes, glycerol phosphate phosphatase and dihydroxyacetone kinase is uncertain. These enzymes might occur about equally in both major compartments (cytoplasm and chloroplast) or be mitochondrial or they might be loosely associated with a membrane system. Implications of these results for regulation of the glycerol cycle are discussed.

Diurnal Fluctuation of Quinolizidine Alkaloid Accumulation in Legume Plants and Photomixotrophic Cell Suspension Cultures

Abstract: Fluctuations of quinolizidine alkaloid content in leaflets of Lupinus polyphyllus, L. hartwegii, Baptisia australis, and Sarothamnus scoparius were studied over a 36 h period. The alkaloid contents reached their maximum at noon or early afternoon, and their minimum during the night. The amplitudes of diurnal variations in alkaloid levels lay within a range of 60 to 470% of the early morning contents of alkaloids (= 100%) in leaves. In photomixotrophic cell suspension cultures of L. polyphyllus and S. scoparius cultured under day-night regime, a similar increase of the alkaloid levels was observed within 5 to 8 h after onset of illumination. A subsequent excretion of the alkaloids produced, which also followed a diurnal rhythm, was found. S. scoparius cells excreted lupanine, L. polyphyllus cells 13-cinnamoyloxylupanine. From the cell culture and plant experiments it can be assumed that the alkaloids which are formed during illumination are translocated to some degree afterwards. In cell suspension cultures the alkaloids are subjected to rapid and rhythmic turnover. Exogenous alkaloids, fed to the cultures, are taken up by the cells and disappear usually within the first 72 h. A possible mechanism for a light-mediated regulation of quinolizidine alkaloid biosynthesis which was found to be localized in leaf chloroplast, is discussed.

Equilibrium and kinetic studies of calcium transport and ATPase activity in sarcoplasmic reticulum.

Abstract: A number of equilibrium and kinetic measurements are presented to characterize the partial reactions of the ATPase and transport cycle in sarcoplasmic reticulum vesicles. The cycle begins with calcium and nucleotide binding on sites available on the outer surface of the vesicles. A phosphorylated enzyme intermediate is then formed, and the calcium sites are subjected to a change in their orientation and their affinity for calcium. It is shown that steps involved in calcium release on the inner side of the vesicles are rate limiting for the cycle, and are followed by hydrolytic cleavage of the intermediate with release of inorganic phosphate and recycling of the enzyme.

Detection of Glyceollin on the Cellular Level in Infected Soybean by Laser Microprobe Mass Analysis

Abstract: Laser microprobe mass analysis was explored as a method for the detection at the cellular level of the phytoalexin glyceollin in soybean cotyledons infected with an incompatible race of Phy- tophthora megasperma f. sp. glycinea. For LAMMA® analysis 10 μm freeze microtome sections which were freeze-dried on copper grids were used. The LAMMA spectrum of glyceollin (isomer I) shows a characteristic peak at m/e = 321 which can be attributed to M-OH⁺. This peak was also present in the spectra of infected regions from a cotyledon but was completely absent in the spec­tra of uninfected tissue. One hundred and Fifty LAMMA spectra were taken along a line per­pendicular to the border line of infection. A steep rise in glyceollin content toward the infected area was observed. This is the First time that such highly localized glyceollin accumulation has been shown at the cellular level. The results show that LAMMA analysis is suitable for the de­tection of organic molecules in biological tissues with high lateral resolution.

Changes of C-Phycocyanin in Synechococcus 6301 in Relation to Growth on various Sulfur Compounds Materials and Methods

Abstract: The cyanobacterium Synechococcus 6301 is able to use a limited number of sulfur compounds as the only source of sulfur supply such as sulfate, thiosulfate, thioacetic acid, mercaptoacetic acid, thioacetamide, ʟ-cysteine and glutathione. Compounds containg thioether linkages such as methionin or S-methylcysteine and all compounds investigated so far containing sulfonic acid structures do not support growth. Growth inhibiton was observed by addition of aminomethane- sulfonic acid or cysteamine.When non-growth sustaining sulfur compounds are added as sulfur source, the C-phycocyanin content of the Synechococcus cultures decreased drastically, causing a shift in color from blue- green to yellow-green. An analysis reveals the degradation of C-phycocyanin whereas chlorophyll formation still proceeds to a certain degree in growing sulfur-starved cells. Supplementation of a suitable sulfur source induces a period of intense and preferential C-phycocyanin synthesis prior to resumption of normal growth.

Nanochlorum eucaryotum: a Very Reduced Coccoid Species of Marine Chlorophyceae

Abstract: Nanochlorum eucaryotum was isolated from a sea water aquarium housing different sponge species, cucumarias, small crustaceans and annelids. This bright green marine alga differs from all other known coccoid species. Its most prominent features are its very small cell size (1.5 pm) and its reduced cellular organization. Its cell contains one nucleus, one chloroplast, one mitochondrium and small vacuoles. Sometimes a Golgi apparatus can be seen. No other subcellular features have been observed. The cell wall is thin and smooth and does not contain any material of high electron density; only dividing cells show a rougher surface. The cells split into two daughter cells. No sexual reproduction has been observed in this organism. We have analyzed the ultrastructural cell organization, the amount of total DNA and RNA per cell, the pigment composition, the growth requirements and the sensitivity towards different inhibitors (chloramphenicol, cycloheximid, penicillin, lysozym and cellulase). The results afford the introduction of a new species; a new family or suborder of coccoid green algae is discussed.

Rubins and rubinoid addition products from phycocyanin

Abstract: Abstract The verdin-type Chromophore of denatured C-phycocyanin (1) from Spirulina platensis is reduced to the corresponding rubin (2a) by sodium borohydride. The structure assigned is in agreement with the uv-vis spectroscopic properties of the product and was deduced from model studies with free bile pigments. Analogous model studies using sodium dithionite demonstrated a two-fold reactivity for this reagent, leading to products which are both o f the rubin spectral type under the conditions tested. True rubins (10,22-dihydrobilindions) are formed in low yield only if an excess of reagent is used in methanol/water mixtures. It is accompanied by polar addition product(s) of the same spectral type, which are generally formed exclusively. In particular, no bilirubin was formed under the reaction conditions previously applied for the chemical modification of phycobiliproteins and phytochrome. From this finding and from the strikingly different properties of the borohydride and dithionite products, of phycocyanin upon renaturation, the dithionite product is suggested to be a rubinoid addition product (2b) rather than a hydrogenation product. In contrast to the dithionite addition product 2b of phycocyanin, the chromophore of the true phycorubin (2a) remains stable upon renaturation. The uv-vis spectral properties of the chromophore are not markedly different whether the apoprotein is in its native or denatured state. The different electrophoretic mobilities of native (renatured) phycocyanin compared to the renatured borohydride product suggest that these two have different protein conformations. The preparation of these phycorubins renders the extensive techniques of bilirubin chemistry applicable in the study of biliproteins.

Multicomponent Mandibular Gland Secretions in Three Species of Andrena Bees (Hym., Apoidea)

Abstract: Abstract 50 volatile constituents of the mandibular gland secretions in males and females of three species of Andrena bees, A. wilkella (Chr.), A. ovatula (K .) and A. ocreata (K .), have been identified. The secretions are made up of a series of spiroacetals of four different systems together with mono-terpenes and unbranched acyclic compounds. Many of the components, particularly several of the dominant ones, occur in both sexes of all three species, so that the volatile secretions are qualitatively very similar. Females contain about 100 μg per individuum , which is 3-5 times the amount of the males’ secretions. Major spiroacetals are E,E- and Z ,E-2,8-dimethyl-1,7-dioxa-spiro[5.5]undecane and E,E-and Z,E-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]undecane, while prominent monoterpenes are geraniol and citronellol. Straight chain hydrocarbons C17, C19, C21 and C23 occur in fairly large amounts, mostly with increasing concentrations. With respect to the quantitative distribution of components of minor concentration, the bouquet of A. wilkella is clearly distinguishable from A. ovatula and A. ocreata which from the morphological and ethological point of view are more closely related. Behaviour tests with A. wilkella indicate high biological activity of the main spiroacetal.

Biological activities of sesquiterpene lactones from Helianthus annuus: antimicrobial and cytotoxic properties; influence on DNA, RNA, and protein synthesis.

Abstract: Sesquiterpene lactones, produced in light and capable of inhibiting auxin-induced elongation growth of coleoptile and hypocotyl segments, were isolated from young leaves of Helianthus annuus (Spring and Hager, Planta in press, 1982). These compounds have an antibiotic effect on gram-negative and gram-positive bacteria as well as on some fungi. The minimal inhibiting concentration (MIC) of compound II (15-hydroxy-3-dehydrodesoxyfruticin, Fig. 1), for example, is 15 micrograms/ml for Bacillus brevis, and 95 micrograms/ml for the fungus Eremothecium ashbyi. In addition, cytotoxic effects on mouse myeloma cells (NS-1) were also shown. Compound II causes a 50% inhibition of cell proliferation (ED50) at a concentration of 170 nM, compound I (niveusin C, Fig. 1) at 220 nM. The LD50-values were 0.15 micrograms II/ml and 1.24 micrograms I/ml, respectively. By measuring 14C-labelled thymidine, uridine and leucine incorporation into murine cells of the ascitic form of Ehrlich carcinoma (EAC) it could be shown that compounds I and II inhibit DNA and RNA synthesis, but do not affect the translation processes involved in protein synthesis. Furthermore, it could be shown that the exocyclic methylene group in the molecules of I and II plays an important role in triggering the described inhibitory effects.

Biosynthesis of Photosynthates and Taxonomy of Algae

Abstract: The representatives of the major algal divisions including Chlorophyta, Rhodophyta and Heterokontophyta usually show specific patterns of accumulated photoassimilatory products. Among these compounds, the accumulated low-molecular weight carbohydrates such as mono­saccharides, disaccharides, alditols (i.e. polyhydroxy alcohols) and heterosides are of particular interest. Comparative analyses based on photosynthetic ¹⁴C-labelling provided sufficient evidence that occurrence and distribution of such compounds are in general indicative for particular algal taxa and in some cases useful biochemical parameters for a classiciation of lower taxa even at the ordinal or the generic levels.

The influence of detergents on the Ca2+- and Mg2+-dependent adenosine triphosphatase of the sarcoplasmic reticulum

Abstract: During the stepwise solubilization of sarcoplasmic reticulum vesicles with detergents, the following changes in the structural and enzymatic properties of the preparation are observed: 1. The viscosity of the vesicular suspension initially rises. This change is accompanied by the formation of elongated tubules. Subsequently the membranes are completely desintegrated, resulting in a considerable reduction of the viscosity. 2. A decrease in the activity of the Ca²⁺-dependent ATPase, which is restored after complete solubilization. 3. A decrease in the change of intrinsic tryptophan-fluorescence on removal of calcium ions, which is also restored after complete solubilization. 4. A decrease of the calcium affinity of the ATPase. 5. A decrease in the amount of phosphorylated protein formed by the incorporation of inorganic phosphate. On the other hand, the amount of phosphoprotein formed from ATP is not affected during solubilization. 6. The dependence of the initial rates of phosphoprotein formation from inorganic phosphate on either magnesium or inorganic phosphate at low concentrations of the respective ligand changes from an S-shape profile to a normal hyperbolic profile after solubilization.

Volatile Compounds from Cephalic Secretions of Females in two Cleptoparasite Bee Genera, Epeolus (Hym., Anthophoridae) and Coelioxys (Hym., Megachilidae)

Abstract: Volatile cephalic secretions from females of four cleptoparasitic bee species, Epeolus cruciger (Pz.), E. variegatus, (L.) (Anthophoridae) and Coelioxys (Coelioxys) quadridentata (L.), C. (Schizocoelioxys) mandibularis Nyl. (Megachilidae) were analysed by combined gas chromatography/mass spectroscopy. There are considerable similarities between the two species within each genus, and also some qualitative correspondences between the two genera. The Epeolus species contain spiroacetals, 2-alkanols and pyrazines while the Coelioxys species contain spiroacetals, 3-alkanols and 3-ketones along with unsaturated alcohols. Two of the spiroacetals are first found in nature.

High-and Low-Affinity Binding of Photosystem II Herbicides to Isolated Thylakoid Membranes and Intact Algal Cells

Abstract: Abstract High- and low-affinity binding of photosystem II herbicides to isolated thylakoids of Spinacia oleracea and to intact cells of the unicellular green alga Ankistrodesmus braunii were investigated. Complete mutual displacement of bound diuron-type herbicides (e.g. diuron, atrazine, terbutryn) by either diuron- or phenol-type herbicides (e.g. ioxynil, dinoseb) in thylakoids as well as in intact algal cells was found for herbicide concentrations (< 4 nmol bound herbicide/mg Chl) which gave almost saturated high-affinity binding. This demonstrates a high degree of specific binding of these herbicides towards their receptor sites even in intact algal cells. In contrast, phenol-type herbicides are largely unspecifically bound in algal cells. The mechanism of binding of all photosystem II herbicides at the high-affinity (specific) binding site was found to be competitive. Within the group of diuron-type and of phenol-type herbicides as well as between these two groups, graphical and quantitative analysis of the Lineweaver- Burk plot and of the Dixon plot indicated competitive binding. From this a common binding site for both types of herbicides was concluded. The involvement of two different herbicide binding- proteins is discussed. Low-affinity (unspecific) binding was found to be irreversible in contrast to the easily reversible high-affinity binding. Irreversibility was indicated by a lack of displacement. It is proposed that low-affinity binding represents either a partitioning of the herbicides into the lipophilic parts of the membranes or an attachment to distinct receptor sites. Unspecifically bound herbicides might be responsible for several high concentration effects of the photosystem II herbicides, which are described in the literature. Evidences for the possible existence of a second binding site of these herbicides are presented.

Spatio-Temporal Visual Receptive Fields as Revealed by Spatio-Temporal Random Noise

Abstract: A means was devised to visualize the retinal receptive fields in time and space using the noise on unused television channels as spatio-temporal inputs and performing correlation between the input and output photographically. The method was applied to characterize the receptive fields of catfish retinal ganglion cells. The results were 1) there were two major types of receptive fields, circular and elliptical, 2) shapes and sizes of the field components changed with time (latency), and 3) a field's surround was often localized as hot spots.