Fast and automatic periacetabular osteotomy fragment pose estimation using intraoperatively implanted fiducials and single-view fluoroscopy

Accurate and consistent mental interpretation of fluoroscopy to determine the position and orientation of acetabular bone fragments in 3D space is difficult. We propose a computer assisted approach that uses a single fluoroscopic view and quickly reports the pose of an acetabular fragment without any user input or initialization. Intraoperatively, but prior to any osteotomies, two constellations of metallic ball-bearings (BBs) are injected into the wing of a patient's ilium and lateral superior pubic ramus. One constellation is located on the expected acetabular fragment, and the other is located on the remaining, larger, pelvis fragment. The 3D locations of each BB are reconstructed using three fluoroscopic views and 2D/3D registrations to a preoperative CT scan of the pelvis. The relative pose of the fragment is established by estimating the movement of the two BB constellations using a single fluoroscopic view taken after osteotomy and fragment relocation. BB detection and inter-view correspondences are automatically computed throughout the processing pipeline. The proposed method was evaluated on a multitude of fluoroscopic images collected from six cadaveric surgeries performed bilaterally on three specimens. Mean fragment rotation error was 2.4 ± 1.0 degrees, mean translation error was 2.1 ± 0.6 mm, and mean 3D lateral center edge angle error was 1.0 ± 0.5 degrees. The average runtime of the single-view pose estimation was 0.7 ± 0.2 s. The proposed method demonstrates accuracy similar to other state of the art systems which require optical tracking systems or multiple-view 2D/3D registrations with manual input. The errors reported on fragment poses and lateral center edge angles are within the margins required for accurate intraoperative evaluation of femoral head coverage.

From hepatitis C virus infection to B-cell lymphoma

In addition to liver disorders, hepatitis C virus (HCV) is also associated with extrahepatic immune manifestations and B-cell non-Hodgkin lymphoma (NHL), especially marginal zone lymphoma, de novo or transformed diffuse large B-cell lymphoma and to a lesser extent, follicular lymphoma. Epidemiological data and clinical observations argue for an association between HCV and lymphoproliferative disorders. The causative role of HCV in NHL has been further supported by the response to antiviral therapy. Pathophysiological processes at stake leading from HCV infection to overt lymphoma still need to be further elucidated. Based on reported biological studies, several mechanisms of transformation seem however to emerge. A strong body of evidence supports the hypothesis of an indirect transformation mechanism by which sustained antigenic stimulation leads from oligoclonal to monoclonal expansion and sometimes to frank lymphoma, mostly of marginal zone subtype. By infecting lymphocytes, HCV could play a direct role in cellular transformation, particularly in de novo large B-cell lymphoma. Finally, HCV is associated with follicular lymphoma in a subset of patients. In this setting, it may be hypothesized that inflammatory cytokines stimulate proliferation and transformation of IgH-BCL2 clones that are increased during chronic HCV infection. Unraveling the pathogenesis of HCV-related B-cell lymphoproliferation is of prime importance to optimize therapeutic strategies, especially with the recent development of new direct-acting antiviral drugs.

New lithium metal polymer solid state battery for an ultrahigh energy: nano C-LiFePO₄ versus nano Li1.2V₃O₈

Novel lithium metal polymer solid state batteries with nano C-LiFePO4 and nano Li1.2V3O8 counter-electrodes (average particle size 200 nm) were studied for the first time by in situ SEM and impedance during cycling. The kinetics of Li-motion during cycling is analyzed self-consistently together with the electrochemical properties. We show that the cycling life of the nano Li1.2V3O8 is limited by the dissolution of the vanadium in the electrolyte, which explains the choice of nano C-LiFePO4 (1300 cycles at 100% DOD): with this olivine, no dissolution is observed. In combination with lithium metal, at high loading and with a stable SEI an ultrahigh energy density battery was thus newly developed in our laboratory.

Bioactive compounds in human milk and intestinal health and maturity in preterm newborn: an overview

Premature births are increasing worldwide (about 15 millions per year) due to several reasons (an advanced maternal age, fertility treatments, stress, smoking, nutritional deficiencies) and lead to a high societal overall cost. Among neonatal care procedures, the clinical nutrition practices are essential to promote the development and to minimize the sequelae. Premature newborns are at major risk of death by infections due to the immaturity of their intestine. Human milk provides not only nutrients but also a plethora of biologically active components that are tailored to contribute to the development of the intestinal tract early in postnatal life. Among them, some bioactive molecules exhibit trophic effects (LC—PUFA, sphingomyelin, IGF—I and IGF—II, EGF, insulin, leptin, adiponectin, lactoferrin, lactadherin, probiotics, prebiotics, miRNA) or are part of the intestinal cell membranes (PUFA, LC—PUFA, phospholipids, sphingolipids, cholesterol), others educate the intestine for innate microbial recognition (sCD14, sTLR—2, miRNA), many of them display direct fighting against pathogens (some fatty acids and monoglycerides, some phospholipids and sphingolipids, BSSL, insulin, lactoferrin, sIgAs, MUC—1, lactadherin, probiotics, prebiotics), or contribute to establish the gut microbiota (LC—PUFA, lactoferrin, probiotics, prebiotics). A synergetic action exists between several bioactive molecules. All together these precious agents regulate the maturation of the intestinal mucosal barrier, and might program early in postnatal life the future adult intestinal health. This review lists the main bioactive compounds and addresses their plausible roles and mechanisms of action.

ω6/ω3 Polyunsaturated fatty acid supplementations in renal cell model lead to a particular regulation through lipidome for preserved ω6/ω3 ratios

Polyunsaturated fatty acids (PUFA) supplementations modify cell lipid composition leading to a change in cell function. However, the effect of PUFA supplementations in renal model cell on the kidney epithelial cells membrane fatty acid profile is not known. Therefore, the purpose of this study was to determine the effects of PUFAs with different ω6/ω3 ratios supplementations in the kidney epithelial cells and the type of supplementation that can be used as cellular protection during kidney transplantation. For that, we used as model the LLCPK1 cell and determined their membrane fatty acid (FA) composition after supplementation with three different commercial food supplements. These supplements consist of S1: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) with ω6/ω3 ratio = 0.1, S2: DHA, EPA, linoleic acid (LA) and γ-linoleic acid (GLA) with ω6/ω3 ratio = 2.5, or S3: α-linolenic acid (ALA) and LA with ω6/ω3 ratio near 1. Cells were incubated for 24 hr with 30 μM of ω3 fatty acids from each supplement. Fatty acid composition of control and experimental groups was analysed by gas chromatography after extraction of lipids and fatty acids methylation. The efficiency of cell PUFA supplementation was achieved by showing 2 to 4 fold increases in cell PUFA incorporation. Whatever the supplementation used, the cell saturated fatty acids (SFA) were decreased by 50% following the three supplementations used (p<0.001) as compared to control group. These decreases in SFA were compensated in part by increasing monounsaturated fatty acid levels. All these changes were observed with constant of cell ω6/ω3 ratio whatever the supplementations used. These data suggest that the supplements, with long chain polyunsaturated fatty acids or their precursors, lead to important regulation in the lipidome (desaturases and elongases) associated to preserved ω6/ω3 ratios. The fatty acids remodeling may represent an interesting new mechanism by which renal FA homoestasis could occurred.

Novel Cathode Materials Based on Organic Couples for Lithium Batteries

The electrochemical reduction of the oxocarbons: squarate, croconate and especially rhodizonate lithium salts have been studied in all solid state lithium batteries. Lithium rhodizonate cells were tested on cycling in the 1.5 – 3.5 V potential range The reduction of lithium rhodizonate occurs in two waves of two electrons. The number of electrons transferred in reduction on the first cycle was around 3.5 based on a capacity of 515 mA.h.g−1 and a discharge depth of 87 %. This process is quite reversible but we observed a fast decline of the capacity on cycling. This loss of capacity may be attributed to residual water in the salt. The reduction of the lithium croconate occurs at a potential of 1.8 V in a quasi-irreversible process. We could not observe the reduction of lithium squarate which occurs in the potential range where the lithium is inserted in carbon black. We also report an investigation on rhodizonate salts of transition metals. The best results, in term of capacity, on the 1.5 – 3.5 V potential range, were obtained with copper rhodizonate which exhibits a capacity of 579 mA.h.g−1 on the first discharge.

Understanding the Electro-thermal and Phase-transformation Processes in Phase-change Materials for Data Storage Applications

Attempts at the practical utilization of Sb-Te based alloys beyond optical data storage have been made recently by employing these materials in both scanning probe type memories, and in electrical memory devices - namely Phase-Change Random Access Memory (PC-RAM). We have developed models to simulate the electrical, thermal, and phase-change characteristics of this important class of material. In this paper we describe the physical basis of our models and present simulation results for different memory configurations and operating conditions.

A 3.6 V lithium-based fluorosulphate insertion positive electrode for lithium-ion batteries

Li-ion batteries have contributed to the commercial success of portable electronics, and are now in a position to influence higher-volume applications such as plug-in hybrid electric vehicles. Most commercial Li-ion batteries use positive electrodes based on lithium cobalt oxides. Despite showing a lower voltage than cobalt-based systems (3.45 V versus 4 V) and a lower energy density, LiFePO(4) has emerged as a promising contender owing to the cost sensitivity of higher-volume markets. LiFePO(4) also shows intrinsically low ionic and electronic transport, necessitating nanosizing and/or carbon coating. Clearly, there is a need for inexpensive materials with higher energy densities. Although this could in principle be achieved by introducing fluorine and by replacing phosphate groups with more electron-withdrawing sulphate groups, this avenue has remained unexplored. Herein, we synthesize and show promising electrode performance for LiFeSO(4)F. This material shows a slightly higher voltage (3.6 V versus Li) than LiFePO(4) and suppresses the need for nanosizing or carbon coating while sharing the same cost advantage. This work not only provides a positive-electrode contender to rival LiFePO(4), but also suggests that broad classes of fluoro-oxyanion materials could be discovered.

Conjugated dicarboxylate anodes for Li-ion batteries

Present Li-ion batteries for portable electronics are based on inorganic electrodes. For upcoming large-scale applications the notion of materials sustainability produced by materials made through eco-efficient processes, such as renewable organic electrodes, is crucial. We here report on two organic salts, Li(2)C(8)H(4)O(4) (Li terephthalate) and Li(2)C(6)H(4)O(4)(Li trans-trans-muconate), with carboxylate groups conjugated within the molecular core, which are respectively capable of reacting with two and one extra Li per formula unit at potentials of 0.8 and 1.4 V, giving reversible capacities of 300 and 150 mA h g(-1). The activity is maintained at 80 degrees C with polyethyleneoxide-based electrolytes. A noteworthy advantage of the Li(2)C(8)H(4)O(4) and Li(2)C(6)H(4)O(4) negative electrodes is their enhanced thermal stability over carbon electrodes in 1 M LiPF(6) ethylene carbonate-dimethyl carbonate electrolytes, which should result in safer Li-ion cells. Moreover, as bio-inspired materials, both compounds are the metabolites of aromatic hydrocarbon oxidation, and terephthalic acid is available in abundance from the recycling of polyethylene terephthalate.

On foundations of discrete element analysis of contact in diarthrodial joints

Information about the stress distribution on contact surfaces of adjacent bones is indispensable for analysis of arthritis, bone fracture and remodeling. Numerical solution of the contact problem based on the classical approaches of solid mechanics is sophisticated and time-consuming. However, the solution can be essentially simplified on the following physical grounds. The bone contact surfaces are covered with a layer of articular cartilage, which is a soft tissue as compared to the hard bone. The latter allows ignoring the bone compliance in analysis of the contact problem, i.e. rigid bones are considered to interact through a compliant cartilage. Moreover, cartilage shear stresses and strains can be ignored because of the negligible friction between contacting cartilage layers. Thus, the cartilage can be approximated by a set of unilateral compressive springs normal to the bone surface. The forces in the springs can be computed from the equilibrium equations iteratively accounting for the changing contact area. This is the essence of the discrete element analysis (DEA). Despite the success in applications of DEA to various bone contact problems, its classical formulation required experimental validation because the springs approximating the cartilage were assumed linear while the real articular cartilage exhibited non-linear mechanical response in reported tests. Recent experimental results of Ateshian and his co-workers allow for revisiting the classical DEA formulation and establishing the limits of its applicability. In the present work, it is shown that the linear spring model is remarkably valid within a wide range of large deformations of the cartilage. It is also shown how to extend the classical DEA to the case of strong nonlinearity if necessary.

Physicochemical properties of lipids: new strategies to manage fatty acid bioavailability

Fatty acid bioavailability can be managed through the physicochemical properties of lipid such as lipid-droplet size, lipid-droplet ultrastructure (lipids organization between core and surface), structure of triglycerides and of phospholipids. The lipid-droplet size exhibits a major effect on lipase activity during lipid digestion. The lipid-droplet ultrastructure is a dynamic factor controling lipase interaction at the lipid interface via the surface phospholipid layer, and also lipase activity via the proportion of triglyceride molecules able to locate at the surface. Triglyceride structure affects in a strong manner digestion, absorption and fatty acid metabolism. Finally, optimal fatty acid transport to specific tissues is dependent on the vehicle molecule (triglyceride or ethyl ester or phospholipid). All these aspects provide convincing support for the possibility of using biotechnologically remodeled lipids with specific physicochemical properties for health benefits.

Gastric proteolysis in preterm infants fed mother's milk or formula

Gastric proteolysis is assumed to be low in the newborn (Britton & Koldovsky 1989). Postprandial pepsin output is significantly lower in preterm infants than adults, 589 vs. 3352U/kg, respectively (Armand et al. 1995, 1996). We now report on gastric proteolysis in preterm infants (gestation age, 29 weeks; postnatal age, 5-6 weeks) gavage-fed mother's milk or preemie formula. The data show that a) the nonprotein component is higher in human milk than formula, b) net proteolysis amounts to 15% of protein, c) gastric proteolysis is lower than lipolysis and, contrary to the latter, is not enhanced by milk feeding (Armand et al. 1996). We suggest that stomach pH, enzyme output, and food structure are the reasons for differences in gastric digestion of protein and fat in infants.

Issues and challenges facing rechargeable lithium batteries

Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges that remain regarding the synthesis, characterization, electrochemical performance and safety of these systems.

Relationship between time- and frequency-domain analyses of angular head movements in the squirrel monkey

We used the three-dimensional magnetic search-coil recording technique to study the range of active angular head movements made by squirrel monkeys. There were two goals in this study: (1) to determine the range of angular velocities and accelerations as well as the bandwidth and other frequency characteristics of active head movements and (2) to compare analyses of transients of velocity and acceleration that are studied by residual analysis, Fourier transform, and wavelet transform of the head velocity signal. The residual analysis showed that the shape and duration of the transients affected the bandwidth. During the time after the head had begun to accelerate, the frequency content of the head movement extended into the range of 6 to 12 Hz. When considering all three planes of rotation, approximately 75% of the transients had peak acceleration between 2,000 and 10,000 deg/s(2) and a peak velocity of 50 to 400 deg/s. A peak acceleration of >10,000 deg/s(2) was recorded in 10% of the transients. These findings indicate that active head movements in squirrel monkeys cover a higher range of frequencies, accelerations, and velocities than have typically been used in previous eye-movement and neuronal studies of the reflexes that control gaze. We further conclude that the choice of a method for analyzing transient, time-varying biological signals is dependent on the desired information. Residual analysis provides detailed resolution in the time domain, but estimation of the frequency content of the signal is dependent on the portions selected for analysis and the choice of filters. Fourier transform provides a representation of the power spectrum in the frequency domain but without any inherent temporal resolution. We show that the wavelet transform, a novel method as applied to the signal analysis goals of this study, is the most useful technique for relating time- and frequency-domain information during a continuous signal.

Processing of vitamin A and E in the human gastrointestinal tract

We aimed to provide basic data on the processing of vitamin A and E in the human gastrointestinal tract and to assess whether the size of emulsion fat globules affects the bioavailability of these vitamins. Eight healthy men received intragastrically two lipid formulas differing in their fat-globule median diameter (0.7 vs. 10. 1 microm. Formulas provided 28 mg vitamin A as retinyl palmitate and 440 mg vitamin E as all-rac alpha-tocopherol. Vitamins were measured in gastric and duodenal aspirates, as well as in chylomicrons, during the postprandial period. The gastric emptying rate of lipids and vitamin A and E was similar. The free retinol/total vitamin A ratio was not significantly modified in the stomach, whereas it was dramatically increased in the duodenum. The proportion of ingested lipid and vitamins was very similar in the duodenal content. The chylomicron response of lipids and vitamins was not significantly different between the two emulsions. Our main conclusions are as follows: 1) there is no significant metabolism of vitamin A and E in the human stomach, 2) the enzyme(s) present in the duodenal lumen is significantly involved in the hydrolysis of retinyl esters, and 3) the size of emulsion fat globules has no major effect on the overall absorption of vitamin A and E.

Green tea extract (AR25®) inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro

In this study, we aimed to evaluate in vitro the inhibitory activity of a green tea extract (AR25 standardized at 25% catechins) on gastric and pancreatic lipase activities. We first used tributyrin as a substrate to evaluate the capability of AR25 to induce digestive lipase inhibition. Gastric lipase was totally inhibited by 40 mg AR25/g tributyrin whereas pancreatic lipase inhibition was maximum (78.8 +/- 0.7%) with 80 mg AR25/g tributyrin. We then used triolein, a long-chain triglyceride, to check whether AR25 could alter lipase activities on a physiologic substrate. AR25 60 mg/g triolein induced a dramatic inhibition of gastric lipase (96.8 +/- 0.4%) whereas pancreatic lipase activity was partially reduced (66.50 +/- 0.92%). Finally, the concerted action of gastric and pancreatic lipases was studied with an excess of enzymes to mimic the physiologic conditions observed in vivo. Incubation of AR25 with an excess of digestive lipases resulted in a drastic decrease in gastric lipolysis but the inhibitory effect on pancreatic lipase was less marked. On the whole, as compared to the control, lipolysis of triolein under the successive action of the two digestive lipases was reduced by 37 +/- 0.6% in the presence of AR25. Because a lipid/water interface is necessary for lipolysis to occur, lipid emulsification and emulsion droplet size were measured in gastric and duodenal media in the presence of AR25. In gastric and duodenal conditions, AR25 inhibited the lipid emulsification process. From these data we conclude that (1) in vitro, fat digestion is significantly inhibited by 60 mg AR25/g triolein, and (2) gastric as well as pancreatic lipase inhibition could be related to altered lipid emulsification in gastric or duodenal media. The green tea extract AR25 exhibiting marked inhibition of digestive lipases in vitro is likely to reduce fat digestion in humans.

Digestion and absorption of 2 fat emulsions with different droplet sizes in the human digestive tract

BACKGROUND

The extent of fat emulsification affects the activity of digestive lipases in vitro and may govern digestion and absorption of dietary fat.

OBJECTIVE

We investigated the effect of the fat globule size of 2 enteral emulsions on fat digestion and assimilation in humans.

DESIGN

Healthy subjects received intragastrically a coarse (10 microm) and a fine (0.7 microm) lipid emulsion of identical composition in random order. Gastric and duodenal aspirates were collected throughout digestion to measure changes in fat droplet size, gastric and pancreatic lipase activities, and fat digestion. Blood lipids were measured postprandially for fat assimilation.

RESULTS

Despite an increase in droplet size in the stomach (2.75-6.20 microm), the fine emulsion retained droplets of smaller size and its lipolysis was greater than that of the coarse emulsion (36.5% compared with 15.8%; P < 0.05). In the duodenum, lipolysis of the fine emulsion was on the whole higher (73.3% compared with 46.3%). The overall 0-7-h plasma and chylomicron responses given by the areas under the curve were not significantly different between the emulsions, but the triacylglycerol peak was delayed with the fine emulsion (3 h 56 min compared with 2 h 50 min).

CONCLUSIONS

Fat emulsions behave differently in the digestive tract depending on their initial physicochemical properties. A lower initial fat droplet size facilitates fat digestion by gastric lipase in the stomach and duodenal lipolysis. Overall fat assimilation in healthy subjects is not affected by differences in initial droplet size because of efficient fat digestion by pancreatic lipase in the small intestine. Nevertheless, these new observations could be of interest in the enteral nutrition of subjects suffering from pancreatic insufficiency.

Protective function of human milk: the milk fat globule

Human milk contains many components that protect the newborn against infection at a time when the infant's own defense mechanisms are poorly developed. Fat is one of the major nutrients in human milk. The fat is contained within milk fat globules composed of a core of triglyceride and a membrane consisting of phospholipids, cholesterol, proteins, and glycoproteins. Both the membrane and the core components can provide protection against microorganisms. The major protective membrane glycoproteins, mucin, and lactadherin are resistant to conditions in the newborn's stomach and maintain their structure and function even at low pH and in the presence of the proteolytic enzyme pepsin. The core triglycerides upon hydrolysis by digestive lipases (especially gastric lipase, which is well developed in the newborn) produce free fatty acids and monoglycerides, amphiphylic substances able to lyse enveloped viruses, bacteria, and protozoa. Therefore, in addition to its nutritional value, the fat in human milk has a major protective function.

Milk fat globule glycoproteins in human milk and in gastric aspirates of mother's milk-fed preterm infants

Human milk fat globule (HMFG) glycoproteins can prevent infections by microorganisms in breast-fed infants; the MUC-1 mucin inhibits binding of S-fimbriated Escherichia coli to buccal mucosa, and lactadherin may prevent symptomatic rotavirus infections. In this study, the survival of these HMFG glycoproteins in the stomach of human milk-fed preterm infants (gestational age = 27.5 +/- 0.4 wk) was assessed, and levels in their mothers' milk determined, using specific RIAs. Butyrophilin, a major component of HMFG membrane that has no demonstrated antimicrobial activity, was studied for comparison. The levels of mucin, lactadherin, and butyrophilin in 41 milk samples of 20 mothers were 729 +/- 75, 93 +/- 10, and 41 +/- 3 microg/mL, respectively. Mucin and lactadherin were significantly higher in early milk samples (<15 d postpartum) than in later milk samples (15-90 d postpartum), whereas butyrophilin showed no such difference. Significant amounts of mucin and lactadherin were found in almost all gastric aspirates of human milk-fed infants, even 4 h after feeding (mucin, 270 +/- 30 microg/mL; lactadherin, 23.2 +/- 4.4 microg/mL), whereas butyrophilin was rapidly degraded in the majority of aspirates. Western blot analysis demonstrated that the immunoreactive mucin, lactadherin, and butyrophilin in the milk-fed gastric aspirates had the expected native molecular weights. Mucin and lactadherin survived at all gastric pH values, whereas butyrophilin was found only at pH > 4. Neither lactadherin nor butyrophilin were detected in gastric aspirates of formula-fed infants (gestational age = 27.8 +/- 0.5 wk), whereas the very low level of mucin (9.1 +/- 1.1 microg/mL) in this group is presumably cross-reacting gastric mucin. These results demonstrate that two HMFG glycoproteins implicated in prevention of infection, MUC-1 mucin and lactadherin, survive and maintain their integrity in the stomachs of human milk-fed preterm infants.

Stepping over obstacles during locomotion: insights from multiobjective optimization on set of input parameters

In this study we investigate possible objectives that the central nervous system (CNS) may consider in planning a strategy for stepping over an obstacle. A link segment simulation model has been developed based on Lagrangian dynamics, with which muscle force inputs can be optimized to best satisfy the postulated objectives for landing stability, obstacle clearance, and efficiency of the movement. A direct optimization approach with multiobjective criteria based on the kinematic and kinetic characteristics of the swing phase of locomotion is used in the simulation. The role of initial conditions at toe-off and biarticular muscle forces during the swing phase was also investigated. The optimization was performed for both leading limb and the trailing limb during the swing phase. The simulation results demonstrate that the use of biarticular muscles is sufficient to clear a range of obstacles with the trailing limb (obstacle encountered during early swing). Stride length or landing stability objectives need not be specified suggesting a simpler control of trailing limb trajectory by the CNS (one of stride length or landing stability objectives were not necessary). In contrast while the use of biarticular muscles can be sufficient to clear obstacles with the leading limb (obstacle encountered during mid to late swing), a stable landing and smooth toe and knee trajectories are compromised without suitable initial conditions at toe-off. The results suggest that the set of postulated objectives for the lead limb is adequate, although not complete.

Effects of graded amounts (0-50 g) of dietary fat on postprandial lipemia and lipoproteins in normolipidemic adults

Eight normolipidemic males ingested on separate days and in a random order five mixed meals containing 0, 15, 30, 40, or 50 g fat. Fasting and postprandial blood samples were obtained for 7 h and chylomicrons and lipoproteins were isolated. The nonfat and 15-g fat meals did not generate noticeable postprandial variations except for HDL phospholipids (P < 0.05). The serum and chylomicron triacylglycerol responses obtained after the meals correlated positively with the amount of fat ingested and peaked after 2-3 h. Serum free cholesterol and phospholipids increased and esterified cholesterol decreased postprandially in a dose-response manner. At the same time, triacylglycerol-rich-lipoprotein triacylglycerols, esterified cholesterol, LDL free cholesterol, HDL triacylglycerols, phospholipids, and free cholesterol increased whereas LDL and HDL esterified cholesterol decreased when the amount of ingested fat increased. The data showed that increasing the amount of fat in the usual range of ingestion (0-50 g) led to stepwise increases in the postprandial rise of chylomicron and serum triacylglycerols and induced marked changes in serum lipoproteins postprandially. The existence of a no-effect level of dietary fat (15 g) on postprandial lipemia and lipoproteins in healthy adults was shown.

Postprandial chylomicron and plasma vitamin E responses in healthy older subjects compared with younger ones

The effect of ageing on vitamin E bioavailability in humans was assessed by comparing chylomicron and plasma alpha-tocopherol postprandial concentrations after a dose of vitamin E (432 or 937 IU as d1-alpha-tocopherol acetate), in eight young (20-30 years old) and eight healthy elderly men (64-72 years old). The fasting plasma alpha-tocopherol concentration was significantly higher in the elderly (33 +/- 2 mumol L-1) than in the young (22 +/- 2 mumol L-1). In both groups, the plasma and chylomicron alpha-tocopherol postprandial concentrations were significantly, approximately twofold, higher after the 937-IU meal than after the 432-IU meal. For both test meals, the chylomicron alpha-tocopherol areas under the curve were significantly lower in the elderly than in the young subjects: 98.9 +/- 16.5 (young group) vs. 55.3 +/- 7.8 (elderly group) mumol L-1 h for the 937-IU test meal and 60.4 +/- 14.1 (young group) vs. 26.0 +/- 7.6 (elderly group) mumol L-1 h for the 432-IU test meal, whereas the plasma alpha-tocopherol area under the curve was significantly higher in elderly than in young subjects: 337.56 +/- 16.11 (937-IU test meal) vs. 159.81 +/- 35.55 (432-IU test meal) mumol L-1 h in the young group and 709.55 +/- 69.33 (937-IU test meal) vs. 436.39 +/- 41.08 (432-IU test meal) mumol L-1 h in the elderly group. We concluded that (a) the amount of vitamin E appearing in plasma is proportional to the dose ingested (up to 937 IU); (b) the intestinal absorption of vitamin E is not increased, even possibly decreased, in the elderly; and (c) the amount of vitamin E transported by non-chylomicron lipoproteins is apparently higher in the elderly. This suggests that vitamin E postprandial transport is affected by ageing, mainly as the consequence of age-related modifications of lipoprotein metabolism.

Effect of human milk or formula on gastric function and fat digestion in the premature infant

The effect of diet, human milk or formula, on gastric function (lipase and pepsin activity, pH, and volume) and intragastric digestion of fat was assessed in 28 appropriate for gestational age preterm infants (gestational age, 28.9 +/- 1.4, 29.1 +/- 0.9, 29.5 +/- 0.6 wk; birth weight, 1.00 +/- 0.14 to 1.18 +/- 0.07 kg). The infants were fed either human milk (n = 11), SMA Super Preemie formula (n = 9), or Similac, Special Care formula (n = 8). Fasting and postprandial activity of digestive enzymes, pH, and gastric volume (measured before or during 50 min after gavage feeding) did not differ as a function of diet among the three groups of infants. Gastric lipase output, 23.1 +/- 5.1, 28.3 +/- 6.6, and 22.5 +/- 6.4 (U/kg of body weight) in human milk-, SMA SP-, or Similac SC-fed infants was comparable to the gastric lipase output of healthy adults fed a high fat diet (22.6 +/- 3.0). Pepsin output was, however, significantly lower (597 +/- 77, 743 +/- 97, and 639 +/- 142 U/kg of body weight) in human milk-, SMA SP-, and Similac SC-fed infants) than in healthy adults (3352 +/- 753 U/kg). The hydrolysis of dietary fat was 1.7-2.5-fold higher (p < 0.01) in human milk-fed infants than in infants fed either formula. We conclude that differences in type of feeding, i.e. different fatty acid profiles (long chain or medium chain triglycerides), different emulsions (natural or artificial), and different fat particle sizes do not affect the level of activity of gastric enzymes. However, the triglyceride within milk fat globules appears to be more accessible to gastric lipase than that within formula fat particles. We suggest that the contribution of gastric lipase to overall fat digestion might be greater in the newborn (a period of pancreatic insufficiency) than in the adult.

Postprandial appearance of dietary deuterated cholesterol in the chylomicron fraction and whole plasma in healthy subjects

This study examined the appearance of dietary cholesterol in the chylomicron fraction (chylomicrons plus chylomicron remnants) and whole plasma in healthy normolipidemic subjects during a 0-7-h postprandial period. Six adult males were given two diet sequences in random order: a low-fiber diet (standard Western diet for 14 d) followed by a labeled low-fiber test meal or a fiber-supplemented diet (40 g oat bran/d for 14 d) followed by a labeled oat bran (40 g) test meal. The test meals provided 192.5 mg cholesterol, including 80.1 mg octadeuterated cholesterol. Fasting and hourly postmeal blood samples were obtained for 7 h. Isotopic cholesterol ratios [tracer:(tracer+native cholesterol)] were determined by gas chromatography-mass spectrometry. Chylomicron triacylglycerol and cholesterol concentrations peaked after 2-3 h and returned to baseline after 7 h. After the low-fiber test meal, the isotopic cholesterol ratio continuously increased until 7 h in the chylomicron fraction (4.2 +/- 1.2 x 10(-3)) and whole plasma (1.04 +/- 0.39 x 10(-3)). At 7 h postprandial, the maximum dietary cholesterol concentration in the chylomicron fraction and plasma cholesterol was 1 in 99 and 1 in 397 cholesterol molecules, respectively. No marked differences were obtained after the high-fiber sequence compared with the low-fiber one; there was a comparable isotopic cholesterol ratio and concentration in the chylomicron fraction and a slightly lower (-44%, P < 0.10) 0-7 h area under the curve whole-plasma deuterated cholesterol concentration. Thus, dietary cholesterol supplied as a single meal does not simultaneously appear in the chylomicron fraction postprandially with endogenous cholesterol and triacylglycerols and fiber feeding does not markedly alter this process in healthy normolipidemic humans.