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Biomedical subjects

D L Nelson

Publications and source records attributed to D L Nelson.

556 records · Page 31Linked to original sources
PubMedDate not supplied

The 44-kDa regulatory subunit of the Paramecium cAMP-dependent protein kinase lacks a dimerization domain and may have a unique autophosphorylation site sequence.

The 44-kDa regulatory subunit (R44) of one form of cAMP-dependent protein kinase of Paramecium was purified, and two partial internal amino acid sequences from it were used to clone the corresponding cDNA. This R44 cDNA clone was 1022-bp long, including 978 bp of coding sequence and 7 bp and 37 bp of 5' and 3' untranslated sequences, respectively. A 1.1-kb mRNA was labeled on a Northern blot. The deduced R44 amino acid sequence had 31%-38% positional identity to the sequences of other cloned cAMP-dependent protein kinase regulatory subunits. R44 sequence showed equal sequence similarity to mammalian types I and II regulatory subunits. The N-terminal sequence encoding the regulatory subunit dimerization domain found in most regulatory subunits is not present in the R44 clone, confirming the lack of regulatory subunit dimer formation previously reported for the Paramecium cAMP-dependent protein kinase. The putative autophosphorylation site of R44 contains the amino acid sequence TRTS, distinct from the consensus sequence RRXS, where X is any residue, found in other autophosphorylated cAMP-dependent protein kinase regulatory subunits and many cAMP-dependent protein kinase substrates.

Amino Acid Sequence↗
PubMedDate not supplied

Paramecium has two regulatory subunits of cyclic AMP-dependent protein kinase, one unique to cilia.

The subunit composition and intracellular location of the two forms of cAMP-dependent protein kinase of Paramecium cilia were determined using antibodies against the 40-kDa catalytic (C) and 44-kDa regulatory (R44) subunits of the 70-kDa cAMP-dependent protein kinase purified from deciliated cell bodies. Both C and R44 were present in soluble and particulate fractions of cilia and deciliated cells. Crude cilia and a soluble ciliary extract contained a 48-kDa protein (R48) weakly recognized by one of several monoclonal antibodies against R44, but not recognized by an anti-R44 polyclonal serum. Gel-filtration chromatography of a soluble ciliary extract resolved a 220-kDa form containing C and R48 and a 70-kDa form containing C and R44. In the large enzyme, R48 was the only protein to be autophosphorylated under conditions that allow autophosphorylation of R44. The subunits of the large enzyme subsequently were purified to homogeneity by cAMP-agarose chromatography. Both C and R48 were retained by the column and eluted with I M NaCl; no other proteins were purified in this step. These results confirm that the ciliary cAMP-dependent protein kinases have indistinguishable C subunits, but different R subunits. The small ciliary enzyme, like the cell-body enzyme, contains R44, whereas R48 is the R subunit of the large enzyme.

Animals↗
PubMedDate not supplied

A nucleoside diphosphate kinase from Paramecium tetraurelia with protein kinase activity.

Nucleoside diphosphate kinase (NDP kinase) from Paramecium was purified to homogeneity. The native enzyme was 80 kDa (by gel filtration), with subunits of 18 and 20 kDa. Near the amino terminus, 15 of 20 residues were identical with those in human NDP kinase, and 17 of 20 with the awd gene product from Drosophila. NDP kinase bound alpha-labeled ATP and GTP, and a photoreactive GTP analog labeled both subunits. Purified NDP kinase underwent autophosphorylation on a histidine and a serine residue using either ATP or GTP as a substrate. The enzyme also catalyzed acid-stable phosphorylation of casein and phosvitin. This protein kinase activity is distinct from the histidine phosphorylation that is part of the NDP kinase catalytic cycle. Antiserum against the purified protein from Paramecium cross-reacted with 16- to 20-kDa proteins in most species tested, and with a larger protein (44 kDa) in Paramecium, Xenopus, and two human lines. The multiple forms (20 and 44 kDa) of the NDP kinase in Paramecium and its protein kinase activity, suggest that the protein is more than a housekeeping enzyme; it may have regulatory roles such as those of the NDP kinase-like awd protein of Drosophila and Nm23 protein of humans.

Adenosine Triphosphate↗
PubMedDate not supplied

Effect of SERCA pump inhibitors on chemoresponses in Paramecium.

Inhibitors of SERCA (sarcoplasmic/endoplasmic reticulum Ca(2+)-dependent ATPase) calcium pumps were used to investigate the involvement of internal Ca2+ stores in the GTP response in Paramecium. External application of these inhibitors was found to dramatically alter the typical behavioral and electrophysiological responses of Paramecium to extracellular chemical stimulation. In particular, 2,5-di-tert-butylhydroquinone (BHQ) strongly inhibited the backward swimming response of paramecia to externally applied GTP, though it did not inhibit the associated whirling response. BHQ also prolonged the normally brief electro-physiological response of these cells to GTP. BHQ completely blocked the behavioral and electrophysiological responses of Paramecium to extracellular Ba2+, but had no measurable effect on the behavioral or electrophysiological responses of these cells to another depolarizing stimulus, elevated external K+ concentration. These results suggest the involvement of nonciliary Ca2+ ions in the GTP and Ba2+ responses.

Animals↗
PubMedDate not supplied

Pharmacokinetic aspects of tert-butylaminoethyl disulfide, an experimental drug against schistosomiasis in mice.

A preliminary study of the pharmacokinetic parameters of t-Butylaminoethyl disulfide was performed after administration of two different single doses (35 and 300 mg/kg) of either the cold or labelled drug. Plasma or blood samples were treated with dithiothreitol, perchloric acid, and, after filtration, submitted to further purification with anionic resin. In the final step, the drug was retained on a cationic resin column, eluted with NaCl 1M and detected according to the method of Ellman (1958). Alternatively, radioactive drug was detected by liquid scintillation counting. The results corresponding to the smaller dose of total drug suggested a pharmacokinetic behavior related to a one open compartment model with the following parameters: area under the intravenous curve (AUCi.v.): 671 +/- 14; AUCoral: 150 +/- 40 micrograms.min.ml-1; elimination rate constant: 0.071 min-1; biological half life: 9.8 min; distribution volume: 0.74 ml/g. For the higher dose, the results seemed to obey a more complex undetermined model. Combining the results, the occurrence of a dose-dependent pharmacokinetic behavior is suggested, the drug being rapidly absorbed and rapidly eliminated; the elimination process being related mainly to metabolization. The drug seems to be more toxic when administered I.V. because by this route it escapes first pass metabolism, while being quickly distributed to tissues. The maximum tolerated blood level seems to be around 16 micrograms/ml.

Animals↗
PubMedDate not supplied

Pharmacokinetic profile of tert-butylaminoethanethiol.

A preliminary study of the pharmacokinetic parameters of t-Butylaminoethanethiol (TBAESH) was performed after administration of a single dose (35 mg/kg) either orally or intravenously. Plasma or blood samples were treated with dithiothreitol, perchloric acid and, after filtration, submitted to further purification with anionic resin. In the final step the drug was retained on a cationic resin column, eluted with NaCl lM and detected according to the method of Ellman (1958). The results suggested a pharmacokinetic behavior related to a one open compartment model with the following values for the total drug: area under the intravenous curve (AUCi.v.): 443 +/- 24.0; AUCoral: 85.5 +/- 14.5 micrograms min.ml-1; elimination rate constant: 0.069 +/- 0.0055 min-1, biological half-life: 10.0 +/- 0.80 min; distribution volume 1.15 +/- 0.15 ml/g; biodisponibility: 0.19 +/- 0.02. From a pharmacokinetic standpoint, TBAESH seems to have no advantage over the analogous disulfide compound.

Animals↗
PubMedDate not supplied

Schistosomicidal activity of alkylaminooctanethiosulfuric acids.

The schistosomicidal activity of a new series of alkylaminooctanethiosulfuric acids was studied in white Swiss mice infected with the L.E. strain of Schistosoma mansoni (Belo Horizonte, MG, Brazil). In a preliminary screening of six compounds, two derivatives - 2-[(1-methylpropyl)amino]-1-octanethiosulfuric acid and 2-[(1-methylethyl)-amino]-1-octanethiosulfuric acid - given orally in doses of 300 mg/kg/day for five consecutive days, caused interruption of the oviposition and the hepatic shift of more than 90% of the worms. Both compounds caused a significant reduction in worm burden and, interestingly, the female schistosomes were more susceptible. With the therapeutic schedule of two doses of 800 mg/kg over a 20 day interval, the death of almost all the females and about 50% of the males was observed. Female worms recovered from treated mice showed scattered vitteline glands. Results of in vitro experiments against different developmental stages of the parasite revealed the induction of paralysis and damage to the tegument membrane. The drugs presented no toxic effects on the animals.

Animals↗
PubMedDate not supplied

Therapeutic occupation: a definition.

This article builds on prior work and defines terms basic to the profession of occupational therapy. The prior work defined occupation as the relationship between occupational form and occupational performance and defined related terms, such as meaning, purpose, developmental structure, impact, and adaptation. This article shows how these terms relate to therapeutic occupation, a special type of occupation. Therapeutic occupation through occupational synthesis is the core of occupational therapy. Occupational synthesis is the design of the occupational form by the occupational therapist in collaboration with the recipient of services to advance therapeutic evaluation or achieve a therapeutic goal. Therapeutic occupation, then, is meaningful, purposeful occupational performance leading to assessment, adaptation, and compensation, all in the context of occupational synthesis. Finally, the idea of therapeutic occupation through occupational synthesis is related to frames of reference and models of practice in occupational therapy today.

Adaptation, Psychological↗
PubMedDate not supplied

The effects of hands-on occupation versus demonstration on children's recall memory.

OBJECTIVE: Hands-on learning has been an important aspect of the profession of occupational therapy since its founding. The purpose of this study was to determine whether children engaged in hands-on learning would be able to recall more of the steps and more of the correct order of the steps of an occupation than children engaged in a demonstration teaching method. METHOD: After being randomly assigned, 73 healthy third-graders (42 girls and 31 boys) either participated in making a model of a volcano or observed the making of a model of a volcano. Following task completion, both groups were asked to recall and state as many of the 41 syntactical units as possible in their proper order. The children's responses were audiotaped and scored in a blind fashion according to predetermined criteria. Interrater reliability was excellent. RESULTS: A t-test revealed a significant difference between conditions in terms of free recall scores, with children in the hands-on condition having a greater recall score, t (71) = 2.63, p < .005. The effect size d equaled .62. A MannWhitney U Test revealed no significant difference between conditions in terms of remembering the steps in proper order (the lack of a significant difference may have been due to a problem of measurement). CONCLUSION: The results of this study demonstrated that participants were able to recall more information when engaged in a hands-on teaching method as compared with a demonstration method. It is suggested that the learning advantages of hands-on occupation are related to the enhanced sensory/perceptual experiences and the feelings of success that are characteristic of hands-on learning, as opposed to passive forms of learning.

Child↗
PubMedDate not supplied

Health administration can be stressful ... but not necessarily distressful.

Stress is the natural response to personal and organizational demands. It is manifested in elevated heart rate, respiration, blood pressure, and adrenaline in the blood. It is not something over which we have conscious control. Stress has both beneficial and destructive consequences. It is the destructive consequences with which we are the most familiar. These include tension, cardiovascular diseases, peptic ulcers, sexual dysfunctions, and depression. These are the undesirable consequences of stress; they constitute distress. They are not an inevitable consequence of stressful events. The purpose of this article is to discuss the unique demands of hospital administration and several methods of preventive stress management. There are no universal ways to prevent or treat distress. Preventive stress management and treatment aimed at increasing healthy stress and preventing distress must be established by each particular hospital or administrator interested in creating a healthy work environment.

Decision Making↗
PubMedDate not supplied

Elevated soluble interleukin-2 receptor levels early after heart transplantation and long-term survival and development of coronary arteriopathy.

Rejection dynamics after heart transplantation might be characterized by soluble interleukin-2 receptor levels. To determine whether elevated levels early (measured by enzyme-linked immunosorbent assay once weekly the first 3 weeks at time of heart biopsy) after transplantation predict mortality and development of coronary disease, the means of these three determinations and the endomyocardial biopsy scores (McAllister scale 0-10) were compared for survivors and nonsurvivors and patients who had coronary arteriopathy develop and those who did not. Fifty-five patients alive 30 days after heart transplantation were prospectively followed up. Overall, 47 patients were male (85%), and the median age was 51 years. Mean +/- SD follow-up was 26 +/- 15 months (range, 1 to 54 months). There were 38 survivors (69%), and coronary arteriopathy developed in 15 patients (27%). Whereas mean +/- SD heart biopsy scores for the early weeks were similar between survivors and nonsurvivors (3.6 +/- 1.4 vs 4.4 +/- 1.6; p greater than 0.05), the difference in soluble interleukin-2 receptor levels was significant (703 +/- 362 U/ml vs 1793 +/- 1070 U/ml; p less than 0.001). A mean level less than 1000 U/ml in any given patient predicted long-term survival with a 76% sensitivity, 79% specificity, and 88% negative predictive value. Mean receptor levels for those patients in whom coronary arteriopathy did not develop were 880 +/- 846 U/ml and for those with this difficulty, 1410 +/- 590 U/ml (p = 0.001). Late morbidity and mortality after heart transplantation seem predicted by early elevation of plasma soluble interleukin-2 receptor levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗
PubMedDate not supplied

Determination of menthol in honey by gas chromatography.

A gas chromatographic method was developed for the determination of L-menthol in honey at levels as low as 0.1 ppm. The method includes steam distillation and hexane extraction with an internal standard (2,6-dimethylphenol). Beehives treated to control Acarapis woodi over 21 days with 30-60 g L-menthol contained L-menthol residues in honey and beeswax. L-Menthol was found only in treated portions of the hive and not later transferred to added honey supers. The highest levels of residues in honey (18 ppm) and beeswax (2790 ppm) were found when pure L-menthol was adsorbed into foam strips placed on top of the hives. L-Menthol residues in honey were not reduced by storage in open containers at room temperature for up to 55 days. Untrained panelists could not detect L-menthol in honey until the levels approached 36 ppm.

Chromatography, Gas↗