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N Mataga

Publications and source records attributed to N Mataga.

At least 37 records · Page 2Linked to original sources
PubMed1994

Analysis of internal motion of single tryptophan in Streptomyces subtilisin inhibitor from its picosecond time-resolved fluorescence.

A mode of internal motion of single tryptophan, Trp 86, of Streptomyces subtilisin inhibitor, was analyzed from its time-resolved fluorescence. The intensity and anisotropy decays of Trp 86 were measured in the picosecond range. These decays were analyzed with theoretical expressions derived assuming that the indole ring of tryptophan as an asymmetric rotor rotates around covalent bonds connecting indole with the peptide chain and an effective quencher of fluorescence of Trp 86 is the nearby SS bond of Cys 35-Cys 50. First, the intensity decays at 6 degrees, 20 degrees, and 40 degrees C were analyzed, and then the both decays of the intensity and anisotropy at 20 degrees C were simultaneously simulated with common parameters. Constants concerning geometrical structures of the protein used for the analysis were obtained from x-ray crystallographic data. Best fit between the observed and calculated decay curves was obtained by a nonlinear least squares method by adjusting a quenching constant averaged over the rotational angles, koq height of the potential energy, p, and three of six diffusion coefficients, Dxx, Dyy, Dzz, Dxy, Dyz, and Dzx, as variable parameters. The obtained results revealed that the internal motion of the indole ring became faster, the quenching rate of the fluorescence of Trp 86 was enhanced and the height of potential energy became lower at higher temperatures, and suggested that Trp 86 was wobbling around the long axis of the indole ring in the protein.

Amino Acid Sequence↗
PubMed1993

Behavioral activation by stimulation of a GABAergic mechanism in the preoptic area of rat.

The locomotor activity and grooming of conscious freely moving rats were recorded during a 60-min unilateral perfusion of the preoptic area with neuroactive compounds using the microdialysis technique. The GABA agonist, muscimol (10, 20 and 100 microM) induced a dose-dependent increase in locomotor activity and grooming which was attenuated by co-perfusion with the GABA antagonist, bicuculline (10 microM), and was blocked by systemic injection of haloperidol, a preferential dopamine D2 receptor antagonist (0.25 mg/kg). Muscimol-induced hyperactivity was associated with a simultaneous increase of striatal extracellular dopamine. These data suggest that the preoptic area is functionally linked with the extrapyramidal dopaminergic system possibly via GABAergic system.

Animals↗
PubMed1993

Gliotoxin-induced suppression of ocular dominance plasticity in kitten visual cortex.

We studied the role of astrocytes in the regulation of ocular dominance plasticity. A small quantity of 10 microM fluorocitrate (0.2 nmol in 20 microliters) was pressure-injected into the visual cortex of 7-9-week-old kittens (subcortical depth: 0-5 mm, 20 microliters/10 min). Immediately after injection, 1 eye contralateral to the injected cortex was closed for 3 days. Single-unit recordings revealed that the proportion of binocular cells was significantly higher in a region close (approximately 1 mm) to the fluorocitrate injection site than that in a remote region (> 4 mm) within the same hemisphere and that in the opposite hemisphere. The results suggest that reduction of glial functions by fluorocitrate retarded the usual process of shift in ocular dominance of visual cells following monocular deprivation.

Animals↗
PubMed1992

L-threo-3,4-dihydroxyphenylserine enhanced ocular dominance plasticity in adult cats.

We studied whether ocular dominance plasticity can be restored to the aplastic visual cortex of the adult cat by peripheral administration of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS), an exogenous precursor of L-noradrenaline (NA). We found that NA output in the visuocortical dialysate was significantly increased by a single administration of L-threo-DOPS (200 mg or 1 g, i.p.). Single unit recordings revealed a significant reduction of binocular cells (binocularity = 0.30) in juvenile cats (7-8 months of age) that had been monocularly deprived for one month in combination with L-threo-DOPS (200 mg/day, per os). These results suggest that peripheral administration of L-threo-DOPS enhances ocular dominance plasticity, presumably through activation of the central noradrenergic system.

Animals↗
PubMed1992

Differential specificities of single mitral cells in rabbit olfactory bulb for a homologous series of fatty acid odor molecules.

1. The molecular specificities of single mitral cells and their locations in the rabbit olfactory bulb were studied using extracellular recordings of single-unit spike discharges and oscillatory local field potentials. A panel of carboxylic acid molecules including a homologous series of fatty acids was used as odor stimuli. 2. Mitral cells showing excitatory responses to fatty acid molecules of different hydrocarbon chain length were localized near each other in a region in the dorsomedial part of the olfactory bulb. 3. Individual mitral cells in the dorsomedial region tended to respond to subsets of fatty acid odor molecules having similar hydrocarbon chain length or structure. Mitral cells responding to subsets of fatty acids of different chain length were distributed with partially shifted overlaps in this region. 4. The results show that stereochemical features of odor molecules are encoded by individual bulbar neurons.

Animals↗
PubMed1992

Coding of odor molecules by mitral/tufted cells in rabbit olfactory bulb. I. Aliphatic compounds.

1. Recordings of extracellular spike responses were made from single mitral/tufted cells in the main olfactory bulb of urethan-anesthetized rabbits. Olfactory epithelium ipsilateral to the recorded olfactory bulb was stimulated with homologous series of aliphatic compounds using periodic artificial inhalations. 2. In the dorsomedial part of the main olfactory bulb, single mitral/tufted cells were activated by subsets of n-fatty acids with similar hydrocarbon chain lengths. Response selectivities of single mitral/tufted cells were examined in detail using a series of n-fatty acids at five different concentrations. The results indicate that although the range of effective fatty acids is broader at the higher concentrations, the best response at higher concentrations was similar to that determined at lower concentrations. 3. Analysis of single-unit responses to the panel of fatty acids, including those with branched hydrocarbon chains, suggested that the determinants for the response specificities of individual mitral/tufted cells in the dorsomedial region include the overall size of hydrocarbon chains of the odor ligand molecules. 4. Single mitral/tufted cells in the dorsomedial region tended to be activated not only by fatty acids but also by n-aliphatic aldehydes. For a panel of a homologous series of n-aldehydes at five different concentrations, individual mitral/tufted cells showed response selectivity to subsets of aldehydes with similar hydrocarbon chain lengths. 5. In most cases, normal aliphatic alcohols and alkanes were ineffective in activating mitral/tufted cells in the dorsomedial region. This suggests that carbonyl group (--C = O) in the odor molecules plays an important role in determining response specificity of these neurons. 6. Examination with an expanded panel of stimulus odor molecules that included ketones and esters indicated that single mitral/tufted cells sensitive to subsets of fatty acids and n-aliphatic aldehydes were also responsive to subsets of ketones and/or esters having hydrocarbon chain lengths similar to those of the effective fatty acids and aldehydes. 7. The present results show a clear correlation between the tuning specificity of individual mitral/tufted cells and the stereochemical structure of the odor molecules, with respect to 1) length and/or structure of hydrocarbon chain, 2) difference in functional group, and 3) position of the functional group within the molecule. 8. A hypothetical diagram suggesting functional convergence of olfactory nerve input to individual glomeruli is proposed to explain the mechanism for selective activation of individual mitral/tufted cells by a range of odor molecules with similar stereochemical structures.

Action Potentials↗
PubMed1992

Effects of sulpiride and oxypertine on the dopaminergic system in the rat striatum.

We have examined the effects of sulpiride, oxypertine and haloperidol on the behavioral and biochemical dopamine receptor function in the rat striatum. Although acute treatment with haloperidol or oxypertine induced catalepsy, tolerance to catalepsy developed following chronic treatment with haloperidol but not with oxypertine. Rats treated with acute or chronic sulpiride did not show signs of catalepsy. Intracerebroventricular administration of sulpiride, however, induced catalepsy and tolerance developed after chronic treatment. After chronic treatment with either of these three drugs, dopamine D2 receptors were up-regulated in the striatum. While acute administration of haloperidol, sulpiride or oxypertine increased the concentration of homovanillic acid in the striatum, the rate of increases was attenuated following chronic treatment with haloperidol or sulpiride, but not with oxypertine. While acute administration of sulpiride or oxypertine decreased dopamine, the decrease was attenuated following repeated administration of sulpiride but not of oxypertine. These results suggest that the unique pharmacological profile of oxypertine may be related to its therapeutic effect of activating apathetic patients, and that both sulpiride and oxypertine may cause tardive dyskinesia, as haloperidol does.

Animals↗
PubMed1991

Determination of rates and yields of interchromophore (folate----flavin) energy transfer and intermolecular (flavin----DNA) electron transfer in Escherichia coli photolyase by time-resolved fluorescence and absorption spectroscopy.

Escherichia coli DNA photolyase, which photorepairs cyclobutane pyrimidine dimers, contains two chromophore cofactors, 1,5-dihydroflavin adenine dinucleotide (FADH2) and 5,10-methenyltetrahydrofolate (MTHF). Previous work has shown that MTHF is the primary photoreceptor which transfers energy to the FADH2 cofactor; the FADH2 singlet excited state then repairs the photodimer by electron transfer. In this study, we have determined the rate constants for these photophysical processes by time-resolved fluorescence and absorption spectroscopy. From time-resolved fluorescence, we find that energy transfer from MTHF to FADH2 and FADH degrees occurs at rates of 4.6 x 10(9) and 3.0 x 10(10) s-1, respectively, and electron transfer from FADH2 to a pyrimidine dimer occurs at a rate of 5.5 x 10(9) s-1. Using Förster theory for long-range energy transfer and assuming K2 = 2/3, the interchromophore distances were estimated to be 22 A in the case of the MTHF-FADH2 pair and 21 A for the MTHF-FADH degrees pair. Picosecond absorption spectroscopy identified an MTHF single state which decays to yield the first excited singlet state of FADH2. The lifetimes of MTHF and FADH2 singlets and the rates of interchromophore energy transfer, as well as the rate of electron transfer from FADH2 to DNA measured by time-resolved fluorescence, were in excellent agreement with the values obtained by picosecond laser flash photolysis. Similarly, fluorescence or absorption lifetime studies of the folate-depleted enzyme with and without photodimer suggest that FADH2, in its singlet excited state, transfers an electron to the dimer with 89% efficiency. The distance between FADH2 and the photodimer was calculated to be ca. 14 A.

Apoenzymes↗
PubMed1991

6R-tetrahydrobiopterin perfusion enhances dopamine, serotonin, and glutamate outputs in dialysate from rat striatum and frontal cortex.

The effect of 6R-tetrahydrobiopterin (R-THBP) on neurotransmitter release was investigated using in vivo brain microdialysis in urethane-anesthetized rats. Perfusion of 1.0 mM R-THBP enhanced the level of dopamine output in dialysates collected from the striatum and frontal cortex. R-THBP perfusion also increased serotonin (striatum) and glutamate outputs (striatum and frontal cortex). Dopaminergic terminals in the striatum were destroyed unilaterally by continuous infusion of 6-hydroxydopamine (6-OHDA) using an osmotic minipump system. The effect of R-THBP administration on glutamate level was found to be almost completely suppressed in the 6-OHDA-lesioned side of striatum, while in the intact side of striatum the glutamate level in the dialysates responded normally to R-THBP perfusion. These results suggest that R-THBP may play a role in the mechanisms of release of dopamine, serotonin, and glutamate. The functioning of the catecholaminergic system probably mediates the increase in glutamate output due to R-THBP perfusion.

Animals↗
PubMed1988

Neurotransmitters, receptors and neuropeptides in post-mortem brains of chronic schizophrenic patients.

In the analysis of post-mortem brains of 14 chronic schizophrenic patients and 10 controls, biochemical evidence of a hyperdopaminergic state was found in the basal ganglia of schizophrenics; tyrosine hydroxylase activity was increased with a concomitant increase of homovanillic acid. Unusually high tyrosine hydroxylase activity was noted in 2 schizophrenic cases. The Bmax value of 3H-spiperone binding for schizophrenics was higher than the controls. We also found increased specific binding of 3H-kainic acid to the prefrontal cortex in schizophrenics. A negative correlation existed between 3H-kainic acid binding in the medial frontal cortex, and glutamic acid content in various brain areas. Increased immunoreactivity of substance P was found in more than ten brain areas. Methionine-enkephalin was also increased in three areas of the prefrontal cortex of schizophrenics. These results suggest that the hyperdopaminergic state co-existed with glutamatergic hypofunction and increased neuropeptides in various brain areas of chronic schizophrenic patients.

Adult↗
PubMed1988

Effects of chronic treatment with trihexyphenidyl and carbamazepine alone or in combination with haloperidol on substance P content in rat brain: a possible implication of substance P in affective disorders.

To assess the roles of substance P in neurologic or psychiatric illnesses, effects of acute or chronic (40- or 80-day dietary) treatment with trihexyphenidyl and carbamazepine alone or in combination with haloperidol on substance P content were investigated in the rat brain. Either acute or chronic trihexyphenidyl administration did not alter substance P content when administered alone and did not prevent the haloperidol-induced substance P decrease in the striatum and substantia nigra when coadministered with haloperidol. Chronic dietary carbamazepine administration dose-dependently increased substance P content in the striatum and substantia nigra, but not in the raphe area, in a haloperidol-reversible manner. Carbamazepine also dose-dependently increased gamma-aminobutyric acid levels in the substantia nigra without altering the striatal dopamine turnover rate. The lack of effect of trihexyphenidyl, an anticholinergic drug used to treat antipsychotic drug-induced extrapyramidal (Parkinson) syndromes, suggests that antipsychotic drug-induced reduction in substance P content is not involved in the extrapyramidal side effects. Since the effects of carbamazepine on substance P content are identical with previously described effects of lithium, an alteration in substance P neurotransmission may be one of the neurochemical bases of common clinical and behavioral effects of carbamazepine and lithium on affective disorders.

Animals↗
PubMed1987

Fluorescence quenching dynamics of tryptophan in proteins. Effect of internal rotation under potential barrier.

In many proteins fluorescence from single tryptophan exhibits a nonexponential decay function. To elucidate the origin of this nonexponential decay, we have examined the fluorescence decay function and time-resolved fluorescence anisotropy of a fluorophore covalently bound to a macromolecule by solving a rotational analogue of the Smoluchowski equation. An angular-dependent quenching constant and potential energy for the fluorophore undergoing internal rotation were introduced into the equation of motion for fluorophore. Results of numerical calculations using the equations thus obtained predict that both the fluorescence decay function and time-resolved anisotropy are dependent on rotational diffusion coefficients of fluorophore and potential energy for the internal rotation. The method was applied to the observed fluorescence decay curve of the single tryptophan in apocytochrome c from horse heart. The calculated decay curves fit the observed ones well.

Animals↗
PubMed1984

Increased brain serotonin metabolism during rebound sleep in sleep-deprived rats.

Adult male Wistar rats were almost totally deprived of sleep by handling for 24 hr. 5-Hydroxyindolacetic acid concentrations in the dorsal raphe nucleus area and thalamus increased by 140-180%, immediately after sleep deprivation and when the rats had a 3- or 30-min rebound sleep. The higher levels of 5-hydroxyindolacetic acid were still observed after the rats were awakening from a 4-hr sleep. The concentrations of 5-hydroxytryptamine (serotonin) decreased after sleep deprivation and increased during and after sleep, but the differences were not significant. Tryptophan accumulated in the dorsal raphe area and thalamus after sleep deprivation, and an elevated level did not return to baseline concentrations until the rats were awakening. Tryptophan hydroxylase activity did not change in the dorsal raphe area during and after sleep deprivation. These results suggest that the release and synthesis of 5-hydroxytryptamine in the dorsal raphe area and thalamus increased when the rats had a sleep pressure or a rebound sleep after total sleep deprivation. An increased transport of tryptophan into the brain may be closely involved in sleep-inducing mechanisms.

Animals↗
PubMed1984

Twenty-four hour rhythms of norepinephrine and serotonin in nucleus suprachiasmaticus, raphe nuclei, and locus coeruleus in the rat.

Twenty-four hour rhythms, at 4 h intervals, of norepinephrine (NE) and serotonin (5-HT) contents were investigated in the rat brain regions where sleep-wakefulness regulation is believed to occur: Nucleus suprachiasmaticus (SC), n. raphe dorsalis (RD) and medialis (RM), and locus coeruleus. Cosinor method of Halberg was applied to evaluate sinusoidal rhythmicity of the measured values. In the SC only NE showed a significant rhythm with a peak value at the beginning of the light period, which suggests that a NE mechanism may be involved in oscillating biological rhythms in rats. In the RD and RM, 5-HT and 5-hydroxyindoleacetic acid increased significantly during the light period. Moreover, 5-HT rhythm in the RD was maintained even under constant dark conditions, which suggests that 5-HT rhythm in the RD may be endogenous.

Animals↗