A quantitative histologic study of bone turnover in young adult beagles

Thirty-six regions of trabecular bone from two 18-month-old beagles and transilial biopsies of 25 female beagles aged 28–52 months were studied following in vivo double tetracycline labeling. Turnover rate varied from about 20% per year to 200% per year among the 36 regions. It was highest in the vertebral bodies and the proximal humerus, and lowest in the proximal ulna and foot-bones. The mineral apposition rate varied from 0.35 to 1.02 μm/day, with a mean of about 0.7 μm/day, tending to be lower in areas of lower turnover. The specific surface varied from 10.9 to 23.8 mm/mm² with a mean of 17.5 mm/mm², tending to be higher in areas of high turnover. Specific surface varied only about twofold around the skeleton, while turnover varied by one order of magnitude. The average annual turnover rate for all trabecular bone in the young adult beagle is estimated at 140% per year. The accuracy of this estimate would be improved by knowing the exact mass of trabecular bone at each site. The annual turnover rate in the ilium of 25 female beagles was 134 ± 94% per year. The iliac trabecular bone turnover rate is two to three times faster in young adult female beagles than in young adult female humans. Using a human to beagle ratio of 1:2.5, the average annual turnover rate for all trabecular bone in the young adult human could be estimated at 40–55% per year. The beagle may be an appropriate model for certain experiments involving the adult bone remodeling system, because it may show a quicker response than humans to various experimental conditions and drugs, due to its faster turnover rate.     

Effect of fitness and physical activity on bone mass in adolescents: the HELENA Study

Our aim is to analyse the effect on bone mass of: (1) physical fitness performance on a specific group of physical activity (PA) and, (2) PA on a specific physical fitness performance group. Bone mineral content (BMC) by dual energy X-ray absorptiometry (DXA) and PA by accelerometers was assessed in 373 Spanish adolescents (182 males). Adolescents were classified as: active and non-active (≥60 or <60 min day⁻¹ of moderate-vigorous PA). Fitness was assessed through speed/agility, strength and cardiorespiratory tests. Adolescents were classified by tertiles (T1, T2 and T3). ANCOVA was used for the analysis with sex, height, lean mass, calcium intake and pubertal status as covariates. Adolescents with lower strength, speed/agility and cardiorespiratory fitness (CRF) showed lower BMC in the whole body and extremities compared with adolescents with better results in these tests, mainly those non-active adolescents. Non-active adolescents with high fitness levels showed higher BMC (whole body and upper limbs) than active ones. The conclusions included: (1) within the non-active group, lower levels of fitness were associated with lower BMC; this might be through PA or trough an effect of PA on muscle mass. (2) Non-active adolescents with high level of fitness in most fitness tests showed higher BMC than their active peers, in spite of their lower PA levels. These unexpected results could be influenced by several factors such as genetics, nutrition, type of exercise or sport, hormones and skeletal age.     

Effect of isoflavones on lipids and bone turnover markers in menopausal women

OBJECTIVES: The purpose of this analysis was to compare the effects of two dietary supplements derived from red clover to placebo on lipids and bone turnover markers in symptomatic menopausal women. METHODS: The study was a 12-week randomized, double-blind, placebo-controlled trial. Two hundred and fifty-two menopausal women ages 45-60 years experiencing > or =35 hot flashes per week were randomly assigned to Promensil (82 mg total isoflavones), Rimostil (57.2 mg total isoflavones), or placebo. Primary outcome measures were mean absolute changes for HDL-cholesterol, serum osteocalcin, and urinary N-telopeptide. Secondary outcome measures were mean changes of total cholesterol, LDL-cholesterol, the ratio of HDL- to LDL-cholesterol, and triglycerides. RESULTS: Ninety-eight percent of participants completed the 12-week protocol. Women taking Rimostil or Promensil compared to those taking placebo had greater mean increases in HDL-cholesterol; however, this change was small in magnitude (<2 mg/dl) and did not reach significance. There was a significant decrease in triglyceride levels among women taking Rimostil (14.4 mg/dl, P = 0.02) or Promensil (10.9 mg/dl, P = 0.05) compared to those taking placebo. The decrease was primarily among women with elevated baseline triglyceride levels (P for interaction = 0.009). There were no differences in mean changes of total cholesterol, LDL-cholesterol, or the ratio of HDL- to LDL-cholesterol among treatment groups. There were no statistically significant differences among treatment groups for bone turnover markers. CONCLUSIONS: Compared with placebo, both of the supplements containing isoflavones decrease levels of triglycerides in symptomatic menopausal women; however, this effect is small in magnitude.     

Effect of physical activity on bone mineral density assessed by limb dominance across the lifespan

Bone mineral density is higher in dominant vs. nondominant limbs, implying that the greater use of dominant limbs in everyday activities results in the deposition of more bone or that the dominant limb is genetically larger. The objective of the present study was to determine whether bone mineral density differences between dominant and nondominant arms were greater in older vs. younger women. To determine whether this was due to a greater lifetime of preferential loading of the dominant arm, differences between dominant and nondominant arms were compared to accumulated amounts of physical activities which emphasized use of the dominant arm. Bone mineral density of dominant and nondominant arms was assessed by dual-energy X-ray absorptiometry in groups of younger (n = 35; age = 20.9) and older (n = 53; age = 57.4) women. The difference between arms was greater in the older vs. the younger group (5.2% vs. 1.9%, respectively, P < 0.01). Within the older group, total lifetime energy expenditure during activities emphasizing loading of the dominant arm correlated with the bone mineral difference between dominant and nondominant arms (r = 0.47, P < 0.01). This implies that a greater lifetime of preferential loading of the dominant arm in the older group resulted in a greater difference between arms. Am. J. Hum. Biol. 12:633–637, 2000. © 2000 Wiley-Liss, Inc.     

Body fatness and physical activity levels of young children

BACKGROUND: The decline in physical activity levels of young children seems to be combined with a high prevalence of obesity and overweight and a reduction in the participation in organized sport. With the ever-increasing interest in exploring the relationship between physical activity and obesity amongst children, it is important to provide a more precise estimate of both physical activity and body fatness. A significant proportion of previous research on this topic has relied on self-report methods to assess physical activity and body mass index as a proxy for actual body fatness. There is a need to investigate the relationships between physical activity and fatness in children using objective methods. AIM: This study was conducted in order to explore the relationship between physical activity patterns and percentage body fat amongst a group of primary school children. Subjects and methods: Forty-seven primary school children (boys, n = 23; girls, n = 24) participated in this study. They were randomly selected from children in years 5 and 6 (9-11 year olds) of four schools drawn from the same catchment area in the city of Birmingham, UK. The frequency, intensity and duration of physical activity were determined using continuous heart rate monitoring from 8:30 am to 8:30pm over three separate days (two weekdays and one weekend day). Percentage body fat was assessed using air displacement plethysmography. RESULTS: Results indicated that 52% of children did not achieve a single 15-min bout of sustained moderate physical activity over the three days of monitoring. Independent t-tests revealed that girls were significantly fatter (t44 = -3.126, p=0.003) than boys. There was no significant difference (t45 = 0.225, p > 0.05) between boys and girls in accumulated time spent with heart rates above the moderate physical activity threshold. Pearson's product moment correlation coefficients revealed no significant (r= -0.017, p> 0.05) relationship between per cent body fat and average daily time spent in moderate and vigorous activity. CONCLUSION: Despite the prediction to the contrary, there was no evidence of a significant relationship between percentage body fat of children and time spent in moderate and vigorous activity. Additionally, while there were no significant gender differences in physical activity patterns, children were more physically active during weekdays than weekends.     

Relaxation training combined with increased physical activity lowers the psychophysiological activation in community-home boys

Resting electrical activity (EMG) in the frontalis, temporalis, trapezius and erector trunci muscles, as well as systolic and diastolic blood pressure (BP), were measured in boys in a community home, and in controls of the same age in an ordinary school. EMG in the community-home boys was significantly higher than in controls, whereas BP did not yield any difference. The community-home boys participated in a programme consisting of relaxation training and increased physical activity for 4 months. After this intervention, EMG in all muscle groups was decreased, and the level of EMG was also lower than the values measured in controls. Systolic and diastolic BP in the community-home boys was also lowered, but the decrease was not significant as compared to the control group. In conclusion, relaxation training and/or increased physical activity is effective in decreasing the elevated activation observed in community-home boys.     

Ace I/D polymorphism is associated with habitual physical activity in pubertal boys

We investigated the association between the angiotensin I-converting enzyme (ACE) gene insertion (I)/deletion (D) polymorphism and physical activity levels in boys at early pubertal stage (calendar age 12.04 ± 0.77 years). Body composition by DXA, pubertal stage and cardiovascular fitness on cycle ergometer were measured in addition to 7-day accelerometry. DNA was separated from the whole blood. Sedentary behaviour level was significantly lower in DD subjects compared to I allele carriers. A significant main effect of the D allele was found on total physical activity (F _1,256 = 5,453; p = 0.020; η ² = 0.021] and on light physical activity (F _1,256 = 4.74; p = 0.030; η ² = 0.018). Adding screen time as a covariate did not change ACE I/D polymorphism effect on total physical activity levels (F _2,256 = 3,326; p = 0.041; η ² = 0.025). Carriers of the D allele had significantly higher light physical activity (F _1,256 = 4,710; p = 0.031; η ² = 0.20), with screen time as covariate. In conclusion, ACE gene has a significant effect on sedentary, light and total physical activity levels in healthy 12-year-old boys.     

氟化钠对去势大鼠骨转换和骨丢失的影响

目的　探讨氟化钠对切除卵巢 (去势 )大鼠椎骨和胫骨干骺端松质骨的作用。方法　用不脱钙骨切片的形态计量方法和血钙、磷、碱性磷酸酶和骨钙指标 ,检测去势大鼠给氟化钠 (1.0mg kg体重 )后骨吸收、骨形成、骨转换率和骨量的变化。结果　施加氟化钠后对骨吸收无明显抑制作用 ,骨形成明显活跃 ,骨转换率未降低。腰椎椎体松质骨体积百分比为 (18.73%± 3.0 4% )虽高于去势对照组大鼠 (15 .0 7%± 2 .45 % ) ,P <0 .0 5 ,也低于假去势对照组大鼠 (2 2 .44 %± 1.82 % ) ,P <0 .0 5 ;胫骨松质骨体积 (14.30 %± 5 .87% )亦如此 ,虽高于去势对照组大鼠 (8.81%± 2 .6 0 % ) ,P <0 .0 5 ,也低于假去势对照组大鼠 (2 4.87%± 4.0 2 % ) ,P <0 .0 1。结论　氟化钠对去势大鼠的松质骨骨转换率无影响 ,但在一定程度上可减少骨丢失。     

Effect of the difference of bone turnover on peri-titanium implant osteogenesis in ovariectomized rats

High and low bone turnover situations, both of which are typically observed as postmenopausal and senile osteoporosis, were created by ovariectomy (OVX), and then an investigation of whether or not the difference of bone turnover affected peri-titanium (Ti) implant osteogenesis in rats was conducted. Female rats were divided into four groups. The experimental and control groups underwent OVX or sham operations at 15 or 27 weeks of age, as high or low bone turnover groups, respectively. Ti implants were inserted into the tibiae at 30 weeks, then fluorochromes were injected 10 or 20 days after the implantation for histometry. The implants were retained for 30 days and then ground sections were prepared. Afterward, the cortical bone growth rate, bone contact ratio (BCR) of the implant in both the cortical bone area and medullary canal area, and the average trabecular bone thickness around the implant were evaluated. Biochemical markers of bone turnover were also measured. Biochemical measurements indicated both increasing osteocalcin production in OVX rats and decreasing tartrate-resistant acid phosphatase activity in the low-turnover group. Histometrical measurements showed decreasing cortical growth and low BCR in the medullary canal of the low-turnover group. The high-turnover group demonstrated BCR as high as that of the control group. There was no significant difference in the average trabecular bone thickness around the implant among the groups. As a result, two types of osteoporotic situations were confirmed and it was shown that the difference of bone turnover was clearly due to the diverse osteogenesis around the Ti implant.     

Effect of chronic activity-based therapy on bone mineral density and bone turnover in persons with spinal cord injury

Purpose

Osteoporosis is a severe complication of spinal cord injury (SCI). Many exercise modalities are used to slow bone loss, yet their efficacy is equivocal. This study examined the effect of activity-based therapy (ABT) targeting the lower extremities on bone health in individuals with SCI.

Methods

Thirteen men and women with SCI (age and injury duration = 29.7 ± 7.8 and 1.9 ± 2.7 years) underwent 6 months of ABT. At baseline and after 3 and 6 months of training, blood samples were obtained to assess bone formation (serum procollagen type 1 N propeptide (PINP) and bone resorption (serum C-terminal telopeptide of type I collagen (CTX), and participants underwent dual-energy X-ray absorptiometry scans to obtain total body and regional estimates of bone mineral density (BMD).

Results

Results demonstrated significant increases (p < 0.05) in spine BMD (+4.8 %; 1.27 ± 0.22–1.33 ± 0.24 g/cm²) and decreases (p < 0.01) in total hip BMD (?6.1 %; 0.98 ± 0.18–0.91 ± 0.16 g/cm²) from 0 to 6 months of training. BMD at the bilateral distal femur (?7.5 to ?11.0 %) and proximal tibia (? 8.0 to ?11.2 %) declined but was not different (p > 0.05) versus baseline. Neither PINP nor CTX was altered (p > 0.05) with training.

Conclusions

Chronic activity-based therapy did not reverse bone loss typically observed soon after injury, yet reductions in BMD were less than the expected magnitude of decline in lower extremity BMD in persons with recent SCI.     

The effects of a confectionery snack on attention in young boys

The relationship between consumption of a confectionery snack after an overnight fast and cognitive function was examined using a variety of cognitive tasks, including spatial memory, verbal memory, attention, visual perception and short-term memory, in a sample of 21 boys, ages 9-12 years. Performance on the vigilance attention task was significantly improved when the participants consumed a confectionery snack compared to consumption of a noncalorie snack. Participants had significantly higher hit rates and significantly lower miss rates after the confectionery snack. In addition, false alarm rates increased as a function of time for the placebo condition and decreased for the confectionery condition. Thus, the confectionery snack enhanced ability to stay on task for an extended period of time, enabling the children to more accurately identify target information, as well as correctly reject nontarget information. Analysis of the types of errors made also revealed that when the children were in the confectionery condition they were less likely to make more glaring errors. No significant differences were found in tests of digit span, verbal memory, spatial memory or visual perception.     

Body dimensions,exercise capacity and physical activity level of adolescent Nandi boys in western Kenya

The aim of this study was to characterize untrained Nandi boys (mean age 16.6 years) from a town (n = 11) and from a rural area (n = 19) in western Kenya (altitude ?2000 m.a.s.l.) in regard to their body dimensions, oxygen uptake and physical activity level. The town boys had a mean maximal oxygen uptake (VO_2max) of 50 (range: 45–60) mL?kg^?1?min^?1, whereas the village boys reached a value of 55 (37?63)?mL?kg^?1?min^?1 (?p<0.01) in VO_2max. The running economy, determined as the oxygen cost at a given running speed, was 221?mL?kg^?1?km^?1 (597?mL?kg^?0.75?km^?1) for town as well as for village boys. The body mass index (BMI) was very low for town as well as for village boys (18.6 vs 18.4?kg?m^?2). The daily mean time spent working in the field during secondary school and doing sports were significantly higher in village boys compared to town boys (working in the field: 44.2 (0–128) vs 1.3 (0–11)?min, p<0.01; sports: 32.0 (11–72) vs 12.8 (0–35)?min, p<0.01, respectively). A positive correlation between the daily time spent doing sports and VO_2max was found when pooling the data from the town and the village boys (R = 0.55, p<0.01). It is concluded that the body dimensions of adolescent Nandi town and village boys corresponds well with findings in Kenyan elite runners. They are very slender with relatively long legs. In addition, the VO_2max of the village boys was higher than that of the town boys, which is probably due to a higher physical activity level of the village boys during secondary school.     

Body dimensions, exercise capacity and physical activity level of adolescent Nandi boys in western Kenya

The aim of this study was to characterize untrained Nandi boys (mean age 16.6 years) from a town (n = 11) and from a rural area (n = 19) in western Kenya (altitude approximately 2000 m.a.s.l.) in regard to their body dimensions, oxygen uptake and physical activity level. The town boys had a mean maximal oxygen uptake (VO(2 max)) of 50 (range: 45-60) mL kg(-1) min(-1), whereas the village boys reached a value of 55 (37-63) mL kg(-1) min(-1) ( p<0.01) in VO(2 max). The running economy, determined as the oxygen cost at a given running speed, was 221 mL kg(-1) km(-1) (597 mL kg(-0.75) km(-1)) for town as well as for village boys. The body mass index (BMI) was very low for town as well as for village boys (18.6 vs 18.4 kg m(-2)). The daily mean time spent working in the field during secondary school and doing sports were significantly higher in village boys compared to town boys (working in the field: 44.2 (0-128) vs 1.3 (0-11) min, p<0.01; sports: 32.0 (11-72) vs 12.8 (0-35) min, p<0.01, respectively). A positive correlation between the daily time spent doing sports and VO(2 max) was found when pooling the data from the town and the village boys (R = 0.55, p<0.01). It is concluded that the body dimensions of adolescent Nandi town and village boys corresponds well with findings in Kenyan elite runners. They are very slender with relatively long legs. In addition, the VO(2 max) of the village boys was higher than that of the town boys, which is probably due to a higher physical activity level of the village boys during secondary school.     

Spectral and bout detection analysis of physical activity patterns in healthy,prepubertal boys and girls

Little is known about the frequency-intensity patterns of naturally occurring physical activity in children. A data set obtained previously by direct observation of physical activity in 8 girls and 7 boys (all prepubertal, ages 6–10) was analyzed with spectral analysis to detect significant frequency-intensity relationships. Pulse detection algorithms were used to characterize the number of exercise bouts, their duration and relative intensity. Spectral analysis revealed that physical activity bouts were frequent, pulsatile, and random with no significant frequencies detected during many 24-min periods of observation. An average of 83 ± 11 bouts per hour were observed in boys and 89 ± 12 bouts per hour in girls, and the mean duration of an exercise bout was 21 ± 5 sec for boys and 20 ± 4 sec for girls (NS). While high-intensity exercise bouts comprised less than 20% of the time spent in physical activity, duration of high intensity exercise bouts tended to be longer and accounted for about 40% of the energy expenditure associated with physical activity. Spontaneous physical activity in prepubertal children is characterized by frequent bouts of brief, mostly low intensity exercise, randomly interspersed with less frequent, but metabolically substantial high intensity bouts. These findings are potentially useful in assessing the impact of disease on quality of life in children, investigating the relationship between physical activity and mechanisms of growth and development, and creating new approaches for in-laboratory exercise testing in children. Am. J. Hum. Biol. 10:289–297, 1998. © 1998 Wiley-Liss, Inc.     

Gender differences in the physical activity levels of young African-American adults.

This study examines gender differences in the physical activity levels of young African-American adults. One hundred twenty-seven African-American college freshmen (57 males and 70 females) completed the Lipid Research Clinic''s Physical Activity questionnaire. Using a four-point scoring method (ie, very low active, low active, moderately active, and high active), approximately 71% of females compared with 49% of males were classified as very low active or low active. Statistical analysis revealed significant gender differences between groups. Post hoc analysis revealed that the difference existed in the high-activity category for females, with few females being categorized as high active. The results of this study suggest that young African-American adult females are less active than their male counterparts.     

Iron metabolism in boys involved in intensive physical training

The purpose of the present study was to compare some haematological and iron-related parameters of prepubertal boys (10-12 years old) involved in intensive physical training program in preparation for the national championship with nontrained age-matched subjects. For this purpose, iron stores, haemoglobin, ferritin and serum transferrin receptor concentrations were taken into account. The athletes' dietary intakes were similar to the respective intakes in the control group. Mean ferritin concentration was similar in investigated groups of boys at the start of the study, but significant changes between those groups occurred during the 8 months of study. Compared with the control group, the trained ones have shown significantly higher serum transferrin receptor concentration during the competition period of the training season, just when they reached maximum performance capacity. Similarly, significant difference in total body iron, estimated as the sum of the individual's red blood cells iron and iron stores, between investigated groups occurred only during the competition period. The main finding of this study is that the endurance training in boys brings about significant decrease in serum ferritin, as well as iron stores in the body. Haematological parameters and iron status of trained children revealed latent anaemia (15%) or even manifest anaemia (9%). These findings indicate high prevalence of nonanaemic iron deficiency in young athletes and bear relationship to swimming training.     

Water turnover in children and young adults

Water homeostasis is essential for life and optimal function and considerable interest surrounds the issue of recommendations for water consumption in healthy individuals. Objective data on water turnover in free-living individuals are limited, however. The aim of the present work was to measure water turnover in children and young adults using isotopically labeled water to provide objective data on magnitude and variability in relation to body weight, fat-free mass and physical activity level. Water turnover was measured by deuterated water dilution in 91 healthy children (40 boys, 51 girls; age 5–14 years) and 109 healthy young adults (80 women, 29 men; age 18–27 years) with a wide range of body mass index (13.3–51.8 kg/m²) and percent body fat (6.1–59.3%). Total energy expenditure (TEE) and resting metabolic rate were measured by the doubly labeled water technique and indirect calorimetry, respectively. Water turnover was 1.77 ± 0.57 (SD), 1.79 ± 0.44, 2.85 ± 0.82, and 3.90 ± 0.81 L/day in girls, boys, women, and men, respectively. Water turnover indexed to body surface area did not differ significantly between girls and women but was higher in men than boys. Water turnover indexed to TEE was 0.8 mL/kcal in girls and boys and 1.0 mL/kcal in women and men. This study provides objective data on water turnover for children and young adults in a temperate climate and shows that anthropometric parameters can account for the variation between girls, boys and women but not between these groups and the more active men.