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Biomedical subjects

R A Cooper

Publications and source records attributed to R A Cooper.

At least 109 records · Page 6Linked to original sources
PubMed1996

A simple procedure for determining the aqueous half-lives of pyrrolic metabolites of pyrrolizidine alkaloids.

We report a simple and rapid procedure for estimating the aqueous half-lives of the reactive metabolites of pyrrolizidine alkaloids that are responsible for toxicity. The metabolites (dehydroalkaloids; DHAs) were rapidly added to a 0.5 mM HEPES solution, pH 8.0. The subsequent fall in pH, due to ester hydrolysis, was followed potentiometrically. The change in pH was well described by single-component exponential decay, allowing the derivation of rate constants and half-lives of hydrolysis. Half-lives varied from 0.31 sec for dehydro-7-acetyllycopsamine to 5.36 sec for dehydrotrichodesmine. The results support the view that alkaloids whose DHA metabolites have longer half-lives produce greater extrahepatic toxicity.

Animals↗
PubMed1996

Pushrim forces and joint kinetics during wheelchair propulsion.

OBJECTIVE: To investigate pushrim forces and joint kinetics during wheelchair propulsion and to discuss the differences between inexperienced and experienced wheelchair users. DESIGN: Cohort study. SETTING: Human engineering laboratory at a state university. SUBJECTS: Four men who use manual wheelchairs for mobility and four nondisabled men who did not have extensive experience pushing a wheelchair; all subjects were asymptomatic for upper extremity pain or injury. METHODS: Subjects pushed a commonly used wheelchair fitted with a force-sensing pushrim on a stationary wheelchair dynamometer. Video and force data were collected for 5 strokes at one speed of propulsion. Pushrim forces and net joint forces and moments were analyzed. MAIN OUTCOME MEASURES: Pushrim forces, radial (Fr) and tangential (Ft), were analyzed and compared for both groups in relation to peak values and time to peak values and as ratios of overall forces generated. Net joint forces and moments were analyzed in a similar fashion. RESULTS: Pushrim forces and joint moments were similar to those previously reported, with radial forces averaging between 34 and 39N and tangential forces ranging on average between 66 and 95N. Tangential forces were higher than radial forces, and mean ratios of tangential forces to the resultant force were approximately 75%, whereas mean radial force ratios were approximately 22%. All subjects showed higher joint moments at the shoulder than at the elbow or wrist. A large component of vertical reaction force was seen at the shoulder. Significant differences (p < .05) were found between groups for peak tangential force and time to peak tangential and peak vertical forces, with wheelchair users having lower values and longer times to reach the peak values. CONCLUSIONS: Discrete variables from the force-time curves can be used to distinguish between wheelchair users and nonusers. The experienced users tended to push longer, used forces with lower peaks, and took longer time to reach peak values. This propulsive pattern may have been developed to reduce the chance of injury by minimizing the forces at the joints, as a means of maximizing efficiency or as a combination of these factors. More work investigating 3-dimensional forces and the influence of seating position and various conditions of propulsion such as speed changes, ramps, and directional changes on injury mechanisms needs to be completed.

Adult↗
PubMed1996

Cardiac perforation associated with continuous infusional chemotherapy.

The case history is reported of a 51-year-old man with metastatic colonic carcinoma who was receiving a continuous 5-fluorouracil infusion via a central venous catheter and who developed cardiac perforation and pericardial effusion. This complication has not previously been reported in association with continuous chemotherapy infusion.

Antineoplastic Agents↗
PubMed1996

A medical school-based GME consortium in Milwaukee.

Consortia have been recommended as a local mechanism for allocating housestaff positions and overseeing graduate medical education (GME) training programs. They also could serve to simplify the execution of a national health care policy in the future. Such a consortium has existed in Milwaukee for the last 16 years. It involves 23 health care institutions affiliated with the Medical College of Wisconsin. Known as the Medical College of Wisconsin Affiliated Hospitals, Inc. (MCWAH), this consortium employs 749 housestaff, for whom it provides salary and benefits. It also ensures accreditation of all of its residency and fellowship programs and assists in providing direction and coordination for the member institutions. The authors describe the genesis and operation of the MCWAH in detail. The accomplishments of existing consortia, in Milwaukee and elsewhere, indicate that a GME consortium should enable its members to function effectively and efficiently in meeting the challenging GME training requirements of the future.

Career Choice↗
PubMed1996

In vitro formation of a catabolic plasmid carrying Klebsiella pneumoniae DNA that allows growth of Escherichia coli K-12 on 3-hydroxybenzoate.

The four enzymes needed to convert 3-hydroxybenzoate to pyruvate and fumarate via the gentisate pathway, as well as a putative positive regulator protein, were encoded on an 8 kb Sphl fragment of Klebsiella pneumoniae DNA. The five genes were clustered in the order regulator-gentisate dioxygenase-fumarylpyruvate hydrolase-3-hydroxybenzoate monooxygenase-maleylpyruvate isomerase (mhbRDHMI), with the catabolic genes transcribed in the dioxygenase to isomerase direction. 2-Hydroxybenzoate was found to be a non-metabolizable inducer analogue for the mhb genes, supporting the view that gentisate rather than maleylpyruvate was the physiological inducer. The plasmid pNDR20 encoding the full gentisate catabolic pathway endowed Escherichia coli with the ability to grow on 3-hydroxybenzoate but the host cell appeared to be responsible for substrate uptake.

Cloning, Molecular↗
PubMed1996

Projection of the point of force application onto a palmar plane of the hand during wheelchair propulsion.

The objective of this study was to develop and test a method for projecting the pushrim point of force application (PFA) onto a palmar plane model of the hand. Repetitive wheelchair use often leads to hand and wrist pain or injury. The manner by which the hands grasp the pushrim and how the forces and moments applied to the pushrim are directed may contribute to the high incidence of pain and injury. The projections of the PFA onto the palmar surface model of the hand reside primarily within zone II. These results are in agreement with previous studies which have assumed the PFA to be coincident with one of the metacarpophalangeal (MP) joints. However, the results from three subjects show different PFA patterns within the palmar surface of the hand which can be related to each subject's propulsion pattern, and the PFA is not focused at a single MP joint. Projection of the world coordinates of the four hand marker system onto the palmar plane show the resolution to be within 3 mm, or one half the diameter of the passive reflective markers. The errors in the planar model assumption were greatest for the second and fifth MP markers. This was expected because as the hand grasp changes these markers do not remain coplanar. The results of this study indicate that new knowledge about how forces are applied by the hand onto the pushrim can be obtained using this method. This technical note provides insight into understanding the details within the kinetics of wheelchair propulsion and describes a technique for estimation of the PFA on the palmar surface of the hand. This technical note provides initial results from three different wheelchair users.

Adult↗
PubMed1996

Determination of wheelchair dynamic load data for use with finite element analysis.

A methodology is introduced for the experimental determination of the dynamic loads which act on a wheelchair. A box frame wheelchair and a cantilever frame wheelchair were tested on an ANSI/RESNA curb-drop tester [1]. The accelerations of an ANSI/RESNA test dummy [1] were recorded with an array of 12 accelerometers mounted as four three-axis groups. Signal averaging was used to produce a composite dynamic load history. The dynamic loads were calculated from the acceleration data and the inertia of the test dummy using software written by the authors. These loads were imported into a finite element program (ALGOR) [5], [6] as load cases. A prototype carbon fiber design was then optimized through design and analysis iterations. The results of the acceleration data indicate that the curb-drop test produces an asymmetric loading scheme. One of the rear wheels hits the ground before the other, placing most of the dynamic load on one side of the wheelchair. The favored side appears to be fixed at the time of setup. Preliminary results are given for the design of a modular carbon fiber wheelchair using the finite element (FE) method. These results indicate, however, that the use of a static factor of safety is, in most cases, inadequate for the dynamic loads present in the curb-drop test.

Acceleration↗
PubMed1996

Comparison of optimised planar scintigraphy with SPECT thallium, exercise ECG and angiography in the detection of coronary artery disease.

BACKGROUND: Thallium SPECT has been shown to be more sensitive than planar imaging in the detection of coronary heart disease (CAD) in a number of reported series. Early (< 10 minutes) redistribution on planar imaging has been demonstrated in clinical studies and this may partly contribute to its lower sensitivity. AIM: To determine whether thallium SPECT is superior to planar scintigraphy (with the timing of imaging performed optimally so that it was commenced within five minutes of injection) in the detection of CAD. METHODS: Planar and SPECT studies were performed in 44 patients with significant (> 70% stenosis) CAD, seven patients with borderline stenoses (50-69%) and in 18 patients with no significant CAD. RESULTS: The sensitivity of planar imaging was 66% which was higher than exercise ECG 54% (ns) but significantly lower than SPECT 86% (p < 0.005). The specificity of planar thallium scintigraphy was 100% which was higher than SPECT (83%) and significantly higher than exercise ECG 72% (p < 0.05). SPECT had a significantly higher sensitivity for LAD and single vessel disease than planar imaging and this was unrelated to a history of prior myocardial infarction. CONCLUSION: Even when planar imaging is timed optimally to minimise the impact of early redistribution, SPECT is more sensitive than either planar imaging or exercise ECG in the detection of CAD, but its specificity is lower.

Adult↗
PubMed1996

Internal cardioversion in two patients with atrial fibrillation refractory to external cardioversion.

A 26-year-old man underwent an electrophysiological study for evaluation of a history of congenital heart disease, presyncope, and wide complex tachycardia. During the study the patient developed sustained atrial fibrillation with a rapid ventricular response. A 17-year-old man with a history of sick sinus syndrome developed sustained atrial fibrillation. Both patients failed four attempts at external cardioversion with a maximum delivered energy of 360 J. Low energy cardioversion was successful in both patients using biphasic waveforms and internal transvenous defibrillation electrodes. Internal cardioversion using a transvenous electrode system can be successful in patients with atrial fibrillation refractory to external cardioversion.

Adolescent↗
PubMed1996

Distal radioulnar joint arthrography: simplified technique.

Three-compartment arthrography has been advocated in the current literature for evaluation of the intrinsic ligaments of the wrist. Previous techniques for distal radioulnar joint (DRUJ) injection introduce the needle directly into the joint space. As is done in shoulder arthrography, however, the needle tip can be positioned at the distal-radial margin of the ulnar head, allowing it to lie within the capsule. Retrospective review of 45 cases of wrist arthrography with this technique disclosed no complications.

Arthrography↗
PubMed1996

Trends in the education and practice of alternative medicine clinicians.

This study projects that the per capita supply of alternative medicine clinicians (chiropractors, naturopaths, and practitioners of oriental medicine) will grow by 88 percent between 1994 and 2010, while physician supply will grow by 16 percent. This increase is associated with growth in the number and size of alternative medicine colleges and in the opportunities these graduates have for licensure and practice. This study calls for an assessment of the education and regulation of clinicians across the range of disciplines who will be providing patient care in the twenty-first century.

Chiropractic↗
PubMed1996

Epidermal inclusion cysts in the male breast.

The authors present the second and third reported cases of an epidermal inclusion cyst presenting as a breast mass in a male. In each of the two patients the mass appeared on mammography as a well-defined, noncalcified mass, and breast cancer was suspected. Biopsy was required to establish the correct diagnosis.

Aged↗
PubMed1996

Life-cycle analysis of depot versus rehabilitation manual wheelchairs.

The proper selection of a wheelchair requires making several critical decisions, not the least of which is what type of wheelchair is appropriate. The International Organization for Standards (ISO) continues to develop and refine wheelchair standards. Standards allow the objective comparison of products from various sources, permitting consumers or clinicians to assess wheelchairs with which they are not familiar by comparing test results. This study consisted of three components: 1) the comparison of fatigue test results with a planar ANSI/RESNA test dummy to a HERL contoured test dummy; 2) the comparison of fatigue test results for common depot versus common rehabilitation manual wheelchairs; and 3) the comparison of fatigue test results for manual rehabilitation wheelchairs with solid 8-inch casters versus those with pneumatic 8-inch casters. Rehabilitation wheelchairs lasted on average 13.2 times longer than the depot wheelchairs. Both types, tested with the standard ISO-ANSI/RESNA dummy, lasted on average 2.1 times longer than those wheelchairs tested using the contoured dummy. The three rehabilitation wheelchairs equipped with 8-inch pneumatic casters lasted on average 3.2 times longer than the 6 rehabilitation wheelchairs equipped with solid 8-inch casters. The depot wheelchairs cost about 3.4 times as much to operate per cycle or per meter than the rehabilitation wheelchairs. The rehabilitation wheelchairs tended to experience component failures, while the depot wheelchairs tended to experience frame failures. Our testing indicates that the tests in the ISO-ANSI/RESNA standards can relate design features to fatigue test results and durability. Rehabilitation wheelchairs tend to use higher quality materials and better manufacturing practices, and they provide greater mobility for wheelchair users. Purchasers and prescribers of wheelchairs should consider the life-cycle cost and not just the purchase price for wheelchairs.

Analysis of Variance↗
PubMed1995

Sequence of the Escherichia coli C homoprotocatechuic acid degradative operon completed with that of the 2,4-dihydroxyhept-2-ene-1,7-dioic acid aldolase-encoding gene (hpcH).

The homoprotocatechuic acid (HPC) pathway is a typical catabolic sequence for converting peripheral metabolites into intermediates of central metabolism. How the pathway enzymes that catalyse such natural sequences have arisen is as yet uncertain, but the explanation is likely to be of interest in devising pathways to catabolise the man-made chemicals that are increasingly found in the environment. The nucleotide (nt) sequence of the Escherichia coli C 2,4-dihydroxyhept-2-ene-1,7-dioic acid (HHED) aldolase-encoding gene (hpcH) reported here completes the sequencing of the HPC pathway genes, and so makes it possible to assess the relatedness of all the pathway enzymes. There were no striking amino acid (aa) sequence identities between any of the pathway enzymes, suggesting that they had not arisen by duplication of an ancestral gene, with subsequent divergence. The HHED aldolase showed no striking identity (16-22%) with the aldolases from five other bacteria catalysing the analogous reaction in the catechol meta-fission pathway. However, there was significant aa identity (47.8%) with an E. coli K-12 open reading frame (ORF) of as yet unknown function, suggesting that this ORF may encode an aldolase of some kind.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Cellular location influences copper-dependent topaquinone formation for phenylethylamine oxidase expressed in Escherichia coli K-12.

Arthrobacter globiformis amine oxidase produced by Escherichia coli cells grown in copper-depleted media was reported to undergo activation due to formation of its topaquinone cofactor in a copper-dependent autocatalytic reaction. Likewise, a mutated E. coli amine oxidase located in the cytoplasm was reported to form topaquinone autocatalytically in an EDTA-sensitive reaction. Here we show unequivocally that formation of an amine oxidase lacking topaquinone is primarily a consequence of the location of the enzyme in the cytoplasm rather than the level of copper in the growth medium. For E. coli, insertion of copper into apoamine oxidase and subsequent topaquinone formation occur after export of the apoenzyme into the periplasm.

Amine Oxidase (Copper-Containing)↗