Iodine content of commercially-prepared cat foods

Twenty-eight varieties of commercially-available cat food (23 canned, 5 dried) were analysed for iodine. The iodine concentration varied from less than 0.37 micromol/kg to 41.8 pmol/kg, wet weight (less than 1.48 micromol/kg to 167 micromol/kg, dry weight). Excessive or insufficient iodine intake or wide swings in iodine intake over prolonged periods may contribute to thyroid disorders in cats.     

An evaluation of an oral formulation of moxidectin against selected anthelmintic-resistant and -susceptible strains of nematodes in lambs

The efficacy of an oral formulation of the newly developed parasiticide, moxidectin, was tested against benzimidazole-resistant Haemonchus contortus, Trichostrongylus colubriformis, and Nematodirus spathiger, levamisole-resistant Ostertagia circumcincta, and susceptible Cooperia curticei infections in weaned lambs. Thirty-two lambs were experimentally infected with mixed doses of the above strains of nematodes. They were allocated into four treatment groups by stratified randomisation using liveweights and faecal egg counts 28 days later. One group received moxidectin at 0.2 mg/kg liveweight, one group oxfendazole at 4.5 mg/kg liveweight, one group levamisole at 7.5 mg/kg liveweight and the last group remained untreated as the control. Worm burdens in the lambs at slaughter 10 days after oral treatment confirmed the resistance status of the nematode strains used, and showed that moxidectin had a greater than 99.9% efficacy (p<0.01) against all of them. No adverse effects due to treatment with moxidectin were observed in any of the animals.     

Serum lipase determination in the dog: a comparison of a titrimetric method with an automated kinetic method

An enzymatic, kinetic method for determining serum lipase activity was evaluated and compared to a standard manual method for use in dogs. The kinetic method was a commercial kit adapted for use on a tandem access clinical chemistry analyzer and utilized a series of coupled enzymatic reactions based on the hydrolysis of 1,2-diglyceride by lipase. The manual method was the Cherry-Crandall technique based on the titration of base against the acid formed by hydrolysis of an olive oil substrate by lipase. The correlation between the two methods was very good (r = 0.94). The reference range for 56 clinically healthy dogs assayed by the kinetic method was 90 to 527 U/L. Diseases associated with a greater than twofold elevation in serum lipase activity as determined by the kinetic method included pancreatitis, gastritis with liver disease, and oliguric renal failure with metabolic acidosis. In some cases, pancreatitis was seen with other clinical problems, such as gastroenteritis, diabetic ketoacidosis, duodenal mass, disseminated intravascular coagulation, and septic peritonitis. Diseases associated with serum lipase activity within the reference range or elevated less than twofold included gastritis, gastric ulcer, cholestasis, phenobarbital-induced hepatopathy, colitis, copper hepatopathy, abdominal hematoma, apocrine gland adenocarcinoma, and thrombocytopenia with pneumonia.     

Temperature cycling periods affect growth and tuberization in potatoes under continuous irradiation

Plants of the potato (Solanum tuberosum L.) cultivars Denali, Norland, Haig and Kennebec were grown for 42 days under three temperature cycling periods (thermoperiods) with continuous irradiation in two repeated experiments to help determine if temperature cycling might be varied to optimize tuber development of potatoes in controlled environments. Thermoperiods of 6/6 hours, 12/12 hours and 24/24 hours were established with the same temperature change of 22/14C and same controlled vapor pressure deficit of 0.60 kPa. The thermoperiod of 24/24 hours significantly promoted tuber initiation but slowed tuber enlargement in all four cultivars, compared to the thermoperiods of 6/6 hours and 12/12 hours. Denali' produced the highest tuber and total dry weights under the 6/6 hours thermoperiod. Kennebec' produced the highest tuber dry weight under the 12/12 hours thermoperiod. Thermoperiods had no significant effect on shoot and root dry weights of any cultivars. The major effect of thermoperiods was on initiation and enlargement of tubers.     

‘Plantibodies’: a flexible approach to design resistance against pathogens

Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3′-ends, but also the 5′-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (V_L) and heavy chain (V_H) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location.     

Virus transmission by aphids in potato crops

This paper reviews the contribution of vector activity and plant age to virus spread in potato crops. Determining which aphid species are vectors is particularly important for timing haulm destruction to minimize tuber infection by potato virus Y (PVY). Alate aphids of more than 30 species transmit PVY, and aphids such asRhopalosiphum padi, that migrate in large numbers before flights of the more efficient vector,Myzus persicae, appear to be important vectors. Differences in methodology, aphid biotypes and virus strains prevent direct comparisons between estimates of vector efficiencies obtained for aphids in different countries in north western Europe. M. persicae is also the most efficient vector of potato leafroll virus (PLRV), but some clones ofMacrosiphum euphorbiae transmit PLRV efficiently toNicotiana clevelandii and potato test plants. The removal of infected plants early in the season prevents the spread of PLRV in cool regions with limited vector activity. The proportion of aphids acquiring PLRV from infected potato plants decreases with plant age, and healthy potato plants are more resistant to infection later in the season. Severe symptoms of secondary leafroll developed on progeny plants of cv. Maris Piper derived from mother plants inoculated with PLRV in June or July of the previous year. Progeny plants derived from mother plants inoculated in August showed only mild symptoms, but the concentration of PLRV in these plants was as high as that in the plants with severe symptoms.     

Response of five temperate deciduous tree species to water stress

Gas exchange, tissue water relations, and leaf/root dry weight ratios were compared among young, container-grown plants of five temperate-zone, deciduous tree species (Acer negundo L., Betula papyrifera Marsh, Malus baccata Borkh, Robinia pseudoacacia L., and Ulmus parvifolia Jacq.) under well-watered and water-stressed conditions. There was a small decrease (mean reduction of 0.22 MPa across species) in the water potential at which turgor was lost (Psi(tlp)) in response to water stress. The Psi(tlp) for water-stressed plants was -1.18, -1.34, -1.61, -1.70, and -2.12 MPa for B. papyrifera, A. negundo, U. parvifolia, R. pseudoacacia, and M. baccata, respectively. Variation in Psi(tlp) resulted primarily from differences in tissue osmotic potential and not tissue elasticity. Rates of net photosynthesis declined in response to water stress. However, despite differences in Psi(tlp), there were no differences in net photosynthesis among water-stressed plants under the conditions of water stress imposed. In A. negundo and M. baccata, water use efficiency (net photosynthesis/transpiration) increased significantly in response to water stress. Comparisons among water-stressed plants showed that water use efficiency for M. baccata was greater than for B. papyrifera or U. parvifolia. There were no significant differences in water use efficiency among B. papyrifera, U. parvifolia, A. negundo, and R. pseudoacacia. Under water-stressed conditions, leaf/root dry weight ratios (an index of transpiration to absorptive capacity) ranged from 0.77 in R. pseudoacacia to 1.05 in B. papyrifera.