Medicine and nursing. Problems of hierarchy are not confined to nursing.
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Clinical Nursing Research↗
Biomedical subjects
S Knight
Publications and source records attributed to S Knight.
Factors associated with lowered intelligence in homozygous sickle cell disease.
The intelligence quotient (IQ) of 60 patients with homozygous sickle cell (SS) disease and 60 age and sex matched controls with a normal haemoglobin (AA) genotype aged 15-18 years, followed up in a cohort study from birth, was assessed by the Wechsler intelligence scales for children or for adults. IQ appeared to be normally distributed in both genotypes but mean values in SS disease were 5.6 points (95% confidence interval (CI) 1.0 to 10.2) lower than in AA controls (p = 0.016). The difference occurred in both verbal (5.5 points, p = 0.017) and performance (5.0 points, p = 0.044) subscales of the IQ score and the IQ defect in SS disease was associated with a significantly lower attention factor score (p = 0.005) but not with other factor scores. The genotype difference in IQ was not accounted for by differences in parental occupational level, school absenteeism, or school drop out, or reported activity level. In SS disease, IQ was not related to mean steady state haemoglobin, fetal haemoglobin, or mean cell haemoglobin concentration, or clinical severity as judged by the frequency of painful crises, hospital admission, or sick visits. IQ, at age 15-18 years, correlated with the patients' height at all ages from 1 to 10 years (partial correlations increasing from 0.14 (p = 0.15) at age 1 to 0.27 (p = 0.004) at age 10). Adjusting for height reduced the mean genotype difference in IQ to 5.5 (95% CI 0.6 to 10.3) points at age 1 and to 2.6 points (95% CI to -2.3, 7.5) at age 10. Prepubertal height therefore accounted for much of the genotype difference in IQ. It is speculated that early factors, possible nutritional, contribute to both impaired growth and mental development in sickle cell disease.
Adolescent↗
2.2 A resolution structure of the amino-terminal half of HIV-1 reverse transcriptase (fingers and palm subdomains).
BACKGROUND: HIV-1 reverse transcriptase (RT) catalyzes the transformation of single-stranded viral RNA into double-stranded DNA, which is integrated into host cell chromosomes. The molecule is a heterodimer of two subunits, p51 and p66. The amino acid sequence of p51 is identical to the sequence of the amino-terminal subdomains of p66. Earlier crystallographic studies indicate that the RT molecule is flexible, which may explain the difficulty in obtaining high-resolution data for the intact protein. We have therefore determined the structure of a fragment of RT (RT216), which contains only the amino-terminal half of the RT molecule ('finger' and 'palm' subdomains). RESULTS: The crystal structure of RT216 has been refined at 2.2 A resolution to a crystallographic R-value of 20.8%. The structure is very similar to that of the corresponding part of the p66 subunit in the p66/p51 heterodimer, although there is a small difference in the relative orientation of the two subdomains compared with the structure of an RT-DNA-antibody fragment complex. There are a large number of stabilizing contacts (mainly hydrogen bonds and hydrophobic interactions) between the subdomains. The locations of conserved amino acids and the position of some important drug-resistant mutations are described. CONCLUSIONS: The RT216 structure provides detailed three-dimensional information of one important part of HIV-1 RT (including the critical active site residues). We propose a model to explain the inhibitory effect of non-nucleoside inhibitors, which partially accounts for their effect in terms of conformational changes of active site residues.
Binding Sites↗
Food-purchasing behaviour in an Aboriginal community. 1. Results of a survey.
Attempts to improve the nutritional status of Aboriginal people through nutritional education programs should be informed by an understanding of contemporary patterns of food procurement, preparation and distribution. This paper describes the results of a survey of food-purchasing behaviour in a central-Australian Aboriginal community. Every transaction occurring in each food outlet in the community over a two-week period was recorded and the data analysed. The results show that women play a much greater role than men in food purchasing, that there is a significant recourse to takeaway foods, that there is a cycle of expenditure determined by distribution of pension and Community Development Employment Project cheques, and that children have sufficient disposable income to be able to provision themselves from the food outlets, so that much of their food consumption is not determined by adult members of their family.
Adolescent↗
Food-purchasing behaviour in an Aboriginal community. 2. Evaluation of an intervention aimed at children.
The previously described survey of food-purchasing behaviour in a central-Australian Aboriginal community demonstrated that children have sufficient disposable income to provision themselves directly from food outlets. Subsequently, a community-based intervention project developed strategies to provide healthier choices for these children. Two years after the initial survey, a follow-up survey was conducted in which all food purchases by children under the age of 15 in the community were recorded over a two-week period. The results demonstrate an improvement in the quality of foods and beverages purchased by children at the time of the second survey.
Adolescent↗
Formation of the active site of ribulose-1,5-bisphosphate carboxylase/oxygenase by a disorder-order transition from the unactivated to the activated form.
Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) catalyzes the key first step in photosynthetic CO2 fixation, the reaction that incorporates CO2 into sugar. In this study, refined crystal structures of unactivated tobacco RuBisCO and activated RuBisCO from spinach and tobacco, in complex with the reaction-intermediate analog 2-carboxyarabinitol 1,5-bisphosphate (CABP), are compared. Both plant enzymes are hexadecameric complexes of eight large and eight small subunits with a total relative molecular mass of approximately 550,000. The comparison of activated and unactivated forms of RuBisCO provides insight into the dynamics of action of this enzyme. The catalytic site, which is open to the solvent in the unactivated enzyme, becomes shielded in the activated CABP complex. This shielding is accomplished by a 12-A movement of the active-site "loop 6" (residues 331-338) and a disorder-order transition of three loops near the active-site entrance, the N terminus, the C terminus, and a loop comprising residues 64-68. All these residues belong to the catalytic large subunit. Domain rotations of about 2 degrees are observed, also tightening the active-site cleft. These observations provide an explanation for the extremely tight binding (Kd < or = 10(-11) M) of the CABP molecule. A striking correlation exists between crystallographic temperature factors in the activated enzyme and the magnitude of the atomic movement upon activation.
Amino Acid Sequence↗
Crystal structure of activated tobacco rubisco complexed with the reaction-intermediate analogue 2-carboxy-arabinitol 1,5-bisphosphate.
The crystal structure of activated tobacco rubisco, complexed with the reaction-intermediate analogue 2-carboxy-arabinitol 1,5-bisphosphate (CABP) has been determined by molecular replacement, using the structure of activated spinach rubisco (Knight, S., Andersson, I., & Brändén, C.-I., 1990, J. Mol. Biol. 215, 113-160) as a model. The R-factor after refinement is 21.0% for 57,855 reflections between 9.0 and 2.7 A resolution. The local fourfold axis of the rubisco hexadecamer coincides with a crystallographic twofold axis. The result is that the asymmetric unit of the crystals contains half of the L8S8 complex (molecular mass 280 kDa in the asymmetric unit). The activated form of tobacco rubisco is very similar to the activated form of spinach rubisco. The root mean square difference is 0.4 A for 587 equivalent C alpha atoms. Analysis of mutations between tobacco and spinach rubisco revealed that the vast majority of mutations concerned exposed residues. Only 7 buried residues were found to be mutated versus 54 residues at or near the surface of the protein. The crystal structure suggests that the Cys 247-Cys 247 and Cys 449-Cys 459 pairs are linked via disulfide bridges. This pattern of disulfide links differ from the pattern of disulfide links observed in crystals of unactivated tobacco rubisco (Curmi, P.M.G., et al., 1992, J. Biol. Chem. 267, 16980-16989) and is similar to the pattern observed for activated spinach tobacco.
Binding Sites↗
Dendritic cells are potent antigen-presenting cells for microbial superantigen.
Dendritic cells (DC) were found to be more efficient than macrophages (MO) in activating T cell responses to Staphylococcal enterotoxin B (SEB) using the hanging drop techniques and DC as antigen presenting cells (APC). When superantigen was presented via DC, the activation of T cells was not dependent on antigen processing and MHC class II molecules IA and IE were involved.
Animals↗
Deliberate self-harm: an audit of a service to patients.
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Data Collection↗
Cefuroxime and cefuroxime axetil versus amoxicillin plus clavulanic acid in the treatment of lower respiratory tract infections.
In a large multinational study, the clinical and bacteriological efficacy of intravenous cefuroxime 750 mg t.i.d. followed by oral cefuroxime axetil 500 mg b.i.d. was compared to that of amoxicillin plus clavulanic acid (CA) administered as 1.2 g intravenously t.i.d. followed by 625 mg orally t.i.d. in the treatment of lower respiratory tract infections in hospitalised patients. A total of 512 patients were entered (256 in each treatment group). All were suffering from pneumonia or acute exacerbations of chronic bronchitis or bronchiectasis and required initial parenteral antibiotic therapy. Parenteral therapy lasted 48 to 72 h and was followed by five days of oral therapy. The clinical responses in the two treatment groups were very similar: 223 of 256 (87.1%) patients were cured or improved with cefuroxime/cefuroxime axetil compared to 220 of 256 (85.9%) with amoxicillin/CA. Positive pre-treatment sputum samples were obtained from 44% of the patients. Clearance rates obtained were again similar: 72.8% with cefuroxime/cefuroxime axetil and 70% with amoxicillin/CA. Ten percent of the isolates were beta-lactamase producers, similar numbers of which were cleared in both groups. Both regimens were generally well tolerated, with only 5% of patients treated with the cefuroxime regimen and 4.3% of patients treated with amoxicillin/CA experiencing drug-related adverse events. Cefuroxime/cefuroxime axetil "follow-on" therapy produces clinical and bacteriological efficacy equivalent to that of amoxicillin/CA, with the advantage of twice daily oral administration.
Administration, Oral↗
Crystallographic analysis of ribulose 1,5-bisphosphate carboxylase from spinach at 2.4 A resolution. Subunit interactions and active site.
The X-ray structure of the quaternary complex of ribulose 1,5-bisphosphate carboxylase/oxygenase from spinach with CO2, Mg2+ and a reaction-intermediate analogue (CABP) has been determined and refined at 2.4 A resolution. Cyclic non-crystallographic symmetry averaging around the molecular 4-fold axis and phase combination were used to improve the initial multiple isomorphous replacement phases. A model composed of one large subunit and one small subunit was built in the resulting electron density map, which was of excellent quality. Application of the local symmetry gave an initial model of the L8S8 molecule with a crystallographic R-value of 0.43. Refinement of this initial model was performed by a combination of conventional least-squares energy refinement and molecular dynamics simulation using the XPLOR program. Three rounds of refinement, interspersed with manual rebuilding at the graphics display, resulted in a model containing all of the 123 amino acid residues in the small subunit, and 467 of the 475 residues in the large subunit. The R-value for this model is 0.24, with relatively small deviations from ideal stereochemistry. Subunit interactions in the L8S8 molecule have been analysed and are described. The interface areas between the subunits are extensive, and bury almost half of the accessible surface areas of both the large and the small subunit. A number of conserved interaction areas that may be of functional significance have been identified and are described, and biochemical and mutagenesis data are discussed in the structural framework of the model.
Amino Acid Sequence↗
Comparison of the crystal structures of L2 and L8S8 Rubisco suggests a functional role for the small subunit.
Comparison of the crystal structures of the L2 and L8S8 forms of ribulose-1,5-bisphosphate carboxylase from Rhodospirillum rubrum and spinach respectively, reveals a remarkable similarity in the overall architecture of the L2 building blocks in the two enzymes. Within the L subunits, no large conformational differences such as domain-domain rotations were found. In spite of a somewhat different packing of the L subunits in the L2 dimer, the active sites of the two enzymes are highly conserved. Significant local conformational differences are, however, observed for the C-terminal part of the polypeptide chains as well as for loop 7, helix alpha 7, loop 8 and helix alpha 8 in the barrel domain. The small subunit forms extensive interactions with one of these alpha helices, alpha 8, in the spinach L8S8 enzyme. The loops are at the active site and one of them forms a phosphate binding site for the substrate. We suggest that the small subunit modulates substrate binding and, possibly, the carboxylation/oxygenation ratio by inducing conformational changes in the active site through interactions distant from this site.
Amino Acid Sequence↗
Retrophrenic location of the internal mammary artery graft.
A technique of locating the internal mammary artery behind the phrenic nerve is described, which extends the application of internal mammary artery grafting to the lateral wall of the left ventricle. The technique also facilitates the performance of the posterolateral anastomosis between the internal mammary and circumflex coronary arteries.
Humans↗
Residues in three conserved regions of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase are required for quaternary structure.
To explore the role of individual residues in the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), small subunits with single amino acid substitutions in three regions of relative sequence conservation were produced by directed mutagenesis of the rbcS gene from Anabaena 7120. These altered small subunits were cosynthesized with large subunits (from an expressed Anabaena rbcL gene) in Escherichia coli. Mutants were analyzed for effects on quaternary structure and catalytic activity. Changing Glu-13S (numbering used is that of the spinach enzyme) to Val, Trp-67S to Arg, Pro-73S to His, or Tyr-98S to Asn prevented accumulation of stable holoenzyme. Interpretation of these results using a model for the three-dimensional structure of the spinach enzyme based on x-ray crystallographic data suggests that our small subunit mutants containing substitutions at positions 13S and 67S probably do not assemble because of mispairing or nonpairing of charged residues on the interfacing surfaces of the large and small subunits. The failure of small subunits substituted at positions 73S or 98S to assemble correctly may result from disruption of intersubunit or intrasubunit hydrophobic pockets, respectively.
Amino Acid Sequence↗
Analysis of very late gene expression by Autographa californica nuclear polyhedrosis virus and the further development of multiple expression vectors.
The consequences of locating the polyhedrin gene coding sequences and the p10 promoter at heterologous positions within the Autographa californica nuclear polyhedrosis virus (AcMNPV) genome were investigated. Positioning the polyhedrin or beta-galactosidase coding sequences under the control of the p10 gene promoter via the use of the new transfer vector, pAcUW1, resulted in viable recombinant viruses able to produce high levels of each non-fused gene product at the appropriate time. Polyhedra were also produced by the virus with the p10 promoter-polyhedrin hybrid gene and appeared normal in thin sections. Therefore the combination of polyhedrin promoter and coding sequences is evidently not essential for efficient expression of this protein. The p10 promoter can serve this function equally well. Viruses with the p10 promoter and beta-galactosidase coding sequences placed upstream from the polyhedrin gene in either orientation produced large amounts of beta-galactosidase protein in infected cells, thus demonstrating that the p10 promoter can function at an alternative position within the virus genome. A second transfer vector, pAcUW2B, was constructed, with a copy of the p10 gene promoter placed upstream and in opposition to the polyhedrin gene. This mediates the insertion of any foreign gene under the control of the p10 promoter while preserving normal p10 gene expression. The advantages of these constructs over the conventional vectors presently used to express foreign genes in insect cell systems and their utilization in the production of virus insecticides are discussed.
Animals↗
Muramic acid is not detectable in Chlamydia psittaci or Chlamydia trachomatis by gas chromatography-mass spectrometry.
By using the powerful separation technique of capillary gas chromatography combined with the selectivity of mass spectrometric detection, muramic acid was not detectable in purified elementary bodies of Chlamydia psittaci Cal 10 (less than or equal to 0.006%) or C. trachomatis serovar E (less than or equal to 0.02%). This confirms previous reports which suggested the absence of a typical peptidoglycan in Chlamydia spp.
Chlamydia trachomatis↗
Isolation of a gene that down-regulates nitrate assimilation and influences another regulatory gene in the same system.
Glutamine is the preferred source of nitrogen of Neurospora crassa. In its presence and that of the gene product of MS5 (nmr-1), the fungus represses the assimilation of less preferred forms of nitrogen, such as nitrate. In the absence of glutamine and the presence of the product of gene nit-2, less preferred forms of nitrogen are assimilated as long as a specific pathway for their assimilation is induced. We report here the isolation, from a cosmid bank, of a gene that complements MS5 and can also complement nit-2. We speculate that this result suggests an interaction between the MS5 and nit-2 gene products and that this is important in the regulation of nitrate assimilation.
Cosmids↗