Calcitonin gene-related peptide-mediated ischemic preconditioning in the rat heart: influence of age

In the present study, we examined whether age-related reduction of ischemic preconditioning is related to calcitonin gene-related peptide (CGRP) release in the rat heart. Thirty minutes of global ischemia and 40 min of reperfusion caused a significant decrease of cardiac function and a marked increase of creatine kinase (CK) release at 2, 6 and 20 months of age. Ischemic preconditioning and pretreatment with CGRP for 5 min significantly improved cardiac function and reduced CK release during reperfusion at 2 and 6 months of age but not at 20 months of age. The content of CGRP in the coronary effluent during ischemic preconditioning was significantly increased in the first cycle at 2, 6 months of age but not at 20 months of age. These results suggest that the protection afforded by ischemic preconditioning is decreased in aging hearts, and the age-related change may be related to reduction of the release and effect of CGRP in the rat heart.

Role of calcitonin gene-related peptide in ischaemic preconditioning in diabetic rat hearts

1. It has been suggested that calcitonin gene-related peptide (CGRP) is involved in the protection provided by ischaemic preconditioning in rat hearts and that ischaemic preconditioning is absent in diabetic rat hearts. 2. In the present study, we tested the relationship between sensory nerve function and ischaemic preconditioning in diabetic rats. 3. In 4- and 8-week diabetic rats and age-matched non- diabetic controls, 30 min global ischaemia and 40 min reperfusion caused a significant decrease in cardiac function and a marked increase in creatine kinase (CK) release. Ischaemic preconditioning, by three cycles of 5 min ischaemia and 5 min reperfusion, improved the recovery of cardiac function and decreased CK release during reperfusion in 4-week diabetic rat hearts. However, the cardioprotection afforded by ischaemic preconditioning was lost in 8-week diabetic rat hearts. Pretreatment with CGRP for 5 min also significantly improved the recovery of cardiac function and decreased CK release in rats subjected to 4 or 8 weeks of diabetes. 4. The content of CGRP in the coronary effluent during ischaemic preconditioning was significantly increased in 4-week diabetic rat hearts (P < 0.05). However, only a slight increase in the release of CGRP was shown in 8-week diabetic rat hearts (P > 0.05). 5. In summary, the present results suggest that the protection afforded by ischaemic preconditioning is attenuated in diabetic rats and that the change may be related to the reduction in CGRP release in diabetic rat hearts.

[Effects of retinoic acid on proliferation and differentiation of human lung squamous carcinoma cell line]

Human lung squamous carcinoma cell line(TUL cell) was treated with 5 x 10(-6) mol.L-1 all-trans retinoic acid(ATRA). Cell numbers were estimated by 0.4% trypon blue stain. MTT test was used for determining the percentage of cell growth inhibition(GI). DNA syntheses of cells were evaluated by 3H-thymidine incorporation. Cell ultrastructure was examined by transmission electron microscope(TEM). TUL cells were treated with or without ATRA, and transplanted in cutaneous of Balb/c nude mice. The results showed that: 1. The speed of cell growth in study group was smaller than that in control group. 2. The GI of cell lines TUL was 42.3%. 3. The percentage of 3H-thymidine incorporation of TUL cells was declined significantly. 4. Ultrastructure under TME showed that TUL cells treated with ATRA was suppressed. These results suggest that ATRA has the effects on growth-inhibition and differentiation-induction of TUL cell.

Effects of genomic length on translocation of hepatitis B virus polymerase-linked oligomer

Accurate translocation of the polymerase-linked oligomer to the acceptor site (DR1*) in reverse transcription is crucial for maintaining the correct size of the hepatitis B virus (HBV) genome. Various sizes of foreign sequences were inserted at different sites of the HBV genome, and their effects on accurate translocation of polymerase-linked oligomer to DR1* were tested. Three types of replicate DNA products were observed in these insertion mutants: RC (relaxed circle) and type I and type II DL (duplex linear) DNA. Our results indicated that the minus strand of RC and type I DL form was elongated from DR1*, while the minus strand of the type II DL form was elongated from multiple internal acceptor sites (IAS), such as IAS2. These IASs were also found to be used by wild-type HBV but with a very low frequency. Mutation of IAS2 by base substitution abrogated polymerase-linked oligomer transferring to IAS2, demonstrating that base pairing also plays an important role in the function of IAS2 as a polymerase-linked oligomer acceptor site. Data obtained from our insertion mutants also demonstrate that the distance between the polymerase-linked oligomer priming site and the acceptor is important. The polymerase-linked oligomer prefers to translocate to an acceptor, DR1* or IAS2, which are ca. 3.2 kb apart. However, it will translocate to both DR1* and IAS2 if they are not located 3.2 kb apart. These results suggest that the polymerase-linked oligomer may be able to scan bidirectionally for appropriate acceptor sites at a distance of 3.2 kb. A model is proposed to discuss the possible mechanism of polymerase-linked oligomer translocation.

Identification and characterization of a structural protein of hepatitis B virus: a polymerase and surface fusion protein encoded by a spliced RNA

The hepatitis B virus (HBV) genome is known to contain four conserved and overlapped open reading frames (ORFs) encoding the viral core, polymerase (P), surface (S), and X proteins. Whether HBV encodes other proteins has long been a major interest in the field. Using (32)P-labeling of an introduced protein kinase A site attached to the N- or C-terminus of the HBV polymerase gene, a 43-kDa P-S fusion protein was detected in cell lysate, secreted virions, and 22-nm subviral particles. Immunobiochemical studies showed that the 43-kDa protein contains the epitopes of the N-terminus of polymerase and most parts of the surface proteins. This 43-kDa protein was shown to be a glycoprotein, similar to the surface protein. RT-PCR and sequence analyses identified a spliced mRNA which was derived from pregenomic RNA with a deletion of 454 nucleotides (nt) from nt 2447 to 2902. This splice event creates a P-S fusion ORF. This finding is consistent with the result obtained from an immunobiochemical study. Mutations at the splice donor or acceptor site on the HBV genome abrogated the production of the 43-kDa protein. These mutants had no effect on viral replication in transfected HuH-7 cells. However, this P-S fusion protein is able to substitute for the LS protein in virion maturation. On the basis of these results, we conclude that the 43-kDa protein is a polymerase-surface fusion protein encoded by a spliced RNA. Similar to the LS protein, the 43-kDa P-S fusion protein is a structural protein of HBV and might play a role in the HBV life cycle.

The cardioprotective effects of nitroglycerin-induced preconditioning are mediated by calcitonin gene-related peptide

Previous investigations have shown that endogenous calcitonin gene-related peptide (CGRP) may play an important role in the mediation of ischemic preconditioning and that nitroglycerin evokes the release of CGRP. In the present study, we examined whether nitroglycerin provides a preconditioning stimulus, and whether the cardioprotective effects of nitroglycerin-induced preconditioning involve endogenous CGRP. Thirty minutes of global ischemia and 30 min of reperfusion caused a significant impairment of cardiac contractile function and an increased release of creatine kinase. Pretreatment with nitroglycerin at the concentration of 3x10(-7) or 10(-6) M for 5 min produced a significant improvement of cardiac function and a decrease in the release of creatine kinase. The content of CGRP-like immunoreactivity in coronary effluent was increased during nitroglycerin perfusion. However, the cardioprotection afforded by nitroglycerin was abolished by CGRP-(8-37) (10(-7) M), a selective CGRP receptor antagonist. Pretreatment with capsaicin (50 mg/kg, s.c.), which specifically depletes the transmitter content of sensory nerves, also abolished the protective effects of nitroglycerin and markedly reduced the release of CGRP from the heart during nitroglycerin perfusion. These findings suggest that nitroglycerin-induced preconditioning is related to stimulation of CGRP release in rat hearts.

Analysis of T cell receptor Vbeta gene usage during the course of disease in patients with chronic hepatitis B

The T cell receptor (TCR) is a heterodimeric molecule expressed on the surface of T cells and recognizes foreign peptides presented by the major histocompatibility complex on the surface of antigen-presenting cells or virus-infected cells. Analysis of TCR usage by T cells which recognize hepatitis B virus (HBV) provides further insight into the participation of T cell populations during the course of disease. In this study, we examined the T-cell-proliferative response and the TCR Vbeta gene usage of peripheral blood mononuclear cells in 3 patients with clinical evidence typical of chronic hepatitis B. All 3 patients had significant T-cell proliferative responses against HBV core antigen (HBcAg) during the remission stage, while no responses were detected during the acute exacerbation stage. In addition, the TCR Vbeta7 gene was utilized more frequently in T cells recognizing HBcAg during remission, while TCR Vbeta1 and Vbeta2 were utilized at a higher percentage during acute exacerbation. On the contrary, the T cell proliferative response against HBV surface antigen was undetectable and no specific Vbeta gene was utilized more frequently by all 3 patients, regardless of disease state. Our longitudinal studies, although based on a small sample of patients, demonstrate that the population of HBcAg-activated T cells alters during the course of disease in chronic hepatitis B patients.

Fission yeast cdc24(+) encodes a novel replication factor required for chromosome integrity

A mutation within the Schizosaccharomyces pombe cdc24(+) gene was identified previously in a screen for cell division cycle mutants and the cdc24(+) gene was determined to be essential for S phase in this yeast. We have isolated the cdc24(+) gene by complementation of a new temperature-sensitive allele of the gene, cdc24-G1. The DNA sequence predicts the presence of an open reading frame punctuated by six introns which encodes a pioneer protein of 58 kD. A cdc24 null mutant was generated by homologous recombination. Haploid cells lacking cdc24(+) are inviable, indicating that cdc24(+) is an essential gene. The transcript of cdc24(+) is present at constant levels throughout the cell cycle. Cells lacking cdc24(+) function show a checkpoint-dependent arrest with a 2N DNA content, indicating a block late in S phase. Arrest is accompanied by a rapid loss of viability and chromosome breakage. An S. pombe homolog of the replicative DNA helicase DNA2 of S. cerevisiae suppresses cdc24. These results suggest that Cdc24p plays a role in the progression of normal DNA replication and is required to maintain genomic integrity.

Parallel hybridization analysis of multiple protein kinase genes: identification of gene expression patterns characteristic of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the major causes of human cancer deaths worldwide. To identify alterations of the genetic program associated with human HCC, we designed a new protocol based on the high-density replica method to analyze protein kinase gene expression in normal liver, HCC, and HCC-derived cell lines. RNA was prepared for reverse transcription and cDNA was used for PCR amplification of the conserved catalytic domain of protein kinase genes. Initially, from a pair of HCC and the adjacent noncancerous tissues, we sequenced 228 samples and identified 26 genes that represent different tyrosine kinase subfamilies. High-density grid filters were then prepared to assist the identification, by hybridization, of genes that are differentially expressed in normal vs HCC samples. Eleven tyrosine kinase genes were tested, and positive signals were reliably scored by doubly offset duplicates and by two independent gene-specific probes. Of the 11 genes tested, PDGF receptor-beta, MEKK-3, axl, and FGFR-4 are preferentially expressed in tumor samples. Additionally, we analyzed protein kinase gene expression in five HCC cell lines and identified distinct kinase gene expression patterns in different cell lines. Our results suggest that multiple kinases are activated in different tumors and confirm that there is molecular heterogeneity in the mechanisms sustaining autonomous cell growth in liver tumor formation.

Anti-tumor effects of d-dicentrine from the root of Lindera megaphylla

d-Dicentrine, a naturally occurring aporphine type isoquinoline alkaloid, isolated from the root of Lindera megaphylla Hemsl. (Lauraceae), was evaluated for its potential anti-cancer activity. We found d-dicentrine significantly inhibited the growth of human hepatoma cell line HuH-7 by delaying its doubling time in tissue culture. An in vitro colony forming assay showed that d-dicentrine decreased the colony formation efficiency in both hepatoma cell lines, HuH-7 and MS-G2, used in our study. Biosyntheses of the macromolecules DNA and RNA were also strongly inhibited. An MTT assay in 21 tumor cell lines also revealed that d-dicentrine was most cytotoxic to esophageal carcinoma HCE-6, lymphoma cell lines Molt-4 and CESS, leukemia cell lines HL60 and K562, and hepatoma cell line MS-G2. An in vitro tumor growing assay in the Severe Combined immunodeficiency (SCID) mice showed that intraperitoneal injection of d-dicentrine at the dose of 100 micrograms twice a week for 4 weeks significantly inhibited the tumor incidence of leukemia cell line K562 in SCID mice. All these data indicated that d-dicentrine has potential anti-tumor applications.

Platelet-derived growth factor is an autocrine stimulator for the growth and survival of human esophageal carcinoma cell lines

Platelet-derived growth factors (PDGF) are important mitogens for mesenchyme-derived cells. Neither PDGF nor PDGF receptors (PDGFR) are expressed in epithelial cells under normal physiological conditions. However, we have found that PDGF-BB induces c-jun expression and promotes the growth of the human esophageal carcinoma cell line CE48T/VGH. Scatchard analysis revealed the presence of 6 x 10(5) binding sites for PDGF-BB per cell, with a Kd of 9.7 nM. Furthermore, our data indicate that CE48T/VGH expresses beta type PDGFR (PDGFRbeta) with in vitro auto-kinase activity. We have also found that CE48T/VGH expresses the mRNA of the PDGF-A and PDGF-B chains and secretes PDGF molecules. Addition of anti-PDGF neutralizing antibody significantly decreased cell numbers of CE48T/VGH under serum-free conditions. The detached cells underwent apoptosis characterized by micronucleation. These results suggest that expression of the PDGF autocrine system may not only provide the growth advantage but also prevent the apoptosis for CE48T/VGH.

Osthole increases glycosylation of hepatitis B surface antigen and suppresses the secretion of hepatitis B virus in vitro

During screening of Chinese herbal medicines for the activities against hepatitis B virus (HBV), a known pure compound, osthole, was found to inhibit the secretion of HBV surface antigens in vitro. The secretion of hepatitis B surface antigen (HBsAg) in culture medium of MS-G2 and HuH-7 cells transfected with HBV DNA decreased by 60% to 70% after osthole treatment, without any detectable cytotoxic effects. Both 42-nm Dane particles and 22-nm subviral HBsAg particles were significantly reduced as revealed by density gradient analysis of viral particles and the endogenous; HBV DNA polymerase assay. The production of naked HBcAg particles was not changed by osthole treatment. The steady-state level of HBV-specific messenger RNA (mRNA) was not altered by osthole treatment, as revealed by Northern blot analysis, Immunoprecipitation of culture medium showed that the ratio of glycosylated versus nonglycosylated HBsAg increased after osthole treatment. Kinetic studies revealed that osthole increased the glycosylation rate of HBsAg, thus altering the ratio of glycosylated to unglycosylated HBsAg. The increase of glycosylation of HBsAg by osthole was blocked by tunicamycin, an inhibitor of protein glycosylation. We conclude that osthole suppresses the secretion of HBV in cell culture probably because of its novel function in increasing the glycosylation of HBsAg.

Deletion of integrated hepatitis B virus genome and cellular flanking sequences in hepatocellular carcinoma cells in BALB/c mice

We have previously reported the establishment of well-differentiated BALB/c mouse liver (ML) cell lines. Transfection of these cell lines with hepatitis B virus (HBV) DNA led to the expression of HBV-specific antigens and integration of HBV sequences in the cellular genome. Two cloned HBV-transfected ML cell lines, ML-2(HBV) and ML-3(HBV), expressed viral antigens and were highly tumorigenic in nude mice. However, the tumorigenicity of the two cell lines was significantly reduced in BALB/c mice. Southern blot analyses showed that the integrated HBV sequences were retained in tumors growing in nude mice but deleted in tumors growing in BALB/c mice. Furthermore, the deletion of HBV DNA was accompanied by deletion of chromosomal sequences flanking the HBV integration sites. In ML-2(HBV) cells, a significant reduction in chromosomal number was also observed. These results suggest that the immune response of BALB/c mice selected against hepatocellular carcinoma (HCC) cells expressing viral antigens and led to the proliferation of cells with deleted HBV sequences and concomitant chromosome aberrations. By using this mechanism, HCC cells escape the immune surveillance and gain the advantage of cell growth.

Expression of multiple oncogenes in human esophageal carcinomas

To study the oncogenesis of human esophageal carcinoma, the expression of a variety of oncogenes was studied in 10 esophageal carcinoma cell lines and 16 pairs of tumor and nontumor tissues removed from patients with esophageal carcinoma. Northern blot analyses using 11 different oncogene probes revealed that 5 oncogenes, i.e. c-myc, c-H-ras, c-sis, c-raf, and c-fos, were expressed. Among them, a variant c-sis mRNA transcript of 2.7 kilobase (kb) was expressed in 7 of 10 cell lines and in 9 of 16 tumor tissues. Furthermore, an overexpression and an amplification of c-myc gene was observed in some cell lines. These results suggest that multiple oncogene expression may be required for the induction, maintenance, and progression of esophageal carcinoma. The expression of a 2.7-kb transcript, of c-sis and overexpression of c-myc gene may play some role in the carcinogenesis of esophageal carcinoma.

Elimination of malignant tumor cells from human bone marrow using monoclonal antibodies and immunomagnetic beads

Conditions for depletion of malignant tumor cells from human bone marrow using monoclonal antibodies and immunomagnetic beads were studied. Human hepatoma HA22T/VGH cells labeled with the supravital DNA binding dye Hoechst 33342 were seeded into normal human bone marrow at a ratio of tumor cells to marrow cells of 1:9. The immunobeads used were M-450 magnetic microspheres coated with sheep anti-mouse immunoglobulin. The marrow-tumor cell mixtures were incubated with a panel of antihuman hepatoma cell monoclonal antibodies (9B2, E10A1, and C2E6) at 4 degrees C for 40 min, and then reacted with immunomagnetic beads for 60 min longer. After incubation, the bead-coated tumor cells were removed from the marrow with a magnetic particle concentrator. Tumor residual was measured in a limiting dilution test, and the recovery of marrow progenitor cells was assessed by CFU-GM assay. The efficiency of tumor depletion was closely related to the amount of monoclonal antibody bound to tumor cells and the immunobead/tumor cell ratio. Monoclonal antibodies used in combination were more effective than their individual use alone. Two cycles of purging with both monoclonal antibodies and immunomagnetic beads resulted in an apparent improvement in tumor depletion as compared with one cycle. Using a cocktail of three monoclonal antibodies and purging the marrow for two cycles, 4 to 5 logs of tumor cells could be removed with a sufficient recovery (70%) of CFU-GM. However, multiple purging treatments (> or = 3 cycles) would be apparently damaging to hematopoietic progenitor cells.

Immune reactions against hepatitis B viral antigens lead to the rejection of hepatocellular carcinoma in BALB/c mice

Human hepatitis B virus (HBV) is closely associated with hepatocellular carcinoma. However, the mechanism of carcinogenesis and the immune responses to HBV infection and hepatocellular carcinoma are not clearly understood. Recently, we established BALB/c mouse liver (ML) cell lines and demonstrated that transfection of ML cell lines with HBV dimer DNA resulted in the expression of HBV antigens (1). The HBV-transfected ML cells and the parental ML cells showed similar tumorigenicity in nude mice. However, the HBV-transfected cells had much lower tumorigenicity in BALB/c mice. Similar results were also obtained in two cloned ML cell lines, ML-1.1 and ML-1.2, transfected with plasmid DNA containing HBs, HBc, or HBx gene. Furthermore, adoptive transfer of spleen cells from BALB/c mice immunized with HBsAg- or HBcAg-expressing ML-1.1 cells caused regression of tumor cells expressing the corresponding antigens in nude mice. In addition, transfer of spleen cells from BALB/c mice immunized with purified HBsAg or HBcAg also caused tumor regression. These results demonstrate that HBsAg and HBcAg can induce immunity which leads to the rejection of hepatocellular carcinoma in vivo.

Proliferative and cytotoxic T-cell clones recognize endogenously synthesized HBcAg in an asymptomatic HBsAg carrier

The characterization of immune responses to hepatitis B virus is crucial for the understanding of hepatitis B virus-caused liver disease. However, lack of a suitable autologous effector-target cell system makes a precise study of the pathogenesis of hepatitis B difficult. In this study we established a model system by using autologous HBcAg-expressing Epstein-Barr virus-immortalized lymphoblastoid cell lines as stimulator/target cells. T-cell cultures were established by repetitive stimulation with recombinant HBcAg or autologous HBcAg-expressing lymphoblastoid cell lines. Both proliferative and cytotoxic T-cell clones were obtained from the peripheral blood of an asymptomatic HBsAg carrier. Clones T12 (CD8+) and T2B (CD4+) were cytotoxic clones specific against autologous lymphoblastoid cell lines expressing endogenously synthesized HBcAg, whereas five CD4+ T-cell clones proliferated in response to lymphoblastoid cell lines incubated with exogenous recombinant HBcAg and autologous HBcAg-expressing lymphoblastoid cell lines. These results indicate that autologous HBcAg-expressing lymphoblastoid cell lines are appropriate stimulator/target cells for the study of HBcAg-specific T lymphocytes. By using this approach, we have demonstrated that both proliferative and cytotoxic T lymphocytes recognizing endogenously synthesized HBcAg are induced during chronic hepatitis B virus infection.

Hepatitis B virus replication in well differentiated mouse hepatocyte cell lines immortalized by plasmid DNA

The primary hepatocytes cultured from adult BALB/c mice were readily transfected by plasmid DNA and could be immortalized at a frequency of approximately 0.1 to 0.6 x 10(-7) cells/micrograms of the transfected DNA. There was no detectable plasmid DNA at the tenth cell passages. A total of five mouse hepatocyte cell lines were established. Most of them were tumorigenic. Three of the established mouse hepatocyte cell lines were well differentiated, since they expressed liver-specific genes. Further transfection of these three well differentiated mouse hepatocyte cell lines with hepatitis B virus (HBV) DNA showed that the HBV-transfected cells had integrated HBV genomes, HBV-specific mRNA transcripts, and expression of hepatitis B surface and hepatitis B core antigens. One of the lines, ML-3Neo (HBV), even secreted HBV-like particles. Furthermore, circulating hepatitis B surface antigens were detected in the sera of BALB/c mice bearing ML-3Neo (HBV) tumors. These cell lines provide a convenient model for future studies on the host immune reaction against HBV and on the transformation of hepatocytes by HBV and other cellular oncogenes and the determination of their effects on hepatocellular differentiation.

Characterization of a cis element required for packaging and replication of the human hepatitis B virus

The hepatitis B virus (HBV) is a DNA virus; however, it replicates through a pregenomic RNA intermediate. Several HBV-specific mRNAs are transcribed, but only the pregenomic RNA transcript is encapsidated. The encapsidation of the HBV genome, therefore, is a highly specific and selective process. Using mutational analyses and complementation tests, we have defined a 99-nucleotide cis element located at the pre-C/C region of the HBV genome which is essential for encapsidation and the replication. Furthermore, HBV genome truncated down to 1.5 kb and HBV mutants carrying foreign DNA inserts could still replicate in our complementation system.

In vivo stimulation of myelopoiesis in cyclophosphamide-treated mice by purified human GM-CSF

Human granulocyte-macrophage colony-stimulating factor (hGM-CSF) secreted by a hepatoma cell line, HA22T/GVH, was purified and assessed for its effects in vivo on blood leukocytes and bone marrow granulocyte-macrophage progenitor cells (CFU-GM) in ICR mice pretreated with a sublethal dose of cyclophosphamide (cytoxan). The hGM-CSF preparations were natural and had no detectable endotoxin. Five days after the administration of 300 mg/kg cytoxan, severe leukopenia with marked myelopoietic suppression was induced. The cytoxan-treated mice were then injected intraperitoneally with 10,000 units of purified hGM-CSF/mouse daily for three days. Leukopenia was totally abrogated and the leukocyte number greatly increased to a level 2- to 3-fold higher than in GM-CSF-uninjected mice. Differential white cell count showed that the subpopulations of leukocytes responsive to hGM-CSF stimulation were mainly of neutrophils and monocytes, while the lymphocytes remained unaffected. Meanwhile, in the bone marrow, hGM-CSF administration induced an apparent (3-fold) increase in the number of myeloid progenitor cells, CFU-GM. However, the effect in vivo of a single hGM-CSF injection could only maintain for 48 hrs. In addition, the loss in body weight caused by cytoxan was less in the mice with subsequent hGM-CSF than those without CSF. These results suggest that injection of GM-CSF can effectively reconstitute the cytotoxic drug-damaged myelopoiesis without apparent in vivo toxic reaction.

Differential formation of disulfide linkages in the core antigen of extracellular and intracellular hepatitis B virus core particles

Our understanding of the assembly of hepatitis B virus is still very limited. We present evidence to demonstrate that the HBc antigen formed oligomers through disulfide linkages in the extracellular hepatitis B virus core (HBc) particles. However, the intracellular HBV core particles did not contain disulfide-linked HBc antigens. Furthermore, the extracellular particles which had disulfide bonds were more stable than intracellular particles at pH 7.5 and 10 and in 3 M NaCl and 4 M urea. These data suggest that the formation of disulfide bonds in the HBc antigen is important for the integrity of the viral core particles.

Overexpression of epidermal growth factor and insulin-like growth factor-I receptors and autocrine stimulation in human esophageal carcinoma cells

The growth-stimulatory effects of epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), and insulin-like growth factor-I (IGF-I) on the human esophageal carcinoma cell line CE48T/VGH were evaluated. Under serum-free conditions, EGF, TGF-alpha, and IGF-I promoted 3.6- to 4.1-fold increased cell proliferation. Scatchard analyses and Northern blot hybridization revealed that both the EGF/TGF-alpha receptor and the IGF-I receptor were overexpressed in CE48T/VGH cells. Furthermore, ligand-dependent autophosphorylation of the EGF receptor and the IGF-I receptor was clearly detected using antireceptor and antiphosphotyrosine antibodies. Autocrine regulation was strongly indicated by the following evidence: (a) CE48T/VGH cells were found to express TGF-alpha and IGF-I genes, (b) serum-free conditioned medium promoted the growth of CE48T/VGH cells and stimulated the autophosphorylation of the EGF/TGF-alpha receptor and the IGF-I receptor, and (c) the addition of IGF-I receptor antibodies significantly suppressed CE48T/VGH cell growth under serum-free conditions. Our studies suggest that the overexpression of EGF and IGF-I receptors and autocrine growth regulation may concertedly control the proliferation of esophageal carcinoma cells.

MHC class II antigens on canine bronchoalveolar cells

To evaluate the expression of MHC (major histocompatibility complex) antigens on canine bronchoalveolar cells (BAC), bronchoalveolar lavages (BAL) were performed in mongrel and German shepherd dogs. MHC class II antigens on canine BAC and peripheral blood mononuclear cells (PBMC) were detected by monoclonal antibodies (mAbs) B1F6, 7.5.10.1 and Q5/13 recognising canine MHC class II antigens, using cytofluorometry. These mAbs reacted with more than 20% of BAC and PBMC in both breeds of dog. The percentage of MHC class II positive cells in BAC were lower than those in PBMC. There was no significant difference in the percentages of MHC class II positive BAC and PBMC in mongrel and German shepherd dogs. To further identify the expression of MHC class II antigens on BAC, the cells were separated into adherent and nonadherent cells by petri dish adherence. The percentages of MHC class II positive cells in adherent and non-adherent cell populations were similar. Nearly half the lymphocytes in normal BAC were T cells detected by mAbs F3-20-7 and 1A1; B cells were scarce and represented less than 10% of nonadherent cells. Immunoprecipitation by anti-MHC class II mAbs, and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) revealed MHC class II-like molecules on canine BAC and PBMC. After stimulation with phytohaemagglutinin (PHA), the percentages of class II positive cells in BAC and PBMC were significantly increased. Thus, these anti-MHC class II mAbs may prove to be of advantage in experiments designed to evaluate the changes in class II antigen expression on canine BAC during the course of immune response in the lung, as in pulmonary allograft rejection.

Encapsidation of truncated human hepatitis B virus genomes through trans-complementation of the core protein and polymerase

Mutational analyses and complementation tests were used to analyze the strategy of packaging and of replication of human hepatitis B virus (HBV). By creating new restriction enzyme sites and by varying the genome length of HBV mutants, we identified that the mutated genomes could be encapsidated through trans-complementation of the polymerase and/or core protein. This study demonstrates that the polymerase of HBV, similar to that of duck hepatitis B virus (DHBV), is synthesized de novo instead of through a core-polymerase fusion protein. The results also indicate that both the polymerase and the core protein can be supplied in trans during viral packaging, and that the complementation is not due to recombination between the cotransfected plasmids. Furthermore, HBV genome deleted down to 2.4 kb is still able to be encapsidated, as measured by the endogenous polymerase reaction. Taken together, these results provide a basis for using HBV as a vector to deliver foreign genes into hepatocytes and for defining the location of the packaging signal on the HBV genome.