Change over time in adolescent smoking, cannabis use and their association: findings from the School Health Research Network in Wales.

BACKGROUND: While tobacco smoking has declined among UK youth in recent decades, cannabis use has begun to show some growth. Given their interrelationship, growth in cannabis use may act as a barrier to continued reduction in youth smoking. This paper assesses recent tobacco and cannabis use trends in Wales, and their association, to explore whether change in cannabis use might have impacted youth tobacco smoking prevalence. METHODS: Repeat cross-sectional data on tobacco and cannabis use were obtained from biennial Welsh Student Health and Wellbeing surveys between 2013 and 2019. Data were pooled and analysed using logistic regression with adjustment for school-level clustering. RESULTS: No change in regular youth tobacco smoking was observed between 2013 and 2019. In contrast, current cannabis use increased during this time, and cannabis users had significantly greater odds of regular tobacco smoking. After adjusting for change in cannabis use, a significant decline in youth tobacco smoking was observed (OR 0.95; 95% confidence intervals: 0.92, 0.97). CONCLUSION: Recent growth in cannabis use among young people in Wales may have offset prospective declines in regular tobacco smoking. Further reductions in youth smoking may require more integrated policy approaches to address the co-use of tobacco and cannabis among adolescents.

Wolbachia effects in natural populations of Chorthippus parallelus from the Pyrenean hybrid zone.

We evaluate for the first time the effect of Wolbachia infection, involving two different supergroups, on the structure and dynamics of the hybrid zone between two subspecies of Chorthippus parallelus (Orthoptera) in the Pyrenees. Wolbachia infection showed no effects on female fecundity or a slight increment in females infected by F supergroup, although in the last case it has to be well established. Cytoplasmic incompatibility (CI) is confirmed in crosses carried out in the field between individuals from a natural hybrid population. This CI, registered as the relative reduction in embryo production (sh ), was of sh = 0.355 and sh = 0.286 in unidirectional crosses involving B and F supergroups, respectively. CI also occurred in bidirectional crosses (sh = 0.147) but with a weaker intensity. The transmission rates of the two Wolbachia strains (B and F) were estimated by the optimization of a theoretical model to reach the infection frequencies observed in certain population. To fit this scenario, both supergroups should present transmission rates close to 1. Further, we have simulated the infection dynamics, and hence, the capacity of Wolbachia to structure the population of the host insects and to affect to reproduction and genetic introgression in the hybrid zone. This represents a first example of the influence of Wolbachia in an insect natural hybrid zone.

Cryptic or mystic? Glacial tree refugia in northern Europe.

Here, we examine the evidence for tree refugia in northern Europe during the Late Pleniglacial (LPG) interval of maximum tree-range contraction. Our review highlights the often equivocal nature of genetic data and a tendency to overestimate potential tree distributions due to warm climate-model bias, and also reveals a convergence of macrofossil and pollen evidence. What emerges is the absence of temperate trees north of 45°N and a west-east (W-E) asymmetry in boreal tree distribution, with a treeless Western Europe north of 46°N, while restricted boreal populations persisted in Eastern Europe up to 49°N, and higher latitudes east of the Fennoscandian ice-sheet. These results have implications for current thinking on European genetic diversity patterns, species migration capacity, and conservation strategies.

Hybridization and speciation.

Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky-Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock-on effects on speciation both within and outside regions of hybridization.

Strong polymer-turbulence interactions in viscoelastic turbulent channel flow.

This paper is focused on the fundamental mechanism(s) of viscoelastic turbulence that leads to polymer-induced turbulent drag reduction phenomenon. A great challenge in this problem is the computation of viscoelastic turbulent flows, since the understanding of polymer physics is restricted to mechanical models. An effective state-of-the-art numerical method to solve the governing equation for polymers modeled as nonlinear springs, without using any artificial assumptions as usual, was implemented here on a three-dimensional channel flow geometry. The capability of this algorithm to capture the strong polymer-turbulence dynamical interactions is depicted on the results, which are much closer qualitatively to experimental observations. This allowed a more detailed study of the polymer-turbulence interactions, which yields an enhanced picture on a mechanism resulting from the polymer-turbulence energy transfers.

Stagnation point von Kármán coefficient.

On the basis of various direct numerical simulations (DNS) of turbulent channel flows the following picture is proposed. (i) At a distance y from either wall, the Taylor microscale lambda is proportional to the average distance l(s) between stagnation points of the fluctuating velocity field, i.e., lambda(y)=B(1)l(s)(y) with B(1) constant, for delta(nu) << y < or approximately equal to delta, where the wall unit delta(nu) is defined as the ratio of kinematic viscosity nu to skin friction velocity u(tau) and delta is the channel's half-width. (ii) The number density n(s) of stagnation points varies with height according to n(s)=(C(s)/delta(nu)(3))y(+)(-1) where y(+) identical with y/delta(nu) and C(s) is constant in the range delta(nu) << y < or approximately equal to delta. (iii) In that same range, the kinetic energy dissipation rate per unit mass, equals 2/3(E(+)((u(tau)(3)/kappa(s)y) where E(+) is the total kinetic energy per unit mass normalized by u(tau)(2) and kappa(s)=B(1)(2)/C(s) is the stagnation point von Kármán coefficient. (iv) In the limit of exceedingly large Reynolds numbers Re(tau) identical with delta/delta(nu), large enough for the Reynolds stress -(uv) to equal u(tau)(2) in the range delta(nu) << y << delta, and assuming that production of turbulent kinetic energy balances dissipation locally in that range and limit, the mean velocity U(+), normalized by u(tau), obeys (d/dy)U(+) approximately equal to 2/3(E(+)/kappa(s)y) in that same range. (v) It follows that the von Kármán coefficient kappa is a meaningful and well-defined coefficient and the log law holds in turbulent channel/pipe flows only if E(+) is independent of y(+) and Re(tau) in that range, in which case kappa approximately kappa(s). (vi) In support of (d/dy)U(+) approximately equal to 2/3(E(+)/kappa(s)y), DNS data of turbulent channel flows which include the highest currently available values of Re(tau) are best fitted by E(+) approximately equal to 2/3(B(4)y(+)(-2/15)) and (d/dy(+))U(+) approximately equal to (B(4)/kappa(s))y(+)(-1-2/15) with B4 independent of y in delta(nu) << y << delta if the significant departure from -(uv) approximately equal to u(tau)(2) at these Re(tau) values is taken into account.

Genetic structure of European sheep breeds.

Large-scale evaluations of genetic diversity in domestic livestock populations are necessary so that region-specific conservation measures can be implemented. We performed the first such survey in European sheep by analysing 820 individuals from 29 geographically and phenotypically diverse breeds and a closely related wild species at 23 microsatellite loci. In contrast to most other domestic species, we found evidence of widespread heterozygote deficit within breeds, even after removing loci with potentially high frequency of null alleles. This is most likely due to subdivision among flocks (Wahlund effect) and use of a small number of rams for breeding. Levels of heterozygosity were slightly higher in southern than in northern breeds, consistent with declining diversity with distance from the Near Eastern centre of domestication. Our results highlight the importance of isolation in terms of both geography and management in augmenting genetic differentiation through genetic drift, with isolated northern European breeds showing the greatest divergence and hence being obvious targets for conservation. Finally, using a Bayesian cluster analysis, we uncovered evidence of admixture between breeds, which has important implications for breed management.

Genetic diversity and subdivision of 57 European and Middle-Eastern sheep breeds.

The population structure and genetic diversity of 57 European and Middle Eastern marginal and cosmopolitan sheep breeds from 15 countries were analysed by typing 31 microsatellite markers. Mean unbiased expected heterozygosities ranged from 0.63 in British Exmoor Horn to 0.77 in Albanian Ruda. South-eastern European and Middle-Eastern sheep breeds were significantly more variable than northwestern and western European breeds. An overall heterozygote deficiency (f) across all loci was observed (P < 0.001), while genetic differentiation (theta) was 5.7%. Principal component analysis and Bayesian model-based clustering indicate a south-east to north-west cline, but also revealed distinct groups of Middle-Eastern fat-tailed sheep, south-eastern European sheep and north-western/western European sheep. Within the last group, two less-distinct clusters comprised the Merino-type and Alpine breeds respectively. The incomplete demarcations of most clusters probably reflects cross-breeding and/or upgrading.

Development and testing of a questionnaire to measure patient satisfaction with intermediate care.

BACKGROUND: Individual trials have suggested high levels of general patient satisfaction with intermediate care, but this topic has not been examined in detail. AIMS: To identify the key elements of patient satisfaction with intermediate care, and to see whether these can be validly measured using a questionnaire. METHOD: A questionnaire was developed on the basis of a literature review and piloting with patients and staff on participating schemes (phase I). In phase II, the questionnaire was tested for validity and reliability in a group of patients recently discharged from two "hospital-at-home" intermediate-care schemes. In phase III, a shortened version of the questionnaire was psychometrically tested in five sites taking part in a national evaluation of intermediate care. RESULTS: 96 patients with an average age of 76.5 years took part in phase II. Test-retest reliability was evaluated by repeating the questionnaire 2 weeks later in a subsample of 42 patients. This was "moderate" (kappa 0.4-0.6) for 12 questions, "fair" (kappa 0.2-0.4) for 6 questions and "poor" (kappa 0.1-0.2) for 5 questions. Scores correlated well with the Client Satisfaction Questionnaire (Spearman's r = 0.75, p<0.001). 843 patients (57% of those eligible) from five intermediate-care schemes took part in phase III. Principal components analysis suggested six factors or subscales: general satisfaction, affective response, cognitive response, timing of discharge, coordination after discharge, and access to pain relief, although the last three factors comprised only one question each. The intraclass correlation coefficients in the first three subscales varied from 0.82 to 0.89. Scores for all subscales differed by scheme, suggesting construct validity. Only one question (on general satisfaction) was found to be redundant. CONCLUSION: The questionnaire, with some minor amendments to improve performance, could be used as a validated tool for audit and research in intermediate care. An amended version and scoring programme is available from us on request.

The nutritional vulnerability of older Guyanese in residential homes / Vulnerabilidad nutricional de los ancianos guyaneses en los hogares de ancianos

OBJECTIVE: To assess the nutritional status, functional ability and food intake of older Guyanese in residential care. METHODS: Eighty-four residents of one public and two private homes underwent an anthropometric and functional ability assessment including height, weight, armspan, arm and calf circumferences and handgrip strength. Food intake in two private homes was measured over seven days by direct weighing and the use of consumption units. RESULTS: The overall prevalence of underweight was 26.2% and of overweight was 17.8% but the prevalence of underweight was higher in the public home (29.3% underweight and 17.2% overweight in the public home, and 19.2% underweight and 19.2% overweight in the private home). Mean handgrip strength was 26 kg in males and 17.7 kg in females. The nutritional adequacy of the diet provided by one of the homes was poor with the food providing less than 50% of the required amount of zinc and vitamins A, D and C. Neither home met the requirement for energy. CONCLUSION: A high prevalence of malnutrition exists in a public home for the elderly and, to a lesser degree, in two private homes. In the context of a rapidly ageing population and tight financial constraints, the challenge of providing an adequate diet must be given priority.

Objetivo: Evaluar el estatus nutricional, la capacidad funcional, y la ingestión de alimentos de ancianos guyaneses en el cuidado residencial. Métodos: Ochenta y cuatro residentes de dos hogares privados y uno público fueron sometidos a una evaluación antropométrica y de su capacidad funcional, que incluyó altura, peso, medida de la distancia de los brazos abiertos, brazos, circunferencias de la pantorrilla, y fuerza del puño. La ingestión de alimentos en dos hogares privados fue medida durante siete días mediante el peso directo y el uso de unidades de consumo. Resultados: La prevalencia general del bajo peso corporal fue de 26.2% y la del peso corporal excesivo de 17.8%, pero la prevalencia del bajo peso fue más alta en el hogar público (29.3% de bajo peso frente a 17.2% de peso excesivo en el hogar público, y 19.2% de bajo peso frente a 19.2% de peso excesivo en el hogar público). La fuerza media del puño fue 26 kg en los hombres y 17.7 kg en las mujeres. La adecuación nutricional de la dieta suministrada por uno de los hogares fue pobre, formada por alimentos que proveían menos del 50% de las cantidades requeridas de zinc y vitaminas A, D, y C. Ninguno de los hogares satisfacía los requerimientos energéticos. . Conclusion: En el hogar público para los ancianos, la prevalencia de la malnutrición es alta en grado alarmante, y lo mismo ocurre, en menor grado, en los dos hogares privados. En el contexto de una población que se avejenta rápidamente y que experimenta serias limitaciones financieras, hay que dar prioridad al reto de suministrar una dieta adecuada.

Evolution of spider silks: conservation and diversification of the C-terminus.

Analysis of DNA sequences coding for the C-terminus of spider silk proteins from a range of spiders suggests that many silk C-termini share a common origin, and that their physical properties have been highly conserved over several hundred million years. These physical properties are compatible with roles in protein synthesis, silk function and in recruiting accessory proteins. Phylogenetic relationships among different silk genes suggest that any recombination has been insufficient to homogenize the different types of silk gene, which appear to have evolved independently of one another. The types of nucleotide substitutions that have occurred suggest that selection may have operated differently in the various silk lineages. Amino acid sequences of flagelliform silk C-termini differ substantially from the other types of spider silk studied, but they are expected to have very similar physical properties and may perform a similar function.

Disjunct distributions during glacial and interglacial periods in mountain butterflies: Erebia epiphron as an example.

Over several decades, the distribution patterns and evolution of alpine disjunct species has become an increasingly discussed subject. Large scale genetic analysis has allowed the resolution of the past range changes and intraspecific evolution of many species, in Europe especially of Mediterranean origin. However, the phylogeographic structures of species with arctic-alpine disjunct distribution patterns are relatively poorly studied. The existing phylogeographic analysis (mostly of alpine plant species) supports disjunct distributions during glacial as well as post-glacial periods for a number of species. However, several questions still remain unresolved and we therefore analysed the Mountain Ringlet Erebia epiphron as a model for such alpine disjunct species. We found strong differentiation into five different lineages supporting five differentiation centres: (i) the eastern Pyrenees, (ii) the mountain ranges between the central Pyrenees and south-western Alps, (iii, iv) two areas along the southern Alps margin and (v) the northern Alps margin. We propose that these patterns evolved due to the humidity requirements of this species, which did not allow survival in the dry glacial steppes, but along the margins of the wetter glaciated high mountain ranges.

The nutritional vulnerability of older Guyanese in residential homes.

OBJECTIVE: To assess the nutritional status, functional ability and food intake of older Guyanese in residential care. METHODS: Eighty-four residents of one public and two private homes underwent an anthropometric and functional ability assessment including height, weight, armspan, arm and calf circumferences and handgrip strength. Food intake in two private homes was measured over seven days by direct weighing and the use of consumption units. RESULTS: The overall prevalence of underweight was 26.2% and of overweight was 17.8% but the prevalence of underweight was higher in the public home (29.3% underweight and 17.2% overweight in the public home, and 19.2% underweight and 19.2% overweight in the private home). Mean handgrip strength was 26 kg in males and 17.7 kg in females. The nutritional adequacy of the diet provided by one of the homes was poor with the food providing less than 50% of the required amount of zinc and vitamins A, D and C. Neither home met the requirement for energy. CONCLUSION: A high prevalence of malnutrition exists in a public home for the elderly and, to a lesser degree, in two private homes. In the context of a rapidly ageing population and tight financial constraints, the challenge of providing an adequate diet must be given priority.

Dietary advice for reducing cardiovascular risk.

BACKGROUND: Changes in population diet are likely to reduce cardiovascular disease and cancer, but the effect of dietary advice is uncertain. OBJECTIVES: To assess the effects of providing dietary advice to achieve sustained dietary changes or improved cardiovascular risk profile among healthy adults. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register on The Cochrane Library (Issue 2 2000), MEDLINE (January 1966 to December 2000), EMBASE (January 1985 to December 2000), DARE (December 2000), CAB Health (December 1999), dissertation abstracts, and reference lists of articles. We contacted researchers in the field. SELECTION CRITERIA: Randomised studies with no more than 20% loss to follow-up, lasting at least three months involving healthy adults comparing dietary advice with no advice or less intensive advice. Trials involving children, trials to reduce weight or those involving supplementation were excluded. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data. Study authors were contacted for additional information. MAIN RESULTS: Twenty-three trials with 29 intervention arms (comparisons) comparing dietary advice with no advice were included in the review. Dietary advice reduced total serum cholesterol by 0.13 mmol/l (95% CI 0.03 to 0.23) and LDL cholesterol by 0.13 mmol/l (95% CI 0.01 to 0.25) after 3-12 months. Mean HDL cholesterol levels were unchanged. Dietary advice reduced blood pressure by 2.10 mmHg systolic (95% CI 1.37 to 2.83) and 1.63 mmHg diastolic (95% CI 0.56 to 2.71) and 24-hour urinary sodium excretion by 44.2 mmol (95% CI 33.6 to 54.7) after 3-36 months. Plasma triglycerides, ss-carotene and red cell folate were each measured in one small study which suggested no significant effect. Self-reported dietary intake may be subject to reporting bias, and there was significant heterogeneity in all the following analyses. Compared to no advice, dietary advice increased fruit and vegetable intake by 1.24 servings/day (95% CI 0.43 to 2.05). Dietary fibre intake increased with advice by 7.22 g/day (95% CI 2.84 to 11.60), while total dietary fat as a percentage of total energy intake fell by 6.18 % (95% CI 4.00 to 8.36) with dietary advice and saturated fat intake fell by 3.28 % (95% CI 1.92 to 4.64). AUTHORS' CONCLUSIONS: Dietary advice appears to be effective in bringing about modest beneficial changes in diet and cardiovascular risk factors over approximately 9 months but longer term effects are not known.

Understanding the phylogeographic patterns of European hedgehogs, Erinaceus concolor and E. europaeus using the MHC.

The genome of the European hedgehog, Erinaceus concolor and E. europaeus, shows a strong signal of cycles of restriction to glacial refugia and postglacial expansion. Patterns of expansion, however, differ for mitochondrial DNA (mtDNA) and preliminary analysis of nuclear markers. In this study, we determine phylogeographic patterns in the hedgehog using two loci of the major histocompatibility complex (MHC), isolated for the first time in hedgehogs. These genes show long persistence times and high polymorphism in many species because of the actions of balancing selection. Among 84 individuals screened for variation, only two DQA alleles were identified in each species, but 10 DQB alleles were found in E. concolor and six in E. europaeus. A strong effect of demography on patterns of DQB variability is observed, with only weak evidence of balancing selection. While data from mtDNA clearly subdivide both species into monophyletic subgroups, the MHC data delineate only E. concolor into distinct subgroups, supporting the preliminary findings of other nuclear markers. Together with differences in variability, this suggests that the refugia history and/or expansion patterns of E. concolor and E. europaeus differ.

Genetic consequences of climatic oscillations in the Quaternary.

An appreciation of the scale and frequency of climatic oscillations in the past few million years is modifying our views on how evolution proceeds. Such major events caused extinction and repeated changes in the ranges of those taxa that survived. Their spatial effects depend on latitude and topography, with extensive extinction and recolonization in higher latitudes and altitudinal shifts and complex refugia nearer the tropics. The associated population dynamics varied with life history and geography, and the present genetic constitution of the populations and species carry attenuated signals of these past dynamics. Phylogeographic studies with DNA have burgeoned recently and studies are reviewed from the arctic, temperate and tropical regions, seeking commonalities of cause in the resulting genetic patterns. Arctic species show distinct shallow genetic clades with common geographical boundaries. Thus Beringia is distinct phylogeographically, but its role as a refugial source is complex. Arctic taxa do not show the common genetic pattern of southern richness and northern purity in north-temperate species. Temperate refugial regions in Europe and North America show relatively deep DNA divergence for many taxa, indicating their presence over several Ice Ages, and suggesting a mode of speciation by repeated allopatry. DNA evidence indicates temperate species in Europe had different patterns of postglacial colonization across the same area and different ones in previous oscillations, whereas the northwest region of North America was colonized from the north, east and south. Tropical montane regions contain deeply diverged lineages, often in a relatively small geographical area, suggesting their survival there from the Pliocene. Our poor understanding of refugial biodiversity would benefit from further combined fossil and genetic studies.

The genetic pattern of population threat and loss: a case study of butterflies.

Recent decreases in biodiversity in Europe are commonly thought to be due to land use and climate change. However, the genetic diversity of populations is also seen as one essential factor for their fitness. Genetic diversity in species across the continent of Europe has been recognized as being in part a consequence of ice age isolation in southern refugia and postglacial colonization northwards, and these phylogeographical patterns may themselves affect the adaptability of populations. Recent work on butterfly species with different refugia, colonization paths and genetic structures allows this idea to be examined. The 'chalk-hill blue' pattern is one of decreasing genetic diversity from south to north, whereas the 'woodland ringlet' pattern shows greater genetic diversity in eastern than in western lineages. Comparison of population demographic trends in species with these biogeographical patterns reveals higher rates of decrease with lower genetic diversity. This indicates reduced adaptability due to genetic impoverishment as a result of glacial and postglacial range changes. Analysis of phylogeographical pattern may be a useful guide to interpreting demographic trends and in conservation planning.

No evidence for parallel sympatric speciation in cichlid species of the genus Pseudotropheus from north-western Lake Malawi.

To test the hypothesis of parallel speciation by sexual selection, we examined length variation at six microsatellite loci of samples from four sites of four to six putative species belonging to two subgenera of rocky shore mbuna cichlids from Lake Malawi. Almost all fixation indices were significantly different from zero, suggesting that there is presently little or no gene flow among allopatric populations or sympatric species. Analysis of variance indicated that genetic distances among allopatric populations of putative conspecifics were significantly lower than among sympatric populations of heterospecifics. The topology of trees based on distance matrices was also largely consistent with the hypothesis that the putative species are monophyletic and have thus not evolved in parallel in their present locations. If parallel speciation does occur in Malawi cichlids, it may be on a larger spatial scale than investigated in our study.