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Biomedical subjects

D L Johnson

Publications and source records attributed to D L Johnson.

At least 289 records · Page 16Linked to original sources
PubMed1983

The investigation of radiopharmaceutical components by fast atom bombardment mass spectrometry: the identification of Tc-HIDA and the epimers of Tc-CO2DADS.

The nature of two technetium-labeled radiopharmaceutical components has been established by means of fast-atom-bombardment mass spectrometry (FABMS) in combination with carrier-added (CA) and no-carrier-added (NCA) reversed-phase high-pressure liquid chromatography (HPLC). Negative-ion FABMS was used to determine that the epimers of Tc-CO2DADS are the oxo[N,N'-(1-carboxyethylene)-bis-(2-mercaptoacetimido)]technetate(V) ions; positive-ion FABMS showed that Tc-HIDA is bis[N-(2,6-dimethylphenyl-carbamoylmethyliminodiaceto]technetate(III).

Chromatography, High Pressure Liquid↗
PubMed1982

The Houston Parent--Child Development Center and the primary prevention of behavior problems in young children.

This study reports the effectiveness of the Houston Parent--Child Development Center (PCDC) program for preventing behavior problems in young children. The PCDC is a 2-year, intensive parent-child education program for children 1-3 and their parents. Low-income Mexican American families were randomly assigned to program or control groups. A follow-up of the program 1-4 years later, when children averaged 5 1/2 years of age, was carried out with 128 mothers who were interviewed about behavior problems of their children. A MANCOVA showed main effects for group and sex as well as a group by sex interaction. The principle result was that control boys were more destructive, overactive, negative attention-seeking, and less emotionally sensitive than program boys and girls and control girls. The program is seen as an effective primary prevention approach to behavior problems. Prior evaluations have shown that it also enhances children's cognitive skills. Other parent--child education programs should be examined as approaches to primary prevention.

Child↗
PubMed1982

Effects of gunfire on hearing level for selected individuals of the Inter-Industry Noise Study.

Using the information available from Inter-Industry Noise Study, the hearing levels of 68 pairs of workers, matched for sex, age, and exposure level, were evaluated. For each pair, one of the participants had indicated exposure to nonoccupational gunfire during the previous year. Differences in mean hearing levels between the male participants exposed to gunfire and those not exposed were clearly apparent and varied between 9 to 16 dB for the frequencies at 3000, 4000, and 6000 Hz. There were no significant differences in female hearing threshold levels. These changes in male hearing are equivalent to the effect of an occupational exposure of 89 dB for 20 years. However the results do not indicate that there are any synergistic effects between gun exposures during a participants recreational time and noise exposure during his working hours.

Adult↗
PubMed1982

Eukaryotic tRNA gene transcription is controlled by signals within and outside the mature coding sequence.

We have identified the region within a eukaryotic tRNA gene required for initiation of transcription. These results were obtained by systematically constructing deletions extending from the 5'- or the 3'-flanking regions into a cloned Drosophila tRNAArg gene using nuclease BAL-31. Two control regions within the coding sequence were identified. The first was essential for transcription and was contained between nucleotides 8 to 25 of the mature tRNA sequence. Genes devoid of the second control region, which was contained between nucleotides 50 to 58 of the mature tRNA sequence, could be transcribed but with reduced efficiency. Thus, the promoter regions within a tRNA gene encode the tRNA sequences of the D-stem and D-loop, the invariant U at position 8, and the semi-invariant GTpsi C sequence. While transcription of Drosophila tRNA genes is controlled by signals within the mature tRNA coding region deletion analysis has revealed an oligonucleotide sequence in the 5'-flanking region of a Drosophila tRNA2Lys gene to be responsible for the poor transcriptional activity of this and of other tRNA genes. The oligonucleotide responsible for transcriptional repression is GGCAGTTTTTG and is located 13 nucleotides upstream from the mature tRNA coding sequence. Since the sequence of the undecanucleotide is well conserved within the 5'-flanking region of Drosophila tRNA2Lys genes an investigation of why the transcription of all these genes is not similarly repressed revealed that the position of this oligonucleotide, relative to the mature coding sequence, influences the extent of transcriptional repression.

Animals↗
PubMed1981

Unusual structures in single-stranded ribonucleic acid: proton nuclear magnetic resonance of AUCCA in deuterium oxide.

Conformational features of the oligoribonucleic acid (oligo-RNA) A1-U2-C3-C4-A5 are explored by proton nuclear magnetic resonance (NMR). The sequence is a molecular cognate of a portion of the T psi C loop and stem regions of yeast tRNAPhe. The molecule forms at least two classes of flexible yet ordered structures. Class I states are similar in spectral properties to the component oligomers, AU, AUC, and AUCC, and are likely to be standard right-helical structures. Class II states are characterized by a 2'-endo pucker at A1 and unusually large shielding of several C3 and U2 protons. Most of these features are consistent with identifying the class II solution structures with the "arch" conformation for the T psi C region determined by X-ray crystallography of yeast tRNAPhe.

Base Sequence↗
PubMed1981

The uses of hypnotherapy with learning disabled children.

Explored the impact of group hypnotic and self-hypnotic training on the academic performance and self-esteem of learning disabled (LD) children. Three hypnotic training sessions and instructions for 6 weeks of daily self-hypnotic practice that contained suggestions for imagery related to improvement in these areas were given to 15 children (12 males and 3 females, ages from 7 to 13), their reading teacher, and both their parents, and their responses were compared to a similar but untreated control group of 18. No overall differences were observed between groups. A multiple regression analysis revealed important predictors of self-esteem improvement for the experimental group. The child's hypnotic susceptibility score and self-hypnotic practice by children and parents were the most relevant. These LD children were at least as hypnotically susceptible as a normative sample. Hypnotherapy is seen as feasible in group administration by persons only moderately trained in hypnosis and of potential benefit to self-esteem improvement in LD children, depending on individual difference factors.

Adolescent↗
PubMed1981

Stoichiometry and composition of an aminoacyl-tRNA synthetase complex from rat liver.

The particulate aminoacyl-tRNA synthetases of rat liver were copurified about 1000-fold with more than 20% yields for individual synthetase activities. Measurements of aminoacylation activities showed that lysyl-, arginyl-, leucyl-, isoleucyl-, and methionyl-tRNA synthetases in the purified complex cosedimented at 18 S. The molecular weight of the synthetase complex is about one million, as estimated by gel filtration. The stoichiometry of the synthetase in the complex was determined by active site titration with aminoacyl adenylates. Results indicate that the 18S synthetase complex contains one subunit of methionyl-tRNA synthetase and two subunits of lysyl-tRNA synthetase. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed that the 18S synthetase complex contains eight major protein bands. Proteins with subunit molecular weights of 104,000, 92,000, 69,000, and 67,000 are present in molar ratios of 1:1:2:2, while proteins with subunit molecular weights of amounts. These results suggest that the particulate aminoacyl-tRNA synthetases exist as a heterotypic multienzyme complex with defined structure.

Amino Acyl-tRNA Synthetases↗
PubMed1981

Effects of beta-adrenergic agents on the murine lymphocyte response to mitogen stimulation.

The presence of beta-adrenergic receptors on murine lymphocytes has recently been demonstrated (8). beta-adrenergic agonists and antagonists have been found to alter the murine lymphocyte's response to either Concanavalin A or Lipopolysaccharide B. The regulation of the response to Concanavalin A or Lipopolysaccharide B by these beta-adrenergic ligands is most effective if the beta-adrenergic ligand is added within one hour of the addition of mitogen and at concentrations greater than 1 x 10(-7) M. The possibility that adrenergic modulation of the lymphocyte response may be beta-receptor mediated is supported by the observation of competition between adrenergic agonists and antagonists.

Adrenergic beta-Agonists↗
PubMed1981

Effect of chronic beta-adrenergic therapy on the human lymphocyte response to concanavalin A.

Lymphocytes isolated from cystic fibrosis patients chronically treated with beta-adrenergic agonists respond significantly differently to epinephrine modulation of mitogen challenge than either cystic fibrosis patients not receiving beta-adrenergic therapy or normal human volunteers. Those patients on chronic beta-adrenergic therapy are insensitive to the modulating effects of 1-epinephrine. This observation is discussed in terms of adrenergic receptor alteration and/or different cystic fibrosis disease states.

Adrenergic beta-Agonists↗
PubMed1980

Purification and characterization of lysyl-tRNA synthetase after dissociation of the particulate aminoacyl-tRNA synthetases from rat liver.

The major aminoacyl-tRNA synthetase complex (the 24 S complex) isolated from rat liver, which contains lysyl-, leucyl-, and arginyl-tRNA synthetase activities, is dissociated into fully active free aminoacyl-tRNA synthetases by column chromatography on diaminooctyl-Sepharose. During the hydrophobic interaction chromatography, more than a quantitative yield of the lysyl-tRNA synthetase activity is obtained. The free lysyl-tRNA synthetase, dissociated from the synthetase complex, is purified about 2,000-fold with a 13% yield by conventional column chromatography. Lysyl-tRNA synthetase is also purified from the 24 S synthetase complex by affinity column chromatography on lysyl-diaminohexyl-Sepharose. Free lysyl-tRNA synthetase as dissociated from the synthetase complex, is evidently a dimeric enzyme with a subunit molecular weight of 66,000 +/- 3,000, as determined by gel electrophoresis, sucrose gradient centrifugation and gel filtration.

Amino Acyl-tRNA Synthetases↗
PubMed1980

Characteristics of adrenergic binding sites associated with murine lymphocytes isolated from spleen.

Beta-adrenergic binding sites have been identified and characterized on murine lymphocytes. The binding sites are of two distinct classes, a high affinity class which has an apparent dissociation constant of about 1 x 10(-9)M and numbers about 500 sites per cell, and a higher capacity binding class that appears to be more characteristic of a non-specific binding site. The binding of a beta-adrenergic radioligand at concentrations about equal to the Kd (dissociation constant) for the high affinity site can be competed for with classical adrenergic ligands, is reversible and does not display cooperative interactions.

Animals↗