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Biomedical subjects

C Woodward

Publications and source records attributed to C Woodward.

At least 73 records · Page 4Linked to original sources
PubMed1991

Escherichia coli glutaredoxin: cloning and overexpression, thermodynamic stability of the oxidized and reduced forms, and report of an N-terminal extended species.

Escherichia coli glutaredoxin (MW 9700) catalyzes intracellular redox reactions utilizing a disulfide/dithiol enzymatic mechanism involving the active-site residues -Cys-Pro-Tyr-Cys-. It is functionally related to the thioredoxin family and is expected to share similar three-dimensional structure [Eklund, H., Cambillau, C., Sjöberg, B.-M., Holmgren, A., Jörnvall, H., Höög, J.-O., & Brändén, C.-I. (1984) EMBO J. 3, 1443-1449]. We constructed an overexpression system in which production of glutaredoxin is controlled by temperature-sensitive expression of the phage T7 promoter. In addition to glutaredoxin, a second gene product is observed; this species, which we call glutaredoxin N, is glutaredoxin extended by the sequence Met-Arg-Arg-Glu-Ile- at the N terminus. We have begun characterization of the structure and stability of the oxidized and reduced forms of glutaredoxin (grx-S2 and grx-(SH)2, respectively). Secondary structure calculated from CD data agrees with that predicted from the three-dimensional model of Eklund et al. The cooperative denaturation reactions of oxidized and reduced glutaredoxin were measured in temperature-induced and guanidine hydrochloride induced unfolding experiments. Surprisingly, oxidized and reduced glutaredoxins are very similar in stability. In heat-induced denaturation, monitored by CD, Tm is 55 and 57 degrees C for oxidized and reduced, respectively. In GuHCl denaturation, monitored by fluorescence, the midpoint denaturant concentrations are 2 M for both oxidized and reduced. It follows that the redox potentials of the disulfide bond are similar in unfolded and folded glutaredoxin. This is unexpected because in E. coli thioredoxin the oxidized form is far more stable than the reduced [Kelley, R.F., Shalongo, W., Jagannadham, M.V., & Stellwagen, E. (1987) Biochemistry 26, 1406-1411] and the redox potential of folded thioredoxin is significantly more negative than that of unfolded thioredoxin [Lin, T.-Y., & Kim, P. (1989) Biochemistry 28, 5282-5287].

Amino Acid Sequence↗
PubMed1991

Evaluation of degenerative lesions of the rotator cuff. A comparison of arthrography and ultrasonography.

A prospective study was performed to determine the accuracy of arthrography compared with ultrasonography in the evaluation of thirty-two patients who had a degenerative lesion of the rotator cuff. Both tests were done preoperatively, and the condition of the rotator cuff was determined intraoperatively. Arthrography was accurate in the diagnosis of twenty-eight (87 per cent) of the thirty-two patients (twenty who had a full-thickness tear, seven who had a partial-thickness tear, and five who had an untorn rotator cuff and tendinitis), while ultrasonography was diagnostic in only twelve (37 per cent). In this specific population of patients, arthrography was found to be superior to ultrasonography.

Adult↗
PubMed1990

Medical-legal concerns among Canadian anaesthetists.

This paper reports the results of a national survey of anaesthetists which was undertaken to determine the effect of liability concerns on the practice of anaesthesia. Four hundred seventy-six anaesthetists from four regions (East, Quebec, Ontario and the West) (overall usable response rate of 73.3 per cent) responded to a series of questions on sources of liability information, changes in practice patterns over the past five years, changes in style of practice and attitudes towards the physician-patient relationship and to medical-legal concerns. The major findings were that the respondents rated liability concerns as the first or second most important reason for making major changes in their practice. Some of the changes in practice were related to increased use of monitoring, more time spent with patients discussing the risks of anaesthesia and increased documentation. On the negative side, respondents had decreased the administration of obstetrical and paediatric anaesthesia and were ordering more laboratory tests and x-rays. The majority of respondents agreed that the physician-patient relationship has suffered in recent years and physicians who had been in practice for longer periods of time were more likely to be dissatisfied and to consider leaving the field of medicine. However, the survey could not show a cause-and-effect relationship between claimed practice changes and fear of litigation.

Anesthesia Department, Hospital↗
PubMed1990

Electrostatic contributions to the binding of Ca2+ in calbindin mutants. A Monte Carlo study.

Monte Carlo simulation is used to calculate the free energy of binding of calcium ions to the native and several mutant forms of bovine calbindin D(9K) in salt solution. The simulations are performed in the canonical ensemble wherein free energies are calculated with a modified Widom method. The protein is modelled as a set of fixed hard spheres of fractional or unit charge with the surrounding solution as a dielectric continuum containing counterions and added salt particles. The interior of the protein is assumed to have the same dielectric permittivity as the solvent, which turns out to be an excellent approximation. Indeed, this simple model is able to predict accurately experimentally measured shifts in the calcium binding constants of up to five orders of magnitude, due to mutations and added salt.

Journal Article↗
PubMed1990

Viral and toxoplasma gondii infections in children after liver transplantation.

The incidence and morbidity of viral and Toxoplasma gondii infections were studied in 40 children who underwent liver transplantation between December 1983 and February 1988. The incidence of primary and reactivated cytomegalovirus (CMV) infection was 19% and 47%, respectively; primary infection caused clinical disease in all five cases affected and was fatal in one. Primary Epstein-Barr virus (EBV) infection occurred in 10 (26%) recipients but caused only mild disease. No reactivated EBV infection was recorded and no lymphoproliferative disorders associated with EBV were found after a maximum of four years' follow up. Adenovirus infection occurred in seven (18%) patients; this was associated in one case with fatal pneumonia and fulminant hepatitis, but otherwise with only mild respiratory disease. Primary T gondii infection was detected in one patient who remained asymptomatic. Other viruses causing infection included herpes simplex, varicella zoster, and respiratory syncytial virus. Surveillance for these infections and the long term sequelae should be included in the follow up of all children who undergo transplantation.

Adenovirus Infections, Human↗
PubMed1989

Escherichia coli thioredoxin folds into two compact forms of different stability to urea denaturation.

The urea-induced denaturation of Escherichia coli thioredoxin and thioredoxin variants has been examined by electrophoresis on urea gradient slab gels by the method of Creighton [Creighton, T. (1986) Methods Enzymol. 131, 156-172]. Thioredoxin has only two cysteine residues, and these form a redox-active disulfide at the active site. Oxidized thioredoxin-S2 and reduced thioredoxin-(SH)2 each show two folded isomers with a large difference in stability to urea denaturation. The difference in stability is greater for the isomers of oxidized than for the isomers of reduced thioredoxin. At 2 degrees C, the urea concentrations at the denaturation midpoint are approximately 8 and 4.3 M for the oxidized isomers and 4.8 and 3.7 M for the reduced isomers. The difference between the gel patterns of samples applied in native versus denaturing buffer, and at 2 and 25 degrees C, is characteristic for the involvement of a cis-proline-trans-proline isomerization. The data very strongly suggest that the two folded forms of different stabilities correspond to the cis and trans isomers of the highly conserved Pro 76 peptide bond, which is cis in the crystal structure of oxidized thioredoxin. Urea gel experiments with the mutant thioredoxin P76A, with alanine substituted for proline at position 76, corroborate this interpretation. The electrophoretic banding pattern diagnostic for an involvement of proline isomerization in urea denaturation is not observed for oxidized P76A. In broad estimates of delta G degree for the native-denatured transition, the difference in delta G degree (no urea) between the putative cis and trans isomers of the Ile 75-Pro 76 peptide bond is approximately 3 kcal/mol for oxidized thioredoxin and approximately 1.5 kcal/mol for reduced thioredoxin. Since cis oxidized thioredoxin is much more stable than trans, folded oxidized thioredoxin is essentially all cis. In folded reduced thioredoxin, cis and trans interconvert slowly, on the minute time scale at 2 and 25 degrees C. In the absence of urea, the folded reduced thioredoxin is less than a few percent trans. Three additional mutants with additions or substitutions at the active site also show electrophoresis banding patterns consistent with a difference in stability between cis and trans isomers.

Bacterial Proteins↗
PubMed1988

Billing patterns of general practitioners and family physicians in Ontario: a comparison of graduates of McMaster Medical School with graduates of other Ontario medical schools.

This descriptive study which uses data obtained from the Ontario Health Insurance Plan has identified a number of differences in the style of practice chosen by general practice/family medicine (gp/fm) physicians who graduated from McMaster medical school from that of other contemporary Ontario gp/fm graduates who are practicing in Ontario. McMaster gp/fms were more likely to be certified in Family Medicine, saw fewer patients per month than the comparison group, and billed less services but the cost per service billed was somewhat higher.

Curriculum↗
PubMed1988

A randomized controlled trial assessing the impact of problem-based versus didactic teaching methods in CME.

A Continuing Medical Education short course was designed to examine the effect of presenting topics in three learning formats - traditional lectures, large-group, case discussions or small-group, problem-solving sessions, on knowledge and performance of family physicians. The physicians in the small group session rated the CME short course higher and performed better on one aspect of patient management than the lecture or large group physicians but there were no other differences between groups on knowledge or physician performance.

Clinical Competence↗
PubMed1987

Hydrogen exchange of primary amide protons in basic pancreatic trypsin inhibitor: evidence for NH2 group rotation in buried asparagine side chains.

Hydrogen-deuterium exchange is measured for the buried primary amide groups of Asn-43 and Asn-44 in bovine pancreatic trypsin inhibitor. Amide protons trans and cis to the amide carbonyl oxygen (HE and HZ, respectively) exchange at indistinguishable rates. Uncorrelated exchange of HE and HZ is established for both residues by following the nuclear Overhauser enhancement from HE to HZ during the deuterium exchange. The exchange of Asn-43 and Asn-44 side-chain protons differs qualitatively from exchange of primary amide groups in fully solvated model compounds, for which HE generally exchanges faster than HZ. The equal rates for the buried primary amide HE and HZ in BPTI are not a consequence of coupled exchange. The data indicate rapid rotation around the CO-NH2 bond for both Asn-43 and Asn-44 and suggest considerable lability of intramolecular hydrogen bonds. The side chain of Asn-43 has all of its polar atoms integrated into the very stable hydrogen-bonded structure of the protein. Asn-44 is hydrogen-bonded to side chains and to a buried water molecule. Solvent isotope exchange is several orders of magnitude more restricted by protein secondary and tertiary structure than the CO-NH2 rotation, indicating that N delta H2 groups flip many times before hydrogen isotope exchange occurs.

Aprotinin↗
PubMed1987

Structure of form III crystals of bovine pancreatic trypsin inhibitor.

The structure of bovine pancreatic trypsin inhibitor has been solved in a new crystal form III. The crystals belong to space group P2(1)2(1)2 with a = 55.2 A, b = 38.2 A, c = 24.05 A. The structure was solved on the basis of co-ordinates of forms I and II of the inhibitor by molecular replacement, and the X-ray data extending to 1.7 A were used in a restrained least-squares refinement. The final R factor was 0.16, and the deviation of bonded distances from ideality was 0.020 A. Root-mean-square discrepancy between C alpha co-ordinates of forms III and I are 0.47 A, whilst between forms II and III the discrepancy is 0.39 A. These deviations are about a factor of 3 larger than the expected experimental errors, showing that true differences exist between the three crystal forms. Two residues (Arg39 and Asp50) were modeled with two positions for their side-chains. The final model includes 73 water molecules and one phosphate group bound to the protein. Sixteen water molecules occupy approximately the same positions in all three crystal forms studied to date, indicating their close association with the protein molecule. Temperature factors also show a high degree of correlation between the three crystal forms.

Amino Acid Sequence↗
PubMed1987

Solvent exchange of buried water and hydrogen exchange of peptide NH groups hydrogen bonded to buried waters in bovine pancreatic trypsin inhibitor.

Solvent exchange of 18O-labeled buried water in bovine pancreatic trypsin inhibitor (BPTI), trypsin, and trypsin-BPTI complex is measured by high-precision isotope ratio mass spectrometry. Buried water is labeled by equilibration of the protein in 18O-enriched water. Protein samples are then rapidly dialyzed against water of normal isotope composition by gel filtration and stored. The exchangeable 18O label eluting with the protein in 10-300 s is determined by an H2O-CO2 equilibration technique. Exchange of buried waters with solvent water is complete before 10-15 s in BPTI, trypsin, and BPTI-trypsin, as well as in lysozyme and carboxypeptidase measured as controls. When in-exchange dialysis and storage are carried out at pH greater than or equal to 2.5, trypsin-BPTI and trypsin, but not free BPTI, have the equivalent of one 18O atom that exchanges slowly (after 300 s and before several days). This oxygen is probably covalently bound to a specific site in trypsin. When in-exchange dialysis and storage are carried out at pH 1.1, the equivalent of three to seven 18O atoms per molecule is associated with the trypsin-BPTI complex, apparently due to nonspecific covalent 18O labeling of carboxyl groups at low pH. In addition to 18O exchange of buried waters, the hydrogen isotope exchange of buried NH groups H bonded to buried waters was also measured. Their base-catalyzed exchange rate constants are on the order of NH groups that in the crystal are exposed to solvent (static accessibility greater than 0) and hydrogen-bonded main chain O, and their pH min is similar to that for model compounds. The pH dependence of their exchange rate constants suggests that direct exchange with water may significantly contribute to their observed exchange rate.

Aprotinin↗