Investigation of humoral immune factors from selected groups of southern bluefin tuna, Thunnus maccoyii (Castelnau): implications for aquaculture

Serum immunoglobulin, lysozyme and classical and alternative complement activity were analysed in different groups of wild and captive southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), from ambient water temperatures of 12 ± 1 and 20 ± 1 °C. Groups held captive for the longest time were found to have the highest levels of these humoral immune mediators, despite a drop in ambient temperature from 20 ± 1 to 12 ± 1 °C during the captivity period. Therefore, it may be that the immune response in these endothermic fish is not inhibited by low temperature to the extent seen in poikilothermic fish. Also, length of time in captivity appears to be associated with increased antigen exposure to maintain high levels of humoral immune mediators in these groups. Lysozyme activity was optimal at pH 5.8 and 6.2, suggesting that two isoforms, with different pH optima, are present. The SBT serum was found to lyse sheep erythrocytes by both classical and alternative complement pathways. Classical pathway activity occurred in the absence of prior sensitization with antiserum to sheep red blood cells, suggesting that natural antibodies may be present (or lectin or C-reactive protein mediated activation). Complement activity was relatively resistant to freezing at −20 °C but heating at between 45 and 50 °C for 20 min destroyed all complement activity.     

Southern Ocean iron enrichment experiment: carbon cycling in high- and low-Si waters

The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide.     

Establishment of a cell line for assessing drugs as canine P‐glycoprotein substrates: proof of principle

P‐glycoprotein (P‐gp), encoded by the ABCB1 (MDR1) gene, dramatically impacts drug disposition. P‐gp is expressed in the intestines, biliary canaliculi, renal tubules, and brain capillaries where it functions to efflux substrate drugs. In this capacity, P‐gp restricts oral absorption, enhances biliary and renal excretion, and inhibits central nervous system entry of substrate drugs. Many drugs commonly used in veterinary medicine are known substrates for canine P‐gp (vincristine, loperamide, ivermectin, others). Because these drugs have a narrow therapeutic index, defective P‐gp function can cause serious adverse drug reactions due to enhanced brain penetration and/or decreased clearance. P‐gp dysfunction in dogs can be intrinsic (dogs harboring ABCB1‐1Δ) or acquired (drug interactions between a P‐gp inhibitor and P‐gp substrate). New human drug candidates are required to undergo assessment for P‐gp interactions according to FDA and EMA regulations to avoid adverse drug reactions and drug–drug interactions. Similar information regarding canine P‐gp could prevent adverse drug reactions in dogs. Because differences in P‐gp substrates have been documented between species, one should not presume that human or murine P‐gp substrates are necessarily canine P‐gp substrates. Thus, our goal was to develop a cell line for assessing drugs as canine P‐gp substrates.     

B cell lymphoma and secondary leukaemia in a mule

A 20‐year‐old mule was evaluated for anorexia and fever. Haematological evaluation revealed a population of large, immature lymphoid cells and significant anaemia. Bone marrow aspiration was unsuccessful, and abdominal ultrasonographic evaluation was unremarkable. The mule was subjected to euthanasia due to poor prognosis, and necropsy and histological evaluation revealed multicentric B cell lymphoma. The leukaemic phase of lymphoma is rarely documented in equids, and is regarded as an indication of advanced or aggressive disease. To the authors' knowledge, lymphoma in a mule has been reported only once previously.     

Relationship between the melanocortin-1 receptor (MC1R) variant R306ter and physiological responses to mechanical or thermal stimuli in Labrador Retriever dogs

Objective

Variants in the MC1R gene have been associated with red hair color and sensitivity to pain in humans. The study objective was to determine if a relationship exists between MC1R genotype and physiological thermal or mechanical nociceptive thresholds in Labrador Retriever dogs.

Comparison of chemotherapeutic drug resistance in cells transfected with canine ABCG2 or feline ABCG2

ABCG2 (ATP binding cassette subfamily G, member 2) mediates resistance to a variety of cytotoxic agents. Although human ABCG2 is well characterized, the function of canine ABCG2 has not been studied previously. Feline ABCG2 has an amino acid substitution in the adenosine triphosphate‐binding domain that decreases its transport capacity relative to human ABCG2. Our goal was to compare canine ABCG2‐mediated chemotherapeutic drug resistance to feline ABCG2‐mediated chemotherapeutic drug resistance. HEK‐293 cells stably transfected with plasmid containing canine ABCG2, feline ABCG2 or no ABCG2 were exposed to carboplatin, doxorubicin, mitoxantrone, toceranib or vincristine, and cell survival was subsequently determined. Canine ABCG2 conferred a greater degree of chemotherapy resistance than feline ABCG2 for mitoxantrone. Neither canine nor feline ABCG2 conferred resistance to doxorubicin, vincristine or toceranib. Canine, but not feline, ABCG2 conferred resistance to carboplatin, a drug that is not reported to be a substrate for ABCG2 in other species.     

Review of idiopathic feline vestibular syndrome in 75 cats

Idiopathic feline vestibular syndrome, a peripheral vestibular deficit of unknown cause, was diagnosed in 75 cats at the New York State College of Veterinary Medicine Teaching Hospital from July 1975 to October 1984. Review of the medical records of these cats indicated that the syndrome was seen in more cats in July and August (P less than 0.001) than in other months. Clinical signs included head tilt, ataxia, rolling, rotatory or horizontal nystagmus, and occasional vomiting.