Ciliated protozoa of two antarctic lakes: analysis by quantitative protargol staining and examination of artificial substrates

Planktonic and artificial substrate-associated ciliates have been identified in two perennially ice-covered antarctic lakes of the McMurdo Dry Valleys. Abundances estimated by quantitative protargol staining ranged from <5 to 31690 cells · l⁻¹, levels that are comparable to those previously obtained using other methods. Nineteen ciliate taxa were identified from these lakes, with the most frequently encountered genera being Plagiocampa, Askenasia, Monodinium, Sphaerophrya and Vorticella. The taxonomic findings compare favorably with those of previous investigators; however four previously unreported genera were observed in both Lakes Fryxell and Hoare. The variability in the depth distributions of ciliates in Lake Fryxell is explained in terms of lake physicochemical properties and ciliate prey distributions, while factors related to temporal succession in the Lake Hoare assemblage remain unexplained. Local marine or temperate zone freshwater habitats are a more likely source than the surrounding dry valleys soils for present ciliate colonists in these lakes. Although the taxonomic uncertainties require further examination, our results suggest that ciliate populations in these antarctic lakes undergo significant fluctuations and are more diverse than was previously recognized. Accepted: 27 July 1998     

Effects of four monoterpenoids on growth and reproduction of the German cockroach (Blattodea: Blattellidae).

The effects of the monoterpenoids d-limonene, linalool, beta-myrcene, and alpha-terpineol on the growth and development of the German cockroach Blattella germanica (L.) were examined. We evaluated the chemicals' attractiveness in cockroach diet, quantified growth effects induced by monoterpenoids, examined embryotoxic properties of the compounds, and examined their effects on reproduction when administered by oral, topical, and vapor routes of entry. Untreated diet was significantly preferred compared with diet treated with high levels of d-limonene, linalool, and alpha-terpineol. The threshold for acceptance was between 1 and 10% (AI). All four monoterpenoids significantly influenced the days required by nymphs to reach the adult stage; in general, higher monoterpenoid concentrations in the diet were associated with a reduction in the days required by nymphs to mature. Application of high doses of d-limonene or linalool to oothecae of gravid female cockroaches significantly decreased the probability of young emerging from them but did not affect female mortality. Feeding on diet treated with monoterpenoids during nymphal development and through the early, premating period of the adult stage did not significantly influence numbers of broods produced per pair, numbers of offspring per brood, days required to produce a brood, total offspring produced by a pair, or female life span. Topical applications of linalool, beta-myrcene, or alpha-terpineol at near lethal rates to adult cockroaches before they mated had no significant influence on the reproductive parameters examined. A single exposure to sublethal levels of monoterpenoid vapors before mating had no significant influence on any reproductive parameters examined.     

A comparative analysis of the synergistic interaction between N1-phenylsulfanilamides and benzylpyrimidines using qsar techniques

Growth inhibition of E. coli cell culture has been determined for a series of 4-substituted-N1-phenylsulfonilamides tested in the presence and absence of synergistic concentrations of trimethoprim. Quantitative structure-activity relationships, established by regression analysis, exhibit an identical dependence of bacterial growth inhibition on sulfonamide pKa irrespective of the presence or absence of trimethoprim. Examination of a small series of benzylpyrimidines in the presence or absence of 4-dimethylamino-N1-phenylsulfanilamide gave similar results. Since the presence of a synergistic agent affords no change in structure-activity relationships, it is concluded that no direct interaction between sulfonamides and benzylpyrimidines occurs and that the synergism observed is solely the result of the kinetic consequences of sequential blockade of the folate biosynthetic pathway.     

Distinct Lipid A Moieties Contribute to Pathogen-Induced Site-Specific Vascular Inflammation

Several successful pathogens have evolved mechanisms to evade host defense, resulting in the establishment of persistent and chronic infections. One such pathogen, Porphyromonas gingivalis, induces chronic low-grade inflammation associated with local inflammatory bone loss and systemic inflammation manifested as atherosclerosis. P. gingivalis expresses an atypical lipopolysaccharide (LPS) structure containing heterogeneous lipid A species, that exhibit Toll-like receptor-4 (TLR4) agonist or antagonist activity, or are non-activating at TLR4. In this study, we utilized a series of P. gingivalis lipid A mutants to demonstrate that antagonistic lipid A structures enable the pathogen to evade TLR4-mediated bactericidal activity in macrophages resulting in systemic inflammation. Production of antagonistic lipid A was associated with the induction of low levels of TLR4-dependent proinflammatory mediators, failed activation of the inflammasome and increased bacterial survival in macrophages. Oral infection of ApoE^−/− mice with the P. gingivalis strain expressing antagonistic lipid A resulted in vascular inflammation, macrophage accumulation and atherosclerosis progression. In contrast, a P. gingivalis strain producing exclusively agonistic lipid A augmented levels of proinflammatory mediators and activated the inflammasome in a caspase-11-dependent manner, resulting in host cell lysis and decreased bacterial survival. ApoE^−/− mice infected with this strain exhibited diminished vascular inflammation, macrophage accumulation, and atherosclerosis progression. Notably, the ability of P. gingivalis to induce local inflammatory bone loss was independent of lipid A expression, indicative of distinct mechanisms for induction of local versus systemic inflammation by this pathogen. Collectively, our results point to a pivotal role for activation of the non-canonical inflammasome in P. gingivalis infection and demonstrate that P. gingivalis evades immune detection at TLR4 facilitating chronic inflammation in the vasculature. These studies support the emerging concept that pathogen-mediated chronic inflammatory disorders result from specific pathogen-mediated evasion strategies resulting in low-grade chronic inflammation.     

The BOS™ as a species-specific method to deliver baits to wild boar in a Mediterranean area

The impact of wild boar Sus scrofa and feral pigs on ecosystems and human activities is of interest worldwide. Bait-delivered pharmaceuticals such as contraceptives or disease vaccines are increasingly advocated to assist the management of such impacts. We evaluated the Boar-Operated-System (BOS?) to deliver baits to wild boar in a Mediterranean area with a large community of potential nontarget species. In a pre-trial phase (BOS? open), both wild boar and 12 nontarget species (wildlife and livestock) visited the BOS? and eight species consumed the baits. In the trial phase, when the BOS? were closed, only wild boar consumed baits. From pre-trial to trial, the rate of visits by nontarget species to the BOS? decreased significantly, but that of wild boar did not change. We observed that crested porcupines Hystrix cristata prevented the wild boar from using BOS?. We confirmed the effectiveness of BOS? to deliver baits selectively to wild boar in a Mediterranean area.     

Disposition of Atrazine Metabolites Following Uptake and Degradation of Atrazine in Switchgrass

Extensive use of the agricultural herbicide atrazine has led to contamination of numerous ground and surface water bodies. Research has shown that it can have a variety of negative impacts on numerous non-target organisms in the environment. Phytoremediation is one strategy that has been studied to remove atrazine contamination. This paper investigates the hypothesis that switchgrass (Panicum virgatum) can exude metabolites of atrazine after uptake and degradation, which has been suggested by prior research. Pots planted with switchgrass were treated with a 4 ppm solution of atrazine spiked with [¹⁴C]atrazine. After 4 days, switchgrass plants were transplanted to new pots with fresh sand. Four days later, the pots were sacrificed, and sand and plant samples were extracted. Plant and sand samples were analyzed for the presence of atrazine and its major metabolites. The percentage of radiotracer remaining as the parent atrazine was observed to decrease over the course of the study while the percentages of the metabolites were observed to increase. The presence of the metabolite cyanuric acid in a switchgrass phytoremediation system is reported for the first time.