That sex differences in the potency and effectiveness of opioids increased with decreases in the opioid's relative efficacy and with increases in the nociceptive stimulus intensity suggests that the relative efficacy of mu opioids as antinociceptive agents is greater in male than female rats.

Three porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evaluation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight-bearing was achieved.

Maximal expiratory and inspiratory static airway pressures at different lung volumes were measured in 56 normal subjects of both sexes ranging in age from 6 to 64 years. A new method was used requiring a special mouthpiece, a series of containers of different volumes (allowing volume combinations from 1.5 to 200 liters), and a manometer. The subjects breathed into or out of the containers as forcibly as possible; the lung volumes corresponding to the maximal pressures developed were calculated by Boyle's law. The results are compared with those obtained by other authors. The maximal pressures developed by our subjects, particularly on expiration, were considerably higher than most published values. This was probably the result of using a special mouthpiece which provided an adequate seal even at high pressures. One experienced subject obtained pressures as high as 300 cm H2O on expiration and 200 cm H2O on inspiration. strength; muscles; pressures; chest Submitted on November 29, 1963

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