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D H Crawford

Publications and source records attributed to D H Crawford.

At least 19 recordsLinked to original sources

Activation of cationic amino acid transport through system y+ correlates with expression of the T-cell early antigen gene in human lymphocytes.

Lysine influx (2 microM) into activated human B and T lymphocytes through transport systems y+ and y+L was measured. In activated T cells very substantial activation of system y+ was detected; system y+L was also activated in these cells but with a slower time course and to a smaller extent. No stimulation of either system was found in activated B cells. The time course of activation of system y+ precisely matched the expression of the T cell early antigen gene described by MacLeod et al, 1990. The functional significance of these observations with respect to L-arginine transport and nitric oxide synthesis in activated T lymphocytes is discussed.

Amino Acids

Glomerular abnormalities in children undergoing orthotopic liver transplantation.

A prospective study of renal function was undertaken on an unselected group of 8 children with chronic progressive liver disease on whom a renal biopsy was performed subsequently at the time of orthotopic liver transplantation. Two patients had abnormal urinalyses and 2 elevated urinary albumin/creatinine ratios. The remainder had no clinical evidence of renal dysfunction. All had normal serum creatinine concentrations. Glomerular abnormalities were present in all renal biopsies and were of two types: hepatic glomerulosclerosis (n = 5) and minor glomerular abnormalities (n = 3). IgM immunofluorescence was present in all biopsies and IgA in 6. Elevated serum immunoglobulin levels were observed in all patients, with IgM elevation in 6, IgA in 4 and IgG in 6. C3 and/or C4 were reduced in 5 patients and increased circulating immune complexes containing IgM were noted in 4. The clinical significance of these cirrhosis-associated glomerular abnormalities can only be established by long-term follow-up studies after orthotopic liver transplantation.

Albuminuria

Universal occurrence of glomerular abnormalities in patients receiving liver transplants.

We conducted a prospective study of renal histology and function in 18 consecutive nonalcoholic patients who underwent orthotopic liver transplantation (OLT). Despite well-preserved renal function, all patients had abnormal renal biopsies. Four patterns of glomerular injury were identified: minor glomerular abnormalities (eight patients), hepatic glomerulosclerosis (seven), membranoproliferative glomerulonephritis (one), and IgA nephropathy (one). In one patient there was insufficient tissue to allow classification. There was a trend toward lower plasma bilirubin and higher plasma albumin in patients with minor glomerular abnormalities than in the group of patients with more severe forms of glomerular injury (29 v 82 mumol/L, 35.5 v 30 g/L; P = 0.1, 0.1 greater than P greater than 0.05, respectively). Glomerular changes persisted in the three patients who died within 7 weeks post-OLT. IgM immunofluorescence was present in all biopsies and IgA in 11. IgM-containing circulating immune complexes occurred in five patients, suggesting a pathogenic role for IgM immune complex deposition. The significance of cirrhosis-associated glomerular abnormalities is not yet known. They may contribute to the hepatorenal syndrome and the renal dysfunction that occurs in up to 94% of patients post-OLT.

Adolescent

Circulating Epstein-Barr virus-carrying B cells in acute malaria.

Epstein-Barr virus (EBV) infection and Plasmodium falciparum malaria are two known cofactors in the aetiology of endemic Burkitt's lymphoma. To assess the relation between these factors, limiting dilution analysis was used to assess the number of EBV-carrying B cells in the circulation of Gambian children during and after acute malaria. Numbers of virus-carrying cells were five times higher in acute malaria patients and in UK patients with infectious mononucleosis than in convalescent malaria patients and in healthy control adults from the UK. Spontaneous outgrowth in limiting dilution cultures from acute malaria samples was inhibited by acyclovir, a viral DNA polymerase inhibitor. The mechanism of outgrowth, therefore, was virus release from the in-vivo infected cell, which led to infection and immortalisation of co-cultured normal B cells. The findings provide evidence that acute malaria is associated with an increase in the number of EBV-carrying B cells in the circulation. Because of this increase, there is a greater chance of a cytogenetic abnormality occurring in such a cell, with consequent evolution of Burkitt's lymphoma.

Acute Disease

Current concepts in rational therapy for haemochromatosis.

Genetic haemochromatosis is characterised by an inappropriately high rate of iron absorption by the small intestine. The disease is transmitted as an autosomal recessive condition. The gene frequency in the Caucasian population is approximately 1 in 20 and the disease frequency is 1 in 400. Excessive iron deposition occurs in the liver, pancreas, heart, pituitary and joints and hepatic iron concentrations above approximately 400 mumol/g dry weight are always associated with fibrosis and usually with cirrhosis and progressive liver failure. Accurate diagnosis depends upon the demonstration of elevated hepatic iron stores. An hepatic iron index [hepatic iron concentration (in mumol/g dry weight) divided by patient age] of greater than 2.0 distinguishes homozygous subjects from the other conditions in which slight increases in hepatic iron concentration may occur, e.g. in a subject heterozygous for haemochromatosis or alcoholic liver disease. If cirrhosis is present, patients are at a high risk of developing hepatocellular carcinoma. Therefore, they should undergo regular abdominal ultrasound and alpha-fetoprotein estimation. In the absence of cirrhosis, phlebotomy restores life expectancy to normal. Venesection should be continued until all excess iron stores are removed as judged by failure of a rise in haemoglobin concentration on cessation of phlebotomy. Screening of first degree relatives should commence from a young age (e.g. 10 years). If serum ferritin or transferrin saturation are abnormal, liver biopsy should be undertaken. HLA typing of the family allows for the identification of those siblings who are most likely to develop the disease. Secondary iron overload is often multifactorial in origin. Iron chelation therapy with subcutaneous deferoxamine (desferrioxamine) should only commence after careful consideration of the potential benefits in each individual patient.

Bloodletting

The oncogenic potential of Epstein-Barr virus.

Epstein-Barr (EB) virus is a herpesvirus which is the causative agent of infectious mononucleosis. It can also be classified as a human DNA tumor virus as it is also etiologically associated with the development of Burkitt's lymphoma (BL) and nasopharyngeal carcinoma. EB virus involvement in these human tumors is suggested by seroepidemiological studies and the detection of virus DNA and proteins in tumor biopsies. Furthermore, EB virus can be detected in lymphoproliferations and malignant tumors arising from immunosuppressed individuals which further emphasizes its oncogenic potential. EB virus immortalizes B lymphocytes in vitro giving rise to continuously proliferating lymphoblastoid cell lines (LCL). These LCL are not tumorigenic, which suggests that cellular infection by virus alone is not sufficient for full tumorigenicity. This has led to the development of a multistep scenario for the development of BL where EB virus, in conjunction with other suggested cofactors, is necessary to induce the tumorigenic phenotype.

Animals

Epstein-Barr virus gene expression and epithelial cell differentiation in oral hairy leukoplakia.

Hairy leukoplakia (HL) is an Epstein-Barr (EB) virus related lesion of oral mucosa that is principally associated with human immunodeficiency virus-induced immunosuppression. To understand the nature of EB virus involvement in these lesions, this study compares the distribution of EB virus DNA and EB viral gene products with the pattern of keratinocyte differentiation in 12 lateral tongue biopsies of HL. Evidence of replicating EB viral infection and abundant virus production was demonstrated in the superficial epithelium of most (92%) samples by means of in situ hybridization and immunocytochemical techniques. Epstein-Barr virus latent membrane protein also was identified in 45% of samples, suggesting that this viral gene product, which is usually associated with EB virus latent infection, may be transiently expressed during viral replication in HL epithelium. The absence of detectable EB virus involvement in basal keratinocytes, however, fails to support the theory that latent infection occurs in basal epithelium. From this study, EB viral gene expression in HL appears to be linked with epithelial maturation. Conversely, the normal patterns of keratinocyte differentiation in these lesions do not appear to be appreciably altered by association with EB virus.

Adult

Aetiology and pathogenesis of non-Hodgkin lymphoma in AIDS.

The AIDS-NHLs constitute a histologically diverse group of tumours. Comparisons with some groups of non-AID-NHLs, including eBL, sBL and large cell lymphoma, have been made and similar pathogenetic mechanisms postulated for such groups. However, the incidence of the different pathological types of NHL in AIDS is not yet clear, and further work is necessary to determine the contribution of factors such as c-myc translocations and the presence of EBV. AIDS-NHLs are clearly a more diverse group of tumours than their non-AIDS counterparts, and this probably reflects the involvement of a whole range of different pathogenetic stimuli that occur in individual AIDS cases.

Burkitt Lymphoma

Deregulated c-myc expression in Epstein-Barr-virus-immortalized B-cells induces altered growth properties and surface phenotype but not tumorigenicity.

Endemic Burkitt's lymphoma (eBL) is characterized by the presence of Epstein-Barr virus (EBV) and a chromosomal translocation which results in deregulation and constitutive expression of the c-myc proto-oncogene. In order to examine the role played by activation of c-myc in determining the eBL phenotype, we have introduced into EBV-immortalized lymphoblastoid cells (LCL) plasmids which permit constitutive expression of c-myc. The resulting cells show a reduced serum dependence, reduced homotypic cell aggregation, and changes in surface characteristics. In particular, levels of the cell adhesion molecule, LFA-I, are greatly reduced. However, the cells continue to express all the EBV latent antigens associated with the LCL phenotype and they remain nontumorigenic. These results suggest that, whilst constitutive expression of c-myc may contribute to the malignant phenotype, it is insufficient to induce tumorigenicity.

Burkitt Lymphoma

Effects of a phorbol ester on activation and immortalization of leukaemic B cells by Epstein-Barr virus.

Immortalization of chronic leukaemic B cells by Epstein-Barr virus (EBV) was investigated. Immortalization resistant and susceptible cell populations were defined by chronic lymphocytic leukaemia (CLL) and prolymphocytic leukaemia (PLL) cells respectively. These cell types could be distinguished by the effects of a phorbol ester on [3H]-thymidine incorporation by EBV-infected cells. A synergistic effect was observed in the non-immortalizing CLL samples, whereas this response was inhibited in the immortalizing PLL. Under the conditions used in the study, TPA did not cooperate with EBV to immortalize CLL cells.

B-Lymphocytes

Immunohistology of Epstein-Barr virus-associated antigens in B cell disorders from immunocompromised individuals.

Proliferating B cell lesions developing in a series of immunosuppressed organ transplant recipients and patients with X-linked lymphoproliferative syndrome were examined for Epstein-Barr virus and cellular gene expression using immunocytochemistry and immunoblotting techniques. Results indicate that all the lesions examined from the patients in this series expressed Epstein-Barr virus gene products that were consistent with a latent, nonproductive type of infection. No lytic cycle antigens associated with productive viral infection were detected. This pattern is similar to the viral gene expression in normal B cells immortalized by Epstein-Barr virus in vitro. The demonstration in this study of Epstein-Barr virus viral gene expression in posttransplant and X-linked proliferative syndrome B cell disorders provides important new evidence for the primary role of Epstein-Barr virus in the development of these lesions. This is in contrast to the subsidiary role that the Epstein-Barr virus has in the etiology of Burkitt's lymphoma.

Antibodies, Monoclonal

Immortalization of Epstein-Barr virus-infected CD23-negative B lymphocytes by the addition of B cell growth factor.

Epstein-Barr (EB) virus-immortalized B lymphocytes coexpress the EB viral latent gene products (EB viral nuclear antigens 1 to 6, the latent membrane protein and the terminal protein gene products) and the cellular activation antigen CD23. Immortalized B cells can be separated from those which are infected but not immortalized on the basis of CD23 expression as early as 2 days after in vitro infection. In the present report we have confirmed these data, but show that if left in culture for 7 days after infection before separation the CD23-negative cells show a donor-related ability to become CD23-positive and immortalize. CD23-negative cells separated 2 days after infection can be induced to immortalize by the addition of low Mr B cell growth factor but not by the addition of recombinant interleukin 1, 4 or soluble CD23. At 2 to 3 days after infection the EB viral nuclear antigens 1, 2 and the high Mr species 3, 4 and 6, as well as the latent membrane protein can be detected in the CD23-positive fraction. In contrast at this time only nuclear antigens 1 and 2 could be detected in the CD23-negative fraction. This difference in gene expression may account for the inability of the CD23-negative fraction to immortalize. In the light of these observations the mechanism of viral persistence in vivo is discussed.

Adult