If f: G → Y is an irreducible closed continuous mapping defined on a regular weakly collectionwise normal first-countable meta-Lindelöf locally σ paratopological group G onto a T 1-space Y which has a neighborhood ωω -base at a point y ∈ Y, then f −1(y) is σ-compact in G. We prove that if a Fréchet-Urysohn space X has strong α 4 -property and a weakly countably complete base , then X is first-countable, where M is a separable and metrizable space and = {F: F is a non-empty compact subset of M } and with the Vietoris topology. By this result we can get the first-countability of certain paratopological groups.