Egg shape mimicry in parasitic cuckoos.

Parasitic cuckoos lay their eggs in nests of host species. Rejection of cuckoo eggs by hosts has led to the evolution of egg mimicry by cuckoos, whereby their eggs mimic the colour and pattern of their host eggs to avoid egg recognition and rejection. There is also evidence of mimicry in egg size in some cuckoo-host systems, but currently it is unknown whether cuckoos can also mimic the egg shape of their hosts. In this study, we test whether there is evidence of mimicry in egg form (shape and size) in three species of Australian cuckoos: the fan-tailed cuckoo Cacomantis flabelliformis, which exploits dome nesting hosts, the brush cuckoo Cacomantis variolosus, which exploits both dome and cup nesting hosts, and the pallid cuckoo Cuculus pallidus, which exploits cup nesting hosts. We found evidence of size mimicry and, for the first time, evidence of egg shape mimicry in two Australian cuckoo species (pallid cuckoo and brush cuckoo). Moreover, cuckoo-host egg similarity was higher for hosts with open nests than for hosts with closed nests. This finding fits well with theory, as it has been suggested that hosts with closed nests have more difficulty recognizing parasitic eggs than open nests, have lower rejection rates and thus exert lower selection for mimicry in cuckoos. This is the first evidence of mimicry in egg shape in a cuckoo-host system, suggesting that mimicry at different levels (size, shape, colour pattern) is evolving in concert. We also confirm the existence of egg size mimicry in cuckoo-host systems.

Phylogenetic convergence and multiple shell shape optima for gliding scallops (Bivalvia: Pectinidae).

An important question in evolutionary biology is how often, and to what extent, do similar ecologies elicit distantly related taxa to evolve towards the same phenotype? In some scenarios, the repeated evolution of particular phenotypes may be expected, for instance when species are exposed to common selective forces that result from strong functional demands. In bivalved scallops (Pectinidae), some species exhibit a distinct swimming behaviour (gliding), which requires specific biomechanical attributes to generate lift and reduce drag during locomotive events. Further, a phylogenetic analysis revealed that gliding behaviour has independently evolved at least four times, which raises the question as to whether these independent lineages have also converged on a similar phenotype. Here, we test the hypothesis that gliding scallops display shell shape convergence using a combination of geometric morphometrics and phylogenetic comparative methods that evaluate patterns of multivariate trait evolution. Our findings reveal that the gliding species display less morphological disparity and significant evolutionary convergence in morphospace, relative to expectations under a neutral model of Brownian motion for evolutionary phenotypic change. Intriguingly, the phylomorphospace patterns indicate that gliding lineages follow similar evolutionary trajectories to not one, but two regions of morphological space, and subsequent analyses identified significant differences in their biomechanical parameters, suggesting that these two groups of scallops accomplish gliding in different ways. Thus, whereas there is a clear gliding morphotype that has evolved convergently across the phylogeny, functionally distinct morphological subforms are apparent, suggesting that there may be two optima for the gliding phenotype in the Pectinidae.

A search for quantitative trait loci exhibiting imprinting effects on mouse mandible size and shape.

Genomic imprinting refers to the pattern of monoallelic parent-of-origin-dependent gene expression where one of the two alleles at a locus is expressed and the other silenced. Although some genes in mice are known to be imprinted, the true scope of imprinting and its impact on the genetic architecture of a wide range of morphometric traits is mostly unknown. We therefore searched for quantitative trait loci (QTL) exhibiting imprinting effects on mandible size and shape traits in a large F(3) population of mice originating from an intercross of the LG/J (Large) and SM/J (Small) inbred strains. We discovered a total of 51 QTL affecting mandible size and shape, 6 of which exhibited differences between reciprocal heterozygotes, the usual signature of imprinting effects. However, our analysis showed that only one of these QTL (affecting mandible size) exhibited a pattern consistent with true imprinting effects, whereas reciprocal heterozygote differences in the other five all were due to maternal genetic effects. We concluded that genomic imprinting has a negligible effect on these specific morphometric traits, and that maternal genetic effects may account for many of the previously reported instances of apparent genomic imprinting.

The change-in-stage and updated smoking status results from a cluster-randomized trial of smoking prevention and cessation using the transtheoretical model among British adolescents.

BACKGROUND: The transtheoretical model (TTM) and computer technology are promising technologies for changing health behavior, but there is little evidence of their effectiveness among adolescents. METHOD: Four thousand two hundred twenty-seven Year 9 (ages 13-14) pupils in 26 schools were randomly allocated to control and 4,125 in 26 schools were allocated to TTM intervention. TTM pupils received three whole class lessons and three sessions with an interactive computer program. Control pupils received no special intervention. Positive change in stage and smoking status was assessed from a questionnaire completed at baseline, 1 year, and 2 years. Random effects logistic regression was used to compare the change in stage and smoking status between the arms. RESULTS: Eighty-nine percent of the TTM group and 89.3% of the control group were present at 1-year and 86.0 and 83.1%, respectively, were present at 2-year follow-up. The adjusted odds ratio (95% confidence interval) for positive stage movement in the TTM relative to control was 1.13 (0.91-1.41) at 1 year and 1.25 (0.95-1.64) at 2 years and for regular smoking was 1.14 (0.93-1.39) at 1 year and 1.06 (0.86-1.31) at 2 years. Subgroup analysis by initial smoking status revealed no benefit for prevention or cessation. CONCLUSIONS: The intervention was ineffective.

Analysis of a polycytosine tract and heteroplasmic length variation in the mitochondrial DNA D-loop of patients with diabetes, MELAS syndrome and race-matched controls.

AIM: The T to C substitution at position 16189 nt of the human mitochondrial genome has been associated with the development of heteroplasmic length variation in the control region of mtDNA. Previous reports have suggested that this defect may be associated with the development of other pathogenic mtDNA mutations, including the diabetogenic A to G mutation in the tRNALEU(UUR). Recently the 16189 nt variant has also been associated with insulin resistance in British adult men. In order to investigate these associations further we studied 23 patients with the 3243 nt mutation, 150 patients with Type 2 diabetes and 149 non-diabetic controls. METHODS: The region around 16189 nt was investigated by polymerase chain reaction-restriction fragment length polymorphism analysis and automated sequencing. RESULTS: We find that the T to C substitution at 16189 nt is associated with heteroplasmic length variation only when the resultant polycytosine tract is not interrupted by a second mutation. There are no significant differences in the prevalence of the 16189 nt variant or heteroplasmic length variation between patients with the 3243 nt mutation, patients with Type 2 diabetes or race-matched normal controls. CONCLUSIONS: We conclude that these variants are likely to represent normal polymorphisms and that previously reported associations should be treated with caution unless they can be replicated in other populations.

A comparison of dietary behaviour in Central England and a French Mediterranean region.

UNLABELLED: BJECTIVEe: The investigation involves comparison of dietary behaviour between UK and Mediterranean France by characterizing the pattern of the current French Mediterranean diet compared with the current British diet. DESIGN: The findings of two dietary surveys, one in the UK and one in France, are compared. An interviewer-administered questionnaire was used in both countries. Questions on food frequency were used to assess dietary behaviour, which were regrouped in the French survey to correspond with UK groupings. Dietary indices were constructed to describe dietary behaviour in relation to cancer recommendations for intake of fat, fibre, meat, fruit and vegetables. SETTING: The UK study was conducted in Leicestershire, central England and the French study was carried out in Hérault, southern France. SUBJECTS: UK: n=418 subjects (57.9% female and 42.1% male; mean age=45.0 y); France: n=635 subjects (50.1% female and 40.9% male; mean age=49.8 y). Age range of both samples: 20-74 y. RESULTS: There were positive and negative trends in food consumption in each country. UK respondents reported eating more beans and pulses (P=0.000), less cheese (P=0. 000), red meat (P=0.001), and processed meats (P=0.000) than French respondents. However, on the negative side, they ate less fruit and vegetables (P=0.000), fish and poultry (P=0.000), cereals (P=0.000), and more sweets and chocolates (P=0.000), and cakes, pastries, biscuits and puddings (P=0.000). Women had healthier diets in both countries. CONCLUSIONS: Overall the southern French diet was healthier as French respondents scored significantly better for indices for fat, dietary fibre, fruit and vegetables (P=0.000 in all cases). However, the French sample scored poorer for the meat index (P=0.000). SPONSORSHIP: This study was supported by a grant from l'Association de la Recherche contre le Cancer (ARC) awarded to M Holdsworth.

Cluster randomised controlled trial of expert system based on the transtheoretical ("stages of change") model for smoking prevention and cessation in schools.

OBJECTIVES: To examine whether a year long programme based on the transtheoretical model of behaviour change, incorporating three sessions using an expert system computer program and three class lessons, could reduce the prevalence of teenage smoking. DESIGN: Cluster randomised trial comparing the intervention to a control group exposed only to health education as part of the English national curriculum. SETTING: 52 schools in the West Midlands region. PARTICIPANTS: 8352 students in year 9 (age 13-14 years) at those schools. MAIN OUTCOME MEASURES: Prevalence of teenage smoking 12 months after the start of the intervention. RESULTS: Of the 8352 students recruited, 7444 (89.1%) were followed up at 12 months. The intention to treat odds ratio for smoking in the intervention group relative to control was 1.08 (95% confidence interval 0.89 to 1.33). Sensitivity analysis for loss to follow up and adjustment for potential confounders did not alter these findings. CONCLUSIONS: The smoking prevention and cessation intervention based on the transtheoretical model, as delivered in this trial, is ineffective in schoolchildren aged 13-14.

Differential expression of mRNA in human thyroid cells depleted of mitochondrial DNA by ethidium bromide treatment.

A wide variety of human diseases have been associated with defects in mitochondrial DNA (mtDNA). The exact mechanism by which specific mtDNA mutations cause disease is unknown and, although the disparate phenotypes might be explained on the basis of impaired mitochondrial gene function alone, the role of altered nuclear gene expression must also be considered. In recent years, the experimental technique of depleting cells of mtDNA by culturing them with ethidium bromide has become a popular method of studying mitochondrial disorders. However, apart from depleting mtDNA, ethidium bromide may have many other intracellular and nuclear effects. The aim of the present study was to investigate the effects of ethidium bromide treatment on nuclear gene expression. A simian-virus-40-transformed human thyroid cell line was depleted of mtDNA by culture in ethidium bromide, and differential display reverse transcriptase-PCR (DDRT-PCR) was then employed to compare mRNA expression between wild-type, mtDNA-replete (rho(+)) and ethidium bromide-treated, mtDNA-depleted (rho(0)) cells. Expression of the majority of nuclear-encoded genes, including those for subunits involved in oxidative phosphorylation, remained unaffected by the treatment. Seven clones were found to be underexpressed; three of the clones showed significant similarity with sequences of the human genes encoding RNase L inhibitor, human tissue factor and ARCN1 (archain vesicle transport protein 1), a highly conserved species which is related to vesicle structure and trafficking proteins. We conclude that the effects of ethidium bromide treatment on nuclear gene expression are not simply limited to changes in pathways directly associated with known mitochondrial function. Further studies will be required to elucidate which of these changes are due to mtDNA depletion, ATP deficiency or other disparate effects of ethidium bromide exposure. Given that most genes appear unaffected, the results suggest that depleting cells of mtDNA by ethidium bromide treatment is a valuable approach for the study of mitochondrial mutations by cybrid techniques.

Mitochondrial DNA variations in patients with Type 2 (non-insulin dependent) diabetes mellitus and a Welsh control population. Mutation in brief no. 239. Online.

Type 2 (non-insulin dependent) diabetes mellitus may be inherited along the maternal line and a variety of mitochondrial DNA (mtDNA) variants have been implicated in the pathogenesis. We have previously reported mutations in five regions of the mitochondrial genome which encompass 11 of the 22 tRNA genes. Now we employ the technique of single stranded conformational polymorphism (SSCP) analysis to investigate a further 6 regions of the mitochondrial genome, covering the remaining 11 tRNA genes in 40 patients with Type 2 diabetes and 30 racially-matched normal controls. A variety of homoplasmic mutations were detected in patients with diabetes and these will be of value in further population association studies.

Phylogenetic analysis of mitochondrial DNA in type 2 diabetes: maternal history and ancient population expansion.

Several studies have suggested a maternal excess in the transmission of type 2 (non-insulin-dependent) diabetes. However, the majority of these reports rely on patients recalling parental disease status and hence are open to criticism. An alternative approach is to study mitochondrial DNA (mtDNA) lineages. The hypervariable region 1 of the rapidly evolving noncoding section of mtDNA is suitable for investigating maternal ancestry and has been used extensively to study the origins of human racial groups. We have sequenced this 347-bp section of mtDNA from leukocytes of subjects with type 2 diabetes (n = 63) and age- and race-matched nondiabetic control subjects (n = 57). Consensus sequences for the two study groups were identical. Pairwise sequence analysis showed unimodal distribution of pairwise differences for both groups, suggesting that both populations had undergone expansion in ancient times. The distributions were significantly different (chi2 = 180, df = 11, P < 0.001); mean pairwise differences were 4.7 and 3.8 for the diabetic and control subjects, respectively. These data suggest that the diabetic subjects belong to an ancient maternal lineage that expanded before the major expansion observed in the nondiabetic population. Phylogenetic trees constructed using maximum parsimony, neighbor-joining, Fitch-Margolish, or maximum likelihood methods failed to show the clustering of all (or a subset) of the diabetic subjects into one or more distinct lineages.

Contemporary nutritional attitudes and practices: a factor analysis approach.

The results reported here are based upon a survey of the nutritional attitudes and practices of a sample of adults aged between 18 and 74 years. The scaled responses to two inventories of statements were subjected to a factor analysis in order to assess the extent to which it is possible to identify a set of coherent dimensions which underly the range of "surface" issues which figure consistently in the sociological literature. The results broadly confirm the utility of the inventories, and do suggest the presence of a series of underlying themes, some of which are very much along anticipated lines. However, one theme, that of deference to what might be thought of as "authoritative agencies" within the food system, was less expected, and deserves further attention. Additionally, selected factors were aggregated by summing the scores of their component variables, and correlated with the key independent variables of age, sex and social class, with a view to identifying the social profiles of their adherents. The results obtained were by no means clear cut, with a number of the anticipated features of such profiles being absent. Moreover, where the profiles were as anticipated, the correlations, although statistically significant, were relatively weak. This raised the issue of whether such an outcome was a methodological artefact, or a reflection of the possibility that differences in nutritional attitudes and practices are shaped by a range of lifestyle variables which do not coincide with conventional indicators of social differentiation.

Genetic linkage study of a major susceptibility locus (D2S125) in a British population of non-insulin dependent diabetic sib-pairs using a simple non-isotopic screening method.

A polymorphic microsatellite marker (D2S125) was recently reported to show significant linkage to non-insulin dependent diabetes mellitus (NIDDM) in a population of Mexican-American affected sib-pairs. We have used a simple non-isotopic screening technique employing the polymerase chain reaction (PCR) with a biotinylated primer to study the genetic linkage and allele frequency distribution of the D2S125 marker in a population of 109 British NIDDMs (62 possible affected sib-pairs). The analysis provided no evidence for linkage of the D2S125 marker in the British subjects (MLS = 0.029, P > 0.05). The PCR screening method used proved to be a convenient and reliable alternative to the radiolabelling of PCR products.

Mitochondrial DNA defects: a widening clinical spectrum of disorders.

1. Mitochondrial DNA has a number of interesting properties including maternal transmission, the ability to replicate in post-mitotic cells, a high mutation rate and an extremely compact molecular architecture with no introns and no large non-coding sequences. 2. Point mutations, deletions and duplications of mitochondrial DNA may occur. Mitochondrial DNA defects may co-exist with wild-type sequence within a cell (heteroplasmy). The level of heteroplasmy may vary in different tissues within the same individual (segregative replication). 3. A number of neurological disorders are characterized by morphological and biochemical mitochondrial defects. It is now clear that mitochondrial DNA mutations underlie these conditions although there is not always a clear correlation between a particular mutation and clinical presentation. 4. Mitochondrial DNA defects, particularly deletions, accumulate in senescent tissue and studies have been performed with the aim of linking such somatic mutations with degenerative disorders. 5. Recently mitochondrial DNA mutations have been implicated in a wider range of clinical disorders including diabetes and nerve deafness. 6. Nuclear gene defects may result in mitochondrial disorders by predisposing to multiple mitochondrial DNA deletions or quantitative depletions of mitochondrial DNA content.

The nutritional health of the nation: diet, exercise and health.

Public health initiatives aimed at changing the nation's diet rely on simple messages to persuade people to eat more from certain food groups and less from others. The underlying rationale of this strategy is that control is located firmly in the hands of the individual who can 'choose' health by following the guidelines. The research reported in this article found high levels of public awareness of nutritional guidelines, and a sense of personal control over health. However, accounts of other health-related agendas showed that being in control may mean choosing to become fitter or slimmer. Within these pursuits, nutritional concerns were prioritized only in so far as they were seen to serve the attainment of a desired body shape. Health professionals need to be aware that nutritional guidelines may be competing with other mediating factors along the chosen route to health.

Nonradioactive characterization of low-level heteroplasmic mitochondrial DNA mutations by SSCP-PCR enrichment.

Mitochondrial DNA (mtDNA) mutations have been implicated in an increasing number of human diseases. Many of these mutations are heteroplasmic and are only present at low levels in readily accessible human tissue such as blood. The technique of single-stranded conformational polymorphism (SSCP) allows the detection of mtDNA variants from peripheral blood, but characterization of these variants by automated sequencing is hampered by the low level of heteroplasmy. We have therefore developed a technique for the enrichment of mtDNA mutations that allows reliable sequence data to be obtained even if the variant mtDNA represents only 1% of the total mtDNA. The procedure involves the excision, purification and subsequent PCR amplification of selected DNA fragments from SSCP gels. The techniques can be applied to other heterogeneous mutations such as mosaic mutations in skin biopsies or somatic oncogene mutations in tumor tissue.

Molecular scanning of candidate mitochondrial tRNA genes in type 2 (non-insulin dependent) diabetes mellitus.

Mitochondrial DNA (mtDNA) gene defects may play a role in the development of non-insulin dependent diabetes mellitus (NIDDM). In order to search for potentially diabetogenic mtDNA defects we have applied the technique of single stranded conformational polymorphism (SSCP) analysis to 124 patients with a history of NIDDM and 40 non-diabetic controls. No new heteroplasmic mutations were detected. However, a variety of homoplasmic variants were found in patients with NIDDM; some of these merit further investigation.