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Biomedical subjects

M D Snow

Publications and source records attributed to M D Snow.

8 recordsLinked to original sources
PubMed1996

Teratogenic potential of almokalant, dofetilide, and d-sotalol: drugs with potassium channel blocking activity.

Drugs with class III antiarrhythmic activity are potential human teratogens because of their ability to cause bradycardia in the embryo during the organogenic period. Three drugs with class III antiarrhythmic activity, almokalant, dofetilide and d-sotalol, were compared in vitro using rat embryo culture. Each of these drugs caused a concentration-dependent bradycardia in 11- or 13-day rat embryos. For each drug the effective concentration was considerably greater than the human therapeutic plasma concentration. The reproductive outcome was also compared in vivo in Sprague-Dawley rats by oral administration of almokalant or dofetilide on single days during the organogenic period. Both drugs caused increased resorptions and the same stage-dependent malformations. Dosing on gestational day (GD) 11 was associated with right-sided oblique cleft lip and short tail, while dosing on day 13 caused digital hypoplasia and/or amputation. Susceptibility to these drugs started on GD 9 when the embryonic heart starts beating and ended on GD 15. The malformations were preceded by hemorrhage; which is consistent with the proposed pathogenesis that the drug-induced bradycardia caused embryonic hypoxia/ischemia. This study indicates that the induction of malformations/embryonic death by class III antiarrhythmic drugs which inhibit Ikr is a class effect secondary to a common pharmacological action on the embryonic heart.

Abnormalities, Drug-Induced↗
PubMed1995

Cephalometric analysis of Deutero-Malay Indonesians.

A cephalometric study using Downs' analysis was undertaken with lateral cephalometric radiographs for a mixed sample of 50 child, adolescent and young adult Indonesians who presented with Angle Class I occlusions. Significant differences between this study group and the published results from comparative racial types were found for Downs' angle of convexity, Y-axis and incisor inclinations, indicating that Indonesians can be differentiated from other races with similar occlusions by using Downs' analysis.

Adolescent↗
PubMed1991

The effect of orthognathic surgery on head posture.

Changes in resting head and neck posture were studied in 201 patients following five different orthognathic surgery procedures: (1) LeFort I osteotomy for superior repositioning (intrusion) of the maxilla (n = 45); (2) bilateral sagittal split ramus osteotomy for mandibular advancement (n = 78); (3) mandibular setback (n = 19); (4) combined maxillary intrusion and mandibular advancement (n = 46); (5) combined maxillary intrusion and mandibular setback (n = 13). Head and neck posture were measured on standardized serial cephalograms taken in natural head position prior to, immediately after, and 1 year after surgery for each subject. Immediately after surgery, there was flexion of the head as measured by the craniovertical and craniocervical angles in all of the groups except the mandibular setback group, which showed little change. By 1 year post-surgery, the mean craniovertical and craniocervical angles were approximately the same as before surgery in the groups with one-jaw surgery. Statistically significant head flexion at 1 year (P less than 0.05) was observed in the combined maxillary intrusion and mandibular advancement group, and with maxillary intrusion plus mandibular setback, there was a trend toward persistent flexion. Neck posture showed no significant short- or long-term changes in any of the surgical groups.

Adult↗
PubMed1991

Surgical mandibular advancement in adolescents: postsurgical growth related to stability.

Ten of 12 adolescents treated with surgical mandibular advancement showed postsurgical mandibular growth, as indicated by an increase in the distance from condylion to pogonion. In all cases, the growth was expressed vertically relative to the cranial base, so that the chin did not come forward. None of the patients had significant increments of anterior maxillary growth postsurgically. Several patients had vertical maxillary growth, which was compensated by vertical mandibular growth, so that the anteroposterior position of the chin was maintained. Forward growth of the maxilla is minimal after the peak of the adolescent growth spurt, and results of mandibular advancement surgery can be acceptably stable after that time.

Adolescent↗
PubMed1985

Evaluation of a system for the imposition of plant water stress.

A system which imposes a range of water stress levels was developed and evaluated. Water stress was controlled by employing a screen to suspend roots above a water column of known height. Levels of water stress were imposed by changing water column height and/or hydraulic conductivity of the medium in the column. The system was evaluated in a series of growth chamber experiments in which sunflowers (Helianthus annuus L. cv NK894) were given three levels of water availability for a period of 3 weeks. Third leaf midday water potentials at the end of the trials ranged from -0.73 +/- 0.04 to -2.35 +/- 0.17 megapascals in waterstressed plants compared to -0.40 +/- 0.02 megapascals for control plants. Repetition of experiments showed no statistical differences in leaf water potentials, plant leaf areas, or plastochron indices between trials. During the experiments, the severity and pattern of water stress developments was related to both water column height and conductivity of the medium. Control plants exhibited normal diurnal water relations and transpirational behavior. Use of this system avoids many problems associated with other techniques and provides a means for subjecting plants to reproducible water stress levels for extended periods of time.

Journal Article↗