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2.
Anal Chim Acta ; 1104: 105-109, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32106940

RESUMO

Solid-state 13C and 19F NMR spectroscopy offers a non-destructive, highly selective protocol for the identification of forensically relevant synthetic cannabinoids on herbal substrates. Using this technique, well resolved 13C spectra were obtained that readily enabled structural identification; in some instances complemented by 19F spectral data. The approach described has potential for related applications such as the direct detection of pesticides on plants.


Assuntos
Canabinoides/análise , Drogas Desenhadas/análise , Ressonância Magnética Nuclear Biomolecular/métodos , Preparações de Plantas/química , Turnera/química , Canabinoides/química , Drogas Desenhadas/química , Estrutura Molecular
3.
J Appl Stat ; 46(2): 351-363, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-38504925

RESUMO

We encountered a problem in which a study's experimental design called for the use of paired data, but the pairing between subjects had been lost during the data collection procedure. Thus we were presented with a data set consisting of pre and post responses but with no way of determining the dependencies between our observed pre and post values. The aim of the study was to assess whether an intervention called Self-Revelatory Performance had an impact on participant's perceptions of Alzheimer's disease. The participant's responses were measured on an Affect grid before the intervention and on a separate grid after. To address the underlying question in light of the lost pairing we utilized a modified bootstrap approach to create a null hypothesized distribution for our test statistic, which was the distance between the two Affect Grids' Centers of Mass. Using this approach we were able to reject our null hypothesis and conclude that there was evidence the intervention influenced perceptions about the disease.

4.
Ir Med J ; 111(8): 806, 2018 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-30547551

RESUMO

Anorexia nervosa affects 0.5% of the population (90% female) with the highest mortality of any psychiatric illness, usually suicide, or cardiovascular or neurological sequelae of either malnutrition or refeeding syndrome. The latter two conditions occur in the inpatient setting, carry a high mortality and are thoroughly avoidable with careful informed clinical management. This paper provides an overview of the service and care of these patients in a general hospital setting in Ireland. In response to a number of acute presentations a cross discipline Pop-up Eating Disorder Unit (psychiatrist, physician, dietician, nurse) was established in Sligo University Hospital in 2014 and has experience of 20 people treated according to the MARSIPAN guideline (Management of Really Sick Inpatients with Anorexia Nervosa). They are nursed in a designated ward with continuous cardiac monitoring (in addition 2 required ICU admission), with one-to-one continuous supervision, complete bed rest, careful calorie titration (usually nasogastric) with twice daily phosphate, magnesium, calcium and potassium concentrations measured and replaced. Sabotaging behaviour witnessed includes micro-exercising, requests for windows to be opened (in order to shiver/micro exercise), food concealment, faecal/urinary loading on weighing days, heavy hair accessories, vigorous page turning/toothbrushing/use of computer keypads and animated conversations. A cross disciplinary coordinated approach to this cohort, who often inventive in their resistance to treatment, allows safe management in a general hospital setting.

5.
Res Involv Engagem ; 3: 28, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29225922

RESUMO

PLAIN ENGLISH SUMMARY: It is important for health care workers to know the needs and expectations of their patients. Therefore, service users have to be involved in research. To achieve a meaningful dialogue between service users, healthcare workers and researchers, participatory methods are needed. This paper describes how the application of a specific participatory methodology, Participatory Learning and Action (PLA) can lead to such a meaningful dialogue. In PLA all stakeholders are regarded as equal partners and collaborators in research.During 2011-2015, a European project called RESTORE used PLA in Austria, Greece, Ireland, The Netherlands and the UK to investigate how communication between primary health care workers and their migrant patients could be improved.Seventy eight migrants, interpreters, doctors, nurses and other key stakeholders (see Table 2) participated in 62 PLA sessions. These dialogues (involving discussions, activities, PLA techniques and evaluations) were generally 2-3 h long and were recorded and analysed by the researchers.Participants reported many positive experiences about their dialogues with other stakeholders. There was a positive, trusting atmosphere in which all stakeholders could express their views despite differences in social power. This made for better understanding within and across stakeholder groups. For instance a doctor changed her view on the use of interpreters after a migrant explained why this was important. Negative experiences were rare: some doctors and healthcare workers thought the PLA sessions took a lot of time; and despite the good dialogue, there was disappointment that very few migrants used the new interpreting service. ABSTRACT: Background In order to be effective, primary healthcare must understand the health needs, values and expectations of the population it serves. Recent research has shown that the involvement of service users and other stakeholders and gathering information on their perspectives can contribute positively to many aspects of primary healthcare. Participatory methodologies have the potential to support engagement and dialogue between stakeholders from academic, migrant community and health service settings. This paper focuses on a specific participatory research methodology, Participatory Learning and Action (PLA) in which all stakeholders are regarded as equal partners and collaborators in research.Our research question for this paper was: "Does the application of PLA lead to meaningful engagement of all stakeholders, and if so, what elements contribute to a positive and productive inter-stakeholder dialogue?". Methods We explored the use of PLA in RESTORE, a European FP7-funded project, during 2011-2015 in 5 countries: Austria, Greece, Ireland, the Netherlands and the UK. The objective of RESTORE was to investigate and support the implementation of guidelines and training initiatives (G/TIs) to enhance communication in cross-cultural primary care consultations with migrants.Seventy eight stakeholders (migrants, interpreters, doctors, nurses and others - see Table 2) participated in a total of 62 PLA sessions (discussions, activities, evaluations) of approximately 2-3 h' duration across the five sites. During the fieldwork, qualitative data were generated about stakeholders' experiences of engagement in this dialogue, by means of various methods including participatory evaluations, researchers' fieldwork reports and researcher interviews. These were analysed following the principles of thematic analysis. Results Stakeholders involved in PLA inter-stakeholder dialogues reported a wide range of positive experiences of engagement, and very few negative experiences. A positive atmosphere during early research sessions helped to create a sense of safety and trust. This enabled stakeholders from very different backgrounds, with different social status and power, to offer their perspectives in a way that led to enhanced learning in the group - they learned with and from each other. This fostered shifts in understanding - for example, a doctor changed her view on interpreted consultations because of the input of the migrant service-users. Conclusion PLA successfully promoted stakeholder involvement in meaningful and productive inter-stakeholder dialogues. This makes it an attractive approach to enhance the further development of health research partnerships to advance primary healthcare.

6.
Int J Equity Health ; 16(1): 32, 2017 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-28222736

RESUMO

BACKGROUND: Cross-cultural communication in primary care is often difficult, leading to unsatisfactory, substandard care. Supportive evidence-based guidelines and training initiatives (G/TIs) exist to enhance cross cultural communication but their use in practice is sporadic. The objective of this paper is to elucidate how migrants and other stakeholders can adapt, introduce and evaluate such G/TIs in daily clinical practice. METHODS: We undertook linked qualitative case studies to implement G/TIs focused on enhancing cross cultural communication in primary care, in five European countries. We combined Normalisation Process Theory (NPT) as an analytical framework, with Participatory Learning and Action (PLA) as the research method to engage migrants, primary healthcare providers and other stakeholders. Across all five sites, 66 stakeholders participated in 62 PLA-style focus groups over a 19 month period, and took part in activities to adapt, introduce, and evaluate the G/TIs. Data, including transcripts of group meetings and researchers' fieldwork reports, were coded and thematically analysed by each team using NPT. RESULTS: In all settings, engaging migrants and other stakeholders was challenging but feasible. Stakeholders made significant adaptations to the G/TIs to fit their local context, for example, changing the focus of a G/TI from palliative care to mental health; or altering the target audience from General Practitioners (GPs) to the wider multidisciplinary team. They also progressed plans to deliver them in routine practice, for example liaising with GP practices regarding timing and location of training sessions and to evaluate their impact. All stakeholders reported benefits of the implemented G/TIs in daily practice. Training primary care teams (clinicians and administrators) resulted in a more tolerant attitude and more effective communication, with better focus on migrants' needs. Implementation of interpreter services was difficult mainly because of financial and other resource constraints. However, when used, migrants were more likely to trust the GP's diagnoses and GPs reported a clearer understanding of migrants' symptoms. CONCLUSIONS: Migrants, primary care providers and other key stakeholders can work effectively together to adapt and implement G/TIs to improve communication in cross-cultural consultations, and enhance understanding and trust between GPs and migrant patients.


Assuntos
Comunicação , Competência Cultural/educação , Emigrantes e Imigrantes , Pessoal de Saúde/educação , Guias de Prática Clínica como Assunto , Atenção Primária à Saúde , Migrantes , Barreiras de Comunicação , Educação , Europa (Continente) , Feminino , Grupos Focais , Fidelidade a Diretrizes , Humanos , Masculino , Aprendizagem Baseada em Problemas , Pesquisa Qualitativa , Encaminhamento e Consulta
7.
Child Neuropsychol ; 23(3): 300-315, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-26507931

RESUMO

This study investigates the relationship between motor function and processing speed in preterm children. Processing speed was compared in 145 adolescents, born 25-41 weeks gestational age, utilizing tasks including differing motor demands. The influence of motor cortex excitability and functional motor skills on task performance was assessed. For tasks with motoric demands, differences in performance between preterm and term-born children were mediated by the relationship between gestational age, corticomotor excitability, and motor function. There were no differences in non-motor processing speed task performance between preterm and term-born children. Measures of processing speed may be confounded by a timed motor component.


Assuntos
Destreza Motora , Transtornos do Neurodesenvolvimento/diagnóstico , Estimulação Magnética Transcraniana/métodos , Adolescente , Criança , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino
8.
Early Hum Dev ; 89(2): 69-74, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22884007

RESUMO

BACKGROUND: Previous research has linked family sleep disruption and dysfunction in children; however, the mechanism is unknown. AIMS: This study examined whether maternal sleep and postnatal depression (PND) mediate the relationship between infant sleep disruption and family dysfunction. STUDY DESIGN AND PARTICIPANTS: Mothers of infants aged 12 months old (N=111; 48% male) completed infant and parent sleep surveys, the Edinburgh Postnatal Depression Scale and the Family Assessment Device. RESULTS: Poor infant sleep was related to poor maternal sleep, which was associated with higher PND and higher level of family dysfunction. CONCLUSIONS: Results are consistent with the proposition that identification of both infant and maternal sleep problems during infancy can be relevant to reduction of PND and improved family functioning.


Assuntos
Depressão Pós-Parto/complicações , Distúrbios do Início e da Manutenção do Sono/etiologia , Depressão Pós-Parto/psicologia , Relações Familiares , Feminino , Humanos , Lactente , Masculino
9.
Int J Obstet Anesth ; 20(1): 73-6, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21035323

RESUMO

An intravenous bolus of phentolamine was inadvertently given to a parturient during an emergency caesarean section following delivery of her infant when the intention had been to give an intravenous bolus of 5 IU Syntocinon. Root cause analysis identified a series of errors originating in the hospital pharmacy when one drug package was mistakenly issued in place of another. Subsequent checks failed to detect the original mistake. The final and most important check immediately before intravenous administration was also at fault. This case highlights a systems failure that permitted issue, transportation and administration of the wrong drug to a parturient. Robust measures to ensure avoidance of drug administration errors should be evaluated and introduced where possible.


Assuntos
Antagonistas Adrenérgicos alfa/efeitos adversos , Cesárea , Erros Médicos , Fentolamina/efeitos adversos , Adulto , Embalagem de Medicamentos , Feminino , Humanos , Recém-Nascido , Injeções Intravenosas , Ocitócicos/uso terapêutico , Ocitocina/uso terapêutico , Gravidez
10.
J Nutr Health Aging ; 12(9): 657-62, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18953465

RESUMO

OBJECTIVES: To investigate the effects of glucose, or a combination of saccharides, or a placebo on the memory performance of middle-aged adults. DESIGN: A double-blind, placebo controlled design was used. A population-based sample of 45 men and women (aged 40-63 years) completed a series of memory tasks following administration of a single dose of either glucose, a combination of saccharides or placebo. Memory tasks included immediate and delayed recall, recognition, short-term memory, working memory, and a test of general cognitive ability. RESULTS: There were no statistically significant effects of treatments on any of the outcome measures. CONCLUSION: The pattern of means in the combination of saccharides group suggests potential enhancement effects of memory performance in middle-aged adults that deserves further investigation.


Assuntos
Cognição/efeitos dos fármacos , Carboidratos da Dieta/farmacologia , Glucose/farmacologia , Memória/efeitos dos fármacos , Adulto , Cognição/fisiologia , Método Duplo-Cego , Feminino , Humanos , Masculino , Memória/fisiologia , Rememoração Mental , Pessoa de Meia-Idade
11.
Ir J Med Sci ; 177(4): 379-81, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18825476

RESUMO

BACKGROUND: The Irish childhood obesity epidemic, one of the highest ranking internationally, represents a major threat to public health. We sought to perform a retrospective observational study of a clinic based cohort of obese Irish children. METHODS: Clinical data relating to gender, age, height, weight, body mass index and blood pressure were analysed, from 206 children referred to a paediatric endocrine referral centre over a 15-year period for assessment of obesity. RESULTS: Younger patients tended to have a higher standardised body mass index at initial presentation; 92% of boys and 96% of girls referred were obese (age-related BMI >/= 95th percentile). Boys (51%) and girls (49%) had initial blood pressure measurements in the hypertensive range. There was a correlation between the degree of obesity and systolic blood pressure, particularly in boys. CONCLUSIONS: Obese Irish children present with significant long-term health risks, including hypertension at baseline.


Assuntos
Pressão Sanguínea/fisiologia , Hipertensão/fisiopatologia , Obesidade/fisiopatologia , Sobrepeso/fisiopatologia , Adolescente , Determinação da Pressão Arterial , Índice de Massa Corporal , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Hemodinâmica , Humanos , Hipertensão/epidemiologia , Irlanda/epidemiologia , Masculino , Obesidade/epidemiologia , Oscilometria/instrumentação , Sobrepeso/epidemiologia , Saúde Pública , Estudos Retrospectivos
13.
Philos Trans A Math Phys Eng Sci ; 366(1871): 1789-806, 2008 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-18222904

RESUMO

Conventional and digital holographies are proving to be increasingly important for studies of marine zooplankton and other underwater biological applications. This paper reports on the use of a subsea digital holographic camera (eHoloCam) for the analysis and identification of marine organisms and other subsea particles. Unlike recording on a photographic film, a digital hologram (e-hologram) is recorded on an electronic sensor and reconstructed numerically in a computer by simulating the propagation of the optical field in space. By comparison with other imaging techniques, an e-hologram has several advantages such as three-dimensional spatial reconstruction, non-intrusive and non-destructive interrogation of the recording sampling volume and the ability to record holographic videos. The basis of much work in optics lies in Maxwell's electromagnetic theory and holography is no exception: we report here on two of the numerical reconstruction algorithms we have used to reconstruct holograms obtained using eHoloCam and how their starting point lies in Maxwell's equations. Derivation of the angular spectrum algorithm for plane waves is provided as an exact method for the in-line numerical reconstruction of digital holograms. The Fresnel numerical reconstruction algorithm is derived from the angular spectrum method. In-line holograms are numerically processed before and after reconstruction to remove periodic noise from captured images and to increase image contrast. The ability of the Fresnel integration reconstruction algorithm to extend the reconstructed volume beyond the recording sensor dimensions is also shown with a 50% extension of the reconstruction area. Finally, we present some images obtained from recent deployments of eHoloCam in the North Sea and Faeroes Channel.


Assuntos
Holografia/métodos , Fotografação/instrumentação , Plâncton/fisiologia , Algoritmos , Ecossistema , Oceanos e Mares , Fotografação/métodos
14.
Spinal Cord ; 46(8): 547-51, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18071354

RESUMO

STUDY DESIGN: Comparison of two self-report instruments with a structured diagnostic interview. OBJECTIVE: To investigate the properties of the Depression Anxiety Stress Scales-21 (DASS-21) in patients with spinal cord injuries. SETTING: South Australian Spinal Cord Injuries Service, Hampstead Rehabilitation Centre, Northfield, South Australia. METHODS: Forty paraplegic or tetraplegic patients participated. Two self-report measures, DASS-21 and Brief Symptom Inventory (BSI), assessed Depression, Anxiety and Stress. These measures were compared with each other and with diagnoses based on the Mini International Neuropsychiatric Interview. RESULTS: Mean scores on both self-report measures were below clinical threshold levels. Prevalence rates of anxiety and depression were higher on DASS-21 than on BSI. DASS-21 was as sensitive as BSI, but had lower specificity to detect anxiety and depression. CONCLUSION: DASS-21 is a promising screening measure for patients with spinal cord injury in a rehabilitation setting. It has greater sensitivity for identifying those with possible anxiety disorders than it does for those with depressive disorders.


Assuntos
Ansiedade/diagnóstico , Depressão/diagnóstico , Inquéritos e Questionários , Adulto , Idoso , Idoso de 80 Anos ou mais , Ansiedade/etiologia , Depressão/etiologia , Feminino , Humanos , Entrevista Psicológica , Masculino , Pessoa de Meia-Idade , Escalas de Graduação Psiquiátrica , Sensibilidade e Especificidade , Austrália do Sul/epidemiologia , Traumatismos da Medula Espinal/complicações
15.
Diabetologia ; 50(7): 1500-8, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17393133

RESUMO

AIMS/HYPOTHESIS: Early-onset type 2 diabetes is associated with marked visceral obesity and extreme insulin resistance, but its pathogenesis and response to treatment are not completely understood. We studied physical fitness, whole-body and hepatic glucose turnover, and insulin secretion in young obese Irish subjects before and after 3 months of aerobic exercise training. We hypothesised that exercise alone, with stable diet, should improve insulin sensitivity. MATERIALS AND METHODS: Anthropometric parameters and maximum volume of oxygen utilisation (VO(2max)) were measured in 13 subjects with type 2 diabetes and 18 non-diabetic control subjects, matched for age and BMI. Insulin sensitivity and hepatic glucose turnover were measured using the hyperinsulinaemic-euglycaemic clamp. Insulin secretion was assessed from an OGTT and a modified intravenous glucose tolerance test. Some subjects (seven type 2 diabetic, 14 non-diabetic control subjects) then completed a 12-week supervised aerobic exercise programme. All measurements were repeated on completion of the exercise programme. RESULTS: Type 2 diabetic subjects had higher WHR, systolic blood pressure and triacylglycerols than non-diabetic control subjects. They were significantly more insulin-resistant as measured both by the clamp and oral glucose insulin sensitivity. They also displayed marked defects in insulin secretion in response to oral and intravenous glucose challenges. Exercise intervention had no significant effect on whole-body or hepatic insulin sensitivity or insulin secretion. VO(2max) increased significantly in the non-diabetic control subjects, but not in the type 2 diabetic subjects after exercise training. CONCLUSIONS/INTERPRETATION: Young obese subjects with type 2 diabetes are severely insulin-resistant with marked loss of beta cell function compared with control subjects matched for age and obesity. Neither group responded metabolically to aerobic exercise intervention.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Exercício Físico , Resistência à Insulina , Células Secretoras de Insulina/metabolismo , Obesidade/complicações , Adolescente , Adulto , Idade de Início , Índice de Massa Corporal , Dieta , Feminino , Glucose/metabolismo , Teste de Tolerância a Glucose , Humanos , Masculino , Obesidade/metabolismo , Oxigênio/metabolismo , Triglicerídeos/metabolismo
17.
Toxicology ; 212(1): 1-9, 2005 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-15905016

RESUMO

Epidemiological data supports lead exposure as a risk factor for cataract development. Previous studies which demonstrated oxidative imbalances in the lens following in vivo Pb(2+) exposure support the idea that lead exposure can alter the lens biochemical homeostasis which may ultimately lead to loss of lens clarity with time. alpha-Crystallin, a major lens structural protein and molecular chaperone, undergoes various post-translational modifications upon aging which may contribute to decreased chaperone function and contribute to loss of lens clarity. This study evaluated the impact of 5 weeks of oral Pb(2+) exposure (peripheral Pb(2+) level approximately 30 microg/dL) on the alphaA-crystallin protein profile of the lens from Fisher 344 rats. Decreases in relative protein spot intensity of more acidic forms of alphaA- and betaA(4)-crystallin and of truncated forms of alphaA-crystallin were noted. This data indicates that changes in post-translational processing of crystallins do occur in vivo following short courses of clinically relevant Pb(2+)-exposure. In addition, organ culture of lenses from 4.5-month-old rats in 5 microM Pb(2+) resulted in opacities, demonstrating that lead is toxic to the lens and can induce a loss of lens clarity.


Assuntos
Catarata/induzido quimicamente , Catarata/genética , Cristalino/efeitos dos fármacos , Compostos Organometálicos/toxicidade , Análise Serial de Proteínas/métodos , Cadeia A de alfa-Cristalina/genética , Animais , Catarata/metabolismo , Cristalino/metabolismo , Técnicas de Cultura de Órgãos , Ratos , Ratos Endogâmicos F344 , Ratos Sprague-Dawley , Cadeia A de alfa-Cristalina/biossíntese
18.
Arch Environ Contam Toxicol ; 44(3): 417-20, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-12712304

RESUMO

Lead poisoning has been extensively studied over the years. Many adverse physiological and behavioral impacts on the human body have been reported due to the entry of this heavy metal. It especially affects the neural development of children. The current study investigates the effect of lead exposure in young (1.5 months) and adult (10 months) male Fisher 344 rats. Five weeks of lead administration resulted in a profound change in the lead levels in the red blood cells (RBCs) of the young lead-exposed group (37.0 +/- 4.47 microg/dl) compared to the control (<1 microg/dl) and adult (27.4 +/- 8.38 microg/dl) lead-exposed groups. Therefore, this study confirms the fact that gastrointestinal absorption of lead in young is greater than that of adults. Furthermore, glutathione and glutathione disulfide (GSSG) levels in RBCs, liver, and brain tissues were measured to determine thiol status; malondialdehyde (MDA) levels of lipid peroxidation and catalase activity were measured to assess changes in oxidative stress parameters. Liver GSSG and MDA levels were significantly higher in the young lead-exposed group than those in the adult lead-exposed group. In RBCs and brains, however, adult lead-exposed animals have shown more elevated MDA levels than young animals exposed to the same lead treatment.


Assuntos
Envelhecimento/metabolismo , Intoxicação por Chumbo/fisiopatologia , Chumbo/toxicidade , Estresse Oxidativo/fisiologia , Animais , Encéfalo/metabolismo , Catalase/metabolismo , Modelos Animais de Doenças , Glutationa/metabolismo , Dissulfeto de Glutationa/metabolismo , Absorção Intestinal , Chumbo/sangue , Chumbo/farmacocinética , Intoxicação por Chumbo/metabolismo , Fígado/metabolismo , Masculino , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Endogâmicos F344
19.
J Opt Soc Am A Opt Image Sci Vis ; 18(9): 2321-30, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11551066

RESUMO

Motion-defined motion can play a special role in the discussion of whether one or two separate systems are required to process first- and second-order information because, in contrast to other second-order stimuli, such as contrast-modulated contours, motion detection cannot be explained by a simple input nonlinearity but requires preprocessing by motion detectors. Furthermore, the perceptual quality that defines an object (motion on the object surface) is identical to that which is attributed to the object as an emergent feature (motion of the object), raising the question of how these two object properties are linked. The interaction of first- and second-order information in such stimuli has been analyzed previously in a direction-discrimination task, revealing some cooperativity. Because any comprehensive integration of these two types of motion information should be reflected in the most fundamental property of a moving object, i.e., the direction in which it moves, we now investigate how motion direction is estimated in motion-defined objects. Observers had to report the direction of moving objects that were defined by luminance contrast or in random-dot kinematograms by differences in the spatiotemporal properties between the object region and the random-noise background. When the dots were moving coherently with the object (Fourier motion), direction sensitivity resembled that for luminance-defined objects, but performance deteriorated when the dots in the object region were static (drift-balanced motion). When the dots on the object surface were moving diagonally relative to the object direction (theta motion), the general level of accuracy declined further, and the perceived direction was intermediate between the veridical object motion direction and the direction of dot motion, indicating that the first- and second-order velocity vectors are somehow pooled. The inability to separate first- and second-order directional information suggests that the two corresponding subsystems of motion processing are not producing independent percepts and provides clues for possible implementations of the two-layer motion-processing network.


Assuntos
Percepção de Movimento/fisiologia , Percepção Visual/fisiologia , Adulto , Sensibilidades de Contraste/fisiologia , Sinais (Psicologia) , Discriminação Psicológica/fisiologia , Feminino , Análise de Fourier , Humanos , Luz , Masculino , Psicofísica/métodos
20.
Curr Top Med Chem ; 1(6): 529-39, 2001 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11895129

RESUMO

Toxic metals (lead, cadmium, mercury and arsenic) are widely found in our environment. Humans are exposed to these metals from numerous sources, including contaminated air, water, soil and food. Recent studies indicate that transition metals act as catalysts in the oxidative reactions of biological macromolecules therefore the toxicities associated with these metals might be due to oxidative tissue damage. Redox-active metals, such as iron, copper and chromium, undergo redox cycling whereas redox-inactive metals, such as lead, cadmium, mercury and others deplete cells' major antioxidants, particularly thiol-containing antioxidants and enzymes. Either redox-active or redox-inactive metals may cause an increase in production of reactive oxygen species (ROS) such as hydroxyl radical (HO.), superoxide radical (O2.-) or hydrogen peroxide (H2O2). Enhanced generation of ROS can overwhelm cells' intrinsic antioxidant defenses, and result in a condition known as "oxidative stress". Cells under oxidative stress display various dysfunctions due to lesions caused by ROS to lipids, proteins and DNA. Consequently, it is suggested that metal-induced oxidative stress in cells can be partially responsible for the toxic effects of heavy metals. Several studies are underway to determine the effect of antioxidant supplementation following heavy metal exposure. Data suggest that antioxidants may play an important role in abating some hazards of heavy metals. In order to prove the importance of using antioxidants in heavy metal poisoning, pertinent biochemical mechanisms for metal-induced oxidative stress should be reviewed.


Assuntos
Metais Pesados/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Animais , Antioxidantes/metabolismo , Poluentes Ambientais/farmacologia , Poluentes Ambientais/toxicidade , Humanos , Metais Pesados/farmacologia , Estresse Oxidativo/fisiologia , Espécies Reativas de Oxigênio/metabolismo
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