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Biomedical subjects

M Tsuda

Publications and source records attributed to M Tsuda.

At least 505 records · Page 28Linked to original sources
PubMed1986

The effect of ipriflavone (TC-80) on bone resorption in tissue culture.

The fetal long bone culture system developed by Raisz for the assessment of bone resorption was modified to improve the sensitivity, by using radii and ulnae separately, based on the observation of the consistently higher release of 45Ca from the radii than ulnae. Effects of ipriflavone (TC-80), an isoflavonoid derivative currently under clinical trial for its effect on osteoporosis, on bone resorption were examined in this new system. Ipriflavone and its metabolites (5 out of 6) at 10 micrograms/ml or more inhibited basal 45Ca release from bones. The inhibitory effects were still demonstrated in the presence of submaximal concentration of parathyroid hormone (12.5 ng/ml). The effect of ipriflavone on bone resorption was apparently not due to its toxicity on bone cells, since the inhibition was reversible.

Animals↗
PubMed1986

Photoenergetics of octopus rhodopsin. Convergent evolution of biological photon counters?

The enthalpy changes associated with each of the major steps in the photoconversion of octopus rhodopsin have been measured by direct photocalorimetry. Formation of the primary photoproduct (bathorhodopsin) involves energy uptake of about 130 kJ/mol, corresponding to storage of over 50% of the exciting photon energy, and is comparable to the energy storage previously observed in bovine rhodopsin. Subsequent intermediates involve the step-wise dissipation of this energy to give the physiological end-product (acid metarhodopsin) at a level only slightly above the parent rhodopsin. No significant differences in energetics are observed between rhodopsin in microvilli membrane suspensions or detergent dispersions. Use of different buffer systems in the calorimetric experiments shows that conversion of rhodopsin to acid metarhodopsin involves no light-induced protonation change, whereas alkali metarhodopsin photoproduction occurs with the release of one proton per molecule and an additional enthalpy increase of about 50 kJ/mol. Van't Hoff analysis of the effect of temperature on the reversible metarhodopsin equilibrium gives an enthalpy for the acid----alkali transition consistent with this calorimetric result, and the proton release is confirmed by direct observation of light-induced pH changes. Acid-base titration of metarhodopsin yields an apparent pK of 9.5 for this transition, though the pH profile deviates slightly from ideal titration behaviour. We suggest that a high energy primary photoproduct is an obligatory feature of efficient biological photo-detectors, as opposed to photon energy transducers, and that the similarity at this stage between cephalopod and vertebrate rhodopsins represents either convergent evolution at the molecular level or strong conservation of a crucial functional characteristic.

Animals↗
PubMed1986

Increase in the levels of N-nitrosoproline, N-nitrosothioproline and N-nitroso-2-methylthioproline in human urine by cigarette smoking.

The effects of cigarette smoking on the urinary excretions of N-nitrosoproline (NPRO) and the sulfur-containing N-nitrosamino acids, N-nitrosothioproline (NTPRO) and N-nitroso-2-methylthioproline (NMTPRO), in a male volunteer were examined. This subject smoked for 20 non-consecutive days and did not smoke for another 20 non-consecutive days during a 4-month-period, and 24-h urine samples were collected. On the days of urine collection, he was given a fixed diet. On the smoking days, the urinary levels of NPRO, NTPRO and NMTPRO increased significantly from 1.1 +/- 0.5 (mean +/- S.D.) micrograms/day to 1.8 +/- 0.9 (P less than 0.01), from 3.9 +/- 1.1 to 8.7 +/- 4.6 micrograms/day (P less than 0.001), and from 5.6 +/- 1.9 to 8.5 +/- 4.1 micrograms/day (P less than 0.01), respectively. Thus, the total amount of these 3 N-nitrosamino acids in the urine also increased significantly by smoking from 10.6 +/- 2.8 to 19.0 +/- 6.5 micrograms/day (P less than 0.001). These results indicated that NOx in cigarette smoke can contribute to in vivo formation of N-nitroso compounds.

Chromatography, Gas↗
PubMed1986

Tissue-specific transcription enhancement of the fibroin gene characterized by cell-free systems.

Six cell-free extracts have been used to characterize the nature of DNA signals and trans-acting factors responsible for the transcription enhancement of the Bombyx mori fibroin gene. The upstream element of the fibroin gene involved in the enhancement can be divided into two regions. The proximal region, -72 to -32, is recognized as a common enhancing signal by all B. mori extracts from the posterior silk gland, the middle silk gland, the ovarian tissue, and an embryonic cell line. It is weakly recognized by an Antheraea silkworm cell line extract but not by a HeLa cell extract. The distal region, -238 to -73, appears to be a tissue-specific enhancing signal that is recognized more effectively by the posterior silk gland extract than by the middle silk gland extract. These observations suggest that the use of these cell-free systems can offer a means for the biochemical characterization of the trans-acting factors involved in the tissue-specific regulation of the fibroin gene.

Animals↗
PubMed1986

Participation of the upstream region of the fibroin gene in the formation of transcription complex in vitro.

The addition of exogenous histones has an inhibitory effect on fibroin gene transcription in posterior silk gland extracts. The histones probably disturb a process in complex formation, because when transcription complexes were constructed by preincubation of the templates with the extracts, the inhibitory effect of histones was greatly reduced. Transcription of a fibroin gene construct, pFb5' delta-238, having the upstream region beyond the TATA box was relatively less inhibited than that of pFb5' delta-44 lacking the upstream region. This tendency toward differential inhibition was observed in the silk gland extracts but not in a HeLa cell extract and persisted even after complex formation in the silk gland extracts, suggesting a specific interaction of the upstream region with some factors in the extracts. The complexes formed on pFb5' delta-44 are probably more susceptible to the inhibitory effect of histones. On the basis of these results we propose a participation of the upstream region of the fibroin gene in the formation of stable transcription complexes at the promoter through an interaction with specific factors in the silk gland. Since the transcription-enhancing effect via the upstream region is augmented at a high histone/DNA ratio, it may mimic the in vivo situation in which the fibroin gene can be transcribed in the posterior silk gland even in the presence of excess suppressive materials.

Animals↗
PubMed1986

Inhibition of human DNA polymerase alpha by alpha 1-antichymotrypsin.

alpha 1-Antichymotrypsin (ACT), which is known as an efficient serum protease inhibitor and is detected in tumor cell nuclei, was found to inhibit the activity of DNA polymerase alpha purified from human stomach adenocarcinoma. The concentration of ACT required for 50% inhibition was 1.0 mg/ml and the manner of its inhibition showed the partially competitive relationship between ACT and DNA in the assay system. Furthermore the removal of ACT by anti-ACT antibody lost its antichymotryptic and anti-DNA polymerase activities in parallel. On the other hand, it did not inhibit the activity of human DNA polymerase beta. Other human serum proteins including serum albumin, alpha 1-acid glycoprotein, alpha 1-antitrypsin, and immunoglobulin G as well as other protease inhibitors such as leupeptin, pepstatin, phenylmethylsulfonyl fluoride, and chymostatin did not affect the activity of DNA polymerase alpha. Furthermore ACT heated at 60 degrees C did not inhibit DNA polymerase alpha, although it could still bind to DNA as well as native ACT. It was therefore concluded that the inhibitory action of ACT on DNA polymerase alpha was a direct phenomenon unrelated to its protease inhibitory or DNA binding activities.

Blood Proteins↗
PubMed1986

Incorporation of alpha-1-antichymotrypsin into carcinoma cell nuclei of human stomach adenocarcinoma transplanted into nude mice.

Human stomach adenocarcinomas containing alpha-1-antichymotrypsin (ACT) in their cell nuclei were transplanted into nude mice. The presence of ACT was monitored using an immunohistochemical technique with horseradish peroxidase-labeled rabbit anti-ACT Fab' as well as single radial immunodiffusion. Two weeks after transplantation, ACT could be found neither in transplanted carcinoma cells nor in the sera of carcinoma-bearing nude mice. However, if human ACT was injected i.v., it could be detected in the transplanted carcinoma cell nuclei 2 h after injection. The ACT was detected immunohistochemically and was confirmed by biochemical fractionation using 125I-labeled ACT. On the other hand, the amount of ACT production was not sufficient to indicate biosynthesis. These results demonstrated that ACT detected in stomach carcinoma cell nuclei was not synthesized in carcinoma cells but was incorporated from the blood circulation.

Adenocarcinoma↗