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D W Leonard

Publications and source records attributed to D W Leonard.

22 records · Page 2Linked to original sources
PubMedDate not supplied

Double responding in classical nictitating membrane conditioning with single-CS dual-ISI training.

Rabbits were classically conditioned under a single-CS dual-ISI paradigm. Contrary to a previous experiment by Frey (1970), a separate CR was conditioned at each interstimulus interval (ISI), producing a double response (DR) on long-ISI trials. Further experiments indicated that DR development is facilitated by (a) circumorbital US-location and (b) relatively high US-intensity. However, subsequent shifts to nonoptimal conditions did not produce substantial decreases in DR frequency. The presence of DRs appears to be readily amenable to interpretation in terms of a Pavlovian stimulus-trace mechanism in which the US becomes associated with a particular temporal portion of the CS. An instrumental-response-shaping hypothesis of classical conditioning can explain these data only if the hypothetical reinforcement mechanism is assumed to be considerably more complex than had previously been supposed.

Animals↗
PubMedDate not supplied

Blindness after bilateral neck dissection: case report and review.

The primary objective of this review of the literature is to identify the probable causes of blindness after bilateral radical neck dissections. This case report and literature review also discusses possible preventive measures that may avert this catastrophic outcome. Cases of blindness after bilateral radical neck dissection were identified by an electronic literature search, as well as cross-checking all references of the above-identified papers. Eleven previous cases of blindness after bilateral neck dissection were identified. The most common cause was posterior ischemic optic neuropathy (PION), which was permanent. We present the only case in the literature in which blindness occurred after radical neck dissections separated by a span of 9 years. The cause of blindness in our patient was posterior ischemic optic neuropathy. Contributing factors included anemia, hypotension, and disruption of collateral venous return from the neck.

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PubMedDate not supplied

Experimental myospherulosis of the paranasal sinuses: a histologic rabbit study.

Myospherulosis or lipogranuloma formation is frequently iatrogenic and is caused by a petrolatum, lanolin, or paraffin-based ointment becoming trapped within tissue. Four different ointments, including the newly available Bactroban nasal, were studied in a rabbit paranasal sinus model to evaluate their proclivity to induce myospherulosis. The maxillary sinuses of 16 New Zealand white rabbits were bilaterally inoculated with Bactroban, Bactroban nasal, tetracycline, or bacitracin ointments and compared to saline controls in two rabbits. Sinus specimens were harvested at 2 and 4-week intervals and processed for histologic study. Myospherulosis formation was uniformly induced with the Bactroban nasal, bacitracin, and tetracycline ointments in 8/8, 7/8, and 8/8 sinuses, respectively. In contrast, myospherulosis was not induced in the 5/8 of the sinuses using Bactroban. The data from this investigation indicate that Bactroban nasal (paraffin vehicle) is similar to bacitracin and tetracycline ointments (petrolatum and petrolatum-lanolin vehicles) in that they all can cause myospherulosis. In contrast, Bactroban (a water-soluble, polyethylene glycol base) causes myospherulosis to a much smaller extent. Our results emphasize the differences between the two types of Bactroban preparations and provide objective data that can be evaluated by otolaryngologists who apply these ointments following nasal cavity surgery.

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