Concentration Of Large Particles Research Articles

Use of plasma metabolomics to analyze phenotype-genotype relationships in young hypercholesterolemic females

Hypercholesterolemia is characterized by high plasma LDL cholesterol and often caused by genetic mutations in LDL receptor (LDLR), APOB, or proprotein convertase subtilisin/kexin type 9 (PCSK9). However, a substantial proportion of hypercholesterolemic subjects do not have any mutations in these canonical genes, leaving the underlying pathobiology to be determined. In this study, we investigated to determine whether combining plasma metabolomics with genetic information increases insight in the biology of hypercholesterolemia. For this proof of concept study, we combined plasma metabolites from 119 hypercholesterolemic females with genetic information on the LDL canonical genes. Using hierarchical clustering, we identified four subtypes of hypercholesterolemia, which could be distinguished along two axes represented by triglyceride and large LDL particle concentration. Subjects with mutations in LDLR or APOB preferentially clustered together, suggesting that patients with defects in the LDLR pathway show a distinctive metabolomics profile. In conclusion, we show the potential of using metabolomics to segregate hypercholesterolemic subjects into different clusters, which may help in targeting genetic analysis.

Paradox of hypercholesterolaemia in highly trained, keto-adapted athletes

ObjectiveA growing number of ultra-endurance athletes have switched to a very low-carbohydrate/high-fat eating pattern. We compared markers of cholesterol and the lipoprotein profile in a group of elite ultra-runners consuming...

High-Density Lipoprotein Particles, Cell-Cholesterol Efflux, and Coronary Heart Disease Risk.

Objective- The cell-cholesterol efflux capacity of HDL (high-density lipoprotein) is inversely associated with coronary heart disease risk. ABCA1 (ATP-binding cassette transporter A1) plays a crucial role in cholesterol efflux from macrophages to preβ-1-HDL. We tested the hypothesis that coronary heart disease patients have functionally abnormal preβ-1-HDL. Approach and Results- HDL cell-cholesterol efflux capacity via the ABCA1 and the SR-BI (scavenger receptor class B type I) pathways, HDL antioxidative capacity, apo (apolipoprotein) A-I-containing HDL particles, and inflammatory- and oxidative-stress markers were measured in a case-control study of 100 coronary heart disease cases and 100 sex-matched controls. There were significant positive correlations between ABCA1-dependent cholesterol efflux and the levels of small lipid-poor preβ-1 particles ( R2=0.535) and between SR-BI-dependent cholesterol efflux and the levels of large lipid-rich (α-1+α-2) HDL particles ( R2=0.712). Cases had significantly higher (87%) preβ-1 concentrations than controls, but the functionality of their preβ-1 particles (preβ-1 concentration normalized ABCA1-dependent efflux capacity) was significantly lower (-31%). Cases had significantly lower (-12%) mean concentration of large HDL particles, but the functionality of their particles (α-1+α-2 concentration normalized SR-BI-dependent efflux capacity) was significantly higher (22%) compared with that of controls. HDL antioxidative capacity was significantly lower (-16%) in cases than in controls. There were no significant correlations between either preβ-1 functionality or large HDL particle functionality with HDL antioxidative capacity or the concentrations of inflammatory- and oxidative-stress markers. Conclusions- HDL cell-cholesterol efflux capacity is significantly influenced by both the concentration and the functionality of specific HDL particles participating in cell-cholesterol efflux. Coronary heart disease patients have higher than normal preβ-1 concentrations with decreased functionality and lower than normal large HDL particle concentrations with enhanced functionality.

Characterization of submicron aerosols and CCN over the Yellow Sea measured onboard the Gisang 1 research vessel using the positive matrix factorization analysis method

Aerosol size distributions and cloud condensation nuclei (CCN) number concentrations were measured in spring 2017 over the Yellow Sea on board the research vessel Gisang 1. The average number concentration of particles larger than 10 nm and CCN at 0.65% supersaturation (S) were 7622 ± 4038 cm−3 and 4821 ± 1763 cm−3, respectively. Characteristics of aerosol size distribution data were analyzed using a positive matrix factorization (PMF) method. It was found that only 6 Factors could explain the aerosol size distribution reasonably well. Factors 1 and 2 indicated nucleation mode particles, Factor 3 indicated Aitken mode particles, and Factors 4, 5, and 6 indicated accumulation mode particles. The concentrations of nucleation and Aitken mode particles showed a clear wind direction dependence; high under westerly winds due to the high concentrations of particles and precursor gases in eastern China. Meanwhile, the concentration of larger particles and CCN showed no significant wind direction dependence. Aerosol size distribution was also significantly influenced by meteorology. Small particles were predominant during clear days. In contrast during mist or fog days, the aerosol size distribution shifted to larger sizes. A CCN closure experiment was conducted using results of the PMF analysis. The assumption of internally mixed particles led to overestimation of predicted CCN concentrations but agreement was significantly better when externally mixed particles were considered. The logarithmic curve fit of NCCN(S) = 4825 ∗ log S + 4933 was found to very well explain measured CCN concentrations at a few S over the Yellow Sea, and therefore is recommended as input CCN spectral data for numerical models that explicitly treat CCN activation.

The kinematics of bidisperse granular roll waves

Small perturbations to a steady uniform granular chute flow can grow as the material moves downslope and develop into a series of surface waves that travel faster than the bulk flow. This roll wave instability has important implications for the mitigation of hazards due to geophysical mass flows, such as snow avalanches, debris flows and landslides, because the resulting waves tend to merge and become much deeper and more destructive than the uniform flow from which they form. Natural flows are usually highly polydisperse and their dynamics is significantly complicated by the particle size segregation that occurs within them. This study investigates the kinematics of such flows theoretically and through small-scale experiments that use a mixture of large and small glass spheres. It is shown that large particles, which segregate to the surface of the flow, are always concentrated near the crests of roll waves. There are different mechanisms for this depending on the relative speed of the waves, compared to the speed of particles at the free surface, as well as on the particle concentration. If all particles at the surface travel more slowly than the waves, the large particles become concentrated as the shock-like wavefronts pass them. This is due to a concertina-like effect in the frame of the moving wave, in which large particles move slowly backwards through the crest, but travel quickly in the troughs between the crests. If, instead, some particles on the surface travel more quickly than the wave and some move slower, then, at low concentrations, large particles can move towards the wave crest from both the forward and rearward sides. This results in isolated regions of large particles that are trapped at the crest of each wave, separated by regions where the flow is thinner and free of large particles. There is also a third regime arising when all surface particles travel faster than the waves, which has large particles present everywhere but with a sharp increase in their concentration towards the wave fronts. In all cases, the significantly enhanced large particle concentration at wave crests means that such flows in nature can be especially destructive and thus particularly hazardous.

Composition inversion in mixtures of binary colloids and polymer.

Understanding the phase behaviour of mixtures continues to pose challenges, even for systems that might be considered "simple." Here, we consider a very simple mixture of two colloidal and one non-adsorbing polymer species, which can be simplified even further to a size-asymmetrical binary mixture, in which the effective colloid-colloid interactions depend on the polymer concentration. We show that this basic system exhibits surprisingly rich phase behaviour. In particular, we enquire whether such a system features only a liquid-vapor phase separation (as in one-component colloid-polymer mixtures) or whether, additionally, liquid-liquid demixing of two colloidal phases can occur. Particle-resolved experiments show demixing-like behaviour, but when combined with bespoke Monte Carlo simulations, this proves illusory, and we reveal that only a single liquid-vapor transition occurs. Progressive migration of the small particles to the liquid phase as the polymer concentration increases gives rise to composition inversion-a maximum in the large particle concentration in the liquid phase. Close to criticality, the density fluctuations are found to be dominated by the larger colloids.

Abstract 176: Preoperative Small HDL Particle Concentration is Associated with Paraoxonase-1 activity and the Risk of Acute Kidney Injury After Cardiac Surgery

Acute kidney injury (AKI) after cardiac surgery occurs in up to 30% of patients and predicts death. We have reported that a higher preoperative HDL particle concentration is independently associated with a decreased risk of AKI after cardiac surgery. HDL has known anti-oxidant properties that may attenuate AKI. We hypothesized that HDL particle size is associated with paraoxonase-1 (PON-1) activity and with the risk of AKI after cardiac surgery. We selected 90 patients who developed mild, moderate, severe, or no AKI from a prospective trial of perioperative atorvastatin to prevent post-cardiac surgery AKI. PON-1 paraoxonase activity was measured in apoB-depleted serum with fluorescent substrate 7-diethylphospho-6,8-dixuor-4-methylumbelliferyl. HDL particle size was assessed using the NMR Lipoprofile test. Linear regression was used to assess the association between preoperative small, medium, and large HDL particle concentrations and PON-1 activity. We assessed the association between HDL particle levels and the maximum serum creatinine change from baseline in the first 48 postoperative hours using two-component latent variable mixture models adjusted for AKI risk factors. A higher preoperative small HDL particle concentration was associated with a higher preoperative PON-1 activity (p=0.003, Figure 1A). Medium and large HDL particle concentrations were not associated with PON-1 activity. Small HDL particle concentration was found to be independently associated with postoperative serum creatinine change (p=0.02, Figure 1B), while medium and large HDL particle concentrations were not. Conclusions: A higher preoperative small HDL particle concentration was associated with a higher PON-1 activity and a decreased risk of AKI after cardiac surgery. Future work will characterize HDL throughout the surgical course to identify the mechanism underlying the protective association between HDL and AKI.

Three-dimensional particle tracking velocimetry algorithm based on tetrahedron vote

A particle tracking velocimetry algorithm based on tetrahedron vote, which is named TV-PTV, is proposed to overcome the limited selection problem of effective algorithms for 3D flow visualisation. In this new cluster-matching algorithm, tetrahedrons produced by the Delaunay tessellation are used as the basic units for inter-frame matching, which results in a simple algorithmic structure of only two independent preset parameters. Test results obtained using the synthetic test image data from the Visualisation Society of Japan show that TV-PTV presents accuracy comparable to that of the classical algorithm based on new relaxation method (NRX). Compared with NRX, TV-PTV possesses a smaller number of loops in programming and thus a shorter computing time, especially for large particle displacements and high particle concentration. TV-PTV is confirmed practically effective using an actual 3D wake flow.

Dust Reduction Efficiency of a Single-Row Vegetative Barrier (Maclura pomifera)

Little is known about the dust removal efficiency of common vegetative barriers. This study of blowing dust reduction was conducted on one of the most common vegetative barriers used for wind erosion control in Kansas and the U.S. Great Plains, the deciduous tree species (Osage orange). A dust generator and distributor were fabricated to generate dust particles for determining the dust removal efficiency of a single-row Osage orange barrier. Simultaneous upwind and downwind dust concentrations were measured using mini-vol samplers for total suspended particulates (TSP) at heights of 1.5, 3.0, 4.5, and 6.0 m above the ground. Measurements were made using two towers located at upwind and downwind distances equal to the height of the barrier. Particle size distribution (PSD) analysis of the initial generated dust showed that most particles were large (GMD = 102.8 µm), while about 5% of the dust was particulate matter less than 2.5 µm in diameter (PM2.5) and 15% was less than 10 µm (PM10). Laser diffraction analysis of particles from the sample filters was used to determine the dust reduction efficiency of the barrier. Results showed that dust reduction was significantly related to reduction in wind speed at lower heights, causing an overall decrease in dust concentration as particles passed through the barrier. Concentrations of larger particles (~100 µm) were also reduced relative to smaller particles when dust passed through the barrier. The data also showed that 4.5 m above the ground, near the crown of the canopy, was most efficient at removing the PM2.5 (15% to 54%) and PM10 (23% to 65%) fractions of the generated dust. Keywords: Generated dust, Osage orange, PM2.5, PM10, TSP, Wind erosion.

Substantial large-scale feedbacks between natural aerosols and climate

The terrestrial biosphere is an important source of natural aerosol. Natural aerosol sources alter climate, but are also strongly controlled by climate, leading to the potential for natural aerosol–climate feedbacks. Here we use a global aerosol model to make an assessment of terrestrial natural aerosol–climate feedbacks, constrained by observations of aerosol number. We find that warmer-than-average temperatures are associated with higher-than-average number concentrations of large (>100 nm diameter) particles, particularly during the summer. This relationship is well reproduced by the model and is driven by both meteorological variability and variability in natural aerosol from biogenic and landscape fire sources. We find that the calculated extratropical annual mean aerosol radiative effect (both direct and indirect) is negatively related to the observed global temperature anomaly, and is driven by a positive relationship between temperature and the emission of natural aerosol. The extratropical aerosol–climate feedback is estimated to be −0.14 W m−2 K−1 for landscape fire aerosol, greater than the −0.03 W m−2 K−1 estimated for biogenic secondary organic aerosol. These feedbacks are comparable in magnitude to other biogeochemical feedbacks, highlighting the need for natural aerosol feedbacks to be included in climate simulations.

Residual Risk of Atherosclerotic Cardiovascular Events in Relation to Reductions in Very-Low-Density Lipoproteins.

BackgroundIt is uncertain whether pharmacological reductions in very‐low‐density lipoproteins (VLDLs), and their component triglyceride and cholesterol could reduce residual risk of atherosclerotic cardiovascular disease (ASCVD) events among individuals in whom low‐density lipoprotein cholesterol (LDL‐C) has been adequately lowered. We examined whether individuals with greater on‐statin reductions in VLDL‐related measures—beyond reductions in LDL‐C—were at further reduced risk of ASCVD.Methods and ResultsIn 9423 participants in the JUPITER (Justification for the Use of Statins in Prevention) trial (NCT00239681), at baseline and on statin we measured standard lipids, 400‐MHz proton nuclear magnetic resonance spectroscopy‐measured VLDL particle subclasses (small, medium, and large VLDL lipoprotein particle concentration), and total VLDL cholesterol mass. Compared with individuals allocated to placebo, we examined risk of incident ASCVD (N=211) among statin‐allocated participants who achieved minimal (<median) or greater (≥median) marker reductions using adjusted Cox models. On‐statin changes in VLDL‐related markers were only modestly correlated (Spearman r≤0.29) with change in LDL‐C. On‐statin median LDL‐C was 54 mg/dL and triglyceride was 101 mg/dL. Dose‐response reductions in ASCVD risk were observed for greater reductions in LDL‐C, VLDL cholesterol mass, and small VLDL lipoprotein particle concentration; the latter 2 remained significant after incremental adjustment for change in LDL‐C (P≤0.006). Conversely, there was no further risk reduction with greater reductions in triglycerides or large/medium VLDL lipoprotein particle concentration.ConclusionsPharmacological reduction in small, cholesterol‐enriched, triglyceride‐depleted VLDL was associated with reduction in ASCVD risk. Chemically measured triglycerides may not sufficiently capture risk related to VLDL pathways. These findings also support broader profiling of lipid and lipoprotein changes in response to statins as prognostic markers of individual benefit, supporting more precision‐medicine, individualized approaches to cardiovascular risk reduction.Clinical Trial RegistrationURL: https://www.clinicaltrials.gov. Unique identifier: NCT00239681.

Long-term fire activity under the East Asian monsoon responding to spring insolation, vegetation type, global climate, and human impact inferred from charcoal records in Lake Biwa sediments in central Japan

Records of sedimentary charcoal provide fire histories for assessing the relationship between fires and climate conditions, vegetation, human impact, and other factors. We analyzed charcoal particles in sediments from Lake Biwa in central Japan, dating back to 150,000 years ago. The sediments are well dated, homogenous, and had a constant sedimentation rate, making them ideal for assessing the long-term fire history through charcoal concentration analysis. Low charcoal concentrations in the glacial periods of Marine Isotope Stage (MIS) 2 and 6 indicate that few fires occurred in the periods under the cold climatic conditions. Variations in the microcharcoal concentration between 40,000 and 130,000 years ago, with a periodicity of 21,000–23,000 years, correspond to variations in the spring insolation in central Japan, vegetation type, and global climate, suggesting that the long-term fire activity in central Japan was determined mainly by spring insolation and vegetation type under the influence of global climate change. This finding suggests that insolation changes induced by precession cycles could influence a long-term phenomenon in an area as a direct local effect. Between 16,000 and 3000 years ago, sediments were characterized by an extraordinarily high concentration of large charcoal particles (>50 μm) and the predominance of elongated charcoal particles, suggesting that grassland fires (presumably anthropogenic) occurred frequently in the lakeside area. The frequent fire occurrence presumably contributed to the inflow of a large amount of organic materials, resulting in changes in the aquatic environment of Lake Biwa and/or its adjacent area.

Plasma Lipoprotein Particle Subclasses in Preterm Infants.

A pilot study to determine lipoprotein classes and subclasses in premature infants and examine associations with nutritional intake, gestational age (GA), and morbidity. Plasma lipoprotein particle concentrations were analyzed in a cohort of 15 premature infants in the first 5 days of life and again at 2 weeks. Breast milk samples were analyzed for fatty acid content. Associations between lipoprotein particle subclasses and GA, breast milk intake, milk fatty acid intake, and chronic lung disease (CLD) were determined. At 2 weeks of age, more premature infants had higher concentrations of total very low-density lipoprotein and lower concentrations of total high-density lipoprotein (HDL) and large HDL particles (similar to profiles seen in adults and children with infectious disease, cardiometabolic disease, and diabetes). Lower total HDL, large HDL, and medium HDL and a higher small HDL:total HDL ratio at 2 weeks were each associated with CLD with GA a likely confounder. Intake of human milk C18 and C20 fatty acids was inversely correlated with plasma total LDL concentration at 2 weeks of age. Dyslipidemia was common in extremely premature infants and was associated with CLD and with lower intake of specific long chain fatty acids.

Study of formation damage caused by retention of bi-dispersed particles using combined pore-scale simulations and particle flooding experiments

The infiltration of solid particles (fines) into a reservoir during drilling or water reinjection is a long-standing problem in the petroleum industry because of the associated production decline or injectivity loss. Solid particle infiltration is also an active area of research in other fields such as waste water treatment and fines migration in clay-rich reservoirs.In this work, we perform experiments to study particle infiltration into sintered glass bead core plugs and measure the changes in porosity and permeability using computed tomography (CT) scanning and pressure transducers, respectively. Suspensions of prescribed bimodal particle sizes, concentrations, and flowrates are flooded through the core plugs. Permeability changes are measured continuously over time, and the porosity change is measured after flowing a fixed mass of invaded particles.A dual pore-scale numerical model approach (a combination of a direct pore-scale discrete element method (DEM) and a pore-scale network model) is used to predict permeability reduction by particle filtration in porous media. Large particle deposition is modeled using the DEM in a disordered sphere pack geometry; the result is a prediction of deposition as a function of large particle concentration. Small particle deposition is modeled using the network model; the result is a prediction of deposition as a function of small particle concentration. Crucially, the geometry of the network model depends on the amount of large particles deposited. In this way, the deposition of large and small sized particles is coupled together.The permeability and porosity reduction of the network due to the deposition of small and large particles are then calculated from the functions above. We compare the experimental results with simulation predictions and find that the dual pore-scale model is capable of predicting the permeability of the invaded core in the regions away from the injection face. Permeability prediction in the region adjacent to the injection face is improved by incorporating the influence of the external filter cake.

Greater circulating concentrations of large HDL particles associate with more favorable HDL functionality in young adults

Greater circulating concentrations of large HDL particles associate with more favorable HDL functionality in young adults

Reduced ultrafine particle levels in S\xe3o Paulo\u2019s atmosphere during shifts from gasoline to ethanol use

Despite ethanol’s penetration into urban transportation, observational evidence quantifying the consequence for the atmospheric particulate burden during actual, not hypothetical, fuel-fleet shifts, has been lacking. Here we analyze aerosol, meteorological, traffic, and consumer behavior data and find, empirically, that ambient number concentrations of 7–100-nm diameter particles rise by one-third during the morning commute when higher ethanol prices induce 2 million drivers in the real-world megacity of São Paulo to substitute to gasoline use (95% confidence intervals: +4,154 to +13,272 cm−3). Similarly, concentrations fall when consumers return to ethanol. Changes in larger particle concentrations, including US-regulated PM2.5, are statistically indistinguishable from zero. The prospect of increased biofuel use and mounting evidence on ultrafines’ health effects make our result acutely policy relevant, to be weighed against possible ozone increases. The finding motivates further studies in real-world environments. We innovate in using econometrics to quantify a key source of urban ultrafine particles.

Influence of HDL particles on cell-cholesterol efflux under various pathological conditions

It has been reported that low cell-cholesterol efflux capacity (CEC) of HDL is an independent risk factor for CVD. To better understand CEC regulation, we measured ABCA1- and scavenger receptor class B type I (SR-BI)-dependent cell-cholesterol efflux, HDL anti-oxidative capacity, HDL particles, lipids, and inflammatory- and oxidative-stress markers in 122 subjects with elevated plasma levels of triglyceride (TG), serum amyloid A (SAA), fibrinogen, myeloperoxidase (MPO), or β-sitosterol and in 146 controls. In controls, there were strong positive correlations between ABCA1-dependent cholesterol efflux and small preβ-1 concentrations (R2 = 0.317) and SR-BI-dependent cholesterol efflux and large (α-1 + α-2) HDL particle concentrations (R2 = 0.774). In high-TG patients, both the concentration and the functionality (preβ-1 concentration-normalized ABCA1 efflux) of preβ-1 particles were significantly elevated compared with controls; however, though the concentration of large particles was significantly decreased, their functionality (large HDL concentration-normalized SR-BI efflux) was significantly elevated. High levels of SAA or MPO were not associated with decreased functionality of either the small (preβ-1) or the large (α-1 + α-2) HDL particles. HDL anti-oxidative capacity was negatively influenced by high plasma β-sitosterol levels, but not by the concentrations of HDL particles, TG, SAA, fibrinogen, or MPO. Our data demonstrate that under certain conditions CEC is influenced not only by quantitative (concentration), but also by qualitative (functional) properties of HDL particles.

New Type Of Medium – Gases With High Concentration Of Nanoparticles

The article gives an overview of the works, the results of which indicate the necessity of posing the problem of describing new types of continuous media containing large concentrations of nanoscale particles. The importance of this problem is underlined for understanding modern technological processes in which nanopowders of various nature are formed, and in the form of nanoparticles whose concentration reaches significant values is increasingly used. Examples of practically important flows of powder materials are considered. The concept of a new continuous medium with a high concentration of nanoparticles is proposed, and the «hot-anemometric method» is applied.

Modelling compressible dense and dilute two-phase flows

Many two-phase flow situations, from engineering science to astrophysics, deal with transition from dense (high concentration of the condensed phase) to dilute concentration (low concentration of the same phase), covering the entire range of volume fractions. Some models are now well accepted at the two limits, but none are able to cover accurately the entire range, in particular regarding waves propagation. In the present work, an alternative to the Baer and Nunziato (BN) model [Baer, M. R. and Nunziato, J. W., “A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials,” Int. J. Multiphase Flow 12(6), 861 (1986)], initially designed for dense flows, is built. The corresponding model is hyperbolic and thermodynamically consistent. Contrarily to the BN model that involves 6 wave speeds, the new formulation involves 4 waves only, in agreement with the Marble model [Marble, F. E., “Dynamics of a gas containing small solid particles,” Combustion and Propulsion (5th AGARD Colloquium) (Pergamon Press, 1963), Vol. 175] based on pressureless Euler equations for the dispersed phase, a well-accepted model for low particle volume concentrations. In the new model, the presence of pressure in the momentum equation of the particles and consideration of volume fractions in the two phases render the model valid for large particle concentrations. A symmetric version of the new model is derived as well for liquids containing gas bubbles. This model version involves 4 characteristic wave speeds as well, but with different velocities. Last, the two sub-models with 4 waves are combined in a unique formulation, valid for the full range of volume fractions. It involves the same 6 wave speeds as the BN model, but at a given point of space, 4 waves only emerge, depending on the local volume fractions. The non-linear pressure waves propagate only in the phase with dominant volume fraction. The new model is tested numerically on various test problems ranging from separated phases in a shock tube to shock–particle cloud interaction. Its predictions are compared to BN and Marble models as well as against experimental data showing clear improvements.

Short-term cooling increases serum triglycerides and small high-density lipoprotein levels in humans

Cold exposure and β3-adrenergic receptor agonism, which both activate brown adipose tissue, markedly influence lipoprotein metabolism by enhancing lipoprotein lipase-mediated catabolism of triglyceride-rich lipoproteins and increasing plasma high-density lipoprotein (HDL) levels and functionality in mice. However, the effect of short-term cooling on human lipid and lipoprotein metabolism remained largely elusive. The objective was to assess the effect of short-term cooling on the serum lipoprotein profile and HDL functionality in men. Body mass index-matched young, lean men were exposed to a personalized cooling protocol for 2hours. Before and after cooling, serum samples were collected for analysis of lipids and lipoprotein composition by 1H-nuclear magnetic resonance. Adenosine triphosphate-binding cassette A1 (ABCA1)-mediated cholesterol efflux capacity of HDL was measured using [3H]cholesterol-loaded ABCA1-transfected Chinese hamster ovary cells. Short-term cooling increased serum levels of free fatty acids, triglycerides, and cholesterol. Cooling increased the concentration of large very low-density lipoprotein (VLDL) particles accompanied by increased mean size of VLDL particles. In addition, cooling enhanced the concentration of small LDL and small HDL particles as well as the cholesterol levels within these particles. The increase in small HDL was accompanied by increased ABCA1-dependent cholesterol efflux invitro. Our data show that short-term cooling increases the concentration of large VLDL particles and increases the generation of small LDL and HDL particles. We interpret that cooling increases VLDL production and turnover, which results in formation of surface remnants that form small HDL particles that attract cellular cholesterol.