Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex

The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S nuclear ribosomal DNA sequence and the intervening 5.8S region were sequenced from three individuals in each of eight taxa of the Mimulus guttatus species complex. Three discrete variants, or "types," of ITS sequences were found, among which 30%-40% of sites differed, compared with 1%-2% within types. Dot plots indicate that these types were not related by conspicuous rearrangements or inversions. More than one ITS type was often found in the same taxon, and two of three ITS types span species boundaries, indicating their presence prior to speciation. These ITS sequences showed essentially no positional homology with the nearest sequenced relative, tomato. In contrast, the 5.8S region was relatively unvaried, with 8 of 162 sites varied in the sample among all eight taxa. The phylogeny inferred by the most common ITS sequence type, rooted by the two other ITS types, agreed with isozymes in showing the distinctness of M. nudatus, M. laciniatus, and M. tilingii from the other five taxa.      

POPULATION GENETIC STRUCTURE IN DIPLOID BLUEBERRY VACCINIUM SECTION CYANOCOCCUS (ERICACEAE)

Vaccinium section Cyanococcus comprises diploid, tetraploid, and hexaploid species (x = 12) all of which are highly self-sterile. In order to assess the distribution of genetic variation within and among the diploids, population genetic analyses of allozyme data were conducted on three species: V. elliottii, V. myrtilloides, and V. tenellum. Populations were located throughout the range of these taxa in eastern North America. Data were collected at 20 loci, 12 of which are mendelian based on formal genetic analyses. Consistent with expectations for out-crossing taxa, these species exhibited high levels of variation within populations. Eighteen loci were polymorphic with the number and frequency of alleles varying among taxa. Mean values for the number of alleles per polymorphic locus, proportion of polymorphic loci, and expected heterozygosity were 2.8, 48.2, and 0.148, respectively. High infraspecific genetic identities exceeding 0.9 indicated that these taxa are homogeneous. All populations were in Hardy-Weinberg equilibrium with slight heterozygote excess observed in V. myrtilloides and V. tenellum. Although total genetic diversity was lower than that observed for other predominantly out-crossing species, it was apportioned similarly. The majority could be attributed to differences among individuals within populations. Conspecific populations were relatively undifferentiated with genetic differentiation similar to other self-incompatible species.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

Population genomic evidence for plant glacial survival in Scandinavia

Quaternary glaciations have played a major role in shaping the genetic diversity and distribution of plant species. Strong palaeoecological and genetic evidence supports a postglacial recolonization of most plant species to northern Europe from southern, eastern and even western glacial refugia. Although highly controversial, the existence of small in situ glacial refugia in northern Europe has recently gained molecular support. We used genomic analyses to examine the phylogeography of a species that is critical in this debate. Carex scirpoidea Michx subsp. scirpoidea is a dioecious, amphi‐Atlantic arctic–alpine sedge that is widely distributed in North America, but absent from most of Eurasia, apart from three extremely disjunct populations in Norway, all well within the limits of the Weichselian ice sheet. Range‐wide population sampling and variation at 5,307 single nucleotide polymorphisms show that the three Norwegian populations comprise unique evolutionary lineages divergent from Greenland with high between‐population divergence. The Norwegian populations have low within‐population genetic diversity consistent with having experienced genetic bottlenecks in glacial refugia, and host private alleles that probably accumulated in long‐term isolated populations. Demographic analyses support a single, pre‐Weichselian colonization into Norway from East Greenland, and subsequent divergence of the three populations in separate refugia. Other refugial areas are identified in North‐east Greenland, Minnesota/Michigan, Colorado and Alaska. Admixed populations in British Columbia and West Greenland indicate postglacial contact. Taken together, evidence from this study strongly indicates in situ glacial survival in Scandinavia.     

Allozyme evidence for genetic autopolyploidy and high genetic diversity in tetraploid cranberry, Vaccinium oxycoccos (Ericaceae)

Polyploidy has been important in the evolution of angiosperms and may significantly affect population genetic diversity and structure. Nineteen isoenzyme loci were studied in diploid and tetraploid populations of Vaccinium oxycoccos (Ericaceae), and the results are compared with data previously reported for the related V. macrocarpon. Diploid V. oxycoccos and V. macrocarpon were readily discriminated based on their allozymic variation. No evidence for fixed heterozygosity was found in tetraploid V. oxycoccos. In contrast, all polymorphic loci exhibited both balanced and unbalanced heterozygotes, with some individuals exhibiting a pattern consistent with the presence of three alleles. These results support an autopolyploid origin for tetraploid V. oxycoccos. However, tetraploid V. oxycoccos possessed a suite of alleles not found in diploid V. oxycoccos; half of these alleles were shared with V. macrocarpon. This suggests that autotetraploid V. oxycoccos may have undergone hybridization with V. macrocarpon or that the autotetraploid retained the genetic variation present in an ancestral diploid species. Following theoretical expectations, proportion of polymorphic loci, mean number of alleles, and observed heterozygosity were significantly higher for the autotetraploid than for the diploid. Mean inbreeding (F(IS)) was similar for diploid and tetraploid V. oxycoccos. The latter exhibited population differentiation (F(ST)) exceeding both diploid species.     

Effects of long-term fixation on histological quality of undecalcified murine bones embedded in methylmethacrylate

While long-term fixation and storage of specimens is common and useful for many research projects, it is particularly important for space flight investigations where samples may not be returned to Earth for several months (International Space Station) or years (manned mission to Mars). We examined two critical challenges of space flight experimentation: the effect of long-term fixation on the quality of mouse bone preservation and the preservation of antigens and enzymes for both histochemical and immunohistochemical analyses, and how the animal/sample processing affects the preservation. We show that long-term fixation minimally affects standard histological staining, but that enzyme histochemistry and immunolabeling are greatly compromised. Further, we demonstrate that whole animal preservation is not as suitable as whole leg or stripped leg preservation for long-term fixation and all histological analyses. Overall, we recommend whole leg processing for long-term storage of bone specimens in fixative prior to embedding in plastic for histological examination.     

Evidence for genetic allopolyploidy in <Emphasis Type="Italic">Eutrema edwardsii</Emphasis> (Brassicaceae): implications for conservation

Eutrema edwardsii R.Br. (Brassicaceae) is an arctic-alpine mustard with a circumpolar distribution. Its closest relative, Eutrema penlandii Rollins, is a federally listed, threatened species that is endemic to the Mosquito Range in the Southern Rocky Mountains of Colorado, USA. As part of a larger project addressing the systematics of this species complex in North America, we conducted chromosome counts, flow cytometry, and allozyme analysis to test the hypothesis that these taxa comprise an autopolyploid complex. Within that context, it should be noted that a chromosome count has not been reported previously for E. penlandii. Results obtained from mitotic counts obtained for two populations of E. penlandii reveal this taxon to be diploid. Diploidy was confirmed using flow cytometry for an additional 15 individuals representing four populations. Previously published chromosome counts for E. edwardsii reveal a polyploid complex of tetraploid, hexaploid, and octaploid populations for which an autopolyploid origin has been presumed. However, allozyme analysis revealed an allopolyploid origin for E. edwardsii, as evidenced from fixed heterozygosity at six loci. Although our data suggest that E. penlandii is a close relative of one of the progenitors of E. edwardsii, the taxonomic identity of the other progenitor(s) cannot be elucidated from these data. The data reported herein support the recognition of E. penlandii as taxonomically distinct, which has implications for conservation, and reveal cryptic variation within E. edwardsii.     

Acute toxicity effects of ibuprofen on behaviour and haematological parameters of African catfish Clarias gariepinus (Burchell, 1822)

Indiscriminate discharge of pharmaceutical waste into the aquatic ecosystem may pose serious health challenges to aquatic biota. The effect of acute exposure to ibuprofen was evaluated using changes in behaviour and haematological parameters under static bio-assay method in Clarias gariepinus. Test specimens were exposed to acute concentrations of ibuprofen (0.28, 0.33, 0.38, 0.43 and 0.48 mg l^?1) for 24, 48, 72 and 96 h durations respectively. Behavioural and phenotypic changes were observed in surviving fish. There were significant (p < 0.05) concentration and duration-dependent increases in erythrocyte (RBC), haemoglobin (Hb), pack cell volume (PCV) and leukocytes (WBC) in treated fish compared to the control. Insignificant decreases (p > 0.05) in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were observed in treated fish compared to the control. Ibuprofen elicited dose and duration- dependent decrease in neutrophil counts with the decreases being significant (p < 0.05) in the higher doses of 0.43 and 0.48 mg l^?1. Ibuprofen did not elicit any significant changes in monocytes, basophils and eosinophils. Changes observed in this study showed that ibuprofen negatively affected the health of the fish and we recommend that discharge of ibuprofen into the aquatic environment should be monitored and controlled.     

QMEANclust: estimation of protein model quality by combining a composite scoring function with structural density information

Background  

The selection of the most accurate protein model from a set of alternatives is a crucial step in protein structure prediction both in template-based and ab initio approaches. Scoring functions have been developed which can either return a quality estimate for a single model or derive a score from the information contained in the ensemble of models for a given sequence. Local structural features occurring more frequently in the ensemble have a greater probability of being correct. Within the context of the CASP experiment, these so called consensus methods have been shown to perform considerably better in selecting good candidate models, but tend to fail if the best models are far from the dominant structural cluster. In this paper we show that model selection can be improved if both approaches are combined by pre-filtering the models used during the calculation of the structural consensus.