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Biomedical subjects

A C Bell

Publications and source records attributed to A C Bell.

At least 19 recordsLinked to original sources
PubMed2006

Overweight and obesity prevalence in children based on 6- or 12-month IOTF cut-points: does interval size matter?

The International Obesity Taskforce (IOTF) recommends using age- and gender-specific body mass index (BMI) cut-points for defining the prevalence of overweight and obesity in children. These are given in both 6- and 12-month age intervals. Since the BMI-for-age curves are nonlinear, a degree of bias will be introduced when age intervals are wide. We aimed to quantify this bias in prevalence estimates in 2178 Australian children aged 4-12 years using 12- versus 6-month age intervals. Using the 12-month interval, the prevalence of overweight and obesity was underestimated by 1.4% compared to the 6-month interval estimates; however, this was age-dependent. It overestimated prevalence for 4-year olds, but underestimated it for older ages by up to 2.6%. Overweight prevalence was generally affected more than obesity prevalence. The use of different age intervals for IOTF cut-points introduces a small but systematic bias in prevalence estimates of overweight and obesity.

Age Factors↗
PubMed2006

Active transport to work in Australia: is it all downhill from here?

Physical inactivity is increasing in Australia and active forms of transportation may be one way to increase the working population's daily physical activity. We used travel-to-work data from employed persons aged 15 years and over participating in the 1996 (n = 7,636,319) and 2001 (n = 8,298,606) Australian censuses to determine prevalence and trends in walking and cycling to work by state and gender, and differences in prevalence by age. In 2001, 3.8% of Australians walked to work and < 1% cycled. Over 64% travelled to work by car. There have been small declines in walking (men and women) and cycling (men) over the 5-years from 1996 to 2001. People were more likely to walk or cycle to work if they lived in the Northern Territory, if they were male or if they were aged 15 to 24 years. They were more likely to travel by car if they lived in the Australian Capital Territory, if they were male, or if they were aged 45-54 years. Few people walk or cycle to work in Australia. Efforts to encourage active transportation are urgently needed.

Adolescent↗
PubMed2005

Contribution of 'noncore' foods and beverages to the energy intake and weight status of Australian children.

OBJECTIVES: The Australian Guide to Healthy Eating is based on five core food groups and water. Foods or beverages that do not fit into these groups are considered extra or 'noncore'. We tested the hypotheses that noncore foods and beverages make a greater proportional contribution to mean daily energy intakes of: (1) children, compared with other age groups; and (2) overweight and obese children, compared with healthy weight children. DESIGN, SETTING AND SUBJECTS: We used data from 13 858 participants aged 2 to 80+ y who had 24-h dietary recall data collected in the 1995 cross-sectional Australian National Nutrition Survey. ANOVA was used to compare the percentage of energy provided by noncore foods and beverages by age and weight status. RESULTS: Children (5 to 12 y) and adolescents (13 to 18 y) obtained significantly more (P < 0.001) of their daily food energy from noncore foods (41.5 and 43.4%, respectively) than all other age groups. These age groups also obtained significantly more (P < 0.001) of their daily beverage energy from noncore beverages (30.7 and 36.9%, respectively). Results were not consistent with weight status, although very young (2-4 y) obese children obtained significantly more energy (P < 0.05) from noncore beverages than children in a healthy weight range. Younger children may also have consumed a greater quantity of foods and beverages. Under-reporting may have obscured similar results for older children. CONCLUSIONS: By definition, noncore foods and beverages are surplus to the requirements of a healthy diet. We found that Australian children consume these foods and beverages in excess.

Adolescent↗
PubMed2005

Lunchbox contents of Australian school children: room for improvement.

OBJECTIVE: In light of the increasing prevalence of obesity in children and the potential of schools as a setting for intervention, we aimed to identify the main foods and beverages consumed at primary school and to determine differences in consumption patterns between children who used the school canteen and those who did not. DESIGN: Cross-sectional survey of school foods in 1681 5-12 y old children, 2003-2004. SETTING: Barwon South-Western region of Victoria, Australia. RESULTS: The school food provided an average (+/-s.e.m.) of 3087+/-26 kJ. Bread was the most frequently consumed food and contributed 20% of total energy at school, biscuits 13%, fruit 10%, muesli/fruit bars 8%, packaged snacks 7%, and fruit juice/cordial 6%. About 10% of children used the school canteen and these children obtained more total energy and more energy from cakes, fast foods and soft drink than noncanteen users (P<0.001). In all, 68% of children had fruit in their lunchboxes, however, over 90% of children had energy-dense, micronutrient-poor snacks ('junk food'). CONCLUSIONS: Fruit intake in primary schools seems reasonably high but could be targeted for further increase as part of promoting a healthy diet. Of concern, however, are the excessive amounts of energy-dense foods in school lunchboxes. These should be considered a priority for health promotion efforts along with reducing the consumption of sweetened drinks. These measures are urgently needed to improve the school-based diets of Australian children and attempt to curb the increasing prevalence of childhood obesity.

Age Factors↗
PubMed2004

What are the key food groups to target for preventing obesity and improving nutrition in schools?

OBJECTIVE: To determine differences in the contribution of foods and beverages to energy consumed in and out of school, and to compare consumption patterns between school canteen users and noncanteen users. DESIGN: Cross-sectional National Nutrition Survey, 1995. SETTING: Australia. SUBJECTS ON SCHOOL DAYS: A total of 1656 children aged 5-15 y who had weekday 24-h dietary recall data. RESULTS: An average of 37% of total energy intake was consumed at school. Energy-dense foods and beverages such as fat spreads, packaged snacks, biscuits and fruit/cordial drinks made a greater contribution to energy intake at school compared to out of school (P< or =0.01). Fast foods and soft drinks contributed 11 and 3% of total energy intake; however, these food groups were mostly consumed out of school. Fruit intake was low and consumption was greater in school. In all, 14% of children purchased food from the canteen and they obtained more energy from fast food, packaged snacks, desserts, milk and confectionary (P< or =0.05) than noncanteen users. CONCLUSIONS: : Energy-dense foods and beverages are over-represented in the Australian school environment. To help prevent obesity and improve nutrition in schools, biscuits, snack bars and fruit/cordial drinks brought from home and fast food, packaged snacks, and confectionary sold at canteens should be replaced with fruit and water.

Adolescent↗
PubMed2001

Heart disease and diabetes risk factors in Pacific Islands communities and associations with measures of body fat.

AIMS: To describe the prevalence of obesity and other coronary heart disease and Type 2 diabetes risk factors by age and ethnic group in Pacific Island communities and to determine the associations between these risk factors and body mass index. METHODS: Cross-sectional data from commuity-based intervention projects were combined to provide anthropometric, blood sample and blood pressure data on 1,175 Pacific Islands people (467 men, 708 women) aged 20 years and over from church communities in South, Central and West Auckland. Self-reported data on diabetes status and leisure-time physical activity were also collected. RESULTS: Based on an ethnic-specific mass index (BMI) cut-off (> 32 kg/m2), 45% of men and 66% of women were obese. The age-standardised prevalence of known diabetes was 12%. Men and women aged 40-60 years had the highest risk factor levels and were the most sedentary. Tongans had higher risk factor levels than Samoans. In men, BMI and waist circumference were associated (p<0.05), in the direction of greater disease risk, with blood pressure and concentrations of total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, and blood glucose. In women, these associations were similar but less consistent. CONCLUSIONS: While these data are not representative for all Pacific people living in New Zealand, they do show an extremely high prevalence of obesity and significant associations between obesity and other cardiovascular risk factors. These communities warrant a very high priority as part of public health efforts to address New Zealand's growing obesity epidemic.

Adolescent↗
PubMed2001

The effect of knee-flexion angle on wheelchair turning.

The increasingly popular hyperflexed knee-flexion angle was evaluated to determine its effects on wheelchair turning. Twenty able-bodied subjects were tested comparing the effect of full knee extension and full knee flexion on a number of parameters. We empirically measured the angular velocity of subjects spinning 720 degrees in place, subjects' perceived ease of wheelchair turning, the overall length of the wheelchair, the anteroposterior position of the center of mass (COM), rolling resistance, turning resistance and rear-wheel traction. The combined moment of inertia of the wheelchair and system was modeled. We found that, in comparison with full extension, fully flexing the knees increased angular velocity by 40% and was perceived to be 66% easier by subjects. Overall length decreased by 39%, COM moved rearward 38%, rolling and turning resistance decreased by 21% and 17% respectively, rear-wheel traction increased by 12% and moment of inertia decreased by 42%. All empirically tested parameters were statistically significant (p<0.007). We conclude that the knee-flexion angle has a significant effect on wheelchair turning. The implications of these findings for wheelchair design and prescription will need to be validated on actual wheelchair users and for smaller increments in knee-flexion range.

Adolescent↗
PubMed2001

A nutrition and exercise intervention program for controlling weight in Samoan communities in New Zealand.

OBJECTIVE: To promote weight loss in Samoan church communities through an exercise program and nutrition education. METHODS: A quasi-experimental design was used to assess weight change, over 1 y, in cohorts of people aged 20-77 y from three non-randomised Samoan church communities (two intervention, n=365 and one control, n=106) in Auckland, New Zealand. The intervention churches received aerobics sessions and nutrition education about dietary fat. RESULTS: Baseline body mass index for the intervention and control churches was (mean+/-s.e.) 34.8+/-0.4 and 34.3+/-0.9 kg/m(2), respectively. The intervention churches lost an average of 0.4+/-0.3 kg compared to a 1.3+/-0.6 kg weight gain in the control church (P=0.039, adjusted for confounders). The number of people who were vigorously active increased by 10% in the intervention churches compared to a 5% decline in the control church (P=0.007). Nutrition education had little apparent impact on knowledge or behaviour. CONCLUSION: Samoan communities in New Zealand are very obese and have high rates of annual weight gain. A community-based intervention program arrested this weight gain in the short term.

Adult↗
PubMed2001

Weight gain and its predictors in Chinese adults.

OBJECTIVE: To describe 8 y weight change in Chinese adults and to determine the baseline characteristics of those who gained weight. DESIGN: A population-based cohort study of weight change and its predictors from 1989 to 1997. PARTICIPANTS: A cohort of 2488 adults aged 20-45 in 1989 drawn from seven provinces in China using multistage, random cluster sampling. MEASUREMENTS: Weight change over 8 y was the outcome variable. The key exposures were baseline energy intake, physical activity at work, alcohol consumption and smoking status. Baseline weight, weight status, height, age, residence, income and educational attainment were control variables. RESULTS: Overweight (body mass index, BMI>or=25 kg/m(2)) doubled in females (10.4-20.8%) and almost tripled in males (5.0-14.1%). Low physical activity was a strong predictor of weight gain. Compared to those whose weight remained stable (+/-2 kg/8 y), males and females who experienced large weight gain (>5 kg/8 y) were 3 and 1.8 times more likely to engage in light rather than heavy work-related physical activity. CONCLUSION: The prevalence of overweight increased dramatically in this cohort. Light work-related physical activity was the strongest predictor of this weight gain.

Activities of Daily Living↗
PubMed2000

Methylation of a CTCF-dependent boundary controls imprinted expression of the Igf2 gene.

The expression of the insulin-like growth factor 2 (Igf2) and H19 genes is imprinted. Although these neighbouring genes share an enhancer, H19 is expressed only from the maternal allele, and Igf2 only from the paternally inherited allele. A region of paternal-specific methylation upstream of H19 appears to be the site of an epigenetic mark that is required for the imprinting of these genes. A deletion within this region results in loss of imprinting of both H19 and Igf2 (ref. 5). Here we show that this methylated region contains an element that blocks enhancer activity. The activity of this element is dependent upon the vertebrate enhancer-blocking protein CTCF. Methylation of CpGs within the CTCF-binding sites eliminates binding of CTCF in vitro, and deletion of these sites results in loss of enhancer-blocking activity in vivo, thereby allowing gene expression. This CTCF-dependent enhancer-blocking element acts as an insulator. We suggest that it controls imprinting of Igf2. The activity of this insulator is restricted to the maternal allele by specific DNA methylation of the paternal allele. Our results reveal that DNA methylation can control gene expression by modulating enhancer access to the gene promoter through regulation of an enhancer boundary.

Animals↗
PubMed2000

Structural and functional conservation at the boundaries of the chicken beta-globin domain.

We show that the 3' boundary of the chicken beta-globin locus bears striking structural similarities to the 5' boundary. In erythroid cells a clear transition in DNase I sensitivity of chromatin at the 3' end of the locus is observed, the location of this transition is marked by a constitutive DNase I hypersensitive site (HS), and DNA spanning this site has the enhancer-blocking capacity of an insulator. This HS contains a binding site for the transcription factor CTCF. As in the case of the 5' insulator, the CTCF site is both necessary and sufficient for the enhancer-blocking activity of the 3' boundary. The position of this insulator is consistent with our proposal that it may function to maintain the distinct regulatory programs of the globin genes and their closely appended 3' neighbor, an odorant receptor gene. We conclude that both boundaries of the chicken beta-globin domain are capable of playing functionally similar roles and that the same protein is a necessary component of the molecular mechanism through which these boundaries are defined.

Animals↗
PubMed1999

Positional enhancer-blocking activity of the chicken beta-globin insulator in transiently transfected cells.

It is thought that insulators demarcate transcriptionally and structurally independent chromatin domains. Insulators are detected by their ability to block enhancer-promoter interactions in a directional manner, and protect a transgene from position effects. Most studies are performed in stably transformed cells or organisms. Here we analyze the enhancer-blocking activity of the chicken beta-globin insulator in transient transfection experiments in both erythroid and nonerythroid cell lines. We show that four tandem copies of a 90-bp fragment of this insulator were able to block an enhancer in these experiments. In circular plasmids, placement on either side of the enhancer reduced activity, but when the plasmid was linearized, the enhancer-blocking activity was observed only when the insulator was placed between the promoter and the enhancer. These observations are consistent with the position-dependent enhancer-blocking activity of the insulator observed in stable transformation experiments.

Animals↗
PubMed1999

The protein CTCF is required for the enhancer blocking activity of vertebrate insulators.

An insulator is a DNA sequence that can act as a barrier to the influences of neighboring cis-acting elements, preventing gene activation, for example, when located between an enhancer and a promoter. We have identified a 42 bp fragment of the chicken beta-globin insulator that is both necessary and sufficient for enhancer blocking activity in human cells. We show that this sequence is the binding site for CTCF, a previously identified eleven-zinc finger DNA-binding protein that is highly conserved in vertebrates. CTCF sites are present in all of the vertebrate enhancer-blocking elements we have examined. We suggest that directional enhancer blocking by CTCF is a conserved component of gene regulation in vertebrates.

Amino Acid Sequence↗
PubMed1999

Stopped at the border: boundaries and insulators.

Boundaries in chromatin are often marked by the presence of insulator elements. New results in Drosophila have identified an insulator with a proven boundary function essential for development. Other studies suggest a connection between the activity of some insulators and Drosophila trithorax-Group and Polycomb-Group genes. Several examples of vertebrate insulators have now been found; their locations suggest important boundary functions. Enhancer-blocking studies in oocytes and position-effect studies in transformed cells shed new light on insulator mechanisms.

Animals↗
PubMed1999

The impact of modernisation on the diets of adults aged 20-40 years from Samoan church communities in Auckland.

The objective of this study was to describe the food and nutrient intakes of adults in three Samoan church communities located in Auckland, New Zealand. The study had a cross-sectional design and measured usual dietary intake in 437 participants, aged 20 years and over, using a self-completed, 89-item quantitative food frequency questionnaire. Median daily energy and nutrient intakes were calculated and compared by gender and age groups. Men obtained a significantly (p < 0.05) lower proportion of their energy from breads and cereals, fruits and vegetables and fats and oils than women. Compared to those aged 40+ years, those aged < 40 obtained a significantly (p < 0.01) lower proportion of their energy from meat, pulses and eggs, fruit and vegetables, and starchy staples. A significantly (p < 0.01) higher proportion of their energy intake came from takeaways, soft drinks, snacks and dairy products. Nutrient analysis revealed that those aged < 40 years obtained significantly (p < 0.001) more energy from fat and sugar, and less energy from protein (p < 0.001) than the older group. They also had significantly lower intakes, per 1000 kilocalories, of a wide selection of vitamins and minerals. A dietary transition has occurred for New Zealand Samoans, reflecting a shift from traditional to modern dietary patterns and a decline in the nutritional quality of the diet.

Adult↗
PubMed1998

Effect of delayed supplementation of fetal calf serum to culture medium on bovine embryo development in vitro and following transfer.

Supplementation of synthetic oviduct fluid (SOF) medium plus amino acids and bovine serum albumin (BSA) with either fetal calf serum (FCS) or charcoal-treated FCS (CT-FCS) from Day 5 of development was investigated to determine if either in vitro or post-transfer development was altered. Development to the compact morula stage or beyond was similar for all 3 treatments. However, blastocyst development at Day 7 was accelerated when serum was added to the medium (21.6, 40.1 and 39.4% blastocysts from cleaved embryos for BSA, FCS and CT-FCS, respectively; P < 0.01), but cell number of the resulting embryos was unaffected. Furthermore, addition of CT-FCS decreased the between replicate variation in embryo development and produced more Grade 1 and 2 quality embryos (25.8%) than BSA supplementation (18.1%; P < 0.05). The transfer of Grade 1 and 2 embryos at Day 7 following culture resulted in similar pregnancy and embryo survival rates for the 3 treatments, with a tendency for lower embryo survival of embryos cultured in FCS (embryo survival at Day 50 = 37.7% vs 53.3% and 57.6% for FCS, BSA and CT-FCS, respectively; P = 0.1). Significant fetal loss from Day 50 to term occurred within all 3 treatments. There were no birth weight differences for calves amongst the 3 culture treatments; however, one of the sires produced calves that were significantly heavier than expected, suggesting a possible sire-by-embryo interaction. These results demonstrate that addition of FCS may promote blastocyst development; however, there was also a tendency for lower embryo survival. Thus charcoal treatment of FCS is recommended, because it decreases variability in embryo development between runs and results in embryo survival rates to term similar to that BSA-supplemented media.

Animals↗
PubMed1997

Body size of New Zealand Pacific Islands children and teenagers.

AIM: To describe the mean height, weight and body mass index of Pacific Islands children aged 5-18 years residing in New Zealand and compare them with international reference charts commonly used in New Zealand. METHODS: Data from three data sets were used, which included 816 children from most Pacific countries with measurements being obtained in Auckland and Wellington. Mean values and 95% confidence intervals were compared to National Center for Health Statistics (USA) standards for height and weight. RESULTS: The mean height of males and females was on about the 95th percentile from age 5 to about age 10-11. During the teenage years it moved to the 50th percentile. Mean weight remained close to the 95th percentile until the mid teens and then it fell below the 95th percentile later in the teenage years. CONCLUSION: Mean body height and weight of Pacific Islands children were very high compared with international standards especially between 5-12 years and new Polynesian standards need to be developed.

Adolescent↗