Differential elongation of growth plates is the process by which growth-plate chondrocytes translate the same sequence of gene regulation into the appropriate timing pattern for a given rate of elongation. While some of the parameters associated with differential growth are known, the purpose of this study was to test the hypothesis that eight independent variables are involved. We tested this hypothesis by considering four different growth plates in 28-day-old Long-Evans rats. Temporal parameters were provided by means of oxytetracycline and bromodeoxyuridine labeling techniques. Stereological parameters were measured with standard techniques. For all four growth plates, the calculated number of new chondrocytes produced per day approximated the number of chondrocytes lost per day at the chondro-osseous junction. This suggests that the proposed equations and associated variables represent a comprehensive set of variables defining differential growth. In absolute numbers, the proximal tibial growth plate produced about four times as many chondrocytes per day as the proximal radial growth plate (16,400 compared with 3,700). In the proximal tibia, 9% of growth is contributed by cellular division; 32%, by matrix synthesis throughout the growth plate; and 59%, by chondrocytic enlargement during hypertrophy. In the more slowly elongating growth plates, the relative contribution to elongation from cellular enlargement decreases from 59 to 44%, with a relative increase in contribution from matrix synthesis ranging from 32% in the proximal tibia 49% in the proximal radius. This study suggests that differential growth is best depicted as a complex interplay among cellular division, matrix synthesis, and cellular enlargement during hypertrophy. Differential growth is best explained by considering a set of eight independent variables, seven of which vary from growth plate to growth plate. Thus, this study confirms the importance of cellular hypertrophy during elongation and adds to our understanding of the importance of locally mediated regulatory systems controlling growth-plate activity.

The oil spill resulting from the explosion of the Deepwater Horizon drilling platform initiated immediate concern for marine wildlife, including common bottlenose dolphins in sensitive coastal habitats. To evaluate potential sublethal effects on dolphins, health assessments were conducted in Barataria Bay, Louisiana, an area that received heavy and prolonged oiling, and in a reference site, Sarasota Bay, Florida, where oil was not observed. Dolphins were temporarily captured, received a veterinary examination, and were then released. Dolphins sampled in Barataria Bay showed evidence of hypoadrenocorticism, consistent with adrenal toxicity as previously reported for laboratory mammals exposed to oil. Barataria Bay dolphins were 5 times more likely to have moderate-severe lung disease, generally characterized by significant alveolar interstitial syndrome, lung masses, and pulmonary consolidation. Of 29 dolphins evaluated from Barataria Bay, 48% were given a guarded or worse prognosis, and 17% were considered poor or grave, indicating that they were not expected to survive. Disease conditions in Barataria Bay dolphins were significantly greater in prevalence and severity than those in Sarasota Bay dolphins, as well as those previously reported in other wild dolphin populations. Many disease conditions observed in Barataria Bay dolphins are uncommon but consistent with petroleum hydrocarbon exposure and toxicity.

Abstract. We describe a case of a dog with hepatosplenic lymphoma, a disease characterized by infiltration of the liver, spleen, and bone marrow with ␥␦ T cells, absence of peripheral lymphadenopathy, and an aggressive clinical course. Physical examination findings, hematologic and biochemical abnormalities, and clinical course of the disease in this patient were similar to those in humans. Immunophenotyping of liver and spleen aspirates supported an antemortem diagnosis of T-cell lymphoma consistent with hepatosplenic lymphoma. The diagnosis was confirmed postmortem by a combination of routine histopathology, showing a consistent pattern of organ involvement, and immunohistochemistry showing the infiltrating neoplastic lymphocytes to be T cells expressing the ␥␦ T-cell receptor. To our knowledge, this is the first reported case of hepatosplenic lymphoma in a dog.

Delayed analysis of canine CSF by 4-8 hours is unlikely to alter diagnostic interpretation, especially for samples with protein concentrations > or =50 mg/dL. The likelihood of misinterpretation is higher for samples with low cellularity or low protein concentration. We provide specific recommendations for adding FCS or hetastarch to samples that will not be analyzed within 1 hour.