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Biomedical subjects

M D Mitchell

Publications and source records attributed to M D Mitchell.

At least 199 records · Page 11Linked to original sources
PubMed1988

Secretion of progesterone and prostaglandins by cells of bovine corpora lutea from three stages of the luteal phase.

The secretion of prostaglandins (PGs) by bovine corpora lutea was investigated. Corpora lutea from the early, early-mid and late-mid stages of the luteal phase were dissociated by collagenase treatment and cultured in monolayer in Dulbecco's modified Eagle's medium containing 10% (v/v) fetal calf serum. Treatment with either LH (100 ng/ml) or dibutyryl cyclic AMP (dbcAMP; 1 mmol/l) had no effect on progesterone secretion by early luteal phase cells but stimulated progesterone secretion two- to fourfold by cells from the latter stages. The secretion rates, per microgram cell protein, of 6-keto-PGF1 alpha, PGE2 and PGF2 alpha were substantially greater in cells from the early luteal phase than in those from the latter stages, however, all changes in PG secretion in response to treatments were qualitatively similar between cells from the three stages of the luteal phase. The secretion rate of 6-keto-PGF1 alpha was greater than that of PGE2 or PGF2 alpha and was inhibited by treatment with indomethacin (28 mumol/l) but unaltered by treatment with LH, dbcAMP or butyrate (1 mmol/l). Secretion of PGE2 was inhibited by indomethacin but stimulated two- to threefold by treatment with either dbcAMP or butyrate. Secretion of PGF2 alpha was minimal and not inhibited further by treatment with indomethacin, but was stimulated 10- to 40-fold with dbcAMP. Indomethacin treatment inhibited the stimulatory effect of dbcAMP; butyrate had no effect on PGF2 alpha secretion. Treatment with LH had no effect on any of the PGs measured. In these experiments the secretion of progesterone appeared unrelated to any changes in the secretion of PGs.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Arachidonic acid metabolism in human trabecular meshwork cells.

Prostaglandins and other eicosanoids in the trabecular meshwork may play important physiological and pharmacological roles in the aqueous outflow pathway. In the present studies, we employed [14C]-arachidonic acid to explore potentially important pathways for the production of eicosanoids in cultured human trabecular meshwork cells (HTM). In these cells, we demonstrated that prostaglandin E2 (PGE2) and PGF2 alpha are major cyclooxygenase products, with some 6-keto-PGF1 alpha also detected. The amount of radiolabelled PGE2 formed was substantially higher than the PGF2 alpha formed in the early time periods. The amount of PGF2 alpha in the culture media increased at a time when the amount of PGE2 was declining, suggesting a possible metabolic conversion between the prostaglandins. HTM produced a range of products of the lipoxygenase pathway. Products co-eluting with 5, 12, and 15-hydroxyeicosatetraenoic acids (HETEs) were detected, with 12 and 15-HETEs predominating. A large amount of radiolabelled product was detected also in peaks co-eluting with leukotriene B4 (LTB4) and an LTB4 degradation product. Biosynthesis of lipoxygenase products was markedly inhibited by BW 755c and partially inhibited by dexamethasone. These data emphasize that HTM cells are capable of converting arachidonic acid into a wider variety of biologically active products than previously recognized.

Arachidonic Acid↗
PubMed1988

Endotoxin stimulates prostaglandin E2 production by human amnion.

The studies presented in this report were designed to evaluate whether bacterial endotoxin alters the rate of biosynthesis of prostaglandin E2 (PGE2) by human amnion. Amnion cells were established in primary monolayer culture from women undergoing elective cesarean sections. Endotoxin from Escherichia coli and Salmonella typhosa were incubated with amnion cells for 16 hours, and radioimmunoassay was used to measure PGE2 released into the media. Bacterial endotoxin demonstrated a concentration-dependent stimulatory effect on the rate of PGE2 synthesis by amnion cells. These observations suggest a mechanism for the onset of labor associated with intra-amniotic infection.

Amnion↗
PubMed1987

Amniotic fluid prostaglandin D2 in spontaneous and augmented labor.

Prostaglandin D2 (PGD2) was quantified in human amniotic fluid obtained from women in various phases of the first stage of spontaneous labor, augmented labor, and induced labor. PGD2 increased significantly only in late labor in the spontaneous and augmented labor groups.

Amniotic Fluid↗
PubMed1987

Epidermal growth factor actions on arachidonic acid metabolism in human amnion cells.

Epidermal growth factor (EGF) from human and murine sources increased prostaglandin E2 production by human amnion cells. An anti-EGF receptor monoclonal antibody abolished this stimulatory action of EGF and reduced the basal rate of amnion prostaglandin E2 biosynthesis. The rates of formation of arachidonate lipoxygenase products were also enhanced by EGF.

Amnion↗
PubMed1987

A product from human decidua inhibits prostaglandin production by human amnion.

Human decidua was obtained from nonlaboring women after elective cesarean section. Decidua was incubated with media alone for 20 hours and this media (decidual conditioned media) was then incubated with amnion cells in monolayer culture and amnion rings. A 90% decrease in PGE2 production by amnion cells in monolayer culture was demonstrated in the presence of decidual conditioned media when compared to controls. In short term incubations with fresh amnion, decidual conditioned media decreased the production of PGE2 in amnion by greater than 25% of the control rate of production in 17 of 21 experiments. These observations suggest that human decidua produces a factor capable of inhibiting prostaglandin production by amnion.

Amnion↗
PubMed1987

Arachidonic acid metabolism by lipoxygenase pathways in uterine and intrauterine tissues of pregnant sheep.

The formation of arachidonate lipoxygenase products by uterine and intrauterine tissues of sheep in the last third of gestation has been evaluated. Maternal and fetal cotyledon, myometrium and fetal membrane exhibited evidence of arachidonate 5-, 12-, and 15- lipoxygenase activities. The major lipoxygenase product formed by fetal membrane and fetal cotyledon was leukotriene B4 (LTB4) whereas maternal cotyledon and myometrium produced mainly 12-hydroxyeicosatetraenoic acid (12-HETE). Arachidonate lipoxygenase products may play significant roles in the regulation of fetal and uteroplacental hemodynamics and it is speculated that the formation of leukotriene B4 predominantly by tissues of fetal origin may be of significance in the immunologic adaptations of pregnancy.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Arachidonic acid metabolism by lipoxygenase pathways in intrauterine tissues of women at term of pregnancy.

Intrauterine tissues from women at term of pregnancy metabolized arachidonic acid by way of lipoxygenase pathways that included 5-, 12-, and 15- lipoxygenases. The major lipoxygenase product formed by amnion obtained before labor was leukotriene B4 and after labor was 12- hydroxyeicosatetraenoic acid (12-HETE). Chorion laeve and decidua vera synthesized predominantly 15-HETE at all times and placenta produced mainly 12-HETE. Trends existed for increased prostaglandin formation with labor by amnion, chorion laeve and decidua vera and for increased lipoxygenase product formation by chorion laeve, decidua vera and placenta. It is suggested that products of arachidonic acid metabolism by way of lipoxygenase and cyclooxygenase pathways play significant roles in the control of fetal and uteroplacental hemodynamics and the mechanism(s) of parturition.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Epidermal growth factor-stimulated prostaglandin E2 production in human amnion cells: specificity and nonesterified arachidonic acid dependency.

The production of prostaglandin E2 (PGE2) by human amnion cells in primary monolayer culture was stimulated 2- to 150-fold by mouse epidermal growth factor (mEGF). The effect of mEGF on amnion cell PGE2 production was dependent on the time of treatment and the concentration of mEGF used. The rate of PGE2 production by these cells was maximal between 2 and 4 h of treatment with mEGF; thereafter, the rate of production of PGE2 declined. The stimulation of PGE2 production was maximal at concentrations of mEGF of greater than 5 ng/ml. A number of other growth factors, steroid and protein hormones, and various other test agents were ineffective or only minimally in stimulating PGE2 production by amnion cells. The stimulatory effect of mEGF on PGE2 production in these cells was dependent on the presence of serum in the culture medium; alternatively, mEGF was effective in stimulating PGE2 production by amnion cells in serum-free medium that was supplemented with arachidonic acid bound to albumin. Thus, we conclude that the marked stimulation of PGE2 production by amnion cells treated with mEGF is not due to an action of mEGF to stimulate the release of arachidonic acid from cellular glycerophospholipid storage forms; rather, these data are supportive of the conclusion that mEGF-stimulated PGE2 production is dependent on the presence of nonesterified, i.e., free, arachidonic acid in the medium.

Amnion↗
PubMed1987

Arachidonate lipoxygenase metabolites in amniotic fluid of women with intra-amniotic infection and preterm labor.

This study was undertaken to examine the effects of intrauterine infection and preterm labor on the amniotic fluid concentrations of arachidonate lipoxygenase metabolites in women with premature rupture of membranes. Amniotic fluid was obtained from four groups of women with premature rupture of membranes: group 1, women without labor or infection; group 2, women with labor but without infection; group 3, women with intra-amniotic infection but without labor; and group 4, women with both infection and labor. 12-Hydroxyeicosatetraenoic acid, 15-hydroxyeicosatetraenoic acid, and leukotriene B4 were measured by radioimmunoassays. Amniotic fluid concentrations of 12-hydroxyeicosatetraenoic acid were found not to differ significantly among the four groups. Amniotic fluid concentrations of 15-hydroxyeicosatetraenoic acid in group 4 were significantly higher than in women in groups 1 and 3 (p less than 0.05). In addition, amniotic fluid concentrations in leukotriene B4 were significantly higher in group 4 than in any of the other three groups (p less than 0.05). Leukotriene B4 concentrations were higher in groups 2 and 3 than in group 1, suggesting that the presence of both labor and infection increases the concentration of this metabolite in amniotic fluid. Infection and labor had an additive effect in the elevation of amniotic fluid concentrations of leukotriene B4. These results suggest that the amniotic fluid concentrations of arachidonate lipoxygenase metabolites are affected differently by the presence of infection and labor in women with premature rupture of membranes.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Prostaglandin concentrations in amniotic fluid of women with intra-amniotic infection and preterm labor.

This study was undertaken to examine the effects of intrauterine infection and preterm labor on the amniotic fluid concentrations of prostaglandins in women with premature rupture of the membranes. Amniotic fluid was obtained from four groups of patients with premature rupture of the membranes: group 1, patients without labor or infection; group 2, patients with labor but without infection; group 3, patients with an intra-amniotic infection but without labor; group 4, patients with both infection and labor. Prostaglandins E2 and F2a were measured by radioimmunoassays. Preterm labor, in the absence of infection, was not associated with significant increases in amniotic fluid concentrations of prostaglandins. Women with preterm labor and intra-amniotic infections had higher amniotic fluid concentrations of prostaglandins than women with preterm labor in the absence of infection or women with intra-amniotic infection in the absence of labor. These observations are compatible with the participation of prostaglandins in the mechanisms of onset of preterm labor associated with intra-amniotic infection.

Adult↗
PubMed1987

Stimulation of prostaglandin E production in superfused human amnion by human amniotic fluid.

We studied the effects of human amniotic fluid (HAF) on the production of prostaglandin E (PGE) by amnion tissues using a technique of fresh-tissue superfusion. The production of PGE was linear with time for 4.5 h by amnion tissues superfused either with medium alone or with medium plus HAF (30% v/v). Tissues superfused with medium plus HAF produced significantly more PGE than tissues superfused with medium alone. Additionally, amnion tissue obtained at cesarean section, prior to labor, displayed a greater responsiveness to HAF than did amnion obtained after spontaneous labor.

Amnion↗
PubMed1987

Increased concentrations of arachidonic acid lipoxygenase metabolites in amniotic fluid during parturition.

This study was undertaken to examine whether spontaneous labor at term is associated with changes in the amniotic fluid concentrations of arachidonate lipoxygenase metabolites. Amniotic fluid was obtained from 15 women at term in active labor (with cervical dilatation of at least 6 cm) and from 15 nonlaboring control women matched for maternal age, parity, and gestational age. Cultures of amniotic fluid for bacteria and mycoplasma were negative. Products of arachidonate lipoxygenase metabolism--12-hydroxyeicosatetraenoic acid (12-HETE), 15-hydroxyeicosatetraenoic acid (15-HETE), and leukotriene B4--were measured by radioimmunoassay. The median concentrations of 12-HETE, 15-HETE, and leukotriene B4 in the amniotic fluid of nonlaboring women were 11.50 ng/mL, 0.45 ng/mL, and 21 pg/mL, respectively, and in the amniotic fluid of laboring women, 24.63 ng/mL, 4.34 ng/mL, and 96 pg/mL, respectively. The differences between labor and nonlabor amniotic fluid concentrations of all three lipoxygenase products were significant (P less than .05, Wilcoxon test). These observations are consistent with involvement of products of the lipoxygenase pathway of arachidonic acid metabolism in the mechanism of human parturition.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

Effect of fetal and maternal intravascular antipyrine infusion on maternal plasma prostaglandin concentrations in the pregnant sheep at 104 to 127 days' gestation.

Antipyrine is commonly used to measure umbilical and uterine blood flow in the pregnant sheep. In the present experiment we investigated the effect of antipyrine on prostaglandin metabolism. Four pregnant ewes at 104 to 127 days' gestation were infused with either 1, 4, or 15 mg of antipyrine per minute via the fetal jugular vein. The 15 mg X min-1 dose was also infused into the maternal jugular vein in a fourth experiment. Prostaglandins in the uterine vein draining the pregnant horn were measured by radioimmunoassay and antipyrine by high-performance liquid chromatography. No change in the concentrations of either 13,14-dihydro-15-keto-prostaglandin F2 alpha or 6-keto-prostaglandin F1 alpha was observed with infusion of antipyrine at 1 mg X min-1. The 4 and 15 mg X min-1 infusion rates into the fetal jugular vein induced a significant decrease (p less than 0.05) in maternal uterine vein 13,14-dihydro-15-keto-prostaglandin F2 alpha plasma concentrations. These concentrations decreased from 669.3 +/- 161.3 pg X ml-1 (mean +/- SD) before infusion to 306.5 +/- 104.0 pg X ml-1 after 3 hours of infusion at 4 mg X min-1 and from 744.2 +/- 256.8 to 105.0 +/- 24.2 pg X ml-1 at 15 mg X min-1. Significant changes in maternal uterine vein plasma 6-keto-prostaglandin F1 alpha and the 6-keto-prostaglandin F1 alpha/13,14-dihydro-15-keto-prostaglandin F1 alpha ratio occurred only at the 15 mg X min-1 infusion of antipyrine into the fetal jugular vein (p less than 0.05). Maternal uterine vein 6-keto-prostaglandin F1 alpha fell from 86.0 +/- 31.6 to 37.0 +/- 11.5 pg X ml-1 and the 6-keto-prostaglandin F1 alpha/13,14-dihydro-15-keto-prostaglandin F2 alpha ratio rose from 0.14 +/- 0.10 to 0.35 +/- 0.10. We conclude that: antipyrine at doses currently used to measure uterine and umbilical blood flows inhibits 13,14-dihydro-15-keto-prostaglandin F2 alpha production and infusion rates of antipyrine less than 1 mg X min-1 probably do not affect maternal prostaglandin metabolism. We therefore recommend that if this method is to be used for measuring blood flow, antipyrine infusion rates should be less than 1 mg X min-1.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Response of human amnion cells in culture to 1,25-dihydroxycholecalciferol: increased 25-hydroxycholecalciferol 24-hydroxylase activity and prostaglandin E2 formation.

We investigated the possibility that 1,25-dihydroxycholecalciferol acts in human amnion as a physiologic calcium ionophore to effect increased prostaglandin E2 production in this tissue. This possibility was based on the propositions that this metabolite of vitamin D3 acts in other target tissues, that is, bone, intestine, chorioallantoic membrane, kidney, and intestine, to effect increased calcium absorption, that 1,25-dihydroxycholecalciferol is present in amniotic fluid, which bathes the amnion, and that the mobilization of calcium in amnion is associated with stimulation of enzymes, namely, phospholipase A2 and phosphatidylinositol-specific phospholipase C that act ultimately to effect the release of arachidonic acid, which in turn leads to increased prostaglandin E2 production. We found that human amnion cells, maintained in primary monolayer culture, are responsive to 1,25-dihydroxycholecalciferol. Treatment of these cells with 1,25-dihydroxycholecalciferol for 18 hours brought about the induction, in a dose-dependent manner, of 25-hydroxycholecalciferol 24-hydroxylase, a marker of 1,25-dihydroxycholecalciferol action. In addition, treatment of human amnion cells in monolayer culture with 1,25-dihydroxycholecalciferol caused, within 12 hours, a significant increase in the synthesis of prostaglandin E2, which was maintained for the duration of treatment, that is, 48 hours. These findings may be indicative of a significant physiologic role for 1,25-dihydroxycholecalciferol in metabolic processes that are important in amnion, including transport, amniotic fluid volume homeostasis, and the initiation of parturition.

Amnion↗