Wolbachia density and virulence attenuation after transfer into a novel host

The factors that control replication rate of the intracellular bacterium Wolbachia pipientis in its insect hosts are unknown and difficult to explore, given the complex interaction of symbiont and host genotypes. Using a strain of Wolbachia that is known to over-replicate and shorten the lifespan of its Drosophila melanogaster host, we have tracked the evolution of replication control in both somatic and reproductive tissues in a novel host/Wolbachia association. After transinfection (the transfer of a Wolbachia strain into a different species) of the over-replicating Wolbachia popcorn strain from D. metanogaster to Drosophila simulans, we demonstrated that initial high densities in the ovaries were in excess of what was required for perfect maternal transmission, and were likely causing reductions in reproductive fitness. Both densities and fitness costs associated with ovary infection rapidly declined in the generations after transinfection. The early death effect in D. simulans attenuated only slightly and was comparable to that induced in D. metanogaster. This study reveals a strong host involvement in Wolbachia replication rates, the independence of density control responses in different tissues, and the strength of natural selection acting on reproductive fitness.

The benefits of physical activity during pregnancy

The aims of this paper are (1) to comment on the evidence relating to the health risks and benefits of physical activity (PA) for pregnant women and their unborn foetuses, and (2) to discuss the public health benefits of participation in appropriate physical activity during pregnancy. Evidence from recent original research and review papers suggests that there are potential benefits of appropriate PA in terms of maternal weight control and fitness, which are likely to have significant long term public health benefits. Concerns about the potential ill-effects of PA during pregnancy, such as hyperthermia, shortened gestational age and decreased birth weight are not supported by the most recent scientific reviews. The physiological adaptations to exercise during pregnancy appear to protect the foetus from potential harm and, while an upper level of safe activity has not been established, the benefits of continuing to be active during pregnancy appear to outweigh any potential risks. All decisions about participation in physical activity during pregnancy should however be made by women in consultation with their medical advisers.

Behaviour of the black flying fox Pteropus alecto: 2. Territoriality and courtship

Flying foxes are commonly thought of as highly social mammals, yet little is known about the dynamics of their social interactions at a day roost. The aim of the present study was to examine the nature of the seasonal activities of territoriality and courtship amongst wild flying foxes in Australia. Focal observations were conducted at two permanent roosts of black flying foxes Pteropus alecto during periods of peak social interaction in the summers of 1999 and 2000 in urban Brisbane, Queensland. Observations of male territoriality were conducted at dawn and began eight weeks prior to the commencement of mating. The majority of defense bouts (87%) consisted of ritualised pursuit, while 13% of bouts involved physical contact expressed as either wrestling or hooking. One male with an unusually large territory took significantly longer to defend it than other males with less territory to defend. Observations of courtship revealed repetitive courtship sequences, including pre-copulatory approaches by the males, copulation attempts and grooming/resting periods. Thirty-four complete courtship sequences incorporating 135 copulation attempts were recorded over two seasons. Females actively resisted courtship approaches by males, forcing males to display a continuous determination to mate over time where determination can be considered an indicator of 'fitness'. The courtship bout length of females with suckling young was significantly longer ((x) over bar +/- SE; 230.9 +/- 22.16 s) than that of females unencumbered by large pups (158.5 +/- 9.69 s), although the length of copulations within those courtships was not (45.6 +/- 5.19 versus 36.2 +/- 3.43 s).

Toward a better understanding of the influences on physical activity: The role of determinants, correlates, causal variables, mediators, moderators, and confounders

Background: For research on physical activity interventions to progress systematically, the mechanisms of action must be studied. In doing so, the research methods and their associated concepts and terminology become more complex. It is particularly important to clearly distinguish among determinants, correlates, mediators, moderators, and confounder variables used in physical activity research. This article examines the factors that are correlated with and that may have a causal relationship to physical activity. Methods and Results: We propose that the term correlate be used, instead of determinant, to describe statistical associations or correlations between measured variables and physical activity. Studies of the correlates of physical activity are reviewed. The findings of these studies can help to critique existing theories of health behavior change and can provide hypotheses to be tested in intervention studies from which it is possible to draw causal inferences. Mediator, moderator, and confounder variables can act to influence measured changes in physical activity. Intervening causal variables that are necessary to complete a cause-effect pathway between an intervention and physical activity are termed mediators. The relationship between an intervention and physical activity behaviors may vary for different groups; the strata by which they vary are levels of moderators of the relationship. Other factors may distort or affect the observed relationships between program exposure and physical activity, and are known as confounders. Conclusions: Consistent use of terms and additional research on mediators and moderators of intervention effects will improve our ability to understand and influence physical activity.

Biodiversity conservation and vegetation clearing in Queensland: Principles and thresholds

Clearing of native vegetation is a major threat to biodiversity in Australia. In Queensland, clearing has resulted in extensive ecosystem transformation, especially in the more fertile parts of the landscape. In this paper, we examine Queensland, Australian and some overseas evidence of the impact of clearing and related fragmentation effects on terrestrial biota. The geographic locus is the semi-arid regions. although we recognise that coastal regions have been extensively cleared. The evidence reviewed here suggests that the reduction of remnant vegetation to 30% will result in the loss of 25-35% of vertebrate fauna, with the full impact not realised for another 50-100 years, or even longer. Less mobile, habitat specialists and rare species appear to be particularly at risk. We propose three broad principles For effective biodiversity conservation in Queensland: (i) regional native vegetation retention thresholds of 50910: (ii) regional ecosystem thresholds of 30%: and (iii) landscape design and planning principles that protect large remnants, preferably > 2000 ha, as core habitats. Under these retention thresholds. no further clearing would be permitted in the extensively cleared biogeographic regions such as Brigalow Belt and New England Tablelands. Some elements of the biota. however, will require more detailed knowledge and targeted retention and management to ensure their security. The application of resource sustainability and economic criteria outlined elsewhere in this volume should be applied to ensure that the biogeographic regions in the north and west of Queensland that are largely intact continue to provide extensive wildlife habitat.

The E(NK) model: extending the NK model to incorporate gene-by-environment interactions and epistasis for diploid genomes

The haploid NK model developed by Kauffman can be extended to diploid genomes and to incorporate gene-by-environment interaction effects in combination with epistasis. To provide the flexibility to include a wide range of forms of gene-by-environment interactions, a target population of environment types (TPE) is defined. The TPE consists of a set of E different environment types, each with their own frequency of occurrence. Each environment type conditions a different NK gene network structure or series of gene effects for a given network structure, providing the framework for defining gene-by-environment interactions. Thus, different NK models can be partially or completely nested within the E environment types of a TPE, giving rise to the E(NK) model for a biological system. With this model it is possible to examine how populations of genotypes evolve in context with properties of the environment that influence the contributions of genes to the fitness values of genotypes. We are using the E(NK) model to investigate how both epistasis and gene-by-environment interactions influence the genetic improvement of quantitative traits by plant breeding strategies applied to agricultural systems. © 2002 Wiley Periodicals, Inc.

Evolution of additive and nonadditive genetic variance in development time along a cline in Drosophila serrata

Latitudinal clines provide natural systems that may allow the effect of natural selection on the genetic variance to be determined. Ten clinal populations of Drosophila serrata collected from the eastern coast of Australia were used to examine clinal patterns in the trait mean and genetic variance of the life-history trait egg-to-adult development time. Development time significantly lengthened from tropical areas to temperate areas. The additive genetic variance for development time in each population was not associated with latitude but was associated with the population mean development time. Additive genetic variance tended to be larger in populations with more extreme development times and appeared to be consistent with allele frequency change. In contrast, the nonadditive genetic variance was not associated with the population mean but was associated with latitude. Levels of nonadditive genetic variance were greatest in the region of the cline where the gradient in the change in mean was greatest, consistent with Barton's (1999) conjecture that the generation of linkage disequilibrium may become an important component of the genetic variance in systems with a spatially varying optimum.

Relationship between oviposition preference and offspring performance in Australian Helicoverpa armigera (Hubner) (Lepidoptera : Noctuidae)

We investigated the oviposition preference and larval performance of Helicoverpa armigera under laboratory conditions to determine if the oviposition preference of individual females on maize, cowpea and cotton correlates with offspring performance on the leaves of the same host plants. The host-plant preference hierarchy of females did not correlate with their offspring performance. Female moths chose host plants that contributed less to their offspring fitness. Plant effects accounted for the largest amount of variation in offspring performance, while the effects of female (family) was low. The offspring of most females (80%, n = 10) were broadly similar, but 20% (two out of 10), showed marked difference in their offspring performance across the host-plant species. Similarly, there was no relation between larval feeding preference and performance. However, like most laboratory experiments, our experi-mental design does not allow the evaluation of ecological factors (for example, natural enemies, host abundance, etc.) that can play an important role in larval performance in the field. Overall, the results highlight the importance of carrying out preference performance analysis on the individual or family level, rather than pooling individuals to obtain average population data.

Codon usage bias and A+T content variation in human papillomavirus genomes

We analyzed the codon usage bias of eight open reading frames (ORFs) across up to 79 human papillomavirus (HPV) genotypes from three distinct phylogenetic groups. All eight ORFs across HPV genotypes show a strong codon usage bias, amongst degenerately encoded amino acids, toward 18 codons mainly with T at the 3rd position. For all 18 degenerately encoded amino acids, codon preferences amongst human and animal PV ORFs are significantly different from those averaged across mammalian genes. Across the HPV types, the L2 ORFs show the highest codon usage bias (73.2 +/- 1.6% and the E4 ORFs the lowest (51.1 +/- 0.5%), reflecting as similar bias in codon 3rd position A + T content (L2: 76.1 +/- 4.2%; E4: 58.6 +/- 4.5%). The E4 ORF, uniquely amongst the HPV ORFs, is G + C rich, while the other ORFs are A + T rich. Codon usage bias correlates positively with A + T content at the codon 3rd position in the E2, E6, L1 and L2 ORFs, but negatively in the E4 ORFs. A general conservation of preferred codon usage across human and non-human PV genotypes whether they originate from a same supergroup or not, together with observed difference between the preferred codon usage for HPV ORFs and for genes of the cells they infect, suggests that specific codon usage bias and A + T content variation may somehow increase the replicational fitness of HPVs in mammalian epithelial cells, and have practical implications for gene therapy of HPV infection. (C) 2003 Elsevier B.V. All rights reserved.

Control of familial and renal cardiac diseases in English bull terriers: How to repair a damaged breed?

Control recommendations are presented for four genetic or familial diseases that cause significant morbidity and mortality in affected English Bull Terriers. Bull Terrier polycystic kidney disease is an autosomal dominant disease diagnosed by detecting a minimum of three renal cysts, with cysts present in both kidneys, and similarly affected family members to confirm the inherited nature of the cysts. Bull Terrier hereditary nephritis is an autosomal dominant disease diagnosed in otherwise normal animals with urinary protein: creatinine ratios persistently >0.3 and no significant urinary sediment, a family history of the disease, and characteristic glomerular basement membrane lesions. Mitral valve myxomatous degeneration and left ventricular outflow tract obstruction in Bull Terriers are familial diseases diagnosed by auscultating characteristic murmurs in affected animals. Excluding animals with these clinical signs from the breeding pool will reduce the prevalence rates of these diseases, however maintenance of an effective population size is also important. Providing breeders with information on genetics, including the risks associated with inbreeding and the benefits of outcrossing, is likely to improve canine breeding practices, thus increasing fitness and fecundity of these purebred dogs.

Applied physiology and game analysis of rugby union

Increased professionalism in rugby has elicited rapid changes in the fitness profile of elite players. Recent research, focusing on the physiological and anthropometrical characteristics of rugby players, and the demands of competition are reviewed. The paucity of research on contemporary elite rugby players is highlighted, along with the need for standardised testing protocols. Recent data reinforce the pronounced differences in the anthropometric and physical characteristics of the forwards and backs. Forwards are typically heavier, taller, and have a greater proportion of body fat than backs. These characteristics are changing, with forwards developing greater total mass and higher muscularity. The forwards demonstrate superior absolute aerobic and anaerobic power, and Muscular strength. Results favour the backs when body mass is taken into account. The scaling of results to body mass can be problematic and future investigations should present results using power function ratios. Recommended tests for elite players include body mass and skinfolds, vertical jump, speed, and the multi-stage shuttle run. Repeat sprint testing is a possible avenue for more specific evaluation of players. During competition, high-intensity efforts are often followed by periods of incomplete recovery. The total work over the duration of a game is lower in the backs compared with the forwards; forwards spend greater time in physical contact with the opposition while the backs spend more time in free running, allowing them to cover greater distances. The intense efforts undertaken by rugby players place considerable stress on anaerobic energy sources, while the aerobic system provides energy during repeated efforts and for recovery. Training should focus on repeated brief high-intensity efforts with short rest intervals to condition players to the demands of the game. Training for the forwards should emphasise the higher work rates of the game, while extended rest periods can be provided to the backs. Players should not only be prepared for the demands of competition, but also the stress of travel and extreme environmental conditions. The greater professionalism of rugby union has increased scientific research in the sport; however, there is scope for significant refinement of investigations on the physiological demands of the game, and sports-specific testing procedures.

Gender differences in CF phenotype associated with low bone mineral density

Adolescents and adults with CF have lower bone mineral density (BMD) than normal, but its relationship with phenotype is not well understood. Point FEV1% predicted (FEV) and rate of change of FEV are biased estimates of disease severity, because progressively older subjects represent a selected survivor population, with females at greater risk of death than males. To investigate the relationship between BMD and phenotype we used an index (predicted age at death) derived from Bayesian estimates of slope and intercept of FEV, age at last measurement and survival status. Predictive equations for the index were derived from 97 subjects (78 survivors) from the RCH CF clinic, and applied to a group of 102 comparable subjects who had BMD measured, classified as having‘mild’ ()75th), ‘moderate’ (25– 75th), or ‘severe’ (-25th centile) phenotype. Total body (TB) and lumbar spine (LS) BMD z-scores (Z) were compared, adjustingfor gender effects, using 2-way ANOVA. Annual mean change in FEV segregated, as expected, according to phenotype, ‘severe’ (ns25), ‘moderate’ (ns51) and ‘mild’ (ns25) y3.01(y3.73 to y2.30)%, y0.85(y1.36 to y0.35)%, 2.70(1.92 to 3.46)%, respectively, with no gender difference. LS and TB BMDZ were different in each phenotype (P-s 0.002), LS BMDZ for ‘severe’, ‘moderate’ and ‘mild’ y1.63(CI: y2.07 to y 1.19), y0.86(CI: y1.17 to y0.55), y0.06(CI: y0.54 to 0.41). Males had lower LS BMDZ than females overall (y1.22 (CI: y1.54 to y0.91) vs. y0.48(CI: y 0.84 to y0.12) Ps0.002). In the ‘severe’ group, males had lower TB BMDZ and LS BMDZ (PF0.002). Low BMD is associated with ‘moderate’ and ‘severe’ phenotypes, with relative preservation in females in the ‘severe’ group. Female biology (reproductive fitness) might promote resistance to bone resorption at a critical level of BMD loss.

Evaluating a model of parental influence on youth physical activity

Objective: To test a conceptual model linking parental physical activity orientations, parental support for physical activity, and children's self-efficacy perceptions with physical activity participation. Participants and Setting: The sample consisted of 380 students in grades 7 through 12 (mean age, 14.0 +/- 1.6 years) and their parents. Data collection took place during the fall of 1996. Main Outcome Measures: Parents completed a questionnaire assessing their physical activity habits, enjoyment of physical activity, beliefs regarding the importance of physical activity, and supportive behaviors for their child's physical activity. Students completed a 46-item inventory assessing physical activity during the previous 7 days and a 5-item physical activity self-efficacy scale. The model was tested via observed variable path analysis using structural equation modeling techniques (AMOS 4.0). Results: An initial model, in which parent physical activity orientations predicted child physical activity via parental support and child self-efficacy, did not provide an acceptable fit to the data. Inclusion of a direct path from parental support to child physical activity and deletion of a nonsignificant path from parental physical activity to child physical activity significantly improved model fit. Standardized path coefficients for the revised model ranged from 0.17 to 0.24, and all were significant at the p < 0.0001 level. Conclusions: Parental support was an important correlate of youth physical activity, acting directly or indirectly through its influence on self-efficacy. Physical activity interventions targeted at youth should include and evaluate the efficacy of individual-level and community-level strategies to increase parents' capacity to provide instrumental and motivational support for their children's physical activity.

Efeitos agudos do alongamento estático no desempenho da força dinâmica em homens jovens

Introdução: O alongamento muscular é frequentemente utilizado nas práticas desportivas, com o objetivo de aumentar a flexibilidade muscular e amplitude articular, assim como diminuir o risco de lesões e melhorar o desempenho atlético. Objetivo: Analisar o efeito agudo do alongamento com diferentes tempos no desempenho da força dinâmica de membros superiores e inferiores em homens jovens. Métodos: Participaram da amostra 14 voluntários do sexo masculino com idade de 23 ± 2 anos, peso corporal de 84 ± 10kg, estatura de178 ± 7cm, IMC de 26 ± 2kg/m2 e percentual de gordura de 11 ± 3%. Eles foram avaliados com o teste de 10RM em três situações distintas: condição sem alongamento (SA), aquecimento especifico seguido do teste de 10-RM; condição com oito minutos de alongamento (AL-8), uma sessão de alongamento estático com oito minutos de duração, seguido do aquecimento e teste de 10RM; e a condição alongamento 16 minutos (AL-16), 16 minutos de alongamento seguidos dos procedimentos descritos anteriormente. Os testes foram feitos no supino reto e leg-press 45º; os alongamentos foram selecionados de forma a atingir as musculaturas solicitadas nos respectivos exercícios. Resultados: Houve redução de 9,2% da força muscular dinâmica de membros superiores em comparação dos grupos SA e AL16, e entre os grupos AL8 e AL16 (p < 0,001). Em membros inferiores essa redução de força (p < 0,001) foi de 4,8% para AL-8 e de 14,3% para AL-16 em comparação com o grupo SA. Conclusão: Sessões de alongamentos estáticos efetuados antes de atividades que envolvam força dinâmica possuem a capacidade de alterar negativamente o desempenho dessa qualidade física, acarretando pior rendimento em longos períodos de alongamento.