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PubMed2000

Levels and correlates of LDL and VLDL particle sizes among children: the Bogalusa heart study.

Levels of lipids and lipoproteins among children vary by sex and race/ethnicity, and are correlated with age, obesity, and other characteristics. There is, however, little information on the distribution and correlates of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) subclasses in early life. We used nuclear magnetic resonance (NMR) spectroscopy to determine mean LDL and VLDL particle sizes among 10- to 17-year-olds (n=918) who participated in the 1992-94 examination of the Bogalusa heart study. As compared with girls, boys had a smaller (0.1 nm) mean LDL particle size and a larger (0.9 nm) mean VLDL size; furthermore, the average size of VLDL particles increased with age among white boys but not among other children. Although there were also black/white differences in particle sizes, with black children having larger LDL and smaller VLDL particles, these racial contrasts could be attributed to differences in lipid levels. Levels of triglycerides, insulin, and relative weight were associated with the size of VLDL (positive) and LDL (negative) particles. These results suggest that the analysis of lipoprotein subclasses may provide a better understanding of the role of various risk factors in the development of coronary heart disease

Adolescent↗

PubMed1987

[Effect of particle size and emulsifier on pharmacokinetic values of a parenterally administered fat emulsion].

To evaluate pharmacokinetic data during parenteral application of a fat emulsion a controlled study in healthy volunteers was performed. Another aim of the study was to investigate whether these kinetics could be changed by modification of the emulsion. For this purpose, 10 male medical students--free of any metabolic disorders--received modified batches of one fat emulsion (Lipovenös), differing with respect to particle size or emulsifier. The emulsions were applied using a pump-controlled continuous infusion technique. The dosage was calculated according to body weight: 0.1 g/kg B.W./h. There was a 7-10 day interval between one application and the following study period, again using the same volunteers. Thus every volunteer served as his own control. Routine laboratory parameters as well as parameters relating to fat metabolism were measured. While routine laboratory parameters were not statistically different between the groups, pharmacokinetic data showed differences according to the batches used. Highest triglyceride and free fatty acid levels i.s. were present after application of the emulsion with low medium particle size, while lowest levels were found after increasing the particle size to 380 nm. In addition, it could be documented that an increase in medium particle size resulted in higher elimination rate, transfer and pool size. The modified emulsifier led to an additional increase of these effects, thus inducing beneficial metabolic profiles. The results of the present investigation might perhaps enable us to adjust the profile of future fat emulsions, with the aim of optimizing or restoring metabolic hemostasis.

Adult↗

PubMed2004

Effect of process variables on particle size of gelatin microspheres containing lactic acid.

Gelatin microspheres containing lactic acid were prepared by a polymerization technique using glutaraldehyde as the cross-linking agent. Because particle size distribution of microspheres is a vital factor in the characterization of microspheres, the present study was carried out to evaluate the effect of process variables on the microspheres size distribution. It was found that concentration of a gelatin solution is the most important parameter that influences the particle size of microspheres. By using different concentrations of gelatin solution, microspheres with different size ranges were prepared. Both the stirring rate of the system and the volume ratio of aqueous and oil phases exerted a great influence on microsphere-size distribution, whereas, cross-linking time and cross-linker concentration only affected the yield. Lower-phase volume ratios resulted in small uniform microspheres with smooth surfaces and a narrow size range. The effect of emulsifier concentration (span 80), below 1% (w/w, with respect to the weight of the oil phase), on particle size was appreciable. However, at higher concentrations, little effect was observed.

Cross-Linking Reagents↗

PubMed2002

A 16-week fenofibrate treatment increases LDL particle size in type IIA dyslipidemic patients.

OBJECTIVE: The objective of the present study was to compare the effects of a 16-week pharmacotherapy with fenofibrate (200 mg) or pravastatin (initially 20 mg for 8-weeks and, if necessary, increased to 40 mg) on low density lipoprotein (LDL) particle size assessed by gradient gel electrophoresis among patients with type IIa dyslipidemia. METHODS: For that purpose, type IIa dyslipidemic patients (cholesterol, 7.45+/-1.18 (S.D.) mmol/l; LDL cholesterol, 5.57+/-1.16 mmol/l; triglycerides (TGs), 1.66+/-0.43 mmol/l) were randomized to either fenofibrate (n=36) or pravastatin (n=43) therapy for 16 weeks. Fasting plasma lipoprotein levels as well as the LDL peak particle size (using 2-16% polyacrylamide gel electrophoresis) were assessed at baseline and after the 16-week treatment period. RESULTS: Whereas significant improvements in the plasma lipoprotein-lipid variables were observed with both fenofibrate and pravastatin treatments, LDL peak particle size was only significantly increased with fenofibrate therapy (+2.11+/-5.18 A, P<0.05). Among patients under fenofibrate therapy, changes in TG levels were negatively associated with changes in LDL peak particle size (r=-0.54, P<0.0007), whereas no such association was found in pravastatin-treated patients. The prevalence of patients with small, dense LDL particles (as defined by LDL particle diameter <255.5 A) was reduced from 69.4 to 30.6% (P<0.05) among fenofibrate-treated patients as opposed to 81.4 to 72.1% (NS) in patients who received pravastatin. CONCLUSION: As pravastatin treatment had no effect on LDL size, it is suggested that the additional effect of fenofibrate therapy on LDL size may contribute to reduce the risk of coronary heart disease (CHD) beyond what can be expected from the reduction in LDL cholesterol concentration in type IIa dyslipidemic patients.

Adult↗

PubMed2001

Effect of compression force, compression speed, and particle size on the compression properties of paracetamol.

The compression characteristics of two particle size fractions (< 90 microm, 105-210 microm) of paracetamol were examined. Each fraction produced extremely weak tablets and displayed a high tendency to cap. Low correlation coefficients of the initial parts of the Heckel plots, a low strain rate sensitivity, and an increase in mean yield pressure (from 34.2 to 45.5 MPa) with decrease in particle size all confirmed that the main mechanism during the compaction of paracetamol was fragmentation. The 105-210-microm particles underwent more fragmentation than the less than 90-microm powder. Heckel analysis confirmed that the larger size fraction of paracetamol produced denser compacts than the smaller fraction. The 105-210-microm fraction resulted in tablets with lower elastic recoveries and elastic energies. The elastic, plastic energy ratios indicated that the majority of energy involved during the compaction of paracetamol was utilized as elastic energy, indicative of massive elastic deformation of paracetamol particles under pressure.

Acetaminophen↗

PubMed2003

Development of a measuring technique for simultaneous in situ detection of nanoscaled particle size distributions and gas temperatures.

Point measurements of time-resolved LII signals have been performed in sooting premixed low pressure flames. Soot particle size distribution and gas temperature in these flames are known from independent measurements. This data is used to validate parameters of an improved LII model, where special emphasis is taken on the accurate modelling of mass and heat transfer rates. Using this model particle size distributions and gas temperatures can be estimated from time-resolved LII signals using non-linear regression. Standard numerical methods are applied. An experimental setup is presented, which allows measuring one-dimensional maps of particle size distribution and gas temperature. The technique is based on the one-dimensional and time-resolved detection of LII signals using a Streak camera.

Air Pollutants↗

PubMed2001

Particle size and chemical species 'fingerprinting' of aerosols in primary nickel production industry workplaces.

A field study was conducted at a range of worksites at a number of plants, for two companies, in the primary nickel production industry. The aim of the field study was to provide direct measurements of the distributions of both particle size and relevant nickel species groups (soluble, sulfidic, metallic and oxidic). and to use the data to characterize health-relevant aerosol exposures of workers at the worksites in question. Since there was no commercially-available sampler that could provide samples of sufficient quantity to enable chemical speciation for the species fractions of interest, as well as particle size distribution information, new instrumentation was developed, based on a modified version of the Andersen cascade impactor, incorporating a porous foam media top stage that produced particle classification over the upper end of the inhalable range (Kerr, Vincent and Ramachandran, Annals of Occupational Hygiene, 2001, in the press). This modified-Andersen sampler was used in extensive field studies, along with other sampling instruments, including, in particular, the IOM personal inhalable aerosol sampler. The results of the field study provided results that could be represented succinctly in terms of the distributions of the four nickel species groups and the three health-related particle-size fractions: inhalable, thoracic and respirable. They showed that, for practical purposes, the distributions of the four nickel species groups were consistently uniform across the full range of particle-size distribution. For the purpose of characterizing the distribution of nickel species for each worksite, this finding enabled incorporation of additional data taken at those same sites using the IOM personal inhalable aerosol sampler. This yielded a data set sufficient to permit the development of exposure 'fingerprints' for each worksite. Such 'fingerprints' make it possible for the occupational hygienists at the plants in question to estimate workers' exposure to individual nickel species fractions based on measurement only of overall inhalable nickel. In addition, by reference to the differing threshold limit values (TLV) for the various nickel species, the 'fingerprints' also allow the individual worksites to be characterized by hazard indices (in the form of 'equivalent sulfidic fractions', or ESFs) that reflect the weightings of the risks experienced by workers at each worksite.

Aerosols↗

PubMed2005

Particle size distribution and evolution in tablet structure during and after compaction.

The objective of this study was to investigate the effect of the distribution in size of free-flowing particles for the evolution in tablet structure and tablet strength. For sucrose and sodium chloride, three powders of different size distributions were prepared by mixing predetermined quantities of particle size fractions. For paracetamol, three batches with varying particle size distributions were prepared by crystallisation. The powders were formed into tablets. Tablet porosity and tensile strength were determined directly after compaction and after short-term storage at two different relative humidities. Tablets were also formed after admixture of a lubricant (magnesium stearate) and the tablet tensile strength was determined. For the test materials used in this study, the spread in particle size had no influence on the evolution in tablet porosity and tensile strength during compression. However, the spread in particle size had a significant and complex influence on the short-term post-compaction increase in tablet tensile strength. The effect of the spread was related to the instability mechanism and the presence of lubricant. It is concluded that the distribution in size of free-flowing particles is not critical for the tablet porosity but may give significant effects on tablet tensile strength due to a post-compaction reaction.

Acetaminophen↗

PubMed1981

Standardization of inhalation provocation tests: influence of nebulizer output, particle size, and method of inhalation.

Standardization of inhalation tests requires a knowledge of factors that will affect the response. We measured the output and particle size of six types of nebulizers used for inhalation tests. Output varied considerably between nebulizers of different types (0.12 to 1.59 ml/min) and to a lesser extent between nebulizers of the same type. Particle size varied between 0.8 and 5.2 micrometer aerodynamic mass median diameter (AMMD). The influence of these two properties on bronchial response to inhaled methacholine was examined. Nebulizer output but not particle size (between 1.3 and 3.6 micrometer AMMD) altered the response. We also examined the effect of change in inspiratory time during inhalation from residual volume to total lung capacity on lung deposition of radiolabeled aerosol and on the provocative concentration of histamine required to reduce the 1-sec forced expiratory volume (FEV1) by 20% (PC20). A reduction in inspiratory time from 8 to 2 sec resulted in a lower total lung dose, relatively more aerosol deposited in central airways, and a higher PC20. The results emphasize the importance of keeping nebulizer output and pattern of breathing constant when performing inhalation provocation tests if consistent results are to be obtained.

Aerosols↗

PubMed2005

Effect of MePEG molecular weight and particle size on in vitro release of tumor necrosis factor-alpha-loaded nanoparticles.

AIM: To study the in vitro release of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) encapsulated in poly (methoxypolyethyleneglycol cyanoacrylate-co-n-hexadecyl cyanoacrylate) (PEG-PHDCA) nanoparticles, and investigate the influence of methoxypolyethyleneglycol (MePEG) molecular weight and particle size. METHODS: Three sizes (approximately 80, 170, and 240 nm) of PEG-PHDCA nanoparticles loading rHuTNF-alpha were prepared at different MePEG molecular weights (M(r) =2000, 5000, and 10,000) using the double emulsion method. The in vitro rHuTNF-alpha release was studied in PBS and rat plasma. RESULTS: A higher burst-release and cumulative-release rate were observed for nanoparticles with higher MePEG molecular weight or smaller particle size. A decreased cumulative release of rHuTNF-alpha following the initial burst effect was found in PBS, while the particle sizes remained constant and MePEG liberated. In contrast, in rat plasma, slowly increased cumulative-release profiles were obtained after the burst effect. During a 5-h incubation in rat plasma, more than 50% of the PEG-PHDCA nanoparticles degraded. CONCLUSION: The MePEG molecular weight and particle size had an obvious influence on rHuTNF-alpha release. rHuTNF-alpha released from PEG-PHDCA nanoparticles in a diffusion-based pattern in PBS, but in a diffusion and erosion-controlled manner in rat plasma.

Animals↗

PubMed1996

Lasalocid and particle size of corn grain for dairy cows in early lactation. 1. Effect on performance, serum metabolites, and nutrient digestibility.

The effects were examined of corn grain particle size and the ionophore lasalocid on performance, blood parameters, and nutrient digestibility of early lactation cows. Smaller corn particle size was expected to result in faster rate of digestion and ruminal fermentation of starch. Eight multiparous and 4 primiparous cows in early lactation were fed diets (44% forage) with cracked or ground, dried shelled corn grain and with or without lasalocid (360.mg/d per cow). The experiment was a replicated (n = 3) 4 x 4 Latin square design with 21-d periods and a 2 x 2 factorial arrangement of treatments. Lasalocid tended to improve DMI. Lasalocid and ground corn decreased body condition loss and milk fat and increased milk protein. Ground corn tended to increase milk yield but had no effect on 4% FCM, lactose, and BW. For all cows, milk yield, 4% FCM, lactose, and BW were unaffected by lasalocid; however, subsequent analysis of individual squares revealed that milk yield of primiparous cows increased with lasalocid. Ground corn increased total tract starch digestibility and decreased NDF digestibility. Interactions between lasalocid and particle size of corn grain were observed only for change in serum insulin concentration before and after meals.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Effect of corn particle size on site and extent of starch digestion in lactating dairy cows.

Two experiments were conducted to determine the effects of corn particle size (CPS) on site and extent of starch digestion in lactating dairy cows. Animals were fitted with ruminal, duodenal, and ileal cannulas. Dry corn grain accounted for 36% of dry matter intake. In experiment 1, 6 cows were used in a duplicate 3 x 3 Latin square design. Semiflint corn was used. Corn processing methods were grinding, medium rolling, and coarse rolling. The mean particle size of the processed corn was 730, 1807, and 3668 microm, respectively. Rumen digestibility of starch linearly decreased from 59% with ground corn to 36% with coarsely rolled corn. Similarly, small intestine digestibility linearly decreased with increased CPS, and consequently, the amount of starch digested in the small intestine was not affected by corn processing. In experiment 2, 4 cows were used in a 2 x 2 crossover design. Dent corn was used. Corn processing methods were grinding and coarse rolling. The mean particle size of the processed corn was 568 and 3458 microm, respectively. Rumen digestibility of starch decreased from 70% with ground corn to 54% with coarsely rolled corn. Small intestine digestibility of starch was not significantly affected by CPS, and the amount of starch digested in the small intestine tended to be greater for rolled than for ground corn. In both experiments, starch total tract digestibility decreased with increased CPS. In conclusion, CPS is an efficient tool to manipulate rumen degradability of cornstarch. In midlactation cows, the decrease in the amount of starch digested in the rumen between grinding and coarse rolling is partly compensated for by an increase in the amount of starch digested in the small intestine with dent genotype, but with semiflint genotype postruminal digestion is not increased and rumen escape starch is not utilized by the animal.

Animals↗

PubMed2006

Particle-size effect of nanoscale platinum catalysts in oxygen reduction reaction: an electrochemical and 195Pt EC-NMR study.

Oxygen reduction reaction (ORR) measurements and (195)Pt electrochemical nuclear magnetic resonance (EC-NMR) spectroscopy were combined to study a series of carbon-supported platinum nanoparticle electrocatalysts (Pt/CB) with average diameters in the range of roughly 1-5 nm. ORR rate constants and H(2)O(2) yields evaluated from hydrodynamic voltammograms did not show any particle size dependency. The apparent activation energy of 37 kJ mol(-1), obtained for the ORR rate constant, was identical to that obtained for bulk platinum electrodes. Pt/CB catalysts on Nafion produced only 0.7-1% of H(2)O(2), confirming that the direct four-electron reduction of O(2) to H(2)O is the predominant reaction. NMR spectral features showed characteristic size dependence, and the line shapes were reproduced by using the layer-deconvolution model. Namely, the variations in the NMR spectra with particle size can be explained as due to the combined effect of the layer-by-layer variation of the s-type and d-type local density of states. However, the surface peak position of (195)Pt NMR spectra and the spin-lattice relaxation time of surface platinum atoms showed practically no change with the particle size variation. We conclude that there is a negligible difference in the surface electronic properties of these Pt/CB catalysts due to size variations and therefore, the ORR activities are not affected by the differences in the particle size.

Catalysis↗

PubMed2005

Molar mass and molar mass distribution of polystyrene particle size standards.

Monodisperse polystyrene microspheres and nanospheres are often used as particle size standards for calibration of size-measuring instruments. They are potentially useful as the mass standards for particle mass spectrometry as well. We demonstrated in this work that it is possible to achieve high-precision mass determination for single polystyrene spheres using a quadrupole ion trap. We introduced the particles into the trap by laser-induced acoustic desorption and probed them with light scattering. Mass-to-charge ratios of the individual particles were determined from applied trap-driving frequencies, voltage amplitudes and the observed starlike oscillatory trajectories projected on the radial plane. Creation of one-electron differentials through charge-state changes by electron bombardment allowed determination for the absolute mass of a single trapped particle to a precision better than 0.1%. Both molar mass and molar mass distribution were deduced from a large number of measurements for NIST polystyrene particle size standards (SRMs 1690 and 1691). Our results are in excellent agreement with the size measurement for the 0.895-microm spheres (NIST SRM 1690), but a small discrepancy (4%) in number-average mass was found for the 0.269-microm spheres (NIST SRM 1691).

Journal Article↗

PubMed2001

Effect of Particle Size on the Sticking Probability.

In the literature the transport of particles toward an oppositely charged collector in stagnation point flow is described theoretically with the Smoluchowski-Levich solution of the convective-diffusion equation. Using optical reflectometry, the initial adsorption rate in the case of adsorption of negatively charged polystyrene latex particles onto a glass collector covered with positively charged poly(propylene imine) dendrimers was studied at low ionic strength and constant pH. For latex particle sizes varying from 10 to 100 nm, the experimentally obtained values for the initial adsorption rate are systematically lower than the theoretical predictions. The deviations are captured by a sticking probability or collision efficiency that increases linearly from 0.5 to 0.8 within the experimental window. This can be explained by the fact that with particle size the contact area between the incoming particles and the amorphous collector increases and with this the number of sites involved in binding. Copyright 2001 Academic Press.

Journal Article↗

PubMed1987

Effect of particle size of bronchodilator aerosols on lung distribution and pulmonary function in patients with chronic asthma.

The particle size of bronchodilator aerosols may be important in determining the site of deposition in the lung and their therapeutic effect. The distribution of aerosols (labelled with technetium-99m diethylene triamine pentacetic acid) of two different particle sizes has been studied by gamma camera imaging. The particles had mass median aerodynamic diameters (geometric standard deviations) of 1.4 (1.4) and 5.5 (2.3) micron, and they were administered from a jet nebuliser to eight patients with chronic severe stable asthma. There was no significant difference in peripheral lung deposition with the two aerosols in any patient. The bronchodilator effect of the two aerosols was determined from cumulative dose-response studies. To avoid large doses that might mask possible differences in effect due to aerosol size, small, precisely determined incremental amounts of salbutamol (25-250 micrograms total lung dose) were used. The two doses were given via a nebuliser on separate occasions and the bronchodilator response was measured from FEV1, forced vital capacity, and peak expiratory flow 30 minutes after each dose. Bronchodilatation was similar with the two aerosols at each dose of salbutamol. There was therefore no difference in distribution within the lung or any difference in bronchodilator effect between an aerosol of small (1.4 micron) particle size and an aerosol of 5.5 microns in patients with severe but stable asthma.

Albuterol↗

PubMed1991

The effect of airborne lead particle size on worker blood-lead levels: an empirical study of battery workers.

Theoretical models and experimental data suggest that the particle size distribution of lead aerosols should affect the lead dose absorbed by exposed workers. In the present study, 44 workers in five major operations in a high-volume, lead-acid battery plant were studied for the influence of lead aerosol size on lead-in-blood (PbB) levels. A multiple linear regression analysis based on particle size assumptions made in the model used by the Occupational Safety and Health Administration to help select the permissible exposure level (PEL) for lead showed no improvement in prediction of PbB over that already present without any consideration of particle size. The use of the American Conference of Governmental Industrial Hygienists (ACGIH) regional size-selective criteria also failed to improve the prediction of PbB. However, when deposition models developed by Heyder et al were used in which the lead aerosol was separated into alveolar and extra-alveolar fractions, corresponding to what is considered respirable and ingestible lead, the coefficient of determination (R2) associated with the fractionated lead particulate increased approximately 25% over that attributable to only the total lead concentration. In addition, the deposition model, which closely matched the ACGIH reference worker criteria, resulted in ratios of the coefficients for the respirable to ingestible lead contributions to PbB that appeared to agree with experimental data, suggesting approximately a 10 to 1 ratio in absorption efficiency of the lung versus the gastrointestinal tract.

Aerosols↗

PubMed1976

Oxytetracycline tablet formulations: the effect of wet mixing time, particle size and batch variation on granule and tablet properties.

The wet mixing time has been shown to influence the properties of an oxytetracycline dihydrate tablet formulation, wet granulated with PVP solution. Increased time of wet mixing produced larger, stronger and more dense granules, which compressed into tablets with longer disintegration and dissolution times. Decreased drug particle size aggravated these trends. A decrease in drug particle size also produced larger, stronger and more dense granules. Above an oxytetracycline mean particle diameter of about 6 mum, the tablet dissolution was satisfactory. As the oxytetracycline particle size was decreased further, however, the distintegration and dissolution of the corresponding tablets was markedly slower.

Drug Compounding↗