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1.
Silvia Konetschny-Rapp Günther Jung Hans-Georg Huschka Günther Winkelmann 《Biometals》1988,1(2):90-98
Summary The plant pathogenic hyphomyceteBotrytis cinerea has been shown to produce several trihydroxamate siderophores under conditions of low-iron stress. The total siderophores amounted to approximately 30 mg/l culture filtrate after 5 days of incubation in an asparagine/salt/glucose medium. Thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) on a reversed phase indicated that ferrirhodin is the predominant siderophore of this fungus. Chemical characterization of the principal siderophore by fast-atom-bombardment (FAB) mass spectrometry, nuclear magnetic resonance (1H-NMR,13C-NMR) and comparison with a reference revealed the identity with ferrirhodin. NMR studies performed on desferrirhodin (desferrirhodin) in dimethylsulfoxide and water revealed the existence of two conformers in D2O resulting from acis-trans isomerization of the hydroxamic acid groups. Comparative iron-uptake studies showed the following order of uptake inB. cinerea: ferrichrysin (100%), ferrirubin (57%), ferrirhodin (45%), hexahydroferrirhodin (45%), coprogen 6%. Concentration-dependent uptake of ferrirhodin resulted in saturation kinetics only in the low concentration range of 0–30 M (K
m = 2.5 M,V
max = 80 pmol min–1 mg(–1). A non-saturable, linear uptake was observed in the high concentration range of 30–80 M. The low concentration range appears to be the physiologically significant range, where siderophore-mediated iron transport inB. cinerea occurs. 相似文献
2.
Production of extracellular enzymes by Thermomonospora curvata during growth on protein-extracted lucerne fibres 总被引:1,自引:1,他引:0
After extraction of food protein from lucerne, the residual fibre was used as a carbon and energy source by the thermophilic actinomycete, Thermomonospora curvata. Induction of catabolic exoenzymes during growth for 7 d on the fibre at 53°C in a mineral salts minimal medium was compared with that on a variety of other inductive substrates. A fibre concentration of 1.5% (w/v) was optimal for total protein secretion. The fibre was a poor substrate for amylase production due to lack of inducer rather than to catabolite repression by soluble sugars released during degradation. β-Glucosidase release during growth on the fibre was about 10 times that observed in cultures grown on cellobiose or cellulose, but production of other cellulolytic enzymes was about one-half that produced on cellulose. Pectinolytic activity (measured as polygalacturonate lyase) was equal to that produced on pectin. Cells grown on the fibre released about eight times as much proteinase as those grown on cellulose, but proteolytic activity was transient and decreased rapidly during later growth. Xylanase appeared to be co-ordinately induced with cellulolytic enzymes; comparable maximal activities, observed during growth on either the fibre or cellulose, were three times that produced on xylan or xylose. 相似文献
3.
Hartmut Böhm Hans-Georg Heinzel Hans Scharstein Gernot Wendler 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(6):671-683
The wind-orientated walk of carrion beetles Necrophorus humator F. was analysed under closed-loop conditions with a walking compensator and under openloop conditions with a paired tread wheel (Fig. 1).
相似文献
1. | On the walking compensator an animal runs stable courses with a preferred direction relative to an air current (velocity =; 100 cm/s, Fig. 2B-D). A change in the air-current direction causes a corresponding adjustment of the mean walking direction (Fig. 3). Such course adjustment works best for changes in the air-current direction by an absolute value of 90° (Table 2). |
2. | Under closed-loop conditions the animal shows deviations of less than ± 45° around its preferred direction relative to the wind (Fig. 2B-D). The characteristic curve which describes the animal's angular velocity as a function of the animal's walking direction relative to the air-current stimulus is therefore revealed only in this angular range (Fig. 3, top). |
3. | Under open-loop conditions, however, complete characteristic curves can be obtained because the animal's walking reaction in response to any given angle of air-current stimulus is measurable on the paired tread wheel (Fig. 4). The characteristic curves are approximately sinusoidal functions. They can either show a shift parallel to the ordinale by a superimposed direction-independent constant angular velocity alone or, at the same time, they can independently exhibit an angular shift along the abscissa (Fig. 5). |
4. | The walking tracks straighten with increasing air-current velocity (Fig. 6A, insets), i.e. the animal more rapidly compensates deviations from a preferred course. This corresponds to higher amplitudes of the characterisic curve and steeper slopes at the negative zero-crossing point under open- as well as under closed-loop conditions (Fig. 6). |
5. | Walking in an air-current field can be explained by a model of the course control system using a feedback loop (Fig. 7). This model operates according to a sinusoidal characteristic function on which is superimposed a Gaussian white noise process of angular velocity which is independent of walking direction. The model produces realistic walking tracks in an air-current field (Fig. 8). |
4.
The multicatalytic proteinase from rat skeletal muscle, a non-lysosomal high molecular weight enzyme active at neutral to alkaline pH, has been examined in the electron microscope as well as by dynamic laser light scattering. Both methods reveal monodisperse particles. Electron micrographs show a cylinder-shaped complex with a diameter of 11 nm and a length of 16 nm in negatively stained, and a diameter of 9.6 nm and a length of 14.3 nm in freeze-dried, heavy metal replicated specimens. The molecule is composed of four rings or disks. 相似文献
5.
Hans-Georg Herbig 《Pal?ontologische Zeitschrift》1986,60(3-4):189-225
Limestone pebbles of the post-lower Bashkirian Marbella Formation (Malaguides, Internal Zone of the Betic Cordillera) yielded sixteen species of rugose corals belonging to eleven genera and two species of heterocorals belonging to two genera. The fauna is of uppermost Viséan age (V3b-V3c). Its paleogeographic significance within the western Mediterranean is discussed. Lonsdaleia corbariensis, known up to now only from debris flow deposits of the Mouthoumet massif (Southern France), covers approximately half of the total fauna.Hexaphyllia mirabilis is shown to have juvenile stages with five septa. 相似文献
6.
Induction of autolysis of staphylococci by the basic peptide antibiotics Pep 5 and nisin and their influence on the activity of autolytic enzymes 总被引:12,自引:0,他引:12
Pep 5 and nisin are cationic bactericidal peptides which were shown to induce autolysis in Staphylococcus cohnii 22. In contrast to nisin, Pep 5 induced lysis could be stimulated in the presence of glucose. Addition of lipoteichoic acids (LTA) (d-alanine:phosphorus=0.475:1) inhibited all effects of Pep 5 on susceptible cells in a molar ratio LTA:Pep 5 of 10:1. Treatment of S. cohnii 22 with Pep 5 or nisin for 20 min and subsequent washing with 2.5 M NaCl released autolysin activity. Crude preparations of the hydrolyzing enzymes produced free amino groups as well as polysaccharide fragments from the murein backbone, suggesting the presence of a muramidase or glucosamidase, and endopeptidase or amidase. Both enzyme activities were inhibited by lipoteichoic acid; they could be fully reactivated by addition of Pep 5 in sufficient concentrations. The velocity of hydrolysis was not influenced by nisin, whereas it was doubled in presence of Pep 5. The results are discussed in view of a possible mechanism of induction of lysis by Pep 5 and nisin.Abbreviations A.U.
arbitrary unit
- CCCP
carbonylcyanide-m-chlorophenyl hydrazone
- DNase
deoxyribonuclease
- CYG
casein yeast extract glucose
- IT
initial turbidity
- LTA
lipoteichoic acid
- RNase
ribonuclease
- TSB
Tryptone Soy Broth 相似文献
7.
The effects of sodium tetradecyl sulfate (STS), β-phenethyl alcohol (PEA), and p-nitrophenylglycerol (PNPG) on motility, swarming, flagellation, and growth of Proteus were examined. Growth-inhibitory concentrations (GIC) and swarming-inhibitory concentrations (SIC) were determined. A characterization of the swarming-inhibitory efficacy of these compounds was based on their GIC/SIC ratio and their concentration inhibition curves. Using the homologous series of sodium alkyl sulfates as a standard reference, we showed that PNPG was more effective than STS, which was the most effective of the homologous series. PEA was less effective than sodium decyl sulfate but more effective than sodium octyl sulfate. Motility tests in liquid medium and electron microscope investigations indicated that the modes of action of the three compounds, all of which effectively inhibit the swarming of Proteus, are different. Whereas STS and PEA inhibit swarming by inhibition of motility, PNPG seems to act on the swarming mechanism sensu strictori, without impairment of motility. STS immobilizes by inhibition of flagellum formation or by some lytic action on the flagella already synthesized. PEA acts by impairing flagellar function, but leaves the flagella morphologically intact. 相似文献
8.
Inhibition of Swarming of Proteus by Sodium Tetradecyl Sulfate, beta-Phenethyl Alcohol, and p-Nitrophenylglycerine
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The effects of sodium tetradecyl sulfate (STS), β-phenethyl alcohol (PEA), and p-nitrophenylglycerol (PNPG) on motility, swarming, flagellation, and growth of Proteus were examined. Growth-inhibitory concentrations (GIC) and swarming-inhibitory concentrations (SIC) were determined. A characterization of the swarming-inhibitory efficacy of these compounds was based on their GIC/SIC ratio and their concentration inhibition curves. Using the homologous series of sodium alkyl sulfates as a standard reference, we showed that PNPG was more effective than STS, which was the most effective of the homologous series. PEA was less effective than sodium decyl sulfate but more effective than sodium octyl sulfate. Motility tests in liquid medium and electron microscope investigations indicated that the modes of action of the three compounds, all of which effectively inhibit the swarming of Proteus, are different. Whereas STS and PEA inhibit swarming by inhibition of motility, PNPG seems to act on the swarming mechanism sensu strictori, without impairment of motility. STS immobilizes by inhibition of flagellum formation or by some lytic action on the flagella already synthesized. PEA acts by impairing flagellar function, but leaves the flagella morphologically intact. 相似文献
9.
Immunohistochemical absence of adrenergic neurons in the dorsal part of the solitary tract nucleus in sudden infant death 总被引:1,自引:0,他引:1
F Chigr M Najimi D Jordan L Denoroy J Pearson M Tommasi R Gilly N Kopp 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1989,309(12):543-549
The immunohistochemical distribution of TH and PNMT containing neuronal elements was investigated utilizing peroxidase anti-peroxidase methods in newborn control and sudden infant death syndrome (SIDS) brainstems. The TH immunoreactive neurons, within the medulla oblongata, displayed a similar distribution in both control and SIDS tissue. However, PNMT immunoreactive neurons seen in the dorsal part of the nucleus of tractus solitarius in control tissue were not observed in SIDS tissue. This alteration of adrenergic neurons in the dorsal part of NTS (region reported to be implicated in the control of blood pressure and respiration) could explain the cardiorespiratory disorders in SIDS. 相似文献
10.
Agonist-induced desensitization of cholinergically stimulated phosphoinositide breakdown is independent of endogenously activated protein kinase C in HT-29 human colon carcinoma cells. 总被引:1,自引:0,他引:1
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Activation of M3 muscarinic receptors in HT-29 cells by carbachol rapidly increases polyphosphoinositide breakdown. Pretreatment of these cells with carbachol (0.1 mM) for 5 h completely inhibits the subsequent ability of carbachol to increase [3H]inositol monophosphate ([3H]InsP) accumulation, paralleled by a total loss of muscarinic binding sites. In contrast, protein kinase C (PK-C)-mediated desensitization by incubation with phorbol esters [PMA (phorbol 12-myristate 13-acetate)], leading to a time- and dose-dependent inhibition of cholinergically stimulated InsP release (95% inhibition after 4 h with 0.1 microM-PMA), is accompanied by only a 40% decrease in muscarinic receptor binding, which suggests an additional mechanism of negative-feedback control. Neither carbachol nor PMA pretreatment had any effect on receptor affinity. Incubation with carbachol for 15 min caused a small increase of membrane-associated PK-C activity (15% increase, P less than 0.05) as compared with the potency of phorbol esters (PMA) (3-4-fold increase, P less than 0.01). Long-term incubation (4-24 h) with PMA resulted in a complete down-regulation of cytosolic and particulate PK-C activity. Stimulation of InsP release by NaF (20 mM) was not affected after a pretreatment with phorbol esters or carbachol, demonstrating an intact function of G-protein and phospholipase-C (PL-C) at the effector side. Determination of PL-C activity in a liposomal system with [3H]PtdInsP2 as substrate, showed no change in PL-C activity after carbachol (13 h) and short-term PMA (2.5 h) pretreatment, whereas long-term preincubation with phorbol esters (13 h) caused a small but significant decrease in PL-C activity (19%, P less than 0.05). Our results indicate that agonist-induced desensitization of phosphoinositide turnover occurs predominantly at the receptor level, with a rapid loss of muscarinic receptors. Exogenous activation of PK-C by phorbol esters seems to dissociate the interaction between receptor and G-protein/PL-C, without major effects on total cellular PL-C activity. 相似文献