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A Kistler

Publications and source records attributed to A Kistler.

64 records · Page 4Linked to original sources
PubMed1975

Metal ion dependence of the binding of triiodothyronine by cytosol proteins of bullfrog tadpole tissues.

The binding of triiodothyronine by Rana catesbeiana tadpole tail fin, tail muscle, kidney, and liver cytosol was studied using dextran-coated charcoal to separate bound and free hormone. A metal ion dependency was suggested by the fact that EDTA decreased the binding of triiodothyronine 80 to 90% in tail fin and tail muscle cytosol. Inhibition of binding in kidney or liver was less, 40 to 50%. This inhibition could be restored by adding an excess of divalent cations with an order of potency of Mn2+ greater than Ca2+ congruent to Co2+ greater than Sr2+ greater than Ba2+ greater than Mg2+. Other chelators, e.g. o-phenanthroline, 8-hydroxyquinoline, and ethylene glycol bis(beta-aminoethylether)-N,N'-tetraacetate also decreased the binding of triiodothyronine, whereas citrate, oxalate, imidazole, and glycine had no effect. The triiodothyronine binding capacity of tail fin cytosol was reduced by EDTA treatment and dialysis against buffer. Ca2+ in the 1 to 10 mM range and Mn2+ at 1 mM could restore the binding to normal levels. Higher Mn2+ increased binding 70% above normal or to Ca2+-restored levels. The triiodothyronine cytosol binding activity was nondialyzable, heat-labile. pH-dependent, pronase-digestible, but unaffected by incubation with trypsin, RNase, and DNase, suggesting that the cytosol binding sites are acidic proteins. Scatchard analysis of triiodothyronine binding by the cytosol of different tissues, revealed Kassoc of 7.1 x 10(6) M(-1), 11.6 x 10(6) M(-1), 3.6 X 10(6) M(-1), and 68.0 x 10(6) M(-1) for tail fin, tail muscle, kidney, and liver cytosol, respectively. The corresponding maximal binding capacities in picomoles per mg of crude cytosol protein in these four tissues were 10.4, 0.86, 1.3, and 0.04, respectively.

Animals↗
PubMed1975

Binding by thyroid hormones by nuclei of cells from bullfrog tadpole tail fins.

The regression of the tadpole tail is under the direct control of the thyroid hormones and offers a unique system for the study of the action of these hormones. We have examined the binding of L-triiodothyronine (T3) and L-thyroxine (T4) in vitro using tail fin bricks which included epidermal and connective cells. The binding of 125I-labeled hormones was followed in both nuclear and extranuclear fractions. High affinity and limited capacity sites for T3 and T4 were observed only for the nuclear fraction. Scatchard plots gave similar apparent dissociation constants for both hormones, about 10(-10)M. The maximum number of binding sites per nucleus for T3 was about 1500 and for T4 about 800. There was no significant change in the chemical identity of [125I]T3 and [125I]T4 which was associated with binding in the nuclei. Nuclear binding of [125I]T4 was inhibited competitively for both unlabeled T3 and T4, but unlabeled T3 displaced [125I]T3 significantly more than unlabeled T4. Thus, both binding and competition data support the conclusion that tadpole tail nuclei had more T3 than T4 binding sites.

Animals↗
PubMed1975

Binding of thyroxine and triiodothyronine by nuclei of isolated tadpole liver cells.

The binding of L-triiodothyronine (T3) and L-thyroxine (T4) to cytoplasm and nuclei has been studied in isolated Rana catesbeiana tadpole liver cells. Nuclear binding for both thyroid hormones occurred more slowly at 4 C than at 25 C, but reached the same level as at 25 S. Scatchard analyses suggest high affinity, saturable binding sites for both hormones in the nuclear but not in the cytoplasmic fraction. Apparent equilibrium dissociation constants were 6.8 X 10(-10)M and 4.6 X 10(-10)M for T3 and T4, respectively. The maximum number of binding sites per nucleus for T3 was about 12,300 and for T4 about 2,300. Unlabeled T3 competed for the binding of [125I]T3 to nuclei more effectively than unlabeled T4. No difference in the competition of [125I]T4 binding with non-radioactive T3 or T4 was found. Chromatographic analysis of the bound nuclear radioactivity demonstrated no chemical modification for either hormone.

Animals↗
PubMedDate not supplied

Chondrogenesis of limb-bud cells: improved culture method and the effect of the potent teratogen retinoic acid.

A new apparatus for the mild and reproducible dissociation of rat limb buds into single cells is described. The growth and differentiation of the embryonic mesenchyme cells into chrondrocytes was markedly affected by the conditions of tissue dissociation and the serum used. The degree of chondrogenesis was assessed by alcian blue staining, specific for cartilage matrix. Retinoic acid, a known teratogen, inhibited chondrogenesis completely in a dose-dependent manner. The determination of the quantifiable end-point, IC50 in this cell-culture system, may be suitable to compare the activity of various retinoids and eventually to determine their teratogenic potential.

Animals↗