Trichostrongylus colubriformis: egg lethality due to Bacillus thuringiensis crystal toxin

A toxin from crystals of Bacillus thuringiensis israelensis was lethal in vitro to eggs of the ruminant nematode Trichostrongylus colubriformis, with an LD50 of 1.8 ng/ml. Larval viability declined after a 2-hr exposure to B. t. israelensis and was dependent on the development period of eggs prior to exposure. Alkaline solubilization suggested that the insecticidal delta-endotoxin of B. t. israelensis was not responsible for nematicidal activity. Filtration of the toxin through 0.2- or 0.45-micron-pore filters revealed that the nematicidal activity was retained on the filter. Toxicity for nematode eggs was decreased by the enzyme inhibitor L-1-tosylamide 2-phenylethylchloromethyl ketone (10(-4) M) or ethylenediaminetetraacetic acid (10(-5) M) and phenylmethylsulfonyl fluoride (10(-6) M). Ethylenediaminetetraacetic acid from 10(-9) to 10(-5) M had no effect on the toxicity while phenylmethylsulfonyl fluoride from 10(-9) to 10(-5) M inhibited toxicity. Fourteen mammalian and microbial enzymes had no significant effect on larval viability while 12 sugars and lipids failed to reduce the toxicity. Addition of 5 mM calcium to the eggs' medium decreased the B. t. israelensis toxicity by 20-fold. The calcium-dependent inhibition of toxicity was reversed by ethylenediaminetetraacetic acid (10(-5) M) and lanthanum chloride (100 microM). The ionophore A-23187 decreased the LD50 by 18-fold to 33.5 ng/ml. Addition of 5 mM calcium chloride to the ionophore and toxin yielded an LD50 of 9.2 ng/ml. Treatment of nematode eggs with B. t. israelensis toxin for 2 or 24 hr had no effect on subsequent binding of selected fluoresceinated lectins to the eggshell.     

Trichostrongylus colubriformis: isolation and characterization of ovicidal activity from Bacillus thuringiensis israelensis

Bioassay of media fractions from cultivation of Bacillus thuringiensis israelensis revealed that ovicidal activity for eggs of the ruminant nematode Trichostrongylus colubriformis was found in microbial crystals, but was not released into culture medium. The purified delta-endotoxin of B. t. israelensis, composed of two 25 kDa proteins, had no effect on nematode eggs. A fraction that had high ovicidal activity for eggs of T. colubriformis was isolated by high performance liquid chromatography from crystals of B. t. israelensis. Retention of the compound(s) on size exclusion columns indicated a mol wt of 1510 when compared to standards. The LD50 of this fraction for nematode eggs was not altered significantly by 5 mM calcium chloride with and without ethylenediaminetetraacetic acid or the enzyme inhibitor phenylmethylsulfonyl fluoride (10(-6) M). The fraction was susceptible to proteolytic hydrolysis by bacterial protease VI whereas the fungal protease XIII slightly decreased the ovicidal effects of the fraction. The ovicidal activity was stable for 2 days at ambient temperature or 2 months at 0 C, but declined after 7 days at ambient temperature. Little activity was lost after heating to 100 C for 60 min. The ovicidal effects were also pH dependent with increased toxicity at alkaline pH values. The fraction, however, had no effect on larvae of the mosquito Aedes aegypti or mice after intraperitoneal injection.     

Factors influencing lethality of Bacillus thuringiensis kurstaki toxin for eggs and larvae of Trichostrongylus colubriformis (Nematoda)

A toxin from Bacillus thuringiensis kurstaki was lethal to eggs and first- and second-stage larvae of the ruminant nematode Trichostrongylus colubriformis. Sheathed and exsheathed third-stage larvae were also killed by the toxin. However, susceptibility of the ova to the toxin decreased after several hours of development. Heating at 65 C for 1 hr or freezing at 0 C for 3 mo did not affect stability of the toxin. Ovicidal activity of the toxin was not altered by treatment with 13 microbial or mammalian enzymes, but toxicity was reduced by the antibiotics streptomycin or penicillin G and the enzyme inhibitor L-1-tosylamide 2-phenylethylchloromethyl ketone. Cuprous, ferrous, and zinc chlorides also inhibited the ovicidal activity of the toxin. Increased osmolarity of the assay media or solubilization of the toxin from pH 3 to 11 had no effect on toxicity for eggs. The membrane agents sodium vanadate and 4,4'-diisothiocyano-2,2' disulfonic acid stilbene increased (9-fold) and decreased (333-fold) toxicity, respectively. N-acetylneuraminic acid was the only tested sugar that reduced the toxicity of B. t. kurstaki.     

In-vitro Assays of Meloidogyne incognita and Heterodera glycines for Detection of Nematode-antagonistic Fungal Compounds

In-vitro methods were developed to test fungi for production of metabolites affecting nematode egg hatch and mobility of second-stage juveniles. Separate assays were developed for two nematodes: root-knot nematode (Meloidogyne incognita) and soybean cyst nematode (Heterodera glycines). For egg hatch to be successfully assayed, eggs must first be surface-disinfested to avoid the confounding effects of incidental microbial growth facilitated by the fungal culture medium. Sodium hypochlorite was more effective than chlorhexidine diacetate or formaldehyde solutions at surface-disinfesting soybean cyst nematode eggs from greenhouse cultures. Subsequent rinsing with sodium thiosulfate to remove residual chlorine from disinfested eggs did not improve either soybean cyst nematode hatch or juvenile mobility. Soybean cyst nematode hatch in all culture media was lower than in water. Sodium hypochlorite was also used to surface-disinfest root-knot nematode eggs. In contrast to soybean cyst nematode hatch, root-knot nematode hatch was higher in potato dextrose broth medium than in water. Broth of the fungus Fusarium equiseti inhibited root-knot nematode egg hatch and was investigated in more detail. Broth extract and its chemical fractions not only inhibited egg hatch but also immobilized second-stage juveniles that did hatch, confirming that the fungus secretes nematode-antagonistic metabolites.     

Immobilization of Alginate-Encapsulated Bacillus thuringiensis var. israelensis Containing Different Multivalent Counterions for Mosquito Control

Immobilized techniques have been used widely for the controlled release formulation of mosquitoes. Among the microbial formulations, polymeric matrices play an important role in the controlled release of microbial pesticide at rates sufficiently effective to kill mosquitoes in the field. The advantage of these matrices is that they enhance the stability of both spores and toxin against pH, temperature variations, and UV irradiation. The disadvantage of using calcium alginate beads is that they are unstable upon contact with phosphate of potassium or sodium ions rich in the mosquito habitats. To overcome these problems, attempts were made to encapsulate Bacillus thuringiensis var. israelensis within alginate by using different multivalent counterions, namely, calcium chloride, zinc sulfate, copper sulfate, cobalt chloride, and ferric chloride, and the beads formed were tested for its mosquito larvicidal activity. Among all the beads tested, zinc alginate beads resulted in maximum larvicidal activity of 98% (+/-1.40 SE) against Culex quinquefasciatus IIIrd instar larvae and maximum spore count of 3.36 x 10(5) (+/-5291.50 SE) CFU/ml. Zinc alginate beads maintained their structure for up to 48 h when shaken vigorously on a rotary shaker at 180 rpm in the presence of 10 mM potassium phosphate buffer (pH 6.8 +/- 0.1). In conclusion, our results suggest that the use of zinc sulfate as counterions to encapsulate B. thuringiensis var. israelensis within alginate may be a potent mosquito control program in the habitats where more phosphate ions are present.     

Exopeptidase activity in eggs of Trichostrongylus colubriformis (Nematoda)

Summary

A supernatant from eggs of the ruminant nematode Trichostrongylus colubriformis contained an enzyme that was similar to leucine aminopeptidase (LAP), based on hydrolysis of the substrate L-leucine β-naphthylamide to β-naphthylamine. A Michaelis-Menten constant (K _m) of 0.155 mM was obtained. Rate of hydrolysis of 16 substrates revealed that L-phenylalanine and L-tyrosine β-naphthylamides were hydrolyzed most readily while seven additional substrates were hydrolyzed at lesser rates. The optimum pH for enzymatic activity was 6.75–7.5. Enzymatic activity was lost by heating the egg supernatant to 60°C for 5 min or freezing at 0°C for 28 days. Addition of millimolar concentrations of the chlorides of zinc, manganese and magnesium to the egg supernatant had no stimulatory effect on enzyme activity while 10 and 100 mM concentrations significantly reduced activity. Ethylenediamine tetraacetic acid at 10^?4 M had no effect on enzymatic activity. Activity was inhibited by 10^?4 M 1,10-phenanthroline, but the inhibition was reversed by zinc chloride at 10^?3 M. Di-isopropylphosphofluoridate at 10^?3 M reduced enzymatic activity moderately. Enzyme activity in egg supernatant increased 2.2-fold from 21 days to 60–90 days of a primary infection in the host while a 3.3-fold increase was found in primary versus secondary infections.     

Cystic fibrosis transmembrane conductance regulator facilitates ATP release by stimulating a separate ATP release channel for autocrine control of cell volume regulation

These studies provide evidence that cystic fibrosis transmembrane conductance regulator (CFTR) potentiates and accelerates regulatory volume decrease (RVD) following hypotonic challenge by an autocrine mechanism involving ATP release and signaling. In wild-type CFTR-expressing cells, CFTR augments constitutive ATP release and enhances ATP release stimulated by hypotonic challenge. CFTR itself does not appear to conduct ATP. Instead, ATP is released by a separate channel, whose activity is potentiated by CFTR. Blockade of ATP release by ion channel blocking drugs, gadolinium chloride (Gd(3+)) and 4,4'-diisothiocyanatostilbene-2,2'disulfonic acid (DIDS), attenuated the effects of CFTR on acceleration and potentiation of RVD. These results support a key role for extracellular ATP and autocrine and paracrine purinergic signaling in the regulation of membrane ion permeability and suggest that CFTR potentiates ATP release by stimulating a separate ATP channel to strengthen autocrine control of cell volume regulation.     

The survival of Ostertagia circumcincta and Trichostrongylus colubriformis in faecal culture as a source of bias in apportioning egg counts to worm species.

When cultured alone or concurrently with Trichostrongylus colubriformis in sheep faeces, Ostertagia circumcincta produced fewer infective larvae per 100 eggs than did T. colubriformis. Averaged over five trials 60% of T. colubriformis eggs were recovered as infective larvae while for O. circumcincta the figure was only 39%. This result was observed for two strains of O. circumcincta and was independent of when larvae were harvested from culture (days 6-10 at 25 degrees C). The mortalities of both species occurred at the first and second larval stages. These observations are of concern when using larval differentiation from faecal culture to make quantitative estimates of worm egg numbers for each species present. Species such as T. colubriformis which have a low mortality during culture are likely to have their egg numbers overestimated when cultured with a species, like O. circumcincta, that suffers high mortality in culture.     

Ovipositional and ovicidal effects of the microbial agent Bacillus thuringiensis israelensis on Culex quinquefasciatus say (Diptera: Culicidae).

The magnitude of oviposition as well as the size, shape and the number of eggs per of egg rafts egg raft were determined after gravid Culex quinquefasciatus Say oviposited on water treated with water dispersible granules (WDG) of Bacillus thuringiensis ssp. israelensis (Bti) and on untreated water. The mean number of eggs/raft was lower in the treated than in the untreated water. Bti concentrations from 0.5 to 2.0mg/L affected the shape of egg rafts and number of eggs in each raft. As the concentration of Bti increased from 0.5 to 2.0 mg/L the shape of egg rafts became more irregular with fewer eggs in each raft. Exposure to Bti at 2- and 26-h reduced the hatching rates, and fewer eggs hatched at 26-h of exposure to Bti. As the concentration of Bti WDG increased from 0.5 to 2.0 mg/L, the hatching rate decreased. Eggs exposed for 2-h to 2.0mg/ L Bti had a hatch of 30% after 24 h, the rate increasing to 57% after 72 h. In contrast, in 26-h exposed eggs to 2.0 mg/L Bti, the hatching rate after 24 h was only 12% and this rate increased to 39% after 72 h. In larvae from eggs exposed for 2 h, the survival rate was 40% at 2.0 mg/L Bti and 87% in untreated controls. In contrast, the survival rates of larvae from 26-h exposed eggs was 91% in controls while it was 30% at 2.0 mg/L Bti. As the concentration of Bti increased from 0.5 to 2.0 mg/ 1 the survival rates of larvae decreased. The combined effects of reductions of egg rafts, low number of eggs per egg raft, and reduced hatching and survival rates could have significant cumulative effects on the yield of adult mosquitoes, and this could result in a greater control potential of this microbial agent.     

Voltage-dependent chloride conductance of the squid axon membrane and its blockade by some disulfonic stilbene derivatives

When giant axons of squid, Sepioteuthis, were bathed in a 100 mM Ca-salt solution containing tetrodotoxin (TTX) and internally perfused with a solution of 100 mM tetraethylammonium-salt (TEA-salt) or tetramethylammonium-salt (TMA-salt), the membrane potential was found to become sensitive to anions, especially Cl-. Membrane currents recorded from those axons showed practically no time-dependent properties, but they had a strong voltage-dependent characteristic, i.e., outward rectification. Cl- had a strong effect upon the voltage-dependent membrane currents. The nonlinear property of the currents was almost completely suppressed by some disulfonic stilbene derivatives applied intracellularly, such as 4-acetoamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) and as 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), which are blockers of chloride transport. On the basis of these experimental results, it is concluded that a voltage-dependent chloride-permeable channel exists in the squid axon membrane. The chloride permeability (PCl) is a function of voltage, and its value at the resting membrane (Em = -60 mV) is calculated, using the Goldman-Hodgkin-Katz equation, to be 3.0 X 10(-7) cm/s.     

Lipolytic action of cholera toxin on fat cells. Re-examination of the concept implicating GM1 ganglioside as the native membrane receptor.

The possible role of galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (GM1) ganglioside in the lipolytic activity of cholera toxin on isolated fat cells has been examined. Analyses of the ganglioside content and composition of intact fat cells, their membranous ghosts, and the total particulate fraction of these cells indicate that N-acetylneuraminylgalactosylglucosylceramide (GM3) represents the major ganglioside, with substantial amounts of N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (GM2) and smaller amounts of other higher homologues also present. Native GM1 was not detected in any of these preparations. Examination of the relative capacities of various exogenously added radiolabeled sphingolipids to bind to the cells indicated that GM2 and glucosylsphingosine were accumulated by the cells to extents comparable to GM1. Galactosylsphingosine and sulfatide also exhibited significant, although lesser, binding affinities for the cells. The adipocytes appeared to nonspecifically bind exogenously added GM1; saturation of binding sites for GM1 could not be observed up to the highest concentration tested (2 X 10(-4) M), wherein about 7 X 10(9) molecules were associated with the cells. Essentially all of this exogenously added GM1 was found bound to the plasma membrane "ghost" fraction. Investigation of the biological responses of the cells confirmed their sensitivities to both cholera toxin and epinephrine-stimulated lipolysis, as well as the lag period displayed during the toxin's action. While we could confirm that the toxin's lipolytic activity can be enhanced by prior treatment of the fat cells with GM1, several of the observed characteristics of this phenomenon differ from earlier reported findings. Accordingly, added GM1 was able to enhance only the subsequent rate, but not the extent, of toxin-stimulated glycerol release (lipolysis) from the cells. We also were unable to confirm the ability of GM1 to enhance the toxin's activity at either saturating or at low toxin concentrations. The limited ability of added GM1 to enhance the toxin's activity appeared in a unique bell-shaped dose-response manner. The inability of high levels of GM1 to stimulate a dose of toxin that was ineffective on native cells suggests that the earlier reported ability of crude brain gangliosides to accomplish this was due to some component other than GM1 in the crude extract. While several glycosphingolipids and some other carbohydrate-containing substances that were tested lacked the ability to mimic the enhancing effect of GM1, 4-methylumbelliferyl-beta-D-galactoside exhibited an effect similar to, although less pronounced than, that of GM1. The findings in these studies are unable to lend support to the earlier hypothesis that (a) GM1 is cholera toxin's naturally occurring membrane receptor on native fat cells, and (b) the ability of exogenously added GM1 to enhance the toxin's lipolytic activity represents the specific creation of additional natural receptors on adipocytes...     

Leucine Aminopeptidase in Eggs of the Soybean Cyst Nematode Heterodera glycines

Supernatant from a sonicated macerate of eggs of Heterodera glycines hydrolyzed L-leucine β-naphthylamide and L-leucine 7-amido-4-methylcoumarin. Rate of substrate hydrolysis was influenced by pH and increased with the duration of incubation. A Michaelis-Menten constant of 0.15 mM was obtained. Rate of substrate hydrolysis was decreased by freezing egg supernatant for 26 days or heating above 60 C for 5 minutes. When egg supernatant was incubated with six different substrates, L-leucine β-naphthylamide was hydrolyzed most readily and L-valine β-naphthylamide the least readily. The rate of substrate hydrolysis by egg supernatant was not increased by pretreatment of eggs with 3 mM zinc chloride for up to 14 days.     

Fungal parasitism of the cyst nematode Heterodera schachtii: infection and enzymatic activity

Abstract Fungal egg parasites isolated from eggs of the cyst nematode Heterodera avenae in Sweden were investigated with respect to their ability to infect cyst nematode eggs of H. schachtii in vitro. The infection was studied by interference phase contrast microscopy of whole cysts and of cryosections of cysts exposed to the fungi on agar plates.
Verticillium suchlasporium was the most effective parasite, infecting 53% of the nematode eggs, while V. chlamydosporium infected 12% of the eggs. The fungi Paecilomyces lilacinus, Cylindrocarpon destructans or Fusarium oxysporum did not parasitize nematode eggs; nor did Arthrobotrys oligospora , a nematode trapping fungus nor Penicillium viridicatum which served as a control fungus.
The ability of the fungi to infect eggs was correlated with their lytic enzyme activity. Fungi that readily infected eggs also showed chitinase activity and presence of proteolytic activity. The Verticillium species had an activity between 3.7 and 14.6 μmol N -acetyl-glucosamine per mg protein per hour (CU) while it was 4.5 CU or lower for P. lilacinus . Other isolates did not shown any chitinase activity.     

Regulation of ooplasmic sodium and potassium activities in developing locust eggs

Ooplasmic activities of potassium and sodium were measured with ion sensitive microelectrodes before and during the period of maximal water uptake which occurs 3–5 days after oviposition for eggs incubated at 37°C. Potassium activity increased from 84 mM in eggs before fertilization at 118 mM in eggs 1 day after fertilization (d1). Sodium activity increased from 8 mM to 29 mM over the same period. These changes exceeded those predicted from the decrease in water content (8%) during the first day after oviposition. Between d1 and d3, potassium and sodium activities decreased to values predicted on the basis of the 88% increase in egg water content. Although water content increased an additional 46% between d3 and d5, ooplasmic sodium activity remained constant at 11 mM and potassium activity increased from 64 mM to 74 mM during this time. Declines in concentrations of sodium and potassium measured in whole eggs by atomic absorption spectrometry mirrored the increase in egg water content. The results suggest that regulation of ooplasmic sodium and potassium activities is accomplished by release of these ions from internal stores, possibly the york spheres. © 1992 Wiley-Liss, Inc.     

Identification and characterisation of an aspartyl protease inhibitor homologue as a major allergen of Trichostrongylus colubriformis

Allergens were identified from the gastrointestinal nematode of sheep, Trichostrongylus colubriformis, by probing Western blots of infective larvae (third stage) somatic antigen with IgE purified from the serum of sheep grazed on worm contaminated pasture. A 31 kDa allergen was frequently recognised by sera from immune sheep, particularly those deriving from a line that has been genetically selected over 23 years for parasite resistance. Using a proteomic approach, the 31 kDa allergen was identified as an aspartyl protease inhibitor homologue. The entire coding sequence of T. colubriformis aspartyl protease inhibitor (Tco-api-1) was obtained and the mature protein expressed in Escherichia coli. Anti-Tco-API-1 antibodies revealed that a commonly observed 21 kDa T. colubriformis allergen species is a truncated form of Tco-API-1. Specific IgE responses to T. colubriformis aspartyl protease inhibitor were significantly correlated with the degree of resistance to nematode infection as measured by faecal egg count in sheep. Surprisingly, IgE responses to Tco-API-1 were not correlated with breech soiling (dag score), which is thought to be caused, in part, by allergic hypersensitivity to worms. Therefore, a specific IgE response to this allergen may be a suitable marker for identifying lambs at an early age that will develop strong immunity to gastrointestinal nematodes.     

Alginate films for delivery of root-knot nematode inoculum and evaluation of microbial interactions

A method was developed for utilizing alginate films to deliver inoculum into soil and evaluate microbial antagonistic activity against nematode eggs. Eggs of Meloidogyne incognita were harvested from galled tomato roots (Lycopersicon esculentum), surface disinfested, suspended in 2% (w/v) aqueous sodium alginate, and applied to 2.5 × 5.0 cm polyvinyl chloride coated fiberglass screens (1.5 mm² mesh size) at a uniform thickness of 0.5 mm. The alginate solution was gelled by dipping in 0.25 M CaCl₂. Films containing eggs were observed in vitro and egg development was evaluated. The number of immature eggs and eggs with first stage juveniles declined linearly over time while the number of empty eggs shells, and hatched juveniles increased over time, indicating that the alginate gel did not inhibit development and motility of M. incognita juveniles. In a greenhouse experiment using cucumber (Cucumis sativus) the number of galls g^-1 root was correlated with the number of eggs in alginate films placed in each pot at planting. Films containing M. incognita eggs were buried in field soil containing organic amendments, incubated, removed from soil, rinsed with water, and observed. The number of immature eggs in grids from soil amended with chitin or flax seed meal were lower than in untreated soil; percent parasitized eggs was also greater in films from amended soil than from untreated soil.     

Toxicity of Bacillus thuringiensis to parasitic and free-living life-stages of nematode parasites of livestock

A collection of Bacillus thuringiensis (Bt) strains (Bts) were screened for activity against the free-living larval stages of nematode parasites of livestock. Two strains were identified with significant activity in inhibiting larval development of Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia circumcincta. These strains were also toxic to the adult parasitic stages of these nematode species in vitro. Adult H. contortus and O. circumcincta showed complete cessation of movement within 2 and 4 days, respectively. Trichostrongylus colubriformis adults were less affected, however, movement was still significantly reduced compared with controls. The in vitro activity against the larval stages was of a magnitude similar to or greater than that seen with the anthelmintic drugs thiabendazole and levamisole. N-terminal amino acid sequencing indicated that the two Bts contained either Cry5A and Cry5B proteins, or a Cry13 protein, and the presence of the corresponding cry5A, cry5B and cry13 genes was confirmed by PCR and sequencing. Bacillus thuringiensis spore-crystal suspensions exposed to acidic pH conditions (pH相似文献   

The effects of immunization of sheep with Trichostrongylus colubriformis larvae on worm burdens acquired during grazing

The effects of immunization of sheep with Trichostrongylus colubriformis larvae on worm burdens acquired during grazing. International Journal for Parasitology 19: 177-181. Romney sheep, reared helminth-free in pens to 5 months of age, were immunized against Trichostrongylus colubriformis by giving two doses of 200,000 T. colubriformis infective larvae at 15 day intervals to assess protection from natural challenge during grazing. Five immunized sheep and five unimmunized sheep were grazed on infested pasture for 4 weeks, and were then returned to the pens for 4 weeks before slaughter. Worm burdens, gastrointestinal histology and mucus antiparasite activity were examined at slaughter. Faecal egg counts and haematological examinations were carried out at regular intervals throughout the trial. Significant protection (P less than 0.05) was afforded immunized sheep against adult T. colubriformis (87%), T. axei (67%), Nematodirus spathiger (91%) and Ostertagia spp. (42%). Greater numbers of immature Nematodirus spp. and Ostertagia spp. were present in immunized sheep Overall, a significant (P less than 0.05) 42% reduction in total nematode burdens was afforded by immunization of the sheep with T. colubriformis larvae. Immunized sheep had significantly (P less than 0.05) more globule leukocytes, mast cells and eosinophils in gastrointestinal tissue and significantly (P less than 0.05) higher levels of mucous antiparasite activity than unimmunized sheep. Haematological observations showed some sheep had transient eosinophilia during immunization or grazing. Both immunized and unimmunized sheep showed depressed (P less than 0.05) total leukocyte counts during grazing which returned to pre-grazing levels within 1 week of return of the sheep to the pens. Overall, haematological parameters reflected parasite challenge and were unrelated to worm burdens acquired.     

The effect of anions on Mg-ATPase in red blood cells.

Anions exert an influence on the passive permeability of Na+ and K+ in erythrocytes. THE EFFECT ON Mg-ATPase activity has been studied in human erythrocytes. 40 mM bicarbonate increased the activity as compared to the effect of 40 mM chloride; 20 mM sulphate inhibited it. Salicylate acted first as an activator then as an inhibitor of Mg-ATPase; maximum activity was reached at 60 mM CONCENTRATION. Thiocyanate inhibited saponin-stimulated Mg-ATPase, Ki = 1.85 X 10(-2)M. The probable mechanisms of action of the above anions on Mg-ATPase and possible relation to passive permeability of Na+ and K+ ions are discussed.     

Changes in Morphology of Trichostrongylus colubriformis Eggs and Juveniles Caused by Bacillus thuringiensis israelensis

Eggs and rhabditiform juveniles of the ruminant parasite Trichostrongylus colubriformis developed normally in Caenorhabditis briggsae Maintenance Medium. A toxin from a crystal-enriched preparation of the bacterium Bacillus thuringiensis israelensis was lethal to nematode eggs and juveniles within 24 hours and to eggs and juveniles after 24 hours of development. Treated eggs had refractive granules and development was arrested, whereas nontreated eggs developed normally. Eggs treated after 24 hours of development contained juveniles that were granulated, had esophageal derangements, and were moribund or dead. The ovicidal toxin from B. t. israelensis may facilitate microbial control of parasitic nematodes.