Showing papers by "University of Freiburg published in 1979"

Phytochrome-induced appearance of mRNA activity for the apoprotein of the light-harvesting chlorophyll a/b protein of barley (Hordeum vulgare).

Abstract: Illumination of dark-grown barley plants induces a massive insertion of the light-harvesting chlorophyll u/b protein into the developing thylakoid membrane. Light induces specifically the appearance of mRNA activity for the apoprotein of this chlorophyll-binding protein [Apel, K. and Kloppstech, K. (1978) Eur. J. Biochem. 85, 581–588]. This change in mRNA activity can also be induced by a 15-s red light pulse followed by 4 h darkness. The red light effect is reversed by a subsequent far-red light treatment. It is concluded that the change in mRNA activity is controlled by phytochrome. In continuous white light the light-harvesting chlorophyll a/b protein appears within the membrane after a lag period of 4–5 h. This lag period could be partially eliminated by a red light pulse given prior to the onset of continuous illumination. The possible role of the phyto- chrome-induced appearance of mRNA activity as a rate-limiting step of the greening process is discussed. The light-harvesting chlorophyll a/b protein could not be detected among the plastid membrane proteins of plants which had been treated with a red light pulse alone. The assembly of the light-harvesting chlorophyll a/b protein takes place only under continuous illumination which allows chlorophyll synthesis. Thus, the synthesis and ultimate assembly of this chlorophyll-binding protein depends on the cooperation of two distinct light reactions.

Polymerization of diacetylenes in multilayers

Abstract: The synthesis of extended and oriented very thin layers of polymers by solid-state polymerization of multilayers built up from monomolecular films of suitable monomers by means of the Langmuir-Blodgett (LB) technique has been felt to be a particular challenge for a long time. Attempts to make use of radiation-induced free radical polymerization of long-chain vinyl derivatives have been successful only in part (1–5).

Nucleotide sequence of the transposable DNA-element IS2

Abstract: The complete sequence of the transposable DNA element IS2 in gal OP-308:: IS2 (I) has been determined. This element is 1.327 bp long. The integrated element is flanked by a five base pair long sequence duplication. The termini of IS2 are not perfect inverted repeats, but a close approximation.

Control of Seed Germination by Abscisic Acid: I. Time Course of Action in Sinapis alba L.

Abstract: The germination process of mustard seeds (Sinapis alba L.) has been characterized by the time courses of water uptake, rupturing of the seed coat (12 hours after sowing), onset of axis growth (18 hours after sowing), and the point of no return, where the seeds lose the ability to survive redesiccation (12 to 24 hours after sowing, depending on embryo part). Abscisic acid (ABA) reversibly arrests embryo development at the brink of radicle growth initiation, inhibiting the water uptake which accompanies embryo growth. Seeds which have been kept dormant by ABA for several days will, after removal of the hormone, rapidly take up water and continue the germination process. Seeds which have been preincubated in water lose the sensitivity to be arrested by ABA after about 12 hours after sowing. This escape from ABA-mediated dormancy is not due to an inactivation of the hormone but to a loss of competence to respond to ABA during the course of germination. The sensitivity to ABA can be restored in these seeds by redrying. It is concluded that a primary action of ABA in inhibiting seed germination is the control of water uptake of the embryo tissues rather than the control of DNA, RNA, or protein syntheses.

Lymphotropic papovaviruses isolated from African green monkey and human cells.

Abstract: A lymphotropic papovavirus was isolated from a lymphoblastoid cell line of African green monkey (AGM) cells which also contained a herpesvirus and a paramyxovirus-like agent. The papovavirus was analyzed by restriction endonuclease cleavage; its biochemical and serological crossreactivity with SV40 and host range have been determined. Thus far, only B-lymphoblasts of primate and human origin have been found to be susceptible to infection. Although more than 50% of the tested monkey sera were reactive with antigens of this virus, all human sera tested failed to react. Cleavage patterns and hybridization studies with the viral DNA indicate that the virus represents a novel member of the papovavirus group that is characterized by its lymphotropic host range. Papovavirus particles were also demonstrated in a human lymphoblastoid cell line (CCRF-SB) originally derived from a leukemic child. These cells revealed nuclear fluorescence when tested with human sera, but failed to react with AGM sera. Although characterization of this agent has not yet been completed, available evidence suggests that it represents another lymphotropic papovavirus which seems to be spread within the human population.

The social structure and ecology of elephant-shrews

Abstract: Zusammenfassung Formica rufa verfugt uber optische Orts- und Objektkenntnisse. Sie bevorzugt, unabhangig von der Art der Aufgliederung, in jedem Fall die jeweils geschlossenere Figur. Senkrechte Streifen werden waagrechten immer vorgezogen. Mit immer feineren, senkrechten und waagrechten Streifen wurde die Sehscharfe bestimmt. Sie betragt bei einer Leuchtdichte von 1,26 × 10−4 sb + 1% etwa 34′. Das physiologische Auflosungsvermogen ist also weit feiner als das morphologische. Fur die Bevorzugung senkrechter vor waagrechten Streifen geben wahrscheinlich senkrecht geordnete Reizwechsel den auslosenden Komplexreiz. Die Alternativen, gegliedert bzw. ungegliedert, senkrecht- bzw. waagrechtstreifig, sind fur das Formensehen der Insekten zwei unabhangige Variable, Versuche mit Eristalis tenax und Stenus bipunctatus legen nahe, das das Ansprechen auf bestimmte Streifenmuster als okologische Anpassung zu betrachten ist. Gegen die Spontanbevorzugung senkrechter Streifen ist keine Dressur moglich, wohl aber auf die starker gegliederte Figur. Beides sind also fur die Ameisen qualitativ verschiedene Formmerkmale. Summary Formica rufa shows optical recognition of objects and localities. It always prefers the more closed figure, independent of the nature of the articulation. Vertical stripes are always preferred to horizontal ones. The visual acuity was tested by making the vertical and horizontal stripes finer and finer. With a luminous flux of 1.26 × 10−4 sb + 1%, the acuity is about 34′. Thus the physiological resolution is much finer than the anatomical. Vertically arranged stimulation changes probably provide the key stimulus complex for the preference of vertical to horizontal stripes. The alternatives articulated-unarticulated and vertically-horizontally striped constitute two independent variables for the form vision of insects. Experiments with Eristalis tenax and Stenus bipunctatus suggest that preferences for particular stripe arrangements must be considered as ecological adaptations. The spontaneous preference for vertical stripes cannot be changed by training, but that for the less articulated figure can be reversed. Thus these are qualitatively different form properties for the ants.

Inhibition of carotenoid biosynthesis by the herbicide SAN 9789 and its consequences for the action of phytochrome on plastogenesis.

Abstract: Treatment of the mustard (Sinapis alba L.) seedling with the herbicide SAN 9789 inhibits synthesis of colored carotenoids and interferes with the formation of plastid membrane lipids without affecting growth and morphogenesis significantly. In farred light, which is hardly absorbed by chlorophyll, development of plastid ultrastructure, synthesis of ribulosebisphosphate carboxylase and synthesis of chlorophyll are not affected by SAN 9789. It is concluded that normal phytochrome actions on plastid structural development, protein and chlorophyll syntheses are not affected by the absence of carotenoids provided that there is no significant light absorption in chlorophyll. The findings show that the inhibition of synthesis of one set of plastid membrane components (the carotenoids) does not stop synthesis of other components such as chlorophyll and does not halt membrane assembly. Supplementary experiments with the closely related compound SAN 9785, which affects the amount and composition of plastid lipids but not carotenoid and chlorophyll syntheses, suggest that the effect of the herbicide SAN 9789 is due exclusively to its inhibition of synthesis of colored carotenoids. In the presence of SAN 9789 white or red light at high fluence rate causes photodestruction of chlorophyll and ribulosebisphosphate carboxylase and photodecomposition of thylakoids. These effects are interpreted as resulting exclusively from the self-photooxidation and photosensitizing action of chlorophyll once the protection by carotenoids of chlorophyll against self- and sensitized photooxidation is lost.

The independence of dynamic spatial orientation from luminance and refractive error

Abstract: The effect of refractive error and luminance on circularvection, the illusory sensation of self-motion resulting from rotation of the visual field, was determined. Neither reduction of luminance to levels near absolute scotopic threshold nor induced refractive errors of more than 16 diopters abolished circularvection or influenced any of its latency measures. The results are discussed in terms of the role of the peripheral visual field and the nature of the visual stimulus in ego orientation.

Pattern of activity of nucleolus organizers during spermatogenesis in mammals as analyzed by silver-staining.

Abstract: Silver-staining in the nuclei and chromosomes of spermatogenesis of four species of mammals (Man, Mus musculus, Rattus norvegicus, and Cavia cobaya) was investigated qualitatively and quantitatively. These species show a very similar pattern of activity of the nucleolus organizer regions (NORs) during the various stages of spermatogenesis. Silver precipitates are detectable in growing spermatogonia and up until the pachytene stage of meiotic prophase. During the meiotic metaphases I and II and during interkinesis silver-stainability disappears completely. A resumption of silverstainability occurs in round spermatids indicating a postmeiotic reactivation of NORs. This process does not persist beyond the early elongation phase. The quantitative determination of the silver-covered areas in relation to the total nuclear areas reveals minor differences between the species investigated with regard to the times and extents of maximum activation. The known localizations of the NORs in the karyotypes of the species investigated was confirmed using metaphase-preparations derived from somatic tissues.

Star-free regular sets of ω-sequences

Abstract: The sets of ω-sequences over a finite alphabet which are definable in an appropriate first-order language are characterized in terms of star-free regular sets of words. This settles a problem of Ladner (1977)Inform. Contr. 33, 281–303 .

Reaction of Azide Radicals with Amino Acids and Proteins

Abstract: SummaryThe azide radical N·3 reacts selectively with amino acids, in neutral solution preferentially with tryptophan (k(N·3 + TrpH) = 4·1 × 109 dm3 mol−1s−1) and in alkaline solution also with cysteine and tyrosine (k(N·3 + CyS−) = 2·7 × 109 dm3 mol−1s−1 and k(N·3 + TyrO−) = 3·6 × 109 dm3 mol−1s−1). Oxidation of the enzyme yADH by N·3 involves primary attacks, mainly at tryptophan residues, and subsequent slow secondary reactions. N·3-induced inactivation of yADH is likely to occur upon oxidation of tryptophan residues in the substrate binding pocket (58-TrpH and 93-TrpH) since the substrate ethanol, although unreactive with N·3, protects yADH and since elADH, which does not contain tryptophan in the substrate pocket, is comparatively resistant against N·3-attack. N·3 exhibits low reactivity with nucleic acid derivatives and it is inert towards aliphatic compounds such as methanol and sodium dodecylsulphate.

Flavanone Synthase from Petroselinum hortense

Abstract: Flavanone synthase from irradiated cell suspension cultures of parsley was purified to apparent homogeneity. Molecular weights of about 77000 for the enzyme and about 42000 for the subunits were determined respectively by sedimentation-equilibrium measurements and disc-gel electrophoresis in the presence of dodecyl sulfate. A specific antiserum was prepared for the enzyme and was used in an assay for flavanone synthase mRNA activity in partially purified RNA preparations. The apparent molecular size of flavanone synthase mRNA was estimated by sucrose gradient centrifugation and gel electrophoresis under partially denaturing conditions. Values of about 17 S and Mr= 0.62 × 106 were obtained. The fractionation patterns suggested that flavanone synthase mRNA was homogeneous in size. All together, the results support the idea that the enzyme is composed of two subunits which are probably identical. Amino acid analysis and a microbial assay were carried out to test the possible occurrence of cysteamine, β-alanine, and pantothenate in the enzyme. The results were negative, indicating the absence of pantetheine or a similar residue. The possible similarity in mechanism between flavanone synthase and 3-oxoacyl-(acyl carrier protein) synthase is discussed.

Hepatic Glutamine Metabolism under the Influence of the Portal Ammonia Concentration in the Perfused Rat Liver

Abstract: 1 l-Glutamine, when added to the portal perfusate in a system of isolated perfused rat liver (non-recirculating open system) at physiological concentration of 0.6 mM, does not lead to an extra production of urea and ammonia, but it does so when ammonium ions at physiological concentration of 0.3 mM are simultaneously present. This stimulatory effect of ammonium ions on glutaminase activity is readily reversible. The effect of portal ammonium ions is half-maximal at 0.2–0.3 mM and maximal at about 0.6 mM. 2 The maximal rate of production of urea-N plus ammonia from glutamine is exhibited at 10–12 mM glutamine, amounting to about 2.6 μmolxmin−1 xg wet weight−1. 3 The modulatory effects of ammonium ions on the disposition of glutamine by the liver were demonstrated (a) by the extra release of nitrogen from glutamine, (b) by the release of 14CO2 from [U-14C]glutamine, and (c) by measurement of glutamine uptake. 4 The simultaneous operation of glutamine synthetase and glutaminase activities in liver was demonstrated to exist (futile cycle), based on 14CO2 release from [U-14C]glutamine and the positive glutamine balance across the hepatic and portal veins, and further on the effects of methionine sulfoximine. This inhibitor of glutamine synthetase abolished net glutamine release and left the rate of 14CO2 relcase from [U-14C]glutamine unaltered. Moreover, there is an extra O2 uptake by the liver upon glutamine addition which is not accounted for by extra urea synthesis; the extra O2 uptake increases with the portal glutamine supply. An estimate of the rate of this futile cycle at 0.6 mM glutamine is given, approx. 0.1 μmol × min−1× g wet wt liver−1. 5 The stimulatory effect of portal ammonium ions on hepatic glutamine breakdown is discussed in terms of an inter-organ feed-forward mechanism, e. g. between small intestine and liver during conditions of increased glutamine supply and, therefore, increased requirement of glutamine removal from the circulation.

Quaternary Structure of Higher Plant Glyceraldehyde‐3‐Phosphate Dehydrogenases

Abstract: 1 NAD(P)+-induced changes in the aggregational state of prepurified NADP-linked glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) were used to isolate the enzyme from Spinacia oleracea, Pisum sativum and Hordeum vulgare. Each of the three plant species contains two separate isoenzymes. Isoenzyme 1 (fast moving during conventional electrophoresis) precipitates with the ammonium sulfate fraction 55–70% saturation. It shows two separate subunits in dodecylsulfate gels, which are probably arranged as A2B2 in the native enzyme molecule. Isoenzyme 2 (slow moving during conventional electrophoresis) precipitates with the ammonium sulfate fraction 70–95%. It contains a single subunit of the same Mr as subunit A in isoenzyme 1 and is apparently a tetramer (A4). The molecular weights of subunits A/B for spinach, peas and barley were determined as 38000/40000, 38000/42000 and 36000/39000 respectively. 2 The NAD-specific glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) was purified from Spinacia oleracea and Pisum sativum by affinity chromatography on blue Sepharose CL-6B. The enzyme from both plant species is shown to be a tetramer of subunits with Mr 39000. 3 The present findings contrast with heterogeneous results obtained previously by other authors. These results suggested that there are considerable interspecific differences in the quaternary structure of glyceraldehyde-3-phosphate dehydrogenases from higher plants.

Boundary structure and curvature of convex bodies

Abstract: One of the fascinating features of the theory of convex bodies is the wealth of substantial results that spring from the mere assumption of convexity. The present survey is concerned with the implications that convexity of a point set has on the structure of its boundary. We have tried to collect the known results which describe, or are connected with, local geometric properties of the boundary of a convex body. Some open problems in this field will also be mentioned.

XY gonadal dysgenesis and the H-Y antigen. Report on 12 cases.

Abstract: H-Y antigen was determined in 12 patients affected by XY gonadal dysgenesis. Of these, three proved to be H-Y negative, and nine, including two sisters, were H-Y positive; two of the unrelated positive cases exhibited a reduced antigen titer. Therefore, this clinical condition must be genetically heterogeneous. It is assumed that in the negative cases and possibly in those with reduced antigen titer, the H-Y generating system is affected by mutation, while in the regular positive cases the target cells are unable to respond due to a defect of the gonad-specific H-Y antigen receptor.

Bile salt binding to serum components. Taurocholate incorporation into high-density lipoprotein revealed by photoaffinity labelling.

Abstract: 1. Photoaffinity labelling of human serum albumin with the sodium salts of (3 beta-azido-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino[2(-3)H (N)]ethanesulfonic acid, (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino[2(-3)H (N)]ethanesulfonic acid and (11 zeta-azido-12-oxo-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino[2(-3)H (N)]ethanesulfonic acid resulted, in each case, in a considerable covalent incorporation of radioactivity into the protein. 2. Photoaffinity labelling of whole serum, obtained from fasting test persons, revealed with all three photolabile derivatives of taurocholate at the physiological concentration of 2.1 microM the incorporation of radioactivity not only into albumin but also into high-density lipoprotein, as demonstrated by density gradient centrifugation and by immunological characterization. 3. The bulk of radioactivity incorporated into high-density lipoprotein by photoaffinity labelling of whole serum was found to have been associated with the lipids. Only 10-20% of the label was covalently bound to apolipoproteins, predominantly to the apolipoproteins A-I and A-II. 4. The interaction of taurocholate with high-density lipoprotein has been confirmed by density gradient centrifugation using 14C-labelled taurcholate. It is assumed that the interaction of taurocholate with high-density lipoprotein is physiologically of significance.

DNA sequences and structural homologies of the replication origins of lambdoid bacteriophages

Abstract: The DNA sequences for the origins of replication of the lambdoid bacteriophages φ80, 434, φ21, and λimm21 (identical to φ21) have been determined and compared to the λ structure. Two presumptive elaborate binding sites for two initiator proteins have been identified in their outer sections, while a replicational primer start site seems to be located in their centres.

Charge transfer in peptides . Pulse radiolysis investigation of one-electron reactions in dipeptides of tryptophan and tyrosine

Abstract: SummaryOne-electron oxidation of TyrOH-TrpH or TrpH-TyrOH in aqueous solutions by N·3 radicals occurs predominantly at the tryptophyl residue. The corresponding indolyl radicals (absorbing at 510 nm) are subsequently transformed into phenoxyl radicals (absorbing at 390/405 nm): The first-order radical transformation rates are independent of the (initial) concentration of N·3 or peptide and unaffected by urea (as a modifier of hydrogen bond structures). Intermolecular conversion of indolyl into phenoxyl radicals, e.g. by reaction of GlyH-Trp· with TyrOH-GlyH, is very slow and inefficient. It is concluded that reactions (5) and (7) occur by intramolecular charge transfer across the peptide bond.

Investigation of the topochemical solid‐state polymerization of a diacetylene by X‐ray methods and brillouin‐spectroscopy

Abstract: The topochemical polymerization of the substituted diacetylene, 2,4-hexadiynylene bis(p-toluenesulfonate) (1), has been followed by X-ray crystallography and by determination of the elastic constants of polymerizing crystals. For the first time the crystal structure of a polymerizable diacetylene monomer has been solved and the coordinates of all atoms prior and after the reaction have been determined. The length of the growing polymer chains and their distribution in the monomer matrix can be determined by the evaluation of the Brillouin spectra in terms of a model which considers the polymerizing crystal as a composite material of high-modulus rod-like macromolecules dispersed in the low-modulus matrix of the residual monomer.