Interactions of bovine thrombin and plasma albumin with low-energy surfaces.

Surface configurations are vessels fabricated from tubing and plate, films deposited on the surface of vessels, and beads confined in vessels. The average association constant between thrombin and sites on commercial poly(methyl methacrylate) surface (Lucite) is near 4 X 10(8) liters/mole at 22 degrees C, pH 7.0, and ionic strength 0.15. Depending on Lucite composition, average adsorption U, in molecules/cm2 of apparent solution-surface interface, ranges from 0.7 to 8.8 X 10(11). Analysis based on the assumptions that solution dimensions are preserved, adsorption is random, and surface rearrangement is negligible indicates a paucity of surface sites. Plasma albumin competes with thrombin for surface sites. Attempts to detect, by thrombin adsorption, the presence of free sites at 4.5 X 10-9M albumin or the displacement of bound albumin indicate an albumin-site association contrast greater than 1.6 X 10(9). Cross-linked poly(methyl acrylate) bead surface has U less than 5 X 10(10). In contrast to acrylic resins are silicone gum, polypropylene, and polyisobutylene, for which U ranges from 15 to 20 X 10(11). Analysis as above indicates that sites are of frequent occurrence. Material composition suggests that thrombin can interact with nonpolar groups. Further characteristics of low-energy surfaces are that progressive surface denaturation is small and there is a large variance between nominally equivalent configurations.

Women in pediatrics: the experience in Quebec.

OBJECTIVES: To compare the practice patterns of female pediatricians in Quebec with those of their male counterparts and to identify specific factors influencing these practice patterns. DESIGN: Matched cohort questionnaire survey. SETTING: Primary, secondary and tertiary care pediatric practices in Quebec. PARTICIPANTS: All 146 female pediatricians and 133 of the 298 male pediatricians, matched for age as well as type and site of practice; 119 (82%) of the female and 115 (86%) of the male pediatricians responded. MAIN OUTCOME MEASURES: Demographic and family data as well as detailed information about the practice profile. RESULTS: The two groups were comparable regarding demographic data, professional work and patient care. Compared with the male respondents, the female pediatricians were younger and saw more outpatients. The mean number of hours worked per week, excluding on-call duty, was 40.5 (standard deviation [SD] 12.4) for the women and 48.9 (SD 12.0) for the men (p < 0.001). The female pediatricians were more likely than their male counterparts to have spouses who were also physicians (40%) or in another profession (45%). The female pediatricians without children worked significantly fewer hours than the male pediatricians with or without children (p < 0.001). Children (p = 0.006), but not the number of children (p = 0.452), had a significant effect on the number of hours worked by the female pediatricians. CONCLUSION: The duality of the role of female physicians as mothers and professional caregivers must be considered during workload evaluations. If the same style of practice and the increase in the proportion of female pediatricians continue, about 20% more pediatricians will be needed in 10 years to accomplish the same workload.