Maternal clutch reduction in the pied flycatcher Ficedula hypoleuca: an undescribed clutch size adjustment mechanism

During eight years of study of a population of pied flycatchers Ficedula hypoleuca breeding in central Spain, we observed throughout incubation 22 cases of intact eggs being placed on the nest rim and clearly outside of the nest bowl and remaining there, with consequent embryo mortality. We assume that the removal of eggs had been performed by the incubating female. There is no evidence that pied flycatcher parents can detect embryo mortality and eject unhatchable eggs. Maternal egg ejection constitutes a direct mechanism of clutch size adjustment during incubation and before hatching of any young of the brood. This adjustment of clutch size happened when the mean and minimum temperature of the day before ejection were especially low. Also, clutch-reducing females were significantly more prone to show moult-breeding overlap than other females, suggesting a lower disposition to invest in reproduction. Clutch-reducing females were also frequently older than four years and had indications of a lower immunocompetence than females not ejecting eggs. Our results support the hypothesis that adverse conditions can elicit parental family size adjustment at every stage of reproduction without the need to depend on mechanisms of sibling competition.     

In silico predicted robustness of viroids RNA secondary structures. I. The effect of single mutations

Viroids are plant subviral pathogens whose genomes are constituted by a single-stranded and covalently closed small RNA molecule that does not encode for any protein. Despite this genomic simplicity, they are able of inducing devastating symptoms in susceptible plants. Most of the 29 described viroid species fold into a rodlike or quasi-rodlike structure, whereas a few of them fold as branched structures. The shape of these RNA structures is perhaps one of the most characteristic properties of viroids and sometimes is considered their only phenotype. Here we use RNA thermodynamic secondary structure prediction algorithms to compare the mutational robustness of all viroid species. After characterizing the statistical properties of the distribution of mutational effects on structure stability and the wideness of neutral neighborhood for each viroid species, we show an evolutionary trend toward increased structural robustness during viroid radiation, giving support to the adaptive value of robustness. Differences in robustness among the 2 viroid families can be explained by the larger fragility of branched structures compared with the rodlike ones. We also show that genomic redundancy can contribute to the robustness of these simple RNA genomes.     

Distinct white collar-1 genes control specific light responses in Mucor circinelloides

Light regulates many developmental and physiological processes in a large number of organisms. The best-known light response in the fungus Mucor circinelloides is the biosynthesis of beta-carotene. Here, we show that M. circinelloides sporangiophores also respond to light, exhibiting a positive phototropism. Analysis of both responses to different light wavelengths within the visible spectrum demonstrated that phototropism is induced by green and blue light, whereas carotenogenesis is only induced by blue light. The blue regulation of both responses suggests the existence of blue-light photoreceptors in M. circinelloides. Three white collar-1 genes (mcwc-1a, mcwc-1b and mcwc-1c) coding for proteins showing similarity with the WC-1 photoreceptor of Neurospora crassa have been identified. All three contain a LOV (light, oxygen or voltage) domain, similar to that present in fungal and plant blue-light receptors. When knockout mutants for each mcwc-1 gene were generated to characterize gene functions, only mcwc-1c mutants were defective in light induction of carotene biosynthesis, indicating that mcwc-1c is involved in the light transduction pathway that control carotenogenesis. We have also shown that positive phototropism is controlled by the mcwc-1a gene. It seems therefore that mcwc-1a and mcwc-1c genes control different light transduction pathways, although cross-talk between both pathways probably exists because mcwc-1a is involved in the light regulation of mcwc-1c expression.     

Investigations of the antioxidant properties of plant extracts using a DNA-electrochemical biosensor

In this work, the results of a method based on an electrochemical biosensor to detect DNA damage in vitro for the evaluation of the antioxidant properties of plant extracts are reported. The biosensor consisted of a dsDNA immobilized on a screen-printed electrode surface (SPE). DNA damage was promoted by the generation of the *OH radicals via Fenton-type reaction. The interaction of the radical species with immobilised DNA in the absence and presence of antioxidants was evaluated by means of changes in the guanine oxidation peak obtained by square wave voltammetry. The results demonstrated that the DNA-based biosensor is suitable as a rapid screening test for the evaluation of antioxidant properties of samples.     

Design, synthesis, and vasorelaxant and platelet antiaggregatory activities of coumarin-resveratrol hybrids

We have synthesized the coumarin-resveratrol hybrid 4 and its dimethoxy derivative 3 by a very direct synthetic route involving a Pechmann procedure. Compound 4 has also been synthesized by an alternative route (Perkin), which also allowed the synthesis of compounds 9-13. In addition, we have evaluated the potential vasorelaxant activity of the new compounds in endothelium-containing rat aorta rings pre-contracted with noradrenaline, as well as the inhibitory effects on platelet aggregation induced by thrombin in washed human platelets. The compounds reported here relaxed vascular smooth muscle and inhibited platelet aggregation with a profile similar to that of trans-resveratrol (t-RESV) and, in some cases, showed activity higher than that of the natural compound. This is the case for compound 13, which has a vasorelaxant activity that is twice as high as that of t-resveratrol and a platelet antiaggregant activity that is six times higher. These results suggest that these novel compounds may have potential as structural templates for the design and subsequent development of new vasodilatory and platelet antiaggregatory drugs.     

K<Subscript>ATP</Subscript> channel Kir6.2 E23K variant overrepresented in human heart failure is associated with impaired exercise stress response

ATP-sensitive K⁺ (K_ATP) channels maintain cardiac homeostasis under stress, as revealed by murine gene knockout models of the KCNJ11-encoded Kir6.2 pore. However, the translational significance of K_ATP channels in human cardiac physiology remains largely unknown. Here, the frequency of the minor K23 allele of the common functional Kir6.2 E23K polymorphism was found overrepresented in 115 subjects with congestive heart failure compared to 2,031 community-based controls (69 vs. 56%, P < 0.001). Moreover, the KK genotype, present in 18% of heart failure patients, was associated with abnormal cardiopulmonary exercise stress testing. In spite of similar baseline heart rates at rest among genotypic subgroups (EE: 72.2 ± 2.3, EK: 75.0 ± 1.8 and KK: 77.1 ± 3.0 bpm), subjects with the KK genotype had a significantly reduced heart rate increase at matched workload (EE: 32.8 ± 2.7%, EK: 28.8 ± 2.1%, KK: 21.7 ± 2.6%, P < 0.05), at 75% of maximum oxygen consumption (EE: 53.9 ± 3.9%, EK: 49.9 ± 3.1%, KK: 36.8 ± 5.3%, P < 0.05), and at peak VO₂ (EE: 82.8 ± 6.0%, EK: 80.5 ± 4.7%, KK: 59.7 ± 8.1%, P < 0.05). Molecular modeling of the tetrameric Kir6.2 pore structure revealed the E23 residue within the functionally relevant intracellular slide helix region. Substitution of the wild-type E residue with an oppositely charged, bulkier K residue would potentially result in a significant structural rearrangement and disrupted interactions with neighboring Kir6.2 subunits, providing a basis for altered high-fidelity K_ATP channel gating, particularly in the homozygous state. Blunted heart rate response during exercise is a risk factor for mortality in patients with heart failure, establishing the clinical relevance of Kir6.2 E23K as a biomarker for impaired stress performance and underscoring the essential role of K_ATP channels in human cardiac physiology.     

Initial characterization of a recombinant kynureninase from Trypanosoma cruzi identified from an EST database

Kynureninase has been described in bacteria, fungi and animals as an enzyme involved in the catabolic degradation pathway of l-tryptophan. This pyridoxal 5′-phosphate (PLP)-dependent enzyme catalyzes the hydrolytic cleavage of l-kynurenine and 3-hydroxy-l-kynurenine to yield l-alanine and either anthranilic or 3-hydroxyanthranilic acid, respectively. We identified a putative kynureninase gene from a Trypanosoma cruzi project aiming at the structural and functional characterization of more than 100 proteins differentially expressed during metacyclogenesis. This gene encodes a protein similar in size and sequence to kynureninases from other sources. This open reading frame was cloned and the recombinant enzyme was overexpressed. Recombinant T. cruzi kynureninase was purified to homogeneity and its identity was confirmed by mass spectrometry. The apparent molecular mass of the native T. cruzi kynureninase was estimated by gel filtration, suggesting that the protein is a homodimer. Circular dichroism spectrum indicated a mixture of α-helix and β-sheet structure, expected for an aminotransferase fold. l-kynurenine, preferentially hydrolyzed by prokaryotic inducible kynureninases, and 3-hydroxy-l-kynurenine, the preferred substrate in fungi and vertebrates, are both catabolized equally well by T. cruzi kynureninase. Further experimental assays will be performed to fully understand the importance of this enzyme for T. cruzi metabolism.     

Evaluation of l-glutamine for cryopreservation of boar spermatozoa

The aim of the present study was to evaluate the protective effect of l-glutamine (l-Gln) against cryopreservation injuries on boar sperm. In Experiment 1, l-Gln from 20 to 80 mM was evaluated as a supplement for a standard freezing extender (egg yolk – EY – 20%, and glycerol 3%). No significant improvement (P > 0.05) was obtained for any post-thaw sperm parameter assessed (objective sperm motility – CASA system – and flow cytometric analysis of plasma and acrosomal membrane integrity −SYBR14/PI/PE-PNA− and plasma membrane stability −M540/YoPro1−). In Experiment 2, l-Gln was evaluated as a partial glycerol substitute in the freezing extender. Significant (P < 0.05) enhancement of post-thaw sperm motion parameters was achieved in sperm frozen in the presence of 2% glycerol and 80 mM l-Gln compared to control (3% glycerol). In Experiment 3, l-Gln was evaluated as an EY substitute in the freezing extender, and no functional sperm were recovered after thawing sperm frozen in the presence of l-Gln and the absence of EY. In conclusion, l-Gln has the ability to cryoprotect boar sperm when it is used as a partial glycerol substitute in the freezing extender.     

Brain-penetrating 2-aminobenzimidazole H1-antihistamines for the treatment of insomnia

The benzimidazole core of the selective non-brain-penetrating H₁-antihistamine mizolastine was used to identify a series of brain-penetrating H₁-antihistamines for the potential treatment of insomnia. Using cassette PK studies, brain-penetrating H₁-antihistamines were identified and in vivo efficacy was demonstrated in a rat EEG/EMG model. Further optimization focused on strategies to attenuate an identified hERG liability, leading to the discovery of 4i with a promising in vitro profile.     

Comparison of classification methods for detecting associations between SNPs and chick mortality

Multi-category classification methods were used to detect SNP-mortality associations in broilers. The objective was to select a subset of whole genome SNPs associated with chick mortality. This was done by categorizing mortality rates and using a filter-wrapper feature selection procedure in each of the classification methods evaluated. Different numbers of categories (2, 3, 4, 5 and 10) and three classification algorithms (naïve Bayes classifiers, Bayesian networks and neural networks) were compared, using early and late chick mortality rates in low and high hygiene environments. Evaluation of SNPs selected by each classification method was done by predicted residual sum of squares and a significance test-related metric. A naïve Bayes classifier, coupled with discretization into two or three categories generated the SNP subset with greatest predictive ability. Further, an alternative categorization scheme, which used only two extreme portions of the empirical distribution of mortality rates, was considered. This scheme selected SNPs with greater predictive ability than those chosen by the methods described previously. Use of extreme samples seems to enhance the ability of feature selection procedures to select influential SNPs in genetic association studies.