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N Fujiwara

Publications and source records attributed to N Fujiwara.

At least 181 records · Page 10Linked to original sources
PubMed1987

Effects of hypoxia on rat hippocampal neurones in vitro.

1. The effects of hypoxia on the rat hippocampal CA1 neurones in tissue slices of the rat brain were studied in vitro by intracellular recording. 2. In response to superfusion of a hypoxic medium equilibrated with 95% N2-5% CO2, a majority of the neurones showed a hyperpolarization of 5-15 mV in amplitude and 4-12 min in duration. The hyperpolarization was, in turn, followed by a slow depolarization which within 20 min of hypoxic exposure reached a plateau level of about 25 mV above the pre-hypoxic resting potential. Both the initial hyperpolarization and subsequent depolarization were associated with a reduction in membrane resistance. 3. The hyperpolarization reversed in polarity at a membrane potential of -83 mV. There was an almost linear relationship between amplitude of the hyperpolarization and membrane potential. The hyperpolarization was markedly enhanced in potassium-free media and was depressed in high-potassium solutions. 4. The hyperpolarization was not significantly affected by low-chloride or low-sodium medium or by solution containing tetraethylammonium (10 mM), 4-aminopyridine (1.5 mM) or caesium (3 mM). Moreover, intracellular injection of ethyleneglycol-bis-(beta-aminoethylether)N,N-tetraacetic acid (EGTA) did not alter the hyperpolarization. On the other hand, barium (0.5 mM)-containing medium reduced the amplitude of the hyperpolarization by 20-40%. 5. Superfusion of ouabain (5-7 microM)-containing medium in normoxic conditions produced hyperpolarizing and depolarizing responses similar to those elicited by hypoxic exposure. The slow depolarization was also mimicked by elevation of the extracellular potassium concentration to 10-20 mM. 6. Evoked i.p.s.p.s were abolished within 4 min of hypoxic exposure while evoked e.p.s.p.s were maintained for about 20 min of hypoxic superfusion. Soma spikes of the neurones elicited by a depolarizing pulse were also well preserved. Their threshold was, however, raised, concomitant with a decrease in the peak amplitude. 7. When the slice was reoxygenated after 20-40 min of hypoxic exposure, the neurones immediately began to repolarize and showed a transient hyperpolarization of 5-10 mV in amplitude and 1-2 min in duration. The membrane potential, input resistance and action potential returned to the pre-hypoxic levels after 15-20 min of reoxygenation. The amplitude of the reoxygenation-induced hyperpolarization was not significantly changed when the membrane was hyperpolarized or depolarized. The hyperpolarization was eliminated by potassium-free medium or solution containing ouabain (1 microM).(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1986

Opiate-antagonist reversal of neurological deficits--experimental and clinical studies.

The proximal left M1 and the common trunk of A2 were clipped in 12 adult dogs. Naloxone was injected after placing the clips onto 6 dogs. Neither the systemic blood pressure nor the local cerebral blood flow were influenced by naloxone. In another group of 6 dogs with chronic right hemiplegia, naloxone proved passably effective in improving the hemiplegia. Eight patients with neurological deficits of various etiologies were administered levallorphan. The improvement in motor performance and/or elevation of mental activity was observed more or less in all but 2 of the patients. It was considered that the effect of opiate antagonists is based partially on the facilitation of synaptic transmission exaggerated by the arousal response.

Adult↗
PubMed1985

An experimental model of deafferented pain in the cat.

Deafferentation hyperactivity, produced unilaterally in the neurons of the subnucleus caudalis of the spinal trigeminal nucleus (STNcd) in cats by left Gasserian ganglionectomy, was studied neurochemically and electrophysiologically. Analysis of neuronal activities on both sides of the STNcd was done 11-63 days after the denervation. On the denervated side, 37 (57%) of the 65 neurons identified showed deafferentation hyperactivity. Continuous and spontaneous firing of these hyperactive neurons were inhibited neither by the intraventricular administration of morphine or enkephalinamide nor by the electrical stimulation of periaqueductal gray. In contrast, the facilitation of the pain perceptive neuronal activities in the STNcd of the nondenervated side was remarkably inhibited, both by the administration of the same drugs and by periaqueductal gray stimulation. The deafferentation hyperactivity produced in this experiment in the STNcd of the denervated side might have a close physiological relationship to the deafferented pain of clinical patients.

Afferent Pathways↗
PubMed1985

Sensory and motor responses to deep brain stimulation. Correlation with anatomical structures.

Motor and sensory responses induced by trial stimulation were examined before stereotaxically implanting a permanent stimulating electrode for pain relief in 11 patients with intractable pain of central origin. The total number of points eliciting a response when stimulated was 70. The points of stimulation were determined as exactly as possible from Schaltenbrand and Bailey's Atlas. Motor responses were detected upon stimulating 21 points, the majority of which were in the posterior third of the posterior limb of the internal capsule (IC). Stimulation of these 21 points was accompanied by pain relief in only two points (10%). Warm (22) or cool sensations (three) were provoked in the most posteromedial portion of the posterior limb of the IC, nucleus reticularis pulvinaris, and area triangularis, and seven (28%) of these 25 sensations were accompanied by pain relief. A burning sensation was found upon stimulation of 12 points, with stimulation in the mesencephalic lateral tegmental field eliciting the most severe burning pain. A tingling sensation was elicited at 12 points, in a distribution similar to that of the warm sensation. Five (42%) of these 12 points provided pain relief. The best stimulating point for pain relief is not in the center of the posterior limb of the IC, directly lateral to the posterior commissure, but rather in its most posteromedial part; that is, at the nucleus reticularis pulvinaris or area triangularis.

Adult↗
PubMed1985

[beta-Endorphin and monoamine metabolite concentrations in patients with intractable pain--changes before and after deep brain or spinal dorsal column stimulation].

Baseline concentrations of beta-endorphin (beta-EP) and monoamine metabolites (MHPG: 3-methoxy-4-hydroxy-phenylglycol, HVA: homovanillic acid, 5-HIAA: 5-hydroxyindoleacetic acid) in lumbar CSF (LCSF) and ventricular CSF (VCSF) were measured in 18 patients with intractable pain; 10 with deafferented pain and 8 with peripheral pain. Control values were obtained from 37 individuals of various ages. Changes in the concentrations of these substances were determined before and after giving stimulations (2-5 V, 0.2-0.5 msec, 40-50 Hz, 20-sec duration) to 6 patients through electrodes implanted in deep brain structures (DBS; posterior limb of the internal capsule in 5 patients and rostral mesencephalic lemniscus medialis in one patient), and to 2 other patients through electrodes implanted in the spinal dorsal column (DCS). The control value of beta-EP in LCSF was 57.6 +/- 24.7 pg/ml, which was not significantly different from that of VCSF. Great variation in the individual control LCSF beta-EP concentrations was found, but it was not related to differences in age. The mean baseline LCSF beta-EP concentration was significantly higher (p less than 0.05) than the control in the patients with deaffernted pain before stimulation. One of the monoamine-metabolites, MHPG, showed higher level in the patients with peripheral pain (p less than 0.01). The LCSF beta-EP concentration was not affected by deep brain stimulation, but was increased by dorsal column stimulation. In one patient with excellent pain relief by stimulation of the posterior limb of the internal capsule, the LCSF HVA and 5-HIAA concentrations were conspicuously increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1982

Purification of human seminal plasma no. 7 antigen by immunoaffinity chromatography on bound monoclonal antibody.

Human seminal plasma (HSP) No. 7 antigen was purified by immunoaffinity chromatography on bound 1C4 monoclonal antibody (Moab) (Shigeta et al., 1980b). The pooled HSP protein was applied to a CNBr-activated Sepharose 4B column of bound 1C4 Moab gamma globulin and the antibody bound fraction (fr) eluted was further purified by rechromatography in the same way. The purified antigen in the antibody bound fr obtained by rechromatography gave a single band on SDS-PAGE in a position corresponding to a molecular weight of 15,000 daltons. This preparation was 196.2 times more effective than the original HSP protein in neutralizing the sperm immobilizing activity of 1C4 Moab. The purified HSP No. 7 antigen contained iron, but was different from lactoferrin and transferrin. It did not show any enzymatic activities, such as those of acid phosphatase, LDH or trypsin inhibitor, and shared antigenicity with human milk protein. It was present in seminal plasma as a molecule with a higher molecular weight but seemed to be cleaved to a monomer of 15,000 daltons during purification procedures. This antigen is present on spermatozoa as sperm-coating antigen and the corresponding antibody can immobilize spermatozoa with complement.

Antibodies, Monoclonal↗
PubMed1978

Studies on the cutaneous sensitization reaction of guinea pigs to purified aromatic chemicals.

The sensitization reactions to purified cinnamic aldehyde and its chemically related substances were investigated using the maximization test on guinea pigs. Mutual cross-sensitivities were also examined. Cinnamic aldehyde was found to be the most potent sensitizer in this series, and a strong cross-sensitizer. From the chemical structures of these substances, the following speculations were made. There was a tendency that as the number of hydrocarbons of alkyl groups replacing the alpha-hydrogen in the molecule increased, the rate of sensitization reaction declined. The conjugated system of double bonds was suspected to be a determinant factor in relation to the sensitization ability of the substances in this series.

Aldehydes↗