Fetal Surgery: Gastroschisis Model in Rabbits

This study was to develop a technique for creating gastroschisis by fetal surgery on a pregnant New Zealand white rabbit and to develop a technique for full-term delivery of a mature fetal rabbit after the repair of the abdominal wall incision in the fetal rabbit. The fetal surgery was done on the 24th or the 25th day of pregnancy and the experiment was divided into two parts: the creation of gastroschisis in the fetal rabbit and celiotomy-repair in the fetal rabbit. To creat gastroschisis, celiotomy and evisceration of the intes-tine in the fetal rabbit was made at both cornua on the 24th or the 25th day of pregnancy. After 6 days, a Caesarean section was done to deliver two gastroschisis fetal rabbits and two normal fetal rabbits. For the celiotomy-repair, celiotomy-evisceration and immediate repair of the fetal rabbit was made at both cornua on the 24th or the 25th day of pregnancy. After 6 days, a Caesarean section was done to deliver two experimental fetal rabbits and two normal fetal rabbits. Gastroschisis was successfully produced in 10 out of the 38 fetal rabbits operated on. Celiotomy-repair was done in 38 fetal rabbits. The abdominal wound was successfully repaired in 9 out of these 38 cases. Microscopically, inflammation or scarring was found neither at the gastroschisis wall margin nor at the repaired abdominal wound; however, fibroblast proliferation was found at the repaired abdominal wound. This result coincided with the general tissue finding of the fetal surgery. The conclusions are as follows: 1. By fetal surgery, experimental gastroschisis was created in fetal rabbits, and 2. The experimental abdominal wound was successfully repaired by surgery on the fetal rabbits.

Physical and Biological Activity of Domestic Product of Modified Bovine Lung Surfactant

PURPOSE: Neonatal respiratory distress syndrome is caused by the deficiency of lung surfactant in premature babies. For the treatment of RDS at present surfactants such as Surfacten (Tokyo-Tanabe Co., Japan) and Exosurf (Wellcome Co., USA) are used. As awarded the grant from the Ministry of Science and Technology for a model research project of Medium-Technology program, we have modified (supplemented) the bovine lung extracts to get YY-38, for which we have performed physical and biological activities. METHODS: For physical properties, we performed stable microbubble test (SMR) and measured surface tension lowering activity using a pulsating bubble surfactometer. Minimum and maximum surface tensions measured at 1 and 5 minutes gave surface tension-surface area diagrams, from which compressibility at surface tension 10mN/m was also calculated. As to the biological activity, we used premature rabbit fetuses as a model for the study of pressure-lung volume relationship. The lung pathology was examined on the lung tissues subsequently obtained, and aerated area ratios were calculated based on the area measured by an image analyzer. RESULTS: The minimum surface tensions of YY-38 at 1 and 5 minutes for all different concentrations were low at 10mN/m, while the maximum surface tensions ranged from 33.01mN/m to 41.07mN/m. The surface tension-surface area curve showed a definite hysteresis at 1 and 5 minutes for all concentrations, and the surface tension fell below 10mN/m with 20% surface area compression. The compressibilities at surface tension 10mN/m at 5minutes for all concentrations were all below 0.02. In animal experiments, the mean lung volume of premature rabbit fetuses was inflated to 80.9ml/kg at maximum 30cmH2O, while the lung volume was maintained at 38.3mg/kg when the lung was deflated to 5cmH2O. The overall aerated area ratio was 45.4%. CONCLUSIONS: YY-38 formed sufficient amount of stable microbubbles and had a surface tension low enough to maintain alveolar stability and to exhibit a good hysteresis curve. In animal experiments it helped the expansion of premature lungs during inspiratory phase and was effective in the prevention of collapse during expiratory phase.