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Biomedical subjects

J C Reed

Publications and source records attributed to J C Reed.

At least 505 records · Page 28Linked to original sources
PubMed1988

Dexamethasone inhibition of interleukin 1 beta production by human monocytes. Posttranscriptional mechanisms.

Dexamethasone is known to have an inhibitory effect on IL-1 production. To determine the mechanism(s) of this inhibition, adherent human blood monocytes were stimulated with Escherichia coli lipopolysaccharide (LPS) (10 micrograms/ml) in the presence of dexamethasone. Nuclear transcription run-off assays showed that LPS induced IL-1 beta gene transcription two- to fourfold and that this induction was unaffected by dexamethasone exposure (10(-5) M). The lack of dexamethasone's transcriptional effects was further supported by the absence of any significant change in IL-1 beta mRNA accumulation between LPS-stimulated monocytes exposed or unexposed to dexamethasone, as determined by Northern blot analysis. Posttranscriptionally, dexamethasone was found to have multiple effects: slight prolongation of IL-1 beta mRNA half-life, moderate inhibition of translation of the IL-1 beta precursor, and profound inhibition of the release of IL-1 beta into the extracellular fluid. The data indicate that IL-1 beta is first translated as the 33,000-D pro-IL-1 beta protein, the predominant intracellular form, and the processed to a 17,500-D IL-1 beta protein before or during extracellular transport. The major inhibitory effects of dexamethasone appear to be directed at the translational and posttranslational steps involved in these events.

Dexamethasone↗
PubMed1987

Regulation of bcl-2 proto-oncogene expression during normal human lymphocyte proliferation.

The bcl-2 and c-myc proto-oncogenes are brought into juxtaposition with the immunoglobulin heavy chain locus in particular B-cell lymphomas, resulting in high levels of constitutive accumulation of their messenger RNAs. Precisely how the products of the bcl-2 and c-myc genes contribute to tumorigenesis is unknown, but observations that c-myc expression is rapidly induced in nonneoplastic lymphocytes upon stimulation of proliferation raise the possibility that this proto-oncogene is involved in the control of normal cellular growth. In addition to c-myc, the bcl-2 proto-oncogene also was expressed in normal human B and T lymphocytes after stimulation with appropriate mitogens. Comparison of the regulation of the expression of these proto-oncogenes demonstrated marked differences and provided evidence that, in contrast to c-myc, levels of bcl-2 messenger RNA are regulated primarily through transcriptional mechanisms.

Blood Proteins↗
PubMed1987

Sensitivity of mouse Skh:HR-2 to ultraviolet radiation: melanocyte inactivation.

The hairless mouse, Skh:HR-2, was exposed to doses of ultraviolet (UV) radiation known to induce skin pigmentation. Three parameters associated with perturbations in skin pigmentation were monitored following UV exposure. These include spectroscopy (skin darkness), histology (melanocyte density), and biochemistry (melanin). Within 90 min of UV exposure, the skin became lighter. This was associated with a reduction of quantifiable melanin and the inactivation of epidermal melanocytes.

Animals↗
PubMed1987

Treatment of multiple facial neurofibromas with dermabrasion.

Three patients with multiple facial neurofibromas were treated by dermabrasion with good cosmetic results. Wound healing was entirely normal and no complications were observed. There was no evidence of accelerated regrowth of tumors during follow-up.

Adult↗
PubMed1987

Differential promoter utilization by the c-myc gene in mitogen- and interleukin-2-stimulated human lymphocytes.

Transcription of the c-myc gene is initiated from two principal promoters, P1 and P2. We demonstrate here that a shift in promoter utilization occurred with time in human peripheral blood mononuclear cells (PBMC) that had been stimulated to proliferate. The P1/P2 ratio reached a maximum of approximately 1.3 at 4 h after phytohemagglutinin stimulation and a minimum of 0.31 at 48 h. Actinomycin decay experiments demonstrated that both P1 and P2 transcripts had similar half-lives at early and late times after mitogen stimulation, indicating that the shift in promoter utilization was probably not posttranscriptionally regulated. Addition of interleukin-2 to previously activated PBMC increased c-myc mRNA, but unlike increases after mitogen stimulation, the P1/P2 ratio stayed less than 0.5. Our findings demonstrated that there was a difference between mitogen- and interleukin-2-stimulated increases in c-myc RNA in PBMC.

Cells, Cultured↗
PubMed1987

Expression of c-myc proto-oncogene in normal human lymphocytes. Regulation by transcriptional and posttranscriptional mechanisms.

Aberrant expression of the c-myc gene results from nonrandom chromosomal translocations involving the transcriptionally active antigen receptor gene loci, in particular lymphocytic leukemias and lymphomas, and is believed to contribute to the etiology of these neoplasms. In addition to its expression in abnormal lymphocytes, increased accumulation of c-myc mRNA occurs rapidly in normal B- and T-lymphocytes after stimulation with appropriate mitogens. The mechanisms that mediate these mitogen-induced elevations in c-myc mRNA levels, however, have not been determined for normal B and T cells. By using enriched populations of B- and T-lymphocytes obtained from freshly isolated human tonsils and stimulated with Staphylococcus-A or with phytohemagglutinin, respectively, we observed marked elevations (20-40-fold) in the steady state levels of accumulated c-myc messenger RNA (mRNA) within 1 h of exposure of cells to mitogens; modest increases (three- to fivefold) in the relative rate of transcription of the c-myc gene through protein synthesis-independent (cycloheximide-insensitive) mechanisms; and rapid rates of degradation of mature c-myc mRNAs through protein synthesis-dependent (cycloheximide-sensitive) mechanisms. These findings corroborate previous studies in other cell types and provide evidence for both transcriptional and posttranscriptional control of c-myc proto-oncogene expression in normal human lymphocytes.

B-Lymphocytes↗
PubMed1987

Proto-oncogene expression in cloned T lymphocytes: mitogens and growth factors induce different patterns of expression.

We have compared the effects of a mitogenic lectin, concanavalin A (Con A), and a growth factor, interleukin-2 (IL-2), on the expression of the c-myc, c-fos, and c-myb proto-oncogenes in cloned T lymphocytes. Accumulation of c-myc mRNA was induced by both ConA and IL-2 in these cells. In contrast, expression of c-fos was stimulated primarily by ConA, and accumulation of c-myb mRNA was induced predominantly by IL-2. Thus, ConA and IL-2 induce expression of overlapping, but non-identical, sets of proto-oncogenes in T lymphocytes. Investigations with several different cloned T cells revealed that: (1) c-myb is not induced in all T cells stimulated to grow, indicating that its expression may not be absolutely required for their proliferation; and (2) expression of c-myc, even in combination with c-fos, can be insufficient for growth, demonstrating functional differences between cellular and viral oncogenes in T cells. These observations provide insight into the roles of the c-myc, c-fos, and c-myb proto-oncogenes in normal T cell responses.

Cell Division↗
PubMed1986

Alterations in T4 (CD4) protein and mRNA synthesis in cells infected with HIV.

Cells infected with the human immunodeficiency virus (HIV) show decreased expression of the 58-kilodalton T4 (CD4) antigen on their surface. In this study, the effect of HIV infection on the synthesis of T4 messenger RNA (mRNA) and protein products was evaluated in T-cell lines. Metabolically labeled lysates from the T4+ cell line Sup-T1 were immunoprecipitated with monoclonal antibodies to T4. Compared with uninfected cells, HIV-infected Sup-T1 cells showed decreased amounts of T4 that coprecipitated with both the 120-kilodalton viral envelope and the 150-kilodalton envelope precursor molecules. In four of five HIV-producing T-cell lines studied, the steady-state levels of T4 mRNA were also reduced. Thus, the decreased T4 antigen on HIV-infected cells is due to at least three factors: reduced steady-state levels of T4-specific mRNA, reduced amounts of immunoprecipitable T4 antigen, and the complexing of available T4 antigen with viral envelope gene products. The data suggested that the T4 protein produced after infection may be complexed with viral envelope gene products within infected cells. Retroviral envelope-receptor complexes may thus participate in a general mechanism by which receptors for retroviruses are down-modulated and alterations in cellular function develop after infection.

Acquired Immunodeficiency Syndrome↗
PubMed1986

The role of the accessory cell in mitogen-stimulated human T cell gene expression.

The role of the accessory cell in optimizing T cell proliferative responses to mitogens is a well known but poorly understood phenomenon. To further dissect the function of the accessory cell in allowing T cell proliferation, we compared mitogen-induced c-myc, interleukin 2 (IL 2), and IL 2 receptor gene expression in peripheral blood mononuclear cells (PBMC) and in T cells rigorously depleted of accessory cells through differential adherence and anti-Dr (anti-class II major histocompatibility antigen) monoclonal antibody complement-directed cytotoxicity. In cultures stimulated with phytohemagglutinin (PHA), a mitogen that requires accessory cells to induce T cell proliferation, expression of all measured genes was accessory cell dependent, since accumulation of their mRNA in PBMC was greater than that in cultures depleted of accessory cells. These genes varied in their accessory cell dependence, with IL 2 expression most dependent, c-myc expression least dependent, and IL 2 receptor expression intermediate in dependency. Use of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or ionomycin, mitogens that stimulate T cell proliferation independent of accessory cells, induced equal levels of gene expression in PBMC and in T cells depleted of accessory cells. These results suggest that PHA-stimulated T cells are dependent on an accessory cell signal(s) for optimal expression of the genes for c-myc, IL 2, and IL 2 receptor, and for proliferation. In addition, this signal(s) appears to be delivered early in the course of T cell activation events, since it can be bypassed by mitogens that directly activate protein kinase C (TPA) or induce calcium translocation (ionomycin). In addition, these data provide further evidence that expression of the c-myc protooncogene is insufficient for T cell mitogenesis, since PHA-induced accumulation of c-myc mRNA was only partially accessory cell dependent, whereas proliferation was completely accessory-cell dependent.

Antigen-Presenting Cells↗
PubMed1986

Effect of cyclosporin A and dexamethasone on interleukin 2 receptor gene expression.

Here we demonstrate that CsA and DEX, at concentrations that markedly inhibited PHA-induced proliferation and IL 2 mRNA accumulation, partially diminished the expression of receptors for IL 2 on PBMC. This inhibition of IL 2 receptor expression occurred at a pretranslational level and involved a reduction in both high affinity and low affinity forms of the receptor. Although both CsA and DEX inhibited IL 2 receptor expression by about 50%, only CsA blocked the PHA-mediated induction of IL 2 responsivity in PBMC cultures. These data provide evidence that 1) CsA and DEX suppress the proliferation of T lymphocytes through distinct (though perhaps overlapping) mechanisms, 2) CsA (but not DEX) blocks the PHA-mediated induction of signals necessary for T cells to become capable of proliferating in response to IL 2, and 3) T cells regulate the expression of their genes for IL 2 and IL 2 receptors, at least in part, through independent mechanisms.

Antigens, Surface↗
PubMed1986

Characterization of left ventricular chamber distortion: alterations in cavity shape and orientation in mitral stenosis.

Distortion of the left ventricular (LV) chamber silhouette was identified in 28 patients with mitral stenosis (MS) by disparity between normally identical chamber volumes calculated independently from the frontal (AP) and lateral (LAT) views of biplane cineangiograms (AP end diastolic volume 157.8 +/- 10.0 ml, LAT end diastolic volume 115.6 +/- 7.2 ml, p less than .001). Similar systematic disparity was observed in estimates of end systolic volume in these views. While no directional difference in ejection fraction was found, identical (+/- 10%) AP and LAT measurements were obtained in only 36% of patients, indicating poor reproducibility of the estimate of LV function between single radiographic views. A technique was also devised for determining the spatial orientation of the LV long axis (mid mitral valve to apex) from biplane cineangiograms; this axis was shown to intercept the frontal plane at an angle of 50.9 +/- 2.4 degrees in 12 subjects with normal LV anatomy and 36.1 +/- 4.5 degrees in seven patients with MS, indicating that the long axis was rotated posteriorly toward alignment with the frontal plane in the latter group. The presence and magnitude of LV chamber distortion was clearly related to the degree of angiographically estimated right ventricular dilatation. Implications of these observations, particularly with reference to the estimation of single plane LV volume characteristics in patients with MS, are discussed.

Angiocardiography↗
PubMed1986

Sequential expression of protooncogenes during lectin-stimulated mitogenesis of normal human lymphocytes.

The proliferation of non-neoplastic T lymphocytes is regulated, in part, by the coordinated expression of genes encoding T-cell growth factor (interleukin 2, IL2), IL2 receptors (IL2R), and transferrin receptors (TFR). In addition to growth factors and their receptors, protooncogenes may regulate lymphocyte proliferation. We used cloned cDNAs homologous to 21 different protooncogenes to screen for their expression at the mRNA level in human peripheral blood mononuclear cells (PBMC) stimulated with the mitogenic lectin phytohemagglutinin (PHA), and we compared the time course of accumulation of mRNAs for these protooncogenes to that of mRNAs for the IL2, IL2R, TFR, and histone H3 genes. mRNAs for c-abl, c-ets, c-yes, and N-ras were present in unstimulated PBMC. After stimulation of PBMC by PHA, we detected marked increases within 10 min in the levels of mRNA for c-fos and c-myc; within 6 hr for IL2 and IL2R mRNAs; within 14 hr for c-myb, p53, N-ras, and TFR mRNAs; and within 24-36 hr for H3 mRNA. Expression of c-abl, c-ets, and c-yes increased gradually following stimulation with PHA. None of the other protooncogenes tested was expressed in PBMC. Addition of the protein synthesis inhibitor cycloheximide, before the addition of PHA to cultures, abolished the PHA-induced accumulation of mRNAs for c-myb, N-ras, and TFR, but not of mRNAs for c-fos, c-myc, IL2, and IL2R. These data indicate that c-fos, c-myc, IL2, and IL2R belong to a group of genes expressed early, whereas c-myb, N-ras, and TFR belong to a group of genes expressed later in PHA-activated PBMC, and that the products of the c-fos and c-myc protooncogenes are not required for expression of IL2 or IL2R genes. Addition of purified IL2 augmented the expression of the later-expressed genes c-myb, p53, N-ras, and TFR in PHA-stimulated cultures of PBMC, as well as of the early genes c-myc and IL2R, but not of c-fos and IL2, thus suggesting that PHA and IL2 stimulate the expression of overlapping, but nonidentical, sets of genes in PBMC.

Cells, Cultured↗
PubMed1986

The lymphokine "inhibitor of DNA synthesis" (IDS) suppresses human T lymphocyte proliferation by an interleukin-2-independent mechanism.

IDS is a soluble glycoprotein product of activated T cells that inhibits lymphocyte proliferation induced by antigens and by lectin mitogens. This immunosuppressive lymphokine has been distinguished from lymphotoxin, Proliferation Inhibitory Factor, Colony Inhibitory Factor, Macrophage Inhibitory Factor, and interferon. Using IDS partially purified by isoelectric focusing from culture supernatants of concanavalin A-stimulated human peripheral blood mononuclear cells (PBMC), we investigated IDS inhibition of T cell proliferation with respect to the interleukin pathway. At concentrations that produced 75-90% suppression of proliferation in PHA-stimulated PBMC cultures, IDS caused no decrease in interleukin 2 (IL2) production (determined by bioassay) or in IL2 receptor expression (determined with anti-Tac antibody). Moreover, adding exogenous IL2 to IDS-inhibited cultures failed to restore proliferation. IDS inhibited growth of several IL2-dependent and IL2-independent cell lines, and suppressed proliferation of PBMC induced by the phorbol ester TPA (12-0-tetradecanoyl-13-phorbol acetate) or by the calcium ionophore A23187, thus distinguishing its mechanism of action from that of cyclosporin A, dexamethasone, OKT11A antibody, and other inhibitors. These data extend earlier findings that IDS acts late in G1 phase of the cell cycle, and provide evidence that IDS inhibits T cell proliferation through an IL2-independent mechanism.

Animals↗
PubMed1985

Regulation of c-myc mRNA levels in normal human lymphocytes by modulators of cell proliferation.

Increased expression of the cellular oncogene c-myc has recently been demonstrated in some types of proliferating non-neoplastic cells, including lectin mitogen-stimulated lymphocytes, suggesting a role for this protooncogene in the regulation of growth of normal cells. Here we report the effects of several modulators of lymphocyte proliferation on the steady-state levels of c-myc mRNA in human peripheral blood mononuclear cells (PBMC). Stimulating PBMC with lectin mitogen phytohemagglutinin (PHA), phorbol ester phorbol 12-myristate 13-acetate, calcium ionophore ionomycin, or monoclonal antibody OKT3 (anti-antigen receptor complex) produced marked increases in c-myc mRNA levels within 3 hr. Recombinant interleukin 2 (rIL-2; Cetus) had little effect on c-myc expression but, in combination with PHA, it augmented levels of c-myc transcripts measured at 24 hr but not at 3 hr. Adding various inhibitors of lymphocyte proliferation to PHA-stimulated cultures revealed that cyclosporin A, dexamethasone, and OKT11A antibody (anti-sheep erythrocyte receptor) diminished levels of c-myc mRNA measured at 3 hr and 24 hr, whereas anti-Tac (anti-IL-2-receptor) inhibited at 24 hr but not at 3 hr. Thus, cyclosporin A, dexamethasone, and OKT11A interfere with early events of T-cell activation, whereas anti-Tac acts later. Hydroxyurea and 42/6 antibody (anti-transferrin receptor), which impair the G1----S transition in cycling cells, failed to inhibit c-myc expression and instead delayed the decrease in c-myc mRNA levels that normally occurs with the onset of DNA synthesis. These data indicate that c-myc is regulated (in normal lymphocytes) at several points in the cell cycle.

Antibodies, Monoclonal↗
PubMed1985

Recombinant interleukin 2 regulates levels of c-myc mRNA in a cloned murine T lymphocyte.

The cellular oncogene c-myc has been implicated in the regulation of growth of normal and neoplastic cells. Recently, it was suggested that c-myc gene expression may control the G0----G1-phase transition in normal lymphocytes that were stimulated to enter the cell cycle by the lectin concanavalin A (ConA). Here we describe the effects of purified recombinant interleukin 2 (rIL2) and of ConA on levels of c-myc mRNA in the noncytolytic murine T-cell clone L2. In contrast to resting (G0) primary cultures of lymphocytes, quiescent L2 cells have a higher RNA content than resting splenocytes and express receptors for interleukin 2 (IL2). Resting L2 cells are therefore best regarded as early G1-phase cells. Purified rIL2 was found to stimulate the rapid accumulation of c-myc mRNA in L2 cells. Levels of c-myc mRNA became maximal within 1 h and declined gradually thereafter. In contrast, ConA induced slower accumulation of c-myc mRNA in L2 cells, with increased levels of c-myc mRNA becoming detectable 4 to 8 h after stimulation. Experiments with the protein synthesis inhibitor cycloheximide demonstrated that the increase in levels of c-myc mRNA that were induced by ConA was a direct effect of this lectin and not secondary to IL2 production. Cyclosporin A, an immunosuppressive agent, markedly reduced the accumulation of c-myc mRNA that was induced by ConA but only slightly diminished the accumulation of c-myc mRNA that was induced by rIL2. Taken together, these data provide evidence that (i) c-myc gene expression can be regulated by at least two distinct pathways in T lymphocytes, only one of which is sensitive to cyclosporine A, and (ii) the accumulation of c-myc mRNA can be induced in T cells by IL2 during the G1 phase of the cell cycle.

Animals↗
PubMed1985

Suppression of interleukin 2 receptor acquisition by monoclonal antibodies recognizing the 50 KD protein associated with the sheep erythrocyte receptor on human T lymphocytes.

Monoclonal antibodies OKT11A, 9.6, and 35.1 recognize epitopes on a 50000 dalton surface molecule (p50) identical to or closely associated with the sheep erythrocyte receptor (E receptor) on human T lymphocytes. These three antibodies were investigated for ability to inhibit T cell proliferation and interleukin 2 (IL 2) receptor acquisition (determined with anti-Tac antibody in an immunofluorescence assay) induced by the lectin mitogen phytohemagglutinin (PHA) or by the phorbol ester 12-O-tetradecanoyl-phorbol-13 acetate (TPA). OKT11A, 9.6, and 35.1 were found to suppress [3H]thymidine incorporation and IL 2 receptor acquisition stimulated by PHA but not by TPA. This inhibition was not attributable to a lag in kinetics, but was sustained throughout 4 to 5 days of culture. Because OKT11A and 9.6 have been reported to suppress lectin mitogen-induced IL 2 production, we attempted to overcome inhibition of proliferation with exogenous IL 2 (MLA144 supernatants or immunoaffinity-purified human IL 2). Adding IL 2 at the initiation of culture abrogated the suppressive effect of all three anti-p50 antibodies on proliferation and on the acquisition of IL 2 receptors, raising the possibility that IL 2 may up-regulate expression of its cellular receptor on human T lymphocytes. These data, together with previous reports, indicate that OKT11A, 9.6, and 35.1 suppress lectin mitogen-induced T cell proliferation by impairing both IL 2 elaboration and IL 2 receptor acquisition, and suggest that IL 2 may be capable, at least under some conditions, of increasing expression of IL 2 receptors on human T lymphocytes.

Animals↗