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T Segawa

Publications and source records attributed to T Segawa.

At least 145 records · Page 8Linked to original sources
PubMed1984

Developmental changes of cerebral cortical [3H]clonidine binding in rats: influences of guanine nucleotide and cations.

Cerebral cortical [3H]clonidine binding and influences of GTP and cations were investigated in developing rats. The results from Scatchard plots were compatible with the presence of two populations of binding sites [high-affinity binding (KD = 0.59 nM) and low-affinity binding (KD = 7.12 nM)] in 70-day-old rats but only high-affinity binding (KD = 0.27 nM) on day 1. Low-affinity binding was detectable on day 7. KD values in high- and low-affinity binding were not significantly changed during development after 7 days. Bmax of high-affinity binding reached a peak on day 15, and the value of low-affinity binding gradually increased with age. The addition of 10 microM GTP caused a significant reduction in Bmax of high-affinity binding after day 7. Neither KD nor Bmax of low-affinity binding was affected by 10 microM GTP during development. NaCl (10 and 100 mM) diminished the binding on days 7 and 70. MnCl2 (0.1 and 1.0 mM) markedly increased the binding on days 15 and 70 but not on day 7. It is suggested that: (1) single binding sites of alpha 2-adrenoceptors with higher affinity seem to be present on day 1; (2) low-affinity binding appears on day 7; (3) the number of high-affinity binding sites reaches a peak on day 15, followed by changes in populations of high-affinity as well as low-affinity sites without changing affinity; (4) the regulatory mechanism in alpha 2-receptors by guanine nucleotide reaches functional maturity between days 1 and 7; and (5) the involvement of Na+ and Mn2+ in alpha 2-receptor binding becomes functional by days 7 and 15, respectively.

Aging↗
PubMed1984

Active uptake system for substance P carboxy-terminal heptapeptide (5-11) into a fraction from rabbit enriched in glial cells.

In the present study, we demonstrated the existence of an active uptake system for substance P carboxy-terminal heptapeptide, (5-11)SP. When a fraction from rabbit brain enriched in glial cells was incubated with [3H] (5-11)SP, an uptake of [3H](5-11)SP was observed. The uptake system has the properties of an active transport mechanism. Kinetic analysis indicated two components of [3H](5-11)SP uptake, one representing a high and the other a low affinity transport system. After unilateral ablation of the striatum, approximately 30% of the high affinity [3H](5-11)SP uptake capacity of substantia nigra slices disappeared. The subcellular distribution of the high affinity uptake indicated that [3H] 5-hydroxytryptamine was taken up mostly into the P2B fraction (synaptosomal fraction), whereas [3H](5-11)SP was taken up into the P2A fraction (myelin fraction) to the same extent as into the P2B fraction. These results suggest that when SP is released from nerve terminals, it is hydrolysed into (5-11)SP, which is in turn accumulated into glial cells as well as nerve terminals and that this high affinity uptake mechanism may play an important role in terminating the synaptic action of SP.

Animals↗
PubMed1983

Striatal [3H]GTP binding in developing rats: involvement of sulfhydryl residues, Ca2+ and Mg2+.

The influence of sulfhydryl reagents and cations on specific [3H]GTP binding to striatal membranes was investigated in developing rats. Two components of non-cooperative [3H]GTP binding sites were observed in 15, 30, 70 and 360 day old rats but only a single component in 1 and 7 day old ones. The KD for low affinity binding increased with age. Bmax values for both high and low affinity binding increased with age and reached a peak at 30 days, followed by a decrease at 70 and 360 days. At 7 and 70 days, NaCl 1-100 mM did not affect [3H]GTP binding but CaCl2 and MgCl2 significantly inhibited the binding over a concentration range of 1-100 mM. TLC analysis of [3H]GTP and the metabolites in the binding medium and membranes showed that [3H]GTP in both membranes and in the medium was decreased by addition of 1 mM CaCl2 and 1 mM MgCl2 into the binding medium. On days 7 and 70, p-chloromercuriphenyl sulfonate strongly inhibited [3H]GTP binding, and dithiothreitol significantly increased binding but dopamine, apomorphine, spiperone and alpha-flupenthixol did not increase binding up to 0.1 mM. It is suggested that sulfhydryl residues, Ca2+ and Mg2+ are involved in the regulation of guanine nucleotide binding and that the regulatory mechanism becomes functional at 7 days. Ca2+ and Mg2+ seem to act by stimulating degradation of [3H]GTP. In addition, the density of GTP binding sites reaches a peak at around 30 days and the affinity decreases with age.

4-Chloromercuribenzenesulfonate↗
PubMed1983

Determination of pipecolic acid in rat brain areas by high-performance liquid chromatography of dansyl derivatives with fluorimetric detection.

A method for the determination of pipecolic acid in the rat brain is reported. The identification and quantification of pipecolic acid is accomplished with reverse-phase high-performance liquid chromatography including precolumn dansylation procedure by using nipecotic acid, a regio-isomer of pipecolic acid, as an internal standard. The lower limit of quantification for the method is in the picomole range. Higher concentration of pipecolic acid in the rat brain regions were found in cerebellum, medulla oblongata, hypothalamus, and midbrain than the other regions. The method establishes the usefulness of dansyl chloride for the simple and sensitive detection of pipecolic acid, and is easily adapted to routine analysis of pipecolic acid in the rat brain regions.

Animals↗
PubMed1983

Influences of isoproterenol pretreatment on cerebral cortical bindings of [3H]clonidine and [3H]dihydroalprenolol in infant and adult rats.

Specific bindings of [3H]clonidine and [3H]dihydroalprenolol [( 3H]DHA) to crude synaptic membranes were measured after cerebral cortical slices or synaptic membranes were pre-incubated with isoproterenol, 200 microM at 37 degrees C for 40 min, in 7- and 70-day-old rats. Isoproterenol caused a significant increase of the Bmax value of [3H]clonidine binding sites at both days 7 and 70, without changing the Kd. Scatchard analysis of [3H]clonidine binding to adult synaptic membranes which was examined by using a wide range of [3H]clonidine concentration (0.05-15 nM), showed that the Bmax in only high-affinity binding sites was 4-fold increased by pretreatment of synaptic membranes with isoproterenol 200 microM. In contrast, the Bmax of [3H]DHA binding sites was significantly reduced by isoproterenol at 7 and 70 days. These results suggest that the possible interrelationship between beta- and alpha 2-adrenoceptors which exists in synaptic membranes, matures by day 7 in the cerebral cortex of rats.

Alprenolol↗
PubMed1983

Interactions of divalent metal ions with bovine, human, and goat alpha-lactalbumins.

Bovine, human, and goat alpha-lactalbumins prepared by the ordinary methods were found to contain 1.1-1.3 atoms of Ca per protein molecule. Removal of Ca2+ was shown to destabilize the tertiary structures in the three proteins. The three apoproteins were indicated to change in the conformation by heat from the native-like to the unfolded state. Degree of restoration of the native tertiary structure in 5 mM Tris-HCl and 0.1 mM EDTA at pH 7.2 and 25 degrees C by addition of Ca2+ was determined from change in CD ellipticity at 270 nm, and the apparent binding constant of Ca2+ was analyzed to be 2.5 X 10(8) (bovine), 3.0 X 10(8) (human), and 2.8 X 10(8) M-1 (goat). Also, value of the binding constant of Ca2+ to the native-like apoform was estimated from the apparent binding constant and equilibrium constant of the conformational change of the apoform. The binding properties of Mn2+, Mg2+, and Zn2+ to the bovine protein at neutral pH are also discussed.

Animals↗
PubMed1983

Influence of thyrotropin-releasing hormone on general behavior and striatal [3H]spiperone binding in developing rats.

An intraperitoneal administration of thyrotropin-releasing hormone (TRH, 2 or 20 mg/kg) produced behavioral excitement and consequently an increase in ANIMEX counts 15 min after the injection in a dose-dependent manner in 70-day-old rats. On the other hand, TRH (2 or 20 mg/kg)-induced behavioral excitement appeared more slowly (90-150 min) and more persistently in 7-day-old animals than in 70-day-old animals. TRH (2 or 20 mg/kg) significantly reduced specific [3H]spiperone binding to striatal membranes in 7- and 70-day-old rats compared to control, when the binding was examined in the membranes obtained from animals sacrificed 15 min and 150 min following TRH injection. In vitro addition of TRH up to 0.1 mM did not affect [3H]spiperone binding on days 7 and 70. From these results, it is suggested that striatal dopamine receptors could be involved in TRH-induced behavioral excitement in developing rats.

Animals↗
PubMed1983

Effect of concanavalin A on 3H-5-hydroxytryptamine uptake in rabbit blood platelets: interaction with adenylate cyclase activity.

Concanavalin A (Con A) was shown to have inhibitory effect on platelet adenylate cyclase as well as 5-hydroxytryptamine (5HT) uptake. These effects of Con A were antagonized by alpha-methyl-D-mannoside, a specific inhibitor of Con A binding to glycoprotein. The effect of Con A on adenylate cyclase was partial inhibition, and Con A had no effect on prostaglandin E1 stimulated activity, indicating the adenylate cyclase which is thought to be involved in 5HT uptake might be a minor component. The same result as Con A was demonstrated in the inhibitory effect of N-ethylmaleimide (NEM) on this activity. Impermeable sulfhydryl blocking reagents and iodoacetamide had no effect on 5HT uptake. It might be necessary for the sulfhydryl blocking reagent to pass through the cell membrane in order to exert its inhibitory effect on 5HT uptake. Furthermore, the inhibitory effect of Con A on 5HT uptake was antagonized by sulfhydryl reducing reagents and adenosine. It is postulated that a NEM sensitive, sub-membrane contractile protein system might mediate the effect of Con A, and Con A might inhibit platelet 5HT uptake by affecting the adenylate cyclase system through some possible transmembrane regulatory mechanism.

Adenosine↗
PubMed1982

Effects of acute and chronic toluene inhalation on behavior and (3H)-serotonin binding in rat.

Toluene inhalation (0.7% in air) induced in rats abnormal neurological states resembling the serotonin syndrome, such as hindlimb abduction, resting tremor and head weaving. The frequency and intensity of these responses were unchanged after two weeks of exposure (0.7% in air, 15 min/day for 14 days), indicating an absence of tolerance development. An examination of specific serotonin (3H-5HT) binding to crude synaptic membranes prepared from brains of rats subjected to acute and chronic toluene exposure revealed that while no changes in either apparent Kd or apparent Bmax occurred in acutely exposed animals, in chronically treated animals specific (3H)-5HT binding decreased in hippocampus and pons + medulla oblongata. These results indicate that serotonergic mechanisms may play a role in some of the effects of toluene inhalation in rats, but cannot explain the absence of tolerance development after chronic exposure to toluene.

Animals↗
PubMed1982

Effect of methiothepin on imipramine- or mianserin- induced subsensitivity of serotonergic receptors.

Effect of methiothepin on imipramine- or mianserin- induced subsensitivity of serotonergic receptors was examined in rat brain. Treatment with either imipramine plus methiothepin or mianserin plus methiothepin for 4 days resulted in a significant decrease in [3H]5-hydroxytryptamine ([3H]5-HT) binding in synaptic membranes. The binding was not significantly decreased after treatment for this period of time with either methiothepin, imipramine or mianserin alone. It is suggested that the elevated intrasynaptic 5-HT levels could contribute to potentiation effect of methiothepin on imipramine- or mianserin-induced down regulation of serotonergic receptors.

Animals↗
PubMed1982

The increase of cardiac beta 1-subtype of beta-adrenergic receptors in adult rats following neonatal 6-hydroxydopa treatment.

An analysis of Hofstee plots of specific [3H]dihydroalprenolol ([3H]DHA) binding in the presence of various concentrations of practolol showed that KD and Bmax in beta 1-subtype adrenoceptors were 19.2-fold lower and 2.76-fold higher than those in beta 2-subtype in adult rat hearts, respectively. Neonatal treatment with 6-hydroxydopa produced a significant increase only in Bmax in beta 1-adrenoceptors without changing Bmax and KD in beta 2-receptors. "Up' regulation in the density of beta 2-type of adrenoceptors seems to be caused by the 6-hydroxydopa-induced sympathetic lesion.

Animals↗
PubMed1982

Ontogenetic development of the striatal [3H]spiperone binding: regulation by sodium and guanine nucleotide in rats.

Ontogenetic development of specific [3H]spiperone binding to crude synaptic membranes and its regulation by Na+ and GTP was investigated in the rat striatum. (d)-Butaclamol more effectively inhibited [3H]spiperone binding than (l)-butaclamol. The ratio of inhibitory activity of (d)- and (l)-butaclamol for [3H]spiperone binding was not different between 1-, 7-, and 70-day-old animals but eight- to ninefold lower at 18 days of gestation than during the postnatal period. A Scatchard plot of specific binding indicated the presence of two types of binding: low-affinity (KD = 1.51 nM) and high-affinity (KD = 0.09 nM) binding on day 70. Only one component (KD = 0.075 nM) was observed on days 1 and 7 and both types of binding were found on day 15. Bmax gradually increased with age and reached a peak on day 30, followed by a decline on days 70 and 360. Na+, 100 mM, significantly increased specific binding on days 1, 7, 15, and 70. GTP, 50 microM, completely reversed the Na+-induced decrease in IC50 of apomorphine on both days 15 and 70, but not on day 7. It is suggested that receptors could recognize ligand stereospecificity on day 1. The density in dopamine receptors in the striatum reaches a peak on day 30, followed by a decrease on days 70 and 360. In addition, regulation by Na+ and GTP in agonist binding to dopamine receptors seems to become functional between 1 and 2 weeks after birth.

Aging↗
PubMed1982

Involvement of central noradrenergic system in thyrotropin-releasing hormone-induced behavioral excitement in 6-OHDOPA-treated, infant rats.

A subcutaneous (s.c.) injection of thyrotropin-releasing hormone (TRH) 20 mg/kg, produced body shake and struggle, consequently induced an increase of count in ANIMEX activity meter in 7-day-old rats pretreated with 6-hydroxydopa (6-OHDOPA), 75 mg/kg, on days 0, 2 and 4. TRH-induced behavioral excitement was markedly attenuated in the infant animals which were injected desmethylimipramine, 5 mg/kg, 30 min before 6-OHDOPA on days 0, 2 and 4. It is suggested that central catecholaminergic, in particular, noradrenergic system is involved in TRH-induced body shake and struggle in 6-OHDOPA-treated, infant rats.

Animals↗