Seasonal water quality of shallow and eutrophic Lake Pamvotis, Greece: implications for restoration

Lake Pamvotis is a moderately sized (22 km²) shallow (z _avg=4 m) lake with a polymictic stratification regime located in northwest Greece. The lake has undergone cultural eutrophication over the past 40 years and is currently eutrophic (annual averages of FRP=0.07 mg P l^-1, TP=0.11 mg P l^-1, NH₄ ⁺=0.25 mg N l^-1, NO₃ ^–=0.56 mg N l^-1). FRP and NH₄ ⁺ levels are correlated to external loading from streams during the winter and spring, and to internal loading during multi-day periods of summer stratification. Algal blooms occurred in summer (July–August green algae, August–September blue-green algae), autumn (October blue-green algae and diatoms), and winter (February diatoms), but not in the spring (March–June). The phytoplankton underwent brief periods of N- and P-limitation, though persistent low transparency (secchi depth of 60–80 cm) also suggests periods of light limitation. Rotifers counts were highest from mid-summer to early autumn whereas copepods were high in the spring and cladocerans were low in the summer. Removal of industrial and sewage point sources a decade ago resulted in a decrease in FRP. A phosphorus mass balance identified further reductions in external loading from the predominately agricultural catchment will decrease FRP levels further. The commercial fishery and lake hatchery also provides opportunities to control algal biomass through biomanipulation measures.     

Nitric oxide-scavenging properties of some chalcone derivatives.

The implication of NO in many inflammatory diseases has been well documented. We have previously reported that some chalcone derivatives can control the iNOS pathway in inflammatory processes. In the present study, we have assessed the NO-scavenging capacity of three chalcone derivatives (CH8, CH11, and CH12) in a competitive assay with HbO(2), a well-known physiologically relevant NO scavenger. Our data identify these chalcones as new NO scavengers. The estimated second-order rate constants (k(s)) for the reaction of the three derivatives with NO is in the same range as the value obtained for HbO(2), with CH11 exerting the greatest effect. These results suggest an additional action of these compounds on NO regulation.     

Low virulence of a morphological Candida albicans mutant

The DNA fragment encoding malonate decarboxylase, involved in malonate assimilation, was cloned from Pseudomonas putida. The 11-kb DNA fragment contained nine open reading frames, which were designated mdcABCDEGHLM in the given order. N-terminal protein sequencing established that the mdcA, mdcC, mdcD, mdcE and mdcH genes encoded subunits alpha, delta, beta, gamma and epsilon of the malonate decarboxylase, respectively. Malonate decarboxylase was functionally expressed in Escherichia coli from plasmid harboring the entire gene cluster or the mdc genes lacking the mdcL and mdcM genes. The mdcL and mdcM genes encode membrane proteins and disruption of the genes of P. putida by the insertion of a kanamycin resistance cassette reduced the malonate uptake activity of the organism. Thus, we conclude that MdcLM is a malonate transporter.     

A new method for the isolation of the simple and highly complex glycosphingolipids from animal tissue

The most widely used methods for the extraction of glycosphingolipids from animal tissues are based on the use of chloroform/methanol mixtures. These methods, although suitable for a great majority of lipids, fail to remove highly complex glycosphingolipids. Reported here is a method for the isolation of the entire population of glycosphingolipids by means of a gradual degradation of tissue components and enrichment in carbohydrate conjugates resistant to alkali and proteases. Fresh gastric mucosa was homogenized and treated with alkali (β-elimination) and RNAase and DNAase to decrease the viscosity of the homogenate, followed by pronase digestion. Each treatment was completed by exhausitive dialysis against distilled water. The resultant tissue digest was partitioned with chloroform/methanol (2 : 1) to remove simple glycosphingolipids. The aqueous portion of the system was adjusted to 1.0% with Zwittergent?-314 and solubilized for 24 h by mixing. Thus, prepared sample subjected to Bio-Gel P60 column chromatography afforded five fractions. Of these, three were free of protein and contained carbohydrates, fatty acids and sphingosine. Further fractionation on Bio-Gel P10 and P6 columns followed by thin-layer chromatography afforded homogeneous components with all the characteristics of highly complex glycosphingolipids.     

Antioxidant Action of Benzylisoquinoline Alkaloids

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe²⁺/ascorbate, CCl₄/NADPH or by Fe³⁺ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl₄/NADPH or Fe³⁺ -ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.     

Microbial antibiotics take the lead in the fight against plant pathogens

The plant microbiome is essential for plant fitness and health. Antibiotics produced by plant-associated bacteria have been shown to play an important role in protecting plant hosts against phytopathogens. Here, we highlight the strong biotechnological potential of (i) antibiotic producing plant-associated bacteria as biocontrol agents and (ii) the heterologous expression of antibiotic biosynthetic gene clusters in non-pathogenic plant-associated bacteria. We also provide the complete list of the active substances based on bacteria, fungi, and viruses currently approved or pending approval in the European Union, as an indication of the significant emergence and biotechnological applicability of biopesticides. Further progress in this field of research will enable the development of novel biopesticides for the biocontrol of agricultural pests.     

Survival, metabolic activity and conjugative interactions of indigenous and introduced streptomycete strains in soil microcosms

The growth and activity of introduced (S. lividans TK24 pIJ673 and S.lividans TK23) and indigenous (S.griseus CAG17) streptomycete strains in soil was studied, under controlled conditions. The effect of environmental parameters such as temperature, soil water content and nutrient availability on the growth and activity of these strains, was studied using a highly dynamic fed-batch soil microcosm system. Using this new system, repeated cycles of active streptomycete growth were achieved, allowing long-term investigation of metabolic activity, plasmid stability and conjugative plasmid transfer. In long-term experiments, respiration rates and enzyme activity patterns matched the pattern of germination/sporulation cycles of the inoculants. In situ hybridisation, using fluorescently labelled oligonucleotides, also proved the presence of metabolically active streptomycete mycelia in sterile soil. Plasmid stability under varying temperatures and selective pressure was studied using the above system. In both sterile and non sterile amended antibiotic containing soil, no intraspecific transfer of plasmid pIJ673 from S.lividans TK24 to S.griseus CAG17 was detected. The soil microcosm system used, though, permitted detection of intraspecific conjugative transfer of this plasmid from S.lividans TK24 to S.lividans TK23 in soil.     

Response of rat fasciculata-reticularis cells in primary culture to bacterial lipopolysaccharide

The aim of this study was to determine the direct effect of a wide range of concentrations of lipopolysaccharide (LPS) of Escherichia coli O111:B4 on fasciculata-reticularis cells in primary cultures. In short-term cultures of fasciculata-reticularis cells, the presence of low (1-10 microg/ml) doses of LPS in the medium produced a decrease in ACTH-induced corticosterone secretion, in a dose-dependent manner and independent of the culture medium. The corticosterone production stimulated by db-cAMP was slightly decreased by the presence of LPS in culture medium, while the pregnenolone induced corticosterone biosynthesis was not modified. LPS modified the binding of [125I]-Tyr23-ACTH to the fasciculata-reticularis cell membrane and the signal transduction pathway, as LPS reduced ACTH-induced cAMP production. In long-term cultures, the presence of LPS in the medium produces a decrease in the specific binding of [125I]-Tyr23-ACTH, while the presence of ACTH in the culture medium produced an increase in its specific binding. The use of high doses of LPS (100-250 microg/ml) has helped to clarify some aspects of the LPS action. These doses of LPS severely inhibited ACTH-induced corticosterone production, and clearly reduced the corticosterone production stimulated by db-cAMP and the binding of ACTH to its receptors. In long-term cultures, LPS decreased the number of ACTH receptors, an effect that was reversed by subsequent exposure to ACTH. These results indicate that LPS exerts a direct action on fasciculata-reticularis cells and a model of the mechanism of LPS action is proposed.     

Cytochrome P450 aromatase expression in human seminoma

Background  

The enzyme cytochrome P450 aromatase, catalysing the conversion of androgens into estrogens, has been detected in normal human testicular cells suggesting a physiological role of local estrogen biosynthesis on spermatogenesis control. Estrogens, regulating cell growth and apoptosis, can also be involved in tumorigenesis process, but the possible link between estrogens and testicular neoplastic process is, up to now, scarcely known. This study examined aromatase expression in human seminoma, which is the most common germ cell tumour of the testis.     

Genes encoding subunits of stable complexes are clustered on the yeast chromosomes: an interpretation from a dosage balance perspective

Genomic evidence for colocalization of functionally related genes on eukaryote chromosomes is mounting. Here we show that a statistically significant fraction of yeast genes coding for subunits of stable complexes are located within 10-30 kb of each other. Clustering of genes encoding subunits of complexes may ensure better coregulation and maintain the right stoichiometry of complexes upon duplication of chromosomal segments.