Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A primary rat choroidal epithelial cell culture system was developed to investigate mechanisms of heavy metal toxicity on the blood-cerebrospinal fluid (CSF) barrier. Epithelial cells were dissociated from choroidal tissue by pronase digestion and cultured in standard DMEM culture media supplemented with 10% fetal bovine serum and 10 ng epithelial growth factor per ml. The procedure yielded 2-5 x 10(4) cells from pooled plexuses of three to four rats, and a viability of 77-85%. The cultures displayed a dominant polygonal type of epithelial cells, with a population doubling time of 2-3 d. The cultures were of distinct choroidal epithelial origins. For example, immunocytochemical studies using monospecific rabbit anti-rat TTR polyclonal antibody revealed a strong positive stain of transthyretin (TTR), a thyroxine transport protein exclusively produced by the choroidal epithelia. Also, reverse-transcriptase polymerase chain reaction (PCR) confirmed the presence of specific TTR mRNA in the cultures. The cultures were further adapted to grow on a freely permeable membrane sandwiched between two culture chambers. The formation of an impermeable confluent monolayer occurred within 5 d after seeding and was verified by the presence of a steady electrical resistance across the membrane (80 +/- 10 ohm per cm2). The epithelial barriers appeared to actively transport [125I]-thyroxine from the basal to apical chamber. These results suggest that this primary cell culture system possesses typical choroidal epithelial characteristics and appears to be a suitable model for in vitro mechanistic investigations of blood-CSF barrier.
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PMID:Primary culture of choroidal epithelial cells: characterization of an in vitro model of blood-CSF barrier. 954 34

Embryonic stem (ES) cells are pluripotent cells derived from the inner cell mass of fertilized blastocysts in vitro. ES cells can be induced to undergo differentiation into potentially all cell types. The aim of this study is to examine the differentiating potential of mouse ES cells into hepatocytes in the presence of retinoic acid (RA), hepatocyte growth factor (HGF), and beta-nerve growth factor (beta-NGF). RA, HGF, and beta-NGF were added to the cell culture. Hepatocyte induction was confirmed morphologically, as well as biochemically, through immunohistochemical assays of alpha1-antitrypsin (alpha1-AT) and alfafetaprotein (AFP) expression and reverse-transcriptase polymerase chain reaction tests for the presence of albumin, transthyretin, glucose 6 phosphates, hepatic nuclear factor 4, and SAPK/ERK kinase-1 (SEK1) messenger RNA, produced only by functioning hepatocytes. Fifteen days after the addition of HGF and beta-NGF to the cell culture, many epithelioid cells were noticed. alpha1-AT, AFP, albumin, transthyretin, glucose 6 phosphates, hepatic nuclear factor 4, and SEK1 messenger RNA expression also was detected, indicating successful ES cell differentiation into functioning hepatocytes. However, in the presence of RA alone, only transthyretin messenger RNA was positive, whereas no other expression pertaining to functioning hepatocytes could be detected. In the presence of HGF and beta-NGF, mouse ES cells can differentiate into functioning hepatocytes, whereas RA function is limited.
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PMID:Generation of hepatocytes from cultured mouse embryonic stem cells. 1452 6

Two porcine cell lines of yolk-sac visceral endoderm, designated as PE-1 and PE-2, were derived from in vivo 11-d porcine blastocysts that were either ovoid (PE-1) or at the early tubular stage of elongation (PE-2). Primary and secondary culture of the cell lines was done on STO feeder cells. The PE-1 and PE-2 cells morphologically resembled visceral endoderm previously cultured from in vivo-derived ovine and equine blastocysts and from in vitro-derived bovine blastocysts. Analysis of the PE-1- and PE-2-conditioned medium by 2D-gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry demonstrated that they produced serum proteins. Reverse transcriptase polymerase chain reaction analysis showed that the cells expressed several genes typical for yolk-sac endoderm differentiation and function including GATA-6, DAB-2, REX-1, HNF-1, transthyretin, alpha-fetoprotein, and albumin. Unlike a porcine liver cell line, the PE-1 and PE-2 cell lines had relatively low inducible P-450 content and EROD activity, and, while they cleared ammonia from the cell culture medium, they did not produce urea. Transmission electron microscopy revealed that the cells were a polarized epithelium connected by complex junctions resembling tight junctions and by lateral desmosomes. Rough endoplasmic reticulum was prominent within the cells. Immunocytochemistry indicated that the PE-1 cells expressed cytokeratin 18 and had robust microtubule networks similar to those observed in in vivo porcine yolk-sac endoderm. Metaphase spreads prepared at passage 26 of the PE-1 cell line indicated a diploid porcine karyotype of 38 chromosomes. The cells have been grown for over 1 yr for multiple passages at 1:10 or 1:20 split ratios on STO feeder cells. The cell lines will be of interest as an in vitro model of the porcine preimplantation yolk-sac tissue.
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PMID:Isolation and characterization of porcine visceral endoderm cell lines derived from in vivo 11-day blastocysts. 1757 21