Studying Particle Retention

To study particle retention, noninvasive and invasive techniques are available (102). Noninvasive methods use radioactive, fluorescent, or magnetic particles. So far they are the only feasible techniques in humans, and they allow repeated measurements in the same individual. These techniques are extensively discussed in Chapter 5. However, even single-photon emission computed tomography 

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In the third part, we describe the methods of studying particle retention. We thereby focus on techniques that allow quantitative studies concomitant with qualitative ultrastructural analyses, and on new methods to preserve the extracellular lining layer with the surfactant film at the air-liquid interface. 

Boecker et al. (1969) studied the retention of two different size distributions of heat-treated l44Ce oxide aerosols. For the smaller particle size distribution (0.88-1.1 /an), they observed a pulmonary retention that could be approximated with an effective half-time of 140 d the larger particle size distribution (1.8-2.3 /an) had a pulmonary retention that could be approximated with a half-time of 185 d. 

Lakatos et al. (1979) also studied the retention of HPAM in unconsolidated silica sand. The HPAM polymers used had a range of molecular weight of 0.7-4.8 X 10 and degree of hydrolysis of 0-40%. A silica sand of particle size 100-200 m and with a specific surface area between 0.1 (by mercury permeometry) and 0.18m /g (by krypton adsorption) was used to construct sandpacks 20cm long for all the polymer flow experiments. 

Slauson et al. (119) have studied deposition, retention, and clearance of inhaled cobalt oxide particles from the lungs of calves with acute inflammatory... 

There is considerable evidence to suggest that coexposures to oxidants and particles may increase the severity of particle-induced interstitial fibrosis. Oxidants, such as cigarette smoke, greatly enhance both whole-lung particle retention and particle uptake by epithelia in experimental animals (43), and also increase the severity of particle-induced interstitial fibrosis (44). A variety of radiographic studies have shown that smoking increases the incidence of asbestosis in heavily exposed asbestos workers (45-47). 

We have used a rat traeheal explant system to examine the role of AOS in particle uptake. When traeheal explants are briefly immersed in a suspension of a mineral dust, dust partieles adhere to the epithelial cell surfaces if the explants are then maintained in organ eulture in air, the epithelial cells slowly take up particles from the apical surface (see Fig. 1). The relative basal level of uptake of different types of particles is quite different (see Table 3), but every type of mineral particle thus far examined (asbestos, carbon, titanium dioxide, iron oxide, talc, wollastonite, or silicon carbide) enters the epithelial cells (3,4,51-54). This system offers several simplifying advantages for studying particle uptake, ineluding lack of airspace inflammatory cells, maintenance of normal levels of intraeel-lular antioxidant defense (Churg A, unpublished data), and retention of a polarized cell structure with normal apical differentiation. 

The methacrylic backbone structure makes the spherical Toyopearl particles rigid, which in turn allows linear pressure flow curves up to nearly 120 psi (<10 bar), as seen in Fig. 4.45. Toyopearl HW resins are highly resistant to chemical and microbial attack and are stable over a wide pH range (pH 2-12 for operation, and from pH 1 to 13 for routine cleaning and sanitization). Toyopearl HW resins are compatible with solvents such as methanol, ethanol, acetone, isopropanol, -propanol, and chloroform. Toyopearl HW media have been used with harsh denaturants such as guanidine chloride, sodium dodecyl sulfate, and urea with no loss of efficiency or resolution (40). Studies in which Toyopearl HW media were exposed to 50% trifluoroacetic acid at 40°C for 4 weeks revealed no change in the retention of various proteins. Similarly, the repeated exposure of Toyopearl HW-55S to 0.1 N NaOH did not change retention times or efficiencies for marker compounds (41). 

Nevertheless, this method was successfully applied by Gulyaeva et al. for the log P and log D determination of 15 P-sympatholytic drugs [56]. Another study by Welerowicz and Buszewski compared the HpophiHcity values of P-blockers obtained with a column made of a monoHthic-silica Cjg with a conventional porous silica particles Cjg as reference material [27]. A modified method was used for evaluating logP with two main differences (i) logfeg was considered rather than retention times, and (ii) benzene and butyl-benzene were used as calibration compounds. 

There are also significant species differences in respiratory tract deposition and clearance of inhaled particles (Thomas, 1972). Data from a number of studies are summarized in Table 14 to assist in evaluating the several factors that influence the retention of inhaled materials. In studies with rats, Syrian hamsters, Chinese hamsters, and mice, the l44Ce was generally lost at a more rapid rate from the pulmonary region than was noted for the dog. A major factor in this difference may be differences in initial deposition sites and perhaps... 

Nanosized objects perform various functions in the biomedical field. In the human body, nanosized particulate substances behave very differently from larger particles. In 1986, Maeda et al. found that the stained albumin, having a size of several nanometers, naturally accumulates in the region of cancerous tissues, which is now well known as the enhanced permeability and retention (EPR) effect. Many studies in the field of nanoparticles are based on this finding. Another application of nanoparticles is the delivery system using various polyplexes that are composed of carrier molecules and plasmid DNA or nucleic acid drugs such as antisenses and siRNA. In addition, nanofibers are mainly used for biodegradable scaffolds in tissue... 

Thus, RP-HPLC-MS has been employed for the analysis of sulphonated dyes and intermediates. Dyes included in the investigation were Acid yellow 36, Acid blue 40, Acid violet 7, Direct yellow 28, Direct blue 106, Acid yellow 23, Direct green 28, Direct red 79, Direct blue 78 and some metal complex dyes such as Acid orange 142, Acid red 357, Acid Violet 90, Acid yellow 194 and Acid brown 355. RP-HPLC was realized in an ODS column (150 X 3 mm i.d. particle size 7 /.an). The composition of the mobile phase varied according to the chemical structure of the analytes to be separated. For the majority of cases the mobile phase consisted of methanol-5 mM aqueous ammonium acetate (10 90, v/v). Subsituted anthraquinones were separated in similar mobile phases containing 40 per cent methanol. The flow rate was 1 ml/min for UV and 0.6 ml/min for MS detection, respectively. The chemical structure of dye intermediates investigated in this study and their retention times are compiled in Table 3.28. It was found that the method is suitable for the separation of decomposition products and intermediates of dyes but the separation of the original dye molecules was not adequate in this RP-HPLC system [162],... 

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