Neck and vulvar papules in an 8-year-old girl.
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Child↗
Biomedical subjects
R A Scott
Publications and source records attributed to R A Scott.
Human conjunctiva contains high endothelial venules that express lymphocyte homing receptors.
Lymphocyte trafficking into tissues has been shown to occur across vessels with specialized endothelial cells called high endothelial venules. High endothelial venules naturally occur in lymph nodes and mucosal lymphoid tissues. The presence of high endothelial venules in the conjunctiva has not been demonstrated previously and the purpose of this study was to determine whether there is such a specialized vasculature to facilitate lymphocyte trafficking in conjunctiva associated lymphoid tissue.Samples of conjunctiva from four different individuals were analysed morphometrically for the presence of high endothelial venules by light and electron microscopy, and by immunohistochemistry using antibodies specific for high endothelial venules and for two adhesion molecules namely, Vascular Adhesion Protein-1 and Mucosal Addressin Cell Adhesion Molecule-1, expressed on high endothelial venules found in other tissues. Blood vessels with anatomical features of high endothelial venules were demonstrated in relation to conjunctival follicles and in the lamina propria. Immunohistochemical studies showed positive staining of vessels with anti-high endothelial venule antibodies, and with antibody against Vascular Adhesion Protein-1 but not with antibody against Mucosal Addressin Cell Adhesion Molecule-1. This study reveals that some of the blood vessels associated with conjunctival follicles and lamina propria have features of high endothelial venules. These vessels may play a significant role in lymphocyte homing to the conjunctiva and Vascular Adhesion Protein-1 (but not Mucosal Addressin Cell Adhesion Molecule-1) is one of the vascular addressin/adhesion molecules.
Cell Adhesion Molecules↗
X-ray absorption spectroscopic analysis of Fe(II) and Cu(II) forms of a herbicide-degrading alpha-ketoglutarate dioxygenase.
The first step in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by Ralstonia eutropha JMP134 is catalyzed by the alpha-ketoglutarate (alpha-KG)-dependent dioxygenase TfdA. Previously, EPR and ESEEM studies on inactive Cu(II)-substituted TfdA suggested a mixture of nitrogen/oxygen coordination with two imidazole-like ligands. Differences between the spectra for Cu TfdA and alpha-KG- and 2,4-D-treated samples were interpreted as a rearrangement of the g-tensor principal axis system. Herein, we report the use of X-ray absorption spectroscopy (XAS) to further characterize the metal coordination environment of Cu TfdA as well as that in the active, wild-type Fe(II) enzyme. The EXAFS data are interpreted in terms of four N/O ligands (two imidazole-like) in the Cu TfdA sample and six N/O ligands (one or two imidazole-like) in the Fe TfdA sample. Addition of alpha-KG results in no significant structural change in coordination for Cu or Fe TfdA. However, addition of 2,4-D results in a decrease in the number of imidazole ligands in both Cu and Fe TfdA. Since this change is seen both in the Fe and Cu EXAFS, loss of one histidine ligand upon 2,4-D addition best describes the phenomenon. These XAS data clearly demonstrate that changes occur in the atomic environment of the metallocenter upon substrate binding.
2,4-Dichlorophenoxyacetic Acid↗
Characterization of metal-substituted Klebsiella aerogenes urease.
Urease possesses a dinuclear Ni active site with the protein providing a bridging carbamylated lysine residue as well as an aspartyl and four histidyl ligands. The apoprotein can be activated in vitro by incubation with bicarbonate/CO2 and Ni(II); however, only approximately 15% forms active enzyme (Ni-CO2-ureaseA), with the remainder forming inactive carbamylated Ni-containing protein (Ni-CO2-ureaseB). In the absence of CO2, apoprotein plus Ni(II) forms a distinct inactive Ni-containing species (Ni-urease). The studies described here were carried out to better define the metal-binding sites for the inactive Ni-urease and Ni-CO2-ureaseB species, and to examine the properties of various forms of Co-, Mn-, and Cu-substituted ureases. Xray absorption spectroscopy (XAS) indicated that the two Ni atoms present in the Ni-urease metallocenter are coordinated by an average of two histidines and 3-4 N/O ligands, consistent with binding to the usual enzyme ligands with the lysine carbamate replaced by solvent. Neither XAS nor electronic spectroscopy provided evidence for thiolate ligation in the inactive Ni-containing species. By contrast, comparative studies of Co-CO2-urease and its C319A variant by electronic spectroscopy were consistent with a portion of the two Co being coordinated by Cys319. Whereas the inactive Co-CO2-urease possesses a single histidyl ligand per metal, the species formed using C319A apoprotein more nearly resembles the native metallocenter and exhibits low levels of activity. Activity is also associated with one of two species of Mn-CO2-urease. A crystal structure of the inactive Mn-CO2-urease species shows a metallocenter very similar in structure to that of native urease, but with a disordering of the Asp360 ligand and movement in the Mn-coordinated solvent molecules. Cu(II) was bound to many sites on the protein in addition to the usual metallocenter, but most of the adventitious metal was removed by treatment with EDTA. Cu-treated urease was irreversibly inactivated, even in the C319A variant, and was not further characterized. Metal speciation between Ni, Co, and Mn most affected the higher of two pKa values for urease activity, consistent with this pKa being associated with the metal-bound hydrolytic water molecule. Our results highlight the importance of precisely positioned protein ligands and solvent structure for urease activity.
Amino Acid Substitution↗
Highly crosslinked, PEG-containing copolymers for sustained solute delivery.
Novel ionizable polymer networks were prepared from oligo(ethylene glycol) (OEG) multiacrylates and acrylic acid (AA) employing bulk radical photopolymerization techniques. The properties of these materials exhibited a complex dependence on the network structure and composition, and the materials were therefore used in the design of controlled release devices with precisely controlled properties. The release kinetics of model solute proxyphylline exhibited a strong compositional dependence, with measured diffusion coefficients varying over several orders of magnitude, depending on the polymer network structure and the pH of the release medium. Varying the OEG chain length provided a means of coarsely adjusting the proxyphylline release rate, while varying the AA content and the pH offered a more precise measure of control.
Acrylates↗
A 14-year experience with 6 cm as a criterion for surgical treatment of abdominal aortic aneurysm.
BACKGROUND: It remains unclear when to recommend operation for an asymptomatic abdominal aortic aneurysm (AAA). This study examined a prospective series of patients for whom standard criteria were applied. METHODS: Some 584 consecutive patients with an AAA of diameter 3 cm or greater detected by ultrasonographic screening have been observed for up to 14 years. Repeat ultrasonographic examinations have been performed at intervals. Surgery was not considered unless the aneurysm measured 6 cm in diameter, expanded at a rate equivalent to at least 1 cm per year, caused the patient symptoms, or an iliac aneurysm was present that required treatment. RESULTS: Operation was performed on 127 patients; the majority (80; 63 per cent) had an aneurysm that reached 6 cm in diameter. Use of the above criteria prevented rupture in all but 24 (4 per cent) of the 584 patients over the 14-year interval. Of these 24 patients, 11 were unfit for planned surgery and eight declined operation or follow-up. Rupture in the five remaining patients (1 per cent) who were available for treatment compared favourably with the reported 30-day mortality rate for elective surgical treatment of 1.4-12 per cent. CONCLUSION: Repeated observation is preferable to surgical intervention until an aortic aneurysm measures 6 cm in diameter, expands by 1 cm per annum or causes symptoms. Presented as a poster to the 52nd Annual Meeting of the Society for Vascular Surgery, San Diego, California, USA, June 1998
Aged↗
A description of the roles, activities, and skills of clinical nurse specialists in the United States.
Clinical nurse specialists (CNSs) frequently adapt to meet the challenging and changing needs of patients, families, nurses, physicians, and institutions, thus creating an advance practice role that is problematic in definition and description. The two dilemmas associated with CNSs have been role confusion and ambiguity, and the inability to explicate CNSs' value in economic terms. The purpose of this study was to describe the roles, activities, skills, and the cost-saving and revenue-generating activities of Master's-prepared nurses who function in traditional CNS roles in the United States. A descriptive research design was employed, using Role Theory as a framework to guide the study. The tool used to measure CNS practice included a 68-item instrument. It was pretested and used in two pilot studies. Content validity was supported by three experienced CNSs who were, at the time, in a doctoral nursing program. Instrument reliability was 0.89. Surveys were mailed to all individuals who subscribed (n = 2379) to the Clinical Nurse Specialist Journal. From the convenience sample, 724 CNSs participated, providing a margin of error of +/- 4 percentage points with a 99% confidence level. Regarding the five role components, CNSs reported (listed from most frequently to least frequently) spending time in the role of expert practitioner, educator, consultant, administrator, and researcher. Most of the activities listed in each of the roles were typical of CNS practice. Of the advanced practice roles, the two with the most surprising results were the expert practitioner and administrator roles. The results indicated a trend toward performing advanced skills that have been in the past considered solely medical practice and toward increasing administrative responsibilities. A small number of CNSs were able to identify cost-saving and revenue-generating activities, including the monetary value of the activity.
Adult↗
Incidence among men of asymptomatic abdominal aortic aneurysms: estimates from 500 screen detected cases.
OBJECTIVES: To determine the incidence of asymptomatic abdominal aortic aneurysms and the implications for an ultrasound screening programme in England and Wales. METHODS: First screen data were obtained from the Chichester and Huntingdon screening studies and used to estimate the prevalence of abdominal aortic aneurysms. The incidence of new, asymptomatic aneurysms was estimated from the prevalence rates observed in the Huntingdon screening study. SETTING: Screening programmes in Huntingdon and Chichester using ultrasound to screen all men over the age of 50 and men over age 65 respectively. RESULTS: The prevalence of abdominal aortic aneurysms ranged between 5.32% and 8.02% and between 6.18% and 9.88% of men aged between 65 and 79 in Chichester and Huntingdon respectively. Annual incidence rates, estimated by age, rose steadily reaching a peak of 0.67% of the Huntingdon population per year at age 65. Thereafter incidence falls. Estimates of the incidence of new asymptomatic abdominal aortic aneurysms, based on the observed prevalence data, were calculated and showed a peak at age 65. CONCLUSIONS: Hypotheses are offered to explain this unexpected early peak in incidence. This information should allow the definition of the optimum age for screening, and the relative benefits of screening at different intervals if widespread screening is adopted in the future.
Age Factors↗
A bullous eruption in an acutely ill child.
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Child↗
The core metal-recognition domain of MerR.
MerR, the metalloregulatory protein of the mercury-resistance operon (mer) has unusually high affinity and specificity for ionic mercury, Hg(II). Prior genetic and biochemical evidence suggested that the protein has a structure consisting of an N-terminal DNA binding domain, a C-terminal Hg(II)-binding domain, and an intervening region involved with communication between these two domains. We have characterized a series of MerR deletion mutants and found that as little as 30% of the protein (residues 80-128) forms a stable dimer and retains high affinity for Hg(II). Biophysical measures indicate that this minimal Hg(II)-binding domain assumes the structural characteristics of the wild-type full-length protein both in the Hg(II) center itself and in an immediately adjacent helical protein domain. Our observations are consistent with the core Hg(II)-binding domain of the MerR dimer being constituted by a pair of antiparallel helices (possibly in a coiled-coil conformation) comprised of residues cysteine 82 through cysteine 117 from each monomer followed by a flexible loop through residue cysteine 126. These antiparallel helices would have a potential Hg(II)-binding site at each end. However, just as in the full-length protein, only one of these potential binding sites in the deleted proteins actually binds Hg(II).
Amino Acid Sequence↗
Monitoring protein expression in whole bacterial cells with MALDI time-of-flight mass spectrometry.
We report the application of matrix-assisted laser desorption ionization (MALDI) to monitor recombinant protein expression in whole bacteria. This technique is characterized by rapid sample preparation that provides analysis of samples extracted directly from the growth media in less than 10 min. The mass spectrometric method holds several advantages over gel electrophoresis, the conventional method for examining the protein content of cells. Comparisons between the two methods of analysis are presented in terms of increased speed, efficiency, resolution, and mass accuracy. Delayed extraction time-of-flight mass spectrometry identifies posttranslational modifications and other changes in the expected structure which are not recognized by gel electrophoresis. The utility of this method is demonstrated for proteins with molecular masses ranging from 5 to 50 kDa. Low molecular mass proteins (< 10 kDa) can be efficiently analyzed without any treatment of the bacterial broth prior to MALDI sample preparation. The MALDI analysis of higher molecular weight proteins shows enhanced sensitivity when the bacterial solutions are first sonicated.
Bacterial Proteins↗
Abdominal aortic aneurysm rupture rates: a 7-year follow-up of the entire abdominal aortic aneurysm population detected by screening.
PURPOSE: The goal of the current study was to identify the risk of rupture in the entire abdominal aortic aneurysm (AAA) population detected through screening and to review strategies for surgical intervention in light of this information. METHODS: Two hundred eighteen AAAs were detected through ultrasound screening of a family practice population of 5394 men and women aged 65 to 80 years. Subjects with an AAA of less than 6.0 cm in diameter were followed prospectively with the use of ultrasound, according to our protocol, for 7 years. Patients were offered surgery if symptomatic, if the aneurysm expanded more than 1.0 cm per year, or if aortic diameter reached 6.0 cm. RESULTS: The maximum potential rupture rate (actual rupture rate plus elective surgery rate) for small AAAs (3.0 to 4.4 cm) was 2.1% per year, which is less than most reported operative mortality rates. The equivalent rate for aneurysms of 4.5 to 5.9 cm was 10.2% per year. The actual rupture rate for aneurysms up to 5.9 cm using our criteria for surgery was 0.8% per year CONCLUSION: In centers with an operative mortality rate of greater than 2%, (1) surgical intervention is not indicated for asymptomatic AAAs of less than 4.5 cm in diameter, and (2) elective surgery should be considered only for patients with aneurysms between 4.5 and 6 cm in diameter that are expanding by more than 1 cm per year or for patients in whom symptoms develop. In centers with elective mortality rates of greater than 10% for abdominal aortic aneurysm (AAA) repair, the benefit to the patient of any surgical intervention for an asymptomatic AAA of less than 6.0 cm in diameter is questionable.
Aged↗
An in vitro study of a new design of acetabular cement pressurizer.
Aseptic loosening of the acetabular component remains one of the limiting factors in the long-term success of total hip arthroplasty. Cement pressurization has been shown to improve fixation. A new pressurizer has been designed that seals around the rim of the acetabulum and covers the transverse ligament notch with a flap. The results of in vitro testing of this device are presented and compared with those of pressure generated by insertion of an acetabular cup. The pressurizer allowed sustained, uniform cement pressurization. Peak pressures with the new pressurizer were 180 kPa at both the iliac region of the rim and the pole of an instrumented model acetabulum, compared with 55 kPa at the rim and 120 kPa at the pole on cup insertion. Pressures were maintained in the range of 80-90 kPa. The flap was effective in preventing cement leakage from the notch, and pressures were higher than when the flap was absent. Cup insertion alone gave only transient pressurization, substantially less near the rim of the acetabulum than at the pole. Peripheral pressurization may be significant in producing secure local fixation at the rim of the acetabulum, in particular in the region of the ilium (Charnley zone 1), where radiolucencies are most commonly observed and where stresses in the implanted acetabulum are highest. Improved rim fixation may also play a role in preventing the ingress of wear debris.
Acetabulum↗
Screening for abdominal aortic aneurysm: is opportunistic detection a realistic alternative?
OBJECTIVES: To determine whether abdominal aortic aneurysms (AAA) may be detected during investigation for concurrent disease and to assess whether opportunistic detection is a feasible alternative to a formal screening programme. DESIGN: A prospective review of previous investigations in subjects attending for aortic screening. MATERIALS AND METHODS: 276 men aged 65-80 attended the Chichester AAA screening programme. They were asked whether they had consulted their General Practitioner and whether they had undergone radiological investigation within the preceding 5 years. RESULTS: Two-hundred and sixty-one subjects had consulted their General Practitioner (94.6%) within the past 5 years. Fifty-six patients had been investigated with radiological imaging: in 22 cases (8.0%) the investigation had the potential to detect an AAA. The opportunistic detection rate was 0.4% (one AAA) in comparison to 12.0% for the screening programme (33 AAA). Imaging investigations with the potential to pick up AAA failed to detect five out of six aneurysms in this group. CONCLUSIONS: Opportunistic screening for AAA is not a realistic alternative to a formal screening programme but may improve the detection rate in the community.
Aged↗
Growth rates and risk of rupture of abdominal aortic aneurysms.
BACKGROUND: Early identification of abdominal aortic aneurysms (AAAs) may reduce the risk of death from rupture by providing the opportunity for elective repair. Before a screening policy for AAA is implemented, the growth rates of AAAs and the accompanying risk of rupture without intervention should be established. METHODS: The growth rates of AAAs were calculated using longitudinal aneurysmal growth data from screening studies in Chichester and Huntingdon. Estimates of the growth rates of AAAs and the risks of rupture over time were made taking measurement error and individual variability into account. RESULTS: Growth rate estimates were found to vary by initial aortic diameter, with a more rapid growth seen in large aneurysms (50 mm or more). The rate of aneurysm growth did not differ with age or sex. The estimated risk of rupture of an AAA with an initial diameter of 45 mm did not exceed 20-5 per cent over 5 years. An AAA with an initial diameter of 30 mm has a 4.0 per cent or less chance of rupture over 5 years. CONCLUSION: The study provides a more accurate assessment of the risk of aneurysm rupture without surgery and helps to define rescreening intervals for those with an enlarged aortic diameter.
Aged↗
Blue papules and macules in a newborn.
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Diagnosis, Differential↗
Assembly of a [2Fe-2S]2+ cluster in a molecular variant of Clostridium pasteurianum rubredoxin.
The rubredoxin from Clostridium pasteurianum contains a single iron atom bound to the polypeptide chain by cysteines 6, 9, 39, and 42. The C42A variant of this protein has been prepared by site-directed mutagenesis and heterologous expression of the gene in Escherichia coli. The mutated protein was found to contain an unexpected chromophore that has been characterized by a variety of techniques. UV-visible absorption and resonance Raman spectra were strongly reminiscent of those of [2Fe-2S] proteins. Mössbauer spectra of the oxidized chromophore isolated in oxygen-free conditions indicated low-temperature diamagnetism resulting from antiferromagnetically coupled high-spin ferric ions. Analysis of X-ray absorption fine structure spectra yielded an Fe-Fe distance of 2.68 A. Colorimetric assays of iron and inorganic sulfide showed that the two elements are present in a 1:1 ratio. Electrospray-ionization mass spectra displayed a major component at M = 6190 Da, i.e. the molecular mass of the C42A apoprotein plus two atomic masses of iron and two atomic masses of sulfur. Taken together, these data show that a mere point mutation allows the stabilization of a binuclear [2Fe-2S] cluster in a protein that normally accommodates a mononuclear Fe(Scys)4 site. Assembly of a [2Fe-2S] cluster may occur because rubredoxin assumes a similar fold around its metal center as the [2Fe-2S] Rieske protein. Alternatively, a more extensive structural rearrangement of the polypeptide chain of the C42A rubredoxin variant may be considered as well.
Binding Sites↗
Biophysical and mutagenic analysis of Thermoanaerobacter ethanolicus secondary-alcohol dehydrogenase activity and specificity.
The Thermoanaerobacter ethanolicus 39E adhB gene encoding the secondary-alcohol dehydrogenase (secondary ADH) was overexpressed in Escherichia coli at more than 10% of total protein. The recombinant enzyme was purified in high yield (67%) by heat-treatment at 85 degrees C and (NH4)2SO4 precipitation. Site-directed mutants (C37S, H59N, D150N, D150Eand D150C were analysed to test the peptide sequence comparison-based predictions of amino acids responsible for putative catalytic Zn binding. X-ray absorption spectroscopy confirmed the presence of a protein-bound Zn atom with ZnS1(imid)1(N,O)3 co-ordination sphere. Inductively coupled plasma atomic emission spectrometry measured 0.48 Zn atoms per wild-type secondary ADH subunit. The C37S, H59N and D150N mutant enzymes bound only 0.11, 0.13 and 0.33 Zn per subunit respectively,suggesting that these residues are involved in Zn liganding. The D150E and D150C mutants retained 0.47 and 1.2 Zn atoms per subunit, indicating that an anionic side-chain moiety at this position preserves the bound Zn. All five mutant enzymes had </= 3% of wild-type catalytic activity, suggesting that the T. ethanolicus secondary ADH requires a properly co-ordinated catalytic Zn atom. The His-59 and Asp-150 mutations also altered secondary ADH affinity for propan-2-ol over a 140-fold range, whereas the overall change in affinity for ethanol spanned a range of only 7-fold, supporting the importance of the metal in secondary ADH substrate binding. The lack of significant changes in cofactor affinity as a result of these catalytic Zn ligand mutations suggested that secondary ADH substrate-and cofactor-binding sites are structurally distinct. Altering Gly198 to Asp reduced the enzyme specific activity 2.7-fold, increased the Km(app) for NADP+ 225-fold, and decreased the Km(app) for NAD+ 3-fold, supporting the prediction that the enzyme binds nicotinamide cofactor in a Rossmann fold. Our data indicate therefore that, unlike the liver primary ADH,the Rossmann-fold-containing T. ethanolicus secondary ADH binds its catalytic Zn atom using a sorbitol dehydrogenase-like Cys-His-Asp motif and does not bind a structural Zn atom.
Alcohol Dehydrogenase↗