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Biomedical subjects

Y Shishiba

Publications and source records attributed to Y Shishiba.

At least 109 records · Page 6Linked to original sources
PubMed1982

In vitro detection of anti-thyroglobulin antibody forming cells from the lymphocytes of chronic thyroiditis patients and analysis of their regulation.

Anti-thyroglobulin (anti-Tg) antibody forming cells were detected by plaque forming cell (PFC) assay, using B cells depleted of sheep erythrocyte (SRBC) binding cells and T cells separated without SRBC interaction. When 2 x 10(5) non-T cells were combined with the same number of T cells from chronic thyroiditis patients, more than 20 PFC were detected; few, if any, PFC developed from normal lymphocytes. T cells were generally needed to produce quantifiable PFC, suggesting that helper T cells are required for this autoantibody formation. A positive relationship existed between the number of PFC and the serum anti-Tg antibody titres of the same patients. The generation of Tg-specific PFC from patient lymphocytes was markedly suppressed by normal T cells or T cells from patients whose lymphocytes did not produce PFC. The same level of suppression was also seen on the addition of culture supernatant from Tg antigen stimulated T cells. Autologous T cells, from patients whose lymphocytes produced PFC, did not show such suppressor effects, suggesting that in chronic thyroiditis patients, the regulatory T cell function preventing anti-Tg autoantibody formation is impaired.

Antibodies, Anti-Idiotypic↗
PubMed1980

Potassium deficiency enhances the effect of thyroid hormone on NaK-ATPase in liver and kidney.

In order to examine the possibility that the changes in electrolytes in tissue alter the effect of thyroid hormone on NaK-ATPase, rats were fed either synthetic K-deficient diet or synthetic K-normal diet. K-deficient diet induced a reduction in K content in serum or kidney, while that of the liver remained unchanged. When a daily dose of 2.5 micrograms T3 was administered for 7 days to k-deficient rats, both Mg- and NaK-ATPase of the homogenate of liver and kidney were elevated, while the same dose failed to influence those enzymes in K-normal rats. Furthermore, T3 dose increased the Na content of liver and kidney in K-deficient rats, resulting in a significant decrease in th K/Na ratio in those tissue. Based on the estimation from chloride space, the decrease in K/Na was deemed to have occurred mainly in the intracellular space. As the levels of serum thyroid hormone and liver T3 were not influenced by K-deficiency, the effect of K depletion is likely to be mediated not through the alteration in thyroid hormone kinetics, but through some other mechanism such as the elevation of intracellular Na. The present study demonstrates that K deficiency may sensitize NaK-ATPase to the effect of thyroid hormone.

Adenosine Triphosphatases↗
PubMed1979

[A comparison of various indicators of murine thyroid stimulation by LATS (author's transl)].

To obtain an in vitro method of LATS assay which is equally sensitive to a McKenzie bioassay, we compared the quality of cAMP generation-stimulation, thyroidal adenyl cyclase stimulation, and the stimulation of T3-release from mouse thyroid slices. Among those indicators of thyroid stimulation, stimulation by IgG of the release of T3 from incubated thyroid slices is the most sensitive, reproducible and reliable indicator, reflecting faithfully the results of a McKenzie bioassay. Stimulation of cAMP generation in slice manifested less sensitivity, but reasonable reproducibility. However, adenyl cyclase stimulation by IgG of patients with Graves' disease was erratic in two successive experiments, probably due to a non-specific effect of IgG. When adenyl cyclase stimulation was adopted as a sole indicator of thyroid stimulation, the results must be interpreted cautiously.

Adenylyl Cyclases↗
PubMed1979

Inactivation of human thyroid stimulator by human thyroid extract.

To determine whether the thyroid stimulating activity of IGG of patients with Graves' disease is associated with the reaction with a putative human thyroid antigen, the inactivation of the property of IgG to stimulate cAMP generation in human thyroid slices incubated in vitro was studied by pretreating the IgG with human thyroidal particulate fraction. In the preliminary experiment, it was demonstrated that to cause cAMP generation stimulation, on incubation period of 120 min is required to allow the IgG to penetrate the tissue. When human thyroid slices were incubated with normal IgG without or with pretreatment by human thyroid particulate fraction obtained from 100 mg tissue, cAMP content in the slices was 142 +/- 25 or 138 +/- 26 f moles/mg, respectively, indicating that basal thyroidal cAMP levels were not influenced at all by normal IgG even after pretreatment with thyroid particulate fraction. When the slices were incubated with gG of Graves' disease without or with the similar pretreatment, cAMP content was 320 +/- 31 or 140 +/- 25 f moles/mg, respectively, demonstrating an almost complete inhibition of the activity of the IgG to cause cAMP generation stimulation.

Cyclic AMP↗
PubMed1979

Solubilization of thyroxine-5'-deiodinase activity from rat liver microsome fraction.

The greater part of T3 is converted from T4 in liver or kidney. The majority of this activity exists in microsomal fraction. In the present study, we investigated whether this activity can be solubilized from rat liver microsomal pellet with various concentrations of deoxycholate (DOC). The extent of solubilization was compared with that of protein, rotenone insensitive NADH cytochrome c reductase or NADH cytochrome b5 reductase, which have been shown to associate with microsomal membrane rather than luminar contents. When 0.05% of DOC which was capable of releasing luminar contents of microsomal vesicles was applied to microsomal suspension, only a limited part of NADH cytochrome b5 reductase, rotenone insensitive NADH cytochrome c reductase or T4-5'-deiodinase activity was solubilized. When the concentration of DOC was increased to 0.125%, 41% of T4-5'-deiodinase activity was solubilized. Solubilization of protein, NADH cytochrome b5 reductase or rotenone insensitive NADH cytochrome c reductase was increased abruptly to 66%, 58% or 63%, respectively. The highest specific activity was obtained at 0.125% DOC. These results suggest that the T4-5'-deiodinase is associated with microsomal membrane instead of luminar contents.

Animals↗
PubMed1978

LATS-protector activity in thyrotoxicosis measured by thyroidal intracellular colloid droplet formation.

A modified assay method of LATS and LATS protector (LATSP) was devised employing murine thyroidal intracellular colloid droplet formation. This method is 4- to 8-fold more sensitive to stimulators than is the regular McKenzie bioassay. For the assay of LATSP, IgG to be tested was incubated with human thyroid homogenate, then LATS-IgG was added and it was further incubated. The potency of LATS in the mixture was assayed. The adequacy of the present method for the assay of LATSP was supported by the facts that the LATSP activity was roughly related to the dose of IgG tested and that the inactivation of LATSP was observed when the IgG was pretreated with human thyroid particulate fraction and then assayed. With this method, 7 out of 32 patients with thyrotoxicosis showed LATS and 18 showed LATSP. Changes in LATSP were followed up in 7 cases out of the 18. LATSP activity decreased and then disappeared in 6 out of the 7 cases, when they had been euthyroid for a certain period of time. At 12-20 months after the treatment either by thionamide medication or by subtotal thyroidectomy. LATSP and 131I-thyroid uptake were measured in these 6 patients. In all of the 6, LATSP was negative regardless of thyroid suppressibility.

Animals↗
PubMed1978

Effect of ethanol on the peripheral metabolism of thyroxine.

To determine the effect of ethanol on peripheral metabolism of T4, deiodinative clearance of T4 and serum concentration of T4, T3 and rT3 were measured in rats isotopically equilibrated with T4. Ethanol 8 g/Kg weight/day was given for 3 days to fasted rats and the results were compared with those normally fed or totally fasted animals. In fasted rats, deiodinative clearance of T4 and serum T4 and T3 concentration, and T3/T4 ratio, were decreased significantly, while serum rT3 concentration and serum rT3/T4 ratio was increased significantly when compared to those in normal rats. When ethanol was administered to fasted rats, deiodinative clearance of T4, serum T4 and T3 concentration and serum T3/T4 returned to normal level while serum rT3 concentration and rT3/T4 ratio remained at higher levels than in normally fed animals. These results could not be interpreted on the basis of shift of 5 monodeiodinase to 5' form or vise versa, and imply that the two deionative process may be independent each other.

Animals↗
PubMed1977

Characterization of T3 immunoreactivity release from thyroid gland in vitro a reflection of colloid droplet formation.

T3 immunoreactivity release from the thyroid gland in vitro was shown to be increased by TSH. In the present study, we sought to determine whether the T3 immunoreactivity release is an indicator of thyroid hormone secretion or due to hormone synthesis. When thyroid glands from mice were incubated with TSH, T3 immunoreactivity release was increased in parallel with intracellular colloid droplet formation in a dose related manner. When colchicine, a known inhibitor of colloid droplet formation, was added, both T3 immunoreactivity release and colloid droplet formation were inhibited, whereas MMI, an inhibitor of hormone synthesis, failed to influence both aspects. Thus T3 immunoreactivity release as a reflection of colloid droplet formation was demonstrated. The analysis of the released immunoreactivity by Sephadex column and subsequent radioimmunoassay suggested that the T3 immunoreactivity was, to a considerable extent, due to macromolecule instead of T3 itself. The effect of I- or Li+ to inhibit thyroid hormone secretion was shown to be on the step prior to, but not subsequent to, colloid droplet formation.

Animals↗