A case report of live-stranded rough-toothed dolphin (Steno bredanensis) with plastic debris ingestion on the Pacific coast of Japan.

A juvenile rough-toothed dolphin (Steno bredanensis) was live-stranded and rescued in Kanagawa Prefecture, Japan. From the results of diagnostic examinations, blood tests indicated that the dolphin was malnourished, dehydrated, and anemic. The dolphin died on sixth day of rescue despite treatment. At autopsy, 570 g of foreign material, including 34 pieces of cellophanes and plastic debris (PD), were found in the forestomach. Additional gross findings, including some endoparasitism and presence of accessory spleens were also identified. This is the first case in Japan which accidental ingestion of foreign bodies, including PD, was suspected to be the cause of death in a cetacean.

Lipopolysaccharide-induced innate immune factors in the bottlenose dolphin (Tursiops truncatus) detected in expression sequence tag analysis.

EST analysis based on the megaclone-megasorting method was performed using leukocytes from the bottlenose dolphin (Tursiops truncatus) with or without LPS stimulation. A total of 849 upregulated and 384 downregulated EST clones were sequenced, annotated, and functionally classified. Ferritin heavy peptide I was the most abundant upregulated transcript, suggesting that LPS stimulation induced high production of reactive oxygen species, which were sequestered in ferritin. Among the immune factors, the transcripts coding for an IL-1Ra, homologs to bovine serum amyloid A3, and canine intercellular adhesion molecule-1 were highly expressed. Markedly downregulated transcripts of immune factors were those for homologs of calcium-binding proteins belonging to the S100 family, S100A12, S100A8, and S100A6. Time-course experiments on the expression of some immune factors including IL-1Ra suggested that these factors interact and control cetacean innate immunity.

Characteristic metabolism of free amino acids in cetacean plasma: cluster analysis and comparison with mice.

From an evolutionary perspective, the ancestors of cetaceans first lived in terrestrial environments prior to adapting to aquatic environments. Whereas anatomical and morphological adaptations to aquatic environments have been well studied, few studies have focused on physiological changes. We focused on plasma amino acid concentrations (aminograms) since they show distinct patterns under various physiological conditions. Plasma and urine aminograms were obtained from bottlenose dolphins, pacific white-sided dolphins, Risso's dolphins, false-killer whales and C57BL/6J and ICR mice. Hierarchical cluster analyses were employed to uncover a multitude of amino acid relationships among different species, which can help us understand the complex interrelations comprising metabolic adaptations. The cetacean aminograms formed a cluster that was markedly distinguishable from the mouse cluster, indicating that cetaceans and terrestrial mammals have quite different metabolic machinery for amino acids. Levels of carnosine and 3-methylhistidine, both of which are antioxidants, were substantially higher in cetaceans. Urea was markedly elevated in cetaceans, whereas the level of urea cycle-related amino acids was lower. Because diving mammals must cope with high rates of reactive oxygen species generation due to alterations in apnea/reoxygenation and ischemia-reperfusion processes, high concentrations of antioxidative amino acids are advantageous. Moreover, shifting the set point of urea cycle may be an adaptation used for body water conservation in the hyperosmotic sea water environment, because urea functions as a major blood osmolyte. Furthermore, since dolphins are kept in many aquariums for observation, the evaluation of these aminograms may provide useful diagnostic indices for the assessment of cetacean health in artificial environments in the future.

Host-virus specificity of morbilliviruses predicted by structural modeling of the marine mammal SLAM, a receptor.

Signaling lymphocyte activation molecule (SLAM) is thought to be a major cellular receptor for high-host specificity morbilliviruses, which cause devastating and highly infectious diseases in mammals. We determined the sequences of SLAM cDNA from five species of marine mammal, including two cetaceans, two pinnipeds and one sirenian, and generated three-dimensional models to understand the receptor-virus interaction. Twenty-one amino acid residues in the immunoglobulin-like V domains of the SLAMs were shown to bind the viral protein. Notably, the sequences from pinnipeds and dogs were highly homologous, which is consistent with the fact that canine distemper virus was previously shown to cause a mass die-off of seals. Among these twenty-one residues, eight (63, 66, 68, 72, 84, 119, 121 and 130) were shared by animal groups susceptible to a particular morbillivirus species. This set of residues appears to determine host-virus specificity and may be useful for risk estimation for morbilliviruses.

Cetacean Toll-like receptor 4 and myeloid differentiation factor 2, and possible cetacean-specific responses against Gram-negative bacteria.

Toll-like receptor 4 (TLR4) and myeloid differentiation factor 2 (MD-2) are essential for recognizing the lipopolysaccharides (LPS) of Gram-negative bacteria. We determined the sequences of cDNAs encoding TLR4 and MD-2 from cetaceans and generated three-dimensional (3D) models for a better understanding of their modes of interaction and LPS recognition. The 3D reconstructions showed that cetacean TLR4 and MD-2 formed a horseshoe-like structure comprised of parallel ß-strands and a ß-cup structure consisting of two anti-parallel ß-sheets, respectively. The (TLR4-MD-2)(2) duplex-heterodimer was shown to form a symmetrical structure. Comparison with the interfaces of the complexes in other mammals revealed that cetacean TLR4s have some amino acid residue substitutions involved in duplex-heterodimer formation and in species variation for LPS recognition. These substitutions in the changed amino acid residues may alter the interaction among TLR4, MD-2, and LPS and modify the TLR4/MD-2 immunological responses.