Biomedical subjects

T Akamizu

Publications and source records attributed to T Akamizu.

At least 91 records · Page 5Linked to original sources

PubMed1990

Thyrotropin receptor processing and interaction with thyrotropin.

In vitro transcription/translation, using rat thyrotropin receptor cDNA, results in the formation of nonglycosylated proteins able to bind thyrotropin, one of which approximates the 87 Kd size predicted for the receptor. In the presence of canine pancreatic microsomal membranes, putative glycosylation sites are modified as evidenced by digestion with endoglycosidase H. Using a deletion mutant, the presence of a hydrophobic peptide after the initiation signal is established as a signal peptide critical to post translational processing by the canine pancreatic membranes but not to binding thyrotropin.

Acetylglucosaminidase↗

PubMed1990

Cloning, chromosomal assignment, and regulation of the rat thyrotropin receptor: expression of the gene is regulated by thyrotropin, agents that increase cAMP levels, and thyroid autoantibodies.

A rat thyrotropin (thyroid-stimulating hormone, TSH) receptor cDNA was isolated that encoded a protein of 764 amino acids, Mr 86,528. Transfection of the cDNA caused COS-7 cells to develop a TSH-sensitive adenylate cyclase response and the ability to bind 125I-labeled TSH; both activities were similar to those of rat FRTL-5 thyroid cells and not duplicated by lutropin. The gene represented by the cDNA was assigned to mouse chromosome 12 and human chromosome 14. Northern analyses identified two species of mRNA, 5.6 and 3.3 kilobases, in FRTL-5 thyroid cells; the transcripts appeared to differ only in the extent of their 3' noncoding sequences. There were minimal amounts of the two mRNAs in rat ovary, and neither was detected in RNA preparations from rat testis, liver, lung, brain, spleen, and FRT thyroid cells, which do not have a functional TSH receptor. TSH decreased both mRNA species 3- to 4-fold within 8 hr in FRTL-5 thyroid cells; down-regulation was dependent on TSH concentration and duplicated by forskolin, cholera toxin, or 8-bromo-cAMP but not by a phorbol ester. Down-regulation was also duplicated by thyroid-stimulating autoantibodies, which increased cAMP levels, but not by thyrotropin binding-inhibiting auto-antibodies, which actually increased TSH receptor mRNA levels.

Amino Acid Sequence↗

PubMed1989

Receptors of the thyroid: the thyrotropin receptor is only the first violinist of a symphony orchestra.

A basic reason for undertaking these studies was to further our knowledge of the structure and function of the TSH receptor as well as its interaction with other receptors on thyroid cells. The multiplicity of observations suggests the approach is bearing fruit, does not provide a simple answer, and can have pitfalls. We hope they may also contribute to understanding the structure and function of autoantigens in Graves' disease and glycoprotein hormone receptors in general. The authors are grateful to their collaborators in the National Dental Institute, particularly Drs. Bellur Prabhakar, Edward Oates, and Abner Notkins, in the National Cancer Institute, Drs. W. O. McBride and M. Lerman for their contributions to the cloning studies.

Amino Acid Sequence↗

PubMed1988

Purification of TSH receptor from porcine thyroid membrane and effect of various protease inhibitors on receptor stability.

Purification of porcine thyroid TSH receptors was attempted by using Lubrol, TSH-Sepharose, gel filtration and the immunoabsorption by anti-thyroglobulin (Tg) antibody-Sepharose. The effects of microbial protease inhibitors on the degradation of TSH receptors were also evaluated. Porcine thyroid membrane was solubilized with 1% Lubrol-PX and TSH receptors were purified by TSH affinity chromatography, followed by gel filtration on TSKgel-G3000SW. A partial purification was achieved; a 692-fold purification and 49.3% recovery of high affinity binding site and a 409-fold purification and 29.1% recovery of low affinity binding site, respectively. Rechromatography on G3000SW gel and immunoabsorption by anti-Tg antibody-Sepharose resulted in further reduction of contaminants. Among 10 protease inhibitors studied, a low concentration of chymostatin was the only one that showed a significant protective effect on the degradation of the receptors (p less than 0.05).

Animals↗

PubMed1988

Significance of serum thyrotropin and plasma dopamine concentration in the regulation of thyroid function in elderly subjects.

In our previous study, we observed a tendency towards an age-related increase in the serum thyrotropin (TSH) concentration. Regulatory mechanisms of TSH secretion in elderly subjects were studied. In 43 elderly subjects, serum TSH did not correlate significantly with serum T4, T3 free T4 or rT3. Further, those with increased TSH (greater than 5 mU/l, 9 subjects) did not overlap with those with low T3 (less than 0.92 nmol/1, 8 subjects). Increases in serum TSH were not associated with the presence of circulating anti-thyroid autoantibodies. A TRH test using a 500 micrograms single bolus injection was performed in 15 subjects. TSH response (basal: 1.92 +/- 1.42 (s.d.) mU/1, peak: 11.25 +/- 5.33 mU/1, sigma: 26.74 +/- 12.89 mU/1, respectively) did not differ significantly from that of younger subjects. T3 response after TRH varied greatly and a close correlation was observed between basal T3 and peak T3 (r = 0.86), and also between peak T3 and delta T3 (r = 0.81). A significant correlation was observed between sigma TSH and basal T3 (r = 0.60). Neither plasma cortisol, epinephrine nor norepinephrine concentrations showed any significant correlation with basal and TRH-stimulated TSH or T3 concentrations. However, the plasma dopamine concentration correlated significantly with sigma TSH (r = 0.60) and basal T3 (r = 0.52), respectively. In conclusion, the increase in serum TSH observed in elderly subjects was felt to represent a physiological adaptation to maintain serum T3. Low T3 subjects appear to have a disturbance in this mechanism, with decreased TSH and T3 response to TRH stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1988

Effects of low dose L-triiodothyronine administration on mental, behavioural and thyroid states in elderly subjects.

Decreased serum T3 concentrations in elderly subjects and their possible relationship with the development of dementia have been indicated. To see the effects of a passive increase in the serum T3 concentration, low dose T3 administration was undertaken. Forty-four subjects from 65 to 93 years of age (average 81.0 +/- 7.8) were divided into 2 groups. The grade of dementia was determined by Hasegawa's dementia rating scale (DR score). In 22 subjects, 25 micrograms per day of T3 was administered for 4 W, while the control group was given a placebo. The DR score was measured before and immediately after the study. Changes in behaviour were monitored in a double-blind fashion. The administration of T3 induced a 0.65 nmol/l increase in serum T3 in 2 W and 0.36 nmol/l in 4 W. These T3 increases were not associated with significant changes in the DR score but 7 of 22 subjects showed apparent improvement in behaviour. TSH was suppressed to less than 1 mU/l in 2 W and then slightly increased by the 4th week, but T4, rT3 and fT4 all showed significant and progressive decreases. The DR score after T3 correlated significantly with the rT3/T4 ratio (before T3: -0.55, changes: +0.50) and also with changes in rT3 (r = 0.49). In conclusion, T3 administration to the elderly subjects was associated with behavioural improvement in some individuals, but the intellectual ability as assessed by the DR score in those with low T3 or elevated rT3 were hardly improved by passive T3 elevation.

Administration, Oral↗

PubMed1987

Biological effect of anti-fucosyl GM1 ganglioside antibody on cyclic adenosine 3',5'-monophosphate production in FRTL5 rat thyroid cells.

Addition of specific anti-fucosyl GM1 antibody raised in a rabbit caused dose-dependent inhibition of endogenous and thyrotropin (TSH)- or thyroid stimulating antibody-stimulated cyclic adenosine 3',5'-monophosphate (cAMP) production in cultured FRTL5 rat thyroid cells. Further, the antibody inhibited the cAMP increase induced by prostaglandin E1 and forskolin. However, anti-fucosyl GM1 antibody did not affect the binding of [125I]bovine TSH to solubilized porcine thyroid TSH receptor or to FRTL5 cells. In conclusion, fucosyl GM1 is one of the specific membrane components of thyrocytes and appears to be involved in adenylate cyclase stimulation or cAMP generation. Further, the biological effects of the ganglioside do not seem to be mediated by the TSH receptor, suggesting a post receptor mechanism.

Alprostadil↗

PubMed1987

Clinical significance of elevated labeled TSH binding (LTB) activity in sera of patients with Graves' disease and other thyroid disorders.

Labeled TSH binding (LTB) of individual serum samples was monitored simultaneously using the thyrotropin binding inhibitor immunoglobulin (TBII) assay. In 643 TBII determinations, 86 sera (13.4%) showed elevated LTB. The incidence of elevated LTB in active Graves' patients (17.5%) was much higher than that of inactive Graves' patients (6.7%). After TBII activities were corrected by LTB, 79% of the active Graves' patients who had negative raw TBII were found to be positive. In patients with untreated active Graves' disease, the detectability of TBII increased from 85% to 91% after LTB correction, while those in inactive Graves' and other thyroid disorders did not increase so much (1.6 and 0%, respectively). Further, most of elevated LTB seen in other thyroid disorders were found to be different from those in Graves' disease by heat stability experiment. Serial observations of LTB and TBII in 24 Graves' patients showed 2 patterns. Parallel alterations were observed in 13 patients and reciprocal alterations in 11 patients. Patients showing parallel alteration had smaller goiter and were more sensitive to antithyroid drugs than those showing the latter pattern.

Graves Disease↗

PubMed1987

Triiodothyronine effects on RNA polymerase activities in isolated neuronal and glial nuclei of the mature rat brain cortex.

Our previous study demonstrated that a high level of nuclear triiodothyronine receptors (NT3R), which are identical to the hepatic NT3R, exists in neuronal nuclei of the cerebral cortex from an adult rat brain. To investigate whether thyroid hormone acts through binding to nuclear receptors, we measured RNA polymerase activities in isolated neuronal and glial nuclei of cerebral cortices prepared from three groups of rats with different T3 levels: T3 (20 micrograms/100 g BW/d, for three days)-injected hyperthyroid rats, control normal rats, and thyroidectomized rats. The enzyme activities in both nuclear fractions were assayed under the condition of dose-response linearity. When RNA polymerase I activity in neuronal nuclei from control rats was expressed as 100%, the activities from T3-injected and hypothyroid rats were 112.3 +/- 3.4% (n = 5, P less than .05) and 86.9 +/- 3.5% (n = 5, P less than .05), respectively. The increase in the enzyme activities were parallel to the increase in T3 content in neuronal nuclei among the groups. Glial nuclear RNA polymerase I showed the same tendency in response to T3, although the enzyme activity was smaller than from neuronal nuclei. RNA polymerase II, however, showed no significant change in response to altered T3 levels. The existence of numerous receptors and an induction of increased RNA polymerase I activity by T3 in neuronal nuclei raise the possibility that thyroid hormone through a NT3R pathway in the cerebral cortex of even the mature rat brain.

Animals↗

PubMed1987

Anti-TSH antibody with high specificity to human TSH in sera from a patient with Graves' disease: its isolation from, and interaction with, TSH receptor antibodies.

A patient with thyrotoxic Graves' disease had an apparent measurable level of serum TSH (2.5 microU/ml) by double-antibody radioimmunoassay (RIA). The serum IgG bound with both [125I]human(h)TSH and [125I]bovine(b)TSH. The [125I]hTSH binding was more effectively displaced by human than bovine TSH, whereas [125I]bTSH binding was displaced exclusively by bTSH. Scatchard analyses revealed that [125I]hTSH binding showed two components, whereas [125I]bTSH binding had only one component. Serum TSH determined by RIA became undetectable 21 months after antithyroid drug treatment with a parallel decrease of [125I]hTSH binding IgG activity. Four thyrotrophin binding inhibitory immunoglobulins (TBII) from other patients did not interfere with the binding of the patient's serum to [125I]h- or bTSH. Furthermore, the in-vitro thyroid stimulating activities of three thyroid stimulating antibodies (TSAb) were not affected by the addition of this patient's IgG. On the other hand, this patient's Ig (3 mg/ml) abolished the in-vitro thyroid stimulation by bTSH (100 microU/ml), but did not affect that by hTSH (100 microU/ml). The anti-hTSH antibody, TSH receptor antibody and anti-bTSH antibody in the serum, which contains TSAb as well as anti-TSH antibodies, could be partially purified by hTSH-agarose and subsequently by guinea pig fat cell membrane affinity absorptions. However, the anti-hTSH antibody fraction obtained had both hTSH binding activity and thyroid stimulating activity, and this fraction did not show any inhibitory effect on the in-vitro thyroid stimulation of autologous TSH receptor antibody or hTSH. The possible significance of anti-TSH antibodies is discussed.

Adult↗

PubMed1987

Disappearance of blocking type thyrotropin binding inhibitor immunoglobulin (TBII) during thyroid and steroid medication in a patient with autoimmune thyroiditis.

A 55 year-old female had suffered from 3 consecutive diseases for a year. The diseases were ulcerative colitis, primary hypothyroidism and idiopathic thrombocytopenic purpura, and had been treated with L-thyroxine (50 micrograms daily) and betamethasone (0.5 to 1.5 mg daily). On examination, the thyroid gland was not palpable at all, thyroid 99 mTc pertechnetate uptake was 0%, and an echogram revealed the existence of an atrophic gland. Thyrotropin binding inhibitor immunoglobulin (TBII) in the serum was elevated to 58.0% and her IgG almost completely inhibited the in vitro cAMP increase due to bTSH. After 5 months TBII turned out to be negative and the inhibitory IgG activity was reduced significantly. The thyroid gland also became visible scintigraphically. Thyroid medication was then stopped. Four months after the cessation of thyroxine, she felt quite well and her thyroid functions remained within the normal ranges. Antibody to Yersinia enterocolitica was positive at a low titer (X20) in the early stages, but elevated reciprocally with the fall in TBII and finally reached X320. In conclusion, evidence of the disappearance of blocking type TBII from the serum was demonstrated for the first time. Steroid might have caused some favorable effects, and this clinical report indicates the possibility that remission of hypothyroidism due to blocking type TBII can be expected.

Antibodies, Bacterial↗

PubMed1987

Histological, clinical and laboratory findings of acute exacerbation of Hashimoto's thyroiditis--comparison with those of subacute granulomatous thyroiditis.

As reported previously, acute exacerbation of Hashimoto's thyroiditis shows quite unique histological findings, namely localized edematous inflammation. Similar histological characteristics and clinical manifestations were observed in 7 of 492 patients with Hashimoto's thyroiditis (A group). Their clinical and laboratory findings were compared with those of 15 cases with subacute granulomatous thyroiditis (S group). Age and sex distribution and goiters in A group were 39 +/- 21 years old (mean +/- s.d.), 7/0 (F/M), and 6/1 (diffuse/nodular), respectively. These were somewhat different from those of S group (45 +/- 9, 12/3, and 3/12, respectively). Thyroid functions in A group showed wide variation: 3 cases were euthyroid, 2 were mildly hypothyroid, and one was mildly thyrotoxic and one borderline thyrotoxic, and all of the S group patients were thyrotoxic. Their thyroid radiopertechnetate uptake, scintigraphy, duration from the onset till the first visit, and ESR and CRP values were also different from those of S group. Clinical courses and outcomes of A group were generally favorable, but one of them finally underwent a total thyroidectomy. Per os and intrathyroidal administrations of steroid were effective, but there was observed a recurrence of symptoms in 3 cases. Finally, all 6 cases were left with diffuse goiters, 4 of them remaining euthyroid, and 2 falling into hypothyroidism. The acute exacerbation of Hashimoto's thyroiditis is a rare complication, which is found to be different from subacute thyroiditis on histological, clinical and laboratory findings and is generally subtle. Steroid medication is considered to be the therapeutic choice but careful observation is necessary to avoid a recurrence.

Clinical Protocols↗

PubMed1986

Thyroid hormone receptors in neuronal and glial nuclei from mature rat brain.

To elucidate the mechanism of thyroid hormone action in the mature brain, we analyzed nuclear T3 receptors (NT3R) in neuronal and glial nuclei. Neuronal and glial nuclear fractions were prepared from mature rat brains with about 80% and 98% purity, respectively. Results from Scatchard analyses showed that NT3R capacity in neurons was 684.2 +/- 95.4 pg T3/mg DNA (mean +/- SD) in isolated nuclei and 345.6 +/- 77.6 pg T3/mg DNA in nuclear protein extracted with 0.4 M KCl. Glial NT3R had only one eighth the capacity of neuronal receptors. Displacement studies with several T3 analogs showed highly selective affinity of the receptors for L-T3. The relative affinities for several analogs were similar to those of liver NT3R. In addition, the elution profiles of the nuclear extracts through HPLC using gel filtration or diethylaminoethyl ion exchange columns exhibited similarity between neuronal and hepatic NT3R. The receptors in neuronal and glial nuclear fractions were analyzed in three groups of rats with different T3 levels: T3 (20 micrograms/100 g BW daily, for 3 days)-injected hyperthyroid rats, intact rats, and thyroidectomized rats. There were no significant alterations in capacity or affinity of the receptors among groups. The present studies demonstrate that numerous NT3R, which seem identical to hepatic NT3R, exist in neuronal nuclei. This raises the possibility that thyroid hormone acts through binding to NT3R in the cerebral cortex of the mature rat brain.

Animals↗

PubMed1986

Pathological characteristics of acute exacerbation of Hashimoto's thyroiditis--serial changes in a patient with repeated episodes.

A 76-year-old female patient with known Hashimoto's thyroiditis had 12 episodes of acute exacerbation, characterized by high fever and spontaneous pain in the thyroid over a period of 4 months. Percutaneous needle biopsies were performed before and serially after local steroid injection. Histological examination of the thyroid tissue involved obtained before steroid administration revealed quite a unique localized edematous and inflammatory appearance with rich but loosely arranged collagen fibers, and destruction of follicular structures and swollen degenerated epithelia. Neither remarkable cellular infiltrations nor granulomatous changes were observed in the area involved. Ultrasonogram showed an extremely hypoechoic lesion coincident with the location of pain and tenderness. Intrathyroidal administration of triamcinolone acetate (40 mg) resulted in an immediate relief of pain, fever and localized swelling. Surprisingly, remarkable histological improvements were observed even on the day following the injection. However, clinical manifestations as well as histological changes were reversed again within one week or so. After various therapeutic means, total thyroidectomy was performed which induced disappearance of the manifestations. The etiology remains unclear, but pathological findings observed in this patient may provide an insight into the pathogenesis of this rare but intractable condition.

Acute Disease↗

PubMed1986

Incidence and specificities of labeled thyrotropic hormone (TSH) binding immunoglobulins (LTB-Igs) in patients with Graves' disease and other thyroid disorders.

Using [125I]bTSH, labeled TSH binding (LTB) in sera from 203 patients with various thyroid disorders was studied. Four of them with known potent anti-TSH antibody showed extremely high LTB, as has been reported previously. Excluding these 4 sera, the mean +/- s.d. of serum LTB from 199 patients was calculated to be 8.6 +/- 2.1%. LTB exceeding 10.7% (mean + 1 s.d.) was observed in 16 sera; these were taken as increased. LTB measured by polyethyleneglycol (PEG) precipitation correlated significantly with the serum IgG concentration; however, sera with increased LTB had high values irrespective of the serum IgG concentration. Specificities of increased LTB in 13 sera were further analyzed by means of binding to Protein A-sepharose and displacement studies using bTSH and nonradioactively iodinated bTSH. A significant correlation was observed between the LTB obtained by PEG and those by Protein A-sepharose. BTSH specificity was confirmed in 5 of the 13 sera; 7 of the remaining 8 sera showed displacement only by iodinated bTSH. None of the control Graves' sera showed any significant displacement. Comparisons of the results of measurement of LTB by Protein A-sepharose and those by the displacement studies disclosed that most of displaced sera had increased LTB to the IgG fraction. Disease distributions of 203 overall cases and 20 increased LTB cases revealed that apparently higher incidence (22.9%) of increased LTB in untreated Graves' patients than the others, though some increased LTB cases were also observed in patients with inactive Graves' or other thyroid disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

A predicted case with neonatal transient hypothyroidism due to blocking type thyrotropin binding inhibitor immunoglobulins (TBII).

A 26-yr-old female with primary hypothyroidism due to potent blocking type thyrotropin binding inhibitor immunoglobulins (TBII) was advised of the high risk of bearing a baby with neonatal transient hypothyroidism. This prediction proved valid and her baby was found to be hypothyroid with a potent TBII. By expressing the baby's TBII as the absolute concentration, we found an almost linear regression of TBII and the half-life was calculated as 18.0 days. The TBII became undetectable by the 6th month and thyroid medication was stopped, however the baby remained euthyroid with subsequent normal physical and mental development.

Adult↗

PubMed1985

Changes in thyrotropin binding inhibitor immunoglobulin (TBII) concentration before and after various treatments in a patient with infiltrative Graves' ophthalmopathy.

In a patient with active Graves' disease an infiltrative ophthalmopathy developed during antithyroid drug therapy. Her eye symptoms were effectively treated with a large dose of prednisolone (PD), plasma exchanges (PE), cyclophosphamide, orbital irradiation, antithyroid drug and a supplemental dose of triiodothyronine. Before, during and after these treatments thyrotropin binding inhibitor immunoglobulin (TBII) activities in a unit serum immunoglobulin (IgG) were measured after adjusting the IgG concentration by adding normal IgG. Relative TBII concentrations were calculated by extrapolating individual data on a standard curve constructed from serial dilutions of the most potent IgG. Approximately a 5 fold increase in the TBII concentration was observed during the 2 months of progression of the ophthalmopathy, while TBII activity revealed only a 13.3% increase. After treatment TBII concentrations decreased gradually showing a close relation with the severity of the eye symptoms. Every PE was found to remove 48.5 +/- 7.9 (s.e.m.) % of TBII. After PE TBII returned to the preexchange level very rapidly and then overshot it in 2 to 3 weeks. Sixty mg of PD failed to prevent the overshoot but a 100 mg initial dose of PD after 5 PEs inhibited it to some extent. The effectiveness of combined therapy with PE, PD and cyclophosphamide appeared to confirm a role of humoral factors in the pathogenesis of Graves' ophthalmopathy. Serial determinations of TBII in a relative concentration were considered quite useful in analyzing the effectiveness of treatment in Graves' ophthalmopathy.

Eye Diseases↗

PubMed1985

Effect of bromocriptine on serum TSH in euthyroid patients with endocrine disorders.

In 10 euthyroid subjects a single 2.5 mg per os dose of bromocriptine caused rapid and remarkable decreases in serum TSH. As much as a 0.85 +/- 0.18 (s.d.) microU/ml decrease from the basal level (56 +/- 9%) was observed at 5 hours. A good correlation was observed between the basal TSH level and the TSH decrease after bromocriptine (r = 0.786). In 4 patients taking 5 to 15 mg bromocriptine daily (chronic administration group), another 2.5 mg bromocriptine also caused significant decreases in serum TSH, but the degree (0.42 +/- 0.03 microU/ml, 43 +/- 26% of basal) and duration (maximal at 4 hours) were less than those observed in the untreated group. The lowest TSH levels in these two groups did not differ significantly (0.80 +/- 0.45 and 0.78 +/- 0.53 microU/ml, respectively). The TSH decrease after bromocriptine in the untreated group was found not to correlate significantly with TRH induced TSH increase (r = 0.300). TRH induced TSH increase in the chronic administration group was similar to or greater than that of control subjects with matched basal TSH. The TSH lowering effects of per os prednisolone and triiodothyronine were also studied. Prednisolone exerted a quite similar effect to bromocriptine, but a certain time lag was observed in the case of triiodothyronine. A single dose of bromocriptine was found to lower serum TSH levels even in euthyroid subjects. The effect was considered to be independent of TRH-TSH regulation and to act directly on the TSH release.

Adult↗