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Biomedical subjects

D Button

Publications and source records attributed to D Button.

At least 19 recordsLinked to original sources
PubMed2002

Intermuscle differences in activation.

The objective of this study was to investigate differences within individual subjects in the ability to activate the quadriceps, plantar flexors (PF), dorsiflexors (DF), and elbow flexors (EF) during isometric contractions. Twelve male subjects performed submaximal and maximal voluntary isometric contractions, and maximal tetanic contractions were also induced by electrical stimulation. The interpolated twitch technique was used to gauge the extent of muscle inactivation or inability to produce maximum force. Measurements included torque output, absolute and relative rate of force development (RFD), and percentage of muscle inactivation. The quadriceps exceeded all other muscle groups in voluntary and tetanic torque output, voluntary absolute RFD, and absolute and relative tetanic RFD. The quadriceps also exceeded the PF and DF in voluntary relative RFD and had greater muscle inactivation (15.5%) than the EF (5.0%), PF (5.0%), and DF (1.3%). Although the higher RFD may suggest a higher percentage of type II fibers in the quadriceps, their higher threshold of recruitment leads to greater difficulty in fully activating the quadriceps.

Adult↗
PubMed2000

Nonrandom rearrangements of 6p in malignant hematological disorders.

It is very uncommon to observe nontranslocation abnormalities (NTAs) involving the short arm of chromosome 6 (6p) in malignant hematological disorders (MHDs). By using conventional cytogenetics and fluorescence in situ hybridization (FISH) with chromosome-microdissection probes specific for 6p21 and 6p25, we observed five patients with myeloid malignancies and two patients with lymphoid malignancies to have 6p NTAs. On the basis of our data and those in the literature, it is possible to divide 6p NTAs into the following three groups in MHD: The first group presents with 6p NTAs as a sole or primary change in myeloid malignancies. There are only two cases reported in this group, including one case with del(6)(p23) and the present case with ins(6)(q23p23p25) identified by FISH only. The second group presents with 6p deletions as a sole or primary change in lymphoid malignancies. Three cases have been reported in this group, including one case with del(6)(p21p23), one with del(6)(p21), and the present case 2 with del(6)(p21). The third group has 6p deletions in addition to other known primary changes, present in both myeloid and lymphoid disorders, with 36 cases reported, including five cases from our series. Deletions involving 6p21, 6p22, or 6p23 have been observed in both myeloid and lymphoid disorders. The present data provide cogent information for further molecular characterization of 6p anomalies in MHD.

Adult↗
PubMed1998

Consensus guidelines for the promotion and management of continence by primary health care teams: development, implementation and evaluation. NHS Executive Nursing Directorate.

A project was undertaken as part of the NHS Executive Strategy for Major Clinical Guidelines, involving the development of national clinical guidelines for the promotion and management of continence by primary health care teams, through the process of managed consensus based on scientific review. The guidelines were then implemented at one urban general practice. This article outlines the development and implementation of the guidelines and describes the study undertaken to evaluate the impact of implementation on clinical outcomes. The study involved a pre-and post-implementation postal survey of a random sample of 17% of patients aged 18 years and over from the practice (n = 1503). The pre-implementation survey determined the period prevalence of incontinence, related biological data and data on the pre-implementation management of incontinence. Incontinence sufferers were invited to have their condition assessed or reviewed. All sufferers who agreed to be followed-up were sent the post-implementation survey, which identified those patients who had sought help, and ascertained reasons for not seeking help. Data on the management of incontinence post-implementation were also obtained. Clinical outcomes measured pre- and post-implementation were a validated severity index for urinary incontinence, (also adapted for faecal incontinence) and perception of the incontinence as a problem. A 3-month period was allowed between pre- and post-implementation surveys. The study confirmed previous research which showed that few incontinence sufferers respond to invitations to seek help, and that help-seeking behaviour was significantly related to severity of incontinence. The guidelines did not have any positive impact on the clinical outcomes measured, although slight improvements in approaches taken by the primary health care team to the promotion and management of continence were recorded. However, the study was limited by the small sample size and short time scale. Further evaluation of the impact of the guidelines on these outcomes is therefore recommended.

Female↗
PubMed1996

A novel class of 5-HT2A receptor antagonists: aryl aminoguanidines.

Local delivery of serotonin (5-HT) produces a rapid edematous response in soft tissues via increased fluid extravasation which is prevented by 5-HT2 antagonists such as ketanserin or mianserin. Here we report the effects of a new class of aminoguanidine 5-HT2 antagonists, with relative selectivity for 5-HT2A receptors which are potent inhibitors of 5-HT-induced paw edema in the rat. Radioligand binding studies with 125I DOI on human 5-HT2A and 5-HT2C receptors and with 3H-5-HT on human 5-HT2B receptors demonstrated that, LY314228, and LY320954 displayed some selectivity for the 5-HT2A receptor. When compared to binding at other 5-HT2 receptor subtypes, LY314228 had an 18.6-fold greater affinity for the 5-HT2A site over the 5-HT2B site, and 2.6 fold greater at the 5-HT2C site. LY320954 displayed similar preference for 5-HT2A sites. Both compounds also inhibited 5-HT-induced paw swelling in rats, with ED50's of 6.4 and 4.8 mg/kg (for LY314228 and LY320954, respectively). These studies offer evidence for a novel class of pharmacophores for the 5-HT2 receptor family which show greater relative affinities for the 5-HT2A receptor subclass.

Animals↗
PubMed1996

Experiences of encouraging student-centred learning within a wellness-oriented curriculum.

This paper describes the use of learning logs as a tool for self-assessment and reflection during a 'well people' module within a Bachelor of Nursing programme. A qualitative analysis of the students' learning goals and reflective accounts from the learning logs are presented, together with extracts from the written evaluation of the module. Recommendations are made for enhancing the potential of the learning log as a flexible learning tool which can help students to draw upon professional knowledge in order to make sense of their experiences.

Curriculum↗
PubMed1996

Aequorin targeted to the endoplasmic reticulum reveals heterogeneity in luminal Ca++ concentration and reports agonist- or IP3-induced release of Ca++.

A chimeric protein (ERaeq) comprised of the invariant chain (Ii) of class II major histocompatability complex (MHC-II) and aequorin was localized in the endoplasmic reticulum (ER) of transfected human embryonal kidney 293 cells. The targeted aequorin resided in the lumen of the ER membrane system, including the nuclear cistern, and following addition of the chromophore coelenterazine underwent Ca(++)-activated chemiluminescence. The majority of chemiluminescence produced by coelenterazine treatment of ERaeq-expressing 293 cells was consumed rapidly (within 2-4 min) upon re-addition of Ca++ to coelenterazine-loaded cells, a finding consistent with very high Ca++ concentrations (approximately 10(-5)-10(-3) M Ca++ ion) inside the ER. However, following the initial rapid consumption of ERaeq chemiluminescence, the activity that remained (10-30% of total sample luminescence of permeabilized cells or 50-70% of total sample luminescence of intact cells) was found to produce a stable baseline corresponding to a Ca++ ion concentration < or = 1-2 microM. The stable baseline of luminescence observed following rapid consumption of the majority of the sample's activity was not derived from re-binding of fresh chromophore to spent photoprotein, suggesting that a minority fraction of the ER membrane system within which the ERaeq chimera was distributed contained a relatively low Ca++ concentration. Addition of IP3 to digitonin-permeabilized cells, or agonist treatment of intact cells decreased this residual signal. Luminescence recordings from cells expressing an ER-targeted aequorin with relatively high affinity for Ca++ thus reveal heterogeneity in luminal ER Ca++ concentration and permit observation of receptor- and IP3-activated release of Ca++ from the ER membrane system.

Aequorin↗
PubMed1994

A rapid colorimetric assay of killer toxin activity in yeast.

The pale yellow redox indicator 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) is reduced to a dark blue end-product, MTT-Formazan, by the mitochondrial dehydrogenases of living cells. MTT reduction can be measured spectrophotometrically at a wavelength of 570 nm and a method is described to assay the cidal activity of Williopsis mrakii killer toxin against sensitive cells of Candida glabrata. The MTT assay is rapid, quantitative and compares favourably with traditional plating techniques for the assessment of sensitive viability.

Candida↗
PubMed1994

Agonist-selective regulation of polyphosphoinositide metabolism in pulmonary artery smooth muscle cells.

Using a rat pulmonary artery smooth muscle cell line (PAC1), detailed analysis of polyphosphoinositide (PPI) metabolism reveals receptor type-selective patterns in the formation of inositol phosphates and 3-hydroxyphosphorylated PPIs. Responses to several agonists that stimulate hypertrophy or proliferation were examined, and distinct categories of response profile were observed. Thrombin and angiotensin II stimulated the hydrolysis of phosphatidylinositol (PI) 4,5-bisphosphate and the formation of several cytosolic species of inositol phosphates without the activation of PI 3-hydroxykinase. The response to thrombin was distinctive because a very large production of inositol 1,4-bisphosphate was accompanied by hydrolysis of PI 4-phosphate. The response to platelet-derived growth factor (PDGF) was distinguished by the production of the PI 3-hydroxykinase product, PI 3,4,5-trisphosphate, and the appearance of PI 3-hydroxykinase activity in immunoprecipitates. PDGF treatment of PAC1 cultures did not produce accumulation of detectable amounts of inositol 1,4,5-trisphosphate, although a small sustained elevation in the level of inositol monophosphate and a gradual accumulation of inositol 1,3,4-trisphosphate were observed. Characterization of these distinctive responses permitted us to correlate agonist-regulated PPI metabolism with induction of immediate-early genes and stimulation of hypertrophy or proliferation of PAC1 cultures (Rothman, A., Wolner, B., Button, D., and Taylor, P. (1994) J. Biol. Chem. 269, 6399-6404). Thrombin-stimulated PPI turnover and the production of a high level of inositol bisphosphate may be early signals linked to the induction of fosB and PAC1 cell hypertrophy, whereas the activation of PI 3-hydroxykinase and the accumulation of PI 3,4,5-trisphosphate in response to PDGF appear to be associated with mitogenesis.

Angiotensin II↗
PubMed1994

Immediate-early gene expression in response to hypertrophic and proliferative stimuli in pulmonary arterial smooth muscle cells.

Remodeling of the pulmonary vascular tree in pulmonary hypertension is associated with hypertrophy and proliferation of smooth muscle cells. Since the stimuli and signaling pathways for these processes are not well understood, we used a rat pulmonary arterial smooth muscle cell line (PAC1) to examine the effects of thrombin and platelet-derived growth factor (PDGF) on cellular growth and immediate-early gene expression. Over 72 h, thrombin (1 unit/ml) caused hypertrophy as reflected by a 102 +/- 12% increase in protein synthesis and a 49 +/- 11% increase in protein content per cell, but no change in cell number. PDGF (2.5 ng/ml) stimulated proliferation as evidenced by an increase in cell number (doubling in 5 days), but no significant change in protein content per cell. Immediate-early gene expression was examined by Northern blotting: both thrombin and PDGF induced egr-1, c-fos, c-jun, junB, and fra-1 mRNAs within 15 min; the response was maximal at 30-60 min (increases ranging from 2.9- to 9.3-fold over control serum-deprived cells) and returned to base-line levels within 2-4 h. Neither agent affected junD mRNA levels. However, thrombin but not PDGF, caused an increase in fosB mRNA levels (7.7 +/- 4.0-fold higher than control, n = 12, p < 0.0005). The immediate-early gene response to both agonists was generally dependent on extracellular Ca2+, Na2+/H+ exchange, and protein kinase C activation, but not on cAMP. The exception was c-jun mRNA, the levels of which were not affected by inhibition of protein kinase C, but decreased significantly by prevention of cAMP formation. Thapsigargin-sensitive intracellular Ca2+ stores were necessary for the response to thrombin, but not to PDGF. These results demonstrate that thrombin is a hypertrophic agent and that PDGF is a proliferative agent in PAC1 cells. These two agonists stimulate increases in a variety of immediate-early gene mRNAs, but only thrombin induces fosB mRNA.

Animals↗
PubMed1994

Students' evaluation of the process of conducting a patient assessment.

A Qualitative Evaluation Strategy was adopted to explore an early curriculum experience of undergraduate pre-registration student nurses. Open-ended narratives, in the style of Illuminative Evaluation (Parlett & Hamilton 1972), were used to encourage students to reflect upon their experience of conducting their first patient assessment using a model of nursing. A content analysis of the students' reflections is presented and discussed with reference to studies whose findings they corroborate and support. Aspects of the learning experience which influence the development of nursing skills were elucidated, together with the learning processes involved in the acquisition of patient assessment skills. Evaluating the context of the students' learning environment revealed some of the realities of learning nursing 'in the field', a lack of role models in clinical areas and the persistence of a theory-practice gap. In addition, this study shed light on the process of professional socialisation in student nurses. Encouraging reflection helped the students recognise how much they had learnt, and enabled us to evaluate our effectiveness as learning facilitators. An electic approach combining both qualitative and quantitative paradigms is advocated for holistic evaluation of the curriculum. Inferences from this evaluation may have particular relevance for designers and teachers of Project 2000 style courses.

Education, Nursing, Baccalaureate↗
PubMed1993

Phase II trial of the novel sulphonylurea sulofenur in advanced breast cancer.

A total of 18 women with advanced breast cancer were treated with sulofenur [LY186641; N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)-urea], a diarylsulfonylurea that has broad-spectrum activity against a number of murine mammary tumour xenografts. The dosage chosen on the basis of pre-clinical and phase I studies was 700 mg/m2 given orally once daily for 14 days, with treatments being repeated every 3 weeks. There was no response. All patients experienced at least grade 1 anaemia, and two patients developed symptomatic methaemoglobinaemia. Two patients developed grade 4 rises in serum liver-function values along with histological changes consistent with drug-induced toxicity. The mean plasma concentrations of 176 micrograms/ml were lower than the levels required to exert anti-tumour effect in the mouse model.

Administration, Oral↗
PubMed1993

Aequorin-expressing mammalian cell lines used to report Ca2+ mobilization.

Mammalian cells that stably express jellyfish aequorin have been used to report activation of Ca2+ mobilization by cell-surface receptors. Expression of aequorin cDNA (pAEQ) was driven by the cytomegalovirus (CMV) promoter in CHO-K1 and 293 cells. Clonal isolates were obtained which express high levels of apo-aequorin protein, the Ca(2+)-dependent luminescence of which is generated by treatment of living cells with the coelenterate luciferin, coelenterazine. Transient expression of aequorin in COS cells results in even greater abundance of luminescent protein. Aequorin protein is lost from digitonin-permeabilized cells to the same extent and at the same rate as lactate dehydrogenase (LDH), indicating cytosolic location of the indicator. Aequorin expressing cells treated with agonists of endogenous receptors were used in luminescence measurements to demonstrate that the reporter lines offer a highly sensitive and robust means of assaying changes in the concentration of cytosolic Ca2+ ion. Transient co-expression of the substance P receptor in aequorin reporter cells was also performed to demonstrate the feasibility of using this convenient and sensitive assay system for large scale screening of ligands that activate cell surface receptors coupled to increases in intracellular Ca2+.

Aequorin↗
PubMed1991

A phase II clinical and pharmacokinetic study of Lonidamine in patients with advanced breast cancer.

Lonidamine is a substituted indazole carboxylic acid with a unique mechanism of action and early clinical studies have reported anti-tumour activity. In a phase II study 32 patients with previously treated advanced breast cancer were given Lonidamine in a daily divided oral dose of 600 mg. Of 28 patients evaluable for response, three (11%) achieved a partial response (4-24+ months) and three (11%) a minor response. Two patients have stable disease (greater than 3 months) and 20 progressed. Toxicity was very mild. Sixteen (53%) of 31 patients had myalgia which lasted a median of 2 weeks. This was investigated with nuclear magnetic resonance spectroscopy in four patients but the changes were unrelated to the degree of myalgia. No other major side-effect was seen, and no dose reduction was required. Lonidamine pharmacokinetics have been investigated in 17 patients 1 month after the start of therapy. Lonidamine was detected in the plasma of all patients, but there was no clear relationship between Lonidamine levels and clinical response or toxicity. Lonidamine appears to be active against advanced breast cancer and its low toxicity would allow combination studies with chemotherapy.

Adenosine Triphosphate↗
PubMed1991

The pharmacokinetics of oral lonidamine in breast and lung cancer patients.

The plasma levels of lonidamine have been studied in 24 breast or lung cancer patients as part of the Phase II evaluation of the drug. The pharmacokinetic studies were performed when the patients had been on oral lonidamine therapy for 27 to 47 days (mean 32 days) and the studies were conducted over a 24 hour period. Lonidamine was administered in three divided doses of 150 mg (t = 0h), 150 mg (t = 7h), and 150 mg or 300 mg (t = 14h). Plasma levels of lonidamine were determined by high-performance liquid chromatography (HPLC) with fluorescence detection. Lonidamine was detected in the plasma of all patients studied, and the absolute range for the peak plasma levels of the drug following the first and second doses were 4.6-33.8 and 4.8-33.3 micrograms/ml, respectively. The range of times after administration at which the peak occurred was 0.5 to 4.2 hours for the first dose and 0.5 to 4.1 hours for the second. The absolute range for the trough levels observed over the 24-hour study period was 1.0 to 12.6 micrograms/ml and in 19 of the patients it was possible to define the apparent half life of lonidamine that was found to be within the range 2.5 to 11.7 hours. In addition to lonidamine, a number of fluorescent components were detected in the plasma of patients following lonidamine treatment that were not detected in pretreatment plasma samples. One component, a compound that eluted from the HPLC more rapidly than lonidamine, was found in some patients to be sensitive to hydrolysis with beta-glucuronidase. Comparison of the pharmacokinetic data with patient characteristics and clinical biochemistry results failed to establish any clear relationship. Similarly there was no relationship between lonidamine pharmacokinetics and either drug-induced myalgia or testicular pain. Insufficient responses were seen in the patient group studied to allow the relationship between lonidamine pharmacokinetics and response to be evaluated.

Absorption↗
PubMed1988

Simple method for scanning immunoblots.

Scanning laser densitometry was performed on immuno- and dot blots developed on nitrocellulose by treatment of the nitrocellulose with xylene. This method permits the development of simple methods for recording results of immunoblots and of producing semi-quantitative assays from dot blots.

Antigens, Fungal↗
PubMed1987

Regulation of ligand-receptor dynamics by guanine nucleotides. Real-time analysis of interconverting states for the neutrophil formyl peptide receptor.

Intact neutrophils exhibit interconverting active and inactive receptor states with half-times for dissociation of 10 s and 2 min, respectively. We examined the effect of guanine nucleotides on ligand-receptor dynamics at 37 degrees C in neutrophils permeabilized with digitonin using continuous fluorometric measurements. The permeabilized cells exhibit a single class of slowly dissociating receptors with a half-time similar to the inactive state. The slowly dissociating state is lengthened in the presence of 10 mM by Mg2+ about two-fold but is relatively insensitive to substitutions of Na+ or K+. When guanine nucleotide is added the receptors dissociate uniformly with a half-time similar to the active state but are sensitive to the substitution of Na+ or K+ (K+ or K+/Mg2+ approximately 10 s; Na+ or Na+/Mg2+ approximately 4 s). When receptors in permeabilized cells are ADP-ribosylated with pertussis toxin the rapidly dissociating state is detected. In the presence of nonsaturating nucleotide or incomplete ribosylation, complex rates of ligand dissociation intermediate between the active and inactive forms are observed. Micromolar concentrations of Ca2+ block the effect of guanine nucleotide on the receptor. The relationships between ligand-receptor dynamics in intact neutrophils and interconverting states regulated by guanine nucleotides and ions in permeabilized cells are discussed.

Adenosine Diphosphate Ribose↗