Masaomi Obata

Repeated administration of low-dose lipopolysaccharide induces preterm delivery in mice: a model for human preterm parturition and for assessment of the therapeutic ability of drugs against preterm delivery.

OBJECTIVE Our purpose was to establish a new animal model for human preterm delivery for assessment of the protective effect of drugs against preterm delivery. STUDY DESIGN C3H/HeN, C3H/HeN, and BALB/c female mice impregnated by C3H/HeN, B6D2F1, and B6D2F1 male mice, respectively, were treated intraperitoneally with Escherichia coli lipopolysaccharide (0 to 100 microgram/kg, single dose or repeated doses at 1- to 6-hour intervals) on days 12 through 17 of pregnancy. On day 15 of pregnancy, the C3H/HeN females that had been impregnated by B6D2F1 males and administered lipopolysaccharide were treated intraperitoneally with indomethacin (1000 microgram/kg), ritodrine hydrochloride (1000 microgram/kg), urinary trypsin inhibitor (25 x 10(4) units/kg), or gabexate mesylate (100 mg/kg); preterm or term delivery was recorded for these mice. RESULTS C3H/HeN females impregnated by B6D2F1 males revealed the highest (100%) incidence of preterm delivery when the females were treated with 50 microgram/kg lipopolysaccharide twice at a 3-hour interval on day 15 or 17 of pregnancy. Indomethacin and urinary trypsin inhibitor used separately significantly decreased the incidence of preterm delivery, but only urinary trypsin inhibitor, and not any of the other drugs, significantly increased the incidence of term delivery in the mice. CONCLUSION A new animal model for investigation of preterm delivery was established, and its usefulness for assessment of the protective effect of drugs against preterm delivery was demonstrated.

Age-Related Changes in Coagulation, Fibrinolysis, and Platelet Aggregation in Male WBN/Kob Rats

We investigated the age-related changes in blood coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats, animals that exhibit spontaneously diabetes mellitus at more than 6 months of age. The rats aged 6 months or more showed significant hyperglycemia, hypoinsulinemia, and hyperlipidemia. As changes in coagulation parameters, the data indicated significant increases in factors II, V, VII, VIII, IX, X, and XII activities; a significant decrease in antithrombin III activity in rats more than 6 months of age; significant increases in fibrinogen level and factor XI activity; and significant decreases in prothrombin time and activated partial thromboplastin time in those more than 9 months of age. As changes in fibrinolytic parameters, the animals showed significant decreases in plasminogen and tissue-type plasminogen activator, and significant increases in alpha2-plasmin inhibitor and plasminogen activator inhibitor at more than 6 months of age. In addition, there were significant correlations between the plasma levels of coagulation/fibrinolytic markers and the 4-hour fasting glucose or lipids. Furthermore, they displayed significant increases in ADP- or collagen-induced platelet aggregation and in cholesterol/phospholipid molar ratio in platelets at more than 9 months of age. The increase in cholesterol/phospholipid ratio may be responsible for hyperaggregation of platelets in diabetic animals. These findings suggest that WBN/Kob rats are suitable for research on blood coagulation abnormalities in diabetes. However, further studies are needed to clarify the details of the mechanisms involved.

Role of urinary trypsin inhibitor in the maintenance of pregnancy in mice

Objective To investigate the mechanisms whereby urinary trypsin inhibitor prevents lipopolysaccharide-induced preterm delivery in mice. Methods On day 15 of pregnancy, C3H/HeNCrg female mice impregnated by Crg:B6D2F1 male mice were treated intraperitoneally with lipopolysaccharide (50 μg/kg, twice at a 3-hour interval) to induce preterm delivery. Urinary trypsin inhibitor (2.5 × 104, 7.5 × 104, or 25 × 104 units/kg, ten times at 1-hour intervals) or saline solution was administered intraperitoneally to the animals. Results The incidence of preterm delivery was significantly decreased on a dose-related basis by urinary trypsin inhibitor treatment. Urinary trypsin inhibitor prevented the morphologic and functional changes in fetal membranes and cervical ripening preceding the onset of preterm delivery. Urinary trypsin inhibitor also suppressed the increase in plasma and amniotic fluid concentrations of interleukin-1α, interleukin-6, and tumor necrosis factor-α after the lipopoly-saccharide dosing in this animal model for preterm delivery. Conclusion Urinary trypsin inhibitor prevents the pathogenicity of preterm delivery through the suppression of cytokine production.