Neale R Towers

Genetic selection foror against resistance to the mycotoxicosis, facial eczema (FE), was begun in a Romney flock in 1975. Randomly selected ewes were mated with rams which had been previously identified by progeny testing as resistant (R) or susceptible (S) to FE. In subsequent years (until 1982), the same ewes and their daughters were again mated within flock to progeny-tested rams. From 1983 until 1987, performance testing was substituted for progeny testing. The most resistant R rams ...

The acute toxicity of the phycotoxin gymnodimine to female Swiss mice by intraperitoneal injection and by oral administration has been determined. Gymnodimine was highly toxic by injection, the LD50 being only 96 microg/kg. Animals either died within 10 min of injection or made a full recovery with no perceptible long-term effects. Gymnodimine was also toxic after oral administration by gavage (LD50 755 microg/kg), but was much less toxic when administered with food. No signs of toxicity ...

Genetic selection for or against susceptibility to facial eczema (FE) was begun in Romney sheep in 1975, with the establishment of a resistant (R) selection flock, a susceptible (S) selection flock, and later a control (C) flock. For all but the initial years, rams were identified by performance testing with a sporidesmin challenge, ranking them on relative elevation of the liver enzyme, gamma glutamyltransferase (GGT) measured in serum. A different dose rate of sporidesmin was used for ...

We have developed a simple and effective method for isolating pectenotoxin-2 (PTX-2) from Dinophysis cells collected from a natural bloom. A two-step extraction procedure followed by two column chromatography steps produced PTX-2 in high purity suitable for use as an analytical standard and for toxicological studies. Incubation of purified PTX-2 with the supernatant from ultracentrifuged blue (Mytilus edulis) or Greenshell (Perna canaliculus) mussel hepatopancreas homogenate caused rapid ...

We developed a radioimmunoassay (RIA) using a sheep anti-brevetoxin antiserum to evaluate detection of brevetoxin on blood collection cards from mice treated with the brevetoxin congener PbTx-3. The RIA has high affinity for PbTx-3 [half-maximal effective concentration (EC(50)) +/- SE = 1.2 +/- 0.2 nM; n = 10] and recognizes both type 1 and type 2 brevetoxins, but not ciguatoxin. Direct comparison of the RIA with a radiolabeled [(3)H]-PbTx-3 receptor-binding assay (RBA) revealed ...

Cyanobacteria (blue-green algae) (e.g., Microcystis and Nodularia spp.) capable of producing toxic peptides are found in fresh and brackish water worldwide. These toxins include the microcystin (MC) heptapeptides (>60 congeners) and the nodularin pentapeptides (ca. 5 congeners). Cyanobacterial cyclic peptide toxins are harmful to man, other mammals, birds, and fish. Acute exposure to high concentrations of these toxins causes liver damage, while subchronic or chronic exposure may promote ...

Five Finnish Landrace (F) rams and 10 Romney (R) rams were mated with F and R ewes to generate F × F, F? × R?, and R × R lambs. These lambs were compared for their susceptibility to an oral challenge with sporidesmin, the toxin causing facial eczema. All lambs of 17.0 kg or above were dosed at 4 months of age with sporidesmin (0.15 mg/kg liveweight). Resistance or susceptibility was assessed by taking a blood sample 21 days after challenge, and measuring serum gamma‐glutamyltransferase ...

Polyclonal antibodies were produced for the development of competitive enzyme-linked immunoassays for use in quantifying yessotoxins in shellfish, algal cells, and culture supernatants. Immunizing and plate coating antigens were prepared by derivatization of yessotoxin either by ozonolysis or bromination and conjugation to proteins. Two assays that were the most sensitive for yessotoxin were optimized and characterized. Cross-reactivity studies indicated that the antibodies raised have ...

Ovine antibodies raised against conjugates linked through the secondary amino group of domoic acid (1) were used, together with activated-ester-derived conjugates of domoic acid (DA) as the plate coater, to develop a robust indirect competitive enzyme-linked immunosorbent assay (cELISA) for DA in shellfish and seawater. The ELISA was used to analyze shellfish samples for DA, and was compatible with several extraction procedures. The ELISA had a detection limit below 0.01 ng ml(-1), a ...

Mating and lambing data from the Romney facial eczema (FE) selection flocks at Ruakura were collated in order to study the effects of FE susceptibility on subsequent reproduction. The data analysed were ewe fertility (numbers of ewes lambing, as a % of those joined), litter size at birth, and postnatal lamb survival. Two of the flocks, selected for resistance (R) or susceptibility (S) to FE, were established from similar foundation stock in 1975. Two other flocks were established in ...

Facial eczema (FE) is a hepatogenous photosensitization disease of ruminant animals, particularly in sheep which vary widely in their susceptibility to the disease. The liver damage is caused by the mycotoxin, sporidesmin. There is evidence that the toxicity of sporidesmin is due to its ability to generate 'active oxygen' species. We evaluated the catalase gene, which encodes an enzyme with antioxidant functions, as a candidate for determining the susceptibility of sheep to the disease. ...

Facial eczema (FE) is a secondary photosensitization disease arising from liver cirrhosis caused by the mycotoxin sporidesmin. The disease affects sheep, cattle, deer and goats, and costs the New Zealand sheep industry alone an estimated NZ$63M annually. A long-term sustainable solution to this century-old FE problem is to breed for disease-resistant animals by marker-assisted selection. As a step towards finding a diagnostic DNA test for FE sensitivity, we have conducted a genome-scan ...

Mycotoxicoses are some of the most important diseases of animals grazing pastures in New Zealand, especially in northern areas where the disease, facial eczema, occurs. New Zealand scientists have led the world in research on facial eczema and endophyte-related diseases associated with tremoring. Facial eczema (pithomycotoxicosis) was one of the first mycotoxicoses to be studied systematically and successful methods for its control now exist. Toxicity is caused by the concentration of ...

Ten East Friesian (EF), eight Romney Control (RC), and two Romney Facial Eczema Resistant (RR) rams were mated with Romney (R) ewes to generate EF × R, RC × R, and RR × R lambs. These lambs were compared for their susceptibility to an oral challenge with sporidesmin, the toxin causing facial eczema. All lambs of 16.0 kg or above (average weight 21.3 kg) were dosed after weaning with sporidesmin (0.14 mg kg‐1 liveweight) at an average age of 83 days. Resistance or susceptibility was ...