Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 90
Filtrar
1.
Acta Psychiatr Scand ; 142(1): 27-39, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-31953847

RESUMO

This article discusses initiatives aimed at preventing and reducing 'coercive practices' in mental health and community settings worldwide, including in hospitals in high-income countries, and in family homes and rural communities in low- and middle-income countries. The article provides a scoping review of the current state of English-language empirical research. It identifies several promising opportunities for improving responses that promote support based on individuals' rights, will and preferences. It also points out several gaps in research and practice (including, importantly, a gap in reviews of non-English-language studies). Overall, many studies suggest that efforts to prevent and reduce coercion appear to be effective. However, no jurisdiction appears to have combined the full suite of laws, policies and practices which are available, and which taken together might further the goal of eliminating coercion.


Assuntos
Coerção , Idioma , Serviços de Saúde Mental/ética , Humanos , Saúde Mental
2.
Opt Lett ; 44(12): 3002-3005, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-31199366

RESUMO

We demonstrate a novel way to form and deplete a vapor-cell magneto-optic trap (MOT) using a reversible, solid-state alkali-metal source via an applied polarized voltage. Using ∼100 mW of electrical power, a trapped-atom number of 5×106 has been achieved, starting from near zero and the timescales of the MOT formation and depletion of ∼1 s. This fast, reversible, and low-power alkali-atom source is desirable in both tabletop and portable cold-atom systems. The core technology of this device should translate readily to other alkali and alkaline-earth elements that could find a wide range of uses in cold-atom systems and instruments.

3.
Diabetes Obes Metab ; 14 Suppl 3: 68-77, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22928566

RESUMO

Amyloid forms within pancreatic islets in type 2 diabetes from aggregates of the ß-cell peptide islet amyloid polypeptide (IAPP). These aggregates are toxic to ß-cells, inducing ß-cell death and dysfunction, as well as inciting islet inflammation. The ß-cell is subject to a number of other stressors, including insulin resistance and hyperglycaemia, that may contribute to amyloid formation by increasing IAPP production by the ß-cell. ß-Cell dysfunction, evident as impaired glucose-stimulated insulin secretion and defective prohormone processing and exacerbated by metabolic stress, is also a likely prerequisite for islet amyloid formation to occur in type 2 diabetes. Islet transplants in patients with type 1 diabetes face similar stressors, and are subject to rapid amyloid formation and impaired proinsulin processing associated with progressive loss of ß-cell function and mass. Declining ß-cell mass is predicted to increase metabolic demand on remaining ß-cells, promoting a feed-forward cycle of ß-cell decline.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Hiperglicemia/metabolismo , Polipeptídeo Amiloide das Ilhotas Pancreáticas/metabolismo , Ilhotas Pancreáticas/metabolismo , Estresse Fisiológico , Animais , Apoptose , Diabetes Mellitus Tipo 2/genética , Humanos , Hiperglicemia/genética , Resistência à Insulina , Polipeptídeo Amiloide das Ilhotas Pancreáticas/genética , Ratos , Estresse Fisiológico/genética
4.
Nat Med ; 6(6): 689-92, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10835687

RESUMO

New strategies are required to identify the most important targets of protective immunity in complex eukaryotic pathogens. Natural selection maintains allelic variation in some antigens of the malaria parasite Plasmodium falciparum. Analysis of allele frequency distributions could identify the loci under most intense selection. The merozoite surface protein 1 (Msp1) is the most-abundant surface component on the erythrocyte-invading stage of P. falciparum. Immunization with whole Msp1 has protected monkeys completely against homologous and partially against non-homologous parasite strains. The single-copy msp1 gene, of about 5 kilobases, has highly divergent alleles with stable frequencies in endemic populations. To identify the region of msp1 under strongest selection to maintain alleles within populations, we studied multiple intragenic sequence loci in populations in different regions of Africa and Southeast Asia. On both continents, the locus with the lowest inter-population variance in allele frequencies was block 2, indicating selection in this part of the gene. To test the hypothesis of immune selection, we undertook a large prospective longitudinal cohort study. This demonstrated that serum IgG antibodies against each of the two most frequent allelic types of block 2 of the protein were strongly associated with protection from P. falciparum malaria.


Assuntos
Variação Antigênica/genética , Malária Falciparum/imunologia , Proteína 1 de Superfície de Merozoito/genética , Plasmodium falciparum/genética , África/epidemiologia , Animais , Anticorpos Antiprotozoários/sangue , Anticorpos Antiprotozoários/imunologia , Variação Antigênica/imunologia , Sudeste Asiático/epidemiologia , Criança , Pré-Escolar , Feminino , Humanos , Malária Falciparum/epidemiologia , Masculino , Proteína 1 de Superfície de Merozoito/imunologia , Plasmodium falciparum/classificação , Plasmodium falciparum/imunologia , Estudos Prospectivos
5.
Trop Med Int Health ; 14(3): 294-300, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19187521

RESUMO

OBJECTIVES: To assess the efficacy of amodiaquine-artesunate in an area with high chloroquine resistance in western Kenya. METHODS: Twenty-eight day in-vivo efficacy trial of amodiaquine-artesunate in 103 children aged 6-59 months in western Kenya with smear-confirmed uncomplicated Plasmodium falciparum malaria. RESULTS: The 28-day uncorrected adequate clinical and parasitological response (ACPR) was 69.0%, with 15.5% Late Clinical Failure and 15.5% Late Parasitologic Failure rates. The PCR-corrected 28-day ACPR was 90.2%. Clinical risk factors for recurrent infection (recrudescences and reinfections) were lower axillary temperature at enrollment and low weight-for-age Z-score. The presence of single nucleotide polymorphisms pfcrt 76T and pfmdr1 86Y at baseline was associated with increased risk of recurrent infections, both reinfections and recrudescences. CONCLUSION: Although artemether-lumefantrine (Coartem) is the first line ACT in Kenya, amodiaquine-artesunate is registered as an option for treatment of uncomplicated P. falciparum and remains an effective alternative to Coartem in western Kenya. Continued amodiaquine monotherapy in the private sector may jeopardize the future use of amodiaquine-artesunate as an alternative artemisinin-based combination therapy.


Assuntos
Amodiaquina/uso terapêutico , Antimaláricos/uso terapêutico , Artemisininas/uso terapêutico , Malária Falciparum/tratamento farmacológico , Amodiaquina/efeitos adversos , Animais , Antimaláricos/efeitos adversos , Artemisininas/efeitos adversos , Pré-Escolar , Combinação de Medicamentos , Resistência a Medicamentos , Feminino , Seguimentos , Humanos , Lactente , Malária Falciparum/parasitologia , Masculino , Proteínas de Membrana Transportadoras/genética , Proteínas Associadas à Resistência a Múltiplos Medicamentos/genética , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/genética , Polimorfismo de Nucleotídeo Único , Proteínas de Protozoários/genética , Recidiva , Resultado do Tratamento
6.
Science ; 191(4231): 1046-8, 1976 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-1251214

RESUMO

Midwater squid respond to overhead illumination by turning on numerous downward-directed photophores; they turn off the photophores when overhead illumination is eliminated. The squid are invisible when the intensity of the photophores matches the intensity of the overhead illumination. These results strongly support the theory of ventral bioluminescent countershading.


Assuntos
Decapodiformes/fisiologia , Luminescência , Meio Ambiente , Luz
7.
J Clin Invest ; 82(1): 48-56, 1988 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-2839552

RESUMO

To examine putative relationships between adrenergic receptors on accessible circulating cells and relatively inaccessible extravascular catecholamine target tissues, we measured mononuclear leukocyte (MNL) and lung beta-adrenergic receptors and platelet and lung alpha-adrenergic receptors in tissues obtained from 15 patients undergoing pulmonary resection. Plasma catecholamine concentrations were measured concurrently to explore potential regulatory relationships between the activity of the sympathochromaffin system and both intravascular and extravascular adrenergic receptors. MNL and lung membrane beta-adrenergic receptor densities were correlated highly (r = 0.845, P less than 0.001). Platelet alpha 2-adrenergic receptor and lung alpha 1-adrenergic receptor densities were not. Lung alpha 1-adrenergic receptor densities were positively related to plasma norepinephrine (r = 0.840, P less than 0.01) and epinephrine (r = 0.860, P less than 0.01) concentrations; in contrast, lung beta-adrenergic receptor densities were not positively related to plasma catecholamine concentrations (they tended to be inversely related to plasma norepinephrine and epinephrine [r = -0.698, P less than 0.05] levels). This apparent reciprocal regulation of alpha- and beta-adrenergic receptors by the sympathochromaffin system was only demonstrable with adrenergic receptor measurements in the extravascular catecholamine target tissue. Neither MNL beta-adrenergic receptor nor platelet alpha-adrenergic receptor densities were correlated with plasma catecholamine levels. Thus, although measurements of beta-adrenergic receptors on circulating mononuclear leukocytes can be used as indices of extravascular target tissue beta-adrenergic receptor densities (at least in lung and heart), it would appear that extravascular tissues should be used to study adrenergic receptor regulation by endogenous catecholamines in humans. These data provide further support for the concept of up regulation, as well as down regulation, of some adrenergic receptor populations during short-term activation of the sympathochromaffin system in humans.


Assuntos
Plaquetas/metabolismo , Sistema Cromafim/fisiologia , Leucócitos Mononucleares/metabolismo , Pulmão/metabolismo , Receptores Adrenérgicos alfa/análise , Receptores Adrenérgicos beta/análise , Adulto , Idoso , Sistema Cromafim/metabolismo , Epinefrina/sangue , Feminino , Humanos , Pulmão/irrigação sanguínea , Masculino , Pessoa de Meia-Idade , Norepinefrina/sangue , Prazosina , Receptores Adrenérgicos alfa/fisiologia , Receptores Adrenérgicos beta/fisiologia
8.
Curr Mol Med ; 6(2): 253-60, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16515515

RESUMO

Successful malaria control depends heavily on efficacious anti-malarial drugs for the treatment of malaria. Artesunate-containing Combination Treatments (ACT) are increasingly recommended as first line malaria treatment in endemic countries, but implementation of this recommendation is limited by the small number of available and affordable co-formulated anti-malarial drugs. In recent years Intermittent Preventive Treatment has been recommended for malaria control in pregnancy and has been shown to be of potential public health importance in the prevention of malaria and anaemia in children. The use of drugs for malaria treatment or prevention is associated with the development of resistance and recent advances in molecular biology facilitate the evaluation of the impact on drug resistance of new drug-based strategies. This review concentrates on the challenges surrounding the use of ACT, the current understanding of IPT in infants and the use of molecular approaches to enhance our understanding of the effects of interventions on the spread of drug resistance.


Assuntos
Antimaláricos/uso terapêutico , Malária Falciparum/tratamento farmacológico , Animais , Resistência a Medicamentos , Quimioterapia Combinada , Humanos , Malária Falciparum/prevenção & controle , Plasmodium/efeitos dos fármacos , Plasmodium/crescimento & desenvolvimento
9.
J Psychiatr Ment Health Nurs ; 14(1): 85-91, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17244010

RESUMO

It is now a clear policy expectation that consumers of mental health services be given the opportunity to be active participants in all aspects of mental health service development and delivery. Psychiatric nurses have an important role to play in ensuring opportunities for genuine participation; however, the literature suggests that this role is not always realized in practice. Negative attitudes of health professionals (including nurses) to consumer has been identified as a significant barrier to the realization of this policy goal, with education and training recognized as an important strategy for developing more positive attitudes. This paper describes the implementation of a mental health consumer academic position, through the personal reflections of a nurse academic and a consumer academic. More specifically, the paper addresses the reactions of some nurses to the work of the consumer academic and the apparent feeling of being attacked as nurses. By recognizing this defensiveness, nurses and other health professionals may more effectively move towards promoting consumer participation in mental health care.


Assuntos
Atitude , Comportamento Cooperativo , Culpa , Relações Enfermeiro-Paciente , Enfermagem Psiquiátrica/métodos , Vergonha , Participação da Comunidade , Humanos
10.
Epidemiol Psychiatr Sci ; 26(5): 535-544, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-27515597

RESUMO

AIMS: There are growing calls to reduce, and where possible eliminate, the use of seclusion and restraint in mental health settings, but the attitudes and beliefs of consumers, carers and mental health professionals towards these practices are not well understood. The aim of this study was to compare the attitudes of mental health service consumers, carers and mental health professionals towards seclusion and restraint in mental health settings. In particular, it aimed to explore beliefs regarding whether elimination of seclusion and restraint was desirable and possible. METHODS: In 2014, an online survey was developed and widely advertised in Australia via the National Mental Health Commission and through mental health networks. The survey adopted a mixed-methods design, including both quantitative and qualitative questions concerning participants' demographic details, the use of seclusion and restraint in practice and their views on strategies for reducing and eliminating these practices. RESULTS: In total 1150 survey responses were analysed. A large majority of participants believed that seclusion and restraint practices were likely to cause harm, breach human rights, compromise trust and potentially cause or trigger past trauma. Consumers were more likely than professionals to view these practices as harmful. The vast majority of participants believed that it was both desirable and feasible to eliminate mechanical restraint. Many participants, particularly professionals, believed that seclusion and some forms of restraint were likely to produce some benefits, including increasing consumer safety, increasing the safety of staff and others and setting behavioural boundaries. CONCLUSIONS: There was strong agreement across participant groups that the use of seclusion and restraint is harmful, breaches human rights and compromises the therapeutic relationship and trust between mental health service providers and those who experience these restrictive practices. However, some benefits were also identified, particularly by professionals. Participants had mixed views regarding the feasibility and desirability of eliminating these practices.


Assuntos
Atitude do Pessoal de Saúde , Cuidadores/psicologia , Transtornos Mentais/terapia , Isolamento de Pacientes , Pacientes/psicologia , Psiquiatria/métodos , Restrição Física , Adolescente , Adulto , Austrália , Estudos de Viabilidade , Feminino , Humanos , Masculino , Transtornos Mentais/psicologia , Saúde Mental , Serviços de Saúde Mental , Pessoa de Meia-Idade , Pesquisa Qualitativa , População Rural , Inquéritos e Questionários , População Urbana
11.
Acta Trop ; 99(1): 106-11, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16905111

RESUMO

We previously reported a high baseline prevalence of mutations in the dhfr and dhps genes of Plasmodium falciparum throughout Senegal. The highest prevalence of the triple dhfr pyrimethamine associated mutations were found in isolates obtained in the western part of the country near the capital city of Dakar. In this study, we sought out to determine the relatedness of dhfr wild type and mutated strains by analyzing three microsatellite regions upstream of the dhfr locus. Twenty-six of the 31 wild type strains had a unique microsatellite pattern. In contrast, of the 17 isolates containing the triple mutation in dhfr, 11 had an identical microsatellite pattern. Diverse geographical isolates in Senegal containing the triple dhfr mutation have arisen from a limited number of ancestral strains. In addition, we demonstrate that these isolates have shared ancestry with the previously reported triple mutation haplotype found in Tanzania, South Africa, and southeast Asia. This common ancestry may have implications for the malaria control strategy for reducing the spread of sulfadoxine-pyrimethamine resistance in Senegal and elsewhere in Africa.


Assuntos
Antimaláricos/uso terapêutico , Evolução Molecular , Malária Falciparum/parasitologia , Plasmodium falciparum/genética , Tetra-Hidrofolato Desidrogenase/genética , Animais , DNA de Protozoário/química , DNA de Protozoário/genética , Resistência a Medicamentos/genética , Eletroforese Capilar , Humanos , Malária Falciparum/tratamento farmacológico , Repetições de Microssatélites/genética , Plasmodium falciparum/enzimologia , Mutação Puntual , Reação em Cadeia da Polimerase , Senegal , Tetra-Hidrofolato Desidrogenase/química
12.
J Psychiatr Ment Health Nurs ; 13(4): 416-22, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16867125

RESUMO

This paper critiques the conventional concept of 'insight' within the mental status assessment, seeking to unseat its taken-for-granted definition and the status it has acquired in research and practice. Drawing on social theory, consumer perspective and interdisciplinary research, the paper focuses on the impact of 'thin' biomedical understandings of insight, in disqualifying and demoralizing persons subjected to assessment and at the same time creating punitive scrutineers out of well-intentioned practitioners. Nurses and their mental health colleagues are encouraged to reconsider their reliance on the concept of insight. We entertain the alternative idea that insight is a quality of perception that mental health practitioners can cultivate, to more deeply understand their work, culture and the self.


Assuntos
Conscientização , Transtornos Mentais , Relações Enfermeiro-Paciente , Poder Psicológico , Enfermagem Psiquiátrica/organização & administração , Autoavaliação (Psicologia) , Atitude do Pessoal de Saúde , Competência Clínica , Humanos , Intuição , Julgamento , Conhecimento , Transtornos Mentais/enfermagem , Transtornos Mentais/psicologia , Papel do Profissional de Enfermagem/psicologia , Avaliação em Enfermagem , Teoria de Enfermagem , Cooperação do Paciente/psicologia , Filosofia em Enfermagem , Pós-Modernismo , Teoria Psicológica , Psicometria , Sociologia Médica
13.
Toxicol In Vitro ; 34: 55-70, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26989001

RESUMO

A prospective multicentre study of the reconstructed human corneal epithelial tissue-based in vitro test method (SkinEthic™ HCE) was conducted to evaluate its usefulness to identify chemicals as either not classified for serious eye damage/eye irritation (No Cat.) or as classified (Cat. 1/Cat. 2) within UN GHS. The aim of this study was to demonstrate the transferability and reproducibility of the SkinEthic™ HCE EITS protocol for solids and define its predictive capacity. Briefly, 60 chemicals were three times tested (double blinded) in 3 laboratories and 35 additional chemicals were tested three times in one laboratory. Good within laboratory reproducibility was achieved of at least 95% (57/60) and 96.8% (92/95) for the extended data set. Furthermore, the overall concordance between the laboratories was 96.7% (58/60). The accuracy of the SkinEthic™ HCE EITS for the extended dataset, based on bootstrap resampling, was 81.0% (95% CI: 78.9% to 83.2%) with a sensitivity of 90.5% (95% CI: 88.1% to 92.9%) and specificity of 73.6% (95% CI: 71.7% to 75.5%). Overall, 200 chemicals were tested (105 liquids (EITL protocol) and 95 solids (EITS protocol)) resulting in a sensitivity of 95.2%, specificity of 72.1% and accuracy of 83.7%, thereby meeting all acceptance criteria for predictive capacity.


Assuntos
Alternativas aos Testes com Animais , Epitélio Corneano/efeitos dos fármacos , Irritantes/toxicidade , Humanos , Técnicas In Vitro , Laboratórios , Reprodutibilidade dos Testes , Testes de Toxicidade/métodos
14.
Toxicol In Vitro ; 31: 43-53, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26612353

RESUMO

A prospective multicentric study of the reconstructed human corneal epithelial tissue-based in vitro test method (SkinEthic™ HCE) was conducted to evaluate its usefulness to identify chemicals as either not classified for serious eye damage/eye irritation (No Cat.) or as classified (Cat. 1/Cat. 2) within UN GHS. The aim of this study was to demonstrate the transferability and reproducibility of the SkinEthic™ HCE EITL protocol for liquids and define its predictive capacity. Briefly, 60 chemicals were three times tested (double blinded) in 3 laboratories and 45 additional chemicals were tested three times in one laboratory. Good within laboratory reproducibility was achieved of at least 88.3% (53/60) and 92.4% (97/105) for the extended data set. Furthermore, the overall concordance between the laboratories was 93.3% (56/60). The accuracy of the SkinEthic™ HCE EITL for the extended dataset, based on bootstrap resampling, was 84.4% (95% CI: 81.9% to 87.6%) with a sensitivity of 99.0% (95% CI: 96.4% to 100%) and specificity of 68.5% (95% CI: 64.0% to 74.0%), thereby meeting all acceptance criteria for predictive capacity. This efficient transferable and reproducible assay is a promising tool to be integrated within a battery of assays to perform an eye irritation risk assessment.


Assuntos
Alternativas aos Testes com Animais , Epitélio Corneano/efeitos dos fármacos , Irritantes/toxicidade , Bioensaio , Humanos , Laboratórios , Reprodutibilidade dos Testes
15.
J Pharm Sci ; 94(3): 632-8, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15666298

RESUMO

In vitro measurements of skin absorption are an increasingly important aspect of regulatory studies, product support claims, and formulation screening. However, such measurements are significantly affected by skin variability. The purpose of this study was to determine inter- and intralaboratory variation in diffusion cell measurements caused by factors other than skin. This was attained through the use of an artificial (silicone rubber) rate-limiting membrane and the provision of materials including a standard penetrant, methyl paraben (MP), and a minimally prescriptive protocol to each of the 18 participating laboratories. "Standardized" calculations of MP flux were determined from the data submitted by each laboratory by applying a predefined mathematical model. This was deemed necessary to eliminate any interlaboratory variation caused by different methods of flux calculations. Average fluxes of MP calculated and reported by each laboratory (60 +/- 27 microg cm(-2) h(-1), n = 25, range 27-101) were in agreement with the standardized calculations of MP flux (60 +/- 21 microg cm(-2) h(-1), range 19-120). The coefficient of variation between laboratories was approximately 35% and was manifest as a fourfold difference between the lowest and highest average flux values and a sixfold difference between the lowest and highest individual flux values. Intralaboratory variation was lower, averaging 10% for five individuals using the same equipment within a single laboratory. Further studies should be performed to clarify the exact components responsible for nonskin-related variability in diffusion cell measurements. It is clear that further developments of in vitro methodologies for measuring skin absorption are required.


Assuntos
Técnicas de Laboratório Clínico/normas , Variações Dependentes do Observador , Técnicas de Laboratório Clínico/estatística & dados numéricos , Difusão , Cultura em Câmaras de Difusão/métodos , Cultura em Câmaras de Difusão/normas , Cultura em Câmaras de Difusão/estatística & dados numéricos , Internacionalidade , Controle de Qualidade , Padrões de Referência , Valores de Referência , Absorção Cutânea/fisiologia
16.
Mol Biochem Parasitol ; 61(1): 15-24, 1993 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-8259128

RESUMO

DNA typing systems currently used in parasitology involve either hybridising Southern blots with repetitive sequence probes or amplifying genomic sequences using the polymerase chain reaction (PCR). Both such approaches assay allelic length variation, usually in unexpressed tandemly repeated DNA sequences. Where an appropriate target locus exists, an alternative PCR-based strategy which reveals allelic sequence variation in tandemly repeated DNA offers a more accurate and internally controlled assay. We describe such a strategy for the rapid extraction of information on tandem repeat sequence variation from hypervariable alleles, and apply it to the Plasmodium falciparum CS gene. The extreme variability of such DNA 'barcodes' can be used to identify parasite stocks and lineages. This system is also potentially useful for population genetic and epidemiological studies since it offers the possibility of following the spread of distinctively marked parasite genotypes in samples taken from infected individuals.


Assuntos
DNA de Protozoário/genética , Plasmodium falciparum/genética , Proteínas de Protozoários/genética , Sequências Repetitivas de Ácido Nucleico , Animais , Sequência de Bases , Southern Blotting , Dados de Sequência Molecular , Plasmodium falciparum/classificação , Plasmodium falciparum/isolamento & purificação , Reação em Cadeia da Polimerase
17.
Mol Biochem Parasitol ; 115(2): 145-56, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11420101

RESUMO

Comparing patterns of genetic variation at multiple loci in the genome of a species can potentially identify loci which are under selection. The large number of polymorphic microsatellites in the malaria parasite Plasmodium falciparum are available markers to screen for selectively important loci. The Pfs48/45 gene on Chromosome 13 encodes an antigenic protein located on the surface of parasite gametes, which is a candidate for a transmission blocking vaccine. Here, genotypic data from 255 P. falciparum isolates are presented, which show that alleles and haplotypes of five single nucleotide polymorphisms (SNPs) in the Pfs48/45 gene are exceptionally skewed in frequency among different P. falciparum populations, compared with alleles at 11 microsatellite loci sampled widely from the parasite genome. Fixation indices measuring inter-population variance in allele frequencies (F(ST)) were in the order of four to seven times higher for Pfs48/45 than for the microsatellites, whether considered (i) among populations within Africa, or (ii) among different continents. Differing mutational processes at microsatellite and SNP loci could generally affect the population structure at these different types of loci, to an unknown extent which deserves further investigation. The highly contrasting population structure may also suggest divergent selection on the amino acid sequence of Pfs48/45 in different populations, which plausibly indicates a role for the protein in determining gamete recognition and compatibility.


Assuntos
Variação Genética/genética , Malária Falciparum/epidemiologia , Glicoproteínas de Membrana/genética , Repetições de Microssatélites/genética , Plasmodium falciparum/genética , Proteínas de Protozoários/genética , África/epidemiologia , Alelos , Animais , Brasil/epidemiologia , Frequência do Gene , Genética Populacional , Haplótipos , Humanos , Malária Falciparum/parasitologia , Malásia/epidemiologia , Plasmodium falciparum/crescimento & desenvolvimento , Polimorfismo de Nucleotídeo Único
18.
Mol Biochem Parasitol ; 114(1): 63-70, 2001 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-11356514

RESUMO

The Plasmodium falciparum erythrocyte binding antigen-175 gene (eba-175) has highly divergent allelic segments (Cseg and Fseg) in one part of the gene (region III), but only a small number of single nucleotide polymorphisms (SNPs) in the rest of the sequence. Here, evidence for the possible importance of the Cseg/Fseg dimorphism was sought in a molecular population genetic analysis of the gene. First, allele frequency distributions were determined for the Cseg/Fseg dimorphism and five SNPs in a sample of five populations in Africa. The inter-population variance in frequencies was higher for Cseg/Fseg (F(ST)=0.18) than for the SNPs (F(ST) values from 0.03 to 0.10), but these values were entirely dependent on the inclusion of one particularly divergent population (Sudan). Second, linkage disequilibrium was measured among the intragenic loci. There was the expected trend of declining linkage disequilibrium with increasing molecular distance, but it is notable that the Cseg allele was in absolute linkage disequilibrium with the two flanking SNPs, whereas the Fseg allele was associated with a broader range of SNP haplotypes. Finally, there was no association between the Cseg/Fseg alleles of eba-175 in parasites and the M/N alleles of the glycophorin A erythrocyte receptor in the human subjects.


Assuntos
Proteínas de Transporte/genética , Genética Populacional , Plasmodium falciparum/genética , Polimorfismo de Nucleotídeo Único/genética , Proteínas de Protozoários/genética , África , Alelos , Animais , Antígenos de Protozoários/genética , Eritrócitos/parasitologia , Frequência do Gene , Geografia , Glicoforinas/genética , Haplótipos , Interações Hospedeiro-Parasita/genética , Humanos , Desequilíbrio de Ligação
19.
Mol Biochem Parasitol ; 111(1): 163-71, 2000 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11087926

RESUMO

The origin and geographical spread of Plasmodium falciparum is here determined by analysis of mitochondrial DNA sequence polymorphism and divergence from its most closely related species P. reichenowi (a rare parasite of chimpanzees). The complete 6 kb mitochondrial genome was sequenced from the single known isolate of P. reichenowi and from four different cultured isolates of P. falciparum, and aligned with the two previously derived P. falciparum sequences. The extremely low synonymous nucleotide polymorphism in P. falciparum (pi=0.0004) contrasts with the divergence at such sites between the two species (kappa=0.1201), and supports a hypothesis that P. falciparum has recently emerged from a single ancestral population. To survey the geographical distribution of mitochondrial haplotypes in P. falciparum, 104 isolates from several endemic areas were typed for each of the identified single nucleotide polymorphisms. The haplotypes show a radiation out of Africa, with unique types in Southeast Asia and South America being related to African types by single nucleotide changes. This indicates that P. falciparum originated in Africa and colonised Southeast Asia and South America separately.


Assuntos
DNA Mitocondrial/genética , Genoma de Protozoário , Malária Falciparum/parasitologia , Plasmodium falciparum/genética , Plasmodium/genética , África , Animais , Sudeste Asiático , DNA de Protozoário/genética , Evolução Molecular , Haplótipos , Humanos , Dados de Sequência Molecular , Plasmodium falciparum/classificação , Polimorfismo de Nucleotídeo Único , Seleção Genética , América do Sul
20.
Immunol Lett ; 71(2): 117-26, 2000 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-10714439

RESUMO

In areas of unstable transmission malaria affects all age groups, but the malaria incidence is lower in adults compared to children and teenagers. Under such conditions subclinical Plasmodium falciparum infections are common and some infections are controlled, because blood parasitaemia is maintained at low densities. Here, we test the hypothesis that the presence or absence of antibodies against variant antigens on the surface of P. falciparum-infected erythrocytes protect individuals against some infectious challenges and render them susceptible to others. Plasma collected in Daraweesh, eastern Sudan, before and after the malaria season from individuals who had (susceptible) or did not have malaria (protected) during the season, were tested for reactivity against variant antigens on the surface of nine parasite isolates by flow cytometry. Both protected and susceptible individuals acquired antibodies to variant antigens during the malaria season. The presence of antibody to a Ghanaian isolate before the season was statistically significantly associated with protection against malaria. When considering all nine isolates, the patterns of antibody acquisition differed between susceptible and protected individuals. Together, the results indicate that pre-existing anti-PfEMP1 antibodies can reduce the risk of contracting clinical malaria when challenged by novel parasite clones expressing homologous, but not heterologous variable surface antigens. The results also confirm that antibodies to variant antigens are induced by both clinical and subclinical infections, and that antibodies against several var sero-types are induced during an infection.


Assuntos
Anticorpos Antiprotozoários/sangue , Membrana Eritrocítica/parasitologia , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Plasmodium falciparum/imunologia , Adolescente , Adulto , Fatores Etários , Animais , Antígenos de Protozoários , Criança , Pré-Escolar , Membrana Eritrocítica/imunologia , Feminino , Humanos , Malária Falciparum/sangue , Masculino , Proteínas de Membrana/imunologia , Pessoa de Meia-Idade , Parasitemia/sangue , Parasitemia/imunologia , Parasitemia/parasitologia , Proteínas de Protozoários/imunologia , Estações do Ano , Sudão
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA