A predictive model for freshwater bioassessment (Mondego River,Portugal)

We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model. At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207 taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality, substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model, the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and increasing the number of ellipses that define quality bands. Handling editor: K. Martens     

Nutrient and chlorophyll a temporal patterns in eutrophic mountain ponds with contrasting macrophyte coverage

Hydrobiologia - In shallow lakes, macrophytes have important effects on food webs, community structure and nutrient dynamics. For this reason they play a significant role in the restoration of...     

Lymphocyte transformation and macrophage migration inhibition by electrofocused and gel-filtered fractions of group A streptococcal filtrate

Culture filtrates of group A streptococci were fractionated either by isoelectric focusing on a sucrose gradient at pH 3–10, or by gel filtration on a G-75 Superfine Sephadex column. Some fractions induced lymphocyte transformation, others inhibition of macrophage migration, and others both. With the two types of fractionation here used the lymphocyte transformation activity was concentrated in a single peak, while the activity responsible for macrophage migration inhibition was scattered over multiple fractions. The significance of these findings is discussed.     

Fine root distribution of trees and understory in mature stands of maritime pine (Pinus pinaster) on dry and humid sites

Maritime pine (Pinus pinaster) is the main tree cropping species in the Landes of Gascogne forest range in south western France. Soils are nutrient poor, sandy podzosols and site fertility is determined essentially by organic matter content and depth of water table, which is known to limit root growth. We hypothesised, with an ultimate goal of constructing a nutrient uptake model applicable to this region, that the organic top horizons together with the depth of the water table should be the most important parameters related to fine root distribution and presence of associated mycorrhiza. To test this hypothesis, we compared two adult Pinus pinaster stands, contrasting in depth of water table and soil fertility and evaluated fine roots (diameter ≤2 mm) of understory species and fine roots and ectomycorrhizal morphotypes of Pinus pinaster down to 1.2 m, using a soil corer approach. Total fine root biomass of Pinus pinaster was not significantly different between both sites (3.6 and 4.5 t ha⁻¹ for the humid, respectively, dry site), but root distribution was significantly shallower and root diameter increased more with depth at the humid site, presumably due to more adverse soil conditions as related to the presence of a hardpan, higher amount of aluminium oxides and / or anoxia. Fine roots of Pinus pinaster represented only about 30% of total fine root biomass and 15% of total fine root length, suggesting that the understory species cannot be ignored with regards to competition for mineral nutrients and water. A comparison of the ectomycorrhizal morphotypes showed that the humid site could be characterised by a very large proportion of contact exploration types, thought to be more relevant in accessing organic nutrient sources, whereas the dry site had a significantly higher proportion of both long-distance and short-distance exploration types, the latter of which was thought to be more resistant to short-term drought periods. These results partly confirm our hypothesis on root distribution as related to the presence of soil mineral nutrients (i.e. in organic matter), point out the potential role of understory plant species and ectomycorrhizal symbiosis and are a valuable step in building a site-specific nutrient uptake model.     

Identification, sequencing and mutagenesis of the gene for a d-carbamoylase from Agrobacterium radiobacter

Abstract A clone positive for d-carbamoylase activity (2.7 kb Hin dIII- Bam H1 DNA fragment) was obtained by screening a genomic library of Agrobacterium radiobacter in Escherichia coli . This DNA fragment contains an open reading frame of 912 bp which is predicted to encode a peptide of 304 amino acids with a calculated molecular mass of 34247 Da. The d-carbamoylase gene. named cauA , was placed under the control of T7 RNA-dependent promoter and expressed in E. coli BL21 (DE3). After induction with isopropyl-thio-β-d-galactopyranoside, the synthesis of d-carbamoylase in E. coli reached about 40% of the total protein. The expressed protein was shown to possess a molecular mass, on SDS-PAGE, of 36 kDa and showed an enhanced allowed us to establish that a Pro¹⁴→Leu¹⁴ exchange leads to an inactive enzyme species, while a Cys²⁷⁹→Ser²⁷⁹ exchange did not impair the functional properties of the enxyme.     

Two of the three influenza viral polymerase proteins expressed by using baculovirus vectors form a complex in insect cells.

Each of the influenza virus polymerase (P) genes PB1, PB2, and PA was inserted into a baculovirus vector under the control of the polyhedrin promoter. In insect (Spodoptera frugiperda) cells infected by each baculovirus recombinant containing a P gene insert, a large amount of the encoded P protein was synthesized. Gel electrophoretic analysis of the total proteins in infected cells revealed the presence of a new protein band corresponding to the encoded P protein that was abundant enough to be stained with Coomassie blue. In cells infected simultaneously with both the PB1 and PB2 baculovirus recombinants, a PB1-PB2 complex was formed that was immunoprecipitated with an antiserum specific for either PB1 or PB2. In cells infected simultaneously with all three P baculovirus recombinants, a PB1-PB2 complex lacking the PA protein was formed. Formation of this PB1-PB2 complex partially mimics events that occur in influenza virus-infected cells, where all three P proteins form a complex with each other (B. M. Detjen, C. St. Angelo, M. G. Katze, and R. M. Krug, J. Virol. 61:16-22, 1987). These results indicate that the ability of PB1 and PB2 to form a complex is an intrinsic property of these two proteins that does not require the participation of other influenza viral gene products. Possible reasons for the absence of the PA protein from the immunoprecipitable P protein complex in insect cells infected by the three P baculovirus recombinants are discussed.     

Adoptive immunity in mice challenged with L1210/DTIC clones

Summary New antigenic specificities, not detectable on parental cells, have been induced by many investigators in mouse lymphomas by treatment with the antitumor agent 5(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide (DTIC). The antigens are transmissible, after withdrawal of the drug treatment, as an inheritable character. The mechanism of induction, the molecular nature, and the number of the new antigenic specificities have not been completely elucidated. Four clones from murine leukemia L1210 isolated and expanded in vitro were treated in vivo with DTIC and the new sublines were studied in detail. The four drug-treated sublines studied exhibited strong immunogenicity since they were rejected by syngeneic animals. Immunosuppressed animals challenged with 10⁷ A/DTIC or P/DTIC cells were reciprocally protected by the adoptive transfer of spleen cells from donors that had rejected a lethal challenge of A/DTIC or P/DTIC clones. In a similar fashion, the adoptive transfer of spleen cells obtained from animals that had rejected the Q/DTIC or the R/DTIC clones protected immunosuppressed mice challenged with Q/DTIC or R/DTIC cells. No antitumor activity was observed in cross-protective schedules other than those indicated. It was been concluded that (a) the L1210 leukemia line does not have antigenic cells, (b) four DTIC-treated clone sublines were rejected by compatible hosts, and (c) two mutually exclusive sets of antigens were expressed in four antigenic clone sublines.Research supported in part by P.F.O. Contract Grant from C. N. R., Rome, Italy     

Photosynthetic properties of leaves of a yellow green mutant of wheat compared to its wild type

We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O₂ evolution of the leaf tissue in saturating light and CO₂ was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO₂ assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f cytochrome f - chl chlorophyll - PS II photosystem II - Pn_max maximum photosynthesis - RuBCase Ribulose, 1-5,bisphosphate carboxylase