Invasive plants negatively impact native,but not exotic,animals

Despite our growing understanding of the impacts of invasive plants on ecosystem structure and function, important gaps remain, including whether native and exotic species respond differently to plant invasion. This would elucidate basic ecological interactions and inform management. We performed a meta‐analytic review of the effects of invasive plants on native and exotic resident animals. We found that invasive plants reduced the abundance of native, but not exotic, animals. This varied by animal phyla, with invasive plants reducing the abundance of native annelids and chordates, but not mollusks or arthropods. We found dissimilar impacts among “wet” and “dry” ecosystems, but not among animal trophic levels. Additionally, the impact of invasive plants increased over time, but this did not vary with animal nativity. Our review found that no studies considered resident nativity differences, and most did not identify animals to species. We call for more rigorous studies of invaded community impacts across taxa, and most importantly, explicit consideration of resident biogeographic origin. We provide an important first insight into how native and exotic species respond differently to invasion, the consequences of which may facilitate cascading trophic disruptions further exacerbating global change consequences to ecosystem structure and function.     

Identification of Naegleria fowleri in domestic water sources by nested PCR

The free-living amoeboflagellate Naegleria fowleri is the causative agent of primary amoebic meningoencephalitis (PAM), a rapidly fatal disease of the central nervous system. In the United States, the disease is generally acquired while swimming and diving in freshwater lakes and ponds. In addition to swimming, exposure to N. fowleri and the associated disease can occur by total submersion in bathwater or small backyard wading pools. In the present study, swipe samples and residual pipe water from homes in Arizona were examined for N. fowleri by nested PCR due to the death of two previously healthy children from PAM. Since neither child had a history of swimming in a freshwater lake or pond prior to the onset of disease symptoms, the domestic water supply was the suspected source of infection. Of 19 samples collected from bathroom and kitchen pipes and sink traps, 17 samples were positive for N. fowleri by PCR. A sample from a Micro-Wynd II filter was obtained by passing water from bathtubs through the filter. Organisms attached to the filter also tested positive by PCR. The two samples that tested negative for N. fowleri were one that was obtained from a kitchen sink trap and a swipe sample from the garbage disposal of one home.     

Hypertrophy, increased ejection fraction, and reduced Na-K-ATPase activity in phospholemman-deficient mice

Phospholemman (FXYD1), a 72-amino acid transmembrane protein abundantly expressed in the heart and skeletal muscle, is a major substrate for phosphorylation in the cardiomyocyte sarcolemma. Biochemical, cellular, and electrophysiological studies have suggested a number of possible roles for this protein, including ion channel modulator, taurine-release channel, Na(+)/Ca(2+) exchanger modulator, and Na-K-ATPase-associated subunit. We have generated a phospholemman-deficient mouse. The adult null mice exhibited increased cardiac mass, larger cardiomyocytes, and ejection fractions that were 9% higher by magnetic resonance imaging compared with wild-type animals. Notably, this occurred in the absence of hypertension. Total Na-K-ATPase activity was 50% lower in the phospholemman-deficient hearts. Expression (per unit of membrane protein) of total Na-K-ATPase was only slightly diminished, but expression of the minor alpha(2)-isoform, which has been specifically implicated in the control of contractility, was reduced by 60%. The absence of phospholemman thus results in a complex response, including a surprisingly large reduction in intrinsic Na-K-ATPase activity, changes in Na-K-ATPase isoform expression, increase in ejection fraction, and increase in cardiac mass. We hypothesize that a primary effect of phospholemman is to modulate the Na-K-ATPase and that its reduced activity initiates compensatory responses.     

Nest site selection by yellow-faced honeyeaters Lichenostomus chrysops

When choosing subsequent nest sites, species that produce multiple broods in a single breeding season have the option of dispersing from a site where they previously suffered depredation, i.e., a predator-avoidance tactic. In our study on yellow-faced honeyeaters Lichenostomus chrysops it was found that 89% of nest failures were attributed to nest depredation, the primary cause of reproductive failure. Pairs re-nested further from depredated nesting attempts than from successful nesting attempts and progressively higher above the ground as the breeding season progressed. Pairs nesting in dioecious Coprosma quadrifida plants only nested in non-fruiting male plants. Artificial nests were used to test the hypothesis that nest height and plant preferences were strategies to reduce the risk of depredation. There was no evidence that either higher nests or nests in non-fruiting C. quadrifida achieved reduced levels of depredation during 14 days of artificial nest exposure. Specific nest site characteristics were not found to be associated with nest outcome for either natural or artificial nests. Our study provides further evidence that species may choose a diverse range of nest sites in order to avoid predators from developing specific search images and then, following depredation, compensate by rapidly re-nesting away from the failed attempt.     

Parasite-mediated predation between native and invasive amphipods

Parasites can structure biological communities directly through population regulation and indirectly by processes such as apparent competition. However, the role of parasites in the process of biological invasion is less well understood and mechanisms of parasite mediation of predation among hosts are unclear. Mutual predation between native and invading species is an important factor in determining the outcome of invasions in freshwater amphipod communities. Here, we show that parasites mediate mutual intraguild predation among native and invading species and may thereby facilitate the invasion process. We find that the native amphipod Gammarus duebeni celticus is host to a microsporidian parasite, Pleistophora sp. (new species), with a frequency of infection of 0-90%. However, the parasite does not infect three invading species, G. tigrinus, G. pulex and Crangonyx pseudogracilis. In field and laboratory manipulations, we show that the parasite exhibits cryptic virulence: the parasite does not affect host fitness in single-species populations, but virulence becomes apparent when the native and invading species interact. That is, infection has no direct effect on G. d. celticus survivorship, size or fecundity; however, in mixed-species experiments, parasitized natives show a reduced capacity to prey on the smaller invading species and are more likely to be preyed upon by the largest invading species. Thus, by altering dominance relationships and hierarchies of mutual predation, parasitism strongly influences, and has the potential to change, the outcome of biological invasions.     

Requirement of both the second and third BIR domains for the relief of X-linked inhibitor of apoptosis protein (XIAP)-mediated caspase inhibition by Smac

The inhibitor of apoptosis proteins (IAP) are endogenous caspase inhibitors in the metazoan and characterized by the presence of baculoviral IAP repeats (BIR). X-linked IAP (XIAP) contains three BIR domains and directly inhibits effector caspases such as caspase-7 via a linker_BIR2 fragment and initiator caspases such as caspase-9 via the BIR3 domain. A mitochondrial protein Smac/DIABLO, which is released during apoptosis, antagonizes XIAP-mediated caspase inhibition by interacting directly with XIAP. Here, using glutathione S-transferase pulldown and caspase activity assay, we show that Smac is ineffective in relieving either caspase-7 or caspase-9 inhibition by XIAP domain fragments. In addition, Smac forms a ternary complex with caspase-7 and linker_BIR2, suggesting that Smac/linker_BIR2 interaction does not sterically exclude linker_BIR2/caspase-7 interaction. However, Smac is effective in removing caspase-7 and caspase-9 inhibition by XIAP fragments containing both the BIR2 and BIR3 domains. Surface plasmon resonance measurements show that Smac interacts with the BIR2 or BIR3 domain in micromolar dissociation constants. On the other hand, Smac interacts with an XIAP construct containing both BIR2 and BIR3 domains in a subnanomolar dissociation constant by the simultaneous interaction of the Smac dimer with the BIR2 and BIR3 domains of a single XIAP molecule. This 2:1 Smac/XIAP interaction not only possesses enhanced affinity but also sterically excludes XIAP/caspase-7 interaction, demonstrating the requirement of both BIR2 and BIR3 domains for Smac to relieve XIAP-mediated caspase inhibition.     

Historical demography and colonization pathways of the widespread intertidal seaweed Hormosira banksii (Phaeophyceae) in southeastern Australia

The palaeoceanography of southern Australia has been characterized by fluctuating sea levels during glacial periods, changing temperature regimes and modified boundary currents. Previous studies on genetic structuring of species in southeastern Australia have focused mainly on the differentiation of eastern and western populations while the potential role of Bass Strait as a region of overlap for three biogeographic provinces (Peronia, Maugea, and Flindersia) has been largely ignored. This study aimed to explore the likely roles of historic and contemporary factors in determining divergence patterns in the habitat‐forming intertidal seaweed Hormosira banksii in southeastern Australia with a special focus on postglacial dispersal into Bass Strait. We examined the genetic diversity of 475 Hormosira specimens collected from 19 sites around southern Australia using DNA sequence analysis of cytochrome oxidase 1. Three major haplotype groups were identified (western, centre and eastern) corresponding with the three existing biogeographical provinces in this region. Historic break points appeared to be retained and reinforced by modern day dispersal barriers. Phylogeographic grouping of Hormosira reflected a combination of historic and contemporary oceanography. As western and eastern group haplotypes were largely absent within Bass Strait, re‐colonization after the last glacial maximum appeared to have originated from refuges within or near present day Bass Strait. Patterns of genetic structure for Hormosira are consistent with other marine species in this region and highlight the importance of biogeographical barriers in contributing to modern genetic structure.     

Attraction of Culex pipiens to uropygial gland secretions does not explain feeding preference for American robins

Culex pipiens, the endemic mosquito vector of West Nile virus in eastern North America, is responsible for maintenance of the virus in avian reservoir hosts, the most important of which appears to be the American robin. One reason for the greater involvement of robins is believed to be the feeding preference of Cx. pipiens, however, the basis of this preference is not understood. We tested the hypothesis that the species‐specific chemical profile of avian uropygial gland secretions are used by Cx. pipiens as cues to locate birds and, therefore, may contribute to the observed feeding preferences. We used gas chromatography‐mass spectrometry to identify the semi‐volatile components of the uropygial gland secretions of American robins and two other common reservoir host species, the house sparrow and European starling. We found that the chemical composition of the robin secretions was different from those of the sparrows and starlings. Through behavioral choice trials conducted in a dual‐port olfactometer, we also found that Cx. pipiens did not prefer the secretions of robins over the other two species. Surprisingly, however, we found that Cx pipiens were more often attracted to live starlings over robins and to the secretions of starlings over those of robins.     

Terpenoids from Zingiber officinale (Ginger) Induce Apoptosis in Endometrial Cancer Cells through the Activation of p53

Novel strategies are necessary to improve chemotherapy response in advanced and recurrent endometrial cancer. Here, we demonstrate that terpenoids present in the Steam Distilled Extract of Ginger (SDGE) are potent inhibitors of proliferation of endometrial cancer cells. SDGE, isolated from six different batches of ginger rhizomes, consistently inhibited proliferation of the endometrial cancer cell lines Ishikawa and ECC-1 at IC₅₀ of 1.25 µg/ml. SDGE also enhanced the anti-proliferative effect of radiation and cisplatin. Decreased proliferation of Ishikawa and ECC-1 cells was a direct result of SDGE-induced apoptosis as demonstrated by FITC-Annexin V staining and expression of cleaved caspase 3. GC/MS analysis identified a total of 22 different terpenoid compounds in SDGE, with the isomers neral and geranial constituting 30–40%. Citral, a mixture of neral and geranial inhibited the proliferation of Ishikawa and ECC-1 cells at an IC₅₀ 10 µM (2.3 µg/ml). Phenolic compounds such as gingerol and shogaol were not detected in SDGE and 6-gingerol was a weaker inhibitor of the proliferation of the endometrial cancer cells. SDGE was more effective in inducing cancer cell death than citral, suggesting that other terpenes present in SDGE were also contributing to endometrial cancer cell death. SDGE treatment resulted in a rapid and strong increase in intracellular calcium and a 20–40% decrease in the mitochondrial membrane potential. Ser-15 of p53 was phosphorylated after 15 min treatment of the cancer cells with SDGE. This increase in p53 was associated with 90% decrease in Bcl2 whereas no effect was observed on Bax. Inhibitor of p53, pifithrin-α, attenuated the anti-cancer effects of SDGE and apoptosis was also not observed in the p53^neg SKOV-3 cells. Our studies demonstrate that terpenoids from SDGE mediate apoptosis by activating p53 and should be therefore be investigated as agents for the treatment of endometrial cancer.