The objective was to assess the aerobic capacity of skeletal muscles in pinnipeds. Samples of swimming and nonswimming muscles were collected from Steller sea lions (Eumetopias jubatus, n = 27), Northern fur seals (Callorhinus ursinus, n = 5), and harbor seals (Phoca vitulina, n = 37) by using a needle biopsy technique. Samples were either immediately fixed in 2% glutaraldehyde or frozen in liquid nitrogen. The volume density of mitochondria, myoglobin concentration, citrate synthase activity, and beta-hydroxyacyl-CoA dehydrogenase was determined for all samples. The swimming muscles of seals had an average total mitochondrial volume density per volume of fiber of 9.7%. The swimming muscles of sea lions and fur seals had average mitochondrial volume densities of 6.2 and 8.8%, respectively. These values were 1.7- to 2.0-fold greater than in the nonswimming muscles. Myoglobin concentration, citrate synthase activity, and beta-hydroxyacyl-CoA dehydrogenase were 1.1- to 2. 3-fold greater in the swimming vs. nonswimming muscles. The swimming muscles of pinnipeds appear to be adapted for aerobic lipid metabolism under the hypoxic conditions that occur during diving.

The anatomy of the lymphoid organs was studied during the course of detailed dissections of 50 beachstranded bottlenose dolphins, Tursiops truncatus. Constant lymph nodes occur in 4 groups, based on their location and structure. These groups are somatic, including nodes of the cervical region and pelvic recess ; lung-associated, included marginal, diaphragmatic and hilar nodes ; visceral, including the mesenteric, pancreatic, pericolic and porta hepatis nodes ; and aortic arch nodes. Lymphatic drainage of the lung is primarily to the marginal and diaphragmatic nodes. The mesenteric node mass is well-endowed with capsular and trabecular smooth muscle, and a network of muscle fascicles within the organ implies an important contractile function in the circulation of lymph. In addition to constant nodes, occasionally nodes are found in relation to the thoracic aorta, the kidney, and under the scapula. Gut-associated structures include dorsal and ventral oropharyngeal tonsils, mucosal aggregates in the straight segment of the intestine (colon) and anal tonsils ; this gut-associated lymphoid tissue tends to involute with age, being greatly reduced by puberty. Formed lymphoid organs include the thymus and the spleen, the latter being relatively small in relation to body size. None of these structures is unique among cetaceans, but the anal tonsils are particularly well developed in T. truncatus. The lymphoid aggregates in the colon resemble the arrangement in the vermiform appendix, which is lacking in most cetaceans, and may have functions analogous to that organ.

Background Access to readily available large animal models and sensitive non-invasive techniques that can be used for the evaluation of microbicide-induced changes in tissue could significantly facilitate pre-clinical evaluations of microbicide safety. The sheep cervicovaginal tract, with stratified squamous epithelium similar to humans, holds promise as a large animal model used prior to non-human primates. In addition, optical coherence tomography (OCT) could enable high resolution visualization of tissue morphology and non-invasive assessment of microbicide-induced epithelial injury. Methods We evaluated the dose response of sheep cervicovaginal tract to benzalkonium chloride (BZK). Twenty sheep received treatment with phosphate buffered saline (PBS) or BZK solution (2%, 0.2%, or 0.02%). Pre- and post-treatment colposcopy and OCT images were collected and graded based on WHO criteria and a previously reported scoring system, respectively. Biopsies were collected and the degree of epithelial injury and its thickness was assessed based on histology and OCT. Results The sheep cervicovagina exhibited anatomical and microscopic features similar to the human. Extensive loss of the epithelium was noted on colposcopy and OCT following application of 2% BZK. Colposcopy detected findings in half of sheep and OCT in all sheep treated with 0.2% BZK. OCT detected differences in the 0.02% BZK-treated group compared to controls whereas colposcopy failed to detect any changes. Conclusions The sheep cervicovagina is similar to humans, and exhibits dose dependent epithelial changes following BZK treatment. These findings suggest that the sheep model and OCT may become valuable tools for the safety evaluation of candidate microbicides, and warrant continued development. Short summary Optical coherence tomography, a high resolution imaging method, used with colposcopy in the sheep cervicovaginal tract detected a dose-dependent response to benzalkonium chloride, demonstrating potential for microbicide safety evaluations.

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