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Biomedical subjects

R J Petrella

Publications and source records attributed to R J Petrella.

At least 19 recordsLinked to original sources
PubMed2002

FIM after hip fracture: is telephone administration valid and sensitive to change?

OBJECTIVES: It has been reported recently that follow-up FIM trade mark scores have been obtained from stroke patients via telephone interviews with either the former patient or proxy caregivers. We studied the validity and sensitivity of change of a "phone FIM" score in a sample of hip fracture patients after rehabilitation. DESIGN: We compared FIM scores among hip fracture patients in a specialized musculoskeletal rehabilitation program. Sample size estimate of 27 was determined before the study. Patients included those with hip fracture returning to independent living in their own home. RESULTS: Twenty-nine patients were identified as a convenience sample of admitted patients. The phone FIM score at 8 wk was a valid predictor of the discharge FIM score and the observed FIM and phone FIM scores at 8 wk were similar. The sensitivity to change over 8 wk was similar between observed and phone FIM scores compared with the discharge FIM score. CONCLUSIONS: The phone FIM instrument presents a useful clinical instrument to monitor patient functional status in the community, showing excellent psychometric properties. Ease of use and low cost should encourage greater use in clinical management of these patients.

Activities of Daily Living↗
PubMed2001

The energetics of off-rotamer protein side-chain conformations.

Non-rotameric ("off-rotamer") conformations are commonly observed for the side-chains of protein crystal structures. This study examines whether such conformations are real or artifactual by comparing the energetics of on and off-rotamer side-chain conformations calculated with the CHARMM energy function. Energy-based predictions of side-chain orientation are carried out by rigid-geometry mapping in the presence of the fixed protein environment for 1709 non-polar side-chains in 24 proteins for which high-resolution (2.0 A or better) structures are available. For on-rotamer conformations, 97.6 % are correctly predicted; i.e. they correspond to the absolute minima of their local side-chain energy maps (generally to within 10 degrees or less). By contrast, for the observed off-rotamer side-chain conformations, 63.8 % are predicted correctly. This difference is statistically significant (P<0.001) and suggests that while most of the observed off-rotamer conformations are real, many of the erroneously predicted ones are likely to be artifacts of the X-ray refinements. Probabilities for off-rotamer conformations of the non-polar side-chains are calculated to be 5.0-6.1 % by adaptive umbrella-sampled molecular dynamics trajectories of individual amino acid residues in vacuum and in the presence of an average protein or aqueous dielectric environment. These results correspond closely to the 5.7 % off-rotamer fraction predicted by the rigid-geometry mapping studies. Since these values are about one-half of the 10.2 % off-rotamer fraction observed in the X-ray structures, they support the conclusion that many of the latter are artifacts. In both the rigid-geometry mapping and the molecular dynamics studies, the discrepancies between the predicted and observed fractions of off-rotamer conformations are largest for leucine residues (approximately 6 % versus 16.6 %). The simulations for the isolated amino acid residues indicate that the real off-rotamer frequency of 5-6 % is consistent with the internal side-chain and local side-chain-backbone energetics and does not originate from shifts due to the protein. The present results suggest that energy-based rotation maps can be used to find side-chain positional artifacts that appear in crystal structures based on refinements in the 2 A resolution range.

Amino Acids↗
PubMed2001

A self-paced step test to predict aerobic fitness in older adults in the primary care clinic.

OBJECTIVES: To study the potential usefulness of a submaximal self-paced step test as a prediction of maximal aerobic capacity (VO2max) in older adults in the primary care setting. DESIGN: Data were collected during a prospective randomized study of an exercise program. SETTING: Four university family medical clinics in London, Ontario, Canada. PARTICIPANTS: A random sample of 240 healthy older (> or =65) men (n = 118) and women (n = 122) from four family medical clinics underwent self-paced step testing in the clinic with a family physician (n = 16), and step testing and a maximal exercise treadmill test with measurement of respired gases in an exercise laboratory. Testing was done in random order (clinic/laboratory) separated by 2 weeks and then repeated at 52 weeks, following introduction of an exercise program. Relationships between outcome variables were examined by Pearson correlation coefficients while prediction of VO2max was examined using multivariate regression analysis. Cross-validation with 30 age-matched hypertensive and 40 age-matched post-hip arthroplasty patients was used to test the accuracy of the predictive models. MEASUREMENTS: Measured VO2max, predicted VO2max, step test time, step test heart rate, body mass index (BMI), and O2 pulse. RESULTS: Two hundred women (n = 108) and men (n = 92) completed both the initial and 52-week assessments. Stepping time, heart rate, age, BMI, and O2 pulse were strongly associated with VO2max for both a normal and a fast step pace and were chosen to develop the predictive model. Normal step-pace correlation with VO2max (ml/kg/min) was no different (female 0.93: male 0.91) from fast pace (0.95:0.90) with no difference between clinic and laboratory measurement at baseline or 52 weeks. Cross-validation showed no significant difference from the main group using the predictive model. CONCLUSIONS: The self-paced step test is a safe and simple clinical instrument that strongly and reliably predicts VO2max, is sensitive to change, and is generalizable in the family practice setting among community-dwelling older adults differing in fitness and health status.

Aged↗
PubMed2000

An office-based instrument for exercise counseling and prescription in primary care. The Step Test Exercise Prescription (STEP).

BACKGROUND: Available evidence suggests that despite physicians' positive attitudes toward exercise as an important part of promoting a healthy lifestyle, few physicians actually prescribe exercise for their patients. One barrier may be lack of a standard office instrument. OBJECTIVES: To determine the (1) exercise counseling habits among a large group of Canadian family physicians and (2) acceptance and utilization of an exercise counseling instrument geared to primary care practice. DESIGN: Randomized control trial. SETTING: Primary care practice. PARTICIPANTS: Family physicians (N = 400) from 3 regions of Canada, representing both rural and urban practice (ratio of 1:3). Patients (10 per practice) were healthy community dwellers older than 65 years obtained as a convenience sample in their family practice. INTERVENTIONS: In phase 1, 400 physicians listed as being in general or family practice by their provincial registries were randomly selected from a larger group listed by these registries and contacted by telephone. A total of 362 completed a 10-minute questionnaire that detailed practice demographics, preventive practice, and exercise counseling habits. In phase 2, 293 agreed to further participate in the administration of an exercise prescription randomly assigned to them by the study team. Two methods of exercise prescription were compared: counseling using the American College of Sports Medicine guidelines (control) and counseling using guidelines and an office-based step test (Step Test Exercise Prescription [STEP]) to determine fitness level and prescribe an exercise training heart rate. Physicians were asked to deliver their assigned exercise prescription to a convenience sample of the next 10 healthy patients older than 65 years who presented to the office. MAIN OUTCOME MEASURES: Primary outcome measures were physician exercise counseling confidence and knowledge before and after the study. Secondary outcomes included details of the exercise counseling sessions (e.g., time required). RESULTS: In phase 1, more than 90% of the 362 physicians claimed to practice preventive health counseling, and 70% claimed to include exercise counseling. Only 67.4% felt confident regarding their exercise prescribing, and most (93.8%) were interested in improving their exercise prescribing skills. The leading barriers to exercise prescription were described in order as inadequate time, lack of necessary skills and tools, and lack of reimbursement. In phase 2, no difference in physician profile, patient profile, or indications for exercise counseling were observed between control (n = 145) and STEP (n = 148) groups. STEP was significantly longer (16.4 vs 12.9 min; P = .001) to administer; however, improvement in physician confidence (P = .01) and knowledge (P = .009) were significantly greater compared with controls. CONCLUSIONS: Most family physicians practiced preventive exercise counseling but reported lack of time and skills as barriers to this practice. Physicians randomized to the STEP group took longer to deliver exercise advice but felt more confident and knowledgeable compared with controls.

Aged↗
PubMed2000

Viscosupplementation effect on proprioception in the osteoarthritic knee.

OBJECTIVE: To test the hypothesis that treatment of the osteoarthritic knee with intraarticular hyaluronan may improve proprioception. METHODS: Forty-six patients with unilateral osteoarthritis of the knee were recruited for this study from primary care clinics in the Department of Family Medicine at the University of Western Ontario. Inclusion required (1) the presence of pain with activities of daily function and (2) radiographic confirmation of medial compartment osteoarthritis. Proprioception was measured with an electrogoniometer attached to the study knee. Subjects performed an angle reproduction test in the closed kinetic position. The difference between the target test angle and the reproduced angle was labeled the absolute angular error (AAE). Eleven angles were tested in random order before beginning therapy, after 3 weeks, and after 12 weeks. RESULTS: Twenty-one men and 19 women completed the study (22 subjects received hyaluronan injections and 18 subjects received a placebo injection). No significant differences existed between the study groups in age, the timing of injections, or proprioceptive testing. A 2 x 3 repeated measures analysis of variance (ANOVA) comparing injection groups at all times revealed no significant differences in AAE. The AAE proprioception data was examined for differences due to fatigue caused by the number of test angles (p < .001) and differences explained by angulations in various divisions of the normal range of motion (p < .001). After accounting for these potential confounds, a two-way ANOVA still did not detect any significant differences in AAE between hyaluronan and placebo groups. CONCLUSION: Other studies have found that proprioception may be impaired in osteoarthritic knees and that viscosupplementation therapy with hyaluronan may decrease pain and increase function in these knee joints. The results of the present study suggest that this therapy does not adversely affect proprioception and that a longer, longitudinal study is required to determine if viscosupplementation treatments could attentuate proprioceptive decline.

Aged↗
PubMed2000

Determination of prefracture physical function in community-dwelling people who fracture their hip.

BACKGROUND: Prefracture physical function must be accurately determined to set appropriate and attainable goals for rehabilitation following hip fracture. This is especially important for people who were living independently prior to their fracture. This study determines reliability and internal consistency of a prefracture physical function questionnaire (PFPFQ) completed by both patients and knowledgeable informants (KIs). METHODS: A 20-item PFPFQ, including ambulation, transfers, balance, and self-care domains, was developed using focus groups. Community-dwelling patients with a hip fracture (N = 40, 77.9 +/- 8 years) completed the PFPFQ on two occasions during postoperative acute care. Forty KIs were identified by the patients and also completed the PFPFQ on two occasions via telephone interview. Day-to-day reliability of the patients and KIs [intraclass correlation coefficients (ICC)], and internal consistency [Kuder-Richardson coefficient (KR)] of the PFPFQ were determined. RESULTS: Intrarater reliability was high with ICCs (95% confidence interval) of 0.94 (0.89, 0.96) for patients and 0.96 (0.93, 0.98) for KIs. Interrater reliability on occasion 1 had an ICC of 0.81 (0.69, 0.88). Internal consistency of the patient responses on the first occasion was high (KR coefficient = 0.896). CONCLUSIONS: The PFPFQ is a reliable and internally consistent instrument for determining prefracture physical function in community-dwelling people who fracture their hip. In situations where patients with a hip fracture are unable to provide this necessary information, KIs can provide reliable estimates of prefracture function to assist in setting appropriate rehabilitation goals.

Aged↗
PubMed2000

Is exercise effective treatment for osteoarthritis of the knee?

OBJECTIVE: To review and determine the effectiveness of exercise treatment in osteoarthritis of the knee. METHODS: A computerised literature search of Medline was carried out searching between June 1966 and January 2000. RESULTS: Twenty three randomised controlled trials were identified from the literature. Only three trials were sufficiently powered. Small to moderate beneficial effects of exercise treatment were found for pain, small beneficial effects on disability outcome measures, and moderate to great beneficial effects were observed according to patient global assessment of effect. It was not possible to obtain evidence on the content of exercise interventions, as studies were hampered by lack of attention to proper concealment, reporting of adverse effects, and long term effects of exercise treatment. The lack of standard outcomes measures is also noted. CONCLUSIONS: The available evidence indicates beneficial short term effects of exercise treatment in patients with osteoarthritis of the knee. However, the number of available studies is limited, and more research is needed to expand this recommendation. Specifically, additional trials should provide information on adherence, home based interventions, interaction with pharmacological treatments, functional outcomes measures relevant to exercise treatment in these patients, and long term effects. At present, doctors should recommend exercise to all patients with mild/moderate disease. Further study should be encouraged and exercise should be continued to be recommended as a mainstay of non-pharmacological treatment of osteoarthritis of the knee.

Exercise Therapy↗
PubMed2000

Home based exercise therapy for older patients with knee osteoarthritis: a randomized clinical trial.

OBJECTIVE: This 8 week randomized, double blind clinical trial compared the effect of a combined home based progressive exercise program and treatment with the nonsteroidal medication oxaprozin to treatment with oxaprozin alone on pain and physical functioning in older community dwelling patients with unilateral knee osteoarthritis (OA). METHODS: Efficacy variables measured before and after 8 weeks included (1) pain using the Western Ontario McMaster (WOMAC) pain, physical disability, and stiffness subscales and a 10 point visual analog scale (VAS) before and after self-paced walking (SPW) and stepping (SPS) functional tasks; (2) physical function using the time to complete a self-paced 40 m walk (SPW) and 20 cycles of 2 steps (SPS): (3) physical activity level using the Physical Activity Scale for Elderly (PASE); (4) clinical measures of knee functioning (range of motion). One hundred seventy-nine men and women (mean age 74 +/- 6 yrs) with radiographic evidence of mild/moderate medial compartment OA were randomized to either a progressive home based knee exercise program (n = 88) or a control program (n = 89). All patients were given oxaprozin 1,200 mg per os daily. RESULTS: We observed significant reduction from baseline in activity related pain (VAS); and improvement in SPW and SPS test time, passive range of motion, and PASE after 8 weeks in both groups. These changes were significantly greater (p < 0.05) in the exercise versus sham group. CONCLUSION: Addition of a progressive exercise program to nonsteroidal antiinflammatory therapy in patients with knee OA can improve measures of activity and activity related pain more than medication alone.

Aged↗
PubMed2000

Left ventricular diastolic filling and cardiovascular functional capacity in older men.

We investigated anaerobic threshold (< theta(L)) gas exchange kinetics and maximal oxygen uptake (VO2,max) among older men with reduced left ventricular end-diastolic filling (LVDF). Ten men (mean age, 73 years) with LVDF impairment and low fitness, but without other cardiovascular dysfunction were studied. Treatments compared to control included: 5 days, high intensity exercise training protocol; 5 days, calcium channel blockade (240 mg verapamil); 21 days, detraining/washout; and 5 days, combined treatments. Results indicated no changes in resting left ventricular systolic function with any treatment. Significant resting diastolic function changes included increased early:late flow velocity (control, 0.87; training, 1.28; verapamil, 1.32), and a decreased isovolumic relaxation time (control, 0.10 s; training, 0.08 s; verapamil, 0.08 s). The combined treatments were not additive. Sub-threshold oxygen uptake kinetics (tauVO2, s) were significantly faster following either training or verapamil (tauVO2,control, 62+/-12; tauVO2,training, 44+/-9; tauVO2,verapamil, 48+/-10) and combined treatments (tauVO2, 41+/- 8). V O2,max (ml kg(-1) min(-1)) was significantly increased (control, 21.8+/-2.2; training, 27.3+/-2.2; verapamil, 25.2+/-3.4; combined treatments, 26.9+/-2.3). Increasing ventricular preload with either exercise training or calcium channel blockade was coincident with faster tauVO2 and increased VO2,max.

Aged↗
PubMed1999

Lifestyle modifications to prevent and control hypertension. 4. Recommendations on physical exercise training. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada.

OBJECTIVE: To provide updated, evidence-based recommendations for health care professionals concerning the effects of regular physical activity on the prevention and control of hypertension in otherwise healthy adults. OPTIONS: People may engage in no, sporadic or regular physical activity that may be of low, moderate or vigorous intensity. For sedentary people with hypertension, the options are to undertake or maintain regular physical activity and to avoid or moderate medication use; to use another lifestyle modification technique; to commence or continue antihypertensive medication; or to take no action and remain at increased risk of cardiovascular disease. OUTCOMES: The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the period 1966-1997 with the terms exercise, exertion, physical activity, hypertension and blood pressure. Both reports of trials and review articles were obtained. Other relevant evidence was obtained from the reference lists of these articles, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Physical activity of moderate intensity involving rhythmic movements with the lower limbs for 50-60 minutes, 3 or 4 times per week, reduces blood pressure and appears to be more effective than vigorous exercise. Harm is uncommon and is generally restricted to the musculoskeletal injuries that may occur with any repetitive activity. Injury occurs more often with jogging than with walking, cycling or swimming. The costs include the costs of appropriate shoes, garments and equipment, but these were not specifically measured. RECOMMENDATIONS: (1) People with mild hypertension should engage in 50-60 minutes of moderate rhythmic exercise of the lower limbs, such as brisk walking or cycling, 3 or 4 times per week to reduce blood pressure, (2) Exercise should be prescribed as an adjunctive therapy for people who require pharmacologic therapy for hypertension, especially those who are not receiving beta-blockers. (3) People who do not have hypertension should participate in regular exercise as it will decrease blood pressure and reduce the risk of coronary artery disease, although there is no direct evidence that it will prevent hypertension. VALIDATION: These recommendations agree with those of the World Hypertension League, the American College of Sports Medicine, the report of the US Surgeon General on physical activity and health, and the US National Institutes of Health Consensus Development Panel on Physical Activity and Cardiovascular Health. These guidelines have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.

Adrenergic beta-Antagonists↗
PubMed1999

Physician contact with older community patients: is there an association with physical fitness?

BACKGROUND: Contact with family physicians by older adults may be linked to their physical fitness in addition to other health, behavioral, and sociodemographic determinants. We studied a stratified random sample of urban community-dwelling elderly patients in London, Ontario, Canada, to describe the interaction of physical fitness measures and a number of health and lifestyle behaviors and sociodemographic outcomes with family physician contact over 1 year. We hypothesized that physician contact would be associated with lower indices of physical fitness and that association would be similar to other known determinants of physician utilization. METHODS: Three hundred seventy-five noninstitutionalized elderly men (N = 185) and women (N = 190) ages 55 to 84 years were recruited from the municipal tax assessment list for the city of London (population 280,000). Four categories of independent variables were selected to reflect common determinants of health (physical fitness, self-reported and clinically measured health, lifestyle behaviors, and sociodemographics). The association between these categories of variables and self-reported contact with family physicians and a variety of health professionals was determined for the year prior to the study. RESULTS: Forty-six percent of the subjects had at least one physician contact in the month prior to the study and 79% within the previous year. None of the other health professions (including nursing, chiropractic, physiotherapy, homemaking, and dentistry) were contacted more than once in the previous year. Lifestyle and sociodemographic variables including activity habits, smoking, income, marital status, and education were not associated with physician contact, whereas poor self-reported cardiovascular health and use of cardiovascular and pulmonary medications were associated with physician contact. Interestingly, physical fitness variables including maximal aerobic capacity, grip strength, and hip flexibility were not associated with physician contact. CONCLUSIONS: The absence of an association among physical fitness, lifestyle, and sociodemographic variables and physician contact was not anticipated and may be due to the selection of individuals who were independent, active community dwellers. It may be that most of the physician contact in this relatively healthy and physically fit sample was preventive in nature, for example, monitoring common chronic disease states in the elderly including cardiovascular and pulmonary disease. This paper reports baseline data from a longitudinal study of the interaction between physical fitness and health outcomes in groups of older community-dwelling individuals. As this group ages further, it would be interesting to determine the use of the health care system in relation to their changing functional and health status. In particular, do chronic health conditions such as cardiovascular disease, which increase in prevalence with age, become modified through maintenance of physical fitness and does this impact on health service use?

Aged↗
PubMed1999

Cardiovascular responses to facial cooling are age and fitness dependent.

PURPOSE: Aging of the cardiovascular system may be altered by differences in physical fitness. We investigated the cardiovascular responses to brief periods of facial cooling (5 degrees C) in 20 healthy men differing in age and aerobic fitness (VO2max). METHODS: Facial cooling was administered at rest in the supine position during 60-s quiet breathing to 6 fit young (FY; VO2max = 75.8 +/- 18 mL x kg(-1) x min(-1); 29 +/- 7 yr), 6 sedentary young (SY; VO2max = 36.0 +/- 2.2 mL x kg(-1) x min(-1); 27 +/- 3 yr), 6 fit old (FO; VO2max = 56.1 +/- 4.0 mL x kg(-1) x min(-1); 54 +/- 5 yr), and 6 sedentary old (SO; VO2max = 29.6 +/- 5.0 mL x kg(-1) x min(-1); 62 +/- 2 yr) volunteers. The following were measured before and after facial cooling: heart rate (HR), mean arterial blood pressure (MAP), pressure-rate product (PRP), and M-mode echocardiographically determined left ventricular internal dimensions, peak circumferential shortening (peak V(CF)), and ejection fraction (EF). RESULTS: Facial cooling produced a statistically significant bradycardia in all groups except for the SO whereas MAP was increased in the young groups but unchanged in the older groups. Pressure-rate product was significantly reduced in the FY, unchanged in the SY and FO, and significantly increased in the SO group. None of the groups showed a change in left ventricular dimensions, whereas only the SO group showed an increase in peak V(CF) (P < 0.05). CONCLUSIONS: These data suggest that endurance training and fitness level do not significantly alter cardiovascular responses to facial cooling in young men or physically fit older men. However, in older subjects, a sedentary lifestyle appears to be associated with an absent facial cooling reflex bradycardia, an increased PRP, and contractility (peak V(CF)).

Adult↗
PubMed1999

Exercise gas transport determinants in elderly normotensive and hypertensive humans.

This study examined the effect of the phenylalkylamine calcium channel blocker verapamil, on resting left ventricular (LV) function and O2 uptake rate (VO2) during exercise at maximal and submaximal work rates. Nine older hypertensive (71 years; OH), 10 older sedentary normotensive (69 years; OS), 10 older active (71 years; OA) and 10 young (24 years; Y) individuals volunteered. Studies were completed in the control condition and 4-6 h following 240 mg verapamil SR per os. Resting LV systolic (fractional shortening; FS) and diastolic (early: late (E/A) flow velocity ratio and isovolumic relaxation time (IVRT) were measured by Doppler echocardiography. Maximal oxygen uptake (VO2,max) and, on subsequent test days, four transitions to and from a 6 min square wave exercise perturbation at a sub-anaerobic threshold intensity of 40 W (OH, OS, OA) or 100 W (Y) for determination of VO2 kinetics were performed on a cycle ergometer. Breath-by-breath VO2 transients were fitted with a monoexponential equation, starting at phase 2 of the response, while heart rate (HR) was fitted from phase 1, for the determination of the time constant of VO2 (tau VO2) and HR (tau HR). Baseline left ventricular FS was significantly greater in the OS (32%), OA (34%) and Y (34%) than in the OH (23%) groups, while E/A was significantly greater in the OA (1.16) and Y (2.34) than in the OH (0.9) and OS (0.82) groups (P < 0.05). Baseline VO2,max was higher and tau VO2 faster in the young (41.4 ml kg-1 min-1; 25.2 s) than in the older groups and in the OA (28.8 ml kg-1 min-1; 44.3 s) than in both OH (20.8 ml kg-1 min-1; 71.3 s) and OS (22.0 ml kg-1 min-1; 59.5 s) groups (P < 0.05). Heart rate kinetics showed similar differences to VO2 kinetics among the groups. After verapamil, no significant changes in FS, E/A or IVRT were observed in the OA and Y groups. In the OH group, FS (32%) and E/A (1.15) increased while IVRT decreased significantly (from 0.103 to 0.07; P < 0.05). In the OS group, only E/A increased significantly (0.82 to 1.0; P < 0.05). None of the exercise variables (VO2,max, tau VO2 or tau HR) were altered for the OA or Y groups. VO2,max increased (from 20.8 to 22.8 ml kg-1 min-1) in the OH and (from 22.0 to 24.1 ml kg-1 min-1) in the OS (P < 0.05). tau VO2 was accelerated from 71.3 to 49.2 s in the OH group and from 59.5 to 48.2 s in the OS group (P < 0.05). These results suggest that VO2 responses at maximal and submaximal work rates may be dependent upon the initial cardiac pump function of the study population.

Adult↗
PubMed1998

Protein sidechain conformer prediction: a test of the energy function.

BACKGROUND: Homology modeling is an important technique for making use of the rapidly increasing number of protein sequences in the absence of structural information. The major problems in such modeling, once the alignment has been made, concern the positions of loops and the orientations of sidechains. Although progress has been made in recent years for sidechain prediction, current methods appear to have a limit on the order of 70% in their accuracy. It is important to have an understanding of this limitation, which for energy-based methods could arise from inaccuracies of the potential function. RESULTS: A test of the CHARMM function for sidechain prediction was performed. To eliminate the multiple-residue search problem, the minimum energy positions of individual sidechains in ten proteins were calculated in the presence of all other sidechains in their crystal orientations. This test provides a necessary condition that any energy function useful for sidechain placement must satisfy. For chi1 x chi2 rotations, the accuracies were 77.4% and 89.5%, respectively, and in the presence of crystal waters were 86.5% and 94.9%, respectively. If there was an error, the crystal structure usually corresponded to an alternative local minimum on the calculated energy map. Prediction accuracy correlated with the size of the energy gap between primary and secondary minima. CONCLUSIONS: The results indicate that the errors in current sidechain prediction schemes cannot be attributed to the potential energy function per se. The test used here establishes a necessary condition that any proposed energy-based sidechain prediction method, as well as many statistically based methods, must satisfy.

Crystallography, X-Ray↗
PubMed1998

How effective is exercise training for the treatment of hypertension?

OBJECTIVE: Exercise is often recommended as therapy for hypertension, yet its use is not widespread among clinicians. Reasons include uncertainty regarding its efficacy, the relative importance of the exercise prescription determinants (intensity and frequency), or confounding variables including patient characteristics such as age and gender. This review will present the evidence for exercise as a treatment for hypertension using a search of the English language literature from January 1966 to January 1998. DATA SOURCES: A search of MEDLINE articles using the MESH headings and textwords of blood pressure, hypertension, exercise, and exertion as well as hand searches in related articles and cross-referencing. DATA EXTRACTION AND SYNTHESIS: Identified articles were reviewed for their design characteristics, and specific attention was made of the subject characteristics, the exercise training protocol, the magnitude of the blood pressure-lowering response, and the influence of pharmacologic treatment on blood pressure lowering. RESULTS: A total of 39 studies representing random and nonrandom designs using predominantly walking-jogging exercise were identified. These studies showed reductions in blood pressure (systolic blood pressure/diastolic blood pressure) of -13/ -18 mm Hg in hypertensive patients. Most of the antihypertensive effect of exercise training was observed after 10 weeks, whereas training more than three times per week or for more than 50 minutes did not confer added benefit. Lower intensity exercise resulted in greater blood pressure reduction than did high intensity exercise. No gender differences in the antihypertensive effect of exercise were observed although most studies were performed in men. Although few studies were performed in older patients, there did not appear to be an age-dependent antihypertensive effect of exercise. There was a paucity of literature regarding the interaction of pharmacologic therapy and exercise in hypertensive patients. CONCLUSIONS: The results support the use of exercise as an effective therapy in hypertension. Studies were generally lacking in adequate control groups. Future research opportunities are many and should include studies using ambulatory monitoring and stratification of patients with different degrees of hypertension, undergoing different pharmacologic regimens.

Clinical Trials as Topic↗