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Biomedical subjects

R Takada

Publications and source records attributed to R Takada.

52 records · Page 3Linked to original sources
PubMed1992

Transcription factor TFIID induces DNA bending upon binding to the TATA element.

The TATA box-binding factor TFIID plays a primary role in the process of transcription initiation by RNA polymerase II and its regulation by various gene-specific factors. Here we employ a permuted binding site/gel retardation assay with recombinant yeast and human TFIID to show that this factor induces DNA bending around the TATA element. These results are consistent with the presence of G + C-rich sequence elements flanking the consensus TATA element and led to the recently confirmed suggestion that TFIID interacts with the TATA element via the minor groove. They also raise the possibility that TFIID-induced bending might facilitate promoter interactions of other general factors in the preinitiation complex or interactions between general transcription factors and regulatory factors bound at upstream sites.

Base Sequence↗
PubMed1991

Mouse DNA primase plays the principal role in determination of permissiveness for polyomavirus DNA replication.

We have investigated the species-specific replication of polyomavirus DNA in the cell-free system that was established previously (Y. Murakami, T. Eki, M. Yamada, C. Prives, and J. Hurwitz, Proc. Natl. Acad. Sci. USA 83:6347-6351, 1986). Extracts from various species of cells supported polyomavirus DNA replication in a species-specific manner that was consistent with the host range specificity of polyomavirus; extracts prepared from mouse and hamster cells were active, whereas extracts prepared from human, monkey, and insect cells were inactive. The addition of DNA polymerase alpha-primase purified from mouse cells induced the replication of polyomavirus DNA in a cell-free system containing polyomavirus large tumor antigen and nonpermissive cell extracts, such as human and insect cell extracts. Isolated mouse DNA primase alone also induced polyomavirus DNA replication in human cell extracts but not in insect cell extracts, indicating that mouse DNA primase plays the principal role in determining permissiveness for polyomavirus DNA replication.

Animals↗
PubMed1990

Repressive effect of the nef cDNA of human immunodeficiency virus type 1 on the promoter activity of the viral long terminal repeat.

The nef gene product of human immunodeficiency virus type 1 (HIV-1) has been implicated as a negative factor for viral replication and is suspected to play an important role in the maintenance of viral latency. However, there seems to be evidence both for and against the negative effect of nef gene product. In the present report, we reevaluated the function of the nef gene by means of transient CAT assays with two human T cell lines. In most of the experiments, carefully controlled triplicate studies were carried out. We observed that not only the nef-expression plasmid, but also an effector plasmid containing the nef cDNA sequence in a reverse orientation, not expressing the Nef protein, showed a similar extent of repression of the HIV-1 promoter activity. We also examined the repressive effect of the nef cDNA with deletion mutants of HIV-1 long terminal repeat and heterologous promoters. The results led us to conclude that the apparent "repressor"-like action of the nef cDNA itself could be explained by competition for certain transcription factors required for HIV-1 gene expression by identical sequences also present in the nef cDNA.

Binding, Competitive↗
PubMed1987

Effect of thromboxane synthetase inhibitors on yohimbine-induced norepinephrine release in the circulation.

The role of thromboxane on norepinephrine release mediated by the presynaptic alphareceptor is studied in conscious rabbits. Intravenous administration of yohimbine, a preferential alpha-2 receptor antagonist increases mean arterial pressure (MBP) by 10 to 15%; the plasma norepinephrine concentration by 71 to 125%. OKY-046, a specific thromboxane synthetase inhibitor, fail to affect the baseline levels as well as yohimbine-induced increases in the MBP and plasma norepinephrine. Yohimbine administration increased plasma renin activity by 27 to 41% which are not affected by OKY administration. These results indicate that the thromboxane system does not affect the norepinephrine release from the nerve terminals by the presynaptic receptor-mediated mechanism. The effect of thromboxane on the renin release is minor and the thromboxane system per se may not play an important role for the renal renin regulation.

Acrylates↗
PubMed1980

Studies on protein binding of antibiotics. I. Effect of cefazolin on protein binding and pharmacokinetics of cefoperazone.

The effect of cefazolin (CEZ) on the protein binding and the pharmacokinetics of cefoperazone (T-1551) was investigated. For the simultaneous determination of T-1551 and CEZ, high pressure liquid chromatography (HPLC) was used. The extent of protein binding, the number of binding sites and the association constant to human serum albumin were 90.4%, 0.87 and 2.16 X 10(4) in T-1551, and 89.2%, 0.78 and 2.46 X 10(4) in CEZ, respectively. T-1551 and CEZ appeared to bind to the same site on the protein, since each drug competitively inhibited the binding of the other to serum protein. The mode of the binding of T-1551 to serum protein was similar to that of CEZ. When T-1551 and CEZ were co-administered, the serum level of T-1551 was lower than that with the single administration, while, urinary excretion was higher. These results suggested that the concomitantly administered drugs influenced one another's binding to serum protein in vivo and subsequently an increase in the concentration of the unbound drug in the serum made the drug available for glomerular filtration. It seemed that the high protein binding of T-1551 to serum was an important factor affecting its pharmacokinetics.

Animals↗
PubMedDate not supplied

Effect of ethanol on hippocampal GABA receptors in the rat brain.

The effect of ethanol on GABA receptors was studied in hippocampal slices and membrane preparations of the rat brain. In slice preparation, ethanol enhanced the GABA inhibition of the population spikes evoked in CA 1 pyramidal cells by Schaffer collateral stimulation. The effect of ethanol was dose-dependent being observed with minimal concentration of 70 mM. In 3H-GABA binding experiments, ethanol enhanced the binding to fresh membranes with no change in the affinity. Maximal stimulation was observed at ethanol concentration of 70 mM. In hippocampal slices or membrane preparations obtained from ethanol- or barbital-administered rats chronically, ethanol failed to enhance GABA function. Thus, the present study demonstrated the involvement of GABA in central effect of ethanol. Also suggested in GABA was the involvement in the development of cross-tolerance between ethanol and barbiturates.

Action Potentials↗
PubMedDate not supplied

Multifocal electroretinograms in patients with branch retinal artery occlusion.

PURPOSE: We recorded multifocal electroretinograms (M-ERG) in patients with branch retinal artery occlusion (BRAO) and compared the waveforms in the area of retinal artery occlusion with those in the normal area, to evaluate the influence of the damage to the inner retina shown by M-ERG responses. METHODS: Three patients who had normal visual acuity and visual field loss of more than one quadrant due to BRAO were examined. The central 50 degrees of ocular fundus was stimulated through dilated pupils by an array of 103 hexagonal elements for 4 minutes. The waveforms of the first order and second order kernel responses of M-ERG in the area of the retinal artery occlusion were compared with those of the vertically symmetrical, normally perfused area of the same eye. RESULTS: The amplitude of the averaged tracing decreased in the first negative wave (N1), first positive wave (P1), and second negative wave (N2) in the first order kernel responses in the area of retinal artery occlusion in comparison with the normally perfused area. Furthermore, prolongation of latency was noted for N1, P1, and N2 in the same area. Second order kernel responses were not detected in the area of the retinal artery occlusion. CONCLUSIONS: The damage to the inner retina affected parts of N1, P1, and N2 of the first order kernel responses, with N2 being the most seriously affected. Furthermore, second order kernel responses clearly reflected the condition of the inner retina.

Adolescent↗
PubMedDate not supplied

Coordinate induction of peroxisomal acyl-CoA oxidase and UCP-3 by dietary fish oil: a mechanism for decreased body fat deposition.

Rats fed dietary fats rich in 20- and 22-carbon polyenoic fatty acids deposit less fat and expend more energy at rest than rats fed other types of fats. We hypothesized that this decrease in energetic efficiency was the product of: (a) enhanced peroxisomal fatty acid oxidation and/or (b) the up-regulation of genes encoding proteins that were involved with enhanced heat production, i.e. mitochondrial uncoupling proteins (UCP-2, UCP-3) and peroxisomal fatty acid oxidation proteins. Two groups of male Fisher 344 rats 3-4 week old (n=5 per group) were pair fed for 6 weeks a diet containing 40% of its energy fat derived from either fish oil or corn oil. Epididymal fat pads from rats fed the fish oil diet weighed 25% (P < 0.05) less than those found in rats fed corn oil. The decrease in fat deposition associated with fish oil ingestion was accompanied by a significant increase in the abundance of skeletal muscle UCP-3 mRNA. The level of UCP-2 mRNA skeletal muscle was unaffected by the type of dietary oil, but the abundance of UCP-2 mRNA in the liver and heart were significantly lower (P < 0.05) in rats fed fish oil than in rats fed corn oil. In addition to inducing UCP-3 expression, dietary fish oil induced peroxisomal acyl-CoA oxidase gene expression 2-3 fold in liver, skeletal muscle and heart. These data support the hypothesis that dietary fish oil reduces fat deposition by increasing the expression of mitochondrial uncoupling proteins and increasing fatty acid oxidation by the less efficient peroxisomal pathway.

Acyl-CoA Oxidase↗