The role of ATP as a mediator in the action of iron complexes on cellular calcium homeostasis

The effects of the interaction between low molecular weight iron complexes (citrate, lactate, and ATP complexes) with ATP and proteins, on the modification of Ehrlich carcinoma cell calcium homeostasis have been studied. In that modification the ferric-ATP complex shows much higher activity than the others. Sodium ATP, by iron translocation from citrate and lactate, increases their activity. This phenomenon implicates ATP as a mediator on the cellular activity of the complexes. Proteins, particularly ferritin, appear to moderately reduce their activity, whereas glutathione and ascorbic acid, acting as lipid peroxidation-inhibitors, show only a slight reduction of the iron complex’s effects on cellular calcium uptake.     

Variation in digestive performance between geographically disjunct populations of Atlantic salmon: countergradient in passage time and digestion rate

European Atlantic salmon (Salmo salar) populations inhabit rivers from northern Portugal to northern Norway across a wide spectrum of environmental variability. To address whether single physical factors might lead to genetic divergence of isolated populations, we compared the digestive performances total digestibility, relative nitrogen digestibility, passage time, and digestion rate (g dry matter · h^–1) — of northern (Scotland) and southern (Asturias, northern Spain) populations at three temperature regimes (5, 12, and 20° C). Total dry matter digestibilities increased directly with temperature but were similar for both populations at each of the three trials. Relative nitrogen digestibility did not differ between populations nor among temperature regimes. In contrast, passage time was significantly longer for low-than for high-latitude fish at both 5 and 20° C. When the percentage of food digested and the passage time were integrated as digestion rates (food digested per unit time), a significant population × temperature interaction consistent with a genotype × environment interaction was detected in addition to the population and temperature effects. This implies that not only is the digestive performance of the high-latitude population higher throughout the range of temperatures examined, but moreover the difference is reinforced at high temperatures, where the digestion rate of high-latitude fish was 1.6 times greater. Taken together, these two results provide preliminary evidence for countergradient variation in digestive rates of salmonids in response to variation in growth opportunity. The data support our previous work on the same two populations showing differences in growth rates, and underlie one of the possible mechnisms leading to more rapid growth of the high-latitude fish when both populations are reared in a common environment.     

Morphological evolution and changes in foraging behaviour of island and mainland populations of Blue Tit (Parus caeruleus) — a test of convergence and ecomorphological hypotheses

Summary We study the leg morphology and feeding postures of two subspecies of the Blue Tit (Parus caeruleus; Tenerife island and the Iberian Peninsula) and the Coal Tit (Parus ater; Iberian Peninsula). We search for evidence supporting the hypothesis of convergent evolution in morphological and ecological traits and we discuss the role of ecomorphological hypotheses as predictors of foraging differences at the intraspecific level. To overcome the problems introduced by environmental characteristics not related to locomotion and competition, we make observations under controlled situations to manage food quality and food access. We determine that the island Blue Tit has a longer tarsometatarsus, larger foot span and a more proximal insertion of the tibialis cranialis muscle (flexor of the tarsometatarsus) than the mainland Blue Tit. These morphological differences are consistent with the more frequent use of hanging and clinging head-up postures by the Iberian Blue Tit. Several ecomorphological hypotheses obtained at the interspecific level with other taxa, have proved to be of high predictive value for explaining ecological differences considering morphological evolution. The Tenerife Blue Tit and the Iberian Coal Tit clearly show close convergence in both feeding postures and leg structure, although some differences in morphology were found between these two species. Convergence in foraging methods between the island Blue Tit and the mainland Coal Tit can be explained without considering current interspecific competition as a determinant of niche space.     

Sucrose and fructan metabolism in wheat roots at chilling temperatures

Sucrose and fructan metabolism were studied in wheat ( Triticuin aotiirum L. cv. Tribal 800) roots during a period at chilling temperature. Enzyme activities related to fructan and sucrose metabolism were measured. Sucrose-sucrose fructosyl transfer-ase (EC 2.4.1.99) activity increased more than 25-fold when plants were cooled to 4°C. Sucrose synthase (EC 2.4.1.13) and sucrose-phosphate synthase (EC 2.4.1.14) activities also increased, but low temperatures had no significant effect on invertaso (EC 3.2.1.26) or on fructan hydrolase (EC 3.2.1.26) activities. The accumulation pattern of fructan in roots was different to that in leaves. In roots chilling stimulated the synthesis of fructans of high degree of polymerization.     

Three new HLA-G alleles and their linkage disequilibria with HLA-A

Three new allelic forms of the HLA-G DNA sequence (HLA-G*II, HLA-G*III, and HLA-G*IV) have been identified. With the HLA-G*I sequence (previously designated HLA 6.0) as a reference, HLA-G*II shows a silent (G A) mutation at the third base of codon 57, HLA-G*III bears a non-synonymous (A T), but conservative, (Thr Ser) substitution at the first base of codon 31, and HLA-G*IV shows two silent substitutions: (A T) at the third base of codon 107 and (G A) at the third base of codon 57. A rapid method of singling out each allele on genomic DNA has been developed by using polymerase chain reaction amplification followed by restriction endonuclease treatment. Also, more or less strong linkage disequilibria has been found between most HLA-A alleles and either HLA-G*I or *II, both being the most prevalent alleles in the population, with a genotypic frequency of 0.55 and 0.38, respectively; HLA-G*III is very rare and HLA-G*IV has a genotypic frequency of 0.07. An evolutive classification of HLA-A alleles results according to their association with either HLA-G*I or HLA-G*II, which does not correlate with the classical serological cross-reacting groups classification. The finding of a strong and selective A/G linkage disequilibria with most HLA-A alleles, together with the existence of less frequent random A/G associations, may suggest that there exist in different haplotypes true and varied A/G genetic distances (and not a recombinational hotspot). It may be inferred from preliminary data that in primates HLA-A/G haplotypes bearing G*II may have appeared later than those bearing G*I.The nucleotide sequence data reported in this paper have been submitted to the GenBank and EMBL nucleotide sequence databases and have been assigned the following accession numbers: EMBL-X60983 (HLA-G*II), GenBank-M99048 (HLA-G*III), and GenBank-L07784 (HLA-G*IV).The contribution to this paper by P. Morales and A. Corell is equal, and the order of authorship is arbitrary. Correspondence to: A. Arnaiz-Villena.     

A strong protein unfolding activity is associated with the binding of precursor chloroplast proteins to chloroplast envelopes

Protein conformational changes related to transport into chloroplasts have been studied. Two chimaeric proteins carrying the transit peptide of either ferredoxin or plastocyanin linked to the mouse cytosolic enzyme dihydrofolate reductase (EC 1.5.1.3.) were employed. In contrast to observations in mitochondria, we found in chloroplasts that transport of a purified ferredoxin-dihydrofolate reductase fusion protein is not blocked by the presence of methotrexate, a folate analogue that stabilizes the structural conformation of dihydrofolate reductase. It is shown that transport competence of this protein in the presence of methotrexate is not a consequence of alteration of the folding characteristics or methotrexate binding properties of dihydrofolate reductase by fusion to the ferredoxin transit peptide. Binding of dihydrofolate reductase fusion proteins to chloroplast envelopes is not inhibited by low temperature and it is only partially diminished by methotrexate. It is demonstrated that the dihydrofolate reductase fusion proteins unfold, despite the presence of methotrexate, on binding to the chloroplast envelopes. We propose the existence of a strong protein unfolding activity associated to the chloroplast envelopes.     

Molecular characterization of the proteinase-encoding gene, prb1, related to mycoparasitism by Trichoderma harzianum

The soil fungus Trichoderma harzianum is a mycoparasitic fungus known for its use as a biocontrol agent of phytopathogenic fungi. Among other factors, Trichoderma produces a series of antibiotics and fungal cell wall-degrading enzymes. These enzymes are believed to play an important role in mycoparasitism. Among the hydrolytic enzymes, we have identified a basic proteinase (Prb1) which is induced by either autoclaved mycelia, fungal cell wall preparation or chitin; however, the induction does not occur in the presence of glucose. The proteinase was purified and biochemically characterized as a serine proteinase of 31 kDa and pl 9.2. Based on the sequence of three internal peptides, synthetic oligonudeotide probes were designed. These probes allowed subsequent isolation of a cDNA and its corresponding genomic clone. The deduced amino acid sequence indicates that the proteinase is synthesized as a pre-proenzyme and allows its classification as a serine proteinase. Northen analysis shows that the induction of this enzyme is due to an increase in the corresponding mRNA level.     

Heterostyly in the Canarian endemic Jasminum odoratissimum (Oleaceae)

Jasminum odoratissimum is a Madeira and Canary Islands endemic showing classic heterostyly, i.e. with long-styled flowers with anthers at a low level in the corolla tube and short-styled flowers with anthers at a high level in the corolla tube. Short-styled flowers have large pollen, whereas long-styled flowers have small pollen. The two types are present in equal frequencies in the population.     

Modeling Lanthanide Complexes: Towards the Theoretical Design of Light Conversion Molecular Devices

Theoretical techniques have been developed and/or improved to predict the molecular structure of lanthanide complexes which were used to calculate their electronic properties, in particular, their electronic spectra and energy levels necessary to calculate the rates of energy transfer from the ligands to the metal ion. The molecular structure has been obtained by the SMLC/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes – Austin Model 1) model where the lanthanide ion is simulated by a sparkle implemented into the AM1 Hamiltonian used to perform a HF-SCF (Hartree-Fock Self-Consistent Field) calculation. The previous implementation of the SMLC/AM1 model (sparkle/1) involving only two parameters has been generalized to be consistent with the AM1 Hamiltonian and the new model (sparkle/2) significantly improved the prediction of molecular structures of Eu(III) complexes. For the electronic spectra and energy level calculations of the lanthanide complexes the model replaces the metal ion by a point charge with the ligands held in their positions as determined by the SMLC/AM1 model, and uses a INDO/S-CI (intermediate neglect of differential overlap/spectroscopic-configuration interaction) model. A preliminary study of the solvent effects on the absorption spectra of the free ligand is also presented. For the ligand-lanthanide ion energy transfer Fermi's golden rule is used with the multipolar and exchange mechanisms being implemented and tested for several complexes. These theoretical techniques have been applied to several complexes yielding very good results when compared to experimental data as well as predictions for the molecular and electronic structures and the relative contributions of the mechanisms for the energy transfer rates. This revised version was published online in June 2006 with corrections to the Cover Date.