Where did the northern peatland species survive the dry glacials: cloudberry (Rubus chamaemorus) as an example

Aim During the last ice age large parts of the north boreal and subarctic zones were covered by ice, while the climate in ice‐free regions of northern Asia was extremely cold and dry. The extensive peatlands of these zones with their characteristic vegetation developed at the beginning of the Holocene. We combine a phylogeographical approach with maps of pollen records to identify regions where Rubus chamaemorus, a plant of moist, peaty soils, was likely to grow during this period. Location Circumarctic/circumboreal. Methods Samples were collected from 45 locations throughout much of the range of R. chamaemorus and 398 plants were analysed with amplified fragment length polymorphism (AFLP). Estimates of diversity and differentiation, principal coordinates analysis and Bayesian clustering methods were used for the analysis of genetic data. Dated pollen records were retrieved from the European and the Global Pollen Databases. Results The plants from Sakhalin are highly divergent from the rest of the material and represent the previously described var. pseudochamaemorus. The main genetic division in R. chamaemorus sensu stricto is found in the Taymyr region in central Eurasia. Genetic diversity and the relative number of rare markers are highest in central Siberia and eastern Asia and decrease towards Europe and to a lesser extent eastwards through North America. Pollen dating back to the last ice age is found in central and eastern Siberia and Alaska. The maximum observed clone size is about 250 m, and more than one clone is found in nearly every local population. Main conclusions The genetic data are consistent with the pollen records and indicate that R. chamaemorus was growing in several areas of northern central Siberia and Beringia during the last glaciation. This finding suggests that sufficient humidity for this and other species of peaty soils was present locally in different parts of the generally dry ice‐free areas of northern Asia, as had been previously documented for Beringia. The AFLP data show that var. pseudochamaemorus, which is also morphologically quite divergent, clearly represents a distinct genetic entity.     

Dynamic light scattering of the bacteriophage T4B: determination of translational diffusion coefficients and centres of rotation

Using dynamic light scattering, the translational diffusion coefficient (D_T) and the distance between the hydrodynamic centre and the centre of the head (r₀) of the bacteriophage T4B have been determined. For a particle with retracted tail fibres we found D_T20.w =2.88 (2.88 ± 0.02) × 10^?8cm²s^?1 and r₀ = 52 ± 1 nm. For a phage with fully extended tail fibres D_T20w = (.210 ± 0.02) × 10^?8cm²s^?1 and r₀ = 112 ± nm. These data were obtained by interpreting the correlation function using a theory which takes into account the influence of the lollipop shape of the phage. In the literature this influence has not been taken into account, which has led to erroneous values of diffusion coefficients for T4B and other phages. The sedimentation coefficient of T4B phage is 1040 ± 5 S (fibres retracted) or 829 ± 4 S (fibres extended). With the above mentioned diffusion coefficients, these values correspond to a molecular weight of 236 × 10⁶ ± 3 × 10⁶. Finally, the theory used in this study is applied to other bacterial viruses, to correct reported values of the translational diffusion coefficients and of the corresponding molecular weights of these viruses.     

Orientation of the chromophore dipoles in the TOTO-DNA system.

BACKGROUND:Flow cytometry has been applied successfully to the sizing of medium to large-sized DNA molecules, thanks to the excellent staining properties of cyanine chromophores such as TOTO (homodimer of thiazole orange) (Petty et al.: Anal Chem 67:1755-1761, 1995). The hydrodynamic flow, used to focus the sample molecules in a small laser-illuminated volume, is also responsible for their alignment, thereby allowing the determination of the TOTO-dipole orientation with respect to the DNA axis (Agronskaia et al.: Appl Opt 38:714-719, 1999). METHODS:We present model calculations of the fluorescence yield of TOTO-stained DNA measured in a flow-cytometric setup with high numerical aperture. The models consider different orientations of the chromophore dipoles. RESULTS:Comparison of measurement and calculation suggests that the absorption dipoles of the TOTO molecule make a mean angle of 61 degrees with the helix axis of the DNA molecule. This mean angle can be the consequence of two binding modes. CONCLUSIONS: Our results indicate that any model with a significant contribution of perpendicularly-oriented chromophores fails to reproduce the experimental results.     

Ovulation and Embryonic Developmental Rate Following hCG-stimulation in Sows

The hCG induced ovulation in sows was studied by use of ultrasonography, and an investigation of the development and diversity of the zygotes/embryos was performed at 24 h after ovulation. Crossbred sows (N=48) were weaned (day 0) and checked for heat twice daily from day 3 onwards. From day 4, the ovaries were transrectally scanned twice daily On day 4, the sows were given an injection of 750 iu hCG im and inseminated 27 ± 2 h (X ± SD) and 38 ± 1 h later. From 38 to 48 h after the hCG injection, the ovaries were scanned at 60 to 90 min intervals. At 24 h after ovulation the oviducts were surgically flushed in 18 sows. Out of the 48 sows, 34 showed heat at 12–36 h after the hCG-treatment and 14 showed heat before the hCG treatment. In the former group of sows, 20 (59%) ovulated within the interval of 38 to 48 h after the hCG treatment, and the follicular size immediately before ovulation was 7.8 ± 0.6 mm. Among the sows which showed heat before hCG treatment only 7 (50%) ovulated within the above interval and the preovulatory follicle size was larger (8.3 ± 0.5, p<0.05) than in the former group of sows, which showed heat after the hCG treatment. The flushing of 18 sows yielded a total of 243 ova, 70 (29 %) 1-cell stages, 160 (66 %) 2-cell stages and 13 (5%) 4-cell stages. A pronounced difference in the degree of variation in embryonic development was seen between sows: 4 animals yielded 1- to 4-cell stages, one exclusively 2-cell stage. In conclusion, the control of ovulation in sows by hCG treatment will affect the follicular growth and the exact timing of ovulation can not always be relied on. It is strongly recommended to use ultrasonography to monitor the time of ovulation if this parameter is important. Ova recovered at 24±1 h after the median time of ovulation revealed a pronounced diversity (1- to 4- cell stage) within sows. No obvious relation with this embryonic diversity and the follicular size at ovulation was seen in these data.     

Interspecific interaction: The analysis of complex structures in carnivorous zooplankton populations

Linear unidirectional dependence of one population upon another is rather atypical among zooplankton species, as carnivory is not only characteristic of high trophic levels but also part of omnivory in many species of copepods. The feeding on its predatorjuveniles may be important for the survival of a copepod population, more in regard to the impact on the predator than to the nutritional benefit obtained. Such complex interrelationships are important for predictive ecosystem models. Ctenophore-copepod interrelationships have been analysed in experiments, and the results produced have been used for constructing simulation models. Details of experimentation and of modelling are described and discussed.     

Associations between beta-tubulin and mitochondria in adult isolated heart myocytes as shown by immunofluorescence and immunoelectron microscopy

We have investigated the associations between beta-tubulin and mitochondria in freshly isolated cardiac myocytes from the rat. Beta-tubulin was identified by using monoclonal antibodies for immunofluorescence and high resolution immunogold electron microscopy. In addition, conventional transmission and scanning electron microscopic studies were performed. After chemical stabilization in a formaldehyde solution, the myocytes were shock-frozen at -150 degrees C, cryosectioned at -70 degrees C and subsequently processed for immunohistochemical and immunocytochemical microscopy. A characteristic of the rod shaped myocytes is the presence of a dense network of microtubules in the cytoplasm displaying a pattern of strong anti-beta-tubulin reaction. The complexity of this network however varies considerably among the myocytes reflecting microtubule dynamic instability. Further, our findings demonstrate that the beta-tubulin label in rod cells is confined to the perinuclear and interfibrillar spaces and, therefore, is largely colocalized with the cytoplasmic organelles. In myocytes undergoing severe contracture the distribution of beta-tubulin is entirely restricted to the outer mitochondrial-containing domain. This implies that, in a cell model with marked segregation of the contractile filaments and organelles, mitochondria are codistributed with microtubules in the total absence of desmin intermediate filaments. Moreover, our immunogold preparations demonstrate anti-beta-tubulin labelling in the outer mitochondrial membrane as well as of fibres in close apposition to this membrane. These results indicate the presence of a specific beta-tubulin binding to the outer mitochondrial membrane that probably also involves microtubule based translocators and/or MAPs.