Composition and distribution of zooplankton across an upwelling front on the northern Portuguese coast during summer

Zooplankton was sampled during the summer of 1995 from a grid of 34 shelf stations located off the Ria de Aveiro (northwestern Portugal), which were arranged into cross-shore transects extending either to the shelf break or to the 50 m isobath. At each station, a bongo net was hauled obliquely from close to the bottom or a maximum depth of 50 m to the surface. STD casts were made also at each station and wind data were obtained from a land station. Analysis of salinity and temperature data detected the presence of strong thermohaline stratification and a lens of reduced salinity water at the surface. A well-defined front, located at a depth of 10 to 35 m, separated cold water close to shore from warmer offshore water. Isopycnals between the front and the shore were bent towards the surface. The structure of the thermohaline features was consistent with the upwelling-favourable winds measured during the sampling period. A classification and a multivariate analysis of variance of the more abundant species showed the presence of two distinct assemblages that were separated by the front, indicating that these formations are important features structuring the zooplanktonic community of upwelling areas. The data further indicate that the zooplankton was composed of Palaeartic Atlantic and Mediterranean neritic species, and that oceanic species were absent from the samples. The absence of oceanic species is interpreted as resulting from the offshore displacement of the slope poleward flow and of the Portugal Current that takes place during the summer, as a response to upwelling-favourable winds.     

Therapeutic failure of praziquantel in the treatment of Schistosoma haematobium infection in Brazilians returning from Africa

Several cases of therapeutic failure of praziquantel used for the treatment of urinary schistosomiasis have been reported. Alternative drugs, like niridazol and metrifonate, have shown a lower therapeutic effect and more side effects than praziquantel. Twenty-six Brazilian military men (median age of 29 years) with a positive urine parasitological exam who were part of a United Nation peace mission in Mozambique in 1994 were treated with 40 mg/kg body weight praziquantel, single dose. They swam in Licungo river (Mocuba city, Mozambique) during the weekends. After this, they presented haematuria, dysuria, polakiuria, and lumbar pain. Control cystoscopy examinations carried out between 6 and 24 months after each treatment (including two additional treatments at a minimum interval of 6 months) revealed the presence of viable eggs. Granulomas in the vesical submucosa were observed in 46.2% (12/26) of the individuals. A vesical biopsy confirmed the presence of granulomas in all of these patients and the presence of viable eggs in 34.3% (9/26) of individuals who no longer excreted eggs in urine. The eggs filled with miracidia showed characteristics of viability. Histopathological examination using different strains demonstrated therapeutic failure and the need for repeated treatment. In this study, we demonstrated a low efficacy of praziquantel in the treatment of schistosomiasis haematobia, and the necessity of the urinary bladder biopsy as criterion of cure.     

Fermentation of fructooligosaccharides and inulin by bifidobacteria: a comparative study of pure and fecal cultures

The utilization of fructooligosaccharides (FOS) and inulin by 55 Bifidobacterium strains was investigated. Whereas FOS were fermented by most strains, only eight grew when inulin was used as the carbon source. Residual carbohydrates were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection after batch fermentation. A strain-dependent capability to degrade fructans of different lengths was observed. During batch fermentation on inulin, the short fructans disappeared first, and then the longer ones were gradually consumed. However, growth occurred through a single uninterrupted exponential phase without exhibiting polyauxic behavior in relation to the chain length. Cellular beta-fructofuranosidases were found in all of the 21 Bifidobacterium strains tested. Four strains were tested for extracellular hydrolytic activity against fructans, and only the two strains which ferment inulin showed this activity. Batch cultures inoculated with human fecal slurries confirmed the bifidogenic effect of both FOS and inulin and indicated that other intestinal microbial groups also grow on these carbon sources. We observed that bifidobacteria grew by cross-feeding on mono- and oligosaccharides produced by primary inulin intestinal degraders, as evidenced by the high hydrolytic activity of fecal supernatants. FOS and inulin greatly affected the production of short-chain fatty acids in fecal cultures; butyrate was the major fermentation product on inulin, whereas mostly acetate and lactate were produced on FOS.     

50-Hz extremely low frequency electromagnetic fields enhance cell proliferation and DNA damage: possible involvement of a redox mechanism

HL-60 leukemia cells, Rat-1 fibroblasts and WI-38 diploid fibroblasts were exposed for 24-72 h to 0.5-1.0-mT 50-Hz extremely low frequency electromagnetic field (ELF-EMF). This treatment induced a dose-dependent increase in the proliferation rate of all cell types, namely about 30% increase of cell proliferation after 72-h exposure to 1.0 mT. This was accompanied by increased percentage of cells in the S-phase after 12- and 48-h exposure. The ability of ELF-EMF to induce DNA damage was also investigated by measuring DNA strand breaks. A dose-dependent increase in DNA damage was observed in all cell lines, with two peaks occurring at 24 and 72 h. A similar pattern of DNA damage was observed by measuring formation of 8-OHdG adducts. The effects of ELF-EMF on cell proliferation and DNA damage were prevented by pretreatment of cells with an antioxidant like alpha-tocopherol, suggesting that redox reactions were involved. Accordingly, Rat-1 fibroblasts that had been exposed to ELF-EMF for 3 or 24 h exhibited a significant increase in dichlorofluorescein-detectable reactive oxygen species, which was blunted by alpha-tocopherol pretreatment. Cells exposed to ELF-EMF and examined as early as 6 h after treatment initiation also exhibited modifications of NF kappa B-related proteins (p65-p50 and I kappa B alpha), which were suggestive of increased formation of p65-p50 or p65-p65 active forms, a process usually attributed to redox reactions. These results suggest that ELF-EMF influence proliferation and DNA damage in both normal and tumor cells through the action of free radical species. This information may be of value for appraising the pathophysiologic consequences of an exposure to ELF-EMF.     

Functional characterization of a novel Cx26 (T55N) mutation associated to non-syndromic hearing loss

Mutations of the GJB2 gene, encoding connexin 26, are the most common cause of hereditary congenital hearing loss in many countries and account for up to 50% of cases of autosomal-recessive non-syndromic deafness. By contrast, only a few GJB2 mutations have been reported to cause an autosomal-dominant form of non-syndromic deafness. Here, we report a family from Southern Italy affected by non-syndromic autosomal dominant post-lingual hearing loss, due to a novel missense mutation in the GJB2 gene, a threonine to asparagine amino acid substitution at codon 55 (T55N). Functional studies indicated that the mutation T55N produces a protein that, although expressed to levels similar to those of the wt counterpart, is deeply impaired in its intracellular trafficking and fails to reach the plasma membrane. The mutation T55N is located at the apex of the first extracellular loop of the protein, a region suggested to play a role in protein targeting and a site for other two mutations, G59A and D66H, causing dominant forms of deafness.     

Structural bioinformatics study of PNP from Schistosoma mansoni

The parasite Schistosoma mansoni lacks the de novo pathway for purine biosynthesis and depends on salvage pathways for its purine requirements. Schistosomiasis is endemic in 76 countries and territories and amongst the parasitic diseases ranks second after malaria in terms of social and economic impact and public health importance. The PNP is an attractive target for drug design and it has been submitted to extensive structure-based design. The atomic coordinates of the complex of human PNP with inosine were used as template for starting the modeling of PNP from S. mansoni complexed with inosine. Here we describe the model for the complex SmPNP-inosine and correlate the structure with differences in the affinity for inosine presented by human and S. mansoni PNPs.     

Interaction of shikimic acid with shikimate kinase

The crystal structure of shikimate kinase from Mycobacterium tuberculosis (MtSK) complexed with MgADP and shikimic acid (shikimate) has been determined at 2.3A resolution, clearly revealing the amino acid residues involved in shikimate binding. In MtSK, the Glu61 strictly conserved in SK forms a hydrogen bond and salt-bridge with Arg58 and assists in positioning the guanidinium group of Arg58 for shikimate binding. The carboxyl group of shikimate interacts with Arg58, Gly81, and Arg136, and hydroxyl groups with Asp34 and Gly80. The crystal structure of MtSK-MgADP-shikimate will provide crucial information for elucidation of the mechanism of SK-catalyzed reaction and for the development of a new generation of drugs against tuberculosis.     

Three-dimensional structure of human adenine phosphoribosyltransferase and its relation to DHA-urolithiasis

In mammals, adenine phosphoribosyltransferase (APRT, EC 2.4.2.7) is present in all tissues and provides the only known mechanism for the metabolic salvage of adenine resulting from the polyamine biosynthesis pathway or from dietary sources. In humans, APRT deficiency results in serious kidney illness such as nephrolithiasis, interstitial nephritis, and chronic renal failure as a result of 2,8-dihydroxyadenine (DHA) precipitation in the renal interstitium. To address the molecular basis of DHA-urolithiasis, the recombinant human APRT was crystallized in complex with adenosine 5'-monophosphate (AMP). Refinement of X-ray diffraction data extended to 2.1 A resolution led to a final crystallographic R(factor) of 13.3% and an R(free) of 17.6%. This structure is composed of nine beta-strands and six alpha-helices, and the active site pocket opens slightly to accommodate the AMP product. The core of APRT is similar to that of other phosphoribosyltransferases (PRTases), although the adenine-binding domain is quite different. Structural comparisons between the human APRT and other "type I" PRTases of known structure revealed several important features of the biochemistry of PRTases. We propose that the residues located at positions corresponding to Leu159 and Ala131 in hAPRT are responsible for the base specificities of type I PRTases. The comparative analysis shown here also provides structural information for the mechanism by which mutations in the human APRT lead to DHA-urolithiasis.     

Complexation of vanadium(V) oxyanions with hexopyranose- and mannopyranoseuronic acid-containing polysaccharides: stereochemical considerations

Carbohydrates containing galactopyranosyl and mannopyranosyl units with vicinal cis-diols were treated with NaVO(3) in D(2)O, and complexation was determined by (51)V NMR spectroscopy. Me alpha-Galp, Me beta-Galp (3,4-cis-diols), and Me alpha-Manp (2,3-cis-diol) complexed, but Me beta-Manp barely did so. This low degree of complexation also occurred with a beta-mannan containing alternate (1-->3)- and (1-->4)-linkages and an alginate having beta-ManpA blocks. In contrast, branched alpha-mannans complexed readily, although the (51)V resonances for one with side chains terminated with alpha-Manp-(1-->3)-alpha-Manp-(1--> differed from another with only alpha-Manp-(1-->2)-alpha-Manp-(1--> groups. The anomeric configuration of Me alpha-Galp and Me beta-Galp, each with 3,4-cis-diols remote from C-1, gave rise to three (51)V signals of complexes with similar shifts and proportions. The shifts of a galactomannan with terminal alpha-Galp-(1-->2)-alpha-Manp- were the same as those with alpha-Galp-(1-->6)-beta-Manp- groups, but fewer complexes were formed with the former structure, probably due to greater steric crowding of the vanadate esters. Most of the complexes gave rise to a signal in the delta515 region, consistent with the dimeric trigonal-bipyramidal structure.