Diversity and transmission of koala retrovirus: a case study in three captive koala populations.

Koala retrovirus is a recently endogenized retrovirus associated with the onset of neoplasia and infectious disease in koalas. There are currently twelve described KoRV subtypes (KoRV-A to I, K-M), most of which were identified through recently implemented deep sequencing methods which reveal an animals' overall KoRV profile. This approach has primarily been carried out on wild koala populations around Australia, with few investigations into the whole-population KoRV profile of captive koala colonies to date. This study conducted deep sequencing on 64 captive koalas of known pedigree, housed in three institutions from New South Wales and South-East Queensland, to provide a detailed analysis of KoRV genetic diversity and transmission. The final dataset included 93 unique KoRV sequences and the first detection of KoRV-E within Australian koala populations. Our analysis suggests that exogenous transmission of KoRV-A, B, D, I and K primarily occurs between dam and joey. Detection of KoRV-D in a neonate sample raises the possibility of this transmission occurring in utero. Overall, the prevalence and abundance of KoRV subtypes was found to vary considerably between captive populations, likely due to their different histories of animal acquisition. Together these findings highlight the importance of KoRV profiling for captive koalas, in particular females, who play a primary role in KoRV exogenous transmission.

Determination of the surface free energy of crystalline and amorphous lactose by atomic force microscopy adhesion measurement.

PURPOSE: This study was conducted to accurately measure the dispersive surface free energy of lactose solids in ordered and disordered states. METHODS: Atomic force microscopy (AFM) was used to determine the contact adhesion force between an AFM tip and lactose under low humidity (ca. 1% RH). The geometry of the tip contacting apex was characterized by scanning a porous aluminum film with ultrasharp spikes (radius 2-3 nm). A sphere vs. flat surface model was employed to relate the adhesion force determined to the surface energy based upon the Johnson-Kendal-Roberts theory. Spray-dried amorphous lactose in a compressed-disk form and single crystals of alpha-lactose monohydrate were prepared as model samples. RESULTS: The condition of the smooth sample surface and sphere-shaped tip used was shown to be appropriate to the application of the JKR model. The surface energy of crystalline [(0,-1,-1) face] and amorphous lactose was determined to be 23.3 +/- 2.3 and 57.4 +/- 7.9 mJ m(-2), respectively. CONCLUSIONS: We have demonstrated the capability of AFM to measure the dispersive surface free energy of pharmaceutical materials directly through a blank probe at the nanometer scale. These data, although consistent with results from more traditional methods, illustrate some unique attributes of this approach, namely, surface energies are directly derived from solid-solid interactions, measurements may be made on specific crystalline faces, and the potential exists to identify the submicron heterogeneity of organic solids in terms of their molecular energy states (such as ordered and disordered lactose).