The first decade of oligotrophication of Lake Constance

In Lake Constance, after several decades of cutrophication, a decrease in phosphorus loading over the last decade has lead to a partial recovery from eutrophication. Here we analyse the shift in the taxonomic composition of phytoplankton during the first decade of oligotrophication in Lake Constance. During the 1980s, spring total P concentrations decreased from ca. 130 to less than 50 ·l^–1. This decrease was reflected by an approximately proportional decrease in summer phytoplankton biomass while spring phytoplankton biomass seemed unresponsive. Major taxonomic changes occured during both growth seasons. In spring, the proportion of diatoms, green algae and Chrysophyta increased while the proportion of Cryptophyta decreased. The summer trend was very different: the relative importance of diatoms decreased and Cryptophyta and Chrysophyta increased, while Chlorophyta reached their peak around 1985. These trends are also analysed at the genus level. Comparison with taxonomic trends during the eutrophication period shows the expected reversals in most cases. Comparison with other lakes shows general similarities, with the notable exception that Planktothrix rubescens has never been important in Lake Constance. The increase of diatoms during spring is attributed to their improved competitive performance with increasing Si:P ratios. Their decrease during summer is explained by the increasing silicate removal from the epilimnion by increasing spring populations.     

Organotypic brain-slice cultures from adult rats: approaches for a prolonged culture time

Animal experiments are widely used in neurobiological and neuropharmacological research. Today, juvenile brain organotypic slice cultures have partially replaced in vivo experiments, but there is no adequate in vitro counterpart for the adult brain. The present study was aimed at the long-term culture of physiologically intact hippocampal slices from adult rats, by improving the conditions for preparation and culture, and the development of a new culture medium. A cerebrospinal fluid (CSF)-like medium was used, which was modified with a variety of supplements, including energy precursors, free-radical scavengers, and compounds known to inhibit neurotoxicity. The population spike amplitude (PSA) was used as a measure of viability, and amplitudes larger than 1mV indicated viable cultures. The addition of MK-801 during slice preparation improved PSA values during the first two days in vitro (DIV). Ascorbic acid and insulin prolonged the culture time up to DIV 4. FK-506 and vitamin E, alone or in combination, supported slice culture up to DIV 5. An increase in ATP, unless combined with vitamin E, and/or insulin, increased culture time up to DIV 6. Vitamins B(1), B(2), B(12) and D(2) had no effect. The modified CSF-like medium developed in this study permits the culture of adult hippocampal tissue for at least 6 days.     

Structure of a highly phosphorylated lipopolysaccharide core in the Delta algC mutants derived from Pseudomonas aeruginosa wild-type strains PAO1 (serogroup O5) and PAC1R (serogroup O3)

Lipopolysaccharides (LPS) were isolated from rough-type mutant strains of Pseudomonas aeruginosa (Delta algC) derived from wild-type strains PAO1 (serogroup O5) and PAC1R (serogroup O3). Structural studies of the LPS core region with a special focus on the phosphorylation pattern were performed by 2D NMR spectroscopy, including a 1H,(31)P HMQC-TOCSY experiment, MALDI-TOF MS, and Fourier-transform ion cyclotron resonance ESIMS using the capillary skimmer dissociation technique. Both LPS were found to contain two residues each of 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) and L-glycero-D-manno-heptose (Hep), one residue of N-(L-alanyl)-D-galactosamine and one O-carbamoyl group (Cm) on the distal Hep residue. The following structures of a tetrasaccharide trisphosphate from strain PAC1R Delta algC and that carrying an additional ethanolamine phosphate group (PEtN) from strain PAO1 Delta algC were elucidated: [carbohydrate structre: see text] where R=P in PAC1R Delta algC and PPEtN in PAO1 Delta algC. To our knowledge, in this work the presence of ethanolamine diphosphate is unambiguously confirmed and its position established for the first time in the LPS core of a rough-type strain of P. aeruginosa. In addition, the structure of the complete LPS core of wild-type strain P. aeruginosa PAO1 was reinvestigated and the position of the phosphorylation sites was revised.     

Species–area relationships of butterflies in Europe and species richness forecasting

Species–area relationships (SARs) of European butterfly species (Rhopalocera) appear to follow power functions with Mediterranean butterflies having a much higher slope value (z=0.49) compared to the slope for the northern and eastern European countries (z=0.10). A simulated process of species extinction by a stepwise density dependent random elimination of species affected species–area patterns differently. For Mediterranean countries SAR slopes decreased, for other European countries slopes increased during the extinction process. Comparisons of species numbers before and after extinction with those predicted by a classical SAR approach differed widely and revealed that SARs are not able to predict future species numbers at local scales. For Mediterranean countries the classical SAR approach underestimated the number of species remaining after simulated extinction, for all other European countries SARs highly overestimated species numbers. These contrasting patterns indicate that changes in SAR patterns do not unequivocally point to changes in species diversity or community structure as assumed by current theory. On the other hand, the results strongly indicate that simplified applications of SARs for forecasting might give misimpressions about species loss and future biodiversity if the initial community structure, especially relative densities and numbers of species with restricted range size, are not taken into account.     

Alterations of Red Cell Membrane Properties in Nneuroacanthocytosis

Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an “acanthocytic state” of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration.     

The origin of chloroplasts: Constantin S. Merezhkowsky (1855–1921) and symbiogenesis

Journal of Plant Biochemistry and Biotechnology - One century ago (Jan. 9, 1921), the Russian biologist Constantin S. Merezhkowsky, who proposed the endosymbiotic origin of plastids, committed...     

No sex in fungus-farming ants or their crops

Asexual reproduction imposes evolutionary handicaps on asexual species, rendering them prone to extinction, because asexual reproduction generates novel genotypes and purges deleterious mutations at lower rates than sexual reproduction. Here, we report the first case of complete asexuality in ants, the fungus-growing ant Mycocepurus smithii, where queens reproduce asexually but workers are sterile, which is doubly enigmatic because the clonal colonies of M. smithii also depend on clonal fungi for food. Degenerate female mating anatomy, extensive field and laboratory surveys, and DNA fingerprinting implicate complete asexuality in this widespread ant species. Maternally inherited bacteria (e.g. Wolbachia, Cardinium) and the fungal cultivars can be ruled out as agents inducing asexuality. M. smithii societies of clonal females provide a unique system to test theories of parent–offspring conflict and reproductive policing in social insects. Asexuality of both ant farmer and fungal crop challenges traditional views proposing that sexual farmer ants outpace coevolving sexual crop pathogens, and thus compensate for vulnerabilities of their asexual crops. Either the double asexuality of both farmer and crop may permit the host to fully exploit advantages of asexuality for unknown reasons or frequent switching between crops (symbiont reassociation) generates novel ant–fungus combinations, which may compensate for any evolutionary handicaps of asexuality in M. smithii.     

Alterations in Glial Cell Metabolism During Recovery from Chronic Osmotic Stress

NMR spectroscopy of F98 glioma cell extracts showed that chronic hypertonic conditions largely increased the intracellular content of small, osmotically active molecules. Moreover, hypertonic stress decreased the incorporation of ¹³C-labeled amino acids into the cellular proteins albeit their cytosolic concentrations were increased, which reflects an inhibition of protein synthesis under these conditions. Reincubation with isotonic medium restored almost completely the control values for the cytosolic metabolites but not for amino acid incorporation into the protein. An increased amount of ¹³C label was found in the phospholipids, which indicates stimulation of membrane synthesis processes due to the recovery-induced cell swelling. On the other hand, chronic hypotonic conditions largely decreased the steady state concentration and synthesis of small, cytosolic molecules, whereas the effect on the incorporation of ¹³C-labeled amino acids into the cellular proteins was variable. Reincubation with isotonic medium partially restored the depressed cytosolic metabolite content and also the incorporation of labeled amino acids into cellular protein, but induced an inhibition of phospholipid synthesis. The results verify that readaptation of glial cell metabolism during recovery from chronic osmotic stress is impaired or at least seriously retarded.