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Biomedical subjects

A S Ward

Publications and source records attributed to A S Ward.

At least 37 records · Page 2Linked to original sources
PubMed1997

The effects of a monetary alternative on marijuana self-administration.

The availability of alternative reinforcers can reduce drug self-administration. This 21-day residential study investigated the effect of monetary alternatives on marijuana self-administration. Three female and four male participants performed computer tasks (baseline) in the morning before smoking a sample marijuana cigarette (0.0, 1.8, or 3.9% delta 9-tetrahydrocannabinol (THC) and receiving the sample alternative ($5.00 voucher). In the afternoon, participants had five opportunities to choose either the marijuana cigarette sampled earlier or a voucher for $5.00. Participants were required to meet a criterion level of task performance to obtain each choice. The monetary performance criterion varied from day to day (80, 100, or 120% of baseline); the marijuana performance criterion remained constant at 100% of baseline. Choices were delivered in the evening, after task completion. Marijuana choice varied as a function of THC concentration and criterion to earn money. Active marijuana was always chosen more often than placebo, and active and placebo marijuana were chosen over money when the criterion to earn money was high. Task performance improved when criteria were imposed, even after participants had smoked the sample marijuana cigarette. Subjective ratings of drug effects increased with increasing THC concentration, but did not predict choice. The availability of a monetary alternative was effective in shifting choice to self-administer marijuana, and marijuana choice was sensitive to contingency manipulations. The results further indicate that contingency manipulations may override the performance-impairing effects of marijuana observed in other studies.

Adult↗
PubMed1997

Binge cocaine self-administration by humans: smoked cocaine.

Tolerance develops to the cardiovascular and subjective effects of intravenous cocaine during single self-administration sessions, but diminishes within 3 h after the session ends. To examine whether a similar pattern of tolerance occurs to smoked cocaine, seven adult 'crack' cocaine users completed a protocol investigating changes in behavior during the repeated self-administration of smoked cocaine. During sessions, participants could self-administer up to 6 doses of smoked cocaine (50 mg per dose), one every 14 min. Both two- and three-day binge conditions were tested. During the two-day binge, a 2.5 h cocaine self-administration session began at 1200 h and again at 1600 h on two consecutive days, while during the three-day binge, self-administration sessions occurred at 1200 h and 1600 h on three consecutive days. The first one or two cocaine doses in each session increased cardiovascular and subjective effects ratings; subsequent cocaine inhalations during the session did not increase these measures further, suggesting the development of acute tolerance to these effects. Ratings of 'I want cocaine' decreased slightly across three days of repeated smoked cocaine self-administration, while anxiety scores increased slightly across three days, suggesting that some effects of smoked cocaine may persist beyond a binge.

Adult↗
PubMed1997

Factors influencing marijuana self-administration by humans.

The self-administration of marijuana cigarettes varying in tetrahydrocannabinol (THC) content was measured by having participants choose between marijuana and an alternative reinforcer, i.e., snack food. Twelve marijuana users (eight men, four women), in groups of four, participated in a 16-day residential study. Each day, participants had the opportunity to choose repeatedly between a marijuana cigarette and a snack. The THC concentration of the cigarette changed each day (0.0, 2.2 or 3.9% delta 9-THC w/w), as did the number of snack items (one or two); each THC concentration was compared to each snack condition twice. Days were divided into a work period (09.15-16.45 h), comprising performance and subjective-effects tasks, and a recreation period (17.15-23.30 h). Each day at 10.00 h, participants "sampled" a marijuana cigarette containing the delta 9-THC concentration available that day, and selected the number of snack items available that day. Six "choice" trials occurred from 14.00-19.00 h, when participants responded under a modified progressive ratio schedule for either marijuana or snacks. At 18.15 h, participants could participate in a 10-min math task, in which each correct answer earned $1.00. Cigarettes containing 2.2 or 3.9% delta 9-THC were self-administered more often than placebo. The only other factor influencing marijuana choice was the opportunity to earn additional money, with participants choosing not to smoke immediately before the math task. By the end of the study, active marijuana had smaller effects on ratings of "high", "stimulated," and "good drug effect." These data demonstrate that: (a) delta 9-THC is an essential reinforcing component of marijuana; (b) marijuana use may be manipulated by monetary contingencies; and (c) tolerance may develop more readily to marijuana's subjective effects than its reinforcing effects.

Adult↗
PubMed1996

Variations in cocaine self-administration by inbred rat strains under a progressive-ratio schedule.

This study investigated the influence of genetics on extent of cocaine taking in rats that were self-administering cocaine under a progressive-ratio schedule. Fischer 344, ACI and Brown Norway rats were subjects because previous genetic studies on dopamine receptor loci have indicated that these are genetically divergent strains. All subjects were assessed for acquisition and stability of cocaine self-administration under a progressive ratio schedule. Subsequently, a dose-effect curve for cocaine self-administration was determined for each strain. Fischer 344 rats maintained a higher average breaking point than did the ACI or Brown Norway strains. In addition, dopamine receptor antagonists differentially reduced the ability of cocaine to serve as a reinforcer across the three strains. The D1-selective dopamine receptor antagonist, SCH 23390, and the D2/D3-selective dopamine receptor antagonist, eticlopride were significantly more effective in reducing the self-administration of cocaine in Brown Norway rats than for the other two strains. The results of this study demonstrate that genetic differences may play an important role in determining responding under progressive-ratio schedules for cocaine, possibly due to differences in the reinforcing efficacy of cocaine.

Animals↗
PubMed1995

Arteriovenous fistulae complicating orthopaedic procedures.

Arterial injuries in general and arteriovenous fistulae in particular are uncommon complications of orthopaedic procedures. We report the case of a 75 year old patient who suffered an arteriovenous fistula following bone graft insertion for an un-united tibial fracture. Aetiology diagnosis and management of these potentially serious injuries are reviewed.

Aged↗
PubMed1994

Peripheral thrombolysis with tissue plasminogen activator. Results of two treatment regimens.

OBJECTIVE: The purpose of this study was to document the response to tissue plasminogen activator given as either a low-dose intra-arterial infusion or a bolus infusion in patients with peripheral arterial or bypass graft occlusion. DESIGN: Fifty thrombolytic procedures were carried out in 45 patients with a recent occlusion of a peripheral artery (41) or bypass graft (nine). A continuous infusion of 1.0 mg/h of tissue plasminogen activator was used in 27 patients (group A), while 23 patients were given a 20-mg bolus followed by an infusion of 1.0 mg/h (group B). Patients in the two groups were followed up for 12.1 +/- 9.3 months and 11.1 +/- 9.1 months, respectively. RESULTS: In group A, the angiographic lysis rate was 74% and clinical success rate was 67%. In group B, the comparable rates were 70% and 48%. Lysis was quicker when a bolus infusion was used, the mean lysis time being 14.4 +/- 7.9 hours compared with 26.7 +/- 9.4 hours following infusion alone (P = .0005). There was one instance of major hemorrhage in group A and eight in group B (P = .0022), including two patients with cerebral hemorrhage, one of whom died. CONCLUSION: Low-dose tissue plasminogen activator infusion is safe and reasonably effective, although a long treatment time is required. A bolus infusion regimen speeds lysis but is attended by a high incidence of serious hemorrhage.

Aged↗
PubMed1994

Thrombolysis with tissue-plasminogen activator: results with a high-dose transthrombus technique.

PURPOSE: Low-dose intraarterial tissue plasminogen activator (t-PA) is effective in peripheral thrombolysis but treatment time is prolonged. The aim of this study was to determine whether a transthrombus bolus of t-PA before low-dose infusion shortens lysis time. METHODS: Twenty-three patients with peripheral arterial or bypass graft occlusion were treated with an initial bolus of 20 mg t-PA followed by a continuous infusion of 1 mg/hr. RESULTS: Angiographic lysis was achieved in 16 patients (70%) with a mean time to complete lysis of 14.4 +/- 7.9 hours. Two patients had reocclusion on days 1 and 3, respectively. There were three deaths within the first week of treatment, one from cerebral hemorrhage and two from myocardial infarction. A clinically successful outcome was achieved in 11 patients (48%). Those patients with patency at 1 week maintained this response at a mean follow-up of 11.7 +/- 9.1 months. Thrombolysis was unsuccessful in seven instances. In three of these cases the infusion had to be discontinued prematurely because of serious hemorrhage. Of the seven unsuccessful cases, three patients subsequently underwent a femorodistal bypass, two were left with tolerable ischemic symptoms, and two required a major amputation. There were eight major bleeding complications (35%), four at or adjacent to the catheter entry site and four at a distance, including two cases of cerebral hemorrhage, one of which was fatal. CONCLUSIONS: Transthrombus bolus delivery of tissue plasminogen activator followed by a low-dose infusion shortens lysis time, but this technique appears to be associated with an increased risk of serious hemorrhage.

Adult↗
PubMed1994

Distant haemorrhagic effects in intra-arterial tissue plasminogen activator--the effect of a bolus dose.

Details are reported of four patients who developed serious distant haemorrhagic complications while undergoing peripheral arterial thrombolysis with intra-arterial tissue plasminogen activator (t-PA). The thrombolytic regime comprised a 20 mg bolus of t-PA followed by a continuous infusion of 1 mg/hr. Four additional cases of haemorrhage at the catheter entry site were also encountered in a group of 23 patients exposed to the bolus-infusion t-PA regimen. The high haemorrhage rate (31%) is a significant disadvantage of this thrombolytic protocol.

Aged↗
PubMed1993

Use of Blount's epiphyseal staples to control massive iliac venous haemorrhage.

Significant injuries to major veins are life-threatening events and may lead to patient exsanguination. Treatment usually consists of direct suture repair. A case in which a serious iliac venous haemorrhage was not able to be controlled with the usual surgical procedures is reported. A desperate attempt to achieve haemostasis using orthopaedic staples was successful. The simplicity of this technique makes it a useful addition to the surgeon's armamentarium when dealing with life-threatening venous haemorrhage.

Aged↗
PubMed1992

Aortic aneurysmal disease. A generalized dilating diathesis.

The association of dilated peripheral arteries with aortic aneurysmal disease has previously been suspected, but is not well documented. To test this association, the diameters of the common femoral, popliteal, brachial, common carotid, internal carotid, and external carotid arteries were measured with a color-flow duplex scan in 30 control subjects and 36 patients with aortic aneurysm matched for age, sex, smoking habits, and hypertension. Mean peripheral artery diameter was significantly greater in patients with aortic aneurysm than in controls at all measurement sites. Peripheral artery dilatation was identified at sites that are seldom, if ever, involved in atherosclerosis. These findings lend support to the view that there is a generalized dilating diathesis in aortic aneurysmal disease that may be unrelated to atherosclerosis.

Aged↗
PubMed1992

Perioperative experience: an essential component for nursing education.

1. Many of today's nursing curricula have limited or no exposure in perioperative nursing. This deficit probably has contributed to the current crisis level in the shortage of nurses occurring in this area. 2. As a recruitment tool and orientation package, the clinical practicum and perioperative elective are a cost-effective means of teaching, increase the self-esteem of the graduates, and provide long-term problem solving experiences. 3. In addition to applying accrued theory to a clinical setting for an extended period, students are allowed to experience an area of nursing without a formal commitment to an agency.

Education, Nursing↗