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Table 2 Synthetic data set in which nanoparticles are non-randomly distributed in different pulmonary tissue compartments. The hypothetical data were generated to provide an example of particles mainly taken up by macrophages or retained inside the lumen of the alveolar ducts/alveoli.

From: Visualization and quantitative analysis of nanoparticles in the respiratory tract by transmission electron microscopy

Compartment N O P NE RDI X2 Fraction of total X2 [%]
Conductive airway (lumen) 5 150 61.86 0.08 52.26 2.76
Alveolus (lumen) 527 1125 463.94 1.14 8.57 0.45
Macrophages 50 3 1.24 48.76 1781.45 94.22
Epithelial cell 12 38 15.67 0.77 0.86 0.05
Interstitium 13 34 14.02 0.93 0.07 0.004
Endothelial cell 12 38 15.67 0.77 0.86 0.05
Residual 0 113 46.6 0 46.6 2.46
Total 619 1501 619 1 1890.67 100
  1. Note. With 6 degrees of freedom (7-1 compartments × 2-1 groups) and a total chi-squared value 1890.67 the null-hypothesis of random particle distribution has to be rejected with p < 0.001. The alveolar macrophages are the only compartment that fulfils the criteria for preferential particle localization: RDI > 1 and the partial chi-squared contributes substantially (more than 10%) to the non-randomness of the distribution, i.e. the total chi-squared [34, 103]. However, although the nanoparticles are preferentially located in the macrophages it is interesting to note that they deposit mainly in the alveolar region and are not found in the lumen of the blood vessels which are contained in the compartment residual. Abbreviations: NO = Number of observed particles; NE = Number of expected particles; P = Number of observed points; RDI = Relative deposition index; X2 = Chi squared values.