A systematic review of recall errors associated with portion size estimation aids in children.

To reduce errors in portion size estimation, a number of aids have been developed and tested. This systematic review synthesizes what is known about error associated with use of different portion size estimation aids (PSEAs) within self-reported dietary recall studies in children (aged ≤18 years). Eight electronic databases were searched using relevant keywords. From 8184 records identified and screened, 327 full texts were retrieved, with 10 records representing 9 studies meeting inclusion criteria. Studies using proxy reporting were excluded. Thirteen PSEAs were identified. To facilitate comparisons between different types of aids they were categorized into 'physical 2-dimensional (2D)', 'digital 2D' and '3-dimensional' PSEAs. Seven were physical 2D (e.g. food atlas), two were digital 2D (i.e. computer-based), and four were 3D (e.g. modelling clay, household items). Comparisons of PSEAs within studies found the smallest estimation errors for digital 2D and largest for 3D aids. Errors in relation to food type were varied, with portions of amorphous foods overestimated in multiple studies. No effects for recall interval time or sex were identified. One study reported a significant improvement in estimation error with increasing age. Across studies, large variations in study design and reporting of estimation error hindered the synthesis of evidence regarding the influence of different types of PSEAs on accuracy. While a definitive conclusion about the most accurate PSEA could not be drawn, a check-list to guide future PSEA development and testing has been proposed in the current review. This will assist comparability with future studies of PSEAs for children facilitate development of more accurate PSEAs in the future.

Dietary glycemic index and glycemic load in relation to changes in body composition measures during adolescence: Northern Ireland Young Hearts Study.

BACKGROUND: Epidemiologic evidence on the influence of dietary glycemic index (GI) and glycemic load (GL) on the development of obesity is limited. OBJECTIVE: This prospective study examined the associations between dietary GI and GL and changes in body composition measures during adolescence. DESIGN: In a representative sample of Northern Irish adolescents aged 12 years at baseline and 15 years at follow-up (n=426), dietary intake was assessed by a diet history interview. Body composition measures included body mass index (BMI; kg m(-2)), BMI z-score, sum of four skinfold thicknesses, percentage body fat, fat mass index (FMI; kg m(-2)) and fat-free mass index (kg m(-2)). RESULTS: After adjustment for potential confounding factors, baseline GI was associated with increased change in FMI. Mean (95% confidence interval) values of changes in FMI according to tertiles of baseline GI were 0.41 (0.25, 0.57), 0.42 (0.26, 0.58) and 0.67 (0.51, 0.83) kg m(-2), respectively (P for trend=0.03). There was no significant association of baseline GI with changes in other body composition measures (P for trend≥0.054). Conversely, baseline GL showed no association with changes in any of the measures (P for trend≥0.41). Furthermore, changes in GI or GL were not associated with changes in any of the measures (P for trend≥0.16). CONCLUSION: Dietary GI at age 12 years was independently associated with increased change in FMI between ages 12 and 15 years in a representative sample from Northern Ireland, whereas dietary GL showed no association with changes in any of the body composition measures examined.

Perceived 'healthiness' of foods can influence consumers' estimations of energy density and appropriate portion size.

OBJECTIVE: To compare portion size (PS) estimates, perceived energy density (ED) and anticipated consumption guilt (ACG) for healthier vs standard foods. METHODS: Three pairs of isoenergy dense (kJ per 100 g) foods-healthier vs standard cereals, drinks and coleslaws-were selected. For each food, subjects served an appropriate PS for themselves and estimated its ED. Subjects also rated their ACG about eating the food on a scale of 1 (not at all guilty) to 5 (very guilty). RESULTS: Subjects (n=186) estimated larger portions of the healthier coleslaw than that of the standard version, and perceived all healthier foods to be lower in ED than their standard alternatives, despite being isoenergy dense. Higher ACG was associated with the standard foods. Portion estimates were generally larger than recommendations and the ED of the foods was underestimated. CONCLUSIONS: The larger portions selected for the 'reduced fat' food in association with lower perceived ED and ACG suggests that such nutrition claims could be promoting inappropriate PS selection and consumption behaviour. Consumer education on appropriate portions is warranted to correct such misconceptions.

Supermarket own brand foods: lower in energy cost but similar in nutritional quality to their market brand alternatives.

BACKGROUND: The present study aimed to compare the nutritional quality (NQ) and energy costs (EC) (£ MJ(-1) ) of own brand (OB) versus market brand (MB) foods in 2010 and 2012. METHODS: A list of processed foods (n = 32) was identified based on the most frequently consumed foods in the UK. Total fat, saturated fat, sugars, salt and energy density (ED) (kJ g(-1) ) in 2010 and 2012 were compared for six OB and one MB version of each food using a NQ scoring method based on the Food Standards Agency's Traffic Light System (TLS). Additional information (fruit, vegetable and nut content; protein; fibre and sodium) was recorded in 2012, and NQ was assessed using the Food Standards Agency's nutrient profiling model (NPM). The EC of the food baskets (FB) was compared in 2010 and 2012. RESULTS: There were no differences in overall NQ between OB and MB FB in 2010 (TLS, P = 0.978) or 2012 (TLS, P = 0.840; NPM, P = 0.696). However, the MB FB was highest in EC in 2010 and 2012 (both P < 0.001). There was an inverse relationship between the ED and EC of the MB foods in 2010 (r = -0.484; P = 0.005) and 2012 (r = -0.452; P = 0.009). CONCLUSIONS: The MB FB was higher in EC than the OB FB in 2010 and 2012 but not superior in overall NQ based on both the TLS and NPM.

Aging and arteriosclerosis. The increased proliferation of arterial smooth muscle cells isolated from old rats is associated with increased platelet-derived growth factor-like activity.

In vivo studies have suggested that the aorta from an old animal responds to injury with an exaggerated proliferation of smooth muscle cells (SMCs) compared with the response of this aorta from a young animal. In this study we compared proliferation of SMCs derived from uninjured old (less than 19 mo) and young (3-4 mo) rat aortas. Old SMCs grew more rapidly than young SMCs in the presence of medium containing competence factors (10% FCS or platelet-derived growth factor [PDGF]) as well as in their absence (2% PDS or serum-free media) as determined both by a short-term thymidine incorporation assay and by cell counts. Lysates prepared from old SMCs that had been grown in the absence of serum or PDGF stimulated proliferation of target cells more than lysates prepared from young SMCs; the effect was inversely related to cell density of the SMCs. This stimulatory effect of lysates was completely blocked by antibody to PDGF. After the growth-promoting activity of lysates was eliminated by anti-PDGF, growth-inhibiting activity was revealed. Lysates prepared from old SMCs had significantly less capacity to inhibit target cell growth. In the presence of exogenous heparin both the serum- or PDGF-stimulated proliferation and serum-free proliferation of old SMCs were decreased to the level of proliferation of young SMCs. These results suggest that the balance between growth-promoting and growth-inhibiting factors is altered in SMCs from old rats. This may contribute to the increased proliferative capacity of these cells in culture and may facilitate the development of atherosclerosis with age.

Transforming growth factor-beta activity is potentiated by heparin via dissociation of the transforming growth factor-beta/alpha 2-macroglobulin inactive complex.

The control of smooth muscle cell (SMC) proliferation is determined by the combined actions of mitogens, such as platelet-derived growth factor, and the opposing action of growth inhibitory agents, such as heparin and transforming growth factor-beta (TGF-beta). The present studies identify an interaction between heparin and TGF-beta in which heparin potentiates the biological action of TGF-beta. Using a neutralizing antibody to TGF-beta, we observed that the short term antiproliferative effect of heparin depended upon the presence of biologically active TGF-beta. This effect was observed in rat and bovine aortic SMC and in CCL64 cells, but not in human saphenous vein SMC. Binding studies demonstrated that the addition of heparin (100 micrograms/ml) to medium containing 10% plasma-derived serum resulted in a 45% increase in the specific binding of 125I-TGF-beta to cells. Likewise, heparin induced a twofold increase in the growth inhibitory action of TGF-beta at concentrations of TGF-beta near its apparent dissociation constant. Using 125I-labeled TGF-beta, we demonstrated that TGF-beta complexes with the plasma component alpha 2-macroglobulin, but not with fibronectin. Heparin increases the electrophoretic mobility of TGF-beta apparently by freeing TGF-beta from its complex with alpha 2-macroglobulin. Dextran sulfate, another highly charged antiproliferative molecule, but not chondroitin sulfate or dermatan sulfate, similarly modified TGF-beta's mobility. Relatively high, antiproliferative concentrations of heparin (1-100 micrograms/ml) were required to dissociate the TGF-beta/alpha 2-macroglobulin complex. Thus, it appears that the antiproliferative effect of heparin may be partially attributed to its ability to potentiate the biological activity of TGF-beta by dissociating it from alpha 2-macroglobulin, which normally renders it inactive. We suggest that heparin-like agents may be important regulators of TGF-beta's biological activity.

Decreased type II/type I TGF-beta receptor ratio in cells derived from human atherosclerotic lesions. Conversion from an antiproliferative to profibrotic response to TGF-beta1.

Atherosclerosis and postangioplasty restenosis may result from abnormal wound healing. The present studies report that normal human smooth muscle cells are growth inhibited by TGF-beta1, a potent wound healing agent, and show little induction of collagen synthesis to TGF-beta1, yet cells grown from human vascular lesions are growth stimulated by TGF-beta1 and markedly increase collagen synthesis. Both cell types increase plasminogen activator inhibitor-1 production, switch actin phenotypes in response to TGF-beta1, and produce similar levels of TGF-beta activity. Membrane cross-linking of 125I-TGF-beta1 indicates that normal human smooth muscle cells express type I, II, and III receptors. The type II receptor is strikingly decreased in lesion cells, with little change in the type I or III receptors. RT-PCR confirmed that the type II TGF-beta1 receptor mRNA is reduced in lesion cells. Transfection of the type II receptor into lesion cells restores the growth inhibitory response to TGF-beta1, implying that signaling remains responsive. Because TGF-beta1 is overexpressed in fibroproliferative vascular lesions, receptor-variant cells would be allowed to grow in a slow, but uncontrolled fashion, while overproducing extracellular matrix components. This TGF-beta1 receptor dysfunction may be relevant for atherosclerosis, restenosis and related fibroproliferative diseases.

Genomic instability in the type II TGF-beta1 receptor gene in atherosclerotic and restenotic vascular cells.

Cells proliferating from human atherosclerotic lesions are resistant to the antiproliferative effect of TGF-beta1, a key factor in wound repair. DNA from human atherosclerotic and restenotic lesions was used to test the hypothesis that microsatellite instability leads to specific loss of the Type II receptor for TGF-beta1 (TbetaR-II), causing acquired resistance to TGF-beta1. High fidelity PCR and restriction analysis was adapted to analyze deletions in an A10 microsatellite within TbetaR-II. DNA from lesions, and cells grown from lesions, showed acquired 1 and 2 bp deletions in TbetaR-II, while microsatellites in the hMSH3 and hMSH6 genes, and hypermutable regions of p53 were unaffected. Sequencing confirmed that these deletions occurred principally in the replication error-prone A10 microsatellite region, though nonmicrosatellite mutations were observed. The mutations could be identified within specific patches of the lesion, while the surrounding tissue, or unaffected arteries, exhibited the wild-type genotype. This microsatellite deletion causes frameshift loss of receptor function, and thus, resistance to the antiproliferative and apoptotic effects of TGF-beta1. We propose that microsatellite instability in TbetaR-II disables growth inhibitory pathways, allowing monoclonal selection of a disease-prone cell type within some vascular lesions.

Specific inhibition of eIF-5A and collagen hydroxylation by a single agent. Antiproliferative and fibrosuppressive effects on smooth muscle cells from human coronary arteries.

Restenosis occurs in 35% of patients within months after balloon angioplasty, due to a fibroproliferative response to vascular injury. These studies describe a combined fibrosuppressive/antiproliferative strategy on smooth muscle cells cultured from human primary atherosclerotic and restenotic coronary arteries and from normal rat aortas. L-Mimosine suppressed the posttranslational hydroxylation of the precursors for collagen and for eukaryotic initiation factor-5A (eIF-5A) by directly inhibiting the specific protein hydroxylases involved, prolyl 4-hydroxylase (E.C. 1.14.11.2) and deoxyhypusyl hydroxylase (E.C. 1.14.99.29), respectively. Inhibition of deoxyhypusyl hydroxylation correlated with a dose-dependent inhibition of DNA synthesis. Inhibition of prolyl hydroxylation caused a dose-dependent reduction in the secretion of hydroxyproline-containing protein and decreased the formation of procollagen types I and III. The antifibroproliferative action could not be attributed to nonspecific or toxic effects of mimosine, appeared to be selective for the hydroxylation step in the biosynthesis of the procollagens and of eIF-5A, and was reversible upon removal of the compound. The strategy of targeting these two protein hydroxylases has important implications for the pathophysiology of restenosis and for the development of agents to control fibroproliferative diseases.

High-level expression of Egr-1 and Egr-1-inducible genes in mouse and human atherosclerosis.

To understand the mRNA transcript profile in the human atherosclerotic lesion, RNA was prepared from the fibrous cap versus adjacent media of 13 patients undergoing carotid endarterectomy. cDNA expression arrays bearing 588 known genes indicated that lesions express unexpectedly high levels of the early growth response gene, Egr-1 (NGFI-A), a zinc-finger transcription factor that modulates a cluster of stress-responsive genes including PDGF and TGF-beta. Expression of Egr-1 was an average of 5-fold higher in the lesion than in the adjacent media, a result confirmed by RT-PCR, and many Egr-1-inducible genes were also strongly elevated in the lesion. Time-course analyses revealed that Egr-1 was not induced ex vivo. Immunocytochemistry indicated that Egr-1 was expressed prominently in the smooth muscle-actin positive cells, particularly in areas of macrophage infiltration, and in other cell types, including endothelial cells. Induction of atherosclerosis in LDL receptor-null mice by feeding them a high-fat diet resulted in a progressive increase in Egr-1 expression in the aorta. Thus, induction of Egr-1 by atherogenic factors may be a key step in coordinating the cellular events that result in vascular lesions.

TGF-betas and TGF-beta receptors in atherosclerosis.

Based on diverse evidence in animals and humans, it has been hypothesized that atherosclerosis, and other injury-induced hyperplasias such as restenosis, may result from a failure in endogenous inhibitory systems that normally limit wound repair and induce regression of wound repair cells. A key defect in one of these inhibitory pathways, the TGF-beta system, has been identified and characterized in both animal models and in human lesions and lesion-derived cells. Cells derived from human lesions are resistant to the antiproliferative and apoptotic effects of TGF-beta, while their normal counterparts from the vascular media are potently inhibited and killed. Both cell types increase PAI-1 production, switch actin phenotypes in response to TGF-beta1, and produce similar levels of TGF-beta activity. Membrane cross-linking of (125)I-TGF-beta1 indicates that normal human SMC express Type I, II and III receptors. The Type II receptor is strikingly decreased in lesion cells, with little change in the Type I or III receptors. RT-PCR confirmed that the Type II TGF-beta1 receptor mRNA is reduced in lesion cells. Subsequent analysis of human lesion vs normal tissues confirmed that the Type I receptor was consistently present in the lesion, while the Type II receptor was much more variable, and commonly absent in both coronary artery and carotid artery lesions. Transfection of the Type II receptor into lesion cells partially restores the growth inhibitory response to TGF-beta1, implying that signaling remains intact. A subset of patients, and cells derived from their lesions, exhibit acquired mutations in the Type II receptor that would explain their resistance, though the majority of cells are resistant without obvious mutational defects. Thus, it is currently being tested whether transcriptional defects or abnormalities in receptor processing may explain the low levels of the Type II receptor. Because TGF-beta1 is overexpressed in fibroproliferative vascular lesions, receptor-negative cells would be allowed to grow in a slow, but uncontrolled fashion, while overproducing extracellular matrix components.

Evidence for an age-related dysfunction in the antiproliferative response to transforming growth factor-beta in vascular smooth muscle cells.

Previous studies have indicated that aged animals show an increased intimal hyperplasia after arterial injury. The present studies examined the hypothesis that the increased serum-free proliferation of aged smooth muscle cells (SMC), in vitro, was due to a loss of an antiproliferative signal, such as transforming growth factor-beta 1 (TGF-beta 1). Northern blot analysis of the mRNA derived from old (> 19 mo) or young (3-4 mo) rat aortic SMC indicated that both groups had an equivalent level of the 2.5 kB TGF-beta 1 message. Metabolic labeling with 35S-methionine and immunoprecipitation for TGF-beta 1 confirmed the de novo synthesis of TGF-beta 1 in rat SMC. Old and young SMC supernatants showed equal levels of active or latent (acid-activated) TGF-beta activity. Despite the similarities in the production of TGF-beta 1, old SMC were refractory to inhibition by TGF-beta 1, whereas young SMC were markedly inhibited (80%) by low levels of TGF-beta 1 (IC50 < 5 pg/ml). Binding studies at 4 degrees C indicated that old SMC exhibited reduced binding capacity for 125I-TGF-beta 1. Cross-linking studies confirmed that old SMC showed reduced binding of 125I-TGF-beta 1 to membrane sites corresponding to the high molecular weight type III receptor, as well as the 85-kDa type II and 65-kDa type I receptor. However, at 37 degrees C, old SMC degraded 125I-TGF-beta 1 more rapidly than young SMC. Combined, this data suggests that SMC derived from older animals are capable of normal production of TGF-beta 1 but fail to respond to the autocrine growth inhibitory effects of this agent, thereby leading to enhanced proliferation.

Investigation of the medium-term effects of Olibratrade mark fat emulsion on food intake in non-obese subjects.

OBJECTIVE: To investigate the effect of Olibra fat emulsion on medium-term food intake and appetite in non-obese subjects. DESIGN: Double-blind, placebo-controlled, within-subject crossover. SETTING: University of Ulster, Coleraine. SUBJECTS: A total of 28 subjects (14 male, 14 female). INTERVENTIONS: Subjects were randomly assigned to receive either a 200 g portion of test (5 g of Olibra fat) or control (5 g milk fat) yoghurt for breakfast for 2 x 3 week 'study' phases, separated by a 3-week 'wash-out' phase. On days 1, 8 and 22 of the study phases, food intake 4 h post-consumption of the yoghurt was assessed by pre- and post-covert weighing at an ad libitum buffet-style test lunch. Throughout each of these study days, appetite was assessed using visual analogue scales (VAS) at regular intervals. For the remainder of the study days, and the following 24 h ('post-study days'), subjects reported their food intake using weighed dietary records. RESULTS: Consumption of the Olibra emulsion had no significant effect on mean energy, macronutrient or amounts of food consumed at the lunch 4 h post-consumption. Self-reported food intakes indicated that there was no significant effect of the emulsion on energy intakes for the remainder of each study day and post-study days. There was considerable individual variation in food intakes following consumption of the Olibra emulsion, with 46, 59 and 57% of subjects reducing their energy intakes at lunch on days 1, 8 and 22. There was no consistent effect of the emulsion on appetite ratings. CONCLUSIONS: In contrast to earlier studies, there was no evidence of a short- or medium-term effect of the Olibra emulsion on food intake or appetite. This could be owing to numerous confounding factors influencing eating behaviour and/or the different study design used in the present study.

Independent effects of estradiol on water and food intake.

Six experiments examined the effects of estradiol on ingestive behaviors of guinea pigs. Estradiol treatment was found to reduce water intake independently of its actions on food intake and body weight. In the first experiment, minimum intake and body weight of intact female guinea pigs coincided with rupture of the vaginal membrane, the estimated time of ovulation. In a second experiment, injections of 3 micrograms of estradiol benzoate per day to ovariectomized females significantly depressed food intake, water intake, and body weight, compared with oil injections. The ratio of water intake per gram of food intake did not change significantly during the estrous cycle or following estradiol injections, results suggesting that the reduced drinking might be a consequence of the reduced feeding. However, reducing food rations to 30% below ad lib levels in Experiment 3 by itself had no significant effect on drinking. In Experiment 4, therefore, ovariectomized females were first placed on a food ration 30% below ad lib levels and then injected daily with either 3 micrograms of estradiol benzoate or oil. Compared with oil injections, these estradiol injections significantly reduced water intake, while food intake did not decline significantly. In these experiments, the reduction in food intake was therefore neither a sufficient nor a necessary condition for the estradiol-induced suppression of water intake. The last two experiments verified that estradiol has independent actions on feeding. The daily water ration was reduced to 30% below ad lib levels in Experiment 5, with no significant effect on food intake. In the sixth experiment, the water ration was first reduced to 30% below ad lib levels, and then the ovariectomized females were injected with either oil or 3 micrograms of estradiol benzoate per day. With this reduced water ration, the estradiol significantly suppressed food intake while producing only minimal and insignificant changes in water intake. These findings established that estradiol can independently influence water intake and food intake in the guinea pig and thereby indicate that estradiol operates through di different mechanisms to produce these two effects.

Effects of female hormonal condition on body weight of male partners: dependence on testicular factors.

Four experiments explored the short-term effects of female estrous condition or gonadal hormones on male body weight. Body weights of male guinea pigs and their ovulating female partners were initially found to show a significant periovular suppression relative to those of female cagemates that were not ovulating at that time. Similar effects in male rats have been hypothesized to result from postcopulatory increases in circulating testosterone and the conversion of that testosterone to estradiol. For evaluation of the probable role of the guinea pig testes in the observed phenomenon, intact and castrated male guinea pigs were housed with ovariectomized females. Female estrus, induced by injecting the females with estradiol and progesterone, resulted in an immediate decline in body weight of the intact male partners, but the body weight of castrated male partners was unaffected. Additional tests evaluated the direct effects of estradiol and testosterone on body weight of male guinea pigs. Injections of up to 1 mg per day of testosterone propionate were insufficient to produce short-term suppression of body weight in either intact or castrated males. However, treatment of the males with estradiol readily reduced their body weight. Overall, these results are not consistent with the hypothesis that short-term reductions in body weight of mated males result from immediate postcopulatory increases in circulating testosterone. It is suggested that other, possibly more estrogenic, testicular factors may play a role in the observed phenomenon.

Transforming growth factor-beta receptor types I and II are expressed in renal tubules and are increased after chronic unilateral ureteral obstruction.

Transforming growth factor-beta (TGF-beta) is a profibrotic cytokine which has been implicated in the renal fibrosis which follows unilateral ureteral obstruction (UUO) in the rat. TGF-beta receptor type I (TGF-RI) and TGF-beta receptor type II (TGF-RII) are part of the complex which mediates the response to TGF-beta. We sought to determine if TGF-RI and TGF-RII are found in the kidney, and if their expression is changed as a result of UUO. Polymerase chain reaction (PCR) was used to determine expression of mRNA for TGF-RI and TGF-RII in the kidney. Immunoperoxidase was used to localize and quantify the expression of these receptors at 3, 7, 14, 21 and 28 days after UUO, and in sham-operated animals. Expression of mRNA for TGF-RI and TGF-RII was demonstrated in sham operated, obstructed and contralateral unobstructed kidneys using PCR. Using immunoperoxidase, a uniform distribution of TGF-RI and TGF-RII was found in cortical tubules of sham operated kidneys, whereas medullary tubules showed a patchy TGF-RI distribution and no TGF-RII staining. After UUO, an increased tubular expression of TGF-RI and TGF-RII was noted in both obstructed and contralateral kidneys compared to sham operated kidneys. No staining for either TGF-RI or TGF-RII was noted in glomeruli, vasculature or interstitial cells. TGF-beta receptors I and II were found exclusively in renal tubules and were shown to increase in both the obstructed and contralateral kidneys relative to sham operated animals. Upregulation of TGF-beta receptors in both kidneys suggests that TGF-beta may contribute to the fibrotic response in the obstructed kidney and the hypertrophic response of the contralateral kidney.

Diverse effects of estradiol-17 beta: concurrent suppression of appetite, blood pressure and vascular reactivity in conscious, unrestrained animals.

Evidence from epidemiological and clinical investigations have suggested a relationship between estrogen-containing oral contraceptives and hypertension. The present series of studies, however, documents the ability of estradiol-17 beta, a natural ovarian estrogen, to lower resting blood pressure and pressor responses to norepinephrine in conscious, unrestrained guinea pigs. Arterial measurements were made of resting blood pressure and heart rate, plus pressor responses to intravenous infusions of 1.56 micrograms norepinephrine. Injection of 30 micrograms estradiol-17 beta reduced resting pressures up to 12% and pressor responses up to 20% in the interval from 12 to 48 hours postinjection. The estradiol treatment also significantly and reversibly lowered food intake, water intake, and body weight. These effects could be induced by either 3 or 30 micrograms of estradiol benzoate for up to 4 days if estradiol treatment was continued. Parallel studies indicated that NE-induced contractions of the isolated aorta were markedly reduced by pretreatment with estradiol. These studies indicate that natural ovarian estrogens may reduce blood pressure by reducing the contractility of the arterial smooth muscle.

Childhood obesity prevention studies: lessons learned and to be learned.

OBJECTIVE: To provide an overview of methodological issues in the design, delivery and evaluation of childhood obesity prevention programmes. DESIGN: Review of existing literature. SETTING: International. RESULTS: Interventions have varied considerably with regard to their design, subject selection criteria, sample size, attrition rates, intervention components and duration of both the intervention and the follow-up phases. However, overall, there is only a limited body of consistent, high-quality evidence on which valid and generalisable conclusions can be drawn about best practices for the prevention of childhood obesity. CONCLUSIONS: Although the rationale for targeting children and adolescents through primary prevention is now compelling, effective obesity prevention remains elusive. There is increasing consensus that prevention of childhood obesity necessitates multifaceted health promotion interventions based on population health principles. By definition, such interventions should have a range of outcome indicators of effectiveness, generalisability and sustainability, not just the traditional ones focused on individual lifestyle behaviour change. Given the complexity and intricacy of population-based intervention programmes, multiple methods of data collection which combine both qualitative and quantitative approaches will need to be fully exploited in order to move towards evidence-based practice in the future.

A rapid fluorometric DNA assay for the measurement of cell density and proliferation in vitro.

Many research efforts require the accurate determination of cell density in vitro. However, physical cell counting is inaccurate, time-intensive and requires removal of the cells from their growth environment, thereby introducing a host of potential artifacts. The current studies document a very simple method of determining cell density in microtiter wells via DNA-enhanced fluorescence. Fixed cells are stained with the A-T intercalating DNA stains DAPI or Hoechst 33342 and then fluorescence is quantified in a plate fluorometer. Fluorescence is shown to be linearly related to cell density as determined by two physical counting methods. The validity of the method is established in determining serum-stimulated growth of smooth muscle cells and in mitogen-induced growth of endothelial cells. The fixed cells can be stored for prolonged periods, thus allowing time-course proliferation assays without interassay variations. The fixed cells are also suitable for determinations of antigens of interest by ELISA. This method is potentially valuable in many in vitro systems where the quantification of cell density and proliferation is necessary.