St Bartholomew's Hospital

About: St Bartholomew's Hospital is a healthcare organization based out in London, United Kingdom. It is known for research contribution in the topics: Population & Cancer. The organization has 11054 authors who have published 13229 publications receiving 501102 citations. The organization is also known as: St. Bartholomew's Hospital & The Royal Hospital of St Bartholomew.

Low-dose phase contrast tomography with conventional x-ray sources

Abstract: Purpose: The edge illumination (EI) x-ray phase contrast imaging (XPCi) method has been recently further developed to perform tomographic and, thus, volumetric imaging. In this paper, the first tomographic EI XPCi images acquired with a conventional x-ray source at dose levels below that used for preclinical small animal imaging are presented. Methods: Two test objects, a biological sample and a custom-built phantom, were imaged with a laboratory-based EI XPCi setup in tomography mode. Tomographic maps that show the phase shift and attenuating properties of the object were reconstructed, and analyzed in terms of signal-to-noise ratio and quantitative accuracy. Dose measurements using thermoluminescence devices were performed. Results: The obtained images demonstrate that phase based imaging methods can provide superior results compared to attenuation based modalities for weakly attenuating samples also in 3D. Moreover, and, most importantly, they demonstrate the feasibility of low-dose imaging. In addition, the experimental results can be considered quantitative within the constraints imposed by polychromaticity. Conclusions: The results, together with the method's dose efficiency and compatibility with conventional x-ray sources, indicate that tomographic EI XPCi can become an important tool for the routine imaging of biomedical samples.

Reactions of papain and of low-molecular-weight thiols with some aromatic disulphides. 2,2′-Dipyridyl disulphide as a convenient active-site titrant for papain even in the presence of other thiols

Abstract: 1. The u.v.-spectral characteristics of 5,5′-dithiobis-(2-nitrobenzoic acid) (Nbs2), 2,2′-dipyridyl disulphide (2-Py–S–S–2-Py), 4,4′-dipyridyl disulphide (4-Py–S–S–4-Py), 5-mercapto-2-nitrobenzoic acid (Nbs), 2-thiopyridone (Py–2-SH) and 4-thiopyridone (Py–4-SH) were determined over a wide range of pH and used to calculate their acid dissociation constants. 2. The reactions of l-cysteine, 2-mercaptoethanol and papain with the above-mentioned disulphides were investigated spectrophotometrically in the pH range 2.5–8.5. 3. Under the conditions of concentration used in this study the reactions of both low-molecular-weight thiols with all three disulphides resulted in the stoicheiometric release of the thiol or thione fragments Nbs, Py–2-SH and Py–4-SH at all pH values. The rates of these reactions are considerably faster at pH8 than at pH4, which suggests that the predominant reaction pathway in approximately neutral media is nucleophilic attack of the thiolate ion on the unprotonated disulphide. 4. The reaction of papain with Nbs2 is markedly reversible in the acid region, and the pH-dependence of the equilibrium constant for this system in the pH range 5–8 at 25°C and I=0.1 is described by: [Formula: see text] 5. Papain reacts with both 2-Py–S–S–2-Py and 4-Py–S–S–4-Py in the pH range 2.5–8.5 to provide release of the thione fragments, stoicheiometric with the thiol content of the enzyme. 6. Whereas the ratios of the second-order rate constant for the reaction at pH4 to that at pH8 for the cysteine–2-Py–S–S–2-Py reaction (kpH4/kpH8=0.015) and for the papain–4-Py–S–S–4-Py reaction (kpH4/kpH8=0.06) are less than 1, that for the papain–2-Py–S–S–2-Py reaction is greater than 1 (kpH4/kpH8=15). 7. This high reactivity of papain has been shown to involve reaction of the thiol group of cysteine-25, the enzyme's only cysteine residue, which is part of its catalytic site. 8. That this rapid and stoicheiometric reaction of the thiol group of native papain is not shown either by low-molecular-weight thiols or by the thiol group of papain after its active conformation has been destroyed by acid or heat denaturation, strongly commends 2-Py–S–S–2-Py as one of the most useful papain active-site titrants discovered to date. This reagent has been shown to allow accurate titration of papain active sites in the presence of up to 10-fold molar excess of l-cysteine and up to 100-fold molar excess of 2-mercaptoethanol.

Full-field digital versus screen-film mammography: comparison within the UK breast screening program and systematic review of published data.

Abstract: Purpose: To (a) compare the performance of full-field digital mammography (FFDM), using hard-copy image reading, with that of screen-film mammography (SFM) within a UK screening program (screening once every 3 years) for women aged 50 years or older and (b) conduct a meta-analysis of published findings along with the UK data. Materials and Methods: The study complied with the UK National Health Service Central Office for Research Ethics Committee guidelines; informed patient consent was not required, since analysis was carried out retrospectively after data anonymization. Between January 2006 and June 2007, a London population-based screening center performed 8478 FFDM and 31 720 SFM screening examinations, with modality determined by the type of machine available at the screening site. Logistic regression was used to assess whether breast cancer detection rates and recall rates differed between screening modalities. For the meta-analysis, random-effects models were used to combine study-specific estimate...

The diagnosis and differential diagnosis of Cushing's syndrome.

Abstract: Cushing's syndrome is defined as the symptoms and signs of glucocorticoid excess, but the precise diagnosis may be difficult to establish and harder to localise. The clinicial, biochemical and imaging features of the syndrome are discussed in the light of our own extensive experience and the published literature. We describe the optimal diagnostic routines currently recommended in major centres, and analyse the sensitivities and specialities of the various tests employed. Only by means of establishing a precise diagnosis can the disorder be successfully treated.