Helminthiasis and toxoplasmosis among exotic mammals at the Santiago National Zoo

Parasitologic evaluations of 112 fecal specimens from 292 mammals from the Santiago National Zoo (36 specimens were pooled specimens from greater than or equal to 2 animals) indicated that 51 mammals had protozoa or helminths in their feces. Most of the parasites in the herbivorous species were trichurids and strongylids, whereas most of the parasites in the carnivorous species were ascarids. Coccidia spp and Giardia spp were the most frequently detected protozoans in the mammals evaluated. Of 127 captive mammals serologically evaluated for antibodies against Toxoplasma gondii (indirect hemagglutination test), 35 (27.5%) were positive for T gondii: 7 (46.6%) of 15 carnivores, 24 (25.2%) of 95 artyodactyls, and 4 (22.5%) of 17 nonhuman primates. Antibodies against T gondii also were found in 8 of 10 domestic cats captured within the zoo and in 6 of 13 volunteer zookeepers.     

Photoreceptors in primitive chordates: fine structure, hyperpolarizing receptor potentials, and evolution

Two species of primitive chordates have hyperpolarizing photoreceptor potentials, as vertebrates do. In Salpa the photoreceptive membrane is composed of microvilli, whereas in Amaroucium it is modified from cilia. There appears to be no functional correlation between fine structure of photoreceptive membrane and polarity of response to light.     

Sensitivity analysis of sea scallop (Placopecten magellanicus) larvae trajectories to hydrodynamic model configuration on Georges Bank and adjacent coastal regions

The previous larval-trajectory modeling studies on Georges Bank were assessed through process-oriented Lagrangian-tracking comparison experiments using the high-resolution Gulf of Maine/Georges Bank Finite-Volume Coastal Ocean Model (GOM-FVCOM). The results indicate that in a strong nonlinear system such as Georges Bank, the passive tracer movement is driven by a fully three-dimensional Lagrangian flow field that varies in space and time due to large tidal excursion and steep bottom topography. The particle-tracking methods developed based on the assumption of weak nonlinearity of the flow field are not applicable to Georges Bank. The results of previous larval transport studies driven by circulation fields constructed under the weak-nonlinearity assumption need to be interpreted with caution. In the present work, the influence of model physical setups on sea scallop larval dispersal and settlement on Georges Bank and adjacent shelf regions is examined. Distinct differences in the spatial distribution of the passive larvae predicted by the model under various physical conditions suggest that a fully nonlinear model driven by realistic spatially and temporally varying forcing should be employed for Lagrangian-based studies of fishery population dynamics on Georges Bank.     

The role of B‐type esterases in conferring insecticide resistance in the tobacco whitefly,Bemisia tabaci (Genn)

Separation of non‐specific esterases on electrophoretic gels has played a key role in distinguishing between races or biotypes of the tobacco whitefly, Bemisia tabaci. One intensively staining esterase in particular (termed E_0.14) has assumed significance as a diagnostic of B‐type whiteflies (aka Bemisia argentifolii), despite any knowledge of its biological function. In this study, a whitefly strain (B‐Null) homozygous for a null allele at the E_0.14 locus that had been isolated from a B‐type population was used to demonstrate a significant role for E_0.14 in resistance of B‐type populations to pyrethroids but not to organophosphates (OPs). Bioassays with pyrethroids, following pre‐treatment with sub‐lethal doses of the OP profenofos (to inhibit esterase activity), coupled with metabolism studies with radiolabelled permethrin, supported the conclusion that pyrethroid resistance in a range of B‐type strains expressing E_0.14 was primarily due to increased ester hydrolysis. In the same strains, OP resistance appeared to be predominantly conferred by a modification to the target‐site enzyme acetylcholinesterase. © 2000 Society of Chemical Industry     

新疆B型烟粉虱对不同类型杀虫剂的抗性与分析

应用浸叶法研究了新疆B型烟粉虱对4类不同作用机制杀虫剂的抗药性。结果表明,被测种群对氯氰菊酯和联苯菊酯的抗性指数分别为2100～6200和1000～2200,属于高抗性;对氯化烟酰类杀虫剂产生了低至中等抗性,对吡虫啉的抗性指数为4～86,且抗性指数呈上升趋势,对噻虫嗪的抗性指数为10～22,对啶虫脒的敏感性最佳;对昆虫生长调节剂吡丙醚的抗性指数为22～54;对阿维菌素仍然表现敏感。由此认为,拟除虫菊酯类杀虫剂在新疆已不再适用于烟粉虱的防治,而对受抗药性影响较小的氯化烟酰类杀虫剂(如吡虫啉、噻虫嗪和啶虫脒)、昆虫生长调节剂吡丙醚以及阿维菌素等新型杀虫剂,仍然可以限制性地在不同化合物间交替使用。     

Transient expression shows ligand gating and allosteric potentiation of GABAA receptor subunits

Human gamma-aminobutyric acid A (GABAA) receptor subunits were expressed transiently in cultured mammalian cells. This expression system allows the simultaneous characterization of ligand-gated ion channels by electrophysiology and by pharmacology. Thus, coexpression of the alpha and beta subunits of the GABAA receptor generated GABA-gated chloride channels and binding sites for GABAA receptor ligands. Channels consisting of only alpha or beta subunits could also be detected. These homomeric channels formed with reduced efficiencies compared to the heteromeric receptors. Both of these homomeric GABA-responsive channels were potentiated by barbiturate, indicating that sites for both ligand-gating and allosteric potentiation are present on receptors assembled from either subunit.     

Natural hybridization between two sibling species of Anolis lizards: chromosome cytology

The Lesser Antillean lizards Anolis trinitatis and Anolis aenous were both apparently introduced to Trinidad where they are hybridizing. The parental species have 36 and 34 chromosomes, respectively. Hybrids have 35 chromosomes. Meiosis in hybrids is abnormal. There is an accumulation of cells at metaphase I, and poor homolog pairing, characterized by a low frequency of chiasmata and numerous univalents.     

A comparison of the F-test, Friedman’s test, and several aligned rank tests for the analysis of randomized complete blocks

Several tests for randomized complete block designs are compared, including the F-test, Friedman’s test, and a few aligned rank tests. An additive model was used in this simulation study with random errors that were generated independently from one of nine distributions. These distributions included the uniform, normal, double exponential, and six skewed distributions from the generalized lambda family. The simulations showed that Friedman’s test has low power compared with the aligned rank tests if the number of treatments does not exceed six. A new aligned rank F-test is proposed that maintains its significance level and has relatively high power. The simulations also showed that the proposed aligned rank test has higher power than the F-test for the double exponential and the skewed distributions if there is a large number of experimental units. If the number of experimental units exceeds 30, the proposed aligned rank test is recommended for skewed or long-tailed distributions. If the number of experimental units does not exceed 30, the normal theory F-test is recommended.