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.     

Distinct Contributions of the Dorsolateral Prefrontal and Orbitofrontal Cortex during Emotion Regulation

The lateral prefrontal and orbitofrontal cortices have both been implicated in emotion regulation, but their distinct roles in regulation of negative emotion remain poorly understood. To address this issue we enrolled 58 participants in an fMRI study in which participants were instructed to reappraise both negative and neutral stimuli. This design allowed us to separately study activations reflecting cognitive processes associated with reappraisal in general and activations specifically related to reappraisal of negative emotion. Our results confirmed that both the dorsolateral prefrontal cortex (DLPFC) and the lateral orbitofrontal cortex (OFC) contribute to emotion regulation through reappraisal. However, activity in the DLPFC was related to reappraisal independently of whether negative or neutral stimuli were reappraised, whereas the lateral OFC was uniquely related to reappraisal of negative stimuli. We suggest that relative to the lateral OFC, the DLPFC serves a more general role in emotion regulation, perhaps by reflecting the cognitive demand that is inherent to the regulation task.     

Considering Future Potential Regarding Structural Diversity in Selection of Forest Reserves

A rich structural diversity in forests promotes biodiversity. Forests are dynamic and therefore it is crucial to consider future structural potential when selecting reserves, to make robust conservation decisions. We analyzed forests in boreal Sweden based on 17,599 National Forest Inventory (NFI) plots with the main aim to understand how effectiveness of reserves depends on the time dimension in the selection process, specifically by considering future structural diversity. In the study both the economic value and future values of 15 structural variables were simulated during a 100 year period. To get a net present structural value (NPSV), a single value covering both current and future values, we used four discounting alternatives: (1) only considering present values, (2) giving equal importance to values in each of the 100 years within the planning horizon, (3) applying an annual discount rate considering the risk that values could be lost, and (4) only considering the values in year 100. The four alternatives were evaluated in a reserve selection model under budget-constrained and area-constrained selections. When selecting young forests higher structural richness could be reached at a quarter of the cost over almost twice the area in a budget-constrained selection compared to an area-constrained selection. Our results point to the importance of considering future structural diversity in the selection of forest reserves and not as is done currently to base the selection on existing values. Targeting future values increases structural diversity and implies a relatively lower cost. Further, our results show that a re-orientation from old to young forests would imply savings while offering a more extensive reserve network with high structural qualities in the future. However, caution must be raised against a drastic reorientation of the current old-forest strategy since remnants of ancient forests will need to be prioritized due to their role for disturbance-sensitive species.     

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.     

Ecotypic differentiation in relation to soil nitrogen in northern Scandinavian Cochlearia officinalis

Ecotypic differentiation of Cochlearia officinalis L. was studied in four populations, roughly described as "beach", "bird cliff", "spring" and "estuary", which occupy different habitats in the northern part of Norway. The plants were cultivated under controlled conditions on soil to which nitrogen was applied at various amounts (0, 0.2 and 1.0 g N pot⁻¹). The above ground part of the "bird cliff" population showed the highest dry weight and nitrogen uptake at the highest nitrogen concentration. No effect of nitrogen treatment and the lowest dry weight were found in the "estuary" population. The differences in population response to added nitrogen were correlated to the nitrogen content of the soil in their natural habitat. Morphological features of the populations were also significantly different. The "estuary", "beach" and "bird cliff" populations showed differences in all characteristics measured – ratio of length/width of the leaves, shape of the leaf base, and length of the petiole. "Beach" and "spring" differed significantly in petiole length, while "bird cliff" and "spring" differed significantly in both leaf ratio and shape of the leaf base. These morphological features were not significantly altered by the application of nitrogen to the soil. This study shows that the four populations of Cochlearia officinalis are discrete biotypes characteristic of distinct habitats, and therefore, should be considered ecotypes.     

The Photoreceptor Outer Segments of the River Lamprey (Lampreta fluviatilis). An Electron-, Fluorescence- and Light Microscopic Study

The outer segment of long and short photoreceptors in the retina of the river lamprey, Lampetra fluviatilis, were studied by light- and fluorescence microscopy together with some different electron microscopic methods. The outer segments show characteristics of both rods and cones and are suggested to represent intermediate kinds of photoreceptors.