No Evidence for Adaptive Micro-Evolution to a Decrease in Phosphorus-Loading of a Daphnia Population Inhabiting A Pre-Alpine Lake

Many polluted lakes in Europe are being restored and phosphorus concentrations have dropped dramatically in these lakes. We studied the genetic structure of Daphnia galeata over the past 30 years in Lake Greifensee, Switzerland, a period during which the phosphorus concentration in the lake reduced dramatically. Distinct genotypes of D. galeata were hatched from diapausing eggs extracted from six different time horizons in dated sediments. We compared juvenile growth, size and egg production of D. galeata reared on high-P and low-P algae to investigate whether Daphnia have evolved to grow better on phosphorus-limited algae. Our results indicate that life histories of D. galeata differed significantly between both food types. We also found significant clone effects for size and egg number. But we found no significant interaction between the depth from which the clones were selected and food quality. This means that we found no evidence for adaptive micro-evolution in response to P reduction in the lake. We discuss our results in relation to other studies that found evidence for adaptive micro-evolution in comparable time frames.     

INFLUENCE OF CERTAIN PLANT GROWTH REGULATORS AND CROWN-GALL RELATED SUBSTANCES ON BUD FORMATION AND GAMETOPHORE DEVELOPMENT OF THE MOSS PYLAISIELLA SELWYNII

Bud formation and gametophore development were studied in the moss Pylaisiella selwynii (Kindb.) Steere and Anderson grown from spores in a liquid medium consisting of inorganic salts. Indoleacetic acid and ethrel increased bud formation within a narrow concentration range. Copious bud formation was obtained with the five cytokinins tested at concentrations varying from 5 X 10⁻⁶ to 5 X 10⁻¹⁴ M. Except for about 10 % of the buds obtained with 6-γ, γ-dimethylallylaminopurine at 5 times 10⁻¹⁴ m, the cytokinin-induced buds failed to develop into normal gametophores. Octopine, lysopine, and octopinic acid, substances obtained from crown-gall tumors, increased bud formation at 10⁻³ m. On lysopine-treated plants these buds developed into typical gametophores. Gemma-like structures were obtained with octopine but no gametophores. l -arginine and l -lysine, the amino acids which respectively occur in octopine and lysopine, failed to induce gametophore formation although buds were obtained with 10⁻³ m lysine. γ-Guanidinobutyric acid induced bud formation at 10⁻³ m, but these buds developed into highly abnormal gametophores. The failure of buds obtained with many of these treatments to develop into gametophores appeared to result from the formation of new cell walls in other than the normal geometrical relationship during initial divisions of the pro-bud. The relevance of the findings to the crown-gall problem is discussed.     

Binding of beta-galactosidase from rat epididymal fluid to the sperm surface by high-affinity sites different from phosphomannosyl receptors.

beta-Galactosidase, known to be secreted by epithelial cells lining the rat epididymal duct, binds to the surface of spermatozoa from the caudal region with high affinity and in a saturable form. The binding was not inhibited by mannose-6-phosphate, but was inhibited by fructose phosphate derivatives, a peculiarity previously demonstrated for the membranes of epididymal tissue. Fructose phosphate derivatives released 55% of beta-galactosidase activity from the spermatozoa. These results suggest that in the epididymis there is a special transport system for hydrolases, which could be involved in the secretion of enzymes destined for spermatozoa. This transport would require receptors that recognize sugar ligands other than mannose-6-phosphate. These receptors were present in the epididymal tissue and on the sperm surface.     

How Much Is Too Little to Detect Impacts? A Case Study of a Nuclear Power Plant

Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the potentially impacted site and multiple reference sites are sampled through time, before and after the impact. Often, however, the lack of information regarding the potential overall impact, the lack of knowledge about the environment in many regions worldwide, budgets constraints and the increasing dimensions of human activities compromise the reliability of the impact assessment. We evaluated the impact, if any, and its extent of a nuclear power plant effluent on sessile epibiota assemblages using a suitable and feasible sampling design with no ‘before’ data and budget and logistic constraints. Assemblages were sampled at multiple times and at increasing distances from the point of the discharge of the effluent. There was a clear and localized effect of the power plant effluent (up to 100 m from the point of the discharge). However, depending on the time of the year, the impact reaches up to 600 m. We found a significantly lower richness of taxa in the Effluent site when compared to other sites. Furthermore, at all times, the variability of assemblages near the discharge was also smaller than in other sites. Although the sampling design used here (in particular the number of replicates) did not allow an unambiguously evaluation of the full extent of the impact in relation to its intensity and temporal variability, the multiple temporal and spatial scales used allowed the detection of some differences in the intensity of the impact, depending on the time of sampling. Our findings greatly contribute to increase the knowledge on the effects of multiple stressors caused by the effluent of a power plant and also have important implications for management strategies and conservation ecology, in general.     

The SANT2 domain of the murine tumor cell DnaJ-like protein 1 human homologue interacts with alpha1-antichymotrypsin and kinetically interferes with its serpin inhibitory activity

The murine tumor cell DnaJ-like protein 1 or MTJ1/ERdj1 is a membrane J-domain protein enriched in microsomal and nuclear fractions. We previously showed that its lumenal J-domain stimulates the ATPase activity of the molecular chaperone BiP/GRP78 (Chevalier, M., Rhee, H., Elguindi, E. C., and Blond, S. Y. (2000) J. Biol. Chem. 275, 19620-19627). MTJ1/ERdj1 also contains a large carboxyl-terminal cytosolic extension composed of two tryptophan-mediated repeats or SANT domains for which the function(s) is unknown. Here we describe the cloning of the human homologue HTJ1 and its interaction with alpha(1)-antichymotrypsin (ACT), a member of the serine proteinase inhibitor (serpin) family. The interaction was initially identified in a two-hybrid screening and further confirmed in vitro by dot blots, native electrophoresis, and fluorescence studies. The second SANT domain of HTJ1 (SANT2) was found to be sufficient for binding to ACT, both in yeast and in vitro. Single tryptophan-alanine substitutions at two strictly conserved residues significantly (Trp-497) or totally (Trp-520) abolished the interaction with ACT. SANT2 binds to human ACT with an intrinsic affinity equal to 0.5 nm. Preincubation of ACT with nearly stoichiometric concentrations of SANT2 wild-type but not SANT2: W520A results in an apparent loss of ACT inhibitory activity toward chymotrypsin. Kinetic analysis indicates that the formation of the covalent inhibitory complex ACT-chymotrypsin is significantly delayed in the presence of SANT2 with no change on the catalytic efficiency of the enzyme. This work demonstrates for the first time that the SANT2 domain of MTJ1/HTJ1/ERdj1 mediates stable and high affinity protein-protein interactions.     

Cloning of the <Emphasis Type="Italic">Arthrobacter</Emphasis> sp. FG1 dehalogenase genes and construction of hybrid pathways in <Emphasis Type="Italic">Pseudomonas putida</Emphasis> strains

An Arthrobacter strain, able to utilize 4-chlorobenzoic acid as the sole carbon and energy source, was isolated and characterized. The first step of the catabolic pathway was found to proceed via a hydrolytic dehalogenation that leads to the formation of 4-hydroxybenzoic acid. The dehalogenase encoding genes (fcb) were sequenced and found highly homologous to and organized as those of other 4-chlorobenzoic acid degrading Arthrobacter strains. The fcb genes were cloned and successfully expressed in the heterologous host Pseudomonas putida PaW340 and P. putida KT2442 upper TOL, which acquired the ability to grow on 4-chlorobenzoic acid and 4-chlorotoluene, respectively. The cloned dehalogenase displayed a high specificity for para-substituted haloaromatics with affinity Cl > Br > I > F, in the order.     

Anemia secondary to valproic acid therapy in a 13- year-old boy: a case report

ABSTRACT: INTRODUCTION: Valproic acid is a commonly used anti-epileptic drug. Hematological toxicities are among theoccasionally observed adverse effects of this medication. CASE PRESENTATION: We present the case of a 13-year-old Caucasian boy who demonstrated mild anemia 12months after the introduction of valproic acid therapy. A bone marrow biopsy revealedmaturation arrest of proerythroblasts. CONCLUSION: Prompt diagnosis and valproic acid discontinuation resulted in the patient's recovery.