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D T Masuoka

Publications and source records attributed to D T Masuoka.

At least 19 recordsLinked to original sources
PubMed1983

Further studies on age-related unusual catecholamine structures in brain.

The occurrence of large, intensely fluorescent (LIF) catecholamine-containing spots in the brains of mice and rats has been studied by fluorescence microscopy. LIF spots in C57BL/6J mice increased in number progressively with age. Apparent differences between sexes in the number of spots were not significant at any age. A greater number of LIF spots were present in older mice and rats of different strains indicating that LIF spot formation is neither strain nor species specific. Long-term feeding of antioxidants (ascorbic acid, alpha-tocopherol, and beta-mercaptoethylamine) to C57BL/6J mice did not alter significantly the number of LIF spots, suggesting that age-related LIF spots are formed by a mechanism other than endogenous free radical damage.

Age Factors↗
PubMed1982

[3H]Dopamine release by d-amphetamine from striatal synaptosomes of reserpinized rats.

The injection of reserpine, 5 mg/kg i.p. (ipRes), the regimen employed by a majority of investigators, results in synaptosomal and vesicular preparations which are incompletely reserpinized as determined by [3H]dopamine ([3H]DA) accumulation. Reserpine administered by the subcutaneous route, 5 mg/kg (scRes), appears to produce complete reserpinization. Release of [3H]DA by d-amphetamine (Amph) was observed from striatal synaptosomes prepared both from normal rats and those pretreated with reserpine intraperitoneally but not from those injected subcutaneously. In the more completely reserpinized scRes synaptosomes, so little [3H]DA had accumulated that release by Amph was not measurable, indicating that if a labile, reserpine-resistant, extravesicular DA storage pool releasable by Amph is present under these conditions, it must be extremely small. In scRes monoamine oxidase (MAO)-inhibited preparations, Amph released preloaded [3H]DA located in the cytosol in the absence of functional vesicles. Although chromatographic analysis of the superfusate from ipRes striatal synaptosomes showed that significant amounts of preloaded [3H]DA were released by Amph, the level of dihydroxyphenylacetic acid was not increased over controls, indicating that Amph releases only DA and not its metabolite and is also acting as a MAO inhibitor. No [3H]DA could be released by Amph from superfused hyposmotically shocked normal or ipRes synaptosomes, suggesting that an intact membrane is required for Amph-induced release.

Animals↗
PubMed1979

Aging and unusual catecholamine-containing structures in the mouse brain.

Brains of C57BL/6J mice, aged 4, 8 and 20--29 months, were examined by the Falck-Hillarp histochemical fluorescence technique. Numerous large, intensely fluorescent green to yellow-green spots (LIFS) were observed in the brains of senescent mice. LIFS were generally round to ovoid in shape and ranged in size from about 10 micrometer to about 30 micrometer. Histochemical and pharmacological procedures and spectral analysis indicated that the formaldehyde-induced fluorescence of the LIFS was due to the presence of catecholamines (CA) rather than aging pigment. Their distribution in the brain suggests an association with nerve axons or terminals rather than cell bodies. The number of LIFS in the hypothalamus increased progressively during aging. It is proposed that LIFS may represent age-related, unusual CA accumulation in enlargements proximal to axonal or terminal portions undergoing spontaneous degeneration.

Aging↗
PubMed1975

An autoradiographic method of mapping the distribution and density of monoamine neurons in mouse brain.

A combined in vitro uptake and autoradiographic procedure as an important complement to the histochemical fluorescence method is described. Slabs of fresh mouse brain were incubated with 14C-NE, 14C-DA or 14C-5-HT, freeze-dried, and placed against X-ray film for autoradiography, Catecholamine nerve terminals were labeled by in vitro incubation with 14C-NE or 14C-DA. Dopaminergic terminals were labeled by 14C-NE incubation preceded by desipramine (to block uptake into NE terminals). With 14C-5-HT incubation, the uptake pattern indicated the possibility that 5-HT nerve terminals were being labeled. Advantages of this method are that it allows the visualization of overall density and distribution of selected monoamine nerve terminals or uptake sites of other putative neurotransmitters in whole coronal or sagittal sections, so that data are obtained from many areas of brain or spinal cord rather than in only those areas preselected for microscopic viewing.

Animals↗