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1.
J Eat Disord ; 10(1): 133, 2022 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-36068623

RESUMO

OBJECTIVE: Technological and economic globalisation has been suggested as a cause of increasing rates of body dissatisfaction and eating disorders globally, especially as regards the impact of mass media on internalised body ideals. This process is rarely observed in action, however. The current work investigates multiple aspects of body ideals, body image, sociocultural attitudes and eating attitudes in 62 Creole and Mestizo women living in communities at differing stages of technological development on the Caribbean coast of Nicaragua METHOD/RESULTS: In Study 1, women used 3D avatar software to create their own 'ideal' body without the constraints of ready-made stimuli. Analyses of resulting avatars showed that components of the ideal body shape (upper and lower body curvaceousness) but not body size (body mass) were associated with levels of film and television consumption. In Study 2, women completed measures of variables in the sociocultural model of eating disorder risk. As expected, body dissatisfaction mediated the relationship between internalisation of sociocultural body ideals and pathological eating attitudes. In contrast, body appreciation reduced pathological eating attitudes, via reduced body dissatisfaction. Finally, Study 3 measured sociocultural influences, body image and eating attitudes at 2 or 3 timepoints per woman; body dissatisfaction covaried with pathological eating attitudes across time. Ethnicity varied in its effects across studies. DISCUSSION: Together these data show that even at early stages of media acculturation, women may show similar patterns of association between sociocultural internalisation, body dissatisfaction and eating disorder risk as in high income nations. However, they also demonstrate unique aspects of this population's body shape ideals, and the independent protective effect of body appreciation.


Body dissatisfaction and eating disorders are increasing on a global scale. It has been suggested that increasing access to globalised media maybe one factor in rising risk of eating disorders in low- and middle-income countries. We examined 3-dimensional body ideals, body satisfaction, and eating disorder risk in a population with relatively recent access to mass media. We find that although women in these communities maintain higher body weight ideals, and greater body appreciation, than Western women, those women who are internalising globalised cultural messaging about appearance are at greater risk of body dissatisfaction and, in turn, increased risk of eating disorders. This was true both when comparing between women and looking at how individual women's attitudes varied over time. These data show that cultural messaging about appearance has implications for body image and eating disorder risk even in populations which do not have a long history of promoting thin ideals.

2.
J Hum Nutr Diet ; 32(6): 745-753, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31411771

RESUMO

BACKGROUND: The prevalence of weight loss attempts has increased worldwide, although the extent to which sustained weight loss is achieved is unknown. There is insufficient research into weight loss maintenance (WLM) in individuals with overweight or obesity who have recently lost clinically significant amounts of weight (≥5%), particularly in the European general population. The present study aimed to determine the prevalence and retrospective predictors of WLM in population-based samples of European adults with overweight or obesity who had made a recently completed weight loss attempt. METHODS: Participants (N = 2000) in UK, Denmark and Portugal completed an online survey about loss and regain in their most recent completed weight loss attempt, features of their attempt (duration, self-weighing, lapses, strategies), as well as loss of control and binge eating. Multiple regression analysis was used to determine factors retrospectively associated with WLM in those who achieved clinically significant weight loss (n = 1272). RESULTS: Mean (SD) self-reported weight loss was 9% (8%) and mean (SD) regain was 96.3% (9%) of participants' start weight. Twenty-three percent of the total sample had maintained weight loss of ≥5% for at least 1 month. Controlling for weight loss and time since attempt, predictors of better WLM were avoidance of a temporary lapse, infrequent/absent loss of control and binge eating, and use of a greater number of dietary strategies for WLM (r2  = 0.338, P < 0.001). PRINCIPAL CONCLUSIONS: Factors associated with recent successful WLM indicate the importance of the continued use of dietary and other strategies for WLM, particularly in the face of a lapse, as well as the need to manage dysfunctional eating behaviours.


Assuntos
Obesidade/terapia , Sobrepeso/terapia , Redução de Peso , Cirurgia Bariátrica , Índice de Massa Corporal , Dinamarca , Dietoterapia , Exercício Físico , Comportamento Alimentar , Feminino , Humanos , Masculino , Portugal , Estudos Retrospectivos , Inquéritos e Questionários , Resultado do Tratamento , Reino Unido , Aumento de Peso
3.
Clin Obes ; 5(3): 136-44, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25872866

RESUMO

Weight loss outcomes in overweight and obese individuals may be influenced by individual weight loss expectations (WLEs). Research on these phenomena in older women is lacking. This cross-sectional study compared groups of younger and older women on their WLEs and related attitudes (body dissatisfaction and disordered eating). Twenty-six younger (18-38 years) and 33 older (60-78 years) overweight and obese women were recruited from a weight loss clinic, prior to treatment. Disordered eating attitudes and body dissatisfaction were assessed using validated questionnaires and a pictorial figure-choice scale. Participants reported 10 WLEs categorized according to personal, lifestyle and social factors. Overall, women with a higher body mass index had greater WLEs. Older women reported lower WLEs than younger women (-14.5 kg vs. -22.4 kg) in all categories except past weight. Older women perceived that career success would necessitate the greatest level of weight loss (-18.5 kg), whereas younger women derived their greatest WLEs from mass media (-28.5 kg). Both older and younger groups perceived that their families would be supportive of the smallest amount of weight loss (-8.4 and -17.6 kg, respectively). The groups did not differ on body dissatisfaction, but younger women's disordered eating attitudes were significantly higher (p < .001). Older overweight and obese women have lower WLEs than younger women but experience similar levels of body dissatisfaction and healthier eating attitudes. The attitudinal constructs underlying these differences may be useful in clinical practice to tailor age-specific weight loss interventions.


Assuntos
Atitude Frente a Saúde , Comportamentos Relacionados com a Saúde , Sobrepeso/psicologia , Redução de Peso , Adolescente , Adulto , Fatores Etários , Idoso , Imagem Corporal , Estudos Transversais , Comportamento Alimentar/psicologia , Feminino , Humanos , Pessoa de Meia-Idade , Obesidade/psicologia , Satisfação Pessoal , Adulto Jovem
4.
Knee ; 16(5): 398-404, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19269183

RESUMO

This study has assessed the relative proportions of type I and II collagens and IIA procollagen in full depth biopsies of repair tissue in a large sample of patients treated with autologous chondrocyte implantation (ACI). Sixty five full depth biopsies were obtained from knees of 58 patients 8-60 months after treatment by ACI alone (n=55) or in combination with mosaicplasty (n=10). In addition articular cartilage was examined from eight individuals (aged 10-50) as controls. Morphology and semi-quantitative immunohistochemistry for collagen types I and II and procollagen IIA in the repair tissue were studied. Repair cartilage thickness was 2.89+/-1.5 mm and there was good basal integration between the repair cartilage, calcified cartilage and subchondral bone. Sixty five percent of the biopsies were predominantly fibrocartilage (mostly type I collagen and IIA procollagen), 15% were hyaline cartilage (mostly type II collagen), 17% were of mixed morphology and 3% were fibrous tissue (mostly type I collagen). Type II collagen and IIA procollagen were usually found in the lower regions near the bone and most type II collagen was present 30-60 months after treatment. The presence of type IIA procollagen in the repair tissue supports our hypothesis that this is indicative of a developing cartilage, with the ratio of type II collagen:procollagen IIA increasing from <2% in the first two years post-treatment to 30% three to five years after treatment. This suggests that cartilage repair tissue produced following ACI treatment, is likely to take some years to mature.


Assuntos
Cartilagem Articular/cirurgia , Condrócitos/transplante , Colágeno Tipo II/metabolismo , Colágeno Tipo I/metabolismo , Fibrocartilagem/metabolismo , Técnicas Imunoenzimáticas/métodos , Adulto , Biomarcadores/metabolismo , Biópsia , Cartilagem Articular/metabolismo , Cartilagem Articular/patologia , Transplante de Células , Condrócitos/metabolismo , Fibrocartilagem/patologia , Técnica Direta de Fluorescência para Anticorpo , Humanos
5.
Eur Spine J ; 15 Suppl 3: S312-6, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16773379

RESUMO

Intervertebral discs demonstrate degenerative changes relatively early in life. Disc degeneration, in turn, is associated with back pain and disc herniation, both of which cause considerable clinical problems in the western world. Cell senescence has been linked to degenerative diseases of other connective tissues such as osteoarthritis. Thus we investigated the degree of cell senescence in different regions of discs from patients with different disc disorders. Discs were obtained from 25 patients with disc herniations; from 27 patients undergoing anterior surgery for either back pain due to degenerative disc disease (n = 25) or spondylolisthesis (n = 2) and from six patients with scoliosis. In addition, four discs were obtained post-mortem. Samples were classified as annulus fibrosus or nucleus pulposus and tissue sections were assessed for the degree of cell senescence (using the marker senescence-associated-beta-galactosidase (SA-beta-Gal)) and the number of cells present in clusters. There were significantly more SA-beta-Gal positive cells in herniated discs (8.5% of cells) than those with degenerative disc disease, spondylolisthesis, scoliosis, or cadaveric discs (0.5% of cells; P < 0.001). There was more senescence of cells of the nucleus pulposus compared to those of the annulus fibrosus and in herniated discs a higher proportion of cells in cell clusters (defined as groups of three or more cells) were SA-beta-Gal positive (25.5%) compared to cells not in clusters (4.2%, P < 0.0001). This study demonstrates an increased degree of cell senescence in herniated discs, particularly in the nucleus where cell clusters occur. These clusters have been shown previously to form via cell proliferation, which is likely to explain the increased senescence. These findings could have two important clinical implications: firstly, that since senescent cells are known to behave abnormally in other locations, they may lead to deleterious effects on the disc matrix and so contribute to the pathogenesis and secondly, cells from such tissue may not be ideal for cell therapy and repair via tissue engineering.


Assuntos
Envelhecimento/patologia , Senescência Celular/fisiologia , Deslocamento do Disco Intervertebral/patologia , Disco Intervertebral/patologia , Adolescente , Adulto , Idoso , Biomarcadores/metabolismo , Proliferação de Células , Criança , Fibrocartilagem/metabolismo , Fibrocartilagem/patologia , Humanos , Disco Intervertebral/metabolismo , Deslocamento do Disco Intervertebral/metabolismo , Pessoa de Meia-Idade , beta-Galactosidase/metabolismo
6.
Anal Chem ; 73(19): 4722-8, 2001 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-11605853

RESUMO

The use of liquid chromatography coupled to sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) for the specific detection of sulfur-containing compounds is described. In the sulfur-containing drug substance cimetidine, structurally related impurities well below the 0.1% mass fraction level relative to the main drug substance could easily be detected. The structure of most of the impurities was confirmed by electrospray mass spectrometry (ESI-MS), and thus, the complementarity of the two techniques for drug analysis is shown. The limit of detection by SF-ICP-MS for cimetidine in solution was approximately 4-20 ng x g(-1), but it was blank-limited.


Assuntos
Cromatografia Líquida/métodos , Cimetidina/análise , Contaminação de Medicamentos , Espectrometria de Massas por Ionização por Electrospray/métodos , Enxofre/análise , Sensibilidade e Especificidade , Especificidade por Substrato
7.
J Chromatogr A ; 928(1): 91-8, 2001 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-11589474

RESUMO

High-performance chelation ion chromatography, using a neutral polystyrene substrate dynamically loaded with 0.1 mM dipicolinic acid, coupled with sector-field inductively coupled plasma mass spectrometry has been successfully used for the separation of the actinides thorium, uranium, americium, neptunium and plutonium. Using this column it was possible to separate the various actinides from each other and from a complex sample matrix. In particular, it was possible to separate plutonium and uranium to facilitate the detection of the former free of spectral interference. The column also exhibited some selectivity for different oxidation states of Np, Pu and U. Two oxidation states each for plutonium and neptunium were found, tentatively identified as Np(V) and Pu(III) eluting at the solvent front, and Np(IV) and Pu(IV) eluting much later. Detection limits were 12, 8, and 4 fg for 237Np, 239Pu, and 241Am, respectively, for a 0.5 ml injection. The system was successfully used for the determination of 239Pu in NIST 4251 Human Lung and 4353 Rocky Flats Soil, with results of 570+/-29 and 2939+/-226 fg g(-1), respectively, compared with a certified range of 227-951 fg g(-1) for the former and a value of 3307+/-248 fg g(-1) for the latter.


Assuntos
Elementos da Série Actinoide/análise , Quelantes/química , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Solo/análise , Calibragem , Humanos , Padrões de Referência , Sensibilidade e Especificidade
8.
Spine (Phila Pa 1976) ; 25(23): 3005-13, 2000 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-11145811

RESUMO

STUDY DESIGN: A comprehensive immunohistochemical study of matrix metalloproteinase activity in discs from patients with different disc diseases. OBJECTIVES: To identify individual matrix metalloproteinase enzymes that could contribute to the degeneration of the matrix of the intervertebral disc, to identify the cells that produce matrix metalloproteinases (for example, the endogenous disc cells or invading cells associated with vascularisation), and to determine if "aggrecanase" contributes to degradation of proteoglycans in disc disorders. SUMMARY OF BACKGROUND DATA: Matrix disorganization and loss of substance are the most common findings in degenerate discs, and proteinase enzyme activity is one means of causing these changes. METHODS: Forty-nine discs from 46 patients with degenerative disc disease, posterior anular tears, spondylolisthesis, or disc herniation were studied immunohistochemically to determine the presence of matrix metalloproteinases 1, 2, 3, 7, 8, 9 and 13, tissue metalloproteinases 1 and 2, and proteoglycan degradation products generated by either matrix metalloproteinases or aggrecanase activity. In addition, in situ zymography was used to confirm matrix metalloproteinase activity. RESULTS: The most extensive staining was seen for matrix metalloproteinases 1, 2, 3, and 9, with 91%, 71%, 65%, and 72% of samples having some immunopositivity for the respective antibodies. In contrast, staining for matrix metalloproteinases 7 and 8 was much less (38% for both). Tissue inhibitor of metalloproteinases 1 and 2 were expressed in 34% and 79% of specimens, respectively. Matrix metalloproteinases were found particularly in cell clusters and blood vessels of degenerate discs, with staining correlating positively with macroscopic degenerative grade. For all of the enzymes, there was most staining in the herniation specimens and least in the autopsy samples. The opposite was true of staining for the matrix metalloproteinases inhibitor, tissue inhibitor of metalloproteinases 2, with most found in the autopsy specimens. Enzyme activity was confirmed by in situ zymography and staining for matrix metalloproteinase degradation products of proteoglycans. In addition, there was staining with antibodies demonstrating aggrecanase degradation products. CONCLUSIONS: Matrix metalloproteinase activity is more prevalent in herniated discs than in other disc disorders studied, although matrix metalloproteinases may have been more common earlier in the disease progression. Matrix metalloproteinases can be produced by invading blood vessels and associated cells, as well as by indigenous disc cells. Aggrecanase activity, although present in some samples, was not as obvious as that of matrix metalloproteinases. In addition to altered matrix metalloproteinase production, there appears to be a change in the balance between enzymes and endogenous inhibitors, tissue inhibitors of metalloproteinases. This study highlights specific matrix metalloproteinases that might be most efficient to target in developing therapeutics for minimizing degradation of the extracellular matrix of the disc.


Assuntos
Endopeptidases/metabolismo , Deslocamento do Disco Intervertebral/enzimologia , Disco Intervertebral/enzimologia , Vértebras Lombares/enzimologia , Metaloproteinases da Matriz/metabolismo , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Cadáver , Criança , Feminino , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Espondilolistese/enzimologia , Inibidor Tecidual de Metaloproteinase-1/metabolismo , Inibidor Tecidual de Metaloproteinase-2/metabolismo
9.
J Bone Joint Surg Br ; 81(6): 1064-8, 1999 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-10615987

RESUMO

Tissue engineering is an increasingly popular method of addressing pathological disorders of cartilage. Recent studies have demonstrated its clinical efficacy, but there is little information on the structural organisation and biochemical composition of the repair tissue and its relation to the adjacent normal tissue. We therefore analysed by polarised light microscopy and immunohistochemistry biopsies of repair tissue which had been taken 12 months after implantation of autologous chondrocytes in two patients with defects of articular cartilage. Our findings showed zonal heterogeneity throughout the repair tissue. The deeper zone resembled hyaline-like articular cartilage whereas the upper zone was more fibrocartilaginous. The results indicate that within 12 months autologous chondrocyte implantation successfully produces replacement cartilage tissue, a major part of which resembles normal hyaline cartilage.


Assuntos
Cartilagem Articular/cirurgia , Condrócitos/transplante , Adolescente , Adulto , Idoso , Cartilagem Articular/metabolismo , Cartilagem Articular/patologia , Células Cultivadas , Sulfatos de Condroitina/análise , Colágeno/análise , Humanos , Imuno-Histoquímica , Sulfato de Queratano/análise , Articulação do Joelho/cirurgia , Microscopia de Polarização , Proteoglicanas/metabolismo
10.
Spine (Phila Pa 1976) ; 20(24): 2645-51, 1995 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-8747242

RESUMO

STUDY DESIGN: The present study investigated the occurrence and morphology of mechanoreceptors in human and bovine intervertebral discs and longitudinal ligaments. OBJECTIVE: To determine the type and frequency of mechanoreceptors present in intervertebral discs and anterior longitudinal ligaments in two patient groups, those with low back pain and those with scoliosis. Bovine coccygeal discs were examined. SUMMARY OF BACKGROUND DATA: Nerves have been described in intervertebral tissues, but there is little information on the endings of these nerves and their receptors, stimulation of which can cause a nerve impulse. METHODS: The presence of mechanoreceptors were investigated by immunolocalization of nerves and neuropeptides. By examining sequential sections, the frequency of receptors was assessed. RESULTS: Immunoreactivity to neural antigens showed mechanoreceptors in the anulus fibrosus and longitudinal ligaments of bovine and human specimens. Their morphology resembled Pacinian corpuscles, Ruffini endings, and, most frequently, Golgi tendon organs. They were found in 50% of discs investigated from patients with low back pain and in 15% of those with scoliosis. CONCLUSIONS: Mechanoreceptors were found in the outer 2-3 lamellae of the human intervertebral disc and anterior longitudinal ligament. Physiologic studies in other tissues indicate that these provide the individual with sensation of posture and movement, and in the case of Golgi tendon organs, of nociception. In addition to providing proprioception, mechanoreceptors are thought to have roles in maintaining muscle tone and reflexes. Their presence in the intervertebral disc and longitudinal ligament can have physiologic and clinical implications.


Assuntos
Disco Intervertebral/inervação , Mecanorreceptores/fisiologia , Neuropeptídeos/análise , Adolescente , Adulto , Fatores Etários , Animais , Especificidade de Anticorpos , Peptídeo Relacionado com Gene de Calcitonina/análise , Bovinos , Cóccix/ultraestrutura , Humanos , Imuno-Histoquímica , Disco Intervertebral/ultraestrutura , Ligamentos Longitudinais/química , Ligamentos Longitudinais/inervação , Ligamentos Longitudinais/ultraestrutura , Dor Lombar/patologia , Região Lombossacral/inervação , Pessoa de Meia-Idade , Proteínas do Tecido Nervoso/imunologia , Escoliose/patologia , Tioléster Hidrolases/análise , Ubiquitina Tiolesterase
11.
J Chromatogr Sci ; 32(7): 282-5, 1994 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-8063886

RESUMO

Inductively coupled plasma-mass spectrometry is investigated for the detection of metalloporphyrins (cobalt protoporphyrin, hemin, and zinc protoporphyrin) separated by liquid chromatography. A Hypersil SAS C1 column with mobile phase containing 68% methanol at a pH of 4.5 is used. The detection limits obtained are in the nanogram range for cobalt and zinc protoporphyrins, whereas for hemin, detection limits are in the microgram range. The accuracy of the method is evaluated by determining zinc protoporphyrin from the whole blood of a lead-poisoned patient.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Protoporfirinas/sangue , Cobalto/sangue , Humanos , Ferro/sangue , Intoxicação por Chumbo/sangue , Nebulizadores e Vaporizadores , Reprodutibilidade dos Testes
13.
J Chromatogr A ; 654(2): 261-8, 1993 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-8275180

RESUMO

This paper describes the effect of inorganic tin chloride on the separation of trimethyl-, tributyl- and triphenyltin-chlorides by reversed-phase ion-pair high-performance liquid chromatography with detection by inductively coupled plasma mass spectrometry. The detection limits are 1.6 pg, 1.5 pg and 2.3 pg as tin for trimethyltin, tributyltin and triphenyltin, respectively. The relative standard deviation for ten injections of 20 ng of the tin compounds was less than 5%. Inorganic tin was held strongly on the columns used, to a greater extent on the silica column compared to the polymer column. Extraction and determination of tributyltin and triphenyltin as chlorides in fish tissue (certified reference material) and tuna fish (grocery store) were performed. The recovery study from fish tissue showed an efficiency of over 90% for both tributyltin and triphenyltin and over 60% recovery for spiked tuna.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Compostos Orgânicos de Estanho/análise , Compostos de Estanho/análise , Animais , Peixes , Análise de Alimentos , Reprodutibilidade dos Testes , Atum
15.
New Phytol ; 122(3): 501-506, 1992 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33874211

RESUMO

Chlorophyll fluorescence decay profiles have been measured in the wavelength range 680-720 nm for needles from Norway spruce [Picea abies (L.) Karst] trees which have been exposed to ozone. All profiles required three exponential components of lifetime 100-150 ps, 400-600 ps and 3.5-5.0 ns to fit the experimental data. Compared to control samples, the ozone-treated needles exhibited a greater amount of the longest-lived chlorophyll fluorescence and a redistribution in intensity for both the other components from 720 + to 690 nm. These observations are interpreted in terms of disruption of energy transfer and break-up of light-harvesting complexes on exposure to ozone. The potential for use of the technique in monitoring forest decline is discussed.

16.
Biochem J ; 210(2): 473-6, 1983 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-6407476

RESUMO

Ca2+ has been shown to be essential for the retention of maximal O2-evolving activity in Photosystem 2 particles extracted by using dodecyldimethylamine oxide from Anacystis nidulans thylakoids. The effect cannot entirely be mimicked by using Mg2+. Ca2+ stimulates electron transport from diphenylcarbazide to 2,6-dichloroindophenol catalysed by lead-inhibited cation-free preparations, showing the presence of two cation-binding sites in these particles. Photosystem 2 preparations extracted in Ca2+-containing buffer show the presence of three polypeptides at mol. wt. 30000, 33000 and 36000, which are absent or much decreased in preparations extracted in Mg2+-containing buffer. The calmodulin antagonist chlorpromazine inhibits activity of the Photosystem 2 preparation, suggesting the presence of a Ca2+-binding protein.


Assuntos
Cálcio/farmacologia , Cloroplastos/metabolismo , Cianobactérias/metabolismo , Oxigênio/metabolismo , Cloroplastos/efeitos dos fármacos , Clorpromazina/farmacologia , Cianobactérias/efeitos dos fármacos , Difenilcarbazida/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Magnésio/farmacologia , Peptídeos/metabolismo , Água/metabolismo
17.
Eur J Biochem ; 118(1): 81-4, 1981 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-6269849

RESUMO

Reduced photosystem I samples, which give the electron paramagnetic resonance (EPR) signals associated with A, A and B, and A, B and X centres, have been studied using Mössbauer spectroscopy. The Mössbauer spectra obtained from each type of sample is different, which indicates that iron is associated with all three centres. The spectra are similar to those obtained from ferredoxins with 4Fe-4S centres and were fitted with oxidized and reduced components, the relative proportions depending on the degree of reduction of the sample as monitored by EPR. The sample which gave only the A EPR signal showed about 26% of the reduced component, the sample which gave A and B EPR signals showed about 48% of the reduced component, while the sample which gave A, B and X EPR signals showed about 65% of the reduced component. The measurements are consistent with X being a 4Fe-S4 centre.


Assuntos
Cianobactérias/metabolismo , Proteínas de Plantas/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Cinética , Oxirredução , Complexo de Proteínas do Centro de Reação Fotossintética , Complexo de Proteína do Fotossistema I , Análise Espectral
18.
Biochem J ; 196(2): 489-93, 1981 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-6797405

RESUMO

Fractions enriched in Photosystem 1 or Photosystem 2 activity have been isolated from the cyanobacterium Chlorogloea fritschii after extraction of the membranes with digitonin and Triton X-100. Separation of the extract into the two components was achieved by using a Sepharose 6B column, calibration of which gave Kd values of 0.3 for the Photosystem 1 fraction and 0.53 for Photosystem 2. These values corresponded to molecular weights of approx. 500000 and 90000 respectively. The Photosystem 1 particle was shown to aggregate on storage and EDTA was shown to be necessary to separate the Photosystem 1 and 2 fractions.


Assuntos
Cianobactérias , Ácido Edético , Fotossíntese , Fracionamento Celular/métodos , Membrana Celular/metabolismo , Clorofila/metabolismo , Cromatografia de Afinidade , Cianobactérias/metabolismo , Peso Molecular , Peptídeos/análise , Espectrofotometria
20.
Biochem J ; 182(3): 861-5, 1979 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-229829

RESUMO

Substantial amounts of iron have been shown by Mössbauer spectroscopy to be present in Photosystem-I preparations from the blue-green alga Chlorogloeta fritschii. Changes in the spectra on chemical reduction provide evidence that some of this iron is very similar to that found in the 4Fe-4S centres of ferredoxins. Such reduced samples also show e.p.r. signals consistent with maximum reduction of iron-sulphur centres A and B of Photosystem I. An unchanged component in the spectra indicates, assuming all centres A and B are reduced, the presence of another iron-containing species.


Assuntos
Cianobactérias/análise , Fotossíntese , Membrana Celular/análise , Espectroscopia de Ressonância de Spin Eletrônica , Ferro/análise , Oxirredução , Espectrofotometria
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