Biomedical subjects

C W Dawson

Publications and source records attributed to C W Dawson.

25 records · Page 2Linked to original sources

PubMed1993

Overexpression of wild-type p53 and c-Myc in human fetal cells transformed with adenovirus early region 1.

The expression of p53 in a large panel of adenovirus (Ad) 2/5- and 12-transformed human, rat, and mouse cells has been examined. In all cases, in the absence of the larger Ad E1B protein, the level of p53 is very low. In human and rat cells when the Ad 12 E1B 54K polypeptide is expressed, p53 is much more abundant, although this is not the case in Ad 12 E1-transformed mouse cells. We conclude that expression of p53 is determined by virus serotype, host cell type, and viral proteins expressed. p53 in Ad 12 E1-transformed human cells is wild type but has an extended half-life. Stabilization is not through protein-protein interaction with the Ad E1B protein. The level of expression of c-Myc is also elevated in Ad-transformed human cells but this does not correlate with the presence of the E1B protein or with p53. However, Northern blot analysis indicates a direct correlation between mRNA and protein levels. We conclude that c-Myc is regulated at the transcriptional level, whereas p53 is regulated at the post-translational level in adenovirus transformants.

Adenovirus E1B Proteins↗

PubMed1992

Epstein-Barr virus infection and replication in a human epithelial cell system.

Epstein-Barr virus, a human herpesvirus with oncogenic potential, infects two target tissues in vivo: B lymphocytes, where the infection is largely non-productive, and stratified squamous epithelium in which virus replication occurs. The interaction with B cells, initiated through virus binding to the B-cell surface molecule CR2 (ref. 4), has been studied in vitro and the virus 'latent' genes associated with B-cell growth transformation defined. By comparison, viral infection of epithelium remains poorly understood, reflecting the lack of an appropriate cell-culture model. Here we describe the development of such a model using as targets CR2-expressing transfected cells of two independent human epithelial lines. A high proportion of these cells bind virus and become actively infected, expressing the small EBER RNAs (small non-polyadenylated virus-coded RNAs) and the Epstein-Barr nuclear antigen 1 but not other latent proteins; thereafter, under conditions favouring epithelial differentiation, up to 30% of the cells can be induced to enter virus productive cycle with some progressing to full virus replication. We find significant differences between laboratory virus strains in their ability to infect epithelium that do not correlate with their B-cell growth-transforming activity.

Antigens, Differentiation, B-Lymphocyte↗

PubMed1990

Epstein-Barr virus latent membrane protein inhibits human epithelial cell differentiation.

Epstein-Barr virus (EBV), a human herpesvirus, is strongly linked with two relatively rare forms of B-cell lymphoma and with a much more prevalent epithelial malignancy, undifferentiated nasopharyngeal carcinoma (NPC). The availability of suitable culture systems has allowed detailed analysis of EBV-induced growth transformation in B lymphocytes, but little is known about the virus--epithelial cell interaction or about the possible effector role of viral proteins in the pathogenesis of NPC. Here we describe an experimental system to monitor the effects of introduced viral or cellular genes upon human epithelial cell growth and differentiation. We transfected a human epithelial cell line, which retains several features of normal keratinocyte behaviour in vitro, with the EBV gene encoding latent membrane protein (LMP), one of only two viral proteins known to be expressed in NPC cells in vivo. LMP expression was accompanied by changes in the epithelial cell surface phenotype, mimicking surface changes observed in NPC cells, and by severe impairment of the cellular response to differentiation signals. The ability of LMP to inhibit terminal differentiation indicates a mechanism whereby EBV infection of squamous epithelium could contribute to the multi-step pathogenesis of NPC.

Antigens, Viral↗

PubMed1989

Identification of a human epithelial cell surface protein sharing an epitope with the C3d/Epstein-Barr virus receptor molecule of B lymphocytes.

This work examines the basis for our earlier observation that certain monoclonal antibodies (MAbs) specific for the B-cell-associated C3d/Epstein-Barr virus (EBV) receptor molecule CD21 also react with the surface of some epithelial cells. Of 9 proven anti-CD21 MAbs now examined on frozen sections of human nasopharynx, tonsil and ecto-cervix, only 3 (HB5, anti-B2, AB1) showed staining of stratified epithelium; 2 of these (HB5, anti-B2) also reacted with the surface of epithelial cells freshly dispersed from these sites. The proportion of HB5- and anti-B2-reactive cells in primary epithelial cultures fell to a low but stable level within days of explantation, while almost all permanently established epithelial cell lines, whether SV40 virus-transformed or of malignant origin, were not reactive with either MAb. This contrasts with the pattern of expression of another surface marker also found selectively on cells of the lymphoid and epithelioid lineages, the CDw40 antigen. Staining with CDw40 MAbs on epithelial sections was usually restricted to the basal (proliferating) layer, but the proportion of CDw40-positive cells increased to a relatively high level in normal epithelial cultures; furthermore, most epithelial cell lines expressed this antigen. Immunoprecipitation from the surface of metabolically labelled epithelial cells with the anti-CD21 MAb HB5 yielded a protein of approximate MW 200 kDa, clearly different in size from the 145 kDa CD21 molecule on B cells. This 200 kDa protein was identified on fresh ecto-cervical epithelium, on primary cultures of a laryngeal carcinoma and on one unusual SV40-transformed epithelial cell line. We conclude that stratified human epithelial cells express a 200 kDa surface molecule which is antigenically related to, but not identical with, the CD21 antigen on B cells. It remains to be seen whether this epithelial cell protein can function as an EBV receptor.

Antibodies, Monoclonal↗

PubMed1988

Epstein-Barr virus gene expression in nasopharyngeal carcinoma.

Epstein-Barr virus (EBV), an agent with growth transforming potential for human B cells, is associated with certain B cell lymphomas in man and also with an epithelial tumour, undifferentiated nasopharyngeal carcinoma (NPC). Since B cell growth transformation is associated with the constitutive expression of a small number of EBV-coded latent proteins, the nuclear antigens EBNA 1, EBNA 2, EBNA 3 and EBNA-LP and the latent membrane protein (LMP), the present work sought to determine whether this same pattern of virus gene expression occurred in NPC. Tumour biopsies were taken from NPC patients from three areas of differing tumour incidence (Kenya, Algeria, Britain) and immediately snap-frozen, as were biopsies of non-EBV-related carcinomas for controls. Immunoblotting of PAGE-separated proteins with selected human sera identified 24 NPC biopsies clearly expressing EBNA 1. When the analysis was extended using selected human sera with antibodies against the other EBNAs, there was no detectable expression of EBNA 2, EBNA 3 or EBNA-LP in any of these 24 biopsies; their EBNA 2-negative status was confirmed using a monoclonal antibody (MAb) PE2 which was reactive in immunoblotting and in immunoprecipitation with EBNA 2A and EBNA 2B proteins. Similar experiments with two different LMP-specific MAbs, CS1 to 4 and S12, revealed heterogeneity between NPC biopsies; 9/24 biopsies were demonstrably LMP-positive, the degree of expression varying considerably between individual tumours in a manner which was not related to the level of EBNA 1 expression. None of the 24 NPC biopsies expressed detectable amounts of EBV lytic cycle antigens. A nude mouse-passaged NPC cell line, C15, likewise expressed EBNA 1 and LMP but none of the other EBV latent proteins nor lytic cycle antigens. This work identifies a novel type of EBV-cell interaction in NPC cells which is distinct from that seen in in vitro transformed B cell lines and from that seen to date in EBV-positive B cell lymphomas.

Antibodies, Monoclonal↗

PubMed1982

Anergy and altered lymphocyte function in the injured patient.

The failure of the host-defense mechanism following trauma has been recognized, but the site of the deficit is unknown. The immunologic competence of 16 patients, including 15 who had minor injuries and required less than 4 transfusions, was prospectively studied with skin testing, leukocyte counts, and protein electrophoresis. The stimulation ratio (SR) and index of lymphocyte response to phytohemagglutanin (PHA) were measured as the ratio of thymidine uptake in stimulated cells to that of resting cells in both pooled normal serum as well as each patient's serum. Six patients, including the one patient with major injury, had no response to any of the four skin test antigens and were considered anergic (AN). Ten patients with minor trauma responded to at least one of the antigen skin tests and were considered nonanergic (NA). The anergic patients had significantly more shock and more blood transfusions and had significantly lower serum albumin levels. There was no statistical difference between the anergic and nonanergic groups in leukocyte count, absolute lymphocyte count, gamma-globulin fraction, or age. The average PHA Stimulation Ratio of patient lymphocytes in patient serum was significantly higher than the PHA Stimulation Ratio of patient lymphocytes in control serum. This suggests that the lymphocytes of injured patients respond in a greater magnitude when bathed in autologous-serum than when bathed in control pooled serum. Furthermore, the autologous serum did not inhibit the PHA response of control or normal lymphocytes. The presence of an enhancing factor in injured patients' sera or an absence of a supressor substance may be responsible for this phenomenon.

Adult↗

PubMed1981

Altered interstitial fluid space dynamics and postresuscitation hypertension.

Hypertensin occurred 24 to 48 hours after resuscitation in 35 of 86 injured patients, who had combined systolic and diastolic hypertensin (150/100 mmHg) for six or more consecutive hours. Plasma volume (PV), RBC volume, extracellular fluid (ECF) volume by the inulin dilution technique, renal plasma flow, glomerular filtration rate, and peripheral renin levels were measured in hypertensive and nonhypertensive patients an average of 40 hours after injury. The hypertensive patients had an average mean arterial pressure (MAP) of 114 mmHg, compared with 95 mmHg in the nonhypertensive patients. The RBC volume and ECF were comparable for both groups, whereas PV was increased in the hypertensive patients (3.6 L vs 3.3 L). Calculated interstitial fluid space (IFS) volume was greater in the nonhypertensive patients, as was the ratio PV/IFS. The MAP in both groups correlated directly with PV/IFS and serum albumin concentrations, and inversely with peripheral renin concentrations. This suggests that postresuscitative hypertension is not due to fluid overload but rather to the fluid maldistribution related to altered IFS compliance as reflected by the increased PV/IFS.

Blood Pressure↗