The actions of formamidine pesticides on identified central neurones of Helix aspersa

Membrane potential and voltage clamp measurements of the responses to octopamine, dopamine, O-acetylcholine, and the formamidine derivatives chlordimeform (CDM) and N¹-demethylchlordimeform (DCDM) have been made on identified central neurones of Helix aspersa. DCDM and CDM were agonists on both the inhibitory and excitatory octopamine receptors on these neurones but were less potent than octopamine. The direct inhibitory effect of DCDM was antagonised by both phentolamine and cyproheptadine. DCDM was also found to antagonise the effects of octopamine, dopamine and O-acetylcholine on these neurones. The pA₂ values for DCDM against dopamine and O-acetylcholine were 5.2 (±0.1) and 5.35 (±0.15), respectively. The pA₂ value=log[DR-(1/I)], where I is the concentration of the antagonist, and DR=dose ratio =A2/A1; A1 is the dose of agonist required to produce 50% of the maximum response, and A2 is the dose of agonist needed to produce the same degree of response in the presence of the antagonist. It is concluded that DCDM and CDM act specifically on the octopamine receptors of H. aspersa central neurones, both as agonists and antagonists. The antagonist effect of DCDM against dopamine receptors is probably non-specific.     

Effect of prolonged subclinical infection with Trichostrongylus colubriformis on the performance and nitrogen metabolism of growing lambs

Ten 5-month-old lambs, reared free of parasites and prepared with abomasal and ileal cannulas, were paired and given rations of pelleted dried grass by means of continuous feeders. From 7 months of age one of each pair was dosed daily with 2500 Trichostrongylus colubriformis larvae for 34 weeks. An untreated animal served as a pair-fed control to each infected lamb. During 5 experimental periods (pre-infection, and Weeks 6-8, 12-14, 18-20 and 29-34 of dosing) measurements were made of the amounts of N leaving the small intestine, the digestibility of 35[S]-labelled microbial protein in the small intestine, and the amounts of plasma protein leaking into the digestive tract. The infection caused a growth check (P less than 0.05) from Week 6 to approximately Week 13 of dosing. This resulted from inappetence, but also from a disruption in the N digestion and metabolism of the lambs. There was a marked eosinophilia at this time. Measurements of ileal flow rates during Weeks 6 and 12 indicated that significantly more N flowed to the terminal ileum of infected lambs during this period (Week 6, 3.1 g N day-1 P less than 0.05; Week 12, 5.0 g N day-1 P less than 0.001). Plasma N leakage into the intestine during Weeks 8 and 14 was higher in infected lambs (1.2 g N day-1 P less than 0.01 and 0.9 g N day-1 P less than 0.05, respectively) but the digestibility of 35[S]-labelled microbial protein was depressed below that of the controls during the later part of this period, i.e. during Week 13. Continued larval challenge beyond this point caused a less severe nutritional penalty. Voluntary feed intake increased and the animals started to gain weight. The amount of extra N flowing to the terminal ileum of infected lambs was less at Week 18 of dosing (3.5 g N day-1 P less than 0.01) than it had been at Week 12. Similarly, extra plasma N leakage into the tract of infected lambs was less during Week 20 (0.26 g N day-1) than during Week 14. There was however, still a detectable reduction in the coefficient of digestibility of 35S microbial protein in infected lambs during Week 19. By Weeks 29-34 the only detectable difference between the infected and control lambs was in their eosinophil counts.     

Performance and carcass characteristics of swine when fed diets containing canola oil and added copper to alter the unsaturated:saturated ratio of pork fat.

A 3 x 2 trial was conducted to determine the effects of adding canola oil (0, 5, or 10%) and copper sulfate (0 or 250 ppm Cu) to diets of growing-finishing swine on performance, carcass characteristics, and carcass fat fatty acid composition. The trial used 180 pigs (27 kg). Grower diets (.80% lysine for 0% canola oil diet) were given from 27 to 57 kg of BW and finisher diets (.64% lysine) from 57 to 102 kg. Diets were formulated to constant ME:lysine ratio within the grower and finisher phases. Over the entire growing-finishing period, the addition of canola oil to the diets resulted in linear improvements in rate of gain (P less than .05) and feed efficiency (P less than .01). Dietary additions of canola oil had no effect (P greater than .10) on resulting backfat thickness or longissimus muscle area but resulted in reductions (P less than .01) in loin marbling and color and carcass fat firmness, mostly noted in pigs fed the diets with 10% canola oil. Canola oil additions at 5 and 10% levels, respectively, resulted in a 23 and 37% reduction (P less than .01) in saturated fatty acids, 3 and 8% increase (P less than .01) in monounsaturated fatty acids, and 37 and 77% increase (P less than .01) in polyunsaturated fatty acids in the carcass fat compared with the diets without canola oil. The addition of canola oil to diets of growing-finishing swine had a favorable influence on animal performance and on increasing the unsaturated:saturated ratio of the carcass fat.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental infection of goat fetuses in utero with a stable, rough mutant of Brucella abortus.

Fetuses of goats in their last trimester of pregnancy were experimentally infected with Brucella abortus strain RB51, a stable rough mutant deficient in the perosamine O-chain content of its lipopolysaccharide. RB51 maintained its rough phenotype in vivo and did not induce abortion. Infection with RB51 resulted in the production of significant levels of IgG type antibodies specific for B abortus cellular antigens distinct from the perosamine O-chain. These findings suggest that strain RB51 will be useful in the pregnant goat for studying the role of brucella antigens other than the lipopolysaccharide O-chain in the immune response to brucellosis.     

Thyroid function in the cat: assessment by the TRH response test and the thyrotrophin stimulation test

Changes in total thyroxine (T4), free T4 and total tri-iodothyronine (T3) were measured in 13 cats after the intravenous injection of varying doses of thyrotrophin stimulating hormone (TSH) (0–5 U/cat n = 6; 1 U/cat n = 8; 1 U/kg bodyweight, n = 7) or thyrotrophin releasing hormone (TRH) (100 ug/cat, n = 10). All three doses of TSH resulted in a significant (P < 0–05) rise in T4, free T4 and T3 levels, with the mean peak in hormone concentrations occurring six to eight hours after injection. The three doses of TSH all appeared to produce maximal stimulation of thyroid hormone secretion. The mean percentage increase in hormone concentrations at seven hours following the three doses of TSH ranged from 167 to 198 per cent for T4, 240 to 365 per cent for free T4, and 73 to 116 per cent for T3. Following administration of TRH there was also a significant (P < 0–05) rise in T4, and free T4. The mean peak in T4 and free T4 levels occurred at four hours, and mean increases in hormone levels at this time were 92 per cent for T4, and 198 per cent for free T4. The administration of TRH produced little change in T3 levels. TSH administration resulted in a significantly higher (P < 0–05) percentage peak increase in T4, free T4 and T3 levels at all three dosages than did TRH.     

Lack of antibodies to porcine circovirus type 2 virus in beef and dairy cattle and horses in western Canada.

Porcine circovirus type 2 (PCV2) is a recently recognized agent that is consistently associated with postweaning multisystemic wasting disease in swine. There are conflicting data concerning the ability of this virus to infect and cause disease in other species. To determine if normal cattle, cattle affected with various illnesses, and normal horses in endemic areas of PCV2 infection in swine have had PCV2 infections, 100 randomly selected bovine sera, 100 equine sera, and 100 colostrum samples from clinically normal dairy cattle were examined for the presence of antibodies to porcine circoviruses by using ELISAs. All samples tested were negative for antibodies to porcine circoviruses. As well, a seronegative neonatal Holstein calf and 6 seronegative, 6-month-old beef calves that were experimentally infected with PCV2 failed to develop antibodies to the virus. These results suggest that natural infection of cattle and horses with PCV2 does not occur, or is a rare event, in western Canada.     

Identification of Theileria infections in the salivary glands of Hyalomma anatolicum anatoli cum and Rhipicephalus appendiculatus using isoenzyme electrophoresis

Lysates prepared from the salivary glands of uninfected Hyalomma anatolicum anatolicum and Rhipicephalus appendiculatus and from ticks of these species infected with 2 strains of Theileria annulata and 1 strain of T. parva respectively have been examined for enzyme polymorphism using thin layer starch gel electrophoresis. Representative enzymes from 3 of the major metabolic pathways, the tricarboxylic acid cycle, the glycolytic pathway and the pentose phosphate pathway were investigated. Only 1 enzyme, glucose phosphate isomerase, showed differences between the host cell activity and the parasite activity and also inter- and intraspecific differences between the parasites. This technique represents a useful complement to the present histochemical methods for identification of Theileria infections in the salivary glands of ticks.     

Pulse Oximetry For Estimation Of Oxygenation In Dogs With Experimental Pneumothorax

The purpose of this study was the evaluation of pulse oximetry for estimating the oxygen saturation of hemoglobin (S_pO₂) in dogs with pneumothorax. Values for measured by pulse oximetry with transducers on the tongues and toes of six dogs were compared with saturation values (S_aO₂) computed from arterial oxygen tensions (P_aO₂) during experimentally induced pneumothorax (30,45, and 60 ml/kg of ambient air in the pleural space). Values for S_pO₂, S_aO₂, and P_aO₂ decreased with increasing volume of air. Compared to computed S_aO₂ values, S_pO₂ values obtained from the tongue tended to be less variable than those obtained from the toe, but both locations gave valuable information. Pulse oximetry appears to be a useful, relatively inexpensive method of estimating hemoglobin saturation in dogs with experimentally induced pneumothorax, and it appears to have clinical application in management of critical or traumartized dogs.