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C Bell

Publications and source records attributed to C Bell.

At least 73 records · Page 4Linked to original sources
PubMed1999

Structural organization of the mormyrid electrosensory lateral line lobe

The electrosensory lateral line lobe (ELL) of mormyrid teleosts is the first central stage in electrosensory input processing. It is a well-developed structure with six main layers, located in the roof of the rhombencephalon. Its main layers are, from superficial to deep, the molecular, ganglionic, plexiform, granular, intermediate and deep fiber layers. An important input arises from electroreceptors, but corollary electromotor command signals and proprioceptive, mechanosensory lateral line and descending electrosensory feedback inputs reach the ELL as well. The ELL input is processed by at least 14 cell types, which frequently show plastic responses to different inputs. The large ganglionic and large fusiform cells are the ELL projection cells. They are glutamatergic and project to the isthmic preeminential nucleus and the midbrain lateral toral nucleus. Interneurons are located in all ELL layers and are mostly GABAergic. The most remarkable interneurons are large multipolar cells in the intermediate layer, which have myelinated dendrites making presynaptic terminals contacting granular cells. With respect to the synaptic organization and microcircuitry of the ELL, a number of qualitative and quantitative aspects have been elucidated using electron microscopical and intracellular labeling techniques. However, the pathways by which primary afferent input influences the ELL projection cells are still undetermined: primary afferents do not seem to contact large fusiform or large ganglionic cells directly, but seem to terminate exclusively on granular cells, the axonal properties of which are not known. Consequently, more information of the structural organization of the ELL is still necessary for a detailed understanding of the neural basis of the plastic electrosensory input processing in mormyrids.

Journal Article↗
PubMed1999

Paroxetine and its uses in psychiatry.

Paroxetine is one of the specific serotonin-reuptake inhibitor antidepressants which is used in a variety of psychiatric disorders. It has recently gained considerable publicity because of its use in social anxiety disorder and its subsequent labelling by the media as a 'lifestyle drug'. This review summarizes current indications for paroxetine and outlines doses and duration of treatment for each condition.

Antidepressive Agents, Second-Generation↗
PubMed1999

Novel PCR-based diagnostic tools for Charcot-Marie-Tooth type 1A and hereditary neuropathy with liability to pressure palsies.

The majority of cases of Charcot-Marie-Tooth type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are the result of DNA duplications and deletions respectively of a 1.5 Mb region on 17p11.2. The region contains the peripheral myelin protein 22 gene (PMP-22) and is flanked by homologous proximal and distal CMT1A-REP elements. The majority of duplications and deletions arise during meiotic recombination following misalignment and unequal crossing-over between the proximal and distal CMT1A-REP elements. The cross-over breakpoints are most frequently located within a 1.7 Kb hotspot of recombination and produce novel duplication or deletion junctional CMT1A-REPs with unique restriction patterns. Here we describe the use of PCR based tests, which amplify a 3.6 Kb region including the 1.7 Kb hotspot from specific CMT1A-REPs, for the rapid diagnosis of CMT1A and HNPP patients. In an analysis of 96 CMT1A and 30 HNPP patients, duplication and deletion events were detected in all samples with cross-over breakpoints known to be within the region amplified by PCR.

Charcot-Marie-Tooth Disease↗
PubMed1999

Oxygen uptake kinetics of older humans are slowed with age but are unaffected by hyperoxia.

Cross-sectional studies have compared the oxygen uptake (VO2) kinetics during the on-transient of moderate intensity exercise in older and younger adults. The slower values in the older adults may have been due to an age-related reduction in the capacity for O2 transport or alternatively a reduced intramuscular oxidative capacity. We studied: (1) the effects of ageing on VO2 kinetics in older adults on two occasions 9 years apart, and (2) the effect of hyperoxia on VO2 kinetics at the second test time. After a 9 year period, follow-up testing was undertaken on seven older adults (78 +/- 5 years, mean +/- S.D.). They each performed six repeats of 6 min bouts of constant-load cycle exercise from loadless cycling to 80% of their ventilatory threshold. They breathed one of two gas mixtures (euoxia: inspired O2 fraction, FI,O2, 0.21; hyperoxia: FI,O2, 0.70) on different trials determined on a random basis. Breath-by-breath VO2 data were time aligned and ensemble averaged. VO2 kinetics, modelled with a single exponential from phase 2 onset (+20 s) to steady state and described by the exponential time constant (tau) were compared with data collected from the same adults 9 years earlier. One-way repeated measures analysis of variance revealed that tau was slowed significantly with age (from 30 +/- 8 to 46 +/- 10 s), but was unaffected by hyperoxia (43 +/- 15 s). We concluded that: (1) in older adults studied longitudinally over a 9 year period, the on-transient VO2 kinetics are slowed, in agreement with, but to a greater extent, than from cross-sectional data; and (2) the phase 2 time constant (tau) for these older adults was not accelerated by hyperoxic breathing. Thus the expected hyperoxia-induced increase in the capacity for O2 transport was not associated with faster on-transient VO2 kinetics suggesting either that O2 transport may not limit VO2 kinetics during the 8th decade, or that O2 transport was not improved with hyperoxia.

Aged↗
PubMed1999

The effects of caffeine on the kinetics of O2 uptake, CO2 production and expiratory ventilation in humans during the on-transient of moderate and heavy intensity exercise.

In order to test the hypothesis that glycogen sparing observed early during exercise following caffeine ingestion was a consequence of tighter metabolic control reflected in faster VO2 kinetics, we examined the effect of caffeine ingestion on oxygen uptake (VO2), carbon dioxide production (VCO2) and expiratory ventilation (VE) kinetics at the onset of both moderate (MOD) and heavy (HVY) intensity exercise. Male subjects (n = 10) were assigned to either a MOD (50% VO2,max, n = 5) or HVY (80% VO2,max, n = 5) exercise condition. Constant-load cycle ergometer exercise was performed as a step function from loadless cycling 1 h after ingestion of either dextrose (placebo, PLAC) or caffeine (CAFF; 6 mg (kg body mass)-1). Alveolar gas exchange was measured breath-by-breath. A 2- or 3-component exponential model, fitted through the entire exercise transient, was used to analyse gas exchange and ventilatory data for the determination of total lag time (TLT: the time taken to attain 63% of the total exponential increase). Caffeine had no effect on TLT for VO2 kinetics at either exercise intensity (MOD: 36 +/- 14 s (PLAC) and 41 +/- 10 s (CAFF); HVY: 99 +/- 30 s (PLAC) and 103 +/- 26 (CAFF) (mean +/- S.D.)). TLT for VE was increased with caffeine at both exercise intensities (MOD: 50 +/- 20 s (PLAC) and 59 +/- 21 s (CAFF); HVY: 168 +/- 35 s (PLAC) and 203 +/- 48 s (CAFF)) and for VCO2 during MOD only (MOD: 47 +/- 14 s (PLAC) and 53 +/- 17 s (CAFF); HVY: 65 +/- 13 s (PLAC) and 69 +/- 17 s (CAFF)). Contrary to our hypothesis, the metabolic effects of caffeine did not alter the on-transient VO2 kinetics in moderate or heavy exercise. VCO2 kinetics were slowed by a reduction in CO2 stores reflected in pre-exercise and exercise endtidal CO2 pressure (PET,CO2) and plasma PCO2 which, we propose, contributed to slowed VE kinetics.

Adult↗
PubMed1998

A bedside clinical prediction rule for detecting moderate or severe aortic stenosis.

OBJECTIVE: To evaluate a bedside clinical prediction rule for detecting moderate or severe aortic stenosis. DESIGN: Cross-sectional study with independent comparison to a diagnostic reference standard, doppler echocardiography. SETTING: Urban university hospital. PARTICIPANTS: Consecutive hospital inpatients (n = 124) who had been referred for echocardiography. MEASUREMENTS AND MAIN RESULTS: Participants were examined by a third-year general internal medicine resident and a staff general internist. We hypothesized in advance that absence of a murmur over the right clavicle would rule out aortic stenosis, while the presence of three or four associated findings (slow carotid artery upstroke, reduced carotid artery volume, maximal murmur intensity at the second right intercostal space, and reduced intensity of the second heart sound) would rule in aortic stenosis. Study physicians were unaware of echocardiographic findings. The outcome was echocardiographic moderate or severe aortic stenosis, defined as a valve area of 1.2 cm2 or less, or a peak instantaneous gradient of 25 mm Hg or greater. Absence of a murmur over the right clavicle ruled out aortic stenosis (likelihood ratio [LR] 0.10; 95% confidence interval [CI] 0.01, 0.44). The presence of three or four associated findings ruled in aortic stenosis (LR 40; 95% CI 6.6, 240). If a murmur was present over the right clavicle, but no more than two associated findings were present, then the examination was indeterminate (LR 1.8; 95% CI 0.93, 2.9). CONCLUSION: A clinical prediction rule, using simple bedside maneuvers, accurately ruled in and ruled out aortic stenosis.

Adult↗
PubMed1998

Kinetic analyses of Biolog community profiles to detect changes in inoculum density and species diversity of river bacterial communities.

The kinetics of response curves from Biolog community profiles for heterotrophic bacteria from a river in Nova Scotia, Canada have been analyzed to generate lag, slope, and asymptote parameters. The river water samples were treated with one of three supplements of Escherichia coli (in situ levels, 10(3) CFU/mL, or 10(6) CFU/mL) and one of five concentrations of chlorine (0, 1, 3, 5, or 7 ppm) to satisfy a full factorial design. The chlorine treatments decreased the inoculum density by up to 2 log values and decreased the species evenness. The E. coli supplements increased the inoculum density and decreased the species richness. Examination of the asymptotes did not reveal any significant effects owing to E. coli, but differences owing to the chlorine were detected. Analyses of the slopes showed a similar insignificance of the effects of E. coli and a lack of treatment effect owing to chlorine. The lag analyses also showed no significant E. coli effects, but showed a significant effect owing to chlorine. The discrepancy produced with the slope analysis (i.e., no chlorine effect) may represent an anomaly of the Biolog community approach. The use of lag phase was impaired because of the problem of infinite lags from wells that had no response, but a principle component analysis with a reduced set of substrates did suggest some influence of E. coli on the community profile. An examination of the substrates metabolized by the river water compared with pure E. coli revealed that the Biolog profiles of the river communities were not a simple summation of the component parts. In light of the lack of uniformity between these analyses, where the outcome depended on which parameter was used, caution is advised in interpreting Biolog community profiles on the basis of only one parameter.

Analysis of Variance↗
PubMed1997

Isolation and characterization of 2'-fluoro-, 2'-amino-, and 2'-fluoro-/amino-modified RNA ligands to human IFN-gamma that inhibit receptor binding.

CD4+ Th cells produce cytokines that play a pivotal role in the induction and regulation of cell-mediated and humoral immunity. Th1 cells, characterized by their secretion of IFN-gamma, induce macrophage cytotoxicity, delayed hypersensitivity, and enhanced cellular immunity. Secretion of IFN-gamma may even suppress Th2-enhanced humoral immunity. A counterproductive Th1 response and concomitant secretion of IFN-gamma may result in inflammatory and autoimmune diseases. IFN-gamma regulation of T cell function has potential for therapeutic intervention. To isolate high affinity oligonucleotide inhibitors of IFN-gamma activity, combinatorial libraries of RNA molecules modified at the 2' position of pyrimidine nucleotides with fluoro (F), amino (NH2), or a mixture of F and NH2 (2'-F/NH2) were screened using the SELEX (systematic evolution of ligands by exponential enrichment) combinatorial chemistry process. Each modified library of RNA molecules provides an expanded repertoire of molecules with increased structural diversity and unique binding properties. This added diversity increases the possibility of isolating molecules with the desired functional properties. These RNAs modified at the 2' position have also been shown to be nuclease resistant. High affinity ligands to human IFN-gamma from each modified library were isolated and characterized. The K(d)s of these ligands were determined and their secondary structures were predicted. The specificity of these ligands for IFN-gamma binding was confirmed, and their ability to inhibit binding of IFN-gamma to its receptor on A549 human lung carcinoma cells was determined. A 2'-NH2-modified ligand (2'-NH2-30) is described that binds IFN-gamma with high affinity and inhibits IFN-gamma-induced expression of MHC class I and ICAM-1 by human myeloid leukemia cells.

Base Sequence↗
PubMed1997

Does this patient have an abnormal systolic murmur?

Our objective was to review the available evidence of the precision and accuracy of the clinical examination for abnormal systolic murmurs. We conducted a MEDLINE search, manually reviewed all reference lists, and contacted authors of published studies. Each study was independently reviewed by 2 observers and graded for methodologic quality. We found that most studies were conducted using cardiologist examiners. In the clinical setting, the reliability of detecting systolic murmurs was fair (kappa, 0.30-0.48). The most useful findings for ruling in aortic stenosis are a slow rate of rise of the carotid pulse (positive likelihood ratio, 2.8-130), mid to late peak intensity of the murmur (positive likelihood ratio, 8.0-101), and decreased intensity of the second heart sound (positive likelihood ratio, 3.1-50). The most useful finding for ruling out aortic stenosis is the absence of murmur radiation to the right carotid artery (negative likelihood ratio, 0.05-0.10). Smaller, lower-quality studies indicate that cardiologists can accurately rule in and rule out mitral regurgitation, tricuspid regurgitation, hypertrophic cardiomyopathy, and echocardiographic mitral valve prolapse. We conclude that the clinical examination by cardiologists is accurate for detecting various causes of abnormal systolic murmurs. Studies of the clinical examination by noncardiologists are needed.

Cardiology↗