Biomedical subjects

N Matsuki

Publications and source records attributed to N Matsuki.

At least 37 records · Page 2Linked to original sources

PubMed2000

Extracellular ATP reduces optically monitored electrical signals in hippocampal slices through metabolism to adenosine.

Electrical signals in rat hippocampal slices were optically monitored using a voltage-sensitive dye to determine whether extracellular ATP exhibits direct effects through its own receptors or indirect effects after its hydrolysis to adenosine. The dentate gyrus was stimulated and electrical signals in the CA1 and the CA3 region were analyzed. The signals were divided into two components: a transient component peaking within 10 ms (fast component) and a subsequent sustained component (slow component). ATP (10 to 100 microM) inhibited both the fast and the slow components in the CA1 region by about 30% and 70%, respectively. ADP, AMP and adenosine also inhibited the fast and the slow components. The inhibition by ATP was antagonized by aminophylline and other adenosine receptor antagonists, and by alpha,beta-methylene ADP, an inhibitor of 5'-nucleotidases. These results suggest that extracellular ATP inhibits neuronal electrical signals in hippocampal slices after its metabolism to adenosine.

Adenosine↗

PubMed2000

The development of the emetic reflex in the house musk shrew, Suncus murinus.

The emetic (retching and vomiting) reflex is an important component of the body's defence system against accidentally ingested toxins and emesis is also a common symptom of disease and a side-effect of a number of pharmacological therapies. The development of the reflex has been the subject of few systematic studies. The aim of this study was to characterise the development of the emetic reflex in Suncus murinus (the house musk shrew) using emetic stimuli acting via three different afferent pathways: motion via the vestibular system, pyrogallol via abdominal vagal afferents and resiniferatoxin (a capsaicin analog) via the brainstem. The emetic reflex was not present to any stimulus prior to postnatal day 10 but the onset of the response to motion lagged behind that to the other stimuli in not being present until postnatal day 15. Body weight was not a determinant of the presence of the reflex. It is proposed that the delayed presence of the emetic reflex in Suncus makes it an ideal species in which to investigate factors regulating its development.

Age Factors↗

PubMed2000

Bidirectional actions of docosahexaenoic acid on hippocampal neurotransmissions in vivo.

Docosahexaenoic acid (DHA), a 22-carbon fatty acid with six double bonds, is one of the major polyunsaturated fatty acids in fish oils or in the mammalian central nervous system and is believed to be essential for neuronal plasticity and development. In the present study, we evaluated the effect of DHA on hippocampal neurotransmissions using anesthetized rats. Field excitatory postsynaptic potential (fEPSP) evoked by stimulation of the Schaffer collaterals was recorded from the CA1 stratum radiatum. Following intracerebroventricular injection of DHA 25 nmol, the fEPSP slope decreased gradually in 30 min and was eventually suppressed by about 30%. On the other hand, when fEPSP was evoked by stimulation of the perforant path was recorded in the molecular layer of the dentate gyrus, an increase in fEPSP slope occurred over a similar time course after DHA injection. These phenomena were independent of N-methyl-D-aspartate receptor activity. Linoleic acid, one of polyunsaturated fatty acids, was virtually ineffective. Furthermore, we investigated the effect of DHA on hippocampal synaptic plasticity. Although DHA did not alter the profile of paired-pulse facilitation, it inhibited the induction of long-term potentiation in the CA1 area but not in the dentate gyrus. Thus, DHA exerts regionally different effects on hippocampal neurotransmission and may be a good tool for clarifying physiological functions of the hippocampus.

Animals↗

PubMed2000

Reversible defects in natural killer and memory CD8 T cell lineages in interleukin 15-deficient mice.

C57BL/6 mice genetically deficient in interleukin 15 (IL-15(-/-) mice) were generated by gene targeting. IL-15(-/-) mice displayed marked reductions in numbers of thymic and peripheral natural killer (NK) T cells, memory phenotype CD8(+) T cells, and distinct subpopulations of intestinal intraepithelial lymphocytes (IELs). The reduction but not absence of these populations in IL-15(-/-) mice likely reflects an important role for IL-15 for expansion and/or survival of these cells. IL-15(-/-) mice lacked NK cells, as assessed by both immunophenotyping and functional criteria, indicating an obligate role for IL-15 in the development and functional maturation of NK cells. Specific defects associated with IL-15 deficiency were reversed by in vivo administration of exogenous IL-15. Despite their immunological defects, IL-15(-/-) mice remained healthy when maintained under specific pathogen-free conditions. However, IL-15(-/-) mice are likely to have compromised host defense responses to various pathogens, as they were unable to mount a protective response to challenge with vaccinia virus. These data reveal critical roles for IL-15 in the development of specific lymphoid lineages. Moreover, the ability to rescue lymphoid defects in IL-15(-/-) mice by IL-15 administration represents a powerful means by which to further elucidate the biological roles of this cytokine.

Animals↗

PubMed2000

Pharmacological property of tributyltin in vivo and in vitro.

Tributyltin (TBT), an assumed endocrine-disrupting chemical, is widely known to show harmful effects in invertebrates including the dioecious snails. As for mammals, there are several reports concerning TBT toxicology, but few indications about general pharmacology of TBT. In the present study, we comprehensively examined the pharmacological effects of TBT both in vivo and in vitro. TBT (0.3 or 1.0 mg/kg) attenuated the small intestinal propulsive activity measured by the charcoal method in vivo, and caused concentration-dependent relaxation of isolated guinea-pig ileum in vitro (1.0x10(-8)-3.0x10(-6) M). TBT induced concentration-dependent relaxation of guinea-pig trachea, which was not inhibited by pre-treatment with a beta-adrenoceptor antagonist. TBT caused a concentration-dependent contraction of rat aortae, and also evoked endothelium-dependent relaxation in the presence of an alpha-adrenoceptor antagonist. The relaxation was inhibited by a muscarinic receptor antagonist. TBT reduced the electrically evoked, sympathetic contractile responses of rat vas deferens, which were slightly prevented by an alpha(2)-adrenoceptor antagonist. These results suggest that TBT possesses diverse pharmacological properties in mammalian organs.

Journal Article↗

PubMed2000

Laminin degradation by plasmin regulates long-term potentiation.

Plasmin is converted from its zymogen plasminogen by tissue type or urokinase type plasminogen activator (PA) and degrades many components of the extracellular matrix (ECM). To explore the possibility that the PA-plasmin system regulates synaptic plasticity, we investigated the effect of plasmin on degradation of ECM and synaptic plasticity by using organotypic hippocampal cultures. High-frequency stimulation produced long-term potentiation (LTP) in control slices, whereas the potentiation was induced but not maintained in slices pretreated with 100 nM plasmin for 6 hr. The baseline synaptic responses were not affected by pretreatment with plasmin. The impairment of LTP maintenance was not observed in slices pretreated with 100 nM plasmin for 6 hr, washed, and then cultured for 24-48 hr in the absence of plasmin. To identify substrates of plasmin, the expression of three major components of ECM, laminin, fibronectin, and type IV collagen, was investigated by immunofluorescence imaging. The three ECM components were widely distributed in the hippocampus, and only laminin was degraded by plasmin pretreatment. The expression level of laminin returned to normal levels when the slices were cultured for 24-48 hr after washout of plasmin. Furthermore, preincubation with anti-laminin antibodies prevented both the degradation of laminin and the impairment of LTP maintenance by plasmin. These results suggest that the laminin-mediated cell-ECM interaction may be necessary for the maintenance of LTP.

Animals↗

PubMed2000

Positive reactions to common allergens in 42 atopic dogs in Japan.

Clinically important allergens for the diagnosis and treatment of atopic dermatitis vary geographically. In order to identify the most prevalent allergens in atopic dogs in Japan, 42 dogs with a clinical diagnosis of atopy were tested using both in vivo (intradermal skin test (IDST)) and in vitro (antigen-specific IgE assay) allergy tests. Allergens used for IDST included 26 allergen extracts from eight allergen groups: trees, weeds, grasses, house dust mites (HDM), molds, foods, epithelia, and arthropods. Immunodot assay was used to measure antigen-specific IgE against 24 allergens from these eight groups and against fish such as cod and sole. In the 42 dogs, the most common positive allergen reaction was to HDM on both IDST (29/42 dogs or 69%) and in vitro testing (23/42 or 54.8%). The second most frequent positive allergen reaction was to Japanese cedar pollen (21/42 or 50.0% for IDST and 7/42 or 16.7% for in vitro testing). In both tests, less than 20% of dogs had positive reactions to molds or foods. Positive reactions to cat epithelia were frequently found on IDST, but rarely found on in vitro testing. Agreement between the two tests was found in 26 instances: HDM (21 dogs), Japanese cedar pollen (five dogs) and wheat (one dog). In this study, the two most common allergens involved in atopic dermatitis in dogs in Japan were HDM and Japanese cedar pollen.

Allergens↗

PubMed2000

Cytotoxicity of tributyltin in rat hippocampal slice cultures.

The neurotoxic effects of tributyltin (TBT), an endocrine-disrupting chemical, were evaluated in organotypic slice cultures of immature rat hippocampus. Confocal microscopy study with propidium iodide showed that TBT induced severe neuronal death in a concentration- and time-dependent manner with CA3 > CA1 > dentate gyrus ranking of vulnerability of the hippocampal subfields. Dead or damaged neurons exhibited chromatin condensation, which is one of the morphological characteristics of apoptosis, as revealed by acridine orange staining. TBT neurotoxicity was alleviated by application of free radical scavengers or antioxidants, such as catalase, superoxide dismutase, Trolox and alpha-tocopherol but not by ascorbic acid or N-acetyl-L-cysteine, which suggests an involvement of free radicals, particularly reactive oxygen species. Neurons displayed a long-lasting increase in intracellular Ca2+ concentrations after TBT treatment. Although neither N-methyl-D-aspartate (NMDA) receptor inhibitors nor voltage-sensitive Ca2+ channel blockers protected hippocampal neurons against TBT neurotoxicity, non-NMDA receptor antagonist completely prevented TBT-induced neurodegeneration. These data suggest that TBT provokes apoptosis-like neuronal cell death, which might be mediated by intracellular Ca2+ elevation and free radical generation via non-NMDA receptor activation.

Acridine Orange↗

PubMed2000

Measurement of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction activity and lactate dehydrogenase release using MTT.

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay and lactate dehydrogenase (LDH) release assay have been widely used for evaluating cell viability in culture. MTT reduction assay measures the redox activity of living cells, while LDH assay measures the activity of LDH released into the medium from dead cells. In this paper, we introduce a quick and simple method of measuring cellular MTT reduction and LDH release with the same dye, MTT. The substrate mixture for measuring LDH activity contained lactate, beta-nicotinamide adenine dinucleotide, 1-methoxyphenazine methosulfate, MTT and Triton X-100. When the medium containing LDH was mixed with the substrates, MTT was converted into MTT formazan in proportion to LDH activity. This method was successfully applied for evaluating t-butyl hydroperoxide toxicity in cultured rat cortical astrocytes and glutamate toxicity in cultured rat hippocampal neurons. Our method is economical and convenient especially for measuring cellular MTT reduction and LDH release in the same culture.

Animals↗

PubMed2000

Effective priming of cytotoxic T lymphocyte precursors by subcutaneous administration of peptide antigens in liposomes accompanied by anti-CD40 and anti-CTLA-4 antibodies.

Recently it has been shown that modulation of CD40 molecules on antigen (Ag) carrying dendritic cells (DC) can bypass T cell help, resulting in priming cytotoxic T lymphocytes (CTL) specific for the Ag. In the present study we attempted to prime peptide Ag-specific CTL by a new method in which a peptide Ag in liposome (liposomal peptide), consisting of phosphatidylserine and phosphatidylcholine (3:7), was administrated subcutaneously with anti-CD40 and/or CTLA-4 monoclonal antibodies (mAb) to mice. We found that the subcutaneous administration of the liposomal peptide with both anti-CD40 and anti-CTLA-4 mAb enhanced CTL responses comparing with those induced by the liposomal peptide alone or the liposomal peptide plus each mAb. It was shown that liposomes were critical for induction of the CTL activity. Flow cytometry analysis of a peptide-bearing DC in lymph nodes (LN) and measurement of serum IL-12 indicated that anti-CD40 mAb promoted migration of DC to the LN, where DC might differentiate and acquire ability of priming CTL. These findings provide a possibility that our procedure is applicable to cancer patients.

Abatacept↗

PubMed2000

Delayed clearance of zymosan-induced granuloma and depressed phagocytosis of macrophages with concomitant up-regulated kinase activities of Src-family in a human monocyte chemoattractant protein-1 transgenic mouse.

A human monocyte chemoattractant protein-1 (hMCP-1) transgenic mouse (Tgm) line which constitutively produces a large amount of hMCP-1 (7-13 ng/ml in the serum) was established. Although expression of the transgene was detected in various tissues, an accumulation of macrophages (Mphi) was seen in only lymphoid organs which might be attributed to the high concentration of hMCP-1 in these organs. A reduced phagocytosis by peritoneal Mphi in vivo and a delayed clearance of granulomas in the liver following zymosan administration were observed in these Tgm. However, peritoneal exudate cells (PEC) from Tgm exhibited normal in vitro phagocytic activity and nitric oxide (NO) production upon stimulation with IFN-gamma as compared with those from non-Tgm. In addition, high activities of src-family protein tyrosine kinases (PTK), Fgr and Hck, were also noted in the peritoneal resident cells from Tgm, whereas the level of mitogen-activated protein kinase (MAPK) activity was almost the same as that of non-Tgm. It was suggested that the low functional activities of Tgm Mphi seen in vivo were attributed to down-regulation of the unique transducing system of hMCP-1 signals under the influence of a high concentration of the hMCP-1. It seemed that the depressed functions were recovered when the peritoneal cells were released ex vivo from such a high hMCP-1 environment.

Animals↗

PubMed2000

Distance of target search of isolated rat hippocampal neuron is about 150 microm.

Although the survival of neuronal cells is highly dependent on neural connections with afferents or targets,(10,14,15) little is known about the survival of immature neurons that have not yet encountered the partners. Herein, using cultures of isolated hippocampal neurons of rat embryos, we have attempted to elucidate the contribution of neurite outgrowth to neuron survival and found that neurons died at a certain degree of neurite length with apoptotic characteristics in cases of no contact with other neurons. The threshold was 143.4microm, which was about five times as long as the cell body diameter. It was altered by depolarization or in the presence of basic fibroblast growth factor. Thus, neurons may be designed to kill themselves if they cannot find their targets after exploration within a particular area, the extent of which is variable due to cellular conditions.

Animals↗

PubMed2000

L-type Ca(2+) channel blocker inhibits mossy fiber sprouting and cognitive deficits following pilocarpine seizures in immature mice.

Behavioral and cognitive deficits are one of the most frequent sequelae of childhood epilepsy. Accumulating evidence indicates that epilepsy induces aberrant development of the mossy fibers in the hippocampus, the region that is commonly accepted to play a key role in learning and memory. We have therefore proposed that such abnormal maturation of the central nervous system may cause the adverse prognoses following epilepsy. Based on this hypothesis, using primary cultures of the dentate granule cells, we showed that the L-type Ca(2+) channel blocker nicardipine was neuroprotective against excessive mossy fiber synaptogenesis induced by prolonged depolarization that was assumed to mimic epileptiform conditions. Therefore, we evaluated the in vivo effect of nicardipine on aversive sequelae following epileptiform seizures. We found aberrant sprouting of the mossy fibers and poor performance of spatial and contextual tasks in the mice that had received treatment with pilocarpine at their early postnatal age. Repetitive administration of nicardipine prevented the mossy fiber sprouting and ameliorated the cognitive deterioration, although it did not show anticonvulsant actions against pilocarpine seizures. In the present study, we proposed two in vitro and in vivo models for evaluating epilepsy sequelae and noticed that L-type Ca(2+) channel blocker nicardipine was effective in both models. L-type Ca(2+) channel blocker may be a good candidate for a preventive for childhood epilepsy sequelae. Likewise, these useful systems will disclose additional candidates in future.

Animals↗

PubMed2000

The emetic and anti-emetic effects of the capsaicin analogue resiniferatoxin in Suncus murinus, the house musk shrew.

1. In SUNCUS: murinus the ultrapotent capsaicin analogue resiniferatoxin (RTX) induced an emetic response in the dose range 1 - 1000 microg kg(-1), s.c. The latency was inversely related to dose and ranged from 41.2+/-4.4 min. (1 microg kg(-1), s.c.) to 2.7+/-0.6 min. (1000 microg kg(-1), s.c.). 2. The emetic response to RTX (10 or 100 microg kg(-1), s.c.) was blocked or markedly reduced by pre-treatment with RTX (100 microg kg(-1), s.c.), 8-OH-DPAT (100 microg kg(-1), s.c.), morphine (2 mg kg(-1), s.c.), neonatal capsaicin (100 mg kg(-1), s.c.) and the NK(1) receptor antagonist CP-99,994 (10 - 20 mg kg(-1), s.c.) but not by the 5-HT(3) receptor antagonist tropisetron (200 microg kg(-1), s.c.). 3. RTX (100 microg kg(-1), s.c.) induced c-fos-like immunoreactivity in the area postrema and parts of the nucleus tractus solitarius. This pattern is consistent with the proposal that the emetic effect is mediated via one or both of these structures and an involvement of substance P is discussed. 4. RTX (10 and 100 microg kg(-1), s.c.) had broad-spectrum antiemetic effects in Suncus as indicated by its ability to block or markedly reduce the emetic response to motion (1 Hz, 4 cm lateral, 10 min.), cisplatin (20 mg kg(-1), i.p.), intragastric copper sulphate (40 mg kg(-1), p.o.), nicotine (10 mg kg(-1), s.c.) and RTX (100 microg kg(-1), s.c.) itself. 5. It is proposed that the site of the anti-emetic effect is in the nucleus tractus solitarius and mechanisms involving the modulation of substance P release are discussed. 6. The general utility of SUNCUS: for investigations of vanilloid receptors is reviewed in the light of the exquisite sensitivity of the emetic reflex in this species to resiniferatoxin.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2000

Ca2+-independent phospholipase A2 inhibitor impairs spatial memory of mice.

Pharmacological blockade of Ca2+-independent phospholipase A2 (PLA2) is reported to disintegrate hippocampal synaptic plasticity, which is thought to be the cellular mechanism underlying learning and memory. Therefore, we investigated the effect of the Ca2+-independent PLA2 inhibitor bromoenol lactone (BEL) on spontaneous alteration behaviors of mice. When 3 nmol BEL was intracerebroventricularly injected 30 min prior to the test, the mice showed a poor alternation ratio, compared with control animals. The data suggest that Ca2+-independent PLA2 activity is required for spatial memory.

Animals↗

PubMed2000

Intracellular Ca2+ increase in neuro-2A cells and rat astrocytes following stimulation of bradykinin B2 receptor.

Murine neuroblastoma cell line Neuro-2A cells and rat brain astrocytes showed a dose-dependent increase in intracellular Ca2+ in response to bradykinin, when assessed by a single cell image analyzing system. The Ca2+ increase in Neuro-2A cells by bradykinin was also examined by a suspension fluorescent assay using fura-2 loading. The Ca2+ increase in both cases was suppressed by a bradykinin B2 receptor antagonist, Hoe 140, but not by a B1 receptor antagonist, des-Arg-Hoe 140, suggesting that the effect occurred via specific B2 receptor activation. RT-PCR for bradykinin B2 receptor mRNA showed that both Neuro-2A cells and the astrocytes expressed B2 receptor mRNA. Binding of [3H]bradykinin to Neuro-2A cells was assessed, and a specific binding constant of 0.75 nM was determined. Furthermore, the increase in [Ca2+]i by bradykinin could be caused by a release of Ca2+ from storage sites in the endoplasmic reticulum, since thapsigargin and U-73122 attenuated the effect of bradykinin in Neuro-2A as well as in astrocytes. These results indicate that both astrocytes and neuroblastoma Neuro-2A cells stimulated by bradykinin could express a bradykinin B2 receptor-mediated intracellular Ca2+ increase leading to signal transduction.

Animals↗

PubMed2000

Cortical astrocytes exposed to tributyltin undergo morphological changes in vitro.

We investigated the effect of tributyltin (TBT), an endocrine-disrupting chemical, on the morphology and viability of cultured rat cortical astrocytes. Cultured astrocytes exhibited smooth and planiform morphology under normal conditions. Following exposure to TBT, however, they showed rapid morphological changes that are characterized by asteriated cell bodies and process formation in a time- and concentration-dependent manner. Higher concentrations of TBT produced progressive cell death of the astrocytes. In serum-free medium, TBT at a concentration as low as 200 nM induced the stellation. Pharmacological studies revealed that the morphological changes were alleviated by application of diverse free radical scavengers or antioxidants such as catalase, superoxide dismutase, Trolox, ascorbic acid and N-acetyl-L-cysteine, suggesting that TBT-induced stellation is caused by oxidative stress involving free radicals, particularly reactive oxygen species. Furthermore, we found that the astrocyte stellation was abolished by treatment with inhibitors of phospholipase C, mitogen-activated protein kinase kinase or tyrosine phosphatase. The data suggest that TBT causes the stellation through intracellular signaling cascades rather than its non-specific toxicity. These findings provide an important insight for reconciling the problems in assumed aversive actions of this environmental pollutant for mammals.

Animals↗

PubMed1999

Antibodies against the PH domain of phospholipase C-delta1 inhibit Ins(1,4,5)P3-mediated Ca2+ release from the endoplasmic reticulum.

The pleckstrin homology domain (PH domain) is now well known as a structural module for the binding of inositol compounds. In the present study, polyclonal antibodies against the peptide KVKSSSWRRERFYK, derived from the N-terminal of the PH domain of phospholipase C-delta1 (PLC-delta1), were raised in rabbits. These were then tested for their ability to inhibit the binding of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] to the binding proteins including the receptor molecule. The Fab fragment of the antibodies but not the whole molecule inhibited the binding of Ins(1,4,5)P3 not only to PLC-delta1 but also to the Ins(1,4,5)P3 receptor, indicating that the antibodies raised recognized the binding site for Ins(1,4, 5)P3 in the receptor. Rat basophilic leukemic cells were permeabilized with saponin and assayed for Ins(1,4,5)P3-mediated Ca2+ release. Pretreatment of permeabilized RBL cells with the Fab fragment of the antibodies diminished the release of Ca2+ caused by Ins(1,4,5)P3, and further absorption experiments using a variety of synthetic peptides suggested that the tripeptide KVK is the epitope of the antibodies. Structural information about KVK will help in screening for Ins(1,4,5)P3 antagonists.

Animals↗