PubMed Health⌕ Search

Biomedical subjects

D S Ramsay

Publications and source records attributed to D S Ramsay.

9 recordsLinked to original sources
PubMed1992

Paradoxical effects of nitrous oxide on human memory.

Using the method of adjusted learning, subjects learned number-noun pairs while breathing either placebo or 30% nitrous oxide. Subjects breathing nitrous oxide required more acquisition trials to attain a learning criterion than did subjects breathing placebo. Two weeks later, half of the subjects from each group were administered either placebo or nitrous oxide and were asked to recall the noun that had accompanied each number cue. Results showed that: 1) nitrous oxide inhalation can decrease the accessibility of to-be-recalled material and 2) nitrous oxide administered during the acquisition of material can paradoxically improved the recall of that material 2 weeks later. The additional number of acquisition trials subjects received during nitrous oxide inhalation could potentially account for this paradoxical enhancement of delayed recall; however, correlational analyses suggest this was not the case. No evidence for any state-dependent effects of nitrous oxide on cued recall were found.

Adolescent↗
PubMed1992

Prenatal exposure to heavy metals: effect on childhood cognitive skills and health status.

Prenatal exposure to seven heavy metals (cadmium, chromium, cobalt, lead, mercury, nickel, and silver) was determined for amniotic fluid taken from 92 pregnant women undergoing amniocentesis at approximately 16 to 18 weeks' gestation. Follow-up assessment of their children's cognitive skills and health status was conducted when the children were approximately 3 years of age. The presence of these metals co-occurred in amniotic fluid. A prenatal toxic risk score was derived which was a weighted score reflecting the presence of the various metals in amniotic fluid. The toxic risk score was negatively related to performance on the McCarthy Scales of Children's Abilities and positively related to the number of child illnesses reported. These results suggest the need for further prospective research on the adverse effects of prenatal exposure to various metals in combination.

Adult↗
PubMed1991

Orthognathic surgery and pulpal blood flow: a pilot study using laser Doppler flowmetry.

The purpose of this study was to analyze the effect of Le Fort I osteotomy on pulpal circulation. A laser Doppler flowmeter was used to measure pulpal blood flow of maxillary right and left central incisors and a randomly selected mandibular canine in 14 volunteers prior to surgery and at various intervals during the 6 months following surgery. Custom-made splints allowed accurate and reproducible positioning of the measurement probe. The data showed a significant reduction in vascular supply at the final observation. However, a high variability of individual blood flow patterns was found. In some patients, transient periods of ischemia were observed shortly after surgery. Also, numerous teeth demonstrated hyperemia at later intervals. One patient developed discoloration of a central incisor, and another lost marginal periodontal support around both central incisors. However, in none of the 14 subjects was pulpal blood flow found to be absent following surgery.

Adolescent↗
PubMed1991

Reliability of pulpal blood-flow measurements utilizing laser Doppler flowmetry.

Pulpal blood flow can now be measured non-invasively in the clinic utilizing laser Doppler flowmetry. The purpose of our study was to test (1) whether the position of the measurement probe on the tooth affects blood-flow measurements and (2) whether measurements from identical locations vary over time. Blood flow of one maxillary central incisor was measured in each of 13 volunteers. Measurements were recorded at five different locations on the labial surface of each tooth. Four measurement sessions were performed, and two sets of measurements were recorded at each session. Custom-made splints ensured accurate and reproducible positioning of the measurement probe at each session. Spatial position of the probe had a clear effect on the pulpal blood-flow measurements (p less than 0.0001). Measurements made at incisal and gingival locations were less and greater (p less than 0.05), respectively, than those made at central locations. Measurements from various mesio-distal locations did not differ (p greater than 0.05) when made at the same height on the tooth. Pulpal blood-flow measurements recorded at a given site were not consistent across all of the testing sessions (p less than 0.0001). Our data suggest that reliable interpretation of longitudinal measurements of pulpal blood flow obtained with laser Doppler flowmetry requires accurate repositioning of the measurement probe. In addition, an adequate control condition should be included to account for bias due to temporal variation.

Adult↗
PubMed1990

Case report MM. Surgical-orthodontic correction of bilateral buccal crossbite (Brodie syndrome)

A surgical approach to treatment was required for this 35-year-old patient to correct a malocclusion characterized by a bilateral buccal crossbite. Surgical procedures included a LeFort 1 osteotomy to reduce maxillary width and correct the vertical asymmetry. The mandible was lengthened with a bilateral sagittal split osteotomy. Treatment options for the nongrowing patient are limited in the correction of severe skeletal disharmonies.

Adult↗
PubMed1987

Problematic gagging: principles of treatment.

The causes of problematic gagging are discussed and a behavioral method for its treatment is recommended. Four case studies illustrating the application of this approach are presented.

Adult↗