Participation rates of childhood cancer survivors to self-administered questionnaires: a systematic review.

This review aimed to assess participation rates of childhood cancer survivors (CCS) invited to fill out a health-related questionnaire. Additionally, effects of study and CCS characteristics on participation rates were examined. PubMed, Web of Science, Ovid (EMBASE) and CINAHL databases were searched. Publications included were questionnaire-based studies among CCS diagnosed with cancer before the age of 21, alive at least 5 years past diagnosis and aged 16 years or older at the time of study. Thirty-five studies were included; the median participation rate was 65%. Sixteen studies reported information about CCS actively declining participation (median rate 5%). Five study characteristics seemed to influence participation rates: the use of reminders and incentives, the option to answer a shortened questionnaire, the recruitment of participants through their general practitioner and a pre-notification before sending out the questionnaire. Furthermore, CCS characteristics related to improved participation were female gender, Caucasian ethnicity and a higher educational level. The results of this study will help to improve the (methodological) quality of future questionnaire-based studies among CCS, thereby increasing our knowledge about late effects among this group of survivors.

Factors influencing implementation success of guideline-based clinical decision support systems: A systematic review and gaps analysis.

OBJECTIVE: To provide an integrated and differentiated understanding of factors influencing guideline-based CDSS implementation and illustrate the gaps in the current literature. MATERIALS AND METHODS: A systematic literature review and in-depth exploration of factors impeding or facilitating successful implementation of guideline-based CDSS supporting physicians in clinical decision-making was performed. Factors were identified thematically by textual analysis of the included publications and were individually mapped to the human, organization and technology-fit (HOT-fit) framework for evaluating implementations of health information systems. RESULTS: A total of 421 factors were found in 35 included publications from a total of 3676 publications. The mapping of factors concerning CDSS implementation on the HOT-fit framework revealed gaps in each domain of the framework and showed that research has mainly focused on human and technology factors and less on organizational factors. CONCLUSIONS: Future research within the field of guideline-based CDSS should focus on evaluating implementations through the use of socio-technical models to study guideline-based CDSS system implementations from a multidimensional view. Furthermore, research is needed to explore whether use of these models during the planning phases of a CDSS project is useful in anticipating and preventing implementation barriers from occurring and exploiting facilitators to a successful implementation of the system.

Uncovering healthcare practitioners' information processing using the think-aloud method: From paper-based guideline to clinical decision support system.

OBJECTIVE: To investigate whether the use of the think-aloud method with propositional analysis could be helpful in the design of a Clinical Decision Support System (CDSS) providing guideline recommendations about long-term follow-up of childhood cancer survivors. MATERIALS AND METHODS: The think-aloud method was used to gain insight into healthcare professionals' information processing while reviewing a paper-based guideline. A total of 13 healthcare professionals (6 physicians and 7 physician assistants) prepared 2 fictitious patient consults using the paper-based guideline. Propositional analysis was used to analyze verbal protocols of the think-aloud sessions. A prototype CDSS was developed and a usability study was performed, again with the think-aloud method. RESULTS: The analysis revealed that the paper-based guideline did not support healthcare practitioners in finding patient-specific recommendations. An information processing model for retrieving recommendations was developed and used as input for the design of a CDSS prototype user interface. Usability analysis of the prototype CDSS showed that the navigational structure of the system fitted well with healthcare practitioners' daily practices. CONCLUSIONS: The think-aloud method combined with propositional analysis of healthcare practitioners' verbal utterances while they processed a paper-based guideline was useful in the design of a usable CDSS providing patient-specific guideline recommendations.

Factors known to influence acceptance of clinical decision support systems.

Clinical Decision Support Systems (CDSS) have been shown to improve clinical performance and patient outcomes, but the failure rate of such systems is still over 50 percent. To contribute to a wider understanding of issues surrounding CDDS acceptance, we performed a systematic review of studies that evaluated CDSS implementations in clinical care to determine the factors that are associated with acceptance of CDSS by physicians. The factors that were found were categorized according to the HOT-fit framework. The mapping of factors concerning CDSS acceptance on the HOT-fit framework revealed gaps in each domain of the framework and showed that research has mainly focused on human and technology factors and a lack of research on organizational factors. A potential area of research could thus be studying the organizational factors that may influence CDSS acceptance.

Cellular cholesterol efflux mediated by cyclodextrins. Demonstration Of kinetic pools and mechanism of efflux.

The efflux of cholesterol from cells in culture to cyclodextrin acceptors has been reported to be substantially more rapid than efflux induced by other known acceptors of cholesterol (Kilsdonk, E. P. C., Yancey, P., Stoudt, G., Bangerter, F. W., Johnson, W. J., Phillips, M. C., and Rothblat, G. H. (1995) J. Biol. Chem. 270, 17250-17256). In this study, we compared the kinetics of cholesterol efflux from cells with 2-hydroxypropyl-beta-cyclodextrins and with discoidal high density lipoprotein (HDL) particles to probe the mechanisms governing the remarkably rapid rates of cyclodextrin-mediated efflux. The rate of cholesterol efflux was enhanced by shaking cells growing in a monolayer and further enhanced by placing cells in suspension to achieve maximal efflux rates. The extent of efflux was dependent on cyclodextrin concentration, and maximal efflux was observed at concentrations >50 mM. For several cell types, biexponential kinetics of cellular cholesterol efflux were observed, indicating the existence of two kinetic pools of cholesterol: a fast pool (half-time (t1/2) approximately 19-23 s) and a slow pool with t1/2 of 15-30 min. Two distinct kinetic pools of cholesterol were also observed with model membranes (large unilamellar cholesterol-containing vesicles), implying that the cellular pools are in the plasma membrane. Cellular cholesterol content was altered by incubating cells with solutions of cyclodextrins complexed with increasing levels of cholesterol. The number of kinetic pools was unaffected by raising the cellular cholesterol content, but the size of the fast pool increased. After depleting cells of the fast pool of cholesterol, this pool was completely restored after a 40-min recovery period. The temperature dependence of cyclodextrin-mediated cholesterol efflux from cells and model membranes was compared; the activation energies were 7 kcal/mol and 2 kcal/mol, respectively. The equivalent activation energy observed with apo-HDL-phospholipid acceptor particles was 20 kcal/mol. It seems that cyclodextrin molecules are substantially more efficient than phospholipid acceptors, because cholesterol molecules desorbing from a membrane surface can diffuse directly into the hydrophobic core of a cyclodextrin molecule without having to desorb completely into the aqueous phase before being sequestered by the acceptor.

Cellular cholesterol efflux mediated by cyclodextrins.

In this study, we compared cholesterol efflux mediated by either high density lipoproteins (HDL3) or beta-cyclodextrins, cyclic oligosaccharides that are able to dissolve lipids in their hydrophobic core. beta-Cyclodextrin, 2-hydroxypropyl-beta-cyclodextrin, and methyl-beta-cyclodextrin at 10 mM induced the release of 50-90% of L-cell [3H]cholesterol after 8 h of incubation, with a major portion of this cholesterol being released in the first 1-2 h of incubation. The cholesterol efflux kinetics are different if cells are incubated with HDL3, which induces a relatively constant rate of release of cholesterol throughout an 8-h incubation. Cholesterol efflux to cyclodextrins was much greater than phospholipid release. To test the hypothesis that maximal efflux rate constants for a particular cell are independent of the type of acceptor, we estimated the maximal rate constants for efflux (Vmax) of cellular cholesterol from L-cells, Fu5AH cells, and GM3468A fibroblasts. The rate constant for HDL3-mediated efflux varied among cell lines in the order Fu5AH > L-cells > fibroblasts. However, these differences were not evident when cyclodextrins were used as cholesterol acceptors. The estimated Vmax values for cyclodextrin-mediated efflux were 3.5-70-fold greater than for HDL3 for the three cell lines. The very high efficiency of cyclodextrins in stimulating cell cholesterol efflux suggests that these compounds can be used in two general ways for studies of atherosclerosis: 1) as research tools to probe mechanisms of cholesterol transport and aspects of membrane structure or 2) as potential pharmacological agents that could modify in vivo cholesterol metabolism and influence the development of the atherosclerotic plaque.

Inhibition of cellular cholesterol efflux by 25-hydroxycholesterol.

The effect of oxysterols on efflux of cholesterol from mouse L-cell fibroblasts, rat Fu5AH hepatoma cells, J774 macrophages, and human EA.hy 926 endothelial cells was studied. Cells were preincubated with 25-hydroxycholesterol (25-OHC) either during labeling of the cells with [3H]cholesterol or during equilibration after labeling. Subsequently, the release of [3H]cholesterol into medium containing 0.2 mg HDL3/ml was measured and the fractional release of cellular [3H]cholesterol was calculated. Pretreatment with 25-OHC (1 microgram/ml) caused a 30% reduction in [3H]cholesterol efflux from L-cells during 8 h of incubation with HDL3. 25-OHC also inhibited cholesterol efflux from Fu5AH and J774 cells, but the effect was less marked. There was only a small, nonsignificant reduction of efflux from EA.hy 926 cells. The mechanisms of 25-OHC-induced inhibition of cellular cholesterol efflux was further studied in L-cells, because of their sensitivity to 25-OHC treatment. The effect of 25-OHC on cholesterol efflux was dose-dependent, with significant effects seen at 25-OHC concentrations as low as 50 ng/ml. The half-time for cholesterol efflux from 25-OHC-treated cells (5 micrograms/ml) was 13.0 +/- 3.3 h compared to 5.7 +/- 1.0 in control cells, corresponding to a 55% reduction in the rate of cholesterol release. Other oxysterols, including 7-ketocholesterol, 7 alpha- and 7 beta-hydroxycholesterol, and 22(S)-hydroxycholesterol also inhibited [3H]cholesterol efflux from L-cells significantly, but to a lesser degree. 25-Hydroxycholesterol (5 micrograms/ml) reduced efflux from both normal and cholesterol-enriched cells by 31 and 14%, respectively. Inhibition of efflux was similar when reconstituted HDL3-apolipoprotein/phosphatidylcholine particles or small unilamellar phosphatidylcholine vesicles were used as cholesterol acceptors instead of HDL3. The content of phospholipids, cholesterol and the FC/PL ratio of intact cells and from isolated plasma membrane vesicles were the same for control and 25-OHC-treated cells. Efflux of [3H]cholesterol from plasma membranes isolated from 25-OHC-treated cells was 20% less than efflux from membranes from control cells. The difference in efflux observed in intact cells is partially explained by the reduction in efflux from the plasma membrane. In conclusion, our studies suggest that oxysterols, especially 25-hydroxycholesterol, can reduce cellular cholesterol efflux in vitro. Therefore oxysterols, either endogenous or derived from the diet, may influence cellular cholesterol efflux in vivo, the first step in reverse cholesterol transport.

Net transport of cholesterol from cells of the human EA.hy 926 endothelial cell line to high density lipoproteins.

EA.hy 926 cells, a human endothelial cell line, show characteristics of differentiated endothelial cells. The cells express saturable binding of apo E-free 125I-high density lipoprotein3 (HDL3). Bmax increased from 71 to 226 ng HDL3 bound/mg cell protein after cholesterol loading of the confluent endothelial cells with cationized low density lipoprotein (LDL). The affinity did not change after cholesterol enrichment (Kd was 37 micrograms HDL3 protein/ml for control cells and 31 micrograms/ml for loaded cells). Incubation of cholesterol-loaded EA.hy 926 cells with native HDL and LDL had different effects on cellular cholesterol levels. Incubation with HDL decreased both esterified and unesterified cellular cholesterol, but LDL did not change total cellular cholesterol. However, LDL tended to increase cellular cholesteryl esters, with a concomitant decrease of unesterified cellular cholesterol. Incubation of endothelial cells with both HDL and LDL also resulted in decreased total cellular cholesterol levels. These data show that cationized LDL-loaded human endothelial EA.hy 926 cells can be used to study the net transport of cellular cholesterol to HDL, the first step in reverse cholesterol transport.

Effect of LCAT on HDL-mediated cholesterol efflux from loaded EA.hy 926 cells.

1. Human endothelial cells (EA.hy 926 line) were loaded with cholesterol, using cationized LDL, and the effect of lecithin:cholesterol acyltransferase (LCAT) on cellular cholesterol efflux mediated by high density lipoproteins (HDL) was measured subsequently. 2. In plasma, lecithin:cholesterol acyltransferase (LCAT) converts unesterified HDL cholesterol into cholesteryl esters, thereby maintaining the low UC/PL ratio of HDL. It was tested if further decrease in UC/PL ratio of HDL by LCAT influences cellular cholesterol efflux in vitro. 3. Efflux was measured as the decrease of cellular cholesterol after 24 hr of incubation with various concentrations of HDL in the presence and absence of LCAT. LCAT from human plasma (about 3000-fold purified) was added to the cell culture, resulting in activity levels in the culture media of 60-70% of human serum. 4. Although LCAT had a profound effect on HDL structure (UC/TC and UC/PL ratio's decreased), the enzyme did not enhance efflux of cellular cholesterol, using a wide range of HDL concentrations (0.05-2.00 mg HDL protein/ml). 5. The data indicate that the extremely low unesterified cholesterol content of HDL, induced by LCAT, does not enhance efflux of cholesterol from loaded EA.hy 926 cells. It is concluded that the HDL composition (as isolated from plasma by ultracentrifugation) is optimal for uptake of cellular cholesterol.

Binding of modified high density lipoproteins to endothelial cells: relation with cellular cholesterol efflux?

Human endothelial cells (EA.hy 926 line) were enriched with cholesterol using cationized low density lipoprotein (LDL). Cholesterol-loaded cells interacted with native apolipoprotein (apo) E-free high density lipoprotein3 (HDL)3 as well as with dimethyl suberimidate-modified HDL3 (DMS-HDL3). At 4 degrees C both HDL preparations showed a saturable high affinity binding with a KD of 31 and 50 micrograms of protein/ml and a Bmax of 226 and 436 ng/mg cell protein for native HDL3 and DMS-HDL3 particles, respectively. Competition of binding of 5 micrograms apo E-free 125I-labelled HDL3/ml by unlabelled DMS-HDL3 and tetranitromethane-treated HDL3 (TNM-HDL3) was very poor, whereas unlabelled native HDL3 competed very effectively with 125I-labelled HDL3 binding. Thus, both types of modified HDL did not compete for the high affinity binding sites for native HDL. Unlabelled native HDL3 and unlabelled DMS-HDL3 both competed for the binding of 125I-labelled DMS-HDL3 very effectively. These experiments indicate that there are two distinct high affinity binding sites for HDL on cationized LDL-loaded EA.hy 926 cells: one specific HDL binding site, which only binds native HDL, and a second binding site for both native HDL and DMS-HDL. The modified HDL fractions were used to study the relation between HDL binding and HDL-mediated efflux. Efflux of cell cholesterol was measured as the increase of cholesterol mass in the medium after 24 h of incubation with 0.2 mg native HDL3/ml, or the same amount of modified HDL3. DMS-HDL3-mediated efflux was identical to efflux mediated by native HDL3. TNM-HDL3 also induced efflux of cell cholesterol; however, efflux induced by TNM-HDL3 was only 45-50% of the amount obtained with native HDL3. So both DMS- and TNM-modified HDL3 induced efflux of cholesterol, although these particles do not bind to the specific high affinity sites for native HDL. These results do not indicate a link between binding of HDL to specific receptors for native HDL and HDL-mediated efflux of cholesterol from loaded endothelial cells.

Effect of phospholipid fatty acid composition of endothelial cells on cholesterol efflux rates.

Human endothelial cells (EA.hy 926 line) were loaded with cationized low density lipoprotein (LDL) and subsequently incubated with fatty acid/bovine serum albumin complexes. The fatty acids were palmitic, oleic, linoleic, arachidonic, and eicosapentaenoic acids. The preincubations resulted in extensively modified fatty acid profiles in cell membrane phospholipids and in cellular cholesteryl esters. The cholesterol efflux from these fatty acid-modified cells was measured using 0.2 mg high density lipoprotein3 (HDL3)/ml medium. The efflux was significantly higher for the palmitic acid-treated cells, compared to all other fatty acid treatments. These differences in efflux rates were not caused by changes in the binding of HDL3 to high affinity receptors on the EA.hy 926 cells. Efflux mediated by dimethyl suberimidate-treated HDL3, which does not interact with high affinity HDL receptors, was similar to efflux induced by native HDL3 after all fatty acid treatments. Our results indicate that high affinity HDL receptors are not important for HDL-mediated efflux of cell cholesterol. The fatty acid composition of the cell membrane phospholipids may be an important determinant.

Endothelial EA.hy 926 cells can be loaded with cationized LDL, but not with acetylated LDL.

EA.hy 926 cells, a human endothelial cell line, show characteristics of differentiated endothelial cells. Endothelial cells normally express membrane scavenger receptors. Therefore modified LDL, eg., acetylated LDL, can be taken up, causing accumulation of mass amounts of cholesterol. We have shown that EA.hy 926 cells cannot be loaded with cholesterol using acetylated LDL, but can be efficiently enriched with cholesterol by incubation with cationized LDL. The loaded cells may serve as models for studies on reverse cholesterol transport.

Cholesterol efflux from cells to immunopurified subfractions of human high density lipoprotein: LP-AI and LP-AI/AII.

Using immunoaffinity chromatography, we separated human high density lipoprotein (HDL) into two subfractions: LP-AI, in which all particles contain apolipoprotein A-I (apoA-I) but no apoA-II, and LP-AI/AII, in which all particles contain both apoA-I and apoA-II. To compare LP-AI and LP-AI/AII as acceptors of cell cholesterol, the isolated subfractions were diluted to 50 micrograms phospholipid/ml, and then incubated with monolayer cultures of cells in which whole-cell and lysosomal cholesterol has been labeled with 14C and 3H, respectively. We used three cell types (Fu5AH rat hepatoma cells, normal human skin fibroblasts, and rabbit aortic smooth muscle cells). When these cells were prepared to contain normal physiological quantities of cholesterol (20-35 micrograms/mg protein), LP-AI and LP-AI/AII were nearly equally efficient in promoting efflux of both whole-cell and lysosomal cholesterol. For whole-cell cholesterol, the rate constants for efflux to LP-AI and LP-AI/AII were: 0.050/h and 0.053/h, respectively, with Fu5AH cells; 0.0063/h and 0.0074/h with GM3468 human skin fibroblasts; and 0.0076/h and 0.0079/h with rabbit aortic smooth muscle cells. When cholesterol in hepatoma cells or fibroblasts was elevated two- to threefold above normal, there was still not difference in efflux of whole-cell cholesterol to LP-AI and LP-AI/AII. In longterm incubations, the net depletion of cholesterol mass from cholesterol-enriched cells was either identical with the two HDL subfractions, or somewhat greater with LP-AI/AII.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of human high-density lipoprotein subclasses LP A-I and LP A-I/A-II and binding to HepG2 cells.

Plasma HDL can be classified according to their apolipoprotein content into at least two types of lipoprotein particles: lipoproteins containing both apo A-I and apo A-II (LP A-I/A-II) and lipoproteins with apo A-I but without apo A-II (LP A-I). LP A-I and LP A-I/A-II were isolated by immuno-affinity chromatography. LP A-I has a higher cholesterol content and less protein compared to LP A-I/A-II. The average particle mass of LP A-I is higher (379 kDa) than the average particle weight of LP A-I/A-II (269 kDa). The binding of 125I-LP A-I to HepG2 cells at 4 degrees C, as well as the uptake of [3H]cholesteryl ether-labelled LP A-I by HepG2 cells at 37 degrees C, was significantly higher than the binding and uptake of LP A-I/A-II. It is likely that both binding and uptake are mediated by apo A-I. Our results do not provide evidence in favor of a specific role for apo A-II in the binding and uptake of HDL by HepG2 cells.