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Biomedical subjects

S Hamada

Publications and source records attributed to S Hamada.

At least 19 recordsLinked to original sources
PubMed1979

Increase in liver nuclear tri-iodothyronine receptors associated with increased deoxyribonucleic acid by long-term administration of tri-iodothyronine in thyroidectomized rats.

The effect of long-term administration of small amounts of tri-iodothyronine was examined on the nuclear tri-iodothyronine receptors in rat liver. The maximal binding capacity (C(max.)) and association constant (K(a)) of the receptors were determined in thyroidectomized rats given vehicle alone (group A), 2mug of tri-iodothyronine/100g body wt. (group B) or 7mug of tri-iodothyronine/100g body wt. (group C) for 2 weeks. Scatchard analyses with correction for the amount of endogenous tri-iodothyronine revealed that C(max.) values per g of liver were increased to 1.5 and 2.7 times the control value in groups B and C respectively. Since concentrations of DNA per g of liver were significantly increased in the two groups of hormone-treated rats, C(max.) values per mg of DNA were nearly the same in group B, but still increased significantly in group C compared with group A. K(a) values remained unchanged in all three groups of animals. Mitochondrial alpha-glycerophosphate dehydrogenase activity was 9.6 and 28.7 times as high in groups B and C, respectively, as in group A. Concentrations of endogenous tri-iodothyronine bound to non-histone protein were substantially increased in groups B and C, although concentrations of serum tri-iodothyronine remained rather low. The results obtained indicate that the long-term administration of tri-iodothyronine in small doses induces an increase in the nuclear receptors associated with increased DNA with and without accompanying a relative increase in the receptor concentration in thyroidectomized rats. Also the hormonal effect is closely related to the total number of the nuclear receptors and the concentrations of nuclear tri-iodothyronine bound to the receptors rather than the serum tri-iodothyronine concentrations.

Animals↗
PubMed1979

Tri-iodothyronine-induced increase in rat liver nuclear thyroid-hormone receptors associated with increased mitochondrial alpha-glycerophosphate dehydrogenase activity.

The effect of tri-iodothyronine injection on the nuclear tri-iodothyronine receptor (putative thyroid-hormone receptor) was examined in rat liver. Nuclear receptors were extracted from isolated nuclei with 0.4 M-KCl, and their association constants (Ka) and maximal binding capacities (Cmax.) were determined by Scatchard analyses with and without correction for the endogenous hormone. The amount of endogenous tri-iodothyronine bound to non-histone protein was estimated on the basis of the specific radio-activity of [125I]tri-iodothyronine injected 2 h before the rats were killed. It was demonstrated that Cmax. of the nuclear receptors was 2.5-fold higher in severely hyperthyroid than in hypothyroid rats. However, irrespective of the thyroid status, the Ka of the receptors remained unchanged when corrected for endogenous tri-iodothyronine bound to non-histone protein. The validity of the correction was supported by experiments in vitro in which nuclear receptors were preincubated with unlabelled tri-iodothyronine. The increase in Cmax. of nuclear receptors was directly related to mitochondrial alpha-glycerophosphate dehydrogenase activity. These results suggest a hormonal modulation of the nuclear receptors which is associated with hormonal action.

Animals↗
PubMed1979

Sequential changes in rat liver nuclear tri-iodothyronine receptors and mitochondrial alpha-glycerophosphate dehydrogenase activity after administration of tri-iodothyronine.

The dynamics of the induction of nuclear tri-iodothyronine receptors and mitochondrial alpha-glycerophosphate dehydrogenase were studied in rat liver after a single injection of tri-iodothyronine. The maximal binding capacity (C(max.)) and association constant (K(a)) of the nuclear receptors were determined by Scatchard analyses with and without correction for the endogenous tri-iodothyronine measured by radioimmunoassay. The administration of tri-iodothyronine induced sequential increases in the concentration of nuclear receptors and alpha-glycerophosphate dehydrogenase activity in the liver. The nuclear-receptor concentration was increased to 2.5 times that in the hypothyroid rat 1 day after the administration of hormone, and then decreased, with a half-life of about 2 days. alpha-Glycerophosphate dehydrogenase activity changed in parallel with the nuclear-receptor concentration, showing a delayed response. The total amount of non-histone protein in the liver was significantly increased 3 days after the administration. It seems likely therefore that the tri-iodothyronine-induced increase in nuclear-receptor concentration is responsible, at least in part, for the induction of this enzyme. The possibility is also suggested that nuclear receptors may be one of the non-histone proteins selectively synthesized at an early stage of the hormonal stimulation. Throughout the time course, the K(a) values of the nuclear receptors for tri-iodothyronine remained unchanged, when corrected for endogenous tri-iodothyronine bound to the non-histone proteins, although they were apparently changed when the correction was not made. The results obtained provide further evidence for hormonal modulation of the nuclear receptors which is closely linked with the hormonal effect.

Animals↗
PubMed1979

Serotype-dependent inhibition of glucan synthesis and cell adherence of Streptococcus mutans by antibody against glucosyltransferase of serotype e S. mutans.

A crude glucosyltransferase (GTase) preparation was obtained from the culture supernatant of Streptococcus mutans strain MT703 (serotype e) by 50% ammonium sulphate precipitation. Antiserum specific against the GTase was prepared by immunizing rabbits intramuscularly with the GTase in Freund incomplete adjuvant, followed by GTase without adjuvant intravenously. Gamma globulin fractions of the antiserum and normal serum were partially purified by 1/3 saturated ammonium sulphate precipitation. The antibody strongly inhibited the GTase activity (greater than 90%) of type c, e and f S. mutans, whereas the GTase of type a, d and g was not affected by the antibody. The GTase from type b S. mutans was slightly inhibited. The adherence of viable cells of type c, e, and f S. mutans to a glass surface due to synthesis of glucan by the cell-associated GTase was also significantly inhibited by the antibody to the enzyme. These results suggest that type c, e, and f and types a, d, and g S. mutans can be separated into two major groups in terms of the immunological relationship of GTase.

Antibodies, Bacterial↗
PubMed1979

Chemical composition of Streptococcus mutans cell walls and their susceptibility to Flavobacterium L-11 enzyme.

The susceptibility to a cell wall lytic L-11 enzyme from Flavobacterium sp. and the quantitative and/or qualitative composition of the cell walls of some strains of cariogenic Streptococcus mutans and a non-cariogenic strain of Streptococcus mitis were determined. The purified cell walls of S. mutans strains HS-1 (serotype a), BHT (b), NCTC10449 (c), C67-1 (c), C67-25 (c), OMZ 176 (d), MT703 (e), MT557 (f), OMZ65 (g), and AHT (g), and S. mitis CHT contained glutamic acid, alanine, and lysine as well as muramic acid and glucosamine as a peptidoglycan component. Besides these amino acids, significant amounts of threonine were detected in strains HS-1, OMZ65, and AHT cell walls, and considerable amounts of aspartic acid and/or threonine as well as several other amino acids in OMZ176, OMZ65, and CHT cell walls. Rhamnose was a common special component of the cell walls of S. mutans strains BHT, NCTC10449, MT703, B2 (e), MT557, and AHT, and S. mitis CHT. An additional sugar component, glucose, was detected in the cell walls of all of these strains except BHT, and galactose was found in BHT, AHT, and CHT cell walls. Galactosamine was present in S. mitis CHT cell walls. Varying amounts of phosphorus were detected in the cell walls of all the strains examined. The cell walls of all these streptococcal strains except MT703, 6715, and AHT were susceptible to the lytic action of the L-11 enzyme to various extents. No consistent relationship was observed between the amino acid and sugar composition of these cell walls and their susceptibility to the L-11 enzyme. The chemical composition of these cell walls is discussed in terms of the serological classification of S. mutans.

Amino Acids↗
PubMed1979

Smouldering epidemic of Yersinia pseudotuberculosis in barn rats.

Yersinia pseudotuberculosis was isolated from 8 (8 Rattus norvegicus) of 270 (259 R. norvegicus and 11 R. rattus) rats examined. Seasonal variation was not found in the incidence of isolations. The isolation occurred almost equally in both young and old rats. The isolated strains were determined as serovar IB in one rat, and serovar IVA in seven rats. The strains were isolated from the contents of the intestinal tract (the duodenum, jejunum, ileum, cecum, colon, and rectum), the spleen, liver and mesenteric lymph nodes; they were not detected in the kidneys. Agglutinin titer in the eight rats was no more than 32.

Animals↗
PubMed1979

Longitudinal survey of the distribution of various serotypes of Streptococcus mutans in infants.

The establishment of various serotypes of Streptococcus mutans was studied serologically in plaque samples collected from label surfaces of upper primary incisors of 22 infants (starting age, 5 to 13 months) over a period fo 30 months. Clinical examinations were also performed. No clear-cut association between the initiation of dental caries and previous detection of S. mutans was noted. However, all 12 of the infants with caries had S. mutans isolated at some time during the course of this study. The most common serotype isolated at the initial establishment of S. mutans on the tooth surfaces was serotype c, whereas types d, e, and g became established in a few cases. During the test period, changes in the distribution of serotypes of S. mutans were observed in some cases. The initiation of carious lesions could be found in a few cases even when S. mutans comprised about 1% or less of the total streptococcal count of the specimen from the tooth surfaces. Serotype d/g strains tended to develop carious lesions on smooth surfaces, although serotype c was isolated from almost all individuals who developed caries.

Child, Preschool↗
PubMed1979

Inhibitory effect of certain drugs on thyroid hormone binding by human liver cytosol.

Effects of dinitrophenol (DNP), salicylate, diphenylhydantoin (DPH) and heparin on thyroid-hormone binding by human liver cytosol were studied using Pevikon thin-layer electrophoresis. Thyroxine (T4) binding by the major cytosol T4-binding protein, hT4-2, was significantly depressed with these drugs, and the displaced T4 was bound by another cytosol binding protein, hT4-1. Triiodothyronine (T3) binding by the major cytosol T3-binding protein, hT3-2, was significantly decreased with DPH and heparin, but not with DNP and salicylate. Comparative studies using human serum indicated that T4 binding by serum T4-binding prealbumin (TBPA) was inhibited with DNP and salicylate, and that binding of T4 and T3 by serum T4-binding globulin (TBG) was decreased only with DPH. The results obtained indicate that these drugs inhibit thyroid-hormone binding by the liver cytosol binding proteins for T4 and T3, and that the displaced hormones may be responsible for changes in free hormone levels in serum, and within the cells, and for the accelerated turnover of hormones.

Adult↗
PubMed1979

[Measurement for serum thyroxine-binding globulin (TBG) and its clinical assessment in diagnosis of thyroid states (author's transl)].

Serum levels of thyroxine (T4)-binding globulin (TBG) were determined by a radioimmunoassay using cellulose-linked antibody to TBG. Values obtained in healthy young adults averaged 1.62 +/- 0.25 (SD) mg/100 ml, and no significant difference wwas detected between males and females. The TBG levels remained within the normal limit in hyperthyroidism while they were significantly increased in hypothyroidism. Interestingly enough, TBG levels were significantly elevated in chronic thyroidities with no overt hypothyroidism. In normal pregnancy, TBG was increased slightly in the first trimester, and markedly in the second and third trimesters. In one case of congenital TBG deficiency, no immunoreactive TBG was detected. It was demonstrated, further, that an inverse relationship (r = -0.7593) existed between the TBG level and serum triiodothyronine uptake index, and that a direct relation (r = +0.6557) was present between the TBG level and T4 in sera from normal subjects and pregnancy. Ratios of T4/TBG were markedly increased in hyperthyroidism, and decreased in hypothyroidism, showing no overlap with the normal subjects, whereas they were below the normal limit in half the cases in the second and third trimesters of pregnancy. The radioimmunoassay for TBG was useful in evaluating hypothyroid states, because it could differentiate the increase in T4 associated with elevated TBG from hyperthyroidism.

Adult↗
PubMed1979

Serological properties of cellular and extracellular glycerol teichoic acid antigens of Streptococcus mutans.

Cell-free supernatant of Streptococcus mutans cultures was concentrated by 50% ammonium sulphate precipitation to 1/50 of the original culture volume. Most extracellular glucosyltransferase activity was detected in the supernatant. Furthermore, the supernatant reacted with serotype specific antiserum, showing immunological identities with the serotype specific polysaccharide antigen obtained from whole cells by hot saline or NaOH extraction in double diffusion tests. Immunoelectrophoretic analysis also revealed that the supernatant antigen possessed significant quantities of lipid-bound and free glycerol teichoic acid antigens. The lipoteichoic acid (LTA) was obtained from whole cells by phenol-water extraction. The lipid-teichoic acid linkage was easily split by mild acid or alkaline hydrolysis. The supernatant and phenol antigens spontaneously sensitized sheep red blood cells. These antigens were adsorbed to hydroxyapatite powder. The extracellular LTA and glucosyltransferase were found to be closely associated and difficult to separate chromatographically. In vivo significance of these properties of LTA and GTase is discussed in terms of the ecology of S. mutans and other oral streptococci.

Antigens, Bacterial↗