Biomedical subjects

N Iwaki

Publications and source records attributed to N Iwaki.

14 recordsLinked to original sources

PubMed1998

[A study on the response selection and inhibition in a cognitive conflict task using event-related potentials].

This study examined the hypothesis (Eriksen & Schultz, 1979) that a subject checks whether a prepared response is correct or not in the Eriksen and Eriksen (1974) cognitive conflict task, using event-related potentials (ERPs). Fourteen right-handed subjects were required to respond selectively to a central target letter flanked with compatible (e.g., HHHHHHH) or incompatible (e.g., SSSHSSS) noise letters, or not to respond to asterisks (*******). The results showed that the lateralized readiness potential indicating an incorrect preparation and the NO-GO potential reflecting a response inhibition emerged for incompatible stimuli. These findings indicate that a prepared response was recognized as erroneous, and was inhibited. Therefore, it is suggested that the check operation functioned in the cognitive conflict task. Furthermore, the result that the NO-GO potential latency for incompatible stimuli was longer than that for NO-GO stimuli suggests that the timing of NO-GO decision and response inhibition by the check operation influenced the NO-GO potential latency.

Adult↗

PubMed1997

Effects of proglumide on cholecystokinin-8-induced exocrine and endocrine pancreatic responses in conscious sheep.

The effects of cholecystokinin (CCK)-8, either alone or together with the CCK antagonist, proglumide on both exocrine and endocrine pancreatic responses were examined in conscious sheep. Intravenous infusions of CCK-8 (120 pmol/kg/min for 40 min) with vehicle (0 mumol/kg/min proglumide) significantly increased both amylase output in pancreatic juice and plasma insulin concentrations (P < 0.05). Concomitant infusions of proglumide (5-40 mumol/kg/min for 50 min) inhibited both amylase and insulin secretory responses induced by CCK-8 infusion. The antagonistic effects of proglumide occurred in a dose-dependent manner, and proglumide infusion at dose of 20 mumol/kg/min or above simultaneously inhibited CCK-8-induced amylase and insulin responses. In conclusion, although the type of receptor involved is not characterized at present, exogenously infused CCK-8 acts on B cells via a CCK-receptor-mediated mechanism and induces insulin secretion in sheep.

Amylases↗

PubMed1997

[A study of information processing of cognitive conflict using event-related potentials].

This study examined whether cognitive conflict, reported by Eriksen and Eriksen (1974), could be explained by a model of reciprocal inhibition between correct and incorrect response preparation. Subjects responded selectively to a central target letter with flanking compatible (e.g., HHHHH) or incompatible (e.g., SSHSS) noise letters. In the mixed condition all four stimuli were mixed randomly in a block, and in the blocked condition only two stimuli with identical noises were used. The results showed that the reaction times to incompatible stimuli were delayed in the mixed condition compared with that to compatible stimuli, while the delay was significantly reduced in the blocked condition. This blocking effect was also shown on P3 latencies, an event-related potential measure of stimulus evaluation, but not on lateralized readiness potentials (LRPs), a measure of response preparation. Furthermore, irrespective of blocked/mixed conditions, LRPs indicating incorrect preparation were observed. These findings suggest that cognitive conflict could not be explained by the reciprocal inhibition model based on response preparation, but by a model based on stimulus evaluation.

Adult↗

PubMed1995

Effects of intravenous infusions of cholecystokinin (CCK)-8 on exocrine and endocrine pancreatic secretion in conscious sheep.

The effects of cholecystokinin (CCK)-8 on both exocrine and endocrine pancreatic functions were examined simultaneously in five conscious sheep. Intravenous infusions of CCK-8 (0, 5, 10, 20, 30, 60, 120 and 240 pmol/kg/min for 40 min) induced dose-dependent increases in flow rate, and in protein and amylase outputs in pancreatic juice. The same CCK-8 infusions induced dose-dependent increases in plasma insulin, but no change in plasma glucagon concentrations. The threshold dose (10-30 pmol/kg/min) of CCK-8 infusion for stimulating insulin secretion was similar to that for stimulating amylase output. In conclusion, using amylase output as an indicator of physiological action, CCK is one of the potential candidates as a physiological regulator of insulin, but not glucagon secretion in sheep.

Amylases↗

PubMed1994

Effects of intravenous infusions of cholecystokinin-8 and pentagastrin on plasma concentrations of insulin and glucagon in sheep.

The effects of cholecystokinin-8 (CCK-8) and pentagastrin on insulin and glucagon secretion were studied in conscious sheep. Intravenous infusions of CCK-8 (3 to 1000 pmol kg-1 min-1 for 30 minutes) induced a dose-dependent increase in plasma insulin, but did not alter plasma glucagon concentration. The threshold dose of CCK-8 for stimulation of insulin secretion was 10 to 30 pmol kg-1 min-1. Pentagastrin was infused intravenously at doses of 10 to 3000 pmol kg-1 min-1. The maximal dose of pentagastrin slightly stimulated insulin, but not glucagon, secretion. The insulin secretory activity of pentagastrin was only 1/300 that of CCK-8 on a molar basis. The threshold dose of CCK-8 for stimulation of insulin secretion was similar to that for exocrine pancreatic secretion obtained in earlier studies. In conclusion, CCK is a potential candidate as a physiological factor regulating insulin secretion in sheep.

Animals↗

PubMed1992

Optical resolution of (+/-)-all-trans-3-hydroxyretinal by use of high-performance liquid chromatography.

Racemic all-trans-3-hydroxyretinal (3-OH-RAL) (1) was converted by a reaction with (-)-camphanic acid chloride (CpCl) into a diastereomixture of camphanates (2a) and (2b) which was separated by preparative high-performance liquid chromatography (HPLC) to give two esters (2a) and (2b) in pure state, respectively. Saponification of (2a) and (2b) independently afforded optically active (3S)- and (3R)-3-OH-RALs (3a) and (3b), respectively, whose absolute structures were determined by circular dichroism (CD) spectra. Racemic 3-OH-RAL was separated to two peaks by HPLC using chiral column (ChiraSpher, Merck). Cochromatography with authentic specimens (3a) and (3b) showed that the peak with a short retention time corresponded to (3R)-isomer and the other to (3S).

Chromatography, High Pressure Liquid↗

PubMed1974