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PubMed1977

Determinations of microbial loads associated with microscopic-size particles of Kennedy Space Center soil.

Plate counts for six fractions, of micrometer-size, of Kennedy Space Center soil provided estimates of aerobic, mesophilic, heterotrophic, microbial loads on single soil particles. Analyses included unheated particles, particles subjected to wet heat at 80 degrees C for 20 min, and particles subjected to dry heat at 110 degrees C for 1 hr. Unheated particles yielded mean counts ranging from 6 colonies per particle for the smallest (44-53 micrometers) soil fraction to approximately 55 colonies per particle for the largest size (105-125 micrometers) soil fraction tested. Mean counts for heat-resistant forms ranged from 2 colonies per particle for the smaller particles to 12-15 colonies for the largest particles analyzed.

Bacteria↗
PubMed1984

Distribution of freeze-fracture particle sizes in Duchenne muscle plasma membrane.

We studied the distribution of freeze-fracture intramembranous particle (IMP) sizes in Duchenne muscle biopsies and controls. We found that the previously reported decrease in muscle plasma membrane particle density in Duchenne includes a variety of different IMPs, but does not preferentially involve IMPs of any one size.

Cell Membrane↗
PubMed1996

Factors influencing Lp[a]- particle size as determined by gradient gel electrophoresis.

This study examined factors influencing the particle diameter of Lp[a]-, the low density lipoprotein (LDL)-like moiety of Lp[a], in 26 subjects chosen to provide a range of Lp[a] and triglyceride levels. Lp[a] and LDL fractions were isolated by vertical density ultracentrifugation. Lp[a] was further purified using a lysine-Sepharose affinity column and Lp[a]- obtained by incubating Lp[a] with dithiothreitol. Lp[a], LDL, and Lp[a]- fractions were run on 3-13% gradient gels to determine particle diameter. Lp[a] size correlated positively with LDL size (r = 0.62; P < 0.001), but the association between Lp[a]- size and LDL size was stronger (r = 0.82; P < 0.0001). Log triglyceride level correlated inversely with Lp[a]- size (r = -0.72; P < 0.0001) and LDL size (r = 0.69; P < 0.0001). HDL cholesterol level correlated positively with Lp[a]- size (r = 0.67; P < 0.0005) and LDL size (r = 0.64; P < 0.0005). The strong correlation between LDL size and Lp[a]- size may be due to extracellular utilization of circulating LDL in the production of Lp[a] or may reflect the same metabolic processes influencing both these particles once Lp[a] has been formed.

Apolipoproteins A↗
PubMed1999

Capillary electrophoresis of subcellular-sized particles.

Utilization of capillary electrophoresis (CE) for characterization and analytical separation of submicron- and micron-sized organic and inorganic particles as well as biological vesicles is reviewed. CE has been applied to charged polystyrene size standards, inorganic and organic colloidal particles, lipoprotein particles, liposomes, microsomes and viruses. These particle separations generally occur in a size-dependent manner and provide values of electrophoretic mobility which are in good agreement with those obtained by other electrophoretic techniques.

Electrophoresis, Capillary↗
PubMed1977

[Intrapulmonary deposition of submicron-size particles].

Inhalation studies of ultrafine aerosol particles are described. Chambers with controlled atmospheres have been built, in which known volumes of clear air and aerosol particles are introduced. By means of an electrical mobility analyzer the size distribution of the aerosol in the chamber determined down to a mean diameter of 0,01 micron. Such aerosol is inhaled by the subject and exhaled into an identical chamber, previously filled with clean air. The size distribution of the resulting aerosol is determined with the same measuring system. The particle number distributions of inhaled and exhaled particles are then suitably correlated and compared. In this paper data are reported based on the retention of cigarette smoke referred to male subjects in the age group from 24 to 44 years old. These results are compared with the experimental data which appeared most recently in the medical literature. A standardization is proposed of the experimental conditions for measurements of intrapulmonary deposition of inhaled particles. This is because of the importance that the results of such studies might have in the field of prevention and industrial hygiene, in particular in the nuclear field.

Adult↗
PubMed1992

Effect of the human cholesteryl ester transfer protein on the particle size redistribution of specific subpopulations of high density lipoproteins-3.

The effect of the cholesteryl ester transfer protein (CETP) on the size redistribution of high density lipoprotein-3 (HDL3) particles containing either apolipoprotein A-I without apolipoprotein A-II, designated HDL3 (A-I w/o A-II), or apolipoprotein A-I with apolipoprotein A-II, designated HDL3 (A-I w A-II), was investigated by incubating HDL3 at 37 degrees C in the presence of a purified preparation of CETP. At the end of the incubation, the distribution of total HDL3 as well as HDL3 (A-I w/o A-II) particles, recovered after immunoprecipitation of HDL3 (A-I w A-II) particles with anti-apo A-II antibodies, was determined by non-denaturing polyacrylamide gradient gel electrophoresis. Total HDL3 ultracentrifugally isolated from plasma consisted of two distinct subpopulations of particles with apparent diameters of 8.5 and 7.8 nm. The distribution profile of HDL3 (A-I w/o A-II) particles, revealed that the HDL3 subpopulation with a mean diameter of 8.5 nm comprised two typs of particles, containing either only apo A-I or apo A-I with apo A-II, while the lipoprotein subpopulation with a mean diameter of 7.8 nm consisted exclusively of particles containing both apolipoproteins. During incubation at 37 degrees C, CETP induced the redistribution of HDL3 with a mean apparent diameter of 8.5 nm towards particle subpopulations of larger (9.4 nm diameter) and smaller (7.8 and 7.4 nm diameter) size. It was demonstrated that the CETP-mediated conversion of HDL3 concerned both type of particles. CETP preferentially induced the transformation of HDL3 (A-I w A-II) particles with a mean diameter of 8.5 nm into larger (9.4 nm diameter) and smaller (7.8 nm diameter) particles containing apo A-I and apo A-II. Secondly, CETP induced a shift of HDL3 (A-I w/o A-II) particles with a mean diameter of 8.5 nm towards particles of smaller size (7.4 nm diameter) containing only apo A-I, while HDL3 (A-I w A-II) particles with mean diameters of 7.8 and 9.4 nm remained stable. In addition, this study demonstrated that the redistribution of HDL3 particles was accompanied by a dissociation of apolipoprotein A-I from the lipoprotein surfaces. The effect of myristic acid on CETP-induced HDL3 redistribution was mainly due to a redistribution of HDL3 (AI w/o AII) particles.

Apolipoprotein A-I↗
PubMed2000

Cytotoxic and mutagenic effects, particle size and concentration analysis of diesel engine emissions using biodiesel and petrol diesel as fuel.

Diesel engine exhaust particles (DEP) contribute substantially to ambient air pollution. They cause acute and chronic adverse health effects in humans. Biodiesel (rapeseed oil methyl ester. RME) is used as a "green fuel" in several countries. For a preliminary assessment of environmental and health effects of RME, the particulate-associated emissions from the DEP of RME and common fossil diesel fuel (DF) and their in vitro cytotoxic and mutagenic effects were compared. A test tractor was fuelled with RME and DF and driven in a European standard test cycle (ECE R49) on an engine dynamometer. Particle numbers and size distributions of the exhausts were determined at the load modes "idling" and "rated power". Filter-sampled particles were extracted and their cytotoxic properties tested using the neutral red assay. Mutagenicity was tested using the Salmonella typhimurium/microsome assay. Despite higher total particle emissions, solid particulate matter (soot) in the emissions from RME was lower than in the emissions from DF. While the size distributions and the numbers of emitted particles at "rated power" were nearly identical for the two fuels, at "idling" DF emitted substantially higher numbers of smaller particles than RME. The RME extracts caused fourfold stronger toxic effects on mouse fibroblasts at "idling" but not at "rated power" than DF extracts. The extracts at both load modes were significantly mutagenic in TA98 and TA100. However, extracts of DF showed a fourfold higher mutagenic effect in TA98 (and twofold in TA100) than extracts of RME. These results indicate benefits as well as disadvantages for humans and the environment from the use of RME as a fuel for tractors. The lower mutagenic potency of DEP from RME compared to DEP from DF is probably due to lower emissions of polycyclic aromatic compounds. The higher toxicity is probably caused by carbonyl compounds and unburned fuel, and reduces the benefits of the lower emissions of solid particulate matter and mutagens from RME.

Animals↗
PubMedDate not supplied

Determination of particle sedimentation rate by ultrasonic interferometry: role of particle size, density and volume fraction.

The sedimentation rate (SR) of non-aggregated spherical particles in suspension was determined using an ultrasonic interferometry technique (Echo-Cell); this method is based on A-mode echography and measures the rate of formation of a sediment on a solid plate during settling. The particle accumulation rate, which is related to SR, is obtained from the interference of two waves reflected by two interfaces: one between the plate and the sediment and the other between the sediment and the suspension. Studies were carried out at 25 degrees C using latex spheres of different diameters (7 to 20 micron) and densities (1.062 to 1.190 g/cm3) suspended in distilled water at various volume fractions (1% to 5%). As anticipated by the Stokes model, linear relations were found between SR and both particle density and the square of particle radius. Experimental SR values decreased with increasing suspension particle concentration; these concentration effects were in good agreement with those predicted by the Steinour model. Our results thus serve to validate the theoretical aspects of the Echo-Cell method and suggest its usefulness as a tool for studies of RBC interaction and RBC aggregation.

Blood Sedimentation↗
PubMed1978

Dust levels and particle-size distributions in high-capacity cotton gins.

Dust samples were collected inside high-capacity cotton gins with the personal, stationary personal, and the vertical elutriator cotton dust samplers. Dust particles collected on the filters were sized with a particle measurement computer system. Particle-distribution data revealed that gin dust contains a high percentage of dust particles larger than 20 micrometers in diameter.

Air Pollutants↗
PubMed1990

The effect of virus particle size on chemiluminescence induction by influenza and Sendai viruses in mouse spleen cells.

Suspensions of orthomyxo- and paramyxoviruses are composed of pleomorphic particles ranging from large filaments to small spheres. Influenza and Sendai viruses were separated according to size by gel filtration and the induction of luminol-dependent chemiluminescence (CL) by particles of similar size was studied in suspensions of mouse spleen cells known to contain phagocytes. CL reflects the generation by the cells of reactive oxygen species. CL induction decreased with particle size for both viruses. Compared with small spheres, large influenza filaments were approximately 10 times as efficient in activating cellular light emission while the ratio between large and small Sendai viruses was 3:1. Small Sendai virus particles were also less efficient in lysing red cells and had lower neuraminidase activity. By contrast, with influenza virus, only neuraminidase and not the hemolytic activity decreased with the virus size. When influenza virus filaments were broken into smaller particles by sonication, the capacity to induce chemiluminescence dropped markedly while the hemolytic and hemagglutinating activities increased and neuraminidase activity remained unaltered. These results suggest that the presentation of influenza virus hemagglutinin and neuraminidase glycoproteins in a large particle, leading to extensive receptor crosslinking, may be an important factor in the efficient activation of CL by filamentous influenza virus. We suggest that radical generation as reflected in cellular CL may relate to the toxic in vivo effects that contribute to the pathogenesis of influenza and infections with paramyxoviruses.

Animals↗
PubMed2005

Speciation and leachability of copper in mine tailings from porphyry copper mining: influence of particle size.

Mine tailing from the El Teniente-Codelco copper mine situated in VI Region of Chile was analysed in order to evaluate the mobility and speciation of copper in the solid material. Mine tailing was sampled after the rougher flotation circuits, and the copper content was measured to 1150 mg kg (-1) dry matter. This tailing was segmented into fractions of different size intervals: 0-38, 38-45, 45-53, 53-75, 75-106, 106-150, 150-212, and >212 microm, respectively. Copper content determination, sequential chemical extraction, and desorption experiments were carried out for each size interval in order to evaluate the speciation of copper. It was found that the particles of smallest size contained 50-60% weak acid leachable copper, whereas only 32% of the copper found in largest particles could be leached in weak acid. Copper oxides and carbonates were the dominating species in the smaller particles, and the larger particles contained considerable amounts of sulphides.

Adsorption↗
PubMed1989

Relationship of lipid secretion and particle size to diffuse interstitial change in pneumoconiosis: a pathogenetic perspective.

Simple pneumoconiosis due to compact particles, notably in coal workers, sometimes departs from its customary focal formations and a more diffuse distribution of dust-impregnated fibrosis is superimposed. To account for this change, which may be reflected in the acquisition of radiologically irregular opacities in addition to rounded ones, attention is directed first toward type II alveolar epithelium. These cells come early into contact with inhaled particles and the lipid secretion provoked prevents their characteristic aggregation, so they remain in a more dispersed state and the consequent fibrotic reaction then tends to become diffuse. Second, submicron particles appear to act not from within the alveolus like the more usual larger ones, but after direct passage through type I epithelium into the interstitium, where lacking focal accumulation they are able to produce diffuse changes. Complexities, however, remain, among which are coalescence of focal lesions as their severity increases and interplay of agents producing interstitial fibrosis in the general population.

Animals↗