Heterogeneity of cardiac rat and human elongation factor 2

Elongation factor 2 (EF-2) catalyses the last step of the elongation cycle, translocation, in the course of protein biosynthesis. A system for analyzing post-translational modifications of EF-2, which is a single polypeptide of 857 amino acids, is reported and its application to cytosolic extracts of cultured neonatal rat heart myocytes, neonatal and adult rat cardiac tissue, and extracts of human left ventricular myocardium is described. Comparing different pH ranges in immobilized pH gradient-isoelectric focusing (IPG-IEF), a range of pH 3 - 10 and 4 - 9 resulted in a highly defined and reproducible resolution of six different EF-2 variants of all extracts in the first dimension. These six variants were detected by the "imaging plate" (phosphor radiation image sensor) after specific labeling with Pseudomonas exotoxin A catalyzed [32P]ADP-ribosylation. This finding could be confirmed in Western blot analysis with a specific polyclonal rabbit antibody. Using two-dimensional polyacrylamide gel electrophoresis (2-D-PAGE), five to six EF-2 variants could be demonstrated in all extracts. By application of a second IPG indicator strip to the 2-D gel, they could be aligned with corresponding spots in a silver-stained 2-D separation of human myocardial tissue, revealing that the EF-2 variants belong to the group of low-abundance proteins.     

Molecular beam chemiluminescence XI: kinetic and internal energy dependence of the NO + O3 → NO2*,→ NO23 reaction

Seeded supersonic NO beams were used to study the kinetic energy dependence of both the electronic (NO₂^*) and vibrational (NO₂³) chemiluminescence of the NO + O₃ reaction. In addition the electronic CL is found to be enhanced by raising the NO internal temperature. This is shown to be due to enhanced reactivity of the NO(²Π,_{$\text{3}\text{2}$}) fine structure component. By difference NO(²Π_{$\text{1}\text{2}$}) is concluded to yield predominantly groundstate NO₂³. The excitation function for NO₂^* formation from NO(²Π_{$\text{3}\text{2}$}) is of the form σ_{$\text{3}\text{2}$}(E) = C(E/E₀ - 1)ⁿ over the 3–6 kcal energy range where n = 2.4 ± 0.15, C = 0.163 Ų and E₀ = 3.2 ± 0.3 kcal/mole. Vibrational IR emission from NO₂³ has an energy dependence different from electronic NO₂^* emission, confirming that emitters are formed predominantly in distinct reaction channels rather than via a common precursor (either NO₂^* or NO₂³). The short wavelength cutoff of the CL spectra recorded at elevated collision energies E ? 15 kcal/mole corresponds to the total available energy. These and literature results are discussed in the light of general properties of the (generally unknown) ONO₃ potential energy surfaces. The formation of electronically excited NO₂^* rather than energetically preferred O₂ (¹ Δg) (Gauthier and Snelling) can be rationalized in terms of surface hopping near a known intersection of potential energy surfaces more easily than by vibronic interaction in the asymptotic NO₂ product.     

Estimating patient dielectric losses in NMR imagers

Dielectric losses in the patient may impair radiofrequency receiver coil sensitivity, and transmitter coil efficiency, in nuclear magnetic resonance (NMR) imagers. The frequency dependence of this loss mechanism is derived. Patient losses in a solenoidal head coil used for imaging heads were simulated by a cylindrical saline phantom. The frequency dependence of the loss introduced by the phantom can indicate whether dielectric losses in the patient will be significant compared to eddy current losses. The detuning caused by the phantom is used to calculate an upper limit for the distributed stray capacitance between coil and patient. Given the approximate conductivity of the patient, an upper limit for the dielectric loss can be estimated. Some methods of reducing patient dielectric losses are suggested.     

Magnetic resonance imaging screening in women at genetic risk of breast cancer: imaging and analysis protocol for the UK multicentre study. UK MRI Breast Screening Study Advisory Group

The imaging and analysis protocol of the UK multicentre study of magnetic resonance imaging (MRI) as a method of screening for breast cancer in women at genetic risk is described. The study will compare the sensitivity and specificity of contrast-enhanced MRI with two-view x-ray mammography. Approximately 500 women below the age of 50 at high genetic risk of breast cancer will be recruited per year for three years, with annual MRI and x-ray mammography continuing for up to 5 years. A symptomatic cohort will be measured in the first year to ensure consistent reporting between centres. The MRI examination comprises a high-sensitivity three-dimensional contrast-enhanced assessment, followed by a high-specificity contrast-enhanced study in equivocal cases. Multiparametric analysis will encompass morphological assessment, the kinetics of contrast agent uptake and determination of quantitative pharmacokinetic parameters. Retrospective analysis will identify the most specific indicators of malignancy. Sensitivity and specificity, together with diagnostic performance, diagnostic impact and therapeutic impact will be assessed with reference to pathology, follow-up and changes in diagnostic certainty and therapeutic decisions. Mammography, lesion localisation, pathology and cytology will be performed in accordance with the UK NHS Breast Screening Programme quality assurance standards. Similar standards of quality assurance will be applied for MR measurements and evaluation.     

A regio- and stereocontrolled approach to pyranosyl C-nucleoside synthesis

Six novel diastereomerically pure C-nucleosides have been synthesized from nonchiral starting materials, using the ene/intramolecular Sakurai cyclization reaction demonstrating a simple, general, and stereocontrolled approach to pyranosyl C-nucleosides.     

The measurement of fetal liver T(*)(2) in utero before and after maternal oxygen breathing: progress towards a non-invasive measurement of fetal oxygenation and placental function

Utero-placental insufficiency is thought to be a major cause of growth retardation in utero and an important risk factor in the perinatal period. The purpose of this study was to investigate whether MRI could detect changes of fetal oxygenation, based on the blood oxygenation level dependence (BOLD) of the MRI tissue signal. Nine third trimester women (34-38 weeks) with normal pregnancies underwent abdominal MRI examinations. Following localization of the fetal liver using T(2)-weighted single-shot HASTE scans, up to 7 breath-held transaxial single-slice gradient-echo image sets were obtained through the fetal liver. The mother then commenced oxygen breathing with the imaging procedure repeated after 20 minutes of O(2) breathing. For each image set, T(*)(2) values are calculated using linear regression of log (signal) versus TE for a region of interest within the fetal liver selected by the attending radiologist. Fetal liver T(*)(2) values were calculated before and after O(2) breathing for each multi-echo image acquisition set. A signed rank test was used to test for a significant change in fetal liver T(*)(2) between the pre-O(2) and post-O(2) image sets. A significant increase in T*(2) (alpha < 0.05) was seen in 5 of the 9 fetal livers, a smaller increase (of borderline statistical significance, alpha = 0.057) in 2 livers, and no significant change (alpha > 0.05) in 2 livers. Our study indicates that T(*)(2) measurement of the fetal liver may detect alteration in fetal oxygen level following maternal oxygenation using the BOLD effect. This technique may potentially be applied to the identification and understanding of placental dysfunction in intra-uterine growth retardation.