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Biomedical subjects

B Abbott

Publications and source records attributed to B Abbott.

103 records · Page 6Linked to original sources
PubMed1993

Evaluation of a supplementary retention program for black allied health sciences students.

The Medical College of Georgia's (MCG's) Minority Academic Advising Program (MAAP), which began in 1984, is a supplementary retention program for Black students. This paper describes an evaluation study of the effectiveness of MAAP within the MCG School of Allied Health Sciences (SAHS). The study sample consisted of 89 Black students who enrolled in the SAHS from fall 1978 to fall 1982 (preMAAP period) plus 129 Black students who entered the SAHS from fall 1984 through fall 1988 (MAAP period). The comparison group consisted of all other students who entered the SAHS (n = 1,884) within those same time periods. Using an evaluation design produced by merging a quasi-experimental and a time-series design, the authors found that the MAAP succeeded in increasing both the Black student retention-to-graduation rate and the time-persisted-in-program, to the extent that Black students achieved parity with other SAHS students.

Black or African American↗
PubMed1992

Free fatty acids activate the hypothalamic-pituitary-adrenocortical axis in rats.

Intravenous administration of Intralipid 10% increases blood levels of essential free fatty acids. In rats and man, this is associated with an inhibition of GH secretion from the anterior pituitary. Because GH is lipolytic, the inhibition of its secretion may represent a negative feedback action of the fats on pituitary sensitivity to GH-releasing hormone. Since corticosterone, the final secretory product of the rat hypothalamic-pituitary-adrenocortical (HPA) axis, is also lipolytic, we tested the hypothesis that FFA would inhibit the HPA axis. Rats were cannulated via the jugular vein and infused with different doses of heparin-Intralipid 10% or heparin-saline; sequential blood samples were obtained and analyzed for ACTH, corticosterone, FFA, and glucose. Intralipid at 2.85 ml/kg increased plasma FFA to over 3 meq/liter by 15 min, with a return to baseline by 60-90 min. There was no effect of the infusion on plasma osmolarity or pH. At 60 min, plasma ACTH levels were significantly elevated to over 1500 pg/ml in Intralipid-infused rats, but were unchanged in saline controls. This dose of Intralipid increased corticosterone levels by nearly 20-fold at 120 min. At 180 min, corticosterone levels were still significantly greater than those in saline controls. Lower doses of Intralipid also significantly elevated both FFA and corticosterone levels, but by 180 min, levels of both were similar to those in controls. The effects of Intralipid on corticosterone secretion could not be attributed to the presence of glycerol in the suspension, since glycerol infusions had no significant effect on steroid levels compared to those in saline controls. In dexamethasone-pretreated rats, there was no significant rise in plasma corticosterone after either of two Intralipid doses, suggesting that the action of Intralipid was at a site within the HPA axis above the adrenal gland. This finding also suggested that the high steroid levels after Intralipid treatment were not due to interference with the corticosterone RIA. This was verified by the finding that there was no increase in plasma immunoreactive corticosterone after Intralipid infusion into adrenalectomized rats. Intralipid also caused an increase in plasma glucose levels that was first significant at 60 min and declined to baseline by 180 min, possibly reflecting increased autonomic activity or peripheral insensitivity to insulin. The results suggest that high circulating FFA levels activate, rather than inhibit, the HPA axis in rats. Since stress activates glucocorticoid production and increases FFA levels due to lipolysis, it is possible that FFA and the HPA axis constitute a previously unrecognized positive feedback loop.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗
PubMed1991

CY 208-243 behaves as a typical D-1 agonist in the reserpine-treated mouse.

The object of this study was to determine if the newly developed phenanthridine derivative, CY 208-243, retains its apparent in vivo preference for dopamine D-1 receptors under conditions of dopamine depletion, as a starting point to understanding why CY 208-243 possesses antiparkinson activity and the selective D-1 agonist SKF 38393 does not. Three hours after receiving reserpine (5 mg/kg), mice were strongly sedated and completely unresponsive to the motor stimulant effects of CY 208-243 (0.1-10 mg/kg) or the selective D-2 agonist RU 24213 (0.5-5 mg/kg) administered alone. After 24 h reserpine, the akinesia was partially and dose-dependent reversed by both CY 208-243 (0.1-10 mg/kg) and RU 24213 (0.5-5 mg/kg) alone. CY 208-243 also stimulated rearing and grooming, while RU 24213 gave rise to strong head-down sniffing. The response to 1 mg/kg CY 208-243 was practically abolished by pretreatment with the D-1 antagonist SCH 23390 (0.2 mg/kg). On the other hand, blocking D-2 receptors with metoclopramide (0.25 mg/kg) unexpectedly facilitated CY 208-243-induced locomotion and rearing, but suppressed grooming. When CY 208-243 (1 mg/kg) was injected together with RU 24213 (0.5-5 mg/kg), the two drugs interacted synergistically to stimulate locomotion at all times after reserpine. These animals also exhibited a greater preponderance of grooming, sniffing, gnawing and oral dyskinesia. Apart from the potentiation of some elements of CY 208-243-stimulated motor behaviour by D-2 blockade, these results are qualitatively indistinguishable from those previously obtained with the prototype D-1 agonist SKF 38393.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1990

Perinatal decortication impairs performance on an 8-arm radial maze task.

Two experiments evaluate the role of the neocortex in rodent spatial learning. In Experiment 1, perinatally decorticated rats and sham-operated controls began ten training sessions at day 200 on an 8-arm radial maze. Decorticated rats made more errors than controls, but showed improvement by the tenth session. In the second experiment, training was extended to determine whether decorticates could eventually match control performance levels if given sufficient training. Spontaneous activity levels were also recorded and compared to maze performance to investigate the relationship between poor performance on the radial maze and activity. More than half of the decorticates reached criterion performance. Decorticates had significantly elevated spontaneous activity levels when compared to controls, and the magnitude of this hyperactivity was related to performance deficits on the radial maze. These results suggest that with extended training decorticates can learn a spatial task. Performance deficits may reflect the hyperactive tendency of decorticates rather than a specific impairment of spatial learning abilities.

Animals↗
PubMed1984

Choosing between predictable shock schedules: Long- versus short-duration signals.

Two experiments assessed the relative aversiveness of different duration preshock signals (5 and 20 seconds) and different duration stimuli identifying shock-free periods. In the first experiment, the responding of 15 of 18 rats was maintained when it produced changes from a predictable-shock condition with a 5-second preshock signal to an identical schedule with a 20-second preshock signal; responding was not maintained when it produced the opposite changes. These results occurred with intershock intervals of both 120 seconds and 240 seconds. The second experiment assessed whether changing to the 20-second schedule was maintained by properties of the preshock signals identifying the shock periods or by properties of the stimuli identifying the shock-free periods. Four subjects were given training with the two signaled schedules in an operant chamber and then later given off-baseline preference tests in a shuttlebox. When given a choice between preshock signals, subjects chose the 5-second signals over the 20-second signals. However, when given a choice between stimuli identifying shock-free periods, subjects chose the stimulus identifying the shorter shock-free periods (i.e., the one previously correlated with the 20-second signals). These findings are discussed within the Rescorla and Wagner model of stimulus compounds and within the context of safety as a contrast phenomenon.

Journal Article↗
PubMed1979

Choice for signaled over unsignaled shock as a function of signal length.

Subjects chose between signaled and unsignaled shock conditions while signal length was varied between .5 and 2.0 seconds in steps of .5 seconds in both ascending and descending series. Preference for the signaled condition failed to develop initially for five of six subjects when signals were .5 or 1.0 seconds but became strong for all subjects when signals were 2.0 seconds (ascending series). Preference declined when signals were shortened, but for most subjects this decline was small (descending series). Since discriminable shock-free periods were present in the signaled condition at all signal lengths, these results suggest that safety may not be a sufficient condition for preference to develop for signaled shock.

Acoustic Stimulation↗
PubMed1976

Choice and the dependability of stimuli that predict shock and safety.

This study assessed whether choosing a signalled shock condition over an unsignalled one is controlled by a stimulus that predicts the presence of shock (Experiment I), or by a stimulus that predicts the absence of shock (Experiment II). The dependability of these stimuli as predictors of either the presence or the absence of shock was parametrically varied over a wide range, and subjects (rats) were given an option to change from an unsignalled to a signalled condition. In the first experiment, all shocks were preceded by signals; however, the probability of a signal being followed by shock varied from 1.0 to 0.02. The data obtained indicate that the dependability of the signal as a predictor of shock is unimportant. Rats changed to the signalled condition when the signal was completely dependable (all signals followed by shock) and when the dependability of the signal was systematically degraded. In the second experiment, all signals were followed by shock; however, some shocks were not preceded by a signal. The data show that the dependability of a stimulus predicting the absence of shock is important in that, as dependability decreases, changing to the signalled condition also decreases.

Journal Article↗