Showing papers by "Spanish National Research Council published in 1999"

Starburst99: Synthesis Models for Galaxies with Active Star Formation

Abstract: Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data set previously published by Leitherer & Heckman. We have upgraded our code by implementing the latest set of stellar evolution models of the Geneva group and the model atmosphere grid compiled by Lejeune et al. Several predictions which were not included in the previous publication are shown here for the first time. The models are presented in a homogeneous way for five metallicities between Z = 0.040 and 0.001 and three choices of the initial mass function. The age coverage is 106—109 yr. We also show the spectral energy distributions which are used to compute colors and other quantities. The full data set is available for retrieval at a Web site, which allows users to run specific models with nonstandard parameters as well. We also make the source code available to the community.

The effective temperature scale of giant stars (F0–K5) - II. Empirical calibration of versus colours and [Fe/H]

Abstract: We present calibrations of the effective temperatures of giant stars versus [Fe/H] and colours , , , , , , , , , , and . These calibrations are based on a large sample of field and globular cluster stars which roughly cover spectral types from F0 to K5. Their effective temperatures, scaled to direct determinations via reliable angular diameter measurements, were derived by applying the infrared flux method. The empirical relations have been fitted to polynomials of the form by using the least squares method. The precision of the fits ranges from 40 K for to 170 K for . We tabulate intrinsic colours of giant stars in the ranges: 3500 K 8000 K; -3.0 . We also present the calibration of BC(V) as a function of log and metallicity. Finally, we compare the resulting scale of temperatures with previous works.

Interspecific Killing among Mammalian Carnivores

Abstract: Interspecific killing among mammalian carnivores is common in nature and accounts for up to 68% of known mortalities in some species. Interactions may be symmetrical (both species kill each other) or asymmetrical (one species kills the other), and in some interactions adults of one species kill young but not adults of the other. There is a positive significant relationship between the body masses of solitary killer species and body masses of their victim species, and grouping species kill larger victims than solitary species. Interactions and consumption of the victim appear more common when food is scarce or disputed. In response to killers, victim species may alter their use of space, activity patterns, and form groups. Consequences of interspecific killing include population reduction or even extinction, and reduction and enhancement of prey populations, and may therefore have important implications for conservation and management of carnivores and their prey.

Identification of yeasts by RFLP analysis of the 5.8S rRNA gene and the two ribosomal internal transcribed spacers.

Abstract: The identification and classification of yeasts have traditionally been based morphological, physiological and biochemical traits. Various kits have been developed as rapid systems for yeast identification, but mostly for clinical diagnosis. In recent years, different molecular biology techniques have been developed for yeast identification, but there is no available database to identify a large number of species. In the present study, the restriction patterns generated from the region spanning the internal transcribed spacer (ITS1 and ITS2) and the 5.8S rRNA gene were used to identify a total of 132 yeast species belonging to 25 different genera, including teleomorphic and anamorphic ascomycetous and basidiomycetous yeasts. In many cases, the size of the PCR products and the restriction patterns obtained with endonucleases Cfol, Haelll and Hinfl yielded a unique profile for each species. Accordingly, the use of this molecular approach is proposed as a new rapid and easy method of routine yeast identification.

Opening the Iron Box: Transcriptional Metalloregulation by the Fur Protein

Abstract: It is generally accepted that iron is the most important micronutrient used by bacteria. With members of the family Lactobacillae being the only exceptions so far ([3][1]), this metal is essential for cellular metabolism, since it is needed as a cofactor for a large number of enzymes ([96][2]).

Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra

Abstract: We start from our six absolutely calibrated continuous stellar spectra from 1.2 to 35 ?m for K0, K1.5, K3, K5, and M0 giants. These were constructed as far as possible from actual observed spectral fragments taken from the ground, the Kuiper Airborne Observatory, and the IRAS Low Resolution Spectrometer, and all have a common calibration pedigree. From these we spawn 422 calibrated spectral templates for stars with spectral types in the ranges G9.5?K3.5 III and K4.5?M0.5 III. We normalize each template by photometry for the individual stars using published and/or newly secured near- and mid-infrared photometry obtained through fully characterized, absolutely calibrated, combinations of filter passband, detector radiance response, and mean terrestrial atmospheric transmission. These templates continue our ongoing effort to provide an all-sky network of absolutely calibrated, spectrally continuous, stellar standards for general infrared usage, all with a common, traceable calibration heritage. The wavelength coverage is ideal for calibration of many existing and proposed ground-based, airborne, and satellite sensors, particularly low- to moderate-resolution spectrometers. We analyze the statistics of probable uncertainties, in the normalization of these templates to actual photometry, that quantify the confidence with which we can assert that these templates truly represent the individual stars. Each calibrated template provides an angular diameter for that star. These radiometric angular diameters compare very favorably with those directly observed across the range from 1.6 to 21 mas.

DREAM is a Ca2+-regulated transcriptional repressor.

Abstract: Fluxes in amounts of intracellular calcium ions are important determinants of gene expression1,2,3. So far, Ca2+-regulated kinases and phosphatases have been implicated in changing the phosphorylation status of key transcription factors and thereby modulating their function4,5. In addition, direct effectors of Ca2+-induced gene expression have been suggested to exist in the nucleus2, although no such effectors have been identified yet. Expression of the human prodynorphin gene, which is involved inmemory acquisition and pain6,7, is regulated through its downstream regulatory element (DRE) sequence, which acts as a location-dependent gene silencer8. Here we isolate a new transcriptional repressor, DRE-antagonist modulator (DREAM), which specifically binds to the DRE. DREAM contains four Ca2+-binding domains of the EF-hand type. Upon stimulation by Ca2+, DREAM's ability to bind to the DRE and its repressor function are prevented. Mutation of the EF-hands abolishes the response of DREAM to Ca2+. In addition to the prodynorphin promoter, DREAM represses transcription from the early response gene c-fos. Thus, DREAM represents the first known Ca2+-binding protein to function as a DNA-binding transcriptional regulator.

Attractive and repulsive tip-sample interaction regimes in tapping-mode atomic force microscopy

Abstract: Attractive and repulsive tip-sample interaction regimes of a force microscope operated with an amplitude modulation feedback were investigated as a function of tip-sample separation, free amplitude, and sample properties. In the attractive regime, a net attractive force dominates the amplitude reduction while in the repulsive regime the amplitude reduction is dominated by a net repulsive force. The transition between both regimes may be smooth or steplike, depending on free amplitude and sample properties. A steplike discontinuity is always a consequence of the existence of two oscillation states for the same conditions. Stiff materials and small free amplitudes give rise to steplike transitions while the use of large free amplitudes produce smooth transitions. Simulations performed on compliant samples showed cases where the cantilever dynamics is fully controlled by a net attractive force. Phase-shift measurements provide a practical method to determine the operating regime. Finally, we discuss the influence of those regimes in data acquisition and image interpretation.

Worldwide large-scale fluctuations of sardine and anchovy populations

Abstract: Decade-scale regimes of sardine Sardinops sagax and anchovy Engraulis spp. have been observed in the productive coastal waters of the North-Western, North-Eastern and South-Eastern Pacific and the South-Eastern Atlantic. In each of these systems, the two genera fluctuate out of phase with each other. The subdominant genus may initiate a recovery while the other species is still abundant, so population growth is not necessarily a response to a vacant niche. Rather, it appears to be triggered by formation of one or a few powerful year-classes. At high population levels, quality of sardine and their eggs decreased in Japan, leading to decreased production and survival of eggs, poor year-classes and stock collapse. Excessive fishing of strong year-classes early in the recovery stage may prevent a species from assuming dominance, so influencing the natural succession of species. This may greatly alter the structure and functioning of an ecosystem. For example, a mesopelagic forage fish may replace an epipelagi...

Creation of entangled states of distant atoms by interference

Abstract: We propose a scheme to create distant entangled atomic states. It is based on driving two (or more) atoms with a weak laser pulse, so that the probability that two atoms are excited is negligible. If the subsequent spontaneous emission is detected, the entangled state is created. We have developed a model to analyze the fidelity of the resulting state as a function of the dimensions and location of the detector, and the motional properties of the atoms.

Significance of size and nucleic acid content heterogeneity as measured by flow cytometry in natural planktonic bacteria.

Abstract: Total bacterial abundances estimated with different epifluorescence microscopy methods (4′,6-diamidino-2-phenylindole [DAPI], SYBR Green, and Live/Dead) and with flow cytometry (Syto13) showed good correspondence throughout two microcosm experiments with coastal Mediterranean water. In the Syto13-stained samples we could differentiate bacteria with apparent high DNA (HDNA) content and bacteria with apparent low DNA (LDNA) content. HDNA bacteria, “live” bacteria (determined as such with the Molecular Probes Live/Dead BacLight bacterial viability kit), and nucleoid-containing bacteria (NuCC) comprised similar fractions of the total bacterial community. Similarly, LDNA bacteria and “dead” bacteria (determined with the kit) comprised a similar fraction of the total bacterial community in one of the experiments. The rates of change of each type of bacteria during the microcosm experiments were also positively correlated between methods. In various experiments where predator pressure on bacteria had been reduced, we detected growth of the HDNA bacteria without concomitant growth of the LDNA bacteria, such that the percentage contribution of HDNA bacteria to total bacterial numbers (%HDNA) increased. This indicates that the HDNA bacteria are the dynamic members of the bacterial assemblage. Given how quickly and easily the numbers of HDNA and LDNA bacteria can be obtained, and given the similarity to the numbers of “live” cells and NuCC, the %HDNA is suggested as a reference value for the percentage of actively growing bacteria in marine planktonic environments.

The chemokine SDF-1alpha triggers CXCR4 receptor dimerization and activates the JAK/STAT pathway.

Abstract: The chemokine stromal cell-derived factor (SDF-1α), the ligand for the CXCR4 receptor, induces a wide variety of effects that include calcium mobilization, chemotactic responses, bone marrow myelopoiesis, neuronal patterning, and prevention of HIV-1 infection. Nonetheless, little is known of the biochemical pathways required to achieve this variety of responses triggered after receptor–chemokine interaction. We developed a set of monoclonal antibodies that specifically recognize the CXCR4 receptor and used them to identify the signaling pathway activated after SDF-1α binding in human T cell lines. Here we demonstrate that SDF-1α activation promotes the physical association of Gαi with the CXCR4. Furthermore, within seconds of SDF-1α activation, the CXCR4 receptor becomes tyrosine phosphorylated through the activation and association with the receptor of JAK2 and JAK3 kinases. After SDF-1α binding, JAK2 and JAK3 associate with CXCR4 and are activated, probably by transphosphorylation, in a Gαi-independent ...

Spectroscopic Classification of Late-M and L Field Dwarfs

Abstract: We present spectra for 12 new ultracool dwarfs found in the DENIS infrared survey. Seven of them have spectral types at the bottom of the M-class (M8–M9.5), and the other five belong to the cooler "L" class. We also present spectra for the two new L dwarfs found by the EROS 2 proper-motion survey. We introduce a scheme for L dwarf classification that is based on an extension to cooler spectra of a pseudocontinuum ratio previously defined for M dwarfs. For calibrating the spectral subclasses, we use a temperature scale for late-M and L dwarfs recently obtained by Basri et al. from synthetic spectrum fitting of high-resolution profiles of Cs I and Rb I resonance lines. We define that the subclass range from L0 to L6 corresponds to the temperature range from 2200 K to 1600 K. Our subclasses L0, L1, and L2 agree with recent findings by Kirkpatrick et al., but then they diverge such that our L6 is equivalent to their L8. We find that late-M and L dwarf subclasses can be assigned either in the optical with the PC3 index or in the near-infrared with the H2O H-band index. We discuss the main photospheric features present in L dwarf spectra, in particular in the region 400–650 nm, which has never been shown before. The TiO bands at 549.7, 559.7, 615.9, and 638.4 nm fade with decreasing temperature, but do not vanish until well inside the L domain (~L5). The Na I 589.0, 589.6 nm resonance doublet in our latest object (L6) becomes the broadest atomic feature ever seen in any cool dwarf. We do not detect Hα emission in our L dwarfs later than L3. We discuss the ages and masses of our objects using their temperatures and absence or presence of lithium. Finally, we compare two L1 dwarfs with different gravities (one with lithium and one without it) and discuss differences in spectral features.

Automatic Extraction of Biological Information from Scientific Text: Protein-Protein Interactions

Abstract: We describe the basic design of a system for automatic detection of protein-protein interactions extracted from scientific abstracts. By restricting the problem domain and imposing a number of strong assumptions which include pre-specified protein names and a limited set of verbs that represent actions, we show that it is possible to perform accurate information extraction. The performance of the system is evaluated with different cases of real-world interaction networks, including the Drosophila cell cycle control. The results obtained computationally are in good agreement with current biological knowledge and demonstrate the feasibility of developing a fully automated system able to describe networks of protein interactions with sufficient accuracy.

Disease states associated with telomerase deficiency appear earlier in mice with short telomeres

Abstract: Mice deficient for the mouse telomerase RNA (mTR −/− ) and lacking telomerase activity can only be bred for approximately six generations due to decreased male and female fertility and to an increased embryonic lethality associated with a neural tube closure defect. Although late generation mTR −/− mice show defects in the hematopoietic system, they are viable to adulthood, only showing a decrease in viability in old age. To assess the contribution of genetic background to the effect of telomerase deficiency on viability, we generated mTR −/− mutants on a C57BL6 background, which showed shorter telomeres than the original mixed genetic background C57BL6/129Sv. Interestingly, these mice could be bred for only four generations and the survival of late generation mTR −/− mice decreased dramatically with age as compared with their wild‐type counterparts. Fifty percent of the generation 4 mice die at only 5 months of age. This decreased viability with age in the late generation mice is coincident with telomere shortening, sterility, splenic atrophy, reduced proliferative capacity of B and T cells, abnormal hematology and atrophy of the small intestine. These results indicate that telomere shortening in mTR −/− mice leads to progressive loss of organismal viability.

Molecular evidence on the evolutionary and biogeographical patterns of European cyprinids.

Abstract: The phylogenetic relationships of 106 European cyprinid taxa were determined based on the complete nucleotide sequence (1140 bp) of the mitochondrial cytochrome b gene. The molecular phylogeny was used (1) to revise the current systematics of European cyprinids, (2) to establish the phylogenetic utility of traditional morphological characters that are widely used in Cyprinidae systematics, and (3) to discuss alternative hypotheses on the biogeography of the family in Europe. The age of the major lineages within European cyprinids was tentatively estimated with a molecular clock and showed full agreement with the fossil record of the group. Moreover, the results provided unambiguous evidence for a close phylogenetic affinity of some Caucasian and Greek endemic cyprinid taxa (e.g., B. capito and B. brachycephalus and Leuciscus keadicus, Barbus graecus, and B. albanicus, respectively) to Iberian and North African, but not Central European, cyprinids. The existence of such unexpected phylogenetic relationships refutes the classical hypothesis on the biogeography of European cyprinids, which assumes a dispersal of the cyprinid fauna from central Europe to southern Europe and northern Africa during the Miocene (and, hence, predicts a close phylogenetic relationship of all Caucasian, Greek, Iberian, and North African cyprinids to central European taxa). Instead, the existence of a Mediterranean realm independent of the central European route seems plausible based on the molecular evidence. It is likely that the new biogeographical scenario proposed here might apply to other primary freshwater European animals with low dispersal abilities, including fish, amphibians, and invertebrates.

Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana

Abstract: The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins.

Structure and dynamics of membrane proteins as studied by infrared spectroscopy.

Abstract: Infrared (IR) spectroscopy is a useful technique in the study of protein conformation and dynamics. The possibilities of the technique become apparent specially when applied to large proteins in turbid suspensions, as is often the case with membrane proteins. The present review describes the applications of IR spectroscopy to the study of membrane proteins, with an emphasis on recent work and on spectra recorded in the transmission mode, rather than using reflectance techniques. Data treatment procedures are discussed, including band analysis and diAerence spectroscopy methods. A technique for the analysis of protein secondary and tertiary structures that combines band analysis by curve-fitting of original spectra with protein thermal denaturation is described in detail. The assignment of IR protein bands in H2O and in D2O, one of the more diAcult points in protein IR spectroscopy, is also reviewed, including some cases of unclear assignments such as loops, b-hairpins, or 310-helices. The review includes monographic studies of some membrane proteins whose structure and function have been analysed in detail by IR spectroscopy. Special emphasis has been made on the role of subunit III in cytochrome c oxidase structure, and the proton pathways across this molecule, on the topology and functional cycle of sarcoplasmic reticulum Ca 2+ -ATPase, and on the role of lipids in determining the structure of the nicotinic acetylcholine receptor. In addition, shorter descriptions of retinal proteins and references to other membrane proteins that have been studied less extensively are also included. # 1999 Elsevier Science Ltd. All rights reserved.

The interaction of p62 with RIP links the atypical PKCs to NF-kappaB activation.

Abstract: The two members of the atypical protein kinase C (aPKC) subfamily of isozymes (zetaPKC and lambda/iotaPKC) are involved in the control of nuclear factor kappaB (NF-kappaB) through IKKbeta activation. Here we show that the previously described aPKC-binding protein, p62, selectively interacts with RIP but not with TRAF2 in vitro and in vivo. p62 bridges the aPKCs to RIP, whereas the aPKCs link IKKbeta to p62. In this way, a signaling cascade of interactions is established from the TNF-R1 involving TRADD/RIP/p62/aPKCs/IKKbeta. These observations define a novel pathway for the activation of NF-kappaB involving the aPKCs and p62. Consistent with this model, the expression of a dominant-negative mutant lambda/iotaPKC impairs RIP-stimulated NF-kappaB activation. In addition, the expression of either an N-terminal aPKC-binding domain of p62, or its C-terminal RIP-binding region are sufficient to block NF-kappaB activation. Furthermore, transfection of an antisense construct of p62 severely abrogates NF-kappaB activation. Together, these results demonstrate that the interaction of p62 with RIP serves to link the atypical PKCs to the activation of NF-kappaB by the TNFalpha signaling pathway.