bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual selection in the barn swallow (Hirundo rustica). V. Geographic variation in ornament size
Authors: Møller Anders Pape
Published: December 2004

Models of sexual selection in a cline predict the patterns of clinal variation in female mate preference and male secondary sexual characters. These predictions were tested for the nominate subspecies of the barn swallow Hirundo rustica which demonstrates clinal variation in morphology, with several characters in both sexes showing increasing size at higher latitudes. Sexual size dimorphism in the length of the tail ornament and the short, central tail feathers increase with increasing latitude while size dimorphism in other morphological characters is independent of latitude. The main reason for the two divergent patterns of sexual size dimorphism appears to be the higher foraging cost of having a long tail ornamental at low latitudes. The control of development decreases with increasing latitude as demonstrated by an increasing latitudinal cline in fluctuating asymmetry of tail length. Phenotypic variance in tail length increases with latitude in males, but not in females, as shown by the coefficients of variation. Clinal variation in morphology is not due to natural selection associated with a latitudinal increase in the distance between breeding and wintering areas. The geographic patterns of morphological variation suggest that the tail character has diverged geographically as a result of a sexual process of reliable signalling.
Reproductive features of homospecific hybridogenetically‐derived stick insects suggest how unisexuals can evolve
Authors: Tinti Fausto , Mantovani Barbara , Scali Valerio
Published: December 2004

Hybridogenetic reproduction has been demonstrated in both vertebrate and invertebrate unisexual hybrids. Its most peculiar feature is the transmission to the progeny of one invariant genome (hemiclone) through the egg and the replacement of the other by host fathering males. Bacillus hybridogens are the only known example of hemiclonal invertebrates; their comparison to Poeciliopsis and Rana systems helps in understanding peculiar and shared features of vertebrate and insect hybridogenesis. In P. monacha‐lucida, the experimental production of non‐hybrid progeny through the reunion of the maternal hemiclone with a homospecific paternal genome provided by males of the maternal ancestor leads to inviable or severely impaired sterile specimens, whereas in Rana esculenta viable offspring are the rule. The comparable synthetic B. rossius progeny (Rr) embodying the maternal R hemiclone and a paternal r haploset, appear perfectly viable and fertile, clearly demonstrating compatibility between the two homospecific genomes, and also supporting a lack of deterioration of the R hemiclone. This condition can be ascribed to the recent origin of the hemiclones, and also to the absence of lethal recessives, owing to their most likely derivation from an automictic doubling in the parthenogenetic mechanisms of the maternal ancestor. However, the hybridogenetic system breaks down in the gamete production of the majority of Rr females, since normal allele segregation also occurs in their progeny. These reproductive modes suggest a likely evolutionary dynamic for newly originated hybridogens: to achieve stability, an interruption of reproductive interactions with the maternal ancestor seems necessary. In stick insects, this constraint appears to be fulfilled in both areas of sympatry. The microevolutionary pathway suggested by the ecological scenario also supports the possibility that a shift of hemiclonal stick insect strains to clonality has occurred.
Reaction norms of Arabidopsis. I. Plasticity of characters and correlations across water, nutrient and light gradients
Authors: Pigliucci M. , Whitton J. , Schlichting C. D.
Published: December 2004

The univariate and multivariate study of variation for phenotypic plasticity is central to providing a clear understanding of hypotheses about the genetic control and evolution of reaction norms in natural populations. Arabidopsis thaliana is an ideal organism for the study of Genotype × Environment interactions (i.e., genetic variation for plasticity), because of the ease with which it can be grown in large numbers and due to the amount of information already available on its genetics, physiology and developmental biology. In this paper, we report on the plasticity, genetic variation and G × E interactions of four populations of A. thaliana in response to three environmental gradients (water, light and nutrients), each characterized by four levels of the controlled parameter. We measured nine traits and obtained their reaction norms. Path analysis was used to study the plasticity of character correlations. We found a tendency for A. thaliana reaction norms to be linear (either flat, i.e. no plasticity, or with a significant slope), in accordance with previous studies. We detected substantial amounts of genetic variation for plasticity in the light and nutrient gradients, but not in the water gradient. Dramatic restructuring of character correlations was induced by changes in environmental conditions, although some paths tended to be stable irrespective of the environment, thereby suggesting some degree of canalization.
Stress and limits to adaptation: Sexual ornaments
Authors: Parsons P. A.
Published: December 2004

Limits to adaptation of sexual ornaments are discussed in the context of the stressful environments of free‐living populations. A trade‐off occurs whereby the energetic demands from the development and maintenance of sexual ornaments of increasing size are countered by (1) the energetic cost of stress in particular from parasites and climatic extremes, and (2) a lack of energy from nutritional inadequacy. Furthermore, at times of environmental deterioration followed by high extinction rates, sexually dimorphic species should be particularly vulnerable. However, at these unfavourable times, individuals carrying genes for stress resistance should have the potential for developing the most extreme ornaments.
Testing the generation time hypothesis using DNA/DNA hybridization between artiodactyls
Authors: Douzery E. , Lebreton J.‐D. , Catzeflis F. M.
Published: December 2004

Heterogeneous rates of molecular change between some mammalian lineages are commonly explained by contrasts in generation time length. Here the generation time hypothesis is tested by comparing the relative rates of molecular change in related artiodactyl taxa differing by their generation time. A demographic model based on allometric relations with the adult body weight is used to estimate the cohort generation time in Bovidae and Cervidae families (Artiodactyla, Mammalia). Two pairs of closely related taxa (two cervids, two bovids) were selected, each showing clear ratios (1.5 to 3.5 times) in their generation time. Rates of genetic change in non‐repeated nuclear DNA were estimated by DNA/DNA hybridization experiments performed among these ruminants and a camelid outgroup. Relative rate tests were applied to the two pairs of ingroup taxa differing by their generation time, in order to test if shorter generation time would correspond to higher rate of molecular change. Contradictory statistical results did not show a greater accumulation of nucleotide changes in the lineage leading to the short generation time species. The recorded differences in branch lengths of sister taxa were either conflicting or too small (relative to the contrasted generation times) to reveal a generation time effect. Alternative hypotheses are suggested to explain these preliminary results.
Limitations of the RAPD technique in phylogeny reconstruction in Drosophila
Authors: Van De Zande Louis , Bijlsma R.
Published: December 2004

In this study the limitations of the RAPD technique for phylogenetic analysis of very closely related and less related species of Drosophila are examined. In addition, assumptions of positional homology of amplified fragments in different species are examined by cross‐hybridization of RAPD fragments. It is demonstrated that in Drosophila the use of RAPD markers is very efficient in identification of species. For assessment of phylogenetic relationships, however, the method is limited to sibling species, and reliable measures for genetic distances cannot be obtained. Hybridization experiments demonstrate that fragments of similar length amplified from different species are not always derived from corresponding loci, and that not all RAPD fragments within the same amplification pattern are independent.
Effects of maternal parasite load on offspring life‐history traits in the common lizard (Lacerta vivipara)
Authors: Sorci G. , Clobert J.
Published: December 2004

We studied the effect of maternal ectoparasite load (measured at parturition) on the life‐history traits of the offspring of the host Lacerta vivipara, the European common lizard. The ectoparasite, a mite belonging to the family Laelapidae, had a detrimental effect on its host: parasite load was associated with increased host mortality, and was negatively correlated with host body mass. Parasite load was persistent over time, suggesting that parasite load can be predictable. Offspring of highly parasitised mothers had higher values of several fitness components early in life than offspring of parasite‐free mothers or lightly infested mothers. This was expressed in terms of increased F1 yearling growth rate, and reproductive investment at first reproduction (measured as F2 hatchling mass). These results are interpreted as a host adaptation to attenuate the impact of parasites. Indeed, if high parasite loads arise from long exposure time to a constant population of parasites, and if the negative effects of parasites are additive over time, hosts could reduce the impact of parasites simply by investing more during the earlier stages of life. Naturally, having better performance early in life should lead to higher mortality rates and/or lower fecundity later in life.
On the origin of feathers
Authors: Brush A. H.
Published: December 2004

The appearance of feathers defines the appearance of birds. A number of changes defined, preceded or accompanied the event. The changes were hierarchical in nature and included revolutions in genomic organization (i.e., HOX and the feather keratin genes), protein sequence and shape, the large scale organization of proteins into filaments, and in the geometry of the cells and their roles in the follicle. Changes at each of these levels differ or produced different products than found in its analog in reptiles. They are essentially unique to birds and produced an evolutionary novelty. I used analysis of extant structure and information on development to reconstruct key events in the evolution of feathers. The ancestral reptilian epidermal structure, while probably a scale or tubercles, is still unidentified. The structural genes of feather proteins (φ‐keratin) are tandem repeats probably assembled from pre‐existing exons. They are unlike the alpha‐keratin of vertebrate soft epidermis. Amino‐acid composition, shape, and behavior of feather keratins are unique among vertebrates. The 3‐dimensional organization of the follicle and the developmental processes are also unique.

Although we lack a complete understanding of the appearance and early role of feathers, they are clearly the results of novel events.
Pharyngeal biting mechanics in centrarchild and cichlid fishes: insights into a key evolutionary innovation
Authors: Galis F. , Drucker E. G.
Published: December 2004

This study compares the pharyngeal biting mechanism of the Cichlidae, a family of perciform fishes that is characterized by many anatomical specializations, with that of the Centrarchidae, a family that possesses the generalized perciform anatomy. Our objective was to trace the key structural and functional changes in the pharyngeal jaw apparatus that have arisen in the evolution from the generalized to derived (cichlid) perciform condition.

We propose a mechanical model of pharyngeal biting in the Centrarchidae and compare this with an already existing model for pharyngeal biting in the family Cichlidae. Central to our centrarchid model is a structural coupling between the upper and lower pharyngeal jaws. This coupling severely limits independent movement of the pharyngeal jaws, in contrast to the situation in the speciose Cichlidae, in which the upper and lower pharyngeal jaw movements are to a large extent independent. We tested both models by electrically stimulating nine muscles of the branchial and hyoid apparatuses in three centrarchild and three cichlid species. The results confirmed the coupled movement of the upper and lower pharyngeal jaws in the Centrarchidae and the independence of these movements in the Cichlidae.

We suggest that the key structural innovation in the development of the functionally versatile cichlid (labroid) pharyngeal jaw apparatus was the decoupling of epibranchials 4 from the upper pharyngeal jaws. This structural decoupling implies the decoupling of the movements of the upper and lower pharyngeal jaws and leads to a cichlid (labroid) type of pharyngeal bite. The initial decoupling facilitated a cascade of changes, each leading to improved biting effectiveness and/or to increased mobility and mechanical flexibility of the pharyngeal jaws. The shift of insertion of the m. levator externus 4 which has been considered the primary innovation in the transformation probably arose secondarily.

The transformation of the pharyngeal biting mechanism in the perciforms is an excellent example of decoupling of structures associated with diversification of form and function and with increased speciation rates.
Within population genetic differentiation in traits affecting clonal growth: Festuca rubra in a mountain grassland
Authors: Skálová H. , Pecháčková S. , Suzuki J. , Herben T. , Hara T. , Hadincová V. , Krahulec F.
Published: December 2004

Festuca rubra , a clonal grass of mountain grasslands, possesses a considerable variability in traits related to spatial spreading (rhizome production, length and branching; tussock architecture). Since these traits highly influence the success of the species in a spatially heterogeneous system of grasslands, a combined field and growth chamber approach was adopted to determine the within‐population variation in these parameters. Clones were sampled in a mountain grassland (The Krkonoše Mts., Czech Republic); the environment (mean neighbour density) of individual clones varied highly. Before the clones were collected, shoot demography and tussock architecture within these clones were recorded in the field for four seasons. Their clone identity was determined using DNA RAPD. Vegetatively propagated plants from these clones were cultivated in a common garden experiment to demonstrate variation in tussock growth and architecture. Their response to change in red/far red light ratio was determined in the growth chamber.

Highly significant variation among clones was found in almost all parameters. In the common garden, the clones differed in tussock growth (mean tillering rate), architecture (mean shoot angle, mean tussock density) and proportion of flowering shoots. In the growth chamber, both the aboveground parameters and parameters of the rhizome system were strongly affected by red/far red ratio; among‐clone variation was also almost always significant. The genotype × environment interaction was significant for tillering rate and rhizome architecture. The structure of the rhizome system (which is the major component of clonal spread in space) is a complex result of several components whose inter‐clone variations differ: (i) genetically determined mean rhizome system size, (ii) overall plasticity in rhizome system size (with no significant genetic variation in plasticity), and (iii) genetically determined plasticity in rhizome architecture. Because of the variation in plasticity in rhizome architecture, some c lones seemed to possess the ability to exploit a favourable habitat patch by producing short branches when there; whereas the remaining clones appeared to possess only a simple escape mechanism from unfavourable patches.

Environmental variation in the light levels in the studied grassland is fine grained; horizontal growth rates of F. rubra are sufficient to make genets experience different patches in their lifetime. The high variation in both genotype means and plasticities is likely to be due to selection early in genet life in an environment which is heterogeneous at a fine scale.
Herbivores and the evolution of the semelparous perennial life‐history of plants
Authors: Klinkhamer P. G. L. , Kubo T. , Iwasa Y.
Published: December 2004

The relationship between a plant and its potential enemies changes drastically after reproduction has started. Using a dynamic modelling approach we study the effects of herbivores and pathogens, that are attracted by reproducing plants, on optimal allocation of resources, and life‐history strategies. We assume that the level of attack increases with the investment in reproduction, which may lead to a reduction of current years reproductive success, a reduction of storage efficiency or an increase of plant mortality. If herbivores or pathogens attracted by flowering plants mainly reduce current years reproductive success, the optimal life‐history is annual or iteroparous perennial if the attack is an all or nothing event. If the level of consumption increases with the number of herbivores attracted, the optimal life‐history is most likely iteroparity with or without mast years. Only under very restricted conditions this may lead to semelparity. If herbivores mainly reduce the efficiency of the resources stored for next year, the optimal life‐history is iteroparity. If herbivores mainly reduce survival, the optimal solution is likely to be mast years or semelparity. For parameter values that are realistic for Cynoglossum officinale, a semelparous perennial from calcereous soils, the model predicts that reproduction should start in the third year and that 99% of the available resources at the end of season should be invested in reproduction and only 1% saved for growth next year. With such an investment only c. 1% of the plants would survive after reproduction, so the optimal life‐history is close to semelparity. For the small fraction of plants that reproduce more than once, years of vegetative growth only and years with reproduction should alternate. Multiple reproduction is rare in C. officinale. However, such a life history is very common for plants known as semelparous perennial. Although the available empirical evidence is, as yet, circumstantial rather than conclus ive we propose that reproduction related mortality mediated through herbivores or pathogens may play a role in the evolution of the semelparous perennial life‐history.
Consequences of Wolbachia transmission process on the infection dynamics
Authors: Guillemaud T. , Rousset F.
Published: December 2004

In some species displaying Wolbachia‐induced cytoplasmic incompatibility, the intensity of incompatibility depends on the density of symbionts in both parents. Although modalities of the transmission process are poorly known, it appears that the density of Wolbachia within the offspring of a female is variable and is correlated with that of the mother. Assuming that the infection level of an host is a continuous trait, we examine some theoretical consequences of the Wolbachia transmission process on the evolution of the infection level within a population. The hypotheses of this model concern two main points: the transmission of Wolbachia is affected by stochastic processes and a deterministic bias, and the bacterial load of the parents of a cross affects their compatibility relationships. It is shown that the variance of the number of bacteria transmitted induced by the stochastic processes tends to counteract the effect of bacterial curing on the dynamics of infection. A general consequence of the model is that the extinction of Wolbachia is possible even if there is strong incompatibility and no selective disadvantage for the host to bear the bacteria. The model indicates that the evolution of bacterial mutants does not depend on the level of incompatibility they induce, but that mutants with higher transmission variance can be selected for. Moreover, the mean infection level of the host population increases in the presence of such bacteria.
Lerista bougainvillii, a case study for the evolution of viviparity in reptiles
Authors: Qualls C. P. , Shine R.
Published: December 2004

Many factors, both environmental and biotic, have been suggested to facilitate or hinder the evolution of viviparity (live‐bearing) in reptiles. Viviparity has evolved recently within the Australian scincid lizard Lerista bougainvillii and the species includes oviparous, viviparous, and reproductively intermediate (with prolonged egg retention) populations; thus, it offers an exceptional opportunity to evaluate the validity of these hypotheses. We carried out such tests by (i) comparing environmental conditions over the geographic ranges occupied by oviparous, viviparous, and intermediate populations (to identify possible selective forces for the evolution of viviparity), and (ii) comparing morphological, reproductive and ecological traits of L. bougainvillii with those of other sympatric scincid species (to identify traits that may have predisposed this taxon to the evolution of viviparity). The areas occupied by viviparous L. bougainvillii are significantly colder than those occupied by both their intermediate and oviparous conspecifics, in accord with the “cold‐climate” hypothesis for reptilian viviparity. Rainfall is similar over the ranges of the three forms. Climatic unpredictability (as assessed by the magnitude of year‐to‐year thermal variation) is lower for viviparous animals, in contradiction to published speculations. Comparison with 31 sympatric scincid species showed that L. bougainvillii is not atypical for most of the traits we measured (e.g., body size, clutch size, thermal preferenda and tolerances). However, oviparous L. bougainvillii do display several traits that have been suggested to facilitate the evolution of viviparity. For example, pregnancy does not reduce locomotor ability of females; the lizards are semi‐fossorial; even the oviparous females produce only a single clutch of eggs per year; and they ovulate relatively late in summer, so that the time available for incubation is limited.
Precise control of sex allocation in pseudo‐arrhenotokous phytoseiid mites
Authors: Nagelkerke C. J. , Sabelis M. W.
Published: December 2004

Can sex allocation be controlled by haplo‐diploid organisms where both males and females arise from fertilised eggs but males become effectively haploid by paternal genome loss (pseudo‐arrhenotoky)? If so, how does the control of mean and variance of sex allocation compare with haplo‐diploids where males arise from unfertilised eggs (arrhenotoky)? These questions are addressed by experiments with two species of pseudo‐arrhenotokous plant‐inhabiting predatory mites: Typhlodromus occidentalis Nesbitt and Phytoseiulus persimilis Athias‐Henriot (Acari: Phytoseiidae).

It is shown that females conditionally adjust offspring sex ratio in response to the presence of conspecifics or their cues. The sex ratios are precise in that their variance is less than expected from a binomial distribution. Because eggs are produced one‐by‐one at regular intervals, it is not possible to designate separate clutches, thus rendering conventional clutch‐based estimates of precision inadequate. To remedy this a range of time scales was investigated and this showed an increase in precision with time scale (and hence “clutch” size). Markovian analysis of son‐daughter sequences showed that this increase arises only if the predator “memorizes” the mean sex ratio of all eggs laid before.

Control of mean and variance of sex allocation is selectively advantageous when local mating groups vary in size and are usually small, as is the case for the phytoseiid mites under study. Predictions of the optimal sex ratio from local mate competition models were in agreement for T. occidentalis. However, P. persimilis, exhibited a stronger female bias than predicted. We suggest that this may be due to selection levels operating at a larger spatial scale than the local mating group.

Control of sex allocation seems as good as in arrhenotokous arthropods, suggesting that — in this respect — pseudo‐arrhenotoky is not at a disadvantage compared to arrhenotoky.
Mate recognition in a freshwater fish: geographical distance, genetic differentiation, and variation in female preference for local over foreign males
Authors: Wong B. B. M. , Keogh J. S. , Jennions M. D.
Published: December 2004

It often is assumed that more distant allopatry should reflect reduced rates of contemporary gene flow and/or greater divergence in mate recognition systems. This assumption, however, is rarely tested and may not always be appropriate. Here we investigated female preference for local and foreign males in a morphologically variable Australian freshwater fish, the Pacific blue-eye Pseudomugil signifer. Using a multidisciplinary approach that combined molecular phylogeography with conventional mate choice experiments, we found female blue-eyes spent more time in association with local males only when the alternative was a foreigner from a geographically and genetically more distant population. When offered the choice between two foreign males, females associated more with males from the population that was more closely adjacent to their own. Our results suggest that female preference for local over foreign males in blue-eyes may depend on how genetically and geographically separated populations are from one another.
Participation of acetaldehyde dehydrogenases in ethanol and pyruvate metabolism of the yeast Saccharomyces cerevisiae
Authors: Boubekeur Samira , Camougrand Nadine , Bunoust Odile , Rigoulet Michel , Guérin Bernard
Published: December 2004

This work was undertaken to clarify the role of acetaldehyde dehydrogenases in Saccharomyces cerevisiae metabolism during growth on respiratory substrates. Until now, there has been little agreement concerning the ability of mutants deleted in gene ALD4, encoding mitochondrial acetaldehyde dehydrogenase, to grow on ethanol. Therefore we constructed mutants in two parental strains (YPH499 and W303‐1a). Some differences appeared in the growth characteristics of mutants obtained from these two parental strains. For these experiments we used ethanol, pyruvate or lactate as substrates. Mitochondria can oxidize lactate into pyruvate using an ATP synthesis‐coupled pathway. The ald4Δ mutant derived from the YPH499 strain failed to grow on ethanol, but growth was possible for the ald4Δ mutant derived from the W303‐1a strain. The co‐disruption of ALD4 and PDA1 (encoding subunit E1α of pyruvate dehydrogenase) prevented the growth on pyruvate for both strains but prevented growth on lactate only in the double mutant derived from the YPH499 strain, indicating that the mutation effects are strain‐dependent. To understand these differences, we measured the enzyme content of these different strains. We found the following: (a) the activity of cytosolic acetaldehyde dehydrogenase in YPH499 was relatively low compared to the W303‐1a strain; (b) it was possible to restore the growth of the mutant derived from YPH499 either by addition of acetate in the media or by introduction into this mutant of a multicopy plasmid carrying the ALD6 gene encoding cytosolic acetaldehyde dehydrogenase. Therefore, the lack of growth of the mutant derived from the YPH499 strain seemed to be related to the low activity of acetaldehyde oxidation. Therefore, when cultured on ethanol, the cytosolic acetaldehyde dehydrogenase can partially compensate for the lack of mitochondrial acetaldehyde dehydrogenase only when the activity of the cytosolic enzyme is sufficient. However, when cultured on pyruvate and in the absence of pyruvate dehydrogenase, the cytosolic acetaldehyde dehydrogenase cannot compensate for the lack of the mitochondrial enzyme because the mitochondrial form produces intramitochondrial NADH and consequently ATP through oxidative phosphorylation.
Modeled ligand‐protein complexes elucidate the origin of substrate specificity and provide insight into catalytic mechanisms of phenylalanine hydroxylase and tyrosine hydroxylase
Authors: Maaß Astrid , Scholz Joachim , Moser Andreas
Published: December 2004

NMR spectroscopy and X‐ray crystallography have provided important insight into structural features of phenylalanine hydroxylase (PAH) and tyrosine hydroxylase (TH). Nevertheless, significant problems such as the substrate specificity of PAH and the different susceptibility of TH to feedback inhibition by l‐3,4‐dihydroxyphenylalanine (l‐DOPA) compared with dopamine (DA) remain unresolved. Based on the crystal structures 5pah for PAH and 2toh for TH (Protein Data Bank), we have used molecular docking to model the binding of 6(R)‐l‐erythro‐5,6,7,8‐tetrahydrobiopterin (BH4) and the substrates phenylalanine and tyrosine to the catalytic domains of PAH and TH. The amino acid substrates were placed in positions common to both enzymes. The productive position of tyrosine in TH·BH4 was stabilized by a hydrogen bond with BH4. Despite favorable energy scores, tyrosine in a position trans to PAH residue His290 or TH residue His336 interferes with the access of the essential cofactor dioxygen to the catalytic center, thereby blocking the enzymatic reaction. DA and l‐DOPA were directly coordinated to the active site iron via the hydroxyl residues of their catechol groups. Two alternative conformations, rotated 180° around an imaginary iron–catecholamine axis, were found for DA and l‐DOPA in PAH and for DA in TH. Electrostatic forces play a key role in hindering the bidentate binding of the immediate reaction product l‐DOPA to TH, thereby saving the enzyme from direct feedback inhibition.
nNOS inhibition, antimicrobial and anticancer activity of the amphibian skin peptide, citropin 1.1 and synthetic modifications
Authors: Doyle Jason , Brinkworth Craig S. , Wegener Kate L. , Carver John A. , Llewellyn Lyndon E. , Olver Ian N. , Bowie John H. , Wabnitz Paul A. , Tyler Michael J.
Published: December 2004

A large number of bioactive peptides have been isolated from amphibian skin secretions. These peptides have a variety of actions including antibiotic and anticancer activities and the inhibition of neuronal nitric oxide synthase. We have investigated the structure–activity relationship of citropin 1.1, a broad‐spectrum antibiotic and anticancer agent that also causes inhibition of neuronal nitric oxide synthase, by making a number of synthetically modified analogues. Citropin 1.1 has been shown previously to form an amphipathic α‐helix in aqueous trifluoroethanol. The results of the structure–activity studies indicate the terminal residues are important for bacterial activity and increasing the overall positive charge, while maintaining an amphipathic distribution of residues, increases activity against Gram‐negative organisms. Anticancer activity generally mirrors antibiotic activity suggesting a common mechanism of action. The N‐terminal residues are important for inhibition of neuronal nitric oxide synthase, as is an overall positive charge greater than three. The structure of one of the more active synthetic modifications (A4K14‐citropin 1.1) was determined in aqueous trifluoroethanol, showing that this peptide also forms an amphipathic α‐helix.
Interactions of the antimicrobial β‐peptide β‐17 with phospholipid vesicles differ from membrane interactions of magainins
Authors: Epand Raquel F. , Umezawa Naoki , Porter Emilie A. , Gellman Samuel H. , Epand Richard M.
Published: December 2004

We have studied the interaction of β‐17, a potent synthetic antimicrobial β‐peptide, with phospholipids. We find that unlike other antimicrobial peptides such as magainin II, β‐17 facilitates the formation of nonbilayer phases, indicating that the peptide promotes negative curvature. Studies of liposomal leakage also indicate a different mode of membrane interaction relative to magainin II, but both leakage and membrane binding show that β‐17, like magainin II, has strong affinity for membranes containing anionic lipids. This is likely to be an important factor contributing to the antimicrobial specificity of the β‐peptide.
Reduction of S‐nitrosoglutathione by human alcohol dehydrogenase 3 is an irreversible reaction as analysed by electrospray mass spectrometry
Authors: Hedberg Jesper J. , Griffiths William J. , Nilsson Stina J. F. , Höög Jan‐Olov
Published: December 2004

Human alcohol dehydrogenase 3/glutathione‐dependent formaldehyde dehydrogenase was shown to rapidly and irreversibly catalyse the reductive breakdown of S‐nitrosoglutathione. The steady‐state kinetics of S‐nitrosoglutathione reduction was studied for the wild‐type and two mutated forms of human alcohol dehydrogenase 3, mutations that have previously been shown to affect the oxidative efficiency for the substrate S‐hydroxymethylglutathione. Wild‐type enzyme readily reduces S‐nitrosoglutathione with a kcat/Km approximately twice the kcat/Km for S‐hydroxymethylglutathione oxidation, resulting in the highest catalytic efficiency yet identified for a human alcohol dehydrogenase. In a similar manner as for S‐hydroxymethylglutathione oxidation, the catalytic efficiency of S‐nitrosoglutathione reduction was significantly decreased by replacement of Arg115 by Ser or Lys, supporting similar substrate binding. NADH was by far a better coenzyme than NADPH, something that previously has been suggested to prevent reductive reactions catalysed by alcohol dehydrogenases through the low cytolsolic NADH/NAD+ ratio. However, the major products of S‐nitrosoglutathione reduction were identified by electrospray tandem mass spectrometry as glutathione sulfinamide and oxidized glutathione neither of which, in their purified form, served as substrate or inhibitor for the enzyme. Hence, the reaction products are not substrates for alcohol dehydrogenase 3 and the overall reaction is therefore irreversible. We propose that alcohol dehydrogenase 3 catalysed S‐nitrosoglutathione reduction is of physiological relevance in the metabolism of NO in humans.
TRAF6 and C‐SRC induce synergistic AP‐1 activation via PI3‐kinase–AKT–JNK pathway
Authors: Funakoshi‐Tago Megumi , Tago Kenji , Sonoda Yoshiko , Tominaga Shin‐ichi , Kasahara Tadashi
Published: December 2004

Interleukin‐1 (IL‐1) induces multiple genes via activation of transcription factors that include NF‐κB and activator protein‐1 (AP‐1). We found that IL‐1‐mediated c‐Src activation was required for AP‐1 activation, but not for NF‐κB activation and also revealed that c‐Src‐induced AP‐1 activation was enhanced synergistically by the coexpression of TNF receptor associated factor 6 (TRAF6). In addition, c‐Src interacts with TRAF6 in response to IL‐1 and this interaction is required for c‐Src activity. However, neither dominant negative mutants of TRAF6 (TRAF6 DN) nor kinase‐dead mutant of c‐Src (c‐Src KD) counteracted each‐induced AP‐1 activation, suggesting no hierarchy between these two molecules. During the TRAF6 and c‐Src‐induced AP‐1 activation, phosphatidylinositol 3 (PI3)‐kinase, its downstream signaling molecule, Akt and c‐Jun N‐terminal kinase (JNK) were significantly activated and inhibition of these kinase activities down‐regulated AP‐1 activation through the suppression of c‐fos expression. Furthermore, TRAF6 and c‐Src‐induced JNK activation was significantly inhibited by PI3‐kinase inhibitor or a dominant negative mutant of Akt (Akt DN). Taken together, our results demonstrate that c‐Src and TRAF6 are key mediators of IL‐1‐induced AP‐1 activation and provide evidence of cross talk between c‐Src and TRAF6 molecules through PI3 kinase–Akt–JNK pathways.
Kinetic mechanisms of glycine oxidase from Bacillus subtilis
Authors: Molla Gianluca , Motteran Laura , Job Viviana , Pilone Mirella S. , Pollegioni Loredano
Published: December 2004

The kinetic properties of glycine oxidase from Bacillus subtilis were investigated using glycine, sarcosine, and d‐proline as substrate. The turnover numbers at saturating substrate and oxygen concentrations were 4.0 s−1, 4.2 s−1, and 3.5 s−1, respectively, with glycine, sarcosine, and d‐proline as substrate. Glycine oxidase was converted to a two‐electron reduced form upon anaerobic reduction with the individual substrates and its reductive half‐reaction was demonstrated to be reversible. The rates of flavin reduction extrapolated to saturating substrate concentration, and under anaerobic conditions, were 166 s−1, 170 s−1, and 26 s−1, respectively, with glycine, sarcosine, and d‐proline as substrate. The rate of reoxidation of reduced glycine oxidase with oxygen in the absence of product (extrapolated rate ≈ 3 × 104 m− 1·s−1) was too slow to account for catalysis and thus reoxidation started from the reduced enzyme:imino acid complex. The kinetic data are compatible with a ternary complex sequential mechanism in which the rate of product dissociation from the reoxidized enzyme form represents the rate‐limiting step. Although glycine oxidase and d‐amino acid oxidase differ in substrate specificity and amino acid sequence, the kinetic mechanism of glycine oxidase is similar to that determined for mammalian d‐amino acid oxidase on neutral d‐amino acids, further supporting a close similarity between these two amine oxidases.
Multidentate pyridinones inhibit the metabolism of nontransferrin‐bound iron by hepatocytes and hepatoma cells
Authors: Chua Anita C. G. , Ingram Helen A. , Raymond Kenneth N. , Baker Erica
Published: December 2004

The therapeutic effect of iron (Fe) chelators on the potentially toxic plasma pool of nontransferrin‐bound iron (NTBI), often present in Fe overload diseases and in some cancer patients during chemotherapy, is of considerable interest. In the present investigation, several multidentate pyridinones were synthesized and compared with their bidentate analogue, deferiprone (DFP; L1, orally active) and desferrioxamine (DFO; hexadentate; orally inactive) for their effect on the metabolism of NTBI in the rat hepatocyte and a hepatoma cell line (McArdle 7777, Q7). Hepatoma cells took up much less NTBI than the hepatocytes (< 10%). All the chelators inhibited NTBI uptake (80–98%) much more than they increased mobilization of Fe from cells prelabelled with NTBI (5–20%). The hexadentate pyridinone, N,N,N‐tris(3‐hydroxy‐1‐methyl‐2(1H)‐pyridinone‐4‐carboxaminoethyl)amine showed comparable activity to DFO and DFP. There was no apparent correlation between Fe status, Fe uptake and chelator activity in hepatocytes, suggesting that NTBI transport is not regulated by cellular Fe levels. The intracellular distribution of iron taken up as NTBI changed in the presence of chelators suggesting that the chelators may act intracellularly as well as at the cell membrane. In conclusion (a) rat hepatocytes have a much greater capacity to take up NTBI than the rat hepatoma cell line (Q7), (b) all chelators bind NTBI much more effectively during the uptake phase than in the mobilization of Fe which has been stored from NTBI and (c) while DFP is the most active chelator, other multidentate pyridinones have potential in the treatment of Fe overload, particularly at lower, more readily clinically available concentrations, and during cancer chemotherapy, by removing plasma NTBI.
Transport of l‐arginine and nitric oxide formation in human platelets
Authors: Signorello Maria G. , Pascale Raffaele , Leoncini Giuliana
Published: December 2004

The results of the present study show that human platelets take up l‐arginine by two transport systems which are compatible with the systems y+ and y+L. These Na+independent transporters have been distinguished by treating platelets with N‐ethylmaleimide that blocks selectively system y+. System y+, that accounts for 30–40% of the total transport, is characterized by low affinity for l‐arginine, is unaffected by l‐leucine, is sensitive to changes of membrane potential and to trans‐stimulation. The other component of l‐arginine transport identified with the system y+L (approximately 60–70% of the total flux) shows high affinity for l‐arginine, is insensitive to N‐ethylmaleimide treatment, unaffected by changes in membrane potential, sensitive to trans‐stimulation and inhibited by l‐leucine in the presence of Na+.

Moreover a strict correlation between l‐arginine transport and nitric oxide (NO) production in whole cells was found. N‐ethylmaleimide and l‐leucine decreased NO production as well as cGMP elevation, and the effect on NO and cGMP were closely related. It is likely that the l‐arginine transport systems y+ and y+L are both involved in supplying substrate for NO production and regulation in human platelets.
The role of residues R97 and Y331 in modulating the pH optimum of an insect β‐glycosidase of family 1
Authors: Marana Sandro R. , Mendonça Lúcio M. F. , Andrade Eduardo H. P. , Terra Walter R. , Ferreira Clélia
Published: December 2004

The activity of the digestive β‐glycosidase from Spodoptera frugiperda (Sfβgly50, pH optimum 6.2) depends on E399 (pKa = 4.9; catalytic nucleophile) and E187 (pKa = 7.5; catalytic proton donor). Homology modelling of the Sfβgly50 active site confirms that R97 and Y331 form hydrogen bonds with E399. Site‐directed mutagenesis showed that the substitution of R97 by methionine or lysine increased the E399 pKa by 0.6 or 0.8 units, respectively, shifting the pH optima of these mutants to 6.5. The substitution of Y331 by phenylalanine increased the pKa of E399 and E187 by 0.7 and 1.6 units, respectively, and displaced the pH optimum to 7.0. From the observed ΔpKa it was calculated that R97 and Y331 contribute 3.4 and 4.0 kJ·mol−1, respectively, to stabilization of the charged E399, thus enabling it to be the catalytic nucleophile. The substitution of E187 by D decreased the pKa of residue 187 by 0.5 units and shifted the pH optimum to 5.8, suggesting that an electrostatic repulsion between the deprotonated E399 and E187 may increase the pKa of E187, which then becomes the catalytic proton donor. In short the data showed that a network of noncovalent interactions among R97, Y331, E399 and E187 controls the Sfβgly50 pH optimum. As those residues are conserved among the family 1 β‐glycosidases, it is proposed here that similar interactions modulate the pH optimum of all family 1 β‐glycosidases.
Pair Bonding and Multiple Paternity in the Polygamous Common QuailCoturnix coturnix
Authors: Rodríguez‐Teijeiro J. D. , Puigcerver M. , Gallego S. , Cordero P. J. , Parkin D. T.
Published: December 2004

The common quail (Coturnix coturnix) is one of the few species in which mate‐switching (when different pair bonds are established within a single breeding attempt), has been recorded. In this study, we report the characteristics of pair bonds (description, number of males per female and duration) by monitoring a wild population of common quail (28 females and 49 males) by radiotracking. 57% of the females studied (n = 14) showed mate‐switching, whereas 22% of the males were serially polygynous, successively forming pairs with a series of females. The fitness of females with mate‐switching, measured in terms of clutch size and hatching success, did not differ from that of females bonded with one male. The analysis of paternity in three families by multilocus DNA fingerprinting revealed genetic polygamy in two of the nests studied. A male sired offspring with two females, and we obtained genetic evidence for intraspecific brood parasitism. We discuss how these behavioural and ecological observations may relate to the particular mating system of the common quail.
Direct vs. Indirect Benefits of Caching by Gray Squirrels (Sciurus carolinensis)
Authors: Spritzer Mark D. , Brazeau Daniel
Published: December 2004

Individuals of many species cache food to gain direct benefits from consuming their own caches, but individuals of a few species also gain indirect benefits by sharing caches with kin. We investigated whether gray squirrels cache primarily to gain direct benefits or if they also gain indirect benefits by sharing caches with kin. If squirrels share caches with kin, then genetically related squirrels should live near one another and cache near one another to facilitate cache sharing. In contrast, if squirrels cache primarily for direct benefits, then they should clump their caches near the center of their ranges to facilitate cache defense. This study was conducted with 140 squirrels in a 10 ha forest. DNA was extracted from blood samples taken from squirrels, and genetic similarity scores from randomly amplified polymorphic DNA (RAPD) loci were used to measure relatedness. Squirrels were given piles of pecans for caching at six sites and observed from a blind. We recorded the direction squirrels took nuts from piles and at one site determined the location of caches. For male–female comparisons, related squirrels lived significantly closer to one another than unrelated squirrels, but this was not the case for female–female and male–male comparisons. The genetic similarity of neighboring squirrels did not influence the location of caches or the direction that squirrels took nuts from piles. Squirrels clumped their own caches and moved nuts toward their own home range centers. These results suggest that gray squirrels cache primarily to gain direct benefits rather than indirect benefits.
A centric fission and heterochromatin polymorphism inEquus asinusSpanish breeds
Authors: Alaoui N. , Jordana J. , Ponsá M.
Published: December 2004

In this work a chromosomal study inEquus asinusis presented. Forty‐two specimens, belonging to five different Spanish breeds in risk of disappearing, have been analysed. Metaphases have been sequentially stained (uniform, G‐banded and C‐banded) and analysed. All specimens, except one, presented 2n = 62 chromosomes. Variation in chromosome number (2n = 63) is because of a fission in one chromosome of pair no. 3, resulting in two acrocentric chromosomes. Polymorphisms affecting the size of heterochromatic C+ bands and the presence of hetrochromatic 1p and 4p arms are also analysed. The results show no polymorphisms which can be attributed to a particular breed. From the chromosomal point of view, all Spanish asinine specimens correspond to a single population. Rearrangements detected suggest a fission tendency in the homologousE. asinusno. 3 chromosome in Equidae species.
Population density and group composition of Japanese sika deer (Cervus nippon yakushimae) in an evergreen broad‐leaved forest in Yakushima, southern Japan
Authors: Agetsuma Naoki , Sugiura Hideki , Hill David A. , Agetsuma‐Yanagihara Yoshimi , Tanaka Toshiaki
Published: December 2004

The population density of Japanese sika deer (Cervus nippon yakushimae Kuroda and Okada) in an evergreen broad‐leaved forest in Yakushima, southern Japan, was surveyed over 4 years from 1998 to 2001. Two approximately 50 ha study sites, Hanyama and Kawahara, were established with a total of 4 km of census trails at each site. The estimated densities of sika deer at the two sites were 43–70 deer km−2 at Hanyama and 63–78 deer km−2 at Kawahara, although these values might be underestimates. The adult sex ratio (number of adult males : number of adult females) ranged from 0.6 to 1.0 at Hanyama, and from 0.4 to 0.9 at Kawahara. Mean group size was 1.9 deer (male group, 1.5 deer; female group, 1.6 deer; mixed group, 3.6 deer). The population density of sika deer was relatively high compared to other sites in Japan, with the exception of very small (<10 km2) islands. Possible explanations for this naturally high density of sika deer in an evergreen broad‐leaved forest in Yakushima are discussed.