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Estimating the 3-D pose of instruments is an important part of robotic minimally invasive surgery for automation of basic procedures as well as providing safety features, such as virtual fixtures. Image-based methods of 3-D pose estimation provide a non-invasive low cost solution compared with methods that incorporate external tracking systems. In this paper, we extend our recent work in estimating rigid 3-D pose with silhouette and optical flow-based features to incorporate the articulated degrees-of-freedom (DOFs) of robotic instruments within a gradient-based optimization framework. Validation of the technique is provided with a calibrated ex-vivo study from the da Vinci Research Kit (DVRK) robotic system, where we perform quantitative analysis on the errors each DOF of our tracker. Additionally, we perform several detailed comparisons with recently published techniques that combine visual methods with kinematic data acquired from the joint encoders. Our experiments demonstrate that our method is competitively accurate while relying solely on image data.

Soluble and insoluble polysaccharides were derivatized with diethylenetriaminepentaacetic acid (DTPA) and/or spin-labeled with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). Polysaccharides derivatized with DTPA were prepared via cyanogen bromide activation, coupling to a diamine linker, and to DTPA anhydride. Spin-labeled polysaccharides were also prepared via cyanogen bromide activation. The extent of derivatization for dextran (18 kDa) was about 120 glucose units per DTPA, and for cellulose and starch about 15-30 units per DTPA. For spin-labeled polysaccharides, the average loading ranged from 1 nitroxide per 16 glucose units for starch to 181 for dextran (82 kDa). These derivatized paramagnetic polysaccharides were shown to be more effective relaxants than the small paramagnetic molecules alone. Both soluble and insoluble polysaccharide-linker-DTPA-Gd(III) complexes were effectively cleared from the body (rats) after oral administration. After intravenous administration, the biodistribution of dextran-linker-DTPA-Gd(III) complexes differed significantly from that of GdDTPA. Reduction of the nitroxide by ascorbic acid was retarded in the polysaccharide derivatives, particularly in starch derivatized with both nitroxide and linker-DTPA-Cu(II). These agents showed contrast enhancement in the gastrointestinal tract of rabbits.

Ligation of the largest preovulatory follicle (F1) or the second largest preovulatory follicle (F2) delayed terminal oviposition for at least 2 h. Ligation of the fourth or fifth largest preovulatory follicle had no effect on the time of terminal oviposition. The conclusion reached was that some factor produced by the most mature follicles in the ovarian hierarchy influenced the timing of oviposition. Since the terminal oviposition occurs independently of ovulation, the authors concluded that the influence of the F1 and F2 follicles was independent of any preovulatory endocrine changes.

A structural, profile-based algorithm was used to identify interleukin 20 (IL-20), a novel IL-10 homolog. Chromosomal localization of IL-20 led to the discovery of an IL-10 family cytokine cluster. Overexpression of IL-20 in transgenic (TG) mice causes neonatal lethality with skin abnormalities including aberrant epidermal differentiation. Recombinant IL-20 protein stimulates a signal transduction pathway through STAT3 in a keratinocyte cell line, demonstrating a direct action of this ligand. An IL-20 receptor was identified as a heterodimer of two orphan class II cytokine receptor subunits. Both receptor subunits are expressed in skin and are dramatically upregulated in psoriatic skin. Taken together, these results demonstrate a role in epidermal function and psoriasis for IL-20, a novel cytokine identified solely by bioinformatics analysis.

The paper describes a program to import and breed black rhinoceros ex situ at Western Plains Zoo in Australia. Nine rhinoceros (7 females and 2 males) captured in 1992 in Chete National Park, Zimbabwe, were transported to Australia via Cocos Island. The veterinary treatment of the animals before and during quarantine in Zimbabwe and on Cocos (Keeling) Islands is described. Three animals died; an adult male on Cocos Islands and a juvenile male and an adult female at Western Plains Zoo, Dubbo, New South Wales. The juvenile male died as a result of trauma sustained shortly after arrival and the two adults after developing a severe hepatopathy. The group of 6 females and an additional 4 males imported from the USA in 1994 have adapted well to captivity and to the climate and environment of central west New South Wales.

High affinity binding of platelet-derived growth factor (PDGF) has been proposed to involve the interaction of the dimeric PDGF ligand with two receptor subunits, designated alpha and beta. We have cloned and expressed a human PDGF receptor cDNA which differs in sequence from the beta-subunit and which has the PDGF binding properties and monoclonal antibody recognition, predicted for the alpha-subunit. Scatchard analysis indicated that PDGF-AA and PDGF-AB bound to transfected alpha-subunits with affinities of Kd = 0.06 and 0.05 nM, respectively. PDGF-BB bound with a significantly lower affinity (Kd = 0.4 nM). Nevertheless, this affinity is still great enough to mediate substantial PDGF-BB binding at physiological concentrations and would be considered to be "high affinity." We have used wild-type and kinase-inactive human beta-subunits to show that PDGF binding promotes receptor subunit dimerization in intact cells. In addition, we found that PDGF stimulates tyrosine phosphorylation of the kinase-inactive beta-subunit when it is expressed with alpha-subunits. The kinase-inactive beta-subunits were phosphorylated at tyrosine 857 and 751, the major phosphorylation sites of the wild-type beta-subunit, indicating either that intra- and intermolecular phosphorylation occurs on the same sites, or that a significant fraction of receptor tyrosine phosphorylation is intermolecular.

An injection of 5 micrograms of gonadotropin-releasing hormone (GnRH) into hens 8 h prior to oviposition advanced the expected time of oviposition by approximately 1 h. The plasma concentration of progesterone increased approximately 1 h earlier in GnRH-injected hens in comparison to saline-injected hens. The plasma concentration of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) increased significantly (p less than 0.05) at the time of oviposition in both the GnRH- and saline-injected hens. Significantly (p less than 0.05) greater concentrations of prostaglandin F2 alpha (PGF2 alpha) were assayed in media containing the largest preovulatory follicles collected at oviposition than in media containing the second and fifth largest preovulatory follicles collected at the same time. No prostaglandin was detected in media containing small, nonhierarchial follicles. The concentration of PGF2 alpha in media containing granulosa cells from the largest preovulatory follicle was significantly greater (p less than 0.05) than in media containing 4 times as many theca cells. Ovine luteinizing hormone (oLH) alone or in combination with arachidonic acid had no effect on PGF2 alpha output from granulosa cells collected 6 h before oviposition, whereas A23187 caused a small stimulation of PGF2 alpha output. However, treating cells first with oLH and then with A23187 stimulated a 15- to 20-fold increase in PGF2 alpha. None of these stimuli enhanced the already high output of PGF2 alpha when added to incubations of granulosa cells collected within 5 min after oviposition. These data suggest that the granulosa cells of the largest preovulatory follicle are the major intraovarian source of prostaglandin and that production of PGF2 alpha is associated with the preovulatory surges of gonadotropins and steroid hormones preceding oviposition.

The gene encoding the alpha-subunit of the human platelet-derived growth factor receptor (PDGFRA) maps to band q11-q12 of chromosome 4 by in situ hybridization, which was confirmed by Southern analysis of a Chinese hamster x human cell hybrid that retains only human chromosome 4.

The relationship between iron deficiency and protein deficiency and infestation of the rat with the nematode Nippostrongylus brasiliensis was investigated. There was a significant delay in the expulsion of N. brasiliensis from the small intestine of both iron deficient and protein deficient animals and those with a combined deficiency of iron and protein. Iron repletion returned the time of worm expulsion to normal and this would appear to be related to iron deficiency per se rather than to anaemia. Antibody initiated damage to worms was normal in the control animals and in animals with nutritional deficiencies. This suggests that the defect in worm expulsion occurs either in the cell-mediated immune system or in one of the other mediators of expulsion. Extrapolation to the human situation has important therapeutic implications in that iron and protein deficiency may play an important role in the perpetuation of helminth infestations. Thus, to be successful antihelminth therapy should be accompanied by iron and protein supplementation.

The platelet-derived growth factor (PDGF) is a mitogen derived from human platelets consisting of two related polypeptides termed A and B chains. The entire B chain of PDGF is highly (96%) homologous to a portion of p28sis, the transforming protein of simian sarcoma virus. It has been suggested that p28sis exerts its transforming potential by mimicking the growth promoting activity of PDGF and stimulating the cell in an autocrine manner. We have directly examined the mitogenic potential of p28sis and the B chain homologous region by expressing these heterologous sequences in the yeast Saccharomyces cerevisiae. In our constructions, these proteins are encoded by portions of the v-sis gene. Expression and secretion from the yeast cell is achieved by using a yeast promoter and the alpha-factor pheromone secretory leader. The sis proteins thus expressed and secreted are immunoreactive with anti-PDGF antisera and are mitogenic for cultured fibroblasts. Furthermore, they mediate this mitogenic activity by specific binding to the PDGF cell surface receptor. Gel electrophoresis and cell binding analysis indicates that the mitogenic species is primarily a disulphide-bonded dimer. We are able to conclude that p28sis is a mitogen and that a polypeptide corresponding to the B chain alone is sufficient to account for the mitogenic activity attributed to PDGF.

The result of a field trial investigating the anthelmintic effect of disophenol against H. contortus in sheep raised under Asian small farming practice is reported. it was clearly shown that a single injection of disophenol suppressed the numbers of H. contortus to very low levels for periods up to 3 months despite the presence of large populations of H. contortus infective larvae available on pasture and herbage grasses.

The Nippostrongylus brasiliensis-rat model was used to determine whether iron and protein deficiency, which are commonly associated with parasitic infections, affected the pharmacokinetic behaviour of fenbendazole as measured by plasma concentrations and uptake by worms. Plasma 14C concentrations after [14C] fenbendazole administration were higher in iron and protein-deficient rats than in sufficient rats. However, the uptake of 14C by N. brasiliensis in iron and protein-deficient rats was significantly less than in worms from diet-sufficient rats. The reduced anthelmintic uptake by worms in protein and iron-deficient hosts may account, in part, for reduced anthelmintic efficacy under these circumstances. These findings are relevant to understanding variations in response to chemotherapy in populations of parasitised hosts containing malnourished individuals.

Rejection of Nippostrongylus brasiliensis is impaired in iron and protein deficient rats and this suggests that iron and protein deficiency directly or indirectly suppresses the immune response. The site of the immunological defect in deficient rats was investigated using the technique of cellular transfer of resistance. The functional activity of immune mesenteric lymph node cells obtained from iron and protein deficient donors was not depressed as measured by their capacity to cause parasite rejection in nutritionally sufficient recipients. In contrast, immune lymph node cells obtained from either sufficient or deficient donors did not result in parasite rejection in iron and protein deficient recipients. These results indicate that there is no permanent defect of lymphocyte function in iron and protein deficient rats and suggest that either some other component of the rejection mechanism is defective, or that lymphocyte function is blocked in an iron and protein deficient environment.

Fenbendazole (methyl-5-(phenylthio)-2-benzimidazole carbamate) at dose rates of 5 mg/kg and above was 100 per cent effective in eliminating a naturally acquired Dictyocaulus filaria infection in sheep. The drug was 100 per cent effective in eliminating concurrent infections of adult Trichostrongylus axei, Haemonchus contortus, Haemonchus placei, Ostertagia circumcincta, Ostertagia ostertagii, Cooperia oncophora, Cooperia mcmasterii, Nematodirus spathiger, Neumatodirus filcollis, Oesophagostomum venulosum and Chabertia ovina. Fenbendazole was 93 per cent and 97 per cent effective at doses of 5 and 10 mg/kg respectively in removing infection with adult T colubriformis, and post-treatment worm-egg production was completely suppressed in surviving female worms. No adverse side-effects were observed in treated sheep at either of the two dose rates used.

Sheep infected with benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis were used to compare the anthelmintic efficacy of fenbendazole given as a single dose or administered in a divided dose regime over five days. Statistical analysis showed no significant difference between the two methods of administration for H contortus. On the other hand, divided dose fenbendazole was significantly less effective than single doses against adult T colubriformis at dose rates of 5 and 7.5 mg/kg. In the case of H contortus a highly significant correlation coefficient between post treatment egg counts and worm counts (r = 0.789) was obtained. This suggests that reduction in faecal egg output following drug treatment would provide a useful field indication of anthelmintic performance of fenbendazole (and possibly related compounds) against benzimidazole resistant strains of this parasite.

The anthelmintic efficacy of low-dose phenothiazine therapy, administered as a 1:40 phenothiazine: molasses mixture, was tested against patent infections of strains of Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia spp susceptible or resistant to thiabendazole (an other benzimidazoles), levamisole and morantel tartrate. Phenothiazine reduced faecal egg output for both susceptible and resistant strains of all three nematodes. In daily doses of 0.25 g per sheep per day and above it completely inhibited larval production in susceptible strains. Against resistant strains, there was a reduced efficiency with 82.3 per cent inhibition of egg hatch at the 0.25 g per sheep per day level. Phenothiazine treatment had no significant effect on worm numbers for either susceptible or resistant worms. It is suggested that benzimidazole-resistant strains may be cross-resistant to phenothiazine.

Large amounts of ascorbic acid were readily removed from neural tissue by washing with warmed saline solutions. In areas where the original level was highest, such as cortex and cerebellum, a higher percentage was removed than from areas of lower concentration, such as pons-medulla. The residual level in both types of tissue was similar. During scurvy, the ascorbic acid retained in the guinea pig brain is more readily removed by washing than is that of the normal brain.

Malnutrition, anaemia, and gut parasites are commonly interrelated. Using the Nippostrongylus brasiliensis-rat model, the effect of iron and protein deficiency on the efficacy of benzimidazole anthelmintics was studied. It was demonstrated that the anthelmintics mebendazole and fenbendazole were significantly less effective in eradicating parasites when animals were deficient in iron and protein. This decreased efficacy of anthelmintics in iron and protein deficiency could not be overcome by intraperitoneal administration of the drug. Since nutritional deficiencies may act via impairment of the immune response, anthelmintic efficacy was determined in adequately nourished rats treated with the immunosuppressive drug dexamethasone. A similar decrease in efficacy of mebendazole was shown when these animals were treated with dexamethasone. Thus it is possible that lowered anthelmintic efficacy in iron and protein deficient animals is mediated by immune deficiency. These findings may be relevant to anthelmintic programmes in malnourished communities.

Fetal rat liver can synthesize ascorbic acid after 16 days of gestation. Fetal kidney was inactive and neither fetal guinea pig liver nor kidney possessed ascorbic acid synthetic ability.

Sheep given a primary infection of Fasciola hepatica were challenged 18 weeks later with Taenia hydatigena or F hepatica, or both parasites together, or were not challenged. At the same time, control sheep were infected with T hydatigena and/or F hepatica separately or concurrently. All sheep were killed seven weeks after challenge and the number of cysts and flukes counted. Challenge infection with T hydatigena did not affect the numbers of flukes recovered from either primary or challenge F hepatica infections. On the other hand, the numbers of cysticerci were reduced in sheep previously infected with F hepatica but not in those given T hydatigena and F hepatica concurrently.

Field strains of Trichostrongylus colubriformis and Ostertagia circumcincta, designated PF4 and PF5 respectively, were recovered from a farm on which the sole use of levamisole over a preceding 12 year period led to the development of anthelmintic resistance. The results of field observations and preliminary critical trials in both Merino and crossbred sheep showed that both species have varying degrees of resistance to three major anthelmintics; levamisole, morantel tartrate and thiabendazole. Mean worm count reductions for adult T colubriformis (PF4) for therapeutic doses of morantel tartrate, thiabendazole and levamisole in crossbreds were 45.7 per cent, 97.3 per cent and zero respectively, and for Merinos 80.7 per cent, 88.3 per cent and 92.0 per cent respectively. Against O circumcincta the corresponding reductions for crossbreds were 51.4 percent, 95.4 per cent and 20.3 per cent and for Merinos, 52.5 per cent, 73.1 per cent and 29.8 per cent. There was no statistically significant difference in the responses of both parasite species to either levamisole or morantel. This result suggests that resistance to the two chemically unrelated drugs may be co-inherited.

Strains of Trichostrongylus colubriformis (designated PF4) and Ostertagia sp (O circumcincta/O trifurcata, designated PF5), with varying degrees of resistance to levamisole, morantel tartrate and thiabendazole were isolated into pure culture. Detailed dose response studies showed that both T colubriformis and Ostertagia sp were highly resistant to levamisole and morantel with low level resistance to thiabendazole. The effective dose required to remove 80 per cent worm burdens (ED80) was calculated for each anthelmintic. For T colubriformis the ED80 for levamisole and thiabendazole were 12.6 and 40.1 mg/kg respectively. For Ostertagia sp, the ED80 for levamisole, thiabendazole and morantel were 20.4, 45.2 and 35.8 mg/kg respectively. The implications of these results are discussed with reference to alternative means of chemical control.

Merino and Border Leicester cross Merino sheep, nine months old, were infected with 10,000 third stage larvae of both Trichostrongylus colubriformis (PF4) and Ostertagia circumcincta/O trifurcata (PF5), known to have varying degrees of resistance to levamisole, morantel tartrate and thiabendazole. Crossbred sheep carried heavier Ostertagia sp worm burdens but there was no difference in susceptibility between the two breeds of sheep to infection with T colubriformis. The anthelmintic efficacy of thiabendazole, at 50 mg/kg, against T colubriformis was 81.8 per cent and 92.4 per cent for Merinos and crossbreds respectively while levamisole, at 6.75 mg/kg, was 12.3 per cent and 18 per cent effective. Thiabendazole removed 92.3 per cent and 83.8 per cent of Ostertagia sp in Merinos and crossbreds respectively. However, worm burdens in levamisole treated sheep were not significantly different from controls. No significant breed differences were found in 24 h faecal egg outputs. It is suggested that breed differences previously described in four-month-old sheep may have been due to differences in the rate of development of immune responsiveness. This disparity was no longer detectable in the immunologically mature sheep used in this study.

Ultrafiltration has been used to investigate the interaction of ascorbate with bovine serum albumin in 0.1 M sodium phosphate buffer, pH 6.5. The results are interpreted in terms of the binding of ascorbate to four equivalent and independent protein sites, governed by an intrinsic association constant of 2 600 +/- 700 M-1 at 20 degrees C, thereby providing evidence for specificity of the interaction over a range of vitamin concentration (0.08-1.5 mM) pertinent to the physiological situation.

Guinea pigs infected with Trichostrongylus colubriformis were used to develop an assay for anthelmintic resistance by determination of worm burdens following treatment with test anthelmintics. To achieve comparable efficacy with the recommended dose of thiabendazole and levamisole in sheep, dose rates in guinea pigs had to be increased two to four fold. For example, thiabendazole at 100 mg/kg in guinea pigs was 96.6 per cent effective against a thiabendazole susceptible (GS) strain of T colubriformis, but had no effect against a thiabendazole-resistant (VRSG) strain. In sheep 50 mg/kg of thiabendazole would have a similar efficacy against each strain respectively. Morantel tartrate at 10 mg/kg in guinea pigs was 99 to 100 per cent effective against the GS strain but only 54 per cent effective against a morantel resistant (PF4) strain. A slope ratio assay was used to calculate the relative potency of anthelmintics by comparing efficacies against resistant strains with efficacy against the GS strain. Resistance of the VRSG strain to thiabendazole was confirmed with a relative potency for this drug of 0.047 in guinea pigs. The PF4 strain was resistant to both thiabendazole and levamisole which had relative potencies of 0.168 and 0.255 respectively. The advantages of this statistical treatment together with the cost and time savings of the guinea pig model over a conventional critical anthelmintic assay in sheep are discussed.

Ascorbic acid in fetal rat brain increases from 374 mg/g on the 15th day of gestation to 710 mg/g by the 20th day and remains at that level until birth. There is an 18% drop from this plateau after birth.

Human hydatidosis is caused by infection with the cystic stage of the hydatid tapeworm of dogs, Echinococcus granulosus. Although the disease is entirely preventable, the prevalence of hydatidosis in Australia has not decreased since the first surveys were taken in the early part of this century. Principal reasons for this appear to be a general lack of knowledge of the life history, epidemiology and control methods for E. granulosus, coupled with ineffective community based eradication campaigns. The purpose of this paper is to briefly discuss the important facts relevant to control and eventual eradication of hydatid disease.

Maternal rat lung, liver, kidney and portions of small intestine lost up to 40% of their ascorbic acid between early pregnancy and the 15th day of gestation. From then to the end of pregnancy, the ascorbic acid content of the tissues increased by 30 to 60%. Ascorbic acid in fetal lung doubled in concentration on the 18th day of fetal life before a pre and post natal value of 200 micrograms/g tissue was established. Fetal liver had a minor rise in ascorbic acid concentration on the 18th day. Just prior to birth, the ascorbic acid content in fetal lung was 30% and fetal liver 50% higher than maternal.

Man has acquired helminth infections at different times during his evolutionary history and animals have and do serve an important role in supplementing these acquisitions. Helminth species are divided into those which accompanied man as he emerger as a species and those which he has since acquired from domestic, wild and domiciliated animals by breakdown of ecological, physiological and immunological barriers (Sprent 1969). With particular reference to helminth zoonoses transmitted through domesticated animals, the role played by dogs and cats in disease transmission to man (in urban environments) has been largely overlooked. In the Australasian region, the most important helminth zoonoses transmitted by dogs and cats in heavily urbanised areas as Toxocara sp., Ancylostoma sp. and Dirofilaria immitis. The prevalence, geographic distribution and major epidemiological considerations for each parasite are discussed with the view that future control and/or eradication programs should be based on a sound epidemiological understanding of the natural life history of the helminths concerned.

The level of ascorbic acid in the brain of growing rats was not influenced by efforts to accelerate neural activity. Treatments used to depress neural activity included thyroidectomy which produced a 13%-20% loss of ascorbic acid in cortical and cerebellar tissue and diazepam which produced a significant rise in the cerebellum. Ethanol and barbital were without effect.

Rats and sheep were infected with Fasciola hepatica by subcutaneous, intramuscular or oral (intraruminal--sheep) inoculation with encysted metacercariae and the development of flukes from these primary infections assessed. Additional rats and sheep similarly infected were challenged with encysted metacercariae orally (rats), or intraruminally (sheep) to assess the level of acquired resistance generated by previous infection by each of the three routes of administration. In both rats and sheep 0--5 per cent, 0--5 per cent and 20--25 per cent of metacercariae given by the subcutaneous, intramuscular or oral (intraruminal--sheep) routes were recovered as flukes in the liver four and 12 weeks after infection of rats, or 17 weeks after infection of sheep. Primary infection of rats with F hepatica by each of the three routes generated strong protection against oral challenge whereas no protection was generated in sheep, irrespective of route of infection.

The efficacy of two recently introduced benzimidazole anthelmintics, albendazole and fenbendazole, was determined for six-day, 10-day and adult stages of resistant strains of Haemonchus contortus and Trichostrongylus colubriformis. Albendazole, at 3.8 mg/kg reduced H contortus worm counts by 92.4, 70.8 and 67.1 per cent while fenbendazole, at 5.0 mg/kg, reduced worm burdens by 51.7, 95.5 and 93.4 per cent against six-, 10- and 25-day-old parasites respectively. For T colubriformis, the corresponding reductions with albendazole were 97.7, 95.8 and 64.9 per cent and for fenbendazole 29.0, 66.3 and 33.4 per cent. Compared with susceptible strains of H contortus and T colubriformis, for which therapeutic doses of benzimidazole anthelmintics are generally highly active against all stages of development, the present results show that these drugs do not have a uniform level of activity against all developmental stages of resistant strains.

Magnetite (Fe 3 O 4 ) particles 0.1–0.5 μm in diameter doped with either 99m Tc or 111 In have been prepared and characterized by electron microscopy and Mossbauer spectroscopy. The time courses of their distributions after injection into rats were determined, including studies by γ-camera imaging; the main targets were the liver and lung. The radiolabelled magnetic agents may be of value in research studies combining radio- and magnetic resonance imaging procedures.

A high performance liquid chromatographic (HPLC) technique is described for the determination of residue levels of the anthelmintic drug phenothiazine in sheep tissues. Phenothiazine was administered to sheep which were slaughtered after withholding periods of 24, 48, and 72 h. Residues of phenothiazine were then extracted from tissue samples by homogenization in methanol. The HPLC analysis of the extracts involved separation on a 10 micrometer silica column using a mobile phase of 0.3% n-propanol in cyclohexane. The lower limit of detection by ultraviolet absorption at 254 nm was 0.05 ppm.

Third-stage larvae of Ancyclostoma caninum were exsheathed either by carbon dioxide or sodium hypochlorite treatment. Exsheathment per se reduced the infectivity of third-stage larvae by 45% to 59% without affecting larval motility. Both ensheathed and exsheathed larvae were frozen over liquid nitrogen for 90 days, and thawed. Frozen ensheathed larvae were all killed; but frozen exsheathed larvae were 40-54% as infective as non-frozen exsheathed larvae, and the addition of 10% dimethyl sulphoxide raised the infectivity to 89%, relative to non-frozen exsheathed larvae. Taken together, the deleterious effects of exsheathment and freezing resulted in an infectivity of 16-37%, relative to normal larvae.

Low-dose daily phenothiazine therapy, administered as a 1:40 phenothiazine:molasses mixture, was tested against sequential infections of strains of Haemonchus contortus. Trichostrongylus colubriformis and Ostertagia spp susceptible or resistant to thiabendazole, levamisole and morantel tartrate. Phenothiazine at a dose rate of 0.5 g per sheep per day significantly reduced the numbers of worm eggs per gram of faeces in both susceptible and resistant strains by an average of 48 per cent and 60 per cent respectively. Phenothiazine completely inhibited larval production in susceptible strains. With resistant worms, larval production was depressed by up to 85.7 per cent. Treatment with phenothiazine : molasses mixture reduced the numbers of worms which became established in resistant Ostertagia spp and susceptible T colubriformis but had no effect on the establishment of susceptible H contortus and Ostertagia spp or resistant H contortus and T colubriformis.

The benzimidazole anthelmintics mebendazole and fenbendazole have been shown to be much less effective against Nippostrongylus brasiliensis infections in the rat on a combined iron and protein deficient diet. In the present experiments it was shown that the anthelmintic efficacy of mebendazole was significantly impaired in the rat on either an iron deficient or a protein deficient diet. Furthermore, iron and protein deficiency reduced the efficacy of the anthelmintics pyrantel and piperazine but not levamisole. The finding that nutritional deficiencies reduce anthelmintic efficacy may well be relevant to worm eradication programmes in iron deficient and protein calorie malnourished populations.

The level of PGE is increased 10-fold in intestinal tissues during primary infection of the rat with Nippostrongylus brasiliensis. Peak levels (ca. 7,000 pg/cm) were assayed in the jejunal site of infection on day 7 of infection and similar levels were recorded in 'post-infection' (ileal) segments at this time. The level of PGE in 'post-infection' segments showed further increase to 12,000 pg/cm on day 10. The level of PGE also increased in 'pre-infection' (duodenal) but this was delayed by 4-5 days. The level of PGF also increased during primary infection (from about 100 to 950 pg/cm) but this occurred after expulsion. Increase in the level of PGE occurred earlier (at 3-4 days) during secondary challenge given 19 days after primary infection, but the PGE levels followed the primary response when challenge was given 10 weeks after primary infection. It is suggested that PGE plays a dual role in parasite immunity. (1) PGE may directly affect metabolism of the parasite. In this event it is also suggested that protective antibodies cause the release of PG. (2) Elevated levels of PGE act indirectly by affecting gastrointestinal function which alters the microenvironment at the site of infection. The duodenal migration of parasites may be due to this effect of PGE.

Benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis were each diluted with equal numbers of their respective susceptible genotypes and passaged in separate worm-free sheep. The progeny of the mixed susceptible and resistant infections were diluted with equal numbers of susceptible genotypes before passaging on two further consecutive occasions in worm-free sheep. In H contortus the amount of thiabendazole required to prevent a 50 per cent egg hatching (LC50) was reduced at each generation, but the reduction was significant (P less than 0.05) only at the third passage. In T colubriformis the LC50 for thiabendazole was reduced only at the first passage and thereafter remained constant. The reduction was not significant. In another experiment, the dilution with susceptible genotypes was made only at the first passage. Thereafter for two further generations the progeny produced from the mixed infection were passaged in worm-free sheep. In H contortus a reduced amount of thiabendazole was required to prevent a 50 per cent egg hatching at each generation, but did not reach a level of significance. The result for T colubriformis was identical to the continuous dilution experiment.

Vaccination of 6–8-month-old Merino sheep with irradiated Trichostrongylus colubriformis larvae gave a high level of protection (81 %) against single-species challenge with normal infective larvae of the same species. The level of protection (34%) was substantially reduced against challenge with a closely related species ( T. vitrinus ) and no significant protection occurred against single-species challenge with a generically unrelated nematode (Nematodirus spathiger). These results suggest that antigen(s) which stimulate protective immunity are shared by the related Trichostrongylus species but not by N. spathiger . By contrast with the results obtained for single-species challenge, vaccination with irradiated T. colubriformis produced 98–100% protection against all 3 species in animals challenged simultaneously with infective larvae of the 3 species. Comparison of the levels of protection recorded following the 2 types of challenge indicate that although a specific antigenic trigger is required to provoke an appropriate response, the results obtained, particularly in the case of N. spathiger , suggest that the terminal effector mechanism is not immunologically specific. The implications of these conclusions are discussed in relation to theories of the mechanism of resistance to gastrointestinal nematodes and the potential efficacy of vaccination in the field.

The anthelmintic efficacy of fenbendazole (methyl 5-(phenyl-thio)-2-benzimidazole-carbamate) against Moniezia expansa and Trichuris ovis was tested. At dose rates of 5 mg per kg and above, efficacies were found to be greater than 91 percent against M expansa and greater than 92 per cent against T ovis. At these dose rates efficacy on egg suppression was 100 per cent for Moniezia and greater than 97 per cent for Trichuris.