Jesús I. Martínez

Human-caused wildfire risk rating for prevention planning in Spain

This paper identifies human factors associated with high forest fire risk in Spain and analyses the spatial distribution of fire occurrence in the country. The spatial units were 6,066 municipalities of the Spanish peninsular territory and Balearic Islands. The study covered a 13-year series of fire occurrence data. One hundred and eight variables were generated and input to a dedicated Geographic Information System (GIS) to model different factors related to fire ignition. After exploratory analysis, 29 were selected to build a predictive model of human fire ignition using logistic regression analysis. The binary model estimated the probability of high or low occurrence of forest fires, as defined by an ignition danger index that is currently used by the Spanish forest service (number of fires divided by forest area in each municipality). Thirteen explanatory variables were identified by the model. They were related to agricultural landscape fragmentation, agricultural abandonment and development processes. The prediction agreement found between the model binary outputs and the historical fire data was 85.3% for the model building dataset (60% of municipalities). A slightly lower predictive power (76.2%) was found for the validation data (the remaining 40%). The probabilistic output of the logistic was significantly related to the raw ignition index (Spearman correlation of 0.710) used by the Spanish Forest Service. Therefore, the model can be considered a good predictor of human-caused fire risk, aiding spatial decisions related to prevention planning in Spanish municipalities.

Functional roles of Akt signaling in mouse skin tumorigenesis

The mouse skin carcinogenesis protocol is a unique model for understanding the molecular events leading to oncogenic transformation. Mutations in the Ha-ras gene, and the presence of functional cyclin D1 and the EGF receptor, have proven to be important in this system. However, the signal transduction pathways connecting these elements during mouse skin carcinogenesis are poorly understood. This paper studies the relevance of the Akt and ERK pathways in the different stages of chemically induced mouse skin tumors. Akt activity increases throughout the entire process, and its early activation is detected prior to increased cyclin D1 expression. ERK activity rises only during the later stages of malignant conversion. The observed early increase in Akt activity appears to be due to raised PI-3K activity. Other factors acting on Akt such as ILK activation and decreased PTEN phosphatase activity appear to be involved at the conversion stage. To further confirm the involvement of Akt in this process, PB keratinocytes were transfected with Akt and subsequently injected into nude mice. The expression of Akt accelerates tumorigenesis and contributes to increased malignancy of these keratinocytes as demonstrated by the rate of appearance, the growth and the histological characteristics of the tumors. Collectively, these data provide evidence that Akt activation is one of the key elements during the different steps of mouse skin tumorigenesis.

Copper-containing dendromesogens: the influence of the metal on the mesomorphism

The synthesis and liquid crystalline behaviour of the first and second generations of a dendrimeric structure based on poly(propyleneimine)(DAB-dendr(NH2)x) are reported. 4-(4-n-Alkoxybenzoyloxy)salicylaldehydes are used as mesogenic moieties attached at the peripheral amino groups of the dendrimers giving rise to dendromesogens with four and eight mesogenic branches. From these dendromesogens, considered as organic ligands, were prepared six metal-containing dendrimers which incorporate two or four copper atoms in their structures. All the dendrimeric ligands and three of the metal-containing dendrimers exhibit liquid crystalline properties which were studied by optical microscopy, DSC, X-ray diffraction and EPR spectroscopy.

Foraging activity and use of space by Lesser Kestrel Falco naumanni in relation to agrarian management in central Spain

Summary Arthropod abundance in most places across Europe has suffered a dramatic decline induced by modifications in agricultural practices, and this could induce changes in the selection of breeding habitat and foraging behaviour of several endangered raptor species. We studied a 6,500 ha Special Protection Area (SPA) in Spain created for the benefit of its important steppe bird populations and examined the patterns of land-use selection and use of vegetation structure by the Lesser Kestrel Falco naumanni in relation to prey-capture success. We also studied the spatial relationship between foraging sites and the location of colonies in that breeding area. The type of land-use most frequently used by foraging Lesser Kestrels was unploughed fallow (positively selected) while kestrels significantly avoided areas with cereal crops. The relationship between foraging sites and colonies (kestrels forage preferentially in areas close to the colonies) indicates that not only is farmland management important, but also the spatial relationships between foraging areas and breeding sites. Maintaining the Spanish traditional rotation of cultivation (called barbechos) may improve the correct habitat management for Lesser Kestrels in agricultural areas in Spain.

Influence of parasitization by Trichinella spiralis on the levels of heat shock proteins in rat liver and muscle.

To examine levels of heat shock proteins (HSPs) in host responses to helminth infection, rats were infected with Trichinella spiralis. The kinetics of HSP25, HSP60, HSP70 and HSP90 production in the liver and muscle of infected rats was compared with that of non-infected controls. HSPs were detected using electrophoretic analysis of fixed amounts of proteins (0.02 mg) and then blotting and incubation of membranes with polyclonal anti-HSP25 antibody, or monoclonal antibody against HSP60, or HSP70 or HSP90. Quantitation of blotted separated polypeptides reactive with the specific anti-HSP antibodies was achieved using an image analyser. Enhancement of HSP25 production was observed in the liver of infected rats, whereas muscle from the same rats exhibited enhanced production of HSP25 and HSP60 one day after infection only. These data indicate that HSPs levels can be used successfully to measure stress injury brought about by helminth infection in organs and tissues of the host.

Persistence of short range order in the fluid phases of a mesogen copper complex studied by EPR

Abstract The synthesis and thermal characterization of a new copper complex, bis[N-(4-n-pentoxyphenyl)-4-n-decyloxysalicylaldiminate] Cu(II), having mesomorphic properties is given. The EPR spectrum of this material has been measured for its different phases as a function of temperature. The results are compared with those for two other Cu(II) compounds, bis[4-n-decyloxysalicylate] Cu[II] and bis[N-(n-pentyl)-4-n-decyloxysalicylaldiminate] Cu(II) which have a related molecular structure, but are not mesomorphic. The influence on the spectra of exchange interactions in all the phases, as well as the molecular motion in the fluid phases is discussed, and it is concluded that the exchange interactions are not destroyed by the molecular motion. These facts suggest that molecular motion in the high temperature phases takes places whilst keeping a short range order, resulting in a locally correlated motion.

Site‐directed mutagenesis and spectral studies suggest a putative role of FurA from Anabaena sp. PCC 7120 as a heme sensor protein

The transcriptional repressor Fur (ferric uptake regulator) is one of the most important switches regulating prokaryotic iron metabolism. Cyanobacterial FurA binds heme in the micromolar concentration range and this interaction negatively affects its in vitro DNA binding ability in a concentration‐dependent manner. Using site‐directed mutagenesis along with difference absorption UV–visible, circular dichroism and electronic paramagnetic resonance spectroscopies, we further analyse the nature of heme binding in FurA. Our data point to Cys141, within a Cys‐Pro motif, as an axial ligand of the Fe(III) high‐spin heme. In the Fe(II) oxidation state, the heme shows low‐spin form with an electronic absorption spectrum typical of six‐coordinated low‐spin heme proteins with a Soret absorption maximum blue‐shifted by 25 nm in relation to typical low‐spin thiolate‐ligated Fe(II) heme proteins. Moreover, the ferrous C141S mutant shows Soret, α and β bands almost identical to those observed for ferrous wild‐type heme–FurA, indicating that the heme in ferrous C141S is in the same six‐coordinated heme ligation as the ferrous native form. Therefore, Cys141 is not a ligand of the Fe(II) heme centre, suggesting a redox‐dependent ligand switch undergone by this regulator. Our results indicate that the binding of heme to FurA exhibits the same physicochemical features as previously described for heme sensor proteins.

Detachment faulting and late Paleozoic epithermal Ag-base-metal mineralization in the Spanish central system

Hydrothermal activity during late Hercynian time resulted in epithermal silver-base-metal (Pb-Zn-Cu) vein formation in the eastern part of the Spanish central system. During the Hercynian orogeny, the central Iberian crust was thickened by compressional tectonics, heated, weakened, and subsequently overthickened by massive late Hercynian granitic intrusions. Subsequently, the central Iberian crustal welt underwent extensional collapse through lithosphere-scale, low-angle detachment faulting. The detachment systems evolved through tectonic denudation, isostatic rebound, and upward arching to define an extensional province much like the U.S. Basin and Range. Andesitic volcanism and hydrothermal activity occurred during extension, inducing epithermal-type hydrothermal convecting systems that leached, transported, and precipitated silver and base metals along fractures crosscutting the Hiendelaencina metamorphic core complex.

Smectic Cu(II), Pd(II) and VO(IV) complexes: synthesis, EPR and thermogravimetric studies

The octadecanoate of N(-(4-hexyloxyphenyl)salicylaldimine and the corresponding Cu(II), Pd(II) and VO(IV) complexes were synthesized and studied. The compounds were characterized by IR, 1H NMR, elemental and thermal analysis and polarized light microscopy. Thermogravimetric analysis and electronic spectra of the complexes are reported. Electron paramagnetic resonance (EPR) measurements were performed.

Electron-Nuclear Double Resonance and Hyperfine Sublevel Correlation Spectroscopic Studies of Flavodoxin Mutants from Anabaena sp. PCC 7119

The influence of the amino acid residues surrounding the flavin ring in the flavodoxin of the cyanobacterium Anabaena PCC 7119 on the electron spin density distribution of the flavin semiquinone was examined in mutants of the key residues Trp(57) and Tyr(94) at the FMN binding site. Neutral semiquinone radicals of the proteins were obtained by photoreduction and examined by electron-nuclear double resonance (ENDOR) and hyperfine sublevel correlation (HYSCORE) spectroscopies. Significant differences in electron density distribution were observed in the flavodoxin mutants Trp(57) --> Ala and Tyr(94) --> Ala. The results indicate that the presence of a bulky residue (either aromatic or aliphatic) at position 57, as compared with an alanine, decreases the electron spin density in the nuclei of the benzene flavin ring, whereas an aromatic residue at position 94 increases the electron spin density at positions N(5) and C(6) of the flavin ring. The influence of the FMN ribityl and phosphate on the flavin semiquinone was determined by reconstituting apoflavodoxin samples with riboflavin and with lumiflavin. The coupling parameters of the different nuclei of the isoalloxazine group, as detected by ENDOR and HYSCORE, were very similar to those of the native flavodoxin. This indicates that the protein conformation around the flavin ring and the electron density distribution in the semiquinone form are not influenced by the phosphate and the ribityl of FMN.