Midsummer heat wave effects on lacustrine plankton: Variation of assemblage structure and fatty acid composition

The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002.     

Protein binding and stability of norepinephrine in human blood plasma. Involvement of prealbumin, alpha 1-acid glycoprotein and albumin

The binding of norepinephrine (NE) to plasma proteins of fresh human blood obtained from healthy volunteers was studied by ultrafiltration at different NE concentrations and incubation times at 37 degrees C. At 1.7 nM L-[3H]-NE binding was approximately 25%. The binding was rapid and was not influenced by the incubation time. [3H]-NE could be dissociated from its binding sites by acid precipitation and, after HPLC, showed to be unchanged NE. No difference in NE binding was found between plasma collected in EGTA-GSH or heparin solution. There was no degradation of NE when incubated in plasma at 37 degrees C for 10 h, even without the addition of antioxidants. Therefore, in the present study, binding represented interaction of unchanged NE with plasma proteins. The whole plasma binding was saturable over the range of 0.66 nM to 0.59 mM of NE. Scatchard plot of specific binding revealed high-affinity sites with a Kd of 5.4 nM and a Bmax of 3.9 fmoles.mg-1 protein, and low-affinity sites with a Kd of 2.7 microM and a Bmax of 3.3 pmoles.mg-1 protein. Electrophoretic characterization of NE-binding proteins showed that about 60% of bound NE was associated to albumin, and 20% to prealbumin. NE binding to pure human plasma proteins was also studied using ultrafiltration. Scatchard analyses revealed a single class of very high-affinity binding sites for prealbumin (Kd 4.9 nM), a single class of binding sites for alpha 1-acid glycoprotein (Kd 54 microM) and two classes of binding sites for albumin with high (Kd 1.7 microM) and low (Kd 0.8 mM) affinities respectively. The main results obtained in this study - a) reversibility of NE binding, b) stability of free and bound NE in plasma, c) involvement of the prealbumin as a specific binding protein - point out to a specific transport for NE in human blood plasma.     

Lens regeneration from cultured newt irises stimulated by retina-derived growth factors (EDGFs)

It has been shown that lens regeneration from the iris of the newt Notophthalmus viridescens is dependent on the presence of neural retinal tissue in organ culture and in vivo. The recent discovery of various eye-derived growth factors (EDGFs) in the bovine retina [14] prompted us to investigate whether one of these factors may be involved in the stimulation of lens regeneration. Dorsal irises were cultured for 20 days in serum-supplemented diluted Eagle's medium. Growth factors from bovine retina of various degrees of purification were added. Lens regeneration was assessed on the basis of morphological lens-regeneration stages and by immunofluorescent detection of a lens-specific marker protein, alpha-crystallin. Crude isotonic retinal extract at 80-800 micrograms/ml significantly augmented lens regeneration. Very similar results were obtained when EDGF III, the nonretained retinal factor after heparin-affinity chromatography, was present at 2-20 micrograms/ml. Lens regeneration was also significantly increased when EDGF II, the retinal form of acidic fibroblast growth factor (aFGF) at 50-500 ng/ml was added to the cultures. On the other hand, EDGF I at 4-40 ng/ml and brain basic FGF at 5-50 ng/ml did not seem to significantly stimulate lens regeneration under the conditions used. Our results suggest that at least two retina-derived growth factors (EDGF II and III) can stimulate lens regeneration. These growth factors may be the putative signal that is naturally produced by the retina during lens regeneration in the newt.     

Isolation and purification of the extracellular ribonuclease from Physarum polycephalum

Summary The myxomycete Physarum polycephalum has been reported to produce an extracellular ribonuclease. A quick procedure is described for the isolation and purification of the ribonuclease from the culture supernatant. It involves an initial concentration of the culture supernatant by slow freezing, followed by ammonium sulfate precipitation. The enzyme was adsorbed onto DEAE-cellulose and eluted with a sodium chloride gradient.     

Impact on energy metabolism of quantitative and functional cyclosporine-induced damage of kidney mitochondria

In this study we have measured, under experimental conditions which maintained efficient coupling, respiratory intensity, respiratory control, oxidative phosphorylation capacity and protonmotive force. Succinate cytochrome-c reductase and cytochrome-c oxidase activities were also studied. These investigations were carried out using kidney mitochondria from cyclosporine-treated rats (in vivo studies) and from untreated rats in the presence of cyclosporine (in vitro studies). Inhibition of respiratory intensity by cyclosporine did not exceed 21.1% in vitro and 15.9% in vivo. Since there was no in vitro inhibition of succinate cytochrome-c reductase and cytochrome-c oxidase activities, the slowing of electron flow observed can be interpreted as a consequence of an effect produced by cyclosporine between cytochromes b and c₁. Cyclosporine had no effect on respiratory control either in vitro or in vivo. Statistically significant inhibition of the oxidative phosphorylation was observed both in vitro (6.6%) and in vivo (12.1%). Moreover, cyclosporine did not induce any change of membrane potential either in vivo or in vitro. Our findings show that cyclosporine is neither a protonophore, nor a potassium ionophore. In cyclosporine-treated rats we noticed a decrease of protein in subcellular fraction, including the mitochondrial fraction. The role of the inhibition respiratory characteristics by cyclosporine in nephrotoxicity in vivo must take account of these two parameters: inhibition of the respiratory characteristics measured in vitro and diminution of mitochondrial protein in cyclosporine-treated rats.     

Structure of a new nonasaccharide isolated from human milk: VI2Fuc,V4Fuc,III3Fuc-p-lacto-N-hexaose

The structure of a new nonasaccharide isolated from human milk has been investigated. By using methylation analysis, FAB-MS and¹H-and¹³C-NMR spectroscopy as basic methods of structural investigation, this oligosaccharide was identified as VI²--Fuc,V⁴-Fuc,III³--Fuc-p-lacto-n-hexaose: Fuc1-2Gal1-3[Fuc1-4]GlcNAc1-3Gal1-4[Fuc1-3]GlcNAc1-3Gal1-4Glc.Abbreviations COSY correlation spectroscope - DP degree of polymerisation - FAB-MS fast atom bombardment-mass spectrometry - HPLC high performance liquid chromatography - NMR nuclear magnetic resonance - GLC gas-liquid chromatography     

The convergent trajectories of bird communities along ecological successions in european forests

Summary There is much more variation in the composition of bird communities in the earlier open and semi-open seral stages of ecological successions in forested landscapes of Europe than later on in preforested and forested climactic stages. The demonstration of this trend is achieved from the study of four habitat gradients, two in the mediterranean region (Provence and Corsica) and two in central Europe (Burgundy, France and Poland). A multivariate analysis has been used to illustrate the dynamics of communities along these succession. Displays of the results in bivariate space as well as an illustration of the distributional profiles of some of the most characteristic species show that: i) there is a discrimination between the two mediterranean gradients and the two medioeuropean ones and ii) each succession starts with a very distinct set of species and then the four gradients regularly converge in the last climactic stage where there is almost no discrimination between communities. These results are discussed in the light of the history of European biotas during the Pleistocene. The reason why there is more variation in species composition in the earlier seral stages than in the later forested stages are discussed according to current theories on the role of habitat selection on speciation processes.     

Selective binding of Dolichos biflorus agglutinin to L3T4-, Lyt-2- thymocytes. Expression of terminal alpha-linked N-acetyl-D-galactosamine residues defines a subpopulation of fetal and adult murine thymocytes

Using histochemical and immunocytochemical techniques, a lectin with nominal specificity for alpha-linked N-acetyl-D-galactosamine, Dolichos biflorus agglutinin (DBA), was found to preferentially label thymocytes with an L3T4-, Lyt-2- phenotype from fetal/newborn and adult mice. Through days 14 to 16 of gestation, virtually all thymocytes bound DBA, followed by a dramatic reduction of DBA labeling during the last 4 days of gestation, reaching adult levels of about 2 to 4% of total thymocytes. At later stages of fetal development, the DBA+ cells were confined to the subcapsular area of the thymus. This apparent loss of DBA+ cells was caused by an expansion of the thymocyte population not labeled with this lectin. Affinity purification of thymocyte cell surface components with insolubilized DBA indicated that virtually all of the lectin binding to fetal thymocytes was mediated by a 120-kDa glycoprotein. In addition to thymocytes, DBA also labeled about 5% of bone marrow cells from both normal or nude mice and a small population of spleen cells as well. These results suggest that this lectin may be useful to positively select for LT34-, Lyt-2- thymocytes, and, possibly, other immature populations within the T cell lineage.     

Enhancement of shoot regeneration potential by liquid medium culture from mature cotyledons of sunflower (Helianthus annuus L.)

We describe here a liquid culture system for the regeneration of shoots at high frequencies from mature cotyledon tissues of three genotypes of sunflower (Helianthus annuus L.) one of which had previously been found to be recalcitrant to regeneration when cotyledons were cultured on solid medium. Cotyledons were excised from 2-day-old seedlings and incubated in liquid Murashige and Skoog's modified medium supplemented with 5.4 M naphthaleneacetic acid (NAA) and 4.4 M benzylaminopurine (BAP). After two weeks in culture, the whole upper surface of regenerating explants was covered with green shootlets. The percentages of regenerating explants of three genotypes varied between 60 and 70%, and the number of shoots per regenerating explant was highly increased. The shootlets were transferred to solid Murashige and Skoog's medium allowing shoot development, then to rooting medium. Rooted plantlets were successfully acclimatized and gave fertile plants. The role of liquid medium culture in the induction of sunflower regeneration is discussed.Abbreviations BAP 6-benzylaminopurine - NAA 1-naphthaleneacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid