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Biomedical subjects

Y Ikarashi

Publications and source records attributed to Y Ikarashi.

At least 91 records · Page 5Linked to original sources
PubMed1994

Hypothalamic cholinergic and noradrenergic neurons in hyperglycemia induced by 2-deoxyglucose.

To investigate the contribution of the hypothalamic cholinergic and noradrenergic neurons in 2-deoxyglucose (2-DG) induced hyperglycemia, we after microwave irradiation analyzed the contents of the neurotransmitters and the metabolites in the microdissected hypothalamic nucleus, ventromedial hypothalamic nucleus (VMH), paraventricular nucleus (PVN) and lateral hypothalamus (LH). A dose dependent decrease in the acetylcholine (ACh) content and a corresponding increase in the choline content was observed in those hypothalamic nuclei 20 min after intravenous administration of 250 or 500 mg/kg 2-DG. The norepinephrine content decreased in 500 mg/kg 2-DG group but did not change significantly in the 250 mg/kg group. These results suggest the involvement and importance of the hypothalamic cholinergic system in 2-DG induced hyperglycemia and, furthermore, that the hyperglycemic response can not be solely attributed to the noradrenergic system.

Acetylcholine↗
PubMed1994

Temporal changes in extracellular acetylcholine and CA1 pyramidal cells in gerbil hippocampus following transient cerebral ischemia.

Temporal changes in cholinergic functions following transient cerebral ischemia (10 min) were studied in the hippocampus of awake unrestrained gerbils using in vivo microdialysis. These data were compared with the results for temporal change in the area of each CA1 cell soma, measured with a microcomputer imaging device. KCl-induced release of acetylcholine (ACh) tended to be lower within 1 day after recirculation, and was significantly lower on the 4th, 7th and 14th days. Atropine-induced release of ACh gradually decreased over the test period. In histological estimation, no differences were observed within the 1st day, but a significant decrease of the area of CA1 cell soma was observed from the 4th to 14th days. Moreover, ischemia over 2 min decreased KCl- and atropine-induced ACh release on the 14th day without significant changes of hippocampal CA1 pyramidal cell. From these results, it is clear that ischemia produced dysfunction of hippocampal cholinergic neurons, and that dysfunction of the hippocampal cholinergic system following transient ischemia precedes pyramidal cell damage in the hippocampal CA1 subfield.

Acetylcholine↗
PubMed1994

Effect of transient cerebral ischaemia on acetylcholine release in the gerbil hippocampus.

To clarify the relationship between presynaptic cholinergic dysfunction and postsynaptic cell death in the hippocampus, extracellular levels of acetylcholine (ACh) were assayed and CA1 pyramidal cells were histologically investigated in gerbils which had undergone 2, 5 and 10 min ischaemia. It was found that the KCl- and atropine-induced release of ACh, an index of the functioning cholinergic system at the presynaptic terminals, was significantly lower in the ischaemic groups than in control groups. The hippocampal CA1 pyramidal cell area of the 5 and 10 min ischaemic animals was also significantly decreased, but the 2 min ischaemia caused no cell damage. These findings indicate that the presynaptic terminals of the cholinergic neurone are vulnerable to ischaemic insult and that cholinergic dysfunction precedes postsynaptic CA1 pyramidal cell death in the hippocampus.

Acetylcholine↗
PubMed1994

Improved sensitivity and decreased sample size in a cytotoxicity test for biomaterials: a modified colony microassay using a microplate and crystal violet staining.

Modified Eagle's minimum essential medium supplemented with 5% fetal calf serum was highly sensitive to cytotoxicity and formed large control colonies in the V79 colony assay. A highly sensitive cytotoxicity test was developed using 96-well microtiter plates. Test chemicals or extracts of polyurethane materials containing the same chemicals were added 24 h after inoculation of cell suspensions. The cells were fixed and stained with crystal violet after additional culture for 6 days (V79 cells) or 10 days (Balb/3T3 cells). In terms of sensitivity and rapid quantitative measurement, this modified colony microassay, using a low cell density in 96-well microplates, was superior to various cytotoxicity tests such as colony, growth inhibition, cytolethality, and agar diffusion assays.

Animals↗
PubMed1994

Nicotine improves cognitive disturbance in senescence-accelerated mice.

Senescence-accelerated mice (SAM), a murine model of age-related deterioration in learning ability, were studied as to the acetylcholine (ACh) contents in the brain tissues and the effect of nicotine administration. We found that the ACh content of SAM-P/8 (accelerated senescence-prone) mice was lower than that of SAM-R/1 (accelerated senescence-resistant) mice in the midbrain thalamus and the hypothalamus. In addition, an IP administration of nicotine was found to improve learning ability of SAM-P/8 as shown by performance of a passive avoidance task. Nicotine may potentiate cognitive function in SAM-P/8.

Acetylcholine↗
PubMed1994

Aspects of hypothalamic neuronal systems in VMH lesion-induced obese rats.

To clarify neuronal disturbance in the hypothalamus reflecting the development of obesity in ventromedial hypothalamic nucleus (VMH)-lesioned rats, we investigated the contents of neurotransmitters in the hypothalamus after pretreatment by microwave irradiation, contents of neurotransmitter metabolites in third ventricle fluid and catecholamine contents in the adrenal gland. The hypothalamic contents of norepinephrine (NE) and dopamine (DA) were selectively decreased, but acetylcholine (ACh) and serotonin (5-HT) levels were not changed from those in controls. In the lateral part of the hypothalamus, also, a significant decrease of NE content was detected. On the other hand, NE and DA metabolites, MHPG, DOPAC and HVA were increased in the third ventricle fluid in VMH lesion-induced obese rats. Wet weight and content of epinephrine in the adrenal gland were decreased, though the content of NE was preserved. These results indicate that a disturbance of NE and DA neurons in the hypothalamus is involved in the development of VMH lesion-induced obesity. In addition, an increment of the activities of NE and DA systems in the central nervous system as a whole and some irregularity in the sympatho-adrenal system might contribute to VMH obesity.

Adrenal Glands↗
PubMed1994

Assessment of contact sensitivity of four thiourea rubber accelerators: comparison of two mouse lymph node assays with the guinea pig maximization test.

Contact sensitivity of four thiourea rubber accelerators, diphenylthiourea (DPTU), dilaurylthiourea (DLTU), dibutylthiourea (DBTU) and diethylthiourea (DETU), was evaluated by a new sensitive mouse lymph node assay (SLNA) and the murine local lymph node assay (LLNA). The results of the SLNA and LLNA were compared with the data of the guinea pig maximization test (GPMT). In the LLNA and SLNA, the sensitizing activity was measured as a function of draining lymph node activation following application of the test chemicals. Of these four thioureas, three (DETU, DBTU and DPTU) were not classified as skin sensitizers in the LLNA. The SLNA successfully detected the sensitivity of all thioureas tested. This result indicated that the SLNA was, in these cases, more sensitive than the LLNA for identification of contact allergens. The order of sensitization potential observed from the SLNA was DPTU (greatest), DLTU, DBTU and then DETU (least). The predictions of sensitizing potential and the order of the sensitizing capacity of four thioureas by the SLNA and the GPMT are very similar.

Administration, Topical↗
PubMed1994

Striatal extracellular choline and acetylcholine in choline-free plasma rats.

Choline (Ch)-free plasma rats were induced successfully by intravenous (IV) injection of choline oxidase (ChO) (16). However, brain acetylcholine (ACh) levels were not affected by ChO treatment, maintaining the same levels as those in controls, although brain Ch levels were significantly decreased. To clarify the reasons for this, in vivo microdialysis was carried out in the treated rats' striata. The ChO treatment induced not only a 70% decrease of extracellular Ch levels but also a 40% decrease of extracellular ACh levels, reflecting the amount of ACh released from cholinergic terminals. In addition, plasma-bound Ch levels and choline acetyltransferase (CAT) and acetylcholinesterase (AChE) activities in the brain were examined in the rats receiving ChO treatment. No significant differences from controls were observed in these levels. The results suggest that: approximately 70% of striatal extracellular Ch is physiologically supplied from circulating plasma-free Ch; the inhibition of ACh release is related to the maintenance of tissue (intraneuronal) ACh levels under the condition of halting of the supply of free Ch from blood to the brain; if there is a compensative supply of free Ch from de novo synthesis, autocannibalism, or plasma-bound Ch, this may be supplied within neuronal cells, because the level of extracellular-free Ch maintained its depressed level even 11-14 h after ChO treatment.

Acetylcholine↗
PubMed1994

Hypothalamic cholinergic systems in mercuric chloride-induced hyperglycemia.

The roles of hypothalamic neuron mechanisms in regulation of blood glucose were studied in rats. Microinjection of HgCl2 and neostigmine into the third ventricle under anesthesia caused marked hyperglycemia. To characterize the effective neurons in the hypothalamus, tissue contents of neurotransmitters and extracellular levels of metabolites in the ventromedial part of the hypothalamus were measured by microwave irradiation and in vivo brain microdialysis. HgCl2 increased both the content and the extracellular levels of choline. Neostigmine increased the acetylcholine content. In both instances, norepinephrine (NE) and dopamine (DA) content were decreased. Extracellular levels of DA metabolites were increased. On the other hand, serotonin content and extracellular serotonin metabolite level remained constant. In medulloadrenalectomized and atropine-coadministered rats, no marked hyperglycemia was induced by HgCl2 or neostigmine. These results show that the muscarinic cholinergic system participates in the HgCl2-induced central hyperglycemic effect through the function of the adrenal medulla. NE neurons may also be related to hypothalamic glycoregulation, and DA neurons might modulate the regulatory mechanisms.

Animals↗
PubMed1994

Contact sensitivity of and cross-sensitivity between 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Tinuvin P) and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (Tinuvin 326) evaluated by lymph node cell proliferation and ear swelling response in mice.

Contact sensitivity of and cross-sensitivity between 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Tinuvin P, TP) and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (Tinuvin 326, T326) were investigated in BALB/c mice. Mice received an intradermal injection and subsequent topical application of the test chemical. Following final application, auricular lymph node cell (LNC) proliferation was measured. In another experiment, the appearance of contact sensitivity was assessed by increases in ear thickness following challenge of the test chemical. Application of TP to mice caused a significant increase in LNC proliferation. Challenge of these mice with TP resulted in an increase in ear thickness. However, TP-sensitized mice did not show an increase in ear thickness by challenge with T326. Under the same conditions, application of T326 failed to induce either LNC proliferation or ear swelling response. The induction of LNC proliferative response was closely related to the ear swelling response by challenge. Following intradermal injection of TP, topical application of T326 to mice did not induce LNC proliferation. A significant ear swelling response was not induced by first challenge with TP or T326 but induced by rechallenge with TP. Topical exposure of mice to TP following injection of T326 failed to induce LNC proliferation or any ear responses by challenge with T326 and TP. These data suggest that TP is a sensitizer, while T326 is not a sensitizer, and these chemicals do not cross-sensitize.

Administration, Topical↗
PubMed1994

Contact sensitivity to Tinuvin P in mice.

The contact sensitizing potential of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Tinuvin P) was investigated using the murine local lymph node assay (LLNA) and the mouse ear swelling test with some modification in the induction procedure (modified MEST). Topical exposure of the ears to Tinuvin P in acetone:olive oil (AOO) for 3 consecutive days induced no increase in auricular lymph node weight and lymph node cell proliferation. In the LLNA, Tinuvin P was negative, and its sensitizing potential was determined as not strong. In the modified MEST, mice were sensitized with a combination of an intradermal injection of 0.2% Tinuvin P in Freund's complete adjuvant into the shaved abdomen and topical application of 1% Tinuvin P in AOO on both ears for 3 consecutive days. The ear thickness in mice previously treated with Tinuvin P increased significantly on challenge with Tinuvin P. A cross-reaction test between Tinuvin P and various substituted benzotriazole ultraviolet light (UV) absorbers was performed. Challenge with these benzotriazole compounds on the ears of the mice previously sensitized to Tinuvin P showed no increase in ear thickness. These data indicated that Tinuvin P had a contact sensitizing ability, while Tinuvin P-sensitized mice did not cross-react with the other benzotriazole UV absorbers.

Animals↗
PubMed1994

Expansion of intermediate T-cell receptor cells in mice with autoimmune-like graft-versus-host disease.

Chronic graft-versus-host disease (GVHD) following bone marrow transplantation often gives rise to a severe autoimmune-like state. To investigate the immunopathogenesis of this diseased state, mice receiving a transplant of lymphocytes with major histocompatibility complex (MHC) class II disparity (the simplest model of chronic GVHD) were examined. (B10.Thy-1.1 x B6.C-H-2bm12) F1 mice were injected with parental B10.Thy-1.1 CD4+ splenic T cells. These mice showed intensive lymphocyte infiltration of the target organs, including the liver, salivary glands and pancreas. Indeed, the cell numbers yielded from the spleen and liver were increased, and polyclonal B-cell activation was induced by 14 days after injection. More strikingly, more than 80% of such expanding lymphocytes in the target organs became T cells with T-cell receptors (TCR) of intermediate intensity (i.e. intermediate TCR cells) that carried the properties of extrathymic origin. Despite the homogeneous expansion of intermediate TCR cells in GVHD mice, these T cells were polyclonal in terms of V beta usage. These results, in conjunction with the data using the thymectomized mice as recipients, suggested that extrathymic, intermediate TCR cells possibly of recipient origin might be intimately related to the pathogenesis of the autoimmune-like state resulting from chronic GVHD.

Animals↗
PubMed1993

Binding characteristics of various neurochemicals to glassy carbon.

The determination of acetylcholine and choline using liquid chromatography with electrochemical detection using the approach of Potter et al. [J. Neurochem., 41 (1983) 188] normally requires isolation of the desired species before an analysis of tissue samples can be undertaken due to coeluting interferences afforded by other neutrochemicals. We have recently shown that this problem can be overcome by the use of a glassy carbon precolumn to effectively trap the interfering species [Ikarashi et al., J. Chromatogr., 575 (1992) 29]. We now report on the nature and mechanism of this adsorption onto glassy carbon for norepinephrine, dopamine, serotonin, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid. For both the acidic and basic compounds which comprise this group, distinct Langmuir adsorption processes appear to be involved for both the neutral and ionic forms of the individual compounds. Using various data fitting approaches, we have attempted to derive appropriate adsorption constants for the two forms of each compound. Theoretical predictions employing these derived constants provided results which match reasonably well with the observed adsorption data in most cases.

Adsorption↗
PubMed1993

Liquid chromatography with electrochemical detection for quantitation of bound choline liberated by phospholipase D hydrolysis from phospholipids containing choline in rat plasma.

This report describes the optimal conditions for the determination of bound choline in rat plasma. The method used was based on the liberation of choline by phospholipase D from phospholipids containing choline in plasma, followed by high-performance liquid chromatographic analysis. Normal concentrations of total, free and bound choline in rat plasma were found to be 1278.7 +/- 132.5, 11.5 +/- 2.2 and 1267.2 +/- 125.5 nmol/ml, respectively. The described procedure has the advantages of rapidity, specificity, excellent precision and the need for only a small amount of the sample.

Animals↗
PubMed1993

Intraventricular injection of neostigmine increases dopaminergic and noradrenergic nerve activities: hyperglycemic effects and neurotransmitters in the hypothalamus.

The contents of hypothalamic neurotransmitters were examined under inducement of hyperglycemia by intraventricular administration of neostigmine, after pretreatment with microwave irradiation. Extracellular levels of the metabolites of these neurotransmitters were also measured using in vivo microdialysis. Our data suggest that neostigmine affects not only the cholinergic system but also the noradrenergic and dopaminergic systems in the hypothalamus. In order to clarify the relationship between excitement or regulation of physiological events and activities of central specific neurons, we therefore suggest that studies by chemical stimulation are insufficient on their own; it is also necessary to measure fluctuations both in neurotransmitter content and in extracellular levels of their metabolites.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Use of high-performance liquid chromatography continuous-flow fast atom bombardment mass spectrometry for simultaneous determination of choline and acetylcholine in rodent brain regions.

This report describes a method for assay of choline (Ch) and acetylcholine (ACh) levels in rodent brain regions by high-performance liquid chromatography combined with continuous-flow fast atom bombardment mass spectrometry. Following an investigation of various extraction procedures and chromatographic conditions, we found that homogenization in acetonitrile in the presence of magnesium sulphate followed by heptane extraction and then a flow rate programme for chromatographic separation yielded the best results of the protocols tested. Under these conditions, the recoveries of Ch and ACh were 75% and 80%, respectively, with detection limits of 5 pmol for Ch and 2 pmol for ACh. Using this method, Ch and ACh levels in rat and mouse brain regions were similar to those reported by other researchers.

Acetylcholine↗
PubMed1993

Comparative studies of the toxicity of standard reference materials in various cytotoxicity tests and in vivo implantation tests.

Polyurethane films that contained various amounts of zinc diethyldithiocarbamate (ZDEC) and zinc dibutyldithiocarbamate (ZDBC) were prepared as standard reference materials (SRM). Using three cell lines of V79, L929, and Balb/3T3 cells, the cytotoxicity of the dithiocarbamates and the SRM films were compared by agar diffusion assay, filter diffusion assay, neutral red assay, cell growth assay, and colony assay. Among these in vitro cytotoxicity tests, colony assay was found to be the most sensitive method for detecting the cytotoxicity. The cytotoxic potentials of extracts from SRM films correlated well with the concentrations of ZDEC or ZDBC involved in SRM. When various rubber materials including SRM and surgical rubber latex materials were tested, cytotoxic potentials of these extracts were also correlated with the inflammatory tissue capsule thickness in short-term implantation tests. On the basis of these results, the SRM is judged to be useful for validating test sensitivity, and comparing the correlation between in vitro and in vivo responses.

3T3 Cells↗