Essential role of Glu-C66 for menaquinol oxidation indicates transmembrane electrochemical potential generation by Wolinella succinogenes fumarate reductase

Quinol:fumarate reductase (QFR) is a membrane protein complex that couples the reduction of fumarate to succinate to the oxidation of quinol to quinone, in a reaction opposite to that catalyzed by the related enzyme succinate:quinone reductase (succinate dehydrogenase). In the previously determined structure of QFR from Wolinella succinogenes, the site of fumarate reduction in the flavoprotein subunit A of the enzyme was identified, but the site of menaquinol oxidation was not. In the crystal structure, the acidic residue Glu-66 of the membrane spanning, diheme-containing subunit C lines a cavity that could be occupied by the substrate menaquinol. Here we describe that, after replacement of Glu-C66 with Gln by site-directed mutagenesis, the resulting mutant is unable to grow on fumarate and the purified enzyme lacks quinol oxidation activity. X-ray crystal structure analysis of the Glu-C66-->Gln variant enzyme at 3.1-A resolution rules out any major structural changes compared with the wild-type enzyme. The oxidation-reduction potentials of the heme groups are not significantly affected. We conclude that Glu-C66 is an essential constituent of the menaquinol oxidation site. Because Glu-C66 is oriented toward a cavity leading to the periplasm, the release of two protons on menaquinol oxidation is expected to occur to the periplasm, whereas the uptake of two protons on fumarate reduction occurs from the cytoplasm. Thus our results indicate that the reaction catalyzed by W. succinogenes QFR generates a transmembrane electrochemical potential.     

The wider perinatal significance of the Australian in vitro fertilization data collection program

The most recent report (1986) from the Australian Register of In Vitro Fertilization pregnancies comprises 2242 in vitro fertilization (IVF) pregnancies and 261 gamete intrafallopian transfer (GIFT) pregnancies. A review of this data base indicated that this population had a relatively high incidence of both obstetric and perinatal morbidity and perinatal mortality. About 58% of the IVF pregnancies resulted in live births and 36.4% of the infants weighted less than 2500 gm at birth. These high rates could be partially accounted for by maternal prepregnancy risk factors, such as age, and by risk factors associated with the infertility management, such as multiple pregnancy (22% of all pregnancies more than 20 weeks), which accounted for approximately 50% of the preterm births (less than 37 weeks). Singleton pregnancies also had a higher incidence of preterm birth (17.8% at gestational age 24 to 36 weeks), low-birthweight babies (15.9% less than 2500 g) and perinatal mortality rates (35.4% per 1000 live births) than the Australian population at large. This warrants these patients being regarded as high risk. It is reassuring that the incidence of major malformations in IVF births (2.2%) is similar to that in the general population (1.4%).     

Correlation of cellular atypia and human papillomavirus deoxyribonucleic acid sequences in exfoliated cells of the uterine cervix

Restriction enzyme digestion and Southern blot hybridization were used to analyze deoxyribonucleic acid (DNA) extracted from exfoliated cervical cells for the presence of human papillomavirus sequences and these results were correlated with cytologic findings on Papanicolaou smears. Specimens (N = 204) were obtained from a nonselected population of women undergoing routine cytologic screening and human papillomavirus DNA sequences were detected in 33 (16%) women. Thirteen smears contained atypical squamous cells, ranging from very mild dysplasia to moderate dysplasia; all showed associated morphologic evidence of human papillomavirus infection characterized by koilocytosis, nuclear enlargement, wrinkling, and hyperchromasia, and human papillomavirus DNA was demonstrable in 12 (92%) smears. Of the remaining 191 samples with normal cytology, 21 (11%) also contained human papillomavirus DNA sequences. Reevaluation of the smears from these women resulted in a revision of the cytologic diagnosis to very mild dysplasia in four cases. These data suggest that human papillomavirus infection occurs more frequently than predicted by cytologic screening.     

Hip displacement in spastic cerebral palsy: repeatability of radiologic measurement

Radiologic measures of migration percentage (MP) and acetabular index (AI) taken from plain radiographs of the pelvis are the most commonly used tools for determining hip displacement and management options in children with cerebral palsy and spastic hip disease. This study determined interrater and intrarater reliability of MP and AI on pelvic radiographs chosen to represent a wide range of age (11 months to 8 years 5 months), MP (0%-56%), and AI (9 degrees -33 degrees ). The study demonstrated that an experienced rater would be expected to measure MP on a single radiograph to within +/-5.8% of the true value and a change in MP between two radiographs taken at different times to within +/-8.3% of the true value. Similarly for AI, the measurement error for a typical rater would be within +/-2.6 degrees on a single reading and +/-3.7 degrees if recording change between two occasions. The authors believe that the results indicating true change are acceptable in clinical practice, provided treatment decisions are based on a series of radiographs taken at 6-month intervals, methods and training are standardized, and consistent raters are used.     

Variations in use of tertiary cardiac services in part of North-West England

We assess the extent to which the need for tertiary cardiac care is being met uniformly within two Health Authorities in North-West England. We analyse small-area data from 1993-1996 on standardised rates of investigation (angiography) and surgery (bypass grafts and angioplasty). Utilisation by electoral ward is shown to be related to material deprivation. Small areas in which the Asian population is high have significantly fewer angiograms and angioplasties than might be expected according to need, while there is some evidence that women do not receive the levels of bypass surgery that might be expected.     

Social cognition and neurocognitive deficits in schizophrenia

While research equivocally supports a relationship between social cognition and neurocognition, it is less clear whether social cognition is related to general cognitive functioning or whether specific aspects of social cognition are linked with specific forms of neurocognition. Thus, this study sought to investigate the relationships between various domains of neurocognition and two forms of social cognition, social cue recognition and social problem solving, for 40 people with schizophrenia spectrum disorders. Step-wise multiple regressions found that performance on neurocognitive tests was able to predict 47% and 38% of the variance on measures of the ability to recognize actual and suggested social cues, respectively, and 13% of participants' ability to problem solve in ambiguous social situations. Once estimated intelligence and hospitalization history were controlled, however, neurocognition no longer significantly predicted social problem solving. Executive functioning was uniquely related to each type of social cue recognition, while memory predicted only the recognition of concrete social cues.     

Literature and medicine: evaluating a special study module using the nominal group technique

OBJECTIVES: To evaluate a special study module in literature and medicine that aimed for clinical relevance. METHODS: We organised a 4-week course around themes such as empathy, death and dying, disability, madness and creativity, addiction, domestic violence, ethical dilemmas, doctor/patient communication, doctors' emotions and end of life decisions. We used a diversity of texts and genres to address these themes. We explicitly encouraged the students to engage with both content and form when studying literature. To evaluate the course we used a nominal group technique. Students identified a range of items in response to open questions about the content and methods of the course. After clarifying and reducing the items generated, they ranked them in order of importance. To investigate perceived clinical relevance, we grouped the individual items into broader themes using a previously suggested taxonomy of clinical relevance. RESULTS: The students attached the highest importance to the insights gained into patients and their experience of illness. These encompassed aspects of understanding, knowledge and empathy. They also perceived that they had improved clinically relevant skills including communication, analysis, presentation, writing and ethical reasoning. The remaining items were more broadly concerned with themes of personal growth, development and pleasure. CONCLUSIONS: There are many objectives in studying literature. We focussed on designing a special study module that explicitly emphasised clinical relevance. Our evaluation shows that students identified clinically relevant improvements in knowledge, skills and attitudes from having taken the course.     

Leucocyte versus erythrocyte thioguanine nucleotide concentrations in children taking thiopurines for acute lymphoblastic leukaemia

PURPOSE: The aim of this study was to compare leucocyte and erythrocyte thioguanine nucleotide (TGN) cytotoxic metabolite concentrations in children with lymphoblastic leukaemia taking mercaptopurine (MP) or thioguanine (TG) as part of their long-term remission maintenance chemotherapy. METHODS: Ten consecutive children treated on the MRC ALL97 protocol were studied. Six were randomized to TG and four to MP. Leucocyte and erythrocyte thiopurine nucleotide metabolites were measured after the children had been titrated to the standard thiopurine protocol dose, or higher. RESULTS: Children taking TG accumulated significantly higher erythrocyte TGN concentrations than those taking MP (median difference 1171 pmol/8 x 10(8) erythrocytes, 95% CI 766 to 2169, P<0.02), but there was no significant difference in the concentration range of leucocyte TGNs generated from TG or MP. In those children taking TG, median TGN concentrations were 5142 pmol/8 x 10(8) leucocytes and 1472 pmol/8 x 10(8) erythrocytes (3.5-fold difference, median difference 3390 pmol/8 x 10(8) cells, 95% CI 1559 to 7695, P=0.005), compared to 5422 pmol/8 x 10(8) leucocytes and 261 pmol/8 x 10(8) erythrocytes (20-fold difference, median difference 5054 pmol/8 x 10(8) cells, 95% CI 2281 to 6328, P=0.03) in those taking MP. CONCLUSIONS: Despite the accumulation of significantly higher erythrocyte TGN concentrations for TG compared with MP, the accumulation of leucocyte TGNs in children taking TG was similar to the range of leucocyte TGNs in children taking MP. Therefore, when correlating intracellular TGNs to clinical effect, the range of erythrocyte TGN metabolites will be higher for those children taking TG than in those taking MP.