Biomedical subjects

M Niwa

Publications and source records attributed to M Niwa.

At least 289 records · Page 16Linked to original sources

PubMed1992

Activation of protein kinase C suppresses the gamma-aminobutyric acidB receptor-mediated inhibition of the vesicular release of noradrenaline and acetylcholine.

Modulation of the gamma-aminobutyric acidB (GABAB) receptor-mediated response by protein kinase C (PKC) was examined with regard to inhibition by stimulation of the GABAB receptor of stimulation-evoked release of noradrenaline (NA) from slices of cerebellar cortex and of acetylcholine (ACh) from strips of ileum. 12-O-Tetradecanoylphorbol 13-acetate (TPA) potentiated the high K(+)-evoked Ca2+-dependent release of NA and ACh, but not the ouabain-evoked release, even in the presence of external Ca2+. The potentiating effect was antagonized by sphingosine, thereby suggesting that PKC participates in the exocytotic-vesicular release of neurotransmitters, but does not do so in case of a nonvesicular release. GABA inhibited the high K(+)-evoked release of NA and ACh, but not the ouabain-evoked Ca(2+)-independent release. The effect of GABA was mimicked by baclofen and was antagonized by phaclofen, thereby suggesting that stimulation of the GABAB receptor inhibits the vesicular but not the nonvesicular release of neurotransmitters. TPA suppressed the GABAB receptor-mediated inhibition of high K(+)-evoked release of NA and ACh. The effect of TPA was antagonized by sphingosine. These results indicate that stimulation of the GABAB receptor inhibits the stimulation-evoked Ca(2+)-dependent release of neurotransmitters and that activation of PKC suppresses the GABAB receptor-mediated response.

Acetylcholine↗

PubMed1992

[Affinity of Z-105 to the 1,4-dihydropyridine type calcium channel and several other receptor bindings in the central nervous system].

The affinity of a 1,4-dihydropyridine (DHP) type calcium channel blocker, NZ-105 ((+/-)-2-[benzyl (phenyl) amino] ethyl 1,4-dihydro-2, 6-dimethyl-5- (5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinan- 2-yl)-4-(3-nitrophenyl)-3-pyridinecarboxylate hydrochloride ethanol), on the DHP-binding site in the central nervous system and various receptor sites were compared with nicardipine and diltiazem by the use of a receptor binding assay technique. NZ-105 exhibited a displacement effect against [3H]nimodipine in the rat brain DHP-binding site with a potency similar to that of nicardipine. Nicardipine also inhibited the specific binding of several other [3H]-labelled ligands to their receptor such as adrenergic alpha 1, alpha 2, beta, dopamine D1, D2, opioid mu, delta, and kappa-type receptors. Diltiazem also showed a similar inhibitory property. However, NZ-105 showed only weak inhibition against the binding to these receptors. These results suggest that Z-105 has strong affinity to the DHP-binding site in voltage-dependent calcium channels with higher specificity.

Animals↗

PubMed1992

Nebracetam (WEB 1881FU) prevents N-methyl-D-aspartate receptor-mediated neurotoxicity in rat striatal slices.

The effects of nebracetam were investigated on N-methyl-D-aspartate (NMDA) receptor- and voltage-operated Ca2+ channels (VOCC)-mediated neural dysfunction by directly monitoring the real-time dynamics of dopamine released from rat striatal slices. Nebracetam (10(-5) and 10(-4) M) completely protected against striatal dopaminergic impairment induced by L-glutamate and NMDA, respectively. BAY K-8644-evoked striatal dysfunction was not blocked by nebracetam (10(-4) M). Therefore, nebracetam seems to produce a neuroprotective action by interacting, at least in part, with NMDA receptor-operated Ca2+ channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

[The effects of long-term intake of a low concentration of sodium fluoride on bone loss in the growing senescence-accelerated mouse (SAM-P/6)].

The long-term effects of low concentrations of sodium fluoride (0, 1 and 5 mg/l) in drinking water on bone metabolism were examined in the growing senescence accelerated mouse (SAM-P/6) as a spontaneous experimental model of senile osteoporosis. In 4 and 8 months of age respectively, there were almost no differences in body weight, and serum calcium, phosphorus and alkaline phosphatase levels between controls and fluoride groups. Calcium contents per dry weight of femoral bone were higher in fluoride groups than in controls. The bone mass of the trabecular was not affected by the low-concentration sodium fluoride intake. However, sodium fluoride decreased the rate of bone mass loss associated with aging in the cortical bone in SAM-P/6 compared with the control. The results of this study suggest that, in growing SAM-P/6 mice, a long-term low-concentration sodium fluoride intake affects the skeletal metabolism.

Animals↗

PubMed1992

[Central autonomic mechanism and neurotransmitters].

Neurotransmitters involved in the central regulation of the autonomic function have, to some extent, been elucidated. Substance P, adrenaline and glutamate neurons originating from the rostral ventrolateral medulla oblongata (VLM) produce a tonic excitation of sympathetic preganglionic neurons. The A1 noradrenaline neurons in the caudal VLM inhibit sympathetic activity by inhibiting neurons in the rostral VLM. In the dorsal medulla, the baroreceptor afferents with substance P converge to the adrenaline-neuropeptide Y (NPY) interneurons located in the dorsal strip of the nucleus tractus solitarius (NTS). These interneurons suppress neuronal activity of the A2 noradrenaline neurons, a vasopressor system, by interacting with alpha 2-adrenergic and NPY receptors. The area postrema, a circumventricular organ devoid of the blood-brain barrier, has access to regulatory information of blood-borne angiotensin II and atrial natriuretic peptide at specific receptors on the neuronal elements. The information is then transmitted to the NTS and dorsal motor nucleus of the vagus. Studies focusing on the physiological and pharmacological profiles of neurotransmitters are expected to enhance our knowledge of the central regulation of the autonomic function.

Autonomic Nervous System↗

PubMed1992

[A study of DNA ploidy pattern, proliferation index and PCNA in duodenal carcinoma].

12 cases of duodenal carcinoma were studied for nuclear DNA ploidy patterns, the proliferation index (PI), proliferating cell nuclear antigen (PCNA) positive score (1 = 0-25%, 2 = 26-50%, 3 = 51-75%, 4 = 76-100%) and PCNA positive rate. DNA aneuploidy was observed in 9 cases (75%) and PCNA staining was positive in 11 cases (91.6%). DNA ploidy patterns, PI, PCNA positive scores and positive rates were not related to each other. No relationship DNA ploidy patterns for PCNA positive scores and PCNA positive rates could be found. The relationship between PI and PCNA positive score was found not to be significant (P less than 0.10). PI was revealed to correlate significantly (P less than 0.05) to PCNA positive rate.

Aneuploidy↗

PubMed1992

[Borrmann 4 gastric cancer treated with l-LV and 5-FU combination--a case report].

The patient was a 44-year-old female who had Borrmann type 4 gastric cancer with enlarged intra-abdominal lymph node metastasis. L-leucovorin (l-LV, 100 mg/m2/day by intravenous bolus for a period of one minute) and fluorouracil (5-FU, 370 mg/m2/day by intravenous bolus) was administered for 5 consecutive days, with a 28-day interval. Dysphagia was subsided 4 weeks after the initial treatment. After 11 weeks, abdominal lymph node metastasis had been reduced in its size (reduced rate 89%). After 16 weeks, gastric structure were remarkably improved (62.2% enlarged in its focus space) in upper GI X-ray. Therefore, total gastrectomy was performed 20 weeks after the initial combination therapy. She has been alive for the past year after the initial treatment. We concluded a combination therapy of l-LV and 5-FU was effective in this patient.

Adenocarcinoma↗

PubMed1991

Cloning and nucleotide sequence of a human Zn-alpha 2-glycoprotein cDNA and chromosomal assignment of its gene.

A cDNA clone of Zn-alpha 2-glycoprotein (Zn alpha 2gp) was isolated from a human prostate library. The amino acid sequence of prostate Zn alpha 2gp deduced from the nucleotide sequence was identical to the one previously reported on the Zn alpha 2gp protein purified from human blood plasma, except at three positions: the 65th and 222nd amino acid residues were Gln (----Glu) and Glu (----Gln), and there was a two amino acid insertion (Ile-Phe) between the 75th (Glu) and 76th (Met) amino acids. Southern blot analysis of human genomic DNA, however, suggested a single gene encoding Zn alpha 2gp. Using a panel of rodent-human somatic cell hybrids, the Zn alpha 2 gp gene was assigned to human chromosome 7.

Amino Acid Sequence↗

PubMed1991

Neurones with epileptiform discharge in the central nervous system and chronic pain. Experimental and clinical investigations.

Epileptiform discharge was recorded from neurons in the thalamic nuclei of chronic pain patients during stereotactic surgery. Hyperactive neurons showed regular firing of 3-5 trains of epileptic-like group discharges with a frequency of 4 to 5 Hz. As described by Lombard et al. (1979), we operated on the dorsal root unilaterally, sectioning C5 to Thl in male Wistar rats. One to three months after the operation, hyperactive neurons were examined in the contra-lateral thalamic nuclei (VP, zona incerta), and lemniscus medialis. The firing patterns and distribution of hyperactive neurons in these animals was very similar to those of humans. The hyperactive neuron was unaffected by electrical stimulation of the nucleus raphe dorsalis (NRD) and locus ceruleus (LC). Administration of phenytoin and diazepam reduced the firing. However, no effect was seen with valproic acid. During spreading depression of the sensorimotor cortex, a remarkable reduction was seen on the firing of thalamic hyperactive neurons. This suggested that hyperactive neurons of the thalamic nuclei received facilitory effects from the sensorimotor cortex with little influence from adrenergic or serotoenergic systems.

Animals↗

PubMed1991

Involvement of the dorsal hippocampus in mediation of the antianxiety action of tandospirone, a 5-hydroxytryptamine1A agonistic anxiolytic.

The effect of tandospirone, a 5-hydroxytryptamine (5-HT)1A agonist/anxiolytic, injected directly into dorsal hippocampus, on Vogel-type conflict behavior in rats was investigated and the findings were compared with the effects of diazepam and zopiclone. Tandospirone (30 micrograms/2 microliters and 60 micrograms/2 microliters) and diazepam (40 micrograms/2 microliters) but not zopiclone (20 micrograms/2 microliters), produced a potent anticonflict action in rats. The anticonflict action of tandospirone (30 micrograms/2 microliters), injected into the dorsal hippocampus, was significantly blocked by (-)-propranolol (5 mg/kg i.p.). The present findings provide evidence that suggests that tandospirone has an antianxiety action, presumably by stimulating 5-HT1A receptors in the dorsal hippocampus.

Animals↗

PubMed1991

Biological actions of beta-hydroxy-l-glutamic acid, a synthesized structural analogue of glutamic acid.

1. Biological actions of beta-hydroxy-L-glutamic acid (BHGA), a synthesized analog of L-glutamic acid (Glu), were examined using voltage-clamp, electrophysiological and binding assay techniques. 2. Application of BHGA to the voltage-clamped snail neurons elicited an inward current which was blocked by Na(+)-free saline but not by Co(2+)-substituted Ca(2+)-free saline in the voltage-clamped snail neurons. 3. This response exhibited a potency about 10 times stronger than Glu, and was not completely blocked by DL-2-amino-5-phosphonovaleric acid or kynurenic acid. 4. Intraventricular injection of BHGA caused burst discharges in the electrocorticograph (ECoG) of rats whose pattern was similar to that elicited by Glu, but quite different from the ECoG charges induced by NMDA, quisqualic acid, or kainic acid. 5. Receptor binding assays using specific radioactive ligands showed that the binding affinity of BHGA to the Glu receptor was different from that of other agonists tested.

Animals↗

PubMed1991

An immunohistochemical study of the distribution of lysozyme, lactoferrin, alpha 1-antitrypsin and alpha 1-antichymotrypsin in salivary adenoid cystic carcinoma.

The immunohistochemical expression of lysozyme (Ly), lactoferrin (La), alpha 1-antitrypsin (alpha 1-AT), and alpha 1-antichymotrypsin (alpha 1-Ach) was described, and their distributions were compared to each other in 28 cases of adenoid cystic carcinoma (ACC) of the salivary glands. ACC materials were obtained from the parotid gland (7), the submandibular gland (4), the sublingual gland (8), and minor oral salivary glands (9). Histopathologically, ACC was classified into cribriform (14), tubular (3), and basaloid or solid patterns (11). Positive staining for Ly was found in 1 case of solid ACC in the sublingual gland; La was found in 4 cases (2 cribriform, 1 tubular, 1 basaloid) in the sublinguals (3) and parotid glands (1); alpha 1-AT was found in 6 cases and alpha 1-Ach in 17 cases. The immunohistochemical localization of Ly and La was usually confined to luminal tumor cells of tubulo-ductal structures, irrespective of the pathologic types. Positive staining for alpha 1-AT and alpha 1-Ach appeared in tumor cells of cribriform, tubular and solid ACC. Tumor cells with positive La staining coincided with a positive reaction to alpha 1-AT and alpha 1-Ach, and tumor cells with alpha 1-AT positive deposition were also positive for alpha 1-Ach. The contents of pseudocysts in the cribriform pattern showed a positive reaction to La, alpha 1-AT, and alpha 1-Ach. Of the 28 cases of ACC, positive expressions for Ly, La, alpha 1-AT and alpha 1-Ach were found with a high frequency of alpha 1-Ach staining (17 in 28 cases were positive). In sublingual ACC (8), 7 cases were positive for immunohistochemical reactions. Co-expression or simultaneous expression for Ly, La, alpha 1-AT, and alpha 1-Ach in ACC suggest that tumor cells are protected from proteolysis or degradation.

Carcinoma, Adenoid Cystic↗

PubMed1991

Expression of cDNA for batroxobin, a thrombin-like snake venom enzyme.

The cloned cDNA for batroxobin has been expressed in E. coli. Batroxobin could only be obtained as intracellular aggregates of fusion proteins, fused with a small peptide. To obtain the mature batroxobin, the recognition sequence for thrombin was inserted between the peptide and the mature batroxobin. This fusion protein accumulated in an insoluble form and could easily be purified. After site-specific cleavage of the fusion protein with thrombin, recombinant batroxobin was isolated by preparative electrophoresis. Batroxobin with enzymatic activity was obtained by the refolding of recombinant batroxobin.

Amino Acid Sequence↗

PubMed1991

Receptors for endothelin in the central nervous system.

The quantitative receptor autoradiographic method we used revealed that specific [125I]endothelin-1 ([125I]ET-1) binding sites are highly concentrated in the choroid plexus (ChP), subfornical organ (SFO), lacunosum molecular layer of the hippocampus (LMol), and granular layer of the cerebellum (GC) of the rat brain. [125I]ET-1 bound to the rat ChP and LMol with a high affinity and to the SFO and GC with a low affinity. The possibility that ET-1 acts as a neuropeptide within the central nervous system by interacting with specific receptors would have to be considered.

Animals↗

PubMed1991

Mutation of the AAUAAA polyadenylation signal depresses in vitro splicing of proximal but not distal introns.

To investigate the relationship between splicing and polyadenylation during the production of vertebrate mRNAs, we examined the effect of mutation of a poly(A) site on splicing of upstream introns. Mutation of the AAUAAA polyadenylation consensus sequence inhibited in vitro splicing of an upstream intron. The magnitude of the depression depended on the magnesium concentration. Dependence of splicing on polyadenylation signals suggests the existence of interaction between polyadenylation and splicing factors. In multi-intron precursor RNAs containing duplicated splice sites, mutation of the poly(A) site inhibited removal of the last intron, but not the removal of introns farther upstream. Inhibition of removal of only the last intron suggests segmental recognition of multi-exon precursor RNAs and is consistent with previous suggestions that signals at both ends of an exon are required for effective splicing of an upstream intron.

Adenoviridae↗

PubMed1991

Dopaminergic unique affinity of tetrahydroberberine and l-tetrahydroberberine-d-camphor sulfonate.

l-Tetrahydroberberine-d-camphor sulfonate (THB-CS) possessed an inhibitory effect on apomorphine-induced chewing movement in a similar manner to that of tetrahydroberberine (THB). Both compounds enhanced barbiturate-induced hypnosis. They did not have an anticonvulsant effect on convulsive seizures induced by bicuculline, pentetrazole or strychnine. THB and THB-CS blocked dopamine-stimulated adenylate cyclase activity. These compounds showed almost equipotent affinities to dopamine D1 (3H-SCH-23390) and D2 (3H-spiperone) receptors but did not have significant affinity to mu-opioid, muscarinic and alpha 2-adrenergic receptors, and benzodiazepine binding sites. Furthermore, both compounds did not elicit cataleptogenic behavior, even at very high doses. These data suggest that THB and THB-CS have a central depressant effect through both D1 and D2 dopaminergic receptors and may have different modes of action from that of standard neuroleptics.

Animals↗

PubMed1991

Inhibitory effect of tachyplesin I on the proliferation of human immunodeficiency virus in vitro.

An antimicrobial peptide, tachyplesin I, isolated from hemocytes of the Japanese horseshoe crab (Tachypleus tridentatus) was examined for its inhibitory effects on human immunodeficiency virus (HIV) infection in vitro. At a concentration of 7.5 micrograms/ml, tachyplesin I suppressed the development of cytopathic effects (CPE) by more than 70% in MT-4 cells infected with HIV (lymphadenopathy-associated virus). This inhibitory effect was observed only when the drug was added during the adsorption period of the virus to the cells. In cocultures of MOLT-4 and persistently HIV-infected cells (MOLT-4/HIV), tachyplesin I at the same concentration completely inhibited multinucleated giant cell formation. Infectivity of HIV was reduced by 10(-2.5) in medium free from fetal calf serum containing tachyplesin I at a concentration of 200 micrograms/ml. Tachyplesin I did not show any inhibitory effect on reverse transcriptase activity of HIV at concentrations of 9-80 micrograms/ml at which tachyplesin I inhibited HIV infection. These results suggest that the anti-HIV action of tachyplesin I was due to the inhibition of virus adsorption.

Animals↗

PubMed1991

Direct virus inactivation of tachyplesin I and its isopeptides from horseshoe crab hemocytes.

Direct virus inactivation of tachyplesin I and related isopeptides, which are antimicrobial peptides isolated from the hemocytes of the horseshoe crab (Tachypleus tridentatus and Limulus polyphemus), was examined against several viruses. Vesicular stomatitis virus (VSV) was inactivated by incubation with tachyplesin I and its isopeptides. Influenza A (H1N1) virus was slightly inactivated by tachyplesin I, whereas herpes simplex virus 1 and 2, adenovirus 1, reovirus 2 and poliovirus 1 were resistant to inactivation. The inactivation of VSV by tachyplesin I depended on the concentration, the time and the temperature of incubation. Pretreatment of tachyplesin I with trypsin or lipopolysaccharide of gram-negative bacteria entirely abolished the antiviral activity. Electron microscopy of VSV treated with tachyplesin I showed naked and damaged virions. These data suggest that tachyplesin I directly inactivates the VSV by destroying its envelope subunits.

Amino Acid Sequence↗