Search PubMed⌕ Search

Biomedical subjects

J R Butler

Publications and source records attributed to J R Butler.

At least 37 records · Page 2Linked to original sources
PubMed1994

Chemotactic peptides induce phosphorylation and activation of MEK-1 in human neutrophils.

Extracellular signal-regulated kinase (Erk) (mitogen-activated protein (MAP) kinase) is rapidly activated when neutrophils are stimulated. Several isoforms of MAP/Erk kinase (MEK), a kinase capable of phosphorylating and activating Erk, have been identified, but their distribution and differential roles in leukocytes are unknown. We studied the effect of chemotactic stimulation on MEK-1, using isoform-specific antibodies. MEK-1 was found to be phosphorylated on serine and threonine residues in unstimulated human neutrophils. Stimulation by the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP) enhanced serine/threonine phosphorylation of MEK-1, while reducing its electrophoretic mobility. MEK-1 activity, measured as autophosphorylation or as phosphorylation of a glutathione S-transferase-Erk fusion protein, was undetectable in unstimulated cells but became evident after treatment with chemoattractant. Phosphorylation and activation of MEK-1 were rapid and transient, peaking after 1-2 min and returning to base line by 10 min. Experiments using electropermeabilized cells indicated that elevation of cytosolic Ca2+ is not required for activation of MEK-1 by fMLP. Moreover, MEK-1 was not stimulated by either platelet-activating factor or thapsigargin, which increase Ca2+ to levels comparable with those attained in chemoattractant-activated cells. In contrast, activation of MEK-1 was induced by phorbol esters, and the stimulatory effect of fMLP was blocked by an antagonist of protein kinase C. Stimulation of MEK-1 was also blocked by concentrations of erbstatin that prevent the fMLP-induced accumulation of tyrosine-phosphorylated proteins. The data suggest that MEK-1 is largely responsible for the activation of Erk in chemoattractant-stimulated neutrophils and that protein kinase C and/or tyrosine kinases mediate this effect, whereas elevated cytosolic Ca2+ is not essential.

Amino Acid Sequence↗
PubMed1993

Receptor-mediated activation of multiple serine/threonine kinases in human leukocytes.

Activation of the microbicidal response of phagocytes requires cytosolic ATP and is associated with extensive protein phosphorylation, suggesting the involvement of protein kinases in the signal transduction cascade. An in vitro renaturation assay was used to identify the protein kinase(s) activated by chemoattractants in human blood neutrophils. Four distinct kinases were activated by the chemotactic peptide formyl-methionyl-leucyl-phenyl-alanine with molecular masses of 72, 65, 49, and 41 kDa (designated PK72, PK65, PK49, and PK41, respectively). PK72 and PK65 were activated very rapidly (5-15 s), yet transiently. By comparison, PK49 and PK41 responded in a slower, more sustained manner. Treatment of extracts of activated cells with alkaline phosphatase reverted the stimulation of the kinases, suggesting that phosphorylation is the post-translational modification that underlies activation of the kinases. Stimulation of PK72 and PK65 by chemoattractant was independent of calcium and protein kinase C. In contrast, elevation of cytosolic free calcium levels was sufficient and appeared to be necessary for full activation of PK49 and PK41. While phorbol esters can mimic the effects of formyl-methionyl-leucyl-phenylalanine on PK49 and PK41, inhibition of protein kinase C by staurosporine did not prevent the receptor-mediated activation of these kinases. PK41 most likely corresponds to the Erk-1 isoform of mitogen-activated protein (MAP) kinase. Accordingly, PK41 effectively phosphorylated myelin basic protein, known to be a good substrate for Erk-1. The electrophoretic mobility of PK49 is similar to that of MAP kinase-kinase (MAP/Erk kinase). However, immunoprecipitation experiments indicated that PK49 is not MAP/Erk kinase. The identity of this and other kinases remains to be defined, but possible candidates are discussed. In addition to autophosphorylating, PK72, PK65, and PK41 were shown to effectively phosphorylate exogenous substrates. These kinases may therefore play a role in signal transduction during stimulation by chemoattractants.

Base Sequence↗
PubMed1992

Bending strength of Fuji and Ketac glass ionomers after sonication.

Glass ionomer cements mixed by conventional methods contain voids that can decrease their overall strength. This study evaluated the effect of sonication on the reduction of air entrapment by measuring the bending strength in glass ionomer cements (Fujj-II and Ketac-fil). Glass ionomer cement was placed in identical-test vials and sonicated for 45s, 10s, or 0s. The bending strengths were measured (0.005 in min-1) after setting times of 1 or 2 weeks. Mean bending strengths (MPa +/- SD) for the 12 treatment both cements (P < 0.001) and sonication times (P < 0.001). The effect of setting time produced minimal increases in bending strength (P < 0.218). The sonication of freshly mixed glass ionomer cements is a possible solution for reducing voids to increase bending strength.

Analysis of Variance↗
PubMed1992

Association of a cGMP-binding activity with nuclei isolated from amoebae of Dictyostelium discoideum and Polysphondylium violaceum.

When vegetative and early slug stage amoebae of Dictyostelium discoideum or Polysphondylium violaceum were lysed by filter breakage in a nuclear isolation buffer not containing detergents, substantial levels of a cGMP-binding activity with slow-dissociation kinetics were detected. After fractionation by centrifugation, 50% or more of this binding activity was associated with isolated nuclei. In addition, with Polysphondylium cells, the fraction of stable, nuclear-associated binding activity appeared to increase during cell aggregation. These results support the idea that cGMP might function in the nucleus during early development.

Animals↗
PubMed1990

Effect of immune system imagery on secretory IgA.

This study was an investigation of the effects of physiologically-oriented mental imagery on immune functioning. College students with normal medical histories were randomly selected to one of three groups. Subjects in Group 1 participated in short educational training on the production of secretory immunoglobulin A. They were then tested on salivary IgA, skin temperature, and the Profile of Mood States (POMS) before and after listening to a 17-minute tape of imagery instructions with specially composed background "entrainment" music designed to enhance imagery. Subjects in Group 2 (placebo controls) listened to the same music but received nor formal training on the immune system. Group 3 acted as a control and subjects were tested before and after 17 minutes of no activity. Treatment groups listened to their tapes at home on a bi-daily basis for six weeks. All groups were again tested at Weeks 3 and 6. Secretory IgA was analyzed using standard radial immunodiffusion techniques. Repeated measures analyses of variance with planned orthogonal contrasts were used to evaluate the data. Significant overall increases (p less than 0.05) were found between pre- and posttests for all three trials. Groups 1 and 2 combined (treatment groups) yielded significantly greater increases in sIgA over Group 3 (control) for all three trials. Group 1 (imagery) was significantly higher than Group 2 (music) in antibody production for Trials 2 and 3. Symptomatology, recorded by subjects at Weeks 3 and 6, was significantly lower for three symptoms (rapid heartbeat, breathing difficulty, and jaw clenching), favoring both treatment groups over the control group.

Humans↗
PubMed1988

The economy of time in general practice: an assessment of the influence of list size.

A lack of time is one of the major reasons given to account for low quality care provided in general practice. One of the basic assumptions inherent in this explanation is that activities in general practice are shaped by the level of patient demand and general practitioners have little control over their work. The objective of this study is to explore empirically this assumption that general practice is demand led by examining the relationship between list size and the time general practitioners spend at work-related activities. The analysis uses data gathered from a survey carried out on a nationally representative sample of unrestricted principals (N = 1419) living in England and Wales. The results show that list size is statistically significantly associated with each of the different indices of time allocation, although it is only relatively strongly associated with hours spent on surgery consultations and surgery consultation rates. The implications of these findings are discussed and it is suggested that the demand led model provides only a partial explanation for variations in time allocation in general practice.

Appointments and Schedules↗
PubMed1987

List sizes and use of time in general practice.

The claim that list sizes in general practice should continue to fall towards a national average of 1700 patients rests heavily on the assumption that the extra time available to doctors would be used mainly for longer consultations, resulting in better standards of care. Evidence suggests, however, that the time is more likely to be used to increase rates of consultation in surgeries and home visits and to reduce the length of the working week. A national, random sample of 2104 principals in general practice in England and Wales were questioned about their allocation and use of time. The response rate was 67%, and no large biases in response were detected. The smaller their personal list size the less time general practitioners spent on all aspects of their work and the higher their rates of consultation and home visiting. The effects of further reductions in list sizes would be haphazard, being differentially distributed across the range of list sizes. Longer consultations would probably result, but most of the extra time would probably be used in higher rates of consultation in surgeries and home visits and some would be taken as free time.

Appointments and Schedules↗
PubMed1985

NAD+ kinase--a review.

NAD+ kinase catalyzes the only (known) biochemical reaction leading to the production of NADP+ from NAD+. Most evidence indicates it is found in the cytoplasm, but reports of its presence in (other) cell bodies can not be discounted. Viewed as a protein, our knowledge of NADK composition and architecture is rudimentary. Though recognized as a large multimeric protein, no agreement is evident for the molecular weight (Mr = approximately 4-65 X 10(4] of the native protein. Is calmodulin an integral subunit of (some, all) NAD+ kinases (analogous to phosphorylase kinase in skeletal muscle)? Or is it an external modulator? Consensus is evident that a subunit of molecular weight 30-35 X 10(3) is a component of the mammalian and yeast kinase. In one case (rabbit liver) two types of subunits are reported to give rise to oligomers differing in molecular weight and catalytic activities. Viewed as an enzyme it is not known why such a complex aggregate is needed for what might otherwise appear to a routine phosphorylation reaction. Rapid equilibrium random (for pigeon liver and C. utilis preparations) and ping-pong (for A. vinelandii kinase) mechanisms have been proposed for the reaction, with multiple reactant binding sites indicated for the random cases. From the perspective of enzyme modulation, the demonstration that green plant and sea urchin egg kinases are targets for calmodulin regulation by intracellular Ca2+ links NADP+ production in these sources to the multi-level discriminatory control functions inherent to this Ca2+-protein complex. Significant questions arise from the results of various investigators considered in this review. These queries offer fertile ground for the selective design of key experiments directed to a better understanding of NAD+ kinase function and pyridine nucleotide biochemistry.

Calmodulin↗
PubMed1982

Candida utilis NAD+ kinase: purification, properties and affinity gel studies.

1. NAD+ kinase (ATP:NAD+ 2' phosphotransferase, EC 2.7.1.23) has been purified to apparent enzymic homogeneity on Blue Sepharose CL-6B. 2. The molecular weight of the active species is about 260,000 as determined by PAGE and gel chromatography. Protein staining (PAGE) revealed minor bands with molecular weight values of 40,000, 140,000 and 550,000. Subunit studies (SDS-PAGE) gave evidence of a single band of molecular weight approximately 32,000. 3. On the basis of the release patterns of this enzyme from several affinity gels, an elution diagram is proposed as a device to assess the contribution of any of the several displacing agents that can be used to manipulate the desorption of a (enzyme) ligate from an immobilized ligand.

Candida↗
PubMed1982

Candida utilis NAD+ kinase: kinetic and inhibition studies with ADP.

1. Initial velocity and product inhibition studies using ADP were carried out on cytoplasmic NAD+ kinase (ATP:NAD 2' phosphotransferase, EC 2.7.1.23) purified from Candida utilis. Initial velocity studies were also carried out on a sample of chicken liver NAD+ kinase. 2. The data indicate both enzymes followed a sequential mechanism of reactant binding. 3. Product inhibition studies on C. utilis NAD+ kinase suggest the mechanism of NAD+, ATP addition is best described as rapid equilibrium random with multiple binding of ADP to the free enzyme and the E X ATP and E X NAD+ complexes. 4. The characteristics of this enzyme, prepared from several sources, are briefly summarized.

Adenosine Diphosphate↗