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Biomedical subjects

D R Young

Publications and source records attributed to D R Young.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effect of cisplatin chemotherapy on extracortical tissue formation in canine diaphyseal segmental replacement.

The reconstruction of large bone and joint defects after the resection of malignant tumors remains a major challenge. Chemotherapy has significantly lowered the risk of metastasic disease, but complications associated with reconstructive techniques continue to result in late morbidity. In the present study, biomechanical torsion testing, gait analysis, and histomorphometric and scanning electron microscopic evaluations of 24 dogs were used to examine the effects of preoperative and postoperative administration of cisplatin on the biologic fixation of a porous-coated segmental replacement prosthesis. The chemotherapy consisted of four cycles of cisplatin administered at a dosage of 75 mg/m2 preoperatively or postoperatively. The healing was enhanced by use of an autogenous corticocancellous bone graft. The graft was placed evenly around the prosthesis and the adjacent femoral cortex. Mechanical analyses of torsional stiffness, yield strength, and maximum strength revealed no statistically significant differences between the groups at 12 weeks. Such lack of difference was mainly due to the penetration of highly organized fibrous tissue into the porous surface; this provided strong fixation of the implant to bone even in the absence of bone ingrowth. Although bone ingrowth into the prostheses was not affected, electron microscopic, histomorphometric, and radiologic analyses showed a clear difference in the formation of new bone around the prosthesis. Preoperative chemotherapy did not alter the formation of new bone, but specimens from animals treated postoperatively with cisplatin showed significantly less bone graft resorption and less new bone formation. Hence, the effect of cisplatin administration caused only a temporary delay, not a permanent effect, on extracortical capsule formation. The formation of extracortical bone and soft tissue might prevent debris-incised osteolysis and, therefore, prevent late complications by forming a tight capsule around the bone-prosthetic interface.

Animals↗
PubMed1997

The short-term effects of cisplatin chemotherapy on bone turnover.

Cisplatin is an effective agent in the treatment of osteosarcoma of bone but little is known of its effects on normal bone turnover. Twenty-four dogs divided into three study groups were used to study the effect of cisplatin on normal bone turnover at the distant site of surgery. Group 1 served as the control group, group 2 received four cycles of cisplatin every 3 weeks before the surgery, and group 3 received four cycles postoperatively. The bone turnover rate was evaluated by measuring levels of systemic bone markers, osteocalcin, alkaline phospohatase, urine pyridinoline cross-links, and by determination histomorphometric indices. Histomorphological analysis showed poor correlation on bone formation with systemic bone markers at distant sites of surgery. Histomorphometrically normal bone turnover was affected by administration of cisplatin, but the effect was temporary, late, and less significant than what occurred at the surgical site. Our data showed that significant effects of cisplatin are observed at the site of active cellular induction and proliferation, such as implant-host interface, and less effects are seen at the sites of normal bone turnover.

Alanine Transaminase↗
PubMed1996

Effect of community health education on physical activity knowledge, attitudes, and behavior. The Stanford Five-City Project.

The authors studied the effectiveness of community-wide health education on physical activity knowledge, attitudes, self-efficacy, and behavior. Random samples of residents aged 18-74 years who lived in four central California cities (baseline, n = 1,056 men and 1,183 women) were evaluated in 1979-1980 and approximately every 2 years thereafter to obtain four independent samples. Moreover, every subject in the initial independent samples was asked to return for follow-up every 2 years thereafter; subjects who completed all four examinations constituted the cohort sample (n = 408 men and 499 women). Two medium-sized cities received health education and two similarly sized cities served as controls. Results indicated little consistent evidence of a treatment effect on physical activity knowledge, attitudes, or self-efficacy in either men or women. Among physical activity measures, there was an indication of a positive treatment effect for men in the independent samples for estimated daily energy expenditure and percent participation in vigorous activities (p < 0.01), and for women in the independent (p = 0.014) and cohort (p < 0.01) samples for engagement in the number of moderate activities. These results underscore the need for development of more effective interventions to change physical activity than is provided by a broad-based, community-wide health education program and for more sensitive and reliable measures of knowledge, attitudes, and behavior with regard to physical activity.

Adolescent↗
PubMed1995

Long-term effects of varying intensities and formats of physical activity on participation rates, fitness, and lipoproteins in men and women aged 50 to 65 years.

BACKGROUND: Although exercise parameters such as intensity and format have been shown to influence exercise participation rates and physiological outcomes in the short term, few data are available evaluating their longer-term effects. The study objective was to determine the 2-year effects of differing intensities and formats of endurance exercise on exercise participation rates, fitness, and plasma HDL cholesterol levels among healthy older adults. METHODS AND RESULTS: Higher-intensity, group-based exercise training; higher-intensity, home-based exercise; and lower-intensity, home-based exercise were compared in a 2-year randomized trial. Participants were 149 men and 120 postmenopausal women 50 to 65 years of age who were sedentary and free of cardiovascular disease. Recruitment was achieved through a random digit-dial community telephone survey and media promotion. All exercise occurred in community settings. For higher-intensity exercise training, three 40-minute endurance training sessions per week were prescribed at 73% to 88% of peak treadmill heart rate. For lower-intensity exercise, five 30-minute endurance training sessions per week were prescribed at 60% to 73% of peak treadmill heart rate. Treadmill exercise performance, lipoprotein levels and other heart disease risk factors, and exercise adherence were evaluated at baseline and across the 2-year period. Treadmill exercise test performance improved for all three training conditions during year 1 and was successfully maintained during year 2, particularly for subjects in the higher-intensity, home-based condition. Subjects in that condition also showed the greatest year 2 exercise adherence rates (P < .003). Although no significant increases in HDL cholesterol were observed during year 1, by the end of year 2 subjects in the two home-based training conditions showed small but significant HDL cholesterol increases over baseline (P < .01). The increases were particularly pronounced for subjects in the lower-intensity condition, whose exercise prescription required more frequent exercise sessions per week. For all exercise conditions, increases in HDL cholesterol were associated with decreases in waist-to-hip ratio in both men and women (P < .04). CONCLUSIONS: While older adults can benefit from initiating a regular regimen of moderate-intensity exercise in terms of improved fitness levels and small improvements in HDL cholesterol levels, the time frame needed to achieve HDL cholesterol change (2 years) may be longer than that reported previously for younger populations. Frequency of participation may be particularly important for achieving such changes. Supervised home-based exercise regimens represent a safe, attractive alternative for achieving sustained participation.

Aged↗
PubMed1995

Associations of physical activity with performance-based and self-reported physical functioning in older men: the Honolulu Heart Program.

OBJECTIVE: To examine the association of self-reported physical activity with performance-based and self-reported physical functioning measured 3 to 5 years later. DESIGN: A population-based, longitudinal study. SETTING: The island of Oahu, Hawaii. PARTICIPANTS: Subjects were 3640 Japanese-American men older than 70 years of age. MEASUREMENTS: Estimated daily energy expenditure evaluated from self-reported engagement in a variety of activities determined from a mail survey in 1988; physical functioning status determined from both self-report and performance-based measures 3 to 5 years later. The effect of physical activity on physical functioning scores was determined through multiple logistic regression and analysis of covariance techniques for subjects who had chronic diseases as well as those in a healthy subsample. RESULTS: For the healthy subsample, those who were highly active in 1988 were more likely to have optimal function for the basic activities of daily living score (odds ratio 2.3; confidence interval (CI) 1.1 to 4.9), home management skills score (odds ratio 1.5; CI 1.1 to 2.1), and physical endurance-type tasks score (odds ratio 1.7; CI 1.2 to 2.4) than subjects classified as low active. A significant linear trend was found additionally across physical activity level for time to walk 10 feet and grip strength (P values < .001). Similar results were found for subjects with chronic diseases; however, most of the benefit of physical activity for this subsample occurred for subjects who were at least physically active at a moderate level. CONCLUSION: Engaging in physical activity is predictive of a high level of physical functioning in older men with and without chronic diseases. Participation in at least moderate physical activity may be sufficient to maintain optimal physical functioning in subjects afflicted with chronic diseases.

Activities of Daily Living↗
PubMed1995

Internal validity of the physical activity index over 26 years in middle-aged and older men.

OBJECTIVE: To determine the internal validity of the physical activity index (PAI). DESIGN: Three time periods over a 26-year period (1965/68 examination, n = 7911; 1980/82 examination, n = 2054; 1991/93 examination, n = 3425). SETTING: Honolulu, Hawaii. PARTICIPANTS: Middle-aged to older Japanese-American men. MEASUREMENTS: PAI, other physical activity measures, body mass index (BMI), tricep skinfold thickness, subscapular skinfold thickness, and HDL cholesterol. RESULTS: PAI levels was associated significantly with levels of other physical activity measures at all time periods. Higher PAI level was associated with lower BMI at the baseline examination (1965/68), lower subscapular skinfold thickness at the 1965/68 and 1980/82 examinations, lower tricep skinfold thickness at all examinations, and higher HDL cholesterol at the 1980/82 examination. Change in PAI level from 1965/68 to 1980/82 was associated with change in BMI, subscapular, and tricep skinfold thickness levels, but there were no significant associations between change in PAI level and change in BMI, skinfold thicknesses, or HDL cholesterol levels from 1980/82 to 1991/93. CONCLUSION: PAI level is a relatively valid estimate of overall daily energy expenditure that may be an acceptable general measure across the middle-to-late stages of life. The PAI may also be sensitive enough to discern a shift toward less physical demanding activities as a population becomes older, although further studies should be conducted to better determine its validity in older populations.

Aged↗
PubMed1995

Associations among baseline physical activity and subsequent cardiovascular risk factors.

To determine stability of cross-sectional associations between physical activity and cardiovascular risk factors and provide information regarding possible independent effects of physical activity on reduced cardiovascular disease, this report examined associations among baseline physical activity and risk factors measured over 15 yr. Subjects were 1,379 Honolulu Heart Program participants who were evaluated at baseline and three subsequent examinations. For men initially 45-54 yr, higher physical activity level was significantly associated cross-sectionally and at 2 yr with lower diastolic blood pressure, body mass index, and skinfold thicknesses, and at 5 yr with higher high density lipoprotein (HDL) cholesterol. By the 15-yr examination, only associations between physical activity level and skinfold thicknesses remained significant. For men 55-68 yr, significant cross-sectional and 2-yr associations were found between higher physical activity level and lower skinfold thicknesses, and higher HDL cholesterol at 5 yr. Higher physical activity continued to be associated with lower skinfold thicknesses and was related to lower systolic blood pressure by the 15-yr examination. Results suggest that most cross-sectional associations between physical activity and risk factors diminish over time, providing support for prospective investigations that find physical activity has a beneficial effect on reduced cardiovascular disease partially independent of traditional risk factors.

Activities of Daily Living↗
PubMed1995

Sources of social support as predictors of exercise adherence in women and men ages 50 to 65 years.

Examines types of social support that best predicts adherence at different time points during a 1-year endurance exercise program in 269 women and men ages 50 to 65 years. Results indicate that social support had similar effects on exercise participation for women and men, and support specific to exercise was a better predictor of exercise adherence than general social support. A preference for receiving a lesser amount of initial support from exercise staff was the strongest social support-related predictor of exercise adherence during the initial 6 months of the program. Support currently received from family and friends and exercise staff at Month 6 was found to be the strongest predictor of adherence during Months 7 to 12. Format of exercise was also a strong predictor of exercise adherence with home-based programs related to greater adherence. Additionally, divorced nonsmokers appear to be at increased risk for poor early exercise adherence and should be targeted in interventions to promote exercise participation.

Aged↗
PubMed1994

Can cardiorespiratory fitness moderate the negative effects of stress on coronary artery disease risk factors?

This investigation evaluated whether cardiorespiratory fitness was associated with a moderation of the negative effects of stress for coronary artery disease risk factors. Cardiorespiratory fitness; self-reported general stress and job stress; physiological risk factors of systolic and diastolic blood pressure, total cholesterol, and HDL cholesterol; and behavioral risk factors of Type A behavior pattern and smoking habits were collected on 412 male law enforcement officer volunteers. Partial correlational analyses between the stress measures and the risk factors suggested that cardiorespiratory fitness had no moderating effect on either the physiological or behavioral risk factors. However, for smokers, fitness may have slightly suppressed the stress-related amount of cigarettes smoked per day, although the change in correlation was small and may not have been meaningful. Since neither stress measure was associated with any physiological risk factors, the potential moderating effect of cardiorespiratory fitness was not optimally tested.

Adult↗
PubMed1994

Ambulatory blood pressure and heart rate responses to the stress of work and caregiving in older women.

BACKGROUND: Although the informal caregiving role is associated with a range of stressors that are both chronic and severe, little is known concerning the acute physical and psychological effects of caregiving in the natural setting. This study evaluated the hemodynamic and psychological responses of five women identified as family caregivers who also worked outside the home and five matched working noncaregivers. METHODS: Subjects wore an ambulatory blood pressure monitor that recorded blood pressure and heart rate on an hourly basis throughout a one- to two-day period. They also completed hourly logs evaluating psychological, physical, and health-related variables through use of a preprogrammed pocket computer. Within- and between-group responses were compared in clinical, work, and postwork settings. RESULTS: Caregivers and noncaregivers showed comparable ambulatory blood pressure levels in the clinic and work settings. However, in contrast to noncaregivers, who showed the expected decrease in blood pressure level upon leaving the work setting (p values < .03), caregivers demonstrated a significant increase in systolic blood pressure levels following work when they were in the presence of the care recipient (p < .0002). The differences observed in blood pressure responses between the two groups were similarly reflected in the patterns of affective response recorded in the work and postwork settings. CONCLUSIONS: The results provide initial evidence of the acute iatrogenic effects of caregiving on physiological as well as psychological response systems.

Affect↗
PubMed1993

Associations between changes in physical activity and risk factors for coronary heart disease in a community-based sample of men and women: the Stanford Five-City Project.

Aerobic exercise training studies involving volunteers generally result in an improved cardiovascular risk factor profile. Little is known, however, about associations between physical activity change and risk factor change in a more representative sample, such as a community. This investigation evaluated correlations between a composite physical activity change score and change in cardiovascular risk factors from 1979 to 1985 in the cohort sample of the Stanford Five-City Project. Men (n = 380) and women (n = 427) between the ages of 18 and 74 years were evaluated for change in self-reported physical activity and change in total cholesterol, high density lipoprotein cholesterol (HDL cholesterol), systolic blood pressure, resting pulse rate, and body mass index (weight (kg)/height (m)2). For men, improvement in the composite physical activity score significantly correlated with an increase in HDL cholesterol (r = 0.14, p = 0.005) and decreases in body mass index (r = -0.16, p = 0.001) and estimated 10-year coronary heart disease risk score (r = -0.10, p = 0.056). For women, improvement in the physical activity score was associated with changes in HDL cholesterol (r = 0.11, p = 0.028) and resting pulse rate (r = -0.15, p = 0.001). These data demonstrate that an increase in physical activity over 5 years is favorably associated with changes in major cardiovascular disease risk factors in men and women and support the public health efficacy of community-wide promotion of physical activity.

Adolescent↗
PubMed1993

A mechanical comparison of gluteus medius attachment methods in a canine model.

Seven techniques of gluteus medius attachment were compared in vitro in a canine model. Four methods were used for tendon to tendon attachment: (a) two modified Bunnell-Mayer sutures, (b) two Kessler locking loop sutures, (c) two horizontal mattress sutures, and (d) two sutures with a looped suture technique. The two methods of tendon to bone attachment were repair with a 1 cm spiked staple and repair with a spiked washer and screw, and the method of bone to bone attachment involved two figure-eight cerclage wires. The contralateral limb served as a control. Compared with the bone to bone attachment, the four tendon to tendon attachments and the two tendon to bone attachments had significantly less strength (31 and 30% of the ultimate load for bone to bone repair, respectively) and tensile stiffness (24 and 39% of the tensile stiffness for bone to bone attachment, respectively) (p < 0.0001). The control specimens were significantly stronger and stiffer than all specimens (p < 0.05) except those that had bone to bone fixation. There were no significant differences among the four tendon to tendon suture repairs with regard to either strength or stiffness; the values ranged from 28-45% of those of the controls. Among the tendon to bone repairs, fixation with a spiked washer and screw was significantly stronger than that with a spiked staple (p = 0.032), but there was no difference between these two techniques with regard to stiffness.

Analysis of Variance↗
PubMed1993

The importance of physical fitness versus physical activity for coronary artery disease risk factors: a cross-sectional analysis.

Numerous epidemiological investigations have shown that low physical fitness and low physical activity are related to the incidence of coronary artery disease (CAD). Most studies, however, have not examined both variables concurrently to determine which has the strongest association with CAD risk. The purpose of this investigation was to cross-sectionally examine the relationships among physical fitness, physical activity, and risk factors for CAD. Male law enforcement officers (N = 412) from the City of Austin, Texas, were subjects for this study. Physical fitness, physical activity, and risk factors for CAD were assessed through health screenings and from data collected as part of an annual physical fitness assessment. Multivariate analysis of covariance revealed that physical fitness, but not physical activity, was related to several single CAD risk factors. Percent body fat, smoking habits, and Type A behavior score were negatively related to physical fitness level, and high density lipoprotein (HDL) cholesterol was positively related to physical fitness level. Univariate analysis of variance found both physical fitness and physical activity to be significantly related to a composite CAD risk score. Low physical fitness and low physical activity were associated with a high CAD risk score. These data suggest that physical activity must be sufficient to influence physical fitness before statistically significant risk-reducing benefits on single CAD risk factors are obtained, although minimal engagement in weekly vigorous activity provides a significant benefit for the composite CAD risk score. It is plausible, however, that physical fitness is a stronger measure than physical activity and optimally characterizes the relationship among physical activity and CAD risk factors.

Adult↗
PubMed1992

Psychological attributes of participants and nonparticipants in a worksite health and fitness center.

This study examined differences in psychological attributes (eg, estimation of physical ability, attraction to physical activity, self-motivation, and attitudinal commitment to physical activity) among 646 participants and nonparticipants in an onsite health and fitness program. An analysis of the data, using stepwise multiple regression and controlling for age and sex, revealed that the psychological attributes significantly predicted group membership (R2 = .27). Increased participation was related to higher levels of attitudinal commitment (beta = .48) and self-motivation (beta = .16). Increased participation, however, was inversely related to estimation of physical ability (beta = -.17). Results of the stepwise multiple discriminant analysis showed that nonparticipants and high active participants could be classified using the predetermined variables with an accuracy of 32.7% and 40.1% gain above base rate, respectively. Low active and moderately active participants were classified at a rate only equal to chance. The authors discuss implications for programming strategies to increase participation in onsite programs.

Adaptation, Psychological↗
PubMed1991

Quantitative evaluation of the remodeling response of the proximal sesamoid bones to training-related stimuli in Thoroughbreds.

Eight untrained 2-year-old Thoroughbred horses were used in a study of the remodeling response of the proximal sesamoid bone (PSB) to training-related stimuli. Two horses each were assigned to 1 of 4 groups: group 1, untrained, pasture turnout (control); group 2, modified-classically trained, dirt track; group 3, classically trained, dirt track; and group 4, classically trained, wood chip track. Horses were given fluorochromic bone labels every 28 days during training. All horses were euthanatized after 5 months of training, and the proximal sesamoid bones (PSB) were removed. A midsagittal section of bone 85- to 95-microns thick was prepared for histomorphometric analysis by use of computerized image analysis and epifluorescent microscopy. Porosity (percent), trabecular width (micrometer), extent of anisotropy (percent), mineralizing surface (percent), fractional mineralizing surface (percent), and mineral apposition rate (micrometers per day) were determined at 5 circular regions of each specimen. Region 1 was located within the apex of the PSB, regions 2, 3, and 4 were subjacent to the subchondral plate, and region 5 was within the basilar articular margin. Data were pooled to allow comparison by training group and by region. The PSB from horses trained on dirt tracks (groups 2 and 3) had significantly (P less than 0.05) lower porosities and greater trabecular width, compared with the control group. The PSB from all training group specimens had significantly larger mineralizing surfaces than control group specimens. The fractional mineralizing surface revealed a rapid and vigorous response of the endosteal surface of the PSB in horses trained on dirt tracks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Mechanical and morphometric analysis of the third carpal bone of Thoroughbreds.

The third carpal bone (C3) was collected from both forelimbs of 27 Thoroughbreds. On the basis of age, training, and history, specimens were assigned to 1 of 5 groups: yearling, untrained horses (group 1, n = 4); 2- to 3-year-old, untrained horses (group 2, n = 7); trained 2-year-old horses (group 3, n = 6); trained 3-year-old horses (group 4, n = 6); and 3-year-old, trained horses with carpal pathologic features (group 5, n = 4). A transverse section of subchondral bone 5-mm thick was cut in a precise fashion 10 mm below the proximal articular surface of all specimens. After high-detail radiography was done, indentation testing was performed on the proximal surface of the section at points 5 mm apart. The stiffness of the subchondral cancellous bone was determined from the slope of the load vs displacement curve. Topographic plots of stiffness measurements were compared with radiographs of each specimen. Point determinations were averaged to derive measures for the radial and intermediate facets, and for regions 5, 10, 15, and 20 mm from the dorsal margin of C3. Area fraction (1-p; p = porosity) was measured for the radial and intermediate facets, using an automated image analysis system. Significant (P less than 0.05) increases in stiffness and area fraction were found in the C3 from trained horses (groups 3 to 5), compared with untrained horses (groups 1 to 2). Stiffness and area fraction of the radial facet of pathologic C3 were significantly higher than the same variables measured in C3 from any other group.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗