Follicular Lumen Research Articles

Induction of Graves-like disease in mice by immunization with fibroblasts transfected with the thyrotropin receptor and a class II molecule.

Graves disease is an autoimmune thyroid disease characterized by the presence of antibodies against the thyrotropin receptor (TSHR), which stimulate the thyroid to cause hyperthyroidism and/or goiter. By immunizing mice with fibroblasts transfected with both the human TSHR and a major histocompatibility complex class II molecule, but not by either alone, we have induced immune hyperthyroidism that has the major humoral and histological features of Graves disease: stimulating TSHR antibodies, thyrotropin binding inhibiting immunoglobulins, which are different from the stimulating TSHR antibodies, increased thyroid hormone levels, thyroid enlargement, thyrocyte hypercellularity, and thyrocyte intrusion into the follicular lumen. The results suggest that the aberrant expression of major histocompatibility complex class II molecules on cells that express a native form of the TSHR can result in the induction of functional anti-TSHR antibodies that stimulate the thyroid. They additionally suggest that the acquisition of antigen-presenting ability on a target cell containing the TSHR can activate T and B cells normally present in an animal and induce a disease with the major features of autoimmune Graves.

Vanishing Psammoma Bodies in the Anterior Pituitary of the Human Newborn: An Immunohistochemical and Histometric Study.

Adenohypophyses of human newborns contain characteristic psammoma bodies. Their numbers are maximal within 2 weeks of the neonatal period and diminish thereafter. They are very rare in infant pituitaries, seeming to disappear by shrinkage in that there is a significant direct correlation between their number and size. The bodies were found to contain a high concentration of endogenous peroxidase, thus suggesting that the enzyme may be responsible for their disappearance. A statistical majority of psammoma bodies were located within follicular lumens. By immunohistochemistry, the follicular epithelium surrounding psammoma bodies showed immunoreactivity for various pituitary hormones. Light microscopy demonstrated that adenohypophysial cells surrounding psammoma bodies contain randomly scattered granules or globules exhibiting peroxidase activity. Extrusion of such granules into follicular lumens may play a role in the genesis of the concretions. The conspicuous lamellar nature of the calcified psammoma bodies suggests that waves of calcium deposition occur during their morphogenesis. Despite histologic similarities, the histochemical characteristics of this type of psammoma body differ from those in other organs as well as from the calcification encountered in prolactin (PRL)-producing pituitary adenomas.

Carbohydrate and protein determinants are involved in thyroglobulin recognition by FRTL 5 cells.

To avoid premature lysosomal degradation, thyrocytes have a system able to recycle internalized immature thyroglobulin molecules (Tg) to the follicular lumen via the Golgi apparatus. It has been shown that this quality control system depends on recognition of exposed N-acetylglucosamine (GlcNAc) determinants (Miquelis et al., J Cell Biol, 1993, 123, 1695) present on immature Tg (Bastiani et al., 1995, Endocrinology, 1995, 136, 4204). However, the same in vitro kinetics studies also showed that GlcNAc residues alone induce only weak recycling. The latter finding led us to investigate the possibility that protein determinants might also be involved in binding. For this purpose, we studied binding of Tg to FRTL 5 cells, a widely available TSH-dependent cell line and found that binding to plasma membranes occurred at acidic pH in the presence of calcium, i.e. under conditions previously reported for binding of GlcNAc-BSA to porcine thyroid cell membranes. As expected, binding was GlcNAc- and oligosaccharide-dependent because Bandeiraea Simplificiola II affinity column analysis indicated that GlcNAc-bearing Tg were preferentially bound and N-glycanase treatment of Tg inhibited interaction. Ovomucoid, GlcNAc-BSA, and porcine Tg oligosaccharides did not inhibit binding, indicating that carbohydrates were not the sole determinants for binding. The fact that pronase digestion of Tg totally abolished binding implied that peptide determinants were involved in the interaction. This involvement is supported by the observation that porcine, rat, bovine, and human Tg bound FRTL 5 cell membranes and that monoclonal antibodies raised against human Tg interfered with the binding of both human and porcine Tg. Based on these findings we conclude that, besides the involvement of GlcNAc-bearing oligosaccharides, Tg receptors form a stable bond with peptide determinants.

Dissociation between serum interleukin-6 rise and other parameters of disease activity in subacute thyroiditis during treatment with corticosteroid.

Increased serum interleukin-6 (IL-6) concentrations have recently been reported in patients with subacute thyroiditis, possibly because of cytokine release from damaged thyroid cells. To investigate the changes in serum IL-6 concentrations in subacute thyroiditis during treatment with corticosteroid, serum IL-6 concentrations were determined by an enzyme-linked immunosorbent assay method in five patients with subacute thyroiditis. Serum IL-6 concentrations were increased moderately, and simultaneously, serum levels of T4, thyroglobulin, and C-reactive protein and erythrocyte sedimentation rate were increased markedly. The treatment with prednisolone rapidly and progressively decreased serum levels of thyroglobulin, T4, and C-reactive protein and the erythrocyte sedimentation rate. In contrast, serum IL-6 concentrations increased markedly 7 days after the treatment with prednisolone in all five patients and two of five patients showed further increases in serum IL-6 concentration on the 17th day. The rise in serum IL-6 levels in untreated patients with subacute thyroiditis in this study is compatible with previous reports. The rise in serum IL-6 levels after treatment with corticosteroid in subacute thyroiditis may reflect the dissociation between the persistent release of IL-6 from the damaged thyroid cells, immediate inhibition of secondary inflammatory reactions by corticosteroid, and the release of thyroglobulin and T4 from performed colloid stores in follicular lumen destroyed by subacute thyroiditis.

Cells of the photoreceptor line in the pineal organ of an adult marsupial, Didelphis albiventris

We report the presence of atypical pinealocytes as components of epiphyseal follicles in the adult South American opossum Didelphis albiventris. Their main characteristic is a bulbous-shaped apical cytoplasmic extension which protrudes towards the follicular lumen among the microvilli and cilia of neighbouring ependymal cells. They resemble the photoreceptor-like pinealocytes of sauropsids and developing photoreceptors in the retina of newborn mammals. Morphological characteristics enable us to classify them as cells of the receptor line.

The juxtatesticular body of jawfishes (Teleostei, Opistognathidae): Comparative morphology and fine structure

A peculiar gland, the juxtatesticular body (JTB), ductless and consisting of follicles, had previously been discovered in males of two Opistognathus species (Teleostei, Opistognathidae). In this paper, we describe (1) the general morphology of the JTB in an additional two Opistognathus species, O. aurifrons and O. macrognathus, comparing it with that of the previously described species, and (2) the fine structure of the JTB of Opistognathus whitehurstii and O. maxillosus. Interspecific variability occurs both in the general organization of this gland and in the number of follicular cells. Fine structural analysis of the JTB, both in O. whitehurstii and O. maxillosus, reveals strong similarities with thyroid follicular cells, suggesting a similar pattern of synthesis and secretion. JTB follicular cells are arranged as a monolayered epithelium that surrounds a follicular lumen; they show a polarity in organelle distribution and membrane specialization typical of secreting cells. On the basis of their cytological and histochemical characteristics we propose that JTB follicular cells perform two major types of secretory activities: the secretion of a glycoprotein from the apical part of the cells into the follicular lumen and the endocrine, or paracrine, secretion of a still unknown substance(s) from the basal part of the cell either into the extrafollicular space or the blood or both. A hypothesis concerning the functional cycle of JTB follicle is also discussed. © 1995 Wiley-Liss, Inc.

The process of apoptosis in follicular epithelial cells in the rabbit ovary, with special reference to involvement by macrophages.

Using rabbit ovaries, this study investigated the fate of follicular epithelial cells undergoing apoptosis in follicle atresia, especially in atretic Graafian follicles. This is the first report to apply the TUNEL method and histochemistry for acid phosphatase in order to demonstrate macrophages immigrating into the follicles to eliminate the apoptotically dead epithelial cells. At initial stages of atresia, a few epithelial cells solitarily revealed the condensation of nuclear chromatin characteristic of apoptosis, simultaneously reacting positive to the TUNEL method. At advanced stages, chromatin condensation and separation as well as cytoplasmic fragmentation spread to the entire follicular epithelium. In such an advanced atretic follicle, large round cells appeared in the follicular lumen; these could be identified as macrophages by their morphologies and positive reactions for acid phosphatase. These macrophages were adhering to and internalizing apoptotic epithelial cells and their fragments until the lumen became completely free of dead cells and fragments.

Age-Related Changes in Thyroid Lesions and Function in F344/DuCrj Rats.

Age-related thyroid changes, such as those in weight, histology, morphometry, and hormonal concentrations were evaluated in 460 male and 460 female F344 rats from 9 to 109 weeks of age. The absolute weight of the thyroid increased with age in both sexes, but the relative weight was unaffected by age. Ectopic thymus and ultimobranchial cyst were observed in rats of both sexes from 9 to 109 weeks of age. The incidence of both congenital anomalies decreased with age. The incidence of follicular cyst, which was first observed in rats at 20 weeks of age, increased at 109 weeks. Hyperdistention of the follicle with infiltration of macrophages in the lumen and deposition of brown pigments in the cytoplasm of epithelial cells were observed in a few rats at 59 weeks of age. These follicular lesions were found in 29% of the males and 7% of the females at 109 weeks. The first thyroid tumor was seen at 59 weeks of age. In 109-week-old rats, 5% of males had follicular tumors, and 18% of males and 10% of females had C-cell tumors. At 82 weeks of age, the follicular area and the area of the follicular lumen increased, and the height of follicular epithelial cells decreased. Serum T3, T4 and TSH concentrations decreased with age and were significantly reduced at 82 weeks. These results suggest that in F344 male rats the thyroid structural and functional changes occurred with age, and thyroid function decreased after 82 weeks of age.

Thyroid Epithelial Morphogenesis in Vitro: A Role for Bumetanide-Sensitive Cl - Secretion during Follicular Lumen Development

The structural and functional unit of the thyroid gland is the follicle, consisting of a closed lumen surrounded by a single layer of polarized epithelial cells. In this paper we have attempted to characterize the process of lumenal development when primary cultures of porcine thyroid cells reorganized to form follicles. Cells incubated with the loop diuretic, bumetanide, an inhibitor of NaK2Cl cotransport, aggregated but failed to form normal follicles. Laser scanning confocal microscopy combined with immunohistochemical markers of thyroid cell-surface proteins demonstrated that in the presence of bumetanide cells polarized and assembled ZO-1-containing tight junctions separating their apical and basolateral membrane domains. Cultures formed small lumena but their subsequent growth was inhibited by bumetanide. Electrophysiological studies confirmed that bumetanide-sensitive Cl - transport was the major contributor to the transepithelial electrical potential difference across the follicular wall after 48 h incubation. Other potential mechanisms did not contribute significantly to follicular lumenal growth. In particular, bumetanide did not affect cell proliferation and, in contrast to tissue follicles, thyroglobulin could not be detected within the lumena of cultured follicles. We conclude that thyroid follicular reorganization involves two distinct and separate phases of lumenal development: initial lumen formation which probably reflects the assembly of a specialized apical membrane domain; and subsequent lumenal growth which is mediated by the inward transport of Cl - by polarized epithelial cells.

Congenital euthyroid goitre with impaired thyroglobulin transport

A case of congenital goitre with defective thyroglobulin (Tg) synthesis was studied from the clinical, biochemical and morphological perspectives. The patient, 5.5-year-old boy, who was clinically euthyroid, showed a positive perchlorate discharge test (37.2%). However, the iodination system seemed to be normal since radioiodine uptake into the thyroid was very high, and inspection of the H2O2-generating system using thyroid slices and an assay for peroxidase activity in microsomes showed no abnormalities. On the other hand, virtually no Tg was detected in the serum, and the amount of Tg in thyroid tissue, estimated with gel electrophoresis, was below 10% of the normal value, the quality of Tg being unchanged. Morphological observations demonstrated the presence of Tg in the markedly distended rough endoplasmic reticulum of the cytoplasm of follicular cells and a lack of Tg in the colloid of the follicular lumen. These results suggest that the thyroid is defective in Tg synthesis, probably associated with impaired transport of Tg from the cells to the lumen.

Immunohistochemical study of desmosomes in acne vulgaris

Desmosomes contribute towards adhesion between adjacent keratinocytes. In acne vulgaris, increased intercellular adhesion is thought to contribute to the retention of keratinocytes within the follicular lumen during comedogenesis. Therefore, the distribution of different desmosomal components was investigated in normal and acne subjects. Biopsies were cryostat-sectioned (6 microns), and stained with antibodies to different desmosomal components: desmoplakin 1/2, desmoglein 1, desmocollin 3a/3b, and a late desmosomal antigen, G36-19. Desmoplakin 1/2, desmoglein 1 and desmocollin 3a/3b shared a similar distribution in follicles from control skin, from acne-affected skin, and in non-inflamed lesions. All three proteins were expressed around the periphery of keratinocytes of all the intrafollicular epidermis, except the basal lamina and the upper stratum corneum. In inflamed lesions, the expression of desmoglein 1 and desmocollin 3a/3b was diminished; in 12.5%, staining for these two proteins was completely abolished, and in 81.25% of the lesions investigated the staining was patchy. The antibody G36-19 bound to an antigen in the upper granular layer in the infundibular epidermis. No differences were noted in the staining pattern of the follicular epithelia of controls, non-inflamed, and inflamed lesions. This study, using monoclonal antibodies, did not identify any changes in the desmosomal components which might explain the increased adhesion between follicular keratinocytes during comedogenesis.

Radioiodine Uptake as a Function of Stored Iodine and Thyroglobulin in Thyroid Follicles:In VitroQuantitative Imaging Approach with Secondary Ion Mass Spectrometry (SIMS) Microscopy in Human Nontoxic Goiter

We studied by an imaging technique, secondary ion mass spectrometry (SIMS) microscopy, the ability of thyroid follicles to pick-up and organify radioiodine (125I) according to the amounts of iodine (127I) and sulfur previously stored in thyroglobulin (Tg). After incubation with radioiodine in miniorgan culture, the SIMS analysis of 14 fragments from 12 goitrous patients permitted the observation of 3 iodine distribution profiles. In group 1 125I and 127I were easily detected by imaging; 125I concentration in follicular lumen was 80-fold lower than that of 127I. In group 2 125I images were obtained after long-term exposure and image processing. 125I concentration was not measurable while that of 127I was about 1.7-fold higher than that observed in group 1. In group 3 it was not possible to detect 125I while only traces of 127I were detected. This last profile can coexist with profile 1 in the same specimen. Tg sulfur concentration was 2-fold lower in group 3 than in the other 2 groups in which they were almost the same and significantly correlated with those of 127I. These data provide new insight into Tg and 127I traffic in the development of nonfunctioning goiters.

Development of the vasculature of the anterior pituitary: ontogeny of basic fibroblast growth factor.

This study correlates the ontogeny of basic fibroblast growth factor (FGF) with the development of the vasculature of the anterior pituitary (AP) in two strains of rat, Sprague-Dawley (SD) and Fischer 344 (F344). Immunolocalization of FGF was followed from the first appearance of Rathke's pouch (RP) in 12-day (12d) fetuses, through each day of fetal development, and in 5, 20, and 50d postnatal female rats. In addition, the ontogeny of folliculo-stellate cells (FSC) is described, since previous studies suggested that these unique cells might function as phagocytes in the regulation of FGF. In both rat strains, vascularization of the AP commenced in 16d fetuses. In 15-20d fetuses, dense foci of immunopositivity for extracellular FGF were apparent at sites of capillary penetration adjacent to partially disrupted, immature gonadotropes. Localization of FGF was first detected in immature gonadotropes in 18d fetuses and persisted in the cytosol of a subpopulation of gonadotropes thereafter. In 15d fetuses, FGF was localized within the cytosol intimately associated with the peripheral-facing plasma membranes of all cells of the adenohypophysis, and persisted to variable degrees in later fetal stages. Localization of FGF within nuclei of AP parenchymal cells was evident only in 16-17d fetuses. Although the ontogeny of FGF and vascularization of the AP was very similar in both rat strains, the ontogeny of FSC differed markedly. In both strains, follicular lumens contained FGF during late fetal and early postnatal development. However, both electron microscopy and immunostaining for S-100 marker protein revealed that the postero-lateral edges of the AP of F344 rats often lacked FSC when compared to SD rats, a situation which could compromise regulation of FGF by FSC at the AP periphery in that strain, and thereby contribute to the neovascularization from systemic blood vessels known to occur in that strain during prolactinoma formation.

Thyroglobulin molecules internalized by thyrocytes are sorted in early endosomes and partially recycled back to the follicular lumen.

Thyroglobulin (Tg) molecules stored in thyroid follicle lumens are heterogeneous in terms of iodine and hormone contents. It has been suggested that thyroid hormone is preferentially produced from the most highly iodinated Tg molecules and that thyrocytes are capable of selecting these molecules. The cellular localization as well as the molecular basis of such a selection process are not known. The present work was undertaken to determine whether there is selectivity at the step of endocytosis and, if not, to discover other possible mechanisms. Studies were conducted on reconstituted thyroid follicles (RTF) in culture. We compared the ability of thyrocytes to internalize Tg and an exogenous protein, BSA, which is neither iodinated nor glycosylated. To identify the protein, Tg and BSA were coupled to gold particles of different size and microinjected in a fixed ratio into the lumen of RTF. Neither of the two protein gold probes detected by transmission electron microscope bound at the cell surface, and both entered the cells at a similar rate and were concentrated in early endosomes. After 20 min, both Tg-G and BSA-G were segregated into distinct vacuolar structures. At 60 min, the intracellular content of BSA-G (mainly in prelysosomes and lysosomes) was 2- to 3-fold higher than that of Tg-G. At the same time, there was a marked reduction in the BSA-G/Tg-G ratio in the lumen. The differences between the Tg-G and BSA-G distribution patterns that were amplified in TSH-treated RTF are in keeping with a back-transfer of internalized Tg toward the lumen. The existence of a cell to lumen transport of previously endocytosed Tg was further documented using intralumenal [125I]Tg as a marker. RTF pulse labeled with tracer amounts of [125I]iodide were shortly incubated with TSH to induce [125I]Tg endocytosis, and the fate of internalized [125I] Tg was studied in a chase incubation period of up to 4 h. At 20 C, where the degradation of internalized Tg is blocked, we observed a time-dependent decrease in intracellular [125I]Tg and a corresponding increase in the lumenal [125I]Tg content. This cell to lumen [125I]Tg transfer was inhibited by primaquine. In conclusion, our data show that 1) the thyroid apical endocytic process does not exhibit selectivity for Tg; 2) the thyrocyte possesses a sorting machinery for endocytosed ligands; and 3) internalized Tg molecules can be recycled back to the follicular lumen.(ABSTRACT TRUNCATED AT 400 WORDS)

Thyroglobulin molecules internalized by thyrocytes are sorted in early endosomes and partially recycled back to the follicular lumen

Thyroglobulin (Tg) molecules stored in thyroid follicle lumens are heterogeneous in terms of iodine and hormone contents. It has been suggested that thyroid hormone is preferentially produced from the most highly iodinated Tg molecules and that thyrocytes are capable of selecting these molecules. The cellular localization as well as the molecular basis of such a selection process are not known. The present work was undertaken to determine whether there is selectivity at the step of endocytosis and, if not, to discover other possible mechanisms. Studies were conducted on reconstituted thyroid follicles (RTF) in culture. We compared the ability of thyrocytes to internalize Tg and an exogenous protein, BSA, which is neither iodinated nor glycosylated. To identify the protein, Tg and BSA were coupled to gold particles of different size and microinjected in a fixed ratio into the lumen of RTF. Neither of the two protein gold probes detected by transmission electron microscope bound at the cell surface, and both entered the cells at a similar rate and were concentrated in early endosomes. After 20 min, both Tg-G and BSA-G were segregated into distinct vacuolar structures. At 60 min, the intracellular content of BSA-G (mainly in prelysosomes and lysosomes) was 2- to 3-fold higher than that of Tg-G. At the same time, there was a marked reduction in the BSA-G/Tg-G ratio in the lumen. The differences between the Tg-G and BSA-G distribution patterns that were amplified in TSH-treated RTF are in keeping with a back-transfer of internalized Tg toward the lumen. The existence of a cell to lumen transport of previously endocytosed Tg was further documented using intralumenal [125I]Tg as a marker. RTF pulse labeled with tracer amounts of [125I]iodide were shortly incubated with TSH to induce [125I]Tg endocytosis, and the fate of internalized [125I] Tg was studied in a chase incubation period of up to 4 h. At 20 C, where the degradation of internalized Tg is blocked, we observed a time-dependent decrease in intracellular [125I]Tg and a corresponding increase in the lumenal [125I]Tg content. This cell to lumen [125I]Tg transfer was inhibited by primaquine. In conclusion, our data show that 1) the thyroid apical endocytic process does not exhibit selectivity for Tg; 2) the thyrocyte possesses a sorting machinery for endocytosed ligands; and 3) internalized Tg molecules can be recycled back to the follicular lumen.

A CASE OF CONGENITAL EUTHYROID GOITER WITH IMPAIRED THYROGLOBULIN (TG) TRANSPORT: IHHUNOHISTOCHEMICAL EVIDENCE OF INTRACELLULAR TG IODINATION

Thyroglobulin (Tg) is believed to be iodinated immediately after secretion of Tg into the follicular lumen. In recent years, however, Tg has reportedly been suggested to be iodinated in follicle cells on the basis of biochemical studies. We encountered a boy with goiter diagnosed at the age of 5.5 years, the pathogenesis of which was considered to be Tg deficiency because of Tg secretion failure in blood.

Ultrastructural study of post-hatching development in the pineal gland of the Japanese quail.

The pineal gland of the Japanese quail (Coturnix coturnix japonica) retained numerous follicular structures, each of which was composed mostly of pinealocytes and supporting cells radially arranged around the follicular lumen during the first 6 weeks of age. In the pinealocytes, paraboloids and regular stacks of lamellar disks, which were demonstrated at 1 day of age in a previous study [14], rapidly decreased in number after 1 week of age. From 1 to 6 weeks of age, the pinealocytes had more developed lamellar whorls in the follicular lumen with the increased numbers of mitochondria in their apical protrusions and synaptic ribbons in their basal processes. In addition to these photosensory elements, pigment-containing cells occasionally accumulated in the basal side of the follicular structure. Their pigment granules, which were considered as melanin, gradually became larger and more roundish in shape after 1 week of age. The histological elements associated with the secretory function of the quail pineal were dense-cored vesicles and lysosomes in the pinealocytes and dense bodies in the supporting cells. The synaptic ribbons and the dense-cored vesicles in the pinealocytes rapidly increased in number at 1 week of age, scarcely exhibiting distinct changes thereafter. Thus, it is clarified that the foregoing photosensory and secretory elements change during the post-hatching development. Furthermore, it is suggested that, in respect of these elements, the pineal gland of the quail assumes more active appearances than that of the chicken.

Structural and functional aspects of the thyroid follicular epithelium

The thyroid epithelium is morphologically and functionally polarized, with an apical surface facing the follicular lumen containing colloid and a basolateral surface facing the interstitium. Iodination and thyroid hormone synthesis occur in the colloid at the apical plasma membrane. The introduction by Mauchamp et al. of primary cultures of porcine thyroid cells grown as a polarized, confluent monolayer on a filter in a bicameral chamber system has now made it possible to study in more detail the barrier function and vectorial ion transport in the thyroid epithelium. The follicular cells form a very tight monolayer (transepithelial resistance > 6000 ohm cm 2) and establish a transepithelial potential difference (apical medium negative) of about 20 mV. These parameters are rapidly influenced by TSH, mainly by an action on apical sodium channels, and by EGF. The integrity of the barrier is, as in other epithelia, dependent on extracellular calcium. A calcium-dependent cell adhesion molecule, uvomorulin, is expressed at the lateral plasma membrane surface. EGF induces cell proliferation as well as migration of some of the epithelial cells to a position below the monolayer, which however maintains its polarity and barrier function. In contrast, during TPA-induced proliferation the barrier function is disrupted. Iodide is vectorially transported in basoapical direction while the epithelial layer is virtually impermeable for iodide transfer in the opposite direction. Iodide is concentrated in the cell by the basolateral “iodide-pump” and its efflux across the apical plasma membrane is rapidly and selectively increased by TSH via cAMP. EGF inhibits vectorial basoapical iodide transport mainly by reducing the iodide permeability of the apical plasma membrane. Together, these recent observations indicate that the ion content of the follicular lumen is strictly controlled by the thyroid epithelium.

Significance of SIMS microscopy for the radioiodine detection in animal and human thyroid tissue

We defined the SIMS conditions for radioiodine detection in animal and man thyroid follicles, in tissue sections (3 μm) chemically fixed and resin embedded. Two radioisotopes were tested: 125I and 129I, of high (14 mCi 125I μg −1) and low specific activity (1.07 10 −6 mCi 129I μg −1). In animal study, Wistar rats fed a normal iodine diet (10 μg 127I day −1) were injected ip 24 h before sacrifice either with 125I (7 10 −3 μg) or with 129I at a dose identical to iodine diet (10 μg) or 3 times higher (30 μg). No SIMS signal of 125I was obtained in vivo due to its too low concentration, while radioiodine distribution was evidenced with both doses of 129I. Local concentration of previously stored 127I in follicular lumen was not modified, when compared to control (4.14 ± 0.03 μg/mg, m ± SE), by 125I or 129I at a dose of 10 μg, but was nearly doubled with 129I at a dose of 30 μg, proof of a pharmacological effect on thyroid iodine regulation. In human study 129I was excluded due to its long half-life (1.6 10 7 years), and 125I was tested only in vitro on two surgical specimens of normal perinodular thyroid tissue maintained in mini-organ culture for 48 h in presence of 100 μCi/ml of 125I. The 125I was detectable, its concentration was 1000-fold higher than that of 127I (1.5 ± 0.004 μg/mg). For both in vivo and in vitro studies, a positive correlation exists between newly organified radioiodine ( 125I or 129I) and previously stored iodine ( 127I). In conclusion, the radioisotope 129I used at a dose of 10 μg is well adapted for SIMS detection in vivo of thyroid exchangeable iodine, but only in animal, while 125I isotope is especially adapted for in vitro study in man.

Hyposialylated thyroglobulin in a patient with congenital goiter and hypothyroidism.

A large family (14 children) with congenital goiter whose parents are first cousins was studied. Thyroid tissue was obtained, after 125I in vivo labeling, from one of the siblings (JBM). Gel filtration of thyroid proteins indicated that thyroglobulin (Tg) eluted as a single symmetrical peak in the same position as authentic 19S Tg. Gel electrophoresis in a 7.5% sodium dodecyl sulfate-polyacrylamide gel revealed a major band with the same mobility and immunoreactivity as normal 19S Tg. Hydrolysis of the patient's Tg indicated that most of the radioactivity was mono- and diiodotyrosines. The yield of T4 from JBM Tg (26 pmol/mg protein) was 5-fold less than normal thyroid tissue (140 pmol/mg protein) and approximately half of that in thyroid tissue from endemic goiter (51 pmol/mg). Total T3 released from JBM Tg was similar to the other two tissues. When the carbohydrate content of normal and patient Tg was analyzed, there was no differences in glucosamine, galactose or mannose content. However, unlike normal and endemic-goiter Tg, that had a mean sialic acid content of 7.3 and 5.6 micrograms/mg protein, respectively, the sialic acid concentration of the patients Tg was only 0.3 microgram/mg. Sialyltransferase activity was readily demonstrated in homogenate from normal thyroid or endemic goiter, but no sialyltransferase activity was detectable in a homogenate of JBM-thyroid tissue. We conclude that the finding of severely hyposialylated Tg is linked to a defect in iodotyrosine coupling seen in this patient with a possibly abnormal migration of Tg into the follicular lumen.