[Preoperative arterial infusion chemotherapy of colorectal carcinoma pathological and clinical effects]

OBJECTIVE

To investigate the pathological and clinical effects of preoperative selective intra-arterial infusion chemotherapy on colorectal carcinoma.

METHODS

30 patients with colorectal carcinoma underwent selective regional arterial angiography by Seldinger's method followed by intra-arterial infusion chemotherapy.

RESULTS

changes of karyopyknosis, karyorrhexis, coagulation and necrosis of cytoplasm in cancer cells around vascular vessels were found in all cases. Interstitial edema, invasion of inflammatory cells, fibroelastosis around cancer cells, proliferous intima, thrombus and inflammation of vessels were also found at the same sites.

CONCLUSIONS

Histological changes are significant after preoperative selective intra-arterial infusion chemotherapy for colorectal carcinoma. This therapy can relieve symptoms.

Expression of the IL-12 receptor beta 1 and beta 2 subunits in human tuberculosis

To determine whether the Th1 response in tuberculosis correlated with IL-12R expression, we measured expression of the IL-12R beta 1 and IL-12R beta 2 subunits, as well as IL-12R beta 2 mRNA expression in tuberculosis patients and healthy tuberculin reactors. In tuberculosis patients, IFN-gamma production by Mycobacterium tuberculosis-stimulated PBMC was reduced, the percentages of T cells expressing IL-12R beta 1 and IL-12R beta 2 were significantly decreased, and IL-12R beta 2 mRNA expression was also markedly reduced. In contrast, in pleural fluid and lymph nodes at the site of disease in tuberculosis patients, in which IFN-gamma production is enhanced, IL-12R beta 2 mRNA expression was also increased. In M. tuberculosis-stimulated peripheral blood T cells from tuberculosis patients, anti-IL-10 and anti-TGF-beta enhanced IL-12R beta 1 and IL-12R beta 2 expression, and IFN-gamma production. In M. tuberculosis-stimulated peripheral blood T cells from healthy tuberculin reactors, recombinant IL-10 and TGF-beta reduced IL-12R beta 1 and IL-12R beta 2 expression, as well as IFN-gamma production. In combination with prior studies showing increased production of TGF-beta by blood monocytes from tuberculosis patients, this suggests that increased TGF-beta production is the underlying abnormality that reduces IL-12R beta 1 and IL-12R beta 2 expression in tuberculosis. Our findings provide evidence that IL-12R expression correlates well with IFN-gamma production in human tuberculosis, and that expression of IL-12R beta 1 and IL-12R beta 2 may play a central role in mediating a protective Th1 response.

Cellular protein hnRNP-A1 interacts with the 3'-end and the intergenic sequence of mouse hepatitis virus negative-strand RNA to form a ribonucleoprotein complex

We previously showed that several cellular proteins specifically bind to the 3'-end and the intergenic sequences of the negative-strand RNA of mouse hepatitis virus (MHV), and proposed that these distant RNA sequences can be brought together by cellular and viral proteins (Furuya and Lai, 1993; Zhang et al., 1994; Zhang and Lai, 1995). The cellular protein p35 has been identified as a heterogeneous nuclear ribonucleoprotein (hnRNP) A1. We have now expressed hnRNP-A1 as a glutathione-S-transferase (GST) fusion protein and demonstrated that the amino terminal two-thirds of hnRNP-A1 interacted with the two MHV regulatory RNA sequences (3'-end and intergenic sequences) through protein-RNA interaction while its carboxy-terminal glycine-rich domain mediated homomeric (protein-protein) interactions. In a partially reconstituted reaction, in which the two MHV RNA fragments and the purified GST-hnRNP-A1 fusion protein were mixed, an RNP complex was formed. Depletion of either hnRNP-A1 or one of the RNA components abolished the complex formation. These results indicate that hnRNP-A1 can mediate the formation of an MHV RNP complex, which includes both the negative-strand leader and intergenic sequences. Site-directed mutagenesis revealed that mutations in the MHV intergenic sequences, which inhibited MHV RNA transcription, also inhibited the RNP complex formation. Deletion analysis showed that the amino terminal RNA-binding domains of hnRNP-A1 is essential for the RNP complex formation while the carboxy-terminal protein-binding domain enhanced the complex formation by 90-fold. These findings provide direct evidence demonstrating that the negative-strand leader RNA and intergenic sequences can form an RNP complex mediated by cellular protein hnRNP-A1.

Functional involvement of urokinase-type plasminogen activator receptor in pemphigus acantholysis

Urokinase-type plasminogen activator (uPA) has been well documented in the development of pemphigus acantholysis. The function of its receptor (uPA-R) in pemphigus acantholysis has only recently attracted attention. Increased expression of uPA-R has been demonstrated in pemphigus vulgaris. In this study, we have further explored the functional involvement of uPA-R in pemphigus acantholysis. Our results show that uPA-R expression is significantly increased in acantholytic foci of pemphigus vulgaris and pemphigus foliaceus but not in bullous pemphigoid or normal skin specimens; the expression of uPA-R in cultured human keratinocytes is subjected to regulation by pemphigus vulgaris IgG but not by pemphigoid IgG or normal human IgG; furthermore, anti-uPA-R monoclonal antibody effectively inhibits pemphigus vulgaris IgG induced acantholysis in skin organ cultures. These data suggest that uPA-R may play an important role in the pathogenesis of pemphigus acantholysis.

Production of monocyte chemoattractant protein 1 in tuberculosis patients

To investigate the role of monocyte chemoattractant protein 1 (MCP-1) in the immune response to Mycobacterium tuberculosis, we studied MCP-1 production in tuberculosis patients. CD14+ blood monocytes from tuberculosis patients spontaneously expressed higher levels of MCP-1 mRNA and protein than CD14+ monocytes from healthy tuberculin reactors. MCP-1 production in lymph nodes from tuberculosis patients was also markedly increased. These findings suggest that MCP-1 can contribute to the antimycobacterial inflammatory response by attracting monocytes and T lymphocytes.

Expression of a 50 kDa putative receptor for bovine viral diarrhea virus in bovine fetal tissues

The expression of a 50 kDa bovine viral diarrhea virus putative receptor in different bovine fetal tissues from 3-month old fetuses was studied. The receptor expression was examined by immunocytochemical staining and by immunoblotting using antiidiotypic probe (anti-D89). Intense specific staining in enterocytes of the small and large intestines, cortical tubular epithelial cells of kidneys, respiratory epithelial cells of the trachea and esophageal mucosal epithelial cells was observed, demonstrating the strong expression of bovine viral diarrhea virus receptor in the tissues. Weak staining was found in cerebellum, thymus, spleen, liver, cerebrum, and lung tissues; however, heart tissues were negative. Immunoblotting results correlated with the immunoperoxidase staining assays. Thus, the expression levels of the receptor are variable in different tissues. This pattern of expression may provide clues to the pathogenic potential of bovine viral diarrhea virus in the bovine fetus.

Immunoglobulin heavy chain junctional diversity in young and aged humans

The causes of observed deficiencies to the humoral immune response in aged humans are unknown. Since a major source of antibody diversity is generated at the VH-D-JH junctional regions of the immunoglobulin heavy chain, we determined whether differences in junctional diversity are manifested with aging. We compared the CDR3 regions of IgM heavy chain transcripts isolated from young adult and aged humans. A PCR assay that measures CDR3 length in the majority of mu-heavy chains showed the same average size and normal range of CDR3 length in aged individuals as observed in young adults. To characterize the features of junctional diversity of aged adults in more detail, we determined the CDR3 sequences of a subset of the mu-heavy chain repertoire that utilizes members of the VH 5 family. In general CDR3 length, D family usage, and JH gene usage were similar in aged compared to young adults. Thus, in contrast to dramatic changes in heavy chain junctional diversity associated with fetal to adult development, no major differences were found between young and aged adults. Since the CDR3 repertoire generated in aged individuals appears to be as diverse as that observed in younger adults, the decline in humoral immunocompetence with aging cannot be attributed to a restriction in heavy chain junctional diversification processes.

Detection of bovine immunodeficiency virus antibodies in cattle by western blot assay with recombinant gag protein

A western blot assay using purified recombinant bovine immunodeficiency virus gag protein has been developed for detection of bovine immunodeficiency virus antibodies in bovine serum samples. The test was standardized with known bovine immunodeficiency virus positive and negative bovine serum samples and the monoclonal antibody to gag protein. Both naturally and experimentally infected cattle sera demonstrated positive test results. The result of western blot assay was compared with polymerase chain reaction test results in 134 blood samples collected from Kansas. Twenty-six samples tested positive for bovine immunodeficiency virus DNA with polymerase chain reaction (18.7%) and 25 were positive for the antibody to gag protein by western blot analysis (17.9%). Of 26 cattle testing positive using the polymerase chain reaction assay, 24 were antibody-positive by western blot assay, thus establishing a strong correlation between the two tests. The sensitivity and specificity of western blot relative to polymerase chain reaction are 0.92 and 0.99, respectively. The western blot assay proved to be a specific and sensitive test.

Detection of proviral DNA of bovine immunodeficiency virus in bovine tissues by polymerase chain reaction (PCR) and PCR in situ hybridization

In this study, experiments were designed to investigate the distribution of bovine immunodeficiency virus (BIV) proviral DNA in the tissues and cells of infected calves by solution-phase polymerase chain reaction (SP-PCR) and PCR in situ hybridization (PCR-ISH). Total DNA samples extracted from tissues of 10 BIV-infected and 5 uninfected calves were amplified by SP-PCR with the primers directed to the BIV conserved pol gene segment. The identity of the SP-PCR product was confirmed by Southern hybridization with a BIV pol gene cDNA probe. SP-PCR results demonstrated that BIV proviral DNA was present predominantly in neural tissues and some lymphoid tissues in BIV-infected calves. It also was detected frequently in other tissues including lung, heart, esophagus, and pancreas. Further investigation on cell location of BIV proviral DNA was performed by in situ amplification of DNA on formalin-fixed tissue sections. The amplified DNA was subjected to in situ hybridization with an internal biotinylated probe and detected with streptavidin-gold followed by silver enhancement. Specific BIV proviral DNA signals were observed in neurons, microglial cells, lymphocytes, septal macrophages, smooth muscle cells, and endothelial cells. On the basis of these results, we conclude that BIV replicates in a variety of bovine tissues in vivo and has a broad cell tropism.

Characterization of a putative receptor protein for bovine viral diarrhea virus

In a previous communication, we reported a 50-kDa cell surface protein from Madin-Darby bovine kidney (MDBK) cells as a putative receptor for bovine viral diarrhea virus (BVDV). The present study delineates further characterization of the receptor protein. Protease treatment of cultured MDBK cells adversely affected the receptor, thus abolishing the binding of anti-D89 (BVDV anti-idiotypes) to the cells. However, pretreatment of the cells with either phospholipases or glycosidases did not significantly change the anti-D89 binding to the cells. Additionally, pretreatment of cell monolayers with proteases decreased BVDV attachment and replication in the cells. These results suggested that the receptor for BVDV is a protein in nature, and glycosylation and phosphorylation may not play a direct role in BVDV attachment to cells. The BVDV receptor gradually regenerated on the cell surface after the protease-treated cells were cultured in normal growth medium. Regeneration of the BVDV receptor to a normal level took about 4 h as indicated by flow cytometric analysis and this process was inhibited in the presence of cycloheximide, a protein synthesis inhibitor. The 50-kDa receptor protein purified by electro-elution inhibited BVDV infection in a plaque reduction assay. It also inhibited anti-D89 binding to cells as analyzed by flow cytometry. These data demonstrated the nature of the 50-kDa protein as a specific receptor for BVDV.

[Study on conversion of RARalpha/PML fusion gene in acute promyelocytic leukemia]

OBJECTIVE

To analyze the conversion of RARalpha/PML gene in acute promyelocytic leukemia (APL) patients before and after treatment with all-trans retinoic acid (ATRA) followed by intensive consolidation chemotherapy (ICC) and allogeneic bone marrow transplantation (allo-BMT).

METHODS

RARalpha/ PML fusion gene was detected in 22 APL patients before and after treatment by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

RARalpha/PML fusion gene was positive in 75% of the patients after achieving complete remission with ATRA, and turned negative in 83% of the patients after ICC. The durations of conversion to the RT-PCR negative status varied from 1 to 39 months. Ten patients received allo-BMT, and all of them were RARalpha/PML fusion gene negative in 4 months post allo-BMT.

CONCLUSION

APL patients could achieve biological remission after ICC and allo-BMT, and the latter seemed to eliminate residual leukemic cells sooner in vivo than the former did.

Urokinase-type plasminogen activator receptors associate with beta1 and beta3 integrins of fibrosarcoma cells: dependence on extracellular matrix components

We have shown previously that the urokinase-type plasminogen activator receptor (uPAR) physically associates with beta2 integrins on human leukocyte membranes. We now report that uPAR associates with certain members of the beta1 and beta3 integrin families expressed by a nonhematopoietic fibrosarcoma cell line (HT1080) when adherent to certain extracellular matrix molecules. Flow cytometry studies indicated that HT1080 cells expressed uPAR and beta1 and beta3 integrins. Double staining immunofluorescence was used to label uPAR and beta1 and beta3 integrins. The staining patterns of uPAR and beta1 integrins were strikingly similar when attached to fibronectin, laminin, or vitronectin but not polylysine-coated substrates. Resonance energy transfer (RET) between uPAR and beta1 integrins was observed, especially at focal adhesion plaques; this indicates that these molecules are within about 7 nm of each other on these cell membranes. uPAR and beta3 integrin coclustering and RET were also observed on tumor cells adherent to vitronectin but not to fibronectin, laminin, or polylysine-coated surfaces. Because N-acetyl-D-glucosamine was found previously to inhibit beta2 integrin-uPAR association, we tested the effect of saccharides on the beta1-uPAR and beta3-uPAR colocalization and RET. Colocalization and RET between uPAR and beta1 or beta3 integrins were effectively inhibited by N-acetyl-D-glucosamine on extracellular matrix-coated surfaces. To better define which members of beta1 and beta3 integrin families associate with uPAR, we studied the association of several alpha subunits with uPAR on tumor cells. We found that: (a) alpha5 colocalizes with uPAR on cells attached to fibronectin-coated surfaces; (b) alpha5 and alpha(v) colocalize with uPAR on cells adherent to vitronectin; and (c) alpha3 and alpha6 associate with uPAR on cells attached to laminin. In further support of physical associations between integrins and uPAR on tumor cells, uPAR was found to coimmunoprecipitate with beta1 integrins in Brij-58 lysates of HT1080 cells (as detected by anti-uPAR Western blotting of material isolated from an anti-beta1 integrin immunoaffinity column). Thus, uPAR may laterally associate with integrins of tumor cells when attached to specific extracellular matrix elements to enable directional proteolysis for tumor cell migration and invasion.

Synthesis, characterization, and mutagenicity of nitrated 7H-dibenzo[c,g]carbazole and its phenolic derivatives

The nitrated N-heterocyclic aromatic hydrocarbons (NAHs) are found in a variety of environmental sources; many of them have been determined to be mutagenic in short-term assays and/or carcinogenic in animal tests. In this laboratory, we synthesized and characterized nitrated 7H-dibenzo[c,g]carbazole (DBC) and the nitrophenolic metabolites of DBC as potential mutagenic and carcinogenic xenobiotics. The nitro group was formed exclusively at the 5 and/or the symmetric 9 position of DBC, 2-hydroxy-DBC, 3-hydroxy-DBC, and 4-hydroxy-DBC. Ames plate incorporation mutagenicity assays were conducted using Salmonella typhimurium strains TA98 and TA100, with or without rat liver homogenates (S9). Mutagenicities of the nitrated DBCs were higher than the parent DBC in strain TA98, 5,9-Dinitro-DBC had stronger mutagenic responses than 5-nitro-DBC in all assays, particularly in strain TA98 with S9. 5,9-Dinitro-DBC had a higher reduction potential relative to 5-nitro-DBC (-1.09 V and -1.37 V, respectively). Hydroxyl derivatives of 5-nitro-DBC at the 2, 3, 4, 10, or 12 position, synthesized through nitration of the corresponding hydroxy-DBC, possessed greater mutagenicity than the parent 5-nitro-DBC, especially in strain TA100 with or without S9. Our data suggest that nitrated DBC undergoes both nitroreduction and ring oxidation as the primary pathways for the metabolic activation leading to mutagenesis. The relative mutagenicities of the nitrohydroxy-DBC isomers are generally consistent with the resonance stabilization of the positive charge at the arylnitrenium ion, formed from the nitro functional group, as the proposed active electrophile responsible for genotoxic effects.

Immune suppression in calves with bovine immunodeficiency virus

The present study was designed to evaluate the effect of bovine immunodeficiency virus (BIV) infection on immune functions and possible interactions between BIV and other bovine viruses in calves. Ten calves were inoculated intravenously with BIV, and five served as controls. An increased lymphocyte proliferation to BIV gag protein was demonstrated 2 to 6 weeks after BIV inoculation (P < 0.05). Lymphocyte subset differentiation revealed a decreased CD4/CD8 ratio (P < 0.05) during weeks 2 to 7, suggesting a possible immune dysfunction in BIV-infected calves. When the calves were inoculated with bovine herpesvirus type 1 (BHV-1), the antibody response to BHV-1 in BIV-infected calves was delayed and the antibody titers were significantly lower (P < 0.05). Injection of bovine viral diarrhea virus vaccine also elicited a lower neutralizing antibody response in BIV-infected calves. The results indicated that immune suppression occurred in BIV-infected calves.

[Detection of minimal residual disease after allogeneic bone marrow transplantation in chronic myeloid leukemia]

OBJECTIVE

To detect minimal residual disease (MRD) after allogeneic bone marrow transplantation (allo-BMT) in chronic myeloid leukemia (CML).

METHODS

M-bcr/abl mRNA was assayed by reverse transcriptase polymerase chain reaction (RT-PCR) in bone marrow cells from 46 successfully sibling marrow engrafted CML patients.

RESULTS

About 70% of the patients achieved genetic complete remission in 3 months post allo-BMT. Four patients were M-bcr/abc mRNA positive at 1.5 to 2 months post allo-BMT and turned to be negative at 3 to 9 months post allo-BMT. One patient was still M-bcr/abl(+) after disease-free survival(DFS) for more than 6 years, while another one was M-bcr/abl(-) after DFS for more than 4 years.

CONCLUSION

RT-PCR is so far the most sensitive method for MRD detection in CML, but its limitation should not be ignored.

A 50 kDa membrane protein from bovine kidney cells is a putative receptor for bovine viral diarrhea virus (BVDV)

A 50 kDa cell surface protein from MDBK cells has been identified as a putative receptor for bovine viral diarrhea virus (BVDV) by using a BVDV specific anti-idiotypic antibody (Anti-D89). This study delineates further characterization of the receptor protein. Protease treatment of cultured MDBK cells adversely affected the receptor thus abolishing the binding of anti-D89 to the cells. However, pretreatment of the cells with either phospholipases or glycosidases did not signficantly alter the extent of anti-D89 binding. Additionally, pretreatment of cell monolayers with proteases decreased BVDV attachment and replication in the cells. These results suggested that the receptor for BVDV is a protein in nature, and glycosylation and phosphorylation of the receptor protein may not play a direct role in BVDV attachment to cells. The BVDV receptor protein gradually regenerated on cells when they were maintained in culture following protease treatment. The purified 50 kDa receptor protein also significantly inhibited BVDV infection in a plaque reduction assay.

Degradation of Pyrene, Benz[a]anthracene, and Benzo[a]pyrene by Mycobacterium sp. Strain RJGII-135, Isolated from a Former Coal Gasification Site

Volume 62, no. 1, p. 14, column 1, line 20: "250 (mu)g each of yeast extract, peptone, and soluble starch ml(sup-1)" should read "250 (mu)g each of yeast extract, peptone, and soluble starch liter(sup-1)." [This corrects the article on p. 13 in vol. 62.].

Identification of bovine viral diarrhea virus receptor in different cell types

Anti-idiotypic antibodies (anti-ids) have been used successfully in studies on bovine viral diarrhea virus (BVDV) receptor(s) in our laboratory. The anti-ids specifically bound to cultured cells and identified a 50 kDa cellular membrane protein, which is thought to be a specific receptor for BVDV. In this study, flow cytometric analyses demonstrated that the anti-ids also specifically bound to different cell types, namely MDBK, EBK, BT, PK15, MA1O4, and Vero. Experiments on virus attachment and replication showed that BVDV adsorbed to all cells and replicated in them except monkey kidney cells MA 104 and Vero (non-permissive). Results from plaque reduction assays indicated that cellular membrane proteins from all cell lines competitively inhibited BVDV attachment to cultured MDBK cells, suggesting the presence of BVDV receptor on all cells. Immunoblotting of cell membrane proteins with the anti-ids revealed a 50 kDa protein in both permissive and nonpermissive cells. Subcloned or synchronized MDBK cells demonstrated no significant difference of binding with anti-ids as compared to normal cultured cells.

Comparative carcinogenicity, metabolism, mutagenicity, and DNA binding of 7H-dibenzo[c,g]carbazole and dibenz[a,j]acridine

Complex mixtures that are produced from the combustion of organic materials have been associated with increased cancer mortality. These mixtures contain homocyclic and heterocyclic polycyclic aromatic hydrocarbons (PAHs), many of which are known carcinogens. In particular, N-heterocyclic aromatic compounds (NHA) are present in these mixtures. Studies to determine the metabolic activation of these compounds have been undertaken. The purpose of this review is to compare and contrast the metabolic activation and biological effects of two NHA, 7H-dibenzo[c,g]carbazole (DBC) and dibenz[a,j]acridine (DBA), in order to better assess the contribution of NHA to the carcinogenic potency of complex mixtures and to develop biomarkers of the carcinogenic process. DBC has both local and systemic effects in the mouse; it is a potent skin and liver carcinogen following topical application and a lung carcinogen following i.p. application. On the other hand, DBA is a moderate mouse skin carcinogen following topical application and a lung carcinogen following subcutaneous injection. The biological differences for DBC and DBA are reflected in target organ-specific proximate and mutagenic metabolites and DNA adduct patterns.

Degradation of pyrene, benz[a]anthracene, and benzo[a]pyrene by Mycobacterium sp. strain RJGII-135, isolated from a former coal gasification site

The degradation of three polycyclic aromatic hydrocarbons (PAH), pyrene (PYR), benz[a]anthracene (BAA), and benzo[a]pyrene (BaP), by Mycobacterium sp. strain RJGII-135 was studied. The bacterium was isolated from an abandoned coal gasification site soil by analog enrichment techniques and found to mineralize [14C]PYR. Further degradation studies with PYR showed three metabolites formed by Mycobacterium sp. strain RJGII-135, including 4,5-phenanthrene-dicarboxylic acid not previously isolated, 4-phenanthrene-carboxylic acid, and 4,5-pyrene-dihydrodiol. At least two dihydrodiols, 5,6-BAA-dihydrodiol and 10,11-BAA-dihydrodiol, were confirmed by high-resolution mass spectral and fluorescence analyses as products of the biodegradation of BAA by Mycobacterium sp. strain RJGII-135. Additionally, a cleavage product of BAA was also isolated. Mass spectra and fluorescence data support two different routes for the degradation of BaP by Mycobacterium sp. strain RJGII-135. The 7,8-BaP-dihydrodiol and three cleavage products of BaP, including 4,5-chrysene-dicarboxylic acid and a dihydro-pyrene-carboxylic acid metabolite, have been isolated and identified as degradation products formed by Mycobacterium sp. strain RJGII-135. These latter results represent the first example of the isolation of BaP ring fission products formed by a bacterial isolate. We propose that while this bacterium appears to attack only one site of the PYR molecule, it is capable of degrading different sites of the BAA and BaP molecules, and although the sites of attack may be different, the ability of this bacterium to degrade these PAH is well supported. The proposed pathways for biodegradation of these compounds by this Mycobacterium sp. strain RJGII-135 support the dioxygenase enzymatic processes reported previously for other bacteria. Microorganisms like Mycobacterium sp. strain RJGII-135 will be invaluable in attaining the goal of remediation of sites containing mixtures of these PAH.

Antigenic differences between a field isolate and vaccine strains of bovine viral diarrhea virus

Antigenic diversity among the bovine viral diarrhea virus (BVDV) cytopathic strains 87-2552 (field isolate) and NADL and Singer (prototype strains) was demonstrated with monoclonal antibodies (MAbs) in enzyme-linked immunosorbent, immunofluorescence, virus neutralization, and immunoprecipitation assays. Two MAbs against BVDV strain 87-2552, designated D11 and B7, strongly neutralized this field strain and were specific for the 48-kDa glycoprotein of the virus. These two MAbs have different subisotypes, immunoglobulin G1 for D11 and immunoglobulin G3 for B7. MAbs against BVDV strains 87-2552 and NADL were specific for their respective strains in virus neutralization assays. The results indicated significant antigenic differences between BVDV strain 87-2552 and the NADL and Singer strains.

32P-postlabelling analysis of dibenz[a,j]acridine-DNA adducts in mice: identification of proximate metabolites

N-Heterocyclic polynuclear aromatics are widely-occurring environmental pollutants formed during the pyrolysis of nitrogen-containing organic chemicals. Dibenz[a,j]acridine (DBA), a member of this class, has been shown to be a skin carcinogen in mice. We undertook studies to determine the organ distribution of DBA-DNA adducts and to identify the DBA metabolites which lead to the formation of carcinogen-DNA adducts in vivo. DBA and its metabolites, trans-DBA-1,2-dihydrodiol (DBA-1,2-DHD) trans-DBA-3,4-dihydrodiol (DBA-3,4-DHD) and trans-DBA-5,6-dihydrodiol (DBA-5,6-DHD), were topically applied on mice. DNA was isolated using enzyme-solvent extraction methods, and analyzed for carcinogen-DNA adducts using 32P-postlabelling. In skin, DBA produced two distinct adducts (Adducts 1 and 2). The same two adducts were seen when DBA-3,4-DHD was applied. In addition, the total adduct level elicited by DBA-3,4-DHD was twice that of the parent compound. Two adducts (Adducts 3 and 4) were also seen in mouse skin when DBA-5,6-DHD was applied, but these differed chromatographically from adducts seen with DBA. However, when DBA-3,4-DHD was applied and analyzed using sensitive nuclease P1 32P-postlabelling, all four adducts could be detected. These results suggest that the major route of DBA activation to DNA-binding species in skin is through formation of DBA-3,4-DHD and subsequent metabolism of this compound to a bay-region diol-epoxide. However, we postulate that another activation pathway may proceed through a bis-dihydrodiol-epoxide.

Locus-specific somatic hypermutation in germinal centre T cells

Somatic hypermutation and affinity-driven selection of active immunoglobulin genes occur in germinal centres (GCs), resulting in the generation of high-affinity memory B cells. In contrast, T lymphocytes do not require the germinal centre microenvironment to establish memory and the T-cell antigen receptor (TCR) genes, though homologous to immunoglobulin genes, are believed to be incapable of hypermutation. Here we present direct evidence that the small population of antigen-specific T cells that are recruited into splenic GCs acquire mutations in the variable region of genes encoding TCR alpha-chains (V alpha) but not those of beta-chains. These locus-specific mutations reach frequencies comparable to mutated immunoglobulin VH exons recovered from the same site and exhibit similar substitution biases and DNA strand polarity. T cells bearing identical mutations appear in multiple GCs, raising the possibility that some cells bearing mutant TCRs may re-enter the peripheral lymphocyte pool.