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At least 415 records · Page 23Linked to original sources
PubMed1988

Effect of particle size on labeling density for catalase in protein A-gold immunocytochemistry.

Effect of particle size on labeling intensity in protein A-gold immunocytochemistry was studied. Catalase labeling of rat liver peroxisomes was used as a labeling model. Ultra-thin sections of Lowicryl K4M-embedded rat liver were stained for catalase with protein A-gold (pAg) probes. Five different sizes of colloidal gold probes, from 5 nm to 38 nm in diameter, were prepared. Labeling intensity decreased as the particle size of the pAg probes increased. The highest labeling was obtained by the 5-nm pAg probe and the lowest by the 38-nm pAg probe. Quantitative analysis also showed that labeling density was inversely proportional to the size of gold particles. The results suggest that the pAg probe with small gold particles has high sensitivity.

Animals↗
PubMed2003

Factors affecting the particle size and in vitro release of bovine serum albumin from polyethylene glycol microparticles.

Bovine serum albumin was encapsulated in polyethylene glycol (20,000 MW) microparticles using a modified double emulsion method. Particle size, release rate, and encapsulation efficiency were measured for microparticles when varying multiple process factors such as sonication time, sonication intensity and drug loading. For all procedures, ninety percent of the particles were less than 2 microns in diameter. Particle size was reduced by extending the preparation's exposure to sonication over a range of 30 to 120 s, increasing the sonication intensity from 5 to 20 W or varying the polymer to protein ratios from 10 to 100:1. Perhaps of more interest, the particle size distribution was substantially narrowed at the upper end of each parameter compared to the lower end. Substantial differences were observed at the upper and lower end of each varied process parameter. Upon examination of protein release from microparticles over 120 minutes, the burst effect was minimized at the upper end of each parameter. Encapsulation efficiency and the time to release 50% of the entrapped protein were greatest at the lower end. In conclusion, production process parameters significantly affect protein release rates while their effect on particle size is less significant. These particles could be utilized when delayed, but not necessarily extended, release period is desired.

Animals↗
PubMed2003

99mTc-SnF2 colloid "LLK": particle size, morphology and leucocyte labelling behaviour.

99mTc-SnF2 colloid (Radpharm LLK) leucocyte labelling agent is used in whole blood, exploiting phagocytosis. The objectives of this work were to optimize leucocyte labelling in leucocyte-enriched plasma, and to investigate: (i) the effect of temperature and other factors on labelling efficiency; (ii) the selectivity for different leucocyte types; (iii) the viability of the labelled cells and efflux of the radiolabel; and (iv) the physical characteristics of the colloid. Density gradient centrifugation was used to investigate the labelling efficiency, cell selectivity and efflux, Trypan blue to study the viability, and laser scattering, electron microscopy and membrane filtration to investigate particle size and morphology. Particles appeared as loose, coiled, chain-like aggregates of much smaller particles (<0.05 microm). The aggregate diameter ranged from <0.1 to >5 microm and increased with time. The distribution of radioactivity amongst the particle sizes varied widely. The labelling efficiency in leucocyte-rich plasma was enhanced at 37 degrees C compared to room temperature, and by centrifuging during labelling. The selectivity for different leucocyte types varied markedly between batches and blood samples, in some cases showing preference for mononuclear cells and in others for granulocytes. Viability was excellent and comparable with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO)-labelled cells. A significant fraction of radiolabel, comparable to that observed with 99mTc-HMPAO, was lost from leucocytes during incubation in vitro over 4 h. Thus, 99mTc-SnF2 is a convenient, efficient labelling agent for leucocytes, but shows variable cell selectivity which may be linked to particle size variability, and there is significant efflux of radioactivity from labelled cells.

Cell Survival↗
PubMed2004

Impact of particle size and aerosolization time on the metabolic effect of an inhaled insulin aerosol.

The effects were compared of varying aerosol particle size and aerosolization time within each breath on the metabolic effect elicited by inhalation of a liquid insulin aerosol in comparison with that after subcutaneous injection (s.c.) of regular insulin. In this single-center, open-label euglycemic glucose clamp study, 13 healthy non-smoking subjects received five administrations of insulin in randomized order on separate study days, once by s.c. (0.15 U/kg of regular insulin) and four times by inhalation. Subjects inhaled 1.5 U/kg of liquid insulin aerosol administered by the Aerodose Insulin Inhaler (Aerogen Inc., Mountain View, CA) configured to deliver two aerosol particle sizes--fine [F, 4.4 +/- 0.3 microm (mean +/- SD)] or very fine (VF, 3.5 +/- 0.2 microm)--and two aerosolization times (aerosol released for the first 2 or 4 s after the start of each 5-s inhalation). Glucose infusion rate (GIR) values necessary to keep blood glucose concentrations constant at 5.0 mmol/L were determined over a 6-h period following insulin administration. After inhalation of insulin, the onset of action was substantially more rapid on all four inhalation study days than after s.c. insulin, and the time to maximal action [t(GIRmax) (min)] was reached earlier: F/2 s, 127 +/- 54; F/4 s, 128 +/- 55; VF/2 s, 158 +/- 91; VF/4 s, 132 +/- 72; s.c., 175 +/- 69 (P < 0.0001). The longer aerosolization time (4 vs. 2 s) resulted in higher maximal metabolic action [GIR(max) (mg/kg/min), F/4 s 8.1 +/- 3.6, VF/4 s 8.4 +/- 2.7 vs. F/2 s 6.6 +/- 2.4, VF/2 s 7.2 +/- 2.4 (P = 0.01 for 4 s vs. 2 s, grouped data)], total metabolic activity [area under the curve of GIR 0-6 h (g/kg), F/4 s 1.97 +/- 0.92, VF/4 s 2.14 +/- 0.86 vs. F/2 s 1.56 +/- 0.68, VF/2 s 1.78 +/- 0.60 (P = 0.01)], and relative biopotency [F/4 s 10.6 +/- 4.0%, VF/4 s 11.7% +/- 4.1% vs. F/2 s 8.5 +/- 3.2%, VF/2 s 9.7 +/- 2.4% (P = 0.01)]. None of these summary measures was significantly affected by particle size. No drug- or device-related adverse events were observed. This study shows that aerosolization time, but not particle size, in the ranges studied, had an impact on the metabolic effect elicited by inhaled insulin, allowing rational selection of delivery parameters for further clinical testing. Based on the observed biopotency and the rapid onset of action, inhalation of a liquid insulin aerosol generated by the Aerodose Insulin Inhaler shows promise for covering prandial insulin requirements.

Administration, Inhalation↗
PubMed2001

Comparison of particle sizing techniques in the case of inhalation dry powders.

The objectives of this work were (i) to validate electrical zone sensing and laser diffraction for the analysis of primary particle size in the case of inhalation dry powders and (ii) to study the influence of the aggregation state of the powder on the sizing techniques. Free-flowing dry powders were prepared by spray-drying with a combination of albumin, lactose, and dipalmitoylphosphatidylcholine. The replacement of lactose by mannitol, the removal of albumin, and the atomization at high relative humidity all increased powder cohesion. Automated measurements were compared with primary particle sizes collected by light and electron microscopy. The mass mode obtained by electrical zone sensing and the mass median diameter measured by laser diffraction following dispersion with compressed air at a pressure of 3 bar or following suspension in water and ultrasonic dispersion at a power of 60 W for 30 s each provided primary particle sizes close to microscopy measurements. However, these conditions only applied in the case of slightly to moderately aggregated powders. For strongly agglomerated powders, an exact measurement of the size was only collected by laser diffraction in the wet state combined with ultrasonic dispersion. Our study underlies how measurement of primary particle size highly depends on both powder material and proper particle dispersion.

Administration, Inhalation↗
PubMed2000

The metabolic syndrome, LDL particle size, and atherosclerosis: the Atherosclerosis and Insulin Resistance (AIR) study.

An operative definition of the metabolic syndrome has been suggested by a working group associated with the World Health Organization in 1998. The aim of this study was to examine whether small, low density lipoprotein (LDL) particle size was associated with the metabolic syndrome and with subclinical atherosclerosis as measured by ultrasound in the carotid and femoral arteries. The study was performed in a population-based sample of clinically healthy men (N=391), all 58 years old and not undergoing any treatment with cardiovascular drugs. Exclusion criteria were cardiovascular or other clinically overt diseases or continuous medication with cardiovascular drugs. The results showed that subjects characterized by the metabolic syndrome (n=62) had a thicker mean intima-media complex (IMT) in both the carotid and femoral arteries (0.86 versus 0.77 mm, P:<0.001, and 1.03 versus 1. 00 mm, P:=0.022, respectively) and also lower mean values for LDL particle size (25.78 versus 26.80 nm, respectively, P:<0.001) compared with subjects with no risk factors (n=77). The group with the metabolic syndrome (n=62) also had higher mean values for serum cholesterol and heart rate. In the whole study group (N=391), there were significant but weak negative relationships between small LDL particle size, increasing IMT, and increasing cross-sectional intima-media area of the carotid and femoral arteries and also negative relationships between LDL particle size and plaque occurrence and size in the carotid and femoral arteries. In summary, this is the first large-scale study to demonstrate a relationship between the clustering of risk factors that constitute the metabolic syndrome and a small LDL particle size pattern and the occurrence of preclinical atherosclerosis in the carotid and femoral arteries, as assessed by the ultrasound technique, in healthy 58-year-old men recruited from the general population.

Arteriosclerosis↗
PubMed1997

Metered dose inhalers III: Metaproterenol sulphate; particle size distribution and dose uniformity.

Three American products and one Canadian product were examined for content uniformity and particle size distribution. The results showed that not all products performed equally well. Some of the products exhibited high sprays early in the canister lifetime and all products demonstrated loss of prime. The particle size distributions were determined using the Andersen cascade impactor (USP Induction Port) and the fine particle fraction was determined using the twin impinger. The results showed that three of the four products had similar particle size distribution profiles. Both the Andersen cascade impactor and the twin impinger yielded the same trends in the amount of drug substance delivered to the fine particle fraction.

Bronchodilator Agents↗
PubMed1988

Effect of viscosity on particle size, deposition, and clearance of nasal delivery systems containing desmopressin.

The effect of methylcellulose on the particle size distribution and dosing accuracy of pre-metered spray pump devices containing the peptide desmopressin (DDAVP) was investigated. Using gamma scintigraphy, the influence of methylcellulose on the in vivo deposition and clearance of nasal solutions administered as drops or spray was studied. Nasal formulations containing 0, 0.25, and 0.50% methylcellulose produced a dose-related increase in average particle size from 51 micron for 0% to 81 and 200 micron for 0.25 and 0.50% methylcellulose, respectively. However, no effect was observed on the dosing accuracy of the spray pumps. The addition of methylcellulose gave a more localized in vivo deposition in the anterior region of the nasal vestibule. However, the net effect on clearance followed a biphasic pattern which showed an increase in retention time for the 0.25% solution, followed by a decrease in retention time and faster clearance time for the 0.50% solution. The spray delivers well-controlled doses to the nasal cavity. These findings show that viscosity, particle size, and nasal clearance are important parameters in the design of nasal delivery systems.

Administration, Intranasal↗
PubMed1996

Qualitative investigation of uptake of fine particle size microcrystalline cellulose following oral administration in rats.

A subchronic toxicity study was conducted to evaluate the potential toxicological effects associated with intestinal translocation of a special fine particle size (median particle size 6 microns) microcrystalline cellulose (MCC). Four groups of Sprague-Dawley rats (20/sex/group) received either 0 (control), 500, 2500 or 5000 mg/kg/day MCC (25% w/v in tap water) daily by oral gavage for 90 d. At study termination, organs and tissues from high-dose and control animals, including multiple sections of intestine with gut-associated lymphoid tissue, were processed for light microscopy with subsequent examination under polarised light for the presence of birefringent MCC particles. None were observed in any tissue examined. No toxicologically significant effects or lesions were found in any other parameter or organ evaluated. The 'no observed adverse effect level' (NOAEL) for toxicological effects was greater than 5000 mg/kg/day MCC, which was the highest dosage tested. These results further verify the safety of commercial MCC products for use in food and pharmaceutical applications.

Administration, Oral↗
PubMed1984

The influence of agitation intensity, particle size and pH of dissolution fluid on the in-vitro release of drug from hard gelatin capsules.

The influence of agitation intensity on the in-vitro release of controlled particle size fractions of acetylsalicylic acid from hard gelatin capsules into buffered dissolution fluids has been investigated employing a dissolution technique. The value of T50 decreased as the stirring rate increased from 120 to 320 rev min-1 for all particle size fractions and pH values. A further increase in the stirring rate had a limited effect on the value of T50 and the changes were particle size dependent. The influence of the drug solubility, induced by changing the pH of the dissolution fluid, was decreased by increased agitation. When the capsules were filled at bulk densities above the maximum tapped bulk density, the value of T50 was increased, the extent of increase being greater the smaller the particle size of the drug. The kinetics of the solution process were influenced by agitation intensity and particle packing.

Aspirin↗
PubMed2005

Effect of premolar and molar occlusal angle on feed digestibility, water balance, and fecal particle size in horses.

OBJECTIVE: To determine whether occlusal angle of the premolar and molar teeth (ie, molar occlusal angle) was associated with feed digestibility, water balance, or fecal particle size in adult horses. DESIGN: Observational study. ANIMALS: 40 pregnant mares ranging from 3 to 19 years old. PROCEDURE: The horses were randomly allocated to 1 of 5 feeding groups with 8 horses/group. Horses were sedated, and molar occlusal angle was measured with 2 methods. An oral examination was performed, and total number of dental abnormalities was recorded. Feed digestibility, water balance, and fecal particle size were measured 7 and 16 weeks later. RESULTS: Molar occlusal angle ranged from 6.3 degrees to 19.3 degrees and was not significantly associated with feed digestibility, water balance, or fecal particle size. The number of dental abnormalities was not associated with feed digestibility. Molar occlusal angle did not vary significantly with horse age. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that molar occlusal angles between 6 degrees and 19 degrees do not adversely affect feed digestibility, water balance, or fecal particle size in adult horses. Additionally, there was no association between age and molar occlusal angle.

Animals↗
PubMed2001

Change in particle size of pectin reacted with pectinesterase isozymes from pea (Pisum sativum L.) sprout.

Four pectinesterase (PE) isozymes were isolated by CM-Sepharose CL-6B chromatography from etiolated pea (Pisum sativum L.) sprouts and then reacted with citrus pectin (degree of esterification = 68%, 30-100 kDa) to observe the change in pectin particle size using a laser particle size analyzer. After incubation of a pectin-PE mixture (pH 6.5) at 30 degrees C for 4 h, PE 1 was observed to catalyze the transacylation reaction most remarkably, increasing the particle size from approximately 50-70 to approximately 250-350 nm, followed by PE 3, PE 2, and PE 4.

Carboxylic Ester Hydrolases↗
PubMed1999

Relationship between the apolipoprotein E and angiotensin-converting enzyme genotypes and LDL particle size in Japanese subjects.

We investigated whether the apolipoprotein E (apoE) and the angiotensin-converting enzyme (ACE) genotypes contribute to the variance in low-density lipoprotein (LDL) particle size in Japanese subjects (n = 136; M/F= 106/30). ACE polymorphism was associated with neither LDL size nor individual lipid levels. In contrast, the subjects with the epsilon2 allele of the apoE genotype had significantly lower levels of total cholesterol (P = 0.002) and LDL cholesterol (P = 0.004) compared with those without the epsilon2 allele. The subjects with the epsilon4 allele had a significantly smaller LDL particle size than those without the epsilon4 allele (P = 0.012). Separate analyses of the male subjects showed similar associations. A stepwise regression analysis revealed the epsilon4 allele to be an independent contributing variable that could affect LDL particle size. Our results suggest that the apoE genotype is associated with the development of atherosclerotic disease, since the epsilon2 and epsilon4 alleles relate to a decrease in LDL cholesterol levels and a decrease in LDL particle size, respectively.

Adult↗
PubMed2005

Distribution of aged 14C-PCB and 14C-PAH residues in particle-size and humic fractions of an agricultural soil.

Organic matter is considered to be the single most importantfactor limiting availability and mobility of persistent organic pollutants (POPs) in soil. This study aimed to characterize the distribution of 14C-PCB (congeners 28 and 52) and 14C-PAH (fluoranthene and benzo[a]pyrene) residues in an Orthic Luvisol soil obtained from two lysimeter studies initiated in 1990 at the Agrosphere Institute (Forschungszentrum Jülich GmbH, Germany). The lysimeter soils contained a low-density OM fraction, isolated during soil washing, which contained a significant fraction (3-12%) of the total 14C-activity. Soils were also fractionated according to three particle sizes: >20, 20-2, and <2 microm. Relative affinity values of 14C-activity for the different particle sizes varied in the order 20-2 microm > (<2 microm) approximately (>20 microm) for the PCBs. Relative affinity values of 14C-activity for the different particle sizes varied in the order 20-2 microm > (<2 microm) > (>20 microm) for the PAHs. The distribution of 14C-PCB or 14C-PAH residues in the organic and inorganic matrixes of the particle-size fractions was determined using methyl isobutyl ketone (MIBK). 14C-PCB and 14C-PAH-associated activities were primarily located in the humin fraction of the 20-2 and <2 microm particle-size fractions of the soil. A small fraction was associated with the fulvic and humic acid fractions; these were quantitatively more important for the PAHs than the PCBs. There appeared to be a high degree of association of 14C-activity with the mineral fraction following MIBK separation of the humic fractions, ranging between 8 and 52% for 14C-PCBs and 57-80% for 14C-PAHs. The mineral (inorganic) component of the soils apparently played a significant (previously unreported) role in the sequestration of both PCBs 28 and 52 and the PAHs fluoranthene and benzo[a]pyrene.

Agriculture↗
PubMed1998

Particle size dependent molecular rearrangements during the dehydration of trehalose dihydrate in situ FT-Raman spectroscopy.

PURPOSE: (1) To characterise the different phases of trehalose using FT-Raman spectroscopy. (2) To monitor the changes in the structure of trehalose dihydrate on isothermal heating at 80 degrees C. METHODS: Different phases of trehalose were prepared and FT-Raman spectra obtained. Trehalose dihydrate was sieved to < 45 microns and > 425 microns particle size fractions and FT-Raman spectra were obtained at various time intervals during heating at 80 degrees C. RESULTS: During heating at this temperature, the spectra of a < 45 microns particle size fraction showed a loss of peak resolution with time and after 210 minutes resembled the spectrum of amorphous trehalose prepared by lyophilisation, indicating that the material was rendered amorphous by heating. In contrast, spectra obtained from a > 425 micron particle size fraction altered with time and became characteristic of the crystalline anhydrate. The approximate kinetics of this transformation to the anhydrate were monitored by analysis of peak intensity ratios with time. A two state rearrangement was indicated; some functional groups appeared to manoeuvre into the spatial arrangement found in the anhydrate initially before the rest of the ring structure relaxed into this conformation. This may be due to some parts of the molecule being immediately affected by the loss of the water molecules on dehydration prior to the subsequent reorientation of the entire molecule into the anhydrate crystal lattice. CONCLUSIONS: The < 45 micron particle size fraction becomes disordered on dehydration induced by heating at 80 degrees C whilst the > 425 micron particle size fraction crystallises to the anhydrate under the same conditions.

Calorimetry, Differential Scanning↗
PubMed2002

Characterization of synthetic adsorbents with fine particle sizes for preparative-scale chromatographic separation.

Synthetic adsorbents with fine particle sizes (15-30 microm) were manufactured. These adsorbents are made of poly(styrenedivinylbenzene) and polymethacrylate, and have the same chemical structure as analytical- (5-10 microm) or industrial- (200-600 microm) grade synthetic adsorbents. Both of them have very similar porous structure to those of analytical or industrial sizes, so that they can adsorb compounds of various molecular masses. Chromatographic separation characteristics of newly manufactured fine-particle grades of synthetic adsorbents were evaluated and compared to those of analytical or industrial adsorbents. Reasonable dependency of separation performance on particle size of synthetic adsorbents was obtained. Hydraulic properties of fine-grade adsorbents had also been measured in view of column operations. Furthermore, scalability and applicability of these adsorbents for preparative-scale chromatographic separation of bioactive compounds was evaluated. Separation of soybean isoflavones and tea catechin derivatives had revealed that fine-grade synthetic adsorbents could be well applied with scalability under the same elution conditions used for analytical use. Scalability up to a 22400-fold loading amount was achieved from a small column packed with analytical-grade adsorbent used for method development to a scale-up preparative column packed with fine-grade adsorbent used for preparative purification. These results showed the usefulness of the fine-grade synthetic adsorbents for more precise purification of bioactive compounds, including pharmaceuticals and functional food additives with higher recovery.

Adsorption↗
PubMed2003

Application of frequency domain photon migration to particle size analysis and monitoring of pharmaceutical powders.

The frequency domain photon migration (FDPM) technique was employed to determine mean particle size of pharmaceutical powders. Results show that the FDPM-measured scattering coefficient increases linearly with reciprocal mean particle size of powdered samples. In contrast to near-infrared spectroscopy techniques, FDPM technique enables determination of scattering and absorption separately so that it does not require data pretreatment and chemometric calibration models. In addition, this unique advantage provides more detailed information about powder samples, which can be used as a potential tool for on-line monitoring of not only variation of active pharmaceutical ingredient concentrations from changes in the absorption coefficient but also variation of particle sizes from changes in the scattering coefficient.

Chemistry, Pharmaceutical↗