Biomedical subjects

G Bechtner

Publications and source records attributed to G Bechtner.

21 records · Page 2Linked to original sources

PubMed1987

Evidence that thyroid growth promoting activity of immunoglobulin preparations is due to contamination with EGF.

Immunoglobulin (IG) preparations may be contaminated with growth factors. Therefore, we investigated whether the growth promoting activity in IG preparations (thyroid growth stimulating immunoglobulins = TGI) from patients with sporadic goitre may be caused by contaminating EGF (epidermal growth factor). EGF in sera as well as in indifferently prepared IG of patients with recurrent goitre (n = 23), Graves' disease (n = 19) and normals (n = 17) was determined by EGF receptor assay. Comparatively, the ability for stimulating thyroid cell growth was determined in these IG preparations (2 mg/ml). EGF in ammoniumsulphate (AS) precipitates was about 2-fold higher than serum EGF. The growth promoting activity of indifferent IG preparations correlated with the EGF content. After additional purification on protein A-sepharose, neither EGF, nor a growth promoting activity was found in these IG preparations. We therefore conclude, that the growth promoting activity of crude IG preparations may be due to a contamination with EGF.

Animals↗

PubMed1987

Paracrine interaction between thyrocytes and fibroblasts.

Cell free supernatants (conditioned medium) of isolated porcine thyroid follicles, stimulated with EGF (5 ng/ml) or TSH (1-1000 microU/ml), were tested for a mitogenic activity for fibroblasts. Whereas TSH-conditioned medium dose-dependently stimulated [3H]thymidine incorporation into DNA of fibroblasts, only a weak stimulation was found with EGF. However, when the changes in cell number were determined, a significant increase was only found with EGF-conditioned medium from thyroid follicles. The cause of this discrepancy is a dose-dependent stimulation of [3H]thymidine incorporation into fibroblasts by cAMP and thyroid hormones. Cyclic AMP, however, does not stimulate growth of fibroblasts. IGF I production is stimulated in fibroblasts by basal as well as EGF stimulated conditioned medium of thyroid follicles. In contrast, TSH-conditioned medium inhibited IGF I production in fibroblasts. Conditioned medium itself is free of detectable IGF I. As IGF I stimulates not only growth of fibroblasts, but also of thyrocytes, we conclude, that conditioned medium from thyrocytes stimulates IGF I production in fibroblasts, which itself stimulates fibroblast and thyrocyte growth.

Animals↗

PubMed1985

Characterization of microheterogeneity of human thyroglobulin from different thyroid disorders.

Human thyroglobulin (Tg) was isolated to apparent purity from various thyroid tissue samples obtained after surgery. Iodine and iodothyronine content of Tg was determined. Isoelectric focussing (IEF) was performed on thin layer agarose gels. Tg revealed a microheterogeneity of 6 bands in the range between pH 4.2 and 4.6. The intensity of the single bands depended on the iodothyronine content of Tg. With increasing degree of iodination, the bands with a lower pI (pI 4.35, 4.40) became more prominent, whereas the bands with higher pI (pI 4.55, 4.60) diminished. This typical change in microheterogeneity pattern could be confirmed by kinetic in vitro iodination and consecutive iodothyronine formation of low iodinated Tg (0.05% iodine). After in vitro desialylation, the bands shifted to a higher pH range (pH 4.60 to pH 4.90), but no reduction of the number of bands occurred. Even in desialylated Tg microheterogeneity is still dependent on iodine content. These results suggest, that the microheterogeneity of Tg is influenced, but not caused by different iodine and NANA content. Different polypeptide composition may be responsible for the microheterogeneity of Tg. In thyroid diseases without disturbance in Tg synthesis (endemic, diffuse and nodular goitre, Graves' disease) variations in relative intensity of single bands could be related to differences in iodine content. In thyroid cyst fluid and cold nodules in addition to low iodinated Tg, further bands were found with pI-values comparable to desialylated Tg.

Adenoma↗