Hildegard Sourgens

Changes in TSH-immunoreactivity in the pars tuberalis and pars distalis of the fetal rat hypophysis following maternal administration of propylthiouracil and thyroxine

SummaryThe pars tuberalis (pt) of the adenohypophysis is unique in its close spatial relationship to the neurohemal contact area of the median eminence. The morphology of pt-specific secretory cells does not resemble cell types of the pars distalis (pd); the functional role of these cells within the endocrine system is still unknown. One group of young mature female Wistar rats received propylthiouracil (PTU), a second group thyroxine (T4) (10 mg/l each in drinking water) from about 3 weeks prior to the expected pregnancy and throughout the experiment. On gestation day 20, the fetuses were obtained by laparatomy. Serial sections from the rostral portion of the pt and from the pd were immunostained using the peroxidase-antiperoxidase method. TSH concentrations were determined by RIA in serum and pituitaries; T4 was measured in serum. An antiserum against rat (r) TSH revealed a moderate positive reaction of nearly all cells of the pt in the control group. In both experimental groups the pt-specific cells showed weak or no immunoreactivity. Sections of all groups were negative with anti(r)-LH,-GH,-PRL. In contrast to controls, only a few immature TSH-cells could be found in sections of the pd in the T4-group, while concentrations of TSH in blood and hypophysis were very low. TSH-cells in the PTU-group were enlarged and less intensely stained. TSH-concentrations were decreased in the hypophysis, blood levels were elevated. All sections of the pd-specific cell populations showed positive immunoreactions with anti(r)-LH,-GH,-PRL. The present results suggest that pt-specific secretory cells of the fetal rat possess TSH immunoreactivity but do not resemble the thyrotropes of the pd. Marked differences in immunoreactivity displayed by the experimental groups indicate that pt-specific cells respond to changes in the fetal thyroid status and are a component of the thyroid-regulating system in addition to the thyrotropes of the pd. This novel aspect of pt function is discussed in connection with recent results concerning melatonin receptors found in the pt and the inhibitory influence of the pineal gland exerted on the thyroid gland.

Severe Tardive Dyskinesia in Affective Disorders: Treatment with Vitamin E and C

Tardive dyskinesia caused by antipsychotic treatment is a severe problem not only in the management of schizophrenia, but also of affective disorders. Vitamin E monotherapy has been used in schizophrenic patients with tardive dyskinesia. Pharmacologists warn against high dosage of vitamin E because of its pro-oxidative effects on low-density lipoprotein with consecutive cardiac risks. Addition of vitamin C probably reduces this risk because of its interactions with vitamin E, i.e. vitamin C reduces vitamin E radicals formed when vitamin E scavenges the oxygen radicals. We have therefore tested the safety and efficacy of combining vitamin C and E in a sample of patients with affective disorders and tardive dyskinesia who had previously been treated with antipsychotics due to psychotic symptoms. In all 6 patients, a reduction of tardive symptomatology was seen. In our sample, no side effects were observed. Further studies on this combination therapy are suggested.

The relative merits of polyethyleneglycol as a separating agent in the radioimmunoassay of thyroid hormones

Polyethyleneglycol (PEG) has been recommended as a separating agent in the assay of some peptide hormones (Desbuquois, B. and Aurbach, G.D. (1971) J. Clin. Endocrinol. 33, 732) and several substances of low molecular weight (Ratcliffe, J.G. (1974) Br. Med. Bull. 30, 32). In the present study the PEG-separation technique has been modified and adapted for the assay of thyroid hormones. Separation with PEG has the advantage of being cheap, rapid and relatively non-susceptible to disturbances as compared with the charcoal and double-antibody-solid phase techniques. The influence of different buffer systems, varying pH and ionic strength, on the precipitation process with PEG also has been investigated. Of the different systems tested barbital buffer containing 0.1% human serum albumin proved to be the best, preferably in the presence of bovine gamma-globulin. In the radioimmunoassay of T3 variations in pH and ionic strength are of minor importance whereas in the radioimmunoassay of T4 the adherence to a certain pH is recommended. Barbital buffer containing 0.1% bovine serum albumin was inadequate in the T3 radioimmunoassay, while Tris and phosphate buffers did not give satisfying results for either radioimmunoassay.

Ultrastructure of fetal pars-tuberalis-specific secretory cells under the influence of propylthiouracil and thyroxine.

The rat pituitary pars tuberalis (pt) is a functional and morphological unique component of the adenohypophysis. It mainly consists of specific secretory cells whose morphological and functional characterization is far from being complete. In this study the ultrastructure of fetal secretory pt cells developing under hypo- and hyperthyroid conditions was examined. Besides controls, young mature pregnant Wistar rats were treated with propylthiouracil (PTU) or thyroxine (T4). Areas of pt cells and of their nuclei were measured. Different cell organelles per cell were counted, and area densities of these organelles were determined. While the number of dictyosomes per cell area did not change, the area densities of long ribbons increased significantly in the experimental groups. Lysosomes and secretory granules, however, were found to be significantly diminished in pt cells of T4- and PTU-treated animals. The latter finding corresponds to earlier investigations when changes of the thyroid-stimulating-hormone-like immunoreactivity of fetal pt-specific cells were observed under the same experimental conditions. Results indicate that fetal pt-specific cells respond to changes of thyroid status in a manner different from pars distalis thyrotrophs. An interaction of pt-specific cells in thyroid regulation mechanisms is assumed.

Effects of Lithospermum officinale and Related Plants on Hypophyseal and Thyroid Hormones in the Rat

AbstractThe antihormonal activity of Lithospermum officinale (Boraginaceae) and Lycopus virginicus and other Lamiaceae has been investigated in the rat. L. officinale cold water freeze dried extracts (FDE) significantly lowered thyroid hormone content in the serum whereas an inactivated extract exhibited a considerable loss of biological activity. The efficacy of different plant extracts greatly depended on the extraction procedure: extraction of powdered leaves with boiling water or ethanol yielded FDEs without thyroid hormone-lowering capacity. The chemical oxidation of a hot-water (100°C) extract by KMnO4 served to reintroduce the antihormonal effectiveness. In a goiter suppression test, the chronic administration of L. officinale FDE greatly suppressed TSH-levels and consequently goiter weight. The antithyrotropic and antithyroidal activity of a variety of plant extracts was accompanied by an additional prolactin diminution. Lithospermum officinale exhibited a strong antigonadotropic effectiveness and...

Pharmacodynamic Effects of Lithospermum Officinale on the Metabolism of Thyroid Hormones in the Rat

The antithyroid properties of Lithospermum officinale which had been investigated in the guinea pig, were confirmed in the rat. Serum hormone levels of thyroxine and triiodothyronine and the secretion rate (endocytosis) were examined. Several sites of action are discussed.