Ultrastructural localization of thyrotropin (TSH)-like immunoreactivity in specific secretory cells of the hypophyseal pars tuberalis in the Djungarian hamster,Phodopus sungorus

Summary Specific secretory cells in the hypophyseal pars tuberalis of Djungarian hamsters maintained under different photoperiods were investigated immunocytochemically by means of the colloidal gold technique using antibodies against rat thyrotropin (TSH). Secretory cells of animals kept under long photoperiods (LD16:8) showed positive staining of secretory granules (diameters 90–130 nm), whereas other intracellular structures were free of immunoreactivity. In animals kept under short photoperiods (LD8:16) secretory cells displayed increased numbers of secretory granules, but these organelles were devoid of immunoreactivity. In contrast, immunoreactivity of thyrotropes in the pars distalis did not differ between the two groups of animals investigated. The present results confirm earlier light-microscopical studies that in the pars tuberalis specific secretory cells show TSH-like immunoreactivity; however, they differ in their reactivity pattern from classical thyrotropes in the pars distalis.     

Human Lutropin (hLH) and Choriogonadotropin (CG) Are Assembled by Different Pathways: A MODEL OF hLH ASSEMBLY

The glycoprotein hormones are all structurally related heterodimers consisting of an α-subunit and a ligand-specific β-subunit that confers their unique biological activity. Crystal structures showed how the β-subunit surrounds a part of the α-subunit, and we showed the existence of the two mechanisms responsible for that assembly. In human choriogonadotropin, the β-subunit is folded before the subunits dock, and the α-subunit becomes incorporated into the dimer by a mechanism we termed “threading,” passing between parts of the preassembled β-subunit. Here, we show that the human lutropin β-subunit is not folded completely prior to its interaction with the α-subunit and show that docking of the subunits enables the α-subunit to serve as a chaperone to the β-subunit. Based on data described here, we propose that the α-subunit facilitates formation of the human lutropin β-subunit by two mechanisms. First, the cystine knot of the α-subunit potentiates formation of the β-subunit cystine knot, and second, contacts between α-subunit loop 2 and a hydrophobic tail in the β-subunit facilitate formation of the seatbelt latch disulfide, which stabilizes the heterodimer. The primary influence of the α-subunit was seen when the hydrophobic tail was present or absent, but the secondary mechanism was required only when the hydrophobic tail of the β-subunit was present. During the evolution of human choriogonadotropin, neither of these α-subunit roles was necessary for folding of the β-subunit. The complex mechanism for lutropin assembly may be required to provide an additional control on its positive feedback function in vertebrate reproduction.     

Functional significance of the thyrotropin receptor germline polymorphism D727E

In a toxic thyroid adenoma we identified a novel somatic mutation that constitutively activates the thyrotropin receptor (TSHR). Two heterozygous point mutations at adjacent nucleotides led to a substitution of alanine with asparagine at codon 593 (A593N) in the fifth transmembrane helix of TSHR. This somatic mutation resided on the same TSHR allele with the germline polymorphism D727E. The functional characteristics of the single TSHR mutants A593N and D727E and of the double mutant A593N/D727E were studied in transiently transfected COS-7 cells. The TSHR mutants A593N and A593N/D727E constitutively activated the cAMP cascade, whereas the D727E mutant did not differ from the wild-type TSHR. Surprisingly, the double mutant's specific constitutive activity was 2.3-fold lower than the A593N mutant. Thus, the polymorphism significantly ameliorates G(alphas) protein activation in the presence of the gain-of-function mutation A593N, although it is functionally inert in the context of the wild-type TSHR.     

On the identity of the thyrotropic cell in the red-spotted newt

Summary Although the pars distalis of the red-spotted newt has previously undergone extensive cytological examination, the identity of its thyrotropic cells has remained uncertain. From the present ultrastructural study, cells of type 3 (Masur, 1969) containing granules 150–180 nm in diameter are concluded to be the thyrotropes. Such cells were found to be present in the regions of the pars distalis where thyroidectomy cells arise after ablation of the thyroid gland. Cells of type 3 are probably identical with a population of cells containing granules which stain with silver methenamine indicating the presence of a glycoprotein such as thyroid stimulating hormone (TSH). Thyroidectomy cells containing a few residual granules 150–180 nm in diameter were occasionally found in partes distales from newts killed 3 or 7 days after ablation of the thyroid gland, and were abundant in pituitaries 21 days after thyroidectomy. Only cells of type 3 responded (by vacuolation of granules) when animals were immersed in water containing 10 g/l of thyroxine. No cells of the pars distalis showed cytological change after administration of synthetic thyrotropic releasing hormone (TRH) giving additional support to the view that this hormone has no stimulatory role in amphibians.Work supported in part by research grant 1 R01 AM 16731-01 from the Institute of Arthritis, Metabolism and Metabolic Diseases and in part by grant PCM 75-17637 from the National Science Foundation     

Funktionsentwicklung der thyrotropen Zellen der Adenohypophyse des Goldhamsters

Zusammenfassung Die Entwicklung der thyrotropen Zellen in der Adenohypophyse des Goldhamsters wurde an Schnittserien untersucht. Zur Klärung der Frage, inwieweit zwischen dem Beginn der thyrotropen Aktivität und der Funktionsaufnahme der fetalen Schilddrüse ein zeitlicher Zusammenhang besteht, wurden die fetalen Schilddrüsen in die Untersuchung einbezogen. Ausgewertet wurden in erster Linie Präparate, die — nach Aufoxydation der für das thyrotrope Hormon charakteristischen Cystingruppen — mit Alcianblau (pH 0,3) und Dichlorpseudoisocyanin gefärbt worden waren.Thyrotrope Zellen treten in der fetalen Goldhamsterhypophyse erstmals am 14. Tag (untersuchtes Stadium: 13d 17 h) auf. Es sind große, längsoval-birnenförmige bis polygonale Zellen, welche häufig über einen sockelartig ausgezogenen Zellfortsatz mit einer Kapillarwand in Kontakt treten. Das färbbare granuläre Material ist hauptsächlich in der Zellperipherie konzentriert, wodurch es zu einer charakteristischen, scharfen Konturierung dieser Zellen kommt.Zu demselben Zeitpunkt zeigt die fetale Schilddrüsenanlage als erste Zeichen der spezifischen Funktionsaufnahme Follikel- und Kolloidbildung.Während der weiteren Entwicklung nimmt die Zahl der thyrotropen Zellen stetig zu. Zellform und -große sowie die Art der Granulation bleiben dabei nahezu unverändert. An den ältesten untersuchten Stadien (14 Tage p.p.) sind als gonadotrop zu charakterisierende Zellen noch nicht eindeutig nachweisbar.

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Development of function of the thyrotropin secreting cells in the pituitary gland of the golden hamster

Summary The development of thyrotropin secreting cells in the pituitary gland of the golden hamster has been investigated in serial sections. With regard to the relationship between the beginning of thyrotropic activity in the fetal pituitary gland and onset of function in the fetal thyroidea the latter also has been investigated. Thyrotropic cells have been identified by staining with alicanblue (pH 0.3) or dichlorpseudoisocyanin after oxidation with performic acid or potassium permanganate. These reactions are based upon the relative high cystine content of TSH. Thyrotropic cells firstly are to be seen the 14th day of fetal life. These large cells of oval or angular form often have contact with the wall of a sinusoid via a long cytoplasmatic process. The grannies of the thyrotrophs show a marked tendency to be more concentrated at the cell borders giving the cell a characteristic hard outline. At the same time the thyroideaanlage shows first signs of specific function as represented by forming of follicles and production of colloid. During the further development the number of thyrotrophs increases. Form and size of the TSH-cells and the kind of granulation of these cells do not change. In the oldest stages examined (14th day p.p.) gonadotropic cells could not be identified.

Sasse (1968) konnte weiterhin zeigen, wie es etwa zum selben Zeitpunkt zu einem plötzlichen Anstieg der Aktivität der Glucose-6-Phosphat-Dehydrogenase und der cytoplasmatischen RNS in den Schilddrüsenepithelien kommt. Die Bedeutung der G-6-P-DH liegt in der Bereitstellung der für die Nucleinsäuresynthese notwendigen Pentosen über den Pentose-Phosphat-Cyclus (Sasse, 1968). Die plötzliche Steigerung der Aktivitätsrate der G-6-P-DH beruht möglicherweise auf der zum gleichen Zeitpunkt einsetzenden thyrotropen Aktivität des HVL. Hierauf weist jedenfalls die in vitro an Gewebsschnitten beobachtete spezifische Stimulierung des Pentose-Phosphat-Cyclus nach TSH-Zusatz hin (Condliffe und Robbins, 1967). Die Bedeutung des thyrotropen Hormons für die Synthese der Ribonucleotide in der fetalen Schilddrüse wird auch durch Befunde unterstrichen, nach denen TSH eine Umwandlung des glatten agranulären in das rauhe, d. h. mit Ribosomen besetzte, endoplasmatische Retikulum bewirkt. Wesentlicher Mechanismus scheint dabei zu sein, daß durch TSH eine Funktionsumstellung der DNS von der Phase reiner Proliferation auf die Entwicklung der spezifischen Schilddrüsenfunktion, d.h. der thyroidealen Hormonsynthese bewirkt wird (Szentágothai et al., 1968).     

Effect of gonadotropins,thyrotropin, and adrenocorticotropin on the development of 12-day chick embryonic gonads

Summary Gonadotropins (FSH+LH) and thyrotropin (TSH) stimulated the development of 12-day embryonic gonads, whereas adrenocorticotropin (ACTH) did not show any significant effect. It is concluded that the gonads of 12-day chick embryos have the capacity to respond to both gonadotropic and thyrotropic stimulation. This suggests that at the time when the hypothalamo-pituitary-thyroid axis begins to develop, the capacity of gonadal receptors to distinguish between gonadotropins and thyrotropin has not been established.     

Characterization of Immunoreactive Thyrotropin Releasing Hormone in Human Fetal Cerebellum

Abstract— High concentrations (411 ± 30 pg/mg protein; mean ± S.E., n = 12) of immunoreactive TRH (TRH_i) were detected in extracts of human fetal cerebellum (13-26 weeks gestation). The TRH_i in the cerebellar extracts, when subjected to gel filtration and high performance liquid chromatography (HPLC), co-migrated with synthetic TRH. In each instance, no TRHⁱ was detected which did not share identical chromatographic mobilities with synthetic TRH. Like synthetic TRH, the TRH_i in extracts of fetal cerebellum and hypothalamus was insoluble in diethyl ether and was efficiently degraded when incubated at 37°C with adult rat serum. No significant degradation of TRH_i occurred when the incubation was conducted at 0°C or when the extracts were incubated with rat serum that had been preheated at 60°C for 20 min. Neither synthetic TRH nor TRH_i in extracts of fetal cerebellum or hypothalamus was degraded when incubated with human umbilical cord serum at 37°C or 0°C. The results of this study are supportive of the view that the TRHⁱ in extracts of human fetal cerebellum is identical to TRH.     

Morphine inhibits TRH-induced intestinal transit increases

The current study examined the effects of intraperitoneal (IP) and intracisternal (IC) administration of the opiate agonist, morphine, and an opioid, central beta-endorphin, on thyrotropin releasing hormone (TRH)-induced small intestinal transit increases. Anesthetized rats, 14-day and older, were studied to determine age-related differences. Results showed that in all age groups IP morphine (2 mg/kg) blocked TRH (15 μg)-induced increases in transit of a charcoal bolus. Morphine 1 μg and beta-endorphin 1 μg administered IC in 0.6 μl failed to block TRH (10 μg)-induced increases in intestinal transit in 14-day-old rats. However, both morphine and beta-endorphin 1 μg IC blocked TRH-induced increases in adult rats. Dose-response studies demonstrated that higher doses (> 1 μg) of morphine IC were required to block TRH-induced increases in preweaning rats.     

促甲状腺素受体抗体及白细胞介素-2、白细胞介素-6在Graves病131I治疗中的变化及临床意义

目的:研究促甲状腺素受体抗体(TRAb)及白细胞介素-2(IL-2)、白细胞介素-6(IL-6)在Graves病~(131)I治疗中的变化并分析其临床意义。方法:选取2015年8月-2016年8月于我院接受~(131)I治疗的Graves病患者112例为研究对象,按照第6个月的甲状腺功能检查结果的不同分为治愈组(n=54),缓解组(n=21)和甲减组(n=37)。分别比较治疗前、治疗3个月、6个月后三组患者的甲状腺功能指标以及TRAb、IL-2、IL-6水平。结果:治疗前三组患者游离T3(FT3)、游离T4(FT4)、促甲状腺激素(TSH)水平比较差异无统计学意义(P0.05),治疗3个月、6个月后三组患者FT3、FT4水平均明显低于治疗前,而TSH水平明显高于治疗前(P0.05)。治疗3个月、6个月后甲减组FT3、FT4水平均明显低于治愈组、缓解组,治愈组又明显低于缓解组,TSH水平明显高于治愈组、缓解组,治愈组又明显高于缓解组(P0.05)。治疗前三组患者TRAb、IL-2、IL-6水平比较差异无统计学意义(P0.05)。治疗3个月后三组患者TRAb水平均明显高于治疗前(P0.05),治疗6个月后治愈组与甲减组患者TRAb水平与治疗前比较无统计学差异(P0.05),但缓解组患者TRAb水平高于甲减组,差异有统计学意义(P0.05)。治疗3个月、6个月后,治愈组与甲减组患者IL-2、IL-6水平均低于治疗前,而缓解组高于甲减组,差异均有统计学意义(P0.05)。结论:TRAb、IL-2、IL-6可作为评估Graves病~(131)I治疗后的指标,通过检测三项指标治疗前后水平变化情况,从而为临床预后评估提供指导作用。     

Actions of intracerebroventricular administration of kyotorphin and an analog on thermoregulation in the mouse

Intracerebroventricular (ICV) administration of kyotorphin (L-Tyr-L-Arg) and cyclo (N-methyl-L-Tyr-L-Arg), its analog, produced significant dose-dependent hypothermic responses in mice at an ambient temperature of 24°C. The hypothermic action of kyotorphin was much greater than that of Met-enkephalin (Met-ENK) but less than that of cyclo NMTA. This action was slightly but not significantly reversed by intraperitoneally administered naloxone (8 mg/kg), an opioid receptor antagonist. Met-ENK utilized as a control peptide in this study also produced a dose-dependent hypothermia which was slightly antagonized by naloxone (8 mg/kg, IP). Thyrotropin releasing hormone (TRH) injected ICV produced hyperthermia dose-dependently. The hypothermia induced by kyotorphin, its cyclic analog and Met-ENK was prevented by a small dose of TRH (0.18 μg=0.5 nmol/animal) which by itself had little effect on body temperature. A TRH neuronal system in the brain may explain the mechanism of kyotorphin-induced hypothermia. However, there was little evidence of involvement of opioid receptors. The present study demonstrates a potent action of kyotorphin and its analog on thermoregulation.