Comparison of seven structurally related coumarins on the inhibition of Quorum sensing of Pseudomonas aeruginosa and Chromobacterium violaceum.

Quorum sensing (QS) is a cell-to-cell signaling communication system that controls the virulence behavior of a broad spectrum of bacterial pathogens, participating also in the development of biofilms, responsible of the antibiotic ineffectiveness in many infections. Therefore, QS system is an attractive target for antimicrobial therapy. In this study, we compare the effect of seven structurally related coumarins against bacterial growth, biofilm formation and elastase activity of Pseudomonas aeruginosa. In addition, the anti-pathogenic capacity of the seven coumarins was evaluated on the wild type and the biosensor strain of Chromobacterium violaceum. The comparative study of coumarins showed that molecules with hydroxyl groups on the aromatic ring displayed higher activity on the inhibition of biofilm formation of P. aeruginosa over coumarins with substituents in positions 3 and 4 or without the double 3,4-bond. These 3 or 4-hydroxylated positions caused a decrease in the anti-biofilm activity obtained for coumarin. However, the hydroxyl group in position 3 of the pyrone ring was important for the inhibition of C. violaceum QS and elastolytic activity of P. aeruginosa. The effects observed were active independently of any effect on growth. According to our results, coumarin and its hydroxylated derivatives represent an interesting group of compounds to use as anti-virulence agents against the human pathogen P. aeruginosa.

An intravaginal controlled-release prostaglandin E2 pessary for cervical ripening and initiation of labor at term.

The purpose of this randomized, double-blind study was to evaluate the efficacy and safety of a new controlled-release hydrogel pessary for ripening the cervix and initiating labor. Subjects had an entry Bishop score of 4 or less and gestational age of 37 or more weeks. One hundred fourteen women received a placebo pessary and 101 received the hydrogel pessary, containing 10 mg of prostaglandin (PG) E2. Compared with the placebo group, those given the PGE2 pessary were more likely to have an increase in Bishop score of 3 or more (60 or 59% versus 21 or 18%; P less than .0001), change to a Bishop score of 6 or higher (59 or 58% versus 18 or 16%; P less than .0001), and active labor (68 or 67% versus 15 or 13%; P less than .0001). Including the crossover study, uterine hyperstimulation (28 of 182, 15%) and fetal heart rate abnormalities (18 of 182, 10%) in PGE2-treated subjects were reversed on removal of the pessary with no apparent harm to the mother or fetus. These temporary adverse effects appeared while the pessary was in place and after the onset of active labor. Oxytocin was unnecessary in 89 of 182 (49%) of the PGE2-treated cases and was used more often to augment than to induce labor. We conclude that the described controlled-release PGE2 vaginal pessary induces appreciable cervical ripening and frequently initiates active labor with little or no need for oxytocin. The pessary may cause uterine hyperstimulation or fetal heart rate abnormalities, but these would be expected to reverse on removal of the pessary.

Ontogeny of insulin effect in fetal sheep.

Compared with fetuses near term, midgestation fetal sheep at about 75 d of gestation have higher weight-specific glucose uptake rates, higher plasma glucose concentrations, lower plasma insulin concentrations, higher red blood cell insulin receptor concentrations and affinity, and a lower proportion of body weight accounted for by potentially insulin-sensitive skeletal muscle. Based on these observations, we measured the net rate of glucose uptake by the fetus from the uteroplacenta under basal and hyperinsulinemic conditions in eight fetal sheep at 76 d of gestation and eight fetal sheep at 132 d of gestation (term approximately 150 d). Hyperinsulinemia (414 +/- 90 pM) in the 76-d fetal sheep decreased plasma glucose concentration by 0.20 +/- 0.03 mM (-13%, p < 0.01) and increased the net rate of glucose uptake (8.4 +/- 2.2 mumol/min/kg, +21.3%, p < 0.05) and glucose clearance (11.4 +/- 2.6 mL/min/kg, +39%, p < 0.01). In the 132-d fetuses, a comparable hyperinsulinemia (306 +/- 36 pM) decreased plasma glucose concentration (-0.31 +/- 0.02 mM, -26%, p < 0.05) and increased glucose clearance (16.7 +/- 1.8 mL/min/kg, +73.6%, p < 0.05) to a greater extent than in the 76-d fetuses (p < 0.05 and p < 0.01, respectively). Net glucose uptake rate increased significantly in the 132-d fetuses (6.7 +/- 1.1 mumol/min/kg, +27.5%, p < 0.05), but not differently from the 76-d fetuses (p = 0.21). These data define brisk and significant effects of insulin on glucose metabolism in fetal sheep, even as early as approximately 50% of gestation. The midgestation fetal sheep, particularly in relation to its larger fractional content of body water and smaller fractional content of insulin-sensitive tissues, demonstrates glucose metabolic responses to insulin at least as great as those that occur near term.

Placental oxygen transport in sheep with different hemoglobin types.

To study the effect of genetic differences in the maternal oxyhemoglobin dissociation curve on fetal O2 supply, we compared eight pregnant ewes homozygous for high O2 affinity hemoglobin (A) with eight pregnant ewes homozygous for low O2 affinity hemoglobin (B). Each ewe carried a single fetus. Fetal weights were not significantly different (A, 3,000 +/- 170 g; B, 3,070 +/- 270 g). The A ewes had significantly higher arterial O2 saturation (95 vs. 89.4%), uterine blood flow per kilogram of fetus (464 vs. 374 ml/min), uterine venous O2 saturation (78.1 vs. 67.5%), and placental-to-fetal weight ratio (0.107 vs. 0.085). Uterine venous PO2 was significantly less in A ewes (41.7 vs. 47.6 Torr), but umbilical venous and arterial PO2 and fetal O2 uptake were virtually equal in the two groups. We conclude that the difference in O2 affinity between A and B hemoglobins is fully compensated for by differences in arterial O2 saturation, in the rate of perfusion of the pregnant uterus, and in the degree of PO2 equilibration between the uterine and umbilical circulations so that the single fetuses of A and B hemoglobin carriers have equal levels of oxygenation.

Uterine blood flow, oxygen and glucose uptakes at mid-gestation in the sheep.

In early ovine fetal development, the placenta grows more rapidly than the fetus so that at mid-gestation the aggregate weight of placental cotyledons exceeds fetal weight. The purpose of this study was to compare two separate methods of measuring uterine blood flow and glucose and oxygen uptakes in seven mid-gestation ewes, each carrying a single fetus. Uterine blood flow to both uterine horns was measured by microsphere and by tritiated water steady-state diffusion methodology. Calculations of tritiated water blood flows and oxygen and glucose uptakes were based on measurements of arteriovenous concentration differences across each uterine horn. The distribution of blood flow and oxygen uptake between the two uterine horns was strongly correlated with placental mass distribution. The two methods gave comparable results for uterine blood flow (457 +/- 35 vs 476 +/- 35 ml/min), oxygen uptake (457 +/- 35 vs 476 +/- 35 mumol/min), and glucose uptake (63 +/- 8 vs 64 +/- 6 mumol/min). Uterine blood flow was approximately 38% of the late gestation value and 56.1 +/- 1 times higher than umbilical blood flow. Uteroplacental oxygen consumption was about 58% of late gestation measurements and 3.9 +/- 0.5 times higher than fetal oxygen uptake. We confirm that the large placental mass of mid-gestation is associated with high levels of maternal placental blood flow and placental oxidative metabolism.

Gestational maturation of placental glucose transfer capacity in sheep.

The net transfer rate of glucose to the fetus from the placenta (Rf,up) increases approximately 10-fold over the second half of pregnancy. To examine the mechanism underlying this increase, we measured Rf,up at different glucose concentration gradients between maternal arterial (GA) and umbilical arterial (Ga) glucose and at three fetal ages: midgestation (76.0 +/- 0.6 days, n = 6), late gestation (131.5 +/- 2.1 days, n = 8), and an intermediate age (103.3 +/- 1.9 days, n = 4). The GA -- Ga gradient was varied by changing Ga below and above control values with fetal insulin and glucose infusions, respectively, while GA was kept constant at 70 +/- 2 mg/dl by a glucose clamp procedure. The slope of the line relating Rf,up to GA -- Ga increased from 0.15 to 1.01 dl/min in the 76- to 131.5-day period, while the intercept in the GA -- Ga axis remained approximately constant at 34 mg/dl. This indicates a fivefold increase in the ability of the placenta to supply glucose to the fetus at fixed values of maternal and fetal glucose concentration (placental glucose transfer capacity). Concomitant with this increase, there was a significant (P less than 0.001) decrease in control Ga from 26.7 +/- 1.3 to 20.3 +/- 0.3 mg/dl, leading to a significant increase in the GA -- Ga gradient and an 11-fold increase in control Rf,up (from 1.53 to 16.77 mg/min). We conclude that, in the second half of pregnancy, fetal glucose demand grows much more rapidly than placental glucose transfer capacity and requires a decrease in fetal glucose concentration to balance glucose supply and demand.

Effect of insulin on glucose/oxygen and lactate/oxygen quotients across the hindlimb of fetal lambs.

In order to determine whether insulin stimulates glucose uptake by the hindlimb tissue of the fetal lamb, we performed 7 paired, euglycemic glucose 'clamp' experiments in 7 chronically prepared fetal sheep. Four sample sets for oxygen content, glucose and lactate concentration were drawn from the external iliac artery and vein during a control period and repeated during a euglycemic, hyperinsulinemic 'clamp' period. Insulin was infused at constant rate (4 mU/min/kg) and the fetal arterial glucose concentration was maintained by variable glucose infusion. The glucose/oxygen quotient increased significantly: 1.05 +/- 0.07 (control) versus 2.02 +/- 0.16 (hyperinsulinemia). There was no change in lactate/oxygen quotient. The data demonstrate that with maximal insulin stimulation, fetal hindlimb tissues increase glucose uptake by 92% with no large change in lactate production, indicating a net accumulation of glucose carbon under these experimental conditions.

Penicillin allergy and desensitization in serious infections during pregnancy.

Penicillin allergy presents a major obstacle to the successful management of some antepartum infections. We studied 15 pregnant women with histories of penicillin allergy confirmed by positive immediate wheal-and-flare skin tests. Thirteen had syphilis, one listeria sepsis, and one Streptococcus viridans endocarditis. Each patient was desensitized over four to six hours by oral administration of increasing doses of penicillin V. At the completion of the procedure, full-dose parenteral therapy with penicillin G or ampicillin was instituted. No extracutaneous reactions were detected. Five of the subjects (33 per cent) experienced pruritus (three) or urticaria (two), but no interruption of desensitization or therapy was necessary. All clinically apparent maternal infections were cured. The pregnancy complicated by listeriosis aborted in the first trimester. The 11 neonates delivered to date are normal. These results indicate that oral desensitization is an acceptably safe approach to therapy in pregnant women who are allergic to penicillin and have infections that require beta-lactam drugs.