bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic disturbances in obesity versus sleep apnoea: the importance of visceral obesity and insulin resistance
Authors: Vgontzas A. N. , Bixler E. O. , Chrousos G. P. 
Published: June 2003

Abstract.  Vgontzas AN, Bixler EO, Chrousos GP (Penn State College of Medicine, Hershey, PA; National Institutes of Health, Bethesda, MD, USA). Metabolic disturbances in obesity versus sleep apnoea: the importance of visceral obesity and insulin resistance (Minisymposium). J Intern Med 2003; 254:–.Obstructive sleep apnoea (OSA) is a very prevalent disorder particularly amongst middle‐aged, obese men, although its existence in women as well as in lean individuals is increasingly recognized. Despite the early recognition of the strong association between OSA and obesity, and OSA and cardiovascular problems, sleep apnoea has been treated as a ‘local abnormality’ of the respiratory track rather than as a ‘systemic illness’. In 1997, we first reported that the pro‐inflammatory cytokines interleukin (IL)‐6 and tumour necrosis factor‐α (TNFα) were elevated in patients with disorders of excessive daytime sleepiness (EDS) and proposed that these cytokines were mediators of daytime sleepiness. Also, we reported a positive correlation between IL‐6 or TNFα plasma levels and the body mass index (BMI). In subsequent studies, we showed that IL‐6, TNFα, leptin and insulin levels were elevated in sleep apnoea independently of obesity and that visceral fat, was the primary parameter linked with sleep apnoea. The association of OSA with insulin resistance and diabetes type 2 has been confirmed since then in several epidemiological and clinical studies. Furthermore, our findings that women with polycystic ovary syndrome (PCOS, a condition associated with hyperandrogenism and insulin resistance) were much more likely than controls to have sleep disordered breathing (SDB) and daytime sleepiness support the pathogenetic role of insulin resistance in OSA. Other findings that support the view that sleep apnoea and sleepiness may be manifestations of a serious metabolic disorder, namely the Metabolic or Visceral Obesity Syndrome, include: obesity without sleep apnoea is associated with daytime sleepiness; PCOS and diabetes type 2 are independently associated with EDS after controlling for SDB, obesity and age; and increased prevalence of sleep apnoea in postmenopausal women, with hormonal replacement therapy associated with a significantly reduced risk for OSA.In conclusion, accumulating evidence provides support to our model of the bi‐directional, feedforward, pernicious association between sleep apnoea, sleepiness, inflammation and insulin resistance, all promoting atherosclerosis and cardiovascular disease.
Sleep as restitution: an introduction
Authors: Åkerstedt T. , Nilsson P. M. 
Published: June 2003

Abstract.

Åkerstedt T, Nilsson PM (Karolinska Institutet, Stockholm, University Hospital, Malmö, Sweden). Sleep as restitution: an introduction (Minisymposium). J Intern Med 2003; 254: 6–12.This paper summarizes a symposium that has shown that sleep is a state of altered metabolism, and that disturbances and curtailments of sleep have far‐reaching effects on endocrinology, immunology and metabolism, changes that may be linked to disease. As yet, the entire causal chain is weak but there are indications that, in particular, the risk of type 2 diabetes and cardiovascular disease may result from disturbed sleep. It is hypothesized that both insulin resistance and chronic low‐grade inflammation may be involved.
Hydrophobic residues within the predicted N‐terminal amphiphilic α‐helix of a plant mitochondrial targeting presequence play a major role in in vivo import
Authors: Duby Geoffrey , Oufattole Mohammed , Boutry Marc 
Published: June 2003

SummaryA deletion and mutagenesis study was performed on the mitochondrial presequence of the β‐subunit of the F1‐ATP synthase from Nicotiana plumbaginifolia linked to the green fluorescent protein (GFP). The various constructs were tested in vivo by transient expression in tobacco protoplasts. GFP distribution in transformed cells was analysed in situ by confocal microscopy, and in vitro in subcellular fractions by Western blotting. Despite its being highly conserved in different species, deletion of the C‐terminal region (residues 48–54) of the presequence did not affect mitochondrial import. Deletion of the conserved residues 40–47 and the less conserved intermediate region (residues 18–39) resulted in 60% reduction in GFP import, whereas mutation of conserved residues within these regions had little effect. Further shortening of the presequence progressively reduced import, with the construct retaining the predicted N‐terminal amphiphilic α‐helix (residues 1–12) being unable to mediate mitochondrial import. However, point mutation showed that this last region plays an important role through its basic residues and amphiphilicity, but also through its hydrophobic residues. Replacing Arg4 and Arg5 by alanine residues and shifting the Arg5 and Leu6 (in order to disturb amphiphilicity) resulted in reduction of the presequence import efficiency. The most dramatic effects were seen with single or double mutations of the four Leu residues (positions 5, 6, 10 and 11), which resulted in marked reduction or abolition of GFP import, respectively. We conclude that the N‐terminal helical structure of the presequence is necessary but not sufficient for efficient mitochondrial import, and that its hydrophobic residues play an essential role in in vivo mitochondrial targeting.
Effects of nutrient availability on primary sexual traits and their response to selection in Spergularia marina (Caryophyllaceae)
Authors: Mazer S. J. , Lowry D. E. , Hansen T. 
Published: June 2003

Abstract
Theoretical models of the evolution of sex allocation generally assume a negative genetic correlation between components of male and female investment or function. To test this assumption, and to determine whether the expression of the correlation is sensitive to environmental conditions, we conducted an artificial selection experiment targeting primary sexual traits in the autogamous herb, Spergularia marina. Mass selection favouring individuals with high (or low) pollen and ovule production per flower had previously been conducted for two generations under uniform conditions. Following a third episode of selection (reported here) within the high-pollen-, high-ovule-, low-pollen- and low-ovule-producing lineages, selected maternal seed families were replicated and cultivated in three nutrient treatments. With this design, we observed the effects of nutrient availability on: floral phenotype, the realized response to selection and the expression of genetic variation in, and covariation between, male and female investment. The first two episodes of selection Mazer et al. 1999 (Evolution 53:717–731) detected evidence for a genetically based negative correlation between ovule and anther production. Following the third episode of selection, phenotypic differences among the selected lines were maintained in all treatments, but evidence for a negative correlation between male and female investment nearly disappeared. Only under low-nutrient conditions, in which plants selected for low ovule production exhibited elevated anther production, was a genetic trade-off expressed. Either genetic drift or the combination of novel growing conditions (relative to previous generations) and G × E interactions may have caused the change in the expression of the genetic correlation. This experiment also allowed us to test the prediction that autogamous selfers should exhibit higher canalization of the ratio of male to female investment than of its components. Supporting this prediction, the A : O ratio was more strongly buffered against environmental variation than either anther or ovule production per flower.
Overwintering in Drosophila melanogaster: outdoor field cage experiments on clinal and laboratory selected populations help to elucidate traits under selection
Authors: Hoffmann A. A. , Scott M. , Partridge L. , Hallas R. 
Published: June 2003

Abstract
Insects can adapt to temperate environments by increasing levels of resistance to cold conditions over winter and/or altering reproductive patterns to focus reproduction in favourable conditions. In temperate areas, Drosophila melanogaster persists over winter at the adult stage. A previous experiment, conducted with flies kept in outdoor population cages in the temperate winter, indicated that temperate populations produced more eggs than did tropical populations following an abrupt increase in reproduction in late winter. In contrast, the tropical populations produced more eggs prior to the increase. Both patterns resulted in a higher net number of surviving offspring for temperate populations. Here we again examine the clinal pattern in reproduction using outdoor cages, this time held under tropical winter conditions. In this environment, surprisingly, egg production was higher and on average earlier in populations originating from temperate areas. However, mortality rates also increased with latitude of origin, and the relationship of lifetime egg production to latitude should therefore be measured. To test the role of altered pattern of egg production per se in the reproductive advantage of temperate populations in the temperate winter, we tested the performance of laboratory lines selected for altered reproductive patterns, under temperate winter conditions. Lines selected for high early fecundity exhibited this characteristic in the field cages and lines selected for late reproduction exhibited a relatively high fecundity in spring. The timing of the abrupt increase in egg production was identical in these sets of lines and occurred at the same time in recently collected populations, suggesting evolutionary conservation of the switch. These findings suggest that changes in early and late reproduction per se determine adaptation to temperate winter conditions, and illustrate how laboratory selection lines can be used to understand traits underlying adaptive shifts in field performance.
Ecology, life history and resource allocation in the ant, Leptothorax nylanderi
Authors: Foitzik S. , Strätz M. , Heinze J. 
Published: June 2003

Abstract
We aimed at identifying the causal basis of previously shown interrelations between demographic and genetic colony structure, ecological factors and split sex ratios in the ant, Leptothorax nylanderi. Colony-level variation in sex allocation was only partly explained by annual fluctuations during eight study years and by resource availability as indicated by sexual production of colonies. Allocation ratios were highly male-biased in dense populations with ephemeral nest sites and high frequencies of colonies containing several unrelated matrilines. Field observations and experimental manipulations showed that nest site limitation leads to such heterogeneous colonies. Laboratory experiments demonstrated that genetic heterogeneity directly causes male-biased investment, although relatedness asymmetry is not influenced by invasion of unrelated queens. The influence of genetic composition on allocation strategies might either be explained by negative feedback mechanisms connected with habitat saturation or by a lower efficiency of heterogeneous colonies. Our results thus demonstrate which factors other than variation in relatedness asymmetry can explain split sex ratios in ants. An empirical test of a model on reproductive allocation revealed on-going queen–worker conflict over colony growth and sexual reproduction. Workers controlled reproductive allocation, but queen–worker conflict ceased in large colonies with a high survival rate.
Phenotypic variation in growth trajectories in the Arctic charr Salvelinus alpinus
Authors: Björklund M. , Hirvonen H. , Seppä T. , Peuhkuri N. , Piironen J. 
Published: June 2003

Abstract
Animals with determinate growth have shown little variation in individual growth patterns, but similar analyses for animals with indeterminate growth have been lacking. We analysed the amount of phenotypic variation in growth patterns across ages among individuals of a hatchery-based population of Arctic charr, Salvelinus alpinus, Salmonidae, using the infinite-dimensional model and including the effects of group size structure. There was little phenotypic variation in growth trajectories: individuals that were small (in relation to the mean) early in life were among the smallest 2.5 years later. If the genetic variation reflects phenotypic variation, not much evolutionary change can be expected. Our results show that there are ecological conditions that determine the strong covariation of size across ages, most likely size-related dominance behaviour, which can mask the true variation of growth patterns. Thus, social interactions can have strong evolutionary effects on traits not directly involved in the behavioural interactions.
The evolution of trade-offs: geographic variation in call duration and flight ability in the sand cricket, Gryllus firmus
Authors: Roff D. A. , Crnokrak P , Fairbairn D. J. 
Published: June 2003

Abstract
Quantitative genetic theory assumes that trade-offs are best represented by bivariate normal distributions. This theory predicts that selection will shift the trade-off function itself and not just move the mean trait values along a fixed trade-off line, as is generally assumed in optimality models. As a consequence, quantitative genetic theory predicts that the trade-off function will vary among populations in which at least one of the component traits itself varies. This prediction is tested using the trade-off between call duration and flight capability, as indexed by the mass of the dorsolateral flight muscles, in the macropterous morph of the sand cricket. We use four different populations of crickets that vary in the proportion of macropterous males (Lab = 33%, Florida = 29%, Bermuda = 72%, South Carolina = 80%). We find, as predicted, that there is significant variation in the intercept of the trade-off function but not the slope, supporting the hypothesis that trade-off functions are better represented as bivariate normal distributions rather than single lines. We also test the prediction from a quantitative genetical model of the evolution of wing dimorphism that the mean call duration of macropterous males will increase with the percentage of macropterous males in the population. This prediction is also supported. Finally, we estimate the probability of a macropterous male attracting a female, P, as a function of the relative time spent calling (P = time spent calling by macropterous male/(total time spent calling by both micropterous and macropterous male). We find that in the Lab and Florida populations the probability of a female selecting the macropterous male is equal to P, indicating that preference is due simply to relative call duration. But in the Bermuda and South Carolina populations the probability of a female selecting a macropterous male is less than P, indicating a preference for the micropterous male even after differences in call duration are accounted for.
Opposites attract? Mate choice for parasite evasion and the evolutionary stability of sex
Authors: Howard R. S. , Lively C. M. 
Published: June 2003

Abstract
If sex is naturally selected as a way to combat parasites, then sexual selection for disease resistance might increase the overall strength of selection for outcrossing. In the present study, we compared how two forms of mate choice affect the evolutionary stability of outcrossing in simultaneous hermaphrodites. In the first form, individuals preferred to mate with uninfected individuals (condition-dependent choice). In the second form, individuals preferred to mate with individuals that shared the least number of alleles in common at disease-resistance loci. The comparisons were made using individual-based computer simulations in which we varied parasite virulence, parasite transmission rate, and the rate of deleterious mutation at 500 viability loci. We found that alleles controlling both forms of mate choice spread when rare, but their effects on the evolutionary stability of sex were markedly different. Surprisingly, condition-dependent choice for uninfected mates had little effect on the evolutionary stability of sexual reproduction. In contrast, active choice for mates having different alleles at disease-resistance loci had a pronounced positive effect, especially under low rates of deleterious mutation. Based on these results, we suggest that mate choice that increases the genetic diversity of offspring can spread when rare in a randomly mating population, and, as an indirect consequence, increase the range of conditions under which sexual reproduction is evolutionarily stable.
The evolution of polyandry: patterns of genotypic variation in female mating frequency, male fertilization success and a test of the sexy-sperm hypothesis
Authors: Simmons L. W. 
Published: June 2003

Abstract
The sexy-sperm hypothesis predicts that females obtain indirect benefits for their offspring via polyandy, in the form of increased fertilization success for their sons. I use a quantitative genetic approach to test the sexy-sperm hypothesis using the field cricket Teleogryllus oceanicus. Previous studies of this species have shown considerable phenotypic variation in fertilization success when two or more males compete. There were high broad-sense heritabilities for both paternity and polyandry. Patterns of genotypic variance were consistent with X-linked inheritance and/or maternal effects on these traits. The genetic architecture therefore precludes the evolution of polyandry via a sexy-sperm process. Thus the positive genetic correlation between paternity in sons and polyandry in daughters predicted by the sexy-sperm hypothesis was absent. There was significant heritable variation in the investment by females in ovaries and by males in the accessory gland. Surprisingly there was a very strong genetic correlation between these two traits. The significance of this genetic correlation for the coevolution of male seminal products and polyandry is discussed.
A phylogenetic approach to assessing the targets of microbial warfare
Authors: Riley M. A. , Goldstone C. M. , Wertz J. E. , Gordon D. 
Published: June 2003

Abstract
Bacteriocins are the most abundant and diverse defense systems in bacteria. As a result of the specific mechanisms of bacteriocin recognition and translocation into the target cell it is assumed that these toxins mediate intra-specific or population-level interactions. However, no published studies specifically address this question. We present here a survey of bacteriocin production in a collection of enteric bacteria isolated from wild mammals in Australia. A subset of the bacteriocin-producing strains was assayed for the ability to kill a broad range of enteric bacteria from the same bacterial collection. A novel method of estimating killing breadth was developed and used to compare the surveyed bacteriocins in terms of the phylogenetic range over which they kill. The most striking result is that although bacteriocin-producers kill members of their own species most frequently, some kill phylogenetically distant taxa more frequently than they kill closer relatives. This study calls into question the role these toxins play in natural populations. A significant number of bacteriocins are highly effective in killing inter-specific strains and thus bacteriocins may serve to mediate bacterial community interactions.
Antidepressant and anxiolytic‐like effects in mice lacking the group III metabotropic glutamate receptor mGluR7
Authors: Cryan John F. , Kelly Peter H. , Neijt Hans C. , Sansig Gilles , Flor Peter J. , Van Der Putten Herman 
Published: June 2003

AbstractGlutamatergic neurotransmission has been strongly implicated in the pathophysiology of affective disorders, such as major depression and anxiety. Of all glutamate receptors, the role of group III metabotropic glutamate receptors (mGluR4, mGluR6, mGluR7, mGluR8) in such disorders is the least investigated because of the lack of specific pharmacological tools. To this end, we examined the behavioural profiles of mice with a targeted deletion of the gene for mGluR7 (mGluR7−/−) in animal models of depression and anxiety. mGluR7−/− mice were compared with wild‐type (mGluR7+/+) littermates and showed substantially less behavioural immobility in both the forced swim test and the tail suspension test. Both behavioural paradigms are widely used to predict antidepressant‐like activity. Further, mGluR7−/− mice displayed anxiolytic activity in four different behavioural tests, i.e. the light–dark box, the elevated plus maze, the staircase test, and the stress‐induced hyperthermia test, while their cognitive performance was normal in the passive avoidance paradigm. Analysis of locomotor activity in a novel environment demonstrated that mGluR7−/− mice were slightly more active in the initial minutes following placement in the chamber only. Together, these data suggest that mGluR7 may play a pivotal role in mechanisms that regulate behavioural responses to aversive states. Therefore, drugs acting at mGluR7 may provide novel treatments for psychiatric disorders such as depression and anxiety.
Molecular biology and electrophysiology of neuronal nicotinic receptors of rat chromaffin cells
Authors: Di Angelantonio Silvia , Matteoni Cosetta , Fabbretti Elsa , Nistri Andrea 
Published: June 2003

AbstractNeuronal nicotinic acetylcholine receptors of chromaffin cells in the adrenal medulla are physiologically activated by acetylcholine to mediate catecholamine release into the bloodstream. The present study examined the subunit composition and functional properties of rat chromaffin cell neuronal nicotinic acetylcholine receptors using molecular biology, immunocytochemistry and whole‐cell patch‐clamp. Reverse transcription‐polymerase chain reaction analysis indicated the presence of α2, α3, α4, α5, α7, β2 and β4 transcripts (α6 and β3 could not be detected). Immunocytochemistry revealed most cells positive for α3, β2, β4 and α5 proteins. Few cells were immunoreactive for α2 and α4, while none was for α7. At single‐cell level, colocalization could be demonstrated for α3α5 and α4β2. Western blot analysis confirmed antibody specificity for α3, α4, α5, β2 and β4 subunits. Inward currents elicited by nicotine pulses were insensitive to α‐bungarotoxin and low doses of methyllycaconitine, demonstrating lack of functional α7 receptors. Partial block of nicotine currents was observed with either AuIB α‐conotoxin (selective against α3β4 receptors) or MII α‐conotoxin (selective against α3β2 receptors). With high concentrations of co‐applied toxins, antagonism occlusion developed, suggesting loss of subunit selectivity. Antagonism by dihydro‐β‐erythroidine summated nonlinearly with AuIB and MII inhibition, confirming heterogeneity of neuronal nicotinic acetylcholine receptor block. The present results suggest that the most frequently encountered receptors of rat chromaffin cells should comprise α3β4, α3β2 with the addition of α5 subunits. Because of the prevailing subunit composition, rat chromaffin cell neuronal nicotinic acetylcholine receptors are suitable models, particularly for the α3β4 subclasses of mammalian brain receptors recently demonstrated in discrete cerebral areas.