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Biomedical subjects

L A Turner

Publications and source records attributed to L A Turner.

60 records · Page 4Linked to original sources
PubMed1985

Developmental progressions and regressions in the selective remembering strategies of EMR individuals.

Developmental changes in the use of strategies to eliminate interference from irrelevant information in memory were investigated. The participants in the first experiment were 11-, 15-, and 18-year-old EMR students, and those in the second experiment were 30-year-old retarded and nonretarded adults. In both experiments a directed forgetting paradigm was used in which the person was presented two sets of pictures but only recalled one set on a trial. On some trials there was a cue to forget the first set and to remember only the second set. The cue to forget was not used by the youngest group of students. The 15- and 18-year-olds used the cue, but interference from the to-be-forgotten items remained. The 30-year-old retarded group regressed to the performance pattern of the youngest group, whereas the nonretarded adults used appropriate selective remembering strategies. The implications of developmental changes in the memory performance of retarded persons were discussed.

Adolescent↗
PubMed1980

In vivo changes in canine ventricular cardiac conduction during halothane anesthesia.

Changes in the ventricular conduction system associated with halothane anesthesia were investigated by direct methods of His bundle recording, pacing, and premature stimulation in a canine model. In eight animals a change from 1.5% to 2.4% halothane concentrations was associated with significant prolongation of epicardial activation times by an average of 2.4 and 2.9 msec during atrial and His bundle paced rhythms, respectively. Ventricular functional refractory periods decreased significantly by an average of 7.3 msec, the effective refractory period of the ventricular conduction system did not system did not change, and epicardial conduction delays at the effective refractory period decreased. In six other animals the addition of 1.5% halothane to basal thipental anesthesia was not associated with prolongation of epicardial activation times or decreased ventricular functional refractory periods. However, the effective refractory period of the ventricular conduction system significantly decreased by an average of 9.1 msec, and epicardial conduction delays at the effective refractory period significantly increased by an average of 9.6 msec. A change in halothane concentrations from 1.5% to 2.4% is associated with depression of ventricular conduction and shortened duration of refractory periods in the ventricular conduction system in vivo in a manner consistent with the reported actions of halothane on Purkinje fibers in vitro.

Anesthesia↗
PubMedDate not supplied

2,4-Dichlorophenoxyacetic acid residues in semen of Ontario farmers.

Although paternal exposures to environmental toxicants probably play a role in adverse pregnancy outcomes, few data are available on the extent of this exposure. One semen and two 24-h urine samples were collected from 97 Ontario farmers who had recently used the phenoxy herbicides 2,4-D (2.4-dichlorophenoxyacetic acid) and/or MCPA ([4-chloro-2-methylphenoxyl acetic acid). Both samples were analyzed for 2,4-D using an immunoassay-based technique. Approximately 50% of the semen samples had detectable levels of 2, 4-D (> or =5.0 pph (ng/mL)). Semen levels of 2.4-D were correlated more closely with the second of the two urine samples. Although several studies have measured 2.4-D in the urine of applicators, this study is the first to attempt to measure 2,4-D levels in semen. As these pesticides can be excreted in the semen, they could be toxic to sperm cells and be transported to the woman and developing embryo/fetus. Further research is needed to understand how pesticide handling practices can affect semen pesticide residues and the relationship between the levels observed and reproductive health.

2,4-Dichlorophenoxyacetic Acid↗
PubMedDate not supplied

Effect of thoracic epidural anesthesia on spontaneous postinfarction ventricular dysrhythmia in awake dogs.

BACKGROUND AND OBJECTIVES: Sympathetic neural activity contributes to the genesis of ventricular ectopic activity, particularly in the setting of myocardial ischemia and infarction, so thoracic epidural anesthesia should diminish ventricular ectopy by blocking sympathetic innervation of the heart. However, the possible antidysrhythmic effect of epidural anesthesia has been studied only in the presence of general anesthesia. We therefore examined changes in spontaneous postinfarction ventricular dysrhythmia during thoracic epidural anesthesia in awake dogs. METHODS: A survivable myocardial infarction was created by two-stage ligation of the left anterior descending coronary artery. The following day, multifocal idioventricular tachycardia was the predominant cardiac rhythm. Lidocaine was administered either by thoracic epidural catheter to achieve block of at least the first five thoracic segments or intravenously as a control for direct effects, without concurrent general anesthesia or sedation. Electrocardiographic recordings were analyzed for the number of ventricular ectopic and sinoatrial depolarizations. RESULTS: Epidural and intravenous administration both produced plasma lidocaine concentrations of about 2 mg/mL. There was no change in rhythm following intravenous lidocaine. During epidural anesthesia, total ectopic beats per minute decreased from 167 +/- 8 to 135 +/- 14 (mean +/- SE, P < .05), and the dysrhythmic ratio (ventricular beats/total beats) decreased from 0.93 +/- 0.03 to 0.81 +/- 0.08 (P < .05). However, ventricular tachydysrhythmia remained the predominant rhythm. CONCLUSIONS: Epidural block modestly reduces spontaneous ventricular dysrhythmia in a perioperative setting in dogs following a large myocardial infarction. These findings do not support the choice of thoracic epidural anesthesia for the purpose of preventing or decreasing severe ventricular dysrhythmia.

Anesthesia, Epidural↗