The microtubule cross-linker Feo controls the midzone stability, motor composition, and elongation of the anaphase B spindle in Drosophila embryos.

Chromosome segregation during anaphase depends on chromosome-to-pole motility and pole-to-pole separation. We propose that in Drosophila embryos, the latter process (anaphase B) depends on a persistent kinesin-5-generated interpolar (ip) microtubule (MT) sliding filament mechanism that "engages" to push apart the spindle poles when poleward flux is turned off. Here we investigated the contribution of the midzonal, antiparallel MT-cross-linking nonmotor MAP, Feo, to this "slide-and-flux-or-elongate" mechanism. Whereas Feo homologues in other systems enhance the midzone localization of the MT-MT cross-linking motors kinesin-4, -5 and -6, the midzone localization of these motors is respectively enhanced, reduced, and unaffected by Feo. Strikingly, kinesin-5 localizes all along ipMTs of the anaphase B spindle in the presence of Feo, including at the midzone, but the antibody-induced dissociation of Feo increases kinesin-5 association with the midzone, which becomes abnormally narrow, leading to impaired anaphase B and incomplete chromosome segregation. Thus, although Feo and kinesin-5 both preferentially cross-link MTs into antiparallel polarity patterns, kinesin-5 cannot substitute for loss of Feo function. We propose that Feo controls the organization, stability, and motor composition of antiparallel ipMTs at the midzone, thereby facilitating the kinesin-5-driven sliding filament mechanism underlying proper anaphase B spindle elongation and chromosome segregation

Ten polymorphic microsatellite primers in the tropical tree caimito, Chrysophyllum cainito (Sapotaceae).

UnlabelledPremise of the studyWe developed microsatellite primers for the tropical tree Chrysophyllum cainito (Sapotaceae) to determine the native range of the species, investigate the origin of cultivated populations, and examine the partitioning of genetic diversity in wild and cultivated populations. •Methods and resultsWe developed 10 polymorphic primers from C. cainito genomic DNA libraries enriched for di-, tri-, and tetranucleotide repeat motifs. The loci amplified were polymorphic in samples collected from Jamaica and Panama. The number of alleles per locus ranged from two to 10 and three to 12, while observed heterozygosities ranged from 0.074 to 0.704 and 0.407 to 0.852 in Jamaica and Panama, respectively. •ConclusionsThe microsatellite primers will be useful in future population genetic studies as well as those aimed at understanding the geographic origin(s) of wild and cultivated populations

Unified line profiles for hydrogen perturbed by collisions with protons: satellites and asymmetries

We present new calculations of unified line profiles for hydrogen perturbed by collisions with protons. We report on new calculations of the potential energies and dipole moments which allow the evaluation of profiles for the lines of the Lyman series up to Lyman$\delta$ and the Balmer series up to Balmer10. Unified calculations only existed for the lines Lyman$\alpha$ to Lyman$\gamma$ and Balmer$\alpha$ including the H$_2^+$ quasi-molecule. These data are available as online material accompanying this paper and should be included in atmosphere models, in place of the Stark effect of protons, since the quasi-molecular contributions cause not only satellites, but large asymmetries that are unaccounted for in models that assume Stark broadening of electrons and protons are equal.Comment: 13 pages, 25 figures. Accepted for publication in MNRA

Transaction Costs in Dealer Markets: Evidence From The London Stock Exchange

This paper describes regularities in the intraday spreads and prices quoted by dealers on the London Stock Exchange. It develops a measure of spread-related transaction costs, one that recognizes dealers' willingness to price trades within their quoted spreads. This measure of transaction costs shows that trading costs are systematically related to a trade's size, characteristics of the trading counterparties, and security characteristics. Customers pay the full spread on small trades while medium to large trades receive more favorable execution. Market makers only discount very large customer trades while dealers regularly discount medium to large trades. Inter-dealer trades generally receive favorable execution, and discounts increase in size. Market makers do not discount trades with each other over the phone, but do discount when trading anonymously using inter-dealer-brokers. Quoted and touch spreads are falling in the number of market makers. The rate of decline is interpreted as reflecting economies of scale in market making.

International Equity Transactions and U.S. Portfolio Choice

This paper studies the cross-border transactions in equity by investors in Canada, Germany,Japan, the U.K. and the U.S. We find that investors from different countries make very different decisions about the allocation of their portfolio across markets. In contradiction to the notion that high variable transactions costs hinder international diversification, we find that the volume of gross equity flows vastly exceeds net equity flows and the turnover rate on foreign equity investments by some investors even exceeds domestic turnover rates. We also reject the hypothesis that U.S. investors follow the standard CAPM in allocating their global equity portfolio.