Highly unsaturated fatty acid (HUFA) binding at the sn-2 position of phospholipids (PL) becomes a resource for prostaglandin, leukotriene, resolvin, and protectin synthesis. Both triacylglycerol (TAG) and PL synthesis pathways in vivo are via phosphatidic acid; therefore, the distribution of fatty acid species at the sn-2 position must theoretically be the same for TAG and PL if rearrangement does not occur. However, it is known that little HUFA is located at the sn-2 position of TAG in marine mammals. Therefore, distribution of fatty acid species at the sn-2 position of TAG and PL was compared between marine fishes and mammals in this study. The composition of fatty acids binding at the sn-2 or sn-1,3 position of PL and TAG was analyzed via hydrolysis with enzymes and GC-FID. The results showed that 20:4n-6, 20:5n-3, 22:5n-3, and 22:6n-3 were primarily located at the sn-1,3 positions of TAG in marine mammals. Comparison of the binding positions of HUFA and 16:0 in PL and TAG suggested the existence of Lands' cycle in marine fishes and mammals. In conclusion, both marine fishes and mammals condensed HUFA as a source of eicosanoid at the sn-2 position of PL. Furthermore, abundance ratios for 22:5n-3 or 22:6n-3 at the sn-2 position (sn-2 ratio) in TAG and PL (calculated by the equation: [abundance ratio at sn-2 position of TAG]/[abundance ratio at sn-2 position of PL]) was less than 0.35 in marine mammals; however, it was greater than 0.80 in marine fishes. These differences suggested that the HUFA consisted of 22 carbon atoms and had different roles in marine fishes and mammals.
Laboratory of Veterinary Pathology, Obihiro University of Agriculture and Veterinary Medicine, W2-11, Inada, Obihiro, Hokkaido, 080-8555, Japan. snakagun@gmail.com.
A 4-year-old captive ringed seal (Pusa hispida) was treated with subcutaneous antibacterial injections for pus exuding wounds in the skin and associated blubber following a bite attack. Three months after the incident, the animal presented nystagmus and died the following day. At necropsy, there was a 25?×?18?×?25 mm well-delineated, opaque nodular mass in the lung, besides the skin ulcers and localized areas of discoloration in the blubber correlating with the bite wound and injection sites. Histopathology of the pulmonary mass demonstrated severe eosinophilic inflammatory infiltration among numerous intralesional fungal hyphae. The hyphae were irregularly branched, broad and aseptate, consistent of zygomycosis. Magnetic resonance imaging was conducted on the head, which was initially frozen intact, revealing diffuse areas of hyperintensity in the cerebellum. Restricted histopathologic examination of the cerebellum showed severe granulomatous inflammation well spread within the neuroparenchyma, associated with abundant intralesional fungal hyphae similar to those appreciated in the pulmonary mass. Molecular analyses of the fungi in the pulmonary and cerebellar tissue identified the etiologic agent in both sites as Rhizomucor pusillus. The likely route of infection is through inhalation of R. pusillus spores or fragmented hyphae from the environment that developed into an initial pulmonary infection, becoming the source of hematogenous dissemination to the cerebellum. The skin and blubber lesions likely contributed to immunosuppression. Zygomycosis is uncommon in pinnipeds, and the present report emphasizes the importance of considering zygomycete dissemination even when the primary focus is highly confined.
Laboratory of Veterinary Pathology, Obihiro University of Agriculture and Veterinary Medicine, W2-11, Inada, Obihiro, Hokkaido, 080-8555, Japan. snakagun@gmail.com.
A 4-year-old captive ringed seal (Pusa hispida) was treated with subcutaneous antibacterial injections for pus exuding wounds in the skin and associated blubber following a bite attack. Three months after the incident, the animal presented nystagmus and died the following day. At necropsy, there was a 25?×?18?×?25 mm well-delineated, opaque nodular mass in the lung, besides the skin ulcers and localized areas of discoloration in the blubber correlating with the bite wound and injection sites. Histopathology of the pulmonary mass demonstrated severe eosinophilic inflammatory infiltration among numerous intralesional fungal hyphae. The hyphae were irregularly branched, broad and aseptate, consistent of zygomycosis. Magnetic resonance imaging was conducted on the head, which was initially frozen intact, revealing diffuse areas of hyperintensity in the cerebellum. Restricted histopathologic examination of the cerebellum showed severe granulomatous inflammation well spread within the neuroparenchyma, associated with abundant intralesional fungal hyphae similar to those appreciated in the pulmonary mass. Molecular analyses of the fungi in the pulmonary and cerebellar tissue identified the etiologic agent in both sites as Rhizomucor pusillus. The likely route of infection is through inhalation of R. pusillus spores or fragmented hyphae from the environment that developed into an initial pulmonary infection, becoming the source of hematogenous dissemination to the cerebellum. The skin and blubber lesions likely contributed to immunosuppression. Zygomycosis is uncommon in pinnipeds, and the present report emphasizes the importance of considering zygomycete dissemination even when the primary focus is highly confined.
