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Biomedical subjects

M E Johnson

Publications and source records attributed to M E Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1986

Selective detection of rapid motions in spectrin by NMR.

Human erythrocyte spectrin molecules exhibit relatively sharp (30-50 Hz) proton NMR signals in the aliphatic region. A standard solvent presaturation pulse sequence that also partially suppresses the broad envelope from protons with rigid structures in spectrin and selectively enhances the sharp resonances has been used to characterize the behavior of these resonances. The overall resonance pattern strongly resembles that of the denatured spectrin. The observed spectra are also quite similar to the line-broadened spectrum from a mixture of amino acids that corresponds to the composition of the spectrin molecule. These data indicate the existence of regions exhibiting rapid internal motions within the intact spectrin molecule, and suggest that the amino acid composition of the residues giving rise to the sharp resonances is quite similar to that of the full spectrin molecule.

Actins↗
PubMed1986

A case study in pastoral counseling.

When Michael Jones was admitted to the hospital with AIDS, he was quite alone. Always a private person, with few personal friends, he had isolated himself from those around him after his diagnosis. Although Michael had long felt alienated from religion, daily visits from a hospital chaplain proved enjoyable and helpful for him. Their conversations helped Michael to understand the difference between religion and spirituality. He acknowledged his relationship with God and began to realize the connection between relating to God and relating to others. He desired inner healing and the healing of some broken relationships. Through the pastoral visits, Michael not only was given comfort and assurance, but he was helped in his journey toward spiritual reconciliation.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Evaluation of the radial immunodiffusion enzyme assay for the detection of antibodies to pseudorabies virus.

The validity of radial immunodiffusion enzyme assay (RIDEA) as a diagnostic test for antibodies to pseudorabies virus (PRV) in porcine serum was determined. Serum samples from sows and offspring were tested for the presence of antibodies to PRV, using both the RIDEA and the PRV serum-neutralization (SN) test. Overall sensitivity and specificity of the RIDEA done on serums from the sows were 95.7% and 95.2%, respectively. This sensitivity compares with 97.3% sensitivity of the SN test of the same serums. In 658 swine serum samples from routine submissions to the University of Missouri-Columbia Veterinary Diagnostic Laboratory that were tested by the RIDEA, the calculated sensitivity and the specificity were 94.3% and 98.9%. The RIDEA and SN test were equally sensitive (99.0%) to detect antibodies resulting from infection with a field strain of virus. They had reduced sensitivity (RIDEA, 91.7%; SN test, 95.2%) in tests of serums from vaccinated sows. For the detection of passively transferred antibodies in young pigs, sensitivity of the RIDEA was 76.1%, and specificity was 100%. In all instances, RIDEA was 100% sensitive at SN titers of 1:16 or greater. In testing serum samples of swine after field virus infection, sensitivity and specificity of the RIDEA approximated those of the SN test. This reliability, together with its ease of performance, makes the RIDEA an ideal field test in programs to detect PRV-infected herds and in programs designed to free herds of PRV infection.

Animals↗
PubMed1984

Binding of a spin-labeled phenylalanine analog to sickle hemoglobin: EPR and NMR studies.

We have synthesized a spin-label analog of phenylalanine as a competitive inhibitor probe of the sickle hemoglobin aggregation process. Sickle hemoglobin gelation measurements indicate that the spin-label phenylalanine analog is a potent inhibitor of deoxy sickle hemoglobin aggregation. We have also used spin label EPR and high-resolution proton NMR to study the interaction of the phenylalanine analog with hemoglobin, and find that the kinetic off-rate is comparable to, or slower than the hemoglobin rotational rate (i.e., greater than or equal to 10(8) s-1), and that at least one, and perhaps two significant localized interaction region(s) exist within a few angstroms of the beta chain N- and C-termini. Correlation with other known structural information suggests that the observed interaction sites may be relevant to the mechanism for inhibition of sickle hemoglobin aggregation.

Binding Sites↗
PubMed1984

Consequences of nonverbal expression of pain: patient distress and observer concern.

Two studies examined the effects on others of nonverbal expressiveness of pain. Subjects viewed one of three videotapes of a simulated doctor-patient interview, with identical verbal content but different levels of expressiveness, and then completed a rating form. In Study I subjects were 44 senior nursing students. High nonverbal expressiveness yielded significantly higher ratings of patient pain and distress and observer concern. These variables also were inversely related to amount of nursing experience. Expressiveness had no significant effects on psychological support or nursing aids recommended for the patient. In Study II, 88 female undergraduates were categorized as low, medium or high on a measure of their need to nurture others. Irrespective of nurturance, ratings of patient distress, but not pain, were significantly higher in the high expressive condition. Nonverbal expressiveness of pain appears to influence ratings of the patient's affective state (distress) and the observer's affective response (concern).

Emotions↗
PubMed1984

Confirmation of pseudorabies virus infection, using virus recrudescence by dexamethasone treatment and in vitro lymphocyte stimulation.

A corticosteroid treatment regimen, together with peripheral blood lymphocyte transformation and virus isolation, were used as epizootiologic tools to study pigs seropositive to pseudorabies (PR) virus, but of unknown PR viral infection status. After treatment with 160 mg of dexamethasone daily for 5 days, PR virus was isolated from 2 of 3 adult littermate boars that carried antibodies to PR virus. These pigs also transferred infection to a specific-pathogen-free sentinel penmate . After dexamethasone treatment, increased lymphocyte stimulation indices were detected in all PR virus seropositive pigs. Pseudorabies virus was not isolated from a seronegative littermate gilt of the seropositive boars. The gilt also remained PR virus seronegative and negative for lymphocyte transformation. Before dexamethasone treatment, the 3 boars and 1 gilt were seronegative to the PR viral serum neutralization (SN) test at 11 weeks of age. At 13 weeks of age while still SN negative, these pigs were moved to a building and randomly penned with 76 other SN-negative pigs. At 18 weeks of age, all pigs in the building were PR virus seronegative, but at 25 weeks of age, the 3 boars were seropositive and the gilt was seronegative. There were no other pigs in the building that had antibodies to PR virus before the addition or after the removal of these pigs. Seemingly, the 3 boars were infected with PR virus before 13 weeks of age indicating that PR virus infection of swine may occur in the absence of detectable SN antibodies.

Animals↗
PubMed1983

Probable binding region of small hydrophobic molecules on hemoglobin. Spin label-induced nuclear magnetic relaxation.

The interactions of phenylalanine, valine and alanine with hemoglobin have been compared using spin lattice nuclear magnetic relaxation and spin label-enhanced nuclear magnetic relaxation measurements. The results indicate that phenylalanine exhibits weak hydrophobic binding to hemoglobin, and that the binding site is probably located within about 7-13 A of the nitroxide free electron of spin-labeled hemoglobin. This distance is consistent with the binding site being located within a hydrophobic region comprised of the side chains of the beta-chain residues, phenylalanine beta 85, leucine beta 88 and leucine beta 91, and perhaps a segment of the beta heme porphyrin ring.

Alanine↗
PubMed1983

Saturation transfer electron paramagnetic resonance detection of sickle hemoglobin aggregation during deoxygenation.

Spin-label saturation transfer EPR (ST-EPR) methods have been used to study the sickle hemoglobin (HbS) aggregation behaviors induced by slow deoxygenation at a constant temperature of 30 degrees C, and by a rapid temperature increase from 1 degree to 30 degrees C for fully deoxygenated HbS. For slow deoxygenation at 30 degrees C, we find that the effective HbS correlation time exhibits a continuous increase, without any abrupt transitions, suggesting that polymer formation in concentrated HbS at high temperature occurs even at high oxygenation levels. Upon a rapid temperature increase, fully deoxygenated HbS exhibits a short delay time, then an abrupt increase in effective correlation time. These results also indicate that ST-EPR provides a useful method for probing the molecular dynamics of HbS aggregation.

Electron Spin Resonance Spectroscopy↗
PubMed1983

The influence of verapamil on calcium transport and uptake in segments of rat intestine.

The effects of verapamil on calcium transport and uptake in duodenal and jejunal segments of intestine in young male rats were determined using the everted gut-sac technique. Verapamil added to both the mucosal and serosal surface of duodenal segments decreased calcium transport and tissue uptake in a dose-related fashion over a concentration range of 1-2 mM. In jejunal segments verapamil (1 mM) added to both the mucosal and serosal surface reduced calcium transport but did not alter tissue uptake. Similarly, verapamil (1 mM) added to either the mucosal or serosal surface alone in duodenal segments reduced transport but did not depress tissue uptake. The results of this study indicate that verapamil alters calcium translocation in intestinal tissue in a fashion which is similar to that reported in other biological tissue.

Animals↗
PubMed1982

Models for slow anisotropic rotational diffusion in saturation transfer electron paramagnetic resonance at 9 and 35 GHz.

Model systems of cholestane and 5-doxylstearic acid analogue spin probes in lipid bilayer dispersions of dipalmitoylphosphatidylcholine and cholesterol (9:1 w/w) are used to analyze saturation transfer electron paramagnetic resonance spectral behavior for slow rotational diffusion in an anisotropic medium. Measurements are made at both 9 and 35 GHz to provide enhanced spectral resolution for different types of motion. Parameter correlation plots of spectral parameters from different regions of the saturation transfer spectra appear to be potentially useful in characterizing different types of motion. Anisotropic rotational diffusion about a symmetry axis coincident with the nitroxide y principal axis is clearly distinguishable from isotropic rotational diffusion and may be distinguishable from rotational diffusion about the nitroxide z principal axis. Approximate anisotropic rotational diffusion about a symmetry axis coincident with the nitroxide z principal axis is distinguishable from isotropic rotational diffusion under some, but not all, conditions.

Cholestanes↗
PubMed1982

A comparison of resolution-enhancement methods in saturation-transfer EPR. 15N isotopically substituted spin labels and 35 GHz high-frequency operation.

The use of (15)N isotopic substitution and 35 GHz (Q-band) operation as resolution enhancement methods in saturation-transfer electron paramagnetic resonance (ST-EPR) are compared. We find that both methods offer roughly comparable enhancements in ST-EPR resolution. The most powerful approach to resolving complex ST-EPR spectral behavior, however, will probably be the combined use of multiple-frequency X- and Q-band operation with (15)N isotopically substituted spin labels.

Electron Spin Resonance Spectroscopy↗
PubMed1982

Studies on the technique of vitreous fluorophotometry.

We examined the sources of artifacts of vitreous fluorophotometry (VF), a technique used to assess the permeability of the blood-retinal barrier. By performing in vitro measurements in a model eye and in vivo readings in humans, we investigated the influence of various concentrations of fluorescein in the anterior chamber and in the retina on the measurements performed in the vitreous. Upper limits for the artifactual effects are set under clinical conditions, and a way to account for them is proposed. Special attention is given to depth resolution, which was investigated as a function of the region being scanned, the beam width, and the probe size. Further, preliminary results indicate that a procedure to account for light attenuation by the lens is feasible. It appears that reliable quantitative results can be obtained by VF, provided that the artifacts are acknowledged, minimized, and corrected.

Anterior Chamber↗
PubMed1981

Apparent hydrogen bonding by strongly immobilized spin-labels.

The hyperfine separations of nitroxide spin-labels which are tightly bound within hemoglobin exhibit a substantial temperature dependence even when the hemoglobin is immobilized by freezing or precipitation. It is shown that NO.--HX hydrogen bond formation by the spin-label within its binding site is a good explanation for the observed temperature dependence. Comparative studies using different hemoglobin derivatives and two different spin-labels suggest that the HX group may be some element of the protein matrix and that this hydrogen bond may be a factor in the stabilization of the label within its binding site. The hyperfine separation of a fatty acid spin probe incorporated into aqueous bilayer dispersons of dipalmitoylphosphatidylcholine also exhibits a temperature dependence at low temperature which is qualitatively similar to that of the spin-labeled hemoglobin systems. Saturation transfer electron paramagnetic resonance measurements indicate that label motion is not the source of this temperature dependence. A hydrogen-bond equilibrium between water molecules and the nitroxide NO. group appears to be a plausible source of the temperature-dependent hyperfine separation in the lipid bilayer system. Small amplitude torsional oscillation or librational motion by the nitroxide may also produce additional changes in the hyperfine separation which are difficult to distinguish from hydrogen-bonding effects under some circumstances. The apparent hydrogen-bond equilibrium exhibits a strong thermal and environmental dependence which may be of importance in a number of biophysical spin-label measurements.

Electron Spin Resonance Spectroscopy↗