Evaluating DMS measurements and model results in the Northeast subarctic Pacific from 1996–2010

About a decade of dimethylsulphide (DMS) measurements in the North East Pacific are summarized and compared to model simulations. Bottle samples at various depths have been taken three times per year along Line P from the British Columbia coast to Ocean Station Papa (145°?W, 50°?N). Despite the long timeseries, DMS measurements are still sparse and the data show large variabilities in concentrations both spatially and temporally. DMS concentrations in late summer have been consistently high, while spring measurements at the offshore stations suggest a downward trend over the past years. Low values in spring, however, have also been recorded in the late 1990s, which might hint to interannual variability in the onset of the spring bloom and/or plankton assemblage rather than to a response to recent climate change. Some of the variability, both short-term and interannual, can be caused by regional or local preconditioning of the physical environment. The model simulations provide examples where periods of low winds, shallow mixed layers and sometimes high irradiance follow a mixing event and cause DMS peaks on various time scales as well as consistently elevated DMS concentrations for longer timeperiods. The model in its current configuration, which has been calibrated with measurements in the late 1990s/early 2000s, is not able to capture the low values in winter and spring observed in recent years. We suggest that this is due to missing or misrepresented links in the biogeochemical parameterizations of the model, e.g., an incomplete representation of variations in the phytoplankton assemblage. Including a seasonally varying S:N ratio to account for the absence of dinoflagellates in winter and spring significantly improves the simulation. Variability in DMS concentrations can also be induced by natural iron fertilization, which the model reproduces when timing is specified. For example, the model can reproduce the effects of natural volcanic Fe fertilization on surface water plankton dynamics and mixed layer DMS accumulation. The model also shows that the amplitude of the short term variability (days) increases when DMSP producing phytoplankton are less iron limited.     

New insights into stability of recombinant adenovirus vector genomes in mammalian cells

Recombinant adenoviruses are widely used in basic virology research, therapeutic applications, vaccination studies or simply as a tool for genetic manipulation of eukaryotic cells. Dependent on the application, transient or stable maintenance of the adenoviral genome and transgene expression are required. The newest generation of recombinant adenoviral vectors is represented by high-capacity adenoviral vectors (HC-AdVs) which lack all viral coding sequences. HC-AdVs were shown to result in long-term persistence of transgene expression and phenotypic correction in small and large animal models with negligible toxicity.Although there is evidence that adenoviral vectors predominantly persist as episomal DNA molecules with a low integration frequency into the host genome, detailed information about the nuclear fate and the molecular status of the HC-AdV genome once inside the nucleus is lacking. In recent years we have focused on analyzing and modifying the nuclear fate of HC-AdVs after infection of mammalian cells. We have focused on investigating the molecular DNA forms of HC-AdV genomes and we have designed strategies to excise and stably integrate a transgene from an episomal adenovirus vector genome into the host chromosomes by recombinases. This review article provides a state-of-the art overview of the current knowledge of episomal HC-AdV persistence and it discusses strategies for changing the nuclear fate of a transgene inserted into the HC-AdV genome by somatic integration into host chromosomes.     

Interspecific somatic hybrids between <Emphasis Type="Italic">Cyclamen persicum</Emphasis> and <Emphasis Type="Italic">C. coum</Emphasis>, two sexually incompatible species

By applying polyethylene glycol (PEG)-mediated protoplast fusion, the first somatic hybrids were obtained between Cyclamen persicum (2n = 2x = 48) and C. coum (2n = 2x = 30)—two species that cannot be combined by cross breeding. Heterofusion was detected by double fluorescent staining with fluorescein diacetate and scopoletin. The highest heterofusion frequencies (of about 5%) resulted from a protocol using a protoplast density of 1 × 10⁶/mL and 40% PEG. The DNA content of C. coum was estimated for the first time by propidium iodide staining to be 14.7 pg/2C and was 4.6 times higher than that of C. persicum. Among 200 in vitro plantlets regenerated from fusion experiments, most resembled the C. coum parent, whereas only 5 plants showed typical C. persicum phenotypes and 46 had a deviating morphology. By flow cytometry, six putative somatic hybrids were identified. A species-specific DNA marker was developed based on the sequence of the 5.8S gene in the ribosomal nuclear DNA and its flanking internal transcribed spacers ITS1 and ITS2. The hybrid status of only one plant could be verified by the species-specific DNA marker as well as sequencing of the amplification product. RAPD markers turned out to be less informative and applicable for hybrid identification, as no clear additivity of the parental marker bands was observed. Chromosome counting in root tips of four hybrids revealed the presence of the 30 C. coum chromosomes and 2–41 additional ones indicating elimination of C. persicum chromosomes.     

Structural characterization of the alpha-hemolysin monomer from Staphylococcus aureus

Alpha-hemolysin from Staphylococcus aureus is secreted as a water-soluble monomer and assembles on membranes to oligomerize into a homo-heptameric, water-filled pore. These pores lead to lysis and cell death. Although the structure of the heptameric pore is solved by means of X-ray crystallography, structures of intermediate states-from the soluble monomer to all potential "pre-pore" structures-are yet unknown. Here, we propose a model of the monomeric alpha-hemolysin in solution based on molecular modeling, verified by small angle X-ray scattering data. This structure reveals details of the monomeric conformation of the alpha-hemolysin, for example inherent flexibility, along with definite differences in comparison to the structures used as templates.     

Metabolic profile of the perivertebral muscles in small therian mammals: implications for the evolution of the mammalian trunk musculature

In order to gain a better understanding of the ancestral properties of the perivertebral muscles of mammals, this study investigated the fiber type composition of these muscles in six small, extant therians (two metatherians and four eutherians) similar in body shape to early mammals. Despite a few species-specific differences, the investigated species were very similar in their overall distribution of fiber types indicating similar functional demands on the back muscles in mammals of this body size and shape. Deep and short, mono- or multisegmental muscles (i.e., mm. interspinales, intermammillares, rotatores et intertransversarii) consistently showed the highest percentage of slow, oxidative fibers implying a function as local stabilizers of the vertebral column. Superficial and large, polysegmental muscles (i.e., mm. multifidus, sacrospinalis, iliopsoas et psoas minor) were predominantly composed of fast, glycolytic fibers suggesting they function to both globally stabilize and mobilize the spine during rapid non-locomotor and locomotor activities. Some muscles contained striking accumulations of oxidative fibers in specific regions (mm. longissimus et quadratus lumborum). These regions are hypothesized to function independently from the rest of the muscle belly and may be comparable in their functionality to regionalized limb muscles. The deep, central oxidative region in the m. longissimus lumborum appears to be a general feature of mammals and likely serves a proprioceptive function to control the postural equilibrium of the pelvic girdle and lumbar spine. The potential functions of the m. quadratus lumborum during ventilation and ventral stabilization of the vertebral column are discussed. Because representatives of the stem lineage of mammals were comparable in their body proportions and probably also locomotor parameters to the species investigated here, I suggest that the described fiber type distribution is representative of the ancestral condition in mammals. The origin of mammals was associated with a substantial enlargement of the epaxial muscles and the addition of subvertebral muscle mass. Because this novel muscle mass is mainly composed of fast, glycolytic fibers in extant species, it is plausible that these changes were associated with the evolution of increased sagittal mobility in the posterior trunk region in the therapsid ancestors of mammals. The caudally increasing role of sagittal bending in body propulsion is consistent with the overall increase in the percentage of glycolytic fibers in the cranio-caudal direction. The evolution of mammals was also associated with a loss of ribs in the posterior region of the trunk. This loss of ribs is thought to have decreased the stability of the posterior trunk, which may explain the observed greater oxidative capacity of the caudal local stabilizers. The increased need for postural feedback in the more mobile lumbar region may also explain the evolution of the proprioceptive system in the m. longissimus lumborum. Furthermore, the anatomical subdivision of the transversospinal muscle into several smaller muscle entities is suggested to facilitate their functional specialization.