Evolution of Caenorhabditis elegans host defense under selection by the bacterial parasite Serratia marcescens.

Parasites can impose strong selection on hosts. In response, some host populations have adapted via the evolution of defenses that prevent or impede infection by parasites. However, host populations have also evolved life history shifts that maximize host fitness despite infection. Outcrossing and self-fertilization can have contrasting effects on evolutionary trajectories of host populations. While selfing and outcrossing are known to affect the rate at which host populations adapt in response to parasites, these mating systems may also influence the specific traits that underlie adaptation to parasites. Here, we determined the role of evolved host defense versus altered life history,in mixed mating (selfing and outcrossing) and obligately outcrossing C. elegans host populations after experimental evolution with the bacterial parasite, S. marcescens. Similar to previous studies, we found that both mixed mating and obligately outcrossing host populations adapted to S. marcescens exposure, and that the obligately outcrossing populations exhibited the greatest rates of adaptation. Regardless of the host population mating system, exposure to parasites did not significantly alter reproductive timing or total fecundity over the course of experimental evolution. However, both mixed mating and obligately outcrossing host populations exhibited significantly reduced mortality rates in the presence of the parasite after experimental evolution. Therefore, adaptation in both the mixed mating and obligately outcrossing populations was driven, at least in part, by the evolution of increased host defense and not changes in host life history. Thus, the host mating system altered the rate of adaptation, but not the nature of adaptive change in the host populations.

Huperzine a as potential treatment of Alzheimer's disease: an assessment on chemistry, pharmacology, and clinical studies.

Alzheimer's disease (AD) is the fourth leading cause of death in adults, characterized by hallmark neuritic plaques and neurofibrillary tangles. Current treatments focus only on symptom relief. As a possible new treatment option for AD, huperzine A's chemistry, pharmacology, and clinical effectiveness are assessed. The chemical synthesis of huperzine A has been optimized, while an in vitro technique has provided a renewable plant source. Pharmacological studies showed that the drug inhibits the enzyme acetylcholinesterase reversibly and selectively. Huperzine A also displayed good pharmacokinetics with a rapid absorption and a wide distribution in the body at a low to moderate rate of elimination. Presently, inadequate toxicity data in human have been reported, yet animal studies demonstrated mild to moderate cholinergic side effects at therapeutic doses. Previous clinical trials have shown improvement in memory function using MMSE, MQ, ADAS-COG, and ADL tests. In an unpublished phase II clinical trial, the ADAS-COG and MMSE tests indicated cognitive enhancement at a dose of 0.4 mg, yet no improvement was observed at a dose of 0.2 mg. The MMSE scores indicated cognitive enhancement at 0.4 mg. Promising data suggested that huperzine A is well tolerated at doses up to 0.4 mg for 24 weeks. Therefore, huperzine A seems to be a potential treatment option for AD.