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Biomedical subjects

K Takazawa

Publications and source records attributed to K Takazawa.

89 records · Page 5Linked to original sources
PubMed1986

Iodide-induced hypothyroidism in a patient with anorexia nervosa.

A 39-year-old woman who had been suffering from anorexia nervosa was found to have hypothyroidism. Serum T4, free T4, T3, free T3 and TSH were 3.19 micrograms/dl, 0.5 ng/dl, 15.3 ng/dl, 1.2 pg/ml and 162.1 microU/ml, respectively. On careful questioning, she was found to have taken an iodine-rich diet. The serum iodine concentration was 122 micrograms/dl (normal: 4-9 micrograms/dl) and urinary iodide excretion was 13.05 mg/day (normal: less than 2 mg). After withdrawal of the iodine-rich diet, her serum T4 gradually increased and TSH returned to the normal range. She was diagnosed as having iodide-induced hypothyroidism. However, no significant elevation of serum T3 or free T3 was observed. Serum T4, free T4, T3, free T3 and TSH were 7.85 micrograms/dl, 0.8 ng/dl, 13.6 ng/dl, 4.3 pg/ml and 6.02 microU/ml, respectively. The iodide-perchlorate discharge test result was negative. These findings suggest that there exists some unknown mechanism by which a patient with anorexia nervosa may be sensitive to excess iodide. Furthermore, it is of interest to note that in a recovery phase from the hypothyroid state, normalization of serum T4 rather than T3 is well-correlated to TSH secretion.

Adult↗
PubMed1985

Parvalbumin exists in rat endocrine glands.

Simple and rapid purification procedures for parvalbumin, one of the Ca2+-binding proteins (extracted from rat skeletal muscle), were developed, and its antiserum was produced in rabbits to measure the parvalbumin content of various rat tissues by RIA. The heat treatment, ammonium sulfate fractionation, and trichloroacetic acid precipitation of soluble fraction from rat skeletal muscle followed by single diethylaminoethyl Sephadex A-50 column chromatography yielded a pure 120 mg protein from 150 g skeletal muscle. Amino acid analysis, together with electrophoretic mobility, indicated that the protein was identical to parvalbumin. The antisera to this rat skeletal muscle parvalbumin (raised in rabbits) did not cross-react with calmodulin or S-100 proteins. The RIA for parvalbumin using this antisera and [125I]parvalbumin revealed that skeletal muscle and brain contained high levels of the antigen; the values of which were 69,486 +/- 4,933.1 and 881 +/- 165.6 ng/mg protein, respectively. However, the parvalbumin antigen in the heart, lung, liver, and spleen could not be detected. On the other hand, the contents of the antigen in the endocrine glands (in nanograms per mg protein) were as follows: pituitary (125 +/- 46.6), thyroid (108 +/- 50.0), adrenal (341 +/- 64.3), testes (227 +/- 37.2), and ovaries (218 +/- 10.1). All of these values were comparable to levels of antigen found in the brain sample. These results suggest an important role for parvalbumin in endocrine glands.

Adrenal Glands↗
PubMed1985

Interaction of left ventricular contraction and aortic input impedance in experimental and clinical studies.

Implication of aortic input impedance and left ventricular coupling were investigated in three series of studies. In a clinical study, the ascending aortic flow velocity and pressure were simultaneously recorded from a multisensor catheter, and input impedance was calculated from 8 harmonics of aortic pressure and flow. Left ventricular wall stress was calculated from diameters and wall thickness of cineventriculogram and simultaneous recording of left ventricular pressure. In the experimental study, programmable artificial pulsatile pump was used to control pulsatile blood flow in dogs. The pressure-flow relationship in the arterial system had slightly convex curves toward the pressure axis with a critical turning pressure, so the arterial system had low output--high resistance and high output--low resistance characteristics. Therefore, the failed heart should inevitably eject the blood against stiffened vascular beds. Increased work load of the ventricle as expressed by sustained ventricular wall stress was determined mainly by the exaggerated late systolic pressure due to increased input resistance and increased low frequency pulsatile component of the input impedance. These findings are especially important for relieving additional work load of the ischemic heart, which have higher pressure wave reflection.

Animals↗
PubMed1985

[Prediction of coronary lesions by two-dimensional echocardiography in patients with healed myocardial infarction].

Regional left ventricular wall motion abnormalities were assessed by two-dimensional echocardiography (2-DE) in 66 patients with healed myocardial infarction (MI) and the results were compared with those of coronary angiography which was performed at nearly the same time as 2-DE. The left ventricular wall was divided into 14 segments and asynergy was assessed in each segment. To compare the severity of segmental asynergy with coronary artery lesions, relation between segments and coronary artery perfusion was assumed as follows: the anterior wall, anterior septum and apex corresponded to the anterior descending artery (LAD); the lateral and inferior walls corresponded to the left circumflex artery (LCX); and the posterior septum and inferior wall corresponded to the right coronary artery (RCA). One vessel disease: In all 24 patients with MI induced by LAD lesions, regional asynergy was identified in the anterior wall, anterior septum and apex. All patients had advanced asynergy (severe hypokinesis, akinesis or dyskinesis) except one with subendocardial infarction. Advanced asynergy was identified in the other segments including the lateral wall (one patient) and the posterior septum (11 patients), but such asynergy was not associated with that of the inferior wall. In four patients with MI induced by RCA lesions, regional asynergy appeared in localized segments of the posterior septum and inferior wall, and the asynergy was severe in all patients except one in whom collaterals were well-developed. In four patients with MI induced by LCX lesions, asynergy was observed in both the lateral and inferior walls. In only one patient, mild asynergy was identified in the apex. Multi-vessel disease: In both groups with double vessel (16 patients) and triple vessel (16 patients) disease, asynergy was recognized in the affected areas of the major coronary artery which was considered responsible for the infarction, irrespective of the severity of the coronary stenosis. Also, there was no significant correlation between the severity of coronary artery stenosis and segmental wall motion abnormalities in non-infarcted areas. No significant correlation was observed between the severity of regional wall motion abnormalities in the infarcted areas and the degree of development of collaterals. In patients with MI induced by LAD lesions, more extensive asynergy in the anterior wall and anterior septum at the basal portion was observed in the patient group with proximal stenosis than in the group with distal stenosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1978

The biphasic stimulatory and inhibitory effects of concanavalin A on thyroid activation induced by thyrotropin.

Concanavalin A (Con A) was tested for its ability to affect thyroid activation induced by TSH in mouse thyroid lobes. Pretreatment of thyroid lobes with Con A at concentrations from 1.55--400 microgram/ml was found to have biphasic stimulatory and inhibitory effects of the TSH-induced accumulation of cAMP and formation of colloid droplets. Low concentrations of Con A potentiated TSH activation of thyroidal formation of cAMP and endocytosis. In contrast, higher concentrations of Con A markedly inhibited these TSH effects. The inhibitory effects observed after preincubation with Con A were abolished by the addition of alpha-methyl-D-glucoside to the incubation medium. A high concentration of Con A also inhibited cAMP formation induced either by prostaglandin E2 or the long-acting thyroid stimulator. However, the basal and TSH-stimulated glucose oxidation in mouse thyroid lobes was not depressed by a high concentration of Con A. Uptake of 125 I-labeled Con A by thyroid tissues increased with time up to 1 h and was directly proportional to tissue weight. These findings suggest that the specific interaction between Con A and its receptors may lead to conformational changes in the structure of the membranes of the thyroid follicular cells which facilitate TSH-induced thyroid hormone secretion via the adenylate cyclase-cAMP system.

Animals↗
PubMed1978

Evidence for activation by beta2-adrenergic receptors of adenosine 3',5'-monophosphate formation in Ehrlich ascites tumor cells.

The existence of aminergic receptors in mouse Ehrlich ascites tumor cells was studied. L-Isoproterenol in vitro stimulated the formation of cAMP in isolated Ehrlich ascites tumor cells. Stimulation by isoproterenol of cAMP formation was not significantly inhibited by practolol, a beta1-adrenoceptor antagonist-Salbutamol, a beta2-adrenoceptor agonist, markedly stimulated the formation of cAMP in Ehrlich ascites tumor cells at concentrations from 10(-8)-10(-3) M. After the addition of salbutamol, cAMP levels reached a maximum in 10 min and declined to about 2-fold of the basal level to 30 min. The stimulation by salbutamol of cAMP formation was markedly inhibited by butoxamine, a beta2-adrenoceptor antagonist, but not by practolol. Furthermore, the effect of a maximal dose of salbutamol was additive to that of prostaglandin E2. Histamine and 4-methylhistamine, a histamine H2 receptor agonist, had no significant effects. Therefore, it is suggested that a beta2-adrenergic receptor exists in the membranes of Ehrlich ascites tumor cells in terms of the adenylate cyclase-cAMP system.

Albuterol↗
PubMed1977

Evidence for the existence of a histamine H2-receptor in the mouse thyroid.

The existence of a histamine H2-receptor in the thyroid was investigated. Histamine in vitro stimulated the formation of cyclic AMP and colloid droplet formation in mouse thyroid lobes. Stimulation by histamine of cyclic AMP formation in mouse thyroid lobes was significantly inhibited by metiamide, a histamine H2-receptor antagonist. 4-Methylhistamine, a histamine H2-receptor agonist, markedly stimulated cyclic AMP formation, whereas 2-methylhistamine, a histamine H1-receptor agonist, was ineffective. The stimulation by 4-methylhistamine of cyclic AMP formation was markedly inhibited by metiamide, but not by chlorpheniramine, a histamine H1-receptor antagonist. In contrast, metiamide did not affect cyclic AMP formation induced either by TSH or by the long-acting thyroid stimulator. Therefore, it is suggested that there exists a histamine H2-receptor in the membranes of the thyroid follicular cells which facilitate thyroid hormone secretion via the adenylate cyclase-cyclic AMP system.

Animals↗
PubMed1976

[Studies on the thyrotropin receptor in the thyroid: positive cooperativity of Concanavalin A binding and its biphasic effects on thyroid activation induced by thyrotropin (author's transl)].

Concanavalin A (Con A) was tested for its ability to affect thyroid activation induced by the thyroid stimulators in mouse thyroid tissues. Con A was found to have the biphasic stimulatory and inhibitory effects of thyrotropin (TSH)-induced cyclic AMP formation and endocytosis, a step in thyroid hormone secretion, in mouse thyroid tissues. Low concentrations of Con A potentiated TSH-stimulated cyclic AMP formation and endocytosis. In contrast, high concentrations of Con A markedly inhibited TSH stimulations. These effects were reversed by the addition of methyl-alpha-D-glucoside to the second preincubation medium (without Con A) prior to TSH. A high concentration of Con A alone did not depress the basal levels of cyclic AMP or basal glucose oxidation in thyroid tissues. A high concentration of Con A also inhibited cyclic AMP formation induced by prostaglandin E2 and the long-acting thyroid stimulator (LATS). Binding of 125I-labeled Con A to thyroid tissues increased with time up to 75 min and was very slowly reversible after attainment of equilibrium. Binding was directly proportional to tissue weight. Scatchard plot analysis on the binding of 125I-labeled Con A to thyroid tissues indicated a positive cooperativity which seemed to be well correlated to the biphasic effects.

Animals↗
PubMed1976

The inhibitory effect of acute administration of excess iodide on the formation of adenosine 3', 5'-monophosphate induced by thyrotropin in mouse thyroid lobes.

In a previous paper, we demonstrated that an inhibitory action of excess iodide on thyrotropin-induced thyroid hormone secretion occurs at a site subsequent to the generation of cyclic AMP. In the present study, however, we have found that thyroidal cyclic AMP formation induced by thyrotropin in vitro was markedly inhibited by the acute administration of excess iodide to mice fed a low iodine diet. In contrast, excess iodide failed to produce inhibition in animals fed a regular diet. In vitro stimulation by long-acting thyroid stimulator (LATS), prostaglandin E2, and 4-methylhistamine of cyclic AMP formation in mouse thyroid lobes was also significantly inhibited by the acute in vivo administration of excess iodide. The inhibition was completely relieved by the administration of methimazole prior to excess iodide. Furthermore, it has been shown that thyroid adenylate cyclase activity induced by thyrotropin was markedly depressed by excess iodide under similar experimental conditions. Therefore, it is suggested that one of the inhibitory actions of excess iodide is on the adenylate cyclase-cyclic AMP system and further, that iodide can elicit its inhibitory action after its conversion to some form of organic iodine.

Adenylyl Cyclases↗
PubMedDate not supplied

[Intravascular ultrasound assessment at the site of balloon angioplasty: comparison with quantitative coronary angiography].

The effect of coronary angioplasty is usually evaluated on the basis of coronary angiography. However, angiographic images taken after angioplasty vary and the angiographic assessment of the therapeutic success of angioplasty is limited by local disruptions and dissections at the site of the dilatation, which are often difficult to detect by angiography. Intravascular ultrasound imaging is a new method for evaluation of coronary dimensions and wall morphology. Quantitative coronary angiographic analysis was compared with intravascular ultrasound assessment after balloon angioplasty in 42 patients. A diagnostic ultrasound imaging catheter was used during percutaneous transluminal coronary angioplasty (PTCA) to image both the lesion and the vessel segment just proximal (reference segment). Correlation between angiographic and ultrasound findings of vessel diameters and areas at reference segments was closer (r = 0.78, 0.66) than at the sites of PTCA (r = 0.54, 0.36). Dilated sites were analyzed in two subgroups segregated by degree of lumen eccentricity. An eccentric vessel lumen, defined as a circular shape factor of less than 0.92, was present at 25 of 42 sites. The correlation between angiographic and ultrasonic cross sectional area was not as close for these eccentric segments (r = 0.37). The difference in luminal areas between eccentric lumens estimated by edge detection and densitometry methods was 0.93 +/- 0.3 mm2, significantly greater than 0.54 +/- 0.31 mm2 in the circular group (p < 0.01). Luminal area after balloon angioplasty is clinically important to confirm by intravascular ultrasound especially in patients with large differences in measured values by quantitative coronary angiography.

Adult↗