Search PubMed⌕ Search

Biomedical subjects

T Muraki

Publications and source records attributed to T Muraki.

At least 91 records · Page 5Linked to original sources
PubMed1990

Serum concentrations of thyroid hormones and activity of iodothyronine deiodinase in peripheral tissues of the house musk shrew, Suncus murinus.

Serum concentrations of thyroid hormones and the properties of iodothyronine deiodinase in tissues of the house musk shrew, Suncus murinus, were examined and compared with those of the rat. Serum concentrations of thyroxine (T4) and 3,3',5'-tri-iodothyronine (rT3) were higher, while the serum concentration of 3,5,3'-tri-iodothyronine (T3) was lower in the shrew than in the rat. Among liver, kidney, skeletal muscle, heart, brown adipose tissue (BAT), spleen, lung, testes and thymus homogenates of the shrew, T(4)5'-deiodinase (5'D) activity was highest in BAT, and rT3 5'D activity was highest in both the liver and BAT. Intermediate or low T3 5-deiodinase activity was noted in all tissues examined. Activity of 5'D for T4 and rT3 in liver and kidney was much lower, while that of BAT was much higher in the shrew than in the rat. Liver and kidney 5'D may be type-I and that of BAT may be type-II in the shrew, judging from its response to 6-n-propyl-2-thiouracil and iopanoic acid and substrate preference. Thus 5'D of the shrew was similar to that of the rat in type, but was different with respect to its activity in some peripheral tissues. This difference may have relevance to the low T3 state of the shrew.

Adipose Tissue, Brown↗
PubMed1989

Effect of reserpine pretreatment on brown fat iodothyronine 5'-deiodinase of mouse.

The effect of pretreatment with reserpine (1 mg kg-1 i.p. daily for 7 days) on the regulation of iodothyronine 5'-deiodinase (5'D) in mouse brown adipose tissue (BAT) has been examined. 5'D activity of BAT homogenate was assessed by the in-vitro formation of 3,5,3'-triiodothyronine from thyroxine and 3,3'-diiodothyronine from 3,3',5'-triiodothyronine in the presence of 20 mM dithiothreitol. Reserpine treatment decreased the stimulation of BAT 5'D induced by acute cold exposure (4 degrees C, 2 h) without a significant decrease in the basal 5'D activity, whereas stimulation of BAT 5'D elicited by noradrenaline (0.4 and 0.8 mg kg-1 s.c. 2 h previously) was not augmented after reserpine treatment. Although both noradrenaline and acute cold exposure increase BAT 5'D through alpha 1-adrenoceptors, our results show that chronic reserpine treatment prevents the effect of cold, but does not induce alpha 1-adrenoceptor supersensitivity in BAT.

Adipose Tissue, Brown↗
PubMed1989

Developmental changes in the effects of carbachol and morphine on cGMP contents of plasma, heart, and lung of mice.

It is considered that carbachol increases plasma cGMP levels by acting on muscarinic receptors and morphine increases these levels by acting on opioid receptors, followed by stimulation of muscarinic receptors. We investigated the ability of carbachol and morphine to increase cGMP contents of plasma, heart, and lung and the guanylate cyclase activity of heart and lung homogenate in 1-, 2-, 3-, and 7-week-old mice. The increase in plasma cGMP levels induced by carbachol showed a peak at 2 and 3 weeks of age. The basal cGMP contents in heart and lung and their rise induced by carbachol, as well as the guanylate cyclase activity of these organs, were decreased in 7-week-old mice. The effects of morphine on the cGMP contents showed a similar developmental change, except for no effect in 1-week-old mice. These changes in the effects of carbachol and morphine may be the result of developmental changes of the muscarinic receptor--guanylate cyclase system and opioid receptors.

Aging↗
PubMed1989

[Some properties of various composite resin inlay products].

Several problems associated with materials and clinical techniques are pointed out for posterior composite resin restoration. One of the solutions to these problems is the application of the indirect composite resin inlays. Three kinds of products for composite resin inlay are being marketed at present. We examined the mechanical properties, surface roughness and radiopacity for each product. Inlay/Onlay (Ivoclar), Brilliant D.I. (Colténe) and CR Inlay (Kuraray) were used in this study, and composite resin inlays were fabricated in accordance with the manufacturers' instructions. The highest values of mechanical properties after immersion in water for 24 hours are shown below: table; see text The mechanical properties of the composite resin inlay, subjected to thermal cycling at 4 degrees C and 60 degrees C for 3 minutes each for 5,000 cycles, tended to decrease in comparison with those immersed in water for 24 hours. Inlay/Onlay showed the smallest surface roughness (Ra), i.e. the best smoothness value below: table; see text The radiopacity was highest for Inlay/Onlay with Brilliant D.I. and CR Inlay being successively lower.

Composite Resins↗
PubMed1987

Genetic analysis of hypothermia induced by morphine in two strains of inbred mice.

The degree of hypothermia elicited by morphine was greater in DBA/2 than C57BL/6 strain mice of both sexes. Hypothermia elicited by morphine was antagonized by naloxone in both strains of mice, suggesting the involvement of opioid receptors. To examine the role of genetic factors in the strain difference of morphine-induced hypothermia, the effect of morphine on changes in the rectal temperature was studied in the 6 generations of male mice, including the 2 inbred strains, P1 (DBA/2) and P2 (C57BL/6), their F1 and F2 hybrids, and 2 backcrosses, B1 (F1 X P1) and B2 (F1 X P2). The order of mean temperature decrease determined 40 min after 20 mg/kg morphine injection was P1 greater than B1 greater than F1 = F2 greater than B2 greater than P2. There was no maternal effect on the morphine responses of the F1 generation. Biometrical analysis revealed that DBA/2 (P1) is partially dominant over C57BL/6 (P2) and contribution of polygenes was suggested.

Animals↗
PubMed1987

Alpha 1-adrenoceptor production of inositol phosphates mediates the inhibition of thyroxine release from the mouse thyroid.

To examine the mechanism of the alpha 1-adrenoceptor-mediated inhibition of the release of thyroid hormones in the mouse thyroid, the effect of noradrenaline on the production of inositol phosphates was investigated using thyroids preloaded with [3H]inositol. Noradrenaline increased [3H]inositol accumulation into inositol phosphates in the mouse thyroid during a 30-min incubation whereas TSH (10 mU/ml) was without effect. The effect of noradrenaline was mimicked by phenylephrine, but not by clonidine or isoprenaline. Prazosin antagonized the effect of noradrenaline, while yohimbine had no effect. These results suggest that noradrenaline-induced production of inositol phosphates is mediated by alpha 1-adrenoceptors. The inhibition of release of thyroid hormones elicited by alpha 1-adrenergic agonists in the mouse thyroid is possibly mediated through the hydrolysis of membrane phosphoinositides followed by the generation of second messengers such as inositol phosphates and diacylglycerol.

Animals↗
PubMed1986

Strain difference in the effects of morphine on the rectal temperature and respiratory rate in male mice.

Effects of morphine on the rectal temperature and respiratory rate, and [3H]naloxone binding to brain membranes from seven brain regions were compared among six strains of male mice, including DBA/2N, C57BL/6N, BALB/c, C3H/HeN, A/J and ICR. The administration of 10 and 20 mg/kg doses of morphine HCl to these strains of mice decreased rectal temperature and respiratory rate. However, there was a significant strain difference in these two measures of the effect of morphine. The DBA/2N strain was the most sensitive in both measures of morphine action. The magnitude of hypothermia was positively correlated with respiratory depression among six strains of mice after the administration of 10 and 20 mg/kg morphine HCl, suggesting common mechanisms. Strain difference in naloxone binding in the brain regions could not explain that of the morphine responses, because there was no correlation between the intensity of morphine-induced hypothermia or respiratory depression and the regional [3H]naloxone binding for the mouse strains.

Animals↗
PubMed1986

The staining properties of halo- and alkyl-thiazolylazophenol derivatives in histochemical staining of cadmium.

In the continuous research for a more sensitive chelator for cadmium, halothiazolylazodiethyaminophenol and alkylthiazolylazophenol derivatives were synthesized, and their staining sensitivity for cadmium chelates were examined with respect to a substituent group. 2-(4-Methyl- and 4,5-dimethyl-2-thiazolylazo)-5-diethylami-nonphenol showed low staining density in the 005-sections of cadmium, to date they showed the highest staining sensitivity for cadmium among the thiazolylazophenol analogs. The appropriate combination of substituent groups as based on their electron donative strength may be the decisive factor in determining the staining sensitivity of thiazolylazophenol analogs.

Animals↗
PubMed1986

Effects of clonidine and yohimbine on plasma cyclic nucleotide levels in clonidine-naive and clonidine-treated mice.

Effects of clonidine and yohimbine on plasma cyclic nucleotide levels were investigated in both clonidine-naive and clonidine-treated male mice. Clonidine increased plasma cyclic GMP but decreased slightly cyclic AMP levels in clonidine-naive mice. Clonidine treatment for 10-14 days in the drinking water did not decrease the cyclic GMP response to clonidine indicating that no tolerance develops to the effect of clonidine on plasma cyclic GMP. alpha 2-Agonists, such as clonidine, oxymetazoline and naphazoline, were more potent than phenylephrine, an alpha 1-agonist, in increasing cyclic GMP, although azepexole, a weak alpha 2-agonist, had no effect. Inhibition of clonidine-induced increase in plasma cyclic GMP by yohimbine, hexamethonium and atropine, but not by prazosin suggests that the effect of clonidine is mediated by the central alpha 2-adrenoceptors, activating the muscarinic receptor-linked guanylate cyclase through the stimulation of vagal activity. Yohimbine increased plasma cyclic AMP levels in clonidine-naive mice. Inhibition of this effect by hexamethonium and propranolol suggests that yohimbine increases plasma cyclic AMP through increasing the sympathetic tone. The increase in plasma cyclic AMP elicited by yohimbine was potentiated by chronic clonidine treatment. Enhancement of the cyclic AMP effect of yohimbine found in clonidine-treated mice may be regarded as a precipitated withdrawal symptom and indicate development of dependence on clonidine.

Animals↗
PubMed1985

Genetic analysis of the effects of morphine on plasma cyclic nucleotides and locomotor activity in male mice.

A biometric analysis of morphine-induced changes in locomotor activity and plasma cyclic nucleotide levels was conducted in two inbred strains of mice, DBA/2N and C57BL/6N, and their F1 hybrid and backcross progenies. C57BL/6N was partially dominant over DBA/2N for morphine-induced motor activity, whereas DBA/2N was partially dominant over C57BL/6N with respect to the effect of morphine on the cyclic nucleotides. The strain difference in the effect of morphine on motor activity and on plasma cyclic GMP was shown to be genetically determined, whereas the genetic influence on plasma cyclic AMP was statistically not confirmed. The number of gene pairs which regulate the effect of morphine on motor activity was assumed to be more than one; however, the contribution of more than one segregating unit in the effect of morphine on plasma cyclic GMP was not demonstrated.

Animals↗
PubMed1985

Histochemical staining of exogenous chromium and iron with the catalytic oxidation of phenylamines.

A highly sensitive and specific method for staining exogenous chromium and iron in tissues is described. This method is superior to conventional complex-forming methods with regard to its sensitivity and specificity for these metals. The staining reaction is based on the metal-catalysed oxidation of phenylamines. Tissue sections were incubated in a medium containing hydrogen peroxide and phenylamines, p-phenylenediamine or phenylhydrazine. Results obtained from test-tube experiments concerning the catalytic activities of metals indicated that the staining reactions depends on the activities of metals in tissues.

Aniline Compounds↗
PubMed1984

Inhibition of benzodiazepine and GABA receptor binding by amino-gamma-carbolines and other amino acid pyrolysate mutagens.

The effect of several pyrolysate mutagens on the benzodiazepine and GABA receptors was investigated. Of amino-gamma-carbolines, Trp-P-1 antagonized the suppressive effect of diazepam on the pentylenetetrazol-induced convulsions and death, whereas Trp-P-2 by itself precipitated seizures and death in male mice. Both Trp-P-1 and Trp-P-2 inhibited the specific binding of [3H]diazepam and [3H]muscimol in rat brain membranes mainly by increasing Kd, indicating that these gamma-carbolines bind on benzodiazepine and GABA receptors. IC50S of Trp-P-1 and Trp-P-2 on specific [3H]flunitrazepam binding were not changed by addition of GABA. The Hill coefficient of Trp-P-1 for displacing [3H]diazepam binding was about unity whereas that of Trp-P-2 was less than unity. These results suggest that Trp-P-1 and Trp-P-2 act as active antagonists or inverse agonists at benzodiazepine receptors. The convulsant effect of the gamma-carbolines may be mediated by an action on the central benzodiazepine receptors; however, the role of the effect on GABA receptors is not clear.

Animals↗
PubMed1984

A genetic analysis of morphine responses in mice.

To investigate whether genetic factors may play a role in the difference of the responses to morphine between inbred strains of mice, we determined the effect of morphine on the plasma cyclic nucleotides, the motor activity and the rectal temperature in the 2 progenitor strains of mice, DBA and C57BL, their F1 and F2 hybrids, and the 2 backcross progenies between F1 and parental strains. C57BL was partially dominant over DBA concerning the motor activity induced by morphine, whereas DBA was partially dominant over C57BL in terms of the increase in plasma cyclic nucleotides and the hypothermia elicited by morphine. The biometric analysis suggested that the strain difference in the effects of morphine was genetically determined except for plasma cyclic AMP, and that among these quantitative traits, the effects of morphine on motor activity and rectal temperature were controlled by more than one allelic gene pairs.

Animals↗
PubMed1984

Effect of morphine on the tissue cyclic AMP and cyclic GMP content in two strains of mice.

The effect of morphine on the cyclic (c) AMP and cyclic (c) GMP concentrations in several organs, and its reversal by naloxone have been investigated in C57BL and DBA strains of mice. Morphine increased the cAMP contents in lungs and muscle, and the cGMP contents in lungs, intestine, heart, liver and muscle in a naloxone-reversible way in C57BL mice only. This is consistent with our previous observation that morphine increased plasma cyclic nucleotide levels in C57BL mice, whereas such an increase was marginal in the DBA strain. These results show that there is a strain difference in the effect of morphine on tissue cyclic nucleotide contents and the possible origin of the plasma cyclic nucleotides which are increased by morphine.

Animals↗
PubMed1984

Predominance of alpha 2-adrenoceptors in porcine thyroid: biochemical and pharmacological correlations.

alpha-Adrenergic agonists such as norepinephrine and clonidine, but not methoxamine, inhibited the increase in cAMP accumulation elicited by TSH in porcine thyroid slices. The inhibitory effect of norepinephrine was abolished by yohimbine but not by prazosin. Likewise, the in vitro release of T4 from the pig thyroid slice stimulated by TSH was inhibited by norepinephrine and the inhibition was antagonized by yohimbine but not by prazosin. These results suggest that the inhibitory effect of alpha-adrenergic agonists is mediated through alpha 2-adrenoceptors. Preincubation of the thyroid slices with islet-activating protein, pertussis toxin, decreased the inhibitory effect of norepinephrine on the cAMP content, suggesting the involvement of guanine nucleotide regulatory protein (Ni) in the inhibition mediated through alpha 2-adrenoceptors. Binding studies with [3H]yohimbine and [3H]prazosin to porcine thyroid membranes revealed the specific and saturable binding of both radioligands. Scatchard analysis of the specific binding revealed a single class of binding sites for each radioligand; however, the maximum number of binding sites for [3H]yohimbine was about 10 times more than that for [3H]prazosin. In accordance with the pharmacological results, binding studies showed a predominance of alpha 2-adrenoceptors in the pig thyroid.

Animals↗