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Biomedical subjects

N C Wright

Publications and source records attributed to N C Wright.

15 recordsLinked to original sources
PubMed2001

Response to high-intensity eccentric muscle contractions in persons with myopathic disease.

Although the response to intense eccentric muscle contractions is well described in normal subjects, concern exists about possible untoward effects in persons with myopathic diseases. We investigated 14 subjects with slowly progressive muscular dystrophies including myotonic muscular dystrophy (n = 9), facioscapulohumeral dystrophy (n = 2), limb-girdle syndrome (n = 2), and Becker muscular dystrophy (n = 1). Control subjects consisted of 18 able-bodied persons. Subjects performed two sets of eight maximal-effort eccentric repetitions of the elbow flexors, with measurement of maximal concentric strength, serum creatine kinase, resting and flexed arm angle, arm circumference, and soreness at days 0, 3, and 7. Although the myopathic group had less initial strength, both groups demonstrated a similar response to the protocol over 7 days. Both groups had a significant rise in serum creatine kinase, which was still elevated at 7 days (P < 0.05). The control group demonstrated a slightly greater injury response in terms of soreness, resting and flexed arm angles, and arm swelling. Both groups of subjects appeared to respond similarly to an acute bout of eccentric contractions. However, the potential long-term effects of this type of exercise in persons with myopathic diseases remains unknown.

Adult↗
PubMed2000

24-hour lung preservation: simplified versus conventional University of Wisconsin solution in a porcine model.

BACKGROUND: Experimentally, the University of Wisconsin solution (UW) has been shown to be superior to the EuroCollins solution (EC) for lung graft preservation. We showed previously that the inclusion of the trisaccharide raffinose as an impermeant in the UW is largely responsible for this superiority. In this study, we used a new porcine model of isolated lung reperfusion to evaluate the use of a simple solution of phosphate-buffered raffinose (PBr) for lung preservation. METHODS: Lungs were stored for 24 hr at 4 degrees C after a single pulmonary artery flush with either UW (n = 5) or PBr (n = 5) solution. Left lungs were ventilated with room air and reperfused for 4 hr by venovenous extracorporeal circulation from a support animal. Controls (n = 5) were flushed with UW and reperfused without storage. RESULTS: Control lungs performed better than those stored in either solution in terms of oxygenation (P = 0.034) and airway pressure (P = 0.032). There were no significant differences between the two stored groups for any parameters. Data for stored lungs after 4 hr of reperfusion (means with 95% confidence intervals) include oxygenation (mm Hg): control 101.6 (14.5), UW 85.2 (14.5), PBr 75.0 (14.5); blood flow (ml/ min): control 572 (90), UW 466 (90), PBr 468 (90); peak airway pressure (mm Hg): control 15.9 (3.0), UW 21.0 (3.0), PBr 22.6 (3.0); pulmonary artery pressure (mm Hg): control 17.5 (3.2), UW 22.3 (2.9), PBr 24.5 (2.9). Graft edema (percentage tissue water): control 86.4 (0.8), UW 89.9 (1.8), PBr 89.3 (1.0). CONCLUSION: PBr is a far simpler and less expensive alternative to UW, and appears to provide a similar level of lung graft protection.

Adenosine↗
PubMed2000

High-pressure suction drainage via a polyurethane foam in the management of poststernotomy mediastinitis.

BACKGROUND: This study was performed to evaluate the effectiveness of suction drainage in the management of early poststernotomy mediastinitis. METHODS: From September 1998 to August 1999, we encountered nine cases of poststernotomy mediastinitis out of 1,209 adult median sternotomies performed in this time period. All these cases were treated with suction drainage, which was recently introduced to our management protocol. From September 1997 to August 1998, we encountered 11 cases of poststernotomy mediastinitis of 1,343 adult median sternotomies. All these cases were initially treated by closed drainage and irrigation, which was our previous first-line management. We used the latter group as historical controls for the evaluation of suction drainage. Lengths of hospitalization were compared using the Mann-Whitney U test, and success versus failure of the primary treatment was compared using the chi2 test. RESULTS: Treatment with the suction dressing resulted in a decreased length of hospitalization after treatment starts (p = 0.02) and a lower rate of treatment failure (p = 0.03). CONCLUSIONS: The use of high-pressure suction drainage is a valuable adjunct in the early management of poststernotomy mediastinitis.

Aged↗
PubMed2000

Simulated work performance tasks in persons with neuropathic and myopathic weakness.

OBJECTIVES: To determine the test-retest reliability of selected simulated work performance tasks in persons with neuropathic and myopathic weakness and control subjects, and the association between muscular performance during these work tasks and conventional isolated muscle group testing. DESIGN: Measurement of three tasks performed on a work simulation device on two different days separated by 1 week. Associations between work task performance and previously reported strength measures in six muscle groups by hand-held dynamometry (HHD) were examined. SETTING: Human performance laboratory of a university. PARTICIPANTS: Convenience sample of ambulatory outpatients with hereditary motor and sensory neuropathy, type I (n = 9), myotonic muscular dystrophy (n = 10), and able-bodied controls (n = 11). MAIN OUTCOME MEASURES: For work simulation, isokinetic peak torque and total work; and for HHD, maximal isometric torque. RESULTS: Mean between-session differences for work simulation tasks ranged from -11% to +4% for peak torque and from -12% to +12% for total work; test sessions did not differ significantly for either patient or control groups. All groups had between-session intraclass correlation coefficients usually >.80, indicating good consistency. In general, correlations between peak torque during work simulation and HHD were strongest in the control group. CONCLUSION: Persons with neuromuscular weakness reliably performed the simulated work tasks examined in this investigation. Work simulation tasks may be a useful tool to assess muscular performance in persons with neuromuscular weakness.

Aged↗
PubMed2000

A porcine ex vivo paracorporeal model of lung transplantation.

A technique is described which allows perfusion of an isolated, ventilated pig lung with an extracorporeal veno-venous circuit from a support animal. This model is stable for up to 4 h, and avoids some of the disadvantages of alternative small animal and large animal models of lung transplantation. It may be useful in the investigation of factors affecting lung preservation and reperfusion injury.

Animals↗
PubMed1998

Energy expenditure, physical activity, and body composition of ambulatory adults with hereditary neuromuscular disease.

Persons with neuromuscular disease (NMD) have progressive weakness and wasting of skeletal muscle, reduced fat-free mass, and increased fat mass relative to healthy control subjects. To test the hypothesis that resting energy expenditure (REE), estimated total daily energy expenditure (TEE), and physical activity patterns are altered in ambulatory adults with NMD, 26 adult men and women with slowly progressive NMD and 19 able-bodied control subjects similar in age and weight were evaluated. REE was measured after an overnight fast by indirect calorimetry, TEE by heart rate monitoring, and body composition by air-displacement plethysmography. REE was not significantly different between NMD and control subjects; however, TEE was significantly reduced in NMD subjects compared with control subjects, respectively (women: 7.8 +/- 1.5 compared with 10.5 +/- 2.8; men: 10.2 +/- 3.6 compared with 12.7 +/- 2.6 MJ/d; P < or = 0.01), indicating that NMD subjects expended less energy in physical activity than did control subjects. NMD subjects also tended toward an increased energy cost of physical activity, particularly at higher activity levels (P = 0.06). Multiple regression analysis indicated that for all subjects combined, adiposity was positively associated with age and TEE and negatively associated with time spent in the active heart rate range and fat-free mass (P < or = 0.0001). This relation did not differ between NMD and control subjects, nor did it differ between men and women. We hypothesize that because of their reduced physical activity and increased adiposity, persons with NMD may be at risk for developing secondary conditions such as cardiovascular disease, hypertension, and diabetes.

Adult↗
PubMed1998

Nutritional aspects of neuromuscular diseases.

Evidence suggests that individuals with DMD have reduced skeletal development, including decreased linear growth and bone mineral density, compared to normal subjects. Despite their reduced muscle mass, a high percentage of DMD patients are overweight. Body composition measurements can assist with monitoring changes in fat mass and skeletal muscle mass as the disease progresses. Weight management in overweight DMD patients is indicated because excess adiposity burdens mobility and breathing, but only one study in two DMD patients has documented that weight reduction can be done safely. In the latter stages of the disease most DMD subjects become underweight because of an acceleration in skeletal muscle protein degradation relative to its synthesis. Studies of energy, protein and branched chain amino acid supplementation in DMD have yielded promising but inconclusive results, and more well-designed studies are needed in this area. Although there is currently no cure for DMD, studies on the role of nutritional therapy in increasing the quality of life in these patients are urgently needed. Studies in adults with various SP-NMDs indicate a reduction in fat-free mass and an increase in fat mass relative to controls. The newly developed method of air displacement plethysmography for measuring body composition is ideally suited for SP-NMD subjects because it requires very little effort and the measurement procedure is relatively fast. Dual energy x-ray absorptiometry technology has been proposed for distinguishing myogenic from neurogenic SP-NMDs from calculation of the fat-to-lean soft tissue ratio, which is higher in patients with myogenic muscular atrophy. Studies on the energy metabolism of ambulatory SP-NMD subjects indicate that their basal metabolic rate is either similar to or slightly lower than controls, but 24-hour energy expenditure is about 25% lower than controls. This reduction in 24-hour energy expenditure is due to a reduction in physical activity in SP-NMD. Studies examining the roles of energy expenditure, physical activity, and diet in the development of adiposity and risk for secondary chronic diseases in SP-NMD subjects are currently underway.

Adolescent↗
PubMed1997

Hand-held dynamometry reliability in persons with neuropathic weakness.

OBJECTIVE: To determine test-retest reliability of hand-held dynamometry (HHD) in measuring strength of persons with neuropathic weakness. DESIGN: Intratester and intertester reliability of HHD-measured strength over a 7- to 10-day period. In addition, HHD knee strength was compared with criterion standard of fixed dynamometry (FD). SETTING: Human performance laboratory of a university. PARTICIPANTS: Convenience sample of ambulatory outpatients with Hereditary Motor and Sensory Neuropathy, Type I (HMSN) (n = 10) and able-bodied controls (CTL) (n = 11). MAIN OUTCOME MEASURE: Maximal isometric torque. RESULTS: Intratester intraclass correlation coefficients (ICCs) were high, generally ranging from .82 to .96 for HHD- and FD-measured strength for both HMSN and CTL groups. There were no significant differences between sessions for HHD-measured strength, while FD-measured strength was only significantly different for knee extension (p < .01). Intertester reliability was generally good for both HHD- and FD-measured strength, with ICCs ranging from .72 to .97 for HMSN and CTL groups. Exceptions were knee extensors and ankle dorsiflexors for the CTL group. Knee extensor strength was significantly lower measured by HHD compared with FD (p < .01), but knee flexor strength was similar for the two methods. CONCLUSION: HHD appears to be a reliable method to measure maximal isometric strength in persons with neurogenic weakness, and may be useful to quickly and objectively evaluate strength in the clinical setting.

Adult↗
PubMed1996

Aerobic walking in slowly progressive neuromuscular disease: effect of a 12-week program.

OBJECTIVE: Poor cardiorespiratory endurance is a common finding in neuromuscular disease (NMD), and the capacity of such patients to respond to aerobic training is unclear. This study was conducted to determine if a 12-week walking program results in increased aerobic capacity in slowly progressive NMD subjects, whether such a program is safely tolerated, and whether such patients can adhere to a self-monitored, home-based training program. DESIGN: Before-after trial. SETTING: Subjects' homes. PATIENTS: A cohort of 8 slowly progressive NMD subjects (4 men, 4 women) followed in the neuromuscular disease clinic participated (age, 36.6 +/- 8.0 yrs; ht, 170 +/- 11 cm; wt, 74.3 +/- 19.0 kg) (Mean +/- SD). INTERVENTION: Subjects walked 15 to 30 min 3 to 4 days a week at 50% to 60% of their heart rate reserve. MAIN OUTCOME MEASURES: Resting, submaximal, and peak heart rates, systolic and diastolic blood pressures, oxygen uptake, and peak power output. RESULTS: Graded exercise testing to volitional fatigue using a semirecumbent cycle ergometer before and after the training program found significant decreases in submaximal heart rate by 7 +/- 3 beats/min (Mean +/- SEM) (95% CI = -23 to 9) (p = .046) and submaximal systolic blood pressure by 11 +/- 4 mmHg (95% CI = -31 to 9) (p = .019), and nonsignificant increases in peak power output and VO2. CONCLUSIONS: These results suggest that moderate-intensity aerobic exercise training is well tolerated and may provide modest improvement in aerobic capacity in slowly progressive NMD subjects.

Adult↗
PubMed1994

The effect of a high resistance exercise program in slowly progressive neuromuscular disease.

A 12-week high resistance home exercise program was completed by 10 subjects with slowly progressive neuromuscular diseases (NMD) and 6 normal control subjects (CTL). After evaluating baseline maximal isometric and isokinetic strength of the elbow flexors and knee extensors, subjects completed the home program using adjustable ankle and wrist cuff weights. One side of the body was randomly chosen for exercise. Subjects initially performed 1 set of 10 repetitions on 3 days a week and gradually increased to 5 sets of 10 repetitions on 4 days a week. The NMD group demonstrated significant (p < 0.05) gains in several knee extension isokinetic strength measures but loss of elbow flexion eccentric peak torque and work per degree. The CTL group demonstrated significant gains in all measures of knee extension strength, with improvement of elbow isokinetic eccentric work per degree as well. There was evidence of cross training to the nonexercised limbs for both groups. A high resistance training program, although well tolerated in NMD subjects with mild to moderate weakness, may cause some deleterious effects to diseased skeletal muscle. A high resistance training program appears to offer no advantage over a moderate resistance training program in this population.

Adult↗
PubMed1989

The role of interconnection between supraoptic nucleus and anterior third ventricular region in osmoregulation in the rat.

1. To determine the importance of the region of the hypothalamus anterior and ventral to the third ventricle (AV3V) in the osmotic regulation of neurohypophysial hormone release, extracellular recordings were made in the urethane-anaesthetized rat from neurones in the supraoptic nucleus (SON) and in the AV3V using a ventral surgical approach. 2. In the first series of experiments, recordings were made from SON cells (n = 41) which could be antidromically activated from the neural stalk in control rats and rats 2 weeks after electrolytic destruction of the AV3V (n = 74). Destruction of AV3V significantly (P less than 0.01) reduced the responsiveness of SON cells to an osmotic challenge (1 ml of 1.5 M-NaCl I.P.). 3. In the second series of experiments recordings were made in the AV3V region while stimulus pulses were applied to the region of the SON. The cells recorded could be divided into five groups; those which were inhibited (presumably synaptically; OD-; n = 97), those which were excited (also presumably synaptically; OD+; n = 73), those which could be antidromically activated (AD; n = 50), those which showed a complex cycle of excitation and inhibition after the stimulus (n = 40) and those which did not respond to the stimulus (n = 47). 4. The characteristic response of OD- cells to an osmotic challenge was inhibition (six out of ten cells) and that of OD+ cells was excitation (thirteen out of seventeen cells). No AD cells showed excitation following I.P. NaCl injection (nine out of nine). 5. Our experiments provide clear evidence that the AV3V region is important for the normal responsiveness of the cells of the SON to raised plasma osmolality and for an interaction between the SON and the AV3V region. 6. Our results also suggest, contrary to our expectation, that the SON exerts both excitatory and inhibitory influences on the AV3V. Since the cells which project from the AV3V to the SON region are not osmoresponsive, the importance of the direct projection from the AV3V to SON may be to maintain the responsiveness of SON neurones rather than to provide osmotic drive.

Animals↗
PubMedDate not supplied

Profiles of neuromuscular diseases. Design of the protocol.

The purpose of this 10-yr investigation was to develop comprehensive impairment and disability profiles of the clinical characteristics of seven neuromuscular diseases: spinal muscular atrophy, hereditary motor sensory neuropathy, Duchenne muscular dystrophy, Becker's muscular dystrophy, facioscapulohumeral muscular dystrophy, limb-girdle syndrome, and myotonic dystrophy. Based on the World Health Organization's classification of disablement, as applied to neuromuscular diseases, impairment was evaluated by measurements of strength, range of motion, spine deformity, cardiac and pulmonary function, and intellectual capacity. Disability was evaluated by measures of mobility and upper extremity function, cardiopulmonary adaptations, cardiac and pulmonary complications, and psychosocial adjustment.

Clinical Protocols↗