A detailed study of the ecology of subsistence agriculture in the Tari Basin was conducted to investigate the stability of intensive agroecosystems in the highlands of Papua New Guinea. The highly intensive agricultural systems that have evolved in the wetland environments in the lowest parts of the basin were found to be extremely stable and capable of further intensification. Both soil fertility and sweet potato yields showed no signs of degradation even though some areas had been under continuous cultivation for hundreds of years. In the dryland environments with volcanic ash soils there was evidence of ecological instability in the form of declining soil fertility and sweet potato yields over time and the progressive replacement of forest vegetation with grasslands having a much lower biomass and nutrient content. Higher altitude dryland environments were the most susceptible to degradation due to lower fertility soils, higher rainfall and higher rates of soil loss by erosion. The Huli people have responded to these differences in ecological stability by concentrating their agricultural activities increasingly on to the more fertile wetland areas. Much of this movement into the lower parts of the basin is thought to have occurred in the period since European contact, over the last 50 years. These findings have implications for much of the Papua New Guinea highlands where volcanic ash soils occur. Although these soils are highly suitable for growing sweet potato and have been able to support large rural populations with their pigs, they are unable to remain productive under continuous cultivation even though the cropping practices of most highland groups are well adjusted to conserving soil fertility and maximizing crop yields. The chemical fertility of volcanic ash soils is being progressively depleted and much greater efforts are needed to promote the restoration of soil fertility during the fallow period. Much greater emphasis is needed on improving fallow practices such as the promotion of woody regrowth and forest regeneration and the growing of leguminous cover crops to protect soils against erosion and to provide a large volume of nutrient-rich plant material suitable for composting.
Fertility ; Soil ; Asymmetric Septal Hypertrophy ; Ecology ; Agriculture

The optimal cell culture method of autologous oral mucosal epithelial cell sheet is not well established for a safe transplantation on to the patients' ocular surface. Animal serum and 3T3 mouse feeder cells are currently being used to stimulate the growth of the epithelial cells. However, the use of animal compounds can have potential side effects for the patient after transplantation of the engineered cell sheet. In the present study, we focused on engineering a rabbit oral mucosal epithelial cell sheet without 3T3 mouse feeder cells using a mix of Dulbecco's Modified Eagle Medium/Bronchial Epithelial Cell Growth Medium culture media (DMEM/BEGM). Autologous oral mucosal epithelial cell sheets, engineered with DMEM/BEGM feeder cell free culture media, were compared to those cultured in presence of serum and feeder cells. Using a DMEM/BEGM mix culture media, feeder cell free culture condition, autologous oral mucosal epithelial cells reached confluence and formed a multilayered sheet. The phenotype of engineered cell sheets cultured with DMEM/BEGM were characterized and compared to those cultured with serum and feeder. Hematoxylin and eosin staining showed the formation of a similar stratified multilayer cell sheets, in both culture conditions. The expression of deltaN-p63, ABCG2, PCNA, E-cadherin, Beta-catenin, CK3, CK4, CK13, Muc5AC, was similar in both culture conditions. We demonstrated that rabbit autologous oral mucosal epithelial cell sheet can be engineered, in feeder cell free conditions. The use of the DMEM/BEGM culture media to engineer culture autologous oral mucosa epithelial cell sheet will help to identify key factors involved in the growth and differentiation of oral mucosal epithelial cells.
Animals ; beta Catenin ; Cadherins ; Cell Culture Techniques ; Culture Media ; Eagles ; Eosine Yellowish-(YS) ; Epithelial Cells* ; Feeder Cells* ; Hematoxylin ; Humans ; Methods ; Mice ; Mouth Mucosa* ; Phenotype ; Proliferating Cell Nuclear Antigen