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Biomedical subjects

A Prentice

Publications and source records attributed to A Prentice.

At least 127 records · Page 7Linked to original sources
PubMed1995

Calcium requirements of lactating Gambian mothers: effects of a calcium supplement on breast-milk calcium concentration, maternal bone mineral content, and urinary calcium excretion.

The calcium requirement for prolonged lactation was investigated in a randomized supplementation study of Gambian mothers consuming a low-calcium diet (7.1 mmol/d, or 283 mg/d). Sixty women were studied from 10 d to 78 wk of lactation, receiving calcium or placebo for the first 12 mo. The supplement increased average calcium intake by 17.9 mmol/d (714 mg/d). Supplementation had no effect on breast-milk calcium concentration or on maternal bone mineral content. Urinary calcium output was higher in supplemented than in unsupplemented mothers by 1.18 mmol/d (47 mg/d), P < or = 0.005. Longitudinal changes in urinary calcium output and bone mineral content made a substantial contribution to calcium requirements for lactation. This study suggests that, in women with low calcium intakes, there is no direct benefit from increasing calcium intake during lactation, and that physiological mechanisms operate to furnish calcium for breast-milk production.

Adolescent↗
PubMed1995

Effect of calcium supplements and stage of lactation on the calcium absorption efficiency of lactating women accustomed to low calcium intakes.

The effect of calcium intake on the calcium absorption efficiency from 100 mL cow milk was measured in lactating Gambian mothers habituated to a low-calcium diet [mean intake 7.08 mmol (283 mg)/d], and compared with UK lactating mothers consuming high-calcium diets [mean intake 29.2 mmol (1168 mg)/d] by using a double stable-isotope technique (oral 44Ca and intravenous 42Ca). In a double-blind trial starting 9 d postpartum, Gambian mothers were given a calcium supplement [17.85 mmol (714 mg)/d] or placebo for 12 mo. At 3 and 12 mo postpartum, mean (+/- SEM) calcium absorption from isotopically enriched milk was 52.3 +/- 3.1% (n = 25) and 47.2 +/- 4.8% (n = 24) in the unsupplemented Gambian mothers and 48.8 +/- 2.8% (n = 28) and 42.9 +/- 3.7% (n = 24) in the supplemented mothers, respectively. There was no effect of supplementation or stage of lactation on the efficiency of calcium absorption. At 3 mo postpartum the UK mothers absorbed 32.2 +/- 3.8% of the isotopically enriched calcium added to milk, which was significantly less than that of the Gambian mothers (P < 0.01).

Absorption↗
PubMed1995

Osteoporosis in severe congenital neutropenia treated with granulocyte colony-stimulating factor.

Recombinant human granulocyte colony-stimulating factor (G-CSF) has substantially improved life expectancy for children with severe congenital neutropenia (SCN). Severe osteoporosis, reported in this population, may relate to the disease process, or be a therapeutic side-effect. This report details bone loss, quantitated absorptiometrically and histomorphometrically, in a child with SCN and vertebral collapse, and the positive response to anabolic steroid and bisphosphonate therapy.

Anabolic Agents↗
PubMed1995

Rate of radial bone mineral accretion in healthy children.

Radial bone width and mineral content were measured in 392 healthy Cambridge children aged 6-12 years from a cohort of 420 children studied 2 years previously. The typical rate of bone mineral accretion was 0.044 g/cm/year for boys across the whole age range and 0.042 g/cm/year for girls up to a mean age of 9 years, rising rapidly thereafter in association with changes in body size. The factors best predicting bone mineral accretion rate were mean bone mineral content, mean height, height velocity, weight velocity and bone width velocity. After adjusting for anthropometry, age did not contribute to the model. These are the first available longitudinal reference data for the rate of radial bone mineral accretion in healthy children.

Anthropometry↗
PubMed1994

Calcium intakes and bone densities of lactating women and breast-fed infants in The Gambia.

The calcium required for breast-milk production and infant growth can be a substantial proportion of dietary intakes especially in regions of the world were calcium consumption is low. Insufficient calcium supply might lead to maternal bone loss, reduced breast-milk calcium secretion and impaired infant bone growth. However, changes in calcium absorption and excretion may be sufficient to allow these requirements to be met without affecting maternal or infant health. A limited number of studies have investigated changes in maternal bone mineral, absorption, excretion and metabolism during lactation but few have addressed whether any changes are influenced by calcium intakes. Ongoing detailed research by the MRC Dunn Nutrition Unit in a rural area of The Gambia amongst mothers and infants with habitually low calcium intakes will provide valuable information about calcium needs during lactation and growth.

Bone Density↗
PubMed1994

Maternal calcium requirements during pregnancy and lactation.

Recommendations for calcium intakes during pregnancy and lactation differ around the world, reflecting the inadequacy of knowledge about calcium requirements in human reproduction. In theory, insufficient calcium supply during pregnancy and lactation could result in maternal bone loss, reduced breast-milk calcium secretion or impaired infant bone development. However, although calcium intakes vary widely, no specific problems associated with dietary calcium deficiency have been identified. Alterations in absorption, metabolism, and excretion may conserve calcium when requirements increase. Bone changes have been observed in pregnancy and lactation, but the relationship with diet is unknown. Similarly, the effects of maternal calcium intake on breast-milk calcium and infant bone growth are not understood. Calcium salts (1-2 g Ca/d) may reduce hypertensive disorders in pregnancy, but the role of dietary calcium needs exploration. More research is required before we can be confident about advising women to increase their calcium intakes during pregnancy and lactation.

Bone Density↗
PubMed1994

Uncritical use of bone mineral density in absorptiometry may lead to size-related artifacts in the identification of bone mineral determinants.

Epidemiological studies of bone mineral determinants rely heavily on measurements made with absorptiometric techniques such as single-photon absorptiometry and dual-energy x-ray absorptiometry. In general, absorptiometric data are expressed as areal densities (bone mineral density, BMD), obtained by dividing bone mineral content (BMC) by bone area or width (BA, BW). This size correction assumes that BMC and BA (BW) are directly proportional to one another, such that a 1% change in BA (BW) is matched by a 1% change in BMC. This is rarely the case, and the exact relationship depends on the population group, skeletal site, body size, instrumentation, and scanning conditions. Size adjustment determined by using predefined indexes, such as BMD and body mass index (BMI, wt/ht2), may fail to correct BMC fully for bone and body size, and may lead to spurious associations with other size-related variables such as calcium intake, energy expenditure, and grip strength. A general approach to size adjustment is described, in which BA (BW), weight, and height are incorporated in all regression models of BMC. Although BMD plays a valuable role in fracture-risk assessment and clinical management, we advocate that its use in epidemiological research be discontinued.

Absorptiometry, Photon↗
PubMed1994

Oestrogen and progesterone do not regulate the expression of retinoic acid receptors and retinoid 'X' receptors in human endometrial stromal cells in vitro.

Elucidation of the gene structure for retinoic acid receptor-beta (RAR-beta) has suggested a potential role for oestrogen in regulating the expression of RAR-beta. We have previously shown that all three RAR types are expressed in human endometrial stromal cells in vitro and that RAR-beta expression is induced in response to retinoic acid. The aim of this study was to ask whether oestradiol and progesterone could play a part in regulating the expression of RARs in human endometrial stromal cells and to establish the patterns of expression of a related group of nuclear retinoid receptors, retinoid 'X' receptors (RXRs) and their potential for regulation by steroid hormones. The RAR expression patterns of endometrial stromal cells, grown in steroid-free medium, did not change in response to the presence of steroid hormones. Furthermore, the retinoic acid-mediated induction of RAR-beta was not affected by oestradiol or progesterone, and was dependent on the continued presence of retinoic acid. Of the three RXR types, only RXR-alpha was detectably expressed in stromal cells in vitro and the expression of RXR-alpha did not change in response to steroid hormones or retinoic acid. These data indicate that oestradiol and progesterone are not important in the regulation of RAR and RXR expression in human endometrial stromal cells.

Base Sequence↗
PubMed1994

Expression of integrin adhesion molecules in endometrium and endometriosis.

OBJECTIVE: To compare the expression of cell adhesion molecules by endometrium and endometriosis. DESIGN: A comparative study of integrin expression, determined immunohistochemically, in eutopic and ectopic endometrium biopsied synchronously from patients with endometriosis diagnosed at laparoscopy or laparotomy. SETTING: University Departments of Obstetrics and Gynaecology, and Pathology, Southampton; Department of Obstetrics and Gynaecology, Newcastle upon Tyne. SAMPLES: Eighteen paired samples of endometria and endometriosis. RESULTS: A wide distribution of collagen-laminin receptor proteins was demonstrated. alpha 1 integrin expression was limited to secretory endometrium. beta 3 expression was only demonstrated on proliferative endometrium. CONCLUSIONS: Expressions of the integrin proteins differed between the various elements of the endometrium. Cyclical changes in integrin expression also were demonstrated. No difference in cell adhesion molecule expression was seen when comparing endometrial and endometriosis samples.

Cell Adhesion Molecules↗