  We consider brane gas models based on type II string theories and analyze the
mass, the Ramond-Ramond charge and the charge on moduli fluctuations of branes
wrapping over cycles of a compactified space in the four-dimensional Einstein
frame. A six-dimensional torus and Calabi-Yau threefolds are considered for the
Kaluza-Klein reduction. A large volume of the compactified space and a weak
string coupling gives rise to point particles of the wrapped branes which have
a light mass and a small charge of the Ramond-Ramond flux and of the moduli
fluctuations, while the particles become very heavy in the string frame. We
find that the masses and the charges satisfy the sea-saw like dual relations
which become time-independent in the four-dimensional Einstein frame.
