Biomedical subjects

T J Freeman

Publications and source records attributed to T J Freeman.

7 recordsLinked to original sources

PubMed1992

Stimulus control of behavioral history.

Pigeons were exposed to two different reinforcement schedules under different stimulus conditions in each of two daily sessions separated by 6 hr (Experiments 1 and 2) or in a single session (Experiment 3). Following this, either a fixed-interval (Experiment 1) or a variable-interval schedule (Experiments 2 and 3) was effected in both stimulus conditions. In the first two experiments, exposure to fixed-ratio or differential-reinforcement-of-low-rate schedules led to response-rate, but not pattern, differences in subsequent performance on fixed- or variable-interval schedules that persisted for up to 60 sessions. The effects of reinforcement-schedule history on fixed-interval schedule performance generally were more persistent. In Experiment 3, a history of high and low response rates in different components of a multiple schedule resulted in subsequent response-rate differences under identical variable-interval schedules. Higher response rates initially occurred in the component previously correlated with high response rates. For 3 of 4 subjects, the differences persisted for 20 or more sessions. Previous demonstrations of behavioral history effects have been confined largely to between-subject comparisons. By contrast, the present results demonstrate strong behavioral effects of schedule histories under stimulus control within individual subjects.

Animals↗

PubMed1990

The ventral 'L' island flap. A refined model for skin flap research.

The rat has long been used as an experimental model for obtaining preliminary data in skin flap research. Unfortunately, there has been a great deal of inconsistency both in the experimental design of the skin flaps used in this animal model and in their inherent survival pattern. We have developed a ventral "L" flap based on clear anatomic landmarks that offers a number of advantages over previously described rat skin flaps including a more consistent survival pattern. This flap was elevated in 23 rats, resulting in an average necrosis of 16.7% +/- 7.6% 7 days postoperatively. Our article outlines the details of this flap's design and its use. The ventral L flap offers a refined tool for skin flap research in the rat animal model.

Animals↗

PubMed1990

Inhibition of endogenous superoxide dismutase with diethyldithiocarbamate in acute island skin flaps.

Oxygen free radicals have been implicated in postischemic tissue damage in a variety of experimental models including the island skin flap. Previous studies have demonstrated that supplementing animals with exogenous superoxide dismutase (SOD), a free radical scavenger, improves tissue survival in island flaps. No studies to our knowledge have attempted to inhibit endogenous SOD in a skin flap model. In this experiment 20 control rats demonstrated a 12.00% flap necrosis 7 days after a modified ventral island skin flap was raised. A second group of 20 rats were supplemented with exogenous SOD (50,000 U/kg 30 minutes preoperatively and 12 hours postoperatively) and demonstrated a statistically significant decreased flap necrosis of 5.28%. A third group of 20 rats received diethyldithiocarbamate (DDC, 0.5 gm/kg 12 hours preoperatively), an agent previously shown to inhibit SOD, and demonstrated a statistically significant increased flap necrosis of 19.77%. In a final group of 20 rats the effect of DDC was overcome by supplementation with exogenous SOD, obtaining a flap necrosis of 8.35%. Our results add further support to the importance of SOD and oxygen free radicals in postischemic tissue damage by demonstrating increased tissue necrosis with inhibition of endogenous SOD. This suggests that there is a baseline degree of SOD activity in ischemic areas working to preserve tissue. It appears that the copper-containing species of SOD found primarily in the cytoplasm plays a pivotal role in preservation of postischemic tissue.

Animals↗

PubMed1989

Acute airway obstruction due to necrotizing tracheobronchial aspergillosis in immunocompromised patients: a new clinical entity.

Two immunocompromised patients with severe neutropenia developed acute airway obstruction due to Aspergillus mycetoma formation in the trachea and main bronchi. The mycetomas caused transmural necrosis of the airway. In one patient, the necrosis extended through the bronchus intermedius into the pulmonary artery, resulting in a fatal hemorrhage during bronchoscopy.

Adult↗

PubMed1989

Response-reinforcer dependency location in interval schedules of reinforcement.

In five experiments we studied the effects on pigeons' key pecking of the location of four or more successive response-dependent reinforcers imbedded in a schedule arranging otherwise response-independent reinforcers. In Experiment 1, high local response rates early in the session were extended farther into the session as the number of response-dependent reinforcers at the beginning of the session increased. A block of four successive response-dependent reinforcers then was scheduled at the beginning, middle, or end of the session (Experiment 2) resulting in higher local response rates at those times in the session when the response-dependent reinforcers were arranged. When placed in random locations in successive sessions (Experiment 3), uniform local rates occurred throughout the session. In Experiments 1, 2, and 3, delivery of the remaining response-independent reinforcers was precluded until the response-dependent reinforcers were collected. Experiment 4 was similar to Experiments 1 and 2, except that all response-independent reinforcers occurred irrespective of whether the response-dependent reinforcers had been collected. This yielded results similar to those obtained in the first two experiments. In Experiment 5, responding early in the session had no consequence other than allowing access to the schedule of response-independent food delivery. As in the first experiment, local rates generally were higher early in the session. The results indicate that the location of response-reinforcer dependencies precisely control behavior and that such effects often are not captured by descriptions of behavior in terms of overall response rates.

Journal Article↗

PubMed1985

Extended follow-up of total inferior turbinate resection for relief of chronic nasal obstruction.

Total inferior turbinectomy has been proposed as a treatment for chronic nasal airway obstruction refractory to other, more conservative, methods of treatment. Traditionally, it has been criticized because of its adverse effects on nasophysiology. In this study, patients who had previously undergone total inferior turbinectomy were evaluated with the use of an extensive questionnaire. It confirms that total inferior turbinectomy carries significant morbidity and should be condemned.

Adult↗

PubMed1984

Setting the stage for improved record content.

The quality of the medical record depends, in large part, upon those who document within the record. When documentation is suboptimal, the medical record practitioner must develop strategies to change others' documentation practices. This article describes a technique used to improve record content, and at the same time, make better use of medical record committee time.

Documentation↗