A two-component theory of aerosol deposition in lung airways

The deposition of aerosol particles in the human lung airways is due to two distinct mechanisms. One is by direct deposition resulting from diffusion, sedimentation and impaction as the aerosol moves in and out of the lung. The other is an indirect mechanism by which particles are transported mechanically from the tidal air to the residential air and eventually captured by the airways due to intrinsic particle motion. This last mechanism is not well understood at present. Using a trumpet airway model constructed from Weibel's data, a two-component theory is developed. In this theory, the particle concentrations in the airways and the alveoli at a given airway depth are considered to be quantitatively different. This difference in concentrations will cause a net mixing between the tidal and residential aerosol as the aerosol is breathed in and out. A distribution parameter is then introduced to account for the distribution of ventilation. The effect of intrinsic particle motion on the aerosol mixing is also included. From this theory, total and regional deposition in the lung at the steady mouth breathing without pause is calculated for several different respiratory cycles. The results agree reasonably well with the experimental data.     

Implications of stochastic inheritance

Imperfect coordination between an autonomous genetic element, or plasmid, and a host bacterium reproducing by binary fission is shown to have two effects. The proportion of cells which have lost the plasmid completely tends to a constant for populations growing under constant selective pressure. At the same time, the average number of copies of the plasmid per cell—averaged over those cells which inherit one or more—tends to a constant, which is determined essentially by the ratio of two characteristic probabilities: that of failure of the plasmid to duplicate before a cell divides, and that of failure—of any two copies of the plasmid resulting from the same act of duplication—to separate to opposite halves of a dividing cell.The theory given predicts the proportion of cells which fail to inherit plasmid-like particles after any number of generations of bacterial growth. The manner in which the mean number of particles per particle-containing cell approaches its final constant value is also predicted.The effect of non-random inheritance on cells containing non-replicating particles is determined.Application of the theory is illustrated by experimental data from the literature.     

Some generalized stochastic compartment models for digesta flow

Digesta flow models have been based on linear compartment theory that assumes exponential retention times, and on a generalized theory that incorporates nonexponential (Erlang) retention times (Matis, 1987, Journal of Theoretical Biology 124, 371-376). This paper develops a new family of passage models for heterogeneous digesta by mixing the previous models with assumed parametric, usually gamma, mixing distributions. The utility of the resulting models is demonstrated with experimental data on two treatments, namely a chopped and a ground straw, given to each of four cows. Treatment differences are apparent in the preferred model form and in the means of the estimated mean residence times. The models are relatively easy to fit to data using standard estimation procedures, and they should have broad application to other compartment modeling problems with "heterogeneous particles."     

A theoretical approach to the analysis of axonal transport.

A theoretical model of intra-axonal transport is proposed that presupposes a carrier system moving down the axon in a distal direction. Protein and particle transport is achieved by their reversible association with the distally moving carriers. Mathematical equations representing the concentrations of moving carriers and proteins and/or particles within the axon at any position and time are proposed. Analysis of the equations demonstrates that a traveling wave solution for the particle concentration (an experimental fact) is possible provided the chemical interaction between particles and carriers exhibits positive cooperativity. The phase velocity of the wave solution is interpreted as the observed velocity of the intra-axonal transport, known to be independent of position of observation. In addition, the theory predicts a spectrum of transport velocities for different proteins, in agreement with observations. The velocity of a given protein is dependent on its affinity to the carrier.     

Effect of microfield fluctuations on Coulomb collisions

The effect of plasma microfields on Coulomb collisions between the particles is considered. It is shown that perturbations from other particles insignificantly affect the frequency of short-range collisions. The results of calculating the pair correlation function of the particles in a plasma for distances much shorter than the interparticle distance agree well with predictions of the binary theory.     

Zum Problem der genetischen Rekombination von Bakteriophagen

Summary The mating theory ofVisconti andDelbrück describes quantitatively the recombination kinetics in phage. One special assumption of this theory is thepairwise mating of complete parental structures randomly chosen from the pool, which can lead to the production of a new recombinant particle. On the other hand it seems possible to assume a mechanism, by which the number of templates involved in the formation of a new replica is not restricted to two particles. The hypothesis of complete cooperation presented here suggests the participation ofN+1 random templates in the formation of a new replica carryingN recombination sites. Such a mechanism may be interpreted in different ways, e.g. by a partical replica model or by a partical pairing, which connects more than two parental structures. A differential equation is given, describing this assumption and leading to formulas very similar to those of the mating theory.

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Compartmental models with restricted movement

A restriction is imposed on the number of particles that can possibly move at any time from a compartment, so that any other particles present in the compartment must wait until such particles have moved out. The equations for such a system are formulated and the solution is given for a single compartment system; increased variability of the compartmental particle count is one effect of this restriction.     

Macromolecular diffusion in crowded solutions.

The effects of crowding on the self or tracer diffusion of macromolecules in concentrated solutions is an important but difficult problem, for which, so far, there has been no rigorous treatment. Muramatsu and Minton suggested a simple model to calculate the diffusion coefficient of a hard sphere among other hard spheres. In this treatment, scaled particle theory is used to evaluate the probability that the target volume for a step in a random walk is free of any macromolecules. We have improved this approach by using a more appropriate target volume which also allows the calculation to be extended to the diffusion of a hard sphere among hard spherocylinders. We conclude that, to the extent that proteins can be approximated as hard particles, the hindrance of globular proteins by other proteins is reduced when the background proteins aggregate (the more so the greater the decrease in particle surface area), the hindrance due to rod-shaped background particles is reduced slightly if the rod-like particles are aligned, and the anisotropy of the diffusion of soluble proteins among cytoskeletal proteins will normally be small.     

Laboratory measurements of the spectral properties of estuarine suspended particles

Laboratory measurements have been made of the spectral reflectance of size-fractionated suspended sediments from two estuarine systems. The results show that reflectance at wavelengths between 400 and 1000 nm increases with decreasing particle size for given sediment masses. Preliminary interpretation suggests that a new factor, target area, which is derived from the volume and number distribution of particles in a suspension, is proportional to the reflectance of the suspension. Reflectance in the near infra-red is shown to be unaffected by other in-water parameters and is also largely independent of the colour or nature of the particles. The relationship between spectral reflectance in the near infra-red and target area therefore provides a means of estimating suspended sediment concentration from remotely sensed imagery if the particle size distribution is known or can be estimated.     

Defective Virions of Reovirus

When purified preparations of stock reovirus, type 3, were digested with chymotrypsin, the virions were converted into two different types of particle. These new particles could be separated from each other by isopycnic centrifugation in cesium chloride gradients. One particle banded at a buoyant density of 1.43 g/cm(3), the other at a density of 1.415 g/cm(3). The former particle is termed the heavy (H) particle, the latter is the light (L) particle. The ratio of H/L particles varied between 0.5 and 0.25 in various purified preparations of virus. In electron micrographs, both H and L particles had the appearance and dimensions of viral cores. H particles were infectious for L cells. When plaques formed by stock virus, or by H particles, were picked and propagated in L cells, the majority of the clones gave rise only to H particles on chymotrypsin digestion. On continued serial passage of the clones, virions containing L particles again appeared in the progeny. The simplest explanation of these results was that stock virus was comprised of two populations of virions. One type of virion which contained H particles was infectious, whereas the other, which contained L particles, was not itself infectious and could replicate only in cells coinfected with an H particle virion. Added weight was given to this hypothesis by two observations. First, a small but definite separation of H and L virions could be achieved by isopycnic centrifugation in a gradient of cesium chloride. Second, L particles and virions containing L particles were both shown to lack the largest of the ten segments of double-stranded ribonucleic acid genome. Thus, L particle virions have defective genomes.     

THE MECHANISM OF THE INFLAMMATORY PROCESS : III. ELECTROPHORETIC MIGRATION OF INERT PARTICLES AND BLOOD CELLS IN GELATIN SOLS AND GELS WITH REFERENCE TO LEUCOCYTE EMIGRATION THROUGH THE CAPILLARY WALL.

1. Quartz particles and certain other particles move cataphoretically in certain soft gelatin gels, with the same velocity as in the sol. The speed is a function of the true viscosity of the sol or gel, and it is See PDF for Structure apparently not altered in these soft gels by the presence of gel structure. It is proportional to the applied difference of potential. 2. This finding is compatible with the fact that certain sols undergo gelation with no increase of the true viscosity although a marked change in the apparent viscosity takes place. 3. Red cells in soft gelatin-serum gels show a distinct difference in behavior. They migrate through the sol or gel with a speed that is about twice as great as the leucocytes and quartz particles, which latter particles migrate with the same velocity. This ratio has been found to hold for serum and plasma. The absolute velocities are comparatively slightly decreased by the presence of the gel. 4. In more concentrated or stiffer gels, leucocytes, red cells and quartz particles all move at first with the same velocity. By producing mechanical softening of these gels (shearing from cataphoretic movement of the micells within the cell) the red cells presently resume their previous property of independent migration through the gel. 5. The movements of particles in gelatin gels produced by a magnetic force or the force of gravity are of a different nature than those movements produced by cataphoresis. 6. The mechanical nature of obstruction to the cataphoretic migration of leucocytes and red cells in fibrin gels is briefly described. 7. The correlation of cataphoresis of microscopic particles in gels with the order of magnitude and nature of the potential differences in the capillary wall, lends additional evidence to the theory that polymorphonuclear leucocyte emigration and migration are dependent upon these potential differences.     

Cellular spin resonance: Theory and experiment

Living and dead cells, as well as certain inanimate particles, can be made to spin in a rotating electric field, such as that produced by a four-pole electrode system. The theory for the effects and the experimental results for a number of cells are given. Yeast cells (Saccharomyces cerevisiae, dead, and as protoplasts;Schizosaccharomyces octospora); an alga (Chlorella pyrenoidosa); mouse myeloma cells; human Hela cells; and several model particles were studied. Their spectra of spin response are shown to agree with the theory presented. Interestingly, live cells spin in a contrafield direction, while dead ones spin co-field in the low-frequency range. The result indicate that this new technique of cellular spin resonance (CSR) will be useful in determining the effective dielectric constant of individual cells, for the direction and magnitude of the CSR is directly proportional to the effective dielectric constant, and the spin rate can readily and directly be determined over a wide frequency range.     

A method for determining the dielectric constant and the conductivity of membrane-bounded particles of biological relevance.

Numerical assessment is made regarding Pauly and Schwan's theory which describes the dielectric behavior of a suspension of "shell spheres" as a model of biological membrane-bounded particles. The results indicate that approximate expressions of the theory may give rise to serious errors when applied to particles smaller than about 1 mum in diameter. With a view to performing analysis according to a general expression of the theory, some of the characteristic responses of dielectric parameters upon changes in phase parameters are examined with particular reference to some numerical ranges of biological interest. On this basis a simplified and systematic procedure is proposed for estimating the phase parameters of particles whose shell phase can be regarded as non-conductive. As the application of the procedure proposed, a set of dielectric data of a synaptosome suspension is analyzed, so that the following three phase parameters are successfully determined: membrane capacitance (or shell phase dielectric constant), interval phase conductivity and internal phase dielectric constant. Some limitations of the procedure are discussed for the cases of conducting shells and small particles.     

A method for determining the dielectric constant and the conductivity of membrane-bounded particles of biological relevance

Numerical assessment is made regarding Pauly and Schwan's theory which describes the dielectric behaviour of a suspension of “shell spheres” as a model of biological membrane-bounded particles. The results indicate that approximate expressions of the theory may give rise to serious errors when applied to particles smaller than about 1 Μm in diameter. With a view to performing analysis according to a general expression of the theory, some of the characteristic responses of dielectric parameters upon changes in phase parameters are examined with particular reference to some numerical ranges of biological interest. On this basis a simplified and systematic procedure is proposed for estimating the phase parameters of particles whose shell phase can be regarded as non-conductive. As the application of the procedure proposed, a set of dielectric data of a synaptosome suspension is analyzed, so that the following three phase parameters are successfully determined: membrane capacitance (or shell phase dielectric constant), internal phase conductivity and internal phase dielectric constant. Some limitations of the procedure are discussed for the cases of conducting shells and small particles.     

Structural studies on the organization of proteins in mitochondrial membranes using proteolytic enzymes

Proteolytic enzymes, pronase and trypsin, digest protein in ETP and in SU-particles (devoid of the soluble ATPase) at similar rates and to the same extents for intact and lipid-depleted membranes, showing that lipids do not constitute a barrier to the action of the proteases. The rates and extents of hydrolysis are slightly depressed when membranes are reconstituted from lipid-depleted particles and phospholipids. The hydrolysis rates for the various particles are not greatly enhanced by detergent solubilization nor by other denaturing treatments, indicating that the rates measured in absence of treatments are maximal under the conditions used. The circular dichroism spectra of pronase treated ETP are noticeably altered showing modification of the original conformation. Moreover, enzymic activities of mitochondria and submitochondrial particles are progressively affected by proteases according to their localization at, or near to, a given surface of the membrane. The matrix enzyme, malate dehydrogenase, is not apparently released from mitochondria during the initial incubation period. The results are tentatively discussed in terms of organization of lipids and proteins in the mitochondrial membrane.     

Physical nature of the electric current produced by the asymmetry of particle motion in toroidal magnetic confinement systems

A new type of longitudinal electric current is revealed by analyzing the drift trajectories of charged particles in a tokamak—the current that may be referred to as the asymmetry current because it is associated with the asymmetry of the boundary between trapped and transit particles in phase space. The generation of this current is explained by the fact that the motions of the particles that cross the magnetic surface at a given point in opposite directions are qualitatively different. The asymmetry current results from the toroidal variations of the magnetic field and is maintained by the radial momentum flux of transit particles. The contribution of the particles of different species to the asymmetry current density is proportional to their pressure, is independent of the gradients of the plasma parameters, is maximum at the magnetic axis, and decreases toward the plasma periphery. In contrast to standard neoclassical theory, the asymmetry current can be found only from exact particle trajectories. The asymmetry current is calculated for tokamaks with differently shaped magnetic surfaces and for a model stellarator. By exploiting the newly revealed asymmetry current, together with the bootstrap current, it may be possible to substantially simplify the problem of creating a tokamak reactor.     

Cellular spinning in pulsed rotating electric fields

Living cells, dead cells, and other particles suspended in aqueous media of low conductivity can be easily caused to spin if a rotating electrical field is applied. The background and theory are presented for the use of three-electrode systems provided with seriate square electrical pulses to spin cells.     

Particles and macrophages in murine Peyer's patches

Mice were given 1% suspensions of 5 insoluble particles (chrysotile asbestos, quartz, carmine, carbon, and iron oxide) in drinking water for 3 months. The particles were subsequently sought in intestinal Peyer's patches by light microscopy. Carbon and iron oxide particles were visible in Peyer's patch macrophages, particularly in the subepithelial region, but the other particles could not be detected. The findings suggest that particle surface properties as well as particle size govern accumulation in Peyer's patches. The cytochemistry of subepithelial, mid-dome, tingible-body, and serosal macrophages of control mice indicated diversity of macrophages within the patch. Macrophages of asbestos-fed mice contained more lysosomes than macrophages of controls. Macrophage abundance in the dome apex was not significantly altered by asbestos ingestion. The other particles did not produce detectable alterations in macrophage morphology.     

A method for predicting the location of particles sedimenting in sucrose gradients

A theory was developed for the calculation of the positions of zones of particles sedimenting through a sucrose gradient. Equations were derived for particles sedimenting through gradients in which the sucrose concentration is (a) a linear function of radius, or (b) a hyperbolic function of radius. Computations were made for both swing-out and zonal rotors. The theory, which is based on direct integration of the sedimentation equation, exploits equations relating (a) the density of sucrose solutions to sucrose concentration and (b) the viscosity of sucrose solutions to sucrose concentration, and also the concept of reduced time (T/2 = S20.w integral of t to w2dt) of Fujita. The required computations may be made using a scientific calculator. Experimental support for the theory was obtained.     

Light scattering turbidity changes as a measure of the kinetics of Ca2+ -promoted aggregation of chromaffin granule membrane ghosts.

Changes in turbidity seen when chromaffin granule membrane ghosts are aggregated by Ca2+ can be modelled as dimerization of hollow spheres using Rayleigh-Gans-Debye light-scattering theory. The experimental changes agree well with the calculations. Thus, if shape or refractive index changes produced by osmotic perturbation, ion uptake, etc. can be excluded, turbidity readings can be used to follow the progress of the aggregation reaction of storage vesicles and other small particles or macromolecules.