Biomedical subjects

I Cheynel

Publications and source records attributed to I Cheynel.

3 recordsLinked to original sources

PubMed2000

Revised T3 uptake and T4-to-T3 conversion in brain and cerebellum of 10-day-old rats: a compartment analysis.

The peripheral and cerebral metabolism of thyroid hormones in 10-day-old rats was evaluated by measuring the kinetics of thyroxine (T4) and 3,5,3'-triiodothyronine (T3) fluxes. Labeled iodo-compounds were measured in the plasma, cerebellum and brain (without cerebellum) for 24 hours after the intravenous injection of [125I]T4 plus [131I]T3. Data were interpreted by compartment analysis. T4 was produced at 8.93 pmol x h(-1) and T3 at 2.26 pmol x h(-1) for 22.7 g body weight. The T4 and T3 distribution volumes were 4.26 and 22.7 ml, whereas the extra-cellular fluid volume was 9.42 ml. T4 was therefore considered to be mostly extra-cellular and T3 mostly intracellular. This was confirmed in the brain and cerebellum, where the extra-cellular fluid (ECF) fraction was 0.021 ml/g organ and the tissue-to-plasma ratio of labeled and endogenous hormones was 0.54-6.54 ml plasma/g tissue for T3 and 0.048-0.136 ml plasma/g tissue for T4. The T3 in the brain and cerebellum was distributed in several pools. The first, representing 11% of the cerebellum and 8% of the brain (without cerebellum) T3, was quickly exchanged with circulating T3. The second pool, derived from the local T4 5'-deiodination, represented 48% of the cerebellum and 94% of the brain (without cerebellum) hormone; a possible third pool (41% of the hormonal content) in the cerebellum appeared to be unlabeled by radioactive T3, and motionless. The in vivo T4 to T3 conversion, as a function of weight, accounted for 21% of cerebellum needs and 43% of brain needs. The rest was provided by T3 uptake.

Animals↗

PubMed1999

5'-deiodinase activity in cultured glial and fibroblastic cells from the cerebella of newborn rats.

The cerebellum of young rats contains significant 5'-deiodinase (5'-D) activity, but technical difficulties have made it impossible to identify the enzyme in cultured cerebellar astrocytes. We have developed a culture method which allows cerebellar astrocytes from 6-day-old rats to grow and develop 5'-D activity. Astrocytes cultured for 2 weeks in medium containing 3.25 microM reduced glutathione (GSH) and 0.21 microM vitamin E (VitE) as alpha-tocopherol had 5'-D activity which was stimulated by 1 mM dibutyryl cyclic adenosine monophosphate (dBcAMP) given 16 hours before measuring enzyme activity. Cells cultured without GSH and VitE showed little 5'-D activity, which was not stimulated by dBcAMP Primary cultures of cerebellar astrocytes were cultured for four weeks with or without GSH+VitE, and stimulated by dBcAMP had high 5'-D activity, but were also sometimes contaminated with fibroblasts. The effect of such contamination on the astrocyte 5'-D activity was assessed by preparing primary cultures of fibroblasts from the meninges surrounding 6-day-old rat cerebella. They were grown in the same media and under the same conditions as the astrocytes. The cultured fibroblasts had 5'-D activity independent of GSH+VitE or culture time. The 5'-D activity of both cell populations could be type II 5'-deiodinase (5'-DII) because it was not inhibited by 6-n-propylthiouracil (PTU). Thus, cerebellar astrocytes cultured for 2 weeks in medium containing GSH and VitE have 5'-DII activity. Prolonged cultures favor enzyme activity, but also enhance contamination with fibroblasts, which may also show 5'-DII activity.

Animals↗

PubMed1997

Interactions between the human RNA polymerase II subunits.

As an initial approach to characterizing the molecular structure of the human RNA polymerase II (hRPB), we systematically investigated the protein-protein contacts that the subunits of this enzyme may establish with each other. To this end, we applied a glutathione S-transferase-pulldown assay to extracts from Sf9 insect cells, which were coinfected with all possible combinations of recombinant baculoviruses expressing hRPB subunits, either as untagged polypeptides or as glutathione S-transferase fusion proteins. This is the first comprehensive study of interactions between eukaryotic RNA polymerase subunits; among the 116 combinations of hRPB subunits tested, 56 showed significant to strong interactions, whereas 60 were negative. Within the intricate network of interactions, subunits hRPB3 and hRPB5 play a central role in polymerase organization. These subunits, which are able to homodimerize and to interact, may constitute the nucleation center for polymerase assembly, by providing a large interface to most of the other subunits.

Baculoviridae↗