30 resultados para Clonal organ


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In clonal plants, vegetative parts may outcompete seeds in the absence of disturbance, limiting the build-up of genotypic diversity through repeated seedling recruitment (RSR). Herbivory may provide disturbance and trigger establishment of strong colonizers (seeds) at the expense of strong competitors (clonal propagules). In the clonal aquatic fennel pondweed Potamogeton pectinatus, two distinct herbivore guilds may modify the dynamics of propagation. In winter, Bewick's swans may deplete patches of tubers, promoting seedling establishment in spring. In summer, seed consumption by waterfowl can reduce the density of viable seeds but grazing may also reduce tuber production and hence facilitate seedling establishment. This study is among the first to experimentally test herbivore impact on plant genotypic diversity. We assess the separate and combined effects of both herbivore guilds on genotypic diversity and structure of fennel pondweed beds. Using microsatellites, we genotyped P. pectinatus from an exclosure experiment and assessed the contribution of herbivory, dispersal and sexual reproduction to the population genetic structure. Despite the predominance of clonal propagation in P. pectinatus, we found considerable genotypic diversity. Within the experimental blocks, kinship among genets decreased with geographic distance, clearly identifying a role for RSR in the maintenance of genotypic diversity within the fennel pondweed beds. However, over a period of five years, none of the herbivory treatments affected genotypic diversity. Hence, sexual reproduction on a local scale is important in this putatively clonal plant and possibly sufficient to ensure a relatively high genotypic diversity even in the absence of herbivores. Although we cannot preclude a role of herbivory in shaping genotypic diversity of a clonal plant, after five years of exclusion of the two investigated herbivore guilds no measurable effect on genotypic diversity was detected. © 2014 The Authors.

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BACKGROUND: Despite the success of the Breakthrough Collaborative Methodology (BCM) in increasing organ donation rates there has been little published evidence on the effect of the BCM on the wider attitudes and experiences of those involved in organ donation. This study sought to identify whether the National Organ Donation Collaborative in Australia had any additional influence on improving the experiences of staff and family members in the organ donation process. METHODS: IN-depth qualitative interviews with 17 family members from 13 families who had agreed to the organ donation of a deceased relative and 25 nurses and intensive care specialists at the Alfred Hospital, Melbourne, Victoria were carried out. RESULTS: The key factor in family members' decision to donate was prior knowledge of the deceased's donation wish. Although most family members did not regret their decision to donate, many were deeply dissatistified and, at times, confused by the technical and administrative nature of the donation process. Most staff members commented that the key community message about donation should be to encourage people to discuss donation rather than urging people to sign donor registers. CONCLUSION: This study identified valuable insights into the processes by which family members and intensive care unit staff deal with the actual processes of donation. Findings suggest that the process for families is far more complex than a simple agreement or refusal to donate. This study suggests that we should not assume that 'rates' of donation in Australia would increase merely through administrative programmes or marketing campaigns.

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Seagrasses are ecosystem engineers that offer important habitat for a large number of species and provide a range of ecosystem services. Many seagrass ecosystems are dominated by a single species, with research showing that genotypic diversity at fine spatial scales plays an important role in maintaining a range of ecosystem functions. However, for most seagrass species, information on fine-scale patterns of genetic variation in natural populations is lacking. In this study, we use a hierarchical sampling design to determine the levels of genetic and genotypic diversity at different spatial scales (centimeters, meters, kilometers) in the Australian seagrass Zostera muelleri. Our analysis shows that at fine spatial scales (<1 m), levels of genotypic diversity are relatively low (R(Plots) = 0.37 ± 0.06 SE), although there is some intermingling of genotypes. At the site (10’s m) and meadow location (km) scale, we found higher levels of genotypic diversity (R(sites) = 0.79 ± 0.04 SE; R(Locations) = 0.78 ± 0.04 SE). We found some sharing of genotypes between sites within meadows, but no sharing of genotypes between meadow locations. We also detected a high level of genetic structuring between meadow locations (FST = 0.278). Taken together, our results indicate that both sexual and asexual reproductions are important in maintaining meadows of Z. muelleri. The dominant mechanism of asexual reproduction appears to occur via localized rhizome extension, although the sharing of a limited number of genotypes over the scale of 10’s of meters could also result from the localized dispersal and recruitment of fragments. The large number of unique genotypes at the meadow scale indicates that sexual reproduction is important in maintaining these populations, while the high level of genetic structuring suggests little gene flow and connectivity between our study sites. These results imply that recovery from disturbances will occur through both sexual and asexual regeneration, but the limited connectivity at the landscape scale implies that recovery at meadow-scale losses is likely to be limited.

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In the last decade, health authorities in China have made a series of policy announcements concerning organ procurement programs and changes in practice have been intermittently reported (1). The international community of transplant professionals has followed these reports closely, preoccupied with one fundamental issue: the procurement of organs from executed prisoners, a practice that for many years has provided the majority of organs transplanted in China. Sharif et al. describe this practice as “ethically indefensible” (2), an evaluation that reflects the position embraced by the international community for more than two decades (3-5). Sharif et al. express concern that whilst some transplant programs in China have ceased using organs from executed prisoners, others continue to do so, and that all organs procured from the deceased may be allocated through a collective pool as part of the new China Organ Transplant Response System, effectively “laundering” organs obtained from prisoners. They also note that one of the new strategies to encourage deceased donation of organs among the Chinese public has involved financial incentives for donor families, another practice that has been strongly critiqued by the international professional community and global health authorities (6,7).

In China and in the United States, proponents of organ procurement from executed prisoners have argued that prisoners should not be denied the option to donate organs after their death if they so choose, as this may provide them or their families solace and an opportunity for moral, spiritual or social redemption (8,9). However, the predominant argument in favour of the practice appears to be essentially pragmatic: prisoners condemned to death represent an additional pool of potential “donors” with organs that will otherwise “go to waste” (10). In contrast, international professional societies and the World Health Organization among others have argued that the practice not only violates the core principles of medical ethics but also thereby undermines efforts to establish a sufficient supply of deceased donor organs. In this commentary, we reaffirm the ethics policy of The Transplantation Society (TTS) concerning organ procurement from executed prisoners (4), and briefly discuss the implications of this policy for international professional engagement with China at this time of significant evolution of Chinese organ procurement programs.

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The supply of organs—particularly kidneys—donated by living and deceased donors falls short of the number of patients added annually to transplant waiting lists in the United States. To remedy this problem, a number of prominent physicians, ethicists, economists and others have mounted a campaign to suspend the prohibitions in the National Organ Transplant Act of 1984 (NOTA) on the buying and selling of organs. The argument that providing financial benefits would incentivize enough people to part with a kidney (or a portion of a liver) to clear the waiting lists is flawed. This commentary marshals arguments against the claim that the shortage of donor organs would best be overcome by providing financial incentives for donation. We can increase the number of organs available for transplantation by removing all financial disincentives that deter unpaid living or deceased kidney donation. These disincentives include a range of burdens, such as the costs of travel and lodging for medical evaluation and surgery, lost wages, and the expense of dependent care during the period of organ removal and recuperation. Organ donation should remain an act that is financially neutral for donors, neither imposing financial burdens nor enriching them monetarily.

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This paper reviews the policy and practice of organ donation and transplantation in Qatar that has developed since January 2011. The important features of the Doha Model (the ‘Model’) are explored, including: (i) all legal residents of Qatar have an equal right to access deceased donor organs and transplantation regardless of their citizenship status; (ii) no prioritisation in organ allocation is given to Qatari citizens; (iii) a multilingual and multicultural education and promotional program about donation has been implemented to engage the diverse national communities resident within Qatar; (iv) financial incentives or fungible rewards for living or deceased donation are prohibited. The ethical framework of this policy will be examined in the light of the national self-sufficiency paradigm, which advocates reciprocity and solidarity among resident populations seeking to meet all needs for transplantation equitably. We review some preliminary evidence of the impact of the Model with respect to engagement of a highly diverse multinational population in a donation and transplantation program, and argue that the Model may inform policy and practice in other countries, particularly those with non-citizen resident populations.

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By 2005, human organ trafficking, commercialization, and transplant tourism had become a prominent and pervasiveinfluence on transplantation therapy. The most common source of organs was impoverished people in India,Pakistan, Egypt, and the Philippines, deceased organ donors in Colombia, and executed prisoners in China. Inresponse, in May 2008, The Transplantation Society and the International Society of Nephrology developed theDeclaration of Istanbul on Organ Trafficking and Transplant Tourism consisting of a preamble, a set of principles, anda series of proposals. Promulgation of the Declaration of Istanbul and the formation of the Declaration of IstanbulCustodian Group to promote and uphold its principles have demonstrated that concerted, strategic, collaborative,and persistent actions by professionals can deliver tangible changes. Over the past 5 years, the Declaration of IstanbulCustodian Group organized and encouraged cooperation among professional bodies and relevant international, regional,and national governmental organizations, which has produced significant progress in combating organ traffickingand transplant tourism around the world. At a fifth anniversary meeting in Qatar in April 2013, the DICGtook note of this progress and set forth in a Communique´ a number of specific activities and resolved to furtherengage groups from many sectors in working toward the Declaration’s objectives.

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In the past 3 years there have been attempts to counter the international campaignagainst a market in organs from the living. In parallel to these attempts,support for a market in organs from the deceased has gained some traction. Inthis article we describe the various forms of this phenomenon, analyze itsimplications, and call upon policy makers to take steps to halt its progress.

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The dark history of transplant tourism in Pakistan demonstrates the hazards of unregulated cross-border markets in human organs. Trading on existing national and international social inequities, ‘transplant tourism’ offers dubious benefits for transplant recipients and attractive profits to those facilitating the industry at the expense of the world’s poor. The impact of Pakistan’s 2007 Transplantation of Human Organs and Tissue Ordinance and the sustained efforts of transplant professionals and societal groups led by the Sindh Institute of Urology and Transplantation, show that organ trading can be effectively discouraged and equitable programs of organ procurement and transplantation pursued despite multiple challenges. In this paper, the factors that have contributed to Pakistan’s progress towards self-sufficiency in organ transplantation are identified and discussed. The case of Pakistan highlights the need for countries to protect their own organ and tissue providers who may be vulnerable in the global healthcare market. Pakistan provides an excellent example for other countries in the region and throughout the world to consider when regulating their own transplantation programs and considering the pursuit of national self-sufficiency.

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Governmental and private programs that pay next of kin who give permission for the removal of their deceased relative's organs for transplantation exist in a number of countries. Such payments, which may be given to the relatives or paid directly for funeral expenses or hospital bills unrelated to being a donor, aim to increase the rate of donation. The Declaration of Istanbul Custodian Group-in alignment with the World Health Organization Guiding Principles and the Council of Europe Convention Against Trafficking in Human Organs-has adopted a new policy statement opposing such practices.Payment programs are unwise because they produce a lower rate of donations than in countries with voluntary, unpaid programs; associate deceased donation with being poor and marginal in society; undermine public trust in the determination of death; and raise doubts about fair allocation of organs. Most important, allowing families to receive money for donation from a deceased person, who is at no risk of harm, will make it impossible to sustain prohibitions on paying living donors, who are at risk.Payment programs are also unethical. Tying coverage for funeral expenses or healthcare costs to a family allowing organs to be procured is exploitative, not "charitable." Using payment to overcome reluctance to donate based on cultural or religious beliefs especially offends principles of liberty and dignity. Finally, while it is appropriate to make donation "financially neutral"-by reimbursing the added medical costs of evaluating and maintaining a patient as a potential donor-such reimbursement may never be conditioned on a family agreeing to donate.

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Book review of The Red Market: On the Trail of the World's Organ Brokers, Bone Thieves, Blood Farmers, and Child Traffickers. Scott Carney, 2011, William Morrow (New York, 978-0-06-193646-3, 272 pp.)

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BACKGROUND: Using multinational collections of methicillin-susceptible Staphylococcus aureus (MSSA) isolates from infective endocarditis (IE) and soft tissue infections (STIs), we sought to (1) validate the finding that S. aureus in clonal complex (CC) 30 is associated with hematogenous complications and (2) test the hypothesis that specific genetic characteristics in S. aureus are associated with infection severity. METHODS: IE and STI isolates from 2 cohorts were frequency matched by geographic origin. Isolates underwent spa typing to infer CC and multiplex polymerase chain reaction for presence of virulence genes. RESULTS: 114 isolate pairs were genotyped. IE isolates were more likely to be CC30 (19.5% vs 6.2%; P = .005) and to contain 3 adhesins (clfB, cna, map/eap; P < .0001 for all) and 5 enterotoxins (tst, sea, sed, see, and sei; P ≤ .005 for all). CC30 isolates were more likely to contain cna, tst, sea, see, seg, and chp (P < .05 for all). CONCLUSIONS: MSSA IE isolates were significantly more likely to be CC30 and to possess a distinct repertoire of virulence genes than MSSA STI isolates from the same region. The genetic basis of this association requires further study.

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The avian bill is a textbook example of how evolution shapes morphology in response to changing environments. Bills of seed-specialist finches in particular have been the focus of intense study demonstrating how climatic fluctuations acting on food availability drive bill size and shape. The avian bill also plays an important but under-appreciated role in body temperature regulation, and therefore in energetics. Birds are endothermic and rely on numerous mechanisms for balancing internal heat production with biophysical constraints of the environment. The bill is highly vascularised and heat exchange with the environment can vary substantially, ranging from around 2% to as high as 400% of basal heat production in certain species. This heat exchange may impact how birds respond to heat stress, substitute for evaporative water loss at elevated temperatures or environments of altered water availability, or be an energetic liability at low environmental temperatures. As a result, in numerous taxa, there is evidence for a positive association between bill size and environmental temperatures, both within and among species. Therefore, bill size is both developmentally flexible and evolutionarily adaptive in response to temperature. Understanding the evolution of variation in bill size however, requires explanations of all potential mechanisms. The purpose of this review, therefore, is to promote a greater understanding of the role of temperature on shaping bill size over spatial gradients as well as developmental, seasonal, and evolutionary timescales.