The effect of aging on cell-free protein synthesis in the free-living nematode Turbatrix aceti

The age-related reduction in cell-free synthesis in the free-living nematode Turbatrix aceti is due to a defect in the ribosomes. Addition of young ribosomal wash or use of young medium does not improve the activity of old, run-off ribosomes in the presence of phenylalanine and poly(U). It appears that some of the old ribosomes are incapable of binding the EF-1-GTP-aminoacyl-tRNA complex. These ineffective ribosomes are present in the 80 S (monosomal) fraction. Old ribosomes obtained from polysomes appear to bind normally.     

Microfluidic tools for developmental studies of small model organisms –nematodes,fruit flies,and zebrafish

Studying the genetics of development with small model organisms such as the zebrafish (Danio Rerio), the fruit fly (Drosophila melanogaster), and the soil-dwelling nematode (Caenorhabditis elegans), provide unique opportunities for understanding related processes and diseases in humans. These model organisms also have potential for use in drug discovery and toxicity-screening applications. There have been sweeping developments in microfabrication and microfluidic technologies for manipulating and imaging small objects, including small model organisms, which allow high-throughput quantitative biological studies. Here, we review recent progress in microfluidic tools able to manipulate small organisms and project future directions and applications of these techniques and technologies.     

Nippostrongylus brasiliensis: Female incubation,release of pheromone,fractionation of incubates

The release of pheromone by female Nippostrongylus brasiliensis as a crude incubate was linear for the first 2 hr, but declined after this period. Pheromone release in solution increased with temperature elevations until a 37 C incubation temperature was reached. Higher temperatures of incubation apparently caused diminished pheromone release. Gel filtration of female pheromone that was prepared as a crude incubate revealed biologically active elutions at K_av, 0.64 and 1.0. The timed release of female pheromone activity at these two elution regions coincided additively with the production of activity as a crude incubate. Each individual Chromatographic fraction from females accounted for about 50% of the pheromone activity of the crude, nonfractionated incubate, based on the male's bioassay response. Recombination of the K_av 0.64 and 1.0 elutions enabled recovery of pheromone activity that was similar to crude incubate. The gel filtration elution of 260-nm absorbance from male- or female-produced incubate was qualitatively similar, but a range of quantitative differences were evident. The fractionation of incubate from several female densities revealed only quantitative differences.     

The natural decline of an introduced species following its initial increase in abundance; an explanation for Ommatoiulus moreletii in Australia

Summary The black Portuguese millipede, Ommatoiulus moreletii, an exotic species first reported in Australia in 1953, shows a pattern of initial eruption and subsequent decline in abundance following its introduction to sites in South Australia. Comparative sampling of new, erupted populations and older, declined populations was done in an attempt to find testable hypotheses to account for the decline. We report on laboratory and field experiments which show that a native rhabditid nematode appears to be the causal agent for the decline of populations of O. moreletii in South Australia. Implications for the biological control of introduced species are discussed in terms of this work.     

Use of chitin for controlling plant plant-parasitic nematodes

Summary Bean and tomato seedlings, treated with different amounts of ammonia and chitin, and inoculated with the root-knot nematode,Meloidogyne javanica, were reared in two consecutive 35-day growth of shoot and root and the condition of the root systems of both plant species and degree of infection byM. javanica were decreased by increasing amounts of ammonia. Chitin caused a relatively small reduction in gall formation but almost no changes in fresh shoot weights. The effect of chitin on plant growth and nematode attack were also compared in irradiated and non-irradiated soil. In the first cycle galling index of the chitin treated plant was similar to that of untreated plants maintained in the irradiated soil conditions, while in the non-irradiated soil, chitin treatment reduced galling index. In the second cycle, chitin treatment reduced galling index in both irradiated and non-irradiated soils, especially in the latter, where galling index greatly decreased compared with the non-treated plants. Differences in fresh shoot weight between nematode-infected and nematode-free plants amended with chitin were greater under non-irradiated than irradiated conditions, especially in the second cycle. In non-irradiated soil, a higher level of chitinolytic microorganisms, particularly actinomycetes, was found in the second cycle. Contribution from the Agricultural Research Organization (ARO), Bet Dagan, Israel. No. 1520-E, 1985 series.     

A freeze-fracture study of the surface of the infective-stage larva of the nematode Trichinella

The surface layers of the cuticle of the infective, first-stage larva of the nematodes Trichinella spiralis and T. spiralis var. pseudospiralis have been studied by means of the freeze-fracturing technique. No obvious differences between the two nematodes were found. A double-layered structure covers the cuticle. Its outermost layer consists of particles embedded in an amorphous matrix; its inner layer is composed of a sheet of fine filaments which may be composed of globular subunits. This unique double layered structure is not like a normal cell membrane in structure. The surface of the cuticle beneath it is relatively smooth except for impressions from the inner surface of the double-layered structure. The cuticle surface did not fracture in the manner of a cell membrane.     

Equal-frequency Tolerance Ellipses for Population Studies of Belonolaimus longicaudatus

A biometrical method, using x-y plots of measurements of normaUy-distributed bivariate characters to construct a 95% equal-frequency ellipse representing 95% o f the specimens within its boundary, is presented. Comparisons of ellipses of four populations of Belonolaimus longicaudatus Rau show mean stylet lengths are relatively stable compared to mean tail lengths and there is greater styler length variability in short stylet forms. The extent of variability and regression between the populations can be seen by superimposing the bivariate means and orienting the longitudinal axes o f the ellipses. To compare ellipses the 95% binomial distribution is used to determine whether a sample population is significantly different from the model. The method is useful for graphic representation of morphological relationships within a nematode population, its relationship to other populations or species and to estimate environmental, ecological and genetic effects upon population morphology.     

NemChR-DB: a database of parasitic nematode chemosensory G-protein coupled receptors

Nematode Chemosensory G-Protein Coupled Receptors have expanded within nematodes, where they play important roles in foraging and host-seeking behaviour. Nematode Chemosensory G-Protein Coupled Receptors are most highly expressed during free-living stages when chemosensory signalling is required for host detection and nematode activation in various parasitic nematodes, and therefore position Nematode Chemosensory G-Protein Coupled Receptors at the transition from infective to parasitic stages, making them important regulators to study in terms of host-seeking and host specificity. To facilitate the analysis of Nematode Chemosensory G-Protein Coupled Receptors, here we describe an integrative database of nematode chemoreceptors called NemChR-DB. This database enables users to study diverse parasitic nematode chemoreceptors, functionally explore sequence entries through structural and literature-based annotations, and perform cross-species comparisons.     

The Compatibility of Control Agents used for the Control of the South American Leafminer, Liriomyza huidobrensis

The compatibility of infective juveniles (IJs) of the entomopathogenic nematode, Steinernema feltiae, the parasitic wasps Diglyphus isaea and Dacnusa sibirica, and chemical insecticides to control larval stages of the South American leafminer, Liriomyza huidobrensis, on leafy salad crops was investigated. In intact leaf mines, leafminer larvae already parasitized by D. isaea which had developed to the larval or pupal stage, and D. sibirica in the larval stage were subsequently also infected by S. feltiae following a foliar application. This reduced the potential of the wasps to survive until the adult stage. In similar tests foliar applied chemical insecticides reduced the survival to adulthood of D. sibirica and their host larvae. However, a soil drench of imidaclorpid did not cause a significant reduction in the number of D. sibirica which survived the treatment and developed to adult emergence. Tests to investigate the utilisation of parasitoids following foliar applications of nematodes found that adult D. isaea did not discriminate between the healthy and nematode-infected leafminer larvae for host feeding, although 98% of eggs laid by the female wasps were deposited alongside healthy larvae.     

Changes in water content and volume accompanying exsheathment of Haemonchus contortus

Davey K. G. and Rogers W. P. 1982. Changes in water content and volume accompanying exsheathment of Haemonchus contortus, International Journal for Parasitology12: 93–96. The exchange water volume was determined for ensheathed larvae, for larvae exsheathed by exposure to CO₂ and for larvae desheathed by exposure to a solution of NaOCl. Larvae exsheathed by exposure to CO₂ lose approx. 66 pl. of water while those desheathed by exposure to NaOCl lose approx. 50 pl. Larvae first desheathed by exposure to NaOCl lose a further 20 pl of water when subsequently exposed to CO₂. Volumes calculated from linear measurements of larvae demonstrate that larvae exsheathed by exposure to CO₂ lose about 69 pl of their total volume, while those desheathed by NaOCl lose about 54 pl. It is concluded that exsheathment may involve at least two parallel processes. Both processes are initiated by CO₂, while one is mimicked by exposure to NaOCl.