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Biomedical subjects

A Prentice

Publications and source records attributed to A Prentice.

At least 37 records · Page 2Linked to original sources
PubMed1999

Comparison of adult and paediatric spine and whole body software for the Lunar dual energy X-ray absorptiometer.

Simple phantoms were devised to compare the performance of adult (software 3.64) and paediatric (software 3.8 g) spine and whole body software developed for the Lunar dual energy X-ray absorptiometer. Rectangular slabs of aluminium with high (1.18 g cm-2) and low (0.57 g cm-2) density were used to represent bone mineral. For spine measurements, the phantoms were scanned in water at depths of 5-20 cm. For whole body measurements, the phantoms were scanned with known amounts of oil and water to represent fat and lean tissue. This simulated tissue depths of 5.5-19.7 cm and body composition ranging from 14-29% fat. There were systematic differences in spine and whole body bone mineral content (BMC), bone area (BA) and bone mineral density (BMD) measurements and also between adult and paediatric software versions. The magnitude and direction of these differences were dependent on BMD of the phantom and tissue depth. Similar systematic differences were observed in vivo when volunteers were scanned using adult and paediatric software. Paediatric software enabled measurements to be made at low tissue depths. The weights of fat, lean and total soft tissue measured by the adult and paediatric whole body software were similar to the values calculated from the known composition of the phantom. Precision estimates for all softwares were excellent. In conclusion, paediatric software should improve bone mineral measurements of children but the discrepancies between adult and paediatric softwares may cause problems in longitudinal studies of skeletal growth and when compiling reference data from infancy through to adulthood.

Absorptiometry, Photon↗
PubMed1999

Bone mineralization and turnover in preterm infants at 8-12 years of age: the effect of early diet.

Our previous studies raised two hypotheses: first that suboptimal early nutrition and second that human milk have enhancing effects on long-term bone mineralization. To test these hypotheses experimentally, we measured whole body and regional bone mineral content (BMC) and bone mineral density (BMD), using dual-energy X-ray absorptiometry and single-photon absorptiometry, and bone turnover at 8-12 years in 244 preterm children (128 boys) who participated in a prospective randomized study of diet during the neonatal period. Dietary randomizations studied were: banked human milk (BBM, n = 87) versus preterm formula (PTF, n = 96) as the sole diet or as a supplement to mother's expressed breast milk (EBM); PTF (n = 25) versus term formula (TF, n = 36) as sole diet. Ninety-five term children of the same age were also studied. First, preterm children were shorter and lighter than term children (height SD scores -0.49 (1.1) vs. +0.22 (0.9), weight SD scores -0.41 (1.2) vs. +0.38 (1.0)) and had significantly lower whole-body BMC than their peers; decrements were also evident at some regional sites. These differences disappeared after adjusting for bone area, body size, and pubertal status. Second, children previously randomized to BBM versus PTF or TF versus PTF showed no significant differences in anthropometry, BMC, BMD, or osteocalcin (OC). Third, there was no independent effect of the proportion of EBM on BMC, BMD, or OC and no interaction between randomized diet and the amount of EBM received. Fourth, plasma OC was significantly higher in preterm children than in term children (12.4 vs. 11.0 ng/ml, p < 0.005) and in preterm children who had received a low-nutrient (BBM/TF) as opposed to a high-nutrient diet (PTF) during the neonatal period (12. 9 vs. 11.9 ng/ml, p = 0.03). In conclusion, preterm children are shorter, lighter, and have lower bone mass than their peers at age 8-12 years. The lower BMC is, however, appropriate for the bone and body size achieved. Despite large differences in early mineral intake, early diet does not affect bone mass in preterm children, and fresh human milk has no specific effect. However, poor nutrition during the neonatal period may result in higher bone formation rates during childhood.

Biomarkers↗
PubMed1999

Plasma pyridoxal phosphate and pyridoxic acid and their relationship to plasma homocysteine in a representative sample of British men and women aged 65 years and over.

Concentrations of pyridoxal phosphate and pyridoxic acid were measured in fasting plasma samples from British men and women aged 65 years and over, participating in a National Diet and Nutrition Survey during 1994-5, selected to be representative of the population of mainland Britain. In this population, the concentration of pyridoxal phosphate declined, whereas pyridoxic acid rose, with increasing age and frailty; however, both status indicators were strongly and directly (with a positive coefficient) correlated with estimates of vitamin B6 intake. This was little affected by the inclusion of food energy and protein intakes in the model. Forty-eight percent of the participants living in the community and 75% of those living in institutions had plasma pyridoxal phosphate concentrations below a range considered normal from other studies. In a univariate regression model, plasma pyridoxal phosphate concentrations were inversely correlated with plasma homocysteine concentrations, consistent with the hypothesis that vitamin B6 status may influence plasma homocysteine levels, and hence vascular disease risk. However, this relationship was partly attenuated in a multiple regression model including age, sex, domicile and biochemical status indices, including those of folate and vitamin B12. There was evidence that plasma pyridoxal phosphate was sensitive to metabolic conditions associated with inflammation and the acute-phase reaction, and that plasma pyridoxic acid was sensitive to renal function. Thus, neither index is an ideal predictor of vitamin B6 status in older people, unless these confounding factors are allowed for. Since poor vitamin B6 status may have health implications, e.g. for immune function, cognition, and for essential intermediary metabolic pathways in older people, it needs to be investigated as a possible public health problem.

Adolescent↗
PubMed1998

Estimation of the use of dietary supplements in the National Diet and Nutrition Survey: people aged 65 years and Over. An observed paradox and a recommendation.

OBJECTIVE: To compare the evidence derived from blood biochemical status indices with the evidence from a questionnaire and from a 4-day weighed dietary record of micronutrient supplement use in the British National Diet and Nutrition Survey (NDNS) of People Aged 65 Years and Over; to resolve some apparent incompatibility between nutrient intake and status estimates, and to recommend an approach towards supplement recording that should improve accuracy. DESIGN: The survey procedures described in the National Diet and Nutrition Survey Report (1998) included a health-and-lifestyle questionnaire, a 4-day weighed diet record, and fasting blood and urine sample for biochemical indices, including a wide range of micronutrients. SETTING: Eighty randomly selected postcode sectors from mainland Britain during 1994-1995. SUBJECTS: Of 2060 people interviewed, 1467 provided a blood sample and 1217 provided both a blood sample, and a complete 4-day diet record. About 20% were living in institutions such as nursing homes, and the remainder were living in private households. RESULTS: After assigning the subjects to four categories by the use of dietary supplements (A, those not taking supplements (by questionnaire or by the 4-day record); B, those taking supplements (excluding prescribed ones) by questionnaire only; C, those taking supplements by 4-day record only; and D, those taking supplements by both questionnaire and 4-day record), these categories were then compared with respect to estimated total nutrient intakes and blood biochemical indices. Those in category B had estimated (4-day) nutrient intakes (from foods and supplements) that were indistinguishable from those in category A, but had biochemical indices that indicated significantly higher dietary intakes of several vitamins. CONCLUSIONS AND RECOMMENDATION: The 4-day weighed intake record may not have identified all of the subjects who were regularly taking micronutrient supplements in amounts sufficient to improve their biochemical status. Because survey respondents may use supplements irregularly or change their usual patterns of supplement use during a period of intensive diet-recording, it is important to design a dietary instrument that will minimise this potential source of inaccuracy. We therefore recommend that population surveys in which an accurate estimate of micronutrient intakes is required, from supplements as well as from food, should record supplement use for a period longer than 4-days. It is likely that a better estimate of long-term intakes can be achieved by combining a 4-day weighed diet record with a structured recall or several weeks of diary records, which focus specifically on the use of supplements.

Aged↗
PubMed1998

Bone changes after 3 mo of lactation: influence of calcium intake, breast-milk output, and vitamin D-receptor genotype.

Factors influencing the change in bone mineral after 3 mo of lactation were investigated in 47 breast-feeding mothers, 11 formula-feeding mothers, and 22 nonpregnant, nonlactating control subjects. At 6-8 wk postpartum, the breast-feeding group had a mean (+/-SD) calcium intake of 34.8+/-13.2 mmol/d and breast-milk volume, calcium concentration, and calcium output of 0.865+/-0.230 L/d, 7.41+/-1.25 mmol/L, and 6.41+/-2.00 mmol/d, respectively. There was no relation between calcium intake and any breast-milk variable. Dual-energy X-ray absorptiometry of the whole body, spine, hip, and forearm was performed at 0.5 and 3 mo. There were significant decreases in bone mineral content at the spine (3.96%; 95% CI: 4.86%, 3.06%), femoral neck (2.39%; 95% CI: 3.61%, 1.17%), total hip (1.51%; 95% CI: 2.45%, 0.60%), and whole body (0.86%; 95% CI: 1.29%, 0.43%) in breast-feeding mothers but not in formula-feeding mothers or nonpregnant, nonlactating women. These changes were not related to calcium intake, breast-milk calcium concentration, vitamin D-receptor genotype, postpartum weight change, or use of the progesterone-only contraceptive pill. After adjustment for bone area, breast-milk volume and height were identified as significant predictors at the spine, such that greater decreases were associated with taller mothers (P = 0.007) and those with greater breast-milk volume (P = 0.001). This finding suggests that the marked bone mineral changes observed in breast-feeding mothers represented a physiologic response to lactation that was independent of dietary calcium supply.

Absorptiometry, Photon↗
PubMed1998

Does vitamin C reduce blood pressure? Results of a large study of people aged 65 or older.

OBJECTIVE: To characterize relationships among blood pressure, pulse rate, vitamin C status and other protective and risk factors for older British people, from a national survey. DESIGN: A cross-sectional analysis of survey data. SETTING: A population study, representative of mainland Britain. SUBJECTS: Among 914 people of both sexes living in the community, 373 were taking blood-pressure-lowering drugs and were therefore excluded from the analyses. INTERVENTIONS: Completion of an interview on health, lifestyle and dietary habits, recording of a 4-day dietary record, anthropometry and taking of a blood sample to determine haematological and biochemical status. MAIN OUTCOME MEASURES: Systolic and diastolic blood pressures, pulse rate, indices of micronutrient status including plasma ascorbate concentration, nutrient intake and haematology. RESULTS: Plasma ascorbate concentration was inversely correlated to systolic and diastolic blood pressures and pulse rate. Other covariates of blood pressure included age, sex, domicile, plasma retinol, fibrinogen and gamma-tocopherol concentrations, erythrocyte count, prothrombin time and urine sodium: creatinine ratio. Covariates of pulse rate included sex, domicile, plasma fibrinogen and platelet count. Blood pressure was also correlated to intake of vitamin C. CONCLUSIONS: Plasma ascorbate concentration and intake of vitamin C are covariates of blood pressure in older people living in Britain. New intervention studies are now needed, to test for possible causalities.

Aged↗
PubMed1998

Bile salt-stimulated lipase and digestion of non-breast milk fat.

BACKGROUND: 13 Carbon (13C)-lipid breath tests are an effective, noninvasive way of repeatedly measuring fat digestion. The purpose of this study was to assess the contribution of bile salt-stimulated lipase (BSSL) in human milk to the digestion of non-breast-milk fat in Gambian infants. METHODS: Twelve Gambian infants (aged 3-8 months) were studied on 4 days. 13C-Trioctanoin (7.5 mg/kg, digested by BSSL preduodenal and pancreatic lipases) and 13C-cholesteryl octanoate (25 mg/kg, digested by BSSL and pancreatic lipases) were used as substrates. The percentage dose recovery (PDR) of 13C in breath during 5 hours was compared after ingestion of each substrate with fresh, expressed breast milk (FBM) or heated, expressed breast milk (HBM). Gas isotope ratio-mass spectrometry was used to measure 13C enrichment, and breast milk samples were analysed for esterase activity. RESULTS: Heating breast milk significantly decreased esterase activity (mean +/- SD values: FBM = 12.2 +/- 2.9 IU/ml; HBM = 0.5 +/- 0.3 IU/ml), and there was no difference in the volumes of milk ingested on each test day (approximately 50 ml). The PDR of 13C was comparable to that previously described in healthy English infants and was not increased by BSSL. The mean +/- SD PDR of 13C from trioctanoin was 36.3 +/- 8.4% for FBM and 34.6 +/- 6.3% for HBM (NS). From cholesteryl octanoate, the mean +/- SD PDR of 13C was 24.3 +/- 8.7% for FBM and 27.1 +/- 7.5% for HBM (NS). CONCLUSIONS: Bile salt-stimulated lipase may enhance fat digestion in younger or malnourished infants who have a greater degree of pancreatic enzyme deficiency. However, this study suggests that it does not increase the digestion of non-breast-milk fat in healthy, well-nourished infants aged 3 to 8 months from an underprivileged background, who typically ingest frequent small quantities of breast milk.

Caprylates↗
PubMed1998

Calcium requirements of breast-feeding mothers.

A randomized, placebo-controlled calcium supplementation study has investigated the benefits of increased calcium intake during 6 months of full breast-feeding and during the weaning period for lactating women with a dietary calcium intake below 800 mg/day, compared with nonlactating women who had recently given birth. The calcium supplement of 1000 mg/day had no impact on breast milk calcium concentration or on lactation-associated bone mineral changes in the lumbar spine, radius, or total body. Calcium supplementation produced a modest increase in spine bone mineral density in both lactating and nonlactating women, but the potential significance of this effect is unclear. The results of this study support and extend the findings from three previous supplementation studies and suggest that women do not need to consume extra calcium during breast-feeding.

Breast Feeding↗
PubMed1998

Biochemical markers of calcium and bone metabolism during 18 months of lactation in Gambian women accustomed to a low calcium intake and in those consuming a calcium supplement.

The effect of 18 months of lactation on indexes of calcium and bone metabolism was studied in 60 Gambian women accustomed to a very low calcium intake. Half the women consumed a calcium supplement from 10 days postpartum for 52 weeks (supplement, 714 mg Ca/day; total Ca intake, 992 +/- 114 mg/day), and half consumed placebo (total Ca intake, 288 +/- 128 mg/day). Fasting blood and 24-h urine samples were collected at 1.5, 13, 52, and 78 weeks of lactation and analyzed for calciotropic hormones (intact PTH, 1,25-dihydroxyvitamin D, and calcitonin), bone turnover markers (osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline), and plasma minerals (calcium and phosphate). The first months of lactation were associated with increased bone turnover and plasma phosphate, and decreased PTH and 1,25-dihydroxyvitamin D. These effects diminished by 52 weeks, although breast milk volumes remained high. The Gambians had higher PTH, 1,25-dihydroxyvitamin D, and bone formation than British women with a greater customary calcium intake. None of the biochemical indexes was affected by calcium supplementation, with the possible exception of bone alkaline phosphatase (-29% at 52 weeks; P = 0.015). These data demonstrate that lactation-associated changes in calcium and bone metabolism are physiological and are independent of dietary calcium supply in women with very low calcium intakes.

Adolescent↗
PubMed1998

Zinc and phytate intake of rural Gambian infants: contributions from breastmilk and weaning foods.

Zinc and phytate intakes of 183 rural Gambian infants were obtained from weighed records of breastmilk and food intake and measured contents in foods. Total zinc intake of 2.7 mg/d in the first month of age declined to 1.5 mg/d at 3 months, then increased to 4.3 mg/d by 17 months. Breastmilk was an important source of zinc, but the predominant cereal and groundnut-based foods had high [phytate]/[Zn] molar ratios ranging from 13 to 28, indicating potential impaired zinc bioavailability. The [phytate]/[Zn] molar ratio for the diet as a whole was low in early infancy, but increased to 13 in the second year. In contrast, this ratio was less than 6 for the diet of 48 Cambridge breastfed infants up to 18 months. A further disadvantage to the Gambian infants was indicated by their lower intake of protein of animal origin. However, calcium intake was estimated in both communities to be below the level which could give rise to zinc chelation in association with phytate. Compared to 'basal' and 'normative' requirements, total zinc intake of the Gambian infants showed the greatest shortfall between 3 and 12 months, making this the age band for maximum probable benefit from focused intervention programmes.

Child, Preschool↗
PubMed1998

Evaluation of facilitated communication.

Two case studies are presented to demonstrate the effectiveness of Facilitated Communication (FC). A wide variety of sources of data have been examined and consistent behaviour found within FC interactions. There are indications that changes in behaviour of both people resulted at least in part from the use of FC.

Adult↗
PubMed1997

Plasma total homocysteine in a representative sample of 972 British men and women aged 65 and over.

OBJECTIVES: To provide a reference range for plasma total homocysteine (tHcy), an independent risk factor for vascular disease, and to explore relationships with nutritional indices for people aged 65 y and over, in the UK National Diet and Nutrition Survey (NDNS). DESIGN: The survey procedures described in the National Diet and Nutrition Survey Report (1997) included a health-and-lifestyle interview, a four-day weighed diet record, anthropometric and blood pressure measurements and a fasting blood sample for biochemical indices, including tHcy. SETTING: Eighty randomly selected postcode sectors from mainland Britain during 1995-1996. SUBJECTS: Of 2060 people interviewed, 1527 were visited by the nurse, 1276 gave a blood sample and 972 had tHcy measured. About 80% were in their own homes and the remainder were in nursing homes or similar institutions. RESULTS: Significant cross-sectional relationships, both univariate and multivariate were found between tHcy and index concentrations of folate and vitamin B12 (P < 0.0001), and between tHcy and plasma creatinine, urea, calcium, zinc, alpha 1-antichymotrypsin, lutein and cysteine (P = 0.013 to < 0.0001). Dietary nutrient analyses showed an association with folate intake. tHcy was also correlated with age and with domicile (free-living or institution), with history of vascular disease and with use of four classes of drugs, two of which are prescribed for vascular diseases. There was a north-south gradient in tHcy (P = 0.005), and also in food choices, blood micronutrient indices and vascular disease prevalence. CONCLUSIONS: The concentrations of tHcy found in this study provide a reference range for people aged 65 y and over, in mainland Britain. tHcy is a valuable functional index of micronutrient status and intakes for British people aged 65 y and over, which can assist the development of health-promotion strategies.

Aged↗