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Biomedical subjects

T Saitoh

Publications and source records attributed to T Saitoh.

At least 397 records · Page 22Linked to original sources
PubMed1988

Studies on the toxicity of 1-methyl-4-phenylpyridinium ion (MPP+) against mitochondria of mouse brain.

Effects of 1-methyl-4-phenylpyridinium ion (MPP+) on cellular respiration were studied using mitochondria prepared from mouse brains. State 3 and state 4 respiration supported by glutamate plus malate or pyruvate plus malate were significantly inhibited by 0.05 mM MPP+. On the other hand, respirations supported by succinate or alpha-glycerophosphate were not inhibited at all. Activity of mitochondrial NADH-ubiquinone oxidoreductase was significantly inhibited by MPP+. This inhibition was markedly potentiated by preincubating mitochondria with MPP+ together with glutamate plus malate. The latter observation suggested accumulation of MPP+ within the mitochondria during preincubation. When mitochondria were pretreated with an uncoupling agent such as carbonylcyanide m-chlorophenylhydrazone (CCCP) or dinitrophenol, MPP+-induced inhibition of state 3 respiration or of activity of complex I could no longer be seen. A potassium ionophore, valinomycin, showed a similar effect. Adenosine triphosphate (ATP) synthesis was also inhibited by MPP+. Among the NAD+-linked dehydrogenases in the tricarboxylic acid cycle, alpha-ketoglutarate dehydrogenase complex was significantly inhibited by MPP+. This inhibition was reversible and competitive with NAD+. Energy crisis appears to be one of the most important mechanisms of neuronal degeneration in MPTP-induced parkinsonism. Biochemical mechanisms underlying MPP+-induced inhibition of mitochondrial respiration were discussed.

1-Methyl-4-phenylpyridinium↗
PubMed1988

Suppression of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neurotoxicity in mouse brain by piroheptine and trihexyphenidyl.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces a parkinsonian state in monkeys and humans and a marked 3,4-dihydroxyphenylethylamine (dopamine) depletion in mouse striatum. In this study, we found that pretreatment with 3-(10,11,-dihydro-5H-dibenzo-[a,d]-cycloheptan-5-ylidene)-1-ethyl- 2- methylpyrrolidine (piroheptine), an anticholinergic drug which also inhibits dopamine uptake completely prevented loss of striatal dopamine in MPTP-treated mice. Trihexyphenidyl partially protected against the neurotoxicity of MPTP. However, clomipramine, a selective 5-hydroxytryptamine uptake inhibitor, did not prevent the loss of striatal dopamine. Piroheptine is another agent which was found to prevent MPTP neurotoxicity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1988

Hepatic lesions induced by graft-versus-host reaction across MHC class II antigens: an implication for animal model of primary biliary cirrhosis.

To induce graft-versus-host reaction (GVHR), C57B1/6 (B6) spleen cells were injected into (B6 x bm1)F1, (B6 x bm12)F1, and (bm1 x bm12)F1 mice. Since the strains bm1 and bm12 are mutant at the H-2Kb and I-Ab regions of major histocompatibility complex (MHC), respectively, we can assess MHC class I- or class II-different GVHR. As reported earlier, immunological perturbations assessed by the number of immunoglobulin-producing cells and immune complex deposition in renal glomeruli were demonstrated in MHC class II-different GVHR. A conspicuous finding in this report is that epithelioid granuloma formation was observed in the portal area and around the central vein of liver of (B6 x bm12)F1 mice injected with B6 spleen cells. The epithelioid granuloma formation was not observed in (B6 x bm1)F1 nor (bm1 x bm12)F1 recipient mice. Degenerative changes resembling chronic nonsuppurative destructive cholangitis in primary biliary cirrhosis were also observed in the bile duct epithelium in (B6 x bm12)F1 and (bm1 x bm12)F1 mice. These lesions were already obvious at the 2 week postinjection of donor cells and were continuously observed up to 10 weeks when immunological perturbations subsided. Thus, class II-disparate GVHR in this experimental system might provide a novel animal model of protracted disease, primary biliary cirrhosis.

Animals↗
PubMed1988

Increased Mr 60,000 protein phosphorylation is correlated with neocortical neurofibrillary tangles in Alzheimer's disease.

Increased Mr 60,000 protein phosphorylation has been found in the cytosol fraction of brain tissue from Alzheimer's disease patients. A correlation between this biochemical change and the morphologic abnormalities found in Alzheimer's disease was sought. Three neuropathologic features were studied: neurofibrillary tangles and neuritic plaques, findings characteristic of Alzheimer's disease, and gliosis, a non-specific change. The number of tangles correlated well with the extent of Mr 60,000 protein phosphorylation (p less than 0.001); but the number of plaques did not. To investigate the possibility that gliosis causes the increased Mr 60,000 protein phosphorylation, cases of Pick's disease and multi-infarct dementia were also studied. The levels of Mr 60,000 protein phosphorylation in these cases were comparable to those seen in normal controls. These findings suggest that the increased Mr 60,000 protein phosphorylation is closely related to diseased, tangle-bearing neurons and is not directly related to neuritic plaque formation or secondary gliosis.

Alzheimer Disease↗
PubMed1988

Alz-50, ubiquitin and tau immunoreactivity of neurofibrillary tangles, Pick bodies and Lewy bodies.

Immunocytochemical and quantitative immunochemical techniques were used to study the expression of Alz-50 antigen, ubiquitin and Tau in neurologic disorders characterized by the formation of filamentous neuronal inclusions. Alz-50, anti-ubiquitin and Tau-1 immunostained the intraneuronal neurofibrillary tangles and the neuritic component of plaques, both in Alzheimer's disease and in the brains of patients without dementia, but extraneuronal tangles were largely unstained. These antibodies also reacted with Pick bodies, and with the neurofibrillary tangles of Kufs' disease and Guam Parkinsonism-dementia. In sections from the brain of a patient with progressive supranuclear palsy, virtually all of the tangles were immunostained with Tau-1 but only a few with Alz-50 or anti-ubiquitin. Anti-ubiquitin also labelled Lewy bodies and the inclusions of granulovacuolar degeneration. Quantitative analysis of immunoblots of homogenized frontal cortex showed significantly more Alz-50 antigen in the brains of patients with Alzheimer's and Pick's disease than in controls. The level of this antigen was increased both in the crude homogenates and in the cytosolic fraction. Ubiquitin immunoreactivity was increased only in the brains of patients with Alzheimer's disease and then only in the crude homogenates. The finding that antigenic determinants for Alz-50, anti-ubiquitin and Tau-1 are shared by several filamentous neuronal inclusions occurring in diverse neurologic disorders may reflect common metabolic defects underlying the formation of these inclusions, or common metabolic responses to their presence.

Adult↗
PubMed1988

Activation of synthesis of hexacosenoic acid by sulfhydryl reagents in swine cerebral microsomes.

The elongation of icosenoyl-CoA (20:1-CoA) in swine cerebral microsomes resulted in the synthesis of docosenoic acid (22:1) and tetracosenoic acid (24:1), but the synthesis of hexacosenoic acid (26:1) was negligible. In contrast, in the presence of sulfhydryl reagents (0.6 mM N-ethylmaleimide [NEM] or 0.3 mM p-chloromercuriphenylsulfonic acid [PCMPS]) the synthesis of 26:1 was remarkably enhanced. We suggest that the synthesis of 26:1 from 20:1-CoA was more enhanced by NEM or PCMPS as a result of activation of the condensation step in the elongation of 24:1 (intermediate) to 26:1.

4-Chloromercuribenzenesulfonate↗
PubMed1988

Effect of oleic acid on mitochondrial cytochrome c oxidase activity.

Both Km and Vmax values of cytochrome c oxidase for cytochrome c were elevated in oleic acid-incorporated mitochondria, whereas the amount of oleic acid incorporated into submitochondrial particles was smaller than that into mitochondria and the fatty acid had little effect on the enzyme activity. The degree of change in the bulk membrane fluidity was, however, almost the same in mitochondria and submitochondrial particles. Solubilized cytochrome c oxidase was insensitive to the effect of oleic acid. Oleic acid may act as a modifier of the interaction between cytochrome c oxidase and membrane lipids.

Animals↗
PubMed1988

[Character of a human cholangiocarcinoma CHGS, serially transplanted to nude mice].

With the progress in surgical technique, remarkable improvement has been noted in the treatment of bile duct carcinoma. However, in the cholangiocarcinoma at porta hepatis or in the progressive carcinoma, many cases have been reported, for which radical surgery is not achievable. In recent years, discussion has been concentrated on the necessity of multidisciplinary treatment for the bile duct carcinoma, but fundamental research has not been done enough. In the present paper, the process for obtaining CHGS strain implantable to the nude mouse derived from a human cholangiocarcinoma as achieved in our department was discussed, and its biological characteristics-above all, the sensitivity to carcinostatic agents and to radiation-were evaluated. The doubling time of CHGS strain is 6.2 days, and nude mice showed stable proliferation with 100% viability. Histologically, it was tubular adenocarcinoma similar to the primary tumor. It has high mucin producing ability, and necrosis hardly occurs. The search for DNA ploidy by flow cytometry revealed the presence of two types of cells: The cells of diploid pattern and aneuploid pattern. In the tests to determine the sensitivity of CHGS strains to carcinostatic in MMC, ADR, 5-FU and CDDP groups, and to radiation according to the Battele Columbus Laboratories Protocol, the regression of tumor was observed in MMC, ADR, CDDP groups. Particularly, in MMC group, some of the tumors had disappeared. Recurrence was also noted in this case, but the survival, was still recognized nearly four years after the operation through the postoperative auxiliary therapy. This was regarded as the case, where the sensitivity test using the nude mouse implantable tumor strain was reflected well in clinical application.

Adenoma, Bile Duct↗
PubMed1987

Inhibition of ATP synthesis by 1-methyl-4-phenylpyridinium ion (MPP+) in isolated mitochondria from mouse brains.

Effect of 1-methyl-4-phenylpyridinium ion (MPP+) on adenosine triphosphate (ATP) synthesis was studied using isolated mitochondrial preparations from mouse brains. Oxidation of glutamate + malate in the mitochondria estimated by polarography was significantly inhibited by MPP+, and synthesis of ATP was inhibited to approximately 9% of that of control by 0.06 mM of MPP+. Oxidation of alpha-glycerophosphate and succinate was not inhibited, and ATP was synthesized normally. Energy crisis appears to be one of the most important mechanisms of neuronal degeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced experimental parkinsonism.

1-Methyl-4-phenylpyridinium↗
PubMed1987

Inhibition of mitochondrial alpha-ketoglutarate dehydrogenase by 1-methyl-4-phenylpyridinium ion.

Effects of 1-methyl-4-phenylpyridinium ion (MPP+) on the activities of NAD+- or NADP+-linked dehydrogenases in the TCA cycle were studied using mitochondria prepared from mouse brains. Activities of NAD+- and NADP+-linked isocitrate dehydrogenases, NADH- and NADPH-linked glutamate dehydrogenases, and malate dehydrogenase were little affected by 2 mM of MPP+. However, alpha-ketoglutarate dehydrogenase activity was significantly inhibited by MPP+. Kinetic analysis revealed a competitive type of inhibition. Inhibition of alpha-ketoglutarate dehydrogenase may be one of the important mechanisms of MPP+-induced inhibition of mitochondrial respiration, and of neuronal degeneration.

1-Methyl-4-phenylpyridinium↗
PubMed1987

Inhibition of mitochondrial NADH-ubiquinone oxidoreductase activity by 1-methyl-4-phenylpyridinium ion.

Effect of 1-methyl-4-phenylpyridinium ion (MPP+) on the activity of NADH-ubiquinone oxidoreductase was studied using mitochondria prepared from rat brains. At first, inhibition of oxygen consumption by MPP+ with pyruvate + malate or glutamate + malate as substrates was confirmed polarographically using a Clark-type oxygen electrode. Then, activity of NADH-ubiquinone oxidoreductase in the same samples used in polarography was assayed. Incubation of mitochondria with 0.05 mM of MPP+ together with glutamate, malate and ADP resulted in approximately 50% inhibition of NADH-ubiquinone oxidoreductase activity. Significance of the results was discussed with respect to the mechanism of neuronal degeneration by MPP+.

1-Methyl-4-phenylpyridinium↗
PubMed1987

Long-term effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on striatal dopamine content in young and mature mice.

Long-term effects of MPTP on striatal dopamine (DA) content and the influence of aging on the recovery were investigated in mice. Male C57BL/6J mice, young (2-month-old) and mature (10-month-old), were used. Two different dosage schedules of MPTP, i.e., 4 doses subcutaneous injections of 20 mg/kg each, and 4 doses subcutaneous injections of 40 mg/kg each, were given to both young and mature mice at 12-h intervals. Assays of striatal DA and 3,4-dihydroxyphenylacetic acid (DOPAC) content were performed 1 week, 1 month, 2 months, and 3 months after the last injection of MPTP. MPTP produced a marked reduction (-75% to -80%) of striatal DA content in both young and mature mice 1 week after the last injection of MPTP. In young mice, the striatal DA content showed a partial recovery in the subsequent stages studied. In contrast, no apparent recovery occurred in mature mice until as long as 3 months after the last injection. The results suggest that mice have a capacity for partial recovery of the striatal DA contents which was depleted by MPTP, and this capacity for recovery appears to be impaired in mature mice.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1987

Neurophysiological analysis of ataxia in capsular ataxic hemiparesis.

A quantitative analysis of ataxia and the readiness potential were studied in four cases of ataxic hemiparesis resulting from a small infarct in the posterior limb of the internal capsule. The ataxia appeared to be the result of involvement of the corticopontine tract originating from the precentral region (areas 4 and 6) at this level. The voluntary movements of the affected limbs were characterized by slowness and irregularity similar to those seen in cerebellar ataxia. The weakness per se was not such that it could account for the ataxia. The dentato-rubro-thalamo-cortical system did not appear to be significantly involved on the basis of normal readiness potentials.

Ataxia↗
PubMed1987

Photoaffinity labeling of adenylate cyclase-linked serotonin receptors in Aplysia neurons.

Serotonin stimulated adenylate cyclase in Aplysia neurons with a Kact of 0.7 microM. Under the same conditions, 1-[2-(4-aminophenyl)ethyl]4-(3-trifluoromethylphenyl)piperazine stimulated adenylate cyclase with a Kact of 20 microM. The azido derivative of this compound, 1-[2-(4-azidophenyl)ethyl]4-(3-trifluoromethylphenyl)piperazine, or of serotonin, (4-amino, 3-nitrophenylazido-serotonin), also stimulated the cyclase in the dark, but with lower efficiency (Kact greater than 10(-4) M). Irradiation of the membranes in the presence of 100 microM 1-[2-(4-azidophenyl)ethyl]4-(3-trifluoromethylphenyl)piperazine abolished 75% of the cyclase activity stimulated by 5 microM serotonin. Under the same conditions, 100 microM 4-amino, 3-nitrophenylazido-serotonin did not inhibit serotonin-stimulated adenylate cyclase activity. When [3H]1-[2-(4-azidophenyl)ethyl]4-(3-trifluoromethylphenyl)piperazine (20 microM) was irradiated with membranes for 5 min at 4 degrees C, a dozen peptides were labeled, as revealed by a fluorogram of sodium dodecyl sulfate-polyacrylamide gels. Among them, the labeling of five polypeptides (molecular weights of 45,000, 55,000, 63,000, 80,000, and 94,000) was protected by the presence of 0.2 mM serotonin during photolysis. These peptides may be related to serotonin receptors.

Adenylyl Cyclases↗
PubMed1987

Control of the amount of a 34K Ca2+-dependent membrane binding protein (calelectrin).

A 34,000-Da Ca2+-dependent membrane binding protein (34K) was purified from the electric organ of Torpedo marmorata. Specific antibodies to this protein were raised in rabbits, and radioimmunoassay was used to test the presence of 34K in different tissues of Torpedo as well as in other species. In Torpedo, not only the electric organ, but also the muscle, the spleen, and the liver contained 34K antigenicity. Blood was the only tissue in which 34K antigenicity could not be detected. A 34,000-Da protein (Mr 32,000-36,000) that bound to Torpedo acetylcholine receptor (AChR)-rich membrane in a Ca2+-dependent manner and cross-reacted with anti-(Torpedo 34K) antibody was found in chicken muscle, rat muscle, marine mollusk (Aplysia) central ganglia, and rat and human brain. The concentration of 34K seems to be controlled during development. Chicken 34K antigenicity reached a peak on embryonic day 18, declined, and finally gained its maximal value after synaptic maturation. The AChR concentration in chicken legs also changed in the course of muscle development, although it showed a peak on embryonic day 12 and then declined rapidly. In rat diaphragm, both AChRs and 34K were concentrated in the subsynaptic region. Transection of the phrenic nerve induced the synthesis of AChRs in postsynaptic muscle fibers. This operation did not increase the amount of 34K in the diaphragm. On the contrary, it reduced 34K content to the extrasynaptic level. Taken together, these results support the idea that 34K is an important structural constituent of mature synapses, an observation suggesting the involvement of this protein in the function of the mature synapse.

Animals↗