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Biomedical subjects

J L Chambers

Publications and source records attributed to J L Chambers.

At least 19 recordsLinked to original sources
PubMed2001

Simple bedside additive tool for prediction of in-hospital mortality after percutaneous coronary interventions.

BACKGROUND: Risk-adjustment models for percutaneous coronary intervention (PCI) mortality have been recently reported, but application in bedside prediction of prognosis for individual patients remains untested. METHODS AND RESULTS: Between July 1, 1997 and September 30, 1999, 10 796 consecutive procedures were performed in a consortium of 8 hospitals. Predictors of in-hospital mortality were identified by use of multivariate logistic regression analysis. The final model was validated by use of the bootstrap technique. Additional validation was performed on an independent data set of 5863 consecutive procedures performed between October 1, 1999, and August 30, 2000. An additive risk-prediction score was developed by rounding coefficients of the logistic regression model to the closest half-integer, and a visual bedside tool for the prediction of individual patient prognosis was developed. In this patient population, the in-hospital mortality rate was 1.6%. Multivariate regression analysis identified acute myocardial infarction, cardiogenic shock, history of cardiac arrest, renal insufficiency, low ejection fraction, peripheral vascular disease, lesion characteristics, female sex, and advanced age as independent predictors of death. The model had excellent discrimination (area under the receiver operating characteristic curve, 0.90) and was accurate for prediction of mortality among different subgroups. Near-perfect correlation existed between calculated scores and observed mortality, with higher scores associated with higher mortality. CONCLUSIONS: Accurate predictions of individual patient risk of mortality associated with PCI can be achieved with a simple bedside tool. These predictions could be used during discussions of prognosis before and after PCI.

Age Factors↗
PubMed1994

Reappraisal of duplex criteria to assess significant carotid stenosis with special reference to reports from the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial.

PURPOSE: Duplex examination is today the principal initial method of assessing extracranial carotid or vertebral artery disease. However, varying haemodynamic criteria have been described to categorize the degree of internal carotid artery stenosis, and similarly the degree of stenosis detected with angiography has been assessed with different methods as highlighted in studies performed by the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. This study looks at the correlation between two commonly used methods of assessing carotid artery stenosis with duplex criteria and the two methods of angiographic interpretation used in these trials. Duplex parameters are also identified to determine the greater than 70% stenosis group identified as at risk in these studies. METHODS: A total of 120 carotid bifurcations were studied in patients who underwent both carotid duplex and angiography. Correlations of duplex with angiography were assessed with duplex criteria described by Zwiebel and by Strandness and the angiographic methods used in studies performed by the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. Receiver operator curves were constructed from the duplex data for the detection of stenosis greater than 70% based on the angiographic assessment used in the study performed by the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: The duplex criteria described by Zwiebel and Strandness differed in their accuracy depending on which of the two methods was used to report the angiograms. Zwiebel's criteria agreed more with the angiographic method used in the study performed by the European Carotid Surgery Trial (sensitivity 98%, specificity 81%, accuracy 88%), whereas Strandness' criteria agreed more with the angiographic method used in the study performed by the North American Symptomatic Carotid Endarterectomy Trial (sensitivity 96%, specificity 85%, accuracy 89%). For the detection of a stenosis greater than 70%, a peak systolic velocity greater than 270 cm/sec and end diastolic velocity greater than 110 cm/sec provided a sensitivity of 96%, specificity of 91%, and accuracy of 93%. CONCLUSIONS: The accuracy of duplex studies compared with angiography in the assessment of extracranial vascular disease depends on the method of angiographic determination of carotid stenosis. Vascular laboratories should validate the duplex criteria they use against a standard method of angiographic assessment of carotid artery stenosis, with special reference to the recently reported studies noting the significance of a stenosis greater than 70% in patients with symptoms.

Blood Flow Velocity↗
PubMed1994

Fibromuscular hyperplasia in an aberrant subclavian artery and neurogenic thoracic outlet syndrome: an unusual combination.

An aberrant right subclavian artery arising distal to the origin of the left subclavian artery is the most common anomaly of the aortic arch. Degenerative diseases of aberrant subclavian arteries including aneurysms and occlusive disease have been reported previously. We believe that this case is the first reported case of fibromuscular hyperplasia affecting an aberrant subclavian artery. A 25-year-old woman admitted with a history consistent with neurogenic thoracic outlet syndrome was found to have a reduced pulse and blood pressure on the ipsilateral side caused by fibromuscular hyperplasia of an aberrant subclavian artery. A carotid-subclavian bypass via a supraclavicular incision was performed at the same time as thoracic outlet decompression. Histologic examination confirmed the presence of fibromuscular hyperplasia in the aberrant subclavian artery. This case is discussed with reference to the available literature.

Adult↗
PubMed1992

Leaf water status and root system water flux of shortleaf pine (Pinus echinata Mill.) seedlings in relation to new root growth after transplanting.

Water relations and root growth of shortleaf pine (Pinus echinata Mill.) were studied four weeks after seedlings from a half-sib family had been transplanted to one of three regimes of soil water availability at a root zone temperature of either 15 or 20 degrees C. About one-third of the variation in new root growth was explained by the root zone environment. The interaction between root zone temperature and soil water availability accounted for 10% of the variation in new root growth. In the most favorable root environment, new roots averaged 620 mm(2) of projected surface area. Leaf water potential increased exponentially with new root projected surface area, becoming constant at about 300 mm(2). Leaf conductance and root system water flux increased linearly with new root growth.

Journal Article↗
PubMed1988

Primary iliac-appendiceal fistula.

Primary aorto-appendiceal fistula has been reported only once previously. A further case is presented in which bleeding, per rectum, occurred in association with rupture of an aorto-iliac aneurysm adherent to an acutely inflamed appendix. Postoperatively the patient had several complications including permanent asymmetrical L1 paraplegia and delayed presentation of an intramedullary abscess of the femur which grew Bacteroides fragilis organisms. These complications highlight the high morbidity associated with aortocolic fistulae.

Abscess↗
PubMed1982

A comparison of non-invasive methods in the assessment of extracranial carotid artery disease.

The accuracy of four-invasive methods used in the evaluation of the extracranial carotid arterial system are presented. Three of the methods were the flow dependent whilst the fourth was an ultrasonic imaging system. A consecutive series of 67 patients, (134 carotid arteries), having carotid angiography were investigated by means of carotid phonoangiography (CPA), oculoplethysmography (OPG), supra orbital Doppler (SOD) and B mode ultrasound scanning. The sensitivity of the B mode ultrasound was 81% with the OPG, CPA and Doppler method yielding sensitivities of 51%, 56% and 63% respectively. The specificity of both the OPG 95% and the Doppler 90% wqs high. The combined use of both B Mode ultrasound and OPG or Doppler will provide an improved overall accuracy in the assessment of extra cranial carotid stenosis.

Arterial Occlusive Diseases↗
PubMed1979

Dimensions of Picture Identification Test need associations.

To find a simple and more general structure for need association matrices obtained from Picture Identification Test (PIT) results, PIT need association matrices of eight college student groups were analyzed by INDSCAL, a multidimensional scaling technique. A common three dimensional structure was found. Based on the scale locations of the 22 needs, the dimensions were labeled the Combative, the Personal, and the Competitive dimensions. The INDSCAL model was used as a target for six other comparison groups including male and female English college students, male addicts and controls, and male delinquents and controls. There was enough similarity between the dimensional structure of the need associations of the comparison and target groups to assume that all groups shared the same basic structure of need associations. There were enough differences, however, to suggest that personality characteristics of groups may be related to deviations in the associative structure of their motivation systems. Applications of the techniques to clinical and personality evaluations of groups and individuals were discussed.

Journal Article↗
PubMed1977

Structure of bovine trypsinogen at 1.9 A resolution.

The three-dimensional crystal structure of bovine trypsinogen at approximately pH 7.5 was initially solved at 2.6 A resolution using the multiple isomorphous replacement method. Preliminary refinement cycles of the atomic coordinates trypsinogen have been carried out first to a resolution of 2.1 A, and later to 1.9 A, using constrained difference Fourier refinement; During the process, structure factors Fc and phi c were calculated from the trypsinogen structure and final interpretation was based on an electron-density map computed with terms (2 Fo - Fc) and phases phic at a resolution of 1.9 A. Crystals of trypsinogen grown from ethanol-water mixtures are trigonal with space group P3121, and cell dimension a = 55.17 A and c = 109.25 A. The structure is compared with the bovine diisopropylphosphoryltrypsin structure at approximately pH 7.2, oirginally determined from orthohombic crystals by Stroud et al. (Stroud, R.M., Kay L.M., and Dickerson, R.E. (1971), Cold Spring Harbor Symp. Quant. Biol. 36, 125-140; Stroud, R.M., Kay, L.M., and Dickerson, R.E. (1974), J. Mol. Biol. 83, 185-208), and later refined at 1.5 A resolution by Chambers and Stroud (Chambers, J.L., and Stroud, R.M. (1976), Acta Crystallogr. (in press)). At lower pH, 4.0-5.5 diogen, with cell dimensions a = 55.05 A and c = 109.45 A. This finding was used in the solution of the six trypsinogen heavy-atom derivatives prior to isomorphous phase analysis, and as a further basis of comparison between trypsinogen and the low pH trypsin structure. There are small differences between the two diisopropylphosphoryltrypsin structures. Bovine trypsinogen has a large and accessible cavity at the site where the native enzyme binds specific side chains of a substrate. The conformation and stability of the binding site differ from that found in trypsin at approximately pH 7.5, and from that in the low pH form of diisopropylphosphoryltrypsin. The catalytic site containing Asp-102, His-57, and Ser-195 is similar to that found in trypsin and contains a similar hydrogen-bounded network. The carboxyl group of Asp-194, which is salt bridged to the amino terminal of Ile-16 in native trypsin or other serine proteases, is apparently hydrogen bonded to internal solvent molecules in a loosely organized part of the zymogen structure. The unusually charged N-terminal hexapeptide of trypsinogen, whose removal leads to activation of the zymogen, lies on the outside surface of the molecule. There are significant structural changes which accompany activation in neighboring regions, which include residues 142-152, 215-550, 188A-195. The NH group of Gly-193, normally involved in stabilization of reaction intermediates (Steitz, T.A., Henderson, R., and Blow, D.M. (1969), J. Mol. Biol. 46, 337-348; Henderson, R. (1970), J. Mol. Biol. 54, 341-354; robertus, J.D., Kraut, J., Alden, R.A., and Birkoft, J.J. (1972), Biochemistry 11, 4293-4303) in the enzyme, is moved 1.9 A away from its position in trypsin...

Animals↗
PubMed1977

Need associations and psychopathology.

The 1960 Picture Identification Test (PIT) provides association scores for 210 need dyads derived from 21 Murray needs. Association scores for 16 clinical-control group pairs were analyzed for differences by t test. The clinical groups represented schizophrenic, neurotic, sex disturbance, and behavior disorder categories. Assertive needs produced the largest number od dyads which discriminated (p less than .05) clinical and control groups. Schizophrenic groups had the largest number of differences from normal controls. Schizophrenics tended to under-associate pairs of Assertive needs, as compared to normals, whereas other groups tended to over-associate these needs. Clinical groups in general over-associated 379 need dyads and under-associated 99 dyads (p less than .05). These results suggest that the frustations of maladjusted people, with regard to need association, are most generally related to insuficient conceptual differentiation of needs.

Adult↗
PubMed1975

Need associations of male prisoners: a multi-dimensional assessment of Murray needs.

Previous studies have revealed quantitative differences between delinquents and nondelinquents in the strength of Murray needs. To provide clarification and elaboration of such past findings, need associations derived from the Picture identification Test were analyzed by t test and discriminant analysis for a group of 112 male prisoners and 112 male nonincracerated normals matched with the prisoners for age and education. Greater than chance (.05 level) numbers of association score differences were obtained between the two groups. Differences in need association scores were interpreted in light of past findings. Need association differences were revealed for the Achievement, Affiliation, Sex, and Order needs among others.

Journal Article↗