149 research outputs found
Community Biodiversity Management: Promoting resilience and the conservation of plant genetic resources
This book is the first to set out a clear overview of CBM as a methodology for meeting socio-environmental changes. CBM is shown to be a key strategy that promotes community resilience, and contributes to the conservation of plant genetic resources. The authors present the underlying concepts and theories of CBM as well as its methodology and practices, and introduce case studies primarily from Brazil, Ethiopia, France, India, and Nepal. Contributors include farmers, leaders of farmers’ organizations, professionals from conservation and development organizations, students and scientists
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Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion
Animals modulate the power output needed for different locomotor tasks through changes in muscle force production and fascicle strain rate. To generate sufficient force, appropriate motor unit recruitment must occur. Given that faster motor units contract with faster strain rates and have faster activation-deactivation rates, it is therefore likely that faster motor units are recruited for more rapid movements. The goals of this study were to 1) describe changes in motor unit recruitment patterns that occur with changes in locomotor dynamics and 2) test whether motor unit recruitment can be directly related to in vivo measures of muscle force and fascicle strain and strain rate, and thus mechanical work. Myoelectric, sonomicrometric, and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of the goat hind limb during level and incline walking and trotting, and level galloping. Myoelectric signals were analyzed using wavelet and principal component analysis in order to quantify changes to the myoelectric frequency spectra across locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rate was calculated from the tendon force data. The results of this study demonstrate that, under certain locomotor conditions such as level galloping and incline walking, where EMG activity were similar but had different frequency components, faster and slower motor units are recruited in patterns that were task-specific. The study also shows that the recruitment patterns of different motor unit types are related to in vivo fascicle strain rates in addition to myoelectric intensity and force. Together, these data provide evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks.Organismic and Evolutionary Biolog
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A Muscle’s Force Depends on the Recruitment Patterns of Its Fibers
Biomechanical models of whole muscles commonly used in simulations of musculoskeletal function and movement typically assume that the muscle generates force as a scaled-up muscle fiber. However, muscles are comprised of motor units that have different intrinsic properties and that can be activated at different times. This study tested whether a muscle model comprised of motor units that could be independently activated resulted in more accurate predictions of force than traditional Hill-type models. Forces predicted by the models were evaluated by direct comparison with the muscle forces measured in situ from the gastrocnemii in goats. The muscle was stimulated tetanically at a range of frequencies, muscle fiber strains were measured using sonomicrometry, and the activation patterns of the different types of motor unit were calculated from electromyographic recordings. Activation patterns were input into five different muscle models. Four models were traditional Hill-type models with different intrinsic speeds and fiber-type properties. The fifth model incorporated differential groups of fast and slow motor units. For all goats, muscles and stimulation frequencies the differential model resulted in the best predictions of muscle force. The in situ muscle output was shown to depend on the recruitment of different motor units within the muscle.Organismic and Evolutionary Biolog
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Accuracy of gastrocnemius muscles forces in walking and running goats predicted by one-element and two-element Hill-type models
Hill-type models are commonly used to estimate muscle forces during human and animal movement —yet the accuracy of the forces estimated during walking, running, and other tasks remains largely unknown. Further, most Hill-type models assume a single contractile element, despite evidence that faster and slower motor units, which have different activation-deactivation dynamics, may be independently or collectively excited. This study evaluated a novel, two-element Hill-type model with “differential” activation of fast and slow contractile elements. Model performance was assessed using a comprehensive data set (including measures of EMG intensity, fascicle length, and tendon force) collected from the gastrocnemius muscles of goats during locomotor experiments. Muscle forces predicted by the new two-element model were compared to the forces estimated using traditional one-element models and to the forces measured in vivo using tendon buckle transducers. Overall, the two-element model resulted in the best predictions of in vivo gastrocnemius force. The coefficient of determination, r2, was up to 26.9% higher and the root mean square error, RMSE, was up to 37.4% lower for the two-element model than for the one-element models tested. All models captured salient features of the measured muscle force during walking, trotting, and galloping (r2 = 0.26 to 0.51), and all exhibited some errors (RMSE = 9.63 to 32.2% of the maximum in vivo force). These comparisons provide important insight into the accuracy of Hill-type models. The results also show that incorporation of fast and slow contractile elements within muscle models can improve estimates of time-varying, whole muscle force during locomotor tasks.Organismic and Evolutionary Biolog
How Strong Do Global Commodity Prices Influence Domestic Food Prices in Developing Countries? A Global Price Transmission and Vulnerability Mapping Analysis
This paper analyzes the transmission from global commodity to domestic food prices for a large set of countries. First, a theoretical model is developed to explain price transmission for different trade regimes. Drawing from the competitive storage model under rational expectations, it is shown that domestic prices can respond instantaneously to global prices even if no trade takes place but future trade is expected. Using a global database on food prices, we construct national and international grain price indices. With an autoregressive distributed lag model, we empirically detect countries in which food prices are influenced by global commodity prices, including futures prices. Mapping transmission elasticities with the size of the population below the poverty line which spends typically a large share of its income on food, we are able to estimate the size of vulnerable population. Our empirical analysis reveals that 90 percent of the global poor (income below 1.25$/day) live in countries where domestic food prices respond to international prices - but the extent of transmission varies substantially. For 360 million poor people, international prices transmit to their country at rates of 30 percent or higher within three months
Socioeconomic Status Is Associated With Antibody Levels Against Vaccine Preventable Diseases in the Netherlands.
Background: We investigated whether low socioeconomic status (SES), which is associated with reduced health and life expectancy, might play a role in increased risk for infectious diseases. Therefore, we explored the association between SES and immunoglobulin G (IgG) levels against various pathogens. Methods: We analyzed the association between SES [educational level and net household income (NHI)] and serum IgG concentration against measles, mumps, rubella, varicella, Haemophilus influenzae type B (HiB), pneumococcus, meningococcus serogroup C (MenC), and cytomegalovirus (CMV) collected within a national cross-sectional serosurvey (2006/2007) using linear regression analyses among non-vaccinated individuals. Results: Higher educational level was associated with higher IgG concentrations against measles (GMC ratio 1.34, 95% CI 1.18-1.53) and rubella (1.13, 1.02-1.25) compared to low education level. In contrast, higher education level was associated with lower IgG concentrations against pneumococcus (0.78, 0.70-0.88), MenC (0.54, 0.44-0.68), and CMV (0.23, 0.18-0.31) compared to low education level. This pattern was also evident when NHI was used as SES indicator. Conclusion: Our study suggests that socioeconomic status is associated with antibody levels in a pathogen-dependent manner. The results suggest that differences in serological response upon infection or differences in exposure might be involved in the variation in IgG levels between SES groups
Non-specific effects of measles, mumps, and rubella (MMR) vaccination in high income setting: population based cohort study in the Netherlands.
Objectives To investigate whether measles, mumps, and rubella (MMR) vaccine has positive non-specific effects in a high income setting and to compare rates of hospital admissions for infections between children aged ≤2 years who received live MMR vaccine and those who received an inactivated vaccine against diphtheria, tetanus, pertussis, polio, and Haemophilus influenzae type b (DTaP-IPV-Hib) as their most recent vaccination.Design Nationwide population based cohort study.Setting In the Netherlands, DTaP-IPV-Hib+pneumococcal vaccination (PCV) is recommended at ages 2, 3, 4, and 11 months and MMR + meningococcal C (MenC) vaccination at age 14 months. Data from the national vaccine register were linked to hospital admission data.Participants 1 096 594 children born in 2005-11 who received the first four DTaP-IPV-Hib+PCV vaccines.Main outcome measures Hazard ratio for admission to hospital for infection in children with MMR+MenC compared with the fourth DTaP-IPV-Hib+PCV as their most recent vaccination. Cox regression was performed with most recent vaccination as time dependent variable, adjusted for potential confounders. Analyses were repeated with admission for injuries or poisoning as a negative control outcome. In addition, rate of admission for infection was compared between the fourth and third DTaP-IPV-Hib+PCVas most recent vaccination.Results Having had MMR+MenC as the most recent vaccination was associated with a hazard ratio of 0.62 (95% confidence interval 0.57 to 0.67) for admission to hospital for infection and 0.84 (0.73 to 0.96) for injuries or poisoning, compared with the fourth DTaP-IPV-Hib+PCV as most recent vaccination. The fourth DTaP-IPV-Hib+PCV as most recent vaccination was associated with a hazard ratio of 0.69 (0.63 to 0.76) for admission to hospital for infection, compared with the third DTaP-IPV-Hib+PCV as most recent vaccination.Conclusions Healthy vaccinee bias could at least partly explain the observed lower rate of admission to hospital with infection after MMR vaccination. The lower rate is associated with receipt of any additional vaccine, not specifically MMR vaccine. This emphasises the caution required in the interpretation of findings from observational studies on non-specific effects of vaccination
Early adversity predicts adoptees’ enduring emotional and behavioral problems in childhood
Children adopted from the public care system are likely to experience a cluster of inter-related risk factors that place them on a trajectory of mental health problems that persist across the life course. However, the specific effects of putative risk factors on children’s mental health post-placement are not well understood. We conducted a prospective, longitudinal study of children placed for adoption between 2014 and 2015 (N = 96). Adoptive parents completed questionnaires at approximately 5-, 21-, 36-, and 48 months post-placement. We used time series analysis to examine the impact of pre-adoptive risk factors (adverse childhood experiences [ACEs], number of moves, days with birth parents and in care) on children’s internalizing and externalizing problems, and prosocial behaviour over four years post-placement. Adoptees’ internalizing and externalizing problems remained consistently high over the four-year study period but more ACEs predicted increases in internalizing and externalizing problems. Contrary to expectations, more pre-placement moves and time in care predicted fewer problems over time, but exploratory analyses of interactive effects revealed this was only the case in rare circumstances. We identify pre- and post-removal factors that may incur benefits or have a deleterious impact on adoptees’ outcomes in post-adoptive family life. Our findings provide knowledge for front-line professionals in the support of adoptive families and underscore the vital need for effective early intervention
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