Synergistic role of nitric oxide and progesterone during the establishment of pregnancy in the rat.
(25/7446)
Successful pregnancy is strictly dependent on the trophoblast-decidual interaction and on an adequate blood supply to the implantation sites. Nitric oxide (NO) has been shown to play an important role during advanced gestation, although its role during early pregnancy is unclear. The aim of the present study in rats was to evaluate whether NO plays a role during the preimplantation [days 1-4 post coitum (p.c.)] and peri-implantation (days 6-8 p.c.) phases of pregnancy. The rats were treated with the non-specific nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME), and the iNOS inhibitor aminoguanidine in the presence and absence of low-dose antiprogestin, onapristone, and evaluated on days 9 p.c. and 19 p.c., respectively. Before implantation, the treatments alone (L-NAME, aminoguanidine, onapristone) had little effect on pregnancy outcome. Conversely, aminoguanidine plus onapristone treatment completely prevented pregnancy, whereas L-NAME plus onapristone reduced the pregnancy rate to approximately 50%. In addition, both treatments drastically reduced decidualization. Oviductal flushing experiments revealed arrest of embryo development at around the 8-cell stage after aminoguanidine plus onapristone treatment on days 1-4 p.c. Similarly, treatment during the peri-implantation period with L-NAME, aminoguanidine, and onapristone each had only marginal effects on pregnancy. However, a combination of L-NAME and onapristone, and aminoguanidine plus onapristone prevented pregnancy in 71% and 42% of dams, respectively, as determined on day 19 p.c. These treatments also markedly inhibited the decidualization process. This study demonstrates synergistic effects of NOS inhibitors and an antiprogestin in preventing pregnancy. NOS, particularly the cytokine- and progesterone-inducible iNOS, may represent a new target for novel therapeutic agents capable of promoting or inhibiting pregnancy. (+info)
Interleukin-8 potentiates the effect of interleukin-1-induced uterine contractions.
(26/7446)
The aim of this research was to study the effect of exogenous interleukin (IL)-8, IL-1 and IL-8 + IL-1 on uterine contractions in rabbits. Four equal groups of non-pregnant rabbits (n = 24) were investigated using either placebo or experimental drugs in the form of vaginal suppositories. The suppositories contained human recombinant IL-8 (200 ng), IL-1 (200 ng), IL-8 (200 ng) + IL-1 (200 ng) or vehicle Witepsol base, 500 microliters). Subsequently, the plasma concentration of prostaglandin (PG) E2 was estimated 3 h after the last dose of treatment. Neutrophil infiltration in the endometrial tissue was studied with anti-rabbit RT2 staining. Suppositories with IL-1 and IL-8 + IL-1 produced contractile responses with increased frequency (P < 0.003, P < 0.0005) and amplitude (P < 0.0001) in vivo, compared with vehicle. IL-1 and IL-8 + IL-1 also caused similar contractile effects with increased frequency (P < 0.01, P < 0.0007) and amplitude (P < 0.0001) in an in-vitro experiment than vehicle. The frequency and amplitude of uterine contractions were more significant with IL-8 + IL-1 than that of IL-1, both in vivo (P < 0.002, P < 0.05) and in vitro (P < 0.005, P < 0.01). IL-8 did not induce any contractions. Prostaglandin concentration was increased approximately 8-fold with IL-8 + IL-1 (P < 0.0001) and 2.5-fold with IL-1 treatment (P < 0.0001). Neutrophil numbers were significantly increased with IL-8 + IL-1 > IL-8 > IL-1 (P < 0.002, P < 0.0003 and P < 0.008) compared with vehicle. Our data suggest that IL-8 stimulates IL-1-induced uterine contractions through PGE2 production and could be an important process during labour and delivery. (+info)
Effects of implants on daily gains of steers wintered on dormant native tallgrass prairie, subsequent performance, and carcass characteristics.
(27/7446)
Fall-weaned crossbred steer calves (n = 300; 184 +/- 2.9 kg) received either no implant (Control) or were implanted with Synovex-C (SC = 10 mg estradiol benzoate + 100 mg progesterone), Synovex-S (SS = 20 mg estradiol benzoate + 200 mg progesterone), or Revalor-G (RG = 8 mg estradiol-17beta + 40 mg trenbolone acetate) to determine the effects of implants on weight gain during winter grazing on dormant tallgrass prairie, subsequent grazing and finishing performance, and carcass characteristics. Steers grazed two dormant tallgrass prairie pastures from October 16, 1996, until March 29, 1997 (164 d), and received 1.36 kg/d of a 25% CP supplement that supplied 100 mg of monensin/steer. Following winter grazing, all steers were implanted with Ralgro (36 mg zeranol) and grazed a common tallgrass prairie pasture until July 17 (110 d). After summer grazing, all steers were implanted with Revalor-S (24 mg estradiol-17beta + 120 mg trenbolone acetate), and winter implant treatment groups were equally allotted to four feedlot pens. Steers were harvested November 17, 1997, after a 123-d finishing period. Daily gains during the winter grazing phase averaged .28, .32, .32, or .35 kg/d, respectively, for Control, SC, SS, or RG steers and were greater (P < .01) for implanted steers than for Controls. Summer daily gains were similar (1.05 +/- .016 kg/d; P > or = .61) for all treatment groups. Feedlot daily gains were also similar (1.67 +/- .034 kg/d; P > or = .21), with implanted steers weighing 14 kg more than Control steers (P = .05) at harvest, despite similar management during summer grazing and feedlot phases. Control steers tended (P = .06) to have lower yield grades. There were no differences (P = .99) in marbling between implanted and nonimplanted steers. Steers implanted during the wintering phase had increased skeletal and overall (P < .01) carcass maturities compared with nonimplanted steers, which resulted in more "B" and "C" maturity carcasses. Because carcass maturity score affects quality grade, the increased maturities of implanted steers resulted in a $9.04 decrease in carcass value/100 kg (P < .01) compared with Controls. The results of this study indicate that growth-promoting implants are efficacious for cattle wintered on dormant native range despite low daily gains. This increased weight is maintained through the summer grazing and feedlot phases; however, the benefit of the increased weight may be offset by decreased carcass quality grade and value due to increased carcass maturity. (+info)
Activation of NADPH oxidase by docosahexaenoic acid hydroperoxide and its inhibition by a novel retinal pigment epithelial protein.
(28/7446)
PURPOSE: In an earlier study, a novel retinal pigment epithelial protective protein (RPP) was described, which suppresses the superoxide generation of activated polymorphonuclear leukocytes (PMNs). In experimental autoimmune uveitis, docosahexaenoic acid hydroperoxide (22:6OOH) has been shown to be the major lipid peroxidation product in photoreceptors. This hydroperoxide was also found to be chemotactic to PMNs. This study was undertaken to evaluate the activation capability of 22:6OOH in resting PMNs and the possible inhibition of this activation by RPP. METHODS: The 22:6OOH was obtained from pure 22:6 and was purified by thin-layer and high-performance liquid chromatography. Intact rabbit peritoneal PMNs (7-8 X 10(5)) were coincubated with 0.5 microM formyl-methionyl-leucyl-phenylalanine (fMLP), 1.3 microM 22:6OOH, or 5.0 microM 22:6. These systems were coincubated with and without 0.25 microg/ml RPP. From PMN cell-free preparations, the reconstitutes each containing 21 microg plasma membranes and 276 microg cytosolic factors were coincubated with arachidonate, 22:6OOH, or 22:6, each at 100 microM. The inhibition of superoxide production was estimated by adding 0.20 microg/ml RPP. Superoxide generation was measured by superoxide dismutase-inhibitable cytochrome C reduction. RESULTS: In 30 minutes, 22:6OOH-activated PMNs produced 11.10 +/- 0.68 nanomoles superoxide, and production was suppressed 72% by RPP. Under the same conditions, fMLP induced production of 34.6 +/- 2.77 nanomoles superoxide, and RPP inhibited 60% of production. In the PMN cell-free systems, 100 microM 22:6OOH induced 74.7 nanomoles superoxide per milligram plasma membrane proteins per 5 minutes, and RPP suppressed 50% of production. These results were comparable with those generated by arachidonate, a known stimulator for this system. RPP was effective only when it was added before assembly of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. CONCLUSIONS: The inflammation-mediated retinal peroxidation product 22:6OOH significantly activates resting PMNs, either in intact cells or in cell-free preparations, to increase further the release of superoxide from PMNs, thus accelerating inflammation-mediated tissue damage. This profound amplification process seems to be effectively downregulated by an RPE-generated protein RPP. (+info)
Effect of Ox-LDL on endothelium-dependent response in pig ciliary artery: prevention by an ET(A) antagonist.
(29/7446)
PURPOSE: To investigate whether oxidized low-density lipoprotein (Ox-LDL) affects endothelium-dependent responses in isolated porcine ciliary arteries. METHODS: In a myograph system for isometric force measurements, quiescent vessels were incubated with 50 microg/ml, 100 microg/ml, or 200 microg/ml Ox-LDL; 100 microg/ml native LDL (n-LDL); 1 microM of the ET(A)- endothelin receptor antagonist BQ 123; 100 microg/ml Ox-LDL coadministered with 1 microM BQ 123; or 100 microg/ml Ox-LDL coadministered with 50 microM of the protein synthesis inhibitor cycloheximide. Vessels with nonfunctional endothelium (intentionally and mechanically damaged) were also exposed to 100 microg/ml Ox-LDL. Two hours later, vessels were washed, precontracted with the thromboxane A2 analog U 46619 (approximately 0.1 microM), and exposed to bradykinin (0.1 nM to 3 microM), an endothelium-dependent relaxing agent. RESULTS: In quiescent vessels, Ox-LDL evoked delayed contractions. In contrast, no contractions were observed after exposure to n-LDL, BQ 123, Ox-LDL with BQ 123, or Ox-LDL with cycloheximide. In vessels with nonfunctional endothelium, Ox-LDL did not evoke contraction. Bradykinin-induced relaxations were inhibited in a dose-dependent manner by Ox-LDL, but not by n-LDL, BQ 123 alone, Ox-LDL with BQ 123, or Ox-LDL with cycloheximide. CONCLUSIONS: In porcine ciliary arteries, Ox-LDL affects endothelium-dependent responses through the activation of ET(A)- endothelin receptors. As Ox-LDL can accumulate in atherosclerotic plaques, such a mechanism might be involved in the occlusion of the ophthalmic circulation observed in patients with hypercholesterolemia and atherosclerosis. (+info)
Free fatty acids impair hepatic insulin extraction in vivo.
(30/7446)
Hyperinsulinemia is a common finding in obesity and results from insulin hypersecretion and impaired hepatic insulin extraction. In vitro studies have shown that free fatty acids (FFAs), which are often elevated in obesity, can impair insulin binding and degradation in isolated rat hepatocytes. To investigate whether FFAs impair hepatic insulin extraction (E(H)) in vivo, either saline (SAL) or 10% Intralipid (0.03 ml x kg(-1) x min(-1)) plus heparin (0.44 U x kg(-1) x min(-1)) (IH) was infused into normal dogs to elevate FFA levels. Insulin was infused intraportally at 18 pmol x kg(-1) x min(-1) for 150 min (period A, high insulin dose), and then at 2.4 pmol x kg(-1) x min(-1) for another 150 min (period B, low insulin dose). After the low portal insulin dose, additional insulin was infused peripherally at 8.4 pmol x kg(-1) x min(-1) for 120 min (period C) to assess the clearance of insulin from the peripheral plasma. In 16 paired experiments, FFA levels were 1,085 +/- 167, 1,491 +/- 240, 1,159 +/- 221 micromol/l (IH) and 221 +/- 44, 329 +/- 72, 176 +/- 44 micromol/l (SAL) in periods A, B, and C, respectively. Peripheral insulin levels were greater with IH (P < 0.001) than with SAL in all periods (1,620 +/- 114, 126 +/- 12, 1,050 +/- 72 pmol/l for IH vs. 1,344 +/- 168, 96 +/- 4.2, 882 +/- 60 pmol/l for SAL). Glucose clearance was impaired by IH in all periods (P < 0.05), whereas glucose production was slightly increased by IH during period B. Peripheral insulin clearance (Cl) and E(H) were calculated from the insulin infusion rate and insulin concentration data in each period by taking into account the nonlinearity of insulin kinetics. Cl was lower (P < 0.01) with IH (9.6 +/- 0.6, 12.0 +/- 0.9, 10.2 +/- 0.6 ml x kg(-1) x min(-1)) than with SAL (11.2 +/- 1, 13.6 +/- 0.7, 11.9 +/- 0.9 ml x kg(-1) x min(-1)) in periods A, B, and C. E(H) was also lower (P < 0.05) with IH (25 +/- 4, 40 +/- 5, 32 +/- 5%) than with SAL (30 +/- 2.8, 47 +/- 3, 38 +/- 3%). We conclude that FFAs can impair hepatic insulin extraction in vivo at high and low insulin levels, an effect that may contribute to the peripheral hyperinsulinemia of obesity. (+info)
Glucocorticoids and insulin promote plasminogen activator inhibitor 1 production by human adipose tissue.
(31/7446)
Plasminogen activator inhibitor 1 (PAI-1) is likely to play a role in vascular disease, primarily in subjects with android obesity. It has been demonstrated that PAI-1 is overexpressed in adipose tissue from obese subjects and that visceral adipose tissue produced more PAI-1 than subcutaneous fat. In the present study, the effect of insulin and glucocorticoids, which are key mediators of adipose tissue metabolism, was examined in relation to PAI-1 synthesis by human adipose tissue explants (HAT), collagenase isolated human adipocytes (IHA), cultured human stromal cells (cSC), and differentiated adipocytes from the murine clonal cell line 3T3-F442A. A significant increase in PAI-1 antigen release (1.5-fold) from HAT was detectable after 16 h of treatment with insulin concentrations of at least 10(-8) mol/l. This was associated with a PAI-1 mRNA increase. Concomitant addition of insulin (10(-8) mol/l) to forskolin (5 x 10(-5) mol/l) reversed the decrease in PAI-1 antigen caused by forskolin alone. No effect on PAI-1 antigen was observed when insulin was incubated with IHA or cSC. 3T3 F442A cells were sensitive to insulin with a four- and twofold increase in PAI-1 antigen and mRNA levels, respectively, after 16 h of stimulation with 10(-8) mol/l. Dexamethasone (DXM) significantly enhanced PAI-1 antigen and mRNA expression by HAT (1.5- and 2.5-fold increase, respectively) at concentrations of at least 10(-8) mol/l. A higher stimulation was observed with IHA (sevenfold increase) and with the differentiated 3T3 F442 cell line. Cortisol was found to be less potent than DXM. No effect was observed when glucocorticoids were incubated with cSC. Coincubation of HAT with insulin (10(-7) mol/l) and DXM (10(-7) mol/l) led to an additive effect on PAI-1 synthesis. These results support the hypothesis that PAI-1 expression in human adipose tissue is controlled by insulin and glucocorticoids and may help to explain the increase in plasma PAI-1 levels observed in patients with android obesity. (+info)
Prevention of nonsteroidal anti-inflammatory drug-induced gastropathy: clinical and economic implications of a single-tablet formulation of diclofenac/misoprostol.
(32/7446)
Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to manage arthritis. While controlling symptoms and improving quality of life, NSAID use is associated with gastroduodenal injury and a 2%-4% annual risk for symptomatic gastroduodenal ulceration, hemorrhage, and perforation. This requires clinicians to balance the efficacy of NSAIDs against the potential risk of serious gastrointestinal events. Identification and stratification of risk can help guide the optimal approach for arthritis management of individual patients or large populations such as managed care organizations. NSAID-induced gastroenteropathy carries considerable economic consequences; 46% of arthritis costs are related to managing serious adverse events. It is reasonable to assume that these costs may not be incurred if high-risk patients are recognized and optimally managed. Newer therapies with proven safety margins present an attractive option, especially for patients at higher risk. The single-tablet formulations of diclofenac and misoprostol (Arthrotec) offer an alternative in managing NSAID patients because of their inherent safety profile. Studies with diclofenac/misoprostol indicate its effectiveness in treating signs and symptoms of arthritis and in reducing the incidence of NSAID-induced gastroenteropathy. As such, this agent may provide improved medical and economic outcomes. This review discusses the clinical aspects of NSAID-induced gastroenteropathy, including available preventive therapies. Approaches to assessing patients' risk for developing complications, and the relationship of medical risk and economic outcomes, are also examined. Although not all patients require preventive therapy, patients with heightened risk may benefit clinically and economically from gastroprotective NSAIDs. Additional research or modeling may provide further insight into the economic implications of managing and preventing NSAID-induced gastroenteropathy. (+info)