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Showing papers by "University of Hohenheim published in 1984"


Journal ArticleDOI
TL;DR: Favourable analytical conditions allowing amino acid analysis in biological fluids, acquired from small human biopsy specimens, were achieved by considering various derivatization methods, the mode of detection and the column used.

228 citations


Journal ArticleDOI
TL;DR: It can be assumed that the various types of root-induced acidification of the rhizosphere are of considerable ecological importance for the plant-soil relationships in general and for mobilization of mineral nutrients from sparingly soluble sources in particular.
Abstract: Proton extrusion by roots of intact sunflower plants ( Helianthus annuus L.) was studied in nutrient solutions or in agar media with a pH indicator. Proton extrusion was enhanced by either iron deficiency, addition of fusicoccin, or single salt solutions of ammonium or potassium salts. The three types of proton extrusion differ in both localization along the roots and capacity. From their sensitivity to ATPase inhibitors it seems justified to characterize them as proton pumps driven by plasma membrane APTases. Enhanced proton extrusion induced by preferential cation uptake from (NH 4 ) 2 SO 4 or K 2 SO 4 was uniformly distributed over the whole root system. In contrast, the enhancement effect of fusicoccin was confined to the basal root zones and that of iron deficiency to the apical root zones. Also the rates of proton extrusion per unit of root fresh weight differed remarkably and increased in the order: Fusicoccin ≪ K 2 SO 4 4 ) 2 SO 4 Under iron deficiency the average values of proton extrusion for the whole root system are 5.6 micromoles H + per gram fresh weight per hour; however, for the apical root zones values of about 28 micromoles H + can be calculated. This high capacity is most probably related to the iron deficiency-induced formation of rhizodermal transfer cells in the apical root zones. It can be assumed that the various types of root-induced acidification of the rhizosphere are of considerable ecological importance for the plant-soil relationships in general and for mobilization of mineral nutrients from sparingly soluble sources in particular.

205 citations


Journal ArticleDOI
13 Mar 1984-Nature
TL;DR: The longest continuous tree-ring chronology is based on the bristlecone pine (Pinus aristata and Pinus longaeva) growing in the White Mountains of California as discussed by the authors.
Abstract: Long tree-ring chronologies provide a unique calendrical record that is of value for archaeological dating, climatic and post-glacial studies. They also form a standard for the calibration of the radiocarbon time scale. The world's longest continuous tree-ring chronology is based on the bristlecone pine (Pinus aristata and Pinus longaeva) growing in the White Mountains of California1–3. The great age of living and sub-fossil trees of this species enabled a continuous tree-ring sequence of 8,681 years to be established, providing absolutely dated wood samples for the first radiocarbon calibration4,5. We have now established an unbroken west European tree-ring sequence spanning the past 7,272 years.

186 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented quantiques quantiques d'isomerisation trans-cis and cis-trans a 313 and 436 nm, respectively, for azobenzene.

156 citations


Journal ArticleDOI
TL;DR: A much higher zinc level was necessary to inhibit root elongation in the zinc tolerant ecotype as compared to the non-tolerant ecotype of Deschampsia caespitosa, consistent with a model of zinc tolerance in which zinc is complexed with citrate in the vacuole.

106 citations


Journal ArticleDOI
TL;DR: In this article, the effect of high tuber temperature (30 °C) on the growth rate and carbohydrate metabolism of tubers was studied with three cultivars differing in heat tolerance, and it was concluded that high soil temperatures may decrease starch content of potato tubers directly by inhibition of the conversion of sugars into starch.
Abstract: The effect of high tuber temperature (30 °C) on the growth rate and carbohydrate metabolism of tubers was studied with 3 cultivars differing in heat tolerance. Subjecting individual tubers to 30°C for 6 days caused cessation of tuber growth. During this period, non-treated tubers (20°C) on the same plant increased in volume. At 30°C, incorporation of14C-labelled assimilates into the ethanol-insoluble fraction (mainly starch) as well as the starch content was significantly reduced. In contrast, the incorporation of14C-labelled assimilates into the sugar fraction was not affected by high tuber temperature. At 30°C the activity of some of the enzymes involved in starch metabolism was depressed. Varietal differences in responses of tuber growth rate and carbohydrate metabolism to high tuber temperature were insignificant. From these preliminary results it is concluded that high soil temperatures may decrease starch content of potato tubers directly by inhibition of the conversion of sugars into starch.

103 citations


Journal ArticleDOI
TL;DR: A number of polypeptide antibiotics of the peptaibol class, i.e., trichotoxin, alamethicin, suzukacillin, hypelcin and paracelsin, have been separated into components and isolated by high-performance liquid chromatography on spherical, porous octadecylsilyl bonded phases.

103 citations


Journal ArticleDOI
TL;DR: Neocortical areas, which are rich in gray matter, have a four‐ to fivefold higher ganglioside content than white matter‐rich samples such as optic chiasm, capsula interna, or corpus callosum, while all diencephalic nuclei tend to favor slightly “b‐gangliosides,” while the mesencephalicuclei are very heterogeneous in their gangLioside composition.
Abstract: Forty different brain samples, consisting of neocortical, archicortical, and paleocortical areas; telencephalic, diencephalic, and mesencephalic subcortical nuclei; and the cerebellum as well as some of the corresponding white matter bundles were analyzed with respect to total content of ganglioside-sialic acid and the ganglioside pattern. The total content of gangliosides seems to depend mainly on the proportions of gray and white matter. Thus, neocortical areas, which are rich in gray matter, have a four- to fivefold higher ganglioside content (per milligram of protein) than white matter-rich samples such as optic chiasm, capsula interna, or corpus callosum. White matter-rich regions, although very heterogeneous in ganglioside composition, are further characterized by appreciable amounts of the myelin-enriched GM4. In the neocortex a remarkable degree of regional pattern differences was revealed. In the frontal and parietal areas there is a moderate, and in the temporal region a strong preponderance of sialic acid bound to gangliosides of the a-pathway (GD1a, GM1). In contrast, the occipital cortex favors the b-pathway of ganglioside synthesis (GQ1b, GT1b, GD1b). A predominance of “b-gangliosides” was found in all structures that are related to the visual system (optic chiasm, pulvinar-thalamus, superior colliculi, visual cortex) as well as in the cerebellum and the nucleus ruber. All diencephalic nuclei tend to favor slightly “b-gangliosides,” while the mesencephalic nuclei are very heterogeneous in their ganglioside composition. A preponderance of “a-gangliosides” was found in the periamygdalar cortex, putamen, inferior colliculi, substantia nigra, frontal white matter, internal capsule, globus pallidus, basal nucleus of Meynert, and corpus callosum as well as in the frontal, parietal, and temporal cortices. An exceptional predominance of GM1 and GD1a was revealed for the hippocampal archicortex and the amygdala, suggesting a possible functional correlation to glutaminergic synaptic transmission.

85 citations


Journal ArticleDOI
TL;DR: This result clearly shows, that 4-chlorobenzoate dehalogenase catalyzes the hydrolytic cleavage of the halogen-carbon bond, without the involvement of molecular oxygen, a reaction not yet described.

84 citations




Journal ArticleDOI
TL;DR: The very recently accomplished sequence determination of paracelsin allows the discussion of the results with regard to the closely related analogues, alamethicin and suzukacillin, of the peptaibol class, exhibiting various kinds of biological activity.
Abstract: Paracelsin, a hemolytic and membrane active polypeptide antibiotic of the peptaibol class which is excreted by the moldTrichderma reesei, was obtained by a simplified and isolation procedure utilziing hydrophobic adsorber resin. Investigation by13C nuclear magnetic resonance spectroscopy and circular dichroism revealed considerable helical portions in solution, and the very recently accomplished sequence determination of paracelsin allows the discussion of the results with regard to the closely related analogues, alamethicin and suzukacillin. A selective cleavage of the peptide was achieved by careful treatment with various acids, and a buffer of pH 8.25 and of high ionic strength made possible the quantitative determination of the C-terminal phenylalaninol released by means of ion-exchange chromatography. The significance of the production of paracelsin and related mycotoxins of the peptaibol class, exhibiting various kinds of biological activity, is discussed with respect to the extensive effort being made towards biotechnological applications of species, strains and cellulolytically highly active mutants of the fungusTrichoderma.

Journal ArticleDOI
01 Aug 1984
TL;DR: The absorption and fluorescence spectra of all isomeric hydroxyflavones and methoxyflavone, except for the photolabile 3-methoxyflava, have been measured in organic solvents and in aqueous solutions of various acidity as mentioned in this paper.
Abstract: The absorption and fluorescence spectra of all isomeric hydroxyflavones and methoxyflavones, except for the photolabile 3-methoxyflavone, have been measured in organic solvents and in aqueous solutions of various acidity. With the exception of 5-hydroxyflavone, all are found to be fluorescent in methanol and water solution. On the other hand, there is virtually no fluorescence observed in cyclohexane solution, a fact that is interpreted in terms of high intersystem crossing rates and the El-Sayed selection rules. – Except for the 3-hydroxy and 7-hydroxy isomers, the anions of hydroxyflavones are non-fluorescent, whereas the protonated forms exhibit strong fluorescence emission. Methoxyflavones have higher fluorescence quantum yields than the corresponding hydroxyflavones and have fluorescence decay times ranging from 1.3 to 6.9 ns in methanol at room temperature. – The ground state pKa values of the hydroxyflavones range from 7.8 to 9.8, except for the 5-hydroxy isomer (11.6). The pKa's governing the protonation step range from – 1.22 to – 1.55, again with the exception of the 5-hydroxy isomer (– 3.1). The dissociation constants of the first excited singlet state were calculated with the help of the Forster-Weller equation. The results predict a reversal of the most basic and most acidic sites of the hydroxyflavones. In aqueous solutions, this should result in the formation of excited state tautomers which, however, could be detected only for the 3-hydroxy and 7-hydroxy isomers. Apparently, the lifetimes of the other isomers are too short to allow the establishment of excited state equilibria.

Journal ArticleDOI
TL;DR: The results with ripened, AVG-treated apples indicate a dose-response relationship between ethylene and enhancement of ACC synthase activity with a half-maximal response at approximately 0.8 mul/l ethylene; a reversal of ethylene-enhanced ACC synthases activity by CO(2); and a enhancement ofACC synth enzyme activity by the ethylene/CO(2) analog propylene.
Abstract: Apples (Malus sylvestris Mill, cv Golden Delicious) were treated before harvest with aminoethoxyvinylglycine (AVG). AVG is presumed to reversibly inhibit 1-aminocyclopropane-1-carboxylic acid (ACC) activity, but not the formation of ACC synthase. AVG treatment effectively blocked initiation of autocatalytic ethylene production and ripening of harvested apples. Exogenous ethylene induced extractable ACC synthase activity and ripening in AVG-treated apples. Removal of exogenous ethylene caused a rapid decline in ACC synthase activity and in CO(2) production. The results with ripened, AVG-treated apples indicate (a) a dose-response relationship between ethylene and enhancement of ACC synthase activity with a half-maximal response at approximately 0.8 mul/l ethylene; (b) reversal of ethylene-enhanced ACC synthase activity by CO(2); (c) enhancement of ACC synthase activity by the ethylene-activity analog propylene.Induction of ACC synthase activity, autocatalytic ethylene production, and ripening of preclimacteric apples not treated with AVG were delayed by 6 and 10% CO(2), but not by 1.25% CO(2). However, each of these CO(2) concentrations reduced the rate of increase of ACC synthase activity.

Journal ArticleDOI
TL;DR: The findings suggest that gastric emptying is controlled by the depth of the antral waves, the pyloric opening, the receptive relaxation of the duodenum and the type of theduodenal contractions.
Abstract: The aim of this study was to determine the mechanisms controlling gastric emptying of viscous meals. In four conscious dogs the antral, pyloric and duodenal activities were recorded with strain-gauge transducers and induction coils during gastric evacuation of an inert cellulose meal and of four nutrient meals containing mannitol, casein, glucose or oleic acid. Gastric emptying and the internal pyloric and duodenal diameters were measured from radiographs. The nutrients delayed gastric emptying and diminished to a various extent the antral and duodenal motility as well as the pyloric opening. The motility gradient between antral and duodenal activity showed no relationship to the emptying delay. The duodenal lumen was reduced and the propulsive contractions of the duodenum decreased while the segmental activity increased. The findings suggest that gastric emptying is controlled by (1) the depth of the antral waves, (2) the pyloric opening, (3) the receptive relaxation of the duodenum and (4) the type of the duodenal contractions. By contrast the sequence of the terminal antral contraction and the pyloric closure, as well as the co-ordination between pyloric and duodenal contractions, played no important role in regulating gastric emptying.

Journal ArticleDOI
TL;DR: With high probability the effects observed have been at least partly due to bacterial N2-fixation, because the N-yield of the grains was increased, and the most pronounced response was found on sand without any N-fertilizer added.
Abstract: Spring wheat (Triticum aestivum var. Arkas) was associated withAzospirillum lipoferum under greenhouse and field conditions of a temperate region. Controls were treated with autoclaved bacteria. The soils used were: sand, sandy loam, and a peat-clay mixture. In experiments run over a period of three years, there were increases in grain yield, N-yield of the grains, and 1000 grain weight. Depending from environmental conditions, increase changed from year to year, and within one given year. There was, however, no experiment without positive response to the inoculation. Highest grain yield increase (70%) was found on sand supplemented with P and K only, but up to 32% were also obtained on peat-clay soil containing 0.28% total N. Under greenhouse conditions, one third of technical N-fertilizer could be saved by bacterial activities. With high probability the effects observed have been at least partly due to bacterial N2-fixation, because the N-yield of the grains was increased (up to 33%), and the most pronounced response was found on sand without any N-fertilizer added.

Journal ArticleDOI
TL;DR: The versatility of the methods described is demonstrated with the detection and sequence determination of the new membrane-altering eicosapeptide named gliodeliquescin A from the soil fungus establishing the occurence of peptaibols in that fungal genus for the first time.
Abstract: A rapid and simple detection procedure of Aib-containing “peptaibol” polypeptide antibiotics (mycotoxins) in fungal culture broths is described which employs alkylsilica (Sep-Pak®) cartridges for a selective enrichment, and the utilization of the unusualα-aminoisobutyric acid (Aib) and amino alcohols as specific marker constituents, which are easily detectable in total hydrolysates. Preparative isolations from fermentation broths is facilitated by adsorber resin (XAD) column chromatography, and purification of crude isolates is achieved by silica gel- and sephadex LH-20 chromatography. Preparative HPLC using spherical, totally porous ODS-bonded phases enables the isolation of uniform peptides, completely free of sequence analogs, from microheterogeneous peptaibol mixtures, and analytical HPLC of highest resolution allows a “fingerprint” assignment of microheterogeneous peptaibols of different fungal origin. Fast atom bombardment mass spectrometry is demonstrated to be a rapid and precise method for the complete sequence determination of peptaibols when employing sophisticated liquid matrix systems including both, lipophilic tetraethylenglycol and hydrophilic glycerol combined with a selective, trifluoroacetolytic cleavage step carried out directly “on target” (in situ). The versatility of the methods described is demonstrated with the detection and sequence determination of the new membrane-altering eicosapeptide named gliodeliquescin A from the soil fungusGliocladium deliquescens NRRL 3091 establishing the occurence of peptaibols in that fungal genus for the first time.

Journal ArticleDOI
TL;DR: Most important for the FAB mass spectral analysis of the extremely hydrophobic polypeptides was the development of oligoethylene-glycols and -glycol ethers as suitable liquid matrix systems, yielding high sensitivity and structurally significant fragment ions of high abundance.
Abstract: Specific and sensitive procedures have been developed which enabled the structure elucidation of the polypeptide antibiotics (peptaibols), paracelsin isolated from Trichoderma reesei, and of trichotoxin A-50 from Trichoderma viride, by fast atom bombardment and field desorption mass spectrometry. Both peptides were found to exhibit a pronounced microheterogeneity by single and multiple exchange of amino acids. Separation by analytical and semipreparative high-performance liquid chromatography (HPLC) on octadecylsilyl-bonded, reversed-phase columns afforded a series of sequence analogues for each polypeptide. Unequivocal molecular weight and sequence identifications were obtained by positive and negative ion fast atom bombardment (FAB), and field desorption (FD) mass spectrometry, in combination with a single, selective acidolytic cleavage step. Most important for the FAB mass spectral analysis of the extremely hydrophobic polypeptides was the development of oligoethylene-glycols and -glycol ethers as suitable liquid matrix systems, yielding high sensitivity and structurally significant fragment ions of high abundance. At these conditions, the positive ion FAB mass spectra exhibit regular abundant sequence ions with acylium end groups by peptide bond cleavage from the N-terminus, which provided direct sequence determinations for 13 of 20 residues of paracelsin, and for 12 of 18 residues of trichotoxin A-50. The sequence-specific fragmentation precisely continues up to, and ends at the preferential acidolytic cleavage sites (Pro residues). The remaining C-terminal sequence data was obtained by FD and FAB mass spectra of prolyl-hexa- and -heptapeptaibols produced by acidolytic cleavage in situ with aqueous trifluoroacetic acid. In contrast to the original polypeptides, glycerol as a polar matrix was most suitable for the analysis of prolylpeptaibol fragments in the hyrolysis mixture. By contrast, treatment of paracelsins and trichotoxins A-50 with trifluororacetic acid under anhydrous conditions yielded the corresponding trifluoroacetylated polypeptide derivatives which served to ascertain the position of the C-terminal amino alcohol residues. With this procedure, the structures of 14 closely related, partially isobaric sequence analogues of trichotoxin A-50, and of four sequence analogues of paracelsin were determined with amounts of material in the low nanomole range, which provide an exact pattern of the variable and the conservative sequence areas for these polypeptides.

Journal ArticleDOI
TL;DR: A new gram-positive filamentous bacterium with coccoid cells has been isolated from bulking sludge from five sewage treatment plants in West-Germany and is classified as a new genus and species of the family Streptococcaceae.
Abstract: A new gram-positive filamentous bacterium with coccoid cells has been isolated from bulking sludge from five sewage treatment plants in West-Germany. The characteristics of five strains are described. Their fatty acids and cell wall composition are similar to the Streptococcaceae and they mainly degrade monomeric and dimeric carbon sources. They are classified as a new genus and species of the family Streptococcaceae: Trichococcus flocculiformis gen. nov. sp. nov.

Journal ArticleDOI
TL;DR: In this article, the involvement of light in nest-site selection by domestic fowls was tested in two strains of laying hens at two stages of maturity, and the results suggest that light intensity is not a fundamental factor influencing nest site selection.

Journal ArticleDOI
TL;DR: The influence of ABA following anthesis was limited to an indirect effect on grain number through reductions in sucrose uptake, although grain number was not as sensitive to the sucrose supply at this time as it was at meiosis.
Abstract: Using detached ears of wheat cultured in nutrient solution the effect of sucrose and ABA supply on grain number was examined. In ears detached prior to ear emergence, to correspond with the time of pollen mother cell meiosis, higher levels of sucrose uptake were associated with higher grain number per ear. ABA indirectly caused a reduction in grain number by decreasing uptake of sucrose through decreasing stomatal conductance and transpiration. There was possibly also a direct effect of ABA on grain number. At higher levels of ABA the negative effect on grain number was decreased by increasing the sucrose concentration. In ears detached one to three days after anthesis grain number was also influenced by the amount of sucrose taken up, although grain number was not as sensitive to the sucrose supply at this time as it was at meiosis. The influence of ABA following anthesis was limited to an indirect effect on grain number through reductions in sucrose uptake.

Journal ArticleDOI
TL;DR: In this article, the main results of an empirical research project dealing with the prognosis and surveillance of corporate credit risks were reported, where quantitative (balance sheet analysis, current accounts data analysis) and qualitative (assessment of management) methods were applied.
Abstract: This paper reports the main results of an empirical research project dealing with the prognosis and surveillance of corporate credit risks. In the course of the research programme both quantitative (balance sheet analysis, current accounts data analysis) and qualitative (assessment of management) methods were applied. Each of the three parts of the project is independently usable However, the combined application of the three approaches avoids deficiencies of using only one of the components and improves the early detection of credit risks.



Journal ArticleDOI
TL;DR: Betacyanin-forming callus of the red-flowering Portulaca grandiflora, Hook, is shown to contain dopamine, adrenaline, noradrenaline, and epinine, and the synthesis of dopamine via DOPA can be demonstrated by the use of inhibitors.

Journal ArticleDOI
TL;DR: In this article, a collodion film was used to extract the epicuticular wax from the adaxial leaflet side of blackberry (Rubus fruticosus).

Journal ArticleDOI
TL;DR: Experiments indicate that the biosynthesis of factor III in the “archaebacterium” M. barkeri is similar to the corrinoid biosynthesis in the anaerobic “eubacteria” Eubacterium limosum, Clostridium barkeri, and Clostridgeium thermoaceticum.
Abstract: Exogenous 5-hydroxy-[2-14C]benzimidazole was transformed by Methanosarcina barkeri into 5-hydroxy-[2-14C]benzimidazolylcobamide. Thereby the endogenous biosynthesis of 5-hydroxybenzimidazole was completely blocked.

Journal ArticleDOI
H. Hörnicke1, G. Ruoff1, Barbara Vogt1, W. Clauss1, H.-J. Ehrlein1 
TL;DR: The close link between caecatrophy and caecal contractions can, however, be upset by either time-restricted feeding or by fasting, and all 3 functions seem to depend on the same circadian clock.
Abstract: In rabbits kept under 12:12 h light conditions, caecal contractions were recorded by implanted strain gauges or induction coils. In animals fed ad libitum caecal contraction frequency varied cyclically in phase with the circadian rhythm of feed intake. Both had their minimum during the time of soft faeces production. Thus all 3 functions seem to depend on the same circadian clock. The close link between caecotrophy and caecal contractions can, however, be upset by either time-restricted feeding or by fasting.


Journal ArticleDOI
TL;DR: A remarkable dissociating influence of serotonin on ganglioside-Ca2+ and phosphatidylserine- Ca2+ complexes is observed and the possible functional role of phospholipids andgangliosides in vivo is discussed with regard to the specific Ca2-binding properties of these lipids.