A group G is called a CI-group if, for any subsets S, T ⊂ G, whenever two Cayley graphs Cay(G, S) and Cay(G, T ) are isomorphic, there exists an element σ ∈ Aut(G) such that S = T . The problem of seeking finite CI-groups is a longstanding open problem in the area of Cayley graphs. This paper contributes towards a complete classification of finite CI-groups. First it is shown that the Frobenius...

Penetration of Trypanosoma cruzi into mammalian cells depends on the activation of the parasite's protein tyrosine kinase and on the increase in cytosolic Ca2+ concentration. We used metacyclic trypomastigotes, the T. cruzi developmental forms that initiate infection in mammalian hosts, to investigate the association of these two events and to identify the various components of the parasite sig...

To identify parameters of Leishmania infection within a population of infected sand flies that reliably predict subsequent transmission to the mammalian host, we sampled groups of infected flies and compared infection intensity and degree of metacyclogenesis with the frequency of transmission. The percentage of parasites within the midgut that were metacyclic promastigotes had the highest corre...

Acquisition of the variable antigen-containing surface coat of Trypanosoma brucei occurs at the metacyclic stage in the salivary glands of the tsetse fly vector. The differentiation of the metacyclic trypanosome in the gland has been studied by scanning electron microscopy and by transmission electron microscopy of thin sections and freeze-fracture replicas. The uncoated epimastigote trypanosom...

Adult triatomine insects, Panstrongylus megistus, naturally infected with the protozoa, Trypanosoma cruzi, contained significantly more metacyclic trypomastigote forms in their digestive tracts than did P. megistus nymphs. Metacyclics were scarce in all stages of triatomines fed once on infected mammalian hosts and subsequently starved. In contrast, triatomines fed repeatedly on infected mammal...

BACKGROUND The binding of Leishmania promastigotes to the midgut epithelium is regarded as an essential part of the life-cycle in the sand fly vector, enabling the parasites to persist beyond the initial blood meal phase and establish the infection. However, the precise nature of the promastigote stage(s) that mediate binding is not fully understood. METHODOLOGY/PRINCIPAL FINDINGS To address ...