Controversy in the management of convergence excess esotropia.
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Child↗
Biomedical subjects
J Burke
Publications and source records attributed to J Burke.
Crystallization and preliminary X-ray analysis of glucose dehydrogenase from Haloferax mediterranei.
Glucose dehydrogenase (E.C. 1.1.1.47; GlcDH) from Haloferax mediterranei has been overexpressed in Escherichia coli, solubilized by the addition of 8 M urea and refolded by rapid dilution. The protein has been purified by conventional techniques and crystallized by the hanging-drop vapour-diffusion method using sodium citrate as the precipitant. Two crystal forms representing the free enzyme and the binary complex with NADP(+) grow under these conditions. Crystals of form I diffract to beyond 3.5 A resolution and belong to the hexagonal space group P622, with unit-cell parameters a = b = 89.1, c = 214.6 A, alpha = beta = 90, gamma = 120 degrees. Crystals of form II diffract to greater than 2.0 A and belong to the orthorhombic space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 61.8, b = 110.9, c = 151.7 A, alpha = beta = gamma = 90 degrees. Calculated values for V(M) and consideration of the packing for both crystal forms suggests that the asymmetric units in both crystal forms contain a monomer.
Crystallization↗
The crystal structure of Thermotoga maritima maltosyltransferase and its implications for the molecular basis of the novel transfer specificity.
Maltosyltransferase (MTase) from the hyperthermophile Thermotoga maritima represents a novel maltodextrin glycosyltransferase acting on starch and malto-oligosaccharides. It catalyzes the transfer of maltosyl units from alpha-1,4-linked glucans or malto-oligosaccharides to other alpha-1,4-linked glucans, malto-oligosaccharides or glucose. It belongs to the glycoside hydrolase family 13, which represents a large group of (beta/alpha)(8) barrel proteins sharing a similar active site structure. The crystal structures of MTase and its complex with maltose have been determined at 2.4 A and 2.1 A resolution, respectively. MTase is a homodimer, each subunit of which consists of four domains, two of which are structurally homologous to those of other family 13 enzymes. The catalytic core domain has the (beta/alpha)(8) barrel fold with the active-site cleft formed at the C-terminal end of the barrel. Substrate binding experiments have led to the location of two distinct maltose-binding sites; one lies in the active-site cleft, covering subsites -2 and -1; the other is located in a pocket adjacent to the active-site cleft. The structure of MTase, together with the conservation of active-site residues among family 13 glycoside hydrolases, are consistent with a common double-displacement catalytic mechanism for this enzyme. Analysis of maltose binding in the active site reveals that the transfer of dextrinyl residues longer than a maltosyl unit is prevented by termination of the active-site cleft after the -2 subsite by the side-chain of Lys151 and the stretch of residues 314-317, providing an explanation for the strict transfer specificity of MTase.
Binding Sites↗
Generalized transduction in Streptomyces coelicolor.
We report the isolation of generalized transducing phages for Streptomyces species able to transduce chromosomal markers or plasmids between derivatives of Streptomyces coelicolor, the principal genetic model system for this important bacterial genus. We describe four apparently distinct phages (DAH2, DAH4, DAH5, and DAH6) that are capable of transducing multiple chromosomal markers at frequencies ranging from 10(-5) to 10(-9) per plaque-forming unit. The phages contain DNA ranging in size from 93 to 121 kb and mediate linked transfer of genetic loci at neighboring chromosomal sites sufficiently close to be packaged within the same phage particle. The key to our ability to demonstrate transduction by these phages was the establishment of conditions expected to severely reduce superinfection killing during the selection of transductants. The host range of these phages, as measured by the ability to form plaques, extends to species as distantly related as Streptomyces avermitilis and Streptomyces verticillus, which are among the most commercially important species of this genus. Transduction of plasmid DNA between S. coelicolor and S. verticillus was observed at frequencies of approximately 10(-4) transductants per colony-forming unit.
Bacteriophages↗
Glycerol dehydrogenase. structure, specificity, and mechanism of a family III polyol dehydrogenase.
BACKGROUND: Bacillus stearothermophilus glycerol dehydrogenase (GlyDH) (glycerol:NAD(+) 2-oxidoreductase, EC 1.1.1.6) catalyzes the oxidation of glycerol to dihydroxyacetone (1,3-dihydroxypropanone) with concomitant reduction of NAD(+) to NADH. Analysis of the sequence of this enzyme indicates that it is a member of the so-called iron-containing alcohol dehydrogenase family. Despite this sequence similarity, GlyDH shows a strict dependence on zinc for activity. On the basis of this, we propose to rename this group the family III metal-dependent polyol dehydrogenases. To date, no structural data have been reported for any enzyme in this group. RESULTS: The crystal structure of B. stearothermophilus glycerol dehydrogenase has been determined at 1.7 A resolution to provide structural insights into the mechanistic features of this family. The enzyme has 370 amino acid residues, has a molecular mass of 39.5 kDa, and is a homooctamer in solution. CONCLUSIONS: Analysis of the crystal structures of the free enzyme and of the binary complexes with NAD(+) and glycerol show that the active site of GlyDH lies in the cleft between the enzyme's two domains, with the catalytic zinc ion playing a role in stabilizing an alkoxide intermediate. In addition, the specificity of this enzyme for a range of diols can be understood, as both hydroxyls of the glycerol form ligands to the enzyme-bound Zn(2+) ion at the active site. The structure further reveals a previously unsuspected similarity to dehydroquinate synthase, an enzyme whose more complex chemistry shares a common chemical step with that catalyzed by glycerol dehydrogenase, providing a striking example of divergent evolution. Finally, the structure suggests that the NAD(+) binding domain of GlyDH may be related to that of the classical Rossmann fold by switching the sequence order of the two mononucleotide binding folds that make up this domain.
Amino Acid Sequence↗
Combined strabismus and phacoemulsification cataract surgery: a useful option in selected patients.
PURPOSE: To evaluate the role of combined strabismus and phacoemulsification cataract extraction in patients with symptomatic cataract and strabismus. METHODS: Four procedures of combined strabismus and cataract surgery are described in 3 elderly patients with strabismus of differing aetiologies. Two patients underwent one procedure; the other patient underwent two combined procedures, one to each eye. RESULTS: The visual acuity improved in all 3 patients. Post-operative alignment of the visual axis was achieved which allowed resolution of symptomatic diplopia in patient 1, functional binocular single vision in patient 2 and a noticeably reduced compensatory head posture in patient 3. CONCLUSIONS: Combined strabismus and cataract surgery is a safe procedure that can optimise visual alignment and improve visual acuity with a minimum number of operations.
Aged↗
Using talking lights to assist brain-injured patients with daily inpatient therapeutic schedule.
OBJECTIVES: To test the ability of patients with brain injury to use a patient locator and minder (PLAM) system to assist in their adherence to therapy schedules. PARTICIPANTS: Five patients with acquired brain injury who were inpatients on an acute rehabilitation floor of a rehabilitation hospital. MEASURES: The number of human prompts necessary to direct a patient to, and ensure arrival at, a scheduled therapy destination and the proportion of therapy sessions requiring no prompting was measured both before and after the introduction of the PLAM system. RESULTS: With the PLAM system, the average number of human prompts dropped by more than 50%, and the number of sessions requiring no prompting increased from 7% to 44%. CONCLUSION: The PLAM system described in this article seems feasible and useful for patients with acquired brain injury in assisting them with arrival at their therapy destinations without the assistance of staff.
Adult↗
Purification, crystallization and quaternary structure analysis of a glycerol dehydrogenase S305C mutant from Bacillus stearothermophilus.
Bacillus stearothermophilus glycerol dehydrogenase (GlyDH) is a 39.5 kDa molecular weight metalloenzyme which catalyzes the oxidation of glycerol to dihydroxyacetone with the concomitant reduction of NAD(+) to NADH. Despite its classification as a member of the 'iron-containing' polyol dehydrogenase family, studies on recombinant B. stearothermophilus GlyDH have shown this enzyme to be Zn(2+)-dependent. Crystals of a S305C GlyDH mutant were obtained by the hanging-drop vapour-diffusion method, using ammonium sulfate and PEG 400 as precipitating agents, in the presence and absence of NAD(+). The crystals belong to space group I422, with approximate unit-cell parameters a = b = 105, c = 149 A and one subunit in the asymmetric unit, corresponding to a packing density of 2.6 A(3) Da(-1). The crystals diffract X-rays to at least 1.8 A resolution on a synchrotron-radiation source. Determination of the structure will provide insights into the key determinations of catalytic activity of this class of enzymes, for which no structures are currently available.
Crystallization↗
Stroke and complementary medicine.
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Complementary Therapies↗
A ditelosomic line of 'Chinese Spring' wheat with augmented acquired thermotolerance.
A study of the ditelosomic series of 'Chinese Spring' wheat has yielded a number of lines displaying either an increased or decreased ability to acquire thermotolerance. One such ditelosomic (DT) is termed DT1BS which refers to the missing short arm of chromosome 1 in the B genome. The DT1BS line has the ability to acquire thermotolerance at lower induction temperatures and provide greater protection to the plant against otherwise lethal elevated temperatures. Using a chlorophyll accumulation assay to measure plant health, we show that DT1BS accumulates chlorophyll optimally at the same temperature, and to similar levels as 'Chinese Spring'. We also show that maximum acquired thermotolerance against a 48 degrees C challenge is induced at 40 degrees C, but significant levels of protection can be obtained at temperatures as low as 34 degrees C in DT1BS or 36 degrees C in 'Chinese Spring'. Heat-shock protein accumulation is observed in DT1BS at temperatures 4 degrees C lower than the 'Chinese Spring' and is correlated with the induction of acquired thermotolerance.
Journal Article↗
Domain-domain interface packing at conserved Trp-20 in class alpha glutathione transferase impacts on protein stability.
The folding and assembly of the dimeric glutathione transferases (GST) involves the association of two structurally distinct domains per subunit. A prominent and conserved domain-domain interaction in class alpha GSTs is formed by the packing of the indole side chain of Trp-20 from domain I into a hydrophobic pocket in domain II. Stability studies have shown that partial dissociation of the domains near Trp-20 occurs as an initial fast event during the unfolding kinetics of human GSTA1-1 (Wallace et al., Biochemistry 37 (1998) 5320-5328; Wallace et al., Biochem. J. 336 (1998) 413-418). The contribution of Trp-20 toward stabilising the domain-domain interface was investigated by mutating it to either a phenylalanine (W20F) or alanine (W20A) and determining the functionality (catalysis and non-substrate ligand binding) and stability (thermal- and urea-induced denaturation) of the mutant proteins. The replacement of Trp-20 did not impact on the protein's gross structural properties. Functionally, the W20F was non-disruptive, whereas the cavity-creating W20A mutation was. Both mutants destabilised the native state with W20A exerting the greatest effect. Reduced m-values as well as the protein concentration dependence of the urea unfolding transitions for W20F GSTA1-1 suggest the presence of a dimeric intermediate at equilibrium that is not observed with wild-type protein. Unfolding kinetics monitored by stopped-flow tyrosine fluorescence was mono-exponential and corresponded to the global unfolding of the protein during which the dimeric intermediate unfolds to two unfolded monomers. The similar unfolding kinetics data for wild-type and W20F A1-1 indicates that the global unfolding event was not affected by amino acid replacement. We propose that the packing interactions at the conserved Trp-20 plays an important role in stabilising the intrasubunit domain I-domain II interface of class alpha GSTs.
Amino Acid Sequence↗
The effect of patient race and socio-economic status on physicians' perceptions of patients.
Despite its potential influence on quality of care, there has been little research on the way physicians perceptions of and beliefs about patients are affected by patient race or socio-economic status. The lack of research in this area creates a critical gap in our understanding of how patients' demographic characteristics influence encounter characteristics, diagnoses, treatment recommendations, and outcomes. This study uses survey data to examine the degree to which patient race and socio-economic status affected physicians' perceptions of patients during a post-angiogram encounter. A total of 842 patient encounters were sampled, out of which 193 physicians provided data on 618 (73%) of the encounters sampled. The results of analyses of the effect of patient race and SES on physician perceptions of and attitude towards patients, controlling for patient age, sex, race, frailty/sickness, depression, mastery, social assertiveness and physician characteristics, are presented. These results supported the hypothesis that physicians' perceptions of patients were influenced by patients' socio-demographic characteristics. Physicians tended to perceive African-Americans and members of low and middle SES groups more negatively on a number of dimensions than they did Whites and upper SES patients. Patient race was associated with physicians' assessment of patient intelligence, feelings of affiliation toward the patient, and beliefs about patient's likelihood of risk behavior and adherence with medical advice; patient SES was associated with physicians' perceptions of patients' personality, abilities, behavioral tendencies and role demands. Implications are discussed in terms of further studies and potential interventions.
Attitude of Health Personnel↗
Effects of activity-rest schedules on physiological strain and spinal load in hospital-based porters.
Workers in physically demanding occupations require rest breaks to recover from physiological stress and biomechanical loading. Physiological stress can increase the risk of developing musculoskeletal disorders and repeated loading of the spine may increase the potential for incurring back pain. The aim of the study was to assess the impact of an altered activity-rest schedule on physiological and spinal loading in hospital-based porters. An existing 4-h activity-rest schedule was obtained from observations on eight male porters. This schedule formed the normal trial, which included two 5- and one 15-min breaks. An alternative 4-h schedule was proposed (experimental condition) that had two breaks each of 12.5 min. It was hypothesized that the experimental trial is more effective in promoting recovery from physiological strain and spinal shrinkage than the normal trial, due to the 5-min breaks being insufficient to allow physiological variables to return to resting levels or the intervertebral discs to reabsorb fluid. Ten males performed both test conditions and oxygen uptake VO2, heart rate, minute ventilation VE, perceived exertion and spinal shrinkage were recorded. There were no significant differences in any of the measured variables between the two trials (p > 0.05). Median heart rates were 78 (range 71-93) and 82 (71-90) beats.min(-1) for the normal trial and the experimental trial respectively, indicating that the activity was of low intensity. The light intensity was corroborated by the oxygen uptakes (0.75, range 0.65-0.94 1.min(-1)). Spinal shrinkage occurred to the same extent in the two trials (2.12 +/- 3.16 mm and 2.88 +/- 2.92 mm in the normal trial and the experimental trial respectively). Varying the length and positioning of the rest breaks did not significantly affect the physiological responses or magnitude of spinal shrinkage between the two trials. More physically demanding work than the porters' schedule should induce greater physiological fatigue and spinal shrinkage. The ratio between activity and rest breaks would then become more important.
Adult↗
Unusual extravasation of urine diagnosed on bone scan.
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Aged↗