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Muscle mass may play an important role in the metabolic profile of individuals with or without excess weight. Metabolic phenotypes classify individuals as healthy or unhealthy based on certain metabolic conditions. We investigated the association between skeletal mass indices (SMI) and the metabolically unhealthy phenotype in normal-weight and overweight/obese adults. A total of 660 adults aged 20 to 59 years were assessed by a population-based cross-sectional study. Muscle mass of the limbs or appendicular lean mass (ALM) adjusted for weight (SMIweight) and BMI (SMIBMI) was used to evaluate SMI. Logistic regression was employed to estimate the association between SMIweight, SMIBMI and metabolic phenotypes of normal-weight and overweight/obese individuals. Metabolically unhealthy individuals were older in both sexes. Metabolically unhealthy men had lower SMI values and higher fat percentage than metabolically healthy men. SMIweight was inversely associated with the metabolically unhealthy phenotype, both in normal-weight men (OR 0·49, 95 % CI 0·24, 0·99, P = 0·04) and in overweight/obese men (OR 0·32, 95 % CI 0·16, 0·64, P = 0·001). SMIBMI was inversely associated with the metabolically unhealthy phenotype in overweight/obese men (OR 0·36, 95 % CI 0·18, 0·72, P = 0·004), but not in normal-weight men (OR 0·70, 95 % CI 0·34, 1·43, P = 0·33). Among women, SMI showed no significant association with the phenotypes. In conclusion, the SMI are inversely associated with the metabolically unhealthy phenotype in men, especially among overweight/obese men.
The work reported in this research communication investigated the occurrence of Mycoplasma bovis (M. bovis) in milk samples from cows with clinical mastitis on dairy farms from seven Brazilian states. We hypothesized that M. bovis was present in bovine clinical mastitis milk in Brazil. A total of 561 milk samples were cultured on Hayflick agar and incubated in a microaerophilic atmosphere at 5% CO2. Polymerase chain reaction (PCR) was performed for the detection of Mycoplasma spp. and Mycoplasma bovis in milk samples. Mycoplasma spp. were isolated in 2% of the milk samples, and Mycoplasma bovis was verified in 3% of the milk samples by PCR. The results showed that Mycoplasma bovis is involved in clinical mastitis in Brazilian dairy herds. We emphasize the need for further studies to investigate the infection by this agent in clinical mastitis cases, particularly in Brazil, due to the lack of knowledge about its prevalence.
Introduction: Inhaled toxins from tobacco smoking, cannabis leaf smoking as well as vaping/e-cigarette products use are known causes of cardio-respiratory injury. While tobacco smoking has decreased among Canadian adults, there are now several other forms of legal inhalant products. While legal, the evidence of benefit and safety of vaping is limited. Of concern, cases of e-cigarette or vaping products use associated lung injury (EVALI) have been accumulating in the U.S. and now in Canada. Despite this, very little is known about the inhalation exposure of emergency department (ED) patients; this study was designed to explore lung health in the ED. Methods: We investigated the prevalence of exposure to vaping, tobacco and cannabis among patients presenting to a Canadian ED from July to November 2019. Ambulatory (CTAS 2 to 5), stable, adult (≥ 17 years) patients were prospectively identified and invited to complete a survey addressing factors related to lung health (previous diagnosis of respiratory conditions and respiratory symptoms at the ED presentation) and information on current exposure to vaping, tobacco and cannabis smoking. Categorical variables are reported as frequencies and percentages; continuous variables are reported as medians with interquartile range (IQR). The study was approved by the Health Research Ethics Board. Results: Overall, 1024 (71%) of 1433 eligible patients completed the survey. The median age was 43.5 (IQR: 29, 60), and 51% were female. A total of 351 (31%) participants reported having been previously diagnosed with ≥1 respiratory conditions, and 177 (17%) were visiting the ED as a result of ≥1 respiratory symptoms (e.g., cough, shortness of breath, wheezing). Daily tobacco smoking was reported by 190 (19%), and 83 (8%) reported using vaping/e-cigarette products. Cannabis use within 30 days was described by 80 (15%) respondents. Exposure to tobacco and vaping products was reported by 39 (4%) participants, 63 (6%) reported using tobacco in combination with cannabis smoking, and 3% reported combining vaping and cannabis use. Conclusion: Patients seeking care in the ED are exposed to a large quantity of inhaled toxins. Vaping products, considered the cause of the most recent epidemic of severe lung injury, are used in isolation and in combination with other smoking products in Canada. These exposures should be documented and may increase the risk of lung health injuries and exacerbations of chronic respiratory conditions.
Introduction: Management of acute atrial fibrillation or flutter (AFF) in the emergency department (ED) can be performed with chemical or electrical cardioversion. Procainamide is the most common chemical agent used in Canada; however, there is substantial practice variation. The objective of this systematic review was to provide comparative evidence on return to normal sinus rhythm (NSR) and adverse events to better support clinical decisions. Methods: Systematic search of five electronic databases and grey literature. Randomized controlled trials (RCTs) and prospective controlled cohort studies including adults (≥17 years) with recent-onset of AFF comparing intravenous procainamide with other cardioversion strategies (e.g., electrical cardioversion, placebo or other antiarrhythmic drugs) were eligible. Two independent reviewers performed study selection and data extraction. Relative risks (RR) with 95% confidence intervals (CIs) were calculated using a random-effects model. The protocol was registered with PROSPERO (CRD42019142080). Results: From 4060 potentially relevant citations, 7 studies were considered eligible and three RCTs and two cohort studies included in the analysis. Procainamide was less effective in promoting return to NSR at 1st attempt compared to other chemical (RR 0.76; 95% CI: 0.65 to 0.90) and electrical (RR 0.58; 95% CI: 0.53 to 0.64) options. Electrical cardioversion was more effective in restoring NSR compared to procainamide when used as 2nd attempt in one RCT (RR 0.46; 95% CI: 0.23 to 0.92). Pre-specified serious adverse events were assessed and reported by two studies showing that hypotension was more common in patients receiving procainamide in comparison with electrical cardioversion (RR 20.57; 95% CI: 1.59 to 265.63). Treatment discontinuation due to adverse events was infrequently reported with only two studies reporting that no patients withdrew from the study following treatment with procainamide. The remaining studies provided incomplete data reporting on adverse events. Conclusion: Shared decision-making for patients with acute AFF in the ED requires knowledge of the effectiveness and safety of comparative interventions. Overall, procainamide is less effective than other chemical options and electrical cardioversion strategies to restore NSR. Evidence shows that hypotension is a concern when procainamide is administered; however, the overall adverse events information provided from the studies is suboptimal.
Introduction: Patients frequently present to the Emergency Department (ED) with predictable complications associated with radiation and chemotherapy for active cancer. Care alternatives have been proposed to reduce ED visits; however, no systematic review related to ED presentations has been completed. The objective of this scoping review was to examine the effectiveness of interventions designed to reduce ED visits among patients receiving active cancer treatment. Methods: A comprehensive literature search involving nine electronic databases and the grey literature was completed. Inclusion criteria considered studies assessing the impact of any intervention to reduce ED utilization among patients with active cancer. Two reviewers independently assessed relevance and inclusion; disagreements were resolved through third party adjudication. Dichotomous and continuous outcomes were summarized as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CIs) using a random-effects model, wherever appropriate. Results: From 3303 citations, a total of 25 studies were included. Interventions identified in these studies comprised: routine and symptom-based patient follow-up, oncology outpatient clinics, early symptom detection, comprehensive inpatient management, hospital at home, and patient navigators. Six out of eight studies assessing oncology outpatient clinics reported a decrease in the proportion of patients presenting to the ED. A meta-analysis of three of these studies did not demonstrate reduction in ED utilization (RR 0.78; 95% CI: 0.56 to 1.08; I2 = 77%) when comparing oncology outpatient clinics to standard care; however, sensitivity analysis removing one study reporting rare events supported a decrease in ED visits (RR 0.86; 95% CI: 0.74 to 0.99; I2 = 47%). Three studies assessing patient follow-up interventions showed no difference in ED utilization (RR 0.69; 95% CI: 0.38 to 1.25; I2 = 86%). Conclusion: A variety of interventions designed to mitigate ED presentations by patients receiving active cancer treatment have been developed and evaluated. Limited evidence suggests that an oncology outpatient clinic may be an effective strategy to reduce ED utilization; however, additional high-quality studies are needed.
Introduction: Despite being legal in Canada, the vaporized liquid of vaping systems contains several chemicals presenting unknown risks to lung health and little is known about their use in patients visiting the emergency department (ED). This study explores associations between exposure to inhaled products and respiratory presentations in the ED. Methods: A cross-sectional lung health survey among patients presenting to a Canadian ED was conducted, exploring the association between inhaled toxic exposures (e.g., vaping, cannabis and cigarette smoking) and visits related to respiratory symptoms. Eligible participants were ambulatory (CTAS 2 to 5), stable, adults (≥ 17 years) visiting the ED from July to November, 2019. Results are described as frequencies and percentages (categorical variables) and medians with interquartile range (IQR, continuous variables). Univariate and multivariate logistic regression models report associations as odds ratios (OR) with 95% confidence intervals (CIs). The Health Research Ethics Board approved the study. Results: From 1433 eligible patients, 1024 (71%) completed the survey. The median age was 43.5 (IQR: 29, 60), and 51% were female. Overall, 177 (17%) reported ≥1 respiratory symptoms and 83 (8%) reported using any vaping products. In a univariate regression analysis, exposure to vaping was positively associated with ED visits related to respiratory symptoms (OR 2.11, 95% CI: 1.26 to 3.54). In the multivariate model, vaping and a previous diagnosis of ≥1 respiratory conditions showed positive association with respiratory-related ED visits (OR 1.86, 95% CI: 1.03 to 3.33; and OR 2.13, 95% CI: 1.50 to 3.02, respectively). There was evidence of an additive effect of the combined exposure to cigarettes and vaping and respiratory-related ED visits (OR 3.22, 95% CI: 1.61 to 6.43). Smoking cannabis and cigarettes alone were not associated with increased risk of respiratory-related visits. Conclusion: Using vaping products increased the occurrence of respiratory-related ED visits, particularly in people with pre-existing lung conditions. A dose-response relationship exists where the risk is highest in patients inhaling a combination of toxins. Contrary to previous assumptions, the use of vaping products has a negative impact on lung health.
Introduction: Acute migraine headaches are common causes of presentation to the emergency department (ED). There is great variability in the efficacy of the available parenteral agents to manage pain, though triptans are among the recommended treatments. The objective of this systematic review was to update a previous review examining the effectiveness of parenteral agents for the treatment of acute migraine in the ED or equivalent acute care setting; our review examined pain management in emergency settings and assessed the effectiveness of triptan agents. Methods: A comprehensive search of 10 electronic databases and grey literature was conducted to supplement the previous systematic review. Two independent reviewers completed study selection, quality assessment, and data extraction. Any discrepancies were resolved by third party adjudication. Pain scale scores were analyzed using standardized mean difference (SMD) with 95% confidence intervals (CIs) calculated using a random effects model; heterogeneity (I2) was reported. Results: Titles and abstracts of 5039 unique studies were reviewed, of which, 51 studies were included. Sixty-four studies from the original review were included, resulting in a total of 115 included studies. Pain was measured within the ED or equivalent acute care setting using a variety of pain scales, most commonly the 0-10 cm or 100 mm visual analog scale. Four studies compared pain scores between patients receiving sumatriptan vs. other agents, of which, patients receiving sumatriptan reported higher pain scale scores (SMD = 0.53; 95% CI: 0.04, 1.02; I2 = 80%). In particular, patients receiving sumatriptan reported higher pain scale scores than patients receiving metoclopramide (SMD = 0.68; 95% CI: 0.31, 1.04; n = 1) or ketorolac (SMD = 1.39; 95% CI: 0.56, 2.21; n = 1). Overall, studies comparing anti-inflammatory agents (i.e., ketorolac or dexketoprofen) to other agents reported improved pain scale scores among patients receiving anti-inflammatory agents (SMD = -0.38; 95% CI: -0.73, -0.03; I2 = 66%; n = 5). Conclusion: Limited evidence suggests that patients treated with metoclopramide or anti-inflammatory agents experience greater pain reduction compared to patients treated with sumatriptan. This review will conduct a network analysis of parenteral agents to examine the comparative effectiveness of parenteral agents to manage pain among patients with acute migraine. Further analysis will also consider the balance between efficacy and adverse events.
Introduction: Although a variety of parenteral agents exist for the treatment of acute migraine, relapse after an emergency department (ED) visit is still a common occurrence. The objective of this systematic review was to update a previous review examining the effectiveness of parenteral agents for the treatment of acute migraine in the ED or equivalent acute care setting; our review focused on those studies aiming a reduction in relapse after an ED visit. Methods: A comprehensive search of 10 electronic databases and grey literature was conducted to identify comparative studies to supplement the previous systematic review. Two independent reviewers completed study selection, quality assessment, and data extraction. Any discrepancies were resolved by third party adjudication. Relative risks (RR) with 95% confidence intervals (CIs) were calculated using a random effects model and heterogeneity (I2) was reported. Results: Titles and abstracts of 5039 unique studies were reviewed, of which, 51 studies were included. Sixty-four studies from the original review were included, resulting in a total of 115 included studies. Relapse was reported in 44 (38%) included studies and occurred commonly in patients receiving placebo or no interventions (median = 39%; IQR: 14%, 47%). Overall, no differences in headache relapse were found between patients receiving sumatriptan or placebo (RR = 1.09; 95% CI: 0.55, 2.17; I2 = 93%; n = 8). Conversely, patients receiving neuroleptic agents experienced fewer relapses compared to placebo (RR = 0.27; 95% CI: 0.12, 0.58; I2 = 0%; n = 3); however, patients receiving neuroleptics reported an increase in adverse events (RR = 1.87; 95% CI: 1.17, 3.00; I2 = 0%; n = 3). Compared to placebo, patients receiving dexamethasone were less likely to experience a headache recurrence (RR = 0.71; 95% CI: 0.53, 0.95; I2 = 60%, n = 9); however, no differences were found in reported adverse events (RR = 1.09; 95% CI: 0.81, 1.47; I2 = 0%; n = 3). Conclusion: Relapse is a common occurrence for patients with migraine headaches. This review found patients receiving neuroleptics or dexamethasone experienced fewer headache recurrences. Conversely, triptan agents appear to have minimal effect on reducing the risk for headache recurrence following discharge from an acute care setting. Limited available data on adverse events is an important limitation to inform decision-making. Guidelines should be revised to reflect these results.
Sourdough fermentation is considered to have beneficial effects on postprandial satiety and metabolic responses, but studies demonstrating effects at physiological conditions are lacking. The aim of this acute breakfast intervention study was to determine the effect of consumption of sourdough-fermented and unfermented rye crispbread on self-rated appetite, postprandial glucose and insulin response in healthy subjects. In all, twenty-four Swedish adults were included in a single-blinded, randomised cross-over trial. Three crispbreads (sourdough-fermented and unfermented whole grain rye and yeast-fermented refined wheat as control) were consumed as part of a standardised breakfast. Subjective appetite score, assessed using visual analogue scale, and plasma glucose and insulin concentrations were measured at baseline and postprandially until 360 and 240 min, respectively. Structural changes and viscosity during mastication and gastric digestion were investigated using in vitro methods. Hunger and desire to eat were lower (P<0·05) based on AUC measurements after intake of sourdough-fermented rye crispbread compared with after intake of yeast-fermented refined wheat crispbread. On the basis of AUC (0–230 min), insulin response was lowest after intake of unfermented rye crispbread compared with sourdough-fermented rye and yeast-fermented refined wheat crispbread. Degradation of viscous fibres and faster bolus disintegration for the sourdough-fermented bread may partly explain the less favourable metabolic responses compared with unfermented bread. Our results showed that food processing affects the composition and structural characteristics of rye bread, which has implications for appetite and metabolic responses.
In chemodynamical evolution models it is usually assumed that the Milky Way galaxy forms from the inside-out implying that gas inflows onto the disk decrease with galactocentric distance. Similarly, to reproduce differences between chemical abundances of the thick disk and bulge with respect to those of the thin disk, higher accretion fluxes at early times are postulated. By using a suite of Milky Way-like galaxies extracted from cosmological simulations, we investigate the accretion of gas on the simulated stellar disks during their whole evolution. In general, we find that the picture outlined above holds, although the detailed behavior depends on the assembly history of the Galaxy and the complexities inherent to the physics of galaxy formation.
The Brazilian Twin Registry (BTR) was established in 2013 and has impelled twin research in South America. The main aim of the initiative was to create a resource that would be accessible to the Brazilian scientific community as well as international researchers interested in the investigation of the contribution of genetic and environmental factors in the development of common diseases, phenotypes, and human behavior traits. The BTR is a joint effort between academic and governmental institutions from Brazil and Australia. The collaboration includes the Federal University of Minas Gerais (UFMG) in Brazil, the University of Sydney and University of Melbourne in Australia, the Australian Twin Registry, as well as the research foundations CNPq and CAPES in Brazil. The BTR is a member of the International Network of Twin Registries. Recruitment strategies used to register twins have been through participation in a longitudinal study investigating genetic and environmental factors for low back pain occurrence, and from a variety of sources including media campaigns and social networking. Currently, 291 twins are registered in the BTR, with data on demographics, zygosity, anthropometrics, and health history having been collected from 151 twins using a standardized self-reported questionnaire. Future BTR plans include the registration of thousands of Brazilian twins identified from different sources and collaborate nationally and internationally with other research groups interested on twin studies.
Specimens of Fissidentalium candidum collected at Campos Basin, south-eastern Brazil, had their diet investigated in order to assess its feeding habits. Benthic prey exceeded the planktonic ones as expected and Foraminifera constituted the most frequent prey taxa, comprising about 99.5% of the scaphopod diet; the remaining components included a few molluscs (gastropods, bivalves and scaphopods), a nematode, an ostracod crustacean, fish otoliths, unknown partial organisms and inorganic material (e.g. sediment grains and polymetallic nodules). Amongst the species previously studied, F. candidum stood out by presenting the highest dietary diversity (H = 3.35) and species richness (N = 118). Predator and prey dimensions were not correlated and no spatial variation was observed in the diet amongst the three collection sites in the mid-slope of Campos Basin. Generalism, high rate of rare or unimportant species and high contribution of within-phenotype component to the niche width were important features of the trophic ecology of F. candidum. Inhabiting the deep water of Campos Basin, this dentaliid obtained most of its energy from the benthic microfauna, being a specialized foram predator with moderate preference for, and moderate selection against, several species.
Crude glycerin, a potential energy source for ruminant animals, has been evaluated, mainly, in diets with high starch content. However, a limit number of studies have evaluated the inclusion of crude glycerin in low starch diets. This study aimed to evaluate the effects of the association of crude glycerin with corn grain or citrus pulp on carcass traits and meat quality of Nellore bulls (n=30, 402±31 kg initial weight). The treatment consisted of: CON=control, without crude glycerin; CG10=10% of crude glycerin and corn grain; CG15=15% of crude glycerin and corn grain; CP10=10% of crude glycerin and citrus pulp; CP15=15% of crude glycerin and citrus pulp. The performance parameters and carcass traits were not affected by treatments (P>0.05). The inclusion of crude glycerin decreased yellow color intensity and increased fatty acids pentadecanoic and heptadecenoic in meat (P<0.05), without affecting neither the concentration of polyunsaturated fatty acids nor the relationship of saturated and unsaturated fatty acids. The association of crude glycerin with corn or citrus pulp has no adverse effects on carcass characteristics and meat quality.
Government regulations have created new markets for non-timber forest products such as tropical forest seeds for ecological restoration and agroforestry in Brazil. This paper examines whether and how participation in the seed market has affected assets that will shape households’ ability to pursue new livelihood opportunities. These impacts may vary across different dimensions of capital and among sociocultural groups. Impacts were characterized through semi-structured interviews following the sustainable livelihoods approach; 40 producers in the Xingu Seed Network, from settler farmer, urban and indigenous groups, were interviewed. The groups differed in perceptions of impacts on their natural, social and human capital, which could be related to the sociocultural background and vulnerability context of each group. Communities that were already organized were most likely to strengthen their social capital through participation. Cash income earned from sale of seeds was correlated with household-reported gains in financial capital, but not correlated with changes in other dimensions of capital. Contrary to expectations, sociocultural groups less integrated with the market achieved better livelihood outcomes through participation in the seed market.
The objective of this work was to estimate genetic parameters for a measure of persistency of milk yield and to evaluate its association with 305-d cumulative milk yield and lactation length. 12 346 records from 8202 dairy Gyr cows including lactations up to fifth calving were used. The measure of persistency was obtained from one of the parameters of a quadratic model that describes the cumulative yield across lactation as a function of days in milk. A three-trait multivariate analysis was done. Heritability and repeatability for persistency were 0·08 and 0·21, respectively. Deviance Information Criterion provided evidence that the additive genetic covariance between the measure of persistency studied and 305-d cumulative yield is zero. Genetic correlations between persistency and lactation length were 0·50 and 0·27 for first or all lactations, respectively. Milk yield persistency as measured in this study has low heritability. Selection for persistency can increase lactation length. The measure of milk yield persistency studied here is genetically independent of total milk yield and can be included in routine genetic evaluations of dairy cattle.
In order to understand the Barium abundance distribution in the Galactic disk based on Cepheids, one must first be aware of important effects of the corotation resonance, situated a little beyond the solar orbit. The thin disk of the Galaxy is divided in two regions that are separated by a barrier situated at that radius. Since the gas cannot get across that barrier, the chemical evolution is independent on the two sides of it. The barrier is caused by the opposite directions of flows of gas, on the two sides, in addition to a Cassini-like ring void of HI (caused itself by the flows). A step in the metallicity gradient developed at corotation, due to the difference in the average star formation rate on the two sides, and to this lack of communication between them. In connection with this, a proof that the spiral arms of our Galaxy are long-lived (a few billion years) is the existence of this step. When one studies the abundance gradients by means of stars which span a range of ages, like the Cepheids, one has to take into account that stars, contrary to the gas, have the possibility of crossing the corotation barrier. A few stars born on the high metallicity side are seen on the low metallicity one, and vice-versa. In the present work we re-discuss the data on Barium abundance in Cepheids as a function of Galactic radius, taking into account the scenario described above. The [Ba/H] ratio, plotted as a function of Galactic radius, apparently presents a distribution with two branches in the external region (beyond corotation). One can re-interpret the data and attribute the upper branch to the stars that were born on the high metallicity side. The lower branch, analyzed separately, indicates that the stars born beyond corotation have a rising Barium metallicity as a function of Galactic radius.
To evaluate the association between food and nutrition insecurity and asthma in children from Latin America.
São Francisco do Conde, Bahia, north-eastern Brazil.
The study included 1307 children aged 6–12 years from public elementary schools. Asthma symptoms were collected using a questionnaire that was translated and adapted from the International Study of Asthma and Allergies in Childhood, phase III. The diagnosis of asthma was determined based on reports of wheezing in the previous 12 months. The Brazilian Food Insecurity Scale was used to identify food insecurity. We also obtained demographic, socio-economic and anthropometric information for each participant. We used multivariate logistic regression analyses to assess the associations of interest.
Of the children surveyed, 10·4 % had a history of wheezing and 64·5 % had some degree of food and nutrition insecurity. We found a positive dose–response relationship and statistically significant associations of asthma with moderate (OR = 1·71, 95 % CI 1·01, 2·89) and severe (OR = 2·51, 95 % CI 1·28, 4·93) food and nutrition insecurity.
The results show that moderate and severe food and nutrition insecurity are markers of vulnerability to wheezing. It is important to note that the results of studies in this field have potential implications for social policies that promote food security. Further studies to identify the mechanisms involved in the relationship between food and nutrition insecurity and asthma are needed.
Resonances play an important role in the evolution of the disks of spiral galaxies, and in particular in the chemical abundance evolution. The dominant effect is that of corotation; this effect can be even used as a tool to estimate the age of the present spiral arm pattern, which are usually found to be long-lived, contrary to a recent common belief. We investigated a sample of galaxies for which the corotation radius is known and for which there are available in the literature measurements of abundance gradients for Oxygen. A very good correlation is found between corotation radii and the radii at which there is a break in the slope of the gradients. The gradients are usually decreasing in the inner regions and become flat or rising at larger radii. In several galaxies, including the Milky Way, one observes not only a change in the slope of the abundance gradient, but also an abrupt step in metallicity, at corotation. This step is due to the fact that corotation separates the disk of a galaxy in two regions (inside corotation and outside corotation) which are isolated one from the other, so that the two sides evolve in an independent way. The barrier between the two regions is produced by the flow of gas in opposite directions in the two sides and by the ring-shaped void of gas observed at corotation. Besides this, an independent effect of corotation is a minimum of star formation associated with the minimum velocity at which the spiral arms (seen as potential wells) are fed with interstellar gas. Still another effect is the scattering of stars by the resonance, which causes their migration to different galactic radii. Other resonances, like 4:1, have properties almost opposite to corotation; they stimulate star-formation, and tend to gather the stars in the resonant orbit, instead of scattering them out, as shown by numerical simulations. Due to this property, one can see arms which have the shape of resonant stellar orbits, which depart from logarithmic spirals.