Ultrastructural changes in rabbit ciliary body after extraocular mitomycin C.

PURPOSE: To study the ultrastructural changes in ciliary body epithelium of the rabbit eye after subconjunctival injections of mitomycin C. METHODS: One eye of six New Zealand white rabbits was given a subconjunctival injection at the 12-o'clock position with 0.005, 0.02, 0.08, 0.1, 0.12, or 0.16 mg mitomycin C. The fellow eye was given a subconjunctival injection of balanced salt solution. Two weeks after treatment, the eyes were enucleated, and the ciliary body was exposed and submerged in fresh 4% paraformaldehyde/2% glutaraldehyde in 0.1 M phosphate buffer, pH 7.4, at 4 degrees C. Electron microscopy of the ciliary body was performed at two sites: the injection site (12-o'clock position) and 180 degrees away (6-o'clock position). RESULTS: At dosages of 0.1 mg and higher, ciliary body epithelial cells beneath the injection site were thinned. There were vacuoles and expansion of intracellular and intercellular spaces. Plasma membrane infoldings were disrupted, and the apical membrane was thinned. Mitochondria and nuclei were normal. Ciliary body epithelium at 6-o'clock position showed only mild architectural distortion of the plasma membrane infoldings. Eyes that received lower doses of mitomycin C (0.005 mg, 0.02 mg, and 0.08 mg) and balanced salt solution showed normal ciliary body epithelium at the injection site and 180 degrees away. CONCLUSIONS: Subconjunctival injection of mitomycin C in the rabbit produces dose-dependent localized ultrastructural changes of the ciliary body epithelium.

Primary adenocarcinoma of the lacrimal gland. A retrospective study.

BACKGROUND: Primary adenocarcinoma of the lacrimal gland is rare and usually appears in the literature as case reports. The authors retrospectively studied cases of primary adenocarcinoma of the lacrimal gland to determine which of the currently used methods was most effective in treating this tumor. METHODS: The authors requested cases of primary adenocarcinoma of the lacrimal gland from orbital surgeons and ocular pathologists worldwide. Of the cases referred, 13 examples of primary adenocarcinoma of the lacrimal gland could be confirmed and studied for clinical features, management, and outcome. RESULTS: The authors have follow-up data on all 13 patients. Six patients died of cancer, three are alive with recurrence, and four are alive and disease-free. CONCLUSION: Based on the results of this study, the authors ascertain that primary adenocarcinoma of the lacrimal gland is not inevitably fatal and should be treated with exenteration and adjuvant radiotherapy as soon as a histologic diagnosis is established. Shorter duration of symptoms before treatment appears to decrease the chance of metastases and increase the chance of long-term survival.

The effects of number of responses on pause length with temporal variables controlled.

A change in the size of a fixed-ratio schedule involves a simultaneous change in number of responses, in time to complete the ratio (work time), and in the interval between successive reinforcements (interreinforcement interval). Previous studies have suggested the importance of work time and the interreinforcement interval in controlling the length of the post-reinforcement pause. The present study sought to determine whether number of responses is also a significant factor. Pigeons were trained on a multiple fixed-ratio x fixed-ratio 2 plus timeout schedule in which the size of the fixed-ratio x was manipulated. When the work times (Experiment I) or interreinforcement intervals (Experiment II) were equated for the two components, the pause before the fixed-ratio x was longer than the pause before the fixed-ratio 2 plus timeout. As fixed-ratio x size increased, the relative difference in the lengths of the two types of pauses also increased. Because the fixed-ratio x component contained a larger number of responses than the fixed-ratio 2 plus timeout component, the relatively longer pause preceding the fixed-ratio x indicates that number of responses played a significant role in determining the length of the post-reinforcement pause.