Impacto de la infección materna asintomática por SARS-CoV-2 sobre el crecimiento fetal / Impact of asymptomatic maternal SARS-CoV-2 infection on foetal growth

Introducción: La repercusión de la infección asintomática por SARS-CoV-2 sobre el crecimiento fetal no ha sido bien establecida. El objetivo de este estudio fue determinar si existe un incremento del riesgo de retraso de crecimiento intrauterino en gestaciones con una infección asintomática por SARS-CoV-2 durante el embarazo. Material y métodos: Estudio retrospectivo caso-control en gestantes con feto pequeño para la edad gestacional o restricción del crecimiento intrauterino. Los grupos se constituyeron según el percentil de peso al nacimiento. El antecedente de infección por SARS-CoV-2 ha sido definido por la presencia de IgG en el momento del ingreso hospitalario para el parto. Resultados: No se encontraron diferencias significativas entre el grupo control y el grupo caso en cuanto a anticuerpos IgG positivos (11,5 vs. 8,8%). Tampoco se registraron diferencias en la prematuridad ni el tipo de parto. Conclusiones: La infección asintomática por SARS-CoV-2 durante el embarazo no parece afectar al crecimiento fetal.(AU)

Introduction: The impact of asymptomatic infection by SARs-CoV-2 on foetal growth has not been described. The purpose of our study is to determine whether there is an increased risk of foetal growth restriction in pregnancies in which asymptomatic or mild infection by SARS-CoV-2 has been detected. Material and methods: Retrospective case-control study with a subset of pregnant women with a small for gestational age foetus. Groups were established according to birth weight percentile. Previous SARS-CoV-2 infection was defined by positive antibodies obtained on admission to hospital for delivery. Results: No statistically significant differences between controls and cases were recorded in terms of positive IgG antibodies (11.5 vs. 8.8%). There were no premature births or significant differences in the date or type of delivery. Conclusions: Asymptomatic infection by SARs-CoV-2 during pregnancy does not seem to affect foetal growth.(AU)

[Impact of asymptomatic maternal SARS-CoV-2 infection on foetal growth]. / Impacto de la infección materna asintomática por SARS-CoV-2 sobre el crecimiento fetal.

Introduction: The impact of asymptomatic infection by SARs-CoV-2 on foetal growth has not been described. The purpose of our study is to determine whether there is an increased risk of foetal growth restriction in pregnancies in which asymptomatic or mild infection by SARS-CoV-2 has been detected. Material and methods: Retrospective case-control study with a subset of pregnant women with a small for gestational age foetus. Groups were established according to birth weight percentile. Previous SARS-CoV-2 infection was defined by positive antibodies obtained on admission to hospital for delivery. Results: No statistically significant differences between controls and cases were recorded in terms of positive IgG antibodies (11.5 vs. 8.8%). There were no premature births or significant differences in the date or type of delivery. Conclusions: Asymptomatic infection by SARs-CoV-2 during pregnancy does not seem to affect foetal growth.

[Is there a relationship between white matter lesions associated with migraine and patent foramen ovale? Analysis of a series of patients with chronic migraine]. / ¿Existe relación entre las lesiones de la sustancia blanca asociadas a migraña y el foramen oval permeable? Análisis de una serie de pacientes con migraña crónica.

INTRODUCTION: White matter lesions are more prevalent in migraine patients than in the general population, especially those with a high frequency of attacks. A patent foramen ovale has been described as a possible link between migraine and white matter lesions. AIM: To determine the existence of a possible relationship between a patent foramen ovale and white matter lesions in a series of patients with chronic migraine. PATIENTS AND METHODS: Observational, single-centre, case-control study. Eighty-nine women with chronic migraine were selected. The persistence and characteristics of the patent foramen ovale were assessed by means of a transcranial Doppler study. The patent foramen ovale was classified as small, moderate or massive. Those detected at rest were considered permanent, and the others were classified as latent. The MRI protocol included T1-enhanced sagittal images, FLAIR-T2-enhanced axial images, and a proton density and T2-FSE combined sequence. The white matter lesions were classified as deep, periventricular or both. RESULTS: The prevalence of patent foramen ovale (53.6% versus 48.5%; p = 0.80) and the proportion of massive, permanent patent foramen ovale were similar among patients with and without white matter lesions. Neither was there any difference in the prevalence (55.6% versus 52.6%; p = 1.00) or the characteristics of the patent foramen ovale as a function of the distribution of white matter lesions. CONCLUSION: The results do not suggest that a patent foramen ovale intervenes in the pathophysiology of the white matter lesions observed in patients with migraine.

TITLE: ¿Existe relación entre las lesiones de la sustancia blanca asociadas a migraña y el foramen oval permeable? Análisis de una serie de pacientes con migraña crónica.Introducción. Las lesiones de la sustancia blanca son más prevalentes en los pacientes migrañosos que en la población general, especialmente en los que tienen una alta frecuencia de ataques. El foramen oval permeable se ha descrito como posible nexo de unión entre la migraña y las lesiones de la sustancia blanca. Objetivo. Determinar la existencia de una posible relación entre el foramen oval permeable y las lesiones de la sustancia blanca en una serie de pacientes con migraña crónica. Pacientes y métodos. Estudio observacional, unicéntrico, de casos y controles. Se seleccionó a 89 mujeres con migraña crónica. La persistencia y las características del foramen oval permeable se evaluaron mediante un estudio Doppler transcraneal. El foramen oval permeable se clasificó como pequeño, moderado o masivo. Se consideraron permanentes los detectados en reposo, y latentes, el resto. El protocolo de resonancia magnética incluyó imágenes sagitales potenciadas en T1, axiales potenciadas en FLAIR-T2 y secuencia combinada de densidad protónica y T2-FSE. Las lesiones de la sustancia blanca se clasificaron como profundas, periventriculares o ambas. Resultados. La prevalencia de foramen oval permeable (53,6% frente a 48,5%; p = 0,80) y la proporción de foramen oval permeable masivo y permanente fueron similares entre los pacientes con y sin lesiones de la sustancia blanca. Tampoco se encontraron diferencias en la prevalencia (55,6% frente a 52,6%; p = 1,00) o las características del foramen oval permeable en función de la distribución de las lesiones de la sustancia blanca. Conclusión. Los resultados no sugieren la intervención del foramen oval permeable en la fisiopatología de las lesiones de la sustancia blanca observadas en pacientes migrañosos.

Temblor ortostático como manifestación aislada de tirotoxicosis tras arteriografía cerebral / Orthostatic tremor as the only manifestation of thyrotoxicosis following cerebral angiography

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Effect of high-intensity resistance circuit-based training in hypoxia on aerobic performance and repeat sprint ability.

Recent acute studies have shown that high-intensity resistance circuit-based (HRC) training in hypoxia increases metabolic stress. However, no intervention studies have yet proven their effectiveness. This study aimed to analyze the effect of 8 weeks of HRC in hypoxia on aerobic performance, resting energy expenditure (REE), repeat sprint ability (RSA) and hematological variables. Twenty-eight subjects were assigned to hypoxia (FiO2  = 15%; HRChyp : n = 15; age: 24.6 ± 6.8 years; height: 177.4 ± 5.9 cm; weight: 74.9 ± 11.5 kg) and normoxia (FiO2  = 20.9%; HRCnorm : n = 13; age: 23.2 ± 5.2 years; height: 173.4 ± 6.2 cm; weight: 69.4 ± 7.4 kg) groups. Each training session consisted of two blocks of three exercises (Block 1: bench press, leg extension, front pull down; 2: deadlift, elbow flexion, ankle extension). Each exercise was performed at 6 repetitions maximum. Participants exercised twice weekly for 8 weeks and before and after the training program blood test, REE, RSA and treadmill running test were performed. Fatigue index in the RSA test was significantly decreased in the HRChyp (-0.9%; P < .01; ES = 2.75) but not in the HRCnorm . No changes were observed in REE and hematological variables. Absolute (4.5%; P = .014; ES = 0.42) and relative (5.2%; P = .008; ES = 0.43) maximal oxygen uptake (VO2 max), speed at VO2 max (4%; P = .010; ES = 0.25) and time to exhaustion (4.1%; P = .012; ES = 0.26) were significantly increased in HRChyp but not in the HRCnorm . No significant differences between groups were found. Compared with normoxic conditions, 8 weeks of HRC training under hypoxic conditions efficiently improves aerobic performance and RSA without changes in REE and red blood O2 -carrying capacity.

Effects of whole-body vibration training in patients with multiple sclerosis: A systematic review. / Efectos del entrenamiento vibratorio de cuerpo completo en pacientes con esclerosis múltiple: una revisión sistemática.

INTRODUCTION: Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system. MS is characterised by nerve demyelination that can alter nerve transmission and lead to such symptoms as fatigue, muscle weakness, and impaired motor function. There are 47 000 people with MS in Spain. Vibration training can be an effective and complementary alternative to traditional exercise to treat patients with MS. The aim of this study was to analyse the effectiveness of vibration training programmes in patients with MS. DEVELOPMENT: We searched 5 electronic databases (PubMed, SPORTDiscus, SciELO, Lilacs, IBECS, and ISI Web of Knowledge) in August 2015. By using a set of keywords, we found studies linking vibration training and MS and included randomised controlled trials that applied vibration training to patients with MS. Our search yielded 71 studies. Only 9 of them were included after removing duplicate studies and those which were not relevant according to our selection criteria. These studies obtained different outcomes. CONCLUSIONS: Some studies found improvements in muscle strength, functional capacity, coordination, resistance, balance, and some areas of MSSS-88. However, we identified limitations in some of these studies and there are still few publications on vibration training and multiple sclerosis to ensure training effectiveness.

The Boltzmann project.

The International Committee for Weights and Measures (CIPM), at its meeting in October 2017, followed the recommendation of the Consultative Committee for Units (CCU) on the redefinition of the kilogram, ampere, kelvin and mole. For the redefinition of the kelvin, the Boltzmann constant will be fixed with the numerical value 1.380 649 × 10-23 J K-1. The relative standard uncertainty to be transferred to the thermodynamic temperature value of the triple point of water will be 3.7 × 10-7, corresponding to an uncertainty in temperature of 0.10 mK, sufficiently low for all practical purposes. With the redefinition of the kelvin, the broad research activities of the temperature community on the determination of the Boltzmann constant have been very successfully completed. In the following, a review of the determinations of the Boltzmann constant k, important for the new definition of the kelvin and performed in the last decade, is given.

[Analysis of the direct costs associated with mechanical thrombectomy and intravenous fibrinolysis in the Hospital Universitario Central de Asturias]. / Analisis de los costes directos asociados a la trombectomia mecanica y a la fibrinolisis intravenosa en el Hospital Universitario Central de Asturias.

INTRODUCTION: The increase in the indications for mechanical thrombectomy and its implementation in Spanish hospitals makes it necessary to determine the costs related to this treatment so as to be able to streamline economic resources and allow them to be distributed in an appropriate manner. AIMS: To analyse the direct costs associated with patients with acute ischaemic stroke who are treated with intravenous fibrinolysis and with mechanical thrombectomy, and to assess the effectiveness and safety of both treatments during the first 90 days of progression in the Hospital Universitario Central de Asturias. PATIENTS AND METHODS: A retrospective analysis was performed that included 44 patients who received intravenous fibrinolysis and 61 patients treated with mechanical thrombectomy, in whom a series of clinical and economic variables were analysed. RESULTS: The mean final total cost per patient was 16,059 euros in treatments with thrombectomy and 8,169 euros in those in which intravenous fibrinolysis was administered. The percentage of patients with a good functional prognosis at 90 days was 63.93% in those treated by endovascular means and 56.82% in those who received intravenous fibrinolysis. Mortality rates were 18.03 and 11.36%, respectively. CONCLUSIONS: The mean cost of treatment with mechanical thrombectomy, as well as the total mean cost per patient during the acute phase of the disease associated with this technique, is higher than in the case of intravenous fibrinolysis. In our setting, both intravenous fibrinolysis and mechanical thrombectomy are considered to be effective and safe.

TITLE: Analisis de los costes directos asociados a la trombectomia mecanica y a la fibrinolisis intravenosa en el Hospital Universitario Central de Asturias.Introduccion. La ampliacion de las indicaciones de la trombectomia mecanica y su implementacion en los hospitales españoles hacen necesario conocer los costes relacionados con este tratamiento para racionalizar los recursos economicos y permitir una adecuada distribucion de estos. Objetivos. Analizar los costes directos asociados a los pacientes con ictus isquemico agudo tratados con fibrinolisis intravenosa y con trombectomia mecanica, y valorar la efectividad y seguridad de ambos tratamientos durante los primeros 90 dias de evolucion en el Hospital Universitario Central de Asturias. Pacientes y metodos. Se realizo un analisis retrospectivo en el que se incluyo a 44 pacientes que recibieron fibrinolisis intravenosa y a 61 pacientes tratados con trombectomia mecanica, en los que se analizaron una serie de variables clinicas y economicas. Resultados. El coste total final medio por paciente fue de 16.059 euros en los tratados con trombectomia y de 8.169 euros en los que se administro fibrinolisis intravenosa. El porcentaje de pacientes con buen pronostico funcional a los 90 dias fue del 63,93% en los tratados de forma endovascular y del 56,82% en los que recibieron fibrinolisis intravenosa. Las tasas de mortalidad fueron del 18,03% y 11,36%, respectivamente. Conclusiones. El coste medio del tratamiento con trombectomia mecanica, asi como el coste medio total por paciente durante la fase aguda de la enfermedad asociado a esta tecnica, es mayor que en el caso de la fibrinolisis intravenosa. Tanto la fibrinolisis intravenosa como la trombectomia mecanica se configuran en nuestro medio como tratamientos efectivos y seguros.

A preliminary study on topical cetirizine in the therapeutic management of androgenetic alopecia.

BACKGROUND: Androgenetic alopecia (AGA) is a common form of scalp hair loss that affects up to 50% of males between 18 and 40 years old. Several molecules are commonly used for the treatment of AGA, acting on different steps of its pathogenesis (Minoxidil, Finasteride, Serenoa repens) and show some side effects. In literature, on the basis of hypertrichosis observed in patients treated with analogues of prostaglandin PGF2a, it was supposed that prostaglandins would have an important role in the hair growth: PGE and PGF2a play a positive role, while PGD2 a negative one. OBJECTIVE: We carried out a pilot study to evaluate the efficacy of topical cetirizine versus placebo in patients with AGA. PATIENTS AND METHODS: A sample of 85 patients was recruited, of which 67 were used to assess the effectiveness of the treatment with topical cetirizine, while 18 were control patients. RESULTS: We found that the main effect of cetirizine was an increase in total hair density, terminal hair density and diameter variation from T0 to T1, while the vellus hair density shows an evident decrease. The use of a molecule as cetirizine, with no notable side effects, makes possible a good compliance by patients. CONCLUSION: Our results have shown that topical cetirizine 1% is responsible for a significant improvement of the initial framework of AGA.

Physical performance of elite and subelite Spanish female futsal players.

The aim of this study was to determine the parameters distinguishing top female futsal players from lower level players. Twenty-seven female futsal players participated in the study, composed of professional first division (elite; n = 15) players and semi-professional second division players (sub-elite; n = 14). Active and passive straight leg raise tests, isokinetic strength of the knee extensor and flexor muscles at 60° · s(-1) angular velocity, squat and counter movement jumps, 30 m sprint, 30 m agility, repeated sprint ability test and maximum ball speed during shooting were measured. The elite players were more agile and kicked harder than sub-elite players in maximum ball speed during the shooting test (P ≤ 0.05). However, no significant differences between teams were observed in active and passive hamstring flexibility, jumping ability, repeated sprint ability test, 30 m sprint time, H/Q ratio and absolute and relative torque from 60° · s(-1) angular velocity. Based on these findings we conclude that agility and maximum ball speed during shooting may be important determinant factors of Spanish female futsal actions and could distinguish ability at high-level games.

Dissemination of thermodynamic temperature above the freezing point of silver.

The mise-en-pratique for the definition of the kelvin at high temperatures will formally allow dissemination of thermodynamic temperature either directly or mediated through high-temperature fixed points (HTFPs). In this paper, these two distinct dissemination methods are evaluated, namely source-based and detector-based. This was achieved by performing two distinct dissemination trials: one based on HTFPs, the other based on absolutely calibrated radiation thermometers or filter radiometers. These trials involved six national metrology institutes in Europe in the frame of the European Metrology Research Programme joint project 'Implementing the new kelvin' (InK). The results have shown that both dissemination routes are possible, with similar standard uncertainties of 1-2 K, over the range 1273-2773 K, showing that, depending on the facilities available in the laboratory, it will soon be possible to disseminate thermodynamic temperatures above 1273 K to users by either of the two methods with uncertainties comparable to the current temperature scale.

Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points.

The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.

Effectiveness of pelvic floor muscle training in treating urinary incontinence in women: A current review. / Efectividad del entrenamiento de la musculatura del suelo pélvico en el tratamiento de la incontinencia urinaria en la mujer: una revisión actual.

OBJECTIVE: To analyse the content of various published studies related to physical exercise and its effects on urinary incontinence and to determine the effectiveness of pelvic floor training programmes. METHOD: We conducted a search in the databases of PubMed, CINAHL, the Cochrane Plus Library, The Cochrane Library, WOS and SPORTDiscus and a manual search in the Google Scholar metasearcher using the search descriptors for documents published in the last 10 years in Spanish or English. The documents needed to have an abstract or complete text on the treatment of urinary incontinence in female athletes and in women in general. RESULTS: We selected 3 full-text articles on treating urinary incontinence in female athletes and 6 full-text articles and 1 abstract on treating urinary incontinence in women in general. The 9 studies included in the review achieved positive results, i.e., there was improvement in the disease in all of the studies. CONCLUSIONS: Physical exercise, specifically pelvic floor muscle training programmes, has positive effects on urinary incontinence. This type of training has been shown to be an effective programme for treating urinary incontinence, especially stress urinary incontinence.

The effects of intermittent hypoxia training on hematological and aerobic performance in triathletes.

The aim of the present research was to analyze modifications on hematological and aerobic performance parameters after a 7-week intermittent hypoxia training (IHT) program. Eighteen male trained triathletes were divided in two groups: an intermittent hypoxia training group (IHTG: n: 9; 26.0 ± 6.7 years; 173.3 ± 5.9 cm; 66.4 ± 5.9 kg; VO2max: 59.5 ± 5.0 ml/kg/min) that conducted a normoxic training plus an IHT and a control group (CG: n: 9; 29.3 ± 6.8 years; 174.9 ± 4.6 cm; 59.7 ± 6.8 kg; VO2max: 58.9 ± 4.5 ml/kg/min) that performed only a normoxic training. Training process was standardized across the two groups. The IHT program consisted of two 60-min sessions per week at intensities over the anaerobic threshold and atmospheric conditions between 14.5 and 15% FiO2. Before and after the 7-week training, aerobic performance in an incremental running test and hematological parameters were analyzed. After this training program, the IHTG showed higher hemoglobin and erythrocytes (p < 0.05) values than in the CG. In terms of physiological and performance variables, between the two groups no changes were found. The addition of an IHT program to normoxic training caused an improvement in hematological parameters but aerobic performance and physiological variables compared to similar training under normoxic conditions did not increase.

Effect of 6 weeks of whole body vibration training on total and segmental body composition in healthy young adults.

The applied use of new technologies to enhance performance and improve health has been increasing. Initially, whole body vibration training (WBVT) was used as system to improve elite athlete performance. However, this is also used to improve body composition, especially there is a great attention on the effectiveness of WBVT to reduce fat and body weight, with a potential increase in muscle tissue. The aim of this study was to investigate the effects of a 6-week vibration-training program on total and segmental body composition in a group of physically healthy participants. The final study sample included 64 healthy young adults. Subjects were randomly allocated into the control group (CG: n = 26; 16 males and 10 females) and the experimental group (EGWBVT: n = 38; 19 males and 19 females). The program lasted six weeks with a frequency of three sessions per week and each session varied in intensity. There were not found statistically significant differences in any of the body composition variables analysed. This study suggests that a six-week vibration-training program with an increasing intensity (7.2 g-32.6 g) in healthy young adults that are not overweight did not alter total and segmental body composition.

Aplicación del modelo de Educación Deportiva en segundo de Educación Primaria. Percepciones del alumnado y el profesorado / Sport Education model in second grade. Teachers and students’ perceptions / A aplicação do Modelo de Educação Desportiva no Segundo ano do primeiro ciclo de ensino. Perceções de alunos e professores

El presente trabajo pretende analizar la viabilidad del modelo de Educación Deportiva en segundo de Educación Primaria (7-8 años), a partir del análisis de las percepciones de una alumna en prácticas, su maestra colaboradora y los alumnos participantes, en el desarrollo de una unidad didáctica de balón prisionero. Se analizaron las percepciones de los docentesa través de entrevistas, y las de los alumnos mediante un cuestionario (Physical Education Season Survey; Mohr, Townsend, Rairigh y Mohr, 2003;Hastie y Sinelnikov, 2006) y la realización de dibujos. Los resultados mostraron percepciones muy positivas por parte de docentes y alumnos. Los resultados, en cuanto a dificultades y beneficios percibidos, coinciden conlo mostrado en la literatura tanto nacional como internacional en la percepción del modelo por parte de docentes y alumnos de mayor edad, lo cual parece indicar que el modelo de Educación Deportiva puede implementarse con éxito con alumnos de 7 años (AU)

This work analyzes the appropriateness of implementing Sport Education with second graders, through the experience of a pre-service teacher, the collaborator teacher, and students' perceptions during a teaching unit of Dodgeball conducted following the features of Sport Education. Pre-service teacher's and collaborator teacher's perceptions were analyzed through interviews. Students' perceptions were analyzed through the "Physical Education Season Survey" (Mohr, Townsend, Rairigh y Mohr, 2003; Hastie y Sinelnikov, 2006) and through drawings. Results are consistent with Spanish and international literature conducted with older students, thus, it can be conclude that Sport Education model can be appropriate for students as young as seven years old

Este trabalho analisa a viabilidade de implementar o Modelo de Educação Desportiva no Segundo ano do primeiro ciclo de ensino (7-8 anos), a partir da análise das perceções de um estudante-estagiário, do professor cooperante e dos alunos participantes numa unidade de ensino de dodgeball. As perceções dos professores foram captadas através de entrevistas e as dos alunos por meio de um questionário e da análise de desenhos (Physical Education Season Survey; Mohr, Townsend, Rairigh, y Mohr, 2003; Hastie y Sinelnikov, 2006). Os resultados mostraram que professores e alunos percecionaram ter vivido uma experiência extremamente positiva. A natureza dos benefícios percebidos e dos constrangimentos encontrados estão em concordância com achados anteriores, tanto da literatura espanhola como na internacional, sobre as perceções que professores e alunos mais velhos sustêm sobre o modelo. É fortemente sugerido que o Modelo de Educação Desportiva tem potencial para ser implementado com sucesso também com alunos na faixa etária dos 7 anos

Drug resistance of a viral population and its individual intrahost variants during the first 48 hours of therapy.

Using hepatitis C virus (HCV) and interferon (IFN) resistance as a proof of concept, we have devised a new method for calculating the effect of a drug on a viral population, as well as the resistance of the population's individual intrahost variants. By means of next-generation sequencing, HCV variants were obtained from sera collected at nine time points from 16 patients during the first 48 h after injection of IFN-α. IFN-resistance coefficients were calculated for individual variants using changes in their relative frequencies, and for the entire intrahost viral population using changes in viral titer. Population-wide resistance and presence of IFN-resistant variants were highly associated with pegylated IFN-α2a/ribavirin treatment outcome at week 12 (P = 3.78 × 10(-5) and 0.0114, respectively). This new method allows an accurate measurement of resistance based solely on changes in viral titer or the relative frequency of intrahost viral variants during a short observation time.

Whole-genome sequencing of two North American Drosophila melanogaster populations reveals genetic differentiation and positive selection.

The prevailing demographic model for Drosophila melanogaster suggests that the colonization of North America occurred very recently from a subset of European flies that rapidly expanded across the continent. This model implies a sudden population growth and range expansion consistent with very low or no population subdivision. As flies adapt to new environments, local adaptation events may be expected. To describe demographic and selective events during North American colonization, we have generated a data set of 35 individual whole-genome sequences from inbred lines of D. melanogaster from a west coast US population (Winters, California, USA) and compared them with a public genome data set from Raleigh (Raleigh, North Carolina, USA). We analysed nuclear and mitochondrial genomes and described levels of variation and divergence within and between these two North American D. melanogaster populations. Both populations exhibit negative values of Tajima's D across the genome, a common signature of demographic expansion. We also detected a low but significant level of genome-wide differentiation between the two populations, as well as multiple allele surfing events, which can be the result of gene drift in local subpopulations on the edge of an expansion wave. In contrast to this genome-wide pattern, we uncovered a 50-kilobase segment in chromosome arm 3L that showed all the hallmarks of a soft selective sweep in both populations. A comparison of allele frequencies within this divergent region among six populations from three continents allowed us to cluster these populations in two differentiated groups, providing evidence for the action of natural selection on a global scale.