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Biomedical subjects

M Oishi

Publications and source records attributed to M Oishi.

At least 235 records · Page 13Linked to original sources
PubMed1987

Dimethyl sulfoxide-inducible cytoplasmic factor involved in erythroid differentiation in mouse erythroleukemia (Friend) cells.

A previous report described an intracellular factor (differentiation-inducing factor I, or DIF-I) that seems to play a role in erythroid differentiation in mouse erythroleukemia (MEL) cells. We have detected another erythroid-inducing factor in cell-free extracts from dimethyl sulfoxide- or hexamethylenebis(acetamide)-treated MEL cells, which acts synergistically with DIF-I. The partially purified factor (termed DIF-II) triggered erythroid differentiation when introduced into undifferentiated MEL cells that had been potentiated by the induction of DIF-I. The activity in the extracts appeared in an inducible manner after addition of dimethyl sulfoxide or hexamethylenebis(acetamide), reached a maximum at 6 hr, and then rapidly decreased. The induction was inhibited by phorbol 12-myristate 13-acetate and also by cycloheximide. No induction was observed in a mutant MEL cell line defective in erythroid differentiation. These characteristics are consistent with the supposition that DIF-II is one of the putative dimethyl sulfoxide-inducible factors detected in previously reported cell-fusion and cytoplast-fusion experiments. The role of DIF-II in MEL-cell differentiation and in vitro differentiation in general is discussed.

Animals↗
PubMed1987

Multicopy plasmid with a structure related to the polyoma virus genome.

In a subclone derived from mouse L(tk-) cells, we found a plasmid present in a high copy number (greater than 5000 copies per cell) that was stably maintained extrachromosomally without any cytopathic effect to the host cells. This plasmid, termed L factor, has two forms: 5.3 and 5.5 kilobase pairs. DNA sequencing and restriction enzyme mapping showed that, although the structure contains DNA sequences common to polyoma virus, plasmid sequences belonging to the regulatory region (the enhancer region) and other regions are quite different from those in polyoma. In cells bearing the plasmid, we detected a low level of material that cross-reacts with antibody to polyoma tumor antigens, suggesting that the plasmids replicate and are maintained in the cells by a mechanism different from that functioning during propagation following infection of papovaviruses.

Animals↗
PubMed1987

The level of c-myc transcript in differentiation-defective mouse erythroleukemia cells.

We isolated several mouse erythroleukemia (MEL) cell lines, deficient in in vitro erythroid differentiation, and examined the change in level of c-myc mRNA after exposing the cells to dimethyl sulfoxide (DMSO). The results showed all the mutant MEL cells to exhibit a similar change in c-myc mRNA level to that in parental (DS19) cells with regard to both an initial decline and a subsequent increase to the pretreatment level. The c-myc mRNA level did not, however, decline again thereafter, as observed in the parental cells, but remained at the pretreatment level, even on prolonged culture in the presence of DMSO. Essentially the same results were obtained for the parental cells in the presence of DMSO and either 12-O-tetradecanoylphorbol 13-acetate (TPA) or dexamethasone, specific inhibitors of MEL cell differentiation. These results suggest that the crucial stage in MEL cell differentiation, regarding c-myc mRNA level, is the late stage, when the MEL cells become committed to differentiation.

Animals↗
PubMed1986

An intracellular factor that induces erythroid differentiation in mouse erythroleukemia (Friend) cells.

We have previously shown that in vitro erythroid differentiation of mouse Friend cells is a result of a synergistic action of two distinctive intracellular reactions. We now have evidence that a factor in the cell free extract is involved in one of the reactions. This factor triggers erythroid differentiation when introduced into undifferentiated mouse Friend cells, provided the cells have been briefly exposed to dimethyl sulfoxide. The factor is induced in nonerythroid cells as well following treatment of the cells by agents that affect DNA replication. Cycloheximide inhibited the induction of the factor. The factor, which is in the cytoplasm, was partially purified and proteinaceous. When introduced into the cells the partially purified factor converts 60% to 70% of undifferentiated Friend cells to erythroid cells, at an efficiency almost equivalent to the efficiencies achieved by typical inducing agents. The factor's biochemical characteristics and possible role in erythroid differentiation are also discussed.

Animals↗
PubMed1986

A procedure to introduce protein molecules into living mammalian cells.

Although several methods are now available by which to introduce macromolecules into cultured living mammalian cells, each has limitations on its adoption as a general means, for a variety of purposes. We describe here a simple procedure to introduce protein molecules into various living mammalian cells. This procedure is based upon the finding that mammalian cells, after exposure to a low concentration of a phospholipid (L-alpha-lysophosphatidylcholine) in the presence of high (hypertonic) concentrations of glycerol became permeable to protein molecules and that a significant portion of the exposed cells regain their viability following incubation in the appropriate growth medium. We have demonstrated that diphtheria toxin (A fragment), horseradish peroxidase and antibodies against SV40 T-antigens are incorporated into living mouse erythroleukemia (Friend) cells, baby hamster kidney (BHK) cells and mouse fibroblasts (C3H), respectively. The volume introduced into a single cell (mouse Friend cells) is approx. 3 X 10(-15) liter, which is comparable to those with other systems. Parameters affecting permeability to protein molecules and viability of the treated cells were also investigated with these and other cell lines.

Animals↗
PubMed1986

A repetitive DNA family (Sau3A family) in human chromosomes: extrachromosomal DNA and DNA polymorphism.

In this paper, we report a tandemly repeated DNA sequence found in human chromosomes. The DNA sequence, which is present at approximately 1000 copies per haploid genome, consists of a basic unit 849 base pairs (bp) long with a single specific restriction enzyme (Sau3AI) cutting site. The unit is further composed of five subunits, each approximately 170 bp long. When DNAs from various sources were examined by Southern hybridization using the repetitive DNA as a probe, a considerable degree of restriction fragment length polymorphism was observed. Furthermore, a substantial percentage (approximately 1.0%) of the same DNA sequence was also found extrachromosomally in the cultured human (HeLa) cells as monomers and oligomers of the basic unit in the form of covalently closed circular DNA. These results suggest that the repetitive DNA is unstable and prone to be excised from the chromosomes through homologous recombination.

Base Sequence↗
PubMed1985

Stationary negative potentials near the source vs. positive far-field potentials at a distance.

We studied the field distribution of referentially recorded negative potentials after stimulation of the median nerve at the wrist in 15 normal subjects. When recorded from multiple sites along the lateral aspect of the arm with the reference electrode at the knee, 3 negative peaks, N3, N6 and N9, appeared at fixed latencies. Of these N3 and N6 were highest in amplitude at the distal insertion of the brachioradialis and the distal end of the deltoid, respectively, and N9, at the acromion. With stimulation of the finger, the negative peaks shifted in latency by about 3 msec, indicating an anatomically fixed generator source for each component. When compared to far-field potentials, N9 was of the same latency as scalp recorded P9, that extended to the arm contralateral to the side of stimulation and to the upper half of the trunk. In contrast, N6 extended to the scalp with P6 spreading to the lower half of the body. When two subjects were connected by the arm, stationary negative or positive peaks were transmissible from the stimulated to the non-stimulated subject. When the stimulated arm of the first subject was in contact with the second subject, N3, N6 and N9 were recorded in the latter. Only P9 was registered when the unstimulated arm was in contact with the second subject. We conclude that N3, N6 and N9 are stationary negative potentials generated at certain points along the nerve pathway, probably representing a negative counterfield for positive far-field peaks, P3, P6 and P9. These stationary potentials can spread widely in a volume conductor and can even be detected in a non-stimulated subject making a close contact to the generator source.

Adolescent↗
PubMed1985

Induction of erythroid differentiation by cytoplast fusion in mouse erythroleukemia (Friend) cells.

An intracellular activity, which is induced by dimethyl sulfoxide (DMSO) or hexamethylenebisacetamide (HMBA) and leads to erythroid differentiation in mouse Friend cells, was characterized by cell fusion between genetically marked intact cells and cytoplasts. For this, a procedure for rapid selection of cybrids was devised by sensitizing non-fused cells with oligomycin. We were able to demonstrate that cytoplasts derived from DMSO- (or HMBA)-treated cells trigger erythroid differentiation upon fusion with UV-irradiated cells. The activity in the cytoplasts remained only transiently and its induction was inhibited by biologically active phorbol esters or cycloheximide. The activity, however, was not induced in cytoplasts by directly treating them with DMSO (or HMBA). These results indicate that (1) the intracellular erythroid-inducing activity is located in cytoplasts, (2) it acts in trans and induces erythroid differentiation as a dominant factor and (3) its production requires de novo nuclear protein synthesis. The mechanisms of the induction of the intracellular activity and of how it triggers erythroid differentiation are discussed.

Animals↗
PubMed1985

The ribosomal RNA genes of Locusta migratoria: copy number and evidence for underreplication in a polyploid tissue.

From libraries of Locusta migratoria genomic DNA in bacteriophage lambda, clones have been isolated that hybridize with one or both of the 18S and 28S components of locust rRNA. Six clones studied show common patterns of restriction sites in the coding sequences and some include an intron in the 28S region. Subcloned sequences from within the 18S and 28S coding regions were used as probes in dot hybridization assays of the rRNA gene copy number in DNA prepared from several locust tissues and stages. The 18S and 28S probes gave similar results, showing about 4000 copies/haploid genome in testis, embryo, and fat body from larvae and immature adults of both sexes. This is by far the greatest rRNA gene copy number yet reported for any insect. DNA from reproductively mature adult female fat body showed a consistent reduction in the copy number by about one-third. Mature adult male fat body DNA showed no significant reduction in the copy number. It therefore appears that the final round of DNA replication in the adult female fat body, which produces 8-ploid and 16-ploid cells active in vitellogenin synthesis, involves underreplication of rDNA.

Animals↗
PubMed1985

Visual evoked potentials by different check sizes in patients with multiple sclerosis.

Visual evoked potentials (VEPs) were obtained using three checks of different size (25', 50', and 100' of arc) in 20 normal controls and 1,006 patients. The test was abnormal in 270 patients regardless of the check size, whereas in 53 patients, a prolongation of P100 latency occurred only with checks of a certain size. The procedure was most sensitive in detecting abnormalities with combined application of 25' and 100' checks and least sensitive with the 50' checks alone. In occasional subjects showing W-shaped responses, the use of another check size often elicited the usual V-shaped pattern, alleviating the problem of selecting the peak for latency determination.

Adolescent↗
PubMed1985

Induction of a novel nuclear protein (p54) by phorbol esters in mouse erythroleukemia (Friend) cells.

Tumor-promoting phorbol esters including 12-O-tetradecanoylphorbol-13-acetate (TPA), specific inhibitors for erythroid differentiation in mouse Friend cells, induce a newly identified nuclear protein with a molecular weight of 54,000 (p54) in Friend cells. Phorbol, an analogue of TPA with neither tumor-promoting nor differentiation-inhibitory activity, did not induce p54. In a variant cell line of Friend cells which exhibits resistance to TPA in erythroid differentiation, p54 was not induced by TPA. The induction of p54 by TPA was counteracted by erythroid-inducing agents including dimethyl sulfoxide, hexamethylenebisacetamide, and actinomycin D. Throughout these experiments, we have observed an inverse relationship between p54 induction and cellular potential for erythroid differentiation.

Animals↗
PubMed1984

Stimulation of DNA-mediated transformation by UV irradiation of recipient (mouse FM3A) cells.

DNA-mediated transformation for thymidine autotrophs (Tk+) was stimulated severalfold when the recipient (mouse FM3A) (Tk-) cells were preirradiated by UV light. The effect was most prominently seen with the cells irradiated 12-16 hours prior to DNA addition. A similar stimulatory effect was observed when the cells were treated with novobiocin or mitomycin C. The effect, however, was blocked when cycloheximide was present during postirradiation period, suggesting that de novo protein synthesis is required for producing the effect. Most of the Tk+ transformants arised from the UV-irradiated cells carried the donor DNA sequences in their chromosomes.

Animals↗
PubMed1984

Influence of histamine and prostaglandin on desensitization to neurotensin in rat blood pressure.

Triphasic depressor-pressor-depressor blood pressure responses to neurotensin (NT: 1.67 micrograms/kg i.v.) in anesthetized rats were not elicited when the second dose of NT was administered 20 min after the first injection. Pretreatment of animals with histamine markedly reduced the depressor response to NT, and vice versa. The triphasic blood pressure pattern remained unaffected with acetylcholine and serotonin treatment, and hypotensive effects of acetylcholine and serotonin were not modified by NT. Attenuation of depressor response induced by the second injection of NT was antagonized by pretreatment with prostaglandin synthesis inhibitors such as indomethacin, mefenamic acid and acetylsalicylic acid. These results suggest that histamine and prostaglandins play a role in the development of desensitization to NT in rat blood pressure.

Acetylcholine↗