Population dynamics and reproduction of Northern Lapwings Vanellus vanellus in a meadow restoration area in central Sweden

To investigate the effectiveness of a meadow restoration programme, we studied the relationships between population changes and environmental changes, return rates and hatching success in a population of Northern Lapwings Vanellus vanellus. The study was performed on mixed farmland (59 km²) in central Sweden, an area that underwent extensive meadow restoration between 1985 and 1994. The study included more than 2600 nests, supplemented with observations of 127 individually colour-ringed Northern Lapwings. The breeding population varied (2.7–5.3 pairs/km²), but showed no significant trend with time. The population increased in years with high spring flooding levels. Population size was unrelated to demographic factors (e.g. hatching success the previous year (14–50%), and return rate). Lapwings moved considerably between years and their nest site fidelity was unrelated to previous hatching success or other factors, suggesting that changes in habitat quality and migration between populations were important in regulating population size. Recent extensive meadow restoration did not seem to aid the Northern Lapwing population; birds continued nesting on tillage even though most nests were destroyed by farming activities. A relatively high relaying frequency improved hatching success, which was still lowest in the most preferred habitats (spring sown crops, total hatching success c. 30%). The few Northern Lapwings breeding in the least preferred habitats (meadows and cultivated grassland) had a better hatching success (> 70% total hatching success), suggesting that habitat selection was not determined by hatching success. From these results, recommendations are made for the management of Northern Lapwing (and associated species) populations on farmland.     

Generation of Metal-Binding Staphylococci through Surface Display of Combinatorially Engineered Cellulose-Binding Domains

Ni²⁺-binding staphylococci were generated through surface display of combinatorially engineered variants of a fungal cellulose-binding domain (CBD) from Trichoderma reesei cellulase Cel7A. Novel CBD variants were generated by combinatorial protein engineering through the randomization of 11 amino acid positions, and eight potentially Ni²⁺-binding CBDs were selected by phage display technology. These new variants were subsequently genetically introduced into chimeric surface proteins for surface display on Staphylococcus carnosus cells. The expressed chimeric proteins were shown to be properly targeted to the cell wall of S. carnosus cells, since full-length proteins could be extracted and affinity purified. Surface accessibility for the chimeric proteins was demonstrated, and furthermore, the engineered CBDs, now devoid of cellulose-binding capacity, were shown to be functional with regard to metal binding, since the recombinant staphylococci had gained Ni²⁺-binding capacity. Potential environmental applications for such tailor-made metal-binding bacteria as bioadsorbents in biofilters or biosensors are discussed.     

Dinophysis blooms in the deep euphotic zone of the Baltic Sea: do they grow in the dark?

In situ growth rates of the toxin-producing dinoflagellate Dinophysis norvegica collected in the central Baltic Sea were estimated during the summers of 1998 and 1999. Flow cytometric measurements of the DNA cell cycle of D. norvegica yielded specific growth rates (μ) ranging between 0.1 and 0.4 per day, with the highest growth rates in stratified populations situated at 15–20 m depth. Carbon uptake rates, measured using ¹⁴C incubations followed by single-cell isolation, at irradiances corresponding to depths of maximum cell abundance were sufficient to sustain growth rates of 0.1–0.2 per day. The reason for D. norvegica accumulation in the thermocline, commonly at 15–20 m depth, is thus enigmatic. Comparison of depth distributions of cells with nutrient profiles suggests that one reason could be to sequester nutrients. Measurements of single-cell nutrient status of D. norvegica, using nuclear microanalysis, revealed severe deficiency of both nitrogen and phosphorus as compared to the Redfield ratio.It is also possible that suitable prey or substrate for mixotrophic feeding is accumulating in the thermocline. The fraction of cells containing digestive vacuoles ranged from 2 to 22% in the studied populations. Infection by the parasitic dinoflagellate Amoebophrya sp. was observed in D. norvegica in all samples analysed. The frequency of infected cells ranged from 1 to 3% of the population as diel averages, ranging from 0.2 to 6% between individual samples. No temporal trends in infection frequency were detected. Estimated loss rates based on observed infection frequencies were 0.5–2% of the D. norvegica population daily, suggesting that these parasites were not a major loss factor for D. norvegica during the periods of study.     

Spatial and temporal variation in distribution of Gelidium canariensis (Rhodophyta) from natural populations of the Canary Islands

This study was designed to investigate spatial and temporal variation in Gelidium canariensis populations at two shores in northern Gran Canaria during two years. Spatial scales ranged from some hundred meters (distance between shores), 10 to 30 m (distance between plots) to less than 3 m (distance between quadrats). Gelidium individuals were defined as distinct Gelidium clumps. The results show a significant difference in size of clumps between shores, but not on the smaller spatial scales. No significant temporal variation was found. There was no significant temporal or spatial variation in standing crop or density (counts made in quadrats where Gelidium was present, rather than counts for the total shore). Sporophytic and gametophytic clumps were also distinguished by identifying reproductive structures in the field. The total proportion of sporophytes was larger than the proportion of gametophytes, but at a smaller scale there could be a shift in dominance. The survival rate of clumps was similar between shores with a mean survival rate of 85%, but there was a significant difference in recruitment between shores. The results indicate a stable population structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Formation and characterisitcs of hepatic dexamethasone-receptor complexes of different molecular weight

The dexamethasone-binding receptor protein in rat liver cytosol has a Stokes radius of 61 Å and a sedimentation coefficient of 4.0 S. In contrast, cell nuclei labelled with [³H]dexamethasone in vivo or in vitro (reconstitution experiments with [³H]dexamethasone-labelled cytosol and isolated unlabelled nuclei) contain a high-salt-extractable dexamethasone-receptor complex with a Stokes radius of 30–36 Å and a sedimentation coefficient of 3.2 S. Exposure of liver homogenate or 1000 × g homogenate supernatant to low ionic strenght during preparation of cytosol resulted in conversion of the 61 Å to a 36 Å complex very similar to the intranuclear form of dexamethasone receptor. 61 → 36 Å complex-verting activity was present in both the 100 × g ?10 000 × g sediment of liver homogenate, from which it could be extracted by hypotonic media, and in the liver cell nuclei, from which it could be extracted by hypertonic media. Mild digestion of the 61 Å dexamethasone-receptor complex with trypsin also gave rise to a complex with a Stokes radius of 36 Å. Reconstitution experiments with isolated liver cell nuclei indicated that both the 61 Å and 36 Å dexamethasone-receptor complexes were taken up by the nuclei; reextraction of the nuclei incubated with the 61 Å complex revealed that this form had been converted to the 30–36 Å complex.Further digestion of teh 61 and 36 Å [³H]dexamethasone-receptor complexes with hypotonic extract of the 1000 × g ?10 000 × g sediment of liver homogenate or with trypsin resulted in formation of a third complex with a Stokes radius of 19 Å and a sedimentation coefficient of 2.5 S. The approximate molecular weights of the 61, 36 and 19 Å dexamethasone-receptor complexes were calculated as 102 000, 46 00 and 19 000, respectively, and the frictional ratios of the molecules as 1. 84, 1. 38 amd 1.00, respectively.It is concluded that the nuclear 30–36 Å dexamethasone-receptor complex is formed from the cytosol 61 Å complex by proteolytic digestion and that this latter protein contains at least two sites with a relatively high sensitivity to protelytic cleavage.     

Cell wall polypeptides of Polyphysa (Acetabularia) cliftonii: amino acid composition of stalk and cap cell wall polypeptides

The amino acid composition of stalk and cap cell wall polypeptides of the unicellular alga $\text{Polyphysa (A.) cliftonii}$ has been investigated. In spite of chemical and physical differences between stalk and can cell wall polysaccharides, the amino acid composition of the cell wall polypeptides appeared qualitatively similar in both structures. however, quantitative differences have been observed. The results are discussed on the basis of a possible role of the polypeptides in the growth of the cell wall.