Structural view of the Ran-Importin beta interaction at 2.3 A resolution.

Transport receptors of the Importin beta family shuttle between the nucleus and cytoplasm and mediate transport of macromolecules through nuclear pore complexes. They interact specifically with the GTP-binding protein Ran, which in turn regulates their interaction with cargo. Here, we report the three-dimensional structure of a complex between Ran bound to the nonhydrolyzable GTP analog GppNHp and a 462-residue fragment from Importin beta. The structure of Importin beta shows 10 tandem repeats resembling HEAT and Armadillo motifs. They form an irregular crescent, the concave site of which forms the interface with Ran-triphosphate. The importin-binding site of Ran does not overlap with that of the Ran-binding domain of RanBP2.     

Infection dynamics of different Wolbachia-types within one host population

Wolbachia are widespread intracellular symbionts of arthropods which are known to cause several reproductive manipulations in their hosts, the commonest of which being cytoplasmic incompatibility (CI), male killing (MK), and the induction of parthenogenesis (PI). Strains of endosymbionts inducing one of these effects can be referred to as 'Wolbachia-types'. Here, we try to ascertain whether two of these Wolbachia-types can stably coexist within one population. We investigate this question by means of two discrete-time mathematical models which describe the dynamics of an infection of a host population with either CI- and MK- or CI- and PI-Wolbachia. We derive analytical solutions for two special cases of each model showing that stable coexistence of the respective Wolbachia-types is not possible if no doubly infected individuals occur within the population and that stable coexistence is possible when doubly infected hosts do exist and transmission of the endosymbionts is perfect. Moreover, we show that a population infected with either CI- or MK-Wolbachia at equilibrium can resist invasion of the respective other Wolbachia-type as a single infection. In contrast, a population infected with CI-Wolbachia can be invaded by PI-Wolbachia as a single infection with the CI-Wolbachia going extinct. Computer simulations confirmed these findings for the general models. We discuss our results with respect to the prevalence of the Wolbachia-types considered here and the emergence of PI- from CI-Wolbachia.     

Effect of Separation Conditions on Automated Isoelectric Focusing of Carbohydrate-Deficient Transferrin and Other Human Isotransferrins Using the PhastSystem

To investigate the effect of automated isoelectric focusing conditions in the PhastSystem, e.g., the point of sample application, prerun and separation times, and minimized gels on isotransferrin band pattern, human sera were analyzed with native transferrin iron load, after iron saturation or iron depletion in vitro. Varying the focusing conditions we found (i) Point of sample application (anode, middle of the gel, cathode) strongly affected transferrin iron loss. It was greatest at the anode and least at the cathode. (ii) Without prerun, distinct transferrin iron loss also occurred. A short prerun time prevented iron loss, but increasing it did not improve transferrin iron load stability as stated by others. (iii) An inappropriately long separation time inevitably yielded iron loss. In conclusion, inappropriate isoelectric focusing conditions strongly affect iron load stability of isotransferrins (obviously via low pH within the gel), resulting in transferrin iron release and cofocusing of isotransferrins with different sialic acid or iron contents. For determination of carbohydrate-deficient transferrin, such conditions resulted in overestimation of the marker of chronic alcohol abuse. Our findings may be of guiding importance for isoelectric focusing of protein-ligand complexes. We recommend the procedure described for development of isoelectric focusing of protein-ligand complexes.     

Inductive stimulation

Electrical stimulation, which has long been known, has recently been complemented by electromagnetic stimulation. This method is based on the law of induction and employs coils in place of electrodes. The effect of this process is deduced from both the relationship between magnetic and electrical fields and the stimulating effect. A new type of stimulator has been developed from a resonant circuit, thus allowing nerves to be excited with low-frequency pulses up to fusion frequency.     

Rostock zooplankton studies off West Africa

Since the beginning of the seventies, upwelling research has become increasingly popular in the path of the Canary and Benguela Current, because of economic consideration, particularly in the relation to fisheries and marine geology. Many expeditions were carried out between 1970 and 1977, including 8 cruises of the German R. V. “A. v. Humboldt” operating from Rostock. Measurements covered scales ranging in time from minutes to several years and in space from hundreds of metres to several thousands of kilometres. Zooplankton studies focussed on quantitative, metabolic, taxonomic, and parasitological aspects. Plankton was collected with a WP-2-UNESCO standard net to a maximum depth of 200 m. The epipelagic mesozooplankton consists mainly of copepods, especially calanoids with developmental times of about 20 to 23 days. After an upwelling event, zooplankton is able to double its biomass. This typical biomass increase is independent of coastal distance and depth. The upwelling response lasts about 3 weeks in nearsurface waters, and 6 to 8 weeks in depths below 75m. A relationship was observed between the duration of seasonal upwelling (that means the numbers of single upwelling events) and the cumulative increase of biomass. This net growth rate of zooplankton biomass is most pronounced at the shelf break, the area with the highest fish biomass, and in the upper 25 m. Differences between the expected and the real rate values in conjunction with the known amount of nutritive demands of fishes allow the estimation of the fish biomass in a given area. The near coastal Ekman upwelling, which is an event in the time scale of about two weeks, also shows seasonality in some areas. Off Northwest Africa the largest expansion was recorded in the first half of the year, extending from 10° N to 24° N, more than 400 km offshore and at least down to 200 m. It contracts in the second half of the year to an area between 20°N and 22°N, 100 to 200 km off the coast and in an average depth of 25 m. These zooplankton biomass patterns are superimposed by mesoscale phenomena, originated by other than Ekman upwelling events. Those are, for example, long coastal parallel waves, producing cells of intensified upwelling and downwelling, and eddies, caused by instabilities in a frontal zone parallel to the coast. Different water masses can be distinguished by indicator species, species combinations or the significant absence of species. This was demonstrated for chaetognaths. The calanoidCalanus helgolandicus (Claus, 1863), a typical species of the North Atlantic, indicates North Atlantic Central Water, whereasCalanoides carinatus (Krøyer, 1849) is an indicator of South Atlantic Central Water. Finally, comparisons of near coastal current regimes, transport velocities, and developmental rates of calanoids allow one to conclude that a suitable mechanism is present to maintain plankton in the coastal environment.     

Prostaglandin analog synthesis using hexamethylphosphorous triamide — Alkenylcuprate(I)

The synthesis of Prostaglandin PGE₁ and 11-desoxy PGE₁ analogs via a new solubilized mixed organo cuprate reagent, hexamethylphosphorous triamide — alkenylcuprate(I), has been accomplished in overall yields of 30% to 45% from the corresponding cyclopentenones ($\text{3}$a;b).