Search PubMed⌕ Search

Biomedical subjects

M H Sullivan

Publications and source records attributed to M H Sullivan.

At least 73 records · Page 4Linked to original sources
PubMed1991

Changes in platelet function in pregnancies complicated by fetal growth retardation.

Platelet function was investigated in three patients with severely decreased fetal growth rates detected by ultrasound scanning. Only one patient had hypertension, which was mild and developed after decreased fetal growth and altered platelet responses had been detected. Much higher concentrations of platelet-activating factor (PAF) (20-500 nM) were required to stimulate maximal platelet aggregation in all three patients compared with the concentrations of PAF (5-10 nM) required in control pregnancies of similar gestational age. In a fourth patient, platelet desensitisation was observed 5 weeks before the detection of decreased fetal growth. These results are similar to those observed in women with hypertensive disorders of pregnancy, and indicate that there may be a similar change in platelet function in gestational hypertension and in fetal growth retardation, although the clinical manifestations are different.

Blood Platelets↗
PubMed1991

Detection of platelet desensitization in pregnancy-induced hypertension is dependent on the agonist used.

The aggregation of platelets from women with pregnancy-induced hypertension (P.I.H.), or with normal pregnancies, in response to arachidonic acid, ADP, collagen or platelet activating factor (PAF) was examined. No differences in platelet aggregation between the normotensive and hypertensive women were detected when arachidonic acid or collagen were used to stimulate in vitro platelet aggregation. Higher concentrations of ADP and PAF were required to aggregate platelets from women with P.I.H. compared with platelets from normotensive controls. Platelets from women with normotensive pregnancies (n = 80) aggregated maximally in response to 20 nM PAF without exception. Reversible aggregation by platelets from women with P.I.H. (n = 25) was observed at the same concentration of PAF; again, this was found in all subjects tested. These results indicate that PAF at a concentration of 20 nM can clearly demonstrate differences in aggregation of platelets from women with normotensive pregnancy and women with P.I.H.

Adenosine Diphosphate↗
PubMed1991

A comparison of two populations of decidual cells by immunocytochemistry and prostaglandin production.

The decidua has been implicated in the control of human labour, particularly through changes in prostaglandin production, but this tissue contains a number of different cell types. A density gradient system was used to obtain two populations of cells from term human decidua, and these populations were characterised. The more dense cells (population B) was a mixed population, predominantly macrophages (80%), but small numbers of T- and B-lymphocytes were also present, as identified by immunocytochemistry. Most of these cell types also contained detectable levels of cyclooxygenase enzyme. The less-dense cell population (population A) did not contain significant numbers of the above cell types and released prolactin, suggesting that they were decidual stromal cells. This preparation of decidual stromal cells may be of use in defining the functions of these cells in labour.

Antibodies, Monoclonal↗
PubMed1991

Effect of cell purity, cell concentration, and incubation conditions on rat testis Leydig cell steroidogenesis.

This study examines the effects of cell purity and incubation conditions on testosterone production by rat testis Leydig cells in short-term primary culture. Both basal and luteinizing hormone (LH)-stimulated testosterone production were affected by the purity of the cell preparation, i.e., as the purity of the cell preparation was increased the amount of testosterone produced per Leydig cell was also found to increase. The stimulation ratio of testosterone production, calculated as the secretion of testosterone in the presence of LH (100 ng/ml) divided by the basal secretion of testosterone, increased with the increase in plating density (20,000 to 200,000 cells per well). This pattern of change was independent of the vessel and volume of incubation. In terms of the absolute amount of testosterone produced, increasing the plating density led to a decrease in the amount of steroid produced both basally and in response to LH. Composition of the incubation medium also had an effect on testosterone production; phenol red and sodium bicarbonate exerted negative effects. At all temperatures studied (4 degrees, 24 degrees, 34 degrees, and 37 degrees C), LH increased testosterone production and the degree of stimulation increased with temperature. We conclude that cell purity and incubation conditions markedly affect rat Leydig cell steroidogenesis in vitro. Furthermore, the manner in which the results are presented can affect their interpretation.

Animals↗
PubMed1991

Prostaglandin production in human endometrium following continuous exposure to low-dose levonorgestrel released from a vaginal ring.

Arachidonic acid metabolites produced by primary cultures of human endometrial cells derived from biopsies obtained before and after exposure to 20 micrograms/day levonorgestrel for 84 +/- 1 days were analysed by reverse phase HPLC. This revealed a significant increase in PGF1 alpha and an epoxide metabolite upon levonorgestrel stimulation. The proportion of epoxide metabolite, PGF1 alpha and PGE2 were positively correlated with serum levonorgestrel levels while HETES, PGE2 and epoxide were similarly correlated with serum oestradiol. The extent of intermenstrual bleeding during exposure to levonorgestrel was correlated with the proportion of epoxide and HETES products in vitro which is discussed in relation to their physiological function.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Production of urinary 11-keto-thromboxane B2 in normal and hypertensive pregnancies.

Urinary levels of 11-keto-thromboxane B2 (11-keto-TXB2), were elevated at all gestational ages (12-41 weeks) compared with non-pregnant levels. 11-keto-TXB2 levels exceeded those of TXB2 throughout pregnancy, which suggested that 11-keto-TXB2 may be the major urinary metabolite of TXA2 in normotensive pregnancy, as in the non-pregnant state. This was reversed in women with mild pregnancy-induced hypertension (P.I.H.), such that urinary levels of TXB2 were higher (p less than 0.01) than those of 11-keto-TXB2. Since the 11-thromboxane dehydrogenase enzyme is found in the placenta, the low levels of 11-keto-TXB2 may be the result of placental damage decreasing the activity of the enzyme. The relationship between these findings and the aetiology of P.I.H. is not clear, but changes in urinary 11-keto-TXB2 may be of use in identifying those women at risk of developing P.I.H.

Adult↗
PubMed1991

Quantitative production of prostaglandin E2 and its metabolites by human fetal membranes.

Cultured amnion, choriodecidua and intact fetal membrane produced similar quantities of prostaglandin E2 (PGE2) (1-5 ng/ml). Choriodecidua and intact fetal membrane also produced very high levels of PGE2 metabolites (100-1000 ng/ml). The total production of PGE (PGE2 + PGE2 metabolites) was similar in intact fetal membrane and in choriodecidua, suggesting that the amnion, although a source of PGE2, contributes little to the overall PGE production by fetal membranes.

Amnion↗
PubMed1991

Metabolism of prostaglandin E2 on the fetal and maternal sides of intact fetal membranes.

The metabolism of prostaglandin E2 (PGE2) added to the chorio-decidual side or the amnion side of the intact fetal membrane was compared. Similar rates of metabolism were found when the PGE2 was added to the fetal side or the maternal side of the membrane, even though the amnion (on the fetal side of the membrane) contains no metabolizing enzymes. The appearance of PGE2 metabolites on the opposing side of the membrane was also independent of whether the PGE2 was added to the fetal or maternal side, which suggests that the chorion, which lies between the amnion and the decidua, is the major determinant of the rate of metabolism of PGE2. Furthermore, it might be expected that less PGE2 metabolism subsequent to diffusion across the membrane may occur on the amnion side, since this tissue contains no metabolizing enzymes, but no evidence for this was found. PGE2 synthesized by the amnion would therefore have little effect on PGE2 levels on the maternal side of the fetal membrane, and may not be directly involved in labour.

Chromatography, High Pressure Liquid↗
PubMed1991

Differential metabolism of intracellular and extracellular arachidonic acid by decidual stromal cells and macrophages.

Term decidual stromal cells metabolized extracellular arachidonic acid to cyclo-oxygenase, lipoxygenase and epoxygenase products. Prostaglandins were the major metabolites from extracellular arachidonic acid. In contrast, intracellular arachidonic acid was metabolized mainly to an epoxygenase product, together with some lipoxygenase products. Decidual macrophages showed similar results, though these cells had higher production rates per cell of most metabolites. The calcium ionophore A23187 increased the levels of arachidonic acid released from the intracellular stores of decidual stromal cells and had variable effects on the production of cyclo-oxygenase, lipoxygenase and epoxygenase metabolites. Less than 15% of the total metabolites released from A23187-stimulated cells were cyclo-oxygenase products, which suggested that the cyclo-oxygenase products released by decidual stromal cells or macrophages may be mainly derived from extracellular arachidonic acid. This implies that the regulation of decidual cyclo-oxygenase may have a major role in determining prostaglandin output from this tissue.

Arachidonic Acids↗
PubMed1991

Differences of metabolism of prostaglandin E2 and F2 alpha by decidual stromal cells and macrophages in culture.

Intact decidual stromal cells and macrophages metabolized 3H-prostaglandins E2 and F2 alpha although the rate of metabolism of both prostaglandins was higher in the decidual macrophages than in decidual stromal cells. PGE2 was metabolised mainly to 13,14-dihydro-15-keto-PGE2 together with smaller quantities for PGB2 and 13,14-dihydro-15-keto-PGA2, whereas PGF2 alpha was metabolised to 13,14-dihydro-15-keto-PGF2 alpha, PGE2 and PGB2, and it seems that similar metabolic pathways were present in both cell types. The half-lives of both prostaglandins (8.8 +/- 3.4 h for PGE2 and 15.0 +/- 8.2 h for PGF2 alpha sigma in the presence of decidual stromal cells show that during incubations lasting more than a few hours significant metabolism of prostaglandins, especially PGE2, will occur, and that this must be allowed for in any assessment of total prostaglandin production by cultured decidual cells. One of the 6 tissue samples examined metabolised both prostaglandins very rapidly, such that the half-lives were less than 2 h. This may be the result of the presence of very high levels of metabolic enzymes, since the overall pattern of metabolites was similar to that from the other 5 samples.

Cells, Cultured↗
PubMed1990

Use of a new simplified assay for phospholipase A2 to measure bacterial enzyme levels.

During investigation of possible phospholipase A2 (PLA2) production by pathogenic bacteria associated with preterm labour, a rapid and simple assay method was developed which involved few steps and which could be applied easily to large numbers of samples. The principle difference from previously described methods lies in separation of the reaction products by partitioning them between organic and aqueous solvents, rather than by using thin layer chromatography. This enabled us to determine that none of the bacteria studied released PLA2 into the culture medium spontaneously, and that only Escherichia coli contained high levels of PLA2.

Carbon Radioisotopes↗
PubMed1990

Equivalent inhibition of in vivo platelet function by low dose and high dose aspirin treatment.

In vitro platelet function was inhibited in healthy volunteers by two different doses of aspirin, as confirmed by measurement of maximum serum production of thromboxane B2 (TXB2) by platelets. 75 mg aspirin did not fully inhibit serum TXB2 production after 24 hours, whereas 300 mg aspirin did. Inhibition of platelet function in vitro was maintained by both 75 mg/day aspirin or 300 mg/alternate day aspirin. In contrast, in vivo production of TXB2, measured as urinary levels of the 11-keto-TXB2 metabolite, was inhibited similarly by both doses of aspirin throughout the study. These findings suggest that 75 mg/day aspirin may be sufficient adequately to inhibit platelet aggregation in vivo.

Aspirin↗
PubMed1990

Production of intracellular arachidonic acid metabolites by human granulosa cells.

The major intracellular metabolites of arachidonic acid within human granulosa cells are an epoxy-eicosatrienoic acid (EET), and a dihydroxy-metabolite. The former which was present at higher levels, co-migrated with 5,6-EET on HPLC. Incubation of the cells with LH for 5 min stimulated the production of both 5,6-EET and the dihydroxy compound 2-4 fold. The production of other intracellular arachidonic acid metabolites was unaffected by stimulation with LH. These results suggest that one or both of these metabolites may have a role in steroidogenesis in human granulosa cells.

Arachidonic Acids↗
PubMed1990

Fatty acid control of growth of human cervical and endometrial cancer cells.

Stearic acid and iodo-stearic and inhibited cell growth in a cervical cancer cell line (HOG-1) in a dose-related manner, with a half maximal effect at 50 microM stearic acid. Addition of oleic acid abrogated the effect of stearic acid. EGF-stimulated DNA synthesis and growth of HOG-1 cells was inhibited in the presence of stearic acid without any apparent effect on EGF receptor number or affinity.

Cell Division↗