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Biomedical subjects

C M MacLeod

Publications and source records attributed to C M MacLeod.

At least 37 records · Page 2Linked to original sources
PubMed1989

Single-dose study of the effect of terfenadine on theophylline absorption and disposition.

Terfenadine, a nonsedating antihistamine, and theophylline, a methylxanthine used extensively in the treatment of asthma, have potential for frequent concomitant administration. A single-dose pharmacokinetic study was performed to investigate the potential for a drug-drug interaction affecting serum theophylline concentrations. No statistically significant effect on theophylline absorption or elimination was found when 60 mg of terfenadine was concomitantly administered with 4 mg/kg of theophylline in 17 normal healthy male volunteers. The results of this single-dose study suggest there is no significant acute pharmacokinetic interaction affecting serum theophylline concentrations when terfenadine and theophylline are administered concomitantly as single isolated doses. Further investigation is needed to determine if repeated administration of terfenadine is equally without effect on theophylline absorption or disposition.

Adult↗
PubMed1988

Training and Stroop-like interference: evidence for a continuum of automaticity.

Three experiments varied the extent of practice in an analog of the Stroop color-work task. Each experiment involved four phases: (a) baseline naming of four familiar colors, (b) training in consistently naming four novel shapes by using the names of the same four colors, (c) naming the colors when they appeared in the form of the shapes, and (d) naming the shapes when they appeared in color. In Experiment 1, with up to 2 hr of training in shape naming, colors were named much faster than shapes. Interference was observed only in Phase 4. In Experiment 2, with 5 hr of training, shape naming sped up, but was still slower than color naming. Nevertheless, there was symmetrical interference in Phases 3 and 4, and this persisted 3 months later without further training. Experiment 3 replicated this pattern and then extended practice to 20 hr, by which time shape and color naming were equally rapid. After 20 hr, interference appeared only in Phase 3, reversing the original asymmetry. The overall pattern is inconsistent with a simple speed of processing account of interference. The alternative idea of a continuum of automaticity--a direct consequence of training--remains plausible, and the implications of this perspective are considered.

Attention↗
PubMed1988

Forgotten but not gone: savings for pictures and words in long-term memory.

Five experiments examined the relearning of words, simple line-drawing pictures, and complex photographic pictures after retention intervals of 1 to 10 weeks. For those items that were neither recalled nor recognized, the identical item was relearned better than an unrelated control item, as measured by a recall test following relearning. This relearning advantage in recall held for all three classes of material and extended to the cross-modality case (i.e., picture-word and word-picture) and the same-referent case (i.e., two pictures of the same object). However, recognition tests of relearning failed to detect this same relearning advantage for apparently forgotten items. Taken together, these findings conflict with the existing account of savings. Most fundamental, the classic argument that relearning serves a trace-strengthening function is undetermined by the observed recall-recognition contrast. An alternative explanation of savings is suggested wherein relearning assists retrieval of information, thereby affecting recall in particular.

Form Perception↗
PubMed1986

Aztreonam penetration into synovial fluid and bone.

Eighteen patients with uncomplicated degenerative joint disease requiring joint replacement (hip or knee) were given a single 2-g intravenous dose of aztreonam over a 5-min period preoperatively. The mean concentration in synovial fluid of 83.0 +/- 9.2 micrograms/ml averaged 0.99 times the concomitant levels in serum. The mean concentration in cancellous bone of 16.0 +/- 4.3 micrograms/g averaged 0.20 times the concomitant levels in serum.

Adult↗
PubMed1985

Picture recognition improves with subsequent verbal information.

In three experiments, subjects studied photographs presented alone or followed by a descriptive sentence. The sentence provided additional information not available in the picture. Subsequent yes-no recognition tests for the pictures demonstrated better memory for those pictures that had been followed by descriptive sentences. Experiment 1 showed that described pictures were remembered better regardless of whether comparison was to undescribed pictures presented in immediate succession or to undescribed pictures followed by a blank period equal in duration to the descriptive sentence. Experiment 2 demonstrated that although both unrelated and related sentences aided picture recognition, related sentences were significantly more helpful. Experiment 3 revealed that increasing the amount of related information (low, medium, and high) had no differential effect on picture recognition. Three explanations of these results are considered: integration of the sentence with the picture, formation of a semantic representation in addition to the pictorial one, and elaboration of the pictorial representation initiated by the sentence. Taken together, the findings seem most consistent with the elaboration account--A post-picture sentence improves attention to and perhaps rehearsal of the representation of the picture following its display.

Adolescent↗
PubMed1984

A horse race of a different color: Stroop interference patterns with transformed words.

Four experiments investigated Stroop interference using geometrically transformed words. Over experiments, reading was made increasingly difficult by manipulating orientation uncertainty and the number of noncolor words. As a consequence, time to read color words aloud increased dramatically. Yet, even when reading a color word was considerably slower than naming the color of ink in which the word was printed, Stroop interference persisted virtually unaltered. This result is incompatible with the simple horse race model widely used to explain color-word interference. When reading became extremely slow, a reversed Stroop effect--interference in reading the word due to an incongruent ink color--appeared for one transformation together with the standard Stroop interference. Whether or not the concept of automaticity is invoked, relative speed of processing the word versus the color does not provide an adequate overall explanation of the Stroop phenomenon.

Attention↗
PubMed1984

Effects of cirrhosis on kinetics of aztreonam.

Aztreonam was administered as a single, 3-min, 1-g intravenous infusion to 18 subjects, including 6 with biopsy-proven, primary biliary cirrhosis, 6 with biopsy-proven, stable alcoholic cirrhosis, and 6 age- and sex-matched control subjects with normal hepatic functions. Aztreonam was well tolerated by all subjects. Multiple blood samples and timed, cumulative urine samples were taken for assay of aztreonam content and determination of pharmacokinetic profiles. Protein-free filtrates of serum were also assayed for drug levels. Analyses by microbiological and high-pressure liquid chromatographic procedures gave equivalent results. The kinetic data were described by an open, linear, two-compartment model. There were significant differences in elimination half-life (3.2 versus 1.9 h), serum clearance (0.8 versus 1.1 ml/min per kg), and nonrenal clearance (0.2 versus 0.4 ml/min per kg) between the alcoholic cirrhosis group and the normal control group and in elimination half-life (2.2 versus 1.9 h) between the primary biliary cirrhosis group and the normal control group. There was also a difference in nonrenal clearance between the alcoholic cirrhosis and primary biliary cirrhosis groups (0.2 versus 0.5 ml/min per kg). Although the handling of aztreonam differed in the three groups, the magnitude of the difference would warrant a change in aztreonam dosing only for the alcoholic cirrhosis group. In this group, dose adjustment might be required if long-term therapy with high doses of aztreonam is indicated.

Anti-Bacterial Agents↗
PubMed1981

Beta-blocking effect of single oral doses of carteolol.

Carteolol is a nonselective beta-adrenergic blocking agent with intrinsic sympathomimetic activity. The duration of beta blockade after single oral doses of carteolol was studied in normal men for 72 hr by determining the heart rate response to an external stimulus, bolus intravenous isoproterenol, and an internal stimulus (graded treadmill exercise designed to achieve 85% of the subjects' maximal heart rate in 12 min). Each subject first received 5 mg of carteolol and then, at 3-wk intervals, 2.5, 15, and 60 mg carteolol and placebo in a randomized, double-blind fashion. Beta blockade was maximal 1 to 2 hr after dosing and the heart rate response to isoproterenol and exercise remained less (P less than 0.05) than placebo responses for the 72 hr after each dose of carteolol. The double product (maximal exercise heart rate x systolic blood pressure during the twelfth minute of exercise) was below (P less than 0.05) baseline values for 24 hr after all doses, for 48 hr after 15 mg, and for 72 hr after 60 mg of carteolol.

Administration, Oral↗
PubMed1978

Memory impairment in epileptic patients: selective effects of phenobarbital concentration.

Nineteen epileptic patients were tested first under medium (week 1) and then under high (week 2) therapeutic levels of phenobarbital. Relative to response times of 20 controls with equivalent practice but without medication, response times of patients in a short-term memory scanning task were strikingly slowed during week 2. However, increased phenobarbital did not slow responses in a task requiring access to information in long-term memory.

Adult↗