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Biomedical subjects

R K Miller

Publications and source records attributed to R K Miller.

At least 145 records · Page 8Linked to original sources
PubMed1978

Materno-fetal transport of creatine in the rat.

The transfer of 14C-creatine to the rat fetus was studied following continuous i.v. infusion into the mother. In the presence of a relatively constant maternal plasma 14C-creatine concentration, creatine was accumulated by the chorioallantoic placenta and visceral yolk sac to concentrations higher than that found in maternal or fetal plasma. The ability of the extraembryonic membranes to accumulate creatine changed during gestation; nevertheless, these membranes concentrated creatine against a gradient throughout the period studied (14-22 days of gestation). Neither 14C-creatine nor 14C-urea were concentrated in the placentae or fetal plasma when compared to maternal plasma. Simultaneous infusion of beta-guanidinopropionic acid with 14C-creatine reduced both movement and accumulation of creatine into the fetoplacental unit. It is concluded that the accumulation of creatine by the chorioallantoic placenta and by the visceral yolk sac is an active process with creatine diffusing down its concentration gradient into the fetal circulation.

Animals↗
PubMed1977

Reliability and validity enhancement: a treatment package for increasing fidelity of self-report.

This study investigated the effects of reliability and validity "enhancers" on fidelity of self-report data in an analogue therapy situation. Under the guise of a Concentration Skills Training Program, 57 Ss were assigned randomly to one of the following conditions: (a) Reliability Enhancement; (b) Truth Talk; (c) No Comment Control. Results indicated significant differences among groups (p less than .05). In addition, tests of multiple comparisons revealed that Reliability Enhancement was significantly different from Truth Talk in occurrences of unreliability (p less than .05). These findings are discussed in light of the increased reliance on self-report data in behavioral intervention, and recommendations are made for future research.

Alpha Rhythm↗
PubMedDate not supplied

Pharmacokinetic studies of enalaprilat in the in vitro perfused human placental lobule system.

The objectives of this study were to evaluate the transplacental kinetics and effects on placental function of the angiotensin converting enzyme (ACE) inhibitor, enalaprilat, in the dually perfused human placental lobule system. When placed in the maternal perfusate at a high therapeutic serum concentration (150 ng/ml), enalaprilat was rapidly transferred from the maternal perfusate into placental tissue followed by a gradual release from the placenta into the fetal perfusate. Cmax and AUC values for enalaprilat in the maternal perfusate were approximately 3 times higher than in the fetal perfusate, and drug levels did not equilibrate between maternal and fetal perfusates during the 4-6 hours of perfusion. The more highly perfused regions of the placental lobule had higher drug levels than non-perfused areas. At the end of the perfusion period, the mean percent of total drug added in the maternal perfusate was 59%, with 23% in the fetal perfusate and the remainder (18%) in placental tissue. Despite the relatively high levels of drug found in placental tissue, there were no alterations in placental function as measured by fetal volume loss, fetal pressure, glucose utilization, lactate production, hCG release, net fetal oxygen transfer, and oxygen consumption. Results from this study clearly document placental transfer of enalaprilat in the perfused human placental lobule system. The lack of effect on placental function suggests that enalaprilat has no direct effect on fetoplacental vascular beds, and that fetal hypotension occurring from ACE inhibitor exposure may be due to direct effects on the fetal kidney and not to decreased perfusion of fetoplacental vascular beds; these findings require further validation in an in vivo model.

Area Under Curve↗
PubMedDate not supplied

Sonographic investigation of flow patterns in the perfused human placenta and their modulation by vasoactive agents with enhanced visualization by the ultrasound contrast agent Albunex.

PURPOSE: Our objective was to demonstrate sonographically the flow distribution in the circulation of human placentae as well as the sensitivity of the human fetal capillary bed to vasoconstriction and dilatation. METHODS: Five human full-term placental lobules were maintained in vitro with fetal and maternal flow. Commercial ultrasound scanners were used for imaging. Albunex (1 ml bolus) was administered to the fetal "artery" to monitor patterns of flow. U46619 (1 ml, 10(-6) M; a thromboxane agonist and potent vasoconstrictor) and/or nitroglycerin (a potent vasodilator) were added to the fetal artery. RESULTS: Following the addition of U46619, mean "fetal pressures" rapidly rose from 23.2 +/- 0.8 to 118 +/- 2. 9 mm Hg (mean +/- standard error of mean; p < 0.001); venous flow rates decreased. As demonstrated by color Doppler imaging, flow markedly changed from a pattern of general distribution throughout the lobule to flow only near the chorionic plate. Color persistence was 94.4 +/- 6.5 seconds with Albunex after nitroglycerin and 39.8 +/- 3.4 seconds with Albunex after injection of U46619 (p < 0.001). Nitroglycerin had no effect when injected by itself but returned "constricted" flow to a "normal" pattern when injected after U46619. CONCLUSIONS: The contrast medium Albunex improved visualization of the fetal circulation throughout the lobule. Flow in the human placental capillary bed can be regionally manipulated throughout the placental lobule by vasomodulators and monitored by Albunex-enhanced sonographic examination.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMedDate not supplied

Human choriocarcinoma (JAr) cells grown as multicellular spheroids.

JAr choriocarcinoma cells grew as multicellular spheroids, and exhibited a logarithmic pattern of growth, reaching geometric mean diameters of at least 1200 microns after 21 days in culture. HCG, E2 and P4 were secreted into the culture medium throughout the entire culture period, in proportion to spheroid size. This, along with the presence of lipid droplets, non-staining glycogen, Golgi apparatus and microvilli on the spheroid surface and in intercellular spaces indicated that the JAr cells within spheroids were functionally active. While spheroids of less than 800 microns GMD attached to culture dishes and produced cellular outgrowth, larger spheroids showed impaired attachment, and a delay in the subsequent production of outgrowth, which was not correlated with the development of a necrotic core. This outgrowth contained more multinucleated cells and cellular projections than that of smaller spheroids, suggesting that the cells in larger spheroids had undergone early differentiative changes. The spheroid culture system will be applied to the study of processes, such as implantation, which may require a three-dimensional arrangement of placental cells.

Choriocarcinoma↗
PubMedDate not supplied

Villous culture of first trimester human placenta--model to study extravillous trophoblast (EVT) differentiation.

During implantation and subsequent placentation the human extravillous trophoblast (EVT) cells invade the endometrium and maternal vasculature within the uterus. The origin of the EVT and signals triggering its differentiation, migration and invasion are poorly understood. First and second trimester human chorionic villi explants were used as a source of EVT and a variety of substrates which resemble extracellular matrix (ECM) in vivo have been tested to induce EVT differentiation and migration. The obtained results demonstrate that villous explants from both 5-7 and 8-10 weeks of gestation give rise to EVT cells in vitro if maintained on the surface of Matrigel or decidual extract supplemented collagen gel. Fetal calf serum (FCS) supplemented media was essential for EVT differentiation and villous trophoblast viability. Immunostaining of both EVT cells and cells from the cytotrophoblastic column with monoclonal antibody Ki67 (cell proliferation marker) indicate that EVT cells differentiate in vitro by proliferation from the tip of anchoring villi. These mononucleated, round-shaped, migrating cells are HLA-A,B,C class I antigen (W6/32) antibody and low molecular weight cytokeratin positive, and do not immunostain with PAI-1 (plasminogen activator inhibitor) and HPL antibodies. Differentiation of EVT was restricted to first trimester villous tissue; explants from second trimester placentae did not give rise to EVT. Tissue viability as monitored by glucose utilization, lactate, progesterone and hCG production rates correlated with EVT differentiation. The production rates for hCG demonstrated significant variation among individual placentae and was maintained constant for 10 days consistently only in explants cultured on decidual extract supplemented collagen matrix. The described villous tissue culture system may be, therefore, a unique in vitro model to study proliferation and differentiation of EVT from cytotrophoblastic columns, the regulation of EVT proliferation and differentiation, the role of ECM in the induction of the migration and the interaction of extravillous and villous trophoblast at the level of the cytotrophoblastic column.

Cell Differentiation↗
PubMedDate not supplied

Cadmium and glutathione: effect on human placental thromboxane and prostacyclin production.

Cadmium toxicity, noted in rodents during late gestation, has been compared with preeclampsia, a condition associated with an imbalance between thromboxane A2 and prostacyclin. This study examines the effect of cadmium on the human placental production of thromboxane A2 and prostacyclin, as reflected by their hydrolysis products (TxB2, 6-keto-PGF1 alpha). Following two 12-h exposures, 6-keto-PGF1 alpha production by placental explants was 74.8 and 39.9% of unexposed tissue values at 40 and 100 microM cadmium, respectively, with no significant effect on TxB2. The effect of glutathione on placental TxB2 and 6-keto-PGF1 alpha production was also examined. Sulfhydryl concentrations have been shown to affect thromboxane and prostacyclin production, and glutathione binds to cadmium reducing its toxicity. Although glutathione at concentrations up to 1 mM had no effect on explant function, glutathione did prevent the effects of cadmium on 6-keto-PGF1 alpha. This study indicates that acute exposure to cadmium at high concentrations directly affects the placental production of 6-keto-PGF1 alpha, disturbing the thromboxane A2/prostacyclin ratio.

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

Cell-specific increases in metallothionein expression in the human placenta perfused with cadmium.

Metallothionein (MT) is a cysteine-rich protein that may have both a nutritional and a protective role by binding either physiologic or toxic concentrations of metals in cells. The objective of this investigation was to measure the inducibility of MT mRNA and protein, and to determine their specific cellular localization following exposure to 20 microM cadmium (Cd) in the perfused human placenta for periods up to 8 h. MT mRNA was quantitated using slot blot hybridization with an MT IIa genomic clone and MT transcripts were localized via in situ hybridization. MT protein was measured using a 109Cd-binding assay and localized by immunocytochemistry using a monoclonal antibody to MT in fresh placental tissue from nonsmoking mothers and in tissue perfused for 4 or 8 h with CdCl2 (20 microM). Perfusions were performed on placentae from which fresh samples were also obtained. In fresh term placentae, MT mRNA was barely detectable using both slot blot and in situ hybridization. Slot blot hybridization for MT message demonstrated a dramatic increase of at least 70-fold above fresh after 8 h of perfusion with 20 microM CdCl2. In this time frame, however, statistically significant increases in MT protein were not detected. Following perfusion for 4 and 8 h with 20 microM CdCl2, accumulation of MT transcripts was shown, in situ, to occur in stromal and endothelial cells with a small but detectable increase in trophoblast cells. These results were consistent with the localization of the MT protein after perfusion with Cd and also correlated with areas of stromal edema. Thus, while the trophoblast cells are in direct contact with Cd in maternal perfusate, the cells of the villous core and fetal endothelial cells are most responsive to Cd exposure with regard to MT expression. Lower levels of MT expression in trophoblast cells may leave this cell type more susceptible to Cd toxicity, while higher levels of MT expression in cells of the villous core and endothelial cells may provide these cells with more protection.

Blotting, Northern↗
PubMedDate not supplied

In vitro differentiation and ultrastructure of human extravillous trophoblast (EVT) cells.

Tissue explants of anchoring villi from the first trimester placentae cultured on extracellular matrix (Matrigel) give rise to EVT cells in vitro. This study was designed to address two issues important for further application of the described in vitro model: first, were the observed EVT cells derived by cell proliferation in vitro and second, what is the degree of homology between the in vivo and the in vitro differentiated EVT cells. The cultures (tissue and matrix) were prepared for light and electron microscopic (EM) examinations. Semi-thin sections from Spurr epoxy resin-embedded tissue were used to 'pop-off' the selected area for EM examination. Cell proliferation in vitro was assessed immunohistochemically using proliferative cell nuclear antigen (PCNA) antibodies. Since positive hPL immunostaining has been consistently demonstrated in the invasive subpopulation of EVT cells from placental bed in situ, hPL staining was used as a marker of EVT cell differentiation in vitro. It has been demonstrated that PCNA antibodies immunostained nuclei of cytotrophoblast cells from cell column at the base of the anchoring villi, indicating that these cells expressed proliferative activity in vitro. Cytotrophoblast proliferation resulted in the formation of the flattened zone of cell outgrowths at the tip of anchoring villi. Cells from the distal layer of the cell column detached gradually and migrated into the surrounding matrix. These cells appeared as individual, round-shaped EVT cells with smooth surface cell membrane. Their cytoplasm was rich in glycogen and contained large lipid droplets and flattened cisternae of the RER. Positive PCNA immunostaining, along with the presence of mitotic figures, indicated that EVT cells in vitro retained the ability for cell proliferation. As a result of cell proliferation and migration, the number of EVT cells increased during the culture period of 4 days. EVT cell glycogen content and lipid stores decreased progressively as they migrated into the matrix. Individual EVT cells, as well as EVT cell clusters, became surrounded by the clear zone of digested matrix. Some cells started to express strong positive staining with hPL antibodies as soon as they had migrated outside the villous explant. By day 4 of culture, a small percentage of EVT cells (about 5-10%) ceased to migrate, firmly attached to the substratum and appeared as irregular shaped cells with filopodia-like projections. Their cytoplasm contained dilated cisternae of RER, a small number of glycogen granules and bundles of actin-like filaments located in the cytoplasm inside the plasma membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell Differentiation↗