Histomorphometric effects of calcitonin on pharyngeal bone in fed and starved goldfish Carassius auratus

ABSTRACT: The effects of salmon calcitonin (sCT) on osteoblasts and osteoclasts were histologically and histomorphometrically investigated in the pharyngeal bone of fed and starved goldfish Carassius auratus . The thickness of the osteoid and the height of osteoblasts were also measured. Fish were given sCT intraperitoneally at a dose of 10 ng/g bodyweight four times every other day under either fed or starved conditions. The sCT treatment induced the retraction of osteoclasts and their disengagement from the bone surface. Salmon calcitonin had no effect on the histomorphometric parameters of bone formation activity, but suppressed the parameter (OcP/EP) that showed osteoclast activity. Salmon calcitonin did not affect the thickness of the osteoid, but increased the height of osteoblasts in starved fish. Histological and histomorphometric results demonstrated that osteoclast activity was suppressed when sCT was given to starved estrogenized goldfish five times for 10 days. Overall, results suggest that calcitonin is involved in bone assimilation by suppressing osteoclast activity and by enhancing osteoblast activity in the pharyngeal bone of goldfish.     

A pathological study of the salivary glands of rabid dogs in the Philippines

Rabies is a zoonotic disease caused by the rabies virus. While the salivary glands are important as exit and propagation sites for the rabies virus, the mechanisms of rabies excretion remain unclear. Here, we investigated the histopathology of the salivary glands of rabid dogs and analyzed the mechanism of excretion into the oral cavity. Mandibular and parotid glands of 22 rabid dogs and three control dogs were used. Mild to moderate non-suppurative sialadenitis was observed in the mandibular glands of 19 of the 22 dogs, characterized by loss of acinar epithelium and infiltration by lymphoplasmacytic cells. Viral antigens were detected in the mucous acinar epithelium, ganglion neurons and myoepithelium. Acinar epithelium and lymphocytes were positive for anti-caspase-3 antibodies and TUNEL staining. In contrast, no notable findings were observed in the ductal epithelial cells and serous demilune. In the parotid gland, the acinar cells, myoepithelium and ductal epithelium all tested negative. These findings confirmed the path through which the rabies virus descends along the facial nerve after proliferation in the brain to reach the ganglion neurons of the mandibular gland, subsequently traveling to the acinar epithelium via the salivary gland myoepithelium. Furthermore, the observation that nerve endings passing through the myoepithelium were absent from the ductal system suggested that viral proliferation and cytotoxicity could not occur there, ensuring that secretions containing the virus are efficiently excreted into the oral cavity.