Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea-Baltic Sea salinity gradient.

Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea-Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30 psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea-Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone.

Effects of grazer presence on genetic structure of a phenotypically diverse diatom population.

Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.

Prosomes (proteasomes) of higher plants.

From different plant tissues such as tobacco (Nicotiana rustica), potato (Solanum tuberosum), and mung bean (Phaseolus radiatus), ring- or cylinder-shaped particles called prosomes were isolated by either sucrose gradient centrifugation or fast protein liquid chromatography (FPLC). These particles have a diameter of 12 to 14 nm and a length of 16 to 18 nm. They migrate under conditions of nondenaturing gel electrophoresis as one distinct band. Sedimentation coefficient and buoyant density in Cs2SO4 of the plant prosomes were determined by analytical ultracentrifugation to be approximately 23S and 1.23 g/cm3, respectively. The total molecular mass was estimated by gel filtration to be 650 kDa. Plant prosomes are composed of 12 to 15 proteins with molecular masses in the range of 24 to 35 kDa with isoelectric points of pH 5 to 7 as revealed by two-dimensional gel electrophoresis. The protein patterns of prosomes from the three different plant species are very similar. Polyclonal antisera against potato prosomes reacted in Western blots with prosomal proteins of all three plant species. They also bind to some prosomal proteins of animal species. Antisera against animal prosomes react with some proteins of plant prosomes. As shown by lectin blotting, plant prosomes are glycosylated carrying glucosyl- or mannosyl, and N-acetylgalactosaminyl residues. Prosomal preparations contain non-stoichiometric amounts of small RNA of about 80 kDa. These results suggest that plant prosomes are structurally and functionally homologous to prosomes of other eukaryotic cells.

[The possibility of side effects during the application of roentgenologic contrast media by the method of the biphasic bolus/perfusor injection and the monophasic bolus injection (author's transl)]. / Vergleich der Häufigkeit von Nebenwirkungen zwischen der zweiphasigen Bolusperfusor- und der einphasigen Bolusinjektion eines Röntgenkontrastmittels in der kranialen Computertomographie.

In spite to lower the dose dependent side effects by the application of roentgenologic contrast media in the computed tomography a system of a biphasic injection per bolus and perfusor was installed and compared with that of the monophasic bolus injection. Special rules on the installation of the perfusor at CT should be observed.

[Informative potential of computer-aided tomography (CAT), as compared to bilateral pedal lymphangiography, for the detection of gynaecological tumours, with particular reference to carcinoma of the cervix (author's transl)]. / Aussagewert der computerassistierten Tomographie (CAT) im Vergleich zur bilateralen pedalen Lymphangiographie bei gynäkologischen Tumoren unter Berücksichtigung des Zervixkarzinoms.

Experience so far obtained from whole-body computer-aided tomography is likely to suggest that the dimensions of primary tumours in the parametrial, paravesical, and pararectal regions can be defined with high accuracy, provided tumour diameters in excess of 2 cm. CAT also was found to be superior to other conventional diagnostic methods, when it came to better assessment of correlations between the tumour and neighbouring organs. CAT also helped to identify lymphomas in the retroperitoneal region, for example, in the pelvic retroperitoneum, and in the mesenteric region, although the same lymphomas were not or rarely identifiable by means of bipedal prefacial lymphangiography. - However, computer-aided tomography cannot replace lymphangiography, when it comes to an assessment of alterations of intranodular structures. Nevertheless, being a non-invasive diagnostic method, CAT can be successfully used in conjunction with lymphangiography to gain more information on the actual extent of lymph node formation. Hence, it can contribute to more accurate "in vivo" grading. - The method, for its non-invasive nature, may be highly useful in after-care tumour attention. CAT provides quasi-anatomic cross sections of the patient's body and is, consequently, a good basis for high-accuracy planning of radiotherapy.

Prosomes exist in plant cells too.

A 19S particle was purified from tobacco (Nicotiana rustica) leaf cells. Its density was determined as 1296 g/cm3 in Cs2SO4-DMSO gradients, indicating the presence of RNA and protein. Polyacrylamide gel electrophoresis (PAGE) revealed eight distinct proteins in the range of 20-30 kD and RNA in the range of 70-80 nucleotides. Electron microscopic examination showed the same raspberry-shaped structure with a central depression as described for prosomes. We conclude that tobacco 19S particles represent small cytoplasmic complexes, possessing biochemical and structural characteristics similar to the hither-to known prosomes of animal cells.

Schwannoma of the sellar region.

A 25-year-old woman who had experienced brief periods of loss of consciousness and grand mal seizures was found to have a midline mass in the sellar region as evidenced by computer tomography and angiography. Preoperatively, it was thought to be a meningioma but histologically and ultrastructurally it turned out to be a Schwannoma. Since cranial nerves were not involved, clinically or morphologically, this nerve sheath tumour could have originated from Schwann cells of sensory, possibly trigeminal, nerves, vasomotor nerves, or ectopic Schwann cells.

[A continuous position marker for whole-body computed tomography (author's transl)]. / Ein körperbezogenes CT-Lineal.

A new continuous position marker for whole-body computed tomography marks the distance from an anatomical point or from a radiation field, the left side of the patient, and the zero level in front of or behind the CT-picture.