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Biomedical subjects

M Fujiwara

Publications and source records attributed to M Fujiwara.

At least 811 records · Page 45Linked to original sources
PubMed1981

Species and regional differences in cholinergic blocking actions of beta-bungarotoxin.

Effects of beta-bungarotoxin (beta-BuTX) on cholinergic transmission were examined in various tissues and species. In the guinea-pig atrial preparation, beta-BuTX in concentrations ranging from 0.01 to 10 microgram/ml abolished the negative inotropic and chronotropic responses to electrical stimulation of the vagus nerve. However, such a blocking action of beta-BuTX was not obtained in the mouse, rat or rabbit atrial preparations. beta-BuTX blocked the neuromuscular transmission in the phrenic nerve-diaphragm preparations of guinea pig, mouse and rat, but the onset was earlier in the guinea pig than in the mouse and rat. Since these results suggest that the guinea pig is the most sensitive to beta-BuTX among the mammalian species so far tested, the effect of beta-BuTX on the cholinergic transmission in various tissues of this species was examined. In the guinea-pig stomach preparation, the cholinergic contractile response to electrical stimulation of the vagal preganglionic nerves was abolished by beta-BuTX, whereas the noradrenergic relaxing response to stimulation of the vagal preganglionic nerve was not affected. In the ileal preparation, the cholinergic contractile response to stimulation of the intramural nerve was little attenuated. These results show that beta-BuTX has not only neuromuscular but also parasympathetic blocking actions and that there are species and regional differences in these blocking actions.

Animals↗
PubMed1981

[A case of intracranial hypoglossal neurinoma (author's transl)].

A case of intracranial hypoglossal neurinoma was reported and the literature was reviewed. A 46-year-old woman with a three-year history of suboccipital pain, dizziness, blurred vision, swallowing disturbance, cysarthria, dysesthesia and weakness of the four extremities, was admitted to our hospital on July 9, 1978. General physical examination on admission were unremarkable. Café au lait spot was not found. Neurological examination revealed nystagmus, ataxic gait and impairment of the finger to nose test on the right side. Atrophy of the tongue with fasciculation on the right side was also noted. Computed tomography demonstrated a round low density area in the posterior fossa which was enhanced with contrast medium. Antero-posterior view of the skull tomography showed enlargement of the right hypoglossal canal. Vertebral angiography and ventriculography disclosed a mass located at the foramen magnum. On July 27, suboccipital craniectomy with C1 laminectomy was performed in prone position. The encapsulated tumor which arouse from the right hypoglossal nerve was totally removed. Histological diagnosis was Antoni A type schwannoma. Postoperative course was uneventful and she was discharged on August 31. Intracranial hypoglossal neurinomas are very rare and our case marks the 17th reported observation of such a lesion. because of their rarity, complicated natural history and variety of associated symptoms and signs, early diagnosis of these lesions is difficult. Among the diagnostic procedures, computed tomography, vertebral angiography and skull tomography were useful for localizing the lesion. Especially skull tomography which showed enlargement of the right hypoglossal canal could offer very important informations. It should be recognized that early diagnosis by means of neurological and radiological maneuvers mentioned above is essential to good prognosis.

Cranial Nerve Neoplasms↗
PubMed1981

Effects of 4-aminopyridine on the adrenergic nerve terminals of rabbit arteries.

Adrenergic nerves of the rabbit pulmonary artery and aorta were stimulated by electrical pulses (0.3 or 5 msec duration) and also by nicotine. The effects of 4-aminopyridine (4-AP), a potassium channel inhibitor, were investigated on contractile responses of these arteries or on 3H-efflux from [3H]norepinephrine-treated pulmonary artery in response to these stimuli. Tetrodotoxin (0.1-0.3 micro M) abolished the contractions and the 3H-efflux induced by an electrical pulse of 0.3 msec duration, but not the adrenergic responses induced by a pulse of 5 msec duration or by nicotine. The adrenergic responses to an electrical pulse of 5 msec (with tetrodotoxin) or nicotine were inhibited by guanethidine (10 micro M) or removal of the extracellular calcium. Thus, a short electrical pulse indirectly stimulates the adrenergic nerve terminals through conducted action potentials, whereas a long pulse or nicotine stimulates directly the terminals. 4-AP in concentrations over 10 micro M markedly augmented the adrenergic responses to these two electrical stimuli. The adrenergic response induced by nicotine was little affected by 4-AP in concentrations up to 100 micro M. At 300 micro M, 4-AP, the concentration-contraction curve of nicotine, shifted to the right and 3H-efflux was markedly reduced. This inhibitory effect of 4-AP on the contraction was not affected by alterations in the concentrations of extracellular calcium. 4-AP did not affect the responses to exogenously applied norepinephrine. These results indicate that 4-AP has inhibitory effects on nicotinic receptors of adrenergic nerve terminals and that nicotine releases norepinephrine in a manner which differs from the release seen with electrical stimulation.

4-Aminopyridine↗
PubMed1981

Experimental allergic encephalomyelitis (EAE) in two inbred guinea pigs. II. Strain differences in susceptibility to passive transfer of EAE.

Two inbred strains of guinea pigs, Strain 13 and JY-1, were compared with regard to their susceptibility to the elicitation of experimental allergic encephalomyelitis (EAE) by passively transferred sensitized lymph node cells. Recipient guinea pigs were injected with more than 2 X 10(8) of viable lymph node cells from donors that had been immunized for the elicitation of EAE 8 days prior to the cell transfer. 1) Clinical course of EAE in all adult guinea pigs passively transferred with adult and juvenile sensitized lymph node cells was acute. 2) Sensitized cells required for successful passive transfer of EAE was less in JY-1 guinea pigs than in Strain 13 guinea pigs. 3) The sensitized cells from juvenile Strain 13 guinea pigs were less competent to transfer EAE than the adult ones whereas in JY-1 guinea pigs the juvenile cells were as effective as the adult ones.

Age Factors↗
PubMed1980

Central effect of nicotine on gastric acid secretion in rats.

The central effect of nicotine on gastric acid secretion was examined in rats anesthetized with urethane. Intraventricular administration of nicotine 5 and 20 microgram/animal induced a dose-related increase in acid output. This nicotine-induced increase was blocked by treatment with hexamethonium 50 microgram/animal given intraventricularly or atropine 100 microgram/kg given intravenously. Changes in acid output after intravenous administration of nicotine 100 microgram/kg were inconsistent; however, a significant increase was observed with 500 microgram/kg of this alkaloid given by the same route. This increase was also blocked by hexamethonium 50 microgram/animal given intraventricularly. The level of gastrin in the gastric juice, after the intraventricular administration of nicotine 20 microgram/animal, did not significantly differ from the control. These results suggest that nicotine administered intraventricularly stimulates nicotinic receptors in the brain, and that there is a subsequent excitation of cholinergic muscarinic receptors in the stomach after which the secretion of acid increases.

Animals↗
PubMed1980

The hypotensive effect of centrally administered tyrosine.

Intraventricular injection of 15 microgram L-tyrosine results in a significant reduction in blood pressure in the spontaneously hypertensive rat. An increase in the turnover of norepinephrine as indexed by MOPEG-SO4 is observed concurrently. The data are consistent with the previously suggested depressor role of certain central noradrenergic neurons.

Animals↗
PubMed1980

Stereospecificity of hepatic L-tryptophan 2,3-dioxygenase.

Tryptophan 2,3-dioxygenase [L-tryptophan--oxygen 2,3-oxidoreductase (decyclizing), EC 1.13.11.11] has been reported to act solely on the L-isomer of tryptophan. However, by using a sensitive assay method with D- and L-[ring-2-14C]tryptophan and improved assay conditions, we were able to demonstrate that both the D- and L-stereoisomers of tryptophan were cleaved by the supernatant fraction (30000 g, 30 min) of liver homogenates of several species of mammals, including rat, mouse, rabbit and human. The ratio of activities toward D- and L-tryptophan was species variable, the highest (0.67) in ox liver and the lowest (0.07) in rat liver, the latter being hitherto exclusively used for the study of hepatic tryptophan 2,3-dioxygenase. In the supernatant fraction from mouse liver, the ratio was 0.23 but the specific activity with D-tryptophan was by far the highest of all the species tested. To identify the D-tryptophan cleaving enzyme activity, the enzyme was purified from mouse liver to apparent homogeneity. The specific activities toward D- and L-tryptophan showed a parallel rise with each purification step. The electrophoretically homogeneous protein had specific activities of 0.55 and 2.13 mumol/min per mg of protein at 25 degrees C toward D- and L-tryptophan, respectively. Additional evidence from heat treatment, inhibition and kinetic studies indicated that the same active site of a single enzyme was responsible for both activities. The molecular weight (150000), subunit structure (alpha 2 beta 2) and haem content (1.95 mol/mol) of the purified enzyme from mouse liver were similar to those of rat liver tryptophan 2,3-dioxygenase. The assay conditions employed in the previous studies on the stereospecificity of hepatic tryptophan 2,3-dioxygenase were apparently inadequate for determination of the D-tryptophan cleaving activity. Under the assay conditions in the present study, the purified enzyme from rat liver also acted on D-tryptophan, whereas the pseudomonad enzyme was strictly specific for the L-isomer.

Animals↗