Search PubMed⌕ Search

Biomedical subjects

E Evans

Publications and source records attributed to E Evans.

At least 19 recordsLinked to original sources
PubMed2006

The 5th International Conference on Basic and Therapeutic Aspects of Botulinum and Tetanus Neurotoxins. Workshop review: assays and detection.

The development of diagnostic tests for the botulinum neurotoxins is complicated by their extremely high potencies and the considerable diversity observed within the neurotoxin family. Current approaches for the detection of the toxins and the organism include amplified immunoassays and PCR techniques. Assays which exploit the biological activities within the botulinum toxins are also in development. These are based on both antibody and mass spectrometric techniques which measure the endopeptidase activities of the neurotoxins. This overview of the Assays and Detection Workshop of the 5th International Conference of on Basic and Therapeutic Aspects of Botulinum and Tetanus Neurotoxins discusses recent progress in the development of these assay systems and the issues that need to be overcome prior to their implementation.

Animals↗
PubMed2005

Randomised controlled trial of patient controlled analgesia compared with nurse delivered analgesia in an emergency department.

OBJECTIVE: To compare effectiveness, safety, and patient satisfaction of patient controlled analgesia (PCA) with titrated, intravenous opioid injections for the management of acute traumatic pain in the emergency department (ED). METHODS: The study took place in the ED of a teaching hospital. Patients suffering traumatic injury requiring opioid analgesia, and meeting other inclusion criteria, were consented and randomised to either the study group or control group. The study group were given morphine through the PCA system, whereas the control group were given morphine via the conventional route of nurse titration. Pain levels were measured using a visual analogue scale. Both groups had their vital signs (blood pressure, pulse, oxygen saturations, Glasgow coma score, respiratory rate) and pain scores monitored at 0, 15, 30, 45, 60, 90, and 120 minutes, and any adverse events were noted. Patients were followed up with a questionnaire asking about their experience of pain relief in the department. RESULTS: 86 patients were recruited to the study, 43 in each group. There was no significant difference between the groups in terms of pain relief (p = 0.578) and patient satisfaction (p = 0.263). No severe adverse events were observed, although 20.7% (n = 9) of the PCA group experienced mild sedation compared with 7% (n = 3) of the control group. CONCLUSIONS: PCA is at least as effective as titrated intravenous injections for relief of traumatic pain. It has considerable potential for use in the ED.

Adult↗
PubMed2005

Effects of BioChlor and Fermenten on microbial protein synthesis in continuous culture fermenters.

Meta analysis models were constructed from a data-set of 15 continuous culture fermenter trials and 118 observations on studies with either BioChlor (n = 23 observations) or Fermenten (n = 95) included at 10 and 3%, respectively, of dietary dry matter (DM) to evaluate effects of the ingredients BioChlor and Fermenten (B/F) on rumen function. Digestibility of crude protein was significantly increased by 11% with B/F treatment. This was reflected in significant increases in digestibility of DM and organic matter (OM) by 3.6 and 7.9%, respectively. Increased amounts of sugar in the diet in the presence of B/F tended to reduce digestibility of non-structural carbohydrates (NSC); however, the net effect on NSC digestion was small. There was no effect of treatment on most individual volatile fatty acids (VFA) or total VFA production. Propionate production, however, was significantly reduced in treated fermenters. The main effect of B/F as well as of starch and soluble fiber when combined with the treatment was to increase propionate production; however, the interaction between B/F treatment and sugar decreased propionate production markedly, resulting in a net decrease. The acetate-to-propionate ratio increased by 6% with B/F, largely as a result of the decrease in propionate. Production of nonammonia nitrogen was 1% less in B/F-treated fermenters, and interactions between treatment and starch, sugar, or soluble fiber were significant. Treated fermenters produced 15.7% more microbial nitrogen, in association with a significant 37% increase in rumen protein digestion. Interactions between treatment and starch, soluble fiber, or sugar influenced these results. The interaction of B/F and sugar resulted in a decrease in undegradable protein N and an increase in microbial nitrogen production. Ammonia nitrogen concentrations were increased by 24.6% in treated fermenters. Efficiency of microbial nitrogen production from DM, OM, or carbohydrate was significantly increased by B/F. Sugar content increased efficiency of microbial protein production/kg of OM digested or carbohydrate digested in the presence of treatment by >10 times the increase that was attributable to the interaction of treatment with starch. Treatment with B/F reduced moles of VFA produced/kg of microbial nitrogen produced by 16%. This effect was also substantially influenced by interactions between B/F and sugar. If the fermenter results are representative of those in vivo, milk production responses to treatment with B/F will depend on amounts of starch, soluble fiber, and, particularly, sugar in diets. Milk production responses will also depend on the quality of protein in the diet and the comparative benefit that increased flux of microbial nitrogen provides. Increased digestibility of OM should allow additional ruminant production benefits.

Amino Acids↗
PubMed2004

Trans-bonded pairs of E-cadherin exhibit a remarkable hierarchy of mechanical strengths.

Classical cadherins are primary mediators of calcium-dependent cell interactions in multicellular organisms. Organized in five tandemly repeated E-cadherin (EC) modules, the extracellular segments of these membrane-spanning glycoproteins interact homophilically between opposing cells to create highly regulated patterns of attachment stabilized by cytoskeletal elements inside the cells. Despite many structural and functional studies, a significant controversy exists in regard to the organization of cadherin binding in adhesion sites. Supported by considerable evidence, perhaps the most widely held view is that opposing N-terminal EC1-EC2 (EC12) domains form a "zipper" of bonds. However, immobilized on two atomically smooth surfaces and pushed to adhesive contact, opposing cadherins become fully interdigitated and unbind through three discrete jumps comparable with domain dimensions when pulled apart. So the question remains as to whether mechanical adhesion strength emanates solely from interactions between the peripheral N-terminal domains or involves multiple overlapping domains. It is also unclear whether a primary adhesion complex is formed by a single opposing pair of cadherins or whether the complex involves a more complicated network of cis-bonded multimers. To address these questions, we used a special jump/ramp mode of force spectroscopy to test isolated pairwise interactions between recombinant fragments of ECs. Besides the formation of strong trans-bonded dimers, we find a remarkable hierarchy of rupture strengths for bonds between the full five-domain fragments that suggests multiple mechanical functions for cadherins, perhaps providing distinct properties needed for transient-specific recognition as well as stable tissue formation.

Animals↗
PubMed2003

Symptoms of depression in older adults with multiple sclerosis (MS): comparison with a matched sample of younger adults.

The study considered for the first time depression in older adults with multiple sclerosis (MS). Depression symptom scores of 27 persons aged over 65 years who were part of a large study of persons with MS (n = 529), were compared with those of a matched sample of younger adults from the same study. The association between cognitive (attitudinal) variables known to explain significant variance in depressive symptoms in younger adults with MS was then considered in the older adult sample. Consistent with findings from studies with general community samples, older adults with MS reported significantly fewer depressive symptoms than younger adults with MS. The relationship between cognitive variables and depressive symptoms found previously in younger adults was also evident for the older adults. Multiple sclerosis related helplessness was found to be significantly higher in older as opposed to younger adults with MS, the opposite of what was predicted given the differences between the groups in depression scores. Differences in the cognitive variables do not appear to explain the differences between older and younger adults with MS in terms of depressive symptoms. This finding offers support for the view that a decrease in emotional responsiveness may explain differences in depressive symptoms between younger and older adults with MS, rather than this being the result of differences in emotional control exerted via cognitive means.

Adult↗
PubMed2002

Comparison of sport achievement orientation between wheelchair and able-bodied basketball athletes.

Differences in sport achievement orientations between 31 recreational wheelchair and 76 able-bodied basketball athletes were tested. Athletes from the New England region completed the three subscales of the Sport Orientation Questionnaire (competitiveness, win orientation, and goal orientation). Wheelchair athletes responded higher on the Competitiveness and Goal Orientation subscales. In discriminative function analysis competitiveness scores were the only significant discriminator between the two groups.

Achievement↗
PubMed2001

Chemically distinct transition states govern rapid dissociation of single L-selectin bonds under force.

Carbohydrate--protein bonds interrupt the rapid flow of leukocytes in the circulation by initiation of rolling and tethering at vessel walls. The cell surface carbohydrate ligands are glycosylated proteins like the mucin P-selectin glycoprotein ligand-1 (PSGL-1), which bind ubiquitously to the family of E-, P-, and L-selectin proteins in membranes of leukocytes and endothelium. The current view is that carbohydrate-selectin bonds dissociate a few times per second, and the unbinding rate increases weakly with force. However, such studies have provided little insight into how numerous hydrogen bonds, a Ca(2+) metal ion bond, and other interactions contribute to the mechanical strength of these attachments. Decorating a force probe with very dilute ligands and controlling touch to achieve rare single-bond events, we have varied the unbinding rates of carbohydrate--selectin bonds by detachment with ramps of force/time from 10 to 100,000 pN/sec. Testing PSGL-1, its outer 19 aa (19FT), and sialyl Lewis(X) (sLe(X)) against L-selectin in vitro on glass microspheres and in situ on neutrophils, we found that the unbinding rates followed the same dependence on force and increased by nearly 1,000-fold as rupture forces rose from a few to approximately 200 pN. Plotted on a logarithmic scale of loading rate, the rupture forces reveal two prominent energy barriers along the unbinding pathway. Strengths above 75 pN arise from rapid detachment (<0.01 sec) impeded by an inner barrier that requires a Ca(2+) bond between a single sLe(X) and the lectin domain. Strengths below 75 pN occur under slow detachment (>0.01 sec) impeded by the outer barrier, which appears to involve an array of weak (putatively hydrogen) bonds.

Calcium↗
PubMed2001

Elastic thickness compressibilty of the red cell membrane.

We have used an ultrasensitive force probe and optical interferometry to examine the thickness compressibility of the red cell membrane in situ. Pushed into the centers of washed-white red cell ghosts lying on a coverglass, the height of the microsphere-probe tip relative to its closest approach on the adjacent glass surface revealed the apparent material thickness, which began at approximately 90 nm per membrane upon detection of contact (force approximately 1-2 pN). With further impingement, the apparent thickness per membrane diminished over a soft compliant regime that spanned approximately 40 nm and stiffened on approach to approximately 50 nm under forces of approximately 100 pN. The same force-thickness response was obtained on recompression after retraction of the probe, which demonstrated elastic recoverability. Scaled by circumferences of the microspheres, the forces yielded energies of compression per area which exhibited an inverse distance dependence resembling that expected for flexible polymers. Attributed to the spectrin component of the membrane cytoskeleton, the energy density only reached one thermal energy unit (k(B)T) per spectrin tetramer near maximum compression. Hence, we hypothesized that the soft compliant regime probed in the experiments represented the compressibility of the outer region of spectrin loops and that the stiff regime < 50 nm was the response of a compact mesh of spectrin backed by a hardcore structure. To evaluate this hypothesis, we used a random flight theory for the entropic elasticity of polymer loops to model the spectrin network. We also examined the possibility that additional steric repulsion and apparent thickening could arise from membrane thermal-bending excitations. Fixing the energy scale to k(B)T/spectrin tetramer, the combined elastic response of a network of ideal polymer loops plus the membrane steric interaction correlated well with the measured dependence of energy density on distance for a statistical segment length of approximately 5 nm for spectrin (i.e., free chain end-to-end length of approximately 29 nm) and a hardcore limit of approximately 30 nm for underlying structure.

Biomechanical Phenomena↗
PubMed2001

Probing the relation between force--lifetime--and chemistry in single molecular bonds.

On laboratory time scales, the energy landscape of a weak bond along a dissociation pathway is fully explored through Brownian-thermal excitations, and energy barriers become encoded in a dissociation time that varies with applied force. Probed with ramps of force over an enormous range of rates (force/time), this kinetic profile is transformed into a dynamic spectrum of bond rupture force as a function of loading rate. On a logarithmic scale in loading rate, the force spectrum provides an easy-to-read map of the prominent energy barriers traversed along the force-driven pathway and exposes the differences in energy between barriers. In this way, the method of dynamic force spectroscopy (DFS) is being used to probe the complex relation between force-lifetime-and chemistry in single molecular bonds. Most important, DFS probes the inner world of molecular interactions to reveal barriers that are difficult or impossible to detect in assays of near equilibrium dissociation but that determine bond lifetime and strength under rapid detachment. To use an ultrasensitive force probe as a spectroscopic tool, we need to understand the physics of bond dissociation under force, the impact of experimental technique on the measurement of detachment force (bond strength), the consequences of complex interactions in macromolecular bonds, and effects of multiply-bonded attachments.

Biophysical Phenomena↗
PubMed2000

Water permeability and mechanical strength of polyunsaturated lipid bilayers.

Micropipette aspiration was used to test mechanical strength and water permeability of giant-fluid bilayer vesicles composed of polyunsaturated phosphatidylcholine PC lipids. Eight synthetic-diacyl PCs were chosen with 18 carbon chains and degrees of unsaturation that ranged from one double bond (C18:0/1, C18:1/0) to six double bonds per PC molecule (diC18:3). Produced by increasing pipette pressurization, membrane tensions for lysis of single vesicles at 21 degrees C ranged from approximately 9 to 10 mN/m for mono- and dimono-unsaturated PCs (18:0/1, 18:1/0, and diC18:1) but dropped abruptly to approximately 5 mN/m when one or both PC chains contained two cis-double bonds (C18:0/2 and diC18:2) and even lower approximately 3 mN/m for diC18:3. Driven by osmotic filtration following transfer of individual vesicles to a hypertonic environment, the apparent coefficient for water permeability at 21 degrees C varied modestly in a range from approximately 30 to 40 microm/s for mono- and dimono-unsaturated PCs. However, with two or more cis-double bonds in a chain, the apparent permeability rose to approximately 50 microm/s for C18:0/2, then strikingly to approximately 90 microm/s for diC18:2 and approximately 150 microm/s for diC18:3. The measurements of water permeability were found to scale exponentially with the reduced temperatures reported for these lipids in the literature. The correlation supports the concept that increase in free volume acquired in thermal expansion above the main gel-liquid crystal transition of a bilayer is a major factor in water transport. Taken together, the prominent changes in lysis tension and water permeability indicate that major changes occur in chain packing and cohesive interactions when two or more cis-double bonds alternate with saturated bonds along a chain.

Kinetics↗
PubMed2000

Effect of chain length and unsaturation on elasticity of lipid bilayers.

Micropipette pressurization of giant bilayer vesicles was used to measure both elastic bending k(c) and area stretch K(A) moduli of fluid-phase phosphatidylcholine (PC) membranes. Twelve diacyl PCs were chosen: eight with two 18 carbon chains and degrees of unsaturation from one double bond (C18:1/0, C18:0/1) to six double bonds per lipid (diC18:3), two with short saturated carbon chains (diC13:0, diC14:0), and two with long unsaturated carbon chains (diC20:4, diC22:1). Bending moduli were derived from measurements of apparent expansion in vesicle surface area under very low tensions (0.001-0.5 mN/m), which is dominated by smoothing of thermal bending undulations. Area stretch moduli were obtained from measurements of vesicle surface expansion under high tensions (>0.5 mN/m), which involve an increase in area per molecule and a small-but important-contribution from smoothing of residual thermal undulations. The direct stretch moduli varied little (< +/-10%) with either chain unsaturation or length about a mean of 243 mN/m. On the other hand, the bending moduli of saturated/monounsaturated chain PCs increased progressively with chain length from 0.56 x 10(-19) J for diC13:0 to 1.2 x 10(-19) J for diC22:1. However, quite unexpectedly for longer chains, the bending moduli dropped precipitously to approximately 0.4 x 10(-19) J when two or more cis double bonds were present in a chain (C18:0/2, diC18:2, diC18:3, diC20:4). Given nearly constant area stretch moduli, the variations in bending rigidity with chain length and polyunsaturation implied significant variations in thickness. To test this hypothesis, peak-to-peak headgroup thicknesses h(pp) of bilayers were obtained from x-ray diffraction of multibilayer arrays at controlled relative humidities. For saturated/monounsaturated chain bilayers, the distances h(pp) increased smoothly from diC13:0 to diC22:1 as expected. Moreover, the distances and elastic properties correlated well with a polymer brush model of the bilayer that specifies that the elastic ratio (k(c)/K(A))(1/2) = (h(pp) - h(o))/24, where h(o) approximately 1 nm accounts for separation of the headgroup peaks from the deformable hydrocarbon region. However, the elastic ratios and thicknesses for diC18:2, diC18:3, and diC20:4 fell into a distinct group below the correlation, which showed that poly-cis unsaturated chain bilayers are thinner and more flexible than saturated/monounsaturated chain bilayers.

Biophysical Phenomena↗
PubMed2000

The Saccharomyces cerevisiae Msh2 mismatch repair protein localizes to recombination intermediates in vivo.

Mismatch repair proteins act during double-strand break repair (DSBR) to correct mismatches in heteroduplex DNA, to suppress recombination between divergent sequences, and to promote removal of nonhomologous DNA at DSB ends. We investigated yeast Msh2p association with recombination intermediates in vivo using chromatin immunoprecipitation. During DSBR involving nonhomologous ends, Msh2p localized strongly to recipient and donor sequences. Localization required Msh3p and was greatly reduced in rad50delta strains. Minimal localization of Msh2p was observed during fully homologous repair, but this was increased in rad52delta strains. These findings argue that Msh2p-Msh3p associates with intermediates early in DSBR to participate in the rejection of homeologous pairing and to stabilize nonhomologous tails for cleavage by Rad1p-Rad10p endonuclease.

Base Pair Mismatch↗