Bird versus bat pollination in the genus Marcgravia and the description of a new species

A short account on the history of observations into the pollination ecology in Marcgravia ( Marcgraviaceae ) is given. The different pollination syndromes encountered in the genus are discussed. The circumstances of the discovery of a new species in southern Ecuador are presented. This new species, Marcgravia helverseniana , is described and is illustrated here for the first time.     

Analysis of heterodimer formation by Xklp3A/B, a newly cloned kinesin-II from Xenopus laevis.

kinesin-II motor proteins are composed of two different kinesin-like motor proteins and one cargo binding subunit. Here we report the cloning of a new member of the kinesin-II superfamily, Xklp3A from Xenopus laevis, which forms a heterodimeric complex with Xklp3B. The heterodimer formation properties between Xklp3A and B have been tested in vitro using reticulocyte lysate expression and immunoprecipitation. To this end we produced a series of Xklp3A and B constructs of varying length and tested their propensity for heterodimer formation. We could demonstrate that, in contrast to conventional kinesin, the critical domains for heterodimer formation in Xklp3A/B are located at the C-terminal end of the stalk. Neither the neck nor the highly charged stretches after the neck region, which are typical of kinesins-II, are required for heterodimer formation, nor do they prevent homodimer formation. Dimerization is controlled by a cooperative mechanism between the C-terminal coiled-coil segments. Classical trigger sites were not identified. The critical regions for dimerization exhibit a very high degree of sequence conservation among equivalent members of the kinesin-II family.     

Bullatantriol,a sesquiterpene from annona bullata

Bullatantriol has been isolated from Annona bullata. Its constitution and relative configuration have been established by X-ray analysis. Its absolute configuration has been assigned by chiroptical investigation of the corresponding 7-ketone.     

A population genetics study of Anopheles darlingi (Diptera: Culicidae) from Colombia based on random amplified polymorphic DNA-polymerase chain reaction and amplified fragment lenght polymorphism markers

The genetic variation and population structure of three populations of Anopheles darlingi from Colombia were studied using random amplified polymorphic markers (RAPDs) and amplified fragment length polymorphism markers (AFLPs). Six RAPD primers produced 46 polymorphic fragments, while two AFLP primer combinations produced 197 polymorphic fragments from 71 DNA samples. Both of the evaluated genetic markers showed the presence of gene flow, suggesting that Colombian An. darlingi populations are in panmixia. Average genetic diversity, estimated from observed heterozygosity, was 0.374 (RAPD) and 0.309 (AFLP). RAPD and AFLP markers showed little evidence of geographic separation between eastern and western populations; however, the F ST values showed high gene flow between the two western populations (RAPD: F ST = 0.029; Nm: 8.5; AFLP: F ST = 0.051; Nm: 4.7). According to molecular variance analysis (AMOVA), the genetic distance between populations was significant (RAPD:phiST = 0.084; AFLP:phiST = 0.229, P < 0.001). The F ST distances and AMOVAs using AFLP loci support the differentiation of the Guyana biogeographic province population from those of the Chocó-Magdalena. In this last region, Chocó and Córdoba populations showed the highest genetic flow.     

Endocytosis optimizes the dynamic localization of membrane proteins that regulate cortical polarity

Diverse cell types require the ability to maintain dynamically polarized membrane-protein distributions through balancing transport and diffusion. However, design principles underlying dynamically maintained cortical polarity are not well understood. Here we constructed a mathematical model for characterizing the morphology of dynamically polarized protein distributions. We developed analytical approaches for measuring all model parameters from single-cell experiments. We applied our methods to a well-characterized system for studying polarized membrane proteins: budding yeast cells expressing activated Cdc42. We found that a balance of diffusion, directed transport, and endocytosis was sufficient for accurately describing polarization morphologies. Surprisingly, the model predicts that polarized regions are defined with a precision that is nearly optimal for measured endocytosis rates and that polarity can be dynamically stabilized through positive feedback with directed transport. Our approach provides a step toward understanding how biological systems shape spatially precise, unambiguous cortical polarity domains using dynamic processes.     

In vitro production of cat blastocysts of predetermined sex using flow cytometrically sorted semen

Sex preselection in cats can have applications for both breeding purposes and as an experimental model for endangered felids. The present study examined the ability to produce cat embryos from in vitro fertilization (IVF) of in vitro matured (IVM) cat oocytes with flow cytometrically sorted spermatozoa and to verify the sex of the embryos obtained from sexed spermatozoa by PCR. In the first experiment, a total of 224 oocytes were fertilized with spermatozoa from six ejaculates sorted without sex separation. The sorting process did not influence the cleavage rate (sorted 44.0% versus unsorted 46.1%), day 6 morula-blastocyst rate (sorted 26.6% versus unsorted 29.6%) and day 7 blastocyst rate (sorted 16.5% versus unsorted 16.5%). In the second experiment, a total of 84 IVM oocytes were fertilized with sorted X- and Y-chromosome bearing spermatozoa from four ejaculates in order to obtain embryos of preselected sex. Embryonic sex determination by PCR revealed that 21 out of 24 embryos reaching morula/blastocyst stage (87.5%) were of the desired sex. In particular 12 out of 14 embryos (85.7%) derived from X-bearing spermatozoa were female and 9 embryos out of 10 (90%) derived from Y-bearing spermatozoa were male. Our results show, for the first time, that X- and Y-chromosome bearing spermatozoa sorted by high-speed flow cytometry can be successfully used in an IVM-IVF system to obtain cat embryos of a predetermined sex.