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At least 19 recordsLinked to original sources
PubMed1979

Effect of drug content and drug particle size on the change in particle size during tablet compression.

Three size fractions for each of three poorly soluble drugs were compressed into 10 mm diameter tablets of four different dilution ratios. The compression was carried out on a physical testing instrument at four compression levels of 49.0, 98.1, 196.2 and 294.3 MN m-2. The effect of drug content and drug particle size on the change in particle size during tableting was examined by the determination of the dissolution rate for disintegrated tablets. A linear relation was obtained when plotting 1n(T80%) versus drug content. There was a critical particle size where the phenomena of cleavage and bonding during tableting balanced each other, but this varied with drug content.

Chemistry, Pharmaceutical↗
PubMed1991

Effects of grass maturity and legume substitution on large particle size reduction and small particle flow from the rumen of cattle.

Five ruminally and abomasally cannulated heifers (average weight 365 kg) were fed 6 kg/d of early (EOG) or late (LOG) maturity orchardgrass (OG) hay with or without replacement of EOG or LOG by 1.5 kg/d red clover hay (RC) in a 5 x 5 Latin square design. A fifth treatment, of LOG supplemented with 100 g/d casein (LOG + C), was used to evaluate the effect of supplemental protein. In situ fiber digestion, in vivo nutrient digestion and rate of passage from the rumen of large (retained on a 1.68-mm screen; labeled with La) and small (passed a 1.68-mm screen; labeled with Sm) EOG and LOG particles were determined in heifers fed these diets. Early maturity OG hay had 20% and 62%, respectively, greater (P less than .05) rates, and 61% and 73%, respectively, greater (P less than .05) extents of in situ NDF and ADF disappearance than LOG. Red clover substitution for OG increased (P less than .05) in situ extent of NDF disappearance by 6%. Early maturity OG large and small particles had 40% and 36%, respectively, greater (P less than .05) rates of passage than LOG. Large and small particle ruminal pool sizes were increased (P less than .05) by 115% and 33%, respectively, with LOG. Red clover substitution for OG increased (P less than .10) large and small particle output (kg/d) from the rumen by 15% and large particle rate of passage by 20%. Grass maturity may be affecting intake through rate of large particle size reduction and passage and small particle passage, although legume supplementation of OG may influence intake by increasing rate of large particle size reduction and passage.

Animal Feed↗
PubMed1975

Biopharmaceutical factors influencing LD50. Part II: Particle size.

The effect of particle size on the time elapsing between administration and loss of righting reflex and % of deaths by determining the LD50 has been studied in mice. The drug used was pentobarbituric acid. In one preparation the particle size was less than 44 mum and in the other preparation it was greater than 297 mum and less than 420 mum. For both preparations a 1% sodium carboxymethylcellulose solution was used as suspending medium. It was found that both the curve for loss of righting reflex and the log dose-response curve, and hence the LD50, were significantly shifted to the right. There is a reflex LRR between the suspended pentobarbituric acid and the equivalent amount of sodium pentobarbital, both in 1% sodium carboxymethylcellulose solution. In reporting LD50 data it is essential not only to state the exact composition of the vehicle (viscosity factor) but also to state the exact particle size or particle size range, because by using increasing particle size the LD50 decreases.

Absorption↗
PubMed1991

Effect of particle size on phagocytosis of latex particles by guinea-pig polymorphonuclear leucocytes.

The effect of the size of foreign particles on phagocytosis by guinea-pig polymorphonuclear leucocytes (PMNs) was investigated using latex particles having approximately the same surface potentials but different sizes. Two types of latexes with different negative surface potentials, those having amino groups (Ami-latexes) and those having carboxylic acid groups (Ca-latexes), were used in this experiment. Since Ca-latexes had different surface potentials for different particle sizes, the carboxylic acid groups were modified by the carbodiimide method to make the surface potentials almost equal. Phagocytosis was estimated by the rate of oxygen consumption. It was found that the phagocytosis reached its maximum when the latex particle size was about 0.5 microns. This finding was plausibly explained by considering the two probabilities that a latex particle comes into contact with a PMN surpassing a potential barrier and the contact takes place at certain receptor areas favourable to phagocytosis on the PMN surface.

Animals↗
PubMed1991

Nominal response of passage rates to fiber particle size in rats.

The influence of wheat bran particle size on the rate of passage of digesta through the rat gut was investigated. Small and large particle size wheat bran-supplemented diets were used in combination with the particulate digestion marker chromium mordanted bran (CrMB) and the soluble digestion marker cobalt-EDTA (Co EDTA). The particle size of CrMB did not significantly affect the estimates of marker residence halftime (t 1/2), mean retention time or transit time, when administered to animals fed a large particle bran diet. Utilization of different particle size bran diets and a common small particle CrMB marker tended to result in a longer t 1/2 and mean retention time in the smaller particle bran diet. Therefore, the selection of dietary particle size, but not CrMB particle size, tended to influence the estimates of t 1/2 and mean retention time. Similarly, the Co EDTA t 1/2, mean retention time and transit time tended to be longer in small particle bran-fed animals than in large particle bran-fed animals. In some comparisons the mean retention time of Co EDTA was significantly less (P less than 0.05) than that of CrMB, indicating that preferential retention of particles relative to solutes can occur in rats. Nevertheless, the overall movement of the liquid and particles largely corresponded.

Animals↗
PubMedDate not supplied

Effect of particle size on lead absorption from the gut.

The relationship between particle size and absorption of lead particles from the gastrointestinal tract of the rat has been investigated. Preparations of metallic lead of particle size between 0 and 250 micron were incorporated in laboratory rat diets and absorption determined by measurement of tissue lead concentrations attined under standard conditions. An inverse relationship was found between particle size and lead absorption; this relationship was most marked in the 0 to 100 micron range. A five-fold enhancement of absorption was observed from the diet with lead particles of mean size 6 micron, compared with 197 micron particle size. Lead absorption from dried pain films containing lead chromate and lead octoate was measured using a similar technique. A marked enhancement of absorption was observed for both paints when particle size was reduced from 500 to 1,000 micron to less than 50 micron.

Animals↗
PubMed1992

Fat emulsion particle-size distribution in total nutrient admixtures.

The fat particle-size distribution in and physical stability of two commercially available lipid emulsions before and after their use in total nutrient admixtures (TNAs) are reported. Four TNAs without electrolytes and four TNAs with electrolytes were prepared; each type of TNA was prepared with Liposyn II and with Intralipid. Particle size was measured in the < 1-micron range by using photon correlation spectroscopy and in the 2-60-microns range by using light blockage. Admixtures with or without electrolytes were stored for two or nine days at 4 degrees C followed by one day at 25 degrees C. For the fraction of fat particles of < 1 micron in diameter, Intralipid and Liposyn II had a mean particle size of 374 and 313 nm, respectively. The admixtures containing electrolytes showed a decrease in mean particle size of about 7%. Admixtures with Intralipid contained 2 x 10(7) particles larger than 2 microns per milliliter (1.7% of total fat), compared with 1 x 10(6) particles per milliliter (0.05-0.15% of total fat) for admixtures with Liposyn II. The addition of electrolytes increased the particle counts for Liposyn II-containing admixtures. Upon storage, Intralipid-containing admixtures with electrolytes showed an initial increase followed by a decrease in the mean diameter of particles of < 1 micron. All the admixtures were stable in terms of pH and visual appearance. Intralipid-containing admixtures with electrolytes showed a decrease in the number of particles in the 2-60-microns size range, while Liposyn II-containing admixtures with electrolytes showed an increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Incompatibility↗
PubMed1979

Colloidal particle-size determination by gel filtration.

The particle sizes of technetium-99m sulfur colloid and technetium-99m antimony sulfide colloid are determined by gel filtration. These results are compared with those obtained by electron microscopy and by ultrafiltration. It is shown that gel filtration is suitable for particle-size determination below 100 nm, whereas above this size ultrafiltration provides the most convenient method.

Chromatography, Gel↗
PubMed1992

Low density lipoprotein particle size and coronary artery disease.

Decreased plasma low density lipoprotein (LDL) particle size has been associated with premature coronary artery disease (CAD). We examined LDL particle size by 2-16% gradient gel electrophoresis in 275 men with CAD (greater than 75% cross-sectional-area stenosis) and 822 controls. Seven major LDL size bands (with LDL-1 [d = 1.025-1.033 g/ml] being the largest and LDL-7 [d = 1.050-1.063 g/ml, the smallest]) were identified. Because most subjects had two or more adjacent LDL bands, an LDL score was calculated for each subject, with the relative area in each band taken into consideration. Four major LDL particle size groups were classified in the present studies: large LDL, intermediate LDL, small LDL, and very small LDL. The use of beta-blockers was significantly associated with smaller LDL particles. After adjusting for use of this medication, small LDL particles were still more prevalent in CAD patients (39%) compared with controls (27%). The prevalence of large LDL particles was lower in CAD patients (3%) than in controls (24%). Intermediate LDL particles were the most prevalent in both groups, 49% in CAD patients and 46% in controls. The difference in LDL particle size between CAD patients and controls was not independent but was highly associated (p less than 0.0001) with elevated triglyceride levels and decreased high density lipoprotein (HDL) cholesterol levels. Significantly higher LDL cholesterol levels were found in subjects with intermediate and small LDL particles than in those with large or very small LDL particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1975

The effect of particle size on absorption of inhaled lead.

Baboons were exposed to dust clouds of Ph3O4 of different size distribution but of the same total gravimetric concentration. Blood samples were taken immediately after each exposure of 4 hours and the total blood lead was determined. The exposure to the lead-bearing dust was stopped after four weeks, but the blood sampling continued for another six weeks. Graphs are presented comparing the patterns of lead absorption obtained with different sized lead particles. The coarser lead particles resulted in a higher blood lead concentration than the finer.

Absorption↗
PubMed1992

Changes in particle size of high density lipoproteins during incubation with very low density lipoproteins, cholesteryl ester transfer protein and lipoprotein lipase.

Previous reports have produced conflicting views of the effects of lipoprotein lipase (LPL) on the particle size distribution of high density lipoproteins (HDL). In this study we have investigated the changes in particle size of HDL promoted by the interaction of LPL, the cholesteryl ester transfer protein (CETP) and very low density lipoproteins (VLDL). When the plasma fraction of d less than 1.21 g/ml (containing all lipoprotein fractions) was incubated for 24 h with bovine milk LPL alone or with CETP alone, there was relatively little change in the particle size distribution of HDL. When both LPL and CETP were added to the lipoprotein mixture, there was a substantial reduction in the particle size of HDL. This reduction in HDL particle size was found to be a direct function of the concentration of CETP. It was also influenced by the concentrations of VLDL and LPL, although in these cases the relationships were complex. When mixtures of the plasma fraction of d = 1.006-1.21 g/ml (this fraction includes low density lipoproteins and HDL but not VLDL) were supplemented with both LPL and CETP and incubated in the presence of varying concentrations of added VLDL, there was a progressive increase in the conversion of HDL into very small HDL particles of radius 3.7 nm as the concentration of VLDL triacylglycerol increased up to about 400 nmol/nml. However, further increases in the concentration of VLDL were accompanied by a progressive reduction in the formation of small HDL particles until, at higher VLDL concentrations, the effect was all but abolished. There was a similar enhancement in the formation of small HDL when LPL was added at low but not at high concentrations. These findings are consistent with the existence of two opposing processes. On the one hand there is likely to be a synergism between CETP and the non-esterified fatty acids (NEFA) released by LPL; this will favour a reduction in HDL particle size. On the other hand, the transfer of lipolysis products from VLDL to HDL may mask any such particle size reduction. The fact that the reduction in HDL particle size promoted by LPL, CETP and VLDL was found to be all but abolished by adding fatty acid-poor albumin to the incubation mixture is consistent with the proposition that NEFA are involved in the process. It also suggests, however, that the phenomenon may have little if any physiological significance.

Adult↗
PubMed1991

Effects of various non-esterified fatty acids on the particle size redistribution of high density lipoproteins induced by the human cholesteryl ester transfer protein.

The effects of various non-esterified fatty acids on the CETP-mediated particle size redistribution of HDL were studied by incubating HDL3 and CETP for 24 h at 37 degrees C in the absence or in the presence of either saturated, monounsaturated or polyunsaturated non-esterified fatty acids. In the absence of non-esterified fatty acids, CETP induced a redistribution of the initial population of HDL3 (Stokes' radius 4.3 nm) by promoting the appearance of one larger (Stokes' radius 4.8 nm) and two smaller (Stokes' radii 3.9 and 3.7 nm) HDL subpopulations. Whereas the non-esterified fatty acids alone did not modify the HDL3 distribution profile, they were able to alter markedly the capacity of CETP to induce the particle size redistribution of HDL. All the saturated fatty acids with at least 10 carbons were able to increase the formation of the very small sized particles (Stokes' radius 3.7 nm) in a concentration dependent manner, the medium chain fatty acids (12 and 14 carbons) being the best activators. The potential effect of non-esterified fatty acids was also influenced by the presence of double bonds in their monomeric carbon chain. While at low concentrations of non-esterified fatty acids (0.1 mmol/l) the enhancement of the formation of very small HDL particles appeared to be greater with oleic and linoleic acids than with stearic acid, at higher concentrations (0.4 mmol/l), oleic, linoleic and arachidonic acids decreased the formation of the 3.7 nm radius particles. The inhibition of the process at high concentrations of unsaturated fatty acids was linked to the degree of unsaturation of their carbon chain, arachidonic acid being the strongest inhibitor. The present study has demonstrated that non-esterified fatty acids can modulate the particle size redistribution of HDL3 mediated by the cholesteryl ester transfer protein even in the absence of any other lipoprotein classes. The effect of non-esterified fatty acid is dependent on both the length and the degree of unsaturation of their monomeric carbon chain.

Carrier Proteins↗
PubMed1978

The influence of digoxin particle size on absorption of digoxin and the effect of propantheline and metoclopramide.

1 The influence of particle size on absorption of digoxin was studied in ten healthy volunteers who received 0.5 mg digoxin as two standard Lanoxin tablets, or tablets containing micronized digoxin or large particle size digoxin. Tablets were given 30 min after 15 mg propantheline, 10 mg metoclopramine or a placebo tablet, and following an overnight fast. 2 The overall mean cumulative 4 day urinary excretion of digoxin was significantly lower (P less than 0.01) after large particle size digoxin than after standard or micronized digoxin. Mean cumulative urinary excretion following large particle size digoxin was reduced when administered after metoclopramide and increased after propantheline, the difference between these two treatments being significant (P less than 0.05). There was a significantly lower (P less than 0.05) overall mean cumulative excretion following standard by comparison with micronized digoxin. However, by comparison with placebo, neither metoclopramide nor propantheline significantly altered mean cumulative excretion after standard or micronized digoxin. Propantheline and metoclopramide affect absorption of digoxin from formulations of large particle size and slow dissolution rate only.

Adult↗
PubMed1976

Particle size of dexamethasone incorporated in ointment and its behaviour during penetration in the stratum corneum of living skin.

The particle size of dexamethasone was microscopically determined in polarized light in two emulsion ointments: a standard water-in-old formula (aqueous wool alcohol ointment), and a standard oil-in-water formula (aqueous hydrophilic ointment), both containing 0.023% dexamethasone. The distribution of dexamethasone was on average smaller and finer in the water-in-oil emulsion than in the oil-in-water emulsion. In a further series of experiments we studied by means of the adhesive tape-stripping method the proportions of the particle size and counted the total number of particles in various layers of the stratum corneum in vivo. The difference between the two emulsion types once again proved to be significant, but only as far as the epidermal barrier. A new, uniform particle size spectrum was formed at this level, having a maximum value of 24 mum, which, irrespective of the type of ointment, allows a release of the desamethasone in the live epidermis and dermis. The original particle size distribution is thus qualitatively insignificant in so far as the therapeutic effect of dexamethasone below the barrier zone is concerned. Since the particle size has a strongly distorted frequency distribution, with amarked shift to the left, only about 0.5% of the particles in the w/o emulsion and only about 2% in the o/w emulsion are in fact larger than 56mum, the maximum value measured lying just below the surface of the horny layer. Any loss during further penetration is probably negligible.

Administration, Topical↗
PubMed1991

Abnormal particle size of lipoprotein in non-insulin-dependent diabetics and nondiabetics with and without hyperlipidemia.

To clarify the mechanism of the high incidence of ischemic heart disease in the diabetics, we studied the particle size of the lipoprotein with particular attention to the structural abnormality. Using high performance liquid chromatography, the particle size of the lipoprotein was determined with elution volume, which was precisely correlated with the particle size. The particle size of low density lipoprotein (LDL) from the diabetics with normolipidemia is larger than that from the nondiabetics (p less than 0.001) in the elution pattern of triglyceride. The examination of the elution pattern of the triglyceride and cholesterol revealed that this large LDL was composed of a large amount of triglyceride. These characteristics of the large LDL resembled that of the atherogenic intermediate density lipoprotein. The particle size of high density lipoprotein (HDL) from the diabetics with normolipidemia was larger than that from the nondiabetic controls (p less than 0.001), detected by the elution pattern of triglyceride. The comparison of the triglyceride and cholesterol elution pattern indicated that also the large HDL in the diabetics with normolipidemia was rich with triglyceride, which was reported to inhibit the activity of the lipid transfer protein. These facts revealed that the disorder of the lipid metabolism not accompanied with hyperlipidemia produced the large LDL and HDL, which might lead to the excess mortality rate of the ischemic heart disease in the diabetics even with normolipidemia.

Chromatography, High Pressure Liquid↗
PubMed1978

Variable-cut particle-size classification by opposing jets.

A new technique of aerodynamic particle-size classification has been developed utilizing axisymmetrically-opposed air jets. For a fixed geometry the cut size can be varied from 0.8 to 3.6 micrometer by changing the jet flow rates. Future designs are expected to extend the useful particle-size range. Particles remain airborne after size separation, permitting the use of continuous, automated methods for analyzing the particle concentration and chemical compositon.

Air Pollutants↗