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1.
Radiography (Lond) ; 29(1): 101-108, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36327514

RESUMO

INTRODUCTION: Pain and discomfort has a negative impact on a patient's overall experience and may impact on subsequent re-attendance to mammography. Pain during mammography remains a significant issue. Assessment of interventions to reduce levels of pain associated with mammography are essential to increase attendance to breast services and improve user experience. METHODS: Participants (n = 60) were invited to take part in the study at one hospital Trust within the UK. Postal invitations were sent 2 weeks prior to appointment to patients older than 40 years with previous mammography attendance at the same Trust to allow for comparison of previous and current pain scores/compression values. Patients were randomised into 3 groups: Binaural music (BM), non-binaural music (NBM) and standard care (C). A numerical rating scale (NRS) was used to rate pain. RESULTS: Patient tolerance is increased by the application of both the non-binaural and binaural music. Binaural music was most effective in improving patient tolerance (p = 0.02). When applied compression increased some patients recorded less pain, which may have implications to image quality and radiation dose for patients. Binaural music reduces the perception of mammographic pain within this data set. CONCLUSION: 5 min exposure to binaural music improves patient experience and tolerance for mammography which could be utilised to improve attendance rates in screening and symptomatic services. IMPLICATIONS FOR PRACTICE: There is an indication for further research looking at application prior and during interventional biopsies. Music intervention can be offered to patients in the severe pain category who refuse mammography. It is acknowledged from these findings that the introduction of BM and NBM prior to mammography would be a low risk, cost effective intervention within the hospital setting.


Assuntos
Música , Dor , Humanos , Dor/etiologia , Dor/prevenção & controle , Pressão , Mamografia/métodos , Mama
2.
Breast J ; 2022: 1863519, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35711886

RESUMO

Background: The rate of inpatient mastectomies remains high despite multiple studies reporting favourably on outpatient mastectomies. Outpatient mastectomies do not compromise quality of patient care and are more efficient than inpatient care. The objective of this study was to evaluate the feasibility of outpatient mastectomy. Materials and Methods: Implementation of an outpatient mastectomy program was evaluated in a retrospective study. All patients who underwent mastectomy between January 2019 and September 2021 were included. Results: 213 patients were enrolled in the study: 62.4% (n = 133) outpatient mastectomies versus 37.6% (n = 80) inpatient mastectomies. A steady rise in outpatient mastectomies was observed over time. The second quarter of 2020, coinciding with the first COVID-19 wave, showed a peak in outpatient mastectomies. The only significant barrier to outpatient mastectomy proved to be bilateral mastectomy. Unplanned return to care was observed in 27.8% of the outpatient versus 36.3% of the inpatient mastectomies (P=0.198); the reason for unplanned return of care was similar in both groups. Conclusions: Outpatient mastectomy is shown to be feasible and safe with a steady increase during the study period. A barrier to outpatient mastectomy was bilateral mastectomy. Incidence of unplanned return to care or complications did not differ significantly between the outpatient and inpatient cohorts.


Assuntos
Neoplasias da Mama , COVID-19 , Neoplasias da Mama/cirurgia , Feminino , Humanos , Mastectomia , Pacientes Ambulatoriais , Estudos Retrospectivos
3.
Artigo em Inglês | MEDLINE | ID: mdl-33935382

RESUMO

RadiaBeam has developed a 6 MeV accelerator that is compact and light enough to be placed on a robotic arm or light truck. The main drivers of size and weight in conventional accelerators are the power source and the shielding. Small dimensions are enabled by operation at 9.3 GHz frequency (X-band), which allows reducing the size and weight of all accelerator components. Thanks to the robust design of the accelerating structure, the accelerator can be used as a source for novel cargo inspection and radiotherapy techniques. In this paper, we present the linac design and its components, as well the results of the experimental demonstration of beam acceleration.

4.
BMC Cancer ; 18(1): 892, 2018 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-30217171

RESUMO

BACKGROUND: Frailty is an indicator of physiological reserve in older people. In non-cancer settings, frailty indices are reliable predictors of adverse health outcomes. The aims of this study were to 1) derive and validate a frailty index (FI) from comprehensive geriatric assessment (CGA) data obtained in the solid tumour chemotherapy setting, and 2) to explore whether the FI-CGA could predict chemotherapy decisions and survival in older cancer patients with solid tumours. METHODS: Prospective cohort study of a consecutive series sample of 175 cancer patients aged 65 and older with solid tumours. A frailty index was calculated using an accumulated deficits model, coding items from the comprehensive geriatric assessment tool administered prior to chemotherapy decision-making. The domains of physical and cognitive functioning, nutrition, mood, basic and instrumental activities of daily living, and comorbidities were incorporated as deficits into the model. RESULTS: The FI-CGA had a right-skewed distribution, with median (interquartile range) of 0.27 (0.21-0.39). The 99% limit to deficit accumulation was below the theoretical maximum of 1.0, at 0.75. The FI-CGA was significantly related (p < 0.001) to vulnerability as assessed by the Vulnerable Elders Survey-13 and to medical oncologists' assessments of fitness or vulnerability to treatment. Baseline frailty as determined by the FI-CGA was also associated with treatment decisions (Treatment Terminated, Treatment Completed, No Planned Treatment) (p < 0.001), with the No Planned Treatment group significantly frailer than the other two groups. CONCLUSION: The FI-CGA is a potentially useful adjunct to cancer clinical decision-making that could predict chemotherapy outcomes in older patients with solid tumours.


Assuntos
Fragilidade/epidemiologia , Avaliação Geriátrica , Neoplasias/epidemiologia , Atividades Cotidianas , Idoso , Idoso de 80 Anos ou mais , Feminino , Idoso Fragilizado , Fragilidade/fisiopatologia , Humanos , Masculino , Neoplasias/fisiopatologia , Neoplasias/terapia
5.
MMWR Morb Mortal Wkly Rep ; 64(15): 421-3, 2015 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-25905896

RESUMO

Neural tube defects (NTDs) such as spina bifida, anencephaly, and encephalocele are serious birth defects of the brain and spine that occur during the first month of pregnancy when the neural tube fails to close completely. Randomized controlled trials and observational studies have shown that adequate daily consumption of folic acid before and during early pregnancy considerably reduces the risk for NTDs. The U.S. Public Health Service recommends that women capable of becoming pregnant consume 400 µg of folic acid daily for NTD prevention. Furthermore, fortification of staple foods (e.g., wheat flour) with folic acid has decreased folate-sensitive NTD prevalence in multiple settings and is a highly cost-effective intervention.


Assuntos
Eritrócitos/química , Ácido Fólico/sangue , Guias como Assunto , Defeitos do Tubo Neural/prevenção & controle , Organização Mundial da Saúde , Adulto , Feminino , Ácido Fólico/administração & dosagem , Alimentos Fortificados , Fidelidade a Diretrizes/estatística & dados numéricos , Humanos , Defeitos do Tubo Neural/epidemiologia , Gravidez , Estados Unidos/epidemiologia
6.
Br J Nutr ; 113(12): 1965-77, 2015 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-25917925

RESUMO

Serum and erythrocyte (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured the serum folate forms (5-methyltetrahydrofolate (5-methylTHF), unmetabolised folic acid (UMFA), non-methyl folate (sum of tetrahydrofolate (THF), 5-formyltetrahydrofolate (5-formylTHF), 5,10-methenyltetrahydrofolate (5,10-methenylTHF)) and MeFox (5-methylTHF oxidation product)) by HPLC-MS/MS and RBC total folate by microbiologic assay in US population ≥ 1 year (n approximately 7500) participating in the National Health and Nutrition Examination Survey 2011-2. Data analysis for serum total folate was conducted including and excluding MeFox. Concentrations (geometric mean; detection rate) of 5-methylTHF (37·5 nmol/l; 100 %), UMFA (1·21 nmol/l; 99·9 %), MeFox (1·53 nmol/l; 98·8 %), and THF (1·01 nmol/l; 85·2 %) were mostly detectable. 5-FormylTHF (3·6 %) and 5,10-methenylTHF (4·4 %) were rarely detected. The biggest contributor to serum total folate was 5-methylTHF (86·7 %); UMFA (4·0 %), non-methyl folate (4·7 %) and MeFox (4·5 %) contributed smaller amounts. Age was positively related to MeFox, but showed a U-shaped pattern for other folates. We generally noted sex and race/ethnic biomarker differences and weak (Spearman's r< 0·4) but significant (P< 0·05) correlations with physiological and lifestyle variables. Fasting, kidney function, smoking and alcohol intake showed negative associations. BMI and body surface area showed positive associations with MeFox but negative associations with other folates. All biomarkers showed significantly higher concentrations with recent folic acid-containing dietary supplement use. These first-time population data for serum folate forms generally show similar associations with demographic, physiological and lifestyle variables as serum total folate. Patterns observed for MeFox may suggest altered folate metabolism dependent on biological characteristics.


Assuntos
Ácido Fólico/sangue , Inquéritos Nutricionais , Estado Nutricional , Adolescente , Adulto , Biomarcadores/sangue , Índice de Massa Corporal , Criança , Pré-Escolar , Cromatografia Líquida de Alta Pressão , Eritrócitos/química , Etnicidade , Feminino , Humanos , Lactente , Leucovorina/sangue , Estilo de Vida , Masculino , Pessoa de Meia-Idade , Valores de Referência , Fatores Sexuais , Espectrometria de Massas em Tandem , Tetra-Hidrofolatos/sangue , Estados Unidos/epidemiologia , Adulto Jovem
7.
J Obstet Gynaecol ; 33(2): 165-70, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23445141

RESUMO

The aim of this study was to compare the effect of low-dose metformin and rosiglitazone on clinical, biochemical, ultrasound features and endothelial function in patients with polycystic ovary syndrome (PCOS). After randomisation, a group of 17 women received metformin 500 mg b.d. (MG) and a group of 18 received rosiglitazone 4 mg o.d. (RG) for 3 months. Serum FSH, LH, testosterone, fasting glucose, insulin, IGF-1, IGFBP-3, CRP were measured at baseline and follow-up. Ovarian scan and microcirculation studies were also performed. It was found that there was a reduction in hyperandrogenaemia, insulin resistance, lipidaemia, CRP levels, ovarian volume and number of follicles in both groups. No improvement in endothelial- dependent function was noted but a significant improvement in endothelial-independent function in rosiglitazone group. It was concluded that low-dose therapeutic regimen with rosiglitazone and metformin, has comparable beneficial impacts on metabolic, hormonal and morphological features of PCOS but no obvious effect on vascular parameters in a population of predominantly mild PCOS.


Assuntos
Hipoglicemiantes/administração & dosagem , Metformina/administração & dosagem , Síndrome do Ovário Policístico/tratamento farmacológico , Tiazolidinedionas/administração & dosagem , Adulto , Quimioterapia Combinada , Endotélio Vascular/efeitos dos fármacos , Feminino , Humanos , Ovário/diagnóstico por imagem , Ovário/efeitos dos fármacos , Síndrome do Ovário Policístico/sangue , Síndrome do Ovário Policístico/diagnóstico por imagem , Rosiglitazona , Resultado do Tratamento , Ultrassonografia
8.
J Surg Case Rep ; 2012(8): 17, 2012 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-24960775

RESUMO

Extramedullary haemopoiesis (EMH) is the abnormal development and growth of haemopoietic tissue outside the bone marrow. It is usually asymptomatic and occurs in the presence of myelodysplastic syndromes. In this report, we describe the first post-traumatic EMH presenting with lower urinary tract symptoms.

9.
Int J Vitam Nutr Res ; 80(2): 144-54, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20803428

RESUMO

OBJECTIVE: To assess the prevalence of folate, vitamin B(12), and iron deficiencies and their associations with anemia among women of childbearing age in northern China, an area with a reported high incidence of neural tube defects. METHODS: Plasma folate, vitamin B(12), ferritin, and hemoglobin levels were measured among 1,671 non-pregnant women of childbearing age from Xianghe County, Hebei Province, China in June 2004. RESULTS: Geometric means [95 % confidence interval (CI)] of plasma concentrations were 9.3 (4.0, 21.6) nmol/L for folate, 213.1 (82.4, 550.9) pmol/L for vitamin B(12), 17.4 (1.1, 278.6) microg/L for ferritin, and 129.9 (104.6, 161.4) g/L for hemoglobin (Hb). Approximately 24 % of women had biochemical evidence of folate deficiency (<6.8 nmol/L), 21.4 % were deficient (<148 pmol/L) in vitamin B(12), 30.2 % had iron depletion (<15 microg/L), and anemia (Hb < 120 g/L) was detected among 15.4 % of women. Of the three nutrients, only iron depletion (ferritin < 15 microg/L) was independently associated with anemia (adjusted odds ratio = 6.4, 95 % CI 4.8, 8.6). CONCLUSIONS: Although there were substantial proportions of folate and vitamin B(12) deficiencies among women of childbearing age in northern China, iron deficiency was the most important contributor to anemia.


Assuntos
Anemia/epidemiologia , Deficiência de Ácido Fólico/epidemiologia , Deficiências de Ferro , Deficiência de Vitamina B 12/epidemiologia , Adulto , Anemia/sangue , Anemia Ferropriva/sangue , Anemia Ferropriva/epidemiologia , China/epidemiologia , Estudos Transversais , Feminino , Ferritinas/sangue , Ácido Fólico/sangue , Deficiência de Ácido Fólico/sangue , Hemoglobinas , Humanos , Ferro/sangue , Razão de Chances , Prevalência , População Rural/estatística & dados numéricos , Vitamina B 12/sangue , Deficiência de Vitamina B 12/sangue
11.
Am J Clin Nutr ; 85(5): 1409-16, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17490980

RESUMO

BACKGROUND: Neural tube defects are serious birth defects of the brain and spinal cord. Up to 70% of neural tube defects can be prevented by the consumption of folic acid by women before and early during pregnancy. OBJECTIVE: The objective was to examine folic acid intake in women of childbearing age in the United States. DESIGN: We analyzed nutrient intake data reported by 1685 nonpregnant women aged 15-49 y who participated in the National Health and Nutritional Examination Survey, 2001-2002. RESULTS: The adjusted geometric mean consumption of folic acid from fortified foods was 128 microg/d (95% CI: 123, 134 microg/d) in nonpregnant women. Eight percent (95% CI: 5.8%, 11.0%) of nonpregnant women reported consuming >or=400 microg folic acid/d from fortified foods. This proportion was lower among non-Hispanic black women (5.0%) than among non-Hispanic white (8.9%) or Hispanic (6.8%) women. A smaller percentage of non-Hispanic black (19.1%) and Hispanic (21%) women than of non-Hispanic white women (40.5%) consumed >or=400 microg folic acid from supplements, fortified foods, or both, in addition to food folate, as recommended by the Institute of Medicine to reduce the frequency of neural tube defects. CONCLUSIONS: Most nonpregnant women of childbearing age in the United States reported consuming less than the recommended amount of folic acid. The proportion with low daily folic acid intake was significantly higher in non-Hispanic black and Hispanic women than in non-Hispanic white women. At the present level of folic acid fortification, most women need to take a folic acid-containing dietary supplement to achieve the Institute of Medicine recommendation.


Assuntos
Dieta , Ácido Fólico/administração & dosagem , Defeitos do Tubo Neural/prevenção & controle , Inquéritos Nutricionais , Complexo Vitamínico B/administração & dosagem , Adolescente , Adulto , Negro ou Afro-Americano , Dieta/etnologia , Suplementos Nutricionais , Etnicidade , Feminino , Alimentos Fortificados , Hispânico ou Latino , Humanos , Pessoa de Meia-Idade , Política Nutricional , Necessidades Nutricionais , Cuidado Pré-Concepcional , Estados Unidos
13.
J Exp Clin Cancer Res ; 25(2): 259-67, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16918139

RESUMO

Ras activating mutations result in constitutive activation of Ras signalling pathways and occur in 30% of human malignancies. K-ras encodes two splice variants, K-ras 4A and 4B, and K-ras activating mutations which jointly affect both isoforms are prevalent in lung, pancreatic and colorectal cancers. Using RT-PCR we examined their expression in normal adult human tissues and addressed whether K-ras splicing is altered in sporadic colorectal cancer by comparing normal colon with colon carcinoma cell lines, and 'matched' tumour and tumour-free colon tissues from the same patient. K-ras 4B was expressed ubiquitously and was the predominant splice variant. K-ras 4A was expressed differentially, with detection in colorectal tumours and cell lines, and normal colon, pancreas and lung--sites where tumours with K-ras activating mutations arise. Both K-ras splice variants were co-expressed by single colon carcinoma cells. The K-ras 4A/4B ratio was significantly reduced in all 6 cell lines examined, including two that lacked K-ras activating mutations, and in 4/9 primary adenocarcinomas. We conclude that K-ras activating mutations do not affect K-ras splicing per se, both isoforms may play a role in neoplastic progression, and altered splicing of either the K-ras proto-oncogene or oncogene, in favour of K-ras 4B, may modulate tumour development.


Assuntos
Adenocarcinoma/genética , Neoplasias Colorretais/genética , Genes ras/genética , Mutação , Adenocarcinoma/metabolismo , Colo/metabolismo , Neoplasias Colorretais/metabolismo , Análise Mutacional de DNA , Humanos , Isoformas de Proteínas/genética , Proto-Oncogene Mas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Células Tumorais Cultivadas
14.
Proc Natl Acad Sci U S A ; 103(2): 323-8, 2006 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-16387853

RESUMO

The conservation of structure across homolog proteins often diffuses the impact of drug-based inhibition by promoting alternative protein-ligand associations that may lead to toxic side effects. However, sticky packing defects are typically not conserved across homologs, making them valuable a priori targets to enhance specificity. By introducing a homology to quantify packing differences among proteins, we enable a previously undescribed strategy for the design of highly selective drug inhibitors involving ligands that wrap nonconserved packing defects. The selectivity of these ligands is validated by performing affinity assays on a cancer-related pharmacokinome. Minor reengineering of a powerful inhibitor guided by wrapping differences across its target kinome can selectively direct its impact toward a specific kinase. Thus, nonconserved packing defects may be used as selectivity switches across homolog targets, using spatial displacements of packing defects across aligned protein structures.


Assuntos
Proteínas/antagonistas & inibidores , Proteínas/química , Desenho de Fármacos , Modelos Moleculares , Estrutura Terciária de Proteína , Sensibilidade e Especificidade
15.
Transgenic Res ; 14(5): 691-702, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16245160

RESUMO

Gonadal effects of the Denys-Drash syndrome (DDS) mutation Wt1(tmT396 )were examined in chimaeric and heterozygous mice. Since the only heterozygote was 41,XXY, Sertoli cell function was assessed by comparison with age-matched control XXY testes. Control XXY Sertoli cells showed immuno-expression of WT1 and androgen receptor (AR) indistinguishable from wild-type (40,XY), but expressed anti-Mullerian hormone (AMH). In contrast, DDS Sertoli cells showed only faint immuno-expression of WT1 and did not express AR or AMH. While XY<-->XY DDS chimaeras were male, XX<-->XY chimaeras were predominantly female. In the rare XX<-->XY DDS males the Sertoli cell lineage was largely derived from Wt1 mutant XY cells. We conclude that DDS mutant cells can form Sertoli cells, that the dominant mutation does not cause male sex reversal in mice but distorts the sex ratio of XX<-->XY chimaeras, and that there may be a link between WT1, AMH and AR expression by Sertoli cells in vivo.


Assuntos
Síndrome de Denys-Drash/genética , Síndrome de Denys-Drash/patologia , Testículo/patologia , Proteínas WT1/genética , Animais , Hormônio Antimülleriano , Quimera/genética , Síndrome de Denys-Drash/metabolismo , Modelos Animais de Doenças , Feminino , Expressão Gênica , Glicoproteínas/genética , Heterozigoto , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Transgênicos , Mutação , Receptores Androgênicos/genética , Células de Sertoli/metabolismo , Células de Sertoli/patologia , Razão de Masculinidade , Hormônios Testiculares/genética , Testículo/metabolismo
16.
J Phys Chem A ; 109(38): 8637-41, 2005 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-16834264

RESUMO

Equilibrium NPT and NVT molecular dynamics simulations were performed on liquid benzene over an extended range of temperature (from 260 to 360 K) using the COMPASS force field. Densities and enthalpies of vaporization (from cohesive energy densities) were within 1% of experiment at all temperatures. tumbling and spinning rotational diffusion coefficients, D(perpendicular) and D(parallel), computed as a function of temperature, agreed qualitatively with the results of earlier reported experimental and computational investigations. Generally, it was found that D(parallel)/D(perpendicular) approximately 1.4-2.5 and the activation energy for tumbling was significantly greater than for spinning about the C6 axis [Ea(D(perpendicular)) = 8.1 kJ mol(-1) and Ea(D(parallel)) = 4.5 kJ mol(-1)]. Calculated translational diffusion coefficients were found to be in quantitative agreement with experimental values at all temperatures [deviations were less than the scatter between different reported measurements]. In addition, translational diffusion coefficients were computed in the molecule-fixed frame to yield values for Dxy (diffusion in the plane of the molecule) and Dz (diffusion perpendicular to the plane). It was found that the ratio Dxy/Dz approximately 2.0, and that the two coefficients have roughly equal activation energies. This represents the first atomistic molecular dynamics study of translational diffusion in the molecular frame.

17.
Int J Oral Maxillofac Surg ; 33(6): 610-2, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15308263

RESUMO

Cutaneous mucinous adenocarcinoma is a rare neoplasm. It occurs most commonly on the facial skin. We present a case of an apparently recurrent primary mucinous adenocarcinoma of the facial skin and highlight the necessary diagnostic work up and management of this tumour.


Assuntos
Adenocarcinoma Mucinoso/patologia , Neoplasias Faciais/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Invasividade Neoplásica , Recidiva Local de Neoplasia
18.
Cell Prolif ; 37(4): 279-94, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15245564

RESUMO

A mathematical model for the kinetics of haemopoietic cells, including CD34+cells, is proposed. This minimal model reflects the known kinetics of haemopoietic progenitor cells, including peripheral blood CD34+ cells, white blood cells and platelets, in the presence of granulocyte colony-stimulating factor. Reproducing known perturbations within this system, subjected to granulocyte colony-stimulating factor treatment and apheresis of peripheral blood progenitor cells (CD34+ cells) in healthy individuals allows validation of the model. Predictions are made with this model for reducing the length of time with neutropenia after high-dose chemotherapy. Results based on this model indicate that myelosuppressive treatment together with infusion of CD34+ peripheral blood progenitor cells favours a faster recovery of the haemopoietic system than with granulocyte colony-stimulating factor alone. Additionally, it predicts that infusion of white blood cells and platelets can relieve the symptoms of neutropenia and thrombocytopenia, respectively, without drastically hindering the haemopoietic recovery period after high dose chemotherapy.


Assuntos
Hematopoese , Células-Tronco Hematopoéticas/fisiologia , Modelos Teóricos , Antígenos CD34/metabolismo , Plaquetas/fisiologia , Fator Estimulador de Colônias de Granulócitos e Macrófagos/fisiologia , Transplante de Células-Tronco Hematopoéticas , Humanos , Cinética , Leucócitos/fisiologia , Neutropenia/fisiopatologia , Neutropenia/terapia
19.
J Mol Biol ; 331(3): 693-711, 2003 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-12899838

RESUMO

The populations and transitions between Ramachandran basins are studied for combinations of the standard 20 amino acids in monomers, dimers and trimers using an implicit solvent Langevin dynamics algorithm and employing seven commonly used force-fields. Both the basin populations and inter-conversion rates are influenced by the nearest neighbor's conformation and identity, contrary to the Flory isolated-pair hypothesis. This conclusion is robust to the choice of force-field, even though the use of different force-fields produces large variations in the populations and inter-conversion rates between the dominant helical, extended beta, and polyproline II basins. The computed variation of conformational and dynamical properties with different force-fields exceeds the difference between explicit and implicit solvent calculations using the same force-field. For all force-fields, the inter-basin transitions exhibit a directional dependence, with most transitions going through extended beta conformation, even when it is the least populated basin. The implications of these results are discussed in the context of estimates for the backbone entropy of single residues, and for the ability of all-atom simulations to reproduce experimental protein folding data.


Assuntos
Entropia , Peptídeos/química , Dobramento de Proteína , Algoritmos , Simulação por Computador , Cinética , Modelos Químicos , Modelos Moleculares , Movimento (Física) , Peptídeos/metabolismo , Maleabilidade , Conformação Proteica
20.
Lancet ; 361(9355): 380-4, 2003 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-12573374

RESUMO

BACKGROUND: Folic acid supplements are recommended for women of childbearing age to prevent neural tube defects in their offspring. Results of some studies, however, suggest an increase in multiple births associated with use of vitamin supplements that contain folic acid during pregnancy. Our aim was to assess this association. METHODS: We used data from a population-based cohort study from which we assessed the occurrence of multiple births in women (n=242015) who had participated in a campaign to prevent neural tube defects with folic acid supplements (400 microg per day) in China. Folic acid use was ascertained before pregnancy outcome was known. We studied the relation between multiple births and any use of folic acid pills before or during early pregnancy; additionally, we investigated mechanisms by which folic acid could potentially affect the occurrence of multiple births by examining pill-taking at three time periods: before ovulation, around the time of fertilisation, and after conception. FINDINGS: 1496 (0.62%) multiple births occurred in a cohort of 242015 women who had registered with the study between October, 1993, and September, 1995, and who had a pregnancy not affected by a birth defect; the rate of multiple births in women who did and did not take folic acid before or during early pregnancy was 0.59% and 0.65%, respectively (rate ratio 0.91; 95% CI 0.82-1.00). INTERPRETATION: Our findings suggest that consumption of folic acid supplements during pregnancy is not associated with an increased occurrence of multiple births.


Assuntos
Ácido Fólico/uso terapêutico , Prole de Múltiplos Nascimentos/estatística & dados numéricos , Defeitos do Tubo Neural/prevenção & controle , Resultado da Gravidez/epidemiologia , Adulto , Índice de Massa Corporal , China/epidemiologia , Estudos de Coortes , Escolaridade , Feminino , Fertilização/efeitos dos fármacos , Humanos , Idade Materna , Ocupações/estatística & dados numéricos , Ovulação/efeitos dos fármacos , Paridade , Gravidez , Sistema de Registros , Fatores de Tempo
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