PubMed Health⌕ Search

Biomedical subjects

W Höppner

Publications and source records attributed to W Höppner.

60 records · Page 4Linked to original sources
PubMed1985

Effect of thyroid state on cyclic AMP-mediated induction of hepatic phosphoenolpyruvate carboxykinase.

Hepatic phosphoenolpyruvate carboxykinase (PEPCK) is significantly increased in the hyperthyroid starved rat, and moderately decreased in the hypothyroid starved rat. As tri-iodothyronine by itself has only a small and sustained effect on the induction of this enzyme, as was previously shown in the isolated perfused organ, the effect of hypo- and hyper-thyroidism on the increase in cytosolic PEPCK provoked by dibutyryl cyclic AMP (Bt2cAMP) was investigated in vivo and in the isolated perfused liver. Compared with euthyroid fed controls, in hypothyroid fed rats Bt2cAMP provoked in 2 h only a small increase in translatable mRNA coding for PEPCK. In contrast, in hyperthyroid animals PEPCK mRNA as measured by translation in vitro was already increased in the fed state, and further enhanced by Bt2cAMP injection to values as in euthyroid controls. Under all thyroid states a close correlation between PEPCK mRNA activity and PEPCK synthesis was observed. In the isolated perfused liver from the hyperthyroid fed rat, the increase in PEPCK provoked by Bt2cAMP or Bt2cAMP + isobutylmethylxanthine was considerably enhanced compared with those obtained in livers of hypothyroid rats. Also, adrenaline provoked a stimulated induction of PEPCK in hyperthyroid rats compared with hypothyroid rats. To summarize, our data indicate that the primary action of thyroid hormones on the synthesis of hepatic cytosolic PEPCK is to accelerate the cyclic AMP- or adrenaline-induction of the enzyme, acting primarily at a pretranslational level.

Animals↗
PubMed1985

Study on the carbohydrate specificity of antibodies formed in rabbits to synthetic glycoproteins with the carbohydrate structure of asialo-glycophorin A.

Antibodies formed in rabbits to synthetic glycoproteins with the disaccharide structure beta-D-Gal-(1-3)-D-GalNAc, the carbohydrate moiety of desialylated glycophorin A, were investigated for their carbohydrate specificity by hemagglutination techniques and radioimmunoassay. The synthetic disaccharide was coupled to human serum albumin as carrier protein using different spacer groups and different configurations of the disaccharide spacer linkage. Radioimmunological inhibition experiments using a number of different derivatives of the carbohydrate group as inhibitors revealed a significant specificity of the antibodies for the oligosaccharide structure. However, the nature of the conjugation of the disaccharide to the carrier protein was found to be important for defining the specificity of the antibodies. Furthermore the arrangement of the hapten groups in the synthetic antigen had an important influence on the antigen-antibody reaction. No cross-reactions were observed between asialo-glycophorin A and the different synthetic antigens. Synthetic antigens provide a valuable tool for generating carbohydrate-specific antibodies. However, if the synthetic hapten molecule is small compared to the combining site of antibodies, the specificity of the immunological reaction is significantly influenced by the synthetic spacer arm or even the carrier protein.

Animals↗
PubMed1985

Use of synthetic antigens with the carbohydrate structure of asialoglycophorin A for the specification of Thomsen-Friedenreich antibodies.

The panagglutination phenomenon described by Thomsen and Friedenreich (TF) is due to the reaction of naturally occurring TF-antibodies with the carbohydrate group beta-D-Gal-(1-3)-D-GalNAc of desialylated glycophorin A, the major glycoprotein component of the erythrocyte membrane. The specificity of human TF-antibodies reacting with this disaccharide was investigated by hemagglutination inhibition assay and radioimmunoassay using various synthetic oligosaccharides and neoglycoproteins as well as asialoglycophorin A. The results indicate that TF-antibodies represent a heterogeneous mixture of carbohydrate-specific antibodies. The disaccharide beta-D-Gal-(1-3)-D-GalNAc is the common structure recognized by all TF-antibodies. However, the conjugation mode of the carbohydrate to the carrier protein is important for defining the specificity of different subpopulations of TF-antibodies. The immunological reaction depends on the configuration of the glycosidical linkage as well as on the chemical nature of the aglycon, which is coupled to the disaccharide. These findings suggest that the heterogeneity of natural TF-antigens is due to the wide distribution of the carbohydrate structure beta-D-Gal-(1-3)-D-GalNAc. The characterization of TF- or TF-like antibodies directed to particular natural TF-antigens (e.g. asialoglycophorin A, tumor TF-antigens, glycolipids, bacterial antigens) requires TF-analogues, which contain the additional molecular regions together with the TF-disaccharide. These structures, apart from the TF-hapten, are obviously important for defining the immunodeterminant group of TF-antigens of different origin.

Antibodies↗
PubMed1984

Permissive action of thyroid hormones in the cAMP-mediated induction of phosphoenolpyruvate carboxykinase in hepatocytes in culture.

Thyroid hormones are known to stimulate in vivo the synthesis of several liver proteins. In order to determine their role in the regulation of important hepatic proteins at the cell level, the effect of T3 on the induction of the glucoregulatory enzyme phosphoenolpyruvate carboxykinase (PEPck) was investigated in cultured hepatocytes. The cells were isolated from adult hypothyroid rats and exposed to a chemically defined medium, devoid of serum supplement and hormone-free over a period of 48 h. Addition of T3 to the medium had only a minor effect on PEPck induction. Dibutyryladenosine 3',5'-monophosphate (Bt2cAMP) or epinephrine provoked significant increase in PEPck synthesis within 4-6 h. Simultaneous addition of T3 was found significantly to promote the Bt2cAMP-mediated enzyme induction. Physiological concentrations of T3 (10 pM to 1 nM) were found to be effective in enhancing this cAMP-mediated signal. Exposure of the cells to T3 for only 90 min, 16 h prior to addition of Bt2cAMP was nearly as effective as continuous exposure to T3 in enhancing the cAMP-effect on PEPck synthesis. In contrast, no effect of T3 on the Bt2cAMP-induced tyrosine-aminotransferase activity could be detected. It is concluded that the role of T3 on the cAMP-elicited PEPck synthesis is selective, rapid, primarily permissive and significant within the physiological range of the hormone. In addition, these data indicate that such hepatocyte cultures prepared from hypothyroid rats are ideally suited to the analysis of the regulatory role of thyroid hormones on specific gene expression.

Animals↗
PubMedDate not supplied

[Examination of the fertility of patients with malignant testicular cancer at the time of orchiectomy. The question of the opinion on cryopreservation].

Semen analyses from 29 patients with testicular tumours were done, 19 were examined before and after orchidectomy but before any other treatment. There was no evident difference in both of these examinations. Therefore it is possible to obtain enough time for cryopreservation, because the stricken patients can be first treated by unilateral orchidectomy without loss in quality of the semen. Hendry et al. (1983) accepted for sperm freezing only samples with more than 10 mill/ml spermatozoa and more than 30% motility. 17 of our 29 patients (58.6%) fulfilled that condition. Thus, in more patients cryopreservation can be considered.

Fertility↗