Drosophila chromosome condensation proteins Topoisomerase II and Barren colocalize with Polycomb and maintain Fab-7 PRE silencing

Mechanisms of cellular memory control the maintenance of cellular identity at the level of chromatin structure. We have investigated whether the converse is true; namely, if functions responsible for maintenance of chromosome structure play a role in epigenetic control of gene expression. We show that Topoisomerase II (TOPOII) and Barren (BARR) interact in vivo with Polycomb group (PcG) target sequences in the bithorax complex of Drosophila, including Polycomb response elements. In addition, we find that the PcG protein Polyhomeotic (PH) interacts physically with TOPOII and BARR and that BARR is required for Fab-7-regulated homeotic gene expression. Conversely, we find defects in chromosome segregation associated with ph mutations. We propose that chromatin condensation proteins are involved in mechanisms acting in interphase that regulate chromosome domain topology and are essential for the maintenance of gene expression.     

Phytoplankton and particulate matter at the Weddell / Scotia Confluence (47°W) in summer 1989, as a final step of a temporal succession (EPOS project)

During January 1989, phytoplankton biomass and species composition were studied in a north / south transect at the Weddell / Scotia Confluence (47°W), between 57° and 61°30′S. Results showed a diatom bloom in the Scotia Sea (chlorophyll a 1.9 μg l⁻¹, particulate organic carbon 239 μg l⁻¹), dominated by Fragilariopsis cylindrus, Dactyliosolen antarcticus and Chaetoceros dichaeta. Low chlorophyll a / phaeopigments ratios (about 1.4) and silicate concentrations (15 μmol l⁻¹) suggested that this was an advanced bloom phase, probably linked to high grazing pressure. Minimum chlorophyll a values of 0.1–0.2 μg l⁻¹ and particulate organic carbon 46 μg l⁻¹ were found at the Weddell / Scotia Front and in a subsurface layer of the Weddell Sea Water. In the southern part of the transect (61°30′S), in the Weddell Sea, a second surface maximum was found (chlorophyll a 0.9 μg l⁻¹, particulate organic carbon 120 μg l⁻¹), but with a different species composition, with Cryptomonas sp. dominant. Our results show a succession within the diatom community in the Weddell / Scotia Confluence Waters when comparing the three EPOS legs. In the Weddell Sea from spring to summer, nanoflagellates, with only a minor contribution from diatoms, persist over a long period with little change in the community structure. We suggest that the frontal system, together with the receding ice edge and the grazing pressure of either krill or protozooplankton, are mainly responsible for the phytoplankton distribution patterns found. Received: 3 July 1996 / Accepted: 3 November 1996     

Structural Features of the Regulatory ACT Domain of Phenylalanine Hydroxylase

Phenylalanine hydroxylase (PAH) catalyzes the conversion of L-Phe to L-Tyr. Defects in PAH activity, caused by mutations in the human gene, result in the autosomal recessively inherited disease hyperphenylalaninemia. PAH activity is regulated by multiple factors, including phosphorylation and ligand binding. In particular, PAH displays positive cooperativity for L-Phe, which is proposed to bind the enzyme on an allosteric site in the N-terminal regulatory domain (RD), also classified as an ACT domain. This domain is found in several proteins and is able to bind amino acids. We used molecular dynamics simulations to obtain dynamical and structural insights into the isolated RD of PAH. Here we show that the principal motions involve conformational changes leading from an initial open to a final closed domain structure. The global intrinsic motions of the RD are correlated with exposure to solvent of a hydrophobic surface, which corresponds to the ligand binding-site of the ACT domain. Our results strongly suggest a relationship between the Phe-binding function and the overall dynamic behaviour of the enzyme. This relationship may be affected by structure-disturbing mutations. To elucidate the functional implications of the mutations, we investigated the structural effects on the dynamics of the human RD PAH induced by six missense hyperphenylalaninemia-causing mutations, namely p.G46S, p.F39C, p.F39L, p.I65S, p.I65T and p.I65V. These studies showed that the alterations in RD hydrophobic interactions induced by missense mutations could affect the functionality of the whole enzyme.     

A High Throughput Genotyping Approach Reveals Distinctive Autosomal Genetic Signatures for European and Near Eastern Wild Boar

The lack of a Near Eastern genetic signature in modern European porcine breeds indicates that, although domestic pigs from the Fertile Crescent entered Europe during the Neolithic, they were completely replaced by their European counterparts in a short window of time. Whilst the absence of such genetic signature has been convincingly demonstrated at the mitochondrial level, variation at the autosomal genomes of European and Near Eastern Sus scrofa has not been compared yet. Herewith, we have explored the genetic relationships among 43 wild boar from Europe (N = 21), Near East (N = 19) and Korea (N = 3), and 40 Iberian (N = 16), Canarian (N = 4) and Mangalitza (N = 20) pigs by using a high throughput SNP genotyping platform. After data filtering, 37,167 autosomal SNPs were used to perform population genetics analyses. A multidimensional scaling plot based on genome-wide identity-by-state pairwise distances inferred with PLINK showed that Near Eastern and European wild boar populations are genetically differentiated. Maximum likelihood trees built with TreeMix supported this conclusion i.e. an early population split between Near Eastern and European Sus scrofa was observed. Moreover, analysis of the data with Structure evidenced that the sampled Iberian, Canarian and Mangalitza pigs did not carry any autosomal signature compatible with a Near Eastern ancestry, a finding that agrees well with previous mitochondrial studies.     

Food habits of the ocelot,Leopardus pardalis,in two areas in southeast Brazil

The objective of this study was to compare the diet of the ocelot at two sites in southeastern Brazil: the small (957 ha), isolated Caratinga Biological Station (CBS), Minas Gerais and the large (>44,000 ha) contiguous area, comprised of the Vale do Rio Doce Natural Reserve (VRDNR) and the Sooretama Biological Reserve (SBR). We collected 60 scats in CBS from January 1997 to July 2000. Small rodents, small marsupials and primates were the most important items in terms of frequency of occurrence. In terms of biomass consumed, the brown howler monkey (Alouatta guariba) was the most important item. In the VRDNR/SBR we collected 77 scats from April 1995 to September 1996 and from January 1999 to September 2000. The main food items were armadillo (Dasypus sp.), small rodents, teju (Tupinambis merianae), and small marsupials. In VRDNR/SBR the ocelot had a more diverse diet, probably reflecting the diversity of prey species found in this area. The occurrence of ocelots in CBS indicates the adaptive flexibility of this felid to forests fragments, probably facilitated by the high biomass of potential prey – in this case, the primate Alouatta guariba.     

Biofouling of reverse osmosis membranes used in river water purification for drinking purposes: analysis of microbial populations

Biofouling in water treatment processes represents one of the most frequent causes of plant performance decline. Investigation of clogged membranes (reverse osmosis membranes, microfiltration membranes and ultrafiltration membranes) is generally performed on fresh membranes. In the present study, a multidisciplinary autopsy of a reverse osmosis membrane (ROM) was conducted. The membrane, which was used in sulfate-rich river water purification for drinking purposes, had become inoperative after 6 months because of biofouling and was later stored for 18 months in dry conditions before analysis. SSU rRNA gene library construction, clone sequencing, T-RFLP, light microscope, and scanning electron microscope (SEM) observations were used to identify the microorganisms present on the membrane and possibly responsible for biofouling at the time of removal. The microorganisms were mainly represented by bacteria belonging to the phylum Actinobacteria and by a single protozoan species belonging to the Lobosea group. The microbiological analysis was interpreted in the context of the treatment plant operations to hypothesize as to the possible mechanisms used by microorganisms to enter the plant and colonize the ROM surface.     

Isozyme variability detected by gel electrophoresis: influence of pH and temperature on esterase tested in Ornithogalum montanum Cyr. ex Ten. (Liliaceae)

Abstract

Electrophoretic tests on esterase using the conventional buffer have revealed in O. montanum a monomorphic locus. The use of a different buffer system and/or tests of thermostability have shown a more complex enzymatic system. These results may be considered in neutralist-selectionist controversy, that implies estimation of genetic variability for its solution.     

A mesenchymal stromal cell line resistant to paclitaxel that spontaneously differentiates into osteoblast-like cells

The mesenchymal stromal cell line SR-4987 has been established in our laboratory from the bone marrow of BDF/1 mice. Recent information on mesenchymal stem cells biology and the need to deal with well-characterized cell lines suggest to critically consider the existent data on this cell line by updating them with new investigations on growth parameters, in vitro plasticity, and drug sensitivity to anti-cancer, anti-inflammatory, and a histone deacetylase inhibitor. SR-4987 cells show a population doubling time of 24.5 ± 5.4 h, a plating efficiency of 2.87 ± 1.19%, and under stimulation maintain only in part their multipotency by differentiating towards chondro-osteogenic lineages but not into adipogenic. Surprisingly, these mesenchymal stromal cells differentiate spontaneously into osteoblast-like cells and this is significantly stimulated by valproic acid. SR-4987 cells show a dramatic resistance to paclitaxel (PTX) with a resistance index of 39.6 times (evaluated versus MOLT-4 leukemia) and of 68.2 (versus HT-29 colorectal carcinoma). SR-4987 resistance is reversed by verapamil and correlates with high expression of P-glycoprotein that is down-modulated by PTX. Taken together, our results indicated that SR-4987 line is a very interesting cell model useful to investigate both drug sensitivity resistance and physiopathological aspects related to mesenchymal cell function.     

Identifying Priority Giant Anteater (Myrmecophaga tridactyla) Populations for Conservation in São Paulo State,Brazil

Habitat loss is the main threat to biodiversity conservation worldwide. Some species may be particularly susceptible to the effects of fragmentation and the isolation of populations. The impacts of human activity on wild animal populations may be understood through relationships between individual genetic data and spatial landscape variables, particularly when considering local population dynamics influenced by fragmented habitats. Thus, the objective of this study was to analyze the population structure and genetic diversity of the giant anteater (Myrmecophaga tridactyla) using an individual sampling scheme (ISS) on a regional geographic scale. Data were collected from 41 specimens from twenty different locations in São Paulo State, Brazil, and six polymorphic microsatellite loci were genotyped. Our results indicate that barriers to gene flow exist and have segregated individuals of the farther away areas into two spatially structured clusters. The populations were also found to have high genetic diversity. The experimental sampling approach used herein enabled an analysis of the population dynamics of the giant anteater on a regional scale, as well as the identification of priority populations for genetic resource conservation for this species. The results reflect the need for adequate management plans. The efficacy of the sampling scheme may vary based on the study model used, but we argue that the use of an ISS combined with suitable molecular markers and statistical methods may serve as an important tool for initial analyses of threatened or vulnerable species, particularly in anthropized regions where populations are small or hard to characterize.