The fine structure of nerve endings on rat thyroid follicular cells

Summary Axon profiles in thyroid glands obtained from adult male Wistar rats were studied electron-microscopically, using common and serial thin sections.Bouton profiles of nerve fibers, resembling the terminal or en passant type, often appeared closely associated with vascular smooth muscle cells via basement membranes. These structures are probably adrenergic, since they contained mainly small-core vesicles (mean diameter: 41.2 nm), in addition to a few large-core (mean diameter: 88.4 nm) and flattened vesicles.Nerve fibers containing microtubules and sometimes mitochondria and vesicles were seen lying between basement membranes and follicular cells. The incidence of nerve fiber contacts on profiles of follicular cells was 0.0177±0.0092 (S.D.). Using serial sections, follicles were seen to have up to two nerve endings, separated from the plasma membranes of the follicular cells by a gap of 22 nm. They contained mainly flattened vesicles and several large-core vesicles (mean diameter: 95.1 nm). Small-core vesicles were rarely seen in these nerve endings. Furthermore, subsurface cistern-like rough endoplasmic reticulum was found immediately under the plasma membranes of follicular cells facing membranes of nerve endings. These results suggest that the nerve fibers in contact with follicular cells are different from the adrenergic type.     

Ultrastructural changes in the nerves innervating the cerebral artery after sympathectomy

Summary The ultrastructure of the innervation of the anterior cerebral artery of the rat was studied in control animals and in animals after superior cervical ganglionectomy.Fluorescence histochemistry shows a periarterial network of intensely fluorescent fibers which are divided into two groups, adventitial and periadventitial. The fluorescence begins to decrease 26 hours after, and completely disappears about 32 hours after, ganglionectomy.Fine structural changes are first observed 18 hours after ganglionectomy, when the axoplasm of degenerating axons becomes electron dense. This density gradually increases up to about 32 hours. By 32 hours most axons with disintegrating axolemmas become inclusion bodies of the Schwann cells. At this stage, synaptic vesicles can still be distinguished as less dense areas, but the membrane structures of synaptic vesicles and mitochondria are difficult to recognize. The degenerating axons are gradually absorbed and by 38 hours dense, residual bodies are observed in the Schwann cells. Generally speaking, the degeneration occurs first in the adventitial fibers and then in the periadventitial fibers. The transient appearance of small, granular vesicles is noticed in axon terminals about 18 hours after denervation, although very few small, granular vesicles are seen in control tissue or at later stages of degeneration.     

Avian enteric nerve plexuses

Summary The enteric nerve plexuses of the domestic fowl (Gallus domesticus) were investigated in sections and stretch preparations by means of the cholinesterase and glyoxylic acid fluorescence histochemical techniques. Cholinesterase-positive and varicose and non-varicose fluorescent nerve fibres were distributed at all levels of the gut in myenteric, submucosal, muscle and mucosal plexuses, and in a perivascular plexus. The density of the innervation and the detailed distribution of the nerves varied in different parts of the intestinal tract. All nerve plexuses appeared to be best developed in the rectum. Whereas the circular muscle coat contained a substantial number of nerves at all levels of the gut, the longitudinal coat was well innervated only in the rectum. The major portion of the mucosal plexus appeared to be associated with the intestinal glands. The nerve cell bodies were restricted to the myenteric and submucosal plexuses and were mainly cholinesterase-positive. Fluorescent ganglion cells were not observed. Pretreatment of stretch preparations with NADH: Nitro BT to stain ganglion cells showed that the majority of the cells were surrounded by a meshwork of fluorescent varicose fibres, although none of the fibres appeared to be associated with individual cells. The perivascular plexus was mainly associated with the arteries. The functional significance of the innervation is discussed.We would like to thank the British Council for financial support for Mr. H.A. Ali     

Cholinergic nerves in the human liver

Summary The cholinergic innervation of the human liver was studied. Slices (150–200m thick) of human liver and of the greater hepatic blood vessels (hepatic artery and vein, portal vein) were incubated in a solution of 6-hydroxydopamine (6-HDA) in order to obtain a selective degeneration of adrenergic nerves. Controls were prepared from samples incubated with buffer alone. The slices were cut on a cryostat into 15–20m thick sections and processed for the histochemical detection of cholinesterases.Cholinergic nerve fibres innervate the extra hepatic and the intrahepatic branches of the hepatic artery, the portal vein as well as the hepatic vein. Fewer cholinergic fibres innervate the hepatocytes and the hepatic sinusoids. The 6-HDA treatment does not seem to alter the pattern of the cholinergic innervation of the liver. The findings indicate the presence of a cholinergic parasympathetic innervation in the human liver.     

Effect of aging on the morphology and function of the thyroid gland of the cream hamster

Summary The effect of aging on the morphology and function of the thyroid gland of the cream hamster was studied by light and electron microscopy coupled with autoradiography or histochemistry.Morphologically, aging induces an accumulation of lysosomal dense bodies and a loss of the phagocytosis of colloid droplets after stimulation with TSH. Iodine uptake and organification occur normally and thyroglobulin synthesis, estimated by autoradiography with ³H-leucine, is not different from that observed in young animals. The basal T₄ and T₃ plasma levels are lower in the old animals. A low iodine diet administered for several months prevents the age related accumulation of lysosomal dense bodies. Hormone secretion seems to proceed by two different mechanisms; phagocytosis of colloid droplets, the classical mechanism that decreases with age, and an additional mechanism, probably micropinocytosis, that is maintained during the whole lifespan.Presented at the First French Congress of Endocrinology, Montpellier, September 1980Work was performed under contracts n 3.4523.79 and n 3.4512.80 of the Fonds de la Recherche Scientifique Médicale, thanks to a grant of the Ministère Belge de la Politique Scientifique (Action concertée) and with the help of the Fondation Interuniversitaire pour la Recherche du Processus du Vieillissement, Belgium     

Neuromedin U-like immunoreactivity in the thyroid gland of the rat

Summary Neuromedin U is a novel neuropeptide found to have a widespread distribution extending throughout the mammalian central nervous system, gastrointestinal tract and the endocrine cells of the pituitary gland. In order to investigate the possibility that neuromedin U-like immunoreactivity is also present in the thyroid gland of the adult rat we have examined its localisation and molecular nature by radioimmunoassay, immunocytochemistry and chromatographic analysis. The neuromedin U content of the whole thyroid gland was found to be 331±67 fmol/gland (mean±SEM), and this value significantly decreased (163±17 fmol/gland) as a result of 14 days of treatment with the anti-thyroid agent methimazole (10 mg/rat/day. Thyrotoxicosis induced by exogenous T4 (10 g/rat/day) failed to alter the thyroid content of this peptide. Immunostaining studies localised neuromedin U to a minor population of parafollicular C-cells in untreated animals. Complementary chromatographic studies revealed a single molecular form of neuromedin U-like immunoreactivity in thyroid tissue extracts which was indistinguishable from synthetic rat neuromedin U standard.     

Development of cell-to-cell relationships in the thyroid gland of the chick embryo

Summary Thyroid glands of 7 to 21 day-old chick embryos were examined by electron microscopy using freeze-fracture and thin-section preparations. The primitive follicle lumen first appears between two adjacent epithelial cells in 8 day-old embryos, and is formed in the region of a focal tight junction (macula occludens). The focal tight junction develops into the zonula occludens when the primitive follicle lumen first forms.The zonula occludens is, at first, composed of 4.6 ± 2.45 strands, but with increasing embryonic age the number of strands increases to 5.9 ± 1.41 in 13 day-old, and 8.0 ± 1.75 in 19 day-old embryos.Thyroglobulin stored within the embryonic gland lumina is isolated from the mesenchymal tissue even at the first appearance of these follicle cavities.Well developed gap junctions already occur in the thyroid gland of the 7 day-old embryo, so that an intimate relationship and communication between these cells already exists at the time of their functional differentiation.This study was supported by a grant from the Japan Ministry of Education     

Histological and ultrastructural alterations of rat thyroid gland after short-term treatment with high doses of thyroid hormones

The aim of the present study was to investigate histological alterations of rat thyroid gland after short-term treatment with supraphysiological doses of thyroid hormones. Rats from experimental groups were treated with triiodothyronine (T3) or thyroxine (T4) during five days. In both treated groups, thyrocyte height was reduced and follicular lumens were distended. Progressive involutive changes of the thyroid parenchyma were apparent, including follicular remodeling (fusion) and death of thyrocytes. Morphological changes confirmed by quantitative analysis were more pronounced in the T4-treated group. Our results demonstrate that thyrotoxicosis, whether induced by T3 or T4, leads to different grades of thyroid tissue injury, including some irreversible damages. These changes might be explained at least in part by lack of trophic and cytoprotective effects of the thyroid stimulating hormone. Since the period required for morphophysiological recovery may be unpredictable, findings presented here should be taken into consideration in cases where the thyroid hormones are used as a treatment for thyroid and non-thyroid related conditions.     

Purification and characterization fo a phosvitin kinase from the thyroid gland

1. Two cyclic AMP independent protein kinases phosphorylating preferentially acidic substrates have been identified in soluble extract from human, rat and pig thyroid glands/ Both enzymes were retained on DEAE-cellulose. The first enzyme activity eluted between 60 and 100 mM phosphate (depending on the species), phosphorylated both casein and phosvitin and was retained on phosphocellulose; this enzyme likely corresponds to a casein kinase already described in many tissues. The second enzyme activity eluted from DEAE-cellulose at phosphate concentrations higher than 3000 mM, phosphorylated only phosvitin and was not retained on phophocellulose. These enzymes were neither stimulated by cyclic AMP, cyclic GMP and calcium, nor inhbiited by the inhibitor of the cyclic AMP dependent protein kinases. 2. The second enzyme activity was purified from pig thyroid gland by the association of affinity chromatography on insolubilized phosvitin and DEAE-cellulose chromatography. Its specific activity was increased by 8400. 3. The purified enzyme (phosvitin kinase) was analyzed for biochemical and enzymatic properties. Phosvitin kinase phosphorylated phosvitin with an apparent K_m of 100 μg/ml; casein, histone, protamine and bovine serum albumin were not phosphorylated. The enzyme utilized ATP as well as GTP as phosphate donor with an apparent K_m of 25 and 28 μM, respectively. It had an absolute requirement for Mg²⁺ with a maximal activity at 4 mM and exhibited an optimal activity at pH 7.0. The molecular weight of the native enzyme was 110 000 as determined by Sephacryl S300 gel filtration. The analysis by SDS-polyacrylamide gel electrophoresis revealed a major band with a molecualr weight of 35 000 suggesting a polymeric structure of the enzyme.     

ABCG2蛋白在甲状腺乳头状癌中的表达及临床意义

目的 探讨ABCG2蛋白在甲状腺乳头状癌组织中的表达及其临床意义.方法 收集武汉大学人民医院2000-2006年手术切除及活检的甲状腺乳头状癌标本40例和甲状腺腺瘤标本20例.采用免疫组织化学方法检测甲状腺乳头状癌和甲状腺腺瘤组组织内ABCG2蛋白的表达.利用HPIAS-2000图像分析系统测定ABCG2蛋白在甲状腺乳头状癌及甲状腺腺瘤中表达的平均光密度和平均阳性面积率.结果 甲状腺乳头状癌组织中ABCG2蛋白呈高表达;甲状腺腺瘤中ABCG2蛋白呈低表达;图像分析结果显示两组间差异有显著性意义(P＜0.05).结论 ABCG2在甲状腺乳头状癌组织中的高表达可能参与了甲状腺乳头状癌的发生、发展,而且其在癌组织中的高表达可能参与了甲状腺乳头状癌化疗过程中多药耐药形成.     

On the innervation of the salt gland

Summary The innervation of the salt gland of the goose, the duck and the swan was investigated by means of electron microscopy. Axonal swellings were observed in relationship to secretory cells as well as to central duct cells. The terminals contain synaptic and densecored vesicles. There are no specialized pre- and postsynaptic membranes.Supported by the Deutsche Forschungsgemeinschaft (Ku 210/4).     

Acetylcholinesterase activity in the myotome of the early chick embryo

Summary The myotome of early chick embryos was investigated histochemically by means of the acetylcholinesterase (AChE) reaction.Light-microscopically, at the cervical level, the myotome was first recognized and AChE activity demonstrated at stage 13 (2 day-old embryo). Subsequently, the myotome elongated ventro-laterally along the inner surface of the dermomyotome and reached the ventro-lateral end of the dermomyotome at stage 17 to 18 (3 day-old embryo). AChE activity in the myotome showed subsequent increase in intensity during the course of development. The myotome consisted mainly of AChE-positive cells displaying enzymatic activity along the nuclear membrane and within the cytoplasm. In contrast, almost all cells of the dermomyotome and the interstitial cells were AChE-negative.Electron-microscopically, the myotome cells of the 2 day-old embryo and the cells in the dorso-medial portion of the myotome of the 3 day-old embryo were morphologically undifferentiated; AChE activity was detected in the nuclear envelope and in single short profiles of the endoplasmic reticulum (ER). On the other hand, in the 3 day-old embryo the cells in the ventro-lateral portion of the myotome showed AChE activity in the nuclear envelope, numerous profiles of the ER and some Golgi complexes. These AChE-positive cells were regarded as developing myogenic cells based on their morphological characteristics.The present findings indicate (i) that the appearance of AChE activity in the cytoplasm is the first sign of the differentiation of myogenic cells, and (ii) that in these myogenic cells the increase in AChE activity is based on the development of the ER.     

Postnatal variations in the number and size of C-cells in the rat thyroid gland

The heterogeneous distribution of thyroid C-cells has until now hindered an objective evaluation of changes caused by age or experimental stimuli. To overcome this, a rigorous methodology has been designed to detect variations in shape, size, and number of C-cells throughout development. Using this methodology, we have demonstrated that C-cells do not significantly alter their shape with age. However, their volume increases gradually from 472 m³ in newborn rats to 1653 m³ in 120-day-old animals. Over the same time period, the mean number of C-cells within the thyroid gland increased 9-fold (from 1.6x10⁴ to 1.5x10⁵), and the number of C-cells per unit area decreased (from 6.15x10⁴/mm³ to 2.6x10⁴/mm³). We conclude that there are marked variations in size, total number, and number of C-cells per unit area in the rat thyroid gland after birth.     

Localization of cells producing thyroid stimulating hormone in the pituitary gland of the domestic drake

Summary Cells binding anti-bovine TSH serum were found exclusively in the rostral lobe of the adenohypophysis of the drake using the peroxidase-antiperoxidase complex unlabelled antibody method. The specificity of the binding of the anti-serum to TSH cells was established by relating the morphology and relative abundance of immunochemically stained cells to the TSH content of the adenohypophysis after experimentally altering the activity of the pituitary-thyroid axis. The TSH activity of the adenohypophysis was assessed indirectly, by the weight of the thyroid glands, and directly, by bioassay. As determined by bioassay, the TSH content of the rostral lobe of the adenohypohysis was much greater than that of the caudal lobe. Compared with control drakes, immunochemically stained cells in birds fed a goitrogen, methimazole, seemed to be enlarged and were closer together, while the stained cells in drakes injected with thyroxine were shrunken and less intensely stained. The TSH content of the adenohypophysis was increased in drakes fed methimazole. Castration did not alter the TSH content of the adenohypophysis or change the morphology of immunochemically stained cells. These observations suggest that in the drake: 1) anti-bovine TSH serum binds specifically to TSH cells; 2) the TSH cells occur in the rostral and not in the caudal lobe of the adenohypophysis; and 3) the activity of TSH cells is not inhibited by the feedback effects of gonadal steroids.We thank Dr. L.E. Reichert Jr. and the National Institute of Arthritis, Metabolic and Digestive Diseases for the gift of ovine TSH and Mr. R. Wilkie for technical assistance. We are grateful to Dr. M.F. El Etreby, Professor B.K. Follett, Dr. C.G. Scanes, Dr. J. Seth and Dr. J.G. Pierce for gifts of immunochemicals     

Acetylarsenocholine: A Cholinergic Agonist

Abstract: The pharmacological properties of acetylarsenocholine, an arsenic analogue of acetylcholine, were investigated. Acetylarsenocholine behaved as a cholinergic ligand both in the central and peripheral nervous system. It bound to nicotinic receptors in rat medulla-pons with a K _D of 15 μ M and to muscarinic receptors in rat cerebral cortex with a K _D of 10 μ M . It behaved also as an agonist at presynaptic muscarinic receptors in guinea pig ileum myenteric plexus preparation. Arsenocholine is an alternative substrate for choline acetyltransferase and acetylarsenocholine is an alternative substrate for acetylcholinesterase.