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Biomedical subjects

M D Mitchell

Publications and source records attributed to M D Mitchell.

At least 163 records · Page 9Linked to original sources
PubMed1990

Lymphokine production during term human pregnancy: differences between peripheral leukocytes and decidual cells.

Although the fetus is considered to be an "allograft" there is little information concerning the role of lymphokines in human pregnancy. Lymphokines are polypeptides secreted by stimulated lymphocytes that direct the immune response by enabling immune effector cells to communicate with each other. To characterize lymphokine production during normal human pregnancy, we isolated peripheral leukocytes and decidual lymphocyte-like cells from women undergoing repeat cesarean section at term. After stimulation with mitogen and paternal antigen for 24 hours, culture supernatants were assayed for granulocyte-macrophage colony-stimulating factor and interleukin-2 by enzyme-linked immunosorbent assay. There was no difference in the amount of interleukin-2 produced by stimulated peripheral and decidual cells. However, granulocyte-macrophage colony-stimulating factor production by stimulated decidual lymphocyte-like cells was significantly greater than granulocyte-macrophage colony-stimulating factor produced by peripheral lymphocytes. Decidual lymphocyte-like cells produced granulocyte-macrophage colony-stimulating factor both spontaneously and after stimulation with mitogen or paternal antigen, whereas peripheral leukocytes did not. This suggests that the decidua constitutes a distinct immunologic microenvironment.

Cells, Cultured↗
PubMed1990

Pathophysiology of antiphospholipid antibodies: absence of prostaglandin-mediated effects on cultured endothelium.

Antiphospholipid antibodies are associated with recurrent pregnancy loss and thrombosis. Studies suggest that antiphospholipid antibodies may inhibit the production of prostacyclin by vascular tissues. We incubated sera from women with moderate to high levels of antiphospholipid antibodies with primary human umbilical vein endothelial cell cultures. Intact confluent, subconfluent, hydrogen peroxide-damaged, and mechanically damaged endothelial cell monolayers were evaluated for the production of the prostacyclin metabolite 6-keto-prostaglandin F1 alpha in the presence of sera that were positive and negative for antiphospholipid antibodies. All sera were assayed for baseline concentrations of 6-keto-prostaglandin F1 alpha before incubation with endothelial monolayers. Additionally, the extent of binding of antiphospholipid antibodies to intact and damaged endothelium was studied by immunofluorescent techniques and enzyme-linked immunosorbent assay. Our results indicate that prostacyclin production is not impaired by sera containing antiphospholipid antibodies, regardless of the condition of the endothelium. Further, we were unable to demonstrate binding of immunoglobulin from sera containing antiphospholipid antibodies to intact or damaged endothelium. However, the baseline concentration of 6-keto-prostaglandin F1 alpha was nearly fourfold higher in sera containing antiphospholipid antibodies. The finding of elevated baseline serum concentrations of prostacyclin metabolite in patients with antiphospholipid antibodies suggests a condition of long-term stimulation or altered metabolism of prostacyclin.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Actions of endothelin-1 on prostaglandin production by gestational tissues.

Endothelin-1 (10(-11)M-10(-7)M) was incubated with human umbilical vein endothelial cells and cells derived from amnion and decidua and prostaglandin production was determined. The rates of biosynthesis of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and prostaglandin E2 (PGE2) by endothelial cells were increased significantly by treatment with endothelin-1. Amnion cell PGE2 production was reduced significantly by endothelin-1 treatment whereas decidual PGE2 and prostaglandin F2 alpha production was unaffected by this treatment. Thus, it is possible that endothelins may play a part in the regulation of uteroplacental hemodynamics and the mechanisms of parturition.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

The modulation of prostaglandin synthesis by peritoneal fluids.

Biological fluids from several sources (e.g. blood, fetal urine, amniotic fluid) have been shown to contain factors that modulate prostaglandin (PG) synthesis. In this study, we investigated the possibility that peritoneal fluid contains substances that may regulate PG synthesis. Peritoneal fluids were obtained from women undergoing diagnostic laparoscopy for infertility. Fluids from women without evident pelvic pathology were incubated with prostaglandin synthase prepared from bull seminal vesicles in the presence of excess arachidonic acid, and the production of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha was quantified by specific radioimmunoassay. The untreated fluids inhibited potently the synthesis of PGE2 but such inhibitory activity was not extractable by chloroform:methanol. An ultrafiltrate of the fluid containing molecules smaller than 10,000 Daltons stimulated PGF2 alpha synthesis but this activity was also lost after extraction. The extracted fluid did, however, stimulate the synthesis of prostacyclin (as reflected by 6-keto-PGF1 alpha).

Ascitic Fluid↗
PubMed1990

Amniotic fluid lipoxygenase metabolites during spontaneous labor and after RU486 treatment during late pregnancy in rhesus macaques.

To determine changes in amniotic fluid (AF) lipoxygenase metabolites prior to spontaneous labor and after RU486 administration, we implanted AF and vascular catheters and myometrial electromyographic (EMG) electrodes in 8 rhesus macaques at 120-130 days of pregnancy (term = 167 days). Four animals had AF samples taken serially until they delivered their infants normally at term. The other four animals received RU486 (20 mg/kg/day) for 3 days. AF samples were collected every 2-3 days and at 12 hour intervals for 72 hours before and after treatment with RU486. Uterine activity was monitored continuously. LTB4, 5-HETE and 15-HETE were measured by radioimmunoassay. In untreated animals, LTB4 and 5-HETE concentrations in AF increased significantly (P less than 0.05) 4 days before delivery with no change in 15-HETE. After RU486, mean levels of LTB4 and 5-HETE were increased although the difference was not statistically significant. No change in 15-HETE levels was observed. In conclusion, LTB4 and 5-HETE increase in AF before the onset of spontaneous labor. Progesterone receptor blockade by RU486 does not reproduce the changes in AF lipoxygenase metabolites observed during normal parturition.

Amniotic Fluid↗
PubMed1990

Uteroplacental production of eicosanoids in ovine pregnancy.

Dramatic cardiovascular alterations occur during normal ovine pregnancy which may be associated with increased prostaglandin production, especially of uteroplacental origin. To study this, we examined (Exp 1) the relationships between cardiovascular alterations, e.g., the rise in uterine blood flow and fall in systemic vascular resistance, and arterial concentrations of prostaglandin metabolites (PGEM, PGFM and 6-keto-PGF1 alpha) in nonpregnant (n = 4) and pregnant (n = 8) ewes. To determine the potential utero-placental contribution of these eicosanoids in pregnancy, we also studied (Exp 2) the relationship between uterine blood flow and the uterine venous-arterial concentration differences of PGE2, PGF2 alpha, PGFM, 6-keto-PGF1 alpha, and TxB2 in twelve additional late pregnant ewes. Pregnancy was associated with a 37-fold increase in uterine blood flow and a proportionate (27-fold) fall in uterine vascular resistance (p less than 0.01). Arterial concentrations of PGEM were similar in nonpregnant and pregnant ewes (316 +/- 19 and 245 +/- 38 pg/ml), while levels of PGFM and PGI2 metabolite 6-keto-PGF1 alpha were elevated 23-fold (31 +/- 14 to 708 +/- 244 pg/ml) and 14-fold (12 +/- 4 to 163 +/- 78 pg/ml), respectively (p less than 0.01). Higher uterine venous versus uterine arterial concentrations were observed for PGE2 (397 +/- 36 and 293 +/- 22 pg/ml) and 6-keto-PGF1 alpha (269 +/- 32 and 204 +/- 32 pg/ml), p less than 0.05, but not PGF2 alpha or TxB2. Although PGFM concentrations appeared to be greater in uterine venous (1197 +/- 225 pg/ml) as compared to uterine arterial (738 +/- 150 pg/ml) plasma, this did not reach significance (0.05 less than p less than 0.1). In normal ovine pregnancy arterial levels of PGI2 are increased, which may in part reflect increased uteroplacental production. Moreover the gravid ovine uterus also appears to produce PGE2 and metabolize PGF2 alpha.

Animals↗
PubMed1990

Prostaglandin biosynthesis by human decidual cells: effects of inflammatory mediators.

There is substantial evidence that decidual activation, in association with infection, is linked with the onset of both preterm and term labor. We therefore undertook the present study to evaluate prostaglandin production and its potential regulation by inflammatory mediators in human decidual cells in primary monolayer culture. Upon attaining confluence, the cells were incubated with endotoxin, interleukin 1 alpha (IL1 alpha), interleukin 1 beta (IL1 beta); or tumor necrosis factor (TNF). Production of prostaglandin (PG) E2 and PGF2 alpha was determined using specific radioimmunoassays. Endotoxin and these cytokines all induced significant concentration-dependent increases in PGE2 and PGF2 alpha production. Our results suggest that term human decidual cells are responsive to endotoxin and cytokines and that generation of these substances in the decidua or nearby (eg. in response to infection) will lead to increased prostaglandin production and uterine contractions.

Cells, Cultured↗
PubMed1990

A monokine stimulates prostaglandin-E2 production by human amnion.

The studies reported in this communication were designed to test the hypothesis that products of mononuclear cells are capable of stimulating prostaglandin E2 production by human amnion. Conditioned media obtained from peripheral blood mononuclear cells were incubated with amnion cells in primary culture. A dose dependent increase in PGE2 biosynthesis was observed in response to increasing amounts of the conditioned media. These observations suggest that mononuclear cells produce a factor(s) capable of stimulating prostaglandin production by amnion cells. The signal responsible for the increased biosynthesis of prostaglandins by human amnion associated with parturition in the setting of intraamniotic infection may be of host origin.

Amnion↗
PubMed1990

Immunoglobulin G fractions from patients with antiphospholipid antibodies cause fetal death in BALB/c mice: a model for autoimmune fetal loss.

We determined whether purified immunoglobulin G from patients with antiphospholipid antibodies causes fetal loss in pregnant mice. Sera were obtained from nonpregnant parous women (group 1) and nonpregnant women with antiphospholipid antibodies and a history of fetal loss (group 2). Pregnant BALB/c mice were given an intraperitoneal injection of 15 mg of IgG on day 8 of pregnancy. Typically, mice treated with IgG from antiphospholipid antibodies aborted within 48 hours. When animals were sacrificed on days 9 to 15, the uterus of each animal was inspected for the presence of live, dead, or resorbing fetuses. In contrast to mice injected with control IgG or saline solution, each mouse injected with IgG from antiphospholipid antibodies aborted and no live fetuses were found (p less than 0.05). Histologic examination of the uteroplacental interface showed decidual necrosis in the mice treated with IgG containing antiphospholipid antibodies, and immunofluorescent studies also showed prominent intravascular decidual IgG and fibrin deposition. We conclude that IgG from antiphospholipid antibodies of women with fetal loss causes fetal loss in BALB/c mice. It appears that the fetal loss is mediated by IgG binding in the maternal decidual vasculature.

Animals↗
PubMed1990

Prostaglandins regulate surfactant protein A (SP-A) gene expression in human fetal lung in vitro.

We previously have observed that dexamethasone has a biphasic effect on surfactant protein A (SP-A) mRNA levels in human fetal lung in vitro. At concentrations of 10(-10)-10(-9) M, dexamethasone increases the levels of SP-A mRNA, whereas, at concentrations greater than 10(-8) M, the steroid is markedly inhibitory. In studies to define the molecular mechanisms for these effects, we observed that dexamethasone causes a dose-dependent stimulation of SP-A gene transcription, but paradoxically causes a dose-dependent inhibition of SP-A mRNA stability. In light of the well-characterized inhibitory effect of glucocorticoids on prostaglandin (PG) synthesis in a number of tissues, it was our objective in the present study to investigate the role of PGs on SP-A gene expression in human fetal lung in vitro and to determine whether the action of dexamethasone (greater than 10(-8) M) to reduce SP-A mRNA levels could be mediated by its effect to inhibit PG synthesis. We found that dexamethasone 10(-7) M) caused a marked decrease in the secreted levels of the PGE2 and PGF2 alpha, the prostacyclin metabolite, 6-keto-PGF1 alpha, and the thromboxane A2 metabolite, thromboxane B2. Indomethacin, which also caused a pronounced reduction in the levels of these secreted prostanoids, had a marked effect to reduce SP-A mRNA levels in human fetal lung in vitro. The inhibitory effects of indomethacin were associated with an 73% reduction in cAMP formation by the fetal lung in culture, and were prevented by simultaneous incubation with dibutyryl cAMP or with PGE2. PGE2 markedly increased cAMP formation by the human fetal lung tissue incubated in the absence or presence of indomethacin. Inhibitory effects of dexamethasone and indomethacin also were observed on two morphological indices of lung differentiation, alveolar lumenal volume density, and lamellar body volume density. PGE2 significantly increased lumenal volume density of the human fetal lung explants. The finding that the inhibitory action of dexamethasone (10(-7) M) on SP-A mRNA levels could not be prevented by simultaneous incubation with either PGE2 or dibutyryl cAMP and that dexamethasone had no apparent effect on cAMP formation by the fetal lung in vitro is suggestive that the action of dexamethasone (greater than or equal to 10(-8) M) to reduce SP-A mRNA levels is mediated at least in part by actions alternative to its inhibitory effects on PG synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Maintaining fetal normoglycemia prevents the increase in myometrial activity and uterine 13,14-dihydro-15-keto-prostaglandin F2 alpha production during food withdrawal in late pregnancy in the ewe.

Food deprivation during pregnancy leads to an increase in maternal and fetal prostaglandin (PG) production and increased uterine contractility. We investigated the effect of maintaining fetal normoglycemia during food withdrawal-induced maternal hypoglycemia on uterine 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) production and myometrial activity in late pregnant sheep. Pregnant sheep were surgically instrumented with fetal and maternal catheters and electromyogram leads under halothane anesthesia. Maternal and fetal blood plasma samples were obtained once a day at 0900 h, 24 h before (baseline sample) and after 48 h of food withdrawal. Food, but not water, was withdrawn from ewes in group I (n = 5). During food withdrawal in group II (n = 5), glucose was infused into a fetal vein to maintain fetal normoglycemia. All data were normalized to the concentration in the baseline sample in each animal as 100%. After 48 h of food withdrawal, maternal whole blood glucose fell by 42.2 +/- 4.4% (mean +/- SEM: group I) and 31.4 +/- 6.2% (group II). These values were not significantly different. Fetal blood glucose fell by 40.4 +/- 5.7% (group I). In group II, fetal blood glucose was maintained in the normal range (99.6 +/- 1.6% of baseline). Maternal uterine electromyogram activity, uterine venous estrone sulfate, and uterine veno-arterial difference in PGFM rose significantly during food withdrawal in group I ewes, but not in group II ewes. Maternal and fetal arterial plasma ACTH and cortisol did not change in group II animals. We conclude that maintenance of fetal normoglycemia during 48 h of food withdrawal in sheep prevents the increase in myometrial activity, maternal plasma estrogens, and uterine PGFM production during food withdrawal in late pregnancy.

Adrenocorticotropic Hormone↗
PubMed1990

The Jarisch-Herxheimer reaction complicating syphilotherapy in pregnancy.

Thirty-three gravidas with syphilis were monitored with hourly vital signs and examinations for 24 hours after treatment with benzathine penicillin G. Fifteen (45%) of the subjects had a Jarisch-Herxheimer reaction, including all three, 12 of 20 (60%), and none of ten of those with primary, secondary, and latent syphilis, respectively. The most common symptoms were fever (73%), uterine contractions (67%), and decreased fetal movement (67%). The signs or symptoms began 2-8 hours after treatment; fevers peaked at 6-12 hours post-therapy and the events usually abated by 16-24 hours after treatment. Uterine contractions and decreased fetal activity began concurrent with maternal fever in eight of ten women reporting contractions. Transient late decelerations were detected in three of 11 monitored patients. Three of the women with Jarisch-Herxheimer reactions delivered infants with congenital syphilis, including one stillbirth, but none of those without a detectable reaction had fetal treatment failures. Prostaglandin F2 alpha and prostacyclin metabolites were elevated transiently in the one subject studied, suggesting their role in mediating the cardiovascular and uterine events in the post-treatment period. The Jarisch-Herxheimer reaction in pregnancy is similar in frequency, character, and intensity to that in nonpregnant adults, but gravidas may have increase uterine activity and transient alterations in fetal well-being. The pregnant patient with a severely affected fetus with congenital syphilis may experience preterm labor, preterm delivery, or fetal death in association with the Jarisch-Herxheimer reaction.

Adult↗
PubMed1990

Amniotic fluid interleukin-1 in spontaneous labor at term.

The regulatory signals responsible for the increased biosynthesis of prostaglandins during parturition have not been established. Interleukin-1 (IL-1) is capable of stimulating prostaglandin production by intrauterine tissues and is an inflammation mediator. It has been postulated as a signal for the onset of labor in the setting of intrauterine infection. A study was designed to determine if spontaneous labor at term was associated with changes in IL-1 activity in amniotic fluid. Such fluid was retrieved from 41 women in labor and from 39 women who were not in labor at term. Immunodetectable IL-1 beta was present in 22 of the 41 women in labor but in only 8 of the 39 women without labor. IL-1-like bioactivity was not different between the two groups at a dilution of 1:4, but at dilutions of 1:12, 1:36 and 1:108, amniotic fluid from women in labor had significantly higher bioactivity than that from women not in labor. A significant correlation was found between the bioassay and immunoassay results. Our data show that inhibitors of IL-1 bioactivity are present in amniotic fluid and suggest that in a subset of laboring women at term, an inflammatory reaction may play a role in triggering the onset of parturition.

Amniotic Fluid↗
PubMed1989

Infection and labor. IV. Cachectin-tumor necrosis factor in the amniotic fluid of women with intraamniotic infection and preterm labor.

A growing body of evidence supports a causal link between subclinical intrauterine infection and preterm labor. The mechanisms responsible for the onset of parturition in this setting have not been elucidated. The conventional view has been that bacterial products increase prostaglandin biosynthesis by intrauterine tissues and this, in turn, leads to the onset of labor. An alternative or complementary mechanism is that microbial products activate the host monocyte-macrophage system and that cytokines released during this process signal the initiation of parturition by stimulating prostaglandin biosynthesis by intrauterine tissues. This study was conducted to determine if cachectin-tumor necrosis factor is present in the amniotic fluid of women with intraamniotic infection and whether this cytokine can alter the rate of prostaglandin biosynthesis by intrauterine tissues. Amniotic fluid from 54 women was assayed for tumor necrosis factor. Tumor necrosis factor was not detectable in the amniotic fluid of women without intraamniotic infection regardless of the presence or absence of term or preterm labor. On the other hand, the amniotic fluid of 11 of 15 women with preterm labor and intraamniotic infection had measurable tumor necrosis factor. This cytokine stimulated prostaglandin E2 biosynthesis by amnion cells in monolayer culture in a dose-dependent fashion. These data support the concept that macrophage activation is involved in the onset of human parturition in the setting of infection. We propose that the host (fetus and/or mother) signals the onset of parturition through the secretion of inflammatory cytokines released in response to bacterial invasion.

Amnion↗
PubMed1989

A potential role for epidermal growth factor/alpha-transforming growth factor in human parturition.

Epidermal growth factor (EGF)/alpha-transforming growth factor (alpha-TGF) concentrations were measured in amniotic fluid by radioreceptor assay in non-laboring and laboring patients at term. The median concentrations of EGF/alpha-TGF were 1.28 ng/ml and 5.0 ng/ml in non-laboring and laboring patients respectively (p less than 0.05, Wilcoxon test). EGF was then incubated with amnion cells in monolayer culture to ascertain the effect of this hormone on the release of prostaglandin E2. Experiments were carried out in quadruplicate in 11 separate primary amnion-cell cultures (EGF was used at 1 ng/ml and 5 ng/ml, respectively). An increased release of prostaglandin E2 into the media was found. The response was concentration-dependent (p less than 0.01). We suggest that there may be a role for EGF in the mechanism of human parturition.

Amniocentesis↗
PubMed1989

Interleukin-1 stimulates prostaglandin biosynthesis by human amnion.

The purpose of these studies was to determine if Interleukin-1 (IL-1) alters the rate of prostaglandin biosynthesis by human amnion. Primary monolayer cultures of amnion cells were established from women undergoing elective cesarean section before the onset of labor. Natural purified and recombinant human IL-1 alpha and IL-1 beta were incubated with amnion cells in culture, and prostaglandin E2 (PGE2) biosynthesis was measured by radioimmunoassay in cell-free media. A concentration-dependent increase in PGE2 production by amnion cells occurred in response to natural purified and recombinant IL-1 preparations. No differences in the parameters of the dose-response curves between the two IL-1 gene products could be determined (p greater than 0.05). Indomethacin blocked the effect of IL-1 in prostaglandin biosynthesis by human amnion. Interleukin-1, a fever mediator, could serve as a signal for the initiation of labor in cases of intrauterine or systemic infection.

Amnion↗
PubMed1989

Amniotic fluid concentrations of prostaglandin F2 alpha, 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) and 11-deoxy-13,14-dihydro-15-keto-11, 16-cyclo-prostaglandin E2 (PGEM-LL) in preterm labor.

Although prostaglandins (PGs) are considered the key mediators of human parturition at term, there is a paucity of data regarding their participation in the mechanisms responsible for preterm labor. The purpose of this study was to establish if preterm labor is associated with changes in the amniotic fluid concentrations of prostaglandins. PGF2 alpha, 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) and 11-deoxy-13,14-dihydro-15-keto-11,16-cyclo-prostaglandin E2 (PGEM-ll) were measured by using specific and sensitive radioimmunoassays. Amniotic fluid was retrieved by transabdominal amniocentesis from 55 women with preterm labor and intact membranes. Patients were divided into three groups according to the response to tocolysis and the presence or absence of an intra-amniotic infection. Amniotic fluid concentrations of PGFM and PGEM-ll were significantly greater in women with preterm labor and intra-amniotic infection than in women without infection. In addition, patients unresponsive to tocolysis without intra-amniotic infection also had a significantly greater concentration of PGFM and PGEM-ll in amniotic fluid than those responsive to tocolysis. Amniotic fluid concentrations of PGF2 alpha were greater in women with intra-amniotic infection than in women without intra-amniotic infection. In the absence of intra-amniotic infection, no difference in amniotic fluid PGF2 alpha concentrations could be found between women who responded to tocolytic treatment and those who did not.

Amnion↗