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J J Greene

Publications and source records attributed to J J Greene.

At least 19 recordsLinked to original sources
PubMed1992

Regulation of C-myc and C-Ha-ras oncogene expression by cell shape.

The influence of cell shape on the expression of proto-oncogenes was examined in normal and malignant human cells that varied in their sensitivities to contact-inhibition of proliferation. Cells were constrained into varying degrees of roundness by plating onto culture surfaces coated with different concentrations of poly(2-hydroxyethyl methacrylate) (poly[HEMA]) and assayed for proliferation capacity and levels of c-myc, c-ras, c-fos, and c-fes mRNAs. Proliferation of contact-inhibited normal CUA-1 fibroblasts and the variant HT-IFNr cells was highly coupled to cell shape. As these cells became more rounded, a critical degree of roundness was reached at which proliferation ceased. In contrast, proliferation of non-contact-inhibited malignant HT-1080 cells was independent of cell shape. Northern analysis revealed that expression of c-myc and c-ras was highly sensitive to cell shape in the normal CUA-1 cells but not in the malignant HT-1080 or variant HT-IFNr cells. Levels of c-myc and c-ras mRNAs declined to nearly undetectable levels in CUA-1 cells at degrees of roundness that correlated with loss of proliferative ability. Expression of c-fos and c-fes oncogenes were independent of cell shape in all cells tested. Quantification of transcription rates by the nuclear run-off assay showed that shape modulation of c-myc and c-ras oncogene expression occurred at the transcriptional level. These data suggest that changes in cell shape can modulate expression of certain oncogenes and that these changes correlate with the cell's ability to proliferate. Moreover, inability to regulate c-myc and c-ras oncogene expression is associated with loss of shape-dependent growth controls and contact inhibition but that loss of this regulation alone is not sufficient to release cells from contact-inhibited controls.

Cell Division↗
PubMed1991

Delineation of electric and magnetic field effects of extremely low frequency electromagnetic radiation on transcription.

The relative effects of the electric and magnetic field components of extremely low frequency electromagnetic radiation (ELF) on transcription were examined in human leukemia HL-60 cells. Delineation of the individual field contributions was achieved by irradiating cells in separate concentric compartments of a culture dish within a solenoid chamber. This exposure system produced a homogeneous magnetic field with a coincident electric field whose strength varied directly with distance from the center of the culture dish. Irradiation of HL-60 cells with sine wave ELF at 60 Hz and a field strength of 10 Gauss produced a transient increase in the transcriptional rates which reached a maximum of 50-60% enhancement at 30-120 minutes of irradiation and declined to near basal levels by 18 hours. Comparison of transcription responses to ELF of cells in different concentric compartments revealed that the transcriptional effects were primarily the result of the electric field component with little or no contribution from the magnetic field.

Cell Line↗
PubMed1987

Identification of interferon-modulated proliferation-related cDNA sequences.

To identify genes mediating the antiproliferative action of interferon (IFN), two cDNA libraries were constructed with mRNA from IFN-treated and untreated human fibrosarcoma (HT1080) cells previously shown to be highly sensitive to the antiproliferative effects of IFN. Differential screening of these two libraries identified cloned sequences whose expression was either induced or repressed with IFN treatment. Rescreening of these sequences with cDNA probes constructed from proliferating or quiescent cells led to the identification of one IFN-induced and three IFN-repressed sequences whose expressions also appeared to be modulated by cell proliferation. Blot-hybridization analysis revealed that RNA levels corresponding to the three repressed genes decreased when HT1080 cells were treated with IFN or when proliferation of normal CUA foreskin fibroblast cells became naturally arrested by contact inhibition. Levels of RNA corresponding to the induced gene increased in HT1080 cells within 24 hr after IFN-treatment but declined below basal levels by 48 hr. Expression of these genes was unaffected or only slightly affected by IFN treatment in variant cells resistant to the antiproliferative effects of IFN. Collectively, these results suggest that the identified cDNAs correspond to genes that are involved in the antiproliferative action of IFN. Moreover, these results also suggest that IFN's antiproliferative action may be exerted through genes that contribute to arresting cell proliferation during contact inhibition.

Cell Division↗
PubMed1986

Preferential modulation of embryonic cell proliferation and differentiation by embryonic interferon.

Embryonic-interferon (E-IFN), a novel species of interferon (IFN) produced solely by embryo cells, inhibited the proliferation of embryo cells in early gestation preferentially vis-à-vis fetal cells in late gestation but had little effect on the in vitro differentiation of embryonic pre-adipocytes to adipocytes. In contrast, mature-interferon (M-INF) did not exhibit this preferential inhibition of cell proliferation and did inhibit pre-adipocyte differentiation. These results suggest that the function of E-INF is different from that of M-IFN and that this function may involve modulation of the developmental process.

Adipose Tissue↗
PubMed1986

Shape-dependent regulation of proliferation in normal and malignant human cells and its alteration by interferon.

The relationship between cell morphology, proliferation, and contact inhibition was studied in normal and malignant human cells which varied in their sensitivity to contact inhibition. Their ability to proliferate was examined under conditions where the cells were constrained into different shapes by plating onto plastic surfaces coated with poly(2-hydroxyethyl methacrylate). Poly(2-hydroxyethyl methacrylate) can precisely vary the shape of cells without toxicity. Cell proliferation was quantitated by cell counts and labeling indices were determined by autoradiography. The normal JHU-1 foreskin fibroblasts and IMR-90 lung fibroblasts exhibited contact-inhibited growth with a saturation density of 2.9 X 10(5) and 2.0 X 10(5) cells/cm2, respectively. These cells also exhibited stringent dependency on cell shape with a mitotic index of less than 3% at poly(2-hydroxyethyl methacrylate) concentrations at which the cells were rounded versus a labeling index of 75-90% when the cells were flat. The malignant bladder carcinoma line RT-4 exhibited partial contact-inhibited growth. Its dependency on cell shape was less stringent than that of normal cells with a mitotic index of 37-40% when rounded and 79% when flat. The malignant fibrosarcoma line, HT1080, was not contact inhibited and was entirely shape independent with a mitotic index of 70-90% regardless of cell shape. Treatment of HT1080 cells with low concentration of human fibroblast interferon (less than 40 units/ml) restored shape-dependent proliferation while having little effect on normal cells. Subantiproliferative doses of interferon were also shown to restore contact-inhibited proliferation control to malignant cells previously lacking it. The concordant restoration of contact inhibition and shape-dependent proliferation in malignant cells by interferon suggest that these two types of proliferation controls represent a manifestation of common regulatory mechanisms. However, since these effects occurred at interferon concentrations below that required to produce an antiproliferative effect, these actions of interferon may be distinct from the antiproliferative action.

Cell Communication↗
PubMed1985

Biological and morphological characteristics of phenotypic revertants appearing in interferon-treated mouse cells transformed by a human oncogene.

Phenotypic revertants appearing in interferon-treated mouse cells that had been transformed by an activated human c-Ha-ras1 oncogene (cell line RS485) were tested for several biological properties. The cloned revertants regained the growth characteristics of the untransformed parental NIH 3T3 cell line; unlike RS485 cells the revertants failed to form colonies in soft agar or to form rapidly growing tumors in nude mice. Animals inoculated with RS485 cells developed tumors within one week. In contrast, revertant clonal line 4C3 failed to form tumors four months after transplantation. Revertant 4C8 cells were tumorigenic; however, the developing tumors had increased latency, slower growth rate, and remained smaller than tumors of RS485 cells. Histopathological analysis revealed that revertant-associated fibrosarcomas were less anaplastic, less cellular and had relatively infrequent mitotic figures as compared to fibrosarcomas of RS485 cells. The result suggest the IFN-induced revertants exhibit a significantly less malignant phenotype than their parental transformed cells and that the biological differences are maintained after IFN treatment is discontinued.

Animals↗
PubMed1984

Developmentally regulated expression of the interferon system during Syrian hamster embryogenesis.

Expression of interferon (IFN) during embryogenesis of the Syrian hamster has been characterized with respect to (1) the antiviral activity to IFN; (2) the activity of the IFN-induced enzyme, 2',5'-oligo A synthetase; (3) the subpopulation of IFN producing cells, and (4) the molecular structure of the elaborated IFN. These components of the IFN system were examined in cell cultures derived from embryos excised at 8-13 days of gestation and determined as a function of both in utero gestation and in vitro passaging. The antiviral responsiveness of nine-day gestation cultures (9 dgc) was 1/4-1/6 of that of 13 dgc, but in vitro passaging increased the responsiveness as did in vivo development. IFN enhancement of the synthetase level in 9 dgc was only minimal when compared with that in 13 dgc. However, the 9 dgc contained an unusually high basal level of the enzyme. During in vivo development and in vitro passaging, the basal levels of the enzymes progressively declined while the IFN-induced levels progressively increased. IFN production in embryo cells following induction by Newcastle disease virus differs substantially, depending on the gestational age of the cells. Using an agarose-overlay "zone of protection" assay, 8 dgc were found to contain 10-12 times the number of cells producing zones of protection than 13 dgc. Passaging of 9 dgc cells reduced the number of zones to the level of the 13 dgc, but had no effect on 13 dgc. Chromatographic analysis of IFN produced by 9 dgc and 13 dgc revealed the presence of an additional, unique species of "embryonic" IFN in 9 dgc which was not observed in IFN from 13 dgc. These observations suggest that the expression of various components of the IFN system are under developmental control during embryogenesis.

2',5'-Oligoadenylate Synthetase↗
PubMed1980

Activation of 2',5'-oligo(A) polymerase and protein kinase of interferon-treated HeLa cells by 2'-O-methylated poly (inosinic acid) . poly(cytidylic acid), Correlations with interferon-inducing activity.

An oligonucleotide polymerase and a protein kinase which require double-stranded RNA (dsRNA) for activation are induced in HeLa cells by human fibroblast interferon. The polymerase synthesizes a series of oligonucleotides from ATP, whereas the kinase phosphorylates a polypeptide of Mr = 72,000 and the alpha subunit of initiation factor eIF-2. Partially or fully 2'-O-methylated derivatives of poly(inosinic acid) . poly(cytidylic acid) (rIn . rCn) were used to determine the structural requirements of dsRNA in the activation of these two enzymes. While fully methylated polymers failed to activate either enzyme, partially methylated polymers activated the enzymes in specific manners. The activation of the kinase by the rIn . rCn analogues was affected more severely by the level of methylation than was the activation of the polymerase. Moreover, fully methylated analogues blocked the activation of the kinase by rIn . rCn but not the activation of the polymerase. These observations are consistent with a biphasic model for enzyme activation similar to that proposed for interferon induction, which required the recognition of a relatively small region of rIn . rCn as the last step. Differences in the activation of the polymerase and kinase are explicable on the basis of the polymerase requirement for a smaller recognition region of the rIn . rCn duplex than the kinase. Dependence of polymerase activation on the level of methylation shows striking similarities with the interferon inducing activities of these analogues, suggesting a possible relationship between polymerase activation and interferon induction.

2',5'-Oligoadenylate Synthetase↗
PubMed1980

Species-specific posttranscriptional regulation of interferon synthesis.

Human fibroblast and Syrian hamster embryo cells were induced to synthesize interferon (IF) with rIn . rCn and rIn . rCn + DEAE-dextran, respectively. Following induction, these cells synthesized IF for only a short time before entering into a repressed state and shutting off the synthesis of IF. Homologous and heterologous whole cell translational systems were developed to investigate the molecular basis for the shut-off of IF synthesis. These systems allowedd for the introduction of exogenous hamster and human IF-mRNAs into intact normal and repressed hamster and human cells via an improved CaCl2 precipitation technique. Human IF-mRNA was translated in normal human and hamster cells and in repressed hamster cells but not in repressed human cells. In contrast, the hamster IF-mRNA was translated in normal human, normal hamster, and repressed human cells but not in repressed hamster cells. These results indicate that a species-specific mechanism inhibiting translation of IF-mRNA is directly responsible for the shut-off of IF synthesis in human fibroblasts and Syrian hamster embryo cells.

Animals↗
PubMed1980

Inter- and intra-examiner variability in scoring supragingival plaque: I. The clinical study.

Twenty-four normal healthy patients were scored for plaque by four examiners with different professional backgrounds and different levels of training. Each patient was examined twice by each examiner according to a predetermined random assignment with the assumption of no change in state. All four examiners scored higher on the second examination and there was no apparent consistent relationship between professional background and level of training in the plaque scoring.

Dental Hygienists↗
PubMed1978

Interferon induction and its dependence on the primary and secondary structure of poly(inosinic acid).poly(cytidylic acid).

The synthetic interferon (IF) inducer rIn.rCn was modified by substituting the ribosyl residues with either their corresponding deoxy(dC or dI) or 2'-O-methyl analogues (mC or mI). The polynucleotide duplexes of these analogues are inactive as IF inducers. Circular dichroism (CD) studies revealed that, while the deoxy substitution produces significant changes in the conformation of rIn.rCn, the 2'-O-methyl substitution produces no detectable change. Biological competition experiments indicated that the methylated duplexes mIn.rCn, rIn.mCn, and mIn.mCn all compete with rIn.rCn for IF induction, while the deoxy duplexes dIn.rCn and rIn.dCn do not. These results are consistent with those predicted from the CD data. Copolymer duplexes (mI,rI)n.(mC,rC)n of varying degrees of methylation and residue clustering were also evaluated for IF induction in human fibroblasts. The IF-inducing capabilities of these duplexes correlated highly with the presence of clusters containing six or more consecutive ribosyl residues. These combined observations suggest that interaction of rIn.rCn with the cell in the induction process may occur in a biphasic manner involving first the topological recognition of a large segment of the RNA to allow for proper binding to the putative cellular receptor, followed by recognition of a much smaller region of the RNA corresponding to 6--12 consecutive ribosyl residues (0.5 to 1 helical turn) which is responsible for the triggering of the induction process.

Circular Dichroism↗