Anhydrobiosis in Five Species of Plant Associated Nematodes

Five species of nematodes - Hemicriconemoides pseudobrachyurum, Hemicycliophora conida, Macroposthonia ornata, Aphelenchoides ritzemabosi, and Psilenchus hilarulus -were desiccated to study their capacity to survive anhydrobiotically. Results indicate that the ability of the sheath to shrink quickly and its relatively loose attachment with the nematode body allow H. conida to survive longer than H. pseudobrachyurum; the survival of M. ornata was intermediate, A. ritzemabosi and P. hilarulus survived immersion in paraffin oil for 12 and 17 days, respectively. Both of these nematodes possess multiple contraction ability; i.e., coiling coupled with transverse and longitudinal folding of the cuticle. P. hilarulus is a new addition to the list of anhydrobiotic nematodes.     

Phytoalexins and their Role in the Resistance of Plants to Nematodes

Phytoalexins are antibiotic compounds synthesized in an infected plant in response to infection. Nematodes are capable of eliciting phytoalexins in resistant plants. Resistant lima bean (Phaseolus lunatus) infected by Pratylenchus penetrans produces the phytoalexin coumestrol; soybean (Glycine max) infected by Meloidogyne incognita produces glyceollin; cotton (Gossypium hirsuturn) infected by M. incognita produces terpenoid aldehydes.     

Identification of Entomopathogenic Nematodes in the Steinernematidae and Heterorhabditidae (Nemata: Rhabditida)

This paper contains taxonomic keys for the identification of species of the genera Steinernema and Heterorhabditis. Morphometrics of certain life stages are presented in data tables so that the morphometrics of species identified using the keys can be checked in the tables. Additionally, SEM photographs and diagnoses of the families and genera of Steinernematidae and Heterorhabditidae are presented.     

An Alternative Gelling Agent for Culture and Studies of Nematodes,Bacteria, Fungi,and Plant Tissues

Pluronic F127 polyol, a block copolymer of propylene oxide and ethylene oxide, was studied as an alternative to agar in culture media for nematodes, bacteria, fungi, actinomycetes, and plant tissues or seedlings, At a polyol concentration of 20% w/v, the culture media, semi-solid at room temperature (22 C) but liquid at lower temperatures, had minimal effects on the test organisms. Most of the fungi and bacteria grew as well in 20% polyol as in 1.5% agar media; however, various species of nematodes and plant seedlings or tissues exhibited differential sensitivities to different concentrations of the polyol. In cases where the organisms were unaffected, the polyol media had certain advantages over agar, including greater transparency and less contamination under nonaseptic conditions. Polyol media have potentially greater ease for recovery of embedded organisms or tissues inside the media by merely shifting to lower temperatures.     

Clostridium difficile ribotypes in humans and animals in Brazil

Clostridium difficile is an emerging enteropathogen responsible for pseudomembranous colitis in humans and diarrhoea in several domestic and wild animal species. Despite its known importance, there are few studies aboutC. difficile polymerase chain reaction (PCR) ribotypes in Brazil and the actual knowledge is restricted to studies on human isolates. The aim of the study was therefore to compare C. difficileribotypes isolated from humans and animals in Brazil. Seventy-six C. difficile strains isolated from humans (n = 25), dogs (n = 23), piglets (n = 12), foals (n = 7), calves (n = 7), one cat, and one manned wolf were distributed into 24 different PCR ribotypes. Among toxigenic strains, PCR ribotypes 014/020 and 106 were the most common, accounting for 14 (18.4%) and eight (10.5%) samples, respectively. Fourteen different PCR ribotypes were detected among human isolates, nine of them have also been identified in at least one animal species. PCR ribotype 027 was not detected, whereas 078 were found only in foals. This data suggests a high diversity of PCR ribotypes in humans and animals in Brazil and support the discussion of C. difficile as a zoonotic pathogen.     

Marine Nematodes of Bothnian Bay,Finland: Ethmolaimus hailuotoensis n. sp. (Ethmolaimidae: Nemata)

Ethmolaimus hailuotoensis n. sp. from Bothnian Bay, northern Baltic Sea, is described and illustrated. Ethmolaimus hailuotoensis n. sp. has a strongly sclerotized luminal lining of the terminal esophageal bulb and esophagus. The most characteristic feature is a lateral series of large concentric, sclerotized rings with a fine, internal longitudinal oval sclerotization. In addition, E. hailuotoensis n. sp. is distinguished from other Ethmolaimus species by its smaller body size, fewer number of precloacal supplements (7-8), conical tail, and the position of amphid posterior to the buccal cavity. Females of E. hailuotoensis n. sp. studied were hermaphroditic. Ethmolaimus hailuotoensis n. sp. coexisted with E. pratensis. Ethmolaimus pratensis from Bothnian Bay has a characteristic row of sublateral hypodermal glands, a character not before seen in Ethmolaimidae.     

Aspidosperma (Apocynaceae) plant cytotoxicity and activity towards malaria parasites. Part II: experimental studies with Aspidosperma ramiflorum in vivo and in vitro

Several species of Aspidosperma plants are used to treat diseases in the tropics, including Aspidosperma ramiflorum, which acts against leishmaniasis, an activity that is experimentally confirmed. The species, known as guatambu-yellow, yellow peroba, coffee-peroba andmatiambu, grows in the Atlantic Forest of Brazil in the South to the Southeast regions. Through a guided biofractionation of A. ramiflorum extracts, the plant activity against Plasmodium falciparum was evaluated in vitro for toxicity towards human hepatoma G2 cells, normal monkey kidney cells and nonimmortalised human monocytes isolated from peripheral blood. Six of the seven extracts tested were active at low doses (half-maximal drug inhibitory concentration < 3.8 µg/mL); the aqueous extract was inactive. Overall, the plant extracts and the purified compounds displayed low toxicity in vitro. A nonsoluble extract fraction and one purified alkaloid isositsirikine (compound 5) displayed high selectivity indexes (SI) (= 56 and 113, respectively), whereas compounds 2 and 3 were toxic (SI < 10). The structure, activity and low toxicity of isositsirikine in vitro are described here for the first time in A. ramiflorum, but only the neutral and precipitate plant fractions were tested for activity, which caused up to 53% parasitaemia inhibition of Plasmodium berghei in mice with blood-induced malaria. This plant species is likely to be useful in the further development of an antimalarial drug, but its pharmacological evaluation is still required.     

Genetic Analysis of Esterase Polymorphism in the Soybean Cyst Nematode, Heterodera glycines

The genetic basis of esterase polymorphism in Heterodera glycines was investigated through controlled matings and analysis of F₁ and F₂ progeny. Three nematode lines, each fixed for a different esterase phenotype, were isolated and purified through repeated directional selection and inbreeding. Each phenotype was characterized by its distinct pair of closely spaced bands of esterase activity. Single-female single-male crosses were conducted according to a modified agar-plate mating technique. F₁ progeny were homogeneous, exhibiting both parental esterase phenotypes (codominant heterozygotes) but no hybrid bands. Approximately 1,500 F₂ progeny segregated in a 1:2:1 ratio for expression of the esterase phenotypes of the female parental line, the heterozygote, and the male parental line. Apparently the three esterase phenotypes correspond to three codominant alleles of a single esterase locus. Reciprocal crosses gave similar results, suggesting no maternal inheritance.     

Developmental Nutrition of Nematodes: the Biochemical Role of Sterols,Heme Compounds,and Lysosomal Enzymes

Attempts to develop defined in vitro culture systems for the growth, reproduction and development of free-living nematodes have yielded much basic information about their nutritional requirements and biochemistry. Requirements for sterol and heme have been identified suggesting that some nematodes lack de novo synthesis of these molecules. Possible pathways of metabolism of these nutritional requirements can be derived from in vitro experiments that use a variety of sterol and heine sources as supplements to the culture mediuin. These pathways are reviewed as well as the possible role of sterol and heme in the biology of free-living and parasitic nematodes, Since these molecules must be acquired dietarily, the possible involvement of lysosomal enzymes in digestion is discussed. Also considered is the possibility that lysosomal enzymes change when nematodes are fed on a heine protein source.     

Macroposthonia sicula n. sp. (Nematoda: Criconematidae), a Parasite of Olive Trees in Sicily

Macroposthonia sicula n.sp. collected from rhizosphere and roots of olive (Olea europaea L.) at Kamarina, Sicily, Italy, is described and illustrated. It is distinguished from the related species (M. sphaerocephala and M. maskaka) by the longer styler and the characteristic narrowing postvulval portion of the body.     

Effect of Temperature on the Development of Thelastoma bulhoesi (Oxyurata, Thelastomatida) and Other Nematodes

Embryonation of Thelastoma bulhoesi was monitored at eight temperatures between 0 and 35 C. Cell division did not occur below 15 C or at 35 C. Development was most rapid at 25 and 36 C. The effect of temperature on the rate of embryological development of T. bulhoesi at different stages was measured using the temperature coefficient, Q₁₀. The developmental temperature response curve obtained for T. bulhoesi was similar to enzyme temperature response curves. Our evidence supports the thesis that nematode embryonation, as affected by temperature, varies between species and between stages of development.     

Interactions between Nematodes and Earthworms: Enhanced Dispersal of Steinernema carpocapsae

Dispersal of the nematode Steinernema carpocapsae (All strain), applied on the top or the bottom of soil columns, was tested in the presence or absence of two earthworm species, Lumbricus terrestris or Aporrectodea trapezoides. Nematode dispersal was estimated after a 2-week period with a bioassay against the greater wax moth, Galleria mellonella. Vertical dispersal of nematodes was increased in the presence of earthworms. When nematodes were placed on the surface of soil columns, significantly more nematodes dispersed to the lower half of the columns when either earthworm species was present than when earthworms were not present. When nematodes were placed on the bottom of soil columns, significantly more nematodes dispersed to the upper half of the columns when L. terrestris was present than when A. trapezoides was present or in the absence of earthworms. Because nematodes were found on the exterior and in the interior of earthworms, nematode dispersal may be enhanced by direct contact with the earthworms.     

Effects of Hypoxia on 13NH4+ Fluxes in Rice Roots : Kinetics and Compartmental Analysis

Techniques of compartmental (efflux) and kinetic influx analyses with the radiotracer ¹³NH₄⁺ were used to examine the adaptation to hypoxia (15, 35, and 50% O₂ saturation) of root N uptake and metabolism in 3-week-old hydroponically grown rice (Oryza sativa L., cv IR72) seedlings. A time-dependence study of NH₄⁺ influx into rice roots after onset of hypoxia (15% O₂) revealed an initial increase in the first 1 to 2.5 h after treatment imposition, followed by a decline to less than 50% of influx in control plants by 4 d. Efflux analyses conducted 0, 1, 3, and 5 d after the treatment confirmed this adaptation pattern of NH₄⁺ uptake. Half-lives for NH₄⁺ exchange with subcellular compartments, cytoplasmic NH₄⁺ concentrations, and efflux (as percentage of influx) were unaffected by hypoxia. However, significant differences were observed in the relative amounts of N allocated to NH₄⁺ assimilation and the vacuole versus translocation to the shoot. Kinetic experiments conducted at 100, 50, 35, and 15% O₂ saturation showed no significant change in the K_m value for NH₄⁺ uptake with varying O₂ supply. However, V_max was 42% higher than controls at 50% O₂ saturation, unchanged at 35%, and 10% lower than controls at 15% O₂. The significance of these flux adaptations is discussed.     

Carbohydrate Catabolism in Populations of Bursaphelenchus xylophilus and in B. mucronatus

Genotypically different host specific pathotypes of Bursaphelenchus xylophilus have been identified. These pathotypes elicit different responses in pines depending on susceptibility, tolerance, or resistance. Continued passage of some of these pathotypes on fungal cultures leads to conversion to nonparasitic populations. These populations metabolize carbon substrates to ethanol by an anaerobic pathway, while operating some level of a phosphoenolpyruvate (PEP)-succinate pathway to excrete succinate-lactate and malate. On the other hand, parasitic populations metabolize glucose to lactate-succinate, mainly by a PEP-succinate pathway, and maintain redox balance through glycerol production. Ethanol and malate are not excreted by parasitic populations.     

Drosophila Adiponectin Receptor in Insulin Producing Cells Regulates Glucose and Lipid Metabolism by Controlling Insulin Secretion

Adipokines secreted from adipose tissue are key regulators of metabolism in animals. Adiponectin, one of the adipokines, modulates pancreatic beta cell function to maintain energy homeostasis. Recently, significant conservation between Drosophila melanogaster and mammalian metabolism has been discovered. Drosophila insulin like peptides (Dilps) regulate energy metabolism similarly to mammalian insulin. However, in Drosophila, the regulatory mechanism of insulin producing cells (IPCs) by adipokine signaling is largely unknown. Here, we describe the discovery of the Drosophila adiponectin receptor and its function in IPCs. Drosophila adiponectin receptor (dAdipoR) has high homology with the human adiponectin receptor 1. The dAdipoR antibody staining revealed that dAdipoR was expressed in IPCs of larval and adult brains. IPC- specific dAdipoR inhibition (Dilp2>dAdipoR-Ri) showed the increased sugar level in the hemolymph and the elevated triglyceride level in whole body. Dilps mRNA levels in the Dilp2>dAdipoR-Ri flies were similar with those of controls. However, in the Dilp2>dAdipoR-Ri flies, Dilp2 protein was accumulated in IPCs, the level of circulating Dilp2 was decreased, and insulin signaling was reduced in the fat body. In ex vivo fly brain culture with the human adiponectin, Dilp2 was secreted from IPCs. These results indicate that adiponectin receptor in insulin producing cells regulates insulin secretion and controls glucose and lipid metabolism in Drosophila melanogaster. This study demonstrates a new adipokine signaling in Drosophila and provides insights for the mammalian adiponectin receptor function in pancreatic beta cells, which could be useful for therapeutic application.     

Inter- and Intraspecific Variation in Wild-type and Single Female-derived Populations of Xiphinema americanum-group Nematodes

Ten populations of Xiphinema americanum-group nematodes were reared from individual females to evaluate inter- and intraspecific variation under identical host and environmental conditions. Data indicated that morphometric variability of X. americanum was the result of genetic variation rather than phenotypic plasticity and that genetic heterogeneity was greater than previously thought. Morphometrics of single female derived (SFD) populations identified different genotypes present in the field populations. Stylet length was the least variable morphometric character of SFD populations, but collectively stylet measurements of all individuals formed an uninterrupted continuum ranging from 107-148 μm. Range and frequency of stylet measurements of field populations could be accounted for by the relative proportion of different genotypes in the population. Nine SFD populations were identified as X. americanum sensu stricto, and one SFD population was similar to X. californicum.