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Biomedical subjects

D A Meier

Publications and source records attributed to D A Meier.

8 recordsLinked to original sources
PubMed1991

Quantitation of GLUT1 and GLUT4 mRNA using a solution hybridization assay.

The development of a solution hybridization assay for detecting GLUT1 and GLUT4 mRNA is described. The details of this assay are described in which copy RNA is used to quantitate messenger RNA in total RNA samples. This solution hybridization assay is highly specific and reproducible and is significantly more sensitive than Northern blotting. Since GLUT mRNAs can be quantitated in as little as 25 mg tissue, this technique is essential when the supply of tissue is limited. Furthermore, the elimination of gel-based separation techniques allows for mRNA quantitation in several hundred samples within two days following isolation of samples.

Animals↗
PubMed1991

Differential binding of GH3 and pituitary protein extracts to the estrogen-dependent enhancer of the rat prolactin gene.

Extracts of two prolactin (PRL) producing cells (GH3 cells and rat pituitary tumors) were compared for their ability to bind to a PRL DNA fragment that contained sequences important for estrogen enhancement of PRL transcription. The ability of estradiol (E2) to alter concentrations of existing PRL enhancer binding proteins or to promote the appearance of additional binding proteins was also examined. When diethylstilbestrol (DES)-induced pituitary tumor extracts were examined for protein binding to the same DNA fragment, a different banding pattern was observed than the banding pattern seen using protein extracts from GH3 cells, suggesting that PRL DNA binding proteins differ between GH3 cells and rat pituitary tumors. The differences in PRL DNA binding may result from the fact that approximately 20% of GH3 cells are lactotrophs, while 80% of DES-induced pituitary tumor cells are lactotrophs. In addition, no change in the relative concentrations of proteins binding to the upstream regulatory element was observed following treatment of GH3 cells with E2.

Animals↗
PubMed1990

Estrogen receptor binding to a DNA response element in vitro is not dependent upon estradiol.

Gel shift assays were employed to distinguish between the contribution of 17 beta-estradiol (E2) and a short heating step to the ability of the rat uterine cytosolic estrogen receptor (ER) to bind to the estrogen response element (ERE) from the vitellogenin A2 gene (vitERE). Despite the popularity of models in which the ER is a ligand-activated DNA-binding protein, these studies find that estrogen does not significantly contribute to receptor-DNA complex formation. An avidin-biotin complex with DNA (ABCD) assay was utilized to obtain quantitative measurement of the affinities of the ER for the vitERE and a mutant sequence. Scatchard analysis gave a dissociation constant of 390 +/- 40 pM for the E2-occupied, heated ER to the vitERE. The data fit a one-site model and evidence for cooperatively was not observed. A dissociation constant of 450 +/- 170 pM was obtained for the unoccupied, heated ER, leading to the conclusion that estrogen was not necessary for specific binding to DNA. The percentage of ER capable of binding vitERE varied with each cytosol preparation, ranging from 60 to 100% and estrogen did not appear to affect this variation. Competition against the vitERE with a 2-bp mutant sequence showed a 250-fold lower relative binding affinity of the receptor for the mutant over the vitERE sequence. This ability of the ER to discriminate between target and nonspecific DNA sequences was also not dependent on the presence of estrogen.

Animals↗
PubMed1990

A large substernal goiter as a cause of a pulmonary perfusion defect.

A pulmonary perfusion defect was caused by an extremely large anterior mediastinal mass subsequently proved by I-131 imaging to be an intrathoracic extension of a cervical goiter. Substernal goiter is not known to be reported previously as one of the causes of a perfusion defect in lung scanning.

Aged↗
PubMed1987

Estradiol stimulation of glucose transport in rat uterus.

Glucose transport in rat uterus was investigated in order to determine whether the stimulation of transport by estradiol was the result of an increase in the amount of glucose transport protein in plasma membranes. In cycling rats, transport was highest during proestrus, the day on which serum estradiol concentrations are highest. In ovariectomized rats, the stimulation of transport was estrogen specific and was nearly complete within 2-3 h after injection of 0.1 microgram estradiol per animal. Estradiol stimulation resulted in a 2- to 3-fold increase in Vmax of 2-deoxy-D-glucose transport with no significant change in Michaelis-Menten constant (Km). Inhibition of the stimulation by cycloheximide or actinomycin D could not be demonstrated, although cycloheximide treatment did cause an increase in the basal rate of transport up to that observed with estradiol treatment. Upon polyacrylamide gel electrophoresis followed by Western blotting, a single protein in uterine plasma membranes reacted with a rabbit antiserum made against purified human erythrocyte glucose transport protein. This protein, believed to be the glucose transport protein, had a mol wt of 49,000 and appeared as a broad band as expected for a glycoprotein. It was found by a protein A-linked immunoassay that the amount of transport protein in uterine plasma membranes was 3.2 +/- 0.4% of the amount in human erythrocyte ghosts. Estradiol treatment had no effect on this value. These data suggest that the stimulation of glucose transport by estradiol occurred by an increase in the intrinsic activity of the transport protein rather than by an increase in the amount of transport protein in plasma membranes.

Animals↗