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Biomedical subjects

T Enomoto

Publications and source records attributed to T Enomoto.

At least 271 records · Page 15Linked to original sources
PubMed1987

Characterization of chromosome aberrations induced by incubation at a restrictive temperature in the mouse temperature-sensitive mutant tsFT20 strain containing heat-labile DNA polymerase alpha.

tsFT20 cells derived from a mouse mammary carcinoma cell line, FM3A, which has temperature-sensitive DNA polymerase alpha activity (Y. Murakami, H. Yasuda, H. Miyazawa, F. Hanaoka, and M. Yamada, Proc. Natl. Acad. Sci. USA, 82:1761-1765, 1985) were rapidly committed to death after temperature upshift to 39 degrees C. tsFT20 cells synchronized in S phase were more sensitive to the restrictive temperature than exponentially growing cells. In order to gain insight into the processes from the interruption of DNA synthesis to cell death, we analyzed chromosome aberrations induced in tsFT20 cells which had been incubated for 2 or 4 h at the restrictive temperature and then cultured at the permissive temperature. The majority of metaphase cells showed extensive chromosome aberrations such as chromatid gaps, breaks, and exchanges; chromosome pulverizations; their mixed types; and ring chromosomes. Analyses with the use of cell synchronization and autoradiography revealed that chromosome aberrations were induced only in the cells which synthesized DNA during incubation at 39 degrees C. We classified the chromosome aberrations into five types: gap or break type; exchange type; pulverization type; complex type; and ring type. The temporal order of the appearance of these types of chromosome aberrations was found to be the above described order. It was further found that cycloheximide dramatically repressed the induction of chromosome aberrations, and metaphases with many chromosome aberrations exhibited a large number of sister chromatid exchanges. These results indicate that abnormal cessation of DNA replication in tsFT20 cells at the restrictive temperature due to the inactivation of DNA polymerase alpha results in cell death via induction of double-strand breaks which lead to chromosome aberrations as well as sister chromatid exchanges.

Animals↗
PubMed1987

DNA-dependent adenosinetriphosphatase B from mouse FM3A cells has DNA helicase activity.

We have detected at least four forms of DNA-dependent ATPase in mouse FM3A cell extracts [Tawaragi, Y., Enomoto, T., Watanabe, Y., Hanaoka, F., & Yamada, M. (1984) Biochemistry 23, 529-533]. The purified fraction of one of the four forms, ATPase B, has been shown to have DNA helicase activity by using a DNA substrate which permits the detection of limited unwinding of the helix. The DNA substrate consists of single-stranded circular fd DNA and the hexadecamer complementary to the fd DNA, which bears an oligo(dT) tail at the 3' terminus. The helicase activity and DNA-dependent ATPase activity cosedimented at 5.5 S on glycerol gradient centrifugation. The helicase required a divalent cation for activity (Mg2+ congruent to Mn2+ greater than Ca2+). The optimal concentrations of these divalent cations were 5 mM. The requirement of divalent cations of the DNA helicase activity was very similar to that for the DNA-dependent ATPase activity of ATPase B. The helicase activity was absolutely dependent on the presence of a nucleoside triphosphate. ATP was the most effective cofactor among the ribo- and deoxyribonucleoside triphosphates tested, and considerable levels of helicase activity were observed with other ribo- and deoxyribonucleoside triphosphates. The efficiency of a nucleoside triphosphate to serve as cofactor for the helicase activity correlated with the capacity of the nucleotide to serve as substrate for the DNA-dependent ATPase activity. The nonhydrolyzable ATP analogues such as adenosine 5'-O-(3-thiotriphosphate) were not effective for the helicase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1987

A case of porencephaly associated with aneurysm.

A case of aneurysm of the middle cerebral artery with congenital porencephaly in the same region is reported. The cyst was opened and the aneurysm was wrapped with a muscle strip. The resected specimen of the cyst wall contained a parenchymal layer with hemosiderinladen macrophages. It is speculated that bleeding from the aneurysm during the perinatal period caused the porencephaly.

Brain Diseases↗
PubMed1987

Characterization of revertants derived from a mouse DNA temperature-sensitive mutant strain, tsFT20, which contains heat-labile DNA polymerase alpha activity.

One spontaneous and four N-methyl-N'-nitro-N-nitrosoguanidine-induced revertants of a mouse FM3A mutant, tsTF20, which has heat-labile DNA polymerase alpha activity and cannot grow at 39 degrees C, were isolated and characterized with respect to the thermolability of their DNA polymerase alpha activity, the intracellular level of enzyme activity, growth rate, cell cycle progression, and frequency of initiation of DNA replication at the origin of replicons. DNA polymerase alpha activity in the extracts from the revertant cells showed partial recovery of heat stability. The intracellular level of enzyme activity of the revertant cells was lower than that of wild-type cells even at 33 degrees C. The level of enzyme activity in the revertant cells decreased considerably after a temperature upshift to 39 degrees C, but the DNA synthesizing ability of these cells did not decrease as much as the level of enzyme activity. The growth rates of the wild-type and revertant lines were almost the same at 33 degrees C. At 39 degrees C, the rate for the wild-type increased considerably compared to that at 33 degrees C, while little difference in the growth rates of the revertant lines was observed at the two temperatures. Therefore, the doubling times of the revertant cells were relatively increased compared to those of wild-type cells cultured at the restrictive temperature. Flow microfluorometric analysis and cell cycle analysis to measure labeled mitosis revealed that the increase in the doubling time was due mainly to the increase in the duration of the S phase. Analysis of the center-to-center distance between replicons by DNA fiber autoradiography indicated that the frequency of replicon initiation per unit length DNA at a given time was reduced in the revertant cells growing at 39 degrees C.

Animals↗
PubMed1987

Ossification of the posterior longitudinal ligament: a clinico-radiological study of 74 cases.

A clinico-radiological analysis of 74 cases of ossification of the posterior longitudinal ligament is reported. Eighteen cases (24%) were asymptomatic or only had neck or shoulder pain; 16 cases (22%) showed signs of radiculopathy, and the remaining 40 cases (54%) had myelopathy. Ossification of the posterior longitudinal ligament developed most frequently at C5, and was rare in thoracic and lumbar regions. Ossification of the posterior longitudinal ligament led to stenosis of the spinal canal; more marked stenosis caused clinical myelopathy. The data showed that 30% of stenosis caused by ossification of the posterior longitudinal ligament was critical for the production of myelopathy.

Adult↗
PubMed1987

Extracellular products of Staphylococcus aureus reversibly inhibit the terminal differentiation of cultured mouse epidermal cells.

The effect of extracellular products from Staphylococcus aureus on the differentiation of mouse epidermal cells was studied using an in vitro cell culture system. The extracellular products from a clinical strain of S. aureus isolated from human skin lesions reversibly inhibited the Ca++-induced terminal differentiation of epidermal cells, as determined by their morphology and the extent of cornified envelope formation. This suggests that a similar modification of cell differentiation is involved in the pathogenesis of S. aureus-induced skin disease.

Animals↗
PubMed1987

[A case of hypopharyngeal cancer responding to recombinant interferon-gamma (KW-2202)].

A 66-year-old woman with hypopharyngeal cancer was treated with recombinant interferon-gamma (KW-2202). r-IFN-gamma was administered at a dose of 1-8 X 10(6) U/body every day for six weeks by i.v. drip infusion. After the start of the therapy both the primary tumor and metastatic lymph nodes showed remarkable regression and PR was obtained. Observed side effects, which included fever and hepatic function disorder, were slight and transient. Immunological studies were also carried out on the patients and the results were reported. Further investigation will be necessary in order to confirm the efficacy of the drug and to compile data on immunological parameters.

Aged↗
PubMed1986

Characterization of DNA replication at a restrictive temperature in a mouse DNA temperature-sensitive mutant, tsFT20 strain, containing heat-labile DNA polymerase alpha activity.

tsFT20 cells derived from a mouse mammary carcinoma cell line FM3A have temperature-sensitive DNA polymerase alpha activity (Murakami, Y., Yasuda, H., Miyazawa, H., Hanaoka, F., and Yamada, M. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 1761-1765). DNA replication in tsFT20 cells at the restrictive temperature (39 degrees C) has been characterized in detail. DNA-synthesizing ability of these cells was measured by [3H] thymidine incorporation and autoradiography. The incorporation of [3H]thymidine decreased rapidly after temperature shift-up, and the incorporation was less than 20% of the initial level after 4 h at 39 degrees C. The rapid decrease correlated well with the decrease in the grain number in the individual nucleus but not with the number of cells with labeled nuclei. Alkaline sucrose gradient sedimentation analysis and DNA fiber autoradiography revealed that DNA chain elongation proceeded normally within a replicon in the temperature-sensitive cells incubated at the restrictive temperature and the DNA elongation rate did not change during the incubation at the restrictive temperature up to at least 6 h. On the other hand, the maturation of replicon-sized DNA to higher molecular weight DNA was retarded or inhibited in the temperature-sensitive cells at the restrictive temperature. The analysis of the center to center distance between replicons by DNA fiber autoradiography revealed that the frequency of replicon initiation decreased in tsFT20 cells at 39 degrees C.

Animals↗
PubMed1986

Purification and characterization of a deoxyribonucleic acid dependent adenosinetriphosphatase from mouse FM3A cells: effects of ribonucleoside triphosphates on the interaction of the enzyme with single-stranded DNA.

There are at least four forms of DNA-dependent ATPase in mouse FM3A cells [Tawaragi, Y., Enomoto, T., Watanabe, Y., Hanaoka, F., & Yamada, M. (1984) Biochemistry 23, 529-533]. One of these, ATPase B, has been purified and characterized in detail. During the purification of the enzyme, we encountered the difficulties that the enzyme could not be recovered well from the single-stranded DNA-cellulose column and that the enzyme activity was distributed very broadly. The problems were resolved by the addition of ATP in the elution buffer. The ATPase has a sedimentation coefficient of 5.5 S in both high salt and low salt. The enzyme hydrolyzes rNTPs and dATP, but ATP and dATP are preferred substrates. Adenosine 5'-O-(3-thiotriphosphate) (ATP-gamma-S), 5'-adenylyl methylenediphosphate (AMP-PCP), and 5'-adenylyl imidodiphosphate (AMP-PNP) inhibit the enzyme activity. The enzyme is insensitive to ouabain, oligomycin, novobiocin, and ethidium bromide. A divalent cation (Mg2+ congruent to Mn2+ greater than Ca2+) as well as a nucleic acid cofactor is required for activity. Poly(dT), single-stranded circular DNA, and heat-denatured DNA were very effective. Native DNA was little effective with an efficiency of 29% of that obtained with heat-denatured DNA. In addition, the enzyme showed almost no activity with poly(dA).poly(dT) although it showed very high activity with the noncomplementary combination of poly(dT) and poly(dC), suggesting that ATPase B requires single-stranded DNA for activity. ATP altered the affinity of ATPase B for single-stranded DNA. The interaction of the enzyme with DNA was studied by Sephadex G-200 gel filtration assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1986

Detection and characterization of a novel factor that stimulates DNA polymerase alpha.

A novel factor that stimulates DNA polymerase alpha activity on poly(dA) X oligo(dT) has been identified and partially purified from mouse FM3A cells. The assay system for the factor contained poly(ethylene glycol) 6000. The activities of DNA polymerase alpha on poly(dA) X oligo(dT) in the presence and absence of the stimulating factor were increased greatly by the addition of poly(ethylene glycol). Stimulation by the factor was observed at all the primer to template ratios tested from 0.01 to 0.3. The highest activity was observed at the ratio of 0.05, corresponding to about 3.3 primers on one template in the presence of the factor. The concentration of DNA polymerase alpha used in the assay affected the stimulation by the factor, and the stimulation became more prominent at concentrations of the enzyme lower than 0.04 unit per assay. The stimulating factor lowered the Km value of DNA polymerase alpha for the template-primer, though they had no effect on the Km value for dTTP substrate. The results of product analysis suggested that the stimulation by the factor is mainly due to the increase in the initiation frequency of DNA synthesis from the primers. The stimulating factor specifically stimulated DNA polymerase alpha but not DNA polymerases beta and gamma. Furthermore, the factor formed a complex with DNA polymerase alpha under a certain condition.

Animals↗
PubMed1986

Electroencephalography in minor head injury in children.

EEG and CT scans of 280 cases of minor head injury in children under 15 years of age were studied. Abnormality on initial EEG was shown in 42.5%. Those who lost consciousness had a higher incidence of abnormality than those who did not, and it was higher between 4 and 13 years of age. The sleep state has much influence on the finding. The patients should be awake or in a light sleep stage. The most frequent abnormality was slow waves, seen predominantly in the occipital regions, and which tended to disappear more easily than the paroxysmal ones. The EEGs became or remained normal in 95%, excluding incompletely followed-up cases. There was no case of post-traumatic epilepsy in our series, but 4 cases of post-traumatic early convulsions, in which the EEGs were variable. CT scan disclosed abnormality in 6%.

Adolescent↗
PubMed1986

Further characterization of a murine temperature-sensitive mutant, tsFT20 strain, containing heat-labile DNA polymerase alpha-activity.

tsFT20 cells, which have temperature-sensitive DNA polymerase alpha-activity, were characterized mainly at the cellular level. The cells lost their ability to synthesize DNA immediately after a shift to non-permissive temperature. The extent of decrease in the activity of DNA polymerase alpha in whole-cell extracts was the same as that of the decrease in the DNA replication ability determined by [3H]thymidine incorporation. At 39 degrees C, tsFT20 cells lost most of their colony-forming ability in one doubling time (16 h). The cells could not grow at higher than 38 degrees C, but could grow at 37 degrees C. When tsFT20 cells were synchronized at the G1/S boundary and incubated at 39 degrees C, they could not complete the S phase, ceasing cell cycle progression in mid-S phase. A temperature shift (33 degrees C----39 degrees C) experiment indicated that the whole S phase was temperature-sensitive, whereas the G2 and M phases were not. These results confirmed that DNA polymerase alpha plays a key role in DNA replication in mammalian cells.

Animals↗
PubMed1986

Effect of 3-aminobenzamide on the process of ultraviolet-induced DNA excision repair.

The effect of 3-aminobenzamide, a potent inhibitor of poly(ADP-ribosyl)ation, on UV-induced DNA excision repair was investigated. HeLa cells were treated with DNA replication inhibitors, hydroxyurea (HU) and 1-beta-D-arabinofuranosyl cytosine (araCyt), before and after ultraviolet light (UV) irradiation, to accumulate DNA single-strand breaks. The activity of poly(ADP-ribosyl)ation measured in the permeable cell system of HeLa cells was enhanced in a UV dose-dependent manner after the combined treatment with HU and araCyt in vivo. However, DNA repair synthesis in vitro was not affected by addition of 1 mM 3-aminobenzamide or nicotinamide, while incorporation of [3H]NAD in the same system was completely inhibited. Furthermore, neither the magnitude of UV-induced DNA single-strand breaks accumulated by the combined treatment of HU and araCyt nor the rate of their rejoining after release from the HU and araCyt block were influenced even in the presence of 10 mM 3-aminobenzamide. As the cytotoxicity of UV irradiation was significantly potentiated by 5 mM 3-aminobenzamide, these results suggest that poly(ADP-ribosyl)ation is involved in a process other than DNA excision repair induced by UV irradiation.

Adenosine Diphosphate Ribose↗
PubMed1985

Hepatic coma and amino acids in the nerve endings of the central nervous system.

The levels of amino acids in the cerebral cortex and synaptosomes of 6 autopsied patients who had died of chronic liver diseases with portasystemic shunt were examined and compared with those of controls. The level of threonine in the cerebral cortex and synaptosomes of the 6 patients, who had developed hepatic coma before death, was significantly higher than that of 9 patients without hepatic coma. However, the levels of the neurotransmitters, aspartate, glutamate, and glycine, showed no significant difference between the two groups. In animal experiments, threonine uptake into the synaptosomes was enhanced by an increase of threonine concentration in the cerebral cortex, and at the same time ammonia further promoted threonine uptake. The high level of threonine in the synaptosomes was released just like a neurotransmitter on potassium stimulation in the patients with hepatic coma. Since threonine has no post-synaptic action, it is thought that threonine released in this way somehow interferes with brain action. This phenomenon may play an important role in the development of hepatic coma.

Amino Acids↗