PubMed Health⌕ Search

Biomedical subjects

A Navas

Publications and source records attributed to A Navas.

9 recordsLinked to original sources
PubMed2005

Radionuclides in soils of Byers Peninsula, South Shetland Islands, Western Antarctica.

As a part of a broader study of the surface formations in maritime Antarctica, a preliminary survey on the content of radionuclides has been carried out in soils of Byers Peninsula, located in the western end of Livingston Island, South Shetland Islands. Data on natural and artificial radionuclides are very scarce in Antarctica and the studied soil samples can be representative of the maritime Antarctic environment. Byers Peninsula has an extensive presence of permafrost and an active layer, the studied soils being Criosols and Cryic Leptosols. A series of soil cores between 13 and 40 cm depth have been collected in different lithological and altitudinal contexts. In the southwestern sector of the peninsula, soils have been sampled in seven different sites along a transect on different geomorphological units from an upper marine platform (88 m above sea level) to a Holocene raised beach at an altitude of 24 m a.s.l. The parent materials are mainly Upper Jurassic-Lower Cretaceous marine sandstones and conglomerates and Lower Cretaceous volcanoclastic materials. Individual samples have been obtained from the cores according to textural and colour criteria and analysed for (238)U, (226)Ra, (232)Th, (40)K and (137)Cs by gamma spectrometry. Radionuclides show variations in the depth profile as well as in the different morphoedaphic environments studied. Variability in some radionuclides seems to be related to mineralogy derived from parent materials as well as with cryogenic and soil processes affecting the depth distribution of the granulometric fractions and the organic matter.

Journal Article↗
PubMed2002

238U 226Ra 210Pb, 232Th and 40K activities in soil profiles of the Flysch sector (Central Spanish Pyrenees).

Distributions of natural gamma-emitting radionuclides were determined in three soil profiles developed on Tertiary sedimentary materials in mountain landscapes of the Central Spanish Pyrenees. Radioisotope activities (Bq kg(-1)) lie in the range of 0-53 for 238U; 19-33 for 226Ra; 7-75 for 210Pb; 24-48 for 232Th and 335-562 for 40K. 238U and 210Pb activities show an important variability down the soil profiles. 238U was markedly depleted in all upper soil layers and highly enriched in lower layers of two soil profiles. 210Pb exhibits very dissimilar distribution patterns in all three soils. 226Ra and 232Th had quite uniform depth distributions. 40K showed depletion in both upper and lower layers in one soil profile but remained fairly constant in the other two profiles. 238U/226Ra activity ratios (ARs) have been used to assess equilibrium in the 238U decay chain and as indicators of edaphogenesis in the studied soil profiles. Maintenance of initial proportionality in the ratio of 232Th/238U activities has been assessed through ARs of their progenies. Additionally, a variety of soil properties were measured down the soil profiles. Among soils, variation in radionuclide activies may be due to differences in carbonate content, organic matter and/or grain size. In this environment, soil properties differently affect mobilization of natural radionuclides. The association of some radiologic properties with soil layers suggest a relationship between soil processes and radionuclide distribution.

Journal Article↗
PubMed2000

ACI-1 from Acidaminococcus fermentans: characterization of the first beta-lactamase in Anaerobic cocci.

Acidaminococcus fermentans belongs to the group of strictly anaerobic gram-negative cocci. All previously described Acidaminococcus strains are susceptible to beta-lactam antibiotics. An A. fermentans strain (RYC-MR95) resistant to penicillin and expanded-spectrum cephalosporin (amoxicillin and cefotaxime MICs, 64 microgram/ml) was isolated from a human perianal abscess. A fragment encoding a beta-lactamase from genomic DNA was cloned in Escherichia coli K-12 strain HB101, and the recombinant strain expressed resistance to amoxicillin (MIC, 1,024 microgram/ml) and cefotaxime (MIC, 4 microgram/ml). Clavulanic acid decreased the MICs to 8 and 0.03 microgram/ml, respectively. Analysis of the nucleotide sequence revealed a new class A beta-lactamase, ACI-1. In accordance with its biochemical properties, we propose to assign ACI-1 to functional group 2be. The ACI-1 enzyme (estimated pI 4.3) had <50% amino acid identity with any other class A beta-lactamases, the closest being ROB-1 from Haemophilus influenzae (44%). ACI-1 was closer to class A beta-lactamases from some gram-positive organisms (41 to 44% amino acid identity with Bacillus beta-lactamases) than to most class A enzymes from gram-negative organisms (TEM-1, 24.6%). The aci1 gene had a G+C content of 42.1%, in contrast with 56% G+C content for genomic DNA from A. fermentans, thus suggesting that aci1 may have been obtained by horizontal gene transfer.

Amino Acid Sequence↗
PubMed1993

Phase-modulation fluorescence lifetime immunoassay of dichlorprop.

A homogeneous immunofluorimetric technique to determine dichlorprop herbicide is described. Simultaneous determinations of both free and antibody-bound fluoresceinamine-labeled dichlorprop were carried out by measuring phase-resolved fluorescence or modulation-resolved fluorescence. The difference between the recorded values of the fluorescence lifetimes of the two species quantifies selectivity. Multifrequency heterogeneity analyses of free and bound labeled dichlorprop gave 3.68 +/- 0.03 and 4.28 +/- 0.02 ns, respectively. The differences between the phase-angles of the two species (117.5 degrees and 127.2 degrees) correspond to a difference between fluorescence lifetime values of 600 ps. This lifetime difference permits the quantitative determination of the two species simultaneously. The mean relative standard deviation of the set of three calibration curves when fitted to radioimmunoassay (chi 2 5 x 10(-4)) was 6%. The practical dynamic range was 0.1 to 100 micrograms.ml-1. On the other hand, the fractional contributions of both species, free and bound, to the total lifetime measured by demodulation, permit quantitative calculation of the two components. Both methods gave similar analytical specifications.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Mononuclear cell subsets in IgM mesangial proliferative glomerulonephritis. A comparative study with minimal change nephrotic syndrome and immunonegative mesangial proliferative glomerulonephritis.

Glomerular and interstitial leukocyte subpopulations were analyzed in renal biopsies from 18 patients with IgM mesangial proliferative glomerulonephritis (IgM MPGN), 19 patients with minimal change nephrotic syndrome (MC) and 10 patients with immune-negative mesangial proliferative glomerulonephritis (IN MPGN), by immunoperoxidase techniques with monoclonal antibodies. Mesangial cell proliferation was strongly correlated with absolute numbers of intraglomerular T lymphocytes (r = 0.71; p < 0.01) in IgM MPGN, but not in MC or IN MPGN. Significant differences were found in the numbers of macrophages, CD4- and CD8-positive glomerular cells (Student's t test p < 0.01, 0.05 and 0.01, respectively) in IgM MPGN, but not in MC or IN MPGN. The numbers of CD45-, CD3- and CD8-positive cells also differed in each patient group (ANOVA p < 0.01, 0.05 and 0.05, respectively), the greatest and smallest values appearing in IgM MPGN and MC, respectively. Multiple regression test showed initial proteinuria values in IgM MPGN to be closely dependent on the density of neutrophils, macrophages, T and B lymphocytes and CD4 cell inflammatory infiltrates (r2 = 0.92; p < 0.01). At the end of the follow-up, proteinuria in IgM MPGN, but not in MC or IN MPGN, was dependent on T cell infiltrate (r2 = 0.97; p < 0.01). Our findings suggest that proteinuria in IgM MPGN results from local mesangial damage rather than from the effects of a soluble circulating factor, as has been proposed for MC. The clinical and immunohistochemical differences observed between these two processes support the notion that they should be considered as separate entities.

Adult↗
PubMedDate not supplied

Protein variability in Meloidogyne spp. (Nematoda:Meloidogynidae) revealed by two-dimensional gel electrophoresis and mass spectrometry.

Total protein variation as revealed by two-dimensional electrophoresis (2D-E) was studied in 18 isolates from populations of Meloidogyne arenaria (six isolates), Meloidogyne incognita (10 isolates), and Meloidogyne javanica (one isolate) plus an unclassified isolate. Gels (80 x 60 x 0.75 mm) were silverstained and digitized in order to compare their protein patterns. Optical density and position of protein patterns were measured using statistical cluster analysis and computer-assisted image analysis software. Only those protein stains or positions that were clearly defined (i.e., without background) were considered. The number of positions in gels ranged from 86 to 203. Each of these positions had 95 clearly expressed proteins that were present in at least two replicates for each isolate. Spot position was considered a taxonomical character with two different states: presence (1) and absence (0). Accordingly, genetic distance was estimated among isolates and species, and a phylogenetic tree was constructed following the cladistic approach based on maximum parsimony analysis. Isolates of M. arenaria--M. javanica--Meloidogyne sp. and of M. incognita formed two separate monophyletic groups. Both groups were clearly defined on the basis of two sets of protein positions that can be considered as diagnostic characters. An attempt to identify these proteins by mass spectrometry was made. Group diagnostic proteins for M. incognita and M. arenaria (and for other proteins common to all isolates) were distinguished by protonated mass signals in the MALDI fingerprinting spectrum.

Animals↗
PubMedDate not supplied

Identification of proteins expressing differences among isolates of Meloidogyne spp. (Nematoda: Meloidogynidae) by nano-liquid chromatography coupled to ion-trap mass spectrometry.

Total protein variation (up to ninety-five different positions) was revealed by two-dimensional electrophoresis (2-DE) in 18 isolates from populations of M. arenaria (6 isolates), M. incognita (10), M. javanica (1) plus an unclassified isolate in a previously reported study. Isolates of M. arenaria, M. javanica, Meloidogyne sp., and M. incognita formed two separate groups defined on the basis of two sets of protein positions that could be considered as diagnostic characters, but we could not identify these proteins by MALDI-TOF. To identify these marker positions, nano-liquid chromatography as peptides separation method was coupled to an ion-trap mass spectrometer for induced real-time fragmentation of eluted peptides. Group diagnostic proteins for M. incognita and M. arenaria were in-gel digested and on line analyzed by tandem mass spectrometry (LC-MS/MS). Six proteins out of seven selected spots were unambiguously identified by the analysis of the corresponding MS/MS (MS2) spectrum from parent ions fragmentation: Actin, Enolase, CG3752-PA protein similar to Aldehyde Dehydrogenase, HSP-60 and Translation initiation factor elF-4A. In M. incognita sample, de novo sequencing experiment of doubly charged ion at m/z=936.9 Da in spot 29 identified as enolase, reveals three residue substitutions (K to T, N to T, and D to E) when tentative sequence was compared with that of Anisakis simplex and Onchocerca volvulus enolase, thus three SNPs (single nucleotide polymorphisms) were also possibly identified.

Amino Acid Substitution↗