Effects of cyclosporine A and its immunosuppressive or non-immunosuppressive derivatives [D-Ser]8-CsA and Cs9 on mitochondria from different brain regions

We studied the functional properties of isolated brain mitochondria (BM) prepared from total rat brain (BM(total)) or from cerebral subregions under basal and Ca(2+) overload conditions in order to evaluate the effects of cyclosporine A (CsA) in a regiospecific manner. CsA-induced effects were compared with those of two derivatives-the none-immunosuppressive [O-(NH(2)(CH2)(5)NHC(O)CH(2))-D-Ser](8)-CsA (Cs9) and its congener, the immunosuppressive [D-Ser](8)-CsA. The glutamate/malate-dependent state 3 respiration of mitochondria (state 3(glu/mal)) differed in region-specific manner (cortex > striatum = cerebellum > substantia nigra > hippocampus), but was significantly increased by 1μM CsA (+21±5%) in all regions. Ca(2+) overload induced by addition of 20μM Ca(2+) caused a significant decrease of state 3(glu/mal) (-45 to -55%) which was almost completely prevented in the presence of 1μM CsA, 1μM Cs9 or 1μM [D-Ser](8)-CsA. Mitochondrial Ca(2+) accumulation thresholds linked to permeability transition (PT) as well as the rate and completeness of mitochondrial Ca(2+) accumulation differed between different brain regions. For the first time, we provide a detailed, regiospecific analysis of Ca(2+)-dependent properties of brain mitochondria. Regardless of their immunosuppressive impact, CsA and its analogues improved mitochondrial functional properties under control conditions. They also preserved brain mitochondria against Ca(2+) overload-mediated PT and functional impairments. Since Cs9 does not mediate immunosuppression, it might be used as a more specific PT inhibitor than CsA.     

Between-species correlations in the number of migrants at Ulmeth?chi (Switzerland)

We analysed the number of autumn migrants at a bird ringing station over 41 years in the Jura mountains of Switzerland. For 12 irruptive or potentially irruptive bird species, the correlations between their numbers per year were calculated and the species were clustered accordingly. We found high correlations in the number of migrants between the Coal Tit Periparus ater, Great Tit Parus major and Blue Tit Cyanistes caeruleus. Most correlations of passage number between species pairs changed dramatically over time. Only Blue Tit and Coal Tit showed continuously high correlation in this respect. The variation and changes over time in between-species correlations in the number of migrants needs more attention.     

Comparative action of glyphosate as a trigger of energy drain in eubacteria.

Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa, each possessing a 5-enolpyruvylshikimate 3-phosphate synthase that is sensitive to inhibition by glyphosate [N-(phosphonomethyl)glycine], provide a good cross-section of organisms exemplifying the biochemical diversity of the aromatic pathway targeted by this potent antimicrobial compound. The pattern of growth inhibition, the alteration in levels of aromatic-pathway enzymes, and the accumulation of early-pathway metabolites after the addition of glyphosate were distinctive for each organism. Substantial intracellular shikimate-3-phosphate accumulated in response to glyphosate treatment in all three organisms. Both E. coli and P. aeruginosa, but not B. subtilis, accumulated near-millimolar levels of shikimate-3-phosphate in the culture medium. Intracellular backup of common-pathway precursors of shikimate-3-phosphate was substantial in B. subtilis, moderate in P. aeruginosa, and not detectable in E. coli. The full complement of aromatic amino acids prevented growth inhibition and metabolite accumulation in E. coli and P. aeruginosa where amino acid end products directly control early-pathway enzyme activity. In contrast, the initial prevention of growth inhibition in the presence of aromatic amino acids in B. subtilis was succeeded by progressively greater growth inhibition that correlated with rapid metabolite accumulation. In B. subtilis glyphosate can decrease prephenate concentrations sufficiently to uncouple the sequentially acting loops of feedback inhibition that ordinarily link end product excess to feedback inhibition of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase by prephenate. The consequential unrestrained entry is an energy-rich substrates into the aromatic pathway, even in the presence of aromatic amino acid end products, is an energy drain that potentially accounts for the inability of end products to fully reverse glyphosate inhibition in B. subtilis. Even in E. coli after glyphosate inhibition and metabolite accumulation were allowed to become fully established, a transient period where end products were capable of only partial reversal of growth inhibition occurred. The distinctive metabolism produced by dissimilation of different carbon sources also profound effects upon glyphosate sensitivity.     

Fluorescence of delta 5,7,9(11),22-ergostatetraen-3 beta-ol in micelles, sterol carrier protein complexes, and plasma membranes

The fluorescent sterol analogue delta 5,7,9(11),22-ergostatetraen-3 beta-ol (dehydroergosterol) was synthesized and purified by reverse-phase high-performance liquid chromatography. Dehydroergosterol in aqueous solution had a critical micelle concentration of 25 nM and a maximum solubility of 1.3 microM as ascertained from fluorescence polarization and light scattering properties, respectively. Several lines of evidence indicated a close molecular interaction of dehydroergosterol with purified rat liver squalene and sterol carrier protein (SCP). SCP increased the maximal solubility of dehydroergosterol in aqueous buffer. The fluorescence emission spectrum of dehydroergosterol was blue shifted upon addition of SCP. The fluorescence lifetime of dehydroergosterol in aqueous buffer was 2.3 ns; addition of SCP resulted in the appearance of a second lifetime component near 12.4 ns. The SCP increased the fluorescence polarization of monomeric dehydroergosterol in aqueous buffer from 0.033 to 0.086. Scatchard analysis of the binding data indicated that dehydroergosterol interacted with purified rat liver SCP with an apparent KD = 0.88 microM and Bmax = 4.8 microM. At maximal binding, 1.0 mol of dehydroergosterol was specifically bound per mole of SCP. The close molecular interaction of dehydroergosterol with SCP was also demonstrated by energy-transfer experiments. The intermolecular distance between SCP and bound dehydroergosterol was evaluated by fluorescence energy transfer from tyrosine residues of SCP to the conjugated triene series of double bonds in dehydroergosterol. The transfer efficiency was 36%, and R, the apparent distance between the tyrosine energy donor and the dehydroergosterol energy acceptor, was 19 A. The significance of these data obtained in vitro for dehydroergosterol interaction with SCP was also tested in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tetraludins D to N,eleven new melampolides from Tetragonotheca ludoviciana

Eleven new melampolides, tetraludins D-N, were isolated from aerial parts of Tetragonotheca ludoviciana. Tetraludins D and E, F and G, J and K, and L and M represented epimeric pairs which differed only at one chiral centre of the five-carbon ester side chain at C-8. In benzene-d₆, the ¹H NMR spectra of the diastereomeric pairs of melampolides exhibited well-separated signals in particular for the absorptions due to the ester side chains that differed in chirality.     

Molecular characterization of HymA, an evolutionarily highly conserved and highly expressed protein of Aspergillus nidulans

Aspergillus nidulans reproduces asexually via uninucleate, haploid spores, which are produced on morphologically differentiated aerial structures, called conidiophores. These consist of four distinct cell types, a foot with a terminally swollen stalk, metulae, phialides and conidiospores. The molecular mechanisms underlying the morphological changes that occur during conidiophore development have been studied by mutant analysis. We have isolated the hymA mutant, in which conidiophore development is affected at the metula stage. In the mutant metulae do not differentiate properly but come to resemble hyphae (hym?=?hypha-like metulae). In this paper we have analyzed the corresponding gene. It encodes a highly expressed 44?kDa protein which resides in the cytoplasm and has homologues in yeast, plants, fly, worm, fish, mice and man. We constructed hym deletion strains of Saccharomyces cerevisiae and of A. nidulans and found that the gene is essential in S. cerevisiae but is dispensable in the filamentous fungus. A cellular function for the Hym protein has not yet been defined in any organism. To demonstrate functional conservation we constructed a chimeric protein comprised of the N-terminal half of the A.?nidulans and the C-terminal half of the mouse homologue MO25. This hybrid protein could fully substitute for HymA function in A. nidulans. In addition, the mouse protein itself partially rescued the hymA mutation in the fungus. HymA is thus highly conserved in evolution and probably serves similar functions. The fact that hymA is required for conidiophore development in A. nidulans suggests that homologous genes in other organisms might also be involved in morphogenesis.     

Multiple-level regulation of genes for protocatechuate degradation in Acinetobacter baylyi includes cross-regulation

The bacterium Acinetobacter baylyi uses the branched beta-ketoadipate pathway to metabolize aromatic compounds. Here, the multiple-level regulation of expression of the pca-qui operon encoding the enzymes for protocatechuate and quinate degradation was studied. It is shown that both activities of the IclR-type regulator protein PcaU at the structural gene promoter pcaIp, namely protocatechuate-dependent activation of pca-qui operon expression as well as repression in the absence of protocatechuate, can be observed in a different cellular background (Escherichia coli) and therefore are intrinsic to PcaU. The regulation of PcaU expression is demonstrated to be carbon source dependent according to the same pattern as the pca-qui operon. The increase of the pcaU gene copy number leads to a decrease of the basal expression at pcaIp, indicating that the occupancy of the PcaU binding site is well balanced and depends on the concentration of PcaU in the cell. Luciferase is used as a reporter to demonstrate strong repression of pcaIp when benzoate, a substrate of the catechol branch of the pathway, is present in addition to substrates of the protocatechuate branch (cross-regulation). The same repression pattern was observed for promoter pcaUp. Thus, three promoters involved in gene expression of enzymes of the protocatechuate branch (pobAp upstream of pobA, pcaIp, and pcaUp) are strongly repressed in the presence of benzoate. The negative effect of protocatechuate on pobA expression is not based on a direct sensing of the metabolite by PobR, the specific regulator of pobA expression.     

The need for pluralism in landscape models: a reply to Dunn and Majer

Dunn and Majer discuss limitations of the continuum model proposed by Fischer and Lindenmayer and describe a new patch‐based model. We argue that a range of landscape models are required to solve different problems and meet particular objectives of land management or conservation. The key issue is not whether one type of model is superior to another, but rather: what are the particular strengths and limitations of a particular model? And, given these, under what circumstances will a particular model be most appropriate? The primary value of the continuum model is that it provides a strong theoretical foundation for the management of landscape heterogeneity in addition to the protection of large patches of native vegetation.