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Biomedical subjects

K Johnson

Publications and source records attributed to K Johnson.

At least 487 records · Page 27Linked to original sources
PubMed1983

Functional health status levels of primary care patients.

A cross-sectional study was conducted on functional status of adults visiting primary care practices. Limitations in physical and mental function were assessed independently in 28 practices by patients (N = 1,227) and physicians (N = 47) using a simple global index of disability. Results indicated 12% of patients rated their physical limitations as major and 8% rated major emotional limitations during the past month. Comparable assessments by physicians were 5% and 4%, respectively. Differences between patients and physicians were statistically significant and are demonstrated to be clinically relevant. Patients' functional limitations were associated with increased utilization of ambulatory care, older age, lower level of education, unemployment, and a primary diagnosis of a chronic condition. We conclude that functional status can be routinely recorded in medical practice to help describe severity, predict utilization, and improve the physician-patient relationship.

Activities of Daily Living↗
PubMed1983

Use of multivariate analysis to improve the accuracy of radionuclide angiography with stress in detecting coronary artery disease in men.

A multivariate analysis (MVA) system was derived retrospectively from a population of 76 males with coronary artery disease and 18 control subjects. Posterior probabilities were then derived from such a system prospectively in a new male population of 11 subjects with normal coronary arteries and hemodynamics and 63 patients with coronary artery disease. The sensitivity was 84% compared to that for change in ejection fraction (delta EF) greater than or equal to 5 criterion of 71% (p less than 0.01), the specificity was 91% compared to 73% for the delta EF greater than or equal to 5 criterion (p greater than 0.05), and the correct classification rate was 85% compared to 72% for the delta EF greater than or equal to 5 criterion (p less than 0.01). The significant variables were: change in EF with exercise, percent maximal heart rate, change in end-diastolic volume (delta EDV) with exercise, change in R wave, and exercise duration. Application of the multivariate approach to radionuclide imaging with stress, including both exercise and nuclear parameters, significantly improved the diagnostic accuracy of the test and allowed for a probability statement concerning the likelihood of disease.

Adult↗
PubMed1983

Influence of premicellar and micellar association on the reactivity of methylprednisolone 21-hemiesters in aqueous solution.

Self-association of drug molecules at formulation concentrations can have a major impact on formulation properties. In this study a homologous series of methylprednisolone 21-hemiesters were found to undergo self-association in aqueous solution. The effect of aggregate formation on the solution degradation of these compounds was examined. To determine the nature and extent of association of these steroidal esters, partition coefficients between butyronitrile and aqueous buffer (pH 8.5) were measured as a function of ester concentration. The partitioning data were found to be consistent with dimer formation at low concentration followed by true micelle formation at higher concentration. Chain length increases favored micelle formation, but appeared to have little effect on dimerization. The first-order rate constants for ester hydrolysis and 21 leads to 17 acyl migration in aqueous buffer (pH 8.5) were also found to be dependent on ester concentration. The kinetic data are consistent with a model which assumes stabilization by both dimer and micelle formation, the limiting factor at high concentration being the reactivity of the ester in the micelles. The degree of stabilization due to self-association was found to increase with chain length.

Colloids↗
PubMed1983

Arrangement of MP26 in lens junctional membranes: analysis with proteases and antibodies.

The major membrane protein of the bovine lens fiber cell is a 26-kilodalton (kD) protein (MP26), which appears to be a component of the extensive junctional specializations found in these cells. To examine the arrangement of MP26 within the junctional membranes, various proteases were incubated with fiber cell membranes that had been isolated with or without urea and/or detergents. These membranes were analyzed with electron microscopy and SDS-PAGE to determine whether the junctional specializations or the proteins were altered by proteolysis. Microscopy revealed no obvious structural changes. Electrophoresis showed that chymotrypsin, papain, and trypsin degraded MP26 to 21-22 kD species. A variety of protease treatments, including overnight digestions, failed to generate additional proteolysis. Regions on MP26 which were sensitive to these three proteases overlapped. Smaller peptides were cleaved from MP26 with V8 protease and carboxypeptidases A and B. Protein domains cleaved by these proteases also overlapped with regions sensitive to chymotrypsin, papain, and trypsin. Specific inhibition of the carboxypeptidases suggested that cleavage obtained with these preparations was not likely due to contaminating endoproteases. Since antibodies are not thought to readily penetrate the 2-3 nm extracellular gap in the fiber cell junctions, antibodies to MP26 were used to analyze the location of the protease-sensitive domains. Antisera were applied to control (26 kD) and proteolyzed (22 kD) membranes, with binding being evaluated by means of ELISA reactions on intact membranes. Antibody labeling was also done following SDS-PAGE and transfer to derivatized paper. Both assays showed a significant decrease in binding following proteolysis, with the 22 kD product showing no reaction with the anti-MP26 sera. These investigations suggest that MP26 is arranged with approximately four-fifths of the primary sequence "protected" by the lipid bilayer and the narrow extracellular gap. One-fifth of the molecule, including the C-terminus, appears to be exposed on the cytoplasmic side of the membrane.

Animals↗
PubMed1983

Purification of human milk bile salt-activated lipase.

A modified procedure for a large-scale purification of human milk bile salt-activated lipase (BAL) has been devised. An initial step used cholate-Sepharose affinity chromatography for the partial purification of the enzyme followed by the removal of cholate with a Bio-Rex 5 anion-exchange resin. The final step of purification used heparin-Sepharose affinity chromatography. This procedure of purification resulted in a 50-fold purification of BAL from human skim milk and a specific activity of 50-60 mumol/min/mg with p-nitrophenyl acetate as substrate. From 450 ml of human skim milk, approximately 30 mg of purified enzyme could be obtained. The N-terminal-region amino acid sequence of the purified BAL was determined as follows: Ala-Lys-Leu-Gly-Ala-Val-Tyr-Thr-Glu-Gly-Lys-Phe-Val-Glu-Gly-Val-Asn-Lys-Lys-Leu-Gly-Leu-. Despite the finding that BAL interacts with heparin-Sepharose, soluble heparin had no effect on BAL activity. The possible physiological role of BAL-heparin interaction has also been discussed.

Amino Acid Sequence↗