The effect of parathyroid hormone on the uptake and retention of 25-hydroxyvitamin D in skeletal muscle cells.

Data from our studies, and those of others, support the proposal that there is a role for skeletal muscle in the maintenance of vitamin D status. We demonstrated that skeletal muscle is able to internalise extracellular vitamin D binding protein, which then binds to actin in the cytoplasm, to provide high affinity binding sites which accumulate 25-hydroxyvitamin D3 (25(OH)D3) [1]. This study investigated the concentration- and time-dependent effects of parathyroid hormone (PTH) on the capacity of muscle cells to take up and release 3H-25(OH)D3. Uptake and retention studies for 3H-25(OH)D3 were carried out with C2C12 cells differentiated into myotubes and with primary mouse muscle fibers as described [1]. The presence of PTH receptors on mouse muscle fibers was demonstrated by immunohistochemistry and PTH receptors were detected in differentiated myotubes, but not myoblasts, and on muscle fibers by Western blot. Addition of low concentrations of vitamin D binding protein to the incubation media did not alter uptake of 25(OH)D3. Pre-incubation of C2 myotubes or primary mouse muscle fibers with PTH (0.1 to 100 pM) for 3h resulted in a concentration-dependent decrease in 25(OH)D3 uptake after 4 or 16h. These effects were significant at 0.1 or 1pM PTH (p<0.001) and plateaued at 10pM, with 25(OH)D3 uptake reduced by over 60% (p<0.001) in both cell types. In C2 myotubes, retention of 25(OH)D3 was decreased after addition of PTH (0.1 to 100pM) in a concentration-dependent manner by up to 80% (p<0.001) compared to non-PTH treated-C2 myotubes. These data show that muscle uptake and retention of 25(OH)D3 are modulated by PTH, a physiological regulator of mineral homeostasis, but the cell culture model may not be a comprehensive reflection of vitamin D homeostatic mechanisms in whole animals.

Relationship between vitamin D status, body composition and physical exercise of adolescent girls in Beijing.

UNLABELLED: Little is known about the prevalence of actual vitamin D deficiency in healthy school-aged adolescents, particularly in China. The aim of this study was to examine the prevalence of hypovitaminosis D and to identify whether there was any association between vitamin D status, body composition and physical exercise in 323 Chinese adolescent girls in Beijing, China (40 degrees N). INTRODUCTION: It is well recognized that persistent severe vitamin D deficiency is associated with the bone abnormalities of rickets and osteomalacia. However, there is now evidence suggesting that low vitamin D status, not previously considered to be a state of deficiency is associated with secondary hyperparathyroidism, increased bone remodelling and other clinical signs thought only to be found in severe vitamin D deficiency. Hypovitaminosis D in healthy children and adolescents has been reported frequently in many countries, especially in winter. METHODS: We performed a cross-sectional analysis of 323 Chinese adolescent girls in Beijing in winter. Mean age of the subjects was 15.0 (+/-0.4) years. About 32.8%, 68.4% and 89.2% of the subjects were at risk of vitamin D deficiency when defined as plasma concentrations of 25OHD of 25, 37.5 or 50 nmol/L, respectively. RESULTS: This cross-sectional analysis of 323 Chinese adolescent girls in Beijing in winter showed that hypovitaminosis D was common in these subjects. In addition, body mass index, milk intake, participation in organized sports and total physical activity were all significant independent determinants of vitamin D status. An inverse association was found between plasma 25OHD and intact-parathyroid hormone (iPTH) concentration. Body mass index (BMI), milk intake, participation in organized sports and total physical activity all emerged as major independent determinants of vitamin D status as assessed by plasma 25OHD concentration. Vitamin D status was positively associated with lean body mass (LBM), but there was no association with the degree of body adiposity. Regardless of the concentration of 25OHD in blood used to define vitamin D deficiency, hypovitaminosis D was common in these subjects. CONCLUSION: It is recommended that policies be developed to prevent vitamin D deficiency in adolescent girls. Further studies are needed to identify the mechanisms whereby vitamin D status is related to exercise and to body composition during growth.

National sampling and gross composition of Australian retail pork cuts 2005/2006.

After consideration of five potential sampling designs, 13 retail pork cuts were purchased from randomly selected supermarkets and butchers' stores in urban areas across the socioeconomic scale in three States of Australia in late 2005 and early 2006. They were analysed, raw and cooked, for gross composition (fat, lean, bone and gristle). Gross composition varied considerably within cut associated with large divergences in interpretation of standard pork cuts by butchers. There were no notable differences in gross composition across States, across the socioeconomic range of suburbs of purchase or between outlet types (butcher vs supermarket). Cuts tended to be larger and leaner than those in similar studies in the 80s and 90s. Due to increasing uniformity in breeding and feeding of pigs in Australia, sampling designs in future surveys could be simplified.

Estimation of haemopoietic progenitor cells in peripheral blood by the Advia 120 and BD vantage flow cytometer: a direct comparison for the prediction of adequate collections.

Peripheral blood stem cells are increasingly used to ensure rapid haematological engraftment after myeloablative chemotherapy. After mobilization, progenitor cells in the blood can be enumerated to predict an adequate collection by leukapheresis. The Advia 120 automated counter has an immature cell channel measuring a parameter known as large undifferentiated cells (LUC's), which were quantified to assess their value in refining the timing of apheresis. Data were available from 102 apheresis sessions. Positive correlation was found for peripheral blood CD34+ cells and apheresis counts (r = 0.82, P < 0.0005) but not for total WCC (r = -0.15, P = 0.13) or LUC count (r = 0.12, P = 0.23). Our results indicate that the LUC population in peripheral blood has no relevance to the subsequent CD34 content of the apheresis product and CD34 cell enumeration by flow cytometry is advocated.

Low body weight and its association with bone health and pubertal maturation in Chinese girls.

OBJECTIVE: To investigate the prevalence of low body weight in Beijing pubertal girls and to establish the cut-off for body mass index (BMI) for underweight for Chinese pubertal girls. DESIGN: Cross-sectional study. SETTING: Three socioeconomic areas (rural, suburban and urban) in Beijing, China. SUBJECTS: Random sample of 1214 adolescent girls aged 12-14 y from 13 middle schools. RESULTS: Using a modified Chinese reference, the rate of low body weight (BMI<18) was 32.2% (95% CI 29.6-34.8%). Compared with desirable weight girls (BMI=18-21), girls with low body weight had a lower bone age, delayed breast and pubic hair development, a lower rate of menarche, lower distal one-third radius and ulna bone mineral content (BMC), bone mineral density and bone width. Logistic regression showed that BMI was one of the predictors of one-third ulna BMC after adjustment for confounding variables. When comparing BMI<18 vs BMI=18-21, the risk of BMC being less than the median increased by 82% (odds ratio 1.82, 95% CI 1.06-3.13). Thinness and stunting rates assessed by WHO recommended cut-offs are also reported. CONCLUSIONS: High prevalence of low body weight (BMI<18) was found to be a major health problem among Beijing pubertal girls. BMI<18 is confirmed as the cut-off for delayed general growth and development for Chinese girls and for screening girls at risk of lower bone mineral status.

Milk consumption and bone mineral content in Chinese adolescent girls.

A cross-sectional study of a random sample of 649 girls, aged 12-14 years (mean +/- SD: 12.9 +/- 0.6 years), in the Beijing area examined the relationship between diet and bone mineral status. Food and nutrient intakes over the past year were estimated by means of a semiquantitative food frequency questionnaire. Bone mineral content (BMC) and bone width (BW) at the distal one-third and one-tenth radius and ulna were measured by single-photon absorptiometry. Results showed Beijing pubertal girls had a low mean milk consumption (fresh and powdered milk, vitamin D-fortified milk, and yogurt) at 50 g/day (95% confidence interval [CI] 44-55 g/day whereas one-third consumed no milk at all. Mean calcium intake was 356 +/- 97 mg/day of which only 21% was provided by milk and milk products. Milk intake varied by region (rural, suburban, and urban: 9, 36, and 83 g/day, respectively, p < 0.0005) as did the proportion of milk consumers in the three areas (30%, 64%, and 91%, p < 0.0005). Bone mineral density (BMD) at the distal one-third and one-tenth radius and one-tenth ulna was positively associated with milk consumption (p < 0.05). Multiple regression analysis of BMC on foods and nutrients as well as confounding factors, including weight, bone age, Tanner stage, and School Physical Activity Score (SPAS), showed that milk intake was the only dietary factor included in the models for BMC at the four bone sites measured. The model explained 54%-65% of the variation in BMC, and milk alone accounted for up to 3.2% of the variation. Milk was the only food group with significant partial correlation with BMC. SPAS, weight, bone age, and Tanner stage each accounted for a smaller variation in BMC (<1.8%). The results indicate that milk (presumably as an integrated source of nutrients) had a beneficial effect on bone mass of Beijing pubertal girls and was a better nutritional determinant of BMC than intake of any milk nutrient alone. Promotion of milk consumption should be considered for achieving optimal bone mass in this population group.

Vitamin D deficiency and associated factors in adolescent girls in Beijing.

BACKGROUND: Several locally published reports indicate a high prevalence of vitamin D deficiency among adolescents in China, but no systematic population-based survey has been conducted. OBJECTIVE: The objective was to determine the prevalence of vitamin D deficiency and to study associated factors in adolescent girls in Beijing. DESIGN: A cross-sectional study was conducted in a random sample of 1248 Beijing girls aged 12-14 y. Nutrient intakes, ultraviolet light exposure, anthropometric characteristics, physical activity, signs and symptoms of rickets, and plasma concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and calcium were measured and X-rays of the hand and wrist were taken. RESULTS: The prevalence of clinical vitamin D and calcium deficiency (plasma 25-hydroxyvitamin D <12.5 nmol/L, plasma calcium <2.25 mmol/L, and muscle spasm at least once per week) was 9.4% in winter. The prevalence of subclinical vitamin D deficiency (25-hydroxyvitamin D <12.5 nmol/L) was 45.2% in winter and 6.7% in summer (P < 0.0005). Logistic regression analysis showed that subclinical and clinical vitamin D deficiency in winter were associated with low plasma 25-hydroxyvitamin D concentrations (<12.5 nmol/L) in summer, low calcium intake ( x +/- SD: 280 +/- 48 compared with 440 +/- 61 mg/d), and low plasma calcium concentrations (<2.25 mmol/L) in winter. The odds ratios for these associations were 3.1, 1.5, and 1.5, respectively. CONCLUSIONS: Subclinical vitamin D deficiency was widespread among Beijing adolescent girls in winter. Low plasma 25-hydroxyvitamin D concentrations in summer, low calcium intake, and low plasma calcium concentrations in winter were the main risk factors for vitamin D deficiency in winter.

Improvement of bone health in childhood and adolescence.

Osteoporosis as a worldwide problem is discussed in the present review and the question of improving peak bone mass to reduce the risk of osteoporosis and osteoporotic fracture is addressed. The available evidence points to pre-puberty and puberty as the most opportune periods for intervention, but the potential for achievable increments in bone mass is shown to be small compared with the overwhelming influence of heredity, body composition and hormonal factors on bone. Lean body mass appears to be positively correlated with bone mass, while black-white racial differences in bone mass appear to be related to greater lean mass and lower bone turnover rate in blacks. Within races, twin and parent-offspring models have suggested that 46-80 % of the variance in bone mineral density can be explained by inherited factors; however, the mechanism of the genetic influence on bone density remains poorly understood. Moderate regular exercise seems to maintain bone mass while more vigorous regular exercise increases it in children and young adults. Ca intake has been found to be positively associated with bone mass in many but not all studies, possibly because of a ceiling at about 1300-1500 mg/d for young people. Other nutritional variables, including vitamin D, have been little investigated in relation to childhood and adolescent bone mass. The influence of milk as a source of highly bioavailable Ca and other nutrients has also been less frequently investigated, which is of concern given the cessation of school milk programmes in Western countries over the last three decades. Intervention studies to improve bone health in young people have mainly been based on Ca milk or exercise. The evidence points to the benefits to bone of such interventions, particularly when commenced pre-puberty, and it seems that daily consumption of 200-300 ml milk/d by children and adolescents has no adverse side effects. The benefits to bone are almost universally shown to be lost fairly rapidly after Ca or exercise intervention ceases; there is therefore no justification in terms of bone health for short-term interventions of this nature. The question of withdrawal of milk supplementation has undergone very little examination. Further, very little evidence is available on the effects of long-term interventions of any sort on bone health. Nevertheless, the data obtained so far permit the suggestion that promotion of Ca intake (e.g. at the higher level of current recommendations) and exercise commencing in the pre-pubertal period should be adopted as policy now.

Quantitative determination of isoflavones and coumestrol in soybean by column liquid chromatography.

Four different stationary phases and a variety of solvents in varying proportions were examined in this study. Daidzein, genistein, formononetin, biochanin A and coumestrol were separated within 24 min on a phenyl column with acetonitrile-water (33:67, v/v) as eluent. The proposed method showed an acceptable repeatability with a RSD of quantitation <6%. The mean recoveries of daidzein, genistein, formononetin, biochanin A and coumestrol from soybean ranged from 89 to 104%. The identity of the individual analytes was confirmed by LC-MS-MS. The four isoflavones and coumestrol were isolated from soybean by hydrolysis with acid and heat. Neutralization of the soybean samples prior to identification did not alter the concentration of daidzein and genistein in soybean.

The effect of germ cell complement on the presence of oxytocin in the interstitial and seminiferous tubule fluid of the rat testis.

In the rat testis oxytocin has been localized to the Leydig cells, and these cells have been shown to produce oxytocin in vitro. The present study was performed to determine whether oxytocin is present in the interstitial fluid (IF) and seminiferous tubule fluid (TF) of the rat and whether concentrations of the peptide vary within the two compartments following germ cell destruction. In order to destroy germ cells adult male rats were anaesthetized and their scrotal regions placed in a water bath at 43 degrees C for 20 min. Control animals were subjected to anaesthesia alone. Groups of 6 animals were killed 3, 7 and 21 days after heat treatment and their testes removed for histological examination or fluid extraction. IF and TF were separated and the oxytocin content of the fluids measured by radioimmunoassay. Immunoreactive oxytocin was detected in both the IF (100 +/- 11 pg/ml) and TF (27 +/- 4 pg/ml) of control rats and this immunoreactivity co-eluted with the authentic peptide following HPLC. Three days after heat treatment IF levels of oxytocin were significantly reduced but TF levels of the peptide were significantly increased. These changes were associated with a lack of pachytene spermatocytes in the histological sections. Seven and 21 days after heat treatment the levels of oxytocin in the IF and TF were not significantly different from control levels. Similar changes in IF and TF oxytocin levels were seen in a second experiment when pachytene spermatocytes were removed using the testicular toxicant methoxyacetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Principal sources of dietary fat in Australia: evidence from apparent consumption data and the national dietary survey of adults.

The present study evaluates the evidence about the principal sources of fat in the Australian diet from the national per capita food supply data (apparent consumption; AC) and the national dietary survey of 6255 adults aged 25 to 64 years (NDSA). The AC and the NDSA data were converted to, and expressed on, an equivalent food basis to allow appropriate comparisons of foods consumed, and food sources of dietary fat. The AC figures showed that the principal sources of fat nationally were meat, edible fats, fat spreads and oils, and milk and milk products. As an estimate of adult food consumption the AC underestimated beef and veal, lamb, total meat, and poultry consumption by 41, 10, 29 and 13% respectively, and overestimated offal, milk and milk products, and fats and oils by 15, 61, 20, and 29% respectively. The AC data rated fat spreads and cooking fats as providing more of the fat in the adult diet than did the NDSA, both in terms of total fat and fat as a percentage of energy. Conversely, on this same basis, the AC underrated meats as sources of fat in the adult diet. Other foods were of similar importance as sources of dietary fat in both sets of data. The AC markedly underestimated adult fat intake at 32% of energy compared with the NDSA result of 37%. These results have implications for epidemiological research and for the development of food and nutrition policy and programmes in Australia and similar countries.

Influence of multi-holed shakers on salting on food.

In a study of 2241 Australian adults consuming main meals at a cafeteria, single-and multi-holed (5, 9, 13) salt shakers were weighed before and after use. For all hole numbers, salt use increased linearly with an increase in hole area to a maximum value of 1.1-1.2 g which was the same irrespective of hole number. For a given hole area multi-holed shakers decreased salt use compared with single-holed shakers suggesting that multi-holed shakers are easier for consumers to control. However the greatest restriction in salt use (0.37 g per meal) is obtained by use of a single-holed shaker of 3 mm2 hole area.

Contributions of foods to sodium in the Australian food supply.

The sodium contributions of various foods in the Australian supply have been calculated by applying recent local food composition data to food availability data and to typical notional Australian diets. Sodium available for consumption from the food supply was 3.00 g per capita per day. Of foods which are salted during processing, the three heaviest contributors of sodium were bread (23 per cent of total available sodium), processed meat and fish (14 per cent), and margarine (8 per cent). Other important contributors were breakfast cereals, biscuits, cheese, butter, potato crisps, dried soups and cakes (including pastries, pies and puddings). Foods identified by health authorities as 'highly salted' and thus prime targets for reduced consumption, provided 33 per cent of total available sodium, less than the 50 per cent contributed by other foods salted during processing. Take-away foods per se did not contribute more sodium than processed foods generally.

Salting of take-away foods at point of purchase.

Sodium and potassium levels were determined in ten types of fried take-away foods and sandwiches purchased from retail outlets with and without the addition of salt by the food handler. In virtually all foods the major source of sodium was that added during manufacture of the food ingredients rather than that added by the food preparer.

Sodium and potassium contents of salts, salt substitutes, and other seasonings.

Samples of table, cooking, rock and sea salts, flavoured salts, salt substitutes, seasonings, and monosodium glutamates were analysed for sodium and potassium content. The average sodium content of table, cooking and rock salts was about 16 600 mmol/kg, and that of sea salt was only marginally lower at about 16 100 mmol/kg. Flavoured salts contained about 11 900 mmol/kg, while "low salt" products contained about 9400 mmol/kg. Products marketed as containing "no salt" contained less than 20 mmol/kg (equivalent to less than 0.1 g sodium chloride per 100 g); all other salts contained the equivalent of over 50% sodium chloride. Nomenclature of seasonings was no indication of the sodium content, which ranged from 1060 to 12 960 mmol/kg. The monosodium glutamates contained 5300 mmol sodium per kg. Potassium was present at nutritionally significant levels only in "no salt" (12 800 mmol/kg) and "low salt" products (5300 mmol/kg).

Liquid chromatography, microfluorometry, and dye-titration determination of vitamin C in fresh fruit and vegetables.

The vitamin C content of several fresh fruit and vegetables was determined by a liquid chromatographic (LC) method which gave simultaneous separate values for ascorbic acid and dehydroascorbic acid (DHA) and by the official AOAC methods of microfluorometry and dye-titration. The levels of ascorbic acid obtained by LC and dye-titration were in good agreement, except for a few colored products where it was difficult to determine the end point of the titration. The combined values for ascorbic acid and DHA obtained by LC and microfluorometry were in agreement for most produce, but for about one-third of the samples, the values obtained by microfluorometry were significantly higher.