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1.
The neglected tropical diseases (NTDs) represent some of the most common infections of the poorest people living in the Latin American and Caribbean region (LAC). Because they primarily afflict the disenfranchised poor as well as selected indigenous populations and people of African descent, the NTDs in LAC are largely forgotten diseases even though their collective disease burden may exceed better known conditions such as of HIV/AIDS, tuberculosis, or malaria. Based on their prevalence and healthy life years lost from disability, hookworm infection, other soil-transmitted helminth infections, and Chagas disease are the most important NTDs in LAC, followed by dengue, schistosomiasis, leishmaniasis, trachoma, leprosy, and lymphatic filariasis. On the other hand, for some important NTDs, such as leptospirosis and cysticercosis, complete disease burden estimates are not available. The NTDs in LAC geographically concentrate in 11 different sub-regions, each with a distinctive human and environmental ecology. In the coming years, schistosomiasis could be eliminated in the Caribbean and transmission of lymphatic filariasis and onchocerciasis could be eliminated in Latin America. However, the highest disease burden NTDs, such as Chagas disease, soil-transmitted helminth infections, and hookworm and schistosomiasis co-infections, may first require scale-up of existing resources or the development of new control tools in order to achieve control or elimination. Ultimately, the roadmap for the control and elimination of the more widespread NTDs will require an inter-sectoral approach that bridges public health, social services, and environmental interventions.  相似文献   

2.

Background

An estimated 1.86 million people are living with HIV in Latin America and the Caribbean (LAC). The region is comprised of mainly middle-income countries with steady economic growth while simultaneously there are enormous social inequalities and several concentrated AIDS epidemics. This paper describes HIV spending patterns in LAC countries including analysis of the levels and patterns of domestic HIV spending from both public and international sources.

Methods and Findings

We conducted an extensive analysis of the most recently available data from LAC countries using the National AIDS Spending Assessment tool. The LAC countries spent a total of US$ 1.59 billion on HIV programs and services during the latest reported year. Countries providing detailed information on spending showed that high percentages are allocated to treatment and care (75.1%) and prevention (15.0%). Domestic sources accounted for 93.6 percent of overall spending and 79 percent of domestic funds were directed to treatment and care. International funds represented 5.4 percent of total HIV funding in the region, but they supplied the majority of the effort to reach most-at-risk-populations (MARPs). However, prevalence rates among men who have sex with men (MSM) still reached over 25 percent in some countries.

Conclusions

Although countries in the region have increasingly sustained their response from domestic sources, still there are future challenges: 1) The growing number of new HIV infections and more people-living-with-HIV (PLWH) eligible to receive antiretroviral treatment (ART); 2) Increasing ART coverage along with high prices of antiretroviral drugs; and 3) The funding for prevention activities among MARPs rely almost exclusively on external donors. These threats call for strengthened actions by civil society and governments to protect and advance gains against HIV in LAC.  相似文献   

3.
The vaccine global market is currently growing at a rate of 16.52%. Nowadays the vaccine manufacturing industry is limited in the sense that not all vaccine manufacturers have the capacity to execute all the steps necessary to produce a successful product. The biological variation inherent to vaccine manufacturing and the initial investment required to bring a vaccine to the market are some of the factors that discourage vaccine manufacturing initiatives.Given the current global context in vaccine innovation and production, and the increasing participation of vaccine manufacturers from developing countries in global markets, this paper aims to review vaccine manufacturing capacity in Latin American and Caribbean (LAC) countries with specific focus on trends in national or public sector manufacturing, presenting current challenges and future opportunities for the sector in meeting national and regional (LAC) needs.Despite the overall low vaccine manufacturing capacity reported within the LAC region within this paper, it is considered that the relatively high and concentrated capacity that exists within a number of countries, combined with political commitment of all countries within the Region, can provide the necessary platform for the continued development of capacity in vaccine development and manufacture within LAC.  相似文献   

4.

Background

Limited knowledge on the prevalence and distribution of risk factors impairs the planning and implementation of cardiovascular prevention programs in the Latin American and Caribbean (LAC) region.

Methods and Findings

Prevalence of hypertension, diabetes mellitus, abnormal lipoprotein levels, obesity, and smoking were estimated from individual-level patient data pooled from population-based surveys (1998–2007, n = 31,009) from eight LAC countries and from a national survey of the United States (US) population (1999–2004) Age and gender specific prevalence were estimated and age-gender adjusted comparisons between both populations were conducted. Prevalence of diabetes mellitus, hypertension, and low high-density lipoprotein (HDL)-cholesterol in LAC were 5% (95% confidence interval [95% CI]: 3.4, 7.9), 20.2% (95% CI: 12.5, 31), and 53.3% (95% CI: 47, 63.4), respectively. Compared to LAC region’s average, the prevalence of each risk factor tended to be lower in Peru and higher in Chile. LAC women had higher prevalence of obesity and low HDL-cholesterol than men. Obesity, hypercholesterolemia, and hypertriglyceridemia were more prevalent in the US population than in LAC population (31 vs. 16.1%, 16.8 vs. 8.9%, and 36.2 vs. 26.5%, respectively). However, the prevalence of low HDL-cholesterol was higher in LAC than in the US (53.3 vs. 33.7%).

Conclusions

Major cardiovascular risk factors are highly prevalent in LAC region, in particular low HDL-cholesterol. In addition, marked differences do exist in this prevalence profile between LAC and the US. The observed patterns of obesity-related risk factors and their current and future impact on the burden of cardiovascular diseases remain to be explained.  相似文献   

5.
The demographic origins of aging in Puerto Rican and other Latin American and Caribbean (LAC) countries may have important implications for the profile of health status and mortality of elderly people. For this article we tested a general conjecture about the relation between early childhood conditions and adult health status among Puerto Rican elderly using a rich data set recently collected through an island-wide survey (N = 4,293). We examined the association between markers of early nutritional status, self-reports of health and on socioeconomic conditions during early childhood, and the prevalence of 3 conditions during adult ages: obesity, diabetes, and cardiovascular diseases. Although we found that obesity and diabetes are associated with markers of early malnutrition, that heart disease is associated with early deprivations and selected early childhood conditions, the evidence we were able to tease out from the data provides only fragile support for the conjecture.  相似文献   

6.

Objective

We describe trends in life expectancy at birth (LE) and between-country LE disparities since 1965, in Latin America and the Caribbean.

Methods & Findings

LE trends since 1965 are described for three geographical sub-regions: the Caribbean, Central America, and South America. LE disparities are explored using a suite of absolute and relative disparity metrics, with measurement consensus providing confidence to observed differences. LE has increased throughout Latin America and the Caribbean. Compared to the Caribbean, LE has increased by an additional 6.6 years in Central America and 4.1 years in South America. Since 1965, average reductions in between-country LE disparities were 14% (absolute disparity) and 23% (relative disparity) in the Caribbean, 55% and 51% in Central America, 55% and 52% in South America.

Conclusions

LE in Latin America and the Caribbean is exceeding ‘minimum standard’ international targets, and is improving relative to the world region with the highest human longevity. The Caribbean, which had the highest LE and the lowest between-country LE disparities in Latin America and the Caribbean in 1965-70, had the lowest LE and the highest LE disparities by 2005-10. Caribbean Governments have championed a collaborative solution to the growing burden of non-communicable disease, with 15 territories signing on to the Declaration of Port of Spain, signalling regional commitment to a coordinated public-health response. The persistent LE inequity between Caribbean countries suggests that public health interventions should be tailored to individual countries to be most effective. Between- and within-country disparity monitoring for a range of health metrics should be a priority, first to guide country-level policy initiatives, then to contribute to the assessment of policy success.  相似文献   

7.
《Gender Medicine》2012,9(6):490-510.e5
BackgroundData on the effect of gender in rheumatoid arthritis (RA) in non-Caucasian populations is scarce. Latin America and the Caribbean (LAC) is a large population with unique characteristics, including high admixture.ObjectiveOur aim was to examine the effect of gender in patients with RA in LAC.MethodsThis was a 2-phase study. First we conducted a cross-sectional and analytical study in which 1128 consecutive Colombian patients with RA were assessed. Second, a systematic review of the literature was done to evaluate the effect of gender in LAC patients with RA.ResultsOur results show a high prevalence of RA in LAC women with a ratio of 5.2 women per man. Colombian women with RA are more at risk of having an early age at onset and developing polyautoimmunity and abdominal obesity, and they perform more household duties than their male counterparts. However, male gender was associated with the presence of extra-articular manifestations. Of a total of 641 potentially relevant articles, 38 were considered for final analysis, in which several factors and outcomes related to gender were identified.ConclusionsRA in LAC women is not only more common but presents with some clinical characteristics that differ from RA presentation in men. Some of those characteristics could explain the high rates of disability and worse prognosis observed in women with RA in LAC.  相似文献   

8.

Purpose

Based on the 2005–2014 developments in the Latin American and the Caribbean region (LAC), this paper aims to understand the conditions’ levels for mainstreaming life cycle assessment/life cycle management (LCA/LCM) and map key next actions.

Methods

Along the paper, four mainstreaming conditions are analyzed: expansion of LCM/LCA training activities, availability of LCA studies, national LCA database operating, and existence and activity of national life cycle network(s). Assuming that countries with better conditions are in a better position to develop national LCA based regulations, policies are also researched to complement this study.

Results and discussion

With nine life cycle (LC) networks in 2014, the LAC region has positively developed its networking capacities since 2005 but not the databases area (only one LCA database, Mexicaniuh, is fully operational). It was found that countries with no networks, lack all LCA trainings, studies, and databases.Local capacities are limited which in best case, Chile, does not exceed 18 practitioners per 10 million inhabitants. Based on the total score on mainstreaming conditions, Mexico and Brazil are the most advanced countries, but their markets for LCA professionals are still small (Valdivia et al. 2015), which suggests that tailored made strategies are needed for stronger uptake of LCA by industrial sectors.Argentina, Peru, Chile, and Colombia are in the second tier but still lack a critical mass of business cases and the political will to improve their mainstreaming conditions.

Conclusions

LCA development in the LAC region since 2005 is overall positive but still insufficient to serve the growth of prosperous LCA markets. Well-functioning LC networks are essential to leapfrog LCA. In 2014, about 27 % of LAC countries counted on a LC network. A common language in the region (except for Portuguese in Brazil) has been instrumental for expanding LCA through regional cooperation. LCA-based policies are boosted when local capacities and databases are available following the cases of Mexico, Chile, and Brazil. More data and research are needed to understand the women role in advancing LCA and the causalities and motivations of LAC companies to decide for LCA implementation. The application of the methodology was possible thanks to good quality data available and delivered key findings to develop national road maps for advancing LCA. No indicator used is specific for the LAC region and similar exercises are encouraged in other regions such as Africa and Asia.
  相似文献   

9.
It is estimated that in Latin America and the Caribbean (LAC) at least 13.9 million preschool age and 35.4 million school age children are at risk of infections by soil-transmitted helminths (STH): Ascaris lumbricoides, Trichuris trichiura and hookworms (Necator americanus and Ancylostoma duodenale). Although infections caused by this group of parasites are associated with chronic deleterious effects on nutrition and growth, iron and vitamin A status and cognitive development in children, few countries in the LAC Region have implemented nationwide surveys on prevalence and intensity of infection. The aim of this study was to identify gaps on the mapping of prevalence and intensity of STH infections based on data published between 2000 and 2010 in LAC, and to call for including mapping as part of action plans against these infections. A total of 335 published data points for STH prevalence were found for 18 countries (11.9% data points for preschool age children, 56.7% for school age children and 31.3% for children from 1 to 14 years of age). We found that 62.7% of data points showed prevalence levels above 20%. Data on the intensity of infection were found for seven countries. The analysis also highlights that there is still an important lack of data on prevalence and intensity of infection to determine the burden of disease based on epidemiological surveys, particularly among preschool age children. This situation is a challenge for LAC given that adequate planning of interventions such as deworming requires information on prevalence to determine the frequency of needed anthelmintic drug administration and to conduct monitoring and evaluation of progress in drug coverage.  相似文献   

10.
Abstract

The demographic origins of aging in Puerto Rican and other Latin American and Caribbean (LAC) countries may have important implications for the profile of health status and mortality of elderly people. For this article we tested a general conjecture about the relation between early childhood conditions and adult health status among Puerto Rican elderly using a rich data set recently collected through an island‐wide survey (N=4,293). We examined the association between markers of early nutritional status, self‐reports of health and on socioeconomic conditions during early childhood, and the prevalence of 3 conditions during adult ages: obesity, diabetes, and cardiovascular diseases. Although we found that obesity and diabetes are associated with markers of early malnutrition, that heart disease is associated with early deprivations and selected early childhood conditions, the evidence we were able to tease out from the data provides only fragile support for the conjecture.  相似文献   

11.
ObjectiveTo describe the prevalence of Helicobacter pylori (H. pylori) infection in Latin Americaand the Caribbean (LAC), through systematic review and meta-analysis by age groups and gender.MethodsSystematic review and meta-analysis of the population-based observational epidemiological studies carried out in LAC, focused on the prevalence of H. pylori and published until March, 2018. The databases utilized in the search were MEDLINE, SCIELO andPUBMED. The prevalence described in the meta-analysis and 95% confidence intervals were estimated by the random effects model, and weighted by the size of the study.ResultsThe 22 selected studies were carried out in 14 countries of LAC, and included 24,178 individuals. The studies were conducted between 1987 and 2012, and all were representative of at least one city. The prevalence of H. pylori infection was 57.57% (CI95%:50.43;64.72) for all ages; in children and adolescents the prevalence was 48.36% (CI95%:38.03;58.70) and in adults 69.26%(CI95%:64.54;76.99). No differences were observed regarding sex.ConclusionPrevalence of H. pylori infection in LAC is high for all age groups. These data reinforce the necessity of actions towards the prevention and treatment of H. pylori infection for all age groups. Treating H pylori infection in young ages probably will reduce gastric cancer incidence in the future.  相似文献   

12.

Introduction

Few studies have assessed the nature and quality of randomized controlled trials (RCTs) in Latin America and the Caribbean (LAC).

Methods and Findings

The aims of this systematic review are to evaluate the characteristics (including the risk of bias assessment) of RCT conducted in LAC according to funding source. A review of RCTs published in 2010 in which the author''s affiliation was from LAC was performed in PubMed and LILACS. Two reviewers independently extracted data and assessed the risk of bias. The primary outcomes were risk of bias assessment and funding source. A total of 1,695 references were found in PubMed and LILACS databases, of which 526 were RCTs (N = 73.513 participants). English was the dominant publication language (93%) and most of the RCTs were published in non-LAC journals (84.2%). Only five of the 19 identified countries accounted for nearly 95% of all RCTs conducted in the region (Brazil 70.9%, Mexico 10.1%, Argentina 5.9%, Colombia 3.8%, and Chile 3.4%). Few RCTs covered priority areas related with Millennium Development Goals like maternal health (6.7%) or high priority infectious diseases (3.8%). Regarding children, 3.6% and 0.4% RCT evaluated nutrition and diarrhea interventions respectively but none pneumonia. As a comparison, aesthetic and sport related interventions account for 4.6% of all trials. A random sample of RCTs (n = 358) was assessed for funding source: exclusively public (33.8%); private (e.g. pharmaceutical company) (15.3%); other (e.g. mixed, NGO) (15.1%); no funding (35.8%). Overall assessments for risk of bias showed no statistically significant differences between RCTs and type of funding source. Statistically significant differences favoring private and others type of funding was found when assessing trial registration and conflict of interest reporting.

Conclusion

Findings of this study could be used to provide more direction for future research to facilitate innovation, improve health outcomes or address priority health problems.  相似文献   

13.
Postpartum hemorrhage (PPH) is a leading cause of maternal death. Despite strong evidence showing the efficacy of routine oxytocin in preventing PPH, the proportion of women receiving it after delivery is still below 100%. The Uniject injection system prefilled with oxytocin (Uniject) has the potential advantage, due to its ease of use, to increase oxytocin utilization rates. We aimed to assess its cost-effectiveness in Latin America and the Caribbean (LAC). We used an epidemiological model to estimate: a) the impact of replacing oxytocin in ampoules with Uniject on the incidence of PPH, quality-adjusted life years (QALYs) and costs from a health care system perspective, and b) the minimum increment in oxytocin utilization rates required to make Uniject a cost-effective strategy. A consensus panel of LAC experts was convened to quantify the expected increase in oxytocin rates as a consequence of making Uniject available. Deterministic and probabilistic sensitivity analyses were performed. In the base case, the incremental cost of Uniject with respect to oxytocin in ampoules was estimated to be USD 1.00 (2013 US dollars). In the cost-effectiveness analysis, Uniject ranged from being cost-saving (in 8 out of 30 countries) to having an incremental cost-effectiveness ratio (ICER) of USD 8,990 per QALY gained. In most countries these ICERs were below one GDP per capita. The minimum required increment in oxytocin rates to make Uniject a cost-effective strategy ranged from 1.3% in Suriname to 16.2% in Haiti. Switching to Uniject could prevent more than 40,000 PPH events annually in LAC. Uniject was cost-saving or very cost-effective in almost all countries. Even if countries can achieve only small increases in oxytocin rates by incorporating Uniject, this strategy could be considered a highly efficient use of resources. These results were robust in the sensitivity analysis under a wide range of assumptions.  相似文献   

14.
One of humanity’s major challenges of the 21st century will be meeting future food demands on an increasingly resource constrained-planet. Global food production will have to rise by 70 percent between 2000 and 2050 to meet effective demand which poses major challenges to food production systems. Doing so without compromising environmental integrity is an even greater challenge. This study looks at the interdependencies between land and water resources, agricultural production and environmental outcomes in Latin America and the Caribbean (LAC), an area of growing importance in international agricultural markets. Special emphasis is given to the role of LAC’s agriculture for (a) global food security and (b) environmental sustainability. We use the International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT)—a global dynamic partial equilibrium model of the agricultural sector—to run different future production scenarios, and agricultural trade regimes out to 2050, and assess changes in related environmental indicators. Results indicate that further trade liberalization is crucial for improving food security globally, but that it would also lead to more environmental pressures in some regions across Latin America. Contrasting land expansion versus more intensified agriculture shows that productivity improvements are generally superior to agricultural land expansion, from an economic and environmental point of view. Finally, our analysis shows that there are trade-offs between environmental and food security goals for all agricultural development paths.  相似文献   

15.
Human rabies transmitted by dogs is considered a neglected disease that can be eliminated in Latin America and the Caribbean (LAC) by 2015. The aim of this paper is to discuss canine rabies policies and projections for LAC regarding current strategies for achieving this target and to critically review the political, economic and geographical factors related to the successful elimination of this deadly disease in the context of the difficulties and challenges of the region. The strong political and technical commitment to control rabies in LAC in the 1980s, started with the regional programme coordinated by the Pan American Health Organization. National and subnational programmes involve a range of strategies including mass canine vaccination with more than 51 million doses of canine vaccine produced annually, pre- and post-exposure prophylaxis, improvements in disease diagnosis and intensive surveillance. Rabies incidence in LAC has dramatically declined over the last few decades, with laboratory confirmed dog rabies cases decreasing from approximately 25 000 in 1980 to less than 300 in 2010. Dog-transmitted human rabies cases also decreased from 350 to less than 10 during the same period. Several countries have been declared free of human cases of dog-transmitted rabies, and from the 35 countries in the Americas, there is now only notification of human rabies transmitted by dogs in seven countries (Bolivia, Peru, Honduras, Haiti, Dominican Republic, Guatemala and some states in north and northeast Brazil). Here, we emphasize the importance of the political commitment in the final progression towards disease elimination. The availability of strategies for rabies control, the experience of most countries in the region and the historical ties of solidarity between countries with the support of the scientific community are evidence to affirm that the elimination of dog-transmitted rabies can be achieved in the short term. The final efforts to confront the remaining obstacles, like achieving and sustaining high vaccination coverage in communities that are most impoverished or in remote locations, are faced by countries that struggle to allocate sufficient financial and human resources for rabies control. Continent-wide cooperation is therefore required in the final efforts to secure the free status of remaining countries in the Americas, which is key to the regional elimination of human rabies transmitted by dogs.  相似文献   

16.
Forest cover change directly affects biodiversity, the global carbon budget, and ecosystem function. Within Latin American and the Caribbean region (LAC), many studies have documented extensive deforestation, but there are also many local studies reporting forest recovery. These contrasting dynamics have been largely attributed to demographic and socio‐economic change. For example, local population change due to migration can stimulate forest recovery, while the increasing global demand for food can drive agriculture expansion. However, as no analysis has simultaneously evaluated deforestation and reforestation from the municipal to continental scale, we lack a comprehensive assessment of the spatial distribution of these processes. We overcame this limitation by producing wall‐to‐wall, annual maps of change in woody vegetation and other land‐cover classes between 2001 and 2010 for each of the 16,050 municipalities in LAC, and we used nonparametric Random Forest regression analyses to determine which environmental or population variables best explained the variation in woody vegetation change. Woody vegetation change was dominated by deforestation (?541,835 km2), particularly in the moist forest, dry forest, and savannas/shrublands biomes in South America. Extensive areas also recovered woody vegetation (+362,430 km2), particularly in regions too dry or too steep for modern agriculture. Deforestation in moist forests tended to occur in lowland areas with low population density, but woody cover change was not related to municipality‐scale population change. These results emphasize the importance of quantitating deforestation and reforestation at multiple spatial scales and linking these changes with global drivers such as the global demand for food.  相似文献   

17.
Blackness in Latin America and the Caribbean, volume 1. Norman E. Whitten. Jr. and Arlene Torres, eds. Bloomington: Indiana University Press, 1998. 520 pp.
Blackness in Latin America and the Caribbean, volume 2. Norman E. Whitten. Jr. and Arlene Torres, eds. Bloomington: Indiana University Press, 1998. 557 pp.  相似文献   

18.

Background

Published data on the epidemiology of meningococcal disease in Latin America and the Caribbean region is scarce and, when available, it is often published in Spanish and/or in non-peer-reviewed journals, making it difficult for the international scientific community to have access.

Methods

Laboratory data on 4,735 Neisseria meningitidis strains was collected and reported by the National Reference Laboratories in 19 Latin American countries and the Caribbean Epidemiology Centre (CAREC) between 2006 and 2010 as part of the work carried out by the SIREVA II network. Serogroup and MIC to penicillin, rifampin and chloramphenicol were determined.

Results

Isolates were mainly obtained from patients <5 years, but each year around 25% of isolates came from adult patients. Serogroup distribution was highly variable among countries. Serogroup C was the main cause of disease in Brazil; the majority of disease seen in the Southern cone was caused by serogroup B, but serogroup W135 strains have increased in recent years. In the Andean and Mexico, Central America and Caribbean regions, serogroups B and C were equally present, and serogroup Y was frequently isolated. Isolates were generally susceptible to chloramphenicol, penicillin and rifampin, but almost 60% of isolates characterized in Southern cone countries presented intermediate resistance to penicillin. Five rifampin-resistant isolates have been isolated in Uruguay and Brazil.

Conclusions

Serogroup distribution is highly variable among countries, but some geographic structuring can be inferred from these data. Epidemiological and laboratory data are scarce among Andean and Mexico, Central America and Caribbean countries. Evaluation and implementation of corrective measures on disease surveillance and reporting systems and the implementation of molecular diagnostic techniques and molecular characterization on meningococcal isolates are advised.  相似文献   

19.

Background

Recent reviews have demonstrated an increase in the number of papers on ethnobiology in Latin America. Among factors that have influenced this increase are the biological and cultural diversity of these countries and the general scientific situation in some countries. This study aims to assess the panorama of ethnobiological research in Latin America by analyzing its evolution, trends, and future prospects.

Methods

To conduct this study, we searched for papers in the Scopus (http://www.scopus.com) and Web of Science (http://www.isiknowledge.com) databases. The search was performed using combinations of keywords and the name of each Latin American country. The following countries were included in this study: Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Cuba, Ecuador, Guatemala, Haiti, Honduras, Mexico, Panama, Paraguay, Peru, Venezuela, and Uruguay.

Results and conclusions

According to our inclusion criteria, 679 ethnobiological studies conducted in Latin America were found for the period between 1963 and 2012. Of these studies, 289 (41%) were conducted in Brazil, 153 in Mexico (22%), 61 in Peru (9%), 58 in Argentina (8%), 45 in Bolivia (6%), and 97 (14%) in other Latin American countries. The increased number of publications related to this area of knowledge in recent years demonstrates the remarkable growth of ethnobiology as a science. Ethnobiological research may be stimulated by an increase in the number of scientific events and journals for study dissemination and by the creation of undergraduate courses and graduate programs to train ethnoscientists who will produce high-quality studies, especially in certain countries.
  相似文献   

20.
La Crosse (LAC) virions were cryopreserved by rapid freezing in a thin layer of vitreous ice. The vitrified-hydrated LAC virions were subsequently imaged at -170 degrees C in a transmission electron microscope equipped with a low-temperature specimen holder. This cryoelectron microscopic technique eliminates the artifacts frequently associated with negative staining. Images of vitrified-hydrated LAC virions clearly revealed surface spikes as well as bilayer structure. Size measurements of the vitrified-hydrated LAC virions showed heterogeneity, with diameters ranging from 75 to 115 nm. Regardless of the particle size, the spike was about 10 nm long, and the bilayer was about 4 nm thick. The spikes are interpreted to be one or both of the glycoproteins, and the bilayer is interpreted to be the membrane envelope of the virus. In contrast to the pleomorphic appearance of the negatively stained LAC virions, the vitrified-hydrated LAC virions showed uniform spherical shapes regardless of their sizes.  相似文献   

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