Search PubMed⌕ Search

Biomedical subjects

M D Mitchell

Publications and source records attributed to M D Mitchell.

At least 109 records · Page 6Linked to original sources
PubMed1993

Actions of interleukin-4 on prostaglandin biosynthesis at the chorion-decidual interface.

OBJECTIVE: We determined the effects of interleukin-4 on chorion and decidual prostaglandin production. STUDY DESIGN: Chorion and decidual cells from term placentas were grown to confluence. Cells were then incubated with interleukin-4 either alone or with other known stimulants of prostaglandin production: interleukin-1 beta, epidermal growth factor, ionomycin, or phorbol 12-myristate 13-acetate. Prostaglandin E2 production was determined with a specific radioimmunoassay. RESULTS: Interleukin-4 alone stimulated prostaglandin E2 production in chorion and decidual cells. Interleukin-4 significantly enhanced the stimulatory actions of phorbol 12-myristate 13-acetate, ionomycin, and epidermal growth factor but not interleukin-1 beta on prostaglandin E2 production. CONCLUSION: Interleukin-4 stimulates prostaglandin E2 production by chorion and decidual cells. These data suggest that interleukin-4 production by immune effector cells in gestational tissues may contribute to the pathophysiologic features of preterm labor.

Cells, Cultured↗
PubMed1993

5-Hydroxyeicosatetraenoic acid biosynthesis by gestational tissues: effects of inflammatory cytokines.

OBJECTIVE: Our purpose was to determine whether inflammatory cytokines can modulate the production of arachidonate lipoxygenase metabolites by gestational tissues. STUDY DESIGN: Primary cultures of amnion, chorion, and decidual cells were incubated in the presence and absence of interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-6. Supernatants were assayed for leukotriene B4, leukotriene C4, 5-, 12- and 15-hydroxyeicosatetraenoic acid by means of specific radioimmunoassays. Cellular proteins were determined. RESULTS: 5-Hydroxyeicosatetraenoic acid production was significantly increased by interleukin-1 beta and interleukin-6 treatment in amnion, chorion, and decidual cells. Tumor necrosis factor-alpha elicited a modest increase, which was not statistically significant, in mean 5-hydroxyeicosatetraenoic acid production by these cells. Production rates of leukotrienes B4 and C4 and 12 and 15-hydroxyeicosatetraenoic acid were not affected by treatment with interleukin-1 beta. CONCLUSIONS: Inflammatory cytokines generated in response to intrauterine infection may modulate uterine activity by stimulation of 5-hydroxyeicosatetraenoic acid biosynthesis.

Amnion↗
PubMed1993

The relationship between spontaneous rupture of membranes, labor, and microbial invasion of the amniotic cavity and amniotic fluid concentrations of prostaglandins and thromboxane B2 in term pregnancy.

OBJECTIVE: The purpose of this study was to examine the relationship between rupture of membranes, labor, and microbial invasion of the amniotic cavity and amniotic fluid concentrations of eicosanoids in patients with spontaneous rupture of membranes at term. STUDY DESIGN: Amniotic fluid was retrieved by transabdominal amniocentesis from patients with rupture of membranes and patients with intact membranes at term. Studies to determine the microbial state of the amniotic cavity included culture for bacteria and mycoplasmas, Gram stain, amniotic fluid white blood cell count, and Limulus amebocyte lysate. Eicosanoids (prostaglandin E2, prostaglandin F2 alpha and its stable metabolite, 6-keto-prostaglandin F1 alpha, and thromboxane B2) were determined with sensitive and specific radioimmunoassays validated for human amniotic fluid. Statistical inference was conducted with analysis of variance and linear contrast. RESULTS: (1) Spontaneous rupture of membranes at term was associated with a significant increase in amniotic fluid concentrations of all eicosanoids measured in this study except 6-keto-prostaglandin F1 alpha. (2) Early labor in patients with rupture of membranes was associated with a significant increase in the amniotic fluid concentration of all eicosanoids. (3) A significant increase in amniotic fluid eicosanoids in women with microbial invasion of the amniotic cavity could not be documented. CONCLUSIONS: Whereas preterm labor in the absence of microbial invasion of the amniotic cavity is not associated with a significant increase in amniotic fluid concentrations of prostaglandins, a clear increase was documented in women with early labor after spontaneous rupture of membranes. These observations suggest that there are fundamental differences in the biochemistry of term and preterm parturition.

Amnion↗
PubMed1993

Actions of interleukin-2 on chorio-decidual prostaglandin biosynthesis.

The onset of preterm labor requires increased intrauterine prostaglandin production. Intrauterine infections are frequently associated with preterm labor and increased cytokine production. The cytokine interleukin-2 (IL-2) is a potent T-cell growth factor necessary for effective cell-mediated immunity. In this study we evaluated the effect IL-2 has on prostaglandin E2 (PGE2) biosynthesis by human chorion and decidual cells. IL-2 alone significantly stimulated decidual and chorion PGE2 production. IL-2 enhanced the stimulatory actions of interleukin-1 (IL-1), epidermal growth factor (EGF), ionomycin, and phorbol 12-myristate 13-acetate (PMA) on PGE2 production by decidual cells. Similarly, IL-2 enhanced the stimulatory actions of EGF and PMA, but not IL-1 or ionomycin, on PGE2 production by chorion cells. These data suggest that IL-2 could potentially participate in the mechanisms of preterm labor in association with intrauterine infection.

Cells, Cultured↗
PubMed1993

Tumor necrosis factor alpha stimulates amnion prostaglandin biosynthesis primarily via an action on fatty acid cyclooxygenase.

The purpose of this study was to determine how tumor necrosis factor alpha (TNF alpha) stimulates prostaglandin E2 production in human amnion. Amnion cells were isolated from term placentae and grown to confluence in culture. Incubations were conducted in quadruplicate wells for 16 hours with TNF alpha and protein synthesis inhibitors cycloheximide and actinomycin D, or arachidonic acid, acetylsalicylic acid (ASA), or staurosporine or H7 which inhibit protein kinase C activity. Prostaglandin E2 (PGE2) was measured by radioimmunoassay and cellular protein determined. The stimulatory action of TNF alpha on amnion PGE2 production was blocked by protein synthesis inhibitors, and the addition of arachidonic acid always enhanced the stimulatory properties of TNF alpha. TNF alpha consistently induced more rapid recovery from ASA treatment, and protein kinase C inhibition attenuated the stimulatory effects of TNF alpha. These results suggest that the stimulatory action of TNF alpha on amnion PGE2 production is likely at the level of induction of fatty acid cyclooxygenase activity and is partially dependent upon activation of protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Actions of interleukin-2 on amnion prostaglandin biosynthesis.

Preterm labor is associated with increased intrauterine prostaglandin (PG) production. Intrauterine infections are frequently associated with preterm labor and increased cytokine production. The cytokine interleukin-2 (IL-2) is a potent T-cell growth factor necessary for effective cell-mediated immunity. In this study we evaluated the effects of IL-2 on PGE2 biosynthesis by human amnion cells. IL-2 alone modestly but significantly inhibited amnion PGE2 production. Moreover, IL-2 also attenuated, in a concentration-related fashion, the stimulatory actions of IL-1 beta on PGE2 production by amnion cells. These data suggest that IL-2 could potentially represent a negative regulatory element in the mechanisms of preterm labor in association with intrauterine infection.

Amnion↗
PubMed1993

A murine model of preterm labor: inflammatory mediators regulate the production of prostaglandin E2 and interleukin-6 by murine decidua.

Inflammatory processes may be important in the initiation and propagation of uterine contractions and preterm labor in human pregnancies. Recently, a murine model of preterm labor has been described. The purpose of our study was to determine whether murine decidua responds to inflammatory mediators, such as lipopolysaccharide (LPS) and the inflammatory cytokines interleukin (IL)-1 beta and tumor necrosis factor (TNF). Allogeneic pregnant mice (C3H/Hen females mated with C57/B6 males) were killed at 12-14 days of pregnancy, decidual tissue was isolated, and explants were placed on the polycarbonate membrane of Costar Transwell inserts. Initial validation studies of this explant system, including biochemical and histologic evaluations, indicated that the decidual tissue remained intact, viable, and responsive to IL-1 beta for at least 5 days in explant culture. Treatment of murine decidual explants with LPS, IL-1 beta, and TNF resulted in significant increases in the production of prostaglandin E2 (PGE2) and IL-6. Thus the regulation of PGE2 and IL-6 production from murine decidua by LPS and inflammatory cytokines is similar to findings previously reported for human decidua. Our findings are consistent with the view that the pathophysiology of infection-induced preterm labor in the mouse may be similar to that in human pregnancy and supports the continued development of murine models of preterm labor.

Animals↗
PubMed1993

Pulmonary hypertensive response to rabbit blood components in goats: role of thromboxane.

Transfusion of small quantities of heterologous blood may cause severe pulmonary hypertensive response in certain species. To determine the responsible component in the donor blood and the main mediator, we studied the responses of goats to small quantities of rabbit blood components and observed the effects of several pharmacologic agents on these responses. In anesthetized goats, a bolus injection of 0.004 ml/kg rabbit blood caused the pulmonary arterial pressure to increase from 25.3 +/- 2.8 to 57.1 +/- 11.6 cm H2O within 45 to 90 s, and the aortic thromboxane concentration rose from 44 +/- 38 to 238 +/- 104 pg/ml. Pulmonary vascular resistance increased more than 4-fold, whereas systemic vascular resistance increased moderately (50%). The erythrocyte stroma, mainly cell membranes, caused similar responses; other blood components were all ineffective. By blocking the production of thromboxane, indomethacin and U63557A (thromboxane synthetase inhibitor) abolished nearly all of the hemodynamic responses to rabbit blood. Isoproterenol also largely attenuated the responses to rabbit blood by blocking thromboxane production without interfering with the responses to the thromboxane mimic U46619. Nitrendipine (calcium-channel blocker) equally attenuated rabbit blood and U46619-induced hemodynamic responses but did not block thromboxane production. Chlorpheniramine (H1-receptor antagonist) partially blocked the hemodynamic responses to rabbit blood without affecting thromboxane production or U46619-induced responses. We conclude that the erythrocyte membrane is the responsible component in the donor blood and thromboxane is the predominant mediator. The main action of isoproterenol is to reduce thromboxane production and histamine participates by possible interaction with cyclooxygenase products.

Animals↗
PubMed1993

Interleukin-1 beta (IL-1 beta) modulates prostaglandin production and the natural IL-1 receptor antagonist inhibits ovulation in the optimally stimulated rat ovarian perfusion model.

The rat ovarian perfusion model with bursa removed and intact was used to further characterize the effects of interleukin-1 beta (IL-1 beta) and the natural IL-1 receptor anatagonist (IRAP) on ovulation, steroidogenesis, and prostaglandin production. Twenty-six- to 27-day-old female Sprague-Dawley rats were injected sc with 25 IU PMSG, and 48 h later, the right ovary was dissected (with bursa removed and intact for various experiments) and placed in the perfusion chamber. Ovaries were exposed to various doses of IL-1 beta alone, IL-1 beta with LH, and IL-1 beta with LH and isobutylmethylxanthine (IBMX). The natural IL-1 receptor antagonist was also added to the chambers with LH and IBMX. IL-1 beta at 0.8 (n = 3) and 8.0 (n = 4) nM did not induce LH-independent ovulation in PMSG-stimulated ovaries with bursa removed. In bursa-intact perfusions (n = 3), one ovulation was produced in each compared to control ovaries with bursa intact (n = 3) given an ovulatory trigger of LH alone [2.3 +/- 0.6 (+/- SD) ovulations; P < 0.02]. IL-1 beta enhanced, in a dose- and gonadotropin-dependent fashion, the production of prostaglandin E2 (PGE2) in PMSG-stimulated ovaries with bursa removed given an ovulatory trigger of LH and IBMX compared to that in controls. PGF2 alpha and 6-keto-PGF1 alpha were also modulated by IL-1 beta. Estradiol and progesterone production were not affected. The natural IRAP inhibited ovulation (7.8 +/- 3.9 ovulations vs. 12.4 +/- 1.5; P < 0.04) in PMSG-stimulated ovaries given LH and IBMX as the ovulatory trigger compared to that in controls. This inhibition of ovulation was not associated with reduced steroid or PG levels. IL-1 beta appears to play a potentially significant role in the process of ovulation. The functional importance of the bursa in this model is highlighted in this study. IL-1 beta modulates PG, but not steroid, production. IRAP inhibited ovulation without significantly affecting PG or steroid production.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Inflammatory mediators regulate interleukin-8 production by cultured gestational tissues: evidence for a cytokine network at the chorio-decidual interface.

The physiology of parturition, and the pathophysiology of preterm labor, is incompletely understood. Infection of gestational tissues may account for a significant proportion of women who experience preterm labor. Interleukin-8 (IL-8), or neutrophil-activating protein (NAP-1), is a potent chemotactic and activating factor for neutrophils and has been implicated in the pathogenesis of inflammatory injury to skin and lung, but has yet to be described in gestational tissues. Cultured chorion and decidual cells obtained from normal human pregnancies were used to evaluate whether these tissues produce IL-8 basally and in response to inflammatory cytokines. As measured by specific IL-8 RIA, chorion and decidual cells produce IL-8 constitutively and in response to IL-1 beta and tumor necrosis factor. Cotreatment of chorion cells or decidual cells with IL-1 beta and actinomycin D or cycloheximide abrogated IL-8 production. Northern blot analysis confirmed that IL-1 beta stimulation of chorion and decidual cells resulted in increased IL-8 messenger RNA expression. Our data support the concept that a complex cytokine network between maternal and fetal gestational tissues exists, and that activation of inflammatory cytokine production in these tissues, including IL-8, likely contributes to the pathophysiology of infection-induced preterm labor.

Blotting, Northern↗
PubMed1993

Potential agonist action of the interleukin-1 receptor antagonist protein: implications for treatment of women.

The interleukin-1 receptor antagonist protein (IRAP) caused a concentration-related increase in prostaglandin production by human decidual cells. The degree and time course of this stimulatory action were identical to those induced by interleukin 1 beta (IL-1 beta). IRAP had no inhibitory action on IL-1 beta stimulation of decidual prostaglandin production and at high concentrations had an additive effect. We believe that this represents the first description of a potential agonist action of IRAP and suggests caution in treatment of women with this substance.

Cells, Cultured↗
PubMed1992

Amnion cell biosynthesis of interleukin-8: regulation by inflammatory cytokines.

The cellular constituents of the placenta are important participants in the recruitment and trafficking of inflammatory cells within the placenta. In infection-induced labor, gestational tissues synthesize and release a variety of inflammatory cytokines whose effects include increased prostaglandin biosynthesis and the initiation of uterine contractions. Interleukin-8 (IL-8), a potent neutrophil chemoattractant, has been recently described as being elevated in the amniotic fluid of mothers with chorioamnionitis. We investigated the biosynthesis of IL-8 by human amnion cells and its regulation by other inflammatory cytokines. Cultured amnion cells obtained from normal term placentae were found to produce IL-8 in response to pathophysiologic concentrations of interleukin 1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha). Treatment of amnion cells stimulated by IL-1 beta with cycloheximide resulted in increased IL-8 production, while incubation of IL-1 beta treated amnion cells with actinomycin D resulted in a concentration-dependent decrease in detectable amounts of IL-8. Northern blot analysis of cultured amnion cells stimulated with IL-1 beta demonstrated a rapid increase in IL-8 mRNA which peaked at 2-4 hr. These in vitro results suggest inflammation of gestational tissues in vivo may result in locally produced IL-8 and, in association with other inflammatory mediators, may be important in the pathophysiology of infection-induced labor.

Amnion↗
PubMed1992

A human endometrial explant system: validation and potential applications.

OBJECTIVE: Our objective was to describe an in vitro explant system to study the regulation of prostaglandin production by human endometrium. STUDY DESIGN: Segments of late-luteal-phase endometrium were obtained aseptically at the time of endometrial sampling. The endometrium was cut into 1 mm3 pieces and applied to the polycarbonate membrane of tissue-culture-well inserts for 12-well plates (Costar Transwell cell culture chamber inserts, 0.4 microns pore size). After placing the well inserts, culture medium was carefully applied. The explants were incubated at 37 degrees C in 5% carbon dioxide in air, and the culture medium was changed daily. RESULTS: Electron microscopic examination and lactate dehydrogenase determinations of the explants revealed cellular viability for < or = 5 days of culture. Endometrial explants responded to treatment with interleukin-1 beta and tumor necrosis factor by a concentration-dependent increase in the production of prostaglandin E2. Costimulation of late luteal endometrial explants with interleukin-1 beta (10 ng/ml) and progesterone (10(-6) mol/L) resulted in variable production of prostaglandin E2, suggesting that the histologic examination of the endometrium does not necessarily reflect the functional properties of the endometrium. CONCLUSIONS: Our data show that when used with human endometrial tissue this explant system maintains tissue viability and responsiveness for < or = 5 days. This approach to explant methods is simple and provides a flexible model to study the regulation of the production of bioactive substances by human endometrial tissue.

Culture Techniques↗
PubMed1992

Endothelin-1,2 levels are increased in the amniotic fluid of women with preterm labor and microbial invasion of the amniotic cavity.

The purpose of this study was to determine the effect of gestational age, labor, and microbial invasion of the amniotic cavity on amniotic fluid concentrations of endothelin-1,2. Amniotic fluid was retrieved by amniocentesis from 148 women: patients at term with and without labor, patients with preterm labor with and without intraamniotic infection, and women in the second trimester of pregnancy. Endothelin-1,2 was measured by a sensitive and specific radioimmunoassay. Immunoreactive endothelin-1,2 was detectable in all samples of human amniotic fluid. Advancing gestational age and spontaneous term labor did not result in changes in amniotic fluid concentrations of endothelin-1,2. Women with preterm labor and positive amniotic fluid cultures for microorganisms had higher amniotic fluid concentrations of endothelin-1,2 than did those without microbial invasion of the amniotic cavity (p less than 0.05). These results support a role for endothelins in the mechanisms responsible for preterm delivery associated with intraamniotic infection.

Adult↗
PubMed1992

Circadian rhythm in prostacyclin activity in gastric tissue of the fasting rat.

Gastroduodenal ulcer disease may result from the desynchronization of the circadian rhythms of gastric protective and destructive factors. The purpose of this study was to evaluate whether gastric tissue 6-keto prostaglandin F1 alpha (PGF1 alpha), a catabolic derivative of the putative protective factor prostacyclin, is produced in a circadian fashion in the rat model. Forty-eight male Sprague-Dawley rats were acclimatized in sound-attenuated, lightproof chambers for 3 weeks on a 12:12 hour light/dark entrainment schedule. After an 18-hour fast, six rats were killed at each of eight sampling times. The stomachs were exposed, removed, and assayed for total 6-keto PGF1 alpha content by radioimmunoassay. Cosinor analysis of the data showed significant (p = 0.0262) circadian rhythmicity in 6-keto PGF1 alpha content with an acrophase (peak time) value of 0503 HALO (hours after lights on) or in the middle of the lights-on inactive period for the rats. Hypothetically, the circadian rhythm in some gastric protective factors may render the gastric mucosa vulnerable to injury in a circadian fashion.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Sera from preeclamptic patients contain factor(s) that stimulate prostacyclin production by human endothelial cells.

A relative decrease in endothelial cell prostacyclin production may be pivotal in the genesis of preeclampsia. We determined the effect of sera from preeclamptic women on prostacyclin production by monolayers of normal term human umbilical vein endothelial cells. Endothelial cells were incubated with media containing serum from patients with preeclampsia, non-hypertensive, gestational age-matched pregnant controls, or normal non-pregnant controls (N = 7, all groups). 6-Keto-prostaglandin F1 alpha, the stable metabolite of prostacyclin, was measured directly in the culture medium by radioimmunoassay. Treatment with preeclamptic sera, when associated with a statistically significant increase in prostacyclin metabolite production by endothelial cells. Thus, sera from women with preeclampsia stimulate rather than inhibit prostacyclin production by endothelial cells. We speculate that there is a factor in the sera of women with preeclampsia that functions to activate endothelial cells or which may play a role in the homeostatic mechanisms to balance reduced prostacyclin output in preeclampsia.

6-Ketoprostaglandin F1 alpha↗