Search PubMed⌕ Search

Biomedical subjects

A Prentice

Publications and source records attributed to A Prentice.

At least 37 records · Page 2Linked to original sources
PubMed2003

Older people in China and the United Kingdom differ in the relationships among parathyroid hormone, vitamin D, and bone mineral status.

To explore whether there are ethnic differences in relationships among parathyroid hormone (PTH), vitamin D, and bone mineral status, 352 healthy volunteers, 60-83 years old, were studied in Shenyang, Peoples' Republic of China (108 men, 110 women), and in Cambridge, UK (67 men, 67 women), in late winter. Early morning fasting blood and 2-h fasting urine were analyzed for 25-hydroxyvitamin D (25OH-D), PTH, and free deoxypyridinoline (DPD). Hip bone mineral status was measured using dual-energy X-ray absorptiometry (Lunar). There were significant differences (P < 0.001) in plasma 25OH-D and PTH concentrations between Shenyang and Cambridge [25OH-D nmol/L: Shenyang = 29.0 (SD 12.7), Cambridge = 35.7 (12.9)]; PTH ng/L: Shenyang = 34.3 (13.4), Cambridge = 25.2 (11.0)]. PTH was negatively related to 25OH-D in both populations. The relationship was exponential, best described by an inverse log-log equation with no break point (P < 0.001), indicating that the exponential curve did not tend toward a low plateau. PTH was higher for a given 25OH-D and decreased less with increasing 25OH-D in Shenyang than in Cambridge (country-ln25OH-D interaction, P = 0.0005). After adjusting for bone area, weight, height, age, and sex, hip bone mineral content (BMC) was significantly related to PTH concentration in Cambridge but not in Shenyang [femoral neck coefficient: Cambridge = -0.064 (SE 0.027), P = 0.02; Shenyang = -0.027 (0.028), P = 0.3; trochanter: Cambridge = -0.116 (0.034), P = 0.001; Shenyang = -0.019 (0.027), P = 0.5]. There was a significant country-lnPTH interaction at the trochanter (P = 0.02), but not at the femoral neck (P = 0.7). A weak positive association between BMC at the femoral neck and 25OH-D concentration was found in Cambridge [coefficient: 0.054 (0.028), P = 0.05] but not in Shenyang (coefficient: -0.013, P = 0.5; country-ln25OH-D interaction, P = 0.07). Urinary DPD concentration was also positively related to plasma PTH concentration in Cambridge subjects only [coefficient: 0.2 (0.08), P = 0.02]. These data suggest that although PTH increases when 25OH-D decreases, and Chinese people have a higher PTH for a given 25OH-D, older Chinese adults may be more resistant than Britons to the effects of PTH on bone.

Aged↗
PubMed2003

Inhibitory potency of twice-a-day omeprazole on gastric acidity is enhanced by eradication of H. pylori in duodenal ulcer patients.

The gastric pH-elevating effect of proton pump inhibitors such as omeprazole has been reported to be greater in the presence than in the absence of an H. pylori infection. It is unknown if this effect persists when a higher dose of omeprazole is taken. We undertook both 24-hr pH-metry and 24-hr aspiration studies in 12 H. pylori-positive patients with a history of duodenal ulcer (DU); (1) when not on omeprazole; (2) when on omeprazole 20 mg twice a day for 8 days; (3) two months after eradication of H. pylori and when not on omeprazole; and (4) after eradication of H. pylori and when on omeprazole twice a day. Eradication of H. pylori in DU results in lower mean and median pH; decreased percent pH > or = 3/ > or = 4, and greater median H+ after breakfast, after lunch, and overnight; and omeprazole appears to have less of a pH-elevating effect in the absence than in the presence of an H. pylori infection. The fall in gastric juice NH3 concentration as a result of eradicating H. pylori partially explained the lower pH-elevating effect of omeprazole. The variation in acid inhibitory effect of omeprazole after as compared with before eradication of H. pylori could not be explained by differences; (1) in gastric juice concentrations of IL-1alpha, IL-8, IL-13, or epidermal growth factor; (2) in the fasting or fed total concentration of gastric juice bile acids; (3) in the fasting concentrations or area under-the-curve (AUC) of the gastric H+ concentrations in response to food; or (4) in the pharmacokinetics of omeprazole. The difference in H+ AUC without omeprazole minus with omeprazole was actually greater when compared after versus before eradication of H. pylori. Thus, in DU the pH-elevating potency of omeprazole taken twice a day is greater in the presence than in the absence of an H. pylori infection.

Adult↗
PubMed2003

Relationship between methylmalonic acid, homocysteine, vitamin B12 intake and status and socio-economic indices, in a subset of participants in the British National Diet and Nutrition Survey of people aged 65 y and over.

OBJECTIVE: Assessment of functional vitamin B(12) status in a subset of the respondents in the British National Diet and Nutrition Survey of people aged 65 y and over. SETTING: National Diet and Nutrition Survey: a British nationwide cross-sectional sample of people aged 65 y and over, living either in the community or in institutions such as nursing homes, during one calendar year spanning 1994-1995. METHODS: Methylmalonic acid (MMA) concentrations were measured in plasma samples from 313 subjects (ca 14% of those originally enrolled in the survey). The results were compared with those for serum vitamin B(12), vitamin B(12) intakes and other status and intake estimates and with socio-demographic indices. RESULTS: Of the NDNS participants overall, 20% had serum vitamin B(12) concentrations<150 pmol/l. In the subset studied here, 24% of free-living and 46% of institution-living participants had MMA>0.5 micromol/l. Geometric mean MMA increased with age, from 0.25 micro mol/l in people aged 65-74 y to 0.38 micro mol/l in people aged 85+y. There was little evidence for any gender difference in MMA. It was inversely correlated with serum vitamin B(12) and with red blood cell folate; it was positively correlated directly with total homocysteine, but not significantly with serum folate or with vitamin B(12) intake. Among respondents with high MMA, a subgroup had normal serum vitamin B(12) but higher-than-average plasma urea and creatinine. Socio-demographic co-variates of MMA included receipt of State income benefits, social class of head of household, and educational attainment. These indices were not correlated with serum vitamin B(12). CONCLUSIONS: The progressive increase in MMA with age is metabolic evidence for increasing risk of functional vitamin B(12) deficiency with increasing age in older people. There is evidence that renal function is linked to high MMA in some older people. Age and renal function are thus both important when establishing upper reference limits for MMA. The socio-demographic observations suggest a link between poverty and poor functional vitamin B(12) status in older British people.

Aged↗
PubMed2003

Risk factors for low iron intake and poor iron status in a national sample of British young people aged 4-18 years.

OBJECTIVE: To examine the prevalence and dietary, sociodemographic and lifestyle risk factors of low iron intake and poor iron status in British young people. DESIGN: National Diet and Nutrition Survey of young people aged 4-18 years. SETTING: Great Britain, 1997. SUBJECTS: In total, 1699 young people provided 7-day weighed dietary records, of which 11% were excluded because the participant reported being unwell with eating habits affected. Blood was obtained from 1193 participants, with iron status indicated by haemoglobin, serum ferritin and transferrin saturation. RESULTS: Iron intakes were generally adequate in most young people aged 4-18 years. However, low iron intakes (below the Lower Reference Nutrient Intake) occurred in 44% of adolescent girls (11-18 years), being less prevalent with high consumption of breakfast cereals. Low haemoglobin concentration (<115 g l-1, 4-12 years; <120 or <130 g l-1, 13+ years for girls and boys, respectively) was observed in 9% of children aged 4-6 years, pubertal boys (11-14 years) and older girls (15-18 years). Adolescent girls who were non-Caucasians or vegetarians had significantly poorer iron status than Caucasians or meat eaters, independent of other risk factors. The three iron status indices were correlated significantly with haem, but not non-haem, iron intake. CONCLUSIONS: Adolescent girls showed the highest prevalence of low iron intake and poor iron status, with the latter independently associated with non-Caucasian ethnicity and vegetarianism. Risk of poor iron status may be reduced by consuming (particularly lean red) meat or enhancers of non-haem iron absorption (e.g. fruit or fruit juice) in vegetarians.

Adolescent↗
PubMed2003

The effect of RU486 on the gene expression profile in an endometrial explant model.

Administration of RU486 in vivo during the receptive phase rapidly renders the endometrium non-receptive to the implanting embryo. In order to identify key pathways responsible for endometrial receptivity we have used cDNA arrays to monitor gene expression changes in short-term endometrial explants in response to RU486. Endometrial biopsies from five normal fertile women at mid-secretory phase were cultured in the presence of estradiol and progesterone with or without RU486 for 12 h. cDNA arrays were produced containing approximately 1000 sequence-verified clones which included genes known to be important in angiogenesis, apoptosis, cell signalling, extracellular matrix remodelling and cell cycle regulation. cDNA probes from the paired endometrial samples were hybridized to the arrays and hybridization signals were quantified. A total of 12 genes displayed significant changes in expression; six were up-regulated and six down-regulated following RU486 treatment. For five of these genes this is the first report suggesting that they are regulated by steroids in the endometrium. JAK1 and JNK1 were two of the genes shown by the arrays to be down-regulated in RU486-treated endometrial explants. This was confirmed by real time RT-PCR. JAK1 immunoreactivity was localized to both glandular epithelium and the stroma of normal endometrium and staining was much stronger in the luteal phase of the cycle. These results show that components of two important signalling pathways in endometrium-the JAK/STAT pathway, and the JNK pathway-are altered by RU486. Genes whose expression is controlled by these pathways are likely to be involved in the mechanism by which steroids render the endometrium receptive to the implanting embryo.

Adult↗
PubMed2003

Staging and preparation of human fetal striatal tissue for neural transplantation in Huntington's disease.

Transplantation of human fetal central nervous system tissue has been shown to be of benefit in Parkinson's disease, and is currently being explored as a therapeutic option in Huntington's disease. The success of a neural transplant is dependent on a number of factors, including the requirement that donor cells are harvested within a given developmental window and that the cell preparation protocols take account of the biological parameters identified in animal models. Although many of the criteria necessary for a successful neural transplant have been defined in animal models, ultimately they must be validated in human studies, and some issues can only ever be addressed in human studies. Furthermore, because neural transplantation of human fetal tissue is limited to small numbers of patients in any one surgical center, largely due to practical constraints, it is crucial that tissue preparation protocols are clearly defined and reproducible, so that (i) multicenter trials are possible and are based on consistent tissue preparation parameters, and (ii) results between centers can be meaningfully analyzed. Here we describe the preparation of human fetal striatum for neural transplantation in Huntington's disease, and report on the validation of a method for estimating the developmental stage of the fetus based on direct morphometric measurements of the embryonic tissue.

Algorithms↗
PubMed2002

What are the dietary requirements for calcium and vitamin D?

Dietary recommendations for calcium and vitamin D vary considerably among different advisory bodies. This lack of consensus reflects the different criteria used as a basis for estimating average requirements and population reference values. For calcium (Ca) many have used a factorial approach, where estimates of skeletal accretion rates are coupled with assumptions about Ca absorption and excretion on typical diets. Others have used data derived experimentally from balance studies. A recent refinement of this approach involves the mathematical modelling of balance data to estimate a Ca intake above which Ca retention is maximal or desirable. A third approach was used by a NIH Consensus Conference in 1994, based on the concept of an optimal Ca intake for bone health, in terms of reduced risk of osteoporosis in later life. Although taken up by several special-interest groups, this approach has yet to be adopted fully by any committee advising on nutrition policy because of the lack of quantitative data on which to base estimates of average calcium requirements. Differences in vitamin D recommendations reflect subtle differences in philosophy about how to indicate that while endogenous synthesis is the main source of vitamin D for people with adequate sunshine exposure, there are vulnerable groups that rely on the diet to supply their vitamin D requirements. In addition, they reflect uncertainties about the relationship between vitamin D status and health outcomes.

Calcium↗
PubMed2002

Age- and gender-related differences in bone mineral status and biochemical markers of bone metabolism in Northern Chinese men and women.

The aim of this study was to provide insight into the bone mineral status and biochemical markers of bone metabolism in a Chinese population from Shenyang, in the north of China, where hip fracture incidence is low. A total of 194 healthy men and women, aged 25-35 years and 65-75 years, were studied. Bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN) was measured using dual-energy X-ray absorptiometry. Fasting blood and 24 h urine samples were collected for bone alkaline phosphatase (bAP), osteocalcin, calcium, phosphate, and free deoxypyridinoline (Dpd). Both older women and men had lower BMD compared with younger women and men by 27.2 +/- 3.0% (mean +/- SE) and 9.8 +/- 3.0% at the LS and 22.0 +/- 3.4% and 12.8 +/- 3.4% at the FN, respectively, after adjusting for bone and body size (p < 0.01). BMD at the two sites was lower in older women than in older men by 10.7 +/- 4.1% and 10.2 +/- 4.2%, respectively, after size correction (p < 0.05). Plasma bAP, osteocalcin, calcium, and phosphate concentrations were higher in older women than younger women by 69.3 +/- 9.7%, 77.2 +/- 11.1%, 7.5 +/- 2.3%, and 8.0 +/- 3.8%, respectively, and older men by 67.6 +/- 11.1%, 72.1 +/- 11.0%, 7.7 +/- 2.3%, and 23.8 +/- 3.8%, respectively (p < 0.01). However, plasma osteocalcin, calcium, and phosphate concentrations were lower in older men compared with their younger counterparts by 35.6 +/- 11.0%, 8.7 +/- 2.3%, and 14.1 +/- 3.8%, respectively (p < 0.05). Urinary calcium and phosphate output were lower in older men compared with younger men by 48.0 plus minus 10.3% and 27.6 +/- 6.9%, respectively (p < 0.01), whereas there were no differences between older and younger women. No differences in Dpd between older and younger groups were found. This study demonstrates that bone mineral status is lower in older people in Shenyang, as has been shown in populations elsewhere. The pronounced low bone mineral status in older women may be associated with increased bone turnover, which was not observed in older men.

Adult↗
PubMed2002

Selenium status and associated factors in a British National Diet and Nutrition Survey: young people aged 4-18 y.

OBJECTIVE: Assessment of selenium status to provide normative reference values, and investigation of associated socio-demographic factors, in a national sample of British young people aged 4-18 y. SETTING: National Diet and Nutrition Survey-a nationwide cross-sectional sample of young people aged 4-18 y living in mainland Britain in 1997. METHODS: Selenium status was measured, mainly in fasting blood samples, by plasma selenium concentration in 1127 participants, by red blood cell (RBC) selenium concentration in 1112, and by whole-blood glutathione peroxidase (GPx) activity in 658. RESULTS: No evidence of severe selenium deficiency or toxicity was observed. Plasma selenium concentration was directly correlated with RBC selenium concentration, and both were associated directly, although less strongly, with GPx activity. Plasma and RBC selenium concentrations increased significantly with age, with RBC concentrations significantly higher in older girls than boys. Region of domicile exhibited a significant relationship. Associations also occurred with parental occupational social class, selenium concentrations being higher in more socially advantaged children. Black and Indian children had considerably higher concentrations than Caucasian children. Concentrations, especially of plasma selenium, were significantly lower in children either (or both) of whose parents were smokers, although, unexpectedly, there was no evidence that children who themselves smoked had lower levels. CONCLUSIONS: The observed associations between selenium status indices and age, gender, social class, parental smoking and ethnic group indicate a complex network of biological factors which determine selenium concentrations in blood components, and which thus need to be controlled for when using these indices to assess selenium status in young people. SPONSORSHIP: The survey was commissioned jointly by the Department of Health and the Ministry of Agriculture, Fisheries and Food, whose responsibility has since been transferred to the Food Standards Agency. Support for the further analysis presented in this paper was provided by the Department of Health.

Adolescent↗
PubMed2002

Plasma phylloquinone (vitamin K1) concentration and its relationship to intake in a national sample of British elderly people.

Plasma phylloquinone (vitamin K1) concentration was examined according to season, socio-demographic and lifestyle factors and phylloquinone intake in a nationally representative sample of British people aged 65 years and over from the 1994-5 National Diet and Nutrition Survey. Values for both plasma phylloquinone concentration and phylloquinone intake were available from 1076 participants (561 men, 515 women). Eight hundred and thirty-four were living in private households, 242 in residential or nursing homes. Weighted geometric mean plasma phylloquinone concentrations were 0.36 (inner 95% range [corrected] 0.06, 2.01) and 0.24 (inner 94% range [corrected] 0.06, 0.96) nmol/l in free-living and institution samples respectively. Plasma phylloquinone concentrations did not generally differ between men and women, although values in free-living people were significantly lower during autumn and winter (October to March). Plasma phylloquinone concentration was not significantly associated with age. Plasma phylloquinone concentrations were positively correlated with phylloquinone intake in free-living men and women (r 0.18 and 0.30 respectively, both P<0.001). Stepwise multiple regression analysis found that 11 % of the variation in plasma phylloquinone concentration was explained by phylloquinone intake, season and plasma triacylglycerol concentration. After adjustment for age and corresponding nutrient intakes, plasma phylloquinone concentration was significantly associated (each P<0.01) with plasma concentrations of triacylglycerol, cholesterol, retinol and 25-hydroxyvitamin D in free-living women but not men, and with plasma concentrations of carotenes, alpha- and gamma-tocopherols and lutein in free-living men and women. The possibility of concurrent low fat-soluble vitamin status in elderly populations may be a cause for concern.

Aged↗
PubMed2002

Intake and sources of phylloquinone (vitamin K1): variation with socio-demographic and lifestyle factors in a national sample of British elderly people.

Intake and sources of phylloquinone (vitamin K1) were examined according to socio-demographic and lifestyle factors in free-living British people aged 65 years and over, from the 1994-5 National Diet and Nutrition Survey. Complete 4-d weighed dietary records were obtained from 1152 participants living in private households. Using newly-available, mainly UK-specific food content data, the weighted geometric mean intake of phylloquinone was estimated at 65 (95 % CI 62, 67) microg/d for all participants, with higher intakes in men than in women (70 v. 61 microg/d respectively, P<0.01). The mean nutrient densities of phylloquinone intake were 9.3 and 10.5 microg/MJ for men and women respectively (P<0.01), after adjusting for age group, region and smoking status. Of all the participants, 59 % had phylloquinone intakes below the current guideline for adequacy of 1 microg/kg body weight per d. Participants aged 85 years and over, formerly in manual occupations, or living in Scotland or in northern England reported lower phylloquinone intakes than their comparative groups. Overall, vegetables contributed 60 % of total phylloquinone intake, with cooked green vegetables providing around 28 % of the total. Dietary supplements contributed less than 0.5 % of phylloquinone intake. Participants living in northern England or in Scotland, in particular, derived less phylloquinone from vegetables than those living in southern England.

Aged↗
PubMed2002

Nutrition and health of the elderly: osteoporosis.

Osteoporosis is a debilitating disease that affects many older people. Its aetiology is complex and nutrition is only one of many factors which influence bone mass and the risk of fragility fractures. This review briefly describes the biology and epidemiology of osteoporosis and focuses on role of nutrition in the bone health of older people. An overview of the current evidence relating calcium intake and vitamin D status in the elderly to bone mass and fractures is presented and set in context of recent population-based surveys that have identified important nutritional inadequacies among sub-groups of the elderly population in Europe.

Aged↗
PubMed2001

The relative contribution of diet and genotype to bone development.

The present review addresses the relative contribution of diet and genotype to variability in human bone growth and mineralisation in the context of the aetiology of osteoporosis. Heritability studies indicate that 60-70 % of the variability in bone mineral mass or bone mineral density (BMD) can be accounted for by genetic variation. Cross-trait analyses suggest that a proportion of this variation reflects genetic influences on bone and body size, such as height and lean body mass. Candidate-gene studies have demonstrated associations between several genetic polymorphisms and bone mineral mass but, as yet, genotype determinations have proved unhelpful in identifying individuals at increased risk of osteoporosis. Variations in diet and other environmental factors contribute 30-40 % to total phenotypic variance in bone mineral mass or BMD. Correlations between intakes of individual nutrients and BMD have been reported, but these relationships are subject to confounding due to size. However, no specific dietary factor has been identified from prospective and twin studies as making a significant contribution to environmental variability in BMD or bone loss. This finding may reflect the difficulties in quantifying environmental exposures. both current and over a lifetime. In addition, the influence of diet on bone health may depend on the genotype of the individual. Optimisation of nutrition and lifestyle remains an attractive strategy for the reduction of fracture risk, but more research is required to fully define optimal dietary requirements.

Bone Density↗
PubMed2001

The relationship among dental status, nutrient intake, and nutritional status in older people.

Dental health status may influence nutrition. The objective of this part of the National Diet and Nutrition Survey was to assess if there is a relationship between dental status in people 65 years and older and intake of certain nutrients and any link between dental status and blood-derived values of key nutrients. Random national samples of independently living subjects and those living in institutions had dental examinations, interviews, four-day food diaries, and blood and urine analyzed. In the sample living independently, intakes of most nutrients were lower in edentate than dentate subjects. Intake of non-starch polysaccharides, protein, calcium, non-heme iron, niacin, and vitamin C was significantly lower in edentate subjects. People with 21 or more teeth consumed more of most nutrients, particularly of non-starch polysaccharide. This relationship in intake was not apparent in the hematological analysis. Plasma ascorbate and plasma retinol were the only analytes significantly associated with dental status.

Aged↗
PubMed2001

Obesity and undernutrition and cardiovascular risk factors in rural and urban Gambian communities.

OBJECTIVES: This study documented the prevalence of and cardiovascular risk factors associated with obesity and undernutrition in the Gambia. METHODS: Adults (> or =15 years; N = 5373) from rural and urban areas completed a questionnaire; their height, weight, and waist and hip circumferences were measured, and their cardiovascular risk factors were assessed. RESULTS: Prevalence of undernutrition (body mass index < 18 kg/m(2)) was 18.0%; all strata of society were affected. Prevalence of obesity (body mass index > or =30 kg/m(2)) was 4.0% but was higher (32.6%) among urban women 35 years or older. Cardiovascular risk factors were more prevalent among obese participants. CONCLUSIONS: Undernutrition coexists with obesity, demonstrating a "double burden of disease." Differential interventions should focus on high-risk groups; prevention needs a multisectorial approach.

Adolescent↗