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Biomedical subjects

J C Reed

Publications and source records attributed to J C Reed.

At least 343 records · Page 19Linked to original sources
PubMed1996

PTPN13, a fas-associated protein tyrosine phosphatase, is located on the long arm of chromosome 4 at band q21.3.

PTPN13 is a protein tyrosine phosphatase that associates with the C-terminal negative regulatory domain in the Fas (APO-1/CD95) receptor. The PTPN13 protein contains six GLGF repeats that have been found in the rat postsynaptic density protein (PSD-95) and the Drosophila tumor suppressor protein, lethal-(1)-disc-large-1 (dlg-1). The localization of the PTPN13 gene to human chromosome 4q21.3 was determined by both FISH and PCR analysis of somatic cell hybrids. This 4q21.3 chromosomal region contains a gene for autosomal dominant polycystic kidney disease as well as the region frequently deleted in liver and ovarian cancers, suggesting that PTPN13 is a candidate for one of the putative tumor suppressor genes on the long arm of chromosome 4.

Base Sequence↗
PubMed1996

Gamma-radiation induces upregulation of Bax protein and apoptosis in radiosensitive cells in vivo.

Lymphoid cells and small intestinal epithelial (SIE) cells are among the most radiosensitive in the body. The factors that account for the differential sensitivity to gamma-radiation among different tissue-types remain poorly understood, but can only partly be explained by differences in rates of cell proliferation. Here we demonstrate that exposure of mice to 800 cGy of gamma-radiation results in rapid elevations in the levels of the Bax protein, a pro-apoptotic member of the Bcl-2 protein family, in lymphoid cells and SIEs. gamma-Radiation-induced increase in Bax protein were evident within 2 h and persisted for at least 24 h, as determined by immunoblotting and immunohistochemical assays. Increases in Bax were followed by massive apoptosis in lymphoid organs and in the small intestinal crypts, as determined by morphological criteria and in situ end-labeling of fragmented nuclear DNA by terminal deoxynucleotidyl transferase (TUNEL method). Radiation did not induce elevations in Bax or apoptosis in radioresistant tissues such as heart, skeletal muscle, brain, kidney, liver, lung, vascular smooth muscle and connective tissue. The findings suggest that Bax may be one of the mediators of radiation-induced apoptosis in vivo.

Animals↗
PubMed1996

Expression of the Bcl-2 homologue Mcl-1 correlates with survival of peripheral blood B lymphocytes.

Normal peripheral blood B lymphocytes undergo spontaneous apoptosis in vitro, and this process is regulated positively and negatively by several immunomodulatory stimuli. We have shown previously that Bcl-2 protein levels are unaltered by these factors, suggesting a Bcl-2-independent regulation of apoptosis in this system. Here, we have investigated the possibility that the three recently identified Bcl-2 homologues, Bax, Bcl-x, and Mcl-1, could be involved instead. Freshly isolated cells expressed both Bax and Mcl-1 protein, but only low levels of Bcl-xL and no detectable Bcl-xS, as determined by Western blot analysis. Upon culture of cells with apoptotic or survival stimuli, Bax and Bcl-xL protein levels remained relatively unchanged. By contrast, Mcl-1 levels decreased markedly in cells undergoing apoptosis in medium and, even more dramatically, after treatment with the apoptotic stimuli transforming growth factor beta 1 and forskolin. This decrease was rapid and preceded cell death. Furthermore, all the survival stimuli tested (interleukin 4, anti-IgM antibodies, and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate) prevented the decline in Mcl-1 levels. This striking correlation between cell survival and Mcl-1 expression in peripheral blood B cells suggests the possible involvement of Mcl-1, instead of Bcl-2, in the regulation of apoptosis in these cells. The present study is the first one linking this novel Bcl-2 homologue to the control of cell death in normal cells.

Apoptosis↗
PubMed1996

BCL-2 family proteins: regulators of cell death involved in the pathogenesis of cancer and resistance to therapy.

The BCL-2 gene was first discovered because of its involvement in the t(14;18) chromosomal translocations commonly found in lymphomas, which result in deregulation of BCL-2 gene expression and cause inappropriately high levels of Bcl-2 protein production. Expression of the BCL-2 gene can also become altered in human cancers through other mechanisms, including loss of the p53 tumor suppressor which normally functions as a repressor of BCL-2 gene expression in some tissues. Bcl-2 is a blocker of programmed cell death and apoptosis that contributes to neoplastic cell expansion by preventing cell turnover caused by physiological cell death mechanisms, as opposed to accelerating rates of cell division. Overproduction of the Bcl-2 protein also prevents cell death induced by nearly all cytotoxic anticancer drugs and radiation, thus contributing to treatment failures in patients with some types of cancer. Several homologs of Bcl-2 have recently been discovered, some of which function as inhibitors of cell death and others as promoters of apoptosis that oppose the actions of the Bcl-2 protein. Many of these Bcl-2 family proteins can interact through formation of homo- and heterotypic dimers. In addition, several nonhomologous proteins have been identified that bind to Bcl-2 and that can modulate apoptosis. These protein-protein interactions may eventual serve as targets for pharmacologically manipulating the physiological cell death pathway for treatment of cancer and several other diseases.

Apoptosis↗
PubMed1996

Interleukin-2 receptor common gamma-chain signaling cytokines regulate activated T cell apoptosis in response to growth factor withdrawal: selective induction of anti-apoptotic (bcl-2, bcl-xL) but not pro-apoptotic (bax, bcl-xS) gene expression.

Cytokine deprivation from activated T cells leads to apoptosis associated with down-regulation of the bcl-2 gene product. It is not clear, however, how cytokines other than interleukin-2 (IL-2) may affect this process and regulate the involvement of other apoptosis-modulating genes. We show that a group of cytokines including IL-2 (IL-2R gamma), prevent the apoptosis of IL-2-deprived activated T cells. This rescue involves the induction of the anti-apoptosis genes bcl-2 and bcl-xL), but causes little change in expression of bax and bcl-xS, which promote apoptosis. Furthermore, the prevention of apoptosis and induction of proliferation by the common gamma chain cytokines can be dissociated. Thus, when proliferation is blocked, the common gamma chain cytokines still induce up-regulation of bcl-2 relative to bax and retard apoptosis. These cytokines can thus regulate the persistence or removal of effector T cells by coordinating the balance between genes which promote and those which inhibit apoptosis, events which are probably mediated at least in part by signals through the common gamma chain. These data also implicate inappropriate T cell apoptosis resulting from a dysfunctional common gamma-chain as part of the pathophysiological defect in patients with X-linked severe-combined immunodeficiency (SCID).

Apoptosis↗
PubMed1996

Bcl-2 protects cells from cytokine-induced nitric-oxide-dependent apoptosis.

Cytokine-mediated cell death in tumor cells can be achieved through endogenous nitric oxide (NO) from within tumor cells or exogenous NO from either activated macrophages or endothelial cells. The purpose of this study was to determine the role of Bcl-2 in NO-mediated apoptosis. The incubation of murine L929 and NIH3T3 cells with interleukin-1 alpha (IL-1 alpha) and interferon gamma (IFN gamma) induced high endogenous NO production only in the L929 cells that also underwent apoptosis. NIH3T3 cells were not resistant to NO-mediated apoptosis. In fact, the incubation of L929 and NIH3T3 cells with exogenous NO derived from NO donors, sodium nitroprusside, or S-nitroso-N-acetyl-DL-penicillamine (SNAP) induced death, characterized by typical apoptotic morphology and DNA fragmentation, in both cell types, but to a higher degree in NIH3T3 cells than in the L929 cells. We then measured the effect of Bcl-2 expression on exogenous NO-induced apoptosis. At both the mRNA and protein levels, L929 fibroblasts expressed higher levels of endogenous mouse Bcl-2 than did NIH3T3 cells. At the same time, L929 cells were much more resistant to exogenous NO-induced cell death than were NIH3T3 cells. The inverse correlation between mouse Bcl-2 expression and sensitivity to exogenous NO-mediated cell death was also found in the murine K-1735 melanoma C-23 and X-21 clonal populations. Transfection of both NIH3T3 cells and L929 cells with the human bcl-2 gene led to resistance to both exogenous and endogenous NO-mediated apoptosis. These data demonstrate that NO-mediated apoptosis can be suppressed by expression of Bcl-2, suggesting that abnormal expression of Bcl-2 may influence the efficacy of tumor immunotherapy.

3T3 Cells↗
PubMed1996

The BAX gene maps to the glioma candidate region at 19q13.3, but is not altered in human gliomas.

The bax protein regulates apoptosis in a cellular pathway that involves both bcl-2 and p53, two molecules associated with human glioma tumorigenesis. We therefore evaluated the possibility that BAX functions as a glioma tumor suppressor gene. Somatic cell hybrid panels, fluorescence in situ hybridization and cosmid mapping localized the BAX gene to 19q13.3, approximately 300 kb centromeric to HRC. Thus BAX maps to the region of chromosome 19 most frequently deleted in gliomas. Routine and pulsed-field gel electrophoresis/Southern blotting studies, however, failed to reveal large-scale deletions or rearrangements of the BAX gene in gliomas. In addition, single strand conformation polymorphism analysis of all six BAX exons and flanking intronic sequences did not disclose mutations in 20 gliomas with allelic loss of the other copy of 19q. A C/T polymorphism was detected in intron 3 and was common in the general population. Therefore, although BAX maps to the glioma candidate region on the long arm of chromosome 19, BAX is probably not the 19q glioma tumor suppressor gene.

Base Sequence↗
PubMed1996

Predominant expression of the long isoform of Bcl-x (Bcl-xL) in human lymphomas.

Bcl-x is a member of the bcl-2 family of proteins which are characterized by their ability to modulate apoptosis. Alternative splicing results in two distinct bcl-x mRNAs encoding a long isoform, bcl-xL, which acts as a bcl-2 agonist; and a short isoform, bcl-xS, which inhibits bcl-2 effects. The aim of the study was to determine whether bcl-x is expressed in lymphoma tissues and to characterize the respective production of bcl-xs and bcl-xL. We investigated the expression of bcl-x mRNA in a series of 50 non-Hodgkin's lymphomas (NHL) and Hodgkin's disease (HD) cases using a RT-PCR method in order to amplify both transcripts simultaneously, and to estimate their relative abundance. The rearrangements of the bcl-2 gene were analysed by RT-PCR expression of the hybrid bcl-2-lgH mRNA. In addition, 20 PCR-positive NHL cases and three HD cases were analysed by immunohistochemistry using bcl-x polyclonal antisera. RT-PCR showed bcl-x expression in 43/45 NHLs and 5/5 HD cases. The bcl-xL transcript was predominant in all positive cases and was associated with variable amounts of bcl-xS. There was no significant correlation between the profile of bcl-xL/bcl-xS expression and the histological and immunological subtyping. Bcl-x immunodetection was positive in the neoplastic cell component in all analysed cases, but the degree of staining was highly variable between cases. Expression of the hybrid bcl-2-IgH gene was detected by RT-PCR in five cases of follicular NHL and in one case of HD, but this group of tumours did not display a particular profile of bcl-xL/bcl-xS expression. We conclude that bcl-x is commonly expressed by malignant cells in various types of malignant lymphomas, with a predominance of the bcl-xL transcript. Since the corresponding bcl-xL isoform can block the cell death machinery and potentialize bcl-2 effects, it may be involved in some pathways of lymphomagenesis.

Base Sequence↗
PubMed1996

Evaluation of Bcl-2/B cell transgenic mice (B6) for hybridoma production.

Bcl-2 is an oncogene associated with prevention of apoptosis in a variety of cell types. Bcl-2 expression in B lymphoid cells prolongs antibody production, in vitro and in vivo. A line of transgenic mice (B6) has been developed that expresses human Bcl-2 in the B cells of SWR/SJL mice. B6 transgenic, nontransgenic littermates, and BALB/c mice were immunized with beta-galactosidase (B-gal) or sheep red blood cells (SRBC). The number of spleen cells recovered from immunized B6 mice was 3-4 times greater than syngeneic, nontransgenic littermates or BALB/c mice. Spleen cells from B-gal or SRBC immune B6, SWR/SJL, and BALB/c mice were fused with P3 myeloma cells to produce hybridomas. Forty-eight percent of the wells plated with fused B6 spleen cells produced B-gal-specific antibodies compared to 14% from BALB/c and 12% from SWR/SJL. Antibody-specific wells were subcloned, resulting in enhanced recovery of antigen-specific subclones with B6-derived fusions compared to controls. In the SRBC fusions, 17% of the wells plated with fused B6 spleen cells produced SRBC-specific antibodies compared to 6% for BALB/c and SWR/SJL spleens. After subcloning, B6-derived clones produced 8% positive subclones compared to 9.5% from SWR/SJL and 3.5% from BALB/c. Comparison of the isotype distribution of subclones showed a higher ratio of IgG antibodies compared to IgM from B6 mice in the B-gal fusions. IgA antibodies were recovered only from B6 mice. These data indicate that B6 transgenic mice that overexpress Bcl-2 in their B cells may be superior to other mouse strains for production of antigen-specific hybridomas.

Animals↗
PubMed1996

Types and mechanisms of pulmonary atelectasis.

Atelectasis is one of the most commonly encountered abnormalities in chest radiology and remains a daily diagnostic challenge. At times atelectasis can be overlooked, particularly when pulmonary opacification is minimal or absent, and at other times it might be interpreted as being some other form of intrathoracic pathology, particularly pneumonia. The direct signs of atelectasis are crowded pulmonary vessels, crowded air bronchograms, and displacement of the interlobar fissures. Indirect signs of atelectasis are pulmonary opacification; elevation of the diaphragm; shift of the trachea, heart, and mediastinum; displacement of the hilus; compensatory hyperexpansion of the surrounding lung; approximation of the ribs; and shifting granulomas. For descriptive purposes, atelectasis can be divided into the following types: segmental, lobar, or whole lung; subsegmental; platelike, linear, or discoid; round; and generalized or diffuse. Resorption atelectasis is caused by resorption of alveolar air distal to obstructing lesions of the airways; adhesive atelectasis stems from surfactant deficiency; passive atelectasis is caused by simple pneumothorax, diaphragmatic dysfunction, or hypoventilation; compressive atelectasis is due to tension pneumothorax, space-occupying intrathoracic lesions, or abdominal distention; cicatrization atelectasis stems from pulmonary fibrosis; and gravity-dependent atelectasis is the result of gravity-dependent alterations in alveolar volume. Whenever signs of volume loss are present on a chest radiograph, the radiograph should be interpreted as showing atelectasis. By understanding the various mechanisms leading to atelectasis, and by considering the underlying conditions, the radiologist should be able to develop an appropriate list of the possible causes of atelectasis. The diagnosis of atelectatic pneumonia should be based upon the presence of clinical signs and symptoms of pneumonia coupled with the identification of pathogenic bacteria in sputum, tracheal aspirates, or protected bronchoalveolar lavage or bronchial brush specimens rather than on the radiographic identification of atelectasis alone.

Humans↗
PubMed1996

Radiographic manifestations of lobar atelectasis.

In this article we review the plain radiographic and computed tomographic manifestations of lobar atelectasis. The progression of lobar atelectasis from mild to marked volume loss is emphasized. Common combinations of lobar and whole lung atelectasis are also discussed. Radiographic features that help distinguish lobar atelectasis from pleural thickening, pleural effusion, and mediastinal masses are outlined. Where appropriate, selected examples of segmental atelectasis are also presented. The recognition of lobar atelectasis is important, particularly in cases stemming from obstructing endobronchial tumors. Since all signs of volume loss are not present in any given case, knowing as many signs of lobar atelectasis as possible is useful. Careful analysis of the chest radiograph and subtle alterations in the fissures and hilar vascularity aids in differentiating lobar atelectasis from other intrathoracic processes.

Humans↗
PubMed1996

Clinical and imaging features of pulmonary strongyloidiasis.

We evaluated 20 patients with pulmonary strongyloidiasis for risk factors, clinical and imaging manifestations, complications, treatment, and outcome. Eighteen (90%) had risk factors for strongyloidiasis including steroid use, age greater than 65, chronic lung disease, use of histamine blockers, or chronic debilitating illness. Pulmonary signs and symptoms, including cough, shortness of breath, wheezing, and hemoptysis, were present in 19 (95%); adult respiratory distress syndrome (ARDS) developed in 9 (45%). Pulmonary infiltrates occurred in 18 (90%). Gastrointestinal signs and symptoms were also common. Peripheral blood eosinophilia occurred in 15 (75%). Twelve (60%) had secondary infection, and 3 (15%) had bacterial lung abscesses. All were treated with thiabendazole, 25 mg/kg twice daily; on average, patients without ARDS were treated for 3 days, versus 7 days for those with ARDS. Seventy percent responded to therapy; 30% died. Preexisting chronic lung disease and ARDS were statistically significant predictors of a poor prognosis.

Adolescent↗
PubMed1996

Structure-function comparisons of the proapoptotic protein Bax in yeast and mammalian cells.

Expression of the proapoptotic protein Bax under the control of a GAL10 promoter in Saccharomyces cerevisiae resulted in galactose-inducible cell death. Immunofluorescence studies suggested that Bax is principally associated with mitochondria in yeast cells. Removal of the carboxyl-terminal transmembrane (TM) domain from Bax [creating Bax (deltaTM)] prevented targeting to mitochondrial and completely abolished cytotoxic function in yeast cells, suggesting that membrane targeting is crucial for Bax-mediated lethality. Fusing a TM domain from Mas70p, a yeast mitochondrial outer membrane protein, to Bax (deltaTM) restored targeting to mitochondria and cytotoxic function in yeast cells. Deletion of four well-conserved amino acids (IGDE) from the BH3 domain of Bax ablated its ability to homodimerize and completely abrogated lethality in yeast cells. In contrast, several Bax mutants which retained ability to homodimerize (deltaBH1, deltaBH2, and delta1-58) also retained at least partial lethal function in yeast cells. In coimmunoprecipitation experiments, expression of the wild-type Bax protein in Rat-1 fibroblasts and 293 epithelial cells induced apoptosis, whereas the Bax (deltaIGDE) mutant failed to induce apoptosis and did not associate with endogenous wild-type Bax protein. In contrast to yeast cells, Bax (deltaTM) protein retained cytotoxic function in Rat-1 and 293 cells, was targeted largely to mitochondria, and dimerized with endogenous Bax in mammalian cells. Thus, the dimerization-mediating BH3 domain and targeting to mitochondrial membranes appear to be essential for the cytotoxic function of Bax in both yeast and mammalian cells.

Animals↗
PubMed1996

Retinoic acid receptor beta mediates the growth-inhibitory effect of retinoic acid by promoting apoptosis in human breast cancer cells.

Retinoids are known to inhibit the growth of hormone-dependent but not that of hormone-independent breast cancer cells. We investigated the involvement of retinoic acid (RA) receptors (RARs) in the differential growth-inhibitory effects of retinoids and the underlying mechanism. Our data demonstrate that induction of RAR beta by RA correlates with the growth-inhibitory effect of retinoids. The hormone-independent cells acquired RA sensitivity when the RAR beta expression vector was introduced and expressed in the cells. In addition, RA sensitivity of hormone-dependent cells was inhibited by a RAR beta-selective antagonist and the expression of RAR beta antisense RNA. Introduction of RAR alpha also restored RA sensitivity in hormone-independent cells, but this restoration was accomplished by the induction of endogenous RAR beta expression. Furthermore, we show that induction of apoptosis contributes to the growth-inhibitory effect of RAR beta. Thus, RAR beta can mediate retinoid action in breast cancer cells by promoting apoptosis. Loss of RAR beta, therefore, may contribute to the tumorigenicity of human mammary epithelial cells.

Apoptosis↗