In memoriam Friedrich Krüger (1902–1982)

Ohne Zusammenfassung     

Characterization of the plasma-membrane-bound nitrate reductase in Chlorella saccharophila (Krüger) Nadson

The plasma membranes of Chlorella saccharophila (Krüger) Nadson cells contained a membrane-bound nitrate reductase. This form of nitrate reductase was purified and characterized. Several differences from the soluble form of nitrate reductase were apparent, the most important being: (i) the greater hydrophobicity, as proven using Triton X-114 phase separation, hydrophobic interaction chromatography and stimulation by phosphilipids; (ii) the differences in the native molecular mass compared with Chlorella sorokiniana (Krüger) Nadson; and (iii) the different polypeptide pattern obtained by two-dimensional polyacrylamide gel electrophoresis. Only the plasma-membrane-bound nitrate reductase could be found in both inside-out and right-side-out plasma-membrane vesicles.Abbreviations HIC hydrophobic interaction chromatography - IEF isoelectric focusing - MV methyl viologen - NR nitrate reductase - PM plasma membrane - PMNR plasma-membrane-bound nitrate reductase - SDS-PAGE sodium dodecyl sulfatepolyacrylamide gel electrophoresis This work is part of the Ph.D. Thesis of Christine Stöohr, University of Göttingen. This work was supported by the Deutsche Forschungsgemeinschaft.     

Glycosyl-phosphatidylinositol-anchored proteins exist in the plasma membrane of Chlorella saccharophila (Krüger) Nadson: Plasma-membrane-bound nitrate reductase as an example

Experiments with plasma-membrane vesicles were performed in order to identify the attachment of hydrophobic nitrate reductase at the plasma membrane of Chlorella saccharophila. The enzyme was successfully removed from the plasma membrane with phosphoinositol-specific phospholipase C, and showed cross-reactivity with a monoclonal antibody (clone aGPI-3) raised against the glycosyl-phosphatidylinositol (GPI) anchor of Trypanosoma variant surface protein. The enzyme was labelled in vivo by feeding [³H]ethanolamine to the cells and underwent an hydrophobicity shift after treatment with phosphoinositol-specific phospholipase C. The attachment of this form of nitrate reductase to the plasma membrane via a GPI anchor was demonstrated.Abbreviations GPI glycosyl-phosphatidylinositol - NR nitratereductase - PI-PLC phosphoinositol-specific phospholipase C - PMNR Plasma-membrane-bound nitrate reductase The research was supported by a grant from Deutsche Forschungsgemeinschaft to R.T.     

Weather or weathering? Growth of Nothofagus dombeyi on volcanic soils differing in nitrogen and phosphorus concentrations

Aims We tested whether—in addition to weather conditions—the concentrations of nitrogen and phosphorus in the substrate have an effect on the radial stem increment of Nothofagus dombeyi trees in old-growth forest stands on volcanic soil at the western slopes of the Andes in South-Central Chile.Methods We took soil samples and tree increment cores from five proximate sites (1000–1300 m a.s.l.) that are located in the volcanic region of the Conguillío National Park and differ in the age of the substrate (Miocene—3500 years B.P.) and in its concentrations of nitrogen (N) and phosphorus (P). The soil samples were also analysed on their concentrations of other plant mineral nutrients, carbon (C) and nitrogen isotope ratios (δ 15 N). Tree-ring widths and the stem basal area increment (BAI) were related to climate parameters. In selected tree rings, the stable isotope ratios of carbon (δ 13 C) and oxygen (δ 18 O) were determined and related to growth and climate parameters.Important findings Consistent with theory, the soils on the oldest substrate showed the highest (least negative) δ 15 N values, but mineral N was the only nutrient whose concentration exhibited a straightforward (increasing) relationship with increasing substrate age. The BAI was largest on the soil with the highest concentration of plant-available P. In contrast to BAI, tree-ring chronologies did not differ among the study sites. However, tree-ring chronologies and BAI exhibited significantly positive correlations with summer precipitation, and negative correlations, with summer (December) temperature. A negative correlation was found between δ 13 C and precipitation anomalies in the growing season (November–March). We interpret the negative correlations between growth and temperature, and between δ 13 C and δ 18 O in the tree rings, as an impairment of net carbon assimilation by anomalously warm weather conditions during the growing season. We conclude that the growth of N. dombeyi is mainly affected by high temperature and low precipitation in spring and summer irrespective of the substrate's age, and enhanced by higher concentrations of plant-available P in the soil. Our results may be representative of N. dombeyi stands on volcanic substrate within their principal distribution range along the Andes of South America.     

Changes in the biological activity of agropyrene on combined application with humus substances in the cultivation ofScenedesmus obliquus (TURP.) krüger

The work is concerned with the question of the effect of humic acids on the biological action of agropyrene, the effective substance from the rootstock of Agropyron repens (L.) P. BEAUV. The test organism was the alga Scenedesmus obliquus (TURP.) KRÜGER, cultivated in mineral solution. The basic biological test was the determination of the number and size of the cells of this alga. It was found that the way in which agropyrene acts on combined application with humus acids depends on which humus fraction is used. It can display a synergic action if humic acid is used, since this substance probably facilitates the penetration of agropyrene into the cells. On the other hand, fulvic acid counteracts the activity of agropyrene and this most probably by mutual binding and blocking of active groups and links.     

Effect of Photon Fluence Rate and Specific Growth Rate on Geosmin Production of the Cyanobacterium Oscillatoria brevis (Kütz.) Gom

The production of geosmin from the cyanobacterium Oscillatoria brevis was studied as a function of the photon fluence rate and appears to be related to the chlorophyll content.     

The effects of delta-9-tetrahydrocannabinol on Krüppel-like factor-4 expression,redox homeostasis,and inflammation in the kidney of diabetic rat

Diabetes mellitus is a complex, multifactorial disorder that is attributed to pancreatic β cell dysfunction. Pancreatic β cell dysfunction results in declining utilization of glucose by peripheral tissues as kidney and it leads to nephropathy. Excessive production and accumulation of free radicals and incapable antioxidant defense system lead to impaired redox status. Macromolecular damage may occur due to impaired redox status and also immune imbalance. Δ9-Tetrahydrocannabinol (THC) is the main active ingredient in cannabis. THC acts as an immunomodulator and an antioxidant agent. Our aim was to evaluate the effects of THC in the diabetic kidney. We analyzed macromolecular damage biomarkers as protein carbonyl (PCO), lipid hydroperoxide (LHP), malondialdehyde (MDA), 8-hydroxy-2′-deoxyguanosine (8-OHdG), and antioxidant defense system biomarkers as thiol fractions (T-SH, NP-SH, P-SH) and Cu/Zn-superoxide dismutase activity for the antioxidative effects of THC. Furthermore, mRNA expression of Krüppel-like factor-4, secreted immunopositive cell number changes of interleukin-6, nuclear factor κβ (NF-κβ), and peroxisome proliferator-activated receptor-γ and tumor necrosis factor α (TNF-α) levels were analyzed for the immunomodulatory activity of THC. Diabetic rats showed significantly increased levels of PCO, LHP, MDA, and 8-OHdG when compared with controls (P < 0.05 for each parameter). THC significantly reduced the elevated levels of PCO and 8-OHdG (P < 0.05 for both parameters) and also LHP and MDA levels were insignificantly reduced by THC. Also, thiol fractions insignificantly increased in THC administered diabetic kidney when compared with diabetic rats. The NF-κβ cell number significantly decreased in the diabetic rats treated with THC compared with the diabetic group. According to our data, THC has ameliorative effects on the impaired redox status of diabetic kidney and also it acts as an immunomodulator. Therefore, THC might be used as a therapeutic agent for diabetic kidneys but its usage in the healthy kidney may show adverse effects.     

Dietary administration of Lactobacillus delbrüeckii and Bacillus subtilis, single or combined, on gilthead seabream cellular innate immune responses

The effects of oral administration of Lactobacillus delbrüeckii ssp. lactis and Bacillus subtilis, single or combined, on gilthead seabream cellular innate immune responses were investigated. Fish were fed four different diets: control (non-supplemented); or diet supplemented with 10(7) cfu g(-1)L. delbrüeckii ssp. lactis; 10(7) cfu g(-1)B. subtilis; or with 0.5x10(7) cfu g(-1)L. delbrüeckii ssp. lactis and 0.5x10(7) cfu g(-1)B. subtilis. This feeding regime lasted for 3 weeks, and all experimental groups were then fed the control commercial diet for another week. Six fish were sampled at weeks 1, 2, 3 and 4. Head-kidney leucocytes were isolated and the main cellular innate immune parameters (leucocyte peroxidase content, phagocytosis, respiratory burst activity and cytotoxicity) were evaluated. Leucocyte peroxidase content was lower in all groups at week 3 but the levels tended to recover during the last week of the experiment. Respiratory burst activity was not affected at any time of the experiment in any of the experimental groups. However, phagocytic activity increased after 2 weeks of feeding the single bacteria-supplemented diets, whereas the combination of the two caused an increment which persisted for as long as the bacteria were being administered. Cytotoxic activity was also significantly increased after 3 weeks of feeding the mixture of the two bacteria. After 1 week back on the control diet, the parameters in the experimental groups had recovered or even dropped below those recorded in the control group, suggesting that the bacteria did not persist in the seabream gut.