Origin and fate of the nucleolar channel system of normal human endometrium

Human normal endometrium was examined in ultrathinsections.Nucleolar channel system(NCS)appeared in theendometrial epithelial cells during the early and mid secre-tory phase of menstrual cycle.The NCS was a hollow balllike structure of different sizes and was composed of 2 to 5rows of tubules embedded in an amorphous matrix.On itssurface there were numerous electron dense particles resem-bling ribosomes.It was usually located within or associatedwith the nucleolus.Sometimes,it was close to the nuclearenvelope or protruding out from the nucleus.On occasion,NCS with simplified structure was found in the perinuclearcytoplasm.Concepts concerning the genesis,involution andfunction(s) of the NCS were discussed.     

Developmental strategies in an invasive spider: constraints and plasticity

1. Growth defines the major life‐history traits such as size, weight, and age at maturity that determine an organism's fitness. Different models have been developed to describe growth by means of geometric progressions (e.g. Dyar's rule). However, growth forced along a geometric trajectory might constrain a plastic response to variable environmental conditions (e.g. food availability). 2. The present study investigated growth patterns under varying food conditions in the bridge spider, Larinioides sclopetarius, an extremely successful species in colonising urban habitats. 3. In L. sclopetarius growth ratios of successive instars were not constant but decreased over development. Instead, these spiders' growth is well described by a developmental growth rate (weight gain per moult) and a growth coefficient (weight gain per development time), both of which are based on a geometric progression. All developmental parameters, including developmental growth rate and growth coefficient as well as the intermoult duration and the number of instars, highly depend on food availability in L. sclopetarius and thus show plasticity. 4. Our study shows that geometric growth patterns do not necessarily preclude plasticity and that the parameters of geometric growth are affected by developmental plasticity. We suggest that their high developmental plasticity may facilitate bridge spiders' success in invading urban habitats.     

Counting the spots: a molecular and morphological phylogeny of the spotted darner Boyeria (Odonata: Anisoptera: Aeshnidae) with an emphasis on European taxa

Boyeria irene and Boyeria cretensis are species of spotted dragonflies belonging to the ‘darner’ family, Aeshnidae. In 1991, Peters classified Boyeria from Crete as B. cretensis, based on adult morphological characters. In this study, we used molecular evidence to determine if indeed B. irene and B. cretensis are different species. DNA was sequenced from samples of B. irene (from France, Switzerland, Tunisia, Spain and Italy) and B. cretensis (from Crete). These species were recovered as two different clades with strong support. We conclude that B. irene and B. cretensis are different species, with evidence based on molecular and morphological differences. In addition, we present the first phylogenetic hypothesis for Boyeria for which we have sequenced all but three species. Lastly, we discuss different scenarios that may have led to the present‐day distribution and speciation patterns of Mediterranean Boyeria.     

Microsporogenesis Abortion in Cytoplasmic Male Sterile Plants from H. petiolaris or H. petiolaris fallax Crossed by Sunflower (Helianthus annuus)

The microsporogenesis of two sunflower lines carrying two differentcytoplasmic male sterilities (CMS) from H. petiolaris (PL) andfrom H. petiolaris fallax (PF) has been studied and comparedto the normal process in male fertile lines. The first signsof abortion are, respectively, the vacuolation of the endoplasmicreticulum in PL during the first division of meiosis and theabnormal deposition of the endexine layer in PF during the vacuolationof the microspore. The genotype of the male line seems to modulate the stage ofpollen abortion, Furthermore, two ways of abortion have beenobserved for a single male sterile plant. Consequently, we suggestthat the ultrastructural observations reflect only the mainconsequences of a primary unknown event which takes place earlier. Cytoplasmic male-sterility, meiosis, Helianthus annuus L, H. petiolaris Nutt, microsporogenesis, electron microscopy     

The replicative helicase MCM recruits cohesin acetyltransferase ESCO2 to mediate centromeric sister chromatid cohesion

Chromosome segregation depends on sister chromatid cohesion which is established by cohesin during DNA replication. Cohesive cohesin complexes become acetylated to prevent their precocious release by WAPL before cells have reached mitosis. To obtain insight into how DNA replication, cohesion establishment and cohesin acetylation are coordinated, we analysed the interaction partners of 55 human proteins implicated in these processes by mass spectrometry. This proteomic screen revealed that on chromatin the cohesin acetyltransferase ESCO2 associates with the MCM2‐7 subcomplex of the replicative Cdc45‐MCM‐GINS helicase. The analysis of ESCO2 mutants defective in MCM binding indicates that these interactions are required for proper recruitment of ESCO2 to chromatin, cohesin acetylation during DNA replication, and centromeric cohesion. We propose that MCM binding enables ESCO2 to travel with replisomes to acetylate cohesive cohesin complexes in the vicinity of replication forks so that these complexes can be protected from precocious release by WAPL. Our results also indicate that ESCO1 and ESCO2 have distinct functions in maintaining cohesion between chromosome arms and centromeres, respectively.