Irving F. Miller

On the adsorption of serum proteins on polymer membrane surfaces

Abstract A detailed study of the adsorption and desorption of bovine serum albumin, γ-globulin, and fibrinogen at physiological conditions on a series of polymer membranes, both cation exchangers and neutral, has been carried out. The results obtained indicate that adsorption takes place in two separate and distinct ways simultaneously. Both types of adsorption are apparently Langmuir (monolayer) in type, taking place on separate membrane sites and are noninteracting. One type of adsorption is characterized as being relatively hydrophilic, exothermic, and easily reversible with a heat of adsorption in the neighborhood of −10 kcal/ mole. The other type of adsorption is apparently tightly bound, hydrophobic, and endothermic, with heats of adsorption ranging from ∼5 kcal/mole to ∼20 kcal/mole.

Cardiorespiratory effects of exchange transfusions with synthetic erythrocytes in rats

Synthetic erythrocytes (SE) can maintain life with near-normal hemodynamics in rats with hematocrits (Hct) 45% below the lethal levels, as shown when we exchanged virtually all their blood. We compared cardiorespiratory variables between the SE and control animals, which were hemodiluted with 7% albumin, at the 78% exchange level. In addition, SE animals at 92% exchange were compared with the 78% exchange and baseline levels.All our control rats died at Hct above 5% with corresponding oxygen-carrying capacity of 2.65 ml/dl. All SE rats survived, having a final Hct of 2.96% with an oxygen-carrying capacity of 7.05 ml/dl. SE animals maintained normal BP and marginally increased cardiac output, while control animals did not. Vascular resistance of control animals at 78% exchange was reduced to 30%, while in SE animals at 92% exchange, vascular resistance was lowered to 80% of baseline values.

Effect of Particle Morphology on Emitted Dose of Fatty Acid-Treated Disodium Cromoglycate Powder Aerosols

These studies assess the quantity and morphology of the emitted aerosolized dose of irregularly shaped disodium cromoglycate particles in the fine particle fraction using in vitro methods. Disodium cromoglycate was treated with a homologous series of saturated fatty acids, between C8 and C18, in a range of concentrations. The products of these treatments were powders with a variety of particle size, shape, and aggregation characteristics. Samples of these powders were loaded in gelatin capsules, generated as aerosols from a Rotahaler and collected in a two-stage liquid impinger or eight-stage inertial impactor. Particles were examined directly by scanning electron microscopy and subsequently the images were analyzed to define morphology. The aerodynamic fine-particle fraction determined by the two-stage impinger increased approximately twofold with lauric acid treatment (0.0317 g/g, 6.7%) and threefold with stearic acid treatment (0.58 g/g; 9.7%) compared with disodium cromoglycate alone (0 g/g, 3.56%). The lauric acid formulation appeared to alter deposition primarily by changing particle morphology. Stearic acid altered particle shape to some extent and the increase in the fine-particle fraction appeared to be attributable to improved particle dispersion properties. The uncontrolled presence of irregular-shaped particles can introduce dosing errors due to effects on dispersion and aerodynamic behavior. Conversely, controlled particle morphology and size may be employed to optimize the dose delivered to the lungs particularly if particle-particle and particle-surface interactions can be minimized.

The kinetics of protein adsorption on synthetics and modified natural surfaces

Abstract The kinetics of adsorption of albumin and fibrinogen from phosphate buffered saline (pH 7.35, 280 mosmol) was studied as a function of time, temperature, and bulk protein concentration on Cuprophan (regenerated cellulose), Silastic (silicone rubber), and Shiley heart valve xenografts under static conditions. Adsorption of both proteins on the synthetics appeared to be rapid, irreversible with respect to dilution, and at surface concentrations not exceeding what would be expected for a monolayer. A diffusion-limited model, using the Smoluchowski boundary condition, was derived and was shown to demonstrate the essential characteristics of sorption on synthetics. Both proteins adsorbed to the xenograft with a reversibly bound protein fraction and an irreversibly bound fraction. The reversible fraction was modeled well by a second-order kinetic (Langmuir) process far from saturation. Energies of activation were estimated to be about 3 and 6 kcal/mole for fibrinogen and albumin, respectively. Enthalpies of adsorption were very low, 0.4 kcal/mole for fibrinogen and 1.5 for albumin. The irreversibly bound fraction was modeled well as a diffusion-limited process far from saturation.

Generation of concentrated aerosols for inhalation studies

Abstract A technique is described for generation of concentrated respirable aerosols and their administration to canine lungs. The functional characteristics of the system were delineated using aqueous solutions of disodium fluorescein (DF). The aerosol was generated by delivering pressurized air and disodium fluorescein solution to a Turbotac jet nebulizer. The particles were dried with a sheath of warm air and concentrated using a seven orifice virtual impactor. The input aerosol particles were concentrated up to eight times, resulting in output aerosol concentration of about 10 mg m−3 at a flow rate of 20 l min−1. The particles had predictable mass median aerodynamic diameters between 4 and 7 μm, and geometric standard deviations between 1.7 and 2.0. To conduct inhalation studies on beagle dogs, the aerosol generation and concentration system was pressurized to 18 cm of water. In these experiments the test aerosol consisted of a mixture of disodium fluorescein with technetium-99m tagged to iron oxide colloid, controlled delivery of the aerosol to the dogs was achieved by sequencing low resistance solenoid valves using a logic control box. The animals were anesthetized and endotracheally intubated. The aerosols were carried in the ventilating air stream. The duration of exposure was 3 min. Gamma scintigraphy confirmed deposition of the aerosol in the lower lungs as demonstrated by a total lung retention between 70 and 75% after 24 h. This methodology is applicable for use with solutions and/or colloidal suspensions and can be adapted for continuous aerosol generation and delivery.

Controlled-Release from Condensation Coated Respirable Aerosol-Particles:

Extending the residence time of drugs delivered to the lungs as inhalation aerosols may result in sustained therapeutic drug levels and reduced toxicity. Droplets were generated from 0.25 wt% disodium fluorescein (DF), and 0.25 wt% albuterol sulphate solutions at a rate of 1 ml min−1 using a Turbotac jet nebulizer. These droplets were dried, concentrated and mixed with saturated lauric acid (LA) vapor at bath temperatures of 60–140°C. The resulting coated particles were < 5 μm in size as estimated by inertial impaction and scanning electron microscopy. Powder composition, as determined by gas chromatography, ranged from ratios of 1.2:1 to 2.5:1, of LA: DF. Evidence of coating of DF by LA was derived from i.r. spectroscopy and X-ray microanalysis. Dissolution studies performed on the coated particles in phosphate buffer, pH 7.4 at 37°C and quantified by u.v. spectroscopy, showed that the half-time for dissolution (t2) increased from 4 ± 2 min for uncoated DF particles, to 22 ± 3 − 55 ± 2 min for lauric acid coated DF particles, depending on the coating thickness. The t12 for albuterol sulphate particles increased from 2.5 ± 1.5 min to 12.5 ± 1.9 min for albuterol sulphate particles coated with lauric acid at a bath temperature of 100°C. Inhalation studies performed on beagle dogs with DF particles coated with lauric acid (bath temperature, 100°C) indicated there was a shift and broadening of the peak plasma concentration in comparison with aerosols of DF alone. The average absorption half-time increased from 4.7 ± 0.8 min for uncoated DF particles to 11.5 ± 1.6 min for lauric acid coated DF particles.

Effect of sodium alginate encapsulation on the development of preimplantation mouse embryos

Submitted: December 23, 1986 Accepted: August 4, 1987 (North American Editorial Office) plantation by protecting the zygote, to minimize the associated risk of ectopic pregnancy following embryo transfer by preventing tubal reflux, and to ensure correct placement of IVF embryos in utero. These objectives are met by encapsulating embryos in biodegradable sodium alginate prior to transfer. Previous work has shown that differentiated pancreatic cell lines remain viable in sodium alginate (6), but the method has not been applied to preimplantation embryos. The effects of encapsulation in sodium alginate were tested on two-cell mouse embryos, cultured with controls for 72 hr in vitro.

Regulatory pathways for the stimulation of canine tracheal ciliary beat frequency by bradykinin.

1. The effects of bradykinin, a potent inflammatory nanopeptide, on tracheal ciliary beat frequency in vivo were investigated using barbiturate‐anaesthetized beagles. Tracheal ciliary beat frequency was measured using heterodyne mode correlation analysis laser light scattering, a technique that does not require surgical intervention. 2. Aerosolized 10(‐5) M‐bradykinin in 0.9% saline administered for 3 min to eight barbiturate‐anaesthetized beagles stimulated tracheal ciliary beat frequency from the baseline of 5.3 +/‐ 0.1 Hz to a maximum of 16.6 +/‐ 2.0 Hz, 8 min after aerosol delivery, and ciliary beat frequency remained above baseline for the following 35 min. 3. Intravenously injected hexamethonium bromide, ipratropium bromide or indomethacin did not change baseline tracheal ciliary beat frequency. That down‐regulation of ciliary beat frequency below baseline values was not observed with either the neural or the cyclooxygenase blocking agents suggests that neither of these pathways is involved in the maintenance of the observed basal ciliary beat frequency. 4. Bradykinin‐induced stimulation of tracheal ciliary beat frequency is blocked by hexamethonium bromide, ipratropium bromide or indomethacin. These data suggest that the stimulation of ciliary beat frequency by bradykinin acts through both cellular cyclooxygenase and parasympathetic pathways in series.

Effects of lipid-soluble substances on the thermotropic properties of liposome filtration.

Filtration of dimyristoyl phosphatidylcholine or dipalmitoyl phosphatidylcholine liposomes at various temperatures from 3 to 60 degrees C revealed a discontinuous change in filtration behavior centered about the gel-to-liquid crystal transition temperature. This change was continuous at temperatures immediately above or below the transition temperature. Although pure dipalmitoyl phosphatidylcholine liposomes are in the gel state at 22 degrees C, passage of liposomes composed of dipalmitoyl phosphatidylcholine and cholesterol through the filters at 22 degrees C gave results similar to those obtained with liquid-crystal liposomes. Low cholesterol concentrations were nearly as effective as high concentrations in producing this behavior; this observation is consistent with a shear mechanism for reduction of liposome size, since the stress induced by passage of the otherwise rigid liposome through a small pore would be relieved by fracture at a lattice imperfection. Liposomes composed of egg phosphatidylcholine and cholesterol were retained by the filters to a slightly greater extent than pure egg phosphatidylcholine liposomes; these results are consistent with the known condensing effect of cholesterol on liquid-crystal lipsomes and a shear mechanism occurring with filtration. Liposomes composed of dipalmitoyl phosphatidylcholine and either dipalmitoyl phosphatidic acid or dicetyl phosphate were filtered at 22 degrees C; they showed a filtration characteristic similar to liquid-crystal liposomes. Inclusion of the water-soluble dyes eosin Y or Evans blue in dipalmitoyl phosphatidylcholine liposomes resulted in filtration at 22 degrees C which was similar to that observed for liquid-crystal liposomes. The dyes, sodium fluorescein, 6-carboxyfluorescein and fluoresceinisothiocyanate dextran, did not alter 22 degrees C liposome filtration.

Rotational magnetic particle microrheometry: The Newtonian case

A rotating sphere microrheometer, based on extensions of the work of Valberg [Valberg, P.A., “Magnetometry of Ingested Particles in Pulmonary Macro-Phages,” Science 224, 513–516 (1984); Valberg, P.A., and H. A. Feldman, “Magnetic Particle Motions within Living Cells: Measurement of Cytoplasmic Viscosity and Motile Activity,” Biophys. J. 52, 551–572 (1987)] and Edwards and Yeates [Edwards, P.A., and D. B. Yeates, Viscoelasticity of Biomaterials, Chap. 16, ACS Symposium Series, 489, edited by W. Glasser and H. Hatakeyama (Boston, MA, 1992)], was developed to rapidly (within 10 s) measure the rheological properties of small (∼10 μL) quantities of highly viscous (100–10 000 poise) fluids at small (10−3–10−1 Hz) rates of strain. Previous experimental work was extended by the use of MQP-B™ 1.4-μm-radius particles, which have extremely high coercivity and remanent magnetic field, and in which rotation of magnetic domains within the particle does not occur. The microrheometer was tested with a series of Newtonian viscosity standards (100–10 000 poise) and found to accurately predict viscosity (error range 3%–9%). The effects of shape, size distribution, sedimentation, particle–particle magnetic interactions, and agglomeration were investigated and found to be either negligible or easily determined. This microrheometer can be used to determine the rheological properties of minute quantities of viscous fluids and may be applicable to the measurement of zero-shear-rate viscosity of viscoelastic fluids.A rotating sphere microrheometer, based on extensions of the work of Valberg [Valberg, P.A., “Magnetometry of Ingested Particles in Pulmonary Macro-Phages,” Science 224, 513–516 (1984); Valberg, P.A., and H. A. Feldman, “Magnetic Particle Motions within Living Cells: Measurement of Cytoplasmic Viscosity and Motile Activity,” Biophys. J. 52, 551–572 (1987)] and Edwards and Yeates [Edwards, P.A., and D. B. Yeates, Viscoelasticity of Biomaterials, Chap. 16, ACS Symposium Series, 489, edited by W. Glasser and H. Hatakeyama (Boston, MA, 1992)], was developed to rapidly (within 10 s) measure the rheological properties of small (∼10 μL) quantities of highly viscous (100–10 000 poise) fluids at small (10−3–10−1 Hz) rates of strain. Previous experimental work was extended by the use of MQP-B™ 1.4-μm-radius particles, which have extremely high coercivity and remanent magnetic field, and in which rotation of magnetic domains within the particle does not occur. The microrheometer was tested with a series of Newtonian...