A covariotide model explains apparent phylogenetic structure of oxygenic photosynthetic lineages

The aims of the work were (1) to develop statistical tests to identify whether substitution takes place under a covariotide model in sequences used for phylogenetic inference and (2) to determine the influence of covariotide substitution on phylogenetic trees inferred for photosynthetic and other organisms. (Covariotide and covarion models are ones in which sites that are variable in some parts of the underlying tree are invariable in others and vice versa.) Two tests were developed. The first was a contingency test, and the second was an inequality test comparing the expected number of variable sites in two groups with the observed number. Application of these tests to 16S rDNA and tufA sequences from a range of nonphotosynthetic prokaryotes and oxygenic photosynthetic prokaryotes and eukaryotes suggests the occurrence of a covariotide mechanism. The degree of support for partitioning of taxa in reconstructed trees involving these organisms was determined in the presence or absence of sites showing particular substitution patterns. This analysis showed that the support for splits between (1) photosynthetic eukaryotes and prokaryotes and (2) photosynthetic and nonphotosynthetic organisms could be accounted for by patterns arising from covariotide substitution. We show that the additional problem of compositional bias in sequence data needs to be considered in the context of patterns of covariotide/covarion substitution. We argue that while covariotide or covarion substitution may give rise to phylogenetically informative patterns in sequence data, this may not always be so.      

禾木科植物染色体消除型远缘杂交的研究进展

植物远缘杂交是作物育种中广泛应用的技术。除了核型稳定的种间杂交可以获得杂种以外,还可以利用核型不稳定的种间杂交后父本染色体消除的现象,通过胚培养和染色体加倍处理获得加倍单倍体(     

Crystallization of hen eggwhite riboflavin-binding protein

Crystals of hen eggwhite riboflavin-binding protein have been grown by equilibrium dialysis in solutions buffered with 0.05 m-Tris · HCl (pH 8.5) using ammonium sulphate as the precipitant. The crystals belong to the space group P3₁21 (or enantiomorph) with $\text{a = b = 112.5}\text{A}\text{?}\text{and}\text{c = 72.0}\text{A}\text{?}\text{,}$ and diffract to a resolution of 2.8 Å.     

Syzygium cumini is more effective in preventing the increase of erythrocytic ADA activity than phenolic compounds under hyperglycemic conditions in vitro

Syzygium cumini (S. cumini) is a plant known for its antidiabetic properties. The aim of this study was to evaluate the effect of Sc aqueous leaf extract (ASc) on adenosine deaminase (ADA) activity in erythrocytes (RBCs) exposed to high glucose concentrations (30 mM) in vitro. We also investigated the effects of the main phenolic compounds found in ASc (gallic acid, rutin, and chlorogenic acid) and the effects of insulin, caffeine, and dipyridamole, which are substances involved in the adenosine metabolism, on ADA activity in vitro. Blood samples were obtained from healthy volunteers and a suspension of RBCs was used for the determination of ADA activity. The results showed that: (1) the effect of ASc on ADA activity was more significant than the combination of phenolic compounds; (2) insulin, caffeine, or dipyridamole prevented high glucose increase of ADA activity at doses as low as 50 μU/mL, 25 μM, and 1 μM, respectively; (3) the inhibitory effect caused by ASc on erythrocyte ADA activity remained practically the same after the combination of the extract with insulin or caffeine; (4) when RBCs were exposed to ASc plus dipyridamole, this chemical attenuated the effect of ASc on ADA activity, suggesting an antagonism or a competition with ASc by the same site of action. Therefore, ASc was more effective in preventing the increase in ADA activity than phenolic compounds, suggesting that ASc may collaborate to improve endothelial dysfunction, antioxidant, anti-inflammatory, and antithrombotic properties of adenosine by affecting its metabolism. The results of this study help to provide evidence of the empirically supported benefits of the use of S. cumini in diabetes.     

Trypanosoma evansi: Hematologic changes in experimentally infected cats

This study aimed at evaluating hemogram and erythropoietic changes in cats experimentally infected with Trypanosoma evansi. Thirteen adult female non-breeding Felix catus were separated into two groups: seven animals were infected with 10⁸ trypomastigotes each, and six animals were used as negative controls. Animals were kept in air-conditioned rooms and blood smears were performed daily for 49 days. Blood samples were collected from the jugular vein at days 0, 7, 21, 35 and 49 and stored in blood-collecting tubes containing anticoagulant. Bone marrow was collected from the proximal epiphysis of the right femur at days 14 and 42 post-inoculation (PI). Total erythrocyte count, hematocrit and hemoglobin showed statistical differences among groups from the seventh day PI onwards (P < 0.05). The mean corpuscular volume and the mean corpuscular hemoglobin concentration remained normal, characterizing a normocytic-normochromic anemia. Reticulocyte count increased in the infected group from the 21st day onwards, but remained near normal values suggesting a mild regenerative anemia. Moreover, the myeloid:erythroid ratio significantly reduced at day 42 PI, evidencing a bone marrow hematopoietic response. Based on these results we conclude that cats infected with T. evansi have normocytic, normochromic, regenerative anemia.     

Toll‐deficient Drosophila is susceptible to Pythium insidiosum infection

There is a paucity of animal models of pythiosis, a life‐threatening disease of humans and animals, the immunopathogenesis of which is poorly understood. A pythiosis model was developed by injecting Toll (Tl)‐deficient Drosophila melanogaster flies with Pythium insidiosum zoospores. The infected Tl mutant flies had significantly lower survival rates (73.7%) than did control flies. This study reveals the important role of Tl pathway activation in fly immune response to pythiosis.     

A suitable model for the utilization of Duddingtonia flagrans fungus in small-flock-size sheep farms

Effective alternatives to anthelmintic treatment of nematode parasite infections of sheep are required because of the high prevalence of drug resistance. Within this context, the nematode-trapping fungus Duddingtonia flagrans has become a valuable component of various integrated control strategies. Toward this objective, a small quantity of lyophilized D. flagrans chlamydospores (10⁶ spores per animal) was administered to sheep in a one-year plot study. Animals grazing on native pasture were divided into two homogeneous groups and were kept in 1-ha paddocks in the southern region of Brazil. The oral administration of chlamydospores led to a significant reduction (p < 0.05) in the number of nematode eggs per gram of feces and in the larval availability on herbage (difference of 37.6%) in comparison to the control group. Control animals needed to be dewormed three times during the experiment, whereas the fungus-treated animals maintained a low parasite load, independent of seasonal variation. Although D. flagrans cannot serve as a panacea for nematode parasite control of livestock, it represents a significant advance toward rationalizing the use of endoparasitic drugs in small animals.     

Social and genetic structure in colonies of the social wasp <Emphasis Type="Italic">Microstigmus nigrophthalmus</Emphasis>

Microstigmus (Hymenoptera: Crabronidae) is a genus of social apoid wasps which represents an origin of sociality independent from vespoids, but which has so far received little attention. Though group-nesting is widespread in Microstigmus, genetic relatedness has so far been studied in only one species, M. comes. We report on the social biology of M. nigrophthalmus, drawing from behavioural observations and molecular genetic analyses of relatedness and kinship. There was no evidence of distinctive behavioural suites that distinguished reproductive and non-reproductive individuals. Females could mate more than once, but mating frequency was low. Mean relatedness within nests was high, particularly between females (close to 0.5), but pairwise relatedness values were very variable, as nestmates displayed a wide range of relationships. Such high levels of relatedness should be a factor promoting social nesting and cooperative brood care in this species, as females gain only a slight genetic advantage through rearing their own offspring rather than those of nestmates. This study provides the finest analysis of genetic structure so far in an apoid wasp, and indicates that the form of sociality varies greatly between species of Microstigmus.     

Antiproliferative Effects of Fluoxetine on Colon Cancer Cells and in a Colonic Carcinogen Mouse Model

The antidepressant fluoxetine has been under discussion because of its potential influence on cancer risk. It was found to inhibit the development of carcinogen-induced preneoplastic lesions in colon tissue, but the mechanisms of action are not well understood. Therefore, we investigated anti-proliferative effects, and used HT29 colon tumor cells in vitro, as well as C57BL/6 mice exposed to intra-rectal treatment with the carcinogen N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) as models. Fluoxetine increased the percentage of HT29 cells in the G₀/G₁ phase of cell-cycle, and the expression of p27 protein. This was not related to an induction of apoptosis, reactive oxygen species or DNA damage. In vivo, fluoxetine reduced the development of MNNG-induced dysplasia and vascularization-related dysplasia in colon tissue, which was analyzed by histopathological techniques. An anti-proliferative potential of fluoxetine was observed in epithelial and stromal areas. It was accompanied by a reduction of VEGF expression and of the number of cells with angiogenic potential, such as CD133, CD34, and CD31-positive cell clusters. Taken together, our findings suggest that fluoxetine treatment targets steps of early colon carcinogenesis. This confirms its protective potential, explaining at least partially the lower colon cancer risk under antidepressant therapy.     

Influence of nutrients and currents on the genomic composition of microbes across an upwelling mosaic

Metagenomic data sets were generated from samples collected along a coastal to open ocean transect between Southern California Bight and California Current waters during a seasonal upwelling event, providing an opportunity to examine the impact of episodic pulses of cold nutrient-rich water into surface ocean microbial communities. The data set consists of ∼5.8 million predicted proteins across seven sites, from three different size classes: 0.1–0.8, 0.8–3.0 and 3.0–200.0 μm. Taxonomic and metabolic analyses suggest that sequences from the 0.1–0.8 μm size class correlated with their position along the upwelling mosaic. However, taxonomic profiles of bacteria from the larger size classes (0.8–200 μm) were less constrained by habitat and characterized by an increase in Cyanobacteria, Bacteroidetes, Flavobacteria and double-stranded DNA viral sequences. Functional annotation of transmembrane proteins indicate that sites comprised of organisms with small genomes have an enrichment of transporters with substrate specificities for amino acids, iron and cadmium, whereas organisms with larger genomes have a higher percentage of transporters for ammonium and potassium. Eukaryotic-type glutamine synthetase (GS) II proteins were identified and taxonomically classified as viral, most closely related to the GSII in Mimivirus, suggesting that marine Mimivirus-like particles may have played a role in the transfer of GSII gene functions. Additionally, a Planctomycete bloom was sampled from one upwelling site providing a rare opportunity to assess the genomic composition of a marine Planctomycete population. The significant correlations observed between genomic properties, community structure and nutrient availability provide insights into habitat-driven dynamics among oligotrophic versus upwelled marine waters adjoining each other spatially.