Clinical efficacy of selenium supplementation in patients with Hashimoto thyroiditis: A systematic review and meta-analysis.

BACKGROUND: Evidence suggests that selenium supplementation could be useful in the treatment of Hashimoto thyroiditis (HT), but the available trials are heterogeneous. This study investigates clinically relevant effects of selenium supplementation in patients with HT. METHODS: A systematic search was performed in PubMed, Web of Science, EMBASE, Scopus, and the Cochrane Library. The latest update was performed on December 3, 2022. We investigated the changes in thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) after selenium supplementation. The effect sizes were expressed as weighted mean difference (WMD) with 95% confidence intervals (CIs). RESULTS: After screening and full-text assessment, 7 controlled trials comprising 342 patients were included in the systematic review. The results showed that there was no significant change in TPOAb levels (WMD = -124.28 [95% CI: -631.08 to 382.52], P = .631, I2 = 94.5%) after 3 months of treatment. But there was a significant decrease in TPOAb levels (WMD = -284.00 [95% CI: -553.41 to -14.60], P < .05, I2 = 93.9%) and TgAb levels (WMD = -159.86 [95% CI: -293.48 to -26.24], P < .05, I2 = 85.3%) after 6 months of treatment. CONCLUSIONS: Selenium supplementation reduces serum TPOAb and TgAb levels after 6 months of treatment in patients with HT, but future studies are warranted to evaluate health-related quality or disease progression.

99mTc-Pertechnetate Scintigraphy Predicts Successful Postoperative Ablation in Differentiated Thyroid Carcinoma Patients Treated with Low Radioiodine Activities.

BACKGROUND: Postoperative routine radioiodine (RAI) treatment is currently debated for patients with low-risk differentiated thyroid carcinoma (DTC) patients. If performed, a low ¹³¹I activity (i.e., 1 to 2 GBq) is recommended with the aim to ablate thyroid remnant and facilitate subsequent follow-up by thyroglobulin measurement. The purpose of this study was to evaluate the relationship between postsurgical technetium-99m (99mTc)-pertechnetate scintigraphy and the rate of successful remnant ablation after low activity radioiodine ablation in patients with DTC. METHODS: Enrolled were 193 patients with low risk DTC who underwent total thyroidectomy and RAI ablation with a fixed 1.1 GBq activity of ¹³¹I. 99mTc-pertechnetate scans were done and thyrotropin stimulated thyroglobulin (sTg) levels measured just before ablation. Ablation effectiveness was assessed 6 to 12 months later by sTg measurement, neck ultrasound and diagnostic whole body scan. RESULTS: A negative 99mTc-perthecnetate scans was the best predictor of successful ablation (P<0.001) followed by preablative sTg levels <0.8 ng/mL (P=0.008) and 99mTc-pertechnetate uptake rate values <0.9% (P=0.065). Neither sex nor age of the patient at the time of ablation or tumor histology and size showed a significant association with the rate of successful ablation. CONCLUSION: The 99mTc-pertechnetate scintigraphy is a simple and feasible tool to predict effectiveness of low activity ¹³¹I thyroid to ablate thyroid remnants in patients with DTC.

ER stress contributes to high-fat diet-induced decrease of thyroglobulin and hypothyroidism.

Recent studies revealed the emerging role of excess uptake of lipids in the development of hypothyroidism. However, the underlying mechanism is largely unknown. We investigated the effect of high-fat diet (HFD) on thyroid function and the role of endoplasmic reticulum (ER) in HFD-induced hypothyroidism. Male Sprague-Dawley rats were fed with HFD or control diet for 18 wk. HFD rats showed an impaired thyroid function, with decreased thyroglobulin (Tg) level. We found the ER stress was triggered in HFD rat thyroid glands and palmitate-treated thyrocytes. Luminal swelling of ER in thyroid epithelial cells of HFD rats was also observed. The rate of Tg degradation increased in palmitate-treated thyrocytes. In addition, applying 4-phenyl butyric acid to alleviate ER stress in HFD rats improved the decrease of Tg and thyroid function. Withdrawal of the HFD improved thyroid function . In conclusion, we demonstrate that ER stress mediates the HFD-induced hypothyroidism, probably by impairing the production of Tg, and attenuation of ER stress improves thyroid function. Our study provides the understanding of how HFD induces hypothyroidism.

The Effect of Hypolipidemic Agents on Thyroid Autoimmunity in Women with Hashimoto's Thyroiditis Treated with Levothyroxine and Selenomethionine.

BACKGROUND: Levothyroxine and selenomethionine were found to reduce thyroid antibody titers in patients with Hashimoto's thyroiditis. The same effect was produced by intensive statin therapy. The aim of the present study was to assess whether hypolipidemic agents modulate the impact of thyroid hormone supplementation and selenomethionine on thyroid autoimmunity. METHODS: The study included 62 women with Hashimoto's thyroiditis treated for at least 6 months with levothyroxine and selenomethionine. On the basis of plasma lipids, women were divided into three groups: women with isolated hypercholesterolemia (group A; n=20), women with isolated hypertriglyceridemia (group B; n=17), and women with normal plasma lipids (group C; n=25). Group A were then treated with atorvastatin (20 mg daily), while group B received micronized fenofibrate (200 mg daily). Serum titers of thyroid peroxidase and thyroglobulin antibodies, as well as serum levels of thyrotropin, free thyroxine and free triiodothyronine were measured at the beginning of the study and 6 months later. RESULTS: Fenofibrate decreased triglycerides and increased HDL cholesterol, while simvastatin decreased total and LDL cholesterol. Fenofibrate reduced titers of thyroid peroxidase and, to a lesser extent, thyroglobulin antibodies. Atorvastatin tended to increase thyroid peroxidase antibodies. No changes in thyrotropin, free thyroxine and free triiodothyronine were observed in any treatment group. Fenofibrate-induced changes in thyroid antibody titers correlated with baseline antibody titers, as well as with treatment-induced changes in HDL cholesterol and insulin sensitivity. CONCLUSIONS: The obtained results indicate that only fibrates may potentiate the effect of selenomethionine and levothyroxine on thyroid autoimmunity in women.

TAZ Induction Directs Differentiation of Thyroid Follicular Cells from Human Embryonic Stem Cells.

OBJECTIVE: The differentiation program for human thyroid follicular cells (TFCs) relies on the interplay between sequence-specific transcription factors and transcriptional co-regulators. Transcriptional co-activator with PDZ-binding motif (TAZ) is a co-activator that regulates several transcription factors, including PAX8 and NKX2-1, which play a central role in thyroid-specific gene transcription. TAZ and PAX8/NKX2-1 are co-expressed in the nuclei of thyroid cells, and TAZ interacts directly with both PAX8 and NKX2-1, leading to their enhanced transcriptional activity on the thyroglobulin (TG) promoter and additional genes. METHODS: The use of a small molecule, ethacridine, recently identified as a TAZ activator, in the differentiation of thyroid cells from human embryonic stem (hES) cells was studied. First, endodermal cells were derived from hES cells using Activin A, followed by induction of differentiation into thyroid cells directed by ethacridine and thyrotropin (TSH). RESULTS: The expression of TAZ was increased in the Activin A-derived endodermal cells by ethacridine in a dose-dependent manner and followed by increases in PAX8 and NKX2-1 when assessed by both quantitative polymerase chain reaction and immunostaining. Following further differentiation with the combination of ethacridine and TSH, the thyroid-specific genes TG, TPO, TSHR, and NIS were all induced in the differentiated hES cells. When these cells were cultured with extracellular matrix-coated dishes, thyroid follicle formation and abundant TG protein expression were observed. Furthermore, such hES cell-derived thyroid follicles showed a marked TSH-induced and dose-dependent increase in radioiodine uptake and protein-bound iodine accumulation. CONCLUSION: These data show that fully functional human thyroid cells can be derived from hES cells using ethacridine, a TAZ activator, which induces thyroid-specific gene expression and promotes thyroid cell differentiation from the hES cells. These studies again demonstrate the importance of transcriptional regulation in thyroid cell development. This approach also yields functional human thyrocytes, without any gene transfection or complex culture conditions, by directly manipulating the transcriptional machinery without interfering with intermediate signaling events.

Undetectable serum thyroglobulin levels in patients with medullary thyroid carcinoma after total thyroidectomy without radioiodine ablation.

BACKGROUND: Recently, we reported that the thyroglobulin (Tg) doubling time (DT) was the most potent prognostic factor in patients with papillary thyroid carcinoma (PTC) who underwent total thyroidectomy. Interestingly 16.2% of the study patients had a decrease in Tg levels over time, giving negative values in Tg-DT. These patients had an excellent outcome. However, most of the patients did not receive ablation with radioactive iodine. Therefore, whether the Tg in these patients was derived from persistent disease or residual thyroid tissue could not be concluded. To resolve this question, we measured serum Tg levels in patients with medullary thyroid carcinoma (MTC) who underwent total thyroidectomy using similar surgical techniques for the treatment of PTC. METHODS: Twenty-seven consecutive patients with MTC who underwent total thyroidectomy were selected. Of them, five patients with antibodies to Tg were excluded from the study. In the remaining 22 patients, serum Tg levels were measured before and after surgery. None of the patients received radioactive iodine ablation. They were prescribed levothyroxine as a replacement for the lost thyroid function. RESULTS: Serum Tg levels were detectable preoperatively, while postoperative serum Tg levels were lower than the detectable level, 0.5 ng/mL, in all 22 patients. CONCLUSIONS: The results indicate that most of the patients with detectable Tg levels and negative Tg-DT values after total thyroidectomy for PTC in our previous study had persistent disease, and that their serum Tg was not from residual thyroid tissue, suggesting that up to 50% of patients with persistent PTC have a decrease in serum Tg levels in response to thyroid-stimulating hormone-suppressive therapy.

[Mechanism of the effects of amitrole on the thyroglobulin in Fischer rat thyroid follicle-5 cell].

OBJECTIVE: The mechanisms of the effects of amitrole on the thyroglobulin (TG) was investigated in Fischer rat thyroid follicle-5 cell (FRTL-5 cells) and in the medium. METHODS: FRTL-5 cells were treated with 1, 10 and 100 microg/ml amitrole, and cytotoxicity was tested by 3H-TdR. The effects of amitrole on TG and thyroid transcription factor 1(TTF-1) in FRTL-5 cells were analyzed by RIA and ICC. And the TSHR in FRTL-5 cells was examined by Immunofluorescence analysis. RESULTS: 1,10 and 100 microg/ml amitrole had no significant cytotoxicity to the FRTL-5 cells (P > 0.05). The concentration of TG in the culture was decreased by 10 and 100 microg/ml amitrole (P < 0.05), and the concentration of TG in the cells was decreased by 100 microg/ml (P < 0.05) but the TTF-1 in the cells were not obviously changed (P > 0.05). The TSHR in the surface of FRTL-5 cells was significantly decreased by all doses of amitrole (P < 0.01). CONCLUSION: The influence of amitrole on TG of FRTL-5 cells may be related to significantly reduce TSHR in the surface of FRTL-5 cells.

Recombinant human TSH versus hypothyroidism. Cost-minimization-analysis in the follow-up care of differentiated thyroid carcinoma.

UNLABELLED: The primary aim of this study was to compare pharmacoeconomic effects of hypothyroidism secondary to hormone withdrawal (THW) and recombinant human TSH (rhTSH) for follow-up WBS in patients with differentiated thyroid cancer (DTC). The second aim was to determine patients' preference for one procedure or the other. PATIENTS, METHODS: This retrospective survey included 327 patients with DTC who underwent at least one in-hospital WBS with rhTSH between 1999 and 2006. They had also undergone THW for WBS. Patients received a two-page questionnaire via mail addressing five symptoms and ten items regarding managing their daily life which was answered by 61.6%. The responder group did not differ from the entire group. The medical and societal cost of both procedures for diagnostic WBS was calculated including direct and all ascertainable indirect cost for the reference year 2005. A sensitivity analysis included the German DRG system of 2007 and 2010. RESULTS: After THW, 94% of patients reported hypothyroid symptoms. Using rhTSH, symptoms occurred significantly less. As a result, 97% of patients favored rhTSH over THW. Mean absence from salaried work was 12.3 days after THW compared to 4 days with rhTSH. Family members of salaried employees missed 3 and 0.7 workdays after THW and rhTSH, respectively. Almost twice as often, medical attention was sought after THW (36%) compared to rhTSH (19 %). Undergoing THW, 48% of patients still used their car while hypothyroid. Our cost calculation revealed a slight benefit of about 89.00 Euro in favour of rhTSH stimulation. CONCLUSION: Hypothyroidism after THW causes significant morbidity and safety risks. The clinical and societal benefits associated with rhTSH are roughly gained at equivalent overall cost to that of THW.

Phase II trial of sorafenib in metastatic thyroid cancer.

PURPOSE: Based on the pivotal role of Ras-Raf-MAP-ERK signaling and vascular endothelial growth factor (VEGF) in papillary thyroid cancer (PTC), we conducted a phase II clinical trial of sorafenib targeting RAF and VEGF receptor kinases in PTC. PATIENTS AND METHODS: The primary end point was the objective response rate. Secondary end points included response correlation with serum thyroglobulin (Tg); functional imaging; tumor genotype; and signaling inhibition in tumor biopsies. Using a Simon minimax two-stage design, 16 or 25 chemotherapy-naïve metastatic PTC patients were to be enrolled in arm A (accessible tumor for biopsy). Arm B patients had other subtypes of thyroid carcinoma or prior chemotherapy, and did not require tumor biopsies. Patients received 400 mg orally twice per day of sorafenib. Response was assessed every 2 months using RECIST (Response Evaluation Criteria in Solid Tumors). RESULTS: Of 41 PTC patients, six patients had a partial response (PR; 15%; 95% CI, 6 to 29) and 23 patients (56%; 95% CI, 40 to 72) had stable disease longer than 6 months. Median duration of PR was 7.5 months (range, 6 to 14). Median progression-free survival was 15 months (95% CI, 10 to 27.5). In 14 (78%) of 18 Tg-assessable PTC patients, Tg declined more than 25%. Common grade 3 adverse events included hand-foot skin reaction, musculoskeletal pain, and fatigue. BRAF mutation was detected in 17 (77%) of 22 PTCs analyzed. Four of 10 paired tumor biopsies from PTC patients showed a reduction in levels of vascular endothelial growth factor receptor phosphorylation, ERK phosphorylation, and in VEGF expression during sorafenib therapy. No PRs were noted among non-PTC patients. CONCLUSION: Sorafenib is reasonably well-tolerated therapy with clinical and biologic antitumor activity in metastatic PTC.

Protein:protein aggregation induced by protein oxidation.

When the level of reactive oxygen species (ROS) in cells exceeds a genetically coded defense capacity, the cells experience damage to vital components such as DNA, proteins and lipids that leads to non-specific interactions and the production of a series of high molecular weight protein aggregates. The dynamics of oxidative stress induced aggregation were studied here using model proteins and yeast. Model proteins were oxidized at increasing ROS concentrations and analyzed using size exclusion chromatography (SEC). Changes in the SEC elution profile showed that aggregation happens in stages and protein fragments produced as a result of oxidation also give rise to aggregates. Yeast cells were stressed with hydrogen peroxide to investigate in vivo aggregation. Equal amounts from control and oxidized lysates were chromatographed on a size exclusion column and proteins of molecular weight exceeding 700 kDa were collected from both samples which were then differentially labeled using light and heavy isotope coded N-acetoxysuccinamide and mixed in a 1:1 ratio. The coded mixture was analyzed using LC/MS and peptides that appeared as singlets representing the proteins that aggregated with higher molecular mass protein complexes were identified. Twenty-five proteins were identified to be of this type. Fifteen members in this group were found to have been carbonylated. These proteins are part of the proteome known as the aggresome. The protein content of the aggresome may provide vital information for mechanistic studies targeting disease and aging.

A phase II trial of doxorubicin and interferon alpha 2b in advanced, non-medullary thyroid cancer.

BACKGROUND: The combination of doxorubicin and interferon alpha is supported by preclinical data. We sought to evaluate the efficacy of this combination in patients with advanced thyroid cancer. PATIENTS AND METHODS: Patients with locally recurrent or metastatic, radioiodine- refractory thyroid cancer, excluding medullary carcinoma, were treated with interferon alpha-2b 12 million units/m2 subcutaneously on days 1-5 and doxorubicin 40 mg/m2 intravenously, on day 3, every 28 days. RESULTS: 17 patients, 15 with well differentiated and 2 with anaplastic thyroid carcinoma, were enrolled; median age was 69 years. Three patients had received radiation plus low dose doxorubicin previously. In 16 patients assessable for response, 1 patient (6%), who had follicular carcinoma, achieved a partial response and 10 patients (62.5%) stable disease as best response. Median time to progression was 5.9 months and median overall survival 26.4 months. In 14 evaluable patients, 5 (36%) had a thyroglobulin response (30% or more reduction in serum levels). Grade 3/4 neutropenia occurred in 76% of patients and neutropenic fever in 24%. Other grade 3/4 adverse events included fatigue (41%), rigors (18%), fever (6%), nausea/vomiting (29%), anorexia (29%), stomatitis (24%), vision disturbances (18%), neuropathy (18%), and hyponatremia (6%). One patient developed heart failure. CONCLUSIONS: Doxorubicin and interferon alpha was associated with considerable toxicities but modest antitumor activity in patients with advanced, non-medullary thyroid cancer.

KClO(4) inhibits thyroidal activity in the larval lamprey endostyle in vitro.

An in vitro experimental system was devised to assess the direct effects of the goitrogen, potassium perchlorate (KClO(4)), on radioiodide uptake and organification by the larval lamprey endostyle. Organification refers to the incorporation of iodide into lamprey thyroglobulin (Tg). Histological and biochemical evidence indicated that endostyles were viable at the termination of a 4h in vitro incubation. A single iodoprotein, designated as lamprey Tg, was identified in the endostylar homogenates by polyacrylamide gel electrophoresis and Western blotting. Lamprey Tg was immunoreactive with rabbit anti-human Tg serum and had an electrophoretic mobility similar to that of reduced porcine Tg. When KClO(4) was added to the incubation medium, both iodide uptake and organification by the endostyle were significantly reduced relative to controls as determined by gamma counting, and gel-autoradiography and densitometry, respectively. Western blotting showed that KClO(4) significantly lowered the total amount of lamprey Tg in the endostyle. Based on the results of this in vitro investigation, we conclude that KClO(4) acts directly on the larval lamprey endostyle to inhibit thyroidal activity. These data support a previous supposition from in vivo experimentation that KClO(4) acts directly on the endostyle to suppress the synthesis of thyroxine and triiodothyronine, resulting in a decrease in the serum levels of these two hormones.

Role of thyroglobulin endocytic pathways in the control of thyroid hormone release.

Thyroglobulin (Tg), the thyroid hormone precursor, is synthesized by thyrocytes and secreted into the colloid. Hormone release requires uptake of Tg by thyrocytes and degradation in lysosomes. This process must be precisely regulated. Tg uptake occurs mainly by micropinocytosis, which can result from both fluid-phase pinocytosis and receptor-mediated endocytosis. Because Tg is highly concentrated in the colloid, fluid-phase pinocytosis or low-affinity receptors should provide sufficient Tg uptake for hormone release; high-affinity receptors may serve to target Tg away from lysosomes, through recycling into the colloid or by transcytosis into the bloodstream. Several apical receptors have been suggested to play roles in Tg uptake and intracellular trafficking. A thyroid asialoglycoprotein receptor may internalize and recycle immature forms of Tg back to the colloid, a function also attributed to an as yet unidentified N-acetylglucosamine receptor. Megalin mediates Tg uptake by thyrocytes, especially under intense thyroid-stimulating hormone stimulation, resulting in transcytosis of Tg from the colloid to the bloodstream, a function that prevents excessive hormone release.

Contrasting effects of activating mutations of GalphaS and the thyrotropin receptor on proliferation and differentiation of thyroid follicular cells.

The cyclic AMP pathway is a major regulator of thyrocyte function and proliferation and, predictably, its inappropriate activation is associated with a sub-set of human thyroid tumours. Activating mutations are, however, more common in the thyrotropin receptor (TSHR) than in its downstream transducer, Galphas. To investigate whether this reflects an inherent difference in their oncogenic potency, we compared the effects of retrovirally-transduced mutant (A623I) TSHR or (Q227L) Galphas (GSP), using the rat thyroid cell line FRTL5 and primary human thyrocytes. In FRTL5, expression of GSP or mutant (m) TSHR induced a 2 - 3-fold increase in basal levels of cAMP. This was associated with TSH-independent proliferation (assessed by both cell number and DNA synthesis) and function (as shown by increased expression of thyroglobulin (Tg) and the sodium/iodide symporter). In primary cultures, expression of mTSHR, but not GSP, consistently induced formation of colonies with epithelial morphology and thyroglobulin expression, capable of 10 - 15 population doublings (PD) compared to less than three in controls. Thus, while mTSHR and GSP exert similar effects in FRTL5, use of primary cultures reveals a major difference in their ability to induce sustained proliferation in normal human thyrocytes, and provides the first direct evidence that mTSHR is sufficient to initiate thyroid tumorigenesis.

Thyroid function in postmenopausal breast cancer patients treated with tamoxifen.

Thyroid function was evaluation in 26 postmenopausal women with breast cancer before and at various time intervals during treatment with tamoxifen. Tamoxifen treatment suppressed plasma levels of FT3 and FT4 (p < 0.005 for both) and elevated plasma concentrations of TBG (p < 0.005 and TG (p < 0.025). In general, these changes became significant after 6 months of treatment. Plasma TSH increased significantly after 1 y of treatment (p < 0.025). A fall in FT4 and FT3 combined with increase in TSH suggests a reduced bioavailability of T4 and T3 during tamoxifen treatment. The increase in TG may reflect a reduced synthesis or liberation of T4 resulting in a reduced plasma level of FT4. Our findings suggest that tamoxifen influences the thyroid hormone levels, not only by modulating plasma TBG, but also by interfering with hormone synthesis or secretion in the thyroid gland.

TPA induces a block of differentiation and increases the susceptibility to neoplastic transformation of a rat thyroid epithelial cell line.

The PC Cl 3 cell line is a well-characterized epithelial cell line of rat thyroid origin. This cell line retains in vitro the typical markers of thyroid differentiation: thyroglobulin (TG) synthesis and secretion, iodide uptake, thyroperoxidase (TPO) expression, and dependency on TSH for growth. Although the differentiated phenotype of thyroid cells has been relatively well described, the molecular mechanisms that regulate both differentiation and neoplastic transformation of thyroid cells still need to be investigated in detail. Protein kinase C (PKC), the target of tetradecanoylphorbol acetate (TPA), regulates growth and differentiation of several cell types. Here we show that treatment of PC Cl 3 cells with TPA induces an acute block of thyroid differentiation. TPA-treated PC Cl 3 cells are unable to trap iodide and the expression levels of thyroglobulin, TSH receptor, and TPO genes are drastically reduced by TPA treatment. This differentiation block is not caused by a reduced expression of one of the master genes of thyroid differentiation, the thyroid transcription factor 1 (TTF-1). TPA-treated PC Cl 3 cells display an increased growth rate indicating that, in addition to the differentiation block, TPA also significantly affects the growth regulation of thyroid cells. Finally, TPA treatment dramatically increases the number of transformation foci induced in PC Cl 3 cells by retroviruses carrying v-Ki-ras, v-Ha-ras, and v-mos oncogenes. These findings support the notion that the PKC pathway can influence proliferation, differentiation, and neoplastic transformation of thyroid cells in culture.

[The lysosomal proteolytic system and thyroid functional activity in rats administered chloroquine]. / Proteoliticheskaia sistema lizosom i funktsional'naia aktivnost' shchitovidnoi zhelezy krys pri vvedenii khlorokhina.

A 7-, 14-, and 21-day course of injections of the lysosomotropic drug chloroquine in a dose of 50-mg/kg per day causes a more than two-fold decrease of T3 concentration and insignificant changes in the level of T4 and thyrotropin in the blood serum of rats. In the series with 14- and 21-day courses of chloroquine injections, inhibition of the thiol cathepsins B and L with simultaneous activation of the aspartic proteinase cathepsin D occurred. Permeability of the lysosomal membranes for all hydrolases under study considerably increased after a 7-day course of chloroquine but reduced subsequently to the control level in longer treatment. The possible mechanisms of changes in the spectrum of lysosomal proteinases and functional activity of the thyroid are discussed.

How to examine the antigen-damaging effect of sodium ethoxide on deplasticized epoxy sections.

The purpose of this investigation was to develop a method that could be used to estimate how damaging sodium ethoxide is to different antigens with respect to immunolabeling when epoxy sections are deplasticized. If we obtain weak labeling for an antigen on deplasticized epoxy sections, this might be caused by the damaging effect of the ethoxide solution. It is therefore interesting to develop a method to check if this really is the reason. Fibrin clots and tissues of human kidney and thyroid were embedded in LR White resin. Some thin sections from these specimen blocks were exposed to sodium ethoxide in the same way as epoxy sections are when being deplasticized. Other sections from the same blocks were not exposed to sodium ethoxide. Both categories of sections were immunogold-labeled with anti-fibrinogen, anti-thyroglobulin, anti-IgA, anti-IgG, or anti-IgM. The intensity of immunolabeling of sections treated with ethoxide was compared with the immunolabeling of corresponding sections that were not treated with ethoxide. No significant differences were found in immunolabeling for fibrinogen, IgA, IgG, and IgM. For thyroglobulin, the intensity was approximately 30% less in tissues that were exposed to sodium ethoxide. The practical significance of this method is that we easily can examine the degree to which a given antigen is affected by sodium ethoxide, which is the agent used for deplasticizing epoxy sections.

Transplantable rat thyroid cancer cell line FRTC transformed with muramyl dipeptide.

A rat thyroid cancer cell line, FRTC, was established from the normal rat thyroid cell line, FRTL-5. FRTL-5 cells were cultured in vitro with N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) for 4 days and were transplanted intraperitoneally into Fisher rats. Disseminated tumour formation in the peritoneum was found in ten out of ten rats in which MDP-treated FRTL-5 cells were transplanted. Colloid-like structures stained with anti-thyroglobulin (Tg) antibodies were observed in the tumours. On the other hand, no tumour was found in any of the rats in which untreated FRTL-5 cells were transplanted. No morphological changes were observed in FRTL-5 cells after long-term in vitro culture in the presence of MDP. MDP had no effect on thymidine incorporation, the production of cAMP or the expression of c-myc in FRTL-5 cells in vitro. Cells from the tumour (FRTC) secreted Tg in vitro and expressed Tg, thyroid peroxidase (TPO) and thyrotropin (TSH) receptor mRNA. The expression of TSH receptor mRNA increased in FRTC cells after TSH stimulation. FRTC cells produced cAMP in response to TSH stimulation in a dose-dependent manner. However, the growth of FRTC cells was TSH independent. Expression of c-myc and c-fos was observed in FRTC cells in vivo as well as in vitro. FRTC cells formed tumours in Fisher rats when transplanted subcutaneously. FRTC cells have several characteristics of differentiated thyroid cancer cells and may provide a good model for the study of human differentiated thyroid cancers.