Toxoplasmosis is a disease of prominent health concern that is caused by the protozoan parasite, Toxoplasma gondii. Proliferation of T. gondii is dependent on its ability to invade host cells, which is mediated, in part, by calcium-dependent protein kinase 1 (CDPK1). We have developed ATP competitive inhibitors of TgCDPK1 that block invasion of parasites into host cells, preventing their proliferation. The presence of a unique glycine gatekeeper residue in TgCDPK1 permits selective inhibition of the parasite enzyme over human kinases. These potent TgCDPK1 inhibitors do not inhibit the growth of human cell lines and represent promising candidates as toxoplasmosis therapeutics.

The wound healing response is an essential mechanism to maintain the integrity of epithelia and protect all organisms from the surrounding milieu. In the ''purse-string'' mechanism of wound closure, an injured epithelial sheet cinches its hole closed via an intercellular contractile actomyosin cable. This process is conserved across species and utilized by both embryonic as well as adult tissues, but remains poorly understood at the cellular level. In an effort to identify new players involved in purse-string wound closure we developed a wounding strategy suitable for screening large numbers of Drosophila embryos. Using this methodology, we observe wound healing defects in Jun-related antigen (encoding DJUN) and scab (encoding Drosophila aPS3 integrin) mutants and performed a forward genetics screen on the basis of insertional mutagenesis by transposons that led to the identification of 30 lethal insertional mutants with defects in embryonic epithelia repair. One of the mutants identified is an insertion in the karst locus, which encodes Drosophila b Heavy -spectrin. We show b Heavy -spectrin (b H ) localization to the wound edges where it presumably exerts an essential function to bring the wound to normal closure.

5-Aminopyrazole-4-carboxamide was used as an alternative scaffold to substitute for the pyrazolopyrimidine of a known “bumped kinase inhibitor” to create selective inhibitors of calcium-dependent protein kinase-1 from both Toxoplasma gondii and Cryptosporidium parvum. Compounds with low nanomolar inhibitory potencies against the target enzymes were obtained. The most selective inhibitors also exhibited submicromolar activities in T. gondii cell proliferation assays and were shown to be non-toxic to mammalian cells.

Epithelia have the essential role of acting as a barrier which protects living organisms and its organs from the surrounding milieu. Therefore, it is crucial for epithelial tissues to have robust ways of maintaining its integrity despite the frequent damage caused by injury, inflammation and normal cell turnover. All epithelia have some capacity to repair themselves. However, the wound-healing process differs dramatically between the developmental stage and the type of tissue involved. In this review, we will not analyse all aspects of wound healing; instead we will focus on the capacity which several simple epithelial tissues have to reseal small discontinuities very rapidly and efficiently, a process that we call epithelial resealing. We will start by describing the initial experiments which demonstrated the existence of a purse string mechanism to repair embryonic wounds and we will compare this mechanism with embryonic morphogenetic movements which resolve epithelial discontinuities that arise during the normal course of development. We will then discuss other contexts in which epithelia resealing occurs, both in cell culture systems and in adult tissues, and which suggest that at least some of the mechanisms that regulate epithelial resealing may be conserved, acting in several types of simple epithelia, both in embryos and in adults, and across species. KEY WORDS: wound healing, tissue repair, actomyosin cable, filopodia, lamellipodia Embryonic wound healingThe process of embryonic purse string wound healing was initially described in the chick embryo by Martin and Lewis (1992). Fluorescently tagged phalloidin used to visualize the distribution of filamentous actin, revealed a thick cable of actin in the basal epidermis at the leading edge of the marginal cells surrounding the wound (Martin and Lewis, 1992). It was then put forward that the contraction of such a cable would provide the force necessary to draw the wound edges together to achieve re-epithelialisation. Consistent with this hypothesis, when de novo assembly of filamentous actin is prevented by the addition of cytochalasin D, embryonic mouse wounds completely fail to re-epithelialise (McCluskey et al., 1993;McCluskey and Martin, 1995). A few years later, it was shown that in chick embryos another component of the contractile apparatus, the motor protein Myosin II, was assembled in a co-ordinated manner in the leading edge of the wound margin cells, together with cadherins, that enable the intracellular cable to link via adherens junctions with neighbouring cells (Brock et al., 1996). Excisional wounds in the animal cap of early embryos of the frog Xenopus laevis seem to heal in a very Int. J. Dev. Biol. 53: 1549-1556 (2009) way. These wounds close via three distinct processes: the assembly of an actomyosin purse string in the epithelial cells at the wound margin, the contraction and ingression of exposed deep cells, and the protrusive activity of epithelial cells at the margin (Davidson et al., 2002).Although most of the initial s...

The nature of the relationship between explicit and implicit learning is a topic of considerable debate. In order to investigate this relationship we conducted two experiments on postconditioning revaluation of the unconditional stimulus (UCS) in human fear conditioning. In Experiment 1, the intensity of the UCS was decreased following acquisition for one group (devaluation) and held constant for another group (control). A subsequent test revealed that even though both groups exhibited similar levels of UCS expectancy, the devaluation group had significantly smaller conditional skin conductance responses. The devaluation effect was not explained by differences in the explicit estimates of UCS probability or explicit knowledge that the UCS intensity had changed. In Experiment 2, the value of the UCS was increased following acquisition for one group (inflation) and held constant for another group (control). Test performance revealed that UCS inflation did not alter expectancy ratings, but the inflation group exhibited larger learned skin conductance responses than the control group. The inflation effect was not explained by differences in the explicit estimates of UCS probability or explicit knowledge that the UCS intensity had changed. The SCR revaluation effect was not dependent on explicit memory processes in either experiment. In both experiments we found differences on an implicit measure of learning in the absence of changes in explicit measures. Together, the differences observed between expectancy measures and skin conductance support the idea that these responses might reflect different types of memory formed during the same training procedure and be supported by separate neural systems.