[Experimental and clinical study on chorioamnionitis as a cause of preterm labor].

I performed the following studies to confirm the recent recognition of chorioamnionitis as a cause of preterm labor and to evaluate the effect of antibiotics in the treatment of this disease. 1. Models of chorioamnionitis were prepared using prepartal rabbits by directly inoculating bacteria at various concentrations into the amniotic cavity. Preterm deliveries occurred 2-3 days after inoculation in most of the animals when given no antibiotic, but not when treated with antibiotic after inoculation at 10(3) cells/ml or less. 2. These results were confirmed pathologically and bacteriologically in animals sacrificed 3 days after inoculation. 3. When morphologies of the placenta and umbilical cord obtained at various gestational weeks were examined, it was revealed that patients developing preterm labor or PROM before 33 gestational weeks had significantly severer inflammation than did others. 4. While I have undertaken antibiotic therapy in PROM patients since April, 1985, it has been noted that the length of time between its diagnosis and delivery can be prolonged by antibiotic therapy and that such treatment can also prevent neonatal infection. Thus it is concluded that infection is a cause of preterm labor and should therefore be treated with antibiotics to prevent preterm labor without hesitation.

A functional and structural study of the innervation of the human uterus.

We characterized the innervation of human myometrial tissues by electrical field stimulation and electron microscopy. Nerve-specific parameters (pulse duration 0.6 msec) were used for electrical field stimulation to selectively activate intrinsic nerves. In specimens from nonpregnant, nonparous women (n = 6), tetrodotoxin (10(-6) mol/L) significantly reduced the response to electrical field stimulation by 70%. Contractions to electrical field stimulation were also inhibited to 60% by atropine (10(-5) mol/L) as well as by guanethidine (10(-5) mol/L) and phentolamine (10(-5) mol/L). Propranolol (10(-5) mol/L) had no detectable effect. We obtained similar results from about 50% of the specimens from nonpregnant, parous women (n = 15). The contractile responses of specimens from the term pregnant uterus (n = 13) to electrical field stimulation were not influenced by tetrodotoxin. Ultrastructurally we found nerve profiles in close proximity to muscle cells. About 30% of nerve varicosities in tissues from nonpregnant, nonparous patients could be classified as adrenergic (small, dense-cored vesicles), 53% as cholinergic (small, agranular vesicles), and about 17% as indeterminant (sometimes large, dense-cored vesicles). However, nerve varicosities were rarely observed in term pregnant specimens. These results indicate the presence of tetrodotoxin-sensitive, excitatory innervation of human myometrium consisting of alpha-adrenergic and cholinergic components. Furthermore, denervation may be nearly complete at term and recovery of innervation occurs at a considerable length of time after delivery.