Search PubMed⌕ Search

Biomedical subjects

H Fukuda

Publications and source records attributed to H Fukuda.

At least 991 records · Page 55Linked to original sources
PubMed1986

Spinal reflexes in chinoform-administered rats.

We examined the effects of chinoform (CF) on the spinal reflexes and the descending influences on the spinal reflexes from the locus coeruleus (LC) and the nucleus raphe magnus (NRM) in rats. The spinal reflex potential was recorded from the L5 ventral root following stimulation of the L5 dorsal root, and the effects of electrical stimulation of the LC and the NRM were tested in anesthetized rats. CF was suspended in Tween 80 and administered for two days (400 mg/kg, i. p./day) before the measurement of the spinal reflexes. In all rats treated with CF, death or motor incoordinations such as abnormal gait and hindlimb ataxia were observed. However, the control and CF-treated groups are not different in the amplitude and shape of the reflexes and in the influences of the LC and the NRM on the reflexes from the LC and the NRM. These results suggest that segmental spinal reflexes and descending influences from the LC and the NRM are not affected in rats suffered from motor incoordination by acute CF.

Animals↗
PubMed1986

Ascending and descending pathways of reflex straining in the dog.

The location of ascending and descending pathways of the straining reflex was studied by making bulbar cuts in dogs. Rhythmic increases, which were elicited simultaneously in nervous outflows to the diaphragm and rectus abdominis by activation of pelvic afferent fibers, were used to indicate rhythmic straining. The increases were not affected by cutting the dorsal funiculus at the bulbospinal junction, but stopped after cutting both lateral funiculi and by longitudinally cutting the roof of the central canal just caudal to the obex. The increases were impaired by unilateral section of the bulbospinal junction, but were abolished completely after successive ipsilateral hemisection of the rostral bulb. Moreover, rhythmic increases, which appeared synchronously with rhythmic straining in unit discharges recorded from the Kölliker-Fuse nucleus and neighboring structures, disappeared after the longitudinal bulbar cut. However, reflex discharges elicited in pelvic vesical and rectal branches by stimulation of corresponding pelvic afferent fibers were not reduced. These results show that the indispensable part of the ascending pathway of rhythmic straining passes through the lateral funiculus and decussates at the lower bulb, but the pathway of micturition and defecation reflexes do not cross at that level.

Afferent Pathways↗
PubMed1986

Heat-inactivation of liver glucose-6-phosphate dehydrogenase and malic enzyme in 1- and 12-month-old rats.

The heat-labilities of liver glucose-6-phosphate dehydrogenase and malic enzyme of 1- and 12-month-old rats were observed by incubation of the crude enzymes at 52 and 55 degrees C, respectively. The biphasic heat-inactivation curves were obtained for those enzymes of the 12-month-olds, whereas no biphasic curves were obtained for the enzymes of the 1-month-olds. The age-dependent rapid inactivations of glucose-6-phosphate dehydrogenase and malic enzyme were not relieved by addition of their substrates in the incubation media. However, the rapid age-dependent inactivations of these enzymes disappeared by addition of NADP. It is suggested that the age-dependent heat-inactivation of these enzymes is ascribed to the conformational modification of the proteins.

Aging↗
PubMed1986

Dopaminergic and benzodiazepine receptors studied in vivo by PET.

Using Positron Emission Tomography (PET) and specific radioligands, dopaminergic D2 (DA-D2 receptors) and benzodiazepine receptors (BZ-receptors) were studied in living animals during normal and pathological conditions. In vivo characterization of both receptors was performed using two highly specific antagonists namely: 11C-Ro 15 1788 for BZ-receptors and 76 Br-Bromospiperone for DA-D2 receptors. Changes in 11c-Ro 15 1788 specific binding to BZ-receptors were observed during convulsive seizures. After MPTP treatment, a decrease in the 76 Br-Bromospiperone striatal specific binding was observed, correlated with the establishment of a Parkinson-like syndrome.

Animals↗
PubMed1985

High-performance liquid chromatographic determination of plasma and brain histamine without previous purification of biological samples: cation-exchange chromatography coupled with post-column derivatization fluorometry.

A highly sensitive and specific method was developed for the determination of histamine in biological materials by high-performance liquid chromatography with a cation exchanger and an automated Shore's fluorometric detection system. Since substances causing interference in Shore's o-phthalaldehyde method, such as ammonia, histidine, spermine and spermidine, were completely separated on the column and their fluorescent intensities were much less than that of histamine in this detection system, histamine could be determined by injecting a perchloric acid extract of human plasma or mouse brain tissue directly onto the column without any previous purification procedure. The lower limit of detection of histamine by this method is 0.05 pmol, and the within-day and day-to-day variations in plasma histamine assay are less than 3%. The plasma histamine level in normal human subjects was found to be 4.0 +/- 1.6 pmol/ml (mean +/- S.D., n = 20). A good linear correlation was obtained between values for the histamine contents of mouse brain tissues determined by this method and by a radioenzymatic method with a purified histamine-N-methyltransferase preparation. The histamine levels of whole brain, hypothalamus, thalamus, brain stem and frontal cortex in male ddY mice were 367 +/- 38, 1143 +/- 70, 414 +/- 66, 196 +/- 47 and 467 +/- 91 pmol/g of wet tissue (mean +/- S.D.), respectively.

Adult↗
PubMed1985

Quisqualic acid-induced hippocampal seizures in unanesthetized cats.

An intrahippocampal injection of quisqualic acid (QA) was made in chronically implanted freely moving unanesthetized cats and electrographic and clinical observations were made. Fourteen to 40 micrograms of QA injection resulted in a mild limbic seizure within 24 h after QA injection. Some cats demonstrated a pure hippocampal seizure on an electroencephalogram. Electrographic changes and clinical manifestations were less prominent as compared with those of kainic acid. Histopathological examination showed a selective loss of pyramidal cell layer of the CA3 portion in the injected side of the dorsal hippocampus. A mild but constant epileptogenic potency of QA has an advantage for an experimental model of temporal lobe epilepsy in man.

Animals↗
PubMed1985

Reduction of GABAB receptor binding induced by climbing fiber degeneration in the rat cerebellum.

When the rat cerebellar climbing fibers degenerated, as induced by lesioning the inferior olive with 3-acetylpyridine (3-AP), GABAB receptor binding determined with 3H-(+/-)baclofen was reduced in the cerebellum but not in the cerebral cortex of rats. Computer analysis of saturation data revealed two components of the binding sites, and indicated that decrease of the binding in the cerebellum was due to reduction in receptor density, mainly of the high-affinity sites, the Bmax of which was reduced to one-third that in the control animals. In vitro treatment with 3-AP, of the membranes prepared from either the cerebellum or the cerebral cortex, induced no alteration in the binding sites, thereby indicating that the alteration of GABAB sites induced by in vivo treatment with 3-AP is not due to a direct action of 3-AP on the receptor. GABAA and benzodiazepine receptor binding labelled with 3H-muscimol and 3H-diazepam, respectively, in both of brain regions was not affected by destruction of the inferior olive. These results provide evidence that some of the GABAB sites but neither GABAA nor benzodiazepine receptors in the cerebellum are located at the climbing fiber terminals.

Animals↗