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Biomedical subjects

T Kuga

Publications and source records attributed to T Kuga.

At least 127 records · Page 7Linked to original sources
PubMed1987

Estimation of harmine and its derivatives by HPLC: correlation of brain harmine levels with jumping behavior in rats.

Brain harmine was simply and sensitively determined by high performance liquid chromatography (HPLC), and the relationship between brain harmine concentrations and the jumping behavior induced by harmine and apomorphine was investigated. The concentration of harmine and the peak height in HPLC showed a good correlation, and the detection limit was 0.05 pmole harmine. In rats treated with 2, 5 and 10 mg/kg of harmine, the concentrations of harmine in the brain cortex were 9.0, 21.3 and 43.1 nmole/g tissue (wet wt.), respectively. The regional brain harmine concentrations and the jumping activity measuring by a scoring system increased with increasing doses of harmine administered, and there was a direct relation between the harmine concentrations and the jumping activity. This relation was observed in washed membranes in which about 40% of the harmine in whole homogenate was present. Tissue subfractionation showed that 30% of the harmine in whole brain homogenates was in the P2 fraction, and of this, 70% was located in the synaptosomes. The brain homogenate did not metabolize harmine and no metabolite was detected in the brain 10 min after treatment with harmine and apomorphine. These results suggest that harmine itself, but not its metabolites, may be responsible for inducing the jumping behavior and that the jumping activity is correlated with brain harmine concentrations.

Alkaloids↗
PubMed1987

Two kinds of modification by 5-methoxy-N,N-dimethyltryptamine of contractile responses to electrical stimulation of isolated guinea-pig vas deferens.

Two kinds of electrical stimulation, low frequency stimulation (5 Hz, 1 msec, 5 pulses, every 20 sec) and high frequency stimulation (30 Hz, 0.1 msec, 20 pulses, every 20 sec), produced contractions in isolated guinea-pig vas deferens. These responses were blocked by alpha, beta-methylene-ATP, but not prazosin. Phentolamine potentiated the contractions produced by low frequency stimulation, while it had little or no effect on the contractions produced by high frequency stimulation. The effect of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT), a potent short acting hallucinogen, on the contractile response to two kinds of electrical stimulation was examined. On the contraction produced by low frequency stimulation, 5-MeODMT showed a biphasic action. 5-MeODMT at concentrations of 3 X 10(-8)-10(-6) M reduced the contractile response. 5-MeODMT at concentrations of 3 X 10(-6)-2 X 10(-5) M potentiated the contractile response, and this potentiation was reversed by prazosin and ketanserin. Clonidine caused an inhibition of the contractile response to low frequency stimulation. This action of clonidine was reversed by 5-MeODMT. The reverse action of 5-MeODMT was greatly inhibited in the presence of prazosin and ketanserin. The results suggest that 5-MeODMT exerts two different kinds of modification on the contractile response to low frequency stimulation of isolated guinea-pig vas deferens: in one type of modification, 5-MeODMT at concentrations higher than 3 x 10(-8) M exerts an action similar to that of 5-hydroxytryptamine on postganglionic sympathetic nerve terminals and reduces the release of transmitter presynaptically, and in the other type, 5-MeODMT at concentrations higher than 3 x 10(-6) M causes the release of noradrenaline from postganglionic sympathetic nerve terminals.

Adenosine Triphosphate↗
PubMed1987

Cloning of granulocyte colony-stimulating factor cDNA from human macrophages and its expression in Escherichia coli.

Human granulocyte colony-stimulating factor (hG-CSF) cDNA was cloned, by using a synthetic oligonucleotide probe, from an Okayama-Berg cDNA library of lipopolysaccharide-stimulated human peripheral blood macrophages. The cDNA encodes a polypeptide with an amino acid sequence which completely matches that of the known polypeptide with hG-CSF activity derived from human tumor cell lines. Expression in E. coli of high levels of the protein (about 10% of total cellular proteins) was accomplished under control of the trp promoter, and the purified protein was proved to have hG-CSF activity. Our data provide evidence that human peripheral blood macrophages do produce hG-CSF mRNA when stimulated exogenously, suggesting they are the producer of naturally occurring hG-CSF.

Base Sequence↗
PubMed1986

Pharmacological effects of the tremorgenic mycotoxin fumitremorgin A.

Some pharmacological effects of a potent tremorgenic mycotoxin, fumitremorgin A (FTA), on the rabbit were studied. FTA (10-200 micrograms/kg, i.v.) caused clonic and tonic convulsion accompanied by nystagmus and miosis in conscious rabbits, after a latent period. Even in decorticated or decerebrated rabbits, FTA (100-200 micrograms/kg, i.v.) could induce violent motor effects similar to those observed in conscious rabbits. Under light anesthesia with urethane and chloralose, a higher dosage (more than 100 micrograms/kg) was needed to cause clonic and tonic convulsion. FTA facilitated phrenic nerve discharges as well as efferent discharges of the vagal nerve and the cervical sympathetic nerve. Hypertension induced by FTA was inhibited by phentolamine, while bradycardia and arrhythmia caused by this toxin was abolished by atropine or bilateral vagotomy. The electroencephalogram showed persistent strong arousal response after intravenous injection of FTA. A seizure pattern was never observed. It was suggested that the main site of action of FTA was in the brain stem.

Anesthesia↗
PubMed1986

Probable pre- and postsynaptic modifications by 5-hydroxytryptamine of contractile responses to electrical stimulation of isolated guinea-pig vas deferens.

Two kinds of electrical stimulation, low frequency stimulation (5 Hz, 1 msec, 5 pulses, every 20 sec) and high frequency stimulation (30 Hz, 0.05-0.1 msec, 10 pulses, every 20 sec), produced contractions in the isolated guinea-pig vas deferens. These responses were blocked by tetrodotoxin but not hexamethonium. Phentolamine potentiated the contractions produced by low frequency stimulation, while it reduced the contractions produced by high frequency stimulation. Diametrically, 5-hydroxytryptamine reduced the contractions produced by low frequency stimulation, while it potentiated the contractions produced by high frequency stimulation. These inhibitory and potentiating actions of 5-hydroxytryptamine were reversed by cyproheptadine and 2-bromolysergic acid diethylamide. Moreover, that 5-hydroxytryptamine produced a depolarization of the smooth muscle membrane was shown by the sucrose gap technique. The results suggest that a 5-hydroxytryptamine receptor exists pre- and postsynaptically in the neuroeffector transmission of the guinea-pig vas deferens, that the stimulation of the presynaptic receptor by 5-hydroxytryptamine inhibits the release of a transmitter from noradrenergic nerves, and that the stimulation of the postsynaptic receptor by a high concentration of 5-hydroxytryptamine produces a depolarization of the smooth muscle membrane, and this relates to the potentiation of contractile responses.

Animals↗
PubMed1985

Reduction of ochratoxin A toxicity in mice treated with phenylalanine and phenobarbital.

LD50 of ochratoxin A (OCT A) was estimated to be 29.4 mg/kg in intraperitoneal (i.p.) and 46.0 mg/kg in per os (p.o.) administration in ddY strain male mice. Acute toxicity of OCT A was reduced by simultaneous administration of phenylalanine or by pretreatment with phenobarbital (PB) for 1 week and the LD50 increased to 1.5-2.0 times control. Chromatographic analyses of OCT A and the metabolite, OCT alpha, extracted from urine and bile after administration of OCT A, indicated that amounts of OCT A and OCT alpha decreased in the urine and increased in the bile of PB-pretreated mice, suggesting that a change in metabolism of OCT A could cause the decrease in the toxicity of OCT A in PB-pretreated mice.

Animals↗
PubMed1982

Inhibitory effect of leptophos on carboxylesterase (isocarboxazid amidase) in rat liver.

The organophosphate insecticide, leptophos, inhibited rat liver isocarboxazid amidase (ISOCase) activity to 20% of control at 5.0 mg/kg l h after administration, but at this dose brain cholinesterase (ChE) activity was not affected. The activity of ISOCase decreased to 29 and 0% of control 24 h after treatment with leptophos at doses of 2.5 and 5.0 mg/kg, respectively. With repeated administration of leptophos at a dose of 1 mg/kg for 10 days, ISOCase activity decreased to 34% of control on day 1 and the inhibition increased to 85% on day 10 without inhibition of brain ChE activity. After cessation of three successive daily doses (1 mg/kg/day), the ISOCase activity was gradually restored near to control levels in 8 days. Pretreatment with carboxylesterase inhibitors, triorthocresylphosphate (TOCP) and bis-p-nitrophenylphosphate (BNPP), potentiated the inhibition of brain ChE by leptophos, suggesting that ISOCase might take a role in leptophos detoxification.

Animals↗
PubMed1982

Dual effects of tetrachlorvinphos on procaine toxicity and procainesterase activity in rats.

The effect of tetrachlorvinphos (TCVP) on liver procainesterase (PROCase) and procaine toxicity was studied in rats. TCVP is an organophosphate with an inducible effect on drug metabolizing enzymes. A single oral dose of 500 mg/kg of TCVP caused a remarkable decrease in PROCase (40% of control) 24 hr later and increased the motality after injection of procaine (250 mg/kg, i.p.) from 54% to 87%. Conversely, it was observed that PROCase elevated to 140% of the control and mortality decreased from 54% to 25% on day 3. With repeated administration of TCVP (500 mg/kg/day) for 5 days, the PROCase activity that was inhibited on day 1 was gradually restored to normal levels by 5 days and the mortality altered to 25%. The inducible effect on PROCase was examined using desmethyl-TCVP, a metabolite of TCVP without inhibitory effect on the enzyme; PROCase activity was enhanced to 1.6-fold of the control and procaine concentration in the brain was reduced to 30% of the control, accompanied with no death of rats after procaine injection. Electrophoresis of the solubilized liver microsomal fraction confirmed the inducible effect of TCVP on PROCase; microsomal protein from the TCVP-treated rat was more deeply stained than that from the control, and the PROCase activity of two anodic bands increased in the TCVP-treated microsomes. These results indicate that TCVP has a dual action on PROCase, inducible and inhibitory, and that the direct inhibitory effect of TCVP might mask the increased amount of the enzyme induced by repeated administration of TCVP. The dual effect of TCVP on PROCase would cause the change in procaine toxicity.

Animals↗
PubMed1981

Role of brain monoamine systems in the jumping behavior induced in rats by the combination of harmine and apomorphine.

The role of brain monoamine systems in the jumping behavior induced by the combination of harmine and apomorphine was studied by using a MT pick-up to assess jumping behavior in rats. The jumping induced by the combination of harmine 10 mg/kg and apomorphine 2 mg/kg was enhanced by pretreatment with p-chlorophenylalanine, methysergide and by treatment with clonidine, while, it was reduced by pretreatment with 5-hydroxytryptophan, haloperidol, perphenazine, atropine and pilocarpine. The combination of harmaline or harmane and apomorphine also induced jumping with the aid of p-chlorophenylalanine. The combination of benserazide, L-DOPA and harmine induced jumping similar to that induced by harmine and apomorphine. Despite pretreatment with p-chlorophenylalanine the combination of apomorphine and benzylhydrazine, iproniazid, tranylcypromine or pargyline failed to induce jumping. These results suggest that this jumping behavior is induced not by the monoamine oxidase inhibitory effect of harmine but probably by the specific central action of harmine and on condition that the dopaminergic system is activated. The activation of this system appears to be essential, the noradrenergic system plays a facilitatory role, the serotonergic system an inhibitory role and the cholinergic system probably a specific role.

Alkaloids↗
PubMed1980

Effects of field stimulation on cholinergic fibers of the pelvic region in the isolated guinea pig ureter.

Electrical activities have been recorded in a preparation consisting of the pelvic region and the upper ureter of the guinea pig. Train field stimulation of the pelvic region evoked a train of nerve action potentials followed by a multiphasic smooth muscle action potential after a latency of about 2.5--8.0 sec. This smooth muscle response was abolished by tetrodotoxin and dibucaine, and also by cholinergic blocking agents. The response was furthermore, inhibited by decreasing Ca/4 concentration and increasing Mg/+ concentration in Tyrode solution. This is therefore considered to be the response synaptically evoked by cholinergic fibers in the pelvic region. Mechanical activities have been investigated on the same preparations by the Magnus method. Acetylcholine (10(-7)--10(-4) g/ml) produced a group of twitch responses which were antagonized by cholinergic blocking agents. The responsiveness of the preparations to acetylcholine was markedly decreased by removal of the pelvic region. Cholinesterase activities in the calyx-pelvis and upper ureter have been estimated by the biochemical method. A preparation consisting of calyx-pelvis exhibited twice the enzyme activity as compared with the upper ureter. These results suggesteds that there is a cholinergic innervation in the pelvic region of the guinea pig ureter which also takes part in control of the ureteric activity.

Acetylcholine↗
PubMed1976

[Pharmacological analysis of effects of perimetazine on isolated smooth muscle].

Effects of perimetazine on the motility of the isolated smooth muscle of guinea pig (ileum, taenia coli, uterus, vas deferens and trachea) and the ileum of rabbit were studied. The results obtained are as follows: Perimetazine showed a specific antihistamine, antiadrenaline and antiserotonin action. Moreover, antiacetylcholine and anti-BaC12 actions were observed with high doses of perimetazine as well as chlorpromazine and such actions were attributed to the nonspecific direct action on the smooth muscle. Both the spontaneous movement and the tonus of guinea pig taenia coli were also inhibited by a high concentration of perimetazine. The spontaneous membrane action potentials of the taenia coli recorded by the use of the sucrose-gap method were inhibited by a high concentration of perimetazine both in frequency and in amplitude with relaxation of the tonus. The action potentials were abolished however and change in the resting membrane level was not clearly observed.

Acetylcholine↗