Kazuhiko Mashita

Morphological and biochemical studies on minocycline-induced black thyroid in rats.

The thyroid glands of the rats treated with 100 mg/kg/day of minocycline for 35 days showed black discoloration. In these thyroids, brown pigment granules were seen in the follicle epithelial cells, and they histochemically stained in the same manner as melanin. By electron microscopy, the deposition of the electron-dense material first occurred in lysosome-like granules and, with further administration, was observed also in the rough endoplasmic reticulum in some cells. Thin-layer chromatography showed that the Rf value of the extract from minocycline-treated rat thyroid was the same as that of the black substance obtained by mixing minocycline and 3% hydrogen peroxide but different from that of melanin. In minocycline-treated rats, the release of thyroxine (T4) from perifused thyroids was significantly less than that from control, and the analysis of iodoamino acids showed an increased monoiodotyrosine fraction. Thus, the pigment of thyroid in minocycline-treated rats was demonstrated to be a metabolic derivative of minocycline itself and minocycline may interfere with thyroid function in high-dose, long-term treatment.

THE DIFFERENTIAL DIAGNOSIS OF CYSTIC NECK MASSES BY THE DETERMINATION OF THYROGLOBULIN CONCENTRATIONS IN THE ASPIRATES

Thyroglobulin (Tg) concentrations in the aspirates of various types of cystic neck masses were measured by RIA to assess the usefulness of this determination in differential diagnosis. The subjects consisted of 16 patients, whose final diagnoses were all established on the basis of operative results; three patients had follicular thyroid adenomas (F‐Ad), 11 had papillary thyroid carcinomas (P‐Ca), one had a thyroglossal duct cyst (TDC) and one had a lateral cervical cyst (LCC). Tg concentrations in the cyst fluids of F‐Ad and P‐Ca were very high (0·042–2·83 mg/ml) compared with serum Tg concentrations. There was no difference in Tg concentrations in the fluids of P‐Ca between primary lesions (n= 5) and metastatic lesions (n= 6). On the other hand, Tg concentrations of TDC and LCC were very low (< 100 ng/ml). Difficulty was experienced in diagnosing three patients, even though they had been examined by all nonsurgical diagnostic techniques. However, an occult thyroid carcinoma with lymph node metastasis was diagnosed by demonstrating a high Tg concentration in the aspirate of the cystic lymph node. T3 concentrations in cyst fluids of F‐Ad were higher than those of P‐Ca. T3 concentrations in the fluids of P‐Ca, TDC and LCC did not differ, and were similar to serum T3 levels. Cytology of cyst fluids was positive in four of 10 patients examined with P‐Ca. In conclusion, we can clearly confirm the thyroid origin of a cystic neck mass by demonstrating a high Tg concentration in the aspirate. This is especially useful for diagnosis in patients with thyroid carcinoma, including occult thyroid carcinomas with cystic lymph node metastasis.

THYROTOXIC MYOPATHY ASSOCIATED WITH SUBACUTE THYROIDITIS

We report a case of subacute thyroiditis complicated by thyrotoxic myopathy. Previously thyrotoxic myopathy has been described as being associated with GRAVES disease. The patient in this study was a 35‐year‐old man who developed proximal dominant muscular weakness and atrophy during the course of subacute thyroiditis. His myopathic symptoms regressed as his serum thyroxine and triiodothyronine levels returned to normal, however it took a relatively long period of time for them to do so. This suggests that marked myopathy may develop even in cases of subacute thyroiditis if the thyrotoxic state persists for a long period of time.

Release of 3,5,3'-triiodothyronine, thyroxine and thyroglobulin from TSH-stimulated mouse thyroids in the perifusion system

We established a perifusion system using mouse thyroid glands. In this system, TSH increased the release of T3 and T4 significantly, and the response of thyroglobulin to TSH was delayed in comparison with that of T3 and T4.

The inhibitory effect of forskolin on antibody-dependent cell-mediated cytotoxicity using Chang liver cells as target cells.

The effect of forskolin, a unique adenylate cyclase activator, on antibody-dependent cell-mediated cytotoxicity (ADCC) was examined. ADCC was assayed using Chang liver cells as the target cells, immuned rabbit serum as the antibody and healthy human peripheral blood mononuclear cells (PBMNC) as the effector cells. Forskolin at concentrations ranging from 1 to 20 microM significantly inhibited ADCC in a dose-dependent manner. By the addition of forskolin, cyclic AMP levels did not change in Chang liver cells but increased in PBMNC. Therefore, it appears that forskolin exerted an inhibitory effect on ADCC by increasing the intracellular cyclic AMP levels in PBMNC, the effector cells.

ELEVATED SERUM THYROGLOBULIN AS A MANIFESTATION OF ACUTE HAEMORRHAGE INTO THE THYROID GLAND

Clinical observations and serial determinations of serum thyroglobulin (Tg) were made in five patients with acute haemorrhage into the thyroid gland. Fever, local pain and acceleration of erythrocyte sedimentation rate were minimal or were not observed, and serum T4 and T3 were normal. Although all patients showed an increase in serum Tg, this was most obvious in three subjects and it gradually decreased as the nodule became smaller. There was no correlation between the serum Tg concentration and the nodular size. Acute haemorrhage into the thyroid gland should be added as one of the causes to increase serum Tg concentrations.

Inhibition of TSH-stimulated thyroid hormone release and potentiation of TRH-stimulated TSH release by indomethacin in perifusion systems of rat thyroids and pituitaries

Using indomethacin (Ind), a prostaglandin, synthesis inhibitor, in vivo experiments in rats and in vitro experiments with perifusion systems of rat thyroids and pituitaries were conducted. After 35 days of intragastric infusion of Ind, serum TSH levels were markedly increased, the thyroid was swollen and, as a consequence, T3 and T4 levels were normal. The T3 release from perifused rat thyroids under continuous stimulation with 10 mU/ml TSH was inhibited significantly (p<0.01) by 1.0×10−6 M Ind. On the other hand, the TSH release from perifused rat pituitaries under TRH stimulation was enhanced conspicuously by Ind. It was concluded that Ind decelerated thyroid hormone release from the thyroid and accelerated TSH release from the pituitary in perifusion systems.

α1-adrenergic regulation of thyrotropin-stimulated release of 3, 5, 3’ -triiodothyronine and thyroxine from perifused mouse thyroid

The effect of methoxamine, a specific α1-adrenergic agonist, on the release of T3, T4 and cAMP from perifused mouse thyroid was studied to clarify the role of the α1-adrenergic receptor in the regulation of thyroid hormone secretion. TSH-stimulated T3 and T4 release was inhibited significantly by methoxamine. With regard to cAMP release, methoxamine inhibited TSH-stimulated cAMP release in the presence of 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone but did not inhibit TSH-stimulated cAMP release in the presence of 3-isobutyl-1-methylxanthine. Methoxamine did significantly suppress TSH-stimulated release of T3 and T4 in the presence of each phosphodiesterase inhibitor. Depletion of Ca2+ in the perifusion buffer abolished completely the inhibitory effect of methoxamine on TSH-stimulated T3 and T4 release. The present study suggests that activation of the α1-adrenergic receptor inhibits TSH-stimulated T3 and T4 secretion through a Ca2+ — dependent mechanism in the mouse thyroid gland.

Ionophore A23187 inhibits the release of thyrotropin-stimulated 3, 5, 3’-triiodothyronine from perifused rat thyroid glands

We have studied the effect of ionophore A23187 on the release of T3 and cAMP from perifused rat thyroid glands and on the morphological changes of the follicle epithelial cells. lonophore A23187 at a concentration of 5 µM significantly inhibited TSH-stimulated T3 release. Depletion of Ca2+ in the infusion buffer completely abolished the inhibitory effect of ionophore A23187 on TSH-stimulated T3 release. In the presence of TSH and 3-isobutyl-1 -methylxanthine, ionophore A23187 at 5 µM did not significantly affect either the release of cAMP during a 3-h perifusion or the cAMP content in the thyroid tissues after 1-h perifusion. By electron microscopy, the follicle epithelial cells of the rat thyroid tissues showed marked responses to TSH after 3-h stimulation. By the addition of 5 µM ionophore A23187, the ultrastructural changes such as phagocytotic uptake of luminal colloid and the formation of intracellular colloid droplets were rarely observed in spite of the presence of TSH. The present study indicates that ionophore A23187 at a concentration of 5 µM inhibits both TSH-induced morphological changes of the follicle epithelial cells and TSH-stimulated T3 release without reducing cAMP level stimulated by TSH in rat thyroid glands.