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Biomedical subjects

R A Cooper

Publications and source records attributed to R A Cooper.

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

Rhombohedral crystals of 2-dehydro-3-deoxygalactarate aldolase from Escherichia coli.

2-Dehydro-3-deoxygalactarate (DDG) aldolase (E.C. 4.1.2.20) catalyzes the reversible aldol cleavage of DDG and 2-dehydro-3-deoxyglucarate to pyruvate and tartronic semialdehyde. Rhombohedral crystals of recombinant DDG aldolase from Escherichia coli K-12 were obtained. The crystals belong to space group R32 with unit-cell parameters a = 93 A, alpha = 85 degrees. The crystals diffract to beyond 1.8 A resolution on a Cu Kalpha rotating-anode generator. The asymmetric unit is likely to contain two molecules, corresponding to a packing density of 1.34 A3 Da-1.

Aldehyde-Lyases↗
PubMed1999

Can early timed internal atrial defibrillation shocks reduce the atrial defibrillation threshold?

The defibrillation threshold is markedly reduced very early following the initiation of ventricular fibrillation. The purpose of this study was to determine if the same finding holds true for atrial defibrillation. Sustained, reproducible AF was induced with programmed atrial pacing using acetyl-beta-methylcholine chloride (40-640 microL/min) in six adult sheep (heart weight 245-300 g). Seven timing intervals (125 ms, 200 ms, 1 s, 3 s, 10 s, 30 s, and 5 min after AF induction) and two lead configurations: (1) RA as cathode and CS as anode; and (2) RA as cathode and RV apex as anode were tested. Single capacitor biphasic waveforms (3/1 ms) were delivered and atrial defibrillation thresholds (ADFTs) were determined in random order. No significant differences in leading edge voltage and total energy were detected for the RA-CS configuration for the seven timing intervals. For the RA-RV configuration, a significant difference was detected comparing the voltage for 125 ms to the 5-minute timing interval. For all times except 125 ms, the RA-RV threshold was significantly higher than the RA-CS level. In contrast to ventricular defibrillation, the ADFT does not change significantly within the first 5 minutes after the initiation of AF for the RA-CS configuration. However, if the shock is given very early (125 ms after AF induction) with the RA-RV configuration, the ADFT is lowered almost to the RA-CS level.

Animals↗
PubMed1999

Antibacterial activity of honey against strains of Staphylococcus aureus from infected wounds.

The antibacterial action of honey in infected wounds does not depend wholly on its high osmolarity. We tested the sensitivity of 58 strains of coagulase-positive Staphylococcus aureus, isolated from infected wounds, to a pasture honey and a manuka honey. There was little variation between the isolates in their sensitivity to honey: minimum inhibitory concentrations were all between 2 and 3% (v/v) for the manuka honey and between 3 and 4% for the pasture honey. Thus, these honeys would prevent growth of S. aureus if diluted by body fluids a further seven-fold to fourteen-fold beyond the point where their osmolarity ceased to be completely inhibitory. The antibacterial action of the pasture honey relied on release of hydrogen peroxide, which in vivo might be reduced by catalase activity in tissues or blood. The action of manuka honey stems partly from a phytochemical component, so this type of honey might be more effective in vivo. Comparative clinical trials with standardized honeys are needed.

Honey↗
PubMed1999

Engineering manual and electric powered wheelchairs.

The sophistication required to develop and properly configure a wheelchair is illustrated by the amount and complexity of the research being conducted. At this time there appears to be between 1.5 and 2.0 million full-time wheelchair users within the United States. The reliance of the user on the wheelchair and the amount of time in the wheelchair provide significant challenges for the wheelchair design engineer. Currently there are a wide variety of wheelchair designs that are commercially available. These wheelchairs accommodate a variety of people's needs, and represent significant progress. The current trend among manufacturers of manual wheelchairs seems to be cost-reduction engineering. The ergonomics of long-term wheelchair use are critical to the advancement of wheelchair design and to the clinical selection of wheelchairs. Electric powered wheelchairs appear to be progressing faster than nearly all other types of wheelchairs. This is due to the availability of computing power with low cost microcontrollers and associated peripherals. The greater range and availability of sensors are also making changes into the design of electric powered wheelchairs. The interaction between an electric powered wheelchair and the user can be extremely complex. In many cases, individual solutions are necessary. One of the more challenging questions is determining the abilities of the user required to drive an electric powered wheelchair effectively. There have been substantial improvements in the engineering of all wheelchairs. However, there remain significant issues to be addressed.

Anthropometry↗
PubMed1999

Testing and evaluation of wheelchair caster assemblies subjected to dynamic crash loading.

Wheelchair designs based upon loads applied quasi-statically during normal mobility use are apt to be inadequate to handle the increased level of dynamic crash forces that may be encountered when using the wheelchair as a motor vehicle seat. The purpose of this study was to characterize the integrity of wheelchair caster assemblies under simulated crash conditions. This study utilized dynamic drop (DD) testing, with loading levels and rates adjusted to match those found previously in sled impact testing and computer crash simulations. The results verify that current caster assembly designs may not be able to withstand forces associated with a crash. Five of seven evaluated caster assemblies failed when loaded to 8,007 N, or less, at loading rates seen in sled testing. DD testing used in this study is a valuable tool that can be used in the design of transport wheelchair components.

Accidents↗
PubMed1999

Augmentation of the 100 kg ISO wheelchair test dummy to accommodate higher mass: a technical note.

Most of the 22 approved or developing ISO standards rely on a wheelchair test dummy, a specialized device described in ISO 7176-11. The purpose of this study was to develop a means for modifying the design of the ISO 7176-11 test dummy to be suitable for testing with higher masses. The changes are based upon published data for obese individuals. With these data, we derived equations for determining the distribution of the additional mass among the test dummy components, and the locations of the centers of mass. The results of this study provide guidelines for adding mass to the 100 kg wheelchair test dummy to accommodate testing of wheelchairs designed for obese individuals.

Anthropometry↗
PubMed1999

Research on physical activity and health among people with disabilities: a consensus statement.

Research is required to advance the understanding of issues related to the effect of physical activity on health and disease prevention among people with disabilities. This report is the result of a consensus process using selected experts in health and exercise. The purpose of the consensus conference was to identify research priorities for physical activity and health among people with disabilities. Priorities were established by 30 participants, who were selected by the principal investigators to achieve balance in the areas of engineering, epidemiology, medicine, nutrition, exercise physiology, and psychology. Experts summarized relevant data from their research and from comprehensive review of the scientific literature on the topic areas chosen for the conference. Public commentary was provided by participants in the 1996 Paralympic Congress. Panel members discussed openly all material presented to them in executive session. Commentary from open discussion periods were recorded and transcribed. Selected panelists prepared first drafts of the consensus statements for each research priority question. All of these drafts were distributed to the panelists and pertinent experts. The documents were edited by the drafting committee to obtain consensus. This research priority setting process revealed that greater emphasis must be placed on determining the risks and benefits of exercise among people with disabilities. Exercise must be studied from the perspective of disease prevention while mitigating risk for injury. Five areas were identified as focal points for future work: epidemiological studies; effects of nutrition on health and ability to exercise; cardiovascular and pulmonary health; children with disabilities; and accessibility and safety of exercise programs. As people with disabilities live longer, the need for addressing long-term health issues and risk for secondary disability must receive greater attention. As a consequence of the consensus process, specific recommendations for future research regarding the impact of exercise on the health and quality of life of persons with disabilities were defined.

Cardiovascular Diseases↗
PubMed1999

The relationship between reactivity of metabolites of pyrrolizidine alkaloids and extrahepatic toxicity.

Pyrrolizidine alkaloids (PAs) are a large group of structurally similar toxins. In animals, including man, they are hepatotoxic and in some cases pneumo- and neurotoxic. PAs are metabolized by the liver P450 system to reactive dehydroalkaloid (DHA) intermediates. PA toxicity is a result of alkylation of macromolecules by DHAs. We have measured the relative reactivity of a series of semi-synthetic DHAs by recording the rate at which they alkylate a model nucleophile, 4-(p-nitrobenzyl)pyridine. Rate data fit mono- or biexponential equations. Rank order of reactivity for the macrocyclic and open ester DHAs was the same as those measured for DHA hydrolysis. The reaction with 4-(p-nitrobenzyl)pyridine was easier to follow, however, as rates of reaction can easily be controlled by temperature or level of acid catalysis, and the final product can be measured colorimetrically. DHAs of the primarily hepatotoxic alkaloids, retrorsine and seneciphylline, were more reactive than DHAs of monocrotaline and trichodesmine, which additionally produce pneumo- and neurotoxicity, respectively. This suggests that DHAs with greater stability (longer half-lives) are able to survive long enough to reach target organs downstream form the liver. We believe that differences in PA metabolism and the nature of toxicity ultimately produced are in part related to differences in reactivity of the primary toxic intermediate, the DHA.

Alkylation↗
PubMed1998

Current and projected workforce of nonphysician clinicians.

Nonphysician clinicians (NPCs) are becoming increasingly prominent as health care providers. This study examines 10 such disciplines: nurse practitioners (NPs), physician assistants (PAs), nurse-midwives, chiropractors, acupuncturists, naturopaths, optometrists, podiatrists, nurse anesthetists, and clinical nurse specialists. The aggregate number of NPCs graduating annually in these 10 disciplines doubled between 1992 and 1997, and a further increment of 20% is projected for 2001. Assuming that enrollments remain at the levels attained in 2001, NPC supply will grow from 228000 in 1995 to 384000 in 2005, and it will continue to expand at a similar rate thereafter. The greatest growth is projected among those NPCs who provide primary care services. Moreover, the greatest concentrations of both practicing NPCs and NPC training programs are in those states that already have the greatest abundance of physicians. On a per capita basis, the projected growth in NPC supply between 1995 and 2005 will be double that of physicians. Because of the existing training pipeline, it is probable that most of the growth projected for 2005 will occur. The further expansion of both NPC and physician supply thereafter warrants careful reconsideration.

Acupuncture Therapy↗
PubMed1998

Roles of nonphysician clinicians as autonomous providers of patient care.

Studies were undertaken to assess the practice prerogatives of nonphysician clinicians (NPCs) in 10 disciplines that, collectively, are the major nonphysician contributors to the delivery of medical and surgical services. These disciplines include nurse practitioners, physician assistants, nurse-midwives, chiropractors, acupuncturists, naturopaths, optometrists, podiatrists, nurse anesthetists, and clinical nurse specialists. Marked differences were found in the practice prerogatives that states granted NPCs in the various disciplines. For most disciplines, the magnitude of their prerogatives correlated with the numbers of NPCs practicing in each state. At their maximal levels, state practice prerogatives authorized a high degree of autonomy and a broad range of authority to provide discrete levels of uncomplicated primary and specialty care. The recent growth in these prerogatives is fostering new opportunities for NPCs; however, it also is creating a pluralism that has the potential to further fragment the US health care system. It is time for regulatory integration and professional collaboration so that a health care workforce that includes a diversity of disciplines can be assured of providing a coherent set of patient care services in the future.

Allied Health Personnel↗
PubMed1998

Marked reduction in internal atrial defibrillation thresholds with dual-current pathways and sequential shocks in humans.

BACKGROUND: This study tested the ability of sequential shocks delivered through dual-current pathways to lower the atrial defibrillation threshold (ADFT) compared with a biphasic shock through a standard single-current pathway. METHODS AND RESULTS: Electrodes were positioned in the right atrial appendage (RA), left subclavian vein (LSV), proximal coronary sinus (CSos), and distal coronary sinus (DCS) in 14 patients with chronic atrial fibrillation (170+/-185 days). Using a step-up protocol, we compared ADFTs for a single-current pathway (RA-->DCS) that used a single 7.5/2.5-ms biphasic shock from a 150-microF capacitor with those for a dual-current pathway system (RA-->DCS followed by CSos-->LSV) using sequential 7.5/2.5-ms biphasic shocks with capacitor discharge waveforms for 150-microF and 600-microF capacitors. Both dual-current pathway configurations (2.0+/-0.4 J for 150-microF capacitance, 2.4+/-0.5 J for 600-microF capacitance) had a significantly lower ADFT than the single-current pathway (5.1+/-1.8 J). Whereas the dual-current pathway with 150-microF capacitor shocks had a significantly lower energy threshold, there was no statistical difference in terms of leading-edge voltage compared with the dual-current pathway with 600-microF capacitance shocks. There were no ventricular arrhythmias induced with appropriately synchronized shocks. CONCLUSIONS: For internal atrial defibrillation in humans, sequential biphasic waveforms delivered over dual-current pathways resulted in a markedly reduced (>50% reduction) ADFT compared with a single shock over a single-current pathway.

Adult↗
PubMed1998

Braking electric-powered wheelchairs: effect of braking method, seatbelt, and legrests.

OBJECTIVE: To examine the influence of three electric-powered wheelchair braking conditions and four wheelchair seating conditions on electric-powered wheelchair motion and Hybrid II test dummy motion. This study provides quantitative information related to assessing the safety of electric-powered wheelchair driving. DESIGN: Rehabilitation engineering comparison and ANSI/ RESNA standards testing. Convenience sample of eight different electric-powered wheelchairs. Within-chair comparisons were conducted. INTERVENTION: Electric-powered wheelchairs were compared under three braking scenarios (joystick release, joystick reverse, power-off) and four seating conditions (seatbelt and legrests, seatbelt and no legrests, no seatbelt but legrests, no seatbelt and no legrests). SETTING: A rehabilitation engineering center. MAIN OUTCOME MEASURES: The braking distance, braking time, and braking accelerations for electric-powered wheelchairs during three braking scenarios; trunk motion, head motion, and trunk angular acceleration during three braking scenarios and four seating conditions; and number of falls from the wheelchairs for three braking scenarios and four seating conditions. RESULTS: Significant differences (p < .05) were found in braking distance, braking time, and braking acceleration when comparing the joystick release and joystick reverse scenarios with the power-off scenario. The mean braking distance was shortest with the power-off braking scenario (.89m), whereas it was longest when the joystick was released (1.66m). Significant differences (p < .05) in head displacement and trunk angular displacement were observed among braking conditions and between seating conditions. There were also significant differences (p = .0011) among braking conditions for maximum trunk angular acceleration. The Hybrid II test dummy fell from the wheelchairs with highest frequency when there were no legrests and no seatbelt used. CONCLUSION: The results of this study indicate that use of a seatbelt when driving an electric-powered wheelchair reduces the risk of falling from a wheelchair. Furthermore, the use of legrests can reduce the risk of injury to the wheelchair driver. This study shows that the most abrupt braking occurs when deactivating the power switch.

Accidental Falls↗
PubMed1998

Postural changes with aging in tetraplegia: effects on life satisfaction and pain.

OBJECTIVES: (1) To measure kyphosis and scoliosis in individuals with tetraplegia; (2) to examine the relation between kyphosis and scoliosis and years since injury; and (3) to determine the association between kyphosis and scoliosis and measures of pain, depression, and life satisfaction. DESIGN: Cross-sectional, case-control study. SETTING: University medical center and a free-standing university-affiliated rehabilitation hospital. PARTICIPANTS: (1) Ten individuals with tetraplegia I to 3 years postinjury (NT); (2) 10 individuals with tetraplegia 10 to 20 years postinjury (OT); and (3) 10 control individuals (C) matched to the other subjects on the basis of age, height, and weight. MAIN OUTCOME MEASURES: Radiographic measurements of kyphosis and scoliosis taken in a seated position, pain as measured by the short form of the McGill Pain Questionnaire (SF-MPQ), depression as measured by the Center for Epidemiological Studies-Depression Scale (CES-D), and life satisfaction as measured by the Life Satisfaction Index Assessment (LSIA) and the Craig Handicap Assessment and Reporting Technique (CHART). RESULTS: No significant differences were seen between the OT and NT groups with respect to age, height, or weight. In addition, no significant differences were found between the NT and OT groups with respect to measures of kyphosis and scoliosis. Individuals with tetraplegia had significantly higher (p < .05) measures of kyphosis (42 + 16.0 ) and scoliosis (14 degrees +/-9.2 degrees) than the C subjects (kyphosis, 32 degrees +/- 7.9 degrees ; scoliosis, 5 degrees+/-3.8 degrees). No correlation was found between scores on the SF-MPQ and degree of kyphosis or scoliosis. Significant differences were seen between the NT and OT groups on both CES-D (NT, 15.2+/-8.1; OT, 5.8+/-5.5) and LSIA (NT, 9.9+/-2.8; OT, 14.4+/-2.9). CONCLUSION: This study indicates that seated kyphosis and scoliosis develop early in individuals with tetraplegia and may not be progressive. No association was seen between pain and kyphosis or scoliosis in this relatively young sample (mean age of OT and NT combined, 34.8 years). Future research is needed to determine whether pain becomes a problem in individuals with significant kyphosis or scoliosis as they age.

Adult↗
PubMed1998

An unusual case of carotid body tumour.

Carotid body tumours are uncommon but fascinating lesions, which arise from paraganglionic tissue at the bifurcation of the common carotid artery. We report the case history of a 40-year-old female patient who presented initially with a malignant left-sided tumour, followed by a right-sided tumour 17 years later. Although there is no known family history, it is likely, because of the bilateral tumours and the young age at presentation, that the tumour was inherited in this patient. The literature on carotid body tumours is reviewed, with particular emphasis on malignant and multiple tumours and their treatment. We discuss the recently elucidated mechanism of inheritance and its implications for affected patients and their families.

Adult↗
PubMed1998

Rett syndrome: critical examination of clinical features, serial EEG and video-monitoring in understanding and management.

We studied data on seizures, vacant spells and breathing dysrhythmia from the British Rett Survey and 150 electroencephalographic records from 78 classic cases, including 23 with prolonged synchronous recordings of EEG, respiration and movement. The proportion of abnormal records increased from 6 of 18 (33%) during the first 6 months of the regression period to 44 of 59 (75%) in the later period to 6 years, the increase in abnormality following rather than preceding the onset of regression. In young girls the EEG abnormality increased in sleep but decreased during episodic hyperventilation and breath-holding. Epileptogenic activity was commonly present without clinical seizures. Eleven vacant spells were monitored and were not epileptic but related to the breathing abnormality. Full monitoring is essential when supposed seizures are intractable. The intermittent EEG abnormality and behavioural changes indicate abnormal fluctuating arousal possibly of midbrain or brainstem origin.

Adolescent↗
PubMed1998

Shoulder and elbow motion during two speeds of wheelchair propulsion: a description using a local coordinate system.

Individuals who propel wheelchairs have a high prevalence of upper extremity injuries. To better understand the mechanism behind these injuries this study investigates the motion of the shoulder and elbow during wheelchair propulsion. The objectives of this study are: (1) To describe the motion occurring at the shoulder and elbow in anatomical terms during wheelchair propulsion; (2) to obtain variables that characterize shoulder and elbow motion and are statistically stable; (3) to determine how these variables change with speed. The participants in the study were a convenience sample of Paralympic athletes who use manual wheelchairs for mobility and have unimpaired arm function. Each subject propelled an ultralight wheelchair on a dynamometer at 1.3 and 2.2 meters per second (m/s). Biomechanical data was obtained using a force and moment sensing pushrim and a motion analysis system. The main outcome measures investigated were: maximum and minimum angles while in contact with the pushrim, range of motion during the entire stroke and peak accelerations. All of the measures were found to be stable at both speeds (Cronbach's alpha > 0.8). The following measures were found to differ with speed (data format: measure at 1.3 m/s +/- SD; measure at 2.2 m/s +/- SD): minimum shoulder abduction angle during propulsion (24.5 degrees +/- 6.7, 21.6 degrees +/- 7.2), range of motion during the entire stroke in elbow flexion/extension (54.0 degrees +/- 9.9, 58.1 degrees +/- 10.4) and shoulder sagittal flexion/extension (74.8 degrees +/- 9.4, 82.6 degrees +/- 8.5), and peak acceleration in shoulder sagittal flexion/extension (4044 degrees/s2 +/- 946, 7146 degrees/s2 +/- 1705), abduction/adduction (2678 degrees/s2 +/- 767, 4928 degrees/s2 +/- 1311), and elbow flexion/extension (9355 degrees/s2 +/- 4120, 12889 degrees/s2 +/- 5572). This study described the motion occurring at the shoulder and elbow using a local coordinate system. Stable parameters that characterize the propulsive stroke and differed with speed were found. In the future these same parameters may provide insight into the cause and prevention of shoulder and elbow injuries in manual wheelchair.

Adult↗