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Biomedical subjects

R M Johnson

Publications and source records attributed to R M Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1984

The perceived severity of tinnitus. Some observations concerning a large population of tinnitus clinic patients.

Detailed information about tinnitus was obtained from over 1800 patients attending a tinnitus clinic. Patients rated their tinnitus severity on a scale from 1 to 10 and also provided information concerning the quality, duration, localization, and other attributes of their tinnitus. In addition to standard audiometric tests, patients received tests for tinnitus pitch, loudness, maskability, and residual inhibition, and provided a brief medical history. The severity ratings of over 90% were at or above the scale value of 5. There was no correlation between rated severity and the loudness of tinnitus (obtained by a loudness balance procedure using external sounds matching the tinnitus pitch), thus confirming earlier observations. The severity also was not related to the type, quality, or pitch of tinnitus sound heard. However, severity ratings were highly correlated with incidence of sleep disturbance. Additional observations concerning relationships between perceived severity and other patient characteristics are discussed.

Acoustic Impedance Tests↗
PubMed1983

The phosphorylase kinase activity of hearts from phosphorylase kinase-deficient mice.

In an assay measuring radioactive incorporation from gamma--P32P]ATP into phosphorylase b, cardiac muscle extracts from mice with the phosphorylase kinase deficiency mutation showed significant, calcium-dependent phosphorylase kinase activity that was 10 to 15% of that of Swiss mice, the control strain. Isoproterenol stimulated significant phosphorylase a accumulation in both isolated atria and right ventricular strips of phosphorylase kinase-deficient mice, and the drug-stimulated increases in phosphorylase a activity the the contractile responses of right ventricular strips were similar in Swiss and phosphorylase kinase/deficient mice.

Animals↗
PubMed1983

[Effects of 3 varieties of antisickling substances measured by ektacytometry as a function of oxygen pressure].

The ektacytometer measures with precision the deformability of erythrocytes during a continuous change in oxygen tension. Automation of the instrument renders easily feasible the evaluation of proposed antisickling compounds. Drugs representative of the three modes of action presently recognized have been selected: those which increase oxygen affinity (potassium cyanate); those which inhibit hemoglobin polymerization (butylurea); membrane-active compounds. An anionic phenothiazine (metiazinic acid) had an interesting activity on deformability.

Antisickling Agents↗
PubMed1983

A phenotypically normal revertant of an adenosine deaminase-deficient lymphoblast cell line.

Two lymphoblast lines from a patient with partial adenosine deaminase deficiency have been obtained. The patient has a T cell deficiency, with normal B cell function, and has been successfully treated by multiple partial exchange transfusions with normal erythrocytes. The patient's lymphocytes have about 8% of normal adenosine deaminase activity. The derived lymphoblast line that initially had low adenosine deaminase activity has undergone spontaneous reversion to normal enzyme activity. The HL-A types remain the same as the patient's. Both cell lines have the same HL-A types, and eight isoenzymes are identical. In addition, the isoenzymes of a fibroblast line derived earlier, GM-2445, are identical with those in our lymphoblast lines. The following characteristics of the enzyme in the cell lines are normal: Km, Vmax, inhibitor sensitivity, heat sensitivity, and m.w. This suggests, but does not prove, that the low adenosine deaminase activity in this patient is caused by underproduction of a normal enzyme, and the observed reversion to normal activity in one line is a correction of this regulation defect.

Adenosine Deaminase↗
PubMed1982

Calcium and ionophore A23187 induce the sickle cell membrane phosphorylation pattern in normal erythrocytes.

Pre-treatment of normal erythrocytes with micromolar Ca2+ and ionophore A23187 induces abnormal phosphorylation of membrane polypeptides, as determined by labeling with exogenous 32Pi. The Ca2+ -induced effects, which include increased incorporation of 32P into acid-stable linkages and increased labeling in the Band 3 and 4.5-4.9 regions of SDS gels, are similar to those seen in untreated sickle erythrocytes. Part of the abnormal phosphorylation of sickle cells may be caused by their elevated intracellular Ca2+ levels.

Adenosine Triphosphate↗
PubMed1982

Proteolytic analysis of the topological arrangement of red cell phosphoproteins.

The topology of human erythrocyte membrane phosphoproteins was determined by using protease digestion and selective solubilization. The distribution of 32P among the membrane polypeptides in intact cells differs from the pattern found in isolated ghosts. The following membrane skeleton polypeptides, the nomenclature of Steck [Steck, T.L. (1972a) J. Mol. Biol. 66, 295-305] being used, were phosphorylated: 2, 2.1, 4.1, 4.5b, and 4.9, together with two polypeptides at 105000 and 110000 daltons that are heavily phosphorylated. Among integral proteins, band 3 and glycophorins A and B are phosphorylated. Glycophorin C appears to have little turnover of phosphate. Autoradiograms of trypsin-treated membranes permitted identification of the transmembrane proteolytic fragment of glycophorin A as a dimer of 38000 daltons. The band 5 region contained two phosphoproteins, the peripheral protein 4.9 (48 kdaltons) and PAS-2. Similarly, band 7 resolved into an integral phosphoprotein and a nonphosphorylated protein associated with the membrane skeleton.

Electrophoresis, Polyacrylamide Gel↗
PubMed1982

Interaction of the hnRNA of amphibian oocytes with fibril-forming proteins.

A ribonucleoprotein fraction that contains most of the rapidly labelled hnRNA has been isolated from gently ruptured oocytes of Triturus cristatus. This fraction consists of large aggregates of ribonucleoprotein and has a high (30:1) ratio of protein to RNA. The labelled RNA is contained in ribonucleoprotein particles that have a density of 1.27 g/cm3 in Cs2SO4 gradients (1.39 g/cm3 after formaldehyde fixation in CSCl gradients). Evidence is presented that the particles are associated in vivo with a fibrillar protein network. When the ribonucleoprotein aggregates are treated with ribonuclease, high salt concentration and nonionic detergent, a fibrillar protein residue is produced which contains many species of protein but a few that have electrophoretic characteristics that are identical to major ribonucleoprotein particle proteins. Isolated labelled hnRNA has been shown to bind specifically polypeptides of molecular weight 60 000 and 54 000 that are found in both particle and fibril preparations. In binding assays in vitro, these polypeptides are found to interact with mRNA to a lesser extent and not with rRNA. The isolated 60 000-Mr and 54 000-Mr proteins have the dual ability of forming ribonucleoprotein 'particles' with hnRNA and of polymerizing to generate 10-nm fibrillar structures in the absence of RNA. The possible cellular functions of these proteins are discussed.

Animals↗
PubMed1982

The professional support group: a model for psychiatric clinical nurse specialists.

In addition to the frustrations experienced by any CNS, the psychiatric CNS in the general hospital setting experiences additional pressures which are inherent to his/her role. The major additional pressure is the great demand for the provision of support to patients, families, and staff. This necessitates a source of support for the psychiatric CNS. In response to this need, a group of psychiatric CNSs from general hospital settings developed and implemented a model for a professional support group. The formation and developmental process of this professional support group was consistent with literature descriptions of both small group and professional support group development. Informal evaluation demonstrated that this professional support group is achieving its purposes, and continues to function as an ongoing group.

Group Processes↗
PubMed1982

Temperature dependence of the stability of tobramycin mixed with penicillins in human serum.

The stability of tobramycin in pooled human serum when combined with ampicillin, carbenicillin disodium, or penicillin G potassium after storage at 0, 23, or 37 degrees C was evaluated. Samples of pooled human serum containing tobramycin sulfate 8 micrograms/ml alone or combined with ampicillin, carbenicillin disodium, or penicillin G potassium 200 micrograms/ml were prepared and stored at 0, 23, and 37 degrees C. Single samples were removed periodically for 48 hours and frozen until assayed. Tobramycin concentration was measured by a radioenzymatic assay. A tobramycin degradation rate constant was calculated for the tobramycin control and each tobramycin-penicillin combination at each temperature; from this, the time for the tobramycin concentration to decline to 90% of the initial concentration (t90) was estimated. Stability of the penicillins was not assessed. Tobramycin degradation approximated a log-linear process in all samples for the 48-hour period. The tobramycin control sample was more stable than any of the tobramycin-penicillin solutions at each temperature. At 0 degrees C, tobramycin mixed with ampicillin was the least stable of all mixtures; at 23 and 37 degrees C, tobramycin mixed with carbenicillin was the least stable. Storing tobramycin and carbenicillin samples on ice (0 degrees C) prolonged t90 from 10 hours (23 degrees C) and 12 hours (37 degrees C) to 36 hours. The t90 values for tobramycin when mixed with ampicillin were 19, 16.5, and 20 hours at 0, 23, and 37 degrees C, respectively. Mixed with penicillin G, tobramycin t90 values at 0, 23, and 37 degrees C were 48, 44, and 16 hours, respectively. More than a 10% loss of tobramycin potency occurred in some tobramycin-penicillin solutions under the conditions of this study. Because this loss would affect the accuracy of tobramycin pharmacokinetic calculations, the authors suggested guidelines for handling tobramycin serum samples.

Anti-Bacterial Agents↗
PubMed1981

Interference of cephalosporins and cefoxitin with serum creatinine determination.

The interference of cephalosporins and cefoxitin with serum creatinine (Crs) determinations was studied. Various concentrations of cephapirin, cefazolin, cefamandole, cephalothin, and cefoxitin were added to serum samples. Apparent creatinine concentrations were measured with the Beckman ASTRA, Technicon SMAC, and DuPont ACA analyzers. Pharmacokinetic models were used to predict serum drug concentrations as a function of time and renal function and to estimate the magnitude of interference in varying situations. The magnitude of the interference was proportional to the concentration of the drug in the sample and additive with baseline concentrations of creatinine in the serum. Negligible interferences occurred with cephapirin, cefazolin, and cefamandole. False elevations (i.e., Crs greater than or equal to 0.2 mg/dl over baseline) were detected with clinically achievable serum concentrations of cephalothin and cefoxitin. For patients with normal renal function (creatinine clearance greater than 50 ml/min), this drug interaction would be negligible from 20 minutes to two hours after drug administration, depending on the assay used. For patients with renal failure, measurable interferences could persist for up to 16 hours after dose administration. The critical concentrations were different for the three procedures and both antibiotics. The degree of interference varies with the assay procedure used, the serum concentration of the drug, and the patient's renal function. To minimize drug interference, blood samples for serum creatinine determinations should be drawn at the time of minimum drug concentration.

Cefoxitin↗
PubMed1980

Membrane protein phosphorylation in intact normal and sickle cell erythrocytes.

Membrane protein phosphorylation was measured in intact normal and sickle erythrocytes, by determining the incorporation of 32Pi. The general pattern of radiolabeling is similar for normal and sickle cells, but sickle erythrocytes incorporate approximately twice as much 32P as normal cells, and the detailed distribution of label is altered. Sickle cells incorporate less of their 32P into spectrin band 2 and more into band 4.5 than do normal cells. Although irreversibly sickled cells do not incorporate more 32P than the general sickle cell population, the distribution of label among their membrane polypeptides is more abnormal. These differences between normal and sickle cells are seen throughout an 18-h incubation. All polypeptides become labeled at approximately the same rat. The differences in phosphorylation between sickle and normal cells cannot be attributed to relative cell age, ATP levels, or the rate of 32P labeling of the ATP pool. It appears that altered membrane phosphorylation is an intrinsic characteristic of sickle cell anemia.

Adenosine Triphosphate↗