  The detailed numerical and analytical approximate analysis of wormhole-like
solutions in 5D Kaluza-Klein gravity is given. It is shown that some part of
these solutions with $E \approx H, E>H$ relation between electric $E$ and
magnetic $H$ fields can be considered as a superthin and superlong
gravitational flux tube filled with electric and magnetic fields, namely
$\Delta-$strings. The solution behaviour near hypersurface $ds^2=0$ and the
model of electric charge on the basis of $\Delta-$string are discussed. The
comparison of the properties of $\Delta-$string and ordinary string in string
theory is carried out. Some arguments are given that fermionic degrees of
freedom can be build in on the $\Delta-$string. These degrees of freedom are
connected with quantum wormholes of spacetime foam. It is shown that the
natural theory for these spinor fields is supergravity.
