The sequences of the mitochondrial ND4 gene (1339 bp) and the ND4L gene (290 bp) were determined for all the 14 extant taxa of the Drosophila nasuta subgroup. The average A + T content of ND4 genes is 76.5% and that of ND4L genes is 83.5%. A total of 114 variable sites were scored. The ND4 gene sequence divergence ranged from 0 to 5.4% within the subgroup. The substitution rate of the ND4 gene is about 1.25% per million years. The base substitution of the genes is strongly transition biased. Neighbor-joining and parsimony were used to construct a phylogeny based on the resultant sequence data set. According to these trees, five distinct mtDNA clades can be identified. D. niveifrons represents the most diverged lineage. D. sulfurigaster bilimbata and D. kepulauana form two independent lineages. The other two clades are the kohkoa complex and the albomicans complex. The kohkoa complex consists of D. sulfurigaster sulfurigaster, D. pulaua, D. kohkoa, and Taxon-F. The albomicans complex can be divided into two groups: D. nasuta, D. sulfurigaster neonasuta, D. sulfurigaster albostrigata, and D. albomicans from Chiangmai form one group; and D. pallidifrons, Taxon-I, Taxon-J, and D. albomicans from China form the other group. High genetic differentiation was found among D. albomicans populations. Based on our phylogenetic results, we hypothesize that D. niveifrons diverged first from the D. nasuta subgroup in Papua New Guinea about 3.5 Mya. The ancestral population spread to the north and when it reached Borneo, it diversified sequentially into the kohkoa complex, D. s. bilimbata, and D. kepulauana. About 1 Mya, another radiation occurred when the ancestral populations reached the Indo-China Peninsula, forming the albomicans complex. Discrepancy between morphological groupings and phylogenetic results suggests that the male morphological traits may not be orthologous.
Surface roughness of carrier particles can impact dry powder inhaler (DPI) performance. There are opposing views on the effect of roughness on DPI performance. Hence, a systematic approach is needed to modify carrier surfaces and evaluate the impact on drug delivery. Carrier particle surfaces were modified by fluid bed coating with saturated lactose containing micronized lactose of different sizes (2, 5 and 8 μm) and coated to different levels (20, 40, 60 and 80%). Their drug delivery performance was assessed by the fine particle fraction (FPF). Roughness parameters, mean arithmetic roughness (Ra) and arithmetic mean height (Sa), of the carrier particles, were also evaluated using optical profilometry and scanning laser microscopy. Generally, particles of higher Ra had higher FPF. Higher Sa resulted in higher FPF only for particles with 60 and 80% coat levels. Reduced contact surface area between the drug particle and rougher carrier particle resulted in easier drug detachment during aerosolization. The 5 µm micronized lactose produced optimal carrier particles with respect to FPF and surface roughness. The study highlighted that with the ideal particles for surface roughening and coating level, surface roughening could be efficiently achieved by fluid bed coating for superior DPI performance.