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Biomedical subjects

H Fukuda

Publications and source records attributed to H Fukuda.

At least 1,099 records · Page 61Linked to original sources
PubMed1983

[Characteristics of contralateral suppression along the vertical meridian].

A hypothesis has been advanced which suggests that the magnitude of suppression in binocular rivalry along the horizontal meridian is stronger at the center of the rivalrous pattern than at its peripheral. It was tested whether this hypothesis can be extended to the vertical meridian. Accuracy in detecting a briefly flashed target superimposed upon the completely suppressed pattern during binocular rivalry was measured at each of two target positions combined with two fixation positions along the vertical meridian (Exp. I). As a control experiment, target-detection performance in monocular observation was examined (Exp. II). The results obtained from one of the two subjects supported this hypothesis, although the effect of position within the rivalrous pattern was less marked than that obtained along the horizontal meridian. The results obtained from the other subject suggested that there was little difference in suppression effect between the center and the upper end of the pattern. These results suggest that the variation in suppression effect within the pattern along the vertical meridian is smaller than that along the horizontal meridian.

Adolescent↗
PubMed1983

[Whole body autoradiography by positron emitting radionuclides].

The technique of freezing whole body autoradiography using positron emitting nuclides has been developed in the present study. Because of rapid decay of positron emitters, a frozen section to contact with a X-ray film must be prepared within a few hours. All the procedures to obtain autoradiograms of rats using 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG) or 11C-glucose-fructose mixture (11C-glucose) were described in detail. In the present technique, exposure must be performed at -20 degrees C to keep a section frozen. Density of X-ray films after exposure at 20 degrees C or -20 degrees C was examined using various radioactive sections. The reduction of the density exposed at -20 degrees C was observed. But the density exposed at -20 degrees C was proportional to the radioactivity. Freezing whole body autoradiography of rats bearing subcutaneous AH109A tumors was performed using 18F-FDG (half life of 109.7 min) and 11C-glucose (half life of 20 min). Density of tumors and other organs on the autoradiogram was comparable with tissue distribution studies of 18F-FDG and 11C-glucose. Freezing whole body autoradiography can be feasible for the analysis of tissue distribution on positron emitting radiopharmaceuticals.

Animals↗
PubMed1983

[Effects of lorcainide, a new antiarrhythmic agent, on experimental cardiac arrhythmias].

Antiarrhythmic actions of lorcainide were compared with those of disopyramide on different types of arrhythmias in animal models. It was shown in dogs that lorcainide and disopyramide were approximately equipotent against the arrhythmias following coronary occlusion. In guinea pigs, lorcainide was less effective than disopyramide against the ouabain-induced arrhythmia. Both drugs showed a weak protective action against the aconitine-induced ventricular arrhythmias, but had no effect on the cardiac arrest. In the arrhythmias induced by the application of acetylcholine on the right auricle of guinea pigs, the disappearance of P-waves and the disturbance of R-R intervals were inhibited by disopyramide, but lorcainide had no influence on these events; both prevented the atrial fibrillation induced by acetylcholine application. Both drugs by themselves induced ventricular arrhythmias in guinea pigs.

Acetylcholine↗
PubMed1982

Anisatin modulation of GABA- and pentobarbital-induced enhancement of diazepam binding in rat brain.

Anisatin, a pure toxic substance isolated from the seeds of a Japanese plant (Illicium anisatum) acts as a picrotoxin-like, non-competitive GABA antagonist. Anisatin inhibited [3H]diazepam binding enhanced by either GABA or pentobarbital, without affecting the basal specific binding to rat brain membranes. The inhibition of this pentobarbital enhancement was competitive. These actions of anisatin were even more apparent when the binding assays were carried out at 37 degrees C rather than a 0 degrees C. Thus, at a physiological temperature, anisatin may have a more potent modulatory effect on benzodiazepine-GABA receptor coupling, through the barbiturate-picrotoxin sensitive sites.

Animals↗
PubMed1982

Stimulatory and protective effects of benzodiazepines on GABA receptors labeled with [3H]muscimol.

We investigated the effects of benzodiazepines on [3H]muscimol binding to rat brain membranes and on heat inactivation of GABA receptors. Scatchard analysis of [3H]muscimol binding to frozen and 0.05% Triton X-100 treated membranes revealed two components; a higher affinity (Kd = 2.2 nM, Bmax = 1.2 pmol/mg protein) and a lower affinity component (Kd = 15.9 nM, Bmax = 4.4 pmol/mg protein). Diazepam and flurazepam (3 microM) increases significantly the specific binding of 40 nM but not of 2 nM [3H]muscimol. This stimulation was attributed to an increase in the affinity of the lower affinity component for GABA receptors. The time course of heat inactivation of GABA receptors revealed rapidly and then slowly denaturating Phases. These observations would suggest that there are multiple GABA receptors with different sensitivities to the heat treatment. Diazepam depressed remarkably the slowly denaturating phase(s). After heat treatment for 50 min, the single component of GABA receptors with Kd of 14.3 nM and Bmax of 0.6 pmol/mg protein survived, whereas in the membranes preincubated with 3 microM diazepam, the Kd and Bmax of the still viable GABA receptors were 14.8 nM and 1.14 pmol/mg protein, respectively. In light of these findings, the stimulation of the lower affinity component of GABA receptors may be related to the protective effects of these drugs against heat inactivation.

Animals↗
PubMed1982

Experimental study for cancer diagnosis with positron-labeled fluorinated glucose analogs: [18F]-2-fluoro-2-deoxy-D-mannose: a new tracer for cancer detection.

18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) and 18F-2-fluoro-2-deoxy-D-mannose (18F-FDM) were tested as tumor diagnostic agents in a transplantable rat tumor and rabbit tumors. Tissue distribution studies in rats showed high tumor uptakes of both radiopharmaceuticals. The tumor uptake reached 2.65 +/- 0.61% dose 18 dose F-FDG/g and 2.65 +/- 0.81% dose 18F-FDM/g at 60 min and remained relatively constant until 120 min. Blood clearance both 18F-FDG and 18F-FDM was very rapid and tumor-to-blood ratios reached 22.1 and 29.4 at 60 min, respectively. Tumor-to-tissue ratios of both radiopharmaceuticals were very high in most organs, especially in the liver, kidney, and pancreas. Positron emission tomography (PET) of rabbit tumor with 18F-FDM clearly delineated the main tumor, central necrosis, and lymph node metastases. These data suggested that 18F-FDM, which is a by-product of 18F-FDG synthesis was also an excellent cancer diagnostic agent as well as 18F-FDG. This is not only a new feature of 18F-FDM, but also an economical improvement on cancer diagnosis by PET.

Animals↗
PubMed1982

Ventral root depolarization and spinal reflex augmentation by a TRH analog in rat spinal cord.

The experiments were performed on spinal rats transected at the C 1 level. Intravenous administrations of TRH and its analog DN-1417 (gamma-butyrolactone-gamma-carbonyl-L-histidyl-L-prolinamide), which has less endocrine activity, produced a marked increase in the monosynaptic reflex (MSR) and depolarization of the ventral root, without affecting the dorsal root reflex (DRR) and the resting potential of the dorsal root. Excitation of the monosynaptic reflex was not antagonized by chlorpromazine, haloperidol, atropine or cyproheptadine, and was not influenced by pretreatment with reserpine. The depolarization of the ventral root persisted in the presence of baclofen or tetrodotoxin. These findings suggest that depolarization of the ventral root induced by TRH and DN-1417 is due to a direct action on motoneuronal membranes, and that an increase in the monosynaptic reflex is in part due to a depolarization of motoneurones. The effect of DN-1417 were longer lasting than those of TRH.

Animals↗
PubMed1982

A new enzyme: long acyl aminoacylase from Pseudomonas diminuta.

A new enzyme which hydrolyzes N-long chain acyl glutamic acid was found in cell-free extracts of Pseudomonas diminuta. Two active fractions (long acyl aminoacylase I and II) were separated by DEAE-cellulose column chromatography. The long acyl aminoacylase I was purified about 650-fold, and the purified preparation was electrophoretically homogeneous. The molecular weight was estimated to be 300,000 by gel filtration. The enzyme was unique in its substrate specificity. It hydrolyzed only N-long acyl glutamic acid and could not react with other N-acyl amino acids. Lauroyl (C12)-, myristoyl (C14)-, and palmitoyl (C16)- glutamic acid were good substrates, but acetyl glutamic acid was not hydrolyzed. Therefore this enzyme is considered to be a new acylase which is specific for N-long chain acyl glutamic acid, and it is designated as N-long acyl glutamic acid amidohydrolase [EC 3.5.1 group].

Amidohydrolases↗
PubMed1982

Age-dependent alterations of insulin binding to hepatic plasma membranes, erythrocytes and adipocytes in rat.

The insulin binding to hepatic plasma membranes, erythrocytes and adipocytes of 1-, 2-, and 9-month-old rats was measured by using [125I]insulin. When rats were fed a fat-free diet, the capacities of the insulin bindings significantly decreased with aging, whereas the dissociation constants were not altered. The capacities of 9-month-old rats were decreased to about half those of 1-month-old rats for plasma membranes, and about one-third for erythrocytes and adipocytes. On the other hand, the plasma insulin levels tended to be high with increasing age at 9-10 a.m., while the levels were even more elevated at 8-9 p.m. and not altered by aging. The insulin binding capacities were increased by feeding the fat-free diet to rats adapted to a stock diet and the increases were reduced with aging. The insulin binding capacities correlated well with the magnitudes of induction of lipogenic enzymes as reported previously [Iritani, N., Fukuda, H., & Fukuda, E. (1981) Biochim. Biophys. Acta 665, 636]. Therefore, it is suggested that insulin binding is implicated in age-dependent alterations of lipogenic enzyme induction.

Adipose Tissue↗
PubMed1982

Effects of barbiturates on the decerebrate rigidity in rats.

Effects of barbiturates (phenobarbital, mephobarbital, pentobarbital, hexobarbital and amobarbital) on the tonic and phasic responses of forelimbs were studied in the rats in which rigidity was induced by means of anemic decerebration. The inhibitory pattern of the tonic and phasic responses to phenobarbital was different from those to the other barbiturates, i.e. phenobarbital gradually inhibited both tonic and phasic responses, whereas other barbiturates suppressed significantly only the tonic response immediately after the administration of a relatively low dose (10 mg/kg) but hardly inhibited the phasic response unless at higher doses (20 and 40 mg/kg). Possible involvement of GABA-system in the inhibitory action of phenobarbital and pentobarbital on the rigidity was investigated. Since inhibition of the phasic response to pentobarbital was potentiated by the pretreatment of animals with carboxymethoxylamine hemihydrochloride (AOAA) and suppressed by the pretreatment with semicarbazide, it was suggested that GABAergic mechanism may be involved in the particular inhibition of phasic response to pentobarbital. However, the inhibitory action of phenobarbital appeared to be independent of GABA-system.

Aminooxyacetic Acid↗