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Biomedical subjects

D S Ramsay

Publications and source records attributed to D S Ramsay.

18 recordsLinked to original sources
PubMed1995

Effects of Le Fort I osteotomy on human gingival and pulpal circulation.

The maxillary blood flow during the first 24 h following Le Fort I osteotomy was evaluated by laser Doppler flowmetry. Pulpal blood flow was recorded from two maxillary incisors and gingival blood flow was assessed from a site slightly apical to the interdental papilla of the maxillary central incisors of 12 patients receiving Le Fort I osteotomy, nine control patients receiving mandibular osteotomy, and 10 nonsurgical control subjects without orthodontic appliances. Measurements were made before surgery and at time intervals between 0-8, 8-16, and 16-24 h after surgery. The nonsurgical controls were tested at similar intervals. Gingival and pulpal blood-flow measurements did not change over time in the nonsurgical control group. Presurgical blood-flow values did not differ between the two surgical groups. Following surgery, mean gingival (but not pulpal) blood flow was significantly lower for patients treated with Le Fort I osteotomy than for patients treated with mandibular osteotomy. Follow-up examinations revealed that one patient receiving Le Fort I osteotomy experienced loss of gingiva and bone around both central incisors. This patient had one of the largest reductions in gingival blood flow.

Adult↗
PubMed1995

Developmental change in infants' responses to stress.

Infant stress responses to a well-baby physical examination and inoculation were observed longitudinally at 2, 4, and 6 months of age. In general, there were cortisol increases over base to the procedures. Cortisol level and cortisol response decreased with age. These data indicate a developmental shift in adrenocortical functioning between 2 and 6 months of age. Further evidence for this shift was seen in the stability of individual responses between 4 and 6 months of age. Individual differences in both cortisol and behavioral responses showed the most stability between these 2 ages. Moreover, diurnal variation in baseline cortisol level was present only at 6 months of age. While a sizable minority of infants showed stress-related cortisol decreases to the procedures at a given age, there was no evidence for cross-age consistency in individual infants showing these cortisol decreases.

Age Factors↗
PubMed1995

The effects of birth condition on infants' cortisol response to stress.

UNLABELLED: OBJECTIVE, DESIGN, AND SUBJECTS: To examine the effects of nonoptimal birth condition on cortisol response to routine inoculation in a longitudinal sample of full-term healthy infants at 2, 4, and 6 months of age. MEASUREMENT AND MAIN RESULTS: Optimal versus non-optimal birth condition was defined by a large versus small head circumference and a high versus low 1-minute Apgar score. An optimal birth condition was associated with a high cortisol response at 2 months, but a low cortisol response by 6 months of age. CONCLUSIONS: The findings indicate a reversal in the meaning of high adrenocortical reactivity between 2 and 6 months of age: high cortisol response may index optimal functioning at 2 months, but nonoptimal functioning by 6 months of age. Together with other results, this reversal provides evidence for a developmental shift in adrenocortical functioning during this period. The findings also show that the effects of a nonoptimal birth condition in otherwise healthy full-term infants persist for at least the first 6 months of life.

Analysis of Variance↗
PubMed1994

Developmental change in infant cortisol and behavioral response to inoculation.

Infant cortisol and behavioral responses to receiving 1 versus 2 inoculations on 1 pediatric office visit were observed at 2 and 6 months of age. Cortisol level (pre- plus postinoculation level) decreased with age, whereas cortisol response (post- minus preinoculation level) did not vary with age when the data were aggregated over infants showing a pre- to postinoculation cortisol increase and those showing a decrease. Nonetheless, for those infants who showed a cortisol increase, cortisol level and response decreased with age. Infants quieted faster at the older age. There was a moderate relation between quieting behavior and cortisol response, at least for infants who showed a pre- to postinoculation cortisol increase. These findings indicate a developmental trend for a decline over age in adrenocortical reactivity to inoculation for infants showing a cortisol release following the perturbation. Results were comparable whether infants received 1 or 2 inoculations.

Diphtheria-Tetanus-Pertussis Vaccine↗
PubMed1994

Weight loss in rats following intraventricular transplants of pancreatic islets.

Because of the body's resistance to permanent weight change, obesity remains a major health problem in modern society. It is hypothesized that the regulatory system defending body weight utilizes pancreatic insulin as an indicator of adiposity to the brain. To take advantage of this negative feedback system, we transplanted neonatal (experiment 1) or adult (experiment 2) pancreatic islets containing insulin-secreting cells into the 3rd ventricle of syngeneic Lewis rats. This resulted in an elevation of the insulin signal within the brain and a significant long-term reduction of body weight. Changes in food intake were consistent with the changes of body weight. The implantation of more islets resulted in a greater reduction of body weight, and changes in weight were inversely correlated with the level of insulin achieved in the cerebrospinal fluid. After the two studies were completed, histological examination revealed the presence of insulin-containing cells within the 3rd ventricle and adjacent hypothalamus. These studies suggest that transplanted insulin-secreting cells may provide a potential therapeutic strategy for maintenance of weight loss.

Animals↗
PubMed1993

Differences between Japanese infants and Caucasian American infants in behavioral and cortisol response to inoculation.

The behavioral and cortisol responses of Japanese infants and Caucasian American infants, 4 months of age, were observed during and following routine inoculation. The Caucasian American group showed a more intense initial affective response and a longer latency to quiet than the Japanese group; the Japanese group showed a greater cortisol response. A 4-group taxonomy was created based on high or low behavioral and cortisol response: high behavior-high cortisol, low behavior-low cortisol, high behavior-low cortisol, and low behavior--high cortisol. There were significant differences between the 2 groups of infants using this taxonomy: Infants in the Caucasian American group were more likely to fall in the high behavior-low cortisol group, while infants in the Japanese group were more likely to fall in the low behavior-high cortisol group.

Child Behavior↗
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↗
PubMed1984

Organization and lateralization of reaching in infants: an extension of Bresson et al.

This study tested whether the development of one-handed and collaborative two-handed reaching for an object on a support found by Bresson et al. (Neuropsychologia 15, 311-320, 1977) was related to the fluctuation in hand preference for manipulation and/or banging following duplicated syllable babbling onset found by Ramsay (Devl Psychol. 20, 64-71, 1984). Ramsay found that a preference for object manipulation and/or banging with the right hand emerged on the week of babbling onset, temporarily disappeared 3-4 weeks later and then re-emerged on the subsequent (fifth) week. In the present study, a preference for one-handed reaching with the right hand for objects on a support was present only on the fifth week after babbling onset. No evidence was found for a hand preference in collaborative two-handed reaching.

Child Development↗
PubMed1981

Effects of modeling action sequences on the play of twelve-, fifteen, and nineteen-month-old children.

3 studies examined the relation between the spontaneous occurrence in play of simple 2-part action sequences and the frequency of these sequences and their components following modeling at 12, 15, and 19 months of age. Play following modeling was typically more advanced than play preceding modeling. Moreover, imitation was tied to developmental level. Children at 19 months of age were generally able to imitate complete sequences, though only a few 19-month-olds performed such actions spontaneously. Children at 15 months of age typically did not imitate complete sequences except under simplified experimental conditions, and, even then, their ability to perform sequences was attenuated relative to the 19-month-olds. However, 15-month-olds did imitate many single components of the 2-part combinations and, to a lesser extent, exhibited these components spontaneously. A smaller number of 12-month-olds imitated components, which were rarely displayed spontaneously at this age. The results suggested that a general combinatorial capacity in play emerges between 15 and 19 months of age.

Child Development↗
PubMed1981

Semantic comprehension in infancy: a signal detection analysis.

The purpose of this study was to validate a paradigm by which an infant's comprehension of concrete nouns could be assessed while controlling for (a) response bias, (b) stimulus preference, and (c) maternal cuing. More specifically, we sought to determine whether 11- and 13-month-old infants directed their eye fixations to the referent of an object word said by the mother and to determine whether there was a developmental shift in responding to object words at these 2 ages, as some previous research suggests. Duration of looking at each of 4 corners of an apparatus was measured while the mother (unable to see what the child was doing) uttered a word she felt the infant knew, 1 she felt he/she did not know, and a nonsense word. Analyses based on signal detection theory using "known" words as signal trials and nonsense words as noise revealed that 13-month-olds directed their looking time significantly longer at the referent of the known word when that word was uttered than when the nonsense word was uttered. At neither age did looking at the referent of the unknown word exceed control values. No significant effects were obtained at 11 months of age, nor were there any sex effects.

Discrimination Learning↗