Shao-Qing Shi

Changes in light-induced fluorescence of cervical collagen in guinea pigs during gestation and after sodium nitroprusside treatment

Abstract Lightinduced fluorescence (LIF) of collagen was used to investigate in vivo changes in cervical collagen in guinea pigs during gestation and following sodium nitroprusside treatment. Natural fluorescence of collagen is due to collagen cross-linking molecules that connect single collagen fibers and therefore provide rigidity of the cervical stroma. LIF of cervical collagen was measured from the surface of the exocervix in anesthetized nonpregnant and timed pregnant guinea pigs at different times of gestation with an instrument designed in our lab (Collascope™). Measurements were also performed in guinea pigs at midgestation before and 8 hours after intracervical treat ment with sodium nitroprusside. Collagen fluorescence decreased significantly as pregnancy progressed, reached lowest values at delivery, and increased gradually postpartum. Treatment with sodium nitroprusside, but not with the vehicle, caused a significant decrease in LIF (p = 0.007). We conclude, that LIF changes in the cervix reflect the gradual cervical softening (ripening) during pregnancy and the return to the rigid state of the cervix postpartum. Cervical softening during pregnancy, and after sodium nitroprusside treatment, is associated with a decrease in collagen cross-links. Measurements of LIF can be used to investigate cervical softening in vivo.

Inhibitory effects of electrical stimulation on delivery in pregnant rats.

OBJECTIVE To study the efficacy of uterine electrical stimulation (ES) with various parameters in delaying delivery in term- and preterm-laboring animals. STUDY DESIGN Catheters and electrodes, as well as ES electrodes, were sutured onto the uterine horn in day-15 pregnant rats. ES with various durations/frequencies (five sets of parameters) was tested from gestation day 21 to determine its effects on uterine contractility. The best set of ES parameters was applied in term (day 21) and preterm (day 18-labor induced) animals to determine the effects of ES on delivery. RESULTS (1) Significant reduction in uterine contractions (0.54+/-0.11 vs. 0.86+/-0.08 contractions per minute, P<0.001) was noted with ES of only one of the five sets of parameters (set #5 with pulse train of 10s on and 10s off, 28ms pulse width, frequency of 30Hz and amplitude of 4mA); (2) ES with parameter set 5 delayed delivery by 12.5h (P=0.01) and reduced area under the curve of intrauterine pressure in mmHgs (311+/-147.21 vs. 848.75+/-350.38, P<0.05) and AUC-electromyographic activity is area under rectified (i.e. absolute value) uterine EMG trace in mVs (145.25+/-93.1 vs. 410+/-182.46, P<0.05) in the term rats; and (3) similar effects were noted with ES in preterm rats with a delay in delivery by 28h (P<0.001), and a decrease in IUP-AUC (intrauterine pressure-area under curve) (101.5+/-55.45 vs. 551+/-269.06, P=0.017) and EMG-AUC (64.25+/-43.63 vs. 172.5+/-62.91, P=0.03). CONCLUSION ES of the uterus with appropriate parameters inhibits uterine contractions and delays delivery in both term and preterm rats.