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Biomedical subjects

R A Cooper

Publications and source records attributed to R A Cooper.

At least 91 records · Page 5Linked to original sources
PubMed1998

Comparison of thallium-201 and gallium-67 scintigraphy in the evaluation of non-Hodgkin's lymphoma.

BACKGROUND: Gallium-67 (Ga-67) is widely used in the assessment of patients with lymphoma. Although highly sensitive in Hodgkin's disease and high grade non-Hodgkin's lymphoma (NHL), its sensitivity is reported to be reduced in lower grades of NHL. Several series have suggested that thallium-201 (Tl-201) may be more useful than Ga-67 in the evaluation of low and possibly intermediate grade NHL. AIM: To compare the sensitivity and relative avidities (uptakes) of Tl-201 and Ga-67 in patients with NHL. METHODS: A total of 36 pairs of studies were performed in 33 patients (14 male: 19 female; age range 16-84 years, mean 55 years). All had whole body Ga-67 (400 MBq) and Tl-201 (100-200 MBq) studies (interval 0-three days) which were read by two experienced nuclear medicine physicians blinded to clinical history and results of other investigations. RESULTS: Tl-201 had a higher sensitivity and avidity than Ga-67 in patients with low grade NHL. In contrast, Ga-67 was slightly more sensitive and had a higher avidity in patients with both intermediate and high grade NHL. CONCLUSIONS: We conclude that Tl-201 is more sensitive and avid for low grade NHL than Ga-67 and that consideration should be given to its use in this condition in conjunction with Ga-67 as it may provide complementary information. Routine use in intermediate grade NHL is less convincing as Ga-67 was superior in most cases. Ga-67 is more sensitive than Tl-201 in assessment of high grade NHL.

Adolescent↗
PubMed1998

Kinematic characterization of wheelchair propulsion.

Rehabilitation scientists and biomedical engineers have been investigating wheelchair propulsion biomechanics in order to prevent musculoskeletal injuries. Several studies have investigated wheelchair propulsion biomechanics; however, few have examined wheelchair propulsion stroke patterns. The purpose of this study was to characterize wheelchair propulsion stroke patterns by investigating joint accelerations, joint range of motions, wheelchair propulsion phases, and stroke efficiency. Seven experienced wheelchair users (5 males, 2 females) were filmed using a three-camera motion analysis system. Each subject pushed a standard wheelchair fitted with a force-sensing pushrim (SMARTWheel) at two speeds (1.3 and 2.2 m/s). The elbow angle was analyzed in the sagittal plane, while the shoulder joint was analyzed in the sagittal and frontal planes. Three distinctly different stroke patterns: semi-circular (SC), single looping-over-propulsion (SLOP), and double looping-over-propulsion (DLOP), were identified from the kinematic analysis. Through our analysis of these patterns, we hypothesized that SC was more biomechanically efficient than the other stroke patterns. Future studies using a larger number of subjects and strokes may reveal more significant distinctions in efficiency measures between stroke patterns.

Biomechanical Phenomena↗
PubMed1998

High tumor angiogenesis is associated with poorer survival in carcinoma of the cervix treated with radiotherapy.

The purpose of this study was to examine the relationship between tumor angiogenesis and prognosis in carcinoma of the cervix treated with radiotherapy with a median follow-up time of 55 months. A retrospective study was carried out on 111 patients. Formalin-fixed, paraffin-embedded tumor biopsies were stained with anti-factor VIII using immunohistochemistry. Tumor angiogenesis was assessed by scoring the distance to the closest microvessel from random points within the tumor and the intratumor microvessel density (IMD) in the areas of highest neovascularization. High vascularity, as measured by both methods, was associated with a poor prognosis but was only significant for IMD. The 5-year survival rates for tumors with high versus low values were 50 and 65%, respectively. IMD was a significant prognostic factor within a Cox multivariate analysis. Higher tumor vascularity was associated with lower overall survival and locoregional control, but this association was not significant in the case of metastasis-free survival. The method used to assess tumor vascularity is important. The level of angiogenesis in carcinoma of the cervix is an independent prognostic parameter.

Adenocarcinoma↗
PubMed1997

Haloalkanoate dehalogenase II (DehE) of a Rhizobium sp.--molecular analysis of the gene and formation of carbon monoxide from trihaloacetate by the enzyme.

A 3-kb EcoRI fragment of genomic DNA from a Rhizobium sp. cloned into pUC19 endowed Escherichia coli K-12 with the ability to grow, albeit slowly, with 2-chloropropionic acid as substrate. The construct expressed weakly a gene that encoded a non-stereospecific 2-chloropropionic acid dehalogenase (dehalogenase II; DehE). The dehE gene was not closely linked to the organism's other two dehalogenase genes, dehD and dehL. The derived amino acid sequence of DehE showed little identity with DehD or DehL, but there was significant identity to two other dehalogenases that act non-selectively on 2-chloropropionic acid. The fragment carried a truncated ORF upstream of dehE that was 51% identical to a positively acting regulatory protein, DehR, required for expression of a Pseudomonas putida dehalogenase gene. In its complete form this gene could encode the Rhizobium sp. dehalogenase-regulatory protein. DehE dehalogenated tribromoacetic acid completely, forming stoichiometric amounts of carbon monoxide and carbon dioxide as the other products.

Acetates↗
PubMed1997

Internal cardioversion of atrial fibrillation: marked reduction in defibrillation threshold with dual current pathways.

BACKGROUND: The ultimate acceptance of a fully automatic atrial defibrillator will depend on the reduction of pain to acceptable levels, requiring a marked decrease in defibrillation thresholds. The purpose of this study was to determine whether atrial defibrillation thresholds can be reduced by sequential shocks delivered through two current pathways. METHODS AND RESULTS: Sustained atrial fibrillation was induced with rapid atrial pacing in 12 adult sheep. Defibrillation electrodes were positioned in the right atrial appendage (RAap), distal coronary sinus (DCS), proximal coronary sinus (CSos), main/left pulmonary artery junction (PA), and right ventricular apex (RV). Single-capacitor biphasic waveforms (3/1 ms) were delivered through combinations of these electrodes. Probability-of-success curves were determined for single shocks with a single current pathway and sequential shocks with either single- or dual current pathways. The ED50 for delivered energy for the dual current pathway RAap to DCS then CSos to PA was 0.36+/-0.13 J, which was significantly lower than the ED50 of the standard single current pathway RAap to DCS (1.31+/-0.3 J) and was significantly lower than all other configurations tested. CONCLUSIONS: Internal atrial defibrillation thresholds can be markedly reduced with two sequential biphasic shocks delivered over two current pathways compared with the standard single shock delivered over a single current pathway or with sequential shocks delivered over a single current pathway.

Animals↗
PubMed1997

Internal atrial defibrillation in humans. Improved efficacy of biphasic waveforms and the importance of phase duration.

BACKGROUND: The optimal waveform for internal atrial defibrillation (IAD) in humans is unknown. This study tested the effect of waveform duration and phase duration on the efficacy of biphasic waveforms for IAD. METHODS AND RESULTS: Electrodes were positioned in the right atrial appendage and coronary sinus in 13 patients. In part 1, the atrial defibrillation thresholds (ADFTs) for 5 monophasic waveforms (2, 4, 6, 10, and 20 ms) and 5 symmetrical biphasic waveforms (1/1, 2/2, 3/3, 5/5, and 10/10 ms) were compared in 6 patients. In part 2, the ADFTs for two asymmetrical biphasic waveforms (7.5/2.5 and 2.5/7.5 ms) were compared with those for a symmetrical biphasic waveform (5/5 ms) and a monophasic waveform (10 ms) in 7 patients. In part 1, biphasics with total durations of 4 to 20 ms had significantly lower ADFTs than monophasic waveforms of the same total duration. For a total duration of 2 ms, there was no significant difference in ADFTs between the biphasic and the monophasic waveforms. There was no difference between symmetrical biphasic waveforms of 4 to 20 ms. In part 2, the 7.5/2.5 ms asymmetrical biphasic had significantly lower ADFTs than the three other waveforms tested. Both the 7.5/2.5 ms asymmetrical and the 5/5 ms symmetrical biphasic waveform had significantly lower ADFTs than the 2.5/7.5 ms asymmetrical biphasic and the 10 ms monophasic waveforms. CONCLUSIONS: For IAD in humans, biphasic waveforms were more efficacious than monophasic waveforms. This improved efficacy is related to the total duration of the biphasic waveform and each individual phase duration of the biphasic waveform.

Adult↗
PubMed1997

On the amine oxidases of Klebsiella aerogenes strain W70.

Klebsiella aerogenes W70 was reported previously to produce a membrane-associated tyramine oxidase (TynA) that did not act on 2-phenylethylamine. Subsequently, a gene cloned from K. aerogenes W70 produced a soluble amine oxidase (MaoA) that acted readily on 2-phenylethylamine and tyramine. This enzyme appeared to be equivalent to a 2-phenylethylamine oxidase of Escherichia coli K-12 (MaoA) but was assumed to be the originally described K. aerogenes W70 tyramine oxidase (TynA). However, as described here, whole cells and cell-free extracts of K. aerogenes W70 showed only the tyramine oxidase (TynA) that is inactive against 2-phenylethylamine and not the maoA gene product. It seems that the organism has two amine oxidase genes, tynA and maoA, but only tynA is expressed. Hence, data relating to the expression of the K. aerogenes W70 tynA gene cannot be assumed to apply to the maoA gene of E. coli K-12 because they encode different enzymes.

Amine Oxidase (Copper-Containing)↗
PubMed1997

Performance of selected lightweight wheelchairs on ANSI/RESNA tests. American National Standards Institute-Rehabilitation Engineering and Assistive Technology Society of North America.

OBJECTIVE: This study provides data for clinicians and wheelchair users to compare the durability, stability, and cost effectiveness of three different lightweight wheelchair models: the Everest & Jennings EZ Lite, the Invacare Rolls 2000, and the Quickie Designs Breezy. A second objective was to compare the results from this study to those published for ultralight and institutional depot wheelchairs. DESIGN: Randomized standards testing of three wheelchair models from each manufacturer (nine wheelchairs total). RESULTS: There were no significant differences (p > .05) in fatigue life, life-cycle cost, or static stability between the three models of lightweight wheelchairs (ie, EZ Lite, Rolls 2000, or Breezy). There were, however, significant differences (p < .05) in fatigue life among the lightweight wheelchairs of this study and the published results for ultralight rehabilitation wheelchairs and for depot wheelchairs. The lightweight wheelchairs had an average fatigue life greater than the depot wheelchairs but less than the rehabilitation wheelchairs. A depot-type wheelchair was defined as a manual wheelchair designed for hospital or institutional use. At lightweight wheelchair was defined as a manual wheelchair with minimal adjustments designed for individual or institutional use. An ultralight rehabilitation wheelchair was defined as a manual wheelchair designed for an individual's use as a long-term mobility aid. CONCLUSION: The three models of lightweight wheelchairs tested are substantially similar and their fatigue lives are significantly (p < .05) lower than rehabilitation wheelchairs. Ultralight rehabilitation wheelchairs are the most cost effective over the life of the wheelchair, costing 3.4 times less (dollars per life cycle) than depot wheelchairs, and 2.3 times less (dollars per life cycle) than the lightweight wheelchairs tested in this study.

Cost-Benefit Analysis↗
PubMed1997

Wrist biomechanics during two speeds of wheelchair propulsion: an analysis using a local coordinate system.

OBJECTIVE: To describe motion, forces, and moments occurring at the wrist in anatomic terms during wheelchair propulsion; to obtain variables that characterize wrist function during propulsion and are statistically stable; and to determine how these variables change with speed. DESIGN: Case series. SETTING: Biomechanics laboratory. PARTICIPANTS: Convenience sample of Paralympic athletes (n = 6) who use manual wheelchairs for mobility and have unimpaired arm function. INTERVENTION: Subjects propelled a standard wheelchair on a dynamometer at 1.3m/sec and 2.2m/sec. Biomechanical data were obtained using a force and moment sensing pushrim and a motion analysis system. MAIN OUTCOME MEASURES: Maximum angles, forces, and moments in a local, wrist coordinate system. Each variable was evaluated for stability using Cronbach's alpha. Measures found to be stable (infinity > .8) at each speed were then compared to look for differences associated with speed. RESULTS: The following measures were stable at both speeds: maximum wrist flexion, ulnar deviation, and radial deviation angles, peak moments acting to cause wrist flexion, extension, and ulnar deviation, peak shear forces acting between the radial and ulnar styloids, and peak axial force acting at the wrist. Of these measures, the following measures differed (p < .05) between speeds (+/-SD): maximum radial deviation (1.3m/sec, 25.1 degrees +/- 9.0; 2.2m/sec, 21.4 degrees +/- 6.9), peak flexion moment (1.3m/ sec, 3.4N.m +/- 3.0; 2.2m/sec, 5.2N.m +/- 3.7), peak extension moment (1.3m/sec, 10.4N.m +/- 4.8; 2.2m/sec, 13.6N.m +/- 5.1), peak shear acting from the ulnar styloid to the radial styloid (1.3m/sec, 2.3N +/- 2.7, 2.2m/sec, 8.3N +/- 7.5) and maximum axial force (1.3m/sec, 50.9N +/- 18.2; 2.2m/sec, 65.9N +/- 27.6). CONCLUSION: This study found stable parameters that characterize wrist biomechanics during wheelchair propulsion and varied with speed. Ultimately these parameters may provide insight into the cause and prevention of wrist injuries in manual wheelchair users.

Adult↗
PubMed1997

Uncertainty analysis for wheelchair propulsion dynamics.

Wheelchair propulsion kinetic measurements require the use of custom pushrim force/moment measuring instruments which are not currently commercially available. With the ability to measure pushrim forces and moments has come the development of several dynamic metrics derived for analyzing key aspects of wheelchair propulsion. This paper presents several of the equations used to calculate or derive the primary variables used in the study of wheelchair propulsion biomechanics. The uncertainties for these variables were derived, and then numerically calculated for a current version of the SMARTWheel. The uncertainty results indicate that the SMARTWheel provides data which has better than 5 to 10% uncertainty, depending upon the variable concerned, at the maximum, and during most of the propulsion phase the uncertainty is considerably smaller (i.e., approximately 1%). The uncertainty analysis provides a more complete picture of the attainable accuracy of the SMARTWheel and of the degree of confidence with which the data can be recorded. The derivations and results indicate where improvements in measurement of wheelchair propulsion biomechanical variables are likely to originate. The most efficient approach is to address those variables in the design of the system which make the greatest contribution to the uncertainty. Future research will focus on the point of force application and examination of nonlinear effects.

Persons with Disabilities↗
PubMed1997

An analysis of work postures of manual wheelchair users in the office environment.

The goal of this project was to examine the difficulties manual wheelchair users experience in office activities and ascertain whether such problems may be due to poor relationships between the equipment and the users. Sixty adult manual wheelchair users completed a questionnaire about problems encountered in office activities. Filing and writing were the most problematic activities for this group. Phase II of this study consisted of videotaping four subjects performing each activity in their personal office environments, and having them complete a second questionnaire on body-specific locations of discomfort. Videotaped postures and reports of discomfort were matched to determine the existence of poor equipment-user relationships. In filing, low back pain may have been due to bending forward to access lower drawers while seated. For writing, an inappropriate desk-wheelchair relationship that required subjects to bend forward with their arms on a surface that was too high may have caused back, shoulder, and neck discomfort.

Adult↗
PubMed1997

Methods for determining three-dimensional wheelchair pushrim forces and moments: a technical note.

This technical note illustrates that some of the differences that have been reported regarding wheelchair propulsion may be due to the methods used to calculate key variables. Wheelchair ambulation is a very important form of locomotion that lacks a standard pushrim force and moment analysis system. We have developed tools for analyzing upper limb biomechanics during manual wheelchair propulsion. Among the tools is a system that allows the direct measurement of global coordinate forces F(x), F(y), F(z) and corresponding moments. The analytical techniques presented here allow calculation of radial (F(r)) and tangential (F(t)) forces, the determination of point of force application (PFA), and the moment applied by the hand (M(hz)). Our results show that the PFA can be calculated from kinetic data. Comparison of the PFA to the second metacarpophalangeal (MP) joint, calculated from kinematic data and used in previous studies, resulted in a 0.2 radian difference on average, with the PFA showing greater variation near the beginning and ending of the propulsion phase. Analysis of methods for calculating the applied tangential force showed that using the PFA provides a more accurate measurement of this force than the previous method of assuming negligible hand-moment contribution. The hand moment was compared using the calculated PFA and assuming the PFA was coincident with the second MP joint. Both methods provided similar results with a mean difference of 0.6 N x m. The methods presented in this paper provide a framework for analyzing wheelchair propulsion forces and moments.

Arm↗
PubMed1996

Cloning, sequencing and expression in Escherichia coli of two Rhizobium sp. genes encoding haloalkanoate dehalogenases of opposite stereospecificity.

A 6.5-kp EcoRI fragment of genomic DNA from a Rhizobium sp. cloned into pUC19 was able to endow Escherichia coli K-12 with the novel ability to grow at the expense of 2-chloropropionic acid. Subcloning showed that this property was a consequence of two dehalogenases encoded on a 2.2-kb PstI fragment. Further subcloning of the PstI fragment led to two constructs that encoded, separately, dehalogenase activity that acted stereospecifically on D-2-chloropropionic acid and L-2-cloropropionic acid, respectively. The genes encoding these two stereospecific dehalogenases have been sequenced and shown to be separated by 177 bp of non-coding DNA. Expression of the dehalogenase genes involved the vector promoter, suggesting that the anticipated Rhizobium sp. regulatory sequences were not functional in E. coli. Comparison of the deduced amino acid sequences of the two dehalogenases (18% identity) indicated with any other 2-chloropropionic acid dehalogenase studied so far.

Amino Acid Sequence↗