Evolution of proton pumping ATPases: Rooting the tree of life

Proton pumping ATPases are found in all groups of present day organisms. The F-ATPases of eubacteria, mitochondria and chloroplasts also function as ATP synthases, i.e., they catalyze the final step that transforms the energy available from reduction/oxidation reactions (e.g., in photosynthesis) into ATP, the usual energy currency of modern cells. The primary structure of these ATPases/ATP synthases was found to be much more conserved between different groups of bacteria than other parts of the photosynthetic machinery, e.g., reaction center proteins and redox carrier complexes.These F-ATPases and the vacuolar type ATPase, which is found on many of the endomembranes of eukaryotic cells, were shown to be homologous to each other; i.e., these two groups of ATPases evolved from the same enzyme present in the common ancestor. (The term eubacteria is used here to denote the phylogenetic group containing all bacteria except the archaebacteria.) Sequences obtained for the plasmamembrane ATPase of various archaebacteria revealed that this ATPase is much more similar to the eukaryotic than to the eubacterial counterpart. The eukaryotic cell of higher organisms evolved from a symbiosis between eubacteria (that evolved into mitochondria and chloroplasts) and a host organism. Using the vacuolar type ATPase as a molecular marker for the cytoplasmic component of the eukaryotic cell reveals that this host organism was a close relative of the archaebacteria.A unique feature of the evolution of the ATPases is the presence of a non-catalytic subunit that is paralogous to the catalytic subunit, i.e., the two types of subunits evolved from a common ancestral gene. Since the gene duplication that gave rise to these two types of subunits had already occurred in the last common ancestor of all living organisms, this non-catalytic subunit can be used to root the tree of life by means of an outgroup; that is, the location of the last common ancestor of the major domains of living organisms (archaebacteria, eubacteria and eukaryotes) can be located in the tree of life without assuming constant or equal rates of change in the different branches.A correlation between structure and function of ATPases has been established for present day organisms. Implications resulting from this correlation for biochemical pathways, especially photosynthesis, that were operative in the last common ancestor and preceding life forms are discussed.     

Temperature influence on life table statistics of the chicken miteDermanyssus gallinae (Acari: Dermanyssidae)

An age-specific life table for the chicken miteDermanyssus gallinae (DeGeer, 1778) was based on various observations carried out at 25°C. The generation time was calculated to be 16.8 days; the intrinsic rate of natural increase was 0.12 per day, and the net reproductive rate was 7.2. A nonlinear function was found satisfactory to describe the developmental rate of the different immature lifestages at temperatures below 40°C. The stage-specific survival of the immature life-stages was generally high between 10 and 37°C, but decreased quickly outside this temperature range. Most of the eggs were laid during the first three weeks of the adult life. The proportion of surviving females rapidly decreases after moulting to the adult stage. At a temperature of 30°C, the highest number of eggs (3 eggs per day) was laid.     

Eine einfache methode zur erfassung der parameter von spitzwinkeligen gastropodengehäusen

The D.M. Raup & A. Michelson model of assessing shell-coiling constitutes a method which simplifies the measuring of spiral-coiling gastropod shells. With, this method the information is obtained by measuring the photograph of the object.The newly developed method has the advantage of dispensing with an exact shell orientation (horizontally located axis) and magnification.Instead of photographing the object with a camera the shell is placed upon photographic paper and in this manner a contact showing the shell outlines can be achieved by exposing and developing the print. Correct information is then obtained by means of the conversion factors (1–3) as outlined in this paper.     

Correspondenz

Ohne Zusammenfassung     

Efficient deletion of LoxP-flanked selectable marker genes from the genome of transgenic pigs by an engineered Cre recombinase

Genetically modified (GM) pigs hold great promises for pig genetic improvement, human health and life science. When GM pigs are produced, selectable marker genes (SMGs) are usually introduced into their genomes for host cell or animal recognition. However, the SMGs that remain in GM pigs might have multiple side effects. To avoid the possible side effects caused by the SMGs, they should be removed from the genome of GM pigs before their commercialization. The Cre recombinase is commonly used to delete the LoxP sites-flanked SMGs from the genome of GM animals. Although SMG-free GM pigs have been generated by Cre-mediated recombination, more efficient and cost-effective approaches are essential for the commercialization of SMG-free GM pigs. In this article we describe the production of a recombinant Cre protein containing a cell-penetrating and a nuclear localization signal peptide in one construct. This engineered Cre enzyme can efficiently excise the LoxP-flanked SMGs in cultured fibroblasts isolated from a transgenic pig, which then can be used as nuclear donor cells to generate live SMG-free GM pigs harboring a desired transgene by somatic cell nuclear transfer. This study describes an efficient and far-less costly method for production of SMG-free GM pigs.

     

Age-related changes in neuromuscular function of the quadriceps muscle in physically active adults

Substantial evidence exists for the age-related decline in maximal strength and strength development. Despite the importance of knee extensor strength for physical function and mobility in the elderly, studies focusing on the underlying neuromuscular mechanisms of the quadriceps muscle weakness are limited.The aim of this study was to investigate the contributions of age-related neural and muscular changes in the quadriceps muscle to decreases in isometric maximal voluntary torque (iMVT) and explosive voluntary strength. The interpolated twitch technique and normalized surface electromyography (EMG) signal during iMVT were analyzed to assess changes in neural drive to the muscles of 15 young and 15 elderly volunteers. The maximal rate of torque development as well as rate of torque development, impulse and neuromuscular activation in the early phase of contraction were determined. Spinal excitability was estimated using the H reflex technique. Changes at the muscle level were evaluated by analyzing the contractile properties and lean mass.The age-related decrease in iMVT was accompanied by a decline in voluntary activation and normalized surface EMG amplitude. Mechanical parameters of explosive voluntary strength were reduced while the corresponding muscle activation remained primarily unchanged. The spinal excitability of the vastus medialis was not different while M wave latency was longer. Contractile properties and lean mass were reduced.In conclusion, the age-related decline in iMVT of the quadriceps muscle might be due to a reduced neural drive and changes in skeletal muscle properties. The decrease in explosive voluntary strength seemed to be more affected by muscular than by neural changes.