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R Sato

Publications and source records attributed to R Sato.

At least 379 records · Page 21Linked to original sources
PubMed1983

Parameter estimation of the threshold time function in the neural system.

An algorithm for parameter estimation is presented for the neural system model. Because of its firing mechanism analogous to that of the model based on the first time crossing problem, this problem is solved numerically for our model according to the results of Kostyukov et al. (1981). We propose the algorithm that estimates the parameters of the model considering the equivalence between the probability density function of the 1st crossing time and that of the interspike interval, which is derived from the interspike interval histogram by making use of the spline function technique. The ability of the algorithm is ensured by the application to the simulated interspike interval data. The parameter estimation is carried out also for the practical neural data recorded in the cat's optic tract fibers in both the spontaneous and the stimulated cases. These applications will show the effectiveness of the algorithm in practical cases.

Animals↗
PubMed1983

Light and electron microscopy of the effects of colchicine and vinblastine on maturing rat ameloblasts in vivo.

Both agents caused loss of ruffled membrane and microtubules. Ruffled membrane decreased with time after treatment with vinblastine (4 mg/kg) and almost disappeared 8 h after treatment with either colchicine (4 mg/kg) or vinblastine (4 mg/kg). In vinblastine-treated animals, the number of microtubules were estimated in cross-sections of two regions of both smooth-ended and ruffle-ended ameloblasts; one region was distal and the other juxta-nuclear. In smooth-ended ameloblasts, microtubules of both the distal and juxta-nuclear cytoplasm almost disappeared after 2 h of treatment. In ruffle-ended ameloblasts, microtubules decreased in distal cytoplasm between 2 and 8 h; microtubules in the juxta-nuclear cytoplasm disappeared after 2 h. Both agents caused structural alterations and dislocation of cell organelles. The Golgi apparatus, sometimes separated into two parts, moved towards the proximal cytoplasm and an unusual accumulation of small vesicles was found in the proximal cytoplasm. These findings suggest that formation of ruffled membranes is dependent on microtubular function.

Ameloblasts↗
PubMed1983

Pharmacological characterization of ionophore X537A-induced contractile responses in isolated rabbit taenia coli and aorta.

Pharmacological action of ionophore X537A was studied in taenia coli and aortic strips isolated from rabbit. These isolated smooth muscle preparations contracted by X537A (10(-5)-10(-4) M). A removal of Ca ions from the buffer solution considerably reduced the contraction of taenia coli but not that of aorta. D 600 (methoxyverapamil, 10(-6) M) was without any effect in the contraction of both tissues by X537A (10(-4) M). However, papaverine (10(-4) M) and Aspaminol (1, 1-diphenyl-3-piperidinobutanol hydrochloride, 10(-4) M) inhibited X537A (10(-4) M)-induced contraction markedly in taenia coli but slightly in aorta. Inhibitory effects of these drugs were reversed in taenia coli by increasing Ca ion concentration in buffer solution but not in aorta. X537A (10(-4) M)-induced contraction of aorta was not affected by a pretreatment of rabbit with reserpine and preincubation of the isolated preparations with guanethidine (10(-6) M) or prazosin (10(-7) M). These results suggest that ionophore X537A might produce the contraction through an increase of Ca influx in isolated rabbit taenia coli which are little or not affected by D 600, whereas the contraction of rabbit aorta induced by X537A is mainly due to facilitation of release of Ca sequestered intracellularly.

Animals↗
PubMed1983

Changes in cytosolic androgen receptor after administration of testosterone of androgen-dependent mouse mammary tumor (Shionogi carcinoma) and its sublines of altered androgen dependency.

The effect of testosterone treatment on the cytosolic androgen receptor in an androgen-dependent tumor (Shionogi Carcinoma 115, SC 115) and its sublines of altered hormone-dependency (CS 1, less androgen-dependent, and CS 2, androgen-independent) was examined. In all tumors examined a single, high-affinity binding to 3H-R 1881 was detected in cytosols. The size of the maximum binding sites was in the order SC 115, CS 1 and CS 2. Inhibition experiments revealed that the binding to 3H-R 1881 in cytosols of these tumors was attributable to the androgen receptor. The amount of the androgen receptor in cytosols was decreased at 1 hr after testosterone injection, then replenished gradually towards the pretreatment level. Depletion of the androgen receptor was dependent on the dose of testosterone administered. Multiple injections of testosterone depressed the replenishment of the receptor. Treatment with actinomycin D or cycloheximide did not alter the dynamics of the androgen receptor. Therefore, it was concluded that the depletion and replenishment of the androgen receptor in cytosols of the tumors were caused by receptor recycling. Because a similar pattern of depletion and replenishment of the androgen receptor was also observed in the less androgen-dependent tumors, the growth of tumors was felt to be unrelated to the receptor dynamics.

Animals↗
PubMed1983

Effect of lactose on calcium absorption from the rat small intestine with a non-flushed ligated loop.

To assess the effect of dietary lactose on the utilization of 40Ca and 45Ca, a one-day balance experiment was carried out. The urinary 45Ca excretion and 45Ca deposition in the femur were significantly higher in the 10% lactose diet group. In the second experiment, non-flushed lower small intestine was ligated in situ and calcium absorption was observed shortly after injecting lactose solution into the loop during the postprandial state. The estimated amounts of 40Ca and 45Ca absorbed and of 45Ca deposited in the femur were increased in the presence of lactose in the test solution. These results suggest that dietary lactose stimulates calcium utilization and also increases calcium absorption from the undisturbed small intestine containing digests.

Animals↗
PubMed1982

In vitro synthesis and integration into mitochondria of porin, a major protein of the outer mitochondrial membrane of Saccharomyces cerevisiae.

We have isolated an outer mitochondrial membrane (OMM) fraction from baker's yeast. Saccharomyces cerevisiae, that possesses porin activity and contains a major polypeptide of 29,000 daltons. By analogy to similar data for an OMM fraction from rat liver and mung bean [Zalman, L. S., Nikaido, N. & Kagawa, Y. (1980) J. Biol. Chem. 255, 1771-1774], the 29,000-dalton polypeptide of the isolated yeast OMM fraction has been tentatively identified as porin. Evidence to substantiate this identification was provided by the finding that both the porin activity and the 29,000-dalton polypeptide were entirely resistant when the OMM fraction was exposed to trypsin digestion, with the 29,000-dalton polypeptide being virtually the only polypeptide in the OMM fraction to be unaffected by trypsin digestion. There was no protection when trypsin digestion was carried out in the presence of detergent. Using monospecific antibodies, we have shown that yeast porin is apparently not synthesized as a larger precursor in a cell-free translation system. In vitro-synthesized porin could not be integrated into dog pancreas microsomal vesicles or into an isolated OMM fraction from yeast, either co- or posttranslationally. In vitro-synthesized porin, however, could be integrated posttranslationally into whole isolated mitochondria. This membrane specificity suggests that integration does not proceed by unassisted partitioning. The integration of porin into whole mitochondria occurred with fidelity by the criterion of its resistance to trypsin. Moreover, integration was not inhibited in the presence of the protonophore carbonyl cyanide m-chlorophenyl-hydrazone whereas translocation into the mitochondrial matrix of the in vitro-synthesized gamma subunit of F1-ATPase was inhibited.

Cell-Free System↗
PubMed1982

[Monitoring of the spinal cord function using evoked spinal cord potentials].

Monitoring of the spinal cord function by evoked spinal cord potentials (ESP) has come to be used widely with the establishment of a safe technique using an epidural electrode and the great improvement in medical electronic devices. According to other investigations ESP has been recorded through an electrode placed in the posterior epidural space, it is well known that residual ESP can be actually recorded after transection of the posterior half of the spinal cord and that ESP shows no change after a small transection of the anterior column. If ESP originating from the anterior half of the spinal cord is recorded, it is very useful for monitoring during anterior decompression surgery for myelopathy such as ossification of the posterior longitudinal ligament and cervical spondylosis. The purpose of this report is to analyse ESP originating from the anterior half of the spinal cord experimentally and further investigate the ESP monitoring clinically. Sixty cats were used in this study. ESP recording principally consisted of stimulation to the spinal cord at the level of thoracic or lumbar region and recording of ESP with a monopolar electrode placed in the cervical epidural space. Changes in the ESP after transection and compression of the spinal cord were analysed. Anterior vertebrectomy and laminectomy at C2 and C6 were performed for the purpose of placing an electrode correctly and facilitating transection or compression of the spinal cord. Recording electrodes were placed on both the anterior and posterior surfaces of the dura mater at C2. As the result of this study, it is apparent that there exists the ESP originating from the anterior half of the spinal cord. Such ESPs are more accurately recorded through an anterior placed electrode rather than through that placed posteriorly.

Animals↗
PubMed1981

Involvement of cytochrome b5 and a cyanide-sensitive monooxygenase in the 4-demethylation of 4,4-dimethylzymosterol by yeast microsomes.

According to Ohba et al. (Ohba, M., Sato, R., Yoshida, Y., Nishino, T. and Katsuki, H. (1978) Biochem. Biophys. Res. Commun. 85, 21-27), yeast microsomes catalyze the removal of three methyl groups attached to the C-4 and C-14 positions of [1,7,15,22,26,30-14C]lanosterol (4,4,14 alpha-trimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol) in the presence of NADPH, NAD+ and molecular oxygen, concomitant with the liberation of 14CO2 derived from C-30 (one of the two methyl groups at the C-4 position). In this process the methyl group at the C-14 position is first removed in a cyanide-insensitive reaction and then the two methyl groups at the C-4 position are removed by a cyanide-sensitive enzyme system. In this study it was found that the 14CO2 formation from the 14C-labeled lanosterol was inhibited by antibodies to yeast cytochrome b5 and by palmitoyl-CoA, a substrate of the cytochrome b5-containing fatty acyl-CoA desaturase system of yeast microsomes. However, neither the antibodies nor palmitoyl-CoA inhibited the conversion of lanosterol to 4,4-dimethyl zymosterol (4,4-dimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol). It is concluded that cytochrome b5 and a cyanide-sensitive enzyme are involved in the 4-demethylation of 4,4-dimethylzymosterol, but not the 14 alpha-demethylation of lanosterol, by yeast microsomes. It is suggested that a cyanide-sensitive enzyme acts as the terminal 4-demethylase and cytochrome b5 transfers reducing equivalents from NADPH to the terminal enzyme, as in the case of fatty acyl-CoA desaturation. The cyanide sensitivity of the 4-demethylation was, however, much greater than that of the desaturation.

Antimycin A↗
PubMed1981

Androphilic proteins in the human prostate.

Dihydrotestosterone-binding protein in cytosols from human prostates was different from the R1881- and R5020-binding proteins. The R1881- and R5020-binding proteins in the cytosol were very similar and most of the binding sites for R1881 were capable of binding R5020. However, nuclear extracts showed equal binding to dihydrotestosterone and R1881, but not to R5020, suggesting that there might not be a progestin receptor in the human prostate. Maximum binding sites to dihydrotestosterone, R1881, and R5020 in cytosols were very similar among "normal" and pathological prostates except that dihydrotestosterone binding was higher in "normal" prostates than in the pathological ones. Histochemically, R1881-binding was observed in the epithelial cells and in malignant cells, but not in the stroma.

Androgen-Binding Protein↗
PubMed1981

Covalent binding of polychlorinated biphenyls to proteins by reconstituted monooxygenase system containing cytochrome P-450.

Incubation in the presence of NADPH and molecular oxygen of 14C-labeled polychlorinated biphenyls (PCBs) and two tetrachlorobiphenyl (TCB) isomers with a reconstituted system containing NADPH-cytochrome P-450 reductase and cytochrome P-450, both purified from liver microsomes of phenobarbital(PB)-pretreated rabbits, led to covalent binding of radioactive metabolites of PCBs and TCBs to the protein components of the system. A rabbit liver cytosol fraction added to the system provided more binding sites for the activated metabolites and thus increased the extent of binding markedly. The binding reaction depended absolutely on the reductase, cytochrome P-450 and NADPH, and required dilauroyl phosphatidylcholine and sodium cholate for maximal activity. A further stimulation of the binding was attained by including cytochrome b5 in the reconstituted system. Four forms of cytochrome P-450, purified from liver microsomes of PB- and 3-methylcholanthrene(MC)-treated rabbits and rats, were used to reconstitute the PCB- and TCB-metabolizing systems, and it was found that PB-inducible forms of the cytochrome from both animals were more active than those inducible by MC in catalyzing the PCB- and TCrome P-450, purified from liver microsomes of PB- and 3-methylcholanthrene(MC)-treated rabbits and rats, were used to reconstitute the PCB- and TCB-metabolizing systems, and it was found that PB-inducible forms of the cytochrome from both animals were more active than those inducible by MC in catalyzing the PCB- and TCrome P-450, purified from liver microsomes of PB- and 3-methylcholanthrene(MC)-treated rabbits and rats, were used to reconstitute the PCB- and TCB-metabolizing systems, and it was found that PB-inducible forms of the cytochrome from both animals were more active than those inducible by MC in catalyzing the PCB- and TCB-binding reaction. Sodium dodecyl sulfate(SDS)-polyacrylamide gel electrophoresis indicated that, in the system containing the reductase, cytochrome P-450 and cytochrome b5, PCB metabolites bound to the reductase and cytochrome P-450, but not to cytochrome b5. In the presence of the liver cytosol fraction, the binding took place to many cytosolic proteins in addition to the reductase and cytochrome P-450.

Animals↗