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Biomedical subjects

M J Morgan

Publications and source records attributed to M J Morgan.

209 records · Page 12Linked to original sources
PubMed1972

Fixed-ratio performance under conditions of delayed reinforcement.

Four rats were trained on a schedule in which completion of a fixed number of lever presses initiated a signalled delay period, at the end of which food was delivered. Lever presses made during the delay had no scheduled consequences. Delays of 12, 3, and 0.75 sec were used, and it was found that the latency of the first response after food (the post-reinforcement pause) increased with length of delay. There was, on the other hand, no consistent effect of delay upon rates of responding after the post-reinforcement pause.

Journal Article↗
PubMedDate not supplied

Neck dissection for cutaneous malignant melanoma.

This retrospective study examines the experience of the Sydney Melanoma Unit in the management of cervical lymph nodes among patients with cutaneous melanoma of the head and neck. From 1960 to 1990, 397 patients had neck dissections for cutaneous malignant melanoma of the head and neck. This number represents 40% of all patients treated for head and neck melanoma at the Sydney Melanoma Unit during this period. Neck dissections were therapeutic in 152 patients, elective in 234 patients and for an unknown indication in 11 patients. Lymph nodes were histologically positive in 39% of operations overall and in 7% of elective neck dissections. The incidence of recurrence in the neck after dissection was 24% overall, 28% when nodes were histologically positive and 13% when nodes were histologically negative. Patients who developed recurrent neck disease after neck dissection had a worse prognosis than those with positive nodes who did not recur, but the difference in survival was not statistically significant. Patients with histologically positive nodes had a significantly worse survival than those with negative nodes, 34% vs 67% respectively at 10 years (p less than 0.001). Elective neck dissection was associated with a significant improvement in survival for patients with melanomas 1.5-3.9 mm thick, using univariate analysis. This apparent benefit was lost when multivariate analysis was carried out. Patients having elective neck dissection currently have selective modified radical dissections depending upon the anatomic site of the primary melanoma. Postoperative radiotherapy is used for multiple positive nodes or extracapsular spread.

Female↗
PubMedDate not supplied

Chlordiazepoxide and preference for free food in rats.

Rats continued to lever press for food when a bowl of free food was placed in the experimental chamber. Chlordiazepoxide increased the amount of free food consumed, and tended to reduce the amount of lever pressing. It is argued that the drug decreased container neophobia in the animals, rather than acting like an increase in food deprivation.

Animals↗