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Biomedical subjects

M Hyodo

Publications and source records attributed to M Hyodo.

At least 73 records · Page 4Linked to original sources
PubMed1986

Inhibition in maturation of nascent DNA fragments in cultured mouse FM3A cells after treatment with DNA-damaging agents.

The effect of DNA-crosslinking agents (cisplatin and mitomycin C), a DNA-intercalating agent (adriamycin) or monofunctional psoralen (4-Met-4', 5'-dihydropsoralen plus near-ultraviolet radiation) on DNA replication in cultured mouse FM3A cells was studied by sedimentation of the pulse-labeled DNA in an alkaline sucrose gradient. There was no inhibition of the maturation process of the nascent DNA 1 h after treatment of the cells with cisplatin, mitomycin C or adriamycin. However, this process was inhibited progressively during further incubation for 4 to 16 h without the agents, and accumulation of the nascent DNA fragments was observed. In the case of DNA-crosslinking agents, this inhibition may be correlated with an increase in the number of DNA-crosslinks formed during incubation. However, direct inhibition of maturation was not likely since the number was small, up to 4.9 per 10(9) Da. After treatment of cells with monofunctional psoralen, no inhibition of maturation of the nascent DNA fragments was observed. In all cases, there was no degradation of DNA during incubation.

Animals↗
PubMed1985

An improved method for isolation of mutator mutants from mouse FM3A cells and their characterization.

An improved method to select mutator mutants was developed. By this new method, mutator mutants were isolated efficiently, and 7 mutants were obtained from cultured mouse FM3A cells. These mutator mutants have an elevated rate of spontaneous mutation at 3 genetic loci (resistance to ouabain, blasticidin S, and tunicamycin). The sensitivity of these mutants to aphidicolin and arabinofuranosylcytosine was the same as in the wild-type cells. Determination of the size of the cellular dNTP pool revealed that there was no large imbalance in the precursor pool in the mutator mutants. These results suggested that the mutator character may be due to alteration in some factor(s) correlated directly to DNA replication. Also, there was no change in the sensitivity of all these mutator mutants to DNA damaging agents.

Animals↗
PubMed1985

Effect of DNA-damaging agents on DNA replication and cell-cycle progression of cultured mouse mammary carcinoma cells.

The effects of DNA-crosslinking agents (mitomycin C and cisplatin), a DNA-intercalating agent (adriamycin) and monofunctional psoralen adducts (4-methyl-4',5'-dihydropsoralen plus near-UV radiation or 8-methoxypsoralen plus narrow band 395 nm light) on DNA replication and cell-cycle progression of cultured mouse mammary carcinoma cells were studied and compared at a dose of each agent sufficient to cause complete inhibition of cell growth. In cells treated with the DNA-crosslinking agents, inhibition of incorporation of [8H]thymidine occurred progressively upon incubation of the treated cells, and finally the cells were arrested at the G2 phase. However, although the mode of inhibition of DNA replication or cell-cycle traverse was the same as that of the crosslinking agents, adriamycin did not completely block cell progression at the G2 phase and some of the cells entered the G1 phase. In contrast to these agents, monofunctional psoralen adducts inhibited DNA replication immediately after treatment and no shift in the distribution of cells in the cell-cycle was observed during incubation. These results suggested different responses of the cells to different types of DNA damage.

Animals↗
PubMed1984

Deoxynucleoside triphosphate pool of mouse FM3A cell lines unaffected by mutagen treatment.

The size of deoxynucleoside triphosphate pool in cultured mouse FM3A cells and mutator mutants isolated from this cell line was determined by high-pressure liquid chromatography after treatment of the cells with ultraviolet light, N-methyl-N'-nitro-N-nitrosoguanidine or mitomycin C. The results showed that, in all the FM3A cell clones, no large increase in the dATP or TTP pool was induced after treatment, while in some cases 40-50% decrease in dCTP pool was observed. It is concluded that the induction of large increase in dNTP pool is not the general effect of the mutagens.

Animals↗
PubMed1984

Isolation and characterization of mutator mutants from cultured mouse FM3A cells.

A method to select mutator mutants was developed and 3 mutants were isolated from cultured mouse FM3A cells. Fluctuation analyses revealed that these mutator mutants have increased rates of spontaneous mutation at 3 genetic loci tested (resistance to ouabain, blasticidin S and tunicamycin). None of the 3 mutator mutants showed altered sensitivity to aphidicolin or arabinofuranosylcytosine, and so they differed from the mammalian mutator mutants reported previously. Also, all the mutator mutants had the same sensitivity as wild-type to UV or other DNA-damaging agents. Thus, these mutator mutants do not seem to have any deficiency in the DNA-repair process. To determine whether the mutator activity was due to the intracellular dNTP pool imbalance, 4 dNTPs in these mutator mutants were determined by high-pressure liquid chromatography and compared to that of the wild-type cells. The results show that there is no large dNTP pool imbalance in these mutator mutants. Since the mutator activity is not associated with the dNTP pool imbalance, these mutants may have altered protein(s) directly involved in DNA replication.

Animals↗
PubMed1983

Maturation of nascent DNA fragment is disturbed after treatment of cultured mouse FM3A cells with 8-methoxypsoralen plus near-ultraviolet radiation.

By the method of sedimentation in 5-20% alkaline sucrose gradient, the process of maturation of the nascent DNA fragment was studied with cultured mouse FM3A cells treated with 8-methoxypsoralen plus near-ultraviolet radiation. This treatment is known to cause crosslinks of the chromosomal DNA strands. The profile of the newly-replicated DNA, labeled for 10 min with [3H]thymidine immediately after treatment, was the same as that of the untreated cells, where the incorporated radioactivity was present in the intermediate DNA fragment (about 50-80 S). But, when the treated cells were labeled after several hours of incubation, the labeled DNA became much shorter due to inhibition of maturation of the initial DNA fragment (the Okazaki fragment) to the intermediate DNA. With the use of aphidicolin, a specific inhibitor of eukaryotic DNA polymerase alpha, it became apparent that, in addition to formation of the crosslinks, further DNA replication is required to cause this inhibition of DNA maturation. Aphidicolin also suppressed the inhibition of incorporation of [3H]thymidine into cellular DNA after treatment, but inhibition of this incorporation resumed after its removal.

Animals↗
PubMed1982

DNA crosslinks and DNA replication in mouse FM3A cells after treatment with 8-methoxypsoralen plus near-ultraviolet radiation.

The rate of DNA-chain elongation was studied in mouse FM3A cells after treatment with 8-methoxypsoralen plus near-ultraviolet radiation using the minimal doses (1 microgram/ml 8-methoxypsoralen plus 1-2.5 kJ/m2 of near-ultraviolet radiation) which inhibited cell-cycle progression or DNA replication. A rapid decrease in incorporation of [3H]thymidine and recovery to some extent during incubation after treatment have been reported (Hyodo, M., Fujita, H., Suzuki, K., Yoshino, K., Matsuo, I. and Ohkido, M. (1982) Mutat. Res. 94, 199-211). The results of the present study showed that the rate was not changed suggesting that the decrease in [3H]thymidine incorporation was not due to the rate of DNA-chain elongation, but was due to change in the frequency of initiation of replication. Formation of DNA crosslinks was then studied by the sedimentation of pre-labeled DNA in an alkaline sucrose gradient. The results showed that, at these doses of 8-methoxypsoralen plus near-ultraviolet radiation, approx. 2-7 crosslinks were formed per 10(9) Da. It was also suggested that some of the DNA crosslinks might be repaired during the prolonged incubation, but unrepaired crosslinks were still present after 24 h incubation.

Animals↗
PubMed1982

DNA replication and cell-cycle progression of cultured mouse FM3a cells after treatment with 8-methoxypsoralen plus near UV-radiation.

To investigate the response of cells to one type of DNA damage--namely DNA crosslinks--cell-cycle progression and macromolecular synthesis were studied with cultured mouse FM3A cells. Treatment of the cells with low doses of 8-methoxypsoralen (8-MOP) plus near-UV radiation (0.1 micrograms/ml plus 5 kJ/m2 or 1.0 micrograms/ml plus 1-2.5 kJ/m2) halted the progression of cells through the cell cycle temporarily for the first several hours. Then the cells resumed progression through the cell cycle, and most of the cells reached, and were finally arrested at, the G2 phase of the cycle. There was a rapid decrease of incorporation of [3H]thymidine into cellular Dna immediately after the treatment. Then, after 8 h of incubation, the incorporation of [3H]thymidine recovered to some extent depending on the dose of 8-MOP plus near-UV radiation. Thus the decrease and recovery of the incorporation of [3H]thymidine were correlated with the halt and resumption in the cell-cycle process. Synthesis of RNA and protein was measured by determination of the amounts in the cells or by the incorporation of radioactive precursors after treatment. RNA and protein synthesis were stimulated by low doses of 8-MOP plus near-UV radiation, but inhibited severely by high doses.

Animals↗
PubMed1981

Rapid decrease in thymidine kinase activity of mouse cell temperature-sensitive mutants at a non-permissive temperature.

A rapid decrease in the incorporation of [3H]thymidine into DNA at a non-permissive temperature was observed in two temperature-sensitive mutants that were isolated from mouse FM3A cells. This change was not due to a decrease in the rate of DNA replication, but was closely associated with a decrease in thymidine kinase activity of these cells. Experiments to test thermolability of thymidine kinase in extracts showed that there are two components of the thymidine kinase, but there was no alteration in the sensitivity of the enzyme to high temperature. Also, the decrease in enzyme activity in the temperature-sensitive mutants at the non-permissive temperature occurred much faster than expected from the half-life of the enzyme in wild-type cells, which was measured in the presence of cycloheximide. These results suggested that the enzyme was somehow rapidly inactivated, or degraded, in the cells at the non-permissive temperature.

Animals↗
PubMed1981

An experimental study on the enhancing effects of phenylalanine on acupuncture analgesia.

In this preliminary study we examined the enhancing effect of D-phenylalanine on acupuncture anesthesia. We made 4 different kinds of experiments with 3 volunteers. The results show that D-phenylalanine extends the analgesic effect of acupuncture analgesia remarkably, with no exception in 3 cases. According to these facts, we believe that these findings have an important meaning for those who are engaged in acupuncture treatment or research.

Acupuncture Therapy↗
PubMed1980

Chain elongation of DNA and joining of DNA intermediates in intact and permeabilized mouse cells.

When the sequence of DNA chain elongation in intact mouse cells was analyzed by pulse-labeling the cells with [3H]thymidine followed by sedimentation in an alkaline sucrose gradient, four classes of DNA, different in size, were observed. They were the Okazaki-type initial fragment, two high molecular weight DNA classes which we designated as DNA intermediates I and II, and the bulk of chromosomal DNA. When the size of DNA synthesized in permeabilized cells (cells treated with detergent to make them permeable to nucleoside triphosphates) was analyzed by the same method, we found that one of the intermediate DNAs, DNA intermediate I, was the major product of the in vitro DNA replication and further elongation of the DNA chain from DNA intermediate I to II was lacking. But when a soluble fraction released from the cells after treatment with Triton X-100 was added to the permeabilized cells, the activity of joining chains of DNA intermediate I to form DNA intermediate II was partially revealed by the sedimentation analysis, DNA intermediate I and II seem to correspond to replicon-size DNA and clustered replicon-size DNA, respectively. And our results suggest that there exists some unknown factor or process which is required for the joining of completed replicon-size DNA at the terminals.

Animals↗
PubMed1979

The effects of stimulation of ear acupuncture points on the body's pain threshold.

Six ear acupuncture points, one non-acupuncture ear point, and the body locus Ho-Ku (LI-4) were electrically stimulated in order to compare the effects of stimulation on the body's pain threshold at selected loci on various points on the body by measurement with a radiation heat-type Pain Meter on 5 subjects. The ear points, with the exception of the non-acupuncture ear point, were found to be effective even in peripheral body regions in varying degrees. Ear stimulation did not increase the threshold as rapidly as Ho-Ku. In all cases where the pain threshold was raised, the effect persisted after electrical stimulation had stopped.

Acupuncture Therapy↗