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N Hori

Publications and source records attributed to N Hori.

At least 91 records · Page 5Linked to original sources
PubMed1992

Inhibition of energy metabolism by 3-nitropropionic acid activates ATP-sensitive potassium channels.

3-Nitropropionic acid (1 mM), which inhibits succinate dehydrogenase activity and reduces cellular energy, produces in the pyramidal cell layer of the hippocampal region CA1 a hyperpolarization for variable lengths of time before evoking an irreversible depolarization. Hyperpolarization is caused by an increased potassium conductance that is attenuated by glibenclamide (1-10 microM), a selective antagonist of ATP-sensitive potassium channels; in contrast, diazoxide (0.5 mM), an agonist at this channel, induces a hyperpolarization in CA1 neurons of rat hippocampal slices. The transient hyperpolarization after prolonged (ca. 1 h) application of 3-NPA is followed by a depolarization that is incompletely reversed by brief application of the glutamate antagonists (D-2-amino-5-phosphonopentanoic acid (APV), 6,7-dichloroquinoxaline-2,3-dione (CNQX), 3-(+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), 7-chloro-kynurenic acid (7Cl-KYN)). Early application of glibenclamide (within the initial 5 min) blocked or reduced hyperpolarization and accelerated the depolarization. These data suggest that metabolic inhibition by 3-NPA initially activates ATP-sensitive potassium channels. Events other than activation of glutamate receptors participate in the final depolarization resulting from uncoupling of oxidative phosphorylation.

Adenosine Triphosphate↗
PubMed1992

Large scale cDNA sequencing for analysis of quantitative and qualitative aspects of gene expression.

Large scale sequencing of cDNAs provides a complementary approach to structural analysis of the human genome by generating expressed sequence tags (ESTs). We have initiated the large-scale sequencing of a 3'-directed cDNA library from the human liver cell line HepG2, that is a non-biased representation of the mRNA population. 982 random cDNA clones were sequenced yielding more than 270 kilobases. A significant portion of the identified genes encoded secretable proteins and components for protein-synthesis. The abundance of cDNA species varied from 2.2% to less than 0.004%. Fifty two percent of the mRNA were abundant species consisting of 173 genes and the rest were non-abundant, consisting of about 6,600 genes.

Base Sequence↗
PubMed1992

Long-term potentiation is lost in aged rats but preserved by calorie restriction.

Recordings of synaptic population responses, post-tetanic potentiation (PTP) and long-term potentiation (LTP) were made from area CA1 in hippocampal slices from ad libitum-fed rats at about 2 and 24 months of age, and also in animals at about 24 months of age that had been restricted to 60% of the caloric intake of control animals since weaning. Both PTP and LTP were greatly reduced in the old ad-lib animals. Calorically-restricted rats at about 24 months of age showed hippocampal responses with initial peak amplitudes more like those of 2-month controls than the ad-lib animals at 24 months. These observations suggest that calorie restriction preserves nervous-system functions, including indicators of plasticity such as LTP, which are otherwise lost in aging.

Aging↗
PubMed1992

Functional heterogeneity of rat liver macrophages: interleukin-1 secretion and Ia antigen expression in contrast with phagocytic activity.

To clarify whether immunological heterogeneity exists among liver macrophages and whether this possible heterogeneity corresponds to varying degrees of phagocytic activity, we fractionated liver macrophages according to size via centrifugal elutriation and studied their ability to ingest latex beads, to express Ia antigen and to secrete interleukin-1 (IL-1) in vitro. Larger liver macrophages were found to be more active in ingesting latex beads than smaller ones (p less than 0.01), while smaller liver macrophages were more active in Ia antigen expression and evidenced greater fluorescence at cytofluorometric examination. In addition, smaller liver macrophages elaborated more IL-1 than the larger liver macrophages (p less than 0.05). These results indicate that liver macrophage heterogeneity is seen in at least two important macrophage functions: phagocytosis of large molecules, which provides an important scavenger function, and Ia antigen expression and IL-1 secretion, important components of the immune response.

Animals↗
PubMed1992

Novel disease-modifying antirheumatic drugs. I. Synthesis and antiarthritic activity of 2-(4-methylphenyl)benzothiazoles.

A series of 2-(4-methylphenyl)benzothiazoles was synthesized and evaluated using an adjuvant-induced arthritic rat model. This class of desired compounds affecting the immune response was found using hemagglutination assay. 4-Acetoxy-2-(4-methylphenyl)benzothiazole (7m), KB-2683, was most potent in the adjuvant-induced arthritic rat model and selected for further evaluation. In contrast to nonsteroidal antiinflammatory drugs, compound 7m showed no antiinflammatory or analgesic activities. It did, however, show an immunomodulatory activity in enhanced delayed type hypersensitivity.

Animals↗
PubMed1992

[Effects of oxiracetam on the decrease in population spikes in hypoxic and low glucose media].

Evoked potentials were recorded in rat cerebral cortical slices. The amplitude of the evoked potential was reduced by perfusion with hypoxic (0-25%) or low glucose (0-5 mM) media in a concentration-dependent manner, and the evoked potentials disappeared under severe conditions (below 15% O2, below 3 mM glucose). We investigated the protective effects of oxiracetam on the decrease in evoked potentials under hypoxic (15% O2) and low glucose (3 mM glucose) conditions. Drugs were perfused from 45 min before hypoxic or low glucose perfusion to the end of the experiment. Oxiracetam (10(-6)-10(-5) M) dose-dependently minimized the amplitude reduction of evoked potentials and prolonged their disappearance time. At a concentration of 10(-5) M, oxiracetam protected against the disappearance of evoked potential in 5 of the 6 samples under hypoxic conditions and in all 6 samples under low glucose conditions. Indeloxazine (5 x 10(-6)-10(-5) M) and bifemelane (5 x 10(-6)-10(-5) M) prevented the reduction of the amplitude of evoked potentials under low glucose conditions. However, these drugs had no effect at a concentration of 10(-6) M. These data indicate that oxiracetam has a protective effect against neuronal dysfunction and that this effect develops at a lower concentration than those of indeloxazine and bifemelane.

Animals↗
PubMed1991

Glucocorticoids promote localized activity of rat hippocampal CA1 pyramidal neurons in brain slices.

The effects of glucocorticoids on rat hippocampal CA1 pyramidal neurons were studied using brain slice preparations. At 10 days after bilateral adrenalectomy, a localized region of CA1 showed a drastic reduction of excitability induced by CA3 stimulation as compared to control. The region of CA1 most effected was 1.4-2.0 mm from the most rostral side of the hippocampus. Upon perfusion of corticosterone, the response to synaptic activation was reduced in this region in slices from adrenalatomized animals increased rapidly toward control values, volatile responses in other regions were unaffected. These results suggest that glucocorticoid receptors are concentrated in restricted regions of hippocampus and that these receptors have important roles in regulation of synaptic excitability.

Adrenalectomy↗
PubMed1991

Appearance of NMDA receptors triggered by anoxia independent of voltage in vivo and in vitro.

Using rat hippocampus we have studied the pattern of neuronal death, abnormal discharge and loss of electrical excitability in slices prepared from animals subjected to bilateral, four-vessel cerebral anoxia and in slices prepared from normal animals that are subjected to anoxia in the recording chamber. As others have reported, pyramidal neurons in area CA1 are lost first after anoxia, while CA3 neurons have an intermediate sensitivity, and those in dentate are relatively anoxia-resistant. After anoxic damage to the intact animal, neurons in both CA1 and CA3 show abnormal bursting discharges in response to synaptic activation for several days, and then the response in CA1 decreases in amplitude and finally the area become unexcitable. While antagonists for N-methyl-D-aspartate (NMDA) receptors have essentially no effect on synaptic responses in control animals, they reduce the bursting responses and greatly depress the small responses in CA1 as neurons are becoming unexcitable after anoxia. With intracellular recording CA1 neurons from animals made transiently anoxic, in contrast to controls, show prolonged synaptic responses, the later components of which are blocked by NMDA antagonists. When slices from normal animals are subjected to anoxia such that excitability is totally lost over a period of about 10 min, there is no significant membrane depolarization during the anoxic episode and recovery of excitability occurs with reoxygenation. However, a period of hyperexcitability and bursting follows and electrical excitability is lost in CA1 but not CA3 neurons after about 90 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Chromosome deletions associated with hepatitis B virus integration.

Integrated hepatitis B virus (HBV) DNA is often found in hepatocellular carcinomas which develop in HBV carriers. We previously found that chromosomal abnormalities such as translocations and inversions are often associated with HBV integration. Here we report deletions that were found with three integrants, by comparing the physical maps of the flanking cellular DNA of the integrants with those of the unoccupied cellular sequences. The sizes of the deletions were 25, 12, and 11 kb, respectively. Each integrant carried only a small fragment of the viral genome, from which the cohesive end region, the preferred site of integration, was deleted. We speculate that these deletions were made from primary integrants by recombination of regions between the viral DNA and the flanking cellular sequence.

Base Sequence↗
PubMed1991

Production of 5-methyluridine by immobilized thermostable purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus JTS 859.

5-Methyluridine was produced continuously from thymine and inosine by immobilized enzymes, which consisted of thermostable purine nucleoside phosphorylase and thermostable pyrimidine nucleoside phosphorylase obtained from Bacillus stearothermophilus JTS 859. The process was carried out in a column reactor at 60 degrees C for 17 d without any bacterial contamination under non-aseptical conditions. Half-lives of the activity of the immobilized enzymes were 47 d and 4.5 d at 60 degrees C and 70 degrees C, respectively, although half-life of the crude enzyme was only 14 h at 70 degrees C.

Bacterial Proteins↗
PubMed1991

Enhanced rectal absorption of insulin in rabbits from hollow-type suppositories containing insulin and glyceryl-1-monooctanoate.

The absorption of two kinds of insulin (from porcine or bovine pancreas) from the rectum of rabbits after the administration of hollow-type suppositories containing insulin and glyceryl-1-monooctanoate (GMO) as an absorption-enhancing agent was investigated. Two types of suppositories were employed: type I containing insulin in an aqueous solution (approx. 25 IU/mg/100 microliters citric buffer solution at pH 3.0) in the cavity of the suppository and GMO mixed with a base material (Witepsol H-15), and type II containing insulin in a crystalline form in the same amount as in type I. Without GMO, the insulin and glucose levels in plasma were unchanged, whereas a marked increase in the plasma levels of insulin and a decrease of glucose concentrations were found following coadministration of insulin and GMO by the type I suppository. Similar enhancement of rectal absorption of insulin was obtained from porcine and bovine sources. In the case of the crystalline insulin, despite the use of the same amount of GMO, porcine insulin was more efficiently absorbed than bovine insulin by the type II suppository. GMO enhances the absorption of insulin in an aqueous solution or a crystalline form, and the dissolution rate of insulin may be an important factor in the rectal absorption of insulin.

Administration, Rectal↗
PubMed1991

A novel system for large-scale sequencing of cDNA by PCR amplification.

We have developed a method for constructing a library containing the 3' end fragment of cDNA for large-scale sequencing of cDNA clones. The average size of the insert was 270 bp. Cell lysates that carry plasmids having the cDNA insert were subjected to PCR amplification of the cDNA moiety and the products were subjected to sequencing analysis using an autosequencer. With this protocol, sample preparation became a non-limiting step, that allowed us to sequence as many samples as the autosequencer could handle.

Base Sequence↗
PubMed1990

In vitro and in vivo activities of T4 endonuclease V mutants altered in the C-terminal aromatic region.

Genes encoding mutants of the thymine photodimer repair enzyme from bacteriophage T4 (T4 endonuclease V) having an amino acid substitution (T127M, W128A, W128S, Y129A, K130L, Y131A, Y132A) were constructed by use of a previously obtained synthetic gene and expressed in Escherichia coli under the control of the E. coli tryptophan promoter. An in vitro assay of partially fractionated mutant proteins for glycosylase activity was performed with chemically synthesized substrates containing a thymine photodimer. T127M and K130L showed almost the same activity as the wild-type protein. Although W128S, Y131A, and Y132A were slightly active, W128A and Y129A lost activity. The results indicated that the aromatic amino acids around position 130 may be important for the glycosylase activity. Mutant T127M was purified, and the Km value was found to be of the same order as that of the wild type (10(-8) M). In vivo activities for all mutants were characterized with UV-sensitive E. coli. The results showed that substitution of Thr-127 with Met or Lys-130 with Leu did not have an effect on the survival of the bacteria but substitution of aromatic amino acids (128-132) had various effects on survival.

Amino Acid Sequence↗
PubMed1990

Differential effects of baclofen and gamma-aminobutyric acid (GABA) on rat piriform cortex pyramidal neurons in vitro.

1. The effects of baclofen and GABA on rat piriform cortex neurons were investigated electrophysiologically using a brain slice preparation. 2. At resting potential GABA depolarized and baclofen hyperpolarized the cell, probably through activation of Cl and K conductances acting at GABAA and GABAB receptors, respectively. 3. The GABAA receptors were concentrated on the apical and basal dendrites near the cell body, while the baclofen-sensitive GABA receptors were concentrated particularly on the basal dendrites. 4. The different distributions of receptor localization must have functional consequences which remain to be elucidated.

Animals↗
PubMed1990

Influences of trypsin and collagenase on acetylcholine responses of physically isolated single neurons of Aplysia californica.

1. The influences of enzyme treatments (trypsin and collagenase) on responses to perfused acetylcholine were examined on physically isolated single Aplysia neurons, using the voltage-clamp, internal perfusion, and rapid external perfusion technique. 2. During treatment with trypsin (0.025 to 0.1%) for 10 to 30 min at room temperature (22 to 25 degrees C), the peak amplitude of the Na current induced by acetylcholine increased in a time- and dose-dependent manner, and the decay in the continued presence of acetylcholine was slowed. This effect of trypsin treatment was irreversible after washing for 60 min without enzyme. 3. Edrophonium, a cholinesterase inhibitor, has previously been shown to augment the Na acetylcholine response in this preparation by inhibition of acetylcholinesterase. After treatment of the neuron with trypsin, the augmentation after edrophonium was abolished. Furthermore, in the presence of edrophonium, trypsin also failed to increase the response. The dose-response curve for acetylcholine after treatment of trypsin was similar to that in the presence of edrophonium. These results suggest that the modification of the current response by trypsin is a result of removal of cholinesterase activity from the membrane. 4. In contrast to the effects of trypsin, collagenase (0.03 to 0.1%) for 10 to 60 min did not change the current amplitude of the acetylcholine response. However, collagenase treatment did alter the kinetics of the acetylcholine response in a dose-dependent manner, in that the rate of decay was accelerated. A similar acceleration was seen in the acetylcholine responses on other neurons which were due to Cl or K currents, suggesting that the effect was independent on the type of channel. This effect of collagenase was reversible after 30 to 60 min of washing of the neuron. 5. In the presence of edrophonium or after the treatment with trypsin, collagenase still accelerated the current kinetics of the acetylcholine response, indicating that cholinesterase activity is not related to this effect. Furthermore, heated collagenase (presumably inactivated) had a similar action, suggesting that the enzymatic activity of collagenase is not related to the modification of the response. 6. These results suggest that Aplysia acetylcholinesterase is sensitive to trypsin but not to collagenase. However, the preparation of a collagenase used in these studies contains some factor which alters the response to acetylcholine, but this effect is reversible and unrelated to enzymatic activity.

Acetylcholine↗
PubMed1990

Duration of absorption-enhancing effect of sodium octanoate, sodium hexanoate or glyceryl-1-monooctanoate on rectal absorption of gentamicin in rabbits.

The duration of the absorption-enhancing effect of sodium octanoate (C8), sodium hexanoate (C6) and glyceryl-l-monooctanoate (MO) on the rectal absorption of gentamicin (GM) using the hollow-type suppository was investigated in rabbits. To evaluate the duration of the absorption-enhancing effect by pretreatment (treatment of absorption enhancer before GM administration), suppository I containing each absorption enhancer in the cavity was administered into the rectum. Then suppository II containing GM in the cavity was administered at predetermined times (0.33, 2, 6 and 24 h) after the administration of suppository I. Plasma GM levels obtained by the pretreatment with absorption enhancer were compared with those obtained by the simultaneous administration of GM with absorption enhancer. The AUC and Cmax of GM significantly decreased with the pretreatment of C8 (6 and 24 h), C6 (2 and 6 h) or MO (6 and 24 h) before rectal GM administration, as compared with the simultaneous administration of GM with C8, C6 or MO. A marked decrease in the absorption-enhancing effect of C8, C6 and MO on rectal GM absorption was observed by the prolongation of the period between the pretreatment of each absorption enhancer and GM administration. The duration of the absorption-enhancing effect of C6 was shorter than that of C8, whereas this duration of MO was similar to that of C8. The effect of these absorption enhancers disappeared 24 h after the pretreatment. These results suggested that the lowering of the membrane transport barrier function recovered about one day after the administration of C8 or MO.

Administration, Rectal↗