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Biomedical subjects

Paul Marshall

Publications and source records attributed to Paul Marshall.

18 recordsLinked to original sources
PubMed2006

Changes in the flexion relaxation response following an exercise intervention.

STUDY DESIGN: Pre and post 12-week training study using surface electromyography to measure the flexion relaxation response. OBJECTIVE: To evaluate whether the active or passive phases of the flexion relaxation measurement changes following an exercise intervention in patients with low back pain. SUMMARY OF BACKGROUND DATA: Impaired neuromuscular activation is an area of specific interest in patients with chronic nonspecific low back pain (LBP). The flexion relaxation phenomenon is commonly measured in LBP patients; however, there is insufficient evidence about the changes in this measure following an intervention. METHODS: Fifteen subjects with chronic LBP (7 females, 8 males) performed a 12-week training intervention. The main outcome measures were the Oswestry disability index, visual analog scale, and flexion relaxation response analyzed by the raw electromyograph (EMG) signal, the relative EMG signal, and the flexion relaxation ratio. RESULTS: Disability and pain scores improved significantly after the 12-week intervention. There were no changes in the active components of the flexion relaxation measurement but an approximate 67% decrease in the amount of activity measured during the relaxation phase at full trunk flexion. CONCLUSION: The data suggest that afferent feedback changes may be explaining why there is improved electrical relaxation following an exercise intervention.

Adult↗
PubMed2006

The relationship between active and neural measures in patients with nonspecific low back pain.

STUDY DESIGN: Cross-sectional study of 50 individuals with nonspecific low back pain (LBP). OBJECTIVE: To evaluate the relationship between active and neural measurements in individuals with nonspecific LBP. SUMMARY OF BACKGROUND DATA: The Panjabi model for spinal stability consists of 3 interacting subsystems. Specific musculoskeletal measurements can be identified within the active and neural systems. The relationships among measures within this model have not been identified. METHODS: A total of 50 individuals with nonspecific LBP were evaluated for measures of the active and neural stability systems, and analyzed using a canonical correlation analysis, which is used to measure the relationship between 2 multidimensional variables. RESULTS: There were 2 significant relationships identified. The first identified a relationship among fatigue, flexion relation, and the feedforward abdominal response (r = 0.764, P < 0.001). The second relationship was between the Sorenson endurance test and feedforward abdominal response (r = 0.697, P = 0.006). CONCLUSION: Identification of relationships between back pain measurements may allow discrimination between individuals with different histology and pain levels. This process may assist the specificity of treatment programs prescribed for patients with back pain.

Abdominal Muscles↗
PubMed2006

Thermal dissociation of SO3 at 1000-1400 K.

The thermal dissociation of SO3 has been studied for the first time in the 1000-1400 K range. The experiments were conducted in a laminar flow reactor at atmospheric pressure, with nitrogen as the bath gas. On the basis of the flow reactor data, a rate constant for SO3 + N2 --> SO2 + O + N2 (R1b) of 5.7 x 10(17) exp(-40000/T) cm3/(mol s) is derived for the temperature range 1273-1348 K. The estimated uncertainty is a factor of 2. The rate constant corresponds to a value of the reverse reaction of k1 approximately 1.8 x 10(15) cm6 mol(-2) s(-1). The reaction is in the fall-off region under the investigated conditions. The temperature and pressure dependence of SO2 + O (+N2) was estimated from the extrapolation of low temperature results for the reaction, together with an estimated broadening parameter and the high-pressure limit determined recently by Naidoo, Goumri, and Marshall (Proc. Combust. Inst. 2005, 30, 1219-1225). The theoretical rate constant is in good agreement with the experimental results. The improved accuracy in k(1) allows a reassessment of the rate constant for SO3 + O --> SO2 + O2 (R2) based on the data of Smith, Tseregounis, and Wang (Int. J. Chem. Kinet. 1982, 14, 679-697), who conducted experiments on a low-pressure CO/O2/Ar flame doped with SO2. At the location in the flame where the net SO3 formation rate is zero, k2 = k1[SO2][M]/[SO3]. A value of 6.9 x 10(10) cm3 mol(-1) s(-1) is obtained for k2 at 1269 K with an uncertainty a factor of 3. A recommended rate constant k2 = 7.8 x 10(11) exp(-3065/T) cm3 mol(-1) s(-1) is consistent with other flame results as well as the present flow reactor data.

Journal Article↗
PubMed2006

Thermochemistry is not a lower bound to the activation energy of endothermic reactions: a kinetic study of the gas-phase reaction of atomic chlorine with ammonia.

The rate constant for Cl + NH3 --> HCl + NH2 has been measured over 290-570 K by the time-resolved resonance fluorescence technique. Ground-state Cl atoms were generated by 193 nm excimer laser photolysis of CCl4 and reacted under pseudo-first-order conditions with excess NH3. The forward rate constant was fit by the expression k1 = (1.08 +/- 0.05) x 10(-11) exp(-11.47 +/- 0.16 kJ mol(-1)/RT) cm3 molecule(-1) s(-1), where the uncertainties in the Arrhenius parameters are +/-1 sigma and the 95% confidence limits for k1 are +/-11%. To rationalize the activation energy, which is 7.4 kJ mol(-1) below the endothermicity in the middle of the 1/T range, the potential energy surface was characterized with MPWB1K/6-31++G(2df,2p) theory. The products NH2 + HCl form a hydrogen-bonded adduct, separated from Cl + NH3 by a transition state lower in energy than the products. The rate constant for the reverse process k(-1) was derived via modified transition state theory, and the computed k(-1) exhibits a negative activation energy, which in combination with the experimental equilibrium constant yields k1 in fair accord with experiment.

Journal Article↗
PubMed2006

Modified transition state theory and negative apparent activation energies of simple metathesis reactions: application to the reaction CH3 + HBr --> CH4 + Br.

A modified transition state theory (MTST) has been developed for gas-phase reactions with "negative barriers". The theory was applied to the reactions CH3 + HBr(DBr) --> CH4(CH3D) + Br (1a, 1b), which exhibit negative temperature dependences. Accurate ab initio calculations performed with coupled cluster theory extrapolated to the complete basis set limit revealed a transition state located at -2.3 kJ mol(-1) relative to the ground state of the reactants (in reaction 1a), as well as a shallow bound complex. The negative temperature dependence, the absolute values of the rate constant, and the isotope substitution effect are reproduced with good accuracy (10%), without any adjustment or fitting parameters. Analytical expressions are presented for MTST including angular momentum conservation, centrifugal barriers and tunneling. This analysis uses information about the possibly loose entrance barrier and the transition state but does not invoke a statistical intermediate complex.

Journal Article↗
PubMed2006

Changes in muscle activity and perceived exertion during exercises performed on a swiss ball.

The objective of this study was to determine differences in electromyographic (EMG) activity of prime mover and abdominal muscles while performing squats, push ups, and double leg lowering with a swiss ball. Twelve healthy subjects performed the movements. There was no difference between the surface conditions for muscle activity during the squat exercise; however, individuals had lower perceived exertion for the swiss ball squat. Activity of the triceps and abdominals was highest performing push ups on the swiss ball, whereas the activity of rectus abdominus (RA) only increased during double leg lowering on the swiss ball. Perceived exertion was highest for the push up and leg-lowering exercise performed on the swiss ball. Increased RA activity during double leg lowering can be attributed to its role as a hip flexor, whereas the lack of a rotation aspect to the task prevented increased oblique muscle activity. The swiss ball appears to only increase muscle activity during exercises where the unstable surface is the primary base of support.

Adult↗
PubMed2005

A computational study of the thermochemistry of bromine- and iodine-containing methanes and methyl radicals.

Bromo- and iodomethanes and the corresponding halogenated methyl radicals have been investigated by ab initio methods. Geometries and vibrational frequencies were derived with quadratic configuration interaction methods at the QCISD/6-311G(d,p) level of theory, and energies via QCISD(T)/6-311+G(3df,2p). Core electrons were represented with relativistic effective potentials. Anharmonicity of the out-of-plane bending modes in the methyl radicals was taken into account by numerical integration of the Schrödinger equation with potentials derived from relaxed scans of these modes. The results are in good accord with experimental data where available. Thermochemistry derived via isodesmic reactions referenced to CH3, CH4, and monohalomethanes yields excellent accord with new experiments on dihalomethanes and provides recommendations for the more poorly characterized tri- and tetrahalomethanes and halomethyl radicals. For the methanes CH2Br2, CHBr3, CBr4, CH2I2, CHI3, CI4, CH2BrI, CHBr2I, and CHBrI2 we compute DeltafH degrees (298) values of 4.3, 51.6, 110.6, 108.1, 208.5, 321.3, 56.8, 104.8, and 157.1 kJ mol(-1), respectively. For the methyl radicals CH2Br, CHBr2, CBr3, CH2I, CHI2, CI3, CHBrI, CBr2I, and CBrI2 we compute DeltafH degrees (298) values of 166.6, 191.7, 224.0, 217.2, 290.4, 369.1, 241.6, 320.8, and 272.3 kJ mol(-1), respectively. Recommended confidence limits are +/-3 kJ mol(-1) per Br or I atom. Trends in these values and the corresponding C-H bond strengths are discussed and compared with prior experiments, empirical estimation schemes, and ab initio calculations.

Journal Article↗
PubMed2005

Men and health help-seeking behaviour: literature review.

AIM: This paper reviews the key research literature regarding men's health-related help seeking behaviour. BACKGROUND: There is a growing body of research in the United States to suggest that men are less likely than women to seek help from health professionals for problems as diverse as depression, substance abuse, physical disabilities and stressful life events. Previous research has revealed that the principle health related issue facing men in the UK is their reluctance to seek access to health services. METHOD: The investigation of men's health-related help seeking behaviour has great potential for improving both men and women's lives and reducing national health costs through the development of responsive and effective interventions. A search of the literature was conducted using CINAHL, MEDLINE, EMBASE, PsychINFO and the Cochrane Library databases. RESULTS: Studies comparing men and women are inadequate in explaining the processes involved in men's help seeking behaviour. However, the growing body of gender-specific studies highlights a trend of delayed help seeking when they become ill. A prominent theme among white middle class men implicates "traditional masculine behaviour" as an explanation for delays in seeking help among men who experience illness. The reasons and processes behind this issue, however, have received limited attention. CONCLUSIONS: Principally, the role of masculine beliefs and the similarities and differences between men of differing background requires further attention, particularly given the health inequalities that exist between men of differing socio-economic status and ethnicity. Further research using heterogeneous samples is required in order to gain a greater understanding of the triggers and barriers associated with the decision making process of help seeking behaviour in men who experience illness.

Attitude to Health↗
PubMed2005

Clinical pharmacology of lumiracoxib: a selective cyclo-oxygenase-2 inhibitor.

Lumiracoxib (Prexige) is a selective cyclo-oxygenase (COX)-2 inhibitor developed for the treatment of osteoarthritis, rheumatoid arthritis and acute pain. Lumiracoxib possesses a carboxylic acid group that makes it weakly acidic (acid dissociation constant [pKa] 4.7), distinguishing it from other selective COX-2 inhibitors. Lumiracoxib has good oral bioavailability (74%). It is rapidly absorbed, reaching maximum plasma concentrations 2 hours after dosing, and is highly plasma protein bound. Lumiracoxib has a short elimination half-life from plasma (mean 4 hours) and demonstrates dose-proportional plasma pharmacokinetics with no accumulation during multiple dosing. In patients with rheumatoid arthritis, peak lumiracoxib synovial fluid concentrations occur 3-4 hours later than in plasma and exceed plasma concentrations from 5 hours after dosing to the end of the 24-hour dosing interval. These data suggest that lumiracoxib may be associated with reduced systemic exposure, while still reaching sites where COX-2 inhibition is required for pain relief. Lumiracoxib is metabolised extensively prior to excretion, with only a small amount excreted unchanged in urine or faeces. Lumiracoxib and its metabolites are excreted via renal and faecal routes in approximately equal amounts. The major metabolic pathways identified involve oxidation of the 5-methyl group of lumiracoxib and/or hydroxylation of its dihaloaromatic ring. Major metabolites of lumiracoxib in plasma are the 5-carboxy, 4'-hydroxy and 4'-hydroxy-5-carboxy derivatives, of which only the 4'-hydroxy derivative is active and COX-2 selective. In vitro, the major oxidative pathways are catalysed primarily by cytochrome P450 (CYP) 2C9 with very minor contribution from CYP1A2 and CYP2C19. However, in patients genotyped as poor CYP2C9 metabolisers, exposure to lumiracoxib (area under the plasma concentration-time curve) is not significantly increased compared with control subjects, indicating no requirement for adjustment of lumiracoxib dose in these subjects. Lumiracoxib is selective for COX-2 compared with COX-1 in the human whole blood assay with a ratio of 515 : 1 in healthy subjects and in patients with osteoarthritis or rheumatoid arthritis. COX-2 selectivity was confirmed by a lack of inhibition of arachidonic acid and collagen-induced platelet aggregation. COX-2 selectivity of lumiracoxib is associated with a reduced incidence of gastroduodenal erosions compared with naproxen and a lack of effect on both small and large bowel permeability. Lumiracoxib does not exhibit any clinically meaningful interactions with a range of commonly used medications including aspirin (acetylsalicylic acid), fluconazole, an ethinylestradiol- and levonorgestrel-containing oral contraceptive, omeprazole, the antacid Maalox, methotrexate and warfarin (although, as in common practice, routine monitoring of coagulation is recommended when lumiracoxib is co-administered with warfarin). As such, dose adjustments are not required when co-administering these agents with lumiracoxib. In addition, moderate hepatic impairment and mild to moderate renal impairment do not appear to influence lumiracoxib exposure.

Arthritis, Rheumatoid↗
PubMed2004

Reaction kinetics of the addition of atomic sulfur to nitric oxide.

The reaction of S((3)P(J)) with NO ((2)Pi) in an Ar bath gas has been studied by the laser photolysis-resonance fluorescence technique over 300-810 K at pressures from 60 to 800 mbar. The observed second-order rate constants are close to the low-pressure limit. Fitting of Troe's formalism to experiment, with an estimated F(cent) = 0.78 exp(-T/7445) and k(infinity) given subsequently, yields k(0) = (6.2+/-0.6) x 10(-33) exp(+ (940+/-40)/T) cm(6) molecule(-2) s(-1). Error limits are +/-25%. A theoretical analysis of this value suggests that the average energy transferred during collisions between Ar and the excited intermediate is DeltaE = -360(-160) (+90) cm(-1). Over 300-800 K, the high-pressure limit is predicted to be k(infinity) = 2.2 x 10(-10) (T/300)(0.24) cm(3) molecule(-1) s(-1). Doublet and quartet adducts between S and NO were characterized via CBS-QB3 theory. The kinetic data can be rationalized with SNO ((2)A(')) as the major product, and an ab initio estimate of Delta(f)H(298) for SNO is 176+/-8 kJ mol(-1).

Journal Article↗
PubMed2004

Localised mapping of water movement and hydration inside a developing bioadhesive bond.

Few studies have investigated the internal processes involved in bioadhesive bond formation, particularly where mucus and hydrated polymer contribute jointly to bond structure. This paper reports the first study to spatially map the internal environment within a developing bioadhesive bond, utilising nuclear magnetic resonance (NMR) microscopy to measure localised water self-diffusion coefficients (SDC) and confocal laser scanning microscopy (CLSM) to estimate mucin concentration. In a model bioadhesive bond formed between an alginate matrix and mucin gel, characteristic profiles were observed in which fluorescence measurements showed a region of increasing mucin concentration in the mucus layer region adjacent to the matrix, corresponding closely with a zone of restricted water SDC in the diffusion profiles. These regions extended 144 microm (a normal human gastric layer thickness [Clin. Sci. 95 (1998) 97]) into the mucin layer after just 30 s, increasing to 800 microm after 30 min. The formation of a hydrated polymer layer at the matrix surface, confirmed visually, was also reflected in corresponding gradient changes. The results suggest a progressive dehydration of the mucus gel during bond formation, and the study demonstrates how together, these microscopies can provide non-invasive, quantitative, spatial and time-resolved evidence of internal hydration behaviour during bioadhesive bond formation.

Adhesiveness↗
PubMed2004

Natural turbidity variability and weather forecasts in risk management of anthropogenic sediment discharge near sensitive environments.

Coastal development activities can cause local increases in turbidity and sedimentation. This study characterises the spatial and temporal variability of turbidity near an inshore fringing coral reef in the central Great Barrier Reef, under a wide range of natural conditions. Based on the observed natural variability, we outline a risk management scheme to minimise the impact of construction-related turbidity increases. Comparison of control and impact sites proved unusable for real-time management of turbidity risks. Instead, we suggest using one standard deviation from ambient conditions as a possible conservative upper limit of an acceptable projected increase in turbidity. In addition, the use of regional weather forecast as a proxy for natural turbidity is assessed. This approach is simple and cheap but also has limitations in very rough conditions, when an anthropogenic turbidity increase could prove fatal to corals that are already stressed under natural conditions.

Animals↗
PubMed2004

Cardiac output by Portapres.

Portapres derives continuous estimates of cardiac output from the peripheral pulse and has the potential to be an extremely valuable physiological and clinical tool. We assessed Portapres estimates of cardiac output in healthy subjects at rest, during maximal treadmill exercise ( n = 8) and during decreases caused by orthostatic stress ( n = 8). Comparison with a rebreathing method indicated that Portapres tended to overestimate cardiac output. The random errors of the estimates (precision), expressed as +/- 2 S.D. of the differences between paired estimates during steady states, ranged between 1.2 and 2.6 litres/min. We conclude that these errors indicate that the method is probably only useful for assessing changes in individual subjects where large changes are anticipated, as during exercise. When smaller changes occur, as during orthostasis, the errors preclude the use of individual subject data and only permit group average data to be examined.

Adult↗
PubMed2003

Simulation of the different biological activities of diethylstilbestrol (DES) on estrogen receptor alpha and estrogen-related receptor gamma.

We describe the application of the molecular dynamics (MD) and molecular mechanics-generalized Born/surface area (MM-GB/SA) approaches to the simulation of the different biological activity of diethylstilbestrol (DES) on two highly homologous nuclear receptors-estrogen receptor alpha (ER-alpha) and estrogen-related receptor gamma (ERR-gamma). DES exerts an agonistic effect against ER-alpha and an antagonistic effect against ERR-gamma. Using the x-ray crystal structures of ER-alpha in the canonical agonist bound form (PDB code: 3ERD) and antagonist bound form (PDB code: 3ERT), ERR-gamma homology models have been constructed for the receptor in two different conformations. MM-GB/SA binding free energy calculations of DES in the ER-alpha and ERR-gamma structures suggest that DES exhibits a greater free energy of binding in the agonist bound conformation of ER-alpha, while the antagonist bound conformation is preferred for ERR-gamma. Further dissection of the free energy contributions coupled with calculation of the ligand binding pocket volume suggests that the van der Waals interactions for DES within the smaller binding pocket volume of ERR-gamma are less favorable and this is the main factor for DES antagonism in ERR-gamma. This approach has potential general applicability to the prediction of the biological activity of nuclear receptor ligands.

Amino Acid Sequence↗
PubMed2003

Glucocorticoid receptor antagonism by cyproterone acetate and RU486.

The steroid compound cyproterone acetate was identified in a high-throughput screen for glucocorticoid receptor (GR) binding compounds. Cyproterone (Schering AG) is clinically used as an antiandrogen for inoperable prostate cancer, virilizing syndromes in women, and the inhibition of sex drive in men. Despite its progestin properties, cyproterone shares a similar pharmacological profile with the antiprogestin mifepristone (RU486; Roussel Uclaf SA). The binding affinities of cyproterone and RU486 for the GR and progesterone receptor were similar (K(d), 15-70 nM). Both compounds were characterized as competitive antagonists of dexamethasone without intrinsic transactivating properties in rat hepatocytes (K(i), 10-30 nM). In osteosarcoma cells, RU486 revealed a higher potency than cyproterone acetate to prevent responses to dexamethasone-induced GR transactivation and NF kappa B transrepression. Upon administration to Sprague-Dawley rats, both compounds were found to be orally bioavailable and to inhibit transactivation of liver GR. Molecular docking of cyproterone acetate and RU486 into the homology model for the GR ligand binding domain illustrated overlapping steroid scaffolds in the binding pocket. However, in contrast to RU486, cyproterone lacks a bulky side chain at position C11 beta that has been proposed to trigger active antagonism of nuclear receptors by displacing the C-terminal helix of the ligand-binding domain, thereby affecting activation function 2. Cyproterone may therefore inhibit transactivation of the GR by a molecular mechanism recently described as passive antagonism. New therapeutic profiles may result from compounds designed to selectively stabilize the inactive and active conformations of certain nuclear receptors.

Androgen Antagonists↗
PubMed1989

Attention deficit disorder and allergy: a neurochemical model of the relation between the illnesses.

Empirical studies suggest that allergies play an etiological role in a small subgroup of children who suffer from attention deficit-hyperactivity disorder (ADHD). Research indicates that allergic reactions results in cholinergic hyperresponsiveness and beta-adrenergic hyporesponsiveness in the autonomic nervous system. Evidence is reviewed that similar imbalances in central nervous system cholinergic/adrenergic activity play a causal role in manic and depressive behaviors. It is hypothesized that allergic reactions engender cholinergic/adrenergic activity imbalances in the central nervous system, leading to poorly regulated arousal levels and ADHD behaviors in some children.

Arousal↗
PubMedDate not supplied

The effect of sacroiliac joint manipulation on feed-forward activation times of the deep abdominal musculature.

OBJECTIVES: To determine the incidence of delayed feed-forward activation (FFA) times in a group of healthy young males; to retest those subjects who showed delayed FFA after 6 months to determine the reliability of the measure in the absence of treatment or injury in the intervening period; and to determine the effect of sacroiliac joint manipulation on delayed FFA times. METHODS: Ninety young males were assessed for the FFA of their deep abdominal muscles in relation to rapid upper limb movements. Those who met the criteria for delayed FFA (failure of deep abdominal activation within 50 milliseconds of deltoid activation) were then reassessed 6 months later. These subjects then underwent sacroiliac joint manipulation on the side demonstrating decreased joint movement during hip flexion and lateral flexion. Feed-forward activation times were then reassessed after joint manipulation. RESULTS: Seventeen (18.9%) of 90 subjects met the criteria of impaired FFA. Thirteen of 17 were available to be remeasured at 6-month follow-up. The intraclass correlation coefficient for FFA at this time was greater than 0.70 for all movement directions. There was a significant improvement (38.4%) in FFA times for this group when remeasured immediately after the sacroiliac joint manipulation. CONCLUSIONS: Delayed FFA is a highly reproducible measure at long-term follow-up. This technique appears to be a sensitive marker of the neural effects of sacroiliac joint manipulation. Future prospective studies are needed to determine if delayed FFA times are a marker for those at risk for developing back pain.

Abdominal Muscles↗