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At least 199 records · Page 11Linked to original sources
PubMed1998

Variability of radiation output dynamic range in modern cardiac catheterization imaging systems.

Automatic exposure control (AEC) is one of the most important characteristics for optimizing cardiac catheterization imaging; this allows the X-ray system to provide sufficient radiation output under a variety of clinical conditions so that a satisfactory image is obtained. AEC was assessed in 97 cardiac catheterization laboratories using a standard set of phantoms. Three different copper attenuators were used to simulate three patient sizes. As magnification increased, many systems had limited dynamic range and were unable to increase radiation output. With increasing atttenuator thickness, the problem worsened. With the thickest attenuator and largest magnification (4.5"-5.0" FOV), 60% of systems could not achieve the typical 70% increase in exposure while 20% were unable to increase radiation output at all.

Body Burden↗
PubMed2004

Characterization of wide dynamic range neurons in the deep dorsal horn of the spinal cord in preprotachykinin-a null mice in vivo.

We previously reported that mice with a deletion of the preprotachykinin-A (pptA) gene, from which substance P (SP) and neurokinin A (NKA) are derived, exhibit reduced behavioral responses to intense stimuli, but that behavioral hypersensitivity after injury is unaltered. To understand the contribution of SP and NKA to nociceptive transmission in the spinal cord, we recorded single-unit activity from wide dynamic range neurons in the lamina V region of the lumbar dorsal horn of urethane-anesthetized wild-type and ppt-A null mutant (-/-) mice. We found that intensity coding to thermal stimuli was largely preserved in the ppt-A -/- mice. Neither the peak stimulus-evoked firing nor the neuronal activity during the initial phase (0-4 s) of the 41-49 degrees C thermal stimuli differed between the genotypes. However, electrophysiological responses during the late phase of the stimulus (5-10 s) and poststimulus (11-25 s) were significantly reduced in ppt-A -/- mice. To activate C-fibers and to sensitize the dorsal horn neurons we applied mustard oil (MO) topically to the hindpaw. We found that neither total MO-evoked activity nor sensitization to subsequent stimuli differed between the wild-type and ppt-A -/- mice. However, the time course of the sensitization and the magnitude of the poststimulus discharges were reduced in ppt-A -/- mice. We conclude that SP and/or NKA are not required for intensity coding or sensitization of nociresponsive neurons in the spinal cord, but that these peptides prolong thermal stimulus-evoked responses. Thus whereas behavioral hypersensitivity after injury is preserved in ppt-A -/- mice, our results suggest that the magnitude and duration of these behavioral responses would be reduced in the absence of SP and/or NKA.

Animals↗
PubMed1994

Silica-based room temperature phosphorescence substrates: wide dynamic ranges, low background, and programmable figures of merit.

The use of silica-based substrates for room temperature phosphorescence (RTP) was investigated. Contrary to reports in the literature, bare silica was shown to provide higher sensitivity (S/B) for RTP than filter paper when the specific surface areas of the two substrates were similar. The surface heterogeneity of bare silica resulted in nonlinear, discontinuous response curves for a model analyte, phenanthrene. However, analytically useful calibration curves were obtained on silica thin-layer phases in the presence of coadsorbed surfactant. The dynamic range on the silica substrate was 4 times greater and the background phosphorescence was 2 orders of magnitude lower than filter paper. The programming of figures of merit for silica-based substrates via the silica specific surface area is demonstrated.

Fluorometry↗
PubMed1999

Involvement of peripheral NMDA and non-NMDA receptors in development of persistent firing of spinal wide-dynamic-range neurons induced by subcutaneous bee venom injection in the cat.

To study the roles of peripheral excitatory amino acids receptor subtypes N-methyl-D-aspartate (NMDA) and non-NMDA receptors in persistent nociception, extracellular single unit recording technique was used to assess the effects of a single dose NMDA and non-NMDA receptor antagonists, AP(5) (5-aminophosphonovaleric acid) and CNQX (6-cyano-7-nitroquinoxaline-2,3-dione) or DNQX (6,7-dinitroquinoxaline-2,3-dione), on s.c. bee venom-induced increase in firing of wide-dynamic-range (WDR) neurons in the spinal dorsal horn of the urethane-chloralose anesthetized cats. Subcutaneous bee venom injection into the cutaneous receptive field resulted in a single phase of increased firing of WDR neurons over the background activity for more than 1 h. Local pre-administration of AP(5) (200 microg/100 microl) or CNQX (8.3 microg/100 microl) into the bee venom injection site produced 94% (1.01+/-0.96 spikes/s, n=5) or 76% (2.97+/-0.58 spikes/s, n=4) suppression of the increased neuronal firing when compared with local saline (16.32+/-4.55 spikes/s, n=10) or dimethyl sulfoxide (DMSO) (12.37+/-6.36 spikes/s, n=4) pre-treated group, respectively. Local post-administration of the same dose of AP(5) produced a similar result to the pre-treatment group with a 67% inhibition of the mean firing rate, however, the same treatment with CNQX and even a higher dose of DNQX (100 microg/100 microl) did not produce any inhibition of the neuronal firing induced by s.c. bee venom injection (DNQX vs. DMSO: 23.91+/-0. 25 vs. 22.14+/-0.04 spikes/s, P=0.0298, n=5). In the control experiments, local pre-administration of the same dose of AP(5) or CNQX into a region on the contralateral hindpaw symmetrical to the bee venom injection site produced no significant influence on the increased firing of the WDR neurons [contralateral AP(5) vs. saline: 14.17+/-6.27 spikes/s (n=5) vs. 16.32+/-4.55 spikes/s (n=10), P0.05; contralateral CNQX vs. DMSO: 12.85+/-6.38 spikes/s (n=4) vs. 12. 37+/-6.36 spikes/s (n=4), P0.05], implicating that the suppressive action of local AP(5) or CNQX was not the result of systemic effects. The present results suggest that activation of the peripheral NMDA receptors is involved in both induction and maintenance, while activation of non-NMDA receptors is only involved in induction, but not in the maintenance of persistent firing of the dorsal horn WDR neurons induced by s.c. bee venom injection.

2-Amino-5-phosphonovalerate↗
PubMed2004

Cannabinoid CB2 receptor activation inhibits mechanically evoked responses of wide dynamic range dorsal horn neurons in naïve rats and in rat models of inflammatory and neuropathic pain.

Peripheral cannabinoid 2 receptors (CB2 receptors) modulate immune responses and attenuate nociceptive behaviour in models of acute and persistent pain. The aim of the present study was to investigate whether peripheral CB2 receptors modulate spinal processing of innocuous and noxious responses and to determine whether there are altered roles of CB2 receptors in models of persistent pain. Effects of local administration of the CB2 receptor agonist JWH-133 (5 and 15 microg/50 microL) on mechanically evoked responses of spinal wide dynamic range (WDR) neurons in noninflamed rats, rats with carrageenan-induced hindpaw inflammation, sham operated rats and spinal nerve-ligated (SNL) rats were determined in anaesthetized rats in vivo. Mechanical stimulation (von Frey filaments, 6-80 g) of the peripheral receptive field evoked firing of WDR neurons. Mechanically evoked responses of WDR neurons were similar in noninflamed, carrageenan-inflamed, sham-operated and SNL rats. Intraplantar injection of JWH-133 (15 microg), but not vehicle, significantly (P < 0.05) inhibited innocuous and noxious mechanically evoked responses of WDR neurons in all four groups of rats. In many cases the selective CB2 receptor antagonist, SR144528 (10 microg/50 microL), attenuated the inhibitory effects of JWH-133 (15 microg) on mechanically evoked WDR neuronal responses. The CB1 receptor antagonist, SR141716A, did not attenuate the inhibitory effects of JWH-133 on these responses. Intraplantar preadministration of JWH-133 also inhibited (P < 0.05) carrageenan-induced expansion of peripheral receptive fields of WDR dorsal horn neurons. This study demonstrates that activation of peripheral CB2 receptors attenuates both innocuous- and noxious-evoked responses of WDR neurons in models of acute, inflammatory and neuropathic pain.

Action Potentials↗
PubMed2005

Dynamic range of hepatitis C virus RNA quantification with the Cobas Ampliprep-Cobas Amplicor HCV Monitor v2.0 assay.

Accurate quantification of hepatitis C virus (HCV) RNA is needed in clinical practice to decide whether to continue or stop pegylated interferon-alpha-ribavirin combination therapy at week 12 of treatment for patients with chronic hepatitis C. Currently the HCV RNA quantification assay most widely used worldwide is the Amplicor HCV Monitor v2.0 assay (Roche Molecular Systems, Pleasanton, Calif.). The HCV RNA extraction step can be automated in the Cobas Ampliprep device. In this work, we show that the dynamic range of HCV RNA quantification of the Cobas Ampliprep/Cobas Amplicor HCV Monitor v2.0 procedure is 600 to 200,000 HCV RNA IU/ml (2.8 to 5.3 log IU/ml), which does not cover the full range of HCV RNA levels in infected patients. Any sample containing more than 200,000 IU/ml (5.3 log IU/ml) must thus be retested after dilution for accurate quantification. These results emphasize the need for commercial HCV RNA quantification assays with a broader range of linear quantification, such as real-time PCR-based assays.

Antiviral Agents↗
PubMed1992

Systemic tocainide relieves mechanical hypersensitivity and normalizes the responses of hyperexcitable dorsal horn wide-dynamic-range neurons after transient spinal cord ischemia in rats.

In the present study we examined the effect of systemic tocainide on sensory hypersensitivity in rats after spinal cord ischemia induced by a photochemical technique. After induction of spinal cord ischemia the rats exhibited a sensory disturbance which was mainly expressed as vocalization to innocuous cutaneous mechanical stimuli (allodynia) in the flank area during the following several days. Tocainide at 75 mg/kg i.p., but not 50 mg/kg i.p., significantly increased the vocalization threshold to mechanical pressure for 2 h. The effect of intraarterial (i.a.) tocainide on the responses of dorsal horn wide-dynamic-range (WDR) neurons to suprathreshold electrical stimulation of their receptive fields was also examined in normal rats and after transient spinal cord ischemia, at a time when the animals exhibited typical behavioral allodynia in the dermatomes innervated by the ischemic spinal segments. In normal rats, tocainide (50 mg/kg i.a.) strongly suppressed the responses of WDR neurons to C fiber input with lesser effect on A fiber input. In allodynic rats, tocainide suppressed the augmented A and C fiber mediated responses of WDR neurons to the extent that their responses were similar to those seen in normal rats without tocainide. There was no difference in the overall depression of A and C fiber mediated input by tocainide between normal and allodynic rats. The present results demonstrated the analgesic effect of systemic tocainide in relieving allodynia in rats and indicated that systemic local anesthetics, at doses that do not block nerve conduction, can be effective in suppressing dorsal horn WDR neuronal activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

High-resolution, large dynamic range fiber length measurement based on a frequency-shifted asymmetric Sagnac interferometer.

We propose and experimentally demonstrate a single-mode fiber length and dispersion measurement system based on what we believe to be a novel frequency-shifted asymmetric Sagnac interferometer incorporating an acousto-optic modulator (AOM). By sweeping the driving frequency of the AOM, which is asymmetrically placed in the Sagnac loop, the optical length of the fiber can be determined by measuring the corresponding variation in the phase delay between the two counterpropagating light beams. Combined with a high-resolution data processing algorithm, this system yields a dynamic range from a few centimeters to 60 km (limited by our availability of long fibers) with a resolution of approximately 1 part per million for long fibers.

Journal Article↗
PubMed2000

The dynamic range for gain control of NMDA receptor-mediated synaptic transmission at a single synapse.

Although the level at which NMDA receptors (NMDARs) are activated can profoundly influence the direction and extent of long-term changes in synaptic strength, the probabilistic nature of quantal release at individual synapses makes it difficult to determine the dynamic operating range of NMDAR-mediated synaptic transmission. By continually driving glutamate release from a single high-fidelity auditory synapse with bursts of high-frequency stimuli, I show here that NMDAR-mediated EPSCs exhibited incremental summation in their amplitude and did not reach a plateau until six or seven consecutive stimuli into the train. An increase in the initial quantal output, by broadening presynaptic spikes with the potassium channel blocker tetraethylammonium (TEA, 0.2 mm), slightly increased the plateau amplitude at 200/300 Hz but shifted its peak temporally toward the earlier stimuli. These results suggest that the plateau amplitude in TEA reflects the activation of the entire population of synaptic NMDARs and hence the maximal gain of NMDAR-mediated synaptic transmission. This maximum was estimated to be 3.2-fold of the basal synaptic strength, giving a 31% occupancy of synaptic NMDARs by glutamate. Thus, synaptic NMDARs possess a broad dynamic range within which the activity-dependent control of synaptic strength and plasticity can potentially be tuned by the amount of Ca(2+) influx associated with different levels of NMDAR occupancy within the same synapse.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2000

The dynamic range of protein expression: a challenge for proteomic research.

Proteomic research, for its part, is benefiting enormously from the last decade of genomic research as we now have archived, annotated and audited sequence databases to correlate and query experimental data. While the two-dimensional electrophoresis (2-DE) gels are still a central part of proteomics, we reflect on the possibilities and realities of the current 2-DE technology with regard to displaying and analysing proteomes. Limitations of analysing whole cell/tissue lysates by 2-DE alone are discussed, and we investigate whether extremely narrow p/ranges (1 pH unit/25 cm) provide a solution to display comprehensive protein expression profiles. We are confronted with a challenging task: the dynamic range of protein expression. We believe that most of the existing technology is capable of displaying many more proteins than is currently achievable by integrating existing and new techniques to prefractionate samples prior to 2-DE display or analysis. The availability of a "proteomics toolbox", consisting of defined reagents, methods, and equipment, would assist a comprehensive analysis of defined biological systems.

Chemical Fractionation↗
PubMed1993

Digital dynamic range expansion applied to X-ray densitometric analysis of total hip replacement.

Due to the presence of the stiff prosthetic stem fitted in the medullary canal during total hip replacement, the surrounding cortex of the femur changes its density over time. This bone remodelling takes place with every type of total hip prosthesis; however, its intensity may vary between prostheses and patients. In the worst cases this process can lead to the late failure of the implant. To monitor such bone density evolution, we are developing a tailored Computer-aided Densitometric Image Analysis system (the major part of this our system uses an 8-bit commercial hardware with 256 levels of grey). The equivalent dynamic range of an X-ray picture is about 10 bits. In this paper we present a method to overcome these hardware limitations by improving the software. Using a double-exposure acquisition it is possible to build a 9-bit image that is good enough for most applications involving bone density measurement.

Absorptiometry, Photon↗
PubMed1990

Liposome flow injection immunoassay: implications for sensitivity, dynamic range, and antibody regeneration.

We have developed a liposome-based flow injection immunoassay (FIIA) system for quantitation of a clinical analyte, theophylline. With very minor changes in assay format, this procedure can also be used for the quantitation of anti-theophylline. Automated sequential analyses were performed at room temperature with picomole sensitivity and a day-to-day coefficient of variation of less than 5% for aqueous solutions. The system components include liposomes that contain fluorophores in their aqueous centers and an immobilized-antibody reactor column. The immunoreactor was regenerated hundreds of times over 3 months of continuous use with no measurable loss of antibody activity. The two assay formats studied produced distinct dynamic ranges for their respective analytes. The special advantages of using flow injection analysis for immunoassays and of using liposomes in FIIA are discussed.

Antibodies↗
PubMed2002

Regulated expression of proteins in yeast using the MAL61-62 promoter and a mating scheme to increase dynamic range.

The ability to express heterologous genes in yeast has become indispensable for many biological research techniques. Expression systems that can be regulated are particularly useful because they allow an experimenter to control the timing and levels of gene expression. Despite their many advantages, however, surprisingly few conditional expression systems are available for yeast. Moreover, of those that have been described, many are not ideal either because they have high background expression levels, low induced levels, or because they require restrictive growth conditions. Here we describe a conditional expression system that takes advantage of the yeast MAL62 promoter (MAL62p), which can be controlled by adding maltose or glucose to the growth medium to induce or repress transcription, respectively. In addition, we use a mating scheme to dramatically increase the dynamic range of expression levels possible. We show that MAL62p background activity can be effectively eliminated by maintaining expression constructs in a mal(-) yeast strain. High-level expression can be induced in diploids formed by mating the mal(-) strain with a MAL(+) strain. A similar mating scheme may be useful for other conditional expression systems as well. Among other uses, this approach should aid high throughput yeast two-hybrid assays, which rely on maintaining large libraries of expression strains, which are eventually mated to conduct assays for protein interactions. We demonstrate a two-hybrid system in which MAL62p is used in conjunction with the yeast GAL1 promoter to independently regulate expression of both hybrid proteins, and to allow detection of interactions involving toxic proteins.

Amino Acid Sequence↗
PubMed2007

Wide dynamic range detection of bidirectional flow in Doppler optical coherence tomography using a two-dimensional Kasai estimator.

We demonstrate extended axial flow velocity detection range in a time-domain Doppler optical coherence tomography (DOCT) system using a modified Kasai velocity estimator with computations in both the axial and transverse directions. For a DOCT system with an 8 kHz rapid-scanning optical delay line, bidirectional flow experiments showed a maximum detectable speed of >56 cm/s using the axial Kasai estimator without the occurrence of aliasing, while the transverse Kasai estimator preserved the approximately 7 microm/s minimum detectable velocity to slow flow. By using a combination of transverse Kasai and axial Kasai estimators, the velocity detection dynamic range was over 100 dB. Through a fiber-optic endoscopic catheter, in vivoM-mode transesophageal imaging of the pulsatile blood flow in rat aorta was demonstrated, for what is for the first time to our knowledge, with measured peak systolic blood flow velocity of >1 m/s, while maintaining good sensitivity to detect aortic wall motion at <2 mm/s, using this 2D Kasai technique.

Algorithms↗
PubMed2006

Flat ended steel wires, backscattering targets for calibrating over a large dynamic range.

A series of flat ended stainless steel wires was constructed and experimentally evaluated as point targets giving a calibrated backscattering over a large range (up to 72 dB) for ultrasound frequencies in the range 2 to 10 MHz. Over a range of 36 dB, theory was strictly followed (within +/- 1 dB), giving proportionality with the square of the frequency and the fourth power of the diameter. In this range, the relative scattering strength of targets does not depend on the frequency content of the ultrasound pulse. A deviation of maximal 5 dB at the low side is tentatively ascribed to a failure of simple theory for target diameters smaller than half a wavelength. For large diameters, backscattering is sensitive to orientation of the target: a numerical relation between misalignment and desired accuracy is proposed. A replication test for targets with a diameter of 0.24 mm gave equal scattering strengths within 0.8 dB. It is proposed to apply the targets for calibration of the dynamic range of a scanner and as point targets to establish resolution in three perpendicular directions, axial, lateral and elevational.

Calibration↗
PubMed2004

Ultra-high-efficiency strong cation exchange LC/RPLC/MS/MS for high dynamic range characterization of the human plasma proteome.

High-efficiency nanoscale reversed-phase liquid chromatography (chromatographic peak capacities of approximately 1000: Shen, Y.; Zhao, R.; Berger, S. J.; Anderson, G. A.; Rodriguez, N.; Smith, R. D. Anal. Chem. 2002, 74, 4235. Shen, Y.; Moore, R. J.; Zhao, R.; Blonder, J.; Auberry, D. L.; Masselon, C.; Pasa-Tolic, L.; Hixson, K. K.; Auberry, K. J.; Smith, R. D. Anal. Chem. 2003, 75, 3596.) and strong cation exchange LC was used to obtain ultra-high-efficiency separations (combined chromatographic peak capacities of >10(4)) in conjunction with tandem mass spectrometry (MS/MS) for characterization of the human plasma proteome. Using conservative SEQUEST peptide identification criteria (i.e., without considering chymotryptic or elastic peptides) and peptide LC normalized elution time constraints, the separation quality enabled the identification of proteins over a dynamic range of greater than 8 orders of magnitude in relative abundance using ion trap MS/MS instrumentation. Between 800 and 1682 human proteins were identified, depending on the criteria used for identification, from a total of 365 microg of human plasma. The analyses identified relatively low-level (approximately pg/mL) proteins (e.g., cytokines) coexisting with high-abundance proteins (e.g., mg/mL-level serum albumin).

Amino Acid Sequence↗
PubMed2001

Energized mitochondria increase the dynamic range over which inositol 1,4,5-trisphosphate activates store-operated calcium influx.

In eukaryotic cells, activation of cell surface receptors that couple to the phosphoinositide pathway evokes a biphasic increase in intracellular free Ca2+ concentration: an initial transient phase reflecting Ca2+ release from intracellular stores, followed by a plateau phase due to Ca2+ influx. A major component of this Ca2+ influx is store-dependent and often can be measured directly as the Ca2+ release-activated Ca2+ current (I(CRAC)). Under physiological conditions of weak intracellular Ca2+ buffering, respiring mitochondria play a central role in store-operated Ca2+ influx. They determine whether macroscopic I(CRAC) activates or not, to what extent and for how long. Here we describe an additional role for energized mitochondria: they reduce the amount of inositol 1,4,5-trisphosphate (InsP3) that is required to activate I(CRAC). By increasing the sensitivity of store-operated influx to InsP3, respiring mitochondria will determine whether modest levels of stimulation are capable of evoking Ca2+ entry or not. Mitochondrial Ca2+ buffering therefore increases the dynamic range of concentrations over which the InsP3 is able to function as the physiological messenger that triggers the activation of store-operated Ca2+ influx.

Animals↗
PubMed2006

A further study on the combined use of internal standard and isotope-labeled derivatization reagent for expansion of linear dynamic ranges in liquid chromatography-electrospray mass spectrometry.

The combined use of a so-called internal standard and the isotope-labeled derivatization reagent for the quantification of analytes for liquid chromatography-mass spectrometry (LC/MS) was further studied. The sample solution (containing the analytes and an internal standard) was derivatized with the light form of the derivatization reagent, 7-(N,N-dimethylaminosulfonyl)-4-(aminoethyl)piperazino-2,1,3-benzoxadiazole (DBD-PZ-NH(2)) or 7-(N,N-dimethylaminosulfonyl)-4-piperazino-2,1,3-benzoxadiazole (DBD-PZ). A standard solution of the analytes (containing an internal standard) was derivatized with the isotope (d(6))-labeled derivatization reagent, DBD-PZ-NH(2) (D) or DBD-PZ (D), and served as the isotope-labeled internal standards. The peak heights of the targeted analytes derivatives in the sample solution were corrected using those of the internal standard and the heavy form derivatives of the standards, and the calibration curves were constructed. The curve bending of the calibration curves caused by the ion suppression at the ion source was suppressed and the linear dynamic ranges of the calibration curves were expanded. The derivatives of DBD-PZ-NH(2) were about 10 times more sensitively detected than those of DBD-PZ derivatives and, therefore, DBD-PZ-NH(2) might be suitable for sensitive detection.

Chromatography, Liquid↗