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E A Kerr

Publications and source records attributed to E A Kerr.

27 records · Page 2Linked to original sources
PubMed1984

Assignment of the Fe-N epsilon (His) stretching mode in the resonance Raman spectra of a monomeric insect cyanomethaemoglobin.

Resonance Raman (RR) spectra of the monomeric cyanomethaemoglobin CTT III from insect larvae of Chironomus thummi thummi are shown for the range of 200-550 cm-1. By iron and cyanide isotope exchange a line varying between 307 cm-1 for 57Fe-13C15N and 311 cm-1 for 54Fe-12C14N, has been assigned to the Fe-N epsilon stretching mode of this haem complex. The substitution of 54Fe for 57Fe has no effect on the Fe-C = N bending mode whereas it affects the Fe-CN stretching mode.

Animals↗
PubMed1984

Iron-carbon bond lengths in carbonmonoxy and cyanomet complexes of the monomeric hemoglobin III from Chironomus thummi thummi: a critical comparison between resonance Raman and x-ray diffraction studies.

Soret-excited resonance Raman spectroscopy yields direct information regarding the iron-carbon bonding interactions in the cyanomet and carbonmonoxy complexes of hemoglobin III from Chironomus thummi thummi (CTT III) in solution. By isotope exchange in cyanide (13CN-, C15N-, and 13C15N-) and carbon monoxide (13CO, C18O, and 13C18O), we have assigned the Fe(III)-CN- stretching at 453 cm-1, the Fe(III)-C-N- bending at 412 cm-1, the Fe(II)-CO stretching at 500 cm-1, the Fe(II)-C-O bending at 574 cm-1, and the C-O stretching at 1960 cm-1. The resonance Raman data, in conjunction with those obtained from heme model complexes with well-known Fe-C bond distances, strongly suggest that the Fe(III)-CN- bond (approximately 1.91 A) is longer (hence weaker) than the Fe(II)-CO bond (approximately 1.80 A). This result disagrees with those of x-ray crystallographic studies [Steigemann, W. & Weber, E. (1979) J. Mol. Biol. 127, 309-338] in which the Fe-C bond lengths were reported as 2.2 A in cyanomet and 2.4 A in carbonmonoxy CTT III. Based on Badger's rule and normal mode calculations, the x-ray data would lead to the prediction of 279 cm-1 for the Fe(II)-CO stretching frequency in CTT III . CO, which was not observed. On the other hand, we estimate the Fe-CO bond as approximately equal to 1.82 A, which is very similar to the 1.80-A value in human Hb . CO crystals. Furthermore, we have used isotope shift data to estimate the Fe-C-O angle as 169 +/- 5 degrees, somewhat larger than the 161 degrees value found by Steigemann and Weber. We therefore conclude that there must be errors in the x-ray crystallographic refinement for the ligand geometry in carbonmonoxy and cyanomet CTT III.

Animals↗
PubMed1983

Resonance Raman studies of carbon monoxide binding to iron "picket fence" porphyrin with unhindered and hindered axial bases. An inverse relationship between binding affinity and the strength of iron-carbon bond.

The stretching frequency of the iron-carbon bond, v(Fe-CO), is a direct measure of the iron-carbon bond strength when there is no change in the Fe-C-O geometry. Here we report resonance Raman detection of v(Fe-CO) frequencies in the CO complexes of iron (II) alpha, alpha, alpha, alpha-mesotetrakis(o-pivalamidophenyl)porphyrin, FeII(TpivPP), with trans ligands of varying strength: N-methylimidazole (N-MeIm), 1,2-dimethylimidazole (1,2-Me2Im), pyridine (py), and tetrahydrofuran (THF). It was found that the weaker the iron-trans ligand bond, the stronger the iron-carbon bond. Comparisons of sterically hindered (1,2-Me2Im) and unhindered (N-MeIm) bases are of particular interest because of their implication in the phenomenon of hemoglobin cooperativity and the mechanisms of protein control of heme reactivity. While the CO binding affinity of FeII(TpivPP)(1,2-MeIm) is approximately 400 times lower than that of FeII(TpivPP)(N-MeIm), the v(Fe-CO) frequency for the former (at 496 cm-1) is higher than that for the latter (at 489 cm-1). This example shows that the CO binding affinity cannot be directly correlated with the strength of the iron-carbon bond. Comparison of the CO binding to FeII(TpivPP)(THF) and FeII(TpivPP)(N-MeIm) reveals a similar relationship; the v(Fe-CO) frequency (at 527 cm-1) in FeII(TpivPP)(THF)(CO) is 38 cm-1 higher than that in FeII(TpivPP)(N-MeIm)(CO), but the CO binding affinity is lower for the THF complex.

Carbon Monoxide↗
PubMed1983

Resonance Raman detection of Fe-CO stretching and Fe-C-O bending vibrations in sterically hindered carbonmonoxy "strapped hemes". A structural probe of Fe-C-O distortion.

We report resonance Raman studies of the Fe-C-O distortion in sterically hindered heme-CO complexes. The steric hindrance is provided by a hydrocarbon chain strapped across one face of the heme. Increasing the steric hindrance (by decreasing the chain length), which reduces the CO binding affinity, is found to increase the Fe-CO stretching frequencies: heme 5 (unstrapped), 495 cm-1; FeSP-15, 509 cm-1; FeSP-14, 512 cm-1; FeSP-13, 514 cm-1. This is interpreted in terms of a decrease in the CO effective mass and increased interactions between the C atom of CO and the N atom(s) of the pyrrole ring(s). Resonance Raman enhancement of the Fe-C-O bending mode upon Soret excitation may be correlated with the overlap between the porphyrin (pi*) and CO (pi*) orbitals when the CO ligand is tilted. Its intensity relative to that of the Fe-CO stretching mode increases with increasing steric hindrance in these "strapped hemes". In addition, we have estimated the Fe-C-O angles from isotope data in various heme-CO complexes. It is inferred that the angles are 167 +/- 5 degrees (FeSP-15) and 175 +/- 5 degrees (FeSP-14, FeSP-13, Mb X CO, and Hb X CO).

Carbon Monoxide↗
PubMed1982

Clostridium difficile: epidemiology and clinical features.

To determine the epidemiologic features of Clostridium difficile in Halifax, Nova Scotia, the authors studied two groups of hospitalized patients, one group of outpatients and a fourth group of 54 healthy subjects. The first group consisted of 29 patients with diarrhea, whose stool was found to contain C. difficile or its cytotoxin, or both. Twenty-two underwent sigmoidoscopic examinations; of these, 18 had abnormal colonic mucosa and 6 of the 18 had pseudomembranous colitis. In the second group of 127 patients on general medical wards, 22 (17%) carried C. difficile. Thirteen of the 22 had diarrhea, and 3 had pseudomembranous colitis. Clustering of patients with C. difficile was evident. In vitro production of toxin by isolates of C. difficile from these patients was more likely if antibiotics had been given. Only 1 (4.5%) of the 22 outpatients with various gastrointestinal disorders (group 3) and none of the 54 healthy subjects (group 4) carried C. difficile. The clinical spectrum of infection with C. difficile extended from asymptomatic patients to those with nonspecific colitis and pseudomembranous colitis.

Adult↗
PubMed1981

Susceptibility of anaerobic bacteria to nine antimicrobial agents and demonstration of decreased susceptibility of Clostridium perfringens to penicillin.

The activity of moxalactam, cefoxitin, cephalothin, cefamandole, chloramphenicol, clindamycin, metronidazole, and ticarcillin was determined against 344 isolates of anaerobic bacteria. The activity of penicillin G was determined as well for 234 isolates not of the Bacteroides fragilis group. Moxalactam was more active than cephalothin and cefamandole and slightly less active than cefoxitin. Metronidazole was the most active antimicrobial agent against the B. fragilis group, whereas chloramphenicol was most active overall. Clostridium species were the most resistant group of organisms tested. Relatively high concentrations of penicillin were required to inhibit the C. perfringens strains: 80% at 0.5 U/ml and 100% at 16 U/ml. Our study demonstrates the need for periodic anaerobe susceptibility testing in order to better guide empiric antibiotic therapy.

Anaerobiosis↗
PubMedDate not supplied

What is an error?

CONTEXT: Launched by the Institute of Medicine's report, "To Err is Human," the reduction of medical errors has become a top agenda item for virtually every part of the U.S. health care system. OBJECTIVE: To identify existing definitions of error, to determine the major issues in measuring errors, and to present recommendations for how best to proceed. DATA SOURCE: Medical literature on errors as well as the sociology and industrial psychology literature cited therein. RESULTS: We have four principal observations. First, errors have been defined in terms of failed processes without any link to subsequent harm. Second, only a few studies have actually measured errors, and these have not described the reliability of the measurement. Third, no studies directly examine the relationship between errors and adverse events. Fourth, the value of pursuing latent system errors (a concept pertaining to small, often trivial structure and process problems that interact in complex ways to produce catastrophe) using case studies or root cause analysis has not been demonstrated in either the medical or nonmedical literature. CONCLUSION: Medical error should be defined in terms of failed processes that are clearly linked to adverse outcomes. Efforts to reduce errors should be proportional to their impact on outcomes (preventable morbidity, mortality, and patient satisfaction) and the cost of preventing them. The error and the quality movements are analogous and require the same rigorous epidemiologic approach to establish which relationships are causal.

Causality↗
PubMedDate not supplied

Primary care physicians' satisfaction with quality of care in California capitated medical groups.

CONTEXT: Managed care and capitation have placed new responsibilities on primary care physicians, including formally acting as "gatekeepers" for specialty services and tests. Previous studies have not examined whether primary care physicians who provide services to patients under many coverage arrangements feel differently about caring for patients covered under capitation vs those covered through more traditional forms of insurance. An understanding of whether California primary care physicians feel that they deliver a different level of quality to capitated patients could help signal whether variations in care for patients with different coverage forms are evolving. OBJECTIVE: To evaluate whether primary care physicians in California capitated groups report different satisfaction levels with quality of care for patients in their overall practice than for patients covered by capitated contracts and to examine whether physicians' satisfaction with capitated care quality is influenced by the characteristics of the practice setting. DESIGN: Cross-sectional questionnaire. SETTING: A total of 89 California physician groups with capitated contracts. PARTICIPANTS: A total of 910 primary care physicians (80% response rate). MAIN OUTCOME MEASURE: Satisfaction with 4 aspects of quality of care provided to patients covered by capitated contracts vs patients overall. RESULTS: Physicians reported lower satisfaction with all 4 aspects of care for patients covered by capitated contracts than for patients in their overall practice: 71% were very or somewhat satisfied with relationships with capitated patients (compared with 88% for overall practice), 64% were very or somewhat satisfied with the quality of care they provided to capitated patients (compared with 88% for overall practice), 51% were very or somewhat satisfied with their ability to treat capitated patients according to their own best judgment (compared with 79% for overall practice), and 50% were very or somewhat satisfied with their ability to obtain specialty referrals (compared with 59% for overall practice) (P< or =.001 for all comparisons). Being in a medical group practice (vs an independent practice association) and having a larger percentage of capitated patients were independently associated by multivariate analysis with higher levels of satisfaction with capitated quality of care (P< or =.005). CONCLUSION: These California primary care physicians were less satisfied with the quality of care they deliver to patients covered by capitated contracts than with the quality of care they deliver to patients covered by other payment sources. However, those in medical group practices and with a higher percentage of capitated patients were more satisfied with capitated care. National expansion of capitation should be accompanied by efforts to ensure that the satisfaction of practicing physicians with the care they deliver does not decline.

Attitude of Health Personnel↗