A 6-year-old neutered male domestic short-haired cat was presented to the Comparative Ophthalmology service at Michigan State University with a 3-week history of decreased appetite and redness of the left eye. The left forelimb had been removed 15 months previously because of the presence of a subcutaneous fibrosarcoma. In the left globe, a large iridal mass was associated with increased intraocular pressure and retinal detachment. A smaller mass involving the right iris was also present. Imaging revealed a 2-cm mass in the left caudodorsal lung lobe, and abdominal ultrasound showed multifocal bilateral renal masses. Aspirates of these masses were nondiagnostic. The left globe was removed for palliative reasons, and histopathology showed that fibrosarcoma was infiltrating the iris, choroid, and optic nerve. Despite systemic chemotherapy with doxorubicin, the animal died 4 months after initial presentation. Histopathology confirmed highly angioinvasive metastatic fibrosarcoma also in the right uveal tract, the lungs, and both kidneys.
Benzocaine is a common fish anesthetic. This experiment was undertaken in order to determine the action of benzocaine and the mechanisms of action of calcium in the vascular smooth muscle from the dorsal aorta (LDA) of sea lamprey (Petromyzon marinus). Benzocaine contracted otherwise unstimulated vessels and vessels precontracted with either norepinephrine (NE) or KCl in a dose dependent manner. The vehicle, ethanol, also effected contraction in a dose dependent manner. LDA contracted significantly more when exposed to benzocaine in ethanol than to an equal volume of ethanol alone. LDA stimulated with NE were significantly more sensitive to benzocaine than were either unstimulated LDA or in LDA precontracted with KCl. LDA stimulated with KCl contracted significantly less in the absence of extracellular (EC) Ca2+ but the contractions doubled when EC Ca2+ was added back. Ethanol contractions were insignificant in the absence of EC Ca2+. Benzocaine‐induced contractions of LDA treated with thapsigargin and caffeine were significantly reduced in both the presence and absence of EC Ca2+. Therefore, KCl− and ethanol‐induced contractions were found to be dependent upon EC Ca2+ entry, while benzocaine was dependent upon intracellular Ca2+, most likely from the sarcoplasmic reticulum. These are important considerations to take into account when anesthetizing fish, particularly cyclostomes.
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