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Biomedical subjects

M L Casey

Publications and source records attributed to M L Casey.

At least 91 records · Page 5Linked to original sources
PubMed1986

Prostaglandin E2 9-ketoreductase activity in human decidua vera tissue.

Amnion is believed to be a tissue of central importance in the biochemical processes of parturition. In this tissue, prostaglandin E2 is the near exclusive prostaglandin produced. And although the production of prostaglandin E2 is increased during labor in women, the levels of the major metabolite of prostaglandin E2 in maternal plasma are not elevated; rather, the levels of 13,14-dihydro-15-ketoprostaglandin F2 alpha, the major circulating metabolite of prostaglandin F2 alpha, are increased strikingly. Because of this apparent paradox, we considered the possibility that prostaglandin E2, originating in amnion, chorion laeve, or decidua vera, is converted to prostaglandin F2 alpha in decidua vera by the action of prostaglandin E2-9-ketoreductase. We found that prostaglandin E2 9-ketoreductase, the enzyme that catalyzes the conversion of prostaglandin E2 to F2 alpha, is present in cytosolic fractions prepared from homogenates of uterine decidua vera tissue. The specific activity of 9-ketoreductase in cytosolic fractions of decidua of six women varied from 3.2 to 155 pmol X min-1 X mg-1 protein. We also evaluated the conversion of exogenous prostaglandin E2 to F2 alpha in intact human endometrial stromal cells in monolayer culture. We found that prostaglandin E2, added to the culture medium, was converted to prostaglandin F2 alpha by endometrial stromal cells that were maintained in the presence of inhibitors of prostaglandin synthase. The extent of conversion of exogenous prostaglandin E2 to F2 alpha, however, was low relative to the specific activity of prostaglandin E2 9-ketoreductase found in decidual cytosol. These findings are consistent with the possibility that prostaglandin E2 formed in decidua vera tissue may be converted in that tissue to prostaglandin F2 alpha by 9-ketoreductase; on the other hand, prostaglandin E2 formed in contiguous tissues probably is not converted significantly to prostaglandin F2 alpha by decidual 9-ketoreductase.

Cytosol↗
PubMed1986

Glucocorticosteroid regulation of prostaglandin biosynthesis in human myometrial smooth muscle cells in monolayer culture.

In the present investigation, we evaluated the production of prostaglandins by human myometrial smooth muscle cells maintained in monolayer culture in the absence or presence of glucocorticosteroids. In the presence of cortisol (10(-7) M) or dexamethasone (10(-8) M), the rate of production of prostacyclin (PGI2) by these cells was decreased significantly. The glucocorticosteroid-mediated inhibition of prostaglandin production was attenuated when cortisol-21-mesylate (10(-6) M), a glucocorticosteroid antagonist, was present in the culture medium. The rate of conversion of radiolabeled arachidonic acid to radiolabeled prostaglandins as determined by use of sonicates of myometrial cells and optimal assay conditions, however, was not affected significantly by treatment with cortisol or dexamethasone in concentrations sufficient to inhibit prostaglandin formation by more than 80%. These findings are suggestive that glucocorticosteroids act in human myometrial smooth muscle cells in culture to inhibit prostaglandin formation by way of a receptor-mediated process that does not involve inhibition of enzyme activities that are involved in the biosynthesis of prostaglandins, i.e. the conversion of arachidonic acid to prostaglandin.

Arachidonic Acid↗
PubMed1985

Origin of urinary nonconjugated 19-nor-deoxycorticosterone and metabolism of infused radiolabeled 19-nor-deoxycorticosterone in men and women.

It is known that 19-nor-deoxycorticosterone (19-nor-DOC) is a potent mineralocorticosteroid that is present in urine of rats and humans in a free, i.e., nonconjugated, form. In some forms of hypertension in rats, the levels of free 19-nor-DOC in urine are increased compared with those in urine of normotensive animals. Yet, despite the potential importance of this mineralocorticosteroid in the pathogenesis of certain forms of hypertension, little is known of its site of origin or metabolism. In the present investigation, we evaluated the metabolism of intravenously infused [3H]19-nor-DOC and the possibility that 19-nor-DOC was formed from plasma DOC. We found that the metabolism of [3H]19-nor-DOC infused intravenously in men and women was similar to that of DOC with important exceptions. The majority of the radiolabeled urinary metabolites of intravenously infused [3H]19-nor-DOC were excreted in urine as glucuronosides. Little radioactivity, infused as [3H]19-nor-DOC, was recovered in urine as nonconjugated or sulfoconjugated steroids. There was no free radiolabeled 19-nor-DOC in urine after the simultaneous infusion of [3H]19-nor-DOC and [14C]DOC. A major metabolite of [3H]19-nor-DOC in urine was 19-nor-DOC-21-glucuronoside, whereas little or no intravenously infused radiolabeled DOC was excreted as radiolabeled DOC-glucuronoside. We also found that intravenously infused [14C]DOC was not converted to urinary [14C]19-nor-DOC (glucuronoside) and that other tritium-labeled metabolites of infused [3H]19-nor-DOC contained no carbon-14. The production rate of 19-nor-DOC, computed from the specific activity of urinary 19-nor-DOC (glucuronoside), in one normal man was 16 micrograms/d and in the two women of this study, it was 10 micrograms/d. These findings are supportive of the proposition that free urinary 19-nor-DOC is not formed from plasma DOC; it may be formed in kidney from a precursor other than DOC or it may be formed nonenzymatically in kidney or urine from a precursor such as 19-oic-DOC.

Carbon Radioisotopes↗
PubMed1985

Despite a massive increase in cortisol secretion in women during parturition, there is an equally massive increase in prostaglandin synthesis. A paradox?

In this investigation, we sought to resolve the apparent paradox that is posed by the fact that there is a simultaneous increase in the production of prostaglandin and cortisol in women during labor. A paradox obtains, since in most tissues, cortisol acts to inhibit prostaglandin formation. Using previously characterized model systems for the in vitro study of arachidonic acid metabolism in amnion, decidua, and myometrium, we found that prostaglandin production by amnion and endometrial stromal cells in monolayer culture was not decreased by glucocorticosteroid treatment. On the other hand, prostaglandin production by myometrial smooth muscle cells in culture was inhibited by greater than 90% in response to dexamethasone (10(-7) M) treatment. Importantly, the major prostaglandin produced by myometrium, as well as myometrial smooth muscle cells in culture, is prostacyclin, a prostaglandin that acts to cause uterine quiescence. We suggest that the immunity of amnion and decidua to the action of glucocorticosteroids may allow for the accelerated production of prostaglandins E2 and F2 alpha, which act to cause myometrial contractions; simultaneously, glucocorticosteroid produced in large quantities in women in labor may lead to decreased production of prostacyclin by myometrium, thereby reducing uterine quiescence. In this coordinated manner, the uterine contractions that culminate in delivery of the fetus may proceed uninterrupted in the face of increased cortisol production.

Amnion↗
PubMed1984

Umbilical cord plasma concentrations of deoxycorticosterone sulfate in anencephalic fetuses.

In the present investigation, we determined the levels of deoxycorticosterone sulfate in mixed umbilical cord plasma of anencephalic abortuses and newborn infants. The anencephalic fetus is an interesting model with respect to the production of deoxycorticosterone and deoxycorticosterone sulfate on several accounts. There is profound adrenal atrophy in most such fesuses, and, in consequence, there also is relatively profound hypoestrogenism. This is an important consideration in the formation of deoxycorticosterone and deoxycorticosterone sulfate since it is known that estrogen acts to stimulate extra-adrenal steroid 21-hydroxylase and 21-hydroxysteroid sulfotransferase activities. The plasma levels of deoxycorticosterone sulfate in 22 anencephalic abortuses and newborn infants delivered between 21.5 and 45.5 weeks of gestation ranged from 1.8 to 30.3 ng/ml. The concentrations of deoxycorticosterone sulfate in umbilical cord plasma of anencephalic fetuses and newborn infants were not related to gestational age or method of delivery and, at term, were less than 13% of those in umbilical cord plasma of normal newborn infants. These data can be interpreted to indicate (1) that deoxycorticosterone sulfate normally is secreted directly by the fetal adrenal or (2) that placental estrogen normally derived largely from fetal adrenal dehydroisoandrosterone sulfate is essential for the maintenance of plasma deoxycorticosterone sulfate levels in the fetus by stimulating extra-adrenal deoxycorticosterone sulfate production from plasma progesterone, or both.

Abnormalities, Multiple↗
PubMed1984

Maintenance and characterization of human myometrial smooth muscle cells in monolayer culture.

Human myometrial cells were dispersed from uterine tissue by limited enzymatic digestion of myometrium that was obtained at the time of hysterectomy. The dispersed myometrial cells that are obtained in this manner can be maintained in monolayer culture in the presence of medium that contains fetal bovine serum. In primary culture, as well as after passage, the characteristics of these cells are morphologically and biochemically similar to those of smooth muscle cells and myometrial tissue.

Cells, Cultured↗
PubMed1984

The origin of and metabolic fate of deoxycorticosterone and deoxycorticosterone sulfate in pregnant women and their fetuses.

DOC and DOC-SO4, which are present in large amounts in the blood of pregnant women, are derived from sources other than maternal adrenal. Other investigators demonstrated that treatment of near-term pregnant women with ACTH or dexamethasone did not cause alterations in the blood levels of DOC. To define the source(s) of DOC and DOC-SO4 in plasma of pregnant women, we evaluated the conversion of plasma progesterone (P) to DOC in extraadrenal sites. DOC is formed from plasma P and, provided that the pregnancy is one characterized by the usual large production of estrogen, DOC production in a given woman is proportional to the level of P in plasma. Unlike other steroid conversions or interconversions, however, the fractional conversion of P to DOC among apparently normal persons varied widely 0.011 +/- 0.003 (mean +/- SEM, n = 40, range = 0.001 to 0.030). In women pregnant with a normal living fetus, the product of the production rate of P and the fractional conversion of P to DOC is sufficient to account for the majority of DOC produced in the mother. There may be a second source of DOC, i.e. the transfer of DOC from the fetal to the maternal compartment in a manner that involves (a) direct transfer of DOC by way of trophoblast and (b) by desulfurylation of DOC-SO4 from fetal umbilical arterial plasma in trophoblast and thence transfer of DOC liberated in trophoblast to the maternal compartment. Presently, it is clear that DOC-SO4 in blood of pregnant women is not derived from plasma DOC; and there is little or no evidence in support of the proposition that DOC-SO4 (as a sulfoconjugate) is transferred from the fetal to the maternal compartment because of placental hydrolysis to DOC. Among the extraadrenal tissue sites identified as those in which 21-hydroxylation of plasma P could be effected are some also believed to be tissue sites of mineralocorticosteroid action, viz, kidney, aorta, thymus, and spleen. Quantitatively, the origin of DOC in the fetus is not as clear as in the maternal compartment; yet, many tissues of the fetus have been identified in which both steroid 21-hydroxylase and 21-hydroxysteroid sulfotransferase activity are present. Thus, in the human fetus, extraadrenal as well as adrenal production of DOC and DOC-SO4 are possible.

Adrenocorticotropic Hormone↗
PubMed1984

Characterization of prostaglandin formation by human amnion cells in monolayer culture.

In the present investigation, we found that among the prostanoids that human amnion cells, which are maintained in monolayer culture, secrete into the culture medium, prostaglandin E2 is by far the predominant one. In the presence of inhibitors of prostaglandin synthase, the production of prostaglandin E2 by these cells is abolished. Amnion cells maintained in the presence of fetal calf serum produce greater quantities of prostaglandin E2 than do cells maintained in serumless medium. In the amnion cells, there is little or no metabolism of prostaglandin E2; this also is true of amnion tissue. The unique characteristics of prostaglandin biosynthesis and metabolism by human amnion cells in monolayer culture are identical with those of human amnion tissue. Hence, we suggest that amnion cells in culture constitute an excellent model for investigations of the regulation of prostaglandin E2 biosynthesis in this tissue.

Amnion↗
PubMed1984

The human LDL receptor: a cysteine-rich protein with multiple Alu sequences in its mRNA.

The nucleotide sequence of a cloned 5.3 kilobase cDNA for the human low density lipoprotein receptor revealed five domains in the 839 amino acid protein: 322 NH2-terminal amino acids, extremely rich in disulfide-bonded cysteine residues (15%) and including an 8-fold repeat of 40 residues that may contain the LDL binding site; 350 residues homologous to the precursor of mouse epidermal growth factor; a region immediately outside the plasma membrane, rich in serine and threonine and the site of O-linked glycosylation; 22 hydrophobic amino acids, spanning the plasma membrane; and 50 COOH-terminal amino acids, projecting into the cytoplasm. The mRNA for the receptor contains a 3' untranslated region of 2.5 kilobases that includes multiple copies of the Alu family of repetitive DNAs. Transfection of simian COS cells with the human LDL receptor cDNA linked to the SV40 early promoter resulted in expression of functional cell surface receptors.

Amino Acid Sequence↗
PubMed1984

Stimulation of prostaglandin E2 synthesis in human amnion cells maintained in monolayer culture by a substance(s) in amniotic fluid.

A substance(s) in amniotic fluid of human pregnancies promotes a striking increase in prostaglandin E2 production in human amnion cells maintained in primary monolayer culture. The prostaglandin E2 synthesis-stimulatory factor(s) acts in a time- and dose-dependent manner to accelerate prostaglandin E2 formation. We suggest that a substance of fetal origin enters amniotic fluid by way of fetal urine and acts to regulate prostaglandin E2 synthesis in amnion. Such a process may be of fundamental importance in the regulation of amniotic fluid volume homeostasis and in the initiation of parturition.

Amnion↗
PubMed1984

15-Hydroxyprostaglandin dehydrogenase activity in human fetal kidney tissue.

Human fetal kidney tissue was found to be rich in NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) activity. The enzyme activity was localized primarily in the medullary portion of fetal kidney. Separated cortical and medullary tissue fragments were maintained in organ culture for up to 9 days. The specific activity of PGDH in cortical tissue was low at the commencement of organ culture and remained low throughout the culture period. The specific activity of PGDH in medullary tissue fell precipitously during the first 48 h in organ culture; thereafter, the specific activity of the enzyme increased steadily during the culture period and reached values of up to ten times that in starting tissue by 6-7 days in organ culture. The decline in specific activity of PGDH in medullary tissue during the first 48 h in culture could be prevented by including inhibitors of lysosomal enzyme activity, i.e., chloroquine or ammonium chloride, in the culture medium. We suggest that human fetal kidney tissue explants in organ culture may be an appropriate model for the study of the regulation of PGDH activity. Such an evaluation of the regulation of PGDH is believed to be of importance since PGDH serves to regulate the levels of and, thence, the action of the biologically active prostaglandins.

Ammonium Chloride↗
PubMed1984

Variation in the fractional conversion of plasma estrone to estriol among women and men.

In the present investigation, we determined the transfer constant of conversion of plasma estrone to estriol (E3) ( [rho] E1- E3BU ) in men, postmenopausal women, and premenopausal parous and premenopausal nulliparous women. We found no significant difference in [rho] E1- E3BU among men, postmenopausal women, premenopausal parous or nulliparous women (whether the latter were studied during the midfollicular or midluteal phase of the ovarian cycle), or in women who were ingesting oral contraceptives. On the other hand, there was a striking variation in the [rho]E1- E3BU among individuals, viz. 0.02-0.27, whereas in a given individual, the variation in [rho] E1- E3BU , evaluated on separate occasions, was small. In addition, we found a negative correlation between age at first fullterm pregnancy and [rho] E1- E3BU .

Adult↗
PubMed1983

Origin of prostanoids in human amniotic fluid: the fetal kidney as a source of amniotic fluid prostanoids.

The present study was designed to investigate the origin of prostanoids that are present in amniotic fluid. We evaluated the concentration of prostaglandins in fetal urine that was obtained from newborn infants immediately after delivery either before or after the onset of spontaneous labor or after oxytocin-induced labor. We found that the levels of prostaglandin (PG) E2, PGF2 alpha, 6-keto-PGF1 alpha, and 13, 14-dihydro-15-keto-PGF2 alpha in the fetal urine of newborn infants delivered after the spontaneous onset of labor and after oxytocin-induced labor were significantly greater than the levels in the fetal urine of newborn infants delivered before the spontaneous onset of labor. We conclude that one source of the prostanoids present in amniotic fluid is fetal urine, and, thence, fetal kidneys, and that labor, whether spontaneous or induced, caused increased excretion of prostanoids in fetal urine.

Amniotic Fluid↗
PubMed1983

Catechol-O-methyltransferase activity in erythrocytes of pregnant women with sickle cell disease before, during, and after transfusion and partial exchange transfusion.

In the present investigation we found that the catechol-O-methyltransferase (COMT) activity in erythrocytes of pregnant women with sickle cell disease was strikingly elevated compared with that in erythrocytes of men and pregnant and nonpregnant women. Moreover, the enzyme activity in erythrocytes remained high during and after transfusion or partial exchange transfusion even though the enzyme activity in donor cells was low. This finding is suggestive of the possibility that a factor(s) in plasma of persons with sickle cell disease activates erythrocyte COMT activity.

Anemia, Sickle Cell↗