Tracheal Ligation Research Articles

Effect on lung growth of cervical cord section in the rabbit fetus.

Experiments were performed to clarify the mechanism by which cervical cord transection retards lung growth in the fetal rabbit. In 10 sets of fetuses operated on at 24 1/2 days gestation and studied 3--4 days later, cord section at C1--C3 (high section) caused a significantly greater reduction in lung weight and lung DNA than cord section at C5--C8 (low section) as compared with control littermates. Comparison with the lungs of additional control fetuses removed at the time of operation showed that high section had reduced lung growth by 70% and low section had reduced growth by 40% relative to sham-operated controls. The hypoplastic lungs of the high-section group had poorly expanded, thick-walled terminal sacs, while those of the low section group more nearly resembled the controls. Fetal weights and weights of liver, kidneys, thymus and diaphragm did not differ significantly between the groups, but the hearts of the low-section group were unduly large. In a separate 6 sets of fetuses tracheal ligation at the time of high-cord section was found to result in large fluid-filled lungs with a normal DNA content. The results indicate that preservation of an upper motor neurone supply to the phrenic nucleus is of critical importance for fetal lung growth, and confirm the growth-promoting effects of liquid distension of the fetal lungs. We conclude that normal fetal lung growth depends on development and maintenance of a sophisticated form of function involving integration of respiratory movements and lung lipid secretion. This functional control of fetal lung growth has important implications for perinatal medicine.

1248 INTERACTION EFFECTS BETWEEN TRACHEAL LIGATION ANDI CERVICAL CORD SECTION ON LUNG DEVELOPMENT IN THE FETAL RABBIT

We have reported that cervical cord section at C1 - C3 level in 22 - 26 day rabbit fetuses results in a 43% reduction in lung wet weight and a 16% reduction in lung DNA when compared to sham operated littermates at harvesting on day 28 - 29. This effect could be due to impaired lung liquid secretion in the cord-sectioned (CS) fetuses. To investigate this aspect, tracheal ligation (TL) with or without high cervical CS was performed in rabbit fetuses at 24 - 26 days which were harvested 2 - 4 days later. Lung weight, lung DNA, lung phospholipid phosphorus, lung lecithin phosphorus and lung lecithin palmitate were compared between fetuses subjected to tracheal ligation alone, those with TL + CS and intact littermate controls. TL alone and TL + CS groups had a mean increase in lung weight/gram body weight of 80% and in lung DNA/gram body weight of 15% four days after operation. No consistent change was demonstrated in total lung phospholipid phosphorus, lecithin and lecithin palmitate. Our results indicate: isolated fetal cervical CS results in lung collapse and impaired growth; cervical CS does not impair lung liquid secretion; retained lung liquid secretion has a powerful growth-promoting effect which completely reverses the growth retarding effect of cord section. We hypothesize that the CNS influences fetal lung growth by controlling the retention rather than the formation of lung liquid.

Amniotic Fluid Composition following Fetal Nephrectomy or Tracheal Ligation

Amniotic Fluid Composition following Fetal Nephrectomy or Tracheal Ligation

Transfer of radioactive iodopyracet (131I-Diodrast) from the fetus into amniotic fluid after tracheal ligation

In the pregnant rhesus monkey, approximately 20 per cent of the total amount of radioactive iodopyracet∗∗131I-Diodrast, Abbott Laboratories, North Chicago, Illinois. injected into the fetal circulation moves into the amniotic fluid within 3 hours. To test the hypothesis that the fetal pulmonary tract might be a means of access to amniotic fluid from the fetal circulation, radioactive iodopyracet was administered to the fetus after ligation or catheterization of the fetal trachea in utero. The rate and extent of accumulation of radioactivity in amniotic fluid remained essentially unaltered by the surgical procedure. Tracheal fluid levels of radioactivity failed even to equal those of fetal blood. Tracheal fluid release by the macaque fetus in utero was slight, and the maximum rate of 3.87 μl per minute was observed only during the first 1¼ hours after catheterization. Thus, the pulmonary tract does not appear to provide appreciable egress for radioactive iodopyracet into amniotic fluid.

Cigarette smoke and pulmonary emphysema. Influence of bronchodilators and biogenic amines in experimental induction in rats.

This is the second reported attempt to demonstrate that cigarette smoke can induce pulmonary emphysema in rats. The negative results have been scrutinized to determine the significance of the changes in airway resistance and content of biogenic amines during exposure to cigarette smoke. These changes in the lung are not important in determining the appearance or disappearance of pulmonary emphysema in rats. In the same animal species, tracheal ligation and endotracheal injection of papain produce pulmonary emphysema.

Oral progestagens and experimental pulmonary emphysema

Oral and subcutaneous dimethisterone progesterone and megestrol acetate prevented the bronchoconstrictive effects of nicotine cigarette smoke and lobeline in anesthetized male rats made experimentally emphysemic by tracheal ligation and intratracheal injection of phytohemagglutinin. Physiologic endpoints were pulmonary resistance tidal volume and functional residual capacity. Compared with 10.66 for sham operated controls rats with tracheal ligation had significantly increased functional residual capacity of 18.56 ml/kg. Progesterone 10 mg/kg dimethisterone 10 mg/kg and megestrol acetate .2 mg/kg in .5% methocel vehicle sc 3 times weekly for 4 weeks prevented this increase in functional residual capacity. Dimethisterone 50 mg/kg and megestrol acetate 1 mg/kg orally on the same schedule similarly prevented emphysema. Dimethisterone sc significantly lowered the increase in pulmonary resistance due to 5-10 puffs of cigarette smoke .1 mg/kg nicotine iv or 2 mg/kg lobeline iv. Megestrol acetate sc decreased bronchoconstriction due to nicotine only.