Biomedical subjects

T Tagami

Publications and source records attributed to T Tagami.

At least 37 records · Page 2Linked to original sources

PubMed1997

Differentiation of female chicken primordial germ cells into spermatozoa in male gonads.

In avian species, the developmental fate of different-sex germ cells in the gonads is unclear. The present study attempted to confirm whether genetically female germ cells can differentiate into spermatozoa in male gonads using male germline chimeric chickens produced by the transfer of primordial germ cells (PGC), and employing molecular biological methods. As a result of Southern hybridization, specific sequences of the W chromosome (the female specific sex chromosome in birds) were detected in the genomic DNA extracted from one out of four male germline chimeric chickens. When two-color in situ hybridization was conducted on the spermatozoa of this germline chimera, 0.33% (average) of the nuclei of each semen sample showed the fluorescent signal indicating the presence of the W chromosome. The present study shows that female PGC can differentiate into spermatozoa in male gonads in the chicken. However, the ratio of produced W chromosome-bearing (W-bearing) spermatozoa fell substantially below expectations. It is therefore concluded that most of the W-bearing PGC could not differentiate into spermatozoa because of restricted spermatogenesis.

Animals↗

PubMed1997

Nuclear receptor corepressors activate rather than suppress basal transcription of genes that are negatively regulated by thyroid hormone.

A group of transcriptional cofactors referred to as corepressors (CoRs) were recently shown to play a central role in basal silencing of genes that contain positive triiodothyronine (T3) response elements. In a reciprocal manner, negatively regulated genes are stimulated by unliganded thyroid hormone receptor (TR) and repressed upon the addition of T3. We used a TR beta mutant, called P214R, which fails to interact with CoRs, to examine whether CoRs also play a role in the control of genes that are negatively regulated in response to T3. In studies of three negatively regulated genes (the pituitary thyroid-stimulating hormone alpha-subunit [TSH alpha], TSH beta, and hypothalamic thyrotropin-releasing hormone [TRH] genes), stimulation of basal promoter activity by unliganded TR beta was impaired by introducing the P214R CoR mutation. Coexpression of each of the CoRs SMRT (silencing mediator for retinoid receptors and TRs) and NCoR (nuclear receptor CoR) enhanced basal stimulation of the negatively regulated promoters in a TR-dependent manner, but this effect was not seen with the P214R TR mutant. The mechanism of CoR effects on negatively regulated promoters was explored further with a series of GAL4-TR chimeric receptors and mutants that allowed TR effects to be assessed independently of receptor interactions with DNA. These experiments revealed that, like the negative regulation of genes by wild-type TR, basal activation occurred with GAL4-TR, but not with the GAL4-P214R mutant, and was reversed by the addition of T3. These results suggest that TR interactions with negatively regulated genes may be driven through protein-protein interactions. We conclude that a subset of negatively regulated genes are controlled by a novel mechanism that involves TR-mediated recruitment and basal activation by SMRT and NCoR. Addition of T3 reverses basal activation, perhaps by dissociation of CoRs.

Cell Line↗

PubMed1997

Dimerization properties of mutant thyroid hormone beta-receptors with auxiliary proteins.

Hormonal responsiveness in peripheral tissues is variable in patients with resistance to thyroid hormone (RTH). One cause of this may be differential interaction of RTH mutants of thyroid hormone receptor beta (TR beta) with TR auxiliary proteins (TRAPs). We used gel shift mobility assays to examine the interaction of wild-type and mutant TR beta s with retinoid X receptors (RXRs) and endogenous TRAPs. Some mutants showed reduced homodimerization but retained heterodimerization with recombinant RXRs. Wild-type TR beta formed heterodimeric complexes with multiple TRAPs in nuclear extracts of rat tissues, but RTH mutants showed variably altered heterodimerization with each TRAP. With liver nuclear extract, all mutants with impaired homodimerization also showed impaired TR beta-TRAP heterodimerization. Thus heterodimerizations with RXRs and TRAPs are differently affected by RTH mutations. Our results suggest that multiple TRAPs are expressed in tissue-specific patterns. The variability of TR beta heterodimerization with TRAPs may account, in part, for the variable tissue responsiveness in RTH.

Base Sequence↗

PubMed1997

[Study of serum thrombomodulin(TM) levels in patients with hyper- or hypo- thyroidism].

We studies a relationship between the serum levels of thrombomodulin(TM) and the thyroid functions. Serum TM levels were measured in 48 patients with Graves' disease, 17 patients with primary hypothyroidism, 7 patients with subacute thyroiditis, 5 patients with painless thyroiditis and 2 patients with systematic Refetoff syndrome. These patients did not have malignant tumor, kidney failure, or blood vessel injury. Control sera were obtained from 42 healthy subjects. Serum levels of TM in patients with untreated Graves' disease were significantly higher(p < 0.001) compared with those in controls. Serum levels of TM in patients with hypothyroidism were not significantly changed as compared with those of controls. There were a positive correlation between the serum levels of TM and FT3 as well as FT4. Serial determinations of the serum levels of TM and thyroid function(FT3, FT4 and TH) in patients with Graves' disease during treatment showed that both the serum levels of TM and thyroid hormones (FT3 and FT4) lowered progressively during treatment. After normalization of serum FT3 and FT4, the serum TM levels returned to normal. However, the serum levels of TM in patients with destructive thyroiditis and Refetoff syndrome were normal in spite of high serum levels of thyroid hormones. These data suggest that an increase in serum levels of TM is not the direct result of thyroid hormones themselves but is the result of the prolonged hypermetabolic state induced by their peripheral activities. Thyroid hormones may stimulate the synthesis or metabolism of TM on the surface of vascular endothelial cells in the patients with Graves' disease.

Graves Disease↗

PubMed1996

Starvation-induced decrease in the maximal binding capacity for triiodothyronine of the thyroid hormone receptor is due to a decrease in the receptor protein.

Biological responses to thyroid hormones are mediated by the nuclear thyroid hormone receptor (TR). Alterations in the maximal triiodothyronine (T3)-binding capacity (Cmax) of TR measured using a ligand binding assay have been reported under some pathophysiological conditions. Northern blot analysis has indicated that TR mRNA concentrations do not necessarily correlate with Cmax levels. For example, although the decrease in Cmax in rat liver induced by prolonged fasting is well established, TR mRNA concentrations have been reported to be constant. In the present study, we examined starvation-induced changes in TR by Western blot with anti-TR(alpha 1 + beta)antiserum and by Scatchard plot analysis. Starvation of rats for 72 hours decreased Cmax in the liver to 72.5% of control levels. The 47- and 55-kd TR proteins detected in hepatic nuclear extract by Western blotting also decreased to 64% and 66% of control values, respectively. The starvation-induced changes in Cmax and TR protein levels paralleled the change in total hepatic nuclear protein concentration. These results suggest that the decrease in T3-binding activity of the TR is due to a reduction of the TR protein itself.

Animals↗

PubMed1996

High-dose intravenous steroid pulse therapy in thyroid-associated ophthalmopathy.

To evaluate the efficacy of high-dose intravenous steroid pulse followed by oral steroids in the treatment of thyroid-associated ophthalmopathy, we performed clinical assessment and measurement of retroorbital muscle enlargement in 27 patients before and after the therapy, and followed them up longitudinally. The mean duration of follow up is (mean +/- SD) 29.8 +/- 23.8 months (range 4-92). Diplopia disappeared in 10 patients and ameliorated in 11 patients. The degree of proptosis decreased in 15 patients and the fall in visual acuity improved in a third of the patients. The total ophthalmopathy index (OI) decreased from 7.0 +/- 1.9 to 3.0 +/- 1.5. The extraocular muscle enlargement (EME), expressed as the maximal ratio of extraocular muscle thickness to the diameter of the optic nerve, decreased from 2.33 +/- 0.56 to 1.27 +/- 0.26. No major side effects were found in any patient. The improvement in the eye disease was found immediately after the pulse therapy, prior to the start of the following therapy by oral steroids and/or orbital irradiation. Both of OI and EME decreased with time after the therapy and did not get worse after withdrawing oral steroids. The efficacy of the therapy evaluated by degrees of improvement in OI and in EME was significantly greater in females than in males. Although there was a significant positive correlation between initial OI and EME values and initial TBII and TSAb activities, a significant correlation was seen only between the degrees of improvement in EME and changes in TBII activity due to the therapy. The duration of eye disease, thyroid status, treatment with anti-thyroid drug, smoking and experience of previous treatment did not affect the efficacy of the present therapy. We conclude that high-dose intravenous steroid pulse therapy is effective and safe for thyroid-associated ophthalmopathy.

Adult↗

PubMed1996

[Supporting roles of health centers in community health practice by municipalities].

Staff of community health centers are expected to support those of municipalities so that they can identify health relevant issues in their communities, plan strategies to resolve the issues, implement them and evaluate the action. To illustrate the role of community health centers, the authors report the process of health promotion practice in Taisho-cho, Kochi prefecture, which was supported by Kubokawa health center. The health center took the initiative in identifying issues in community health through analyzing available information. In a practice setting, the health center facilitated involvement and participation by the residents and cooperated with other community resources. The process of support is discussed from the point of view of community organization practice.

Ambulatory Care Facilities↗

PubMed1995

Two consecutive nucleotide substitutions resulting in the T3 receptor beta gene resulting in an 11-amino acid truncation in a patient with generalized resistance to thyroid hormone.

We identified unusual mutations in the T3 receptor (TR) beta gene in a 6-year-old Japanese girl with generalized resistance to thyroid hormone. Two consecutive base substitutions, T to A and C to A at nucleotide positions 1637 and 1638, respectively, changed the 451st codon coding for Phe(TTC) to stop codon (TAA), resulting in an 11-amino acid carboxyl(C)-terminus truncation. The patient was a heterozygote. Western blotting using an anti-TR antibody demonstrated the truncated receptor protein. The patient showed severe mental retardation (IQ41), disturbance in speech development, and attention deficit hyperactivity disorder. Thyroid functional status by clinical evaluation was considered within the normal range in spite of high serum thyroid hormone levels (T4 725.9 nmol/l, T3 12.7 nmol/l, FT4 166.0 pmol/l). TSH increased from 0.6 to 24 mU/L after TRH (150 micrograms) injection. TSH secretion as well as 123I-uptake was suppressed only partially by T3 (75 micrograms/day for a week). Close examination of thyroid functions and TR beta gene analysis were not possible in the family, except for paternal grandmother and one of her two sisters who showed no abnormality. The patient's truncated TR beta showed very low T3 binding activity (Ka = 0.1 x 10-10 M), transcriptional activity, and a very strong dominant negative effect. When co-expressed with wild-type TR beta at the molar ratio 1:1 in CV-1 cells, the mutant receptor inhibited the wild-type TR beta transcriptional activity by 74% at 10 nM T3. Even 1 microM T3 could not normalize these impaired functions.

Amino Acid Sequence↗

PubMed1995

Functional properties of a mutant T3 receptor beta (R338W) identified in a subject with pituitary resistance to thyroid hormone.

Previously, we identified a point mutation of the T3 receptor (TR) beta gene (R338W) in a patient with pituitary resistance to thyroid hormone (PRTH). The mutation existed in one of two hot spot areas in TRbeta gene where clusters of mutations have been found in subjects with generalized resistance to thyroid hormone (GRTH). Interestingly, R338W induces the phenotypical features responsible for PRTH. In the present study, we examined the functional properties of R338W in comparison with those of a GRTH-mutant, K443E. The levels of thyroid hormones and inappropriately elevated TSH (SITSH) were similar between subjects with K443E and R338W. Transcriptional activities and dominant negatives potencies were measured by CAT assay in CV1 cells transfected with each mutant TRbeta1 or along with wild-type TR. When a reporter gene containing T3-responsive elements (TRE), TRE-pal2, DR4 or myosin heavy chain alpha subunit, was used, transcriptional activation induced by R338W was higher than that by K443E. At 50 nM T3, K443E decreased the transcriptional activity of wild-type TRbeta1 on TRE-pal2 by 31.5%, while R338W reduced by 13.6% (n = 15, P < 0.05). Co-expression of retinoid X receptor (RXR) alpha increased transcriptional activity of R338W and K443E, but not of wild-type TRbeta1. Dominant negative activity on TRE-TSHalpha subunit of R338W was milder than that of K443E. When T3-binding activities of mutant TRbeta1s expressed in the cells were assayed under the same cell conditions for CAT assay, both mutant TRbeta1 showed remarkably reduced activity with no difference between the two. Gel mobility shift assay using TRE-DR4 showed poor homodimer formation of R338W. Heterodimerization with RXRalpha was similar between R338W, K443E and wild-type TRbeta1. The result of the present study suggested that R338W had relatively mild transcriptional and dominant negative activities on several TREs including TRE-TSHalpha subunit. We also showed poor homodimerization of R338W, which might be related to its weak dominant negative potency.

Adult↗

PubMed1994

3,5,3'-Triiodothyronine stimulates retinoic acid-induced differentiation in HL-60 cells.

The human acute promyelocytic leukemia (APL) cell line HL-60 differentiates to functionally mature granulocytes by incubation with all-trans-retinoic acid (RA). Since T3 and RA are important in cell differentiation and development, and since their receptors are highly homological, we investigated the T3 effects on RA-induced HL-60 cell differentiation. Although T3 alone did not induce cell differentiation, RA-mediated differentiation was significantly enhanced in the presence of 10(-7) M T3. This effect of T3 was considered to be mediated, at least in part, by increased intracellular cAMP, since the phosphodiesterase inhibitor enhanced, and the protein kinase A antagonist partially blocked, T3 potentiation. When HL-60 cells were pretreated with RA for 20 h, T3 alone stimulated the cell differentiation. The time-course study showed that incubation with RA for 12 h was necessary for HL-60 cells to be primed to respond to T3 for differentiation. The present finding that T3 potentiates RA-induced HL-60 cell differentiation may raise the possibility that T3 supplement increases clinical remission in APL patients who are treated with RA.

1-Methyl-3-isobutylxanthine↗

PubMed1994

Preservation of chick primordial germ cells in liquid nitrogen and subsequent production of viable offspring.

Conservation of genetic material in chickens was attempted by preserving primordial germ cells in liquid nitrogen. Primordial germ cells collected from the blood of embryos at stage 13-15 of White Leghorn and Barred Plymouth Rock breeds were concentrated by Ficoll density gradient centrifugation. The primordial germ cells were then suspended in a freezing medium containing 10% dimethyl sulfoxide. The temperature of the cell suspension was decreased by 1 degree C min-1 to -80 degrees C; the suspension was then placed in liquid nitrogen (-196 degrees C) and stored for 4-5 months. The cell suspension was thawed by taking it out of liquid nitrogen and placing it in water at 4 degrees C. The viability of the frozen-thawed primordial germ cells was 94.2%. One hundred frozen-thawed cells were injected into the bloodstream of recipient embryos (stage 14-15) from the other breed, from which blood had been drawn before the injection. These embryos were cultured in recipient eggshells until hatching. Viable offspring derived from the frozen-thawed primordial germ cells were obtained by mating male and female germline chimaeras or by mating the chimaeras with Barred Plymouth Rock chickens, and the offspring showed normal reproductive performance. This technique for cryopreservation of primordial germ cells giving rise to viable offspring makes it possible to conserve genetic material in avian species.

Animals↗

PubMed1994

[A reevaluation of the criteria for initiating medical treatment of pulmonary tuberculosis patients].

In Japan some registered tuberculosis (TB) patients have had medical treatment initiated for the purpose of preventing development of inactive TB into active stages, or due to differential diagnosis. A reevaluation of the necessity of commencing medical treatment was performed on 91 TB patients to elucidate the special characteristics of TB patients who do not necessarily need medical treatment. The results are as follows: 1) Among the 91 patients, 67 patients were judged to be 'confirmed cases', while 24 patients were judged to be 'suspect cases', with either inactive TB or possibly without TB. 2) The rates of 'suspect cases' were higher in the tubercle bacillus negative groups as well as the X-ray mild cases compared to the tubercle bacillus positive cases and X-ray severe cases. 3) The patient's self-diagnosed symptoms proved to be useful in evaluating the TB patient's severity. It is thought that this information should be used to judge the necessity of commencing medical treatment in TB patients.

Evaluation Studies as Topic↗

PubMed1994

Diffusional anisotropy of the human brain assessed with diffusion-weighted MR: relation with normal brain development and aging.

PURPOSE: To analyze diffusional anisotropy in frontal and occipital white matter of human brain quantitatively as a function of age by using diffusion-weighted MR imaging. METHODS: Ten neonates (< 1 month), 13 infants (1-10 months), 9 children (1-11 years), and 16 adults (20-79 years) were examined. After taking axial spin-echo images of the brain, diffusion-sensitive gradients were added parallel or perpendicular to the orientation of nerve fibers. The apparent diffusion coefficient parallel to the nerve fibers (0) and that perpendicular to the fibers (90) were computed. The anisotropic ratio (90/0) was calculated as a function of age. RESULTS: Anisotropic ratios of frontal white matter were significantly larger in neonates as compared with infants, children, or adults. The ratios showed rapid decrease until 6 months and thereafter were identical in all subjects. In the occipital lobe, the ratios were also greater in neonates, but the differences from other age groups were not so prominent as in the frontal lobe. Comparing anisotropic ratios between frontal and occipital lobes, a significant difference was observed only in neonates. CONCLUSIONS: Diffusion-weighted images demonstrated that the myelination process starts earlier in the occipital lobe than in the frontal lobe. The changes of diffusional anisotropy in white matter are completed within 6 months after birth. Diffusion-weighted imaging provides earlier detection of brain myelination compared with the conventional T1- and T2-weighted images.

Adolescent↗

PubMed1994

[The structural and functional multiplicity of T3 receptor and its gene].

Thyroid hormone receptor (TR) is encoded by the protooncogene c-erb A. There are multiple TR isoforms such as TR beta 1, beta 2, alpha 1, variant alpha 2 and alpha 3. There is also a related gene, Rev-erb A. TR and steroid hormone receptors consist of a superfamily and have a characteristic domain structure including DNA-binding, ligand-binding and dimerization domains. The expression of TR isoforms is tissue and cell type specific and is regulated by development and hormonal status. TR mRNA and protein concentrations do not always correlate. TR beta 2, which exists in the pituitary, may be important for the regulation of TSH secretion. The functional difference of TR alpha 1 and TR beta 1 is still unclear and physiological significance of the TR variants is unknown.

Animals↗

PubMed1993

31P MR spectroscopy in hypertrophic cardiomyopathy: comparison with Tl-201 myocardial perfusion imaging.

Abnormal phosphate metabolism of the myocardium was evaluated in patients with hypertrophic cardiomyopathy (HCM) using 31P magnetic resonance (MR) spectroscopy. The results were compared with those from left ventricular function and thallium 201 (Tl-201) perfusion scintigraphy. Six normal volunteers and 19 patients with HCM were studied with a 1.5 T MR system. The spectra were localized to the myocardium using volume selection with the depth-resolved surface coil spectroscopy (DRESS) technique. Peak areas of 2,3-diphosphoglycerate (DPG), phosphodiesters (PDE), phosphocreatine (PCr), and beta-ATP were determined by fitting Gaussian functions to the phased spectra. The peak areas were corrected for contamination of blood adenosine triphosphate (ATP) and PDE. The corrected PCr/beta-ATP ratio in patients (1.07 +/- 0.10, mean +/- SE) was significantly lower compared with that in normal volunteers (1.71 +/- 0.13, p < .01). The PCr/beta-ATP ratio showed an abnormal decrease (< mean -2 SD of the controls) in 11 (58%) of 19 patients. The averaged PCr/beta-ATP ratio in 15 patients with normal left ventricular ejection fraction (LVEF) was 1.14 +/- 0.10, significantly lower than in healthy subjects. By contrast, the corrected PDE/PCr ratio in HCM did not differ significantly compared with that in healthy subjects (0.46 +/- 0.09 vs 0.36 +/- 0.09). The PDE/PCr ratio was abnormally elevated (> mean + 2 SD of the controls) in only four (21%) of the patients. On Tl-201 myocardial single-photon emission computed tomography (SPECT) imaging, the perfusion of the left ventricular wall looked normal in 6 and abnormal in 5 of 11 HCM patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1993

Estimation of the protein content of thyroid hormone receptor alpha 1 and beta 1 in rat tissues by western blotting.

Recent studies of the expression of c-erbA/thyroid hormone receptor (TR) mRNAs have revealed a dissociation between T3-binding activity and the behavior of the mRNAs that code the functional TRs in some tissues. Compared with T3-binding activity, TR(alpha 1 + beta 1) mRNA is disproportionally high in the brain and low in the liver. Using anti-TR antiserum, 4BII, which recognizes TR alpha 1 and beta 1, but not the alpha 2-variant, we measured TR protein content in rat tissues by Western blotting. Two protein bands of 47 and 55 kilodaltons (kDa) were specifically identified as TR proteins. The positions of the in vitro transcription/translation products of c-erbA/TR alpha 1 and beta 1 cDNA on the gel were consistent with those of the 47- and 55-kDa bands, respectively. The 47- and 55-kDa proteins in nuclear proteins extracted with 0.4 M KCl from rat tissues were analyzed by Western blotting, and the intensity of TR protein bands in each tissue was measured by a densitometer. The relative TR protein concentration was highest in liver, followed by brain, kidney, and testis. We compared the TR protein level measured by Western blotting with the maximal T3-binding capacity (Cmax) in the same aliquot of samples from liver and brain. Both the TR protein level and the Cmax in the brain were about 40% of those in the liver, suggesting that the Cmax per receptor molecule is constant in these two tissues, and an abundant amount of functional TR proteins exists in the liver, corresponding to the high level of T3-binding activity.

Animals↗

PubMed1993

Pituitary resistance to thyroid hormone associated with a base mutation in the hormone-binding domain of the human 3,5,3'-triiodothyronine receptor-beta.

Point mutations in the human T3 receptor-beta (TR beta) gene causing single amino acid substitutions have been identified in several different kindreds with generalized resistance to thyroid hormone. Until now, no study has been reported on the TR gene in cases of pituitary resistance (PRTH). In the present study, we analyzed the TR beta gene in a 30-yr-old Japanese female with PRTH. She exhibited clinical features of hyperthyroidism, elevated serum thyroid hormone levels accompanied by inappropriately increased secretion of TSH, mildly elevated basal metabolic rate, and increased urinary excretion of hydroxyproline. No pituitary tumor was detected. DNA fragments of exons 3-8 of the genomic TR beta gene were generated by the polymerase chain reaction and analyzed by a single stranded conformation polymorphism method. Exon 7 of the patient's TR beta gene showed an abnormal band, suggesting the existence of mutation(s). By subcloning and sequencing the DNA, a point mutation was identified in one allele at nucleotide 1297 (C to T), which altered the 333rd amino acid, arginine, to tryptophan. Neither of her apparently normal parents had any mutations of the TR beta gene. In vitro translation products of the mutant TR beta gene showed remarkably decreased T3-binding activity (Ka, 2.1 x 10(8) M-1; normal TR beta Ka, 1.1 x 10(10) M-1). Since the molecular defect detected in a patient with PRTH is similar to that seen in subjects with generalized resistance to thyroid hormone, both types of the syndrome may represent a continuous spectrum of the same etiological defect with variable tissue resistance to thyroid hormone.

Adult↗

PubMed1992

Loss of thyroid hormone receptor activity in primary cultured rat hepatocytes is reversed by 2-mercaptoethanol.

In primary cultures of rat hepatocytes, specific thyroid-hormone-binding activity diminished with time and was hardly detectable at 24 h. In accordance with the loss of 3,5,3'-tri-iodothyronine (T3) binding, responses to the hormone disappeared, as indicated by low induction of the thyroid-hormone-responsive gene S14. In contrast, thyroid hormone receptor proteins were present, as determined by immunostaining with a specific antibody against the receptor. Thus the loss of T3 binding was due to receptor inactivation. After various attempts to restore the T3-binding activity, we found that 2-mercaptoethanol, a reducing agent, when added to the culture medium restored the hormone binding activity in a dose- and time-dependent manner. The observed kinetics and experiments using cycloheximide suggested that mercaptoethanol prevented inactivation of the newly synthesized receptors. Oxidoreductive conditions within cells may have a role in determining the level of activity of thyroid hormone receptors.

Animals↗