bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Mycobacterium tuberculosis ino1 gene is essential for growth and virulence
Authors: Movahedzadeh Farahnaz , Smith Debbie A. , Norman Richard A. , Dinadayala Premkumar , Murray‐Rust Judith , Russell David G. , Kendall Sharon L. , Rison Stuart C. G. , McAlister Mark S. B. , Bancroft Gregory J. , McDonald Neil Q. , Daffe Mamadou , Av‐Gay Yossef , Stoker Neil G. 
Published: December 2004

SummaryInositol is utilized by Mycobacterium tuberculosis in the production of its major thiol and of essential cell wall lipoglycans. We have constructed a mutant lacking the gene encoding inositol‐1‐phosphate synthase (ino1), which catalyses the first committed step in inositol synthesis. This mutant is only viable in the presence of extremely high levels of inositol. Mutant bacteria cultured in inositol‐free medium for four weeks showed a reduction in levels of mycothiol, but phosphatidylinositol mannoside, lipomannan and lipoarabinomannan levels were not altered. The ino1 mutant was attenuated in resting macrophages and in SCID mice. We used site‐directed mutagenesis to alter four putative active site residues; all four alterations resulted in a loss of activity, and we demonstrated that a D310N mutation caused loss of the active site Zn2+ ion and a conformational change in the NAD+ cofactor.
The RhaS activator controls the Erwinia chrysanthemi 3937 genes rhiN, rhiT and rhiE involved in rhamnogalacturonan catabolism
Authors: Hugouvieux‐Cotte‐Pattat Nicole 
Published: December 2004

Summary Erwinia chrysanthemi causes soft‐rot diseases of various plants by enzymatic degradation of the pectin in plant cell walls. The linear regions of pectin are composed of an acidic sugar, d‐galacturonic acid. The ramified regions of pectin also include neutral sugars, and are rich in l‐rhamnose residues. E. chrysanthemi is able to degrade these polysaccharides, polygalacturonate and rhamnogalacturonate. In E. chrysanthemi, the production of pectinases acting on linear regions is induced in the presence of polygalacturonate by a mechanism involving the repressor KdgR. The induction of the two adjacent E. chrysanthemi genes, designated rhiT and rhiN, is maximal after the simultaneous addition of both polygalacturonate and l‐rhamnose. The rhiT product is homologous to the oligogalacturonide transporter TogT of E. chrysanthemi. The rhiN product is homologous to various proteins of unknown function, including a protein encoded by the plant‐inducible locus picA of Agrobacterium tumefaciens. Both rhiT and rhiN are highly induced during plant infection. Various data suggest that RhiT and RhiN are involved in rhamnogalacturonate catabolism. RhiN is able to degrade the oligomers liberated by the rhamnogalacturonate lyase RhiE. The induction of the rhiTN operon in the presence of polygalacturonate results from control by the repressor KdgR. The additional induction of these genes by rhamnose is directly mediated by RhaS, a protein homologous to the activator of rhamnose catabolism in Escherichia coli. The virulence of an E. chrysanthemi rhaS mutant towards different host plants was clearly reduced. In this phytopathogenic bacterial species, RhaS positively regulates the transcription of the rhaBAD operon, involved in rhamnose catabolism, of the rhiE gene and of the rhiTN operon. The regulator RhaS plays a larger role in E. chrysanthemi than in other enterobacteria. Indeed, the RhaS control is not restricted to the catabolism of rhamnose but is extended to the degradation of plant polysaccharides that contain this sugar.
The d,d‐carboxypeptidase PBP3 organizes the division process of Streptococcus pneumoniae
Authors: Morlot Cécile , Noirclerc‐Savoye Marjolaine , Zapun André , Dideberg Otto , Vernet Thierry 
Published: December 2004

SummaryBacterial division requires the co‐ordination of membrane invagination, driven by the constriction of the FtsZ‐ring, and concomitant cell wall synthesis, performed by the high‐molecular‐weight penicillin‐binding proteins (HMW PBPs). Using immunofluorescence techniques, we show in Streptococcus pneumoniae that this co‐ordination requires PBP3, a d,d‐carboxypeptidase that degrades the substrate of the HMW PBPs. In a mutant deprived of PBP3, the apparent rings of HMW PBPs and that of FtsZ are no longer co‐localized. In wild‐type cells, PBP3 is absent at the future division site and present over the rest of the cell surface, implying that the localization of the HMW PBPs at mid‐cell depends on the availability of their substrate. FtsW, a putative translocase of the substrate of the PBPs, forms an apparent ring that is co‐localized with the septal HMW PBPs throughout the cell cycle of wild‐type cells. In particular, the constriction of the FtsW‐ring occurs after that of the FtsZ‐ring, with the same delay as the constriction of the septal PBP‐rings. However, in the absence of PBP3, FtsW remains co‐localized with FtsZ in contrast to the HMW PBPs. Our work reveals an unexpected complexity in the relationships between the division proteins. The consequences of the absence of PBP3 indicate that the peptidoglycan composition is central to the co‐ordination of the division process.
Nitrergic–purinergic interactions in rat distal colon motility
Authors: Crombruggen K. Van , Lefebvre R. A. 
Published: December 2004

Abstract  Responses of rat distal colon circular muscle strips to exogenous nitric oxide (NO) and adenosine 5′‐triphosphate (ATP) and to electrical field stimulation (EFS) were assessed in the absence/presence of various agents that interfere with nitrergic–purinergic pathways.Exogenous NO (10−6 to 10−4 mol L−1) elicited concentration‐dependent, tetrodotoxin (TTX)‐insensitive relaxations. The soluble guanylyl‐cyclase (sGC) inhibitor 1H[1,2,4,]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ) reduced duration and amplitude; the small conductance Ca2+‐sensitive K+ (SK)‐channel blocker apamin (APA) only shortened the relaxations. ODQ + APA showed a marked inhibitory effect on duration and amplitude.TTX, APA, the NO‐synthase inhibitor N(omega)‐nitro‐l‐arginine methyl ester (l‐NAME) and the purinergic receptor P2Y antagonist Reactive Blue 2 (RB2) shortened the relaxations by exogenous ATP (10−3 mol L−1) but did not influence the amplitude. ODQ had no effect. TTX + l‐NAME did not yield a more pronounced inhibitory effect than TTX alone. The effect of ATP‐γ‐S was similar to that of ATP.Electrical field stimulation (EFS) (40 V, 0.05 ms, 0.5–4 Hz for 30 s) yielded TTX‐sensitive relaxations that were not altered by l‐NAME, ODQ or RB2. APA shortened the relaxations. l‐NAME + APA nearly abolished these relaxations. ODQ + APA and RB2 +l‐NAME reduced the duration.These results suggest that distinct sets of small conductance SK‐channels are involved in the amplitude and the duration of the relaxations and that NO increases their sensitivity to NO and ATP via guanosine 3′,5′‐cyclic monophosphate (cGMP). ATP elicits relaxations via P2Y receptors with subsequent activation of SK‐channels and induces neuronal release of NO. Both nitrergic and purinergic pathways must be blocked to inhibit EFS‐induced relaxations.
Effects of the probiotic yeast Saccharomyces boulardii on the neurochemistry of myenteric neurones in pig jejunum
Authors: Kamm K. , Hoppe S. , Breves G. , Schröder B. , Schemann M. 
Published: December 2004

Abstract  We studied the effects of food supplementation with Saccharomyces boulardii (S. boulardii; synonym S. cerevisiae HANSEN CBS 5926; 1 g per day for 9 days) on the presence and co‐localization patterns of neuronal markers in myenteric neurones of the pig jejunum. The pan neuronal marker Hu revealed no change in the number of neuronal cell bodies per ganglion (37 ± 7 in control vs 34 ± 9 in the S. boulardii group). Ranked by size the following cell populations were identified: choline acetyltransferase (ChAT), calbindin‐28k (CALB), substance P (SP), neurofilament 160 kD (NF‐160), vasoactive intestinal polypeptide (VIP), nitric oxide synthase (NOS), calcitonin gene‐related peptide (CGRP), calretinin (CALRET). We found a significant decrease in the number of CALB myenteric neurones in animals which received S. boulardii supplemented diet. None of the other neuronal markers revealed any difference between controls and S. boulardii treated animals. The study reports transmitter‐localization patterns in the myenteric plexus of the pig jejunum and provides evidence that changes in the neurochemistry of enteric neurones occur with S. boulardii supplemented diet. Although only CALB expression was altered and the functional significance of this finding remains unknown, our study identified a possible new effector level of probiotics in the gut.
The prenatal development of the human cerebellar field in Down syndrome
Authors: Lomholt J.F. , Keeling J.W. , Hansen B.F. , Ono T. , Stoltze K. , Kjær I. 
Published: December 2004

Structured AbstractAuthors – Lomholt JF, Keeling JW, Hansen BF, Ono T,Stoltze K, Kjær IObjectives – To describe the development of the osseous field enclosing the cerebellum and part of the brain stem (the neuro‐osteological cerebellar field) in Down syndrome, and compare the development with normal developmental standard of the field.Design – Radiographic, cephalometric and histologic examination of 58 legally or spontaneously aborted Down syndrome prenatal human fetuses; crown–rump length of 80–255 mm and approximate gestational age from 13 to 26 weeks.Results – The growth of the Down syndrome cerebellar field is smaller in the sagittal and vertical directions than in normal fetuses.Conclusion – In the present study the pathological development of the cerebellar field was described in a genotypic sample. In combining normal and pathological development of neural and osseous tissues a better understanding of the genotype/phenotype interactions is attainable and fields of common gene expression maybe defined.
MHC studies in nonmodel vertebrates: what have we learned about natural selection in 15 years?
Authors: Bernatchez L. , Landry C. 
Published: December 2004

Abstract
Elucidating how natural selection promotes local adaptation in interaction with migration, genetic drift and mutation is a central aim of evolutionary biology. While several conceptual and practical limitations are still restraining our ability to study these processes at the DNA level, genes of the major histocompatibility complex (MHC) offer several assets that make them unique candidates for this purpose. Yet, it is unclear what general conclusions can be drawn after 15 years of empirical research that documented MHC diversity in the wild. The general objective of this review is to complement earlier literature syntheses on this topic by focusing on MHC studies other than humans and mice. This review first revealed a strong taxonomic bias, whereby many more studies of MHC diversity in natural populations have dealt with mammals than all other vertebrate classes combined. Secondly, it confirmed that positive selection has a determinant role in shaping patterns of nucleotide diversity in MHC genes in all vertebrates studied. Yet, future tests of positive selection would greatly benefit from making better use of the increasing number of models potentially offering more statistical rigour and higher resolution in detecting the effect and form of selection. Thirdly, studies that compared patterns of MHC diversity within and among natural populations with neutral expectations have reported higher population differentiation at MHC than expected either under neutrality or simple models of balancing selection. Fourthly, several studies showed that MHC-dependent mate preference and kin recognition may provide selective factors maintaining polymorphism in wild outbred populations. However, they also showed that such reproductive mechanisms are complex and context-based. Fifthly, several studies provided evidence that MHC may significantly influence fitness, either by affecting reproductive success or progeny survival to pathogens infections. Overall, the evidence is compelling that the MHC currently represents the best system available in vertebrates to investigate how natural selection can promote local adaptation at the gene level despite the counteracting actions of migration and genetic drift. We conclude this review by proposing several directions where future research is needed.
Two species of feminizing microsporidian parasite coexist in populations of Gammarus duebeni
Authors: Ironside J. E. , Smith J. E. , Hatcher M. J. , Sharpe R. G. , Rollinson D. , Dunn A. M. 
Published: December 2004

Abstract
The amphipod crustacean Gammarus duebeni hosts two species of vertically transmitted microsporidian parasites, Nosema granulosis and Microsporidium sp. A. Here it is demonstrated that these co-occurring parasite species both cause infected females to produce female-biased broods. A survey of European G. duebeni populations demonstrates that these two parasites co-occur in six of 10 populations. These findings contrast with the theoretical prediction that two vertically transmitted feminizing parasites should not coexist in a panmictic population of susceptible hosts at equilibrium. Possible explanations for the co-occurrence of the two feminizing microsporidia in G. duebeni include the recent invasion of a new parasite, horizontal transmission of one or both parasites and the spread of alleles for resistance to the dominant parasite in host populations.
A linear dominance hierarchy among clones in chimeras of the social amoeba Dictyostelium discoideum
Authors: Fortunato A. , Queller D. C. , Strassmann J. E. 
Published: December 2004

Abstract
Amoebae from different clones of Dictyostelium discoideum aggregate into a common slug, which migrates towards light for dispersal, then forms a fruiting body consisting of a somatic, dead stalk, holding up a head of living spores. Contributions of two clones in a chimera to spore and stalk are often unequal, with one clone taking advantage of the other's stalk contribution. To determine whether there was a hierarchy of exploitation among clones, we competed all possible pairs among seven clones and measured their relative representation in the prespore and prestalk stages and in the final spore stage. We found a clear linear hierarchy at the final spore stage, but not at earlier stages. These results suggest that there is either a single principal mechanism or additive effects for differential contribution to the spore, and that it involves more than spore/stalk competition.
Correlations between ultraviolet coloration, overwinter survival and offspring sex ratio in the blue tit
Authors: Griffith S. C. , Örnborg J. , Russell A. F. , Andersson S. , Sheldon B. C. 
Published: December 2004

Abstract
We studied the correlations between offspring sex ratio, UV coloration and overwinter survival in a population of blue tits, breeding in Gotland, Sweden, over three consecutive breeding seasons. In 2 of 3 years, we found that females paired to males with relatively brighter UV-coloration produced a greater proportion of sons in their broods, and that this effect was significant with all 3 years combined, despite a significant year by male UV interaction. In addition, we found other correlates of sex ratio (breeding time, female age and clutch size) in some, but not all years, and some of these showed significantly different relationships with sex ratio between years. In both years for which data were available, there were indications that males with relatively brighter UV coloration, and that paired with females that produced male-biased clutches, were more likely to survive to the next year. In addition, we also found that in both males and females, individuals produced similar sex ratios in consecutive years. Because correlations with the sex ratio may be expected to be weak, variation in results between years within the same population may be explained by low statistical power or genuine biological differences. Our results suggest that conclusions about sex ratio variation in birds should be based on multiple years. The correlations that we found in some years of this study are consistent with models of adaptive sex ratio adjustment in response to mate quality. However, careful experimental work is required to provide tests of the assumptions of these models, and should be a priority for future work.
Latitudinal countergradient variation in the common frog (Rana temporaria) development rates – evidence for local adaptation
Authors: Laugen A. T. , Laurila A. , Räsänen K. , Merilä J. 
Published: December 2004

Abstract
Adaptive genetic differentiation along a climatic gradient as a response to natural selection is not necessarily expressed at phenotypic level if environmental effects on population mean phenotypes oppose the genotypic effects. This form of cryptic evolution – called countergradient variation – has seldom been explicitly demonstrated for terrestrial vertebrates. We investigated the patterns of phenotypic and genotypic differentiation in developmental rates of common frogs (Rana temporaria) along a ca. 1600 km latitudinal gradient across Scandinavia. Developmental rates in the field were not latitudinally ordered, but displayed large variation even among different ponds within a given latitudinal area. In contrast, development rates assessed in the laboratory increased strongly and linearly with increasing latitude, suggesting a genetic capacity for faster development in the northern than the southern larvae. Experiments further revealed that environmental effects (temperature and food) could easily override the genetic effects on developmental rates, providing a possible mechanistic explanation as to why the genetic differentiation was not seen in the samples collected from the wild. Our results suggest that the higher developmental rates of the northern larvae are likely to be related to selection stemming from seasonal time constrains, rather than from selection dictated by low ambient temperatures per se. All in all, the results provide a demonstration of environmental effects concealing substantial latitudinally ordered genetic differentiation understandable in terms of adaptation to clinal variation in time constrains.
Adaptive sex-specific life history plasticity to temperature and photoperiod in a damselfly
Authors: De Block M. , Stoks R. 
Published: December 2004

Abstract
We investigated four predictions about how temperature, photoperiod and sex affect the life history plasticity and foraging activity of a damselfly. (i) As predicted, increased temperatures increased foraging activity and growth rates, but in contrast with the prediction, late photoperiod (high time stress) did not affect foraging activity and growth rate. (ii) Unexpectedly, the increase in growth rate at increasing temperatures was not larger under high time stress. (iii) As predicted, age and size at emergence decreased at higher temperatures and at the late photoperiod. Temperature-induced life history shifts were direct or the result of behavioural growth mediation depending on the temperature range. Photoperiod-induced life history shifts were direct. (iv) As predicted, males emerged before females but at a smaller size. The degree of sexual size dimorphism was influenced by the joint effects of temperature and photoperiod. We could only detect genetic variation in size plasticity to photoperiod. The match between the sex-specific life history responses to temperature and photoperiod and predictions by relevant optimality models suggests adaptive life history plasticity to these variables.
The effects of parasitism and inbreeding on the competitive ability in Daphnia magna: evidence for synergistic epistasis
Authors: Salathé P. , Ebert D. 
Published: December 2004

Abstract
Synergistic epistasis for fitness is often assumed in models of how selection acts on the frequency and distribution of deleterious mutations. Evidence for synergistic epistasis would exist if the logarithm of fitness declines more quickly with number of deleterious mutations, than predicted by a linear decline. This can be studied indirectly by quantifying the effect of different levels of inbreeding on fitness. Here, six sets (different genetic backgrounds) of three increasingly inbred Daphnia magna clones were used to assess their relative fitness according to changes in frequency in a competition experiment against a tester clone. A novelty of the mating procedure was that the inbreeding coefficients (F) of the three clones belonging to each set increased in steps of 0.25 independent of the (unknown) inbreeding coefficient of the common ancestor. The equal increase of the inbreeding coefficients is important, because deviations influence the quantification of inbreeding depression, its variance and the detection of epistasis. In a simple mathematical model we show that when working with a partially inbred population inbreeding depression is underestimated, the variance of fitness is increased, and the detection of epistasis more difficult. Further, to examine whether an interaction between inbreeding and parasitism exists, each inbred clone was tested with and without a microsporidium infection (Octosporea bayeri). We found a nonlinear decrease of the logarithm of fitness across the three levels of inbreeding, indicating synergistic epistasis. The interaction term between parasitism and inbreeding was not significant. Our results suggest that deleterious mutations may be purged effectively once the level of inbreeding is high, but that parasitism seems not to influence this effect.
Sexual conflict and indirect benefits
Authors: Cameron E. , Day T. , Rowe L. 
Published: December 2004

Abstract
Recent work on sexual selection and sexual conflict has explored the influence of indirect effects on the evolution of female mating behaviour. It has been suggested that the importance of these effects has been underestimated and that the influence of indirect effects may actually be of relatively greater significance than direct effects. Additionally, it has also been suggested that all indirect effects, both good genes and sexy son, are qualitatively equivalent. Here a counterpoint to these suggestions is offered. We argue two main points: (1) it is unlikely that indirect effects will commonly outweigh direct effects, and (2) that there are important differences between good genes and sexy son indirect effects that must be recognized. We suggest that acknowledgement of these distinctions will lead to increased understanding of processes operating in both sexual conflict and sexual selection.
Sex-specific associative learning cues and inclusive fitness benefits in the Seychelles warbler
Authors: Richardson D. S. , Burke T. , Komdeur J. 
Published: December 2004

Abstract
In cooperative breeding vertebrates, indirect fitness benefits would be maximized by subordinates that accurately assess their relatedness to group offspring and preferentially help more closely related kin. In the Seychelles warbler (Acrocephalus sechellensis), we found a positive relationship between subordinate-nestling kinship (determined using microsatellite marker genotypes) and provisioning rates, but only for female subordinates. Female subordinates that helped were significantly more related to the nestlings than were nonhelpers, and the decision to help appears to be based on associative learning cues. High levels of female infidelity means that subordinates cannot trust their legitimacy through the male line, consequently they appear to use the continued presence of the primary female, but not the primary male, as a reliable cue to determine when to feed nestlings. By using effective discrimination, female subordinates are able to maximize the indirect benefits gained within a cooperative breeding system otherwise driven primarily by direct breeding benefits.