Identifying sources of reporting error using measured food intake.

OBJECTIVE: To investigate the magnitude and relative contribution of different sources of measurement errors present in the estimation of food intake via the 24-h recall technique. DESIGN: We applied variance decomposition methods to the difference between data obtained from the USDA's Automated Multiple Pass Method (AMPM) 24-h recall technique and measured food intake (MFI) from a 16-week cafeteria-style feeding study. The average and the variance of biases, defined as the difference between AMPM and MFI, were analyzed by macronutrient content, subject and nine categories of foods. SUBJECTS: Twelve healthy, lean men (age, 39+/-9 year; weight, 79.9+/-8.3 kg; and BMI, 24.1+/-1.4 kg/m2). RESULTS: Mean food intakes for AMPM and MFI were not significantly different (no overall bias), but within-subject differences for energy (EI), protein, fat and carbohydrate intakes were 14, 18, 23 and 15% of daily intake, respectively. Mass (incorrect portion size) and deletion (subject did not report foods eaten) errors were each responsible for about one-third of the total error. Vegetables constituted 8% of EI but represented >25% of the error across macronutrients, whereas grains that contributed 32% of EI contributed only 12% of the error across macronutrients. CONCLUSIONS: Although the major sources of reporting error were mass and deletion errors, individual subjects differed widely in the magnitude and types of errors they made.

The impact of the covert manipulation of macronutrient intake on energy intake and the variability in daily food intake in nonobese men.

OBJECTIVE: To investigate the effect of macronutrient composition on ad libitum food intake in nonobese men. DESIGN: Balanced, incomplete-block, crossover study where subjects received two of three treatments. Macronutrient composition was manipulated by providing 2.1 MJ/day high-carbohydrate (CHO), high-fat (FAT), and/or high-protein (PRO) drinks every day over the course of two, 8-week periods. SUBJECTS: In all, 12 healthy normal weight men (age: 39+/-9 years, BMI: 24.1+/-1.4 kg/m2). MEASUREMENTS: Ad libitum food intake was measured continuously for 16 weeks at the Beltsville Human Nutrition Research Center (BHNRC). Body composition (DEXA) and body weight were also measured. RESULTS: Average energy intake (EI) during weeks 1 and 2 was lower for CHO than FAT (P<0.05), but this effect disappeared by week 3. EI during CHO increased by 11% from week 1 to 8 through the increased selection of carbohydrate and protein-containing foods, but not fat foods. Food intake was variable, both between and within subjects, but was not related to macronutrient composition. CONCLUSION: EI appears to be influenced by macronutrient composition in the short-term when diets are modified, but the effect dissipates in a few weeks if the diet is maintained. These data suggest the presence of macronutrient-specific regulatory mechanisms in the body, but do not support the notion that a high intake of any of the three macronutrients suppresses EI over a prolonged period of time. The high variability in food intake does not appear to be related to macronutrient composition.

Maltodextrin-based proniosomes.

Niosomes are nonionic surfactant vesicles that have potential applications in the delivery of hydrophobic or amphiphilic drugs. Our lab developed proniosomes, a dry formulation using a sorbitol carrier coated with nonionic surfactant, which can be used to produce niosomes within minutes by the addition of hot water followed by agitation. The sorbitol carrier in the original proniosomes was soluble in the solvent used to deposit surfactant, so preparation was tedious and the dissolved sorbitol interfered with the encapsulation of one model drug. A novel method is reported here for rapid preparation of proniosomes with a wide range of surfactant loading. A slurry method has been developed to produce proniosomes using maltodextrin as the carrier. The time required to produce proniosomes by this simple method is independent of the ratio of surfactant solution to carrier material and appears to be scalable. The flexibility of the proniosome preparation method would allow for the optimization of drug encapsulation in the final formulation based on the type and amount of maltodextrin. This formulation of proniosomes is a practical and simple method of producing niosomes at the point of use for drug delivery.

SEM imaging predicts quality of niosomes from maltodextrin-based proniosomes.

PURPOSE: The limits to surfactant loading of proniosomes were determined and a rationale developed for the observed relationship between the composition of proniosomes and the quality of reconstituted niosome suspension. METHODS: A novel method for producing proniosomes with a maltodextrin carrier was recently developed, which provides for rapid reconstitution of niosomes with minimal residual carrier. A slurry of maltodextrin and surfactant was dried to form a free-flowing powder which could be rehydrated by addition of warm water. This method provided facile production of a wide range of proniosome compositions, and thus, allowed us to examine rehydration behavior for similar concentrations of surfactant over a wide range of film thickness. SEM images of proniosomes with various degrees of surfactant loading and images of pure surfactant were compared. Direct observation and particle size measurements by laser light scattering provided characterization of the final niosome preparations. RESULTS: Successful rehydration of surfactant to produce niosomes from dried film requires that the film be as thin as possible to avoid the clumping and precipitation that occurs when pure, granular surfactant is hydrated directly. The appearance of a coarse, broken surface on the proniosomes correlates with inefficient rehydration and occurrence of aggregation and precipitate in the final niosome suspension. CONCLUSIONS: These observations provide an indication of the requirements for dry proniosomes to yield niosome suspensions of high quality.

Conformation of oligodeoxynucleotides associated with anionic liposomes.

There has been significant progress in the development of antisense therapeutics for a wide range of medicinal applications. Further improvement will require better understanding of cellular internalization, intracellular distribution mechanisms and interactions of oligodeoxynucleotides with cellular organelles. In many of these processes interactions of oligodeoxynucleotides with lipid assemblies may have a significant influence on their function. Divalent cations have been shown to assist cellular internalization of certain oligodeoxynucleotides and to affect their conformation. In this work we have investigated conformational changes of phosphorothioate oligodeoxynucleotides upon divalent cation-mediated interaction with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylglycerol (DPPG) liposomes. For the sequences investigated here the native conformation underwent significant change in the presence of anionic DPPG liposomes only when divalent cations were present. This change is sequence-specific, ion-selective and distinct from previously reported changes in oligodeoxynucleotide structure due to divalent cations alone. The conformation of one oligodeoxynucleotide in the presence of calcium and DPPG yields circular dichroism spectra which suggest C-DNA but which also have characteristics unlike any previously reported spectra of liposome-associated DNA structure. The data suggest the possibility of a unique conformation of liposome-associated ODNs and reflect a surprisingly strong tendency of single-stranded DNA to retain a characteristic conformation even when adsorbed to a surface. This conformation may be related to cellular uptake, transport of oligodeoxynucleotides in cells and/or function.

Late presentation of HIV infection associated with prolonged survival following AIDS diagnosis--characteristics of individuals.

Individuals who present late with human immunodeficiency virus (HIV) infection do not benefit from advances in drug therapies that delay their progression to acquired immunodeficiency syndrome (AIDS). This paper describes these individuals and their subsequent survival and investigates predictors of late presentation. All AIDS diagnoses from 1992-1998 notified to the Victorian State AIDS Registry were included. Subjects were grouped as individuals diagnosed with AIDS within 8 weeks of a first positive HIV test (late presenters), or individuals for whom there was more than 8 weeks between AIDS diagnosis and first positive HIV test (non-late presenters). Of 1021 AIDS diagnoses notified, 24% were late presenters. Late presentation was associated with increasing age, being bisexual or heterosexual, being born in Asia, southern Europe or South America and being diagnosed at a hospital. Late presenters survived longer following AIDS diagnosis (P < 0.0001). This increased survival may indicate a positive response by drug naïve patients to antiretroviral therapies following AIDS diagnosis.

Influence of divalent cations on the conformation of phosphorothioate oligodeoxynucleotides: a circular dichroism study.

Phosphorothioate oligodeoxynucleotides (ODNs) have been extensively investigated in vivo and in vitro for antisense control of gene expression. It has been shown that cellular uptake of phosphorothioate ODNs in some in vitro cell systems increases in the presence of divalent cations. In this work, we analyze the conformation of phosphorothioate ODNs and specific changes induced in it by various divalent cations using circular dichroism (CD) spectroscopy. CD data were obtained with several phosphorothioate ODNs in the absence and presence of the divalent cations Mg(2+), Ca(2+), Sr(2+), Ba(2+) and Mn(2+). All CD spectra indicated stable conformations of the ODNs in solution. The spectra were strongly dependent on ODN sequence and composition. Some ODNs such as T(23) and another with 'random' distribution of bases showed CD spectra characteristic of B-form DNA. Other ODNs which had at least three consecutive guanines in their sequences exhibited spectra characteristic of parallel G-tetraplexes. CD spectra of antisense ODNs exhibited specific responses to divalent cations. Changes in the conformation were not simply due to ionic strength effects. Mn(2+) diminished secondary structure in some ODNs. Group II divalent ions stabilized the parallel G-tetraplexes, and Mg(2+) generally had the weakest stabilizing efficiency. Each sequence/ion combination had a specific response so these effects cannot be generalized. These sequence-dependent, divalent ion-sensitive, and structurally unique solution conformations may be related to ion-mediated ODN uptake.

Proniosomes: a novel drug carrier preparation.

A procedure is described for producing a dry product which may be hydrated immediately before use to yield aqueous niosome dispersions similar to those produced by more cumbersome conventional methods. These 'proniosomes' minimize problems of niosome physical stability such as aggregation, fusion and leaking, and provide additional convenience in transportation, distribution, storage, and dosing. This report describes the preparation of dispersions of proniosome-derived niosomes, comparison of these niosomes to conventional niosomes, and optimization of proniosome formulations. In addition, conventional and proniosome-derived niosomes are compared in terms of their morphology, particle size, particle size distribution, and drug release performance in synthetic gastric or intestinal fluid. In all comparisons, proniosome-derived niosomes are as good or better than conventional niosomes.

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-sodium): rationale and design. DASH-Sodium Collaborative Research Group.

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-Sodium) is a multicenter, randomized trial comparing the effects of 3 levels of sodium intake and 2 dietary patterns on blood pressure among adults with higher than optimal blood pressure or with stage 1 hypertension (120-159/80-95 mm Hg). The 2 dietary patterns are a control diet typical of what many Americans eat, and the DASH diet, which, by comparison, emphasizes fruits, vegetables, and low-fat dairy foods, includes whole grains, poultry, fish, and nuts, and is reduced in fats, red meat, sweets, and sugar-containing beverages. The 3 sodium levels are defined as higher (typical of current US consumption), intermediate (reflecting the upper limit of current US recommendations), and lower (reflecting potentially optimal levels). Participants are randomly assigned to 1 of the 2 dietary patterns using a parallel group design and are fed each of the 3 sodium levels using a randomized crossover design. The study provides participants with all of their food during a 2-week run-in feeding period and three 30-day intervention feeding periods. Participants attend the clinic for 1 meal per day, 5 days per week, and take home food for other meals. Weight is monitored and individual energy intake adjusted to maintain baseline weight. The primary outcome is systolic blood pressure measured at the end of each intervention feeding period. Systolic blood pressure is compared across the 3 sodium levels within each diet and across the 2 diets within each sodium level. If effects previously observed in clinical trials are additive, sodium reduction and the DASH diet together may lower blood pressure to an extent not as yet demonstrated for nonpharmacologic treatment. The DASH-Sodium results will have important implications for the prevention and treatment of high blood pressure.

Changes in women's plasma lipid and lipoprotein concentrations due to moderate consumption of alcohol are affected by dietary fat level.

We studied the impact of substituting ethanol for dietary carbohydrate, in high- and low-fat diets, on plasma lipids and lipoprotein concentrations. During a 12-wk, weight maintaining, controlled feeding study, women consumed only food and beverage provided by the Human Studies Facility of the USDA Beltsville Human Nutrition Research Center. Twenty-six women (age 41-59 y) consumed either a high-fat diet (38% of energy from fat) or a low-fat diet (18% of energy from fat) for 12 wk. The 12-wk feeding period was divided into two 6-wk periods in a cross-over design during which either ethanol or carbohydrate was added to the diet (5% of total daily energy intake). When the women consuming the high-fat diet had ethanol added to their diet, they had 6% lower plasma cholesterol (P = 0.003), 11% lower LDL cholesterol (P = 0.001) and 3% higher HDL cholesterol (P = 0.06) than when they had an equal amount (% energy) of carbohydrate added to their diet. The greater HDL cholesterol concentration was due to a 21% greater the HDL(2) subfraction (P = 0. 001). The ratio of LDL to HDL cholesterol was 14% lower. No significant differences existed in plasma lipids in women consuming the low-fat diet between the periods in which they had ethanol or carbohydrate added to their diet. This study suggests that the decreases in cardiovascular disease risk factors typically seen with moderate alcohol consumption may not be evident in individuals consuming a diet low in fat. Therefore changes in the risk factors associated with a low-fat diet and moderate alcohol consumption do not appear to be additive.

Proniosomes: a novel drug carrier preparation.

A procedure is described for producing a dry product which may be hydrated immediately before use to yield aqueous niosome dispersions similar to those produced by more cumbersome conventional methods. These 'proniosomes' minimize problems of niosome physical stability such as aggregation, fusion and leaking, and provide additional convenience in transportation, distribution, storage, and dosing. This report describes the preparation of dispersions of proniosome-derived niosomes, comparison of these niosomes to conventional niosomes, and optimization of proniosome formulations. In addition, conventional and proniosome-derived niosomes are compared in terms of their morphology, particle size, particle size distribution, and drug release performance in synthetic gastric or intestinal fluid. In all comparisons, proniosome-derived niosomes are as good or better than conventional niosomes.

Energy available from corn oil is not different than that from beef tallow in high- or low-fiber diets fed to humans.

The impact of the source of dietary fat and the level of dietary fiber on digestibility and energy metabolism were studied in human (six male, six female) volunteers. Subjects were divided into two diet treatment groups, high fiber [29.0 g total dietary fiber (TDF)/d] and low fiber (18.6 g TDF/d), for the duration of the study. Each participated in three, 2-wk controlled feeding periods. Either beef tallow (BT), corn oil (CO) or carbohydrate (CHO) was added (25% of diet energy) to a base diet in a three-way crossover study. Energy expenditure, substrate oxidation and digestibility determinations were conducted at the end of each period. The protein, fat and CHO digestibility of the base diet was significantly different between the fiber levels. The digestibility (high-fiber/low-fiber) averaged 82%, 90% for protein, 96% and 98% for fat. After adjusting for TDF, the CHO digestibility averaged 96% and was not different between fiber levels. The digestibility of the added CO and BT was 99.6 and 99.8% respectively, and was not significantly different between the fiber levels. No significant differences in 24-h energy expenditure existed nor the thermic effect of food due either to fiber level or between the CHO, BT or CO. Fat oxidation in subjects consuming the low-fiber diet was 14% higher (P < 0.03) with the BT treatment than with the CO treatment but not different in those that consumed the high-fiber diet. The energy value of the two fat sources was not different but their utilization by individuals near energy balance may lead to differences in long-term weight maintenance.

Energy value of moderate alcohol consumption by humans.

We investigated the effects of an equal-energetic substitution of ethanol for dietary carbohydrate in high-and low-fat diets on energy expenditure and body composition. During the controlled feeding study, subjects maintained their weights and consumed only food and drink provided by the US Department of Agriculture Beltsville Human Nutrition Research Center's Diet Study Facility. Subjects (16 men and 32 women) were divided equally into two groups and consumed either a high-or low-fat diet for 16 wk. The feeding period was divided into two 8-wk periods during which either ethanol or carbohydrate was added to the diet (5% of total daily energy intake) in a crossover design. The metabolizable energy content of the diets (with supplements) was determined for all subjects through measurement of total food intake and fecal and urinary losses for 7 d during both 8-wk periods. Energy expenditure, measured for 24 h in a room calorimeter at the end of each 8-wk period, was the same for both periods. Metabolizable energy intake and changes in total-body energy content were used to calculate the total amount of energy expended by each subject for 7 wk during each 8-wk period. Total energy expenditure for 7 wk was the same when subjects consumed either ethanol or carbohydrate. These data clearly show that on an energy basis ethanol and carbohydrate are utilized in the diet with the same efficiency. These data are consistent with the efficiency of use of alcohol for maintenance of metabolizable energy being the same as that for carbohydrate.

Urinary malondialdehyde-equivalents during ingestion of meat cooked at high or low temperatures.

Excretion of malondialdehyde (MDA)-generating substances in the urine has been suggested as an indicator of in vivo lipid peroxidation. However, MDA in the urine also reflects the amount of lipid peroxidation products consumed in the diet. We determined MDA as the thiobarbituric acid (TBA)-MDA complex in urine of 19 healthy adults (10 male and 9 female) fed large quantities (3.6-4.1 g/kg body weight) of ground beef cooked at a low or a high temperature. Subjects ate a controlled diet with no alcohol or nutritional supplements. For 7 d they consumed ground beef cooked at 100 degrees C for 20 min (low-temperature meat) followed by 7 d with meat fried at 250 degrees C for 22 min (high-temperature meat). Prior to the study, subjects consumed their normal free choice diet with moderate amounts of meat. The concentration of MDA in urine at baseline was 2.1 +/- 0.3 mumol TBA-MDA equivalents/day (mean +/- SEM). After 7 d of low-temperature meat, urinary TBA-MDA equivalents increased to 23.1 +/- 1.4 mumol/d. Urinary TBA-MDA equivalents were consistently lower (6.9-8.0 mumol/d) 1, 2, 3, and 7 d after subjects changed to high-temperature meat. After 7 d of treatment, 97% of the MDA-equivalents in the meat was recovered in 24-h urine samples. The low temperature meat had 3-4 times more MDA than did the high-temperature meat. These data indicate that the amount of meat eaten and the cooking procedures used can dramatically alter urinary MDA. Dietary sources of MDA must be controlled if urinary MDA is to be used as an indicator of oxidative stress.

Structure of polymerizable lipid bilayers VII: lateral organization of diacetylenic phosphatidylcholines with short proximal acyl chains.

As an extension of recent results (Rhodes, Xu and Bittman (1992) Biochim. Biophys. Acta 1128, 93; Hui, Xu and Bittman (1992) Langmuir 8, 2724) with a C18 diacetylenic phosphatidylcholine, bilayers of 1,2-bis(pentacosa-4,6-diynoyl)-sn-glycero-3-phosphocholine (C25) were investigated using X-ray diffraction on multibilayers and electron diffraction on Langmuir-Blodgett deposited bilayers. Monolayers of this lipid form solid (gel phase) domains at pi > 14 mN/m. Electron diffraction data indicated that the chain spacing in these domains is 4.25 A and that the chains are tilted at angle of approximately 35 degrees relative to the bilayer plane. Wide angle data from X-ray diffraction experiments indicated a similar spacing and chain tilt. Small angle data showed that the lamellar repeat was 70 A at high humidity and < or = 60 A at low humidity. The bilayer electron density profiles indicated a bilayer structure with no interdigitation. High angle reflections indicate that the principal acyl chain repeat is preserved as a function of hydration but some rearrangement occurs for other reflections. The approximately 10 A reflection corresponding to the headgroup spacing previously observed with C18-diacetylenic phosphatidylcholine bilayers was not observed. The results are interpreted in terms of a packing model and possible limitations or constraints to the polymerization process.

Equilibrium and kinetic studies of the interactions of salmeterol with membrane bilayers.

The interaction of salmeterol with model membranes has been studied with regard to equilibrium and kinetic behavior, including determination of the membrane-based partition coefficient, the rate of dissociation of salmeterol from membranes, and the rate of association. These data were obtained in various membrane preparations and under various conditions (e.g., temperature, cholesterol content). The compound is very lipophilic, compared with other beta 2 agonists such as salbutamol, and has a rapid association rate and a moderate dissociation rate. The equilibrium data support the assertion that the salmeterol action measured in perfused tissue involves an exo-site for nonspecific binding that may be identified with or related to the lipid bilayer. The kinetic data in unilamellar and multilamellar liposomes of synthetic lipids further suggest that the approach to the exo-site and the active site may involve components in the native system other than the lipid bilayer in which the beta 2 receptor is located. These additional components may explain the slow onset and the extraordinarily long duration of action.

Structure of polymerizable lipid bilayers. V. Synthesis, bilayer structure and properties of diacetylenic ether and ester lipids.

Four diacetylenic phosphatidylcholines (PC's) have been synthesized and the structures of bilayers of these lipids have been determined at low resolution by low-angle X-ray diffraction. The PC's all have 18-carbon chains but differ with respect to the ether/ester linkage at the sn-1 and sn-2 positions and the relative position of the diacetylene moiety: diester-PC (1): 1,2-bis(octadeca-4',6'-diynoyl)-sn-glycero-3-phosphocholine diester-PC (2): 1-(octadeca-4',6'-diynoyl)-2-(octadeca-5',7'-diynoy l)-sn- glycero-3-phosphocholine diester-PC (3): 1,2-bis(octadeca-8',10'-diynoyl)-sn-glycerol-3-phosphocholin e diether-PC (4): 1-O-(octadeca-4',6'-diynyl)-2-O-(octadeca-5",7"-din yl)-sn- glycero-3-phosphocholine Only (1) exhibits the typical bilayer profile, whereas (2), (3) and (4) show evidence of interdigitation and/or significant disorder. Only (1) polymerized effectively upon illumination with 254 nm light, turning deep blue in seconds, indicating the formation of long, well-ordered polydiacetylenic structures. Liposomes of these derivatives were tested for permeability by osmotic swelling. Polymerized liposomes of (1) underwent osmotic swelling with urea, glycerol, and acetamide more rapidly than did liposomes of stearoyl-oleoyl-PC, but the initial rates of osmotic swelling of polymerized liposomes of (1) were 3-10-times lower than those of unpolymerized liposomes of (1). Blue polymerized multilayer samples of (1) exhibited an irreversible thermochromic transition to red at approx. 40 degrees C. Differential scanning calorimetry with liposome suspensions of (1) revealed an endotherm at 28.3 degrees C with a transition enthalpy of 40 J/g. PC (1) is a potentially useful diacetylenic lipid which exhibits facile, complete polymerization and a bilayer thickness comparable to that of biomembrane lipids.

Structure of polymerizable lipid bilayers IV. Mixtures of long chain diacetylenic and short chain saturated phosphatidylcholines and analogous asymmetric isomers.

Polymerization of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) is enhanced by addition of short-chain saturated phosphatidylcholines such as 1,2-dinonanoyl-sn-glycero-3- phosphocholine (DNPC). Because of well established constraints on the topochemical polymerisation process, we undertook structure-based experiments to determine the nature of this effect. Two hypotheses were tested: (a) that the DNPC crystalized the proximal (m) and disordered the distal (n) methylene segments of DC8,9PC, thus providing flexibility to accommodate the conformational change upon polymer formation, or (b) that the DNPC forced lateral displacement of DC8,9PC, which would then allow interdigitation of these segments with those of the opposing monolayer and potentially more crystalline alignment of the diacetylene. Low angle X-ray diffraction studies do not support the interdigiated chain model. However, these measurements also indicate that the two lipid species may be phase separated under many conditions. An analogous structure, 1-(tricosa-10,12-diynoyl)2-nonanoyl-sn-glycero-3- phosphocholine (C8,9NPC) did not polymerize, and low angle X-ray diffraction studies indicate that bilayers of this lipid were interdigitated such that the terminal methyl group of the tricosadiynoyl chain on each lipid in the bilayer was adjacent to the diacetylenic moiety of a lipid on the opposing monolayer. Implications of these findings pertinent to identifying significant factors in polymerization of diacetylenic phospholipid bilayers are discussed.

New approaches to drug design and delivery based on drug-membrane interactions.

In this review, the complex physical and chemical interactions of drugs with model and biological membranes under normal and pathological conditions are examined at the molecular level. The results of our own published and unpublished structural studies are discussed and correlated with kinetic binding studies to assess the potential role of nonspecific drug interaction with the membrane bilayer in the overall receptor binding mechanism for membrane-bound receptors in heart and brain.