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Biomedical subjects

S Uchida

Publications and source records attributed to S Uchida.

At least 577 records · Page 32Linked to original sources
PubMed1978

Muscarinic cholinergic receptors in mammalian brain: differences between bindings of acetylcholine and atropine.

Studies were made on the bindings of [3H]-acetylcholine and [3H]-atropine to synaptic plasma membranes from rat brain. Synaptic plasma membranes have reversible, high affinity binding sites for both ligands, the KD values for ACh and atropine being about 20 nM and 1 nM, respectively. The maximal binding capacities for ACh and atropine, respectively, are 0.8-1.2 pmoles and about 1.5 pmoles/mg protein of synaptic membranes. The specific binding of ACh is almost completely inhibited by oxotremorine and atropine. 5,5'-Dithiobis (2-nitrobenzoic acid) (DTNB) increased the ACh-binding to about 1.5 pmole/mg protein. It also increased the inhibition of atropine-binding by ACh about 10-fold. Marked discrepancies were found in the inhibitions of atropine- and ACh-bindings by muscarinic agonists, but not in the inhibitions by antagonists. These findings support the hypothesis that muscarinic receptors have different sites for agonists and antagonists. The possibility that one receptor can be simultaneously occupied by both an agonist and an antagonist is also discussed.

Acetylcholine↗
PubMed1977

Dopamine receptor blocking activity of sulpiride in the central nervous system.

Effects of sulpiride on the central nervous system were studied in catalepsy induction (I) and antagonism to gnawing behaviour (II) induced by apomorphine and methamphetamine in normal rats, and in antagonism to rotational behaviour (III) induced by apomorphine and methamphetamine in rats with substantia nigra unilaterally lesioned chronically by microinjection of 6-hydroxydopamine. Sulpiride was administered orally and intraventricularly, and the effects of sulpiride were compared to those of haloperidol and chlorpromazine administered through the same routes. In oral administration, sulpiride was almost inactive in (I), and was several hundreds to a thousand times less potent than haloperidol in (II) and (III), while chlorpromazine was 20 to 150 times stronger than sulpiride. In intraventricular administration, sulpiride was almost equipotent to haloperidol in (I), and was equally effective to or 2 to 3 times more effective than halopridol in (III), although several times less in all respects. These findings suggest that sulpiride is essentially a potent inhibitory substance on dopamine receptors in the central nervous system and the rather weak central effects of peripherally given sulpiride are due to poor penetration through the blood brain barrier.

Administration, Oral↗
PubMed1977

Effect of 1-(2-chloroethyl)-3-(beta-D-glucopyranosyl)-1-nitrosourea on experimental tumors.

A newly synthesized water-soluble nitrosourea derivative, 1-(2-chloroethyl)-3-(beta-D-glucopyranosyl)-1-nitrosourea (GANU; NSC-254157) has marked activities against experimental tumors such as lymphoid leukemia L-1210, ascites sarcoma- 180, ascites hepatoma AH-130, and Walker carcinosarcoma-256. A single intraperitoneal injection of the compound is more effective than successive injections on the L-1210 system. An especially interesting point is that both the single intraperitoneal and single oral administrations 2 days after tumor implantation showed a high effectiveness. In addition, growth of the mammary adenocarcinoma transplanted subcutaneously on the back of mice was also considerably suppressed by successive intraperitoneal injections of the compound.

Adenocarcinoma↗
PubMed1976

Bound forms of Ca taken up by the synaptic plasma membrane.

Temperature dependent Ca-binding by the synaptic plasma membrane was increased in the presence of ATP and Mg++. Apparent Km for ATP was about 2.8 X 10(-5) M and optimal concentration of Mg++ was 2 mM in the presence of 2 mM ATP. After preincubation with nonradioactive Ca++, ATP and Mg++ to attain a steady state, addition of 45Ca resulted in remarkable labelling of the membrane, indicating rapid turnover of most of the membrane bound Ca. The presence of oxalate (60 mM) greatly increased Ca up-take on prolonged incubation. The Ca uptake in presence and absence of oxalate had similar substrate specificity and was similarly influenced by various monovalent cations. Furthermore, activities for Ca-uptake in the presence and absence of oxalate could not be separated by sucrose density gradient centrifugation of the synaptic plasma membrane fraction. Accordingly, it was considered that Ca++ in the medium was taken up by surface of the membrane, ATP- and temperature-dependently and then transferred into a cavity where the Ca-oxalate complex is formed.

Adenosine Triphosphate↗
PubMed1976

Induction of papillary ependymomas and insulinomas in the Syrian golden hamster by BK virus, a human papovavirus.

Newborn hamsters were inoculated intracerebrally with BK virus. Between 3 and 6 months after inoculation, they developed papillary ependymoma (8 hamsters, 42%) or functional malignant islet cell tumors of the pancreas (insulinoma, 8 hamsters), or both (1 hamster). Both tumors contained an antigen reactive to SV40 T-antibody, suggesting that at least a part of BK virus genomen has been integrated into the tumor cells. No infectious virus was detected in the extract of these tumors.

Adenoma, Islet Cell↗
PubMed1975

Electron microscopic and electron histochemical studies on embryonal rhabdomyosarcoma of the orbit.

A small number of differentiated tumor cells could be found besides a great number of undifferentiated ones. Abnormal dense granules were found in the nuclei of undifferentiated tumor cells, not in differentiated ones. Non-specific filaments were seen in the cytoplasm of undifferentiated tumor cells. Differentiated tumor cells demonstrated various stages of myofibrillar structures such as A, I, and Z bands, many glycogen granules, mitochondria and a basement membrane. Polyglucose particles synthesized from glycose-1-phosphate by phosphorylase activity were located in the cytoplasmic matrix of undifferentiated and differentiated tumor cells and in the karyolymph of undifferentiated tumor cells. Polyglucose partices increased in number according to the degree of differentiation of tumor cells.

Basement Membrane↗
PubMed1975

Characterization of defective simian virus 40 DNA: comparison between large-plaque and small-plaque types.

We characterized defective DNA molecules of large-plaque and small-plaque SV40 produced and accumulated during serial undiluted passages. The electron microscope heteroduplex method revealed that defective SV40 DNA contains deletions, insertions and substitutions. The majority of the large-plaque defective molecules had a simple deletion. The deletions were heterogeneous in size, and the sites of deletion appeared to be mostly overlapping. The majority of the small-plaque defective molecules had a deletion, and more than half of the deletion molecules also had an insertion at a separate site. The small-plaque SV40 genome appeared to have more sites for deletion to occur than large-plaque SV40, and the deletions have occurred at more than two sites. The change of a local nucleo tide sequence resulting from mutation may be related to the difference between the two plaque types.

Cell Transformation, Neoplastic↗